Publications by authors named "Aleksandra Isakovic"

47 Publications

Hallmarks of tumor-associated microglia response to experimental U87 human glioblastoma xenograft.

Tissue Cell 2021 May 23;72:101557. Epub 2021 May 23.

Center for Medical and Pharmaceutical Investigations and Quality Control, Faculty of Medicine, University of Novi Sad, Hajduk Veljkova 3, Novi Sad, 21000, Serbia; Faculty of Medicine, Department of Histology and Embryology, University of Novi Sad, Hajduk Veljkova 3, Novi Sad, 21000, Serbia.

Glioblastoma (GBM) is one of the deadliest primary brain neoplasm, heavily infiltrated with tumor-associated microglia/macrophages (TAM), which has received a great deal of interest. Bearing in mind that the number of peripheral macrophages by the 14 day is negligible, in our study TAM were referred to as microglia. Here we evaluated histopathological characterization of TAM and kinetics of their infiltration in U87 orthotopic GBM, a commonly used model in preclinical research. To mimic different stages of GBM growth, we evaluated three-time points. Our data showed that the highest areal density of TAM was 7 days after GBM inoculation, with ability to proliferate early after initiation of GBM growth. The areal density of TAM within the tumor correlated with GBM growth and proliferation. Moreover, microglia underwent substantial morphological changes upon exposure to GBM cells. A transition from ramified morphology in peritumoral area to ameboid shape with larger soma and shortened, thick branches in the tumor core was observed. Higher areal fraction of blood vessels also correlated with the areal density of TAM. Given these pro-invasive features of microglia, this GBM model represents a good basis for further testing microglia as a target and new strategy to fight with.
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http://dx.doi.org/10.1016/j.tice.2021.101557DOI Listing
May 2021

Study of the venom proteome of Vipera ammodytes ammodytes (Linnaeus, 1758): A qualitative overview, biochemical and biological profiling.

Comp Biochem Physiol Part D Genomics Proteomics 2021 03 9;37:100776. Epub 2020 Nov 9.

Ruđer Bošković Institute, Proteomics and Mass Spectrometry, Zagreb, Croatia.

Vipera ammodytes (Va), is the European venomous snake of the greatest medical importance. We analyzed whole venom proteome of the subspecies V. ammodytes ammodytes (Vaa) from Serbia for the first time using the shotgun proteomics approach and identified 99 proteins belonging to four enzymatic families: serine protease (SVSPs), L-amino acid oxidase (LAAOs), metalloproteinases (SVMPs), group II phospholipase (PLA2s), and five nonenzymatic families: cysteine-rich secretory proteins (CRISPs), C-type lectins (snaclecs), growth factors -nerve (NGFs) and vascular endothelium (VEGFs), and Kunitz-type protease inhibitors (SPIs). Considerable enzymatic activity of LAAO, SVSPs, and SVMPs and a high acidic PLA2 activity was measured implying potential of Vaa to produce haemotoxic, myotoxic, neuro and cardiotoxic effects. Moreover, significant antimicrobial activity of Vaa venom against Gram-negative (Klebsiella pneumoniae, Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus) was found. The crude venom shows considerable potential cytotoxic activity on the C6 and HL60 and a moderate level of potency on B16 cell lines. HeLa cells showed the same sensitivity, while DU 145 and PC-3 are less sensitive than as normal cell line. Our data demonstrated a high complexity of Vaa and considerable enzymatic, antibacterial and cytotoxic activity, implying a great medical potential of Vaa venom as a promising source for new antibacterial and cytostatic agents.
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http://dx.doi.org/10.1016/j.cbd.2020.100776DOI Listing
March 2021

Role of AMPK/mTOR-independent autophagy in clear cell renal cell carcinoma.

J Investig Med 2020 12 21;68(8):1386-1393. Epub 2020 Oct 21.

Institute of Microbiology and Immunology, University of Belgrade Faculty of Medicine, Belgrade, Serbia

We examined the status and role of autophagy, a process of lysosomal recycling of cellular material, in clear cell renal cell carcinoma (ccRCC). Paired samples of tumor and adjacent non-malignant tissue were collected from 20 patients with ccRCC after radical nephrectomy. The mRNA levels of apoptosis (, , , , ) and autophagy (, , , , ) regulators were measured by RT-qPCR. The protein levels of autophagosome-associated LC3-II, autophagy receptor p62, apoptotic marker PARP, as well as phosphorylation of autophagy initiator Unc 51-like kinase 1 (ULK1), its activator AMP-activated protein kinase (AMPK) and 4EBP1, the substrate of ULK1 inhibitor mechanistic target of rapamycin (mTOR), were analyzed by immunoblotting. The mRNA levels of pro-apoptotic , anti-apoptotic and pro-autophagic , and were higher in ccRCC tumors. Autophagy induction was confirmed by an increase in phospho-ULK1 and degradation of the autophagic target p62, while apoptotic PARP cleavage was unaltered. AMPK phosphorylation was reduced and 4EBP1 phosphorylation was increased in ccRCC tissue. The expression of apoptosis regulators did not correlate with clinicopathological features of ccRCC. Conversely, high mRNA levels of and were associated with lower tumor stage, as well as with smaller tumor size and better disease-specific 5-year survival ( and ). Accordingly, low p62 protein levels, corresponding to increased autophagic flux, were associated with lower tumor stage, reduced metastasis and improved 5-year survival. These data demonstrate that transcriptional induction of autophagy in ccRCC is accompanied by AMPK/mTOR-independent increase in ULK1 activation and autophagic flux, which might slow tumor progression and metastasis independently of apoptosis.
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http://dx.doi.org/10.1136/jim-2020-001524DOI Listing
December 2020

Influence of preoperative statins and aspirin administration on biological and magnetic resonance imaging properties in patients with abdominal aortic aneurysm.

Vasa 2021 Feb 16;50(2):116-124. Epub 2020 Jul 16.

School of Medicine, University of Belgrade, Serbia.

: Main objective of this study was to evaluate the influence of statins and/or acetylsalicylic acid on biochemical characteristics of abdominal aortic aneurysm (AAA) wall and intraluminal thrombus (ILT). : Fifty patients with asymptomatic infrarenal AAA were analyzed using magnetic resonance imaging on T1w sequence. Relative ILT signal intensity (SI) was determined as a ratio between ILT and psoas muscle SI. Samples containing the full ILT thickness and aneurysm wall were harvested from the anterior surface at the level of the maximal diameter. The concentration of enzymes such as matrix metalloproteinase (MMP) 9, MMP2 and neutrophil elastase (NE/ELA) were analyzed in ILT and AAA wall; while collagen type III, elastin and proteoglycan 4 were analyzed in harvested AAA wall. Oxidative stress in the AAA wall was assessed by catalase and malondialdehyde activity in tissue samples. : Relative ILT signal intensity (1.09 ± 0.41 vs 0.89 ± 0.21, p = 0.013) were higher in non-statin than in statin group. Patients who were taking aspirin had lower relative ILT area (0.89 ± 0.19 vs 1.13. ± 0.44, p = 0.016), and lower relative ILT signal intensity (0.85 [0.73-1.07] vs 1.01 [0.84-1.19], p = 0.021) compared to non-aspirin group. There were higher concentrations of elastin in AAA wall among patients taking both of aspirin and statins (1.21 [0.77-3.02] vs 0.78 (0.49-1.05) ng/ml, p = 0.044) than in patients who did not take both of these drugs. : Relative ILT SI was lower in patients taking statin and aspirin. Combination of antiplatelet therapy and statins was associated with higher elastin concentrations in AAA wall.
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http://dx.doi.org/10.1024/0301-1526/a000895DOI Listing
February 2021

Magnetic resonance imaging assessment of proteolytic enzyme concentrations and biologic properties of intraluminal thrombus in abdominal aortic aneurysms.

