Effects of radical scavengers and antioxidant on ischemic acute renal failure in rabbits

Exploring the therapeutic potential of sodium benzoate in acetic acid-induced ulcerative colitis in rats

Background Ulcerative colitis is a chronic mucosal inflammation of the large intestine mainly affecting the colon and rectum. The lack of effective and safe therapeutic agents led to the identification of new therapeutic agents to effectively manage the symptoms and complications of ulcerative colitis. The present study aimed to evaluate the protective effect of sodium benzoate in acetic acid-induced ulcerative colitis in rats. Methods Infusion of 3% acetic acid in the colon through the rectum was done to construct a rat model of ulcerative colitis. After 5 days of infusion, macroscopic, biochemical, and histopathological examinations and disease activity scoring of the colon were done to assess colonic damage. Results Acetic acid infusion resulted in severe inflammation in the colon assessed macroscopically and histopathologically. Moreover, it also led to increase in myeloperoxidase (MPO) and reduction in glutathione (GSH) levels. In the present study, repeated administration of sodium benzoate (400 and 800 mg/kg i.p.) and sulfasalazine (500 mg/kg orally) for 7 days, i.e. 2 days before and continued for 5 days after acetic acid infusion, significantly attenuated macroscopic damage and disease activity score as compared to disease control. Further, it also significantly reduced the levels of MPO and enhanced colonic levels of reduced GSH. However, the lower dose of sodium benzoate (200 mg/kg) did not show sufficient protective effect in acetic acid-induced ulcerative colitis. Further, sodium benzoate per se did not show any effect in normal rats. Conclusions The observed protective effect of sodium benzoate may be due to its antioxidant and anti-inflammatory activities in an ulcerative colitis model.

Cardio-protective and antioxidant properties of caffeic acid and chlorogenic acid: Mechanistic role of angiotensin converting enzyme, cholinesterase and arginase activities in cyclosporine induced hypertensive rats

Caffeic acid (CAA) and chlorogenic acid (CHA) are important members of hydroxycinnamic acid with natural antioxidant and cardio-protective properties. The present study aimed to determine the effect of CAA and CHA on systolic blood pressure, heart rates (HR) as well as on the activity of the angiotensin-1-converting enzyme (ACE), acetylcholinesterase (AChE), butrylcholinesterase (BChE) and arginase in cyclosporine-induced hypertensive rats. Experimental rats were distributed into 7 groups (n = 6): normotensive control rats; hypertensive rats (induced rats) as well as hypertensive- treated groups with captopril (10 mg/kg/day), CAA (10 and 15 mg/kg/day) and CHA (10 and 15 mg/kg/day), respectively. The experiment lasted for 7 days and the systolic blood pressure (SBP) and heart rates were recorded using tail-cuff method. Oral administration of captopril, caffeic acid and chlorogenic acid normalized hypertensive effect caused by cyclosporine administration. CAA and CHA significantly (P < 0.05) reduced SBP and HR, activity of ACE, AChE, BChE and arginase in the treated hypertensive rats compared with cyclosporine induced-hypertensive rats. Likewise, CAA and CHA improved nitric oxide (NO) bioavailability, increased catalase activity and reduced glutathione content while malondialdehyde (MDA) level was reduced compared with cyclosporine hypertensive rats. Findings from this study shows that CAA and CHA exhibited blood pressure lowering properties and reduced activities of key enzymes linked to the pathogenesis of hypertension in cyclosporine-induced rats. These might be some of the possible mechanisms of action by which their cardio-protective properties are exhibited.

Food additives such as sodium sulphite, sodium benzoate and curcumin inhibit leptin release in lipopolysaccharide-treated murine adipocytes in vitro

