Microglial Cells Impact Gut Microbiota and Gut Pathology in Angiotensin II-Induced Hypertension

Microglia in the hypothalamic paraventricular nucleus sense hemodynamic disturbance and promote sympathetic excitation in hypertension

Hypertension is usually accompanied by elevated sympathetic tonicity, but how sympathetic hyperactivity is triggered is not clear. Recent advances revealed that microglia-centered neuroinflammation contributes to sympathetic excitation in hypertension. In this study, we performed a temporospatial analysis of microglia at both morphological and transcriptomic levels and found that microglia in the hypothalamic paraventricular nucleus (PVN), a sympathetic center, were early responders to hypertensive challenges. Vasculature analyses revealed that the PVN was characterized by high capillary density, thin vessel diameter, and complex vascular topology relative to other brain regions. As such, the PVN was susceptible to the penetration of ATP released from the vasculature in response to hemodynamic disturbance after blood pressure increase. Mechanistically, ATP ligation to microglial P2Y12 receptor was responsible for microglial inflammatory activation and the eventual sympathetic overflow. Together, these findings identified a distinct vasculature pattern rendering vulnerability of PVN pre-sympathetic neurons to hypertension-associated microglia-mediated inflammatory insults.

Differing contributions of the gut microbiota to the blood pressure lowering effects induced by first-line antihypertensive drugs

BACKGROUND AND PURPOSE

This study analyses whether first-line antihypertensive drugs ameliorate the dysbiosis state in hypertension, and to test if this modification contributes to their blood pressure (BP) lowering properties in a genetic model of neurogenic hypertension.

EXPERIMENTAL APPROACH

Twenty-week-old male Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were untreated or treated with captopril, amlodipine or hydrochlorothiazide. A faecal microbiota transplantation (FMT) experiment was also performed by gavage of faecal content from donor SHR-treated groups to SHR recipients for 3 weeks.

KEY RESULTS

Faeces from SHR showed gut dysbiosis, characterized by lower acetate- and higher lactate-producing bacteria and lower strict anaerobic bacteria. All three drugs increased the anaerobic bacteria proportion, captopril and amlodipine restored the proportion of acetate-producing bacterial populations to WKY levels, whereas hydrochlorothiazide decreased butyrate-producing bacteria. Captopril and amlodipine decreased gut pathology and permeability and attenuated sympathetic drive in the gut. Both drugs decreased neuroinflammation and oxidative stress in the hypothalamic paraventricular nuclei. Hydrochlorothiazide was unable to reduce neuroinflammation, gut sympathetic tone and gut integrity. FMT from SHR-amlodipine to SHR decreased BP, ameliorated aortic endothelium-dependent relaxation to acetylcholine, lowered NADPH oxidase activity, aortic Th17 infiltration and reduced neuroinflammation, whereas FMT from SHR-hydrochlorothiazide did not have these effects.

CONCLUSIONS AND IMPLICATIONS

First-line antihypertensive drugs induced different modifications of gut integrity and gut dysbiosis in SHR, which result in no contribution of microbiota in the BP lowering effects of hydrochlorothiazide, whereas the vasculo-protective effect induced by amlodipine involves gut microbiota reshaping and gut-immune system communication.

Role of Gut Microbiota in Dengue

Dengue is a disease caused by a flavivirus (DENV) and transmitted by the bite of a mosquito, primarily the Aedes aegypti and Aedes albopictus species. Previous studies have demonstrated a relationship between the host gut microbiota and the evolution of dengue. It seems to be a bidirectional relationship, in which the DENV can affect the microbiota by inducing alterations related to intestinal permeability, leading to the release of molecules from microbiota dysbiosis that can influence the evolution of dengue. The role of angiotensin II (Ang II) in the microbiota/dengue relationship is not well understood, but it is known that the renin-angiotensin system (RAS) is present in the intestinal tract and interacts with the gut microbiota. The possible effect of Ang II on the microbiota/Ang II/dengue relationship can be summarised as follows: the presence of Ang II induced hypertension, the increase in angiotensinogen, chymase, and microRNAs during the disease, the induction of vascular dysfunction, the production of trimethylamine N-oxide and the brain/microbiota relationship, all of which are elements present in dengue that could be part of the microbiota/Ang II/dengue interactions. These findings suggest the potential use of Ang II synthesis blockers and the use of AT1 receptor antagonists as therapeutic drugs in dengue.

Nutraceuticals in the management of autonomic function and related disorders: A comprehensive review

Nutraceuticals have been described as phytocomplexes when derived from foods of plant origin or a pool of secondary metabolites when derived from foods of animal origin, which are concentrated and administered in an appropriate form and can promote beneficial health effects in the prevention/treatment of diseases. Considering that pharmaceutical medications can cause side effects, there is a growing interest in using nutraceuticals as an adjuvant therapeutic tool for several disorders involving autonomic dysfunction, such as obesity, atherosclerosis and other cardiometabolic diseases. This review summarizes and discusses the evidence from the literature on the effects of various nutraceuticals on autonomic control, addressing the gut microbiota modulation, production of secondary metabolites from bioactive compounds, and improvement of physical and chemical properties of cell membranes. Additionally, the safety of nutraceuticals and prospects are discussed. Probiotics, resveratrol, quercetin, curcumin, nitrate, inositol, L-carnosine, and n-3 polyunsaturated fatty acids (n-3 PUFAs) are among the nutraceuticals most studied to improve autonomic dysfunction in experimental animal models and clinical trials. Further human studies are needed to elucidate the effects of nutraceuticals formulated of multitarget compounds and their underlying mechanisms of action, which could benefit conditions involving autonomic dysfunction.

Gut microbiota: a potential new regulator of hypertension

Hypertension is a significant risk factor for cardiovascular and cerebrovascular diseases and has become a global public health concern. Although hypertension results from a combination of factors, the specific mechanism is still unclear. However, increasing evidence suggests that gut microbiota is closely associated with the development of hypertension. We provide a summary of the composition and physiological role of gut microbiota. We then delve into the mechanism of gut microbiota and its metabolites involved in the occurrence and development of hypertension. Finally, we review various regimens for better-controlling hypertension from the diet, exercise, drugs, antibiotics, probiotics, and fecal transplantation perspectives.

Microbiota-derived acetate attenuates neuroinflammation in rostral ventrolateral medulla of spontaneously hypertensive rats

BACKGROUND

Increased neuroinflammation in brain regions regulating sympathetic nerves is associated with hypertension. Emerging evidence from both human and animal studies suggests a link between hypertension and gut microbiota, as well as microbiota-derived metabolites short-chain fatty acids (SCFAs). However, the precise mechanisms underlying this gut-brain axis remain unclear.

METHODS

The levels of microbiota-derived SCFAs in spontaneously hypertensive rats (SHRs) were determined by gas chromatography-mass spectrometry. To observe the effect of acetate on arterial blood pressure (ABP) in rats, sodium acetate was supplemented via drinking water for continuous 7 days. ABP was recorded by radio telemetry. The inflammatory factors, morphology of microglia and astrocytes in rostral ventrolateral medulla (RVLM) were detected. In addition, blood-brain barrier (BBB) permeability, composition and metabolomics of the gut microbiome, and intestinal pathological manifestations were also measured.

RESULTS

The serum acetate levels in SHRs are lower than in normotensive control rats. Supplementation with acetate reduces ABP, inhibits sympathetic nerve activity in SHRs. Furthermore, acetate suppresses RVLM neuroinflammation in SHRs, increases microglia and astrocyte morphologic complexity, decreases BBB permeability, modulates intestinal flora, increases fecal flora metabolites, and inhibits intestinal fibrosis.

CONCLUSIONS

Microbiota-derived acetate exerts antihypertensive effects by modulating microglia and astrocytes and inhibiting neuroinflammation and sympathetic output.

Limosilactobacillus fermentum Strains as Novel Probiotic Candidates to Promote Host Health Benefits and Development of Biotherapeutics: A Comprehensive Review

Fruits and their processing by-products are sources of potentially probiotic strains. Limosilactobacillus (L.) fermentum strains isolated from fruit processing by-products have shown probiotic-related properties. This review presents and discusses the results of the available studies that evaluated the probiotic properties of L. fermentum in promoting host health benefits, their application by the food industry, and the development of biotherapeutics. The results showed that administration of L. fermentum for 4 to 8 weeks promoted host health benefits in rats, including the modulation of gut microbiota, improvement of metabolic parameters, and antihypertensive, antioxidant, and anti-inflammatory effects. The results also showed the relevance of L. fermentum strains for application in the food industry and for the formulation of novel biotherapeutics, especially nutraceuticals. This review provides evidence that L. fermentum strains isolated from fruit processing by-products have great potential for promoting host health and indicate the need for a translational approach to confirm their effects in humans using randomized, double-blind, placebo-controlled trials.

