Anemia upregulates lipocalin 2 in the liver and serum

SARS-CoV-2 infection induces expression and secretion of lipocalin-2 and regulates iron in a human lung cancer xenograft model

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leads to various clinical symptoms including anemia. Lipocalin-2 has various biological functions, including defense against bacterial infections through iron sequestration, and it serves as a biomarker for kidney injury. In a human protein array, we observed increased lipocalin-2 expression due to parental SARS-CoV-2 infection in the Calu-3 human lung cancer cell line. The secretion of lipocalin-2 was also elevated in response to parental SARS-CoV-2 infection, and the SARS-CoV-2 Alpha, Beta, and Delta variants similarly induced this phenomenon. In a Calu-3 implanted mouse xenograft model, parental SARSCoV- 2 and Delta variant induced lipocalin-2 expression and secretion. Additionally, the iron concentration increased in the Calu-3 tumor tissues and decreased in the serum due to infection. In conclusion, SARS-CoV-2 infection induces the production and secretion of lipocalin-2, potentially resulting in a decrease in iron concentration in serum. Because the concentration of iron ions in the blood is associated with anemia, this phenomenon could contribute to developing anemia in COVID-19 patients. [BMB Reports 2023; 56(12): 669-674].

Lipocalin-2, Soluble Transferrin Receptor, and Erythropoietin in Anemia During Mild Renal Dysfunction

Background

Mild renal dysfunction (MRD) is a common condition often associated with diabetes or inflammation and regarded as a risk factor for cardiovascular disease in patients with hypertension. Few studies have examined the role of lipocalin-2 (LCN2) as a regulator of iron and a contributor to anemia in MRD. The aim of this study was to investigate the relationship between LCN2, soluble transferrin receptor (sTfR), erythropoietin (EPO), reticulocyte production, and the prevalence of anemia in MRD.

Methods

A total of 235 subjects with MRD were evaluated. LCN2, sTfR, EPO, and iron levels were measured. Reticulocyte maturity index (RMI) and corrected LCN2 (cLCN2) values were calculated using reticulocyte subpopulations and the inflammation index, respectively.

Results

Subjects with LCN2 elevation had significantly higher sTfR and significantly lower RMI levels than those without LCN2 elevation. Compared to subjects without LCN2 elevation, those with LCN2 elevation exhibited significantly lower hemoglobin (12.9 ± 1.6 g/dL vs 14.0 ± 1.7 g/dL, p < 0.001) and more prevalent anemia (27.7% vs 13.3%, p = 0.008). Patients with anemia had significantly higher LCN2 and cLCN2 than those without anemia. LCN2 was positively correlated with sTfR and negatively correlated with RMI but not EPO. Elevated LCN2 led to a 1.3-fold increase in the prevalence of anemia (odds ratio: 1.302; 95% CI: 1.012-2.527; p < 0.001).

Conclusion

LCN2 elevation may contribute to the development of anemia in MRD, particularly in conjunction with restricted iron availability and suppressed reticulocyte production.

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

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

Association between neutrophil gelatinase-associated lipocalin (NGAL) and iron profile in chronic renal disease

NGAL, also known as lipocalin 2, is a stress protein located on the cell surface that is known for its involvement in iron transport. This study is aimed to evaluate the correlation between the iron profile and NGAL concentration in serum among chronic kidney disease patients under dialysis in order to find its diagnostic value with regards to iron deficiency anaemia (IDA). 47 patients under chronic haemodialysis in end-stage renal disease (ESRD) and 15 healthy controls were evaluated to determine the correlation between serum NGAL concentration and IDA characteristics. Our results recorded a significant correlation between IDA (TSAT < 20%) and NGAL serum concentration with a Spearman's coefficient of 0.314. Serum NGAL was also significantly related to serum ferritin, TIBC, uric acid, creatinine and blood sugar whereas, an inverse relationship with albumin, total cholesterol and LDL. Our study reports a positive correlation between IDA and serum NGAL levels in CKD patients.

Iron homeostasis in host and gut bacteria - a complex interrelationship

Iron deficiency is the most frequent nutritional deficiency in the world with an estimated 1.4 billion people affected. The usual way to fight iron deficiency is iron fortification, but this approach is not always effective and can have undesirable side effects including an increase in the growth and virulence of gut bacterial pathogens responsible for diarrhea and gut inflammation. Iron is mainly absorbed in the duodenum and is tightly regulated in mammals. Unabsorbed iron enters the colonic lumen where many microorganisms, referred to as gut microbiota, reside. Iron is essential for these bacteria, and its availability consequently affects this microbial ecosystem. The aim of this review is to provide further insights into the complex relationship between iron and gut microbiota. Given that overcoming anemia caused by iron deficiency is still a challenge today, gut microbiota could help identify more efficient ways to tackle this public health problem.

Associations of Plasma Neutrophil Gelatinase-associated Lipocalin, Anemia, and Renal Scarring in Children with Febrile Urinary Tract Infections

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL), a bacteriostatic agent, is known to inhibit erythropoiesis leading to anemia. We aimed to investigate the associations of NGAL, anemia, and renal scarring in children with febrile urinary tract infections (UTIs).

METHODS

We retrospectively reviewed the medical records of 261 children with febrile UTIs. The relationship between the presence of anemia and plasma NGAL levels was investigated. NGAL performance in comparison with serum C-reactive protein (CRP) at admission and after 72 hours of treatment was also evaluated for the prediction of renal scarring as well as acute pyelonephritis (APN) and vesicoureteral reflux (VUR).

RESULTS

Plasma NGAL levels were elevated in patients with anemia compared with those without anemia. Multiple linear regression analysis showed an inverse relationship between NGAL levels and erythrocyte counts (standard β = -0.397, P < 0.001). Increased NGAL, but not CRP, was independently associated with the presence of anemia (odds ratio [OR], 2.37; 95% confidence interval [CI], 1.07-5.27; P < 0.05). Receiver operating curve analyses showed good diagnostic profiles of pre- and post-treatment NGAL for identifying APN, VUR, and renal scarring (all P < 0.05). For detecting renal scars, the area under the curve of post-treatment NGAL (0.730; 95% CI, 0.591-0.843) was higher than that of post-treatment CRP (0.520; 95% CI, 0.395-0.643; P < 0.05). The presence of anemia and elevated NGAL at admission (> 150 ng/mL) were independent risk factors for renal scarring in children with febrile UTIs. With anemia, NGAL levels increased consecutively in children with febrile UTI without renal involvement, with APN without scar, and with APN with renal scarring.