Obesity leads to the activation of pro-inflammatory pathways, resulting in a state of low-grade inflammation. Recently, several studies have shown that the exposure to lipopolysaccharide (LPS) could initiate and maintain a chronic state of low-grade inflammation in obese people. As the daily intake of food additives has increased substantially, the aim of the present study was to investigate a potential influence of food additives on the release of leptin, IL-6 and nitrite in the presence of LPS in murine adipocytes. Leptin, IL-6 and nitrite concentrations were analysed in the supernatants of murine 3T3-L1 adipocytes after co-incubation with LPS and the food preservatives, sodium sulphite (SS), sodium benzoate (SB) and the spice and colourant, curcumin, for 24 h. In addition, the kinetics of leptin secretion was analysed. A significant and dose-dependent decrease in leptin was observed after incubating the cells with SB and curcumin for 12 and 24 h, whereas SS decreased leptin concentrations after 24 h of treatment. Moreover, SS increased, while curcumin decreased LPS-stimulated secretion of IL-6, whereas SB had no such effect. None of the compounds that were investigated influenced nitrite production. The food additives SS, SB and curcumin affect the leptin release after co-incubation with LPS from cultured adipocytes in a dose- and time-dependent manner. Decreased leptin release during the consumption of nutrition-derived food additives could decrease the amount of circulating leptin to which the central nervous system is exposed and may therefore contribute to an obesogenic environment.

Alterations in membrane transport function and cell viability induced by ATP depletion in primary cultured rabbit renal proximal tubular cells

This study was undertaken to elucidate the underlying mechanisms of ATP depletion-induced membrane transport dysfunction and cell death in renal proximal tubular cells. ATP depletion was induced by incubating cells with 2.5 mM potassium cyanide (KCN)/0.1 mM iodoacetic acid (IAA), and membrane transport function and cell viability were evaluated by measuring Na(+)-dependent phosphate uptake and trypan blue exclusion, respectively. ATP depletion resulted in a decrease in Na(+)-dependent phosphate uptake and cell viability in a time-dependent manner. ATP depletion inhibited Na(+)-dependent phosphate uptake in cells, when treated with 2 mM ouabain, a Na(+) pump-specific inhibitor, suggesting that ATP depletion impairs membrane transport functional integrity. Alterations in Na(+)-dependent phosphate uptake and cell viability induced by ATP depletion were prevented by the hydrogen peroxide scavenger such as catalase and the hydroxyl radical scavengers (dimethylthiourea and thiourea), and amino acids (glycine and alanine). ATP depletion caused arachidonic acid release and increased mRNA levels of cytosolic phospholipase A(2) (cPLA(2)). The ATP depletion-dependent arachidonic acid release was inhibited by cPLA(2) specific inhibitor AACOCF(3). ATP depletion-induced alterations in Na(+)-dependent phosphate uptake and cell viability were prevented by AACOCF(3). Inhibition of Na(+)-dependent phosphate uptake by ATP depletion was prevented by antipain and leupetin, serine/cysteine protease inhibitors, whereas ATP depletion-induced cell death was not altered by these agents. These results indicate that ATP depletion-induced alterations in membrane transport function and cell viability are due to reactive oxygen species generation and cPLA(2) activation in renal proximal tubular cells. In addition, the present data suggest that serine/cysteine proteases play an important role in membrane transport dysfunction, but not cell death, induced by ATP depletion.

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.

Neuroprotective effects of phenylenediamine derivatives independent of an antioxidant pathway in neuronal HT22 cells

Resistance to oxidative stress often determines neuronal survival in the brain. Thus, antioxidants are supposed to be promising neuroprotective compounds against neurodegenerative diseases. For example, N,N'-diphenyl-p-phenylenediamine (DPPD) reportedly exerts cytoprotective effects against oxidative stress possibly by acting as an antioxidant. DPPD can give electron(s) to free radicals and thus scavenge them, and protect the cells from oxidative stress. The antioxidative activities of DPPD are prominent at the micromolar order, but what about its effects at much lower concentrations? We concluded that DPPD has two actions on neuronal cells, antioxidant activity and an unknown neuroprotective effect, which are effective at micromolar and nanomolar levels, respectively. In the present report, we found that DPPD inhibited cell death caused by oxidative stress at nanomolar order (1/1000 lower than concentrations needed for antioxidant activity) and that the effects were independent of antioxidant activities. DPPD inhibited the oxidative glutamate toxicity but not the tumor necrosis factor alpha-, hydrogen peroxide-, or xanthine+xanthine oxidase-induced death of HT22 cells, a mouse neuronal cell line. DPPD and phenylenediamine derivatives protected HT22 cells against oxidative glutamate toxicity at nanomolar concentrations. By studying the structure-function relationship of these compounds, we found the structure of phenyl-amine-phenyl-amine-phenyl (or butyl) to be essential for the neuroprotective effects.

