Inflammation and microvasculopathy in renal ischemia reperfusion injury

Vitamin A and retinoid signaling in the kidneys

Vitamin A (VA, retinol) and its metabolites (commonly called retinoids) are required for the proper development of the kidney during embryogenesis, but retinoids also play key roles in the function and repair of the kidney in adults. Kidneys filter 180-200 liters of blood per day and each kidney contains approximately 1 million nephrons, which are often referred to as the 'functional units' of the kidney. Each nephron consists of a glomerulus and a series of tubules (proximal tubule, loop of Henle, distal tubule, and collecting duct) surrounded by a network of capillaries. VA is stored in the liver and converted to active metabolites, most notably retinoic acid (RA), which acts as an agonist for the retinoic acid receptors ((RARs α, β, and γ) to regulate gene transcription. In this review we discuss some of the actions of retinoids in the kidney after injury. For example, in an ischemia-reperfusion model in mice, injury-associated loss of proximal tubule (PT) differentiation markers occurs, followed by re-expression of these differentiation markers during PT repair. Notably, healthy proximal tubules express ALDH1a2, the enzyme that metabolizes retinaldehyde to RA, but transiently lose ALDH1a2 expression after injury, while nearby myofibroblasts transiently acquire RA-producing capabilities after injury. These results indicate that RA is important for renal tubular injury repair and that compensatory mechanisms exist for the generation of endogenous RA by other cell types upon proximal tubule injury. ALDH1a2 levels also increase in podocytes, epithelial cells of the glomeruli, after injury, and RA promotes podocyte differentiation. We also review the ability of exogenous, pharmacological doses of RA and receptor selective retinoids to treat numerous kidney diseases, including kidney cancer and diabetic kidney disease, and the emerging genetic evidence for the importance of retinoids and their receptors in maintaining or restoring kidney function after injury. In general, RA has a protective effect on the kidney after various types of injuries (eg. ischemia, cytotoxic actions of chemicals, hyperglycemia related to diabetes). As more research into the actions of each of the three RARs in the kidney is carried out, a greater understanding of the actions of vitamin A is likely to lead to new insights into the pathology of kidney disorders and the development of new therapies for kidney diseases.

The combined effect of zinc oxide nanoparticles and milrinone on acute renal ischemia/reperfusion injury in rats: Potential underlying mechanisms

AIM

To investigate the efficacy of zinc oxide nanoparticles (ZnO-NPs) and/or milrinone (MIL) on renal ischemia/reperfusion injury (I/RI) in rats and their possible underlying mechanisms.

MATERIALS AND METHODS

Forty-eight adult male Sprague-Dawley albino rats were randomly assigned into six equal-sized groups (n = 8): normal control, sham-operated, I/R group (45 min/24 h), ZnO-NPs group (10 mg/Kg i.p.), MIL group (0.5 mg/Kg i.p.), and ZnO-NPs + MIL group in the same previous doses.

KEY FINDINGS

In comparison to the I/R-operated group, administration of either ZnO-NPs or MIL significantly decreased serum creatinine and urea concentrations, and renal vascular permeability (p < 0.05). The oxidative stress was significantly declined, as evidenced by increased GPx, CAT, and SOD activities and decreased MDA and NO concentrations. Renal expressions of TNF-α, NF-κB, KIM-1, NGAL, and caspase-3 decreased significantly, while Nrf2 increased significantly. Histopathology investigation revealed improvement with minimal renal lesions and fibrosis after ZnO-NPs or MIL treatments. The combined treatments synergistically improved the studied parameters more than either treatment alone. These findings were validated by molecular modeling, which revealed that MIL inhibited TNF-α, NF-kB, caspase-3, KIM-1 and NGAL.

SIGNIFICANCE

Both ZnO-NPs and MIL exerted cytoprotective effects against acute renal I/RI, and a combination of both was found to be even more effective. This renoprotective effect is suggested to be mediated through activation of Nrf2 and the prevention of the NF-κB activation-induced oxidative stress and inflammation, which may strengthen the potential role of ZnO-NPs or MIL in renal I/RI protection during surgical procedures.

Role of time from transplantation to biopsy in histologic ABMR: A single center report

BACKGROUND

Allograft biopsies with lesions of Antibody-Mediated Rejection (ABMR) with Microvascular Inflammation (MVI) have shown heterogeneous etiologies and outcomes.

METHODS

To examine factors associated with outcomes in biopsies that meet histologic ABMR criteria, we retrospectively evaluated for-cause biopsies at our center between 2011 and 2017. We included biopsies that met the diagnosis of ABMR by histology, along with simultaneous evaluation for anti-Human Leukocyte Antigen (HLA) donor-specific antibodies (DSA). We evaluated death-censored graft loss (DCGL) and used a principal component analysis (PCA) approach to identify key predictors of outcomes.

RESULTS

Out of the histologic ABMR cohort (n = 118), 70 were DSA-positive ABMR, while 48 had no DSA. DSA(+)ABMR were younger and more often female recipients. DSA(+)ABMR occurred significantly later post-transplant than DSA(-)ABMR suggesting time-dependence. DSA(+)ABMR had higher inflammatory scores (i,t), chronicity scores (ci, ct) and tended to have higher MVI scores. Immunodominance of DQ-DSA in DSA(+)ABMR was associated with higher i+t scores. Clinical/histologic factors significantly associated with DCGL after biopsy were inputted into the PCA. Principal component-1 (PC-1), which contributed 34.8% of the variance, significantly correlated with time from transplantation to biopsy, ci/ct scores and DCGL. In the PCA analyses, i, t scores, DQ-DSA, and creatinine at biopsy retained significant correlations with GL-associated PCs.

CONCLUSIONS

Time from transplantation to biopsy plays a major role in the prognosis of biopsies with histologic ABMR and MVI, likely due to ongoing chronic allograft injury over time.

Pathological Mechanisms Induced by TRPM2 Ion Channels Activation in Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion (IR) injury triggers a cascade of signaling reactions involving an increase in Ca^{2 +} charge and reactive oxygen species (ROS) levels resulting in necrosis, inflammation, apoptosis, and subsequently acute kidney injury (AKI).Transient receptor potential (TRP) channels include an essential class of Ca²⁺ permeable cation channels, which are segregated into six main channels: the canonical channel (TRPC), the vanilloid-related channel (TRPV), the melastatin-related channel (TRPM), the ankyrin-related channel (TRPA), the mucolipin-related channel (TRPML) and polycystin-related channel (TRPP) or polycystic kidney disease protein (PKD2). TRP channels are involved in adjusting vascular tone, vascular permeability, cell volume, proliferation, secretion, angiogenesis and apoptosis.TRPM channels include eight isoforms (TRPM1-TRPM8) and TRPM2 is the second member of this subfamily that has been expressed in various tissues and organs such as the brain, heart, kidney and lung. Renal TRPM2 channels have an important role in renal IR damage. So that TRPM2 deficient mice are resistant to renal IR injury. TRPM2 channels are triggered by several chemicals including hydrogen peroxide, Ca²⁺, and cyclic adenosine diphosphate (ADP) ribose (cADPR) that are generated during AKI caused by IR injury, as well as being implicated in cell death caused by oxidative stress, inflammation, and apoptosis.

