IRI-induced Acute Kidney Injury Research Articles

Pioglitazone ameliorates ischemia/reperfusion-induced acute kidney injury via oxidative stress attenuation and NLRP3 inflammasome.

Acute kidney injury (AKI) induced by renal ischemia/reperfusion injury (IRI) is a severe clinical condition. ROS accumulation, antioxidant pathways deficiency, and inflammation are involved in IRI. Pioglitazone (Pio) exerts anti-inflammatory and antioxidant effects. The aim of this study was to explore the protective effects of pioglitazone against IRI-induced AKI. Pathogen-free Sprague-Dawley (SD) rats were arbitrarily divided into four groups: Sham operation group Control (CON) group, CON + Pio group, I/R + Saline group, and I/R + Pio group. In addition, HK-2 cells were subjected to hypoxia and reoxygenation to develop an H/R model for investigation of the protective mechanism of Pio. Pretreatment with pioglitazone in the model rats reduced urea nitrogen and creatinine levels, histopathological scores, and cytotoxicity after IRI. Pioglitazone treatment significantly attenuated renal cell apoptosis, decreased cytotoxicity, increased Bcl-2 expression, and downregulated Bax expression. Besides, the levels of ROS and inflammatory factors, including NLRP3, ASC, pro-IL-1β, pro-caspase-1, cleaved-caspase-1, TNF-α, IL-6, and IL-1β, in I/R rats and H/R cells were normalized by the pioglitazone treatment. Pioglitazone improved IRI-induced AKI by attenuating oxidative stress and NLRP3 inflammasome activation. Therefore, pioglitazone has the potential to serve as a novel agent for renal IRI treatment and prevention.

Ramelteon attenuates renal ischemia and reperfusion injury through reducing mitochondrial fission and fusion and inflammation.

Renal ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury (AKI). This study explored the function and mechanisms of ramelteon on IRI-induced AKI. Mice were randomly divided into five groups: Sham, IRI, IRI + ramelteon (0.3 mg/kg), IRI + ramelteon (1 mg/kg), and IRI + ramelteon (3 mg/kg). Mice were intraperitoneally treated with ramelteon for 7 days before IRI. IRI was accomplished by bilateral renal artery clamping for 30 minutes, after which the clamps were removed for blood reperfusion. HK-2 cells were randomly divided into five groups: control, hypoxia/reoxygenation (H/R), H/R + ramelteon (10 nM), H/R + ramelteon (30 nM), and H/R + ramelteon (60 nM). HK-2 cells were prophylactically treated with ramelteon and then exposed to H/R. Ramelteon attenuated renal injury, inhibited cell apoptosis, decreased reactive oxygen species (ROS) generation, and suppressed levels of interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin 1β (IL-1β). Ramelteon decreased apoptosis-related protein Bax and TLR4-related proteins (TLR4, MyD88, p-IκBα, and p-p65 NF-κB), enhanced apoptosis-related protein Bcl-2. Furthermore, ramelteon increased mitochondrial membrane potential in H/R cells. Mitochondrial-related proteins (Drp1, Fis1, and Mff) were abated, whereas Mfn1 and Mfn2 were enhanced in H/R induced cells. Ramelteon attenuates renal injury induced by IRI and H/R, which is involved in apoptosis, mitochondrial damage, and inflammation.

Cofilin-1 induces acute kidney injury via the promotion of endoplasmic reticulum stress-mediated ferroptosis

Ischemia–reperfusion injury (IRI) leads to acute kidney injury (AKI), which poses serious threat to public health and society. Many clinical studies were conducted to evaluate several biomarkers in AKI, among which Cofilin-1 remains to be a very promising one. To explore the potential mechanism of Cofilin-1 in AKI, we established an oxygen-glucose-deprivation (OGD)-induced AKI cell model. The overexpression and knock-down Cofilin-1 were used for gain- and loss-of-function. Pharmacological inhibitors were employed to study the related pathways. The results showed that Cofilin-1 was significantly upregulated in AKI cells, knocking down Cofilin-1 protected cells against the effect of OGD treatment and alleviated AKI phenotypes. Overexpression of Cofilin-1 might induce AKI by triggering ferroptosis, inhibiting NF-κB signaling or ER stress pathway attenuated Cofilin-1 induced lipid peroxidation and AKI. We also validated our findings in IRI-induced AKI mouse models in vivo. Our work elucidated that Cofilin-1 might induce AKI via promoting ER stress-mediated ferroptosis and argues it as a biomarker for early diagnosis of AKI. We also expect to offer novel insights on future therapeutic interventions.

