Study of the Possible Potential Role of Testosterone in Modulating Collagen-Induced Arthritis in Castrated Male Albino Rats

Rheumatoid arthritis (RA) is a chronic, inflammatory, systemic autoimmune disease that affects about 1% of the general population. Experimental and clinical evidence inditnfcates that immune reactivity is greater in females than in males and suggests that gonadal steroids may play an important role in the regulation of the immune response. Collagen-induced arthritis (CIA) is an experimental autoimmune mediated poly-arthritis that is well accepted in different types of rodents. The aim of the present work is to study the effects of testosterone deprivation, induced by castration of male albino rats, and inhibition of aromatase- induced conversion of androgen into estrogen on the severity of collagen induced arthritis evaluated by peripheral total lymphocytic count, T-and B - lymphocytic count, monocytic counts, plasma levels of tumor necrosis factor-α (TNF-α ), prostaglandin E2 (PGE2), immunoglobulin G(IgG), rheumatoid factor (RF,) and the level of TNF-α in the synovial fluid. The severity of collagen-induced arthritis was also histopathologically assessed. Materials and Methods: 48 adult male albino rats were randomly divided into 3 groups. Group I (control group, n=8 rats) which represented the placebo group, Group II (sham-operated, CIA, n=8 rats) in which rats were injected with collagen type II to induce CIA, and Group III (castrated group, n=32 rats) in which bilateral orchiectomy was performed and rats were subdivided into four subgroups, each included 8 rats; Group III-A (control castrated group) which represented the control group of castrated rats, Group III-B (castrated CIA group) in which CIA was induced in the rats, five days after bilateral orchiectomy, Group III-C (testosterone treated castrated- CIA) in which CIA was induced in rats five days after bilateral orchiectomy and the rats were injected with testosterone oenanthate (Cidotestone) at a dose of 6.25mg/kg, and Group III-D (Letrozol and testosterone treated- castrated-CIA group): In which CIA was induced five days after bilateral orchiectomy and treated with testosterone injection and co-supplemented with non-steroidal aromatase inhibitor. After 35 days, starting from CIA induction, immediately before animals were sacrificed, blood samples were withdrawn from retro-orbital plexus for determination of blood total lymphocyte count, T-lymphocyte, B-lymphocyte, and monocyte counts, plasma TNF-α , RF, PGE2, IgG. Also TNF-α in synovial fluid was measured. The severity of collagen- induced arthritis was also histopathologically assessed. Results: Collagen- induced arthritis in sham operated male albino rats (group II) resulted in significant (p 0.05) increases in the mean values of peripheral blood total lymphocytic count, T-lymphocyte, B-lymphocyte, and monocyte counts, significant (p 0.05) increases in the mean values of plasma levels of TNF-α , PGE2, IgG, RF, and synovial fluid level of TNF-α , and significant (p 0.05) increase in histopathological score of arthritic injury. Plasma testosterone level was insignificantly changed compared to group I. Testosterone deprivation, in group IIIA, resulted in significant (p 0.05) increases in the mean values of peripheral blood total lymphocytic count, T-lymphocyte, B-lymphocyte, and monocyte counts, significant (p 0.05) increases in the mean values of plasma levels of TNF-α , PGE2, and synovial fluid level of TNF-α , insignicant (p 0.05) changes of the mean values of plasma levels of RF, IgG and histopathological score of arthritic injury compared to control rats (group I). Induction of CIA in castrated rats (group IIIB) produced significant (p 0.05) increases in the mean values of total lymphocytic count, T-lymphocyte, B-lymphocytes, and monocyte counts, significant (p 0.05) increases in the mean values of plasma levels of TNF-α , PGE2, and synovial fluid level of TNF-α while the mean values of IgG and RF were insignificantly (p 0.05) changed, and significant increase in histopathological score of arthritic injury compared to group II. Induction of CIA in castrated male rats with testosterone replacement (group IIIC) produced significant decreases in the mean values of total lymphocytic count, T-lymphocyte, B-lymphocyte, and monocyte counts, significant (p 0.05) decreases in the mean values of plasma levels of TNF-α , PGE2, and synovial fluid level of TNF-α , while the mean values of plasma levels of IgG and RF were insignificantly (p 0.05) changed, and significant decrease in histopathological score of arthritic injury compared to group IIIB. Induction of CIA in castrated rats treated with testosterone replacement and aromatase inhibition (group IIID) resulted in significant decreases in the mean values of total lymphocytic count, T-lymphocyte, B-lymphocyte, and monocyte counts significant (p 0.05) decreases in the mean values plasma levels of TNF-α , PGE2, and synovial fluid level of TNF-α while the mean values of IgG and RF were insignificantly (p 0.05) changed compared to group III C. and significant decrease in histopathological score of arthritic injury compared to group IIIC. Androgen deprivation aggravates collagen induced arthritis in male rats. Although androgen replacement therapy improved pro-inflammatory and histopathological changed of CIA in castrated rats, yet androgen therapy for male patients with rheumatoid arthritis are not recommended because of the risks of androgen therapy especially in old patient. Androgen therapy is also not recommended since aromatase-induced estrogens synthesis; include pro-inflammatory and anti-inflammatory metabolites, which are present at relatively low levels in RA synovial fluid. Blockade of TNF-α induced up-regulation of aromatase would particularly increase the level of androgens in males, leading to a better clinical outcome.