Opposite effects of pre- and postischemic treatments with nitric oxide donor on ischemia/reperfusion-induced renal injury

The novel nitric oxide donor PDNO attenuates ovine ischemia-reperfusion induced renal failure

Background

Renal ischemia-reperfusion injury is a common cause of acute kidney injury in intensive care and surgery. Recently, novel organic mononitrites of 1,2-propanediol (PDNO) were synthesized and shown to rapidly and controllably deploy nitric oxide in the circulation when administered intravenously. We hypothesized that intravenous infusion of PDNO during renal ischemia reperfusion would improve post-ischemic renal function and microcirculation.

Methods

Sixteen sheep were anesthetized, mechanically ventilated, and surgically instrumented. The left renal artery was clamped for 90 min, and the effects of ischemia were studied for a total of 8 h. Fifteen minutes prior to the release of the clamp, intravenous infusions of PDNO (n = 8) or vehicle (1,2 propanediol + inorganic nitrite, n = 8) were initiated (180 nmol/kg/min for 30 min, thereafter 60 nmol/kg/min for the remainder of the experiment).

Results

Renal artery blood flow, cortical and medullary perfusion, and diuresis and creatinine clearance decreased in the left kidney post ischemia. However, in the sheep treated with PDNO, diuresis and creatinine clearance in the left kidney were significantly higher post ischemia compared to vehicle-treated animals (1.7 ± 0.5 vs 0.7 ± 0.3 ml/kg/h, p = 0.04 and 7.5 ± 2.1 vs 1.7 ± 0.6 ml/min, p = 0.02, respectively). Left renal medullary perfusion and oxygen uptake were higher in the PDNO group (73 ± 9 vs 37 ± 5% of baseline, p = 0.004 and 2.6 ± 0.4 vs 1.6 ± 0.3 ml/min, p = 0.02, respectively). PDNO significantly increased renal oxygen consumption and reduced the oxygen utilization for sodium reabsorption (p = 0.03 for both). Mean arterial blood pressure was significantly reduced by PDNO (83 ± 3 vs 94 ± 3 mmHg, p = 0.02) but was still within normal limits. Total renal blood flow was not affected, and there were no signs of increased blood methemoglobin concentrations or tachyphylaxis.

Conclusions

The novel nitric oxide donor PDNO improved renal function after ischemia. PDNO also prevented the persistent reduction in medullary perfusion during reperfusion and improved renal oxygen utilization without severe side effects.

Obestatin improves ischemia/reperfusion-induced renal injury in rats via its antioxidant and anti-apoptotic effects: role of the nitric oxide

Obestatin was shown to have anti-inflammatory effects in several inflammatory models. To elucidate the potential renoprotective effects of obestatin, renal I/R injury was induced in male Sprague Dawley rats by placing a clamp across left renal artery for 60min following a right nephrectomy. Clamp was released and the rats were injected with either saline or obestatin (10, 30, 100μg/kg). In some experiments, obestatin (10μg/kg) was administered with L-NAME (10mg/kg) or L-Nil (0.36mg/kg). Following a 24-h reperfusion, the rats were decapitated to measure serum creatinine and nitrite/nitrate levels, renal malondialdehyde (MDA), glutathione (GSH) levels and myeloperoxidase (MPO) activity and to assess cortical necrosis and apoptosis scores. Obestatin treatment reduced I/R-induced increase in creatinine levels, renal MPO activity and renal MDA levels, while renal GSH levels were significantly increased by obestatin. Histological analysis revealed that severe I/R injury and high apoptosis score in the kidney samples of saline-treated rats were significantly reduced and the cortical/medullary injury was ameliorated by obestatin. Expression of eNOS, which was increased by I/R injury, was further increased by obestatin, while serum NO levels were significantly decreased. iNOS inhibitor L-Nil reduced oxidative renal damage and improved the functional and histopathological parameters. I/R-induced elevation in eNOS expression, which was further increased by obestatin, was depressed by L-NAME and L-Nil treatments. The present data demonstrate that obestatin ameliorates renal I/R-injury by its possible anti-oxidative, anti-inflammatory and anti-apoptotic properties, which appear to involve the suppression of neutrophil accumulation and modulation of NO metabolism.

