Increased superoxide formation induced by irradiation preconditioning triggers kidney resistance to ischemia-reperfusion injury in mice

Hsp27 over expression protect against cadmium induced nephrotoxicity in Drosophila melanogaster

Cadmium (Cd) exposure to the animals including humans is reported as nephrotoxic compounds i.e., disturbing redox status (increase oxidative stress), mitochondrial dysfunction, renal cell death and altered transporters in the renal system. Hsp27 (a small heat shock protein) has been shown as one of the modulators in the renal dysfunction and increased against the Cd induced toxicity. However, no studies are reported on the genetic modulation of stress protein against the Cd-induced nephrotoxicity. The current study aimed to examine the protective role of hsp27 overexpression against the Cd-induced nephrotoxicity using Drosophila melanogaster as an animal model. D. melanogaster renal system includes nephrocytes and Malpighian tubules (MTs) that show the functional similarity with mammalian kidney nephron. Overexpression of the hsp27 was found to reduce the Cd induced oxidative stress, rescue cell death in MTs of Cd exposed D. melanogaster larvae. The rescued GSH level, NADPH level and glucose 6 phosphate dehydrogenase (G6PD) activity were also observed in the MTs of the Cd exposed organism. Function (efflux activity and fluid secretion rate) of the MTs was restored in Cd exposed hsp27 overexpressed larvae. Further, results were confirmed by restored brush border microvilli density and reduced uric acid level. Tissue specific knockdown of hsp27 developed Cd like phenotypes in MTs and the phenotypes enhanced in Cd exposed condition. The present study clearly shows the role of hsp27 overexpression in restoration of the MTs function and protection against the Cd induced renal toxicity.

Immunotoxic effects of exposure to the antifouling copper(I) biocide on target and nontarget bivalve species: a comparative in vitro study between Mytilus galloprovincialis and Ruditapes philippinarum

Edible bivalves constitute an important bioresource from an economic point of view, and studies on their immune responses to environmental pollutants are crucial for both the preservation of biodiversity and economic reasons. The worldwide diffusion of copper(I)-based antifouling paints has increased copper leaching into coastal environments and its potential impact on both target and nontarget organisms. In this study, immunotoxicity assays were carried out with short-term (60 min) cultures of hemocytes from the bivalves Mytilus galloprovincialis-a mussel dominant in the macrofouling community-and Ruditapes philippinarum-a clam dominant in the soft-sediment community-exposed to CuCl to compare the toxic effects on their immune responses. The LC50 values were similar, 40 μM (3.94 mg L-1) for the mussel and 44 μM (4.33 mg L-1) for the clam. In both species, apoptosis occurred after exposure to 1 µM (98.9 μg L-1) CuCl, the concentration able to significantly increase the intracellular Ca2+ content. Biomarkers of cell morphology and motility revealed microfilament disruption, a significant decrease in yeast phagocytosis and lysosome hydrolase (β-glucuronidase) inhibition beginning from 0.5 µM (49.5 μg L-1) CuCl in both the mussel and clam. The same concentration of CuCl affected biomarkers of oxidative stress, as a significant decrease in reduced glutathione content in the cytoplasm and inhibition of mitochondrial cytochrome-c oxidase (COX) were detected in both species. Comparison of the biomarkers showed that clam is more sensitive than the mussel regarding alterations to the lysosomal membrane and reactive oxygen species (ROS) production, which supports the potential harmful effects of antifouling biocides on the survival of nontarget pivotal species in the coastal community.

Radiotherapy Advances in Renal Disease-Focus on Renal Ischemic Preconditioning

Ionizing irradiation is widely applied as a fundamental therapeutic treatment in several diseases. Acute kidney injury (AKI) represents a global public health problem with major morbidity and mortality. Renal ischemia/reperfusion (I/R) is the main cause of AKI. I/R injury occurs when blood flow to the kidney is transiently interrupted and then restored. Such an ischemic insult significantly impairs renal function in the short and long terms. Renal ischemic preconditioning (IPC) corresponds to the maneuvers intended to prevent or attenuate the ischemic damage. In murine models, irradiation-induced preconditioning (IP) renders the renal parenchyma resistant to subsequent damage by activating defense pathways involved in oxidative stress, angiogenesis, and inflammation. Before envisioning translational applications in patients, safe irradiation modalities, including timing, dosage, and fractionation, need to be defined.

Repeated Administration of Cisplatin Transforms Kidney Fibroblasts through G2/M Arrest and Cellular Senescence

Cisplatin is a potent chemotherapeutic used for the treatment of many types of cancer, but it has nephrotoxic side effects leading to acute kidney injury and subsequently chronic kidney disease (CKD). Previous work has focused on acute kidney tubular injury induced by cisplatin, whereas the chronic sequelae post-injury has not been well-explored. In the present study, we established a kidney fibroblast model of CKD induced by repeated administration of cisplatin (RAC) as a clinically relevant model. In NRK-49F rat kidney fibroblasts, RAC upregulated α-smooth muscle actin (α-SMA) and fibronectin proteins, suggesting that RAC induces kidney fibroblast-to-myofibroblast transformation. RAC also enhanced cell size, including the cell attachment surface area, nuclear area, and cell volume. Furthermore, RAC induced p21 expression and senescence-associated β-galactosidase activity, suggesting that kidney fibroblasts exposed to RAC develop a senescent phenotype. Inhibition of p21 reduced cellular senescence, hypertrophy, and myofibroblast transformation induced by RAC. Intriguingly, after RAC, kidney fibroblasts were arrested at the G2/M phase. Repeated treatment with paclitaxel as an inducer of G2/M arrest upregulated p21, α-SMA, and fibronectin in the kidney fibroblasts. Taken together, these data suggest that RAC transforms kidney fibroblasts into myofibroblasts through G2/M arrest and cellular senescence.