Exploratory metabolomic analysis based on UHPLC-Q-TOF-MS/MS to study hypoxia-reoxygenation energy metabolic alterations in HK-2 cells

Purpose Renal ischemia-reperfusion injury(IRI)is a major cause of acute kidney injury(AKI), the injury and repair of renal tubular epithelial cells play an important role in the pathological process of IR-AKI. Metabolomics was used to detect cell metabolism alterations and metabolic reprogramming in the initial injury, peak injury, and recovery stage of human renal proximal tubular cells (HK-2 cells) to provide insights into clinical prevention and treatment of IRI-induced AKI. Methods An in vitro ischemia-reperfusion (H/R) injury and the recovery model of HK-2 cells were established at different times of hypoxia/reoxygenation. Comprehensive detection of metabolic alterations in HK-2 cells after H/R induction by nontarget metabolomics. Interconversion of glycolysis and fatty acid oxidation (FAO) in HK-2 cells after H/R induction was examined by western blotting and qRT-PCR. Results Multivariate data analysis found significant differences among the groups, with significant changes in metabolites such as glutamate, malate, aspartate, and L-palmitoylcarnitine. Hypoxia-reoxygenated HK-2 cells are accompanied by altered metabolisms such as disturbance of amino acid and nucleotide metabolism, dysregulation of lipid metabolism, increased glycolysis, and metabolic reprogramming, which manifests as a shift in energy metabolism from FAO to glycolysis. Conclusion The development of IRI-induced AKI in HK-2 cells is accompanied by the disturbance of amino acid, nucleotide, and tricarboxylic acid cycle metabolism and specifically metabolic reprogramming of FAO to glycolytic conversion. The timely recovery of energy metabolism in HK-2 cells is of great significance for treating and prognosis IRI-induced AKI.

Abstract 10422: Sesn2 Mediates Metformin Rescued Age-Related Cardiac Dysfunctions of Cardiorenal Syndrome

Introduction: Cardiorenal syndrome (CRS) consists of disorders of the kidneys and heart, whereby dysfunction of one organ may induce dysfunction of the other. Acute kidney injury (AKI) leads to a reduction in blood flow and energy supply to the heart. AMP-activated protein kinase (AMPK) as an energy sensor regulates energy metabolism via interacting with a scaffold protein Sesn2. The anti-diabetes drug metformin is an AMPK agonist, and it has been reported to regulate substrate metabolism under physiological and pathological conditions. But the beneficial role of metformin in CRS remains unknown. Hypothesis: Age-related impaired AMPK signaling contributes to cardiac intolerance to AKI-induced insults in the elderly. Metformin treatment ameliorates CRS through triggering Sens2/AMPK activation. Methods: Young (3-5 months) and aged (21-23 months) C57BL/6J wild type (WT), cardiomyocyte specific knock out (cSesn2 -/- ) and littermates (Sesn2 f/f ) C57BL/6J mice were subjected to AKI with a laparotomy and the renal artery and vein were clamped for 15 min followed by 72 hr of reperfusion (IRI). Seahorse XF Analyzer for mitochondrial respirational functions. Results: The higher levels of serum creatinine were observed after IRI-induced AKI in the aged versus young WT and cSens2 -/- versus Sesn2 f/f mice. Interestingly, administration of metformin can significantly reduce serum creatinine levels by IRI-induced AKI in young/aged WT and Sesn2 f/f but not cSesn2 -/- mice. Renal histological analysis showed higher incidence of tubular necrosis in the aged versus young AKI mice, the tubular necrosis was significantly reduced in the metformin treated young and aged AKI mice. Echocardiography data showed that AKI caused cardiac systolic dysfunctions in all experimental groups, while metformin treatment improved cardiac functions of young/aged WT and Sesn2 f/f but not cSesn2 -/- mice. Moreover, metformin treatment triggered AMPK activation and improved mitochondrial respiration rate and ATP production of cardiomyocytes from young/aged WT and Sesn2 f/f but not cSesn2 -/- hearts. Conclusions: Aging augments cardiac vulnerability to IRI-induced AKI. Metformin can rescue cardiac dysfunctions and renal injury caused by AKI through Sesn2/AMPK signaling pathway.

