STAT1, NF-κB and ERKs play a role in the induction of lipocalin-2 expression in adipocytes

Peripheral-central network analysis of cancer cachexia status accompanied by the polarization of hypothalamic microglia with low expression of inhibitory immune checkpoint receptors

While the excessive inflammation in cancer cachexia is well-known to be induced by the overproduction of inflammatory mediators in the periphery, microflora disruption and brain dysfunction are also considered to contribute to the induction of cancer cachexia. Hypothalamic microglia play a crucial role in brain inflammation and central-peripheral immune circuits via the production of inflammatory mediators. In the present study, we evaluated possible changes in excessive secretion of gut microbiota-derived endotoxin and the expression timeline of several inflammation-regulatory mediators and their inhibiting modulators in hypothalamic microglia of a mouse model of cancer cachexia following transplantation of pancreatic cancer cells. We demonstrated that the plasma level of lipopolysaccharide (LPS) was significantly increased with an increase in anaerobic bacteria, especially Firmicutes, in the gut at the late stage of tumor-bearing mice that exhibited dramatic appetite loss, sarcopenia and severe peripheral immune suppression. At the early stage, in which tumor-bearing mice had not yet displayed "cachexia symptoms", the mRNA expression of pro-inflammatory cytokines, but not of the neurodegenerative and severe inflammatory modulator lipocalin-2 (LCN2), was significantly increased, whereas at the late "cachexia stage", the level of LCN2 mRNA was significantly increased along with significant decreases in levels of inhibitory immune checkpoint receptors programmed death receptor-1 (PD-1) and CD112R in hypothalamic microglia. In addition, a high density of activated neurons in the paraventricular nucleus (PVN) of the hypothalamus region and a significant increase in corticosterone secretion were found in cachexia model mice. Related to the cachexia state, released corticosterone was clearly increased in normal mice with specific activation of PVN neurons. A marked decrease in the natural killer cell population was also observed in the spleen of mice with robust activation of PVN neurons as well as mice with cancer cachexia. On the other hand, in vivo administration of LPS in normal mice induced hypothalamic microglia with low expression of inhibitory immune checkpoint receptors. These findings suggest that the induction of cancer cachexia may parallel exacerbation of the hypothalamic inflammatory status with polarization to microglia expressed with low levels of inhibitory immune checkpoint receptors following LPS release from the gut microflora.

Dynamic changes and clinical value of lipocalin 2 in liver diseases caused by microbial infections

Lipocalin 2 (LCN2) plays a pivotal role in iron metabolism, particularly in the context of microbial infection resistance (e.g., viruses, bacteria, parasites, etc.). LCN2 combats microbial infection by directly assisting the body in competing with microorganisms for iron, inducing immune cells to secrete various cytokines to enhance systemic immune responses, or recruiting neutrophils to infectious sites. The liver serves as the primary organ for LCN2 secretion during microbial infections. This review encapsulates recent advances in dynamic changes, clinical values, and the effects of LCN2 in infectious liver diseases caused by various microbial microorganisms.

Review of lipocalin-2-mediated effects in diabetic retinopathy

BACKGROUND

Studies have uncovered LCN2 as a marker of inflammation strongly related to obesity, insulin resistance, and abnormal glucose metabolism in humans, and is involved in vascular diseases, inflammatory diseases, and neurological diseases. In recent years, studies have shown that elevated levels of LCN2 have a strong association with diabetic retinopathy (DR), but the pathogenesis is unknown. Here, we reviewed the relevant literature and compiled the pathogenesis associated with LCN2-induced DR.

METHODS

We searched PubMed and Web of Science electronic databases using "lipocalin-2, diabetic retinopathy, retinal degeneration, diabetic microangiopathies, diabetic neuropathy and inflammation" as subject terms.

RESULTS

In diabetic retinal neuropathy, LCN2 causes impaired retinal photoreceptor function and retinal neurons; in retinal microangiopathy, LCN2 induces apoptosis of retinal vascular endothelial cells and promotes angiogenesis; in retinal inflammation, increased secretion of LCN2 recruits inflammatory cells and induces pro-inflammatory cytokines. Moreover, LCN2 has the potential as a biomarker for DR. Recent studies have shown that retinal damage can be attenuated by silencing LCN2, which may be associated with the inhibition of caspase-1-mediated pyroptosis, and LCN2 may be a new target for the treatment of DR.

CONCLUSIONS

In conclusion, LCN2, involved in the development of diabetic retinopathy, is a key factor in diabetic retinal microangiopathy, neurodegeneration, and retinal inflammation. LCN2 is likely to be a novel molecular target leading to DR, and a more in-depth study of the pathogenesis of DR caused by LCN2 may provide considerable benefits for clinical research and potential drug development.

Mild Oxidative Stress Induced by Sodium Arsenite Reduces Lipocalin-2 Expression Levels in Cortical Glial Cells

Astrocytes and microglia, the most abundant glial cells in the central nervous system, are involved in maintaining homeostasis in the brain microenvironment and in the progression of various neurological disorders. Lipocalin-2 (LCN2) is a small secretory protein that can be transcriptionally upregulated via nuclear factor kappa B (NF-κB) signaling. It is synthesized and secreted by glial cells, resulting in either the restoration of damaged neural tissues or the induction of neuronal apoptosis in a context-dependent manner. It has recently been reported that when glial cells are under lipopolysaccharide-induced inflammatory stress, either reduced production or accelerated degradation of LCN2 can alleviate neurotoxicity. However, the regulatory mechanisms of LCN2 in glial cells are not yet fully understood. In this study, we used primary astroglial-enriched cells which produce LCN2 and found that the production of LCN2 could be reduced by sodium arsenite treatment. Surprisingly, the reduced LCN2 production was not due to the suppression of NF-κB signaling. Mild oxidative stress induced by sodium arsenite treatment activated antioxidant responses and downregulated Lcn2 expression without reducing the viability of astroglial-enriched cells. Intriguingly, reduced LCN2 production could not be achieved by simple activation of the nuclear factor erythroid-2-related factor 2 (Nrf2)-Kelch-like ECH-associated protein 1 (Keap1) pathway in astroglial-enriched cells. Thus, it appears that mild oxidative stress, occurring in an Nrf2-independent manner, is required for the downregulation of Lcn2 expression. Taken together, our findings provide new insights into the regulatory mechanisms of LCN2 and suggest that mild oxidative stress may alter LCN2 homeostasis, even under neuroinflammatory conditions.

Lipocalin-2: a therapeutic target to overcome neurodegenerative diseases by regulating reactive astrogliosis

Glial cell activation precedes neuronal cell death during brain aging and the progression of neurodegenerative diseases. Under neuroinflammatory stress conditions, lipocalin-2 (LCN2), also known as neutrophil gelatinase-associated lipocalin or 24p3, is produced and secreted by activated microglia and reactive astrocytes. Lcn2 expression levels are known to be increased in various cells, including reactive astrocytes, through the activation of the NF-κB signaling pathway. In the central nervous system, as LCN2 exerts neurotoxicity when secreted from reactive astrocytes, many researchers have attempted to identify various strategies to inhibit LCN2 production, secretion, and function to minimize neuroinflammation and neuronal cell death. These strategies include regulation at the transcriptional, posttranscriptional, and posttranslational levels, as well as blocking its functions using neutralizing antibodies or antagonists of its receptor. The suppression of NF-κB signaling is a strategy to inhibit LCN2 production, but it may also affect other cellular activities, raising questions about its effectiveness and feasibility. Recently, LCN2 was found to be a target of the autophagy‒lysosome pathway. Therefore, autophagy activation may be a promising therapeutic strategy to reduce the levels of secreted LCN2 and overcome neurodegenerative diseases. In this review, we focused on research progress on astrocyte-derived LCN2 in the central nervous system.

Reduced secretion of LCN2 (lipocalin 2) from reactive astrocytes through autophagic and proteasomal regulation alleviates inflammatory stress and neuronal damage

LCN2/neutrophil gelatinase-associated lipocalin/24p3 (lipocalin 2) is a secretory protein that acts as a mammalian bacteriostatic molecule. Under neuroinflammatory stress conditions, LCN2 is produced and secreted by activated microglia and reactive astrocytes, resulting in neuronal apoptosis. However, it remains largely unknown whether inflammatory stress and neuronal loss can be minimized by modulating LCN2 production and secretion. Here, we first demonstrated that LCN2 was secreted from reactive astrocytes, which were stimulated by treatment with lipopolysaccharide (LPS) as an inflammatory stressor. Notably, we found two effective conditions that led to the reduction of induced LCN2 levels in reactive astrocytes: proteasome inhibition and macroautophagic/autophagic flux activation. Mechanistically, proteasome inhibition suppresses NFKB/NF-κB activation through NFKBIA/IκBα stabilization in primary astrocytes, even under inflammatory stress conditions, resulting in the downregulation of Lcn2 expression. In contrast, autophagic flux activation via MTOR inhibition reduced the intracellular levels of LCN2 through its pre-secretory degradation. In addition, we demonstrated that the N-terminal signal peptide of LCN2 is critical for its secretion and degradation, suggesting that these two pathways may be mechanistically coupled. Finally, we observed that LPS-induced and secreted LCN2 levels were reduced in the astrocyte-cultured medium under the above-mentioned conditions, resulting in increased neuronal viability, even under inflammatory stress.Abbreviations: ACM, astrocyte-conditioned medium; ALP, autophagy-lysosome pathway; BAF, bafilomycin A1; BTZ, bortezomib; CHX, cycloheximide; CNS, central nervous system; ER, endoplasmic reticulum; GFAP, glial fibrillary acidic protein; GFP, green fluorescent protein; JAK, Janus kinase; KD, knockdown; LCN2, lipocalin 2; LPS, lipopolysaccharide; MACS, magnetic-activated cell sorting; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; MTOR, mechanistic target of rapamycin kinase; NFKB/NF-κB, nuclear factor of kappa light polypeptide gene enhancer in B cells 1, p105; NFKBIA/IκBα, nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor, alpha; OVEX, overexpression; SLC22A17, solute carrier family 22 member 17; SP, signal peptide; SQSTM1, sequestosome 1; STAT3, signal transducer and activator of transcription 3; TNF/TNF-α, tumor necrosis factor; TUBA, tubulin, alpha; TUBB3/β3-TUB, tubulin, beta 3 class III; UB, ubiquitin; UPS, ubiquitin-proteasome system.

