CMPK2 Promotes CD4+ T Cell Activation and Apoptosis through Modulation of Mitochondrial Dysfunction in Systemic Lupus Erythematosus.

Abstract

Systemic lupus erythematosus (SLE) is a classic autoimmune disease characterized by abnormal autoantibodies, immune complex deposition, and tissue inflammation. Despite extensive research, the exact etiology and progression of SLE remain elusive. Cytidine/uridine monophosphate kinase 2 (CMPK2), a mitochondrial nucleoside monophosphate kinase, has garnered attention for its potential involvement in the development of various diseases, including SLE, where it has been observed to be dysregulated in affected individuals. However, the specific involvement of CMPK2 in the pathogenesis of SLE remains unclear. This study aims to clarify the expression level of CMPK2 in SLE CD4⁺ T cells and explore its impact on CD4⁺ T cells. The expression levels of the CMPK2 gene and the corresponding CMPK2 protein in CD4⁺ T cells of SLE patients were quantified using RT-qPCR and Western blot, respectively. Immunofluorescence and RT-qPCR were used to assess the mitochondrial function of SLE CD4⁺ T cells. Flow cytometry was used to assess CD4⁺ T cell activation and apoptosis levels. The impact of CMPK2 on CD4⁺ T cells was investigated by gene transfection experiment. We found that CMPK2 was significantly upregulated in SLE CD4⁺ T cells at both gene and protein levels. These cells demonstrated aberrant mitochondrial function, as evidenced by elevated mitochondrial reactive oxygen species (mtROS) levels, mitochondrial membrane potential, and mitochondrial DNA (mtDNA) copy number. Flow cytometry revealed a notable increase in both apoptosis and activation levels of CD4⁺ T cells in SLE patients. Gene transfection experiments showed that suppressing CMPK2 led to a significant improvement in these conditions. These findings suggest that CMPK2 may be involved in the pathogenesis of SLE by regulating mitochondrial dysfunction in CD4⁺ T cells and thus affecting CD4⁺ T cell activation and apoptosis. Our study may provide a new target for the treatment of SLE.