Kanekura T, Laulederkind S J, Kirtikara K, Goorha S, Ballou L R
Department of Medicine, College of Medicine, University of Tennessee, Memphis, USA.
J Invest Dermatol. 1998 Oct;111(4):634-9. doi: 10.1046/j.1523-1747.1998.00340.x.
In this study, we examined the effects of cholecalciferol, a primary keratinocyte metabolite and precursor of the hydroxylated form of vitamin D3, 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3], on prostaglandin E2 (PGE2) production in human keratinocytes by examining its respective effects on cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and cytosolic phospholipase A2 (cPLA2) expression, the rate-limiting enzymes regulating PGE2 biosynthesis and differentiation of keratinocytes. Cholecalciferol induced PGE2 production, whereas 1alpha,25(OH)2D3 had no effect on PGE2 production both in normal human epidermal keratinocytes and in the immortalized human keratinocyte cell line, HaCaT. In HaCaT cells, neither COX-1 mRNA nor protein was detectable without stimulation and COX-1 expression did not increase in response to cholecalciferol treatment. Although cPLA2 mRNA and protein were constitutively expressed in untreated HaCaT cells, expression levels did not increase in response to cholecalciferol treatment; however, unlike COX-1 and cPLA2 expression, COX-2 mRNA and COX-2 protein expression increased in response to cholecalciferol treatment. Calphostin C, a potent protein kinase C inhibitor, significantly reduced cholecalciferol-induced PGE2 production by inhibiting cholecalciferol-enhanced COX-2 mRNA and protein expression. These results indicate that (i) 1alpha,25(OH)2D3 does not induce PGE2 biosynthesis in keratinocytes, (ii) cholecalciferol-induced PGE2 production is primarily COX-2 dependent, and (iii) cholecalciferol enhances both COX-2 mRNA and protein expression, via a protein kinase C-dependent mechanism in human keratinocytes. Furthermore, cholecalciferol increased total cellular transglutaminase activity dose dependently, suggesting a potential role for cholecalciferol in regulating the differentiation of human keratinocytes.
在本研究中，我们通过检测胆钙化醇（一种主要的角质形成细胞代谢产物及维生素D3的羟基化形式1α,25 - 二羟基维生素D3 [1α,25(OH)2D3]的前体）对环氧化酶 - 1（COX - 1）、环氧化酶 - 2（COX - 2）和胞质磷脂酶A2（cPLA2）表达的各自影响，研究了其对人角质形成细胞中前列腺素E2（PGE2）产生的影响，这些酶是调节PGE2生物合成及角质形成细胞分化的限速酶。胆钙化醇诱导PGE2的产生，而1α,25(OH)2D3在正常人表皮角质形成细胞和永生化人角质形成细胞系HaCaT中对PGE2的产生均无影响。在HaCaT细胞中，未刺激时检测不到COX - 1 mRNA和蛋白，且胆钙化醇处理后COX - 1表达未增加。虽然cPLA2 mRNA和蛋白在未处理的HaCaT细胞中组成性表达，但胆钙化醇处理后其表达水平未增加；然而，与COX - 1和cPLA2表达不同，胆钙化醇处理后COX - 2 mRNA和COX - 2蛋白表达增加。强效蛋白激酶C抑制剂钙泊三醇通过抑制胆钙化醇增强的COX - 2 mRNA和蛋白表达，显著降低了胆钙化醇诱导的PGE2产生。这些结果表明：（i）1α,25(OH)2D3不诱导角质形成细胞中PGE2的生物合成；（ii）胆钙化醇诱导的PGE2产生主要依赖COX - 2；（iii）胆钙化醇通过人角质形成细胞中依赖蛋白激酶C的机制增强COX - 2 mRNA和蛋白表达。此外，胆钙化醇剂量依赖性地增加了总细胞转谷氨酰胺酶活性，提示胆钙化醇在调节人角质形成细胞分化中可能发挥作用。
