ABSTRACT
Polyphyllin Ⅰ(PPⅠ)and polyphyllin Ⅱ(PⅡ)are the main active substances in the Paris polyphylla.However,liver toxicity of these compounds has impeded their clinical application and the potential hepatotoxicity mechanisms remain to be elucidated.In this work,we found that PPⅠ and PⅡ exposure could induce significant hepatotoxicity in human liver cell line L-02 and zebrafish in a dose-dependent manner.The results of the proteomic analysis in L-02 cells and transcriptome in zebrafish indicated that the hepa-totoxicity of PPⅡ and PⅡwas associated with the cholesterol biosynthetic pathway disorders,which were alleviated by the cholesterol biosynthesis inhibitor lovastatin.Additionally,3-hydroxy-3-methy-lglutaryl CoA reductase(HMGCR)and squalene epoxidase(SQLE),the two rate-limiting enzymes in the choles-terol synthesis,selected as the potential targets,were confirmed by the molecular docking,the over-expression,and knockdown of HMGCR or SQLE with siRNA.Finally,the pull-down and surface plasmon resonance technology revealed that PPⅠ could directly bind with SQLE but not with HMGCR.Collectively,these data demonstrated that PPⅠ-induced hepatotoxicity resulted from the direct binding with SQLE protein and impaired the sterol-regulatory element binding protein 2/HMGCR/SQLE/lanosterol synthase pathways,thus disturbing the cholesterol biosynthesis pathway.The findings of this research can contribute to a better understanding of the key role of SQLE as a potential target in drug-induced hepatotoxicity and provide a therapeutic strategy for the prevention of drug toxic effects with similar structures in the future.
ABSTRACT
Squalene monooxygenase (SQLE) is the rate-limiting enzyme of cholesterol biosynthesis. It plays a crucial role in regulating cholesterol homeostasis. Increasing evidence shows that SQLE is closely related to the occurrence, development, metastasis, and poor prognosis of various cancers. SQLE can not only promote the proliferation of cancer cells and epithelial-mesenchymal transformation but also play an important role in maintaining the stemness of cancer stem cells and regulating cholesterol homeostasis. SQLE may be a potential molecular target for cancer therapy. In this review, the role of SQLE in regulating cholesterol homeostasis in vivo; its function in the occurrence, development, and metastasis of various cancers; and its molecular mechanism were summarized. Screening new SQLE inhibitors may provide new ideas for targeted cancer therapy.
ABSTRACT
Aim To explore the effect of squalene ep-oxidase ( SQLE) in cervical squamous cell carcinoma and the molecular mechanism. Methods Firstly, the gene expression profiling interactive analysis (GEPIA) database was used to analyze the mRNA expression of SQLE in cervical squamous cell carcinoma and normal cervical tissues, and the human protein atlas ( HPA) database was used to obtain the expression of SQLE protein in cervical squamous cell carcinoma and normal cervical tissues. We researched the correlation between SQLE gene and the clinicopathological characteristics of cervical squamous cell carcinoma through UALCAN database. Then GEPIA database was utilized to evaluate the overall survival (OS) and disease free survival (DFS) of cervical squamous cell carcinoma patients with high expression of SQLE mRNA. Finally, Siha cells were taken as the research object, and the effects of SQLE gene on proliferation, apoptosis, migration and invasion of Siha cells were observed by using small interfering RNA ( siRNA) to inhibit the expression of SQLE gene and transfecting recombinant plasmid to promote the expression of SQLE gene. The mRNA expression of SQLE was assessed by qPT-PCR. Bax, Bcl-2, Vimentin, E-cadherin, PI3K, Akt, p-PI3K and p-Akt protein expression levels were examined by Western blot. Results The mRNA expression and protein expression of SQLE in cervical squamous cell carcinoma was higher than that in normal tissues (P < 0. 05 ), and the OS of patients with high expression of SQLE mRNA was significantly shortened in cervical squamous cell carcinoma ( P < 0. 05 ). The expression of SQLE in stage IV of cervical squamous cell carcinoma was significantly higher than that in stage I, II and III (P < 0. 01). And the expression of SQLE in lymph node metastasis Nl group was markedly higher than that in NO group ( P < 0. 01 ). Cell experiments showed that interference with SQLE could significantly inhibit the proliferation, migration and invasion of Siha cells, and promote their apoptosis (P < 0. 01 ). The trend was opposite when SQLE was overexpressed. SQLE knockdown decreased the protein expression levels of Bcl-2, Vimentin, p-PI3K and p-Akt, increased the protein expression levels of Bax and E-cadherin, and the ratio of Bcl-2/Bax decreased significantly (P < 0. 05, P < 0. 01 ) . The trend was opposite when SQLE was overexpressed. Conclusions SQLE is highly expressed in human cervical squamous cell carcinoma. SQLE may induce Siha cell proliferation, migration, invasion, and inhibit their apoptosis by regulating PDK/Akt signaling pathway.