Protocatechuic acid exhibits hepatoprotective, vasculoprotective, antioxidant and insulin-like effects in dexamethasone-induced insulin-resistant rats.

Protocatechuic acid (PCA), the natural phenolic antioxidant, reportedly exhibited hypoglycemic and insulin-like effects. Recent studies have reported its cardioprotective effect in glucocorticoid (GC)-induced hypertensive rats. Nevertheless, its beneficial role has not been investigated in the setting of GCs excess-induced insulin resistance. This study aimed to investigate the possible protective potential and the plausible mechanisms of pretreatment with PCA against GCs-induced insulin resistance, liver steatosis and vascular dysfunction. Insulin resistance was induced in male Wistar rats by a 7-day treatment with dexamethasone (DEX) (1 mg/kg/day, i.p.). PCA (50, 100 mg/kg/day, orally) was started 7 days before DEX administration and continued during the test period. PCA significantly and dose-dependently attenuated DEX-induced a) glucose intolerance (↓ AUCOGTT), b) hyperglycemia (↓ fasting blood glucose), c) impaired insulin sensitivity [↓fasting plasma insulin and homeostasis model assessment of insulin resistance (HOMA-IR) index)] and d) dyslipidemia (↓total cholesterol, triglycerides, low-density lipoprotein-cholesterol and very low-density lipoprotein-cholesterol). PCA mitigated DEX-induced liver steatosis with associated reduction in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity. Moreover, PCA ameliorated DEX-induced vascular dysfunction and enhanced ACh-induced relaxation in aortic rings. The metabolic ameliorating effects of PCA might be attributed to the enhanced insulin signaling in soleus muscles (↑AKT phosphorylation) and mitigating gluconeogenesis (↓ hepatic mRNA expression of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). The vasculoprotective effect of PCA might be related to its ability to restore normal mRNA expression of [endothelial nitric oxide synthase (eNOS) and NADPH Oxidase 4 (NOX4)]. PCA restored normal oxidative balance [↓ oxidant species, malondialdehyde (MDA) and (↑ antioxidant superoxide dismutase (SOD)]. The findings herein reveal for the first time that PCA may be taken as a supplement with GCs to limit their metabolic and vascular side effects through its hypoglycemic, insulin-sensitizing, hypolipidemic and antioxidant effects.

Protective role of thymoquinone against liver damage induced by tamoxifen in female rats.

One of the major reasons for terminating a clinical trial is the liver toxicity induced by chemotherapy. Tamoxifen (TAM) is an anti-estrogen used in the treatment and prevention of hormone-dependent breast cancer. Tamoxifen therapy may cause hepatic injury. The seeds of Nigella sativa, which contain the active ingredient thymoquinone (TQ), have been used in folk medicine for diverse ailments. TQ is reported to possess anticancer and hepatoprotective effects. In this study, the protective effects of TQ against TAM-induced hepatotoxicity in female rats were evaluated. Four groups of rats were used: control; TAM; TQ; TAM+TQ. TAM (45 mg·(kg body mass)(-1)·day(-1), by intraperitoneal injection (i.p.), for 10 consecutive days) resulted in elevated serum levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase, total bilirubin, and gamma glutamyl transferase, as well as depletion of reduced glutathione in the liver and accumulation of lipid peroxides. Also, TAM treatment inhibited the hepatic activity of superoxide dismutase. Further, it raised the levels of tumor necrosis factor alpha in the liver and induced histopathological changes. Pretreatment with TQ (50 mg·(kg body mass)(-1)·day(-1); orally, for 20 consecutive days, starting 10 days before TAM injection) significantly prevented the elevation in serum activity of the assessed enzymes. TQ significantly inhibited TAM-induced hepatic GSH depletion and LPO accumulation. Consistently, TQ normalized the activity of SOD, inhibited the rise in TNF-α and ameliorated the histopathological changes. In conclusion, TQ protects against TAM-induced hepatotoxicity.

Allicin enhances chemotherapeutic response and ameliorates tamoxifen-induced liver injury in experimental animals.

