Reactive oxygen species and rat renal epithelial cells during hypoxia and reoxygenation

Human umbilical cord mesenchymal stem cells attenuate diabetic nephropathy through the IGF1R-CHK2-p53 signalling axis in male rats with type 2 diabetes mellitus

Diabetes mellitus (DM) is a disease syndrome characterized by chronic hyperglycaemia. A long-term high-glucose environment leads to reactive oxygen species (ROS) production and nuclear DNA damage. Human umbilical cord mesenchymal stem cell (HUcMSC) infusion induces significant antidiabetic effects in type 2 diabetes mellitus (T2DM) rats. Insulin-like growth factor 1 (IGF1) receptor (IGF1R) is important in promoting glucose metabolism in diabetes; however, the mechanism by which HUcMSC can treat diabetes through IGF1R and DNA damage repair remains unclear. In this study, a DM rat model was induced with high-fat diet feeding and streptozotocin (STZ) administration and rats were infused four times with HUcMSC. Blood glucose, interleukin-6 (IL-6), IL-10, glomerular basement membrane, and renal function were examined. Proteins that interacted with IGF1R were determined through coimmunoprecipitation assays. The expression of IGF1R, phosphorylated checkpoint kinase 2 (p-CHK2), and phosphorylated protein 53 (p-p53) was examined using immunohistochemistry (IHC) and western blot analysis. Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum levels of 8-hydroxydeoxyguanosine (8-OHdG). Flow cytometry experiments were used to detect the surface markers of HUcMSC. The identification of the morphology and phenotype of HUcMSC was performed by way of oil red "O" staining and Alizarin red staining. DM rats exhibited abnormal blood glucose and IL-6/10 levels and renal function changes in the glomerular basement membrane, increased the expression of IGF1 and IGF1R. IGF1R interacted with CHK2, and the expression of p-CHK2 was significantly decreased in IGF1R-knockdown cells. When cisplatin was used to induce DNA damage, the expression of p-CHK2 was higher than that in the IGF1R-knockdown group without cisplatin treatment. HUcMSC infusion ameliorated abnormalities and preserved kidney structure and function in DM rats. The expression of IGF1, IGF1R, p-CHK2, and p-p53, and the level of 8-OHdG in the DM group increased significantly compared with those in the control group, and decreased after HUcMSC treatment. Our results suggested that IGF1R could interact with CHK2 and mediate DNA damage. HUcMSC infusion protected against kidney injury in DM rats. The underlying mechanisms may include HUcMSC-mediated enhancement of diabetes treatment via the IGF1R-CHK2-p53 signalling pathway.

Bradykinin induces acute kidney injury after hypothermic circulatory arrest through the repression of the Nrf2-xCT pathway

Postoperative acute kidney injury (AKI) is a common complication in patients undergoing deep hypothermic circulatory arrest (HCA); however, its underlying pathogenesis is unclear. In this study, we established a rat cardiopulmonary bypass model and demonstrated that hypothermia during HCA, rather than circulatory arrest, was responsible for the occurrence of AKI. By recruiting 56 patients who underwent surgery with HCA and analyzing the blood samples, we found that post-HCA AKI was associated with an increase in bradykinin. Animal experiments confirmed this and showed that hypothermia during HCA increased bradykinin levels by increasing kallikrein expression. Mechanistically, bradykinin inhibited the Nrf2-xCT pathway through B2R and caused renal oxidative stress damage. Application of Icatibant, a B2R inhibitor, reversed changes in the Nrf2-xCT pathway and oxidative stress damage. Finally, Icatibant reversed hypothermia-induced AKI in vivo. This finding reveals the pathogenesis of AKI after HCA and helps to provide therapeutic strategy for patients with post-HCA AKI.

A Single-Cell Transcriptome Profiling of Triptolide-Induced Nephrotoxicity in Mice

Triptolide (TP), an active component isolated from the traditional Chinese herb Tripterygium wilfordii Hook F (TWHF), shows great promise for treating inflammation-related diseases. However, its potential nephrotoxic effects remain concerning. The mechanism underlying TP-induced nephrotoxicity is inadequately elucidated, particularly at single-cell resolution. Hence, single-cell RNA sequencing (scRNA-seq) of kidney tissues from control and TP-treated mice is performed to generate a thorough description of the renal cell atlas upon TP treatment. Heterogeneous responses of nephron epithelial cells are observed after TP exposure, attributing differential susceptibility of cell subtypes to excessive reactive oxygen species and increased inflammatory responses. Moreover, TP disrupts vascular function by activating endothelial cell immunity and damaging fibroblasts. Severe immune cell damage and the activation of pro-inflammatory Macro_C1 cells are also observed with TP treatment. Additionally, ligand-receptor crosstalk analysis reveals that the SPP1 (osteopontin) signaling pathway targeting Macro_C1 cells is triggered by TP treatment, which may promote the infiltration of Macro_C1 cells to exacerbate renal toxicity. Overall, this study provides comprehensive information on the transcriptomic profiles and cellular composition of TP-associated nephrotoxicity at single-cell resolution, which can strengthen the understanding of the pathogenesis of TP-induced nephrotoxicity and provide valuable clues for the discovery of new therapeutic targets to ameliorate TP-associated nephrotoxicity.

LncTCONS_00058568 is involved in the pathophysiologic processes mediated by P2X7R in the lower thoracic spinal cord after acute kidney injury

Acute kidney injury (AKI), a prevalent clinical syndrome, involves the participation of the nervous system in neuroimmune regulation. However, the intricate molecular mechanism that governs renal function regulation by the central nervous system (CNS) is complex and remains incompletely understood. In the present study, we found that the upregulated expression of lncTCONS_00058568 in lower thoracic spinal cord significantly ameliorated AKI-induced renal tissue injury, kidney morphology, inflammation and apoptosis, and suppressed renal sympathetic nerve activity. Mechanistically, the purinergic ionotropic P2X7 receptor (P2X7R) was overexpressed in AKI rats, whereas lncTCONS_00058568 was able to suppress the upregulation of P2X7R. In addition, RNA sequencing data revealed differentially expressed genes associated with nervous system inflammatory responses after lncTCONS_00058568 was overexpressed in AKI rats. Finally, the overexpression of lncTCONS_00058568 inhibited the activation of PI3K/Akt and NF-κB signaling pathways in spinal cord. Taken together, the results from the present study show that lncTCONS_00058568 overexpression prevented renal injury probably by inhibiting sympathetic nerve activity mediated by P2X7R in the lower spinal cord subsequent to I/R-AKI.

Exploring the role of Hmox1 in ferroptosis and immune infiltration during renal ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is inevitable in kidney transplantations and, as a complex pathophysiological process, it can be greatly impacted by ferroptosis and immune inflammation. Our study aimed to identify the biomarkers of renal IRI (RIRI) and elucidate their relationship with immune infiltration. In this study, the GSE148420 database was used as a training set to analyze differential genes and overlap them with ferroptosis-related genes to identify hub genes using a protein-protein interaction (PPI) network, the least absolute shrinkage and selection operator (LASSO), and random forest algorithm (RFA). We verified the hub gene and ferroptosis-related phenotypes in a verification set and animal experiments involving unilateral IRI with contralateral nephrectomy in rats. Gene set enrichment analysis (GSEA) of single genes was conducted according to the hub gene to predict related endogenous RNAs (ceRNAs) and drugs to establish a network. Finally, we used the Cibersort to analyze immunological infiltration and conducted Spearman's correlation analysis. We identified 5456 differential genes and obtained 26 ferroptosis-related differentially expressed genes. Through PPI, LASSO, and RFA, Hmox1 was identified as the only hub gene and its expression levels were verified using verification sets. In animal experiments, Hmox1 was verified as a key biomarker. GSEA of single genes revealed the seven most related pathways, and the ceRNAs network included 138 mRNAs and miRNAs. We predicted 11 related drugs and their three-dimensional structural maps. Thus, Hmox1 was identified as a key biomarker and regulator of ferroptosis in RIRI and its regulation of ferroptosis was closely related to immune infiltration.

Clinical significance of Interleukin 17 receptor E in diabetic nephropathy

OBJECTIVE

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease. Since there are limited therapeutic options available for the prevention of DN progression, it is imperative to explore novel differentially expressed genes and therapeutic targets for DN.

METHODS

In this study, mice kidney tissue were subjected to transcriptome sequencing and the results were analysed using bioinformatics methods. Interleukin 17 receptor E (IL-17RE) was screened from the sequencing data and its expression was validated in the animal tissues and a cross-sectional clinical study. Fifty-five DN patients were enrolled and further subdivided into two groups based on the urinary albumin-to-creatinine ratio (UACR). Two control groups were used for comparison (minimal change disease group, 12 patients; normal control group, 6 patients). Correlation analysis was conducted to study the relationship between IL-17RE expression and the clinicopathological indices. Logistic regression and receiver operating characteristic (ROC) curve analyses were conducted to evaluate the diagnostic value.

