Quercetin ameliorates Helicobacter pylori-induced gastric epithelial cell injury by regulating specificity protein 1/lipocalin 2 axis in gastritis.

Helicobacter pylori (HP) infection is the main cause of most cases of gastritis. Quercetin has been shown to have anti-inflammatory, anti-bacterial, and antiviral activities and has been demonstrated to be involved in HP-induced gastric mucosa injury. Moreover, the secretory protein lipocalin-2 (LCN2) was elevated in HP-infected gastric mucosa. Thus, this work aimed to study the interaction between quercetin and LCN2 in HP-triggered gastric injury during gastritis. Human gastric epithelial cell line GES-1 cells were exposed to HP for functional experiments. Cell viability, apoptosis, and inflammation were evaluated by cell counting kit-8, flow cytometry, and enzyme-linked immunosorbent assay, respectively. Levels of genes and proteins were tested using quantitative reverse transcription polymerase chain reaction and western blotting analyses. The interaction between LCN2 and specificity protein 1 (SP1) was validated using chromatin immunoprecipitation assay and dual-luciferase reporter assay. Thereafter, we found quercetin treatment suppressed HP-induced GES-1 cell apoptotic and inflammatory injury and macrophage M1 polarization. LCN2 was highly expressed in HP-infected gastritis patients and HP-infected GES-1 cells, while quercetin reduced LCN2 expression in HP-infected GES-1 cells; moreover, LCN2 knockdown reversed HP-induced GES-1 cell injury and macrophage M1 polarization, and forced expression of LCN2 abolished the protective effects of quercetin on GES-1 cells under HP infection. Mechanistically, SP1 bound to LCN2 promoter and promoted its transcription. Also, SP1 overexpression counteracted the functions of quercetin on HP-stimulated GES-1 cells. In all, quercetin ameliorated HP-induced gastric epithelial cell apoptotic and inflammatory injuries, and macrophage M1 polarization via the SP1/LCN2 axis.

Melittin inhibits tumor cell migration and enhances cisplatin sensitivity by suppressing IL-17 signaling pathway gene LCN2 in castration-resistant prostate cancer.

BACKGROUND: Melittin is a small molecule polypeptide extracted from the abdominal cavity of bees, which is used to treat inflammatory diseases and relieve pain. However, the antitumor effect of melittin and its mechanisms remain unclear, especially in castration-resistant prostate cancer (CRPC). METHODS: Through CCK-8 assay, colony formation assay, wound healing assay and Transwell migration assay, we explored the effect of melittin on CRPC cell lines. In addition, with microarray analysis, gene ontology analysis and kyoto encyclopedia of genes and genomes analysis, this study identified key genes and signaling pathways that influence the growth of PC-3 cells. Meanwhile, the effect of melittin on CRPC was also verified through subcutaneous tumor formation experiments. Finally, we also tested the relevant indicators of human prostate cancer (PCa) specimens through immunohistochemistry and H＆E stating. RESULTS: Here, melittin was verified to inhibit the cell proliferation and migration of CPRC. Moreover, RNA-sequence analysis demonstrated that Interleukin-17 (IL-17) signaling pathway gene Lipocalin-2 (LCN2) was downregulated by melittin treatment in CRPC. Further investigation revealed that overexpression of LCN2 was able to rescue tumor suppression and cisplatin sensitivity which melittin mediated. Interestingly, the expression of LCN2 is highly related to metastasis in PCa. CONCLUSIONS: In brief, our study indicates that LCN2 plays an oncogenic role in CRPC and melittin may be selected as an attractive candidate for CRPC therapy.

HNRNPA2B1-mediated m6A modification of FOXM1 promotes drug resistance and inhibits ferroptosis in endometrial cancer via regulation of LCN2.