CONCLUSION

Increased plasma NGAL levels may be associated with the presence of anemia and renal scarring in children with febrile UTIs.

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

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

Indigofera oblongifolia regulates the hepatic gene expression profile induced by blood stage malaria

Malaria is still a major health problem worldwide. This study aimed to investigate the hepatoprotective role of Indigofera oblongifolia leaf extracts (ILE) against mice hepatic injury induced by Plasmodium chabaudi. Female C57BL/6 mice were treated with 100 mg/kg of ILE after infection with erythrocytes parasitized by P. chabaudi. On day 7 post-infection, the extract improved the histological alteration induced by the parasite. This was evidenced by the decreased histological index induced by ILE. Moreover, ILE was able to increase the hepatic antioxidant capacity and could significantly improve the decrease in erythrocyte count and hemoglobin content in mice blood plasma due to infection. ILE was also able to upregulate the expression of 24 genes related to metabolism and of 3 genes related to the immune response. Furthermore, the extract was able to downregulate the expression of 35 genes related to metabolism and of 82 genes related to immune response. Moreover, the microarray study showed that ILE regulated the change in gene expression induced by the parasite. Among these genes, we quantified the expression of cd209f, cyp7a1, Hsd3b5, Sult2a3, Lcn2, CcI8, Nos2, and saa3-mRNAs. These genes were regulated by ILE. Therefore, our results revealed the protective role of Indigofera oblongifolia against hepatic injury induced by blood stage malaria.

MyD88 Adaptor Protein Is Required for Appropriate Hepcidin Induction in Response to Dietary Iron Overload in Mice

Iron homeostasis is tightly regulated to provide virtually all cells in the body, particularly red blood cells, with this essential element while defending against its toxicity. The peptide hormone hepcidin is central to the control of the amount of iron absorbed from the diet and iron recycling from macrophages. Previously, we have shown that hepcidin induction in macrophages following Toll-like receptor (TLR) stimulation depends on the presence of myeloid differentiation primary response gene 88 (MyD88). In this study, we analyzed the regulation of iron metabolism in MyD88^−/− mice to further investigate MyD88 involvement in iron sensing and hepcidin induction. We show that mice lacking MyD88 accumulate significantly more iron in their livers than wild-type counterparts in response to dietary iron loading as they are unable to appropriately control hepcidin levels. The defect was associated with inappropriately low levels of Smad4 protein and Smad1/5/8 phosphorylation in liver samples found in the MyD88^−/− mice compared to wild-type mice. In conclusion, our results reveal a previously unknown link between MyD88 and iron homeostasis, and provide new insights into the regulation of hepcidin through the iron-sensing pathway.

Altered mitochondrial and peroxisomal integrity in lipocalin-2-deficient mice with hepatic steatosis

Lipocalin-2 (LCN2) is a secreted adipokine that transports small hydrophobic molecules such as fatty acids and steroids. LCN2 limits bacterial growth by sequestering iron-containing siderophores and in mammalian liver protects against inflammation, infection, injury and other stressors. Because LCN2 modulates hepatic fat metabolism and homeostasis, we performed a comparative profiling of proteins and lipids of wild type (WT) and Lcn2-deficient mice fed either standard chow or a methionine- and choline-deficient (MCD) diet. Label-free proteomics and 2D-DIGE protein expression profiling revealed differential expression of BRIT1/MCPH1, FABP5, HMGB1, HBB2, and L-FABP, results confirmed by Western blotting. Gene ontology enrichment analysis identified enrichment for genes associated with mitochondrial membrane permeabilization and metabolic processes involving carboxylic acid. Measurements of mitochondrial membrane potential, mitochondrial chelatable iron pool, intracellular lipid peroxidation, and peroxisome numbers in primary hepatocytes confirmed that LCN2 regulates mitochondrial and peroxisomal integrity. Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF) mass spectrometry imaging identified significant changes to sphingomyelins, triglycerides, and glycerophospholipids in livers of mice fed an MCD diet regardless of LCN2 status. However, two arachidonic acid-containing glycerophospholipids were increased in Lcn2-deficient livers. Thus, LCN2 influences peroxisomal and mitochondrial biology in the liver to maintain triglyceride balance, handle oxidative stress, and control apoptosis.

Elevated Plasma Neutrophil Gelatinase-Associated Lipocalin Level as a Risk Factor for Anemia in Patients with Systemic Inflammation

Studies on neutrophil gelatinase-associated lipocalin (NGAL) as an iron-regulatory protein are limited. This study investigated the relationships between plasma NGAL levels and indices of anemia in 187 patients with systemic inflammation. Plasma NGAL levels were significantly higher in patients with anemia versus in patients without anemia (185 ng/mL versus 98 ng/mL; P < 0.001). Serum iron levels were lower in patients with NGAL > 156 ng/mL than in those with NGAL ≤ 156 ng/mL (27.4 ± 25.3 µg/dL versus 58.1 ± 43.5 µg/dL; P < 0.001). In a receiver operating characteristic curve, the diagnostic ability of NGAL to identify anemia was superior to that of high-sensitivity C-reactive protein [0.712 (95% CI, 0.618-0.787) versus 0.649 (95% CI, 0.573-0.744); P < 0.01]. In a multivariate logistic regression analysis, the elevated NGAL level was significantly associated with the presence of anemia after adjusting for potential confounders [odds ratio, 1.30 (95% CI, 1.07-2.58); P = 0.010]. In conclusion, enhanced NGAL production may contribute to the development of anemia in patients with systemic inflammation.

