Melatonin Attenuates Pulmonary Hypertension in Chronically Hypoxic Rats

Area of Science:

• Pulmonary Medicine
• Cardiovascular Research
• Pharmacology

Background:

• Chronic hypoxia causes pulmonary hypertension and vascular remodeling, relevant to COPD.
• Nitric oxide (NO) deficiency, oxidative stress, and inflammation are key in COPD pathophysiology.
• Melatonin's potential therapeutic role in mitigating these effects requires investigation.

Purpose of the Study:

• To investigate if daily melatonin administration mitigates pulmonary hypertension and vascular remodeling in chronically hypoxic rats.
• To assess melatonin's impact on oxidative stress, inflammation, and nitric oxide synthase (NOS) pathways in the lungs.
• To determine if melatonin can restore endothelial NO synthase (eNOS) phosphorylation.

Main Methods:

• Rats were exposed to chronic hypoxia (10% O₂ for 14 days) and treated with vehicle or melatonin (10 mg/kg).
• Measurements included right ventricular systolic pressure (RVSP), pulmonary arteriolar wall thickness, and markers of oxidative stress (malondialdehyde) and inflammation (TNFα, iNOS, COX-2).
• Lung tissue analysis included eNOS and phosphorylated eNOS (ser1177) expression.

Main Results:

• Hypoxic rats showed increased RVSP, arteriolar wall thickness, oxidative stress, and inflammation markers compared to controls.
• eNOS phosphorylation at ser1177 was decreased in hypoxic rats, despite increased total eNOS expression.
• Melatonin treatment significantly reduced RVSP, arteriolar wall thickness, oxidative stress, and inflammation markers.
• Melatonin markedly increased eNOS phosphorylation in the lungs of hypoxic rats.

Conclusions:

• Melatonin attenuates pulmonary hypertension and vascular remodeling induced by chronic hypoxia.
• Melatonin mitigates oxidative stress and inflammation in the hypoxic lung.
• Melatonin restores NO production by enhancing eNOS phosphorylation, suggesting a therapeutic potential for COPD-related pulmonary hypertension.