Sleep deprivation reduces the baroreflex sensitivity through elevated angiotensin (Ang) II subtype 1 receptor expression in the nucleus tractus solitarii.

Introduction: Sleep insufficiency has been linked to an increased risk of high blood pressure and cardiovascular diseases. Emerging studies have demonstrated that impaired baroreflex sensitivity (BRS) is involved in the adverse cardiovascular effects caused by sleep deprivation, however, the underlying mechanisms remain unknown. Therefore, the present study aims to clarify the role of abnormal renin-angiotensin system in the nucleus tractus solitarii (NTS) in impaired BRS induced by sleep deprivation. Methods: Rats were randomly divided into two groups: normal sleep (Ctrl) and chronic sleep deprivation (CSD) group. Rats were sleep deprived by an automated sleep deprivation system. The blood pressure, heart rate, BRS, the number of c-Fos positive cells and the expression of angiotensin (Ang) II subtype 1 receptors (AT1R) in the NTS of rats were assessed. Results: Compared to Ctrl group, CSD group exhibited a higher blood pressure, heart rate, and reduced BRS. Moreover, the number of c-Fos positive cells and local field potential in the NTS in CSD group were increased compared with the Ctrl group. It was shown that the expression of the AT1R and the content of Ang II and the ratio of Ang II to Ang-(1-7) were increased in the NTS of rats in CSD group compared to Ctrl group. In addition, microinjection of losartan into the NTS significantly improved the impaired BRS caused by sleep deprivation. Discussion: In conclusion, these data suggest that the elevated AT1R expression in the NTS mediates the reduced BRS induced by chronic sleep deprivation.

miR-22-3p in the rostral ventrolateral medulla promotes hypertension through inhibiting ß-arrestin-1.

It has been documented that increased sympathetic activity contributes to the development of cardiovascular diseases, such as hypertension. We previously reported that ß-arrestin-1, a multifunctional cytoskeletal protein, was downregulated in the rostral ventrolateral medulla (RVLM) of the spontaneously hypertensive rat (SHR), and its overexpression elicited an inhibitory effect on sympathetic activity in hypertension. microRNA (miR)-22-3p has been reported to be associated with the pathological progress of hypertension. The purpose of this study was to determine the role of miR-22-3p in ß-arrestin-1-mediated central cardiovascular regulation in hypertension. It was observed that miR-22-3p was upregulated in the RVLM of SHRs compared with normotensive Wistar-Kyoto (WKY) rats, and it was subsequently confirmed to target the ß-arrestin-1 gene using a dual-luciferase reporter assay. miR-22-3p was downregulated in the RVLM using adeno-associated virus with 'tough decoys', which caused a significant increase of ß-arrestin-1 expression and decrease of noradrenaline and blood pressure (BP) in SHRs. However, upregulation of miR-22-3p using lentivirus in the RVLM of WKY rats significantly increased BP. In in vitro PC12 cells, enhanced oxidative stress activity induced by angiotensin II was counteracted by pretreatment with miR-22-3p inhibitor, and this effect could be abolished by ß-arrestin-1 gene knockdown. Furthermore, microglia exhaustion significantly diminished miR-22-3p expression, and enhanced ß-arrestin-1 expression in the RVLM of SHRs. Activation of BV2 cells in vitro evoked a significant increase of miR-22-3p expression, and this BV2 cell culture medium was also able to facilitate miR-22-3p expression in PC12 cells. Collectively, our findings support a critical role for microglia-derived miR-22-3p in inhibiting ß-arrestin-1 in the RVLM, which is involved in central cardiovascular regulation in hypertension. KEY POINTS: Impairment of ß-arrestin-1 function in the rostral ventrolateral medulla (RVLM) has been reported to be associated with the development of sympathetic overactivity in hypertension. However, little is known about the potential mechanisms of ß-arrestin-1 dysfunction in hypertension. miR-22-3p is implicated in multiple biological processes, but the role of miR-22-3p in central regulation of cardiovascular activity in hypertension remains unknown. We predicted that miR-22-3p could directly bind to the ß-arrestin-1 gene (Arrb1), and this hypothesis was confirmed by using a dual-luciferase reporter assay. Inhibition of ß-arrestin-1 by miR-22-3p was further verified in both in vivo and in vitro experiments. Furthermore, our results suggested miR-22-3p as a risk factor for oxidative stress in the RVLM, thus contributing to sympatho-excitation and hypertension. Our present study provides evidence that microglia-derived miR-22-3p may underlie the pathogenesis and progression of neuronal hypertension by inhibiting ß-arrestin-1 in the RVLM.

