Autophagy induced by DAMPs facilitates the inflammation response in lungs undergoing ischemia-reperfusion injury through promoting TRAF6 ubiquitination

Review 2: Primary graft dysfunction after lung transplant-pathophysiology, clinical considerations and therapeutic targets

Primary graft dysfunction (PGD) is one of the most common complications in the early postoperative period and is the most common cause of death in the first postoperative month. The underlying pathophysiology is thought to be the ischaemia–reperfusion injury that occurs during the storage and reperfusion of the lung engraftment; this triggers a cascade of pathological changes, which result in pulmonary vascular dysfunction and loss of the normal alveolar architecture. There are a number of surgical and anaesthetic factors which may be related to the development of PGD. To date, although treatment options for PGD are limited, there are several promising experimental therapeutic targets. In this review, we will discuss the pathophysiology, clinical management and potential therapeutic targets of PGD.

Neutrophil Extracellular Traps (NETs) and Damage-Associated Molecular Patterns (DAMPs): Two Potential Targets for COVID-19 Treatment

COVID-19 is a pandemic disease caused by the new coronavirus SARS-CoV-2 that mostly affects the respiratory system. The consequent inflammation is not able to clear viruses. The persistent excessive inflammatory response can build up a clinical picture that is very difficult to manage and potentially fatal. Modulating the immune response plays a key role in fighting the disease. One of the main defence systems is the activation of neutrophils that release neutrophil extracellular traps (NETs) under the stimulus of autophagy. Various molecules can induce NETosis and autophagy; some potent activators are damage-associated molecular patterns (DAMPs) and, in particular, the high-mobility group box 1 (HMGB1). This molecule is released by damaged lung cells and can induce a robust innate immunity response. The increase in HMGB1 and NETosis could lead to sustained inflammation due to SARS-CoV-2 infection. Therefore, blocking these molecules might be useful in COVID-19 treatment and should be further studied in the context of targeted therapy.

microRNA-223 promotes autophagy to aggravate lung ischemia-reperfusion injury by inhibiting the expression of transcription factor HIF2α

Lung ischemia-reperfusion (I/R) injury severely endangers human health, and recent studies have suggested that certain microRNAs (miRNAs) play important roles in this pathological phenomenon. The current study aimed to ascertain the ability of miR-223 to influence lung I/R injury by targeting hypoxia-inducible factor-2α (HIF2α). First, mouse models of lung I/R injury were established: during surgical procedures, pulmonary arteries and veins and unilateral pulmonary portal vessels were blocked and resuming bilateral pulmonary ventilation, followed by restoration of bipulmonary ventilation. In addition, a lung I/R injury cell model was constructed by exposure to hypoxic reoxygenation (H/R) in mouse pulmonary microvascular endothelial cells (PMVECs). Expression of miR-223, HIF2α and β-catenin in tissues or cells was determined by RT-qPCR and Western blot analysis. Correlation between miR-223 and HIF2α was analyzed by dual luciferase reporter gene assay. Further, lung tissue injury and mouse PMVEC apoptosis was evaluated by HE, TUNEL staining and flow cytometry. Autophagosomes in cells were detected by light chain3 immunofluorescence assay. miR-223 was expressed at a high level while HIF2α/β-catenin was downregulated in tissues and cells with lung I/R injury. Further, miR-223 targeted and repressed HIF2α expression to downregulate β-catenin expression. The miR-223/HIF2α/β-catenin axis aggravated H/R injury in mouse PMVECs and lung I/R injury in mice by enhancing autophagy. Taken together, miR-223 inhibits HIF2α to repress β-catenin, thus contributing to autophagy to complicate lung I/R injury. These findings provide a promising therapeutic target for treating lung I/R injury.

Cigarette smoke-induced HMGB1 translocation and release contribute to migration and NF-κB activation through inducing autophagy in lung macrophages