Kidney-targeted irradiation triggers renal ischaemic preconditioning in mice

Renal ischemia/reperfusion (I/R) causes acute kidney injury (AKI). Ischemic preconditioning (IPC) attenuates I/R-associated AKI. Whole-body irradiation induces renal IPC in mice. Still, the mechanisms remain largely unknown. Furthermore, the impact of kidney-centered irradiation on renal resistance against I/R has not been studied. Renal irradiation (8.5Gy) was done in male 8-12-week-old C57bl/6 mice using Small Animal Radiation Therapy (SmART) device. Left renal I/R was performed by clamping the renal pedicles for 30 minutes, with simultaneous right nephrectomy, at 7, 14, and 28 days post-irradiation. The renal reperfusion lasted 48 hours. Following I/R, blood urea nitrogen (BUN) and creatinine (SCr) levels were lower in pre-irradiated mice compared to controls, so was the histological Jablonski score of AKI. The metabolomics signature of renal I/R was attenuated in pre-irradiated mice. The numbers of PCNA-, CD11b-, and F4-80-positive cells in the renal parenchyma post-I/R were reduced in pre-irradiated versus control groups. Such an IPC was significantly observed as early as D14 post-irradiation. RNA-Seq showed an up-regulation of angiogenesis- and stress response-related signaling pathways in irradiated non-ischemic kidneys at D28. RT-qPCR confirmed the increased expression of VEGF, ALK5, HO1, PECAM1, NOX2, HSP70, and HSP27 in irradiated kidneys compared to controls. In addition, irradiated kidneys showed an increased CD31-positive vascular area compared to controls. A 14-day gavage of irradiated mice with the anti-angiogenic drug Sunitinib before I/R abrogated the irradiation-induced IPC at both functional and structural levels. Our observations suggest that kidney-centered irradiation activates pro-angiogenic pathways and induces IPC, with preserved renal function and attenuated inflammation post-I/R.

Polymethoxyflavone-rich Fraction from Citrus sunki Leaves Alleviates Renal Dysfunction in Mice with Unilateral Ureteral Obstruction

Polymethoxyflavones (PMFs) are flavonoid compounds present in citrus plants that are proposed to be advantageous to human health. However, the advantageous effects of PMFs in the context of renal dysfunction are unclear. In this study, we made a PMF-rich fraction (PRF) from the leaves of Citrus sunki Hort ex. Tanaka and identified its components using liquid chromatography and mass spectrometry. We then investigated the effect of PRF—comprising 9 types of PMF—on renal dysfunction induced by unilateral ureteral obstruction (UUO) in mice. Animals were divided into four experimental groups ( n = 7 per group): I) sham-operated group (Sham); II) UUO group (UUO); III) UUO + Enalapril 0.1 mg/1 mL (UUO + Enap); IV) UUO + PRF 100 mg/kg/day (UUO + PRF). All mice were orally administered with the drugs once a day from 7 days before UUO to 1 week after UUO. After the experiments were over, serum and tissues were taken for biochemical and histological analysis. PRF promoted the recovery of body weight in the background of UUO. Biochemical and histological analysis revealed that PRF ameliorated UUO-induced renal dysfunction and moderately reversed inflammation and tubulointerstitial fibrosis. Further, PRF inhibited the expression of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), transforming growth factor-β (TGF-β), collagen I (Col-I), and collagen IV (Col-IV). These results suggest that PRF improves UUO-induced renal dysfunction by regulating the expression of inflammatory and fibrotic response-related genes.

IFC-305 attenuates renal ischemia-reperfusion injury by promoting the production of hydrogen sulfide (H2S) via suppressing the promoter methylation of cystathionine γ-lyase (CSE)

Renal ischemia-reperfusion (I/R) injury is characterized by elevated expression of homocysteine and decreased production of hydrogen sulfide (H₂S). Cystathionine γ-lyase (CSE) is a key factor in the onset of renal I/R injury, while IFC-305 can regulate the expression of CSE via epigenetic modification. Animal and cellular models of I/R were established in this work, followed by H&E staining to evaluate the extent of renal tissue injury under distinct conditions. Several methods, including ELISA, qPCR and Western blot, were used to analyze the levels of creatinine, CSE and H₂S in various I/R models. Bisulfite sequencing PCR was used to evaluate the level of DNA methylation. The severity of the renal injury was significantly elevated in I/R rats and alleviated by the IFC-305 treatment. The level of Hcy was increased in the renal tissue and peripheral blood of I/R rats, while the IFC-305 treatment inhibited the expression of homocysteine (Hcy). Mechanistically, the DNA methylation in the CSE promoter was dramatically enhanced in I/R rats and cells, while the IFC-305 treatment reduced the level of DNA methylation in the CSE promoter. Moreover, the IFC-305 increased the concentration of H₂S, which was reduced in I/R rats and cells. Finally, I/R rats and cells showed aberrantly high levels of MDA and superoxide, while the IFC-305 treatment reduced the levels of malondialdehyde (MDA) and superoxide. IFC-305, an adenosine derivative, promoted the production of H₂S and attenuated renal injury in cellular and animal models of renal I/R by modifying the methylation status of the CSE promoter.

