Pitavastatin regulates helper T-cell differentiation and ameliorates autoimmune myocarditis in mice

Purpose: Experimental autoimmune myocarditis (EAM) is a mouse model of inflammatory cardiomyopathy, and the involvement of T helper (Th) 1 and Th17 cytokines has been demonstrated. Accumulated evidence has shown that statins have anti-inflammatory and immunomodulatory effects; however, the mechanism has not been fully elucidated. This study was designed to test the hypothesis that pitavastatin affects T cell-mediated autoimmunity through inhibiting Th1 and Th17 responses and reduces the severity of EAM in mice.

Methods: The EAM model was established in BALB/c mice by immunization with murine α-myosin heavy chain. Mice were fed pitavastatin (5 mg/kg) or vehicle once daily for 3 weeks from day 0 to day 21 after immunization.

Results: Pitavastatin reduced the pathophysiological severity of the myocarditis. Pitavastatin treatment inhibited the phosphorylation of signal transducer and activator of transcription (STAT)3 and STAT4, which have key roles in the Th1 and Th17 lineage commitment, respectively, in the heart, and suppressed production of Th1 cytokine interferon-γ and Th17 cytokine interleukin-17 from autoreactive CD4(+) T cells. In in vitro T-cell differentiation experiments, pitavastatin-treated T cells failed to differentiate into Th1 and Th17 cells through inhibiting the transcription of T-box expressed in T-cells (T-bet) and RAR-related orphan receptor γt (RORγT) which have critical roles in the development of Th1 and Th17 cells, respectively, and this failure was rescued by adding mevalonate.

Conclusions: Pitavastatin inhibits Th1 and Th17 responses and ameliorates EAM. These results suggest that statins may be a promising novel therapeutic strategy for the clinical treatment of myocarditis and inflammatory cardiomyopathy.