N6-methyladenosine (m6A) methylation is an extensive posttranscriptional RNA modification, and it is associated with various cellular responses, especially in tumor progression. An m6A "reader"-HNRNPA2B1 has been found oncogenic in multiple malignancies. As a key proliferation-related transcription factor, forkhead box protein M1 (FOXM1) is involved in tumorigenesis. Here, we elucidated the underlying mechanism by which HNRNPA2B1-mediated modification of FOXM1 promotes endometrial cancer (EC). The GSE115810 dataset was used to analyze the upregulated gene mRNA in late-stage EC tissues. The expression levels of HNRNPA2B1, FOXM1, and LCN2 in EC samples were shown by western blotting and qPCR. The interaction among HNRNPA2B1, FOXM1, and LCN2 in EC cells was detected using bioinformatics analysis, RNA immunoprecipitation (RIP), RNA pull-down, RNA decay analysis, and luciferase reporter experiments. Cisplatin (DDP)-resistant EC cells were constructed using HEC-1-A and HEC-1-B cells, named HEC-1-A/DDP and HEC-1-B/DDP, respectively. Proliferation, migration, and invasiveness in treated HEC-1-A/DDP and HEC-1-B/DDP cells were detected by EdU, wound healing, and transwell assays. Ferroptosis-resistant gene expression, MDA level, and ROS level were measured. The m6A modification level in EC tissues was elevated. HNRNPA2B1 and FOXM1 levels were upregulated in EC. HNRNPA2B1 expression was positively related to FOXM1 expression in EC samples, and HNRNPA2B1 bound to the 3'UTR of FOXM1 and stabilized FOXM1 mRNA via m6A modification. FOXM1 positively regulated LCN2 expression in EC cells by binding to the LCN2 promotor. Knockdown of FOXM1 downregulated ferroptosis-resistant gene expression and increased MDA and ROS levels in DDP-resistant EC cells. Rescue assays revealed that LCN2 overexpression eliminated the effects mediated by FOXM1 knockdown on the proliferation, migration, invasiveness, and ferroptosis in DDP-resistant EC cells. In conclusion, HNRNPA2B1-mediated mA modification of FOXM1 facilitates drug resistance and inhibits ferroptosis in EC cells by upregulating LCN2 expression.

Amyloid ß oligomer promotes microglial galectin-3 and astrocytic lipocalin-2 levels in the hippocampus of mice fed a high-fat diet.

Type 2 diabetes is associated with a risk factor for Alzheimer's disease (AD). Activation of glial cells, such as microglia and astrocytes, is crucial for the development of neuroinflammation in both diabetes and AD. The role of amyloid-beta oligomer (AßO) in the hippocampus of diabetic mice has been investigated; however, the effect of galectin-3 and lipocalin-2 (LCN2) on amyloid toxicity-related glial activation in diabetic mice is not known. To fill this knowledge gap, we fed mice a high-fat diet (HFD) for 20 weeks to induce a diabetic state and then injected the hippocampus with AßO. Sholl analysis of iba-1-positive microglia showed retraction of microglial ramifications in the hippocampus of HFD-fed diabetic mice. AßO treatment caused more retraction of microglial process in HFD-fed mice. In particular, microglial galectin-3 levels and astrocytic LCN2 levels were increased in the hippocampus of HFD-fed mice with AßO treatment. These findings suggest that galectin-3 and LCN2 are involved in amyloid toxicity mechanisms, especially glial activation under diabetic conditions.

Lipocalin 2, synthesized using a cell-free protein synthesis system and encapsulated into liposomes, inhibits the adhesion of Porphyromonas gingivalis to human oral epithelial cells.

BACKGROUND AND OBJECTIVE: Lipocalin 2 (LCN2), a glycoprotein expressed in epithelial cells and leukocytes, has an antibacterial effect and plays a role in innate immunity. The delivery of LCN2 encapsulated in liposomes to oral epithelium may be useful to prevent oral infectious diseases. This study aimed to investigate the inhibitory effect of LCN2, artificially synthesized using a cell-free protein synthesis (CFPS) system, on the adhesion of Porphyromonas gingivalis to oral epithelial cells in order to approach oral healthcare using LCN2. METHODS: LCN 2 was synthesized using a CFPS system and assayed by Western blotting, mass spectrometry and enzyme-linked immunosorbent assay (ELISA). The bilayer liposomes were prepared by the spontaneous transfer method using 1,2-dioleoyl-sn-glycero-3 phosphocholine (DOPC), 3-sn-phosphatidylcholine from Egg Yolk (Egg-PC), and 1,2-dioleoyl-sn-glycero-3 phosphoethanolamine (DOPE). The cellular and medium fractions derived from the culture of oral epithelial cells with liposome-encapsulated LCN2 were assayed by Western blotting and ELISA. The effect of the synthesized LCN2 on adhesion of the labeled P. gingivalis to oral epithelial cells was investigated as an evaluation of its antibacterial activity. RESULTS: The synthesized LCN2 protein was identified by Western blotting; its amino acid sequence was similar to that of recombinant LCN2 protein. The additions of DOPE and octa-arginine in the outer lipid-layer components of liposome significantly increased the delivery of liposomes to epithelial cells. When oral epithelial cells were cultured with the synthesized and liposome-encapsulated LCN2, LCN2 was identified in the cellular and medium fractions by Western blotting and its concentration in the cellular fraction from the culture with the synthesized LCN2 was significantly higher than that of a template DNA-free protein. The synthesized LCN2 and liposome-encapsulated LCN2 significantly inhibited the adhesion of P. gingivalis to oral epithelial cells compared with template DNA-free protein. CONCLUSION: LCN2 was artificially synthesized by a CFPS system, encapsulated in liposomes, and delivered to oral epithelial cells, and demonstrated an antibacterial action against P. gingivalis. This approach may become a useful model for oral healthcare.

