Koizumi H, Ohkawara A
Department of Dermatology, Hokkaido University School of Medicine, Sapporo, Japan.
Arch Dermatol Res. 1996 Sep;288(10):611-4. doi: 10.1007/BF02505264.
Cultured normal human epidermal keratinocytes show an increase in doubling time with increasing passage number and finally the cells show growth arrest. This is known as senescence of cultured cells. However, the mechanisms governing senescence of cells remain to be clarified. Stimulation from outside the cell and the response to the stimulation are important essential initial events for cell function. Alteration of intracellular Ca2+ is one of the essential responses of cells to stimulation from outside. Thus we studied whether cultured normal human epidermal keratinocytes show a modulation of the alteration of intracellular Ca2+ during senescence. Epinephrine and histamine induced transient increases in intracellular Ca2+ in the third to eighth passages in normal human epidermal keratinocytes. With increase in the passage number the responsiveness (the number of responding cells per examined cells) decreased particularly beyond the sixth passage. The attenuation of the responses was more obvious with epinephrine than with histamine. All-trans-retinoic acid and 1,25-dihydroxyvitamin D3 did not augment the responsiveness to epinephrine of normal human epidermal keratinocytes. We expected that such an essential and immediate reaction would be confined to living cells, and that during senescence cells would show reduced responsiveness. Some of the changes during senescence of cultured keratinocytes may be due to the attenuation of the responsiveness to stimulation through the cell membrane.
培养的正常人表皮角质形成细胞随着传代次数的增加，倍增时间延长，最终细胞出现生长停滞。这被称为培养细胞的衰老。然而，细胞衰老的调控机制仍有待阐明。细胞外刺激以及细胞对该刺激的反应是细胞功能重要的初始基本事件。细胞内Ca2+的变化是细胞对细胞外刺激的基本反应之一。因此，我们研究了培养的正常人表皮角质形成细胞在衰老过程中细胞内Ca2+变化是否受到调节。肾上腺素和组胺可诱导正常人表皮角质形成细胞在第3至8代时细胞内Ca2+出现短暂升高。随着传代次数的增加，反应性（每检测细胞中反应细胞的数量）降低，尤其是在第6代之后。肾上腺素引起的反应减弱比组胺更明显。全反式维甲酸和1,25-二羟基维生素D3并未增强正常人表皮角质形成细胞对肾上腺素的反应性。我们预期这种基本且即时的反应仅限于活细胞，并且在衰老过程中细胞的反应性会降低。培养的角质形成细胞衰老过程中的一些变化可能是由于对通过细胞膜的刺激反应性减弱所致。
