Rationale Sympathetic nervous system control of inflammation plays a central role in hypertension. The gut receives significant sympathetic innervation, is densely populated with a diverse microbial ecosystem, and contains immune cells that greatly impact overall inflammatory homeostasis. Despite this uniqueness, little is known about the involvement of the gut in hypertension. Objective Test the hypothesis that increased sympathetic drive to the gut is associated with increased gut wall permeability, increased inflammatory status, and microbial dysbiosis and that these gut pathological changes are linked to hypertension. Methods and Results Gut epithelial integrity and wall pathology were examined in spontaneously hypertensive rat (SHR) and chronic Angiotensin II infusion rat models. The increase in blood pressure in SHR was associated with gut pathology that included increased intestinal permeability and decreased tight junction proteins. These changes in gut pathology in hypertension were associated with alterations in microbial communities relevant in blood pressure control. We also observed enhanced gut-neuronal communication in hypertension originating from paraventricular nucleus of the hypothalamus and presenting as increased sympathetic drive to the gut. Finally, angiotensin converting enzyme inhibition (captopril) normalized blood pressure and was associated with reversal of gut pathology. Conclusions A dysfunctional sympathetic-gut communication is associated with gut pathology, dysbiosis, and inflammation, and plays a key role in hypertension. Thus, targeting of gut microbiota by innovative probiotics, antibiotics, and fecal transplant, in combination with current pharmacotherapy, may be a novel strategy for hypertension treatment.
Recent evidence indicates a link between gut pathology and microbiome with hypertension (HTN) in animal models. However, whether this association exists in humans is unknown. Thus, our objectives in the present study were to test the hypotheses that high blood pressure (BP) patients have distinct gut microbiomes and that gut–epithelial barrier function markers and microbiome composition could predict systolic BP (SBP). Fecal samples, analyzed by shotgun metagenomics, displayed taxonomic and functional changes, including altered butyrate production between patients with high BP and reference subjects. Significant increases in plasma of intestinal fatty acid binding protein (I-FABP), lipopolysaccharide (LPS), and augmented gut-targetting proinflammatory T helper 17 (Th17) cells in high BP patients demonstrated increased intestinal inflammation and permeability. Zonulin, a gut epithelial tight junction protein regulator, was markedly elevated, further supporting gut barrier dysfunction in high BP. Zonulin strongly correlated with SBP (R2 = 0.5301, P<0.0001). Two models predicting SBP were built using stepwise linear regression analysis of microbiome data and circulating markers of gut health, and validated in a separate cohort by prediction of SBP from zonulin in plasma (R2 = 0.4608, P<0.0001). The mouse model of HTN, chronic angiotensin II (Ang II) infusion, was used to confirm the effects of butyrate and gut barrier function on the cardiovascular system and BP. These results support our conclusion that intestinal barrier dysfunction and microbiome function are linked to HTN in humans. They suggest that manipulation of gut microbiome and its barrier functions could be the new therapeutic and diagnostic avenues for HTN.
Rationale Microglial activation in autonomic brain regions is a hallmark of neuroinflammation in neurogenic hypertension (HTN). Despite evidence that an impaired sympathetic nerve activity supplying the bone marrow (BM) increases inflammatory cells and decreases angiogenic cells, little is known about the reciprocal impact of BM-derived inflammatory cells on neuroinflammation in HTN. Objective Test the hypothesis that pro-inflammatory BM cells from hypertensive animals contribute to neuroinflammation and HTN via a brain-BM interaction. Methods and Results Following BM ablation in spontaneously hypertensive rats (SHR), and reconstitution with normotensive Wistar-Kyoto (WKY) rat BM, the resultant chimeric SHR displayed significant reduction in mean arterial pressure (MAP) associated with attenuation of both central and peripheral inflammation. In contrast, an elevated MAP along with increased central and peripheral inflammation was observed in chimeric WKY rats reconstituted with SHR BM. Oral treatment with minocycline, an inhibitor of microglial activation, attenuated HTN in both the SHR and chronic angiotensin II (Ang II)-infused rats. This was accompanied by decreased sympathetic drive and inflammation. Furthermore, in chronic Ang II-infused rats, minocycline prevented extravasation of BM-derived cells to the hypothalamic paraventricular nucleus (PVN), presumably via a mechanism of decreased C-C chemokine ligand 2 levels in the cerebrospinal fluid. Conclusions The BM contributes to HTN by increasing peripheral inflammatory cells and their extravasation into the brain. Minocycline is an effective therapy to modify neurogenic components of HTN. These observations support the hypothesis that BM-derived cells are involved in neuroinflammation, and targeting them may be an innovative strategy for neurogenic resistant HTN therapy.
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