Nerve growth factor receptor (Ngfr) induces neurogenic plasticity by suppressing reactive astroglial Lcn2/Slc22a17 signaling in Alzheimer's disease

Neurogenesis, crucial for brain resilience, is reduced in Alzheimer's disease (AD) that induces astroglial reactivity at the expense of the pro-neurogenic potential, and restoring neurogenesis could counteract neurodegenerative pathology. However, the molecular mechanisms promoting pro-neurogenic astroglial fate despite AD pathology are unknown. In this study, we used APP/PS1dE9 mouse model and induced Nerve growth factor receptor (Ngfr) expression in the hippocampus. Ngfr, which promotes neurogenic fate of astroglia during the amyloid pathology-induced neuroregeneration in zebrafish brain, stimulated proliferative and neurogenic outcomes. Histological analyses of the changes in proliferation and neurogenesis, single-cell transcriptomics, spatial proteomics, and functional knockdown studies showed that the induced expression of Ngfr reduced the reactive astrocyte marker Lipocalin-2 (Lcn2), which we found was sufficient to reduce neurogenesis in astroglia. Anti-neurogenic effects of Lcn2 was mediated by Slc22a17, blockage of which recapitulated the pro-neurogenicity by Ngfr. Long-term Ngfr expression reduced amyloid plaques and Tau phosphorylation. Postmortem human AD hippocampi and 3D human astroglial cultures showed elevated LCN2 levels correlate with reactive gliosis and reduced neurogenesis. Comparing transcriptional changes in mouse, zebrafish, and human AD brains for cell intrinsic differential gene expression and weighted gene co-expression networks revealed common altered downstream effectors of NGFR signaling, such as PFKP, which can enhance proliferation and neurogenesis in vitro when blocked. Our study suggests that the reactive non-neurogenic astroglia in AD can be coaxed to a pro-neurogenic fate and AD pathology can be alleviated with Ngfr. We suggest that enhancing pro-neurogenic astroglial fate may have therapeutic ramifications in AD.

TNFα-induced NLRP3 inflammasome mediates adipocyte dysfunction and activates macrophages through adipocyte-derived lipocalin 2

BACKGROUND AND AIMS

Obesity is a state of chronic low-grade systemic inflammation. Recent studies showed that NLRP3 inflammasome initiates metabolic dysregulation in adipose tissues, primarily through activation of adipose tissue infiltrated macrophages. However, the mechanism of NLRP3 activation and its role in adipocytes remains elusive. Therefore, we aimed to examine the activation of TNFα-induced NLRP3 inflammasome in adipocytes and its role on adipocyte metabolism and crosstalk with macrophages.

METHODS

The effect of TNFα on adipocyte NLRP3 inflammasome activation was measured. Caspase-1 inhibitor (Ac-YVAD-cmk) and primary adipocytes from NLRP3 and caspase-1 knockout mice were utilized to block NLRP3 inflammasome activation. Biomarkers were measured by using real-time PCR, western blotting, immunofluorescence staining, and enzyme assay kits. Conditioned media from TNFα-stimulated adipocytes was used to establish the adipocyte-macrophage crosstalk. Chromatin immunoprecipitation assay was used to identify the role of NLRP3 as a transcription factor. Mouse and human adipose tissues were collected for correlation analysis.

RESULTS

TNFα treatment induced NLRP3 expression and caspase-1 activity in adipocytes, partly through autophagy dysregulation. The activated adipocyte NLRP3 inflammasome participated in mitochondrial dysfunction and insulin resistance, as evidenced by the amelioration of these effects in Ac-YVAD-cmk treated 3T3-L1 cells or primary adipocytes isolated from NLRP3 and caspase-1 knockout mice. Particularly, the adipocyte NLRP3 inflammasome was involved in glucose uptake regulation. Also, TNFα induced expression and secretion of lipocalin 2 (Lcn2) in a NLRP3-dependent manner. NLRP3 could bind to the promoter and transcriptionally regulate Lcn2 in adipocytes. Treatment with adipocyte conditioned media revealed that adipocyte-derived Lcn2 was responsible for macrophage NLRP3 inflammasome activation, working as a second signal. Adipocytes isolated from high-fat diet mice and adipose tissue from obese individuals showed a positive correlation between NLRP3 and Lcn2 gene expression.

CONCLUSIONS

This study highlights the importance of adipocyte NLRP3 inflammasome activation and novel role of TNFα-NLRP3-Lcn2 axis in adipose tissue. It adds rational for the current development of NLRP3 inhibitors for treating obesity-induced metabolic diseases.

The role of lipocalin 2 in brain injury and recovery after ischemic and hemorrhagic stroke

Ischemic and hemorrhagic stroke (including intracerebral hemorrhage, intraventricular hemorrhage, and subarachnoid hemorrhage) is the dominating cause of disability and death worldwide. Neuroinflammation, blood–brain barrier (BBB) disruption, neuronal death are the main pathological progress, which eventually causes brain injury. Increasing evidence indicated that lipocalin 2 (LCN2), a 25k-Da acute phase protein from the lipocalin superfamily, significantly increased immediately after the stroke and played a vital role in these events. Meanwhile, there exists a close relationship between LCN2 levels and the worse clinical outcome of patients with stroke. Further research revealed that LCN2 elimination is associated with reduced immune infiltrates, infarct volume, brain edema, BBB leakage, neuronal death, and neurological deficits. However, some studies revealed that LCN2 might also act as a beneficial factor in ischemic stroke. Nevertheless, the specific mechanism of LCN2 and its primary receptors (24p3R and megalin) involving in brain injury remains unclear. Therefore, it is necessary to investigate the mechanism of LCN2 induced brain damage after stroke. This review focuses on the role of LCN2 and its receptors in brain injury and aiming to find out possible therapeutic targets to reduce brain damage following stroke.

Thromboinflammatory Processes at the Nexus of Metabolic Dysfunction and Prostate Cancer: The Emerging Role of Periprostatic Adipose Tissue

Simple Summary

As overweight and obesity increase among the population worldwide, a parallel increase in the number of individuals diagnosed with prostate cancer was observed. There appears to be a relationship between both diseases where the increase in the mass of fat tissue can lead to inflammation. Such a state of inflammation could produce many factors that increase the aggressiveness of prostate cancer, especially if this inflammation occurred in the fat stores adjacent to the prostate. Another important observation that links obesity, fat tissue inflammation, and prostate cancer is the increased production of blood clotting factors. In this article, we attempt to explain the role of these latter factors in the effect of increased body weight on the progression of prostate cancer and propose new ways of treatment that act by affecting how these clotting factors work.

Abstract

The increased global prevalence of metabolic disorders including obesity, insulin resistance, metabolic syndrome and diabetes is mirrored by an increased incidence of prostate cancer (PCa). Ample evidence suggests that these metabolic disorders, being characterized by adipose tissue (AT) expansion and inflammation, not only present as risk factors for the development of PCa, but also drive its increased aggressiveness, enhanced progression, and metastasis. Despite the emerging molecular mechanisms linking AT dysfunction to the various hallmarks of PCa, thromboinflammatory processes implicated in the crosstalk between these diseases have not been thoroughly investigated. This is of particular importance as both diseases present states of hypercoagulability. Accumulating evidence implicates tissue factor, thrombin, and active factor X as well as other players of the coagulation cascade in the pathophysiological processes driving cancer development and progression. In this regard, it becomes pivotal to elucidate the thromboinflammatory processes occurring in the periprostatic adipose tissue (PPAT), a fundamental microenvironmental niche of the prostate. Here, we highlight key findings linking thromboinflammation and the pleiotropic effects of coagulation factors and their inhibitors in metabolic diseases, PCa, and their crosstalk. We also propose several novel therapeutic targets and therapeutic interventions possibly modulating the interaction between these pathological states.