CONTEXT: Tamoxifen (TAM) is widely used for treatment of hormone-dependent breast cancer; however, it may be accompanied with hepatic injury. Allicin is the most abundant thiosulfinate molecule from garlic with the potential to provide beneficial effects on various diseases. OBJECTIVE: To elucidate the effect of commercially available allicin on both antitumor activity and liver injury of TAM. MATERIALS AND METHODS: The cytotoxicity of TAM and/or allicin was evaluated in vitro using cultured Ehrlich ascites carcinoma (EAC) cells and in vivo against murine tumor (solid) model of EAC. TAM induced liver injury in rats by intraperitoneally (i.p.) injection at a dose of 45 mg/kg, for 7 successive days. RESULTS: TAM at a dose of 3 µM (IC50) significantly decreased percent survival of EAC to 52%. TAM combination with allicin (5 or 10 µM) showed a significant cytotoxic effect compared with the TAM-treated group as manifested by a decrease in percent survival of EAC to 35% and 29%, respectively. Allicin (10 mg/kg, orally) enhanced the efficacy of TAM (1 mg/kg, i.p.) in mice as manifested by a significant increase in solid tumor growth inhibition by 82% compared with 70% in the TAM group. In rats, TAM intoxication resulted in a significant decline in SOD, GSH, and total protein with significant elevation in TBARS, ALT and AST, ALP, LDH, total bilirubin, γGT, and TNF-α levels. These changes are abrogated by allicin treatment. DISCUSSION AND CONCLUSION: The results suggest the beneficial role of allicin as an adjuvant to TAM in cancer treatment by alleviating liver injury.

Propolis protects against high glucose-induced vascular endothelial dysfunction in isolated rat aorta.

While propolis is known to have abundant bioactive constituents and a variety of biological activities, it is not clear whether propolis has beneficial effects on high glucose-mediated vascular endothelial impairment. The aim of the present study was to investigate the potential protective effect of propolis extract against the acute vascular endothelial dysfunction resulting from exposure to high glucose load and to elucidate its underlying mechanism. Rat aortic rings were incubated with normal glucose (11 mM), high glucose (44 mM), or mannitol (44 mM) for 3 h with or without propolis extract (400 µg/ml). Contraction to phenylephrine (Phe, 10(-9)-10(-5) M) and relaxation to acetylcholine (ACh, 10(-9)-10(-5) M) and sodium nitroprusside (SNP, 10(-9)-10(-5) M) were measured before and after incubation. Changes in malondialdehyde (MDA), reduced glutathione (GSH), and superoxide dismutase (SOD) were also measured. Phe-induced contraction was impaired by high glucose as the E(max) decreased from 138.87 ± 11.43 to 103.65 ± 11.5 %. In addition, ACh-induced relaxation was impaired as the E(max) decreased from 99.80 ± 7.25 to 39.20 ± 6.5 %. SNP-induced relaxation was not affected. Furthermore, high glucose decreased the levels of both SOD (by 6 U/ml) and GSH (by 68 %) and increased levels of MDA (by 85 %). Propolis extract prevented high glucose-induced impairment of Phe and ACh responses and increased both SOD and GSH, leading to decreased MDA levels. In conclusion, propolis can protect against high glucose-induced vascular dysfunction by reducing oxidative stress.

Cardioprotective effect of grape-seed proanthocyanidins on doxorubicin-induced cardiac toxicity in rats.

CONTEXT: Doxorubicin (Dox) is an anthracycline antibiotic used as anticancer agent. However, its use is limited due to its cardiotoxicity which is mainly attributed to accumulation of reactive oxygen species. OBJECTIVE: This study was conducted to assess whether the antioxidant, proanthocyanidins (Pro) can ameliorate Dox-induced cardiotoxicity in rats. MATERIALS AND METHODS: Male Sprague-Dawely rats were divided into four groups. Group I was control. Group II received Pro (70 mg/kg, orally) once daily for 10 days. Group III received doxorubicin 15 mg/kg i.p. as a single dose on the 7th day and Group IV animals were treated with Pro once daily for 10 days and Dox on the 7th day. The parameters of study were serum biomarkers, cardiac tissue antioxidant status, ECG, and effect on aconitine-induced cardiotoxicity. RESULTS: Cardiac toxicity of doxorubicin was manifested as a significant increase in heart rate, elevation of the ST segment, prolongation of the QT interval and an increase in T wave amplitude. In addition, Dox enhanced aconitine-induced cardiotoxicity by a significant decrease in the aconitine dose producing ventricular tachycardia (VT). Administration of Pro significantly suppressed Dox-induced ECG changes and normalized the aconitine dose producing VT. The toxicity of Dox was also confirmed biochemically by significant elevation of serum CK-MB and LDH activities as well as myocardial MDA and GSH contents and decrease in serum catalase and myocardial SOD activities. Administration of Pro significantly suppressed these biochemical changes. DISCUSSION AND CONCLUSION: These results suggest that proanthocyanidins might be a potential cardioprotective agent against Dox-induced cardiotoxicity due to its antioxidant properties.

Protective potential of MMR vaccine against complete Freund's adjuvant-induced inflammation in rats.