Cisplatin nephrotoxicity is induced via poly(ADP-ribose) polymerase activation in adult zebrafish and mice

Cisplatin is a well-known chemotherapy medication used to treat numerous cancers. However, treatment with cisplatin in cancer therapy has major side effects, such as nephrotoxic acute kidney injury. Adult vertebrate kidneys are commonly used as models of cisplatin-induced nephrotoxic acute kidney injury. Embryonic zebrafish kidney is more simplified and is composed simply of two nephrons and thus is an excellent model for the investigation of cisplatin nephrotoxicity. Here, we developed a novel model to induce cisplatin nephrotoxicity in adult zebrafish and demonstrated that intraperitoneal injection of cisplatin caused a decline in kidney proximal tubular function based on fluorescein-labeled dextran uptake and alkaline phosphatase staining. We also showed that cisplatin induced histological injury of the kidney tubules, quantified by tubular injury scores on the periodic acid-Schiff-stained kidney sections. As shown in a mouse model of cisplatin-induced nephrotoxicity, the activation of poly(ADP-ribose) polymerase (PARP), an enzyme implicated in cisplatin-induced cell death, was markedly increased after cisplatin injection in adult zebrafish. Furthermore, pharmacological inhibition of PARP using a specific PARP inhibitor PJ 34 hydrochloride (PJ34) or 3-aminobenzamide ameliorated kidney proximal tubular functional and histological damages in cisplatin-injected adult zebrafish kidneys. Administration of a combination of PARP inhibitors PJ34 and 3-aminobenzamide additively protected renal function and histology in zebrafish and mouse models of cisplatin nephrotoxicity. In conclusion, these data suggest that adult zebrafish are not only suitable for drug screening and genetic manipulation but also useful as a simplified but powerful model to study the pathophysiology of cisplatin nephrotoxicity and establish new therapies for treating human kidney diseases.

Cyclosporin A aggravates hydrogen peroxide-induced cell death in kidney proximal tubule epithelial cells

Cyclosporin A (CsA) does not only exert a toxic effect on kidney parenchymal cells, but also protects them against necrotic cell death by inhibiting opening of mitochondrial permeability transition pore. However, whether CsA plays a role in hydrogen peroxide-induced kidney proximal tubular cell death is currently unclear. In the present study, treatment with CsA further increased apoptosis and necrosis in HK-2 human kidney proximal tubule epithelial cells during exposure to hydrogen peroxide. In addition, hydrogen peroxide-induced p53 activation and BH3 interacting-domain death agonist (BID) expression were higher in CsA-treated cells than those in non-treated cells, whereas hydrogen peroxide-induced activation of mitogen-activated protein kinases including p38, c-Jun N-terminal kinase, and extracellular signal-regulated kinase and activation of protein kinase B were not significantly altered by treatment with CsA. In oxidant-antioxidant system, reactive oxygen species (ROS) production induced by hydrogen peroxide was further enhanced by treatment with CsA. However, expression levels of antioxidant enzymes including manganese superoxide dismutase, copper/zinc superoxide dismutase, and catalase were not altered by treatment with hydrogen peroxide or CsA. Treatment with CsA further enhanced mitochondrial membrane potential induced by exposure to hydrogen peroxide, although it did not alter endoplasmic reticulum stress based on expression of glucose-regulated protein 78 and 94. Taken together, these data suggest that CsA can aggravate hydrogen peroxide-induced cell death through p53 activation, BID expression, and ROS production.

The Effect of Nitric Oxide on Remote Ischemic Preconditioning in Renal Ischemia Reperfusion Injury in Rats

Although remote ischemic preconditioning (RIPC) is an organ-protective maneuver from subsequent ischemia reperfusion injury (IRI) by application of brief ischemia and reperfusion to other organs, its mechanism remains unclear. However, it is known that RIPC reduces the heart, brain, and liver IRI, and that nitric oxide (NO) is involved in the mechanism of this effect. To identify the role of NO in the protective effect of RIPC in renal IRI, this study examined renal function, oxidative status, and histopathological changes using N-nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor. Remote ischemic preconditioning was produced by 3 cycles of 5 minutes ischemia and 5 minutes reperfusion. Blood urea nitrogen, creatinine (Cr), and renal tissue malondialdehyde levels were lower, histopathological damage was less severe, and superoxide dismutase level was higher in the RIPC + IRI group than in the IRI group. The renoprotective effect was reversed by L-NAME. Obtained results suggest that RIPC before renal IRI contributes to improvement of renal function, increases antioxidative marker levels, and decreases oxidative stress marker levels and histopathological damage. Moreover, NO is likely to play an important role in this protective effect of RIPC on renal IRI.

Beneficial Role of Hydrogen Sulfide in Renal Ischemia Reperfusion Injury in Rats

PURPOSE

Hydrogen sulfide (H₂S) is an endogenous gaseous molecule with important physiological roles. It is synthesized from cysteine by cystathionine γ-lyase (CGL) and cystathionine β-synthase (CBS). The present study examined the benefits of exogenous H₂S on renal ischemia reperfusion (IR) injury, as well as the effects of CGL or CBS inhibition. Furthermore, we elucidated the mechanism underlying the action of H₂S in the kidneys.

MATERIALS AND METHODS

Thirty male Sprague-Dawley rats were randomly assigned to five groups: a sham, renal IR control, sodium hydrosulfide (NaHS) treatment, H₂S donor, and CGL or CBS inhibitor administration group. Levels of blood urea nitrogen (BUN), serum creatinine (Cr), renal tissue malondialdehyde (MDA), and superoxide dismutase (SOD) were estimated. Histological changes, apoptosis, and expression of mitogen-activated protein kinase (MAPK) family members (extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38) were also evaluated.

RESULTS

NaHS attenuated serum BUN and Cr levels, as well as histological damage caused by renal IR injury. Administration of NaHS also reduced oxidative stress as evident from decreased MDA, preserved SOD, and reduced apoptotic cells. Additionally, NaHS prevented renal IR-induced MAPK phosphorylation. The CGL or CBS group showed increased MAPK family activity; however, there was no significant difference in the IR control group.

CONCLUSION

Exogenous H₂S can mitigate IR injury-led renal damage. The proposed beneficial effect of H₂S is, in part, because of the anti-oxidative stress associated with modulation of the MAPK signaling pathways.

Inhibition of Oxidative Stress in Renal Ischemia-Reperfusion Injury

BACKGROUND

Superoxide, nitric oxide (NO), and peroxynitrite are important mediators in the pathogenesis of ischemia-reperfusion (I/R) injury. We tested the renoprotective effects of allopurinol (ALP), a xanthine oxidase inhibitor, N-nitro-L-arginine methyl ester (L-NAME), and 5,10,15,20-tetrakis (N-methyl-4-pyridyl) porphyrinato iron (III) (FeTMPyP) by selective inhibition of superoxide, NO, and peroxynitrite, respectively.

