Ischemia Reperfusion-induced Acute Kidney Injury Research Articles

SIRT3 mediates mitofusin 2 ubiquitination and degradation to suppress ischemia reperfusion-induced acute kidney injury

Ischemia reperfusion-induced acute kidney injury (IR-induced AKI) is a life-threatening disease with many complications. Mitofusin 2 (Mfn2) ubiquitination is related to AKI. But the underlying molecular mechanisms remain unknown. This study aimed to probe the mechanism of Mfn2 ubiquitination in IR-induced AKI development. In IR-induced AKI mouse models, orbital blood and urine were collected for assessing kidney function. The kidney injury, ultrastructure of mitochondria, and histopathology in mice were evaluated after injection of G5, an ubiquitination inhibitor. Oxygen glucose deprivation/reoxygenation (OGD/R) models were established in HK-2 cells, and the mitochondria were extracted. Cell viability, apoptosis, oxidative stress, inflammatory reaction, mitochondrial membrane potential, and ATP production were measured. Mfn2 ubiquitination in mouse and cell models was evaluated. si-SIRT3 and pcDNA3.1-SIRT3 were transfected into cell models. Consequently, kidney function in mice was impaired by IR-induced AKI. Mfn2 ubiquitination and degradation promoted IR-induced AKI. OGD/R induced renal tubular epithelial cell injury and disrupted mitochondrial dynamics and functions through promoting Mfn2 ubiquitination. SIRT3 knockdown led to Mfn2 ubiquitination by binding to UBC; while its overexpression alleviated tubular epithelial cell injury. Briefly, SIRT3 mediates Mfn2 ubiquitination to relieve IR-induced AKI. This investigation may offer new insights for the treatment of IR-induced AKI injury.

Hyaluronic acid coated bilirubin nanoparticles attenuate ischemia reperfusion-induced acute kidney injury

Acute kidney injury (AKI) is a common pathological process that is globally associated with a high morbidity and mortality rate. The underlying AKI mechanisms include over-produced reactive oxygen species (ROS), inflammatory cell infiltration, and high levels of inflammatory mediators. Bilirubin is an endogenous compound with antioxidant, anti-inflammatory and anti-apoptotic properties, and could, therefore, be a promising therapeutic candidate. Nanotechnology-mediated therapy has emerged as a novel drug delivery strategy for AKI treatment. In this study, we report a hyaluronic acid (HA) coated ε-polylysine-bilirubin conjugate (PLBR) nanoparticle (nHA/PLBR) that can selectively accumulate in injured kidneys and alleviate the oxidative/inflammatory-induced damage. The in vitro study revealed that nHA/PLBR has good stability, biocompatibility, and exhibited higher antioxidant as well as anti-apoptotic effects when compared to nPLBR or bilirubin. The in vivo study showed that nHA/PLBR could target and accumulate in the injured kidney, effectively relieve oxidative stress and inflammatory reactions, protect the structure and function of the mitochondria, and more importantly, inhibit the apoptosis of tubular cells in an ischemia/reperfusion-induced AKI rat model. Therefore, nHA/PLBR has the capacity to enhance specific biodistribution and delivery efficiency of bilirubin, thereby providing better treatment for AKI in the future.

Identification of Hub Genes Associated with the Development of Acute Kidney Injury by Weighted Gene Co-Expression Network Analysis

Background: Acute kidney injury (AKI) is a severe clinical syndrome, causing a profound medical and socioeconomic burden worldwide. This study aimed to explore underlying molecular targets related to the progression of AKI. Methods: A public database originated from the NCBI GEO database (serial number: GSE121190) and a well-established and unbiased method of weighted gene co-expression network analysis (WGCNA) to identify hub genes and potential pathways were used. Furthermore, the unbiased hub genes were validated in 2 classic models of AKI in a rodent model: chemically established AKI by cisplatin- and ischemia reperfusion-induced AKI. Results: A total of 17 modules were finally obtained by the unbiased method of WGCNA, where the genes in turquoise module displayed strong correlation with the development of AKI. In addition, the results of gene ontology revealed that the genes in turquoise module were involved in renal injury and renal fibrosis. Thus, the hub genes were further validated by experimental methods and primarily obtained Rplp1 and Lgals1 as key candidate genes related to the progression of AKI by the advantage of quantitative PCR, Western blotting, and in situ tissue fluorescence. Importantly, the expression of Rplp1 and Lgals1 at the protein level showed positive correlation with renal function, including serum Cr and BUN. Conclusions: By the advantage of unbiased bioinformatic method and consequent experimental verification, this study lays the foundation basis for the pathogenesis and therapeutic agent development of AKI.

