Neutrophil gelatinase-associated lipocalin regulates gut microbiota of mice

Gut microbiota and neonatal acute kidney injury biomarkers

One of the most frequent issues in newborns is acute kidney injury (AKI), which can lengthen their hospital stay or potentially raise their chance of dying. The gut-kidney axis establishes a bidirectional interplay between gut microbiota and kidney illness, particularly AKI, and demonstrates the importance of gut microbiota to host health. Since the ability to predict neonatal AKI using blood creatinine and urine output as evaluation parameters is somewhat constrained, a number of interesting biomarkers have been developed. There are few in-depth studies on the relationships between these neonatal AKI indicators and gut microbiota. In order to gain fresh insights into the gut-kidney axis of neonatal AKI, this review is based on the gut-kidney axis and describes relationships between gut microbiota and neonatal AKI biomarkers.

Lipocalin 2-not only a biomarker: a study of current literature and systematic findings of ongoing clinical trials

Lipocalin 2 (Lcn2), also known as neutrophil gelatinase-associated lipocalin, is an innate immune protein encoded by the LCN2 gene. In this study, we investigated various roles and functions of Lcn2 characterized in a systems-based format and evaluated its therapeutic potentials and clinical relevance for diagnosis and prognosis. An additional systematic presentation was presented for 70 ongoing clinical trials utilizing Lcn2 in the diagnostic and prognostic setting as a key outcome measure. With trials being conducted through December 2030, Lcn2 will become all the more relevant given its associations with diseases as a prognostic biomarker. Data also suggests that it plays a role in pathological conditions. The gaps in our understanding of Lcn2, once filled, may improve the immune mediation of acute and chronic disease.

Depletion of Lipocalin 2 (LCN2) in Mice Leads to Dysbiosis and Persistent Colonization with Segmented Filamentous Bacteria

Lipocalin 2 (LCN2) mediates key roles in innate immune responses. It has affinity for many lipophilic ligands and binds various siderophores, thereby limiting bacterial growth by iron sequestration. Furthermore, LCN2 protects against obesity and metabolic syndrome by interfering with the composition of gut microbiota. Consequently, complete or hepatocyte-specific ablation of the Lcn2 gene is associated with higher susceptibility to bacterial infections. In the present study, we comparatively profiled microbiota in fecal samples of wild type and Lcn2 null mice and show, in contrast to previous reports, that the quantity of DNA in feces of Lcn2 null mice is significantly lower than that in wild type mice (p < 0.001). By using the hypervariable V4 region of the 16S rDNA gene and Next-Generation Sequencing methods, we found a statistically significant change in 16 taxonomic units in Lcn2^-/- mice, including eight gender-specific deviations. In particular, members of Clostridium, Escherichia, Helicobacter, Lactococcus, Prevotellaceae_UCG-001 and Staphylococcus appeared to expand in the intestinal tract of knockout mice. Interestingly, the proportion of Escherichia (200-fold) and Staphylococcus (10-fold) as well as the abundance of intestinal bacteria encoding the LCN2-sensitive siderphore enterobactin (entA) was significantly increased in male Lcn2 null mice (743-fold, p < 0.001). This was accompanied by significant higher immune cell infiltration in the ileum as demonstrated by increased immunoreactivity against the pan-leukocyte protein CD45, the lymphocyte transcription factor MUM-1/IRF4, and the macrophage antigen CD68/Macrosialin. In addition, we found a higher expression of mucosal mast cell proteases indicating a higher number of those innate immune cells. Finally, the ileum of Lcn2 null mice displayed a high abundance of segmented filamentous bacteria, which are intimately associated with the mucosal cell layer, provoking epithelial antimicrobial responses and affecting T-helper cell polarization.