Subdiaphragmatic vagal nerve stimulation attenuates the development of hypertension and alters nucleus of the solitary tract transcriptional networks in the spontaneously hypertensive rat

Augmented vagal signaling may be therapeutic in hypertension. Most studies to date have used stimulation of the cervical vagal branches. Here, we investigated the effects of chronic intermittent electric stimulation of the ventral subdiaphragmatic vagal nerve branch (sdVNS) on long-term blood pressure, immune markers, and gut microbiota in the spontaneously hypertensive rat (SHR), a rodent model of hypertension characterized by vagal dysfunction, gut dysbiosis, and low-grade inflammation. We evaluated the effects of sdVNS on transcriptional networks in the nucleus of the solitary tract (NTS), a major cardioregulatory brain region with direct gut vagal projections. Male juvenile SHRs were implanted with radiotelemetry transmitters and vagal nerve cuffs for chronic intermittent electric sdVNS, applied three times per day for 7 consecutive weeks followed by 1 wk of no stimulation. Blood pressure was measured once a week using telemetry in the sdVNS group as well as age-matched sham-stimulated SHR controls. At the endpoint, colonic and circulating inflammatory markers, corticosterone, and circulating catecholamines were investigated. Bacterial 16 s sequencing measured gut bacterial abundance and composition. RNA sequencing evaluated the effects of sdVNS on transcriptional networks in the NTS. SHRs that received sdVNS exhibited attenuated development of hypertension compared with sham animals. No changes in peripheral inflammatory markers, corticosterone, or catecholamines and no major differences in gut bacterial diversity and composition were observed following sdVNS, apart from decreased abundance of Defluviitaleaceale bacterium detected in sdVNS SHRs compared with sham animals. RNA sequencing revealed significant sdVNS-dependent modulation of select NTS transcriptional networks, including catecholaminergic and corticosteroid networks.NEW & NOTEWORTHY We show that stimulation of the ventral subdiaphragmatic vagal nerve branch may be a promising potential approach to treating hypertension. The data are especially encouraging given that rodents received only 30 min per day of intermittent stimulation therapy and in view of the potential of long-term blood pressure effects that are not stimulus-locked.

Targeting gut microbiota in aging-related cardiovascular dysfunction: focus on the mechanisms

The global population is aging and age-related cardiovascular disease is increasing. Even after controlling for cardiovascular risk factors, readmission and mortality rates remain high. In recent years, more and more in-depth studies have found that the composition of the gut microbiota and its metabolites, such as trimethylamine N-oxide (TMAO), bile acids (BAs), and short-chain fatty acids (SCFAs), affect the occurrence and development of age-related cardiovascular diseases through a variety of molecular pathways, providing a new target for therapy. In this review, we discuss the relationship between the gut microbiota and age-related cardiovascular diseases, and propose that the gut microbiota could be a new therapeutic target for preventing and treating cardiovascular diseases.

"Sentinel or accomplice": gut microbiota and microglia crosstalk in disorders of gut-brain interaction

Abnormal brain-gut interaction is considered the core pathological mechanism behind the disorders of gut-brain interaction (DGBI), in which the intestinal microbiota plays an important role. Microglia are the "sentinels" of the central nervous system (CNS), which participate in tissue damage caused by traumatic brain injury, resist central infection and participate in neurogenesis, and are involved in the occurrence of various neurological diseases. With in-depth research on DGBI, we could find an interaction between the intestinal microbiota and microglia and that they are jointly involved in the occurrence of DGBI, especially in individuals with comorbidities of mental disorders, such as irritable bowel syndrome (IBS). This bidirectional regulation of microbiota and microglia provides a new direction for the treatment of DGBI. In this review, we focus on the role and underlying mechanism of the interaction between gut microbiota and microglia in DGBI, especially IBS, and the corresponding clinical application prospects and highlight its potential to treat DGBI in individuals with psychiatric comorbidities.

Unraveling mechanistic insights into the role of microbiome in neurogenic hypertension: A comprehensive review

Neurogenic hypertension, a complex and multifactorial cardiovascular disorder, is known to be influenced by various genetic, environmental, and lifestyle factors. In recent years, there has been growing interest in the role of the gut microbiome in hypertension pathogenesis. The bidirectional communication between the gut microbiota and the central nervous system, known as the microbiota-gut-brain axis, has emerged as a crucial mechanism through which the gut microbiota exerts its influence on neuroinflammation, immune responses, and blood pressure regulation. Recent studies have shown how the microbiome has a substantial impact on a variety of physiological functions, such as cardiovascular health. The increased sympathetic activity to the gut may cause microbial dysbiosis, increased permeability of the gut, and increased inflammatory reactions by altering a number of intestinal bacteria producing short-chain fatty acids (SCFAs) and the concentrations of lipopolysaccharide (LPS) in the plasma. Collectively, these microbial metabolic and structural compounds stimulate sympathetic stimulation, which may be an important stage in the onset of hypertension. The result is an upsurge in peripheral and central inflammatory response. In addition, it has recently been shown that a link between the immune system and the gut microbiota might play a significant role in hypertension. The therapeutic implications of the gut microbiome including probiotic usage, prebiotics, dietary modifications, and fecal microbiota transplantation in neurogenic hypertension have also been found. A large body of research suggests that probiotic supplementation might help reduce chronic inflammation and hypertension that have an association with dysbiosis in the gut microbiota. Overall, this review sheds light on the intricate interplay between the gut microbiome and neurogenic hypertension, providing valuable insights for both researchers and clinicians. As our knowledge of the microbiome's role in hypertension expands, novel therapeutic strategies and diagnostic biomarkers may pave the way for more effective management and prevention of this prevalent cardiovascular disorder. Exploring the potential of the microbiome in hypertension offers an exciting avenue for future research and offers opportunities for precision medicine and improved patient care.

The Regulatory Effect of the Paraventricular Nucleus on Hypertension

Hypertension is among the most harmful factors of cardiovascular and cerebrovascular diseases and poses an urgent problem for the development of human society. In addition to previous studies on its pathogenesis focusing on the peripheral sympathetic nervous system, investigating the central causes of high blood pressure involving the neuroendocrine and neuroinflammatory mechanisms of the hypothalamic paraventricular nucleus (PVN) is paramount. This nucleus is considered to regulate the output of neurohormones and sympathetic nerve activity. In this article, we focussed on the neuroendocrine mechanism, primarily exploring the specific contributions and interactions of various neurons and neuroendocrine hormones, including GABAergic and glutamatergic neurons, nitric oxide, arginine vasopressin, oxytocin, and the renin-angiotensin system. Additionally, the neuroinflammatory mechanism in the PVN was discussed, encompassing microglia, reactive oxygen species, inflammatory factors, and pathways, as well as immune connections between the brain and extracerebral organs. Notably, the two central mechanisms involved in the PVN not only exist independently but also communicate with each other, jointly maintaining the hypertensive state of the body. Furthermore, we introduce well-known molecules and signal transduction pathways within the PVN that can play a regulatory role in the two mechanisms to provide a basis and inspire ideas for further research.

Neuro-Vulnerability in Energy Metabolism Regulation: A Comprehensive Narrative Review

This comprehensive narrative review explores the concept of neuro-vulnerability in energy metabolism regulation and its implications for metabolic disorders. The review highlights the complex interactions among the neural, hormonal, and metabolic pathways involved in the regulation of energy metabolism. The key topics discussed include the role of organs, hormones, and neural circuits in maintaining metabolic balance. The review investigates the association between neuro-vulnerability and metabolic disorders, such as obesity, insulin resistance, and eating disorders, considering genetic, epigenetic, and environmental factors that influence neuro-vulnerability and subsequent metabolic dysregulation. Neuroendocrine interactions and the neural regulation of food intake and energy expenditure are examined, with a focus on the impact of neuro-vulnerability on appetite dysregulation and altered energy expenditure. The role of neuroinflammation in metabolic health and neuro-vulnerability is discussed, emphasizing the bidirectional relationship between metabolic dysregulation and neuroinflammatory processes. This review also evaluates the use of neuroimaging techniques in studying neuro-vulnerability and their potential applications in clinical settings. Furthermore, the association between neuro-vulnerability and eating disorders, as well as its contribution to obesity, is examined. Potential therapeutic interventions targeting neuro-vulnerability, including pharmacological treatments and lifestyle modifications, are reviewed. In conclusion, understanding the concept of neuro-vulnerability in energy metabolism regulation is crucial for addressing metabolic disorders. This review provides valuable insights into the underlying neurobiological mechanisms and their implications for metabolic health. Targeting neuro-vulnerability holds promise for developing innovative strategies in the prevention and treatment of metabolic disorders, ultimately improving metabolic health outcomes.