Maternal serum NGAL in the first trimester of pregnancy is a potential biomarker for the prediction of gestational diabetes mellitus

OBJECTIVE

Gestational diabetes mellitus (GDM) has adverse effects on the health of mothers and their offspring. Currently, no known biomarker has been proven to have sufficient validity for the prediction of GDM in the first trimester of pregnancy. The aim of this study was to investigate the potential relationship between serum neutrophil gelatinase-associated lipocalin (NGAL) levels in the first trimester of pregnancy and later GDM risk and to evaluate the performance of serum NGAL as a biomarker for the prediction of GDM.

METHODS

The study was conducted by recruiting participants at 8-13 weeks of gestation from The First Affiliated Hospital of Chengdu Medical College between January and June 2021; participants were followed up for oral glucose tolerance test (OGTT) screening at 24-28 gestational weeks. We examined the serum NGAL levels of all subjects in the first trimester who met the inclusion and exclusion criteria. Anthropometric, clinical, and laboratory parameters of the study subjects were obtained during the same study period. A logistic regression model was carried out to investigate the potential relationship between serum NGAL levels in the first trimester of pregnancy and later GDM risk. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to assess the discrimination and calibration of serum NGAL as a biomarker for the prediction of GDM in the first trimester of pregnancy.

RESULTS

Serum NGAL levels in the first trimester of pregnancy were significantly higher in women who later developed GDM than in those who did not develop GDM. Serum NGAL levels in the first trimester of pregnancy were positively associated with an increased risk of GDM after adjustment for potential confounding factors. The risk prediction model for GDM constructed by using serum NGAL levels in the first trimester of pregnancy achieved excellent performance.

CONCLUSIONS

Maternal serum NGAL in the first trimester of pregnancy is a potential biomarker for the prediction of GDM, which could help guide the clinical practice of antenatal care.

Adipokines, Hepatokines and Myokines: Focus on Their Role and Molecular Mechanisms in Adipose Tissue Inflammation

Chronic low-grade inflammation in adipose tissue (AT) is a hallmark of obesity and contributes to various metabolic disorders, such as type 2 diabetes and cardiovascular diseases. Inflammation in ATs is characterized by macrophage infiltration and the activation of inflammatory pathways mediated by NF-κB, JNK, and NLRP3 inflammasomes. Adipokines, hepatokines and myokines - proteins secreted from AT, the liver and skeletal muscle play regulatory roles in AT inflammation via endocrine, paracrine, and autocrine pathways. For example, obesity is associated with elevated levels of pro-inflammatory adipokines (e.g., leptin, resistin, chemerin, progranulin, RBP4, WISP1, FABP4, PAI-1, Follistatin-like1, MCP-1, SPARC, SPARCL1, and SAA) and reduced levels of anti-inflammatory adipokines such as adiponectin, omentin, ZAG, SFRP5, CTRP3, vaspin, and IL-10. Moreover, some hepatokines (Fetuin A, DPP4, FGF21, GDF15, and MANF) and myokines (irisin, IL-6, and DEL-1) also play pro- or anti-inflammatory roles in AT inflammation. This review aims to provide an updated understanding of these organokines and their role in AT inflammation and related metabolic abnormalities. It serves to highlight the molecular mechanisms underlying the effects of these organokines and their clinical significance. Insights into the roles and mechanisms of these organokines could provide novel and potential therapeutic targets for obesity-induced inflammation.

The effect of lipocalin-2 (LCN2) on apoptosis: a proteomics analysis study in an LCN2 deficient mouse model

BACKGROUND

Recent studies have shown that lipocalin-2 (LCN2) has multiple functions involved in various biological and pathological processes including energy homeostasis, cancer, inflammation, and apoptosis. We aimed to investigate the effect of LCN2 on apoptosis that influences the pathogenetic process of metabolic diseases and cancer.

METHODS

We performed a proteomics analysis of livers taken from LCN2-knockout mice and wild type mice by using label-free LC-MS/MS quantitative proteomics.

RESULTS

Proteomic analysis revealed that there were 132 significantly differentially expressed proteins (49 upregulated and 83 downregulated) among 2140 proteins in the liver of LCN2-knockout mice compared with wild type mice. Of these, seven apoptosis-associated proteins were significantly upregulated and seven apoptosis-associated proteins downregulated.

CONCLUSION

Proteomics demonstrated that there were seven upregulated and seven downregulated apoptosis-associated proteins in liver of LCN2-knockout mice. It is important to clarify the effect of LCN2 on apoptosis that might contribute to the pathogenesis of insulin resistance, cancer, and various nervous system diseases.

Chronic IL-1 Exposed AR+ PCa Cell Lines Show Conserved Loss of IL-1 Sensitivity and Evolve Both Conserved and Unique Differential Gene Expression Profiles

INTRODUCTION

Inflammation drives prostate cancer (PCa) progression. While inflammation is a cancer hallmark, the underlying mechanisms mediating inflammation-induced PCa are still under investigation. Interleukin-1 (IL-1) is an inflammatory cytokine that promotes cancer progression, including PCa metastasis and castration resistance. We previously found that acute IL-1 exposure represses PCa androgen receptor (AR) expression concomitant with the upregulation of pro-survival proteins, causing de novo accumulation of castration-resistant PCa cells. However, acute inflammation is primarily anti-tumorigenic, while chronic inflammation is pro-tumorigenic. Thus, using the LNCaP PCa cell line as model, we found that PCa cells can evolve insensitivity to chronic IL-1 exposure, restoring AR and AR activity and acquiring castration resistance. In this paper we expanded our chronic IL-1 model to include the MDA-PCa-2b PCa cell line to investigate the response to acute versus chronic IL-1 exposure and to compare the gene expression patterns that evolve in the LNCaP and MDA-PCa-2b cells chronically exposed to IL-1.

METHODS

We chronically exposed MDA-PCa-2b cells to IL-1α or IL-1β for several months to establish sublines. Once established, we determined subline sensitivity to exogenous IL-1 using cell viability assay, RT-qPCR and western blot. RNA sequencing was performed for parental and subline cells and over representation analysis (ORA) for geneset enrichment of biological process/pathway was performed.

RESULTS

MDA-PCa-2b cells repress AR and AR activity in response to acute IL-1 exposure and evolve insensitivity to chronic IL-1 exposure. While cell biological and molecular response to acute IL-1 signaling is primarily conserved in LNCaP and MDA-PCa-2b cells, including upregulation of NF-κB signaling and downregulation of cell proliferation, the LNCaP and MDA-PCa-2b cells evolve conserved and unique molecular responses to chronic IL-1 signaling that may promote or support tumor progression.

CONCLUSIONS

Our chronic IL-1 subline models can be used to identify underlying molecular mechanisms that mediate IL-1-induced PCa progression.

Lipocalin 2 Is a Regulator During Macrophage Polarization Induced by Soluble Worm Antigens

Caused by schistosomes, the human schistosomiasis is a tropical zoonotic parasitic disease. Pathologically, it occurs most often in the intestines and the liver, the sites of Schistosoma japonicum egg accumulation. The parasites' produced eggs cause the main pathology in patients. Deposited parasite eggs in the liver induce the production of multiple cytokines that mediate the immune response, which in turn leads to granulomatous responses and liver fibrosis. These impact the hosts' quality of life and health status, resulting in severe morbidity and even mortality. In this study, differentially expressed genes (DEGs) between ordinary samples and three 6- week infected mice were mined from microarray analysis based on the limma package. In total, we excavated the differential expression LCN2 was exhibited high expressions profile in GSE59276, GSE61376 demonstrated the result. Furthermore, CIBERSORT suggested detailed analysis of the immune subtype distribution pattern. In vivo experiments like real-time quantitative PCR, immunohistochemical (IHC) staining, and immunofluorescence (IF) demonstrated the expressions of LCN2 was significantly upregulated in S. japonicum-infected mice liver tissues and located in macrophages. Previous studies have shown that macrophages act as the first line of defense during schistosome infection and are an important part of liver granuloma. We used S. japonicum soluble worm antigens (SWA) to induce RAW264.7 cells to construct an in vitro inflammatory model. The current study aimed to investigate whether the NF-κB signaling network is involved in LCN2 upregulation induced by SWA and whether LCN2 can promote M1 polarization of macrophages under SWA treatment. Our research work suggests that LCN2 is significant in the development of early infection caused by S. japonicum and is of great value for further exploration. Collectively, the findings indicated that SWA promoted the expression of LCN2 and promoted M1 polarization of macrophages via the upregulation of NF-κB signaling pathway. Our findings demonstrate that NF-κB/LCN2 is necessary for migration and phagocytosis of M1 macrophages in response to SWA infection. Our study highlights the essential role of NF-κB/LCN2 in early innate immune response to infection.