Lipocalin 2 alleviates iron toxicity by facilitating hypoferremia of inflammation and limiting catalytic iron generation

Iron is an essential transition metal ion for virtually all aerobic organisms, yet its dysregulation (iron overload or anemia) is a harbinger of many pathologic conditions. Hence, iron homeostasis is tightly regulated to prevent the generation of catalytic iron (CI) which can damage cellular biomolecules. In this study, we investigated the role of iron-binding/trafficking innate immune protein, lipocalin 2 (Lcn2, aka siderocalin) on iron and CI homeostasis using Lcn2 knockout (KO) mice and their WT littermates. Administration of iron either systemically or via dietary intake strikingly upregulated Lcn2 in the serum, urine, feces, and liver of WT mice. However, similarly-treated Lcn2KO mice displayed elevated CI, augmented lipid peroxidation and other indices of organ damage markers, implicating that Lcn2 responses may be protective against iron-induced toxicity. Herein, we also show a negative association between serum Lcn2 and CI in the murine model of dextran sodium sulfate (DSS)-induced colitis. The inability of DSS-treated Lcn2KO mice to elicit hypoferremic response to acute colitis, implicates the involvement of Lcn2 in iron homeostasis during inflammation. Using bone marrow chimeras, we further show that Lcn2 derived from both immune and non-immune cells participates in CI regulation. Remarkably, exogenous rec-Lcn2 supplementation suppressed CI levels in Lcn2KO serum and urine. Collectively, our results suggest that Lcn2 may facilitate hypoferremia, suppress CI generation and prevent iron-mediated adverse effects.

Identification of potential biomarkers for post-traumatic complications released after trauma-hemorrhage from murine Kupffer cells and its investigation in lung and liver

CONTEXT

Early diagnosis of complications after severe trauma by specific biomarkers remains difficult.

OBJECTIVE

Identify potential new biomarkers for early diagnosis of post-traumatic complications.

MATERIAL AND METHODS

Mice underwent pressure-controlled hemorrhage or sham procedure. Four hours later, genome-wide expression of isolated Kupffer cells was compared with controls using Affymetrix-Genechip-Expression-Analysis and real-time-PCR.

RESULTS

Expression analysis and real-time-PCR revealed a significant increase of gene expression of Cxcl10, Il4ra, Csf2rb2, Lcn2, and Gbp5.

CONCLUSION

Cxcl10, Il4ra, Csf2rb2, Lcn2, and Gbp5 might represent new biomarkers for early diagnosis of post-traumatic complications, if they are linked to the development of post-traumatic complications.

C-reactive protein but not hepcidin, NGAL and transferrin determines the ESA resistance in hemodialysis patients

BACKGROUND

Erythropoiesis-stimulating agents (ESA) are commonly used for the treatment of anemia in hemodialysis (HD) patients, however, 5-10% of these patients have resistance to ESA treatment. Hepcidin and neutrophil-gelatinase associated lipocalin (NGAL) are induced by inflammation and these proteins may take role in ESA resistance. Herein, we aimed to investigate the effects of serum hepcidin, NGAL, transferrin and C-reactive protein (CRP) levels on ESA resistance in HD patients.

METHODS

A total of 63 chronic HD patients (6.0 ± 17 years, M/F:44/19) and 20 healthy controls (6.0 ± 4 years, M/F:14/6) were enrolled. ESA resistance index (ERI) was calculated as weekly ESA dose (IU)/body weight (kg)/hemoglobin level (g/dL). Patients on ESA treatment were divided into two groups depending on the median ERI value as low and high ERI groups.

RESULTS

Serum ferritin, hepcidin and NGAL levels were significantly higher in HD patients compared with controls. Serum transferrin levels were lower in high ESA index group compared with patients without ESA treatment and healthy controls. ERI was significantly correlated with serum CRP levels (r = 0.55, p < 0.001). In HD patients, serum hepcidin levels were associated with ferritin (r = 0.55, p < 0.01) and creatinine (r = 0.27, p = 0.03). Dose of ESA was significantly associated with serum CRP (r = 0.34, p = 0.02), total protein (r = -0.34, p = 0.01), transferrin (r = -0.28, p = 0.04) and ferritin (r = 0.31, p = 0.02). In linear regression analysis to predict ERI, age, gender, serum CRP, hepcidin, NGAL, albumin, ferritin and BMI were included (Model R = 0.62, R(2) =0 .38, p = 0.02). Serum CRP was the only significant factor predicting ERI.

CONCLUSION

CRP was the only predictor of ESA resistance index in HD patients. Hepcidin, NGAL and transferrin were not found to be markers of ESA resistance.

HGF mediated upregulation of lipocalin 2 regulates MMP9 through nuclear factor-κB activation

Lipocalin 2 (LCN2) is a member of lipocalin family that binds and transports a small lipophilic ligand, sharing a highly conserved tertiary structure and can be found as a monomer, homodimer, heterodimer with matrix metalloproteinase 9 (MMP9). The high molecule LCN2/MMP9 complex was found in several cancer types. Yet, the mechanisms of regulation between LCN2 with MMP9 in tumorigenesis is unclear. The aims of the present study were to identify the function of LCN2 associated with MMP9 in gastric cancer growth and metastasis. First, we confirmed that the expression level of LCN2 and MMP9 was upregulated by hepatocyte growth factor (HGF). To identify the association pathway of HGF-induced LCN2, the cells were treated with PI3-kinase inhibitor (LY294002), or MEK inhibitor (PD098059), or p38 inhibitor (SB203580) and then analyzed using western blotting. The HGF-mediated LCN2 protein level was decreased with LY294002. Also, the HGF-mediated MMP9 was decreased with LY294002. The role for LCN2 with HGF mediated MMP9 was determined by knockdown of LCN2. LCN2-sh RNA cells showed a decreased level of HGF-mediated MMP9. The HGF-mediated LCN2 protein level was decreased with treatment of the NFκB inhibitor. We confirmed the role of HGF-mediated LCN2. HGF-mediated cell proliferation and in vitro invasion was decreased in LCN2 knockdown cell. In conclusion, the present study showed that LCN2 upregulated MMP9 through PI3K/AKT/NFκB pathway in gastric cancer. LCN2 has a role in cell proliferation and cell invasion in gastric cancer, which may be a possible target for developing gastric cancer therapy.

