Dendritic cell-intrinsic LKB1-AMPK/SIK signaling controls metabolic homeostasis by limiting the hepatic Th17 response during obesity

Obesity-associated metabolic inflammation drives the development of insulin resistance and type 2 diabetes, notably through modulating innate and adaptive immune cells in metabolic organs. The nutrient sensor liver kinase B1 (LKB1) has recently been shown to control cellular metabolism and T cell priming functions of DCs. Here, we report that hepatic DCs from high-fat diet-fed (HFD-fed) obese mice display increased LKB1 phosphorylation and that LKB1 deficiency in DCs (CD11c Delta LKB1) worsened HFD-driven hepatic steatosis and impaired glucose homeostasis. Loss of LKB1 in DCs was associated with increased expression of Th17-polarizing cytokines and accumulation of hepatic IL-17A+ Th cells in HFD-fed mice. Importantly, IL-17A neutralization rescued metabolic perturbations in HFD-fed CD11c Delta LKB1 mice. Mechanistically, deficiency of the canonical LKB1 target AMPK in HFD-fed CD11c Delta AMPK alpha 1 mice recapitulated neither the hepatic Th17 phenotype nor the disrupted metabolic homeostasis, suggesting the involvement of other and/ or additional LKB1 downstream effectors. We indeed provide evidence that the control of Th17 responses by DCs via LKB1 is actually dependent on both AMPK alpha 1 salt-inducible kinase signaling. Altogether, our data reveal a key role for LKB1 signaling in DCs in protection against obesityinduced metabolic dysfunctions by limiting hepatic Th17 responses.Host-parasite interactio

Direct AMPK activation corrects NASH in rodents through metabolic effects and direct action on inflammation and fibrogenesis

No approved therapies are available for nonalcoholic steatohepatitis (NASH). Adenosine monophosphate–activated protein kinase (AMPK) is a central regulator of cell metabolism; its activation has been suggested as a therapeutic approach to NASH. Here we aimed to fully characterize the potential for direct AMPK activation in preclinical models and to determine mechanisms that could contribute to efficacy for this disease. A novel small-molecule direct AMPK activator, PXL770, was used. Enzyme activity was measured with recombinant complexes. De novo lipogenesis (DNL) was quantitated in vivo and in mouse and human primary hepatocytes. Metabolic efficacy was assessed in ob/ob and high-fat diet–fed mice. Liver histology, biochemical measures, and immune cell profiling were assessed in diet-induced NASH mice. Direct effects on inflammation and fibrogenesis were assessed using primary mouse and human hepatic stellate cells, mouse adipose tissue explants, and human immune cells. PXL770 directly activated AMPK in vitro and reduced DNL in primary hepatocytes. In rodent models with metabolic syndrome, PXL770 improved glycemia, dyslipidemia, and insulin resistance. In mice with NASH, PXL770 reduced hepatic steatosis, ballooning, inflammation, and fibrogenesis. PXL770 exhibited direct inhibitory effects on pro-inflammatory cytokine production and activation of primary hepatic stellate cells. Conclusion: In rodent models, direct activation of AMPK is sufficient to produce improvements in all core components of NASH and to ameliorate related hyperglycemia, dyslipidemia, and systemic inflammation. Novel properties of direct AMPK activation were also unveiled: improved insulin resistance and direct suppression of inflammation and fibrogenesis. Given effects also documented in human cells (reduced DNL, suppression of inflammation and stellate cell activation), these studies support the potential for direct AMPK activation to effectively treat patients with NASH

Schistosoma mansoni egg-derived thioredoxin and Sm14 drive the development of IL-10 producing regulatory B cells