Impact of the gut microbiota on angiotensin Ⅱ-related disorders and its mechanisms

The renin-angiotensin system (RAS) consists of multiple angiotensin peptides and performs various biological functions mediated by distinct receptors. Angiotensin II (Ang II) is the major effector of the RAS and affects the occurrence and development of inflammation, diabetes mellitus and its complications, hypertension, and end-organ damage via the Ang II type 1 receptor. Recently, considerable interest has been given to the association and interaction between the gut microbiota and host. Increasing evidence suggests that the gut microbiota may contribute to cardiovascular diseases, obesity, type 2 diabetes mellitus, chronic inflammatory diseases, and chronic kidney disease. Recent data have confirmed that Ang II can induce an imbalance in the intestinal flora and further aggravate disease progression. Furthermore, angiotensin converting enzyme 2 is another player in RAS, alleviates the deleterious effects of Ang II, modulates gut microbial dysbiosis, local and systemic immune responses associated with coronavirus disease 19. Due to the complicated etiology of pathologies, the precise mechanisms that link disease processes with specific characteristics of the gut microbiota remain obscure. This review aims to highlight the complex interactions between the gut microbiota and its metabolites in Ang II-related disease progression, and summarize the possible mechanisms. Deciphering these mechanisms will provide a theoretical basis for novel therapeutic strategies for disease prevention and treatment. Finally, we discuss therapies targeting the gut microbiota to treat Ang II-related disorders.

Restoration of the gut barrier integrity and restructuring of the gut microbiome in aging by angiotensin-(1-7)

Compromised barrier function of colon epithelium with aging is largely due to gut microbial dysbiosis. Recent studies implicate an important role for angiotensin converting enzymes, ACE and ACE2, angiotensins, and the receptors, AT1 receptor (AT1R) and Mas receptor (MasR), in the regulation of colon functions. The present study tested the hypothesis that leaky gut in aging is associated with an imbalance in ACE2/ACE and that the treatment with angiotenisn-(1-7) (Ang-(1-7)) will restore gut barrier integrity and microbiome. Studies were carried out in Young (3-4 months) and old (20-24 months) male mice. Ang-(1-7) was administered by using osmotic pumps. Outcome measures included expressions of ACE, ACE2, AT1R, and MasR, intestinal permeability by using FITC-dextran, and immunohistochemistry of claudin 1 and occludin, and intestinal stem cells (ISCs). ACE2 protein and activity were decreased in Old group while that of ACE were unchanged. Increased intestinal permeability and plasma levels of zonulin-1 in the Old group were normalized by Ang-(1-7). Epithelial disintegrity, reduced number of goblet cells and ISCs in the old group were restored by Ang-(1-7). Expression of claudin 1 and occludin in the aging colon was increased by Ang-(1-7). Infiltration of CD11b+ or F4/80+ inflammatory cells in the old colons were decreased by Ang-(1-7). Gut microbial dysbiosis in aging was evident by decreased richness and altered beta diversity that were reversed by Ang-(1-7) with increased abundance of Lactobacillus or Lachnospiraceae. The present study shows that Ang-(1-7) restores gut barrier integrity and reduces inflammation in the aging colon by restoring the layer of ISCs and by restructuring the gut microbiome.

Influence of Intestinal Barrier on Alleviating an Increase in Blood Pressure by Sodium Alginate Intake in 2-Kidney, 1-Clip Renovascular Hypertensive Rats

Sodium alginate (SALG) is a substance derived from brown seaweed that has been shown to reduce blood pressure (BP). However, its effects on renovascular hypertension caused by 2-kidney, 1-clip (2K1C) are not yet clear. Previous research suggests that hypertensive rats have increased intestinal permeability, and that SALG improves the gut barrier in inflammatory bowel disease mouse models. Therefore, the goal of this study was to determine whether the antihypertensive effects of SALG involve the intestinal barrier in 2K1C rats. Rats were fed either a 1.0% SALG diet or a control diet for six weeks after being subjected to 2K1C surgery or a sham operation. The systolic BP was measured weekly, and the mean arterial BP was measured at the end of the study. Intestinal samples were taken for analysis, and plasma lipopolysaccharide (LPS) levels were measured. The results showed that BP in 2K1C rats was significantly higher than in SHAM rats when fed CTL, but not when fed SALG. The gut barrier in 2K1C rats was improved by SALG intake. Plasma LPS levels also differed depending on the animal model and diet. In conclusion, dietary SALG may alleviate 2K1C renovascular hypertension by altering the gut barrier.

Comorbidity of Anxiety and Hypertension: Common Risk Factors and Potential Mechanisms

Anxiety is more common in patients with hypertension, and these two conditions frequently coexist. Recently, more emphasis has been placed on determining etiology in patients with comorbid hypertension and anxiety. This review focuses on the common risk factors and potential mechanisms of comorbid hypertension and anxiety. Firstly, we analyze the common risk factors of comorbid hypertension and anxiety including age, smoking, alcohol abuse, obesity, lead, and traffic noise. The specific mechanisms underlying hypertension and anxiety were subsequently discussed, including interleukin (IL)-6 (IL-6), IL-17, reactive oxygen species (ROS), and gut dysbiosis. Increased IL-6, IL-17, and ROS accelerate the development of hypertension and anxiety. Gut dysbiosis leads to hypertension and anxiety by reducing short-chain fatty acids, vitamin D, and 5-hydroxytryptamine (5-HT), and increasing trimethylamine N-oxide (TAMO) and MYC. These shared risk factors and potential mechanisms may provide an effective strategy for treating and preventing hypertension and comorbid anxiety.

Can increased intestinal permeability and low-grade endotoxemia be the triggering pathogenesis in isolated coronary artery ectasia?

PURPOSE

Isolated coronary artery ectasia (ICAE) is a rare coronary artery disease (CAD) encountered during coronary angiography. Although many mechanisms have been suggested today that may be associated with ICAE, the underlying pathogenesis has not been fully understood. In this study, we aimed to reveal the possible relationship between intestinal permeability and ICAE.

METHODS

Of the 12 850 patients who underwent coronary angiography, 138 consecutive patients with ICAE and 140 age- and sex-matched subjects with normal coronary arteries as the control group and 140 subjects with stenotic CAD were included in the study.

RESULTS

Serum zonulin and lipopolysaccharide levels were significantly higher in patients with ICAE than in the control group and CAD group. Additionally, zonulin and lipopolysaccharide levels were significantly higher in the CAD group than in the ICAE group. In the correlation analysis, serum zonulin levels were correlated with the mean diameter and length of the ecstatic segment. In multivariate analysis, zonulin and lipopolysaccharide were identified as independent predictors for ICAE.

CONCLUSION

These results suggest that there may be a pathophysiological relationship between increased intestinal permeability and ICAE.

The gut microbiome and hypertension

A large body of evidence has emerged in the past decade supporting a role for the gut microbiome in the regulation of blood pressure. The field has moved from association to causation in the last 5 years, with studies that have used germ-free animals, antibiotic treatments and direct supplementation with microbial metabolites. The gut microbiome can regulate blood pressure through several mechanisms, including through gut dysbiosis-induced changes in microbiome-associated gene pathways in the host. Microbiota-derived metabolites are either beneficial (for example, short-chain fatty acids and indole-3-lactic acid) or detrimental (for example, trimethylamine N-oxide), and can activate several downstream signalling pathways via G protein-coupled receptors or through direct immune cell activation. Moreover, dysbiosis-associated breakdown of the gut epithelial barrier can elicit systemic inflammation and disrupt intestinal mechanotransduction. These alterations activate mechanisms that are traditionally associated with blood pressure regulation, such as the renin-angiotensin-aldosterone system, the autonomic nervous system, and the immune system. Several methodological and technological challenges remain in gut microbiome research, and the solutions involve minimizing confounding factors, establishing causality and acting globally to improve sample diversity. New clinical trials, precision microbiome medicine and computational methods such as Mendelian randomization have the potential to enable leveraging of the microbiome for translational applications to lower blood pressure.