METHODS

Male Sprague-Dawley rats were randomly assigned to 5 groups (n = 6 per group). Group 1 was a sham-operated group. Group 2 was the renal I/R group (30-minute ischemia followed by 24-hour reperfusion). Rats in groups 3, 4, and 5 received ALP, L-NAME, or FeTMPyP, respectively, at 5 minutes before the reperfusion. Serum creatinine (Cr), blood urea nitrogen (BUN), renal tissue malondialdehyde, superoxide dismutase, histological changes, apoptosis, and monocyte infiltration were evaluated. In addition, the combined treatment with ALP and L-NAME was compared with FeTMPyP in a second independent experiment.

RESULTS

The administration of ALP, L-NAME, and FeTMPyP diminished the increase in Cr (P = .0066 for all) and BUN (P = .0066 for ALP; and P = .013 for L-NAME) induced by I/R injury and decreased the histological damage (P = .0066 for all). In addition, ALP, L-NAME, and FeTMPyP attenuated the oxidative stress response as determined by a decrease in malondialdehyde level (P = .0066 for all), apoptotic renal tubular cells (P = .0066 for all), and monocyte infiltration (P = .0066 for all). The combined treatment of ALP and L-NAME decreased Cr and BUN levels to a greater degree than FeTMPyP (P = .016 for Cr; P = .0079 for BUN).

CONCLUSIONS

Superoxide, NO, and peroxynitrite are involved in renal I/R injury. The reduction of peroxynitrite formation, via inhibition of superoxide or NO, or the induction of peroxynitrite decomposition may be beneficial in renal I/R injury.

Effects of Allopurinol and Apocynin on Renal Ischemia-Reperfusion Injury in Rats

BACKGROUND

This study evaluated the effects of allopurinol (ALP), a xanthine oxidase inhibitor, and apocynin (APC), a NADPH oxidase inhibitor, administered alone or together, on kidney damage caused by renal ischemia-reperfusion (IR) in rats.

METHODS

Thirty rats were randomly assigned to 5 groups. Group 1 was a sham group. Group 2 was the renal IR control group (30-min ischemia followed by 24-h reperfusion). In groups 3 and 4, ALP or APC, respectively, was administered 1 h before the ischemia. In group 5, ALP and APC were co-administered. Blood urea nitrogen (BUN) and serum creatinine (Cr), renal tissue malondialdehyde (MDA) and superoxide dismutase (SOD), and histological changes were evaluated.

RESULTS

A significant increase in BUN and Cr level, and histological damage was seen in the IR control group, indicating renal injury. Elevated MDA and decreased SOD levels in the IR control group demonstrated that renal damage occurred through oxidative stress. Pretreatment with ALP or APC alone or together prevented IR-induced renal damage. However, there was no significant difference between treatment with a single drug and co-administration of ALP and APC.

CONCLUSIONS

The use of ALP and/or APC before ischemia may be beneficial to ameliorate renal IR injury.

High-throughput 16S rRNA gene sequencing reveals alterations of mouse intestinal microbiota after radiotherapy

The mammalian gastrointestinal tract harbors a highly complex microbial community that comprises hundreds of different types of bacterial cells. The gastrointestinal microbiota plays an important role in the function of the host intestine. Most cancer patients undergoing pelvic irradiation experience side effects such as diarrhea; however, little is currently known about the effects of irradiation on the microorganisms colonizing the mucosal surfaces of the gastrointestinal tract. The aim of this study was to investigate the effects of gamma irradiation on the compositions of the large and small intestinal microbiotas. The gut microbiotas in control mice and mice receiving irradiation treatment were characterized by high-throughput sequencing of the bacterial 16S rRNA gene. Irradiation treatment induced significant alterations in the bacterial compositions of the large and small intestines at the genus level. Unexpectedly, irradiation treatment increased the number of operational taxonomic units in the small intestine but not the large intestine. In particular, irradiation treatment increased the level of the genera Alistipes in the large intestine and increased the level of the genus Corynebacterium in the small intestine. By contrast, compared with that in the corresponding control group, the level of the genera Prevotella was lower in the irradiated large intestine, and the level of the genera Alistipes was lower in the irradiated small intestine. Overall, the data presented here reveal the potential microbiological effects of pelvic irradiation on the gastrointestinal tracts of cancer patients.

Protection of NAD(P)H:quinone oxidoreductase 1 against renal ischemia/reperfusion injury in mice

Ischemia/reperfusion (I/R) is the most common cause of acute renal injury. I/R-induced reactive oxygen species (ROS) are thought to be a major factor in the development of acute renal injury by promoting the initial tubular damage.

NAD(P)H

quinone oxidoreductase 1 (NQO1) is a well-known antioxidant protein that regulates ROS generation. The purpose of this study was to investigate whether NQO1 modulates the renal I/R injury (IRI) associated with NADPH oxidase (NOX)-derived ROS production in an animal model. We analyzed renal function, oxidative stress, and tubular apoptosis after IRI. NQO1(-/-) mice showed increased blood urea nitrogen and creatinine levels, tubular damage, oxidative stress, and apoptosis. In the kidneys of NQO1(-/-) mice, the cellular NADPH/NADP(+) ratio was significantly higher and NOX activity was markedly higher than in those of NQO1(+/+) mice. The activation of NQO1 by β-lapachone (βL) significantly improved renal dysfunction and reduced tubular cell damage, oxidative stress, and apoptosis by renal I/R. Moreover, the βL treatment significantly lowered the cellular NADPH/NADP(+) ratio and dramatically reduced NOX activity in the kidneys after IRI. From these results, it was concluded that NQO1 has a protective role against renal injury induced by I/R and that this effect appears to be mediated by decreased NOX activity via cellular NADPH/NADP(+) modulation. These results provide convincing evidence that NQO1 activation might be beneficial for ameliorating renal injury induced by I/R.

