Liver is the major source of elevated serum lipocalin-2 levels after bacterial infection or partial hepatectomy: a critical role for IL-6/STAT3

Interleukin-20 exacerbates acute hepatitis and bacterial infection by downregulating IκBζ target genes in hepatocytes

BACKGROUND & AIMS

Interleukin (IL)-20 and IL-22 belong to the IL-10 family. IL-10 is a well-documented anti-inflammatory cytokine while IL-22 is well known for epithelial protection and its antibacterial function, showing great therapeutic potential for organ damage; however, the function of IL-20 remains largely unknown.

METHODS

Il20 knockout (Il20-/-) mice and wild-type littermates were generated and injected with Concanavalin A (ConA) and Klebsiella pneumoniae (K.P.) to induce acute hepatitis and bacterial infection, respectively.

RESULTS

Il20-/- mice were resistant to acute hepatitis and exhibited selectively elevated levels of the hepatoprotective cytokine IL-6. Such selective inhibition of IL-6 by IL-20 was due to IL-20 targeting hepatocytes that produce high levels of IL-6 but a limited number of other cytokines. Mechanistically, IL-20 upregulated NAD(P)H: quinone oxidoreductase 1 (NQO1) expression and subsequently promoted the protein degradation of transcription factor IκBζ, resulting in selective downregulation of the IκBζ-dependent gene Il6 as well several other IκBζ-dependent genes including lipocalin-2 (Lcn2). Given the important role of IL-6 and LCN2 in limiting bacterial infection, we examined the effect of IL-20 on bacterial infection and found Il20-/- mice were resistant to K.P. infection and exhibited elevated levels of hepatic IκBζ-dependent antibacterial genes. Moreover, IL-20 upregulated hepatic NQO1 by binding to IL-22R1/IL-20R2 and activating ERK/p38MAPK/NRF2 signaling pathways. Finally, the levels of hepatic IL1B, IL20, and IκBζ target genes were elevated, and correlated with each other, in patients with severe alcoholic hepatitis.

CONCLUSIONS

IL-20 selectively inhibits hepatic IL-6 production rather than exerting IL-10-like broad anti-inflammatory properties. Unlike IL-22, IL-20 aggravates acute hepatitis and bacterial infection. Thus, anti-IL-20 therapy could be a promising option to control acute hepatitis and bacterial infection.

LAY SUMMARY

Several interleukin (IL)-20 family cytokines have been shown to play important roles in controllimg inflammatory responses, infection and tissue damage, but the role of IL-20 remains unclear. Herein, we elucidated the role of IL-20 in liver disease and bacterial infection. We show that IL-20 can aggravate hepatitis and bacterial infection; thus, targeting IL-20 holds promise for the treatment of patients with liver disease.

Pathophysiological effects of Klebsiella pneumoniae infection on Galleria mellonella as an invertebrate model organism

Klebsiella pneumoniae is an important human pathogen causing urinary tract infections and pneumonia. Due to the increase in resistant strains and being an opportunistic pathogen, it is very important to determine the virulence process, the cellular damage it causes in the host and the immunological response level of the host. In this study, invertebrate infection model Galleria mellonella larvae were used to investigate cellular damage, antioxidant response and changes in biochemical parameters due to K. pneumoniae infection. The activity of cell damage indicators alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase increased in hemolymph of G. mellonella larvae due to K. pneumoniae virulence. Creatine kinase, alkaline phosphatase, gamma glutamyl transferase and amylase activities were increased to regulate the disrupted energy metabolism due to infection. As a result of the damage caused by K. pneumoniae infection, changes occurred in the amount of non-enzymatic antioxidants, uric acid, bilirubin and albumin. Due to K. pneumoniae infection, the amount of calcium, potassium, magnesium and phosphorus altered. This study showed that G. mellonella larvae was important infection model in the investigation of infectious cell damage and physiological effects, given the opportunistic nature of the K. pneumoniae pathogen and the lack of adequate animal models.

Lipocalin 2 mediates appetite suppression during pancreatic cancer cachexia

Lipocalin 2 (LCN2) was recently identified as an endogenous ligand of the type 4 melanocortin receptor (MC4R), a critical regulator of appetite. However, it remains unknown if this molecule influences appetite during cancer cachexia, a devastating clinical entity characterized by decreased nutrition and progressive wasting. We demonstrate that LCN2 is robustly upregulated in murine models of pancreatic cancer, its expression is associated with reduced food consumption, and Lcn2 deletion is protective from cachexia-anorexia. Consistent with LCN2's proposed MC4R-dependent role in cancer-induced anorexia, pharmacologic MC4R antagonism mitigates cachexia-anorexia, while restoration of Lcn2 expression in the bone marrow is sufficient in restoring the anorexia feature of cachexia. Finally, we observe that LCN2 levels correlate with fat and lean mass wasting and is associated with increased mortality in patients with pancreatic cancer. Taken together, these findings implicate LCN2 as a pathologic mediator of appetite suppression during pancreatic cancer cachexia.

Primary 12α-Hydroxylated Bile Acids Lower Hepatic Iron Concentration in Rats

BACKGROUND

Primary 12α-hydroxylated bile acids (12αOH BAs) enhance intestinal iron uptake due to their ability ex vivo to chelate iron. However, no information is available on their role in vivo, especially in the liver.

OBJECTIVES

To investigate the effects and mechanisms of primary 12αOH BAs on hepatic iron concentration in vivo.

METHODS

Male Wistar King A Hokkaido male rats (WKAH/HkmSlc) rats aged 4-5 weeks were fed a control diet or a diet with cholic acid (CA; 0.5 g/kg diet), the primary 12αOH BA, for 2 weeks (Study 1) or 13 weeks (Study 2). In Study 3, rats fed the same diets were given drinking water either alone or containing vancomycin (200 mg/L) for 6 weeks. The variables measured included food intake (Studies 1-3), bile acid profiles (Studies 1 and 3), hepatic iron concentration (Studies 1-3), fecal iron excretion (Studies 1 and 2), iron-related liver gene expression (Studies 2 and 3), and plasma iron-related factors (Studies 2 and 3).

RESULTS

In Study 1, CA feed reduced the hepatic iron concentration (-16%; P = 0.005) without changing food intake or fecal iron excretion. In Study 2, we found a significant increase in the aortic plasma concentration of lipocalin 2 (LCN2; +65%; P < 0.001), an iron-trafficking protein. In Study 3, we observed no effect of vancomycin treatment on the CA-induced reduction of hepatic iron concentration (-32%; P < 0.001), accompanied by increased plasma LCN2 concentration (+72%; P = 0.003), in the CA-fed rats despite a drastic reduction in the secondary 12αOH BA concentration (-94%; P < 0.001) in the aortic plasma.

CONCLUSIONS

Primary 12αOH BAs reduced the hepatic iron concentration in rats. LCN2 may be responsible for the hepatic iron-lowering effect of primary 12αOH BAs by transporting iron out of the liver.

Beyond Metabolism: Role of the Immune System in Hepatic Toxicity

The liver is primarily thought of as a metabolic organ; however, the liver is also an important mediator of immunological functions. Key perspectives on this emerging topic were presented in a symposium at the 2018 annual meeting of the American College of Toxicology entitled "Beyond metabolism: Role of the immune system in hepatic toxicity." Viral hepatitis is an important disease of the liver for which insufficient preventive vaccines exist. Host immune responses inadequately clear these viruses and often potentiate immunological inflammation that damages the liver. In addition, the liver is a key innate immune organ against bacterial infection. Hepatocytes and immune cells cooperatively control systemic and local bacterial infections. Conversely, bacterial infection can activate multiple types of immune cells and pathways to cause hepatocyte damage and liver injury. Finally, the immune system and specifically cytokines and drugs can interact in idiosyncratic drug-induced liver injury. This rare disease can result in a disease spectrum that ranges from mild to acute liver failure. The immune system plays a role in this disease spectrum.

Controversies and Opportunities in the Use of Inflammatory Markers for Diagnosis or Risk Prediction in Fatty Liver Disease

In the Western society, non-alcoholic fatty liver disease (NAFLD), characterized by the excessive accumulation of fat in the liver, represents the most common cause of chronic liver disease. If left untreated, approximately 15%-20% of patients with NAFLD will progress to non-alcoholic steatohepatitis (NASH), in which lobular inflammation, hepatocyte ballooning and fibrogenesis further contribute to a distorted liver architecture and function. NASH initiation has significant effects on liver-related mortality, as even the presence of early stage fibrosis increases the chances of adverse patient outcome. Therefore, adequate diagnostic tools for NASH are needed, to ensure that relevant therapeutic actions can be taken as soon as necessary. To date, the diagnostic gold standard remains the invasive liver biopsy, which is associated with several drawbacks such as high financial costs, procedural risks, and inter/intra-observer variability in histology analysis. As liver inflammation is a major hallmark of disease progression, inflammation-related circulating markers may represent an interesting source of non-invasive biomarkers for NAFLD/NASH. Examples for such markers include cytokines, chemokines or shed receptors from immune cells, circulating exosomes related to inflammation, and changing proportions of peripheral blood mononuclear cell (PBMC) subtypes. This review aims at documenting and critically discussing the utility of such novel inflammatory markers for NAFLD/NASH-diagnosis, patient stratification and risk prediction.

