Inflammation in alcohol-associated hepatitis: pathogenesis and therapeutic targets.

Alcohol-associated hepatitis (AH) is an acute-on-chronic liver injury that occurs in patients with chronic alcohol-associated liver disease (ALD). Patients with severe AH have high short-term mortality and lack effective pharmacological therapies. Inflammation is believed to be one of the key factors promoting AH progression and has been actively investigated as therapeutic targets over the last several decades, but no effective inflammatory targets have been identified so far. In this review, we discuss how inflammatory cells and the inflammatory mediators produced by these cells contribute to the development and progression of AH with focus on neutrophils and macrophages. The crosstalk between inflammatory cells and liver nonparenchymal cells in the pathogenesis of AH is elaborated. We also deliberate the application of recent cutting-edge technologies in characterizing liver inflammation in AH. Finally, the potential therapeutic targets of inflammatory mediators for AH are briefly summarized.

Dimethyloxalylglycine Suppresses SREBP1c and Lipogenic Gene Expressions in Hepatocytes Independently of HIF1A.

Dimethyloxalylglycine (DMOG) is a representative inhibitor of the prolyl hydroxylase domain (PHD), which mediates the degradation of hypoxia-inducible factor-1-alpha (HIF1A). DMOG exerts its pharmacological effects via the canonical pathway that involves PHD inhibition; however, it remains unclear whether DMOG affects lipogenic gene expression in hepatocytes. We aimed to elucidate the effects of DMOG on sterol regulatory element-binding protein-1c (SREBP1c), a master regulator of fatty acid synthesis in hepatocytes. DMOG treatment inhibited SREBP1c mRNA and protein expression in HepG2 and AML12 hepatocytes and reduced the transcript levels of SREBP1c-regulated lipogenic genes. A luciferase reporter assay revealed that DMOG inhibited the transcriptional activity of SREBP1c. Moreover, DMOG suppressed SREBP1c expression in mice liver. Mechanistically, treatment with DMOG enhanced the expression of HIF1A and insulin-induced gene 2 (INSIG2), which inhibits the activation of SREBP1c. However, HIF1A or INSIG2 knockdown failed to reverse the inhibitory effect of DMOG on SREBP1c expression, suggesting a redundant role of HIF1A and INSIG2 in terms of repressing SREBP1c. DMOG did not function through the canonical pathway involving inhibition of SREBP1c by PHD, highlighting the presence of non-canonical pathways that mediate its anti-lipogenic effect.

Overexpression of Interleukin-8 Promotes the Progression of Fatty Liver to Nonalcoholic Steatohepatitis in Mice.

Nonalcoholic steatohepatitis (NASH) is an advanced stage of fatty liver disease characterized by liver damage, inflammation, and fibrosis. Although neutrophil infiltration is consistently observed in the livers of patients with NASH, the precise role of neutrophil-recruiting chemokines and infiltrating neutrophils in NASH pathogenesis remains poorly understood. Here, we aimed to elucidate the role of neutrophil infiltration in the transition from fatty liver to NASH by examining hepatic overexpression of interleukin-8 (IL8), a major chemokine responsible for neutrophil recruitment in humans. Mice fed a high-fat diet (HFD) for 3 months developed fatty liver without concurrent liver damage, inflammation, and fibrosis. Subsequent infection with an adenovirus overexpressing human IL8 for an additional 2 weeks increased IL8 levels, neutrophil infiltration, and liver injury in mice. Mechanistically, IL8-induced liver injury was associated with the upregulation of components of the NADPH oxidase 2 complex, which participate in neutrophil oxidative burst. IL8-driven neutrophil infiltration promoted macrophage aggregate formation and upregulated the expression of chemokines and inflammatory cytokines. Notably, IL8 overexpression amplified factors associated with fibrosis, including collagen deposition and hepatic stellate cell activation, in HFD-fed mice. Collectively, hepatic overexpression of human IL8 promotes neutrophil infiltration and fatty liver progression to NASH in HFD-fed mice.

