Nitric oxide in the kidney: functions and regulation of synthesis

Alkaline phosphatase affects renal function in never-treated hypertensive patients: effect modification by age

Several studies in patients with chronic kidney disease or normal renal function have shown that high levels of tissue non-specific alkaline phosphatase (ALP) are associated with an increased risk of all cause and cardiovascular (CV) mortality. Considering the independent prognostic role of renal function, we investigated the possible association between ALP levels and estimated glomerular filtration rate (e-GFR) in a large cohort of hypertensive subjects. We enrolled 2157 never-treated uncomplicated hypertensive patients with ALP levels within normal range. In the whole population, e-GFR was strongly related to ALP (r = −0.43, P < 0.0001) with similar magnitude in females and in males, resulting ALP the second independent predictor of renal function. In a multiple linear regression model, both on crude (P < 0.001) and adjusted (P = 0.01) analyses age significantly modified the effect of a fixed increase in ALP (20 UI/L) on renal function so that the reduction in e-GFR associated to a 20 UI/L increase in ALP was of lower magnitude in younger patients and progressively of higher extent from 20 years of age onwards. In conclusion, present data indicate a significant relationship between ALP levels and e-GFR in uncomplicated hypertensive patients that is modulated by age and that persisted after adjusting for several confounders.

Temporal hemodynamic changes in a female mouse model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease characterized by circulating autoantibodies, prevalent hypertension, renal injury, and cardiovascular disease. Onset of the disease often occurs in young women of childbearing age. Although kidney involvement is common to patients with SLE, little is known about temporal changes in renal hemodynamic function and its relationship to the pathogenesis of hypertension during autoimmune diseases. We hypothesized that the loss of immunological tolerance and subsequent production of autoantibodies in SLE leads to impaired renal hemodynamic function that precedes the development hypertension. Female NZBWF1 (SLE) mice and female NZW/LacJ (control) mice were instrumented with carotid artery and jugular vein catheters to determine mean arterial pressure (MAP) and glomerular filtration rate, respectively, at ages of 15, 20, 24, 28, 31, and 34 wk. In addition, urinary albumin excretion, blood urea nitrogen, circulating autoantibodies, and glomerulosclerosis were assessed at each age. Levels of circulating autoantibodies are increased between 24 and 28 wk of age in NZBWF1 mice and were significantly greater than in control mice. Glomerular filtration rate was significantly increased at 28 wk of age in NZBWF1 mice followed by a sharp decline at 34 wk of age. NZBWF1 mice had an increase in MAP that occurred by 34 wk of age. These data show that changes in circulating autoantibodies, renal hemodynamic function, and glomerular injury occur in NZBWF1 mice before changes in MAP, suggesting an important mechanistic role for autoimmunity to directly impair renal hemodynamic function and promote the development of hypertension.

Renal Sympathetic Nerve-Derived Signaling in Acute and Chronic kidney Diseases

The kidney is innervated by afferent sensory and efferent sympathetic nerve fibers. Norepinephrine (NE) is the primary neurotransmitter for post-ganglionic sympathetic adrenergic nerves, and its signaling, regulated through adrenergic receptors (AR), modulates renal function and pathophysiology under disease conditions. Renal sympathetic overactivity and increased NE level are commonly seen in chronic kidney disease (CKD) and are critical factors in the progression of renal disease. Blockade of sympathetic nerve-derived signaling by renal denervation or AR blockade in clinical and experimental studies demonstrates that renal nerves and its downstream signaling contribute to progression of acute kidney injury (AKI) to CKD and fibrogenesis. This review summarizes our current knowledge of the role of renal sympathetic nerve and adrenergic receptors in AKI, AKI to CKD transition and CKDand provides new insights into the therapeutic potential of intervening in its signaling pathways.

Green synthesis of silver nanoparticles from Alpinia officinarum mitigates cisplatin-induced nephrotoxicity via down-regulating apoptotic pathway in rats

The rhizome of A. officinarum possesses immense pharmaceutical properties like antioxidant, anti-inflammatory, antiapoptotic, anticancer activities. The foremost downside of herbal-based drugs is their poor bioavailability, to trounce this we synthesized a herbal based silver nanodrug with Alpinia officinarum rhizome extract and assessed its effect against the cisplatin-induced nephrotoxicity in in vivo model. The A. officinarum biosynthesized silver nanoparticles (AG-AO) were characterized using UV-Spec, FTIR, XRD, TEM and SAED analysis. The antioxidant and the nephroprotective property of biosynthesized AG-AO nanoparticles were assessed by estimating the levels of kidney biomarkers, cytokine, inflammatory markers, free radicals and antioxidants induced in control and experimental. Antiapoptotic effect of AG-AO nanoparticles were evaluated by measuring the levels of apoptotic proteins in control and experimental rats. Further, it is confirmed with histopathological analysis of kidney tissue with haematoxylin and eosin staining. Our physical analysis confirms the biosynthesized silver nanoparticles by A. officinarum and it satisfies the qualities of potent nanoparticles to be used for medication. Our biochemical, molecular and histopathological results confirm the antioxidant, antiapoptotic, anti-inflammatory properties of AG-AO. Overall our results authentically confirm AG-AO is a potent nephroprotective drug, which can be a supplementary drug to prevent cisplatin-induced nephrotoxicity.

Chronic NOS Inhibition Affects Oxidative State and Antioxidant Response Differently in the Kidneys of Young Normotensive and Hypertensive Rats

Deficiency of nitric oxide (NO) and oxidative stress can be a cause, a consequence, or, more often, a potentiating factor for hypertension and hypertensive renal disease. Both NO and superoxide anions are radical molecules that interact with each other, leading to oxidative damage of such organs as the kidney. In the present study, we investigated the effect of chronic-specific (neuronal NOS inhibition) and nonspecific NOS inhibition on the oxidative state and antioxidant response and associated oxidative damage of the kidney of young normotensive and hypertensive rats. Young male normotensive Wistar rats (WRs, age 4 weeks) and spontaneously hypertensive rats (SHRs, age 4 weeks) were divided into three groups for each strain by the type of administered compounds. The first group was treated with 7-nitroindazole (WR+7-NI; SHR+7-NI), the second group was treated with N(G)-nitro-L-arginine-methyl ester (WR+L-NAME; SHR+L-NAME), and the control group was treated with pure drinking water (WR; SHR) continuously for up to 6 weeks. Systolic blood pressure increased in WR+L-NAME after the first week of administration and increased slightly in SHR+L-NAME in the third week of treatment. 7-NI had no effect on blood pressure. While total NOS activity was not affected by chronic NOS inhibition in any of the WR groups, it was attenuated in SHR+7-NI and SHR+L-NAME. Nitration of proteins (3-nitrotyrosine expression) was significantly reduced in WR+7NI but not in WR+L-NAME and increased in SHR+7-NI and SHR+L-NAME. Immunoblotting analysis of SOD isoforms showed decreased SOD2 and SOD3 expressions in both WR+7-NI and WR+L-NAME followed by increased SOD activity in WR+L-NAME. Conversely, increased expression of SOD2 and SOD3 was observed in SHR+L-NAME and SHR+7-NI, respectively. SOD1 expression and total activity of SOD did not change in the SHR groups. Our results show that the antioxidant defense system plays an important role in maintaining the oxidative state during NO deficiency. While the functioning antioxidant system seeks to balance the oxidation state in the renal cortex of normotensive WRs, the impaired antioxidant activity leads to the development of oxidative damage of proteins in the kidney induced by peroxynitrite in SHRs.

