Differential effects of caspase inhibitors on the renal dysfunction and injury caused by ischemia–reperfusion of the rat kidney

Sevoflurane preconditioning prevents acute renal injury caused by ischemia‑reperfusion in mice via activation of the Nrf2 signaling pathway

Oxidative stress, caused by renal ischemia reperfusion (IR)/hypoperfusion, is one of the main causes of acute kidney injury (AKI). Previous studies have demonstrated that sevoflurane (SEV) protects organs from the damage caused by oxidative stress. In the present study, mice were randomly assigned to a sham operation group (Sham), IR-vehicle group (IR+ vehicle), IR + SEV low-dose preconditioning group and an IR + SEV high-dose preconditioning group. The effect of SEV on nuclear factor E2-related factor 2 (Nrf2), a key regulatory protein of the endogenous antioxidant defense system and, consequently oxidative stress, inflammation and apoptosis-related factors, were all quantified using commercial kits or by western blotting. SEV preconditioning was demonstrated to ameliorate kidney injury as a result of decreased blood urine nitrogen and serum creatinine levels, activated Nrf2 expression in the kidney and decreased oxidative stress and inflammatory index levels an AKI mouse model. SEV preconditioning also protected injured kidney via the downregulation of caspase-3 protein expression levels. In addition, using the Nrf2 inhibitor, Brusatol, significantly abolished the SEV preconditioning renal protective effect. Using an in vitro HK-2 cell model of hypoxia/reoxygenation, it was also demonstrated that Nrf2 pathway activation was necessary for SEV to exert its beneficial effect for tubular cell injury caused by hypoxia/reoxygenation. These results indicated that SEV may protect against renal injury caused by IR via Nrf2 upregulation.

Effective Nephroprotection Against Acute Kidney Injury with a Star-Shaped Polyglutamate-Curcuminoid Conjugate

The lack of effective pharmacological treatments for acute kidney injury (AKI) remains a significant public health problem. Given the involvement of apoptosis and regulated necrosis in the initiation and progression of AKI, the inhibition of cell death may contribute to AKI prevention/recovery. Curcuminoids are a family of plant polyphenols that exhibit attractive biological properties that make them potentially suitable for AKI treatment. Now, in cultured tubular cells, we demonstrated that a crosslinked self-assembled star-shaped polyglutamate (PGA) conjugate of bisdemethoxycurcumin (St-PGA-CL-BDMC) inhibits apoptosis and necroptosis induced by Tweak/TNFα/IFNγ alone or concomitant to caspase inhibition. St-PGA-CL-BDMC also reduced NF-κB activation and subsequent gene transcription. In vivo, St-PGA-CL-BDMC prevented renal cell loss and preserved renal function in mice with folic acid-induced AKI. Mechanistically, St-PGA-CL-BDMC inhibited AKI-induced apoptosis and expression of ferroptosis markers and also decreased the kidney expression of genes involved in tubular damage and inflammation, while preserving the kidney expression of the protective factor, Klotho. Thus, due to renal accumulation and attractive pharmacological properties, the application of PGA-based therapeutics may improve nephroprotective properties of current AKI treatments.

The role of nitric oxide signaling in renoprotective effects of hydrogen sulfide against chronic kidney disease in rats: Involvement of oxidative stress, autophagy and apoptosis

The interplay between H₂ S and nitric oxide (NO) is thought to contribute to renal functions. The current study was designed to assess the role of NO in mediating the renoprotective effects of hydrogen sulfide in the 5/6 nephrectomy (5/6 Nx) animal model. Forty rats were randomly assigned to 5 experimental groups: (a) Sham; (b) 5/6 Nx; (c) 5/6Nx+sodium hydrosulfide-a donor of H ₂ S, (5/6Nx+sodium hydrosulfide [NaHS]); (d) 5/6Nx+NaHS+ L-NAME (a nonspecific nitric oxide synthase [NOS] inhibitor); (e) 5/6Nx+NaHS+aminoguanidine (a selective inhibitor of inducible NOS [iNOS]). Twelve weeks after 5/6 Nx, we assessed the expressions of iNOS and endothelial NOS (eNOS), oxidative/antioxidant status, renal fibrosis, urine N-acetyl-b-glucosaminidase (NAG) activity as the markers of kidney injury and various markers of apoptosis, inflammation, remodeling, and autophagy. NaHS treatment protected the animals against chronic kidney injury as depicted by improved oxidative/antioxidant status, reduced apoptosis, and autophagy and attenuated messenger RNA (mRNA) expression of genes associated with inflammation, remodeling, and NAG activity. Eight weeks Nω-nitro-l-arginine methyl ester ( L-NAME) administration reduced the protective effects of hydrogen sulfide. In contrast, aminoguanidine augmented the beneficial effects of hydrogen sulfide. Our finding revealed some fascinating interactions between NO and H ₂ S in the kidney. Moreover, the study suggests that NO, in an isoform-dependent manner, can exert renoprotective effects in 5/6 Nx model of CKD.

