Human Innate Immunity and Acanthamoeba: effect of oral hormonal contraception

PURPOSE. Recently, we have characterize the pattern of pro-inflammatory and anti-inflammatory cytokins released by human peripheral blood mononuclear cells (PBMCs) and human monocyte derived macrophages (MDMs) in response to Acanthamoeba. It is known that sex hormones can strongly regulate immune responses and influence homeostasis of eye and brain, privileged sites of Acanthamoeba infections. Considering the widespread use of oral contraceptives (OCs) and noting that monocytes and macrophages express receptors for sex hormones, the aim of this study was to evaluate whether the use of OCs can affect monocyte and macrophage activity against Acanthamoeba. To this end, we evaluate the effect of OCs on pro-inflammatory and anti-inflammatory cytokines release by PBMCs and MDMs in response to Acanthamoeba-derived cell-free conditioned medium (aCM) and to known agonists of TLR4 and TLR2 receptors (used as positive controls). METHODS. PBMCs from healthy adult women treated (FOCs) or non-treated (Fs) with OCs were isolated during the follicular phase of their menstrual cycle. MDMs were obtained from each sub-population, and characterized by evaluating the decrease in the surface marker CD14. Then all samples were stimulated with either aCM, LPS or Pam2CSK4, in vitro. Release of TNF-α, IL-6, IL-10 and IL-8 was investigated at specific hours post-stimulation, by Enzyme Linked Immuno Sorbent Assay (ELISA). All experiments were performed in triplicate. Statistical difference was evaluated with the two-tailed Student t test and two-way analysis of variance (ANOVA), followed by Bonferroni post test, using Graph-Pad Prism (GraphPad Software Inc.). RESULTS. Of interest, our data showed that, the use of OCs affected mainly on PBMCs aCM-stimulated, significantly reducing the production of all the cytokines studied. Whereas, only a highly significant reduction of IL-8 and IL-10 was detected in FOC-MDMs in comparison with F-MDMs. DISCUSSION. At the moment it is difficult to explain the impact that OCs assumption might have in Acanthamoeba infections, in that it reduce the production of both pro-inflammatory and anti-inflammatory cytokins. However, considering the peculiar ability of Acanthamoeba cause premature release of IL-10 by monocytes/macrophages, we hypothesize that its lower production, by both FOC-PBMCs and FOC-MDMs, might promote the inflammatory response and monocyte/macrophage antimicrobial activity, to the detriment of the protozoan. CONCLUSIONS. For the first time, it is demonstrated that, during the early phase of infection, the use of OCs might interfere in the mechanisms that occur between monocytes/macrophages and Acanthamoeba.