Shedding of the tumor necrosis factor (TNF) receptor from the surface of hepatocytes during sepsis limits inflammation through cGMP signaling

Regulation of plasma soluble receptors of TNF and IL-1 in patients with COVID-19 differs from that observed in sepsis

OBJECTIVES

IL-1α/β and TNF are closely linked to the pathology of severe COVID-19 and sepsis. The soluble forms of their receptors, functioning as decoy receptors, exhibit inhibitory effects. However, little is known about their regulation in severe bacterial and viral infections, which we aimed to investigate in this study.

METHODS

The circulating soluble receptors of TNF (sTNFR1 and sTNFR2) and IL-1α/β (sIL-1R1, sIL-1R2) were evaluated in the plasma of patients with COVID-19, severe bacterial infections, and sepsis and compared with healthy controls. Additionally, IL1R1, IL1R2, TNFRSF1A, and TNFRSF1B expression was evaluated at the single cell level in PBMCs derived from COVID-19 or sepsis patients.

RESULTS

Plasma concentrations of sIL-1R1, sTNFR1, and sTNFR2 were significantly higher in COVID-19 patients compared to healthy subjects. Notably, sIL-1R1 levels were particularly elevated in ICU COVID-19 patients, and transcriptome analysis indicated heightened IL1R1 expression in PBMCs from severe COVID-19 patients. In severe bacterial infections, only sTNFR1 and sTNFR2 exhibited increased levels compared to healthy controls. Sepsis patients had decreased sIL-1R1 plasma concentrations but elevated sIL-1R2, sTNFR1, and sTNFR2 levels compared to healthy individuals, reflecting the heightened expression due to the increased numbers of monocytes present in sepsis. Finally, elevated concentrations of sIL-1R2, sTNFR1, and sTNFR2 were moderately associated with reduced 28-day survival in sepsis patients.

CONCLUSION

Our study reveals distinct regulation of plasma concentrations of soluble IL-1 receptors in COVID-19 and sepsis. Moreover, soluble TNF receptors 1 and 2 consistently rise in all conditions and show a positive correlation with disease severity in sepsis.

Impact of TNFRSF1B (rs3397, rs1061624 and rs1061622) and IL6 (rs1800796, rs1800797 and rs1554606) Gene Polymorphisms on Inflammatory Response in Patients with End-Stage Kidney Disease Undergoing Dialysis

We aimed to study the impact of polymorphisms in the genes encoding interleukin-6 (IL6) and tumor necrosis factor receptor-2 (TNFR2), reported to be mortality risk predictors, in patients with end-stage kidney disease (ESKD) undergoing dialysis. TNFRSF1B (rs3397, rs1061624, and rs1061622) and IL6 (rs1800796, rs1800797, and rs1554606) polymorphisms were studied in patients with ESKD and controls; the genotype and allele frequencies and the associations with inflammatory and erythropoiesis markers were determined; deaths were recorded throughout the following two years. The genotype and allele frequencies for the TNFRSF1B rs3397 polymorphism were different in these patients compared to those in the controls and the global and European populations, and patients with the C allele were less common. Patients with the CC genotype for TNFRSF1B rs3397 presented higher hemoglobin and erythrocyte counts and lower TNF-α levels, suggesting a more favorable inflammatory response that seems to be associated with erythropoiesis improvement. Patients with the GG genotype for TNFRSF1B rs1061622 showed lower serum ferritin levels. None of the TNFRSF1B (rs3397, rs1061624, and rs1061622) or IL6 (rs1800796, rs1800797, and rs1554606) polymorphisms had a significant impact on the all-cause mortality rate of Portuguese patients with ESKD.

PDE5 inhibitors: breaking new grounds in the treatment of COVID-19

INTRODUCTION

Despite the ever-increasing occurrences of the coronavirus disease (COVID-19) cases around the world, very few medications have been validated in the clinical trials to combat COVID-19. Although several vaccines have been developed in the past quarter, the time elapsed between deployment and administration remains a major impediment.

CONTENT

Repurposing of pre-approved drugs, such as phosphodiesterase 5 (PDE5) inhibitors, could be a game-changer while lessening the burden on the current healthcare system. Repurposing and developing phosphodiesterase 5 (PDE5) inhibitors could extrapolate their utility to combat the SARS-CoV-2 infection, and potentially aid in the management of the symptoms associated with its newer variants such as BF.7, BQ.1, BQ.1.1, XBB.1.5, and XBB.1.16.

SUMMARY

Administration of PDE5 inhibitors via the oral and intravenous route demonstrates other potential off-label benefits, including anti-apoptotic, anti-inflammatory, antioxidant, and immunomodulatory effects, by intercepting several pathways. These effects can not only be of clinical importance in mild-to-moderate, but also moderate-to-severe SARS-CoV-2 infections. This article explores the various mechanisms by which PDE5 inhibitors alleviates the symptoms associated with COVID-19 as well as well as highlights recent studies and findings.

OUTLOOK

These benefits of PDE5 inhibitors make it a potential drug in the physicians' armamentarium in alleviating symptoms associated with SARS-CoV-2 infection. However, adequate clinical studies must be instituted to eliminate any untoward adverse events.

Extracellular SOD modulates canonical TNFα signaling and α5β1 integrin transactivation in vascular smooth muscle cells

TNFα activates NADPH oxidase 1 (Nox1) in vascular smooth muscle cells (VSMCs). The extracellular superoxide anion (O2•-) produced is essential for the pro-inflammatory effects of the cytokine but the specific contributions of O2•- to signal transduction remain obscure. Extracellular superoxide dismutase (ecSOD, SOD3 gene) is a secreted protein that binds to cell surface heparin sulfate proteoglycans or to Fibulin-5 (Fib-5, FBLN5 gene), an extracellular matrix protein that also associates with elastin and integrins. ecSOD converts O2•- to hydrogen peroxide (H2O2) which prevents NO• inactivation, limits generation of hydroxyl radical (OH•), and creates high local concentrations of H2O2. We hypothesized that ecSOD modifies TNFα signaling in VSMCs. Knockdown of ecSOD (siSOD3) suppressed downstream TNFα signals including MAPK (JNK and ERK phosphorylation) and NF-κB activation (luciferase reporter and IκB phosphorylation), interleukin-6 (IL-6) secretion, iNOS and VCAM expression, and proliferation (Sulforhodamine B assay, PCNA western blot). These effects were associated with significant reductions in the expression of both Type1 and 2 TNFα receptors. Reduced Fib-5 expression (siFBLN5) similarly impaired NF-κB activation by TNFα, but potentiated FAK phosphorylation at Y925. siSOD3 also increased both resting and TNFα-induced phosphorylation of FAK and of glycogen synthase kinase-3β (GSK3β), a downstream target of integrin linked kinase (ILK). These effects were dependent upon α5β1 integrins and siSOD3 increased resting sulfenylation (oxidation) of both integrin subunits, while preventing TNFα-induced increases in sulfenylation. To determine how ecSOD modified TNFα-induced inflammation in intact blood vessels, mesenteric arteries from VSMC-specific ecSOD knockout (KO) mice were exposed to TNFα (10 ng/ml) in culture for 48 h. Relaxation to acetylcholine and sodium nitroprusside was impaired in WT but not ecSOD KO vessels. Thus, ecSOD association with Fib-5 supports pro-inflammatory TNFα signaling while tonically inhibiting α5β1 integrin activation.

PDE5 inhibitors: breaking new grounds in the treatment of COVID-19

INTRODUCTION

Despite the ever-increasing occurrences of the coronavirus disease (COVID-19) cases around the world, very few medications have been validated in the clinical trials to combat COVID-19. Although several vaccines have been developed in the past quarter, the time elapsed between deployment and administration remains a major impediment.

CONTENT

Repurposing of pre-approved drugs, such as phosphodiesterase 5 (PDE5) inhibitors, could be a game-changer while lessening the burden on the current healthcare system. Repurposing and developing phosphodiesterase 5 (PDE5) inhibitors could extrapolate their utility to combat the SARS-CoV-2 infection, and potentially aid in the management of the symptoms associated with its newer variants such as BF.7, BQ.1, BQ.1.1, XBB.1.5, and XBB.1.16.

