Effect of pentoxifylline on cyclosporine-induced nephrotoxicity in rats

Effect of unique hemorrheologic agent pentoxifylline (PTX) was investigated on cyclosporine (CsA) induced nephrotoxicity in rats. Compared to saline control, CsA produced significant increase in blood urea and serum creatinine. Pentoxifylline treatment prevented the CsA-induced rise in blood urea and serum creatinine. Creatinine clearance (Ccr) and lithium clearance (Licr) was decreased with CsA. PTX treatment prevented the CsA-induced decrease in Ccr and Licr. Malondialdehyde (MDA) was increased with CsA compared to saline treated animals. PTX prevented the CsA-induced MDA rise. Kidney form CsA treated rat showed marked vacuolar degeneration of tubular epithelium with excess of microcalcification. Severity of the lesions was markedly reduced in rats treated with PTX plus CsA. The results indicate that PTX reduces CsA-induced renal toxicity in rats.     

Role of prostanoids and endothelins in the prevention of cyclosporine-induced nephrotoxicity.

Cyclosporine A nephrotoxicity includes both functional toxicity and histological changes, whose seriousness is dependent upon the dose and the duration of the drug administration. Several vasoactive agents have been found to be implicated in cyclosporine induced nephrotoxicity, among which prostanoids and endothelins are the most important. In previous studies we were able to prevent the early stage (7 days) of cyclosporine (37.4 micromol [45 mg]/kg/day) induced nephrotoxicity in rats either by the administration, i) of OKY-046, a thromboxane A(2)synthase inhibitor, ii) of ketanserine, an antagonist of S(2)serotonergic, a(1)adrenergic, and H(1)histaminergic receptors and iii) of nifedipine, a calcium channel blocker, or by diet supplementation either with evening primrose oil or fish oil. All these protective agents elevated ratios of excreted renal prostanoid vasodilators (prostaglandins E(2), 6ketoF(1 alpha)) to vasoconstrictor (thromboxane B(2)), a ratio which was decreased by the administration of cyclosporine alone. Nifedipine averted the cyclosporine induced increase of urinary endothelin-1 release. All protections were associated with the reinstatement of glomerular filtration rate forwards normal levels whereas renal damage defence, consisting of a decrease of the cyclosporine induced vacuolizations, was variable. Ketanserine and evening primrose oil were the only agents which prevented the animal body weight loss. These data suggest that prostanoids and endothelin-1 may mediate functional toxicity while thromboxane A(2)is involved the morphological changes too, provoked in the early stage of cyclosporine treatment. However, other nephrotoxic factors and additional mechanisms could also be implicated in the cyclosporine induced nephrotoxicity.     

Melatonin prevents cyclosporine-induced nephrotoxicity in isolated and perfused rat kidney

Cyclosporine A (CsA) is a potent and effective immunosuppressive agent, but its action is frequently accompanied by severe renal toxicity. The precise mechanism by which CsA causes renal injury is not known. Reactive oxygen species (ROS) have been shown to play a role, since CsA-induced renal lipid peroxidation is attenuated in vivo and in vitro by the concomitant administration of antioxidants such as vitamin E. We show here the effect of the antioxidant melatonin (MLT), a hormone produced by the pineal gland during the dark phase of the circadian cycle, in a model of CsA nephrotoxicity in the isolated and perfused rat kidney. Kidneys isolated from rats were divided into seven groups. At the end of perfusion, malondialdehyde and 4-hydroxyalkenals (MDA+4-HDA), metabolites of nitric oxide N O 2 - +N O 3 - were measured and histopathological examination was performed. CsA treatment induced a significant increase in MDA+4-HDA while not affecting the nitric oxide metabolite level. MLT remarkably prevented glomerular collapse and tubular damage as revealed by morphometric analysis. Our study suggests that lipid peroxidation is an early important event in the pathogenesis of CsA nephrotoxicity and that MLT is able to protect kidneys from CsA at a relatively low concentration.     

