[Drug therapy targeting angiotensin II type 1 receptors in brain against frequent urination].

The production of angiotensin II (Ang II) in the brain plays important roles as neurotransmitter and neuropeptide. Central Ang II is involved in regulating various physiological processes, such as blood pressure and water homeostasis, via Ang II type 1 (AT1) receptors. We have demonstrated that Ang II induces frequent urination via AT1 receptors in the brain even at doses that does not seem to affect the blood pressure in animal experiment. Intracerebroventricular administration of Ang II was also found to reduce the bladder capacity without affecting the maximum voiding pressure, post voiding residual urine volume or voiding efficiency. Additionally, the activation of AT1 receptor downstream signal pathway (phospholipase C/protein kinase C/NADPH oxidase/superoxide anion) and suppression of GABAergic nervous system in the brain are involved in the mechanism underlying the central Ang II-inducted frequent urination. AT1 receptor blockers (ARBs) have been widely used to treat hypertension. We demonstrated that peripherally administered ARBs telmisartan, which can penetrate blood-brain barrier, exerted an inhibitory effect on central Ang II-inducted frequent urination. We present the possible drug therapy targeting AT1 receptors in the brain against frequent urination on the results obtained from our recent research work.

The Angiotensin Antagonist Losartan Modulates Social Reward Motivation and Punishment Sensitivity via Modulating Midbrain-Striato-Frontal Circuits.

Social deficits and dysregulations in dopaminergic midbrain-striato-frontal circuits represent transdiagnostic symptoms across psychiatric disorders. Animal models suggest that interactions between the dopamine (DA) and renin-angiotensin system (RAS) may modulate learning and reward-related processes. The present study therefore examined the behavioral and neural effects of the Angiotensin II type 1 receptor (AT1R) antagonist losartan on social reward and punishment processing in humans. A preregistered randomized double-blind placebo-controlled between-subject pharmacological design was combined with a social incentive delay (SID) functional MRI (fMRI) paradigm during which subjects could avoid social punishment or gain social reward. Healthy volunteers received a single-dose of losartan (50 mg, n = 43, female = 17) or placebo (n = 44, female = 20). We evaluated reaction times (RTs) and emotional ratings as behavioral and activation and functional connectivity as neural outcomes. Relative to placebo, losartan modulated the reaction time and arousal differences between social punishment and social reward. On the neural level the losartan-enhanced motivational salience of social rewards was accompanied by stronger ventral striatum-prefrontal connectivity during reward anticipation. Losartan increased the reward-neutral difference in the ventral tegmental area (VTA) and attenuated VTA associated connectivity with the bilateral insula in response to punishment during the outcome phase. Thus, losartan modulated approach-avoidance motivation and emotional salience during social punishment versus social reward via modulating distinct core nodes of the midbrain-striato-frontal circuits. The findings document a modulatory role of the renin-angiotensin system in these circuits and associated social processes, suggesting a promising treatment target to alleviate social dysregulations.SIGNIFICANCE STATEMENT Social deficits and anhedonia characterize several mental disorders and have been linked to the midbrain-striato-frontal circuits of the brain. Based on initial findings from animal models we here combine the pharmacological blockade of the Angiotensin II type 1 receptor (AT1R) via losartan with functional MRI (fMRI) to demonstrate that AT1R blockade enhances the motivational salience of social rewards and attenuates the negative impact of social punishment via modulating the communication in the midbrain-striato-frontal circuits in humans. The findings demonstrate for the first time an important role of the AT1R in social reward processing in humans and render the AT1R as promising novel treatment target for social and motivational deficits in mental disorders.

Storax Attenuates Cardiac Fibrosis following Acute Myocardial Infarction in Rats via Suppression of AT1R-Ankrd1-P53 Signaling Pathway.

Myocardial fibrosis following acute myocardial infarction (AMI) seriously affects the prognosis and survival rate of patients. This study explores the role and regulation mechanism of storax, a commonly used traditional Chinese medicine for treatment of cardiovascular diseases, on myocardial fibrosis and cardiac function. The AMI rat model was established by subcutaneous injection of Isoproterenol hydrochloride (ISO). Storax (0.1, 0.2, 0.4 g/kg) was administered by gavage once/d for 7 days. Electrocardiogram, echocardiography, hemodynamic and cardiac enzyme in AMI rats were measured. HE, Masson, immunofluorescence and TUNEL staining were used to observe the degree of pathological damage, fibrosis and cardiomyocyte apoptosis in myocardial tissue, respectively. Expression of AT1R, CARP and their downstream related apoptotic proteins were detected by WB. The results demonstrated that storax could significantly improve cardiac electrophysiology and function, decrease serum cardiac enzyme activity, reduce type I and III collagen contents to improve fibrosis and alleviate myocardial pathological damage and cardiomyocyte apoptosis. It also found that storax can significantly down-regulate expression of AT1R, Ankrd1, P53, P-p53 (ser 15), Bax and cleaved Caspase-3 and up-regulate expression of Mdm2 and Bcl-2. Taken together, these findings indicated that storax effectively protected cardiomyocytes against myocardial fibrosis and cardiac dysfunction by inhibiting the AT1R-Ankrd1-P53 signaling pathway.

