Regulatory monocytes in helminth infections: insights from the modulation during human hookworm infection

Abstract

BackgroundWhile the macrophage polarization is well characterized in helminth infections, the natural heterogeneity of monocytes with multiple cell phenotypes might influence the outcome of neglected diseases, such hookworm infection. Here, we report the profile of monocytes in human hookworm infections as a model to study the regulatory subpopulation of monocytes in helminth infections.MethodsBlood samples were collected from 19 Necator americanus-infected individuals and 13 healthy individuals. Peripheral blood mononuclear cells (PBMCs) were isolated, and immunophenotyping was conducted by flow cytometry. The expressions of genes encoding human nitric oxide synthase (iNOS), interleukin 4 (IL-4), arginase-1 (Arg-1) and glyceraldehyde 3-phosphate dehydrogenase were quantified by qPCR. Plasma levels of IL-4 were determined by sandwich ELISA. Unpaired t-tests or Mann-Whitney tests were used depending on the data distribution.ResultsHookworm infected individuals (HWI) showed a significant increase in the number of monocytes/mm3 (555.2 ± 191.0) compared to that of the non-infected (NI) individuals (120.4 ± 44.7) (p < 0.0001). While the frequencies of CD14+IL-10+ and CD14+IL-12+ cells were significantly reduced in the HWI compared to NI group (p = 0.0289 and p < 0.0001, respectively), the ratio between IL-10/IL-12 producing monocytes was significantly elevated in HWI (p = 0.0004), indicating the potential regulatory activity of these cells. Measurement of IL-4 levels and gene expression of IL-4 and Arg-1 (highly expressed in alternatively activated macrophages) revealed no significant differences between the NI and HWI groups. Interestingly, individuals from the HWI group had higher expression of the iNOS gene (associated with a regulatory profile) (20.27 ± 2.97) compared to the NI group (11.28 ± 1.18, p = 0.0409). Finally, individuals from the HWI group had a significantly higher frequency of CD206+CD23+IL-10+ (7.57 ± 1.96) cells compared to individuals from the NI group (0.35 ± 0.09) (p < 0.001), suggesting that activated monocytes are a potential source of regulatory cytokines during hookworm infection.ConclusionsNatural hookworm infection induces a high frequency of circulating monocytes that present a regulatory profile and promote the downmodulation of the proinflammatory response, which may contribute to prolonged survival of the parasite in the host.

Therapeutic efficacy of Schistosoma japonicum cystatin on sepsis-induced cardiomyopathy in a mouse model

“…To further determine whether rSj-Cys reduced LPS-induced cardiomyocyte apoptosis, H9C2 cells were incubated with LPS alone or with rSj-Cys. The flow cytometry results revealed that incubation with LPS induced 14.4% H9C2 cells apoptosis, whereas co-incubation with rSj-Cys significantly reduced LPSinduced apoptosis to the similar level without LPS (ANOVA: F (3,11) =22.68, P < 0.0003) (Fig. 4b).…”

“…LPS is blamed to be the major component to cause cardiac dysfunction in sepsis through inducing the innate immune inflammatory response [35]. In this study, we identified that LPS significantly induced H9C2 cardiomyocytes to release pro-inflammatory cytokines IL-6 and TNF-α (ANOVA: F (3,11) =20.78, P < 0.0004; F (3,11) =18.53, P < 0.0006), but inhibited the release of regulatory cytokines TGF-β and IL-10 (ANOVA: F (3,11) =25.67, P < 0.0002; F (3,11) =14.41, P < 0.0014) compared with cells treated with PBS ( Fig. 4a).…”

“…Treatment of rSj-Cys was able to significantly inhibit the activation of pro-inflammatory pathway possibly through activating regulatory immune pathway. Interestingly, the mRNA level of M1 macrophage marker iNOS was significantly reduced and M2 macrophage maker Arg-1 significantly increased in heart tissues of rSj-Cys-treated sepsis-mice (ANOVA: F (3,11) =4.967, P < 0.0311; F (3,11) = 77.27, P < 0.0001) ( Fig. 3b), indicating the more macrophages were shifted from M1 to M2, the alternatively activated macrophages, after being treated with rSj-Cys.…”

“…4a). After being treated with rSj-Cys, the LPS-induced IL-6 and TNF-α were reduced to the level of medium control (ANOVA: F (3,11) =20.78, P < 0.0004; F (3,11) =18.53, P < 0.0006), and TGF-β and IL-10 were significantly boosted compared to cells without rSj-Cys treatment (ANOVA: F (3,11) =25.67, P < 0.0002; F (3,11) =14.41, P < 0.0014) (Fig. 4a).…”

“…Other alternative approach to better control sepsis and reduce sepsis related myocardial dysfunction is largely needed.Parasitic helminths co-evolve with mammalian hosts to develop some strategies to survive within hosts. These strategies include immune-modulating host immune system to down-regulate their immune response to helminths (parasite-specific immunomodulation) [8], characterized by a dominant Th2-mediated immune response and activated regulatory T cells (Tregs) or monocyte 5 responses [9][10][11]. The helminth-induced regulatory responses not only facilitate the survival of worms in the host, but also benefit host to reach immune homeostasis between the resistance and tolerance and reduce immunopathology [12].…”