The Honeybee Antimicrobial Peptide Apidaecin Differentially Immunomodulates Human Macrophages, Monocytes and Dendritic Cells

Abstract

We show that apidaecin binds to human macrophages, monocytes and dendritic cells, displaying different intracellular distributions and inducing diversified effects. An apidaecin-cell association was detectable at concentrations as low as 5 µM and increased without saturation until 60 µM, was receptor independent and required a physiological temperature (37°C). For apidaecin, cytosolic localization was prevalent in macrophages and endosomal localization in monocytes, and associations with the plasma membrane were predominant in dendritic cells. Apidaecin upregulated T-lymphocyte co-stimulatory molecule CD80 and cytokine/chemokine production in macrophages, but not in monocytes and dendritic cells. Suboptimal stimulatory doses (5–10 µM) of apidaecin partially inhibited the lipopolysaccharide (LPS)-induced increase in major histocompatibility complex class II (MHCII) and CD86 in macrophages, and the release of selected cytokines/chemokines by both macrophages [interleukin (IL)-6 and tumor necrosis factor (TNF)-α] and monocytes [IL-6, TNF-α, basic fibroblast growth factor (FGF) and eotaxin]. Apidaecin had a double-edged effect: at low concentrations it partially antagonized LPS-stimulatory effects on both macrophages and monocytes while it stimulated pro-inflammatory and pro-immune functions of macrophages at higher concentrations.

Absence of in vitro innate immunomodulation by insect‐derived short proline‐rich antimicrobial peptides points to direct antibacterial action in vivo

“…Macrophages are phagocytes with many regulatory and effector immune functions [39,40]. As described previously, some AMPs have been described to be immunostimulatory or immunomodulatory for macrophages, monocytes and DC [32,[42][43][44][45][46]. The identity of the BMDM was confirmed using flow cytometrical detection of the F4/80 antigen as a typical macrophage marker (data not shown).…”

“…Additionally, in accordance to Tavano et al . , we could not detect an immunostimulation of murine BMDC by Api 1b, as assessed by analysis of the expression of surface activation markers and/or inflammatory cytokines (Figures and ). This was also true for oncocin, Onc72 and Api88.…”

Api88 Is a Novel Antibacterial Designer Peptide To Treat Systemic Infections with Multidrug-Resistant Gram-Negative Pathogens

“…Taken together, no evidence was found for in vivo immunomodulatory activities of Api88, which contrasts a recent report about the in vitro effects of native apidaecin 1b. 33 Murine Infection Models. The efficacy of Api88 was first evaluated in a systemic septicemia E. coli ATCC 25922 infection model (with 2.5% mucin) on female NMRI outbred mice (seven animals per group).…”

In vivo Efficacy and Pharmacokinetics of Optimized Apidaecin Analogs

“…The latter effect was studied for Onc72, but no immunomodulatory effects were observed on unstimulated and lipopolysaccharide (LPS)-stimulated murine dendritic cells or murine macrophages (Fritsche et al, 2012). Only human macrophages and monocytes showed a reduction of LPS-induced TNFα release after treatment with Api88 and Api137 indicating a mild anti-inflammatory effect (Tavano et al, 2011; Keitel et al, 2013). Unfortunately, further data on immunomodulatory effects of Api137 on murine cells are missing.…”

“…Therefore, the recovered peptide amounts in kidneys of Api137 treated animals (2.4 μg/g) were slightly higher than in Api88 treated animals (1.8 μg/g). Notably, PrAMPs usually do not penetrate mammalian cells, but immune cells and HeLa cancer cells can internalize apidaecins and Bac7(1–35) after long incubation times (Tavano et al, 2011; Hansen et al, 2012; Pelillo et al, 2014; Bluhm et al, 2016). However, it is unlikely that PrAMPs internalized in kidney cells within 10 min (first time point of the pharmacokinetic study).…”