A systematic review and meta-analysis of cold exposure and cardiovascular disease outcomes.

Background: Cold exposure has been considered an essential risk factor for the global disease burden, while its role in cardiovascular diseases is still underappreciated. The increase in frequency and duration of extreme cold weather events like cold spells makes it an urgent task to evaluate the effects of ambient cold on different types of cardiovascular disease and to understand the factors contributing to the population's vulnerability. Methods: In the present systematic review and meta-analysis, we searched PubMed, Scopus, and Cochrane. We included original research that explored the association between cold exposure (low temperature and cold spell) and cardiovascular disease outcomes (mortality and morbidity). We did a random-effects meta-analysis to pool the relative risk (RR) of the association between a 1°C decrease in temperature or cold spells and cardiovascular disease outcomes. Results: In total, we included 159 studies in the meta-analysis. As a result, every 1°C decrease in temperature increased cardiovascular disease-related mortality by 1.6% (RR 1.016; [95% CI 1.015-1.018]) and morbidity by 1.2% (RR 1.012; [95% CI 1.010-1.014]). The most pronounced effects of low temperatures were observed in the mortality of coronary heart disease (RR 1.015; [95% CI 1.011-1.019]) and the morbidity of aortic aneurysm and dissection (RR 1.026; [95% CI 1.021-1.031]), while the effects were not significant in hypertensive disease outcomes. Notably, we identified climate zone, country income level and age as crucial influential factors in the impact of ambient cold exposure on cardiovascular disease. Moreover, the impact of cold spells on cardiovascular disease outcomes is significant, which increased mortality by 32.4% (RR 1.324; [95% CI 1.2341.421]) and morbidity by 13.8% (RR 1.138; [95% CI 1.015-1.276]). Conclusion: Cold exposure could be a critical risk factor for cardiovascular diseases, and the cold effect varies between disease types and climate zones. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO, identifier: CRD42022347247.

Inflammatory Response: A Crucial Way for Gut Microbes to Regulate Cardiovascular Diseases.

Gut microbiota is the largest and most complex microflora in the human body, which plays a crucial role in human health and disease. Over the past 20 years, the bidirectional communication between gut microbiota and extra-intestinal organs has been extensively studied. A better comprehension of the alternative mechanisms for physiological and pathophysiological processes could pave the way for health. Cardiovascular disease (CVD) is one of the most common diseases that seriously threatens human health. Although previous studies have shown that cardiovascular diseases, such as heart failure, hypertension, and coronary atherosclerosis, are closely related to gut microbiota, limited understanding of the complex pathogenesis leads to poor effectiveness of clinical treatment. Dysregulation of inflammation always accounts for the damaged gastrointestinal function and deranged interaction with the cardiovascular system. This review focuses on the characteristics of gut microbiota in CVD and the significance of inflammation regulation during the whole process. In addition, strategies to prevent and treat CVD through proper regulation of gut microbiota and its metabolites are also discussed.

Oxidative stress in the RVLM mediates sympathetic hyperactivity induced by circadian disruption.

Circadian rhythm plays a significant role in maintaining the function of the cardiovascular system. Emerging studies have demonstrated that circadian disruption enhances the risk of cardiovascular diseases by activating the sympathetic nervous system; however, the underlying mechanisms remain unknown. Therefore, this study aimed to clarify the role of oxidative stress in the rostral ventrolateral medulla (RVLM) in sympathetic hyperactivity induced by circadian disruption. Rats were randomly divided into two groups: the normal light and dark (LD) group and the circadian disruption (CD) group. Sympathetic nerve activity of rats was assessed by recording renal sympathetic nerve activity (RSNA) and indirect methods such as plasma level of norepinephrine (NE). The level of oxidative stress in the RVLM was detected by dihydroethidium probes. Moreover, the expression levels of the oxidative stress-related proteins in the RVLM were detected by Western blotting. Circadian disruption significantly increased blood pressure (BP), RSNA, and plasma levels of NE. Compared to the LD group, the CD group exhibited a more significant depressor response to i.v. hexamethonium bromide, a ganglionic blocker. Furthermore, the reactive oxygen species (ROS) production in the RVLM of rats with circadian disruption was significantly increased. In addition, BP and RSNA of rats with circadian disruption exhibited a greater decrease in the effects of microinjection of tempol, a superoxide scavenger, into the RVLM, compared to artificial cerebrospinal fluid (aCSF). Further investigation of the molecular mechanism by Western blotting showed that nuclear factor-erythroid-2-related factor 2 (Nrf2)/heme oxygenase 1 (HO1)/NAD(P)H: quinone oxidoreductase 1 (NQO1) signaling was down-regulated in the RVLM of circadian disruption rats. These data suggest that oxidative stress in the RVLM mediates sympathetic hyperactivity induced by circadian disruption and possibly by down-regulating Nrf2/HO1/NQO1 signaling.

