The mucosal inflammatory response to non-typhoidal Salmonella in the intestine is blunted by IL-10 during concurrent malaria parasite infection.

Coinfection can markedly alter the response to a pathogen, thereby changing its clinical presentation. For example, non-typhoidal Salmonella (NTS) serotypes are associated with gastroenteritis in immunocompetent individuals. In contrast, individuals with severe pediatric malaria can develop bacteremic infections with NTS, during which symptoms of gastroenteritis are commonly absent. Here we report that, in both a ligated ileal loop model and a mouse colitis model, malaria parasites caused a global suppression of gut inflammatory responses and blunted the neutrophil influx that is characteristic of NTS infection. Further, malaria parasite infection led to increased recovery of Salmonella enterica serotype Typhimurium from the draining mesenteric lymph node (MLN) of mice. In the mouse colitis model, blunted intestinal inflammation during NTS infection was independent of anemia but instead required parasite-induced synthesis of interleukin (IL)-10. Blocking of IL-10 in coinfected mice reduced dissemination of S. Typhimurium to the MLN, suggesting that induction of IL-10 contributes to development of disseminated infection. Thus IL-10 produced during the immune response to malaria in this model contributes to suppression of mucosal inflammatory responses to invasive NTS, which may contribute to differences in the clinical presentation of NTS infection in the setting of malaria

Increased systemic replication of <i>S.</i> Typhimurium (<i>S</i>Tm) during concurrent <i>P. yoelii</i> (<i>Py</i>) infection.

<p><b>A,</b> Parasitemia and anemia in <i>P. yoelii</i>-infected mice (n = 4). Arrows indicate time points at which <i>P. yoelii</i> and <i>S.</i> Typhimurium were inoculated. <b>B,</b> Comparison of parasitemia at 14 d after <i>P. yoelii</i> infection in <i>P. yoelii</i>-infected mice and mice co-infected for 4 d with <i>S.</i> Typhimurium (n = 5). Data are shown as mean ± SEM. <b>C,</b> Colonization (CFU) of the liver at 2 and 4 days after IG infection of <i>P. yoelii</i>-infected or uninfected CBA mice with <i>S.</i> Typhimurium (n = 5–10). Results are from 2 independent experiments. <b>D,</b> CFU of <i>S.</i> Typhimurium in the blood 4 days after IG infection of CBA mice (n = 5). Panels, B, C and D are compiled from the two independent experiments. <b>E–F,</b> CFU in liver (<b>E</b>) and blood (<b>F</b>) at 2 and 3 days after IP infection of <i>P. yoelii</i>-infected or uninfected CBA mice (n = 5). Dots represent individual mice and bars represent the mean ± SEM. Statistical significance was determined using an unpaired Student's <i>t</i> test on log-transformed values and is indicated as *, <i>P</i><0.05; **, <i>P</i><0.01.</p

Liver CD11b⁺ macrophages exhibit increased association with <i>S.</i> Typhimurium and an altered phenotype during malaria parasite co-infection.

<p><b>A,</b> CD11b⁺ liver cells were enriched by positive selection from <i>S.</i> Typhimurium-infected and co-infected CBA mice at 4 days post-<i>S.</i> Typhimurium infection (n = 4). CFU of <i>S.</i> Typhimurium was enumerated from 10⁶ CD11b⁺ liver cells. CD11b⁺ liver cells, <b>B,</b> Expression of <i>Il10</i>, <i>Ym1</i>, <i>Fizz1</i>, and <i>Arg1</i> in CD11b⁺ liver cells was determined by qRT-PCR. Data are expressed as fold change over mock-infected control. All mice were co-infected as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g001" target="_blank">Fig. 1A</a>. Dots represent individual mice and bars represent the mean ± SEM. Statistical significance was determined using an unpaired Student's <i>t</i> test (<b>A</b>) or one-way ANOVA with Tukey's post test (<b>B</b>) on log-transformed values and is indicated as *, <i>P</i><0.05; **, <i>P</i><0.01.</p

Thermogenic adipocytes promote HDL turnover and reverse cholesterol transport

Diabetes mellitus: pathophysiological changes and therap

Macrophage/neutrophil derived IL-10 contributes to increased systemic <i>S.</i> Typhimurium burden during concurrent malaria parasite infection.