Fenofibrate attenuates ischemia reperfusion-induced acute kidney injury and associated liver dysfunction in rats.

Ischemia/reperfusion (I/R) is one of the common reasons for acute kidney injury (AKI) and we need to develop effective therapies for treating AKI. We investigated the role of fenofibrate against I/R-induced AKI and associated hepatic dysfunction in rats. In male wistar albino rats, renal pedicle occlusion for 40 min and 24 h reperfusion resulted in AKI. I/R-induced AKI was demonstrated by measuring serum creatinine, creatinine clearance, urea, uric acid, potassium, fractional excretion of sodium and urinary microproteins. Oxidative stress in rat kidneys was quantified by assaying superoxide anion generation, thiobarbituric acid reactive substances, and reduced glutathione levels. AKI-induced hepatic damage was quantified by assaying serum aminotransferases, alkaline phosphatase and bilirubin levels. Moreover, serum cholesterol, high density lipoprotein and triglycerides were quantified. Hematoxylin-eosin staining of renal and hepatic tissues was done and the kidney and liver injury scores were determined. Immunohistology of endothelial nitric oxide synthase (eNOS) was done in rat kidneys. Fenofibrate was administered for 1 week before subjecting rats to AKI. In separate group, the nitric oxide synthase inhibitor, L-nitroarginine methyl ester (L-NAME) was administered prior to fenofibrate treatment. In I/R group, significant alteration in the serum/urine parameters indicated AKI and hepatic dysfunction along with marked increase in kidney and liver injury scores. Treatment with fenofibrate attenuated AKI and associated hepatic dysfunction. Moreover, I/R-induced decrease in renal eNOS expression was abrogated by fenofibrate. Pre-treatment with L-NAME abolished fenofibrate mediated reno- and hepato-protective effects. In conclusion, fenofibrate attenuates I/R-induced AKI and associated hepatic dysfunction putatively through modulation of eNOS expression.

MiR-20a-5p is enriched in hypoxia-derived tubular exosomes and protects against acute tubular injury.

Exosomes have been shown to effectively regulate the biological functions of target cells. Here, we investigated the protective effect and mechanism of hypoxia-induced renal tubular epithelial cells (TECs)-derived exosomes on acute tubular injury. We found that in vitro hypoxia-induced tubular exosomes (Hy-EXOs) were protective in acute tubular injury by promoting TECs proliferation and improving mitochondrial functions. By using exosome miRNA sequencing, we identified miR-20a-5p was abundant and was a key mechanism for the protective effect of Hy-EXOs on tubular injury as up-regulation of miR-20a-5p enhanced but down-regulation of miR-20a-5p inhibited the protective effect of Hy-EXOs on tubular injury under hypoxia conditions. Further study in a mouse model of ischemia-reperfusion-induced acute kidney injury (IRI-AKI) also confirmed this notion as pre-treating mice with the miR-20a-5p agomir 48 h prior to AKI induction was capable of inhibiting IRI-AKI by lowering serum levels of creatinine and urea nitrogen, and attenuating the severity of tubular necrosis, F4/80(+) macrophages infiltration and vascular rarefaction. Mechanistically, the protective effect of miR-20a-5p on acute kidney injury (AKI) was associated with inhibition of TECs mitochondrial injury and apoptosis in vitro and in vivo. In conclusion, miR-20a-5p is enriched in hypoxia-derived tubular exosomes and protects against acute tubular injury. Results from the present study also reveal that miR-20a-5p may represent as a novel therapy for AKI.

Adenosine kinase inhibition attenuates ischemia reperfusion-induced acute kidney injury

Acute kidney injury (AKI) has a high morbidity and mortality, and there is no targeted treatment yet. One of the main causes of AKI is ischemia-reperfusion (IR). Increased release of adenosine under stress and hypoxia exerts anti-inflammatory and antioxidant effects. Adenosine kinase (ADK) is an important enzyme that eliminates adenosine in cells, and can maintain low adenosine concentration in cells. Our previous studies have shown that pretreatment of adenosine kinase inhibitor ABT-702 could markedly attenuate cisplatin-induced nephrotoxicity both in vivo and in vitro. This study is designed to investigate the effect of ADK inhibition on IR-induced AKI. The results showed that ADK expression was positively correlated with the degree of renal tubular injury, which suggested that the degree of ADK inhibition reflected the severity of acute tubular necrosis. In vivo, ADK inhibitor could reduce IR-induced renal injury, which might play a protective role by increasing tissue adenosine level, inhibiting oxidative stress, and reducing cell apoptosis. In HK2 cells, cobaltous dichloride (CoCl2) increased the level of oxidative stress, up-regulated the production of pro-inflammatory factor, and induced apoptosis, ADK inhibition could alleviate the above damaging effects. Moreover, the anti-apoptotic effect exerted by ADK inhibition was independent of inosine. In summary, our results support the idea that ADK inhibition has protective effects on IR-induced AKI. Adenosine kinase inhibition might provide a new target for AKI prevention and treatment.

