Tissue involution and the acute phase response

Overview of the expression patterns and roles of Lipocalin 2 in the reproductive system

The 25 kDa-sized protein Lipocalin 2 (LCN2) was originally isolated from human neutrophil granulocytes more than 30 years ago. LCN2 is an emerging player in innate immune defense, as it reduces bacterial growth due to its ability to sequester iron-containing bacterial siderophores. On the other hand, LCN2 also serves as a transporter for various hydrophobic substances due to its β-barrel shaped structure. Over the years, LCN2 has been detected in many other cell types including epithelial cells, astrocytes, and hepatocytes. Studies have clearly shown that aberrant expression of LCN2 is associated with a variety of disorders and malignancies, including several diseases of the reproductive system. Furthermore, LCN2 was proposed as a non-invasive prognostic and/or diagnostic biomarker in this context. Although several studies have shed light on the role of LCN2 in various disorders of the female and male reproductive systems, including tumorigenesis, a comprehensive understanding of the physiological function of LCN2 in the reproductive tract is still lacking. However, there is evidence that LCN2 is directly related to fertility, as global depletion of Lcn2 in mice has a negative effect on their pregnancy rate. Since LCN2 expression can be regulated by steroid hormones, it is not surprising that its expression fluctuates greatly during remodeling processes in the female reproductive tract, especially in the uterus. Well-founded details about the expression and regulation of LCN2 in a healthy reproductive state and also about possible changes during reproductive aging could contribute to a better understanding of LCN2 as a target in various diseases. Therefore, the present review summarizes current knowledge about LCN2 in the reproductive system, including studies in rodents and humans, and discusses changes in LCN2 expression during pathological events. The limited data suggest that LCN2 is expressed and regulated differently in healthy male and female reproductive organs.

NGAL Mediates Anaplastic Thyroid Carcinoma Cells Survival Through FAS/CD95 Inhibition

Neutrophil gelatinase-associated lipocalin (NGAL), a siderophore-mediated iron binding protein, is highly expressed in human anaplastic thyroid carcinomas (ATCs) where it plays pleiotropic protumorigenic roles including that of a prosurvival protein. Here we show that NGAL inhibits FAS/CD95 death receptor to control ATC cell survival. FAS/CD95 expression in human specimens from patients with ATC and in ATC-derived cell lines negatively correlate with NGAL expression. Silencing of NGAL in ATC cells leads to FAS/CD95 upregulation, whereas NGAL overexpression determines the opposite effect. As a result, an agonist anti-FAS/CD95 antibody induces cell death in NGAL-silenced cells while it is ineffective on NGAL-overexpressing cells. Interestingly, the inhibitory activity of NGAL on FAS/CD95 is due to its iron carrier property given that perturbing iron homeostasis of NGAL-proficient and -deficient ATC cells directly influences FAS/CD95 expression. Accordingly, conditioned media containing a mutant form of NGAL unable to bind siderophores cannot rescue cells from FAS/CD95-dependent death, whereas NGAL wild type-containing conditioned media abolish the effects of the agonist antibody. We also find that downregulation of FAS/CD95 expression is mediated by iron-dependent NGAL suppression of p53 transcriptional activity. Our results indicate that NGAL contributes to ATC cell survival by iron-mediated inhibition of p53-dependent FAS/CD95 expression and suggest that restoring FAS/CD95 by NGAL suppression could be a helpful strategy to kill ATC cells.

Neutrophil Gelatinase-Associated Lipocalin and Hypertensive Disorders of Pregnancy: A Cohort Study in Twin Pregnancies

Hypertensive disorders complicate more than 10% of twin pregnancies. Several studies showed increased neutrophil gelatinase-associated lipocalin (NGAL) values in women with singleton pregnancies and preeclampsia. This study aimed to assess NGAL values in twin pregnancies complicated by hypertensive disorders. We conducted a study of 242 consecutive twin pregnancies at the Medical University of Vienna. Serum NGAL was evaluated twice during pregnancy and once in the postpartum period. Furthermore, serum NGAL values were compared between women who developed hypertensive disorders and those who had normal blood pressure. In all twin pregnancies, mean NGAL values increased significantly from the first to the second visit (p = 0.004) and, further, after delivery (p < 0.001). NGAL was significantly higher in pregnancies that developed pregnancy hypertension or preeclampsia when compared to the control group at the first visit (109.2 ± 48.9 ng/mL vs. 91.9 ± 29.4 ng/mL, p = 0.04, respectively). The predictive power of first visit NGAL values for development of pregnancy hypertension or preeclampsia was evaluated. When using a cut-off value of 115 ng/mL, we obtained a sensitivity of 45% with a specificity of 77%. We conclude that women with twin pregnancies who develop hypertensive disorders of pregnancy showed increased NGAL values at 11−16 weeks.

Neutrophil gelatinase-associated lipocalin as an immunomodulator in endocrine hypertension

In recent studies, primary aldosteronism (PA) has been reported as the most common etiology for secondary hypertension of endocrine origin, accounting for approximately 10% of cases. In PA, excess aldosterone production can lead to deleterious effects at the cardiovascular (CV) and renal levels by activating mineralocorticoid receptors, which involves an increase in pro-inflammatory and pro-fibrotic mediators. Among these mediators, neutrophil gelatinase-associated lipocalin (NGAL), a secretion glycoprotein belonging to the lipocalin superfamily, has been closely linked to CV and renal damage in several pathological conditions. Because NGAL can be detected in biofluids such as plasma and urine, it has been proposed as a damage biomarker for target tissues and has also been studied for its role in hypertension and associated with PA. NGAL is produced by many different cell types, can be carried on extracellular vesicles, and is modulated by microRNAs, which would support its use as a biomarker for endocrine hypertension due to PA. Over the last decade, studies have shown that NGAL is necessary for the development of aldosterone-induced hypertension and that is associated with end-organ damage. In addition, it has been proposed that some mechanisms are dependent on the activation of immune cells, such as dendritic cells and macrophages, where the release of specific cytokines (i.e., interleukin [IL]-23) or chemokines (i.e., CCL-5) induced by aldosterone would depend on NGAL. Subsequently, this activates the T helper (Th) lymphocytes, such as Th₁₇ and Th₂, resulting in CV and renal fibrosis due to the high aldosterone levels. Although the immune system has been closely associated with essential hypertension, its participation in endocrine hypertension has not been fully elucidated. This review discusses the link between NGAL and endocrine hypertension, particularly in the context of PA, and their possible regulators and mechanisms, with a focus on its role as an immunomodulator.

Lipocalin-2-induced proliferative endoplasmic reticulum stress participates in Kawasaki disease-related pulmonary arterial abnormalities

Clinical cases have reported pulmonary arterial structural and functional abnormalities in patients with Kawasaki disease (KD); however, the underlying mechanisms are unclear. In this study, a KD rat model was established via the intraperitoneal injection of Lactobacillus casei cell wall extract (LCWE). The results showed that pulmonary arterial functional and structural abnormalities were observed in KD rats. Furthermore, proliferative endoplasmic reticulum stress (ER stress) was observed in the pulmonary arteries of KD rats. Notably, the level of lipocalin-2 (Lcn 2), a trigger factor of inflammation, was remarkably elevated in the plasma and lung tissues of KD rats; increased Lcn 2 levels following LCWE stimulation may result from polymorphonuclear neutrophils (PMNs). Correspondingly, in cultured pulmonary artery smooth muscle cells (PASMCs), Lcn 2 markedly augmented the cleavage and nuclear localization of activating transcription factor-6 (ATF6), upregulated the transcription of glucose regulated protein 78 (GRP78) and neurite outgrowth inhibitor (NOGO), and promoted PASMCs proliferation. However, proapoptotic C/EBP homologous protein (CHOP) and caspase 12 levels were not elevated. Treatment with 4-phenyl butyric acid (4-PBA, a specific inhibitor of ER stress) inhibited PASMCs proliferation induced by Lcn 2 and attenuated pulmonary arterial abnormalities and right ventricular hypertrophy and reduced right ventricular systolic pressure in KD rats. In conclusion, Lcn 2 remarkably facilitates proliferative ER stress in PASMCs, which probably accounts for KD-related pulmonary arterial abnormalities.

