Ozone oxidative preconditioning is mediated by A1 adenosine receptors in a rat model of liver ischemia/ reperfusion

The liver is damaged by sustained ischemia in liver transplantation, and the reperfusion after ischemia results in further functional impairment. Ozone oxidative preconditioning (OzoneOP) protected the liver against ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the role of A₁ adenosine receptor on the protective actions conferred by OzoneOP in hepatic I/R. By using a specific agonist and antagonist of the A₁ subtype receptor (2-chloro N6 cyclopentyladenosine, CCPA and 8-cyclopentyl-1,3-dipropylxanthine, DPCPX respectively), we studied the role of A₁ receptor in the protective effects of OzoneOP on the liver damage, nitiric oxide (NO) generation, adenosine deaminase activity and preservation of the cellular redox balance. Immunohistochemical analysis of nuclear factor-kappa B (NF-κB), tumor necrosis factor alpha (TNF-α) and heat shock protein-70 (HSP-70) was performed. OzoneOP prevented and/or ameliorated ischemic damage. CCPA showed a similar effect to OzoneOP + I/R group. A₁AR antagonist DPCPX blocked the protective effect of OzoneOP. OzoneOP largely reduced the intensity of the p65 expression, diminished TNF-α production, and promoted a reduction in HSP-70 immunoreactivity. In summary, OzoneOP exerted protective effects against liver I/R injury through activation of A₁ adenosine receptors (A₁AR). Adenosine and ^.NO produced by OzoneOP may play a role in the pathways of cellular signalling which promote preservation of the cellular redox balance, mitochondrial function, glutathione pools as well as the regulation of NF-κB and HSP-70.     

Effects of Ozone Oxidative Preconditioning on Liver Regeneration after Partial Hepatectomy in Rats

ABSTRACT

Aim: Similar protective effect of ischemic and ozone oxidative preconditioning (OzoneOP) in hepatic ischemia–reperfusion (I/R) injury was demonstrated, providing evidences that both preconditioning settings shared similar biochemical mechanisms of protection. We investigated the effects of OzoneOP on liver regeneration after 70% partial hepatectomy (PHx) in rats. Methods: Rats were divided into three groups: PHx, I/R + PHx, and OzoneOP + I/R + PHx groups. Ozone (intraperitoneal, 1.2 mg/kg) was given to rats subjected to I/R and 70% hepatectomy daily five times before operation. At 24 hr and 48 hr after resection, samples were collected for the measurement of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6). Moreover, liver regeneration rate, proliferating cell nuclear antigen (PCNA) labeling index, mitotic index, and histopathological examination were evaluated. Results: OzoneOP reduced liver injury determined by liver histology and serum transaminases. There was a rise in serum TNF-α and IL-6 levels in the I/R + PHx group whereas OzoneOP significantly decreased the rise in the level of TNF-α but not IL-6 on the 24 hr and 48 hr of reperfusion. Moreover, liver regeneration in OzoneOP + PHx group, as assessed by the regenerated liver weight, mitotic, and PCNA-labeling index, was significantly improved when compared to I/R + PHx group. Conclusion: These results suggest that OzoneOP ameliorates the hepatic injury associated with I/R and has a stimulatory effect on liver cell regeneration that may make it valuable as a hepatoprotective modality.     

The protective effect of nesfatin-1 against renal ischemia–reperfusion injury in rats

Abstract

Introduction: The pathogenetic mechanisms underlying ischemia-reperfusion (I/R) injury involve oxidative stress, inflammation and apoptosis. Nesfatin-1, a novel peptide, has been reported to possess antioxidant, anti-inflammatory and anti-apoptic properties. The study was to examine the potential protective effects of nesfatin-1 on renal I/R injury. Materials and methods: I/R model was induced by placing a clamp across left renal artery for 45?min followed by 24?h reperfusion, along with a contralateral nephrectom. Twenty-four rats divided into three groups: sham-operated group, vehicle-treated I/R and nesfatin-1-treated I/R. Nesfatin-1 was intraperitoneally injected 30?min before renal ischemia. We harvested serum and kidneys at 24?h after reperfusion. Renal function and histological changes were assessed. Marker of oxidative stress and cells in kidney were also evaluated. Results: The animals with nesfatin-1 significantly improved renal functional and histologic lesions induced by I/R injury. The malondialdehyde (MDA) level decreased, whereas superoxide dismutase (SOD) and catalase (CAT) activities were significantly increased. Moreover, nesfatin-1-treated rats had a markedly decrease in apoptotic tubular cells, as well as a decrease in caspase-3 activity and an increase in the bcl-2/Bax ratio. Conclusions: This is the first evidence that nesfatin-1 treatment ameliorates acute renal I/R injury by suppressing oxidative stress and cell apoptosis. Therefore, it is promising as a potential therapeutic agent for renal IR injury.     