Low Serum Neutrophil Gelatinase-associated Lipocalin Level as a Marker of Malnutrition in Maintenance Hemodialysis Patients

Background

Neutrophil gelatinase-associated lipocalin (NGAL or LCN2) is an iron-transporting factor which possesses various activities such as amelioration of kidney injury and host defense against pathogens. Its circulating concentrations are elevated in acute and chronic kidney diseases and show a positive correlation with poor renal outcome and mortality, but its clinical significance in maintenance hemodialysis (HD) patients remains elusive.

Methods

Serum NGAL levels were determined by enzyme-linked immunosorbent assay in out-patient, Japanese HD subjects. Their correlation to laboratory findings and morbidity (as development of severe infection or serum albumin reduction) was investigated using linear regression analysis and χ² test.

Results

Pre-dialysis serum NGAL levels in HD patients were elevated by 13-fold compared to healthy subjects (n=8, P<0.001). In a cross-sectional study of 139 cases, serum NGAL concentrations were determined independently by % creatinine generation rate (an indicator of muscle mass, standardized coefficient β=0.40, P<0.001), peripheral blood neutrophil count (β=0.38, P<0.001) and anion gap (which likely reflects dietary protein intake, β=0.16, P<0.05). Iron administration to anemic HD patients caused marked elevation of peripheral blood hemoglobin, serum ferritin and iron-regulatory hormone hepcidin-25 levels, but NGAL levels were not affected. In a prospective study of 87 cases, increase in serum albumin levels a year later was positively associated to baseline NGAL levels by univariate analysis (r=0.36, P<0.01). Furthermore, within a year, patients with the lowest NGAL tertile showed significantly increased risk for marked decline in serum albumin levels (≥0.4 g/dl; odds ratio 5.5, 95% confidence interval 1.5–20.3, P<0.05) and tendency of increased occurrence of severe infection requiring admission (odds ratio 3.1, not significant) compared to the middle and highest tertiles.

Conclusion

Low serum NGAL levels appear to be associated with current malnutrition and also its progressive worsening in maintenance HD patients.

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

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

The role of lipocalin-2 in liver regeneration

BACKGROUND & AIMS

Various immune mediators such as interleukin-6 (IL-6) have been implicated in the process of liver regeneration. Lipocalin-2 (LCN2) has been recently characterized as a prototypic immune mediator produced by various cell types being involved mainly in host defence. In addition, numerous studies have demonstrated its clinical value as a biomarker. This study aimed at defining the role of LCN2 in liver regeneration.

METHODS

We studied LCN2 expression in wild-type mice in a model of partial hepatectomy (PH). Furthermore, we evaluated liver regeneration after PH in LCN-deficient mice compared to littermate controls. Serum levels of LCN2 were assessed in a small group of patients undergoing hepatic resection.

RESULTS

LCN2 is dramatically induced in livers and sera of wild-type mice after PH, whereas liver LCN2-receptor expression was decreased. Sham operations did not affect hepatic and serum LCN2 expression. Although LCN2-deficient mice exhibited increased baseline liver expression indices, LCN2-deficient mice did not differ from wild-type mice with respect to hepatic proliferation suggesting that this molecule is not involved in hepatic repair. Only serum IL-1β levels were slightly lower in LCN(-/-) mice, whereas IL-6 serum levels did not differ between various tested animal groups. In humans undergoing hepatic resection, LCN2 levels increased significantly within 24 h following surgery.

CONCLUSIONS

LCN2, although massively induced in mice after PH, is not relevant in murine hepatic regeneration. Further, human studies have to define whether LCN2 could evolve as biomarker after liver surgery.

Association between neutrophil geletinase-associated lipocalin and iron deficiency anemia in children on chronic dialysis

BACKGROUND

Iron deficiency anemia (IDA) in children with chronic kidney disease (CKD) is common and associated with higher risk of death. Neutrophil geletinase-associated lipocalin (NGAL) is a small 25 kDa glycoprotein, a member of lipocalin superfamily that released at the response of cellular stress from different cells. In addition, NGAL was studied as an iron regulatory glycoprotein and regulator of iron related gene. The aim of the current study was to determine any association between serum NGAL and body iron status markers in children on chronic dialysis.

MATERIALS AND METHODS

This correlation study was carried out between May 2012 and May 2013 and evaluated all dialysis patients less than 19 years in pediatric dialysis centers in Isfahan that didn't have exclusion criteria. They were 40 children, including 23 persons on hemodialysis (HD) and 17 persons dialyzed by peritoneal dialysis (PD). Furthermore, we selected 40 children as healthy controls. We examined the relationship between plasma NGAL levels and indices of anemia such as ferritin, transferrin saturation (TSAT) and serum iron (SI) in dialysis children.

RESULTS

Serum NGAL level in children on chronic dialysis (group including both PD and HD patients) was significantly higher than healthy controls (P = 0.008). Furthermore, in this group Serum NGAL level had inverse correlation with TSAT (P = 0.04, r = -0.22), SI (P = 0.04, r = -0.2), white blood cells (P = 0.045, r = -0.26) and serum ferritin (P = 0.006, r = -0.3). In addition, HD patients had higher serum NGAL level than PD patients (P = 0.048).

CONCLUSION

High serum NGAL level in low TSAT group demonstrated that NGAL probably has an important role in IDA in children on chronic dialysis; therefore, it can be a new marker for diagnosis of IDA in CKD.

Plasma neutrophil gelatinase-associated lipocalin levels are markedly increased in patients with non-transfusion-dependent thalassemia: Lack of association with markers of erythropoiesis, iron metabolism and renal function

BACKGROUND

Neutrophil Gelatinase-Associated Lipocalin (NGAL) (known as NGAL, Lipocalin 2, Siderocalin, Uterocalin, proteinase-3 and 24p3) is a mammalian small 25-kD peptide that belongs to the lipocalin superfamily, which consists of about 20 small lipoproteins. NGAL was initially discovered as an antibacterial factor of natural immunity and an acute-phase protein. NGAL is also an iron trafficking protein, a member of the non-transferrin-bound iron (NTBI) pool and an alternative to the transferrin-mediated iron-delivery pathway. Of note, NTBI, which is elevated in thalassemic patients, induces cellular toxicity. In this study we investigated the possible association of NGAL with parameters of erythropoiesis, iron metabolism and renal injury in patients with non-transfusion-dependent thalassemia (thalassemia intermedia or TI).

