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. Author manuscript; available in PMC: 2015 Apr 1.
Published in final edited form as: JAMA Dermatol. 2014 Apr;150(4):401–406. doi: 10.1001/jamadermatol.2013.8417

Figure 1. Exposure of lightly pigmented human skin to UVA1 irradiation causes skin darkening, induction of matrix metalloproteinases, and suppression of procollagens in a dose-dependent fashion.

Figure 1

Skin pigmentation was measured using a color meter (chromameter) under the L* variable (luminescence), which ranges from 0 (black) to 100 (white). Lightly pigmented (L*>65) buttock skin of healthy human subjects (n=10) was exposed to the indicated doses of UVA1 irradiation. (a) Changes in skin pigmentation were measured 24 hours later (L* value, n=10). (b) Additionally, skin samples (4 mm) were obtained 24 hours following exposure, and real-time polymerase chain reaction was performed to assess gene expression of matrix metalloproteinase (MMP)-1, MMP-3, type I procollagen (COL-I), and type III procollagen (COL-III) (all n=10). The housekeeping gene acidic ribosomal phosphoprotein P0 (36B4) was used as an internal control. Data are presented as mean fold change + SEM. Asterisk (*) over bars, p<0.05 compared with no UVA1 irradiation. Asterisk (*) over bracket, p<0.05 when comparing response to different UVA1 doses.