臭氧氧化预处理对大鼠肾缺血再灌注损伤的热休克蛋白表达的影响

目的 探讨臭氧氧化预处理通过诱导热休克蛋白70(HSP70)的合成,保护大鼠肾脏缺血再灌注损伤的作用与机制.方法 建立原位大鼠单侧肾缺血再灌注动物模型,I/R前15 d经直肠吹人氧气和臭氧的混合气体5.0～5.5 ml(臭氧浓度50 mg/L,1 mg/kg体重,每日1次).全自动生化分析仪检测尿素氮(BUN)、肌酐(Cr),比色法测定血清的脂质过氧化产物丙二醛(MDA)、超氧化物歧化酶(SOD).Western blot检测HSP70蛋白的含量;逆转录-聚合酶链反应(RT-PCR)方法检测HSPT0的表达.结果 肾缺血再灌注24 h后,血清中BUN、Cr、MDA明显增高,肾组织内HSP70表达明显增强(P＜0.05),经臭氧氧化预处理后,血清中的BUN、Cr、MDA均降低,SOD升高;HSP70表达升高更加明显(P＜0.05).结论 臭氧氧化预处理可以诱导大鼠肾缺血再灌注组织中HSP70表达,减轻大鼠肾脏缺血再灌注损伤.     

臭氧氧化预处理在肾缺血再灌注损伤中对内皮型一氧化氮合酶表达的影响

目的 观察臭氧氧化预处理对大鼠急性肾缺血再灌注损伤的保护作用及其对内皮型一氧化氮合酶（eNOS）表达的影响.方法 38只8周龄雄性Wistar大鼠按随机数字表法随机分为4组.（1）假手术组（n＝8）：仅切除右肾;（2）缺血再灌注组（n＝10）：切除右肾、游离左肾后夹闭左肾动、静脉45 min再开通;（3）臭氧氧化预处理组（n＝10）：与缺血再灌注组建模方法一致,但在建模前15 d起每天1次经直肠灌注法吹入氧气和臭氧的混合气体5~5.5 mL;（4）氧气预处理组（n＝10）：与臭氧氧化预处理组建模方法一致,但经直肠仅吹入氧气（13 mg/kg）.建模后24 h检测各组大鼠血清肌酐、血尿素氮和血清一氧化氮浓度;48 h后采用免疫组织化学法和逆转录PCR法检测各组大鼠肾组织eNOS表达;蛋白质印迹法检测肾组织胞浆eNOS含量.结果 建模后24 h,缺血再灌注组大鼠血清肌酐为（117±20）μmol/L,血尿素氮为（32.8±7.6）mmol/L,血清一氧化氮为（58±12）μmol/L,均高于假手术组,差异有统计学意义（均P〈0.05）.臭氧氧化预处理组血清肌酐为（63±16）μmol/L,血尿素氮为（17.4±5.2）mmol/L,低于缺血再灌注组和氧气预处理组,差异有统计学意义（均P〈0.05）;血清一氧化氮为（84±14）μmol/L,均高于缺血再灌注组和氧气预处理组,差异有统计学意义（均P〈0.05）.臭氧氧化预处理组肾组织学Paller评分（41±6）低于缺血再灌注组（62±9）,eNOS灰度值（163±15）高于缺血再灌注组（126±18）,差异有统计学意义（均P〈0.05）.假手术组大鼠肾组织内有微量eNOS mRNA表达,缺血再灌注组、臭氧氧化预处理组和氧气预处理组eNOS mRNA表达增强,均高于假手术组（均P〈0.05）,臭氧氧化预处理组eNOS mRNA表达高于缺血再灌注组和氧气预处理组（均P〈0.05）.假手术组无明显eNOS蛋白表达,缺血再灌注组、臭氧氧化预处理组和氧气预处理组eNOS蛋白表达增强,均高于假手术组（均P〈0.05）,臭氧氧化预处理组eNOS蛋白表达高于缺血再灌注组和氧气预处理组（均P〈0.05）.结论 臭氧氧化预处理对大鼠肾缺血再灌注损伤有保护作用,作用机制可能与其诱导eNOS合成增多、一氧化氮产生增多有关.     