PATIENTS AND METHODS

Thirty-five patients with TI, 13 men and 22 women, aged 8-63 years, were included in the study, while, 20 healthy individuals served as controls. Plasma NGAL levels were determined using an immunoenzymatic technique. Erythroid marrow activity was estimated by measuring soluble transferrin receptors (sTfR) levels with a turbidimetric technique. NTBI levels were determined using electrothermal atomic absorption spectrometry. Cystatin C, β2-microglobulin and hs-CRP concentrations were measured by means of immunonephelometric techniques.

RESULTS

The main results of the study showed: a) NGAL levels were significantly higher in patients with TI compared to controls (139.1 ± 86.1 vs 51.2 ± 11.8 μg/L, p<0.0001), without significant effect of splenectomy or hydroxyurea on NGAL levels. Only 4 patients had NGAL levels within the control group range, b) no correlation was found between NGAL levels and either the parameters of erythropoiesis Hb, Hb F, reticulocytes and sTfR (p>0.66, p>0.67, p>0.63 and p>0.81 respectively), or with those of iron metabolism ferritin and NTBI (p>0.90 and p>0.95 respectively).

CONCLUSIONS

The increased NGAL levels reported for the first time in TI patients in this study are in agreement with the elevated expression of NGAL observed in TI mouse models. We postulate that the induction of NGAL in these patients may represent either a survival response, facilitating the survival of the less damaged thalassemic erythroid precursors, or a consequence of the abnormal iron regulation in TI.

Adipokines as potential biomarkers in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic inflammatory autoimmune disease characterized by severe joint injury. Recently, research has been focusing on the possible identification of predictor markers of disease onset and/or progression, of joint damage, and of therapeutic response. Recent findings have uncovered the role of white adipose tissue as a pleiotropic organ not only specialized in endocrine functions but also able to control multiple physiopathological processes, including inflammation. Adipokines are a family of soluble mediators secreted by white adipose tissue endowed with a wide spectrum of actions. This review will focus on the recent advances on the role of the adipokine network in the pathogenesis of RA. A particular attention will be devoted to the action of these proteins on RA effector cells, and on the possibility to use circulating levels of adipokines as potential biomarkers of disease activity and therapeutic response.

Friend of GATA and GATA-6 modulate the transcriptional up-regulation of hepcidin in hepatocytes during inflammation

Hepcidin is an antimicrobial peptide hormone that plays a central role in the metabolism of iron and its expression in the liver can be induced through two major pathways: the inflammatory pathway, mainly via IL-6; and the iron-sensing pathway, mediated by BMP-6. GATA-proteins are group of evolutionary conserved transcriptional regulators that bind to the consensus motif-WGATAR-in the promoter region. In hepatoma cells, GATA-proteins 4 and 6 in conjunction with the co-factor friend of GATA (FOG) were shown to modulate the transcription of HAMP. However, it is unclear as to which of the GATA-proteins drive the expression of HAMP in vivo. In this study, using in vitro and in vivo approaches, we investigated the relevance of GATA and FOG proteins in the expression of hepcidin following treatment with IL-6 and BMP-6. We found that treatment of Huh7 cells with either IL-6 or BMP-6 increased the HAMP promoter activity. The HAMP promoter activity following treatment with IL-6 or BMP-6 was further increased by co-transfection of the promoter with GATA proteins 4 and 6. However, co-transfection of the HAMP promoter with FOG proteins 1 or 2 repressed the promoter response to treatments with either IL-6 or BMP-6. The effects of both GATA and FOG proteins on the promoter activity in response to IL-6 or BMP-6 treatment were abrogated by mutation of the GATA response element-TTATCT-in the HAMP promoter region -103/-98. In vivo, treatment of mice with lipopolysaccharide led to a transient increase of Gata-6 expression in the liver that was positively correlated with the expression of hepcidin. Our results indicate that during inflammation GATA-6 is up-regulated in concert with hepcidin while GATA-4 and FOG (1 and 2) are repressed.

Nitric oxide boosts TLR-4 mediated lipocalin 2 expression in chondrocytes

Lipocalin 2 (LCN2) has recently emerged as a novel adipokine involved in different processes including arthritis and chondrocyte inflammatory response. However, little is known about its activity on chondrocyte homeostasis and its regulation by nitric oxide (NO) Hence, we performed a set of experiments aimed to achieve a better understanding of this relationship. Cell vitality was tested in the ATDC5 cell line by the MTT colorimetric assay. Protein expression and gene expression was evaluated by Western blot and real time RT-PCR, respectively. NO production (determined as nitrite accumulation) was assayed by the Griess reaction. First, we demonstrated that LCN2 decreased murine chondrocytes vitality. Next, LCN2 co-stimulation with LPS enhanced NOS2 protein expression by murine chondrocytes. In addition, inhibition of LPS-induced nitric oxide production by aminoguanidine, a selective NOS2 inhibitor, significantly reduced LPS-mediated LCN2 expression. In contrast, treatment of murine chondrocytes with sodium nitroprussiate (SNP), a classic NO donor, scarcely induced LCN2 expression. Intriguingly, SNP addition to LPS-challenged chondrocytes, treated with aminoguanidine, provoked a strong induction of LCN2 expression. Finally, murine ATDC5 cells, co-cultured with LPS pre-challenged macrophages, had higher LCN2 expression in comparison with murine chondrocytes co-cultured with non pre-challenged macrophages. In this work we have described for the first time that NO is able to exert a control on LCN2 expression, suggesting the existence of a feedback loop regulating its expression.

