Publications by authors named "Subhashini Bolisetty"

40 Publications

Ciclopirox olamine induces ferritinophagy and reduces cyst burden in polycystic kidney disease.

JCI Insight 2021 Mar 30. Epub 2021 Mar 30.

Department of Internal Medicine, University of Kansas Medical Center, Kansas City, United States of America.

Despite the recent launch of Tolvaptan, the search for safer polycystic kidney disease (PKD) drugs continues. Ciclopirox (CPX) or its olamine salt (CPX-O) are contained in number of commercially available antifungal agents. CPX is also reported to possess anticancer activity. Several mechanisms of action have been proposed including chelation of iron and inhibition of iron dependent enzymes. Here, we show that CPX-O inhibited in vitro cystogenesis of primary human PKD cyst-lining epithelial cells cultured in a 3D collagen matrix. To assess in vivo role of CPX-O, we treated PKD mice with CPX-O. CPX-O reduced the kidney- to-body weight ratios of PKD mice. This was also associated with decreased cell proliferation, decreased cystic area and improved renal function. Ferritin levels were significantly elevated in cystic kidneys of PKD mice, and CPX-O treatment reduced renal ferritin levels. The reduction in ferritin was associated with increased ferritinophagy marker, NCOA4 which reversed upon CPX-O treatment in PKD mice. Interestingly, these effects on ferritin appeared independent of iron. These data suggest that CPX-O can induce ferritin degradation via ferritinophagy which is associated with decreased cyst growth progression in PKD mice. Most importantly these data indicate that CPX-O has the potential to treat autosomal dominant PKD.
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http://dx.doi.org/10.1172/jci.insight.141299DOI Listing
March 2021

Iron Homeostasis and Ferritin in Sepsis-Associated Kidney Injury.

Nephron 2020 21;144(12):616-620. Epub 2020 Jul 21.

Department of Medicine, Division of Nephrology, University of Alabama at Birmingham, Birmingham, Alabama, USA,

Sepsis associated acute kidney injury (SA-AKI) is a common clinical syndrome that occurs among hospitalized patients and significantly impacts mortality. Furthermore, survival after sepsis is intricately dependent on recovery of kidney function. In this review, we discuss the role of iron imbalance in mediating the pathogenic events during sepsis. Intracellular ferritin serves as a repository for iron and prevents iron-mediated injury and may limit the availability of iron to pathogens. Circulating levels of ferritin also increase during sepsis and often correlate with severity of sepsis. Herein, we examine preclinical and clinical data and discuss recent findings that suggest immunomodulatory roles for ferritin. We also discuss the possible mechanistic roles for ferritin in mitigating the pathogenic sequelae of sepsis and highlight current gaps in knowledge.
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http://dx.doi.org/10.1159/000508857DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7708391PMC
July 2020

Interleukin-1 promotes autoimmune neuroinflammation by suppressing endothelial heme oxygenase-1 at the blood-brain barrier.

Acta Neuropathol 2020 10 11;140(4):549-567. Epub 2020 Jul 11.

Institute for Molecular Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany.

The proinflammatory cytokine interleukin 1 (IL-1) is crucially involved in the pathogenesis of multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). Herein, we studied the role of IL-1 signaling in blood-brain barrier (BBB) endothelial cells (ECs), astrocytes and microglia for EAE development, using mice with the conditional deletion of its signaling receptor IL-1R1. We found that IL-1 signaling in microglia and astrocytes is redundant for the development of EAE, whereas the IL-1R1 deletion in BBB-ECs markedly ameliorated disease severity. IL-1 signaling in BBB-ECs upregulated the expression of the adhesion molecules Vcam-1, Icam-1 and the chemokine receptor Darc, all of which have been previously shown to promote CNS-specific inflammation. In contrast, IL-1R1 signaling suppressed the expression of the stress-responsive heme catabolizing enzyme heme oxygenase-1 (HO-1) in BBB-ECs, promoting disease progression via a mechanism associated with deregulated expression of the IL-1-responsive genes Vcam1, Icam1 and Ackr1 (Darc). Mechanistically, our data emphasize a functional crosstalk of BBB-EC IL-1 signaling and HO-1, controlling the transcription of downstream proinflammatory genes promoting the pathogenesis of autoimmune neuroinflammation.
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http://dx.doi.org/10.1007/s00401-020-02187-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7498485PMC
October 2020

Ferritins in Kidney Disease.

Semin Nephrol 2020 03;40(2):160-172

Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL. Electronic address:

Ferritins are evolutionarily conserved proteins that regulate cellular iron metabolism. It is the only intracellular protein that is capable of storing large quantities of iron. Although the ratio of different subunits determines the iron content of each ferritin molecule, the exact mechanism that dictates organization of these subunits still is unclear. In this review, we address renal ferritin expression and its implication in kidney disease. Specifically, we address the role of ferritin subunits in preventing kidney injury and also promoting tolerance against infection-associated kidney injury. We describe functions for ferritin that are independent of its ability to ferroxidize and store iron. We further discuss the implications of ferritin in body fluids, including blood and urine, during inflammation and kidney disease. Although there are several in-depth review articles on ferritin in the context of iron metabolism, we chose to focus on the role of ferritin particularly in kidney health and disease and highlight unanswered questions in the field.
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http://dx.doi.org/10.1016/j.semnephrol.2020.01.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7172005PMC
March 2020

Dynamic signature of lymphangiogenesis during acute kidney injury and chronic kidney disease.

Lab Invest 2019 09 24;99(9):1376-1388. Epub 2019 Apr 24.

Department of Medicine, University of Alabama at Birmingham, Birmingham, USA.