Body Fluid-Independent Effects of Dietary Salt Consumption in Chronic Kidney Disease

The average dietary salt (i.e., sodium chloride) intake in Western society is about 10 g per day. This greatly exceeds the lifestyle recommendations by the WHO to limit dietary salt intake to 5 g. There is robust evidence that excess salt intake is associated with deleterious effects including hypertension, kidney damage and adverse cardiovascular health. In patients with chronic kidney disease, moderate reduction of dietary salt intake has important renoprotective effects and positively influences the efficacy of common pharmacological treatment regimens. During the past several years, it has become clear that besides influencing body fluid volume high salt also induces tissue remodelling and activates immune cell homeostasis. The exact pathophysiological pathway in which these salt-induced fluid-independent effects contribute to CKD is not fully elucidated, nonetheless it is clear that inflammation and the development of fibrosis play a major role in the pathogenic mechanisms of renal diseases. This review focuses on body fluid-independent effects of salt contributing to CKD pathogenesis and cardiovascular health. Additionally, the question whether better understanding of these pathophysiological pathways, related to high salt consumption, might identify new potential treatment options will be discussed.

Central Glucagon-like Peptide-1 Receptor Signaling via Brainstem Catecholamine Neurons Counteracts Hypertension in Spontaneously Hypertensive Rats

Glucagon-like peptide-1 receptor (GLP-1R) agonists, widely used to treat type 2 diabetes, reduce blood pressure (BP) in hypertensive patients. Whether this action involves central mechanisms is unknown. We here report that repeated lateral ventricular (LV) injection of GLP-1R agonist, liraglutide, once daily for 15 days counteracted the development of hypertension in spontaneously hypertensive rats (SHR). In parallel, it suppressed urinary norepinephrine excretion, and induced c-Fos expressions in the area postrema (AP) and nucleus tractus solitarius (NTS) of brainstem including the NTS neurons immunoreactive to dopamine beta-hydroxylase (DBH). Acute administration of liraglutide into fourth ventricle, the area with easy access to the AP and NTS, transiently decreased BP in SHR and this effect was attenuated after lesion of NTS DBH neurons with anti-DBH conjugated to saporin (anti-DBH-SAP). In anti-DBH-SAP injected SHR, the antihypertensive effect of repeated LV injection of liraglutide for 14 days was also attenuated. These findings demonstrate that the central GLP-1R signaling via NTS DBH neurons counteracts the development of hypertension in SHR, accompanied by attenuated sympathetic nerve activity.

Effects of the nitric oxide synthase inhibitor ronopterin (VAS203) on renal function in healthy volunteers

AIMS

Reduced nitric oxide (NO) availability may adversely affect renal perfusion and glomerular filtration. The aim of the present study was to characterize in detail the pharmacological effects of VAS203, an inhibitor of NO synthase, on renal haemodynamics in humans.

METHODS

This double-blind, randomized, placebo-controlled, cross-over phase-I-study comprised 18 healthy men. Renal haemodynamics were assessed with constant-infusion input-clearance technique with p-aminohippurate and inulin for renal plasma flow (RPF) and glomerular filtration rate (GFR), respectively. After baseline measurement, a constant infusion of the tetrahydrobiopterin analogue ronopterin (VAS203, total 10 mg/kg body weight) or placebo was administered at random order for 6 hours additionally. After a wash-out phase of 28 days, the second course was applied. In parallel, markers of early kidney injury and renal function were assessed repeatedly up to 48 hours after starting VAS203/placebo-infusion.

RESULTS

VAS203-infusion resulted in a significant decrease of RPF (P < .0001) and GFR (P < .001) compared to placebo, but magnitude was within the physiological range. RPF and GFR recovered partly 2 hours after end of VAS203-infusion and was normal at beginning of the second infusion period. Compared to placebo, preglomerular resistance (P < .0001), and to lesser extent postglomerular resistance (P < .0001) increased, resulting in a decrease of intraglomerular pressure (P < .01). No treatment related effect on markers of early kidney injury, and on renal function (P for all >.20) have been observed.

CONCLUSIONS

Our phase-I-study in healthy humans indicates that VAS203 (10 mg/kg body weight) reduces renal perfusion and glomerular function within the physiological range mainly due to vasoconstriction at the preglomerular site.

Extracellular matrix roles in cardiorenal fibrosis: Potential therapeutic targets for CVD and CKD in the elderly

Whereas hypertension, diabetes, and dyslipidemia are age-related risk factors for cardiovascular disease (CVD) and chronic kidney disease (CKD), aging alone is an independent risk factor. With advancing age, the heart and kidney gradually but significantly undergo inflammation and subsequent fibrosis, which eventually results in an irreversible decline in organ physiology. Through cardiorenal network interactions, cardiac dysfunction leads to and responds to renal injury, and both facilitate aging effects. Thus, a comprehensive strategy is needed to evaluate the cardiorenal aging network. Common hallmarks shared across systems include extracellular matrix (ECM) accumulation, along with upregulation of matrix metalloproteinases (MMPs) including MMP-9. The wide range of MMP-9 substrates, including ECM components and inflammatory cytokines, implicates MMP-9 in a variety of pathological and age-related processes. In particular, there is strong evidence that inflammatory cell-derived MMP-9 exacerbates cardiorenal aging. This review explores the potential therapeutic targets against CVD and CKD in the elderly, focusing on ECM and MMP roles.

Protective effects of a Lachnum polysaccharide against liver and kidney injury induced by lead exposure in mice

This study was designed to investigate the liver and kidney protective efficacy of a Lachnum polysaccharide (LEP) against Pb-induced toxicity in mice. The results showed that LEP decreased the Pb-induced bodyweight loss and organ index. Moreover, biochemical analysis showed that treatment of LEP could improve antioxidant status (CAT, GSH-Px and MDA) and the injury of tissues (liver and kidney). In addition, the histopathological observations indicated that LEP could attenuate liver and kidney cell injury induced by Pb. For further studies, key proteins involved in hepatic and kidney apoptosis, including cleaved caspase-3, Bax, Bcl-2, TGF-β1 and α-SMA, were quantified. The present findings demonstrated that LEP is strongly effective in protecting against the liver and kidney injury induced by Pb. We hope this research can offer a theoretical base for development of polysaccharide based on nutraceutical food in future.

A Network Pharmacology Approach to Uncover the Mechanisms of Shen-Qi-Di-Huang Decoction against Diabetic Nephropathy

Shen-Qi-Di-Huang decoction (SQDHD), a well-known herbal formula from China, has been widely used in the treatment of diabetic nephropathy (DN). However, the pharmacological mechanisms of SQDHD have not been entirely elucidated. At first, we conducted a comprehensive literature search to identify the active constituents of SQDHD, determined their corresponding targets, and obtained known DN targets from several databases. A protein-protein interaction network was then built to explore the complex relations between SQDHD targets and those known to treat DN. Following the topological feature screening of each node in the network, 400 major targets of SQDHD were obtained. The pathway enrichment analysis results acquired from DAVID showed that the significant bioprocesses and pathways include oxidative stress, response to glucose, regulation of blood pressure, regulation of cell proliferation, cytokine-mediated signaling pathway, and the apoptotic signaling pathway. More interestingly, five key targets of SQDHD, named AKT1, AR, CTNNB1, EGFR, and ESR1, were significant in the regulation of the above bioprocesses and pathways. This study partially verified and predicted the pharmacological and molecular mechanisms of SQDHD on DN from a holistic perspective. This has laid the foundation for further experimental research and has expanded the rational application of SQDHD in clinical practice.

Pitavastatin Upregulates Nitric Oxide Synthases in the Kidney of Spontaneously Hypertensive Rats and Wistar-Kyoto Rats

BACKGROUND

Clinical trials show potent renoprotective effects of pitavastatin (PTV), although the precise mechanism for these renoprotective effects is not fully clarified. The aim of this study was to examine the antihypertensive and renoprotective effects of PTV, focusing on the nitric oxide (NO) system.

