Rat Model Of Obstructive Sleep Apnea Research Articles

Ocular Inflammation and Oxidative Stress as a Result of Chronic Intermittent Hypoxia: A Rat Model of Sleep Apnea.

Obstructive sleep apnea (OSA) is a sleep disorder characterized by intermittent complete or partial occlusion of the airway. Despite a recognized association between OSA and glaucoma, the nature of the underlying link remains unclear. In this study, we investigated whether mild OSA induces morphological, inflammatory, and metabolic changes in the retina resembling those seen in glaucoma using a rat model of OSA known as chronic intermittent hypoxia (CIH). Rats were randomly assigned to either normoxic or CIH groups. The CIH group was exposed to periodic hypoxia during its sleep phase with oxygen reduction from 21% to 10% and reoxygenation in 6 min cycles over 8 h/day. The eyes were subsequently enucleated, and then the retinas were evaluated for retinal ganglion cell number, oxidative stress, inflammatory markers, metabolic changes, and hypoxic response modulation using immunohistochemistry, multiplex assays, and capillary electrophoresis. Statistically significant differences were observed between normoxic and CIH groups for oxidative stress and inflammation, with CIH resulting in increased HIF-1α protein levels, higher oxidative stress marker 8-OHdG, and increased TNF-α. Pyruvate dehydrogenase kinase-1 protein was significantly reduced with CIH. No significant differences were found in retinal ganglion cell number. Our findings suggest that CIH induces oxidative stress, inflammation, and upregulation of HIF-1α in the retina, akin to early-stage glaucoma.

Crucial Role of Stromal Interaction Molecule-Activated TRPC-ORAI Channels in Vascular Remodeling and Pulmonary Hypertension Induced by Intermittent Hypoxia.

Obstructive sleep apnea (OSA), a sleep breathing disorder featured by chronic intermittent hypoxia (CIH), is associate with pulmonary hypertension. Rats exposed to CIH develop lung vascular remodeling and pulmonary hypertension, which paralleled the upregulation of stromal interaction molecule (STIM)-activated TRPC-ORAI Ca2+ channels (STOC) in the lung, suggesting that STOC participate in the pulmonary vascular alterations. Accordingly, to evaluate the role played by STOC in pulmonary hypertension we studied whether the STOC blocker 2-aminoethoxydiphenyl borate (2-APB) may prevent the vascular remodeling and the pulmonary hypertension induced by CIH in a rat model of OSA. We assessed the effects of 2-APB on right ventricular systolic pressure (RVSP), pulmonary vascular remodeling, α-actin and proliferation marker Ki-67 levels in pulmonary arterial smooth muscle cells (PASMC), mRNA levels of STOC subunits, and systemic and pulmonary oxidative stress (TBARS) in male Sprague-Dawley (200 g) rats exposed to CIH (5% O2, 12 times/h for 8h) for 28 days. At 14 days of CIH, osmotic pumps containing 2-APB (10 mg/kg/day) or its vehicle were implanted and rats were kept for 2 more weeks in CIH. Exposure to CIH for 28 days raised RVSP > 35 mm Hg, increased the medial layer thickness and the levels of α-actin and Ki-67 in PASMC, and increased the gene expression of TRPC1, TRPC4, TRPC6 and ORAI1 subunits. Treatment with 2-APB prevented the raise in RVSP and the increment of the medial layer thickness, as well as the increased levels of α-actin and Ki-67 in PASMC, and the increased gene expression of STOC subunits. In addition, 2-APB did not reduced the lung and systemic oxidative stress, suggesting that the effects of 2-APB on vascular remodeling and pulmonary hypertension are independent on the reduction of the oxidative stress. Thus, our results supported that STIM-activated TRPC-ORAI Ca2+ channels contributes to the lung vascular remodeling and pulmonary hypertension induced by CIH.

