Interferon regulatory factor-1 regulates the autophagic response in LPS-stimulated macrophages through nitric oxide

Salmonella Enteritidis RfbD enhances bacterial colonization and virulence through inhibiting autophagy

Autophagy is a crucial innate immune response that clears pathogens intracellularly. Salmonella enterica serovar Enteritidis (S.E) has emerged as one of the most important food-borne pathogens. Here, we reported that dTDP-4-dehydro-β-ւ-rhamnose reductase (RfbD) was able to enhance bacterial colonization in vivo and in vitro by regulating autophagy. We screened the transposon mutant library of Salmonella Enteritidis strain Z11 by High-Content Analysis System, found that rfbD gene has an effect on autophagy. The Z11ΔrfbD-infected group showed greater expression of LC3-II than the Z11-infected group in HeLa, RAW264.7, and J774A.1 cells. Overall, the survival of Z11ΔrfbD in RAW264.7 cells was reduced after 8 h of infection compared to that of the Z11 wild-type strain. In addition, we observed that inhibition of autophagic flux significantly increased the survival of Z11ΔrfbD in RAW264.7 cells. Mice infection experiments revealed that Z11ΔrfbD virulence was significantly reduced, and bacterial load was reduced in the liver and cecum in mice model, and LC3-II expression was significantly increased. These findings indicate an important role of Salmonella Enteritidis protein as a strategy to suppress autophagy and provides new ideas for manipulating autophagy as a novel strategy to treat infectious diseases.

The Modulation of Interferon Regulatory Factor-1 via Caspase-1-Mediated Alveolar Macrophage Pyroptosis in Ventilator-Induced Lung Injury

Background

To examine the role of interferon regulatory factor-1 (IRF-1) and to explore the potential molecular mechanism in ventilator-induced lung injury.

Methods

Wild-type C57BL/6 mice and IRF-1 gene knockout mice/caspase-1 knockout mice were mechanically ventilated with a high tidal volume to establish a ventilator-related lung injury model. The supernatant of the alveolar lavage solution and the lung tissues of these mice were collected. The degree of lung injury was examined by hematoxylin and eosin staining. The protein and mRNA expression levels of IRF-1, caspase-1 (p10), and interleukin (IL)-1β (p17) in lung tissues were measured by western blot and quantitative real-time polymerase chain reaction, respectively. Pyroptosis of alveolar macrophages was detected by flow cytometry and western blotting for active caspase-1 and cleaved GSDMD. An enzyme-linked immunosorbent assay was used to measure the levels of IL-1β, IL-18, IL-6, TNF-α, and high mobility group box protein 1 (HMGB-1) in alveolar lavage fluid.

Results

IRF-1 expression and caspase-1-dependent pyroptosis in lung tissues of wild-type mice were significantly upregulated after mechanical ventilation with a high tidal volume. The degree of ventilator-related lung injury in IRF-1 gene knockout mice and caspase-1 knockout mice was significantly improved compared to that in wild-type mice, and the levels of GSDMD, IL-1β, IL-18, IL-6, and HMGB-1 in alveolar lavage solution were significantly reduced (P < 0.05). The expression levels of caspase-1 (p10), cleaved GSDMD, and IL-1β (p17) proteins in lung tissues of IRF-1 knockout mice with ventilator-related lung injury were significantly lower than those of wild-type mice, and the level of pyroptosis of macrophages in alveolar lavage solution was significantly reduced.

Conclusions

IRF-1 may aggravate ventilator-induced lung injury by regulating the activation of caspase-1 and the focal death of alveolar macrophages.

Interferon regulatory factor-1 regulates cisplatin-induced apoptosis and autophagy in A549 lung cancer cells

This study aimed to investigate the expression and function of interferon regulatory factor-1 (IRF-1) in non-small cell lung cancer (NSCLC). IRF-1 expression and its prognostic value were investigated through bioinformatic analysis. The protein expression levels of IRF-1, cleaved caspase 3, and LC3-I/II were analyzed by western blotting. A lentiviral vector was used to overexpress or knockdown IRF-1 in vitro. Mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) were analyzed by JC-1 and DCFH-DA staining, respectively. ATP, SOD, MDA, cell viability, LDH release, and caspase 3 activity were evaluated using commercial kits. Compared to the levels in normal tissues, IRF-1 expression was significantly lower in lung cancer tissues and was a prognostic factor for NSCLC. Cisplatin treatment-induced IRF-1 activation, ROS production, ATP depletion, SOD consumption, and MDA accumulation in A549 lung cancer cells. IRF-1 overexpression promoted mitochondrial depolarization, oxidative stress, and apoptotic cell death and inhibited autophagy in A549 cells, and these effects could be reversed by IRF-1 knockdown. These data suggest that IRF-1 regulates apoptosis, autophagy and oxidative stress, which might be served as a potential target for increasing chemotherapy sensitivity of lung cancer.