RESULTS

IL-17RE expression was significantly higher in db/db mice and the kidney tissues of DN patients than the control group. IL-17RE protein levels in the kidney tissues were strongly correlated with neutrophil gelatinase-associated lipocalin (NGAL) levels, UACR, and certain clinicopathological indices. IL-17RE levels, total cholesterol (TC) levels, and glomerular lesions were independent risk factors for macroalbuminuria. ROC curves showed a good detection value for IL-17RE in macroalbuminuria (area under the curve = 0.861).

CONCLUSION

The results of this study provide novel insights into DN pathogenesis. Kidney IL-17RE expression levels were associated with DN disease severity and albuminuria.

Investigations into ferroptosis in methylmercury-induced acute kidney injury in mice

Methylmercury (MeHg) is a highly poisonous form of mercury and a risk factor for kidney impairment in humans that currently has no effective means of therapy. Ferroptosis is a non-apoptotic metabolic cell death linked to numerous diseases. It is currently unknown whether ferroptosis takes part in MeHg-induced kidney damage. Here, we established a model of acute kidney injury (AKI) in mice by gavage with different doses of MeHg (0, 40, 80, 160 μmol/kg). Serological analysis revealed elevated levels of UA, UREA, and CREA; H&E staining showed variable degrees of renal tubule injury; qRT-PCR detection displayed increased expression of KIM-1 and NGAL in the groups with MeHg treatment, indicated that MeHg successfully induced AKI. Furthermore, MDA levels enhanced in renal tissues of mice with MeHg exposure whereas GSH levels decreased; ACSL4 and PTGS2 nucleic acid levels elevated while SLC7A11 levels reduced; transmission electron microscopy illustrated that the density of the mitochondrial membrane thickened and the ridge reduced considerably; protein levels for 4HNE and TfR1 improved since GPX4 levels declined, all these results implying the involvement of ferroptosis as a result of MeHg exposure. Additionally, the observed elevation in the protein levels of NLRP3, p-p65, p-p38, p-ERK1/2, and KEAP1 in tandem with downregulated Nrf2 expression levels indicate the involvement of the NF-κB/NLRP3/MAPK/Nrf2 pathways. All the above findings suggested that ferroptosis and the NF-κB/NLRP3/MAPK/Nrf2 pathways are implicated in MeHg-induced AKI, thereby providing a theoretical foundation and reference for future investigations into the prevention and treatment of MeHg-induced kidney injury.

Vitamin B ameliorates PM2.5-induced kidney damage by reducing endoplasmic reticulum stress and oxidative stress in pregnant mice and HK-2

As an air pollutant, particulate matters 2.5 (PM_2.5) poses a severe risk to kidney and the mechanism involves oxidative stress and endoplasmic reticulum (ER) stress. As an essential nutrient for human health, Vitamin B performs anti-inflammatory and antioxidant functions. In order to study the effect of Vitamin B on PM_2.5-induced kidney damage during pregnancy, the pregnant mice were divided into the four experimental groups randomly: control group, model group, treatment group and VB group. PM_2.5 was sprayed on the trachea of pregnant mice once each three days for six times from pregnancy until delivery. The model group was given 30μL PM_2.5 suspension of 3.456μg/μL and 10mL/(kg·d) PBS. The treatment group was given 30μL PM_2.5 suspension of 3.456μg/μL and 10mL/(kg·d) Vitamin B. The VB group was given 10mL/(kg·d) Vitamin B and the control group was given the same dose of PBS. Vitamin B was composed of Vitamin B6, Vitamin B12 and folic acid, with final concentrations are 1.14, 0.02 and 0.06mg/mL, respectively. The results showed Vitamin B ameliorated PM_2.5-induced kidney damage such as improving histopathological change, decreasing expressions of Bip and Chop, increasing expressions of Nrf2, HO-1 and Nqo1. In addition, HK-2 cells were used for cell experiments and were divided into the four groups, in which the dosage of PM_2.5 was 75μg/mL for 24h and Vitamin B was 5μL/100μL. The results showed Vitamin B ameliorated PM_2.5-induced HK-2 damage, such as decreasing expressions of Bip, Chop, P47^phox and ROS, increasing expressions of Nrf2, HO-1, Nqo1 and NO. Our findings showed Vitamin B ameliorated PM_2.5-induced kidney damage by reducing ER stress and oxidative stress in pregnant mice and in HK-2.

Therapeutic Potential of Two Derivative Prescriptions of Rokumijiogan, Hachimijiogan and Bakumijiogan against Renal Damage in Nephrectomized Rats

Background: Hachimijiogan (HJG) and Bakumijiogan (BJG), two derivative prescriptions of Rokumijiogan (RJG), were selected to investigate their renoprotective potential in the 5/6 nephrectomized (5/6Nx) rat model. Methods: Rats were treated with HJG and BJG orally at 150 mg/kg body weight/day once daily for 10 weeks after resection of 5/6 of the renal volume, and their renoprotective effects were compared with 5/6Nx vehicle-treated and sham-operated control rats. Results: Improvements in renal lesions, glomerulosclerosis, tubulointerstitial injury, and arteriosclerotic lesions estimated by histologic scoring indices in the HJG-treated group were compared with those in the BJG-treated group. HJG- and BJG-treated groups ameliorated the renal function parameters. Elevated levels of renal oxidative stress-related biomarkers were reduced, while decreased antioxidant defence systems (superoxide dismutase and the glutathione/oxidized glutathione ratio) were increased in the HJG-treated group rather than the BJG-treated group. In contrast, BJG administration significantly reduced expression of the inflammatory response through oxidative stress. The HJG-treated group showed a decrease in inflammatory mediators through the JNK pathway. To gain a deeper understanding of their therapeutic action, the effects of the main components detected in HJG and BJG were evaluated using the LLC-PK₁ renal tubular epithelial cell line, which is the renal tissue most vulnerable to oxidative stress. Corni Fructus and Moutan Cortex-originated compositions afforded important protection against oxidative stress induced by peroxynitrite. Conclusions: From our described and discussed analyses, it can be concluded that RJG-containing prescriptions, HJG and BJG are an excellent medicine for chronic kidney disease. In the future, appropriately designed clinical studies in people with chronic kidney disease are necessary to evaluate the renoprotective activities of HJG and BJG.

Icariin synergizes therapeutic effect of dexamethasone on adriamycin-induced nephrotic syndrome

BACKGROUND

Glomerular damage is a common clinical indicator of nephrotic syndrome. High-dose hormone treatment often leads to hormone resistance in patients. How to avoid resistance and improve the efficiency of hormone therapy draws much attention to clinicians.

METHODS

Adriamycin (ADR) was used to induce nephropathy model in SD rats. The rats were treated with dexamethasone (DEX), icariin (ICA), and DEX + ICA combination therapy. The changes in urinary protein (UP), urea nitrogen (BUN), and serum creatinine (SCR) contents in rats were detected by enzyme-linked immunosorbent assay (ELISA), and the degree of pathological injury and the expression level of podocin were detected by HE staining and immunohistochemistry, to test the success of the model and the therapeutic effects of three different ways. The effect of treatments on podocytes autophagy was evaluated via transfection of mRFP-GFP-LC3 tandem adenovirus in vitro.

RESULTS

The contents of UP, SCR, and BUN were significantly increased, the glomerulus was seriously damaged, and the expression of Nephrosis2 (NPHS2) was significantly decreased in the ADR-induced nephrotic syndrome rat model compared to that of the control group. DEX, ICA, and the DEX + ICA combined treatment significantly alleviated these above changes induced by ADR. The combined treatment of DEX + ICA exhibited better outcome than single treatment. The combined treatment also restored the podocyte autophagy, increased the expression of microtubule-associated protein light-chain 3II (LC3II), and reduced the expression of p62 in vitro. The combined treatment protects podocytes by mediating the PI3K/AKT/mTOR (rapamycin complex) signaling pathway.

CONCLUSION

ICA enhances the therapeutic effect of DEX on the nephrotic syndrome.

GPX3 and GSTT1 as biomarkers related to oxidative stress during renal ischemia reperfusion injuries and their relationship with immune infiltration

Background

Renal ischemia reperfusion injuries (IRIs) are very common in clinical diagnoses and treatments, which are a common cause of impaired renal functions, worsening pathological damage, affecting disease progression and hindering recovery. Renal IRIs are an inflammatory disease mediated by the adaptive and innate immune system. There is a complex interaction between oxidative stress and immune cell infiltration. Therefore, we aimed to determine biomarkers associated with oxidative stress during renal IRIs and their relationship with immune cell infiltration.

