Hepatic mitochondrial DNA/Toll-like receptor 9/MicroRNA-223 forms a negative feedback loop to limit neutrophil overactivation and acetaminophen hepatotoxicity in mice

MiR-223 is increased in lungs of patients with COPD and modulates cigarette smoke-induced pulmonary inflammation

Since microRNA (miR)-223-3p modulates inflammatory responses and COPD is associated with amplified pulmonary inflammation, we hypothesized that miR-223-3p plays a role in COPD pathogenesis. Expression of miR-223-3p was measured in lung tissue of 2 independent cohorts with COPD GOLD stage II-IV patients, never smokers and smokers without COPD. The functional role of miR-223-3p was studied in deficient mice and upon overexpression in airway epithelial cells from COPD and controls. We observed higher miR-223-3p levels in patients with COPD stage II-IV compared to (non)-smoking controls, and levels were associated with higher neutrophil numbers in bronchial biopsies of COPD patients. MiR-223-3p expression was also increased in lungs and bronchoalveolar lavage of cigarette smoke (CS)-exposed mice. CS-induced neutrophil and monocyte lung infiltration was stronger in miR-223 deficient mice upon acute (5 days) exposure, but attenuated upon sub-chronic (4 weeks) exposure. Additionally, miR-223 deficiency attenuated acute and sub-chronic CS-induced lung infiltration of dendritic cells and T lymphocytes. Finally, in vitro overexpression of miR-223-3p in non-COPD airway epithelial cells suppressed CXCL8 and GM-CSF secretion and gene expression of the pro-inflammatory transcription factor TRAF6. Importantly, this suppressive effect of miR-223-3p was compromised in COPD-derived cultures. In conclusion, we demonstrate that miR-223-3p is increased in lungs of COPD patients and CS-exposed mice, and is associated with neutrophilic inflammation. In vivo data indicate that miR-223 acts as negative regulator of acute CS-induced neutrophilic and monocytic inflammation. In vitro data suggests that miR-223-3p does so by suppressing pro-inflammatory airway epithelial responses, which is less effective in COPD epithelium.

Emodin Attenuates Acetaminophen-Induced Hepatotoxicity via the cGAS-STING Pathway

Emodin is a natural bioactive compound from traditional Chinese herbs that exerts anti-inflammatory, antioxidant, anticancer, hepatoprotective, and neuroprotective effects. However, the protective effects of emodin in acetaminophen (APAP)-induced hepatotoxicity are not clear. The present study examined the effects of emodin on APAP-induced hepatotoxicity and investigated the potential molecular mechanisms. C57BL/6 mice were pretreated with emodin (15 and 30 mg/kg) for 5 consecutive days and then given APAP (300 mg/kg) to establish an APAP-induced liver injury model. Mice were sacrificed to detect the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and albumin (ALB) and the liver tissue levels of glutathione (GSH), malondialdehyde (MDA), and superoxide dismutase (SOD). Histological assessment, Western blotting, and ELISA were performed. Emodin pretreatment significantly reduced the levels of ALT, AST, and ALP; increased the levels of ALB; alleviated hepatocellular damage and apoptosis; attenuated the exhaustion of GSH and SOD and the accumulation of MDA; and increased the expression of antioxidative enzymes, including nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), and NAD(P)H quinone dehydrogenase 1 (NQO1). Emodin also inhibited the expression of NLRP3 and reduced the levels of pro-inflammatory factors, including interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor-alpha (TNF-α). Emodin inhibited interferon (IFN)-α, cyclic GMP-AMP synthase (cGAS), and its downstream signaling effector stimulator of interferon genes (STING) expression to protect the liver against APAP-induced inflammatory responses and apoptosis. These results suggest that emodin protected hepatocytes from APAP-induced liver injury via the upregulation of the Nrf2-mediated antioxidative stress pathway, the inhibition of the NLRP3 inflammasome, and the downregulation of the cGAS-STING signaling pathway.

Antishock Characteristics of Erythrocyte-mediated Endoplasmic Reticulum Stress in Macrophages in Severe Hemorrhagic Shock Environment Based on TLR9-cGAS-STING-IFN Signal Axis

This study aimed to investigate the protective effects of erythrocyte-mediated endoplasmic reticulum (ER) stress in macrophages in hemorrhagic shock. An hemorrhagic shock model was established in male BALB/c mice. Animals were randomly divided into three groups (n = 8): control group (A), erythrocyte reinfusion group (B), and TLR9 inhibition group (C). Eight healthy BALB/c mice were also included as group N (n = 8). Mice in group A were not treated, while mice in groups B and C were transfused with red blood cells separated from the blood of mice in group N. Flow cytometry was used to detect the expression of erythrocyte surface protein TLR9 in each group. Immunofluorescence assay was used to analyze the distribution and relative expression of protein STING in macrophages. Flow cytometry was used to analyze the expression of STING, ATF6, and IRE1 in macrophages. Enzyme-linked immunosorbent assay was used to analyze the levels of inflammatory signal molecules, including IFN-α, IFN-β, IL-6, CCL4, CCL5, and IL-6. FITC-Annexin V was used to analyze the apoptosis of immune cells (macrophages) in mouse blood samples and to detect the concentration of calcium ions in erythrocyte cytoplasm. The results showed that the expression of erythrocyte surface protein TLR9; the distribution of STING-positive cells in macrophages; the expressions of STING, ATF6, and IRE1 in macrophages; the levels of inflammatory signal molecules; the apoptosis rate of macrophages; and the intracellular calcium concentration in erythrocytes in group B were higher than those in group A, followed by group C. These results suggest that TLR9 regulates ER stress in macrophages of mice with hemorrhagic shock through the TLR9-cGAS-STING-IFN signaling pathway. Increased expression of TLR9 enhanced macrophage activity, reduced apoptosis, enhanced inflammatory response and immune response, and restored electrolyte level, which might be a therapeutic option for the treatment of hemorrhagic shock.

The Role of miRNA in the Pathophysiology of Neuroendocrine Tumors

Neuroendocrine tumors (NETs) represent a tumor group that is both rare and heterogeneous. Prognosis is largely determined by the tumor grading and the site of the primary tumor and metastases. Despite intensive research efforts, only modest advances in diagnostic and therapeutic approaches have been achieved in recent years. For patients with non-respectable tumor stages, prognosis is poor. In this context, the development of novel diagnostic tools for early detection of NETs and prediction of tumor response to therapy as well as estimation of the overall prognosis would greatly improve the clinical management of NETs. However, identification of novel diagnostic molecules is hampered by an inadequate understanding of the pathophysiology of neuroendocrine malignancies. It has recently been demonstrated that microRNA (miRNA), a family of small RNA molecules with an established role in the pathophysiology of quite different cancer entities, may also play a role as a biomarker. Here, we summarize the available knowledge on the role of miRNAs in the development of NET and highlight their potential use as serum-based biomarkers in the context of this disease. We discuss important challenges currently preventing their use in clinical routine and give an outlook on future directions of miRNA research in NET.

MicroRNA-223 inhibits neutrophil extracellular traps formation through regulating calcium influx and small extracellular vesicles transmission

Modulation of miRNAs and neutrophil extracellular traps (NETs) formation are both implicated in inflammatory disorders. Adult-onset Still's disease (AOSD) is a systemic autoinflammatory disease with neutrophilic leukocytosis and unknown etiology. Although the NETs formation is elevated in AOSD patients, the regulatory roles of miRNAs in NETs formation in AOSD remains unclear. We revealed that the circulating levels of IL-18, NETs, and miR-223 were significantly higher in active AOSD patients, compared with inactive AOSD patients or healthy controls (P < 0.005). Moreover, IL-18 increased calcium influx into neutrophils, which led to mitochondrial ROS (mROS) production and NETs formation. Elevated levels of NETs-DNA could induce miR-223 expression in neutrophils through activating Toll-like receptor 9. The upregulated miR-223 expression in neutrophils suppressed mROS production by blocking calcium influx, and subsequently inhibited IL-18-mediated NETs formation. Besides, the increased neutrophil-derived exosomal miR-223 levels were observed in active AOSD patients compared with healthy controls (P < 0.005). Our in vitro assays demonstrated that the neutrophil-derived small extracellular vesicles carried miR-223, which could repress IL-18 production in macrophages. Together, these results suggest a fine-tuned mechanism between inflammatory (IL-18 induced NETs) and anti-inflammatory (miR-223) factors in AOSD. MiR-223, mROS inhibitors, and calcium channel blockers are the potential therapeutics for autoinflammatory diseases such as AOSD.