Association of Antihypertensives That Stimulate vs Inhibit Types 2 and 4 Angiotensin II Receptors With Cognitive Impairment.

Importance: Use of antihypertensive medications that stimulate type 2 and 4 angiotensin II receptors, compared with those that do not stimulate these receptors, has been associated with a lower risk of dementia. However, this association with cognitive outcomes in hypertension trials, with blood pressure levels in the range of current guidelines, has not been evaluated. Objective: To examine the association between use of exclusively antihypertensive medication regimens that stimulate vs inhibit type 2 and 4 angiotensin II receptors on mild cognitive impairment (MCI) or dementia. Design, Setting, and Participants: This cohort study is a secondary analysis (April 2011 to July 2018) of participants in the randomized Systolic Blood Pressure Intervention Trial (SPRINT), which recruited individuals 50 years or older with hypertension and increased cardiovascular risk but without a history of diabetes, stroke, or dementia. Data analysis was conducted from March 16 to July 6, 2021. Exposures: Prevalent use of angiotensin II receptor type 2 and 4-stimulating or -inhibiting antihypertensive medication regimens at the 6-month study visit. Main Outcomes and Measures: The primary outcome was a composite of adjudicated amnestic MCI or probable dementia. Results: Of the 8685 SPRINT participants who were prevalent users of antihypertensive medication regimens at the 6-month study visit (mean [SD] age, 67.7 [11.2] years; 5586 [64.3%] male; and 935 [10.8%] Hispanic, 2605 [30.0%] non-Hispanic Black, 4983 [57.4%] non-Hispanic White, and 162 [1.9%] who responded as other race or ethnicity), 2644 (30.4%) were users of exclusively stimulating, 1536 (17.7%) inhibiting, and 4505 (51.9%) mixed antihypertensive medication regimens. During a median of 4.8 years of follow-up (95% CI, 4.7-4.8 years), there were 45 vs 59 cases per 1000 person-years of amnestic MCI or probable dementia among prevalent users of regimens that contained exclusively stimulating vs inhibiting antihypertensive medications (hazard ratio [HR], 0.76; 95% CI, 0.66-0.87). When comparing stimulating-only vs inhibiting-only users, amnestic MCI occurred at rates of 40 vs 54 cases per 1000 person-years (HR, 0.74; 95% CI, 0.64-0.87) and probable dementia at rates of 8 vs 10 cases per 1000 person-years (HR, 0.80; 95% CI, 0.57-1.14). Negative control outcome analyses suggested the presence of residual confounding. Conclusions and Relevance: In this secondary analysis of SPRINT, prevalent users of regimens that contain exclusively antihypertensive medications that stimulate vs inhibit type 2 and 4 angiotensin II receptors had lower rates of incident cognitive impairment. Residual confounding cannot be ruled out. If these results are replicated in randomized clinical trials, certain antihypertensive medications could be prioritized to prevent cognitive decline.

AGTR1 blocker attenuates activation of Tenon's capsule fibroblasts after glaucoma filtration surgery via the NF-κB signaling pathway.

Activation of Tenon's capsule fibroblasts limits the success rate of glaucoma filtration surgery (GFS), the most efficacious therapy for patients with glaucoma. Angiotensin type 1 receptor (AGTR1) is involved in tissues remodeling and fibrogenesis. However, whether AGTR1 is involved in the progress of fibrogenesis after GFS is not fully elucidated. The aim of this study was to investigate the role of an AGTR1 in scar formation after GFS and the potential anti-fibrosis effect of AGTR1 blocker. AGTR1 expression level was increased in subconjunctival tissues in a rat model of GFS and transforming growth factor-beta 2 (TGF-ß2)-induced human Tenon's capsule fibroblasts (HTFs). AGTR1 blocker treatment suppressed TGF-ß2-induced HTF migration and α-smooth muscle actin (α-SMA) and fibronectin (FN) expression. AGTR1 blocker treatment also attenuated collagen deposition and α-SMA and FN expression in subconjunctival tissues of the rat model after GFS. Moreover, AGTR1 blocker decreased TGF-ß2-induced P65 phosphorylation, P65 nuclear translocation, and nuclear factor kappa B (NF-κB) luciferase activity. Additionally, BAY 11-7082 (an NF-κB inhibitor) significantly suppressed HTF fibrosis. In conclusion, our results indicate that AGTR1 is involved in scar formation after GFS. The AGTR1 blocker attenuates subconjunctival fibrosis after GFS by inhibiting the NF-κB signaling pathway. These findings indicate that targeting AGTR1 is a potential approach to attenuate fibrosis after GFS.