Plasma Lipocalin-2 and Adiponectin are Affected by Obesity Rather Than Type 2 Diabetes Mellitus per se

PURPOSE

Changes in plasma adipocytokines and inflammatory markers in type 2 DM remain controversial as to whether they are due to obesity or directly associated with the diabetic state. Our objective was to study the effect of obesity and diabetes on plasma lipocalin-2 (LCN2), adiponectin, and interleukin-1β (IL-1β) by comparing their levels in non-diabetic obese subjects and non-obese type 2 DM patients, as well as determining the association of these adipocytokines with metabolic syndrome factors and diabetic parameters.

PATIENTS AND METHODS

In this study, 85 Yemeni male volunteers aged 30-60 years old were enrolled, 25 of whom were healthy subjects with BMI < 25 kg/m² served as control; 30 non-diabetic obese subjects (BMI ≥ 30 kg/m² and FBG < 6.1 mmol/l); and 30 non-obese type 2 DM patients (BMI < 25 kg/m² and FBG > 7 mmol/l).

RESULTS

Lipocalin-2 and adiponectin were significantly (p = 0.043 and p = 0.034) lower in non-diabetic obese subjects by 16.2% and 29.7% with respect to control group, with no effect in the non-obese type 2 DM patients. Moreover, LCN2 was significantly (p = 0.04) lower in the non-diabetic obese subjects by 15.8% as compared with the non-obese type 2 DM patients, with no significant difference in adiponectin levels. In contrast, serum IL-1β was significantly (p = 0.001 and p = 0.003) higher in both non-diabetic obese subjects and the non-obese type 2 DM patients by 76.5% and 67.7% as compared to control group. The significant decrease in both LCN2 and adiponectin and the significant increase in IL-1β in the non-diabetic obese subjects disappeared upon adjustment for waist circumference (WC). In contrast, the significant increase in IL-1β in the non-obese Type 2 DM patients was not affected upon adjustment for WC.

CONCLUSION

Plasma LCN2 and adiponectin were not affected by diabetes per se, suggesting that the observed changes in LCN2 and adiponectin in type 2 DM may be due to obesity rather than the diabetic state, whereas IL-1β levels were affected by both obesity and diabetes.

Immunopathobiology and therapeutic targets related to cytokines in liver diseases

Chronic liver injury with any etiology can progress to fibrosis and the end-stage diseases cirrhosis and hepatocellular carcinoma. The progression of liver disease is controlled by a variety of factors, including liver injury, inflammatory cells, inflammatory mediators, cytokines, and the gut microbiome. In the current review, we discuss recent data on a large number of cytokines that play important roles in regulating liver injury, inflammation, fibrosis, and regeneration, with a focus on interferons and T helper (Th) 1, Th2, Th9, Th17, interleukin (IL)-1 family, IL-6 family, and IL-20 family cytokines. Hepatocytes can also produce certain cytokines (such as IL-7, IL-11, and IL-33), and the functions of these cytokines in the liver are briefly summarized. Several cytokines have great therapeutic potential, and some are currently being tested as therapeutic targets in clinical trials for the treatment of liver diseases, which are also described.

Improved prediction of mortality by combinations of inflammatory markers and standard clinical scores in patients with acute-on-chronic liver failure and acute decompensation

BACKGROUND AND AIM

Acute-on-chronic liver failure (ACLF) is a sinister prognosis, and there is a need for accurate biomarkers and scoring systems to better characterize ACLF patients and predict prognosis. Systemic inflammation and renal failure are hallmarks in ACLF disease development and progression. We hypothesized that the combination of specific inflammatory markers in combination with clinical scores are better predictors of survival than the originally developed CLIF-C acute decompensation (AD) and CLIF-C ACLF scores.

METHODS

We reevaluated all previously measured inflammatory markers in 522 patients from the CANONIC study, 342 without and 180 with ACLF. We used the Harrell's C-index to determine the best marker alone or in combination with the original scores and calculated new scores for prediction of mortality in the original CANONIC cohort.

RESULTS

The best markers to predict 90-day mortality in patients without ACLF were the plasma macrophage activation markers soluble (s)CD163 and mannose receptor (sMR). Urinary neutrophil gelatinase associated lipocalin (UNGAL) and sCD163 were predictors for 28-day mortality in patients with ACLF. The newly developed CLIF-C AD + sMR score in patients without ACLF improved 90-day mortality prediction compared with the original CLIF-C AD score (C-index 0.82 [0.78-0.86] vs 0.74 [0.70-0.78, P = 0.004]). Further, the new CLIF-C ACLF + sCD163 + UNGAL improved the original CLIF-C ACLF score for 28-day mortality (0.85 [0.79-0.91] vs 0.75 [0.70-0.80], P = 0.039).

CONCLUSIONS

The capability of these inflammatory markers to improve the original prognostic scores in cirrhosis patients without and with ACLF points to a key role of macrophage activation and inflammation in the development and progression of AD and ACLF.

Antimicrobial peptides: bridging innate and adaptive immunity in the pathogenesis of psoriasis

Antimicrobial peptides (AMPs) are small molecules produced by a myriad of cells and play important roles not only in protecting against infections and sustaining skin barrier homeostasis but also in contributing to immune dysregulation under pathological conditions. Recently, increasing evidence has indicated that AMPs, including cathelicidin (LL-37), human β-defensins, S100 proteins, lipocalin 2, and RNase 7, are highly expressed in psoriatic skin lesions. These peptides broadly regulate immunity by interacting with various immune cells and linking innate and adaptive immune responses during the progression of psoriasis. In this review, we summarize the recent findings regarding AMPs in the pathogenesis of psoriasis with a main focus on their immunomodulatory abilities.

Hepatic lipocalin 2 promotes liver fibrosis and portal hypertension

Advanced fibrosis and portal hypertension influence short-term mortality. Lipocalin 2 (LCN2) regulates infection response and increases in liver injury. We explored the role of intrahepatic LCN2 in human alcoholic hepatitis (AH) with advanced fibrosis and portal hypertension and in experimental mouse fibrosis. We found hepatic LCN2 expression and serum LCN2 level markedly increased and correlated with disease severity and portal hypertension in patients with AH. In control human livers, LCN2 expressed exclusively in mononuclear cells, while its expression was markedly induced in AH livers, not only in mononuclear cells but also notably in hepatocytes. Lcn2-/- mice were protected from liver fibrosis caused by either ethanol or CCl4 exposure. Microarray analysis revealed downregulation of matrisome, cell cycle and immune related gene sets in Lcn2-/- mice exposed to CCl4, along with decrease in Timp1 and Edn1 expression. Hepatic expression of COL1A1, TIMP1 and key EDN1 system components were elevated in AH patients and correlated with hepatic LCN2 expression. In vitro, recombinant LCN2 induced COL1A1 expression. Overexpression of LCN2 increased HIF1A that in turn mediated EDN1 upregulation. LCN2 contributes to liver fibrosis and portal hypertension in AH and could represent a new therapeutic target.

Chronic Carbon Tetrachloride Applications Induced Hepatocyte Apoptosis in Lipocalin 2 Null Mice Through Endoplasmic Reticulum Stress and Unfolded Protein Response

The lack of Lipocalin (LCN2) provokes overwhelming endoplasmic reticulum (ER) stress responses in vitro and in acute toxic liver injury models, resulting in hepatocyte apoptosis. LCN2 is an acute phase protein produced in hepatocytes in response to acute liver injuries. In line with these findings we investigated ER stress responses of Lcn2^−/− mice in chronic ER stress using a long-term repetitive carbon tetrachloride (CCl₄) injection model. We found chronic CCl₄ application to enhance ER stress and unfolded protein responses (UPR), including phosphorylation of eukaryotic initiation factor 2α (eIF2α), increased expression of binding immunoglobulin protein (BiP) and glucose-regulated protein 94 (GRP94). IRE1α/TRAF2/JNK signaling enhanced mitochondrial apoptotic pathways, and showed slightly higher in Lcn2^−/− mice compared to the wild type counterparts, leading to increased hepatocyte apoptosis well evidenced by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Hepatocyte injuries were confirmed by significant high serum alanine transaminase (ALT) levels in CCl₄-treated Lcn2^−/− mice. Lcn2^−/− mice furthermore developed mild hepatic steatosis, supporting our finding that ER stress promotes lipogenesis. In a previous report we demonstrated that the pharmacological agent tunicamycin (TM) induced ER stress through altered protein glycosylation and induced high amounts of C/EBP-homologous protein (CHOP), resulting in hepatocyte apoptosis. We compared TM-induced ER stress in wild type, Lcn2^−/−, and Chop null (Chop^−/−) primary hepatocytes and found Chop^−/− hepatocytes to attenuate ER stress responses and resist ER stress-induced hepatocyte apoptosis through canonical eIF2α/GADD34 signaling, inhibiting protein synthesis. Unexpectedly, in later stages of TM incubation, Chop^−/− hepatocytes resumed activation of IRE1α/JNK/c-Jun and p38/ATF2 signaling, leading to late hepatocyte apoptosis. This interesting observation indicates Chop^−/− mice to be unable to absolutely prevent all types of liver injury, while LCN2 protects the hepatocytes by maintaining homeostasis under ER stress conditions.