High-mobility group box 1 (HMGB1) shows pro-inflammatory activity in various inflammatory diseases and has been found up-regulated in chronic obstructive pulmonary disease (COPD). Lung macrophages play an important role in airway inflammation and lung destruction in COPD, yet whether HMGB1 is involved in cigarette smoke (CS)-induced lung macrophage dysfunction is unknown. We sought to evaluate the intracellular localization and release of HMGB1 in lung macrophages from COPD patients and CS-exposed mice, and to investigate the role of HMGB1 in regulating autophagy in CS extract (CSE)-treated lung macrophages (MH-S cells). Our results showed that HMGB1 was highly expressed in lung tissues and sera of COPD patients and CS-exposed mice, along with predominantly cytoplasmic exporting from nuclei in lung macrophages. In vitro experiments revealed that CSE promoted the expression, nucleocytoplasmic translocation and release of HMGB1 partly via the nicotinic acetylcholine receptor (nAChR). Blockade of HMGB1 with chicken anti-HMGB1 polyclonal antibody (anti-HMGB1) or glycyrrhizin (Gly) attenuated the increase of LC3B-II and Beclin1, migration and p65 phosphorylation, suggesting the involvement of HMGB1 in autophagy, migration and NF-κB activation of lung macrophages. Hydroxychloroquine (CQ), an autophagy inhibitor, enhanced the increase of LC3B-II but not Beclin1 in CSE or rHMGB1-treated MH-S cells, and inhibition of autophagy by CQ and 3-methyladenine (3-MA) abrogated the migration and p65 phosphorylation of CSE-treated cells. These results indicate that CS-induced HMGB1 translocation and release contribute to migration and NF-κB activation through inducing autophagy in lung macrophages, providing novel evidence for HMGB1 as a potential target of intervention in COPD.

Atg7 Silencing Inhibits Laminin-5 Expression to Suppress Tube Formation by Brain Endothelial Cells

Cerebral angiogenesis is a key event during brain development and recovery from brain injury. We previously demonstrated that Atg7 knockout impaired angiogenesis in the mouse brain. However, the role of Atg7 in angiogenesis is not completely understood. In this study, we used human brain microvascular endothelial cells (HBMECs) to investigate the mechanism of Atg7-regulated cerebral angiogenesis. We found that Atg7 depletion specifically diminished the expression of the β3 and γ2 chains of laminin-5, a major component of the extracellular matrix. In contrast, autophagy inhibitors did not affect laminin-5 expression, suggesting that Atg7-regulated laminin-5 expression is autophagy-independent. We also found that Atg7-regulated laminin-5 expression occurred at the transcriptional level through NF-κB signaling. Exogenous laminin-5 or the NF-κB agonist betulinic acid effectively rescued tube formation by Atg7-deficient HBMECs. Taken together, our study identified a novel mechanism by which Atg7 regulates laminin-5 expression via NF-κB to modulate tube formation by brain endothelial cells during cerebral angiogenesis. Anat Rec, 302:2255-2260, 2019. © 2019 American Association for Anatomy.

The role of the LncRNA-FA2H-2-MLKL pathway in atherosclerosis by regulation of autophagy flux and inflammation through mTOR-dependent signaling

Atherosclerosis is a progressive, chronic inflammation in arterial walls. Long noncoding RNAs (lncRNAs) participate in inflammation, but the exact mechanism in atherosclerosis is unclear. Our microarray analyses revealed that the levels of lncRNA-FA2H-2 were significantly decreased by oxidized low-density lipoprotein (OX-LDL). Bioinformatics analyses indicated that mixed lineage kinase domain-like protein (MLKL) might be regulated by lncRNA-FA2H-2. In vitro experiments showed that lncRNA-FA2H-2 interacted with the promoter of the MLKL gene, downregulated MLKL expression, and the binding sites between -750 and 471 were necessary for lncRNA-FA2H-2 responsiveness to MLKL. Silencing lncRNA-FA2H-2 and overexpression of MLKL could activate inflammation and inhibited autophagy flux. Both lncRNA-FA2H-2 knockdown and overexpression of MLKL could significantly aggravate inflammatory responses induced by OX-LDL. We found that the 3-methyladenine (3-MA) and Atg7-shRNA enhanced inflammatory responses induced by knockdown of lncRNA-FA2H-2 and overexpression of MLKL. We demonstrated that the effects of MLKL on autophagy might be associated with a mechanistic target of rapamycin (mTOR)-dependent signaling pathways. In vivo experiments with apoE knockout mice fed a western diet demonstrated that LncRNA-FA2H-2 knockdown decreased microtubule-associated expression of microtubule-associated protein 1 light chain 3 II and lysosome-associated membrane protein 1, but increased expression of sequestosome 1 (p62), MLKL, vascular cell adhesion molecule-1, monocyte chemoattractant protein-1, and interleukin-6 in atherosclerotic lesions. Our findings indicated that the lncRNA-FA2H-2-MLKL pathway is essential for regulation of autophagy and inflammation, and suggested that lncRNA-FA2H-2 and MLKL could act as potential therapeutic targets to ameliorate atherosclerosis-related diseases.

eIF2α promotes vascular remodeling via autophagy in monocrotaline-induced pulmonary arterial hypertension rats

PURPOSE

Eukaryotic initiation factor 2α (eIF2α) plays important roles in the proliferation and survival of pulmonary artery smooth muscle cells (PASMCs) in animal hypoxia-induced pulmonary hypertension models. However, the underlying mechanism remains unknown at large. Autophagy has been reported to play a key role in the vascular remodeling in pulmonary arterial hypertension (PAH). The purposes of this study are to determine the functions of eIF2α and autophagy in the vascular remodeling of the monocrotaline-induced PAH rats and to clarify the correlation between eIF2α and autophagy.

