Stiffness sensing via Piezo1 enhances macrophage efferocytosis and promotes the resolution of liver fibrosis.

Tissue stiffening is a predominant feature of fibrotic disorders, but the response of macrophages to changes in tissue stiffness and cellular context in fibrotic diseases remains unclear. Here, we found that the mechanosensitive ion channel Piezo1 was up-regulated in hepatic fibrosis. Macrophages lacking Piezo1 showed sustained inflammation and impaired spontaneous resolution of early liver fibrosis. Further analysis revealed an impairment of clearance of apoptotic cells by macrophages in the fibrotic liver. Macrophages showed enhanced efferocytosis when cultured on rigid substrates but not soft ones, suggesting stiffness-dependent efferocytosis of macrophages required Piezo1 activation. Besides, Piezo1 was involved in the efficient acidification of the engulfed cargo in the phagolysosomes and affected the subsequent expression of anti-inflammation genes after efferocytosis. Pharmacological activation of Piezo1 increased the efferocytosis capacity of macrophages and accelerated the resolution of inflammation and fibrosis. Our study supports the antifibrotic role of Piezo1-mediated mechanical sensation in liver fibrosis, suggesting that targeting PIEZO1 to enhance macrophage efferocytosis could induce fibrosis regression.

Neutrophil-macrophage communication via extracellular vesicle transfer promotes itaconate accumulation and ameliorates cytokine storm syndrome.

Cytokine storm syndrome (CSS) is a life-threatening systemic inflammatory syndrome involving innate immune hyperactivity triggered by various therapies, infections, and autoimmune conditions. However, the potential interplay between innate immune cells is not fully understood. Here, using poly I:C and lipopolysaccharide (LPS)-induced cytokine storm models, a protective role of neutrophils through the modulation of macrophage activation was identified in a CSS model. Intravital imaging revealed neutrophil-derived extracellular vesicles (NDEVs) in the liver and spleen, which were captured by macrophages. NDEVs suppressed proinflammatory cytokine production by macrophages when cocultured in vitro or infused into CSS models. Metabolic profiling of macrophages treated with NDEV revealed elevated levels of the anti-inflammatory metabolite, itaconate, which is produced from cis-aconitate in the Krebs cycle by cis-aconitate decarboxylase (Acod1, encoded by Irg1). Irg1 in macrophages, but not in neutrophils, was critical for the NDEV-mediated anti-inflammatory effects. Mechanistically, NDEVs delivered miR-27a-3p, which suppressed the expression of Suclg1, the gene encoding the enzyme that metabolizes itaconate, thereby resulting in the accumulation of itaconate in macrophages. These findings demonstrated that neutrophil-to-macrophage communication mediated by extracellular vesicles is critical for promoting the anti-inflammatory reprogramming of macrophages in CSS and may have potential implications for the treatment of this fatal condition.

Oxidized mitochondrial DNA induces gasdermin D oligomerization in systemic lupus erythematosus.

Although extracellular DNA is known to form immune complexes (ICs) with autoantibodies in systemic lupus erythematosus (SLE), the mechanisms leading to the release of DNA from cells remain poorly characterized. Here, we show that the pore-forming protein, gasdermin D (GSDMD), is required for nuclear DNA and mitochondrial DNA (mtDNA) release from neutrophils and lytic cell death following ex vivo stimulation with serum from patients with SLE and IFN-γ. Mechanistically, the activation of FcγR downregulated Serpinb1 following ex vivo stimulation with serum from patients with SLE, leading to spontaneous activation of both caspase-1/caspase-11 and cleavage of GSDMD into GSDMD-N. Furthermore, mtDNA oxidization promoted GSDMD-N oligomerization and cell death. In addition, GSDMD, but not peptidyl arginine deiminase 4 is necessary for extracellular mtDNA release from low-density granulocytes from SLE patients or healthy human neutrophils following incubation with ICs. Using the pristane-induced lupus model, we show that disease severity is significantly reduced in mice with neutrophil-specific Gsdmd deficiency or following treatment with the GSDMD inhibitor, disulfiram. Altogether, our study highlights an important role for oxidized mtDNA in inducing GSDMD oligomerization and pore formation. These findings also suggest that GSDMD might represent a possible therapeutic target in SLE.

The role of type 1 interferons in coagulation induced by gram-negative bacteria.

Bacterial infection not only stimulates innate immune responses but also activates coagulation cascades. Overactivation of the coagulation system in bacterial sepsis leads to disseminated intravascular coagulation (DIC), a life-threatening condition. However, the mechanisms by which bacterial infection activates the coagulation cascade are not fully understood. Here we show that type 1 interferons (IFNs), a widely expressed family of cytokines that orchestrate innate antiviral and antibacterial immunity, mediate bacterial infection-induced DIC by amplifying the release of high-mobility group box 1 (HMGB1) into the bloodstream. Inhibition of the expression of type 1 IFNs and disruption of their receptor IFN-α/ßR or downstream effector (eg, HMGB1) uniformly decreased gram-negative bacteria-induced DIC. Mechanistically, extracellular HMGB1 markedly increased the procoagulant activity of tissue factor by promoting the externalization of phosphatidylserine to the outer cell surface, where phosphatidylserine assembles a complex of cofactor-proteases of the coagulation cascades. These findings not only provide novel insights into the link between innate immune responses and coagulation, but they also open a new avenue for developing novel therapeutic strategies to prevent DIC in sepsis.

The physical and oxidative stabilities of Pickering emulsion stabilized by starch particle and small molecular surfactant.

Sunflower oil-in-water Pickering emulsions were fabricated using octenyl succinic anhydride (OSA) modified starch particles and small molecular surfactants (e.g., SDS, CTAB and Tween 20) as stabilizers. Emulsions were characterized for physical stabilities by cream volume, droplet size distribution and microstructure. Oxidative stabilities of the emulsions were investigated by accelerated oxidation tests at 50 °C. Results showed that cream volumes had little difference after 14 days of storage, while the droplet sizes of emulsions stabilized by starch particles and surfactants decreased greatly compared to those only with starch particles (p < 0.05). Droplet microstructure revealed that small molecular surfactants competed with starch particles for the adsorption at interface. The emulsion stabilized by 1.0% OS-starch particle and 1.0% SDS had the lowest peroxide value and acid value. These findings implied that starch particles were compatible with anionic surfactants and could enhance the stabilities and decrease the oxidation rate of Pickering emulsions.

Bacterial Endotoxin Activates the Coagulation Cascade through Gasdermin D-Dependent Phosphatidylserine Exposure.

Excessive activation of the coagulation system leads to life-threatening disseminated intravascular coagulation (DIC). Here, we examined the mechanisms underlying the activation of coagulation by lipopolysaccharide (LPS), the major cell-wall component of Gram-negative bacteria. We found that caspase-11, a cytosolic LPS receptor, activated the coagulation cascade. Caspase-11 enhanced the activation of tissue factor (TF), an initiator of coagulation, through triggering the formation of gasdermin D (GSDMD) pores and subsequent phosphatidylserine exposure, in a manner independent of cell death. GSDMD pores mediated calcium influx, which induced phosphatidylserine exposure through transmembrane protein 16F, a calcium-dependent phospholipid scramblase. Deletion of Casp11, ablation of Gsdmd, or neutralization of phosphatidylserine or TF prevented LPS-induced DIC. In septic patients, plasma concentrations of interleukin (IL)-1α and IL-1ß, biomarkers of GSDMD activation, correlated with phosphatidylserine exposure in peripheral leukocytes and DIC scores. Our findings mechanistically link immune recognition of LPS to coagulation, with implications for the treatment of DIC.