Lipocalin-2 as mediator of chemokine expression and granulocyte infiltration during ischemia and reperfusion

Lipocalin-2 (Lcn2) expression contributes to ischemia and reperfusion injury (IRI) by enhancing pro-inflammatory responses. The aim of this work was to elucidate the regulation of Lcn2 during hypoxia and its effects on the expression of key chemokines and adhesion molecules. Lcn2 wt and Lcn2(-/-) mice were used in a heterotopic heart transplantation model. Quantitative RT-PCR was applied for chemokine gene expression analysis. Reporter gene studies were used to elucidate the regulation of the Lcn2 promoter by hypoxia. HIF-1β expression led to a 2.4-fold induction of the Lcn2 promoter. Apart from an earlier onset of granulocyte infiltration in the Lcn2 wt setting after 2 h of reperfusion compared with the Lcn2(-/-) setting (P < 0.013), exogenous application of recombinant Lcn2 revealed a trend toward increase of granulocyte infiltration. Analyzed chemokines were expressed significantly higher in the Lcn2 wt setting at 2 h of reperfusion (P ≤ 0.05). The number of apoptotic cells observed in Lcn2(-/-) grafts was significantly higher than in the Lcn2 wt setting. Our results indicate that Lcn2 affects granulocyte infiltration in the reperfused graft by modulating the expression of chemokines, their receptors and the apoptotic rate.

Differential role of lipocalin 2 during immune complex-mediated acute and chronic inflammation in mice

OBJECTIVE

Lipocalin 2 (LCN-2) is an innate immune protein that is expressed by a variety of cells and is highly up-regulated during several pathologic conditions, including immune complex (IC)-mediated inflammatory/autoimmune disorders. However, the function of LCN-2 during IC-mediated inflammation is largely unknown. Therefore, this study was undertaken to investigate the role of LCN-2 in IC-mediated diseases.

METHODS

The up-regulation of LCN-2 was determined by enzyme-linked immunosorbent assay in 3 different mouse models of IC-mediated autoimmune disease: systemic lupus erythematosus, collagen-induced arthritis, and serum-transfer arthritis. The in vivo role of LCN-2 during IC-mediated inflammation was investigated using LCN-2-knockout mice and their wild-type littermates.

RESULTS

LCN-2 levels were significantly elevated in all 3 of the autoimmune disease models. Further, in an acute skin inflammation model, LCN-2-knockout mice exhibited a 50% reduction in inflammation, with histopathologic analysis revealing notably reduced immune cell infiltration as compared to wild-type mice. Administration of recombinant LCN-2 to LCN-2-knockout mice restored inflammation to levels observed in wild-type mice. Neutralization of LCN-2 using a monoclonal antibody significantly reduced inflammation in wild-type mice. In contrast, LCN-2-knockout mice developed more severe serum-induced arthritis compared to wild-type mice. Histologic analysis revealed extensive tissue and bone destruction, with significantly reduced neutrophil infiltration but considerably more macrophage migration, in LCN-2-knockout mice compared to wild-type mice.

CONCLUSION

These results demonstrate that LCN-2 may regulate immune cell recruitment to the site of inflammation, a process essential for the controlled initiation, perpetuation, and resolution of inflammatory processes. Thus, LCN-2 may present a promising target in the treatment of IC-mediated inflammatory/autoimmune diseases.

Low serum lipocalin levels in patients with iron deficiency anemia

In the recent literature, there are studies on the relationship between anemia and lipocalin, but there is no study regarding the relationship between lipocalin and iron deficiency anemia (IDA) up to date. In this study, we aimed to observe lipocalin levels at admission, and after iron therapy in children with IDA. We also compared our findings to those in healthy children. Sixty-one children admitted in our outpatient clinic were included in the study. Thirty of these children had IDA (study group) and the rest were healthy (control group). Thirty patients, meeting the IDA criteria, received oral ferrous sulfate of 4 mg/kg/d. As soon as the hemoglobin value reached >11 g/dL, half dose of oral ferrous sulfate therapy was continued for another month. Serum lipocalin levels before and after iron therapies were compared. Hematologic parameters and serum lipocalin levels were also compared between the 2 groups. Mean values of serum lipocalin were 31.01±14.46 and 74.77 ng/dL in patients with IDA at admission and at third month of therapy, respectively (P<0.0001). The same figure was 57.35±39.51 ng/dL in the control group. Before treatment, mean values of lipocalin levels in patients with IDA was significantly lower than the control group (P=0.001); however, such a difference was not detected after 3 months of therapy (P=0.102). We suggest that decreased serum lipocalin levels in our patients during iron insufficiency were caused by iron deficiency rather than anemia.

Bacterial cell wall constituents induce hepcidin expression in macrophages through MyD88 signaling

Hepcidin is a key regulator of iron recycling by macrophages that is synthesized mainly by hepatocytes but also by macrophages. However, very little is known about the molecular regulation of hepcidin in macrophages. In the present study, we investigated hepcidin regulation in the RAW264.7 macrophage cell line and in murine peritoneal macrophages stimulated with different Toll-like receptor (TLR) ligands. We found that TLR-2 and TLR-4 ligands activated hepcidin expression in RAW264.7 cells and in wild-type murine peritoneal macrophages, but not in murine peritoneal macrophages isolated from TLR2(-/-), TLR-4-deficient or MyD88(-/-) mice. IL-6 production by RAW264.7 cells stimulated with lipopolysaccharide (LPS, TLR4 ligand) was enhanced by high amounts of iron present in the culture medium. We conclude that hepcidin expression in macrophages is regulated mainly through TLR2 and TLR4 receptors via the MyD88-dependent signaling pathway and that autocrine regulation of iron accumulation in macrophages by hepcidin may affect the levels of proinflammatory cytokine production.

Association between plasma neutrophil gelatinase associated lipocalin level and obstructive sleep apnea or nocturnal intermittent hypoxia

BACKGROUND

Both obstructive sleep apnea (OSA) and a novel lipocalin, neutrophil gelatinase associated lipocalin (Ngal), have been reported to be closely linked with cardiovascular disease and loss of kidney function through chronic inflammation. However, the relationship between OSA and Ngal has never been investigated.

OBJECTIVES

To evaluate the relationship between Ngal and OSA in clinical practice.

