Publications by authors named "Homira Behbahani"

30 Publications

  • Page 1 of 1

Insulin-Independent and Dependent Glucose Transporters in Brain Mural Cells in CADASIL.

Front Genet 2020 15;11:1022. Epub 2020 Sep 15.

Department of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Karolinska Institutet, Stockholm, Sweden.

Typical cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by mutations in the human NOTCH3 gene. Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy is characterized by subcortical ischemic strokes due to severe arteriopathy and fibrotic thickening of small vessels. Blood regulating vascular smooth muscle cells (VSMCs) appear as the key target in CADASIL but the pathogenic mechanisms remain unclear. With the hypothesis that brain glucose metabolism is disrupted in VSMCs in CADASIL, we investigated post-mortem tissues and VSMCs derived from CADASIL patients to explore gene expression and protein immunoreactivity of glucose transporters (GLUTs), particularly GLUT4 and GLUT2 using quantitative RT-PCR and immunohistochemical techniques. cell model analysis indicated that both GLUT4 and -2 gene expression levels were down-regulated in VSMCs derived from CADASIL patients, compared to controls. studies further indicated that the down regulation of GLUT4 coincided with impaired glucose uptake in VSMCs, which could be partially rescued by insulin treatment. Our observations on reduction in GLUTs in VSMCs are consistent with previous findings of decreased cerebral blood flow and glucose uptake in CADASIL patients. That impaired ability of glucose uptake is rescued by insulin is also consistent with previously reported lower proliferation rates of VSMCs derived from CADASIL subjects. Overall, these observations are consistent with the development of severe cerebral arteriopathy in CADASIL, in which VSMCs are replaced by widespread fibrosis.
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http://dx.doi.org/10.3389/fgene.2020.01022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7522350PMC
September 2020

Erythrocyte Amyloid Beta Peptide Isoform Distributions in Alzheimer and Mild Cognitive Impairment.

Curr Alzheimer Res 2019 ;16(11):1050-1054

Department of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Karolinska Institutet, Solna, Sweden.

Introduction: We recently showed that Amyloid Beta (Aβ)40 accumulates in erythrocytes and possibly causes cell damage as evidenced by an increased number of assumed injured low-density (kg/L) erythrocytes. Furthermore, we have suggested a separation technique to isolate and concentrate such damaged red blood cells for subsequent analysis.

Objectives: We isolated high- and low-density erythrocytes and investigated the accumulation patterns of the Aβ peptides (Aβ40, Aβ42, and Aβ43) in Alzheimer (AD), mild cognitive impairment (MCI), and Subjective Cognitive Impairment (SCI).

Methods: Whole blood was fractionated through a density gradient, resulting in two concentrated highand presumed injured low-density erythrocyte fractions. After cell lysis, intracellular Aβ40, Aβ42, and Aβ43 were quantified by ELISA.

Results: In both high- and low-density erythrocytes, Aβ40 displayed the lowest concentration in MCI, while it was equal and higher in AD and SCI. Aβ40 was detected at a 10-fold higher level than Aβ42, and in injured low-density erythrocytes, the lowest quantity of Aβ42 was found in AD and MCI. Aβ40 exhibited a 100-fold greater amount than Aβ43, and lighter erythrocytes of MCI subjects displayed less intracellular Aβ43 than SCI.

Conclusion: Red blood cell accumulation patterns of Aβ40, Aβ42, and Aβ43 differ significantly between AD, MCI, and SCI. The data must be verified through larger clinical trials. It is, however, tenable that Aβ peptide distributions in erythrocyte subpopulations have the potential to be used for diagnostic purposes.
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http://dx.doi.org/10.2174/1567205016666191010104355DOI Listing
October 2020

Alzheimer's Disease: Erythrocyte 2,3-diphosphoglycerate Content and Circulating Erythropoietin.

Curr Alzheimer Res 2019 ;16(9):834-835

Department of Neurobiology, Care Sciences, and Society, Center for Alzheimer Research, Division of Clinical Geriatrics, Karolinska Institutet, Solna, Sweden.

Background: Alzheimer's Disease (AD) features the accumulation of β-amyloid in erythrocytes. The subsequent red cell damage may well affect their oxygen-carrying capabilities. 2,3- diphosphoglycerate (2,3-DPG) binds to the hemoglobin thereby promoting oxygen release. It is theorized that 2,3-DPG is reduced in AD and that the resulting hypoxia triggers erythropoietin (EPO) release.

Methods & Objective: To explore this theory, we analyzed red cell 2,3-DPG content and EPO in AD, mild cognitive impairment, and the control group, subjective cognitive impairment.

Results: We studied (i) 2,3-DPG in red cells, and (ii) circulating EPO in AD, and both markers were unaffected by dementia. Disturbances of these oxygen-regulatory pathways do not appear to participate in brain hypoxia in AD.
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http://dx.doi.org/10.2174/1567205016666190827120108DOI Listing
September 2020

Innovative Therapy for Alzheimer's Disease-With Focus on Biodelivery of NGF.

Front Neurosci 2019 5;13:38. Epub 2019 Feb 5.

Division of Clinical Geriatrics, Center for Alzheimer Research, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Huddinge, Sweden.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with abnormal protein modification, inflammation and memory impairment. Aggregated amyloid beta (Aβ) and phosphorylated tau proteins are medical diagnostic features. Loss of memory in AD has been associated with central cholinergic dysfunction in basal forebrain, from where the cholinergic circuitry projects to cerebral cortex and hippocampus. Various reports link AD progression with declining activity of cholinergic neurons in basal forebrain. The neurotrophic molecule, nerve growth factor (NGF), plays a major role in the maintenance of cholinergic neurons integrity and function, both during development and adulthood. Numerous studies have also shown that NGF contributes to the survival and regeneration of neurons during aging and in age-related diseases such as AD. Changes in neurotrophic signaling pathways are involved in the aging process and contribute to cholinergic and cognitive decline as observed in AD. Further, gradual dysregulation of neurotrophic factors like NGF and brain derived neurotrophic factor (BDNF) have been reported during AD development thus intensifying further research in targeting these factors as disease modifying therapies against AD. Today, there is no cure available for AD and the effects of the symptomatic treatment like cholinesterase inhibitors (ChEIs) and memantine are transient and moderate. Although many AD treatment studies are being carried out, there has not been any breakthrough and new therapies are thus highly needed. Long-term effective therapy for alleviating cognitive impairment is a major unmet need. Discussion and summarizing the new advancements of using NGF as a potential therapeutic implication in AD are important. In summary, the intent of this review is describing available experimental and clinical data related to AD therapy, priming to gain additional facts associated with the importance of NGF for AD treatment, and encapsulated cell biodelivery (ECB) as an efficient tool for NGF delivery.
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http://dx.doi.org/10.3389/fnins.2019.00038DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370742PMC
February 2019

Autophagy-lysosomal defect in human CADASIL vascular smooth muscle cells.