Protective Role of microRNA-31 in Acetaminophen-Induced Liver Injury: A Negative Regulator of c-Jun N-Terminal Kinase (JNK) Signaling Pathway

BACKGROUND & AIMS

Sustained c-Jun N-terminal kinase (JNK) activation plays a major role in drug-induced liver injury (DILI). Stress-responsive microRNA-31 (miR-31) has been implicated in regulating different cellular damage, and JNK activation could induce miR-31 expression. However, the regulatory role of miR-31 in DILI has not been studied previously. We aimed to investigate whether miR-31 could ameliorate DILI and ascertain potential molecular mechanism.

METHODS

miR-31 gene knockout (31-KO) and wild-type C57BL/6J mice were used to construct an acetaminophen (APAP)-induced DILI model. Primary mouse hepatocytes, as well as alpha mouse liver 12 (AML-12) cell lines, were used for in vitro experiments. Argonaute 2-associated RNA immunoprecipitation combined with high-throughput sequencing were performed to identify specific targets of miR-31.

RESULTS

31-KO mice showed a higher mortality rate, liver transaminase levels, and hepatic necrosis compared with those in wild-type mice after APAP-induced hepatotoxicity. The protective role of miR-31 on hepatocytes has been analyzed via constructing bone marrow chimeric mice. Mechanistically, we found that hepatic JNK phosphorylation increased significantly in 31-KO mice. This caused mitochondrial phosphorylated Src (p-Src) inactivation and more reactive oxygen species production, which directly amplifies hepatocyte necrotic cell death, while administration of JNK-specific inhibitor SP600125 could abrogate the differences. Moreover, bioinformatics analysis of RNA immunoprecipitation combined with high-throughput sequencing identified that guanosine triphosphatase, cell division cycle protein 42 (Cdc42), the upstream molecule of JNK signaling, was the specific target of miR-31 and could form a miR-31/Cdc42/phosphorylated mixed-lineage kinase 3 (p-MLK3) negative feedback loop to restrict JNK overactivation. Clinically, both miR-31 and phosphorylated JNK (p-JNK) were highly increased in liver tissues of DILI patients with different etiologies.

CONCLUSIONS

miR-31 can down-regulate Cdc42 to restrict overactivation of reactive oxygen species/JNK/mitochondria necrotic death loop in hepatocytes of APAP-induced DILI, which might provide a new therapeutic target for alleviating JNK overactivation-based liver injury.

Circular RNA circUbe2k promotes hepatic fibrosis via sponging miR-149-5p/TGF-β2 axis

Abundant regulatory genes and complex circuits involving non-coding RNAs (ncRNAs) monitor the formation and development of hepatic fibrosis (HF). Circular RNAs (circRNAs) are a class of RNAs generated from protein coding genes by back-splicing, playing crucial roles in various pathological processes, including HF. However, little is known about mechanisms of action of circRNAs, let alone in HF. In this study, we found circUbe2k enhanced in CCl₄ -induced HF mice and LX-2 cells stimulated with TGF-β1, regulating the development of HF. Restraining the expression of circUbe2k inhibited α-SMA and Col1α1 expression in CCl₄ -induced HF mice and in LX-2 cells stimulated with TGF-β1. Furthermore, inhibiting circUbe2k expression reduced hepatic stellate cells (HSCs) activation and proliferation in vivo and in vitro. Mechanistically, we demonstrated a direct interaction between circUbe2k and miR-149-5p, which results in the modulation of TGF-β2 expressions. Together, circUbe2k may act as a "catalyst" of HSCs activation and HF through the circUbe2k/miR-149-5p/TGF-β2 axis. Our results provide unprecedented evidence for a significant role for circUbe2k to serve as a potential biomarker for HF therapy.

Oxidative Stress-A Key Player in the Course of Alcohol-Related Liver Disease

Oxidative stress is known to be an inseparable factor involved in the presentation of liver disorders. Free radicals interfere with DNA, proteins, and lipids, which are crucial in liver metabolism, changing their expression and biological functions. Additionally, oxidative stress modifies the function of micro-RNAs, impairing the metabolism of hepatocytes. Free radicals have also been proven to influence the function of certain transcriptional factors and to alter the cell cycle. The pathological appearance of alcohol-related liver disease (ALD) constitutes an ideal example of harmful effects due to the redox state. Finally, ethanol-induced toxicity and overproduction of free radicals provoke irreversible changes within liver parenchyma. Understanding the underlying mechanisms associated with the redox state in the course of ALD creates new possibilities of treatment for patients. The future of hepatology may become directly dependent on the effective action against reactive oxygen species. This review summarizes current data on the redox state in the natural history of ALD, highlighting the newest reports on this topic.

Role of Noncoding RNAs in Acetaminophen-Induced Liver Injury

Genomic and transcriptomic analyses have well established that the major fraction of the mammalian genome is transcribed into different classes of RNAs ranging in size from a few nucleotides to hundreds of thousands of nucleotides, which do not encode any protein. Some of these noncoding RNAs (ncRNAs) are directly or indirectly linked to the regulation of expression or functions of 25,000 proteins coded by <2% of the human genome. Among these regulatory RNAs, microRNAs are small (2125 nucleotides) RNAs that are processed from precursor RNAs that have stemloop structure, whereas noncoding RNAs >200 nucleotides are termed long noncoding RNAs (lncRNAs). Circular RNAs (circRNAs) are newly identified lncRNA members that are generated by back-splicing of primary transcripts. The functions of ncRNAs in modulating liver toxicity of xenobiotics are emerging only recently. Acetaminophen (N-acetyl-para-aminophenol, paracetamol or APAP) is a safe analgesic and antipyretic drug at the therapeutic dose. However, it can cause severe liver toxicity that may lead to liver failure if overdosed or combined with alcohol, herbs, or other xenobiotics. This review discusses the role of ncRNAs in acetaminophen metabolism, toxicity, and liver regeneration after APAP-induced liver injury (AILI).

Tumor-Associated Neutrophils in Hepatocellular Carcinoma Pathogenesis, Prognosis, and Therapy

Hepatocellular carcinoma represents the most prevalent primary liver cancer worldwide, and it is either caused by intrinsic genetic mutations or by a multitude of extrinsic risk factors. Even though the interplay between chronic inflammatory changes and hepatocarcinogenesis has been at the forefront of clinical investigation for the past few decades, the role of tumor-associated neutrophils (TANs) in HCC development still remains ambiguous. On the one hand, N1 TANs exhibit an anti-tumorigenic activity, mediated by direct or indirect tumor cell lysis, whereas on the other hand, N2 TANs have been correlated with increased HCC growth, invasiveness, and metastasis. The association of an elevated Neutrophil-to-Lymphocyte Ratio (NLR) with poor prognosis in patients with HCC, has been recently brought into spotlight, consolidating its widespread use as a reliable biomarker. Due to the decisive involvement of TANs in HCC pathogenesis and development, the utilization of various neutrophil-centered anticancer treatment modalities has been under clinical experimentation, selectively targeting and modulating the processes of neutrophil recruitment, activation, and migration. This review summarizes current evidence on the role of TANs in HCC pathogenesis and progression, as well as in their potential involvement in tumor therapy, shedding light on emerging anticancer treatment methods targeting neutrophils.

Toll-Like Receptor Signaling Pathways: Novel Therapeutic Targets for Cerebrovascular Disorders

Toll-like receptors (TLRs), a class of pattern recognition proteins, play an integral role in the modulation of systemic inflammatory responses. Cerebrovascular diseases (CVDs) are a group of pathological conditions that temporarily or permanently affect the brain tissue mostly via the decrease of oxygen and glucose supply. TLRs have a critical role in the activation of inflammatory cascades following hypoxic-ischemic events and subsequently contribute to neuroprotective or detrimental effects of CVD-induced neuroinflammation. The TLR signaling pathway and downstream cascades trigger immune responses via the production and release of various inflammatory mediators. The present review describes the modulatory role of the TLR signaling pathway in the inflammatory responses developed following various CVDs and discusses the potential benefits of the modulation of different TLRs in the improvement of functional outcomes after brain ischemia.

CD36 deficiency ameliorates drug-induced acute liver injury in mice

Background

Acetaminophen (APAP) overdose causes hepatotoxicity and even acute liver failure. Recent studies indicate that sterile inflammation and innate immune cells may play important roles in damage-induced hepatocytes regeneration and liver repair. The scavenger receptor CD36 has its crucial functions in sterile inflammation. However, the roles of CD36 in APAP induced acute liver injury remain unclear and warrant further investigation.

Methods

WT C57BL/6 J and CD36^−/− mice were intraperitoneally injected with APAP (300 mg/kg) after fasting for 16 h. Liver injury was evaluated by serum alanine aminotransferase (ALT) level and liver tissue hematoxylin and eosin (H&E) staining. Liver inflammatory factor expression was determined by real-time polymerase chain reaction (PCR). The protein adducts forming from the metabolite of APAP and the metabolism enzyme cytochrome P450 2E1 (CYP2E1) levels were measured by Western blot. Liver infiltrating macrophages and neutrophils were characterized by flow cytometry. RNA sequencing and Western blot were used to evaluate the effect of damage-associated molecular patterns (DAMP) molecule high mobility group B1 (HMGB1) on WT and CD36^−/− macrophages. Moreover, PP2, a Src kinase inhibitor, blocking CD36 signaling, was applied in APAP model.

