Murine epidermal Langerhans cells and keratinocytes express functional P2X7 receptors

Extracellular ATP via the activation of purinergic P2 receptors has an emerging role in cutaneous biology; however, the distribution of these receptors in mouse skin is poorly defined. This study investigated whether murine epidermal cell subpopulations express functional purinergic P2X₇ receptors. P2X₇ expression was examined by immunoblotting and immunofluorescence staining of epidermal cells from C57Bl/6 mice. P2X₇ function was evaluated by nucleotide-induced ethidium⁺ uptake measurements in epidermal cells from C57Bl/6 mice, and from P2X₇ deficient mice and wild-type littermate controls. P2X₇ was detected in whole epidermal cell preparations, and specifically on Langerhans cells (LCs) and keratinocytes (KCs). ATP induced ethidium⁺ uptake into LCs and KCs, with EC₅₀ values of 503 and 482 μm, respectively. BzATP, and to a lesser extent ATPγS and ADP, also induced ethidium⁺ uptake; while UTP, αβ-meth-ATP and NAD were ineffective. ATP-induced ethidium⁺ uptake was impaired by Na⁺ and Mg²⁺, and the P2X₇ antagonist, A-438079 and was absent in LCs and KCs from P2X₇ deficient mice. These results demonstrate that murine LCs and KCs express functional P2X₇, and support a role for this receptor in cutaneous biology.