cGAS-mediated autophagy protects the liver from ischemia-reperfusion injury independently of STING.

Liver ischemia-reperfusion (I/R) injury occurs through induction of oxidative stress and release of damage-associated molecular patterns (DAMPs), including cytosolic DNA released from dysfunctional mitochondria or from the nucleus. Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS) is a cytosolic DNA sensor known to trigger stimulator of interferon genes (STING) and downstream type 1 interferon (IFN-I) pathways, which are pivotal innate immune system responses to pathogen. However, little is known about the role of cGAS/STING in liver I/R injury. We subjected C57BL/6 (WT), cGAS knockout (cGAS-/-), and STING-deficient (STINGgt/gt) mice to warm liver I/R injury and that found cGAS-/- mice had significantly increased liver injury compared with WT or STINGgt/gt mice, suggesting a protective effect of cGAS independent of STING. Liver I/R upregulated cGAS in vivo and also in vitro in hepatocytes subjected to anoxia/reoxygenation (A/R). We confirmed a previously published finding that hepatocytes do not express STING under normoxic conditions or after A/R. Hepatocytes and liver from cGAS-/- mice had increased cell death and reduced induction of autophagy under hypoxic conditions as well as increased apoptosis. Protection could be restored in cGAS-/- hepatocytes by overexpression of cGAS or by pretreatment of mice with autophagy inducer rapamycin. Our findings indicate a novel protective role for cGAS in the regulation of autophagy during liver I/R injury that occurs independently of STING. NEW & NOTEWORTHY Our studies are the first to document the important role of cGAS in the acute setting of sterile injury induced by I/R. Specifically, we provide evidence that cGAS protects liver from I/R injury in a STING-independent manner.

Redox-dependent regulation of hepatocyte absent in melanoma 2 inflammasome activation in sterile liver injury in mice.

Sterile liver inflammation, such as liver ischemia-reperfusion, hemorrhagic shock after trauma, and drug-induced liver injury, is initiated and regulated by endogenous mediators including DNA and reactive oxygen species. Here, we identify a mechanism for redox-mediated regulation of absent in melanoma 2 (AIM2) inflammasome activation in hepatocytes after redox stress in mice, which occurs through interaction with cytosolic high mobility group box 1 (HMGB1). We show that in liver during hemorrhagic shock in mice and in hepatocytes after hypoxia with reoxygenation, cytosolic HMGB1 associates with AIM2 and is required for activation of caspase-1 in response to cytosolic DNA. Activation of caspase-1 through AIM2 leads to subsequent hepatoprotective responses such as autophagy. HMGB1 binds to AIM2 at a non-DNA-binding site on the hematopoietic interferon-inducible nuclear antigen domain of AIM2 to facilitate inflammasome and caspase-1 activation in hepatocytes. Furthermore, binding of HMGB1 to AIM2 is stronger with fully reduced all-thiol HMGB1 than with partially oxidized disulfide-HMGB1, and binding strength corresponds to caspase-1 activation. These data suggest that HMGB1 redox status regulates AIM2 inflammasome activation. CONCLUSION: These findings suggest a novel and important mechanism for regulation of AIM2 inflammasome activation in hepatocytes during redox stress and may suggest broader implications for how this and other inflammasomes are activated and how their activation is regulated during cell stress, as well as the mechanisms of inflammasome regulation in nonimmune cell types. (Hepatology 2017;65:253-268).

Mechanical ventilation enhances extrapulmonary sepsis-induced lung injury: role of WISP1-αvß5 integrin pathway in TLR4-mediated inflammation and injury.