Pro-oxidative synergic bactericidal effect of NO: kinetics and inhibition by nitroxides

NO plays diverse roles in physiological and pathological processes, occasionally resulting in opposing effects, particularly in cells subjected to oxidative stress. NO mostly protects eukaryotes against oxidative injury, but was demonstrated to kill prokaryotes synergistically with H2O2. This could be a promising therapeutic avenue. However, recent conflicting findings were reported describing dramatic protective activity of NO. The previous studies of NO effects on prokaryotes applied a transient oxidative stress while arbitrarily checking the residual bacterial viability after 30 or 60min and ignoring the process kinetics. If NO-induced synergy and the oxidative stress are time-dependent, the elucidation of the cell killing kinetics is essential, particularly for survival curves exhibiting a "shoulder" sometimes reflecting sublethal damage as in the linear-quadratic survival models. We studied the kinetics of NO synergic effects on H2O2-induced killing of microbial pathogens. A synergic pro-oxidative activity toward gram-negative and gram-positive cells is demonstrated even at sub-μM/min flux of NO. For certain strains, the synergic effect progressively increased with the duration of cell exposure, and the linear-quadratic survival model best fit the observed survival data. In contrast to the failure of SOD to affect the bactericidal process, nitroxide SOD mimics abrogated the pro-oxidative synergy of NO/H2O2. These cell-permeative antioxidants, which hardly react with diamagnetic species and react neither with NO nor with H2O2, can detoxify redox-active transition metals and catalytically remove intracellular superoxide and nitrogen-derived reactive species such as (•)NO2 or peroxynitrite. The possible mechanism underlying the bactericidal NO synergy under oxidative stress and the potential therapeutic gain are discussed.

Pre-conditioned mesenchymal stem cells ameliorate renal ischemic injury in rats by augmented survival and engraftment

Background

Ischemia is the major cause of acute kidney injury (AKI), associated with high mortality and morbidity. Mesenchymal stem cells (MSCs) have multilineage differentiation potential and can be a potent therapeutic option for the cure of AKI.

Methods

MSCs were cultured in four groups SNAP (S-nitroso N-acetyl penicillamine), SNAP + Methylene Blue (MB), MB and a control for in vitro analysis. Cultured MSCs were pre-conditioned with either SNAP (100 μM) or MB (1 μM) or both for 6 hours. Renal ischemia was induced in four groups (as in in vitro study) of rats by clamping the left renal padicle for 45 minutes and then different pre-conditioned stem cells were transplanted.

Results

We report that pre-conditioning of MSCs with SNAP enhances their proliferation, survival and engraftment in ischemic kidney. Rat MSCs pre-conditioned with SNAP decreased cell apoptosis and increased proliferation and cytoprotective genes’ expression in vitro. Our in vivo data showed enhanced survival and engraftment, proliferation, reduction in fibrosis, significant improvement in renal function and higher expression of pro-survival and pro-angiogenic factors in ischemic renal tissue in SNAP pre-conditioned group of animals. Cytoprotective effects of SNAP pre-conditioning were abrogated by MB, an inhibitor of nitric oxide synthase (NOS) and guanylate cyclase.

Conclusion

The results of these studies demonstrate that SNAP pre-conditioning might be useful to enhance therapeutic potential of MSCs in attenuating renal ischemia reperfusion injury.

Preventive effect of GGsTop, a novel and selective γ-glutamyl transpeptidase inhibitor, on ischemia/reperfusion-induced renal injury in rats

GGsTop [2-amino-4-{[3-(carboxymethyl)phenyl](methyl)phosphono}butanoic acid], is a novel, highly selective, and irreversible γ-glutamyl transpeptidase (GGT) inhibitor with no inhibitory activity on glutamine amidotransferases. In this study, we investigated the effects of treatment with GGsTop on ischemia/reperfusion-induced renal injury in uninephrectomized rats. Ischemic acute kidney injury (AKI) was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion 2 weeks after contralateral nephrectomy. Renal function in vehicle-treated AKI rats markedly decreased at 1 day after reperfusion. Treatment with GGsTop (1 and 10 mg/kg i.v.) 5 min before ischemia attenuated the ischemia/reperfusion-induced renal dysfunction in a dose-dependent manner. Histopathological examination of the kidney of AKI rats revealed severe renal damage, which was significantly suppressed by the GGsTop treatment. In renal tissues exposed to ischemia/reperfusion, GGT activity was markedly increased immediately after reperfusion, whereas renal superoxide production and malondialdehyde level were significantly increased 6 h after reperfusion. These alterations were abolished by the treatment with GGsTop. In addition, renal glutathione content was decreased by the 45-min ischemia, but its level was markedly elevated by the GGsTop treatment. Our results demonstrate that the novel and highly selective GGT inhibitor GGsTop prevents ischemia/reperfusion-induced AKI. The renoprotective effect of GGsTop seems to be attributed to the suppression of oxidative stress by inhibiting GGT activation, thereby preventing the degradation of glutathione.