Regulation of the autophagy plays an important role in acute kidney injury induced acute lung injury

Aim This study aimed to investigate the regulatory role of autophagy in acute kidney injury (AKI) induced acute lung injury (ALI). Methods The male Sprague–Dawley rats were divided into four groups: normal saline-treated sham rats (sham group), normal saline-treated ischemia-reperfusion injury rats (IRI group), 3-methyladenine-treated IRI rats (3-MA group), and rapamycin-treated IRI rats (RA group). The rats in the IRI rat model received the nephrectomy of the right kidney and was subjected to 60 mins of left renal pedicle occlusion, followed by 12, 24, 48, and 72 h of reperfusion. The levels of Scr, BUN, wet-to-dry ratio of lung, inflammatory cytokines, and oxidative stress were determined. The damage to tissues was detected by histological examinations. The western blot and immunohistochemistry methods were conducted to determine the expression of indicated proteins. Results Renal IRI could induce the pulmonary injury after AKI, which caused significant increases in the function index of pulmonary and renal, the levels of inflammatory cytokines, and biomarkers of oxidative stress. In comparison to the IRI group, the RA group showed significantly decreased P62 and Caspase-3 expression and increased LC-II/LC3-I, Beclin-1, Bcl-2, and unc-51-like autophagy activating kinase 1 expression. Meanwhile, by suppressing the inflammation and oxidative stress, as well as inhibiting the pathological lesions in kidney and lung tissues, the autophagy could effectively ameliorate IRI-induced AKI and ALI. Conclusions Autophagy plays an important role in AKI-induced ALI, which could be used as a new target for AKI therapy and reduce the mortality caused by the complication.

Cellular communication network 2 (connective tissue growth factor) aggravates acute DNA damage and subsequent DNA damage response-senescence-fibrosis following kidney ischemia reperfusion injury

Chronic allograft dysfunction with progressive fibrosis of unknown cause remains a major issue after kidney transplantation, characterized by ischemia-reperfusion injury (IRI). One hypothesis to account for this is that spontaneous progressive tubulointerstitial fibrosis following IRI is driven by cellular senescence evolving from a prolonged, unresolved DNA damage response (DDR). Since cellular communication network factor 2 ((CCN2), formerly called connective tissue growth factor), an established mediator of kidney fibrosis, is also involved in senescence-associated pathways, we investigated the relation between CCN2 and cellular senescence following kidney transplantation. Tubular CCN2 overexpression was found to be associated with DDR, loss of kidney function and tubulointerstitial fibrosis in both the early and the late phase in human kidney allograft biopsies. Consistently, CCN2 deficient mice developed reduced senescence and tubulointerstitial fibrosis in the late phase; six weeks after experimental IRI. Moreover, tubular DDR markers and plasma urea were less elevated in CCN2 knockout than in wild-type mice. Finally, CCN2 administration or overexpression in epithelial cells induced upregulation of tubular senescence-associated genes including p21, while silencing of CCN2 alleviated DDR induced by anoxia-reoxygenation injury in cultured proximal tubule epithelial cells. Thus, our observations indicate that inhibition of CCN2 can mitigate IRI-induced acute kidney injury, DNA damage, and the subsequent DDR-senescence-fibrosis sequence. Hence, targeting CCN2 might help to protect the kidney from transplantation-associated post-IRI chronic kidney dysfunction.