Effects of endothelin receptor blockade on hypervasoreactivity in streptozotocin-diabetic rats: vessel-specific involvement of thromboxane A2

Increased vasoconstrictor response to norepinephrine (NE) and endothelin (ET)-1 in arteries from diabetic animals is ameliorated by chronic endothelin receptor blockade with bosentan and was absent in endothelium-denuded arteries, suggesting the involvement of ET-1 and an endothelium-derived contracting factor such as thromboxane A2 (TxA2). To examine this possibility, we determined the effects of acute blockade of ET receptors or inhibition of TxA2 synthesis on the vascular function of superior mesenteric arteries (SMA) and renal arteries (RA) isolated from nondiabetic and 11-week streptozotocin (STZ) diabetic rats chronically treated with either bosentan or vehicle. Both in vitro incubation with bosentan and a selective ETA receptor blocker, BQ123, eradicated the increase in NE contractile responses in diabetic SMA. Additionally, in vitro incubation with the thromboxane synthase inhibitor, dazmegrel, abrogated the exaggerated NE and ET-1 contractile responses in diabetic SMA. Conversely, in RA, no significant acute effect of bosentan, BQ123, nor dazmegrel on vascular responses to NE was observed. Dazmegrel incubation attenuated the maximum contractile responses to ET-1 in diabetic RA; however, these responses in diabetic RA remained significantly greater than those of other groups. Diabetic RA but not SMA exhibited an enhanced contractile response to the TxA2 analogue U46619, which was corrected by chronic bosentan treatment. Immunohistochemical analyses in diabetic SMA revealed an increase in ETA receptor level that was normalized by chronic bosentan treatment. These data indicate that an interaction between ET-1 and TxA2 may be involved in mediating the exaggerated vasoconstrictor responses in diabetic arteries. Furthermore, the underlying mechanisms appear to be vessel specific.     

Red wine polyphenols prevent cyclosporine-induced nephrotoxicity at the level of the intrinsic apoptotic pathway

Flavonoids, polyphenol derivatives of plant origin, possess a broad range of pharmacological properties. A number of studies have found both pro/anti-apoptotic effects for many of these compounds. For these reasons we investigated whether Provinols flavonoids obtained from red wine, have anti-apoptotic properties. The investigations have been carried out in rats treated with Cyclosporine A (CsA). In particular, four groups of rats have been treated for 21 days with either olive oil (control group), with CsA, with Provinols, or with CsA and Provinols simultaneously. Oxidative stress, systolic blood pressure, body weight, biochemical parameters and different markers of pro/anti-apoptotic pathway were measured. CsA produced an increase of systolic blood pressure, a decrease in body weight, serum creatinine levels, urinary total protein concentration and creatinine clearance. Moreover, CsA induced renal alterations and the translocation of Bax and cytochrome c from cytoplasm to mitochondria and vice versa. These changes activated the caspase cascade pathway, that leads to morphological and biochemical features of apoptosis. Provinols restored morphological and biochemical alterations and prevented nephrotoxicity. In conclusion, this study may augment our current understanding of the controversial pro-/anti-apoptotic properties of flavonoids and their molecular mechanisms.     

Role of thromboxane receptor activation in the bronchospastic response to endothelin

The selective TxA₂/PGH₂ (TP) receptor antagonist, SQ 30, 741, was used to test the hypothesis that TP-receptor activation contributes to the reactivity of airways and isolated trachea to endothelin-1 (ET-1). Dose-dependent contractions of guinea pig tracheal strips to ET-1 in vitro were unaffected by either SQ 30, 741 (1 μM) or indomethacin (2.8 μM). In contrast, maximal bronchospastic responses (increases in airways resistance and decreases in dynamic lung compliance) of anesthetized guinea pigs to ET-1 (.05 and 1.5 nmole/kg i.v.) in vitro were blocked >90% by SQ 30, 741 (1 mg/kg i.v.). Concurrent increases in arterial blood pressure and decreases in leukocyte counts induced by ET-1 were unaffected by SQ 30, 741. In rats, ET-1 (1.5 nmole/kg i.v.) did not affect lung mechanics, but did cause biphasic blood pressure and leukopenia responses which were unaltered by SQ 30, 741. These data demonstrate that there is considerable species variability in the bronchospastic response to ET-1, and that in guinea pigs, this repsonse is caused predominantly by the activation of TP-receptors.     