METHODS

We established a rat model of monocrotaline-induced PAH, and we established a cell model of platelet derived growth factor (PDGF)-induced PASMCs proliferation. The vascular morphology and the expression of eIF2α, LC3B, and p62 were assessed in the pulmonary arterial tissue of Sprague-Dawleyrats and PDGF-induced PASMCs.

RESULTS

Autophagy was significantly active in monocrotaline model group (MCT)-induced PAH rats, which obviously promotes vascular remodeling in MCT-induced PAH rats. Furthermore, the proliferation of PASMCs was induced by PDGF in vitro. The expression of LC3B, eIF2α was increased in the PDGF-induced PASMCs proliferation, and the expression of p62 was reduced in the PDGF-induced PASMCs proliferation. Moreover, eIF2α siRNA downregulated the expression of eIF2α and LC3B, and upregulated the expression of p62 in PDGF-induced PASMCs proliferation. eIF2α siRNA inhibited the PDGF-induced PASMCs proliferation. Finally, chloroquine can upregulate the protein expression of LC3B and p62, it also can inhibit proliferation in PDGF-induced PASMCs.

CONCLUSION

Based on these observations, we conclude that eIF2α promotes the proliferation of PASMCs and vascular remodeling in monocrotaline-induced PAH rats through accelerating autophagy pathway.

DAMPening sterile inflammation of the kidney

Renal ischemia reperfusion injury (IRI) is a serious cause of acute kidney injury (AKI). Danger-associated-molecular pattern molecules (DAMPs) are thought to promote IRI by initiating immune cell infiltration and driving disease progression, but the underlying pathophysiological mechanisms are mainly unclear. Poluzzi et al. demonstrate that soluble biglycan is a bimodal DAMP that both recruits proinflammatory macrophages and initiates resolution of inflammation and tissue remodeling in IRI, identifying a potential therapeutic target.

Normal lung development needs self-eating

Autophagy is a Greek-derived concept that means "self-eating" and is increasingly recognized as an important regulator of homeostasis and disease. In this issue of the JCI, Yeganeh et al. report the important finding that intrinsic autophagy is required for normal progression of lung development. Conditional deletion of the beclin 1-encoding gene (Becn1) specifically within lung epithelial cells of embryonic mice resulted in neonatal lethal respiratory distress that was associated with negative impacts on airway branching and differentiation of airway epithelial cell lineages. The authors draw speculative parallels with the alveolar simplification phenotype of bronchopulmonary dysplasia in premature human infants and suggest that stimulation of autophagy by cAMP-dependent kinase activation might conceivably rescue these phenotypes.

The Evolving Roles of Macrophages in Organ Transplantation

Organ transplantation is a life-saving strategy for patients with end-stage organ failure. Over the past few decades, organ transplantation has achieved an excellent success in short-term survival but only a marginal improvement in long-term graft outcomes. The pathophysiology of graft loss is multifactorial and remains incompletely defined. However, emerging evidence suggests macrophages as crucial mediators of acute and chronic allograft immunopathology. In this process, macrophage-mediated mobilization of first-line defenses, particularly phagocytosis and the release of acute inflammatory mediators, is important, but macrophages also launch adaptive alloimmune reactions against grafts through antigen processing and presentation, as well as providing costimulation. Additionally, crosstalk with other immune cells and graft endothelial cells causes tissue damage or fibrosis in transplanted organs, contributing to graft loss or tolerance resistance. However, some macrophages function as regulatory cells that are capable of suppressing allogeneic T cells, inhibiting DC maturation, inducing the differentiation of Tregs, and subsequently promoting transplant tolerance. This functional diversity of macrophages in organ transplantation is consistent with their heterogeneity. Although our knowledge of the detrimental or beneficial effects of macrophages on transplants has exponentially increased, the exact mechanisms controlling macrophage functions are not yet completely understood. Here, we review recent advances in our understanding of the multifaceted nature of macrophages, focusing on their evolving roles in organ transplantation and the mechanisms involved in their activation and function in allograft transplantation. We also discuss potential therapeutic options and opportunities to target macrophage to improve the outcomes of transplant recipients.