Results

The expression of CD36 was increased in the liver of mice after APAP treatment. Compared with WT mice, APAP treated CD36^−/− mice show less liver injury. There was no significant difference in APAP protein adducts and CYP2E1 expression between these two strains. However, reduced pro-inflammatory factor mRNA expression and serum IL-1β level were observed in APAP treated CD36^−/− mice as well as infiltrating macrophages and neutrophils. Moreover, CD36 deficiency impaired the activation of c-Jun N-terminal kinase (JNK) caused by APAP. Interestingly, the lack of CD36 reduced the activation of extracellular regulated protein kinases (Erk) and v-akt murine thymoma viral oncogene homolog (Akt) induced by HMGB1. RNA transcription sequencing data indicated that HMGB1 has a different effect on WT and CD36^−/− macrophages. Furthermore, treatment with PP2 attenuated APAP induced mouse liver injury.

Conclusion

Our data demonstrated that CD36 deficiency ameliorated APAP-induced acute liver injury and inflammatory responses by decreasing JNK activation. CD36 might serve as a new target to reduce acute liver injury.

Liver-specific deletion of mechanistic target of rapamycin does not protect against acetaminophen-induced liver injury in mice

BACKGROUND

Acetaminophen (APAP) overdose can cause liver injury and liver failure, which is one of the most common causes of drug-induced liver injury in the United States. Pharmacological activation of autophagy by inhibiting mechanistic target of rapamycin (mTOR) protects against APAP-induced liver injury likely via autophagic removal of APAP-adducts and damaged mitochondria. In the present study, we aimed to investigate the role of genetic ablation of mTOR pathways in mouse liver in APAP-induced liver injury and liver repair/regeneration.

METHODS

Albumin-Cre (Alb-Cre) mice, mTOR^f/f and Raptor^f/f mice (C57BL/6J background) were crossbred to produce liver-specific mTOR knockout (L-mTOR KO, Alb Cre+/-, mTOR^f/f) and liver-specific Raptor KO (L-Raptor, Alb Cre+/-, Raptor ^f/f) mice. Alb-Cre littermates were used as wild-type (WT) mice. These mice were treated with APAP for various time points for up to 48 h. Liver injury, cell proliferation, autophagy and mTOR activation were determined.

RESULTS

We found that genetic deletion of neither Raptor, an important adaptor protein in mTOR complex 1, nor mTOR, in the mouse liver significantly protected against APAP-induced liver injury despite increased hepatic autophagic flux. Genetic deletion of Raptor or mTOR in mouse livers did not affect APAP metabolism and APAP-induced c-Jun N-terminal kinase (JNK) activation, but slightly improved mouse survival likely due to increased hepatocyte proliferation.

CONCLUSIONS

Our results indicate that genetic ablation of mTOR in mouse livers does not protect against APAP-induced liver injury but may slightly improve liver regeneration and mouse survival after APAP overdose.

The complex roles of neutrophils in APAP-induced liver injury

Acetaminophen (APAP) is a widely applied drug for the alleviation of pain and fever, which is also a dose‐depedent toxin. APAP‐induced acute liver injury has become one of the primary causes of liver failure which is an increasingly serious threat to human health. Neutrophils are the major immune cells in human serving as the first barrier against the invasion of pathogen. It has been reported that neutrophils patriciate in the occurrence and development of APAP‐induced liver injury. However, evolving evidences suggest that neutrophils also contribute to tissue repair and actively orchestrate resolution of inflammation. Here, we addressed the complex roles in APAP‐induced liver injury on the basis of brief introduction of neutrophil's activation, recruitment and migration.

MicroRNAs as regulators, biomarkers and therapeutic targets in liver diseases

MicroRNAs (miRNAs) are small, non-coding RNAs that post-transcriptionally regulate gene expression by binding to specific mRNA targets and promoting their degradation and/or translational inhibition. miRNAs regulate both physiological and pathological liver functions. Altered expression of miRNAs is associated with liver metabolism dysregulation, liver injury, liver fibrosis and tumour development, making miRNAs attractive therapeutic strategies for the diagnosis and treatment of liver diseases. Here, we review recent advances regarding the regulation and function of miRNAs in liver diseases with a major focus on miRNAs that are specifically expressed or enriched in hepatocytes (miR-122, miR-194/192), neutrophils (miR-223), hepatic stellate cells (miR-29), immune cells (miR-155) and in circulation (miR-21). The functions and target genes of these miRNAs are emphasised in alcohol-associated liver disease, non-alcoholic fatty liver disease, drug-induced liver injury, viral hepatitis and hepatocellular carcinoma, as well liver fibrosis and liver failure. We touch on the roles of miRNAs in intercellular communication between hepatocytes and other types of cells via extracellular vesicles in the pathogenesis of liver diseases. We provide perspective on the application of miRNAs as biomarkers for early diagnosis, prognosis and assessment of liver diseases and discuss the challenges in miRNA-based therapy for liver diseases. Further investigation of miRNAs in the liver will help us better understand the pathogeneses of liver diseases and may identify biomarkers and therapeutic targets for liver diseases in the future.

Neutrophil-to-hepatocyte communication via LDLR-dependent miR-223-enriched extracellular vesicle transfer ameliorates nonalcoholic steatohepatitis

Neutrophil infiltration around lipotoxic hepatocytes is a hallmark of nonalcoholic steatohepatitis (NASH); however, how these 2 types of cells communicate remains obscure. We have previously demonstrated that neutrophil-specific microRNA-223 (miR-223) is elevated in hepatocytes to limit NASH progression in obese mice. Here, we demonstrated that this elevation of miR-223 in hepatocytes was due to preferential uptake of miR-223-enriched extracellular vesicles (EVs) derived from neutrophils as well other types of cells, albeit to a lesser extent. This selective uptake was dependent on the expression of low-density lipoprotein receptor (LDLR) on hepatocytes and apolipoprotein E (APOE) on neutrophil-derived EVs, which was enhanced by free fatty acids. Once internalized by hepatocytes, the EV-derived miR-223 acted to inhibit hepatic inflammatory and fibrogenic gene expression. In the absence of this LDLR- and APOE-dependent uptake of miR-223-enriched EVs, the progression of steatosis to NASH was accelerated. In contrast, augmentation of this transfer by treatment with an inhibitor of proprotein convertase subtilisin/kexin type 9, a drug used to lower blood cholesterol by upregulating LDLR, ameliorated NASH in mice. This specific role of LDLR and APOE in the selective control of miR-223-enriched EV transfer from neutrophils to hepatocytes may serve as a potential therapeutic target for NASH.

Role of Neutrophils in the Pathogenesis of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) includes a spectrum of liver disorders, from fatty liver to nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. Compared with fatty liver, NASH is characterized by increased liver injury and inflammation, in which liver-infiltrating immune cells, with neutrophil infiltration as a hallmark of NASH, play a critical role in promoting the progression of fatty liver to NASH. Neutrophils are the first responders to injury and infection in various tissues, establishing the first line of defense through multiple mechanisms such as phagocytosis, cytokine secretion, reactive oxygen species production, and neutrophil extracellular trap formation; however, their roles in the pathogenesis of NASH remain obscure. The current review summarizes the roles of neutrophils that facilitate the progression of fatty liver to NASH and their involvement in inflammation resolution during NASH pathogenesis. The notion that neutrophils are potential therapeutic targets for the treatment of NASH is also discussed.

Preliminary Study on Hepatoprotective Effect and Mechanism of (-)-Epigallocatechin-3-gallate against Acetaminophen-induced Liver Injury in Rats

Antipyretic acetaminophen (APAP) is a commonly used drug that generally associates with liver injury. (-)-Epigallocatechin-3-gallate (EGCG), an active polyphenol extracted from green tea, is extensively reported to have the potential to impact a variety of human diseases. However, few studies were reported regarding the protective effect of EGCG on APAP-induced liver injury and the mechanism is still unclear. In this study, in-vitro and in-vivo experiments were carried out to verify the hepatoprotective effect of EGCG against APAP-induced liver injury and explore the potential mechanism. Results indicated that EGCG effectively relieved the liver injury caused by APAP, as well as APAP-induced mitochondrial dysfunction. The protective role of EGCG was not only attributed to its antioxidant capacity; but also might be related to the protective effect on hepatic mitochondrial impairment; based on that, EGCG could improve the membrane potential and activities of the respiratory chain complexes in liver mitochondria. Our study casts a new light on the mechanism of EGCG's hepatoprotective effect and suggests that EGCG has considerable potential in developing tonics for relieving APAP-induced liver injury.