A biocompatible nanoparticle-based approach to inhibiting renal ischemia reperfusion injury in mice by blocking thrombospondin-1 activity

Thrombospondin-1 (TSP-1) is a key mediator of renal ischemia-reperfusion injury (IRI), a major cause of kidney dysfunction under various disease conditions and a risk factor of renal allograft rejection. In this study, we developed a nanotechnology-based therapy targeting TSP-1 to prevent renal IRI. A biocompatible nanoparticle (NP) capable of specific binding to TSP-1 was prepared by conjugating NPs with TSP-1-binding (LSKL) peptides. LSKL/NPs not only effectively adsorbed recombinant TSP-1 proteins in vitro, but also efficiently neutralized TSP-1 in mice undergoing renal IRI. IRI-induced elevation of TSP-1 in the kidney was significantly inhibited by post-IR treatment with LSKL/NPs, but not free LSKL or NPs. Furthermore, TSP-1 proteins adsorbed on LSKL/NPs were functionally inactive and unable to induce apoptosis in renal tubular epithelial cells. Importantly, LSKL/NPs induced strong protection against renal IRI, as shown by markedly diminished serum creatinine levels and improved histological lesions of the kidney. Thus, LSKL/NPs provide a useful means of depleting and inactivating TSP-1 and a potential therapy for renal IRI.

A bioinspired carbon monoxide delivery system prevents acute kidney injury and the progression to chronic kidney disease

Renal ischemia-reperfusion (IR)-induced tissue hypoxia causes impaired energy metabolism and oxidative stress. These conditions lead to tubular cell damage, which is a cause of acute kidney injury (AKI) and AKI to chronic kidney disease (CKD). Three key molecules, i.e., hypoxia-inducible factor-1α (HIF-1α), AMP-activated protein kinase (AMPK), and nuclear factor E2-related factor 2 (Nrf2), have the potential to protect tubular cells from these disorders. Although carbon monoxide (CO) can comprehensively induce these three molecules via the action of mitochondrial reactive oxygen species (mtROS), the issue of whether CO induces these molecules in tubular cells remains unclear. Herein, we report that CO-enriched red blood cells (CO-RBC) cell therapy, the inspiration for which is the in vivo CO delivery system, exerts a renoprotective effect on hypoxia-induced tubular cell damage via the upregulation of the above molecules. Experiments using a mitochondria-specific antioxidant provide evidence to show that CO-driven mtROS partially contributes to the upregulation of the aforementioned molecules in tubular cells. CO-RBC ameliorates the pathological conditions of IR-induced AKI model mice via activation of these molecules. CO-RBC also prevents renal fibrosis via the suppression of epithelial mesenchymal transition and transforming growth factor-β1 secretion in an IR-induced AKI to CKD model mice. In conclusion, our results confirm that the bioinspired CO delivery system prevents the pathological conditions of both AKI and AKI to CKD via the amelioration of hypoxia inducible tubular cell damage, thereby making it an effective cell therapy for treating the progression to CKD.

Postresuscitation care and prognostication after cardiac arrest-Does sex matter?

Background

There are conflicting results concerning sex-specific differences in the post-cardiac arrest period. We investigated the sex distribution of patients after successful cardiopulmonary resuscitation (CPR), differences in treatment, complications, outcome and sex-specific performance of biomarkers for prognostication of neurological outcome.

Methods

Prospective observational study including cardiac-arrest (CA) patients treated with mild therapeutic hypothermia (MTH) at 33 °C for 24 h or normothermia. We investigated common complications including pneumonia and acute kidney injury (AKI) and neuron-specific enolase, secretoneurin and tau protein as biomarkers of neurological outcome, which was assessed with the cerebral performance categories score at hospital discharge.

Results

Out of 134 patients 26% were female. Women were significantly older (73 years, interquartile range (IQR) 56–79 years vs. 62 years, IQR 53–70 years; p = 0.038), whereas men showed a significantly higher rate of pneumonia (29% vs. 6%; p = 0.004) and a trend towards higher rates of AKI (62% vs. 45%; p = 0.091). Frequency of MTH treatment was not significantly different (48% vs. 31%; p = 0.081). Female sex was not associated with neurological outcome in multivariable analysis (p = 0.524). There was no significant interaction of sex with prognostication of neurological outcome at 24, 48 and 72 h after CPR. At the respective time intervals p_interaction for neuron-specific enolase was 0.524, 0.221 and 0.519, for secretoneurin 0.893, 0.573 and 0.545 and for tau protein 0.270, 0.635, and 0.110.

Conclusion

The proportion of female patients was low. Women presented with higher age but had fewer complications during the post-CA period. Female sex was not associated with better neurological outcome. The performance of biomarkers is not affected by sex.

Supplementary Information

The online version of this article (10.1007/s00508-022-02026-x) contains supplementary material, which is available to authorized users.

Potent efficacy of Stachybotrys microspora triprenyl phenol-7, a small molecule having anti-inflammatory and antioxidant activities, in a mouse model of acute kidney injury

Acute kidney injury (AKI) increases the risk of chronic kidney disease (CKD), complicates existing CKD, and can lead to the end-stage renal disease. However, there are no approved effective therapeutics for AKI. Recent studies have suggested that inflammation and oxidative stress are the primary causes of AKI. We previously reported the potential anti-inflammatory and antioxidant activities of Stachybotrys microspora triprenyl phenol-7 (SMTP-7). The aim of the present study was to evaluate the efficacy of SMTP-7 in AKI model mice. AKI was induced in mice by ischemia of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after the removal of right kidney. The efficacy of SMTP-7 was determined by measuring the renal function using urine and serum samples and morphological assessment. For deciphering the mechanism of action of SMTP-7, inflammatory cytokines and oxidative stress in kidney were detected. SMTP-7 (0.01, 0.1, 1, 10 mg/kg) dose-dependently improved the renal function. In addition, it improved the damage to renal tubules and exhibited anti-inflammatory and antioxidant activities in the kidney of AKI mice. These results indicate the potential of SMTP-7 as a medicinal compound for the treatment of AKI.

The protective effects of sinapic acid on acute renal ischemia/reperfusion injury

Objectives

The aim of this research was to investigate whether sinapic acid (SA) can alleviate oxidative damage, apoptosis, and inflammation in I/R induced renal injury.

Methods

A total of 24 male rats were randomly separated into four groups as six rats in each group. Group 1 (Sham), Group 2 (I/R), Group 3 (I/R + SA, 10 mg/kg), Group 4 (I/R + SA, 20 mg/kg). In order to evaluate kidney function serum BUN, Cr, and AST were measured in an autoanalyzer. SOD, GSH-Px, MDA, PC and NO oxidative stress parameters were measured with spectrophotometric methods and TNF-α, IL-1β, IL-6, KIM-1 and NGAL parameters were measured with the ELISA method. In addition, H&E method and immunohistochemical examinations were performed for histological evaluations of kidney tissue.

Results

SA significantly decreases the increase in kidney damage, inflammation, oxidative stress, cell death and restore the decrease in antioxidant enzyme activities (p<0.05). Pre-treatment of the rats with SA reduces kidney dysfunction and morphological changes.

Conclusions

The development of oxidative stress and lipid peroxidation seems to be the leading factors that accelerate inflammation and cell death during renal IRI. The antioxidant, anti-inflammatory, and anti-apoptotic features of SA displayed a renoprotective effect.

Role of C5aR1 and C5L2 Receptors in Ischemia-Reperfusion Injury

The role of C5a receptors (C5aR1 and C5L2) in renal ischemia-reperfusion injury (IRI) is uncertain. We generated an in vitro model of hypoxia/reoxygenation with human proximal tubule epithelial cells to mimic some IRI events. C5aR1, membrane attack complex (MAC) and factor H (FH) deposits were evaluated with immunofluorescence. Quantitative polymerase chain reaction evaluated the expression of C5aR1, C5L2 genes as well as genes related to tubular injury, inflammation, and profibrotic pathways. Additionally, C5aR1 and C5L2 deposits were evaluated in kidney graft biopsies (KB) from transplant patients with delayed graft function (DGF, n = 12) and compared with a control group (n = 8). We observed higher immunofluorescence expression of C5aR1, MAC and FH as higher expression of genes related to tubular injury, inflammatory and profibrotic pathways and of C5aR1 in the hypoxic cells; whereas, C5L2 gene expression was unaffected by the hypoxic stimulus. Regarding KB, C5aR1 was detected in the apical and basal membrane of tubular epithelial cells, whereas C5L2 deposits were observed in endothelial cells of peritubular capillaries (PTC). DGF-KB showed more frequently diffuse C5aR1 staining and C5L2 compared to controls. In conclusion, C5aR1 expression is increased by hypoxia and IRI, both in vitro and in human biopsies with an acute injury. C5L2 expression in PTC could be related to endothelial cell damage during IRI.