BACKGROUND: High tidal volume ventilation of healthy lungs or exacerbation of existing acute lung injury (ALI) by more moderate mechanical ventilation (MTV) produces ventilator-induced lung injury. It is less clear whether extrapulmonary sepsis sensitizes the lung to MTV. METHODS: We used a two-hit model of cecal ligation and puncture (CLP) followed 12 h later by MTV (10 ml/kg; 6 h) to determine whether otherwise noninjurious MTV enhances CLP-induced ALI by contrasting wildtype and TLR4-/- mice with respect to: alveolar-capillary permeability, histopathology and intrapulmonary levels of WNT-inducible secreted protein 1 (WISP1) and integrin ß5; plasma levels of cytokines and chemokines (TNF-α, IL-6, MIP-2, MCP-1) and intrapulmonary neutrophil infiltration; and other inflammatory signaling via intrapulmonary activation of JNK, p38 and ERK. A separate cohort of mice was pretreated with intratracheal neutralizing antibodies to WISP1, integrin ß5 or IgG as control and the presented phenotyping repeated in a two-hit model; there were 10 mice per group in these first three experiments. Also, isolated peritoneal macrophages (PM) from wildtype and TLR4-/-, MyD88-/- and TRIF-/- mice were used to identify a WISP1-TLR4-integrin ß5 pathway; and the requisite role of integrin ß5 in WISP1-induced cytokine and chemokine production in LPS-primed PM was examined by siRNA treatment. RESULTS: MTV, that in itself did not cause ALI, exacerbated increases in alveolar-capillary permeability, histopathologic scoring and indices of pulmonary inflammation in mice that previously underwent CLP; the effects of this two-hit model were abrogated in TLR4-/- mice. Attendant with these findings was a significant increase in intrapulmonary WISP1 and integrin ß5 in the two-hit model. Anti-WISP1 or anti-integrin ß5 antibodies partially inhibited the two-hit phenotype. In PM, activation of TLR4 led to an increase in integrin ß5 expression that was MyD88 and NF-κB dependent. Recombinant WISP1 increased LPS-induced cytokine release in PM that was inhibited by silencing either TLR4 or integrin ß5. CONCLUSIONS: These data show for the first time that otherwise noninjurious mechanical ventilation can exacerbate ALI due to extrapulmonary sepsis underscoring a potential interactive contribution of common events (sepsis and mechanical ventilation) in critical care, and that a WISP1-TLR4-integrin ß5 pathway contributes to this phenomenon.

The HIV Protease Inhibitor Saquinavir Inhibits HMGB1-Driven Inflammation by Targeting the Interaction of Cathepsin V with TLR4/MyD88.

Extracellular high-mobility group box 1 (HMGB1) (disulfide form), via activation of toll-like receptor 4 (TLR4)-dependent signaling, is a strong driver of pathologic inflammation in both acute and chronic conditions. Identification of selective inhibitors of HMGB1-TLR4 signaling could offer novel therapies that selectively target proximal endogenous activators of inflammation. A cell-based screening strategy led us to identify first generation HIV-protease inhibitors (PI) as potential inhibitors of HMGB1-TLR4 driven cytokine production. Here we report that the first-generation HIV-PI saquinavir (SQV), as well as a newly identified mammalian protease inhibitor STO33438 (334), potently block disulfide HMGB1-induced TLR4 activation, as assayed by the production of TNF-α by human monocyte-derived macrophages (THP-1). We further report on the identification of mammalian cathepsin V, a protease, as a novel target of these inhibitors. Cellular as well as recombinant protein studies show that the mechanism of action involves a direct interaction between cathepsin V with TLR4 and its adaptor protein MyD88. Treatment with SQV, 334 or the known cathepsin inhibitor SID26681509 (SID) significantly improved survival in murine models of sepsis and reduced liver damage following warm liver ischemia/reperfusion (I/R) models, both characterized by strong HMGB1-TLR4 driven pathology. The current study demonstrates a novel role for cathepsin V in TLR4 signaling and implicates cathepsin V as a novel target for first-generation HIV-PI compounds. The identification of cathepsin V as a target to block HMGB1-TLR4-driven inflammation could allow for a rapid transition of the discovery from the bench to the bedside. Disulfide HMGB1 drives pathologic inflammation in many models by activating signaling through TLR4. Cell-based screening identified the mammalian protease cathepsin V as a novel therapeutic target to inhibit TLR4-mediated inflammation induced by extracellular HMGB1 (disulfide form). We identified two protease inhibitors (PIs) that block cathepsin V and thereby inhibit disulfide HMGB1-induced TLR4 activation: saquinavir (SQV), a first-generation PI targeting viral HIV protease and STO33438 (334), targeting mammalian proteases. We discovered that cathepsin V binds TLR4 under basal and HMGB1-stimulated conditions, but dissociates in the presence of SQV over time. Thus cathepsin V is a novel target for first-generation HIV PIs and represents a potential therapeutic target of pathologic inflammation.

