The P2 purinergic receptors of human dendritic cells: identification and coupling to cytokine release

We investigated the expression of purinoceptors in human dendritic cells, p roviding functional, pharmacological, and biochemical evidence that immatur e and mature cells express P2Y and P2X subtypes, coupled to increase in the intracellular Ca2+ membrane depolarization, and secretion of inflammatory cytokines. The ATP-activated Ca2+ change was biphasic, with a fast release from intracellular stores and a delayed influx across the plasma membrane. A prolonged exposure to ATP was toxic to dendritic cells that swelled, lost typical dendrites, became phase lucent, detached from the substrate, and e ventually died. These changes were highly suggestive of expression of the c ytotoxic receptor P2X(7), as confirmed by ability of dendritic cells to bec ome permeant to membrane impermeant dyes such as Lucifer yellow or ethidium bromide. The P2X(7) receptor ligand 2',3'-(4benzoyl-benzoyl)-ATP was a bet ter agonist then ATP for Ca2+ increase and plasma membrane depolarization. Oxidized ATP, a covalent blocker of P2X receptors, and the selective P2X(7) antagonist KN-62 inhibited both permeabilization and Ca2+ changes induced by ATP. The following purinoceptors were expressed by immature and mature d endritic cells: P2Y(1), P2Y(2), P2Y(5), P2Y(11) and P2X(1), P2X(4), P2X(7). Finally, stimulation of LPS-matured cells with ATP triggered release of IL -1 beta and TNF-alpha. Purinoceptors may provide a new avenue to modulation of dendritic cells function.