P2X7 receptor antagonist improves gastrointestinal disorders in spontaneously hypertensive rats

The purinergic system participates in the control of blood pressure. Hypertension promotes the occurrence of gastrointestinal disorders such as intestinal inflammation and gastric emptying delay. This study aimed i) to investigate the participation of the P2X7 receptor blocker Brilliant Blue G (BBG) on gastric emptying of solids and changes in oxidative stress in the gastric fundus, duodenum, and colon of spontaneously hypertensive rats (SHR) and ii) to study the putative relationship of this effect with the renin-angiotensin system. Rats were divided into five groups: Control, SHR, SHR+BBG, SHR+BBG+ATP, and SHR+BBG+ANG II. In the gastrointestinal tract, we assessed gastric emptying (GE) and oxidative stress markers (NOx, MPO, GSH, SOD). We observed a decrease in the GE rate (P<0.05) in SHR vs control rats (21.8±2.0% vs 42.8±3.5%). The decrease in GE was returned (P<0.05) to control levels by BBG in SHR rats (21.8±2.0% vs 41.6±3.2%). Co-administration of ATP or ANG II together with BBG bypassed the effect of the P2X7 antagonist on GE in SHR (P<0.05) (21.9±5.0% vs 25.6±3.0% vs 41.6±3.2%). The MPO activity increased (P<0.05) in the gastric fundus of SHR compared to control rats (6.12±2.26 vs 0.077±0.02 UMPO/mg tissue); this effect was prevented (P<0.05) by BBG (0.55±0.15 vs 6.12±2.26 UMPO/mg tissue). Data demonstrated that blockage of P2X7 receptors with BBG can improve the GE delay and oxidative stress biomarkers in SHR animals. This preventive effect of BBG on GE delay was abrogated by ANG II and ATP, thus prompting crosstalk between renin-angiotensin and the purinergic signaling systems underlying this phenomenon.

Mineralocorticoid receptor blockade improved gut microbiota dysbiosis by reducing gut sympathetic tone in spontaneously hypertensive rats

Microbiota has a crucial role in the host blood pressure (BP) regulation. The present study analyzes whether the mineralocorticoid receptor antagonist spironolactone ameliorates the dysbiosic state in a genetic model of neurogenic hypertension. Twenty-week-old male Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were randomly allocated into three groups: untreated WKY, untreated SHR, and SHR treated with spironolactone for 5 weeks. Spironolactone restored the Firmicutes/Bacteroidetes proportion, and acetate-producing bacteria populations to WKY levels. Spironolactone reduced the percentage of intestinal aerobic bacteria. The amelioration of gut dysbiosis was linked to a reduction in the gut pathology, an enhanced colonic integrity, a reduced gut permeability and an attenuated sympathetic drive in the gut. Spironolactone was unable to reduce neuroinflammation and oxidative stress in the paraventricular nuclei in the hypothalamus. Spironolactone reduced the higher Th17 cells proportion in mesenteric lymph nodes and Th17 infiltration in aorta, improved aortic endothelial function and reduced systolic BP. This study demonstrates for the first time that spironolactone reduces gut dysbiosis in SHR. This effect could be related to its capability to improve gut integrity and pathology due to reduced sympathetic drive in the gut.

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.

Novel Role of the SIRT1 in Endocrine and Metabolic Diseases

Silent information regulator 1 (SIRT1), a highly conserved NAD⁺-dependent deacetylase, is a cellular regulator that has received extensive attention in recent years and regarded as a sensor of cellular energy and metabolism. The accumulated evidence suggests that SIRT1 is involved in the development of endocrine and metabolic diseases. In a variety of organisms, SIRT1 regulates gene expression through the deacetylation of histone, transcription factors, and lysine residues of other modified proteins including several metabolic and endocrine signal transcription factors, thereby enhancing the therapeutic effects of endocrine and metabolic diseases. These evidences indicate that targeting SIRT1 has promising applications in the treatment of endocrine and metabolic diseases. This review focuses on the role of SIRT1 in endocrine and metabolic diseases. First, we describe the background and structure of SIRT1. Then, we outline the role of SIRT1 in endocrine and metabolic diseases such as hyperuricemia, diabetes, hypertension, hyperlipidemia, osteoporosis, and polycystic ovarian syndrome. Subsequently, the SIRT1 agonists and inhibitors in the above diseases are summarized and future research directions are proposed. Overall, the information presents here may highlight the potential of SIRT1 as a future biomarker and therapeutic target for endocrine and metabolic diseases.

Immune mechanism of gut microbiota and its metabolites in the occurrence and development of cardiovascular diseases

The risk of cardiovascular disease (CVD) is associated with unusual changes in the human gut microbiota, most commonly coronary atherosclerotic heart disease, hypertension, and heart failure. Immune mechanisms maintain a dynamic balance between the gut microbiota and the host immune system. When one side changes and the balance is disrupted, different degrees of damage are inflicted on the host and a diseased state gradually develops over time. This review summarizes the immune mechanism of the gut microbiota and its metabolites in the occurrence of common CVDs, discusses the relationship between gut-heart axis dysfunction and the progression of CVD, and lists the currently effective methods of regulating the gut microbiota for the treatment of CVDs.

GRID2 aberration leads to disturbance in neuroactive ligand-receptor interactions via changes to the species richness and composition of gut microbes

OBJECTIVE

To explore the association between phenotype and the gut microbiome following damage to the GRID2 gene.

METHODS

Ten wild-type (WT) mice and 11 GRID2 knockout heterozygous mice (GRID2(±)) of a similar age and weight were randomly selected. Fresh feces were collected from both groups of mice under specified pathogen-free (SPF) conditions. The bacterial genomes were extracted from the feces, the 16S rRNA genes were sequenced, and the data were analyzed to determine clustering, diversity, abundance, LEfSe, and functional differences. Differential expression and enrichment analyses of the RNA-seq and protein levels of the GRID2 gene were also performed using data in the GENE database and the new version of the Human Protein Atlas portal (www.proteinatlas.org).

RESULTS

The diversity analysis showed differences in species composition between the two groups at different levels. At phylum level, compared with the WT group, the distribution was more bacteriophages but showed a lower content of Tenericutes in the GRID2(±) group. At the order level, compared with the WT group, a higher content of Actinomycetales and Bacteriophages were found in the GRID2(±) group. The species difference analysis showed that 17 species, including E. faecalis and Paracoccus spp., showed differences in content between the two groups. LEfSe analysis showed that the abundance of Clostridiaceae, Allobaculum, and other groups decreased in the GRID2(±) group compared with the WT group, while Mycoplasma, Sphingomonas, and Alphaproteobacteria increased in abundance. Functional analysis revealed eight differential functions between the WT and GRID2(±) group (P &lt; 0.05). The most significantly disrupted were neuroactive ligand-receptor interactions (P &lt; 9.99e-4). In addition, the differential expression and enrichment analyses performed at RNA-seq and protein levels revealed that the GRID2 gene showed organ-specific expression and was mainly enriched in the brain tissue.

CONCLUSIONS

Compared with the WT group, the defective GRID2 gene affected the species richness and composition of gut microbes in the GRID2(±) mice, which in turn affected the function of gut microbes, leading to the disruption of neuroactive ligand-receptor interactions. Our findings indicate that the host gene, GRID2, can influence the abundance of a subset of gut microbes but the exact mechanisms still need further investigation.

Intestinal microbiota: A promising therapeutic target for hypertension

Hypertension has developed into an escalating serious global public health problem with multiple and unclear pathophysiological mechanisms. Recent studies have identified intestinal microbiota as a key perpetrator of hypertension through a variety of mechanisms. In this review, we highlight the potential roles of the intestinal microbiota and its metabolites in the development of hypertension, as well as the therapeutic potential for targeting intestinal microbiomes. We also shed light on the main limitations and challenges of the current research and suggest directions for future investigations. Finally, we discuss the development of accurate and personalized preventive and therapeutic strategies for hypotension by the modulation of intestinal microbes and metabolites.