Role of thromboxane receptor activation in the bronchospastic response to endothelin

The selective TxA2/PGH2 (TP) receptor antagonist, SQ 30,741, was used to test the hypothesis that TP-receptor activation contributes to the reactivity of airways and isolated trachea to endothelin-1 (ET-1). Dose-dependent contractions of guinea pig tracheal strips to ET-1 in vitro were unaffected by either SQ 30,741 (1 microM) or indomethacin (2.8 microM). In contrast, maximal bronchospastic responses (increases in airways resistance and decreases in dynamic lung compliance) of anesthetized guinea pigs to ET-1 (0.5 and 1.5 nmole/kg i.v.) in vivo were blocked greater than 90% by SQ 30,741 (1 mg/kg i.v.). Concurrent increases in arterial blood pressure and decreases in leukocyte counts induced by ET-1 were unaffected by SQ 30,741. In rats, ET-1 (1.5 nmole/kg i.v.) did not affect lung mechanics, but did cause biphasic blood pressure and leukopenia responses which were unaltered by SQ 30,741. These data demonstrate that there is considerable species variability in the bronchospastic response to ET-1, and that in guinea pigs, this response is caused predominantly by the activation of TP-receptors.     

Cyclosporine A exhibits gender-specific nephrotoxicity in rats: Effect on renal tissue inflammation

Cyclosporine A (CSA) is a widely used immunosuppressant drug known to commonly cause cardio and nephrotoxicity. A study looking at the sex specificity of the cardiotoxicity of CSA revealed that sexual dimorphism existed when looking at the electrocardiographs and left ventricles of CSA-treated rats. We hypothesized that cyclosporine A exhibited gender-specific nephrotoxicity by testing various parameters of kidney function in male and female rats treated for 21 days with 15 mg/kg CSA versus control male and female rats that received a vehicle consisting of 18% kolliphore and 2% ethanol in sterile saline. It was found that male rats treated with CSA had significantly higher levels of serum creatinine and lower creatinine clearance than control males. However, serum creatinine and creatinine clearance were not affected by CSA treatment in females. Histopathological examination of kidney cross-sections revealed a heavy aggregation of inflammatory cells and significant vascular congestion in males treated with CSA, which was less prominent in female rats receiving CSA. In addition CSA treated male rats had higher levels of serum cholesterol compared with control while, CSA did not affect serum cholesterol in female rats. Kidney tumor necrosis factor alpha (TNF-α) levels were found to drop in female rats following CSA treatment, whereas no change was observed in male rats before and after treatment. These results suggest that CSA exhibits gender-related nephrotoxicity in rats that might be mediated by differences in the inflammatory response between males and females.     

Effect of nifedipine and amlodipine on dead space wound healing in rats

Effect of two calcium channel blockers (CCBs) nifedipine and amlodipine, was studied on normal and steroid depressed wound healing in albino rats, using the dead space wound model. The drugs enhanced normal healing as evidenced by increase in tensile strength of 10 days old granulation tissue. There was neither a significant change in the hydroxyproline level (or collagen) nor a change in the glycosaminoglycan content in granulation tissue. However, lysyloxidase level was increased significantly. The increase in tensile strength could thus be attributed to better cross-linking and maturation of collagen rather than collagen synthesis per se. The drugs were also able to overcome steroid depressed wound healing. It is likely that the prohealing effects may be related to the improved antioxidant status too, since superoxide dismutase levels were observed to be higher in the CCB- treated animals.     

Relationship between endothelin and thromboxane A2 in rat liver microcirculation.