Lactobacillus paracasei KW3110 Prevents Inflammatory-Stress-Induced Mitochondrial Dysfunction in Mouse Macrophages

Lactobacillus paracasei KW3110 (KW3110) has anti-inflammatory effects, including the prevention of blue light exposure induced retinal inflammation and ageing-related chronic inflammation in mice. The mechanism involves the promotion of anti-inflammatory cytokine interleukin (IL)-10 production by KW3110, leading to reduced pro-inflammatory cytokine IL-1β production. Although various stress-induced mitochondrial damages are associated with excessive inflammatory responses, the effect of KW3110 on inflammatory-stress-induced mitochondrial damage remains unknown. In this study, we investigated the effect of KW3110 on inflammatory stress-induced mitochondrial damage using the murine macrophage-like cell line J774A.1. KW3110 treatment suppressed lipopolysaccharide (LPS)-induced mitochondrial dysfunction, including downregulation of membrane potential, induction of reactive oxygen species, and respiratory dysfunction. In addition, KW3110 prevented LPS-induced disruption of mitochondrial morphology including cristae structures. IL-10 treatment also ameliorated LPS-induced mitochondrial dysfunction and morphology disruption. These results suggest that KW3110 prevents LPS-induced mitochondrial dysfunction, potentially via promoting IL-10 production in mouse macrophages. We are the first to reveal a suppressive effect of lactic acid bacteria on mitochondrial morphology disruption in inflammatory-stressed macrophages. Our findings contribute to understanding inflammatory-stress-induced mitochondrial damage and developing food ingredients with preventive effects on mitochondrial-damage-derived inflammatory conditions.

Lactobacillus paracasei KW3110 Prevents Inflammatory-Stress-Induced Mitochondrial Dysfunction in Mouse Macrophages

Lactobacillus paracasei KW3110 (KW3110) has anti-inflammatory effects, including the prevention of blue light exposure induced retinal inflammation and ageing-related chronic inflammation in mice. The mechanism involves the promotion of anti-inflammatory cytokine interleukin (IL)-10 production by KW3110, leading to reduced pro-inflammatory cytokine IL-1β production. Although various stress-induced mitochondrial damages are associated with excessive inflammatory responses, the effect of KW3110 on inflammatory-stress-induced mitochondrial damage remains unknown. In this study, we investigated the effect of KW3110 on inflammatory stress-induced mitochondrial damage using the murine macrophage-like cell line J774A.1. KW3110 treatment suppressed lipopolysaccharide (LPS)-induced mitochondrial dysfunction, including downregulation of membrane potential, induction of reactive oxygen species, and respiratory dysfunction. In addition, KW3110 prevented LPS-induced disruption of mitochondrial morphology including cristae structures. IL-10 treatment also ameliorated LPS-induced mitochondrial dysfunction and morphology disruption. These results suggest that KW3110 prevents LPS-induced mitochondrial dysfunction, potentially via promoting IL-10 production in mouse macrophages. We are the first to reveal a suppressive effect of lactic acid bacteria on mitochondrial morphology disruption in inflammatory-stressed macrophages. Our findings contribute to understanding inflammatory-stress-induced mitochondrial damage and developing food ingredients with preventive effects on mitochondrial-damage-derived inflammatory conditions.

Autophagic activation of IRF-1 aggravates hepatic ischemia-reperfusion injury via JNK signaling

Increasing evidence has accrued indicating that autophagy is associated with hepatic ischemia-reperfusion injury (IRI). This report demonstrates that interferon regulatory factor-1 (IRF-1) was upregulated in response to hepatic IRI and was associated with autophagic activation. As a result of these processes, there is an aggravation of liver damage, effects that can be offset by IRF-1 depletion. In addition, these effects of IRF-1 are associated with JNK pathway activation followed by increases in Beclin1 protein levels. This JNK-induced autophagic cell death then leads to cell failure, and plays an important role in liver function damage. We conclude that IRF-1 activates autophagy through JNK-mediated autophagy. Accordingly, these findings indicating that the IRF-1/JNK pathway activates autophagy to exacerbate liver IRI in this mouse model may provide new insights into novel protective therapies for hepatic IRI.

Hydrogen-rich saline regulates the polarization and apoptosis of alveolar macrophages and attenuates lung injury via suppression of autophagy in septic rats

Background

Hydrogen-rich saline (HRS) has a protective effect on sepsis-induced lung injury. However, the underlying mechanisms are still unclear. Polarization and apoptosis of macrophages are essential factors in the pathogenesis of acute lung injury (ALI). Moreover, autophagy is involved in the regulation of both macrophage polarization and apoptosis. Therefore, this study investigated the ability of HRS to attenuate ALI through regulation of the polarization and apoptosis of alveolar macrophages (AMs) during sepsis by modulating autophagy.

Methods

Male Sprague-Dawley (SD) rats were used to prepare the sepsis-induced lung injury animal model. Rat lung tissue was harvested after lipopolysaccharide (LPS) treatment, in the presence or absence of HRS, and the AMs were analyzed for changes in polarization, apoptosis, and autophagy. The rat AM cell line NR8383 was used to examine these processes in vitro using Western blot analysis, flow cytometry, and transmission electron microscopy.

Results

LPS-induced ALI in rats was associated with an increase in autophagy, apoptosis, and M1 polarization but a decrease in M2 polarization in AMs. These effects were reversed by administration of HRS. Inhibition of AM autophagy with 3-methyladenine (3-MA) decreased apoptosis and M1 polarization and increased M2 polarization, paralleling the effects of HRS.

Conclusions

HRS could attenuate ALI in septic rats through regulation of AM polarization and a reduction in apoptosis by suppressing autophagy. This may represent a potential novel therapeutic target for the treatment of ALI caused by sepsis.