J Vasc Surg 2020 09 14;72(3):1025-1034. Epub 2020 Feb 14.

School of Medicine, University of Belgrade, Belgrade, Serbia; Clinic for Vascular and Endovascular Surgery, Clinical Center of Serbia, Belgrade, Serbia.

Objective: The aim of the study was to determine whether magnetic resonance imaging (MRI) can be used in assessment of biologic activity of intraluminal thrombus (ILT) and proteolytic processes of the abdominal aortic aneurysm wall.

Methods: Using MRI, 50 patients with asymptomatic infrarenal abdominal aortic aneurysm were analyzed at the maximum aneurysm diameter on T1-weighted images in the arterial phase after administration of contrast material. Relative ILT signal intensity (SI) was determined as the ratio between ILT SI and psoas muscle SI. During surgery, the full thickness of the ILT and the adjacent part of the aneurysm wall were harvested at the maximal diameter for biochemical analysis. The concentrations of matrix metalloproteinase 9 and neutrophil elastase (NE/ELA) were analyzed in harvested thrombi, and the concentrations of collagen type III, elastin, and proteoglycans were analyzed in harvested aneurysm walls.

Results: A significant positive correlation was found between the NE/ELA concentration of the ILT and the relative SI (ρ = 0.309; P = .029). Furthermore, a negative correlation was observed between the elastin content of the aneurysm wall and the relative SI (ρ = -0.300; P = .034). No correlations were found between relative SI and concentration of matrix metalloproteinase 9, NE/ELA, collagen type III, or proteoglycan 4 in the aneurysm wall.

Conclusions: These findings indicate a potential novel use of MRI in prediction of thrombus proteolytic enzyme concentrations and the extracellular matrix content of the aneurysm wall, thus providing additional information for the risk of potential aneurysm rupture.
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http://dx.doi.org/10.1016/j.jvs.2019.11.032DOI Listing
September 2020

Transcriptional block of AMPK-induced autophagy promotes glutamate excitotoxicity in nutrient-deprived SH-SY5Y neuroblastoma cells.

Cell Mol Life Sci 2020 Sep 12;77(17):3383-3399. Epub 2019 Nov 12.

Faculty of Medicine, Institute of Microbiology and Immunology, University of Belgrade, Dr. Subotica 1, 11000, Belgrade, Serbia.

We investigated the role of autophagy, a controlled lysosomal degradation of cellular macromolecules and organelles, in glutamate excitotoxicity during nutrient deprivation in vitro. The incubation in low-glucose serum/amino acid-free cell culture medium synergized with glutamate in increasing AMP/ATP ratio and causing excitotoxic necrosis in SH-SY5Y human neuroblastoma cells. Glutamate suppressed starvation-triggered autophagy, as confirmed by diminished intracellular acidification, lower LC3 punctuation and LC3-I conversion to autophagosome-associated LC3-II, reduced expression of proautophagic beclin-1 and ATG5, increase of the selective autophagic target NBR1, and decreased number of autophagic vesicles. Similar results were observed in PC12 rat pheochromocytoma cells. Both glutamate-mediated excitotoxicity and autophagy inhibition in starved SH-SY5Y cells were reverted by NMDA antagonist memantine and mimicked by NMDA agonists D-aspartate and ibotenate. Glutamate reduced starvation-triggered phosphorylation of the energy sensor AMP-activated protein kinase (AMPK) without affecting the activity of mammalian target of rapamycin complex 1, a major negative regulator of autophagy. This was associated with reduced mRNA levels of autophagy transcriptional activators (FOXO3, ATF4) and molecules involved in autophagy initiation (ULK1, ATG13, FIP200), autophagosome nucleation/elongation (ATG14, beclin-1, ATG5), and autophagic cargo delivery to autophagosomes (SQSTM1). Glutamate-mediated transcriptional repression of autophagy was alleviated by overexpression of constitutively active AMPK. Genetic or pharmacological AMPK activation by AMPK overexpression or metformin, as well as genetic or pharmacological autophagy induction by TFEB overexpression or lithium chloride, reduced the sensitivity of nutrient-deprived SH-SY5Y cells to glutamate excitotoxicity. These data indicate that transcriptional inhibition of AMPK-dependent cytoprotective autophagy is involved in glutamate-mediated excitotoxicity during nutrient deprivation in vitro.
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http://dx.doi.org/10.1007/s00018-019-03356-2DOI Listing
September 2020

Effects of Sideritis scardica Extract on Glucose Tolerance, Triglyceride Levels and Markers of Oxidative Stress in Ovariectomized Rats.

Planta Med 2019 Apr 28;85(6):465-472. Epub 2019 Jan 28.

Institute of Biochemistry, School of Medicine, University of Belgrade, Belgrade, Serbia.

Menopause is characterized by deep metabolic disturbances, including decreased insulin sensitivity, adiposity, and changes in lipid profiles. Estrogen replacement therapy can partially reverse these changes, and while it is safe in most healthy postmenopausal women, there are still existing concerns regarding an increased risk for breast and endometrial cancer as well as a risk for cardiovascular and thromboembolic disease. Therefore, certain natural compounds with positive metabolic effects may be considered as a possible alternative or adjunctive treatment in patients not willing to take estrogens or patients with contraindications for estrogens. The aim of this study was to investigate the influence of (mountain tea) extract on metabolic disturbances induced by ovariectomy in rats. The study included 24 rats divided into three groups: ovariectomized rats treated with 200 mg/kg extract for 24 weeks (n = 8), ovariectomized non-treated (n = 8), and Sham-operated (n = 8) rats. Food intake, weight gain, body composition, fasting glucose levels, response to oral glucose challenge, liver glycogen content, catalase activity, thiol groups, and malondialdehyde concentrations as well as AMP-activated protein kinase activity in liver cells were studied. Ovariectomized rats treated with extract had lower blood triglycerides, reduced fasting glucose levels, as well lower glucose peaks after oral glucose challenge, increased liver glycogen content, and significantly higher catalase activity and thiol group concentration than non-treated ovariectomized rats. The ability of extract to attenuate metabolic disturbances associated with ovariectomy was associated with the activation of AMP-activated protein kinase in liver cells.
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http://dx.doi.org/10.1055/a-0835-6622DOI Listing
April 2019

Betaine modulates oxidative stress, inflammation, apoptosis, autophagy, and Akt/mTOR signaling in methionine-choline deficiency-induced fatty liver disease.

Eur J Pharmacol 2019 Apr 25;848:39-48. Epub 2019 Jan 25.

