Induction of heme oxygenase-1 protects against podocyte apoptosis under diabetic conditions
2009; Elsevier BV; Volume: 76; Issue: 8 Linguagem: Inglês
10.1038/ki.2009.286
ISSN1523-1755
AutoresSang Choel Lee, Seung Hyeok Han, Jin Ji Li, Sun Ha Lee, Dong-Sub Jung, Seung-Jae Kwak, Seung Hye Kim, Dong Ki Kim, Tae‐Hyun Yoo, Jin Hyun Kim, Se-Ho Chang, Dae Suk Han, Shin‐Wook Kang,
Tópico(s)Dialysis and Renal Disease Management
ResumoHeme oxygenase-1 (HO-1) is an anti-oxidant enzyme normally upregulated in response to oxidant injury. Here we determined the role of HO-1 in podocyte apoptosis in glomeruli of streptozotocin-treated rats and in immortalized mouse podocytes cultured in media containing normal or high glucose. HO-1 expression, its activity, the ratio of Bax/Bcl-2 protein, and active caspase-3 fragments were all significantly higher in isolated glomeruli of diabetic rats and in high glucose–treated podocytes. These increases were inhibited by zinc protoporphyrin treatment of the rats or by HO-1 siRNA treatment of the podocytes in culture. The number of apoptotic cells was also significantly increased in the glomeruli of diabetic rats and in high glucose–treated podocytes. Inhibition of HO-1 accentuated the increase in apoptotic cells both in vivo and in vitro. Our findings suggest that HO-1 expression protects against podocyte apoptosis under diabetic conditions. Heme oxygenase-1 (HO-1) is an anti-oxidant enzyme normally upregulated in response to oxidant injury. Here we determined the role of HO-1 in podocyte apoptosis in glomeruli of streptozotocin-treated rats and in immortalized mouse podocytes cultured in media containing normal or high glucose. HO-1 expression, its activity, the ratio of Bax/Bcl-2 protein, and active caspase-3 fragments were all significantly higher in isolated glomeruli of diabetic rats and in high glucose–treated podocytes. These increases were inhibited by zinc protoporphyrin treatment of the rats or by HO-1 siRNA treatment of the podocytes in culture. The number of apoptotic cells was also significantly increased in the glomeruli of diabetic rats and in high glucose–treated podocytes. Inhibition of HO-1 accentuated the increase in apoptotic cells both in vivo and in vitro. Our findings suggest that HO-1 expression protects against podocyte apoptosis under diabetic conditions. Heme oxygenase (HO) is a microsomal rate-limiting enzyme involved in the degradation of heme to biliverdin, which is rapidly converted into bilirubin by biliverdin reductase.1.Nath K.A. Heme oxygenase-1: a provenance for cytoprotective pathways in the kidney and other tissues.Kidney Int. 2006; 70: 432-443Abstract Full Text Full Text PDF PubMed Scopus (259) Google Scholar,2.Kirkby K.A. Adin C.A. Products of heme oxygenase and their potential therapeutic applications.Am J Physiol Renal Physiol. 2006; 290: F563-F571Crossref PubMed Scopus (208) Google Scholar During this step, iron is released from the heme ring and carbon monoxide is generated.1.Nath K.A. Heme oxygenase-1: a provenance for cytoprotective pathways in the kidney and other tissues.Kidney Int. 2006; 70: 432-443Abstract Full Text Full Text PDF PubMed Scopus (259) Google Scholar To date, three distinct isoforms of HO have been identified: HO-1, an inducible form; HO-2, a constitutive form; and HO-3, probably a pseudogene.3.Abraham N.G. Drummond G.S. Lutton J.D. et al.The biological significance and physiological role of heme oxygenase.Cell Physiol Biochem. 