Study on molecular mechanism of benzo (ɑ) pyrene on CMA by HSP90ɑ and HIF-1ɑ.

Objective: The effects of benzo (α) pyrene (BaP) on chaperone mediated autophagy (CMA) through heat shock protein 90 (HSP90) and hypoxia- inducible factor-1 (HIF-1) are studied by RNA interference and subcutaneous tumor formation technique in nude mice.

Methods: 40 nude mice that were inoculated with the silenced HSP90ɑ A549 cells line under the armpits of the forelimbs were divided into 4 groups, and were intragastrically administered with 1.80 mg/kg/d BaP-corn oil solutionfor for 60d (except the Control group), and the growth curves of nude mice and transplanted tumors were recorded. The size and morphological changes of tumors were observed by small animal imaging technique. qPCR, Western blot and Immunohistochemistry were used to detect the expression of HSP90ɑ, HSC70 and Lamp-2A. A549 cells were treated with 0.1 μmol/L, 1 μmol/L and 10 μmol/L BaP for 24 h, EPO and HIF-1ɑ concentration and HIF-1ɑ protein expression were detected by Elisa and Western blot; A549 cells were treated with 10 μmol/L BaP and HIF-1ɑ inhibitor for 24 h, qPCR, Western blot and Immunofluorescence methods were used to detect the expression of HSP90ɑ, HSC70 and Lamp-2A.

Results: The weight of nude mice and transplanted tumors silenced HSP90ɑ was reduced by BaP; the expression of HSP90ɑ, HSC70, Lamp-2A mRNA and proteins in transplanted tumor tissues silenced HSP90ɑ were reduced by BaP; the total number of bioluminescence photons of transplanted tumors silenced HSP90ɑ were reduced by BaP. The concentration of EPO and HIF-1ɑ and the expression of HIF-1ɑ protein in A549 cells was increased by 10 μmol/L BaP; with HIF-1ɑ inhibitors treated, HSP90ɑ, HSC70, Lamp-2A mRNA and proteins expression and the fluorescence intensity of HSP90ɑ were decreased of A549 cells.

Conclusions: The growth of transplanted tumor in nude mice is promoted by BaP, and is inhibited when HSP90ɑ was silenced. BaP promotes the occurrence of CMA by promoting the expression of HSP90ɑ and HIF-1ɑ, which are vital regulatory genes of BaP activation of CMA.