Fisher G J, Talwar H S, Baldassare J J, Henderson P A, Voorhees J J
Department of Dermatology, University of Michigan Medical School, Ann Arbor 48109.
J Invest Dermatol. 1990 Oct;95(4):428-35. doi: 10.1111/1523-1747.ep12555582.
Evidence suggests that the phospholipase C/protein kinase C signal transduction system participates in the regulation of epidermal cell growth and differentiation. Psoriatic epidermis is characterized by hyperproliferation, defective differentiation, and inflammation. In this report, we have determined the activity of phospholipase C-catalyzed hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2) and 1,2-diacylglycerol content in normal and psoriatic involved and uninvolved epidermis. 1,2-diacylglycerol is formed from phospholipase C-catalyzed hydrolysis of PIP2 and is the physiologic activator of protein kinase C. PIP2 hydrolysis was assayed in soluble and particulate fractions prepared from keratome biopsies of normal and psoriatic skin. Total lipids were extracted from normal and psoriatic epidermis and 1,2-diradylglycerol (a mixture of 1,2-diacylglycerol and 1-ether, 2-acyl-glycerol) quantitated by enzyme assay. Because 1,2-diacylglycerol is a more potent activator of protein kinase C, the relative proportions of 1,2-diacyl and 1-ether, 2-acylglycerol in uninvolved and involved psoriatic epidermis were determined. This was accomplished by separation of acetate derivatives of 1,2-diacylglycerol and 1-ether, 2-acyl-glycerol by thin layer chromatography. Soluble and membrane-associated phospholipase C-catalyzed PIP2 hydrolysis were increased 3.7 times (p less than 0.001) and 3 times (p less than 0.004), respectively, in psoriatic involved compared to uninvolved and normal epidermis. 1,2-diradylglycerol content was also significantly elevated (3 times, p less than 0.01) in psoriatic involved versus uninvolved and normal epidermis. Analysis of the acetate derivatives of 1,2-diradylglycerol in psoriatic uninvolved and involved epidermis revealed that 1,2-diacylglycerol was the major species (86% and 95%, respectively). There were no significant differences in either phospholipase C-catalyzed PIP2 hydrolysis or 1,2-diacylglycerol content between uninvolved and normal epidermis. 1,2-diacylglycerol purified from normal and involved psoriatic epidermis was capable of activating protein kinase C from normal epidermis in vitro. In epidermal slices, activation of protein kinase C by addition of 12-0-tetradecanoylphorbol-13-acetate and 1,2-diacylglycerol (1,2-dioctanoylglycerol) resulted in subsequently decreased protein kinase C activity, a process termed down-regulation. These data are consistent with the possibility that the elevation in lesional 1,2-diacylglycerol content may account, in part, for the previously reported reduction of protein kinase C activity in psoriasis (Horn, Marks, Fisher, et al: J Invest Dermatol 88:220-222, 1987).
有证据表明，磷脂酶C/蛋白激酶C信号转导系统参与表皮细胞生长和分化的调节。银屑病表皮的特征是过度增殖、分化缺陷和炎症。在本报告中，我们测定了正常、银屑病累及和未累及表皮中磷脂酶C催化磷脂酰肌醇-4,5-二磷酸（PIP2）水解的活性以及1,2-二酰甘油的含量。1,2-二酰甘油由磷脂酶C催化PIP2水解形成，是蛋白激酶C的生理激活剂。通过对正常和银屑病皮肤角膜刀活检制备的可溶性和颗粒部分进行检测来测定PIP2水解。从正常和银屑病表皮中提取总脂质，并通过酶法对1,2-二烷基甘油（1,2-二酰甘油和1-醚、2-酰基甘油的混合物）进行定量。由于1,2-二酰甘油是蛋白激酶C更有效的激活剂，因此测定了银屑病未累及和累及表皮中1,2-二酰基和1-醚、2-酰基甘油的相对比例。这是通过薄层层析分离1,2-二酰甘油和1-醚、2-酰基甘油的乙酸酯衍生物来完成的。与未累及和正常表皮相比，银屑病累及表皮中可溶性和膜相关磷脂酶C催化的PIP2水解分别增加了3.7倍（p<0.001）和3倍（p<0.004）。银屑病累及表皮中1,2-二烷基甘油含量也显著升高（3倍，p<0.01），与未累及和正常表皮相比。对银屑病未累及和累及表皮中1,2-二烷基甘油的乙酸酯衍生物分析表明，1,2-二酰甘油是主要成分（分别为86%和95%）。未累及和正常表皮之间在磷脂酶C催化的PIP2水解或1,2-二酰甘油含量方面均无显著差异。从正常和银屑病累及表皮中纯化的1,2-二酰甘油能够在体外激活正常表皮中的蛋白激酶C。在表皮切片中，添加12-0-十四烷酰佛波醇-13-乙酸酯和1,2-二酰甘油（1,2-二辛酰甘油）激活蛋白激酶C后，蛋白激酶C活性随后降低，这一过程称为下调。这些数据与以下可能性一致，即皮损中1,2-二酰甘油含量的升高可能部分解释了先前报道的银屑病中蛋白激酶C活性的降低（霍恩、马克斯、费舍尔等人：《皮肤病学研究杂志》88:220-222，1987）。