Clemizole hydrochloride, a potent TRPC5 calcium channel inhibitor, prevents cisplatin-induced nephrotoxicity in Spraque-Dawley rats.

Cis-diamminedichloroplatinum (II) (cisplatin, Cis) is widely employed to treat several types of cancer. It has many important toxic side effects; one of the most important of which is nephrotoxicity. Clemizole hydrochloride (Clem) as the most potent inhibitor of TRPC5 channels was tested in an animal model of Cis-induced nephrotoxicity. Rats were divided into the following groups: control; Cis (8 mg/kg); Cis + 1 mg/kg Clem; Cis + 5 mg/kg Clem; Cis + 10 mg/kg Clem. Kidney injury was detected by histopathological and biochemical analysis. Urine urea nitrogen (UUN), creatinine, urine neutrophil gelatinase-associated lipocalin (NGAL), serum catalase (CAT), and malondialdehyde (MDA) levels were determined by enzyme-linked immunosorbent assay. Total antioxidant status (TAS) and total oxidant status (TOS) were studied using a colorimetric assay. Nephrin, synaptopodin, and Rac family small GTPase 1 (RAC1) expressions were detected by Western blot analysis. Cis was found to induce histopathological alterations, including tubular degeneration, congestion, hemorrhage, hyaline casts, glomerular collapse, and apoptotic cell death. Clem at a dose of 1 and 5 mg/kg attenuated histopathological alterations. UUN, creatinine, and NGAL levels increased in the Cis-administered group, while all doses of Clem decreased in those. CAT and TAS levels decreased, while TOS and oxidative stress index levels increased in the Cis-treated group. A dose of 1 and 5 mg Clem showed antioxidant effects against oxidative stress. Cis induced lipid peroxidation by increasing MDA levels. All doses of Clem reduced MDA levels. Nephrin and synaptopodin expressions were decreased by Cis, and all doses of Clem increased that. All doses of Clem successfully depressed RAC1 expression. Clem showed a highly ameliorating effect on toxicity caused by Cis by blocking TRPC5 calcium channels.

Salvianolic Acid A Improves Rat Kidney Injury by Regulating MAPKs and TGF-ß1/Smads Signaling Pathways.

Salvianolic acid A (SAA) is one of the major components in Salvia miltiorrhiza Bge., with various pharmacological activities, and is likely to be a promising agent for the treatment of kidney diseases. The purpose of this study was to explore the protective effect and mechanisms of SAA on kidney disease. In this study, the improvement effects of SAA (10, 20, 40 mg/kg, i.g.) on kidney injury rats were investigated by detecting the levels of KIM-1, NGAL in serum and UP in the urine of AKI model rats established with gentamicin, as well as the levels of SCr and UREA in serum and IL-6, IL-12, MDA and T-SOD in the kidneys of CKD model rats established with 5/6 nephrectomy. HE and Masson staining were used to observe the histopathological changes in the kidney. Network pharmacology and Western blotting were used to explore the mechanism of SAA in improving kidney injury. The results showed that SAA improved kidney function in kidney injury rats by reducing the kidney index and pathological injury by HE and Masson staining, reducing the levels of KIM-1, NGAL and UP in AKI rats and UREA, SCr and UP in CKD rats, as well as exerting anti-inflammatory and anti-oxidative stress effects by inhibiting the release of IL-6 and IL-12, reducing MDA and increasing T-SOD. Western blotting results showed that SAA significantly reduced the phosphorylation levels of ERK1/2, p38, JNK and smad2/3, and the expression of TLR-4 and smad7. In conclusion, SAA plays a significant role in improving kidney injury in rats and the mechanism may be achieved by regulating the MAPKs and TGF-ß1/smads signaling pathways.