In our previous study, we determined changes in hepatic blood flow using a Laser Doppler blood flow meter after i.v. injection of endothelin-1 (ET-1) or endothelin-3 (ET-3) at 2 nmol/kg in rats and found that ET-3 caused greater decreases in blood flow than ET-1. In the present study, we determined how the arachidonic acid cascade, mainly thromboxane A2 (TXA2), is related to ET-1 and ET-3 using indomethacin (INDO), which inhibits the biosynthesis of prostaglandin (PG), and OKY-046, a selective inhibitor of TXA2 synthesis. In the first series of experiments, ET-1 and ET-3 were administered after inhibiting the biosynthesis of PG by s.c. injection of 2 mg/kg of INDO. While INDO failed to inhibit the slight decrease in hepatic blood flow induced by ET-1, it significantly inhibited the marked decrease in hepatic blood flow elicited by ET-3. In the next series of experiments, ET-1 and ET-3 were administered after administration of 20 mg/kg of OKY-046. OKY-046 showed no effects in animals treated with ET-1, as in those pre-treated with INDO, while it significantly inhibited the decreases in hepatic blood flow induced by ET-3. These findings suggest that ET-1 decreases hepatic blood flow due to its direct effects although to a lesser extent than ET-3, while ET-3 does so due not only to its direct effects but also to TXA2-mediated effects. It is therefore likely that in addition to ET family peptides, PG-mediated mechanisms are involved in the regulation of hepatic microcirculation by ETs.     

Effect of endothelin receptor antagonists on ventricular susceptibility in postinfarcted rats

This study investigated whether selective endothelin (ET) type A (ET(A)) or nonselective ET(A)/ET(B) receptor blockade exerted antiarrhythmic effects through attenuated sympathetic reinnervation after infarction. Twenty-four hours after ligation of the left anterior descending artery, male Wistar rats received either vehicle, ABT-627 (selective ET(A) receptor antagonist), bosentan (nonselective ET(A)/ET(B) receptor antagonist), or hydralazine for 4 wk. The measurement of myocardial ET-1 levels at the remote zone revealed a significant increase in vehicle-treated infarcted rats compared with sham-operated rats, consistent with increased activities of ET-1 after infarction. Sympathetic nerve function changes assessed by the norepinephrine content of myocardium and the dialysate and plasma dihydroxyphenylglycol levels were parallel to ET-1 levels. Immunohistochemical analysis for tyrosine hydroxylase, growth-associated protein 43, and neurofilament also confirmed the change of nerve function. This was accompanied with a significant upregulation of nerve growth factor protein expression and mRNA in the vehicle-treated infarcted rats, which reduced after the administration of either ET(A) or ET(A)/ET(B) blockade to a similar extent. The beneficial effects of ET receptor antagonists on sympathetic nerve function and structures were dissociated from their blood pressure-lowering effect because ET receptor antagonists and hydralazine reduced arterial pressure similarly. Arrhythmic severity during programmed stimulation in ET receptor antagonists-treated rats was significantly lower than that in vehicle-treated infarcted rats. Our data indicate that the ET system, especially via ET(A) receptors, plays an important role in attenuating sympathetic reinnervation after infarction. Independent of their hemodynamic effects, a chronic use of either ET(A) or ET(A)/ET(B) antagonists may modify the arrhythmogenic response to programmed electrical stimulation.     

Vitamin and micronutrient concentrations in cyclosporine-induced renal tumor from diabetic rats

Concentrations of vitamins, biopterin, free inositol and acid-soluble carnitine were determined in cyclosporine A induced renal adenocarcinoma and uninvaded renal tissue from streptozotocin diabetic rats. Vitamin B6, thiamin, riboflavin, nicotinate, free inositol and acid-soluble carnitine were significantly decreased in tumor than nontumor tissue. Concentrations of folic acid, B12, biotin, pantothenate and biopterin were similar in both tissues. These studies suggest that renal adenocarcinoma affects concentrations of only certain vitamins and micronutrients.     