The Lipocalin2 Gene is Regulated in Mammary Epithelial Cells by NFκB and C/EBP In Response to Mycoplasma

Lcn2 gene expression increases in response to cell stress signals, particularly in cells involved in the innate immune response. Human Lcn2 (NGAL) is increased in the blood and tissues in response to many stressors including microbial infection and in response to LPS in myeloid and epithelial cells. Here we extend the microbial activators of Lcn2 to mycoplasma and describe studies in which the mechanism of Lcn2 gene regulation by MALP-2 and mycoplasma infection was investigated in mouse mammary epithelial cells. As for the LPS response of myeloid cells, Lcn2 expression in epithelial cells is preceded by increased TNFα, IL-6 and IκBζ expression and selective reduction of IκBζ reduces Lcn2 promoter activity. Lcn2 promoter activation remains elevated well beyond the period of exposure to MALP-2 and is persistently elevated in mycoplasma infected cells. Activation of either the human or the mouse Lcn2 promoter requires both NFκB and C/EBP for activation. Thus, Lcn2 is strongly and enduringly activated by mycoplasma components that stimulate the innate immune response with the same basic regulatory mechanism for the human and mouse genes.

Lipocalin-2-The myth of its expression and function

Lipocalin-2 is a functional biomarker for acute and chronic kidney diseases, heart failure and obesity-related medical complications. It is rapidly induced in epithelial cells under stress conditions, but constitutively produced from pre-adipocytes and mature adipocytes. Measuring the lipocalin-2 levels represents an effective approach for risk prediction, patient stratification and disease management. Nevertheless, due to ligand-binding, post-translational modification and protein-protein interaction, lipocalin-2 exists as multiple variants that elicit different pathophysiological functions. To characterize the specific structure-functional relationships of lipocalin-2 variants is critical for the development of biomarker assays with sufficient precision and reliability. Moreover, identifying the pathological forms of lipocalin-2 will provide new therapeutic targets and treatment approaches for obesity-related complications.

NGAL promotes recruitment of tumor infiltrating leukocytes

We have previously shown that Neutrophil Gelatinase-Associated Lipocalin (NGAL) is strongly expressed in thyroid carcinomas, especially of anaplastic type, where it protects neoplastic cells from serum deprivation-induced apoptosis and enhances tumor invasivity by regulating MMP-9 activity. Here we demonstrate that NGAL-containing conditioned medium from human anaplastic thyroid carcinoma (ATC) cells is able to induce monocyte migration via up-regulation of a number of different chemokines. The enhanced chemokines transcription is due to the NGAL-mediated intracellular iron uptake. Very importantly, mice tumor allografts raised from subcutaneous injection of syngeneic colon carcinoma cell lines, expressing high levels of NGAL, show a dense leukocyte infiltrate which strongly decreases in tumor allografts from NGAL-depleted cell injected mice.

Our results indicate that the NGAL promotes leukocytes recruitment in tumor microenvironment through iron-mediated chemokines production.

Postpartum psychiatric disorders

Pregnancy is a complex and vulnerable period that presents a number of challenges to women, including the development of postpartum psychiatric disorders (PPDs). These disorders can include postpartum depression and anxiety, which are relatively common, and the rare but more severe postpartum psychosis. In addition, other PPDs can include obsessive-compulsive disorder, post-traumatic stress disorder and eating disorders. The aetiology of PPDs is a complex interaction of psychological, social and biological factors, in addition to genetic and environmental factors. The goals of treating postpartum mental illness are reducing maternal symptoms and supporting maternal-child and family functioning. Women and their families should receive psychoeducation about the illness, including evidence-based discussions about the risks and benefits of each treatment option. Developing effective strategies in global settings that allow the delivery of targeted therapies to women with different clinical phenotypes and severities of PPDs is essential.

A neuro-immune, neuro-oxidative and neuro-nitrosative model of prenatal and postpartum depression

A large body of evidence indicates that major affective disorders are accompanied by activated neuro-immune, neuro-oxidative and neuro-nitrosative stress (IO&NS) pathways. Postpartum depression is predicted by end of term prenatal depressive symptoms whilst a lifetime history of mood disorders appears to increase the risk for both prenatal and postpartum depression. This review provides a critical appraisal of available evidence linking IO&NS pathways to prenatal and postpartum depression. The electronic databases Google Scholar, PubMed and Scopus were sources for this narrative review focusing on keywords, including perinatal depression, (auto)immune, inflammation, oxidative, nitric oxide, nitrosative, tryptophan catabolites (TRYCATs), kynurenine, leaky gut and microbiome. Prenatal depressive symptoms are associated with exaggerated pregnancy-specific changes in IO&NS pathways, including increased C-reactive protein, advanced oxidation protein products and nitric oxide metabolites, lowered antioxidant levels, such as zinc, as well as lowered regulatory IgM-mediated autoimmune responses. The latter pathways coupled with lowered levels of endogenous anti-inflammatory compounds, including ω3 polyunsaturated fatty acids, may also underpin the pathophysiology of postpartum depression. Although increased bacterial translocation, lipid peroxidation and TRYCAT pathway activation play a role in mood disorders, similar changes do not appear to be relevant in perinatal depression. Some IO&NS biomarker characteristics of mood disorders are found in prenatal depression indicating that these pathways partly contribute to the association of a lifetime history of mood disorders and perinatal depression. However, available evidence suggests that some IO&NS pathways differ significantly between perinatal depression and mood disorders in general. This review provides a new IO&NS model of prenatal and postpartum depression.

Motoneuron degeneration in the trigeminal motor nucleus innervating the masseter muscle in Dystonia musculorum mice

Dystonia musculorum (dt) mice, which have a mutation in the Dystonin (Dst) gene, are used as animal models to investigate the human disease known as hereditary sensory and autonomic neuropathy type VI. Massive neuronal cell death is observed, mainly in the peripheral nervous system (PNS) of dt mice. We and others have recently reported a histopathological feature of these mice that neurofilament (NF) accumulates in various areas of the central nervous system (CNS), including motor pathways. Although dt mice show motor disorder and growth retardation, the causes for these are still unknown. Here we performed histopathological analyses on motor units of the trigeminal motor nucleus (Mo5 nucleus), because they are a good system to understand neuronal responses in the mutant CNS, and abnormalities in this system may lead to problems in mastication, with subsequent growth retardation. We report that motoneurons with NF accumulation in the Mo5 nuclei of Dst^Gt homozygous mice express the stress-induced genes CHOP, ATF3, and lipocalin 2 (Lcn2). We also show a reduced number of Mo5 motoneurons and a reduced size of Mo5 nuclei in Dst^Gt homozygous mice, possibly due to apoptosis, given the presence of cleaved caspase 3-positive Mo5 motoneurons. In the mandibular (V3) branches of the trigeminal nerve, which contains axons of Mo5 motoneurons and trigeminal sensory neurons, there was infiltration of Iba1-positive macrophages. Finally, we report atrophy of the masseter muscles in Dst^Gt homozygous mice, which showed abnormal nuclear localization of myofibrils and increased expression of atrogin-1 mRNA, a muscle atrophy-related gene and weaker masseter muscle strength with uncontrolled muscle activity by electromyography (EMG). Taken together, our findings strongly suggest that mastication in dt mice is affected due to abnormalities of Mo5 motoneurons and masseter muscles, leading to growth retardation at the post-weaning stages.