SUMMARY

Administration of PDE5 inhibitors via the oral and intravenous route demonstrates other potential off-label benefits, including anti-apoptotic, anti-inflammatory, antioxidant, and immunomodulatory effects, by intercepting several pathways. These effects can not only be of clinical importance in mild-to-moderate, but also moderate-to-severe SARS-CoV-2 infections. This article explores the various mechanisms by which PDE5 inhibitors alleviates the symptoms associated with COVID-19 as well as well as highlights recent studies and findings.

OUTLOOK

These benefits of PDE5 inhibitors make it a potential drug in the physicians' armamentarium in alleviating symptoms associated with SARS-CoV-2 infection. However, adequate clinical studies must be instituted to eliminate any untoward adverse events.

Zafirlukast Is a Promising Scaffold for Selectively Inhibiting TNFR1 Signaling

Tumor necrosis factor (TNF) plays an important role in the pathogenesis of inflammatory and autoimmune diseases such as rheumatoid arthritis and Crohn's disease. The biological effects of TNF are mediated by binding to TNF receptors, TNF receptor 1 (TNFR1), or TNF receptor 2 (TNFR2), and this coupling makes TNFR1-specific inhibition by small-molecule therapies essential to avoid deleterious side effects. Recently, we engineered a time-resolved fluorescence resonance energy transfer biosensor for high-throughput screening of small molecules that modulate TNFR1 conformational states and identified zafirlukast as a compound that inhibits receptor activation, albeit at low potency. Here, we synthesized 16 analogues of zafirlukast and tested their potency and specificity for TNFR1 signaling. Using cell-based functional assays, we identified three analogues with significantly improved efficacy and potency, each of which induces a conformational change in the receptor (as measured by fluorescence resonance energy transfer (FRET) in cells). The best analogue decreased NF-κB activation by 2.2-fold, IκBα efficiency by 3.3-fold, and relative potency by two orders of magnitude. Importantly, we showed that the analogues do not block TNF binding to TNFR1 and that binding to the receptor's extracellular domain is strongly cooperative. Despite these improvements, the best candidate's maximum inhibition of NF-κB is only 63%, leaving room for further improvements to the zafirlukast scaffold to achieve full inhibition and prove its potential as a therapeutic lead. Interestingly, while we find that the analogues also bind to TNFR2 in vitro, they do not inhibit TNFR2 function in cells or cause any conformational changes upon binding. Thus, these lead compounds should also be used as reagents to study conformational-dependent activation of TNF receptors.

RIPK3 promoter hypermethylation in hepatocytes protects from bile acid-induced inflammation and necroptosis

Necroptosis facilitates cell death in a controlled manner and is employed by many cell types following injury. It plays a significant role in various liver diseases, albeit the cell-type-specific regulation of necroptosis in the liver and especially hepatocytes, has not yet been conceptualized. We demonstrate that DNA methylation suppresses RIPK3 expression in human hepatocytes and HepG2 cells. In diseases leading to cholestasis, the RIPK3 expression is induced in mice and humans in a cell-type-specific manner. Overexpression of RIPK3 in HepG2 cells leads to RIPK3 activation by phosphorylation and cell death, further modulated by different bile acids. Additionally, bile acids and RIPK3 activation further facilitate JNK phosphorylation, IL-8 expression, and its release. This suggests that hepatocytes suppress RIPK3 expression to protect themselves from necroptosis and cytokine release induced by bile acid and RIPK3. In chronic liver diseases associated with cholestasis, induction of RIPK3 expression may be an early event signaling danger and repair through releasing IL-8.

Angiotensin-converting enzyme 2-at the heart of the COVID-19 pandemic

ACE2 is the indispensable entry receptor for SARS-CoV and SARS-CoV-2. Because of the COVID-19 pandemic, it has become one of the most therapeutically targeted human molecules in biomedicine. ACE2 serves two fundamental physiological roles: as an enzyme, it alters peptide cascade balance; as a chaperone, it controls intestinal amino acid uptake. ACE2's tissue distribution, affected by co-morbidities and sex, explains the broad tropism of coronaviruses and the clinical manifestations of SARS and COVID-19. ACE2-based therapeutics provide a universal strategy to prevent and treat SARS-CoV-2 infections, applicable to all SARS-CoV-2 variants and other emerging zoonotic coronaviruses exploiting ACE2 as their cellular receptor.

ADAM10-a "multitasker" in sepsis: focus on its posttranslational target

BACKGROUND

Sepsis has a complex pathogenesis in which the uncontrolled systemic inflammatory response triggered by infection leads to vascular barrier disruption, microcirculation dysfunction and multiple organ dysfunction syndrome. Numerous recent studies reveal that a disintegrin and metalloproteinase 10 (ADAM10) acts as a "molecular scissor" playing a pivotal role in the inflammatory response during sepsis by regulating proteolysis by cleaving various membrane protein substrates, including proinflammatory cytokines, cadherins and Notch, which are involved in intercellular communication. ADAM10 can also act as the cellular receptor for Staphylococcus aureus α-toxin, leading to lethal sepsis. However, its substrate-specific modulation and precise targets in sepsis have not yet to be elucidated.

METHODS

We performed a computer-based online search using PubMed and Google Scholar for published articles concerning ADAM10 and sepsis.

CONCLUSIONS

In this review, we focus on the functions of ADAM10 in sepsis-related complex endothelium-immune cell interactions and microcirculation dysfunction through the diversity of its substrates and its enzymatic activity. In addition, we highlight the posttranslational mechanisms of ADAM10 at specific subcellular sites, or in multimolecular complexes, which will provide the insight to intervene in the pathophysiological process of sepsis caused by ADAM10 dysregulation.

Protein-Labeling Fluorescent Probe Reveals Ectodomain Shedding of Transmembrane Carbonic Anhydrases

Ectodomain shedding is a form of limited proteolysis in which a protease cleaves a transmembrane protein, releasing the extracellular domain from the cell surface. Cells use this process to regulate a wide variety of biological events. Typically, immunological detection methods are employed for the analysis of ectodomains secreted into the cultured media. In this paper, we describe a new strategy using an affinity-based protein-labeling fluorescent probe to study ectodomain shedding. We analyzed the ectodomain shedding of cell surface carbonic anhydrases (CAIX and CAXII), which are important biomarkers for tumor hypoxia. Using both chemical and genetic approaches, we identified that the ADAM17 metalloprotease is responsible for the shedding of carbonic anhydrases. Compared to current immunological methods, this protein-labeling approach not only detects ectodomain released into the culture media but also allows real-time living cell tracking and quantitative analysis of remnant proteins on the cell surface, thereby providing a more detailed insight into the mechanism of ectodomain shedding as well as protein lifetime on the cell surface.

Intraperitoneal injection of class A TLR9 agonist enhances anti-PD-1 immunotherapy in colorectal peritoneal metastases

Peritoneal metastases are associated with a low response rate to immune checkpoint blockade (ICB) therapy. The numbers of peritoneal resident macrophages (PRMs) are reversely correlated with the response rate to ICB therapy. We have previously shown that TLR9 in fibroblastic reticular cells (FRCs) plays a critical role in regulating peritoneal immune cell recruitment. However, the role of TLR9 in FRCs in regulating PRMs is unclear. Here, we demonstrated that the class A TLR9 agonist, ODN1585, markedly enhanced the efficacy of anti-PD-1 therapy in mouse models of colorectal peritoneal metastases. ODN1585 injected i.p. reduced the numbers of Tim4+ PRMs and enhanced CD8+ T cell antitumor immunity. Mechanistically, treatment of ODN1585 suppressed the expression of genes required for retinoid metabolism in FRCs, and this was associated with reduced expression of the PRM lineage-defining transcription factor GATA6. Selective deletion of TLR9 in FRCs diminished the benefit of ODN1585 in anti-PD-1 therapy in reducing peritoneal metastases. The crosstalk between PRMs and FRCs may be utilized to develop new strategies to improve the efficacy of ICB therapy for peritoneal metastases.

