Curcumin mediates both dilation and constriction of peripheral arterioles via adrenergic receptors

Curcumin has wound healing attributes mediated through a plethora of biological activities that in general are not ascribed to specific receptors. Recently, we have demonstrated that intravenous administration of curcumin limits burn injury progression in a rat model. As decreased microvascular perfusion is a central element of burn injury progression, we hypothesized that curcumin may induce vasodilation in peripheral arterioles, to improve perfusion. Using mucosal microcirculation as an in situ assay, cheek pouch tissue was exteriorized in anesthetized (phentobarbital 70 mg kg^-1 intraperitoneal) male hamsters (N60) to observe the terminal feed arterioles (8 m diameter) and the immediately upstream arcade arterioles (20 m). Curcumin (10 12-10 4 mol l 1) was applied dose-wise (micropipette, 60 seconds). Subnanomolar curcumin dilated, whereas micromolar doses constricted, the arterioles. For the terminal arteriole: vasodilation logEC 50 10.30.2, peak dilation 391%; vasconstriction logEC 50 8.00.4, peak constriction 142%. Simultaneous atropine (muscarinic antagonist) or PD142893 (endothelin antagonist) had no effect. Propranolol (Β-adrenergic receptor (Β-Ad) antagonist) enhanced constriction by removing the vasodilation response to curcumin. Phentolamine (α-adrenergic receptor (α-Ad) antagonist) enhanced dilation to curcumin by removing the vasoconstriction response. Thus, the curcumin vasomotor activity on microcirculation was α-Ad and Β-Ad receptor-dependent and its net vasoactive effect was concentration- and time-dependent.