Quercetin, but not its metabolite quercetin-3-glucuronide, exerts prophylactic immunostimulatory activity and therapeutic antiinflammatory effects on lipopolysaccharide-treated mouse peritoneal macrophages ex vivo.

This study investigated the prophylactic or therapeutic effects of quercetin (Q) and its metabolite quercetin-3-glucuronide (Q3G) on lipopolysaccharide (LPS)-induced inflammation in mouse peritoneal macrophages ex vivo. Changes in pro- and antiinflammatory cytokine secretion profiles were determined. The results showed that Q or Q3G in vitro treatments lower than 50 μM did not exhibit cytotoxicity on macrophages. At noncytotoxic doses, Q and Q3G, particularly Q, administration in a prophylactic ex vivo model increased pro-/antiinflammatory cytokine secretion ratios by macrophages in the absence or presence of LPS. Quercetin, but not Q3G, administration in a therapeutic ex vivo model decreased pro-/antiinflammatory cytokine secretion ratios in the absence or presence of LPS. Our results indicated that Q and Q3G administrations in a prophylactic manner might act as an immunostimulatory agent, but Q presented better ability than Q3G. Quercetin might have a therapeutic, but not prophylactic, effect on spontaneous or LPS-induced inflammation in vivo.