Eur J Cell Biol 2018 Nov 22;97(8):557-567. Epub 2018 Oct 22.

Division of Neurogeriatrics, Center for Alzheimer Research, Department of Neurobiology, Care Sciences and Society, Huddinge, Sweden. Electronic address:

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a familial progressive degenerative disorder and is caused by mutations in NOTCH3 gene. Previous study reported that mutant NOTCH3 is more prone to form aggregates than wild-type NOTCH3 and the mutant aggregates are resistant to degradation. We hypothesized that aggregation or accumulation of NOTCH3 could be due to impaired lysosomal-autophagy machinery in VSMC. Here, we investigated the possible cause of accumulation/aggregation of NOTCH3 in CADASIL using cerebral VSMCs derived from control and CADASIL patients carrying NOTCH3 mutation. Thioflavin-S-staining confirmed the increased accumulation of aggregated NOTCH3 in VSMC compared to VSMC. Increased levels of the lysosomal marker, Lamp2, were detected in VSMC, which also showed co-localization with NOTCH3 using double-immunohistochemistry. Increased level of LC3-II/LC3-I ratio was observed in VSMC suggesting an accumulation of autophagosomes. This was coupled with the decreased co-localization of NOTCH3 with LC3, and Lamp2 and, further, increase of p62/SQSTM1 levels in VSMC compared to the VSMC. In addition, Western blot analysis indicated phosphorylation of p-ERK, p-S6RP, and p-P70 S6K. Altogether, these results suggested a dysfunction in the autophagy-lysosomal pathway in VSMC. The present study provides an interesting avenue of the research investigating the molecular mechanism of CADASIL.
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http://dx.doi.org/10.1016/j.ejcb.2018.10.001DOI Listing
November 2018

Increased Active OMI/HTRA2 Serine Protease Displays a Positive Correlation with Cholinergic Alterations in the Alzheimer's Disease Brain.

Mol Neurobiol 2019 Jul 25;56(7):4601-4619. Epub 2018 Oct 25.

Division of Neurogeriatrics, Center for Alzheimer Research, NVS Department, Karolinska Institutet, 141 83, Huddinge, Sweden.

OMI/HTRA2 (high-temperature requirement serine protease A2) is a mitochondrial serine protease involved in several cellular processes, including autophagy, chaperone activity, and apoptosis. Few studies on the role of OMI/HTRA2 in Alzheimer's disease (AD) are available, but none on its relationship with the cholinergic system and neurotrophic factors as well as other AD-related proteins. In this study, immunohistochemical analyses revealed that AD patients had a higher cytosolic distribution of OMI/HTRA2 protein compared to controls. Quantitative analyses on brain extracts indicated a significant increase in the active form of OMI/HTRA2 in the AD brain. Activated OMI/HTRA2 protein positively correlated with stress-associated read-through acetylcholinesterase activity. In addition, α7 nicotinic acetylcholine receptor gene expression, a receptor also known to be localized on the outer membrane of mitochondria, showed a strong correlation with OMI/HTRA2 gene expression in three different brain regions. Interestingly, the activated OMI/HTRA2 levels also correlated with the activity of the acetylcholine-biosynthesizing enzyme, choline acetyltransferase (ChAT); with levels of the neurotrophic factors, NGF and BDNF; with levels of the soluble fragments of amyloid precursor protein (APP); and with gene expression of the microtubule-associated protein tau in the examined brain regions. Overall, the results demonstrate increased levels of the mitochondrial serine protease OMI/HTRA2, and a coherent pattern of association between the activated form of OMI/HTRA2 and several key proteins involved in AD pathology. In this paper, we propose a new hypothetical model to highlight the importance and needs of further investigation on the role of OMI/HTRA2 in the mitochondrial function and AD.
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http://dx.doi.org/10.1007/s12035-018-1383-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6657433PMC
July 2019

Cerebrospinal fluid from Alzheimer patients affects cell-mediated nerve growth factor production and cell survival in vitro.

Exp Cell Res 2018 10 6;371(1):175-184. Epub 2018 Aug 6.

Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Stockholm, Sweden. Electronic address:

Alzheimer's disease (AD) is characterized by early degeneration of cholinergic neurons and decreased levels of nerve growth factor (NGF). Thus, increasing the NGF levels by for instance encapsulated cell bio-delivery (ECB) is a potential treatment strategy. The results from our previous first-in-human studies on ECB of NGF to the basal forebrain cholinergic neurons were promising, but indicated some variability of long-term viability of the encapsulated cells and associated reduced NGF-release. Here we studied the effect of amyloid beta-peptides (Aβ), interleukin 1-beta (IL-1β), and CSF from AD, Lewy body dementia (LBD) or subjective cognitive impairment (SCI) patients on the NGF overproducing cell line NGC-0295. At physiological concentrations, neither Aβ nor Aβ had any major impact on cell viability or NGF-production. In contrast, IL-1β dose-dependently affected NGF-production over time. Exposure of NGF-producing cells to CSF from AD patients showed significantly reduced NGF-release as compared to CSF from LBD or SCI patients. By mass spectrometry we found 3 proteins involved in inflammatory pathways to have an altered expression in AD CSF compared to LBD and SCI. Cell survival and NGF-release were not affected by Aβ. NGF-release was affected by IL-1β, suggesting that inflammation has a negative effect on ECB cells.
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http://dx.doi.org/10.1016/j.yexcr.2018.08.007DOI Listing
October 2018

Differences in proliferation rate between CADASIL and control vascular smooth muscle cells are related to increased TGFβ expression.

J Cell Mol Med 2018 06 13;22(6):3016-3024. Epub 2018 Mar 13.

Karolinska Institute, Department of Neurobiology, Care Sciences and Society, Division of Neurogeriatrics, Center for Alzheimer Research, Huddinge, Sweden.

Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a familial fatal progressive degenerative disorder. One of the pathological hallmarks of CADASIL is a dramatic reduction of vascular smooth muscle cells (VSMCs) in cerebral arteries. Using VSMCs from the vasculature of the human umbilical cord, placenta and cerebrum of CADASIL patients, we found that CADASIL VSMCs had a lower proliferation rate compared to control VSMCs. Exposure of control VSMCs and endothelial cells (ECs) to media derived from CADASIL VSMCs lowered the proliferation rate of all cells examined. By quantitative RT-PCR analysis, we observed increased Transforming growth factor-β (TGFβ) gene expression in CADASIL VSMCs. Adding TGFβ-neutralizing antibody restored the proliferation rate of CADASIL VSMCs. We assessed proliferation differences in the presence or absence of TGFβ-neutralizing antibody in ECs co-cultured with VSMCs. ECs co-cultured with CADASIL VSMCs exhibited a lower proliferation rate than those co-cultured with control VSMCs, and neutralization of TGFβ normalized the proliferation rate of ECs co-cultured with CADASIL VSMCs. We suggest that increased TGFβ expression in CADASIL VSMCs is involved in the reduced VSMC proliferation in CADASIL and may play a role in situ in altered proliferation of neighbouring cells in the vasculature.
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http://dx.doi.org/10.1111/jcmm.13534DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5980144PMC
June 2018

Association of Platelet Serotonin Levels in Alzheimer's Disease with Clinical and Cerebrospinal Fluid Markers.

J Alzheimers Dis 2016 05;53(2):621-30

Department of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division for Neurogeriatrics, Karolinska Institutet, Novum, Huddinge, Stockholm, Sweden.

Introduction: Serotonin (5-HT) is involved in the pathology of Alzheimer's disease (AD).

Objective: We aimed to measure 5-HT level in platelets in AD and explore its association with cerebrospinal fluid (CSF), AD biomarkers (amyloid-β 1-42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau)), and clinical symptoms.

Methods: 15 patients with AD and 20 patients with subjective cognitive impairment (SCI) were included. 5-HT metabolites were measured, in a specific fraction, using high performance liquid chromatography with electrochemical detection (HPLC-ECD).

Results: Significantly lower 5-HT concentrations were observed in AD patients compared to SCI patients both after normalization against total protein (p = 0.008) or platelet count (p = 0.019). SCI patients with lower 5-HT level have higher AD CSF biomarkers, total tau (p = 0.026) and tau/Aβ42 ratio (p = 0.001), compared to those with high 5-HT levels.

Conclusion: AD patients have reduced platelet 5-HT levels. In SCI, lower 5-HT content was associated with a higher AD-CSF biomarker burden.
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http://dx.doi.org/10.3233/JAD-160022DOI Listing
May 2016

Perforin Promotes Amyloid Beta Internalisation in Neurons.

Mol Neurobiol 2017 03 16;54(2):874-887. Epub 2016 Jan 16.

Division for Neurogeriatrics, Department of Neurobiology, Care Sciences and Society (NVS), Center for Alzheimer Research, Karolinska Institutet, Novum 5th floor, Huddinge, 141 57, Sweden.

Studies on the mechanisms of neuronal amyloid-β (Aβ) internalisation are crucial for understanding the neuropathological progression of Alzheimer's disease (AD). We here investigated how extracellular Aβ peptides are internalised and focused on three different pathways: (i) via endocytic mechanisms, (ii) via the receptor for advanced glycation end products (RAGE) and (iii) via the pore-forming protein perforin. Both Aβ and Aβ were internalised in retinoic acid differentiated neuroblastoma (RA-SH-SY5Y) cells. A higher concentration was required for Aβ (250 nM) compared with Aβ (100 nM). The internalised Aβ showed a dot-like pattern of distribution whereas Aβ accumulated in larger and distinct formations. By confocal microscopy, we showed that Aβ and Aβ co-localised with mitochondria, endoplasmic reticulum (ER) and lysosomes. Aβ treatment of human primary cortical neurons (hPCN) confirmed our findings in RA-SH-SY5Y cells, but hPCN were less sensitive to Aβ; therefore, a 20 (Aβ) and 50 (Aβ) times higher concentration was needed for inducing uptake. The blocking of endocytosis completely inhibited the internalisation of Aβ peptides in RA-SH-SY5Y cells and hPCN, indicating that this is a major pathway by which Aβ enters the cells. In addition, the internalisation of Aβ, but not Aβ, was reduced by 55 % by blocking RAGE. Finally, for the first time we showed that pore formation in cell membranes by perforin led to Aβ internalisation in hPCN. Understanding how Aβ is internalised sheds light on the pathological role of Aβ and provides further ideas of inhibitory strategies for preventing Aβ internalisation and the spreading of neurodegeneration in AD.
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http://dx.doi.org/10.1007/s12035-016-9685-9DOI Listing
March 2017

Mitochondrial dysfunction in a transgenic mouse model expressing human amyloid precursor protein (APP) with the Arctic mutation.

J Neurochem 2016 Feb 19;136(3):497-502. Epub 2015 Nov 19.

Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Huddinge, Sweden.

Accumulation of amyloid β-peptide (Aβ) in the brain is an important event in the pathogenesis of Alzheimer disease. We have used a transgenic mouse model expressing human amyloid precursor protein (APP) with the Arctic mutation to investigate whether Aβ deposition is correlated with mitochondrial functions in these animals. We found evidence of mitochondrial dysfunction (i.e., decreased mitochondrial membrane potential, increased production of reactive oxygen species and oxidative DNA damage) at 6 months of age, when the mice showed very mild Aβ deposition. More pronounced mitochondrial abnormalities were present in 24-month-old TgAPParc mice with more extensive Aβ pathology. This study demonstrates for the first time mitochondrial dysfunction in transgenic mice with a mutation within the Aβ peptide (the Arctic APP mutation), and confirms previous studies suggesting that mitochondrial dysfunction and oxidative stress is an early event in the pathogenesis of Alzheimer disease. This study demonstrates mitochondrial dysfunction in transgenic mice with a mutation within the amyloid beta (Aβ) peptide (the Arctic amyloid precursor protein (APP) mutation). We found evidence of mitochondrial dysfunction (i.e. decreased mitochondrial membrane potential (MMP), increased production of reactive oxygen species (ROS) and oxidative DNA damage) at 6 months of age, when very mild Aβ deposition is present in the mice. Also, the cytochrome c (COX) activity was significantly decreased in mitochondria from transgenic mice at 24 months of age.
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http://dx.doi.org/10.1111/jnc.13410DOI Listing
February 2016

Stress Conditions Increase Vimentin Cleavage by Omi/HtrA2 Protease in Human Primary Neurons and Differentiated Neuroblastoma Cells.

Mol Neurobiol 2015 Dec 8;52(3):1077-1092. Epub 2014 Oct 8.

Karolinska Institutet, Department of Neurobiology, Care Sciences and Society (NVS), Center for Alzheimer Research, Division for Neurogeriatrics, Novum 5th floor, SE-141 57, Huddinge, Sweden.

