HMGB1 and pulmonary arterial hypertension: In this study, osthole was visualized to have the capability to restore the expression of Cathepsin S, HMGB1 and Histone H3.3 with PAH progression, thus this compound was able to treat PAH by partially improving the inflammatory process, which was characterized by down regulation of Cathepsin S and up-regulation of Histone H3.3 and HMGB1 in PAH progression.