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Obstructive sleep apnea (OSA) affects 1 billion people worldwide. Its main feature is chronic intermittent hypoxia (IH), responsible for metabolic and cardiovascular (CV) diseases. Type 2 diabetes is highly prevalent in OSA patients and is also recognized to be an independent CV risk factor. The multi-pathologic status of OSA patients partially explains why the gold standard treatment of OSA fails to decrease CV events. Here, we aim at suggest new strategies against OSA-associated comorbidities, based on studies demonstrating that IH induces oxidative stress and metabolic alterations. Photobiomodulation (PBM) is a non-invasive method recently shown to improve insulin resistance in obese mice and alter oxidative stress. We hypothesize that PBM improves insulin resistance induced by IH by preserving insulin signaling pathways and reducing oxidative stress in insulin-sensitive organs. Male C57BL/6J mice were randomized in 4 groups, submitted to either IH (14 days (D), 21–5% FiO 2 , 60s cycle, 8 h/day) or normoxia (N), and treated or not with PBM every day (630 nm, 5J/cm2, 120s). At D11, insulin sensitivity was assessed by insulin tolerance test (0.5 IU/kg, ip). At the end of exposure, liver, skeletal muscle, white adipose tissue (WAT) and heart were harvested to explore canonical insulin signaling pathway by western-blot and, oxidative stress was assessed by enzymatic activity and O 2.- content measurements. IH induces systemic insulin resistance and impairs insulin signaling in liver and WAT, characterized by a decrease in ser473P-Akt/Akt ratio, that was not observed in skeletal muscle and heart. This is associated with an increase in O 2.- content in liver and skeletal muscle without any change in enzymatic activities. PBM significantly and specifically improves systemic insulin sensitivity in IH group. Also, PBM prevents the decrease in ser473P-Akt/Akt ratio induced by IH in WAT and decreases O 2.- content in liver. Depending on the organ, IH alters canonical insulin signaling pathway (WAT and liver) and induces oxidative stress (liver and skeletal muscle); potentially explaining why IH impairs systemic insulin sensitivity. Interestingly, PBM significantly improves systemic insulin sensitivity in IH condition and this could be explained by an abolition of IH-induced insulin signaling pathway alteration in WAT, and oxidative stress in liver. Thus, by increasing insulin sensitivity, PBM could improve metabolic and subsequent CV outcomes in apneic patients. [ABSTRACT FROM AUTHOR]

Patients with obstructive sleep apnea (OSA) exhibit poor prognosis after myocardial infarction (MI). Intermittent hypoxia (IH), the hallmark feature of OSA, promotes sympathetic hyperactivity and systemic insulin resistance, and has been identified as a major contributor to post-MI cardiac remodeling and contractile dysfunction. We hypothesize that sympathetic hyperactivity and metabolic alterations induced by IH participate in the aggravation of ischemic cardiomyopathy via activation of G protein-coupled receptors kinase (GRK2), known to be involved in adrenergic desensitization. To investigate the detrimental role of GRK2, we used paroxetine, described as a specific GRK2 inhibitor. MI is induced in C57bl6 mice by permanent ligation of the left coronary artery. Mice are then randomized to IH (21–5% FiO2, 60 s cycle, 8 h/day) or normoxia (N) for up to 6 weeks. After two weeks exposure, mice are treated with a GRK2 inhibitor, paroxetine (5 mg/kg/d), or 25% DMSO (Alzet® pumps). Longitudinal follow-up of mice includes evaluation of sympathetic activity [spectral analysis of heart rate variability (HRV)], systemic insulin sensitivity (dynamic insulin tolerance test) and determination of cardiac function/remodeling (echocardiography). At the end of the protocol, cardiac interstitial fibrosis and hypertrophy are evaluated by RT-qPCR and histology (Sirius Red and WGA staining, respectively). Assessment of insulin signaling pathway is performed by Western blot 15 minutes after injection of NaCl or insulin (0.5 UI/kg). Compared