Neuro-immune interactions: the concept of Yin Yang for reinnervation and induction of neuropathic pain
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| Year of publication | 2012 |
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| Description | In Asian philosophy, the concept of yin yang is used to describe how seemingly contrary forces are interconnected and interdependent in the natural world, and how they give rise to each other in turn. Opposites thus only exist in relation to each other. Wallerian degeneration is a cascade of stereotype cellular events and molecular alterations in distal reaction to injury of nerve fibers. These events consist of Schwann cells activation, immune cells invasion, up-regulation of neurotrophins and cytokines. The processes prepare essentially conditions for regeneration of damaged axons and restoration of their connections. The invaded macrophages remove myelin debris containing non-permissive molecules for axon growth and activated Schwann cells up-regulate neurotrophins and other molecules supporting axon growth. In addition, activated Schwann cells, recruited macrophages and invaded immune cells produce inflammatory mediators like cytokines and chemokines. Therefore, Wallerian degeneration is considered to be neuroinflammation preparing conditions for neuropathic pain induction. Thus, cellular and molecular events distal to nerve injury prepare simultaneously conditions for both axon regeneration and neuropathic pain induction. The activated Schwann cells are robust source for neurotrophins and immune mediators like cytokines and chemokines. However, interrelations of neurotrophins and immune mediators and their possible complementary, synergistic or antagonistic involvements in axon regeneration and/or neuropathic pain induction are recently obscure. Some recent knowledge on this topic is stressed. Both beneficial and detrimental effects of the immune signal molecules like cytokines, chemokines and transcription factors distal to nerve injury have to be considered in a strategy of axon regeneration promotion on one side and suppression of the initial stages of neuropathic pain on other side. |
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