Yukmijihwang-tang ameliorates ischemia/reperfusion-induced renal injury in rats

The present study was designed to examine whether Yukmijihwang-tang (YJT), which is a Korean decoction for the treatment of renal disease, has an effect on renal functional parameters in association with the expression of aquaporin 2 (AQP 2), Na,K-ATPase, heme oxygenase-1 (HO-1) in rats with ischemia/reperfusion-induced acute renal failure (ARF). Polyuria caused by down-regulation of renal AQP 2 in the ischemia/reperfusion-induced ARF rats was markedly restored by administration of YJT (100 or 200 mg/kg, p.o.) with restoring expression of AQP 2 in the kidney. The expressions of Na,K-ATPase alpha1 and beta1 subunits in the renal medulla and cortex of the ARF rats were also restored in them by the administration of YJT. Administration of YJT lowered the expression of renal HO-1, which was up-regulated in rats with ischemia/reperfusion-induced ARF. The renal functional parameters including creatinine clearance, urinary sodium excretion, urinary osmolality, and solute-free reabsorption were also markedly restored in ischemia-ARF rats by administration of YJT. Histological study also showed that renal damages in the ARF rats were abrogated by administration of YJT. Taken together, these data indicate that YJT ameliorates renal defects in rats with ischemia/reperfusion-induced ARF.

Renal failure secondary to acute tubular necrosis: epidemiology, diagnosis, and management

Acute tubular necrosis (ATN) is a form of acute renal failure (ARF) that is common in hospitalized patients. In critical care units, it accounts for about 76% of cases of ARF. Despite the introduction of hemodialysis > 30 years ago, the mortality rates from ATN in hospitalized and ICU patients are about 37.1% and 78.6%, respectively. The purpose of this review is to discuss briefly the cause, diagnosis, and epidemiology of ARF, and to review in depth the clinical trials performed to date that have examined the influence of growth factors, hormones, antioxidants, diuretics, and dialysis. In particular, the role of the dialysis modality, dialyzer characteristics, and dosing strategies are discussed.

Sodium benzoate attenuates iminodipropionitrile-induced behavioral syndrome in rats

This study reports the effects of the antioxidant sodium benzoate (SB) on iminodipropionitrile (IDPN)-induced excitation with choreiform and circling (ECC) syndrome in adult female Wistar rats. Rats in four different groups (n=8) received i.p. injections of SB (0, 50, 100 and 200 mg/kg) daily for 10 days. IDPN (100 mg/kg, i.p.) was administered daily 30 min before SB for the first 8 days. Two additional groups served as control (vehicle) and SB alone (200 mg/kg) groups. The animals were observed daily for neurobehavioral abnormalities, including dyskinetic head movements, circling, tail hanging, righting reflex and contact inhibition of the righting reflex, characterized as the ECC syndrome. In the IDPN-alone treated group, the onset of ECC syndrome occurred on day 9 (2 out of 8 rats), whereas none of the animals treated with IDPN plus SB (100 or 200 mg/kg) showed any signs of ECC syndrome on that day. All the animals in the IDPN-alone group developed severe dyskinesia on day 11. Treatment of rats with SB significantly and dose-dependently attenuated IDPN-induced behavioral deficits.

Lithospermic acid B isolated from Salvia miltiorrhiza ameliorates ischemia/reperfusion-induced renal injury in rats