Acute kidney injury (AKI) and chronic kidney disease (CKD) are interconnected syndromes with significant attributable morbidity and mortality. The disturbing trend of increasing incidence and prevalence of these clinical disorders highlights the urgent need for better understanding of the underlying mechanisms that are involved in pathogenesis of these conditions. Lymphangiogenesis and its involvement in various inflammatory conditions is increasingly recognized while its role in AKI and CKD remains to be fully elucidated. Here, we studied lymphangiogenesis in three models of kidney injury. Our results demonstrate that the main ligands for lymphangiogenesis, VEGF-C and VEGF-D, are abundantly present in tubules at baseline conditions and the expression pattern of these ligands is significantly altered following injury. In addition, we show that both of these ligands increase in serum and urine post-injury and suggest that such increment may serve as novel urinary biomarkers of AKI as well as in progression of kidney disease. We also provide evidence that irrespective of the nature of initial insult, lymphangiogenic pathways are rapidly and robustly induced as evidenced by higher expression of lymphatic markers within the kidney.
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http://dx.doi.org/10.1038/s41374-019-0259-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6716993PMC
September 2019

Renal control of disease tolerance to malaria.

Proc Natl Acad Sci U S A 2019 03 4;116(12):5681-5686. Epub 2019 Mar 4.

Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal;

Malaria, the disease caused by spp. infection, remains a major global cause of morbidity and mortality. Host protection from malaria relies on immune-driven resistance mechanisms that kill However, these mechanisms are not sufficient per se to avoid the development of severe forms of disease. This is accomplished instead via the establishment of disease tolerance to malaria, a defense strategy that does not target directly. Here we demonstrate that the establishment of disease tolerance to malaria relies on a tissue damage-control mechanism that operates specifically in renal proximal tubule epithelial cells (RPTEC). This protective response relies on the induction of heme oxygenase-1 (; HO-1) and ferritin H chain () via a mechanism that involves the transcription-factor nuclear-factor E2-related factor-2 (). As it accumulates in plasma and urine during the blood stage of infection, labile heme is detoxified in RPTEC by HO-1 and FTH, preventing the development of acute kidney injury, a clinical hallmark of severe malaria.
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http://dx.doi.org/10.1073/pnas.1822024116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431151PMC
March 2019

Ferritin Light Chain Confers Protection Against Sepsis-Induced Inflammation and Organ Injury.

Front Immunol 2019 4;10:131. Epub 2019 Feb 4.

Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States.

Despite the prevalence and recognition of its detrimental impact, clinical complications of sepsis remain a major challenge. Here, we investigated the effects of myeloid ferritin heavy chain (FtH) in regulating the pathogenic sequelae of sepsis. We demonstrate that deletion of myeloid FtH leads to protection against lipopolysaccharide-induced endotoxemia and cecal ligation and puncture (CLP)-induced model of sepsis as evidenced by reduced cytokine levels, multi-organ dysfunction and mortality. We identified that such protection is predominantly mediated by the compensatory increase in circulating ferritin (ferritin light chain; FtL) in the absence of myeloid FtH. Our and studies indicate that prior exposure to ferritin light chain restrains an otherwise dysregulated response to infection. These findings are mediated by an inhibitory action of FtL on NF-κB activation, a key signaling pathway that is implicated in the pathogenesis of sepsis. We further identified that LPS mediated activation of MAPK pathways, specifically, JNK, and ERK were also reduced with FtL pre-treatment. Taken together, our findings elucidate a crucial immunomodulatory function for circulating ferritin that challenges the traditional view of this protein as a mere marker of body iron stores. Accordingly, these findings will stimulate investigations to the adaptive nature of this protein in diverse clinical settings.
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http://dx.doi.org/10.3389/fimmu.2019.00131DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6371952PMC
January 2020

Resident macrophages reprogram toward a developmental state after acute kidney injury.

JCI Insight 2019 Jan 24;4(2). Epub 2019 Jan 24.

Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham, Alabama, USA.

Acute kidney injury (AKI) is a devastating clinical condition affecting at least two-thirds of critically ill patients, and, among these patients, it is associated with a greater than 60% risk of mortality. Kidney mononuclear phagocytes (MPs) are implicated in pathogenesis and healing in mouse models of AKI and, thus, have been the subject of investigation as potential targets for clinical intervention. We have determined that, after injury, F4/80hi-expressing kidney-resident macrophages (KRMs) are a distinct cellular subpopulation that does not differentiate from nonresident infiltrating MPs. However, if KRMs are depleted using polyinosinic/polycytidylic acid (poly I:C), they can be reconstituted from bone marrow-derived precursors. Further, KRMs lack major histocompatibility complex class II (MHCII) expression before P7 but upregulate it over the next 14 days. This MHCII- KRM phenotype reappears after injury. RNA sequencing shows that injury causes transcriptional reprogramming of KRMs such that they more closely resemble that found at P7. KRMs after injury are also enriched in Wingless-type MMTV integration site family (Wnt) signaling, indicating that a pathway vital for mouse and human kidney development is active. These data indicate that mechanisms involved in kidney development may be functioning after injury in KRMs.
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http://dx.doi.org/10.1172/jci.insight.125503DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6413788PMC
January 2019

Myeloid HO-1 modulates macrophage polarization and protects against ischemia-reperfusion injury.

JCI Insight 2018 10 4;3(19). Epub 2018 Oct 4.

Department of Medicine, Division of Cardiology, and.

Macrophages polarize into heterogeneous proinflammatory M1 and antiinflammatory M2 subtypes. Heme oxygenase 1 (HO-1) protects against inflammatory processes such as ischemia-reperfusion injury (IRI), organ transplantation, and atherosclerosis. To test our hypothesis that HO-1 regulates macrophage polarization and protects against IRI, we generated myeloid-specific HO-1-knockout (mHO-1-KO) and -transgenic (mHO-1-Tg) mice, with deletion or overexpression of HO-1, in various macrophage populations. Bone marrow-derived macrophages (BMDMs) from mHO-1-KO mice, treated with M1-inducing LPS or M2-inducing IL-4, exhibited increased mRNA expression of M1 (CXCL10, IL-1β, MCP1) and decreased expression of M2 (Arg1 and CD163) markers as compared with controls, while BMDMs from mHO-1-Tg mice displayed the opposite. A similar pattern was observed in the hepatic M1/M2 expression profile in a mouse model of liver IRI. mHO-1-KO mice displayed increased hepatocellular damage, serum AST/ALT levels, Suzuki's histological score of liver IRI, and neutrophil and macrophage infiltration, while mHO-1-Tg mice exhibited the opposite. In human liver transplant biopsies, subjects with higher HO-1 levels showed lower expression of M1 markers together with decreased hepatocellular damage and improved outcomes. In conclusion, myeloid HO-1 expression modulates macrophage polarization, and protects against liver IRI, at least in part by favoring an M2 phenotype.
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http://dx.doi.org/10.1172/jci.insight.120596DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6237471PMC
October 2018

Resolution Agonist 15-epi-Lipoxin A Programs Early Activation of Resolving Phase in Post-Myocardial Infarction Healing.