Immunological mechanisms and therapeutic targets of fatty liver diseases

Alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) are the two major types of chronic liver disease worldwide. Inflammatory processes play key roles in the pathogeneses of fatty liver diseases, and continuous inflammation promotes the progression of alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH). Although both ALD and NAFLD are closely related to inflammation, their respective developmental mechanisms differ to some extent. Here, we review the roles of multiple immunological mechanisms and therapeutic targets related to the inflammation associated with fatty liver diseases and the differences in the progression of ASH and NASH. Multiple cell types in the liver, including macrophages, neutrophils, other immune cell types and hepatocytes, are involved in fatty liver disease inflammation. In addition, microRNAs (miRNAs), extracellular vesicles (EVs), and complement also contribute to the inflammatory process, as does intertissue crosstalk between the liver and the intestine, adipose tissue, and the nervous system. We point out that inflammation also plays important roles in promoting liver repair and controlling bacterial infections. Understanding the complex regulatory process of disrupted homeostasis during the development of fatty liver diseases may lead to the development of improved targeted therapeutic intervention strategies.

A Potential Role for Mitochondrial DNA in the Activation of Oxidative Stress and Inflammation in Liver Disease

Mitochondria are organelles that are essential for cellular homeostasis including energy harvesting through oxidative phosphorylation. Mitochondrial dysfunction plays a vital role in liver diseases as it produces a large amount of reactive oxygen species (ROS), in turn leading to further oxidative damage to the structure and function of mitochondria and other cellular components. More severe oxidative damage occurred in mitochondrial DNA (mtDNA) than in nuclear DNA. mtDNA dysfunction results in further oxidative damage as it participates in encoding respiratory chain polypeptides. In addition, mtDNA can leave the mitochondria and enter the cytoplasm and extracellular environment. mtDNA is derived from ancient bacteria, contains many unmethylated CpG dinucleotide repeats similar to bacterial DNA, and thus can induce inflammation to exacerbate damage to liver cells and distal organs by activating toll-like receptor 9, inflammatory bodies, and stimulator of interferon genes (STING). In this review, we focus on the mechanism by which mtDNA alterations cause liver injuries, including nonalcoholic fatty liver, alcoholic liver disease, drug-induced liver injury, viral hepatitis, and liver cancer.

NLRP12 negatively regulates EtOH-induced liver macrophage activation via NF-κB pathway and mediates hepatocyte apoptosis in alcoholic liver injury

Alcohol-induced liver injury is characterized by abnormal liver dysfunction and excessive inflammation response. Recent years a wealth of data have been yielded indicating that EtOH (ethyl alcohol)-induced macrophage activation along with liver inflammation plays a dominating role in the progression of alcohol-induced liver injury. Here we found high expression of NLRP12 (Nucleotide-binding oligomerization domain protein 12, which is generally considered to be a negative regulator of inflammatory response) in EtOH-fed mouse liver tissue, primary Kupffer cells and EtOH-induced RAW264.7 cells. Additionally, overexpression of NLRP12 following Ad (adenovirus)-NLRP12-EGFP contributed to the attenuation of steatosis and inflammation in EtOH-fed mice model and EtOH-primed RAW264.7 cells. In parallel, Knockdown of NLRP12 aggravated the inflammatory response in RAW264.7 cells triggered by EtOH. Meanwhile, after administration of overexpression or inhibition of NLRP12 expression in vitro, the expression of phosphorylated protein of NF-kB signaling pathway was significantly affected. After increasing or decreasing the expression of NLRP12 in RAW264.7 cells, AML-12 cells were cultured with the supernatant of RAW264.7 cells stimulated by EtOH, and the percent of apoptosis ratio of AML-12 cells was remarkably altered. The study suggested that reduced inflammatory response induced by NLRP12-mediated inhibition of NF-kB pathway participated in the decrease of hepatocyte apoptosis in alcohol-induced liver injury. Collectively, these findings suggested the significance of NLRP12-mediated macrophage activation in alcohol-induced liver injury.

miR-200b regulates cellular senescence and inflammatory responses by targeting ZEB2 in pulmonary emphysema

Smoking is an important factor in the pathogenesis of chronic obstructive pulmonary disease (COPD), which is commonly characterised by cellular senescence and inflammation. Recently, miR-200b has emerged as an important target to cure lung disease; however, the function of miR-200b in reducing cellular senescence and inflammatory responses has not been reported. In this study, we found that miR-200b was downregulated in the lungs of COPD model mice, and its expression is correlated with cellular senescence and inflammatory responses. We hypothesised that miR-200b may be a potential novel therapy for treating COPD. We performed senescence-Associated-β-galactosidase (SA-β-GAL) staining, western blot, qRT-PCR and ELISA; our data suggested that miR-200b is an anti-aging factor in the lungs that is involved in inflammatory responses. We also confirmed that ZEB2 (Zinc finger E-box binding homeobox 2) is a target gene of miR-200b using luciferase reporter assay. In addition, we verified the function of ZEB2 in cellular senescence and inflammatory responses through transfection experiments. Moreover, we found that the protective effects of miR-200b are inhibited when cells overexpress the ZEB2 protein. In conclusion, our results suggest that miR-200b may attenuate cellular senescence and inflammatory responses by targeting ZEB2 in pulmonary emphysema.

Neutrophils in liver diseases: pathogenesis and therapeutic targets

Previously, it was assumed that peripheral neutrophils are a homogeneous population that displays antimicrobial functions. However, recent data have revealed that neutrophils are heterogeneous and are additionally involved in tissue damage and immune regulation. The phenotypic and functional plasticity of neutrophils has been identified in patients with cancer, inflammatory disorders, infections, and other diseases. Currently, neutrophils, with their autocrine, paracrine, and immune modulation functions, have been shown to be involved in liver diseases, including viral hepatitis, nonalcoholic steatohepatitis, alcoholic liver disease, liver fibrosis, cirrhosis, liver failure, and liver cancer. Accordingly, this review summarizes the role of neutrophils in liver diseases.

Mechanistic Actions of microRNAs in Diabetic Wound Healing

Wound healing is a complex biological process that is impaired under diabetes conditions. Chronic non-healing wounds in diabetes are some of the most expensive healthcare expenditures worldwide. Early diagnosis and efficacious treatment strategies are needed. microRNAs (miRNAs), a class of 18-25 nucleotide long RNAs, are important regulatory molecules involved in gene expression regulation and in the repression of translation, controlling protein expression in health and disease. Recently, miRNAs have emerged as critical players in impaired wound healing and could be targets for potential therapies for non-healing wounds. Here, we review and discuss the mechanistic background of miRNA actions in chronic wounds that can shed the light on their utilization as specific wound healing biomarkers.

Extracellular vesicles in hepatology: Physiological role, involvement in pathogenesis, and therapeutic opportunities

Since the first descriptions of hepatocyte-released exosome-like vesicles in 2008, the number of publications describing Extracellular Vesicles (EVs) released by liver cells in the context of hepatic physiology and pathology has grown exponentially. This growing interest highlights both the importance that cell-to-cell communication has in the organization of multicellular organisms from a physiological point of view, as well as the opportunity that these circulating organelles offer in diagnostics and therapeutics. In the present review, we summarize systematically and comprehensively the myriad of works that appeared in the last decade and lighted the discussion about the best opportunities for using EVs in liver disease therapeutics.

Revisiting Platelets and Toll-Like Receptors (TLRs): At the Interface of Vascular Immunity and Thrombosis

While platelet function has traditionally been described in the context of maintaining vascular integrity, recent evidence suggests that platelets can modulate inflammation in a much more sophisticated and nuanced manner than previously thought. Some aspects of this expanded repertoire of platelet function are mediated via expression of Toll-like receptors (TLRs). TLRs are a family of pattern recognition receptors that recognize pathogen-associated and damage-associated molecular patterns. Activation of these receptors is crucial for orchestrating and sustaining the inflammatory response to both types of danger signals. The TLR family consists of 10 known receptors, and there is at least some evidence that each of these are expressed on or within human platelets. This review presents the literature on TLR-mediated platelet activation for each of these receptors, and the existing understanding of platelet-TLR immune modulation. This review also highlights unresolved methodological issues that potentially contribute to some of the discrepancies within the literature, and we also suggest several recommendations to overcome these issues. Current understanding of TLR-mediated platelet responses in influenza, sepsis, transfusion-related injury and cardiovascular disease are discussed, and key outstanding research questions are highlighted. In summary, we provide a resource—a “researcher’s toolkit”—for undertaking further research in the field of platelet-TLR biology.