High-Mobility Group Box 1 (HMGB1) and Autophagy in Acute Lung Injury (ALI): A Review

Acute lung injury (ALI) is a life-threatening clinical syndrome in critically ill patients. The identification of novel biological markers for the early diagnosis of ALI and the development of more effective treatments are topics of current research. High mobility group box-1 protein (HMGB1) is a late inflammatory mediator associated with sepsis, malignancy, and immune disease. Levels of HMGB1 may reflect the severity of inflammation and tissue damage, indicating a potential role for HMGB1 as a prognostic biomarker in ALI, and a potential target for blocking inflammatory pathways. Several studies have shown that HMGB1 regulates autophagy. Autophagy, or type II programmed cell death, is an essential biological process that maintains cellular homeostasis. Studies have shown that HMGB1 and autophagy are involved in the pathogenesis of many lung diseases including ALI but the specific mechanisms underlying this association remain to be determined. This review aims to provide an update on the current status of the role of HMBG1 and autophagy in ALI.

(-)-Epicatechin attenuates hepatic sinusoidal obstruction syndrome by inhibiting liver oxidative and inflammatory injury

Hepatic sinusoidal obstruction syndrome (HSOS) is a rare liver disease with considerable morbidity and mortality. (-)-Epicatechin (EPI) is a natural flavonol. This study aims to investigate the protection of EPI against monocrotaline (MCT)-induced HSOS and its engaged mechanism. Results of serum alanine/aspartate aminotransferases (ALT/AST) activities, total bilirubin (TBil) and bile acids (TBA) amounts, liver histological evaluation, scanning electron microscope observation and hepatic metalloproteinase-9 (MMP-9) expression all demonstrated the protection by EPI against MCT-induced HSOS in rats. EPI attenuated liver oxidative injury induced by MCT. EPI enhanced the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and increased the expression of its downstream antioxidant genes in rats. Molecular docking results implied the potential interaction of EPI with the Nrf2 binding site in kelch-like ECH-associated protein-1 (Keap1). The EPI-provided protection against MCT-induced HSOS was diminished in Nrf2 knock-out mice when mice were treated with MCT for 24 h but not for 48 h. However, EPI reduced the increased liver myeloperoxidase (MPO) activity, hepatic infiltration of immune cells, pro-inflammatory cytokines expression and nuclear factor κB (NFκB) activation in both wild-type and Nrf2 knock-out mice when mice were treated with MCT for 48 h. EPI reduced the elevated serum heat shock protein 60 (HSP60) content, and reversed the decreased mitochondria expression of HSP60 and Lon in livers from MCT-treated rats. Furthermore, the MCT-induced HSOS was markedly alleviated in mice treated with anti-HSP60 antibody. Taken together, this study demonstrates that EPI attenuates MCT-induced HSOS by reducing liver oxidative injury via activating Nrf2 antioxidant pathway and inhibiting liver inflammatory injury through abrogating NFκB signaling pathway initiated by HSP60.

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EPI attenuates MCT-induced HSOS in rats.

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EPI inhibits MCT induced liver oxidative injury in rats.

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Nrf2 is important for the EPI-provided protection against MCT-induced HSOS.

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EPI also abrogates MCT-induced liver inflammatory injury.

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EPI reduced the release of HSP60.

The Interplay Between Pattern Recognition Receptors and Autophagy in Inflammation

Pattern recognition receptors (PRRs) are sensors of exogenous and endogenous "danger" signals from pathogen-associated molecular patterns (PAMPs), and damage associated molecular patterns (DAMPs), while autophagy can respond to these signals to control homeostasis. Almost all PRRs can induce autophagy directly or indirectly. Toll-like receptors (TLRs), Nod-like receptors (NLRs), retinoic acid-inducible gene-I-like receptors (RLRs), and cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway can induce autophagy directly through Beclin-1 or LC3-dependent pathway, while the interactions with the receptor for advanced glycation end products (RAGE)/high mobility group box 1 (HMGB1), CD91/Calreticulin, and TLRs/HSPs are achieved by protein, Ca2⁺, and mitochondrial homeostasis. Autophagy presents antigens to PRRs and helps to clean the pathogens. In addition, the induced autophagy can form a negative feedback regulation of PRRs-mediated inflammation in cell/disease-specific manner to maintain homeostasis and prevent excessive inflammation. Understanding the interaction between PRRs and autophagy in a specific disease will promote drug development for immunotherapy. Here, we focus on the interactions between PRRs and autophagy and how they affect the inflammatory response.

The progression of HMGB1-induced autophagy in cancer biology

Autophagy is an important process of cellular degradation and has been proven to contribute to tumorigenesis. High-mobility group box 1 (HMGB1) is an abundant nonhistone protein that has been widely reported to play a central role in the induction of autophagy. In nucleus, HMGB1 upregulates the expression of HSP27 to induce autophagy. In cytoplasm, the Beclin-1/PI3K-III complex can be activated by HMGB1 to promote autophagy. Extracellular HMGB1 binds to the receptor for advanced glycation end products to induce autophagy. Recent studies have shown that HMGB1-induced autophagy exerts multiple functions in various cancers like proliferation. Moreover, inhibition of HMGB1-induced autophagy can reverse chemoresistance, which is regulated by noncoding RNAs such as microRNAs and lncRNAs. Here, we provide a brief introduction to HMGB1 and HMGB1-induced autophagy in cancer. We also discuss the challenges associated with performing further investigations on this issue. HMGB1-induced autophagy exerts significant functions in cancer and has potential utility for new strategy to reverse drug resistance.