Low-dose candesartan prevents schizophrenia-like behavioral alterations in a neurodevelopmental two-hit model of schizophrenia.

Schizophrenia is a severe mental disorder with complex etiopathogenesis. Based on its neurodevelopmental features, an animal model induced by "two-hit" based on perinatal immune activation followed by peripubertal unpredictable stress was proposed. Sex influences the immune response, and concerning schizophrenia, it impacts the age of onset and symptoms severity. The neurobiological mechanisms underlying the influence of sex in schizophrenia is poorly understood. Our study aimed to evaluate sex influence on proinflammatory and oxidant alterations in male and female mice exposed to the two-hit model of schizophrenia, and its prevention by candesartan, an angiotensin II type 1 receptor (AT1R) blocker with neuroprotective properties. The two-hit model induced schizophrenia-like behavioral changes in animals of both sexes. Hippocampal microglial activation alongside the increased expression of NF-κB, and proinflammatory cytokines, namely interleukin (IL)-1ß and TNF-α, were observed in male animals. Conversely, females presented increased hippocampal and plasma levels of nitrite and plasma lipid peroxidation. Peripubertal administration of low-dose candesartan (0.3 mg/kg PO) prevented behavioral, hippocampal, and systemic changes in male and female mice. While these results indicate the influence of sex on inflammatory and oxidative changes induced by the two-hit model, candesartan was effective in both males and females. The present study advances the neurobiological mechanisms underlying sex influence in schizophrenia and opens new avenues to prevent this devasting mental disorder.

Angiotensin II type 1 receptor is involved in flow-induced vasomotor responses of isolated middle cerebral arteries: role of oxidative stress.

This study aimed to determine the mechanosensing role of angiotensin II type 1 receptor (AT1R) in flow-induced dilation (FID) and oxidative stress production in middle cerebral arteries (MCA) of Sprague-Dawley rats. Eleven-week old, healthy male Sprague-Dawley rats on a standard diet were given the AT1R blocker losartan (1 mg/mL) in drinking water (losartan group) or tap water (control group) ad libitum for 7 days. Blockade of AT1R attenuated FID and acetylcholine-induced dilation was compared with control group. Nitric oxide (NO) synthase inhibitor Nω-nitro-l-arginine methyl ester (l-NAME) and cyclooxygenase inhibitor indomethacin (Indo) significantly reduced FID in control group. The attenuated FID in losartan group was further reduced by Indo only at Δ100 mmHg, whereas l-NAME had no effect. In losartan group, Tempol (a superoxide scavenger) restored dilatation, whereas Tempol + l-NAME together significantly reduced FID compared with restored dilatation with Tempol alone. Direct fluorescence measurements of NO and reactive oxygen species (ROS) production in MCA, in no-flow conditions revealed significantly reduced vascular NO levels with AT1R blockade compared with control group, whereas in flow condition increased the NO and ROS production in losartan group and had no effect in the control group. In losartan group, Tempol decreased ROS production in both no-flow and flow conditions. AT1R blockade elicited increased serum concentrations of ANG II, 8-iso-PGF2α, and TBARS, and decreased antioxidant enzyme activity (SOD and CAT). These results suggest that in small isolated cerebral arteries: 1) AT1 receptor maintains dilations in physiological conditions; 2) AT1R blockade leads to increased vascular and systemic oxidative stress, which underlies impaired FID.NEW & NOTEWORTHY The AT1R blockade impaired the endothelium-dependent, both flow- and acetylcholine-induced dilations of MCA by decreasing vascular NO production and increasing the level of vascular and systemic oxidative stress, whereas it mildly influenced the vascular wall inflammatory phenotype, but had no effect on the systemic inflammatory response. Our data provide functional and molecular evidence for an important role of AT1 receptor activation in physiological conditions, suggesting that AT1 receptors have multiple biological functions.