Toll-like receptor expression patterns in the rat uterus during post partum involution

Toll-like receptors (TLRs) belong to a family of pathogen recognition receptors and play critical roles in detecting and responding to invading pathogens. TLR expression could be significant because, in the uterus, the reproductive tract is an important site of exposure to and infection by pathogens during the post partum involution period. To clarify the expression and localisation patterns of TLRs in the rat uterus on Days 1, 3, 5 and 10 post partum (PP1, PP3, PP5 and PP10 respectively), immunohistochemistry and western blotting were used to analyse TLR1-7, TLR9 and TLR10. The immunohistochemistry results indicated that TLR1-7, TLR9 and TLR10 were localised in both the cytoplasm and nuclei of luminal and glandular epithelium, stromal fibroblasts and myometrial cells in the rat uterus. In the luminal epithelium, TLR4-7 were also found in lateral membranes, whereas TLR10 was present in apical membranes. Western blot analysis revealed that the expression of TLR proteins increased with the number of days post partum, reaching a maximum on PP10, although levels did not differ significantly from those on PP1 (P>0.05). These findings confirm that TLR1-7, TLR9 and TLR10 are constitutively expressed in uterine cells and that localisation pattern of TLRs in the endometrium varies with structural changes in the uterus on different days of involution. These results suggest that TLRs may play a role in uterine repair and remodelling during physiological involution.

Levels of neutrophil gelatinase-assosciated lipocalin in patients with head and neck squamous cell carcinoma in Indian population from Haryana state

AIM

To study the levels of neutrophil gelatinase associated lipocalin (NGAL) in head and neck squamous cell carcinoma (HNSCC).

METHODS

This was a non randomized case control study conducted at Department of Biochemistry, in collaboration with Regional Cancer Center over a period of one year. The study population included 50 adult newly diagnosed HNSCC patients reporting in outpatient department at Regional Cancer Center and compared with 50 healthy controls. NGAL was estimated by ELISA technique. Student t test and χ2 test were applied for comparison of means of study groups. Correlations between groups were analyzed using Pearson correlation coefficient (r) formula.

RESULTS

Patients with HNSCC exhibited significantly increased levels of NGAL (P < 0.05) as compared to healthy controls (978.88 ± 261.39 ng/mL vs 34.83 ± 7.59 ng/mL). Out of 50, 26 patients (52%) were in stage IV, 21 (42%) in stage III, 1 (2%) patient in stage II and 2 (4%) patients were in stage I. Metastasis was absent in 98% patients and mean NGAL levels were highest in these patients but P value was not significant. Mean NGAL levels were highest in stage IV [1041.54 ± 222.15 ng/mL (stage IV) vs 1040 ± 0.00 ng/mL (stage I); 900 ± 0.00 ng/mL (stage II) and 1031.90 ± 202.55 ng/mL (stage III)] and χ2 test was highly significant (P < 0.001). Thirty-six patients (72%) were having moderately differentiated HNSCC and mean NGAL levels were maximum in patients with well differentiated HNSCC (1164 ± 315.64 ng/mL vs 1013.33 ± 161.19 ng/mL in moderately differentiated and 890 ± 11.55 ng/mL in poorly differentiated) and the results were also highly significant (P < 0.001, χ2 test).

CONCLUSION

The present work demonstrates a potential role of NGAL as cancer biomarker and its use in monitoring the HNSCC progression.

Inflammatory markers in late pregnancy in association with postpartum depression-A nested case-control study

Recent studies indicate that the immune system adaptation during pregnancy could play a significant role in the pathophysiology of perinatal depression. The aim of this study was to investigate if inflammation markers in a late pregnancy plasma sample can predict the presence of depressive symptoms at eight weeks postpartum. Blood samples from 291 pregnant women (median and IQR for days to delivery, 13 and 7-23days respectively) comprising 63 individuals with postpartum depressive symptoms, as assessed by the Edinburgh postnatal depression scale (EPDS≥12) and/or the Mini International Neuropsychiatric Interview (M.I.N.I.) and 228 controls were analyzed with an inflammation protein panel using multiplex proximity extension assay technology, comprising of 92 inflammation-associated markers. A summary inflammation variable was also calculated. Logistic regression, LASSO and Elastic net analyses were implemented. Forty markers were lower in late pregnancy among women with depressive symptoms postpartum. The difference remained statistically significant for STAM-BP (or otherwise AMSH), AXIN-1, ADA, ST1A1 and IL-10, after Bonferroni correction. The summary inflammation variable was ranked as the second best variable, following personal history of depression, in predicting depressive symptoms postpartum. The protein-level findings for STAM-BP and ST1A1 were validated in relation to methylation status of loci in the respective genes in a different population, using openly available data. This explorative approach revealed differences in late pregnancy levels of inflammation markers between women presenting with depressive symptoms postpartum and controls, previously not described in the literature. Despite the fact that the results do not support the use of a single inflammation marker in late pregnancy for assessing risk of postpartum depression, the use of STAM-BP or the novel notion of a summary inflammation variable developed in this work might be used in combination with other biological markers in the future.

LCN2 overexpression in bone enhances the hematopoietic compartment via modulation of the bone marrow microenvironment

Lipocalin-2 (LCN2) is a member of the lipocalin family whose expression is modulated in several conditions, including cell differentiation, innate immunity, stress, and cancer. Although it is known that it is expressed in bone, its function in this tissue remains poorly studied. To this end, we took advantage of transgenic mice lines that expressed LCN2 driven by a bone specific type I collagen (LCN2-Tg). In the bone marrow (BM) of LCN2-Tg mice we observed an increased number of phenotypically long-term hematopoietic stem cells (LT-HSC) that also displayed a higher proliferation rate compared to wild-type controls (Wt). Furthermore, hematopoietic progenitor cells, obtained from LCN2-Tg BM showed an increased clonogenic capacity compared to those obtained from LCN2-Tg spleen, a higher concentration of serum erythropoietin and a higher number of mature erythrocytes in the peripheral blood of old LCN2-Tg animals compared to aged-matched wt. The findings of a combined increase in the BM of the LCN2-Tg mice of SDF-1, SCF, and TIMP-1 levels along with the reduction of both MMP-9 activity and cathepsin K concentration may explain the observed effects on the HSC compartment. This study shows that LCN2 overexpression in bones modifies the BM microenvironment via modulation of the expression of key secreted factors and cytokines, which in turn regulate the HSC niche behavior enhancing both HSC homing in young mice and erythrocytes production in older mice.

