Rheumatoid arthritis (RA) is an autoimmune disorder whose etiopathology involves an interplay between genetic and environmental factors, with oxidative stress being a key contributory factor. This study aimed to establish the impact, if any, of an oxidative, pro-inflammatory milieu upon trans-differentiation of neutrophils and disease progression. In the synovial fluid (SF) and peripheral blood sourced from patients with RA (n = 40) along with healthy controls (n = 25), the proportion of neutrophil-dendritic (N-DC) cell hybrids, i.e. CD66b+/CD83+ was characterized in terms of their antigen presentation (HLA-DR, CD80, andCD86) and cell adhesion and migration (ICAM-1, VCAM-1, and CD62L) properties, along with their ability to generate reactive oxygen species (ROS). In the SF of RA cases, the raised levels of circulating and intra-neutrophilic pro-inflammatory cytokines/chemokines were accompanied by an enhanced proportion of CD66b+ neutrophils, that co-expressed features of antigen presenting cells (APCs) namely CD83, HLA-DR, CD80, CD86, ICAM-1, VCAM-1, and decreased CD62L. These N-DCs as compared to canonical neutrophils demonstrated a higher generation of ROS, and their frequency positively correlated with disease activity score (DAS28). An ex-vivo functional assay validated that oxidative stress supported trans-differentiation and could be attenuated by a free radical scavenger. Taken together, the pro-inflammatory microenvironment in the SF of patients with RA coupled with a higher generation of ROS promoted the trans-differentiation of neutrophils into N-DCs, suggesting the inclusion of anti-oxidants as an add-on therapeutic strategy to limit trans-differentiation.
Keywords: Neutrophil-dendritic cell hybrids; oxidative stress; pro-inflammatory cytokines; reactive oxygen species; rheumatoid arthritis.