Which remote ischemic preconditioning protocol is favorable in renal ischemia-reperfusion injury in the rat?

BACKGROUND

The optimal timing of remote ischemic preconditioning (RIPC) in renal ischemia-reperfusion (I/R) injury is still unclear. We aimed to compare early- and delayed-effect RIPC with hematological, microcirculatory and histomorphological parameters.

METHODS

In anesthetized male CrI:WI Control rats (n = 7) laparotomy and femoral artery cannulation were performed. In I/R group (n = 7) additionally a 45-minute unilateral renal ischemia with 120-minute reperfusion was induced. The right hind-limb was strangulated for 3×10 minutes (10-minute intermittent reperfusion) 1 hour (RIPC-1 group, n = 7) or 24 hour (RIPC-24 group, n = 6) prior to the I/R. Hemodynamic, hematological parameters and organs' surface microcirculation were measured.

RESULTS

Control and I/R group had the highest heart rate (p < 0.05 vs base), while the lowest mean arterial pressure (p < 0.05 vs RIPC-1) were found in the RIPC-24 group. The highest microcirculation values were measured in the I/R group (liver: p < 0.05 vs Control). The leukocyte count increased in I/R group (base: p < 0.05 vs Control), also this group's histological score was the highest (p < 0.05 vs Control). The RIPC-24 group had a significantly lower score than the RIPC-1 (p = 0.0025 vs RIPC-1).

CONCLUSION

Renal I/R caused significant functional and morphological, also in the RIPC groups. According to the histological examination the delayed-effect RIPC method was more effective.

Upregulation of antioxidant nuclear factor erythroid 2-related factor 2 and its dependent genes associated with enhancing renal ischemic preconditioning renoprotection using levosimendan and cilostazol in an ischemia/reperfusion rat model

INTRODUCTION

Ischemic preconditioning (Ipre) provides protection against renal ischemia-reperfusion (I/R) injury with its associated remote organ damage. This study examined the enhancing protective effect of Ipre with levosimendan or cilostazol in I/R-induced kidney and lung injury in a rat model.

MATERIAL AND METHODS

Rats were divided into: sham-operated, I/R control, Ipre control, I/R + cilostazol or levosimendan and Ipre + cilostazol or levosimendan. Drugs were given 30 min before left renal I/R or 4 cycles of Ipre just before renal ischemia.

RESULTS

The Ipre combined with the implemented drugs enhanced physiological antioxidant defense genes including renal nuclear factor erythroid 2-related factor 2 (Nrf2) and its dependent genes heme oxygenase-1 (HO-1) and NADPH-quinone oxidoreductase-1 (NQO-1) and improved malondialdehyde and superoxide dismutase renal tissue levels. The combined effect improved I/R consequences for blood urea, creatinine, and creatinine clearance and improved blood oxygenation and metabolic acidosis. Moreover, the combination improved the renal soluble intercellular adhesion molecule (ICAM), tumor necrosis factor α (TNF-α) and interlukin-6 (IL-6) with histopathological improvement of tubular necrosis with a decrease in the apoptotic marker caspase-3 and an increase in the anti-apoptotic Bcl-2 expression.

CONCLUSIONS

Cilostazol or levosimendan potentiates the renoprotective effect of Ipre against renal I/R injury, associated with upregulation of antioxidant genes Nrf2, HO-1, and NOQ-1 expression.

Protective effects of Gamma Oryzanol on distant organs after kidney ischemia-reperfusion in rats: A focus on liver protection

BACKGROUND

Acute kidney injury (AKI) is the main clinical concern resulted from ischemia-reperfusion injury (IRI). Ample clinical data indicates that AKI is associated with distant organ dysfunctions and poor patients' outcomes. Oxidative stress and inflammation have a critical role in the pathogenesis of organ injuries following IRI. The objectives of this study were to determine the impact of Gamma Oryzanol (GO), extracted from rice bran oil, on distant organs in rats after IRI.

METHODS

Twelve out of 24 Wistar rats were treated by one dosage of GO (100mg/kg) 1 h before I/R induction through both oral gavage and intraperitoneal injection. Then, the AKI model rats were induced by IRI. Oxidative stress and antioxidant protein levels were assessed in the brain, heart, and liver tissues in the experimental groups. Furthermore, the effects of GO on IRI-induced liver dysfunction, apoptosis, and inflammation were measured by Western blot.

RESULTS

GO pretreatment could significantly restore the levels and activity of antioxidant proteins in the brain, heart, and liver tissues (P < 0.05). Moreover, GO pretreatment could decrease the inflammatory cytokine (IL-1, IL-6, and TNF-α) in the liver (P < 0.01). By reducing Bax/Bcl-2 ratio and down-regulating caspase-3, GO could significantly diminish apoptosis in the liver tissue after the kidney I/R (P < 0.01). Additionally, GO could significantly diminish the deterioration of liver function in the kidney I/R model.

CONCLUSION

GO protects distant organs against renal IRI-induced oxidative stress. Furthermore, it ameliorates liver function and remarkably exerts anti-oxidative, anti-inflammatory, and anti-apoptotic roles in the liver as an important detoxifying organ.

Inhibition of myeloid differentiation protein 2 attenuates renal ischemia/reperfusion-induced oxidative stress and inflammation via suppressing TLR4/TRAF6/NF-kB pathway

As a major risk factor of acute kidney injury, renal ischemia/reperfusion (I/R) has a high mortality rate. Myeloid differentiation protein 2 (MD-2) is a secretory glycoprotein that plays an important role in inflammation. Our study aimed to explore the roles of MD-2 in I/R-induced inflammation and oxidative stress in vivo and in vitro. For the in vivo studies, male C57BL/6 mice were randomly divided into four groups: 1) sham, 2) I/R, 3) negative control for siRNA (siNC) and I/R treatment, or 4) MD-2 siRNA (siMD-2) and I/R. Levels of blood urea nitrogen and creatinine in the plasma were tested, and hematoxylin and eosin staining was performed at 24 h after I/R injury. The inflammatory cytokines TNF-α, IL-6, and MCP-1 were measured using ELISA and Real-time qPCR (RT-qPCR). Malondialdehyde (MDA) content and superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activity were estimated. For the in vitro studies, HK-2 cells were transfected with siMD-2 and then exposed to hypoxia/reoxygenation (H/R). Inflammatory cytokine expression and oxidative stress then were evaluated. We found decreased levels of blood urea nitrogen and creatinine levels after MD-2 silencing. MD-2 deficiency improved histological damage. MD-2 downregulation attenuated levels of inflammatory cytokines. Inhibition of MD-2 resulted in reduced MDA content and increased SOD, CAT, and GPx activity. Loss of function of MD-2 inhibited the H/R-induced production and expression of inflammatory cytokines. MD-2 silencing reduced MDA content after H/R, and MD-2 suppression enhanced SOD, CAT, and GPx activity. MD-2 deficiency also blocked H/R-mediated activation of the TLR4/TRAF6/NF-κB pathway, and pyrrolidinedithiocarbamate (PDTC) pretreatment strengthened the anti-inflammatory and antioxidant damage effects of MD-2 silencing. Taken together, our study revealed that MD-2 deficiency ameliorated renal I/R-induced inflammation and oxidative stress via inhibition of TLR4/TRAF6/NF-κB pathway.