臭氧氧化预处理对大鼠肾缺血再灌注损伤的热休克蛋白表达的影响

目的 探讨臭氧氧化预处理通过诱导热休克蛋白70(HSP70)的合成,保护大鼠肾脏缺血再灌注损伤的作用与机制.方法 建立原位大鼠单侧肾缺血再灌注动物模型,I/R前15 d经直肠吹入氧气和臭氧的混合气体5.0～5.5 ml(臭氧浓度50 mg/L,1 mg/kg体蕈,每日 1次).全自动生化分析仪检测尿素氮(BUN)、肌酐(Cr),比色法测定血清的脂质过氧化产物丙二醛(MDA)、超氧化物歧化酶(SOD).Western blot检测HSP70蛋白的含量;逆转录聚合酶链反应(RT-PCR)方法检测HSP70的表达.结果 肾缺血再灌注24 h后,血清中BUN、Cr、MDA明显增高,肾组织内HSPT0表达明显增强(P<0.05),经臭氧氧化预处理后,血清中的BUN、Cr、MDA均降低,SOD升高;HSP70表达升高更加明显(P<0.05).结论 臭氧氧化预处理可以诱导大鼠肾缺血再灌注组织中HSP70表达,减轻大鼠肾脏缺血再灌注损伤.     

Ozone oxidative preconditioning is mediated by A1 adenosine receptors in a rat model of liver ischemia/ reperfusion.

The liver is damaged by sustained ischemia in liver transplantation, and the reperfusion after ischemia results in further functional impairment. Ozone oxidative preconditioning (OzoneOP) protected the liver against ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the role of A(1) adenosine receptor on the protective actions conferred by OzoneOP in hepatic I/R. By using a specific agonist and antagonist of the A(1) subtype receptor (2-chloro N6 cyclopentyladenosine, CCPA and 8-cyclopentyl-1,3-dipropylxanthine, DPCPX respectively), we studied the role of A(1) receptor in the protective effects of OzoneOP on the liver damage, nitiric oxide (NO) generation, adenosine deaminase activity and preservation of the cellular redox balance. Immunohistochemical analysis of nuclear factor-kappa B (NF-kappaB), tumor necrosis factor alpha (TNF-alpha) and heat shock protein-70 (HSP-70) was performed. OzoneOP prevented and/or ameliorated ischemic damage. CCPA showed a similar effect to OzoneOP + I/R group. A(1)AR antagonist DPCPX blocked the protective effect of OzoneOP. OzoneOP largely reduced the intensity of the p65 expression, diminished TNF-alpha production, and promoted a reduction in HSP-70 immunoreactivity. In summary, OzoneOP exerted protective effects against liver I/R injury through activation of A(1) adenosine receptors (A(1)AR). Adenosine and (.)NO produced by OzoneOP may play a role in the pathways of cellular signalling which promote preservation of the cellular redox balance, mitochondrial function, glutathione pools as well as the regulation of NF-kappaB and HSP-70.     

MicroRNA-24 Antagonism Prevents Renal Ischemia Reperfusion Injury

Ischemia-reperfusion (I/R) injury of the kidney is a major cause of AKI. MicroRNAs (miRs) are powerful regulators of various diseases. We investigated the role of apoptosis-associated miR-24 in renal I/R injury. miR-24 was upregulated in the kidney after I/R injury of mice and in patients after kidney transplantation. Cell-sorting experiments revealed a specific miR-24 enrichment in renal endothelial and tubular epithelial cells after I/R induction. In vitro, anoxia/hypoxia induced an enrichment of miR-24 in endothelial and tubular epithelial cells. Transient overexpression of miR-24 alone induced apoptosis and altered functional parameters in these cells, whereas silencing of miR-24 ameliorated apoptotic responses and rescued functional parameters in hypoxic conditions. miR-24 effects were mediated through regulation of H2A histone family, member X, and heme oxygenase 1, which were experimentally validated as direct miR-24 targets through luciferase reporter assays. In vitro, adenoviral overexpression of miR-24 targets lacking miR-24 binding sites along with miR-24 precursors rescued various functional parameters in endothelial and tubular epithelial cells. In vivo, silencing of miR-24 in mice before I/R injury resulted in a significant improvement in survival and kidney function, a reduction of apoptosis, improved histologic tubular epithelial injury, and less infiltration of inflammatory cells. miR-24 also regulated heme oxygenase 1 and H2A histone family, member X, in vivo. Overall, these results indicate miR-24 promotes renal ischemic injury by stimulating apoptosis in endothelial and tubular epithelial cell. Therefore, miR-24 inhibition may be a promising future therapeutic option in the treatment of patients with ischemic AKI.     