Soluble (pro)renin receptor induces endothelial dysfunction and hypertension in mice with diet-induced obesity via activation of angiotensin II type 1 receptor.

Until now, renin-angiotensin system (RAS) hyperactivity was largely thought to result from angiotensin II (Ang II)-dependent stimulation of the Ang II type 1 receptor (AT1R). Here we assessed the role of soluble (pro)renin receptor (sPRR), a product of site-1 protease-mediated cleavage of (pro)renin receptor (PRR), as a possible ligand of the AT1R in mediating: (i) endothelial cell dysfunction in vitro and (ii) arterial dysfunction in mice with diet-induced obesity. Primary human umbilical vein endothelial cells (HUVECs) treated with a recombinant histidine-tagged sPRR (sPRR-His) exhibited IκBα degradation concurrent with NF-κB p65 activation. These responses were secondary to sPRR-His evoked elevations in Nox4-derived H2O2 production that resulted in inflammation, apoptosis and reduced NO production. Each of these sPRR-His-evoked responses was attenuated by AT1R inhibition using Losartan (Los) but not ACE inhibition using captopril (Cap). Further mechanistic exploration revealed that sPRR-His activated AT1R downstream Gq signaling pathway. Immunoprecipitation coupled with autoradiography experiments and radioactive ligand competitive binding assays indicate sPRR directly interacts with AT1R via Lysine199 and Asparagine295. Important translational relevance was provided by findings from obese C57/BL6 mice that sPRR-His evoked endothelial dysfunction was sensitive to Los. Besides, sPRR-His elevated blood pressure in obese C57/BL6 mice, an effect that was reversed by concurrent treatment with Los but not Cap. Collectively, we provide solid evidence that the AT1R mediates the functions of sPRR during obesity-related hypertension. Inhibiting sPRR signaling should be considered further as a potential therapeutic intervention in the treatment and prevention of cardiovascular disorders involving elevated blood pressure.

Localization of angiotensin II type 1 receptor gene expression in rodent and human kidneys.

The kidneys are an important target for angiotensin II (ANG II). In adult kidneys, the effects of ANG II are mediated mainly by ANG II type 1 (AT1) receptors. AT1 receptor expression has been reported for a variety of different cell types within the kidneys, suggesting a broad spectrum of actions for ANG II. Since there have been heterogeneous results in the literature regarding the intrarenal distribution of AT1 receptors, this study aimed to obtain a comprehensive overview about the localization of AT1 receptor expression in mouse, rat, and human kidneys. Using the cell-specific and high-resolution RNAscope technique, we performed colocalization experiments with various cell markers to specifically discriminate between different segments of the tubular and vascular system. Overall, we found a similar pattern of AT1 mRNA expression in mouse, rat, and human kidneys. AT1 receptors were detected in mesangial cells and renin-producing cells. In addition, AT1 mRNA was found in interstitial cells of the cortex and outer medulla. In rodents, late afferent and early efferent arterioles expressed AT1 receptor mRNA, but larger vessels of the investigated species showed no AT1 expression. Tubular expression of AT1 mRNA was species dependent with a strong expression in proximal tubules of mice, whereas expression was undetectable in human tubular cells. These findings suggest that the (juxta)glomerular area and tubulointerstitium are conserved expression sites for AT1 receptors across species and might present the main target sites for ANG II in adult human and rodent kidneys.NEW & NOTEWORTHY Angiotensin II (ANG II) type 1 (AT1) receptors are essential for mediating the effects of ANG II in the kidneys. This study aimed to obtain a comprehensive overview about the cell-specific localization of AT1 receptor expression in rodent and human kidneys using the novel RNAscope technique. We found that the conserved AT1 receptor mRNA expression sites across species are the (juxta)glomerular areas and tubulointerstitium, which might present main target sites for ANG II in adult human and rodent kidneys.

Angiotensin II type 1 receptor mediates pulmonary hypertension and right ventricular remodeling induced by inhaled nicotine.

