Isoliquiritigenin protects against angiotensin II-induced fibrogenesis by inhibiting NF-κB/PPARγ inflammatory pathway in human Tenon's capsule fibroblasts

Purpose: To examine the protective effects of Isoliquiritigenin (ISL) in angiotensin II (ANG II)-induced inflammation and fibrosis on Human Tenon's capsule Fibroblasts (HTFs) and Mouse Peritoneal Macrophages (MPMs). This study also investigated the potential mechanism of action of ISL.

Method: Methyl-thiazolyl tetrazolium (MTT) assay was used to test ISL toxicity. An ELISA and an RT-qPCR assay detected the inflammatory cytokines (TNF-α, IL-6, COX-2, and ICAM-1). A Western blot investigated the expression levels of inflammation-related signals [nuclear factor-κB (NF-κB), peroxisome proliferator-activated receptor γ (PPARγ)], and fibrogenesis, including fibronectin and alpha-smooth muscle actin (α-SMA)]. Protein expressions of α-SMA were measured by immunofluorescence.

Results: Pre-treatment with ISL (10 or 20 μM) dose-dependently decreased the mRNA levels of TNF-α, IL-6, ICAM-1, and COX-2 induced by ANG II (1 μg/ml) in both MPMs and HTFs. ANG II remarkably increased the amount of P65 in the nuclei and decreased the amount of P65 in the cytoplasm. Additionally, ANG II reduced PPARγ expression levels in a time-dependent manner. Furthermore, these effects which were induced by ISL were remarkably neutralized by ISL pre-treatment. Finally, ANG II markedly elevated the expression of fibronectin and α-SMA.

Conclusion: ISL could alleviate ANG II-induced fibrogenesis by inhibiting the NF-κB/PPARγ inflammatory pathway. In addition, ISL may be a potential agent for the treatment of conjunctival fibrosis. Most importantly, the NF-κB/PPARγ signaling pathway could be an effective therapeutic target for the prevention and treatment of conjunctival fibrosis after glaucoma surgery.

Keywords: Angiotensin II; Fibrogenesis; Inflammatory response; Isoliquiritigenin; Tenon's capsule fibroblasts.