Exosomal lncRNA TUG1 derived from human urine-derived stem cells attenuates renal ischemia/reperfusion injury by interacting with SRSF1 to regulate ASCL4-mediated ferroptosis

BackgroundHuman urine-derived stem cells (USCs)-derived exosomes (USC-Exo) could improve kidney ischemia/reperfusion injury (IRI), while the underlying mechanisms of this protective effect remain unclear.MethodsHuman USCs and USC-Exo were isolated and verified by morphology and specific biomarkers. The effects of USC-Exo on ferroptosis and kidney injury were detected in the IRI-induced acute kidney injury (AKI) model in C57BL/6 mice. The effects of USC-Exo on ferroptosis and lncRNA taurine-upregulated gene 1 (TUG1) were detected in hypoxia/reoxygenation (H/R)-treated human proximal tubular epithelial cells (HK-2). The interaction of SRSF1 and TUG1, ACSL4 was checked via RNA pull-down/RIP and RNA stability assays. The effects of LncRNA TUG1 on SRSF1/ACSL4-mediated ferroptosis were verified in H/R-treated HK-2 cells and the IRI-induced AKI mouse models.ResultsUSC-Exo treatment improved kidney injury and ameliorated ferroptosis in IRI-induced AKI mouse models. USC-Exo were rich in lncRNA TUG1, which suppressed ferroptosis in HK-2 cells exposed to H/R. Mechanistically, lncRNA TUG1 regulates the stability of ACSL4 mRNA by interacting with RNA-binding protein SRSF1. In addition, SRSF1 upregulation or ACSL4 downregulation partially reversed the protective effect of lncRNA TUG1 on ferroptosis in H/R-treated HK-2 cells. Further, ACSL4 upregulation partially reversed TUG1’s repression on kidney injury and ferroptosis in IRI-induced AKI mice.ConclusionCollectively, lncRNA TUG1 carried by USC-Exo regulated ASCL4-mediated ferroptosis by interacting with SRSF1 and then protected IRI-induced AKI. Potentially, USC-Exo rich in lncRNA TUG1 can serve as a promising therapeutic method for IRI-AKI.

Indoleamine 2,3 Dioxygenase 1-The Potential Link between the Innate Immunity and the Ischemia-Reperfusion-Induced Acute Kidney Injury?

Ischemia-reperfusion injury (IRI) is of the most common causes of acute kidney injury (AKI); nevertheless, the mechanisms responsible for both early kidney injury and the reparative phase are not fully recognised. The inflammatory response following ischemia is characterised by the crosstalk between cells belonging to the innate immune system—dendritic cells (DCs), macrophages, neutrophils, natural killer (NK) cells, and renal tubular epithelial cells (RTECs). A tough inflammatory response can damage the renal tissue; it may also have a protective effect leading to the repair after IRI. Indoleamine 2,3 dioxygenase 1 (IDO1), the principal enzyme of the kynurenine pathway (KP), has a broad spectrum of immunological activity from stimulation to immunosuppressive activity in inflamed areas. IDO1 expression occurs in cells of the innate immunity and RTECs during IRI, resulting in local tryptophan (TRP) depletion and generation of kynurenines, and both of these mechanisms contribute to the immunosuppressive effect. Nonetheless, it is unknown if the above mechanism can play a harmful or preventive role in IRI-induced AKI. Despite the scarcity of literature in this field, the current review attempts to present a possible role of IDO1 activation in the regulation of the innate immune system in IRI-induced AKI.

Maslinic Acid Attenuates Ischemia/Reperfusion-Induced Acute Kidney Injury by Suppressing Inflammation and Apoptosis Through Inhibiting NF-κB and MAPK Signaling Pathway.

