Depletion of PINK1 sensitizes breast cancer cells to polyphyllin Ⅰ via mitophagy suppression and DRP1-mediated mitochondrial fission

OBJECTIVE To elucidate the molecular mechanism and the anti-breast cancer effect of polyphyllinⅠ,which is a natural compound extracted from Rhizoma of Paris polyphyllin.METHODS Human breast cancer cells were treated with polyphyllinⅠ,after which DRP1-dependent mitochondrial fission and apoptosis,mitophagy and PINK1/PARK2 pathway were evaluated.A genetic approach was employed to determine how knockdown of PINK1 with sh RNA regulates polyphyllinⅠ-induced mitophagy and apoptosis.The inhibitory effect of polyphyllinⅠon tumor growth in a breast cancer cell xenograft mouse model was also examined.RESULTS PolyphyllinⅠenhanced the stabilization of full-length PINK1at the mitochondrial surface,leading to PARK2 recruitment to mitochondria,and culminating in mitophagy.PolyphyllinⅠalso induced dephosphorylation of DRP1 at Ser637 and mitochondrial translocation of DRP1,leading to mitochondrial fission and apoptosis.Knockdown of PINK1 evidently suppressed mitophagy stimulated by polyphyllinⅠ,and markedly enhanced DRP1-dependent mitochondrial fission and apoptosis induced by polyphyl inⅠ.Furthermore,suppression of DRP1 by mdivi-1 or sh RNA inhibits PINK1 knockdown-mediated mitochondrial fragmentation and apoptosis in response to polyphyllinⅠtreatment,suggesting that depletion of PINK1 lead to mitochondrial fragmentation due to excessive fission.Our in vivo study also showed that knockdown of PINK1potentiated polyphyllinⅠ-mediated inhibition of tumor growth in a breast cancer cell xenograft mouse model.CONCLUSION Our study provides a mechanism to support the role of PINK1 in the regulation of polyphyl inⅠ-induced mitophagy and apoptosis,and suggest polyphylinⅠas a potential drug for treatment of breast cancer.

Molecular basis of the anti-inflammatory potential of a diarylheptanoid in murine macrophage RAW 264.7 cells

Natural products play a significant role in human health in relation to the prevention and treatment of inflammatory disorders. In this study, we examined the molecular basis of the anti-inflammatory potential of a diarylheptonoid (DAH) isolated from Alpinia officinarum hexane extract (AOHE) with special emphasis on their ability to modulate the nuclear factor-κB (NF-кB) signaling involved in the inflammatory response. Measurement of Nitrite by Griess reaction which revealed the effect of DAH in RAW 264.7 macrophages showed an inhibition in the nitric oxide production through the suppression of inducible nitric oxide synthase (iNOS) gene level expression. NF-кB reporter gene assay suggests inhibition of NF-кB transcriptional activity, thus inhibiting LPS-induced phosphorylation and degradation of IкBα and a downregulation of NF-кB protein expression confirms the immunomodulatory effect of DAH. Furthermore, downregulation in the gene level expression of NF-кB signaling markers such as IL-1β, TNF-α and COX-2 suggests the anti-inflammatory potential of DAH via inhibition of NF-кB activation.