1996; 6: 129-168Crossref Scopus (231) Google Scholar, 4.McCoubrey Jr, W.K. Maines M.D. The structure, organization and differential expression of the gene encoding rat heme oxygenase-2.Gene. 1994; 139: 155-161Crossref PubMed Scopus (108) Google Scholar, 5.Hayashi S. Omata Y. Sakamoto H. et al.Characterization of rat heme oxygenase-3 gene. Implication of processed pseudogenes derived from heme oxygenase-2 gene.Gene. 2004; 336: 241-250Crossref PubMed Scopus (180) Google Scholar Among these isoforms, HO-1 has been the most extensively studied HO isoenzyme and is known to be upregulated in the kidney under various conditions characterized by oxidative stress, including toxic nephropathy,6.Maines M.D. Veltman J.C. Phenylhydrazine-mediated induction of haem oxygenase activity in rat liver and kidney and development of hyperbilirubinaemia. Inhibition by zinc-protoporphyrin.Biochem J. 1984; 217: 409-417Crossref PubMed Scopus (33) Google Scholar,7.Agarwal A. Balla J. Alam J. et al.Induction of heme oxygenase in toxic renal injury: a protective role in cisplatin nephrotoxicity in the rat.Kidney Int. 1995; 48: 1298-1307Abstract Full Text PDF PubMed Scopus (231) Google Scholar ischemia–reperfusion injury,8.Maines M.D. Mayer R.D. Ewing J.F. et al.Induction of kidney heme oxygenase-1 (HSP32) mRNA and protein by ischemia/reperfusion: possible role of heme as both promotor of tissue damage and regulator of HSP32.J Pharmacol Exp Ther. 1993; 264: 457-462PubMed Google Scholar,9.Lemos F.B. Ijzermans J.N. Zondervan P.E. et al.Differential expression of heme oxygenase-1 and vascular endothelial growth factor in cadaveric and living donor kidneys after ischemia–reperfusion.J Am Soc Nephrol. 2003; 14: 3278-3287Crossref PubMed Scopus (65) Google Scholar contrast nephropathy,10.Goodman A.I. Olszanecki R. Yang L.M. et al.Heme oxygenase-1 protects against radiocontrast-induced acute kidney injury by regulating anti-apoptotic proteins.Kidney Int. 2007; 72: 945-953Abstract Full Text Full Text PDF PubMed Scopus (76) Google Scholar and acute transplant rejection.11.Avihingsanon Y. Ma N. Csizmadia E. et al.Expression of protective genes in human renal allografts: a regulatory response to injury associated with graft rejection.Transplantation. 2002; 73: 1079-1085Crossref PubMed Scopus (55) Google Scholar Oxidants generating molecules such as angiotensin II,12.Aizawa T. Ishizaka N. Taguchi J. et al.Heme oxygenase-1 is upregulated in the kidney of angiotensin II-induced hypertensive rats: possible role in renoprotection.Hypertension. 2000; 35: 800-806Crossref PubMed Scopus (136) Google Scholar,13.Haugen E.N. Croatt A.J. Nath K.A. Angiotensin II induces renal oxidant stress in vivo and heme oxygenase-1 in vivo and in vitro.Kidney Int. 2000; 58: 144-152Abstract Full Text Full Text PDF PubMed Scopus (152) Google Scholar heme,14.Kanakiriya S.K. Croatt A.J. Haggard J.J. et al.Heme: a novel inducer of MCP-1 through HO-dependent and HO-independent mechanisms.Am J Physiol Renal Physiol. 2003; 284: F546-F554Crossref PubMed Scopus (70) Google Scholar proinflammatory cytokine,15.Tetsuka T. Daphna-Iken D. Srivastava S.K. et al.Regulation of heme oxygenase mRNA in mesangial cells: prostaglandin E2 negatively modulates interleukin-1-induced heme oxygenase-1 mRNA.Biochem Biophys Res Commun. 1995; 212: 617-623Crossref PubMed Scopus (25) Google Scholar and transforming growth factor-β116.Hill-Kapturczak N. Truong L. Thamilselvan V. et al.Smad7-dependent regulation of heme oxygenase-1 by transforming growth factor-β in human renal epithelial cells.J Biol Chem. 2000; 275: 40904-40909Crossref PubMed Scopus (84) Google Scholar are also reported to induce HO-1. In addition, pharmacological inhibition of HO activity or deletion of the HO-1 gene worsened renal injury induced by toxic substances and ischemia–reperfusion,7.Agarwal A. Balla J. Alam J. et al.Induction of heme oxygenase in toxic renal injury: a protective role in cisplatin nephrotoxicity in the rat.Kidney Int. 1995; 48: 1298-1307Abstract Full Text PDF PubMed Scopus (231) Google Scholar, 17.Shimizu H. Takahashi T. Suzuki T. et al.Protective effect of heme oxygenase induction in ischemic acute renal failure.Crit Care Med. 2000; 28: 809-817Crossref PubMed Scopus (164) Google Scholar, 18.Shiraishi F. Curtis L.M. Truong L. et al.Heme oxygenase-1 gene ablation or expression modulates cisplatin-induced renal tubular apoptosis.Am J Physiol Renal Physiol. 