Institute of Pathophysiology "Ljubodrag Buba Mihailovic", School of Medicine, University of Belgrade, Belgrade, Serbia. Electronic address:

We examined the effects of betaine, an endogenous and dietary methyl donor essential for the methionine-homocysteine cycle, on oxidative stress, inflammation, apoptosis, and autophagy in methionine-choline deficient diet (MCD)-induced non-alcoholic fatty liver disease (NAFLD). Male C57BL/6 mice received standard chow (control), standard chow and betaine (1.5% w/v in drinking water), MCD, or MCD and betaine. After six weeks, serum and liver samples were collected for analysis. Betaine reduced MCD-induced increase in liver transaminases and inflammatory infiltration, as well as hepatosteatosis and serum levels of low-density lipoprotein, while it increased that of high-density lipoprotein. MCD-induced hepatic production of reactive oxygen and nitrogen species was significantly reduced by betaine, which also improved liver antioxidative defense by increasing glutathione content and superoxide-dismutase, catalase, glutathione peroxidase, and paraoxonase activity. Betaine reduced the liver expression of proinflammatory cytokines tumor necrosis factor and interleukin-6, as well as that of proapoptotic mediator Bax, while increasing the levels of anti-inflammatory cytokine interleukin-10 and antiapoptotic Bcl-2 in MCD-fed mice. In addition, betaine increased the expression of autophagy activators beclin 1, autophagy-related (Atg)4 and Atg5, as well as the presence of autophagic vesicles and degradation of autophagic target sequestosome 1/p62 in the liver of NAFLD mice. The observed effects of betaine coincided with the increase in the hepatic phosphorylation of mammalian target of rapamycin (mTOR) and its activator Akt. In conclusion, the beneficial effect of betaine in MCD-induced NAFLD is associated with the reduction of liver oxidative stress, inflammation, and apoptosis, and the increase in cytoprotective Akt/mTOR signaling and autophagy.
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http://dx.doi.org/10.1016/j.ejphar.2019.01.043DOI Listing
April 2019

Standardized L. leaf extract exhibits protective activity in carbon tetrachloride-induced acute liver injury in rats: the insight into potential mechanisms.

Arch Physiol Biochem 2020 Dec 11;126(5):399-407. Epub 2019 Jan 11.

Biomedical Research, R&D Institute, Galenika a.d., Belgrade, Serbia.

The protective activity of dry olive leaf extract (DOLE) in carbon tetrachloride (CCl)-induced liver damage and possible mechanisms involved in this protection were investigated in rats. Acute CCl intoxication resulted in a massive hepatic necrosis, in increased serum transaminases, and in a perturbation of oxidative stress parameters in liver tissue [malondyaldehide, glutathione (GSH), catalase]. CCl did not affect the expression of caspase-3 and cytochrome c as markers of apoptosis; however, CCl increased the AMP-activated protein kinase (AMPK) activity and the expression of autophagy-related protein LC3II and decreased the expression of p62 protein. The pre-treatment with DOLE significantly improved serum markers of liver damage, liver catalase activity, and GSH concentration, suggesting that antioxidative mechanism is responsible for hepatoprotection. Oral administration of DOLE did not influence LC3II conversion and p62 degradation in liver, but AMPK activity was significantly decreased, suggesting the energy balance perturbation as an additional potential mechanism of DOLE hepatoprotective effect.
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http://dx.doi.org/10.1080/13813455.2018.1550095DOI Listing
December 2020

Graphene quantum dots inhibit T cell-mediated neuroinflammation in rats.

Neuropharmacology 2019 03 22;146:95-108. Epub 2018 Nov 22.

Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, Dr Subotica 1, 11000, Belgrade, Serbia. Electronic address:

We investigated the therapeutic capacity of nano-sized graphene sheets, called graphene quantum dots (GQD), in experimental autoimmune encephalomyelitis (EAE), an animal model of immune-mediated central nervous system (CNS) damage. Intraperitoneally administered GQD (10 mg/kg/day) accumulated in the lymph node and CNS cells of Dark Agouti rats in which EAE was induced by immunization with spinal cord homogenate in complete Freund's adjuvant. GQD significantly reduced clinical signs of EAE when applied throughout the course of the disease (day 0-32), while the protection was less pronounced if the treatment was limited to the induction (day 0-7 post-immunization) or effector (from day 8 onwards) phase of the disease. GQD treatment diminished immune infiltration, demyelination, axonal damage, and apoptotic death in the CNS of EAE animals. GQD also reduced the numbers of interferon-γ-expressing T helper (Th)1 cells, as well as the expression of Th1 transcription factor T-bet and proinflammatory cytokines tumor necrosis factor, interleukin-1, and granulocyte-macrophage colony-stimulating factor in the lymph nodes and CNS immune infitrates. The protective effect of GQD in EAE was associated with the activation of p38 and p42/44 mitogen-activated protein kinases (MAPK) and Akt in the lymph nodes and/or CNS. Finally, GQD protected oligodendrocytes and neurons from T cell-mediated damage in the in vitro conditions. Collectively, these data demonstrate the ability of GQD to gain access to both immune and CNS cells during neuroinflammation, and to alleviate immune-mediated CNS damage by modulating MAPK/Akt signaling and encephalitogenic Th1 immune response.
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http://dx.doi.org/10.1016/j.neuropharm.2018.11.030DOI Listing
March 2019

In vitro and in vivo antimelanoma effect of ethyl ester cyclohexyl analog of ethylenediamine dipropanoic acid.

Melanoma Res 2018 02;28(1):8-20

Institute of Medical and Clinical Biochemistry.

Melanoma, an aggressive skin tumor with high metastatic potential, is associated with high mortality and increasing morbidity. Multiple available chemotherapeutic and immunotherapeutic modalities failed to improve survival in advanced disease, and the search for new agents is ongoing. The aim of this study was to investigate antimelanoma effects of O,O-diethyl-(S,S)-ethylenediamine-N,N'di-2-(3-cyclohexyl) propanoate dihydrochloride (EE), a previously synthesized and characterized organic compound. Mouse melanoma B16 cell viability was assessed using acid phosphatase, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, sulforhodamine B, and lactate dehydrogenase assays. Apoptosis and autophagy were investigated using flow cytometry, fluorescence and electron microscopy, and western blotting. In vivo antitumor potential was assessed in subcutaneous mouse melanoma model after 14 days of treatment with EE. Tumor mass and volume were measured, and RT-PCR was used for investigating the expression of autophagy-related, proapoptotic, and antiapoptotic molecules in tumor tissue. Investigated organic compound exerts significant cytotoxic effect against B16 cells. EE induced apoptosis, as confirmed by phosphatidyl serine externalisation, caspase activation, and ultrastructural features typical for apoptosis seen on fluorescence and electron microscopes. The apoptotic mechanism included prompt disruption of mitochondrial membrane potential and oxidative stress. No autophagy was observed. Antimelanoma action and apoptosis induction were confirmed in vivo, as EE decreased mass and volume of tumors, and increased expression of several proapoptotic genes. EE possesses significant antimelanoma action and causes caspase-dependent apoptosis mediated by mitochondrial damage and reactive oxygen species production. Decrease in tumor growth and increase in expression of proapoptotic genes in tumor tissue suggest that EE warrants further investigation as a candidate agent in treating melanoma.
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http://dx.doi.org/10.1097/CMR.0000000000000409DOI Listing
February 2018

Relationship between Oxidative Stress, Inflammation and Dyslipidemia with Fatty Liver Index in Patients with Type 2 Diabetes Mellitus.