METHODS

In 102 patients, polysomnography was performed to diagnose OSA and plasma Ngal levels were measured. The correlations between Ngal levels and OSA severity and other clinical variables were evaluated. Of the 46 patients who began treatment with continuous positive airway pressure (CPAP), Ngal levels were reevaluated after three months of treatment in 25 patients.

RESULTS

The Ngal level correlated significantly with OSA severity as determined by the apnea hypopnea index (r = 0.24, p = 0.01) and 4% oxygen desaturation index (ODI) (r = 0.26, p = 0.01). Multiple regression analysis showed that the Ngal level was associated with 4%ODI independently of other clinical variables. Compliance was good in 13 of the 25 patients who used CPAP. Although the OSA (4%ODI: 33.1±16.7 to 1.1±1.9/h, p<0.01) had significantly improved in those with good compliance, the Ngal levels were not significantly changed (60.5±18.1 before CPAP vs 64.2±13.9 ng/ml after CPAP, p = 0.27).

CONCLUSIONS

Plasma Ngal levels were positively associated with the severity of OSA. However, the contribution rate of OSA to systemic Ngal secretion was small and changes in Ngal levels appeared to be influenced largely by other confounding factors. Therefore, it does not seem reasonable to use the Ngal level as a specific biomarker of OSA in clinical practice.

Lipocalin 2 in cancer: when good immunity goes bad

The innate immune molecule Lipocalin 2 (LCN2) was initially shown to combat bacterial infection by binding bacterial siderophores, hence impairing microbial iron sequestration. In recent years, it has become apparent that LCN2 is over-expressed in cancers of diverse histological origin and that it facilitates tumorigenesis by promoting survival, growth, and metastasis. Herein, we discuss emerging evidence that substantiates two functional roles for LCN2 in cancer: promotion of the epithelial-to-mesenchymal transition (EMT) that facilitates an invasive phenotype and metastasis, and sequestration of iron that results in cell survival and tumorigenesis. Further, we present evidence that upregulated LCN2 expression in solid tumors is induced by hypoxia and pro-inflammation, microenvironmental noxae that converge to cause an endoplasmic reticulum (ER) stress response. Taken together, it appears that tumor cells exploit the beneficial innate immune function of LCN2 to support uncontrolled growth. This duplicity in function highlights LCN2 and its upstream driver, the ER stress response, as key targets for cancer therapy.

Adipokines: biofactors from white adipose tissue. A complex hub among inflammation, metabolism, and immunity

Until the identification of leptin, the first adipokine discovered in 1994, adipose tissue was considered only as an energy storage tissue. However, it is now clear that adipose tissue is an endocrine/paracrine/autocrine organ, which plays a relevant role in physiopathology of several inflammatory diseases. Actually, it is mainly involved not only in the low-grade inflammatory status in obesity but also in other relevant inflammatory conditions and autoimmune disorders. In this review article, we discuss the main biological activities of leptin, adiponectin, lipocalin-2, resistin, and visfatin, as well as their contributions to certain inflammatory conditions.

What's new in our understanding of the role of adipokines in rheumatic diseases?

Important advances in our understanding of the relationships between adipokines, inflammation and the immune response have been achieved in the past 10 years. White adipose tissue has emerged as a highly dynamic organ that releases a plethora of immune and inflammatory mediators that are involved in numerous diseases, including not only rheumatic diseases such as rheumatoid arthritis, osteoarthritis and systemic lupus erythematosus, but also cardiovascular and metabolic complications that are frequently observed in rheumatic diseases. Our rapidly growing knowledge of adipokine biology is revealing the complexity of these amazing proteins, thereby redefining white adipose tissue as a key element of the inflammatory and immune response in rheumatic diseases. Adipokines exert potent modulatory actions on target tissues and cells involved in rheumatic disease, including cartilage, synovium, bone and various immune cells. In this Review, we describe the most recent advances in adipokine research in the context of rheumatic diseases, focusing primarily on leptin, adiponectin, visfatin and resistin, and also the potential role of newly identified adipokines such as chemerin, lipocalin 2 and serum amyloid A3.

Multiple oxygen tension environments reveal diverse patterns of transcriptional regulation in primary astrocytes

The central nervous system normally functions at O₂ levels which would be regarded as hypoxic by most other tissues. However, most in vitro studies of neurons and astrocytes are conducted under hyperoxic conditions without consideration of O₂-dependent cellular adaptation. We analyzed the reactivity of astrocytes to 1, 4 and 9% O₂ tensions compared to the cell culture standard of 20% O₂, to investigate their ability to sense and translate this O₂ information to transcriptional activity. Variance of ambient O₂ tension for rat astrocytes resulted in profound changes in ribosomal activity, cytoskeletal and energy-regulatory mechanisms and cytokine-related signaling. Clustering of transcriptional regulation patterns revealed four distinct response pattern groups that directionally pivoted around the 4% O₂ tension, or demonstrated coherent ascending/decreasing gene expression patterns in response to diverse oxygen tensions. Immune response and cell cycle/cancer-related signaling pathway transcriptomic subsets were significantly activated with increasing hypoxia, whilst hemostatic and cardiovascular signaling mechanisms were attenuated with increasing hypoxia. Our data indicate that variant O₂ tensions induce specific and physiologically-focused transcript regulation patterns that may underpin important physiological mechanisms that connect higher neurological activity to astrocytic function and ambient oxygen environments. These strongly defined patterns demonstrate a strong bias for physiological transcript programs to pivot around the 4% O₂ tension, while uni-modal programs that do not, appear more related to pathological actions. The functional interaction of these transcriptional ‘programs’ may serve to regulate the dynamic vascular responsivity of the central nervous system during periods of stress or heightened activity.

Induction of lipocalin-2 expression in acute and chronic experimental liver injury moderated by pro-inflammatory cytokines interleukin-1β through nuclear factor-κB activation

BACKGROUND

Lipocalin-2 (LCN2) belongs to the lipocalin superfamily, sharing a barrel-shaped tertiary structure with a hydrophobic pocket and an ability to bind lipophilic molecules. LCN2 has recently emerged as an important modulator of cellular homeostasis in several organs, i.e. heart, lung and kidney, but little is known about the expression of LCN2 in acute and chronic liver injury.