Lipocalin-2 Promotes Endoplasmic Reticulum Stress and Proliferation by Augmenting Intracellular Iron in Human Pulmonary Arterial Smooth Muscle Cells

Endoplasmic reticulum (ER) stress, a feature of many conditions associated with pulmonary hypertension (PH), is increasingly recognized as a common response to promote proliferation in the walls of pulmonary arteries. Increased expression of Lipocalin-2 in PH led us to test the hypothesis that Lipocalin-2, a protein known to sequester iron and regulate it intracellularly, might facilitate the ER stress and proliferation in pulmonary arterial smooth muscle cells (PASMCs). In this study, we observed greatly increased Lcn2 expression accompanied with increased ATF6 cleavage in a standard rat model of pulmonary hypertension induced by monocrotaline. In cultured human PASMCs, Lcn2 significantly promoted ER stress (determined by augmented cleavage and nuclear localization of ATF6, up-regulated transcription of GRP78 and NOGO, increased expression of SOD2, and mild augmented mitochondrial membrane potential) and proliferation (assessed by Ki67 staining and BrdU incorporation). Lcn2 promoted ER stress accompanied with augmented intracellular iron levels in human PASMCs. Treatment human PASMCs with FeSO4 induced the similar ER stress and proliferation response and iron chelator (deferoxamine) abrogated the ER stress and proliferation induced by Lcn2 in cultured human PASMCs. In conclusion, Lcn2 significantly promoted human PASMC ER stress and proliferation by augmenting intracellular iron. The up-regulation of Lcn2 probably involved in the pathogenesis and progression of PH.

Lipopolysaccharide-induced inflammation or unilateral ureteral obstruction yielded multiple types of glycosylated Lipocalin 2

Background

The amount of urinary glycoprotein lipocalin 2 (LCN2) has been known to increase after kidney injury because of failed reabsorption by the proximal tubules or direct secretion from injured tissues. However, the relationship between urinary tract obstruction and the isoform diversity of LCN2 has not been examined.

Methods

The urinary levels of LCN2 isoforms were examined in male mice after an intraperitoneal injection of lipopolysaccharide (LPS) or in a mouse model of unilateral ureter obstruction (UUO). The LCN2 levels in sera, bladder urine, renal pelvic urine, and tissue samples were also analyzed. Endo- and exoglycosidases were used to investigate the different N-glycan patterns of LCN2.

Results

Two isoforms of urinary LCN2 with different molecular weights were identified in an immunoblotting analysis, and the levels of both isoforms were increased 6 h after LPS administration. The primary LCN2 isoform was the lower molecular weight 22-kDa isoform, which was detected in the serum, urine, liver and kidney. In contrast, the 24-kDa LCN2 isoform was detected only in urine. In the UUO experiments, the levels of the 24-kDa LCN2 were increased in the bladder urine but not in the urine accumulated in the renal pelvis due to UUO. The 22-kDa LCN2 was identified in the renal pelvic urine from UUO mice. The peptide-N glycosidase F digestion of the two urinary LCN2 isoforms generated a single protein. Moreover, the two urinary LCN2 proteins were sensitive to neuraminidase and resistant to endoglycosidase H (Endo H). The LCN2 in the serum, lung and kidney was resistant to Endo H, as observed in urine, whereas the LCN2 in the liver and the ureter were degraded by this enzyme.

Conclusions

These results suggest that the difference in the molecular weights of the LCN2 proteins was due to their N-glycan structure. The high molecular weight LCN2 in urine could be detected after the inflammatory response to LPS and UUO. Furthermore, the sensitivity to Endo H identified the presence of two types of carbohydrate moieties, depending on the tissue in which the LCN2 was produced. These findings are useful for widening the clinical applicability of urinary LCN2 analyses.

Bidirectional psychoneuroimmune interactions in the early postpartum period influence risk of postpartum depression

More than 500,000 U.S. women develop postpartum depression (PPD) annually. Although psychosocial risks are known, the underlying biology remains unclear. Dysregulation of the immune inflammatory response and the hypothalamic-pituitary-adrenal (HPA) axis are associated with depression in other populations. While significant research on the contribution of these systems to the development of PPD has been conducted, results have been inconclusive. This is partly because few studies have focused on whether disruption in the bidirectional and dynamic interaction between the inflammatory response and the HPA axis together influence PPD. In this study, we tested the hypothesis that disruption in the inflammatory-HPA axis bidirectional relationship would increase the risk of PPD. Plasma pro- and anti-inflammatory cytokines were measured in women during the 3rd trimester of pregnancy and on Days 7 and 14, and Months 1, 2, 3, and 6 after childbirth. Saliva was collected 5 times the day preceding blood draws for determination of cortisol area under the curve (AUC) and depressive symptoms were measured using the Edinburgh Postpartum Depression Survey (EPDS). Of the 152 women who completed the EPDS, 18% were depressed according to EDPS criteria within the 6months postpartum. Cortisol AUC was higher in symptomatic women on Day 14 (p=.017). To consider the combined effects of cytokines and cortisol on predicting symptoms of PPD, a multiple logistic regression model was developed that included predictors identified in bivariate analyses to have an effect on depressive symptoms. Results indicated that family history of depression, day 14 cortisol AUC, and the day 14 IL8/IL10 ratio were significant predictors of PPD symptoms. One unit increase each in the IL8/IL10 ratio and cortisol AUC resulted in 1.50 (p=0.06) and 2.16 (p=0.02) fold increases respectively in the development of PPD. Overall, this model correctly classified 84.2% of individuals in their respective groups. Findings suggest that variability in the complex interaction between the inflammatory response and the HPA axis influence the risk of PPD.

Deletion of phospholipase A2 group IVc induces apoptosis in rat mammary tumour cells by the nuclear factor-κB/lipocalin 2 pathway

Although some forms of phospholipase A2, the initiator of the arachidonic acid cascade, contribute to carcinogenesis in many organs, the contribution of phospholipase A2 group IVc (Pla2g4c) remains to be clarified and the function of the enzyme in cancer development is unknown. The Hirosaki hairless rat (HHR), a mutant rat strain with autosomal recessive inheritance, derived spontaneously from the Sprague-Dawley rat (SDR). The HHRs showed a lower incidence and much smaller volume of mammary tumours induced by 7,12-dimethylbenz[a]anthracene, and a markedly increased number of TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling)-positive apoptotic cells was detected. Array comparative genomic hybridization and PCR analyses revealed the deletion of 50-kb genomic DNA on 1q21, including Pla2g4c, in HHRs. The Pla2g4c gene was expressed in the ductal carcinoma cells and myoepithelial cells in SDRs, but not in HHRs. The direct involvement of Pla2g4c in the prevention of cell death was demonstrated through the inhibition of its expression in rat mammary tumour RMT-1 cells using siRNA. This treatment also induced expression of lipocalin 2 (Lcn2) and other NF-κB (nuclear factor κB)-related genes. siRNA-induced apoptosis was inhibited by Lcn2 repression or NF-κB inhibitors. This is the first report on Pla2g4c gene-deficient rats and their low susceptibility to mammary carcinogenesis by enhancing NF-κB/Lcn2-induced apoptosis.

Correlation of plasma osteopontin and neutrophil gelatinase-associated lipocalin levels with the severity and clinical outcome of pelvic inflammatory disease

OBJECTIVE

To investigate the correlation of two important inflammatory biomarkers, plasma osteopontin and neutrophil gelatinase-associated lipocalin (NGAL), with the severity and outcome of pelvic inflammatory disease (PID).

MATERIALS AND METHODS

Sixty-one patients with PID, including 25 patients with tubo-ovarian abscess (TOA), were consecutively recruited. Their blood samples were tested for the concentrations of plasma osteopontin and NGAL using enzyme-linked immunosorbent assay. The associations of these biomarkers with TOA, length of hospitalization, and incidence of surgery were also analyzed.