Ionically bridged dexamethasone sodium phosphate-zinc-PLGA nanocomplex in alginate microgel for the local treatment of ulcerative colitis.

Colon-targeted oral drug delivery systems comprising nanoparticles and microparticles have emerged as promising tools for the treatment of ulcerative colitis (UC) because they minimize side effects and maximize the local drug concentration. Dexamethasone sodium phosphate (DSP) is a potent anti-inflammatory glucocorticoid used for the treatment of UC. However, it remains a rather short-term treatment option owing to its side effects. In the present study, we developed the alginate gel encapsulating ionically bridged DSP-zinc-poly(lactic-co-glycolic acid) (PLGA) nanocomplex (DZP-NCs-in-microgel) for the oral local treatment of UC. The successful encapsulation of DSP-zinc-PLGA nanocomplex (DZP-NCs) in alginate microgel was confirmed by SEM imaging. The prepared gel released DZP-NCs in the stimulated intestinal fluid and dampened the release of DSP in the upper gastrointestinal tract. Furthermore, DZP-NCs-in-microgel alleviated colonic inflammation in a mouse model of dextran sodium sulfate-induced colitis by relieving clinical symptoms and histological marks. Our results suggest a novel approach for the oral colon-targeted delivery of dexamethasone sodium phosphate for the treatment of UC.

Pneumatic tactile stimulus delivery system for studying brain responses evoked by active finger touch with fMRI.

BACKGROUND: Primates use their hands to actively touch objects and collect information. To study tactile information processing, it is important for participants to experience tactile stimuli through active touch while monitoring brain activities. NEW METHOD: Here, we developed a pneumatic tactile stimulus delivery system (pTDS) that delivers various tactile stimuli on a programmed schedule and allows voluntary finger touches during MRI scanning. The pTDS uses a pneumatic actuator to move tactile stimuli and place them in a finger hole. A photosensor detects the time when an index finger touches a tactile stimulus, enabling the analysis of the touch-elicited brain responses. RESULTS: We examined brain responses while the participants actively touched braille objects presented by the pTDS. BOLD responses during tactile perception were significantly stronger in a finger touch area of the contralateral somatosensory cortex compared with that of visual perception. CONCLUSION: The pTDS enables MR studies of brain mechanisms for tactile processes through natural finger touch.

Experimental models of fatty liver diseases: Status and appraisal.

Fatty liver diseases, including alcohol-associated liver disease (ALD) and nonalcoholic fatty liver disease nonalcoholic fatty liver disease (NAFLD), affect a large number of people worldwide and become one of the major causes of end-stage liver disease, such as liver cirrhosis and hepatocellular carcinoma (HCC). Unfortunately, there are currently no approved pharmacological treatments for ALD or NAFLD. This situation highlights the urgent need to explore new intervention targets and discover effective therapeutics for ALD and NAFLD. The lack of properly validated preclinical disease models is a major obstacle to the development of clinical therapies. ALD and NAFLD models have been in the development for decades, but there are still no models that recapitulate the full spectrum of ALD and NAFLD. Throughout this review, we summarize the current in vitro and in vivo models used for research on fatty liver diseases and discuss the advantages and limitations of these models.

Novel treatment of acute and acute-on-chronic liver failure: Interleukin-22.

Acute liver failure (ALF) is a life-threatening medical condition, characterized by rapidly progressive hepatic dysfunction, coagulopathy and hepatic encephalopathy in patients without chronic liver disease, while acute-on-chronic liver failure (ACLF) occurs in patients with existing chronic liver disease. ALF and ACLF are often associated with multiple organ failure and a high short-term mortality. In this review, we briefly discuss the causes and pathogenesis of ALF and ACLF, the current options available for the treatment of both deadly maladies and interleukin-22 (IL-22), a novel promising drug that may have great therapeutic potential for ALF and ACLF treatment. IL-22 is a cytokine produced by immune cells but mainly targets epithelial cells including hepatocytes. IL-22 has been shown to protect against organ damage and reduce bacterial infection in many preclinical models and several clinical trials including alcohol-associated hepatitis. The potential application of IL-22 for the treatment of ALF and ACLF is also elaborated.