Sci Rep 2017 08 30;7(1):9999. Epub 2017 Aug 30.

Division of Cardiovascular Disease, The University of Alabama at Birmingham, Alabama, USA.

Following myocardial infarction (MI), overactive inflammation remodels the left ventricle (LV) leading to heart failure coinciding with reduced levels of 15-epi-Lipoxin A (15-epi LXA). However, the role of 15-epi LXA in post-MI acute inflammatory response and resolving phase is unclear. We hypothesize that liposomal fusion of 15-epi-LXA (Lipo-15-epi-LXA) or free 15-epi-LXA will expedite the resolving phase in post-MI inflammation. 8 to 12-week-old male C57BL/6 mice were subjected to permanent coronary artery ligation. Lipo-15-epi-LXA or 15-epi-LXA (1 µg/kg/day) was injected 3 hours post-MI for (d)1 or continued daily till d5. 15-epi-LXA activated formyl peptide receptor (FPR2) and GPR120 on alternative macrophages but inhibited GPR40 on classical macrophages in-vitro. The 15-epi-LXA injected mice displayed reduced LV and lung mass to body weight ratios and improved ejection fraction at d5 post-MI. In the acute phase of inflammation-(d1), 15-epi-LXA primes neutrophil infiltration with a robust increase of Ccl2 and FPR2 expression. During the resolving phase-(d5), 15-epi-LXA initiated rapid neutrophils clearance with persistent activation of FPR2 in LV. Compared to MI-control, 15-epi-LXA injected mice showed reduced renal inflammation along with decreased levels of ngal and plasma creatinine. In summary, 15-epi-LXA initiates the resolving phase early to discontinue inflammation post-MI, thereby reducing LV dysfunction.
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http://dx.doi.org/10.1038/s41598-017-10441-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577033PMC
August 2017

Unique sex- and age-dependent effects in protective pathways in acute kidney injury.

Am J Physiol Renal Physiol 2017 09 5;313(3):F740-F755. Epub 2017 Jul 5.

Division of Nephrology, Nephrology Research and Training Center, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and

Sex and age influence susceptibility to acute kidney injury (AKI), with young females exhibiting lowest incidence. In these studies, we investigated mechanisms which may underlie the sex/age-based dissimilarities. Cisplatin (Cp)-induced AKI resulted in morphological evidence of injury in all groups. A minimal rise in plasma creatinine (PCr) was seen in Young Females, whereas in Aged Females, PCr rose precipitously. Relative to Young Males, Aged Males showed significantly, but temporally, comparably elevated PCr. Notably, Aged Females showed significantly greater mortality, whereas Young Females exhibited none. Tissue KIM-1 and plasma NGAL were significantly lower in Young Females than all others. IGFBP7 levels were modestly increased in both Young groups. IGFBP7 levels in Aged Females were significantly elevated at baseline relative to Aged Males, and increased linearly through , when these levels were comparable in both Aged groups. Plasma cytokine levels similarly showed a pattern of protective effects preferentially in Young Females. Expression of the drug transporter MATE2 did not explain the sex/age distinctions. Heme oxygenase-1 (HO-1) levels (~28-kDa species) showed elevation at in all groups with highest levels seen in Young Males. Exclusively in Young Females, these levels returned to baseline on , suggestive of a more efficient recovery. In aggregate, we demonstrate, for the first time, a distinctive pattern of response to AKI in Young Females relative to males which appears to be significantly altered in aging. These distinctions may offer novel targets to exploit therapeutically in both females and males in the treatment of AKI.
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http://dx.doi.org/10.1152/ajprenal.00049.2017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5625098PMC
September 2017

Heme oxygenase-1 mitigates ferroptosis in renal proximal tubule cells.

Am J Physiol Renal Physiol 2018 05 17;314(5):F702-F714. Epub 2017 May 17.

Nephrology Research and Training Center, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.

Ferroptosis is an iron-dependent form of regulated nonapoptotic cell death, which contributes to damage in models of acute kidney injury (AKI). Heme oxygenase-1 (HO-1) is a cytoprotective enzyme induced in response to cellular stress, and is protective against AKI because of its antiapoptotic and anti-inflammatory properties. However, the role of HO-1 in regulating ferroptosis is unclear. The purpose of this study was to elucidate the role of HO-1 in regulating ferroptotic cell death in renal proximal tubule cells (PTCs). Immortalized PTCs obtained from HO-1 and HO-1 mice were treated with erastin or RSL3, ferroptosis inducers, in the presence or absence of antioxidants, an iron source, or an iron chelator. Cells were assessed for changes in morphology and metabolic activity as an indicator of cell viability. Treatment of HO-1 PTCs with erastin resulted in a time- and dose-dependent increase in HO-1 gene expression and protein levels compared with vehicle-treated controls. HO-1 cells showed increased dose-dependent erastin- or RSL3-induced cell death in comparison to HO-1 PTCs. Iron supplementation with ferric ammonium citrate in erastin-treated cells decreased cell viability further in HO-1 PTCs compared with HO-1 cells. Cotreatment with ferrostatin-1 (ferroptosis inhibitor), deferoxamine (iron chelator), or N-acetyl-l-cysteine (glutathione replenisher) significantly increased cell viability and attenuated erastin-induced ferroptosis in both HO-1 and HO-1 PTCs. These results demonstrate an important antiferroptotic role of HO-1 in renal epithelial cells.
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http://dx.doi.org/10.1152/ajprenal.00044.2017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6031916PMC
May 2018

Heme Oxygenase 1 as a Therapeutic Target in Acute Kidney Injury.