Use of electronic cigarettes is rapidly increasing among youth and young adults, but little is known regarding the long-term cardiopulmonary health impacts of these nicotine-containing devices. Our group has previously demonstrated that chronic, inhaled nicotine induces pulmonary hypertension (PH) and right ventricular (RV) remodeling in mice. These changes were associated with upregulated RV angiotensin-converting enzyme (ACE). Angiotensin II receptor blockers (ARBs) have been shown to reverse cigarette smoking-induced PH in rats. ACE inhibitor and ARB use in a large retrospective cohort of patients with PH is associated with improved survival. Here, we utilized losartan (an ARB specific for angiotensin II type 1 receptor) to further explore nicotine-induced PH. Male C57BL/6 mice received nicotine vapor for 12 h/day, and exposure was assessed using serum cotinine to achieve levels comparable to human smokers or electronic cigarette users. Mice were exposed to nicotine for 8 wk and a subset was treated with losartan via an osmotic minipump. Cardiac function was assessed using echocardiography and catheterization. Although nicotine exposure increased angiotensin II in the RV and lung, this finding was nonsignificant. Chronic, inhaled nicotine significantly increased RV systolic pressure and RV free wall thickness versus air control. These parameters were significantly lower in mice receiving both nicotine and losartan. Nicotine significantly increased RV internal diameter, with no differences seen between the nicotine and nicotine-losartan group. Neither nicotine nor losartan affected left ventricular structure or function. These findings provide the first evidence that antagonism of the angiotensin II type 1 receptor can ameliorate chronic, inhaled nicotine-induced PH and RV remodeling.NEW & NOTEWORTHY Chronic, inhaled nicotine causes pulmonary hypertension and right ventricular remodeling in mice. Treatment with losartan, an angiotensin II type 1 receptor antagonist, ameliorates nicotine-induced pulmonary hypertension and right ventricular remodeling. This novel finding provides preclinical evidence for the use of renin-angiotensin system-based therapies in the treatment of pulmonary hypertension, particularly in patients with a history of tobacco-product use.

Effect of Estrogen and Progesterone Hormones on the Expression of Angiotensin II Receptors in the Heart and Aorta of Male Rats.

BACKGROUND: Activation of the Angiotensin II type 1 receptor (AT1R) has been implicated in the pathogenesis of the cardiovascular disease, while activation of Angiotensin II type 2 receptor (AT2R) leads to effects that are opposite to those mediated by AT1R. The interaction between female sex hormones and the renin-angiotensin system was proven to play an essential role in the pathological changes in the cardiovascular system. OBJECTIVES: To investigate the direct effect of estrogen and progesterone on arterial and cardiac AT1R and AT2R expression in vivo in male. METHOD: Male adult rats were assigned into four groups: Group 1 (control), group 2 (progesterone treated group; 10mg/kg), group 3 (estrogen treated group; 20µg/kg) and group 4 (progesterone; 10mg/kg + estrogen; 20µg/kg treated group). All treatments were administrated subcutaneously every second day for 21days. RESULTS: Estrogen treatments increase the left ventricle (LV) protein expression of AT1R, and progesterone treatment decreased the LV protein expression of AT2R. In the aorta, estrogen treatment increased the mRNA expression levels of AT1R, while progesterone treatment increased the AT2R mRNA expression levels. Estrogen treatment decreases the LV and aortic endothelial nitric-oxide synthase (eNOS) mRNA levels while progesterone treatments decrease the LV eNOS mRNA levels but increase the aortic eNOS mRNA levels. The serum angiotensin II levels were increased by estrogen treatment only. CONCLUSION: Both estrogen and progesterone treatments appear to have a harmful effect on the male rat hearts, possibly by increasing the protein expression of AT1R (for estrogen), decrease the protein and mRNA expression of AT2R (for progesterone), and decrease the eNOS mRNA levels (for both). However, it seems that progesterone but not estrogen exerts a vascular protective effect in males.

An Angiotensin-Responsive Connection from the Lamina Terminalis to the Paraventricular Nucleus of the Hypothalamus Evokes Vasopressin Secretion to Increase Blood Pressure in Mice.

