MMP9 and pulmonary arterial hypertension: In a related baicalin study, the results in rats with chronic hypoxia pretreated with baicalin (30 mg/kg) showed inhibition of p38 MAPK and a downregulation of matrix metalloproteinase 9 (MMP-9) expression in pulmonary arterioles, thus alleviating PAH and pulmonary heart disease (right-side cardiac dysfunction) [97].