Enhanced Ocular Surface and Intraoral Nociception via a Transient Receptor Potential Vanilloid 1 Mechanism in a Rat Model of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA), characterized by low arterial oxygen saturation during sleep, is associated with an increased risk of orofacial pain. In this study, we simulated chronic intermittent hypoxia (CIH) during the sleep/rest phase (light phase) to determine the role of transient receptor potential vanilloid 1 (TRPV1) in mediating enhanced orofacial nocifensive behavior and trigeminal spinal subnucleus caudalis (Vc) neuronal responses to capsaicin (a TRPV1 agonist) stimulation in a rat model of OSA. Rats were subjected to CIH (nadir O2, 5%) during the light phase for 8 or 16 consecutive days. CIH yielded enhanced behavioral responses to capsaicin after application to the ocular surface and intraoral mucosa, which was reversed under normoxic conditions. The percentage of TRPV1-immunoreactive trigeminal ganglion neurons was greater in CIH rats than in normoxic rats and recovered under normoxic conditions after CIH. The ratio of large-sized TRPV1-immunoreactive trigeminal ganglion neurons increased in CIH rats. The density of TRPV1 positive primary afferent terminals in the superficial laminae of Vc was higher in CIH rats. Phosphorylated extracellular signal-regulated kinase (pERK)-immunoreactive cells intermingled with the central terminal of TRPV1-positive afferents in the Vc. The number of pERK-immunoreactive cells following low-dose capsaicin (0.33 µM) application to the tongue was significantly greater in the middle portion of the Vc of CIH rats than of normoxic rats and recovered under normoxic conditions after CIH. These data suggest that CIH during the sleep (light) phase is sufficient to transiently enhance pain on the ocular surface and intraoral mucosa via TRPV1-dependent mechanisms.

Tempol alleviates chronic intermittent hypoxia-induced pancreatic injury through repressing inflammation and apoptosis.

Obstructive sleep apnea (OSA) has been demonstrated to be implicated in disorder of insulin secretion and diabetes mellitus. In this study, we aimed to evaluate the protective role of tempol, a powerful antioxidant, in chronic intermittent hypoxia (IH)-induced pancreatic injury. The rat model of OSA was established by IH exposure. The pathological changes, increased blood-glucose level, and raised proinsulin/insulin ratio in pancreatic tissues of rats received IH were effectively relieved by tempol delivery. In addition, the enhanced levels of pro-inflammatory cytokines, TNF-alpha, IL-1beta, IL-6, and inflammatory mediators, PGE2, cyclooxygenase-2 (COX-2), NO, and inducible nitric oxide synthase (iNOS) in pancreatic tissue were suppressed by tempol. Moreover, tempol inhibited IH-induced apoptosis in pancreatic tissue as evidenced by upregulated Bcl-2 level, and downregulated Bax and cleaved caspase-3 levels. Finally, the abnormal activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB) signaling pathways induced by IH was restrained by tempol administration. In summary, our study demonstrates that tempol relieves IH-induced pancreatic injury by inhibiting inflammatory response and apoptosis, which provides theoretical basis for tempol as an effective treatment for OSA-induced pancreatic injury.

Tempol relieves lung injury in a rat model of chronic intermittent hypoxia via suppression of inflammation and oxidative stress.

Objective(s):Obstructive sleep apnea (OSA) is confirmed to cause lesions in multiple organs, especially in the lung tissue. Tempol is an antioxidant that has been reported to restrain inflammation and oxidative stress, with its role in OSA-induced lung injury being unclear. This study aimed to investigate the beneficial effect of tempol on chronic intermittent hypoxia (IH)-induced lung injury.Materials and Methods:A rat model of OSA was established by IH. There were four groups: normal air (NA), IH, IH+tempol, NA+tempol. Inflammatory response was evaluated by TNF-α, IL-1β, and IL-6 levels. Oxidative stress was detected by MDA and GSH levels, and SOD activity. The protein levels were assessed by Western blot. DNA binding activity of NF-κB or Nrf2 was determined by electrophoretic mobility shift assay.Results:According to the results, tempol administration alleviated pathological changes of the lung tissue, decreased leukocyte count and protein content (P<0.001) in bronchoalveolar lavage fluid (BALF). Inflammation response in lung tissue induced by IH was suppressed by tempol as evidenced by decreased levels of TNF-α, IL-1β, and IL-6 (P<0.001) and protein levels of COX-2 and iNOS (P<0.001). Moreover, tempol inhibited oxidative stress in lung tissue by down-regulating the MDA level (P<0.001) and enhancing SOD activity (P<0.001) and the GSH level (P<0.05). In addition, tempol repressed inflammation response via inactivation of the NF-κB pathway. Furthermore, the results suggested that tempol repressed oxidative stress by activating the Nrf2/HO-1 pathway. Conclusion:Our findings suggest that tempol effectively relieves OSA-induced lung injury.

