Abstract 15685: Inhibition of Site Specific Phosphorylation of Retinoblastoma Protein by a p38 Inhibitor Decreases Apoptosis, Improves Survival and Prevents Cardiomyopathy Caused by a Mutation in LMNA gene.
Background: Mutations in LMNA gene are associated with a wide range of diseases known as laminopathies in which dilated cardiomyopathy (DCM) is a common finding. One such laminopathy is modelled in mice by a missense mutation (N195K) resulting in DCM and sudden death by 6-7 weeks of age. An abnormal activation of the p38 branch of the mitogen-activated protein kinase (MAPK) signalling cascade was seen in hearts of LmnaN195K mice.
Methods & Results: We treated LmnaN195K mice that develop cardiomyopathy with ARRY-371797, an inhibitor of p38 activation. Serial echocardiographic measurements revealed a significant increase in ejection fraction, fractional shortening and a significant decrease in left ventricular end diastolic diameter in treated vs. untreated mutants. Electron microscopy demonstrated preservation of cellular and nuclear architecture in treated vs. untreated mutants where alteration in nuclear shape and disarray in cellular architecture was apparent. Treated N195K mice also showed an increase in lifespan (18%).We investigated the mechanism behind increased survival and noticed a significant increase in apoptosis determined by up regulation of caspase 3 activity and reduction of Bcl2 levels in N195K mice. Increased phosphorylation of retinoblastoma protein (Rb) on Serine 567 and an increase in p53 activity was seen in N195K mutants. Proteins levels of transcriptional factor E2F3 (pro apoptotic in cardiomyocytes) were increased however E2F2 levels remained unchanged. Ratio of cytochrome c concentration (cytosol/mitochondria) and caspase 3/9 were also increased in N195K mice. Blocking p38 activity with the p38 inhibitor prevented phosphorylation of Rb on Serine 567 and resulted in decreased protein levels of E2F3 and p53 as compared to N195K mutants. In addition, ratio of cytochrome c concentration (cytosol/mitochondria) and caspase 3 activity were restored to normal levels. Treatment with ARRY-371797 was well-tolerated and no adverse effects were noted
Conclusion: p38 inhibition prevents cardiomyopathy and increases survival by inhibiting apoptotis in a murine model (Lmna195K) of dilated cardiomyopathy
- © 2011 by American Heart Association, Inc.