Cell death pathologies: targeting death pathways and the immune system for cancer therapy

Alterations in the molecular mechanisms of cell death are a common feature of cancer. These alterations enable malignant cells to survive intrinsic death signalling leading to accumulation of genetic aberrations and helping them to cope with adverse conditions. Regulated cell death has historically been exclusively associated with classical apoptosis; however, increasing evidence indicates that several alternative mechanisms orchestrate multiple death pathways, such as ferroptosis, entosis, necroptosis and immunogenic cell death, each with distinct underlying molecular mechanisms. Although pharmacological targeting of cell death pathways has been the subject of intensive efforts in recent decades with a dominant focus on targeting apoptosis, the identification of these novel death pathways has opened additional venues for intervention in cancer cells and the immune system. In this mini-review, we cover some recent progress on major recently emerged cell death modalities, emphasizing their potential clinical and therapeutic implications. We also discuss the interplay between cell death and immune response, highlighting the potential of the combination of traditional anticancer therapy and immunocheckpoint blockade. While attempting to stimulate discussion and draw attention to the possible clinical impact of these more recently emerged cell death modalities, we also cover the major progress achieved in translating strategies for manipulation of apoptotic pathways into the clinic, focusing on the attempts to target the anti-apoptotic protein BCL-2 and the tumour suppressor p53.

Chaperonin 60 sustains osteoblast autophagy and counteracts glucocorticoid aggravation of osteoporosis by chaperoning RPTOR

Glucocorticoid excess medication interrupts osteoblast homeostasis and exacerbates bone mass and microstructure loss ramping up the pathogenesis of osteoporotic disorders. Heat shock protein 60 (HSP60) is found to maintain protein function within cellular microenvironment upon encountering detrimental stress. In this study, we revealed that supraphysiological dexamethasone decreased HSP60 expression along with deregulated autophagy in osteoblasts cultures. This chaperonin is required to sustain autophagic markers Atg4, and Atg12 expression, LC3-II conversion, and autophagic puncta formation, and alleviated the glucocorticoid-induced loss of osteogenic gene expression and mineralized matrix accumulation. Regulator-associated protein of mTOR complex 1 (RPTOR) existed in HSP60 immunoprecipitate contributing to the HSP60-promoted autophagy and osteogenesis because knocking down RPTOR impaired autophagic influx and osteogenic activity. HSP60 shielded from RPTOR dysfunction by reducing the glucocorticoid-induced RPTOR de-phosphorylation, aggregation, and ubiquitination. In vivo, forced RPTOR expression attenuated the methylprednisolone-induced loss of osteoblast autophagy, bone mass, and trabecular microstructure in mice. HSP60 transgenic mice displayed increased cortical bone, mineral acquisition, and osteoblast proliferation along with higher osteogenesis of bone marrow mesenchymal cells than those of wild-type mice. HSP60 overexpression retained RPTOR signaling, sustained osteoblast autophagy, and compromised the severity of glucocorticoid-induced bone loss and sparse trabecular histopathology. Taken together, HSP60 is essential to maintain osteoblast autophagy, which facilitates mineralized matrix production. It fends off glucocorticoid-induced osteoblast apoptosis and bone loss by stabilizing RPTOR action to autophagy. This study offers a new insight into the mechanistic by which chaperonin protects against the glucocorticoid-induced osteoblast dysfunction and bone loss.

NLRP3/ASC-mediated alveolar macrophage pyroptosis enhances HMGB1 secretion in acute lung injury induced by cardiopulmonary bypass