Dexmedetomidine promotes apoptosis and suppresses proliferation of hepatocellular carcinoma cells via microRNA-130a/EGR1 axis.

Accumulating evidence has revealed the role of microRNAs (miRs) in hepatocellular carcinoma (HCC). Dexmedetomidine, a highly selective α2-adrenergic agonist, is widely used in perioperative settings for analgesia and sedation. Herein, we aimed to determine whether dexmedetomidine might directly regulate miR-130a/early growth response 1 (EGR1) axis in HCC and explore the related mechanisms. miR-130a and EGR1 expression were determined in HCC tissues and their correlation was evaluated. Human HCC cell line HCCLM3 was selected. Upon the determination of the optimal concentration of dexmedetomidine, HCCLM3 cells were treated with dexmedetomidine, miR-130a- or EGR1-related oligonucleotides or plasmids were transfected into cells to explore their functions in cell biological behaviors. miR-130a and EGR1 levels in cells were tested. The targeting relationship between miR-130a and EGR1 was verified. miR-130a was inhibited while EGR1 was elevated in HCC tissues and they were negatively correlated. EGR1 was targeted by miR-130a. With the increase of dexmedetomidine concentration, HCCLM3 cell viability was correspondingly inhibited, miR-130a expression was elevated and EGR1 expression was decreased. Dexmedetomidine, upregulating miR-130a or downregulating EGR1 inhibited proliferation, invasion and migration, and promoted apoptosis of HCCLM3 cells. MiR-130a upregulation/downregulation enhanced/impaired the effect of dexmedetomidine on cell biological behaviors. Our study provides evidence that raising miR-130a enhances the inhibitory effects of dexmedetomidine on HCC cellular growth via inhibiting EGR1. Thus, miR-130a may be a potential candidate for the treatment of HCC.

Adverse Drug Reaction Discovery Using a Tumor-Biomarker Knowledge Graph.

Adverse drug reactions (ADRs) are a major public health concern, and early detection is crucial for drug development and patient safety. Together with the increasing availability of large-scale literature data, machine learning has the potential to predict unknown ADRs from current knowledge. By the machine learning methods, we constructed a Tumor-Biomarker Knowledge Graph (TBKG) which contains four types of node: Tumor, Biomarker, Drug, and ADR using biomedical literatures. Based on this knowledge graph, we not only discovered potential ADRs of antitumor drugs but also provided explanations. Experiments on real-world data show that our model can achieve 0.81 accuracy of three cross-validation and the ADRs discovery of Osimertinib was chosen for the clinical validation. Calculated ADRs of Osimertinib by our model consisted of the known ADRs which were in line with the official manual and some unreported rare ADRs in clinical cases. Results also showed that our model outperformed traditional co-occurrence methods. Moreover, each calculated ADRs were attached with the corresponding paths of "tumor-biomarker-drug" in the knowledge graph which could help to obtain in-depth insights into the underlying mechanisms. In conclusion, the tumor-biomarker knowledge-graph based approach is an explainable method for potential ADRs discovery based on biomarkers and might be valuable to the community working on the emerging field of biomedical literature mining and provide impetus for the mechanism research of ADRs.