Protection by -Biotics against Hypertension Programmed by Maternal High Fructose Diet: Rectification of Dysregulated Expression of Short-Chain Fatty Acid Receptors in the Hypothalamic Paraventricular Nucleus of Adult Offspring

The role of short-chain fatty acids (SCFAs) in the brain on the developmental programming of hypertension is poorly understood. The present study explored dysregulated tissue levels of SCFAs and expression of SCFA-sensing receptors in the hypothalamic paraventricular nucleus (PVN), a key forebrain region engaged in neural regulation of blood pressure of offspring to maternal high fructose diet (HFD) exposure. We further investigated the engagement of SCFA-sensing receptors in PVN in the beneficial effects of -biotics (prebiotic, probiotic, synbiotic, and postbiotic) on programmed hypertension. Maternal HFD during gestation and lactation significantly reduced circulating butyrate, along with decreased tissue level of butyrate and increased expression of SCFA-sensing receptors, GPR41 and olfr78, and tissue oxidative stress and neuroinflammation in PVN of HFD offspring that were rectified by oral supplement with -biotics. Gene silencing of GPR41 or olfr78 mRNA in PVN also protected adult HFD offspring from programmed hypertension and alleviated the induced oxidative stress and inflammation in PVN. In addition, oral supplement with postbiotic butyrate restored tissue butyrate levels, rectified expressions of GPR41 and olfr78 in PVN, and protected against programmed hypertension in adult HFD offspring. These data suggest that alterations in tissue butyrate level, expression of GPR41 and olfr78, and activation of SCFA-sensing receptor-dependent tissue oxidative stress and neuroinflammation in PVN could be novel mechanisms that underlie hypertension programmed by maternal HFD exposure in adult offspring. Furthermore, oral -biotics supplementation may exert beneficial effects on hypertension of developmental origin by targeting dysfunctional SCFA-sensing receptors in PVN to exert antioxidant and anti-inflammatory actions in the brain.

Update on Immune Mechanisms in Hypertension

The contribution of immune cells in the initiation and maintenance of hypertension is undeniable. Several studies have established the association between hypertension, inflammation, and immune cells from the innate and adaptive immune systems. Here, we provide an update to our 2017 American Journal of Hypertension review on the overview of the cellular immune responses involved in hypertension. Further, we discuss the activation of immune cells and their contribution to the pathogenesis of hypertension in different in vivo models. We also highlight existing gaps in the field of hypertension that need attention. The main goal of this review is to provide a knowledge base for translational research to develop therapeutic strategies that can improve cardiovascular health in humans.

Brain Bioenergetics in Chronic Hypertension: Risk Factor for Acute Ischemic Stroke

Chronic hypertension is one of the key modifiable risk factors for acute ischemic stroke, also contributing to determine greater neurological deficits and worse functional outcome when an acute cerebrovascular event would occur. A tight relationship exists between cerebrovascular autoregulation, neuronal activity and brain bioenergetics. In chronic hypertension, progressive adaptations of these processes occur as an attempt to cope with the demanding necessity of brain functions, creating a new steady-state homeostatic condition. However, these adaptive modifications are insufficient to grant an adequate response to possible pathological perturbations of the established fragile hemodynamic and metabolic homeostasis. In this narrative review, we will discuss the main mechanisms by which alterations in brain bioenergetics and mitochondrial function in chronic hypertension could lead to increased risk of acute ischemic stroke, stressing the interconnections between hemodynamic factors (i.e. cerebral autoregulation and neurovascular coupling) and metabolic processes. Both experimental and clinical pieces of evidence will be discussed. Moreover, the potential role of mitochondrial dysfunction in determining, or at least sustaining, the pathogenesis and progression of chronic neurogenic hypertension will be considered. In the perspective of novel therapeutic strategies aiming at improving brain bioenergetics, we propose some determinant factors to consider in future studies focused on the cause-effect relationships between chronic hypertension and brain bioenergetic abnormalities (and vice versa), so to help translational research in this so-far unfilled gap.

Blockade of Microglial Activation in Hypothalamic Paraventricular Nucleus Improves High Salt-Induced Hypertension

BACKGROUND

It has been shown that activated microglia in brain releasing proinflammatory cytokines (PICs) contribute to the progression of cardiovascular diseases. In this study, we tested the hypothesis that microglial activation in hypothalamic paraventricular nucleus (PVN), induced by high-salt diet, increases the oxidative stress via releasing PICs and promotes sympathoexcitation and development of hypertension.

METHODS

High-salt diet was given to male Dahl salt-sensitive rats to induce hypertension. Those rats were bilaterally implanted with cannula for PVN infusion of minocycline, a selective microglial activation blocker, or artificial cerebrospinal fluid for 4 weeks.

RESULTS

High-salt diet elevated mean arterial pressure of Dahl salt-sensitive rats. Meanwhile, elevations of renal sympathetic nerve activity and central prostaglandin E2, as well as increase of plasma norepinephrine, were observed in those hypertensive rats. Tumor necrosis factor-α, interleukin-1β (IL-1β), and IL-6 increased in the PVN of those rats, associated with a significant activation of microglia and prominent disruption of redox balance, which was demonstrated by higher superoxide and NAD(P)H oxidase 2 (NOX-2) and NAD(P)H oxidase 4 (NOX-4), and lower Cu/Zn superoxide dismutase in PVN. PVN infusion of minocycline attenuated all hypertension-related alterations described above.

CONCLUSION

This study indicates that high salt leads to microglial activation within PVN of hypertensive rats, and those activated PVN microglia release PICs and trigger the production of reactive oxygen species, which contributes to sympathoexcitation and development of hypertension. Blockade of PVN microglial activation inhibits inflammation and oxidative stress, therefore attenuating the development of hypertension induced by high-salt diet.

Diosgenin exerts an antihypertensive effect in spontaneously hypertensive rats via gut-brain communication

Gut microbiota is well-established to regulate host blood pressure. Diosgenin is a natural steroid sapogenin with documented anti-inflammatory, antioxidant and antihypertensive properties. We aimed to investigate whether the antihypertensive effects of diosgenin are mediated by the microbiota-gut-brain axis in spontaneously hypertensive rats (SHR). 15-Week-old male Wistar Kyoto rats (WKY) and age-matched SHR were randomly distributed into three groups: WKY, SHR treated with a vehicle, and SHR treated with diosgenin (100 mg kg^-1). Our results showed that diosgenin prevented elevated systolic blood pressure (SBP) and ameliorated cardiac hypertrophy in SHR. Moreover, the gut microbiota composition and intestinal integrity were improved. Furthermore, increased butyrate-producing bacteria and plasma butyrate and decreased plasma lipopolysaccharides were observed in SHR treated with diosgenin. These findings were associated with reduced microglial activation and neuroinflammation in the paraventricular nucleus. Our findings suggest that diosgenin attenuates hypertension by reshaping the gut microbiota and improving the gut-brain axis.

Eucommia ulmoides bark extract reduces blood pressure and inflammation by regulating the gut microbiota and enriching the Parabacteroides strain in high-salt diet and N(omega)-nitro-L-arginine methyl ester induced mice

Hypertension is a major threat to human health. Eucommia ulmoides Oliv. (EU) is a small tree and EU extract is widely used to improve hypertension in East Asia. However, its major constituents have poor absorption and stay in the gut for a long time. The role of the gut microbiota in the anti-hypertensive effects of EU is unclear. Here, we examined the anti-hypertensive effects of EU in high-salt diet and N(omega)-nitro-L-arginine methyl ester (L-NAME) induced mice. After receiving EU for 6 weeks, the blood pressure was significantly reduced and the kidney injury was improved. Additionally, EU restored the levels of inflammatory cytokines, such as serum interleukin (IL)-6 and IL-17A, and renal IL-17A. The diversity and composition of the gut microbiota were influenced by administration of EU; 40 significantly upregulated and 107 significantly downregulated amplicon sequence variants (ASVs) were identified after administration of EU. ASV403 (Parabacteroides) was selected as a potential anti-hypertensive ASV. Its closest strain XGB65 was isolated. Furthermore, animal studies confirmed that Parabacteroides strain XGB65 exerted anti-hypertensive effects, possibly by reducing levels of inflammatory cytokines, such as renal IL-17A. Our study is the first to report that EU reduces blood pressure by regulating the gut microbiota, and it enriches the Parabacteroides strain, which exerts anti-hypertensive effects. These findings provide directions for developing novel anti-hypertensive treatments by combining probiotics and prebiotics.