Inflammation and apoptosis are the major contributors to the mechanisms of acute kidney injury (AKI) due to renal ischemia-reperfusion injury (IRI). Maslinic acid (MA), a pentacyclic triterpene acid mostly found in dietary plants, the current study was to demonstrate the renoprotective effect of MA on IRI-induced AKI, and to investigate the role of inflammation and apoptosis-related signaling pathways as a molecular mechanism. C57BL/6J mice were subjected to IRI for 72 h, and MA was daily administered by intraperitoneal injection during this period. In parallel, rat renal proximal tubule cells (NRK52E) were prophylactically treated with MA and then exposed to hydrogen peroxide (H2O2). MA treatment significantly inhibited the mRNA expression of interleukin (IL-1β), tumor necrosis factor-α (TGF-α), monocyte chemoattractant protein-1 (MCP-1), and intercellular adhesion molecule-1(ICAM-1). Also, MA reduced the expression of Bax/Bcl2 ratio and cleaved caspase-3. In NRK52 cells, MA inhibited the IκBα degradation, blocked NF-κB/p65 phosphorylation, and nuclear translocation. The phosphorylation of ERK, JNK, and p38 was attenuated by MA in IRI-induced kidney injury and H2O2-stimulated NRK52 cells. The expression levels of IL-1β, MCP-1, and ICAM-1 were upregulated in H2O2-stimulated NRK52E cells, which was attenuated by NF-κB inhibitor. H2O2 treatment increased the Bax/Bcl2 ratio and cleaved caspase-3 in NRK52E cells, which was counteracted by MAPK inhibitors. Together, our data demonstrate that MA suppresses IR-induced AKI injury through NF-κB and MAPK signaling pathways and that MA is a promising agent in the treatment of kidney diseases.

Human Endothelial Progenitor Cells Protect the Kidney against Ischemia-Reperfusion Injury via the NLRP3 Inflammasome in Mice.

Ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and progression to chronic kidney disease (CKD). However, no effective therapeutic intervention has been established for ischemic AKI. Endothelial progenitor cells (EPCs) have major roles in the maintenance of vascular integrity and the repair of endothelial damage; they also serve as therapeutic agents in various kidney diseases. Thus, we examined whether EPCs have a renoprotective effect in an IRI mouse model. Mice were assigned to sham, EPC, IRI-only, and EPC-treated IRI groups. EPCs originating from human peripheral blood were cultured. The EPCs were administered 5 min before reperfusion, and all mice were killed 72 h after IRI. Blood urea nitrogen, serum creatinine, and tissue injury were significantly increased in IRI mice; EPCs significantly improved the manifestations of IRI. Apoptotic cell death and oxidative stress were significantly reduced in EPC-treated IRI mice. Administration of EPCs decreased the expression levels of NLRP3, cleaved caspase-1, p-NF-κB, and p-p38. Furthermore, the expression levels of F4/80, ICAM-1, RORγt, and IL-17RA were significantly reduced in EPC-treated IRI mice. Finally, the levels of EMT-associated factors (TGF-β, α-SMA, Snail, and Twist) were significantly reduced in EPC-treated IRI mice. This study shows that inflammasome-mediated inflammation accompanied by immune modulation and fibrosis is a potential target of EPCs as a treatment for IRI-induced AKI and the prevention of progression to CKD.

Selenium nanoparticles alleviate ischemia reperfusion injury-induced acute kidney injury by modulating GPx-1/NLRP3/Caspase-1 pathway.

Rationale: Acute kidney injury (AKI) is a common critical illness in the clinic and currently lacks effective treatment options. Ischemia reperfusion injury (IRI) is a major pathogenic factor for AKI. Due to the deficiency of selenium (Se) in AKI patients, we intended to treat IRI-induced AKI using a Se rebalancing strategy in the present study.Methods: Sodium selenate, ascorbic acid, and bovine serum albumin (BSA) were employed to prepare nanomaterials termed Se@BSA nanoparticles (NPs) using a simple method. Experiments with human renal tubular epithelial HK-2 cells exposed to hypoxia/reoxygenation (H/R) and IRI-AKI mice were used to evaluate the therapeutic efficiency of Se@BSA NPs. Transcriptome sequencing, further molecular biology experiments, and pathologic analysis were performed to investigate the underlying mechanisms.Results: Se@BSA NPs accumulated in mouse kidneys and could be endocytosed by renal tubular epithelial cells after intravenous administration. In vitro studies showed that Se@BSA NP treatment markedly increased the levels of glutathione peroxidase (GPx)-1 and suppressed NLRP3 inflammasome activation in H/R cells, which resulted in reductions in the proteolytic cleavage of pro-Caspase-1 into active Caspase-1 and the maturation of inflammatory factors. Mouse experiments confirmed these findings and demonstrated an inspiring mitigative effect of Se@BSA NPs on IRI-induced AKI. Owing to modulation of the GPx-1/NLRP3/Caspase-1 pathway, Se@BSA NPs dramatically inhibited fibrosis formation after AKI.Conclusion: This study provides an effective therapeutic option by applying easy-to-produce Se-containing nanomaterials to remedy Se imbalance and impede inflammatory responses in the kidney, which is a promising candidate for AKI treatment.

