A selective p38α mitogen-activated protein kinase inhibitor reverses cartilage and bone destruction in mice with collagen-induced arthritis

Destruction of cartilage and bone is a poorly managed hallmark of human rheumatoid arthritis (RA). p38 Mitogen-activated protein kinase (MAPK) has been shown to regulate key proinflammatory pathways in RA, including tumor necrosis factor alpha, interleukin (IL)-1 beta, and cyclooxygenase-2, as well as the process of osteoclast differentiation. Therefore, we evaluated whether a p38 alpha MAPK inhibitor, indole-5-carboxamide (SD-282), could modulate cartilage and bone destruction in a mouse model of RA induced with bovine type II collagen [collagen-induced arthritis (CIA)]. In mice with early disease, SD-282 treatment significantly improved clinical severity scores, reduced bone and cartilage loss, and reduced mRNA levels of proinflammatory genes in paw tissue, including IL-1 beta, IL-6, and cyclooxygenase-2. Notably, SD-282 treatment of mice with advanced disease resulted in significant improvement in clinical severity scoring and paw swelling, a reversal in bone and cartilage destruction as assessed by histology, bone volume fraction and thickness, and three-dimensional image analysis. These changes were accompanied by reduced osteoclast number and lowered levels of serum cartilage oligomeric matrix protein, a marker of cartilage breakdown. Thus, in a model of experimental arthritis associated with significant osteolysis, p38 alpha MAPK inhibition not only attenuates disease progression but also reverses cartilage and bone destruction in mice with advanced CIA disease.