Lipocalin-2: Structure, function, distribution and role in metabolic disorders

Lipocalin-2 (LCN-2) is a novel, 198 amino acid adipocytokine also referred to as neutrophil gelatinase-associated lipocalin (NGAL). LCN-2 is a circulatory protein responsible for the transportation of small and hydrophobic molecules (steroid, free fatty acids, prostaglandins and hormones) to target organs after binding to megalin/glycoprotein and GP330 SLC22A17 or 24p3R LCN-2 receptors. LCN-2 has been used as a biomarker for acute and chronic renal injury. It is present in a large variety of cells including neutrophil, hepatocytes, lung, bone marrow, adipose tissue, macrophages, thymus, non-neoplastic breast duct, prostate, and renal cells. Different functions have been associated with LCN-2. These functions include antibacterial, anti-inflammatory, and protection against cell and tissue stress. Moreover, LCN-2 can increase the pool of matrix metalloproteinase 9 in human neutrophil granulocytes. Other reported functions of LCN-2 include its ability to destroy the extracellular matrix, which could enable cancer progression and spread of metastasis. Recent reports show that the tissue level of LCN-2 is increased in metabolic disorders such as obesity and type 2 diabetes, suggesting an association between LCN-2 and insulin sensitivity and glucose homeostasis. The precise role of LCN-2 in the modulation of insulin sensitivity, glucose and lipid metabolism is still unclear. This review explores the structure of LCN-2, tissue distribution, and its interaction with important metabolic pathways.

The Unfolded Protein Response Is a Major Driver of LCN2 Expression in BCR-ABL- and JAK2V617F-Positive MPN

Lipocalin 2 (LCN2), a proinflammatory mediator, is involved in the pathogenesis of myeloproliferative neoplasms (MPN). Here, we investigated the molecular mechanisms of LCN2 overexpression in MPN. LCN2 mRNA expression was 20-fold upregulated in peripheral blood (PB) mononuclear cells of chronic myeloid leukemia (CML) and myelofibrosis (MF) patients vs. healthy controls. In addition, LCN2 serum levels were significantly increased in polycythemia vera (PV) and MF and positively correlated with JAK2V617F and mutated CALR allele burden and neutrophil counts. Mechanistically, we identified endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) as a main driver of LCN2 expression in BCR-ABL- and JAK2V617F-positive 32D cells. The UPR inducer thapsigargin increased LCN2 expression >100-fold, and this was not affected by kinase inhibition of BCR-ABL or JAK2V617F. Interestingly, inhibition of the UPR regulators inositol-requiring enzyme 1 (IRE1) and c-Jun N-terminal kinase (JNK) significantly reduced thapsigargin-induced LCN2 RNA and protein expression, and luciferase promoter assays identified nuclear factor kappa B (NF-κB) and CCAAT binding protein (C/EBP) as critical regulators of mLCN2 transcription. In conclusion, the IRE1-JNK-NF-κB-C/EBP axis is a major driver of LCN2 expression in MPN, and targeting UPR and LCN2 may represent a promising novel therapeutic approach in MPN.

NLRP3 Triggers Attenuate Lipocalin-2 Expression Independent with Inflammasome Activation

Lipocalin-2 (LCN2), a small secretory glycoprotein, is upregulated by toll-like receptor (TLR) signaling in various cells and tissues. LCN2 inhibits bacterial growth by iron sequestration and regulates the innate immune system. Inflammasome activates the inflammatory caspases leading to pyroptosis and cytokine maturation. This study examined the effects of inflammasome activation on LCN2 secretion in response to TLR signaling. The triggers of NLRP3 inflammasome activation attenuated LCN2 secretion while it induced interleukin-1β in mouse macrophages. In mice, NLRP3 inflammasome activation inhibited TLR-mediated LCN2 secretion. The inhibition of NLRP3 triggers on LCN2 secretion was caused by the inhibited transcription and translation of LCN2. At the same time, no changes in the other cytokines and IκBζ, a well-known transcriptional factor of Lcn2 transcription, were observed. Overall, NLRP3 triggers are a regulator of LCN2 expression suggesting a new linkage of inflammasome activation and LCN2 secretion in the innate immunity.

Lipocalin 2 regulates iron homeostasis, neuroinflammation, and insulin resistance in the brains of patients with dementia: Evidence from the current literature

Dementia accompanied by memory loss is considered one of the most common neurodegenerative diseases worldwide, and its prevalence is gradually increasing. Known risk factors for dementia include genetic background, certain lifestyle and dietary patterns, smoking, iron overload, insulin resistance, and impaired glucose metabolism in the brain. Here, we review recent evidence on the regulatory role of lipocalin 2 (LCN2) in dementia from various perspectives. LCN2 is a neutrophil gelatinase-associated protein that influences diverse cellular processes, including the immune system, iron homeostasis, lipid metabolism, and inflammatory responses. Although its functions within the peripheral system are most widely recognized, recent findings have revealed links between LCN2 and central nervous system diseases, as well as novel roles for LCN2 in neurons and glia. Furthermore, LCN2 may modulate diverse pathological mechanisms involved in dementia. Taken together, LCN2 is a promising therapeutic target with which to address the neuropathology of dementia.

Potential type 2 diabetes mellitus drug HMPA promotes short-chain fatty acid production by improving carbon catabolite repression effect of gut microbiota

BACKGROUND AND PURPOSE

Gut microbiota plays an important role in type 2 diabetes mellitus (T2DM) progression. From our previous work N-(4-Hydroxyphenethyl)-3-mercapto-2-methylpropanamide (HMPA) is a potential T2DM drug. We evaluated the effect of HMPA on gut microbiota and studied the molecular mechanism underlying HMPA's regulation of gut microbiota.

EXPERIMENTAL APPROACH

The pseudo germ-free (PGF) T2DM model and faecal microbiota transplantation method were used to study whether gut microbiota mediates the actions of HMPA. The composition of gut microbiota was detected by using 16S rRNA sequence. Short-chain fatty acids (SCFAs) content was detected by gas chromatography. The HMPA probe was synthesised for finding and identifying the target protein of HMPA. The effect of HMPA on the utilisation of carbon sources in Bifidobacterium was evaluated.

KEY RESULTS

HMPA has a slight effect on the PGF T2DM model. The gut microbiota changed by HMPA can also alleviate the symptoms of T2DM. HMPA can regulate gut microbiota structure, increase SCFAs production and reduce nitrate content in the intestinal tissues. The thickness of the mucus on colon tissues increases after HMPA treatment. The target protein of HMPA in gut microbiota is the nitrogen metabolism global transcriptional regulator (GlnR). HMPA promotes the utilisation of less preferred carbon source in the gut microbiota and increases the fermentation product of SCFAs.

CONCLUSION AND IMPLICATIONS

HMPA plays a hypoglycaemic role through the gut microbiota. HMPA improves the carbon catabolite repression effect of gut microbiota and increases SCFAs production by targeting GlnR. GlnR may be a target for gut microbiota regulation.

Ginsenoside ameliorated ventilator-induced lung injury in rats

Background

Ginsenosides have antioxidant and anti-inflammatory features. This study aimed to evaluate the biologic effects of ginsenoside Rb2 pretreatment on ventilator-induced lung injury (VILI) in rats.

Methods

Rats were divided into four groups with 12 rats per group: control; low tidal volume (TV), TV of 6 mL/kg, VILI, TV of 20 mL/kg, positive end-expiratory pressure of 5 cm H₂O, and respiratory rate of 60 breaths per minute for 3 h at an inspiratory oxygen fraction of 0.21; and ginsenosides, treated the same as the VILI group but with 20 mg/kg intraperitoneal ginsenoside pretreatment. Morphology was observed with a microscope to confirm the VILI model. Wet-to-dry weight ratios, protein concentrations, and pro-inflammatory cytokines in the bronchoalveolar lavage fluid were measured. RNA sequencing of the lung tissues was conducted to analyze gene expression.

Results

High TV histologically induced VILI with alveolar edema and infiltration of inflammatory cells. Ginsenosides pretreatment significantly reduced the histologic lung injury score compared to the VILI group. Wet-to-dry weight ratios, malondialdehyde, and TNF-α in bronchoalveolar lavage fluid were significantly higher in the VILI group and ginsenoside pretreatment mitigated these effects. In the immunohistochemistry assay, ginsenoside pretreatment attenuated the TNF-α upregulation induced by VILI. We identified 823 genes differentially presented in the VILI group compared to the control group. Of the 823 genes, only 13 genes (Arrdc2, Cygb, Exnef, Lcn2, Mroh7, Nsf, Rexo2, Srp9, Tead3, Ephb6, Mvd, Sytl4, and Ube2l6) recovered to control levels in the ginsenoside group.

Conclusions

Ginsenosides inhibited the inflammatory and oxidative stress response in VILI. Further studies are required on the 13 genes, including LCN2.

Mechanisms of Artemisia scoparia's Anti-Inflammatory Activity in Cultured Adipocytes, Macrophages, and Pancreatic β-Cells

OBJECTIVE

An ethanolic extract of Artemisia scoparia (SCO) improves adipose tissue function and reduces negative metabolic consequences of high-fat feeding. A. scoparia has a long history of medicinal use across Asia and has anti-inflammatory effects in various cell types and disease models. The objective of the current study was to investigate SCO's effects on inflammation in cells relevant to metabolic health.

METHODS

Inflammatory responses were assayed in cultured adipocytes, macrophages, and insulinoma cells by quantitative polymerase chain reaction, immunoblotting, and NF-κB reporter assays.

