N-nicotinamide methyltransferase (NNMT) is emerging as an important enzyme in the regulation of metabolism. NNMT is highly expressed in the liver. However, the exact regulatory mechanism(s) ...underlying NNMT expression remains unclear and its potential involvement in alcohol-related liver disease (ALD) is completely unknown.
Both traditional Lieber-De Carli and the NIAAA mouse models of ALD were employed. A small-scale chemical screening assay and a chromatin immunoprecipitation assay were performed. NNMT inhibition was achieved via both genetic (adenoviral short hairpin RNA delivery) and pharmacological approaches.
Chronic alcohol consumption induces endoplasmic reticulum (ER) stress and upregulates NNMT expression in the liver. ER stress inducers upregulated NNMT expression in both AML12 hepatocytes and mice. PERK-ATF4 pathway activation is the main contributor to ER stress-mediated NNMT upregulation in the liver. Alcohol consumption fails to upregulate NNMT in liver-specific Atf4 knockout mice. Both adenoviral NNMT knockdown and NNMT inhibitor administration prevented fatty liver development in response to chronic alcohol feeding; this was also associated with the downregulation of an array of genes involved in de novo lipogenesis, including Srebf1, Acaca, Acacb and Fasn. Further investigations revealed that activation of the lipogenic pathway by NNMT was independent of its NAD+-enhancing action; however, increased cellular NAD+, resulting from NNMT inhibition, was associated with marked liver AMPK activation.
ER stress, specifically PERK-ATF4 pathway activation, is mechanistically involved in hepatic NNMT upregulation in response to chronic alcohol exposure. Overexpression of NNMT in the liver plays an important role in the pathogenesis of ALD.
In this study, we show that nicotinamide methyltransferase (NNMT) – the enzyme that catalyzes nicotinamide degradation – is a pathological regulator of alcohol-related fatty liver development. NNMT inhibition protects against alcohol-induced fatty liver development and is associated with suppressed de novo lipogenic activity and enhanced AMPK activation. Thus, our data suggest that NNMT may be a potential therapeutic target for the treatment of alcohol-related liver disease.
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•Chronic alcohol consumption upregulates NNMT expression and activity in the liver.•The activation of the PERK-ATF4 pathway contributes to alcohol-induced hepatic NNMT upregulation.•Adenoviral knockdown of NNMT protects against fatty liver development in response to ER stress and chronic alcohol exposure.•NNMT inhibition enhances cellular NAD+ levels.•NNMT knockdown suppresses the de novo lipogenesis pathway in hepatocytes and the liver.
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•Au-Pd/ZnIn2S4 photocatalyst was synthesized by the NaBH4 reduction method.•Photocatalyst showed excellent activity for photocatalytic selective oxidation.•Interfacial synergism ...effect was found to be beneficial for reaction.•The reactive radicals was confirmed by ESR and trap experiments.•Possible mechanisms for enhanced photocatalytic activity were proposed.
Visible-light-responsive semiconductor decorated with bi-metal nanoparticles synergistic photocatalysts are promising in photocatalysis. Herein, bi-metal nanoparticles Au-Pd decorated ZnIn2S4 nanosheets photocatalytic system was constructed and applied in reaction of photocatalytic selective oxidation of of aromatic alcohols. Various parameters including loading ratio of two metal, loading amount, solvents, time, reactant were investigated. The optimal 0.5 wt% Au-Pd/ZnIn2S4 photocatalysts was founded to exhibit the highest photocatalytic activity, which is 1.5, 2.0 and 1.3 times higher than pristine ZnIn2S4, Au/ZnIn2S4 and Pd/ZnIn2S4, respectively. Characterization results confirmed enhanced visible-light harvesting capability as well as superior photoinduced carriers’s separation and transfer behavior, enhanced O2 adsorption and reduction ability of Pd and surface reaction kinetics account for enhanced photocatalytic activity, in addition, which ascribed to dual metal synergistic effect and metal-semiconductor interaction in Au-Pd/ZnIn2S4 system. Finally, the corresponding reactive radical species was confirmed by ESR and other method. Based on the experimental data and analysis, possible reaction mechanism is proposed. The photogenerated h+, O2− and carbon centered radicals are responsible for the reaction. This systemic work shed light on the bi-metal decorated semiconductor photocatalyst, where metal-metal interaction as well as metal-semiconductor cooperated together to improve the performance of catalysts in visible-light-driven organic transformations.
