IL-18 cytokine levels modulate innate immune responses and cryptosporidiosis in mice.

IL-18 is known to play a key role limiting Cryptosporidium parvum infection. In this study, we show that IL-18 depletion in SCID mice significantly exacerbates C. parvum infection, whereas, treatment with recombinant IL-18 (rIL-18), significantly decreases the parasite load, as compared to controls. Increases in serum IFN-γ levels as well as the up-regulation of the antimicrobial peptides, cathelicidin antimicrobial peptide and beta defensin 3 (Defb3) were observed in the intestinal mucosa of mice treated with rIL-18. In addition, C. parvum infection significantly increased mRNA expression levels (> 50 fold) of the alpha defensins, Defa3 and 5, respectively. Interestingly, we also found a decrease in mRNA expression of IL-33 (a recently identified cytokine in the same family as IL-18) in the small intestinal tissue from mice treated with rIL-18. In comparison, the respective genes were induced by IL-18 depletion. Our findings suggest that IL-18 can mediate its protective effects via different routes such as IFN-γ induction or by directly stimulating intestinal epithelial cells to increase antimicrobial activity.

Entinostat up-regulates the CAMP gene encoding LL-37 via activation of STAT3 and HIF-1α transcription factors.

Bacterial resistance against classical antibiotics is a growing problem and the development of new antibiotics is limited. Thus, novel alternatives to antibiotics are warranted. Antimicrobial peptides (AMPs) are effector molecules of innate immunity that can be induced by several compounds, including vitamin D and phenyl-butyrate (PBA). Utilizing a luciferase based assay, we recently discovered that the histone deacetylase inhibitor Entinostat is a potent inducer of the CAMP gene encoding the human cathelicidin LL-37. Here we investigate a mechanism for the induction and also find that Entinostat up-regulates human ß-defensin 1. Analysis of the CAMP promoter sequence revealed binding sites for the transcription factors STAT3 and HIF-1α. By using short hairpin RNA and selective inhibitors, we found that both transcription factors are involved in Entinostat-induced expression of LL-37. However, only HIF-1α was found to be recruited to the CAMP promoter, suggesting that Entinostat activates STAT3, which promotes transcription of CAMP by increasing the expression of HIF-1α. Finally, we provide in vivo relevance to our findings by showing that Entinostat-elicited LL-37 expression was impaired in macrophages from a patient with a STAT3-mutation. Combined, our findings support a role for STAT3 and HIF-1α in the regulation of LL-37 expression.

Vitamin D promotes human extravillous trophoblast invasion in vitro.

INTRODUCTION: Incomplete human extravillous trophoblast (EVT) invasion of the decidua and maternal spiral arteries is characteristic of pre-eclampsia, a condition linked to low maternal vitamin D status. It is hypothesized that dysregulated vitamin D action in uteroplacental tissues disrupts EVT invasion leading to malplacentation. METHODS: This study assessed the effects of the active vitamin D metabolite, 1,25-dihydroxyvitamin D3 (1,25-D3), and its precursor, 25-hydroxyvitamin D3 (25-D3), on primary human EVT isolated from first trimester pregnancies. Expression of EVT markers (cytokeratin-7, HLA-G), the vitamin D-activating enzyme (CYP27B1) and 1,25-D3 receptor (VDR) was assessed by immunocytochemistry. EVT responses following in vitro treatment with 1,25-D3 (0-10 nM) or 25-D3 (0-100 nM) for 48-60 h were assessed using quantitative RT-PCR (qRT-PCR) analysis of key target genes. Effects on EVT invasion through Matrigel(®) were quantified alongside zymographic analysis of secreted matrix metalloproteinases (MMPs). Effects on cell viability were assessed by measurement of MTT. RESULTS: EVT co-expressed mRNA and protein for CYP27B1 and VDR, and demonstrated induction of mRNA encoding vitamin D-responsive genes, 24-hydroxylase (CYP24A1) and cathelicidin following 1,25-D3 treatment. EVT could respond to 1,25-D3 and 25-D3, both of which significantly increased EVT invasion, with maximal effect at 1 nM 1,25-D3 (1.9-fold; p < 0.01) and 100 nM 25-D3 (2.2-fold; p < 0.05) respectively compared with untreated controls. This was accompanied by increased pro-MMP2 and pro-MMP9 secretion. The invasion was independent of cell viability, which remained unchanged. DISCUSSION: These data support a role for vitamin D in EVT invasion during human placentation and suggest that vitamin D-deficiency may contribute to impaired EVT invasion and pre-eclampsia.