Connor M J, Nanthur J, Puhvel S M
Department of Medicine, UCLA School of Medicine 90024.
Toxicol Appl Pharmacol. 1994 Nov;129(1):12-5. doi: 10.1006/taap.1994.1223.
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.
有人提出肿瘤坏死因子-α（TNF-α）介导2,3,7,8-四氯二苯并-p-二噁英（TCDD）诱导的毒性。TCDD在无毛的HRS/J小鼠皮肤中诱导类似氯痤疮的反应，但在同基因有毛动物中则不会。我们使用酶联免疫吸附测定法（ELISA）测量了经TCDD处理的有毛和无毛HRS/J小鼠皮肤中的TNF-α水平，以检验TNF-α介导TCDD皮肤毒性这一假说。有毛小鼠皮肤中的TNF-α水平处于或低于最低可检测水平，且TCDD暴露后未发生变化。相比之下，TCDD暴露后无毛小鼠皮肤中的TNF-α水平显著更高。诱导产生的大部分TNF-α存在于真皮中，尽管表皮中也有可检测到的量。为了确定小鼠皮肤细胞是否直接对TCDD产生TNF-α，用不同生物活性剂量的TCDD或溶剂（二甲基亚砜）处理新生表皮角质形成细胞和真皮成纤维细胞培养物，或用脂多糖（LPS）作为阳性对照。在暴露于LPS的24小时内，所有测试细胞的培养基中TNF-α水平均升高。相比之下，在相当的时间段内，或者在暴露后长达6天进行测量时，TCDD处理（10⁻¹¹ M至10⁻⁷ M）未能诱导成纤维细胞或角质形成细胞释放可检测到的TNF-α。TCDD未能刺激角质形成细胞或成纤维细胞产生TNF-α，这表明在体内观察到的真皮TNF-α水平升高不太可能是毒性机制的主要组成部分。我们认为，TCDD处理的无毛小鼠皮肤中真皮TNF-α的来源可能是炎症反应的组成细胞。