Paneth Cell Dysfunction Mediates Alcohol-related Steatohepatitis Through Promoting Bacterial Translocation in Mice: Role of Zinc Deficiency

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.

CREBZF as a Key Regulator of STAT3 Pathway in the Control of Liver Regeneration in Mice

BACKGROUND AND AIMS

STAT3, a member of the signal transducer and activator of transcription (STAT) family, is strongly associated with liver injury, inflammation, regeneration, and hepatocellular carcinoma development. However, the signals that regulate STAT3 activity are not completely understood.

APPROACH AND RESULTS

Here we characterize CREB/ATF bZIP transcription factor CREBZF as a critical regulator of STAT3 in the hepatocyte to repress liver regeneration. We show that CREBZF deficiency stimulates the expression of the cyclin gene family and enhances liver regeneration after partial hepatectomy. Flow cytometry analysis reveals that CREBZF regulates cell cycle progression during liver regeneration in a hepatocyte-autonomous manner. Similar results were observed in another model of liver regeneration induced by intraperitoneal injection of carbon tetrachloride (CCl4 ). Mechanistically, CREBZF potently associates with the linker domain of STAT3 and represses its dimerization and transcriptional activity in vivo and in vitro. Importantly, hepatectomy-induced hyperactivation of cyclin D1 and liver regeneration in CREBZF liver-specific knockout mice was reversed by selective STAT3 inhibitor cucurbitacin I. In contrast, adeno-associated virus-mediated overexpression of CREBZF in the liver inhibits the expression of the cyclin gene family and attenuates liver regeneration in CCl4 -treated mice.

CONCLUSIONS

These results characterize CREBZF as a coregulator of STAT3 to inhibit regenerative capacity, which may represent an essential cellular signal to maintain liver mass homeostasis. Therapeutic approaches to inhibit CREBZF may benefit the compromised liver during liver transplantation.

Lipocalin 2 links inflammation and ankylosis in the clinical overlap of inflammatory bowel disease (IBD) and ankylosing spondylitis (AS)

Background

Little is known about the mechanisms underlying the clinical overlap between gut inflammation and joint ankylosis, as exemplified by the concurrence of inflammatory bowel diseases (IBD) and ankylosing spondylitis (AS). As dysbiosis may serve as a common contributor, the anti-microbial pleiotropic factor lipocalin 2 could be a potential mediator due to its roles in inflammation and bone homeostasis.

Methods

Baseline colonic pathology was conducted in the ank/ank mouse model. Serum lipocalin 2 was analyzed by ELISA, in ank/ank mutants versus C3FeB6-A/A^w-jwt/wt, in patients with concurrent AS-IBD, AS alone, IBD alone, or mechanical back pain, and in healthy controls. In the ank/ank mouse model, the expression of nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) was examined by real-time PCR. Intraperitoneal injection was done with the PPARγ agonist rosiglitazone or antagonist bisphenol A diglycidyl ether for four consecutive days. Serum levels of lipocalin 2 were examined on the sixth day.

Results

This study showed that the ank/ank mice with fully fused spines had concurrent colonic inflammation. By first using the ank/ank mouse model with progressive ankylosis and subclinical colonic inflammation, confirmed in patients with concurrent AS and IBD, elevated circulating lipocalin 2 levels were associated with the coexisting ankylosis and gut inflammation. The intracellular pathway of lipocalin 2 was further investigated with the ank/ank mouse model involving PPARγ. Colonic expression of PPARγ was negatively associated with the degree of gut inflammation. The PPARγ agonist rosiglitazone treatment significantly upregulated the serum levels of lipocalin 2, suggesting a potential regulatory role of PPARγ in the aberrant expression of lipocalin 2.

Conclusions

In summary, lipocalin 2 modulated by PPARγ could be a potential pathway involved in concurrent inflammation and ankylosis in AS and IBD.

The value of ascitic neutrophil gelatinase-associated lipocalin in decompensated liver cirrhosis with spontaneous bacterial peritonitis

Background

Spontaneous bacterial peritonitis (SBP) is one of the most critical complications of decompensated liver cirrhosis. This study aimed to assess whether ascitic neutrophil gelatinase‐associated lipocalin (NGAL), a reliable inflammation biomarker, can be used to detect SBP in decompensated cirrhosis patients and to predict mortality from decompensated cirrhosis‐related SBP.

Methods

This study included 204 hospitalized patients with ascites of decompensated liver cirrhosis and follow‐up of 28 days. We measured ascitic NGAL levels by the latex‐enhanced immunoturbidimetric method. Simultaneously, we observed the patterns of ascitic NGAL levels in the SBP group after 7 days of anti‐infection treatment with third‐generation cephalosporins.

Results

The ascitic NGAL levels significantly increased in the SBP group compared with that in the non‐SBP group, 111(83.9, 178) ng/mL vs 48(35.4, 63) ng/mL, P < .001. Likewise, the ascitic NGAL levels of SBP were higher than non‐SBP with or without renal dysfunction. There was a positive relationship between ascitic NGAL and ascitic polymorphonuclear (PMN) leukocyte and a negative relationship between ascitic NGAL and ascitic albumin in the SBP group. An ascitic NGAL cutoff of 108.95 ng/mL was used for predicting a poor prognosis for SBP patients. Ascitic NGAL and the model for end‐stage liver disease score were independent risk factors in decompensated liver cirrhosis patients with SBP through multivariate Cox regression. A dynamic trend of ascitic NGAL in SBP patients was consistent with the clinical prognosis.

Conclusion

Ascitic NGAL may not only be a biomarker for monitoring SBP but also a predictor for more severe outcomes in decompensated cirrhosis‐related SBP.

Specific Commensal Bacterium Critically Regulates Gut Microbiota Osteoimmunomodulatory Actions During Normal Postpubertal Skeletal Growth and Maturation

The commensal gut microbiota critically regulates immunomodulatory processes that influence normal skeletal growth and maturation. However, the influence of specific microbes on commensal gut microbiota osteoimmunoregulatory actions is unknown. We have shown previously that the commensal gut microbiota enhances T_H17/IL17A immune response effects in marrow and liver that have procatabolic/antianabolic actions in the skeleton. Segmented filamentous bacteria (SFB), a specific commensal gut bacterium within phylum Firmicutes, potently induces T_H17/IL17A‐mediated immunity. The study purpose was to delineate the influence of SFB on commensal gut microbiota immunomodulatory actions regulating normal postpubertal skeletal development. Two murine models were utilized: SFB‐monoassociated mice versus germ‐free (GF) mice and specific‐pathogen‐free (SPF) mice +/− SFB. SFB colonization was validated by 16S rDNA analysis, and SFB‐induced T_H17/IL17A immunity was confirmed by upregulation of Il17a in ileum and IL17A in serum. SFB‐colonized mice had an osteopenic trabecular bone phenotype, which was attributed to SFB actions suppressing osteoblastogenesis and enhancing osteoclastogenesis. Intriguingly, SFB‐colonized mice had increased expression of proinflammatory chemokines and acute‐phase reactants in the liver. Lipocalin‐2 (LCN2), an acute‐phase reactant and antimicrobial peptide, was substantially elevated in the liver and serum of SFB‐colonized mice, which supports the notion that SFB regulation of commensal gut microbiota osteoimmunomodulatory actions are mediated in part through a gut–liver–bone axis. Proinflammatory T_H17 and T_H1 cells were increased in liver‐draining lymph nodes of SFB‐colonized mice, which further substantiates that SFB osteoimmune‐response effects may be mediated through the liver. SFB‐induction of Il17a in the gut and Lcn2 in the liver resulted in increased circulating levels of IL17A and LCN2. Recognizing that IL17A and LCN2 support osteoclastogenesis/suppress osteoblastogenesis, SFB actions impairing postpubertal skeletal development appear to be mediated through immunomodulatory effects in both the gut and liver. This research reveals that specific microbes critically impact commensal gut microbiota immunomodulatory actions regulating normal postpubertal skeletal growth and maturation. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

IL-6-mediated hepatocyte production is the primary source of plasma and urine neutrophil gelatinase-associated lipocalin during acute kidney injury

Neutrophil gelatinase associated lipocalin (NGAL, Lcn2) is the most widely studied biomarker of acute kidney injury (AKI). Previous studies have demonstrated that NGAL is produced by the kidney and released into the urine and plasma. Consequently, NGAL is currently considered a tubule specific injury marker of AKI. However, the utility of NGAL to predict AKI has been variable suggesting that other mechanisms of production are present. IL-6 is a proinflammatory cytokine increased in plasma by two hours of AKI and mediates distant organ effects. Herein, we investigated the role of IL-6 in renal and extra-renal NGAL production. Wild type mice with ischemic AKI had increased plasma IL-6, increased hepatic NGAL mRNA, increased plasma NGAL, and increased urine NGAL; all reduced in IL-6 knockout mice. Intravenous IL-6 in normal mice increased hepatic NGAL mRNA, plasma NGAL and urine NGAL. In mice with hepatocyte specific NGAL deletion (Lcn2hep-/-) and ischemic AKI, hepatic NGAL mRNA was absent, and plasma and urine NGAL were reduced. Since urine NGAL levels appear to be dependent on plasma levels, the renal handling of circulating NGAL was examined using recombinant human NGAL. After intravenous recombinant human NGAL administration to mice, human NGAL in mouse urine was detected by ELISA during proximal tubular dysfunction, but not in pre-renal azotemia. Thus, during AKI, IL-6 mediates hepatic NGAL production, hepatocytes are the primary source of plasma and urine NGAL, and plasma NGAL appears in the urine during proximal tubule dysfunction. Hence, our data change the paradigm by which NGAL should be interpreted as a biomarker of AKI.