Exp Clin Endocrinol Diabetes 2018 Jun 11;126(6):371-378. Epub 2017 Sep 11.

Department of Medical Biochemistry, University of Belgrade - Faculty of Pharmacy, Belgrade, Serbia.

Introduction/aim: Considering the high prevalence of non-alcoholic fatty liver disease (NAFLD) in individuals with type 2 diabetes mellitus (DM2), we aimed to investigate the potential benefit of determining markers of oxidative stress, inflammation and dyslipidemia for prediction of NAFLD, as estimated with fatty liver index (FLI) in individuals with DM2.

Methods: A total of 139 individuals with DM2 (of them 49.9% females) were enrolled in cross-sectional study. Anthropometric and biochemical parameters, as well as blood pressure were obtained. A FLI was calculated.

Results: Multivariate logistic regression analysis showed that high density lipoprotein cholesterol (HDL-c) and malondialdehyde (MDA) were independent predictors of higher FLI [Odds ratio (OR)=0.056, p=0.029; and OR=1.105, p=0.016, respectively]. In Receiver Operating Characteristic curve analysis, the addition of fatty liver risk factors (e. g., age, gender, body height, smoking status, diabetes duration and drugs metabolized in liver) to each analysed biochemical parameter [HDL-c, non-HDL-c, high sensitivity C-reactive protein (hsCRP), MDA and advanced oxidant protein products (AOPP)] in Model 1, increased the ability to discriminate patients with and without fatty liver [Area under the curve (AUC)=0.832, AUC=0.808, AUC=0.798, AUC=0.824 and AUC=0.743, respectively]. Model 2 (which included all five examined predictors, e. g., HDL-c, non-HDL-c, hsCRP, MDA, AOPP, and fatty liver risk factors) improved discriminative abilities for fatty liver status (AUC=0.909). Even more, Model 2 had the highest sensitivity and specificity (89.3% and 87.5%, respectively) together than each predictor in Model 1.

Conclusion: Multimarker approach, including biomarkers of oxidative stress, dyslipidemia and inflammation, could be of benefit in identifying patients with diabetes being at high risk of fatty liver disease.
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http://dx.doi.org/10.1055/s-0043-118667DOI Listing
June 2018

In vitro antiglioma action of indomethacin is mediated via AMP-activated protein kinase/mTOR complex 1 signalling pathway.

Int J Biochem Cell Biol 2017 02 14;83:84-96. Epub 2016 Dec 14.

Institute for Biological Research "Sinisa Stankovic", University of Belgrade, Despot Stefan Blvd. 142, 11000 Belgrade, Serbia. Electronic address:

We investigated the role of the intracellular energy-sensing AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway in the in vitro antiglioma effect of the cyclooxygenase (COX) inhibitor indomethacin. Indomethacin was more potent than COX inhibitors diclofenac, naproxen, and ketoprofen in reducing the viability of U251 human glioma cells. Antiglioma effect of the drug was associated with p21 increase and GM cell cycle arrest, as well as with oxidative stress, mitochondrial depolarization, caspase activation, and the induction of apoptosis. Indomethacin increased the phosphorylation of AMPK and its targets Raptor and acetyl-CoA carboxylase (ACC), and reduced the phosphorylation of mTOR and mTOR complex 1 (mTORC1) substrates p70S6 kinase and PRAS40 (Ser183). AMPK knockdown by RNA interference, as well as the treatment with the mTORC1 activator leucine, prevented indomethacin-mediated mTORC1 inhibition and cytotoxic action, while AMPK activators metformin and AICAR mimicked the effects of the drug. AMPK activation by indomethacin correlated with intracellular ATP depletion and increase in AMP/ATP ratio, and was apparently independent of COX inhibition or the increase in intracellular calcium. Finally, the toxicity of indomethacin towards primary human glioma cells was associated with the activation of AMPK/Raptor/ACC and subsequent suppression of mTORC1/S6K. By demonstrating the involvement of AMPK/mTORC1 pathway in the antiglioma action of indomethacin, our results support its further exploration in glioma therapy.
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http://dx.doi.org/10.1016/j.biocel.2016.12.007DOI Listing
February 2017

Autophagy suppression sensitizes glioma cells to IMP dehydrogenase inhibition-induced apoptotic death.

Exp Cell Res 2017 Jan 4;350(1):32-40. Epub 2016 Nov 4.

Institute of Medical and Clinical Biochemistry, School of Medicine, University of Belgrade, Pasterova 2, Belgrade, Serbia. Electronic address:

We investigated the role of autophagy, a process of controlled self-digestion, in the in vitro anticancer action of the inosine monophosphate dehydrogenase (IMPDH) inhibitor ribavirin. Ribavirin-triggered oxidative stress, caspase activation, and apoptotic death in U251 human glioma cells were associated with the induction of autophagy, as confirmed by intracellular acidification, appearance of autophagic vesicles, conversion of microtubule associated protein 1 light chain 3 (LC3)-I to autophagosome-associated LC3-II, and degradation of autophagic target p62/sequestosome 1. Ribavirin downregulated the activity of autophagy-inhibiting mammalian target of rapamycin complex 1 (mTORC1), as indicated by a decrease in phosphorylation of the mTORC1 substrate ribosomal p70S6 kinase and reduction of the mTORC1-activating Src/Akt signaling. Guanosine supplementation inhibited, while IMPDH inhibitor tiazofurin mimicked ribavirin-mediated autophagy induction, suggesting the involvement of IMPDH blockade in the observed effect. Autophagy suppression by ammonium chloride, bafilomycin A1, or RNA interference-mediated knockdown of LC3 sensitized glioma cells to ribavirin-induced apoptosis. Ribavirin also induced cytoprotective autophagy associated with Akt/mTORC1 inhibition in C6 rat glioma cells. Our data demonstrate that ribavirin-triggered Akt/mTORC1-dependent autophagy counteracts apoptotic death of glioma cells, indicating autophagy suppression as a plausible therapeutic strategy for sensitization of cancer cells to IMPDH inhibition.
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http://dx.doi.org/10.1016/j.yexcr.2016.11.001DOI Listing
January 2017

Structural differences in diarylheptanoids analogues from Alnus viridis and Alnus glutinosa influence their activity and selectivity towards cancer cells.

Chem Biol Interact 2016 Apr 2;249:36-45. Epub 2016 Mar 2.

Institute for Biological Research, Department of Neurobiology, University of Belgrade, Despota Stefana 142, Belgrade, Serbia.

