Interaction of Mycoplasma hominis PG21 with Human Dendritic Cells: Interleukin-23-Inducing Mycoplasmal Lipoproteins and Inflammasome Activation of the Cell

Abstract

Mycoplasma hominis lacks a cell wall, and lipoproteins anchored to the extracellular side of the plasma membrane are in direct contact with the host components. A Triton X-114 extract of M. hominis enriched with lipoproteins was shown to stimulate the production of interleukin-23 (IL-23) by human dendritic cells (hDCs). The inflammasome activation of the host cell has never been reported upon M. hominis infection. We studied here the interaction between M. hominis PG21 and hDCs by analyzing both the inflammation-inducing mycoplasmal lipoproteins and the inflammasome activation of the host cell. IL-23-inducing lipoproteins were determined using a sequential extraction strategy with two nondenaturing detergents, Sarkosyl and Triton X-114, followed by SDS-PAGE separation and mass spectrometry identification. The activation of the hDC inflammasome was assessed using PCR array and enzyme-linked immunosorbent assay (ELISA). We defined a list of 24 lipoproteins that could induce the secretion of IL-23 by hDCs, 5 with a molecular mass between 20 and 35 kDa and 19 with a molecular mass between 40 and 100 kDa. Among them, lipoprotein MHO_4720 was identified as potentially bioactive, and a synthetic lipopeptide corresponding to the N-terminal part of the lipoprotein was subsequently shown to induce IL-23 release by hDCs. Regarding the hDC innate immune response, inflammasome activation with caspase-dependent production of IL-1β was observed. After 24 h of coincubation of hDCs with M. hominis, downregulation of the NLRP3-encoding gene and of the adaptor PYCARD-encoding gene was noticed. Overall, this study provides insight into both protagonists of the interaction of M. hominis and hDCs. IMPORTANCE Mycoplasma hominis is a human urogenital pathogen involved in gynecologic and opportunistic infections. M. hominis lacks a cell wall, and its membrane contains many lipoproteins that are anchored to the extracellular side of the plasma membrane. In the present study, we focused on the interaction between M. hominis and human dendritic cells and examined both sides of the interaction, the mycoplasmal lipoproteins involved in the activation of the host cell and the immune response of the cell. On the mycoplasmal side, we showed for the first time that M. hominis lipoproteins with high molecular mass were potentially bioactive. On the cell side, we reported an activation of the inflammasome, which is involved in the innate immune response.

Activation of NLRP3 inflammasome in macrophages by mycoplasmal lipoproteins and lipopeptides

“…Recently, several studies have reported that mycoplasmas activate inflammasomes to induce IL‐1β production . We have also shown that M. salivarium and M. pneumoniae cells activate the NLRP3 inflammasome to produce IL‐1β in murine dendritic cells and macrophages .…”

“…Recently, several studies have reported that mycoplasmas activate inflammasomes to induce IL-1β production. [22][23][24][25][26][27] We have also shown that M. salivarium and M. pneumoniae cells activate the NLRP3 inflammasome to produce IL-1β in murine dendritic cells and macrophages. 28 However, the detailed mechanism of inflammasome activation triggered by mycoplasmas is not yet fully clarified.…”

The Role of Lipoproteins in Mycoplasma-Mediated Immunomodulation

“…Two of the most well-studied TLRs are TLR2 and TLR6, both of which are pivotal in recognizing Mycoplasmal Macrophage-Activating Lipopeptide-2 (MALP-2), with the absence of either TLR leading to a lack of recognition and macrophage activation ( Takeuchi et al, 2002 ). Mycoplasmal lipoproteins can also activate myeloid cells through the inflammasome ( Chen et al, 2017 ; Goret et al, 2017 ). Amongst the Mycoplasma capable of activating inflammasome with their lipoproteins are M. salivarium and M. pneumoniae ( Shimizu, 2016 ; Sugiyama et al, 2016 ).…”

“…Mycoplasmal lipoproteins in M. hominis such as lipoprotein MHO_4720 were recently shown to induce production of Interleukin-23 (IL-23), by dendritic cells through activation of inflammasome ( Chen et al, 2017 ; Goret et al, 2017 ). Production of proinflammatory cytokines such as IL-23 has been shown to induce the expression of chemokines such as IL-17, allowing for effective containment of the infection ( Wu et al, 2007 ).…”

Integrated Transcriptomic and Proteomic Analyses of the Interaction Between Chicken Synovial Fibroblasts and Mycoplasma synoviae

“…However, only a few MS proteins, including variable lipoprotein hemagglutinin (Narat et al, 1998;Lavric et al, 2007), cysteine protease (Cizelj et al, 2011), neuraminidase (Bercic et al, 2011), the putative nuclease MS53_0284 (Vasconcelos et al, 2005;Cizelj et al, 2016), and matrix metalloproteinase-2 (MMP-2) (Cizelj et al, 2016), have been identified as virulence determinants. In terms of host-pathogen interactions, Goret et al (2017) showed that M. hominis lipoproteins played a role in the activation of human dendritic cells and their immune responses. Addis et al (2011) utilized a proteomic approach to investigate the impact of M. agalactiae infection on mammary epithelium.…”