Hachem Jean-Pierre, Crumrine Debra, Fluhr Joachim, Brown Barbara E, Feingold Kenneth R, Elias Peter M
University of California San Francisco Medical Center, Department of Dermatology, San Francisco, California, USA.
J Invest Dermatol. 2003 Aug;121(2):345-53. doi: 10.1046/j.1523-1747.2003.12365.x.
Both exposure of stratum corneum to neutral pH buffers and blockade of acidification mechanisms disturb cutaneous permeability barrier homeostasis and stratum corneum integrity/cohesion, but these approaches all introduce potentially confounding variables. To study the consequences of stratum corneum neutralization, independent of hydration, we applied two chemically unrelated superbases, 1,1,3,3-tetramethylguanidine or 1,8-diazabicyclo [5,4,0] undec-7-ene, in propylene glycol:ethanol (7:3) to hairless mouse skin and assessed whether discrete pH changes alone regulate cutaneous permeability barrier function and stratum corneum integrity/cohesion, as well as the responsible mechanisms. Both 1,1,3,3-tetramethylguanidine and 1,8-diazabicyclo [5,4,0] undec-7-ene applications increased skin surface pH in parallel with abnormalities in both barrier homeostasis and stratum corneum integrity/cohesion. The latter was attributable to rapid activation (<20 min) of serine proteases, assessed by in situ zymography, followed by serine-protease-mediated degradation of corneodesmosomes. Western blotting revealed degradation of desmoglein 1, a key corneodesmosome structural protein, in parallel with loss of corneodesmosomes. Coapplication of serine protease inhibitors with the superbase normalized stratum corneum integrity/cohesion. The superbases also delayed permeability barrier recovery, attributable to decreased beta-glucocerebrosidase activity, assessed zymographically, resulting in a lipid-processing defect on electron microscopy. These studies demonstrate unequivocally that stratum corneum neutralization alone provokes stratum corneum functional abnormalities, including aberrant permeability barrier homeostasis and decreased stratum corneum integrity/cohesion, as well as the mechanisms responsible for these abnormalities.
角质层暴露于中性pH缓冲液以及酸化机制的阻断均会扰乱皮肤渗透屏障的稳态以及角质层的完整性/内聚力，但这些方法均引入了潜在的混杂变量。为了独立于水合作用来研究角质层中和的后果，我们将两种化学性质不相关的超强碱，即1,1,3,3-四甲基胍或1,8-二氮杂双环[5,4,0]十一碳-7-烯，以丙二醇：乙醇（7:3）的比例涂抹于无毛小鼠皮肤上，并评估单独的离散pH变化是否调节皮肤渗透屏障功能和角质层完整性/内聚力，以及相关机制。1,1,3,3-四甲基胍和1,8-二氮杂双环[5,4,0]十一碳-7-烯的应用均使皮肤表面pH升高，同时伴随着屏障稳态和角质层完整性/内聚力的异常。后者归因于丝氨酸蛋白酶的快速激活（<20分钟），通过原位酶谱法评估，随后是丝氨酸蛋白酶介导的角质桥粒降解。蛋白质印迹法显示，关键的角质桥粒结构蛋白桥粒芯糖蛋白1降解，同时伴随着角质桥粒的丧失。将丝氨酸蛋白酶抑制剂与超强碱共同应用可使角质层完整性/内聚力恢复正常。超强碱还延迟了渗透屏障的恢复，这归因于通过酶谱法评估的β-葡萄糖脑苷脂酶活性降低，导致电子显微镜下的脂质加工缺陷。这些研究明确表明，仅角质层中和就会引发角质层功能异常，包括异常的渗透屏障稳态和角质层完整性/内聚力降低，以及导致这些异常的机制。