Diarylheptanoids represent a group of plant secondary metabolites that possess multiple biological properties and are increasingly recognized for their therapeutic potential. A comparative study was performed on structurally analogous diarylheptanoids isolated from the bark of green (Alnus viridis) and black alder (Alnus glutinosa) to address their biological effects and determine structure-activity relationship. The structures and configurations of all compounds were elucidated by NMR, HR-ESI-MS, UV and IR. Diarylheptanoids actions were studied in human non-small cell lung carcinoma cells (NCI-H460) and normal keratinocytes (HaCaT). A. viridis compounds 3v, 5v, 8v and 9v that possess a carbonyl group at C-3 were considerably more potent than compounds without this group. A. viridis/A. glutinosa analogue pairs, 5v/5g and 9v/9g, which differ in the presence of 3' and 3″-OH groups, were evaluated for anticancer activity and selectivity. 5v and 9v that do not possess 3' and 3″-OH groups showed significantly higher cytotoxicity compared to analogues 5g and 9g. In addition, these two A. viridis compounds induced a more prominent apoptosis in both cell lines and an increase in subG0 cell cycle phase, compared to their A. glutinosa analogues. 5v and 9v treatment triggered intracellular superoxide anion accumulation and notably decreased mitochondrial transmembrane potential. In HaCaT cells, 9v and 9g with a 4,5 double bond caused a more prominent loss of mitochondrial transmembrane potential compared to 5v and 5g which possess a 5-methoxy group instead. Although green alder diarylheptanoids 5v and 9v displayed higher cytotoxicity, their analogues from black alder 5g and 9g could be more favorable for therapeutic use since they were more active in cancer cells than in normal keratinocytes. These results indicate that minor differences in the chemical structure can greatly influence the effect of diarylheptanoids on apoptosis and redox status and determine their selectivity towards cancer cells.
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http://dx.doi.org/10.1016/j.cbi.2016.02.019DOI Listing
April 2016

Evaluation of Anticancer and Antioxidant Activity of a Commercially Available CO2 Supercritical Extract of Old Man's Beard (Usnea barbata).

PLoS One 2016 8;11(1):e0146342. Epub 2016 Jan 8.

Institute for Medicinal Plant Research "Dr. Josif Pancic", Belgrade, Serbia.

There is a worldwide ongoing investigation for novel natural constituents with cytotoxic and antioxidant properties. The aim of this study was to investigate chemical profile and stated biological activities of the supercritical CO2 extract (SCE) of old man's beard compared to the extracts obtained using the conventional techniques (Soxhlet extracts and macerate). The most abundant compound identified was usnic acid, which content was inversely proportional to the polarity of the solvent used and was the highest in the SCE, which was the sample revealing the highest cytotoxic activity in tested tumor cell lines (B16 mouse melanoma and C6 rat glioma), with lower IC50 values compared to pure usnic acid. Further investigations suggested both SCE and usnic acid to induce apoptosis and/or autophagy in B16 and C6, indicating higher cytotoxicity of SCE to be related to the higher degree of ROS production. A good correlation of usnic acid content in the extracts and their antioxidant capacity was established, extricating SCE as the most active one. Presented results support further investigations of SCE of old man's beard as a prospective therapeutic agent with potential relevance in the treatment of cancer and/or in oxidative stress-mediated conditions.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0146342PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4706385PMC
June 2016

Statin-mediated inhibition of cholesterol synthesis induces cytoprotective autophagy in human leukemic cells.

Eur J Pharmacol 2015 Oct 8;765:415-28. Epub 2015 Sep 8.

Institute of Histology and Embryology, School of Medicine, University of Belgrade, Visegradska 26, 11000 Belgrade, Serbia. Electronic address:

Statins exhibit anti-leukemic properties due to suppression of the mevalonate pathway by the inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase, and subsequent depletion of cholesterol, farnesylpyrophosphate, and geranylgeranylpyrophosphate. We investigated the role of autophagy, a controlled intracellular self-digestion, in the anti-leukemic action of statins. Treatment with low concentrations (≤6 µM) of statins, cholesterol depletion, and specific inhibition of cholesterol synthesis and protein farnesylation or geranylgeranylation, all inhibited proliferation of leukemic cell lines and primary leukemic cells without inducing overt cell death. Statins and agents that selectively reduce intracellular cholesterol levels, but not the inhibition of protein farnesylation or geranylgeranylation, induced autophagy in leukemic cells. The observed autophagic response was associated with the reduction of phosphorylated Akt levels in the lipid rafts, accompanied by a decrease in the activation of the main autophagy suppressor mammalian target of rapamycin (mTOR) and its substrate ribosomal p70S6 kinase (p70S6K). No significant autophagy induction and downregulation of mTOR/p70S6K activation were observed in normal leukocytes. Autophagy suppression by bafilomycin A1 or RNA interference-mediated knockdown of beclin-1 and microtubule-associated protein 1 light chain 3B induced apoptotic death in statin-treated leukemic cells, an effect attenuated by the addition of mevalonate or squalene, but not farnesylpyrophosphate or geranylgeranylpyrophosphate. Therefore, while the inhibition of cholesterol synthesis, protein farnesylation, and geranylgeranylation all contributed to anti-leukemic effects of statins, the inhibition of cholesterol synthesis was solely responsible for the induction of cytoprotective autophagy. These data indicate that combined treatment with statins and autophagy inhibitors might be potentially useful in anti-leukemic therapy.
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http://dx.doi.org/10.1016/j.ejphar.2015.09.004DOI Listing
October 2015

Lower antioxidative capacity of multidrug-resistant cancer cells confers collateral sensitivity to protoflavone derivatives.

Cancer Chemother Pharmacol 2015 Sep 22;76(3):555-65. Epub 2015 Jul 22.

Institute for Biological Research, Department of Neurobiology, University of Belgrade, Bulevar Despota Stefana 142, 11060, Belgrade, Serbia.

Purpose: Multidrug resistance (MDR) may develop due to a series of adaptive responses under a new stress conditions, such as chemotherapy. Novel strategies are urgently needed to fight MDR in cancer, and chemotherapeutics that are selective for MDR cancer cells offer a promising approach. Certain protoflavones were previously found to have potential in this regard.

Methods: Cytotoxicity of six protoflavones was assessed in different P-glycoprotein overexpressing MDR cancer cell lines and in their non-MDR counterparts. The impacts of compound 5, 6-methylprotoflavone previously published and a new derivative, 6-bromoprotoflavone (compound 6), on the cell cycle distribution were evaluated, and 6 was also studied for its potential to regulate the intracellular antioxidative capacity.

Results: Protoflavones showed a significant cytotoxicity against all cancer cell lines and selectivity toward MDR cancer cells adapted to conventional chemotherapeutics. Inverse sensitivity versus MDR selectivity pattern was observed. Treatment with H₂O₂ showed that MDR cancer cells are more vulnerable to oxidative stress. Compounds 5 and 6 significantly decreased the portion of MDR cells in the G1 phase. The levels of reactive oxygen and nitrogen species (ROS/RNS) between MDR and non-MDR cells significantly differed upon exposure to 6, accompanied by changes in the glutathione (GSH) levels and in the expression of manganese superoxide dismutase (MnSOD), glutathione-S-transferase π (GST π) and hypoxia-inducible factor-1α (HIF-1α).

Conclusions: Our results suggest that MDR cancer cells can be more vulnerable to the pro-oxidative activity of protoflavones due to an impaired antioxidative defense that might arise during the adaptation processes provoked by chemotherapy.
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http://dx.doi.org/10.1007/s00280-015-2821-9DOI Listing
September 2015

Chemo-protective and regenerative effects of diarylheptanoids from the bark of black alder (Alnus glutinosa) in human normal keratinocytes.