Effect of oral administration of Arabic gum on cisplatin-induced nephrotoxicity in rats

It has been recently postulated from our laboratory that Arabic gum (AG) offers a protective effect in the kidney of rats against nephrotoxicity induced by gentamicin via inhibiting lipid peroxidation. It has also recently shown a powerful antioxidant effect through scavenging superoxide anions. In this study we utilized a rat model of cisplatin (CP)-induced nephrotoxicity to determine its peak time following (1, 2, 5, and 7 days) of a single CP (7.5 mg/kg, i.p.) injection. Also, a possible protective effect of cotreatment with AG (7.5 g/kg/day p.o.) on CP-induced nephrotoxicity was investigated. Biochemical as well as histological assessments were carried out. CP-induced nephrotoxicity was manifested by significant elevations of the functional parameters blood urea, serum creatinine, and kidney/body weight ratio. Maximum toxic effects of CP were observed 5 days after its injection, while it started after day 1 in the biochemical parameters, such as glutathione depletion in the kidney tissue with concomitant increases in lipid peroxides and platinum content. Additionally, severe necrosis and desquamation of tubular epithelial cells in renal cortex as well as interstitial nephritis were observed after 5 days in CP-treated animals. Five days after AG cotreatment with CP did not protect the kidney from the damaging effects of CP. However, it significantly reduced CP-induced lipid peroxidation. These findings suggest that lipid peroxidation is not the main cause of CP-induced nephrotoxicity but it is rather more dependent on other factors such as platinum disposition in renal interstitial tubules.     

Effect of rosmarinic acid on inhibition of gentamicin induced nephrotoxicity in rats

The present investigation reports the effect of rosmarinic acid (RA), an antioxidant on gentamicin sulphate (GS)-induced renal oxidative damage in rats. Rosmarinic acid (RA) has been demonstrated to have antioxidant, free radical scavenger and anti-inflamatory effects. Twenty-eight Sprague-Dawley rats were divided in to four equal groups as follows: group 1 (control), group 2 (GS 100 mg/kg/d ip), group 3 (GS 100 mg/kg/d ip + RA 50 mg/kg/d) and group 4 (GS 100 mg/kg/d ip + RA 100 mg/kg/d). Treatments were administrated once daily for 12 days. After 12 days 24 h urine was collected, blood was sampled and kidneys were removed. Serum and kidney tissue MDA assessed by thiobarbituric acid. Kidney paraffin sections (5 μm thickness) from the left kidney stained with periodic acid Schiff. Tubular necrosis was studied semiquantitatively and glomerular volume and volume density of proximal convoluted tubule (PCT) estimated stereologically. Kidney homogenize were prepared from right kidney. Serum creatinine, urea and kidney antioxidant enzymes activity were assessed by special kits. Data were compared by SPSS 13 software and Mann–Whitney test at p < 0.05. Co treatment of GS and RA (High dose) significantly decreased serum creatinine, MDA, urea, tubular necrosis (p < 0.05) and increase renal GSH, GPX, CAT, SOD, volume density of PCT and creatinine clearance significantly in comparison with GS group (p < 0.05). Treatment with RA (high dose) maintained serum creatinine, volume density of PCT, renal GSH, GPX, SOD and MDA as the same level as control group significantly (p < 0.05). In conclusion, RA alleviates GS nephrotoxicity via antioxidant activity, increase of renal GSH content and increase of renal antioxidant enzymes activity.     

Pharmacological blockade of the nephrotoxicity of cisplatin in rats

Cisplatin injection (0.5 mg/100 g body weight) induced 5 days later an increase in serum urea concentration from 3.31 +/- 0.67 to 47.1 +/- 8.68 mg/ml and diuresis decrease following water loading test. Ethacrynic acid, furosemide, paraaminohippurate pre-injections prevented cisplatin nephrotoxicity. The decrease in cisplatin nephrotoxicity took place when furosemide was administered before or 3 h after cisplatin injection; 6 h after cisplatin injection furosemide was not effective. The results suggest that pharmacological blockade of cisplatin nephrotoxicity depends on the drug penetration into secreting cells of proximal tubules.     