Erythropoietin Ameliorates Ischemia/Reperfusion-Induced Acute Kidney Injury via Inflammasome Suppression in Mice.

Acute kidney injury (AKI) is the most common condition in hospitalized patients. As ischemia/reperfusion-induced AKI (IR-AKI) is as a major contributor to end-stage disease, an effective therapeutic intervention for IR-AKI is imperative. Erythropoietin (EPO) is a potent stimulator of erythroid progenitor cells and is significantly upregulated during hypoxia. Here, we investigated the renoprotective effects of EPO in an IR-AKI mouse model. Mice were assigned to sham, EPO only, and IR only groups, and the IR group was treated with EPO prior to injury. EPO was administered twice at 30 min prior to bilateral renal artery occlusion, and 5 min before reperfusion, with all mice sacrificed 24 h after IR-AKI. The serum was harvested for renal functional measurements. The kidneys were subjected to histological evaluation, and the biochemical changes associated with renal injury were assessed. EPO significantly attenuated the renal dysfunction associated with IR-AKI, as well as tissue injury. Apoptotic cell death and oxidative stress were significantly reduced in EPO-treated mice. Macrophage infiltration and expression of ICAM-1 and MCP-1 were also significantly reduced in EPO-treated mice. Furthermore, the expression of inflammasome-related factors (NLRP1, NLRP3, and caspase-1 cleavage), via the activation of the COX-2 and NF-κB signaling pathways were significantly reduced following EPO treatment. To our knowledge, this is the first study to demonstrate that inflammasome-mediated inflammation might be a potential target of EPO as a treatment for ischemic AKI.

Renal Ischemia‐Reperfusion Impairs Whole Kidney Blood Flow Autoregulation in Male and Female Rats

Renal autoregulation is critical in maintaining a stable renal blood flow (RBF) and glomerular filtration rate over a wide range of renal perfusion pressure. Our recent in vitro work demonstrated that accumulating reactive oxygen species (ROS) contribute to loss of renal autoregulatory capability in ischemia reperfusion (IR)‐induced acute kidney injury (IR‐AKI) in male rats. Evidence shows that sex differences might contribute to differential injury in IR‐AKI. Therefore, we hypothesized that renal IR leads to impaired RBF autoregulation which may be associated with ROS accumulation and inflammation in male and female rats. IR was induced by occluding both renal arteries for 60 minutes followed by 24 hours or 1 week of reperfusion. Plasma creatinine was markedly increased in IR rats but more so in males than females at 24 hours (3.8±0.2 vs 1.9±0.4 mg/dl, P<0.05, n=7/group). Plasma creatinine was still elevated in IR males one week post‐IR (1.3±0.1 vs 1.1±0.0 mg/dl in sham, P<0.05, n=13–14/group). Whole kidney autoregulation was assessed in vivo. IR significantly lowered baseline RBF in males (5.9±0.6 vs. 9.1±0.5 ml/min/gkw in sham, P<0.05, n=6/group) but not in females (8.3±0.6 vs. 10.3±0.9 ml/min/gkw in sham, P>0.05, n=5–8/group) 24 hours post‐IR. RBF was lower in IR males compared to IR females (P<0.05). RBF decreased further in IR rats at week 1 (4.1±1.0 ml/min/gkw in males and 4.5±0.2 ml/min/gkw in females, n=2–3). RBF remained constant during stepwise reduction of renal perfusion pressure from 120 to 100 mmHg in both sham males and females at 24 hours and 1 week, indicating intact autoregulation as reflected by autoregulatory index (ARI) between 0.1±0.0 and 0.2±0.1. IR led to impaired RBF autoregulation in males at 24 hours and 1 week, and in females at 24 hours as indicated by ARI between 0.8±0.1 and 1.1±0.2. Interestingly, autoregulation partially recovered in females at week 1 as indicated by ARI of 0.5. Preglomerular microvessels (PGMV) were collected for mRNA measurement (n=4–7 rats/each group). IR increased mRNA expression of p67phox in males at 24 hours (7.3±1.5 vs. 1.1±0.2 in sham, P<0.05) and 1 week (2.2±0.3 vs. 1.0±0.1 in sham, P<0.05). In contrast, IR elevated p67phox mRNA expression in females at 24 hours only (3.9±0.4 vs. 1.5±0.2 in sham, P<0.05) but to a lesser degree compared to IR males (P<0.05). The p47phox mRNA expression was elevated in IR males at 1 week (2±0.3 vs. 1.0±0.1 in sham, P<0.05) but remained unchanged in IR females. IR also markedly increased mRNA expression of MCP‐1 in both male and female rats at 24 hours and 1 week (P<0.05 vs respective sham). TGF‐β mRNA expression tends to increase in IR males at 24 hours and reached statistical significance at week 1 (2.5±0.2 vs 1.1±0.1 in sham, P<0.05). TGF‐β was significantly elevated in IR females though still lower compared to IR males at week 1 (1.7±0.2 vs 2.5±0.2, P<0.05). In conclusion, these results suggest that IR impairs RBF autoregulation in male and female rats which might be associated with activation of NOX, MCP‐1 and TGF‐β pathways in PGMV. Female rats have less kidney injury which might be attributed to less NOX expression in PGMV.Support or Funding InformationThis study was supported by grants from NIH (DK106500) to ZG, and NIH (DK044628 and HL095499) to EWI.

