Testosterone plays a permissive role in angiotensin II-induced hypertension and cardiac hypertrophy in male rats.

Sex hormones contribute to sex differences in blood pressure. Inappropriate activation of the renin-angiotensin system is involved in vascular dysfunction and hypertension. This study evaluated the role of androgens (testosterone) in angiotensin II (Ang II)-induced increase in blood pressure, vascular reactivity, and cardiac hypertrophy. Eight-week-old male Wistar rats underwent sham operation, castration, or castration with testosterone replacement. After 12 weeks of chronic changes in androgen status, Ang II (120 ng/kg per minute) or saline was infused for 28 days via subcutaneous miniosmotic pump, and changes in blood pressure was measured. Vascular reactivity and Ang II receptor levels were examined in mesenteric arteries. Heart weight, cardiac ANP mRNA levels, and fibrosis were also assessed. Ang II infusion increased arterial pressure in intact males. The Ang II-induced increase in hypertensive response was prevented in castrated males. Testosterone replacement in castrated males restored Ang II-induced hypertensive responses. Castration reduced vascular AT1R/AT2R ratio, an effect that was reversed by testosterone replacement. Ang II-induced hypertension was associated with increased contractile response of mesenteric arteries to Ang II and phenylephrine in intact and testosterone-replaced castrated males; these increases were prevented in castrated males. Ang II infusion induced increased left ventricle-to-body weight ratio and ANP mRNA expression, indicators of left ventricular hypertrophy, and fibrosis in intact and testosterone-replaced castrated males, and castration prevented the increase in these parameters caused by Ang II. This study demonstrates that testosterone plays a permissive role in development and maintenance of Ang II-induced vascular dysfunction, hypertension, and cardiac hypertrophy.

Elevated androgen levels induce hyperinsulinemia through increase in Ins1 transcription in pancreatic beta cells in female rats.

Hyperandrogenism is associated with hyperinsulinemia and insulin resistance in adult females. We tested whether androgens dysregulate pancreatic beta cell function to induce hyperinsulinemia through transcriptional regulation of insulin gene (Ins) in the islets. Adult female Wistar rats implanted with dihydrotestosterone (DHT; 7.5-mg, 90-d release) or placebo pellets were examined after 10 weeks. DHT exposure increased plasma DHT levels by 2-fold similar to that in polycystic ovary syndrome in women. DHT exposure induced hyperinsulinemia with increased HOMA-IR index in fasting state and glucose intolerance and exaggerated insulin responses following glucose tolerance test. DHT females had no change in islet number, size and beta cell proliferation/apoptosis but exhibited significant mitochondrial dysfunction (higher ADP/ATP ratio, decreased mtDNA copy number, increased reactive oxygen production and downregulation of mitochondrial biogenesis) and enhanced glucose-stimulated insulin secretion. Ins expression was increased in DHT islets. In vitro incubation of control islets with DHT dose dependently stimulated Ins transcription. Analysis of Ins1 gene revealed a putative androgen responsive element in the promoter. Chromatin-immunoprecipitation assays showed that androgen receptors bind to this element in response to DHT stimulation. Furthermore, reporter assays showed that the promoter element is highly responsive to androgens. Insulin-stimulated glucose uptake in skeletal muscle was decreased with associated decrease in IRß expression in DHT females. Our studies identified a novel androgen-mediated mechanism for the control of Ins expression via transcriptional regulation providing a molecular mechanism linking elevated androgens and hyperinsulemia. Decreased IRß expression in the skeletal muscles may contribute, in part, to glucose intolerance in this model.

Hyperandrogenemia reduces endothelium-derived hyperpolarizing factor-mediated relaxation in mesenteric artery of female rats.