Our previous study showed that high levels of HMGB1 existed in rats following cardiopulmonary bypass (CPB)-induced acute lung injury (ALI) and neutralization of high-mobility group box 1(HMGB1) reduced CPB-induced ALI. However, the mechanism by which CPB increases HMGB1 secretion is unclear. Recent studies have shown that inflammasome-mediated cell pyroptosis promotes HMGB1 secretion. This study aimed to investigate the relationship between inflammasome-mediated pyroptosis and HMGB1 in CPB-related ALI. We employed oxygen-glucose deprivation (OGD)-induced alveolar macrophage (AM) NR8383 pyroptosis to measure HMGB1 secretion. We found that OGD significantly increased the levels of caspase-1 cleaved p10, IL-1β and ASC expression, caspase-1 activity and the frequency of pyroptotic AM, and promoted the cytoplasm transportation and secretion of HMGB1, which were significantly mitigated by ASC silencing or pre-treatment with glyburide (a Nlrp3 inhibitor) in AM. CPB also increased the expression levels of Nlrp3, ASC, caspase-1 P10, and IL-1β, and the percentages of AM pyroptosis in the lungs of experimental rats accompanied by increased levels of serum and bronchoalveolar lavage fluid (BALF) HMGB1. Treatment with glyburide significantly mitigated the CPB-increased ASC, caspase-1 p10 and IL-1β expression, and the percentages of AM pyroptosis in the lungs, as well as the levels of HMGB1 in serum and BALF in rats. Therefore, our data indicated that the Nlrp3/ASC-mediated AM pyroptosis increased HMGB1 secretion in ALI induced by CPB. These findings may provide a therapeutic strategy to reduce lung injury and inflammatory responses during CPB.

MicroRNA-21 prevents excessive inflammation and cardiac dysfunction after myocardial infarction through targeting KBTBD7

The excessive inflammation triggered by damage-associated molecular patterns (DAMPs) after myocardial infarction (MI) is responsible for the development of cardiac dysfunction and adverse remodeling, while the mechanisms by which inflammation is fine tuned remain to be fully elucidated. MicroRNA-21 (miR-21) has been shown to function in cardiovascular diseases, while its role in inflammatory responses and cardiac function post MI in mice remains unknown. Here, we found that miR-21 expression was markedly increased in border and infarct areas of cardiac tissues during the early inflammatory phase of MI model established by ligating the left-anterior descending coronary artery. MiR-21 knockout mice had decreased survival rates, worse cardiac dysfunction, and increased infarct and scar areas after MI compared with WT mice. MiR-21 knockout mice showed significantly higher levels of inflammatory cytokines including IL-1β, IL-6, and TNF-α in cardiac tissues, as well as infiltration of CD11b⁺ monocytes/macrophages with higher expression level of inflammatory cytokines. MI induced the great release of high mobility group protein B1 (HMGB1) and heat shock protein 60 (HSP60) in cardiac tissue. MiR-21 deficiency significantly promoted the inflammatory cytokine production triggered by DAMPs in macrophages, whereas, miR-21 overexpression markedly inhibited the inflammatory cytokine production. Mechanistically, miR-21 deficiency enhanced p38 and NF-κB signaling activation in cardiac tissue post MI and macrophages treated with DAMPs. MiR-21 was found to directly target kelch repeat and BTB (POZ) domain containing 7 (KBTBD7), which promoted DAMP-triggered inflammatory responses in macrophages. Furthermore, KBTBD7 interacted with MKK3/6 and promoted their activation, which in turn enhanced the activation of downstream p38 and NF-κB signaling induced by DAMPs. Therefore, our findings demonstrate that miR-21 attenuates inflammation, cardiac dysfunction, and maladaptive remodeling post MI through targeting KBTBD7 and inhibiting p38 and NF-κB signaling activation, suggesting that miR-21 may function as a novel potential therapeutic target for MI.

MicroRNA-194 Inhibits Lipopolysaccharide-Induced Inflammatory Response in Nucleus Pulposus Cells of the Intervertebral Disc by Targeting TNF Receptor-Associated Factor 6 (TRAF6)

Background

The dramatic increase of intervertebral disc degeneration (IDD) is considered to be a major cause of discogenic low back pain. The current study focused on the regulatory function of microRNA-194 (miR-194) on lipopolysaccharide (LPS)-induced inflammatory response in nucleus pulposus (NP) cells.

Material/Methods

LPS was used to treat NP cells to induce inflammatory responses. MiRNA and gene expression were detected by quantitative PCR. Proteins and protein expression levels were detected by Western blot and ELISA kit. Dual luciferase reporter assay was applied to identify the correlation between an miR-194- and TNF receptor-associated factor 6 (TRAF6) and to test NF-κB activity.

Results

MiR-194 expression was reduced in LPS-induced NP cells. Both miR-194 overexpression and miR-194 inhibitor could regulate extracellular matrix (ECM) genes expression (Aggrecan and collagen II), MMP3, MMP13, ADAMTS4, and ADAMTS5, as well as inflammatory cytokines-associated genes (TNF-α, IL-1, IL-6, PGE2). Through a further study of the molecular mechanism, miR-194 was proved to be involved in the regulation of TRAF6 and its downstream signal molecule, nuclear factor-kappa B (NF-κB).

Conclusions

Finding of our study suggest that miR-194 can inhibit LPS-induced inflammatory response in NP cells of the intervertebral disc (IVD) by targeting TRAF6, which may contribute development of IDD biological therapy.