Bioinformatics Analysis Identifies TNFRSF1A as a Biomarker of Liver Injury in Sepsis TNFRSF1A is a Biomarker for Septic Liver Injury

Sepsis is a severe disease with high mortality, and liver injury is an independent risk factor for sepsis morbidity and mortality. We analyzed co-differentially expressed genes (co-DEGs) to explore potential biomarkers and therapeutic targets for sepsis-related liver injury. Three gene expression datasets (GSE60088, GSE23767, and GSE71530) were downloaded from the Gene Expression Omnibus (GEO). DEGs were screened between sepsis and control samples using GEO2R. The association of these DEGs with infection and liver disease was analyzed by using the CTD database. GO functional analysis, KEGG pathway enrichment analysis, and protein-protein interaction (PPI) network analysis were performed to elucidate the potential molecular mechanism of DEGs. DEGs of different tissues in GSE60088 were analyzed again to obtain specific markers of septic liver injury. Mouse model of sepsis was also established by cecal ligation and puncture (CLP), and the expression of specific markers in liver, lung, and kidney tissues was analyzed using Western blot. Here, we identified 21 DEGs in three datasets with 8 hub genes, all of which showed higher inference scores in liver diseases than bacterial infections. Among them, only TNFRSF1A had a liver-specific differential expression. TNFRSF1A was also confirmed to be specifically reduced in septic liver tissues in mice. Therefore, TNFRSF1A may serve as a potential biomarker for septic liver injury.

Involvement of shedding induced by ADAM17 on the nitric oxide pathway in hypertension

A Disintegrin and Metalloprotease 17 (ADAM17), also called tumor necrosis factor-ɑ (TNF-ɑ) convertase (TACE), is a well-known protease involved in the sheddase of growth factors, chemokines and cytokines. ADAM17 is also enrolled in hypertension, especially by shedding of angiotensin converting enzyme type 2 (ACE2) leading to impairment of angiotensin 1–7 [Ang-(1–7)] production and injury in vasodilation, induction of renal damage and cardiac hypertrophy. Activation of Mas receptor (MasR) by binding of Ang-(1–7) induces an increase in the nitric oxide (NO) gaseous molecule, which is an essential factor of vascular homeostasis and blood pressure control. On the other hand, TNF-ɑ has demonstrated to stimulate a decrease in nitric oxide bioavailability, triggering a disrupt in endothelium-dependent vasorelaxation. In spite of the previous studies, little knowledge is available about the involvement of the metalloprotease 17 and the NO pathways. Here we will provide an overview of the role of ADAM17 and Its mechanisms implicated with the NO formation.

Urinary angiotensin-converting enzyme 2 and metabolomics in COVID-19-mediated kidney injury

Background

Angiotensin-converting enzyme 2 (ACE2), the receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is highly expressed in the kidneys. Beyond serving as a crucial endogenous regulator of the renin-angiotensin system, ACE2 also possess a unique function to facilitate amino acid absorption. Our observational study sought to explore the relationship between urine ACE2 (uACE2) and renal outcomes in coronavirus disease 2019 (COVID-19).

Methods

In a cohort of 104 patients with COVID-19 without acute kidney injury (AKI), 43 patients with COVID-19-mediated AKI and 36 non-COVID-19 controls, we measured uACE2, urine tumour necrosis factor receptors I and II (uTNF-RI and uTNF-RII) and neutrophil gelatinase-associated lipocalin (uNGAL). We also assessed ACE2 staining in autopsy kidney samples and generated a propensity score-matched subgroup of patients to perform a targeted urine metabolomic study to describe the characteristic signature of COVID-19.

Results

uACE2 is increased in patients with COVID-19 and further increased in those that developed AKI. After adjusting uACE2 levels for age, sex and previous comorbidities, increased uACE2 was independently associated with a >3-fold higher risk of developing AKI [odds ratio 3.05 (95% confidence interval 1.23‒7.58), P = .017]. Increased uACE2 corresponded to a tubular loss of ACE2 in kidney sections and strongly correlated with uTNF-RI and uTNF-RII. Urine quantitative metabolome analysis revealed an increased excretion of essential amino acids in patients with COVID-19, including leucine, isoleucine, tryptophan and phenylalanine. Additionally, a strong correlation was observed between urine amino acids and uACE2.

Conclusions

Elevated uACE2 is related to AKI in patients with COVID-19. The loss of tubular ACE2 during SARS-CoV-2 infection demonstrates a potential link between aminoaciduria and proximal tubular injury.

Current Advances in Structure-Function Relationships and Dose-Dependent Effects of Human Milk Oligosaccharides

HMOs (human milk oligosaccharides) are the third most important nutrient in breast milk. As complex glycans, HMOs play an important role in regulating neonatal intestinal immunity, resisting viral and bacterial infections, displaying anti-inflammatory characteristics, and promoting brain development. Although there have been some previous reports of HMOs, a detailed literature review summarizing the structure-activity relationships and dose-dependent effects of HMOs is lacking. Hence, after introducing the structures and synthetic pathways of HMOs, this review summarizes and categorizes identified structure-function relationships of HMOs. Differential mechanisms of different structural HMOs utilization by microorganisms are summarized. This review also emphasizes the recent advances in the interactions between different health benefits and the variance of dosage effect based on in vitro cell tests, animal experiments, and human intervention studies. The potential relationships between the chemical structure, the dosage selection, and the physiological properties of HMOs as functional foods are vital for further understanding of HMOs and their future applications.

Galectin-1 orchestrates an inflammatory tumor-stroma crosstalk in hepatoma by enhancing TNFR1 protein stability and signaling in carcinoma-associated fibroblasts

Most cases of hepatocellular carcinoma (HCC) arise with the fibrotic microenvironment where hepatic stellate cells (HSCs) and carcinoma-associated fibroblasts (CAFs) are critical components in HCC progression. Therefore, CAF normalization could be a feasible therapy for HCC. Galectin-1 (Gal-1), a β-galactoside-binding lectin, is critical for HSC activation and liver fibrosis. However, few studies has evaluated the pathological role of Gal-1 in HCC stroma and its role in hepatic CAF is unclear. Here we showed that Gal-1 mainly expressed in HCC stroma, but not cancer cells. High expression of Gal-1 is correlated with CAF markers and poor prognoses of HCC patients. In co-culture systems, targeting Gal-1 in CAFs or HSCs, using small hairpin (sh)RNAs or an therapeutic inhibitor (LLS30), downregulated plasminogen activator inhibitor-2 (PAI-2) production which suppressed cancer stem-like cell properties and invasion ability of HCC in a paracrine manner. The Gal-1-targeting effect was mediated by increased a disintegrin and metalloprotease 17 (ADAM17)-dependent TNF-receptor 1 (TNFR1) shedding/cleavage which inhibited the TNF-α → JNK → c-Jun/ATF2 signaling axis of pro-inflammatory gene transcription. Silencing Gal-1 in CAFs inhibited CAF-augmented HCC progression and reprogrammed the CAF-mediated inflammatory responses in a co-injection xenograft model. Taken together, the findings uncover a crucial role of Gal-1 in CAFs that orchestrates an inflammatory CSC niche supporting HCC progression and demonstrate that targeting Gal-1 could be a potential therapy for fibrosis-related HCC.

Meprin and ADAM proteases as triggers of systemic inflammation in sepsis

Systemic inflammatory disorders (SIDs) comprise a broad range of diseases characterized by dysregulated excessive innate immune responses. Severe forms of SIDs can lead to organ failure and death, and their increasing incidence represents a major issue for the healthcare system. Protease-mediated ectodomain shedding of cytokines and their receptors represents a central mechanism in the regulation of inflammatory responses. The metalloprotease A disintegrin and metalloproteinase (ADAM) 17 is the best-characterized ectodomain sheddase capable of releasing TNF-α and soluble IL-6 receptor, which are decisive factors of systemic inflammation. Recently, meprin metalloproteases were also identified as IL-6 receptor sheddases and activators of the pro-inflammatory cytokines IL-1β and IL-18. In different mouse models of SID, particularly those mimicking a sepsis-like phenotype, ADAM17 and meprins have been found to promote disease progression. In this review, we summarize the role of ADAM10, ADAM17, and meprins in the onset and progression of sepsis and discuss their potential as therapeutic targets.