Women with polycystic ovary syndrome (PCOS) are often presented with hyperandrogenemia along with vascular dysfunction and elevated blood pressure. In animal models of PCOS, anti-androgen treatment decreased blood pressure, indicating a key role for androgens in the development of hypertension. However, the underlying androgen-mediated mechanism that contributes to increased blood pressure is not known. This study determined whether elevated androgens affect endothelium-derived hyperpolarizing factor (EDHF)-mediated vascular relaxation responses through alteration in function of gap junctional proteins. Female rats were implanted with placebo or dihydrotestosterone (DHT) pellets (7.5 mg, 90-day release). After 12 weeks of DHT exposure, blood pressure was assessed through carotid arterial catheter and endothelium-dependent mesenteric arterial EDHF relaxation using wire myograph. Connexin expression in mesenteric arteries was also examined. Elevated DHT significantly increased mean arterial pressure and decreased endothelium-dependent EDHF-mediated acetylcholine relaxation. Inhibition of Cx40 did not have any effect, while inhibition of Cx37 decreased EDHF relaxation to a similar magnitude in both controls and DHT females. On the other hand, inhibition of Cx43 significantly attenuated EDHF relaxation in mesenteric arteries of controls but not DHT females. Elevated DHT did not alter Cx37 or Cx40, but decreased Cx43 mRNA and protein levels in mesenteric arteries. In vitro exposure of DHT to cultured mesenteric artery smooth muscle cells dose-dependently downregulated Cx43 expression. In conclusion, increased blood pressure in hyperandrogenic females is due, at least in part, to decreased EDHF-mediated vascular relaxation responses. Decreased Cx43 expression and activity may play a role in contributing to androgen-induced decrease in EDHF function.

Postnatal Cardiovascular Consequences in the Offspring of Pregnant Rats Exposed to Smoking and Smoking Cessation Pharmacotherapies.

Approximately 20% of pregnant women smoke despite intentions to quit. Smoking cessation drugs, such as nicotine replacement therapy (NRT) and bupropion, are recommended treatments. Adverse cardiovascular outcomes in offspring have raised concerns about NRT's safety during pregnancy. However, the effect of bupropion is unknown. Using a rat model, we determined whether NRT and bupropion interventions during pregnancy are safer than continued smoking on offspring's cardiovascular function. Male offspring of controls and dams exposed to cigarette smoke (1.6 packs/day, inhalation), nicotine (2 mg/kg/d subcutaneously), and bupropion (13 mg/kg twice daily orally) were assessed for fetoplacental weight, cardiac function, blood pressure, and vascular reactivity. Fetoplacental weights were decreased and spontaneous beating and intracellular calcium in neonatal cardiomyocytes were increased in smoking, nicotine, and bupropion offspring; however, these effects were more accentuated in smoking followed by nicotine and bupropion offspring. Increased heart rate and decreased cardiac output, stroke volume, and left ventricular percent posterior wall thickening were observed in smoking, nicotine, and bupropion offspring. The left ventricular mass was reduced in smoking and nicotine but not in bupropion offspring. Blood pressure was higher with decreased endothelium-dependent relaxation and exaggerated vascular contraction to angiotensin II in smoking and nicotine offspring, with more pronounced dysfunctions in smoking than nicotine offspring. Maternal bupropion did not impact offspring's blood pressure, endothelium-dependent relaxation, and vascular contraction. In conclusion, maternal nicotine intervention adversely affects offspring's cardiovascular outcomes, albeit less severely than continued smoking. However, bupropion causes cardiac derangement in offspring but does not adversely affect blood pressure and vascular function.

Prenatal Testosterone Exposure Decreases Aldosterone Production but Maintains Normal Plasma Volume and Increases Blood Pressure in Adult Female Rats.

Plasma testosterone levels are elevated in pregnant women with preeclampsia and polycystic ovaries; their offspring are at increased risk for hypertension during adult life. We tested the hypothesis that prenatal testosterone exposure induces dysregulation of the renin-angiotensin-aldosterone system, which is known to play an important role in water and electrolyte balance and blood pressure regulation. Female rats (6 mo old) prenatally exposed to testosterone were examined for adrenal expression of steroidogenic genes, telemetric blood pressure, blood volume and Na(+) and K(+) levels, plasma aldosterone, angiotensin II and vasopressin levels, and vascular responses to angiotensin II and arg(8)-vasopressin. The levels of Cyp11b2 (aldosterone synthase), but not the other adrenal steroidogenic genes, were decreased in testosterone females. Accordingly, plasma aldosterone levels were lower in testosterone females. Plasma volume and serum and urine Na(+) and K(+) levels were not significantly different between control and testosterone females; however, prenatal testosterone exposure significantly increased plasma vasopressin and angiotensin II levels and arterial pressure in adult females. In testosterone females, mesenteric artery contractile responses to angiotensin II were significantly greater, while contractile responses to vasopressin were unaffected. Angiotensin II type-1 receptor expression was increased, while angiotensin II type-2 receptor was decreased in testosterone arteries. These results suggest that prenatal testosterone exposure downregulates adrenal Cyp11b2 expression, leading to decreased plasma aldosterone levels. Elevated angiotensin II and vasopressin levels along with enhanced vascular responsiveness to angiotensin II may serve as an underlying mechanism to maintain plasma volume and Na(+) and K(+) levels and mediate hypertension in adult testosterone females.

