Streptococcus mutans activates the AIM2, NLRP3 and NLRC4 inflammasomes in human THP-1 macrophages

Streptococcus mutans(S. mutans), a major aetiologic agent of dental caries, is involved in systemic diseases, such as bacterial endocarditis, if it enters the bloodstream through temporary bacteraemia. Interleukin(IL)-1β, a proinflammatory cytokine, is related to the host defences against pathogens, and its synthesis, maturation, and secretion are tightly regulated by the activation of the inflammasome, an inflammatory signalling complex. This study examined the signalling mechanism of IL-1β secretion and the inflammasome pathway induced by S. mutans to explain the molecular mechanism through which systemic infection by oral streptococci can occur. After infection of THP-1 cells with S. mutans, the expression of inflammasome components was detected using various methods. S. mutans induced IL-1β secretion via caspase-1 activation, and S. mutans-induced IL-1β secretion required absent in melanoma(AIM2), NLR family pyrin domain-containing 3(NLRP3) and NLR family CARD domain-containing 4(NLRC4)inflammasome activation. In particular, the S. mutans-induced NLRP3 inflammasome was mediated by adenosine triphosphate(ATP) release, potassium depletion and lysosomal damage. Our study provides novel insight into the innate immune response against S. mutans infection.

Inflammatory mediator release by Brugia malayi from macrophages of susceptible host Mastomys coucha and THP-1 and RAW 264.7 cell lines

Objective:To investigate which life stage of the parasite has the ability to stimulate release of pro- or anti-inflammatory mediators from macrophages.Methods:The human macrophage/ monocyte cell line THP-1,the mouse macrophage cell line RAW 264.7 and naive peritoneal macrophages（PM） from the rodent host Mastomys coucha（M.coucha） were incubated at 37℃in 5%CO2 atmosphere with extracts of microfilariae（Mf）,third stage infective larvae（L3） and adult worms（Ad） of Brugia malayi.After 48 hr post exposure,IL-1β,IL-6,TNF-α,IL-10 and nitric oxide（NO） in cell-free supernatants were estimated.Results:Extracts of all the life stages of the parasite were capable of stimulating pro-（IL-1β,IL-6 and TNF-α） and anti-inflammatory （IL-10） cytokines in both the cell lines and peritoneal macrophages of M.coucha.Mf was the strongest stimulator of pro-inflammatory cytokines followed by L3 and Ad;however,Ad was a strong stimulator of IL-10 release.Mf was found to have potential to modulate LPS-induced NO release in RAW cells.Ad-induced NO release was concentration dependent with maximum at 20μg/mL in both RAW and PMs.Conclusions:The results show that parasites at all life stages were capable of stimulating pro-（IL-1β,IL-6 and TNF-α） and anti-inflammatory（IL-10） cytokines and NO release from macrophages of susceptible host M.coucha,human and mouse macrophage cell lines.Mf can suppress the LPS-induced NO release in RAW cells.The findings also show that the two cell lines may provide a convenient in vitro system for assaying parasite-induced inflammatory mediator release.

Salidroside Inhibits Lipopolysaccharide-ethanol-induced Activation of Proinflammatory Macrophages via Notch Signaling Pathway

Activation of macrophages is a key event for the pathogenesis of various inflammatory diseases.Notch signaling pathway recently has been found to be a critical pathway in the activation of proinflammatory macrophages.Salidroside (Sal),one of main bioactive components in Rhodiola crenulata (Hook.F.et Thoms) H.ohba,reportedly possesses anti-inflammatory activity and ameliorates inflammation in alcohol-induced hepatic injury.However,whether Sal regulates the activation of proinflammatory macrophages through Notch signaling pathway remains unknown.The present study investigated the effects of Sal on macrophage activation and its possible mechanisms by using both alcohol and lipopolysaccharide (LPS) to mimic the microenvironment of alcoholic liver.Detection of THP-1-derived macrophages exhibited that Sal could significantly decrease the expression of tumor necrosis factor-α(TNF-α),interleukinbeta (IL-1β)and IL-6 in the macrophages at both mRNA and protein levels.Furthermore,Sal significantly suppressed NF-kB activation via Notch-Hes signaling pathway in a dose-dependent manner.Moreover,in the microenvironment of alcoholic liver,the expression of Notch-dependent pyruvate dehydrogenase phosphatase 1 (PDP1) was elevated,and that of Ml gene expression [inducible NO synthase (NOS2)] was up-regulated.These changes could all be effectively ameliorated by Sal.The aforementioned findings demonstrated that Sal could inhibit LPS-ethanol-induced activation of proinflammatory macrophages via Notch signaling pathway.