Fitoterapia 2015 Sep 7;105:169-76. Epub 2015 Jul 7.

Institute for Biological Research, Department of Neurobiology, University of Belgrade, Bulevar Despota Stefana 142, Belgrade, Serbia. Electronic address:

Medicinal plants are recognized from ancient times as a source of diverse therapeutic agents and many of them are used as dietary supplements. Comprehensive approaches are needed that would identify bioactive components with evident activity against specific indications and provide a better link between science (ethno-botany, chemistry, biology and pharmacology) and market. Recently, the bark of black alder (Alnus glutinosa) appeared at market in the form of food supplement for treatment of different skin conditions. This study aimed to evaluate protective effects of two diarylheptanoids isolated from the bark of black alder: platyphylloside, 5(S)-1,7-di(4-hydroxyphenyl)-3-heptanone-5-O-β-D-glucopyranoside (1) and its newly discovered analog 5(S)-1,7-di(4-hydroxyphenyl)-5-O-β-D-[6-(E-p-coumaroylglucopyranosyl)]heptane-3-one (2) towards doxorubicin damaging activity. To that end, we employed HaCaT cells, non-cancerous human keratinocytes commonly used for skin regenerative studies. Diarylheptanoids significantly antagonized the effects of doxorubicin by lowering the sensitivity of HaCaT cells to this drug. Compound 2 prevented doxorubicin-induced cell death by activating autophagy. Both 1 and 2 protected HaCaT cells against doxorubicin-induced DNA damage. They significantly promoted migration and affected F-actin distribution. These results indicate that chemo-protective effects of diarylheptanoids may occur at multiple subcellular levels. Therefore, diarylheptanoids 1 and 2 could be considered as protective agents for non-cancerous dividing cells during chemotherapy.
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http://dx.doi.org/10.1016/j.fitote.2015.07.003DOI Listing
September 2015

Neuroprotective arylpiperazine dopaminergic/serotonergic ligands suppress experimental autoimmune encephalomyelitis in rats.

J Neurochem 2015 Oct 15;135(1):125-38. Epub 2015 Jul 15.

Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, Belgrade, Serbia.

Arylpiperazine-based dopaminergic/serotonergic ligands exert neuroprotective activity. We examined the effect of arylpiperazine D2 /5-HT1A ligands, N-{4-[2-(4-phenyl-piperazin-1-yl)-ethyl}-phenyl]-picolinamide (6a) and N-{3-[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-picolinamide (6b), in experimental autoimmune encephalomyelitis (EAE), a model of neuroinflammation. Both compounds (10 mg/kg i.p.) reduced EAE clinical signs in spinal cord homogenate-immunized Dark Agouti rats. Compound 6b was more efficient in delaying the disease onset and reducing the maximal clinical score, which correlated with its higher affinity for D2 and 5-HT1A receptors. The protection was retained if treatment was limited to the effector (from day 8 onwards), but not the induction phase (day 0-7) of EAE. Compound 6b reduced CNS immune infiltration and expression of mRNA encoding the proinflammatory cytokines tumor necrosis factor, IL-6, IL-1, and GM-CSF, TH 1 cytokine IFN-γ, TH 17 cytokine IL-17, as well as the signature transcription factors of TH 1 (T-bet) and TH 17 (RORγt) cells. Arylpiperazine treatment reduced apoptosis and increased the activation of anti-apoptotic mediators Akt and p70S6 kinase in the CNS of EAE animals. The in vitro treatment with 6b protected oligodendrocyte cell line OLN-93 and neuronal cell line PC12 from mitogen-activated normal T cells or myelin basic protein-activated encephalitogenic T cells. In conclusion, arylpiperazine dopaminergic/serotonergic ligands suppress EAE through a direct neuroprotective action and decrease in CNS inflammation. Arylpiperazine dopaminergic/serotonergic ligands reduce neurological symptoms of acute autoimmune encephalomyelitis in rats without affecting the activation of autoreactive immune response, through mechanisms involving a decrease in CNS immune infiltration, as well as direct protection of CNS from immune-mediated damage. These data indicate potential usefulness of arylpiperazine-based compounds in the treatment of neuroinflammatory disorders such as multiple sclerosis.
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http://dx.doi.org/10.1111/jnc.13198DOI Listing
October 2015

Development of resistance to antiglioma agents in rat C6 cells caused collateral sensitivity to doxorubicin.

Exp Cell Res 2015 Jul 27;335(2):248-57. Epub 2015 May 27.

Institute for Biological Research "Siniša Stanković", University of Belgrade, Despota Stefana 142, 11060 Belgrade, Serbia. Electronic address:

Chemoresistance is a severe limitation to glioblastoma (GBM) therapy and there is a strong need to understand the underlying mechanisms that determine its response to different chemotherapeutics. Therefore, we induced resistance in C6 rat glioma cell line, which considerably resembles the characteristics of human GBM. The resistant phenotype was developed by 3-bis (2-chloroethyl)-1-nitrosourea (BCNU), one of the most commonly used therapeutic drug in the course of GBM treatment. After confirmation of the cross-resistance to cisplatin (CPt) and temozolomide (TMZ) in newly established RC6 cell line, we examined cell death induction and DNA damage by these drugs. Resistance to apoptosis and deficiency in forming DNA double-strand breaks was followed by significant decrease in the mRNA expression of pro-apoptotic and anti-apoptotic genes. The development of drug resistance was associated with significant increase in reactive oxygen species (ROS) and decrease in oxidized to reduced gluthatione ratio in RC6 cell line indicating a reduced level of oxidative stress. The mRNA expression levels of manganese superoxid dismutase (MnSOD), inducible nitric oxide synthase (iNOS) and gluthatione peroxidase (GPx) were increased while hypoxia-inducible factor 1-α (HIF-1α) was decreased in RC6 compared to C6 cells. This was in line with obtained changes in ROS content and increased antioxidative capacity of RC6 cells. Importantly, RC6 cells demonstrated collateral sensitivity to doxorubicin (DOX). The analysis of this phenomenon revealed increased accumulation of DOX in RC6 cells due to their adaptation to high ROS content and acidification of cytoplasm. In conclusion, newly established RC6 rat glioma cell line could be used as a starting material for the development of allogenic animal model and preclinical evaluation of new antiglioma agents. Collateral sensitivity to DOX obtained after BCNU treatment may prompt new studies aimed to find efficient delivery of DOX to the glioma site in brain.
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http://dx.doi.org/10.1016/j.yexcr.2015.05.018DOI Listing
July 2015

Antioxidative activity of diarylheptanoids from the bark of black alder (Alnus glutinosa) and their interaction with anticancer drugs.

Planta Med 2014 Aug 19;80(13):1088-96. Epub 2014 Aug 19.

Institute for Biological Research, Department of Neurobiology, University of Belgrade, Belgrade, Serbia.

