No abstract

Summary While commensal flora is involved in the regulation of immunity, the interplay between cytokine signaling and microbiota in atherosclerosis remains unknown. We found that interleukin (IL)-23 and its downstream target IL-22 restricted atherosclerosis by repressing pro-atherogenic microbiota. Inactivation of IL-23-IL-22 signaling led to deterioration of the intestinal barrier, dysbiosis and expansion of pathogenic bacteria with distinct biosynthetic and metabolic properties, causing systemic increase in pro-atherogenic metabolites such as lipopolysaccharide (LPS) and trimethylamine N-oxide (TMAO). Augmented disease in the absence of the IL-23-IL-22 pathway was mediated in part by pro-atherogenic osteopontin, controlled by microbial metabolites. Microbiota transfer from IL-23 deficient mice accelerated atherosclerosis, whereas microbial depletion or IL-22 supplementation reduced inflammation and ameliorated disease. Our work uncovers the IL-23-IL-22 signaling as a regulator of atherosclerosis that restrains expansion of pro-atherogenic microbiota, and argues for informed use of cytokine blockers to avoid cardiovascular side effects driven by microbiota and inflammation.

Rationale: Intraerythrocytic polymerization of Hb S promotes hemolysis and vasoocclusive events in the microvasculature of patients with sickle cell disease (SCD). Although plateletneutrophil aggregate-dependent vasoocclusion is known to occur in the lung and contribute to acute chest syndrome, the etiological mechanisms that trigger acute chest syndrome are largely unknown.Objectives: To identify the innate immune mechanism that promotes platelet-neutrophil aggregate-dependent lung vasoocclusion and injury in SCD.Methods: In vivo imaging of the lung in transgenic humanized SCD mice and in vitro imaging of SCD patient blood flowing through a microfluidic system was performed. SCD mice were systemically challenged with nanogram quantities of LPS to trigger lung vasoocclusion.Measurements and Main Results: Platelet-inflammasome activation led to generation of IL-1b and caspase-1-carrying platelet extracellular vesicles (EVs) that bind to neutrophils and promote platelet-neutrophil aggregation in lung arterioles of SCD mice in vivo and SCD human blood in microfluidics in vitro. The inflammasome activation, platelet EV generation, and platelet-neutrophil aggregation were enhanced by the presence of LPS at a nanogram dose in SCD but not control human blood. Inhibition of the inflammasome effector caspase-1 or IL-1b pathway attenuated platelet EV generation, prevented platelet-neutrophil aggregation, and restored microvascular blood flow in lung arterioles of SCD mice in vivo and SCD human blood in microfluidics in vitro.Conclusions: These results are the first to identify that plateletinflammasome-dependent shedding of IL-1b and caspase-1carrying platelet EVs promote lung vasoocclusion in SCD. The current findings also highlight the therapeutic potential of targeting the platelet-inflammasome-dependent innate immune pathway to prevent acute chest syndrome.

We used qLIM to study chronic liver injury, induced by a choline-deficient or DDC diet, in mice. Progression of chronic liver injury was accompanied by loss of bile transporters and tight junction proteins.

Acute lung injury, referred to as the acute chest syndrome, is a major cause of morbidity and mortality in patients with sickle cell disease (SCD), which often occurs in the setting of a vaso-occlusive painful crisis. P-selectin antibody therapy reduces hospitalization of SCD patients by almost 50%, suggesting that an unknown P-selectin-independent mechanism promotes remaining vaso-occlusive events. In SCD patients, intra-erythrocytic polymerization of mutant hemoglobin promotes ischemia-reperfusion injury and hemolysis, which leads to the development of sterile inflammation. Using intravital microscopy in transgenic, humanized SCD mice and in vitro studies with blood from SCD patients, we reveal for the first time that the sterile inflammatory milieu in SCD promotes caspase-4/11-dependent activation of neutrophil-Gasdermin-D (GSDMD), which triggers P-selectin-independent shedding of neutrophil extracellular traps (NETs) in the liver. Remarkably, these NETs travel intravascularly from liver to lung, where they promote neutrophil-platelet aggregation and the development of acute lung injury. This study introduces a novel paradigm that liver to lung embolic translocation of NETs promotes pulmonary vascular vaso-occlusion, and identifies a new GSDMD-mediated, P-selectin-independent mechanism of lung injury in SCD.

We report partially redundant function of catenins at AJ in regulating TJ and contributing to the blood-biliary barrier. Furthermore, concomitant hepatic loss of β- and γ-catenin disrupts structural and functional integrity of AJ and TJ via transcriptional and posttranslational mechanisms. Mice with dual catenin loss develop progressive intrahepatic cholestasis, providing a unique model to study diseases such as PFIC. (Hepatology 2018;67:2320-2337).

BaCKgRoUND aND aIMS:The Wnt/β-catenin signaling pathway has a well-described role in liver pathobiology. Its suppression was recently shown to decrease bile acid (BA) synthesis, thus preventing the development of cholestatic liver injury and fibrosis after bile duct ligation (BDL). appRoaCH aND ReSUltS: To generalize these observations, we suppressed β-catenin in Mdr2 knockout (KO) mice, which develop sclerosing cholangitis due to regurgitation of BA from leaky ducts. When β-catenin was knocked down (KD) in KO for 2 weeks, hepatic and biliary injury were exacerbated in comparison to KO given placebo, as shown by serum biochemistry, ductular reaction, inflammation, and fibrosis. Simultaneously, KO/KD livers displayed increased oxidative stress and senescence and an impaired regenerative response. Although the total liver BA levels were similar between KO/ KD and KO, there was significant dysregulation of BA transporters and BA detoxification/synthesis enzymes in KO/KD compared with KO alone. Multiphoton intravital microscopy revealed a mixing of blood and bile in the sinusoids, and validated the presence of increased serum BA in KO/KD mice. Although hepatocyte junctions were intact, KO/KD livers had significant canalicular defects, which resulted from loss of hepatocyte polarity. Thus, in contrast to the protective effect of β-catenin KD in BDL model, β-catenin KD in Mdr2 KO aggravated rather than alleviated injury by interfering with expression of BA transporters, hepatocyte polarity, canalicular structure, and the regenerative response. CoNClUSIoNS:The resulting imbalance between ongoing injury and restitution led to worsening of the Mdr2 KO phenotype, suggesting caution in targeting β-catenin globally for all cholestatic conditions. (Hepatology 2020;71:1732-1749).

Highlights d YAP1 is expressed in hepatoblasts during liver development d Yap1 loss from hepatoblasts led to absent intrahepatic bile duct (IHBD) formation d YAP1 is required for formation of the second layer of patent IHBD in development d Yap1 KO mice without IHBD survive by altering bile acid transport and metabolism