Sex-specific metabolic functions of adipose Lipocalin-2

OBJECTIVE

Lipocalin-2 (LCN2) is a secreted protein involved in innate immunity and has also been associated with several cardiometabolic traits in both mouse and human studies. However, the causal relationship of LCN2 to these traits is unclear, and most studies have examined only males.

METHODS

Using adeno-associated viral vectors we expressed LCN2 in either adipose or liver in a tissue specific manner on the background of a whole-body Lcn2 knockout or wildtype mice. Metabolic phenotypes including body weight, body composition, plasma and liver lipids, glucose homeostasis, insulin resistance, mitochondrial phenotyping, and metabolic cage studies were monitored.

RESULTS

We studied the genetics of LCN2 expression and associated clinical traits in both males and females in a panel of 100 inbred strains of mice (HMDP). The natural variation in Lcn2 expression across the HMDP exhibits high heritability, and genetic mapping suggests that it is regulated in part by Lipin1 gene variation. The correlation analyses revealed striking tissue dependent sex differences in obesity, insulin resistance, hepatic steatosis, and dyslipidemia. To understand the causal relationships, we examined the effects of expression of LCN2 selectively in liver or adipose. On a Lcn2-null background, LCN2 expression in white adipose promoted metabolic disturbances in females but not males. It acted in an autocrine/paracrine manner, resulting in mitochondrial dysfunction and an upregulation of inflammatory and fibrotic genes. On the other hand, on a null background, expression of LCN2 in liver had no discernible impact on the traits examined despite increasing the levels of circulating LCN2 more than adipose LCN2 expression. The mechanisms underlying the sex-specific action of LCN2 are unclear, but our results indicate that adipose LCN2 negatively regulates its receptor, LRP2 (or megalin), and its repressor, ERα, in a female-specific manner and that the effects of LCN2 on metabolic traits are mediated in part by LRP2.

CONCLUSIONS

Following up on our population-based studies, we demonstrate that LCN2 acts in a highly sex- and tissue-specific manner in mice. Our results have important implications for human studies, emphasizing the importance of sex and the tissue source of LCN2.

Measurement of Neutrophil Gelatinase-Associated Lipocalin Concentration in Canine Cerebrospinal Fluid and Serum and Its Involvement in Neuroinflammation

Neutrophil gelatinase-associated Lipocalin (NGAL) is a glycoprotein involved in inflammation acting as an acute phase protein and chemokine as well as a regulator of iron homeostasis. NGAL has been shown to be upregulated in experimental autoimmune encephalomyelitis (EAE) in mice. Increased NGAL concentration in cerebrospinal fluid (CSF) and expression in central nervous system (CNS) has been described in human neuroinflammatory disease such as multiple sclerosis and neuropsychiatric lupus as well as in bacterial meningitis. We aimed to investigate involvement of NGAL in spontaneous canine neuroinflammation as a potential large animal model for immune- mediated neurological disorders. A commercially available Enzyme-linked Immunosorbent Assay (ELISA) for detection of canine NGAL was validated for use in canine CSF. Concentration in CSF and serum of canine patients suffering from steroid- responsive meningitis- arteriitis (SRMA), Meningoencephalitis of unknown origin (MUO), different non- inflammatory CNS disease and control dogs were compared. Relationship between NGAL concentration in CSF and serum and inflammatory parameters in CSF and blood (IgA concentration, total nucleated cell count (TNCC), protein content) as well as association with erythrocytes in CSF, duration of illness, plasma creatinine and urinary leucocytes were evaluated. In dogs with SRMA and MUO, CSF concentration of NGAL was significantly higher than in dogs with idiopathic epilepsy, compressive myelopathy, intracranial neoplasia and SRMA in remission (p < 0.0001). Patients with acute SRMA had significantly higher levels of NGAL in CSF than neurologically normal controls (p < 0.0001). Serum NGAL concentrations were significantly higher in dogs with SRMA than in patients with myelopathy and intracranial neoplasia (p < 0.0001). NGAL levels in CSF were strongly positively associated with IgA concentration (rSpear= 0.60116, p < 0.0001), TNCC (rSpear= 0.65746, p < 0.0001) and protein content (rSpear= 0.73353, p < 0.0001) in CSF. It can be measured in CSF of healthy and diseased dogs. Higher concentrations in canine patients with SRMA as well as positive association with TNCC in CSF suggest an involvement in pro-inflammatory pathways and chemotaxis in SRMA. High serum levels of NGAL in serum of SRMA patients in different stages of disease might reflect the systemic character of the disease.

Functions and regulation of lipocalin-2 in gut-origin sepsis: a narrative review

Lipocalin-2 (Lcn2), an innate immune protein, has come to be recognized for its roles in iron homeostasis, infection, and inflammation. In this narrative review, we provide a comprehensive description based on currently available evidence of the clinical implications of Lcn2 and its therapeutic potency in gut-origin sepsis. Lcn2 appears to mitigate gut barrier injury via maintaining homeostasis of the microbiota and exerting antioxidant strategy, as well as by deactivating macrophages and inducing immune cell apoptosis to terminate systemic hyper-inflammation. We propose that development of a therapeutic strategy targeting lipocalin-2 could be highly promising in the management of gut-origin sepsis.

TLX3 repressed SNAI1-induced epithelial-mesenchymal transition by directly constraining STAT3 phosphorylation and functionally sensitized 5-FU chemotherapy in hepatocellular carcinoma

TLX3 has an established role as a sequence-specific transcription factor with vital functions in the nervous system. Although several studies have shown that TLX3 is aberrantly up-regulated in leukemia, its expression and function in hepatocellular carcinoma (HCC) remain unknown. We found that TLX3 expression was decreased in 68/100 (68%) HCC cases and negatively correlated with the expression of p-STAT3, SNAI1, and Vimentin, while it was positively associated with E-cadherin expression. ITRAQ proteomic profiling revealed significantly less TLX3 expression in primary HCC tumors than in portal vein tumor thrombi. Comparison of Kaplan-Meier curves showed that down-regulation of TLX3 in HCC was associated with poor post-surgical survival. TLX3 over-expression inhibited HCC cell viability, proliferation, migration, invasion and enhanced 5-FU treatment, whereas silencing TLX3 produced the opposite results. Further experiments showed that TLX3 attenuated the EMT phenotype. In vivo experiments showed that knockdown of TLX3 promoted the growth of HCC xenografts and attenuated the anti-tumor effects of 5-FU treatment. Gene expression microarray analysis revealed that TLX3 inhibited IL-6/STAT3 signaling. In additional mechanistic studies TLX3 reversed the EMT phenotype of HCC cells by binding to STAT3, inhibiting STAT3 phosphorylation, and down-regulating SNAI1 expression. Taken together, loss of expression of TLX3 induces EMT by enhancing IL-6/STAT3/SNAI1 signaling, and accelerates HCC progression while also attenuated the effect of 5-FU on HCCs.

Lipocalin-2 Protects Against Diet-Induced Nonalcoholic Fatty Liver Disease by Targeting Hepatocytes

Hepatocytes are the major source of hepatic lipocalin-2 (LCN2), which is up-regulated in response to inflammation, injury, or metabolic stress. So far, the role of hepatocyte-derived LCN2 in the development of nonalcoholic fatty liver disease (NAFLD) remains unknown. Herein we show that overexpression of human LCN2 in hepatocytes protects against high fat/high cholesterol/high fructose (HFCF) diet-induced liver steatosis and nonalcoholic steatohepatitis by promoting lipolysis and fatty acid oxidation (FAO) and inhibiting de novo lipogenesis (DNL), lipid peroxidation, and apoptosis. LCN2 fails to reduce triglyceride accumulation in hepatocytes lacking sterol regulatory element-binding protein 1. In contrast, Lcn2-/- mice have defective lipolysis, increased lipid peroxidation and apoptosis, and exacerbated NAFLD after being fed an HFCF diet. In primary hepatocytes, Lcn2 deficiency stimulates de novo lipogenesis but inhibits FAO. Conclusion: The current study indicates that hepatocyte LCN2 protects against diet-induced NAFLD by regulating lipolysis, FAO, DNL, lipid peroxidation, and apoptosis. Targeting hepatocyte LCN2 may be useful for treatment of NAFLD.