Diarylheptanoids belong to polyphenols, a group of plant secondary metabolites with multiple biological properties. Many of them display antioxidative, cytotoxic, or anticancer actions and are increasingly recognized as potential therapeutic agents. The aim of this study was to evaluate antioxidant and cytoprotective activity of two diarylheptanoids: platyphylloside 5(S)-1,7-di(4-hydroxyphenyl)-3-heptanone-5-O-β-D-glucopyranoside (1) and its newly discovered analog 5(S)-1,7-di(4-hydroxyphenyl)-5-O-β-D-[6-(E-p-coumaroylglucopyranosyl)]heptane-3-one (2), both isolated from the bark of black alder (Alnus glutinosa). To that end, we have employed a cancer cell line (NCI-H460), normal human keratinocytes (HaCaT), and peripheral blood mononuclear cells. The effects on cell growth were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. Cell death was examined by annexin V/propidium iodide staining on a flow cytometer. Reactive oxygen species production was examined by dihydroethidium staining. Mitochondrial structure and doxorubicin localization were visualized by fluorescent microscopy. Gene expression of manganese superoxide dismutase and hypoxia-inducible factor-1α was determined by reverse transcription polymerase chain reaction. Diarylheptanoids antagonized the effects of either doxorubicin or cisplatin, significantly increasing their IC50 values in normal cells. Diarylheptanoid 1 induced the retention of doxorubicin in cytoplasm and reduced mitochondrial fragmentation associated with doxorubicin application. Diarylheptanoid 2 reduced the reactive oxygen species production induced by cisplatin. Both compounds increased the messenger ribonucleic acid expression of enzymes involved in reactive oxygen species elimination (manganese superoxide dismutase and hypoxia-inducible factor-1α). These results indicate that neutralization of reactive oxygen species is an important mechanism of diarylheptanoid action, although these compounds exert a considerable anticancer effect. Therefore, these compounds may serve as protectors of normal cells during chemotherapy without significantly diminishing the effect of the applied chemotherapeutic.
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http://dx.doi.org/10.1055/s-0034-1382993DOI Listing
August 2014

HER2-positive breast cancer patients: correlation between mammographic and pathological findings.

Radiat Prot Dosimetry 2014 Nov 25;162(1-2):125-8. Epub 2014 Jul 25.

Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia

Human epidermal growth factor receptor 2 (HER2)-positive breast cancers represent a highly aggressive breast cancer subtype and are associated with a worse prognosis. This study was designed to investigate the mammography finding of HER2-positive breast cancer and to compare the results with the characteristics of HER2-negative breast cancer patients. From January 2010 to October 2011, mammography findings of 65 patients with pathologically confirmed HER2-positive breast cancers (n = 22) or HER2-negative breast cancers (n = 43) were retrospectively reviewed. The authors also reviewed pathological reports for information on the histological type and differentiation grade. Among the two types of breast cancer patients, estrogen receptor-negative/PR-negative/HER2-positive breast cancer patients most commonly had associated calcifications (18 of 22) on mammography. On mammography, cases with a cluster of calcifications usually were presented as pleomorphic calcifications (12 of 20) and branching calcifications (4 of 20). Patients with HER2-positive breast cancers showed a histological grade II. HER2-positive breast cancer patients usually had ductal invasive carcinoma (17 of 22). Moreover, postmenopausal patients showed a significantly higher frequency of HER2-positive tumours. Our results suggest that the imaging findings might be useful in diagnosing HER2-positive breast cancer patients.
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http://dx.doi.org/10.1093/rpd/ncu243DOI Listing
November 2014

Isolation, characterization, and in vitro cytotoxicity of new sesquiterpenoids from Achillea clavennae.

Planta Med 2014 Mar 7;80(4):297-305. Epub 2014 Feb 7.

Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, Belgrade, Serbia.

Further phytochemical investigation of the aerial parts of Achillea clavennae has resulted in the isolation of three new sesquiterpene lactones: two highly oxygenated germacranolides (1, 2) and the iso-seco-guaianolide 9(R)-acetoxy-3-O-methyl-iso-seco-tanapartholide (3). Eight known compounds were also found, of which 9α-acetoxycanin (5), sintenin (6), and oleanolic acid (7) were detected for the first time. The structures of the isolated compounds were elucidated by combined spectroscopic methods (1D and 2D NMR, HRESIMS, CIMS, and FTIR). While the predominant metabolite germacranolide sintenin (6) was not cytotoxic, the new iso-seco-guaianolide (3) displayed cytotoxicity comparable to that of cisplatin and the lactone apressin (4), inducing partly apoptotic death in human U251 and rat C6 glioma cell lines.
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http://dx.doi.org/10.1055/s-0033-1360312DOI Listing
March 2014

The mechanisms of in vitro cytotoxicity of mountain tea, Sideritis scardica, against the C6 glioma cell line.

Planta Med 2013 Nov 26;79(16):1516-24. Epub 2013 Sep 26.

Institute of Biochemistry, School of Medicine, University of Belgrade, Belgrade, Serbia.

Sideritis scardica (mountain tea) is an endemic plant on the Balkan Peninsula traditionally used for treating different conditions, mainly of inflammatory nature. This study was aimed to examine the cytotoxic activity of different S. scardica extracts against the rat glioma C6 line and rat astrocytes in primary culture. The obtained data revealed that diethyl ether (extract 2) and ethyl acetate (extract 3) extracts of S. scardica exerted a cytotoxic effect on C6 rat glioma cells. Diethyl ether extract induced an increase in reactive oxygen species production, leading to apoptotic and autophagic cell death. Ethyl acetate extract induced G2 M cell cycle arrest and autophagy. None of the tested extracts was cytotoxic to rat astrocytes in primary culture. Cytotoxic effects of S. scardica extracts were, at least in part, mediated by their flavonoid constituents apigenin and luteolin that, when applied alone, induced cell cycle arrest, apoptosis, and autophagy.
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http://dx.doi.org/10.1055/s-0033-1350809DOI Listing
November 2013

Purine nucleoside analog--sulfinosine modulates diverse mechanisms of cancer progression in multi-drug resistant cancer cell lines.

PLoS One 2013 11;8(1):e54044. Epub 2013 Jan 11.

Faculty of Medicine, University of Belgrade, Doktora Subotića 8, Belgrade, Serbia.

Achieving an effective treatment of cancer is difficult, particularly when resistance to conventional chemotherapy is developed. P-glycoprotein (P-gp) activity governs multi-drug resistance (MDR) development in different cancer cell types. Identification of anti-cancer agents with the potential to kill cancer cells and at the same time inhibit MDR is important to intensify the search for novel therapeutic approaches. We examined the effects of sulfinosine (SF), a quite unexplored purine nucleoside analog, in MDR (P-gp over-expressing) non-small cell lung carcinoma (NSCLC) and glioblastoma cell lines (NCI-H460/R and U87-TxR, respectively). SF showed the same efficacy against MDR cancer cell lines and their sensitive counterparts. However, it was non-toxic for normal human keratinocytes (HaCaT). SF induced caspase-dependent apoptotic cell death and autophagy in MDR cancer cells. After SF application, reactive oxygen species (ROS) were generated and glutathione (GSH) concentration was decreased. The expression of key enzyme for GSH synthesis, gamma Glutamyl-cysteine-synthetase (γGCS) was decreased as well as the expression of gst-π mRNA. Consequently, SF significantly decreased the expression of hif-1α, mdr1 and vegf mRNAs even in hypoxic conditions. SF caused the inhibition of P-gp (coded by mdr1) expression and activity. The accumulation of standard chemotherapeutic agent--doxorubicin (DOX) was induced by SF in concentration- and time-dependent manner. The best effect of SF was obtained after 72 h when it attained the effect of known P-gp inhibitors (Dex-verapamil and tariquidar). Accordingly, SF sensitized the resistant cancer cells to DOX in subsequent treatment. Furthermore, SF decreased the experssion of vascular endothelial growth factor (VEGF) on mRNA and protein level and modulated its secretion. In conclusion, the effects on P-gp (implicated in pharmacokinetics and MDR), GSH (implicated in detoxification) and VEGF (implicated in tumor-angiogenesis and progression) qualify SF as multi-potent anti-cancer agent, which use must be considered, in particular for resistant malignancies.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0054044PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3543365PMC
July 2013

Cyclohexyl analogues of ethylenediamine dipropanoic acid induce caspase-independent mitochondrial apoptosis in human leukemic cells.