Dysfunctional Omi/HtrA2, a mitochondrial serine protease, has been implicated in various neurodegenerative disorders. Despite the wealth of evidence on the roles of Omi/HtrA2 in apoptosis, little is known about its cytosolic targets, the cleavage of which could account for the observed morphological changes such as cytoskeletal reorganizations in axons. By proteomic analysis, vimentin was identified as a substrate for Omi/HtrA2 and we have reported increased Omi/HtrA2 protease activity in Alzheimer disease (AD) brain. Here, we investigated a possible link between Omi/HtrA2 and vimentin cleavage, and consequence of this cleavage on mitochondrial distribution in neurons. In vitro protease assays showed vimentin to be cleaved by Omi/HtrA2 protease, and proximity ligation assay demonstrated an increased interaction between Omi/HtrA2 and vimentin in human primary neurons upon stress stimuli. Using differentiated neuroblastoma SH-SY5Y cells, we showed that Omi/HtrA2 under several different stress conditions induces cleavage of vimentin in wild-type as well as SH-SY5Y cells transfected with amyloid precursor protein with the Alzheimer disease-associated Swedish mutation. After stress treatment, inhibition of Omi/HtrA2 protease activity by the Omi/HtrA2 specific inhibitor, Ucf-101, reduced the cleavage of vimentin in wild-type cells. Following altered vimentin filaments integrity by stress stimuli, mitochondria was redistributed in differentiated SH-SY5Y cells and human primary neurons. In summary, the findings outlined in this paper suggest a role of Omi/HtrA2 in modulation of vimentin filamentous structure in neurons. Our results provide important findings for understanding the biological role of Omi/HtrA2 activity during stress conditions, and give knowledge of interplay between Omi/HtrA2 and vimentin which might affect mitochondrial distribution in neurons.
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http://dx.doi.org/10.1007/s12035-014-8906-3DOI Listing
December 2015

Regulated Extracellular Choline Acetyltransferase Activity- The Plausible Missing Link of the Distant Action of Acetylcholine in the Cholinergic Anti-Inflammatory Pathway.

PLoS One 2013 19;8(6):e65936. Epub 2013 Jun 19.

Division of Alzheimer Neurobiology Center, Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, Huddinge, Stockholm, Sweden.

Acetylcholine (ACh), the classical neurotransmitter, also affects a variety of nonexcitable cells, such as endothelia, microglia, astrocytes and lymphocytes in both the nervous system and secondary lymphoid organs. Most of these cells are very distant from cholinergic synapses. The action of ACh on these distant cells is unlikely to occur through diffusion, given that ACh is very short-lived in the presence of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), two extremely efficient ACh-degrading enzymes abundantly present in extracellular fluids. In this study, we show compelling evidence for presence of a high concentration and activity of the ACh-synthesizing enzyme, choline-acetyltransferase (ChAT) in human cerebrospinal fluid (CSF) and plasma. We show that ChAT levels are physiologically balanced to the levels of its counteracting enzymes, AChE and BuChE in the human plasma and CSF. Equilibrium analyses show that soluble ChAT maintains a steady-state ACh level in the presence of physiological levels of fully active ACh-degrading enzymes. We show that ChAT is secreted by cultured human-brain astrocytes, and that activated spleen lymphocytes release ChAT itself rather than ACh. We further report differential CSF levels of ChAT in relation to Alzheimer's disease risk genotypes, as well as in patients with multiple sclerosis, a chronic neuroinflammatory disease, compared to controls. Interestingly, soluble CSF ChAT levels show strong correlation with soluble complement factor levels, supporting a role in inflammatory regulation. This study provides a plausible explanation for the long-distance action of ACh through continuous renewal of ACh in extracellular fluids by the soluble ChAT and thereby maintenance of steady-state equilibrium between hydrolysis and synthesis of this ubiquitous cholinergic signal substance in the brain and peripheral compartments. These findings may have important implications for the role of cholinergic signaling in states of inflammation in general and in neurodegenerative disease, such as Alzheimer's disease and multiple sclerosis in particular.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0065936PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3686815PMC
October 2017

Modulation of the endoplasmic reticulum-mitochondria interface in Alzheimer's disease and related models.

Proc Natl Acad Sci U S A 2013 May 25;110(19):7916-21. Epub 2013 Apr 25.

Department of Neurobiology, Care Sciences and Society, Karolinska Institutet-Alzheimer's Disease Research Center, Karolinska Institutet, 141 86 Stockholm, Sweden.

It is well-established that subcompartments of endoplasmic reticulum (ER) are in physical contact with the mitochondria. These lipid raft-like regions of ER are referred to as mitochondria-associated ER membranes (MAMs), and they play an important role in, for example, lipid synthesis, calcium homeostasis, and apoptotic signaling. Perturbation of MAM function has previously been suggested in Alzheimer's disease (AD) as shown in fibroblasts from AD patients and a neuroblastoma cell line containing familial presenilin-2 AD mutation. The effect of AD pathogenesis on the ER-mitochondria interplay in the brain has so far remained unknown. Here, we studied ER-mitochondria contacts in human AD brain and related AD mouse and neuronal cell models. We found uniform distribution of MAM in neurons. Phosphofurin acidic cluster sorting protein-2 and σ1 receptor, two MAM-associated proteins, were shown to be essential for neuronal survival, because siRNA knockdown resulted in degeneration. Up-regulated MAM-associated proteins were found in the AD brain and amyloid precursor protein (APP)Swe/Lon mouse model, in which up-regulation was observed before the appearance of plaques. By studying an ER-mitochondria bridging complex, inositol-1,4,5-triphosphate receptor-voltage-dependent anion channel, we revealed that nanomolar concentrations of amyloid β-peptide increased inositol-1,4,5-triphosphate receptor and voltage-dependent anion channel protein expression and elevated the number of ER-mitochondria contact points and mitochondrial calcium concentrations. Our data suggest an important role of ER-mitochondria contacts and cross-talk in AD pathology.
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http://dx.doi.org/10.1073/pnas.1300677110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3651455PMC
May 2013

Experimental studies of mitochondrial function in CADASIL vascular smooth muscle cells.

Exp Cell Res 2013 Feb 1;319(3):134-43. Epub 2012 Oct 1.

Division of Clinical Geriatrics, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden.

