Toll-like receptor 2 signaling induces interferon regulatory factor 8 expression in spinal cord microglia after peripheral nerve injury

Abstract

Although it is well known that spinal cord microglia activation plays a causal role in the development of neuropathic pain after peripheral nerve injury (PNI), the mechanisms of this activation have not been completely elucidated. We have previously shown that toll-like receptor 2 (TLR2) is involved in PNI-induced spinal cord microglia activation. A more recent study showed that PNI induces interferon regulatory factor 8 (IRF8), which is a key transcription factor responsible for microglia activation. In this study, we investigated the putative role of TLR2 in IRF8 expression in spinal cord microglia after PNI. In TLR2 knockout mice, nerve injury-induced spinal cord IRF8 expression was severely compromised. In addition, an intrathecal injection of lipoteichoic acid (LTA), a TLR2 agonist, induced IRF8 mRNA expression in the spinal cord. Lastly, TLR2 stimulation by LTA induced IRF8 mRNA expression in primary spinal cord glial cells. TLR2-induced IRF8 expression was dependent on p38 MAPK and NF-κB activation. Taken together, these data show that TLR2 activation induces IRF8 expression in spinal cord microglia after PNI.