Proteomic characterization of four subtypes of M2 macrophages derived from human THP-1 cells

Macrophages are widely distributed immune cells that contribute to tissue homeostasis.Human THP-1 cells have been widely used in various macrophage-associated studies,especially those involving pro-inflammatory M1 and anti-inflammatory M2 phenotypes.However,the molecular characterization of four M2 subtypes(M2a,M2b,M2c,and M2d)derived from THP-1has not been fully investigated.In this study,we systematically analyzed the protein expression profiles of human THP-1-derived macrophages(M0,M1,M2a,M2b,M2c,and M2d)using quantitative proteomics approaches.The commonly and specially regulated proteins of the four M2 subtypes and their potential biological functions were further investigated.The results showed that M2a and M2b,and M2c and M2d have very similar protein expression profiles.These data could serve as an important resource for studies of macrophages using THP-1 cells,and provide a reference to distinguish different M2 subtypes in macrophage-associated diseases for subsequent clinical research.

Pre-incubated with BSA-complexed free fatty acids alters ER stress/autophagic gene expression by carboxylated multi-walled carbon nanotube exposure in THP-1 macrophages

Recently we found that multi-walled carbon nanotube (MWCNT) exposure alters the mRNA levels of endoplasmic reticulum (ER) stress/autophagic genes, but the impact of biological molecules on this response is unclear. Herein, we compared the different actions of carboxylated MWCNTs (c-MWCNTs) pre-incubated with bovine serum albumin (BSA) or BSA-complexed free fatty acid (denoted as FFA) on macrophages derived from THP-1 monocytes (denoted as THP-1 macrophages). C-MWCNTs exhibited increased diameter and hydrodynamic size as well as decreased absolute zeta potential value after pre-incubation with BSA or FFA, which suggested a coating effect. Cytotoxicity or oxidative stress were not significantly induced after exposure to BSA-or FFA-coated c-MWCNTs. BSA-pre-incubated c-MWCNTs significantly enhanced the expression of the ER stress gene, DDIT3 and the autophagic genes, ATG5, BECN1, and PLIN2, but the mRNA levels of these genes was significantly decreased by FFA-pre-incubated c-MWCNTs. FFA-pre-incubated c-MWCNTs induced significantly higher lipid accumulation and interleukin-6 (IL-6) protein level compared with BSA-pre-incubated c-MWCNTs, which suggested that FFA-pre-incubated c-MWCNTs may more effectively induce the formation of macrophage foam cells. Collectively, our data indicated that pre-incubation with FFA may influence c-MWCNT-induced ER stress/autophagic gene expression and foam cell formation in THP-1 macrophages.

In vitro immunomodulation of magnesium on monocytic cell toward anti-inflammatory macrophages

Biodegradable magnesium(Mg)has shown great potential advantages over current bone fixation devices and vascular scaffold technologies;however,there are few reports on the immunomodulation of corrosive Mg products,the micron-sized Mg particles(MgMPs).Human monocytic leukemia cell line THP-1 was set as the in vitro cell model to estimate the immunomodulation of MgMPs on cell proliferation,apoptosis,polarization and inflammatory reaction.Our results indicated highconcentration of Mg^2+ demoted the proliferation of the THP-1 cells and,especially,THP-1-derived macrophages,which was a potential factor that could affect cell function,but meanwhile,cell apoptosis was almost not affected by Mg^2+.In particular,the inflammation regulatory effects of MgMPs were investigated.Macrophages exposed to Mg^2+ exhibited down-regulated expressions of M1 subtype markers and secretions of pro-inflammatory cytokines,up-regulated expression of M2 subtype marker and secretion of anti-inflammatory cytokine.These results indicated Mg^2+ could convert macrophages from M0 to M2 phenotype,and the bioeffects of MgMPs on human inflammatory cells were most likely due to the Mg^2+-induced NF-jB activation reduction.Together,our results proved Mg^2+ could be used as a new anti-inflammatory agent to suppress inflammation in clinical applications,which may provide new ideas for studying the immunomodulation of Mg-based implants on human immune system.