Regulatory effect of gut microbes on blood pressure

Hypertension is an important global public health issue because of its high morbidity as well as the increased risk of other diseases. Recent studies have indicated that the development of hypertension is related to the dysbiosis of the gut microbiota in both animals and humans. In this review, we outline the interaction between gut microbiota and hypertension, including gut microbial changes in hypertension, the effect of microbial dysbiosis on blood pressure (BP), indicators of gut microbial dysbiosis in hypertension, and the microbial genera that affect BP at the taxonomic level. For example, increases in Lactobacillus, Roseburia, Coprococcus, Akkermansia, and Bifidobacterium are associated with reduced BP, while increases in Streptococcus, Blautia, and Prevotella are associated with elevated BP. Furthermore, we describe the potential mechanisms involved in the regulation between gut microbiota and hypertension. Finally, we summarize the commonly used treatments of hypertension that are based on gut microbes, including fecal microbiota transfer, probiotics and prebiotics, antibiotics, and dietary supplements. This review aims to find novel potential genera for improving hypertension and give a direction for future studies on gut microbiota in hypertension.

Endothelial cyclin I reduces vulnerability to angiotensin II-induced vascular remodeling and abdominal aortic aneurysm risk

BACKGROUND

Retinoblastoma protein (Rb) supports vasoprotective E2F Transcription Factor 1 (E2f1)/Dihydrofolate Reductase (Dhfr) pathway activity in endothelial cells. Cyclin I (Ccni) promotes Cyclin-Dependent Kinase-5 (Cdk5)-mediated Rb phosphorylation. Therefore, we hypothesized that endothelial Ccni may regulate cardiovascular homeostasis, vessel remodeling, and abdominal aortic aneurysm (AAA) formation.

METHODS

Aortic CCNI mRNA expression was analyzed in the Gene Expression Omnibus (GEO) GSE57691 cohort consisting of AAA patients (n = 39) and healthy controls (n = 10). We employed wild-type (WT) mice and endothelial Ccni knockout (Ccnifl/flTie2-Cre) mice to conduct in vivo and ex vivo experimentation using an Angiotensin (Ang) II hypertension model and a CaCl2 AAA model. Mice were assessed for Rb/E2f1/Dhfr signaling, biopterin (i.e., biopterin [B], dihydrobiopterin [BH2], and tetrahydrobiopterin [BH4]) production, cardiovascular homeostasis, vessel remodeling, and AAA formation.

RESULTS

Aortic CCNI mRNA expression was downregulated in AAA patients. Both Ang II- and CaCl2-induced WT mice showed aortic Ccni upregulation coupled with vasculoprotective upregulation of Rb/E2f1/Dhfr signaling and biopterins. Endothelial Ccni knockout downregulated medial Rb/E2f1/Dhfr signaling and biopterins in Ang II-induced hypertensive mice, which exacerbated eNos uncoupling and H2O2 production. Endothelial Ccni knockout impaired in vivo hemodynamic responses and endothelium-dependent vasodilatation in ex vivo mesenteric arteries in response to Ang II. Endothelial Ccni knockout exacerbated mesenteric artery remodeling and AAA risk in response to Ang II and CaCl2.

CONCLUSIONS

Endothelial Ccni acts as a critical negative regulator of eNos uncoupling-mediated ROS generation and thereby reduces vulnerability to hypertension-induced vascular remodeling and AAA development in mice.

The Putative Role of Astaxanthin in Neuroinflammation Modulation: Mechanisms and Therapeutic Potential

Neuroinflammation is a protective mechanism against insults from exogenous pathogens and endogenous cellular debris and is essential for reestablishing homeostasis in the brain. However, excessive prolonged neuroinflammation inevitably leads to lesions and disease. The use of natural compounds targeting pathways involved in neuroinflammation remains a promising strategy for treating different neurological and neurodegenerative diseases. Astaxanthin, a natural xanthophyll carotenoid, is a well known antioxidant. Mounting evidence has revealed that astaxanthin is neuroprotective and has therapeutic potential by inhibiting neuroinflammation, however, its functional roles and underlying mechanisms in modulating neuroinflammation have not been systematically summarized. Hence, this review summarizes recent progress in this field and provides an update on the medical value of astaxanthin. Astaxanthin modulates neuroinflammation by alleviating oxidative stress, reducing the production of neuroinflammatory factors, inhibiting peripheral inflammation and maintaining the integrity of the blood-brain barrier. Mechanistically, astaxanthin scavenges radicals, triggers the Nrf2-induced activation of the antioxidant system, and suppresses the activation of the NF-κB and mitogen-activated protein kinase pathways. With its good biosafety and high bioavailability, astaxanthin has strong potential for modulating neuroinflammation, although some outstanding issues still require further investigation.

Role of Gut Microbiota in Pulmonary Arterial Hypertension

Gut microbiota and its metabolites play an important role in maintaining host homeostasis. Pulmonary arterial hypertension (PAH) is a malignant clinical syndrome with a frightening mortality. Pulmonary vascular remodeling is an important feature of PAH, and its pathogenesis is not well established. With the progress of studies on intestinal microbes in different disease, cumulative evidence indicates that gut microbiota plays a major role in PAH pathophysiology. In this review, we will systematically summarize translational and preclinical data on the correlation between gut dysbiosis and PAH and investigate the role of gut dysbiosis in the causation of PAH. Then, we point out the potential significance of gut dysbiosis in the diagnosis and treatment of PAH as well as several problems that remain to be resolved in the field of gut dysbiosis and PAH. All of this knowledge of gut microbiome might pave the way for the extension of novel pathophysiological mechanisms, diagnosis, and targeted therapies for PAH.

Microglia-Mediated Neuroinflammation: A Potential Target for the Treatment of Cardiovascular Diseases

Microglia are tissue-resident macrophages of the central nervous system (CNS). In the CNS, microglia play an important role in the monitoring and intervention of synaptic and neuron-level activities. Interventions targeting microglia have been shown to improve the prognosis of various neurological diseases. Recently, studies have observed the activation of microglia in different cardiovascular diseases. In addition, different approaches that regulate the activity of microglia have been shown to modulate the incidence and progression of cardiovascular diseases. The change in autonomic nervous system activity after neuroinflammation may be a potential intermediate link between microglia and cardiovascular diseases. Here, in this review, we will discuss recent updates on the regulatory role of microglia in hypertension, myocardial infarction and ischemia/reperfusion injury. We propose that microglia serve as neuroimmune modulators and potential targets for cardiovascular diseases.

Intraventricular Drug Delivery and Sampling for Pharmacokinetics and Pharmacodynamics Study

Although the blood-brain barrier (BBB) protects the brain from foreign entities, it also prevents some therapeutics from crossing into the central nervous system (CNS) to ameliorate diseases or infections. Drugs are administered directly into the CNS in animals and humans to circumvent the BBB. The present protocol describes a unique way of treating brain infections through intraventricular delivery of antibiotics, i.e., polymyxins, the last-line antibiotics to treat multi-drug resistant Gram-negative bacteria. A straightforward stereotaxic surgery protocol was developed to implant a guide cannula reaching into the lateral ventricle in rats. After a recovery period of 24 h, rats can be injected consciously and repeatedly through a cannula that is fitted to the guide. Injections can be delivered manually as a bolus or infusion using a microinjection pump to obtain a slow and controlled flow rate. The intraventricular injection was successfully confirmed with Evans Blue dye. Cerebrospinal fluid (CSF) can be drained, and the brain and other organs can be collected. This approach is highly amenable for studies involving drug delivery to the CNS and subsequent assessment of pharmacokinetic and pharmacodynamic activity.

The AT1 Receptor Blocker Telmisartan Reduces Intestinal Mucus Thickness in Obese Mice

The angiotensin II (type 1) (AT₁) receptor blocker telmisartan (TEL) is beneficial for the treatment of individuals suffering from metabolic syndrome. As we have shown that TEL has an impact on gut microbiota, we investigated here whether TEL influences gut barrier function. C57BL/6N mice were fed with chow or high-fat diet (HFD) and treated with vehicle or TEL (8 mg/kg/day). Mucus thickness was determined by immunohistochemistry. Periodic Acid-Schiff staining allowed the number of goblet cells to be counted. Using western blots, qPCR, and immunohistochemistry, factors related to mucus biosynthesis (Muc2, St6galnac), proliferation (Ki-67), or necroptosis (Rip3) were measured. The influence on cell viability was determined in vitro by using losartan, as the water solubility of TEL was too low for in vitro experiments. Upon HFD, mice developed obesity as well as leptin and insulin resistance, which were prevented by TEL. Mucus thickness upon HFD-feeding was diminished. Independent of feeding, TEL additionally reduced mucus thickness. Numbers of goblet cells were not affected by HFD-feeding and TEL. St6galnac expression was increased by TEL. Rip3 was increased in TEL-treated and HFD-fed mice, while Ki-67 decreased. Cell viability was diminished by using >1 mM losartan. The anti-obese effect of TEL was associated with a decrease in mucus thickness, which was likely not related to a lower expression of Muc2 and goblet cells. A decrease in Ki-67 and increase in Rip3 indicates lower cell proliferation and increased necroptosis upon TEL. However, direct cell toxic effects are ruled out, as in vivo concentrations are lower than 1 mM.