Mice with Established Diabetes Show Increased Susceptibility to Renal Ischemia/Reperfusion Injury: Protection by Blockade of Jnk or Syk Signaling Pathways

Patients with diabetes are at an increased risk for acute kidney injury (AKI) after renal ischemia/reperfusion injury (IRI). However, there is a lack preclinical models of IRI in established diabetes. The current study characterized renal IRI in mice with established diabetes and investigated potential therapies. Diabetes was induced in C57BL/6J mice by low-dose streptozotocin injection. After 7 weeks of sustained diabetes, mice underwent 13 minutes of bilateral renal ischemia and were euthanized after 24 hours of reperfusion. Age-matched, nondiabetic controls underwent the same surgical procedure. Renal IRI induced two- and sevenfold increases in plasma creatinine level in nondiabetic and diabetic mice, respectively (P<0.001). Kidney damage, as indicated by histologic damage, tubular cell death, tubular damage markers, and inflammation, was more severe in the diabetic IRI group. The diabetic IRI group showed greater accumulation of spleen tyrosine kinase (Syk)-expressing cells, and increased c-Jun N-terminal kinase (Jnk) signaling in tubules compared to nondiabetic IRI. Prophylactic treatment with a Jnk or Syk inhibitor substantially reduced the severity of AKI in the diabetic IRI model, with differential effects on neutrophil infiltration and Jnk activation. In conclusion, established diabetes predisposed mice to renal IRI-induced AKI. Two distinct proinflammatory pathways, JNK and SYK, were identified as potential therapeutic targets for anticipated AKI in patients with diabetes.

Effect of NAD+ boosting on kidney ischemia-reperfusion injury.

Acute kidney injury (AKI) is associated with a very high mortality and an increased risk for progression to chronic kidney disease (CKD). Ischemia-reperfusion injury (IRI) is a model for AKI, which results in tubular damage, dysfunction of the mitochondria and autophagy, and in decreased cellular nicotinamide adenine dinucleotide (NAD+) with progressing fibrosis resulting in CKD. NAD+ is a co-enzyme for several proteins, including the NAD+ dependent sirtuins. NAD+ augmentation, e.g. by use of its precursor nicotinamide riboside (NR), improves mitochondrial homeostasis and organismal metabolism in many species. In the present investigation the effects of prophylactic administration of NR on IRI-induced AKI were studied in the rat. Bilateral IRI reduced kidney tissue NAD+, caused tubular damage, reduced α-Klotho (klotho), and altered autophagy flux. AKI initiated progression to CKD, as shown by induced profibrotic Periostin (postn) and Inhibin subunit beta-A, (activin A / Inhba), both 24 hours and 14 days after surgery. NR restored tissue NAD+ to that of the sham group, increased autophagy (reduced p62) and sirtuin1 (Sirt1) but did not ameliorate renal tubular damage and profibrotic genes in the 24 hours and 14 days IRI models. AKI induced NAD+ depletion and impaired autophagy, while augmentation of NAD+ by NR restored tissue NAD+ and increased autophagy, possibly serving as a protective response. However, prophylactic administration of NR did not ameliorate tubular damage of the IRI rats nor rescued the initiation of fibrosis in the long-term AKI to CKD model, which is a pivotal event in CKD pathogenesis.

Renoprotective Effect of Oridonin in a Mouse Model of Acute Kidney Injury via Suppression of Macrophage Involved Inflammation.