The present study was designed to examine whether lithospermic acid B (LSB) isolated from Salvia miltiorrhiza has an ameliorative effect on renal functional parameters in association with the expression of aquaporin 2 (AQP 2) and Na,K-ATPase in the ischemia-reperfusion induced acute renal failure (ARF) rats. LSB showed strong antioxidant activity against production of reactive oxygen species (ROS), ROS-induced hemolysis, and production of lipid peroxide in a dose-dependent manner. Polyuria caused by down-regulation of renal AQP 2 in the ischemia-reperfusion induced ARF rats was partially restored by administration of LSB (40 mg/kg, i.p.), restoring expression of AQP 2, in renal inner and outer medulla. The expression of Na,K-ATPase alpha1 subunit in outer medulla of the ARF rats was also restored in the ARF rats by administration of LSB, while beta1 subunit level was not altered. The renal functional parameters including creatinine clearance, urinary sodium excretion, urinary osmolality, and solute-free reabsorption were also partially restored in ischemia-ARF rats by administration of LSB. Histological study also showed that renal damages in the ARF rats were abrogated by administration of LSB. Taken together, these data indicate that LSB ameliorates renal defects in rats with ischemia-reperfusion induced ARF, most likely via scavenging of ROS.

TEMPONE reduces renal dysfunction and injury mediated by oxidative stress of the rat kidney

Here we investigate the effects of the stable, water-soluble nitroxyl radical, TEMPONE, on renal dysfunction and injury caused by ischemia/reperfusion (I/R) of the rat kidney in vivo. TEMPONE significantly improved both glomerular and tubular function (serum urea, creatinine, creatinine clearance, and fractional excretion of Na(+)) in a dose-dependent manner and significantly attenuated the reperfusion-injury associated with I/R (urinary N-acetyl-beta-D-glucosaminidase, aspartate aminotransferase, assessment of renal histology). TEMPONE also markedly reduced the immunohistochemical evidence of the formation of nitrotyrosine and poly(ADP-ribose), indicating reduction of nitrosative and oxidative stress, respectively. The latter was reflected in vitro, where TEMPONE significantly reduced cellular injury of primary cultures of rat renal proximal tubular (PT) cells caused by hydrogen peroxide in a dose-dependent manner. Importantly, in contrast to its in vivo metabolite TEMPOL (which also provided protective effects against renal I/R and oxidative stress of PT cells), TEMPONE reduced renal dysfunction and injury without causing a significant reduction in blood pressure upon administration. These results suggest, for the first time, that TEMPONE can reduce the renal dysfunction and injury caused by I/R and the injury caused to PT cells by oxidative stress without producing the adverse cardiovascular effects observed when using other nitroxyl radicals.

Protective effect of alpha-lipoic acid against ischaemic acute renal failure in rats

1. In the present study, we investigated whether treatment with alpha-lipoic acid (LA), a powerful and universal anti-oxidant, has renal protective effects in rats with ischaemic acute renal failure (ARF). 2. Ischaemic ARF was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Blood urea nitrogen (BUN), plasma concentrations of creatinine (Pcr) and urinary osmolality (Uosm) were measured for the assessment of renal dysfunction. Creatinine clearance (Ccr) and fractional excretion of Na+ (FENa) were used as indicators of glomerular and tubular function, respectively. 3. Renal function in ARF rats decreased markedly 24 h after reperfusion. Intraperitoneal injection of LA at a dose of 10 mg/kg before the occlusion tended to attenuate the deterioration of renal function. A higher dose of LA (100 mg/kg) significantly (P < 0.01) attenuated the ischaemia/reperfusion-induced increases in BUN (19.1 +/- 0.7 vs 7.2 +/- 0.7 mmol/L before and after treatment, respectively), Pcr (290 +/- 36 vs 78.1 +/- 4.2 micromol/L before and after treatment, respectively) and FENa (1.39 +/- 0.3 vs 0.33 +/- 0.09% before and after treatment, respectively). Treatment with 100 mg/kg LA significantly (P < 0.01) increased Ccr (0.70 +/- 0.13 vs 2.98 +/- 0.27 mL/min per kg before and after treatment, respectively) and Uosm (474 +/- 39 vs 1096 +/- 80 mOsmol/kg before and after treatment, respectively). 4. Histopathological examination of the kidney of ARF rats revealed severe lesions. Tubular necrosis (P < 0.01), proteinaceous casts in tubuli (P < 0.01) and medullary congestion (P < 0.05) were significantly suppressed by the higher dose of LA. 5. A marked increase in endothelin (ET)-1 content in the kidney after ischaemia/reperfusion was evident in ARF rats (0.43 +/- 0.02 ng/g tissue) compared with findings in sham- operated rats (0.20 +/- 0.01 ng/g tissue). Significant attenuation (P < 0.01) of this increase occurred in ARF rats treated with the higher dose of LA (0.24 +/- 0.03 ng/g tissue). 6. These results suggest that administration of LA to rats prior to development of ischaemic ARF prevents renal dysfunction and tissue injury, possibly through the suppression of overproduction of ET-1 in the postischaemic kidney.

