Lack of causal relationship between inducibility/severity of adjuvant arthritis in the rat and disease associated changes in production of nitric oxide by macrophages

Reactive oxygen species (ROS), but not nitric oxide (NO), contribute to strain differences in the susceptibility to experimental arthritis in rats

There is extensive evidence for the critical role of reactive oxygen species (ROS) and nitric oxide (NO) produced by phagocytes in development of inflammatory processes and pathogenesis of numerous diseases, including rheumatoid arthritis (RA). Apart from their function as mediators of inflammation and tissue damage, recent research supports their role as signaling and regulatory molecules. In the present study we have investigated the production of ROS and NO over the course of adjuvant arthritis (AA) and oil-induced arthritis (OIA), by resident peritoneal macrophages of two rat strains: Dark Agouti (DA), susceptible, and Albino Oxford (AO), resistant to induction of AA and OIA. We have compared levels of ROS and NO produced by susceptible vs. resistant rat strain, and investigated their relevancy for arthritis development and severity. In addition, we have stimulated macrophages in vitro with Mycobacterium bovis BCG, and two heat shock proteins (HSP): endogenous HSP47 and mycobacterial HSP71 (mHSP71). Our results suggest a possible contribution of increased ROS production to arthritis resistance of AO rats. The ROS production in AO rats is potentiated by endogenous HSP47, but not with mycobacterial cell and mHSP71, suggesting HSP47 participates in AA control. We have found no fundamental relationship between the magnitude of NO production and AA and OIA susceptibility and severity, suggesting that NO has no effector role in AA and OIA. Our results advocate a regulatory type action of NO molecule might be more significant in arthritis development.

Thermal hyperalgesia and light touch allodynia after intradermal Mycobacterium butyricum administration in rat

We examined the time course (7 weeks) of thermal hyperalgesia and light touch allodynia in rats after intradermal administration of Mycobacterium butyricum. Nociceptive thresholds to heat and light touch were assessed. Paw edema and temperature, motor function, body weight, and propioception were also tested. Some rats developed arthritis (named AA rats) but others did not (named non-AA rats). Both groups were compared with healthy animals. Persistent hyperalgesia was found in both groups; in AA rats it appeared before clinical evidence of arthritis. Transient allodynia ocurred only after edema development and fell when edema decreased. Motor function was impaired only in AA rats. The results of this study demonstrate that hyperalgesia, but not allodynia, appeared after Mycobacterium butyricum in both groups, suggesting that changes in sensitivity were not merely the result of local hypersensitivity of the inflamed tissue, but may also be due to alterations in nociception in the central nervous system.

Genetic variation in in-vitro cytokine-induced production of nitric oxide by murine peritoneal macrophages

Quantitative aspects of the in-vitro interferon (IFN)-gamma-induced nitric oxide (NO) production by peritoneal macrophages of eight inbred strains of mice were investigated. Animals employed in the study can be assorted into three phenotype categories: high, moderate, and low NO-responders. Concentration of nitrites in the 24-h supernatants of cells stimulated with recombinant murine IFN-gamma (25 U/ml) reached the following values (mean +/- SEM; in microM): C57BL/10 (33.7+/-1.88) = C57BL/6 (32.1+/-2.10) > SIL (24.0+/-1.55) > CBA/J (18.1+/-1.79) = C3H/HeN (18.0+/-1.10) > DBA/2 (11.4+/-1.16) = DBA/1 (11.0+/-1.20) = Balb/c (11.0+/-1.16). Approximately 80% of the total variation was found to be controlled by genetic factors. No association between the extent of NO formation and variation in the constitutive expression of macrophage IFN-gamma receptor was observed. Similar magnitude of inter-strain differences was sustained after enhanced NO-stimulation of the cells with IFN-gamma + tumour necrosis factor (TNF)-alpha, but only high (strains BL/10, BL/6, SJL, CBA/J, C3H/HeN) and low (DBA/1, DBA/2, Balb/c) NO-responder phenotypes were detected after the triple cytokine cocktail composed of IFN-gamma + TNF-alpha + interleukin (IL)-10. The strain differences remained unchanged after the supplementation of culture medium with L-arginine or tetrahydrobipopterin. Genetically governed differences in IFN-gamma-induced NO production have been found to be tightly associated with differential expression of inducible nitric oxide synthase mRNA. Possible implications of the findings for various fields of NO biomedical research are discussed.

Activation of T Cells Recognizing an Epitope of Heat-Shock Protein 70 Can Protect Against Rat Adjuvant Arthritis

We have previously reported that CD4+ T cells recognizing a peptide comprising residues 234–252 of the heat shock protein (HSP)70 of Mycobacterium tuberculosis (M.tb) in the context of RT1.B MHC class II molecule emerged in the peritoneal cavity during the course of Listeria monocytogenes infection in rats and suppressed the inflammatory responses against listerial infection via IL-10 production. We report in this work that pretreatment with peptide 234–252 of HSP70 derived from M.tb suppressed the development of adjuvant arthritis (AA) in Lewis rats induced using heat-killed M.tb. T cells from rats pretreated with peptide 234–252 produced a significant amount of IL-10 in response to the epitope. T cells from rats pretreated with the peptide and immunized with M.tb produced the larger amount of IL-10 in response to the peptide, but only a marginal level of IFN-γ in response to purified protein derivative of M.tb. Administration of anti-IL-10 Ab partly inhibited the suppressive effect of pretreatment with peptide 234–252 on the development of AA. Furthermore, transfer of a T cell line specific for the epitope at the time of AA induction markedly suppressed AA. These findings suggested that T cells recognizing peptide 234–252 may play a regulatory role in inflammation during AA via the production of suppressive cytokines including IL-10.

Chemokines, nitric oxide and antiarthritic effects of 9-(2-phosphonomethoxyethyl)adenine (Adefovir)

Antiarthritic effects of two acyclic nucleoside phosphonates, 9-(2-phosphonomethoxyethyl)adenine (PMEA; Adefovir) and 9-(2-phosphonomethoxypropyl)adenine (PMPA), as well as their more bioavailable prodrugs, bis(pivaloyloxymethyl)ester of PMEA [bis(POM)-PMEA; Adefovir Dipivoxil] and bis(isopropyloxycarbonyloxymethyl)ester of PMPA [bis(POC)-PMPA], were investigated in a model of adjuvant-induced arthritis in Lewis rats. The drugs were injected subcutaneously at doses of 5-50 mg/kg. PMEA and its prodrug inhibited by > 80% arthritic paw swelling, splenomegaly and fibroadhesive perisplenitis. Both prophylactic and therapeutic dosing regimens were effective. Neither PMPA nor bis(POC)-PMPA suppressed development of arthritic lesions. Substantially reduced nitrite + nitrate levels were detected in serum and urine of PMEA-treated animals as compared to those of untreated diseased controls. Also, complete suppression of the disease-associated, greatly enhanced systemic levels of the chemokine, RANTES (regulated upon activation, normal T cell expressed and secreted), was observed in rats injected with PMEA. Additional in vitro studies showed that PMEA does not change, PMPA enhances, and both prodrugs inhibit the immune-activated NO production. Under the same conditions PMEA inhibits, while PMPA slightly stimulates, secretion of RANTES. Collectively, these data suggest that the in vivo-inhibited production of nitric oxide (NO) is a consequence rather than a mechanism of antiarthritic action of PMEA. Possible mechanisms for the anti-RANTES activity of PMEA remains to be firmly established.