Modulation of Inflammatory Cytokine Production in Human Monocytes by cGMP and IRAK3

Interleukin-1 receptor-associated kinase-3 (IRAK3) is a critical checkpoint molecule of inflammatory responses in the innate immune system. The pseudokinase domain of IRAK3 contains a guanylate cyclase (GC) centre that generates small amounts of cyclic guanosine monophosphate (cGMP) associated with IRAK3 functions in inflammation. However, the mechanisms of IRAK3 actions are poorly understood. The effects of low cGMP levels on inflammation are unknown, therefore a dose–response effect of cGMP on inflammatory markers was assessed in THP-1 monocytes challenged with lipopolysaccharide (LPS). Sub-nanomolar concentrations of membrane permeable 8-Br-cGMP reduced LPS-induced NFκB activity, IL-6 and TNF-α cytokine levels. Pharmacologically upregulating cellular cGMP levels using a nitric oxide donor reduced cytokine secretion. Downregulating cellular cGMP using a soluble GC inhibitor increased cytokine levels. Knocking down IRAK3 in THP-1 cells revealed that unlike the wild type cells, 8-Br-cGMP did not suppress inflammatory responses. Complementation of IRAK3 knockdown cells with wild type IRAK3 suppressed cytokine production while complementation with an IRAK3 mutant at GC centre only partially restored this function. Together these findings indicate low levels of cGMP form a critical component in suppressing cytokine production and in mediating IRAK3 action, and this may be via a cGMP enriched nanodomain formed by IRAK3 itself.

Soluble TNF receptors predict acute kidney injury and mortality in critically ill COVID-19 patients: A prospective observational study

Background

Although pneumonia is the hallmark of coronavirus disease 2019 (COVID-19), multiple organ failure may develop in severe disease. TNFα receptors in their soluble form (sTNFR) are involved in the immune cascade in other systemic inflammatory processes such as septic shock, and could mediate the inflammatory activation of distant organs. The aim of this study is to analyse plasma levels of sTNFR 1 and 2 in association with organ failure and outcome in critically ill patients with COVID-19.

Methods

After informed consent, we included 122 adult patients with PCR-confirmed COVID-19 at ICU admission. Demographic data, illness severity scores, organ failure and survival at 30 days were collected. Plasma sTNFR 1 and 2 levels were quantified during the first days after ICU admission. Twenty-five healthy blood donors were used as control group.

Results

Levels of sTNFR were higher in severe COVID-19 patients compared to controls (p < 0.001). Plasma levels of sTNFR were associated to illness severity scores (SAPS 3 and SOFA), inflammation biomarkers such as IL-6, ferritin and PCT as well as development of AKI during ICU stay. sTNFR 1 higher than 2.29 ng/mL and? sTNFR 2 higher than 11.7 ng/mL were identified as optimal cut-offs to discriminate survivors and non-survivors 30 days after ICU admission and had an area under the curve in receiver operating characteristic curve of 0.75 and 0.67 respectively.

Conclusion

Plasma levels of sTNFR 1 and 2 were higher in COVID-19 patients compared to controls and were strongly associated with other inflammatory biomarkers, severity of illness and acute kidney injury development during ICU stay. In addition, sTNFR 1 was an independent predictor of 30-day mortality after adjustment for age and respiratory failure.

The pseudoprotease iRhom1 controls ectodomain shedding of membrane proteins in the nervous system

Proteolytic ectodomain shedding of membrane proteins is a fundamental mechanism to control the communication between cells and their environment. A key protease for membrane protein shedding is ADAM17, which requires a non-proteolytic subunit, either inactive Rhomboid 1 (iRhom1) or iRhom2 for its activity. While iRhom1 and iRhom2 are co-expressed in most tissues and appear to have largely redundant functions, the brain is an organ with predominant expression of iRhom1. Yet, little is known about the spatio-temporal expression of iRhom1 in mammalian brain and about its function in controlling membrane protein shedding in the nervous system. Here, we demonstrate that iRhom1 is expressed in mouse brain from the prenatal stage to adulthood with a peak in early postnatal development. In the adult mouse brain iRhom1 was widely expressed, including in cortex, hippocampus, olfactory bulb, and cerebellum. Proteomic analysis of the secretome of primary neurons using the hiSPECS method and of cerebrospinal fluid, obtained from iRhom1-deficient and control mice, identified several membrane proteins that require iRhom1 for their shedding in vitro or in vivo. One of these proteins was 'multiple-EGF-like-domains protein 10' (MEGF10), a phagocytic receptor in the brain that is linked to the removal of amyloid β and apoptotic neurons. MEGF10 was further validated as an ADAM17 substrate using ADAM17-deficient mouse embryonic fibroblasts. Taken together, this study discovers a role for iRhom1 in controlling membrane protein shedding in the mouse brain, establishes MEGF10 as an iRhom1-dependent ADAM17 substrate and demonstrates that iRhom1 is widely expressed in murine brain.

ADAM10 and ADAM17 regulate EGFR, c-Met and TNF RI signalling in liver regeneration and fibrosis

ADAM10 and ADAM17 are proteases that affect multiple signalling pathways by releasing molecules from the cell surface. As their substrate specificities partially overlaps, we investigated their concurrent role in liver regeneration and fibrosis, using three liver-specific deficient mouse lines: ADAM10- and ADAM17-deficient lines, and a line deficient for both proteases. In the model of partial hepatectomy, double deficient mice exhibited decreased AKT phosphorylation, decreased release of EGFR activating factors and lower shedding of HGF receptor c-Met. Thus, simultaneous ablation of ADAM10 and ADAM17 resulted in inhibited EGFR signalling, while HGF/c-Met signalling pathway was enhanced. In contrast, antagonistic effects of ADAM10 and ADAM17 were observed in the model of chronic CCl₄ intoxication. While ADAM10-deficient mice develop more severe fibrosis manifested by high ALT, AST, ALP and higher collagen deposition, combined deficiency of ADAM10 and ADAM17 surprisingly results in comparable degree of liver damage as in control littermates. Therefore, ADAM17 deficiency is not protective in fibrosis development per se, but can ameliorate the damaging effect of ADAM10 deficiency on liver fibrosis development. Furthermore, we show that while ablation of ADAM17 resulted in decreased shedding of TNF RI, ADAM10 deficiency leads to increased levels of soluble TNF RI in serum. In conclusion, hepatocyte-derived ADAM10 and ADAM17 are important regulators of growth receptor signalling and TNF RI release, and pathological roles of these proteases are dependent on the cellular context.

Modulation of the tumor micro-environment by CD8+ T cell-derived cytokines

Upon their activation, CD8⁺ T cells in the tumor micro-environment (TME) secrete cytokines such as IFNγ, TNFα, and IL-2. While over the past years a major interest has developed in the antigenic signals that induce such cytokine release, our understanding of the cells that subsequently sense these CD8⁺ T-cell secreted cytokines is modest. Here, we review the current insights into the spreading behavior of CD8⁺ T-cell-secreted cytokines in the TME. We argue for a model in which variation in the mode of cytokine secretion, cytokine half-life, receptor-mediated clearance, cytokine binding to extracellular components, and feedback or forward loops, between different cytokines or between individual tumors, sculpts the local tissue response to natural and therapy-induced T-cell activation in human cancer.

Actin fence therapy with exogenous V12Rac1 protects against acute lung injury

High mortality in acute lung injury (ALI) results from sustained proinflammatory signaling by alveolar receptors, such as TNF-α receptor type 1 (TNFR1). Factors that determine the sustained signaling are not known. Unexpectedly, optical imaging of live alveoli revealed a major TNF-α–induced surge of alveolar TNFR1 due to a Ca²⁺-dependent mechanism that decreased the cortical actin fence. Mouse mortality due to inhaled LPS was associated with cofilin activation, actin loss, and the TNFR1 surge. The constitutively active form of the GTPase, Rac1 (V12Rac1), given intranasally (i.n.) as a noncovalent construct with a cell-permeable peptide, enhanced alveolar filamentous actin (F-actin) and blocked the TNFR1 surge. V12Rac1 also protected against ALI-induced mortality resulting from i.n. instillation of LPS or of Pseudomonas aeruginosa. We propose a potentially new therapeutic paradigm in which actin enhancement by exogenous Rac1 strengthens the alveolar actin fence, protecting against proinflammatory receptor hyperexpression, and therefore blocking ALI.