Identifying the Transcriptional Response of Cancer and Inflammation-Related Genes in Lung Cells in Relation to Ambient Air Chemical Mixtures in Houston, Texas

Atmospheric pollution represents a complex mixture of air chemicals that continually interact and transform, making it difficult to accurately evaluate associated toxicity responses representative of real-world exposure. This study leveraged data from a previously published article and reevaluated lung cell transcriptional response induced by outdoor atmospheric pollution mixtures using field-based exposure conditions in the industrialized Houston Ship Channel. The tested hypothesis was that individual and co-occurring chemicals in the atmosphere relate to altered expression of critical genes involved in inflammation and cancer-related processes in lung cells. Human lung cells were exposed at an air-liquid interface to ambient air mixtures for 4 h, with experiments replicated across 5 days. Real-time monitoring of primary and secondary gas-phase pollutants, as well as other atmospheric conditions, was simultaneously conducted. Transcriptional analysis of exposed cells identified critical genes showing differential expression associated with both individual and chemical mixtures. The individual pollutant identified with the largest amount of associated transcriptional response was benzene. Tumor necrosis factor (TNF) and interferon regulatory factor 1 (IRFN1) were identified as key upstream transcription factor regulators of the cellular response to benzene. This study is among the first to measure lung cell transcriptional responses in relation to real-world, gas-phase air mixtures.

IRF-1 Intervention in the Classical ROS-Dependent Release of NETs during LPS-Induced Acute Lung Injury in Mice

Previously, we demonstrated that neutrophil extracellular traps (NETs) play an essential role in lipopolysaccharide (LPS)-induced acute lung injury. However, the underlying mechanism is unclear. In this study, we showed that knockout of interferon regulatory factor 1 (IRF-1) in mice strongly attenuated the generation of NETs and reactive oxygen species (ROS) production in neutrophils from bronchoalveolar lavage fluid and alleviated LPS-induced lung injury and systemic inflammation. Our in vitro experiments demonstrated that LPS-stimulated platelets induce NET release through two distinct processes: an ROS-independent early/rapid NETosis and a later ROS-dependent classical NETosis. Notably, the classical ROS-dependent pathway plays a dominant role in the generation of NETs. Furthermore, we showed that IRF-1 knockout does not affect the formation of NETs in early/rapid NETosis, but significantly attenuates ROS production and the generation of NETs in classical NETosis, which determines the total levels of NETs released by LPS-stimulated platelets. In conclusion, IRF-1 deficiency plays a key role in moderating the excessive NETs formed via ROS in the classical pathway and retaining the protective role of the low-NET levels generated in early/rapid NETosis, which may serve as a novel target in acute lung injury/acute respiratory distress syndrome.

Modulating T Cell Responses via Autophagy: The Intrinsic Influence Controlling the Function of Both Antigen-Presenting Cells and T Cells

Autophagy is a homeostatic and inducible process affecting multiple aspects of the immune system. This intrinsic cellular process is involved in MHC-antigen (Ag) presentation, inflammatory signaling, cytokine regulation, and cellular metabolism. In the context of T cell responses, autophagy has an influential hand in dictating responses to self and non-self by controlling extrinsic factors (e.g., MHC-Ag, cytokine production) in antigen-presenting cells (APC) and intrinsic factors (e.g., cell signaling, survival, cytokine production, and metabolism) in T cells. These attributes make autophagy an attractive therapeutic target to modulate T cell responses. In this review, we examine the impact autophagy has on T cell responses by modulating multiple aspects of APC function; the importance of autophagy in the activation, differentiation and homeostasis of T cells; and discuss how the modulation of autophagy could influence T cell responses.

The Relationship Between Sepsis-induced Immunosuppression and Serum Toll-like Receptor 9 Level

BACKGROUND/AIM

Our aim was to determine serum TLR-9 levels in sepsis and evaluate the relationship between sepsis and serum TLR-9 levels.

MATERIALS AND METHODS

The study group consisted of 80 consecutive patients with sepsis and 100 healthy individuals. The demographic characteristics, co-morbidities and hemodynamic data of all patients were recorded.

RESULTS

TLR-9 serum levels in sepsis were statistically significantly lower compared to the control group. It was also seen that when the lactate level was >5 mmol/l in patients in the sepsis group, the serum TLR-9 levels were substantially higher.

CONCLUSION

There is a relationship between sepsis-induced immunosuppression and serum TLR-9 levels. The host immunity system can be activated by means of TLR-9-related systems, while hyperlactatemia may play a stimulating role in the re-activation of the immune system.