Ischemia-reperfusion injury (IRI) is the major cause of acute kidney injury (AKI). The previous studies demonstrated that Oridonin can protect kidney against IRI-induced AKI, but the underlying molecular mechanism is unclear. In this study, it showed that Oridonin significantly improved kidney damage, and inhibited the expression of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and MCP-1, as well as macrophage marker F4/80 in kidney and the secretion of inflammatory cytokins in serum of AKI mice in vivo. In addition, Oridonin also effectively reduced the expression and secretion of lipopolysaccharide (LPS)-induced inflammatory factors in macrophage cell line RAW264.7 in vitro. Notably, Oridonin strongly downregulated Mincle and AKT/nuclear factor-kappaB (NF-κB) signaling both in vivo and in vitro, and the results of cellular recovery experiments of overexpression of Mincle in macrophage suggested that Oridonin suppressed inflammatory response of macrophage through inhibiting Mincle, which may be the underlying mechanism of Oridonin improving injury in kidney of AKI mice. In summary, the above results indicated that Oridonin can protect kidney from IRI-induced inflammation and injury by inhibiting the expression of Mincle in macrophage.

Deciphering the Role of Heme Oxygenase-1 (HO-1) Expressing Macrophages in Renal Ischemia-Reperfusion Injury.

Ischemia-reperfusion injury (IRI) is a leading cause of acute kidney injury (AKI), which contributes to the development of chronic kidney disease (CKD). Renal IRI combines major events, including a strong inflammatory immune response leading to extensive cell injuries, necrosis and late interstitial fibrosis. Macrophages act as key players in IRI-induced AKI by polarizing into proinflammatory M1 and anti-inflammatory M2 phenotypes. Compelling evidence exists that the stress-responsive enzyme, heme oxygenase-1 (HO-1), mediates protection against renal IRI and modulates macrophage polarization by enhancing a M2 subset. Hereafter, we review the dual effect of macrophages in the pathogenesis of IRI-induced AKI and discuss the critical role of HO-1 expressing macrophages.

Resistance Training Enhances Renal Function in Experimental Renal Ischemia-Reperfusion

Acute kidney injury (AKI) resulting from ischemia-reperfusion injury (IRI) is among the most common complications in hospitalized patients. In recent years, it has been argued that exercise is an approach to attenuate impairments caused by AKI. The purpose of this study was to investigate whether eight weeks of resistance training (RT) has protective effects on IRI. Thirty male Wistar rats (210-230 g) were randomly divided into four groups, including RT+ISC (n=7), RT (n=8), ISC (n=7), and sham (n=8). Animals underwent eight weeks of RT, and 48 hours after the last training session, ischemia (45 min) reperfusion (24 h) was induced. Then animals were sacrificed, and blood and kidney tissue samples were collected to measure creatinine (Cr), blood urea nitrogen (BUN), kidney tissue damage score (KTDS), and kidney weight (KW). The results showed that IRI caused a significant increase in Cr, BUN, KTDS, and KW (p-value &lt;0.05), while RT decreased the severity of KTDS, Cr, and BUN remarkably. (p≤0.05). RT, however, did not attenuate KW (p≤0.05). Overall, the findings of our study provide evidence that RT can attenuate IRI-induced AKI considering enhanced biomarkers; However, further research should be conducted to make certain about the protective effects of exercise training, especially RT.

Legumain promotes tubular ferroptosis by facilitating chaperone-mediated autophagy of GPX4 in AKI

