Potential anti-inflammatory effect of lemon and hot pepper extracts on adjuvant-induced arthritis in mice

Arthritis and related disorders, including rheumatoid arthritis (RA), are common diseases affecting millions of people. The present study aimed to investigate the therapeutic potential of lemon and hot pepper extracts on adjuvant induced arthritis (AIA) in mice. Arthritis was induced by injection of complete Freund adjuvant (CFA) subcutaneously at the planter surface of hind paw, the lemon and hot pepper extracts were administered subcutaneously at the same site twice weekly (100 mg/kg), for 2 weeks starting 2 days after CFA injection. Arthritic scores, erythrocyte sedimentation rate (ESR), C reactive protein (CRP), anti-nuclear antibody (ANA), tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6) and paw histopathology were assessed at the end of the experiment. The extract treatments reduced the severity of arthritic scores in the following order: lemon fruit peel (LFP) > lemon leaf (LL) > hot pepper leaf (HL) during the experimental period as compared with positive control (RA). LFP, LL and HL extracts significantly suppressed ESR, ANA, CRP and TNF-α as compared with RA group. HL, LFP and LL reduced the IL-1β by 63.02%, 47.22%, 44.92%, while IL-6 cytokine production significantly decreased by 29.74%, 28.96%, and 23.93% for IL 6 as compared with RA. Hot pepper fruit (HF) extract treated-group showed a significant decrease for ESR on the other hand there was non-significant difference for TNF-α, IL-6, IL1β, CRP and ANA as compared with RA. Histopathological examination indicated that LFP, LL and HL extracts alleviated infiltration of inflammatory cells and synovial hyperplasia as well as protected joint destruction. The data showed that all extracts except HF have significant anti-arthritic and anti-inflammation effects and suggest that these effects may be mediated via the suppression of pro-inflammatory cytokines.