# Tanshinone IIA alleviates liver fibrosis by suppressing hepatic stellate cell proliferation via ERK/cyclin D1/p-Smad3L signaling axis

## TL;DR

Tanshinone IIA reduces liver fibrosis by blocking the proliferation of liver cells through a specific signaling pathway.

## Contribution

The study identifies a novel mechanism involving ERK/cyclin D1/p-Smad3L signaling in the antifibrotic effect of Tanshinone IIA.

## Key findings

- Tanshinone IIA reduced liver damage markers and collagen in both cell and animal models.
- It inhibited cell proliferation by blocking the G1 phase of the cell cycle in hepatic stellate cells.
- The compound suppressed key proteins in the ERK/cyclin D1/p-Smad3L signaling pathway.

## Abstract

Liver fibrosis (LF) is a critical stage in chronic liver disease progression, and effective therapeutic drugs are currently lacking. Tanshinone IIA (Tan IIA), a monomer extracted from Salvia miltiorrhiza, shows potential in treating LF. This research aims to discuss the antifibrotic efficacy and underlying pharmacological mechanism of Tan IIA.

The in vivo model was induced with CCl4 to form a LF model in mice, and the in vitro model was induced by TGF-β1 in LX-2 and HSC-T6 cells. Liver pathology was characterized by HE, Masson, and Sirius red staining, and serum levels of ALT, AST, LDH, and γ-GT were examined. Cell viability and proliferation were detected by Cell Counting Kit-8 and colony formation assays. Cell cycle distribution was detected by flow cytometry. The protein levels of p-ERK, cyclin D1, CDK4, and p-Smad3L were assessed through Western blot, immunohistochemistry, or immunofluorescence assays.

Tan IIA markedly decreased serum levels of ALT, AST, LDH, and γ-GT. Collagen I and α-SMA were reduced, as shown by in vitro and in vivo models. Moreover, while arresting HSCs in the G1 phase was increased, Tan II A markedly inhibited cell viability and colony formation. Mechanistically, Tan IIA decreased the expression of p-ERK, cyclin D1, CDK4, and p-Smad3L proteins in TGF-β1-activated cells and CCl4-induced mice.

Tan IIA may improve LF by regulating the signaling axis of ERK/cyclin D1/p-Smad3L, thereby blocking activated HSCs in the G1 phase and inhibiting their proliferation.