Caspase-3 inhibition prevents the development of hepatopulmonary syndrome in common bile duct ligation rats by alleviating pulmonary injury

BACKGROUND & AIMS

Common bile duct ligation (CBDL) rats is an accepted experimental model of hepatopulmonary syndrome (HPS), defined as liver disease and intrapulmonary vascular dilatation and hypoxaemia. Pulmonary Akt and ERK activation followed by angiogenesis in the later stages of CBDL, contribute to the pathogenesis of HPS. However, the mechanisms behind Akt and ERK activation remain undefined. Pulmonary injury induced by increased bilirubin, endotoxin and inflammatory mediators occurs in the early stages of CBDL. We assessed the effects of relieving pulmonary injury on Akt and ERK activation and on the development of HPS following CBDL.

METHODS

Pulmonary injury, angiogenesis, arterial oxygenation, cell proliferation and, phospho-Akt and ERK1 were evaluated in CBDL animals with or without caspase-3 inhibition (Z-DEVD-FMK). Pulmonary injury was assessed by histology and quantifying apoptosis and aquaporin-1 (AQP1) levels. Lung angiogenesis was assessed by quantifying AQP1 level, vWF-positive cells and microvessel count.

RESULTS

Pulmonary apoptosis and caspase-3 activation were markedly increased in the early stages of CBDL. Caspase-3 inhibition alleviated apoptosis, the reduction in AQP1, phospho-Akt and ERK1 levels and pulmonary injury 1 week after CBDL. Caspase-3 inhibition also reduced AQP1, phospho-Akt and ERK1 levels, vWF-positive cells, cell proliferation, microvessel count, and microvascular dilatation and improved arterial oxygenation 3 weeks following CBDL.

CONCLUSIONS

Caspase-3 inhibition alleviates pulmonary injury, thereby preventing angiogenesis as well as the development of HPS in CBDL rats. These effects are related to the regulation of the Akt and ERK1 pathways.

Caspase-1 activation is increased with human labour in foetal membranes and myometrium and mediates infection-induced interleukin-1β secretion

PROBLEM

Interleukin-1β (IL-1β) is a pro-inflammatory cytokine that is involved in human parturition, especially in the context of infection-induced preterm birth. Caspase-1 is a key component of inflammasomes, which are activated upon infection to trigger the maturation of IL-1β.

METHOD OF STUDY

To determine the effect of human labour on caspase-1 activation in human foetal membranes and myometrium. In addition, the mechanisms by which inflammasome activation regulates IL-1β production were also be assessed.

RESULTS

Higher caspase-1 gene and protein expression were detected in foetal membranes myometrium obtained from term labouring women when compared with samples taken from non labouring women. Lipopolysaccharide induced the transcription and secretion of IL-1β from foetal membranes and myometrium; both events were dependent on nuclear factor kappa B (NF-κB). However, levels of extracellular IL-1β were greatly increased by subsequent treatment with the potassium-proton ionophore Adenosine triphosphate (ATP) or nigericin; an effect that was dependent on active caspase-1. Additionally, ATP induced IL-1β secretion via the purinergic P2X7 receptor, whereas the pannexin-1 channel was required for nigericin induced IL-1β secretion.

CONCLUSION

Taken together, these results demonstrate that caspase-1 activation is increased with human labour in foetal membranes and myometrium, and is required for infection-induced IL-1β secretion.