Ethanol and its Nonoxidative Metabolites Promote Acute Liver Injury by Inducing ER Stress, Adipocyte Death, and Lipolysis.

BACKGROUND & AIMS: Binge drinking in patients with metabolic syndrome accelerates the development of alcohol-associated liver disease. However, the underlying mechanisms remain elusive. We investigated if oxidative and nonoxidative alcohol metabolism pathways, diet-induced obesity, and adipose tissues influenced the development of acute liver injury in a single ethanol binge model. METHODS: A single ethanol binge was administered to chow-fed or high-fat diet (HFD)-fed wild-type and genetically modified mice. RESULTS: Oral administration of a single dose of ethanol induced acute liver injury and hepatic endoplasmic reticulum (ER) stress in chow- or HFD-fed mice. Disruption of the Adh1 gene increased blood ethanol concentration and exacerbated acute ethanol-induced ER stress and liver injury in both chow-fed and HFD-fed mice, while disruption of the Aldh2 gene did not affect such hepatic injury despite high blood acetaldehyde levels. Mechanistic studies showed that alcohol, not acetaldehyde, promoted hepatic ER stress, fatty acid synthesis, and increased adipocyte death and lipolysis, contributing to acute liver injury. Increased serum fatty acid ethyl esters (FAEEs), which are formed by an enzyme-mediated esterification of ethanol with fatty acids, were detected in mice after ethanol gavage, with higher levels in Adh1 knockout mice than in wild-type mice. Deletion of the Ces1d gene in mice markedly reduced the acute ethanol-induced increase of blood FAEE levels with a slight but significant reduction of serum aminotransferase levels. CONCLUSIONS: Ethanol and its nonoxidative metabolites, FAEEs, not acetaldehyde, promoted acute alcohol-induced liver injury by inducing ER stress, adipocyte death, and lipolysis.

Hyaluronic Acid-Conjugated PLGA Nanoparticles Alleviate Ulcerative Colitis via CD44-Mediated Dual Targeting to Inflamed Colitis Tissue and Macrophages.

Although various local anti-inflammatory therapies for ulcerative colitis have been developed, rapid drug elimination from inflamed colitis tissue and off-target side effects reduce their therapeutic efficacy. In this study, we synthesized curcumin (Cur)-loaded hyaluronic acid (HA)-conjugated nanoparticles (Cur-HA-PLGA-NPs) that target inflamed colitis tissue via HA-CD44 interaction with resident colonic epithelial cells and subsequently target activated macrophages for ulcerative colitis therapy. The synthesized spherical Cur-HA-PLGA-NPs showed physicochemical properties similar to those of non-HA-conjugated Cur-PLGA-NPs. HA-PLGA-NPs exhibited selective accumulation in inflamed colitis tissue with minimal accumulation in healthy colon tissue. HA functionalization enhanced targeted drug delivery to intestinal macrophages, significantly increasing HA-PLGA-NP cellular uptake. Importantly, the rectal administration of Cur-HA-PLGA-NPs exhibited better therapeutic efficacy than Cur-PLGA-NPs in animal studies. Histological examination revealed that Cur-HA-PLGA-NPs reduced inflammation with less inflammatory cell infiltration and accelerated recovery with re-epithelialization signs. Our results suggest that Cur-HA-PLGA-NPs are a promising delivery platform for treating ulcerative colitis.

Motivational salience drives habitual gazes during value memory retention and facilitates relearning of forgotten value.

