Comparative analysis of melatonin and sildenafil in a rat model of pulmonary arterial hypertension: Insights into oxidative stress, inflammation, and mitochondrial biogenesis.

Pulmonary artery hypertension (PAH) is characterized by increased pulmonary vascular resistance, leading to the augmented afterload of the right ventricle (RV), hypertrophy, and heart failure. Oxidative stress and inflammation in the RV may be involved in the physiopathology of PAH. Because of their antioxidant properties, melatonin and sildenafil could be possible therapeutic agents for the treatment of PAH. Therefore, the present study evaluated the protective effects of melatonin against oxidative stress, inflammation, and mitochondrial biogenesis in the RV of rats with PAH. Wistar rats were divided into four groups: control (CTR), monocrotaline (MCT), monocrotaline treated with sildenafil (MCT + SIL), and monocrotaline treated with melatonin (MCT + MEL). PAH was induced using a single dose of MCT (60 mg/kg, i. p.). Sildenafil citrate (50 mg/kg/day) and melatonin (10 mg/kg/day) were then administered by gavage, beginning on the first day of the experimental protocol. On the day 21, echocardiographic, morphometric, oxidative/nitrosative stress and Western blotting analyses were performed. Animals that received melatonin or sildenafil demonstrated an increased tricuspid annular plane systolic excursion (TAPSE) when compared with non-treated animals, indicating an improvement in RV contractility. Both melatonin and sildenafil treatment decreased lipid peroxidation (LPO) and reestablished sulfhydryl levels. Melatonin administration decreased the protein expression level of nuclear factor kappa beta (NF-κB), while sildenafil decreased xanthine oxidase expression. Both treatments increased peroxisome proliferator activated receptor gamma co-activator 1 alpha (PGC-1α) expression. Based on our findings, melatonin showed a protective effect similar to sildenafil in the RV of a rats model of PAH.