INTERLEUKIN-6 IN INTACT AND INJURED MOUSE PERIPHERAL-NERVES

The multifunctional cytokine interleukin 6 (IL-6) has direct growth, s urvival and differentiation effects on peripheral and central neurons. Furthermore, it can modulate the production by non-neuronal cells of other cytokines and growth factors, and thereby affect nerve cells ind irectly. We have studied IL-6 expression and production in intact and injured peripheral nerves of C57/BL/6NHSD mice, which display the norm al rapid progression of Wallerian degeneration. The IL-6 mRNA was dete cted in nerves degenerating in vitro or in vivo, but not in intact ner ves. In vitro- and in vivo-degenerating nerve segments and neuroma ner ve segments synthesized and secreted IL-6. The onset of IL-6 productio n was rapid and prolonged. It was detected as early as 2 h after injur y and persisted for the entire period of 21 days tested after the inju ry. Of the non-neuronal cells that reside in intact and injured nerves , macrophages and fibroblasts were the major contributors to IL-6 prod uction. We also studied IL-6 production in intact and injured nerves o f mutant C57BL/6-WLD/OLA/NHSD mice, which display very slow progressio n of Wallerian degeneration. Injured nerves of C57BL/6-WLD/OLA/ NHSD m ice produced significantly lower amounts of IL-6 than did rapidly dege nerating nerves of C57/BL/6NHSD mice.