During chronic schistosome infections, a complex regulatory network is induced to regulate the host immune system, in which IL-10-producing regulatory B (Breg) cells play a significant role. Schistosoma mansoni soluble egg antigens (SEA) are bound and internalized by B cells and induce both human and mouse IL-10 producing Breg cells. To identify Breg-inducing proteins in SEA, we fractionated SEA by size exclusion chromatography and found 6 fractions able to induce IL-10 production by B cells (out of 18) in the high, medium and low molecular weight (MW) range. The high MW fractions were rich in heavily glycosylated molecules, including multi-fucosylated proteins. Using SEA glycoproteins purified by affinity chromatography and synthetic glycans coupled to gold nanoparticles, we investigated the role of these glycan structures in inducing IL-10 production by B cells. Then, we performed proteomics analysis on active low MW fractions and identified a number of proteins with putative immunomodulatory properties, notably thioredoxin (SmTrx1) and the fatty acid binding protein Sm14. Subsequent splenic murine B cell stimulations and hock immunizations with recombinant SmTrx1 and Sm14 showed their ability to dose-dependently induce IL-10 production by B cells both in vitro and in vivo. Identification of unique Breg cells-inducing molecules may pave the way to innovative therapeutic strategies for inflammatory and auto-immune diseases.Author summaryWorm parasites, such as schistosomes, are master regulators of the human immune system, manipulating the host response in order to prolong their survival in their host. As a bystander effect, they also reduce immune responses to allergens and/or auto antigens, thus protecting their host against inflammatory and auto-immune diseases. One of the immune cells involved in immune regulation is the IL-10-producing regulatory B (Breg) cells. Schistosome eggs release various molecules that induce the development of Breg cells, but the identity of these molecules is not yet fully known. In this study, the authors aimed to identify some of these molecules. They investigated both the involvement of glycans on high molecular weight schistosomal egg molecules, as well as dissected the role of proteins with a lower molecular weight coming from schistosomal eggs. Using proteomics, they targeted various interesting molecules, which they recombinantly expressed and confirmed the IL-10 inducing capacity in B cells in vitro and in vivo for 2 molecules. This new knowledge may explain the hyporesponsiveness found in chronic schistosome-infected people and may pave the way to new innovative therapies for inflammatory and auto-immune diseases.Bio-organic Synthesi

Myeloid ATP citrate lyase regulates macrophage inflammatory responses in vitro without altering inflammatory disease outcomes

Macrophages are highly plastic, key regulators of inflammation. Deregulation of macrophage activation can lead to excessive inflammation as seen in inflammatory disorders like atherosclerosis, obesity, multiple sclerosis and sepsis. Targeting intracellular metabolism is considered as an approach to reshape deranged macrophage activation and to dampen the progression of inflammatory disorders. ATP citrate lyase (Acly) is a key metabolic enzyme and an important regulator of macrophage activation. Using a macrophage-specific Acly-deficient mouse model, we investigated the role of Acly in macrophages during acute and chronic inflammatory disorders. First, we performed RNA sequencing to demonstrate that Acly-deficient macrophages showed hyperinflammatory gene signatures in response to acute LPS stimulation in vitro. Next, we assessed endotoxin-induced peritonitis in myeloid-specific Acly-deficient mice and show that, apart from increased splenic Il6 expression, systemic and local inflammation were not affected by Acly deficiency. Also during obesity, both chronic low-grade inflammation and whole-body metabolic homeostasis remained largely unaltered in mice with Acly-deficient myeloid cells. Lastly, we show that macrophage-specific Acly deletion did not affect the severity of experimental autoimmune encephalomyelitis (EAE), an experimental model of multiple sclerosis. These results indicate that, despite increasing inflammatory responses in vitro, macrophage Acly deficiency does not worsen acute and chronic inflammatory responses in vivo. Collectively, our results indicate that caution is warranted in prospective long-term treatments of inflammatory disorders with macrophage-specific Acly inhibitors. Together with our earlier observation that myeloid Acly deletion stabilizes atherosclerotic lesions, our findings highlight that therapeutic targeting of macrophage Acly can be beneficial in some, but not all, inflammatory disorders.Host-parasite interactio

The helminth glycoprotein omega-1 improves metabolic homeostasis in obese mice through type 2 immunity-independent inhibition of food intake

Type 2 immunity plays an essential role in the maintenance of metabolic homeostasis and its disruption during obesity promotes meta-inflammation and insulin resistance. Infection with the helminth parasite Schistosoma mansoni and treatment with its soluble egg antigens (SEA) induce a type 2 immune response in metabolic organs and improve insulin sensitivity and glucose tolerance in obese mice, yet, a causal relationship remains unproven. Here, we investigated the effects and underlying mechanisms of the T2 ribonuclease omega-1 (omega 1), one of the major S mansoni immunomodulatory glycoproteins, on metabolic homeostasis. We show that treatment of obese mice with plant-produced recombinant omega 1, harboring similar glycan motifs as present on the native molecule, decreased body fat mass, and improved systemic insulin sensitivity and glucose tolerance in a time- and dose-dependent manner. This effect was associated with an increase in white adipose tissue (WAT) type 2 T helper cells, eosinophils, and alternatively activated macrophages, without affecting type 2 innate lymphoid cells. In contrast to SEA, the metabolic effects of omega 1 were still observed in obese STAT6-deficient mice with impaired type 2 immunity, indicating that its metabolic effects are independent of the type 2 immune response. Instead, we found that omega 1 inhibited food intake, without affecting locomotor activity, WAT thermogenic capacity or whole-body energy expenditure, an effect also occurring in leptin receptor-deficient obese and hyperphagic db/db mice. Altogether, we demonstrate that while the helminth glycoprotein omega 1 can induce type 2 immunity, it improves whole-body metabolic homeostasis in obese mice by inhibiting food intake via a STAT6-independent mechanism.Radiolog