Prenatal Testosterone Exposure Leads to Gonadal Hormone-Dependent Hyperinsulinemia and Gonadal Hormone-Independent Glucose Intolerance in Adult Male Rat Offspring.

Elevated testosterone levels during prenatal life lead to hyperandrogenism and insulin resistance in adult females. This study evaluated whether prenatal testosterone exposure leads to the development of insulin resistance in adult male rats in order to assess the influence of gonadal hormones on glucose homeostasis in these animals. Male offspring of pregnant rats treated with testosterone propionate or its vehicle (control) were examined. A subset of male offspring was orchiectomized at 7 wk of age and reared to adulthood. At 24 wk of age, fat weights, plasma testosterone, glucose homeostasis, pancreas morphology, and gastrocnemius insulin receptor (IR) beta levels were examined. The pups born to testosterone-treated mothers were smaller at birth and remained smaller through adult life, with levels of fat deposition relatively similar to those in controls. Testosterone exposure during prenatal life induced hyperinsulinemia paralleled by an increased HOMA-IR index in a fasting state and glucose intolerance and exaggerated insulin responses following a glucose tolerance test. Prenatal androgen-exposed males had more circulating testosterone during adult life. Gonadectomy prevented hyperandrogenism, reversed hyperinsulinemia, and attenuated glucose-induced insulin responses but did not alter glucose intolerance in these rats. Prenatal androgen-exposed males had decreased pancreatic islet numbers, size, and beta-cell area along with decreased expression of IR in gastrocnemius muscles. Gonadectomy restored pancreatic islet numbers, size, and beta-cell area but did not normalize IRbeta expression. This study shows that prenatal testosterone exposure leads to a defective pancreas and skeletal muscle function in male offspring. Hyperinsulinemia during adult life is gonad-dependent, but glucose intolerance appears to be independent of postnatal testosterone levels.

Effect of alcoholic extract of Entada pursaetha DC on monosodium iodoacetate-induced osteoarthritis pain in rats.

BACKGROUND & OBJECTIVES: Osteoarthritis (OA) is a degenerative disease characterized by joint pain and progressive loss of articular cartilage. Entada pursaetha has been traditionally used in the treatment of inflammatory disease, liver ailment, etc. In this study we investigated suppressive effect of ethanolic extract of E. pursaetha (EPE) on monosodium iodoacetate (MIA)-induced osteoarthritis pain and disease progression by histopathological changes in joints in a rat model. METHODS: OA was induced in right knee of rat by intra-articular injection of 3 mg of MIA and characterized by pathological progression of disease and pain of affected joint. Spontaneous movements, mechanical, thermal and cold sensitivity were monitored at days 0 (before drug and MIA injection), 7, 14 and 21 of MIA administration. EPE (30, 100 and 300 mg/kg), vehicle or etoricoxib (10 mg/ kg; reference drug) were administered daily for 21 days by oral route. RESULTS: EPE at various doses significantly reduced mechanical, heat, cold hyperalgesia and increased the horizontal and vertical movements in intra-articular MIA injected rats. EPE prevented the damage to cartilage structure and reduced the cellular abnormalities. Articular cartilage of rats treated with EPE at 300 mg/kg group was almost normal with well-developed smooth surface and chondrocytes were distributed individually or arranged in column. INTERPRETATION & CONCLUSIONS: The present findings showed that the EPE was not only able to mitigate pain and hyperalgesia but also inhibited MIA-induced cartilage degeneration in vivo. EPE may have the potential to become therapeutic modality in the treatment of osteoarthritis. However, further studies need to be done to confirm these findings in other models and clinical trials.