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) is a familiar fatal progressive degenerative disorder characterized by cognitive decline, and recurrent stroke in young adults. Pathological features include a dramatic reduction of brain vascular smooth muscle cells and severe arteriopathy with the presence of granular osmophilic material in the arterial walls. Here we have investigated the cellular and mitochondrial function in vascular smooth muscle cell lines (VSMCs) established from CADASIL mutation carriers (R133C) and healthy controls. We found significantly lower proliferation rates in CADASIL VSMC as compared to VSMC from controls. Cultured CADASIL VSMCs were not more vulnerable than control cells to a number of toxic substances. Morphological studies showed reduced mitochondrial connectivity and increased number of mitochondria in CADASIL VSMCs. Transmission electron microscopy analysis demonstrated increased irregular and abnormal mitochondria in CADASIL VSMCs. Measurements of mitochondrial membrane potential (Δψ(m)) showed a lower percentage of fully functional mitochondria in CADASIL VSMCs. For a number of genes previously reported to be changed in CADASIL VSMCs, immunoblotting analysis demonstrated a significantly reduced SOD1 expression. These findings suggest that alteration of proliferation and mitochondrial function in CADASIL VSMCs might have an effect on vital cellular functions important for CADASIL pathology.
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http://dx.doi.org/10.1016/j.yexcr.2012.09.015DOI Listing
February 2013

Erlin-2 is associated with active γ-secretase in brain and affects amyloid β-peptide production.

Biochem Biophys Res Commun 2012 Aug 4;424(3):476-81. Epub 2012 Jul 4.

Karolinska Institutet Dainippon Sumitomo Pharma Alzheimer Center, KI-Alzheimer Disease Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Novum, Stockholm SE-141 86, Sweden.

The transmembrane protease complex γ-secretase is responsible for the generation of the neurotoxic amyloid β-peptide (Aβ) from its precursor (APP). Aβ has a causative role in Alzheimer disease, and thus, γ-secretase is a therapeutic target. However, since there are more than 70 γ-secretase substrates besides APP, selective inhibition of APP processing is required. Recent data indicates the existence of several γ-secretase associated proteins (GSAPs) that affect the selection and processing of substrates. Here, we use a γ-secretase inhibitor for affinity purification of γ-secretase and associated proteins from microsomes and detergent resistant membranes (DRMs) prepared from rat or human brain. By tandem mass spectrometry we identified a novel brain GSAP; erlin-2. This protein was recently reported to reside in DRMs in the ER. A proximity ligation assay, as well as co-immunoprecipitation, confirmed the association of erlin-2 with γ-secretase. We found that a higher proportion of erlin-2 was associated with γ-secretase in DRMs than in soluble membranes. siRNA experiments indicated that reduced levels of erlin-2 resulted in a decreased Aβ production, whereas the effect on Notch processing was limited. In summary, we have found a novel brain GSAP, erlin-2, that resides in DRMs and affects Aβ production.
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http://dx.doi.org/10.1016/j.bbrc.2012.06.137DOI Listing
August 2012

Amyloid precursor protein accumulates in aggresomes in response to proteasome inhibitor.

Neurochem Int 2012 Apr 15;60(5):533-42. Epub 2012 Feb 15.

Department of Physiology, The Wenner-Gren Institute Arrhenius Laboratories F3, Stockholm University, Stockholm, Sweden.

Aggresomes are cytoplasmic inclusions which are localized at the microtubule organizing center (MTOC) as a result of induced proteasome inhibition, stress or over-expression of certain proteins. Aggresomes are linked to the pathogenesis of many neurodegenerative diseases. Here we studied whether amyloid precursor protein (APP), a type-I transmembrane glycoprotein, is localized in aggresomes after exposure to stress condition. Using confocal microscopy we found that APP is located in aggresomes and co-localized with vimentin, γ-tubulin, 20S and ubiquitin at the MTOC in response to proteasome dysfunction. An interaction between vimentin and APP was found after proteasome inhibition suggesting that APP is an additional protein constituent of aggresomes. Suppression of the proteasome system in APP-HEK293 cells overexpressing APP or transfected with APP Swedish mutation caused an accumulation of stable, detergent-insoluble forms of APP containing poly-ubiquitinated proteins. In addition, brain homogenates from transgenic mice expressing human APP with the Arctic mutation demonstrated an interaction between APP and the aggresomal-marker vimentin. These data suggest that malfunctioning of the proteasome system caused by mutation or overexpression of pathological or non-pathological proteins may lead to the accumulation of stable aggresomes, perhaps contributing to the neurodegeneration.
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http://dx.doi.org/10.1016/j.neuint.2012.02.012DOI Listing
April 2012

Altered enzymatic activity and allele frequency of OMI/HTRA2 in Alzheimer's disease.

FASEB J 2011 Apr 16;25(4):1345-52. Epub 2010 Dec 16.

Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.

The serine-protease OMI/HTRA2, required for several cellular processes, including mitochondrial function, autophagy, chaperone activity, and apoptosis, has been implicated in the pathogenesis of both Alzheimer's disease (AD) and Parkinson's disease (PD). Western blot quantification of OMI/HTRA2 in frontal cortex of patients with AD (n=10) and control subjects (n=10) in two separate materials indicated reduced processed (active, 35 kDa) OMI/HTRA2 levels, whereas unprocessed (50 kDa) enzyme levels were not significantly different between the groups. Interestingly, the specific protease activity of OMI/HTRA2 was found to be significantly increased in patients with AD (n=10) compared to matched control subjects (n=10) in frontal cortex in two separate materials. Comparison of OMI/HTRA2 mRNA levels in frontal cortex and hippocampus, two brain areas particularly affected by AD, indicated similar levels in patients with AD (n=10) and matched control subjects (n=10). In addition, we analyzed the occurrence of the OMI/HTRA2 variants A141S and G399S in Swedish case-control materials for AD and PD and found a weak association of A141S with AD, but not with PD. In conclusion, our genetic, histological, and biochemical findings give further support to an involvement of OMI/HTRA2 in the pathology of AD; however, further studies are needed to clarify the role of this gene in neurodegeneration.
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http://dx.doi.org/10.1096/fj.10-163402DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3228343PMC
April 2011

Mitochondrial γ-secretase participates in the metabolism of mitochondria-associated amyloid precursor protein.

FASEB J 2011 Jan 10;25(1):78-88. Epub 2010 Sep 10.

Karolinska Institutet and Dainippon Sumitomo Pharma Alzheimer Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Huddinge, Sweden.

Intracellular amyloid-β peptide (Aβ) has been implicated in the pathogenesis of Alzheimer's disease (AD). Mitochondria were found to be the target both for amyloid precursor protein (APP) that accumulates in the mitochondrial import channels and for Aβ that interacts with several proteins inside mitochondria and leads to mitochondrial dysfunction. Here, we have studied the role of mitochondrial γ-secretase in processing different substrates. We found that a significant proportion of APP is associated with mitochondria in cultured cells and that γ-secretase cleaves the shedded C-terminal part of APP identified as C83 associated with the outer membrane of mitochondria (OMM). Moreover, we have established the topology of the C83 in the OMM and found the APP intracellular domain (AICD) to be located inside mitochondria. Our data show for the first time that APP is a substrate for the mitochondrial γ-secretase and that AICD is produced inside mitochondria. Thus, we provide a mechanistic view of the mitochondria-associated APP metabolism where AICD, P3 peptide and potentially Aβ are produced locally and may contribute to mitochondrial dysfunction in AD.
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http://dx.doi.org/10.1096/fj.10-157230DOI Listing
January 2011

Association of Omi/HtrA2 with γ-secretase in mitochondria.

