Abstract 218: Chemical Induced Reductive Stress Causes Cardiomyocyte Hypertrophy
Background: Progressive accumulation of misfolded or unfolded proteins is a symbol of impaired proteostasis and proteotoxicity. Such a chronic proteotoxicity is amenable to cell types that are post mitotically matured with lack of further differentiation or proliferation. Our recent discovery using a mouse model of familial human cardiac disease displayed protuberant shift in the redox state towards reductive stress (RS) in association with accumulation of toxic protein aggregates. Further, sustained trans-activation of Nrf2/antioxidant signaling caused RS in the myopathy hearts. Accordingly, we hypothesized that whether profound activation of Nrf2/antioxidant signaling and subsequent RS may cause pathological remodeling in cardiomyocyte. The aim of this study was to investigate the effect of sustained pharmacological activation of Nrf2 on cardiac remodeling. Methods: HL1 cardiomyocytes were used as an in vitro model to study the RS-mediated cardiac remodeling. They were treated with 2-10 μM of potential Nrf2-inducers; sulforaphane (SF), di-methyl fumarate (DMF) and novel small molecules (C-38, C-50, C-63 and C-66) to establish RS by sustained activation of Nrf2/antioxidant signaling. Next, we investigated the implications of RS in cardiomyocyte remodeling by analyzing transcriptional and translational mechanisms using immunoblotting, qPCR, immunofluorescence, GSH and NADPH redox measurements in HL1 cells. Results: Dose dependent effects for individual small molecules including known Nrf2 inducers (SF and DMF) revealed distinct pro-reductive and reductive intracellular (i.e. reductive stress) environments. In fact, the obligatory activation of Nrf2 signaling was associated with significant upregulation of antioxidant enzymes and small molecular thiols including glutathione (GSH). Surprisingly, while pro-reductive condition in HL1 cells was subdued, the RS induced cardiomyocyte hypertrophy was evident from microscopic examination and molecular signature (increased expression of ANF and BNF) after 24-48 hrs of Nrf2 activation. Conclusion: In summary, the chemical induced sustained activation of Nrf2 leading to formation of reductive stress showed hypertrophic remodeling in HL1 cardiomyocytes.
Author Disclosures: S.B. Shelar: None. M. Narasimhan: None. G. Shanmugam: None. N.E. Vargees: None. R. Sakthivel: None. C. Brown: None. P. Sethu: None. W.E. Warner: None. V. Darley-Usmar: None. N.S. Rajasekaran: None.
This research has received full or partial funding support from the American Heart Association, Western States Affiliate (California, Nevada & Utah).
- © 2015 by American Heart Association, Inc.