Effects of a cGMP-specific phosphodiesterase inhibitor on expression of endothelial nitric oxide synthase and vascular endothelial growth factor in rats with cyclosporine-induced nephrotoxicity

BACKGROUND

The mechanism of cyclosporine (CsA)-induced nephrotoxicity has been suggested to be vasoconstriction due to reduced nitric oxide (NO), providing tissue fibrosis by elevation of transforming growth factor beta and vascular endothelial growth factor (VEGF). In this study using a rat model of CsA-induced nephrotoxicity, we administered a phosphodiesterase-5 inhibitor to ameliorate the renal injury and alter the expression of endothelial No synthase (eNOS) and VEGF.

METHODS

A right nephrectomy was performed in Sprague-Dawley rats (n = 30; 200-250 g, all male). The Ischemia group (n = 6) underwent ligation of the left renal artery for 45 minutes (IR) before observation for 28 days. After IR, the udenafil group (n = 6) was treated with 10 mg/kg drug orally, the CsA group (n = 6) received 15 mg/kg CsA injected subcutaneously and the CsA plus udenafil group (n = 6) received 15 mg/kg CsA injected subcutaneously together with the oral administration of 10 mg/kg udenafil.

RESULTS

Administration of udenafil significantly decreased serum creatinine either alone (0.21 ± 0.04 mg/dL) or in combination with CsA (1.86 ± 0.35 mg/dL) versus the ischemia (0.85 ± 0.22 mg/dL) and the CsA alone (3. 10 ± 0.77 mg/dL) group. (P = .002; P = .002). Comparing the Hematoxylin-eosin staining of the ischemia (0.41 ± 0.09) and CsA (0.44 ± 0.08) groups showed a significantly decreased loss of nuclei in proximal tubules after the administration of udenafil (0.27 ± 0.05 [P = .004] and 0.26 ± 0.02 [P = .002] respectively). Immunohistochemical staining showed strong eNOS staining in the udenafil and CsA plus udenafil groups. Western blots for eNOS showed decreased expression in the CsA group and increased expression in the udenafil group. Western blots for VEGF revealed reduced expression only in the CsA plus udenafil group. eNOS mRNA was decreased in the CsA (0.017 ± 0.010) compared with the ischemia group (0.048 ± 0.015; P = .000). VEGF mRNA which was decreased in the CsA group (2.026 ± 1.109), showed greater tendency after administration of udenafil (0.440 ± 0.449) (P = .003).

CONCLUSION

The phosphodiesterase inhibitor ameliorated renal injury in a rat model of CsA-induced nephrotoxicity, possibly related to increased eNOS and reduced VEGF expression.

Pharmacotherapy for end-stage coronary artery disease

IMPORTANCE OF THE FIELD

Coronary artery disease remains the leading cause of mortality in the industrialized world. Despite advances in surgical and catheter-based interventions, a select number of patients remain with no options for invasive therapy. The goal of this review is to discuss the current status of pharmacotherapeutic interventions to treat end-stage coronary artery disease.

AREAS COVERED IN THIS REVIEW

Literature review on the topic of therapeutic angiogenesis from 1980 to 2009.

WHAT THE READER WILL GAIN

Insight into current therapeutic strategies employed to manage end-stage coronary artery disease.

TAKE HOME MESSAGE

A promising approach focuses on augmenting the endogenous angiogenic response to chronic myocardial ischemia via the use of growth factors.