Role of Nitric Oxide and Hydrogen Sulfide in Ischemic Stroke and the Emergent Epigenetic Underpinnings

Nitric oxide (NO) and hydrogen sulfide (H₂S) are the key gasotransmitters with an imperious role in the maintenance of cerebrovascular homeostasis. A decline in their levels contributes to endothelial dysfunction that portends ischemic stroke (IS) or cerebral ischemia/reperfusion (CI/R). Nevertheless, their exorbitant production during CI/R is associated with exacerbation of cerebrovascular injury in the post-stroke epoch. NO-producing nitric oxide synthases are implicated in IS pathology and their activity is regulated, inter alia, by various post-translational modifications and chromatin-based mechanisms. These account for heterogeneous alterations in NO production in a disease setting like IS. Interestingly, NO per se has been posited as an endogenous epigenetic modulator. Further, there is compelling evidence for an ingenious crosstalk between NO and H₂S in effecting the canonical (direct) and non-canonical (off-target collateral) functions. In this regard, NO-mediated S-nitrosylation and H₂S-mediated S-sulfhydration of specific reactive thiols in an expanding array of target proteins are the principal modalities mediating the all-pervasive influence of NO and H₂S on cell fate in an ischemic brain. An integrated stress response subsuming unfolded protein response and autophagy to cellular stressors like endoplasmic reticulum stress, in part, is entrenched in such signaling modalities that substantiate the role of NO and H₂S in priming the cells for stress response. The precis presented here provides a comprehension on the multifarious actions of NO and H₂S and their epigenetic underpinnings, their crosstalk in maintenance of cerebrovascular homeostasis, and their "Janus bifrons" effect in IS milieu together with plausible therapeutic implications.

Inhibition of autophagy with 3-methyladenine is protective in a lethal model of murine endotoxemia and polymicrobial sepsis

Here, the regulatory role of autophagy is examined in both an LPS-induced lethal endotoxic shock mouse model and cecal ligation and puncture (CLP) mouse model. Autophagy-inhibitor 3-methyladenine (3-MA) and autophagy-enhancer rapamycin were administrated to mice challenged with LPS or CLP. Animals challenged with LPS or CLP combined with 3-MA displayed increased survival after endotoxemia, but LPS combined with rapamycin worsened the endotoxic shock of the mice. Among the different organs studied, the lungs and intestines exhibited significant differences among LPS alone, LPS combined with 3-MA and LPS combined with rapamycin. LPS combined with 3-MA attenuated the inflammatory damages of these organs as compared with LPS alone. In contrast, LPS combined with rapamycin increased damage in these organs. Consistently, serum inflammatory mediators TNF-α and IL-6 were decreased by the treatment of LPS combined with 3-MA as compared with LPS alone, while administration of LPS combined with rapamycin increased the serum TNF-α and IL-6 levels. Similar results were found in mouse bone marrow-derived macrophages exposed to LPS. Moreover, the regulatory effect of autophagy to endotoxic shock is dependent on the TLR4 signaling pathway. Our results demonstrate the central role of autophagy in the regulation of endotoxic shock and its potential modulation for endotoxic shock treatment.

Interferon Regulatory Factor-1 Mediates Alveolar Macrophage Pyroptosis During LPS-Induced Acute Lung Injury in Mice

Previously, we demonstrated that pyroptosis in alveolar macrophages (AMs) plays an essential role in lipopolysaccharide (LPS)-induced acute lung injury. However, the underlying mechanism remains largely unclear. Here, we show that the absence of interferon regulatory factor 1 (IRF-1) in genetic knock-out mice strongly abrogates pyroptosis in AMs and alleviates the LPS-induced lung injury and systemic inflammation. Our study demonstrates that IRF-1 contributes to caspase-1 activation and apoptosis-associated speck-like protein containing a caspase activation and recruitment domain pyroptosome formation in AMs and leads to downstream inflammatory cytokine release, including that of IL-1β, IL-18, and HMGB1. The nuclear translocation of IRF-1 is linked to the presence of toll-like receptor 4 (TLR4). Our findings suggest that pyroptosis and the downstream inflammatory response in AMs induced by LPS is a process that is dependent on TLR4-mediated up-regulation of IRF-1. In summary, IRF-1 plays a key role in controlling caspase-1-dependent pyroptosis and inflammation.

Role of interferon regulatory factor-1 in lipopolysaccharide-induced mitochondrial damage and oxidative stress responses in macrophages

Sepsis causes many early deaths; both macrophage mitochondrial damage and oxidative stress responses are key factors in its pathogenesis. Although the exact mechanisms responsible for sepsis-induced mitochondrial damage are unknown, the nuclear transcription factor, interferon regulatory factor-1 (IRF-1) has been reported to cause mitochondrial damage in several diseases. Previously, we reported that in addition to promoting systemic inflammation, IRF-1 promoted the apoptosis of and inhibited autophagy in macrophages. In the present study, we hypothesized that lipopolysaccharide (LPS)-induced IRF-1 activation in macrophages may promote mitochondrial damage and oxidative stress. In vitro, LPS was found to promote IRF-1 activation, reactive oxygen species (ROS) production, adenosine triphosphate (ATP) depletion, superoxide dismutase (SOD) consumption, malondialdehyde (MDA) accumulation and mitochondrial depolarization in macrophages in a time- and dose-dependent manner. These effects were abrogated in cells in which IRF-1 was knocked down. Furthermore, IRF-1 overexpression increased LPS-induced oxidative stress responses and mitochondrial damage. In vivo, peritoneal macrophages obtained from IRF-1 knockout (KO) mice produced less ROS and had less mitochondrial depolarization and damage following the administration of LPS, when compared to their wild-type (WT) counterparts. In addition, IRF-1 KO mice exhibited a decreased release of mitochondrial DNA (mtDNA) following the administration of LPS. Thus, IRF-1 may be a critical factor in augmenting LPS-induced oxidative stress and mitochondrial damage in macrophages.