Am J Kidney Dis 2017 Apr 27;69(4):531-545. Epub 2017 Jan 27.

Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham, AL; Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL; Birmingham Veterans Administration Medical Center, Birmingham, AL. Electronic address:

A common clinical condition, acute kidney injury (AKI) significantly influences morbidity and mortality, particularly in critically ill patients. The pathophysiology of AKI is complex and involves multiple pathways, including inflammation, autophagy, cell-cycle progression, and oxidative stress. Recent evidence suggests that a single insult to the kidney significantly enhances the propensity to develop chronic kidney disease. Therefore, the generation of effective therapies against AKI is timely. In this context, the cytoprotective effects of heme oxygenase 1 (HO-1) in animal models of AKI are well documented. HO-1 modulates oxidative stress, autophagy, and inflammation and regulates the progression of cell cycle via direct and indirect mechanisms. These beneficial effects of HO-1 induction during AKI are mediated in part by the by-products of the HO reaction (iron, carbon monoxide, and bile pigments). This review highlights recent advances in the molecular mechanisms of HO-1-mediated cytoprotection and discusses the translational potential of HO-1 induction in AKI.
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http://dx.doi.org/10.1053/j.ajkd.2016.10.037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5366088PMC
April 2017

Early lipid changes in acute kidney injury using SWATH lipidomics coupled with MALDI tissue imaging.

Am J Physiol Renal Physiol 2016 05 24;310(10):F1136-47. Epub 2016 Feb 24.

Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama;

Acute kidney injury (AKI) is one of the leading causes of in-hospital morbidity and mortality, particularly in critically ill patients. Although our understanding of AKI at the molecular level remains limited due to its complex pathophysiology, recent advances in both quantitative and spatial mass spectrometric approaches offer new opportunities to assess the significance of renal metabolomic changes in AKI models. In this study, we evaluated lipid changes in early ischemia-reperfusion (IR)-related AKI in mice by using sequential window acquisition of all theoretical spectra (SWATH)-mass spectrometry (MS) lipidomics. We found a significant increase in two abundant ether-linked phospholipids following IR at 6 h postinjury, a plasmanyl choline, phosphatidylcholine (PC) O-38:1 (O-18:0, 20:1), and a plasmalogen, phosphatidylethanolamine (PE) O-42:3 (O-20:1, 22:2). Both of these lipids correlated with the severity of AKI as measured by plasma creatinine. In addition to many more renal lipid changes associated with more severe AKI, PC O-38:1 elevations were maintained at 24 h post-IR, while renal PE O-42:3 levels decreased, as were all ether PEs detected by SWATH-MS at this later time point. To further assess the significance of this early increase in PC O-38:1, we used matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) to determine that it occurred in proximal tubules, a region of the kidney that is most prone to IR injury and also rich in the rate-limiting enzymes involved in ether-linked phospholipid biosynthesis. Use of SWATH-MS lipidomics in conjunction with MALDI-IMS for lipid localization will help in elucidating the role of lipids in the pathobiology of AKI.
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http://dx.doi.org/10.1152/ajprenal.00100.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4889318PMC
May 2016

Proximal tubule-targeted heme oxygenase-1 in cisplatin-induced acute kidney injury.

Am J Physiol Renal Physiol 2016 Mar 16;310(5):F385-94. Epub 2015 Dec 16.

Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham, Alabama; Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama; and Birmingham Veterans Administration Medical Center, Birmingham, Alabama

Heme oxygenase-1 (HO-1) is a cytoprotective enzyme that catalyzes the breakdown of heme to biliverdin, carbon monoxide, and iron. The beneficial effects of HO-1 expression are not merely due to degradation of the pro-oxidant heme but are also credited to the by-products that have potent, protective effects, including antioxidant, anti-inflammatory, and prosurvival properties. This is well reflected in the preclinical animal models of injury in both renal and nonrenal settings. However, excessive accumulation of the by-products can be deleterious and lead to mitochondrial toxicity and oxidative stress. Therefore, use of the HO system in alleviating injury merits a targeted approach. Based on the higher susceptibility of the proximal tubule segment of the nephron to injury, we generated transgenic mice using cre-lox technology to enable manipulation of HO-1 (deletion or overexpression) in a cell-specific manner. We demonstrate the validity and feasibility of these mice by breeding them with proximal tubule-specific Cre transgenic mice. Similar to previous reports using chemical modulators and global transgenic mice, we demonstrate that whereas deletion of HO-1, specifically in the proximal tubules, aggravates structural and functional damage during cisplatin nephrotoxicity, selective overexpression of HO-1 in proximal tubules is protective. At the cellular level, cleaved caspase-3 expression, a marker of apoptosis, and p38 signaling were modulated by HO-1. Use of these transgenic mice will aid in the evaluation of the effects of cell-specific HO-1 expression in response to injury and assist in the generation of targeted approaches that will enhance recovery with reduced, unwarranted adverse effects.
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http://dx.doi.org/10.1152/ajprenal.00335.2015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4868370PMC
March 2016

Heme Attenuation Ameliorates Irritant Gas Inhalation-Induced Acute Lung Injury.

Antioxid Redox Signal 2016 Jan 14;24(2):99-112. Epub 2015 Dec 14.

1 Division of Molecular and Translational Biomedicine, Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham , Birmingham, Alabama.

Aims: Exposure to irritant gases, such as bromine (Br2), poses an environmental and occupational hazard that results in severe lung and systemic injury. However, the mechanism(s) of Br2 toxicity and the therapeutic responses required to mitigate lung damage are not known. Previously, it was demonstrated that Br2 upregulates the heme degrading enzyme, heme oxygenase-1 (HO-1). Since heme is a major inducer of HO-1, we determined whether an increase in heme and heme-dependent oxidative injury underlies the pathogenesis of Br2 toxicity.