Rabbit anti‐rat thymocyte immunoglobulin preserves renal function during ischemia/reperfusion injury in rat kidney transplantation

Ischemia/reperfusion (I/R) injury is an important cause of renal graft dysfunction in humans. Increases in cold and warm ischemia times lead to a higher risk of early post‐transplant complications including delayed graft function and acute rejection. Moreover, prolonged cold ischemia is a predictor of long‐term kidney graft loss. The protective effect of rabbit anti‐rat thymocyte immunoglobulin (rATG) was evaluated in a rat model of I/R injury following syngeneic kidney transplantation. Serum creatinine concentration was evaluated at 16 h and 24 h post‐transplant. Animals were sacrificed 24 h post‐transplant for evaluation of histology, infiltrating leukocytes, nitrotyrosine staining, and apoptosis. rATG was effective in preventing renal function impairment, tissue damage and tubular apoptosis associated with I/R only when was given 2 h before transplantation but not at the time of reperfusion. Pretransplant rATG treatment of recipient animals effectively reduced the amount of macrophages, CD4⁺, CD8⁺ T cells and LFA‐1⁺ cells infiltrating renal graft subjected to cold ischemia as well as granzyme‐B expression within ischemic kidney. On the other hand, granulocyte infiltration and oxidative stress were not modified by rATG. If these results will be translated into the clinical setting, pretransplant administration of Thymoglobuline^® could offer the additional advantage over peri‐transplant administration of limiting I/R‐mediated kidney graft damage.     

Role of protein synthesis in the protection conferred by ozone-oxidative-preconditioning in hepatic ischaemia/reperfusion

The liver is damaged by sustained ischaemia during liver transplantation, and the reperfusion after ischaemia results in further functional impairment. Ozone oxidative preconditioning (OzoneOP) protected the liver against ischaemia/reperfusion (I/R) injury through different mechanisms. The aim of this study was to investigate the influence of the inhibition of protein synthesis on the protective actions conferred by OzoneOP in hepatic I/R. Rats were treated with cycloheximide (CHX) in order to promote protein synthesis inhibition after OzoneOP treatment. Plasma transaminases, malondialdehyde and 4-hydroxyalkenals and morphological characteristics were measured as an index of hepatocellular damage; Cu/Zn-superoxide dismutase (SOD), Mn-SOD, catalase, total hydroperoxides and glutathione levels as markers of endogenous antioxidant system. OzoneOP increased Mn-SOD isoform and ameliorated mitochondrial damage. CHX abrogated the protection conferred by OzonoOP and decreased Mn-SOD activity. Cellular redox balance disappeared when CHX was introduced. Protein synthesis is involved in the protective mechanisms mediated by OzoneOP. Ozone treatment preserved mitochondrial functions and cellular redox balance.     

Penehyclidine hydrochloride ameliorates renal ischemia–reperfusion injury in rats

Background

Renal ischemia–reperfusion (I/R) injury is a major cause of acute kidney failure by mechanisms that involve oxidative stress, inflammation, and apoptosis. Penehyclidine hydrochloride (PHC), a selective anticholinergic agent, possesses anti-inflammatory, antioxidative stress, and antiapoptotic effects. Therefore, we investigated the ability of PHC to ameliorate renal I/R injury in Sprague–Dawley rats.

Materials and methods

Rats were randomly assigned to three groups (35 rats per group): sham operated, saline-treated I/R, and PHC-treated I/R. After removing the right kidney, renal I/R injury was induced by clamping the left renal artery for 45 min followed by reperfusion. The rats were administered PHC (0.45 mg/kg, intravenously) or saline 30 min before renal ischemia. The blood and kidneys were harvested at 1, 3, 6, 12, or 24 h after reperfusion. Renal function and histologic changes were assessed. Markers of oxidative stress, inflammation, and apoptosis in the kidneys were also measured.