Lipocalin-2 levels in acute and chronic graft-versus-host disease following allogeneic hematopoietic stem cell transplantation

Lipocalin-2 (LCN2) is an immunomodulatory protein holding major metabolic and immune functions. It is involved in several inflammatory processes and induced by cytokines of the interleukin-1 family known as contributors to the morbidity in graft-versus-host disease (GVHD) following hematopoietic stem cell transplantation (HSCT). The possible role of LCN2 in predicting outcome and course of illness has never been elucidated in patients undergoing HSCT for hematologic malignancies. We conducted a prospective cohort study including 40 patients following autologous or allogeneic HSCT by collecting plasma samples at seven time points with respect to GVHD, relapse, and outcome. LCN2 levels were significantly increased in acute patients with GVHD compared with autologous and healthy controls (125.7 ng/mL vs. 65.9 and 71.4 ng/mL) and correlated with its severity. Similarly, LCN2 levels were significantly elevated in chronic GHVD compared with autologous and healthy controls (295.0 ng/mL vs. 54.9 and 76.5 ng/mL). Moreover, LCN2 correlated with mortality. The suspected role of LCN2 as a predictive parameter for outcome and prognosis needs to be further investigated.

Perilipin 5 and Lipocalin 2 Expression in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent and deadly cancers worldwide. Therefore, current global research focuses on molecular tools for early diagnosis of HCC, which can lead to effective treatment at an early stage. Perilipin 5 (PLIN5) has been studied as one of the main proteins of the perilipin family, whose role is to maintain lipid homeostasis by inhibiting lipolysis. In this study, we show for the first time that PLIN5 is strongly expressed in tumors of human patients with HCC as well as in mouse livers, in which HCC was genetically or experimentally induced by treatment with the genotoxic agent diethylnitrosamine. Moreover, the secreted acute phase glycoprotein Lipocalin 2 (LCN2) established as a biomarker of acute kidney injury, is also proven to indicate liver injury with upregulated expression in numerous cases of hepatic damage, including steatohepatitis. LCN2 has been studied in various cancers, and it has been assigned roles in multiple cellular processes such as the suppression of the invasion of HCC cells and their metastatic abilities. The presence of this protein in blood and urine, in combination with the presence of α-Fetoprotein (AFP), is hypothesized to serve as a biomarker of early stages of HCC. In the current study, we show in humans and mice that LCN2 is secreted into the serum from liver cancer tissue. We also show that AFP-positive hepatocytes represent the main source for the massive expression of LCN2 in tumoral tissue. Thus, the strong presence of PLIN5 and LCN2 in HCC and understanding their roles could establish them as markers for diagnosis or as treatment targets against HCC.

P-selectin drives complement attack on endothelium during intravascular hemolysis in TLR-4/heme-dependent manner

Hemolytic diseases are frequently linked to multiorgan failure subsequent to vascular damage. Deciphering the mechanisms leading to organ injury upon hemolytic event could bring out therapeutic approaches. Complement system activation occurs in hemolytic disorders, such as sickle cell disease, but the pathological relevance and the acquisition of a complement-activating phenotype during hemolysis remain unclear. Here we found that intravascular hemolysis, induced by injection of phenylhydrazine, resulted in increased alanine aminotransferase plasma levels and NGAL expression. This liver damage was at least in part complement-dependent, since it was attenuated in complement C3^-/- mice and by injection of C5-blocking antibody. We evidenced C3 activation fragments' deposits on liver endothelium in mice with intravascular hemolysis or injected with heme as well as on cultured human endothelial cells (EC) exposed to heme. This process was mediated by TLR4 signaling, as revealed by pharmacological blockade and TLR4 deficiency in mice. Mechanistically, TLR4-dependent surface expression of P-selectin triggered an unconventional mechanism of complement activation by noncovalent anchoring of C3 activation fragments, including the typical fluid-phase C3(H₂O), measured by surface plasmon resonance and flow cytometry. P-selectin blockade by an antibody prevented complement deposits and attenuated the liver stress response, measured by NGAL expression, in the hemolytic mice. In conclusion, these results revealed the critical impact of the triad TLR4/P-selectin/complement in the liver damage and its relevance for hemolytic diseases. We anticipate that blockade of TLR4, P-selectin, or the complement system could prevent liver injury in hemolytic diseases like sickle cell disease.

PECAM-1 modulates liver damage induced by synergistic effects of TNF-α and irradiation

The mechanisms of radiation‐induced liver damage are poorly understood. We investigated if tumour necrosis factor (TNF)‐α acts synergistically with irradiation, and how its activity is influenced by platelet endothelial cell adhesion molecule‐1 (PECAM‐1). We studied murine models of selective single‐dose (25 Gy) liver irradiation with and without TNF‐α application (2 μg/mouse; i.p.). In serum of wild‐type (wt)‐mice, irradiation induced a mild increase in hepatic damage marker aspartate aminotransferase (AST) in comparison to sham‐irradiated controls. AST levels further increased in mice treated with both irradiation and TNF‐α. Accordingly, elevated numbers of leucocytes and increased expression of the macrophage marker CD68 were observed in the liver of these mice. In parallel to hepatic damage, a consecutive decrease in expression of hepatic PECAM‐1 was found in mice that received radiation or TNF‐α treatment alone. The combination of radiation and TNF‐α induced an additional significant decline of PECAM‐1. Furthermore, increased expression of hepatic lipocalin‐2 (LCN‐2), a hepatoprotective protein, was detected at mRNA and protein levels after irradiation or TNF‐α treatment alone and the combination of both. Signal transducer and activator of transcription‐3 (STAT‐3) seems to be involved in the signalling cascade. To study the involvement of PECAM‐1 in hepatic damage more deeply, the liver of both wt‐ and PECAM‐1‐knock‐out‐mice were selectively irradiated (25 Gy). Thereby, ko‐mice showed higher liver damage as revealed by elevated AST levels, but also increased hepatoprotective LCN‐2 expression. Our studies show that TNF‐α has a pivotal role in radiation‐induced hepatic damage. It acts in concert with irradiation and its activity is modulated by PECAM‐1, which mediates pro‐ and anti‐inflammatory signalling.

Liver parenchymal cells lacking Lipocalin 2 (LCN2) are prone to endoplasmic reticulum stress and unfolded protein response

Unfolded protein response (UPR) is an adaptive mechanism allowing the endoplasmic reticulum (ER) to react to an accumulation of unfolded proteins in its lumen, also known as ER stress. The UPR is interconnected with inflammation through several pathways such as reactive oxygen species (ROS) production resulting from the protein folding or alternatively, activation of nuclear factor-κB (NF-κB) and c-Jun N-terminal kinase (JNK) via IRE1, or induction of acute phase response (APR). Lipocalin 2 (LCN2) is one of the APR proteins induced under inflammatory conditions and up-regulated during ER stress. Upon incubation of Lcn2^-/- and wild type (wt) primary hepatocytes with tunicamycin (TM) or thapsigargin (TG) we found the Lcn2^-/- hepatocytes to react with strong UPR to the ER stress, as evidenced by significantly increased levels of Grp94, Bip and Chop mRNA and protein compared to the wt. TM and TG-treated hepatocytes activated p65 NF-κB and JNK, the pathways that respond to stress stimuli and playing a central role in inflammation and apoptosis, respectively. ER stress further activated and cleaved full-length CREBH/CREB3L3, the hepatocyte specific transcription factor to induce systemic inflammatory responses. Upregulation of the C/EBP homologous protein (CHOP) was very prominent in Lcn2^-/- hepatocytes and sustained until 48 h, resulting in hepatocyte apoptosis as evidenced by increased cleaved caspase 3. We also explored the UPR of the Lcn2 null mouse livers in acute intoxication and inflammation stages with a single application of lipopolysaccharide (LPS) or carbon tetrachloride (CCl₄). The Lcn2 null mice clearly developed stronger UPR in LPS- and CCl₄-induced ER stress compared to the wt. Our findings indicate that the upregulation of LCN2 during ER stress-induced inflammatory responses protects hepatocytes from being overwhelmed by UPR upon liver injury.

Prognostic utility of novel biomarkers in acute-on-chronic liver failure (ACLF) associated with hepatitis B: A multicenter prospective study

AIM

Flare-ups of chronic hepatitis B can sometimes be severe and even progress to acute-on-chronic liver failure (ACLF), with high short-term mortality. A timely estimation of the risk of death should be initiated early. The aim of the present study was to determine whether novel biomarkers add prognostic information beyond current clinical scoring systems.

METHODS

Patients with hepatitis B-associated ACLF were prospectively enrolled from five hospitals in China between August 2017 and March 2018. Their plasma was screened for soluble CD163 (sCD163), neutrophil gelatinase-associated lipocalin (NGAL), and copeptin. The association between these biomarkers and mortality was analyzed. The performance of the Model for End-stage Liver Disease, Asian-Pacific Association for the Study of the Liver-ACLF Research Consortium score, and the Chronic Liver Failure Consortium ACLF score, with or without biomarkers, were compared.