Protective effects of celecoxib on ischemia reperfusion-induced acute kidney injury: comparing between male and female rats.

Objective(s):There is increasing evidence for the importance of gender in different diseases; however, the role of gender in response to treatments is still unknown. Therefore, this study investigated the impact of gender on the protective effects of celecoxib in ischemia reperfusion (IR)-induced acute kidney injury.Materials and Methods:In this experimental study, rats were randomly divided into 6 groups (n=6): IR, sham and celecoxib groups of males and females. In IR groups, after orally receiving saline for 5 days, renal pedicles were clamped for 55 min and then kidneys were reperfused for 24 hr. In the sham groups, clamping of renal pedicles was not performed. In the celecoxib groups, 30 mg/kg celecoxib was given orally for 5 days before induction of ischemia. Plasma was collected to determine creatinine (Cr) and blood urea nitrogen (BUN). Kidney tissue samples were also stored for examining the histopathology and measuring malondialdehyde (MDA) levels and superoxide dismutase (SOD) activities.Results:IR caused significant increases in plasma Cr (P<0.05), BUN (P<0.05) and renal histopathological damages in both genders. Also, induction of IR resulted in significant increase of MDA levels (P<0.05) and decrease of SOD activities (P<0.05) in the kidney in both genders. Celecoxib administration prevented the IR-induced functional, histopathological and oxidative changes in both genders by similar degrees.Conclusion:This study suggested that in similar pathological conditions, celecoxib improves renal function and histopathological damages and attenuates oxidative stress in both genders by the same degrees. These protective effects of celecoxib on IR-induced kidney injury are gender-independent.

Cell Death Patterns Due to Warm Ischemia or Reperfusion in Renal Tubular Epithelial Cells Originating from Human, Mouse, or the Native Hibernator Hamster.

Ischemia–reperfusion injury contributes to the pathogenesis of many diseases, with acute kidney injury included. Hibernating mammals survive prolonged bouts of deep torpor with a dramatic drop in blood pressure, heart, and breathing rates, interspersed with short periods of arousal and, consequently, ischemia–reperfusion injury. Clarifying the differences under warm anoxia or reoxygenation between human cells and cells from a native hibernator may reveal interventions for rendering human cells resistant to ischemia–reperfusion injury. Human and hamster renal proximal tubular epithelial cells (RPTECs) were cultured under warm anoxia or reoxygenation. Mouse RPTECs were used as a phylogenetic control for hamster cells. Cell death was assessed by both cell imaging and lactate dehydrogenase (LDH) release assay, apoptosis by cleaved caspase-3, autophagy by microtubule-associated protein 1-light chain 3 B II (LC3B-II) to LC3B-I ratio, necroptosis by phosphorylated mixed-lineage kinase domain-like pseudokinase, reactive oxygen species (ROS) fluorometrically, and lipid peroxidation, the end-point of ferroptosis, by malondialdehyde. Human cells died after short periods of warm anoxia or reoxygenation, whereas hamster cells were extremely resistant. In human cells, apoptosis contributed to cell death under both anoxia and reoxygenation. Although under reoxygenation, ROS increased in both human and hamster RPTECs, lipid peroxidation-induced cell death was detected only in human cells. Autophagy was observed only in human cells under both conditions. Necroptosis was not detected in any of the evaluated cells. Clarifying the ways that are responsible for hamster RPTECs escaping from apoptosis and lipid peroxidation-induced cell death may reveal interventions for preventing ischemia–reperfusion-induced acute kidney injury in humans.

