Abstract 19795: S-glutathionylation of eNOS occurs in Clinical Obstructive Sleep Apnea (OSA)

Abstract

Obstructive sleep Apnea (OSA) is a risk factor for cardiovascular disease and causes vascular endothelial dysfunction (VED); however, the basis of this VED is unknown. Increased oxidant production is observed in the endothelium of OSA patients. We have recently demonstrated that under oxidant stress eNOS uncoupling is triggered by S-glutathionylation of specific cysteines including C689 of the reductase domain. Since OSA is associated with oxidant stress, we hypothesized that S-glutathionylation of eNOS may occur in OSA and trigger eNOS uncoupling. Methods: 13 patients with recently diagnosed OSA and 10 healthy individuals with low cardiovascular risk were studied. OSA patients underwent subcutaneous forearm biopsy and Doppler measurements of endothelial function by flow mediated dilation (FMD) prior to, and 12 weeks after initiation of treatment. Non-OSA control patients also provided FMD measurements and biopsies. eNOS S-glutathionylation was studied using specific anti-eNOS C689 S-glutathionylation antibody. Superoxide ·( O 2 _ ) levels in the microcirculation were determined using fluorescent probe DHE in the absence or presence of the SOD mimetic, MnTBAP. Results: OSA patients had impaired FMD, compared to non-OSA controls, which decreased after 12 weeks of treatment with CPAP. Immunohistochemical analysis of frozen sections from OSA patients using anti-eNOS C689 glutathionylation antibody revealed that prominent eNOS S-glutathionylation was present in the endothelium of OSA patients that was abolished by treatment with the reducing agent DTT, and was attenuated following CPAP treatment and absent in healthy control subjects. In association with these findings, · O 2 _ production from the endothelium was also decreased with CPAP treatment in OSA patients. Conclusions: These findings demonstrate that eNOS S-glutathionylation occurs in OSA and is associated with endothelial dysfunction with increased superoxide and decreased NO availability.