Abstract: Iso-suillin, a phenolic compound isolated from Suillus flavus, has significant anti-tumor activity. However, the role of iso-suillin in cardiovascular system remains unclear. Herein, primary vascular smooth muscle cells (VSMCs) were pretreated with iso-suillin for 24 or 48 h, and then stimulated by platelet-derived growth factor (PDGF)-BB. The cell proliferation was evaluated by cell counting. VSMC cell cycle distribution was analyzed by flow cytometry. In addition, Western blot was used to examine protein expression, and immuneprecipitation analysis was used to identify the phosphorylation and ubiquitination of smooth muscle 22 alpha (SM22α). The results showed that iso-suillin inhibited PDGF-BB-induced VSMC proliferation. Iso-suillin increased the expression of SM22α (a marker of cell differentiation), and reduced the level of PCNA. Furthermore, iso-suillin decreased the levels of phosphorylated and ubiquitinated SM22α upon PDGF-BB treatment, which may be associated with iso-suillin-decreased protein kinase C (PKC) δ activity. Collectively, these data demonstrated that iso-suillin prevented VSMC phenotype transformation through decreasing PKCδ-mediated SM22α degradation via the ubiquitin-proteasome pathway in VSMCs.

Key words: iso-suillin, vascular smooth muscle cells, phenotypic modulation, smooth muscle 22&alpha, (SM22α)