Rat Adjuvant-Induced Arthritis (AIA)

All animal studies were approved by the ethics committee of the Washington State University and conformed to the NIH Guide for the Care the Use of Laboratory Animals (8th edition, 2011). Rat adjuvant arthritis studied was performed using similar parameters as described previously (14, 15). Briefly, ~120g female Lewis rats were purchased from Envigo (East Millstone, NJ) and allowed to acclimate for 1 week prior to start in campus vivarium accredited by the American Association for Accreditation of Laboratory Animal Care. On day 0, rats were administered 300 μl of 5 mg/ml lyophilized Mycobacterium butyricum (Difco Laboratories, Detroit, MI, USA) in sterile mineral oil subcutaneously at the base of the tail. Clinical parameters measured included articular index (AI) and ankle circumferences (AC) using parameters referenced in Ahmed et al. (14) AI scores were recorded for each hind joint by a consistent observer blinded to the treatment regimen and then averaged for each animal. AI scores were based on a 0–4 scale where 0 = no swelling or erythema, 1 = slight swelling and/or erythema, 2 = low to moderate oedema, 3 = pronounced edema with limited joint usage and 4 = excess oedema with joint rigidity. AC were also measured by the same blinded observer and the change in ankle circumference was presented as delta (Δ) ankle circumference. The Δ ankle circumferences of both the hind ankles from each animal were averaged and “n” is represented as the number of animals used in each of the experimental groups. Treatment of Animals with JWH-015.

JWH-015 was brought into suspension in phosphate buffered saline (PBS) with 3% DMSO. JWH-015 was administered daily via intraperitoneal injection (5 mg/kg) starting on day 9 after arthritis induction when the first signs of joint inflammation and swelling are usually noted and continued until day 17. On day 17, animals were sacrificed for biochemical, cytokine, and serum analysis.