Magnetic resonance imaging with hyperpolarized [1,4-(13)C2]fumarate allows detection of early renal acute tubular necrosis

Acute kidney injury (AKI) is a common and important medical problem, affecting 10% of hospitalized patients, and it is associated with significant morbidity and mortality. The most frequent cause of AKI is acute tubular necrosis (ATN). Current imaging techniques and biomarkers do not allow ATN to be reliably differentiated from important differential diagnoses, such as acute glomerulonephritis (GN). We investigated whether (13)C magnetic resonance spectroscopic imaging (MRSI) might allow the noninvasive diagnosis of ATN. (13)C MRSI of hyperpolarized [1,4-(13)C(2)]fumarate and pyruvate was used in murine models of ATN and acute GN (NZM2410 mice with lupus nephritis). A significant increase in [1,4-(13)C(2)]malate signal was identified in the kidneys of mice with ATN early in the disease course before the onset of severe histological changes. No such increase in renal [1,4-(13)C(2)]malate was observed in mice with acute GN. The kidney [1-(13)C]pyruvate/[1-(13)C]lactate ratio showed substantial variability and was not significantly decreased in animals with ATN or increased in animals with GN. In conclusion, MRSI of hyperpolarized [1,4-(13)C(2)]fumarate allows the detection of early tubular necrosis and its distinction from glomerular inflammation in murine models. This technique may have the potential to identify a window of therapeutic opportunity in which emerging therapies might be applied to patients with ATN, reducing the need for acute dialysis with its attendant morbidity and cost.

Affirmative effects of iloprost on apoptosis during ischemia-reperfusion injury in kidney as a distant organ

OBJECTIVE

Apoptosis and its regulatory mechanisms take part in renal ischemia-reperfusion (I/R) injury which can result in acute renal failure and the inhibition of the caspase is considered as a new therapeutic strategy. In this context, we investigated the antiapoptotic and cytoprotective effects of iloprost, a prostacyclin analog, in kidney as a distant organ.

METHODS

Wistar albino rats were randomized into five groups (n = 12 in each) as sham, ischemia, I/R, iloprost (10 μg kg(-1)), and I/R + iloprost (10 μg kg(-1)). A 4 h reperfusion procedure was carried out after 4 h of ischemia. Caspase-8 was evaluated for death receptor-induced pathways, whereas caspase-9 was evaluated for mitochondria-dependent pathways and caspase-3 was investigated for overall apoptosis. Superoxide dismutase (SOD) enzyme activity and nitrite content as an indicator of nitric oxide (NO) production were also analyzed in kidney tissues.

RESULTS

Caspases-3, -8, and -9 were all significantly elevated in both ischemia and I/R groups compared to the sham group; however, treatment with iloprost reduced caspases-3, -8, and -9. SOD enzyme activity was attenuated by iloprost when compared to ischemic rats. The different effects of NO were found which change according to the present situation in ischemia, I/R, and treatment with iloprost.

CONCLUSIONS

These findings suggested that iloprost prevents apoptosis in both receptor-induced and mitochondria-dependent pathways in renal I/R injury and it may be considered as a cytoprotective agent for apoptosis. Understanding the efficiency of iloprost on the pathways for cell death may lead to an opportunity in the therapeutic approach for renal I/R injury.

Identification of agents that reduce renal hypoxia-reoxygenation injury using cell-based screening: purine nucleosides are alternative energy sources in LLC-PK1 cells during hypoxia

Acute tubular necrosis is a clinical problem that lacks specific therapy and is characterized by high mortality rate. The ischemic renal injury affects the proximal tubule cells causing dysfunction and cell death after severe hypoperfusion. We utilized a cell-based screening approach in a hypoxia-reoxygenation model of tubular injury to search for cytoprotective action using a library of pharmacologically active compounds. Oxygen-glucose deprivation (OGD) induced ATP depletion, suppressed aerobic and anaerobic metabolism, increased the permeability of the monolayer, caused poly(ADP-ribose) polymerase cleavage and caspase-dependent cell death. The only compound that proved cytoprotective either applied prior to the hypoxia induction or during the reoxygenation was adenosine. The protective effect of adenosine required the coordinated actions of adenosine deaminase and adenosine kinase, but did not requisite the purine receptors. Adenosine and inosine better preserved the cellular ATP content during ischemia than equimolar amount of glucose, and accelerated the restoration of the cellular ATP pool following the OGD. Our results suggest that radical changes occur in the cellular metabolism to respond to the energy demand during and following hypoxia, which include the use of nucleosides as an essential energy source. Thus purine nucleoside supplementation holds promise in the treatment of acute renal failure.