Protective role of methionine sulfoxide reductase A against ischemia/reperfusion injury in mouse kidney and its involvement in the regulation of trans-sulfuration pathway

AIMS

Methionine sulfoxide reductase A (MsrA) and methionine metabolism are associated with oxidative stress, a principal cause of ischemia/reperfusion (I/R) injury. Herein, we investigated the protective role of MsrA against kidney I/R injury and the involvement of MsrA in methionine metabolism and the trans-sulfuration pathway during I/R.

RESULTS

We found that MsrA gene-deleted mice (MsrA(-/-)) were more susceptible to kidney I/R injury than wild-type mice (MsrA(+/+)). Deletion of MsrA enhanced renal functional and morphological impairments, congestion, inflammatory responses, and oxidative stress under I/R conditions. Concentrations of homocysteine and H(2)S in the plasma of control MsrA(-/-) mice were significantly lower than those in control MsrA(+/+) mice. I/R reduced the levels of homocysteine and H(2)S in both MsrA(+/+) and MsrA(-/-) mice, and these reductions were significantly more profound in MsrA(-/-) than in MsrA(+/+) mice. I/R reduced the expression and activities of cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE), both of which are H(2)S-producing enzymes, in the kidneys. These reductions were more profound in the MsrA(-/-) mice than in the MsrA(+/+)mice.

INNOVATION

The data provided herein constitute the first in vivo evidence for the involvement of MsrA in regulating methionine metabolism and the trans-sulfuration pathway under normal and I/R conditions.

CONCLUSION

Our data demonstrate that MsrA protects the kidney against I/R injury, and that this protection is associated with reduced oxidative stress and inflammatory responses. The data indicate that MsrA regulates H(2)S production during I/R by modulating the expression and activity of the CBS and CSE enzymes.

Effect of DHA+EPA on oxidative stress and apoptosis induced by ischemia-reperfusion in rat kidneys

Apoptosis, as well as necrosis, has an important role in post-ischemic renal pathology. The effect of pretreatment with Docosahexaenoic acid+Eicosapentaenoic acid (DHA+EPA) on renal injury and apoptotic protein expression was evaluated. Right nephrectomy was completed on male Wistar rats (255-300 g). The rats received DHA+EPA (200 mg/kg/day) of distilled water orally for 14 days before ischemia reperfusion (IR) or sham operation. A total of 81 rats were divided into three main groups with 6, 24 and 48 h of post-operation or reperfusion period. Serum creatinine (SCr), BUN, creatinine clearance (CCr) and fractional excretion of sodium (FEN a ) were measured. Tissue levels of malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) activities, Bax and Bcl-2 protein expressions and renal histological injury were determined. SCr, BUN and FEN a increased 6-48 h of reperfusion (P < 0.01). Tissue MDA content and Bax expression increased (P < 0.01) and CAT and SOD activities decreased (P < 0.05) in the IR group. DHA+EPA decreased SCr and BUN, FEN a , tissue MDA levels (P < 0.05 vs. IR) and increased CAT and SOD activities and Bcl-2 expression (P < 0.05 vs. IR) for 6-48 h after ischemia. IR induced mild (6 h, P < 0.05) and severe (24-48 h, P < 0.01) tissue damage. Mild-to-moderate tissue damage was observed in DHA+EPA groups from 6 to 48 h of reperfusion period (P < 0.05 vs. IR, 24-48 h). In conclusion, the results suggest that pre-ischemic exposure to DHA+EPA could improve the outcome of early graft function by inhibition of IR-induced oxidative stress and apoptosis.

Poly(ADP-ribose) polymerase 1 activation is required for cisplatin nephrotoxicity

Apoptosis, necrosis, and inflammation are hallmarks of cisplatin nephrotoxicity; however, the role and mechanisms of necrosis and inflammation remains undefined. As poly(ADP-ribose) polymerase 1 (PARP1) inhibition or its gene deletion is renoprotective in several renal disease models, we tested whether its activation may be involved in cisplatin nephrotoxicity. Parp1 deficiency was found to reduce cisplatin-induced kidney dysfunction, oxidative stress, and tubular necrosis, but not apoptosis. Moreover, neutrophil infiltration, activation of nuclear factor-κB, c-Jun N-terminal kinases, p38 mitogen-activated protein kinase, and upregulation of proinflammatory genes were all abrogated by Parp1 deficiency. Using proximal tubule epithelial cells isolated from Parp1-deficient and wild-type mice and pharmacological inhibitors, we found evidence for a PARP1/Toll-like receptor 4/p38/tumor necrosis factor-α axis following cisplatin injury. Furthermore, pharmacological inhibition of PARP1 protected against cisplatin-induced kidney structural/functional damage and inflammation. Thus, our findings suggest that PARP1 activation is a primary signal and its inhibition/loss protects against cisplatin-induced nephrotoxicity. Targeting PARP1 may offer a potential therapeutic strategy for cisplatin nephrotoxicity.

Loss of poly(ADP-ribose) polymerase 1 attenuates renal fibrosis and inflammation during unilateral ureteral obstruction

Poly(ADP-ribose) polymerase 1 (PARP1) contributes to necrotic cell death and inflammation in several disease models; however, the role of PARP1 in fibrogenesis remains to be defined. Here, we tested whether PARP1 was involved in the pathogenesis of renal fibrosis using the unilateral ureteral obstruction (UUO) mouse model. UUO was performed by ligation of the left ureter near the renal pelvis in Parp1-knockout (KO) and wild-type (WT) male mice. After 10 days of UUO, renal PARP1 expression and activation were strongly increased by 6- and 13-fold, respectively. Interstitial fibrosis induced by UUO was significantly attenuated in Parp1-KO kidneys compared with that in WT kidneys at 10 days, but not at 3 days, based on collagen deposition, α-smooth muscle actin (α-SMA), and fibronectin expression. Intriguingly, the UUO kidneys in Parp1-KO mice showed a dramatic decrease in infiltration of neutrophil and reduction in expression of proinflammatory proteins including intercellular adhesion molecule-1, tumor necrosis factor-α, inducible nitric oxide synthase, and toll-like receptor 4 as well as phosphorylation of nuclear factor-κB p65, but not transforming growth factor-β1 (TGF-β1) at both 3 and 10 days. Pharmacological inhibition of PARP1 in rat renal interstitial fibroblast (NRK-49F) cell line or genetic ablation in primary mouse embryonic fibroblast cells did not affect TGF-β1-induced de novo α-SMA expression. Parp1 deficiency significantly attenuated UUO-induced histological damage in the kidney tubular cells, but not apoptosis. These data suggest that PARP1 induces necrotic cell death and contributes to inflammatory signaling pathways that trigger fibrogenesis in obstructive nephropathy.