A habitual gaze is critical to efficiently identify and exploit valuable objects. However, it is unclear what salience components drive the habitual gaze choice. Here, we trained subjects to assign positive, neutral, and negative values to objects and found that motivational salience guided habitual gaze choices over 30 days of memory retention. The habitual preference for negatively valued objects emerged during memory retention. This habitual choice was not explained by a general model with salience components driven by physical features of objects and the rank of learned values. Instead, this is better explained by a model that contains an additional component driven by motivational salience. In a simulated value-forgotten condition, these motivational salience-based habitual choices facilitated re-learning. Our data indicate that after long-term retention, habitual gaze results from increased motivational salience, potentially facilitating the re-learning of forgotten values.

On-demand reconstitutable hyaluronic acid-doped azathioprine microcrystals effectively ameliorate ulcerative colitis via selective accumulation in inflamed tissues.

Although CD44-targeted delivery of pure drug microcrystals of azathioprine (AZA) could be a desirable approach to treat ulcerative colitis (UC), premature drug release and systemic absorption before reaching the colitis region remain a major obstacle. In this study, to overcome these limitations, we developed on-demand reconstitutable HA-doped AZA microcrystals (EFS/HA-AZAs) via incorporating hyaluronic acid (HA)-doped AZA microcrystals (HA-AZAs) into a Eudragit FS (EFS) microcomposite. Since EFS acts as a protective layer, the premature release of AZA in the simulated conditions of the stomach and small intestine was substantially reduced, while HA-AZAs were successfully reconstituted from the EFS/HA-AZAs in the colonic environment, resulting from the pH-triggered dissolution of EFS. After complete reconstitution of HA-AZAs in the colon, HA-AZAs selectively accumulated in the inflamed region via the HA-CD44 interaction. Owing to successful colitis-targeted delivery, EFS/HA-AZAs showed potent anti-inflammatory effects in a dextran sulfate sodium-induced murine colitis model within 7 days without systemic toxicity. These results suggest that EFS/HA-AZAs could be a promising drug delivery system for UC treatment.

Distinct histopathological phenotypes of severe alcoholic hepatitis suggest different mechanisms driving liver injury and failure.

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 (Neuhi), 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 Neuhi 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 NCF1-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.

A bioisosteric approach to the discovery of novel N-aryl-N'-[4-(aryloxy)cyclohexyl]squaramide-based activators of eukaryotic initiation factor 2 alpha (eIF2α) phosphorylation.

Inhibition of translation initiation has emerging implications for the development of mechanism-based anticancer therapeutics. Phosphorylation of eIF2α is recognized as a key target that regulates the translation initiation cascade. Based on the bioisosteric replacement of urea-derived eIF2α phosphorylation activator 1, a novel series of N-aryl-N'-[4-(aryloxy)cyclohexyl]squaramide derivatives was designed and synthesized; their effects on the activation of eIF2α phosphorylation was assessed systematically. A brief structure-activity relationship analysis was established by stepwise structural optimization of the squaramide series. Subsequently, the antiproliferative activities of the selected analogues were determined in human leukemia K562 cells. We then identified 10 potent eIF2α phosphorylation activators with considerable anticancer activity. The most promising analogues 19 and 40 possessed higher cancer cell selectivity (SI = 6.16 and 4.83, respectively) than parent 1 (SI = 2.20). Finally, protein expression analysis revealed that compounds 19 and 40 induced eIF2α phosphorylation and its downstream effectors ATF4 and CHOP.

Immune-related pathogenesis and therapeutic strategies of nonalcoholic steatohepatitis.

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and has become prevalent in the adult population worldwide, given the ongoing obesity pandemic. NAFLD comprises several hepatic disorders, ranging from fatty liver to nonalcoholic steatohepatitis (NASH), cirrhosis, and carcinoma. Excessive fat accumulation in the liver can induce the development of fatty liver, whereas the progression of fatty liver to NASH involves various complex factors. The crucial difference between fatty liver and NASH is the presence of inflammation and fibrosis, the emergence of which is closely associated with the action of immune cells and immunological factors, such as chemokines and cytokines. Thus, expanding our understanding of immunological mechanisms contributing to NASH pathogenesis will lead to the identification of therapeutic targets and the development of viable therapeutics against NASH.