Method

A differential gene expression analysis was made based on the GSE148420 dataset from the NCBI Gene Expression Comprehensive Database (GEO) combined with 92 oxidative-stress (OS)-related genes identified in the Molecular Signatures Database. Then we identified differentially-expressed genes (DEOSGs) associated with oxidative stress, which were used for gene ontology (GO) and a Kyoto Encyclopedia of Genomes (KEGG) enrichment analysis. At the same time, we used PPI protein interaction networks and Lasso regression analysis to identify key genes, which were verified by the validation sets GSE58438 and GSE71647, as well as Western Blot detection on rat renal IRI models. At the same time, PAS staining, HE staining and immunohistochemistry were used to detect tissue damage and expression of markers related to oxidative stress during renal ischemia-reperfusion. Single-gene enrichment analysis (GSEA) was used to further clarify the underlying biological functions of key genes. Cibersort was used to analyze the immune cell infiltration during renal IRI and the correlation of key genes with immune cells. At the same time, we constructed a network of transcription-factor (TF)-Hub genes and miRNA-Hub genes. DGIDB was used to predict drugs and molecular compounds that might interact with the Hub genes.

Results

Compared with the control group, a total of 5456 differential genes (DEGs) were measured in the renal IRI group, 2486 of which were upregulated and 2970 were down-regulated. Among them, we found 30 DEGs (DEOSGs) associated with oxidative stress. The results of GO and KEGG enrichment analysis showed that these DEOSGs were mainly enriched in glutathione metabolism, the response to oxidative stress stimulation, the regulation of T cell activation and apoptosis signaling pathways. Through a protein interaction network (PPI) and a LASSO regression analysis, a total of two Hub genes were identified, namely GPX3 and GSTT1, which were validated through external validation sets and animal experiments. Through pathological methods, we found that the pathological damage of renal tissue and the expression of oxidative stress markers increased after renal ischemia-reperfusion. The results of GSEA showed that the Hub genes were related to oxidative stress pathways, apoptosis signaling pathways and immune-response-related signaling pathways. An immunoinfiltration correlation analysis showed that genes GPX3 and GSTT1 were significantly positively correlated with plasma cells and macrophage M0, while were negatively correlated with monocytes and macrophages M1 and M2. Using the Strust, Starbase and DGIDB database, we predicted that 81 transcription factors, 49 miRNAs and 13 drug or molecular compounds might interact with the Hub genes.

Conclusion

Through a comprehensive analysis of gene expression, our findings may provide new potential biomarkers for the pathogenesis of renal IRIs and a reliable basis for its early diagnosis as well as treatment.

BMAL1 regulates mitochondrial homeostasis in renal ischaemia-reperfusion injury by mediating the SIRT1/PGC-1α axis

The regulation of renal function by circadian gene BMAL1 has been recently recognized; however, the role and mechanism of BMAL1 in renal ischaemia‐reperfusion injury (IRI) are still unknown. The purpose of this study was to clarify the pathophysiological role of BMAL1 in renal IRI. We measured the levels of BMAL1 and mitochondrial biogenesis‐related proteins, including SIRT1, PGC‐1α, NRF1 and TFAM, in rats with renal IRI. In rats, the level of BMAL1 decreased significantly, resulting in inhibition of SIRT1 expression and mitochondrial biogenesis. In addition, under hypoxia and reoxygenation (H/R) stimulation, BMAL1 knockdown decreased the level of SIRT1 and exacerbated the degree of mitochondrial damage and apoptosis. Overexpression of BMAL1 alleviated H/R‐induced injury. Furthermore, application of the SIRT1 inhibitor EX527 not only reduced the activities of SIRT1 and PGC‐1α but also further aggravated mitochondrial dysfunction and partially reversed the protective effect of BMAL1 overexpression. Moreover, whether in vivo or in vitro, the application of SIRT1 agonist resveratrol rescued the mitochondrial dysfunction caused by H/R or IRI by activating mitochondrial biogenesis. These results indicate that BMAL1 is a key circadian gene that mediates mitochondrial homeostasis in renal IRI through the SIRT1/PGC‐1α axis, which provides a new direction for targeted therapy for renal IRI.

Mitochondrial Pathophysiology on Chronic Kidney Disease

In healthy kidneys, interstitial fibroblasts are responsible for the maintenance of renal architecture. Progressive interstitial fibrosis is thought to be a common pathway for chronic kidney diseases (CKD). Diabetes is one of the boosters of CKD. There is no effective treatment to improve kidney function in CKD patients. The kidney is a highly demanding organ, rich in redox reactions occurring in mitochondria, making it particularly vulnerable to oxidative stress (OS). A dysregulation in OS leads to an impairment of the Electron transport chain (ETC). Gene deficiencies in the ETC are closely related to the development of kidney disease, providing evidence that mitochondria integrity is a key player in the early detection of CKD. The development of novel CKD therapies is needed since current methods of treatment are ineffective. Antioxidant targeted therapies and metabolic approaches revealed promising results to delay the progression of some markers associated with kidney disease. Herein, we discuss the role and possible origin of fibroblasts and the possible potentiators of CKD. We will focus on the important features of mitochondria in renal cell function and discuss their role in kidney disease progression. We also discuss the potential of antioxidants and pharmacologic agents to delay kidney disease progression.

Caspase-1 Inhibitor Reduces Pyroptosis Induced by Brain Death in Kidney

Brain death (BD) induces an organ-level inflammatory response. However, the underlying mechanisms have not been fully elucidated. Here, we investigated the role of caspase-1-mediated pyroptosis in BD-induced kidney injury in rats. A BD model was established in Sprague-Dawley rats. The rats were intravenously injected with Z-YVAD-FMK 1 h before BD, and sham-operated rats served as controls. After 0, 1, 2, 4, and 6 h of BD, renal injury, and renal expression of the nod-like receptor family pyrin domain-containing 3 (NLRP3), caspase-1, caspase-11, gasdermin D (GSDMD), IL-1β, and IL-18 were assessed using quantitative reverse transcriptase-polymerase chain reaction, western blotting, and immunohistochemistry. Blood urea nitrogen and serum creatinine levels were measured. Additionally, renal tubular epithelial cells (NRK-52E) were subjected to 3 h of hypoxia followed by 6 h of reoxygenation and incubated with Z-YVAD-FMK before hypoxia and reoxygenation. Caspase-11 was knocked-down using small interfering RNA technology. Cell viability and levels of pyroptosis-associated proteins were assessed thereafter. NLRP3, caspase-1, GSDMD, IL-1β, and IL-18 expression levels were upregulated in BD rats. Treatment with Z-YVAD-FMK reduced mRNA and protein levels of caspase-1, GSDMD, IL-1β, and IL-18, improved renal function, and alleviated renal injury. Z-YVAD-FMK efficaciously reduced pyroptosis effects in kidneys in BD rats. Thus, it could be considered as a therapeutic target for BD-induced kidney injury.

Impact of Prolonged Mechanical Ventilation on Ferroptosis in Renal Ischemia/Reperfusion Injury in Rats

We here investigated the impact of mechanical ventilation (MV) time on ferroptosis in a rat renal ischemia/reperfusion injury (IRI) model. Thirty-two male adult Sprague Dawley rats were divided into four groups (n = 8/group): the sham group, IRI group, IRI+MV-4 h group, and IRI+MV-12 h group. Rats in the IRI group were subjected to 45 min bilateral renal ischemia. Rats in the IRI+MV groups were additionally mechanically ventilated with tracheal intubation after 45 min bilateral renal ischemia. Morphological changes associated with kidney injury and ferroptosis were assessed by hematoxylin and eosin staining and electron microscopy. Levels of the central regulator of ferroptosis, glutathione peroxidase 4 (GPX4), and lipid peroxidation markers 4-hydroxynonenal (4HNE) and superoxide dismutase 2 (SOD2) were determined in the kidney tissue by western blotting. Glutathione (GSH) levels were assessed in the serum and kidney homogenate. Scr levels in the IRI+MV-12 h group were significantly higher than those in the sham, IRI, and IRI+MV-4 h groups (all P < 0.001). Electron microscopy revealed the most pronouncedly abnormal mitochondrial morphology, suggestive of ferroptosis, in the IRI+MV-12 h group. The GPX4 and SOD2 protein levels progressively decreased in the following order: sham group > IRI group > IRI+MV-4 h group > IRI+MV-12 h group (P < 0.05 for all comparisons). By contrast, the 4HNE levels progressively increased in the kidney, with the highest values in the IRI+MV-12 h group (P < 0.05, vs. the IRI group and vs. the IRI+MV-4 h group). Further, the GSH levels in the serum and kidney homogenates were significantly reduced in the IRI+MV-12 h group (P < 0.01, vs. IRI group and vs. the IRI+MV-4 h group). A significant positive correlation was observed between the serum and kidney GSH levels (r² = 0.542, P = 0.03). These observations suggested that prolonged MV may exacerbate renal function failure, already initiated by IRI, by ferroptosis. Depletion of GSH may contribute to this effect, which requires further investigation.

HO-1/PINK1 Regulated Mitochondrial Fusion/Fission to Inhibit Pyroptosis and Attenuate Septic Acute Kidney Injury

Background

Endotoxin-associated acute kidney injury (AKI), a disease characterized by marked oxidative stress and inflammation disease, is a major cause of mortality in critically ill patients. Mitochondrial fission and pyroptosis often occur in AKI. However, the underlying biological pathways involved in endotoxin AKI remain poorly understood, especially those related to mitochondrial dynamics equilibrium disregulation and pyroptosis. Previous studies suggest that heme oxygenase- (HO-) 1 confers cytoprotection against AKI during endotoxic shock, and PTEN-induced putative kinase 1 (PINK1) takes part in mitochondrial dysfunction. Thus, in this study, we examine the roles of HO-1/PINK1 in maintaining the dynamic process of mitochondrial fusion/fission to inhibit pyroptosis and mitigate acute kidney injury in rats exposed to endotoxin.