Inhibition of PDE4/PDE4B improves renal function and ameliorates inflammation in cisplatin-induced acute kidney injury

Nephrotoxicity is a known clinical complication of cisplatin that limits the use of this potent antitumor drug. Cyclic nucleotide phosphodiesterases (PDEs) play complex roles in physiology and pathology. PDE4, which is a member of the PDE family, has four subtypes (PDE4A-PDE4D), and PDE4B plays an important role in inflammation. Thus, in the present study, we investigated the effect of PDE4/PDE4B inhibition on renal function and inflammation in a cisplatin nephrotoxicity model. In mice, cisplatin enhanced mRNA and protein expression of PDE4B in renal tubules. After treatment with the PDE4 inhibitor cilomilast, cisplatin-induced renal dysfunction, renal tubular injury, tubular cell apoptosis, and inflammation were all improved. Next, after silencing PDE4B in vivo, we observed a protective effect against cisplatin nephrotoxicity similar to that of the PDE4 inhibitor. In vitro, cisplatin-induced renal tubular cell death was strikingly ameliorated by the PDE4 inhibitor and PDE4B knockdown along with the blockade of the inflammatory response. Considering the known roles of some cell survival pathways in antagonizing insults, we examined levels of PDE4-associated proteins sirtuin 1, phosphatidylinositol 3-kinase, and phosphorylated AKT in cisplatin-treated renal tubular cells with or without cilomilast treatment. Strikingly, cisplatin treatment downregulated the expression of the above proteins, and this effect was largely abolished by the PDE4 inhibitor. Together, these findings indicate the beneficial role of PDE4/PDE4B inhibition in treating cisplatin nephrotoxicity, possibly through antagonizing inflammation and restoring cell survival signaling pathways.

Synergistic renoprotective effects of sesame oil and erythropoietin on ischemic kidney injury after renal transplantation

In this study, we evaluated the combined therapeutic efficacy of erythropoietin (a hematopoietic hormone produced by the fetal liver and kidney in response to inflammation and apoptosis) and sesame oil (from Sesamum indicum L.) on ischemic kidney injury following kidney transplantation in a rat model. Rats were assigned to the following groups: sham, control, 1000 U/kg erythropoietin, 1 mL/kg sesame oil, 1000 U/kg erythropoietin + 1 mL/kg sesame oil, and positive control. We measured the levels of blood urea nitrogen (BUN), creatinine, alanine aminotransferase (ALT), lipid peroxidation, reactive oxygen species (ROS), reduced glutathione (GSH), antioxidant enzymes, and proinflammatory markers and performed renal histopathological evaluation. The combined erythropoietin and sesame oil treatment significantly reduced BUN, ALT, creatinine, lipid peroxidation, ROS, and proinflammatory markers and GSH and antioxidant enzyme levels. Histopathological examination showed that the combined erythropoietin and sesame oil treatment significantly reduced necrosis. Therefore, combined treatment of sesame oil and erythropoietin may represent an effective therapeutic approach against ischemic kidney injury after kidney transplantation.

Glatiramer acetate attenuates renal ischemia reperfusion injury in rat model

Chronic renal failure can ultimately lead to kidney transplantation. Renal transplantation is associated with ischemia-reperfusion injury (I/R).² The subsequent processes of kidney I/R can lead to irreversible damages to the kidney tissue. Glatiramer acetate is an immunomodulatory drug for the treatment of multiple sclerosis (MS) and the anti-inflammatory effects of this drug have already been proven in some inflammatory models. The purpose of this study was to evaluate the protective effects of Glatiramer on reducing the damages arising from kidney ischemia-reperfusion. In this study, 35 Wistar rats were used which divided into 5 groups: sham, control (I/R), I/R + Glatiramer 0.5 mg/kg, I/R + Glatiramer 1 mg/kg, I/R + Glatiramer 2 mg/kg. Renal arteries were clamped bilaterally for 45 min, then the clamps were removed and the reperfusion process continued to 24 h. In the following, serum and kidneys were separated for analysis. In the control group, serum levels of LDH, inflammatory factor TNF-α and renal functional markers such as BUN and Creatinine were remarkably increased, but in the treatment groups, especially in Glatiramer 2 mg/kg received group, a significant decrease in these factors was observed. Tissue concentration of MDA was reduced following Glatiramer treatment. Besides, Glatiramer attenuated the increased kidney level of NF-κB protein using immunohistochemical assay. NFkB migration to the nucleolus increases inflammatory cytokines production. The anti-inflammatory factor, IL-10, in serum was significantly increased in the treatment group of Glatiramer 2 mg/kg. Furthermore, Glatiramer decreased renal tissue injury score according to the histopathological study. These results demonstrate that Glatiramer may play protective effects in kidney ischemia-reperfusion injury by reducing inflammatory and oxidative damages.

Luteolin confers renoprotection against ischemia-reperfusion injury via involving Nrf2 pathway and regulating miR320

This work aims to evaluate the renoprotective effect of luteolin on expression of Nrf2 and miR320 in ischemia-reperfusion (I/R) injury in rats. Thirty rats were randomly divided into five groups; control, Luteolin (50 mg/kg), ischemia-reperfusion (I/R), DMSO (0/1%) + I/R and Luteolin+I/R, (n = 6 each). Administration of luteolin and DMSO was carried out by gavage for 3 days before renal I/R. Then, the rats were subjected to bilateral renal ischemia for 45 min and followed by reperfusion for 2 h. All rats were killed and the renal function, histological changes, oxidative stress degree, in all of groups were evaluated. In addition, the effects of luteolin on renal expression of Nrf2 and miR320 were examined by immunohistochemistry and real time- PCR. Luteolin significantly improved the creatinine (Cr) and blood urea nitrogen (BUN) levels in Luteolin + I/R group compared to I/R group (p < 0.001 and p < 0.001 respectively). Reduction of enzymatic activity of superoxide dismutase, glutathione peroxidase and catalase in I/R and DMSO + I/R groups, was significantly improved by Luteolin (p < 0.05) in Luteolin + I/R group. Pre-treatment with luteolin also resulted in significant reduction in tissue MDA level (p < 0.001), Nrf2 (p < 0.001) and miR320 expression (P < 0.05) that were increased by renal I/R. Also, the rats pretreated with luteolin had nearly normal structure of the kidney. These results indicate that luteolin protects the kidney against I/R injury via reducing oxidative stress, increasing antioxidant enzymes and reducing expression of Nrf2 and miR320.

Short-term dexamethasone treatment transiently, but not permanently, attenuates fibrosis after acute-to-chronic kidney injury

Background

Acute kidney injury (AKI) is an underestimated, yet important, risk factor for the development of chronic kidney disease (CKD). Persistence of inflammation after a renal ischemic injury has been observed, both in experimental models and patients, and is thought to be an important mechanisms underlying progression of acute-to-chronic renal injury. Temporary suppression of inflammation immediately after AKI might therefore be a good first-line therapeutic strategy towards a better long term outcome.

Methods

Male C57Bl/6 J mice (Charles River, 10–12 weeks of age) underwent warm (36 °C body temperature) unilateral ischemia-reperfusion of the kidney for 21 min, after which treatment with intraperitoneal injection of the corticosteroid dexamethasone (10 mg/kg) was initiated for 3 weeks. Both at that time point and after an additional 3 week post-treatment follow up period, fibrosis was quantified by collagen I gene expression and immunostaining, as well as gene expression analysis of fibrosis-related genes Tgfβ, Ccn2 (Ctgf), Pai-1 and Ccn3. Furthermore, inflammation was evaluated by Tnfα gene expression and protein expression of the F4/80 macrophage marker and the α-SMA fibroblast marker. Lastly, renal histopathology was quantified by a morphometric analysis of the tubulointerstitial area.