METHODS

Male, 6-week-old, spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were randomized to receive vehicle or PTV (2 mg/kg bodyweight) for 8 weeks. Blood pressure and urinary albumin excretion were measured every 2 weeks. After 8 weeks, plasma biochemical parameters and renal histology were examined. NO synthase isoform (neuronal, nNOS; inducible, iNOS; and endothelial, eNOS) expression and eNOS phosphorylation were examined by western blotting.

RESULTS

PTV attenuated hypertension and albuminuria development in SHR. PTV decreased glomerular desmin expression and medullary interstitial fibrosis in SHR. PTV tended to increase plasma NO in both strains but significantly increased urinary NO excretion only in WKY. PTV significantly increased nNOS and eNOS expression, enhanced eNOS phosphorylation at serine1177, and inhibited eNOS phosphorylation at threonine495 in the kidney of both strains.

CONCLUSIONS

PTV treatment led to increased renal NOS expression and upregulated eNOS activity in both SHR and WKY. The antihypertensive and renoprotective effects of PTV may be related to upregulation of the NO system.

Nitric Oxide Synthase Inhibition Induces Renal Medullary Hypoxia in Conscious Rats

Background Renal hypoxia, implicated as crucial factor in onset and progression of chronic kidney disease, may be attributed to reduced nitric oxide because nitric oxide dilates vasculature and inhibits mitochondrial oxygen consumption. We hypothesized that chronic nitric oxide synthase inhibition would induce renal hypoxia. Methods and Results Oxygen-sensitive electrodes, attached to telemeters, were implanted in either renal cortex (n=6) or medulla (n=7) in rats. After recovery and stabilization, baseline oxygenation ( pO 2) was recorded for 1 week. To inhibit nitric oxide synthase, N-ω-nitro-l-arginine (L-NNA; 40 mg/kg/day) was administered via drinking water for 2 weeks. A separate group (n=8), instrumented with blood pressure telemeters, followed the same protocol. L-NNA rapidly induced hypertension (165±6 versus 108±3 mm Hg; P<0.001) and proteinuria (79±12 versus 17±2 mg/day; P<0.001). Cortical pO 2, after initially dipping, returned to baseline and then increased. Medullary pO 2 decreased progressively (up to -19±6% versus baseline; P<0.05). After 14 days of L-NNA, amplitude of diurnal medullary pO 2 was decreased (3.7 [2.2-5.3] versus 7.9 [7.5-8.4]; P<0.01), whereas amplitudes of blood pressure and cortical pO 2 were unaltered. Terminal glomerular filtration rate (1374±74 versus 2098±122 μL/min), renal blood flow (5014±336 versus 9966±905 μL/min), and sodium reabsorption efficiency (13.0±0.8 versus 22.8±1.7 μmol/μmol) decreased (all P<0.001). Conclusions For the first time, we show temporal development of renal cortical and medullary oxygenation during chronic nitric oxide synthase inhibition in unrestrained conscious rats. Whereas cortical pO 2 shows transient changes, medullary pO 2 decreased progressively. Chronic L-NNA leads to decreased renal perfusion and sodium reabsorption efficiency, resulting in progressive medullary hypoxia, suggesting that juxtamedullary nephrons are potentially vulnerable to prolonged nitric oxide depletion.

Swimming exercise demonstrates advantages over running exercise in reducing proteinuria and glomerulosclerosis in spontaneously hypertensive rats

Experimental studies in animal models have described the benefits of physical exercise (PE) to kidney diseases associated with hypertension. Land- and water-based exercises induce different responses in renal function. Our aim was to evaluate the renal alterations induced by different environments of PE in spontaneously hypertensive rats (SHRs). The SHRs were divided into sedentary (S), swimming exercise (SE), and running exercise (RE) groups, and were trained for 8 weeks under similar intensities (60 min/day). Arterial pressure (AP) and heart rate (HR) were recorded. The renal function was evaluated through urinary volume at each week of training; sodium and potassium excretions, plasma and urinary osmolarities, glomerular filtration rate (GFR), levels of proteinuria, and renal damage were determined. SE and RE rats presented reduced mean AP, systolic blood pressure, and HR in comparison with S group. SE and RE rats showed higher urine osmolarity compared with S. SE rats showed higher free water clearance (P < 0.01), lower urinary density (P < 0.0001), and increased weekly urine volume (P < 0.05) in comparison with RE and S groups. GFR was increased in both SE and RE rats. The proteinuria of SE (7.0 ± 0.8 mg/24 h) rats was decreased at the 8th week of the PE in comparison with RE (9.6 ± 0.8 mg/24 h) and S (9.8 ± 0.5 mg/24 h) groups. The glomerulosclerosis was reduced in SE rats (P < 0.02). SE produced different response in renal function in comparison with RE, in which only swimming-trained rats had better profile for proteinuria and glomerulosclerosis.

A Multicellular Vascular Model of the Renal Myogenic Response

The myogenic response is a key autoregulatory mechanism in the mammalian kidney. Triggered by blood pressure perturbations, it is well established that the myogenic response is initiated in the renal afferent arteriole and mediated by alterations in muscle tone and vascular diameter that counterbalance hemodynamic perturbations. The entire process involves several subcellular, cellular, and vascular mechanisms whose interactions remain poorly understood. Here, we model and investigate the myogenic response of a multicellular segment of an afferent arteriole. Extending existing work, we focus on providing an accurate—but still computationally tractable—representation of the coupling among the involved levels. For individual muscle cells, we include detailed Ca2+ signaling, transmembrane transport of ions, kinetics of myosin light chain phosphorylation, and contraction mechanics. Intercellular interactions are mediated by gap junctions between muscle or endothelial cells. Additional interactions are mediated by hemodynamics. Simulations of time-independent pressure changes reveal regular vasoresponses throughout the model segment and stabilization of a physiological range of blood pressures (80–180 mmHg) in agreement with other modeling and experimental studies that assess steady autoregulation. Simulations of time-dependent perturbations reveal irregular vasoresponses and complex dynamics that may contribute to the complexity of dynamic autoregulation observed in vivo. The ability of the developed model to represent the myogenic response in a multiscale and realistic fashion, under feasible computational load, suggests that it can be incorporated as a key component into larger models of integrated renal hemodynamic regulation.

Host-Derived Nitric Oxide and Its Antibacterial Effects in the Urinary Tract

Urinary tract infection (UTI) is one of the most common bacterial infections in humans, and the majority are caused by uropathogenic Escherichia coli (UPEC). The rising antibiotic resistance among UPEC and the frequent failure of antibiotics to effectively treat recurrent UTI and catheter-associated UTI motivate research on alternative ways of managing UTI. Abundant evidence indicates that the toxic radical nitric oxide (NO), formed by activation of the inducible nitric oxide synthase, plays an important role in host defence to bacterial infections, including UTI. The major source of NO production during UTI is from inflammatory cells, especially neutrophils, and from the uroepithelial cells that are known to orchestrate the innate immune response during UTI. NO and reactive nitrogen species have a wide range of antibacterial targets, including DNA, heme proteins, iron-sulfur clusters, and protein thiol groups. However, UPEC have acquired a variety of defence mechanisms for protection against NO, such as the NO-detoxifying enzyme flavohemoglobin and the NO-tolerant cytochrome bd-I respiratory oxidase. The cytotoxicity of NO-derived intermediates is nonspecific and may be detrimental to host cells, and a balanced NO production is crucial to maintain the tissue integrity of the urinary tract. In this review, we will give an overview of how NO production from host cells in the urinary tract is activated and regulated, the effect of NO on UPEC growth and colonization, and the ability of UPEC to protect themselves against NO. We also discuss the attempts that have been made to develop NO-based therapeutics for UTI treatment.