2000; 278: F726-F736PubMed Google Scholar, 19.Pedraza-Chaverri J. Murali N.S. Croatt A.J. et al.Proteinuria as a determinant of renal expression of heme oxygenase-1: studies in models of glomerular and tubular proteinuria in the rat.Am J Physiol Renal Physiol. 2006; 290: F196-F204Crossref PubMed Scopus (23) Google Scholar whereas earlier induction of HO-1 protected against renal injury.18.Shiraishi F. Curtis L.M. Truong L. et al.Heme oxygenase-1 gene ablation or expression modulates cisplatin-induced renal tubular apoptosis.Am J Physiol Renal Physiol. 2000; 278: F726-F736PubMed Google Scholar, 20.Horikawa S. Yoneya R. Nagashima Y. et al.Prior induction of heme oxygenase-1 with glutathione depletor ameliorates the renal ischemia and reperfusion injury in the rat.FEBS Lett. 2002; 510: 221-224Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar, 21.Toda N. Takahashi T. Mizobuchi S. et al.Tin chloride pretreatment prevents renal injury in rats with ischemic acute renal failure.Crit Care Med. 2002; 30: 1512-1522Crossref PubMed Scopus (45) Google Scholar, 22.Matsumoto M. Makino Y. Tanaka T. et al.Induction of renoprotective gene expression by cobalt ameliorates ischemic injury of the kidney in rats.J Am Soc Nephrol. 2003; 14: 1825-1832Crossref PubMed Scopus (152) Google Scholar, 23.Rezzani R. Rodella L. Buffoli B. et al.Change in renal heme oxygenase expression in cyclosporine A-induced injury.J Histochem Cytochem. 2005; 53: 105-112Crossref PubMed Google Scholar On the basis of these findings, HO-1 is thought to function as an antioxidant, which is upregulated to alleviate the deleterious consequences of oxidant injury. The number of podocytes is decreased in the glomeruli of diabetic patients and animal models of diabetes (DM),24.Pagtalunan M.E. Miller P.L. Jumping-Eagle S. et al.Podocyte loss and progressive glomerular injury in type II diabetes.J Clin Invest. 1997; 99: 342-348Crossref PubMed Scopus (899) Google Scholar, 25.Steffes M.W. Schmidt D. McCrery R. et al.Glomerular cell number in normal subjects and in type 1 diabetic patients.Kidney Int. 2001; 59: 2104-2113Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar, 26.Susztak K. Raff A.C. Schiffer M. et al.Glucose-induced reactive oxygen species cause apoptosis of podocytes and podocyte depletion at the onset of diabetic nephropathy.Diabetes. 2006; 55: 225-233Crossref PubMed Scopus (888) Google Scholar and apoptosis is known to be involved in podocyte loss under DM conditions.26.Susztak K. Raff A.C. Schiffer M. et al.Glucose-induced reactive oxygen species cause apoptosis of podocytes and podocyte depletion at the onset of diabetic nephropathy.Diabetes. 2006; 55: 225-233Crossref PubMed Scopus (888) Google Scholar,27.Verzola D. Gandolfo M.T. Ferrario F. et al.Apoptosis in the kidneys of patients with type II diabetic nephropathy.Kidney Int. 2007; 72: 1262-1272Abstract Full Text Full Text PDF PubMed Scopus (145) Google Scholar Previous studies have demonstrated that high glucose (HG) per se and transforming growth factor-β1, two major mediators in the development and progression of DM nephropathy, increase reactive oxygen species production and induce apoptosis in cultured podocytes.26.Susztak K. Raff A.C. Schiffer M. et al.Glucose-induced reactive oxygen species cause apoptosis of podocytes and podocyte depletion at the onset of diabetic nephropathy.Diabetes. 