Orange-red light attenuates inhibition of proliferation of rat fibroblasts induced by ultraviolet-A

Excessive UV radiation suppresses processes important for normal functioning of tissues [1, 2]. Therefore, a topical problem is studying the factors which protect cells from the negative effects of UV radiation. One of such factors may be illumination with light of orange-red range of the spectrum [2‐4]. The primary skin-muscular fibroblasts were isolated from 15-day-old embryos of SHR rats with the SPF status (the nursery of Shemyakin‐Ovchinnikov Institute of Bioorganic Chemistry (Pushchino Branch), Russian Academy of Sciences, Pushchino). The suspension of fibroblasts was placed in tissue culture flasks impermeable to UV-A and orange‐red light (ORL). After one day of incubation, the medium with unadhered cells was removed and the adhered fibroblasts were cultured untill formation of a monolayer in DMEM (ICN) supplemented with glutamine, HEPES, and fetal calf serum. The cells were kept in an incubator at 37°C in a 5% CO 2 atmosphere. The fibroblasts of the 4th to 8th passages were used in the experiments. The adhered cells were detached with the use of a mixture of trypsin and Versen (Pan Eko), counted, and placed in flasks for illumination with ORL (0.9‐3.6 J/cm 2 ) or UV-A (0.27‐1.08 J/cm 2 ) or their combinations. A matrix with light-emitting Luxeon Star diodes (Lumileds) with λ m = 625 nm and a light flux intensity of 5.5 mW/cm 2 was used as source of ORL. An MD-108 irradiator (Germany) with λ M = 365 nm and a light flux intensity of 2.5 mW/cm 2 was used as a UV-A source. The suspension of fibroblasts was distributed with the use of pipette in 96-well plates for analysis of the proliferation rate. Each well with culture medium contained 10 4 cells. The fibroblasts were stained with thiazolyl blue 48 and 72 h after illumination. The cells were additionally incubated for 1 h and, then, the medium in the wells was replaced with dimethylsulfoxide. The optical density of the cells was determined with the use of a Spectra Count spectrophotometer (Packard, Germany). Analysis of the fibroblast proliferation 48 h after illumination showed that ORL had a stimulatory effect at a dose of 0.9 J/cm 2 (Fig. 1), which is in agreement