N-acetylcysteine protects against diabetic nephropathy through control of oxidative and nitrosative stress by recovery of nitric oxide in rats

The diabetes mellitus (DM) induces several changes, with substantial increase of reactive oxygen species (ROS). The ROS cause damage to systemic and renal microvasculature, which could be one of the mechanisms involved in the development of diabetic nephropathy (DN). The ROS modulate other substances like the nitric oxide (NO), a vasodilator with important role in the renal function. N-acetylcysteine (NAC) is an antioxidant that acts replenishing intracellular cysteine levels, which is essential for glutathione formation. The aim of this study was to evaluate the effect of early or late NAC treatment on oxidative/nitrosative stress in DN progression. All rats were submitted to unilateral nephrectomy and diabetes was induced with streptozotocin. The animals were allocated into six groups: controls that received water (CTL) or NAC (CTL + NAC); diabetic groups that received early or late, water (DM-E; DM-L) or NAC (DM + NAC-E; DM + NAC-L), started on 5th day (early) or 4th week (late) after diabetes induction, during 8 weeks. After NAC treatment, the rats were placed in individual metabolic cages to obtain urine and blood samples for analysis of metabolic profile, renal function, thiobarbituric acid reactive substances (TBARS) and NO. At the end of the protocol, the renal cortex was removed for TBARS, NOS evaluation, antioxidants markers and histology. The DM-E group compared to CTL showed a significant increase in glycemia and proteinuria and impaired renal function; there was a significant increase of TBARS in plasma, urine and renal tissue, and also a significant decrease in plasma NO, which were reverted after early NAC treatment. The eNOS was decreased and iNOS was increased in DM-E vs. CTL, p < 0.05. The early NAC treatment in DM rats reduced proteinuria, creatinine, urea, TBARS and iNOS and, increased creatinine clearance, NO and eNOS, increasing significantly the antioxidant defenses, promoting elevated catalase and glutathione compared to DM-E group, all p < 0.05. The late NAC treatment in diabetic rats vs.DM-E showed reduced proteinuria and TBARS excretion and higher values of creatinine clearance and NO, all statistically significant. Histological analysis of the animals in DM-E or DM-L showed significant tubular changes with degeneration and vacuolization in tubular cells, dilated tubular lumen, intense glycosidic degeneration, and discreet mesangial expansion with interstitial fibrosis area. The DM + NAC-E group showed moderate glycosidic degeneration, however, did not present tubular degeneration or fibrosis. The DM + NAC-L group showed severe glycosidic degeneration, moderate tubular cell degeneration, light and focal dilatation of the tubules, with no fibrosis. Our study showed that NAC protected the diabetic rats against renal injury, probably due to the control of oxidative stress via recovery of the NO bioavailability, showing that early NAC was more effective than late treatment. All these data suggest that NAC may be useful in the adjuvant treatment in a safe way, in the early phase of the disease. Eventually, prolonged treatment, even if it is started later, could change the natural history of the disease, delaying the complications of diabetes in renal tissue.

Glucose 6-phosphate dehydrogenase and the kidney

PURPOSE OF REVIEW

Glucose 6-phosphate dehydrogenase (G6PD) is the rate-limiting enzyme of the pentose phosphate pathway. G6PD is the main source of the essential cellular reductant, NADPH. The purpose of this review is to describe the biochemistry of G6PD and NADPH, cellular factors that regulate G6PD, normal physiologic roles of G6PD, and the pathogenic role altered G6PD/NADPH plays in kidney disease.

RECENT FINDINGS

NADPH is required for many essential cellular processes such as the antioxidant system, nitric oxide synthase, cytochrome p450 enzymes, and NADPH oxidase. Decreased G6PD activity and, as a result, decreased NADPH level have been associated with diabetic kidney disease, altered nitric oxide production, aldosterone-mediated endothelial dysfunction, and dialysis-associated anemia. Increased G6PD activity is associated with all cancers including kidney cancer. Inherited G6PD deficiency is the most common mutation in the world that is thought to be a relatively mild disorder primarily associated with anemia. Yet, intriguing studies have shown an increased prevalence of diabetes mellitus in G6PD-deficient people. It is not known if G6PD-deficient people are at more risk for other diseases.

SUMMARY

Much more research needs to be done to determine the role of altered G6PD activity (inherited or acquired) in the pathogenesis of kidney disease.

Crocin reverses unilateral renal ischemia reperfusion injury-induced augmentation of oxidative stress and toll like receptor-4 activity

Renal Ischemia (RI) usually develops as a secondary manifestation of hypertension, various cardiovascular disorders and renal transplantation. It exerts hypoxic oxidative stress to kidneys, together with stimulation of several immune-mediated inflammatory cascades. Such events eventually damage renal tubules and glomeruli, driving acute kidney injury (AKI) and ultimately, renal failure. Crocin; the main bioactive constituent of Crocus sativus extract has been reported to demonstrate numerous pharmacological merits. In the current study, unilateral renal ischemia reperfusion injury (URIRI) was induced in rats by unilateral clamping of the left renal pedicle for 45 min followed by 24 h of reperfusion. Daily pre-treatment with crocin (20 mg/kg, orally) for 7 days, significantly improved all signs of renal injury. Biochemically, kidney functions; including serum creatinine (Sr Cr), blood urea nitrogen (BUN), proteinuria and creatinine clearance (Cr Cl) significantly improved. Inflammatory biomarkers; serum lactate dehydrogenase (LDH) and kidney nitric oxide (Nos) contents significantly declined. Oxidant/antioxidant balance was significantly restored; manifested in recovery of renal superoxide dismutase (SOD) activity, glutathione (GSH) concentration, malondialdehyde (MDA) content and restoration of serum catalase activity. Kidney contents of inflammatory cytokine interleukin-6 (IL6) and toll-like receptors 4 (TLR4) significantly declined as well. Histopathologically, crocin pretreatment resulted in signs of improvement with minimal renal lesions with significant decrease in renal inflammatory cells count. In conclusion, crocin induced restoration of normal kidney functions is mediated through multiple mechanisms including mainly attenuation of oxidative stress and inflammation via down-regulation of renal TLR4 and IL6 expression.

Previous Exercise Training Reduces Markers of Renal Oxidative Stress and Inflammation in Streptozotocin-Induced Diabetic Female Rats

The aim of this study is to evaluate the effects of regular moderate exercise training initiated previously or after induction of diabetes mellitus on renal oxidative stress and inflammation in STZ-induced diabetic female rats. For this purpose, Wistar rats were divided into five groups: sedentary control (SC), trained control (TC), sedentary diabetic (SD), trained diabetic (TD), and previously trained diabetic (PTD). Only the PTD group was submitted to treadmill running for 4 weeks previously to DM induction with streptozotocin (40 mg/kg, i.v). After confirming diabetes, the PTD, TD, and TC groups were submitted to eight weeks of exercise training. At the end of the training protocol, we evaluated the following: glycosuria, body weight gain, plasma, renal and urinary levels of nitric oxide and thiobarbituric acid reactive substances, renal glutathione, and immunolocalization of lymphocytes, macrophages, and nuclear factor-kappa B (NF-κB/p65) in the renal cortex. The results showed that exercise training reduced glycosuria, renal TBARS levels, and the number of immune cells in the renal tissue of the TD and PTD groups. Of note, only previous exercise increased weight gain and urinary/renal NO levels and reduced NF-κB (p65) immunostaining in the renal cortex of the PTD group. In conclusion, our study shows that exercise training, especially when initiated previously to diabetes induction, promotes protective effects in diabetic kidney by reduction of renal oxidative stress and inflammation markers in female Wistar rats.