RESULTS

One hundred fifty one patients were enrolled. Advanced ACLF patients had significantly higher levels than early ACLF individuals of plasma biomarkers sCD163 (P = 0.001), NGAL (P = 0.006), and copeptin (P = 0.049). Thirty-four deaths occurred during the 28-day follow-up period (22.5%). Both sCD163 and NGAL showed a strong independent association with 28-day mortality, whereas copeptin did not. Scoring systems incorporating sCD163 and NGAL had better discrimination and calibration, as measured by area under the receiver operating characteristic curves, the Akaike information criteria, integrated discrimination improvement, and net reclassification improvement.

CONCLUSIONS

Soluble CD163 and NGAL are independently associated with short-term mortality in hepatitis B-associated ACLF. Use of a combination of sCD163 and NGAL improves prognostication.

Serum NGAL Is Superior to Cystatin C in Predicting the Prognosis of Acute-on-Chronic Liver Failure

INTRODUCTION AND AIM

Acute-on-chronic liver failure (ACLF) is a syndrome with high short-term mortality, and predicting the prognosis is challenging. This study aimed to compare the performance of neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C (CysC) in predicting the 90-day mortality in patients with hepatitis B virus (HBV)-associated ACLF (HBV-ACLF).

MATERIALS AND METHODS

This prospective, observational study enrolled 54 patients with HBV-ACLF. The serum NGAL and CysC levels were determined. A multivariate logistic regression analysis was used to analyze the independent risk factors of mortality.

RESULTS

Serum NGAL, but not CysC, was found to significantly correlate with the total bilirubin, international normalized ratio, and model for end-stage liver disease (MELD). Serum NGAL [odds ratio (OR), 1.008; 95% confidence interval (CI), 1.004-1.012; P < 0.01], but not CysC, was an independent risk factor for developing hepatorenal syndrome. Moreover, NGAL (OR, 1.005; 95% CI, 1.001-1.010; P < 0.01) along with the MELD score was independently associated with the overall survival in patients with HBV-ACLF. Patients with HBV-ACLF were stratified into two groups according to the serum NGAL level at baseline (low risk: <217.11 ng/mL and high risk: ≥ 217.11 ng/mL). The 90-day mortality rate was 22.73% (5/22) in the low-risk group and 71.88% (23/32) in the high-risk group. Moreover, NGAL, but not CysC, significantly improved the MELD score in predicting the prognosis of HBV-ACLF.

CONCLUSION

The serum NGAL might be superior to CysC in predicting the prognosis of HBV-ACLF with the normal creatinine level.

Lipocalin-2 Functions as Inhibitor of Innate Resistance to Mycobacterium tuberculosis

Lipocalin-2 is a constituent of the neutrophil secondary granules and is expressed de novo by macrophages and epithelium in response to inflammation. Lipocalin-2 acts in a bacteriostatic fashion by binding iron-loaded siderophores required for bacterial growth. Mycobacterium tuberculosis (M.tb) produces siderophores that can be bound by lipocalin-2. The impact of lipocalin-2 in the innate immune response toward extracellular bacteria has been established whereas the effect on intracellular bacteria, such as M.tb, is less well-described. Here we show that lipocalin-2 surprisingly confers a growth advantage on M.tb in the early stages of infection (3 weeks post-challenge). Using mixed bone marrow chimeras, we demonstrate that lipocalin-2 derived from granulocytes, but not from epithelia and macrophages, leads to increased susceptibility to M.tb infection. In contrast, lipocalin-2 is not observed to promote mycobacterial growth at later stages of M.tb infection. We demonstrate co-localization of granulocytes and mycobacteria within the nascent granulomas at week 3 post-challenge, but not in the consolidated granulomas at week 5. We hypothesize that neutrophil-derived lipocalin-2 acts to supply a source of iron to M.tb in infected macrophages within the immature granuloma, thereby facilitating mycobacterial growth.

Intrahepatic T-Cell Receptor β Immune Repertoire Is Essential for Liver Regeneration

T lymphocytes synergize with the cellular immune system to promote hepatocyte regeneration. The T-cell receptor (TCR) immune repertoire is closely associated with the host immune response and regenerative proliferation. High-throughput sequencing of TCR provides deep insight into monitoring the immune microenvironment. Here, we aimed to determine the role of the TCRβ immune repertoire in liver regeneration (LR). We investigated hepatic regeneration in TCRβ chain-deficient (tcrb^-/- ) mice by two-thirds partial hepatectomy (PHx) method. Our results demonstrated that tcrb^-/- mice revealed a reduced capacity for LR, which was characterized by impaired hepatocyte proliferation and enhanced hepatocyte apoptosis. Dysregulation of inflammatory signaling activation and inflammatory factors was observed in regenerated tcrb^-/- livers. Simultaneously, significantly altered immunocyte levels and aberrant cytokine levels were observed during hepatic regeneration. In addition, we first determined the profile of the TCRβ immune repertoire during LR, indicating that PHx resulted in remarkably lower TCRβ diversity in intrahepatic T lymphocytes. Conclusion: Taken together, our data suggest that TCRβ deficiency gives a rise to aberrant intrahepatic immune microenvironment that impairs LR, and the TCRβ reconstitution is required for hepatic immunocyte recruitment and activation during LR.

The Role of Adipokines in Surgical Procedures Requiring Both Liver Regeneration and Vascular Occlusion

Liver regeneration is a perfectly calibrated mechanism crucial to increase mass recovery of small size grafts from living donor liver transplantation, as well as in other surgical procedures including hepatic resections and liver transplantation from cadaveric donors. Regeneration involves multiple events and pathways in which several adipokines contribute to their orchestration and drive hepatocytes to proliferate. In addition, ischemia-reperfusion injury is a critical factor in hepatic resection and liver transplantation associated with liver failure or graft dysfunction post-surgery. This review aims to summarize the existing knowledge in the role of adipokines in surgical procedures requiring both liver regeneration and vascular occlusion, which increases ischemia-reperfusion injury and regenerative failure. We expose and discuss results in small-for-size liver transplantation and hepatic resections from animal studies focused on the modulation of the main adipokines associated with liver diseases and/or regeneration published in the last five years and analyze future perspectives and their applicability as potential targets to decrease ischemia-reperfusion injury and improve regeneration highlighting marginal states such as steatosis. In our view, adipokines means a promising approach to translate to the bedside to improve the recovery of patients subjected to partial hepatectomy and to increase the availability of organs for transplantation.

Hepatocytes and neutrophils cooperatively suppress bacterial infection by differentially regulating lipocalin-2 and neutrophil extracellular traps

Lipocalin-2 (LCN2), also known as neutrophil gelatinase-associated lipocalin (NGAL), a key antibacterial protein, is highly elevated in patients with end-stage liver disease that is often associated with bacterial infection. LCN2 is expressed at high levels in both hepatocytes and neutrophils; however, how hepatocyte-derived and neutrophil-derived LCN2 cooperate to combat bacterial infection remains unclear. Here, by studying hepatocyte-specific and myeloid-specific Lcn2 knockout mice in two models of systemic and local Klebsiella pneumoniae infections, we demonstrated that hepatocytes played a critical role in controlling systemic infection by secreting LCN2 protein into the circulation following intraperitoneal injection of bacteria, whereas neutrophils were more important in combating local lung infection by carrying LCN2 in their specific granules to the local infection site following intratracheal intubation of bacteria. Both hepatocyte-derived and myeloid cell-derived LCN2 were required against bacterial infection in the peritoneal cavity and liver necrotic areas following intraperitoneal injection of Klebsiella pneumoniae. LCN2/NGAL protein was detected in neutrophil extracellular traps (NETs) in activated neutrophils from mice and humans. Disruption of the Lcn2 gene in neutrophils abolished LCN2 on NETs, whereas deletion of this gene in hepatocytes did not affect LCN2 protein on NETs. Genetic deletion of the Lcn2 gene globally or specifically in neutrophils did not affect NET formation but reduced the bactericidal effect of NETs in vitro. Finally, NGAL-positive NETs were detected in the liver from patients with various types of liver diseases.

CONCLUSION

Both hepatocytes and neutrophils combat bacterial infection through the production of LCN2; extracellular LCN2 secreted by hepatocytes limits systemic bacterial infection, whereas neutrophils carry LCN2 protein to the local site and against local bacterial infection through NETs. (Hepatology 2018).

The Clinical Significance of GP73 in Immunologically Mediated Chronic Liver Diseases: Experimental Data and Literature Review

There is significant void in establishing validated non-invasive surrogate biomarkers of liver fibrosis/cirrhosis in chronic liver diseases (CLD). Golgi protein 73 (GP73) has been suggested as a potential serum marker for the diagnosis of hepatocellular carcinoma (HCC). However, significant background of cirrhosis could have accounted for the elevation of serum GP73 in HCC. In this study, we have taken advantage of a well-defined extensive cohort of 3044 patients with either compensated cirrhosis (n = 1247), decompensated cirrhosis (n = 841) or pre-cirrhotic CLD (n = 956) and our ability to quantify serum GP73 to define the potential of serum GP73 as a biomarker of liver cirrhosis/fibrosis in CLD. The diagnostic value of GP73 was compared with aspartate aminotransferase-to-platelet ratio index (APRI), fibrosis index based on four factors (FIB-4) and liver stiffness measurement (LSM). Immunohistochemical analysis was performed to measure hepatic GP73 expression. Receiver operating characteristic curve analysis demonstrated that serum GP73 had a good diagnostic potential for compensated cirrhosis regardless of etiology. The diagnostic performance of GP73 is better than APRI, FIB-4 and similar with LSM, especially in patients with severe inflammation, steatosis and cholestasis. Notably, in patients of autoimmune liver diseases, non-alcoholic fatty liver disease and viral hepatitis, serum GP73 also exhibited diagnostic value for advanced fibrosis as well as cirrhosis. Furthermore, there is also a gradual increase in GP73 expression with disease progression from mild fibrosis to cirrhosis. In conclusion, GP73 is an effective and reliable serological marker for the diagnosis of advanced fibrosis and prediction of appearance of cirrhosis.