Caspase-1 is hepatoprotective during trauma and hemorrhagic shock by reducing liver injury and inflammation

Adaptive immune responses are induced in liver after major stresses such as hemorrhagic shock (HS) and trauma. There is emerging evidence that the inflammasome, the multiprotein platform that induces caspase-1 activation and promotes interleukin (IL)-1β and IL-18 processing, is activated in response to cellular oxidative stress, such as after hypoxia, ischemia and HS. Additionally, damage-associated molecular patterns, such as those released after injury, have been shown to activate the inflammasome and caspase-1 through the NOD-like receptor (NLR) NLRP3. However, the role of the inflammasome in organ injury after HS and trauma is unknown. We therefore investigated inflammatory responses and end-organ injury in wild-type (WT) and caspase-1(-/-)mice in our model of HS with bilateral femur fracture (HS/BFF). We found that caspase-1(-/-) mice had higher levels of systemic inflammatory cytokines than WT mice. This result corresponded to higher levels of liver damage, cell death and neutrophil influx in caspase-1(-/-) liver compared with WT, although there was no difference in lung damage between experimental groups. To determine if hepatoprotection also depended on NLRP3, we subjected NLRP3(-/-) mice to HS/BFF, but found inflammatory responses and liver damage in these mice was similar to WT. Hepatoprotection was also not due to caspase-1-dependent cytokines, IL-1β and IL-18. Altogether, these data suggest that caspase-1 is hepatoprotective, in part through regulation of cell death pathways in the liver after major trauma, and that caspase-1 activation after HS/BFF does not depend on NLRP3. These findings may have implications for the treatment of trauma patients and may lead to progress in prevention or treatment of multiple organ failure (MOF).

Atorvastatin improving renal ischemia reperfusion injury via direct inhibition of active caspase-3 in rats

Caspase-3 is a key molecule involved in the inflammation and apoptosis of ischemia reperfusion (IR) injury. Statins are known to inhibit IR injury, but the mechanism of action remains uncertain. In the present study, the effect and underlying mechanism of ischemia alone, and reperfusion with or without atorvastatin (AT) as a timed intervention were examined, since clinically the kidney is only exposed to drug delivery during reperfusion. Male Sprague‐Dawley rats were subjected to 45‐min clamping of the left renal hilus followed by four hours reperfusion with a right nephrectomy. AT 10 mg/kg was intravenously administered after clamping the renal hilus, but prior to kidney reperfusion. Ischemia alone did cause tubulointerstitial damage (TID), protein carbonylation and caspase-3 activation with an increase in 12 kDa subunit, while reperfusion further enhanced TID, monocyte (ED-1+ cell) infiltration, apoptosis and necrosis together with caspase-3 activity and 17 kDa subunit, but reversed protein carbonylation. AT significantly reduced TID (26%), ED-1+ cell infiltration (74%), tubular apoptosis (47%) and necrosis (73%), and interstitial apoptosis (64%), as well as caspase-3 activity (26%), but did not change serum creatinine and cholesterol. Importantly, without affecting either caspase-3 active protein cleavage or S-nitrosylation, AT directly inhibited caspase-3 active enzyme in a dose-dependent manner in vitro. In conclusions, IR and AT exerted opposing effects on caspase-3 activity by differing mechanisms, with IR stimulating caspase-3 proteolytic cleavage and AT inhibiting active caspase-3 enzyme. This new inhibitory mechanism of AT may improve reperfusion tolerance in ischemic kidneys and benefit transplant recipients.

MnTMPyP, a superoxide dismutase/catalase mimetic, decreases inflammatory indices in ischemic acute kidney injury

OBJECTIVE

This study investigates the effect of a superoxide dismutase mimetic, MnTMPyP, on pro- and anti-inflammatory cytokines in acute renal ischemia-reperfusion (IR).