Evaluation of inducible nitric oxide synthase inhibition on kidney function and structure in high-fat diet-induced kidney disease

NEW FINDINGS

What is the central question of this study? The metabolic pathways regulating the effects of obesity on the kidney remain unknown. We sought to determine whether inducible nitric oxide synthase (iNOS) is involved in the underlying mechanisms of high-fat diet-induced kidney disease using a specific iNOS inhibitor, N6-(1-iminoethyl)-l-lysine hydrochloride (L-NIL). What is the main finding and its importance? We did not demonstrate an upregulation of iNOS renal expression after high caloric intake, suggesting that iNOS might not be a crucial player in the development of obesity-induced kidney disease. Although L-NIL treatment clearly ameliorated systemic metabolic parameters, the effect on loss of renal function, impairment of tubular integrity, oxidative stress and inflammation appeared to be more moderate. Central obesity is related to caloric excess, promoting deleterious cellular responses in targeted organs. Nitric oxide (NO) has been determined as a key player in the pathogenesis of metabolic diseases. Here, we investigated the implication of inducible NO synthase (iNOS) in the development of obesity-induced kidney disease. C57Bl/6 male mice were randomized to a low-fat diet (LFD) or a high-fat diet (HFD) and treated with N6-(1-iminoethyl)-l-lysine hydrochloride (L-NIL), a specific iNOS inhibitor, for 16 weeks. Mice fed an HFD exhibited a significant increase in body weight, fasting blood glucose and plasma concentrations of non-esterified fatty acids, triglyceride and insulin. Inhibition of iNOS prevented these changes in mice fed an HFD. Interestingly, the significant increase in albuminuria and mesangial matrix expansion were not ameliorated with L-NIL, whereas a significant decrease in proteinuria, N-acetyl-β-d-glucosaminidase excretion and renal triglyceride content were found, suggesting that iNOS inhibition is more suitable for tubular function than glomerular function. The urinary concentration of hydrogen peroxide, a stable product of reactive oxygen species production, that was found to be increased in mice fed an HFD, was significantly reduced with L-NIL. Finally, despite a moderate effect of L-NIL on inflammatory processes in the kidney, we demonstrated a positive impact of this treatment on adipocyte hypertrophy and on adipose tissue inflammation. These results suggest that inhibition of iNOS leads to a moderate beneficial effect on kidney function in mice fed an HFD. Further studies are needed for better understanding of the role of iNOS in obesity-induced kidney disease.

The macro- and microcirculation of the kidney

Acute kidney injury (AKI) remains one of the main causes of morbidity and mortality in the intensive care medicine today. Its pathophysiology and progress to chronic kidney disease is still under investigation. In addition, the lack of techniques to adequately monitor renal function and microcirculation at the bedside makes its therapeutic resolution challenging. In this article, we review current concepts related to renal hemodynamics compromise as being the event underlying AKI. In doing so, we discuss the physiology of the renal circulation and the effects of alterations in systemic hemodynamics that lead to renal injury specifically in the context of reperfusion injury and sepsis. The ultimate key culprit of AKI leading to failure is the dysfunction of the renal microcirculation. The cellular and subcellular components of the renal microcirculation are discussed and how their injury contributes to AKI is described.

Antihypertensive Effects of Roselle-Olive Combination in L-NAME-Induced Hypertensive Rats

This study aimed to evaluate the antihypertensive efficacy of a new combination therapy of Hibiscus sabdariffa and Olea europaea extracts (2 : 1; Roselle-Olive), using N(G)-nitro-L-arginine-methyl ester- (L-NAME-) induced hypertensive model. Rats received L-NAME (50 mg/kg/day, orally) for 4 weeks. Concurrent treatment with Roselle-Olive (500, 250, and 125 mg/kg/day for 4 weeks) resulted in a dose-dependent decrease in both systolic and diastolic blood pressure, reversed the L-NAME-induced suppression in serum nitric oxide (NO), and improved liver and kidney markers, lipid profile, and oxidative status. Furthermore, Roselle-Olive significantly lowered the elevated angiotensin-converting enzyme activity (ACE) and showed a marked genoprotective effect against oxidative DNA damage in hypertensive rats. Roselle-Olive ameliorated kidney and heart lesions and reduced aortic media thickness. Real-time PCR and immunohistochemistry showed an enhanced endothelial nitric oxide synthase (eNOS) gene and protein expression in both heart and kidney of Roselle-Olive-treated rats. To conclude, our data revealed that Roselle-Olive is an effective combination in which H. sabdariffa and O. europaea synergistically act to control hypertension. These effects are likely to be mediated by antioxidant and genoprotective actions, ACE inhibition, and eNOS upregulation by Roselle-Olive constituents. These findings provide evidences that Roselle-Olive combination affords efficient antihypertensive effect with a broad end-organ protective influence.

Effects of Nitric Oxide on Renal Proximal Tubular Na+ Transport

Nitric oxide (NO) has a wide variety of physiological functions in the kidney. Besides the regulatory effects in intrarenal haemodynamics and glomerular microcirculation, in vivo studies reported the diuretic and natriuretic effects of NO. However, opposite results showing the stimulatory effect of NO on Na⁺ reabsorption in the proximal tubule led to an intense debate on its physiological roles. Animal studies have showed the biphasic effect of angiotensin II (Ang II) and the overall inhibitory effect of NO on the activity of proximal tubular Na⁺ transporters, the apical Na⁺/H⁺ exchanger isoform 3, basolateral Na⁺/K⁺ ATPase, and the Na⁺/HCO₃⁻ cotransporter. However, whether these effects could be reproduced in humans remained unclear. Notably, our recent functional analysis of isolated proximal tubules demonstrated that Ang II dose-dependently stimulated human proximal tubular Na⁺ transport through the NO/guanosine 3′,5′-cyclic monophosphate (cGMP) pathway, confirming the human-specific regulation of proximal tubular transport via NO and Ang II. Of particular importance for this newly identified pathway is its possibility of being a human-specific therapeutic target for hypertension. In this review, we focus on NO-mediated regulation of proximal tubular Na⁺ transport, with emphasis on the interaction with individual Na⁺ transporters and the crosstalk with Ang II signalling.

Urolithin A Mitigates Cisplatin-Induced Nephrotoxicity by Inhibiting Renal Inflammation and Apoptosis in an Experimental Rat Model

Cumulative kidney toxicity associated with cisplatin is severe and there is no clear consensus on the therapeutic management of the same. The pathogenesis involves activation of inflammatory and apoptotic pathways; therefore, regulating these pathways offers protection. Given the anti-inflammatory and antioxidant effects of urolithin A, a gut microbial metabolite of ellagic acid, our aim was to explore the potential use of urolithin A in the prevention of cisplatin-induced nephrotoxicity in an experimental rat model. For this purpose, animals received a single intraperitoneal dose of cisplatin (5 mg/kg body weight). Six hours prior to cisplatin administration, rats were orally treated with either ellagic acid or urolithin A (50 mg/kg body weight), followed by a daily dose of these compounds during the next 5 days. At the end, plasma and kidneys were collected for analysis. Cisplatin-induced kidney damage was revealed by a significant rise in the plasma creatinine levels accompanied by significant morphologic changes in tubules, T cell Ig and mucin domain-containing protein-1, ionized calcium-binding adapter molecule 1, as well as a marked increase in the number of apoptotic cells localized in tubules. Cisplatin also reduced nitric oxide synthase 3 and nuclear factor kappa-light-chain-enhancer of activated B cells resulting in regulation of various inflammatory cytokines. Urolithin A effectively attenuated cisplatin-induced kidney damage and showed significantly greater effect than its precursor ellagic acid on preserving the normal kidney architecture by downregulating the proinflammatory cytokines. In summary, urolithin A mitigates cisplatin-induced nephrotoxicity in rats by modulation of the inflammatory cascade and inhibition of the proapoptotic pathway.