Renoprotective effects of gamma-aminobutyric acid on ischemia/reperfusion-induced renal injury in rats

Enhanced renal sympathetic nerve activity during ischemic period and the renal venous norepinephrine overflow after reperfusion play important roles in the development of ischemic acute kidney injury. We investigated the effect of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter mainly in the central nervous system, on ischemia/reperfusion-induced acute kidney injury in anesthetized rats. Ischemic acute kidney injury was induced by clamping the left renal artery and vein for 45min followed by reperfusion 2weeks after the contralateral nephrectomy. Intravenous injection of GABA (10 and 50micromol/kg) to ischemic acute kidney injury rats dose-dependently suppressed the enhanced renal sympathetic nerve activity during the renal ischemia, the renal venous norepinephrine overflow after reperfusion and attenuated the ischemia/reperfusion-induced renal dysfunction with histological damage. Intravenous injection of CGP52432 (0.1micromol/kg), a selective GABA(B) receptor antagonist, eliminated the preventive effect by GABA (50micromol/kg) on ischemic acute kidney injury. In contrast, intravenous injection of baclofen (1micromol/kg), a selective GABA(B) receptor agonist, attenuated the ischemia/reperfusion-induced renal injury equivalent to GABA (50micromol/kg). These results indicate that GABA prevents the development of ischemia/reperfusion-induced acute kidney injury presumably via GABA(B) receptor, by suppressing the enhanced renal sympathetic nerve activity during ischemia and the increased norepinephrine overflow from renal sympathetic nerve ending.

Application of nitric oxide and carbon monoxide in a model of renal preservation

Background

Nitric oxide and carbon monoxide exert vasodilatory effects that minimize ischaemia–reperfusion injury. An isolated porcine kidney model was used to assess the effects of administering the nitric oxide donor sodium nitroprusside (SNP) and carbon monoxide-releasing molecule (CORM) 3 during a period of warm preservation followed by reperfusion.

Methods

Kidneys were perfused under warm preservation conditions after 10 min of warm ischaemia and 16 h of cold storage in four groups: SNP, control, CORM-3 and inactive CORM-3 (inactive control). Renal function and viability were assessed.

Results

SNP and CORM-3 increased renal blood flow (RBF) during warm preservation (P = 0·014). After reperfusion, RBF was significantly improved in the CORM-3 group compared with the control group (P = 0·019). The reduction in creatinine clearance was significantly less in the CORM-3 group than in the inactive CORM-3 group (P = 0·021), and serum creatinine levels were significantly lower (P = 0·029). There was a negative correlation between RBF during warm preservation and functional parameters during reperfusion (creatinine concentration: rs = − 0·722, P < 0·001; sodium excretion: rs = − 0·912, P < 0·001).

Conclusion

The beneficial vasodilatory effects of CORM-3 during warm preservation improved renal function during reperfusion; SNP exerted similar, although less pronounced, effects.

Nitric oxide in the kidney : its physiological role and pathophysiological implications

Nitric oxide has been implicated in many physiologic processes that influence both acute and long-term control of kidney function. Its net effect in the kidney is to promote natriuresis and diuresis, contributing to adaptation to variations of dietary salt intake and maintenance of normal blood pressure. A pretreatment with nitric oxide donors or L-arginine may prevent the ischemic acute renal injury. In chronic kidney diseases, the systolic blood pressure is correlated with the plasma level of asymmetric dimethylarginine, an endogenous inhibitor of nitric oxide synthase. A reduced production and biological action of nitric oxide is associated with an elevation of arterial pressure, and conversely, an exaggerated activity may represent a compensatory mechanism to mitigate the hypertension.

Chronic sodium nitrite therapy augments ischemia-induced angiogenesis and arteriogenesis

Chronic tissue ischemia due to defective vascular perfusion is a hallmark feature of peripheral artery disease for which minimal therapeutic options exist. We have reported that sodium nitrite therapy exerts cytoprotective effects against acute ischemia/reperfusion injury in both heart and liver, consistent with the model of bioactive NO formation from nitrite during ischemic stress. Here, we test the hypothesis that chronic sodium nitrite therapy can selectively augment angiogenic activity and tissue perfusion in the murine hind-limb ischemia model. Various therapeutic doses (8.25-3,300 mug/kg) of sodium nitrite or PBS were administered. Sodium nitrite significantly restored ischemic hind-limb blood flow in a time-dependent manner, with low-dose sodium nitrite being most effective. Nitrite therapy significantly increased ischemic limb vascular density and stimulated endothelial cell proliferation. Remarkably, the effects of sodium nitrite therapy were evident within 3 days of the ischemic insult demonstrating the potency and efficacy of chronic sodium nitrite therapy. Sodium nitrite therapy also increased ischemic tissue nitrite and NO metabolites compared to nonischemic limbs. Use of the NO scavenger carboxy PTIO completely abolished sodium nitrite-dependent ischemic tissue blood flow and angiogenic activity consistent with nitrite reduction to NO being the proangiogenic mechanism. These data demonstrate that chronic sodium nitrite therapy is a recently discovered therapeutic treatment for peripheral artery disease and critical limb ischemia.