Blood pressure is controlled by endocrine, autonomic, and behavioral responses that maintain blood volume and perfusion pressure at levels optimal for survival. Although it is clear that central angiotensin type 1a receptors (AT1aR; encoded by the Agtr1a gene) influence these processes, the neuronal circuits mediating these effects are incompletely understood. The present studies characterize the structure and function of AT1aR neurons in the lamina terminalis (containing the median preoptic nucleus and organum vasculosum of the lamina terminalis), thereby evaluating their roles in blood pressure control. Using male Agtr1a-Cre mice, neuroanatomical studies reveal that AT1aR neurons in the area are largely glutamatergic and send projections to the paraventricular nucleus of the hypothalamus (PVN) that appear to synapse onto vasopressin-synthesizing neurons. To evaluate the functionality of these lamina terminalis AT1aR neurons, we virally delivered light-sensitive opsins and then optogenetically excited or inhibited the neurons while evaluating cardiovascular parameters or fluid intake. Optogenetic excitation robustly elevated blood pressure, water intake, and sodium intake, while optogenetic inhibition produced the opposite effects. Intriguingly, optogenetic excitation of these AT1aR neurons of the lamina terminalis also resulted in Fos induction in vasopressin neurons within the PVN and supraoptic nucleus. Further, within the PVN, selective optogenetic stimulation of afferents that arise from these lamina terminalis AT1aR neurons induced glutamate release onto magnocellular neurons and was sufficient to increase blood pressure. These cardiovascular effects were attenuated by systemic pretreatment with a vasopressin-1a-receptor antagonist. Collectively, these data indicate that excitation of lamina terminalis AT1aR neurons induces neuroendocrine and behavioral responses that increase blood pressure.SIGNIFICANCE STATEMENT Hypertension is a widespread health problem and risk factor for cardiovascular disease. Although treatments exist, a substantial percentage of patients suffer from "drug-resistant" hypertension, a condition associated with increased activation of brain angiotensin receptors, enhanced sympathetic nervous system activity, and elevated vasopressin levels. The present study highlights a role for angiotensin Type 1a receptor expressing neurons located within the lamina terminalis in regulating endocrine and behavioral responses that are involved in maintaining cardiovascular homeostasis. More specifically, data presented here reveal functional excitatory connections between angiotensin-sensitive neurons in the lamina terminals and vasopressin neurons in the paraventricular nucleus of the hypothalamus, and further indicate that activation of this circuit raises blood pressure. These neurons may be a promising target for antihypertensive therapeutics.

Elucidating the Association Between the Upregulation of Angiotensin Type 1-Receptors and the Development of Gastrointestinal Malignancies.

The renin-angiotensin system (RAS) is a major regulator of body fluid hemostasis and blood pressure. Angiotensin type 1 receptors (AT1R) are one of the major components of this system and are widely expressed in different organs, including the gastrointestinal (GI) system. Very little known about the physiological roles of AT1R in GI tract but evidence has reported that local AT1Rs are upregulated in pathological conditions like GI malignancies and play role in stimulation of signaling pathways associated with GI cancers progression. AT1Rs axes signaling in tumor microenvironments stimulate inflammation and facilitate vascularization around the tumor cell to display invasive behavior. AT1Rs in stroma cells promote tumor-associated angiogenesis by upregulated of vessel endothelial growth factor (VEGF). Also, AT1Rs by the activation of molecular mechanisms such as PI3/Akt/NF-κB pathways increase the invasion of tumor cells. Experimental and clinical studies have reported that AT1R antagonists have beneficial influences by increasing the survival of patients with GI malignancies and reduction in the proliferation of GI cancer cell lines in vitro, and the growth and metastasis of tumors in vivo, therefore, AT1Rs antagonist have the potential for future anticancer strategies. This review focuses on the pathological roles of AT1Rs in GI malignancies.

Angiotensin AT1 receptor antagonism by losartan stimulates adipocyte browning via induction of apelin.

Adipocyte browning appears to be a potential therapeutic strategy to combat obesity and related metabolic disorders. Recent studies have shown that apelin, an adipokine, stimulates adipocyte browning and has negative cross-talk with angiotensin II receptor type 1 (AT1 receptor) signaling. Here, we report that losartan, a selective AT1 receptor antagonist, induces browning, as evidenced by an increase in browning marker expression, mitochondrial biogenesis, and oxygen consumption in murine adipocytes. In parallel, losartan up-regulated apelin expression, concomitant with increased phosphorylation of protein kinase B and AMP-activated protein kinase. However, the siRNA-mediated knockdown of apelin expression attenuated losartan-induced browning. Angiotensin II cotreatment also inhibited losartan-induced browning, suggesting that AT1 receptor antagonism-induced activation of apelin signaling may be responsible for adipocyte browning induced by losartan. The in vivo browning effects of losartan were confirmed using both C57BL/6J and ob/ob mice. Furthermore, in vivo apelin knockdown by adeno-associated virus carrying-apelin shRNA significantly inhibited losartan-induced adipocyte browning. In summary, these data suggested that AT1 receptor antagonism by losartan promotes the browning of white adipocytes via the induction of apelin expression. Therefore, apelin modulation may be an effective strategy for the treatment of obesity and its related metabolic disorders.

Withaferin A: a potential therapeutic agent against COVID-19 infection.

