Influence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on TNF-alpha levels in the skin of congenic haired and hairless mice.

It has been proposed that TNF-alpha mediates TCDD-induced toxicity. TCDD induces a chloracne-like response in the skin of hairless HRS/J mice but not in congenic haired animals. Using an ELISA, we measured TNF-alpha levels in the skin of TCDD-treated haired and hairless HRS/J mice to test the hypothesis that TNF-alpha mediates the cutaneous toxicity of TCDD. TNF-alpha levels in the skin of haired mice were at or below minimal detectable levels and were unchanged by TCDD exposure. In contrast, TNF-alpha levels were significantly higher in the skin of hairless mice after TCDD exposure. The bulk of the induced TNF-alpha was present in the dermis, although detectable amounts were present in the epidermis. To determine if murine skin cells were producing TNF-alpha in direct response to TCDD, cultures of neonatal epidermal keratinocytes and dermal fibroblasts were treated with varying biologically active doses of TCDD or vehicle (DMSO) or with lipopolysaccharide (LPS) as a positive control. Within 24 hr of exposure to LPS, TNF-alpha levels were increased in the culture media of all cells tested. In contrast, TCDD treatment (10(-11) M to 10(-7) M) failed to induce detectable TNF-alpha release from either fibroblasts or keratinocytes over a comparable time frame or when measured for up to 6 days following exposure. The failure of TCDD to stimulate TNF-alpha production by keratinocytes or fibroblasts suggests that the rise in dermal TNF-alpha levels seen in vivo is unlikely to be a primary component of the mechanism of toxicity. We suggest that the source of the dermal TNF-alpha in TCDD-treated hairless mouse skin is probably component cells of the inflammatory response.