As cancer cells [33,34]. Several key regulatory proteins mediated the interaction of
As cancer cells [33,34]. Several key regulatory proteins mediated the interaction of heat shock proteins to inhibit apoptosis. The intrinsic pathway of caspase-mediated apoptosis was stimulated by c-Jun kinase, PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/26162776 resulting in the release of cytochrome c from the mitochondria, and the subsequent activation of a caspase cascade involving caspase 8 and caspase 3. They were each inhibited by heat shock cognate 71, which interacted with Bcl-2 through Bag-1, enabling the complex to be incorporated into the mitochondrial membrane to inhibit apoptosis [35]. In this study, heat shock cognate 71 was upregulated in the quercetin-pretreated H9C2 cells, implying that heat shock cognate 71 is ResiquimodMedChemExpress S28463 essential for protecting H9C2 cells from doxorubicin-induced apoptosis. Quercetin was also observed to modulate the expression of cytoskeletal proteins (e.g., tubulins) and migrationregulated proteins (e.g., tubulin polymerization-promoting proteins) after encountering doxorubicin-induced damage [36]. Our immunofluorescence study demonstrated that quercetin can promote F-actin organization. Proteomic data also suggested that actin molecules were overexpressed during quercetin pretreatment, implying that quercetin causes the efficient regulation of protrusiondynamics and the wound healing of doxorubicin-damaged cardiomyocytes. Our proteomic analysis indicated that quercetin pretreatment might down-regulate the levels of proteins involving energy metabolism including mitochondrial ATP synthesis, glycolytic proteins and TCA cycle proteins. Similar results were also reported by Dihal et al., who observed that glycolytic proteins were significantly downregulated in their report. Additionally, Shoshan et al. reported that quercetin can modulate mitochondrial energy production by interacting with ATP synthase and blocking the enzyme’s activity [37,38]. The current proteomic analysis corresponded with these results. Our preliminary data indicated that quercetin reduces but enhances the cytotoxicity of doxorubicin on cardiomyocyte H9C2 cells and liver cancer HepG2 cells, respectively (data not shown). This observation suggested the potential of combining quercetin and doxorubicin for treating liver cancer. Although no direct evidence indicates the cooperative effect of quercetin and doxorubicin on other cancer treatment, performing relevant evaluations of other cancers is worthwhile in the future. In summary, this study is the first to report on the principle mechanism of quercetin against doxorubicininduced cytotoxicity in cardiomyocytes, using cell biology and a quantitative proteomic analysis. The information obtained in this study presents the potential of combining quercetin with doxorubicin to achieve reduced cardiotoxicity in cancer chemotherapy.Conclusions This study is the first to report detailed protective mechanisms for the action of quercetin against doxorubicininduced cardiomyocyte toxicity. Quercetin might stimulate cardiomyocytes to repair damage after treating doxorubicin by modulating metabolic activation, protein folding and cytoskeleton rearrangement. Additional filesAdditional file 1: Table S1. Differentially expressed proteins were listed alphabetically after 2D-DIGE and MALDI-TOF Mass spectrometry analysis in H9C2 cells in response to doxorubicin treatment and quercetin pretreatment. The average ratios of these 73 spots are differentially expressed among untreated (control), doxorubicin-treated and quercetin-pretreated followed by doxorubicin-treated.