The outbreak and continued spread of the novel coronavirus disease 2019 (COVID-19) is a preeminent global health threat that has resulted in the infection of over 11.5 million people worldwide. In addition, the pandemic has claimed the lives of over 530,000 people worldwide. Age and the presence of underlying comorbid conditions have been found to be key determinants of patient mortality. One such comorbidity is the presence of an oncological malignancy, with cancer patients exhibiting an approximate two-fold increase in mortality rate. Due to a lack of data, no consensus has been reached about the best practices for the diagnosis and treatment of cancer patients. Interestingly, two independent research groups have discovered that Withaferin A (WFA), a steroidal lactone with anti-inflammatory and anti-tumorigenic properties, may bind to the viral spike (S-) protein of SARS-CoV-2. Further, preliminary data from our research group has demonstrated that WFA does not alter expression of ACE2 in the lungs of tumor-bearing female mice. Downregulation of ACE2 has recently been demonstrated to increase the severity of COVID-19. Therefore, WFA demonstrates real potential as a therapeutic agent to treat or prevent the spread of COVID-19 due to the reported interference in viral S-protein to host receptor binding and its lack of effect on ACE2 expression in the lungs.

Purinergic P2X1 receptor, purinergic P2X7 receptor, and angiotensin II type 1 receptor interactions in the regulation of renal afferent arterioles in angiotensin II-dependent hypertension.

In ANG II-dependent hypertension, ANG II activates ANG II type 1 receptors (AT1Rs), elevating blood pressure and increasing renal afferent arteriolar resistance (AAR). The increased arterial pressure augments interstitial ATP concentrations activating purinergic P2X receptors (P2XRs) also increasing AAR. Interestingly, P2X1R and P2X7R inhibition reduces AAR to the normal range, raising the conundrum regarding the apparent disappearance of AT1R influence. To evaluate the interactions between P2XRs and AT1Rs in mediating the increased AAR elicited by chronic ANG II infusions, experiments using the isolated blood perfused juxtamedullary nephron preparation allowed visualization of afferent arteriolar diameters (AAD). Normotensive and ANG II-infused hypertensive rats showed AAD responses to increases in renal perfusion pressure from 100 to 140 mmHg by decreasing AAD by 26 ± 10% and 19 ± 4%. Superfusion with the inhibitor P2X1Ri (NF4490; 1 µM) increased AAD. In normotensive kidneys, superfusion with ANG II (1 nM) decreased AAD by 16 ± 4% and decreased further by 19 ± 5% with an increase in renal perfusion pressure. Treatment with P2X1Ri increased AAD by 30 ± 6% to values higher than those at 100 mmHg plus ANG II. In hypertensive kidneys, the inhibitor AT1Ri (SML1394; 1 µM) increased AAD by 10 ± 7%. In contrast, treatment with P2X1Ri increased AAD by 21 ± 14%; combination with P2X1Ri plus P2X7Ri (A438079; 1 µM) increased AAD further by 25 ± 8%. The results indicate that P2X1R, P2X7R, and AT1R actions converge at receptor or postreceptor signaling pathways, but P2XR exerts a dominant influence abrogating the actions of AT1Rs on AAR in ANG II-dependent hypertension.

Interaction between angiotensin II and GABA in the spinal cord regulates sympathetic vasomotor activity in Goldblatt hypertension.

Previous studies have been described changes in brain regions contributing to the sympathetic vasomotor overactivity in Goldblatt hypertension (2K1C). Furthermore, changes in the spinal cord are also involved in the cardiovascular and autonomic dysfunction in renovascular hypertension, as intrathecal (i.t.) administration of Losartan (Los) causes a robust hypotensive/sympathoinhibitory response in 2K1C but not in control rats. The present study evaluated the role of spinal γ-aminobutyric acid (GABA)-ergic inputs in the control of sympathetic vasomotor activity in the 2K1C rats. Hypertension was induced by clipping the renal artery. After six weeks, a catheter (PE-10) was inserted into the subarachnoid space and advanced to the T10-11 vertebral level in urethane-anaesthetized rats. The effects of i.t. injection of bicuculline (Bic) on blood pressure (BP), renal and splanchnic sympathetic nerve activity (rSNA and sSNA, respectively) were evaluated over 40 consecutive minutes in the presence or absence of spinal AT1 antagonism. I.t. Bic triggered a more intense pressor and sympathoexcitatory response in 2K1C rats, however, these responses were attenuated by previous i.t. Los. No differences in the gene expression of GAD 65 and GABA-A receptors subunits in the spinal cord segments were found. Thus, the sympathoexcitation induced by spinal GABA-A blockade is dependent of local AT1 receptor in 2K1C but not in control rats. Excitatory angiotensinergic inputs to sympathetic preganglionic neurons are tonic controlled by spinal GABAergic actions in Goldblatt hypertension.

Recent Research Advances in Renin-Angiotensin-Aldosterone System Receptors.