to N condition, IH worsens post-MI contractile dysfunction (i.e. ejection fraction), which is prevented by paroxetine treatment. Whereas IH does not induce cardiomyocyte hypertrophy, it results in increased cardiac interstitial fibrosis, which is limited by paroxetine treatment. In terms of mechanisms, our results evidence an IH-induced sympathetic overactivity in MI mice, characterized by an alteration of the sympathovagal balance (i.e. increase in LF). GRK2 inhibition by paroxetine abolishes the increase in LF in MI-IH condition and restores mRNA expression of β1 and β2 adrenergic receptors. Finally, IH induces post-MI systemic insulin resistance compared to MI-N condition, which is prevented by paroxetine. This beneficial effect of paroxetine on insulin sensitivity could result from an improvement of insulin signaling in the liver and in the muscle of MI-IH mice (pIRβ and pAKT). Inhibition of GRK2 by paroxetine limits the IH-induced worsening of ischemic cardiomyopathy, by limiting both cardiac sympathetic hyperactivity and systemic insulin resistance. [ABSTRACT FROM AUTHOR]

Cardiovascular complications of obstructive sleep apnea syndrome (OSA), such as atherosclerosis, are a real public health concern. They result from endothelial dysfunction induced by intermittent hypoxia (IH). VE-cadherin (VE-cad) undergoes IH-induced cleavage leading to be a biomarker of endothelial dysfunction in several pathologies (sVE). Our hypothesis is that, in OSA, VE-cad cleavage would contribute to the onset of endothelial permeability, resulting in endothelial dysfunction and atherosclerosis. Our aim is to characterize the signalling pathway and proteases that perform VE-cad cleavage in a cellular model of IH and determine if blocking VE-cad cleavage in vitro and in vivo could inhibit IH-induced atherogenesis. Human Aortic Endothelial Cells (HAEC) monolayers were exposed to 6 h IH and treated with tyr-kinase inhibitors (Saracatinib, Pazopanib), HIF-1 inhibitor (Acriflavine) and protease's inhibitors. Candidate proteases (MMP2, PCSK9 and ADAM10) were identified by performing a human protease array in OSA patient's sera. Endothelial permeability was assessed by measuring FITC-Dextran permeability and monocyte passage. VE-cad cleavage was studied by measuring sVE in cells' supernatants. Vascular remodeling and VE-cad regulation were studied in C57BL/6 mice (2 weeks IH), atherosclerotic plaques and arterial pressure were studied in ApoE-/- mice (8 weeks IH), both treated with tyr-kinase and HIF-1 inhibitors. In our IH cellular model, VE-cad cleavage and endothelial permeability increased. These effects were reversed by the HIF-1 and tyr-kinase inhibitors and the proteases' inhibitors. In vivo, IH increased aorta intima-media thickness and sVE serum level, and decreased VE-cad expression in the endothelium of mice. In ApoE-/- mice, IH increased atherosclerotic plaques formation. These effects were blocked by inhibitors of VE-cad cleavage signaling pathway (Fig. 1). We suggest that IH increases endothelial permeability by inducing VE-cad cleavage via the HIF-1 and tyr-kinase pathways, and possibly involving MMP2, PCSK9 and/or ADAM10 proteases. Blocking VE-cad cleavage prevents vascular remodeling and atherosclerotic plaques formation which suggests that VE-cad could be a potential target to a new anti-atherogenesis strategy. [ABSTRACT FROM AUTHOR]

Patients with obstructive sleep apnea (OSA) exhibit poor prognosis after myocardial infarction (MI). Intermittent hypoxia (IH), the hallmark feature of OSA, promotes sympathetic hyperactivity and systemic insulin resistance, and has been identified as a major contributor to post-MI cardiac remodeling and contractile dysfunction. We hypothesize that sympathetic hyperactivity and metabolic alterations induced by IH promote desensitization of cardiac adrenergic and insulin pathways via activation of G protein-coupled receptors (GRK2), and subsequently participate in the aggravation of ischemic cardiomyopathy. MI is induced in C57bl6 mice by permanent ligation of the left coronary artery (MI). Mice are then randomized to IH (21–5% FiO2, 60 s cycle, 8 h/day) or normoxia for up to 6 weeks. After two weeks, mice are treated with a GRK2 inhibitor, Paroxetine (5 mg/kg/d), or 25% DMSO (Alzet® pumps). Longitudinal follow-up of mice includes evaluation of sympathetic activity (spectral analysis of heart rate variability (HRV), systemic insulin sensitivity (dynamic insulin tolerance test) and determination of cardiac function/remodeling (echocardiography). At the end of the protocol, cardiac interstitial fibrosis and hypertrophy are evaluated by RT-qPCR and histology (Sirius Red and WGA staining, respectively). Assessment of insulin signaling pathway is performed by Western blot. IH induces sympathetic hyperactivity in MI mice, demonstrated by a modification of the sympathovagal balance (LF increase). Paroxetine treatment abolishes the increase in LF in MI-IH condition and restores mRNA expression of β1 and β2 adrenergic receptors. MI-IH induces systemic insulin resistance compared to MI-N condition, which is prevented by Paroxetine treatment. In addition, Paroxetine treatment improves insulin signaling in the liver of MI-IH mice (pIRβ and pAKT). IH exacerbates cardiac interstitial fibrosis and worsens contractile dysfunction in MI mice, resulting in a significant decrease in ejection fraction (19.4 ± 2.1% vs. 29.9 ± 3.6% in IH vs. N respectively, P < 0.05). The effect of paroxetine on cardiac remodeling and function is currently being analyzed. These findings demonstrate that IH induces cardiac sympathetic hyperactivity and insulin resistance, which could contribute to the worsening of ischemic heart disease via GRK2. [ABSTRACT FROM AUTHOR]

Patients with obstructive sleep apnea (OSA) exhibit poor prognosis after myocardial infarction (MI). Intermittent hypoxia (IH), the hallmark feature of OSA, promotes sympathetic hyperactivity, hyperinsulinemia and insulin resistance, and has been identified as a major contributor to post-MI cardiac remodeling and contractile dysfunction. We hypothesize that IH-induced sympathetic activation and insulin resistance lead to desensitization of cardiac adrenergic and insulin signaling pathways, which contribute to the progression of ischemic cardiomyopathy. MI is induced in C57bl6 mice by permanent ligation of the left coronary artery. Mice were then randomized to IH (21–5% FiO 2 , 60 s cycle, 8 h/day) or normoxia for up to 6 weeks. Longitudinal follow-up of mice includes evaluation of systemic insulin sensitivity (dynamic insulin tolerance test), cardiac sympathetic activity, spectral analysis of heart rate variability (HRV) and determination of cardiac function/remodeling (echocardiography). Following the completion of IH protocol, cardiac interstitial fibrosis and hypertrophy are evaluated by RT-qPCR and histology (Sirius Red and WGA staining, respectively). Assessment of adrenergic and insulin signaling pathways and there cross-talk are performed by Western blot (WB). IH worsens MI-induced cardiac contractile dysfunction in mice, resulting in a significant decrease in ejection fraction (19.4 ± 2.1% vs. 33.3 ± 3.9% in IH vs. N respectively, P < 0.05). MI causes significant cardiac remodeling in both N and IH groups, characterized by upregulation of several markers of cardiac fibrosis (Col1a1, Col3a1) and hypertrophy (Acta1, MyH7), which tend to be higher in IH compared to N. In our MI model, IH does not induce significant systemic insulin resistance and tends to increase LF power with no significant modification of LF/HF ratio compared to N mice. Histological experiments will be performed to confirm IH-induced aggravation of post-MI cardiac remodeling and ongoing WB will determine whether IH specifically affects cardiac insulin and adrenergic signaling. These findings demonstrate that IH is responsible for aggravation of contractile function in our ischemic cardiomyopathy mice model. Ongoing experiments will determine whether alteration of adrenergic and insulin signalling are involved as contributing mechanisms. [ABSTRACT FROM AUTHOR]