NADPH oxidase-mediated redox signaling: roles in cellular stress response, stress tolerance, and tissue repair

NADPH oxidase (Nox) has a dedicated function of generating reactive oxygen species (ROS). Accumulating evidence suggests that Nox has an important role in signal transduction in cellular stress responses. We have reviewed the current evidence showing that the Nox system can be activated by a collection of chemical, physical, and biological cellular stresses. In many circumstances, Nox activation fits to the cellular stress response paradigm, in that (1) the response can be initiated by various forms of cellular stresses; (2) Nox-derived ROS may activate mitogen-activated protein kinases (extracellular signal-regulated kinase, p38) and c-Jun NH(2)-terminal kinase, which are the core of the cell stress-response signaling network; and (3) Nox is involved in the development of stress cross-tolerance. Activation of the cell survival pathway by Nox may promote cell adaptation to stresses, whereas Nox may also convey signals toward apoptosis in irreversibly injured cells. At later stage after injury, Nox is involved in tissue repair by modulating cell proliferation, angiogenesis, and fibrosis. We suggest that Nox may have an integral role in cell stress responses and the subsequent tissue repair process. Understanding Nox-mediated redox signaling mechanisms may be of prominent significance at the crossroads of directing cellular responses to stress, aiming at either enhancing the stress resistance (in such situations as preventing ischemia-reperfusion injuries and accelerating wound healing) or sensitizing the stress-induced cytotoxicity for proliferative diseases such as cancer. Therefore, an optimal outcome of interventions on Nox will only be achieved when this is dealt with in a timely and disease-and stage-specific manner.

Bone marrow MyD88 signaling modulates neutrophil function and ischemic myocardial injury

Myeloid differentiation factor 88 (MyD88), an adaptor critical for innate immune function, plays a role in neutrophil recruitment and myocardial injury after transient ischemia. However, how MyD88 signaling modulates neutrophil function and myocardial injury remains unclear. In an in vivo model of neutrophil migration and a chimeric model of MyD88 deletion, we demonstrated that Gr-1-positive (Gr-1(+)) neutrophil migration was significantly decreased by 68% in MyD88-deficient (Myd88(-/-)) mice and by 33% in knockout→wild-type (KO→WT; donor→recipient) chimeric mice, which lacked MyD88 in bone marrow cells but maintained normal MyD88 expression in the heart. This marked attenuation in neutrophil migration was associated with decreased peritoneal neutrophil CXCR2 expression and lower peritoneal KC, a neutrophil chemoattractant, in MyD88(-/-) mice. Moreover, in vitro, KC induces significantly more downregulation of CXCR2 expression in MyD88(-/-) than WT neutrophils. In an in vivo model of myocardial ischemia-reperfusion (I/R) injury, KO→WT chimeric mice had significantly smaller infarct sizes compared with the WT→WT mice. While there was a marked increase in proinflammatory cytokine/chemokine expression in the myocardium following I/R, there was no significant difference between WT→WT and KO→WT mice. In contrast, Gr-1(+) neutrophil recruitment in the myocardium was markedly attenuated in MyD88(-/-) mice. Deletion of Toll-interleukin-1 receptor (TIR)-domain-containing adaptor protein-inducing interferon-β-mediated transcription factor (Trif), another innate immune adaptor, had no effect on the KC-mediated CXCR2 downregulation or on myocardial neutrophil recruitment after I/R. Taken together, these findings suggest that MyD88 signaling is essential for maintaining neutrophil migratory function and chemokine receptor expression. MyD88 signaling in bone marrow-derived circulating cells may play a specific and critical role in the development of myocardial I/R-induced injury.

Omi/HtrA2 protease is associated with tubular cell apoptosis and fibrosis induced by unilateral ureteral obstruction

Kidney fibrosis, a typical characteristic of chronic renal disease, is associated with tubular epithelial cell apoptosis. The results of our recent studies have shown that Omi/HtrA2 (Omi), a proapoptotic mitochondrial serine protease, performs a crucial function in renal tubular epithelial apoptotic cell death in animal models of acute kidney injury, including cisplatin toxicity and ischemia-reperfusion insult. However, the role of Omi in tubulointerstitial disease-associated fibrosis in the kidney remains to be clearly defined. We evaluated the potential function and molecular mechanism of Omi in ureteral obstruction-induced kidney epithelial cell apoptosis and fibrosis. The mice were subjected to unilateral ureteral obstruction (UUO) via the ligation of the left ureter near the renal pelvis. UUO increased the protein level of Omi in the cytosolic fraction of the kidney, with a concomitant reduction in the mitochondrial fraction. UUO reduced the X-linked inhibitor of apoptosis protein (XIAP), a substrate of Omi, and pro-caspase-3, whereas it increased cleaved poly(ADP-ribose) polymerase (cleaved PARP) and the number of terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells. When mice were treated with ucf-101, an inhibitor of the proteolytic activity of Omi (6.19 microg/day ip), on a daily basis beginning 2 days before UUO and continuing until the end of the experiment, the Omi inhibitor protected XIAP cleavage after UUO and reduced the increment of PARP cleavage and the numbers of TUNEL-positive cells. Furthermore, the Omi inhibitor significantly attenuated UUO-induced increases in fibrotic characteristics in the kidney, including the atrophy and dilation of tubules, expansion of the interstitium, and increases in the expression of collagens, alpha-smooth muscle actin, and fibronectin. In conclusion, Omi/HtrA2 is associated with apoptotic signaling pathways in tubular epithelial cells activated by unilateral ureteral obstruction, thereby resulting in kidney fibrosis.