Regulation of protein-coding gene and long noncoding RNA pairs in liver of conventional and germ-free mice following oral PBDE exposure

Gut microbiome communicates with the host liver to modify hepatic xenobiotic biotransformation and nutrient homeostasis. Polybrominated diphenyl ethers (PBDEs) are persistent environmental contaminants that are detected in fatty food, household dust, and human breast milk at worrisome levels. Recently, long noncoding RNAs (lncRNAs) have been recognized as novel biomarkers for toxicological responses and may regulate the transcriptional/translational output of protein-coding genes (PCGs). However, very little is known regarding to what extent the interactions between PBDEs and gut microbiome modulate hepatic lncRNAs and PCGs, and what critical signaling pathways are impacted at the transcriptomic scale. In this study, we performed RNA-Seq in livers of nine-week-old male conventional (CV) and germ-free (GF) mice orally exposed to the most prevalent PBDE congeners BDE-47 and BDE-99 (100 μmol/kg once daily for 4-days; vehicle: corn oil, 10 ml/kg), and unveiled key molecular pathways and PCG-lncRNA pairs targeted by PBDE-gut microbiome interactions. Lack of gut microbiome profoundly altered the PBDE-mediated transcriptomic response in liver, with the most prominent effect observed in BDE-99-exposed GF mice. The top pathways up-regulated by PBDEs were related to xenobiotic metabolism, whereas the top pathways down-regulated by PBDEs were in lipid metabolism and protein synthesis in both enterotypes. Genomic annotation of the differentially regulated lncRNAs revealed that majority of these lncRNAs overlapped with introns and 3'-UTRs of PCGs. Lack of gut microbiome profoundly increased the percentage of PBDE-regulated lncRNAs mapped to the 3'-UTRs of PCGs, suggesting the potential involvement of lncRNAs in increasing the translational efficiency of PCGs by preventing miRNA-3'-UTR binding, as a compensatory mechanism following toxic exposure to PBDEs. Pathway analysis of PCGs paired with lncRNAs revealed that in CV mice, BDE-47 regulated nucleic acid and retinol metabolism, as well as circadian rhythm; whereas BDE-99 regulated fatty acid metabolism. In GF mice, BDE-47 differentially regulated 19 lncRNA-PCG pairs that were associated with glutathione conjugation and transcriptional regulation. In contrast, BDE-99 up-regulated the xenobiotic-metabolizing Cyp3a genes, but down-regulated the fatty acid-metabolizing Cyp4 genes. Taken together, the present study reveals common and unique lncRNAs and PCG targets of PBDEs in mouse liver, and is among the first to show that lack of gut microbiome sensitizes the liver to toxic exposure of BDE-99 but not BDE-47. Therefore, lncRNAs may serve as specific biomarkers that differentiate various PBDE congeners as well as environmental chemical-mediated dysbiosis. Coordinate regulation of PCG-lncRNA pairs may serve as a more efficient molecular mechanism to combat against xenobiotic insult, and especially during dysbiosis-induced increase in the internal dose of toxicants.

HMBOX1 in hepatocytes attenuates LPS/D-GalN-induced liver injury by inhibiting macrophage infiltration and activation

The HMBOX1 (Homeobox Containing 1) gene was first isolated from the human pancreatic cDNA libraries and is widely expressed in many tissues. Previously, we detected high expression of HMBOX1 in the liver, but its function was unclear. In this study, hepatocyte-specific HMBOX1 knockout mice (Hm^△hep mice) were generated and used to characterize the function of HMBOX1 in the LPS/D-GalN-induced acute liver failure model. HMBOX1-knockout exhibits exacerbated liver injury induced by LPS/D-GalN, accompanied with high levels of inflammatory cytokines both in the liver and in circulation. Further investigation demonstrated that HMBOX1 negatively regulates NF-κB signal transduction. Therefore, HMBOX1-knockout in hepatocytes promotes CCL2 expression through the activation of NF-κB signaling, which enhanced the infiltration of macrophages into the liver. In addition, the decrease of HMBOX1 in hepatocytes promotes the activation of macrophages, upregulating CD80 and MHCⅡ, as well as inflammatory factors TNF-α and IL-6. Importantly, overexpression of HMBOX1 rescued liver injury in Hm^△hep mice. These findings indicate that HMBOX1 in hepatocytes acts as a key immunosuppressive factor for inflammation and plays a critical protective role in LPS/D-GalN-induced liver injury.

Hepatocyte-Derived Lipocalin 2 Is a Potential Serum Biomarker Reflecting Tumor Burden in Hepatoblastoma

Hepatoblastoma (HB) is the most common pediatric liver malignant tumor. Previously, we reported co-activation of β-catenin and Yes-associated protein-1 (YAP1) in 80% of HB. Hepatic co-expression of active β-catenin and YAP1 via sleeping beauty transposon/transposase and hydrodynamic tail vein injection led to HB development in mice. Here, we identify lipocalin 2 (Lcn2) as a target of β-catenin and YAP1 in HB and show that serum Lcn2 values positively correlated with tumor burden. Lcn2 was strongly expressed in HB tumor cells in our mouse model. A tissue array of 62 HB cases showed highest LCN2 expression in embryonal and lowest in fetal, blastemal, and small cell undifferentiated forms of HB. Knockdown of LCN2 in HB cells had no effect on cell proliferation but reduced NF-κB reporter activity. Next, liver-specific Lcn2 knockout (KO) mice were generated. No difference in tumor burden was observed between Lcn2 KO mice and wild-type littermate controls after sleeping beauty transposon/transposase and hydrodynamic tail vein injection delivery of active YAP1 and β-catenin, although Lcn2 KO mice with HB lacked any serum Lcn2 elevation, demonstrating that transformed hepatocytes are the source of serum Lcn2. More blastemal areas and inflammation were observed within HB in Lcn2 KO compared with wild-type tumors. In conclusion, Lcn2 expressed in hepatocytes appears to be dispensable for the pathogenesis of HB. However, transformed hepatocytes secrete serum Lcn2, making Lcn2 a valuable biomarker for HB.

Chitinase 3-like-1 promotes intrahepatic activation of coagulation through induction of tissue factor in mice

Coagulation is a critical component in the progression of liver disease. Identification of key molecules involved in the intrahepatic activation of coagulation (IAOC) will be instrumental in the development of effective therapies against liver disease. Using a mouse model of concanavalin A (ConA)-induced hepatitis, in which IAOC plays an essential role in causing liver injury, we uncovered a procoagulant function of chitinase 3-like 1 (Chi3l1). Chi3l1 expression is dramatically elevated after ConA challenge, which is dependent on ConA-induced T cell activation and the resulting interferon γ and tumor necrosis factor α productions. Compared with wild-type mice, Chi3l1-/- mice show less IAOC, reduced tissue factor (TF) expression, and attenuated liver injury. Reconstituting Chi3l1-/- mice with recombinant TF triggers IAOC and augments liver injury.

CONCLUSION

Our data demonstrate that Chi3l1, through induction of TF via mitogen-activated protein kinase activation, promotes IAOC and tissue injury. (Hepatology 2018;67:2384-2396).

Endocrine Adiponectin-FGF15/19 Axis in Ethanol-Induced Inflammation and Alcoholic Liver Injury

Alcoholic liver disease (ALD) is the most prevalent form of liver disease, encompassing a spectrum of progressive pathological changes from steatosis to steatohepatitis to fibrosis/cirrhosis and hepatocellular carcinoma. Alcoholic steatosis/steatohepatitis is the initial stage of ALD and a major risk factor for advanced liver injuries. Adiponectin is a hormone secreted from adipocytes. Fibroblast growth factor (FGF) 15 (human homolog, FGF19) is an ileum-derived hormone. Adipocyte-derived adiponectin and gut-derived FGF15/19 regulate each other, share common signaling cascades, and exert similar beneficial functions. Emerging evidence has revealed that dysregulated adiponectin-FGF15/19 axis and impaired hepatic adiponectin-FGF15/19 signaling are associated with alcoholic liver damage in rodents and humans. More importantly, endocrine adiponectin-FGF15/19 signaling confers protection against ethanol-induced liver damage via fine tuning the adipose-intestine-liver crosstalk, leading to limited hepatic inflammatory responses, and ameliorated alcoholic liver injury. This review is focused on the recently discovered endocrine adiponectin-FGF15/19 axis that is emerging as an essential adipose-gut-liver coordinator involved in the development and progression of alcoholic steatohepatitis.