[Notoginsenoside R_1 interferes with renal oxidative stress and Nrf2/HO-1 signaling pathway to alleviate kidney injury in mice with IgA nephropathy and its mechanism].

The purpose of this study was to investigate the effect of notoginsenoside R_1(NGR_1) on alleviating kidney injury by regulating renal oxidative stress and the Nrf2/HO-1 signaling pathway in mice with IgA nephropathy(IgAN) and its mechanism. The mouse model of IgAN was established using a variety of techniques, including continuous bovine serum albumin(BSA) gavage, subcutaneous injections of carbon tetrachloride(CCl_4) castor oil, and tail vein injections of lipopolysaccharide(LPS). After successful modeling, mice with IgAN were randomly separated into a model group, low, medium, and high-dose NGR_1 groups, and a losartan group, and C57BL6 mice were utilized as normal controls. The model and normal groups were given phosphate buffered saline(PBS) by gavage, the NGR_1 groups were given varying dosages of NGR_1 by gavage, and the losartan group was given losartan by gavage for 4 weeks. The 24-hour urine of mice was collected after the last administration, and serum and kidney tissues of mice were taken at the end of the animal experiment. Then urine red blood cell count(URBCC), 24-hour urine protein(24 h protein), serum creatinine(Scr), and blood urea nitrogen(BUN) levels were measured. The enzyme-linked immunosorbent assay(ELISA) was used to detect the levels of galactose-deficient IgA1(Gd-IgA1), kidney injury molecule 1(Kim-1), and neutropil gelatinase-associated lipocalin(NGAL) in the mouse serum. The assay kits were used to detect the levels of malondialdehyde(MDA) and superoxide dismutase(SOD), and immunofluorescence(IF) was used to detect the expression level of glutathione peroxidase 4(GPX4) in the mesangial region. Western blot was used to detect the protein expression of nuclear transcription factor E2 related factor 2(Nrf2)/heme oxygenase 1(HO-1) signaling pathway in the renal tissue. Hematoxylin-eosin(HE) staining was used to observe pathological alterations in the glomerulus of mice. The results revealed that, as compared with the model group, the serum Gd-IgA1 level, URBCC, 24 h protein level, renal damage markers(Kim-1 and NGAL) in the high-dose NGR_1 group decreased obviously and renal function indicators(BUN, Scr) improved significantly. The activity of SOD activity and expression level of GPX4 increased significantly in the high-dose NGR_1 group, whereas the expression level of MDA reduced and protein expression levels of Nrf2 and HO-1 increased. Simultaneously, HE staining of the renal tissue indicated that glomerular damage was greatly decreased in the high-dose NGR_1 group. In conclusion, this study has clarified that NGR_1 may alleviate the kidney injury of mice with IgAN by activating the Nrf2/HO-1 signaling pathway, improving antioxidant capacity, and reducing the level of renal oxidative stress.

N-acetylcysteine Ameliorates Vancomycin-induced Nephrotoxicity by Inhibiting Oxidative Stress and Apoptosis in the in vivo and in vitro Models.

