The vasorelaxant effect of Hibiscus sabdariffa linn. Polyphenol-rich extract (HPE) on rat’s isolated aorta

Hibiscus sabdariffa Linn. or also known as roselle which is rich in polyphenols, has been demonstrated to cause lowering of blood pressure in animal and clinical settings. However its exact mechanism of action particularly from polyphenolic compounds is not clearly understood. Therefore, we aimed to determine the effects of H. sabdariffa polyphenol extract (HPE) towards vascular reactivity and its mechanism of action. The HPE was studied on isolated thoracic aortic rings from normal Sprague-Dawley rats, suspended in a 15-ml organ chambers containing Krebs-Henseleit solution. The changes in tension were recorded by isometric transducer connected to data acquisition. HPE relaxed the contraction induced by phenylephrine (PE, 1 μM) in similar pattern for both endothelium-intact and endothelium denuded aortic rings in dose-dependent manner 0.1 ~ 0.9 mg/ml. The pretreatment with atropine (1 μM), a competitive muscarinic antagonist, and propranolol (1 μM), a non-selective beta- blocker did not alter HPE vasorelaxation response. In addition, HPE did not inhibit the contraction induced by extracellular Ca2+ precontracted by PE (1 μM) or KCl (60 mM), in Ca2+ -free solution, suggesting that the relaxation effect of HPE was not via inhibition of calcium channels. In conclusion, HPE demonstrated vasorelaxation effects on rat thoracic aorta although the underlying mechanism is still unknown. The vasorelaxation effect could be via angiotensin type 1 receptor inhibition in the vascular smooth muscle cells or the activation of hyperpolarizing K+ channel

Resveratrol Supplementation Protects against Nicotine-Induced Kidney Injury

Prolonged exposure to nicotine accelerates onset and progression of renal diseases in habitual cigarette smokers. Exposure to nicotine, either via active or passive smoking is strongly shown to enhance renal oxidative stress and augment kidney failure in various animal models. In this study, we investigated the effects of resveratrol supplementation on nicotine-induced kidney injury and oxidative stress in a rat model. Male Sprague-Dawley rats were given nicotine (0.6 mg/kg, i.p.) alone or in combination with either resveratrol (8 mg/kg, i.p.), or angiotensin II type I receptor blocker, irbesartan (10 mg/kg, p.o.) for 28 days. Upon completion of treatment, kidneys were investigated for changes in structure, kidney injury markers and oxidative stress. Administration of nicotine alone for 28 days resulted in significant renal impairment as shown by marked increase in plasma creatinine, blood urea nitrogen (BUN) and oxidative stress. Co-administration with resveratrol however successfully attenuated these changes, with a concomitant increase in renal antioxidants such as glutathione similar to the conventionally used angiotensin II receptor blocker, irbesartan. These data altogether suggest that targeting renal oxidative stress with resveratrol could alleviate nicotine-induced renal injury. Antioxidants may be clinically important for management of renal function in habitual smokers

Roselle attenuates cardiac hypertrophy after myocardial infarction in vivo and in vitro

Roselle (Hibiscus sabdariffa Linn) has been traditionally used as folk medicine for hypertension and maintaining cardiovascular health, with therapeutic potential in protecting against numerous cardiovascular diseases. However, it remains unclear whether roselle can be used for management of cardiac hypertrophy seen after myocardial in- farction (MI). This study therefore investigated the effects of aqueous roselle extract on cardiac hypertrophy aris- ing from myocardial infarction both in vivo and in vitro. For in vivo study, male Sprague-Dawley rats were divided into control or MI groups (receiving 85 mg/kg isoproterenol s.c. for 2 days) and were given roselle extract (100 mg/kg, p.o daily) for 28 days. Cardiac structure and functional changes were evaluated at study end-point using histology, Langendorff analysis and gene expression analysis. In vitro effects of roselle were also assessed on ANG II-induced cardiomyocytes hypertrophy using H9c2 cells, simulating cardiac hypertrophy evident after MI. Roselle significantly ameliorated MI-induced cardiac systolic and diastolic dysfunction, as seen across improve- ment in left ventricular developed pressure (LVDP) and its derivative (LVdP/dtmax) and isovolumic relaxation (Tau). Oxidative stress evident across elevated pro-oxidant markers (NOX2 subunit of NADPH oxidase and 8- isoprostane) as well as reduced antioxidant markers (superoxide dismutase and glutathione) were also significantly attenuated by roselle. Furthermore, roselle treatment markedly reduced markers of cardiac remodeling (cardiac hypertrophy and fibrosis) compared to the untreated MI rats. On in vitro analysis, roselle significantly attenuated ANG II-induced cardiomyoycte hypertrophy in dose-dependent manner. This study demonstrated that roselle at- nd dysfunction seen after MI both in vivo and in vitro, and these effects are likely mediated by phenolic compounds found in roselle extract