RESULTS

In tumor necrosis factor α-treated adipocytes, SCO mitigated ERK and NF-κB signaling as well as transcriptional responses but had no effect on fatty acid-binding protein 4 secretion. SCO also reduced levels of deleted in breast cancer 1 protein in adipocytes and inhibited inflammatory gene expression in stimulated macrophages. Finally, in pancreatic β-cells, SCO decreased NF-κB-responsive promoter activity induced by IL-1β treatment.

CONCLUSIONS

SCO's ability to promote adipocyte development and function is thought to mediate its insulin-sensitizing actions in vivo. Our findings that SCO inhibits inflammatory responses through at least two distinct signaling pathways (ERK and NF-κB) in three cell types known to contribute to metabolic disease reveal that SCO may act more broadly than previously thought to improve metabolic health.

TNF-α controls Lipocalin-2 expression in PC-3 prostate cancer cells

Prostate cancer (PCa) is one of the most common and deadly cancers in men worldwide. The surrounding tumor microenvironment (TME) is important in tumor progression, as cytokines and soluble mediators including tumor necrosis factor (TNF-α) or lipocalin-2 (LCN2) can influence tumor growth and formation of metastasis. The exact mechanisms on how these pleiotropic factors affect PCa are still unknown. In this study, we showed for the first time that LCN2 mRNA and protein expression are strongly inducible by TNF-α in the highly metastatic human PCa cell line PC-3. In addition, we observed higher levels of secreted LCN2 in cell culture medium of TNF-α-treated PC-3 cells. We found that different signaling pathways such as p38, NF-κB or JNK were activated shortly after TNF-α treatment. Moreover, the mRNA levels of IL-1β and IL-8 were also significantly increased after 24 h stimulation. Mechanistically, the NF-κB pathway and the JNK signaling axis are directly responsible for LCN2 upregulation. This was shown by the fact that pretreatment with the JNK inhibitors SP600125 or JNK-IN-8 strongly downregulated phosphorylation of c-Jun protein and markedly reduced TNF-α-mediated LCN2 upregulation in PC-3 cells. Likewise, the NF-κB inhibitor QNZ was able to repress TNF-α-induced LCN2 expression in PC-3 cells. Taking into consideration that LCN2 has been described as a tumor promoting factor in PCa, our results indicate that JNK regulates LCN2 expression and unmasks the JNK signaling axis as a possible therapeutic target for patients with PCa.

Transcription factor 7-like 2 promotes osteogenic differentiation and boron-induced bone repair via lipocalin 2

Boron-containing mesoporous bioactive glass (B-MBG) scaffolds could be capable of promoting osteogenesis by activating Wnt/β-catenin signaling pathway during the process of bone defect repair. Despite this, more involving molecular controls are still largely unclear. In the present study, we identified that the downstream of Wnt/β-catenin signaling pathway named transcription factor 7-like 2 (TCF7L2) served as a key effector to promote boron-induced bone regeneration and osteogenesis through lipocalin 2 (LCN2). TCF7L2 was highly expressed in osteoblasts when treated with B-MBG scaffold extraction than MBG. LCN2, as a secreted bone factor, positively affected osteogenic differentiation of MC3T3-E1 and osteogenesis in vivo, which could be induced by TCF7L2. In addition, interference of TCF7L2 decreased the osteogenic differentiation of osteoblasts. Finally, we identified that rLCN2 could rescue the poor ability of osteogenic differentiation of MC3T3-E1 whose Tcf7l2 gene was knocked down by lentiviral transfection of shRNA. Our findings provide some new insights into the molecular controls of boron-associated bone regeneration and potential therapeutic targets for the treatment of bone defects.

Dendritic polyglycerols are modulators of microglia-astrocyte crosstalk

Aim: To determine the ability of sulfated dendritic polyglycerols (dPGS) to modulate neuroglia activation challenged with lipopolysaccharide (LPS). Materials & methods: Microglia/astrocyte activation in vivo was determined in transgenic animals expressing TLR2-/GFAP-luciferase reporter. Mechanisms implicated in microglia-astrocyte crosstalk were studied in primary mouse brain cultures. Results & discussion: dPGS significantly reduced microglia activation in vivo, and decreased astrocytic LCN2 production. Activated microglia are necessary for astrocyte stimulation and increase in LCN2 abundance. LCN2 production in astrocytes involves signaling via toll-like receptor 4, activation of NF-κB, IL6 and enhancement of reactive oxygen species. Conclusion: dPGS are powerful modulators of microglia-astrocyte crosstalk and LCN2 abundance; dPGS are promising anti-inflammatory dendritic nanostructures.

Neutrophils homing into the retina trigger pathology in early age-related macular degeneration

Age-related macular degeneration (AMD) is an expanding problem as longevity increases worldwide. While inflammation clearly contributes to vision loss in AMD, the mechanism remains controversial. Here we show that neutrophils are important in this inflammatory process. In the retinas of both early AMD patients and in a mouse model with an early AMD-like phenotype, we show neutrophil infiltration. Such infiltration was confirmed experimentally using ribbon-scanning confocal microscopy (RSCM) and IFNλ- activated dye labeled normal neutrophils. With neutrophils lacking lipocalin-2 (LCN-2), infiltration was greatly reduced. Further, increased levels of IFNλ in early AMD trigger neutrophil activation and LCN-2 upregulation. LCN-2 promotes inflammation by modulating integrin β1 levels to stimulate adhesion and transmigration of activated neutrophils into the retina. We show that in the mouse model, inhibiting AKT2 neutralizes IFNλ inflammatory signals, reduces LCN-2-mediated neutrophil infiltration, and reverses early AMD-like phenotype changes. Thus, AKT2 inhibitors may have therapeutic potential in early, dry AMD.

Paradoxical role of lipocalin-2 in metabolic disorders and neurological complications

Lipocalin-2 (LCN2), also known as 24p3 and neutrophil gelatinase-associated lipocalin (NGAL), is a 25-kDa secreted protein implicated in various metabolic and inflammatory diseases. Early studies suggest the protective function of LCN2 in which it acts as a bacteriostatic agent that competes with bacteria for iron-bound siderophores. However, both detrimental and beneficial roles of LCN2 have recently been documented in metabolic and neuroinflammatory diseases. Metabolic inflammation, as observed in diabetes and obesity, has been closely associated with the upregulation of LCN2 in blood plasma and several tissues in both humans and rodents, suggesting its pro-diabetic and pro-obesogenic role. On the contrary, other studies imply an anti-diabetic and anti-obesogenic role of LCN2 whereby a deficiency in the Lcn2 gene results in the impairment of insulin sensitivity and enhances the high-fat-diet-induced expansion of fat. A similar dual role of LCN2 has also been reported in various animal models for neurological disorders. In the midst of these mixed findings, there is no experimental evidence to explain why LCN2 shows such a contrasting role in the various studies. This debate needs to be resolved (or reconciled) and an integrated view on the topic is desirable. Herein, we attempt to address this issue by reviewing the recent findings on LCN2 in metabolic disorders and assess the potential cellular or molecular mechanisms underlying the dual role of LCN2. We further discuss the possibilities and challenges of targeting LCN2 as a potential therapeutic strategy for metabolic disorders and neurological complications.

Adipose Tissue Dysfunction Occurs Independently of Obesity in Adipocyte-Specific Oncostatin Receptor Knockout Mice

OBJECTIVE

This study examined the phenotypic effects of adipocyte-specific oncostatin M receptor (OSMR) loss in chow-fed mice.

METHODS

Chow-fed adipocyte-specific OSMR knockout (FKO) mice and littermate OSMR^fl/fl controls were studied. Tissue weights, insulin sensitivity, adipokine production, and stromal cell immunophenotypes were assessed in epididymal fat (eWAT); serum adipokine production was also assessed. In vitro, adipocytes were treated with oncostatin M, and adipokine gene expression was assessed.

RESULTS

Body weights, fasting blood glucose levels, and eWAT weights did not differ between genotypes. However, the eWAT of OSMR^FKO mice was modestly less responsive to insulin stimulation than that of OSMR^fl/fl mice. Notably, significant increases in adipokines, including C-reactive protein, lipocalin 2, intercellular adhesion molecule-1, and insulinlike growth factor binding protein 6, were observed in the eWAT of OSMR^FKO mice. In addition, significant increases in fetuin A and intercellular adhesion molecule-1 were detected in OSMR^FKO serum. Flow cytometry revealed a significant increase in leukocyte number and modest, but not statistically significant, increases in B cells and T cells in the eWAT of OSMR^FKO mice.

CONCLUSIONS

The chow-fed OSMR^FKO mice exhibited adipose tissue dysfunction and increased proinflammatory adipokine production. These results suggest that intact adipocyte oncostatin M-OSMR signaling is necessary for adipose tissue immune cell homeostasis.