Neurochem Int 2010 Nov 10;57(6):668-75. Epub 2010 Aug 10.

Karolinska Institutet and Dainippon Sumitomo Pharma Alzheimer Center (KASPAC), Department of Neurobiology, Care Sciences and Society (NVS), Karolinska Institutet, Huddinge, Sweden.

Omi/HtrA2, a mitochondrial serine protease with chaperone activity, is involved in varied intracellular processes. Dysfunctional Omi/HtrA2 has thus been implicated in various neurodegenerative disorders. Previously, we have shown that γ-secretase complexes are present and active in mitochondria. Here, we demonstrate that peptide corresponding to C-terminus of presenilin-1, as previously reported to activate Omi/HtrA2, interacts with Omi/HtrA2 in isolated mitochondria. Moreover, we show that Omi/HtrA2 interacts with presenilin in active γ-secretase complexes located to mitochondria. Using a biotinylated γ-secretase inhibitor and confocal microscopy, we could further confirm the association of γ-secretase complexes with mitochondrial Omi/HtrA2. Furthermore, determination of γ-secretase complex topology in isolated mitochondria revealed an association of γ-secretase complexes with the outer membrane of mitochondria with the extreme PS1 C-terminus facing the inter-membrane space. We have also studied the impact of Omi/HtrA2 on γ-secretase activity, measuring APP intracellular domain (AICD) production. We found reduced AICD production in mitochondria isolated from Omi/HtrA2 knockout mouse embryonic fibroblasts, indicating a significant role of Omi/HtrA2 on γ-secretase activity. Thus, our results provide information for understanding the interplay between mitochondrial Omi/HtrA2 and γ-secretase complexes in AD.
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http://dx.doi.org/10.1016/j.neuint.2010.08.004DOI Listing
November 2010

Synaptic and endosomal localization of active gamma-secretase in rat brain.

PLoS One 2010 Jan 28;5(1):e8948. Epub 2010 Jan 28.

Department of Neurobiology, Care Sciences and Society (NVS), Karolinska Institutet Dainippon Sumitomo Pharma Alzheimer Center, Novum, Huddinge, Sweden.

Background: A key player in the development of Alzheimer's disease (AD) is the gamma-secretase complex consisting of at least four components: presenilin, nicastrin, Aph-1 and Pen-2. gamma-Secretase is crucial for the generation of the neurotoxic amyloid beta-peptide (Abeta) but also takes part in the processing of many other substrates. In cell lines, active gamma-secretase has been found to localize primarily to the Golgi apparatus, endosomes and plasma membranes. However, no thorough studies have been performed to show the subcellular localization of the active gamma-secretase in the affected organ of AD, namely the brain.

Principal Findings: We show by subcellular fractionation of rat brain that high gamma-secretase activity, as assessed by production of Abeta40, is present in an endosome- and plasma membrane-enriched fraction of an iodixanol gradient. We also prepared crude synaptic vesicles as well as synaptic membranes and both fractions showed high Abeta40 production and contained high amounts of the gamma-secretase components. Further purification of the synaptic vesicles verified the presence of the gamma-secretase components in these compartments. The localization of an active gamma-secretase in synapses and endosomes was confirmed in rat brain sections and neuronal cultures by using a biotinylated gamma-secretase inhibitor together with confocal microscopy.

Significance: The information about the subcellular localization of gamma-secretase in brain is important for the understanding of the molecular mechanisms of AD. Furthermore, the identified fractions can be used as sources for highly active gamma-secretase.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008948PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2812513PMC
January 2010

CD147, a gamma-secretase associated protein is upregulated in Alzheimer's disease brain and its cellular trafficking is affected by presenilin-2.

Neurochem Int 2010 Jan 12;56(1):67-76. Epub 2009 Sep 12.

KASPAC (Karolinska Institutet Dainippon Sumitomo Pharma Alzheimer Center), Huddinge, Sweden.

Gamma-secretase activity has been extensively investigated due to its role in Alzheimer's disease. Here, we studied the association of CD147, a transmembrane glycoprotein belonging to the immunoglobulin family, with gamma-secretase and its expression in Alzheimer's disease and control tissues. Subcellular fractionation of postmitochondrial supernatant from rat brain on step iodixanol gradient in combination with co-immunoprecipitation using an anti-nicastrin antibody showed association of limited amount of CD147 to gamma-secretase. By immunoblotting of postnuclear pellets from Alzheimer's disease and control human brain tissues we showed that CD147 with molecular weight 75 kDa is upregulated in frontal cortex and thalamus of the Alzheimer's disease brains. Immunohistochemistry of brain tissues from Alzheimer's disease and control revealed specific upregulation of CD147 in neurons, axons and capillaries of Alzheimer's disease frontal cortex and thalamus. The effect of presenilin-1 and -2, which are the catalytic subunits of gamma-secretase, on CD147 expression and subcellular localization was analyzed by confocal microscopy in combination with flow cytometry and showed that PS2 affected the subcellular localization of CD147 in mouse embryonic fibroblast cells. We suggest that a small fraction of CD147 present in the brain is associated with the gamma-secretase, and can be involved in mechanisms dysregulated in Alzheimer's disease brain.
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http://dx.doi.org/10.1016/j.neuint.2009.09.003DOI Listing
January 2010

Mitochondrial alterations in PINK1 deficient cells are influenced by calcineurin-dependent dephosphorylation of dynamin-related protein 1.

PLoS One 2009 May 27;4(5):e5701. Epub 2009 May 27.

Laboratory of Neurogenetics, National Institute on Aging, Bethesda, Maryland, United States of America.