Background: Oxidative stress-related apoptosis is considered as the key mechanism implicated in the pathophysiology of nephrotoxicity with vancomycin (VCM) therapy. We evaluated the possible effects of N-acetylcysteine (NAC) on VCM-induced nephrotoxicity and the underlying mechanism. Methods: VCM-induced nephrotoxicity was established using HK-2 cells and SD rats and observed by measuring cell survival, kidney histological changes, renal function and kidney injury related markers (KIM-1 and NGAL). Oxidative stress, renal cell apoptosis and the involved signaling pathways were also evaluated. Results: In model rats, NAC could protect against VCM-induced acute kidney injury with histological damage, renal dysfunction, and increased Cre and BUN levels. In HK-2 cells, VCM-induced decreased cell viability was restored by NAC. In addition, increased expression of caspase-3, KIM-1 and NGAL suffering from VCM was also reversed by NAC in vivo and in vitro. NAC inhibited ROS production, decreased cell apoptosis by decreasing the Bax/Bcl-2 ratio and caspase-3 expression in HK-2 cells and regulated oxidative stress indicators in the kidney by decreasing GSH, SOD and CAT activity and increasing MDA levels. Furthermore, NAC could effectively reverse VCM-associated increased P38 MAPK/JNK phosphorylation. Conclusions: The results demonstrated that NAC had a protective effect against nephrotoxicity from VCM by inhibiting oxidative stress and apoptosis via P38 MAPK/JNK.

Protective effects of p-coumaric acid against gentamicin-induced nephrotoxicity in rats.

The most important side effect of gentamicin (GM) is nephrotoxicity. p-Coumaric acid (PCA) is a phenolic compound that scavenges free radicals, reduces fibrosis, and tissue damage. This study investigates the protective effect of PCA on tissue damage and kidney function in gentamicin-induced nephrotoxicity (GIN). Thirty-five rats were separated into five groups and each group contained seven animals: control group, ethanol group, GM group, PCA group, and GM + PCA group. At the end of the seven-day treatment, the rats were sacrificed after blood and kidney tissue samples were taken. While serum urea, creatinine, and neutrophil gelatinase-associated lipocalin (NGAL) levels increased significantly in the GM group compared to the control, they showed a significant decrease in the GM + PCA group compared to the GM. Serum tumor necrosis factor-α (TNF-α) and tissue malondialdehyde (MDA) levels were significantly increased in the GM group compared to the control. While the tissue total oxidant status (TOS) and oxidative stress index (OSI) values of the GM group were significantly higher than the control, they showed a significant decrease in the GM + PCA group compared to the GM. In the histopathological examination, significant tubular necrosis and tubulointerstitial inflammation were detected in the proximal tubules in the GM group compared to the control, while a significant decrease was observed in the severity of these findings in the GM + PCA group compared to the GM. This study shows that PCA has biochemical and histopathological ameliorating effects on GIN in the rat model.

Does G Protein-Coupled Estrogen Receptor 1 Contribute to Cisplatin-Induced Acute Kidney Injury in Male Mice?

Nephrotoxicity is the dose-limiting side-effect of the chemotherapeutic agent cisplatin (Cp). Recent evidence points to renal protective actions of G protein-coupled estrogen receptor 1 (GPER1). In addition, it has been shown that GPER1 signaling elicits protective actions against acute ischemic injuries that involve multiple organ systems; however, the involvement of GPER1 signaling in Cp-induced acute kidney injury (AKI) remains unclear. This study tested whether genetic deletion of GPER1 exacerbates Cp-induced AKI in male mice. We subjected male mice, homozygous (homo) and heterozygous (het) knockout for the GPER1 gene, and wild-type (WT) littermates to Cp or saline injections and assessed markers for renal injury on the third day after injections. We also determined serum levels of proinflammatory markers in saline and Cp-treated mice. Given the protective role of heme oxygenase-1 (HO-1) in Cp-mediated apoptosis, we also investigated genotypic differences in renal HO-1 abundance, cell death, and proliferation by Western blotting, the TUNEL assay, and Ki67 immunostaining, respectively. Cp increased serum creatinine, urea, and neutrophil gelatinase-associated lipocalin (NGAL) levels, the renal abundance of kidney injury molecule-1, and NGAL in all groups. Cp-induced AKI resulted in comparable histological evidence of injury in all genotypes. WT and homo mice showed greater renal HO-1 abundance in response to Cp. Renal HO-1 abundance was lower in Cp-treated homo, compared to Cp-treated WT mice. Of note, GPER1 deletion elicited a remarkable increase in renal apoptosis; however, no genotypic differences in cell proliferation were observed. Cp augmented kidney Ki67-positive counts, regardless of the genotype. Overall, our data do not support a role for GPER1 in mediating Cp-induced renal injury. GPER1 deletion promotes renal apoptosis and diminishes HO-1 induction in response to Cp, suggesting that GPER1 may play cytoprotective and anti-apoptotic actions in AKI. GPER1-induced regulation of HO-1 and apoptosis may offer novel therapeutic targets for the treatment of AKI.

