Infection with the parasite Toxoplasma gondii leads to the induction of a Th1-type response dominated by IFN-γ production and control of this pathogen. Cells of the innate immune system are essential in initiating this response both through the production of IL-12 as well as the presentation of parasite-derived Ags to MHC-restricted T cells. Although dendritic cells (DCs) have been implicated in these events, the contribution of individual DC populations remains unclear. Therefore, multiparameter flow cytometry was used to identify and characterize subsets of murine DCs during acute toxoplasmosis. This approach confirmed that infection leads to the expansion and activation of conventional DC (cDC) subsets. Unexpectedly, however, this analysis further revealed that plasmacytoid DCs are also expanded and that these cells up-regulate MHC class II and costimulatory molecules associated with their acquired ability to prime naive CD4+ T cells. Furthermore, T. gondii-activated plasmacytoid DCs produce high levels of IL-12 and both plasmacytoid DC maturation and cytokine production are dependent on TLR11. Together these studies suggest that pDCs are a prominent DC subset involved in the initial stages of T. gondii infection, presenting parasite Ags and producing cytokines that are important for controlling infection.

BackgroundIn this study, we aimed to investigate the association between UCA1 and miR-27b in gastric cancer and further study their involvement in multi-drug resistance (MDR) of gastric cancer.Material/MethodsThe microarray data of dysregulated lncRNAs in gastric cancer tissues was retrieved in the GEO dataset. QRT-PCR analysis was performed to assess UCA1 expression based on 28 paired cancerous and peritumoral normal tissues. The human gastric cancer cell line SGC-7901, and SGC-7901 derived Adriamycin (doxorubicin) resistant SGC-7901/ADR, cisplatin resistant SGC-7901/DDP, and 5-FU resistant SGC-7901/FU cells were used as in vitro cell models to assess the effect of UCA1 and miR-27b on MDR.ResultsUCA1 was significantly upregulated in the cancerous tissues and its expression was negatively correlated with miR-27b expression level. Inhibition of UCA1 significantly restored miR-27b expression in MDR gastric cancer cells. UCA1 knockdown and miR-27b overexpression reduced IC50 of ADR, DDP, and 5-FU in SGC-7901/ADR cells and increased ADR induced cell apoptosis. UCA1 overexpression and miR-27b inhibition increased the IC50 of ADR, DDP, and 5-FU in SGC-7901 cells and reduced ADR induced cell apoptosis. Western blot analysis showed that UCA1 knockdown and miR-27b overexpression also decreased anti-apoptotic protein BCL-2 and increased apoptotic protein cleaved caspase-3.ConclusionsUCA1 is negatively correlated with miR-27b expression in gastric cancer tissue. Knockdown of UCA1 restored miR-27b expression in gastric cancer cells. The UCA1-miR-27b axis was involved in regulation of chemosensitivity of gastric cancer cells.

The transcription factor T-bet has been most prominently linked to natural killer (NK) and T cell production of interferon-γ (IFN-γ), a cytokine required for the control of a diverse array of intracellular pathogens. Indeed, in mice challenged with the parasite Toxoplasma gondii, NK and T cell responses are characterized by marked increases of T-bet expression. Unexpectedly, T-bet−/− mice infected with T. gondii develop a strong NK cell IFN-γ response that controls parasite replication at the challenge site, but display high parasite burdens at secondary sites colonized by T. gondii and succumb to infection. The loss of T-bet had a modest effect on T cell production of IFN-γ but did not impact on the generation of parasite-specific T cells. However, the absence of T-bet resulted in lower T cell expression of CD11a, Ly6C, KLRG-1, and CXCR3 and fewer parasite-specific T cells at secondary sites of infection, associated with a defect in parasite control at these sites. Together, these data highlight T-bet independent pathways to IFN-γ production, and reveal a novel role for this transcription factor in coordinating the T cell responses necessary to control this infection in peripheral tissues.

Toxoplasma gondii, an intracellular protozoan parasite, is a major cause of opportunistic infectious disease affecting the brain and has been linked to an increased incidence of schizophrenia. In murine hosts, infection with T. gondii stimulates tryptophan degradation along the kynurenine pathway (KP), which contains several neuroactive metabolites, including 3-hydroxykynurenine (3-HK), quinolinic acid (QUIN) and kynurenic acid (KYNA). As these endogenous compounds may provide a mechanistic connection between T. gondii and the pathophysiology of schizophrenia, we measured KP metabolites in both brain and periphery of T. gondii-treated C57BL/6 mice 8 and 28 days post-infection. Infected mice showed early decreases in the levels of tryptophan in brain and serum, but not in the liver. These reductions were associated with elevated levels of kynurenine, KYNA, 3-HK and QUIN in the brain. In quantitative terms, the most significant increases in these KP metabolites were observed in the brain at 28 days post-infection. Notably, the anti-parasitic drugs pyrimethamine and sulfadiazine, a standard treatment of toxoplasmosis, significantly reduced 3-HK and KYNA levels in the brain of infected mice when applied between 28 and 56 days post-infection. In summary, T. gondii infection, probably by activating microglia and astrocytes, enhances the production of KP metabolites in the brain. However, during the first two months after infection, the KP changes in these mice do not reliably duplicate abnormalities seen in the brain of individuals with schizophrenia.

The local production of gamma interferon (IFN-γ) is important to control Toxoplasma gondii in the brain, but the basis for these protective effects is not fully understood. The studies presented here reveal that the ability of IFN-γ to inhibit parasite replication in astrocytes in vitro is dependent on signal transducer and activator of transcription 1 (STAT1) and that mice that specifically lack STAT1 in astrocytes are unable to limit parasite replication in the central nervous system (CNS). This susceptibility is associated with a loss of antimicrobial pathways and increased cyst formation in astrocytes. These results identify a critical role for astrocytes in limiting the replication of an important opportunistic pathogen.