Dermal microdialysis of inflammatory markers induced by aliphatic hydrocarbons in rats

Abstract

In the present study we made an attempt to understand the skin irritation cascade of selected aliphatic hydrocarbons using microdialysis technique. Microdialysis probes were inserted into dermis in the dorsal skin of hairless rats. After 2h of probes insertion, occlusive dermal exposure (2h) was carried out with 230 microl of nonane, dodecane and tetradecane, using Hill top chambers((R)). Inflammatory biomarkers such as substance P (SP), alpha-melanocyte stimulating hormone (alpha-MSH) Interleukin 6 (IL-6) and prostaglandin E2 (PGE(2)) were analyzed in the dialysis samples by enzyme immunoassay (EIA). SP, alpha-MSH and IL6 were released in significant amounts following the dermal exposure of nonane and dodecane, whereas tetradecane did not induce any of these markers in significant amounts compared to control. Nonane increased the PGE(2) levels in significant amounts within 2h of chemical exposure compared to dodecane and tetradecane. IL-6 response was found to be slow and 2-3-fold increase in IL-6 levels was observed after 5h following nonane and dodecane application. The magnitude of skin irritation exerted by all three chemicals was in the order of nonane>or=dodecane>or=tetradecane. The results demonstrate that microdialysis can be used to measure the inflammatory biomarkers in the skin irritation studies and irritation response of chemicals was quantifiable by this method. In conclusion, microdialysis was found to be an excellent tool to measure several inflammatory biomarkers as a function of time after dermal exposures with irritant chemicals.

Fig. 1

Mean concentration of substance P (pg/ml) following insertion of the probe, application of test chemical and 5 h after removal of the chemical. CTL: control baseline and n = 6 animals (A–C).

Fig. 2

Mean concentration of PGE₂ (pg/ml) following insertion of the probe, application of test chemical and 5 h after removal of the chemical. CTL: control baseline and n = 6 animals (A–C).

Fig. 3

Mean concentration of α-MSH (pg/ml) following insertion of the probe, application of test chemical and 5 h after removal of the chemical. CTL: control baseline and n = 6 animals (A–C).

Fig. 4

Mean concentration of IL-6 (pg/ml) following insertion of the probe, application of test chemical and 5 h after removal of the chemical. CMA-20 microdialysis probe perfused with 0.1%, w/v BSA in Krebs ringer solution at flow rate of 0.5 μg/ml and samples vials were diluted with 30 μl of 0.1%, w/v BSA solution. CTL: Control baseline and n = 6 animals (A–C).

Fig. 5

Hypothesized biomolecular interactions in the skin following application of aliphatic hydrocarbons. A) LM-10 linear microdialysis probe B) CMA 20 concentric micordialysis probe. The figure shows that IL-1α, PGE₂ and SP are primary biomarkers in response to skin irritation, these in turn induce the expression of IL-6.