VDAC oligomer pores: A mechanism in disease triggered by mtDNA release

A recent study suggests that voltage-dependent anion channel (VDAC) oligomer pores promote mitochondrial outer membrane permeabilization and allow mitochondrial DNA (mtDNA) to be released into the cytosol in live cells. It challenges the notion that only occurs in apoptotic cells via BAX/BAK macropores. Cytosolic mtDNA activates cyclic GMP-AMP synthase (cGAS)-stimulator of IFN gene (STING) pathway and triggers type I interferon (IFN) response thereafter, which ultimately causes systemic lupus erythematosus. Mechanistically, mtDNA can interact with three positively charged residues (Lys12, Arg15, and Lys20) at the N-terminus of VDAC1, thereby strengthening VDAC1 oligomerization and facilitating mtDNA release. In addition, there are other pathways that can mediate mtDNA release, such as BAX/BAK macropores and virus-derived pores. The mtDNA released into the cytosol also triggers type I IFN response via the generally accepted cGAS-STING-TANK-binding kinase 1-IFN regulatory factor 3 axis. Collectively, VDAC oligomer pores provide us an attractive direction for us to understand mtDNA release-related diseases.

Activation of Farnesoid X Receptor by Schaftoside Ameliorates Acetaminophen-Induced Hepatotoxicity by Modulating Oxidative Stress and Inflammation

Aims: Acetaminophen (APAP) overdose leads to acute liver injury by inducing hepatic mitochondrial oxidative stress and inflammation. However, the molecular mechanisms involved are still unclear. Farnesoid X receptor (FXR) serves as a therapeutic target for the treatment of liver disorders, whose activation has been proved to protect APAP-induced hepatotoxicity. In this study, we examined whether FXR activation by schaftoside (SS), a naturally occurring flavonoid from Desmodium styracifolium, could protect mice against APAP-induced hepatotoxicity via regulation of oxidative stress and inflammation. Results: We first found that SS exhibited potent protective effects against APAP-induced hepatotoxicity in mice. The study reveals that SS is a potential agonist of FXR, which protects mice from hepatotoxicity mostly via regulation of oxidative stress and inflammation. Mechanistically, the hepatoprotective SS is associated with the induction of the genes of phase II detoxifying enzymes (e.g., UGT1A1, GSTα1), phase III drug efflux transporters (e.g., bile salt export pump, organic solvent transporter protein β), and glutathione metabolism-related enzymes (e.g., glutamate-cysteine ligase modifier subunit [Gclm], glutamate-cysteine ligase catalytic subunit [Gclc]). More importantly, SS-mediated FXR activation could fine-tune the pro- and anti-inflammatory eicosanoids generation via altering eicosanoids metabolic pathway, thereby resulting in decrease of hepatic inflammation. In contrast, FXR deficiency can abrogate the above effects. Innovation and Conclusion: Our results provided the direct evidence that FXR activation by SS could attenuate APAP-induced hepatotoxicity via inhibition of nuclear factor kappa-B signaling and fine-tuning the generation of proinflammatory mediators' eicosanoids. Our findings indicate that strategies to activate FXR signaling in hepatocytes may provide a promising therapeutic approach to alleviate liver injury induced by APAP overdose.

Cotinine inhibits TLR4/NF-κB signaling pathway and improves deep vein thrombosis in rats

BACKGROUND

The present study was designed to explore the regulatory mechanisms and influences of cotinine on deep vein thrombosis (DVT) in rats via the toll-like receptor 4/nuclear factor κ binding (TLR-4/NF-κB) pathway.

METHODS

In this experimental study, 30 SD rats were randomly assigned to control group, sham operation group, model group, cotinine (10 μg/kg) group, and model + cotinine (10 μg/kg) group. The thromboxane B2 (TXB2), 6-keto-PGF1α, plasminogen activator inhibitor (PAI), tissue plasminogen activator (t-PA), TLR4, NF-κB, and p65 mRNA and protein expression and tissue changes were analyzed by ELISA, Hematoxylin-Eosin (HE) staining, RT-PCR, and Western blot.

RESULTS

There was no significant difference between the control and sham operation groups (P>0.05). The model and cotinine groups showed significantly higher mRNA and protein levels of TXB2, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), PAI, TLR-4, and NF-κB, and significantly lower levels of 6-keto-PGF1α and t-PA than the control and sham operation groups (P<0.05), and the model + cotinine group showed significantly higher mRNA and protein levels of TXB2, IL-6 and TNF-α, PAI, TLR-4, and NF-κB and significantly lower levels of 6-keto-PGF1α and t-PA than the model group (P<0.05).

CONCLUSION

Cotinine can aggravate thrombus and inflammation in rats with DVT, and the mechanism may be associated with the activation of the TLR-4/NF-κB inflammatory signaling pathway.

Comprehensive characterization of hepatocyte-derived extracellular vesicles identifies direct miRNA-based regulation of hepatic stellate cells and DAMP-based hepatic macrophage IL-1β and IL-17 upregulation in alcoholic hepatitis mice

Extracellular vesicles (EVs) have been growingly recognized as biomarkers and mediators of alcoholic liver disease (ALD) in human and mice. Here we characterized hepatocyte-derived EVs (HC-EVs) and their cargo for their biological functions in a novel murine model that closely resembles liver pathology observed in patients with alcoholic hepatitis (AH), the most severe spectrum of ALD. The numbers of circulating EVs and HC-EVs were significantly increased by 10-fold in AH mice compared with control mice. The miRNA (miR)-seq analysis detected 20 upregulated and 4 downregulated miRNAs (P < 0.001-0.05) in AH-HC-EVs. Treatment of murine primary hepatic stellate cells (HSCs) with AH-HC-EVs induced α-SMA (P < 0.05) and Col1a1 (P < 0.001). Smad7 and Nr1d2 genes, which were downregulated in HSCs from the AH mice, were predicted targets of 20 miRs upregulated in AH-HC-EVs. Among them were miR-27a and miR-181 which upon transfection in HSCs, indeed repressed Nr1d2, the quiescent HSC marker. AH-HC-EVs were also enriched with organelle proteins and mitochondrial DNA (10-fold, P < 0.05) and upregulated IL-1β and IL-17 production by hepatic macrophages (HMs) from AH mice in a TLR9-dependent manner. These results demonstrate HC-EV release is intensified in AH and suggest that AH-HC-EVs orchestrate liver fibrogenesis by directly targeting the quiescent HSC transcripts via a unique set of miRNAs and by amplifying HSC activation via DAMP-based induction of profibrogenic IL-1β and IL-17 by HMs. KEY MESSAGES: • Circulating EVs and HC-EVs were increased in AH mice compared with control mice • AH-HC-EVs were enriched in miRNAs, organelle proteins, and mitochondrial DNA • AH-HC-EVs increased cytokine production by AH-HMs in a TLR9-dependent manner.

Police Violence among Adults Diagnosed with Mental Disorders

Police violence is reportedly common among those diagnosed with mental disorders characterized by the presence of psychotic symptoms or pronounced emotional lability. Despite the perception that people with mental illness are disproportionately mistreated by the police, there is relatively little empirical research on this topic. A cross-sectional general population survey was administered online in 2017 to 1,000 adults in two eastern U.S. cities to examine the relationship between police violence exposure, mental disorders, and crime involvement. Results from hierarchical logistic regression and mediation analyses revealed that a range of mental health conditions are broadly associated with elevated risk for police violence exposure. Individuals with severe mental illness are more likely than the general population to be physically victimized by police, regardless of their involvement in criminal activities. Most of the excess risk of police violence exposure related to common psychiatric diagnoses was explained by confounding factors including crime involvement. However, crime involvement may necessitate more police contact, but does not necessarily justify victimization or excessive force (particularly sexual and psychological violence). Findings support the need for adequate training for police officers on how to safely interact with people with mental health conditions, particularly severe mental illness.

miR-223: A Key Regulator in the Innate Immune Response in Asthma and COPD

Asthma and Chronic Obstructive Pulmonary Disease (COPD) are chronic obstructive respiratory diseases characterized by airway obstruction, inflammation, and remodeling. Recent findings indicate the importance of microRNAs (miRNAs) in the regulation of pathological processes involved in both diseases. MiRNAs have been implicated in a wide array of biological processes, such as inflammation, cell proliferation, differentiation, and death. MiR-223 is one of the miRNAs that is thought to play a role in obstructive lung disease as altered expression levels have been observed in both asthma and COPD. MiR-223 is a hematopoietic cell–derived miRNA that plays a role in regulation of monocyte-macrophage differentiation, neutrophil recruitment, and pro-inflammatory responses and that can be transferred to non-myeloid cells via extracellular vesicles or lipoproteins. In this translational review, we highlight the role of miR-223 in obstructive respiratory diseases, focusing on expression data in clinical samples of asthma and COPD, in vivo experiments in mouse models and in vitro functional studies. Furthermore, we provide an overview of the mechanisms by which miR-223 regulates gene expression. We specifically focus on immune cell development and activation and involvement in immune responses, which are important in asthma and COPD. Collectively, this review demonstrates the importance of miR-223 in obstructive respiratory diseases and explores its therapeutic potential in the pathogenesis of asthma and COPD.

