Abstract
Our previous studies have demonstrated that cold stress or water immersion stress suppresses splenic natural killer (NK) cytotoxicity and induces Fos expression in the hypothalamic paraventricular nucleus (PVN) and the brainstem locus coeruleus (LC) . It is well known that adjuvant-induced arthritis is inflammatory stress. This study was designed to investigate whether splenic NK cytotoxicity is suppressed in adjuvant-induced arthritic rats. Adjuvant arthritis was induced in Sprague-Dawley rats by a single subcutaneous injection of 0.1 ml complete Freund's adjuvant (CFA) into the right hind paw. After CFA injection we could observe the marked edema and inflammation in the paw. On days 3, 7, 14 and 21 after CFA injection, the splenic NK cytotoxicity was measured by 51chromium release assay, and Fos immunoreactivity in PVN and LC were detected. The results showed that the splenic NK cytotoxicity of adjuvant-induced arthritic rats significantly decreased compared with the control group, and the Fos expression in PVN increased significantly compared with the control group on days 3, 7, but without significant effect in PVN on days 14, 21 and in LC on days 3, 7, 14, 21. These results suggest that adjuvant-induced arthritis, inflammatory stress, also suppresses splenic NK cytotoxicity, and the mechanism of suppression of splenic NK cytotoxicity is different from that of cold stress or water immersion stress.
