Toxic Interaction Between Solar Radiation and Cigarette Smoke on Primary Human Keratinocytes

Abstract

Solar radiation and cigarette smoke are two environmental risk factors known to affect skin integrity. Although the toxic effects of these factors on skin have been widely studied separately, few studies have focused on their interaction. The objective of this study was to evaluate and understand the synergistic harmful effects of cigarette smoke and solar rays on human primary keratinocytes. The keratinocytes were exposed to cigarette smoke extract (CSE) and then irradiated with a solar simulator light (SSL). The viability, as determined by measuring metabolic activity of skin cells, and the levels of global reactive oxygen species (ROS) were evaluated after exposure to CSE and SSL. The combination of 3% CSE with 29 kJ m−2 UVA caused a decrease of 81% in cell viability, while with 10% to 20% CSE, the cell viability was null. This phototoxicity was accompanied by an increase in singlet oxygen but a decrease in type I ROS when CSE and SSL were combined in vitro. Surprisingly, an increase in the CSE's total antioxidant capacity was also observed. These results suggest a synergy between the two environmental factors in their effect on skin cells, and more precisely a phototoxicity causing a drastic decrease in cell viability.

The combination of cigarette smoke and solar rays causes effects similar to skin aging in a bilayer skin model

“…Epidemiological studies have also highlighted a possible interaction between UV exposure and cigarette smoking regarding wrinkle formation 13 . A previous study led by our group showed a significant synergy between cigarette smoke and solar rays in their effect on human keratinocytes, especially on cellular viability and oxidative stress via the production of type II ROS 14 . This led us to believe there would be a harmful effect on the skin, in particular the premature aging of the skin.…”

“…Fresh CSE was prepared each day as described previously 14 . Briefly, using an AGI-30 impinger (Ace Glass Inc., Vineland, NJ, USA), 3R4F reference cigarettes (Tobacco-Health Research Institute, University of Kentucky, Lexington, KY) connected to a 60 mL syringe by a 3-way stopcock were smoked by suction in 20 mL of 1X phosphate buffered saline (PBS) 14 .…”

“…Fresh CSE was prepared each day as described previously 14 . Briefly, using an AGI-30 impinger (Ace Glass Inc., Vineland, NJ, USA), 3R4F reference cigarettes (Tobacco-Health Research Institute, University of Kentucky, Lexington, KY) connected to a 60 mL syringe by a 3-way stopcock were smoked by suction in 20 mL of 1X phosphate buffered saline (PBS) 14 . The absorbance spectra of CSE stock solutions were acquired each time using a scanning UV–visible spectrophotometer (Varian Cary® 50 Bio UV–visible spectrophotometer), after a baseline correction using 1X PBS.…”

“…1 , step 2). Based on a previous study led by our group 14 , a concentration of 3% (v/v) CSE was chosen for the treatment of skin substitutes. The 3% CSE was obtained by diluting the CSE stock solution (considered as 100%) with 1X PBS.…”

“…Immediately after the incubation time, skin substitutes were irradiated with an Oriel 1.6 kW solar simulator lamp, with an ozone-free xenon short arc lamp combined with an air mass 1.5G filter (Newport, CA, USA). A Newport’s Colored Glass Alternative long-pass filter with a 345 ± 5 nm cut-on wavelength (CGA-345; Newport, CA, USA) was used to block UVB and UVA2 wavelengths, meaning that only UVA1, VL and IR were transmitted 14 . The irradiance spectrum of the SSL with the long-pass filter can be found in Fig.…”