<p>Mice conditionally deficient for IL-10 expression on myeloid cells (<i>Il10^f/f LysM-cre</i>) or Cre-negative littermate controls were infected with <i>S.</i> Typhimurium or co-infected with <i>S.</i> Typhimurium and <i>P. yoelii</i>. Bacterial colonization was assessed 2 days after IP inoculation with <i>S.</i> Typhimurium and 12 days after <i>P. yoelii</i> inoculation (n = 5–6). <b>A,</b> Colonization of liver tissue (left panel) and blood (right panel) by <i>S.</i> Typhimurium. <b>B,</b> Parasitemia in Cre^+/− and Cre^−/− mice co-infected with <i>P. yoelii</i> and <i>S.</i> Typhimurium <b>C,</b>. Expression of <i>Il10</i> in livers of <i>Il10^f/f LysM-cre</i> mice or littermate controls at 12 after <i>P. yoelii</i> infection and 2 days after <i>S.</i> Typhimurium infection. Bars represent the mean +SEM (n = 5). Dots represent individual mice and bars represent the mean ± SEM. Data are compiled from 2 independent experiments. Statistical significance was determined using an unpaired Student's <i>t</i> test on log-transformed values and is indicated as *, <i>P</i><0.05; **, <i>P</i><0.01.</p

Malaria parasite-induced IL-10 acts on myeloid cells.

<p>Mice conditionally deficient for IL-10 receptor (Il10R) on myeloid cells (<i>Il10R^f/f LysM-cre</i>) or Cre-negative littermate controls were infected with <i>S.</i> Typhimurium or co-infected with <i>S.</i> Typhimurium and <i>P. yoelii</i>. Bacterial colonization was assessed 2 days after IP inoculation with <i>S.</i> Typhimurium and 12 days after <i>P. yoelii</i> inoculation (n = 5–8). <b>A,</b> Colonization of liver tissue by <i>S.</i> Typhimurium. <b>B, </b><i>S.</i> Typhimurium bacteremia. <b>C,</b> Parasitemia in Cre^+/− and Cre^−/− mice co-infected with <i>P. yoelii</i> and <i>S.</i> Typhimurium. Dots represent individual mice and bars represent the mean ± SEM. Data are compiled from 2 independent experiments. Statistical significance was determined using an unpaired Student's <i>t</i> test on log-transformed values and is indicated as *, <i>P</i><0.05; **, <i>P</i><0.01.</p

Decreased neutrophil-mediated pathology in the liver of co-infected mice.

<p><b>A,</b> Quantification of inflammatory lesions in the liver and representative micrographs of H&E stained liver tissue from mock-infected mice, mice infected with <i>P. yoelii</i>, or co-infected mice 4 days after IG inoculation of <i>S.</i> Typhimurium in CBA mice (n = 5–10). Arrows represent pyogranulomatous lesions and arrowheads represent perivascular monocytic infiltrates. Results are from the experiment shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g001" target="_blank">figure 1B</a>. <b>B,</b> Representative flow cytometry plots for neutrophil frequency in singlet live CD3⁻ B220⁻ NK1.1⁻ CD11b⁺ liver cells. Right panel shows quantification of neutrophils from <i>S.</i> Typhimurium and co-infected mice (n = 4–5). Dotted line represents mock-infected mice (n = 2). The gating strategy used for generation of these results is shown in <b>Fig. S2 in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat.1004049.s001" target="_blank">Text S1</a></b>. <b>C,</b> Number of neutrophils (singlet live CD3⁻ B220⁻ NK1.1⁻ CD11b⁺ Ly6G⁺) per 4×10⁶ liver cells determined by AccuCount beads. Results are from data shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g002" target="_blank">figure 2D</a>. <b>D,</b> Number of circulating neutrophils (K/µl) determined by complete blood counts. Results are from data shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g002" target="_blank">figure 2C</a>. <b>E,</b> Expression of <i>Cxcl1</i>, <i>Lcn2</i> and <i>Il10</i> in liver tissue of CBA mice 4 days after IG inoculation with <i>S.</i> Typhimurium (n = 4–9). Data expressed as fold change over mock-infected control. Results are from the experiment shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g001" target="_blank">figure 1B</a>. <b>F,</b> Circulating IL-10 measured 2 days after IG infection with <i>S.</i> Typhimurium. Results are from the experiment shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g001" target="_blank">figure 1B</a>. Data bars represent the mean +SEM. Statistical significance was determined using an unpaired Student's <i>t</i> test (<b>A–D, F</b>) or ANOVA with Tukey's post test (<b>E</b>) on log-transformed values and is indicated as *, <i>P</i><0.05; **, <i>P</i><0.01.</p

IL-10 contributes to increased systemic loads of <i>S.</i> Typhimurium in malaria parasite-infected CBA mice.