Results: C57BL/6 mice were exposed to Br2 gas (600 ppm, 30 min) and returned to room air. Thirty minutes postexposure, mice were injected intraperitoneally with a single dose of the heme scavenging protein, hemopexin (Hx) (3 μg/gm body weight), or saline. Twenty-four hours postexposure, saline-treated mice had elevated total heme in bronchoalveolar lavage fluid (BALF) and plasma and acute lung injury (ALI) culminating in 80% mortality after 10 days. Hx treatment significantly lowered heme, decreased evidence of ALI (lower protein and inflammatory cells in BALF, lower lung wet-to-dry weight ratios, and decreased airway hyperreactivity to methacholine), and reduced mortality. In addition, Br2 caused more severe ALI and mortality in mice with HO-1 gene deletion (HO-1-/-) compared to wild-type controls, while transgenic mice overexpressing the human HO-1 gene (hHO-1) showed significant protection.

Innovation: This is the first study delineating the role of heme in ALI caused by Br2.

Conclusion: The data suggest that attenuating heme may prove to be a useful adjuvant therapy to treat patients with ALI.
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http://dx.doi.org/10.1089/ars.2015.6347DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4742996PMC
January 2016

Leucine-rich repeat kinase 2 deficiency is protective in rhabdomyolysis-induced kidney injury.

Hum Mol Genet 2015 Jul 22;24(14):4078-93. Epub 2015 Apr 22.

Department of Neurology, University of Alabama at Birmingham, Birmingham 35294, USA and

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common known genetic cause of Parkinson's disease, and LRRK2 is also linked to Crohn's and Hansen's disease. LRRK2 is expressed in many organs in mammals but is particularly abundant in the kidney. We find that LRRK2 protein is predominantly localized to collecting duct cells in the rat kidney, with much lower expression in other kidney cells. While genetic knockout (KO) of LRRK2 expression is well-tolerated in mice and rats, a unique age-dependent pathology develops in the kidney. The cortex and medulla of LRRK2 KO rat kidneys become darkly pigmented in early adulthood, yet aged animals display no overt signs of kidney failure. Accompanying the dark pigment we find substantial macrophage infiltration in LRRK2 KO kidneys, suggesting the presence of chronic inflammation that may predispose to kidney disease. Unexpectedly, the dark kidneys of the LRRK2 KO rats are highly resistant to rhabdomyolysis-induced acute kidney injury compared with wild-type rats. Biochemical profiling of the LRRK2 KO kidneys using immunohistochemistry, proteomic and lipidomic analyses show a massive accumulation of hemoglobin and lipofuscin in renal tubules that account for the pigmentation. The proximal tubules demonstrate a corresponding up-regulation of the cytoprotective protein heme oxygenase-1 (HO-1) which is capable of mitigating acute kidney injury. The unusual kidney pathology of LRRK2 KO rats highlights several novel physiological roles for LRRK2 and provides indirect evidence for HO-1 expression as a protective mechanism in acute kidney injury in LRRK2 deficiency.
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http://dx.doi.org/10.1093/hmg/ddv147DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4476452PMC
July 2015

Macrophage and epithelial cell H-ferritin expression regulates renal inflammation.

Kidney Int 2015 Jul 15;88(1):95-108. Epub 2015 Apr 15.

1] Nephrology Research and Training Center, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA [2] Department of Veterans Affairs, Birmingham, Alabama, USA.

Inflammation culminating in fibrosis contributes to progressive kidney disease. Cross-talk between the tubular epithelium and interstitial cells regulates inflammation by a coordinated release of cytokines and chemokines. Here we studied the role of heme oxygenase-1 (HO-1) and the heavy subunit of ferritin (FtH) in macrophage polarization and renal inflammation. Deficiency in HO-1 was associated with increased FtH expression, accumulation of macrophages with a dysregulated polarization profile, and increased fibrosis following unilateral ureteral obstruction in mice: a model of renal inflammation and fibrosis. Macrophage polarization in vitro was predominantly dependent on FtH expression in isolated bone marrow-derived mouse monocytes. Using transgenic mice with conditional deletion of FtH in the proximal tubules (FtH(PT-/-)) or myeloid cells (FtH(LysM-/-)), we found that myeloid FtH deficiency did not affect polarization or accumulation of macrophages in the injured kidney compared with wild-type (FtH(+/+)) controls. However, tubular FtH deletion led to a marked increase in proinflammatory macrophages. Furthermore, injured kidneys from FtH(PT-/-) mice expressed significantly higher levels of inflammatory chemokines and fibrosis compared with kidneys from FtH(+/+) and FtH(LysM-/-) mice. Thus, there are differential effects of FtH in macrophages and epithelial cells, which underscore the critical role of FtH in tubular-macrophage cross-talk during kidney injury.
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http://dx.doi.org/10.1038/ki.2015.102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4490000PMC
July 2015

Heme oxygenase-1 protects corexit 9500A-induced respiratory epithelial injury across species.

PLoS One 2015 2;10(4):e0122275. Epub 2015 Apr 2.

Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States of America.

The effects of Corexit 9500A (CE) on respiratory epithelial surfaces of terrestrial mammals and marine animals are largely unknown. This study investigated the role of CE-induced heme oxygenase-1 (HO-1), a cytoprotective enzyme with anti-apoptotic and antioxidant activity, in human bronchial airway epithelium and the gills of exposed aquatic animals. We evaluated CE-mediated alterations in human airway epithelial cells, mice lungs and gills from zebrafish and blue crabs. Our results demonstrated that CE induced an increase in gill epithelial edema and human epithelial monolayer permeability, suggesting an acute injury caused by CE exposure. CE induced the expression of HO-1 as well as C-reactive protein (CRP) and NADPH oxidase 4 (NOX4), which are associated with ROS production. Importantly, CE induced caspase-3 activation and subsequent apoptosis of epithelial cells. The expression of the intercellular junctional proteins, such as tight junction proteins occludin, zonula occludens (ZO-1), ZO-2 and adherens junctional proteins E-cadherin and Focal Adhesion Kinase (FAK), were remarkably inhibited by CE, suggesting that these proteins are involved in CE-induced increased permeability and subsequent apoptosis. The cytoskeletal protein F-actin was also disrupted by CE. Treatment with carbon monoxide releasing molecule-2 (CORM-2) significantly inhibited CE-induced ROS production, while the addition of HO-1 inhibitor, significantly increased CE-induced ROS production and apoptosis, suggesting a protective role of HO-1 or its reaction product, CO, in CE-induced apoptosis. Using HO-1 knockout mice, we further demonstrated that HO-1 protected against CE-induced inflammation and cellular apoptosis and corrected CE-mediated inhibition of E-cadherin and FAK. These observations suggest that CE activates CRP and NOX4-mediated ROS production, alters permeability by inhibition of junctional proteins, and leads to caspase-3 dependent apoptosis of epithelial cells, while HO-1 and its reaction products protect against oxidative stress and apoptosis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0122275PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383564PMC
March 2016