Biological Roles of Lipocalins in Chemical Communication, Reproduction, and Regulation of Microbiota

Major evolutionary transitions were always accompanied by genetic remodelling of phenotypic traits. For example, the vertebrate transition from water to land was accompanied by rapid evolution of olfactory receptors and by the expansion of genes encoding lipocalins, which - due to their transporting functions - represent an important interface between the external and internal organic world of an individual and also within an individual. Similarly, some lipocalin genes were lost along other genes when this transition went in the opposite direction leading, for example, to cetaceans. In terrestrial vertebrates, lipocalins are involved in the transport of lipophilic substances, chemical signalling, odour reception, antimicrobial defence and background odour clearance during ventilation. Many ancestral lipocalins have clear physiological functions across the vertebrate taxa while many other have - due to pleiotropic effects of their genes - multiple or complementary functions within the body homeostasis and development. The aim of this review is to deconstruct the physiological functions of lipocalins in light of current OMICs techniques. We concentrated on major findings in the house mouse in comparison to other model taxa (e.g., voles, humans, and birds) in which all or most coding genes within their genomes were repeatedly sequenced and their annotations are sufficiently informative.

Screening and Interaction Analysis of Key Genes in miR-542-3p Over- Expressed Osteosarcoma Cells by Bioinformatics

BACKGROUND

Osteosarcoma is one of the most serious primary malignant bone tumors that threaten the lives of children and adolescents. However, the mechanism underlying and how to prevent or treat the disease have not been well understood.

AIMS AND OBJECTIVE

This aim of the present study was to identify the key genes and explore novel insights into the molecular mechanism of miR-542-3p over-expressed Osteosarcoma.

MATERIALS AND METHODS

Gene expression profile data GDS5367 was downloaded from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were screened using GEO2R, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed using the DAVID database. And protein-protein interaction (PPI) network was constructed by the STRING database. In addition, the most highly connected module was screened by plugin MCODE and hub genes by plugin CytoHubba. Furthermore, UALCAN and The Cancer Genome Atlas were performed for survival analysis.

RESULT

In total, 1421 DEGs were identified, including 598 genes were up-regulated and 823 genes were down-regulated. GO analysis showed that DEGs were classified into three groups and DEGs mainly enriched in Steroid biosynthesis, Ubiquitin mediated proteolysis and p53 signaling pathway. Six hub genes (UBA52, RNF114, UBE2H, TRIP12, HNRNPC, and PTBP1) may be key genes with the progression of osteosarcoma.

CONCLUSION

The results could better understand the mechanism of osteosarcoma, which may facilitate a novel insight into treatment targets.

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.

Interleukin-17/interleukin-17 receptor axis elicits intestinal neutrophil migration, restrains gut dysbiosis and lipopolysaccharide translocation in high-fat diet-induced metabolic syndrome model

Sound evidence supports a role for interleukin-17 (IL-17) -producing γδ T cells and IL-17-producing helper T (Th17) cells in intestinal homeostasis, especially in intestinal barrier integrity. In the present study, we aimed to evaluate the role of IL-17 cytokine in the regulation of intestinal immunity and obesity-induced metabolic syndrome (MetS) in an experimental murine model. C57BL/6 wild-type (WT) mice and mice lacking the IL-17 cytokine receptor (IL-17RA^-/- ) were fed either a control diet (CD) or a high-fat diet (HFD) for 9 weeks. Our data demonstrate that IL-17RA^-/- mice are protected against obesity, but develop hyperglycemia, hyperinsulinemia and insulin resistance. In parallel, HFD-fed IL-17RA^-/- mice display intense inflammation in the ileum compared with WT mice on the HFD. IL-17RA^-/- mice fed the HFD exhibit impaired neutrophil migration to the intestinal mucosa and reduced gene expression of the CXCL-1 chemokine and CXCR-2 receptor in the ileum. Interestingly, the populations of neutrophils (CD11b⁺  Ly6G⁺ ) and anti-inflammatory macrophages (CD11b⁺  CX3CR1⁺ ) are increased in the mesenteric lymph nodes of these mice. IL-17RA^-/- mice on the HFD also display increased commensal bacterial translocation into the bloodstream and elevated lipopolysaccharide (LPS) levels in the visceral adipose tissue (VAT). Metagenomic analysis of bacterial 16S gene revealed increased Proteobacteria and Bacteroidetes phyla, the main representatives of Gram-negative bacteria, and reduced Akkermansia muciniphila in the fecal samples of IL-17RA^-/- mice fed the HFD. Together, these data indicate that the IL-17/IL-17R axis drives intestinal neutrophil migration, limits gut dysbiosis and attenuates LPS translocation to VAT, resulting in protection to MetS.