RESULTS

Plasma osteopontin level was significantly increased in PID patients with TOA compared to PID patients without TOA (median 107.77 ng/mL vs. 72.39 ng/mL, p = 0.004). However, there was no significant difference for plasma NGAL. If the cutoff level of plasma osteopontin was set at 81.1 ng/mL, there was a 76.0% sensitivity and a 24.0% false negative rate in predicting TOA in PID patients. Plasma osteopontin significantly correlated with length of hospital stay (r = 0.467, p < 0.001), and this correlation was better than that of NGAL. However, neither biomarker was associated with incidence of surgery.

CONCLUSION

Plasma osteopontin has a better correlation with TOA and length of hospitalization compared to NGAL. If plasma osteopontin level falls below 81.1 ng/mL, PID patients will have about a 20% chance of developing TOA. Incorporating plasma osteopontin, but not NGAL, will allow for an adjuvant diagnostic biomarker for TOA and predictor of length of hospital stay.

Immune changes and dysphoric moods across the postpartum

PROBLEM

Little is known about postpartum immune recovery and relationships of common dysphoric moods, stress, immunology, and endocrinology.

METHOD OF STUDY

Healthy women (n = 72) were followed for six postpartum months with immune and hormone measures and dysphoric moods and stress scales. A panel of cytokines produced in mitogen-stimulated whole blood assays were measured at each time, along with plasma levels of hsC-reactive protein (hsCRP), Interleukin-6 (IL-6), and a panel of hormones.

RESULTS

Cellular immunity, measured by production of Interferon-gamma (IFNγ) and (Interleukin-2 (IL-2) from stimulated whole blood culture, was low in the early postpartum with changes by 3 months. Tumor necrosis factor alpha (TNFα) showed a similar pattern. Plasma levels of CRP and Interleukin-6 (IL-6) showed higher levels in the early postpartum. Mood disturbance scores dropped across the postpartum with a change in slope at 3 months. No significant relationships were found between immune, endocrine, and psychosocial measures.

CONCLUSION

Return to normal cellular immune function may take 3-4 months in the postpartum. Some aspects of early immunology (hsCRP and IL-6) probably reflect the latter stage of pregnancy, the stress of birth and the inflammation associated with involution. Dysphoric moods are higher in the early postpartum but are not related to immune factors or hormones.

Up-regulated lipocalin-2 in pulmonary hypertension involving in pulmonary artery SMC resistance to apoptosis

A key feature of pulmonary hypertension (PH) is the remodeling of small pulmonary arteries due to abnormal pulmonary artery smooth muscle cell (PASMC) proliferation and resistance to apoptosis. However, the cellular mechanisms underlying how PASMCs in the pathological condition of pulmonary hypertension become resistant to apoptosis remain unknown. It was recently reported that lipocalin 2 (Lcn2) is up-regulated in a wide array of malignant conditions, which facilitates tumorigenesis partly by inhibiting cell apoptosis. In this study, we observed that the expression levels of Lcn2 were significantly elevated in a rat PH model induced with monocrotaline and in patients with congenital heart disease-associated PH (CHD-PH) when compared with respective control. Therefore, we hypothesize that Lcn2 could regulate human PASMC (HPASMC) apoptosis through a mechanism. By the detection of DNA fragmentation using the TUNEL assay, the detection of Annexin V/PI-positive cells using flow cytometry, and the detection of cleaved caspase-3 and caspase-3 activity, we observed that Lcn2 significantly inhibited HPASMC apoptosis induced by serum withdrawal and H2O2 treatment. We also observed that Lcn2 down-regulated the proapoptotic protein Bax, decreased the levels of cellular ROS, and up-regulated the expression of superoxide dismutases (SOD1 and SOD2). In conclusion, Lcn2 significantly inhibits HPASMC apoptosis induced by oxidative stress via decreased intracellular ROS and elevated SODs. Up-regulation of Lcn2 in a rat PH model and CHD-PH patients may be involved in the pathological process of PH.

Acute Phase Protein Lipocalin-2 Is Associated with Formalin-induced Nociception and Pathological Pain

Lipocalin-2 (LCN2) is an acute-phase protein induced by injury, infection, or other inflammatory stimuli. LCN2 binds small hydrophobic ligands and interacts with cell surface receptor to regulate diverse cellular processes. The role of LCN2 as a chemokine inducer in the central nervous system (CNS) has been previously reported. Based on the previous participation of LCN2 in neuroinflammation, we investigated the role of LCN2 in formalin-induced nociception and pathological pain. Formalin-induced nociceptive behaviors (licking/biting) and spinal microglial activation were significantly reduced in the second or late phase of the formalin test in Lcn2 knockout mice. Likewise, antibody-mediated neutralization of spinal LCN2 attenuated the mechanical hypersensitivity induced by peripheral nerve injury in mice. Taken together, our results suggest that LCN2 can be therapeutically targeted, presumably for both prevention and reversal of acute inflammatory pain as well as pathological pain.

Altered bone development and turnover in transgenic mice over-expressing lipocalin-2 in bone

Lipocalin-2 (LCN2) is a protein largely expressed in many tissues, associated with different biological phenomena such as cellular differentiation, inflammation and cancer acting as a survival/apoptotic signal. We found that LCN2 was expressed during osteoblast differentiation and we generated transgenic (Tg) mice over-expressing LCN2 in bone. Tg mice were smaller and presented bone microarchitectural changes in both endochondral and intramembranous bones. In particular, Tg bones displayed a thinner layer of cortical bone and a decreased trabecular number. Osteoblast bone matrix deposition was reduced and osteoblast differentiation was slowed-down. Differences were also observed in the growth plate of young transgenic mice where chondrocyte displayed a more immature phenotype and a lower proliferation rate. In bone marrow cell cultures from transgenic mice, the number of osteoclast progenitors was increased whereas in vivo it was increased the number of mature osteoclasts expressing tartrate-resistant acid phosphatase (TRAP). Finally, while osteoprotegerin (OPG) levels remained unchanged, the expression of the conventional receptor activator of nuclear factor-κB ligand (RANKL) and of the IL-6 was enhanced in Tg mice. In conclusion, we found that LCN2 plays a role in bone development and turnover having both a negative effect on bone formation, by affecting growth plate development and interfering with osteoblast differentiation, and a positive effect on bone resorption by enhancing osteoclast compartment.

Knockdown of lipocalin-2 suppresses the growth and invasion of prostate cancer cells

BACKGROUND

Lipocalin-2 (LCN2) is a member of the lipocalin superfamily, and it has an important role in the regulation of cellular oncogenesis and apoptosis. However, the role for LCN2 in prostate cancer remains unclear.

METHOD

LCN2 expression has been determined by Western blotting, qRT-PCR, and immunohistochemistry in the human prostate cell lines PC3, DU145, LNCaP, and 22Rv, and in human prostate tissue array. In this study, we identified shRNA-LCN2 to determine the role of LCN2 in prostate-cancer cell proliferation, migration, and invasion. Cell proliferative ability was measured by MTT, colony-formation, and cell-cycle analysis. The role of LCN2 in prostate-cancer cell migration and invasion was analyzed by cell-migration assay and Matrigel invasion assay. The effect of LCN2 knockdown on prostate tumor growth was assessed in a subcutaneous xenograft model.

