Protein kinase R is highly expressed in dermatomyositis and promotes interferon-beta-induced muscle damage

Dermatomyositis (DM) has been consistently linked to the type I interferon (IFN-I) pathway. However, the precise pathogenesis remains incompletely elucidated. We aimed to explore potential molecular mechanisms and identify promising therapeutic targets in DM. We employed bioinformatics analysis to investigate molecular signatures, aiming to shed light on the pathogenesis of DM. The expression of protein kinase R (PKR) in DM muscle tissues was determined by real-time quantitative PCR, western blot and immunohistochemistry (IHC) analysis. We then assessed the sensitivity and specificity of sarcoplasmic PKR expression by IHC in a consecutive DM cohort and other diseases in this retrospective study. Furthermore, IFN-β was used to stimulate myoblasts and myotubes, and the relationship between PKR and IFN-β-induced pathogenic molecules was investigated in vitro. Bioinformatics analysis indicated two primary pathological processes: viral infection and the IFN-I signalling pathway. We subsequently verified that PKR was notably expressed in the cytoplasm of myofibers in DM patients. The sensitivity and specificity of sarcoplasmic PKR expression in DM were 84.6% and 97.6%, respectively. In vitro studies revealed that IFN-β upregulates the expression of PKR, along with several molecules associated with DM muscle damage. Conversely, inhibiting PKR has been shown to downregulate IFN-β-induced pathogenic molecules in both myoblasts and myotubes. We observed that PKR exhibits specific expression in the cytoplasm of DM muscle and inhibiting PKR ameliorates IFN-β-induced muscle damage in vitro. These findings provide insights into the diagnostic and therapeutic roles of PKR in DM.