Methods

An endotoxin-associated AKI model induced by lipopolysaccharide (LPS) was used in our study. Wild-type (WT) rats and PINK1 knockout (PINK1KO) rats, respectively, were divided into four groups: the control, LPS, Znpp+LPS, and Hemin+LPS groups. Rats were sacrificed 6 h after intraperitoneal injecting LPS to assess renal function, oxidative stress, and inflammation by plasma. Mitochondrial dynamics, morphology, and pyroptosis were evaluated by histological examinations.

Results

In the rats with LPS-induced endotoxemia, the expression of HO-1 and PINK1 were upregulated at both mRNA and protein levels. These rats also exhibited inflammatory response, oxidative stress, mitochondrial fission, pyroptosis, and decreased renal function. After upregulating HO-1 in normal rats, pyroptosis was inhibited; mitochondrial fission and inflammatory response to oxidative stress were decreased; and the renal function was improved. The effects were reversed by adding Znpp (a type of HO-1 inhibitor). Finally, after PINK1 knockout, there is no statistical difference in the LPS-treated group and Hemin or Znpp pretreated group.

Conclusions

HO-1 inhibits inflammation response and oxidative stress and regulates mitochondria fusion/fission to inhibit pyroptosis, which can alleviate endotoxin-induced AKI by PINK1.

Normobaric hyperoxia plays a protective role against renal ischemia-reperfusion injury by activating the Nrf2/HO-1 signaling pathway

Following renal ischemia-reperfusion injury (RIRI), because of the decrease in oxygen supply to the kidney, a large amount of oxygen-free radicals is generated, and in severe cases, tissue cells will undergo apoptosis or even die. Normobaric hyperoxia (NBHO) is a very common clinical adjuvant treatment. It restores the oxygen supply after renal ischemia and combats oxidative stress in tissues, thus playing a protective role. In this study, our aim is to elucidate the protective mechanism of NBHO inhalation in a rat RIRI model. We performed a surgical excision of the left kidney of the rat and established a right kidney solitary kidney model. Later, the right renal pedicle of the rat was clamped using a non-invasive vascular clamp for 45 min. After the vascular clamp was released and reperfused for 24 h, the rat was placed in a closed oxygen chamber. It was subjected to inhalation of high-concentration oxygen (50%-55%), 2 h daily, for 7 days.RIRI induces postoperative weight loss, impaired renal function, increased oxygen free radicals, reduced antioxidant substances, increased histopathological damage, and increased levels of apoptosis. These effects were significantly improved after treatment with NBHO. At the same time, NBHO significantly increased the expression levels of Nrf2 and HO-1 in the tissues after RIRI. To verify whether HO-1 induced by Nrf2 is involved in the resistance to oxidative stress, after the rat RIRI and before inhaling NBHO, we intraperitoneally injected HO-1 specific inhibitor zinc protoporphyrin (ZnPP) (45 μmol/Kg). However, we found that ZnPP reversed the protective effect of NBHO on RIRI in rats. Combining all the results, we have demonstrated the protective effect of NBHO on RIRI, which can be at least partially attributed to the activation of the Nrf2/HO-1 antioxidative stress pathway.

Protection of procyanidin B2 on mitochondrial dynamics in sepsis associated acute kidney injury via promoting Nrf2 nuclear translocation

In septic acute kidney injury (SAKI), the positive feedback between damaged mitochondria and accumulation of reactive oxygen species results in cell and tissue damage through multiple mechanisms. Removing the damaged mitochondria or neutralizing the reactive oxygen species has been considered beneficial to alleviating cell damage. The antioxidant Procyanidin B2 has been reported to inhibits reactive oxygen species and thereby reduces cell injury. However, it is unclear whether this effect is associated with clearance of damaged mitochondria. Here, we evaluated the efficacy of procyanidin B2 on SAKI, and focused on its effects on mitochondrial dynamics and removing damaged mitochondria via mitophagy. The results showed that the renal function, renal tubular cell vacuolization and oxidative stress were decreased in SAKI mice treated with procyanidin B2, moreover, skewed mitochondrial fusion/fission, mitochondrial mediated apoptosis and impaired mitophagy were improved in SAKI mice treated with procyanidin B2. In mechanism, the improvement of procyanidin B2 on mitochondrial dynamics were associated with increased nuclear translocation of the transcription factor, Nrf2. In summary, our findings highlighted that the protective efficacy of procyanidin B2 in reducing cellular damage in SAKI, and mechanisms improving mitochondrial dynamics and quality control at least in part by promoting Nrf2 translocation into the nucleus.

Optimization of a Rhabdomyolysis Model in Mice With Exertional Heat Stroke Mouse Model of EHS-Rhabdomyolysis

Exertional heat stroke (EHS) is a life-threatening disease characterized by high mortality and incidence of rhabdomyolysis (RM). It would therefore be valuable to establish a stable EHS-induced RM model that accurately reflects the clinical characteristics of EHS patients and provides an objective animal model for further study of the pathogenesis of RM. In the current study, 8∼9-week-old, male, wild-type C57BL/6J mice, at the stage of sexual maturity, were randomly divided into four groups: the EHS group, the classical heat stroke (CHS) group, the sham heat exercise group, and sham heat rest group. The survival rate of mice was determined under relatively high levels of temperature and humidity (37.5°C, 65% relative humidity (RH); 37.5°C, 70% RH; 39.5°C, 65% RH; and 39.5°C, 70% RH) as well as a high core temperature (Tc; 42, 42.5, and 43°C). Results showed that the environmental condition of 39.5°C and 65% RH was most suitable for EHS modeling. The end point of EHS evaluation was exhaustion or an individual’s core temperature reaching 43°C. The survival rate of mice in the EHS group within 24 h under these conditions was 37.34%, which is consistent with the high mortality characteristics noted in EHS patients. Severe RM was observed in the EHS group by H&E staining and transmission electron microscopy. Creatine kinase levels in the EHS group mostly exceeded 10,000 U/L, which was approximately 10 times higher than that in the sham heat rest group. Renal tubules of the EHS group exhibited severe necrosis, and calcium overload in the skeletal muscles of this group was also observed using intravital 2-photon microscopy. In conclusion, we made improvements to a stable EHS-induced RM animal model to truly reflect the clinical characteristics of EHS patients. This new model should be helpful in the further study of RM pathogenesis.

MiR-181d-5p Targets KLF6 to Improve Ischemia/Reperfusion-Induced AKI Through Effects on Renal Function, Apoptosis, and Inflammation

Renal tubular epithelial cell (RTEC) death and renal interstitial inflammation are the most crucial pathophysiological changes in acute kidney ischemia/reperfusion injury (IRI). The microRNA (miR)-181d family plays diverse roles in cell proliferation, apoptosis and inflammation, but its renal target and potential role in IRI are unknown. Here, we showed that the expression of miR-181d-5p decreased and Krueppel-like factor 6 (KLF6) increased in a renal cell (HK-2) model of hypoxia/reoxygenation (H/R) injury and a mouse model of renal IRI. They were mainly distributed in the renal tubules. After renal IRI, miR-181d-5p overexpression significantly inhibited inflammatory mediators, reduced apoptosis and further improved renal function. KLF6 exacerbated RTEC damage and acted as a NF-κB co-activator to aggravate the renal IRI inflammatory response. Mechanistically, KLF6 was predicted as a new potential target gene of miR-181d-5p through bioinformatic analysis and luciferase reporter assay verification. After overexpressing miR-181d-5p and inhibiting KLF6, the role of miR-181d-5p was weakened on the renal damage improvement. In conclusion, miR-181d-5p upregulation produced protective antiapoptotic and anti-inflammatory effects against IRI in kidneys in vivo and H/R injury in HK-2 cells in vitro, and these effects were achieved by targeted inhibition of KLF6. Thus, our results provide novel insights into the molecular mechanisms associated with IRI and a potential novel therapeutic target.

Disturbance of mitochondrial dynamics and mitophagy in sepsis-induced acute kidney injury

AIMS

The renal tubule cells require a large number of mitochondria to supply ATP due to their high-energy demand during reabsorption and secretion against chemical gradients and result in mitochondria susceptible to disorder and injury during stress conditions. Injured mitochondria are eventually degraded by mitophagy, and disturbances in mitophagy are associated with the pathogenesis of acute kidney injury (AKI) such as diabetic nephropathy and glomerulosclerosis. However, whether a disturbance in mitophagy has occurred and the role it plays in (SAKI) is still unclear. Therefore, the aim of this study was to investigate the key features of mitophagy and mitochondrial dynamics in sepsis-induced acute kidney injury (SAKI).