Examining the Role of Gut Dysbiosis in Neuroinflammation and Hypertension in a Model of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA), characterized by repeated closure of the upper airway during sleep, is a significant clinical problem and an independent risk factor for systemic hypertension. The importance of a healthy gut microbiota, and detriment of a dysbiotic microbiota, on host physiology is becoming increasingly evident. We have previously demonstrated that gut dysbiosis is associated with the development of hypertension in a rat model of OSA. Transplanting the dysbiotic microbiota from a hypertensive OSA rat into a normotensive rat induces hypertension, demonstrating a causal relationship between gut dysbiosis and hypertension. The mechanisms linking gut dysbiosis to hypertension are unknown. We tested the hypothesis that OSA‐induced gut dysbiosis impairs gut barrier function, causing systemic inflammation and neuroinflammation, which is linked to hypertension. Using an in vivo model of OSA, we exposed high fat fed rats to 2 weeks of sham or OSA (60 apneas/hr). Relative to sham rats, OSA led to a significant increase in TNFα mRNA expression in the cecum wall as well as decreased goblet cells/crypt in the cecum and colon (n=6, p&lt;0.05). OSA resulted in a 3‐fold increase in gut permeability (n=6, p&lt;0.05). Consistent with impaired gut barrier function and bacterial translocation, we observed increased bacterial 16S rRNA signatures in the mesenteric lymph node and visceral adipose tissue following OSA (n=4–7, p&lt;0.05). Flow cytometric analysis using whole brain revealed a significant increase in the number of activated microglia following OSA (n=4–6, p&lt;0.05). Short chain fatty acids play a key role in maintaining gut barrier integrity and regulating immune responses. We found that OSA significantly reduced the acetate concentraction in the cecum (n=5, p&lt;0.05). To increase short chain fatty acid production in the gut, rats were treated with a prebiotic (diet enriched with 20% resistant starch), or probiotic (Clostridium butyricum; 109 CFU by gavage every three days) during the 2 weeks of sham or OSA. Pre‐ and probiotics each prevented OSA‐induced decrease in cecal acetate concentration, prevented OSA‐induced loss of goblet cells, and prevented increased TNFα expression in the cecum of OSA rats (n=5–6, p&lt;0.05 for each). Additionally, pre‐ and probiotics prevented OSA‐induced activation of microglia in brain (n=6–8, p&lt;0.05). Importantly, both the pre‐ and probiotic successfully prevented the development of hypertension in OSA rats. To test the direct effects of acetate, we chronically infused 20μmol/(kg‐min) acetate into the cecum during the 2 weeks of sham or OSA. Cecal acetate infusion prevented OSA‐induced hypertension. These data demonstrate a causal role for gut dysbiosis in the development of hypertension, which involves reduced acetate production, gut barrier disruption, bacterial translocation, and neuroinflammation. Our data suggest that manipulation of the gut microbiota may serve as a novel therapy in the prevention of hypertension.Support or Funding InformationThis project was funded by NINDS R01NS080531 (RMB), AHA 16SDG29970000 (DJD), and by Public Health Service grant DK56338, which funds the Texas Medical Center Digestive Diseases Center (DJD).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Role of Gut Dysbiosis in Obstructive Sleep Apnea Induced Hypertension