Role of capsaicin sensitive sensory nerves in ischemia reperfusion-induced acute kidney injury in rats

Acute kidney injury (AKI) is a common kidney disorder which is associated with a high risk of mortality. Extensive evidence revealed the participation of renal afferent sensory nerves in the pathophysiology of renal ischemia reperfusion (IR) injury, however the role of these nerves in renal IR injury is controversial and remains to be further explored. Here, we report that capsaicin sensitive sensory nerves and neuropeptides prevented renal damage in AKI induced by IR injury. The sensory afferent degeneration model was established by injecting 50 mg/kg of capsaicin to male neonatal rats and verified by the tail flick test and reduced sensory neuropeptide of substance P and calcitonin gene related peptide in spinal cord, dorsal root ganglion and kidney after 12 weeks. Then, a model of renal IR injury was established. The sensory afferent degeneration in the AKI group increased the level of serum creatinine, NGAL and KIM-1, aggravated to some extent renal pathological damage, and enhanced the proinflammatory cytokines expressions and tubular cell apoptosis. In addition, it was also discovered that the level of phospho-ERK/ERK (p-ERK/ERK) showed an increase in spinal cord and kidney after degeneration of capsaicin sensitive sensory nerves. In conclusion, the degeneration of sensory nerves aggravated IR-induced AKI in rats, and the activated ERK signaling in spinal cord and kidney after sensory afferent degeneration might be the possible mechanism in the aggravated renal injury.

Estradiol attenuates ischemia reperfusion-induced acute kidney injury through PPAR-γ stimulated eNOS activation in rats.

We investigated the involvement of peroxisome proliferator activated receptor-γ (PPAR-γ)/endothelial nitric oxide synthase (eNOS) pathway in estradiol mediated protection against ischemia reperfusion (I/R)-induced acute kidney injury (AKI) in rats. To induce AKI, rats underwent 40min of bilateral renal ischemia followed by 24h of reperfusion. I/R-induced kidney damage was quantified by measuring serum creatinine, creatinine clearance, urea nitrogen, uric acid, potassium, fractional excretion of sodium, microproteinuria, and renal oxidative stress (thiobarbituric acid reactive substances, superoxide anion generation, and reduced glutathione). Hematoxylin eosin stain demonstrated renal histology, while renal expression of apoptotic markers (Bcl-2, Bax), PPAR-γ and eNOS were quantified by immunohistochemistry. Estradiol (1mg/kg, i.p.) was administered 30min before I/R in rats. In separate groups, PPAR-γ antagonist, BADGE (30mg/kg, i.p.), and NOS inhibitor, L-NAME (20mg/kg, i.p.) were administered prior to estradiol treatment, which was followed by I/R in rats. I/R caused significant renal damage as demonstrated by biochemical (serum/urine), renal oxidative stress and histological changes alongwith increased expression of Bax and decreased levels of Bcl-2, PPAR-γ and eNOS, which were prevented by estradiol. Pre-treatment with BADGE and L-NAME abolished estradiol mediated renoprotection. Notably, I/R + estradiol + BADGE group revealed decreased expression of PPAR-γ and eNOS in renal tissues. In I/R + estradiol + L-NAME group, eNOS expression was reduced while PPAR-γ levels remained unchanged. These results suggest that estradiol modulates PPAR-γ which consequently regulates eNOS expression in rat kidneys. We conclude that estradiol protects against I/R-induced AKI through PPAR-γ stimulated eNOS activation in rats.

Crosstalk Between Connexin32 and Mitochondrial Apoptotic Signaling Pathway Plays a Pivotal Role in Renal Ischemia Reperfusion-Induced Acute Kidney Injury.

Aims: Perioperative acute kidney injury (AKI) resulting from renal ischemia reperfusion (IR) is not conducive to the postoperative surgical recovery. Our previous study demonstrated that reactive oxygen species (ROS) transmitted by gap junction (GJ) composed of connexin32 (Cx32) contributed to AKI. However, the precise underlying pathophysiologic mechanisms were largely unknown. This study focuses on the underlying mechanisms related to ROS transmitted by Cx32 responsible for AKI aggravation. Results: In a set of in vivo studies, renal IR was found to cause severe impairment in renal tissues with massive ROS generation, which occurred contemporaneously with activation of NF-κB/p53/p53 upregulated modulator of apoptosis (PUMA)-mediated mitochondrial apoptosis pathways. Cx32 deficiency alleviated renal IR-induced AKI, and simultaneously attenuated ROS generation and distribution in renal tissues, which further inhibited NF-κB/p53/PUMA-mediated mitochondrial apoptotic pathways. Correspondingly, in a set of in vitro studies, hypoxia reoxygenation (HR)-induced cellular injury, and cell apoptosis in both human kidney tubular epithelial cells (HK-2s) and rat kidney tubular epithelial cells (NRK52Es) were significantly attenuated by Cx32 inhibitors or Cx32 gene knockdown. More importantly, Cx32 inhibition not only decreased ROS generation and distribution in human or rat kidney tubular epithelial cells but also inhibited its downstream NF-κB/p53/PUMA-mediated mitochondrial apoptotic pathway activation. Innovation and Conclusion: This is the first identification of the underlying mechanisms of IR-induced renal injury integrally which demonstrates the critical role played by Cx32 in IR-induced AKI. Moreover, GJ composed of Cx32 manipulates ROS generation and distribution between neighboring cells, and alters activation of NF-κB/p53/PUMA-mediated mitochondrial apoptotic pathways. Both inhibiting Cx32 function and scavenging ROS effectively reduce mitochondrial apoptosis and subsequently attenuate AKI, providing effective strategies for kidney protection.

