Intermittent hypoxia inhibits epinephrine-induced transcriptional changes in human aortic endothelial cells

Clinical significance of elevated soluble T-cell immunoglobulin and mucin domain 1 and soluble P-selectin in individuals with obstructive sleep apnea-hypopnea syndrome

OBJECTIVES

To assess the serum concentrations of soluble T-cell immunoglobulin and mucin domain 1 (sTIM-1) and soluble P-selectin (sP-selectin) in individuals who had obstructive sleep apnea-hypopnea syndrome (OSAHS).

METHODS

Between December 2020 and November 2022, 134 participants from the Sleep Monitoring Center of the Branch Hospital of Huai'an First People's Hospital, Jiangsu, China, engaged in this cross-sectional study. Participants were categorized as mild OSAHS (n=19), moderate OSAHS (n=22), severe OSAHS (n=57), and non-OSAHS (n=36) groups. Serum levels of sTIM-1, sP-selectin, and interleukin (IL)-6, as well as baseline clinical characteristics and polysomnography outcomes were assessed in each participant.

RESULTS

Compared to the non-OSAHS group, sTIM-1 and sP-selectin levels were considerably elevated in people who had moderate or severe OSAHS (all p<0.05), but there were no notable changes between those who had mild OSAHS and non-OSAHS participants (p>0.05). The sTIM-1 and sP-selectin levels showed positive associations with the apnea-hypopnea index, body mass index (BMI), and IL-6 levels (all p<0.001). While elevated sTIM-1 was independently related to OSAHS (odds ratio [OR]=1.134, p=0.001), sP-selectin was not associated with OSAHS after adjusting for BMI (OR=1.013, p=0.467).

CONCLUSION

People with moderate or severe OSAHS had higher serum sTIM-1 and sP-selectin levels, and elevated sTIM-1 is an independently related factor for OSAHS.

Loss of heme oxygenase 2 causes reduced expression of genes in cardiac muscle development and contractility and leads to cardiomyopathy in mice

Obstructive sleep apnea (OSA) is a common breathing disorder that affects a significant portion of the adult population. In addition to causing excessive daytime sleepiness and neurocognitive effects, OSA is an independent risk factor for cardiovascular disease; however, the underlying mechanisms are not completely understood. Using exposure to intermittent hypoxia (IH) to mimic OSA, we have recently reported that mice exposed to IH exhibit endothelial cell (EC) activation, which is an early process preceding the development of cardiovascular disease. Although widely used, IH models have several limitations such as the severity of hypoxia, which does not occur in most patients with OSA. Recent studies reported that mice with deletion of hemeoxygenase 2 (Hmox2-/-), which plays a key role in oxygen sensing in the carotid body, exhibit spontaneous apneas during sleep and elevated levels of catecholamines. Here, using RNA-sequencing we investigated the transcriptomic changes in aortic ECs and heart tissue to understand the changes that occur in Hmox2-/- mice. In addition, we evaluated cardiac structure, function, and electrical properties by using echocardiogram and electrocardiogram in these mice. We found that Hmox2-/- mice exhibited aortic EC activation. Transcriptomic analysis in aortic ECs showed differentially expressed genes enriched in blood coagulation, cell adhesion, cellular respiration and cardiac muscle development and contraction. Similarly, transcriptomic analysis in heart tissue showed a differentially expressed gene set enriched in mitochondrial translation, oxidative phosphorylation and cardiac muscle development. Analysis of transcriptomic data from aortic ECs and heart tissue showed loss of Hmox2 gene might have common cellular network footprints on aortic endothelial cells and heart tissue. Echocardiographic evaluation showed that Hmox2-/- mice develop progressive dilated cardiomyopathy and conduction abnormalities compared to Hmox2+/+ mice. In conclusion, we found that Hmox2-/- mice, which spontaneously develop apneas exhibit EC activation and transcriptomic and functional changes consistent with heart failure.

Sex Differences in Neurovascular Control: Implications for Obstructive Sleep Apnea

Patients with obstructive sleep apnea (OSA) have a heightened risk of developing cardiovascular diseases, namely hypertension. While seminal evidence indicates a causal role for sympathetic nerve activity in the hypertensive phenotype commonly observed in patients with OSA, no studies have investigated potential sex differences in the sympathetic regulation of blood pressure in this population. Supporting this exploration are large-scale observational data, as well as controlled interventional studies in healthy adults, indicating that sleep disruption increases blood pressure to a greater extent in females relative to males. Furthermore, females with severe OSA demonstrate a more pronounced hypoxic burden (i.e., disease severity) during rapid eye movement sleep when sympathetic nerve activity is greatest. These findings would suggest that females are at greater risk for the hemodynamic consequences of OSA and related sleep disruption. Accordingly, the purpose of this review is three-fold: (1) to review the literature linking sympathetic nerve activity to hypertension in OSA, (2) to highlight recent experimental data supporting the hypothesis of sex differences in the regulation of sympathetic nerve activity in OSA, and (3) to discuss the potential sex differences in peripheral adrenergic signaling that may contribute to, or offset, cardiovascular risk in patients with OSA.