Momoh Audu Yakubu

[3H]yohimbine and [3H]idazoxan bind to different sites on rabbit forebrain and kidney membranes

The binding of the alpha 2-adrenoceptor ligands [3H]yohimbine and [3H]idazoxan to rabbit kidney and forebrain membranes was compared. The maximum number of [3H]yohimbine binding sites was higher than the number of [3H]idazoxan binding sites in forebrain and lower in kidney. Large differences were observed in the ability of noradrenaline, adrenaline, idazoxan, rauwolscine, yohimbine and WY 26392 to displace [3H]yohimbine and [3H]idazoxan from their binding sites. These data suggest that [3H]idazoxan and [3H]yohimbine bind to different sites on rabbit tissue membranes.

Differences in the regulation of [3H]idazoxan and [3H]yohimbine binding sites in the rabbit

In vitro studies suggest that [3H]yohimbine binds to alpha 2-adrenoceptors while [3H]idazoxan binds preferentially at a non-adrenergic site. In order to compare in vitro with in vivo effects male New Zealand White rabbits received the following treatments: 5 days idazoxan 1.1 mg/kg per h, 10 days noradrenaline 46 micrograms/kg per h (intravenous infusion), 21 days amitriptyline 30 mg/kg per day (intraperitoneally) or vehicle. The effect of these treatments on the number of [3H]yohimbine and [3H]idazoxan binding sites was examined. Ten days noradrenaline infusion and 21 days amitripytyline treatment significantly reduced [3H]yohimbine binding in kidney and hindbrain membranes respectively, but had no significant effect on [3H]idazoxan binding. Five days idazoxan infusion significantly increased [3H]yohimbine binding in the forebrain, while a significant reduction in [3H]idazoxan binding sites in the kidney was observed. Thus differential regulation of the two binding sites was observed in vivo. These alterations in binding site number are consistent with the differing affinities of noradrenaline and idazoxan for the [3H]yohimbine and [3H]idazoxan binding sites previously observed in vitro and support the hypothesis that in the rabbit idazoxan binds preferentially at non-adrenergic sites while yohimbine binds to an alpha 2-adrenergic site. The idazoxan site may be an imidazoline type of receptor but further work, including functional studies, is required to substantiate this.

Peroxisome Proliferator-Activated Receptor α Activation-Mediated Regulation of Endothelin-1 Production via Nitric Oxide and Protein Kinase C Signaling Pathways in Piglet Cerebral Microvascular Endothelial Cell Culture

Elevated endothelin (ET)-1 has been implicated in cerebrovascular complications following brain trauma characterized by dysregulation of endothelial nitric oxide synthase (eNOS), protein kinase C (PKC), and cerebral function. Recently, vascular expression of PPARα has been observed and suggested to improve vascular dysfunction. We speculate that activation of PPARα in cerebral microvessels can improve cerebral dysfunction following trauma, and we tested the hypothesis that activation of cerebral endothelial peroxisome proliferator-activated receptor (PPAR)α will attenuate ET-1 production via a mechanism involving nitric oxide (NO) and PKC. Phorbol 12-myristate 13-acetate (PMA) (1 μM), bradykinin (BK, 1 μM), angiotensin II (AII, 1 μM), or hemoglobin (Hem, 10 μM) increased ET-1 levels by 24-, 11.4-, 3.6-, or 1.3-fold increasing ET-1 levels from 0.36 ± 0.08 to 8.6 ± 0.8, 4.1 ± 0.7, 1.30 ± 0.1, or 0.47 ± 0.03 fmol/μg protein (p < 0.05), respectively. Clofibrate (10 μM) reduced basal ET-1 from 0.36 ± 0.08 (control) to 0.03 ± 0.01 and blunted vasoactive agent-induced increase to 0.12 ± 0.07 (PMA), 0.6 ± 0.04 (BK), 0.25 ± 0.03 (AII), or 0.12 ± 0.03 (Hem) fM/μg protein (p < 0.05). l-Arginine methyl ester (100 μM) inhibited clofibrate-induced reduction in basal ET-1 production. Clofibrate increased PPARα expression, accompanied by increased NO production and eNOS expression. PKC inhibition by calphostin C (10 μM) blocked these effects, whereas activation by PMA reduced basal PPARα expression. Thus, PPARα activation attenuated ET-1 production by agents that mediate brain injury through mechanisms that probably result from PPARα-induced increase in eNOS expression/NO production and complex PKC signaling pathways. Therefore, PPARα activators can be appropriate therapeutic agents to alleviate cerebrovascular dysfunction following cerebral vasospasm.