PTEN-induced novel kinase 1 (PINK1) mutations are associated with autosomal recessive parkinsonism. Previous studies have shown that PINK1 influences both mitochondrial function and morphology although it is not clearly established which of these are primary events and which are secondary. Here, we describe a novel mechanism linking mitochondrial dysfunction and alterations in mitochondrial morphology related to PINK1. Cell lines were generated by stably transducing human dopaminergic M17 cells with lentiviral constructs that increased or knocked down PINK1. As in previous studies, PINK1 deficient cells have lower mitochondrial membrane potential and are more sensitive to the toxic effects of mitochondrial complex I inhibitors. We also show that wild-type PINK1, but not recessive mutant or kinase dead versions, protects against rotenone-induced mitochondrial fragmentation whereas PINK1 deficient cells show lower mitochondrial connectivity. Expression of dynamin-related protein 1 (Drp1) exaggerates PINK1 deficiency phenotypes and Drp1 RNAi rescues them. We also show that Drp1 is dephosphorylated in PINK1 deficient cells due to activation of the calcium-dependent phosphatase calcineurin. Accordingly, the calcineurin inhibitor FK506 blocks both Drp1 dephosphorylation and loss of mitochondrial integrity in PINK1 deficient cells but does not fully rescue mitochondrial membrane potential. We propose that alterations in mitochondrial connectivity in this system are secondary to functional effects on mitochondrial membrane potential.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0005701PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2683574PMC
May 2009

The amyloid beta-peptide is imported into mitochondria via the TOM import machinery and localized to mitochondrial cristae.

Proc Natl Acad Sci U S A 2008 Sep 29;105(35):13145-50. Epub 2008 Aug 29.

Karolinska Institutet Dainippon Sumitomo Pharma Alzheimer Center, NVS, Novum, 141 57 Huddinge, Sweden.

The amyloid beta-peptide (Abeta) has been suggested to exert its toxicity intracellularly. Mitochondrial functions can be negatively affected by Abeta and accumulation of Abeta has been detected in mitochondria. Because Abeta is not likely to be produced locally in mitochondria, we decided to investigate the mechanisms for mitochondrial Abeta uptake. Our results from rat mitochondria show that Abeta is transported into mitochondria via the translocase of the outer membrane (TOM) machinery. The import was insensitive to valinomycin, indicating that it is independent of the mitochondrial membrane potential. Subfractionation studies following the import experiments revealed Abeta association with the inner membrane fraction, and immunoelectron microscopy after import showed localization of Abeta to mitochondrial cristae. A similar distribution pattern of Abeta in mitochondria was shown by immunoelectron microscopy in human cortical brain biopsies obtained from living subjects with normal pressure hydrocephalus. Thus, we present a unique import mechanism for Abeta in mitochondria and demonstrate both in vitro and in vivo that Abeta is located to the mitochondrial cristae. Importantly, we also show that extracellulary applied Abeta can be internalized by human neuroblastoma cells and can colocalize with mitochondrial markers. Together, these results provide further insight into the mitochondrial uptake of Abeta, a peptide considered to be of major significance in Alzheimer's disease.
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http://dx.doi.org/10.1073/pnas.0806192105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2527349PMC
September 2008

Active gamma-secretase is localized to detergent-resistant membranes in human brain.

FEBS J 2008 Mar 6;275(6):1174-87. Epub 2008 Feb 6.

Karolinska Institutet (KI) Dainippon Sumitomo Pharma Alzheimer Center, KI-Alzheimer's Disease Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Novum, Huddinge, Sweden.

Several lines of evidence suggest that polymerization of the amyloid beta-peptide (Abeta) into amyloid plaques is a pathogenic event in Alzheimer's disease (AD). Abeta is produced from the amyloid precursor protein as the result of sequential proteolytic cleavages by beta-secretase and gamma-secretase, and it has been suggested that these enzymes could be targets for treatment of AD. gamma-Secretase is an aspartyl protease complex, containing at least four transmembrane proteins. Studies in cell lines have shown that gamma-secretase is partially localized to lipid rafts, which are detergent-resistant membrane microdomains enriched in cholesterol and sphingolipids. Here, we studied gamma-secretase in detergent-resistant membranes (DRMs) prepared from human brain. DRMs prepared in the mild detergent CHAPSO and isolated by sucrose gradient centrifugation were enriched in gamma-secretase components and activity. The DRM fraction was subjected to size-exclusion chromatography in CHAPSO, and all of the gamma-secretase components and a lipid raft marker were found in the void volume (> 2000 kDa). Co-immunoprecipitation studies further supported the notion that the gamma-secretase components are associated even at high concentrations of CHAPSO. Preparations from rat brain gave similar results and showed a postmortem time-dependent decline in gamma-secretase activity, suggesting that DRMs from fresh rat brain may be useful for gamma-secretase activity studies. Finally, confocal microscopy showed co-localization of gamma-secretase components and a lipid raft marker in thin sections of human brain. We conclude that the active gamma-secretase complex is localized to lipid rafts in human brain.
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http://dx.doi.org/10.1111/j.1742-4658.2008.06278.xDOI Listing
March 2008

Leukemia inhibitor factor (LIF) inhibits HIV-1 replication via restriction of stat 3 activation.

AIDS Res Hum Retroviruses 2007 Mar;23(3):398-406

Center for Infectious Medicine, Department of Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden.

Leukemia inhibitor factor (LIF) has been shown to potently inhibit HIV-1 replication in vitro and in human organ explant cultures. Furthermore, LIF activates the Jak/Stat signaling pathway with which many viruses, including HIV-1, interfere. We used CXCR4 and the LIF signaling receptor (gp130)-expressing cMAGI cells transfected with CD4, CCR5, and HIV-LTR-beta-galactosidase as a model system to investigate the potential involvement of Stat proteins in the anti-HIV-1 effect of LIF. Pretreatment with recombinant human (rh)LIF resulted in a significantly reduced uptake of HIV-1(BaL) , HIV-1(LAI), and SIVmac251 viral particles without affecting uptake of murine leukemia retroviral particles. HIV-1(BaL), HIV-1(LAI), as well as rhLIF selectively induced phosphorylation of Stat 3 but not Stat 1 or Stat 5. However, treatment of cMAGI cells with rhLIF prior to HIV-1 infection downregulated the HIV-1-mediated Stat 3 phosphorylation. In addition, peripheral blood mononuclear cells (PBMCs) transfected with Stat 3 siRNA prior to HIV-1(LAI) or HIV-1(BaL) infection produced significantly less HIV-1 p24 antigen as compared to nontransfected HIV-1(LAI) and HIV-1(BaL)-infected PBMCs. Thus, the Jak/Stat signaling pathway is important for the HIV-1 replication life cycle and rhLIF excerts its anti-HIV-1 activity by disrupting this signaling cascade.
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http://dx.doi.org/10.1089/aid.2006.0100DOI Listing
March 2007

Proinflammatory and type 1 cytokine expression in cervical mucosa during HIV-1 and human papillomavirus infection.

J Acquir Immune Defic Syndr 2007 May;45(1):9-19

Center for Infectious Medicine, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.

