Browsing by Subject "Doxorubicin"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
Item Doxorubicin Inhibits Cardiomyocyte Autophagic Flux by Suppressing Lysosomal Acidification(2015-04-09) Li, Dan; Sadek, Hesham A.; Hill, Joseph A.; Levine, Beth; Amatruda, James F.The clinical use of doxorubicin is limited by cardiotoxicity. Dysregulation of autophagy in the myocardium has been implicated in a variety of cardiovascular diseases. However, the role of autophagy in doxorubicin cardiomyopathy remains poorly defined. Most models of acute doxorubicin cardiotoxicity involve intraperitoneal injection of high-dose drug, which elicits lethargy, anorexia, weight loss, and peritoneal fibrosis, all of which confound the interpretation of autophagy. Given this, I first established a model that provokes modest and progressive cardiotoxicity without constitutional symptoms, and is reminiscent of the effects seen in patients of chronic doxorubicin cardiomyopathy. Next, via multiple assays I showed that doxorubicin blocks cardiomyocyte autophagic flux in vivo and in cardiomyocytes in culture. This block was accompanied by robust accumulation of undegraded autolysosomes. Moreover, I went on to localize the site of block as a defect in lysosome acidification. To test the functional relevance of doxorubicin-triggered autolysosome accumulation, I studied animals with diminished autophagic activity due to haploinsufficiency for Beclin 1. Beclin 1+/- mice exposed to doxorubicin manifested restored cardiac autophagic flux, and were protected in terms of structural and functional changes within the myocardium. Conversely, animals over-expressing Beclin 1 manifested an amplified cardiotoxic response, correlating with their aggravated accumulation of autolysosomes in cardiomyocytes after doxorubicin treatments. In summary, I report here that doxorubicin blocks autophagic flux in cardiomyocytes by impairing lysosome acidification and lysosomal function. Further, reducing autophagy initiation may protect against doxorubicin cardiotoxicity.Item Single-Cell Image Analysis Enables High-Throughput Phenotypic Drug Screen and Elucidates Cell-Fate Decision Principles(2019-05-20) Hsu, Chien-Hsiang; Martinez, Elisabeth; Wu, Lani; Altschuler, Steven J.; Amatruda, James F.; Xie, YangCellular phenotypes encode information that can be used to infer the external signals cells experience. Here we applied quantitative image analysis to enable a one-pass multi-class phenotypic drug screen. Our combined experimental and computational approach can functionally annotate large compound libraries across diverse drug classes in a single-pass screen with high prediction accuracy confirmed via orthogonal, secondary validation assays. We further investigated how heterogeneity arose from an isogenic population. We monitored the dynamics of p21 to understand the proliferation-senescence cell-fate decision in single cells under non-lethal dose of chemotherapy via time-lapse microscopy before, during and days after treatment. Surprisingly, while high p21 is associated with senescence at late times, we find the opposite at early times during drug treatment: most senescence-fated cells have low p21 levels, while proliferation-fated cells have much higher p21 expression. Further, we identify a p21 "Goldilocks zone" for proliferation, in which increasing p21 levels has the undesirable effect of increasing proliferative outcomes. Our study identifies a counter-intuitive role for early p21 dynamics in cell-fate decision and pinpoints the source of proliferative cancer cells that emerge after exposure to non-lethal doses of chemotherapy.