MATERIALS AND TREATMENT

Male Sprague-Dawley rats underwent bilateral clamping of the renal arteries for 45 min followed by 1, 4, or 24 h of reperfusion. A subset of animals was treated with MnTMPyP (5 mg/kg, i.p.) or saline. Porcine proximal tubular epithelial cells were ATP-depleted for 4 h followed by recovery for 2 h.

METHODS

Cytokines were analyzed by ELISA, and ED1(+) macrophages and CD8(+) T lymphocytes by immunohistochemistry. Statistical analysis was performed using ANOVA.

RESULTS

MnTMPyP attenuated the IR-mediated increase in serum creatinine and circulating levels of interleukin (IL)-2 following 24 h of reperfusion. Furthermore, treatment attenuated increases in tissue levels of tumor necrosis factor (TNF)-α, IL-2, IL-4, and IL-13. MnTMPyP partially prevented the IR-induced infiltration of ED1(+) macrophages and CD8(+) T lymphocytes in the kidney. ATP depletion-recovery of porcine proximal tubular epithelial cells resulted in decreased IL-6 and IL-10 levels, and MnTMPyP partially restored these cytokines.

CONCLUSIONS

These results show that MnTMPyP is partially effective in reducing inflammation associated with renal IR and that reactive oxygen species play a role in modulating both pro- and anti-inflammatory pathways in acute kidney injury.

Novel aspects of pharmacological therapies for acute renal failure

Acute renal failure (ARF) comprises several syndromes that are associated with a sudden decrease in renal function. ARF is common among critically ill patients, is typically multifactorial and is of great prognostic significance. Indeed, even moderate changes in renal function significantly add to the morbidity and worsen mortality associated with ARF. Recent definitions, namely the renal Risk, Injury, Failure, Loss of renal function and End-stage kidney disease (RIFLE) classification or Acute Kidney Injury Network (AKIN) criteria, which incorporate the levels of oliguria in addition to fractional serum creatinine elevation, are important because the magnitude of kidney injury according to those definitions correlates very well with both short- and long-term patient survival. However, preventive strategies are most effective when started before oliguria or elevated serum creatinine is detectable, as those criteria already reflect established renal tubular cell injury. New biomarkers, including neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty acid binding protein (L-FABP) or kidney injury molecule-1 (KIM-1) that increase prior to the serum creatinine elevation are promising and have been proven to be useful in this regard in a few clinical trials. In addition, genetic profiling may define patients at risk earlier and help to individualize preventive strategies. Well established strategies include limiting dehydration and hypotension by the use of intravenous isotonic fluids at an optimal and individualized rate, as well as avoiding exposure to nephrotoxins, which include aminoglycosides, amphotericin or non-ionic contrast. Generally accepted and evidence-based pharmacological preventive or therapeutic options have not yet been established, although many drugs (e.g. renal vasodilators, diuretics and HMG-CoA reductase inhibitors [statins]) have been tested. New promising agents interfere with the apoptotic signalling that can occur in the setting of toxin exposure or ischaemia-reperfusion injury, limit inflammatory responses or modulate endothelial cell activation. In the future, these new approaches will enable us to extend our therapeutic repertoire.

Aloe-emodin, an anthraquinone, in vitro inhibits proliferation and induces apoptosis in human colon carcinoma cells