RESULTS

LCN2 protein and mRNA expression are higher in PC3 and DU145 cells than in LNCaP and 22Rv cells, and prostate cancer tissue correlated significantly with tumor differentiation (P < 0.017) and Gleason's grade (P < 0.02). LCN2 knockdown in PC3 and DU145 cells decreased cell proliferation, colony formation, cell cycle arrest, migration, and invasion. Conversely, LCN2 overexpression in 22Rv cells produced the opposite effect. Subcutaneous xenografts in mice models showed decreased tumor growth in the LCN2-knockdown mice.

CONCLUSIONS

Our results suggest that LCN2 might play an important role in regulation of proliferation and invasion of human prostate cancer, and that it can be a valuable marker of prostate cancer progression.

Role of lipocalin-2-chemokine axis in the development of neuropathic pain following peripheral nerve injury

Lipocalin 2 (LCN2), which is also known as 24p3 and neutrophil gelatinase-associated lipocalin (NGAL), binds small, hydrophobic ligands and interacts with cell surface receptor 24p3R to regulate diverse cellular processes. In the present study, we examined the role of LCN2 in the pathogenesis of neuropathic pain using a mouse model of spared nerve injury (SNI). Lcn2 mRNA levels were significantly increased in the dorsal horn of the spinal cord after SNI, and LCN2 protein was mainly localized in neurons of the dorsal and ventral horns. LCN2 receptor 24p3R was expressed in spinal neurons and microglia after SNI. Lcn2-deficient mice exhibited significantly less mechanical pain hypersensitivity during the early phase after SNI, and an intrathecal injection of recombinant LCN2 protein elicited mechanical pain hypersensitivity in naive animals. Lcn2 deficiency, however, did not affect acute nociceptive pain. Lcn2-deficient mice showed significantly less microglial activation and proalgesic chemokine (CCL2 and CXCL1) production in the spinal cord after SNI than wild-type mice, and recombinant LCN2 protein induced the expression of these chemokines in cultured neurons. Furthermore, the expression of LCN2 and its receptor was detected in neutrophils and macrophages in the sciatic nerve following SNI, suggesting the potential role of peripheral LCN2 in neuropathic pain. Taken together, our results indicate that LCN2 plays a critical role in the development of pain hypersensitivity following peripheral nerve injury and suggest that LCN2 mediates neuropathic pain by inducing chemokine expression and subsequent microglial activation.

Impaired neutrophil function in 24p3 null mice contributes to enhanced susceptibility to bacterial infections

Lipocalin 24p3 (24p3) is a neutrophil secondary granule protein. 24p3 is also a siderocalin, which binds several bacterial siderophores. It was therefore proposed that synthesis and secretion of 24p3 by stimulated macrophages or release of 24p3 upon neutrophil degranulation sequesters iron-laden siderophores to attenuate bacterial growth. Accordingly, 24p3-deficient mice are susceptible to bacterial pathogens for which siderophores would normally be chelated by 24p3. Specific granule deficiency (SGD) is a rare congenital disorder characterized by complete absence of proteins in secondary granules. Neutrophils from SGD patients, who are prone to bacterial infections, lack normal functions, but the potential role of 24p3 in neutrophil dysfunction in SGD is not known. In this study, we show that neutrophils from mice genetically deficient for lipocalin 24p3 (24p3(-/-)) are defective in many neutrophil functions. Specifically, neutrophils in 24p3(-/-) mice do not extravasate to sites of infection and are defective for chemotaxis. A transcriptome analysis revealed that genes that control cytoskeletal reorganization are selectively suppressed in 24p3(-/-) neutrophils. Additionally, small regulatory RNAs (microRNAs) that control upstream regulators of cytoskeletal proteins are also increased in 24p3(-/-) neutrophils. Further, 24p3(-/-) neutrophils failed to phagocytose bacteria, which may account for the enhanced sensitivity of 24p3(-/-) mice to both intracellular (Listeria monocytogenes) and extracellular (Candida albicans and Staphylococcus aureus) pathogens. Listeria does not secrete siderophores, and additionally, the siderophore secreted by Candida is not sequestered by 24p3. Therefore, the heightened sensitivity of 24p3(-/-) mice to these pathogens is not due to sequestration of siderophores limiting iron availability, but is a consequence of impaired neutrophil function.

Lipocalin-2 is associated with radioresistance in oral cancer and lung cancer cells

The aim of the present study was to identify a target molecule that could predict the efficacy of radiotherapy in oral squamous cell carcinoma (OSCC). We used DNA microarray analysis to identify differences in gene expression after X-ray irradiation. We compared the gene expression profiles between X-ray (8 Gy)-irradiated Ca9-22 cells (an OSCC-derived cell line) and unirradiated Ca9-22 cells. A total of 167 genes with a 2-fold higher level of expression induced by X-ray irradiation were identified. Lipocalin-2 (LCN2) had the greatest increase in expression after X-ray irradiation, and it was categorized in a network that has cancer-related functions with the Ingenuity Pathway Analysis tool. Upregulated expression of LCN2 mRNA was validated by real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) analysis. When the LCN2 gene was knocked down in OSCC cells (Ca9-22 and HSC-2) and lung cancer cells (A549) by using small interfering RNA, the radiosensitivity of these cells was enhanced. Our findings suggest that the overexpression of LCN2 is likely associated with radioresistance in oral cancer and lung cancer cells, and that LCN2 expression levels could be used to predict radioresistance. Thus, regulating the expression or function of LCN2 could enhance the radiation response, resulting in a favorable outcome of radiotherapy.

Genetic control of estrogen-regulated transcriptional and cellular responses in mouse uterus

The uterotropic response of the uterus to 17β-estradiol (E2) is genetically controlled, with marked variation observed depending on the mouse strain studied. Previous genetic studies from our laboratory using inbred mice that are high [C57BL/6J (B6)] or low [C3H/HeJ (C3H)] responders to E2 led to the identification of quantitative trait (QT) loci associated with phenotypic variation in uterine growth and leukocyte infiltration. The mechanisms underlying differential responsiveness to E2, and the genes involved, are unknown. Therefore, we used a microarray approach to show association of distinct E2-regulated transcriptional signatures with genetically controlled high and low responses to E2 and their segregation in (C57BL/6J×C3H/HeJ) F1 hybrids. Among the 6664 E2-regulated transcripts, analysis of cellular functions of those that were strain specific indicated C3H-selective enrichment of apoptosis, consistent with a 7-fold increase in the apoptosis indicator CASP3, and a 2.4-fold decrease in the apoptosis inhibitor Naip1 (Birc1a) in C3H vs. B6 following treatment with E2. In addition, several differentially expressed transcripts reside within our previously identified QT loci, including the ERα-tethering factor Runx1, demonstrated to enhance E2-mediated transcript regulation. The level of RUNX1 in uterine epithelial cells was shown to be 3.5-fold greater in B6 compared to C3H. Our novel insights into the mechanisms underlying the genetic control of tissue sensitivity to estrogen have great potential to advance understanding of individualized effects in physiological and disease states.