Recapitulation of pharmacogenomic data reveals that invalidation of SULF2 enhance sorafenib susceptibility in liver cancer

Gene mutations play critical roles during cancer development and progression, and therefore represent targets for precision medicine. Here we recapitulated the pharmacogenomic data to delineate novel candidates for actionable mutations and therapeutic target drugs. As a proof-of-concept, we demonstrated that the loss-of-function of SULF2 by mutation (N491K) or inhibition enhanced sorafenib sensitivity in liver cancer cells and in vivo mouse models. This effect was mediated by deregulation of EGFR signaling and downstream expression of LCN2. We also report that the liver cancer patients non-responding to sorafenib treatment exhibit higher expression of SULF2 and LCN2. In conclusion, we suggest that SULF2 plays a key role in sorafenib susceptibility and resistance in liver cancer via deregulation of LCN2. Diagnostic or therapeutic targeting of SULF2 (e.g., OKN-007) and/or LCN2 can be a novel precision strategy for sorafenib treatment in cancer patients.

N-Glycosylation of Lipocalin 2 Is Not Required for Secretion or Exosome Targeting

Lipocalin 2 (LCN2) is a highly conserved secreted adipokine acting as a serum transport protein for small hydrophobic molecules such as fatty acids and steroids. In addition, LCN2 limits bacterial growth by sequestering iron-containing siderophores and further protects against intestinal inflammation and tumorigenesis associated with alterations in the microbiota. Human LCN2 contains one N-glycosylation site conserved in other species. It was postulated that this post-translational modification could facilitate protein folding, protects from proteolysis, is required for proper trafficking from the Golgi apparatus to the cell surface, and might be relevant for effective secretion. We here show that the homologous nucleoside antibiotic tunicamycin blocks N-linked glycosylation but not secretion of LCN2 in primary murine hepatocytes, derivatives thereof, human lung carcinoma cell line A549, and human prostate cancer cell line PC-3. Moreover, both the glycosylated and the non-glycosylated LCN2 variants are equally targeted to exosomes, demonstrating that this post-translational modification is not necessary for proper trafficking of LCN2 into these membranous extracellular vesicles. Furthermore, a hydrophobic cluster analysis revealed that the N-glycosylation site is embedded in a highly hydrophobic evolutionarily conserved surrounding. In sum, our data indicate that the N-glycosylation of LCN2 is not required for proper secretion and exosome cargo recruitment in different cell types, but might be relevant to increase overall solubility.

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.

Characterization and expression patterns of ERK1 and ERK2 from Epinephelus coioides against Cryptocaryon irritans infection

Mitogen-activated protein kinases (MAPKs), a group of serine-threonine protein kinases, play a crucial role in immunoreaction response to extra environmental stresses. In this study, two novel MAPKs, Ec-ERK1 and Ec-ERK2, were identified from Epinephelus coioides. Both Ec-ERK1 and Ec-ERK2 sequences contain a highly conserved Thr-Glu-Tyr (TEY) motif, an HRD domain, and an ATP binding loop containing GXGXXG. An analysis of phylogenetic relationships demonstrated that ERK amino acid sequences were conserved between different species indicating that the functions may be similar. Ec-ERK1 and Ec-ERK2 mRNA can be detected in all thirteen tissues examined, but the expression level is different in these tissues. The expression patterns of these two genes in E. coioides were also detected against Cryptocaryon irritans infection, which is capable of killing large numbers of fish in a short time and has a serious impact on aquaculture. The expression was up-regulated in most of the tissues examined, with the highest expressions of Ec-ERK1 (3.9 times) occurring in the head kidney and Ec-ERK2 (3.5 times) occurring in the spleen. There was no significant correlation between the expression of Ec-ERK1/Ec-ERK2 and the expression of nuclear factor kappaB (NF-kB). The results indicated the sequences and the characters of Ec-ERK1/ERK2 were conserved, Ec-ERK1/ERK2 showed tissue-specific expression patterns in healthy grouper, and their expressions were significantly varied post C. irritans infection, suggesting Ec-ERK1/ERK2 may play important roles in these tissues during pathogen-caused inflammation.

TBK1 at the Crossroads of Inflammation and Energy Homeostasis in Adipose Tissue

The noncanonical IKK family member TANK-binding kinase 1 (TBK1) is activated by pro-inflammatory cytokines, but its role in controlling metabolism remains unclear. Here, we report that the kinase uniquely controls energy metabolism. Tbk1 expression is increased in adipocytes of HFD-fed mice. Adipocyte-specific TBK1 knockout (ATKO) attenuates HFD-induced obesity by increasing energy expenditure; further studies show that TBK1 directly inhibits AMPK to repress respiration and increase energy storage. Conversely, activation of AMPK under catabolic conditions can increase TBK1 activity through phosphorylation, mediated by AMPK's downstream target ULK1. Surprisingly, ATKO also exaggerates adipose tissue inflammation and insulin resistance. TBK1 suppresses inflammation by phosphorylating and inducing the degradation of the IKK kinase NIK, thus attenuating NF-κB activity. Moreover, TBK1 mediates the negative impact of AMPK activity on NF-κB activation. These data implicate a unique role for TBK1 in mediating bidirectional crosstalk between energy sensing and inflammatory signaling pathways in both over- and undernutrition.

Cell-specific and region-specific transcriptomics in the multiple sclerosis model: Focus on astrocytes

Changes in gene expression that occur across the central nervous system (CNS) during neurological diseases do not address the heterogeneity of cell types from one CNS region to another and are complicated by alterations in cellular composition during disease. Multiple sclerosis (MS) is multifocal by definition. Here, a cell-specific and region-specific transcriptomics approach was used to determine gene expression changes in astrocytes in the most widely used MS model, experimental autoimmune encephalomyelitis (EAE). Astrocyte-specific RNAs from various neuroanatomic regions were attained using RiboTag technology. Sequencing and bioinformatics analyses showed that EAE-induced gene expression changes differed between neuroanatomic regions when comparing astrocytes from spinal cord, cerebellum, cerebral cortex, and hippocampus. The top gene pathways that were changed in astrocytes from spinal cord during chronic EAE involved decreases in expression of cholesterol synthesis genes while immune pathway gene expression in astrocytes was increased. Optic nerve from EAE and optic chiasm from MS also showed decreased cholesterol synthesis gene expression. The potential role of cholesterol synthesized by astrocytes during EAE and MS is discussed. Together, this provides proof-of-concept that a cell-specific and region-specific gene expression approach can provide potential treatment targets in distinct neuroanatomic regions during multifocal neurological diseases.

Activating the AKT2-nuclear factor-κB-lipocalin-2 axis elicits an inflammatory response in age-related macular degeneration

Age-related macular degeneration (AMD) is a complex and progressive degenerative eye disease resulting in severe loss of central vision. Recent evidence indicates that immune system dysregulation could contribute to the development of AMD. We hypothesize that defective lysosome-mediated clearance causes accumulation of waste products in the retinal pigmented epithelium (RPE), activating the immune system and leading to retinal tissue injury and AMD. We have generated unique genetically engineered mice in which lysosome-mediated clearance (both by phagocytosis and autophagy) in RPE cells is compromised, causing the development of features of early AMD. Our recent data indicate a link between lipocalin-2 (LCN-2) and the inflammatory responses induced in this mouse model. We show that nuclear factor-κB (NF-κB) and STAT-1 may function as a complex in our animal model system, together controlling the upregulation of LCN-2 expression in the retina and stimulating an inflammatory response. This study revealed increased infiltration of LCN-2-positive neutrophils in the choroid and retina of early AMD patients as compared with age-matched controls. Our results demonstrate that, both in our animal model and in human AMD, the AKT2-NF-κB-LCN-2 signalling axis is involved in activating the inflammatory response, making this pathway a potential target for AMD treatment. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Chronic diazepam administration increases the expression of Lcn2 in the CNS

Benzodiazepines (BZDs), which bind with high affinity to gamma-aminobutyric acid type A receptors (GABA_A-Rs) and potentiate the effects of GABA, are widely prescribed for anxiety, insomnia, epileptic discharge, and as anticonvulsants. The long-term use of BZDs is limited due to adverse effects such as tolerance, dependence, withdrawal effects, and impairments in cognition and learning. Additionally, clinical reports have shown that chronic BZD treatment increases the risk of Alzheimer's disease. Unusual GABA_A-R subunit expression and GABA_A-R phosphorylation are induced by chronic BZD use. However, the gene expression and signaling pathways related to these effects are not completely understood. In this study, we performed a microarray analysis to investigate the mechanisms underlying the effect of chronic BZD administration on gene expression. Diazepam (DZP, a BZD) was chronically administered, and whole transcripts in the brain were analyzed. We found that the mRNA expression levels were significantly affected by chronic DZP administration and that lipocalin 2 (Lcn2) mRNA was the most upregulated gene in the cerebral cortex, hippocampus, and amygdala. Lcn2 is known as an iron homeostasis-associated protein. Immunostained signals of Lcn2 were detected in neuron, astrocyte, microglia, and Lcn2 protein expression levels were consistently upregulated. This upregulation was observed without proinflammatory genes upregulation, and was attenuated by chronic treatment of deferoxamine mesylate (DFO), iron chelator. Our results suggest that chronic DZP administration regulates transcription and upregulates Lcn2 expression levels without an inflammatory response in the mouse brain. Furthermore, the DZP-induced upregulation of Lcn2 expression was influenced by ambient iron.