MAIN METHODS

In this study, a murine septic AKI model induced by cecal ligation and puncture (CLP) was built; mitophagy and mitochondrial dynamics were measured in mice kidney in different time point.

KEY FINDINGS

The results showed that mitochondrial dynamics were characterized by fission/fusion aberrant, however more inclined to fission, and mitochondrial associated apoptosis was elevated over-time during SAKI. Furthermore, mitophagy was impaired in the later phase of SAKI, although elevated in early stage of SAKI. The results indicate that the underlying mechanisms of impaired mitophagy may associate with the cleavage of Parkin via caspases activated by NLRP3, at least partly.

SIGNIFICANCE

It is conceivable that this selective autophagic process and quality control machinery was impaired, leading to the accumulation of damaged mitochondria, oxidative stress, and cell death. Therefore, a targeted approach, by enhancing mitophagy during SAKI, may be a promising therapeutic strategy.

G protein-coupled estrogen receptor activation improves contractile and diastolic functions in rat renal interlobular artery to protect against renal ischemia reperfusion injury

OBJECTIVE

This work aimed to investigate whether G protein-coupled estrogen receptor (GPER) can improve the renal interlobular artery vascular function by increasing the NO content, thereby protecting against renal ischemia-reperfusion (IR) injury.

METHODS

This study classified ovariectomised (OVX) female Sprague-Dawley rats into OVX, OVX + IR, OVX + IR + G1 (the GPER agonist G1), OVX + IR + G1+G15 (GPER blocker) and OVX + IR + G1+L-NAME (eNOS blocker) groups. Enzyme-linked immunosorbent assay was performed to detect the estrogen levels in the body and eliminate interference from endogenous estrogens. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) and HE staining, renal function test and Paller scoring were performed to identify the successful model and detect the degree of renal and renal interlobular arteries injury. The in vitro microvascular pressure diameter measurement technique was used to detect the contraction and diastolic activities of the renal interlobular arteries in each group. Immunofluorescence technique was used to observe the localisation and expression levels of GPER and eNOS in renal interlobular arteries. The GPER and eNOS protein expression levels in each group were detected by Western blot. The NO content in the serum of each group was detected by the nitrate reductase method.

RESULT

After OVX, the estrogen level in the body decreased significantly (P < 0.01), and TUNEL staining showed a significant increase in the degree of renal tubular epithelial cell apoptosis in the IR group. Serum creatinine (SCr) and blood urea nitrogen (BUN) levels were significantly increased in the IR group (P < 0.01), and the Paller score showed significantly increased kidney damage. When performing drug treatment, the G1 intervention group significantly decreased serum BUN and SCr levels after IR injury (P < 0.01). The Paller score showed significantly decreased the degree of renal injury (P < 0.01). After IR, the renal interlobular artery contraction rate and systolic velocity of blood vessels were significantly decreased (P < 0.01). The G1 intervention group significantly restored contraction rate and systolic velocity of blood vessels (P < 0.01), and G15 and L-NAME partially reversed this effect (P < 0.01). Immunofluorescence technique showed that GPER was expressed in renal interlobular artery smooth muscle and endothelial cells. After IR injury, the GPER protein expression increased, and the eNOS protein expression decreased significantly (P < 0.01). Western blot showed that after IR injury, the GPER protein expression increased, and the eNOS protein expression decreased significantly. After G1 intervention, the GPER content did not change, and the eNOS content increased significantly (P < 0.01). After ischemia and reperfusion, the serum NO content decreased significantly, but it increased after G1 intervention. G15 and L-NAME reversed the effects of G1 to varying degrees (both at P < 0.01).

CONCLUSION

GPER may improve the renal interlobular artery vascular function by increasing the NO content, thereby protecting against renal IR injury.

Knockdown of NLRC5 attenuates renal I/R injury in vitro through the activation of PI3K/Akt signaling pathway

NLRC5, as the largest member of nucleotide-binding domain and leucine-rich repeat (NLR) family, was involved in various physiological processes, such as inflammation, fibrosis, innate immunity and diabetic nephropathy. However, the role of NLRC5 in acute kidney injury remains unclear. The aim of this study was to investigate the role of NLRC5 in human renal proximal tubular epithelial cells (HK-2) exposed to hypoxia/reoxygenation (H/R). Our results demonstrated that the expression of NLRC5 was significantly up-regulated in HK-2 cells exposed to H/R. Knockdown of NLRC5 significantly improved the viability of HK-2 cells exposed to H/R. In addition, knockdown of NLRC5 efficiently inhibited H/R-induced oxidative stress and apoptosis in HK-2 cells. Mechanistically, knockdown of NLRC5 markedly enhanced the activation of PIK3/Akt signaling pathway in H/R-stimulated HK-2 cells. In summary, our findings indicate that knockdown of NLRC5 attenuates renal I/R injury in vitro through the activation of PI3K/Akt signaling pathway.

Sulodexide pretreatment attenuates renal ischemia-reperfusion injury in rats

Sulodexide is a potent antithrombin agent, however, whether it has beneficial effects on renal ischemia-reperfusion injury (IRI) remains unknown. In the present study, we assessed the therapeutic effects of sulodexide in renal IRI and tried to investigate the potential mechanism. One dose of sulodexide was injected intravenously in Sprague-Dawley rats 30 min before bilateral kidney ischemia for 45 min. The animals were sacrificed at 3h and 24h respectively. Our results showed that sulodexide pretreatment improved renal dysfunction and alleviated tubular pathological injury at 24h after reperfusion, which was accompanied with inhibition of oxidative stress, inflammation and cell apoptosis. Moreover, we noticed that antithrombin III (ATIII) was activated at 3h after reperfusion, which preceded the alleviation of renal injury. For in vitro study, hypoxia/reoxygenation (H/R) injury model for HK2 cells was carried out and apoptosis and reactive oxygen species (ROS) levels were evaluated after sulodexide pretreatment. Consistently, sulodexide pretreatment could reduce apoptosis and ROS level in HK2 cells under H/R injury. Taken together, sulodexide pretreatment might attenuate renal IRI through inhibition of inflammation, oxidative stress and apoptosis, and activation of ATIII.

Protective Role for Antioxidants in Acute Kidney Disease

Acute kidney injury causes significant morbidity and mortality in the community and clinic. Various pathologies, including renal and cardiovascular disease, traumatic injury/rhabdomyolysis, sepsis, and nephrotoxicity, that cause acute kidney injury (AKI), induce general or regional decreases in renal blood flow. The ensuing renal hypoxia and ischemia promotes the formation of reactive oxygen species (ROS) such as superoxide radical anions, peroxides, and hydroxyl radicals, that can oxidatively damage biomolecules and membranes, and affect organelle function and induce renal tubule cell injury, inflammation, and vascular dysfunction. Acute kidney injury is associated with increased oxidative damage, and various endogenous and synthetic antioxidants that mitigate source and derived oxidants are beneficial in cell-based and animal studies. However, the benefit of synthetic antioxidant supplementation in human acute kidney injury and renal disease remains to be realized. The endogenous low-molecular weight, non-proteinaceous antioxidant, ascorbate (vitamin C), is a promising therapeutic in human renal injury in critical illness and nephrotoxicity. Ascorbate may exert significant protection by reducing reactive oxygen species and renal oxidative damage via its antioxidant activity, and/or by its non-antioxidant functions in maintaining hydroxylase and monooxygenase enzymes, and endothelium and vascular function. Ascorbate supplementation may be particularly important in renal injury patients with low vitamin C status.

Differential gene and lncRNA expression in the lower thoracic spinal cord following ischemia/reperfusion-induced acute kidney injury in rats

We used high-throughput RNA sequencing to analyze differential gene and lncRNA expression patterns in the lower thoracic spinal cord during ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) in rats. We observed that of 32662 mRNAs, 4296 out were differentially expressed in the T8-12 segments of the spinal cord upon I/R-induced AKI. Among these, 62 were upregulated and 34 were downregulated in response to I/R (FDR < 0.05, |log₂FC| > 1). Further, 52 differentially expressed lncRNAs (35 upregulated and 17 downregulated) were identified among 3849 lncRNA transcripts. The differentially expressed mRNAs were annotated as “biological process,” “cellular components” and “molecular functions” through gene ontology enrichment analysis. KEGG pathway enrichment analysis showed that cell cycle and renin-angiotensin pathways were upregulated in response to I/R, while protein digestion and absorption, hedgehog, neurotrophin, MAPK, and PI3K-Akt signaling were downregulated. The RNA-seq data was validated by qRT-PCR and western blot analyses of select mRNAs and lncRNAs. We observed that Bax, Caspase-3 and phospho-AKT were upregulated and Bcl-2 was downregulated in the spinal cord in response to renal injury. We also found negative correlations between three lncRNAs (TCONS_00042175, TCONS_00058568 and TCONS_00047728) and the degree of renal injury. These findings provide evidence for differential expression of lncRNAs and mRNAs in the lower thoracic spinal cord following I/R-induced AKI in rats and suggest potential clinical applicability.

