Abstract 13972: Dexmedetomidine Ameliorates Monocrotaline Induced Pulmonary Arterial Hypertension in Rats

Abstract

[Introduction] Pulmonary arterial hypertension (PAH) is characterized by increased proliferation and apoptosis resistance of pulmonary arterial smooth muscle cells (PASMCs). Dexmedetomidine (DEX) is a selective α2-aderenergic receptor agonist that is used for sedation in clinical practice. It has been reported that DEX inhibits inflammatory responses through cytokines, such as TNF-alpha, IL-6. Furthermore other reports show that G-protein-coupled receptors (GPCRs) are regulated by β-arrestins, which are also involved with inflammation. [Hypothesis] DEX ameliorates monocrotaline (MCT)-induced PAH in rats by its anti-inflammatory effect. [Methods] We treated 6 weeks-old male Sprague-Dawley rats with a single 60mg/kg intraperitoneal injection of MCT. After 14 days of injection, one group of rats was started to administer dexmedetomidine (dose: 2μg/kg/hour, MCT+DEX group) continuously using osmotic pumps, the other group was not treated with DEX (MCT group). We performed physiological examination and cardiac catheterization to measure right ventricular systolic pressure (RVSP) at day 23. [Results] Both RVSP and survival rate of rats in MCT+DEX group markedly improved compared with those in MCT group (RVSP; 38mmHg±11mmHg vs 91mmHg±6mmHg, survival rate; 42% vs 0% at day 30). In histological analysis, DEX reduced the medial hypertrophy of pulmonary arterioles, and decreased phosphorylated-NF-kB p65 (p-p65) positive PASMCs in MCT+DEX group compared with those of MCT group. In addition, DEX suppressed PASMCs proliferation with PCNA staining, and induced apoptosis of PASMCs with TUNEL assay. Then we examined the involvement of β-arrestins in PAH. It showed that βarrestin1 expressions reduced in MCT group compared with that of MCT+DEX group with western blotting and immunohistochemistry. However β-arrestin2 expressions had no significant difference between the two groups. [Conclusions] DEX ameliorates MCT-induced PAH in rats, one of the mechanism of which may be NF-kB inhibition through β-arrestin1. DEX can be a new therapeutic tool for PAH.