Results

Treatment with dexamethasone attenuated development of fibrosis, as evidenced by reduced collagen I gene expression and immunostaining, in combination with reduced gene expression of the pro-fibrotic Ccn2 and increased expression of the anti-fibrotic Ccn3. The effects of dexamethasone on renal fibrosis persisted during the 3 week follow up period, as evidenced by stagnation of collagen I deposition in the ischemic kidney, in contrast to vehicle-treatment, where progression of fibrosis was observed. However, expression levels of the pro-fibrotic genes re-approached those of vehicle-treated injured kidneys suggesting that the effects of dexamethasone on fibrosis beyond the treatment period are temporary.

Conclusion

A short term anti-inflammatory therapy with dexamethasone only transiently attenuates ischemia induced fibrosis. Prolonged or persistent anti-inflammatory treatment seems warranted to achieve long term benefit.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1151-7) contains supplementary material, which is available to authorized users.

Hydralazine protects against renal ischemia-reperfusion injury in rats

In this study, we investigated whether hydralazine could reduce renal ischemia and reperfusion (I/R) injury in rats. Renal I/R was induced by a 70-min occlusion of the bilateral renal arteries and a 24-h reperfusion, which was confirmed by the increased the mortality, the levels of blood urea nitrogen (BUN), blood creatinine (Cr), renal tissue NO and the visible histological damage of the kidneys. Apoptosis was evaluated by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) staining. Furthermore, the serum levels of malonaldehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) were significantly elevated in renal I/R group, while the superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) levels were suppressed. However, intragastric pretreatment with hydralazine at doses of 7.5-30 mg/kg before renal I/R significantly limited the increase in mortality, BUN, Cr, oxidative stress, inflammatory factors, histological damage and apoptosis in the kidneys. In addition, hydralazine also increased p-AKT, Bcl-2 expression and decreased iNOS, Bax, cleaved caspase-3 expression in the kidneys. In conclusion, hydralazine reduced renal I/R injury probably via inhibiting NO production by iNOS/NO pathway, inhibiting oxidative stress, inflammatory response and apoptosis by a mitochondrial-dependent pathway.

Tempol, a superoxide dismutase mimetic agent, reduces cisplatin-induced nephrotoxicity in rats

Cisplatin (CP) is one of the most potent anti-cancer drugs used against different types of cancer. Its use is limited due to its nephrotoxicity. This study is aimed to evaluate the role of a super oxide dismutase (SOD) mimetic agent, tempol, in protection against CP nephrotoxicity in rats. Animals were divided into four groups: Group-1: Normal control group, Group-2: CP group (single dose of CP 6 mg/kg, i.p.), Group-3 and Group-4: Tempol-treated groups (50 mg/kg p.o. and 100 mg/kg p.o. respectively) daily for a week before CP injection and continued for an additional four days after CP injection. Urine and blood samples were collected for the evaluation of kidney function including serum creatinine, BUN, cystatin-c, and creatinine clearance. In addition, western blotting was used to determine urine lipocalin-2 content. Furthermore, kidney tissue was collected for the determination of oxidative stress markers, caspase-3 expression, and histopathological examination. We noticed that both doses of tempol significantly improved kidney function, which was deteriorated by CP injection. Tempol significantly elevated kidney glutathione (GSH) content and SOD activity, and decreased kidney lipid peroxidation and NOx production. Tempol also significantly decreased kidney caspase-3 expression which was elevated by CP toxicity. Thus, we conclude that tempol can protect against CP nephrotoxicity. We noticed that both doses of tempol are effective in ameliorating CP-nephrotoxicity.

Zinc mitigates renal ischemia-reperfusion injury in rats by modulating oxidative stress, endoplasmic reticulum stress, and autophagy

Oxidative stress is a major factor involved in the pathogenesis of renal ischemia/reperfusion (I/R). Exogenous zinc (Zn) was suggested as a potent antioxidant; however, the mechanism by which it strengthens the organ resistance against the effects of reactive oxygen species (ROS) is not yet investigated. The present study aims to determine whether acute zinc chloride (ZnCl₂ ) administration could attenuate endoplasmic reticulum (ER) stress, autophagy, and inflammation after renal I/R. Rats were subjected to either sham operation (Sham group, n = 6), or 1 hr of bilateral ischemia followed by 2 hr of reperfusion (I/R groups, n = 6), or they received ZnCl₂ orally 24 hr and 30 min before ischemia (ZnCl₂ group, n = 6). Rats were subjected to 1 hr of bilateral renal ischemia followed by 2 hr of reperfusion (I/R group, n = 6). Our results showed that ZnCl₂ enhances renal function and reduces cytolysis (p < 0,05). In addition, it increased significantly the activities of antioxidant enzymes (SOD, CAT, and GPX) and the level of GSH in comparison to I/R (p < 0,05). Interestingly, ZnCl₂ treatment resulted in significant decreased ER stress, as reflected by GRP78, ATF-6,p-eIF-2α, XPB-1, and CHOP downregulaion. Rats undergoing ZnCl₂ treatment demonstrated a low expression of autophagy parameters (Beclin-1 and LAMP-2), which was correlated with low induction of apoptosis (caspase-9, caspase-3, and p-JNK), and reduction of inflammation (IL-1ß, IL-6, and MCP-1) (p < 0,05). In conclusion, we demonstrated the potential effect of Zn supplementation to modulate ER pathway and autophagic process after I/R.

Cell-Based Therapies in Acute Kidney Injury (AKI)

Acute kidney injury frequently occurs in hospitalized patients all over the world. The prognosis remains poor since specific therapies for promoting kidney regeneration/repair are still missing. In recent years cell-based strategies have improved AKI outcomes under experimental circumstances. Four groups of cells, each of them displaying certain biological and functional characteristics have been evaluated in AKI, induced Pluripotent Stem Cells (iPSCs), Spermatagonial Stem Cells (SSCs), Proangiogenic Cells (PACs) and Endothelial Colony Forming Cells (ECFCs), and Mesenchymal Stem Cells (MSCs). All of these have been documented to stabilize either parameters of kidney excretory dysfunction and/or certain morphological parameters. The mechanisms responsible for AKI protection include direct (cell incorporation) and indirect processes, the latter being mediated by humoral factors and particularly by the production of so-called extracellular vesicles. Cell-derived vesicular organelles have been shown to carry pro-regenerative micro-RNA molecules which stabilize the vascular and tubular function. The first trials in humans have been initiated, the majority of such trials employs MSCs. However, any transfer of cell-based strategies in the clinical practice is potentially associated with significant difficulties. These include cell availability, tolerance and competence. The article intends to summarize essential informations about all of the four populations mentioned above and to discuss implications for the management of human AKI.