Porphyromonas gingivalis and its lipopolysaccharide differently modulate epidermal growth factor-dependent signaling in human gingival epithelial cells

Periodontitis is an inflammatory disease induced by pathogenic bacteria such as Porphyromonas gingivalis. Little is known about epidermal growth factor (EGF) signals in human gingival epithelial cells (HGEC), which are major targets of P. gingivalis, and how the expression of proteins participating in EGF signaling—that is, EGF-receptor (EGFR), suppressor of cytokine signaling-3 (SOCS-3), interferon regulatory factor-1 (IRF-1), and signal transducers and activators of transcription (STAT-3)—are modified. This study aimed to assess the effects of P. gingivalis and its purified lipopolysaccharide (LPS-Pg) on EGF signaling. HGEC were infected for 2 h in a dose-dependent manner with P. gingivalis and with heat-killed P. gingivalis, and activated for 2 and 24 h by 1 µg/mL of purified LPS-Pg. Quantitative reverse transcription polymerase chain reaction and Western blotting were performed to measure mRNA and protein levels for SOCS-3, IRF-1 EGF, EGFR, and STAT-3. The tyrosine-phosphorylation status of STAT-3 was also examined. The results showed that infection of HGEC cells with P. gingivalis, but not with heat-killed P. gingivalis, led to significant reductions in expression levels of mRNAs and proteins for SOCS-3, IRF-1, and EGFR, while LPS-Pg over time significantly increased the expression of these mRNAs and proteins. Tyrosine-phosphorylation of STAT-3 was significantly increased during infection with P. gingivalis and activation by LPS-Pg but not modified during infection with heat-killed P. gingivalis. This study highlights that P. gingivalis and its purified LPS differentially modulated the expression of proteins (SOCS-3, IRF-1, EGFR, and STAT-3) interfering with EGF signaling.

Interferon-regulatory factor-1 (IRF1) regulates bevacizumab induced autophagy

Purpose

Antiangiogenic therapy is commonly being used for the treatment of glioblastoma. However, the benefits of angiogenesis inhibitors are typically transient and resistance often develops. Determining the mechanism of treatment failure of the VEGF monoclonal antibody bevacizumab for malignant glioma would provide insight into approaches to overcome therapeutic resistance.

Experimental Design

In this study, we evaluated the effects of bevacizumab on the autophagy of glioma cells and determined target genes involving in the regulation of bevacizumab-induced autophagy.

Results

We demonstrated that bevacizumab treatment increased expression of autophagy markers and autophagosome formation in cell culture experiments as well as in in vivo studies. Gene expression profile analysis performed on murine xenograft models of glioblastoma showed increased transcriptional levels of STAT1/IRF1 signaling in bevacizumab resistant tumors compared to control tumors. In vitro experiments showed that bevacizumab treatment increased IRF1 expression in a dose and time dependent manner, which was coincident with bevacizumab-mediated autophagy. Down regulation of IRF1 by shRNA blocked autophagy and increased AIF-dependent apoptosis in bevacizumab-treated glioma cells. Consistently, IRF1 depletion increased the efficacy of anti-VEGF therapy in a glioma xenograft model, which was due to less bevacizumab-promoted autophagy and increased apoptosis in tumors with down-regulated IRF1.

Conclusions

These data suggest that IRF1 may regulate bevacizumab-induced autophagy, and may be one important mediator of glioblastoma resistant to bevacizumab.

iLIR database: A web resource for LIR motif-containing proteins in eukaryotes

Atg8-family proteins are the best-studied proteins of the core autophagic machinery. They are essential for the elongation and closure of the phagophore into a proper autophagosome. Moreover, Atg8-family proteins are associated with the phagophore from the initiation of the autophagic process to, or just prior to, the fusion between autophagosomes with lysosomes. In addition to their implication in autophagosome biogenesis, they are crucial for selective autophagy through their ability to interact with selective autophagy receptor proteins necessary for the specific targeting of substrates for autophagic degradation. In the past few years it has been revealed that Atg8-interacting proteins include not only receptors but also components of the core autophagic machinery, proteins associated with vesicles and their transport, and specific proteins that are selectively degraded by autophagy. Atg8-interacting proteins contain a short linear LC3-interacting region/LC3 recognition sequence/Atg8-interacting motif (LIR/LRS/AIM) motif which is responsible for their interaction with Atg8-family proteins. These proteins are referred to as LIR-containing proteins (LIRCPs). So far, many experimental efforts have been carried out to identify new LIRCPs, leading to the characterization of some of them in the past 10 years. Given the need for the identification of LIRCPs in various organisms, we developed the iLIR database ( https://ilir.warwick.ac.uk ) as a freely available web resource, listing all the putative canonical LIRCPs identified in silico in the proteomes of 8 model organisms using the iLIR server, combined with a Gene Ontology (GO) term analysis. Additionally, a curated text-mining analysis of the literature permitted us to identify novel putative LICRPs in mammals that have not previously been associated with autophagy.

Autophagy in sepsis: Degradation into exhaustion?

