Evaluation of skin irritation following weathered crude oil exposure in two mouse strains.

Petroleum crude oil spills are common and vary in size and scope. Spill response workers throughout the course of remediation are exposed to so-called weathered oil and are known to report diverse health effects, including contact dermatitis. A murine model of repeated exposure to weathered marine crude oil was employed utilizing two strains of mice, C57BL/6 and BALB/c, to investigate the pathology of this irritant and identify the principal hydrocarbon components deposited in skin. Histopathology demonstrated clear signs of irritation in oil-exposed skin from both mouse strains, characterized by prominent epidermal hyperplasia (acanthosis). BALB/c mice exposed to oil demonstrated more pronounced irritation compared with C57BL/6 mice, which was characterized by increased acanthosis as well as increased inflammatory cytokine/chemokine protein expression of IL-1ß, IL-6, CXCL10, CCL2, CCL3, CCL4, and CCL11. A gas chromatography/mass spectrometry method was developed for the identification and quantification of 42 aliphatic and EPA priority aromatic hydrocarbons from full thickness skin samples of C57BL/6 and BALB/c mice exposed to oil samples. Aromatic hydrocarbons were not detected in skin; however, aliphatic hydrocarbons in skin tended to accumulate with carbon numbers greater than C16. These preliminary data and observations suggest that weathered crude oil is a skin irritant and this may be related to specific hydrocarbon components, although immune phenotype appears to impact skin response as well.

Keratinocyte-specific deletion of the IL-6RΑ exacerbates the inflammatory response during irritant contact dermatitis.

Irritant Contact Dermatitis (ICD) is the most common occupational skin disorder. During ICD, keratinocytes initiate the inflammatory cascade by producing cytokines including IL-6. This laboratory previously reported that IL-6 deficiency exacerbates skin inflammation during ICD, yet the role of the IL-6Rα in keratinocyte function has yet to be elucidated. To investigate how IL-6Rα function in keratinocytes influences the inflammatory response during ICD, keratinocyte-specific IL-6Rα KO (IL6raΔker) and WT mice were exposed to two well-known occupational irritants; JP-8 jet fuel, and benzalkonium chloride (BKC), or acetone control for three days. Dermatitis lesions were collected and flow cytometric and immunohistochemical analyses revealed that IL6raΔker skin displayed increased populations of CD11b+CD45+ and F4/80+ cells respectively relative to WT. However, IL6raΔker mouse skin contained reduced numbers of γδ T cells relative to WT. Furthermore, IL6raΔker skin expressed increased levels of pro-inflammatory cytokines including IL-1ß, IL-22, and CCL4 but decreased levels of anti-inflammatory cytokines IL-4 and IL-10. These results indicate that epidermal keratinocyte IL-6Rα function modulates epidermal hyperplasia, immune cell infiltration into skin and cytokine expression during ICD and suggests that the previously reported protective effect of IL-6 during ICD might be mediated primarily by keratinocyte derived IL-6Rα.

Interleukin 6 Function in the Skin and Isolated Keratinocytes Is Modulated by Hyperglycemia.

Diabetes currently affects over twenty-five million Americans. Annual health care cost of diabetes exceeds $254 billion and is associated with a distinct set of diabetic complications that include delayed wound healing and diabetic ulcers. Interleukin 6 (IL-6) plays an important role in wound healing and is known to be elevated in the serum of both type I and type II diabetes patients. This study assesses the expression and function of IL-6 in the hyperglycemic epidermis and keratinocyte culture. Streptozotocin-treated mice were wounded six weeks after induction of hyperglycemia. Wound closure, protein, and mRNA expression were assessed up to 13 days of postwounding. Wound closure was delayed 4-5 days in hyperglycemic animals. Hyperglycemic wounds displayed greater IL-6 and IL-6Rα protein expression at 1, 7, and 10 days of postwounding compared to euglycemic control. However, IL-6Rα mRNA expression was reduced at all time points beyond day 1, while IL-6 mRNA expression did not significantly differ at any time point. SOCS3 mRNA expression was higher in the hyperglycemic skin at every time point. Imaging of fluorescent immunohistology also revealed significantly lower expression of SOCS3, but higher nuclear pSTAT3 in the epidermis of the hyperglycemic skin. Primary mouse keratinocytes cultured in high glucose for 7 days displayed 2-fold higher IL-6Rα mRNA and higher rmIL-6-induced nuclear pSTAT3, but lower SOCS3 basal levels compared to normal glucose-cultured cells. Thus, it appears that delayed diabetic skin wound healing is associated with increased induction and expression of IL-6 and its receptor, but its function in epidermal keratinocytes may be impaired.

Associations Between Immune Phenotype and Inflammation in Murine Models of Irritant Contact Dermatitis.

Irritant contact dermatitis (ICD), the most common occupational cutaneous illness, is an acute inflammatory response caused by topical irritant exposure. Multiple factors are associated with the manifestation and severity of ICD and contribute to the lack of effective prophylactic and treatment strategies. To determine the pathomechanism of ICD caused by the irritants, benzalkonium chloride (BKC) and JP-8 jet fuel, 2 mouse strains, C57BL/6 and Balb/c, were assessed due to their differential immune predispositions. Dermatitis lesions were obtained for histological examination, cytokine protein expression analysis, and determination of immune cell infiltration via flow cytometric analysis. Following acute (3-day) BKC exposure C57BL/6 skin displayed increased neutrophils and expression of 19 distinct cytokines, but fewer dendritic cells and lower expression of IL-1α and IL-9 as compared with Balb/c skin. Following prolonged (7-day) exposure to BKC, inflammatory cell populations trended similar to 3-day exposure; however, only 6 distinct cytokines were higher in C57BL/6, whereas Balb/c displayed higher expression of IL-27, 28, and 31. Following acute JP-8 exposure, C57BL/6 skin displayed higher levels of γδ T cell infiltration, G and M-CSF expression, but lower populations of neutrophils, monocytes, and dendritic cells compared with Balb/c skin. As with BKC, skin inflammatory cell populations following 7-day JP-8 exposure trended similar to 3-day exposure. However, C57BL/6 skin displayed higher levels of IL-6 and LIF, whereas Balb/c showed increased IL-1ß, IL-27, G-CSF, TNFα, and 7 additional chemokines. These findings further define the pathology of ICD, partially explain individual variation of ICD, and offer insight into biomarkers for risk assessment.