AIMS

In this study, we wanted to analyse the expression and regulation of LCN2 in models of acute and chronic experimental liver injury.

MATERIALS AND METHODS

We analysed LCN2 expression in livers of rats subjected to bile duct ligation or repeated doses of carbon tetrachloride and tested the impact of various pro-inflammatory cytokines in cultured primary liver cells.

RESULTS

By using primary cultures of hepatic stellate cells and hepatocytes isolated from normal and injured rat livers, we found a significant LCN2 expression in early hepatic stellate cell cultures, a lower expression in fully transdifferentiated myofibroblasts and no expression in freshly isolated hepatocytes. However, LCN2 expression and secretion in hepatocytes increased dramatically during culturing. In addition, chronic in vivo liver injury resulting from both bile duct ligation and repeated application of carbon tetrachloride resulted in rapid and well-sustained induction of LCN2 expression. Immunohistochemistry and primary liver cell isolation identified injured hepatocytes as the main source of LCN2 production. LCN2 is strongly induced in both primary hepatocytes and immortalized hepatocellular carcinoma cell line HepG2 by the pro-inflammatory cytokine interleukin-1β via nuclear factor-κB activation, but not by the profibrotic cytokines platelet-derived growth factor and transforming growth factor-β.

CONCLUSION

LCN2 expression shows clear correlation to liver damage and resulting inflammatory responses, rather than to the degree of liver fibrosis, which in fact may imply a distinct diagnostic value as an early biomarker of liver inflammation.

Serum lipocalin-2 as an insulin resistance marker in patients with polycystic ovary syndrome

BACKGROUND

Our aim was to investigate levels of lipocalin-2 and its relationship with metabolic factors in women with polycystic ovary syndrome (PCOS).

MATERIALS/SUBJECTS AND METHODS

In this cross-sectional study, two groups of women were studied: group 1 consisted of women with PCOS (no.=30), and group 2 consisted of control women with normal ovulatory function (no.=30). The circulating levels of free testosterone (T), DHEAS, glucose, insulin, triglycerides (TG), HDL, LDL and lipocalin were measured. Insulin resistance was assessed using the homeostasis model assessment (HOMA-IR). In order to determine a lipocalin value indicating insulin resistance, receiver operating characteristic (ROC) curves were established.

RESULTS

Serum lipocalin was significantly higher in PCOS subjects (54.26 ± 15.58 vs 26.09 ± 7.47 ng/ml, p=0.0001).We found a close correlation between lipocalin and insulin, lipocalin and HOMA-IR, lipocalin and T, and lipocalin and DHEAS. A cut-off level of >39.54 ng/ml for serum lipocalin has a predictive value for insulin resistance of 81% sensitivity and 82.1% specificity.

CONCLUSION

In our study, lipocalin-2 levels were found to be significantly higher in women with PCOS compared to body mass index-matched controls. Serum lipocalin-2 may prove to be a useful marker for insulin resistance in patients with PCOS.

Neutrophil gelatinase-associated lipocalin induces the expression of heme oxygenase-1 and superoxide dismutase 1, 2

Lipocalin-2 (Lcn2, NGAL) is a member of the lipocalin super family with diverse function such as the induction of apoptosis, the suppression of bacterial growth, and modulation of inflammatory response. Much interest has recently been focused on the physiological/pathological role of the lipocalin-2 that is considered to be a novel protective factor against oxidative stress. However, its precise biological roles in this protection are not fully understood. In this report we intended to test the effect of lipocalin-2 on the expression of heme oxygenase ((1, 2)) and superoxide dismutase ((1, 2)) which are two strong antioxidants. NGAL was cloned to pcDNA3.1 plasmid by using genetic engineering method. The recombinant vector was transfected to CHO and HEK293T to establish stable cell expressing NGAL and the expression of HO-1, 2 and SOD(1, 2) were compared with appropriate controls by RT-PCR and western blot. On the other hand, expression of NGAL was suppressed by siRNA transfection in order to study the effect of lipocalin-2 on mentioned genes/proteins. The results showed that the expression of HO-1 and SOD(1, 2) enzymes were higher in cells expressing recombinant lipocalin-2 compared with the control cells. Although the expression of HO-1 was lower in NGAL silencing cells, the expression of SOD(1) and SOD(2) were higher. Our data suggest that NGAL is a potent inducer of HO-1 and somewhat SOD(1) and SOD(2) and it appears that part of antioxidant property of NGAL could be attributed to the induction of HO-1 and SOD(1, 2).

Neutrophil gelatinase-associated lipocalin (NGAL) reflects iron status in haemodialysis patients

BACKGROUND

An iron deficiency is often present in haemodialysis (HD) patients; however, although transferrin saturation (TSAT) of <20% and/or serum ferritin of <200 ng/mL should express iron scarcity, in HD patients high ferritin levels could be related to inflammation rather than reflecting optimal iron stores.

METHODS

The aim of the present study was to evaluate serum levels of neutrophil gelatinase-associated lipocalin (NGAL), a small siderophore-binding protein, in a cohort of 56 chronic HD patients in order to determine its possible relationships with iron status.

RESULTS

NGAL levels were markedly higher in HD patients than in healthy controls; furthermore, HD patients with TSAT <20% had lower NGAL values than healthy controls, whereas the correction of iron deficiency by means of chronic i.v. iron administration significantly increased NGAL values from baseline. Findings from univariate and multivariate analyses demonstrated that NGAL was a significant predictor of hsCRP, spKT/V and TSAT. In ROC analysis, a NGAL cut-off level of <or=473 ng/mL had a greater sensitivity and specificity than a ferritin level of <200 ng/mL in identifying iron deficiency among HD patients.

CONCLUSIONS

The findings demonstrated that HD patients have altered NGAL values probably because this protein is involved in the maintenance of iron equilibrium. Finally, NGAL might be proposed as a new tool in the assessment of iron deficiency and in the management of iron therapy for HD patients.