G.I. pros: Antimicrobial defense in the gastrointestinal tract.

The gastrointestinal tract is a complex environment in which the host immune system interacts with a diverse array of microorganisms, both symbiotic and pathogenic. As such, mobilizing a rapid and appropriate antimicrobial response depending on the nature of each stimulus is crucial for maintaining the balance between homeostasis and inflammation in the gut. Here we focus on the mechanisms by which intestinal antimicrobial peptides regulate microbial communities during dysbiosis and infection. We also discuss classes of bacterial peptides that contribute to reducing enteric pathogen outgrowth. This review aims to provide a comprehensive overview on the interplay of diverse antimicrobial responses with enteric pathogens and the gut microbiota.

Scavenging Bacterial Siderophores with Engineered Lipocalin Proteins as an Alternative Antimicrobial Strategy.

Iron acquisition mediated by siderophores, high-affinity chelators for which bacteria have evolved specific synthesis and uptake mechanisms, plays a crucial role in microbiology and in host-pathogen interactions. In the ongoing fight against bacterial infections, this area has attracted biomedical interest. Beyond several approaches to interfere with siderophore-mediated iron uptake from medicinal and immunochemistry, the development of high-affinity protein scavengers that tightly complex the siderophores produced by pathogenic bacteria has appeared as a novel strategy. Such binding proteins have been engineered based on siderocalin-also known as lipocalin 2-an endogenous human scavenger of enterobactin and bacillibactin that controls the systemic spreading of commensal bacteria such as Escherichia coli. By using combinatorial protein design, siderocalin was reshaped to bind several siderophores from Pseudomonas aeruginosa and, in particular, petrobactin from Bacillus anthracis, none of which is recognized by the natural protein. Such engineered versions of siderocalin effectively suppress the growth of corresponding pathogenic bacteria by depriving them of their iron supply and offer the potential to complement antibiotic therapy in situations of acute or persistent infection.

Lipocalin-2 is increased in amyotrophic lateral sclerosis.

BACKGROUND: The exact mechanisms underlying neuroinflammation and how they contribute to amyotrophic lateral sclerosis (ALS) pathogenesis remain unclear. One possibility is the secretion of neurotoxic factors, such as lipocalin-2 (LCN2), that lead to neuronal death. METHODS: LCN2 levels were measured in human postmortem tissue using Western blot, quantitative real time polymerase chain reaction, and immunofluorescence, and in plasma by enzyme-linked immunosorbent assay. SH-SY5Y cells were used to test the pro-inflammatory effects of LCN2. RESULTS: LCN2 is increased in ALS postmortem motor cortex, spinal cord, and plasma. Furthermore, we identified several LCN2 variants in ALS patients that may contribute to disease pathogenesis. Lastly, while LCN2 treatment caused cell death and increased pro-inflammatory markers, treatment with an anti-LCN2 antibody prevented these responses in vitro. CONCLUSIONS: LCN2 upregulation in ALS postmortem samples and plasma may be an upstream event for triggering neuroinflammation and neuronal death.

Effects of adipokine administration to the hypothalamic preoptic area on body temperature in rats.

The effects of adipokine administration to the hypothalamic preoptic area (POA), which is one of the body temperature (BT) regulation centers in the central nervous system, on BT were investigated in male Wistar rats. BT was measured in conscious rats using telemetry. Insulin-like growth factor-1 (IGF-1), interleukin-1ß (IL-1ß), monocyte chemoattractant protein-1 and lipocalin-2 produced hyperthermia, and the effects induced by IL-1ß (25 ng) and IGF-1 (5 µg) were sustainable and remarkable. IL-6 did not show any significant effect. The IGF-1-induced effect was inhibited by pretreatment with IGF binding protein 3 (IGFBP3) or NVP-AEW541 (NVP, a selective inhibitor of type 1 IGF receptor tyrosine kinase, IGF1R TK). NVP-induced inhibition was observed only in the early phase of IGF-1-induced hyperthermia. In addition, IGF-1 increased the IL-1ß concentration in the microdialysate of POA perfusion, but did not increase the IL-1ß concentration in the plasma or the PGE2 concentration in the microdialysate. These findings suggested that IGF-1 produced hyperthermia, which was mediated, at least a part, through an increased IL-1ß concentration after activation of IGF1R TK in the POA, and the IGF-IGFBP system possibly participates in BT homeostasis in the POA.