Connexin32 plays a crucial role in ROS-mediated endoplasmic reticulum stress apoptosis signaling pathway in ischemia reperfusion-induced acute kidney injury

BackgroundIschemia–reperfusion (I/R)-induced acute kidney injury (AKI) not only prolongs the length of hospital stay, but also seriously affects the patient’s survival rate. Although our previous investigation has verified that reactive oxygen species (ROS) transferred through gap junction composed of connexin32 (Cx32) contributed to AKI, its underlying mechanisms were not fully understood and viable preventive or therapeutic regimens were still lacking. Among various mechanisms involved in organs I/R-induced injuries, endoplasmic reticulum stress (ERS)-related apoptosis is currently considered to be an important participant. Thus, in present study, we focused on the underlying mechanisms of I/R-induced AKI, and postulated that Cx32 mediated ROS/ERS/apoptosis signal pathway activation played an important part in I/R-induced AKI.MethodsWe established renal I/R models with Cx32+/+ and Cx32−/− mice, which underwent double kidneys clamping and recanalization. ROS scavenger (N-acetylcysteine, NAC) and ERS inhibitors (4-phenyl butyric acid, 4-PBA, and tauroursodeoxycholic acid, TUDCA) were used to decrease the content of ROS and attenuate ERS activation, respectively.ResultsRenal damage was progressively exacerbated in a time-dependent manner at the reperfusion stage, that was consistent with the alternation of ERS activation, including glucose regulated protein 78 (BiP/GRP78), X box-binding protein1, and C/EBP homologous protein expression. TUDCA or 4-PBA application attenuated I/R-induced ERS activation and protected against renal tubular epithelial cells apoptosis and renal damage. Cx32 deficiency decreased ROS generation and distribution between the neighboring cells, which attenuated I/R-induced ERS activation, and improved cell apoptosis and renal damage.ConclusionCx32 mediated ROS/ERS/apoptosis signal pathway activation played an important part in I/R-induced AKI. Cx32 deficiency, ROS elimination, and ERS inhibition all could protect against I/R-induced AKI.

Renoprotective Effects of Artesunate against Renal Ischemia-Reperfusion Injury in Rat Model

Renal ischemia-reperfusion (Renal I/R) leads to acute kidney injury (AKI),a major kidney disease associated with an increasing prevalence and high mortality rates. A variety of experimental models,both in vitro and in vivo,have been used to study the pathogenic mechanisms of ischemic AKI and to test reno-protective strategies. Aim: To study potential protective effects of artesunate on renal I/R injury. Renal I/R injury was unilaterally induced in adult (3 to 5 months) male Sprague-Dawely rats,whose weights ranged from 180 to 390 g. Thereafter,the animals were pre-treated with artesunate intra-peritoneally,and at the end of reperfusion sacrificed humanely. Plasma,serum and tissue samples were obtained for analysis. Plasma concentrations of NGAL (neutrophil gelatinase associated lipocalin),an iron-trafficking protein involved in multiple processes such as apoptosis,innate immunity and renal development,and tissue concentrations of IL-18 (Interleukin-18) were measured via ELISA analysis. Serum urea and creatinine were also measured in the samples. Artesunate improved renal ischemia reperfusion,including renal function and brought about reductions in inflammatory mediators and kidney tissue injury. Plasma concentrations of NGAL and tissue concentrations of IL-18 were significantly (p &lt; 0.05) lower in the artesunatepretreated group than in the vehicle and control groups. Furthermore,serum concentrations of urea and creatinine were significantly (p &lt; 0.05) decreased in the pretreated group as compared to the control group. Artesunate can significantly improve renal function following I/R through down-regulation of inflammatory parameters and NGAL expression. Furthermore,it could serve as a potential therapy in ischemia reperfusion-induced acute kidney injury.

