Interaction of the hydrogen sulfide system with the oxytocin system in the injured mouse heart.

BACKGROUND: Both the hydrogen sulfide/cystathionine-γ-lyase (H2 S/CSE) and oxytocin/oxytocin receptor (OT/OTR) systems have been reported to be cardioprotective. H2 S can stimulate OT release, thereby affecting blood volume and pressure regulation. Systemic hyper-inflammation after blunt chest trauma is enhanced in cigarette smoke (CS)-exposed CSE-/- mice compared to wildtype (WT). CS increases myometrial OTR expression, but to this point, no data are available on the effects CS exposure on the cardiac OT/OTR system. Since a contusion of the thorax (Txt) can cause myocardial injury, the aim of this post hoc study was to investigate the effects of CSE-/- and exogenous administration of GYY4137 (a slow release H2 S releasing compound) on OTR expression in the heart, after acute on chronic disease, of CS exposed mice undergoing Txt.

METHODS: This study is a post hoc analysis of material obtained in wild type (WT) homozygous CSE-/- mice after 2-3 weeks of CS exposure and subsequent anesthesia, blast wave-induced TxT, and surgical instrumentation for mechanical ventilation (MV) and hemodynamic monitoring. CSE-/- animals received a 50 μg/g GYY4137-bolus after TxT. After 4h of MV, animals were exsanguinated and organs were harvested. The heart was cut transversally, formalin-fixed, and paraffin-embedded. Immunohistochemistry for OTR, arginine-vasopressin-receptor (AVPR), and vascular endothelial growth factor (VEGF) was performed with naïve animals as native controls.

RESULTS: CSE-/- was associated with hypertension and lower blood glucose levels, partially and significantly restored by GYY4137 treatment, respectively. Myocardial OTR expression was reduced upon injury, and this was aggravated in CSE-/- . Exogenous H2 S administration restored myocardial protein expression to WT levels.

CONCLUSIONS: This study suggests that cardiac CSE regulates cardiac OTR expression, and this effect might play a role in the regulation of cardiovascular function.