18β-Glycyrrhetinic Acid Ameliorates Endoplasmic Reticulum Stress-Induced Inflammation in Pulmonary Arterial Hypertension Through PERK/eIF2α/NF-κB Signaling

Endoplasmic reticulum stress (ERS)-induced inflammation participates in the occurrence of pulmonary arterial hypertension (PAH) by promoting pulmonary vascular remodeling, which involved in the activation of PERK/eIF2α/NF-κB signaling pathway. 18β-Glycyrrhetinic acid (18β-GA) has been found efficacious for attenuating PAH through its anti-remodeling effects in our previous research and it remains unclear whether 18β-GA has an effect on the remodeling caused by ERS-induced inflammation. In this study, we made observations in monocrotaline-induced PAH rats and found improvement of hemodynamic and histopathological parameters, decreases in the right ventricular hypertrophy index, and alleviation of pulmonary vascular remodeling after 18β-GA administration in vivo . Moreover, 18β-GA could significantly inhibit the proliferation and DNA synthesis of human pulmonary arterial smooth muscle cells (HPASMCs) induced by platelet-derived growth factor BB. At the cellular and molecular levels, we found that 18β-GA could significantly reduce the accumulation of misfolded protein in rat lung tissue, inhibit ERS activation, reduce the expression of GRP78, p-PERK, p-eIF2α, and p-NF-κB p65, and increase IκB protein expression. 18β-GA could inhibit the migration of NF-κB into the nucleus, reduce the contents of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and monocyte chemoattractant protein-1 (MCP-1) in the culture supernatant of HPASMCs, and reduce GRP78, p-PERK, p-eIF2α, p-NF-κB p65, TNF-α, IL-6, and MCP-1 protein expression, increase IκB protein expression in HPASMCs. According to what we observed, this study indicated that 18β-GA could treat PAH, which is related to the inhibition of PERK/eIF2α/NF-κB signaling pathway.