Department of Dermatology, Kaohsiung Medical University Hospital, and College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Department of Medical Laboratory Science and Biotechnology, College of Health Science, Kaohsiung Medical University, Kaohsiung, Taiwan.
J Dermatol Sci. 2019 Apr;94(1):220-228. doi: 10.1016/j.jdermsci.2019.03.005. Epub 2019 Mar 28.
Ultraviolet A (UVA) radiation is the most relevant component of solar radiation-induced skin aging. Sunscreens were used to minimize the harmful effects of UV radiation on our skin by reducing UV irradiance. We previously found that at equivalent fluence, UVB radiation at low irradiance (LI) has higher photocarcinogenic potential as compared to its high irradiance (HI) counterpart.
To examine the effects of equivalent fluence of UVA radiation administered at different irradiance on photoaging.
Both the hairless mice (SKH-1) and human dermal fibroblasts were irradiated with high irradiance UVA (HIUVA) or low irradiance UVA (LIUVA; 50% irradiance of HIUVA) at equivalent fluence. Parameters related to skin photoaging were evaluated.
For hairless mice receiving equivalent fluence of UVA radiation, LIUVA treated mice showed prominent skin aging as compared to its HIUVA treated counterpart. In addition, LIUVA radiation induced higher reactive oxygen species (ROS) production and c-Jun N-terminal kinases (JNK) phosphorylation as compared to their HIUVA treated counterparts. Pretreatment with N-acetylcysteine (NAC) abrogate the difference between HI and LIUVA radiation on fibroblasts in terms of intracellular ROS, JNK phosphorylation, MMP-1 expression and type I collagen expression.
UVA radiation administered at LI (a scenario similar to sunscreen use) led to more severe aging process as compared to its HI counterpart. Unexpected negative effect may be imposed on the skin if sunscreen use is accompanied by longer duration spent under the sun.
紫外线 A（UVA）辐射是太阳辐射引起皮肤老化的最相关成分。防晒霜的使用通过减少紫外线辐照度来最小化紫外线辐射对我们皮肤的有害影响。我们之前发现，在等效剂量下，低辐照度（LI）的 UVB 辐射比其高辐照度（HI）的 counterpart 具有更高的光致癌潜力。
检查不同辐照度下给予等效剂量的 UVA 辐射对光老化的影响。
无毛小鼠（SKH-1）和人真皮成纤维细胞均用高辐照度 UVA（HIUVA）或低辐照度 UVA（LIUVA；HIUVA 的 50%辐照度）进行辐照，达到等效剂量。评估与皮肤光老化相关的参数。
对于接受等效剂量 UVA 辐射的无毛小鼠，与 HIUVA 处理的小鼠相比，LIUVA 处理的小鼠表现出明显的皮肤老化。此外，LIUVA 辐射诱导的活性氧（ROS）产生和 c-Jun N-末端激酶（JNK）磷酸化比 HIUVA 处理的小鼠更高。用 N-乙酰半胱氨酸（NAC）预处理可消除 HI 和 LIUVA 辐射对成纤维细胞在细胞内 ROS、JNK 磷酸化、MMP-1 表达和 I 型胶原表达方面的差异。
与 HI 相比，LI（类似于防晒霜使用的情况）下给予的 UVA 辐射导致更严重的老化过程。如果防晒霜的使用伴随着在阳光下停留的时间更长，可能会对皮肤造成意想不到的负面影响。
