Mode of Action of Aspirin in Experimental Autoimmune Encephalomyelitis.

Multiple sclerosis (MS) is a chronic and debilitating autoimmune disorder of the central nervous system in which the autoimmune T cells destroy myelin, thus causing lesion, damage, and neuronal dysfunction. Experimental autoimmune encephalomyelitis (EAE) is an animal model of MS that is particularly useful for testing new therapeutic approaches against MS. Aspirin (acetyl salicylic acid) is one of the oldest and widely used medicines in the world, and recently it has been shown that low-dose aspirin is capable of suppressing the disease process of EAE in mice. One of the root causes of this autoimmune disease process is the decrease and/or suppression of Foxp3-expressing anti-autoimmune regulatory T cells (Tregs) and associated increase in autoimmune T-helper 1 (Th1) and Th17 cells. Aspirin upregulates Tregs and decreases Th1 and Th17 responses. Accordingly, the suppression of Tregs abrogates the protective effect of aspirin on EAE, indicating that aspirin protects EAE via Tregs. While there are several mechanisms for the maintenance of Tregs under immune insults, aspirin increases the level of interleukin-11 (IL-11), an immunomodulatory cytokine, and IL-11 alone is sufficient to protect Tregs. Being a multifunctional molecule, aspirin stimulates the activation of cAMP-response element-binding (CREB) to promote the recruitment of CREB to the IL-11 gene promoter and stimulate the transcription of IL-11 in splenocytes. Therefore, it appears that low-dose aspirin protects EAE via CREB-mediated stimulation of IL-11-Treg pathway and that aspirin may have therapeutic importance in MS.