Role of ADAM10 and ADAM17 in Regulating CD137 Function

Human CD137 (4-1BB), a member of the TNF receptor family, and its ligand CD137L (4-1BBL), are expressed on immune cells and tumor cells. CD137/CD137L interaction mediates bidirectional cellular responses of potential relevance in inflammatory diseases, autoimmunity and oncology. A soluble form of CD137 exists, elevated levels of which have been reported in patients with rheumatoid arthritis and various malignancies. Soluble CD137 (sCD137) is considered to represent a splice variant of CD137. In this report, however, evidence is presented that A Disintegrin and Metalloproteinase (ADAM)10 and potentially also ADAM17 are centrally involved in its generation. Release of sCD137 by transfected cell lines and primary T cells was uniformly inhibitable by ADAM10 inhibition. The shedding function of ADAM10 can be blocked through inhibition of its interaction with surface exposed phosphatidylserine (PS), and this effectively inhibited sCD137 generation. The phospholipid scramblase Anoctamin-6 (ANO6) traffics PS to the outer membrane and thus modifies ADAM10 function. Overexpression of ANO6 increased stimulated shedding, and hyperactive ANO6 led to maximal constitutive shedding of CD137. sCD137 was functionally active and augmented T cell proliferation. Our findings shed new light on the regulation of CD137/CD137L immune responses with potential impact on immunotherapeutic approaches targeting CD137.

High cut-off dialysis mitigates pro-calcific effects of plasma on vascular progenitor cells

Mortality of patients with end-stage renal disease tremendously exceeds that of the general population due to excess cardiovascular morbidity. Large middle-sized molecules (LMM) including pro-inflammatory cytokines are major drivers of uremic cardiovascular toxicity and cannot be removed sufficiently by conventional high-flux (HFL) hemodialysis. We tested the ability of plasma from 19 hemodialysis patients participating in a trial comparing HFL with high cut-off (HCO) membranes facilitating removal of LMM to induce calcification in mesenchymal stromal cells (MSC) functioning as vascular progenitors. HCO dialysis favorably changed plasma composition resulting in reduced pro-calcific activity. LMM were removed more effectively by HCO dialysis including FGF23, a typical LMM we found to promote osteoblastic differentiation of MSC. Protein-bound uremic retention solutes with known cardiovascular toxicity but not LMM inhibited proliferation of MSC without direct toxicity in screening experiments. We could not attribute the effect of HCO dialysis on MSC calcification to distinct mediators. However, we found evidence of sustained reduced inflammation that might parallel other anti-calcifying mechanisms such as altered generation of extracellular vesicles. Our findings imply protection of MSC from dysfunctional differentiation by novel dialysis techniques targeted at removal of LMM. HCO dialysis might preserve their physiologic role in vascular regeneration and improve outcomes in dialysis patients.

Long noncoding RNA TUG1 is downregulated in sepsis and may sponge miR-27a to downregulate tumor necrosis factor-α

Objectives

Bioinformatics analysis revealed a potential interaction between long noncoding (lnc)RNA TUG1 (taurine-upregulated gene 1) and microRNA (miR)-27a. miR-27a can promote sepsis by upregulating tumor necrosis factor-α (TNF-α). Our objective was to study the roles of TUG1 in sepsis.

Methods

Plasma levels of TUG1 in patients with sepsis and in healthy controls were measured by quantitative PCR assay. The IntaRNA program was used to predict potential interactions between TUG1 mRNA and miR-27a. The interaction between TUG1 and miR-27a was further explored by transfecting TUG1 expression vector or miR-27a mimic into AC16 human cardiomyocytes, and apoptosis was evaluated by cell apoptosis assay.

Results

TUG1 was downregulated in patients with sepsis. TUG1 was able to directly interact with miR-27a, but overexpression of TUG1 or miR-27a failed to affect the expression of each other. In contrast, TUG1 overexpression led to decreased levels of TNF-α, whereas miR-27a overexpression increased TNF-α in cardiomyocytes. Cell apoptosis analysis showed that TNF-α and miR-27a overexpression promoted apoptosis of cardiomyocytes induced by lipopolysaccharide. TUG1 overexpression had the opposite effect and attenuated the effects of TNF-α and miR-27a overexpression.

Conclusion

We conclude that TUG1 is downregulated in sepsis and may act as a molecular “sponge” of miR-27a to downregulate TNF-α.

Could Oral Phosphodiesterase 5 Inhibitors Have a Potential Adjuvant Role in Combating COVID-19 Infection?

INTRODUCTION

The recent global outbreak of coronavirus disease 2019 (COVID-19) has become a pandemic with a lot of sufferers. Excessive inflammation, exaggerated immune response, with ultimate apoptosis contribute to COVID-19 pathology that progress to acute lung acute respiratory distress.

OBJECTIVE

To shed a light on the likely benefits of the oral phosphodiesterase 5 (PDE5) inhibitor adjuvant role in combating COVID-19 infection.

METHODS

A literature review was performed in the PubMed/Medline database, Scopus, Cochrane Library, EMBASE, Academic Search Complete, Google Scholar, and CINAHL databases using the keywords COVID-19; phosphodiesterase-5 inhibitors; cytokine storm; respiratory distress.

RESULTS

Despite the worsening trends of COVID-19, still no drugs are validated to have significant clinical efficacy in the treatment of patients with COVID-19 in large-scale studies. While the progress toward a curative agent and/or vaccine is certainly hopeful, the principal limiting factor in such public health emergencies is always the time. Therefore, a preexisting licensed therapeutic(s) might offer a reprieve to the healthcare systems operating at the edge of capacity. In this context, the innovation of oral PDE5 inhibitors with their valuable effects on erection have provided a breakthrough in the treatment of erectile dysfunction and opened new fields of clinical application for this class of drugs. Oral PDE5 inhibitors have been demonstrated to possess many beneficial useful additional implications with acknowledged anti-inflammatory, antioxidant, immune response regulation, and antiapoptotic properties. These properties have been elucidated through the nitric oxide/soluble guanylyl cyclase/cyclic guanylate monophosphate pathway in addition to the emerged hemeoxygenase-1 enzyme as well as hydrogen sulfide pathways. These properties could support repurposing oral PDE5 inhibitors' potential adjuvant use in targeting different aspects of COVID-19 infection.

CONCLUSION

Oral PDE5 inhibitors retain several acknowledged off-labeled useful implications with anti-inflammatory, antioxidant, immune response regulation, and antiapoptotic properties. These properties may support repurposing oral PDE5 inhibitors' potential adjuvant use in the protocols combating COVID-19 manifestations. Mostafa T. Could Oral Phosphodiesterase 5 Inhibitors Have a Potential Adjuvant Role in Combating Coronavirus Disease 2019 Infection? Sex Med Rev 2021;9:15-22.

Could Oral Phosphodiesterase 5 Inhibitors Have a Potential Adjuvant Role in Combating COVID-19 Infection?

INTRODUCTION

The recent global outbreak of coronavirus disease 2019 (COVID-19) has become a pandemic with a lot of sufferers. Excessive inflammation, exaggerated immune response, with ultimate apoptosis contribute to COVID-19 pathology that progress to acute lung acute respiratory distress.

OBJECTIVE

To shed a light on the likely benefits of the oral phosphodiesterase 5 (PDE5) inhibitor adjuvant role in combating COVID-19 infection.

METHODS

A literature review was performed in the PubMed/Medline database, Scopus, Cochrane Library, EMBASE, Academic Search Complete, Google Scholar, and CINAHL databases using the keywords COVID-19; phosphodiesterase-5 inhibitors; cytokine storm; respiratory distress.