Enalapril Normalizes Endothelium-Derived Hyperpolarizing Factor-Mediated Relaxation in Mesenteric Artery of Adult Hypertensive Rats Prenatally Exposed to Testosterone.

Prenatal exposure to elevated testosterone levels induces adult life hypertension associated with selective impairments in endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation in mesenteric arteries. We tested whether the angiotensin-converting enzyme inhibitor enalapril restores EDHF function through regulating the activities of small (Kcnn3) and intermediate (Kcnn4) conductance calcium-activated potassium channels in mesenteric arteries. Pregnant Sprague-Dawley rats were injected subcutaneously with vehicle or testosterone propionate (0.5 mg/kg/day from Gestation Day 15 to 19), and their 6-mo-old adult male offspring were examined. A subset of rats in these two groups was given enalapril (40 mg/kg/day) for 2 wk through drinking water. Blood pressures were assessed through carotid arterial catheter and endothelium-dependent mesenteric arterial EDHF relaxation, using wire myography. Ace and Kcnn3 and Kcnn4 channel expression levels were also examined. Renal and vascular Ace expression and plasma angiotensin II levels were increased in testosterone offspring. Blood pressure levels were significantly higher in testosterone offspring than in controls, and treatment with enalapril significantly attenuated blood pressure in testosterone offspring. EDHF relaxation in testosterone offspring was reduced compared to that in controls, and it was significantly restored by enalapril treatment. Kcnn4 channel expression and function were similar between control and testosterone rats, but it was not affected by enalapril treatment. Relaxation mediated by Kcnn3 was impaired in testosterone offspring, and it was normalized by enalapril treatment. Furthermore, enalapril treatment restored expression levels of Kcnn3 channels. These findings suggest that enalapril has a positive influence on endothelial function with improvement in EDHF relaxation through normalization of Kcnn3 expression and activity.

Interaction of sodium bicarbonate and Na+/H+ exchanger inhibition in the treatment of acute metabolic acidosis in pigs.

OBJECTIVE: Administration of NaHCO3 does not improve cellular function or reduce the mortality of acute lactic acidosis. This might be related to aggravation of intracellular acidosis, but it could also be due to activation of Na+/H+ exchanger with a deleterious increment in intracellular calcium ([Ca2+]i). This study examined the impact of coadministration of NaHCO3 and a selective inhibitor of Na+/H+ exchanger, sabiporide on cardiovascular function, changes in proinflammatory cytokines, and organ function in a model of acute lactic acidosis produced by hemorrhagic hypotension followed by infusion of lactic acid. DESIGN: Experimental, prospective study. SETTING: Medical Center research laboratory. SUBJECTS: Male Yorkshire pigs. INTERVENTIONS: Anesthetized pigs were subjected to hypovolemia for 30 minutes and followed by DL-lactic acid infusion, and then either saline or sodium bicarbonate was infused. MEASUREMENTS AND MAIN RESULTS: Hypovolemia followed by a DL-lactic acid infusion resulted in severe acidemia with a blood pH~6.8. Administration of NaHCO3 did not improve cardiovascular performance or decrease the levels of proinflammatory responses, whereas administration of sabiporide prior to acid or NaHCO3 infusion improved cardiopulmonary performance and blood oxygenation, reduced nuclear factor-κB activation, neutrophil accumulation, and proinflammatory cytokine production, and attenuated organ injury. Exposure of rat cardiac myocytes to a pH of 7.2 led to a marked increase of [Ca2+]i, and release of lactate dehydrogenase from cells which were further augmented after increase in external pH by addition of NaHCO3. Both the increase in [Ca2+]i and release of lactate dehydrogenase were attenuated in the presence of sabiporide. CONCLUSIONS: Coadministration of Na/H exchanger inhibitor with sodium bicarbonate improves cardiovascular performances, reduces proinflammatory responses, and attenuates organ injury. This improvement in these variables appears to be related to prevention of a rise in intracellular calcium occurring after both exposures to acid and bicarbonate.

