Abstract 14399: Endogenous Lats2 Mediates Ischemia/Reperfusion Injury by Promoting Foxo Degradation and Decreases in Antioxidants
Lats2 is a tumor suppressor and a serine/threonine kinase, acting downstream of mammalian sterile 20 like kinase1 (Mst1), that stimulates apoptosis in cardiomyocytes (CMs). Lats2 is activated by ischemia/reperfusion (I/R) in the heart. In order to elucidate the role of Lats2 in mediating I/R injury, Lats2+/- mice were subjected to ischemia (20 min)/reperfusion (24 h). The size of myocardial infarction (MI)/area at risk was significantly smaller in Lats2+/- than in WT mice (27 and 59%, p<0.01). There were fewer TUNEL positive cells in Lats2+/- than in WT mice (0.05% and 0.15%, p<0.05). These results suggest that endogenous Lats2 mediates I/R injury and CM apoptosis. The level of oxidative DNA damage, as evaluated with 8-OHdG staining, was lower in Lats2+/- mice than in WT mice, suggesting that Lats2 mediates oxidative stress during I/R. In cultured CMs, transduction with adenovirus harboring short hairpin Lats2 (ad-sh-Lats2) significantly decreased H2O2-induced cell death, as evaluated with Cell Titer Blue, compared to in control CMs (40% and 55%, p<0.05). Quantitative PCR showed that downregulation of Lats2 significantly increased mRNA expression of MnSOD and catalase (+100% and +80%, p<0.05), major antioxidants. FoxO1 is known to regulate transcription of these antioxidants. Luciferase reporter assays showed that overexpression of Lats2 adenovirus (ad-Lats2) significantly inhibited (-70%, p<0.05), whereas downregulation of Lats2 increased (+60%, p<0.05), FoxO1-mediated transcriptional activity. Lats2 significantly reduced FoxO1 protein expression (-50%, p<0.05), but FoxO1 mRNA was not changed in ad-Lats2 treated CMs. Pretreatment with MG132, a proteasome inhibitor, attenuated Lats2-induced downregulation of FoxO1 in CMs. Lats2+/- mice showed significantly attenuated FoxO1 downregulation after I/R in vivo compared to WT mice, suggesting that Lats2 negatively regulates FoxO1 protein expression by promoting its degradation during I/R. Taken together, these results suggest that endogenous Lats2 plays an important role in mediating myocardial injury in response to I/R. Activation of Lats2 during I/R downregulates FoxO1, thereby inhibiting transcription of antioxidants, which in turn induce oxidative stress and apoptosis in the heart.
- © 2012 by American Heart Association, Inc.