Green Fluorescent protein (GFP), used as a cellular tag, provides researchers with a valuable method of measuring gene expression and cell tracking. However, there is evidence to suggest that the ...immunogenicity and cytotoxicity of GFP potentially confounds the interpretation of
in vivo
experimental data. Studies have shown that GFP expression can deteriorate over time as GFP tagged cells are prone to death. Therefore, the cells that were originally marked with GFP do not survive and cannot be accurately traced over time. This review will present current evidence for the immunogenicity and cytotoxicity of GFP in
in vivo
studies by characterizing these responses.
MATα1 catalyzes the synthesis of S-adenosylmethionine, the principal biological methyl donor. Lower MATα1 activity and mitochondrial dysfunction occur in alcohol-associated liver disease. Besides ...cytosol and nucleus, MATα1 also targets the mitochondria of hepatocytes to regulate their function. Here, we show that mitochondrial MATα1 is selectively depleted in alcohol-associated liver disease through a mechanism that involves the isomerase PIN1 and the kinase CK2. Alcohol activates CK2, which phosphorylates MATα1 at Ser114 facilitating interaction with PIN1, thereby inhibiting its mitochondrial localization. Blocking PIN1-MATα1 interaction increased mitochondrial MATα1 levels and protected against alcohol-induced mitochondrial dysfunction and fat accumulation. Normally, MATα1 interacts with mitochondrial proteins involved in TCA cycle, oxidative phosphorylation, and fatty acid β-oxidation. Preserving mitochondrial MATα1 content correlates with higher methylation and expression of mitochondrial proteins. Our study demonstrates a role of CK2 and PIN1 in reducing mitochondrial MATα1 content leading to mitochondrial dysfunction in alcohol-associated liver disease.
A major bottleneck underlying nanomaterial‐based tumor therapy lies in complex biological environment and physiological barriers. Micro/nanorobots with the features of self‐propulsion and ...controllable navigation have gradually become a research hotspot in the tumor therapeutic community, exhibiting their advantages in efficient cargo loading, controllable cargo delivery, stimuli‐triggered cargo release, deeper tumor tissue penetration, and enhanced cargo accumulation in tumor tissue. In this review, the self‐propulsion and controllable navigation are introduced as two major properties of micro/nanorobots, in which micro/nanorobots are propelled by chemical reactions, physical fields, and biological systems and could be navigated by chemotaxis, remote magnetic guidance, and light. Then, the recent advances of micro/nanorobots for chemotherapy, immunotherapy, photothermal therapy, photodynamic therapy, chemodynamic therapy, and multimodal tumor therapy would be discussed. Finally, the perspective and challenges are also mentioned. It is expected that this review gives an insight into intelligent micro/nanorobots for improved tumor therapy, aiming for more extensive and in‐depth investigations, and final applications in the clinic.
Complex biological environment and physiological barriers have been major challenges for nanomaterial‐based tumor therapy. Intelligent micro/nanorobots have blossomed with enhanced diffusion and improved tumor therapy. This review introduces the intelligent behaviors of micro/nanorobots and their recent advances in tumor therapy. Finally, the challenges and opportunities of micro/nanorobots would be mentioned.
COVID-19 is associated with liver injury and elevated interleukin-6 (IL-6). We hypothesized that IL-6 trans-signaling in liver sinusoidal endothelial cells (LSECs) leads to endotheliopathy (a ...proinflammatory and procoagulant state) and liver injury in COVID-19.
Coagulopathy, endotheliopathy, and alanine aminotransferase (ALT) were retrospectively analyzed in a subset (n = 68), followed by a larger cohort (n = 3,780) of patients with COVID-19. Liver histology from 43 patients with COVID-19 was analyzed for endotheliopathy and its relationship to liver injury. Primary human LSECs were used to establish the IL-6 trans-signaling mechanism.