Cholesterol metabolites alleviate injured liver function and decrease mortality in an LPS-induced mouse model

BACKGROUND

Oxysterol sulfation plays a fundamental role in the regulation of many biological events. Its products, 25-hydroxycholesterol 3-sulfate (25HC3S) and 25-hydroxycholesterol 3, 25-disulfate (25HCDS), have been demonstrated to be potent regulators of lipid metabolism, inflammatory response, cell apoptosis, and cell survival. In the present study, we tested these products' potential to treat LPS-induced acute liver failure in a mouse model.

METHODS

Acute liver failure mouse model was established by intravenous injection with LPS. The injured liver function was treated with intraperitoneal administration of 25HC, 25HC3S or 25HCDS. Serum enzymatic activities were determined in our clinic laboratory. ELISA assays were used to detect pro-inflammatory factor levels in sera. Western blot, Real-time Quantitative PCR and RT² Profiler PCR Array analysis were used to determine levels of gene expression.

RESULTS

Administration of 25HC3S/25HCDS decreased serum liver-impaired markers; suppressed secretion of pro-inflammatory factors; alleviated liver, lung, and kidney injury; and subsequently increased the survival rate in the LPS-induced mouse model. These effects resulted from the inhibition of the expression of genes involved in the pro-inflammatory response and apoptosis and the simultaneous induction of the expression of genes involved in cell survival. Compared to 25HC, 25HC3S and 25HCDS exhibited significantly stronger effects in these activities, indicating that the cholesterol metabolites play an important role in the inflammatory response, cell apoptosis, and cell survival in vivo.

CONCLUSIONS

25HC3S/25HCDS has potential to serve as novel biomedicines in the therapy of acute liver failure and acute multiple organ failure.

Cisplatin-Induced Nephrotoxicity; Protective Supplements and Gender Differences

Cisplatin (CDDP) has been widely used as a chemotherapeutic agent for solid tumors. The most common side effect of CDDP is nephrotoxicity, and many efforts have been made in the laboratory and the clinic to employ candidate adjuvants to CDDP to minimize this adverse influence. Many synthetic and herbal antioxidants as well as trace elements have been investigated for this purpose in recent years and a variety of positive and negative results have been yielded. However, no definitive supplement has so far been proposed to prevent CDDP-induced nephrotoxicity; however, this condition is gender related and the sex hormone estrogen may protect the kidney against CDDP damage. In this review, the results of research related to the effect of different synthetic and herbal antioxidants supplements are presented and discussed with suggestions included for future work.

The Protective Effect of γ-aminobutyric Acid on Kidney Injury Induced by Renal Ischemia-reperfusion in Ovariectomized Estradiol-treated Rats

Background:

Renal ischemia-reperfusion injury (IRI) is one of the most important causes of kidney injury, which is possibly gender-related. This study was designed to investigate the role of γ-aminobutyric acid (GABA) against IRI in ovariectomized estradiol-treated rats.

Methods:

Thirty-five ovariectomized Wistar rats were used in six experimental groups. The first three groups did not subject to estradiol treatment and assigned as sham-operated, control, and GABA-treated groups. GABA (50 μmol/kg) and saline were injected in the treated and control groups 30 min before the surgery, respectively. The second three groups received the same treatments but received estradiol valerate (500 μg/kg, intramuscularly) 3 days prior to the surgery. The IRI was induced in the control and treated groups by clamping the renal artery for 45 min and then 24 h of reperfusion. All animals were sacrificed for the measurements.

Results:

The serum levels of creatinine and blood urea nitrogen, kidney weight, and kidney tissue damage score significantly increased in the IRI rats (P < 0.05). GABA significantly decreased the aforementioned parameters (P < 0.05). The uterus weight increased significantly in rats that received estradiol (P < 0.05). Serum and kidney levels of nitrite (nitric oxide metabolite) did not alter significantly. Serum level of malondialdehyde increased significantly in the ovariectomized rats exposed to IRI (P < 0.05).

Conclusions:

It seems that GABA improved IRI in ovariectomized rats. Estradiol was also nephroprotective against IRI. However, co-administration of estradiol and GABA could not protect the kidney against IRI.

In Vivo Evaluation of the Ameliorating Effects of Small-Volume Resuscitation with Four Different Fluids on Endotoxemia-Induced Kidney Injury

Acute kidney injury associated with renal hypoperfusion is a frequent and severe complication during sepsis. Fluid resuscitation is the main therapy. However, heart failure is usually lethal for those patients receiving large volumes of fluids. We compared the effects of small-volume resuscitation using four different treatment regimens, involving saline, hypertonic saline (HTS), hydroxyethyl starch (HES), or hypertonic saline hydroxyethyl starch (HSH), on the kidneys of rats treated with lipopolysaccharide (LPS) to induce endotoxemia. LPS injection caused reduced and progressively deteriorated systemic (arterial blood pressure) and renal hemodynamics (renal blood flow and renal vascular resistance index) over time. This deterioration was accompanied by marked renal functional and pathological injury, as well as an oxidative and inflammatory response, manifesting as increased levels of tumor necrosis factor-α, nitric oxide, and malondialdehyde and decreased activity of superoxide dismutase. Small-volume perfusion with saline failed to improve renal and systemic circulation. However, small-volume perfusion with HES and HSH greatly improved the above parameters, while HTS only transiently improved systemic and renal hemodynamics with obvious renal injury. Therefore, single small-volume resuscitation with HES and HSH could be valid therapeutic approaches to ameliorate kidney injury induced by endotoxemia, while HTS transiently delays injury and saline shows no protective effects.

Signalling mechanisms involved in renal pathological changes during cisplatin-induced nephropathy

CONTEXT

Cisplatin, a coordination platinum complex, is used as a potential anti-neoplastic agent, having well recognized DNA-damaging property that triggers cell-cycle arrest and cell death in cancer therapy. Beneficial chemotherapeutic actions of cisplatin can be detrimental for kidneys.

BACKGROUND

Unbound cisplatin gets accumulated in renal tubular cells, leading to cell injury and death. This liable action of cisplatin on kidneys is mediated by altered intracellular signalling pathways such as mitogen-activated protein kinase (MAPK), extracellular regulated kinase (ERK), or C- Jun N terminal kinase/stress-activated protein kinase (JNK/SAPK). Further, these signalling alterations are responsible for release and activation of tumour necrosis factor (TNF-α), mitochondrial dysfunction, and apoptosis, which ultimately cause the renal pathogenic process. Cisplatin itself enhances the generation of reactive oxygen species (ROS) and activation of nuclear factor-κB (NF-κB), inflammation, and mitochondrial dysfunction, which further leads to renal apoptosis. Cisplatin-induced nephropathy is also mediated through the p53 and protein kinase-Cδ (PKCδ) signalling pathways.

OBJECTIVE

This review explores these signalling alterations and their possible role in the pathogenesis of cisplatin-induced renal injury.

Reactive oxygen species and IRF1 stimulate IFNα production by proximal tubules during ischemic AKI

We previously reported that expression of the transcription factor interferon regulatory factor 1 (IRF1) is an early, critical maladaptive signal expressed by renal tubules during murine ischemic acute kidney injury (AKI). We now show that IRF1 mediates signals from reactive oxygen species (ROS) generated during ischemic AKI and that these signals ultimately result in production of α-subtypes of type I interferons (IFNαs). We found that genetic knockout of the common type I IFN receptor (IFNARI-/-) improved kidney function and histology during AKI. There are major differences in the spatial-temporal production of the two major IFN subtypes, IFNβ and IFNαs: IFNβ expression peaks at 4 h, earlier than IFNαs, and continues at the same level at 24 h; expression of IFNαs also increases at 4 h but continues to increase through 24 h. The magnitude of the increase in IFNαs relative to baseline is much greater than that of IFNβ. We show by immunohistology and study of isolated cells that IFNβ is produced by renal leukocytes and IFNαs are produced by renal tubules. IRF1, IFNαs, and IFNARI were found on the same renal tubules during ischemic AKI. Furthermore, we found that ROS induced IFNα expression by renal tubules in vitro. This expression was inhibited by small interfering RNA knockdown of IRF1. Overexpression of IRF1 resulted in the production of IFNαs. Furthermore, we found that IFNα stimulated production of maladaptive proinflammatory CXCL2 by renal tubular cells. Altogether our data support the following autocrine pathway in renal tubular cells: ROS > IRF1 > IFNα > IFNARI > CXCL2.

Protective effects of propofol against hydrogen peroxide-induced oxidative stress in human kidney proximal tubular cells

Background

We investigated the protective effects of propofol in the HK-2 cell line of human kidney proximal tubular cells against hydrogen peroxide (H₂O₂)-induced oxidative stress.

Methods

After pretreatment with different concentrations of propofol (0 µM, 10 µM, 25 µM and 50 µM) for 30 minutes, HK-2 cells were exposed to 8 mM H₂O₂ for 4 hours. Cell death was assessed by measuring the percentage of lactate dehydrogenase (LDH) release and by counting viable cells. The nature of cell death was assessed by doubles-taining cells with fluorescein isothiocyanate-labeled Annexin V and propidium iodide, and then analyzing the cells using flow cytometry.

