Anti-rheumatic activities of linear polarized near-infrared irradiation on collgen-induced arthritis in rats

Abstract

The present investigation was carried out to study the anti-rheumatic activities of linear polarized near-infrared (NIR) irradiation on hind paw inflammation in rat collagen-induced arthritis (CIA) models. CIA rat was induced by immunization of female Lewis rats with intradermal injection of an emulsion of bovine type II collagen and incomplete Freund′s adjuvant. The animals were subdivided into the following groups: control group, CIA group and CIA rats plus NIR irradiation with NIR group (n=7). NIR group was applied on rat knee joint area and was irradiated third weekly for 12 weeks in NIR (600-1,600 nm) at a dose of 5 J/cm2 for 500 s. The hind paw swelling was assessed by the increase in hind paw thickness. The cutaneous temperature of the hind paws were analyzed by infrared thermography, calcaneus bone resorption was evaluated by measuring Micro-CT. The serum levels of the inflammatory cytokines and arthritic factor MMP-3 were determined by ELISA. In NIR group at 2 weeks after arthritis induction, swelling inhibition index was 39.1± 5.2%. The temperature of the hind paws decreased by NIR irradiation. NIR irradiation decreased bone erosion in rats and reduced the bone resorption in CIA rats. IL-1β, IL-6, CRP and MMP-3 serum levels were significantly lower in NIR group.