Autophagy is one of the innate immune defense mechanisms against microbial challenges. Previous in vitro and in vivo models of sepsis demonstrated that autophagy was activated initially in sepsis, followed by a subsequent phase of impairment. Autophagy modulation appears to be protective against multiple organ injuries in these murine sepsis models. This is achieved in part by preventing apoptosis, maintaining a balance between the productions of pro- and anti-inflammatory cytokines, and preserving mitochondrial functions. This article aims to discuss the role of autophagy in sepsis and the therapeutic potential of autophagy enhancers.

Inhibition of Alveolar Macrophage Pyroptosis Reduces Lipopolysaccharide-induced Acute Lung Injury in Mice

Background:

Pyroptosis is the term for caspase-1-dependent cell death associated with pro-inflammatory cytokines. The role of alveolar macrophage (AM) pyroptosis in the pathogenesis of the acute lung injury and acute respiratory distress syndrome (ALI/ARDS) remains unclear.

Methods:

C57BL/6 wild-type mice were assigned to sham, lipopolysaccharide (LPS) + vehicle, LPS + acetyl-tyrosyl-valyl- alanyl-aspartyl-chloromethylketone (Ac-YVAD-CMK) and LPS + Z-Asp-Glu-Val-Asp-fluoromethylketone groups. Mice were given intraperitoneal (IP) injections of LPS. Drugs were IP injected 1 h before LPS administration. Mice were sacrificed 16 h after LPS administration, and AMs were isolated. Western blot analysis for active caspase-1 and cleaved caspase-3, evaluation of lung injury and a cytokine release analysis were performed. AMs were treated with LPS and adenosine triphosphate (ATP); caspase-1-dependent cell death was evaluated using flow cytometry; the apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) pyroptosomes were examined by immunofluorescence.

Results:

The expression of activated caspase-1 in AMs was enhanced following LPS challenge compared with the sham group. In the ex vivo study, the caspase-1/propidium iodide-positive cells, caspase-1 specks and ASC pyroptosomes were up-regulated in AMs following LPS/ATP stimulation. The specific caspase-1 inhibitor Ac-YVAD-CMK inhibited the activation of caspase-1 and pyroptotic cell death. Ac-YVAD-CMK also reduced the lung injury, pulmonary edema and total protein in bronchoalveolar lavage fluid (BALF). In addition, Ac-YVAD-CMK significantly inhibited interleukin-β (IL-1β) release both in serum and BALF and reduced the levels of IL-18, tumor necrosis factor-α (TNF-α), High Mobility Group Box 1 (HMGB1) in BALF during LPS-induced ALI/ARDS.

Conclusions:

This study reported AM pyroptosis during LPS-induced ALI/ARDS in mice and has demonstrated that Ac-YVAD-CMK can prevent AM-induced pyroptosis and lung injury. These preliminary findings may form the basis for further studies to evaluate this pathway as a target for prevention or reduction of ALI/ARDS.

Gene Regulatory Network Inference of Immunoresponsive Gene 1 (IRG1) Identifies Interferon Regulatory Factor 1 (IRF1) as Its Transcriptional Regulator in Mammalian Macrophages

Immunoresponsive gene 1 (IRG1) is one of the highest induced genes in macrophages under pro-inflammatory conditions. Its function has been recently described: it codes for immune-responsive gene 1 protein/cis-aconitic acid decarboxylase (IRG1/CAD), an enzyme catalysing the production of itaconic acid from cis-aconitic acid, a tricarboxylic acid (TCA) cycle intermediate. Itaconic acid possesses specific antimicrobial properties inhibiting isocitrate lyase, the first enzyme of the glyoxylate shunt, an anaplerotic pathway that bypasses the TCA cycle and enables bacteria to survive on limited carbon conditions. To elucidate the mechanisms underlying itaconic acid production through IRG1 induction in macrophages, we examined the transcriptional regulation of IRG1. To this end, we studied IRG1 expression in human immune cells under different inflammatory stimuli, such as TNFα and IFNγ, in addition to lipopolysaccharides. Under these conditions, as previously shown in mouse macrophages, IRG1/CAD accumulates in mitochondria. Furthermore, using literature information and transcription factor prediction models, we re-constructed raw gene regulatory networks (GRNs) for IRG1 in mouse and human macrophages. We further implemented a contextualization algorithm that relies on genome-wide gene expression data to infer putative cell type-specific gene regulatory interactions in mouse and human macrophages, which allowed us to predict potential transcriptional regulators of IRG1. Among the computationally identified regulators, siRNA-mediated gene silencing of interferon regulatory factor 1 (IRF1) in macrophages significantly decreased the expression of IRG1/CAD at the gene and protein level, which correlated with a reduced production of itaconic acid. Using a synergistic approach of both computational and experimental methods, we here shed more light on the transcriptional machinery of IRG1 expression and could pave the way to therapeutic approaches targeting itaconic acid levels.

Clinical application: Restoration of immune homeostasis by autophagy as a potential therapeutic target in sepsis

Sepsis-induced lymphocyte and dendritic cell apoptosis contributes to immunosuppression, resulting in an inability to eradicate the primary infection and a propensity to acquire secondary infections. However, the inhibition of apoptosis may produce unexpected and undesirable consequences. Another cellular process, autophagy, is also activated in immune cells. There is increasing evidence to suggest that autophagy confers a protective effect in sepsis. The protective mechanisms underlying this effect include limiting apoptotic cell death and maintaining cellular homeostasis. Therefore, understanding the regulation of immune cell autophagy and apoptosis may provide insight into novel therapeutic strategies. The present review examined potential novel therapeutic strategies aimed at restoring immune homeostasis by inducing autophagy. The restoration of balance between apoptosis and autophagy may be a novel approach for improving sepsis-induced immunosuppression and decreasing susceptibility to sepsis.

