Purinergic receptors are part of a functional signaling system for proliferation and differentiation of human epidermal keratinocytes.
We investigated the expression of P2X5, P2X7, P2Y1 and P2Y2 receptor subtypes in normal human epidermis and in relation to markers of proliferation (PCNA and Ki-67), keratinocyte differentiation (cytokeratin K10 and involucrin) and markers of apoptosis (TUNEL and anticaspase-3). Using immunohistochemistry, we showed that each of the four receptors was expressed in a spatially distinct zone of the epidermis, suggesting different functional roles for these receptors. Functional studies were performed on primary cultures of human keratinocytes and on explanted rat skin, where different P2 receptor subtype agonists and antagonists were applied to cultured keratinocytes or injected subcutaneously into the skin, respectively. An increase in cell number was caused by low doses of the nonspecific P2 receptor agonist ATP, the P2Y2 receptor agonist UTP (p<0.001), and the P2Y1 receptor agonist 2MeSADP (p<0.05). There was a significant decrease in cell number as a result of treatment with the P2X5 receptor agonist ATPgammaS (p<0.001) and the P2X7 receptor agonist BzATP (p<0.001). Suramin caused a significant block in the effect of 100 microm ATP (p<0.01) and 1000 microm ATP (p<0.001) on cell number. These results imply that different purinergic receptors have different functional roles in the human epidermis with P2Y1 and P2Y2 receptors controlling proliferation, while P2X5 and P2X7 receptors control early differentiation, terminal differentiation and death of keratinocytes, respectively.
Greig
Aina V H
AV
Autonomic Neuroscience Institute, Royal Free and University College Medical School, Royal Free Campus, Rowland Hill Street, London, UK.
Linge
Claire
C
Terenghi
Giorgio
G
McGrouther
D Angus
DA
Burnstock
Geoffrey
G
D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002454:Cell Differentiation; D002455:Cell Division; D002478:Cells, Cultured; D000078404:Epidermal Cells; D004817:Epidermis / Q000033:anatomy & histology / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D007279:Injections, Subcutaneous; D015603:Keratinocytes / Q000166:cytology*; D008297:Male; D058913:Purinergic Agonists; D051381:Rats; D017208:Rats, Wistar; D011983:Receptors, Purinergic / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058485:Receptors, Purinergic P2X5; D058486:Receptors, Purinergic P2X7; D058472:Receptors, Purinergic P2Y1; D058473:Receptors, Purinergic P2Y2; D015398:Signal Transduction; D014018:Tissue Distribution
D015415:Biomarkers; C546465:P2RX5 protein, human; C546468:P2RX7 protein, human; C546382:P2RY1 protein, human; C546385:P2RY2 protein, human; C546467:P2rx5 protein, rat; C546470:P2rx7 protein, rat; C546384:P2ry1 protein, rat; C546387:P2ry2 protein, rat; D058913:Purinergic Agonists; D011983:Receptors, Purinergic; D018048:Receptors, Purinergic P2; D058485:Receptors, Purinergic P2X5; D058486:Receptors, Purinergic P2X7; D058472:Receptors, Purinergic P2Y1; D058473:Receptors, Purinergic P2Y2