Protective effect and mechanisms of exogenous neutrophil gelatinase-associated lipocalin on lipopolysaccharide-induced injury of renal tubular epithelial cell.

PURPOSES: To investigate the protective effect of exogenous neutrophil gelatinase-associated lipocalin (NGAL) on the lipopolysaccharide-induced injury of renal tubular epithelial cells and its regulation of autophagy. METHODS: Renal tubular epithelial cells were treated with lipopolysaccharide (LPS) at different concentrations (0-100 µg/mL) and at different times (0-24 h), the expression of NGAL was detected to determine the optimal time and concentration of LPS treatment. The NGAL gene knockdown lentivirus (NGAL-RNAi) was constructed and verified its knockdown rate and inhibition effect. Renal tubular epithelial cells were randomly divided into Control group, LPS group, LPS + NGAL group, NGAL-RNAi + LPS group, and NGAL-RNAi + LPS + NGAL group. Western blot and immunofluorescence tested the expression of autophagy-associated proteins, the changes in the number of autophagosomes were observed by electron microscopy, analyzed the role of exogenous NGAL. RESULTS: The study showed the expression of autophagy-associated proteins (LC3-II and Beclin-1) in NGAL-RNAi + LPS group was significantly lower than the LPS group (P < 0.0100). The expression of LC3-II and Beclin-1 in the NGAL-RNAi + LPS + NGAL group was significantly higher than the NGAL-RNAi + LPS group (P < 0.0100). After the addition of exogenous NGAL, the autophagosomes in the LPS + NGAL group and the NGAL-RNAi + LPS + NGAL group were significantly increased under the electron microscope compared with the LPS group and the NGAL-RNAi + LPS group, and the cell proliferation rate and cell viability was significantly higher than unjoined groups (P < 0.0500). CONCLUSION: NGAL knockdown can significantly reduce the level of autophagy and decrease the proliferation rate and viability of cells.The addition of exogenous NGAL can increase the level of autophagy. This suggests that NGAL may play a protective role in the LPS-induced injury of renal tubular epithelial cells by promoting autophagy.

Bacterial Siderophores Hijack Neutrophil Functions.

Neutrophils are the primary immune cells that respond to inflammation and combat microbial transgression. To thrive, the bacteria residing in their mammalian host have to withstand the antibactericidal responses of neutrophils. We report that enterobactin (Ent), a catecholate siderophore expressed by Escherichia coli, inhibited PMA-induced generation of reactive oxygen species (ROS) and neutrophil extracellular traps (NETs) in mouse and human neutrophils. Ent also impaired the degranulation of primary granules and inhibited phagocytosis and bactericidal activity of neutrophils, without affecting their migration and chemotaxis. Molecular analysis revealed that Ent can chelate intracellular labile iron that is required for neutrophil oxidative responses. Other siderophores (pyoverdine, ferrichrome, deferoxamine) likewise inhibited ROS and NETs in neutrophils, thus indicating that the chelation of iron may largely explain their inhibitory effects. To counter iron theft by Ent, neutrophils rely on the siderophore-binding protein lipocalin 2 (Lcn2) in a "tug-of-war" for iron. The inhibition of neutrophil ROS and NETs by Ent was augmented in Lcn2-deficient neutrophils compared with wild-type neutrophils but was rescued by the exogenous addition of recombinant Lcn2. Taken together, our findings illustrate the novel concept that microbial siderophore's iron-scavenging property may serve as an antiradical defense system that neutralizes the immune functions of neutrophils.

Lipocalin 2: A New Antimicrobial in Mast Cells.