2-deoxyglucose inhibits induction of chemokine expression in 3T3-L1 adipocytes and adipose tissue explants

OBJECTIVE

To determine the influence of glycolytic inhibition on the adipocyte inflammatory response.

METHODS

To determine the effect of 2-deoxyglucose (2-DOG) on the inflammatory response, mature 3T3-L1 adipocytes were co-treated with 2-DOG and LPS or TNF. To determine the effect of endoplasmic reticulum stress on TNF-induced induction of chemokines, adipocytes were pretreated with thapsigargin or salubrinal. Chemokine mRNA levels were determined using quantitative real-time PCR, and secretion of CCL2 was determined by Western blot.

RESULTS

2-DOG treatment reduced the ability of LPS and TNF to induce CCL2 mRNA levels and reduced secreted CCL2 protein levels in a dose-dependent manner. A similar pattern of mRNA regulation was observed for other chemokines. The attenuation of TNF-induced CCL2 mRNA levels occurred regardless of whether glucose or pyruvate was present in the media, suggesting that mechanisms other than glycolysis might mediate the observed effects. Treatment with the endoplasmic reticulum stressor thapsigargin and the endoplasmic reticulum signaling activator salubrinal reduced chemokine mRNA levels similarly to 2-DOG.

CONCLUSIONS

Collectively, our data indicate that 2-DOG suppresses inflammatory chemokine induction in adipocytes. The effects of 2-DOG do not seem to be linked to glycolysis but correlate with endoplasmic reticulum stress activation.

Molecular Mechanisms Mediating Retinal Reactive Gliosis Following Bone Marrow Mesenchymal Stem Cell Transplantation

A variety of diseases lead to degeneration of retinal ganglion cells (RGCs) and their axons within the optic nerve resulting in loss of visual function. Although current therapies may delay RGC loss, they do not restore visual function or completely halt disease progression. Regenerative medicine has recently focused on stem cell therapy for both neuroprotective and regenerative purposes. However, significant problems remain to be addressed, such as the long-term impact of reactive gliosis occurring in the host retina in response to transplanted stem cells. The aim of this work was to investigate retinal glial responses to intravitreally transplanted bone marrow mesenchymal stem cells (BM-MSCs) to help identify factors able to modulate graft-induced reactive gliosis. We found in vivo that intravitreal BM-MSC transplantation is associated with gliosis-mediated retinal folding, upregulation of intermediate filaments, and recruitment of macrophages. These responses were accompanied by significant JAK/STAT3 and MAPK (ERK1/2 and JNK) cascade activation in retinal Muller glia. Lipocalin-2 (Lcn-2) was identified as a potential new indicator of graft-induced reactive gliosis. Pharmacological inhibition of STAT3 in BM-MSC cocultured retinal explants successfully reduced glial fibrillary acidic protein expression in retinal Muller glia and increased BM-MSC retinal engraftment. Inhibition of stem cell-induced reactive gliosis is critical for successful transplantation-based strategies for neuroprotection, replacement, and regeneration of the optic nerve.

From the periphery to the brain: Lipocalin-2, a friend or foe?

Lipocalin-2 (LCN2) is an acute-phase protein that, by binding to iron-loaded siderophores, acts as a potent bacteriostatic agent in the iron-depletion strategy of the immune system to control pathogens. The recent identification of a mammalian siderophore also suggests a physiological role for LCN2 in iron homeostasis, specifically in iron delivery to cells via a transferrin-independent mechanism. LCN2 participates, as well, in a variety of cellular processes, including cell proliferation, cell differentiation and apoptosis, and has been mostly found up-regulated in various tissues and under inflammatory states, being its expression regulated by several inducers. In the central nervous system less is known about the processes involving LCN2, namely by which cells it is produced/secreted, and its impact on cell proliferation and death, or in neuronal plasticity and behaviour. Importantly, LCN2 recently emerged as a potential clinical biomarker in multiple sclerosis and in ageing-related cognitive decline. Still, there are conflicting views on the role of LCN2 in pathophysiological processes, with some studies pointing to its neurodeleterious effects, while others indicate neuroprotection. Herein, these various perspectives are reviewed and a comprehensive and cohesive view of the general function of LCN2, particularly in the brain, is provided.

The Lcn2-engineered HEK-293 cells show senescence under stressful condition

OBJECTIVES

Lipocalin2 (Lcn2) gene is highly expressed in response to various types of cellular stresses. The precise role of Lcn2 has not been fully understood yet. However, it plays a key role in controlling vital cellular processes such as proliferation, apoptosis and metabolism. Recently it was shown that Lcn2 decreases senescence and increases proliferation of mesenchymal stem cells (MSC) with finite life span under either normal or oxidative stress conditions. However, Lcn2 effects on immortal cell line with infinite proliferation are not defined completely. Materials and.

MATERIALS AND METHODS

HEK-293 cells were transfected with recombinant pcDNA3.1 containing Lcn2 fragment (pcDNA3.1-Lcn2). Expression of lipocalin2 in transfected cells was evaluated by RT-PCR, real time RT-PCR, and ELISA. Different cell groups were treated with H2O2 and WST-1 assay was performed to determine their proliferation rate. Senescence was studied by β-galactosidase and gimsa staining methods as well as evaluation of the expression of senescence-related genes by real time RT-PCR.

RESULTS

Lcn2 increased cell proliferation under normal culture condition, while the proliferation slightly decreased under oxidative stress. This decrease was further found to be attributed to senescence.

CONCLUSION

Our findings indicated that under harmful conditions, Lcn2 gene is responsible for the regulation of cell survival through senescence.

Mutual interaction between iron homeostasis and obesity pathogenesis

Obesity is identified as an important medical problem. One of the pathologic conditions observed in obesity is systemic iron deficiency and hypoferremia. Along with a large number of studies indicating disturbed iron homeostasis in obesity, recent data indicate a cause-effect relationship between iron status and obesity-related pathologies. The primary objective of the article is to consider two aspects of the iron-obesity interplay: (1) the mechanisms leading to impaired iron balance, and (2) the pathways of iron participation in obesity-related pathogenesis. While considering disturbance of iron homeostasis in obesity, a number of potential mechanisms of hypoferremia are proposed. At the same time, the inflammation of obesity and obesity-related hepcidin and lipocalin 2 hyperproduction seem to be the most probable reasons of obesity-related hypoferremia. Oversecretion of these proteins leads to iron sequestration in reticuloendothelial system cells. The latter also leads to increased adipose tissue iron content, thus producing preconditions for adverse effects of local iron overload. Being a redox-active metal, iron is capable of inducing oxidative stress as well as endoplasmic reticulum stress, inflammation and adipose tissue endocrine dysfunction. Iron-mediated mechanisms of toxicity may influence aspects of obesity pathogenesis possibly even leading to obesity aggravation. Thus, a mutual interaction between disturbance in iron homeostasis and obesity pathogenesis is proposed. All sides of this interaction should be considered to design new therapeutic approaches to the treatment of disturbed iron homeostasis in obesity.

Neutrophil gelatinase-associated lipocalin and innate immune responses to bacterial infections

Neutrophil gelatinase-associated lipocalin (NGAL), an essential component of the antimicrobial innate immune system, is present in neutrophils and multiple other tissues. It prevents iron acquisition by microorganisms by sequestering iron-loaded bacterial siderophores. NGAL also modulates neutrophil functions. Its production is inducible following Toll-like receptor 4 activation and release of pro-inflammatory cytokines. NGAL is employed clinically in the diagnosis of acute kidney injury and may be useful in general in the differential diagnosis of a bacterial-mediated infectious process. Elevated levels of NGAL have been detected in the blood of patients with bacterial urinary tract infection, community-acquired pneumonia, sepsis, as well as in the cerebrospinal fluid and peritoneal fluid of patients with bacterial meningitis and peritonitis. Some bacteria have developed resistance to NGAL-mediated iron sequestration by production of modified siderophores that are not recognized by NGAL.

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

Lipocalin-2 (LCN2) was originally isolated from human neutrophils and termed neutrophil gelatinase-associated lipocalin (NGAL). However, the functions of LCN2 and the cell types that are primarily responsible for LCN2 production remain unclear. To address these issues, hepatocyte-specific Lcn2 knockout (Lcn2(Hep-/-)) mice were generated and subjected to bacterial infection (with Klesbsiella pneumoniae or Escherichia coli) or partial hepatectomy (PHx). Studies of Lcn2(Hep-/-) mice revealed that hepatocytes contributed to 25% of the low basal serum level of LCN2 protein (∼ 62 ng/mL) but were responsible for more than 90% of the highly elevated serum LCN2 protein level (∼ 6,000 ng/mL) postinfection and more than 60% post-PHx (∼ 700 ng/mL). Interestingly, both Lcn2(Hep-/-) and global Lcn2 knockout (Lcn2(-/-)) mice demonstrated comparable increases in susceptibility to infection with K. pneumoniae or E. coli. These mice also had increased enteric bacterial translocation from the gut to the mesenteric lymph nodes and exhibited reduced liver regeneration after PHx. Treatment with interleukin (IL)-6 stimulated hepatocytes to produce LCN2 in vitro and in vivo. Hepatocyte-specific ablation of the IL-6 receptor or Stat3, a major downstream effector of IL-6, markedly abrogated LCN2 elevation in vivo. Furthermore, chromatin immunoprecipitation (ChIP) assay revealed that STAT3 was recruited to the promoter region of the Lcn2 gene upon STAT3 activation by IL-6.

