Distribution of Inducible Nitric Oxide Synthase and Tumor Necrosis Factor-α in the Peripheral Nervous System of Lewis Rats during Ascending Paresis and Spontaneous Recovery from Experimental Autoimmune Neuritis

Abstract

Background: Inducible nitric oxide synthase (iNOS) and tumor necrosis factor-α (TNF-α) are pleiotropic molecules with widespread action in autoimmune diseases. Objective: This study characterizes the distribution of iNOS and TNF-α in the spinal nerve roots, dorsal root ganglia and sciatic nerve of Lewis rats during experimental autoimmune neuritis (EAN). Methods: Macrophages and neutrophils were identified by immunofluorescence as cellular sources of iNOS and TNF-α at various stages of EAN induced by synthetic peptide 26. Results: As the disease progressed, iNOS- and TNF-α-bearing cells gradually infiltrated the cauda equina, dorsal root ganglia, Th12–L3 spinal roots, and the sciatic nerve. A severer EAN profile developed when more iNOS- and TNF-α-bearing cells were present, and the recovery from EAN was related to the disappearance of these cells and the regeneration of nerve fibers. Conclusions: This is the first report to show iNOS- and TNF-α-immunoreactive cells in dorsal root ganglia during EAN, suggesting an underlying pathology for the neuropathic pain behavior in EAN. Our results suggest that the cells bearing iNOS and TNF-α in the different parts of the peripheral nervous system are involved in the development of the clinical signs observed at each stage of EAN.