A CCR-5 antagonist inhibits the development of adjuvant arthritis in rats

Sir, Chemokine receptor CCR5 is preferentially expressed on Th1 lymphocytes and has been reported to have important roles in the pathogenesis of rheumatoid arthritis (RA). Yang et al. [1] demonstrated that a CCR5 antagonist inhibits the development of arthritis in the collagen-induced arthritis (CIA) model in mice. They showed that the inhibition of the development of arthritis is not caused by affecting the generation of collagen-sensitized T cells but by interfering with their migration to joint lesions. Recently, Vierboom et al. [2] reported the interesting finding that a CCR5 antagonist inhibited the development of CIA in rhesus monkeys. They showed that systemic administration of a small molecular weight antagonist of CCR5, SCH-X, suppressed the development of CIA in a monkey model of rheumatoid arthritis (RA). Rheumatoid arthritis is a chronic, destructive, inflammatory, polyarticular joint disease, characterized by massive synovial proliferation and subintimal infiltration of inflammatory cells, followed by the destruction of cartilage and bone. In the pathogenesis of RA, inflammatory cytokines such as IL-6 and TNF-α play important roles and this chronic inflammation results in cellular damage of affected joints [3, 4]. Chemokines are involved in the process of leucocyte transmigration into sites of inflammation. CCR5 and CXCR3 are expressed on Th1 cells, and CCR4 and CCR3 on Th2 cells [5, 6]. Evidence shows that RA is a Th1-dominant disorder and that CCR5- and/or CXCR3-expressing cells are enriched in affected joints of RA patients [7, 8]. We now provide evidence showing that systemic administration of TAK-779, a non-peptide compound with a small molecular weight (Mr 531.13) [9], inhibits the development of adjuvant-induced arthritis (AIA) in rats. Seven-week-old female Lewis rats were obtained from Charles River Japan (Yokohama, Japan). Complete Freund's adjuvant (CFA) was prepared by suspending heat-killed Mycobacterium butyricum (Difco Laboratories, Detroit, MI, USA) in liquid paraffin at 10 mg/ml. CFA-induced arthritis was stimulated by injection of 100 μl of the CFA emulsion intradermally at the base of the left paw. TAK-779 was obtained from Takeda (Osaka, Japan). Treatment commenced at the onset of the disease; TAK-779 (once a day) and phosphate-buffered saline (PBS) as a control (once a day) were administered intravenously at the specified doses until 7 days after the onset of arthritis. Each group comprised 10 female Lewis rats. TAK-779 was freshly suspended in 1.0% methyl cellulose (MC) PBS. In each experiment, a group of rats was administered 1.0% MC PBS orally, which served as a control. At days 1, 7 (onset of arthritis), 8, 11 and 14 after immunization, rats were examined for AIA using two clinical parameters: paw swelling and clinical score. The footpad volume was measured with a plethysmometer (TK-101; Unicom Japan, Tokyo, Japan). For clinical evaluation of AIA, we used the following scoring system: ear, forelimb, non-treated hind-limb, and tail were scored 0–5: 0 = normal; 1 = minimal swelling; 2 = mild swelling; 3 = moderate swelling; 4 = severe swelling; 5 = severe and non-weight-bearing arthritis. Each limb was graded, resulting in a maximum clinical score of 20 per animal, as described previously [10]. For histological evaluation, we performed haematoxylin and eosin staining of tissue specimens of the ankle. Ethical approval was not required for this study as it was an entrusted work by Nihon Bioresearch. The Mann–Whitney U-test was used to compare non-parametric data for statistical significance. As shown in Fig. 1, TAK-779 suppressed the progression of clinical arthritis compared with control rats treated with PBS, as demonstrated by paw volume and arthritis score (Fig. 1A). In TAK-779-treated rats, statistically significant effects were observed with higher doses (P<0.01). By day 18, histological analysis of the ankle joint in rats treated with TAK-779 at 1 mg/kg/day, rats treated with TAK-779 at 2 mg/kg/day and control rats (PBS) show that TAK-779 inhibited mononuclear cell infiltration and pannus formation in synovial tissue (Fig. 1B). Histology of a normal rat joint at this age is also shown in Fig. 1B. There was no mortality and no body weight loss in TAK-779-treated rats. These data suggest that TAK-779 has anti-arthritis effects in vivo. Suppression of arthritis development by TAK-779 in an adjuvant-induced arthritis model. (A) TAK-779 suppressed the progression of clinical arthritis compared with control rats treated with PBS, as demonstrated by paw volume and arthritis score. The data are mean ± s.d. *P<0.05; **P<0.01. (B) Histological findings of the foot joint in a normal rat, a TAK-779-treated rat (1 mg/kg/day), a TAK-779-treated rat (2 mg/kg/day) and a control rat (PBS). These results further support the evidence shown by others that CCR5 plays an important role in the development of arthritis in animal models of human RA. Taken together, the results show that therapy with CCR5 antagonists may serve as a new strategy for the treatment of RA. The authors have declared no conflicts of interest.