Poduri Ramarao

Rosiglitazone attenuates the cognitive deficits induced by high fat diet feeding in rats.

The present study was designed to test the hypothesis that insulin resistance plays a role in high fat diet feeding induced cognitive deficits. Rats consuming the high fat diet exhibited characteristic features of insulin resistance viz. mild hyperglycemia, hypertriglyceridemia, hypercholesterolemia, and hyperinsulinemia. Further, these rats showed a severe deficit in learning and memory. In contrast, rosiglitazone at the dose of 5 mg/kg, p.o. for 7 days prior to biochemical and behavioral testing significantly lowered the plasma glucose, triglycerides, cholesterol, and insulin levels. These animals also performed better on Morris water maze task, suggesting improved spatial memory. Our data demonstrate that the insulin sensitizers can overcome the cognitive deficits arising from high fat diet feeding, which may be in part mediated through the development of peripheral insulin resistance.

Antioxidant and antimutagenic effect of quercetin against DEN induced hepatotoxicity in rat.

Diethylnitrosamine (DEN), a potent hepatocarcinogen, is found in tobacco smoke, processed meat as well as in different food products. Quercetin (QC), a naturally occurring flavonoid has excellent antioxidant properties. The present study was aimed to investigate the chemoprotective potential of QC against DEN induced hepatotoxicity in Sprague‐Dawley (SD) rats. Quercetin was administered (10, 30 and 100 mg/kg) for 5 consecutive days after DEN (200 mg/kg) treatment. The animals were killed 24 h after the last dose of QC/saline treatment. The DEN induced hepatotoxicity was evident by elevated malondialdehyde (MDA) and decreased glutathione (GSH) levels in the liver. A significant increase in the levels of plasma aspartate transaminase (AST) and plasma alanine transaminase (ALT) was observed in the DEN treated group. The DEN induced DNA damage was evaluated using a single cell gel electrophoresis (SCGE) assay. A significant increase in the number of TUNEL positive cells was observed in the DEN treated group. Quercetin restored AST, ALT and GSH levels at all the tested doses. Restoration of the MDA level and cellular morphology was observed at doses of 10 and 30 mg/kg of QC. Further, DEN induced DNA damage and apoptosis was ameliorated by QC. The results indicate that QC ameliorates the DEN induced hepatotoxicity in rats and can be a candidate for a good chemoprotectant. Copyright

Methotrexate-induced cytotoxicity and genotoxicity in germ cells of mice: intervention of folic and folinic acid.

Methotrexate (MTX) is an anti-metabolite widely used in the treatment of neoplastic disorders, rheumatoid arthritis and psoriasis. The basis for its therapeutic efficacy is the inhibition of dihydrofolate reductase (DHFR), a key enzyme in the folic acid (FA) metabolism. FA is a water-soluble vitamin which is involved in the synthesis of purines and pyrimidines, the essential precursors of DNA. Folinic acid (FNA) is the reduced form of FA that circumvents the inhibition of DHFR. Folate supplementation during MTX therapy for psoriasis and inflammatory arthritis reduces both toxicity and side effects without compromising the efficacy. Further, FNA supplementation reduces the common side effects of MTX in the treatment of juvenile idiopathic arthritis. FA and FNA are reported to have protective effects on MTX-induced genotoxicity in the somatic cells; however their protective effects on the germ cells have not been much explored. Previously, we evaluated the cytotoxic and genotoxic effects of MTX in the germ cells of mice. In the present study, we have intervened FA and FNA for the protection of germ cell toxicity induced by MTX in male swiss mice. The animals were pre-treated with FA at the doses of 50, 100 and 200 microg/kg for 4 consecutive days per week and on day five; MTX was administered at the dose of 20mg/kg once. FNA was administered at the doses of 2.5, 5 and 10 mg/kg, 6 h (h) after single administration of MTX at the dose of 20 mg/kg. The dosing regimen was continued up to 10 weeks. The germ cell toxicity was evaluated using testes weight (wt), sperm count, sperm head morphology, sperm comet assay, histology, TUNEL and halo assay in testis. The results clearly demonstrate that prior administration of FA and post-treatment with FNA reduces the germ cell toxicity induced by MTX as evident from the decreased sperm head abnormalities, seminiferous tubule damage, sperm DNA damage, TUNEL positive cells and increased sperm counts. In the present study, we report that FA and FNA ameliorate the germ cell toxicity of MTX in mice.