CONCLUSION

Hepatocytes are the major cell type responsible for LCN2 production after bacterial infection or PHx, and this response is dependent on IL-6 activation of the STAT3 signaling pathway. Thus, hepatocyte-derived LCN2 plays an important role in inhibiting bacterial infection and promoting liver regeneration.

Application of RPTEC/TERT1 cells for investigation of repeat dose nephrotoxicity: A transcriptomic study

The kidney is a major target organ for toxicity. Incidence of chronic kidney disease (CKD) is increasing at an alarming rate due to factors such as increasing population age and increased prevalence of heart disease and diabetes. There is a major effort ongoing to develop superior predictive models of renal injury and early renal biomarkers that can predict onset of CKD. In the EU FP7 funded project, Predict-IV, we investigated the human renal proximal tubule cells line, RPTEC/TERT1 for their applicability to long term nephrotoxic mechanistic studies. To this end, we used a tiered strategy to optimise dosing regimes for 9 nephrotoxins. Our final testing protocol utilised differentiated RPTEC/TERT1 cells cultured on filter inserts treated with compounds at both the apical and basolateral side, at concentrations not exceeding IC10, for 14 days in a 24 h repeat application. Transepithelial electrical resistance and supernatant lactate were measured over the duration of the experiments and genome wide transcriptomic profiles were assayed at day 1, 3 and 14. The effect of hypoxia was investigated for a subset of compounds. The transcriptomic data were analysed to investigate compound-specific effects, global responses and mechanistically informative signatures. In addition, several potential clinically useful renal injury biomarkers were identified.

Adipose tissue 12/15 lipoxygenase pathway in human obesity and diabetes

CONTEXT

Visceral adipose tissue (VAT) is a key contributor to chronic inflammation in obesity. The 12/15-lipoxygenase pathway (ALOX) is present in adipose tissue (AT) and leads to inflammatory cascades that are causal for the onset of insulin resistance in rodent models of obesity.

OBJECTIVE

The pathophysiology of the ALOX 12/15 pathway in human AT is unknown. We characterized the ALOX pathway in different AT depots in obese humans with or without type 2 diabetes (T2D).

DESIGN

This study includes a cross-sectional cohort of 46 morbidly obese (body mass index >39 kg/m(2)) nondiabetic (n = 25) and T2D (n = 21) subjects.

SETTING

This study was conducted at Eastern Virginia Medical School (Norfolk, Virginia) in collaboration with Sentara Metabolic and Weight Loss Surgery Center (Sentara Medical Group, Norfolk, Virginia).

PATIENTS

Twenty-five obese (body mass index 44.8 ± 4.4 kg/m(2)) nondiabetic (hemoglobin A1c 5.83% ± 0.27%) and 21 obese (43.4 ± 4.1 kg/m(2)) and T2D (hemoglobin A1c 7.66% ± 1.22%) subjects were included in the study. The subjects were age matched and both groups had a bias toward female gender.

MAIN OUTCOMES AND MEASURES

Expression of ALOX isoforms along with fatty acid substrates and downstream lipid metabolites were measured. Correlations with depot-specific inflammatory markers were also established.

RESULTS

ALOX 12 expression and its metabolite 12(S)-hydroxyeicosatetraenoic acid were significantly increased in the VAT of T2D subjects. ALOX 15A was exclusively expressed in VAT in both groups. ALOX 12 expression positively correlated with expression of inflammatory genes IL-6, IL-12a, CXCL10, and lipocalin-2.

CONCLUSIONS

ALOX 12 may have a critical role in regulation of inflammation in VAT in obesity and T2D. Selective ALOX 12 inhibitors may constitute a new approach to limit AT inflammation in human obesity.

Lipocalin 2 is a regulator of macrophage polarization and NF-κB/STAT3 pathway activation

Lipocalin 2 (Lcn2) has been previously characterized as an adipokine/cytokine and implicated in obesity and inflammation. Herein, we investigated the role and potential mechanism of Lcn2 in the regulation of macrophage polarization in obesity-associated inflammation. We observed that Lcn2-/- mice displayed an up-regulation of expression of M1 macrophage marker Cd11c but a down-regulation of M2 marker arginase 1 in adipose tissue and liver of mice upon a high-fat diet feeding. Lcn2-deficient bone marrow-derived macrophages (BMDMs) were more sensitive to lipopolysaccharide (LPS) stimulation, leading to a more profound up-regulation of expression of pro-inflammatory markers than wild-type (WT) BMDMs. Accordingly, LPS stimulation elicited an increase in the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), c-Jun, and STAT3 signaling pathways as well as an up-regualtion of expression of NF-κB and STAT3 target genes such as IL-1β, IL-6, iNOS, and MCP-1 in Lcn2-/- BMDMs compared with WT controls. Pre-treatment of recombinant Lcn2 attenuated LPS-stimulated degradation of IκBα and STAT3 phosphorylation as well as LPS-induced gene expression of IL-6 and iNOS in Lcn2-/- BMDMs. Moreover, the NFκB inhibitor markedly blocked LPS-stimulated STAT3 phosphorylation in Lcn2-/- BMDMs. These results together with the time course of Lcn2 secretion, NFκB and STAT3 phosphorylation in response to LPS stimulation, suggest that Lcn2 plays a role as an anti-inflammatory regulator in macrophage activation via modulating a feed-forward activation of NFκB-STAT3 loop.

Lipocalin 2 expression and secretion is highly regulated by metabolic stress, cytokines, and nutrients in adipocytes

Lipocalin 2 (Lcn2) has been recently characterized as a new adipokine having a role in innate immunity and energy metabolism. Nonetheless, the metabolic regulation of Lcn2 production in adipocytes has not been comprehensively studied. To better understand the Lcn2 biology, we investigated the regulation of Lcn2 expression in adipose tissue in response to metabolic stress in mice as well as the control of Lcn2 expression and secretion by cytokines and nutrients in 3T3-L1 adipocytes. Our results showed that the mRNA expression of Lcn2 was upregulated in white and brown adipose tissues as well as liver during fasting and cold stress in mice. Among pro-inflammatory cytokines TNFα, IL-1β, and IL-6, IL-1β showed most profound effect on Lcn2 expression and secretion in 3T3-L1 adipocytes. Insulin stimulated Lcn2 expression and secretion in a dose-dependent manner; this insulin effect was significantly abolished in the presence of low concentration of glucose. Moreover, insulin-stimulated Lcn2 expression and secretion was also attenuated when glucose was replaced by 3-O-methyl-d-glucose or by blocking NFκB pathway activation. Additionally, we showed that palmitate and oleate induced Lcn2 expression and secretion more significantly than EPA, while phytanic acid reduced Lcn2 production. Our results demonstrated that Lcn2 production in adipocytes is highly responsive to metabolic stress, cytokines, and nutrient signals, suggesting an important role of Lcn2 in adipocyte metabolism and inflammation.

Waist circumference and neutrophil gelatinase-associated lipocalin in late-life depression

Both visceral obesity and depression are associated with impaired health and excess mortality, possibly through overlapping pathophysiological mechanisms like adipose tissue derived inflammatory markers. These results, however, are primarily based on population-based surveys, often restricted to a young population and depression severity scales instead of patients with established diagnosis of depressive disorder. We examined the relation between waist circumference and late-life depression using the baseline data of The Netherlands Study of Depression in Older people (NESDO). Psychopathology has been assessed with Composite International Diagnostic Interview version 2.1. Adjusted for age, sex, education, lifestyle (smoking, alcohol, physical activity), drug use, cognition and chronic diseases as well as adjusted for body mass index (BMI), analysis of covariance showed that depressed older patients (n=376) had a significantly lower waist circumference (WC) compared to their non-depressed comparisons (n=130): estimated marginal mean (SE)=93.9 (0.5) versus 97.8 (0.8) cm (F=15.9; df=1467; p<.001). Multiple linear regression analyses within the depressed group showed that both, depression severity (Inventory of Depressive Symptoms) as well as duration-related depression characteristics (age of onset, duration of illness, life-time comorbid dysthymia), were associated with the WC. Only the severity of depressive symptoms remained significant after further adjusted for the BMI. Interestingly, a recently discovered adipokine, Neutrophil Gelatinase-Associated Lipocalin (NGAL), was associated with late-life depression, but only in the subgroup of patients with a pathologically increased WC. Population-based findings on the positive association between obesity and depressive symptoms can thus not be generalised to a clinical sample of depressed older patients. The impact of the WC on course and treatment outcome of late-life depression should be examined in clinical samples, taken into account the relative impact of the WC in proportion to the general level of obesity as indexed by the BMI and the role of adipokines.