Dual role for noradrenergic innervation of lymphoid tissue and arthritic joints in adjuvant-induced arthritis

The-role of noradrenergic innervation in the disease outcome of adjuvant-in duced arthritis (AA) has been examined following (1) systemic administratio n of guanethidine and (3) local application of 6-hydroxydopamine (6-OHDA) i nto the lymph nodes that drain the hind limbs (DLN). Sympathetic denervatio n by these different neurotoxins produced directionally opposite effects on disease outcome. These conflicting findings could be explained from differ ential denervation of sympathetic nerves in key target tissues that result from different routes of neurotoxin administration. Alternatively, these co nflicting data could be due to differences in the mechanisms by which guane thidine and 6-OHDA destroy sympathetic nerve terminals. In this study, we c ompared disease outcome in AA following systemic and local DLN application of 6-OHDA to determine whether the route of administration is important to the development and progression of AA. Bilateral local DLN application of 6 -OHDA or vehicle was performed 1 day before injection of Freund's complete adjuvant (CFA) to induce arthritis. For systemic denervation, 6-OHDA or veh icle was given by ip injections on days 1, 3, and 5 prior to CFA challenge and then once a week. Local DLN application of 6-OHDA resulted in significa nt increases in dorsoplantar width in arthritic rats by 27 days following C FA treatment compared to those of non-denervated arthritic rats. In contras t, systemic denervation in arthritic rats significantly decreased dorsoplan tar widths 27 days after CFA treatment compared to those:in sympathetically intact arthritic animals. It-ray analysis confirmed these findings. Furthe r, local DLN application of 6-OHDA exacerbated the disease regardless of wh ether the neurotoxin was administered prior to immunization with CFA or clo ser to the time of disease onset. Our findings indicate that the route of 6 -OHDA administration for denervation of sympathetic innervation is an impor tant parameter in determining disease outcome, presumably due to differenti al sympathetic denervation of target tissues that are involved in disease d evelopment and progression. 6-OHDA administration into local DLN denervated these lymph nodes, but spared sympathetic innervation of the hind Limbs, a pattern of sympathetic denervation that resulted in disease exacerbation. In contrast, systemic 6-OHDA administration which denervated both the arthr itic joints and the secondary lymphoid organs attenuated the severity of AA . This study supports a dual role for NA innervation in modulating the seve rity of AA by innervation of the arthritic joints and lymphoid organs. (C) 1999 Academic Press.