Sphingosine-1-Phosphate Receptor 2 Regulates Proinflammatory Cytokine Production and Osteoclastogenesis.

Sphingosine-1-phosphate receptor 2 (S1PR2) couples with the Gi, Gq, and G12/13 group of proteins, which modulate an array of cellular signaling pathways and affect immune responses to multiple stimuli. In this study, we demonstrated that knockdown of S1PR2 by a specific S1PR2 shRNA lentiviral vector significantly inhibited IL-1ß, IL-6, and TNF-α protein levels induced by oral pathogen Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) in murine bone marrow-derived monocytes and macrophages (BMMs) compared with controls. In addition, knockdown of S1PR2 by the S1PR2 shRNA lentiviral vector suppressed p-PI3K, p-ERK, p-JNK, p-p38, and p-NF-κBp65 protein expressions induced by A. actinomycetemcomitans. Furthermore, bone marrow cells treated with the S1PR2 shRNA lentiviral vector inhibited osteoclastogenesis induced by RANKL compared with controls. The S1PR2 shRNA suppressed the mRNA levels of six osteoclastogenic factors including nuclear factor of activated T-cells cytoplasmic calcineurin-dependent 1 (NFATc1), cathepsin K (Ctsk), acid phosphatase 5 (Acp5), osteoclast-associated receptor (Oscar), dendritic cells specific transmembrane protein (Dcstamp), and osteoclast stimulatory transmembrane protein (Ocstamp) in bone marrow cells. We conclude that S1PR2 plays an essential role in modulating proinflammatory cytokine production and osteoclastogenesis. Blocking S1PR2 signaling might be a novel therapeutic strategy to treat inflammatory bone loss diseases.

LacR mutations are frequently observed in Streptococcus intermedius and are responsible for increased intermedilysin production and virulence.

Streptococcus intermedius secretes a human-specific cytolysin, intermedilysin (ILY), which is considered to be the major virulence factor of this pathogen. We screened for a repressor of ily expression by using random gene disruption in a low-ILY-producing strain (PC574). Three independent high-ILY-producing colonies that had plasmid insertions within a gene that has high homology to lacR were isolated. Validation of these observations was achieved through disruption of lacR in strain PC574 with an erythromycin cassette, which also led to higher hemolytic activity, increased transcription of ily, and higher cytotoxicity against HepG2 cells, compared to the parental strain. The direct binding of LacR within the ily promoter region was shown by a biotinylated DNA probe pulldown assay, and the amount of ILY secreted into the culture supernatant by PC574 cells was increased by adding lactose or galactose to the medium as a carbon source. Furthermore, we examined lacR nucleotide sequences and the hemolytic activity of 50 strains isolated from clinical infections and 7 strains isolated from dental plaque. Of the 50 strains isolated from infections, 13 showed high ILY production, 11 of these 13 strains had one or more point mutations and/or an insertion mutation in LacR, and almost all mutations were associated with a marked decline in LacR function. These results strongly suggest that mutation in lacR is required for the overproduction of ILY, which is associated with an increase in pathogenicity of S. intermedius.

Mucosal macrophages in intestinal homeostasis and inflammation.

Intestinal macrophages are essential for local homeostasis and in keeping a balance between commensal microbiota and the host. However, they also play essential roles in inflammation and protective immunity, when they change from peaceful regulators to powerful aggressors. As a result, activated macrophages are important targets for treatment of inflammatory bowel diseases such as Crohn's disease. Until recently, the complexity and heterogeneity of intestinal macrophages have been underestimated and here we review current evidence that there are distinct populations of resident and inflammatory macrophages in the intestine. We describe the mechanisms that ensure macrophages remain partially inert in the healthy gut and cannot promote inflammation despite constant exposure to bacteria and other stimuli. This may be because the local environment 'conditions' macrophage precursors to become unresponsive after they arrive in the gut. Nevertheless, this permits some active, physiological functions to persist. A new population of pro-inflammatory macrophages appears in inflammation and we review the evidence that this involves recruitment of a distinct population of fully responsive monocytes, rather than alterations in the existing cells. A constant balance between these resident and inflammatory macrophages is critical for maintaining the status quo in healthy gut and ensuring protective immunity when required.

Efectos de la infección in vitro de células monocítico-macrofágicaspor Chlamydia y su relación con los valores de lípidos / Effects in vitro of Chlamydia infection on monocitic-macrophagic cells and its relationship with lipid levels

Introducción: La célula mononuclear-fagocítica es un elemento celular clave en el proceso aterogénico. El monocito forma parte trascendental del proceso inflamatorio característico del inicio y desarrollo de la placa de ateroma. Por otra parte, la infiltración celular es también un elemento que debe tenerse en cuenta en el proceso inflamatorio cuando se ha considerado la asociación entre arteriosclerosis e infección. En la teoría infecciosa los gérmenes más frecuentemente asociados a la patología vascular han sido Citomegalovirus, Helicobacter y Chlamydia. En el presente trabajo nos ha interesado evaluar las características del comportamiento celular en cultivos de células implicadas en el proceso aterogénico infectadas con Chlamydia. Material y métodos: Se han empleado células endoteliales humanas establecidas (células Hep-2), células mononucleares establecidas (células THP-1) y cultivos primarios de monocitos procedentes de sangre periférica de voluntarios. Resultados: Todos los cultivos celulares son fácilmente infectados por Chlamydia. No obstante, sus efectos son distintos dependiendo del tipo celular. Cuando se ha comparado el efecto de sueros normo e hiperlipidémicos en los cultivos de células mononucleares infectadas con Chlamydia, se ha podido comprobar que el efecto que provoca la infección es amortiguado porla existencia de valores elevados de lípidos plasmáticos (AU)

Introduction: The mononuclear-fagocitic cellular type is a key element during the atherogenicprocess. The monocyte takes a transcendental role in the inflammatory process that is relevant at the onset and subsequent development of atheroma plaque. Otherwise, the cellular infiltration is a key feature to consider during the inflammatory process that we can found related with the atherosclerosis/infection association. According with the infectious explanation of atherosclerosis, microorganism more frequent associated with vascular pathology has been: Citomegalovirus, Helicobacter and Chlamydia. In the present paper we are interested to evaluate the characteristics and cellular behaviour of cultures of cells related with atherogenic process that has been previously infected with Chlamydia. Material and methods: We have analized established human endothelial cells (Hep-2 cells),established mononuclear cells (THP-1 cells) and primary cultures of monocytes from blood health volunteers. Results: All of cells types has been easily infected by Chlamydia. Nevertheless, the effects are different according with the different cells types. When we have compared the effect of nor moor hyperlipidemic serum specimens over the cultures of infected mononuclear cells it is possible o show that the effect of infection is amortiguated by the presence of high serum levels oflipids (AU)