Decreased neuropeptide-converting enzyme activities in cerebrospinal fluid during acute but not chronic phases of collagen induced arthritis in rats

Abstract We investigated the effects of collagen II-induced arthritis on two cerebrospinal fluid (CSF) enzymes converting dynorphin A and substance P (SP), namely dynorphin-converting enzyme (DCE) and substance P endopeptidase (SPE). The products generated by these enzymes are the bioactive fragments Leu-enkephalin-Arg 6 and substance P 1–7 , respectively. The strain used (DA rats) is very sensitive towards induction of arthritis. The collagen arthritis is a chronic autoimmune arthritis induced by native rat collagen type II (CII). Following intradermal injection of CII into the tailbase, CSF was sampled on day 21 (acute arthritis) and day 38 (chronic arthritis). Control rats were untreated because the strain used developed an acute adn self-limited arthritis (adjuvant arthritis) when administered vehicle (i.e. incomplete Freund's adjuvant). The DCE activity was significantly lowered in the acute phase of arthritis (P