Sodium fluoride induces hypertension and cardiac complications through generation of reactive oxygen species and activation of nuclear factor kappa beta

Human exposure to sodium fluoride through its daily usage is almost inevitable. Cardiovascular and renal dysfunction has been associated with fluoride toxicity. Therefore, this study investigated the mechanism of action of sodium fluoride (NaF) induced hypertension and cardiovascular complications Forty male albino rats of an average of 10 rats per group were used. Group A received clean tap water. Toxicity was induced in Group B to D by administering graded doses of NaF through drinking water ad libitum for 10 days at 150 ppm, 300 ppm, and 600 ppm concentration respectively. Following administration of NaF, there was significant increase in systolic pressure, diastolic pressure and mean arterial pressure. Markers of oxidative stress; malondialdehyde, hydrogen peroxide, advance oxidation protein products, and protein carbonyl were significantly increased in dose‐dependent pattern in the cardiac and renal tissues of rats together with significant decrease in the GST activity in NaF‐treated rats compared to the control. Also serum markers of inflammation, cardiac, and renal damage including myeloperoxidase, xanthine oxidase, blood urea nitrogen, creatinine, Lactate dehydrogenase (LDH), and Creatinine kinase myocardial band (CK‐MB) significantly increased indicating induction of oxidative stress, renal, and cardiac damage after exposure. Histopathology of the kidney and heart revealed aberrations in the histological architecture in NaF‐treated rats. Also, immunohistochemistry showed higher expression of nuclear factor kappa beta (NF‐kB) in the cardiac and renal tissues of rats administered NaF. Combining all, these results indicate NaF‐induced hypertension through generation of reactive oxygen species and activation of renal and cardiac NF‐kB expressions.

Regulation of cerebral microvascular endothelial cell cyclooxygenase-2 message and activity by blood derived vasoactive agents

We have investigated the effects of prolonged treatment of cerebral microvascular endothelial cells with vasoconstrictor products of blood clot hemolysis on prostanoid production and cyclooxygenase (COX)/prostacyclin synthase activity and message. Confluent primary cultures of endothelial cells derived from piglet cerebral microvessels were incubated with endothelin-1 (ET-1; 10 nM) or thromboxane A(2) analog U-46619 (1 microM), alone or combined, and COX/prostacyclin synthase activity determined following exposure of treated cells to arachidonic acid (10 microM) for 30 min. 6-KetoPGF(1)alpha and PGE(2) levels in the medium were determined using radioimmunoassay. Effect of treatments on COX-2 message was determined by RNAse Protection Assay. Combined treatment with ET-1 (10 nM) and U-46619 (1 microM) for 24h significantly reduced 6-ketoPGF(1)alpha and PGE(2) levels in the media by 57% and 33%. Treatment of cells with U-46619 alone increased both 6-ketoPGF(1)alpha and PGE(2) level in the media by 170% and 42%. Incubation of control cells with arachidonic acid (10 microM) for 30 min increased 6-ketoPGF(1)alpha and PGE(2) production by 163% and 567%. Pretreatment with ET-1 or U-46619 alone for 24h had no significant effect on 6-ketoPGF(1)alpha produced from exogenous arachidonic acid. However, PGE(2) production from exogenous arachidonic acid by cells pretreated with ET-1 but not with U-46619 was attenuated by 35%. Combined treatment with ET-1 and U-46619 reduced both PGE(2) and 6-ketoPGF(1)alpha production from arachidonic acid by 14% and 40%, respectively. Acute incubation of cells with ET-1 or U-46619 did not have any significant effects on COX-2 mRNA. In conclusion, combined ET-1 and U-46619 reduced prostanoid production. The reduction cannot be fully explained by changes in COX/prostacyclin synthase activity and/or message, but the changes could be due to reduced availability of free arachidonic acid potentially resulting from inhibition of endothelial phospholipase A(2).