Hypoxia/Reoxygenation of Rat Renal Arteries Impairs Vasorelaxation via Modulation of Endothelium-Independent sGC/cGMP/PKG Signaling

Ischemia/reperfusion injury holds a key position in many pathological conditions such as acute kidney injury and in the transition to chronic stages of renal damage. We hypothesized that besides a reported disproportional activation of vasoconstrictor response, hypoxia/reoxygenation (H/R) adversely affects endothelial dilatory systems and impairs relaxation in renal arteries. Rat renal interlobar arteries were studied under isometric conditions. Hypoxia was induced by application of 95% N₂, 5% CO₂ for 60 min to the bath solution, followed by a 10 min period of reoxygenation (95% O₂, 5% CO₂). The effect of H/R on relaxation was assessed using various inhibitors of endothelial dilatory systems. mRNA expression of phosphodiesterase 5 (PDE5), NADPH oxidases (NOX), and nitric oxide synthase (NOS) isoforms were determined using qRT-PCR; cGMP was assayed with direct cGMP ELISA. Acetylcholine induced relaxation was impaired after H/R. Inhibition of the NOS isoforms with L-NAME, and cyclooxygenases (COXs) by indomethacin did not abolish the H/R effect. Moreover, blocking the calcium activated potassium channels K_Ca3.1 and K_Ca2.1, the main mediators of the endothelium-derived hyperpolarizing factor, with TRAM34 and UCL1684, respectively, showed similar effects in H/R and control. Arterial stiffness did not differ comparing H/R with controls, indicating no impact of H/R on passive vessel properties. Moreover, superoxide was not responsible for the observed H/R effect. Remarkably, H/R attenuated the endothelium-independent relaxation by sodium nitroprusside, suggesting endothelium-independent mechanisms of H/R action. Investigating the signaling downstream of NO revealed significantly decreased cGMP and impaired relaxation during PDE5 inhibition with sildenafil after H/R. Inhibition of PKG, the target of cGMP, did not normalize SNP-induced relaxation following H/R. However, the soluble guanylyl cyclase (sGC) inhibitor ODQ abolished the H/R effect on relaxation. The mRNA expressions of the endothelial and the inducible NOS were reduced. NOX and PDE5 mRNA were similarly expressed in H/R and control. Our results provide new evidence that impaired renal artery relaxation after H/R is due to a dysregulation of sGC leading to decreased cGMP levels. The presented mechanism might contribute to an insufficient renal reperfusion after ischemia and should be considered in its pathophysiology.

Hypothermia and kidney: a focus on ischaemia-reperfusion injury

Cellular damage after reperfusion of ischaemic tissue is defined as ischaemia–reperfusion injury (IRI). Hypothermia is able to decrease oxygen consumption, preventing a rapid loss of mitochondrial activity. However, even though cooling can help to decrease the deleterious effects of ischaemia, the consequences are not exclusively beneficial, such that hypothermic storage is a compromise between benefits and harm. The present review details the relationship between renal IRI and hypothermia, describing the pathophysiology of IRI and hypothermic protection through experimental evidence. Although experimental models of renal IRI are a valuable tool for understanding the pathophysiology of renal ischaemia–reperfusion, the clinical transfer of experimental results has several limitations, particularly because of anatomical and physiological differences. In this review limitations of animal models but also hypothermia as a strategy to protect the kidney from IRI are discussed. We also attempt to describe three clinical scenarios where hypothermia is used in clinical settings of IRI: transplantation, deceased donors and post-cardiac arrest.

Multifunctional Curcumin Mediate Multitherapeutic Effects

Inflammation can promote the development of arthritis, obesity, cardiovascular, type II diabetes, pancreatitis, metabolic and neurodegenerative diseases, and certain types of cancer. Compounds isolated from plants have been practiced since ancient times for curing various ailments including inflammatory disorders and to support normal physiological functions. Curcumin (diferuloylmethane) is a yellow coloring agent, extracted from turmeric that has been used for the prevention and treatment of various inflammatory diseases. Numerous studies have shown that curcumin modulate multiple molecular targets and can be translated to the clinics for multiple therapeutic processes. There is compelling evidence that curcumin can block cell proliferation, invasion, and angiogenesis as well as reduced the prolonged survival of cancer cells. Curcumin mediates anti-inflammatory effect through downregulation of inflammatory cytokines, transcription factors, protein kinases, and enzymes that promote inflammation and development of chronic diseases. In addition, curcumin induces apoptosis through mitochondrial and receptor-mediated pathways by activating caspase cascades. Curcumin is a safe and nontoxic drug that has been reported to be well tolerated. Available clinical trials support the potential role of curcumin for treatment of various inflammatory disorders. However, curcumin's efficacy is hindered by poor absorption and low bioavailability, which limit its translation into clinics. This review outlines the potential pharmacological and clinical role of curcumin, which provide a gateway for the beneficial role of plant isolated compounds in treatment of various inflammatory diseases and cancer.

Endothelial Colony Forming Cells (ECFCs) in murine AKI - implications for future cell-based therapies

Background

In recent years, early Endothelial Progenitor Cells (eEPCs) have been proven as effective tool in murine ischemic AKI and in diabetic nephropathy. The mechanisms of eEPC-mediated vasoprotection have been elucidated in detail. Besides producing a diverse range of humoral factors, the cells also act by secreting vasomodulatory microvesicles. Only few data in contrast have been published about the role of so-called Endothelial Colony Forming Cells (ECFCs - late EPCs) in ischemic AKI. We thus aimed to investigate ECFC effects on postischemic kidney function over several weeks. Our special interest focused on endothelial-to-mesenchymal transition (EndoMT), peritubular capillary density (PTCD), endothelial alpha-Tubulin (aT - cytoskeletal integrity), and endothelial p62 (marker of autophagocytic flux).

Methods

Eight to twelve weeks old male C57Bl/6 N mice were subjected to bilateral renal pedicle clamping for 35 or 45 min, respectively. Donor-derived syngeneic ECFCs (0.5 × 10⁶) were i.v. injected at the end of ischemia. Animals were analyzed 1, 4 and 6 weeks later.

Results

Cell therapy improved kidney function exclusively at week 1 (35 and 45 min). Ischemia-induced fibrosis was diminished in all experimental groups by ECFCs, while PTCD loss remained unaffected. Significant EndoMT was detected in only two of 6 groups (35 min, week 4 and 45 min, week 6), ECFCs reduced EndoMT only in the latter. Endothelial aT declined under almost all experimental conditions and these effects were further aggravated by ECFCs. p62 was elevated in endothelial cells, more so after 45 than after 35 min of ischemia. Cell therapy did not modulate p62 abundances at any time point.

Conclusion

A single dose of ECFCs administered shortly post-ischemia is capable to reduce interstitial fibrosis in the mid- to long-term whereas excretory dysfunction is improved only in a transient manner. There are certain differences in renal outcome parameters between eEPCs and ECFC. The latter do not prevent animals from peritubular capillary loss and they also do not further elevate endothelial p62. We conclude that differences between eEPCs and ECFCs result from certain mechanisms by which the cells act around and within vessels. Overall, ECFC treatment was not as efficient as eEPC therapy in preventing mice from ischemia-induced mid- to long-term damage.

Effect of Hypertonic Saline 5% on Early Graft Function and Urinary Interleukin 18 and Neutrophil Gelatinase-Associated Lipocalin in Deceased-Donor Kidney Transplantation

Ischemia reperfusion injury (IRI) is one of the main causes of delayed graft function (DGF) in deceased-donor kidney transplantation (DDKT). Evidences suggest that hypertonic saline (HS) has beneficial effects on IRI. The objective of the present study is to determine the effect of intraoperative HS, on graft function and urinary biomarkers of interleukin 18 (IL-18) and neutrophil gelatinase-associated lipocalin (NGAL), in patients with DDKT. The design of the study is a randomized, open-label, pilot trial in patients with DDKT. The intervention of the study is administration of 4 mL/kg HS, 5% before graft reperfusion. The primary endpoint was DGF. Fifty-eight (58) adult patients were randomized (HS, n = 32; control, n = 26). There were no significant differences between the two groups in terms of recipient, donor, and transplant characteristics. The rate of DGF was 20% in the HS group compared with 31.8% in the control group (Relative risk 0.63; 95% CI 0.23-1.67; P = 0.36). Serial serum creatinine in the first two days after surgery in addition to urine volumes during the first day after transplantation was significantly different in the HS group (P ≤ 0.05). The urinary NGAL and IL-18 were significantly lower in HS vs. control, at 24 h after transplantation (P ≤ 0.05). The frequency of adverse reactions was similar between groups. This study did not show any significant benefits from HS administration immediately before allograft reperfusion in terms of reducing DGF, serum creatinine at hospital discharge or length of hospital stay in deceased-donor kidney transplant patients.

