S-Adenosylmethionine suppresses the expression of Smad3/4 in activated human hepatic stellate cells via Rac1 promoter methylation

The aim of the present study was to investigate whether S-adenosylmethionine (SAM) was able to suppress activated human hepatic stellate cells (HSCs). Human LX-2 HSCs were cultured with SAM or NSC23766, and were transfected with plasmids encoding ras-related C3 botulinum toxin substrate 1 (Rac1) protein or an empty expression vector. Cell proliferation was detected by Cell Counting Kit-8. Cell migration and invasion were determined using the Transwell assay. The expression levels of Rac1 and Smad3/4 were detected by reverse transcription‑quantitative polymerase chain reaction (PCR) or western blotting. The methylation status of Rac1 promoters was measured by methylation‑specific PCR. The results demonstrated that SAM and NSC23766 suppressed the expression of Smad3/4 in LX‑2 cells. The overexpression of Rac1 enhanced the proliferation, migration and invasion of LX‑2 cells. In addition, compared with the control groups, a marked increase was observed in the protein expression levels of Smad3/4 in the LX‑2 cells transfected with Rac1 plasmids. The methylation-specific PCR findings showed that SAM increased the methylation of Rac1 promoters. The results of the present study suggested that Rac1 enhanced the expression of Smad3/4 in activated HSCs; however, this increase may be suppressed by SAM-induced methylation of Rac1 promoters.