Analysis of expression of FLI1 and MMP1 in American cutaneous leishmaniasis caused by Leishmania braziliensis infection

FLI1 (Friend leukemia virus integration 1) and IL6 (interleukin 6; IL-6) are associated with Leishmania braziliensis susceptibility. Cutaneous lesions show exaggerated matrix metalloproteinase 1 (MMP1). In other skin diseases, FLI1 promoter methylation reduces FLI1 expression, and low FLI1 down-regulates MMP1. IL-6 increases FLI1 expression. We hypothesized that epigenetic regulation of FLI1 in cutaneous leishmaniasis, together with IL-6, might determine MMP1 expression. While generally low (< 10%), percent FLI1 promoter methylation was lower (P = 0.001) in lesion biopsies than normal skin. Contrary to expectation, a strong positive correlation occurred between FLI1 methylation and gene expression in lesions (r = 0.98, P = 0.0005) and in IL-6-treated L. braziliensis-infected macrophages (r = 0.99, P = 0.0004). In silico analysis of the FLI1 promoter revealed co-occurring active H3K27ac and repressive DNA methylation marks to enhance gene expression. FLI1 expression was enhanced between 3 and 24 hour post infection in untreated (P = 0.0002) and IL-6-treated (P = 0.028) macrophages. MMP1 was enhanced in lesion biopsies (P = 0.0002), induced (P = 0.007) in infected macrophages, but strongly inhibited by IL-6. No correlations occurred between FLI1 and MMP1 expression in lesions or infected macrophages (with/without IL-6). We conclude that MMP1 is regulated by factors other than FLI1, and that the influence of IL-6 on MMP1 was independent of its effect on FLI1.