Aging and IL-6 immunoreactivity changes in the polychaete Ophryotrocha labronica

The aging process is associated with dysregulation of the immune and inflammatory responses including modifications in the regulation and production of cytokines. IL-6 is a pleiotropic pro-inflammatory cytokine thought to play a role in age physiology, even if its possible modulation by aging mechanisms has not been fully defined. The morpho-functional modifications and IL-6 immunoreactivity during the aging process in a simple invertebrate model, the polychaete Ophryotrocha labronica, are reported. The comparison between newly-hatched, juveniles (at 6-11 setigerous segments, max 2 weeks), young adult females (at 14 setigerous segments, about 3 weeks) and 3 month old females showed significant structural differences in the nervous and genital systems. A reduction in the nerve area with a substantial depletion in neurons of the central system was found. A decline in oocyte growth and maturation was observed at the gonad level, even if sexually mature O. labronica continued to produce egg mass until week 16 of their lives. The age induced morphological modifications were associated to a different distribution of IL6-like molecules, that were detected in the central nervous system. A decreased number of reactive nerve cells and in particular in the anterior region of the brain of aged O. labronica was observed.