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INFLAMMATION, IMMUNOPHARMACOLOGY, AND ASTHMA

Serotonin 5-Hydroxytryptamine_2A Receptor Activation Suppresses Tumor Necrosis Factor--Induced Inflammation with Extraordinary Potency

Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, Louisiana

The G protein-coupled serotonin 5-hydroxytryptamine (5-HT)_2A receptor is primarily recognized for its role in brain neurotransmission, where it mediates a wide variety of functions, including certain aspects of cognition. However, there is significant expression of this receptor in peripheral tissues, where its importance is largely unknown. We have now discovered that activation of 5-HT_2A receptors in primary aortic smooth muscle cells provides a previously unknown and extremely potent inhibition of tumor necrosis factor (TNF)--mediated inflammation. 5-HT_2A receptor stimulation with the agonist (R)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane [(R)-DOI] rapidly inhibits a variety of TNF--mediated proinflammatory markers, including intracellular adhesion molecule 1 (ICAM-1), vascular adhesion molecule 1 (VCAM-1), and interleukin (IL)-6 gene expression, nitric-oxide synthase activity, and nuclear translocation of nuclear factor B, with IC₅₀ values of only 10 to 20 pM. It is significant that proinflammatory markers can also be inhibited by (R)-DOI hours after treatment with TNF-. With the exception of a few natural toxins, no current drugs or small molecule therapeutics demonstrate a comparable potency for any physiological effect. TNF--mediated inflammatory pathways have been strongly implicated in a number of diseases, including atherosclerosis, rheumatoid arthritis, psoriasis, type II diabetes, depression, schizophrenia, and Alzheimer's disease. Our results indicate that activation of 5-HT_2A receptors represents a novel, and extraordinarily potent, potential therapeutic avenue for the treatment of disorders involving TNF--mediated inflammation. Note that because (R)-DOI can significantly inhibit the effects of TNF- many hours after the administration of TNF-, potential therapies could be aimed not only at preventing inflammation but also treating inflammatory injury that has already occurred or is ongoing.

Address correspondence to: Dr. Charles D. Nichols, Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, 1901 Perdido St., New Orleans, LA. E-mail: cnich1{at}lsuhsc.edu

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				I. Bab and R. Yirmiya Depression, Selective Serotonin Re-Uptake Inhibitors and the Regulation of Bone Mass IBMS BoneKEy, January 1, 2009; 6(1): 8 - 15. [Abstract] [Full Text] [PDF]