The Endothelial Nitric Oxide Synthase Gene Polymorphism is Associated with the Susceptibility to Immunoglobulin a Nephropathy in Chinese Population

BACKGROUND/AIMS

Endothelial nitric oxide synthase (eNOS) is one of the most important enzymes for producting nitric oxide (NO), which regulate the function of many organs and cells. The single nucleotide polymorphisms (SNPs) of eNOS were found to be associated with many kidney diseases. However, it is lack of relevant studies to evaluate the associations between eNOS polymorphisms and immunoglobulin A nephropathy (IgAN). This case-control study aimed to evaluate the relationship between eNOS polymorphisms and IgAN.

METHODS

We recruited 351 IgAN patients and 310 age- and sex-matched healthy controls from Northwest China. Sequenom MassARRAY was used to detect the genotypes of two common eNOS SNPs (rs1799983 and rs2070744). Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by the Chi square test to evaluate the associations between eNOS and IgAN. Phase 2.1 was used to conduct haplotype analysis.

RESULTS

In the overall analysis, we found that the rs1799983 polymorphism was associated with a decreased risk of IgAN (G/T vs. G/G: OR=0.57, 95%CI=0.34-0.96; G/T+T/T vs. G/G: OR=0.52, 95%CI=0.31-0.86; G/T vs.

G/G-T/T

OR=0.60, 95%CI=0.36-0.99; Log-additive model: OR=0.48, 95%CI=0.30-0.78). Haplotype analysis indicated that Trs1799983Crs2070744 is a protective factor against IgAN (OR=0.62, 95%CI=0.42--0.92). However, no significant differences were found between the two SNPs (rs1799983 and rs2070744) and clinical features (age, sex, blood pressure, and Lee's grade) of IgAN.

CONCLUSION

The eNOS gene rs1799983 polymorphism and Trs1799983Crs2070744 haplotype may reduce the risk of IgAN in Chinese populations.

Restored nitric oxide bioavailability reduces the severity of acute-to-chronic transition in a mouse model of aristolochic acid nephropathy

Aristolochic Acid (AA) nephropathy (AAN) is a progressive tubulointerstitial nephritis characterized by an early phase of acute kidney injury (AKI) leading to chronic kidney disease (CKD). The reduced nitric oxide (NO) bioavailability reported in AAN might contribute to renal function impairment and progression of the disease. We previously demonstrated that L-arginine (L-Arg) supplementation is protective in AA-induced AKI. Since the severity of AKI may be considered a strong predictor of progression to CKD, the present study aims to assess the potential benefit of L-Arg supplementation during the transition from the acute phase to the chronic phase of AAN. C57BL/6J male mice were randomly subjected to daily i.p. injections of vehicle or AA for 4 days. To determine whether renal AA-induced injuries were linked to reduced NO production, L-Arg was added to drinking water from 7 days before starting i.p. injections, until the end of the protocol. Mice were euthanized 5, 10 and 20 days after vehicle or AA administration. AA-treated mice displayed marked renal injury and reduced NO bioavailability, while histopathological features of AAN were reproduced, including interstitial cell infiltration and tubulointerstitial fibrosis. L-Arg treatment restored renal NO bioavailability and reduced the severity of AA-induced injury, inflammation and fibrosis. We concluded that reduced renal NO bioavailability contributes to the processes underlying AAN. Furthermore, L-Arg shows nephroprotective effects by decreasing the severity of acute-to-chronic transition in experimental AAN and might represent a potential therapeutic tool in the future.

Endothelial dysfunction in renal arcuate arteries of obese Zucker rats: The roles of nitric oxide, endothelium-derived hyperpolarizing factors, and calcium-activated K+ channels

The roles of nitric oxide (NO), endothelium-derived hyperpolarizing factors (EDHF), and calcium-activated K⁺ (K_Ca) channels in diabetes-associated endothelial dysfunction of small renal arteries are not clear. The present study investigated acetylcholine (ACh)-induced vasorelaxation of renal arcuate arteries from obese Zucker (OZ) rats at different diabetes durations, and the relative contribution of NO, EDHF, and K_Ca channels to the endothelial dysfunction. OZ rats of 7 weeks (prediabetic stage), 12 weeks (early diabetic stage), and 20 weeks (late diabetic stage), and time-matched lean control rats, were studied. Segments of arcuate arteries (130 to 180 μm) were isolated, cannulated and pressurized. Vascular endothelial functions were tested using ACh-induced vasodilation. Our experiments demonstrated: (1) ACh-elicited vasodilation was impaired in OZ rats of 20 weeks, but not in rats of 7 and 12 weeks; (2) inhibition of NO or EDHF (contributed by epoxyeicosatrienoic acids [EETs]) production significantly decreased ACh-induced vasodilation in both lean and OZ rats of 20 weeks. The reduction of ACh-induced vasodilation by inhibition of NO or EDHF formation was less in OZ rats, as compared to lean rats; and (3) inhibition of K_Ca channels markedly reduced ACh-induced vasodilation in lean control rats, but not in OZ rats of 20 weeks. Our observations indicated that endothelium-dependent vasodilation in renal arcuate arteries is impaired in diabetes mellitus; NO and EDHF, mainly EETs, dominate the ACh-induced vasodilation in renal arcuate arteries; the contribution of NO and EETs is impaired in diabetic rats; K_Ca channels are involved in ACh-induced vasodilation; and the activity of K_Ca channels is downregulated in diabetes mellitus.

The Protective Effect of L-arginine in Cisplatin-induced Nephrotoxicity in Streptozotocin-induced Diabetic Rats

Background:

Cisplatin (CP) is accompanied with a nephrotoxicity. L-arginine (LA) plays an important role in the regulation of renal function. The present study was designed to investigate the protective role of LA supplementation in CP-induced nephrotoxicity in a diabetic rat's model.

Materials and Methods:

Sixteen adult female and male Wistar rats were used and they received a single dose of streptozotocin (STZ) (60 mg/kg i.p.). Diabetic female and male rats were arranged as groups 1–5 and groups 6–10, respectively. Groups 1 and 6 (LA groups) received LA alone. Groups 2 and 7 (CP groups) received CP alone. Groups 3 and 8 (CP + LA [PT] groups) received LA as prophylaxis and then treated with LA and CP. Groups 4 and 9 (CP + LA [T] groups) were treated with LA and CP simultaneously. Groups 5 and 10 (CP + LA [P] groups) received LA as prophylaxis and then treated with CP.

Results:

The serum creatinine (Cr) level of males in Groups 8 and 9 was significantly increased when compared with LA and CP (P < 0.05), whereas no differences were observed in Cr level in female groups. Blood urea nitrogen/Cr ratio and kidney weight were reduced in all CP-receiving male rats. Such observation was not seen in female rats. Different results related to weight loss were obtained between male and female animals. The kidney tissue damage score in CP + LA (PT) male group was significantly greater than CP group (P < 0.05).

Conclusion:

Our findings indicate that administration of LA in female and male rats has no protective effect on the severity of nephrotoxicity induced by CP in diabetic rats.

Regulation of Chemokine Function: The Roles of GAG-Binding and Post-Translational Nitration

The primary function of chemokines is to direct the migration of leukocytes to the site of injury during inflammation. The effects of chemokines are modulated by several means, including binding to G-protein coupled receptors (GPCRs), binding to glycosaminoglycans (GAGs), and through post-translational modifications (PTMs). GAGs, present on cell surfaces, bind chemokines released in response to injury. Chemokines bind leukocytes via their GPCRs, which directs migration and contributes to local inflammation. Studies have shown that GAGs or GAG-binding peptides can be used to interfere with chemokine binding and reduce leukocyte recruitment. Post-translational modifications of chemokines, such as nitration, which occurs due to the production of reactive species during oxidative stress, can also alter their biological activity. This review describes the regulation of chemokine function by GAG-binding ability and by post-translational nitration. These are both aspects of chemokine biology that could be targeted if the therapeutic potential of chemokines, like CXCL8, to modulate inflammation is to be realised.