2006; 55: 225-233Crossref PubMed Scopus (888) Google Scholar, 28.Schiffer M. Bitzer M. Roberts I.S. et al.Apoptosis in podocytes induced by TGF-β and Smad7.J Clin Invest. 2001; 108: 807-816Crossref PubMed Scopus (544) Google Scholar, 29.Lee H.B. Yu M.R. Yang Y. et al.Reactive oxygen species-regulated signaling pathways in diabetic nephropathy.J Am Soc Nephrol. 2003; 14: S241-S245Crossref PubMed Google Scholar Moreover, podocyte apoptosis under these conditions is prevented by the administration of antioxidants, suggesting that oxidative stress with increased reactive oxygen species is responsible for apoptosis of podocytes under DM conditions.26.Susztak K. Raff A.C. Schiffer M. et al.Glucose-induced reactive oxygen species cause apoptosis of podocytes and podocyte depletion at the onset of diabetic nephropathy.Diabetes. 2006; 55: 225-233Crossref PubMed Scopus (888) Google Scholar,30.Siu B. Saha J. Smoyer W.E. et al.Reduction in podocyte density as a pathologic feature in early diabetic nephropathy in rodents: prevention by lipoic acid treatment.BMC Nephrol. 2006; 7: 6Crossref PubMed Scopus (88) Google Scholar On the basis of these findings, an increase in HO-1 expression has been expected and been demonstrated in experimental DM glomeruli, mainly in mesangial cells and podocytes,31.Hayashi K. Haneda M. Koya D. et al.Enhancement of glomerular heme oxygenase-1 expression in diabetic rats.Diabetes Res Clin Pract. 2001; 52: 85-96Abstract Full Text Full Text PDF PubMed Scopus (64) Google Scholar,32.Koya D. Hayashi K. Kitada M. et al.Effects of antioxidants in diabetes-induced oxidative stress in the glomeruli of diabetic rats.J Am Soc Nephrol. 2003; 14: S250-S253Crossref PubMed Google Scholar but the functional significance of this increase has not yet been explored. In this study, we investigated the expression of HO-1 as well as podocyte apoptosis in experimental DM glomeruli and in HG-stimulated cells before and after inhibiting HO activity to elucidate the role of HO-1 in podocyte apoptosis under DM conditions. Body weight and the ratio of kidney weight to body weight were significantly different between DM (275±8 g, 1.12±0.11%) and control (C) rats (398±8 g, 0.69±0.04%) (P<0.05). However, the administration of zinc protoporphyrin (ZnPP) had no effect on either body weight or the ratio of kidney weight to body weight in C and DM rats. The mean blood glucose levels of C, C+ZnPP, DM, and DM+ZnPP were 97.2±7.7, 94.1±5.4, 497.2±14.8, and 488.7±17.2 mg per 100 ml, respectively (P<0.01). Compared with the C group (0.32±0.04 mg/day), 24-h urinary albumin excretion was significantly higher in the DM group (1.18±0.11 mg/day, P<0.05), and was further increased in DM rats by ZnPP treatment (1.59±0.19 mg/day, P<0.05) (Table 1). The administration of ZnPP also significantly aggravated the increase in 24-h urine albumin excretion in female DM rats (1.37±0.15 vs 0.85±0.11 mg/day, P<0.05), suggesting that the effect of ZnPP was not gender-specific.Table 1Animal dataControl (n=8)Control+ZnPP (n=8)DM (N=8)DM+ZnPP (n=8)Body weight (g)398±8405±7275±8*P<0.05 vs control group266±2*P<0.05 vs control groupKidney weight/body weight (%)0.69±0.040.75±0.051.12±0.11*P<0.05 vs control group1.20±0.09*P<0.05 vs control groupBlood glucose (mg per 100 ml)97.2±7.794.1±5.4497.2±14.8#P<0.01 vs control group488.7±17.2#P<0.01 vs control group24-h UAE (mg/day)0.32±0.040.29±0.081.18±0.11*P<0.05 vs control group1.59±0.19#P<0.01 vs control group, †P<0.05 vs DM group.BUN (mg per 100 ml)19.8±1.320.3±2.123.9±2.924.2±3.3Serum creatinine (mg per 100 ml)0.83±0.050.80±0.070.85±0.100.87±0.13Systolic blood pressure (mm Hg)111.1±9.8112.5±8.5115.3±11.8116.7±10.5BUN, blood urea nitrogen; DM, diabetes; UAE, urinary albumin excretion; ZnPP, zinc protoporphyrin.