Experimental silicosis does not aggravate collagen-induced arthritis in mice

Robby Engelmann, Brigitte Müller-Hilke

To investigate the effect of chronic lung inflammation on the incidence and severity of collagen-induced arthritis in mice. Chronic lung inflammation in the form of silicosis was induced via intranasal application of silica particles. Immunization with collagen Type II commenced one week later and mice were sacrificed six weeks after booster immunization. Thereafter, silicosis was confirmed via flow cytometry and arthritis was evaluated performing knee and paw histology. Pronounced lung inflammation in the silica-treated compared to PBS-treated control mice was demonstrated by significantly elevated broncho-alveolar lavage (BAL) cell count, attributable to increased numbers of macrophages and granulocytes. Inflammation in the lungs was not associated with elevated PAD2 and PAD4 expression, yet silica treated animals had significantly higher aCCP serum titers. However, lung inflammation did not lead to an increase in the incidence of arthritis, nor did it exacerbate the macroscopic or histologic joint scores. Chronic lung inflammation resulting from silicosis does not aggravate collagen-induced arthritis in mice.