Anti-inflammatory and chondroprotective effects of atorvastatin in a cartilage explant model of osteoarthritis.

OBJECTIVE: This study aimed to assess the chondroprotective potential of atorvastatin in rat's cartilage explant culture model of osteoarthritis, stimulated by interleukin-1ß (IL-1ß). MATERIALS AND METHODS: The cartilage explants were treated with 20 ng/ml IL-1ß alone or with 20 ng/ml IL-1ß + various concentration of atorvastatin (1, 3, or 10 µM dissolved in DMSO) and incubated at 37 °C for 24 h. Also, control (0.25% DMSO), stimulated (20 ng IL-1ß) and treatment (atorvastatin 10 µM) cartilage explants were incubated without and with 1400W (10 µM). After 24 h of incubation, TNF-α, PGE2, MMP-13, TIMP-1, NO, and superoxide anion formation (O2(-)) concomitant with glycosaminoglycans (GAGs) were estimated in the medium. RESULTS: Atorvastatin inhibited IL-1ß-induced GAGs release, TNF-α, MMP-13, and O2(-) with no effect on TIMP-1 and NO. In addition, the source of NO in normal and atorvastatin-treated cartilage was eNOS, while for IL-1ß-stimulated cartilage it was iNOS. The cartilage degradation was associated with the combined effects of increased NO and O2 (-) rather than only NO. CONCLUSION: The present study suggests that atorvastatin has the ability to protect cartilage degradation following IL-1ß-stimulated cartilage in in vitro OA model and supports additional therapeutic application of atorvastatin in OA.

Des-Arg9-bradykinin causes kinin B1 receptor mediated endothelium-independent contractions in endotoxin-treated porcine coronary arteries.

This study examined responses of isolated pig coronary arteries after kinin B1 receptor induction by endotoxin. Des-Arg9-bradykinin (DBK) induced concentration-dependent, endothelium-independent contractions in lipopolysaccharide (LPS)-treated but not untreated arterial rings. The B1-receptor antagonist SSR240612, but not the B2-receptor antagonist HOE140, prevented the endothelium-independent contractions to DBK. The DBK-induced contractions were blocked by indomethacin (nonselective cyclooxygenase [COX] inhibitor), celecoxib (selective COX-2 inhibitor), and terbogrel (thromboxane-prostanoid [TP] receptor antagonist) but not valeryl salicylate (selective COX-1 inhibitor), AH6809 (an E prostanoid [EP] and PGD2 receptor [DP1] receptor antagonist), AL 8810 (a selective PGF2α [FP] receptor antagonist), or RO1138452 (a selective I prostanoid [IP] receptor antagonist). They were attenuated by N-(p-amylcinnamoyl) anthranilic acid (ACA), and by DETCA plus tiron but not by l-NAME. Quantitative RT-PCR revealed excessive up-regulations of mRNA expressions of B1 receptors, COX-2, and thromboxane A synthase 1 (TBXAS1) following LPS incubation, but not of B2 receptors or COX-1. The present data demonstrate that B1 receptors are coupled to COX-2 in causing endothelium-independent contractions in endotoxin-treated pig coronary arteries. Accordingly, kinin B1 receptor induction during inflammation may have a pathological significance in the vasculature, particular in coronary arteries with dysfunctional endothelial cells.

COX-2 mediated induction of endothelium-independent contraction to bradykinin in endotoxin-treated porcine coronary artery.

This study examined the vascular effects of bradykinin in health and vascular inflammation comparing responses of isolated pig coronary arteries in the absence and presence of endotoxins. Bradykinin induced contractions in lipopolysaccharide-treated, but not untreated, arterial rings without endothelium. The B2-receptor antagonist HOE140, but not the B1-receptor inhibitor SSR240612, blocked these endothelium-independent contractions in response to bradykinin. The bradykinin-induced contractions were blocked by indomethacin, celecoxib, and terbogrel but not valeryl salicylate, AH6809, AL 8810, or RO1138452. They were attenuated by N-(p-amylcinnamoyl) anthranilic acid, and by diethyldithiocarbamate plus tiron but not by L-NAME. Quantitative reverse-transcription polymerase chain reaction revealed significant upregulations of messenger RNA expressions of B1 receptors, COX-2, and thromboxane A synthase 1 (TBXAS1) following lipopolysaccharide incubation but not of B2 receptors or COX-1. The present data demonstrate that bradykinin induces contractions mediated by the COX-2 pathway in endotoxin-treated pig coronary arteries. These results support differential roles of bradykinin in health and disease.

