Glutathione depletion and cardiomyocyte apoptosis in viral myocarditis

Background  The course of viral myocarditis is highly variable. Oxidative stress and Bcl‐2 family genes may play a role in its pathogenesis by regulating the amount of cardiomyocyte apoptosis. Apoptosis is difficult to detect and quantify in vivo . Therefore, we set to look for indicators of this potentially preventable form of cell death during various phases of experimental murine coxsackievirus B3 myocarditis. Methods  BALB/c mice were infected with the cardiotropic coxsackievirus B3 variant. Glutathione (HPLC), cardiomyocyte apoptosis (TUNEL and caspase‐3 cleavage), Bax and Bcl‐X L mRNA expression (real time RT‐PCR), histopathology and viral replication (plaque assay and real time RT‐PCR) were measured from day 3 to day 20 after infection. Results  Infection caused severe myocarditis and led to progressive decrease of plasma glutathione levels. Myocardial mRNA levels of pro‐apoptotic Bax and antiapoptotic Bcl‐X L were significantly increased from day 3 onwards. Bax mRNA and ratio of Bax to Bcl‐X L correlated with cardiomyocyte apoptosis ( r  = 0·77, P  = < 0·001 and r  0·51, P  < 0·01, respectively). Cardiomyocyte apoptosis was highest on day 5, coinciding with a rapid decline in plasma glutathione ( r  = −0·52, P  = 0·003). Conclusions  Systemic oxidative stress as indicated by decreased plasma glutathione levels coincides with cardiomyocyte apoptosis in experimental coxsackievirus myocarditis. Decreased plasma glutathione levels and changes in cardiac Bax and Bcl‐X L mRNA expression identify a phase of myocarditis in which the potentially preventable cardiomyocyte apoptosis is mostly observed.