Maytin E V, Murphy L A, Merrill M A
Cutaneous Biology Research Center, Department of Dermatology, Massachusetts General Hospital, Boston.
Cancer Res. 1993 Oct 15;53(20):4952-9.
Environmental exposure to UVB (290-320 nm) wavelengths of the solar spectrum causes major damage, including carcinogenesis, in the skin. Therefore, cellular responses that protect against UVB damage are of particular interest in cutaneous epithelial cells. In cultured keratinocytes, mild hyperthermia generates a classical stress response with acquired thermotolerance and elevated stress protein synthesis (E. V. Maytin, J. Biol. Chem., 267: 23189-23196, 1992). To test the ability of this stress response to protect against UVB damage, monolayers of primary murine keratinocytes or BALB/MK keratinocytes were heated at 42 degrees C for 1 h and then exposed to UVB at 6 h (typical dose, 40 mJ/cm2). Survival was assessed by fluorescein diacetate/ethidium bromide vital dye uptake and video microscopy. With heat-conditioning prior to UVB, a significant increase in both the percentage viability (2- to 3-fold) and in the absolute number of living (fluorescein diacetate-positive) cells was measurable at 24-48 h. Steady-state incorporation into [3H]DNA and 35S-protein, while suppressed immediately after UVB, showed greater recovery in heat-conditioned cultures compared to sham-conditioned cultures at 48 h. Increased metabolic activity was accompanied by increased proliferative potential since colonies of BALB/MK cells observed at 72 h were larger, more numerous, and more active in the uptake of 5-bromo-2'-deoxyuridine in heat-conditioned cultures. A time course for the development of UVB resistance showed maximal protection when heat and UVB were spaced approximately 6 h apart. Hyperthermic conditioning could induce UVB protection in nonproliferating cells, indicating that cell cycle arrest was not primarily responsible for the UVB-protective effect. In summary, hyperthermia induces a mechanism in epithelial cells which can ameliorate damage from UVB.
环境暴露于太阳光谱中的UVB（290 - 320纳米）波长会对皮肤造成重大损害，包括致癌作用。因此，针对UVB损伤的细胞保护反应在皮肤上皮细胞中备受关注。在培养的角质形成细胞中，轻度热疗会引发经典的应激反应，伴有获得性耐热性和应激蛋白合成增加（E. V. Maytin，《生物化学杂志》，267: 23189 - 23196，1992）。为了测试这种应激反应对UVB损伤的保护能力，将原代小鼠角质形成细胞或BALB/MK角质形成细胞单层在42℃加热1小时，然后在6小时后暴露于UVB（典型剂量，40 mJ/cm²）。通过荧光素二乙酸酯/溴化乙锭活性染料摄取和视频显微镜评估细胞存活率。在UVB照射前进行热预处理后，在24 - 48小时可测量到存活细胞百分比（提高2至3倍）和活细胞（荧光素二乙酸酯阳性）绝对数量均显著增加。虽然UVB照射后立即抑制了[³H]DNA和³⁵S蛋白的稳态掺入，但与假预处理培养物相比，在48小时时热预处理培养物的恢复程度更高。代谢活性增加伴随着增殖潜力增加，因为在72小时观察到的BALB/MK细胞集落在热预处理培养物中更大、更多，并且在摄取5 - 溴 - 2'-脱氧尿苷方面更活跃。UVB抗性发展的时间进程表明，当热疗和UVB间隔约6小时时保护作用最大。热预处理可在非增殖细胞中诱导UVB保护作用，表明细胞周期停滞并非UVB保护作用的主要原因。总之，热疗可在上皮细胞中诱导一种机制，减轻UVB造成的损伤。