Factor VIII, fibrinogen, D-dimer, von Willebrand factor (vWF) activity/antigen (biomarkers of coagulopathy/endotheliopathy) were significantly elevated in patients with COVID-19 and liver injury (elevated ALT). IL-6 positively correlated with vWF antigen (p = 0.02), factor VIII activity (p = 0.02), and D-dimer (p <0.0001). On liver histology, patients with COVID-19 and elevated ALT had significantly increased vWF and platelet staining, supporting a link between liver injury, coagulopathy, and endotheliopathy. Intralobular neutrophils positively correlated with platelet (p <0.0001) and vWF (p <0.01) staining, and IL-6 levels positively correlated with vWF staining (p <0.01). IL-6 trans-signaling leads to increased expression of procoagulant (factor VIII, vWF) and proinflammatory factors, increased cell surface vWF (p <0.01), and increased platelet attachment in LSECs. These effects were blocked by soluble glycoprotein 130 (IL-6 trans-signaling inhibitor), the JAK inhibitor ruxolitinib, and STAT1/3 small-interfering RNA knockdown. Hepatocyte fibrinogen expression was increased by the supernatant of LSECs subjected to IL-6 trans-signaling.
IL-6 trans-signaling drives the coagulopathy and hepatic endotheliopathy associated with COVID-19 and could be a possible mechanism behind liver injury in these patients.
Patients with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection often have liver injury, but why this occurs remains unknown. High levels of interleukin-6 (IL-6) and its circulating receptor, which form a complex to induce inflammatory signals, have been observed in patients with COVID-19. This paper demonstrates that the IL-6 signaling complex causes harmful changes to liver sinusoidal endothelial cells and may promote blood clotting and contribute to liver injury.
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•Liver injury in patients with COVID-19 is associated with elevated IL-6 and coagulopathy.•Patients with COVID-19 exhibit hepatic endotheliopathy which is associated with liver injury.•IL-6 trans-signaling causes endotheliopathy in liver sinusoidal endothelial cells.
Aim
Coronavirus disease (COVID‐19) is characterized by pneumonia with secondary damage to multiple organs including the liver. Liver injury (elevated alanine aminotransferase ALT and aspartate ...aminotransferase AST) often correlates with disease severity in COVID‐19 patients. The aim of this study is to identify pathological microthrombi in COVID‐19 patient livers by correlating their morphology with liver injury, and examine hyperfibrinogenemia and von Willebrand factor (vWF) as mechanisms of their formation.
Methods
Forty‐three post‐mortem liver biopsy samples from COVID‐19 patients were obtained from Papa Giovanni XXIII Hospital in Bergamo, Italy. Three morphological features of microthrombosis (sinusoidal erythrocyte aggregation SEA, platelet microthrombi PMT, and fibrous thrombi) were evaluated.
Results
We found liver sinusoidal microthrombosis in 23 COVID‐19 patients (53%) was associated with a higher serum ALT and AST level compared to those without (ALT: 10‐fold, p = 0.04; AST: 11‐fold, p = 0.08). Of 43 livers, PMT and SEA were observed in 14 (33%) and 19 (44%) cases, respectively. Fibrous thrombi were not observed. Platelet microthrombi were associated with increased ALT (p < 0.01), whereas SEA was not (p = 0.73). In COVID‐19 livers, strong vWF staining in liver sinusoidal endothelial cells was associated with significantly increased platelet adhesion (1.7‐fold, p = 0.0016), compared to those with weak sinusoidal vWF (2‐fold, p < 0.0001). Sinusoidal erythrocyte aggregation in 19 (83%) liver samples was mainly seen in zone 2. Livers with SEA had significantly higher fibrinogen (1.6‐fold, p = 0.031) compared to those without SEA in COVID‐19 patients.
Conclusions
Liver PMT is a pathologically important thrombosis associated with liver injury in COVID‐19, while SEA is a unique morphological feature of COVID‐19 patient livers. Sinusoidal vWF and hyperfibrinogenemia could contribute to PMT and SEA formation.
Increased megamitochondria formation and impaired mitophagy in hepatocytes have been linked to the pathogenesis of alcohol-associated liver disease (ALD). This study aims to determine the mechanisms ...by which alcohol consumption increases megamitochondria formation in the pathogenesis of ALD.