Immunolocalization of Kim-1, RPA-1, and RPA-2 in kidney of gentamicin-, mercury-, or chromium-treated rats: relationship to renal distributions of iNOS and nitrotyrosine

Immunohistochemical studies for kidney injury molecule-1 (Kim-1), renal papillary antigen-1 (RPA-1), and renal papillary antigen-2 (RPA-2) were conducted to explore their relationship to inducible nitric oxide synthase (iNOS) and nitrotyrosine expression. Male Sprague-Dawley rats were exposed to gentamicin (100 mg/kg/day Gen, sc, for 3 days), mercury (0.25 mg Hg/kg, iv, single dose), or chromium (5 mg Cr/kg, sc, single dose) and kidney tissue was examined 24 hours or 72 hours after the last dose of the nephrotoxicant. Another group of kidneys was evaluated 24 hours after rats were administered 3 daily doses (50, 100, 150, 200, or 300 mg/kg/day) of Gen. Gen- and Cr-treated rats exhibited increased immunoreactivity of Kim-1, RPA-1, and RPA-2 largely in the S1/S2 segments and to a lesser extent in the S3 segments of the proximal tubule of the kidney, whereas Hg-treated rats showed increased immunoreactivity of Kim-1, RPA-1, and RPA-2 in the S3 segments. Up-regulation of Kim-1, RPA-1, and RPA-2 expression correlated with injured tubular epithelial cells and also correlated with immunoreactivity of iNOS and nitrotyrosine. It is possible that iNOS activation with nitrotyrosine production in injured nephron segments may be involved in the induction of Kim-1, RPA-1, and RPA-2 following exposure to nephrotoxicants.

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.

The protective effect of oxytocin on renal ischemia/reperfusion injury in rats

AIM

Oxytocin was previously shown to have anti-inflammatory effects in different inflammation models. The major objective of the present study was to evaluate the protective role of oxytocin (OT) in protecting the kidney against ischemia/reperfusion (I/R) injury.

MATERIALS AND METHODS

Male Wistar albino rats (250-300 g) were unilaterally nephrectomized, and subjected to 45 min of renal pedicle occlusion followed by 6 h of reperfusion. OT (1 mg/kg, ip) or vehicle was administered 15 min prior to ischemia and was repeated immediately before the reperfusion period. At the end of the reperfusion period, rats were decapitated and kidney samples were taken for histological examination or determination of malondialdehyde (MDA), an end product of lipid peroxidation; glutathione (GSH), a key antioxidant; and myeloperoxidase (MPO) activity, an index of tissue neutrophil infiltration. Creatinine and urea concentrations in blood were measured for the evaluation of renal function, while TNF-alpha and lactate dehydrogenase (LDH) levels were determined to evaluate generalized tissue damage. Formation of reactive oxygen species in renal tissue samples was monitored by chemiluminescence technique using luminol and lucigenin probes.

RESULTS

The results revealed that I/R injury increased (p<0.01-0.001) serum urea, creatinine, TNF-alpha and LDH levels, as well as MDA, MPO and reactive oxygen radical levels in the renal tissue, while decreasing renal GSH content. However, alterations in these biochemical and histopathological indices due to I/R injury were attenuated by OT treatment (p<0.05-0.001).

CONCLUSIONS

Since OT administration improved renal function and microscopic damage, along with the alleviation of oxidant tissue responses, it appears that oxytocin protects renal tissue against I/R-induced oxidative damage.

Role of endothelial-derived nitric oxide in hypertension and renal disease

PURPOSE OF REVIEW

To highlight recent advances in the field of endothelial-derived nitric oxide regulation of blood pressure and renal homeostasis.

RECENT FINDINGS

Many laboratories have dissected a role for nitric oxide in regulating blood pressure and renal function. In models of hypertension, and chronic and acute renal disease, the loss of nitric oxide bioavailability may occur due to inactivation of endothelial nitric oxide synthase, synthesis of endogenous inhibitors or oxidative inactivation of nitric oxide.

SUMMARY

Understanding the molecular mechanisms of nitric oxide synthesis may lead to novel diagnostics and treatments for cardiovascular disorders.

Nitric oxide and peroxynitrite in health and disease

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.