Heme Oxygenase-1 Regulates Myeloid Cell Trafficking in AKI.

J Am Soc Nephrol 2015 Sep 12;26(9):2139-51. Epub 2015 Feb 12.

Nephrology Research and Training Center, Birmingham Veterans Administration Medical Center, Birmingham, Alabama

Renal ischemia-reperfusion injury is mediated by a complex cascade of events, including the immune response, that occur secondary to injury to renal epithelial cells. We tested the hypothesis that heme oxygenase-1 (HO-1) expression, which is protective in ischemia-reperfusion injury, regulates trafficking of myeloid-derived immune cells in the kidney. Age-matched male wild-type (HO-1(+/+)), HO-1-knockout (HO-1(-/-)), and humanized HO-1-overexpressing (HBAC) mice underwent bilateral renal ischemia for 10 minutes. Ischemia-reperfusion injury resulted in significantly worse renal structure and function and increased mortality in HO-1(-/-) mice. In addition, there were more macrophages (CD45(+) CD11b(hi)F4/80(lo)) and neutrophils (CD45(+) CD11b(hi) MHCII(-) Gr-1(hi)) in HO-1(-/-) kidneys than in sham and HO-1(+/+) control kidneys subjected to ischemia-reperfusion. However, ischemic injury resulted in a significant decrease in the intrarenal resident dendritic cell (DC; CD45(+)MHCII(+)CD11b(lo)F4/80(hi)) population in HO-1(-/-) kidneys compared with controls. Syngeneic transplant experiments utilizing green fluorescent protein-positive HO-1(+/+) or HO-1(-/-) donor kidneys and green fluorescent protein-negative HO-1(+/+) recipients confirmed increased migration of the resident DC population from HO-1(-/-) donor kidneys, compared to HO-1(+/+) donor kidneys, to the peripheral lymphoid organs. This effect on renal DC migration was corroborated in myeloid-specific HO-1(-/-) mice subjected to bilateral ischemia. These mice also displayed impaired renal recovery and increased fibrosis at day 7 after injury. These results highlight an important role for HO-1 in orchestrating the trafficking of myeloid cells in AKI, which may represent a key pathway for therapeutic intervention.
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http://dx.doi.org/10.1681/ASN.2014080770DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4552119PMC
September 2015

Proximal tubule H-ferritin mediates iron trafficking in acute kidney injury.

J Clin Invest 2013 Oct 9;123(10):4423-34. Epub 2013 Sep 9.

Ferritin plays a central role in iron metabolism and is made of 24 subunits of 2 types: heavy chain and light chain. The ferritin heavy chain (FtH) has ferroxidase activity that is required for iron incorporation and limiting toxicity. The purpose of this study was to investigate the role of FtH in acute kidney injury (AKI) and renal iron handling by using proximal tubule-specific FtH-knockout mice (FtH(PT-/-) mice). FtH(PT-/-) mice had significant mortality, worse structural and functional renal injury, and increased levels of apoptosis in rhabdomyolysis and cisplatin-induced AKI, despite significantly higher expression of heme oxygenase-1, an antioxidant and cytoprotective enzyme. While expression of divalent metal transporter-1 was unaffected, expression of ferroportin (FPN) was significantly lower under both basal and rhabdomyolysis-induced AKI in FtH(PT-/-) mice. Apical localization of FPN was disrupted after AKI to a diffuse cytosolic and basolateral pattern. FtH, regardless of iron content and ferroxidase activity, induced FPN. Interestingly, urinary levels of the iron acceptor proteins neutrophil gelatinase-associated lipocalin, hemopexin, and transferrin were increased in FtH(PT-/-) mice after AKI. These results underscore the protective role of FtH and reveal the critical role of proximal tubule FtH in iron trafficking in AKI.
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http://dx.doi.org/10.1172/JCI67867DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3784534PMC
October 2013

Adaptive responses to tissue injury: role of heme oxygenase-1.

Trans Am Clin Climatol Assoc 2013 ;124:111-22

Division of Nephrology, THT 647, University of Alabama at Birmingham, 1900 University Blvd, Birmingham, AL 35294, USA.

Tissue injury may result as a consequence of a physical, chemical, or biological insult. Such injury recruits an adaptive response to restore homeostasis and protect against further injury. One of the most prompt protective and adaptive responses by all tissues is the robust activation of the highly inducible, anti-inflammatory, anti-oxidant, and anti-apoptotic protein, heme oxygenase-1 (HO-1). HO-1, a microsomal enzyme, catalyzes the breakdown of pro-oxidant heme, which is released from heme proteins to equimolar quantities of iron, carbon monoxide, and biliverdin. Biliverdin is converted to bilirubin by biliverdin reductase. The beneficial effects of HO-1 expression are not merely due to heme degradation but are also attributed to the cytoprotective properties of the byproducts of the reaction. Manipulation of this enzymatic system in a myriad of disease models has provided substantial evidence to support its role as a cytoprotective enzyme and is therefore an emerging therapeutic molecule.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3715920PMC
March 2014

Heme oxygenase-1 expression protects the heart from acute injury caused by inducible Cre recombinase.