Differential modulation of bradykinin-induced relaxation of endothelin-1 and phenylephrine contractions of rat aorta by antioxidants

AbstractAim:We tested the hypothesis that bradykinin (BK)-induced relaxation of phe-nylephrine (PE) and endothelin-1 (ET-1) contractions can be differentially modulated by reactive oxygen species (ROS).Methods:Aortic rings isolated from Sprague-Dawley rats were used for the study. The contribution of ROS to PE (1×10−9−1×10−5 mol/L)- and ET-1 (1×10−10−1×10−8 mol/L)-induced contractions and the influence of ROS in BK (1×10−9−1×10−5 mol/L) relaxation of PE (1×10−7 mol/L) or ET-1 (1×10−9 mol/L)-induced tension was evaluated in the aorta in the presence or absence of the following antioxidants: catalase (CAT, 300 U/mL), superoxide dismutase (SOD, 300 U/mL), and vitamin C (1×10−4 mol/L).Results:Tension generated by ET-1 (1 ×10−9 mol/L) or PE (1×10−7 mol/L) was differentially relaxed by BK (1×10−5 mol/L), producing a maximal relaxation of 75%±5% and 35±4%, respectively. The BK (1×10−5 mol/L)-induced relaxation of PE (1×10−7 mol/L) tension was significantly enhanced from 35%±4% (control) to 56%±9%, 60%±5%, and 49%±6% by SOD, CAT, and vitamin C, respectively (P < 0.05, n =8). However, the relaxation of ET-1 (1×10−9 mol/L) tension was significantly attenuated from 75%±5% (control) to 37%±9%, 63%±4%, and 39%±7% by SOD, CAT, and vitamin C, respectively (P < 0.05, n =8). On the other hand, CAT had no effect on PE-induced tension, while SOD enhanced PE-induced tension (36%, P < 0.05, n =10) and vitamin C attenuated (66%, P < 0.05, n = 8) the tension induced by PE. By contrast, SOD or vitamin C had no effect, but CAT attenuated (44%, P < 0.05, n = 9) the tension induced by ET-1.Conclusion:We have demonstrated that O2− and H2O2 differentially modulate BK relaxation in an agonist-specific manner. O2− attenuates BK-induced relaxation of PE contraction, but contributes to the relaxation of ET-1 contraction. O2− seems to inhibit PE contraction, while H2O2 contributes to ET-1-induced contraction. Thus, ROS differentially modulate vascular tone depending on the vasoactive agent that is used to generate the tone.

Ameliorative Effect of Gallic Acid in Doxorubicin-Induced Hepatotoxicity in Wistar Rats Through Antioxidant Defense System

