Inflammation leads through PGE/EP3 signaling to HDAC5/MEF2-dependent transcription in cardiac myocytes.

The myocyte enhancer factor 2 (MEF2) regulates transcription in cardiac myocytes and adverse remodeling of adult hearts. Activators of G protein-coupled receptors (GPCRs) have been reported to activate MEF2, but a comprehensive analysis of GPCR activators that regulate MEF2 has to our knowledge not been performed. Here, we tested several GPCR agonists regarding their ability to activate a MEF2 reporter in neonatal rat ventricular myocytes. The inflammatory mediator prostaglandin E2 (PGE2) strongly activated MEF2. Using pharmacological and protein-based inhibitors, we demonstrated that PGE2 regulates MEF2 via the EP3 receptor, the ßγ subunit of Gi/o protein and two concomitantly activated downstream pathways. The first consists of Tiam1, Rac1, and its effector p21-activated kinase 2, the second of protein kinase D. Both pathways converge on and inactivate histone deacetylase 5 (HDAC5) and thereby de-repress MEF2. In vivo, endotoxemia in MEF2-reporter mice induced upregulation of PGE2 and MEF2 activation. Our findings provide an unexpected new link between inflammation and cardiac remodeling by de-repression of MEF2 through HDAC5 inactivation, which has potential implications for new strategies to treat inflammatory cardiomyopathies.

A Retrospective Comparison of Mycophenolate Mofetil with Low-Exposure Cyclosporine Versus Standard Cyclosporine Therapy in De Novo Liver Transplant Patients.

BACKGROUND Data on low-exposure calcineurin inhibitor therapy with mycophenolate mofetil (MMF) in de novo liver transplant patients are limited and restricted to tacrolimus. MATERIAL AND METHODS Twenty-eight patients receiving cyclosporine and MMF at a single center were identified retrospectively and categorized as low-exposure or standard-exposure CsA (median concentration <80 ng/mL [n=16] or ≥80 ng/mL [n=12] during days 1-7) and analyzed to 12 weeks post-transplant. RESULTS Biopsy-proven acute rejection (Banff ≥4) occurred in 3 low-CsA patients and no standard-CsA patients (p=0.238); graft failure occurred in 4 and zero patients, respectively (p=0.113); no graft loss was attributable to rejection. Mean (SD) estimated GFR at baseline and week 12 was 79.5 (45.3) and 79.3 (24.5) mL/min/1.73 m2 in the low-CsA group (p=0.508), and 106.0 (66.9) and 86.7 (23.2) mL/min/1.73 m2 in the standard-CsA group (p=0.093). Estimated GFR decreased significantly in patients with good baseline renal function (≥80 mL/min/1.73 m2) in the standard-CsA (p=0.028) and increased markedly in patients with poor function (≤60 mL/min/1.73 m2) given low-CsA (p=0.043). There was no significant between-group difference regarding incidence of infections. CONCLUSIONS These preliminary findings suggest that immunosuppressive efficacy is maintained with low-exposure CsA and MMF in de novo liver transplant patients and good baseline renal function may be better preserved, but no benefit for infections was observed.