The present study aimed to investigate the anticancer effect of aloe-emodin, an anthraquinone compound present in the leaves of Aloe vera, on two human colon carcinoma cell lines, DLD-1 and WiDr. Colon carcinoma cells were treated with various concentrations of aloe-emodin for different durations. Cell viability was measured by sodium 3'-[1-(phenylamino-carbonyl)-3,4-tetrazolium]-bis(4-methoxy-6-nitro) benzene-sulfonic acid hydrate assay. DNA fragmentation was analyzed by agarose gel electrophoresis. Nuclear shrinkage was visualized by Hoechst 33258 staining. Western blotting was used to indicate the release of apoptosis-inducing factor and cytochrome c from mitochondria and the phosphorylation of Bid. Caspase-3 and casein kinase II activities were measured by the respective assays. Cell viability analyses showed that aloe-emodin induced cell death in a dose- and time-dependent manner. Notably, the WiDr cells were more sensitive to aloe-emodin than the DLD-1 cells. Aloe-emodin caused the release of apoptosis-inducing factor and cytochrome c from mitochondria, followed by activation of caspase-3 leading to DNA fragmentation, nuclear shrinkage and apoptosis. In addition, exposure of colon carcinoma cells to aloe-emodin suppressed the casein kinase II activity in a time-dependent manner and was accompanied by a reduced phosphorylation of Bid, a downstream substrate of casein kinase II and a pro-apoptotic molecule. These findings showed that the inhibition of casein kinase II activity, the release of apoptosis-inducing factor and cytochrome c, and the caspase-3 activation are involved in aloe-emodin-mediated apoptosis in colon carcinoma cells.

The effect of iloprost on renal dysfunction after renal I/R using cystatin C and beta2-microglobulin monitoring

The purpose of this study was to investigate the effect of iloprost, a cytoprotective prostacyclin analog, on renal injury during unilateral renal I/R in rats and to determine whether the levels of serum cystatin C (CyC) and beta2-microglobulin (B2M), as markers of glomerular function, might denote this injury. Thirty-two Wistar rats were randomized into four groups (n = 8) as follows: control (sham laparotomy), renal I/R (60-min left renal ischemia and 120-min reperfusion), renal I/R + iloprost (20 ng kg(-1) min(-1) infusion during renal I/R period, i.v.), and control + iloprost. Blood and kidney tissue samples were obtained for biochemical and histological analysis from all rats. Serum urea, creatinine, CyC, and B2M levels were evaluated for biochemical analysis. Histopathological changes in renal structure were examined for histological analysis. Serum urea, creatinine, and CyC levels were significantly increased in the renal I/R group. Iloprost treatment decreased these three markers in the renal I/R + iloprost group. beta2-Microglobulin levels were not significantly changed in any group. Histological analyses showed that renal I/R elicited significant renal injury, whereas iloprost significantly decreased I/R-induced renal injury. Serum CyC level is one of the good indicators of acute renal damage due to I/R produced by renal artery occlusion. In contrast, we have shown that there are no significant changes in the levels of serum B2M levels that would make it an accurate diagnostic tool for detecting acute changes in renal injury subject to renal I/R in rats.

Acute protective effects of simvastatin in the rat model of renal ischemia-reperfusion injury: it is never too late for the pretreatment

Acute pretreatment with a single i.v. bolus injection of simvastatin (1 mg/kg) significantly protects rat kidney injured by ischemia-reperfusion (I/R) (45 min + 6 h). We aimed to determine the optimal timing of such a pretreatment. The effects of both injections of simvastatin before ischemia and reperfusion were similar regarding total histological score. However, simvastatin injected 30 min before ischemia was 30% - 75% more effective in reduction of serum creatinine levels and interstitial edema score, while its injections 5 and 30 min before reperfusion were 25% - 60% more effective in reduction of tubular necrosis score and fractional excretion of Na+. However, the observed differences do not seem to offer significant advantage in clinical settings.

Aloe-emodin-induced apoptosis in human gastric carcinoma cells

The purpose of this study was to investigate the anticancer effect of aloe-emodin, an anthraquinone compound present in the leaves of Aloe vera, on two distinct human gastric carcinoma cell lines, AGS and NCI-N87. We demonstrate that aloe-emodin induced cell death in a dose- and time-dependent manner. Noteworthy is that the AGS cells were generally more sensitive than the NCI-N87 cells. Aloe-emodin caused the release of apoptosis-inducing factor and cytochrome c from mitochondria, followed by the activation of caspase-3, leading to nuclear shrinkage and apoptosis. In addition, exposure to aloe-emodin suppressed the casein kinase II activity in a time-dependent manner and was accompanied by a reduced phosphorylation of Bid, a downstream substrate of casein kinase II and a pro-apoptotic molecule. These preclinical studies suggest that aloe-emodin represents a suitable and novel chemotherapeutic drug candidate for the treatment of human gastric carcinoma.

