Loss of AKAP12 aggravates rheumatoid arthritis-like symptoms and cardiac damage in collagen-induced arthritis mice.

A-kinase anchoring protein 12 (AKAP12) has been identified as an anti-inflammatory and anti-fibrotic regulator in chronic inflammation and cardiovascular disease. However, the potential of AKAP12 in autoimmune disorders, rheumatoid arthritis (RA) and associated cardiac complications remains elusive. Here, a murine model of collagen-induced arthritis (CIA) was successfully induced, followed by adenovirus-mediated AKAP12 short hairpin RNA (shRNA) treatment. AKAP12 silenced mice displayed elevated clinical arthritis scores and significant ankle joint swelling. AKAP12 loss in CIA mice increased inflammatory cell infiltration and cartilage erosion, increased the levels of anti-IIC IgG and inflammatory cytokines IL-1β, IL-6, tumor necrosis factor (TNF)-α in serum, and upregulated the expression of cartilage-degrading enzymes MMP-1, MMP-3, MMP-13 in synovium, but reduced IL-10. The number of M1 macrophages and the expression of the markers (CCR7, IL-6, TNF-α and iNOS) was enhanced in synovial tissues, while M2 polarized macrophages and the makers (IL-10 and arginase-1) were reduced in response to AKAP12 loss. Moreover, low expression of AKAP12 was detected in the hearts of CIA mice. Loss of AKAP12 results in increased cardiac inflammation and fibrosis. This work suggests that AKAP12 loss aggravates joint inflammation likely through the promotion of M1 macrophage polarization and exacerbates inflammation-caused cardiac fibrosis.