Effect of κ-opioid receptor agonists on morphine analgesia in morphine-naive and morphine-tolerant rats

The effect of i.p. administration of kappa-opioid receptor agonists, bremazocine, tifluadom and U-50,488H on morphine (8 mg/kg i.p.)-induced analgesia in morphine-naive and morphine tolerant male Sprague-Dawley rats was determined using the tail-flick test. The tolerance to morphine in the rats was induced by s.c., implantation of six morphine pellets during a 7-day period. Implantation of morphine pellets resulted in the development of tolerance as evidenced by the decrease in the analgesic response to morphine when compared to placebo pellets implanted rats. Bremazocine (0.3, 1.0 and 3.0 mg/kg) and U-50,488H (16 mg/kg) antagonized morphine-induced analgesia in morphine-naive rats while tifluadom (8 and 16 mg/kg) potentiated the effect. In morphine-tolerant rats, bremazocine (3 mg/kg) and U-50,488H (16 mg/kg) potentiated morphine-induced analgesia. Tifluadom at any of the doses had no effect on morphine-induced analgesia in morphine-tolerant rats. These results provide evidence that different kappa-opioid agonists modify morphine-induced analgesia differentially in morphine-naive and morphine-tolerant rats.

Insulin-resistance and benign prostatic hyperplasia: The connection

Benign prostatic hyperplasia (BPH) is a highly prevalent disease in the aged men population characterized by augmented cell proliferation and contractility of the prostate gland. Prior studies have demonstrated the relationship between BPH and insulin-resistance syndrome. During insulin-resistance, hyperinsulinemia develops to combat the decreased responsiveness of the body towards insulin. Although, the compensatory hyperinsulinemia prevents development of fasting hyperglycemia in insulin-resistant individuals, the increased level of circulating insulin directly and/or indirectly affects different molecular signaling and can promote prostatic growth. Insulin-resistance syndrome includes group of disorders, such as obesity, dyslipidemia, sympathetic overactivity, hyperinsulinemia and each individually reported as risk factor for the development of BPH. The present review describes the inter-relationships between different insulin-resistance associated factors and their possible involvement in the pathogenesis of BPH.

Cytotoxic and genotoxic effects of methotrexate in germ cells of male Swiss mice

Methotrexate (MTX) is an anti-metabolite drug widely used in the treatment of neoplastic disorders, rheumatoid arthritis and psoriasis. Developed as an analogue of folic acid, it inhibits purine and pyrimidine synthesis that accounts for its therapeutic efficacy as well as for its toxicities. MTX has narrow therapeutic index and its toxicity has been reported in various organ systems including gastrointestinal, haematologic and central nervous system. The objective of the present study is to investigate the germ cell toxicity induced by MTX in male Swiss mice. MTX was administered intraperitoneally (ip) at the doses of 5, 10, 20 and 40 mg/kg to mice (20-25 g) weekly once (wk) for 5 and 10 weeks. The animals were sacrificed 1 week after receiving the last treatment of MTX. The germ cell toxicity was evaluated using testes weight (wt), sperm count, sperm head morphology, sperm comet assay, histology, TUNEL and halo assay in testis. MTX treatment significantly reduced the sperm count and increased the occurrence of sperm head abnormalities in a dose dependent manner. It induced the testicular toxicity as evident from the histology of testis. Sperm comet, TUNEL and halo assay in testis also revealed significant DNA damage after MTX treatment. On the basis of the present study, it can be concluded that MTX induced germ cell toxicity in mice.

Intervention of α-lipoic acid ameliorates methotrexate-induced oxidative stress and genotoxicity: A study in rat intestine

Methotrexate (MTX) is an anti-metabolite, widely used in the cancer chemotherapy and rheumatoid arthritis. However, its long-term clinical use is restricted on account of its severe intestinal toxicity. The present study was aimed to investigate the intestinal toxicity of MTX and the possible protective effect of alpha-lipoic acid (LA) on Sprague-Dawley rats. MTX-induced intestinal toxicity was evaluated at the dose of 2.5mg/kg for short-term (5 days treatment) and 1mg/kg for long-term (5 days in a week for four consecutive weeks treatment) study. The possible protective effect of LA was evaluated in both short- as well as long-term study in a dose-dependent manner. MTX treatment induced diarrhoea and mortality in rats, indicating its severe toxicity in the target organ of investigation, i.e., intestine. Further, the intestinal toxicity of MTX was assessed by evaluating different parameters of oxidative stress, DNA damage, cytotoxicity as well as histological changes. Immunostaining for p53 revealed higher genotoxic assault in the intestinal cells due to MTX treatment. Pretreatment of rats with LA led to significant decrease in the oxidative stress, DNA damage, cellular damage, inflammatory changes and apoptosis as determined by malondialdehyde level, glutathione level, comet assay parameters, histological evaluation, immunostaining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. In the present investigation, we report that LA pretreatment ameliorates MTX-induced intestinal toxicity in rat as evident from the protection against oxidative stress, decrease in DNA damage and protection of cellular morphology as well as improvement in the stool consistency and animal survival rate.

