Anti-Inflammatory Effects of ADAMTS-4 in a Mouse Model of Ischemic Stroke

ADAMTS-4 (a disintegrin and metalloproteinase with thrombospondin motifs type 4) is a metalloprotease capable to degrade chondroitin sulfate proteoglycans leading to cartilage destruction during arthritis or to neuroplasticity during spinal cord injury (SCI). Although ADAMTS-4 is an inflammatory-regulated enzyme, its role during inflammation has never been investigated. The aim of this study was to investigate the role of ADAMTS-4 in neuroinflammation. First, we evidenced an increase of ADAMTS-4 expression in the ischemic brain hemisphere of mouse and human patients suffering from ischemic stroke. Then, we described that ADAMTS-4 has predominantly an anti-inflammatory effect in the CNS. Treatment of primary microglia or astrocyte cultures with low doses of a human recombinant ADAMTS-4 prior to LPS exposure decreased NO production and the synthesis/release of pro-inflammatory cytokines including NOS2, CCL2, TNF-alpha, IL-1 beta and MMP-9. Accordingly, when cell cultures were transfected with silencing siRNA targeting ADAMTS-4 prior to LPS exposure, the production of NO and the synthesis/release of pro-inflammatory cytokines were increased. Finally, the feasibility of ADAMTS-4 to modulate neuroinflammation was investigated in vivo after permanent middle cerebral artery occlusion in mice. Although ADAMTS-4 treatment did not influence the lesion volume, it decreased astrogliosis and macrophage infiltration, and increased the number of microglia expressing arginase-1, a marker of alternatively activated cells with inflammation inhibiting functions. Additionally, ADAMTS-4 increased the production of IL-10 and IL-6 in the peri-ischemic area. By having anti-inflammatory and neuroregenerative roles, ADAMTS-4 may represent an interesting target to treat acute CNS injuries, such as ischemic stroke, SCI or traumatic brain injury.