Role of intratubular pressure during the ischemic phase in acute kidney injury

Acute kidney injury (AKI) induced by clamping of renal vein or pedicle is more severe than clamping of artery, but the mechanism has not been clarified. In the present study, we tested our hypothesis that increased proximal tubular pressure (P_t) during the ischemic phase exacerbates kidney injury and promotes the development of AKI. We induced AKI by bilateral clamping of renal arteries, pedicles, or veins for 18 min at 37°C, respectively. P_t during the ischemic phase was measured with micropuncture. We found that higher P_t was associated with more severe AKI. To determine the role of P_t during the ischemic phase on the development of AKI, we adjusted the P_t by altering renal artery pressure. We induced AKI by bilateral clamping of renal veins, and the P_t was changed by adjusting the renal artery pressure during the ischemic phase by constriction of aorta and mesenteric artery. When we decreased renal artery pressure from 85 ± 5 to 65 ± 8 mmHg, P_t decreased from 53.3 ± 2.7 to 44.7 ± 2.0 mmHg. Plasma creatinine decreased from 2.48 ± 0.23 to 1.91 ± 0.21 mg/dl at 24 h after renal ischemia. When we raised renal artery pressure to 103 ± 7 mmHg, P_t increased to 67.2 ± 5.1 mmHg. Plasma creatinine elevated to 3.17 ± 0.14 mg·dl·24 h after renal ischemia. Changes in KIM-1, NGAL, and histology were in the similar pattern as plasma creatinine. In summary, we found that higher P_t during the ischemic phase promoted the development of AKI, while lower P_t protected from kidney injury. P_t may be a potential target for treatment of AKI.

Protective Effect of the Total Flavonoids from Rosa laevigata Michx Fruit on Renal Ischemia-Reperfusion Injury through Suppression of Oxidative Stress and Inflammation

Renal ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI). Our previous studies have shown that the total flavonoids (TFs) from Rosa laevigata Michx fruit has various activities, however, there were no papers reporting the role of the TFs against renal IRI. In the present work, a hypoxia/reoxygenation (H/R) model in NRK-52E cells and ischemia-reperfusion model in rats were used. The results showed that the TFs significantly attenuated cell injury and markedly decreased serum creatinine (Cr) and blood urea nitrogen (BUN) levels in rats. Further investigation revealed that the TFs markedly decreased the levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH) and glutathione peroxidase (GSH-Px) and intracellular reactive oxygen species (ROS), up-regulated the levels of silent information regulator factor 2-related enzyme 1 (Sirt1), nuclear factor erythroid 2-related factor-2 (Nrf2) and heme oxygenase-1 (HO-1), down-regulated the levels of Kelch like ECH-associated protein-1 (Keap1) and the nuclear translocation of nuclear factor-κBp65 (NF-κBp65), and decreased the mRNA levels of interleukine-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Furthermore, inhibiting Sirt1 by siRNA showed that the role of the natural product in protecting renal IRI was significantly attenuated, suggesting that the effect of the extract against renal IRI depended on Sirt1. Taken together, the TFs has significantly nephroprotective effect against IRI by affecting Sirt1/Nrf2/NF-κB signaling pathway, which should be developed as a new therapeutic agent or food additives to treat acute kidney injury in the future.

Capsulotomy of Ischemically Damaged Donor Kidneys: A Pig Study

BACKGROUND

Ischemia-reperfusion injury of donor kidneys may worsen transplant outcome. Kidneys with severe injury, such as kidneys of donors after circulatory death, develop edema, which may lead to renal compartment syndrome with reduced tissue perfusion.

OBJECTIVE

We studied the effect of capsulotomy during hypothermic machine perfusion (HMP) of ischemically damaged porcine kidneys.

METHODS

Eight pairs of kidneys from slaughterhouse pigs were assigned to two groups (20 and 45 min of warm ischemia). After 21 h of HMP, capsulotomy was performed, and perfusion was continued for 2 h. During perfusion, machine flow (Q), renal resistance (RR), renovascular circulating volume (RCV), intraparenchymal pressure (IPP) and weight were recorded. Parenchymal injury was examined with methylene blue infusion.

RESULTS

Mean Q and RCV increased directly after capsulotomy [percentage increase (95% confidence interval): x0394;Q = 32% (17, 47), p = 0.001, and x0394;RCV = 19% (3, 35), p = 0.023]. Mean RR decreased [x0394;RR = -23% (-31, -15), p < 0.001]. Subanalysis comparing both warm ischemia groups showed no significantly different effect of capsulotomy between groups. There was no methylene blue leakage after capsulotomy in any kidney.

CONCLUSIONS

Renovascular perfusion can be improved with capsulotomy during HMP, without damaging the renal parenchyma. Follow-up studies need to determine which donor kidneys may benefit from capsulotomy.

Protective Effect of Tempol on Acute Kidney Injury Through PI3K/Akt/Nrf2 Signaling Pathway

BACKGROUND/AIMS

Tempol is a protective antioxidant against ischemic injury in many animal models. The molecular mechanisms are not well understood. Nuclear factor erythroid 2-related factor (Nrf2) is a master transcription factor during oxidative stress, which is enhanced by activation of protein kinase C (PKC) pathway. Another factor, tubular epithelial apoptosis, is mediated by activation of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, Akt) signaling pathway during renal ischemic injury. We tested the hypothesis that tempol activates PKC or PI3K/Akt/Nrf2 pathways to transcribe many genes that coordinate endogenous antioxidant defense.

METHODS

The right renal pedicle was clamped for 45 minutes and the left kidney was removed to study renal ischemia/reperfusion (I/R) injury in C57BL/6 mice. The response was assessed from serum parameters, renal morphology and renal expression of PKC, phosphorylated-PKC (p-PKC), Nrf2, heme oxygenase-1 (HO-1), Akt, phosphorylated-Akt (p-Akt), pro-caspase-3 and cleaved caspase-3 in groups of sham and I/R mice given vehicle, or tempol (50 or 100 mg/kg, intraperitoneal injection).

RESULTS

The serum malondialdehyde (MDA, marker of reactive oxygen species) doubled and the BUN and creatinine increased 5- to 10-fold after I/R injury. Tempol (50 or 100 mg/kg) prevented the increases in MDA but only tempol (50 mg/kg) lessened the increases in BUN and creatinine and moderated the acute tubular necrosis. I/R did not change expression of PKC or p-PKC but reduced renal expression of Nrf2, p-Akt, HO-1 and pro-caspase-3 and increased cleaved caspase-3. Tempol (50 mg/kg) prevented these changes produced by I/R whereas tempol (100 mg/kg) had lesser or inconsistent effects.

CONCLUSION

Tempol (50 mg/kg) prevents lipid peroxidation and attenuates renal damage after I/R injury. The beneficial pathway apparently is not dependent on upregulation or phosphorylation of PKC, at lower tempol doses, does implicate upregulation of Akt with expression of Nrf2 that could account for the increase in the antioxidant gene HO-1 and a reduction in the cleavage of the cellular damage marker pro-caspase-3.

Reduction in Renal Ischemia-Reperfusion Injury in Mice by a Phosphoinositide 3-Kinase p110gamma-Specific Inhibitor

BACKGROUND

Although renal ischemia-reperfusion injury (IRI) can cause delayed graft function, a targeted therapy is not yet available. Because phosphoinositide 3-kinases (PI3K) p110γ and p110δ play important roles in immune cell migration and function, we investigated the effects of PI3K p110γ- and p110δ-specific inhibitors in a murine renal IRI model.

METHODS

Renal function was assessed by serum creatine and hematoxylin-eosin staining. Immune cell migration was assessed by flow cytometry and an in vitro cell migration assay using Transwell plates. Gene expression analysis and a multiplex cytokine/chemokine assay were performed to find cytokines/chemokines whose expression was upregulated in renal IRI and affected by p110γ-specific inhibitor.

