NO synthase inhibition attenuates EDHF-mediated relaxation induced by TRPV4 channel agonist GSK1016790A in the rat pulmonary artery: Role of TxA2.

BACKGROUND: The aim of the present study was to observe the concomitant activation of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) pathways by TRPV4 channel agonist GSK1016790A in the rat pulmonary artery and explore the mechanism by which NO synthase inhibition attenuates EDHF-mediated relaxation in endothelium-intact rat pulmonary artery. METHODS: Tension experiments were conducted on the pulmonary artery from male Wistar rats. RESULTS: TRPV4 channel agonist GSK1016790A (GSK) caused concentration-dependent relaxation (Emax 86.9±4.6%; pD2 8.7±0.24) of the endothelium-intact rat pulmonary artery. Combined presence of apamin and TRAM-34 significantly attenuated the relaxation (Emax 61.1±6.0%) to GSK. l-NAME (100µM) significantly attenuated (8.2±2.9%) the relaxation response to GSK that was resistant to apamin plus TRAM-34. However, presence of ICI192605 or furegrelate alongwith l-NAME revealed the GSK-mediated EDHF-response (Emax of 28.5±5.2%; Emax 24.5±4.3%) in this vessel, respectively. Further, these two TxA2 modulators (ICI/furegrelate) alongwith l-NAME had no effect on SNP-induced endothelium-independent relaxation in comparison to l-NAME alone. This EDHF-mediated relaxation was sensitive to inhibition by K(+) channel blockers apamin and TRAM-34 or 60mMK(+) depolarizing solution. Further, combined presence of apamin and TRAM-34 in U46619 pre-contracted pulmonary arterial rings significantly reduced the maximal relaxation (Emax 71.6±6.9%) elicited by GSK, but had no effect on the pD2 (8.1±0.03) of the TRPV4 channel agonist in comparison to controls (Emax, 92.4±4.3% and pD2, 8.3±0.06). CONCLUSION: The present study suggests that NO and EDHF are released concomitantly and NO synthase inhibition attenuates GSK-induced EDHF response through thromboxane pathway in the rat pulmonary artery.

Erythropoietin Reverses Sepsis-Induced Vasoplegia to Norepinephrine Through Preservation of α1D-Adrenoceptor mRNA Expression and Inhibition of GRK2-Mediated Desensitization in Mouse Aorta.

We investigated the effect of erythropoietin (EPO) posttreatment on survival time and vascular functions in a mouse model of sepsis. Sepsis was induced by cecal ligation and puncture. After 20 ± 2 hours of sepsis, thoracic aorta was isolated for assessing its reactivity to norepinephrine (NE) and acetylcholine (ACh). We also measured the tissue nitric oxide (NO) level, inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), G protein-coupled receptor kinase 2 (GRK2), and α1D adrenoceptor messenger RNA (mRNA)/protein expression. In septic mice, EPO moderately improved the survival time from 19.68 ± 0.75 to 34.7 ± 3.2 hours. Sepsis significantly decreased the aortic contractile response to NE along with reduced α1D mRNA and protein expression. Erythropoietin significantly preserved the α1D receptor expression and restored NE-induced contractions to control levels in septic mice. Further, it attenuated the aortic α1D receptor desensitization in sepsis which was evident from reduced GRK2 mRNA expression. Accordingly, a selective GRK2 inhibitor markedly restored the contractile responses to NE in sepsis. Erythropoietin treatment attenuated iNOS mRNA expression and iNOS-induced overproduction of NO, but improved endothelium-dependent relaxation to ACh associated with increased eNOS mRNA expression. In conclusion, EPO seems to reverse sepsis-induced vasoplegia to NE through the preservation of α1D adrenoceptor mRNA/protein expression, inhibition of GRK2-mediated desensitization, and attenuation of NO overproduction in the mouse aorta.

Atorvastatin along with imipenem attenuates acute lung injury in sepsis through decrease in inflammatory mediators and bacterial load.

Lung is one of the vital organs which is affected during the sequential development of multi-organ dysfunction in sepsis. The purpose of the present study was to examine whether combined treatment with atorvastatin and imipenem could attenuate sepsis-induced lung injury in mice. Sepsis was induced by caecal ligation and puncture. Lung injury was assessed by the presence of lung edema, increased vascular permeability, increased inflammatory cell infiltration and cytokine levels in broncho-alveolar lavage fluid (BALF). Treatment with atorvastatin along with imipenem reduced the lung bacterial load and pro-inflammatory cytokines (IL-1ß and TNFα) level in BALF. The markers of pulmonary edema such as microvascular leakage and wet-dry weight ratio were also attenuated. This was further confirmed by the reduced activity of MPO and ICAM-1 mRNA expression, indicating the lesser infiltration and adhesion of inflammatory cells to the lungs. Again, expression of mRNA and protein level of iNOS in lungs was also reduced in the combined treatment group. Based on the above findings it can be concluded that, combined treatment with atorvastatin and imipenem dampened the inflammatory response and reduced the bacterial load, thus seems to have promising therapeutic potential in sepsis-induced lung injury in mice.

Assessment of Indian Rosewood (Dalbergia sissoo) Standardized Leaf Extract on Isoproterenol-Induced Myocardial Injury in Rats.

The present study was undertaken to evaluate the effect of alcoholic extract of Dalbergia sissoo leaf extract (DSE) on isoproterenol (ISP)-induced myocardial injury in rats. Evaluation of three doses (30, 100 and 300 mg/kg of body weight) of DSE was done in ISP-treated rats. ISP was used at 85 mg/kg body weight by subcutaneous route for two subsequent days to induce myocardial injury in rats. Assessment of myocardial injury was done by estimation of different cardiac injury markers like LDH, CK-MB. Serum cholesterol, LDL, HDL, triglycerides in serum, myocardial infarcted area, oxidative stress and histopathology in heart tissue were also assessed in rats. Mean arterial pressure and heart rate were recorded in all the groups. Rats pretreated with DSE (30, 100 and 300 mg/kg of body weight) showed significant (p < 0.05-0.001) improvement in the heart weight/body weight ratio, myocardial infarcted areas, heart rate and mean arterial pressure in ISP-induced myocardial injury. DSE showed significant (p < 0.05-0.001) improvement in serum LDH, CK-MB, cholesterol, LDL and triglyceride levels at all the dose levels. However, DSE pretreatment had no significant effect on serum HDL level. Pretreatment with DSE (30, 100 and 300 mg/kg body weight) showed significant (p < 0.001) reduction in MDA level in comparison with myocardial injured rats. Further, antioxidant potential was also improved in terms of improved activities of reduced glutathione, superoxide dismutase and catalase with the DSE pretreatment. Histopathology also showed significant improvement in heart tissue. The study suggests that DSE showed beneficial effect in ISP-induced myocardial injury in rats.