Lipocalin 2, a new GADD153 target gene, as an apoptosis inducer of endoplasmic reticulum stress in lung cancer cells

Endoplasmic reticulum (ER) stress is activated under severe cellular conditions. GADD153, a member of the C/EBP family, is an unfolded protein response (UPR) responsive transcription factor. Increased levels of lipocalin 2, an acute phase protein, have been found in several epithelial cancers. The aim of this study is to investigate the function of lipocalin 2 in lung cancer cells under ER stress. Treatment with thapsigargin, an ER stress activator, led to increases in cytotoxicity, ER stress, apoptosis, and lipocalin 2 expression in A549 cells. GADD153 silencing decreased lipocalin 2 expression in A549 cells. On chromatin immunoprecipitation assay, ER stress increased GADD153 DNA binding to lipocalin 2 promoter. Furthermore, silencing of lipocalin 2 mitigated ER stress-mediated apoptosis in A549 cells. Our findings demonstrated that lipocalin 2 is a new GADD153 target gene that mediates ER stress-induced apoptosis.

Lipocalin 2 expression is associated with aggressive features of endometrial cancer

Background

Increased expression of lipocalin 2 (LCN2) has been observed in several cancers. The aim of the present study was to investigate LCN2 in endometrial cancer in relation to clinico-pathologic phenotype, angiogenesis, markers of epithelial-mesenchymal transition (EMT), and patient survival.

Methods

Immunohistochemical staining was performed using a human LCN2 antibody on a population-based series of endometrial cancer patients collected in Hordaland County (Norway) during 1981-1990 (n = 256). Patients were followed from the time of primary surgery until death or last follow-up in 2007. The median follow-up time for survivors was 17 years. Gene expression data from a prospectively collected endometrial cancer series (n = 76) and a publicly available endometrial cancer series (n = 111) was used for gene correlation studies.

Results

Expression of LCN2 protein, found in 49% of the cases, was associated with non-endometrioid histologic type (p = 0.001), nuclear grade 3 (p = 0.001), >50% solid tumor growth (p = 0.001), ER and PR negativity (p = 0.028 and 0.006), and positive EZH2 expression (p < 0.001). LCN2 expression was significantly associated with expression of VEGF-A (p = 0.021), although not with other angiogenesis markers examined (vascular proliferation index, glomeruloid microvascular proliferation, VEGF-C, VEGF-D or bFGF2 expression). Further, LCN2 was not associated with several EMT-related markers (E-cadherin, N-cadherin, P-cadherin, β-catenin), nor with vascular invasion (tumor cells invading lymphatic or blood vessels). Notably, LCN2 was significantly associated with distant tumor recurrences, as well as with the S100A family of metastasis related genes. Patients with tumors showing no LCN2 expression had the best outcome with 81% 5-year survival, compared to 73% for intermediate and 38% for the small subgroup with strong LCN2 staining (p = 0.007). In multivariate analysis, LCN2 expression was an independent prognostic factor in addition to histologic grade and FIGO stage.

Conclusion

Increased LCN2 expression is associated with aggressive features and poor prognosis in endometrial cancer.

TIMP3 regulates mammary epithelial apoptosis with immune cell recruitment through differential TNF dependence

Post-lactation mammary involution is a homeostatic process requiring epithelial apoptosis and clearance. Given that the deficiency of the extracellular metalloproteinase inhibitor TIMP3 impacts epithelial apoptosis and heightens inflammatory response, we investigated whether TIMP3 regulates these distinct processes during the phases of mammary gland involution in the mouse. Here we show that TIMP3 deficiency leads to TNF dysregulation, earlier caspase activation and onset of mitochondrial apoptosis. This accelerated first phase of involution includes faster loss of initiating signals (STAT3 activation; TGFβ3) concurrent with immediate luminal deconstruction through E-cadherin fragmentation. Epithelial apoptosis is followed by accelerated adipogenesis and a greater macrophage and T-cell infiltration in Timp3(-/-) involuting glands. Crossing in Tnf deficiency abrogates caspase 3 activation, but heightens macrophage and T-cell influx into Timp3(-/-) glands. The data indicate that TIMP3 differentially impacts apoptosis and inflammatory cell influx, based on involvement of TNF, during the process of mammary involution. An understanding of the molecular factors and wound healing microenvironment of the postpartum mammary gland may have implications for understanding pregnancy-associated breast cancer risk.

Increased plasma levels of lipocalin 2 in mild cognitive impairment

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by an irreversible cognitive decline and neuronal loss associated with neurofibrillary tangles and senile plaques. Mild cognitive impairment (MCI) is a prodromal stage of AD and is associated with memory loss and a high risk of developing AD. Lipocalin 2 (LCN2) is an acute phase protein. Our previous studies have shown that exposure to inflammatory stimuli resulted in elevated LCN2 levels in brain microglia and astrocytes implicating LCN2 in brain inflammation. Therefore, we hypothesize that there may be a significant change in the plasma LCN2 levels in patients with MCI and AD when compared to healthy control subjects.

METHODS

Forty-one patients with MCI, 62 patients with AD and 38 healthy elderly control subjects were recruited for this study. They were given a comprehensive battery of neuropsychological tests including a mini-mental status examination (MMSE) and clinical dementia rating (CDR). A variety of clinical information was collected from the semi-structured questionnaire administered. The LCN2 levels were measured using a specific enzyme-linked immunosorbent assay in the plasma, which had been collected early in the morning after overnight fasting.

RESULTS

The LCN2 levels were significantly higher in MCI patients compared to the healthy control subjects and AD patients [control vs. MCI (p=0.005); MCI vs. AD (p=0.009)]. There was a significant negative correlation between the LCN2 levels and CDR scores (r=-0.245, p=0.014), and there was a positive correlation between the LCN2 levels and MMSE scores (r=0.317, p=0.001) among all of the MCI and AD patients.

CONCLUSION

MCI represents a prodromal stage of AD, and inflammation occurs as one of the earliest pathological events in AD. Thus, increased plasma LCN2 levels during MCI could be helpful in predicting the progression from MCI to AD.

Lipocalin2 protects against airway inflammation and hyperresponsiveness in a murine model of allergic airway disease

BACKGROUND

Allergen-induced bronchial asthma is a chronic airway disease that involves the interplay of various genes with environmental factors triggering different inflammatory pathways.

OBJECTIVE

The aim of this study was to identify possible mediators of airway inflammation (AI) in a model of allergic AI via microarray comparisons and to analyse one of these mediators, Lipocalin2 (Lcn2), for its role in a murine model of allergic airway disease.

METHODS

Gene microarrays were used to identify genes with at least a twofold increase in gene expression in the lungs of two separate mouse strains with high and low allergic susceptibility, respectively. Validation of mRNA data was obtained by Western blotting, followed by functional analysis of one of the identified genes, Lcn2, in mice with targeted disruption of specific gene expression. Epithelial cell cultures were undertaken to define induction requirements and possible mechanistic basis of the results observed in the Lcn2 knock-out mice.

RESULTS

Lcn2 was up-regulated upon allergen sensitization and airway challenges in lung tissues of both mouse strains and retraced on the protein level in bronchoalveolar lavage fluids. Functional relevance was assessed in mice genetically deficient for Lcn2, which showed enhanced airway resistance and increased AI associated with decreased apoptosis of lung inflammatory cells, compared with wild-type controls. Similarly, application of Lcn2-blocking antibodies before airway challenges resulted in increased inflammation and reduced apoptosis.

CONCLUSION

These data indicate a protective role for Lcn2 in allergic airway disease, suggesting a pro-apoptotic effect as the underlying mechanism.

Structural transformations of myocytes during gestation and early postpartum involution of the uterus

Myocytes with large homogeneous vacuoles and numerous protrusions of the cytoplasm into extracellular space (manifestations of clasmatosis) were detected in rat myometrium during normal gestation and early postpartum period. The percentage of vacuolated smooth-muscle cells and numerical density of inflammatory cells in the myometrium were evaluated. The data indicate the absence of typical inflammatory reaction in the myometrium during elimination of smooth-muscle cells in the course of postpartum involution. Clasmatosis and apoptosis are hypothesized to be the main mechanisms providing reduction of the uterine weight after delivery.