Gestational exposure to elevated testosterone levels induces hypertension via heightened vascular angiotensin II type 1 receptor signaling in rats.

Pre-eclampsia is a life-threatening pregnancy disorder whose pathogenesis remains unclear. Plasma testosterone levels are elevated in pregnant women with pre-eclampsia and polycystic ovary syndrome, who often develop gestational hypertension. We tested the hypothesis that increased gestational testosterone levels induce hypertension via heightened angiotensin II signaling. Pregnant Sprague-Dawley rats were injected with vehicle or testosterone propionate from Gestational Day 15 to 19 to induce a 2-fold increase in plasma testosterone levels, similar to levels observed in clinical conditions like pre-eclampsia. A subset of rats in these two groups was given losartan, an angiotensin II type 1 receptor antagonist by gavage during the course of testosterone exposure. Blood pressure levels were assessed through a carotid arterial catheter and endothelium-independent vascular reactivity through wire myography. Angiotensin II levels in plasma and angiotensin II type 1 receptor expression in mesenteric arteries were also examined. Blood pressure levels were significantly higher on Gestational Day 20 in testosterone-treated dams than in controls. Treatment with losartan during the course of testosterone exposure significantly attenuated testosterone-induced hypertension. Plasma angiotensin II levels were not significantly different between control and testosterone-treated rats; however, elevated testosterone levels significantly increased angiotensin II type 1 receptor protein levels in the mesenteric arteries. In testosterone-treated rats, mesenteric artery contractile responses to angiotensin II were significantly greater, whereas contractile responses to K(+) depolarization and phenylephrine were unaffected. The results demonstrate that elevated testosterone during gestation induces hypertension in pregnant rats via heightened angiotensin II type 1 receptor-mediated signaling, providing a molecular mechanism linking elevated maternal testosterone levels with gestational hypertension.

Atorvastatin attenuates neuropathic pain in rat neuropathy model by down-regulating oxidative damage at peripheral, spinal and supraspinal levels.

Atorvastatin is an HMG-CoA reductase inhibitor used in the treatment of hypercholesterolemia and prevention of coronary heart disease. Oxidative stress is considered to be one of the main causes of neuropathic pain after nerve injury. This study aimed to investigate the effect of atorvastatin on oxidative stress and hyperalgesia in chronic constriction injury (CCI) model of neuropathic pain. Pain behaviour in rats was evaluated before and after atorvastatin administration using mechanical and heat hyperalgesia. The markers for oxidative stress in sciatic nerve, spinal cord and pre-frontal cortex (PFC) area of brain were biochemically detected in vehicle and atorvastatin-treated neuropathic CCI rats. Atorvastatin attenuated hyperalgesia. We found a significant increase in malondialdehyde (MDA), nitric oxide (NO), superoxide anion (O2(-)) and protein carbonyl along with a reduction in catalase (CAT), reduced glutathione (GSH), total thiol (SH) and glutathione-S-transferase (GST) and; increase in superoxide dismutase (SOD) levels in the sciatic nerve, spinal cord and PFC of the CCI-induced neuropathic rats. Reduced levels of enzymatic and non enzymatic antioxidants were restored by atorvastatin. The levels of MDA, O2(-), and protein carbonyl in these tissues were significantly reduced in the atorvastatin-treated CCI rats compared to the untreated CCI rats. Our study demonstrated that atorvastatin attenuates neuropathic pain through inhibition of oxidative stress in sciatic nerve, spinal cord and brain suggesting antioxidants as potential drugs in neuropathic pain management. This study provides a new application of atorvastatin in treatment of neuropathic pain.

Antihyperalgesic and anti-inflammatory effects of atorvastatin in chronic constriction injury-induced neuropathic pain in rats.

