Synovial fluids from rheumatoid and psoriatic arthritis patients have high levels of PLA1A. The current study was to understand PLA1A functions in the pathophysiology of rheumatic diseases. We generated Pla1a−/− mice to assess their phenotype and the impact of PLA1A deficiency on the development of mannan-induced psoriatic arthritis (MIP). Mice were evaluated routinely for the induced symptoms. On the day of sacrifice, blood samples were collected for hematology analysis and prepared for plasma. Livers were collected. Lymph node immune cells were analyzed using flow cytometry. We performed μCT scans of hind paws from naïve and mannan-induced female mice. Cytokines/chemokines were quantified using Luminex in hind paw tissues and plasma of female mice. Pla1a−/− mice showed a slight increase in circulating and lymph node lymphocytes. CD4+ T cells contributed most to this increase in lymph nodes (p = 0.023). In the MIP model, the lymph node ratios of CD3+ to CD19+ and CD4+ to CD8+ were higher in Pla1a−/− mice. Pla1a−/− mice were less susceptible to MIP (p < 0.001) and showed reduced bone erosions. Pla1a−/− mice also showed reduced IL-17, KC, IP-10, MIP-1β, LIF, and VEGF in hind paw tissues as compared to WT mice (p < 0.05). These findings indicated that PLA1A deficiency protected from the development of the MIP disease. The data suggested that PLA1A could contribute to MIP through increased activation of lymphocytes, possibly those producing IL-17.
Keywords: IL-17; bone erosions; cytokines; inflammation; lymphocytes; mannan; phospholipase A1A.