Hydrogen Sulfide Maintains Mitochondrial DNA Replication via Demethylation of TFAM

AIMS

Hydrogen sulfide (H2S) exerts a wide range of actions in the body, especially in the modulation of mitochondrial functions. The normal replication of mitochondrial DNA (mtDNA) is critical for cellular energy metabolism and mitochondrial biogenesis. The aim of this study was to investigate whether H2S affects mtDNA replication and the underlying mechanisms. We hypothesize that H2S maintains mtDNA copy number via inhibition of Dnmt3a transcription and TFAM promoter methylation.

RESULTS

Here, we demonstrated that deficiency of cystathionine gamma-lyase (CSE), a major H2S-producing enzyme, reduces mtDNA copy number and mitochondrial contents, and it inhibits the expressions of mitochondrial transcription factor A (TFAM) and mitochondrial marker genes in both smooth muscle cells and aorta tissues from mice. Supply of exogenous H2S stimulated mtDNA copy number and strengthened the expressions of TFAM and mitochondrial marker genes. TFAM knockdown diminished H2S-enhanced mtDNA copy number. In addition, CSE deficiency induced the expression of DNA methyltransferase 3a (Dnmt3a) and TFAM promoter DNA methylation, and H2S repressed Dnmt3a expression, resulting in TFAM promoter demethylation. We further found that H2S S-sulfhydrates transcription repressor interferon regulatory factor 1 (IRF-1) and enhances the binding of IRF-1 with Dnmt3a promoter after reduced Dnmt3a transcription. H2S had little effects on the expression of Dnmt1 and Dnmt3b as well as on ten-eleven translocation methylcytosine dioxygenase 1, 2, and 3.

INNOVATION

A sufficient level of H2S is able to inhibit TFAM promoter methylation and maintain mtDNA copy number.

CONCLUSION

CSE/H2S system contributes to mtDNA replication and cellular bioenergetics and provides a novel therapeutic avenue for cardiovascular diseases.

Interferon regulatory factor-1 signaling regulates the switch between autophagy and apoptosis to determine breast cancer cell fate

Interferon regulatory factor-1 (IRF1) is a tumor suppressor that regulates cell fate in several cell types. Here, we report an inverse correlation in expression of nuclear IRF1 and the autophagy regulator ATG7 in human breast cancer cells that directly affects their cell fate. In mice harboring mutant Atg7, nuclear IRF1 was increased in mammary tumors, spleen, and kidney. Mechanistic investigations identified ATG7 and the cell death modulator beclin-1 (BECN1) as negative regulators of IRF1. Silencing ATG7 or BECN1 caused estrogen receptor-α to exit the nucleus at the time when IRF1 nuclear localization occurred. Conversely, silencing IRF1 promoted autophagy by increasing BECN1 and blunting IGF1 receptor and mTOR survival signaling. Loss of IRF1 promoted resistance to antiestrogens, whereas combined silencing of ATG7 and IRF1 restored sensitivity to these agents. Using a mathematical model to prompt signaling hypotheses, we developed evidence that ATG7 silencing could resensitize IRF1-attenuated cells to apoptosis through mechanisms that involve other estrogen-regulated genes. Overall, our work shows how inhibiting the autophagy proteins ATG7 and BECN1 can regulate IRF1-dependent and -independent signaling pathways in ways that engender a new therapeutic strategy to attack breast cancer.

Ameliorating of Memory Impairment and Apoptosis in Amyloid β-Injected Rats Via Inhibition of Nitric Oxide Synthase: Possible Participation of Autophagy

It has been proposed that appearance of amyloid beta (Aβ) in hippocampus is one of the characteristic features of Alzheimer's disease (AD). The role of Nitric oxide (NO) in neurodegenerative disorders is controversy in different contexts. Here, we examined the effect of NO on spatial memory. For this purpose, we compared the effects of three different concentrations of L-NG-Nitroarginine Methyl Ester (L-NAME) as a nitric oxide synthase (NOS) inhibitor. We used Morris water maze (MWM) for evaluation of behavioral alterations. We also assessed the apoptosis and autophagy markers as two possible interfering pathways with NO signaling by western blot method. We found that in Aβ pretreated rats, intra-hippocampal injection of 1or 2 (μg/side) of L-NAME caused a significant reduction in escape latency and traveled distance comparing to Aβ-treatment group. Our molecular findings revealed that L-NAME could induce autophagy and attenuate apoptosis dose dependently. The protective role of autophagy and the deteriorative role of apoptosis is the hypothesis that can vindicate our findings. Thus using NOS inhibitors at low concentrations can be one of the therapeutic approaches in the future studies.

