The effects of sialidase on the epidermal nerve fiber innervation during inflammatory pain

Abstract

Gangliosides are abundant sialic acids containing glycosphingolipids in neural tissues. We reported that intraplantar injection of ganglioside GT1b caused mechanical allodynia and Arthrobacter ureafaciens sialidase that degrades sialyl conjugates suppressed inflammatory pain. Moreover, F-11 cells (a cell line derived from the dorsal root ganglion neuron) treated with sialidase showed shortened neurites. Several studies reported that the number of nerve fibers in the epidermis is increased during skin inflammation. Thus, we investigated whether sialidase affected the epidermal nerve fiber innervation.

Sialidase injection into the inflamed hind paw of mice one day after injection of complete Freund's adjuvant decreased the length of epidermal nerve fibers. However, it is unclear that the localization of gangliosides in the nerve fibers in the skin tissues. Anti-GT1b antibody stained nerve fibers in the dermis near the epidermal-dermal junction during inflammation, whereas nerve fibers in the naïve hind paw showed poor staining with this antibody. These results indicate that skin inflammation leads to the accumulation of the gangliosides in the nerve fibers, which contributes to nerve fiber elongation.