Inflammation, mitochondrial and lysosomal dysfunction as key players in rheumatoid arthritis?

Rheumatoid arthritis (RA) is an inflammatory joint disease characterized by persistent synovitis and inflammation. The exact mechanism of mitochondrial function in the presence of inflammation and dysregulation of autophagic processes in the pathogenesis of RA is still unclear. The aim of our study is to determine mitochondrial function, gene and protein levels of biomolecules related to inflammation (YKL-40) and autophagy (LAMPs) and to search a connection between them in the RA context. Twenty newly diagnosed RA patients and ten healthy individuals were included in the study. Disease severity was assessed by ultrasonography. Conventional clinico-laboratory parameters, immunological markers and protein levels of LAMPs and YKL-40 were examined in plasma. Gene expression analysis for the quantitative measurement of LAMPs and YKL-40 were conducted in white blood cells (WBC). A real-time metabolic analysis was performed to assess mitochondrial function and cell metabolism in peripheral blood mononuclear cells (PBMCs). Increase in spare respiratory capacity in PBMCs of RA patients was detected. Decreased LAMPs plasma protein levels and increased protein levels of YKL-40 in RA patients compared to healthy individuals were measured. No significant differences were found in gene expressions. Correlations between mitochondrial, ultrasonographic and protein levels of the biomarkers related with inflammation and autophagy were established. New data on mitochondrial dysfunction in RA patients and links to inflammation and mitophagy are reported. The relationship between dysregulation of mitophagy and joint diseases deserves to be thoroughly investigated as it would be a promising therapeutic approach.