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.

Caspase-7, Fas and FasL in long-term renal ischaemia/reperfusion and immunosuppressive injuries in rats

BACKGROUND/AIMS

Ischaemia/reperfusion (I/R) injury is important in kidney transplantation. We have previously demonstrated that long-term I/R injury and immunosuppression affect apoptosis and inflammation, but the underlying mechanisms are far from clear. In this study, the involvement of caspase-7, Fas and FasL was further investigated.

METHODS

The right renal pedicle was clamped for 45 min followed by left nephrectomy in 40 rats. Cyclosporine (CsA), tacrolimus (Tac), rapamycin (Rap) or mycophenolate mofetil (MMF) were administered daily for 16 weeks. Caspase-7, Fas and FasL expression, and their correlations with caspase-3, apoptosis, inflammation, renal structure and function were evaluated.

RESULTS

Active caspase-7 was significantly increased in I/R and CsA-treated kidneys and decreased by Tac, Rap and MMF, while the caspase-7 precursor was enhanced by Rap. Active caspase-7-stained cells were scattered throughout the tubulointerstitium and often had apoptotic features. Fas, but not FasL, was increased in I/R and CsA-treated kidneys and decreased by Rap and MMF. Fas and FasL proteins were mainly located in dilated tubules. There were close correlations among caspase-7, Fas, caspase-3, apoptosis, inflammation, renal structure and function.

CONCLUSION

Caspase-7, associated with caspase-3, apoptosis and inflammation, might be involved in long-term I/R and immunosuppressive injury, at least in part through the Fas-signalling pathway.

Gene expression and biomarkers in renal transplant ischemia reperfusion injury

The incidence of postischemic acute renal allograft failure (ARF) occurs in roughly 25% of cadaveric donor kidney recipients. This high rate remained virtually unchanged over the last decades despite modification in recipient management and modern immunosuppressive strategies. It has recently been shown that among other reasons, the systemic inflammation in the brain death cadaveric organ donor contributes to subsequent ARF in the recipient. This review focuses on the consequences of ischemia and reperfusion on the cellular level and offers potential solutions for the reduction of ARF. Genome-wide gene expression analysis together with sophisticated biostatistical analysis made it possible to identify several candidate gene products and proteins that may act as specific and sensitive biomarker for renal inflammation and ischemia. These markers may be very helpful in the clinical management of patients with a high a priori risk of subsequent ARF such as recipients of marginal donor kidneys. Ongoing clinical trials will evaluate whether immunosuppression of the cadaveric organ donor before organ harvest will have the potential to reduce inflammation in the transplant kidney and subsequently lead to a reduction in the rate of ARF.

Single-dose intravenous simvastatin treatment attenuates renal injury in an experimental model of ischemia-reperfusion in the rat

The effect of acute pretreatment with a single dose of simvastatin (1 mg/kg, i.v.; 30 min before ischemia) on renal dysfunction caused by ischemia-reperfusion (I/R) injury in the rat was investigated. I/R injury was induced by clamping both renal vascular pedicles for 45 min, followed by 4 h of reperfusion with saline (2 ml/kg per hour). Simvastatin significantly improved both parameters of glomerular and tubular dysfunction (e.g., creatinine levels and fractional excretion of Na(+), respectively) and especially improved the histological score, compared to control I/R-injured rats treated with saline or 10% DMSO only.

Allogeneic activation is attenuated in a model of mouse lung perfused with magnesium-deficient blood