Sleep apnea syndrome is characterized by intermittent hypoxia (IH), leading to an increase in blood pressure (BP) and infarct size. Independently, IH has been demonstrated to alter arginine (Arg) metabolism. As Arg availability directly impacts nitric oxide production, we speculate that plasmatic Arg deficiency during IH may contribute to cardiovascular alterations induced by IH. Knowing that citrulline (Cit) is a better precursor of Arg than Arg itself, we propose to assess the impact of chronic Cit supplementation on IH-induced an increase in BP and infarct size. Four groups of rats (n = 11–14), were submitted to normoxia (N) or IH [14 days (d), 8 h per d, 30 s-O2 21%/30 s-O2 5%] and supplemented or not with Cit (1 g.kg−1.d−1). After 14 d, BP was measured by carotid catheterization; hearts were perfused by the Langendorff method and submitted to global and total ischemia (30 min)-reperfusion (120 min) before measuring infarct size related to left ventricle area (I/V) by colorimetry and planimetry. Another set of rats was added (n = 5–6) in order to collect the heart and aorta for histological and biochemical analyses. IH increases systolic BP (144.5 ± 3.5 vs. 165.1 ± 4.2 mmHg in N and IH respectively, n = 11–14, P < 0.01) and I/V (33.7 ± 4.4 vs. 46 ± 2.5% in N and IH, respectively, n = 10–12, P < 0.05). Cit abolishes IH-induced increase in both systolic BP (139.8 ± 4. vs. 155.6 ± 6.6 mmHg NCit and IHCit, respectively) and I/V (35.7 ± 3.3 vs. 38.2 ± 2.1% in NCit and IHCit). Preliminary western blot results show that IH decreases T495P-eNOS in heart whereas it did not affect S1177P-eNOS. Interestingly, Cit supplementation seems to decrease even more the T495P-eNOS in the IHCit group compared to IH and NCit groups. Cit supplementation abolishes the deleterious effects of IH in terms of BP and infarct size. This suggests that citrulline could be a complementary or alternative treatment to the current sleep apnea standard treatment that is not fully efficient. However, biochemical and histological studies (NOx, oxidative stress, S-nitrosylation...) are ongoing to enlighten the specific mechanisms involved in cardiovascular protection induced by citrulline chronic supplementation during IH. [ABSTRACT FROM AUTHOR]

Introduction Obstructive sleep apnea (OSA) is characterized by repetitive pharyngeal collapses during sleep leading to intermittent hypoxia (IH), the main contributor of OSA-related cardiovascular morbidity. OSA patients exhibit increased intima-media thickness (IMT) that correlates with circulating inflammatory markers and severity of nocturnal oxygen desaturation. In mice models, IH also induces hemodynamic alterations and cardiovascular inflammatory remodeling. The non-muscle myosin light chain kinase (nmMLCK) isoform contributes to endothelial cell-cell junction opening, monocyte migration and thus participates to inflammation. nmMLCK deficiency or inhibition has been reported to attenuate systemic, lung and atherosclerotic inflammation. Objective The aim of the present study was to investigate the role of nmMLCK in the IH-induced inflammatory vascular remodeling. We assess vascular remodeling/inflammation in different vascular beds (aorta, carotid and mesenteric arteries). Methods and results 12 week-old C57bl6 or nmMLCK knockout mice were exposed to 14-days IH or normoxia. IH was associated with an elevation of mean arterial pressure, which was prevented by the nmMLCK deletion. We demonstrated that IH induced an inflammatory response in the three vascular beds, characterized by an increased mRNA expression of CD45 and IFNγ, an increased expression of the macrophage marker F4/80 and an increased expression and activity of NFkB. Interestingly nmMLCK deletion prevented the IH-induced vascular inflammatory responses. On-going experiments are characterizing the effect of nmMLCK deletion on IH-induced structural vascular remodeling. Conclusions These results strongly suggest that nmMLCK participates to IH-induced vascular inflammatory remodeling and might represent an attractive target to fight against the occurrence of inflammation and the vascular outcomes of OSA. The author hereby declares no conflict of interest [ABSTRACT FROM AUTHOR]