* P<0.05 vs control group# P<0.01 vs control group† P<0.05 vs DM group. Open table in a new tab BUN, blood urea nitrogen; DM, diabetes; UAE, urinary albumin excretion; ZnPP, zinc protoporphyrin. In contrast, the blood urea nitrogen and serum creatinine levels and systolic blood pressure were comparable among the four groups (Table 1). Double immunofluorescence staining for HO-1 and synaptopodin revealed that podocytes were the main cells responsible for the increase in HO-1 protein under DM conditions (Figure 1). Glomerular HO-1 protein expression assessed by western blot was significantly higher in DM compared with C rats (P<0.05), whereas ZnPP treatment significantly inhibited the increase in HO-1 protein expression in DM rats (P<0.05) (Figure 2). In contrast, ZnPP had little effect on glomerular HO-1 protein expression in C rats. To explore the possible mechanism how ZnPP inhibited HO-1 protein expression, we investigated the effect of ZnPP treatment on the expression of hypoxia-inducible factor-1 (HIF-1). As HO-1 is a downstream factor of HIF-1, we assumed that ZnPP may inhibit HIF-1 expression, leading to the decrease in HO-1 expression. Western blot for HIF-1 revealed that the increase in glomerular HIF-1 protein expression in DM rats was significantly abrogated by ZnPP treatment (P<0.05) (Figure 2a). In the experiments using DM rats treated with insulin, the increases in HO-1 and HIF-1 expression in 6-week DM glomeruli were significantly ameliorated by insulin treatment (P<0.05), suggesting that these changes in STZ-induced DM rats were not because of STZ per se (Figure 2b). Immunohistochemical staining for glomerular HO-1 confirmed the western blot findings, as glomerular HO-1 staining was significantly stronger in DM than in C rats, and ZnPP treatment attenuated the increase in HO-1 staining in DM glomeruli (Figure 3). The mean semiquantitative staining score for glomerular HO-1 was significantly higher in DM (75.7±9.0) compared with C rats (22.4±2.4) (P<0.01), and this increase was inhibited in DM glomeruli by the administration of ZnPP (37.8±5.4) (P<0.05). In addition to HO-1 protein expression, HO activity was also significantly increased in DM compared with C glomeruli (P<0.01), and ZnPP treatment significantly abrogated the increase in glomerular HO activity in DM rats (P<0.05) (Figure 4). Bax and active fragments of caspase-3 protein expression were significantly increased, whereas Bcl-2 protein expression was significantly decreased in DM compared with C glomeruli (P<0.05). The administration of ZnPP significantly aggravated the increases in the ratios of Bax/Bcl-2 (P<0.01) and active fragments of caspase-3 protein expression in DM glomeruli (P<0.05) (Figure 5). In addition to Bax, Bcl-2, and active fragments of caspase-3 protein expression, apoptosis in glomeruli was assessed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) assay. The number of glomerular apoptotic cells was significantly increased in DM compared with C and C+ZnPP rats (P<0.01), and was further increased in DM rats by ZnPP treatment (P<0.05) (Figure 6a). To identify podocyte apoptosis in glomeruli, double immunofluorescence staining with antibodies to synaptopodin, a podocyte marker, and active fragments of caspase-3 was performed. As seen in Figure 6b and c, C+ZnPP rats showed a faint staining of active fragments of caspase-3 with little colocalization with synaptopodin, while the colocalization signal was increased in DM glomeruli and was highest in the glomeruli of DM+ZnPP rats. Compared with C (170.0±4.2) and C+ZnPP rats (168.3±5.9), the number of podocyte tended to be decreased in DM rats (159.1±3.7), and the reduction in podocyte numbers was aggravated in DM rats treated with ZnPP (142.9±3.2) (P<0.05). Western blot analysis revealed that HO-1 small interfering RNA (siRNA) inhibited