Lab Invest 2013 Aug 3;93(8):868-79. Epub 2013 Jun 3.

Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.

The protective effect of heme oxygenase-1 (HO-1) expression in cardiovascular disease has been previously demonstrated using transgenic animal models in which HO-1 is constitutively overexpressed in the heart. However, the temporal requirements for protection by HO-1 induction relative to injury have not been investigated, but are essential to employ HO-1 as a therapeutic strategy in human cardiovascular disease states. Therefore, we generated mice with cardiac-specific, tamoxifen (TAM)-inducible overexpression of a human HO-1 (hHO-1) transgene (myosin heavy chain (MHC)-HO-1 mice) by breeding mice with cardiac-specific expression of a TAM-inducible Cre recombinase (MHC-Cre mice), with mice containing an hHO-1 transgene preceded by a floxed-stop signal. MHC-HO-1 mice overexpress HO-1 mRNA and the enzymatically active protein following TAM administration (40 mg/kg body weight on 2 consecutive days). In MHC-Cre controls, TAM administration leads to severe, acute cardiac toxicity, cardiomyocyte necrosis, and 80% mortality by day 3. This cardiac toxicity is accompanied by a significant increase in inflammatory cells in the heart that are predominantly neutrophils. In MHC-HO-1 mice, HO-1 overexpression ameliorates the depression of cardiac function and high mortality rate observed in MHC-Cre mice following TAM administration and attenuates cardiomyocyte necrosis and neutrophil infiltration. These results highlight that HO-1 induction is sufficient to prevent the depression of cardiac function observed in mice with TAM-inducible Cre recombinase expression by protecting the heart from necrosis and neutrophil infiltration. These findings are important because MHC-Cre mice are widely used in cardiovascular research despite the limitations imposed by Cre-induced cardiac toxicity, and also because inflammation is an important pathological component of many human cardiovascular diseases.
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http://dx.doi.org/10.1038/labinvest.2013.74DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3729748PMC
August 2013

Mitochondria-targeted heme oxygenase-1 decreases oxidative stress in renal epithelial cells.

Am J Physiol Renal Physiol 2013 Aug 29;305(3):F255-64. Epub 2013 May 29.

Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.

Mitochondria are both a source and target of the actions of reactive oxygen species and possess a complex system of inter-related antioxidants that control redox signaling and protect against oxidative stress. Interestingly, the antioxidant enzyme heme oxygenase-1 (HO-1) is not present in the mitochondria despite the fact that the organelle is the site of heme synthesis and contains multiple heme proteins. Detoxification of heme is an important protective mechanism since the reaction of heme with hydrogen peroxide generates pro-oxidant ferryl species capable of propagating oxidative stress and ultimately cell death. We therefore hypothesized that a mitochondrially localized HO-1 would be cytoprotective. To test this, we generated a mitochondria-targeted HO-1 cell line by transfecting HEK293 cells with a plasmid construct containing the manganese superoxide dismutase mitochondria leader sequence fused to HO-1 cDNA (Mito-HO-1). Nontargeted HO-1-overexpressing cells were generated by transfecting HO-1 cDNA (HO-1) or empty vector (Vector). Mitochondrial localization of HO-1 with increased HO activity in the mitochondrial fraction of Mito-HO-1 cells was observed, but a significant decrease in the expression of heme-containing proteins occurred in these cells. Both cytosolic HO-1- and Mito-HO-1-expressing cells were protected against hypoxia-dependent cell death and loss of mitochondrial membrane potential, but these effects were more pronounced with Mito-HO-1. Furthermore, decrement in production of tricarboxylic acid cycle intermediates following hypoxia was significantly mitigated in Mito-HO-1 cells. These data suggest that specific mitochondrially targeted HO-1 under acute pathological conditions may have beneficial effects, but the selective advantage of long-term expression is constrained by a negative impact on the synthesis of heme-containing mitochondrial proteins.
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http://dx.doi.org/10.1152/ajprenal.00160.2013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3742869PMC
August 2013

Mitochondria and reactive oxygen species: physiology and pathophysiology.

Int J Mol Sci 2013 Mar 19;14(3):6306-44. Epub 2013 Mar 19.

Nephrology Division, University of Alabama at Birmingham, Birmingham, AL 35294, USA.

The air that we breathe contains nearly 21% oxygen, most of which is utilized by mitochondria during respiration. While we cannot live without it, it was perceived as a bane to aerobic organisms due to the generation of reactive oxygen and nitrogen metabolites by mitochondria and other cellular compartments. However, this dogma was challenged when these species were demonstrated to modulate cellular responses through altering signaling pathways. In fact, since this discovery of a dichotomous role of reactive species in immune function and signal transduction, research in this field grew at an exponential pace and the pursuit for mechanisms involved began. Due to a significant number of review articles present on the reactive species mediated cell death, we have focused on emerging novel pathways such as autophagy, signaling and maintenance of the mitochondrial network. Despite its role in several processes, increased reactive species generation has been associated with the origin and pathogenesis of a plethora of diseases. While it is tempting to speculate that anti-oxidant therapy would protect against these disorders, growing evidence suggests that this may not be true. This further supports our belief that these reactive species play a fundamental role in maintenance of cellular and tissue homeostasis.
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http://dx.doi.org/10.3390/ijms14036306DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3634422PMC
March 2013

Pleural mesothelial cell differentiation and invasion in fibrogenic lung injury.

Am J Pathol 2013 Apr 9;182(4):1239-47. Epub 2013 Feb 9.

Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0006, USA.