RESULTS

Despite the worsening trends of COVID-19, still no drugs are validated to have significant clinical efficacy in the treatment of patients with COVID-19 in large-scale studies. While the progress toward a curative agent and/or vaccine is certainly hopeful, the principal limiting factor in such public health emergencies is always the time. Therefore, a preexisting licensed therapeutic(s) might offer a reprieve to the healthcare systems operating at the edge of capacity. In this context, the innovation of oral PDE5 inhibitors with their valuable effects on erection have provided a breakthrough in the treatment of erectile dysfunction and opened new fields of clinical application for this class of drugs. Oral PDE5 inhibitors have been demonstrated to possess many beneficial useful additional implications with acknowledged anti-inflammatory, antioxidant, immune response regulation, and antiapoptotic properties. These properties have been elucidated through the nitric oxide/soluble guanylyl cyclase/cyclic guanylate monophosphate pathway in addition to the emerged hemeoxygenase-1 enzyme as well as hydrogen sulfide pathways. These properties could support repurposing oral PDE5 inhibitors' potential adjuvant use in targeting different aspects of COVID-19 infection.

CONCLUSION

Oral PDE5 inhibitors retain several acknowledged off-labeled useful implications with anti-inflammatory, antioxidant, immune response regulation, and antiapoptotic properties. These properties may support repurposing oral PDE5 inhibitors' potential adjuvant use in the protocols combating COVID-19 manifestations. Mostafa T. Could Oral Phosphodiesterase 5 Inhibitors Have a Potential Adjuvant Role in Combating Coronavirus Disease 2019 Infection? Sex Med Rev 2021;9:15-22.

Immune-Responsive Gene 1/Itaconate Activates Nuclear Factor Erythroid 2-Related Factor 2 in Hepatocytes to Protect Against Liver Ischemia-Reperfusion Injury

BACKGROUND AND AIMS

Itaconate, a metabolite of the tricarboxylic acid cycle, plays anti-inflammatory roles in macrophages during endotoxemia. The mechanisms underlying its anti-inflammatory roles have been shown to be mediated by the modulation of oxidative stress, an important mechanism of hepatic ischemia-reperfusion (I/R) injury. However, the role of itaconate in liver I/R injury is unknown.

APPROACH AND RESULTS

We found that deletion of immune-responsive gene 1 (IRG1), encoding for the enzyme producing itaconate, exacerbated liver injury and systemic inflammation. Furthermore, bone marrow adoptive transfer experiments indicated that deletion of IRG1 in both hematopoietic and nonhematopoietic compartments contributes to the protection mediated by IRG1 after I/R. Interestingly, the expression of IRG1 was up-regulated in hepatocytes after I/R and hypoxia/reoxygenation-induced oxidative stress. Modulation of the IRG1 expression levels in hepatocytes regulated hepatocyte cell death. Importantly, addition of 4-octyl itaconate significantly improved liver injury and hepatocyte cell death after I/R. Furthermore, our data indicated that nuclear factor erythroid 2-related factor 2 (Nrf2) is required for the protective effect of IRG1 on mouse and human hepatocytes against oxidative stress-induced injury. Our studies document the important role of IRG1 in the acute setting of sterile injury induced by I/R. Specifically, we provide evidence that the IRG1/itaconate pathway activates Nrf2-mediated antioxidative response in hepatocytes to protect liver from I/R injury.

CONCLUSIONS

Our data expand on the importance of IRG1/itaconate in nonimmune cells and identify itaconate as a potential therapeutic strategy for this unfavorable postsurgical complication.

TNFR1, TNFR2, neutrophil gelatinase-associated lipocalin and heparin binding protein in identifying sepsis and predicting outcome in an intensive care cohort

To date no biomarkers can aid diagnosing sepsis with adequate accuracy. We set out to assess the ability of Tumor necrosis factor receptor (TNFR) 1 and 2, Neutrophil gelatinase-associated lipocalin (NGAL) and Heparin binding protein (HBP) to discriminate sepsis from non-infected critically ill patients in a large ICU cohort, and to evaluate their value to predict mortality at 30 days. Adult patients admitted to the ICU with an arterial catheter were included. Clinical data and blood samples were prospectively recorded daily. Diagnoses were set retrospectively. Descriptive statistics and logistic regression models were used. NGAL, TNFR1 and TNFR2 were higher in sepsis patients compared to other diagnoses, as well as in non-survivors compared to survivors. In addition, these biomarkers increased with increasing stages of acute kidney injury. TNFR1 and TNFR2 performed similarly to NGAL and CRP in identifying sepsis patients, but they performed better than CRP in predicting 30-day mortality in this ICU cohort. Thus, TNFR1 and TNFR2 may be particularly useful in identifying high risk sepsis patients and facilitate relevant health care actions in this group of sepsis patients.

LPS Induces Active HMGB1 Release From Hepatocytes Into Exosomes Through the Coordinated Activities of TLR4 and Caspase-11/GSDMD Signaling

High-mobility group box-1 (HMGB1), a ubiquitous nuclear protein, acts as a late mediator of lethality when released extracellularly during sepsis. The major source of circulating HMGB1 in sepsis is hepatocytes. However, the mechanism of HMGB1 release of hepatocytes during sepsis is not very clear. We have previously shown that bacterial endotoxin [lipopolysaccharide (LPS)] sensing pathways, including Toll-like receptor (TLR)4 and caspase-11, regulate hepatocyte HMGB1 release in response to LPS. Here, we report the novel function of caspase-11 and gasdermin D (GsdmD) in LPS-induced active HMGB1 released from hepatocytes. HMGB1 release during endotoxemia was caspase-11/GsdmD dependent via an active way in vivo and in vitro. Caspase-11/GsdmD was responsible for HMGB1 translocation from nucleus to the cytoplasm via calcium changing-induced phosphorylation of calcium-calmodulin kinase kinase (camkk)β during endotoxemia. Cleaved GsdmD accumulated on the endoplasmic reticulum, suggesting this may lead to calcium leak and intracellular calcium increase. Furthermore, we investigated that exosome was an important pathway for HMGB1 release from hepatocytes; this process was dependent on TLR4, independent of caspase-11 and GsdmD in vivo and in vitro. These findings provide a novel mechanism that TLR4 signaling results in an increase in caspase-11 expression, as well as increased exosome release, while caspase-11/GsdmD activation/cleavage leads to accumulation of HMGB1 in the cytoplasm through a process associated with the release of calcium from the endoplasmic reticulum and camkkβ activation.

Regulation of Staphylococcus aureus-induced CXCR1 expression via inhibition of receptor mobilization and receptor shedding during dual receptor (TNFR1 and IL-1R) neutralization

Our earlier studies proposed a radically new idea suggesting interdependency between TNF-α/TNFR1 and IL-1β/IL-1R pathways in modulation of Staphylococcus aureus-induced CXCL8/CXCR1 axis. However, the effects of inhibition of cytokine receptor mobilization at intracellular level and surface TNFR1 and IL-1R shedding on S. aureus-induced CXCR1 expression have not been studied so far in peritoneal macrophages. This study aimed to investigate the role of inhibition of receptor mobilization from the intracellular pool (using brefeldin A) and surface receptor shedding (using TAPI-1) on CXCR1 expression during dual receptor (TNFR1 plus IL-1R) neutralization in peritoneal macrophages isolated from wild-type Swiss Albino mice. Release of superoxide anion, nitric oxide, and hydrogen peroxide was measured and cytokine production was done by ELISA. Expression of surface receptors (TNFR1, IL-1R, and CXCR1) and inflammatory mediators was studied by Western blot. It was observed that S. aureus-infected macrophages showed elevated ROS production, secretion of TNF-α, IL-1β, and CXCL8, along with increased expression of surface receptors (TNFR1, IL-1R, and CXCR1), and inflammatory markers (iNOS and COX-2) compared with control or treated groups (p < 0.05). However, prior treatment of macrophages with BFA or TAPI-1 in the presence of anti-TNFR1 antibody and IRAP during S. aureus infection showed significant reduction of all these parameters (p < 0.05). We can conclude that targeting of TNFR1 and IL-1R (with major focus on surface expression study) either through blockage of intracellular receptor trafficking pathway or via surface receptor shedding diminishes TNFR1/IL-1R interaction and consequently downregulates CXCR1 expression along with inflammatory signalling pathways during bacterial infections.