Reactive oxygen species differently regulate renal tubular epithelial and interstitial cell proliferation after ischemia and reperfusion injury

Reactive oxygen species (ROS) function as an inducer of cell death and survival or proliferative factor, in a cell-type-specific and concentration-dependent manner. All of these roles are critical to ischemia-induced renal functional impairment and progressive fibrotic changes in the kidney. In an effort to define the role of ROS in the proliferation of tubular epithelial cells and of interstitial cells in kidneys recovering after ischemia and reperfusion (I/R) injury, experimental mice were subjected to 30 min of bilateral kidney ischemia and administered with manganese(III) tetrakis(1-methyl-4-pyridyl) porphyrin (MnTMPyP), a superoxide dismutase mimetic, from 2 to 15 days after I/R for 14 days daily (earlier and longer) and from 8 to 15 days after I/R for 8 days daily (later and shorter). Cell proliferation was assessed via 5′-bromo-2′-deoxyuridine (BrdU) incorporation assays for 20 h before the harvest of kidneys. After I/R, the numbers of BrdU-incorporating cells increased both in the tubules and interstitium. MnTMPyP administration was shown to accelerate the proliferation of tubular epithelial cells, presenting tubule-specific marker proteins along tubular segments, whereas it attenuated the proliferation of interstitial cells, evidencing α-smooth muscle actin, fibroblast-specific protein-1, F4/80, and NADPH oxidase-2 proteins; these results indicated that ROS attenuates tubular cell regeneration, but accelerates interstitial cell proliferation. Earlier and longer MnTMPyP treatment more effectively inhibited tissue superoxide formation, the increment of interstitial cells, and the decrement of epithelial cells compared with later and shorter treatment. After I/R, apoptotic cells appeared principally in the tubular epithelial cells, but not in the interstitial cells, thereby indicating that ROS is harmful in tubule cells, but is not in interstitial cells. In conclusion, ROS generated after I/R injury in cell proliferation and death performs a cell-type-specific and concentration-dependent role, even within the same tissues, and timely intervention of ROS is crucial for effective therapies.

Exocyst Sec10 protects epithelial barrier integrity and enhances recovery following oxidative stress, by activation of the MAPK pathway

Cell-cell contacts are essential for epithelial cell function, and disruption is associated with pathological conditions including ischemic kidney injury. We hypothesize that the exocyst, a highly-conserved eight-protein complex that targets secretory vesicles carrying membrane proteins, is involved in maintaining renal epithelial barrier integrity. Accordingly, increasing exocyst expression in renal tubule cells may protect barrier function from oxidative stress resulting from ischemia and reperfusion (I/R) injury. When cultured on plastic, Madin-Darby canine kidney (MDCK) cells overexpressing Sec10, a central exocyst component, formed domes showing increased resistance to hydrogen peroxide (H2O2). Transepithelial electric resistance (TER) of Sec10-overexpressing MDCK cells grown on Transwell filters was higher than in control MDCK cells, and the rate of TER decrease following H2O2 treatment was less in Sec10-overexpressing MDCK cells compared with control MDCK cells. After removal of H2O2, TER returned to normal more rapidly in Sec10-overexpressing compared with control MDCK cells. In collagen culture MDCK cells form cysts, and H2O2 treatment damaged Sec10-overexpressing MDCK cell cysts less than control MDCK cell cysts. The MAPK pathway has been shown to protect animals from I/R injury. Levels of active ERK, the final MAPK pathway step, were higher in Sec10-overexpressing compared with control MDCK cells. U0126 inhibited ERK activation, exacerbated the H2O2-induced decrease in TER and cyst disruption, and delayed recovery of TER following H2O2 removal. Finally, in mice with renal I/R injury, exocyst expression decreased early and returned to normal concomitant with functional recovery, suggesting that the exocyst may be involved in the recovery following I/R injury.

Attenuation of diabetes-induced renal dysfunction by multiple exposures to low-dose radiation is associated with the suppression of systemic and renal inflammation

Renal protection against diabetes-induced pathogenic injuries by multiple exposures to low-dose radiation (LDR) was investigated to develop a novel approach to the prevention of renal disease for diabetic subjects. C57BL/6J mice were given multiple low-dose streptozotocin (STZ; 6 x 60 [corrected] mg/kg) to produce a type 1 diabetes. Two weeks after diabetes onset, some of diabetic mice and age-matched nondiabetic mice were exposed whole body to 25 mGy X-rays every other day for 2, 4, 8, 12, and 16 wk. Diabetes caused a significant renal dysfunction, shown by time-dependent increase in urinary microalbumin (Malb) and decrease in urinary creatinine (Cre), and pathological changes, shown by significant increases in renal structural changes and PAS-positive staining. However, diabetes-induced renal dysfunction and pathological changes were significantly, albeit partially, attenuated by multiple exposures to LDR. Furthermore, LDR protection against diabetes-induced renal dysfunction and pathological changes was associated with a significant suppression of diabetes-increased systemic and renal inflammation, shown by significant increases in serum and renal TNFalpha, ICAM-1, IL-18, MCP-1, and PAI-1 contents. To further explore the mechanism by which LDR prevents diabetes-induced renal pathological changes, renal oxidative damage was examined by Western blotting and immunohistochemical staining for 3-nitrotyrosine and 4-hydroxynonenal. Significant increase in oxidative damage was observed in diabetic mice, but not diabetic mice, with LDR. Renal fibrosis, examined by Western blotting of connective tissue growth factor and Masson's trichrome staining, was also evident in the kidneys of diabetic mice but not diabetic mice with LDR. These results suggest that multiple exposures to LDR significantly suppress diabetes-induced systemic and renal inflammatory response and renal oxidative damage, resulting in a prevention of the renal dysfunction and fibrosis.

