Injury to the peripheral nervous system (PNS) initiates a response controlled by multiple extracellular mediators, many of which contribute to the development of neuropathic pain. Schwann cells in an injured nerve demonstrate increased expression of LDL receptor–related protein–1 (LRP1), an endocytic receptor for diverse ligands and a cell survival factor. Here we report that a fragment of LRP1, in which a soluble or shed form of LRP1 with an intact α-chain (sLRP-α), was shed by Schwann cells in vitro and in the PNS after injury. Injection of purified sLRP-α into mouse sciatic nerves prior to chronic constriction injury (CCI) inhibited p38 MAPK activation (P-p38) and decreased expression of TNF-α and IL-1β locally. sLRP-α also inhibited CCI-induced spontaneous neuropathic pain and decreased inflammatory cytokine expression in the spinal dorsal horn, where neuropathic pain processing occurs. In cultures of Schwann cells, astrocytes, and microglia, sLRP-α inhibited TNF-α–induced activation of p38 MAPK and ERK/MAPK. The activity of sLRP-α did not involve TNF-α binding, but rather glial cell preconditioning, so that the subsequent response to TNF-α was inhibited. Our results show that sLRP-α is biologically active and may attenuate neuropathic pain. In the PNS, the function of LRP1 may reflect the integrated activities of the membrane-anchored and shed forms of LRP1.
Alban Gaultier, Sanja Arandjelovic, Xiaoqing Li, Julie Janes, Nikola Dragojlovic, George P. Zhou, Jenny Dolkas, Robert R. Myers, Steven L. Gonias, W. Marie Campana