19.    Characterisation of liver X receptors within the pilo-sebaceous unit. 
Louise Russell, Wesley Harrison, C Zouboulis, Jacky Burrin(1) Michael Philpott, Centre for Cutaneous Research, London, UK, 1.Department of Endocrinology, WHI, UK

Liver X receptors (LXR) play a well documented role in the differentiation and proliferation of human keratinocytes. Currently, little is known of their presence and role in the human pilosebaceous unit. Here, we have shown that LXRs are present in numerous cell types derived from the human pilosebaceous unit. Specifically, we used RT-PCR to locate the mRNA of both LXR alpha and beta within not only primary keratinocytes but also within outer root sheath keratinocytes, dermal fibroblasts, connective tissue sheath fibroblast and dermal papilla fibroblasts as well as within the immmortalised keratinocyte cells lines HaCaT and N/TERT and immortalized sebocyte cell line SZ95 (Zouboulis et al. (1999) JID 113(6): 1011-20).
Western blotting analysis was used to identify the proteins of both isoforms within each of these cell types. This was further confirmed by immunohistochemistry using monoclonal and polyclonal LXR antibodies on human hair bearing skin.
We also identified previously unreported functional roles for LXR within human skin. By stimulating SZ95 cells with synthetic LXR agonists TO901317 and GW683965 for 2 days we were able to stimulate lipogenesis. Using the 2-14C-labelled sodium acetate incorporation assay enabled us to quantify the stimulatory effects of these treatments, revealing a significant increase in lipogenesis compared to vehicle treated control cells, indicating an increase in the rate of differentiation. The anti-proliferative qualities of LXR stimulation have been indicated by the treatment of primary keratinocytes, N/TERT and SZ95 with synthetic LXR agonists for 2 and 5 days in vitro. Using the MTT assay a highly significant decrease in cell number was observed in agonist treated cells compared to vehicle treated controls. The effects of LXR agonists acting specificity on functioning endogenous receptors was confirmed using the LXRE-LUC reporter assay.
This study has not only elucidated the previously unknown presence of LXR with the pilosebaceous unit but additionally highlighted potential therapeutic targets within the field of acne.