Effect of pre-treatment with St John's Wort on nephrotoxicity of cisplatin in rats

An herbal health care supplement, St John's Wort (SJW, Hypericum perforatum) has become widely used in the treatment of depression, and is known to interact with therapeutic drugs. Here we report a preventive effect of SJW on cisplatin nephrotoxicity in rats. Rats were given SJW (400 mg/kg/day, p.o.) for 10 consecutive days, and were injected with cisplatin (5 mg/kg, i.v.) on the day after the final SJW treatment. Cisplatin treatment increased the serum creatinine level, which is an index of nephrotoxicity, to 1.51+/-0.22 mg/dl (mean+/-SE) from 0.28+/-0.05 mg/dl (control) on day 5 after the cisplatin injection. This increase fell significantly to 0.86+/-0.13 mg/dl by pre-treatment with SJW. Cisplatin-induced histological abnormality of the kidney was blocked by pre-treatment with SJW. When SJW was administered for 10 days, the amounts of renal metallothionein (MT) and hepatic multidrug resistance protein 2 (Mrp2) were increased to 164.8+/-13.0% and 220.8+/-39.3% (mean+/-SE) of controls, respectively. GSH levels in the kidney and liver were not changed. Total and free cisplatin concentration in serum was not influenced by SJW treatment. In conclusion, the results suggest that pre-treatment with SJW may diminish cisplatin nephrotoxicity.     

Effect of nifedipine on core cooling in rats during tail cold water immersion

Male rats (450 g, n=11/group) were heated at an ambient temperature of 42°C until a rectal temperature of 42.8°C was attained. Rats, then received either saline (30°C)+tail ice water immersion (F+I) or saline (30°C)+tail ice water immersion+Nifedipine, a peripheral vasodilator, (F+I+N) to determine cooling rate effectiveness and survivability. The time to reach a rectal temperature of 42.8°C averaged 172 min in both groups resulting in similar heating rates (0.029°C/min). The cooling rates in group F+I and F+I+N were not significantly different from each other. We conclude that since Nifedipine did not improve cooling rates when combined with fluid+tail ice water immersion, its use as a cooling adjunct does not seem warranted.     

Effect of diumancal,foridon, nifedipine,and verapamil on the myometrium potentials in pregnant rats

All the preparations under study were i.v. administered to pregnant Wistar rats in the doses adequate to therapeutic those on pregnant woman basis. Within 10 minutes, a drop both in the amplitude and in the rate of the myometrium potentials were found.     

Effect of inducers of DT-diaphorase on the haemolytic activity and nephrotoxicity of 2-amino-1,4-naphthoquinone in rats

Reduction of naphthoquinones by DT-diaphorase is often described as a detoxification reaction. This is true for some naphthoquinone derivatives, such as alkyl and di-alkyl naphthoquinones, but the situation with other substances, such as 2-hydroxy-1,4-naphthoquinone, is more complex. In the present study, the effect of several substances that are known to increase tissue activities of DT-diaphorase on the toxicity of 2-amino-1,4-naphthoquinone has been investigated. Like 2-hydroxy-1,4-naphthoquinone, the 2-amino-derivative was found to cause both haemolytic anaemia and renal tubular necrosis in rats. Again like 2-hydroxy-1,4-naphthoquinone, the severity of the haemolysis induced by the 2-amino derivative was increased in animals pre-treated with inducers of DT-diaphorase, but the degree of nephrotoxicity was decreased. With these substances, therefore, DT-diaphorase both activates and detoxifies the quinone, depending on the target organ. It is not possible to generalise with regard to the effects of modulation of tissue levels of DT-diaphorase on naphthoquinone toxicity in vivo, since this may change not only the severity of the toxic effects, but also the target organ specificity. In evaluating the possible therapeutic applications of such compounds, the possibility of toxic effects upon the blood and kidney must be borne in mind. In man, renal damage by compounds such as 2-hydroxy- and 2-amino-1,4-naphthoquinone may be a particular problem, because of the low level of DT-diaphorase in human liver.