Pept. and STAT2 and greater basal ISG mRNA expression and provides greater basal antiviral protection relative to cardiac fibroblasts. Conversely, cardiac fibroblasts express greater basal IFN-/ receptor 1 (IFNAR1) and greater basal cytoplasmic Jak1, Tyk2, STAT2, and IRF9, leading to a greater increase in reovirus T3D- or IFN-induced nuclear activated STAT1 and STAT2 and greater induction of ISGs for a greater IFN-induced antiviral protection relative to cardiac myocytes. Our results suggest that high basal IFN- expression in cardiac myocytes prearms this vulnerable, nonreplenishable cell type, while high basal expression of IFNAR1 and latent Jak-STAT components in adjacent cardiac LY2452473 fibroblasts renders these cells more responsive to IFN and prevents them from inadvertently providing as a reservoir for viral replication and spread to cardiac myocytes. These studies provide the first indication of an integrated network of cell-type-specific innate immune components for organ protection. Viral myocarditis affects an estimated 5 to 20% of the human population. It can be fatal in infants and, although usually resolved in adults, can progress to chronic myocarditis and/or dilated cardiomyopathy with concomitant cardiac failure (11, 28). Recent clinical studies have indicated that alpha interferon (IFN-) (11, 21, 35, 36) and IFN- (29) can reduce the severity of viral myocarditis, inhibiting viral replication and improving cardiac function. Nonetheless, viral myocarditis remains a disease without reliable treatment, and the prognosis remains poor for more than half of patients presenting with clinical symptoms (45). A wide variety of viruses have been implicated in human myocarditis, with the majority of cases being associated with enteroviruses and adenoviruses (4, 30, 34). While Rabbit Polyclonal to 53BP1 enteroviruses induce both immune-mediated damage to (10, 41) and a direct cytopathogenic effect on (8, 23) the heart, adenovirus-induced myocarditis is most likely not immune mediated (34). Reovirus-induced myocarditis is LY2452473 not immune mediated (47, 48) but instead displays virally induced apoptosis of cardiac cells (13). Thus, reovirus infection in a mouse model provides an excellent model for investigating the cardiac response to viral contamination. Previously, we exhibited that nonmyocarditic reoviruses induce more IFN- and/or are more sensitive to the antiviral effects of IFN- than myocarditic reoviruses in main cardiac myocyte cultures (49). In addition, nonmyocarditic reoviruses induce myocarditis in mice pretreated with anti-IFN-/ antibody, demonstrating directly that IFN-/ is usually a determinant of protection against viral myocarditis (49). Interestingly, addition of anti-IFN-/ antibody enhances reovirus spread in main cardiac myocyte cultures but not in differentiated C2C12 (skeletal muscle mass) cell cultures (49), suggesting a unique role for IFN-/ in the heart. IFN-/ exerts its antiviral effects through the induction of IFN-stimulated genes (ISGs), whose promoters are activated through a signal transduction pathway following binding of IFN-/ to the IFN-/ receptor, composed of IFNAR1 and IFNAR2 subunits. Receptor binding activates tyrosine kinases, Jak1 and Tyk2, which in turn phosphorylate transmission transducers and activators of transcription LY2452473 (STATs), STAT1 (STAT1 and STAT1) and STAT2 (22, 39, 44, 52). Upon phosphorylation, STAT1 and STAT2 heterodimerize and associate with p48/IRF9, forming the multimeric protein complex ISG factor 3 (ISGF3) (17, 57). ISGF3 complexes translocate to the nucleus and initiate the transcription of many ISGs, including ISG561 and the transcription factor IRF7, leading to the induction of an antiviral state (12). Cardiac myocytes, like neurons in the central nervous system, are not replenishable. However, there is no cardiac equivalent to the blood-brain barrier, leaving the heart uniquely vulnerable to damage from viral contamination. Accordingly, we have hypothesized that cardiac myocytes may have a unique antiviral protective response, and indeed, we have found differences in responses between cardiac myocytes and cardiac fibroblasts, a readily replenished cardiac cell type. Specifically, in comparing the two cardiac cell types, reovirus T3D induces more IFN- mRNA in cardiac myocytes, yet there is a greater induction of ISG561 and IRF7 mRNA in cardiac fibroblasts (53). This conundrum led us to our current study: to identify the molecular differences between cardiac myocytes and cardiac fibroblasts that determine their protective responses to viral contamination. Here, we statement that cardiac myocytes rely on greater basal expression of IFN-, resulting in greater basal activated nuclear ISGF3 components and greater basal ISG mRNA expression, as a prearming mechanism for protection. In contrast, cardiac fibroblasts express higher basal IFNAR1 and cytoplasmic.