Aerobic Exercise Inhibits CUMS-Depressed Mice Hippocampal Inflammatory Response via Activating Hippocampal miR-223/TLR4/MyD88-NF-κB Pathway

Objective: To investigate the role of aerobic exercise in inhibiting chronic unpredictable mild stress (CUMS) depressed mice hippocampal inflammatory response and its potential mechanisms. Methods: Fifty-four male eight-week-old C57BL/6 mice were divided as control group (CG) (18 mice) and model group (36 mice). Model group mice were treated with 13 chronic stimulating factors for 28 days to set up the CUMS depression model. Neurobehavioral assessment was performed after modeling. The mice in the model group were randomly divided into the control model group (MG) and the aerobic exercise group (EG), with 18mice in each group. The EG group carried out the adaptive training of the running platform: 10 m/min, 0° slope, and increased by 10 minutes per day for 6 days. The formal training was carried for 8 weeks with 10 m/min speed, 0° slope, 60 min/d, 6 d/Week. After the training, a neurobehavioral assessment was performed, and hippocampus IL-1β and IL-10 protein levels were detected by ELISA. RT–PCR was used to detect the expression of miR-223 and TLR4, MyD88, and NF-κB in the hippocampus. Western blot was used to detect the expression of TLR4 and phosphorylated NF-κBp65 protein in the hippocampus. Results: The hippocampus function of CUMS depression model mice was impaired. The forced swimming and forced tail suspension time were significantly prolonged, and inflammatory factors IL-1β were significantly increased in the hippocampus. Aerobic exercise significantly improves CUMS-depressed mice hippocampal function, effectively reducing depressive behavior and IL-1β levels, and increasing IL-10 levels. Besides, aerobic exercise significantly upregulates the expression level of miR-223 and inhibits the high expression of TLR4, MyD88, and NF-κB. Conclusion: Aerobic exercise significantly increases the CUMS-depressed mice hippocampus expression of miR-223, and inhibits the downstream TLR4/MyD88-NF-κB signaling pathway and the hippocampal inflammatory response, which contributes to the improvement of the hippocampal function.

Hesperetin attenuated acetaminophen-induced hepatotoxicity by inhibiting hepatocyte necrosis and apoptosis, oxidative stress and inflammatory response via upregulation of heme oxygenase-1 expression

Acetaminophen (APAP) is a common antipyretic and analgesic drug, but its overdose can induce acute liver failure with lack of effective therapies. Hesperetin, a dihydrogen flavonoid compound, has been revealed to exert multiple pharmacological activities. Here, we explored the protective effects and mechanism of hesperetin on APAP-induced hepatotoxicity. The results showed that pretreatment with hesperetin dose-dependently attenuated APAP-induced acute liver injury in mice, as measured by alleviated serum enzymes activities, hepatic pathological damage and apoptosis. Moreover, hesperetin mitigated APAP-induced oxidative stress and inflammatory response in mice by inhibiting oxidative molecules but increasing antioxidative molecules production, reducing inflammatory cells infiltration and proinflammatory cytokines production, blocking Toll-like receptor (TLR)-4 signal activation. In vitro experiment indicated that hesperetin dose-dependently inhibited APAP-primed cytotoxicity, apoptosis, and reactive oxygen species (ROS) in murine AML12 hepatocytes. Notably, hesperetin up-regulated expression of heme oxygenase-1 (HO-1) mRNA and protein in the liver of mice and AML12 cells exposed to APAP. Furthermore, knockdown of HO-1 by adenovirus-mediated HO-1 siRNA reverted these beneficial effects of hesperetin on APAP-induced hepatocytotoxicity as well as ROS and inflammatory response in vivo and in vitro. These findings demonstrated that hesperetin exerted a protective prophylaxis on APAP-induced acute liver injury by inhibiting hepatocyte necrosis and apoptosis, oxidative stress and inflammatory response via up-regulating HO-1 expression.

Circular RNA circFBXW4 suppresses hepatic fibrosis via targeting the miR-18b-3p/FBXW7 axis

Rationale: Circular RNAs (circRNAs) are a new form of noncoding RNAs that play crucial roles in various pathological processes. However, the expression profile and function of circRNAs in hepatic fibrosis (HF) remain largely unknown. In this study, we show a novel circFBXW4 mediates HF via targeting the miR-18b-3p/FBXW7 axis. Methods: We investigated the expression profile of circRNAs, microRNAs and mRNAs in hepatic stellate cells (HSCs) from HF progression and regression mice by circRNAs-seq and microarray analysis. We found a significantly dysregulated circFBXW4 in HF. Loss-of-function and gain-of-function analysis of circFBXW4 were performed to assess the role of circFBXW4 in HF. Furthermore, we confirmed that circFBXW4 directly binds to miR-18b-3p by luciferase reporter assay, RNA pull down and fluorescence in situ hybridization analysis. Results: We found that circFBXW4 downregulated in liver fibrogenesis. Enforcing the expression of circFBXW4 inhibited HSCs activation, proliferation and induced apoptosis, attenuated mouse liver fibrogenesis injury and showed anti-inflammation effect. Mechanistically, circFBXW4 directly targeted to miR-18b-3p to regulate the expression of FBXW7 in HF. Conclusions: circFBXW4 may act as a suppressor of HSCs activation and HF through the circFBXW4/miR-18b-3p/FBXW7 axis. Our findings identify that circFBXW4 serves as a potential biomarker for HF therapy.

Mechanisms and pathophysiological significance of sterile inflammation during acetaminophen hepatotoxicity

Acetaminophen (APAP) is a widely used analgesic drug, which can cause severe liver injury after an overdose. The intracellular signaling mechanisms of APAP-induced cell death such as reactive metabolite formation, mitochondrial dysfunction and nuclear DNA fragmentation have been extensively studied. Hepatocyte necrosis releases damage-associated molecular patterns (DAMPs) which activate cytokine and chemokine formation in macrophages. These signals activate and recruit neutrophils, monocytes and other leukocytes into the liver. While this sterile inflammatory response removes necrotic cell debris and promotes tissue repair, the capability of leukocytes to also cause tissue injury makes this a controversial topic. This review summarizes the literature on the role of various DAMPs, cytokines and chemokines, and the pathophysiological function of Kupffer cells, neutrophils, monocytes and monocyte-derived macrophages, and NK and NKT cells during APAP hepatotoxicity. Careful evaluation of results and experimental designs of studies dealing with the inflammatory response after APAP toxicity provide very limited evidence for aggravation of liver injury but support of the hypothesis that these leukocytes promote tissue repair. In addition, many cytokines and chemokines modulate tissue injury by affecting the intracellular signaling events of cell death rather than toxicity of leukocytes. Reasons for the controversial results in this area are also discussed.

Neutrophil Chemotaxis and NETosis in Murine Chronic Liver Injury via Cannabinoid Receptor 1/ Gαi/o/ ROS/ p38 MAPK Signaling Pathway

Neutrophils play an essential role in the control of inflammatory diseases. However, whether cannabinoid receptors (CBs) play a role in neutrophil chemotaxis and NETosis in sterile liver inflammation remains unknown. The expression of marker genes on neutrophils was characterized by FACS, immunofluorescence, qRT-PCR, and Western blot. The amount of neutrophils was significantly elevated from 7 days and reached the peak at 2 weeks in carbon tetrachloride (CCl₄)-treated mouse liver. The mRNA expression of neutrophil marker Ly6G had positive correlation with CB1 and CB2 expression in injured liver. In vitro CBs were abundantly expressed in isolated neutrophils and CB1 agonist ACEA promoted the chemotaxis and cytoskeletal remodeling, which can be suppressed by CB1 antagonist AM281. Moreover, ACEA induced NETosis, myeloperoxidase release from lysosome and ROS burst, indicating neutrophil activation, via Gα_i/o. Conversely, CB2 agonist JWH133 had no effect on neutrophil function. ROS and p38 MAPK signaling pathways were involved in CB1-mediated neutrophil function, and ROS was upstream of p38 MAPK. CB1 blockade in vivo significantly attenuated neutrophil infiltration and liver inflammation in CCl₄-treated mice. Taken together, CB1 mediates neutrophil chemotaxis and NETosis via Gα_i/o/ROS/p38 MAPK signaling pathway in liver inflammation, which represents an effective therapeutic strategy for liver diseases.