The Antimicrobial Peptide Cathelicidin protects against ischemia reperfusion-induced acute kidney injury

The Antimicrobial Peptide Cathelicidin protects against ischemia reperfusion-induced acute kidney injury

Administration of Tempol Improves Renal Autoregulation in Ischemia‐reperfusion Induced Acute Kidney Injury

Renal autoregulation is critical for protecting the kidney from fluctuations in arterial pressure by regulating renal vascular resistance to maintain stable renal perfusion and glomerular filtration rate (GFR). Renal ischemia‐reperfusion (IR) induced acute kidney injury (IR‐AKI) is characterized by reduced renal blood flow and a decline in GFR. We hypothesized that increased reactive oxygen species (ROS) contribute to impairment of renal autoregulatory capability in IR‐AKI. Afferent arteriole autoregulatory behavior was assessed using the in vitro blood‐perfused juxtamedullary nephron preparation. IR‐AKI was induced by 60 minutes of bilateral renal artery occlusion followed by 24 hours of reperfusion. We found that plasma creatinine was increased in IR rats (3.86 ± 0.2 mg/dl) compared to 0.93 ± 0.07 mg/dl in sham rats (n=6–7, p&lt;0.05). Baseline afferent arteriole diameter averaged 13.0 ± 0.4 μm (n=5) in kidneys from sham rats and these arterioles exhibited normal autoregulatory behavior. Decreasing renal perfusion pressure from 100 to 65 mmHg increased arteriole diameter from 13.0 ± 0.4 to 15.1 ± 0.8 μm, corresponding to 116 ± 5% of the baseline diameter. Subsequent stepwise increases in perfusion pressure (15 mmHg) caused pressure‐dependent afferent arteriole vasoconstriction to 66 ± 2% of baseline diameter at 170 mmHg. In contrast, pressure‐mediated afferent arteriole responses were markedly attenuated in IR‐AKI rats. Baseline diameter averaged 11.7 ± 0.6 μm and remained between 91 and 101% of baseline over the 65–170 mmHg pressure range tested, indicating a loss of autoregulatory function. In another set of IR‐AKI rats, acute administration of the ROS scavenger, tempol (10−3 M), to afferent arterioles increased baseline diameter by 10 ± 2% from 11.3 ± 0.8 to 12.2 ± 0.9 μm (n=5). Furthermore, scavenging ROS production improved autoregulatory behavior of afferent arterioles from IR‐AKI rats. During exposure to tempol, decreasing renal perfusion pressure from 100 to 65 mmHg resulted in a diameter increase to 110 ± 2 % of the control diameter while increasing perfusion pressure to 170 mmHg decreased arteriole diameter to 78 ± 1% of control (P&lt;0.05 vs IR). In conclusion, these results suggest that renal ischemia‐reperfusion leads to impaired autoregulatory behavior of afferent arterioles. Acutely scavenging endogenous ROS with tempol improves afferent arteriole autoregulatory responsiveness, suggesting that excessive ROS production contributes to impaired renal autoregulation in IR‐AKI.Support or Funding InformationThis study is supported by a Grant‐in‐Aid (15GRNT25240015) from the American Heart Association for ZG and by grants from NIH (DK044628, HL074167, HL098135 and HL095499) for EWI.

Inhibition of PTEN Activity Aggravates Post Renal Fibrosis in Mice with Ischemia Reperfusion-Induced Acute Kidney Injury

Background: Renal fibrosis is a common pathophysiological feature of chronic kidney disease. Acute kidney injury (AKI) is defined as an independent causal factor of chronic kidney disease, with a pathological representation of post renal fibrosis. However, the etiopathogenesis underlying post renal fibrosis induced by AKI is not completely understood. Methods: BALB/c mice were treated with bpv or vehicle controls and were, respectively, the ischemia reperfusion (IR) model group and control group. All of the animals had blood taken from the orbital venous plexus at 24 hours after IR. Six mice in each group were randomly chosen and euthanized 7 days after IR treatment, and the remaining six mice in each group were euthanized 14 days after IR treatment. We examined the effect on post kidney fibrosis of inhibiting PTEN activity in mice in an IR induced AKI experimental model. Results: Compared with vehicle mice, bpv-(PTEN specific inhibitor) treated mice accumulated more bone marrow-derived fibroblasts and myofibroblasts in the kidneys. Inhibition of PTEN activity increased the expression of α-smooth muscle actin and extracellular matrix proteins and post kidney fibrosis. Furthermore, inhibition of PTEN activity resulted in more inflammatory cytokines in the kidneys of mice subjected to IR-induced renal fibrosis. Moreover, inhibition of PTEN activity up-regulated PI3K protein expression and Akt phosphorylation. Conclusions: Our study demonstrated that PTEN played an important role in post renal fibrosis in mice with ischemia reperfusion-induced AKI. These results indicated that the PTEN/PI3K/Akt signaling pathway may serve as a novel therapeutic target for AKI-induced chronic kidney disease.

