Dietary anthocyanidin pelargonidin activates G protein-coupled receptor 35.

G protein-coupled receptors (GPCRs) are the largest superfamily of cell surface receptors. They regulate critical physiological events and serve as potential therapeutic targets. G protein-coupled receptor 35 (GPR35), a class A rhodopsin-like GPCR expressed in various tissues, including adipose tissue and the gastrointestinal tract, has roles in diverse functions, including antioxidant, anticarcinogenic, and anti-inflammatory effects. Although many endogenous and synthetic GPR35 agonists have been identified, the understanding of food-derived agonists is limited. In this study, we discovered pelargonidin as a newly identified food-derived GPR35 agonist through a systematic screening approach. We evaluated 28 dietary phytochemicals using a transforming growth factor α (TGFα) shedding assay to evaluate GPR35 activation, and found that cyanidin, a common 3-hydroxyanthocyanidin present in various red fruits and vegetables, induced GPR35 activation. Among a series of 3-hydroxyanthocyanidins tested, pelargonidin, characterized by its monohydroxylated B-ring, exhibited the most potent agonistic activity. Mutational studies demonstrated that the hydrogen bond between the 3-hydroxy group in the C-ring of pelargonidin and Asn169, as well as the hydrophobic interaction between the A-ring of pelargonidin and Phe163, is crucial for GPR35 activation. Furthermore, pelargonidin inhibited the production of interleukin-8, a pro-inflammatory cytokine, by activating endogenous GPR35 in Caco-2 cells. These findings suggest that GPR35 may serve as a potential receptor for dietary anthocyanidins, such as pelargonidin, and provide new insights into the molecular mechanisms underlying the potential chemopreventive effects of anthocyanidins.