HO-1 protein expression in a dose-dependent manner (Figure 7). In contrast, HG significantly increased HO-1 and HIF-1 protein expression in cultured podocytes by 131 and 103%, respectively, compared with normal glucose (NG) cells (P<0.05), and the increase in HO-1 expression in HG-stimulated podocytes was significantly ameliorated by HO-1 siRNA treatment (Figure 8a).Figure 8A representative western blot of heme oxygenase (HO)-1, hypoxia-inducible factor-1 (HIF-1), and apoptosis-related molecules in cultured podocytes (representative of four blots). (a) There were significant increases in HO-1 and HIF-1 expression in HG-stimulated podocytes compared with NG and NG+M cells, and the increase in HO-1 protein expression in HG podocytes was significantly ameliorated by HO-1 siRNA treatment (20 nmol). (b) The ratios of Bax/Bcl-2 and active fragments of caspase-3 protein expression were significantly increased in HG-stimulated podocytes compared with normal glucose (NG) and NG+M groups, and these increases were accentuated in high glucose (HG) cells by HO-1 siRNA (20 nmol). *P<0.05 vs NG and NG+M groups, #P<0.01 vs HG group, †P<0.05 vs DM group. HG, high glucose; Ng, normal glucose; NG+M, normal glucose plus mannitol.View Large Image Figure ViewerDownload (PPT) In addition to HO-1 protein expression, HO activity was also significantly increased in HG-stimulated podocytes compared with podocytes exposed to NG medium (4.4±0.6 vs 21.8±3.1 pmol bilirubin per mg protein per h, P<0.01), and HO-1 siRNA treatment significantly attenuated the increase in HO activity in HG cells (3.1±0.5 pmol of bilirubin per mg protein per h) (P<0.005). The ratios of Bax/Bcl-2 and active fragments of caspase-3 protein expression were significantly increased in HG-stimulated podocytes compared with podocytes exposed to NG and NG+M media (P<0.05), and these increases were accentuated in HG cells by HO-1 siRNA (P<0.05). In contrast, there were no changes in Bax/Bcl-2 protein ratios and active fragments of caspase-3 protein expression in HO-1 siRNA-treated NG cells (Figure 8b). Hemin pretreatment significantly induced HO-1 protein expression in cultured podocytes exposed to NG and HG media (P<0.005). In addition, HO-1 induction by hemin before HG stimulation significantly attenuated the increases in Bax/Bcl-2 ratios and active fragment of caspase-3 protein expression in HG-stimulated podocytes (P<0.05) (Figure 9). Apoptotic cells assessed by Hoechst 33342 staining were significantly increased in HG-stimulated podocytes compared with NG cells (P<0.05), and apoptosis in HG podocytes was further increased by HO-1 siRNA (P<0.05). In contrast, hemin pretreatment significantly protected HG podocytes against apoptosis (P<0.05) (Figure 10). Earlier studies have demonstrated that HO-1 has a protective role in various kidney diseases in which oxidative stress is thought to have a role.6.Maines M.D. Veltman J.C. Phenylhydrazine-mediated induction of haem oxygenase activity in rat liver and kidney and development of hyperbilirubinaemia. Inhibition by zinc-protoporphyrin.Biochem J. 1984; 217: 409-417Crossref PubMed Scopus (33) Google Scholar, 7.Agarwal A. Balla J. Alam J. et al.Induction of heme oxygenase in toxic renal injury: a protective role in cisplatin nephrotoxicity in the rat.Kidney Int. 1995; 48: 1298-1307Abstract Full Text PDF PubMed Scopus (231) Google Scholar, 8.Maines M.D. Mayer R.D. Ewing J.F. et al.Induction of kidney heme oxygenase-1 (HSP32) mRNA and protein by ischemia/reperfusion: possible role of heme as both promotor of tissue damage and regulator of HSP32.J Pharmacol Exp Ther. 1993; 264: 457-462PubMed Google Scholar, 9.Lemos F.B. Ijzermans J.N. Zondervan P.E. et al.Differential expression of heme oxygenase-1 and vascular endothelial growth factor in cadaveric and living donor kidneys after ischemia–reperfusion.J Am Soc Nephrol. 