Therapeutic Effect of Pentoxifylline and Glycyrrhiza glabra on Antigen Induced Arthritis in mice

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized by joint swelling, joint tenderness, and destruction of synovial joints, leading to severe disability and premature mortality. RA represents the most common form of chronic inflammatory joint diseases; it affects approximately 1-2 % of world’s population. Pentoxifylline (PTX) is a member of Methylxantine family, which reduces both the production and action of cytokines such as TNF-α .Glycyrrhiza glabra (G. glabra) was widely known to have Antioxidative and other pharmacological activities. Oxidative stress is one of several mechanisms involved in RA pathogenesis.
Aim of the study: 1-To study the effect of pentoxifylline on antigen induced arthritis model in mice. 2- To study the effect of aqueous extract of G.glabra on antigen induced arthritis model in mice. 3- To investigate if there is synergism between pentoxifylline and G.glabra on antigen induced arthritis in mice. Materials and Methods
Eighty-four (84) male Swiss albino mice were used in this study. Animals were divided into seven groups each of 12 mice as follows: Group (1) Arthritic mice without treatment (positive control),Group (2) Arthritic mice treated with PTX 40 mg / kg/day ,Group (3) Arthritic mice treated with PTX 500 mg / kg/day, Group (4) Arthritic mice treated with G. glabra aqueous extract 750mg / kg/day ,Group (5) Arthritic mice treated with G. glabra aqueous extract 300 mg / kg/day ,Group ( 6 ) Arthritic mice treated with both G. glabra aqueous extract 750mg / kg/day and PTX 500 mg / kg/day(combination group), Group (7) negative control (nonimmunized, non-treated mice). Mice were immunized subcutaneously with 100-μg Methylated bovine serum albumin (mBSA) in Imject Alum adjuvant. Immunization done on day zero and booster dose were given at day 7 also by subcutaneous injection. Arthritis was induced by injection of 100 μg of the mBSA mixed with the adjuvant, in the left Knee joint at day 21 of experiment. All mice were weighed, and the drugs were measured according to the weight of each mouse. The mice were given the drug orally and the treatment was started from day 1 of the induction of arthritis until day 20, which is the end of the experiment. At day 20 of arthritis (day 41 of experiment), all mice were sacrificed and blood was collected by cardiac puncture. Serum TNF-α and IL-10 were measured using ELISA technique. Biopsies of the left knee joint were taken for histopathological evaluation of arthritis. In addition, clinical evaluation of arthritis was done for each arthritic animal from day 1 of
disease up to day 20. Clinical scores were measured in days (1 – 20) after induction of arthritis. PTX reduced clinical score in dose dependent manner (p<0.05). G. glabra also seems to reduce clinical score in dose dependent manner (p<0.05). The combination of G.glabra + PTX caused a significant reduction in clinical score in comparison with mice given each drug alone (p<0.05). TNF-α level analysis done on day 20 of arthritis showed that PTX caused reduction of serum TNF-α level in a dose dependent manner (p<0.05). G.glabra also reduced serum TNF-α level in dose dependent manner (p<0.05). The combination of G.glabra and PTX have potentiation effect on reduction of serum TNF-α level in the present study (p<0.05). Interlukine-10 serum analysis done on day 20 of the Arthritis induction indicates that PTX elevate serum IL-10 level in dose dependent manner (p<0.05). IL-10 serum analysis also showed that G.glabra caused elevation of serum IL-10 in dose dependent manner (p<0.05). The combination of PTX and G. glabra produced synergistic effect on the elevation of serum IL-10 level (p<0.05). Pentoxifylline seem to reduce the histopathological score in present model of arthritis in dose dependent manner (p<0.05). G. glabra also reduce the histopathological score in dose dependent manner (p<0.05).Mice given the combination of G.glabra + PTX showed a significant reduction in the mean histopathological score in comparison with mice given each drug alone (p<0.05).
1-Both Pentoxifylline and Glycyrrhiza glabra can reduce progression of clinical and histological score of antigen-induced arthritis in mice in dose dependent manner. 2- Both Pentoxifylline and G. glabra caused significant reduction of clinical and histopathological features of antigen-induced arthritis in mice. 3- Both Pentoxifylline and G. glabra caused significant reduction of serum TNF-α concentration and significant elevation of IL-10 serum concentration. 4- Pentoxifylline and G. glabra have potentiative inhibitory effect on mice antigen-induced arthritis model more than each one alone. 5-It is seem that Pentoxifylline and G. glabra alleviate antigen-induced arthritis possibly through inhibition of action of proinflammatory cytokines and antioxidative effect of each one or both respectively