Lipocalin 2 Plays an Important Role in Regulating Inflammation in Retinal Degeneration

It has become increasingly important to understand how retinal inflammation is regulated because inflammation plays a role in retinal degenerative diseases. Lipocalin 2 (LCN2), an acute stress response protein with multiple innate immune functions, is increased in ATP-binding cassette subfamily A member 4 (Abca4) ^-/- retinol dehydrogenase 8 (Rdh8) ^-/- double-knockout mice, an animal model for Stargardt disease and age-related macular degeneration (AMD). To examine roles of LCN2 in retinal inflammation and degeneration, Lcn2^-/-Abca4^-/-Rdh8^-/- triple-knockout mice were generated. Exacerbated inflammation following light exposure was observed in Lcn2^-/-Abca4^-/-Rdh8^-/- mice as compared with Abca4^-/-Rdh8^-/- mice, with upregulation of proinflammatory genes and microglial activation. RNA array analyses revealed an increase in immune response molecules such as Ccl8, Ccl2, and Cxcl10 To further probe a possible regulatory role for LCN2 in retinal inflammation, we examined the in vitro effects of LCN2 on NF-κB signaling in human retinal pigmented epithelial (RPE) cells differentiated from induced pluripotent stem cells derived from healthy donors. We found that LCN2 induced expression of antioxidant enzymes heme oxygenase 1 and superoxide dismutase 2 in these RPE cells and could inhibit the cytotoxic effects of H₂O₂ and LPS. ELISA revealed increased LCN2 levels in plasma of patients with Stargardt disease, retinitis pigmentosa, and age-related macular degeneration as compared with healthy controls. Finally, overexpression of LCN2 in RPE cells displayed protection from cell death. Overall these results suggest that LCN2 is involved in prosurvival responses during cell stress and plays an important role in regulating inflammation during retinal degeneration.

COX-2 contributes to LPS-induced Stat3 activation and IL-6 production in microglial cells

Many stimuli including lipopolysaccharide (LPS) could activate microglial cells to subsequently cause inflammatory nerve injury. However, the mechanism of LPS-induced neuroinflammation in microglial cells is still elusive. Thus, the present study was undertaken to examine the role of COX-2 in mediating the activation of Stat3 and the production of IL-6 in BV2 cells challenged with LPS. After 24 h treatment, LPS dose-dependently enhanced COX-2 expression at both mRNA and protein levels. Meanwhile, IL-6 with other inflammatory cytokines including IL-1β, TNF-α, and MCP-1 were similarly enhanced by LPS. Then a specific COX-2 inhibitor (NS-398) was administered to BV2 before LPS treatment. Significantly, COX-2 inhibition suppressed the upregulation of IL-6 at both mRNA and protein levels in line with the trend blockade on IL-1β, TNF-α, and MCP-1. Stat3 drives proinflammatory signaling pathways and contributes to IL-6 production via a transcriptional mechanism in many diseases. Here we found that inhibition of COX-2 entirely blocked LPS-induced Stat3 phosphorylation, which might contribute to the blockade of IL-6 production to some extent. Meanwhile, COX-2 siRNA approach largely reproduced the phenotypes shown by specific COX-2 inhibitor in LPS-treated BV2 cells. Together, these findings suggested that COX-2 might contribute to LPS-induced IL-6 production possibly through activating Stat3 signaling pathway in microglial cells.

Kupffer cell-derived TNF-α promotes hepatocytes to produce CXCL1 and mobilize neutrophils in response to necrotic cells

The damage-associated molecular pattern molecules (DAMPs) released by necrotic cells can trigger inflammatory response, which will facilitate the clearance of these dead cells. Neutrophil mobilization is a very important step for the dead cell clearance, however the detailed mechanisms for DAMPs induce neutrophil mobilization remains largely elusive. In this study, by using a necrotic cell-induced neutrophil mobilization mice model, we found that both neutrophil number and percentage rapidly (as early as 30 min) increased with necrotic cells but not live cell treatment. CXCL1 was rapidly increased in the serum and was responsible for the neutrophil mobilization when treated with necrotic cells. We further demonstrated that the hepatocytes in the liver were the main source of CXCL1 production in response to necrotic cells challenge. However, the hepatocytes did not express CXCL1 when incubating with necrotic cells alone. When Kupffer cells were ablated, the increased CXCL1 levels as well as neutrophil mobilization were abolished with necrotic cells challenge. Moreover, we clarified Kupffer cells-derived TNF-α activates the NF-κB pathway in hepatocytes and promote hepatocytes to express CXCL1. In summary, we showed that the liver is the main source for necrotic cell-induced CXCL1 production and neutrophil mobilization. Kupffer cells in the liver sense DAMPs and release TNF-α to activate the NF-κB pathway in hepatocytes. The interaction between Kupffer cells and hepatocytes is critical for CXCL1 production.

Interleukin-6/Stat3 signaling has an essential role in the host antimicrobial response to urinary tract infection

The signaling networks regulating antimicrobial activity during urinary tract infection (UTI) are incompletely understood. Interleukin-6 (IL-6) levels increase with UTI severity, but the specific contributions of IL-6 to host immunity against bacterial uropathogens are unknown. To clarify this we tested whether IL-6 activates the Stat3 transcription factor, to drive a program of antimicrobial peptide gene expression in infected urothelium during UTI. Transurethral inoculation of uropathogenic Escherichia coli led to IL-6 secretion, urothelial Stat3 phosphorylation, and activation of antimicrobial peptide transcription, in a Toll-like receptor 4-dependent manner in a murine model of cystitis. Recombinant IL-6 elicited Stat3 phosphorylation in primary urothelial cells in vitro, and systemic IL-6 administration promoted urothelial Stat3 phosphorylation and antimicrobial peptide expression in vivo. IL-6 deficiency led to decreased urothelial Stat3 phosphorylation and antimicrobial peptide mRNA expression following UTI, a finding mirrored by conditional Stat3 deletion. Deficiency in IL-6 or Stat3 was associated with increased formation of intracellular bacterial communities, and exogenous IL-6 reversed this phenotype in IL-6 knockout mice. Moreover, chronic IL-6 depletion led to increased renal bacterial burden and severe pyelonephritis in C3H/HeOuJ mice. Thus, IL-6/Stat3 signaling drives a transcriptional program of antimicrobial gene expression in infected urothelium, with key roles in limiting epithelial invasion and ascending infection.

In silico analysis of expression data during the early priming stage of liver regeneration after partial hepatectomy in rat

The priming stage is the first step of liver regeneration (LR). This stage is characterized by the transition from G0 to cell cycle for 4 hours in rat. In this study, individual gene level and gene set level (GSEA) was performed to identify the candidate genes and significantly changed biological processes at 2 h after partial hepatectomy (PH). The leading edge analysis is performed to identify the key genes and iRegulon was employed for transcription factor (TF) analysis. A total of 53 differentially expressed genes were identified using RMA package based on R language at 2 h after PH, including the transcription factor, enzyme and cytokine. As the most important genes in our analysis, Socs3 was selected with a special analysis so as to find the pathways correlate to the expression of it. The changed significantly pathways in LR involved response to stress, ATP metabolism, and regulation of cell cycle mainly. Several transcription factors were identified including Stat5a, Cnot3 and zfp384. Taken together, at the early priming stage of LR in rat, the liver is experiencing some changes including response to stress, activated ATP metabolism and inhibition of cell cycle. Our analysis provided a detailed and comprehensive map for further research of the early priming stage of LR in rat.

Predicting long-term outcomes after cardiac arrest by using serum neutrophil gelatinase-associated lipocalin

OBJECTIVES

Neutrophil gelatinase-associated lipocalin (NGAL) is secreted by various tissues in pathologic states. Previous studies reported that post-cardiac arrest serum NGAL levels correlate with short-term neurologic outcomes and survival. The aim of this study was to examine the associations between NGAL levels post-cardiac arrest and long-term outcomes and survival.

METHODS

This prospective observational study and retrospective review included adult out-of-hospital cardiac arrest survivors who were treated by hypothermia-targeted temperature management. Serum NGAL was assessed at 0, 24, 48, and 72h after return of spontaneous circulation. The primary outcome was poor outcome at six months after cardiac arrest, defined as cerebral performance category score of 3-5. The secondary outcome was six-month mortality.

RESULTS

In total, 76 patients were analyzed. The patients with poor outcomes showed significantly higher NGAL levels at 24, 48 and 72h after cardiac arrest than the patients with good outcomes. Long-term survival rates were significantly lower in the high-NGAL group than in the low-NGAL group at each time point. Subgroup analysis of patients who survived 72h showed that only serum NGAL 72h after cardiac arrest had prognostic value for long-term outcomes (area under the receiver operating characteristic curve=0.72; p=0.02).

CONCLUSIONS

Post-cardiac arrest serum NGAL is associated with long-term outcomes and survival; particularly, three days post-cardiac arrest is the optimal time point for predicting long-term outcomes. However, the predictive power of NGAL is unsatisfactory, and it should be regarded as an additional prognostic modality.