ABSTRACT Hepatotoxicity has been found to be one of the main side effects associated with doxorubicin (Dox) administration in cancer therapy. The aim of the present study was to examine the ameliorative effect of gallic acid (GA) in Dox-induced hepatotoxicity. Sixty male Wistar rats of 10 rats per group were used in this study and were randomly divided into 6 experimental groups (A–F). Rats in Group A served as the control group and received distilled water orally for 7 days; Group B was given Dox at 15 mg/kg body weight intraperitoneally (IP) on Day 8. Group C was given GA at 60 mg/kg body weight orally for 7 days + Dox at 15 mg/kg IP on Day 8. Group D was given GA at 120 mg/kg body weight orally for 7 days + Dox at 15 mg/kg IP on day 8. Rats in Groups E and F were administered GA alone at 60 and 120 mg/kg body weight orally for 7 days, respectively. Dox administration led to a significant reduction in hepatic reduced glutathione and nonprotein thiol (NPT) together with significant increase in hepatic malondialdehyde, hydrogen peroxide generation, superoxide dismutase, and catalase activity; hepatic glutathione peroxidase and glutathione-S-transferase activity were significantly inhibited in Dox-treated rats. The serum alanine aminotransferase (ALT), alkaline phosphatase, and total bilirubin concentrations were significantly elevated following Dox administration. Pretreatment with GA ameliorated Dox-induced hepatotoxicity and oxidative stress. The results suggest that GA may offer protection against hepatic damage in Dox cancer chemotherapy.

Effect of arsenic acid withdrawal on hepatotoxicity and disruption of erythrocyte antioxidant defense system

Graphical abstract

Ameliorative effect of gallic acid on doxorubicin-induced cardiac dysfunction in rats

Abstract Background: The use of doxorubicin (DOX) as an antineoplastic agent has been greatly limited because of the myriad of toxic sequelae associated with it. The aim of this study was to assess the protective effects of gallic acid (GA) on DOX-induced cardiac toxicity in rats. Methods: Sixty male rats (Wistar strain) were used in this study. They were divided into six groups (A–F) each containing 10 animals. Group A was the control. Rats in Groups B, C, and D were treated with DOX at the dosage of 15 mg/kg body weight i.p. Prior to this treatment, rats in Groups C and D had been treated orally with GA for 7 days at the dosage of 60 and 120 mg/kg, respectively. Animals from Groups E and F received only 60 and 120 mg/kg GA, respectively, which were administered orally for 7 days. Results: The exposure of rats to DOX led to a significant (p<0.05) decrease in the cardiac antioxidant defence system and elevation of creatine kinase myocardial band and lactate dehydrogenase. The electrocardiography results showed a significant decrease in heart rate, QRS, and QT-segment prolongation. GA alone improved the antioxidant defence system. Conclusions: The GA pretreatment significantly alleviated GA-associated ECG abnormalities, restored the antioxidant status and prevented cardiac damage.

Kolaviron, Biflavonoid Complex from the Seed of Garcinia kola Attenuated Angiotensin II- and Lypopolysaccharide-induced Vascular Smooth Muscle Cell Proliferation and Nitric Oxide Production.

Introduction: Kolaviron (KV), a biflavonoid extract from Garcinia kola seeds has been reported to possess anti-inflammatory, anti-oxidant, hepato-protective, cardio-protective, nephro-protective and other arrays of chemopreventive capabilities but the mechanism of action is still not completely understood. Materials and Methods: In this study, we investigated the anti-proliferative, anti-inflammatory and anti-oxidative potential of KV in cultured Vascular Smooth Muscle Cells (VSMCs). Effects of KV (25-100 μg/mL) on VSMC proliferation alone or following treatments with mitogen and proinflammatory agents Angiotensin II (Ag II, 10-6 M) and lipopolysaccharide (LPS, 100 μg/mL) and effects on NO production were determined. Cellular proliferations were determined by MTT assay, nitric oxide (NO) level was determined by Griess assay. KV dose-and time dependently attenuated VSMC growth. Results: Treatment of VSMCs with Ag II and LPS significantly enhanced proliferation of the cell which was significantly attenuated by the treatment with KV. Treatment of VSMC with LPS significantly increased nitric oxide (NO) level in the media which was attenuated by KV. These results demonstrated anti-proliferative anti-inflammatory properties of KV as it clearly inhibited cellular proliferation induced by mitogens as well as LPS-induced inflammatory processes. Conclusion: Therefore, KV may mitigate cardiovascular conditions that involve cell proliferation, free radical generation and inflammatory processes such as hypertension, diabetes and stroke. However, the molecular mechanism of action of KV needs to be investigated.