Soluble mannose receptor induces proinflammatory macrophage activation and metaflammation

Proinflammatory activation of macrophages in metabolic tissues is critically important in the induction of obesity-induced metaflammation. Here, we demonstrate that the soluble mannose receptor (sMR) plays a direct functional role in both macrophage activation and metaflammation. We show that sMR binds CD45 on macrophages and inhibits its phosphatase activity, leading to an Src/Akt/ NF-kappa B-mediated cellular reprogramming toward an inflammatory phenotype both in vitro and in vivo. Remarkably, increased serum sMR levels were observed in obese mice and humans and directly correlated with body weight. Importantly, enhanced sMR levels increase serum proinflammatory cytokines, activate tissue macrophages, and promote insulin resistance. Altogether, our results reveal sMR as regulator of proinflammatory macrophage activation, which could constitute a therapeutic target for metaflammation and other hyperinflammatory diseases.Diabetes mellitus: pathophysiological changes and therap

Immune Regulation of Metabolic Homeostasis by Helminths and Their Molecules

Host-parasite interactio

COMPREHENSIVE STUDY OF SILICA GLASS PRODUCTION USING ICP-MS AND ICP-AES METHODS

International audienc

Sex and vaccination: Insights from female rats vaccinated with juvenile-specific proteases from Fasciola hepatica

Most animal research is less evidence-based for females, with the majority of studies conducted on males. Since immune responses vary between males and females, sexual dimorphism in immunity contributes, among other things, to sex-based differences post-vaccination. However, the issue of sex effects in animal vaccine research is rarely considered in vaccine study design. Previously, we have evaluated the efficacy of cathepsin L3 (FhCL3-1 and FhCL3-2) and B3 proteases (FhCB3) from juvenile Fasciola hepatica as vaccines against fasciolosis in male rats. Their administration resulted in reductions in liver fluke recovery in the range of 4763% when compared with an infection control group. Here, we investigated if the protective effect of vaccination with these proteins can also be observed for female rats. The data indicates females were not protected from F. hepatica infection when vaccinated with juvenile cathepsins. Only in the FhCL3-2 vaccinated group was a low, non-significant, reduction in worm burden observed (21%). Although liver fluke mean body lengths and wet weights were reduced in vaccinated animals when compared with the infection controls, these effects were adjuvant- not vaccine-induced, while for males changes in these parameters were related primarily to vaccination. Specific humoral responses throughout the study were evident; however, trends in antibody responses in females replicated trends observed previously for male humoral responses. Formerly, elevated levels of FhCL3-1 and FhCL3-2 specific IgG1 and IgG2a were suggested to be correlated with protection. Here, despite increased and clear responses of these antibodies, protection was not observed. Hence, in the present study the roles of IgG1 and IgG2 in liver fluke reduction are questionable. Results demonstrated in our study show that observations obtained in one sex are not always applicable to the other sex. Hopefully, the findings of the study will stimulate discussion of the issue of sex i

Intranasal delivery of a formulation containing stage-specific recombinant proteins of Fasciola hepatica cathepsin L5 and cathepsin B2 triggers an anti-fecundity effect and an adjuvant-mediated reduction in fluke burden in sheep

Fasciola hepatica infection continues to be a major problem in the agriculture sector, particularly in sheep and cattle. Cathepsin L and B proteases are major components of the excretory/secretory material of the parasite, and their roles in several important aspects of parasite invasion and survival has led to their use as targets in rational vaccine design. Previous studies in rats demonstrated that the use of stage-specific antigens, cathepsin B2 and cathepsin L5, as part of a multivalent vaccine, was able to confer significant protection against challenge. In the present study, recombinant versions of cathepsin L5 and cathepsin B2 produced in yeast were used in combination to vaccinate sheep. Intramuscular and intranasal forms of administration were applied, and sheep were subsequently challenged with 150 F. hepatica metacercariae. Intramuscular vaccination was able to induce a strong systemic antibody response against both antigens, but failed to confer significant protection. Conversely, no elevated antibody response was detected against the vaccine antigens following nasal vaccination; however, a reduction in parasite egg viability (>92%) and a statistically significant (p = 0.006), predominantly adjuvant-mediated reduction in worm burdens was observed