IL1B and pulmonary arterial hypertension: IL-1β, a proinflammatory cytokine known to induce a PAH-like EC phenotype, downregulated both SOX17 and Nestin and upregulated p16INK4a in PAECs (Fig. 6A and 6B, lanes 1 and 2), subsequently inducing EC senescence (Fig. 6C and 6D, columns 1 and 2).