Chem Res Toxicol 2012 Apr 22;25(4):931-9. Epub 2012 Mar 22.

Institute of Medical and Clinical Biochemistry, Faculty of Medicine, University of Belgrade, Belgrade, Serbia.

We investigated the cytotoxicity of recently synthesized (S,S)-ethylendiamine-N,N'-di-2-(3-cyclohexyl)propanoic acid esters toward human leukemic cell lines and healthy blood mononuclear cells. Cell viability was assessed by acid phosphatase assay, apoptosis, and differentiation were analyzed by flow cytometry and electron microscopy, while intracellular localization of apoptosis-inducing factor (AIF) was determined by immunoblotting. It was demonstrated that methyl, ethyl, and n-propyl esters were toxic to HL-60, REH, MOLT-4, KG-1, JVM-2, and K-562 leukemic cell lines, while the nonesterified parental compound and n-butyl ester were devoid of cytotoxic action. The ethyl ester exhibited the highest cytotoxic activity (IC₅₀ 10.7 μM-45.4 μM), which was comparable to that of the prototypical anticancer drug cisplatin. The observed cytotoxic effect in HL-60 cells was associated with an increase in superoxide production and mitochondrial membrane depolarization, leading to apoptotic cell death characterized by phosphatidylserine externalization and DNA fragmentation in the absence of autophagic response. DNA fragmentation preceded caspase activation and followed AIF translocation from mitochondria to nucleus, which was indicative of caspase-independent apoptotic cell death. HL-60 cells treated with subtoxic concentration of the compound displayed morphological signs of granulocytic differentiation (nuclear indentations and presence of cytoplasmic primary granules), as well as an increased expression of differentiation markers CD11b and CD15. The cyclohexyl analogues of ethylenediamine dipropanoic acid were also toxic to peripheral blood mononuclear cells of both healthy controls and leukemic patients, the latter being more sensitive. Our data demonstrate that the toxicity of the investigated cyclohexyl compounds against leukemic cell lines is mediated by caspase-independent apoptosis associated with oxidative stress, mitochondrial dysfunction, and AIF translocation.
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http://dx.doi.org/10.1021/tx3000329DOI Listing
April 2012

Arylpiperazine dopamineric ligands protect neuroblastoma cells from nitric oxide (NO)-induced mitochondrial damage and apoptosis.

ChemMedChem 2012 Mar 1;7(3):495-508. Epub 2012 Feb 1.

Institute for Biological Research, University of Belgrade, Despot Stefan Blvd 142, 11000 Belgrade, Serbia.

The protective ability of novel arylpiperazine-based dopaminergic ligands against nitric oxide (NO)-mediated neurotoxicity is investigated. The most potent neuroprotective arylpiperazine identified during the study was N-{4-[2-(4-phenyl-piperazin-1-yl)ethyl]-phenyl}picolinamide, which protected SH-SY5Y human neuron-like cells from the proapoptotic effect of NO donor sodium nitroprusside (SNP) by decreasing oxidative stress, mitochondrial membrane depolarization, caspase activation and subsequent phosphatydilserine externalization/DNA fragmentation. The protective effect was associated with the inhibition of proapoptotic (JNK, ERK, AMPK) and activation of antiapoptotic (Akt) signaling pathways, in the absence of interference with intracellular NO accumulation. The neuroprotective action of arylpiperazines was shown to be independent of dopamine receptor binding, as it was not affected by the high-affinity D₁/D₂ receptor blocker butaclamol. These results reported support the further study of arylpiperazines as potential neuroprotective agents.
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http://dx.doi.org/10.1002/cmdc.201100537DOI Listing
March 2012

Anti-inflammatory, gastroprotective, and cytotoxic effects of Sideritis scardica extracts.

Planta Med 2012 Mar 24;78(5):415-27. Epub 2012 Jan 24.

Institute for Medicinal Plant Research "Dr Josif Pančić", Belgrade, Serbia.

Sideritis scardica Griseb. (ironwort, mountain tea), an endemic plant of the Balkan Peninsula, has been used in traditional medicine in the treatment of gastrointestinal complaints, inflammation, and rheumatic disorders. This study aimed to evaluate its gastroprotective and anti-inflammatory activities. Besides, continuously increasing interest in assessing the role of the plant active constituents preventing the risk of cancer was a reason to make a detailed examination of the investigated ethanol, diethyl ether, ethyl acetate, and N-butanol extracts regarding cytotoxicity. Oral administration of the investigated extracts caused a dose-dependent anti-inflammatory effect in a model of carrageenan-induced rat paw edema. Gastroprotective activity of the extracts was investigated using an ethanol-induced acute stress ulcer in rats. The cytotoxic activity of plant extracts was assessed on PBMC, B16, and HL-60 cells and compared to the cytotoxicity of phenolic compounds identified in extracts. Apoptotic and necrotic cell death were analyzed by double staining with fluoresceinisothiocyanate (FITC)-conjugated annexin V and PI. The developed HPLC method enabled qualitative fingerprint analysis of phenolic compounds in the investigated extracts. Compared to the effect of the positive control, the anti-inflammatory drug indomethacine (4 mg/kg), which produced a 50 % decrease in inflammation, diethyl ether and N-butanol extracts exhibited about the same effect in doses of 200 and 100 mg/kg (53.6 and 48.7 %; 48.4 and 49.9 %, respectively). All investigated extracts produced dose-dependent gastroprotective activity with the efficacy comparable to that of the reference drug ranitidine. The diethyl ether extract showed significant dose-dependent cytotoxicity on B16 cells and HL-60 cells, decreasing cell growth to 51.3 % and 77.5 % of control, respectively, when used at 100 µg/mL. It seems that phenolic compounds (apigenin, luteolin, and their corresponding glycosides) are responsible for the diethyl ether extract cytotoxic effect. It also appears that induction of oxidative stress might be involved in its cytotoxicity, since B16 and HL-60 cells increased their ROS production in response to treatment with diethyl ether extract. Neither of the tested extracts nor any phenolic compounds showed significant cytotoxic effect to human PBMC. These results demonstrated the potent anti-inflammatory and gastroprotective activities, as well as the promising cytotoxicity.
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http://dx.doi.org/10.1055/s-0031-1298172DOI Listing
March 2012
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