Exposure to workplace bullying, microRNAs and pain; evidence of a moderating effect of miR-30c rs928508 and miR-223 rs3848900

Prolonged exposure to bullying behaviors may give rise to symptoms such as anxiety, depression and chronic pain. Earlier data suggest that these symptoms often are associated with stress-induced low-grade systemic inflammation. Here, using data from both animals and humans, we examined the moderating role of microRNAs (miRNAs, miRs) in this process. In the present study, a resident-intruder paradigm, blood samples, tissue harvesting and subsequent qPCR analyses were used to screen for stress-induced changes in circulating miRNAs in rats. The negative acts questionnaire (NAQ), TaqMan assays and a numeric rating scale (NRS) for pain intensity were then used to examine the associations among bullying behaviors, relevant miRNA polymorphisms and pain in a probability sample of 996 Norwegian employees. In rats, inhibited weight gain, reduced pituitary POMC expression, adrenal Nr3c1 mRNA downregulation, as well as increased miR-146a, miR-30c and miR-223 in plasma were observed following 1 week of repeated exposure to social stress. When following up the miRNA findings from the animal study in the human working population, a stronger relationship between NAQ and NRS scores was observed in subjects with the miR-30c GG genotype (rs928508) compared to other subjects. A stronger relationship between NAQ and NRS scores was also seen in men with the miR-223 G genotype (rs3848900) as compared to other men. Our findings show that social stress may induce many physiological changes including changed expression of miRNAs. We conclude that the miR-30c GG genotype in men and women, and the miR-223 G genotype in men, amplify the association between exposure to bullying behaviors and pain.Lay summaryUsing an animal model of social stress, we identified miR-146a, miR-30c and miR-223 as potentially important gene regulatory molecules that may be involved in the stress response. Interestingly, human genotypes affecting the expression of mature miR-30c and miR-223 had a moderating effect on the association between exposure to bullying and pain. Subjects with the miR-30c rs928508 GG genotype had a significantly stronger association between exposure to bullying behaviors and pain than other subjects. The same was observed in men with the miR-223 rs3848900 G genotype, as compared to other men.

TLR9 in MAFLD and NASH: At the Intersection of Inflammation and Metabolism

Toll-Like Receptor 9 (TLR9) is an ancient receptor integral to the primordial functions of inflammation and metabolism. TLR9 functions to regulate homeostasis in a healthy system under acute stress. The literature supports that overactivation of TLR9 under the chronic stress of obesity is a critical driver of the pathogenesis of NASH and NASH-associated fibrosis. Research has focused on the core contributions of the parenchymal and non-parenchymal cells in the liver, adipose, and gut compartments. TLR9 is activated by endogenous circulating mitochondrial DNA (mtDNA). Chronically elevated circulating levels of mtDNA, caused by the stress of overnutrition, are observed in obesity, metabolic dysfunction-associated fatty liver disease (MAFLD), and NASH. Clinical evidence is supportive of TLR9 overactivation as a driver of disease. The role of TLR9 in metabolism and energy regulation may have an underappreciated contribution in the pathogenesis of NASH. Antagonism of TLR9 in NASH and NASH-associated fibrosis could be an effective therapeutic strategy to target both the inflammatory and metabolic components of such a complex disease.

Combination of sivelestat and N-acetylcysteine alleviates the inflammatory response and exceeds standard treatment for acetaminophen-induced liver injury

Hepatocyte death during acetaminophen (APAP) intoxication elicits a reactive inflammatory response, with hepatic recruitment of neutrophils and monocytes, which further aggravates liver injury. Neutrophil elastase (NE), secreted by activated neutrophils, carries degradative and cytotoxic functions and maintains a proinflammatory state. We investigated NE as a therapeutic target in acetaminophen-induced liver injury (AILI). C57BL/6 mice were administered a toxic dose of APAP, 2 h prior to receiving the NE inhibitor sivelestat, N-acetylcysteine (NAC), or a combination therapy, and were euthanized after 24 and 48 h. Upon APAP overdose, neutrophils and monocytes infiltrate the injured liver, accompanied by increased levels of NE. Combination therapy of NAC and sivelestat significantly limits liver damage, as evidenced by lower serum transaminase levels and less hepatic necrosis compared to mice that received APAP only, and this to a greater extent than NAC monotherapy. Lower hepatic expression of proinflammatory markers was observed in the combination treatment group, and flow cytometry revealed significantly less monocyte influx in livers from mice treated with the combination therapy, compared to untreated mice and mice treated with NAC only. The potential of NE to induce leukocyte migration was confirmed in vitro. Importantly, sivelestat did not impair hepatic repair. In conclusion, combination of NE inhibition with sivelestat and NAC dampens the inflammatory response and reduces liver damage following APAP overdose. This strategy exceeds the standard of care and might represent a novel therapeutic option for AILI.

Neutrophil extracellular traps activate lung fibroblast to induce polymyositis-related interstitial lung diseases via TLR9-miR-7-Smad2 pathway

Excessive neutrophil extracellular trap (NET) formation may contribute to polymyositis (PM)‐associated interstitial lung diseases (ILD), but the underlying mechanism is not fully revealed. In this study, we found that NET accelerated the progression of ILD and promoted pulmonary fibrosis (PF) in vivo. miR‐7 expression was down‐regulated in lung tissue of PM group than control group, and NETs further decreased miR‐7 expression. TLR9 and Smad2 were up‐regulated in lung tissue of PM group than control group, and NETs further increased TLR9 and Smad2 expressions. In vitro experiments showed that PMA‐treated NETs accelerated the proliferation of LF and their differentiation into myofibroblast (MF), whereas DNase I decreased the promotion effect of NETs. Neutrophil extracellular trap components myeloperoxidase (MPO) and histone 3 also promoted the proliferation and differentiation of LF. In addition, we demonstrated that TLR9 involved in the regulation of NETs on LF proliferation and differentiation, and confirmed the interaction between miR‐7 and Smad2 in LF. Finally, miR‐7‐Smad2 pathway was confirmed to be involved in the regulation of TLR9 on LF proliferation and differentiation. Therefore, NETs promote PM‐related ILD, and TLR9‐miR‐7‐Smad2 signalling pathway is involved in the proliferation of LFs and their differentiation into MFs.

Amlexanox ameliorates acetaminophen-induced acute liver injury by reducing oxidative stress in mice

Amlexanox, a clinically approved small-molecule therapeutic presently used to treat allergic rhinitis, ulcer, and asthma, is an inhibitor of the noncanonical IkB kinase-ε (IKKε) and TANK-binding kinase 1 (TBK1). This study was to investigate the protective mechanism of amlexanox in acetaminophen (APAP)-induced acute liver injury (ALI). Mice were intraperitoneally injected with APAP (300 mg/kg, 12 h) to induce ALI and were orally administrated with amlexanox (25, 50 and 100 mg/kg) one hour after APAP treatment. Inhibition of IKKε and TBK1 by treatment of amlexanox attenuated APAP-induced ALI as confirmed by decreased serum levels of aspartate aminotransferase and alanine aminotransferase. Furthermore, amlexanox significantly decreased hepatocellular apoptosis in injured livers of mice as evidenced by histopathologic observation. Consistently, reduced oxidative stress by amlexanox was observed by increased hepatic glutathione concomitant with decreased levels of malondialdehyde. Amlexanox also enhanced expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) target genes including heme oxygenase 1, NAD(P)H:quinone oxidoreductase 1, and glutamate-cysteine ligase in injured livers of mice. Mechanistic insights into the mode of action of amlexanox against APAP-induced hepatotoxicity were involved in increasing phosphorylation of AMP-activated protein kinase (AMPK) and nuclear translocation of Nrf2, both in vivo and in vitro. Furthermore, the protective effects of amlexanox on APAP-induced hepatotoxicity were abolished by compound C, an AMPK inhibitor. Taken together, our findings suggest that amlexanox exerts antioxidative activities against APAP-mediated hepatotoxicity via AMPK/Nrf2 pathway.

Mitochondrial DNA in liver inflammation and oxidative stress

The function of liver is highly dependent on mitochondria producing ATP for biosynthetic and detoxifying properties. Accumulating evidence indicates that most hepatic disorders are characterized by profound mitochondrial dysfunction. Mitochondrial dysfunction not only exhibits mitochondrial DNA (mtDNA) damage and depletion, but also releases mtDNA. mtDNA is a closed circular molecule encoding 13 of the polypeptides of the oxidative phosphorylation system. Extensive mtDNA lesions could exacerbate mitochondrial oxidative stress and subsequently cause damage to hepatocytes. When mtDNA leaves the confines of mitochondria to the cytosolic and extracellular environment, it can act as damage-associated molecular patterns (DAMPs) to trigger the inflammatory response through the Toll-like receptor 9, inflammasomes, and stimulator of interferon genes (STING) pathways and further exacerbate hepatocellular damage and even remote organs injury. In addition, mtDNA also plays a vital role in hepatitis B virus (HBV)-related liver injury and hepatocellular carcinoma (HCC). In this review, we describe mtDNA alterations during liver injury, focusing on the mechanisms of mtDNA-mediated liver inflammation and oxidative stress injury.

