中文摘要：

从黄乳粘盖牛肝菌（Suillus flavus）中分离得到的异牛肝菌素（iso-suillin）具有显著的抗肿瘤活性，但其在心血管系统的功效尚不明确。本研究用不同浓度的异牛肝菌素预处理原代血管平滑肌细胞（vascular smooth muscle cell，VSMC）24h或48h后，再采用血小板源性生长因子（platelet-derived growth factor，PDGF）-BB处理细胞，细胞计数法检测VSMC增殖活性；流式细胞术检测细胞周期分布；Western blot分析检测蛋白表达情况；免疫沉淀检测平滑肌22alpha（smooth muscle 22 alpha，SM22α）磷酸化和泛素化水平。结果显示，异牛肝菌素显著抑制PDGF-BB引发的VSMC增殖；上调分化标志蛋白SM22α表达，下调增殖相关蛋白PCNA表达；抑制SM22α磷酸化及其泛素化降解，且该过程可能与其阻断蛋白激酶C（protein kinaseC，PKC）δ的活性有关。通过以上结果推测，异牛肝菌素通过抑制PKCδ的活性，降低SM22α磷酸化水平，阻止SM22α泛素化降解，进而抑制VSMC表型转化，发挥血管保护的功能。

英文摘要：

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 for24or48h,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 muscle22alpha(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 SM22αupon PDGF-BB treatment,which may be associated with iso-suillin-decreased protein kinase C(PKC)δactivity.Collectively,these data demonstrated that iso-suillin prevented VSMC phenotype transformation through decreasing PKCδ-mediated SM22αdegradation via the ubiquitin-proteasome pathway in VSMCs.