NO and hepatocellular cancer

NO has broad and sometimes dichotomous roles in cancer. The effects of NO in tumours depend on the type and localization of NOS isoforms, concentration and duration of NO exposure, and cellular sensitivity to NO. Hepatocellular carcinoma (HCC) is a common and lethal disease for which no effective therapy other than surgical resection exists. Over two decades of research has yielded evidence that NO generated by the inducible NOS (iNOS or NOS2) contributes to HCC progression in at least a subset of patients with HCC. The co-expression of iNOS with COX-2 may portend a particularly aggressive cancer phenotype in HCC and at the same time reveal an opportunity for pharmacological intervention. In this review, we focus on what is known about the influence of NO in HCC neoplastic transformation, proliferation and apoptosis, angiogenesis, invasion, and metastasis, cancer stem cells, and the host immune response against the tumour. We discuss the implications of recent findings for targeting the NO pathways in HCC.

Mutagenesis of the ADAM17-phosphatidylserine-binding motif leads to embryonic lethality in mice

ADAM17, prominent member of the "Disintegrin and Metalloproteinase" (ADAM) family, controls vital cellular functions through cleavage of transmembrane substrates. Several of these play central roles in oncogenesis and inflammation, yet despite its importance, the mechanism by which ADAM17 is activated is not fully understood. We recently presented evidence that surface exposure of phosphatidylserine (PS) is the penultimate event required for sheddase activation, which occurs upon binding of a membrane-proximal, cationic binding motif to the anionic phospholipid headgroup. Here, we show that mutagenesis of the 3 amino acids constituting the PS-binding motif leads to embryonic lethality in mice. Heterozygotes showed no abnormalities. Primary hepatocytes and fibroblasts were analysed and found to express the mutant protease on the cell surface. However, PMA-stimulated release of ADAM17 substrates was completely abolished. The results directly support the novel concept of transiently externalised PS as essential trigger of extracellular protease function in vivo.

TLR9 signaling in fibroblastic reticular cells regulates peritoneal immunity

Fibroblastic reticular cells (FRCs), a subpopulation of stromal cells in lymphoid organs and fat-associated lymphoid clusters (FALCs) in adipose tissue, play immune-regulatory roles in the host response to infection and may be useful as a form of cell therapy in sepsis. Here, we found an unexpected major role of TLR9 in controlling peritoneal immune cell recruitment and FALC formation at baseline and after sepsis induced by cecal ligation and puncture (CLP). TLR9 regulated peritoneal immunity via suppression of chemokine production by FRCs. Adoptive transfer of TLR9-deficient FRCs more effectively decreased mortality, bacterial load, and systemic inflammation after CLP than WT FRCs. Importantly, we found that activation of TLR9 signaling suppressed chemokine production by human adipose tissue-derived FRCs. Together, our results indicate that TLR9 plays critical roles in regulating peritoneal immunity via suppression of chemokine production by FRCs. These data form a knowledge basis upon which to design new therapeutic strategies to improve the therapeutic efficacy of FRC-based treatments for sepsis and immune dysregulation diseases.

Noncompetitive inhibitors of TNFR1 probe conformational activation states

Tumor necrosis factor receptor 1 (TNFR1) is a central mediator of the inflammatory pathway and is associated with several autoimmune diseases such as rheumatoid arthritis. A revision to the canonical model of TNFR1 activation suggests that activation involves conformational rearrangements of preassembled receptor dimers. Here, we identified small-molecule allosteric inhibitors of TNFR1 activation and probed receptor dimerization and function. Specifically, we used a fluorescence lifetime-based high-throughput screen and biochemical, biophysical, and cellular assays to identify small molecules that noncompetitively inhibited the receptor without reducing ligand affinity or disrupting receptor dimerization. We also found that residues in the ligand-binding loop that are critical to the dynamic coupling between the extracellular and the transmembrane domains played a key gatekeeper role in the conformational dynamics associated with signal propagation. Last, using a simple structure-activity relationship analysis, we demonstrated that these newly found molecules could be further optimized for improved potency and specificity. Together, these data solidify and deepen the new model for TNFR1 activation.

The metalloprotease ADAM17 in inflammation and cancer

Proteolytic cleavage of transmembrane proteins is an important post-translational modification that regulates the biological function of numerous transmembrane proteins. Among the 560 proteases encoded in the human genome, the metalloprotease A Disintegrin and Metalloprotease 17 (ADAM17) has gained much attention in recent years and has emerged as a central regulatory hub in inflammation, immunity and cancer development. In order to do so, ADAM17 cleaves a variety of substrates, among them the interleukin-6 receptor (IL-6R), the pro-inflammatory cytokine tumor necrosis factor α (TNFα) and most ligands of the epidermal growth factor receptor (EGFR). This review article provides an overview of the functions of ADAM17 with a special focus on its cellular regulation. It highlights the importance of ADAM17 to understand the biology of IL-6 and TNFα and their role in inflammatory diseases. Finally, the role of ADAM17 in the formation and progression of different tumor entities is discussed.

Iranian crack induces hepatic injury through mitogen-activated protein kinase pathway in the liver of Wistar rat

Objectives

Iranian crack (IC) is a heroin-based substance manifesting various pathologic side effects. Herein, we aimed to investigate the mechanism of IC-induced liver injuries in Wistar rats.

Materials and Methods

Twenty male Wistar rats were randomly divided into two groups: control, and IC (0.9 mg/kg/day/IP, for 30 days). Mitochondrial reactive oxygen species (ROS) production was measured by DCF fluorescence staining. The expression of tumor necrosis factor-alpha (TNF-α), interleukin 1β (IL-1β), and phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (c-JNK) were assessed by immunoblotting assay. The intensity of collagen fiber in the liver was also determined by Trichrome-Masson staining. Furthermore, serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) activities were measured using colorimetric methods.

Results

Our results showed that ROS production, p38 MAPK, c-JNK phosphorylation levels, and expression of TNF-α and IL-1β were significantly elevated in the liver tissue of IC group as compared to the control group. Moreover, collagen fiber and ALT activity were increased in the liver tissue of IC group compared to the control group. However, there was no statistically significant difference in the levels of ALP between two groups. In addition, there was a positive correlation between the intensity of collagen fiber and the ALT activity, and the levels of TNF-α and IL-1β and liver enzymes activities including ALP, ALT, and AST.

Conclusion

Our findings revealed that IC-induced liver cells injury is partially mediated by MAPK stress kinases. Therefore, regular liver examination in substance abuse is strongly recommended.

Anoctamin-6 regulates ADAM sheddase function

ADAM17, a prominent member of the "Disintegrin and Metalloproteinase" (ADAM) family, controls vital cellular functions through cleavage of transmembrane substrates including TGF-alpha, Amphiregulin (AREG) and TNF-Receptor 1 (TNFR1). We recently presented evidence that surface exposure of phosphatidylserine (PS) is pivotal for ADAM17 to exert sheddase activity. Anoctamin-6 (ANO6) has Ca2+-dependent phospholipid scramblase activity and it followed that the functions of ANO6 and ADAM17 might be linked. We report that overexpression of ANO6 in HEK293T cells led to increased Ca2+-mediated PS-exposure that was indeed accompanied by enhanced release of AREG and TGF-alpha. The effect was not observed when cells were treated with the PKC-dependent ADAM17 activator PMA. Transformation of cells with a constitutively active ANO6 mutant led to spontaneous PS-exposure and to the release of ADAM17-substrates in the absence of any stimuli. Inhibitor experiments indicated that ANO6-mediated enhancement of substrate cleavage simultaneously broadened the spectrum of participating metalloproteinases. In complementary experiments, siRNA-mediated downregulation of ANO6 was shown to decrease ionophore-mediated release of TNFR1 in human umbilical vein endothelial cells (HUVECs). We conclude that ANO6, by virtue of its scramblase activity, may play a role as an important regulator of the ADAM-network in the plasma membrane.