RESULTS

The PI3K p110γ-specific inhibitor, but not p110δ-specific inhibitor, significantly reduced serum creatine levels and acute tubular necrosis. These were accompanied by reduced infiltration of B cells and reduced expression of CXCL9, a CXCR3 ligand, suggesting that p110γ plays an important role in B-cell migration toward injured kidneys. An in vitro cell migration assay revealed for the first time that B-cell migration to injured kidney cells and to CXCL9 requires p110γ.

CONCLUSIONS

p110γ-specific inhibitor ameliorates renal IRI by reducing necrosis and immune cell migration. This inhibitor may have the potential to reduce renal graft failure caused by renal IRI.

Apoptotic cell administration is detrimental in murine renal ischaemia reperfusion injury

Background

Acute kidney injury induced by renal ischaemia reperfusion injury (IRI) is characterised by renal failure, acute tubular necrosis (ATN), inflammation and microvascular congestion. The administration of apoptotic cells (ACs) has been shown to reduce inflammation in various organs including the liver and kidney. This study explored whether AC administration prior to the induction of renal IRI was protective.

Findings

Renal IRI was induced in Balb/c mice by clamping the renal blood vessels for either 20, 24 or 25 minutes to induce mild, moderate or severe kidney dysfunction respectively. Renal function and injury was determined 24 hours following IRI by measurement of plasma creatinine and ATN scoring respectively. ACs were generated from Balb/c thymocytes and classified as either predominantly early or late apoptotic by Annexin-V and propidium iodide staining. Early AC administration prior to severe IRI had no influence on plasma creatinine or ATN severity. In contrast, administration of early or late ACs significantly worsened renal function in mice with mild or moderate renal IRI, respectively, compared to PBS treated controls, though ATN scores were comparable. Despite ACs exerting pro-coagulant effects, the worsening of renal function was not secondary to increased microvascular congestion, inferred by fibrin and platelet (CD41) deposition, or inflammation, assessed by neutrophil infiltration.

Conclusions

Despite the AC-derived protection demonstrated in other organs, ACs do not protect mice from renal IRI. ACs may in fact further impair renal function depending on injury severity. These data suggest that AC-derived protection is not translationally relevant for patients with acute kidney injury induced by ischaemic injury.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-014-0031-6) contains supplementary material, which is available to authorized users.

Quercetin attenuates renal ischemia/reperfusion injury via an activation of AMP-activated protein kinase-regulated autophagy pathway

Renal ischemia/reperfusion (I/R) is a major cause of acute renal failure. Quercetin, a flavonoid antioxidant, presents in many kinds of food. The molecular mechanism of quercetin on renal protection during I/R is still unclear. Here, we investigated the role of AMP-activated protein kinase (AMPK)-regulated autophagy in renal protection by quercetin. To investigate whether quercetin protects renal cells from I/R-induced cell injury, an in vitro model of I/R and an in vivo I/R model were used. Cell apoptosis was determined by propidium iodide/annexin V staining. Western blotting and immunofluorescence were used to determine the autophagy. AMPK expression was inhibited with appropriate short hairpin RNA (shRNA). In cultured renal tubular cell I/R model, quercetin decreased the cell injury, up-regulated the AMPK phosphorylation, down-regulated the mammalian target of rapamycin (mTOR) phosphorylation and activated autophagy during I/R. Knockdown of AMPK by shRNA transfection decreased the quercetin-induced autophagy but did not affect the mTOR phosphorylation. In I/R mouse model, quercetin decreased the increased serum creatinine level and altered renal histological score. Quercetin also increased AMPK phosphorylation, inhibited the mTOR phosphorylation and activated autophagy in the kidneys of I/R mice. These results suggest that quercetin activates an AMPK-regulated autophagy signaling pathway, which offers a protective effect in renal I/R injury.

Renal telocytes contribute to the repair of ischemically injured renal tubules

Telocytes (TCs), a distinct type of interstitial cells, have been identified in many organs via electron microscopy. However, their precise function in organ regeneration remains unknown. This study investigated the paracrine effect of renal TCs on renal tubular epithelial cells (TECs) in vitro, the regenerative function of renal TCs in renal tubules after ischaemia–reperfusion injury (IRI) in vivo and the possible mechanisms involved. In a renal IRI model, transplantation of renal TCs was found to decrease serum creatinine and blood urea nitrogen (BUN) levels, while renal fibroblasts exerted no such effect. The results of histological injury assessments and the expression levels of cleaved caspase-3 were consistent with a change in kidney function. Our data suggest that the protective effect of TCs against IRI occurs via inflammation-independent mechanisms in vivo. Furthermore, we found that renal TCs could not directly promote the proliferation and anti-apoptosis properties of TECs in vitro. TCs did not display any advantage in paracrine growth factor secretion in vitro compared with renal fibroblasts. These data indicate that renal TCs protect against renal IRI via an inflammation-independent pathway and that growth factors play a significant role in this mechanism. Renal TCs may protect TECs in certain microenvironments while interacting with other cells.

N-acetylcysteine Prevents Kidney and Lung Disturbances in Renal Ischemia/Reperfusion Injury in Rat

BACKGROUND

One of the most common causes of acute kidney injury (AKI) is kidney ischemia/reperfusion injury (IRI). The distant organ injury such as acute lung injury is one of the side effects of AKI or kidney IRI. In this study, we performed bilateral renal IRI in rats and the protective role of N-acetylcysteine (NAC) in kidney and lung was investigated.

METHODS

Rats (n = 30) were randomly assigned to four experiment groups. The group 1 was assigned as sham-operated group. Before kidney IRI performance, the others groups were treated with saline (group 2), 150 mg/kg (group 3) or 500 mg/kg (group 4) of NAC, and the treatment were continued daily after IRI for next 3 days. At day 3, the all groups' animals were subjected for the measurements.

RESULTS

The serum level of blood urea nitrogen (BUN) and creatinine (Cr) in the control group increased significantly (P < 0.05), and administration of NAC (150 mg/kg) decreased the serum levels of Cr and BUN. However, only the serum level of Cr decreased significantly (P < 0.05). NAC did not improve kidney weight and damage; however, its low dose (150 mg/kg) attenuated the lung injury score (P < 0.05) when compared with the control group. No significant differences were observed in lung water content and endothelial permeability, serum levels of malondialdehyde and nitrite between the groups.

CONCLUSIONS

Low dose of NAC as a protectant agent may protect the kidney function and lung tissue damage after kidney IRI.

Curcumin in inflammatory diseases

Curcumin (diferuloylmethane), a yellow coloring agent extracted from turmeric is also used as a remedy for the treatment and prevention of inflammatory diseases. Acute and chronic inflammation is a major factor in the progression of obesity, type II diabetes, arthritis, pancreatitis, cardiovascular, neurodegenerative and metabolic diseases, as well as certain types of cancer. Turmeric has a long history of use in Ayurvedic medicine for the treatment of inflammatory disorders. Recent studies on the efficacy and therapeutic applicability of turmeric have suggested that the active ingredient of tumeric is curcumin. Further, compelling evidence has shown that curcumin has the ability to inhibit inflammatory cell proliferation, invasion, and angiogenesis through multiple molecular targets and mechanisms of action. Curcumin is safe, non-toxic, and mediates its anti-inflammatory effects through the down-regulation of inflammatory transcription factors, cytokines, redox status, protein kinases, and enzymes that all promote inflammation. In addition, curcumin induces apoptosis through mitochondrial and receptor-mediated pathways, as well as activation of caspase cascades. In the current study, the anti-inflammatory effects of curcumin were evaluated relative to various chronic inflammatory diseases. Based on the available pharmacological data obtained from in vitro and in vivo research, as well as clinical trials, an opportunity exists to translate curcumin into clinics for the prevention of inflammatory diseases in the near future.