The Release of Nitric Oxide Is Involved in the ß-Arrestin1-Induced Antihypertensive Effect in the Rostral Ventrolateral Medulla.

ß-Arrestin1 is a multifunctional scaffold protein with the ability to interact with diverse signaling molecules independent of G protein-coupled receptors. We previously reported that overexpression of ß-arrestin1 in the rostral ventrolateral medulla (RVLM) decreased blood pressure (BP) and renal sympathetic nerve activity (RSNA) in spontaneously hypertensive rats (SHRs). Nitric oxide (NO) is widely reported to be involved in central cardiovascular regulation. The goal of this study was to investigate whether NO signaling contributes to the ß-arrestin1-mediated antihypertensive effect in the RVLM. It was found that bilateral injection of adeno-associated virus containing Arrb1 gene (AAV-Arrb1) into the RVLM of SHRs significantly increased NO production and NO synthase (NOS) activity. Microinjection of the non-selective NOS inhibitor N-nitro-L-arginine methyl ester (L-NAME; 10 nmol) into the RVLM prevented the ß-arrestin1-induced cardiovascular inhibitory effect. Furthermore, ß-arrestin1 overexpression in the RVLM significantly upregulated the expression of phosphorylated neuronal NOS (nNOS) by 3.8-fold and extracellular regulated kinase 1/2 (ERK1/2) by 5.6-fold in SHRs. The ß-arrestin1-induced decrease in BP and RSNA was significantly abolished by treatment with ERK1/2 small interfering RNA (ERK1/2 siRNA). Moreover, ERK1/2 siRNA attenuated the ß-arrestin1-induced NO production, NOS activity, and nNOS phosphorylation in the RVLM. Taken together, these data demonstrate that the antihypertensive effect of ß-arrestin1 in the RVLM is mediated by nNOS-derived NO release, which is associated with ERK1/2 activation.

ß-Arrestin1 Reduces Oxidative Stress via Nrf2 Activation in the Rostral Ventrolateral Medulla in Hypertension.

Oxidative stress in the rostral ventrolateral medulla (RVLM), a key region for blood pressure (BP) regulation, has been demonstrated to be responsible for the overactivity of the sympathetic nervous system in hypertension and heart failure. Nuclear factor-erythroid-2-related factor 2 (Nrf2) is a key transcription factor that maintains redox homeostasis by governing a broad array of antioxidant genes in response to oxidative stress. ß-Arrestin1 is a multifunctional scaffold protein with the ability to interact with diverse signaling molecules independent of G protein-coupled receptors (GPCRs), and its overexpression in the RVLM could reduce BP and renal sympathetic nerve activity (RSNA) in spontaneously hypertensive rats (SHR). The goal of this study was to investigate whether Nrf2-mediated antioxidative stress is involved in the antihypertensive effect of ß-arrestin1 in the RVLM. It was found that the activation level of Nrf2 in the RVLM of SHR was significantly reduced, compared with normotensive Wistar-Kyoko (WKY) rats. Overexpression of ß-arrestin1 in the RVLM significantly decreased ROS production and facilitated the Nrf2 activation in the RVLM of SHR, accompanied by upregulating the expression of HO-1 and NQO-1. However, Nrf2 knockdown attenuated the antioxidant effect of ß-arrestin1 overexpression in the RVLM by downregulating HO-1 and NQO-1 expression levels. In conclusion, the current results suggested that the antihypertensive effect of ß-arrestin1 overexpression in the RVLM is mediated by decreased ROS production, which is associated with Nrf2 activation.

Interleukin enhancement binding factor 3 inhibits cardiac hypertrophy by targeting asymmetric dimethylarginine-nitric oxide.