Irreversible effects of trichloroethylene on the gut microbial community and gut-associated immune responses in autoimmune-prone mice

The developing immune system is particularly sensitive to immunotoxicants. This study assessed trichloroethylene (TCE)-induced effects on the gut microbiome and cytokine production during the development in mice. Mice were exposed to TCE (0.05 or 500 μg/mL) at the levels that approximate to environmental or occupational exposure, respectively. Mice were subjected to a continuous developmental exposure to these doses encompassing gestation, lactation and continuing directly in the drinking water postnatally for 154 days (PND154) or PND259. To observe persistence of the effect TCE was removed from the drinking water in a subset of mice on PND154 and were provided regular drinking water until the study terminus (PND259). Abundance of total tissue-associated bacteria reduced only in mice exposed to TCE until PND259. The ratio of Firmicutes/Bacteroidetes did not alter during this continuos exposure; however, cessation of high-dose TCE at PND154 resulted in the increased abundance Bacteroidetes at PND259. Furthermore, high-dose TCE exposure until PND259 resulted in a lower abundance of the genera Bacteroides and Lactobaccilus and increased abundance of genus Bifidobactrium and bacterial family Enterobacteriaceae. TCE exposure until PND154 showed significant changes in the production of interleukin-33; that might play a dual role in maintaining the balance and homeostasis between commensal microbiota and mucosal health. At PND259, interleukin-3, granulocyte-macrophage colony-stimulating factor and Eotaxin were altered in both, the continuous exposure and cessation groups, whereas only a cessation group had a higher level of KC that may facilitate infiltration of neutrophils. The irreversible effects of TCE after a period of exposure cessation suggested a unique programming and potential toxicity of TCE even at the environmental level exposure.

Neutrophil gelatinase-associated lipocalin in patients with sarcoidosis

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) is a glycoprotein that is involved in the innate immune system and increased expression has been detected in diverse diseases. Sarcoidosis is a systemic granulomatous disorder and its clinical course and prognosis are changeable and highly divergent. This study aimed to examine the expression of NGAL in patients with sarcoidosis. In addition, we examined whether NGAL could serve as a marker of disease activity and prognosis.

METHODS

Ninety-six sarcoidosis patients were studied. Serum samples collected at the time of diagnosis were examined for NGAL by cellular enzyme-linked immunosorbent assay. The level of NGAL was compared with clinical, radiological and laboratory data.

RESULTS

Patients with sarcoidosis had significantly higher levels of NGAL (the median [interquartile range] was 35.1 ng/mL [23.5-60.8] in sarcoidosis patients versus 17.2 ng/mL [13.0-27.0] in the reference population, p < .0001). NGAL levels were not correlated with markers for disease activity. During the follow-up period, 26 patients (27.1%) deteriorated and received systemic corticosteroid therapy for organ dysfunction. In those patients, NGAL levels were significantly higher than in those who did not receive corticosteroid therapy (56.5 ng/mL [27.3-92.3] versus 34.3 ng/mL [23.0-53.0], p = .0201). Upon multivariate logistic regression analysis, elevated NGAL levels at diagnosis were associated with subsequent use of systemic corticosteroid therapy (hazard ratio, 1.20; 95% confidence interval, 1.09-1.31; p = .0004).

CONCLUSION

NGAL may be a useful marker to predict the disease course of sarcoidosis.

Lipocalin 2: An Emerging Player in Iron Homeostasis and Inflammation

Lipocalin 2 (Lcn2), an innate immune protein, has emerged as a critical iron regulatory protein during physiological and inflammatory conditions. As a bacteriostatic factor, Lcn2 obstructs the siderophore iron-acquiring strategy of bacteria and thus inhibits bacterial growth. As part of host nutritional immunity, Lcn2 facilitates systemic, cellular, and mucosal hypoferremia during inflammation, in addition to stabilizing the siderophore-bound labile iron pool. In this review, we summarize recent advances in understanding the interaction between Lcn2 and iron, and its effects in various inflammatory diseases. Lcn2 exerts mostly a protective role in infectious and inflammatory bowel diseases, whereas both beneficial and detrimental functions have been documented in neurodegenerative diseases, metabolic syndrome, renal disorders, skin disorders, and cancer. Further animal and clinical studies are necessary to unveil the multifaceted roles of Lcn2 in iron dysregulation during inflammation and to explore its therapeutic potential for treating inflammatory diseases.