Small but powerful: short peptide hormones and their role in autoimmune inflammation.

In the recent years, it has become increasingly clear that the immune response is also influenced by mediators which were first discovered as regulators in the nervous or also cardiovascular system. Here, small peptide hormones may play an important role. Kinins like bradykinins act on the endothelium and play a role for trafficking of lymphocytes over the blood-brain barrier. Neuropeptides like vasoactive intestinal peptide or neuropeptide Y also directly act on T cells and favour the differentiation of Th2 cells or regulatory T cell populations. Recently, the renin-angiotensin system (RAS) came into the focus of interest. Inhibition of the RAS at different levels may influence autoimmune responses and involve T cells as well as antigen-presenting cells, probably via different signalling pathways. Inhibitors of angiotensin converting enzyme and antagonists of the angiotensin 1 receptors are used in the treatment of hypertension, kidney disease or stroke by millions of people worldwide. These inexpensive and safe pharmaceuticals may also represent an interesting and innovative approach for the (combination) treatment of autoimmune diseases like multiple sclerosis.