Alleviative Effects of Tea (Camellia sinensis) on Experimentally-Induced Arthritis in Male Albino Rats

Abstract

Keywords: anti-inflammatory/antioxidant activities; articular/extra articular manifestations; Camellia sinensis; cytokines/chemokine receptor-5; indomethacin;rat adjuvant-induced arthritis.

Rheumatoid arthritis (RA) is a systemic inflammatory auto-immune disease that affects predominantly the synovial jointscausing joints damage and several extra-articular complications.Tea (Camellia sinensis)is consumed mostly in Egypt as black tea (rich in theaflavins and thearubigins) or green tea (rich in catechins). Tea has recently received much attention in alternative/complementary medicine owing to their various beneficialactivities, especially its antioxidant and anti-inflammatory activities. This study aimed toevaluate and comparethe prophylactic/therapeutic abilities of two different doses of green and black tea aqueous extract (GTE and BTE, respectively) with indomethacin (one of non-steroidal anti-inflammatory drugs) in alleviating articular/extra-articular complications in rat adjuvant-induced arthritis (AIA). Furthermore, the current study examined any deleterious/toxic effects caused by tea consumption in healthy rats.Arthritis was induced by a single intra-dermal injection of 0.1 mL of complete Freund’s adjuvant (containing deadMycobacterium tuberculosis) into the palmar surface of the left hind paw after the rats were subjected to light diethyl ether anaesthesia. Arthritic rats received orally/daily distilled water as vehicle,1.0 mg/kg body weight (b.w) of indomethacin, 0.5 g/kg b.w (low dose) of either GTE or BTE, or 1.0 g/kg b.w (high dose) of either GTE or BTEfor 28 consecutive days (from the day of arthritis induction, day 0). Other arthritic animals received orally/daily the low or high doseof either GTE or BTE for 14 consecutive days (from the day of arthritis onset, day 15). The present study showed that only the high dose of GTE (from day 0)significantly alleviated(p<0.05-0.001), as indomethacin,almost all the articular/extra-articular complicationsshown in arthritic rats including the loss in the body weight gain, synovial joints inflammation (oedema and erythema), changes in the weight/cellularity of lymphoid organs, blood leucocytosis(due to lymphocytosis and neutrocytosis),the increase in erythrocyte sedimentation rate, normocytic/normochromic anaemia, and oxidative stress in hepaticand ankle joint tissues. These protective effects of GTE were mediated through increasing the food intake, improvement the enzymic/non-enzymic antioxidant system and hence decreasing tissue lipid peroxidation,and alleviatingthe systemic inflammation that occur at the appearance of polyarthritis by decreasing the systemic production of pro-inflammatory cytokines and the expression of chemokine receptor-5 in synovial tissues. Moreover, the antiarthritic activity of tea was in the following order: High dose of GTE > low dose of GTE  high dose of BTE > low dose of BTE. No harmful effects were detected for tea consumption on all parameters measured in the healthy control rats, except that teainduced leucopenia that resulted from lymphopenia. In conclusion, the present study proved the antiarthritic activity of GTE over BTE and equalto that of indomethacin and suggested that drinking adequate amounts of GTE(5 cups daily) may be effective in prevention/alleviation the RA severity/complications as shown in an AIA rat model.