Persistent cardiac hypertrophy eventually leads to deterioration of heart function and changes to normal morphology. Decreased nitric oxide (NO) production plays a critical role in modulating cardiac hypertrophy. Interleukin enhancement binding factor 3 (ILF3), a member of the double-stranded RNA-binding protein family, is known to regulate the transcription and stability of mRNA. Therefore, the major aim of the present study was to determine the role of ILF3 in reduction of NO production in cardiac hypertrophy. Cardiac hypertrophy models of neonatal rat cardiomyocytes (NRCMs) and adult rats were induced by angiotensin II (Ang II) in this study. First, it was found that ILF3 expression, NO production, and nitric oxide synthase (NOS) activity was decreased in cultured cardiomyocytes and adult rats treated with Ang II, compared with NRCMs treated with vehicle and rats treated with saline infusion, respectively. These effects induced by Ang II were significantly exacerbated by specific ILF3 knockdown. Moreover, the level of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NOS, was increased significantly in the Ang II-induced hypertrophic NRCMs and adult rats. Additionally, decreased protein expression and mRNA level of dimethylarginine dimethylaminohydrolases 1 (DDAH1, which degrades ADMA) were observed. Furthermore, specific ILF3 knockdown further aggravated these effects, but didn't reduce the expression level of NOS isoforms. In conclusion, our data show that ADMA accumulation-mediated decrease in NO production plays an important role in cardiomyocyte remodeling, which may be associated with ILF3-mediated DDAH1 reduction.

UPLC-QTOF/MS-based metabolomics reveals the mechanism of chronic unpredictable mild stress-induced hypertension in rats.

Hypertension is a common chronic disease, and it is the strongest risk factor for cardiovascular disease. Recently, the number of patients with hypertension-related complications has increased significantly, adding a heavy burden to the public health system. It is known that chronic stress plays an important role in the pathogenesis of cardiovascular diseases such as hypertension and stroke. However, the impact of hypertension on the dysfunctions induced by chronic stress remains poorly understood. In this study, using LC-MS-based metabolomics, we established a chronic stress model to demonstrate the mechanisms of stress-induced hypertension. We found that 30 metabolites in chronically stressed rats were changed; of these metabolites, seven had been upregulated, and 23 had been downregulated, including amino acids, phospholipids, carnitines and fatty acids, many of which are involved in amino acid metabolism, cell membrane injury, ATP supply and inflammation. These metabolites are engaged in dysregulated pathways and will provide a targeted approach to study the mechanism of stress-induced hypertension.

Overexpression of ß-Arrestin1 in the Rostral Ventrolateral Medulla Downregulates Angiotensin Receptor and Lowers Blood Pressure in Hypertension.

Background: Hypertension is characterized by sympathetic overactivity, which is associated with an enhancement in angiotensin receptor type I (AT1R) in the rostral ventrolateral medulla (RVLM). ß-arrestin1, a canonical scaffold protein, has been suggested to show a negative effect on G protein-coupled receptors via its internalization and desensitization and/or the biased signaling pathway. The major objectives of the present study were to observe the effect of ß-arrestin1 overexpression in the RVLM on cardiovascular regulation in spontaneously hypertensive rats (SHR), and further determine the effect of ß-arrestin1 on AT1R expression in the RVLM. Methods: The animal model of ß-arrestin1 overexpression was induced by bilateral injection of adeno-associated virus containing Arrb1 gene (AAV-Arrb1) into the RVLM of WKY and SHR. Results: ß-arrestin1 was expressed on the pre-sympathetic neurons in the RVLM, and its expression in the RVLM was significantly (P < 0.05) downregulated by an average of 64% in SHR than WKY. Overexpression of ß-arrestin1 in SHR significantly decreased baseline levels of blood pressure and renal sympathetic nerve activity, and attenuated cardiovascular effects induced by RVLM injection of angiotensin II (100 pmol). Furthermore, ß-arrestin1 overexpression in the RVLM significantly reduced the expression of AT1R by 65% and NF-κB p65 phosphorylation by 66% in SHR. It was confirmed that ß-arrestin1 overexpression in the RVLM led to an enhancement of interaction between ß-arrestin1 and IκB-α. Conclusion: Overexpression of ß-arrestin1 in the RVLM reduces BP and sympathetic outflow in hypertension, which may be associated with NFκB-mediated AT1R downregulation.

The asymmetric dimethylarginine-mediated inhibition of nitric oxide in the rostral ventrolateral medulla contributes to regulation of blood pressure in hypertensive rats.