Legumain is required for maintenance of normal kidney homeostasis. However, its role in acute kidney injury (AKI) is still unclear. Here, we induced AKI by bilateral ischemia-reperfusion injury (IRI) of renal arteries or folic acid in lgmnWT and lgmnKO mice. We assessed serum creatinine, blood urea nitrogen, histological indexes of tubular injury, and expression of KIM-1 and NGAL. Inflammatory infiltration was evaluated by immunohistological staining of CD3 and F4/80, and expression of TNF-α, CCL-2, IL-33, and IL-1α. Ferroptosis was evaluated by Acsl4, Cox-2, reactive oxygen species (ROS) indexes H2DCFDA and DHE, MDA and glutathione peroxidase 4 (GPX4). We induced ferroptosis by hypoxia or erastin in primary mouse renal tubular epithelial cells (mRTECs). Cellular survival, Acsl4, Cox-2, LDH release, ROS, and MDA levels were measured. We analyzed the degradation of GPX4 through inhibition of proteasomes or autophagy. Lysosomal GPX4 was assessed to determine GPX4 degradation pathway. Immunoprecipitation (IP) was used to determine the interactions between legumain, GPX4, HSC70, and HSP90. For tentative treatment, RR-11a was administrated intraperitoneally to a mouse model of IRI-induced AKI. Our results showed that legumain deficiency attenuated acute tubular injury, inflammation, and ferroptosis in either IRI or folic acid-induced AKI model. Ferroptosis induced by hypoxia or erastin was dampened in lgmnKO mRTECs compared with lgmnWT control. Deficiency of legumain prevented chaperone-mediated autophagy of GPX4. Results of IP suggested interactions between legumain, HSC70, HSP90, and GPX4. Administration of RR-11a ameliorated ferroptosis and renal injury in the AKI model. Together, our data indicate that legumain promotes chaperone-mediated autophagy of GPX4 therefore facilitates tubular ferroptosis in AKI.

Phospholipase A2 group XV activity during cardiopulmonary bypass surgery

ObjectivesAll patients who undergo cardiopulmonary bypass (CPB) experience some degree of ischemia reperfusion injury (IRI). Severe IRI-induced acute kidney injury (AKI) occurs in approximately 1–2% of patients undergoing CPB. Previous studies using activity-based protein profiling of urine identified group XV phospholipase A2, PLA2G15/LPLA2, as potentially associated with patients who develop AKI post CPB. The present study examined urinary PLA2G15/LPLA2 activity during CPB and in the near postoperative period for associations with subsequent AKI development. Design & methodsSamples were collected in a nested case controlled cohort of 21 patients per group who either did (AKI) or did not (non-AKI) develop AKI post-operatively. Serum and urine samples from each patient before, during and after CPB were assayed for PLA2G15/LPLA2 activity. ResultsUrine activity significantly increased during the intra operative period. In contrast the activities in paired sera were markedly decreased during CPB. There was no correlation between the serum and urine activity levels of patients. There were no significant differences in activity levels of PLA2G15/LPLA2 in the urine or sera from patients that did and did not develop AKI. ConclusionsThe lack of correlation between serum and urine activity levels suggests that the rapid intraoperative increases in PLA2G15/LPLA2 activity may originate from the kidney and as such offer an intraoperative indicator of early renal response to CPB associated stressors.

Akt1 is involved in tubular apoptosis and inflammatory response during renal ischemia-reperfusion injury.

Renal ischemia-reperfusion injury (IRI) is one of the major causes of acute kidney injury (AKI). Although Akt is involved in renal IRI, it is unclear as to which Akt isoform plays an important role in renal IRI. In this study, we investigated the role of Akt1 in renal IRI. We subjected the C57BL/6 male mice to unilateral IRI with contralateral nephrectomy. Two days after IRI, IRI-kidneys were harvested. The mice were divided into four groups: wild type (WT) IRI, Akt1-/- IRI, WT sham, and Akt1-/- sham. We found that Akt1, not Akt2 or Akt3, was markedly activated in WT IRI than in WT sham mice. The histologic damage score and serum creatinine level significantly increased in WT IRI mice, the increase being the highest in Akt1-/- IRI mice. The number of TdT-mediated dUTP nick-end labeling (TUNEL)-positive tubular cells and expression of cleaved caspase-3/Bax were higher in Akt1-/- IRI mice than in WT IRI mice. The expression of Bcl-2 was lower in Akt1-/- IRI mice than in WT IRI mice. The expression of tumor necrosis factor-α/interleukin-6/interleukin-1β and number of F4/80-positive macrophages were markedly higher in Akt1-/- IRI than in WT IRI mice. The expression of phosphorylated nuclear factor-κB p65 was also higher in Akt1-/- IRI mice than in WT IRI mice. Our results show that Akt1 deletion exacerbates kidney damage as it increases tubular apoptosis and inflammatory response during renal IRI. Akt1 could be a potential therapeutic target for developing treatments against IRI-induced AKI.