MicroRNA-223 Ameliorates Nonalcoholic Steatohepatitis and Cancer by Targeting Multiple Inflammatory and Oncogenic Genes in Hepatocytes

Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of diseases ranging from simple steatosis to more severe forms of liver injury including nonalcoholic steatohepatitis (NASH), fibrosis, and hepatocellular carcinoma (HCC). In humans, only 20%-40% of patients with fatty liver progress to NASH, and mice fed a high-fat diet (HFD) develop fatty liver but are resistant to NASH development. To understand how simple steatosis progresses to NASH, we examined hepatic expression of anti-inflammatory microRNA-223 (miR-223) and found that this miRNA was highly elevated in hepatocytes in HFD-fed mice and in human NASH samples. Genetic deletion of miR-223 induced a full spectrum of NAFLD in long-term HFD-fed mice including steatosis, inflammation, fibrosis, and HCC. Furthermore, microarray analyses revealed that, compared to wild-type mice, HFD-fed miR-223 knockout (miR-223KO) mice had greater hepatic expression of many inflammatory genes and cancer-related genes, including (C-X-C motif) chemokine 10 (Cxcl10) and transcriptional coactivator with PDZ-binding motif (Taz), two well-known factors that promote NASH development. In vitro experiments demonstrated that Cxcl10 and Taz are two downstream targets of miR-223 and that overexpression of miR-223 reduced their expression in cultured hepatocytes. Hepatic levels of miR-223, CXCL10, and TAZ mRNA were elevated in human NASH samples, which positively correlated with hepatic levels of several miR-223 targeted genes as well as several proinflammatory, cancer-related, and fibrogenic genes. Conclusion: HFD-fed miR-223KO mice develop a full spectrum of NAFLD, representing a clinically relevant mouse NAFLD model; miR-223 plays a key role in controlling steatosis-to-NASH progression by inhibiting hepatic Cxcl10 and Taz expression and may be a therapeutic target for the treatment of NASH.

Circ_1639 induces cells inflammation responses by sponging miR-122 and regulating TNFRSF13C expression in alcoholic liver disease

Ethanol is a key factor in the pathogenesis of alcoholic liver disease (ALD), commonly characterized as liver inflammation. Recently, circular (circ)RNAs have emerged as important targets to cure liver diseases. However, there are no studies investigating the role of circ_1639 in reducing inflammatory responses in ALD. In this study, we found that circ_1639 was upregulated in Kupffer cells from the livers of alcohol fed mice. We hypothesized that circ_1639 inhibition is a potential novel therapy for treating ALD. To test this hypothesis, RAW 264.7 cells were treated with ethanol and transfected with circ_1639 overexpression or knockdown plasmids. We present western blotting, qRT-PCR, and ELISA data that suggest that circ_1639 is a proinflammatory factor in the liver and is involved in the activation of the NF-κB signaling pathway. Using luciferase reporter assay, we confirmed that microRNA (miR)-122 is a target gene of circ_1639. We also show that TNFRSF13C is a key regulator of RAW 264.7 cell activation, and acts as a downstream target for miR-122. In summary, our results suggest that inhibition of circ_1639 expression may reduce inflammatory responses in ALD.

Circulating Peroxiredoxin-1 is a novel damage-associated molecular pattern and aggravates acute liver injury via promoting inflammation

Sterile inflammation is initiated by damage-associated molecular patterns (DAMPs) and a key contributor to acute liver injury (ALI). However, the current knowledge on those DAMPs that activate hepatic inflammation under ALI remains incomplete. We report here that circulating peroxiredoxin-1 (Prdx1) is a novel DAMP for ALI. Intraperitoneal injection of acetaminophen (APAP) elicited a progressive course of ALI in mice, which was developed from 12 to 24 h post injection along with liver inflammation evident by macrophage infiltration and upregulations of cytokines (IL-1β, IL-6 and TNF-α); these alterations were concurrently occurred with a robust and progressive production of serum Prdx1. Similar observations were also obtained in carbon tetrachloride (CCl₄)-induced ALI in mice. Removal of the source of serum Prdx1 protected mice deficient in Prdx1 from APAP and CCl₄-induced liver injury, and decreased macrophage infiltration, IL-1β, IL-6 and TNF-α production. As a result, Prdx1^-/- mice were strongly protected from APAP-induced death that was likely progressed from ALI. Additionally, intravenous re-introduction of recombinant Prdx1 (rPrdx1) in Prdx1^-/- mice reversed or reduced all the above events, demonstrating an important contribution of circulating Prdx1 to ALI. rPrdx1 potently induced in primary macrophages the expression of pro-IL-1β, IL-6, TNF-α, and IL-1β through the NF-κB signaling as well as the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signaling, evident by caspase-1 activation. Furthermore, a significant elevation of serum Prdx1 was demonstrated in patients (n = 15) with ALI; the elevation is associated with ALI severity. Collectively, we provide the first demonstration for serum Prdx1 contributing to ALI.

Receptor-Interacting Serine/Threonine-Protein Kinase 3 (RIPK3)-Mixed Lineage Kinase Domain-Like Protein (MLKL)-Mediated Necroptosis Contributes to Ischemia-Reperfusion Injury of Steatotic Livers

Increased hepatic ischemia-reperfusion (IR) injury in steatotic livers is a major reason for rejecting the use of fatty livers for liver transplantation. Necroptosis is implicated in the pathogenesis of fatty liver diseases. Necroptosis is regulated by three key proteins: receptor-interacting serine/threonine-protein kinase (RIPK)-1, RIPK3, and mixed-lineage kinase domain-like protein (MLKL). Here, we found that marked steatosis of the liver was induced when a Western diet was given in mice; steatosis was associated with the inhibition of hepatic proteasome activities and with increased levels of key necroptosis-related proteins. Mice fed a Western diet had more severe liver injury, as demonstrated by increases in serum alanine aminotransferase and necrotic areas of liver, after IR than did mice fed a control diet. Although hepatic steatosis was not different between Mlkl knockout mice and wild-type mice, Mlkl knockout mice had decreased hepatic neutrophil infiltration and inflammation and were protected from hepatic IR injury, irrespective of diet. Intriguingly, Ripk3 knockout or Ripk3 kinase-dead knock-in mice were protected against IR injury at the late phase but not the early phase, irrespective of diet. Overall, our findings indicate that liver steatosis exacerbates hepatic IR injury via increased MLKL-mediated necroptosis. Targeting MLKL-mediated necroptosis may help to improve outcomes in steatotic liver transplantation.

miRNA-223 at the crossroads of inflammation and cancer

miR-223 is an evolutionarily conserved anti-inflammatory microRNA primarily expressed in myeloid cells. miR-223 post-transcriptionally regulates many genes essential in inflammation, cell proliferation, and invasion. Recent studies show that miR-223 is either endogenously expressed or transferred in exosomes or extracellular vesicles to non-phagocytic cells including cancer cells, where it exerts biological functions. In cancerous cells, miR-223 acts either as an oncomiR promoting tumors or as a tumor suppressor in a context-dependent manner. Taken together, miR-223 can regulate tumorigenesis at multiple levels, including by suppressing the inflammatory tumor microenvironment and modulating malignancy of cancer cells.

Shikonin attenuates acetaminophen-induced acute liver injury via inhibition of oxidative stress and inflammation

Acetaminophen (APAP) overdose causes acute liver injury and leads to fatal liver damage. However, the therapies are quite limited. Shikonin is a natural product with antioxidant and anti-inflammatory activities. In the present study, the hepatoprotective effects and the underlying mechanisms of shikonin in APAP-induced hepatotoxicity in vivo and in vitro were investigated. APAP-induced acute liver injury and shikonin pretreatment models were established in vivo and in vitro, as evidenced by serum hepatic enzymes, histological changes, oxidative stress indicators and proinflammatory cytokines. The results revealed that shikonin pretreatment prevented the elevation of serum alanine transaminase (ALT), aspartate transaminase (AST) and lactate dehydrogenase (LDH) levels and markedly reduced APAP-induced histological alterations in liver tissues. Additionally, shikonin restored superoxide dismutase (SOD) expression and glutathione (GSH) content in line with the blockade of oxidative stress. The changes in gene expression involved in oxidative stress including methionine sulfoxide reductase (such as MsrA and MsrB1), heme oxygenase-1 (HO-1), SOD2 and cytochrome P450 2E1 (CYP2E1), were markedly reversed after shikonin therapy. Furthermore, shikonin markedly attenuated the APAP-induced production of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) and suppressed the expression of genes related to inflammation. In AML-12 cells, shikonin pretreatment decreased APAP-induced cytotoxicity as measured by CCK-8 assay and LDH release. The changes in gene expression involved in oxidative stress and the inflammatory response were consistent with those in mouse livers. This study indicated that shikonin attenuated APAP-induced acute liver injury via inhibiting oxidative stress and inflammatory responses in vivo and in vitro. These findings offer new insights into the potential therapy for APAP hepatotoxicity.