Nitric oxide (NO) contributes to the central control of cardiovascular activity. The rostral ventrolateral medulla (RVLM) has been recognized as a pivotal region for maintaining basal blood pressure (BP) and sympathetic tone. It is reported that asymmetric dimethylarginine (ADMA), characterized as a cardiovascular risk marker, is an endogenous inhibitor of nitric oxide synthesis. The present was designed to determine the role of ADMA in the RVLM in the central control of BP in hypertensive rats. In Sprague Dawley (SD) rats, microinjection of ADMA into the RVLM dose-dependently increased BP, heart rate (HR), and renal sympathetic never activity (RSNA), but also reduced total NO production in the RVLM. In central angiotensin II (Ang II)-induced hypertensive rats and spontaneously hypertensive rat (SHR), the level of ADMA in the RVLM was increased and total NO production was decreased significantly, compared with SD rats treated vehicle infusion and WKY rats, respectively. These hypertensive rats also showed an increased protein level of protein arginine methyltransferases1 (PRMT1, which generates ADMA) and a decreased expression level of dimethylarginine dimethylaminohydrolases 1 (DDAH1, which degrades ADMA) in the RVLM. Furthermore, increased AMDA content and PRMT1 expression, and decreased levels of total NO production and DDAH1 expression in the RVLM in SHR were blunted by intracisternal infusion of the angiotensin II type 1 receptor (AT1R) blocker losartan. The current data indicate that the ADMA-mediated NO inhibition in the RVLM plays a critical role in involving in the central regulation of BP in hypertension, which may be associated with increased Ang II.

Exercise Training Improves the Altered Renin-Angiotensin System in the Rostral Ventrolateral Medulla of Hypertensive Rats.

The imbalance between angiotensin II (Ang II) and angiotensin 1-7 (Ang 1-7) in the brain has been reported to contribute to cardiovascular dysfunction in hypertension. Exercise training (ExT) is beneficial to hypertension and the mechanism is unclear. This study was aimed to determine if ExT improves hypertension via adjusting renin angiotensin system in cardiovascular centers including the rostral ventrolateral medulla (RVLM). Spontaneously hypertensive rats (SHR, 8 weeks old) were subjected to low-intensity ExT or kept sedentary (Sed) for 12 weeks. Blood pressure elevation coupled with increase in age was significantly decreased in SHR received ExT compared with Sed. The results in vivo showed that ExT significantly reduced or increased the cardiovascular responses to central application of sarthran (antagonist of Ang II) or A779 (antagonist of Ang 1-7), respectively. The protein expression of the Ang II acting receptor AT1R and the Ang 1-7 acting receptor Mas in the RVLM was significantly reduced and elevated in SHR following ExT, respectively. Moreover, production of reactive oxygen species in the RVLM was significantly decreased in SHR following ExT. The current data suggest that ExT improves hypertension via improving the balance of Ang II and Ang 1-7 and antioxidative stress at the level of RVLM.

The PI3K signaling-mediated nitric oxide contributes to cardiovascular effects of angiotensin-(1-7) in the nucleus tractus solitarii of rats.

Angiotensin-1-7 [Ang-(1-7)], acting via the Mas receptor in the central nervous system, is involved in the regulation of cardiovascular activity. Nitric oxide (NO) is implicated as an important modulator in the nucleus tractus solitarii (NTS), a key region involved in control of cardiovascular activity. The aim of the present study was to determine the role of phosphatidylinositol 3-kinase (PI3K) signaling in mediating the effect of Ang-(1-7) on NO generation in the NTS. In Sprague-Dawley rats, acute injection of Ang-(1-7) into the NTS significantly increased NO generation and neuronal/endothelial NO synthase (n/eNOS) activity, which were abolished by the selective Mas receptor antagonist d-Alanine-[Ang-(1-7)] (A-779), the PI3K inhibitor LY294002, or the Akt inhibitor triciribine (TCN). Western blotting analysis further demonstrated that Ang-(1-7) significantly increased levels of Akt/NOS phosphorylation in the NTS, and Ang-(1-7)-induced e/nNOS phosphorylation was antagonized by LY294002 or TCN. Furthermore, gene knockdown of PI3K by lentivirus containing small hairpin RNA in the NTS prevented the Ang-(1-7)-induced increases in NOS/Akt phosphorylation and NO production. The physiological (in vivo) experiments showed that pretreatment with the NOS inhibitor l-NAME, LY294002, or TCN abolished the decreases in blood pressure, heart rate, and renal sympathetic nerve activity induced by Ang-(1-7) injected into the NTS. Our findings suggest that nitric oxide release meditated by the Mas-PI3K-NOS signaling pathway is involved in the cardiovascular effects of Ang-(1-7) in the NTS.