Mast cells (MCs) play a significant role in the innate immune defense against bacterial infection through the release of cytokines and antimicrobial peptides. However, their antimicrobial function is still only partially described. We therefore hypothesized that MCs express additional antimicrobial peptides. In this study, we used FANTOM 5 transcriptome data to identify for the first time that MCs express lipocalin 2 (LCN2), a known inhibitor of bacterial growth. Using MCs derived from mice which were deficient in LCN2, we showed that this antimicrobial peptide is an important component of the MCs' antimicrobial activity against Escherichia coli (E. coli). Since sphingosine-1-phosphate receptors (S1PRs) on MCs are known to regulate their function during infections, we hypothesized that S1P could activate LCN2 production in MCs. Using an in vitro assay, we demonstrated that S1P enhances MCs antimicrobial peptide production and increases the capacity of MCs to directly kill S. aureus and E. coli via an LCN2 release. In conclusion, we showed that LCN2 is expressed by MCs and plays a role in their capacity to inhibit bacterial growth.

Lipocalin 2 Suppresses Ocular Inflammation by Inhibiting the Activation of NF-κß Pathway in Endotoxin-Induced Uveitis.

BACKGROUND/AIMS: Lipocalin 2 (LCN2), an important mediator of a variety of cellular processes, is involved in regulating the inflammatory response, but its roles in different inflammatory diseases are controversial. Because the role of LCN2 in ocular inflammation has been unclear until now, we explored the function of LCN2 in lipopolysaccharide (LPS)-induced ocular inflammation in vivo and in vitro. METHODS: Endotoxin-induced uveitis (EIU) was induced in male Sprague Dawley rats by the intravitreal injection of LPS. The expression and location of LCN2 in the retina were detected with western blotting and immunohistochemistry, respectively. We determined the clinical scores for anterior inflammation, quantified the infiltrated inflammatory cells, and measured the pro-inflammatory factors to determine the anti-inflammatory effects of LCN2 in EIU eyes. Cultured primary rat Müller cells were stimulated with LPS and the expression and secretion of LCN2 were measured with real-time PCR, western blotting, and an ELISA. After Müller cells were cotreated with LPS and LCN2 or PBS, the expression and secretion of TNF-α, IL-6, and MCP-1 were examined with realtime PCR, western blotting, and ELISAs. Western blotting and immunofluorescence were used to detect the phosphorylation and cellular distribution of nuclear factor kappaB (NF-κB) subunit p65. RESULTS: In EIU, the expression of LCN2 was significantly upregulated in the retina, especially in the outer nuclear layer (mainly composed of Müller cells). LPS stimulation of cultured Müller cells also markedly elevated LCN2 expression. Intravitreal injection of LCN2 significantly reduced the clinical scores, inflammatory infiltration, and protein leakage in EIU, which correlated with the reduced levels of proinflammatory factors in the aqueous humor and retina. LCN2 treatment also reduced the expression and secretion of TNF-α, IL-6, and MCP-1 in LPS-stimulated Müller cells. LCN2 inhibited the inflammatory response by inhibiting the phosphorylation and translocation of NF-κB p65. CONCLUSIONS: LCN2 protects against ocular inflammation, at least in part, by negatively regulating the activation of the NF-κB signaling pathway. LCN2 may be a promising anti-inflammatory therapy for ocular diseases, such as uveitis.

Bone: Another potential target to treat, prevent and predict diabetes.

Type 2 diabetes mellitus is now a worldwide health problem with increasing prevalence. Mounting efforts have been made to treat, prevent and predict this chronic disease. In recent years, increasing evidence from mice and clinical studies suggests that bone-derived molecules modulate glucose metabolism. This review aims to summarize our current understanding of the interplay between bone and glucose metabolism and to highlight potential new means of therapeutic intervention. The first molecule recognized as a link between bone and glucose metabolism is osteocalcin (OCN), which functions in its active form, that is, undercarboxylated OCN (ucOC). ucOC acts in promoting insulin expression and secretion, facilitating insulin sensitivity, and favouring glucose and fatty acid uptake and utilization. A second bone-derived molecule, lipocalin2, functions in suppressing appetite in mice through its action on the hypothalamus. Osteocytes, the most abundant cells in bone matrix, are suggested to act on the browning of white adipose tissue and energy expenditure through secretion of bone morphogenetic protein 7 and sclerostin. The involvement of bone resorption in glucose homeostasis has also been examined. However, there is evidence indicating the implication of the receptor activator of nuclear factor κ-B ligand, neuropeptide Y, and other known and unidentified bone-derived factors that function in glucose homeostasis. We summarize recent advances and the rationale for treating, preventing and predicting diabetes by skeleton intervention.