Inhibitory effects of Rocaglamide-A on PPARγ-driven adipogenesis through regulation of mitotic clonal expansion involving the JAK2/STAT3 pathway.

Inhibition of adipogenesis is an important strategy for obesity treatment. Rocaglamide-A (Roc-A) is a natural herbal medicine isolated from the genus Aglaia (family Meliaceae), which has a cyclopenta[b]benzofuran core structure. Roc-A exhibits various pharmacological effects against diverse human cancer cells. However, the exact role of Roc-A during adipogenesis in adipocytes has not been studied at all. In this study, we demonstrate that Roc-A is crucial for reducing adipogenesis via downregulating PPARγ transcriptional activity. Consistently, Western-blot and RT-PCR analyses clearly showed that Roc-A inhibits the expression of PPARγ target genes and lipogenic markers in a dose-dependent manner along with suppression of lipid accumulation, in both 3T3-L1 cells and mouse adipose-derived stem cells. Mechanistically, Roc-A significantly decreased STAT3 phosphorylation in a dose-dependent manner in 3T3-L1 adipocytes. In particular, we confirmed that Roc-A effectively suppressed the expression of genes involved in cell-cycle regulation, such as cyclin A, B, D1, and E1, early during mitotic clonal expansion in 3T3-L1 adipocytes, and this effect was abolished by the JAK2/STAT3 activator FGF2. Taken together, our results demonstrated that Roc-A reduces adipogenesis by inhibiting PPARγ transactivation and STAT3 phosphorylation and thus may serve as a therapeutic target in obesity.

Crosstalk between Oxidative Stress and Inflammatory Liver Injury in the Pathogenesis of Alcoholic Liver Disease.

Alcoholic liver disease (ALD) is characterized by the injury, inflammation, and scarring in the liver owing to excessive alcohol consumption. Currently, ALD is a leading cause for liver transplantation. Therefore, extensive studies (in vitro, in experimental ALD models and in humans) are needed to elucidate pathological features and pathogenic mechanisms underlying ALD. Notably, oxidative changes in the liver have been recognized as a signature trait of ALD. Progression of ALD is linked to the generation of highly reactive free radicals by reactions involving ethanol and its metabolites. Furthermore, hepatic oxidative stress promotes tissue injury and, in turn, stimulates inflammatory responses in the liver, forming a pathological loop that promotes the progression of ALD. Accordingly, accumulating further knowledge on the relationship between oxidative stress and inflammation may help establish a viable therapeutic approach for treating ALD.

E-Selectin-Dependent Inflammation and Lipolysis in Adipose Tissue Exacerbate Steatosis-to-NASH Progression via S100A8/9.