<p><b>A, </b><i>S.</i> Typhimurium and co-infected CBA mice as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g001" target="_blank">Fig. 1A</a>, were depleted of IL-10 using a blocking antibody, or treated with a control antibody. At 2 d post-<i>S.</i> Typhimurium infection, CFU of <i>S.</i> Typhimurium were enumerated in liver and blood (n = 4–5). Statistical significance was determined using an unpaired Student's <i>t</i> test on log-transformed values, or a Mann-Whitney U test for groups that include all zero values, and is indicated as *, <i>P</i><0.05; **, <i>P</i><0.01. <b>B,</b> Mice were treated with either an anti-RBC antibody to induce anemia, recombinant IL-10 (rIL-10) or both. At 4 days post-<i>S.</i> Typhimurium infection, CFU were enumerated in liver and blood (n = 5). Dots represent individual mice and bars represent the mean ± SEM. Brackets indicate the contributions of anemia and IL-10 to increased bacterial colonization. <b>C,</b> Levels of anemia in experimental groups from (<b>B</b>) at 4 d post IG infection. The number of circulating RBC in mice infected with <i>P. yoelii</i> at 14 d after inoculation is given as a reference. Statistical significance was determined using one-way ANOVA with a Tukey's post test *, <i>P</i><0.05; **, <i>P</i><0.01.</p

IL-10 contributes to blunting of neutrophil chemokines in livers of malaria parasite-infected C57BL/6 mice.

<p><b>A,</b> Mice deficient for IL-10 (<i>Il10^−/−</i>) or controls (C56BL/6) were infected with either <i>S.</i> Typhimurium or co-infected as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g001" target="_blank">Fig. 1A</a>. At 2 days post-<i>S.</i> Typhimurium infection, CFU of <i>S.</i> Typhimurium was enumerated in liver (n = 5–13). Dots represent individual mice. <b>B,</b> Expression of <i>Cxcl1</i>, <i>Lcn2</i> and <i>Il10</i> in liver tissue of control mice, 2 days after <i>S.</i> Typhimurium infection (n = 5–13). Results are from data shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g004" target="_blank">figure 4A</a>. <b>C,</b> Expression of <i>Cxcl1</i> and <i>Lcn2</i> in liver tissue of <i>Il10^−/−</i> mice, 2 days after <i>S.</i> Typhimurium infection (n = 5–8). Results are from data shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004049#ppat-1004049-g004" target="_blank">figure 4A</a>. <b>D,</b> Effect of co-infection with <i>S.</i> Typhimurium in C57BL/6 and <i>Il10^−/−</i> mice on malaria parasitemia. C57BL/6 and <i>Il10^−/−</i> and mice were inoculated IP with blood stage <i>P. yoelii</i>, then at day 10, were inoculated IG with <i>S.</i> Typhimurium. Parasitemia was determined at day 12 (2 days after <i>S.</i> Typhimurium infection). Bars represent the mean +SEM (n = 4–6). Data from control mice are compiled from 3 independent experiments and <i>Il10^−/−</i> from 1 experiment. Statistical significance was determined using an unpaired Student's <i>t</i> test (<b>A</b>, <b>D</b>) or one-way ANOVA with Tukey's post test (<b>B</b>, <b>C</b>) on log-transformed values and is indicated as *, <i>P</i><0.05; **, <i>P</i><0.01.</p

Thermogenic adipocytes promote HDL turnover and reverse cholesterol transport

Brown and beige adipocytes combust nutrients for thermogenesis and through their metabolic activity decrease pro-atherogenic remnant lipoproteins in hyperlipidemic mice. However, whether the activation of thermogenic adipocytes affects the metabolism and anti-atherogenic properties of high-density lipoproteins (HDL) is unknown. Here, we report a reduction in atherosclerosis in response to pharmacological stimulation of thermogenesis linked to increased HDL levels in APOE*3-Leiden.CETP mice. Both cold-induced and pharmacological thermogenic activation enhances HDL remodelling, which is associated with specific lipidomic changes in mouse and human HDL. Furthermore, thermogenic stimulation promotes HDL-cholesterol clearance and increases macrophage-to-faeces reverse cholesterol transport in mice. Mechanistically, we show that intravascular lipolysis by adipocyte lipoprotein lipase and hepatic uptake of HDL by scavenger receptor B-I are the driving forces of HDL-cholesterol disposal in liver. Our findings corroborate the notion that high metabolic activity of thermogenic adipocytes confers atheroprotective properties via increased systemic cholesterol flux through the HDL compartment