2003; 14: 3278-3287Crossref PubMed Scopus (65) Google Scholar, 10.Goodman A.I. Olszanecki R. Yang L.M. et al.Heme oxygenase-1 protects against radiocontrast-induced acute kidney injury by regulating anti-apoptotic proteins.Kidney Int. 2007; 72: 945-953Abstract Full Text Full Text PDF PubMed Scopus (76) Google Scholar, 11.Avihingsanon Y. Ma N. Csizmadia E. et al.Expression of protective genes in human renal allografts: a regulatory response to injury associated with graft rejection.Transplantation. 2002; 73: 1079-1085Crossref PubMed Scopus (55) Google Scholar However, the functional significance of HO-1 in terms of podocyte apoptosis in DM nephropathy has not been elucidated. In this study, we demonstrate that HO-1 expression is increased in experimental DM glomeruli and in HG-stimulated podocytes. In addition, to our knowledge, this is the first study showing that podocyte apoptosis under DM conditions is partly protected by this increase in HO-1 expression. Heme oxygenase is an enzyme that cleaves the heme ring, thereby converting heme into biliverdin and releasing iron and carbon monoxide.1.Nath K.A. Heme oxygenase-1: a provenance for cytoprotective pathways in the kidney and other tissues.Kidney Int. 2006; 70: 432-443Abstract Full Text Full Text PDF PubMed Scopus (259) Google Scholar,2.Kirkby K.A. Adin C.A. Products of heme oxygenase and their potential therapeutic applications.Am J Physiol Renal Physiol. 2006; 290: F563-F571Crossref PubMed Scopus (208) Google Scholar By this process, HO regulates the cellular levels of heme, which is known to act as a pro-oxidant and to induce cell dysfunction. Therefore, when cellular heme levels are increased by denaturation or destabilization of heme protein during cell injury, HO increases to remove heme and replace it with bilirubin, a potent antioxidant.1.Nath K.A. Heme oxygenase-1: a provenance for cytoprotective pathways in the kidney and other tissues.Kidney Int. 2006; 70: 432-443Abstract Full Text Full Text PDF PubMed Scopus (259) Google Scholar,2.Kirkby K.A. Adin C.A. Products of heme oxygenase and their potential therapeutic applications.Am J Physiol Renal Physiol. 2006; 290: F563-F571Crossref PubMed Scopus (208) Google Scholar The cytoprotective role of HO was first suggested by Keyse and Tyrrell33.Keyse S.M. Tyrrell R.M. Heme oxygenase is the major 32-kDa stress protein induced in human skin fibroblasts by UVA radiation, hydrogen peroxide, and sodium arsenite.Proc Natl Acad Sci USA. 1989; 86: 99-103Crossref PubMed Scopus (1108) Google Scholar who identified HO as a sodium arsenite-induced 32-kDa protein in cultured human skin fibroblasts and found that the HO gene is also induced by ultraviolet A radiation, hydrogen peroxide, and heavy metal salts. On the basis of these findings, they suggested that the induction of HO may be a general response to oxidant stress and that HO constitutes an important cellular defense mechanism against oxidative damage. Following this report, numerous studies have investigated the expression and the functional role of HO, especially of HO-1, the isoform of HO induced under stressed conditions. In the kidney, HO-1 is weakly expressed in proximal and distal tubules, in Henle's loop, and in medullary collecting ducts under normal state, but its expression is increased under various conditions.1.Nath K.A. Heme oxygenase-1: a provenance for cytoprotective pathways in the kidney and other tissues.Kidney Int. 2006; 70: 432-443Abstract Full Text Full Text PDF PubMed Scopus (259) Google Scholar The functional role of increased HO-1 expression has been elucidated in toxic nephropathy and in renal ischemia–reperfusion injury,7.Agarwal A. Balla J. Alam