ACAT1: acetyl-coenzyme A acetyltransferase 1; AHA: L-azidohomoalanine; AO: acidic orange; ATG: autophagy related; CLEAR: Coordinated Lysosomal Expression and Regulation; CQ: chloroquine; CTSB: cathepsin B; HATs: histone acetyltransferases; HDACIs: HDACs inhibitors; HDACs: histone deacetylases; IP: immunoprecipitation; MEFs: mouse embryonic fibroblasts; MS: mass spectrometry; MTOR: mechanistic target of rapamycin (serine/threonine kinase); MTORC1: mechanistic target of rapamycin (serine/threonine kinase) complex 1; PTMs: posttranslational modifications; SAHA: suberoylanilidehydroxamic acid; TFEB: transcription factor EB.

Artesunate (ART) is a prominent anti-malarial with significant anti-cancer properties. Our previous studies showed that ART enhances lysosomal function and ferritin degradation, which was necessary for its anti-cancer properties. ART targeting to mitochondria also significantly improved its efficacy, but the effect of ART on mitophagy, an important cellular pathway that facilitates the removal of damaged mitochondria, remains unknown. Here, we first observed that ART mainly localizes in the mitochondria and its probe labeling revealed that it binds to a large number of mitochondrial proteins and causes mitochondrial fission. Second, we found that ART treatment leads to autophagy induction and the decrease of mitochondrial proteins. When autophagy is inhibited, the decrease of mitochondrial proteins could be reversed, indicating that the degradation of mitochondrial proteins is through mitophagy. Third, our results showed that ART treatment stabilizes the full-length form of PTEN induced putative kinase 1 (PINK1) on the mitochondria and activates the PINK1-dependent pathway. This in turn leads to the recruitment of Parkin, sequestosome 1 (SQSTM1), ubiquitin and microtubule-associated proteins 1A/1B light chain 3 (LC3) to the mitochondria and culminates in mitophagy. When PINK1 is knocked down, ART-induced mitophagy is markedly suppressed. Finally, we investigated the effect of mitophagy by ART on mitochondrial functions and found that knockdown of PINK1 alters the cellular redox status in ART-treated cells, which is accompanied with a significant decrease in glutathione (GSH) and increase in mitochondrial reactive oxidative species (mROS) and cellular lactate levels. Additionally, knockdown of PINK1 leads to a significant increase of mitochondrial depolarization and more cell apoptosis by ART, suggesting that mitophagy protects from ART-induced cell death. Taken together, our findings reveal the molecular mechanism that ART induces cytoprotective mitophagy through the PINK1-dependent pathway, suggesting that mitophagy inhibition could enhance the anti-cancer activity of ART.

Two studies concerning multi-frequency impedance measurements are presented. The first uses tetrapolar measurements made on the thorax and the second electrical impedance tomography images, also made from the thorax. The way in which the impedance and the changes in impedance with ventilation depend upon frequency are investigated using Cole-Cole modelling and also a physiological model of lung tissue. There is an excellent fit to the Cole-Cole model, and the results show that it should be possible to identify tissue on the basis of the impedance spectrum and the spectrum of the changes in impedance during breathing.