Repetitive exposures to low-dose X-rays attenuate testicular apoptotic cell death in streptozotocin-induced diabetes rats

To define whether repetitive exposures to low-dose radiation (LDR) can attenuate diabetes-induced testicular cell death, Type 1 diabetic rats were produced by single injection of streptozotocin (STZ). Once hyperglycemia was diagnosed, diabetic rats were treated with and without LDR (25 and 50 mGy X-rays) daily for 4 weeks. Eight and 12 weeks after diabetes onset, testicular apoptotic cell death was examined by flow cytometry with Annexin V/PI staining, Western blotting assay for caspase-3 cleavage, and TUNEL staining for localization of apoptotic cells. Diabetes induced a significant increase in testicular apoptotic cell death, which was able to be attenuated by repetitive exposures to LDR. Diabetes-induced testicular cell death was associated with increased mitochondrial dysfunction, shown by the decreased mitochondrial potential and increased expressions of Bax mRNA and protein. All these changes were significantly attenuated in certain extends by repetitive exposures to LDR. To investigate the mechanisms by which LDR attenuates diabetes-induced testicular apoptotic cell death, serum sex hormone (testosterone, luteinizing hormone and follicle stimulating hormone) levels, and both serum and testicular oxidative damage (lipid peroxides) and antioxidant contents (superoxide dismutase, catalase and glutathione) were measured. Serum sex hormones were significantly decreased in diabetic rats, but not significantly in diabetic rats with multiple exposures to LDR; serum and testicular oxidative damage was significantly increased along with significant decreases in serum and testicular antioxidants in diabetic rats; however, these changes were significantly prevented by repetitive exposures to LDR. Furthermore, diabetic effects on the testicular oxidative damage and cell death were all attenuated by antioxidant N-acetylcysteine. These results suggest that diabetes-induced testicular cell death is probably mediated by increased oxidative stress. LDR protection from diabetes-induced testicular cell death is most likely mediated by its preserving antioxidants.

Reactive oxygen species generated by renal ischemia and reperfusion trigger protection against subsequent renal ischemia and reperfusion injury in mice

Ischemic preconditioning by a single event of ischemia and reperfusion (SIRPC) dramatically protects renal function against ischemia and reperfusion (I/R) induced several weeks later. We recently reported that reactive oxygen species (ROS) and oxidative stress were sustained in a kidney that had functionally recovered from I/R injury, thus suggesting an association between SIRPC and ROS and oxidative stress. However, the role of ROS in SIRPC remains to be clearly elucidated. To assess the involvement of ROS in SIRPC, mice were subjected to SIRPC (30 min of bilateral renal ischemia and 8 days of reperfusion) and then exposed to I/R injury. Thirty minutes of bilateral renal ischemia in the non-SIRPC mice resulted in a marked increase in plasma creatinine levels 4 and 24 h after reperfusion, which was not observed in the I/R in the SIRPC mice. SIRPC resulted in increases in the levels of kidney superoxide. Administrations of manganese(III) tetrakis(1-methyl-4-pyridyl) porphyrin [MnTMPyP; a cell-permeable superoxide dismutase (SOD) mimetic] and N-acetylcysteine (NAc; a ROS scavenger) to SIRPC mice blocked the SIRPC-induced increase in superoxide levels and removed approximately 48-64% of the functional protection of the SIRPC kidney. Additionally, these administrations significantly inhibited I/R-induced increases in superoxide formation, hydrogen peroxide production, and lipid peroxidation, along with the inhibition of I/R-induced reductions in the expression and activity of manganese SOD, copper-zinc SOD, and catalase. Furthermore, administrations of MnTMPyP or NAc inhibited the SIRPC-induced increase in inducible nitric oxide synthase expression but did not inhibit the SIRPC-induced increases in heat shock protein-25 expression. In conclusion, the renoprotection afforded by SIRPC was triggered by ROS generated by SIRPC.

Reactive oxygen species/oxidative stress contributes to progression of kidney fibrosis following transient ischemic injury in mice

Recently, kidney fibrosis following transplantation has become recognized as a main contributor of chronic allograft nephropathy. In transplantation, transient ischemia is an inescapable event. Reactive oxygen species (ROS) play a critical role in ischemia and reperfusion (I/R)-induced acute kidney injury, as well as progression of fibrosis in various diseases such as hypertension, diabetes, and ureteral obstruction. However, a role of ROS/oxidative stress in chronic kidney fibrosis following I/R injury remains to be defined. In this study, we investigated the involvement of ROS/oxidative stress in kidney fibrosis following kidney I/R in mice. Mice were subjected to 30 min of bilateral kidney ischemia followed by reperfusion on day 0 and then administered with either manganese (III) tetrakis(1-methyl-4-pyridyl) porphyrin (MnTMPyP, 5 mg/kg body wt ip), a cell permeable superoxide dismutase (SOD) mimetic, or 0.9% saline (vehicle) beginning at 48 h after I/R for 14 days. I/R significantly increased interstitial extension, collagen deposition, apoptosis of tubular epithelial cells, nitrotyrosine expression, hydrogen peroxide production, and lipid peroxidation and decreased copper-zinc SOD, manganese SOD, and glucose 6-phosphate dehydrogenase activities in the kidneys 16 days after the procedure. MnTMPyP administration minimized these postischemic changes. In addition, MnTMPyP administration significantly attenuated the increases of alpha-smooth muscle actin, PCNA, S100A4, CD68, and heat shock protein 47 expression following I/R. We concluded that kidney fibrosis develops chronically following I/R injury, and this process is associated with the increase of ROS/oxidative stress.