Results

After exposure to 8 mM H₂O₂ for 4 hours, the percentage of LDH release was 45.1 ± 4.2% and the number of viable HK-2 cells was 5.2 ± 6.0%. Pretreatment with propofol suppressed H₂O₂-induced LDH release in a concentration-dependent manner, reducing the percentage of LDH release to 38.1 ± 5.6%, 33.5 ± 6.3%, and 26.2 ± 3.8% of the controls at 10 µM, 25 µM and 50 µM propofol, respectively. Numbers of viable cells increased following propofol pretreatment, with 11.4 ± 10.9%, 19.5 ± 16.1%, and 32.4 ± 23.3% cell survival rates after pretreatment with 10 µM, 25 µM and 50 µM propofol, respectively. Analyses of flow cytometry showed that the propofol pretreatment decreased the percentage of necrotic and late apoptotic cells.

Conclusions

Propofol protects HK-2 human kidney proximal tubular cells against H₂O₂-induced oxidative stress.

Extracellular signal-regulated kinase plays a proapoptotic role in podocytes after reactive oxygen species treatment and inhibition of integrin-extracellular matrix interaction

The effect of reactive oxygen species (ROS) and blocking integrin-extracellular matrix (ECM) interaction on apoptosis in podocytes, and the related signal transduction pathways remain unclear. Primary cultured rat podocytes were exposed to ROS. Integrin-ECM interaction was inhibited with anti-β1-integrin monoclonal antibody (mAb) or RGDS (Arg-Gly-Asp-Ser). Extracellular signal-regulated kinase (ERK) activation was evaluated with Western blotting. U0126 was used to inhibit ERK activation. Terminal deoxynucleotidyl transferase-mediated dUTP-peroxidase nick end-labeling of DNA (TUNEL) was used to evaluate apoptosis. We found that ROS-treated podocytes exhibited increased apoptosis, and both anti-β1-integrin mAb and RGDS induce apoptosis. Addition of ROS to either anti-β1-integrin mAb or RGDS enhanced apoptosis in both conditions. ERK activation was increased by either ROS or blocking integrin-ECM interaction. Preincubation with U0126 decreased apoptosis induced by ROS, anti-β1-integrin mAb or RGDS, respectively. Our study demonstrated that ROS and blocking integrin-ECM interaction induce podocyte apoptosis, which is mediated by ERK activation.

Protective effects of propofol against ischemia/reperfusion injury in rat kidneys

AIM

The purpose of this study was to investigate and compare the efficiency of propofol in the reduction of injury induced by free radicals in a rat model of renal ischemia/reperfusion (I/R).

METHOD

Twenty-four Wistar rats were divided into four groups in our study. Rats in the sham group underwent laparotomy and were made to wait for 120 min without ischemia. Rats in the control group were given nothing with ischemia-reperfusion. Rats in the I/R groups were given propofol (25 mg/kg) and 10% intralipid (250 mg/kg) ip, respectively, 15 min before the ischemia for 60 min followed by reperfusion for 60 min. The kidney tissues of the rats were taken under anesthesia at the end of the reperfusion period. Evaluation of biochemical malondialdehyde (MDA), superoxide dismutase, and catalase activities and histopathological analysis were performed with these samples.

RESULTS

I/R significantly increased MDA levels (p < 0.05). Histopathological findings of the control group confirmed that there was renal impairment by tubular cell swelling, interstitial edema, medullary congestion, and tubular dilatation. MDA levels were lower in the propofol group compared to control group (p < 0.05). In the propofol group, the level of histopathological scores is significantly decreased than control and intralipid groups in ischemia-reperfusion.

CONCLUSION

Our results demonstrate that I/R injury was significantly reduced in the presence of propofol. The protective effects of propofol may be due to their antioxidant properties. These results may indicate that propofol anesthesia protects against functional, biochemical, and morphological damage better than control in renal I/R injury.

Isoflurane protects human kidney proximal tubule cells against necrosis via sphingosine kinase and sphingosine-1-phosphate generation

BACKGROUND/AIMS

We previously showed that the inhalational anesthetic isoflurane protects against renal ischemia reperfusion injury in part via sphingosine kinase (SK)-mediated synthesis of sphingosine-1-phosphate (S1P). In this study, we tested the hypothesis that isoflurane directly targets renal proximal tubule cells via SK activation, S1P synthesis and activation of S1P receptors to initiate cytoprotective signaling.

METHODS AND RESULTS

Isoflurane-mediated phosphorylation of extracellular signal-regulated kinase (ERK) and Akt and induction of HSP70 in human kidney proximal tubule (HK-2) cells were inhibited by dimethylsphingosine (DMS), an SK inhibitor, and VPC23019, an S1P(1/3) receptor selective antagonist, in HK-2 cells. A selective S1P(1) receptor agonist, SEW2781, mimicked isoflurane-induced phosphorylation of ERK and Akt and induction of HSP70. Moreover, isoflurane-mediated protection against H(2)O(2)-induced necrosis of HK-2 cells was significantly attenuated by an S1P(1/3) receptor antagonist, VPC23019, and by SK inhibitors DMS or 4-[[4- (4-chlorophenyl)-2-thiazolyl]amino]phenol. Finally, overexpression of the SK1 enzyme in HK-2 cells protected against H(2)O(2)-induced necrosis.

CONCLUSIONS

Collectively, our study demonstrates that S1P released via isoflurane-mediated SK1 stimulation produces direct anti-necrotic effects probably via S1P(1) receptor-mediated cytoprotective signaling (ERK/Akt phosphorylation and HSP70 induction) in HK-2 cells. Our findings may help to unravel the cellular signaling pathways of volatile anesthetic-mediated renal protection and lead to new therapeutic applications of volatile anesthetics during the perioperative period.

Protection against in vivo focal myocardial ischemia/reperfusion injury-induced arrhythmias and apoptosis by hesperidin

Among the heart diseases, ischemia and reperfusion (I/R) induced arrhythmias contribute to episodes of sudden death. Cardiac arrhythmias during ischemia reperfusion are believed to be related to oxidative stress. Therefore, the aim of this study was to examine whether treatment with hesperidin alleviates arrhythmias and infarct size in experimentally-induced myocardial I/R injury using an in vivo rat model. In this study haemodynamics parameters, markers of inflammation, biomarkers of oxidative stress and tissue nitrite level and infarct size of the heart were estimated in various groups. I/R showed a significant decrease in tissue nitrite and antioxidant level and significant increase in arrhythmias, inflammation and myocardial cell apoptosis. Treatment with hesperidin showed a significant increase in tissue nitrite, antioxidant level and reduction in inflammation, arrhythmias and apoptosis. In conclusion, the protecting effect of hesperidin in I/R induced arrhythmias is due to reduction in inflammation and oxidative stress.

Identification of proteins binding to E-Box/Ku86 sites and function of the tumor suppressor SAFB1 in transcriptional regulation of the human xanthine oxidoreductase gene

The xanthine oxidoreductase gene (XOR) encodes an important source of reactive oxygen species and uric acid, and its expression is associated with various human diseases including several forms of cancer. We previously reported that basal human XOR (hXOR) expression is restricted or repressed by E-box and TATA-like elements and a cluster of transcriptional proteins, including AREB6-like proteins and DNA-dependent protein kinase (DNA-PK). We now demonstrate that the cluster contains the tumor suppressors SAFB1, BRG1, and SAF-A. We further demonstrate that SAFB1 silencing increases hXOR expression and that SAFB1 directly binds to the E-box. Multiple studies in vitro and in vivo including pulldown, immunoprecipitation and chromatin immunoprecipitation analyses indicate that SAFB1, Ku86, and BRG1 associate with each other. The results suggest that the SAFB1 complex binds to the hXOR promoter in a chromatin environment and plays a critical role in restricting hXOR expression via its direct interaction with the E-box, DNA-PK, and tumor suppressors. Moreover, we demonstrate that the cytokine, oncostatin M (OSM), induces the phosphorylation of SAFB1 and that the OSM-induced hXOR mRNA expression is significantly inhibited by silencing the DNA-PK catalytic subunit or SAFB1 expression. The present studies for the first time demonstrate that hXOR is a tumor suppressor-targeted gene and that the phosphorylation of SAFB1 is regulated by OSM, providing a molecular basis for understanding the role of SAFB1-regulated hXOR transcription in cytokine stimulation and tumorigenesis.