Chemical composition and diuretic, natriuretic and kaliuretic effects of extracts of Mimosa bimucronata (DC.) Kuntze leaves and its majority constituent methyl gallate in rats

Objectives

Some species of the genus Mimosa showed promising results in previous investigations, which include diuretic effect; however, no chemical analyses or animal model has been conducted so far to evaluate the biological properties of M. bimucronata.

Methods

Male Wistar rats received the oral treatment with vehicle; hydrochlorothiazide; methanolic extract from M. bimucronata (MEMB), dichloromethane (DCM) and ethyl acetate (EA) fractions or methyl gallate (MG). The cumulative urine volume, electrolytes excretion, pH and osmolality were determined at the end of the experiment.

Key findings

The chemical studies demonstrated that the phenolic compounds are the majorities in the plant, with the MG being the main substance identified. We showed that MEMB and EA fraction, but not DCM, exhibited diuretic and saluretic effects. Similarly, the MG also revealed diuretic, natriuretic and kaliuretic properties to both normotensive and spontaneously hypertensive rats. Atropine, a muscarinic receptor antagonist, fully prevented MG-induced diuresis and saluresis. In addition, MG did not alter the viability of A7r5 and L929 cell lines and neither stimulated nitric oxide generation.

Conclusions

These findings suggest that M. bimucronata extracts and its majority compound MG present diuretic, natriuretic and kaliuretic properties, which was dependent on the activation of muscarinic acetylcholine receptor.

Inhaled nitric oxide prevents NSAID-induced renal impairment in pseudo-normovolaemic piglets

Objective

Inhaled nitric oxide (iNO) is commonly used as a treatment of pulmonary hypertension. Its action is purported to be specific to the lung, but extrapulmonary effects have been reported. The objective of this study was to evaluate if iNO could compensate the renal impairment induced by ketoprofen, a conventional non-steroidal anti-inflammatory drug (NSAID), during general anaesthesia.

Methods

Under pseudo-normovolaemic condition, thirty piglets were randomly assigned into 5 equal groups and equipped for renal and systemic parameters measurements. A first experiment was carried out to validate methods and reproduce the renal effects of iNO (40 ppm) in comparison with a placebo (100% oxygen). In a second experiment, iNO was inhaled for 120 minutes right after NSAID treatment (ketoprofen 2 mg×kg^-1 IV, and 40 ppm iNO; group KiNO) and its effects were compared to ketoprofen alone (2 mg×kg^-1 IV; group K) and placebo (saline; group C).

Results

In this model, iNO increased significantly renal blood flow measured by ultrasonic (RBF_UL: +53.2±17.2%; p = 0.008) and by PAH clearance (RBF_PAH:+78.6±37.6%; p = 0.004) methods, glomerular filtration rate (GFR: +72.6±32.5%; p = 0.006) and urinary output (UO: +47.4±24.2%; p = 0.01). In the second experiment, no significant temporal variation was noted for renal parameters in groups KiNO and C, whereas a significant and constant decrease was observed in the group K for RBF_UL (max -19.0±7.1%), GFR (max -26.6±10.4%) and UO (max -30.3±10.5%).

Clinical significance

Our experiments show that iNO, released from its transport forms after its inhalation, can improve renal safety of NSAIDs. This result is promising regarding the use of NSAIDs in critical conditions, but needs to receive clinical confirmation.

Protective Effect of Edaravone Against Cyclosporine-Induced Chronic Nephropathy Through Antioxidant and Nitric Oxide Modulating Pathways in Rats

BACKGROUND

Cyclosporine A (CsA) is an immunosuppressant with therapeutic indications in various immunological diseases; however, its use is associated with chronic nephropathy. Oxidative stress has a crucial role in CsA-induced nephrotoxicity. The present study evaluates the protective effect of edaravone on CsA-induced chronic nephropathy and investigates its antioxidant and nitric oxide modulating property.

METHODS

Male Sprague-Dawley rats (n=66) were distributed into nine groups, including a control (group 1) (n=7). Eight groups received CsA (15 mg/kg) for 28 days while being treated. The groups were categorized as: Group 2: Vehicle (n=10)Groups 3, 4, and 5: Edaravone (1, 5, and 10 mg/kg) (n=7 each)Group 6: Diphenyliodonium chloride, a specific endothelial nitric oxide synthase (eNOS) inhibitor (n=7)Group 7: Aminoguanidine, a specific inducible nitric oxide synthase (iNOS) inhibitor (n=7)Group 8: Edaravone (10 mg/kg) plus diphenyliodonium chloride (n=7)Group 9: Edaravone (10 mg/kg) plus aminoguanidine (n=7) Blood urea nitrogen and serum creatinine levels, malondialdehyde, superoxide dismutase, and glutathione reductase enzyme activities were measured using standard kits. Renal histopathological evaluations and measurements of eNOS and iNOS gene expressions by RT-PCR were also performed. Data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey's test (SPSS software version 18.0).

RESULTS

Edaravone (10 mg/kg) significantly attenuated CsA-induced oxidative stress, renal dysfunction, and kidney tissue injury. Aminoguanidine improved the renoprotective effect of edaravone. Edaravone reduced the elevated mRNA level of iNOS, but could not alter the level of eNOS mRNA significantly.

CONCLUSION

Edaravone protects against CsA-induced chronic nephropathy using antioxidant property and probably through inhibiting iNOS gene expression.

Post-translational regulation of neuronal nitric oxide synthase: implications for sympathoexcitatory states

INTRODUCTION

Nitric oxide (NO) synthesized via neuronal nitric oxide synthase (nNOS) plays a significant role in regulation/modulation of autonomic control of circulation. Various pathological states are associated with diminished nNOS expression and blunted autonomic effects of NO in the central nervous system (CNS) including heart failure, hypertension, diabetes mellitus, chronic renal failure etc. Therefore, elucidation of the molecular mechanism/s involved in dysregulation of nNOS is essential to understand the pathogenesis of increased sympathoexcitation in these diseased states. Areas covered: nNOS is a highly regulated enzyme, being regulated at transcriptional and posttranslational levels via protein-protein interactions and modifications viz. phosphorylation, ubiquitination, and sumoylation. The enzyme activity of nNOS also depends on the optimal concentration of substrate, cofactors and association with regulatory proteins. This review focuses on the posttranslational regulation of nNOS in the context of normal and diseased states within the CNS. Expert opinion: Gaining insight into the mechanism/s involved in the regulation of nNOS would provide novel strategies for manipulating nNOS directed therapeutic modalities in the future, including catalytically active dimer stabilization and protein-protein interactions with intracellular protein effectors. Ultimately, this is expected to provide tools to improve autonomic dysregulation in various diseases such as heart failure, hypertension, and diabetes.

Effects of asymmetric dimethylarginine on renal arteries in portal hypertension and cirrhosis

AIM

To evaluate the effects of asymmetric dimethylarginine (ADMA) in renal arteries from portal hypertensive and cirrhotic rats.

METHODS

Rat renal arteries from Sham (n = 15), pre-hepatic portal hypertension (PPVL; n = 15) and bile duct ligation and excision-induced cirrhosis (BDL; n = 15) were precontracted with norepinephrine, and additional contractions were induced with ADMA (10^-6-10^-3 mol/L), an endogenous inhibitor of nitric oxide (NO) synthase. Concentration-response curves to acetylcholine (1 × 10^-9-3 × 10^-6 mol/L) were determined in precontracted renal artery segments with norepinephrine in the absence and in the presence of ADMA. Kidneys were collected to determine the protein expression and activity of dimethylarginine dimethylaminohydrolase (DDAH), an enzyme that catabolizes ADMA.