Effect of pentoxifylline on ischemic acute renal failure in rabbits

Previous studies have demonstrated that levels of tumor necrosis factor-alpha (TNF-alpha) or its mRNA expression are increased in acute renal failure of various types including ischemia/reperfusion injury. This study was undertaken to determine whether pentoxifylline (PTX), an inhibitor of TNF-alpha production, provides a protective effect against ischemic acute renal failure in rabbits. Renal ischemia was induced by clamping bilateral renal arteries for 60 min. Animals were pretreated with PTX (30 mg/kg, i.v.) 10 min before release of clamp. At 24 h of reperfusion of blood after ischemia, changes in renal function, renal blood flow, and the expression of TNF-alpha mRNA were evaluated. Ischemia/reperfusion caused a marked reduction in GFR, which was accompanied by an increase of serum creatinine levels. Such changes were significantly attenuated by PTX pretreatment. PTX ameliorated the impairment of renal tubular function, but it had no effect on the reduction of renal blood flow induced by ischemia/reperfusion. The protective effect of PTX on functional changes was supported by morphological studies. The impairment of glucose and phosphate reabsorption in postischemic kidneys was associated with a depression in the expression of Na+-glucose and Na+-Pi transporters. The expression of TNF-alpha mRNA was increased after reperfusion, which was inhibited by PTX pretreatment. The PTX pretreatment in vitro prevented the release of lactate dehydrogenase induced by an oxidant t-butylhydroperoxide in rabbit renal cortical slices, but it did not produce any effect on the oxidant-induced lipid peroxidation, suggesting that PTX protection is not resulted from its antioxidant action. These results suggest that PTX may exert a protective effect against ischemic acute renal failure by inhibiting the production of TNF-alpha in rabbits.

Role of lipid peroxidation and poly(ADP-ribose) polymerase activation in oxidant-induced membrane transport dysfunction in opossum kidney cells

This study was undertaken to examine the role of lipid peroxidation and poly(ADP-ribose) polymerase (PARP) activation in H(2)O(2)-induced inhibition of Na(+)-dependent phosphate (Na(+)-Pi) uptake in opossum kidney (OK) cells. H(2)O(2) inhibited Na(+)-Pi uptake in a dose-dependent manner. H(2)O(2)-induced inhibition of Na(+)-Pi uptake was prevented by dithiothreitol and glutathione. A potent antioxidant, DPPD, had no effect on H(2)O(2) inhibition of Na(+)-Pi uptake, despite completely inhibiting lipid peroxidation induced by H(2)O(2). However, in primary cultured rabbit proximal tubular cells, the effect of H(2)O(2) on Na(+)-Pi uptake was significantly prevented by DPPD, suggesting a species difference in the role of lipid peroxidation in the inhibition of Na(+)-Pi uptake occurring with H(2)O(2). t-Butylhydroperoxide (tBHP) caused the inhibition of Na(+)-Pi uptake that was prevented by DPPD in OK cells and rabbit proximal tubular cells. The PARP inhibitor 3-aminobenzamide completely protected the inhibition of Na(+)-Pi uptake induced by H(2)O(2) but not by tBHP. H(2)O(2)-induced ATP depletion was prevented by 3-aminobenzamide but not by DPPD. tBHP-induced ATP depletion was prevented by DPPD, whereas it was not altered by 3-aminobenzamide. Effects of H(2)O(2) and tBHP on Na(+)-Pi uptake and ATP depletion were prevented by an iron chelator, deferoxamine, suggesting that the oxidants inhibit Na(+)-Pi uptake through an iron-dependent mechanism. The extent of DNA damage by tBHP was similar to that by H(2)O(2). These results indicate that the effect of H(2)O(2) on membrane transport function in OK cells is associated with PARP activation but not lipid peroxidation, whereas the effect of tBHP is associated with lipid peroxidation.