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  • In vascular endothelial cells L arginine produces nitric

    2024-06-21

    In vascular endothelial cells, L-arginine produces nitric oxide (NO) under the action of nitric oxide synthase (NOS), and nitric oxide can activate guanylate cyclase to produce a large amount of cGMP, thereby relaxing vascular smooth muscle and expanding blood vessels. Numerous studies have confirmed that decreased NO/cGMP signaling leads to hypertension and vascular dysfunction (Huang et al., 1995, Groneberg et al., 2010). PDE5 inhibitors such as sildenafil can effectively enhance the amount of nitric oxide, which plays a hypotensive role (Webb et al., 2000). According to a meta-analysis, antihypertensive treatment can significantly reduce the risk of cardiovascular disease and death among patients from different populations (Ettehad et al., 2016). Previous studies show that IcarisideII has mild phosphodiesterase 5 (PDE5) inhibitory activity (Gao et al., 2017). In our study, IcarisideII can lower blood pressure in SHRs, especially in the middle and high dose groups. Moreover, it can also reduce myocardial apoptosis and improve ventricular remodeling. A reduction in blood pressure contributes to a reduction in left ventricle after load and likely decreases the stimulus for the left ventricle, successively leading to improve left heart ventricular remodeling and myocardial apoptosis. Myocardial Benzamil australia are permanent cells and only split during the embryonic period. Therefore, adult cardiomyocytes compensate for the increased load via hypertrophy. When this compensatory capacity exceeds its ability, myocardial cell apoptosis and pathological remodeling can occur. Therefore, the inhibition of myocardial apoptosis is an important measure for the prevention and treatment of cardiac remodeling. A study has shown that IcarisideII could reverse cognitive impairment by reducing neuronal apoptosis (Deng et al., 2017). IcarisideII can also protect PC12 cells from apoptosis induced by H2O2 (Gao et al., 2017). In this study, we found that the number of apoptotic myocardial cells in SHRs is 4.39 times higher than in WKY rats by Tunel staining, and IcarisideII at low, middle and high doses decreased the rate of SHR myocardial apoptosis by 2.1%, 9% and 30%, respectively. Therefore, we suggest that reducing cardiomyocyte apoptosis is also one of the mechanisms by which IcarisideII improves left ventricular remodeling in SHRs. Studies show that a large amount of reactive oxygen species (ROS) will be generated in the myocardial tissues when there is cardiac hypertrophy or heart failure (Zhou et al., 2014). Oxidative stress is caused by the production of reactive oxygen species that exceeds the antioxidant capacity of cells (Dobrian et al., 2004, Giordano, 2005). Excessive reactive oxygen species will result in lipid peroxidation and directly damage cell membranes, generating secondary species containing aldehyde, such as malondialdehyde (MDA), which are biological markers of oxidative tissue damage (Murdoch et al., 2006). Superoxide dismutase (SOD) is an important antioxidant enzyme in cardiac muscle tissues and its activity indirectly reflects the body's ability to eliminate oxygen free radicals. In our study, the generation of H2O2, •OH and MDA were noticeably increased and SOD activity was decreased in SHRs, indicating that oxidative stress was present. After the administration of IcarisideII, reactive oxygen species generation was decreased and SOD activity was enhanced, indicating that IcarisideII could inhibit the generation of reactive oxygen species in left ventricular remodeling and enhance the oxidation resistance of myocardial cells. Increased reactive oxygen species not only leads to oxidative damage but also serves as a second messenger in cell signaling (Maulik and Kumar, 2012). Reactive oxygen species can activate apoptosis signal-regulating kinase 1 (ASK1), which contributes to apoptosis due to reactive oxygen species sensitivity and activates Mitogen-Activated Protein Kinase Kinase Kinase (MAPKKK), which then can activate downstream mitogen-activated protein kinases (MAPKs) such as p38 and c-JUN amino terminal kinase (JNK) (Izumiya et al., 2003). MAPKs can directly act on the mitochondrial outer membrane and on mitochondria to influence mitochondrial function and induce cell apoptosis (Baines et al., 2002). The continuous activation of JNK can activate the transcription factor p53, which is a specific transcription factor for DNA repair and cell cycle arrest and can up-regulate the expression of apoptosis related genes. p38 can induce myocardial apoptosis by Bcl-xl deamidization and can reduce phosphorylation of the pro-apoptotic protein Bad (Ren et al., 2005). In the transgenic mouse heart and cardiomyocytes, the inhibition of p38 can up-regulate Bcl-2 expression (Grethe and Porn-Ares, 2006, Kaiser et al., 2004). In this study, the activation of ASK1, JNK and p38 in left ventricular tissue of SHRs significantly increased, but IcarisideII could reduce their activation (Fig. 8).