Hypomagnesemia, which is frequently observed in patients treated with calcineurin inhibitors to prevent rejection after allogeneic transplantation, has been associated with a faster rate of decline in allograft function. The effect of hypomagnesemia on lung allograft has not been reported yet. In our model of isolated mouse lung, we have evaluated the early effects of allogeneic lung perfusion with blood from magnesium (Mg)-deficient mice for 3 h on lung activation and remodelling, compared to isogeneic perfusion. Hypomagnesemia (0.21+/-0.07 mmol Mg(2+)/l) was observed in blood from Mg-deficient mice, but no inflammatory pattern. The mRNA level of the intercellular adhesion molecule (ICAM)-1, but neither of the vascular cell adhesion molecule (VCAM)-1, nor of the cytokines tumor necrosis factor (TNF)alpha and interleukin (IL)-2, was enhanced (p<0.05). Although caspase-3 mRNA was transiently enhanced, no apoptotic cells were evidenced in lung tissues even after 3 h. Using cDNA array, we found that the genes encoding RANKL, RANK, TNFR2, NFATX, IL-1R2, IL-6R gp130, SOCS3, PDGFRB, P63, CSF3R, CXCL1, CXCL5, CX3CL1, CSF1, which are involved in inflammation and apoptosis regulation, were markedly up-regulated in allogeneic conditions. Our results support a limited allogeneic activation and an early stage of the inflammatory process in lung, at the time of inflammatory cell recruitment without lung tissue remodelling, as a result of hypomagnesemia. These findings suggest that cyclosporine-related hypomagnesemia, observed in most of the transplanted patients, does not constitute an additional risk for lung allograft outcome.

Role of caspases on cell death, inflammation, and cell cycle in glycerol-induced acute renal failure

Caspases are the main executioners of apoptosis as well as interleukin (IL)-1beta and IL-18 conversion to active forms. They are activated after acute kidney injuries. In this study, we evaluated the importance of the caspase family in the pathogenesis and recovery of glycerol-induced acute renal failure in rats (Gly-ARF). Rats were treated with pan-caspase or selective caspase 1 and 3 inhibitors at the moment we injected glycerol. Renal function, renal histology (HE), transferase-mediated deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling staining for apoptosis, leukocytes infiltration (immunohistochemistry), renal expression of IL-1beta and IL-18 (immunohistochemistry and Western blot), tubular regeneration (5-bromo-2'-deoxyuridine (BrdU) incorporation), and P27(Kip) expression (Western blot) were evaluated at appropriate times. All inhibitors reduced the renal function impairment. Pan-caspase and caspase-3 inhibitors reduced cellular death (necrosis and apoptosis) 24 h after Gly-ARF. All caspases inhibitors reduced macrophages infiltration. The expression of total IL-1beta was enhanced in Gly-ARF, but the active IL-1beta and IL-18 forms were abolished in pan-caspase treated rats. Caspase-1 inhibitor attenuated Gly-ARF but not tubular injury suggesting glomerular hemodynamic improvement. There was striking regenerative response 48 h after Gly-ARF characterized by enhanced BrdU incorporation and reduced expression of p27(Kip). This response was not blunted by caspases inhibition. Our findings demonstrate that caspases participate in important pathogenic mechanisms in Gly-ARF such as inflammation, apoptosis, vasoconstriction, and tubular necrosis. The early inhibition of caspases attenuates these mechanisms and reduces the renal function impairment in Gly-ARF.

Cellular and molecular derangements in acute tubular necrosis

PURPOSE OF REVIEW

Acute tubular necrosis secondary to ischemic acute renal failure remains a common clinical problem with serious consequences and unsatisfactory therapeutic options. The purpose of this review is to summarize recent advances that have provided an improved understanding of the underlying cellular and molecular derangements, and have resulted in the design of novel therapeutic approaches.

RECENT FINDINGS

Sophisticated morphologic studies have identified apoptosis and vascular changes as significant novel findings in human acute tubular necrosis. Promising roles for inhibitors of apoptosis have been proposed. Activation of tubuloglomerular feedback, previously thought to contribute to acute tubular necrosis, has now emerged as a potentially beneficial phenomenon. The role of reactive oxygen molecules has been further elucidated, and novel antioxidants and iron chelators have been identified. Genome-wide screening techniques have identified the molecular mechanisms underlying the regeneration and repair processes, and have provided clues towards accelerating recovery from acute renal failure. An improved understanding of the role of inflammation has suggested strategies to target this previously underappreciated aspect of acute tubular necrosis.

SUMMARY

The cellular and molecular tools of modern science have provided critical new insights into the roles of apoptosis, oxidant and iron-mediated injury, endothelial changes, regeneration, and the inflammatory response in the pathogenesis of acute tubular necrosis. Novel strategies that modulate these pathways hold tremendous promise for the proactive treatment of human acute renal failure.