Atorvastatin is a 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitor used in treatment of hypercholesterolemia and prevention of coronary heart disease. The aim of this study is to investigate the antihyperalgesic and anti-inflammatory effects of atorvastatin (3, 10, and 30 mg/kg by oral gavages for 14 days) in chronic constriction injury (CCI) model of neuropathic pain in rats. CCI caused significant increase in tumor necrosis factor-α, interleukin 1 beta, prostaglandin E2, along with matrix metalloproteases (MMP-2) and nerve growth factor (NGF) levels in sciatic nerve and spinal cord concomitant with mechanical and thermal hyperalgesia, which were significantly reduced by oral administration of atorvastatin for 14 days as compared to CCI rats. Our study demonstrated that atorvastatin attenuates neuropathic pain through inhibition of cytokines, MMP-2, and NGF in sciatic nerve and spinal cord suggesting that atorvastatin could be an additional therapeutic strategy in management of neuropathic pain.

Effect of iNOS inhibitor S-methylisothiourea in monosodium iodoacetate-induced osteoathritic pain: implication for osteoarthritis therapy.

Much information is available on the role of nitric oxide (NO) in osteoarthritis (OA). However, its role has not been studied in the monosodium iodoacetate (MIA)-induced model of osteoarthritic pain. The present study was undertaken in rats to investigate the effect of iNOS inhibitor S-methylisothiourea (SMT) in MIA-induced osteoathritic pain and disease progression in rats. Osteoarthritis was produced by single intra-articular injection of the MIA in the right knee joint on day 0. Treatment groups were orally gavazed with different doses of SMT (10, 30 and 100mg/kg) and etoricoxib (10mg/kg) daily for 21 days. On days 0, 3, 7, 14 and 21, pain was measured and histopathology of right knee joint was done on day 21. SMT produced analgesia in a dose-dependent manner as shown by mechanical, heat hyperalgesia, knee vocalization, knee squeeze test, and spontaneous motor activity test. SMT reduced NO production in synovial fluid. Histopathological findings indicated that SMT reduced disease progression as evident from complete cartilage formation in rats treated with SMT at 30 mg/kg. In conclusion, the results indicate that SMT attenuates the MIA-induced pain and histopathological changes in the knee joint. The antinociceptive and antiarthritic effects of SMT were mediated by inhibiting cartilage damage and suppression of NO in synovial fluid. It is suggested that SMT has potential as a therapeutic modality in the treatment of osteoarthritis.

Effect of S-methylisothiourea in acetaminophen-induced hepatotoxicity in rat.

Nitric oxide synthesized from inducible nitric oxide synthase (iNOS) plays role in acetaminophen (APAP)-induced liver damage. The present study was undertaken to evaluate the effect of iNOS inhibitor S-methylisothiourea (SMT) in APAP-induced hepatotoxicity in rats (1 g/kg, i.p.). SMT was (10, 30, and 100 mg/kg; i.p.) given 30 min before and 3 h after APAP administration. At 6 and 24 h, blood was collected to measure alanine transaminase (ALT), aspartate transaminase (AST), and nitrate plus nitrite (NOx) levels in serum. At 48 h, animals were sacrificed, and blood and liver tissues were collected for biochemical estimation. SMT reduced significantly the serum ALT, AST, and NOx levels at 24 and 48 h and liver NOx levels at 48 h as compared with APAP-treated control. The amount of peroxynitrite measured by rhodamine assay was significantly reduced by SMT, as compared with APAP-treated control group. SMT treatment (30 mg/kg) has significantly reduced the lipid peroxidation and protein carbonyl levels, increased SOD and catalase, and reduced glutathione and total thiol levels significantly as compared with APAP-treated control. SMT 30 mg/kg dose has protected animals from APAP-induced hypotension and reduced iNOS gene expression. Hepatocytes were isolated from animals, and effect of SMT on apoptosis, MTP, and ROS generation was studied, and their increased value in APAP intoxicated group was found to be significantly decreased by SMT (30 mg/kg) at 24 and 48 h. In conclusion, nitric oxide produced from iNOS plays important role in toxicity at late hours (24 to 48 h), and SMT inhibits iNOS and reduces oxidative and nitrosative stress.