Anti-inflammatory properties of Liposome-encapsulated clodronate or Anti-Ly6G can be modulated by peripheral or central inflammatory markers in carrageenan-induced inflammation model

Overproduction of inflammatory markers by immune cells, such as macrophages and neutrophils, is one of the main reasons for many inflammatory conditions and inhibiting or suppressing of their production by cell depletion may provide new therapeutic targets or approaches to prevent a variety of inflammatory conditions. In this study, we examined the possible effects of anti-Ly6G-mediated systemic neutrophil depletion and liposome-encapsulated clodronate (LEC)-mediated systemic macrophage depletion on the inflammatory signs (thermal hyperalgesia, mechanical allodynia, oedema and fever) and measured the levels of various inflammation markers (tumour necrosis factor- (TNF-), interleukins (IL)-1, IL-4, IL-10, macrophage inflammatory protein-1 alpha (MIP-1/CCL3) and myeloperoxidase (MPO) in paw and spinal cord tissues in carrageenan (CG)-induced hindpaw inflammation model in rats. CG injection into the paw caused inflammation characterized by redness, swelling, heat and pain hypersensitivities. Anti-Ly6G or LEC significantly ameliorated the pain behaviours, and decreased the oedema and fever. Efficacies of anti-Ly6G or LEC on inflammatory responses changed depend on the degree of inhibition in inflammatory markers of inflamed paw or spinal cord. Anti-inflammatory properties of anti-Ly6G or LEC suggest that macrophages and/or neutrophil-mediated inflammatory cascade in inflamed site and spinal cord which can play key roles in inflammatory pain responses. These systemic or peripheral inflammatory mediators may be therapeutic targets in the treatment of many inflammatory conditions and related various diseases.