Antagonism of the acute pharmacological actions of morphine by panax ginseng extract.

1. The effects of intraperitoneal administration of a standard extract of Panax ginseng alone and in combination with morphine were determined in male Sprague-Dawley rats. 2. Ginseng extract at 200 mg/kg produced analgesia and hypothermia. These effects of ginseng were not reversed by naltrexone. 3. A dose of morphine (8 mg/kg) produced analgesia and hyperthermia. The analgesic response to morphine was antagonized by 25 and 50 mg/kg doses of ginseng but not by 12.5, 100 and 200 mg/kg doses. 4. Morphine-induced hyperthermia was antagonized by 12.5-200 mg/kg doses of ginseng. 5. Administration of morphine (50 mg/kg) produced cataleptic effect which was antagonized by 25 mg/kg of ginseng. 6. The results suggest that ginseng extract at high doses produces analgesia and hypothermia in the rat by a non-opiate mechanism, and antagonizes the acute pharmacological effects of morphine.

Effects of morphine in rats treated chronically with U-50,488 H, a κ opioid receptor agonist

Abstract The pharmacological effects of morphine, namely analgesic, hyperthermic and cataleptic effects, were assessed in rats rendered tolerant to U-50,488H, a κ opioid receptor agonist. Male Sprague-Dawley rats were injected intraperitoneally with U-50,488H (25 mg/kg) twice a day for four days. The rats which served as controls were injected similarly with the vehicle. Chronic administration of U-50,488H resulted in the development of tolerance to its analgesic and hypothermic effects, but not to its diuretic effect. The development of tolerance to the pharmacological effects of U-50,488H was associated with decreased binding of [ 3 H]ethylketocyclazocine ([ 3 H]EKC) to brain and spinal cord membranes. The decreased binding of [ 3 H]EKC in U-50,488H-treated rats was due to changes in the B max value; the K d values remained unaltered. Intraperitoneal administration of morphine (8 mg/kg) to rats produced analgesia (as determined by the tail-flick test) and hyperthermia. A dose of 50 mg/kg of morphine produced cataleptic response. The intensity of analgesic, hyperthermic and cataleptic effects of morphine were unaltered in rats tolerant to U-50,488H. The development of tolerance to analgesic and hypothermic effects of U-50,488H were associated with down-regulation of brain and spinal cord κ opioid receptors. Finally, U-50,488H does not confer cross-tolerance to morphine, a predominantly μ opioid receptor agonist.

The effect of Panax ginseng on the development of tolerance to the pharmacological actions of morphine in the rat

1. The effect of intraperitoneal administration of Panax ginseng on the development of tolerance to the analgesic and hyperthermic actions of morphine was determined in male Sprague-Dawley rats. Rats were rendered tolerant to morphine to different degrees by the subcutaneous implantation of either four pellets of morphine over a 3-day period or six pellets over a 7-day period. Each pellet contained 75 mg of morphine free base. Rats serving as controls were implanted with placebo pellets. 2. Daily administration of ginseng extract (6.25-50.0 mg/kg) for 3 days inhibited the development of tolerance to the analgesic effect but not to the hyperthermic effect of morphine in the four pellet schedule. 3. In six pellet schedule, daily administration of ginseng extract (25 and 50 mg/kg) for 7 days also inhibited the development of tolerance to the analgesic effect of morphine, but the 100 mg/kg dose had no effect. On the other hand, in six pellet schedule, the administration of ginseng extract (50 and 100 mg/kg) once daily for 7 days inhibited the development of tolerance to the hyperthermic effect of morphine. 4. It is concluded that in appropriate doses, ginseng extract has inhibitory activity on the development of tolerance to the pharmacological actions of morphine.