The origin of the myofibroblast in fibrotic lung disease is uncertain, and no effective medical therapy for fibrosis exists. We have previously demonstrated that transforming growth factor-β1 (TGF-β1) induces pleural mesothelial cell (PMC) transformation into myofibroblasts and haptotactic migration in vitro. Whether PMC differentiation and migration occurs in vivo, and whether this response can be modulated for therapeutic benefit, is unknown. Here, using mice recombinant for green fluorescent protein (GFP) driven by the Wilms tumor-1 (WT-1) promoter, we demonstrate PMC trafficking into the lung and differentiation into myofibroblasts. Carbon monoxide or the induction of heme oxygenase-1 (HO-1) inhibited the expression of myofibroblast markers, contractility, and haptotaxis in PMCs treated with TGF-β1. Intrapleural HO-1 induction inhibited PMC migration after intratracheal fibrogenic injury. PMCs from patients with idiopathic pulmonary fibrosis (IPF) exhibited increased expression of myofibroblast markers and enhanced contractility and haptotaxis, compared with normal PMCs. Carbon monoxide reversed this IPF PMC profibrotic phenotype. WT-1-expressing cells were present within fibrotic regions of the lungs in IPF subjects, supporting a role for PMC differentiation and trafficking as contributors to the myofibroblast population in lung fibrosis. Our findings also support a potential role for pleural-based therapies to modulate pleural mesothelial activation and parenchymal fibrosis progression.
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http://dx.doi.org/10.1016/j.ajpath.2012.12.030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3620419PMC
April 2013

Kidney injury accelerates cystogenesis via pathways modulated by heme oxygenase and complement.

J Am Soc Nephrol 2012 Jul 19;23(7):1161-71. Epub 2012 Apr 19.

Department of Medicine, University of Alabama at Birmingham, USA.

AKI accelerates cystogenesis. Because cystogenic mutations induce strong transcriptional responses similar to those seen after AKI, these responses may accelerate the progression of cystic renal disease. Here, we modulated the severity of the AKI-like response in Cys1(cpk/cpk) mice, a model that mimics autosomal recessive polycystic kidney disease. Specifically, we induced or inhibited activity of the renoprotective enzyme heme oxygenase (HO) and determined the effects on renal cystogenesis. We found that induction of HO attenuated both renal injury and the rate of cystogenesis, whereas inhibition of HO promoted cystogenesis. HO activity mediated the response of NFκB, which is a hallmark transcriptional feature common to both cystogenesis and AKI. Among the HO-modulated effects we measured, expression of complement component 3 (C3) strongly correlated with cystogenesis, a functionally relevant association as suggested by Cys1(cpk/cpk) mice with genetically induced C3 deficiency. Because both C3 deficiency and HO induction reduce cyst number and cyst areas, these two factors define an injury-stimulated cystogenic pathway that may provide therapeutic targets to slow the formation of new renal cysts and the growth of existing cysts.
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http://dx.doi.org/10.1681/ASN.2011050442DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3380643PMC
July 2012

In vivo regulation of the heme oxygenase-1 gene in humanized transgenic mice.

Kidney Int 2012 Aug 11;82(3):278-91. Epub 2012 Apr 11.

Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.

Heme oxygenase-1 (HO-1) catalyzes the rate-limiting step in heme degradation, producing equimolar amounts of carbon monoxide, iron, and biliverdin. Induction of HO-1 is a beneficial response to tissue injury in diverse animal models of diseases including acute kidney injury. In vitro analysis has shown that the human HO-1 gene is transcriptionally regulated by changes in chromatin conformation, but whether such control occurs in vivo is not known. To enable such an analysis, we generated transgenic mice, harboring an 87-kb bacterial artificial chromosome expressing human HO-1 mRNA and protein and bred these mice with HO-1 knockout mice to generate humanized BAC transgenic mice. This successfully rescued the phenotype of the knockout mice including reduced birth rates, tissue iron overload, splenomegaly, anemia, leukocytosis, dendritic cell abnormalities, and survival after acute kidney injury induced by rhabdomyolysis or cisplatin nephrotoxicity. Transcription factors such as USF1/2, JunB, Sp1, and CTCF were found to associate with regulatory regions of the human HO-1 gene in the kidney following rhabdomyolysis. Chromosome conformation capture and ChIP-loop assays confirmed this in the formation of chromatin looping in vivo. Thus, these bacterial artificial chromosome humanized HO-1 mice are a valuable model to study the human HO-1 gene, providing insight to the in vivo architecture of the gene in acute kidney injury and other diseases.
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http://dx.doi.org/10.1038/ki.2012.102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3396739PMC
August 2012

Urine albumin as a biomarker in acute kidney injury.

Am J Physiol Renal Physiol 2011 Mar 12;300(3):F626-7. Epub 2011 Jan 12.

Department of Medicine, Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham, Alabama, USA.

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http://dx.doi.org/10.1152/ajprenal.00004.2011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3064133PMC
March 2011

Heme oxygenase-1 inhibits renal tubular macroautophagy in acute kidney injury.

J Am Soc Nephrol 2010 Oct 12;21(10):1702-12. Epub 2010 Aug 12.

Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.

Autophagy is a tightly regulated, programmed mechanism to eliminate damaged organelles and proteins from a cell to maintain homeostasis. Cisplatin, a chemotherapeutic agent, accumulates in the proximal tubules of the kidney and causes dose-dependent nephrotoxicity, which may involve autophagy. In the kidney, cisplatin induces the protective antioxidant heme oxygenase-1 (HO-1). In this study, we examined the relationship between autophagy and HO-1 during cisplatin-mediated acute kidney injury (AKI). In wild-type primary proximal tubule cells (PTC), we observed a time-dependent increase in autophagy after cisplatin. In HO-1(-/-) PTC, however, we observed significantly higher levels of basal autophagy, impaired progression of autophagy, and increased apoptosis after cisplatin. Restoring HO-1 expression in these cells reversed the autophagic response and inhibited apoptosis after treatment with cisplatin. In vivo, although both wild-type and HO-1-deficient mice exhibited autophagosomes in the proximal tubules of the kidney in response to cisplatin, HO-1-deficient mice had significantly more autophagosomes, even in saline-treated animals. In addition, ecdysone-induced overexpression of HO-1 in cells led to a delay in autophagy progression, generated significantly lower levels of reactive oxygen species, and protected against cisplatin cytotoxicity. These findings demonstrate that HO-1 inhibits autophagy, suggesting that the heme oxygenase system may contain therapeutic targets for AKI.
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http://dx.doi.org/10.1681/ASN.2010030238DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3013546PMC
October 2010