Results

PHC treatment significantly attenuated renal dysfunction and histologic damage caused by I/R injury. The treatment also decreased malondialdehyde level and attenuated the reduction in superoxide dismutase activity in the kidney. Moreover, the levels of activated p38 mitogen-activated protein kinase, nuclear factor kappa B, and caspase 3 were lower in the PHC-treated animals.

Conclusions

PHC protected rat kidneys from I/R injury by attenuating oxidative stress, inflammatory response, and apoptosis. Thus, PHC may represent a novel practical strategy for the treatment of renal I/R injury.     

Protective effects of thymoquinone against apoptosis and oxidative stress by arsenic in rat kidney

We aimed to investigate the protective role of thymoquinone (TQ) by targeting its antiapoptotic and antioxidant properties against kidney damage induced by arsenic in rats. We have used the 24 male Sprague-Dawley rats. Rats were divided into three groups. Physiological serum in 10?mL/kg dose as intragastric was given to the control group. Sodium arsenite (10?mg/kg, intragastric by gavage for fifteen days) was given to the arsenic group. Sodium arsenite (10?mg/kg, intragastric by gavage for fifteen days) and TQ (10?mg/kg, intragastric by gavage for 15 days) was given to the arsenic?+?TQ group. After 15 days, the animals’ kidneys were taken theirs, then we have performed histological and apoptotic assessment. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) enzyme activities and malondialdehyde (MDA) levels have examined as the oxidative stress parameters. We have determined the levels of arsenic. Increased renal injury and apoptotic cells have been detected in the arsenic group. Degenerative changes in the arsenic?+?TQ group were diminished. Although the MDA levels were augmented in the arsenic group, SOD, CAT and GSH-Px enzyme activities were lessened than the other groups. Our findings suggest that TQ may impede the oxidative stress, the cells have been damaged and also the generation of apoptotic cells arisen from arsenic. TQ plays a protective role against arsenic-induced toxicity in kidney and may potentially be used as a remedial agent.     

Protection of androgen-dependent human prostate cancer cells from oxidative stress-induced DNA damage by overexpression of clusterin and its modulation by androgen

BACKGROUND: Recent studies reported that oxidative stress is one of the major factors associated with the progression of prostate cancer through the accumulation of DNA damage. In the present study, we investigated the effect of oxidative stress on cell injury using androgen-dependent human prostate cancer LNCaP cells overexpressing clusterin, which has been shown to play crucial roles in the acquisition of resistance to several apoptotic stimuli. METHODS: We introduced clusterin cDNA into LNCaP cells which do not express a detectable level of clusterin expression, and generated a clusterin-overexpressing cell line (LNCaP/Cl) and a control vector only-transfected cell line (LNCaP/Co). The effects of hydrogen peroxide (H2O2) treatment on the LNCaP sublines with and without the addition of dihydrotestosterone (DHT) were analyzed using the in vitro mitogenic assay and lipid peroxidation assay, and morphological changes in the LNCaP sublines after H2O2 treatment were examined by staining with Hoechst 33258. The degrees of DNA damage induced by H2O2 into the LNCaP sublines were evaluated by the measurement of 8-hydroxy-2'-deoxyguanosine (8-OHdG) level. RESULTS: H2O2-induced apoptosis in LNCaP/Cl was significantly suppressed compared with that in LNCaP/Co through the inhibition of membrane damage; however, the measurement of 8-OHdG level demonstrated that DNA damage was more intensively accumulated in LNCaP/Cl cells than LNCaP/Co cells. Furthermore, DHT suppressed the incidence of apoptotic cell death and enhanced the formation of 8-OHdG in both LNCaP/Cl and LNCaP/Co cells after H2O2 treatment in a dose-dependent manner. CONCLUSIONS: These findings suggest that clusterin may contribute to conferring resistance to oxidative stress-mediated cellular injury on prostate cancer cells, especially in the presence of androgen.     

