S-57-6: OBSTRUCTIVE SLEEP APNEA INDUCED GUT DYSBIOSIS STIMULATES A PROINFLAMMATORY RESPONSE THAT PROMOTES NEUROINFLAMMATION AND HYPERTENSION

Abstract

Objective: Obstructive sleep apnea (OSA) is an independent risk factor for hypertension (HT). We have demonstrated that OSA induces gut dysbiosis, and a dysbiotic microbiota is causal in the development of HT. The mechanisms linking gut dysbiosis to blood pressure (BP) regulation are unclear. Recent studies demonstrate gut dysbiosis induces a pro-inflammatory host response resulting in peripheral- and neuro-inflammation, key factors in the development of HT. We hypothesized that OSA induced gut dysbiosis elicits a pro-inflammatory response that promotes neuroinflammation and HT. Methods: OSA was induced in 8-week-old male rats by repeatedly inflating a surgically implanted tracheal balloon. Sham rats underwent balloon implantation without inflations. After two weeks of apneas, lymphocytes were isolated from aorta, brain, cecum, ileum, mesenteric lymph node, and spleen for assessment by flow cytometry. In studies examining IL-17, a monoclonal antibody to neutralize IL-17 was injected every 48 hours during the 2 weeks of OSA. To track lymphocytes originating from the gut, cells in the Peyers patches of the small intestine were labelled by injection of carboxyfluorescein succinimidyl ester (CFSE) dye. Results: Two weeks of OSA significantly decreased anti-inflammatory regulatory T (Treg) cells and increased TH17 (IL-17+) in the brain, cecum, and ileum (n = 7, p < 0.05). A significant increase in the Th17/Treg ratio was observed in brain, cecum and ileum of OSA, versus sham, rats (n = 7, p < 0.05). To examine the role of TH17 cells, we injected an IL-17 neutralizing antibody or control IgG antibody during the 2 weeks of OSA. Compared to OSA rats receiving IgG control, neutralization of IL-17 significantly reduced BP of OSA rats (n = 6, p < 0.05). Additionally, neutralization of IL-17 resulted in a significant increase of Tregs and decreased Th1 cells in brain, cecum and ileum of OSA rats (n = 6, p < 0.01). To examine the distribution of lymphocytes originating from the gut, cells in the Peyers patches of sham and OSA rats were labelled with CFSE. We observed significant increases in CFSE+ Th1, Th2, and Th17 cells in the brain, MLN and spleen of OSA as compared to sham rats (n = 6, p < 0.05). Conclusion: Overall, we found that OSA induced gut dysbiosis is associated with a pro-inflammatory response in the gut and brain that involves IL-17 signaling. Our findings suggest that gut dysbiosis may serve as the trigger for widespread inflammation, and treatment strategies to prevent or reverse gut dysbiosis may prove useful in reducing neuroinflammation and HT.