Released Mitochondrial DNA Following Intestinal Ischemia Reperfusion Induces the Inflammatory Response and Gut Barrier Dysfunction

Ischemia-reperfusion (I/R) injury is a challenging clinical problem, especially injuries involving the gastrointestinal tract. Mitochondrial DNA (mtDNA) is released upon cell death and stress, and can induce the inflammatory response. We aimed to investigate the role of mtDNA in the pathogenesis of intestinal I/R. Intestinal I/R model was established with clamping of the superior mesenteric artery, and IEC-6 cells were incubated under hypoxia/reoxygenation (H/R) conditions to simulate I/R injury. Using in vitro models, H/R up-regulated oxidative stress, disrupted mitochondrial activity and the mitochondrial membrane potential, induced apoptosis and elevated the mtDNA levels in the supernatant of intestinal epithelial cells, and the co-culture of mtDNA with human primary dendritic cells significantly elevated TLR9-MyD88 expression and enhanced the production of inflammatory cytokines and chemokines. MtDNA was also released in a mouse model of intestinal I/R and was associated with the increased secretion of inflammatory cytokines and increased gut barrier injury compared with that of the sham group. We concluded that mtDNA contributes to I/R injury and may serve as a biomarker of intestinal I/R. We further suggest that oxidized mtDNA originated from IECs during intestinal I/R exacerbates the acute proinflammatory process by eliciting the production of proinflammatory cytokines and chemokines.

Up-regulated deubiquitinase USP4 plays an oncogenic role in melanoma

Melanoma is the most malignant skin cancer with increasing incidence worldwide. Although innovative therapies such as BRAF inhibitor and immune checkpoint inhibitor have gained remarkable advances, metastatic melanoma remains an incurable disease for its notorious aggressiveness. Therefore, further clarification of the underlying mechanism of melanoma pathogenesis is critical for the improvement of melanoma therapy. Ubiquitination is an important regulatory event for cancer hallmarks and melanoma development, and the deubiquitinating enzymes including ubiquitin-specific peptidase (USP) families are greatly implicated in modulating cancer biology. Herein, we first found that the expression of the deubiquitinase USP4 was significantly up-regulated in melanoma tissues and cell lines. Furthermore, although USP4 knockdown had little impact on melanoma cell proliferation, it could increase the sensitivity to DNA damage agent cisplatin. We subsequently showed that USP4 regulated cisplatin-induced cell apoptosis via p53 signalling. More importantly, USP4 could accentuate the invasive and migratory capacity of melanoma cells by promoting epithelial-mesenchymal transition. Altogether, our results demonstrate that the up-regulated USP4 plays an oncogenic role in melanoma by simultaneously suppressing stress-induced cell apoptosis and facilitating tumour metastasis.

Regulation of alveolar macrophage death in acute lung inflammation

Acute lung injury (ALI) and its severe form, known as acute respiratory distress syndrome (ARDS), are caused by direct pulmonary insults and indirect systemic inflammatory responses that result from conditions such as sepsis, trauma, and major surgery. The reciprocal influences between pulmonary and systemic inflammation augments the inflammatory process in the lung and promotes the development of ALI. Emerging evidence has revealed that alveolar macrophage (AM) death plays important roles in the progression of lung inflammation through its influence on other immune cell populations in the lung. Cell death and tissue inflammation form a positive feedback cycle, ultimately leading to exaggerated inflammation and development of disease. Pharmacological manipulation of AM death signals may serve as a logical therapeutic strategy for ALI/ARDS. This review will focus on recent advances in the regulation and underlying mechanisms of AM death as well as the influence of AM death on the development of ALI.

The Roles of Autophagy in Acute Lung Injury Induced by Myocardial Ischemia Reperfusion in Diabetic Rats

Patients with diabetes are vulnerable to myocardial ischemia reperfusion (IR) injury, which may also induce acute lung injury (ALI) due to overaccumulation of reactive oxygen species (ROS) and inflammation cytokine in circulation. Despite autophagy plays a significant role in diabetes and pulmonary IR injury, the role of autophagy in ALI secondary to myocardial IR in diabetes remains largely elusive. We aimed to investigate pulmonary autophagy status and its roles in oxidative stress and inflammation reaction in lung tissues from diabetic rats subjected to myocardial IR. Control or diabetic rats were either treated with or without autophagy inducer rapamycin (Rap) or autophagy inhibitor 3-methyladenine (3-MA) before myocardial IR, which was achieved by occluding the left anterior descending coronary artery for 30 min and followed by reperfusion for 120 min. Diabetic rats subjected to myocardial IR showed more serious ALI with higher lung injury score and WET/DRY ratio and lower PaO₂ as compared with control rats, accompanied with impaired autophagy indicated by reduced LC-3II/LC-3I ratio and Beclin-1 expression, decreased superoxide dismutase (SOD) activity, and increased 15-F2t-Isoprostane formation in lung tissues, as well as increased levels of leukocyte count and proinflammatory cytokines in BAL fluid. Improving autophagy with Rap significantly attenuated all these changes, but the autophagy inhibitor 3-MA exhibited adverse or opposite effects as Rap. In conclusion, diabetic lungs are more vulnerable to myocardial IR, which are involved in impaired autophagy. Improving autophagy could attenuate ALI induced by myocardial IR in diabetic rats, possibly through inhibiting inflammatory reaction and oxidative stress.