Effects of colloidal iron overload on renal and hepatic siderosis and the femur in male rats

Genetic hemochromatosis is an iron overload disorder, and osteopenic and osteoporotic. Femoral neck bone mineral density (BMD) appears to fall with rising hepatic iron concentrations. A critical role for iron in mediating tissue injury is played via hydroxyl radical formation in nephrotoxicity. We investigated the effects of a colloidal iron overload on renal function, organ siderosis, and femoral bone in male rats. Iron overload reduced body growth, and increased the weights of the liver and spleen. Marked deposition of iron was noted in liver and kidney. Activities of lactate dehydrogenase and alkaline phosphatase were decreased, and the concentrations of blood urea nitrogen and creatinine were increased with the reduction in plasma calcium and inorganic phosphorus levels, i.e. functions of the liver and kidney might be affected by reactive oxygen species such as the superoxide radical, H2O2, and the hydroxyl radical produced by overloaded iron. Damage to the proximal tubular epithelial cells of the kidney and a loss of connectivity of cancellous bone in the epiphysis and of trabecular bone in the metaphysis of the distal femur were observed in iron-overloaded rats with a reduction of femoral bone mineral density, i.e. reabsorption of calcium from the proximal tubular epithelial cells of the kidney might be affected and urinary discharge of calcium might be elevated. It was suggested that iron overload gave rise to osteoporosis combined with renal dysfunction and liver iron overload syndrome.

Novel pharmacological approaches to the treatment of renal ischemia-reperfusion injury: a comprehensive review

Renal ischemia-reperfusion (I-R) contributes to the development of ischemic acute renal failure (ARF). Multi-factorial processes are involved in the development and progression of renal I-R injury with the generation of reactive oxygen species, nitric oxide and peroxynitrite, and the decline of antioxidant protection playing major roles, leading to dysfunction, injury, and death of the cells of the kidney. Renal inflammation, involving cytokine/adhesion molecule cascades with recruitment, activation, and diapedesis of circulating leukocytes is also implicated. Clinically, renal I-R occurs in a variety of medical and surgical settings and is responsible for the development of acute tubular necrosis (a characteristic feature of ischemic ARF), e.g., in renal transplantation where I-R of the kidney directly influences graft and patient survival. The cellular mechanisms involved in the development of renal I-R injury have been targeted by several pharmacological interventions. However, although showing promise in experimental models of renal I-R injury and ischemic ARF, they have not proved successful in the clinical setting (e.g., atrial natriuretic peptide, low-dose dopamine). This review highlights recent pharmacological developments, which have shown particular promise against experimental renal I-R injury and ischemic ARF, including novel antioxidants and antioxidant enzyme mimetics, nitric oxide and nitric oxide synthase inhibitors, erythropoietin, peroxisome-proliferator-activated receptor agonists, inhibitors of poly(ADP-ribose) polymerase, carbon monoxide-releasing molecules, statins, and adenosine. Novel approaches such as recent research involving combination therapies and the potential of non-pharmacological strategies are also considered.

Heme oxygenase-1 induction improves ischemic renal failure: role of nitric oxide and peroxynitrite

The present study evaluated the effects of heme oxygenase-1 (HO-1) induction on the changes in renal outer medullary nitric oxide (NO) and peroxynitrite levels during 45-min renal ischemia and 30-min reperfusion in anesthetized rats. Glomerular filtration rate (GFR), outer medullary blood flow (OMBF), HO and nitric oxide synthase (NOS) isoform expression, and renal low-molecular-weight thiols (-SH) were also determined. During ischemia significant increases in NO levels and peroxynitrite signal were observed (from 832.1 +/- 129.3 to 2,928.6 +/- 502.0 nM and from 3.8 +/- 0.7 to 9.0 +/- 1.6 nA before and during ischemia, respectively) that dropped to preischemic levels during reperfusion. OMBF and -SH significantly decreased after 30 min of reperfusion. Twenty-four hours later, an acute renal failure was observed (GFR 923.0 +/- 66.0 and 253.6 +/- 55.3 microl.min(-1).g kidney wt(-1) in sham-operated and ischemic kidneys, respectively; P < 0.05). The induction of HO-1 (CoCl(2) 60 mg/kg sc, 24 h before ischemia) decreased basal NO concentration (99.7 +/- 41.0 nM), although endothelial and neuronal NOS expression were slightly increased. CoCl(2) administration also blunted the ischemic increase in NO and peroxynitrite (maximum values of 1,315.6 +/- 445.6 nM and 6.3 +/- 0.5 nA, respectively; P < 0.05), preserving postischemic OMBF and GFR (686.4 +/- 45.2 microl.min(-1).g kidney wt(-1)). These beneficial effects of CoCl(2) on ischemic acute renal failure seem to be due to HO-1 induction, because they were abolished by stannous mesoporphyrin, a HO inhibitor. In conclusion, HO-1 induction has a protective effect on ischemic renal failure that seems to be partially mediated by decreasing the excessive production of NO with the subsequent reduction in peroxynitrite formation observed during ischemia.

Reactive oxygen species mediate central cardiorespiratory network responses to acute intermittent hypoxia

Although oxidative stress and reactive oxygen species generation is typically associated with localized neuronal injury, reactive oxygen species have also recently been shown to act as a physiological signal in neuronal plasticity. Here we define an essential role for reactive oxygen species as a critical stimulus for cardiorespiratory reflex responses to acute episodic hypoxia in the brain stem. To examine central cardiorespiratory responses to episodic hypoxia, we used an in vitro medullary slice that allows simultaneous examination of rhythmic respiratory-related activity and synaptic neurotransmission to cardioinhibitory vagal neurons. We show that whereas continuous hypoxia does not stimulate excitatory neurotransmission to cardioinhibitory vagal neurons, acute intermittent hypoxia of equivalent duration incrementally recruits an inspiratory-evoked excitatory neurotransmission to cardioinhibitory vagal neurons during intermittent hypoxia. This recruitment was dependent on the generation of reactive oxygen species. Further, we demonstrate that reactive oxygen species are incrementally generated in glutamatergic neurons in the ventrolateral medulla during intermittent hypoxia. These results suggest a neurochemical basis for the pronounced bradycardia that protects the heart against injury during intermittent hypoxia and demonstrates a novel role of reactive oxygen species in the brain stem.

ERK promotes hydrogen peroxide-induced apoptosis through caspase-3 activation and inhibition of Akt in renal epithelial cells

Reactive oxygen species, including hydrogen peroxide (H(2)O(2)), are generated during ischemia-reperfusion and are critically involved in acute renal failure. The present studies examined the role of the extracellular signal-regulated kinase (ERK) pathway in H(2)O(2)-induced renal proximal tubular cells (RPTC) apoptosis. Exposure of RPTC to 1 mM H(2)O(2) resulted in apoptosis and activation of ERK1/2 and Akt. Pretreatment with the specific MEK inhibitors, U0126 and PD98059, or adenoviral infection with a construct that encodes a negative mutant of MEK1, protected cells against H(2)O(2)-induced apoptosis. In contrast, expression of constitutively active MEK1 enhanced H(2)O(2)-induced apoptosis. H(2)O(2) induced activation of caspase-3 and phosphorylation of histone H2B at serine 14, a posttranslational modification required for nuclear condensation, which also were blocked by ERK1/2 inhibition. Furthermore, blockade of ERK1/2 resulted in an increase in Akt phosphorylation and blockade of Akt potentiated apoptosis and diminished the protective effect conferred by ERK inhibition in H(2)O(2)-treated cells. Although Z-DEVD-FMK, a caspase-3 inhibitor, was able to inhibit histone H2B phosphorylation and apoptosis, it did not affect ERK1/2 phosphorylation. We suggest that ERK elicits apoptosis in epithelial cells by activating caspase-3 and inhibiting Akt pathways and elicits nuclear condensation through caspase-3 and histone H2B phosophorylation during oxidant injury.

Anti-inflammatory and antinecrotic effects of the volatile anesthetic sevoflurane in kidney proximal tubule cells

Renal ischemia-reperfusion (IR) injury is a major clinical problem without effective therapy. We recently reported that volatile anesthetics protect against renal IR injury, in part, via their anti-inflammatory properties. In this study, we demonstrate the anti-inflammatory and antinecrotic effects of sevoflurane in cultured kidney proximal tubule cells and probed the mechanisms of sevoflurane-induced renal cellular protection. To mimic inflammation, human kidney proximal tubule (HK-2) cells were treated with tumor necrosis factor-α (TNF-α; 25 ng/ml) in the presence or absence of sevoflurane. In addition, we studied the effects of sevoflurane pretreatment on hydrogen peroxide (H2O2)-induced necrotic cell death in HK-2 or porcine proximal tubule (LLC-PK1) cells. We demonstrate that sevoflurane suppressed proinflammatory effects of TNF-α evidenced by attenuated upregulation of proinflammatory cytokine mRNA (TNF-α, MCP-1) and ICAM-1 protein and reduced nuclear translocation of the proinflammatory transcription factors NF-κB and AP-1. Sevoflurane reduced necrotic cell death induced with H2O2in HK-2 cells as well as in LLC-PK1cells. Sevoflurane treatment resulted in phosphorylation of prosurvival kinases, ERK and Akt, and increased de novo HSP-70 protein synthesis without affecting the synthesis of HSP-27 or HSP-32. We conclude that sevoflurane has direct anti-inflammatory and antinecrotic effects in vitro in a renal cell type particularly sensitive to injury following IR injury. These mechanisms may, in part, account for volatile anesthetics' protective effects against renal IR injury.