PURPOSE OF REVIEW: The renin-angiotensin-aldosterone system (RAAS) plays important roles in regulating blood pressure and body fluid, which contributes to the pathophysiology of hypertension and cardiovascular/renal diseases. However, accumulating evidence has further revealed the complexity of this signal transduction system, including direct interactions with other receptors and proteins. This review focuses on recent research advances in RAAS with an emphasis on its receptors. RECENT FINDINGS: Both systemically and locally produced angiotensin II (Ang II) bind to Ang II type 1 receptor (AT1R) and elicit strong biological functions. Recent studies have shown that Ang II-induced activation of Ang II type 2 receptor (AT2R) elicits the opposite functions to those of AT1R. However, accumulating evidence has now expanded the components of RAAS, including (pro)renin receptor, angiotensin-converting enzyme 2, angiotensin 1-7, and Mas receptor. In addition, the signal transductions of AT1R and AT2R are regulated by not only Ang II but also its receptor-associated proteins such as AT1R-associated protein and AT2R-interacting protein. Recent studies have indicated that inappropriate activation of local mineralocorticoid receptor contributes to cardiovascular and renal tissue injuries through aldosterone-dependent and -independent mechanisms. Since the mechanisms of RAAS signal transduction still remain to be elucidated, further investigations are necessary to explore novel molecular mechanisms of the RAAS, which will provide alternative therapeutic agents other than existing RAAS blockers.

Systematic characterization of AT1 receptor antagonists with label-free dynamic mass redistribution assays.

INTRODUCTION: In the drug discovery field, the binding affinities and binding kinetics of drug candidates are very important. Angiotensin II type 1 (AT1) receptor antagonists, e.g., candesartan, telmisartan, irbesartan, losartan and valsartan, show high affinities and long-lasting bindings to the receptor, making them preferred medications for hypertension treatment. However, the molecular binding properties of AT1 receptor antagonists are controversial. METHODS: In this work, we established a profile to study the phenotypic properties of AT1 receptor antagonists with label-free dynamic mass redistribution (DMR) assays in native human cells. With noninvasive features, DMR assay were conducted in multiple formats. Eleven antagonists were systematically evaluated with angiotensin II as an agonist probe in the Hep G2 cell line, which endogenously expresses the AT1 receptor. RESULTS: The IC50 values to the AT1 receptor of individual antagonist varied with different incubation times. The antagonists showed competitive behavior with angiotensin II. Schild analysis was used to analyze the competitive behavior of the antagonist. All of the antagonist showed long-lasting possession of the AT1 receptor, except telmisartan. The systematic evaluation of the antagonists implied that 11 antagonists showed high binding affinity but distinct binding modes to AT1 receptor. DISCUSSION: This study demonstrated that the DMR assay has great potential for determining the pharmacological parameters of ligands. This work may serve as guidance for other receptor and ligand assays.

Injured Podocytes Are Sensitized to Angiotensin II-Induced Calcium Signaling.

BACKGROUND: Inhibition of angiotensin II (AngII) signaling, a therapeutic mainstay of glomerular kidney diseases, is thought to act primarily through regulating glomerular blood flow and reducing filtration pressure. Although extravascular actions of AngII have been suggested, a direct effect of AngII on podocytes has not been demonstrated in vivo. METHODS: To study the effects of AngII on podocyte calcium levels in vivo, we used intravital microscopy of the kidney in mice expressing the calcium indicator protein GCaMP3. RESULTS: In healthy animals, podocytes displayed limited responsiveness to AngII stimulation. In contrast, in animals subjected to either adriamycin-induced acute chemical injury or genetic deletion of the podocin-encoding gene Nphs2, the consequent podocyte damage and proteinuria rendered the cells responsive to AngII and resulted in AngII-induced calcium transients in significantly more podocytes. The angiotensin type 1 receptor blocker losartan could fully inhibit this response. Also, responsiveness to AngII was at least partly mediated through the transient receptor potential channel 6, which has been implicated in podocyte calcium handling. Interestingly, loss of a single Nphs2 allele also increased podocytes' responsiveness to AngII signaling. This direct effect of AngII on injured podocytes results in increased calcium transients, which can further aggravate the underlying kidney disease. CONCLUSIONS: Our discovery that podocytes become sensitized to AngII-induced calcium signaling upon injury might explain results from large, randomized, controlled trials in which improved renal outcomes occur only in the subgroup of patients with proteinuria, indicating podocyte damage. Our findings also emphasize the need to treat every patient with a glomerular disease with either an angiotensin-converting enzyme inhibitor or an angiotensin type 1 receptor blocker.