Abstract 1274: Altered Chromatin Landscape Provides Molecular Basis for Endothelial Dysfunction in Duchenne Muscle Dystrophy.
INTRODUCTION & BACKGROUND: recent studies indicate that in the MDX mouse model of Duchenne muscle dystrophy (DMD) nitric oxide (NO) production is significantly compromised leading to skeletal muscle, vascular and cardiovascular alterations. The expression of Nitric oxide synthases (NOS) is tightly controlled at epigenetic level being regulated by DNA core histones modification and histone deacetylases (HDAC) activity. To investigate the role of epigenetics in the onset of the DMD-associated endothelial dysfunction a series of experiments were performed where covalent histone tail modifications and gene expression were evaluated in freshly isolated MDX pulmonary endothelial cells (PEC).
METHODS & RESULTS: PECs were obtained from normal c57BL-J10 and MDX mice and kept in static (ST) culture or exposed to a laminar shear stress (SS) of 10 dyne/cm2 for 8 to 16 hours to evaluate NO production. In this condition, PEC isolated from MDX mice did not reveal a significant production of NO compared to normal controls. In normal endothelial cells, cFOS protoncogene expression is rapidly induced upon SS induction. Remarkably, western blotting analysis showed that PECs from MDX mice constitutively expressed high levels of c-FOS which expression was inhibited by NO donor treatment suggesting the reduced-NO environment, which characterizes MDX cells, could lead to an altered regulation in gene expression. Accordingly, Affymetrix microchip analysis revealed that unstimulated PECs from MDX mice expressed high levels of different vasoactive peptides including NGF, G-CSF, PDGF-A, and TGF-beta1 further indicating the presence of a transcription dysregulation. These observations prompted us to evaluate the global pattern of histone H3 modification. Compared to control cells, several changes could be detected in PECs from MDX including high levels of acetylated Lysine 14, methylated Lysine 79, and phosphorylated Serine 10. These modifications remained elevated upon SS treatment but were reverted by treatment with NO donors.
CONCLUSIONS: These results indicate that NO-dependent altered chromatin landscape characterizes endothelial cells from MDX mice providing molecular basis for the endothelial dysfunction pathogenesis in Duchenne muscle dystrophy.