J. et al.Induction of heme oxygenase in toxic renal injury: a protective role in cisplatin nephrotoxicity in the rat.Kidney Int. 1995; 48: 1298-1307Abstract Full Text PDF PubMed Scopus (231) Google Scholar, 17.Shimizu H. Takahashi T. Suzuki T. et al.Protective effect of heme oxygenase induction in ischemic acute renal failure.Crit Care Med. 2000; 28: 809-817Crossref PubMed Scopus (164) Google Scholar, 18.Shiraishi F. Curtis L.M. Truong L. et al.Heme oxygenase-1 gene ablation or expression modulates cisplatin-induced renal tubular apoptosis.Am J Physiol Renal Physiol. 2000; 278: F726-F736PubMed Google Scholar, 19.Pedraza-Chaverri J. Murali N.S. Croatt A.J. et al.Proteinuria as a determinant of renal expression of heme oxygenase-1: studies in models of glomerular and tubular proteinuria in the rat.Am J Physiol Renal Physiol. 2006; 290: F196-F204Crossref PubMed Scopus (23) Google Scholar, 23.Rezzani R. Rodella L. Buffoli B. et al.Change in renal heme oxygenase expression in cyclosporine A-induced injury.J Histochem Cytochem. 2005; 53: 105-112Crossref PubMed Google Scholar, 34.Barrera D. Maldonado P.D. Medina-Campos O.N. et al.HO-1 induction attenuates renal damage and oxidative stress induced by K2Cr2O7.Free Radic Biol Med. 2003; 34: 1390-1398Crossref PubMed Scopus (68) Google Scholar, 35.Yoneya R. Nagashima Y. Sakaki K. et al.Hemolysate pretreatment ameliorates ischemic acute renal injury in rats.Nephron. 2002; 92: 407-413Crossref PubMed Scopus (8) Google Scholar, 36.Matsumoto M. Makino Y. Tanaka T. et al.Induction of renoprotective gene expression by cobalt ameliorates ischemic injury of the kidney in rats.J Am Soc Nephrol. 2003; 14: 1825-1832Crossref PubMed Scopus (219) Google Scholar in which oxidative stress has a role in the pathogenesis. Upregulation of HO-1 reduced renal injury induced by cyclosporine23.Rezzani R. Rodella L. Buffoli B. et al.Change in renal heme oxygenase expression in cyclosporine A-induced injury.J Histochem Cytochem. 2005; 53: 105-112Crossref PubMed Google Scholar and potassium dichromate,34.Barrera D. Maldonado P.D. Medina-Campos O.N. et al.HO-1 induction attenuates renal damage and oxidative stress induced by K2Cr2O7.Free Radic Biol Med. 2003; 34: 1390-1398Crossref PubMed Scopus (68) Google Scholar and protected tubular cell injury induced by cisplatin,18.Shiraishi F. Curtis L.M. Truong L. et al.Heme oxygenase-1 gene ablation or expression modulates cisplatin-induced renal tubular apoptosis.Am J Physiol Renal Physiol. 2000; 278: F726-F736PubMed Google Scholar whereas inhibition of HO-1 expression exacerbated renal injury in maleate nephropathy19.Pedraza-Chaverri J. Murali N.S. Croatt A.J. et al.Proteinuria as a determinant of renal expression of heme oxygenase-1: studies in models of glomerular and tubular proteinuria in the rat.Am J Physiol Renal Physiol. 2006; 290: F196-F204Crossref PubMed Scopus (23) Google Scholar and worsened cisplatin-induced cell injury.7.Agarwal A. Balla J. Alam J. et al.Induction of heme oxygenase in toxic renal injury: a protective role in cisplatin nephrotoxicity in the rat.Kidney Int. 1995; 48: 1298-1307Abstract Full Text PDF PubMed Scopus (231) Google Scholar In addition, induction of HO-1 by hemolysate,35.Yoneya R. Nagashima Y. Sakaki K. et al.Hemolysate pretreatment ameliorates ischemic acute renal injury in rats.Nephron. 2002; 92: 407-413Crossref PubMed Scopus (8) Google Scholar tin chloride,21.Toda N. Takahashi T. Mizobuchi S. et al.Tin chloride pretreatment prevents renal injury in rats with ischemic acute renal failure.Crit Care Med. 2002; 30: 1512-1522Crossref PubMed Scopus (45) Google Scholar or cobalt36.Matsumoto M. Makino Y. Tanaka T. et al.Induction of renoprotective gene expression by cob
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