Human alcoholic hepatitis (AH) liver samples were used for electron microscopy, histology, and biochemical analysis. Liver-specific dynamin-related protein 1 (DRP1; gene name DNM1L, an essential gene regulating mitochondria fission ) knockout (L-DRP1 KO) mice and wild-type mice were subjected to chronic plus binge alcohol feeding. Both human AH and alcohol-fed mice had decreased hepatic DRP1 with increased accumulation of hepatic megamitochondria. Mechanistic studies revealed that alcohol feeding decreased DRP1 by impairing transcription factor EB-mediated induction of DNM1L . L-DRP1 KO mice had increased megamitochondria and decreased mitophagy with increased liver injury and inflammation, which were further exacerbated by alcohol feeding. Seahorse flux and unbiased metabolomics analysis showed alcohol intake increased mitochondria oxygen consumption and hepatic nicotinamide adenine dinucleotide (NAD + ), acylcarnitine, and ketone levels, which were attenuated in L-DRP1 KO mice, suggesting that loss of hepatic DRP1 leads to maladaptation to alcohol-induced metabolic stress. RNA-sequencing and real-time quantitative PCR analysis revealed increased gene expression of the cGAS-stimulator of interferon genes (STING)-interferon pathway in L-DRP1 KO mice regardless of alcohol feeding. Alcohol-fed L-DRP1 KO mice had increased cytosolic mtDNA and mitochondrial dysfunction leading to increased activation of cGAS-STING-interferon signaling pathways and liver injury.
Alcohol consumption decreases hepatic DRP1 resulting in increased megamitochondria and mitochondrial maladaptation that promotes AH by mitochondria-mediated inflammation and cell injury.
Intrahepatic neutrophil infiltration has been implicated in severe alcoholic hepatitis (SAH) pathogenesis; however, the mechanism underlying neutrophil-induced injury in SAH remains obscure. This ...translational study aims to describe the patterns of intrahepatic neutrophil infiltration and its involvement in SAH pathogenesis. Immunohistochemistry analyses of explanted livers identified two SAH phenotypes despite a similar clinical presentation, one with high intrahepatic neutrophils (Neu.sup.hi), but low levels of CD8* T cells, and vice versa. RNA-Seq analyses demonstrated that neutrophil cytosolic factor 1 (NCF1), a key factor in controlling neutrophilic ROS production, was upregulated and correlated with hepatic inflammation and disease progression. To study specifically the mechanisms related to Neu.sup.hi in AH patients and liver injury, we used the mouse model of chronic-plus-binge ethanol feeding and found that myeloid-specific deletion of the Ncf1 gene abolished ethanol-induced hepatic inflammation and steatosis. RNA-Seq analysis and the data from experimental models revealed that neutrophilic NCFI-dependent ROS promoted alcoholic hepatitis (AH) by inhibiting AMP-activated protein kinase (a key regulator of lipid metabolism) and microRNA-223 (a key antiinflammatory and antifibrotic microRNA). In conclusion, two distinct histopathological phenotypes based on liver immune phenotyping are observed in SAH patients, suggesting a separate mechanism driving liver injury and/or failure in these patients.
Background and Aims
Microbial dysbiosis is associated with alcohol‐related hepatitis (AH), with the mechanisms yet to be elucidated. The present study aimed to determine the effects of alcohol and ...zinc deficiency on Paneth cell (PC) antimicrobial peptides, α‐defensins, and to define the link between PC dysfunction and AH.
Approach and Results
Translocation of pathogen‐associated molecular patterns (PAMPs) was determined in patients with severe AH and in a mouse model of alcoholic steatohepatitis. Microbial composition and PC function were examined in mice. The link between α‐defensin dysfunction and AH was investigated in α‐defensin‐deficient mice. Synthetic human α‐defensin 5 (HD5) was orally given to alcohol‐fed mice to test the therapeutic potential. The role of zinc deficiency in α‐defensin was evaluated in acute and chronic mouse models of zinc deprivation. Hepatic inflammation was associated with PAMP translocation and lipocalin‐2 (LCN2) and chemokine (C‐X‐C motif) ligand 1 (CXCL1) elevation in patients with AH. Antibiotic treatment, lipopolysaccharide injection to mice, and in vitro experiments showed that PAMPs, but not alcohol, directly induced LCN2 and CXCL1. Chronic alcohol feeding caused systemic dysbiosis and PC α‐defensin reduction in mice. Knockout of functional α‐defensins synergistically affected alcohol‐perturbed bacterial composition and the gut barrier and exaggerated PAMP translocation and liver damage. Administration of HD5 effectively altered cecal microbial composition, especially increased Akkermansia muciniphila, and reversed the alcohol‐induced deleterious effects. Zinc‐regulated PC homeostasis and α‐defensins function at multiple levels, and dietary zinc deficiency exaggerated the deleterious effect of alcohol on PC bactericidal activity.
Conclusions
Taken together, the study suggests that alcohol‐induced PC α‐defensin dysfunction is mediated by zinc deficiency and involved in the pathogenesis of AH. HD5 administration may represent a promising therapeutic approach for treating AH.
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