NAC对缺氧复氧后肾小管上皮细胞凋亡的干预作用

目的：研究缺氧复氧后肾小管上皮细胞凋亡的表达及N-乙酰半胱胺酸（NAC）对其的影响。方法：选用人肾小管上皮细胞（HK2）建立缺氧复氧损伤模型,设正常对照组、单纯缺氧复氧组、不同浓度（1mmol／L、5mmol／L、10mmol／L）NAC干预组。流式细胞术检测细胞内氧化应激水平与细胞凋亡表达。结果：缺氧复氧后HK2细胞内氧化应激水平提高,HK2细胞凋亡细胞和死亡细胞数量增多,且随缺氧时间的延长,细胞内氧化应激水平逐渐升高,凋亡细胞和死亡细胞数量逐渐增多;NAC呈剂量关系抑制细胞内氧化应激水平,同时呈剂量关系减少凋亡细胞和坏死细胞的数量。结论：缺氧复氧诱导细胞内氧化应激的产生,诱导HK2细胞凋亡和死亡;NAC可以通过抑制细胞内氧化应激减少细胞和坏死细胞的数量。     

5-Aminoisoquinolinone reduces renal injury and dysfunction caused by experimental ischemia/reperfusion

BACKGROUND: Poly (ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the development of ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the effects of a water-soluble and potent PARP inhibitor, 5-aminoisoquinolinone (5-AIQ), on the renal injury and dysfunction caused by oxidative stress of the rat kidney in vitro and in vivo. METHODS: Primary cultures of rat renal proximal tubular cells, subjected to oxidative stress caused by hydrogen peroxide (H2O2), were incubated with increasing concentrations of 5-AIQ (0.01 to 1 mmol/L) after which PARP activation, cellular injury, and cell death were measured. In in vivo experiments, anesthetized male Wistar rats were subjected to renal bilateral ischemia (45 minutes) followed by reperfusion (6 hours) in the absence or presence of 5-AIQ (0.3 mg/kg) after which renal dysfunction, injury and PARP activation were assessed. RESULTS: Incubation of proximal tubular cells with H2O2 caused a substantial increase in PARP activity, cellular injury, and cell death, which were all significantly reduced in a concentration-dependent by 5-AIQ [inhibitory concentration 50 (IC50) approximately 0.03 mmol/L]. In vivo, renal I/R resulted in renal dysfunction, injury, and PARP activation, primarily in the proximal tubules of the kidney. Administration of 5-AIQ significantly reduced the biochemical and histologic signs of renal dysfunction and injury and markedly reduced PARP activation caused by I/R. CONCLUSION: This study demonstrates that 5-AIQ is a potent, water soluble inhibitor of PARP activity, which can significantly reduce (1) cellular injury and death caused to primary cultures of rat proximal tubular cells by oxidative stress in vitro, and (2) renal injury and dysfunction caused by I/R of the kidney of the rat in vivo.     

Autophagosome protects proximal tubular cells from aldosterone-induced senescence through improving oxidative stress

Aldosterone exerts an enormous function on proximal tubular cells (PTC) senescence, which is a common pathomechanism contributing to renal dysfunction. Numerous studies have shown that oxidative stress is deeply involved in the pathophysiologic processes of chronic kidney diseases. The study aims to investigate whether autophagy could regulate the process of senescence through oxidative stress in PTC both in vivo and ex vivo. Our results suggested that aldosterone treatment increased the senescence and oxidative stress as evidenced by increased percent of SA-β-Gal positive cells, reactive oxygen species level, expression of NADPH oxidase 4 (NOX4) rather than NOX2, and the up-regulation of p21 in cultured PTC. Furthermore, the alternation of the expression of p62 and LC3-II/LC3-I demonstrated that aldosterone treatment remarkably influenced autophagic flux. NOX4 siRNA treatment or autophagy induction with rapamycin reduced the oxidative stress and senescence in aldosterone-induced PTC. On the contrary, inhibition of autophagy with chloroquine worsened these changes. Similar results were further confirmed in vivo. Our results suggested that autophagy may become a realistic therapeutic strategy against aldosterone-induced PTC injury via improving oxidative stress.     