RESULTS

In renal arteries precontracted with norepinephrine, ADMA caused endothelium-dependent contractions. The pD₂ values to ADMA were similar in the Sham and PPVL groups (4.20 ± 0.08 and 4.11 ± 0.09, P > 0.05, respectively), but were lower than those of the BDL group (4.79 ± 0.16, P < 0.05). Acetylcholine-induced endothelium-dependent relaxation that did not differ, in terms of pD₂ and maximal relaxation, among the 3 groups studied. Treatment with ADMA (3 × 10^-4 mol/L) inhibited acetylcholine-induced relaxation in the 3 groups, but the inhibition was higher (P < 0.05) in the BDL group compared with that for the Sham and PPVL groups. The mRNA and protein expression of DDAH-1 were similar in kidneys from the three groups. Conversely, DDAH-2 expression was increased (P < 0.05) in PPVL and further enhanced (P < 0.05) in the BDL group. However, renal DDAH activity was significantly decreased in the BDL group.

CONCLUSION

Cirrhosis increased the inhibitory effect of ADMA on basal- and induced-release of NO in renal arteries, and decreased DDAH activity in the kidney.

The gene-expression profile of renal medulla in ISIAH rats with inherited stress-induced arterial hypertension

Background

The changes in the renal function leading to a reduction of medullary blood flow can have a great impact on sodium and water homeostasis and on the long-term control of arterial blood pressure. The RNA-Seq approach was used for transcriptome profiling of the renal medulla from hypertensive ISIAH and normotensive WAG rats to uncover the genetic basis of the changes underlying the renal medulla function in the ISIAH rats being a model of the stress-sensitive arterial hypertension and to reveal the genes which possibly may contribute to the alterations in medullary blood flow.

Results

Multiple DEGs specifying the function of renal medulla in ISIAH rats were revealed. The group of DEGs described by Gene Ontology term ‘oxidation reduction’ was the most significantly enriched one. The other groups of DEGs related to response to external stimulus, response to hormone (endogenous) stimulus, response to stress, and homeostatic process provide the molecular basis for integrated responses to homeostasis disturbances in the renal medulla of the ISIAH rats. Several DEGs, which may modulate the renal medulla blood flow, were detected. The reduced transcription of Nos3 pointed to the possible reduction of the blood flow in the renal medulla of ISIAH rats.

Conclusions

The generated data may be useful for comparison with those from different models of hypertension and for identifying the common molecular determinants contributing to disease manifestation, which may be potentially used as new pharmacological targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-016-0462-6) contains supplementary material, which is available to authorized users.

Asymmetric Dimethylarginine and Its Relation As a Biomarker in Nephrologic Diseases

It is encouraging to observe that a search for publications on "asymmetric dimethylarginine (ADMA)" in PubMed, as updated on June 2016, yielded >2500 items, 24 years after a splendid paper published by Vallance et al in which the authors proposed that ADMA accumulation could be a cardiovascular risk factor in chronic kidney diseases. ADMA is the endogenous inhibitor of nitric oxide synthase and is related to endothelial dysfunction, which plays an important role in vascular damage elicited by various cardiometabolic risk factors. Although current knowledge suggests that ADMA has critical central roles in renal diseases, there are still unexplained details. The present article aims to provide a review on ADMA and its relation as a biomarker in nephrologic diseases. We aimed to systematize articles in which ADMA levels were assessed in order to clarify its role in many diseases and establish its reference values in different populations.

A simple method to ensure homogeneous drug distribution during intrarenal infusion

Intrarenal drug infusion plays an important role in renal experimental research. Laminar flow of the blood can cause streaming and inhomogeneous intrarenal distribution of infused drugs. We suggest a simple method to achieve a homogeneous intravascular distribution of drugs infused into the renal artery of anesthetized rats. The method employs a multiple sidehole catheter inserted into the renal artery, which enables an efficient drug mixing with the arterial blood. To verify the efficiency of this method, we use laser speckle imaging and renal artery flowmetry. The results show that, compared with the conventional single-hole catheter, the multiple sidehole catheter provides a more uniform drug distribution and a homogenous vascular response on the surface of the kidney.

Cortisol regulates nitric oxide synthase in freshwater and seawater acclimated rainbow trout, Oncorhynchus mykiss

Cortisol and nitric oxide (NO) are regulators of ion transport and metabolic functions in fish. In the gill, they show opposite effects on Na⁺/K⁺-ATPase (NKA) activity: cortisol stimulates NKA activity while NO inhibits NKA activity. We hypothesized that cortisol may impact NO production in osmoregulatory tissues by regulating NO synthase (NOS) expression. We evaluated the influence of cortisol treatment on mRNA expression of Nos1 and Nos2 in gill, kidney and middle intestine of both freshwater (FW) and seawater (SW) acclimated rainbow trout and found both tissue- and salinity-dependent effects. Nos2 expression was down-regulated in the gill by cortisol injection in both FW and SW trout. This was substantiated by incubating gill tissue with cortisol ex vivo. Similarly, cortisol injection significantly down-regulated Nos2 expression in kidney of SW fish but not in FW fish. In the middle intestine, Nos2 expression was up-regulated by cortisol injection in FW but unchanged in SW fish. Nos1 expression was up-regulated by cortisol injection in FW kidney and down-regulated in SW kidney, whereas it was unaffected in gill and middle intestine of FW and SW fish. Our data provide the first evidence that cortisol may influence NO production in fish by regulating Nos expression. Indeed, the down-regulation of Nos2 expression by cortisol in the gill may prevent the inhibitory effect of NO on NKA activity thereby furthering the stimulatory effect of cortisol on ion-transport.

Angiotensin II stimulates superoxide production by nitric oxide synthase in thick ascending limbs

Angiotensin II (Ang II) causes nitric oxide synthase (NOS) to become a source of superoxide (O2 (-)) via a protein kinase C (PKC)-dependent process in endothelial cells. Ang II stimulates both NO and O2 (-) production in thick ascending limbs. We hypothesized that Ang II causes O2 (-) production by NOS in thick ascending limbs via a PKC-dependent mechanism. NO production was measured in isolated rat thick ascending limbs using DAF-FM, whereas O2 (-) was measured in thick ascending limb suspensions using the lucigenin assay. Consistent stimulation of NO was observed with 1 nmol/L Ang II (P < 0.001; n = 9). This concentration of Ang II-stimulated O2 (-) production by 50% (1.77 ± 0.26 vs. 2.62 ± 0.36 relative lights units (RLU)/s/μg protein; P < 0.04; n = 5). In the presence of the NOS inhibitor L-NAME, Ang II-stimulated O2 (-) decreased from 2.02 ± 0.29 to 1.10 ± 0.11 RLU/s/μg protein (P < 0.01; n = 8). L-arginine alone did not change Ang II-stimulated O2 (-) (2.34 ± 0.22 vs. 2.29 ± 0.29 RLU/s/μg protein; n = 5). In the presence of Ang II plus the PKC α/β1 inhibitor Gö 6976, L-NAME had no effect on O2 (-) production (0.78 ± 0.23 vs. 0.62 ± 0.11 RLU/s/μg protein; n = 7). In the presence of Ang II plus apocynin, a NADPH oxidase inhibitor, L-NAME did not change O2 (-) (0.59 ± 0.04 vs. 0.61 ± ×0.08 RLU/s/μg protein; n = 5). We conclude that: (1) Ang II causes NOS to produce O2 (-) in thick ascending limbs via a PKC- and NADPH oxidase-dependent process; and (2) the effect of Ang II is not due to limited substrate.