Expression of IL-1a and b was demonstrated in sebaceous glands by immunohis-tochemistry (162), and mRNA for IL-1a was detected in cultured sebocytes (163). No change in staining pattern was observed when sebum was extracted from the samples, indicating that IL-1 is not associated with sebum. The function of IL-1 in normal sebaceous glands is unclear, although in vitro IL-1a and tumor necrosis factor a, inhibited sebaceous lipogenesis in sebaceous gland organ culture and induced de-differentiation of human sebocytes into a keratinocyte-like phenotype (152). In organ culture, IL-1a at 1 ng/mL promoted ductal cornification (164) and upregulated mRNA and protein synthesis of vascular endothelial growth factor (VEGF) (165). Thus in follicular diseases, liberation of IL-1 into the dermis may contribute toward inflammation and increased levels of VEGF by follicular kerati-nocytes can stimulate angiogenesis. In acne, high levels of IL-1 a bioactivity existed in comedonal contents (166).
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