Disruption of Renal Tubular Mitochondrial Quality Control by Myo-Inositol Oxygenase in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is associated with oxidative stress and mitochondrial injury. Myo-inositol oxygenase (MIOX), a tubular-specific enzyme, modulates redox imbalance and apoptosis in tubular cells in diabetes, but these mechanisms remain unclear. We investigated the role of MIOX in perturbation of mitochondrial quality control, including mitochondrial dynamics and autophagy/mitophagy, under high-glucose (HG) ambience or a diabetic state. HK-2 or LLC-PK1 cells subjected to HG exhibited an upregulation of MIOX accompanied by mitochondrial fragmentation and depolarization, inhibition of autophagy/mitophagy, and altered expression of mitochondrial dynamic and mitophagic proteins. Furthermore, dysfunctional mitochondria accumulated in the cytoplasm, which coincided with increased reactive oxygen species generation, Bax activation, cytochrome C release, and apoptosis. Overexpression of MIOX in LLC-PK1 cells enhanced the effects of HG, whereas MIOX siRNA or d-glucarate, an inhibitor of MIOX, partially reversed these perturbations. Moreover, decreasing the expression of MIOX under HG ambience increased PTEN-induced putative kinase 1 expression and the dependent mitofusin-2–Parkin interaction. In tubules of diabetic mice, increased MIOX expression and mitochondrial fragmentation and defective autophagy were observed. Dietary supplementation of d-glucarate in diabetic mice decreased MIOX expression, attenuated tubular damage, and improved renal functions. Notably, d-glucarate administration also partially attenuated mitochondrial fragmentation, oxidative stress, and apoptosis and restored autophagy/mitophagy in the tubular cells of these mice. These results suggest a novel mechanism linking MIOX to impaired mitochondrial quality control during tubular injury in the pathogenesis of DKD and suggest d-glucarate as a potential therapeutic agent for the amelioration of DKD.     

Renal tubular epithelial cells injury induced by mannitol and its potential mechanism

Administration of mannitol with high dose could induce extensive isometric renal proximal tubular vacuolization and acute renal failure in clinic. We previously demonstrated that mannitol-induced human kidney tubular epithelial cell (HK-2) injury. The objective of our present work was to further study the cytotoxicity of mannitol in HK-2 cells and its potential mechanism. Cell viability was assessed by an MTT method. Cell morphological changes were observed. Furthermore, levels of malondialdehyde (MDA) and glutathione (GSH) were measured. Flow cytometry was performed to determine cell apoptosis by using Annexin V-FITC and PI. In addition, the F-actin of cells was labeled by FITC-Phalloidin for observation of cytoskeleton. The MTT assay displayed that the cell viability decreased significantly in a dose- and time-dependent manner. The morphological changes were observed, including cell membrane rapture and cell detachment. The GSH concentration in HK-2 cells decreased dramatically in mannitol treatment group, while MDA content increased significantly. The results of flow cytometry indicated that apoptotic percentages of HK-2 cells increased in 250?mmol/L mannitol treatment group. After treatment with 250?mmol/L mannitol for 48?h, HK-2 cells showed disorganization of cytoskeleton and even exhibited a totally destroyed cytoskeleton. Therefore, high dose of mannitol has a toxic effect on renal tubular epithelial cells, which might be attributed to oxidative stress, destroyed cellular cytoskeleton and subsequent cell apoptosis.     

The Protective Effects of Ascorbic Acid against Renal Ischemia-Reperfusion Injury in Male Rats

There is increasing evidence to suggest that toxic oxygen radicals play an essential role in the pathogenesis of ischemia/reperfusion (I/R) injury in the kidney. This study was designed to investigate the effects of ascorbic acid (AA) in I/R-induced renal injury in rats. Thirty two male Sprague-Dawley rats were divided equally into four groups: group 1 (control; dissection of the right renal pedicle without nephrectomy), group 2 (sham operated; unilateral nephrectomy), group 3 (I/R; unilateral nephrectomy?+?I/R); and group 4 (AA+I/R; unilateral nephrectomy and I/R treated with ascorbic acid, 250mg kg^?1 i.p., for one hour prior to ischemia). On the 15th day following nephrectomy, groups 3 and 4 were subjected to 45 min of renal pedicle occlusion followed by 3 h of reperfusion. At the end of the treatment period, kidney samples were taken for histological examination or determination of the renal malondialdehyde (MDA) and glutathione (GSH) levels. Serum creatinine, blood urea nitrogen (BUN), and lactate dehydrogenase (LDH) concentrations were measured for the evaluation of renal function. I/R caused a significant decrease in GSH level, which was accompanied with a significant increase in MDA level of kidney tissues. Similarly, serum BUN and creatinine levels, as well as LDH, were elevated in the I/R group as compared to the control group. In group four, AA treatment reversed all the changes in these biochemical indices, as well as histopathological alterations normally induced by I/R. The findings imply that reactive oxygen species play a causal role in I/R-induced renal injury, and that AA exerts renoprotective effects, probably by radical scavenging and antioxidant activities.