Adenosine A3 receptor

Class

A3 adenosine receptor agonist

The adenosine A3 receptor (A3AR) is a G protein-coupled receptor, one of four subtypes through which the endogenous nucleoside adenosine signals in the body. Adenosine accumulates in tissue under stress, injury, or excessive cell turnover, and acts locally to dampen inflammation and regulate cell survival. The A3 subtype is notable because it is expressed at low levels in most healthy tissue but becomes markedly upregulated in chronically activated immune cells and in certain tumor cells, largely because of persistent activity of the transcription factor NF-κB in those cells. This differential expression makes A3AR an attractive point of pharmacological intervention: an agonist (a molecule that activates the receptor) can, in principle, act preferentially where the receptor is overexpressed, producing anti-inflammatory or antiproliferative effects in diseased tissue while sparing normal cells. This rationale underlies interest in A3 agonists for chronic inflammatory and autoimmune conditions, such as inflammatory joint and skin disease, and for liver diseases including certain liver cancers and fatty liver conditions, where inflammatory and proliferative signaling overlap. Selectively targeting A3, rather than adenosine receptors broadly, is intended to avoid the cardiovascular and central nervous system effects associated with the other adenosine receptor subtypes, which have distinct and sometimes opposing physiological roles.