Myogenic tone is the response of the vascular smooth muscle to an increase in intraluminal pressure with vasoconstriction and with vasodilation when the pressure is decreased. Such myogenic tone contributes a level of physiological basal tone in response to neurohumoral stimuli. In spite of myogenic tone discovery by Sir William Bayliss 100 years ago, questions still remain regarding the underlying signaling mechanism of the myogenic response. Studies have shown that increased intraluminal pressure or wall tension leads to membrane depolarization, voltage-operated calcium channel (VOCC), stretch-activated cation (SAC) channels, extracelullar matrix (ECM) and actin cytoskeleton. Recently, evidence has shown a potential role for reactive oxygen species (ROS) as a key signalling mediator in the genesis of myogenic tone. The identification of the primary mechanosensors in the initiation of pressure-dependent myogenic tone is essential as these components could be potential therapeutical targets in the future.
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.
Penghasilan radikal bebas oleh nikotin dikaitkan dengan kerosakan sistem pembiakan lelaki terutamanya sperma dan testis. Penggunaan rawatan yang berasaskan herba seperti Hibiscus sabdariffa Linn. (HSE) kian meningkat disebabkan kandungan antioksida semula jadi yang tinggi. Oleh itu, kajian ini dijalankan untuk mengkaji kesan ekstrak akueus HSE terhadap kualiti sperma dan tekanan oksidatif testis tikus yang diadministrasi nikotin. Sejumlah 21 ekor tikus jantan Sprague-Dawley dibahagikan secara rawak kepada tiga kumpulan iaitu kumpulan kawalan, nikotin dan nikotin+HSE. Nikotin disuntik secara intraperitoneum pada dos 0.6 mg/kg berat badan manakala HSE diberikan pada dos 100 mg/kg berat badan secara paksaan oral sebelum administrasi nikotin pada setiap hari selama 21 hari berturut-turut. Hasil kajian menunjukkan bilangan, motiliti dan viabiliti sperma lebih tinggi secara signifikan (p<0.05) manakala peratus ketaknormalan morfologi sperma lebih rendah secara signifikan (p<0.05) bagi pada kumpulan nikotin+HSE berbanding kumpulan nikotin. Sementara itu berlakunya penurunan aras malondialdehid (MDA) dan peningkatan aras glutation terturun (GSH) secara signifikan (p<0.05) bagi kumpulan nikotin+HSE berbanding kumpulan nikotin. Pemerhatian histologi mendapati HSE berpotensi melindungi morfologi testis tikus aruhan nikotin. Kesimpulannya, kajian ini menunjukkan bahawa pemberian suplemen ekstrak HSE berpotensi mencegah kerosakan sperma dan testis akibat administrasi nikotin.
UKMR-1, a local variant of mutant Roselle strain (Hibiscus sabdariffa) is enriched with free radical scavenging polyphenols
such as anthocyanin, vitamin C and hydroxycitric acid. However, pharmacological actions of UKMR-1 are not fully known.
This study was conducted to determine whether supplementation of aqueous UKMR-1 calyx extract was able to protect
against nicotine-induced cardiac injury in rats. In this experimental study, healthy male albino rats were randomly
allotted into three groups (n=7 per group): control, nicotine and UKMR-1+Nicotine groups. Nicotine (0.6 mg/kg, i.p.)
was administered to both nicotine and UKMR-1+Nicotine groups for 28 consecutive days. UKMR-1+Nicotine group also
received 100 mg/kg UKMR-1 extract orally via gavage 30 min prior to nicotine injection, daily. UKMR-1+Nicotine group
had significantly (p<0.05) higher lactate dehydrogenase (LDH) activity, as well as lower malondialdehyde content in
heart tissue homogenate than nicotine group, suggesting its cardio protective activity by inhibition of lipid peroxidation.
UKMR-1 also lowered (p<0.05) the blood pressure in nicotine-administered rats. In addition, UKMR-1 significantly (p<0.05)
restored activities of cytosolic superoxide dismutase, glutathione peroxidase and glutathione-S-transferase as well as
redox balance ratio (GSH:GSSG). In conclusion, UKMR-1 was a
Nicotine has been identified as one of the causal factor for oxidative stress, hypertension and hyperlipidemia. Roselle has been widely studied for its potential as an antioxidant, antihyperlipidemic and antihypertensive. However, no studies have been done to investigate if roselle could diminish the oxidative stress caused by nicotine which could further lead to cardiac damages. Thus, this study was aimed to investigate the effect of roselle extract (HSE) on blood pressure, serum lipid profile, oxidative stress marker levels and histological changes to the heart in nicotine-treated rats. A total of 21 Sprague-Dawley rats were randomly divided into 3 groups (n=7 per group): Control group received normal saline (0.5 mL/day, i.p); nicotine group received 0.6 mg/kg/BW nicotine (i.p); and treated group received 100 mg/kg/b.w HSE through oral force feeding followed with 0.6 mg/kg/b.w nicotine (i.p) for 21 consecutive days. The results showed that HSE significantly (p>0.05) reduced the heart rate but no effect to the blood pressure. For lipid profile study, HSE increased the high-density lipoprotein concentration significantly (p<0.05) in rats given with nicotine, without any significant changes in total cholesterol, triglyceride and low-density lipoprotein (LDL) concentration. Besides, HSE treatment was also found to reverse malondialdehyde (MDA) level, superoxide dimustase (SOD) enzyme activity and protein concentration significantly (p<0.05) in nicotine-treated rats. In summary, these results indicated that HSE is an effective antioxidant against oxidative damage in heart caused by nicotine, but not as antihyperlipidemic and antihypertensive agent in this rat model.
Disturbances in immune system contribute to chronic infection among diabetic patients. Hibiscus sabdariffa L. (roselle) fruit extract has been scientifically proven to possess antioxidant, antidiabetic and antiinflammatory properties. The aim of this study was to investigate the effects of H. sabdariffa fruit extract against oxidative stress parameter and T lymphocyte population in spleen of streptozotocin (STZ) induced diabetic rats. Male Sprague-Dawley rats were injected with 45 mg/kg STZ to induce diabetic condition and further treated with 100 mg/kg H. sabdariffa fruit aquoeus extract daily for 28 days. Spleen was harvested to determine the oxidative stress indicators and quantification of T lymphocytes. The results showed a significant decreased in the number of spleen cells and spleen weight in the diabetic rats compared with control rats. However, there were no significant changes in the level of malondialdehyde (MDA), protein carbonyl and superoxide dismutase (SOD) activity the percentage of spleen CD3+ CD4+ and CD3+ CD8+ T lymphocytes amongst groups of study. In addition, histology observation showed no pathological alteration in spleen histology of diabetic rats. The findings suggested that aqueous extract of H. Sabdariffa fruit supplementation has no effect on the oxidative stress and the percentage of CD3+ CD4+ and CD3+ CD8+ T lymphocytes in spleen of diabetic rats.
Keywords: Diabetes, H. sabdariffa, spleen, oxidative stress, T lymphocytes