Aliphatic
hydrocarbons constitute a major portion of jet fuels,
kerosene and other
solvents. This study investigated the effects of dermal exposures of selected aliphatic
hydrocarbons (
nonane,
dodecane and
tetradecane) on the skin irritation (
erythema), transepidermal waterloss (TEWL) and expression of
interleukin-1alpha (IL-1alpha),
tumor necrosis factor (
TNF-alpha) and
monocyte chemoattractant protein-1 (MCP-1) in the skin and blood of hairless rats. Dermal exposures were carried out by occlusive application of chemicals (230 microl for 1 h, using Hill Top Chambers) for 1 h. The expression of IL-1alpha,
TNF-alpha and MCP-1 was measured by
enzyme immunoassay (EIA), and the regulatory
proteins NFkappaB and
IkappaBalpha were measured by Western blot analysis. The skin irritation and TEWL data indicate that the irritation was in the following decreasing order:
nonane >
dodecane >
tetradecane. Likewise,
nonane significantly increased the expression of IL-1alpha,
TNF-alpha and MCP-1 in skin and blood as compared to control at different time points.
Dodecane and
tetradecane did not show any increase in the expression of IL-1alpha and MCP-1 as compared to control (P > 0.05), but the expression of
TNF-alpha by
dodecane and
tetradecane was significantly higher than control at all time points. The release of
cytokines by
nonane exposure was further supported by activation of NFkappaB p65 and corresponding degradation of
IkappaBalpha in the skin. In conclusion, this study demonstrates that the biophysical parameters (TEWL and
erythema scores) were correlated to the
biomarker expressions after dermal exposures with
nonane but not with
dodecane and
tetradecane.
Dodecane produced only mild irritation in response to experimental conditions of the present study and further did not show significant differences in IL-1alpha and MCP-1 levels in skin and blood. However,
TNF-alpha was well expressed in response to all the chemicals.
Tetradecane did not show any visible signs of skin irritation and also did not produce any significant difference in IL-1alpha and MCP-1 release profiles as compared with control. The expression of
TNF-alpha in skin due to
tetradecane support the fact that visually indistinguishable skin irritation reactions can induce significant changes in the
biological marker profile.