Adeno-associated virus-mediated in vivo suppression of expression of EPHX2 gene modulates the activity of paraventricular nucleus neurons in spontaneously hypertensive rats

BACKGROUND

Hypertension can be attributed to increased sympathetic activities. Presympathetic neurons in the paraventricular nucleus (PVN) of the hypothalamus are capable of modulating sympathetic outflow, thus contributing to the pathogenesis of neurogenic hypertension. Epoxyeicosatrienoic acids (EETs) were reported to have anti-hypertensive effects, which could be degraded by soluble epoxide hydrolase (sEH), encoded by EPHX2. However, the potential effect of EETs on PVN neuron activity and the underlying molecular mechanism are largely unknown.

METHODS

Knockdown of EPHX2 in spontaneously hypertensive rats (SHRs) was achieved by tail-intravenous injection of AAV plasmid containing shRNA targeting EPHX2. Whole-cell patch clamp was used to record action potentials of PVN neurons. An LC-MS/MS System was employed to determine 14,15-EET levels in rat cerebrospinal fluid. qPCR and western blotting were applied to examine the expression level of EPHX2 in various tissues. ELISA and immunofluorescence staining were applied to examine the levels of ATP, D-serine and glial fibrillary acidic protein (GFAP) in isolated astrocytes.

RESULTS

The expression level of EPHX2 was higher, while the level of 14,15-EET was lower in SHRs than normotensive Wistar-Kyoto rats (WKY) rats. The spike firing frequency of PNV neurons in SHRs was higher than in WKY rats at a given stimulus current, which could be reduced by either EPHX2 downregulation or 14,15-EET administration. In isolated hypothalamic astrocytes, the elevated intracellular ATP or D-serine induced by Angiotensin II (Ang II) treatment could be rescued by 14,15-EET addition or 14,15-EET combing serine racemase (SR) downregulation by siRNA, respectively. Furthermore, 14,15-EET treatment reduced the Ang II-induced elevation of GFAP immunofluorescence.

CONCLUSIONS

The elevation of EET levels by EPHX2 downregulation reduced presympathetic neuronal activity in the PVN of SHRs, leading to a reduced sympathetic outflow in hypertension rats. The ATP/SR/D-serine pathway of astrocytes is involved in EET-mediated neuroprotection.

Gut Microbiome and Neuroinflammation in Hypertension

Hypertension is a worldwide problem with major impacts on health including morbidity and mortality, as well as consumption of health care resources. Nearly 50% of American adults have high blood pressure, and this rate is rising. Even with multiple antihypertensive drugs and aggressive lifestyle modifications, blood pressure is inadequately controlled in about 1 of 5 hypertensive individuals. This review highlights a hypothesis for hypertension that suggests alternative mechanisms for blood pressure elevation and maintenance. A better understanding of these mechanisms could open avenues for more successful treatments. The hypothesis accounts for recent understandings of the involvement of gut physiology, gut microbiota, and neuroinflammation in hypertension. It includes bidirectional communication between gut microbiota and gut epithelium in the gut-brain axis that is involved in regulation of autonomic nervous system activity and blood pressure control. Dysfunction of this gut-brain axis, including dysbiosis of gut microbiota, gut epithelial dysfunction, and deranged input to the brain, contributes to hypertension via inflammatory mediators, metabolites, bacteria in the circulation, afferent information alterations, etc resulting in neuroinflammation and unbalanced autonomic nervous system activity that elevates blood pressure. This in turn negatively affects gut function and its microbiota exacerbating the problem. We focus this review on the gut-brain axis hypothesis for hypertension and possible contribution to racial disparities in hypertension. A novel idea, that immunoglobulin A-coated bacteria originating in the gut with access to the brain could be involved in hypertension, is raised. Finally, minocycline, with its anti-inflammatory and antimicrobial properties, is evaluated as a potential antihypertensive drug acting on this axis.

Antihypertensive effects of exercise involve reshaping of gut microbiota and improvement of gut-brain axis in spontaneously hypertensive rat

Exercise (Ex) has long been recognized to produce beneficial effects on hypertension (HTN). This coupled with evidence of gut dysbiosis and an impaired gut-brain axis led us to hypothesize that reshaping of gut microbiota and improvement in impaired gut-brain axis would, in part, be associated with beneficial influence of exercise. Male spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats were randomized into sedentary, trained, and detrained groups. Trained rats underwent moderate-intensity exercise for 12 weeks, whereas, detrained groups underwent 8 weeks of moderate-intensity exercise followed by 4 weeks of detraining. Fecal microbiota, gut pathology, intestinal inflammation, and permeability, brain microglia and neuroinflammation were analyzed. We observed that exercise training resulted in a persistent decrease in systolic blood pressure in the SHR. This was associated with increase in microbial α diversity, altered β diversity, and enrichment of beneficial bacterial genera. Furthermore, decrease in the number of activated microglia, neuroinflammation in the hypothalamic paraventricular nucleus, improved gut pathology, inflammation, and permeability were also observed in the SHR following exercise. Interestingly, short-term detraining did not abolish these exercise-mediated improvements. Finally, fecal microbiota transplantation from exercised SHR into sedentary SHR resulted in attenuated SBP and an improved gut-brain axis. These observations support our concept that an impaired gut-brain axis is linked to HTN and exercise ameliorates this impairment to induce antihypertensive effects.

The Bidirectional Signal Communication of Microbiota-Gut-Brain Axis in Hypertension

Hypertension is a critical risk factor of cardiovascular diseases. A new concept of microbiota-gut-brain axis has been established recently, mediating the bidirectional communication between the gut and its microbiome and the brain. Alterations in bidirectional interactions are believed to be involved in the blood pressure regulation. Neuroinflammation and increased sympathetic outflow act as the descending innervation signals from the brain. Increased sympathetic activation plays a recognized role in the genesis of hypertension. The present evidence demonstrates that gut dysbiosis is associated with central nervous system neuroinflammation. However, how the gut influences the brain remains unclear. We reviewed the roles of neuroinflammation and gut microbiota and their interactions in the pathogenesis of hypertension and described the ascending signaling mechanisms behind the microbiota-gut-brain axis in detail. Additionally, the innovative prohypertensive mechanisms of dietary salt through the microbiota-gut-brain axis are summarized. The bidirectional communication mechanisms were proposed for the first time that the descending signals from the brain and the ascending connections from the gut form a vicious circle of hypertension progression, acting as a premise for hypertension therapy.

Molecular imaging of the brain-heart axis provides insights into cardiac dysfunction after cerebral ischemia

Ischemic stroke imparts elevated risk of heart failure though the underlying mechanisms remain poorly described. We aimed to characterize the influence of cerebral ischemic injury on cardiac function using multimodality molecular imaging to investigate brain and cardiac morphology and tissue inflammation in two mouse models of variable stroke severity. Transient middle cerebral artery occlusion (MCAo) generated extensive stroke damage (56.31 ± 40.39 mm³). Positron emission tomography imaging of inflammation targeting the mitochondrial translocator protein (TSPO) revealed localized neuroinflammation at 7 days after stroke compared to sham (3.8 ± 0.8 vs 2.6 ± 0.7 %ID/g max, p < 0.001). By contrast, parenchyma topical application of vasoconstrictor endothelin-1 did not generate significant stroke damage or neuroinflammatory cell activity. MCAo evoked a modest reduction in left ventricle ejection fraction at both 1 weeks and 3 weeks after stroke (LVEF at 3 weeks: 54.3 ± 5.7 vs 66.1 ± 3.5%, p < 0.001). This contractile impairment was paralleled by elevated cardiac TSPO PET signal compared to sham (8.6 ± 2.4 vs 5.8 ± 0.7%ID/g, p = 0.022), but was independent of leukocyte infiltration defined by flow cytometry. Stroke size correlated with severity of cardiac dysfunction (r = 0.590, p = 0.008). Statistical parametric mapping identified a direct association between neuroinflammation at 7 days in a cluster of voxels including the insular cortex and reduced ejection fraction (ρ = - 0.396, p = 0.027). Suppression of microglia led to lower TSPO signal at 7 days which correlated with spared late cardiac function after MCAo (r = - 0.759, p = 0.029). Regional neuroinflammation early after cerebral ischemia influences subsequent cardiac dysfunction. Total body TSPO PET enables monitoring of neuroinflammation, providing insights into brain-heart inter-organ communication and may guide therapeutic intervention to spare cardiac function post-stroke.