Unleashing endogenous TNF-alpha as a cancer immunotherapeutic

Tumor necrosis factor (TNF)-alpha was originally identified in the 1970s as the serum mediator of innate immunity capable of inducing hemorrhagic necrosis in tumors. Today, a wide spectrum of biological activities have been attributed to this molecule, and clinical translation has mainly occurred not in using it to treat cancer, but rather to inhibit its effects to treat autoimmunity. Clinical trials utilizing systemic TNF-alpha administration have resulted in an unacceptable level of toxicities, which blocked its development. In contrast, localized administration of TNF-alpha in the form of isolated limb perfusion have yielded excellent results in soft tissue sarcomas. Here we describe a novel approach to leveraging the potent antineoplastic activities of TNF-alpha by enhancing activity of locally produced TNF-alpha through extracorporeal removal of soluble TNF-alpha receptors. Specifically, it is known that cancerous tissues are infiltrated with monocytes, T cells, and other cells capable of producing TNF-alpha. It is also known that tumors, as well as cells in the tumor microenvironment produce soluble TNF-alpha receptors. The authors believe that by selectively removing soluble TNF-alpha receptors local enhancement of endogenous TNF-alpha activity may provide for enhanced tumor cell death without associated systemic toxicities.

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

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

Protective role of cellular prion protein against TNFα-mediated inflammation through TACE α-secretase

Although cellular prion protein PrP^C is well known for its implication in Transmissible Spongiform Encephalopathies, its functions remain elusive. Combining in vitro and in vivo approaches, we here show that PrP^C displays the intrinsic capacity to protect neuronal cells from a pro-inflammatory TNFα noxious insult. Mechanistically, PrP^C coupling to the NADPH oxidase-TACE α-secretase signaling pathway promotes TACE-mediated cleavage of transmembrane TNFα receptors (TNFRs) and the release of soluble TNFR, which limits the sensitivity of recipient cells to TNFα. We further show that PrP^C expression is necessary for TACE α-secretase to stay at the plasma membrane in an active state for TNFR shedding. Such PrP^C control of TACE localization depends on PrP^C modulation of β1 integrin signaling and downstream activation of ROCK-I and PDK1 kinases. Loss of PrP^C provokes TACE internalization, which in turn cancels TACE-mediated cleavage of TNFR and renders PrP^C-depleted neuronal cells as well as PrP^C knockout mice highly vulnerable to pro-inflammatory TNFα insult. Our work provides the prime evidence that in an inflammatory context PrP^C adjusts the response of neuronal cells targeted by TNFα through TACE α-secretase. Our data also support the view that abnormal TACE trafficking and activity in prion diseases originate from a-loss-of-PrP^C cytoprotective function.

Extracellular sphingomyelinase activity impairs TNF-α-induced endothelial cell death via ADAM17 activation and TNF receptor 1 shedding

ADAM17, a prominent member of the “Disintegrin and Metalloproteinase” (ADAM) family, is an important regulator of endothelial cell proliferation and cell survival. The protease controls vital cellular functions through cleavage of growth factors, cytokines and their receptors including transforming growth factor-alpha (TGF-α), tumor necrosis factor-alpha (TNF-α) and TNF-α receptor 1 (TNFR1). TNF-α is the major inducer of endothelial cell death in cardiovascular diseases. The latter are also characterized by elevated plasma and tissue levels of extracellular sphingomyelinase (SMase). Whether the SMase affects ADAM activity and thus endothelial cell function has not been addressed to date. Here, we analyzed the effect of SMase on ADAM17-mediated shedding in COS7 cells and in human umbilical vein endothelial cells (HUVECs). Exposure to SMase significantly increased ADAM17-mediated release of alkaline-phosphatase (AP)-tagged TGF-α in COS7 cells and shedding of endogenously expressed TNFR1 in HUVECs. We previously presented evidence that surface exposure of phosphatidylserine (PS) is pivotal for ADAM17 to exert sheddase function. We found that SMase treatment led to PS externalization in both cell types. Transient non-apoptotic PS exposure is often mediated by Ca²⁺-dependent phospholipid scramblases. Accordingly, the Ca²⁺-chelator EGTA markedly reduced the breakdown of phospholipid asymmetry and shedding of TGF-α and TNFR1. Moreover, sheddase activity was significantly diminished in the presence of the competing PS-headgroup OPLS. SMase-stimulated TNFR1 shedding strikingly diminished TNF-α-induced signalling cascades and endothelial cell death. Taken together, our data suggest that SMase activity might act as protective factor for endothelial cells in cardiovascular diseases.

Proteomic Substrate Identification for Membrane Proteases in the Brain

Cell-cell communication in the brain is controlled by multiple mechanisms, including proteolysis. Membrane-bound proteases generate signaling molecules from membrane-bound precursor proteins and control the length and function of cell surface membrane proteins. These proteases belong to different families, including members of the “a disintegrin and metalloprotease” (ADAM), the beta-site amyloid precursor protein cleaving enzymes (BACE), membrane-type matrix metalloproteases (MT-MMP) and rhomboids. Some of these proteases, in particular ADAM10 and BACE1 have been shown to be essential not only for the correct development of the mammalian brain, but also for myelination and maintaining neuronal connections in the adult nervous system. Additionally, these proteases are considered as drug targets for brain diseases, including Alzheimer’s disease (AD), schizophrenia and cancer. Despite their biomedical relevance, the molecular functions of these proteases in the brain have not been explored in much detail, as little was known about their substrates. This has changed with the recent development of novel proteomic methods which allow to identify substrates of membrane-bound proteases from cultured cells, primary neurons and other primary brain cells and even in vivo from minute amounts of mouse cerebrospinal fluid (CSF). This review summarizes the recent advances and highlights the strengths of the individual proteomic methods. Finally, using the example of the Alzheimer-related proteases BACE1, ADAM10 and γ-secretase, as well as ADAM17 and signal peptide peptidase like 3 (SPPL3), we illustrate how substrate identification with novel methods is instrumental in elucidating broad physiological functions of these proteases in the brain and other organs.

Design, Synthesis, and Structure-Activity Relationship Study of Novel Indole-2-carboxamide Derivatives as Anti-inflammatory Agents for the Treatment of Sepsis

Sepsis is characterized by a systemic inflammatory response syndrome. Derivatives of indole have been reported to exhibit diverse biological activities. This study reports on the design and synthesis of a new series of indole-2-carboxamide derivatives, which are screened for their anti-inflammatory activities in RAW 264.7 macrophages. A majority of these derivatives effectively inhibited lipopolysaccharides (LPS)-induced expression of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6). Preliminary structure-activity relationship analysis was also conducted. The results indicate that the most promising compounds in the prepared series were 14f and 14g. They were found to effectively reduce LPS-induced pulmonary inflammation and overexpression of a series of inflammatory mediators. Furthermore, in vivo administration of 14f and 14g resulted in remarkable lung histopathological improvements in mice without toxicity in organs. Taken together, these data indicate that the newly discovered indole-2-carboxamide derivatives could be particularly useful for further treatment in inflammatory diseases.

Interferon β (IFN-β) Production during the Double-stranded RNA (dsRNA) Response in Hepatocytes Involves Coordinated and Feedforward Signaling through Toll-like Receptor 3 (TLR3), RNA-dependent Protein Kinase (PKR), Inducible Nitric Oxide Synthase (iNOS), and Src Protein

The sensing of double-stranded RNA (dsRNA) in the liver is important for antiviral defenses but can also contribute to sterile inflammation during liver injury. Hepatocytes are often the target of viral infection and are easily injured by inflammatory insults. Here we sought to establish the pathways involved in the production of type I interferons (IFN-I) in response to extracellular poly(I:C), a dsRNA mimetic, in hepatocytes. This was of interest because hepatocytes are long-lived and, unlike most immune cells that readily die after activation with dsRNA, are not viewed as cells with robust antimicrobial capacity. We found that poly(I:C) leads to rapid up-regulation of inducible nitric oxide synthase (iNOS), double-stranded RNA-dependent protein kinase (PKR), and Src. The production of IFN-β was dependent on iNOS, PKR, and Src and partially dependent on TLR3/Trif. iNOS and Src up-regulation was partially dependent on TLR3/Trif but entirely dependent on PKR. The phosphorylation of TLR3 on tyrosine 759 was shown to increase in parallel to IFN-β production in an iNOS- and Src-dependent manner, and Src was found to directly interact with TLR3 in the endosomal compartment of poly(I:C)-treated cells. Furthermore, we identified a robust NO/cGMP/PKG-dependent feedforward pathway for the amplification of iNOS expression. These data identify iNOS/NO as an integral component of IFN-β production in response to dsRNA in hepatocytes in a pathway that involves the coordinated activities of TLR3/Trif and PKR.