BACKGROUND & AIMS: Nonalcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease, characterized by steatosis and hallmark liver neutrophil infiltration. NASH also is associated with adipose tissue inflammation, but the role of adipose tissue inflammation in NASH pathogenesis remains obscure. The aim of this study was to investigate the interplay between neutrophil recruitment in adipose tissue and the progression of NASH. METHODS: A mouse model of NASH was obtained by high-fat diet (HFD) feeding plus adenovirus-Cxcl1 overexpression (HFD+AdCxcl1). Genetic deletion of E-selectin (Sele) and treatment with an S100A9 inhibitor (Paquinimod) were investigated using this model. RESULTS: By analyzing transcriptomic data sets of adipose tissue from NASH patients, we found that E-selectin, a key adhesion molecule for neutrophils, is the highest up-regulated gene among neutrophil recruitment-related factors in adipose tissue of NASH patients compared with those in patients with simple steatosis. A marked up-regulation of Sele in adipose tissue also was observed in HFD+AdCxcl1 mice. The HFD+AdCxcl1-induced NASH phenotype was ameliorated in Sele knockout mice and was accompanied by reduced lipolysis and inflammation in adipose tissue, which resulted in decreased serum free fatty acids and proinflammatory adipokines. S100A8/A9, a major proinflammatory protein secreted by neutrophils, was highly increased in adipose tissue of HFD+AdCxcl1 mice. This increase was blunted in the Sele knockout mice. Therapeutically, treatment with the S100A9 inhibitor Paquinimod reduced lipolysis, inflammation, and adipokine production, ameliorating the NASH phenotype in mice. CONCLUSIONS: E-selectin plays an important role in inducing neutrophil recruitment in adipose tissue, which subsequently promotes inflammation and lipolysis via the production of S100A8/A9, thereby exacerbating the steatosis-to-NASH progression. Targeting adipose tissue inflammation therefore may represent a potential novel therapy for treatment of NASH.

Type 1 polyisoprenoid diphosphate phosphatase modulates geranylgeranyl-mediated control of HMG CoA reductase and UBIAD1.

UbiA prenyltransferase domain-containing protein-1 (UBIAD1) utilizes geranylgeranyl pyrophosphate (GGpp) to synthesize the vitamin K2 subtype menaquinone-4. The prenyltransferase has emerged as a key regulator of sterol-accelerated, endoplasmic reticulum (ER)-associated degradation (ERAD) of HMG CoA reductase, the rate-limiting enzyme in synthesis of cholesterol and nonsterol isoprenoids including GGpp. Sterols induce binding of UBIAD1 to reductase, inhibiting its ERAD. Geranylgeraniol (GGOH), the alcohol derivative of GGpp, disrupts this binding and thereby stimulates ERAD of reductase and translocation of UBIAD1 to Golgi. We now show that overexpression of Type 1 polyisoprenoid diphosphate phosphatase (PDP1), which dephosphorylates GGpp and other isoprenyl pyrophosphates to corresponding isoprenols, abolishes protein geranylgeranylation as well as GGOH-induced ERAD of reductase and Golgi transport of UBIAD1. Conversely, these reactions are enhanced in the absence of PDP1. Our findings indicate PDP1-mediated hydrolysis of GGpp significantly contributes to a feedback mechanism that maintains optimal intracellular levels of the nonsterol isoprenoid.

Targeting fatty acid metabolism for fibrotic disorders.

Fibrosis is defined by abnormal accumulation of extracellular matrix, which can affect virtually every organ system under diseased conditions. Fibrotic tissue remodeling often leads to organ dysfunction and is highly associated with increased morbidity and mortality. The disease burden caused by fibrosis is substantial, and the medical need for effective antifibrotic therapies is essential. Significant progress has been made in understanding the molecular mechanism and pathobiology of fibrosis, such as transforming growth factor-ß (TGF-ß)-mediated signaling pathways. However, owing to the complex and dynamic properties of fibrotic disorders, there are currently no therapeutic options that can prevent or reverse fibrosis. Recent studies have revealed that alterations in fatty acid metabolic processes are common mechanisms and core pathways that play a central role in different fibrotic disorders. Excessive lipid accumulation or defective fatty acid oxidation is associated with increased lipotoxicity, which directly contributes to the development of fibrosis. Genetic alterations or pharmacologic targeting of fatty acid metabolic processes have great potential for the inhibition of fibrosis development. Furthermore, mechanistic studies have revealed active interactions between altered metabolic processes and fibrosis development. Several well-known fibrotic factors change the lipid metabolic processes, while altered metabolic processes actively participate in fibrosis development. This review summarizes the recent evidence linking fatty acid metabolism and fibrosis, and provides new insights into the pathogenesis of fibrotic diseases for the development of drugs for fibrosis prevention and treatment.