Hypothalamic inflammation in metabolic disorders and aging

The hypothalamus is a critical brain region for the regulation of energy homeostasis. Over the years, studies on energy metabolism primarily focused on the neuronal component of the hypothalamus. Studies have recently uncovered the vital role of glial cells as an additional player in energy balance regulation. However, their inflammatory activation under metabolic stress condition contributes to various metabolic diseases. The recruitment of monocytes and macrophages in the hypothalamus helps sustain such inflammation and worsens the disease state. Neurons were found to actively participate in hypothalamic inflammatory response by transmitting signals to the surrounding non-neuronal cells. This activation of different cell types in the hypothalamus leads to chronic, low-grade inflammation, impairing energy balance and contributing to defective feeding habits, thermogenesis, and insulin and leptin signaling, eventually leading to metabolic disorders (i.e., diabetes, obesity, and hypertension). The hypothalamus is also responsible for the causation of systemic aging under metabolic stress. A better understanding of the multiple factors contributing to hypothalamic inflammation, the role of the different hypothalamic cells, and their crosstalks may help identify new therapeutic targets. In this review, we focus on the role of glial cells in establishing a cause-effect relationship between hypothalamic inflammation and the development of metabolic diseases. We also cover the role of other cell types and discuss the possibilities and challenges of targeting hypothalamic inflammation as a valid therapeutic approach.

Acetylcholinesterase inhibition with Pyridostigmine attenuates hypertension and neuroinflammation in the paraventricular nucleus in rat model for Preeclampsia

Preeclampsia (PE) is characterized by hypertension, autonomic imbalance and inflammation. The subfornical organ (SFO) reportedly relays peripheral inflammatory mediator's signals to the paraventricular nucleus (PVN), a brain autonomic center shown to mediate hypertension in hypertensive rat but not yet in PE rat models. Additionally, we previously showed that Pyridostigmine (PYR), an acetylcholinesterase inhibitor, attenuated placental inflammation and hypertension in PE models. In this study, we investigated the effect of PYR on the activities of these brain regions in PE model. PYR (20 mg/kg/day) was administered to reduced uterine perfusion pressure (RUPP) Sprague-Dawley rat from gestational day (GD) 14 to GD19. On GD19, the mean arterial pressure (MAP) was recorded and samples were collected for analysis. RUPP rats exhibited increased MAP (P = 0.0025), elevated circulating tumor necrosis factor-α (TNF-α, P = 0.0075), reduced baroreflex sensitivity (BRS), increased neuroinflammatory markers including TNF-α, interleukin-1β (IL-1β), microglial activation (P = 0.0039), oxidative stress and neuronal excitation within the PVN and the SFO. Changes in MAP, in molecular and cellular expression induced by RUPP intervention were improved by PYR. The ability of PYR to attenuate TNF-α mediated central effect was evaluated in TNF-α-infused pregnant rats. TNF-α infusion-promoted neuroinflammation in the PVN and SFO in dams was abolished by PYR. Collectively, our data suggest that PYR improves PE-like symptoms in rat by dampening placental ischemia and TNF-α-promoted inflammation and pro-hypertensive activity in the PVN. This broadens the therapeutical potential of PYR in PE.

The Emerging Scenario of the Gut-Brain Axis: The Therapeutic Actions of the New Actor Kefir against Neurodegenerative Diseases

The fact that millions of people worldwide suffer from Alzheimer’s disease (AD) or Parkinson’s disease (PD), the two most prevalent neurodegenerative diseases (NDs), has been a permanent challenge to science. New tools were developed over the past two decades and were immediately incorporated into routines in many laboratories, but the most valuable scientific contribution was the “waking up” of the gut microbiota. Disturbances in the gut microbiota, such as an imbalance in the beneficial/pathogenic effects and a decrease in diversity, can result in the passage of undesired chemicals and cells to the systemic circulation. Recently, the potential effect of probiotics on restoring/preserving the microbiota was also evaluated regarding important metabolite and vitamin production, pathogen exclusion, immune system maturation, and intestinal mucosal barrier integrity. Therefore, the focus of the present review is to discuss the available data and conclude what has been accomplished over the past two decades. This perspective fosters program development of the next steps that are necessary to obtain confirmation through clinical trials on the magnitude of the effects of kefir in large samples.

Moderate Physical Exercise Activates ATR2 Receptors, Improving Inflammation and Oxidative Stress in the Duodenum of 2K1C Hypertensive Rats

Background: In addition to the cardiovascular and renal systems, the gastrointestinal tract also contains angiotensin ATR_1a, ATR_1b, and ATR₂. We previously observed that the 2Kidney-1Clip hypertension model elicits physical exercise and gastrointestinal dysmotility, which is prevented by renin-angiotensin system blockers. Here, we investigate the effect of physical exercise on inflammation, stress biomarkers, and angiotensin II receptors in the duodenum of 2K1C rats. Methods: Arterial hypertension was induced by the 2K1C surgical model. The rats were allocated in Sham, 2K1C, or 2K1C+Exercise groups. One week after surgery, they were submitted to a physical exercise protocol (running 5x/week, 60min/day). Next, we assessed their intestinal contractility, cytokine levels (TNF-α, IL-1β, and IL-6), oxidative stress levels (MPO, GSH, MDA, and SOD), and the gene expression of angiotensin receptors (ATR_1A, ATR_1B, and ATR₂). Results: In comparison with the Sham group, the 2K1C arterial hypertension decreased (p<0.05) the intestinal contractility. In comparison with 2K1C, the 2K1C+Exercise group exhibited lower (p<0.05) MPO activity (22.04±5.90 vs. 78.95±18.09 UMPO/mg tissue) and higher (p<0.05) GSH concentrations in intestinal tissues (67.63±7.85 vs. 31.85±5.90mg NPSH/mg tissue). The 2K1C+Exercise group showed lower (p<0.05) cytokine levels in the intestine than 2K1C rats. In comparison with the Sham group, the 2K1C+Exercise rats showed higher (p<0.05) gene expression of ATR₂ in the duodenum. Conclusion: 2K-1C hypertension elicits an oxidative stress and inflammation process in the duodenum. Physical exercise modulates the expression twice as much of ATR2 receptors, suggesting possible anti-inflammatory and antioxidant effects induced by exercise.

Curcumin ameliorates hypertension via gut-brain communication in spontaneously hypertensive rat

Gut dysbiosis and dysregulation of gut-brain communication have been identified in hypertensive patients and animal models. Previous studies have shown that probiotic or prebiotic treatments exert positive effects on the pathophysiology of hypertension. This study aimed to examine the hypothesis that the microbiota-gut-brain axis is involved in the antihypertensive effects of curcumin, a potential prebiotic obtained from Curcuma longa. Male 8- to 10-week-old spontaneously hypertensive rats (SHRs) and Wistar Kyoto (WKY) rats were divided into four groups: WKY rats and SHRs treated with vehicle and SHRs treated with curcumin in dosage of 100 or 300 mg/kg/day for 12 weeks. Our results show that the elevated blood pressure of SHRs was markedly decreased in both curcumin-treated groups. Curcumin treatment also altered the gut microbial composition and improved intestinal pathology and integrity. These factors were associated with reduced neuroinflammation and oxidative stress in the hypothalamus paraventricular nucleus (PVN). Moreover, curcumin treatment increased butyrate levels in the plasma, which may be the result of increased butyrate-producing gut microorganisms. In addition, curcumin treatment also activated G protein-coupled receptor 43 (GPR 43) in the PVN. These results indicate that curcumin reshapes the composition of the gut microbiota and ameliorates the dysregulation of the gut-brain communication to induce antihypertensive effects.