TRAF molecules in inflammation and inflammatory diseases

Purpose of Review

This review presents an overview of the current knowledge of TRAF molecules in inflammation with an emphasis on available human evidence and direct in vivo evidence of mouse models that demonstrate the contribution of TRAF molecules in the pathogenesis of inflammatory diseases.

Recent Findings

The tumor necrosis factor receptor (TNF-R)-associated factor (TRAF) family of cytoplasmic proteins was initially identified as signaling adaptors that bind directly to the intracellular domains of receptors of the TNF-R superfamily. It is now appreciated that TRAF molecules are widely employed in signaling by a variety of adaptive and innate immune receptors as well as cytokine receptors. TRAF-dependent signaling pathways typically lead to the activation of nuclear factor-κBs (NF-κBs), mitogen-activated protein kinases (MAPKs), or interferon-regulatory factors (IRFs). Most of these signaling pathways have been linked to inflammation, and therefore TRAF molecules were expected to regulate inflammation and inflammatory responses since their discovery in 1990s. However, direct in vivo evidence of TRAFs in inflammation and especially in inflammatory diseases had been lacking for many years, partly due to the difficulty imposed by early lethality of TRAF2^-/-, TRAF3^-/-, and TRAF6^-/- mice. With the creation of conditional knockout and lineage-specific transgenic mice of different TRAF molecules, our understanding about TRAFs in inflammation and inflammatory responses has rapidly advanced during the past decade.

Summary

Increasing evidence indicates that TRAF molecules are versatile and indispensable regulators of inflammation and inflammatory responses and that aberrant expression or function of TRAFs contributes to the pathogenesis of inflammatory diseases.

Myoblast transplantation improves cardiac function after myocardial infarction through attenuating inflammatory responses

Myocardial infarction (MI) is a highly prevalent cardiac emergency, which results in adverse cardiac remodeling and then exacerbates progressive heart failure. Inflammatory responses in cardiac tissue after MI is necessary for myocardium repair and wound healing. However, the excessive inflammation is also a key component of subsequent heart failure pathology. Myoblast transplantation after MI have been fulfilled attractive effects on cardiac repair, but the complications of transplantation and the underlying mechanisms have not been fully elucidated. Here, we found that human myoblast transplantation into minipig myocardium decreased the infiltration of inflammatory cells, the expression levels of many pro-inflammatory genes and the activation of inflammation-related signal pathways, while upregulated the expression levels of anti-inflammatory genes such as IL-10 in cardiac tissue of minipig post-MI, which was contributed to the improved cardiac function, the decreased infarct area and the attenuated myocardial fibrosis. Moreover, co-culture of human myoblasts inhibited the production of IL-1β and TNF-α as well as activation of MAPK and NF-κB signaling pathway induced by damage-associated molecular patterns such as HMGB1 and HSP60 in human THP-1 cells, which was partially attributed to the up-regulated production of IL-10. Collectively, these results indicate that myoblast transplantation ameliorates heart injury and improves cardiac function post-MI through inhibiting the inflammatory response, which provides the novel mechanism for myoblast transplantation therapy of MI.

Ubiquitination in melanoma pathogenesis and treatment

Melanoma is one of the most aggressive skin cancers with fiercely increasing incidence and mortality. Since the progressive understanding of the mutational landscape and immunologic pathogenic factors in melanoma, the targeted therapy and immunotherapy have been recently established and gained unprecedented improvements for melanoma treatment. However, the prognosis of melanoma patients remains unoptimistic mainly due to the resistance and nonresponse to current available drugs. Ubiquitination is a posttranslational modification which plays crucial roles in diverse cellular biological activities and participates in the pathogenesis of various cancers, including melanoma. Through the regulation of multiple tumor promoters and suppressors, ubiquitination is emerging as the key contributor and therefore a potential therapeutic target for melanoma. Herein, we summarize the current understanding of ubiquitination in melanoma, from mechanistic insights to clinical progress, and discuss the prospect of ubiquitination modification in melanoma treatment.