Obstructive sleep apnea (OSA), characterized by repeated closure of the upper airway during sleep, is a significant clinical problem. OSA is an independent risk factor for systemic hypertension, and the most common underlying cause of resistant hypertension. The importance of a healthy gut microbiota, and detriment of a dysbiotic microbiota, on host physiology is becoming increasingly evident. We have previously observed that gut dysbiosis is associated with the development of hypertension in a rat model of OSA. Furthermore we have shown that transplantation of the dysbiotic microbiota from a hypertensive OSA rat into a normotensive rat is capable of inducing hypertension. These studies demonstrate, for the first time, a causal relationship between gut dysbiosis and hypertension. The mechanisms linking gut dysbiosis to hypertension are unknown. We tested the hypothesis that OSA‐induced gut dysbiosis leads to impaired gut barrier function, systemic inflammation, and inflammation of the brain, which is linked to hypertension. Using an in vivo model of OSA, we exposed high fat fed rats to 2 weeks of sham or OSA (60 apneas/hr). Relative to sham rats, OSA led to a significant increase in TNFα mRNA expression in the cecum wall as well as decreased goblet cells/crypt in the cecum and colon (n=4, p&lt;0.05). Consistent with impaired gut barrier function and bacterial translocation, we observed bacterial 16S rRNA signatures in the mesenteric lymph node and visceral adipose tissue, as well as elevated adipose IL‐6 mRNA expression following OSA (n=4–7, p&lt;0.05). Flow cytometric analysis revealed a significant decrease in the number of anti‐inflammatory T‐regulatory cells in the brain of OSA vs. sham rats. This was associated with an increase in the number of activated microglia following OSA (n=3, p&lt;0.05). Short chain fatty acids play a key role in maintaining gut barrier integrity and regulating immune responses. To further examine the role of gut dysbiosis in the development of OSA‐induced hypertension we treated sham and OSA rats with a prebiotic (diet enriched with 20% resistant starch) or probiotic (Clostridium butyricum; 109 CFU by gavage every three days) to increase short chain fatty acids and improve gut barrier function. Pre‐ and probiotics successfully prevented OSA‐induced loss of goblet cells and TNFα expression in the cecum and colon. Compared to vehicle treated rats, the probiotic C. butyricum prevented the OSA‐induced increase in adipose IL‐6 expression, increased total T‐regulatory cells in the brain, and decreased activated microglia (n=3–6, p&lt;0.05). Importantly, both the pre‐ and probiotic successfully prevented the development of hypertension in OSA rats. These data demonstrate a causal role for gut dysbiosis in the development of hypertension, which involves gut barrier disruption, bacterial translocation, and brain inflammation. Our data suggest that manipulation of the gut microbiota, through pre‐ or probiotics, may serve as a novel therapy in the prevention of hypertension.Support or Funding InformationNINDS R01NS080531 (RMB), PHS DK56338 and AHA 16SDG29970000 (DJD)

The impact of chronic intermittent hypoxia on hematopoiesis and the bone marrow microenvironment.

Obstructive sleep apnea (OSA) is a highly prevalent sleep-related breathing disorder which is associated with patient morbidity and an elevated risk of developing hypertension and cardiovascular diseases. There is ample evidence for the involvement of bone marrow (BM) cells in the pathophysiology of cardiovascular diseases but a connection between OSA and modulation of the BM microenvironment had not been established. Here, we studied how chronic intermittent hypoxia (CIH) affected hematopoiesis and the BM microenvironment, in a rat model of OSA. We show that CIH followed by normoxia increases the bone marrow hypoxic area, increases the number of multipotent hematopoietic progenitors (CFU assay), promotes erythropoiesis, and increases monocyte counts. In the BM microenvironment of CIH-subjected animals, the number of VE-cadherin-expressing blood vessels, particularly sinusoids, increased, accompanied by increased smooth muscle cell coverage, while vWF-positive vessels decreased. Molecularly, we investigated the expression of endothelial cell-derived genes (angiocrine factors) that could explain the cellular phenotypes. Accordingly, we observed an increase in colony-stimulating factor 1, vascular endothelium growth factor, delta-like 4, and angiopoietin-1 expression. Our data shows that CIH induces vascular remodeling in the BM microenvironment, which modulates hematopoiesis, increasing erythropoiesis, and circulating monocytes. Our study reveals for the first time the effect of CIH in hematopoiesis and suggests that hematopoietic changes may occur in OSA patients.Electronic supplementary materialThe online version of this article (doi:10.1007/s00424-016-1797-6) contains supplementary material, which is available to authorized users.