ASPP2 attenuates triglycerides to protect against hepatocyte injury by reducing autophagy in a cell and mouse model of non-alcoholic fatty liver disease

ASPP2 is a pro-apoptotic member of the p53 binding protein family. ASPP2 has been shown to inhibit autophagy, which maintains energy balance in nutritional deprivation. We attempted to identify the role of ASPP2 in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). In a NAFLD cell model, control treated and untreated HepG2 cells were pre-incubated with GFP-adenovirus (GFP-ad) for 12 hrs and then treated with oleic acid (OA) for 24 hrs. In the experimental groups, the HepG2 cells were pre-treated with ASPP2-adenovirus (ASPP2-ad) or ASPP2-siRNA for 12 hrs and then treated with OA for 24 hrs. BALB/c mice fed a methionine- and choline-deficient (MCD) diet were used to generate a mouse model of NAFLD. The mice with fatty livers in the control group were pre-treated with injections of GFP-ad for 10 days. In the experimental group, the mice that had been pre-treated with ASPP2-ad were fed an MCD diet for 10 days. ASPP2-ad or GFP-ad was administered once every 5 days. Liver tissue from fatty liver patients and healthy controls were used to analyse the role of ASPP2. Autophagy, apoptosis markers and lipid metabolism mediators, were assessed with confocal fluorescence microscopy, immunohistochemistry, western blot and biochemical assays. ASPP2 overexpression decreased the triglyceride content and inhibited autophagy and apoptosis in the HepG2 cells. ASPP2-ad administration suppressed the MCD diet-induced autophagy, steatosis and apoptosis and decreased the previously elevated alanine aminotransferase levels. In conclusion, ASPP2 may participate in the lipid metabolism of non-alcoholic steatohepatitis and attenuate liver failure.

Inducible nitric oxide synthase drives mTOR pathway activation and proliferation of human melanoma by reversible nitrosylation of TSC2

Melanoma is one of the cancers of fastest-rising incidence in the world. Inducible nitric oxide synthase (iNOS) is overexpressed in melanoma and other cancers, and previous data suggest that iNOS and nitric oxide (NO) drive survival and proliferation of human melanoma cells. However, specific mechanisms through which this occurs are poorly defined. One candidate is the PI3K-AKT-mTOR pathway, which plays a major role in proliferation, angiogenesis, and metastasis of melanoma and other cancers. We used the chick embryo chorioallantoic membrane (CAM) assay to test the hypothesis that melanoma growth is regulated by iNOS-dependent mTOR pathway activation. Both pharmacologic inhibition and siRNA-mediated gene silencing of iNOS suppressed melanoma proliferation and in vivo growth on the CAM in human melanoma models. This was associated with strong downregulation of mTOR pathway activation by Western blot analysis of p-mTOR, p70 ribosomal S6 kinase (p-P70S6K), p-S6RP, and p-4EBP1. iNOS expression and NO were associated with reversible nitrosylation of tuberous sclerosis complex (TSC) 2, and inhibited dimerization of TSC2 with its inhibitory partner TSC1, enhancing GTPase activity of its target Ras homolog enriched in brain (Rheb), a critical activator of mTOR signaling. Immunohistochemical analysis of tumor specimens from stage III melanoma patients showed a significant correlation between iNOS expression levels and expression of the mTOR pathway members. Exogenously supplied NO was also sufficient to reverse the mTOR pathway inhibition by the B-Raf inhibitor vemurafenib. In summary, covalent modification of TSC2 by iNOS-derived NO is associated with impaired TSC2/TSC1 dimerization, mTOR pathway activation, and proliferation of human melanoma. This model is consistent with the known association of iNOS overexpression and poor prognosis in melanoma and other cancers.

Involvement of interleukin-1β in the autophagic process of microglia: relevance to Alzheimer's disease

BACKGROUND

Autophagy is a major pathway of protein and organelle degradation in the lysosome. Autophagy exists at basal constitutive level and can be induced as a defense mechanism under stress conditions. Molecular relationships between autophagy and inflammation at the periphery were recently evidenced, highlighting a role of autophagy in the regulation of inflammation. Impairment of autophagy (with accumulation of autophagic vacuoles) and substantial inflammation are found in neurodegenerative diseases such as Alzheimer's Disease (AD). However, the links between autophagy and inflammation in AD remain to be determined.

METHODS

Here, we examined the inflammatory reaction and autophagy in murine tri-cultures of neurons, astrocytes, and microglia. Tri-cultures were exposed to various inflammatory stresses (lipopolysaccharide (LPS), amyloid peptide (Aβ42) with or without cytokines) for 48 hours. Furthermore, the relationships between inflammation and autophagy were also analyzed in astrocyte- and microglia-enriched cultures. Data for multiple variable comparisons were analyzed by a one-way ANOVA followed by a Newman-keuls' test.

RESULTS

Aβ42 induced a low inflammation without accumulation of acidic vesicles contrary to moderate or severe inflammation induced by LPS or the cytokine cocktail (IL-1β, TNF-α, and IL-6) or IL-1β alone which led to co-localization of p62 and LC3, two markers of autophagy, with acidic vesicles stained with Lyso-ID Red dye. Moreover, the study reveals a major role of IL-1β in the induction of autophagy in tri-cultures in the presence or absence of Aβ42. However, the vulnerability of the autophagic process in purified microglia to IL-1β was prevented by Aβ42.

CONCLUSION

These findings show a close relationship between inflammation and autophagy, in particular a major role of IL-1β in the induction of the microglial autophagy which could be the case in AD. New therapeutic strategies could target inflammasome and autophagy in microglia to maintain its role in the amyloid immunosurveillance.