Stat3 and the inflammation/acute phase response in involution and breast cancer

The transcription factor Stat3 is essential for timely initiation of post-lactational regression and orchestrates the processes of cell death and tissue remodelling that occur during the first 6 days of involution in the mouse. Paradoxically, STAT3 is also frequently found to be constitutively active in breast cancer and tumors can become addicted to STAT3. This raises two interesting questions: 1) do the high levels of active Stat3 present in the mammary epithelium during involution promote tumor spread and 2) how do tumor cells escape the pro-apoptotic effects of Stat3? In order to address these questions, it is essential to understand the role of Stat3 in involution and the mechanisms by which Stat3 regulates both cell death and tissue remodelling. A number of studies have been undertaken using genetically modified mice and microarray analyses and two significant findings arose from these investigations. Firstly, post-lactational regression is associated with an acute phase and inflammatory response in addition to cell death and secondly, Stat3 alone is insufficient to induce involution in the absence of the NF-kappaB regulatory kinase IKKbeta. Both Stat3 and NF-kappaB have been shown to regulate the expression of genes involved in inflammatory signalling and the acute phase response. These findings suggest a role for the innate immune response in mammary epithelial cell fate during involution and highlight potential roles for this response in tissue remodelling-associated breast cancer metastasis.

Lipocalin 2-dependent inhibition of mycobacterial growth in alveolar epithelium

Mycobacterium tuberculosis invades alveolar epithelial cells as well as macrophages. However, the role of alveolar epithelial cells in the host defense against M. tuberculosis remains unknown. In this study, we report that lipocalin 2 (Lcn2)-dependent inhibition of mycobacterial growth within epithelial cells is required for anti-mycobacterial innate immune responses. Lcn2 is secreted into the alveolar space by alveolar macrophages and epithelial cells during the early phase of respiratory mycobacterial infection. Lcn2 inhibits the in vitro growth of mycobacteria through sequestration of iron uptake. Lcn2-deficient mice are highly susceptible to intratracheal infection with M. tuberculosis. Histological analyses at the early phase of mycobacterial infection in Lcn2-deficient mice reveal increased numbers of mycobacteria in epithelial cell layers, but not in macrophages, in the lungs. Increased intracellular mycobacterial growth is observed in alveolar epithelial cells, but not in alveolar macrophages, from Lcn2-deficient mice. The inhibitory action of Lcn2 is blocked by the addition of endocytosis inhibitors, suggesting that internalization of Lcn2 into the epithelial cells is a prerequisite for the inhibition of intracellular mycobacterial growth. Taken together, these findings highlight a pivotal role for alveolar epithelial cells during mycobacterial infection, in which Lcn2 mediates anti-mycobacterial innate immune responses within the epithelial cells.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

The neutrophil gelatinase-associated lipocalin (NGAL), a NF-kappaB-regulated gene, is a survival factor for thyroid neoplastic cells

NF-kappaB is constitutively activated in primary human thyroid tumors, particularly in those of anaplastic type. The inhibition of NF-kappaB activity in the human anaplastic thyroid carcinoma cell line, FRO, leads to an increased susceptibility to chemotherapeutic drug-induced apoptosis and to the blockage of their ability to form tumors in nude mice. To identify NF-kappaB target genes involved in thyroid cancer, we analyzed the secretome of conditioned media from parental and NF-kappaB-null FRO cells. Proteomic analysis revealed that the neutrophil gelatinase-associated lipocalin (NGAL), a protein involved in inflammatory and immune responses, is secreted by FRO cells whereas its expression is strongly reduced in the NF-kappaB-null FRO cells. NGAL is highly expressed in human thyroid carcinomas, and knocking down its expression blocks the ability of FRO cells to grow in soft agar and form tumors in nude mice. These effects are reverted by the addition of either recombinant NGAL or FRO conditioned medium. In addition, we show that the prosurvival activity of NGAL is mediated by its ability to bind and transport iron inside the cells. Our data suggest that NF-kappaB contributes to thyroid tumor cell survival by controlling iron uptake via NGAL.

Interaction of surfactant protein A with the intermediate filaments desmin and vimentin

Surfactant protein A (SP-A), a member of the collectin family that modulates innate immunity, has recently been involved in the physiology of reproduction. Consistent with the activation of ERK-1/2 and COX-2 induced by SP-A in myometrial cells, we reported previously the presence of two major proteins recognized by SP-A in these cells. Here we identify by mass spectrometry one of these SP-A targets as the intermediate filament (IF) desmin. In myometrial preparations derived from desmin-deficient mice, the absence of binding of SP-A to any 50 kDa protein confirmed the identity of this SP-A-binding site as desmin. Our data based on partial chymotrypsin digestion of pure desmin suggested that SP-A recognizes especially its rod domain, which is known to play an important role during the assembly of desmin into filaments. In line with that, electron microscopy experiments showed that SP-A inhibits in vitro the polymerization of desmin filaments. SP-A also recognized in vitro polymerized filaments in a calcium-dependent manner at a physiological ionic strength but not the C1q receptor gC1qR. Furthermore, Texas Red-labeled SP-A colocalized with desmin filaments in myometrial cells. Interestingly, vimentin, the IF characteristic of leukocytes, is one of the major proteins recognized by SP-A in protein extracts of U937 cells after PMA-induced differentiation of this monocytic cell line. Interaction of SP-A with vimentin was further confirmed using recombinant vimentin in solid-phase binding assays. The ability of SP-A to interact with desmin and vimentin, and to prevent polymerization of desmin monomers, shed light on unexpected and wider biological roles of this collectin.

Acute endotoxemia is associated with upregulation of lipocalin 24p3/Lcn2 in lung and liver

Acute endotoxemia is associated with production of acute phase proteins which regulate inflammatory responses to tissue injury. Consistent with DNA microarray experiments, we found that acute endotoxemia, induced by administration of lipopolysaccharide (LPS) to mice (1 mg/kg) or rats (5 mg/kg), resulted in increased expression of the hepatic acute phase protein, lipocalin 24p3, which was evident within 4 h and persisted for 24-48 h. Increases in 24p3 expression were also observed in the lung after LPS administration, as well as in isolated liver and lung macrophages, and Type II alveolar epithelial cells. The actions of LPS are dependent, in part, on Toll-like receptor (TLR) proteins. Macrophages from C3H/HeJ mice, which possess a nonfunctional TLR-4, expressed low levels of 24p3 mRNA when compared to cells from control C3H/OuJ mice. Whereas LPS administration increased 24p3 expression in lung and liver macrophages from control C3H/OuJ mice, minimal effects were observed in TLR-4 mutant mice demonstrating that TLR-4 is important in regulating 24p3 expression during acute endotoxemia. Promoters for genes encoding lipocalin proteins including 24p3 contain consensus sequences for transcription factors including NF-kappaB, and C/EBP. Acute endotoxemia resulted in NF-kappaB nuclear binding activity in both alveolar macrophages and Type II cells. In contrast, C/EBP activation was evident only in Type II cells, suggesting differential effects of LPS on these cell types. These data suggest that the acute phase response to acute endotoxemia involves induction of 24p3 in both the lung and liver. This protein may be important in restoring tissue homeostasis following LPS-induced injury.