Suppression of immune activation and increased inflammation are prevalent during viral infection. To investigate the role of inflammation in HIV transmission, we studied the infectious and inflammatory milieu in cervical mucosa from HIV-1- and human papillomavirus (HPV)-coinfected and HPV-monoinfected women. The numbers of cytokine-, chemokine-, and p24-expressing cells were determined using in situ imaging analysis and intracellular staining of p24 antigen. Significantly higher expression of the proinflammatory cytokines, interleukin (IL)-1alpha/beta, was seen in cervical tissue from HIV/HPV-coinfected as compared with HPV-monoinfected tissues, whereas IL-2- and interferon (IFN)-gamma-expressing cells were higher in HPV-monoinfected tissues. IL-10 was low in both groups, whereas IL-4 was significantly higher in HPV-monoinfected and HIV/HPV-coinfected tissues than in HIV/HPV-negative controls. RANTES and macrophage inflammatory protein (MIP)-1beta but not MIP-1alpha were significantly higher in the genital tract of HIV/HPV-coinfected as compared with HPV-monoinfected individuals and controls. HIV/HPV-coinfected tissues had a higher level of human leukocyte antigen D-related (HLA-DR)-expressing dendritic cells (DCs). There was a positive correlation between the number of CD4(+) and CD8(+) T cells as well as CD1a, IL-1alpha, and RANTES expression and p24 antigen-expressing cells in the HIV/HPV-coinfected tissues. These findings suggest the persistence of immune activation and inflammation in the genital tract of women with HPV monoinfection and in HIV-infected women coinfected with HPV.
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http://dx.doi.org/10.1097/QAI.0b013e3180415da7DOI Listing
May 2007

Differential role of Presenilin-1 and -2 on mitochondrial membrane potential and oxygen consumption in mouse embryonic fibroblasts.

J Neurosci Res 2006 Sep;84(4):891-902

Department of Neurobiology, Karolinska Institutet Dainippon Sumitomo Pharmaceuticals Alzheimer Center, Caring Sciences and Society, Novum, Huddinge, Sweden.

Increasing evidence indicates that mitochondrial alterations contribute to the neuronal death in Alzheimer's disease (AD). Presenilin 1 (PS1) and Presenilin 2 (PS2) mutations have been shown to sensitize cells to apoptosis by mechanisms suggested to involve impaired mitochondrial function. We have previously detected active gamma-secretase complexes in mitochondria. We investigated the impact of PS/gamma-secretase on mitochondrial function using mouse embryonal fibroblasts derived from wild-type, PS1-/-, PS2-/- and PS double knock-out (PSKO) embryos. Measurements of mitochondrial membrane potential (DeltaPsim) showed a higher percentage of fully functional mitochondria in PS1-/- and PSwt as compared to PS2-/- and PSKO cells. This result was evident both in whole cell preparations and in isolated mitochondria. Interestingly, pre-treatment of isolated mitochondria with the gamma-secretase inhibitor L-685,458 resulted in a decreased population of mitochondria with high DeltaPsim in PSwt and PS1-/- cells, indicating that PS2/gamma-secretase activity can modify DeltaPsim. PS2-/- cells showed a significantly lower basal respiratory rate as compared to other cell lines. However, all cell lines demonstrated competent bioenergetic function. These data point toward a specific role of PS2/gamma-secretase activity for proper mitochondrial function and indicate interplay between PS1 and PS2 in mitochondrial functionality.
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http://dx.doi.org/10.1002/jnr.20990DOI Listing
September 2006

Suppression of leukemia inhibitor factor in lymphoid tissue in primary HIV infection: absence of HIV replication in gp130-positive cells.

AIDS 2003 Jun;17(9):1303-10

Center for Infectious Medicine, Department of Medicine, Karolinska Institutet, Huddinge University Hospital, Stockholm, Sweden.

Background: Leukemia inhibitor factor (LIF), a member of the interleukin-6 cytokine family, has recently been shown to inhibit HIV-1 replication both in vivo and in vitro.

Objective: LIF and its corresponding receptors gp130 and LIF receptor-alpha (LIFR-alpha) were studied in lymphoid tissue (LT) to reveal potential systemic immunoregulatory effects during the course of HIV-1 infection.

Methods: LIF, gp130, LIFR-alpha and HIV-1 replicating cells were identified at the single cell level by immunohistochemistry and quantified by computerized in situ imaging in tonsil and lymph nodes biopsies (LT) from patients with primary HIV-1 infection (PHI), chronic HIV-1 infection (cHI), long-term non-progressors (LTNP) and HIV-1 seronegative controls.

Results: LIF and its receptors, gp130 and LIFR-alpha were significantly (P < 0.005) upregulated in LT from PHI patients as compared with HIV-1 seronegative controls. Expression of LIF in cHI was comparable to LIF levels in HIV-1 seronegative controls whereas LTNP showed significantly reduced LIF expression (P < 0.05). LIF receptors, gp130 and LIFR-alpha were significantly upregulated in cHI (P < 0.005) but downregulated in LTNP (P < 0.05 and P < 0.005, respectively). LIF expressing cells could be demonstrated in LT 2 days after onset of acute retroviral syndrome. LIF expression was evident in CD3, CD4 and CD8 cells. Furthermore, high plasma viral load was associated with high expression of LIF in LT. Finally, no HIV-1 replication could be found in CD4 gp130-positive cells in PHI.

Conclusions: LIF, gp130 and LIFR-alpha showed increased expression in LT from patients with PHI. Furthermore, HIV-1 replication did not occur in cells expressing the LIF signaling receptor, gp130, indicating that LIF may be associated with control of HIV-1 replicating cells in vivo.
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http://dx.doi.org/10.1097/00002030-200306130-00004DOI Listing
June 2003

Low levels of perforin expression in CD8+ T lymphocyte granules in lymphoid tissue during acute human immunodeficiency virus type 1 infection.

J Infect Dis 2002 May 16;185(9):1355-8. Epub 2002 Apr 16.

Department of Medicine, Center for Infectious Medicine, Karolinska Institutet, Huddinge University Hospital, Stockholm, Sweden.

Human immunodeficiency virus (HIV)-specific cytotoxic T lymphocyte (CTL) responses are detectable shortly after the acute phase of HIV infection, but they cannot control viral replication and prevent development of chronic immune suppression. This article describes a defect in the coexpression of perforin in granzyme A-positive CD8(+) T cells in lymphoid tissue from patients with acute HIV infection and a reduction in the perforin-dependent nuclear translocation of granzyme A. Furthermore, intracellular levels of HIV DNA and RNA found in lymphoid tissue were higher (10-100 times) than those found in blood, and blood samples showed more-coordinated cellular perforin/granzyme A expression. This suggests that mechanisms inhibiting CTL-mediated cytotoxicity are operative in lymphoid tissue early in the course of HIV infection.
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http://dx.doi.org/10.1086/340124DOI Listing
May 2002