Abstract 064: Role of Sphingosine-1-phosphate 2 Receptor in Renal Microvascular Function of Renal Ischemia-reperfusion Rats

Renal ischemia-reperfusion (IR) induced acute kidney injury (IR-AKI) is accompanied by increased renal vascular resistance and a dramatic decline in glomerular filtration rate. Sphingosine-1-phosphate (S1P), a bioactive sphingolipid metabolite, plays a critical role in IR-AKI. Our recent studies established that exogenous S1P is a potent vasoconstrictor in rat afferent arterioles. We postulated that renal IR enhanced sensitivity of afferent arterioles to S1P-induced vasoconstriction via S1P2 receptor activation. The afferent arteriole response to S1P was assessed using the in vitro blood-perfused juxtamedullary nephron preparation. IR rats were induced by 60 min bilateral renal artery occlusion followed by 24 hours reperfusion. Baseline arteriolar diameter decreased significantly in IR (11.9±0.7 vs. 14.7±0.5 μm in sham, n=7, P&lt;0.05). Exogenous S1P evoked concentration-dependent vasoconstriction in sham rats. Increasing S1P (10 -10 -10 -5 M) decreased diameter to 99±1, 95±2, 89±2, 80±3, 58±4, and 34±2% of baseline (n=7), respectively. Renal IR shifted the S1P vasoconstrictor profile to the left. Arteriolar diameter declined to 93±1, 87±1, 76±1, 64±5, 46±5 and 35±4% of baseline (n=7, P&lt;0.05 vs sham at 10 -10 -10 -7 M S1P). S1P2 receptor blockade with JTE-013 markedly increased baseline diameter by 51±13% in IR (P&lt;0.05, vs. 11±3% in shams, n=3-4), suggesting that endogenous S1P exerts a greater influence on arteriolar tonic in IR than in sham. JTE-013 also markedly attenuated the enhanced vasoconstriction to S1P in IR rats. Arteriolar diameter averaged 112±2, 110±1, 114±3, 102±6, 81±6 and 61±10% of control in response to increasing S1P (P&lt;0.05 vs. JTE-013 untreated-IR) similar to JTE-013 treated sham. In contrast, arteriolar responses to Ang II, endothelin-1 or the S1P precursor, sphingosine were unaltered in IR rats. S1P content increased from 1.3±0.4 to 1.9±0.4 pmol/mg protein (~45%) in the cortical tissue of IR rats and 2.2±0.4 to 3.4±0.2 pmol/mg protein (~55%) in the medullary tissue but reduced the plasma S1P concentration from 2.5±0.3 to 1.3±0.1 μM (~50%, P&lt;0.05, n=3). These data establish that renal IR increases sphingolipid metabolites in rat kidneys and enhances renal microvascular S1P signaling, probably via S1P2 receptor activation.

Curcumin alleviates ischemia reperfusion-induced acute kidney injury through NMDA receptor antagonism in rats

Objective: The present study investigated the role of N-methyl-d-aspartate (NMDA) receptors in curcumin-mediated renoprotection against ischemia reperfusion (I/R)-induced acute kidney injury (AKI) in rats.Methods: Rats were subjected to bilateral renal I/R (40 min I, 24 hours R) to induce AKI. Kidney injury was assessed by measuring creatinine clearance, blood urea nitrogen, plasma uric acid, potassium level, fractional excretion of sodium, and macroproteinuria. Oxidative stress in renal tissues was assessed by measuring myeloperoxidase activity, thiobarbituric acid reactive substances, superoxide anion generation, and reduced glutathione content. Hematoxylin & eosin staining was done to assess histological changes in renal tissues. Curcumin (30 and 60 mg/kg) was administered one hour before subjecting rats to AKI. In separate groups, NMDA receptor agonists, glutamic acid (200 mg/kg), and spermidine (20 mg/kg) were administered prior to curcumin treatment in rats followed by AKI.Results: I/R-induced AKI was demonstrated by significant change in plasma and urine parameters along with marked increase in oxidative stress and histological changes in renal tissues that were aggravated with pretreatment of glutamic acid and spermidine in rats. Administration of curcumin resulted in significant protection against AKI. However, glutamic acid and spermidine pretreatments prevented curcumin-mediated renoprotection.Conclusion: It is concluded that NMDA receptor antagonism significantly contributes towards curcumin-mediated protection against I/R-induced AKI.