The aim of the present study was to investigate the effect of MMR vaccine on inflammation which was induced by complete Freund's adjuvant (CFA) in male Sprague-Dawley rats. Rats were randomly divided into the control, CFA, MMR and CFA + MMR groups. Inflammatory symptoms such as paw oedema was measured in CFA-injected rats' paw. Body weight changes and alterations in some haematological parameters and oxidative stress markers following CFA injection were checked. In CFA-inflammed rats, there was a significant increase in rat paw thickness and decrease in body weight increment. MMR exhibited a significant anti-inflammatory effect as manifested by reduction in paw thickness and normal gain in body weight when administered 1 week prior to induction of inflammation. The altered haematological parameters (TLC) and oxidative stress markers (MDA, GSH, SOD) in the inflammed rats were significantly brought back to near normal by MMR treatment. In conclusion, MMR vaccine showed a reduction in rat paw thickness and it could significantly normalize the haematological and biochemical abnormalities in CFA-induced inflammatory pain model in rats. Our data suggested that MMR could be a potential protective agent against certain types of inflammatory pain. Further histopathological and radiological studies are required to confirm the possibility of developing novel therapeutic vaccines against some forms of arthritis.

Protective effects of propolis and thymoquinone on development of atherosclerosis in cholesterol-fed rabbits.

Hypercholesterolemia, cholesterol-enriched diet and oxidative stress have been shown to increase serum total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C) levels resulting in development of atherosclerosis. Antioxidants play an important role in inhibiting and scavenging free radicals, thus providing protection to humans against infectious and degenerative diseases. The present study was undertaken to examine the possible protective effects of propolis (a resinous hive product collected by honeybees from various plant sources) and thymoquinone (TQ, active constituent of Nigella. Sativa seeds oil) on serum lipid levels and early atherosclerotic lesions in hypercholestrolemic rabbits. New Zealand rabbits were fed on either standard chow or atherogenic diet during four weeks and concomitantly received either propolis or TQ. At the end of experiment period, serum samples were collected to determine lipid profile, kidney functions and antioxidant status. Tissues from aorta, pulmonary artery and kidney were taken for histopathological examination. The cholesterol-enriched diet induced a significant increase in serum TC, triglycerides, LDL-C, thiobarbituric acid-reactive substances concentrations and a significant decrease in high density lipoprotein-cholesterol and in reduced glutathione levels compared to control group. Administration of propolis or TQ with cholesterol-enriched diet significantly (p < 0.05) reduced TC, LDL-C, triglycerides and thiobarbituric acid-reactive substances concentrations, while increased high density lipoprotein-cholesterol concentration, as well as glutathione content compared to high cholesterol (HC) control group. Kidney function parameters were significantly affected by cholesterol diet and both propolis and TQ counterregulated the cholesterol-induced changes. Histopathologically, early atherosclerotic changes were observed in HC control group represented by endothelial damage and thickened foam cells while propolis or TQ provided protection against the HC-induced damage. In conclusion, the present study suggests the potential beneficial effects of both propolis and TQ in diminishing the risk of atherosclerosis via antioxidant mechanism.

Thymoquinone-induced relaxation of isolated rat pulmonary artery.

AIM OF THE STUDY: The effect of thymoquinone (TQ), the main constituent of the volatile oil of black seed (Nigella sativa L. family Ranunculaceae), on the isolated rat pulmonary arterial rings was investigated. MATERIALS AND METHODS: Isolated rat pulmonary arterial rings were precontracted with phenylephrine and concentration-response curves to TQ were constructed. The effects of different receptors antagonists or enzyme inhibitors were examined. RESULTS: TQ caused a concentration-dependent decrease in the tension of the pulmonary arterial rings precontracted by phenylephrine. The effects of TQ were not influenced by pretreatment of the rings with propranolol (a non-selective beta-blocker), atropine (a non-selective blocker for muscarinic receptors), theophylline (an adenosine receptor antagonist), indomethacin (a cyclooxygenase inhibitor), L-NAME (a NO synthase inhibitor), methylene blue (an inhibitor of soluble guanylyl cyclase) and nifedipine (a Ca(2+) channel blocker). The effects of TQ were significantly potentiated by bosentan (an ET(A)/ET(B) receptor antagonist). The effects of TQ were slightly abolished by pretreatment of the rings with glibenclamide (a non-selective blocker of ATP-sensitive K+ channels). TQ totally abolished the pressor effects of serotonin and phenylephrine on the isolated rat pulmonary arterial rings. CONCLUSION: The results of the present study suggest that TQ-induced relaxation of the precontracted pulmonary artery is probably mediated, at least in part, by activation of ATP-sensitive potassium channels and possibly by non-competitive blocking of serotonin, alpha1 and endothelin receptors.