Role of lipocalin-2 in extracellular peroxiredoxin 2-induced brain swelling, inflammation and neuronal death

Lipocalin-2 inhibition alleviates neural injury by microglia ferroptosis suppression after experimental intracerebral hemorrhage in mice via enhancing ferritin light chain expression

INTRODUCTION

Microglia play pivotal roles in post-intracerebral hemorrhage (ICH) neural injury. Iron metabolism, which is dysregulated after ICH, participates in microglial dysfunction. Previous studies have shown that iron metabolism-related lipocalin-2 (LCN2) is involved in regulating microglial function following ICH. In this study, we investigated the role of LCN2 in microglial function following ICH.

METHODS

The BV2 (microglia) cell line, transfected with LCN2 for overexpression/interference, received a blood infusion from C57BL/6 mice in vitro. For the in vivo study of LCN2 function, an LCN2 knockout was conducted in mice. Liproxstatin-1 and RSL3 were used to manipulate ferroptosis and to study the effects of LCN2 on microglia after ICH. A BV2 (microglia) cell line, transfected with ferritin light chain (FTL) for overexpression/interference, was co-cultured with primary cultured neurons for a study on the mechanism of LCN2. Behavioral tests were conducted pre-ICH and on days 3, 7, and 28 post-ICH, and the brains and cultured cells were collected for protein, histological, and morphological studies.

RESULTS

Brain LCN2 expression was upregulated in microglia, astrocytes, and neurons and played hazardous roles after ICH. In microglia, LCN2 promoted ferroptosis, which facilitated neural injury after ICH. LCN2-mediated FTL deficiency was shown to be responsible for microglial ferroptosis-induced neural injury.

CONCLUSION

Our study suggests that LCN2-enhanced microglial ferroptosis plays a detrimental role by inducing FTL deficiency after ICH. The current study reveals a novel molecular mechanism involved in the pathophysiological progression of ICH.

Progress in the Pathogenesis of Diabetic Encephalopathy: The Key Role of Neuroinflammation

Diabetic encephalopathy (DE) is a severe complication that occurs in the central nervous system (CNS) and leads to cognitive impairment. DE involves various pathophysiological processes, and its pathogenesis is still unclear. This review summarised current research on the pathogenesis of diabetic encephalopathy, which involves neuroinflammation, oxidative stress, iron homoeostasis, blood-brain barrier disruption, altered gut microbiota, insulin resistance, etc. Among these pathological mechanisms, neuroinflammation has been focused on. This paper summarises some of the molecular mechanisms involved in neuroinflammation, including the Mammalian Target of Rapamycin (mTOR), Lipocalin-2 (LCN-2), Pyroptosis, Advanced Glycosylation End Products (AGEs), and some common pro-inflammatory factors. In addition, we discuss recent advances in the study of potential therapeutic targets for the treatment of DE against neuroinflammation. The current research on the pathogenesis of DE is progressing slowly, and more research is needed in the future. Further study of neuroinflammation as a mechanism is conducive to the discovery of more effective treatments for DE in the future.

STZ-induced diabetes exacerbates neurons ferroptosis after ischemic stroke by upregulating LCN2 in neutrophils

Diabetic is a major contributor to the unfavorable prognosis of ischemic stroke. However, intensive hypoglycemic strategies do not improve stroke outcomes, implying that diabetes may affect stroke outcomes through other ways. Ferroptosis is a novel programmed cell death pathway associated with the development of diabetes and ischemic stroke. This study aimed to investigate the effect of streptozotocin (STZ)-induced diabetes on ferroptosis after stroke from the immune cell perspective, and to provide a theoretical foundation for the clinical management of ischemic stroke in patients with diabetes. The results revealed that STZ-induced diabetes not only facilitates the infiltration of neutrophils into the brain after stroke, but also upregulates the expression of lipocalin 2 (LCN2) in neutrophils. LCN2 promotes lipid peroxide accumulation by increasing intracellular ferrous ions, which intensify ferroptosis in major brain cell populations, especially neurons. Our findings suggest that STZ-induced diabetes aggravates ischemic stroke partially by mediating ferroptosis through neutrophil-derived LCN2. These data contribute to improved understanding of post-stroke immune regulation in diabetes, and offer a potentially novel therapeutic target for the management of acute-stage ischemic stroke complicated with diabetes.

Peroxiredoxin II exerts neuroprotective effects by inhibiting endoplasmic reticulum stress and oxidative stress-induced neuronal pyroptosis

BACKGROUND

Intracerebral hemorrhage (ICH) is a critical neurological condition with few treatment options, where secondary immune responses and specific cell death forms, like pyroptosis, worsen brain damage. Pyroptosis involves gasdermin-mediated membrane pores, increasing inflammation and neural harm, with the NLRP3/Caspase-1/GSDMD pathway being central to this process. Peroxiredoxin II (Prx II), recognized for its mitochondrial protection and reactive oxygen species (ROS) scavenging abilities, appears as a promising neuronal pyroptosis modulator. However, its exact role and action mechanisms need clearer definition. This research aims to explore Prx II impact on neuronal pyroptosis and elucidate its mechanisms, especially regarding endoplasmic reticulum (ER) stress and oxidative stress-induced neuronal damage modulation.

METHODS AND RESULTS

Utilizing MTT assays, Microscopy, Hoechst/PI staining, Western blotting, and immunofluorescence, we found Prx II effectively reduces LPS/ATP-induced pyroptosis and neuroinflammation in HT22 hippocampal neuronal cells. Our results indicate Prx II's neuroprotective actions are mediated through PI3K/AKT activation and ER stress pathway inhibition, diminishing mitochondrial dysfunction and decreasing neuronal pyroptosis through the ROS/MAPK/NF-κB pathway. These findings highlight Prx II potential therapeutic value in improving intracerebral hemorrhage outcomes by lessening secondary brain injury via critical signaling pathway modulation involved in neuronal pyroptosis.

CONCLUSIONS

Our study not only underlines Prx II importance in neuroprotection but also opens new therapeutic intervention avenues in intracerebral hemorrhage, stressing the complex interplay between redox regulation, ER stress, and mitochondrial dynamics in neuroinflammation and cell death management.

Knockdown of LCN2 Attenuates Brain Injury After Intracerebral Hemorrhage via Suppressing Pyroptosis

Objective

The aims of this study are to screen novel differentially expressed genes (DEGs) for intracerebral hemorrhage (ICH) and reveal the role of Lipocalin-2 (LCN2) in ICH.

Methods

We constructed the ICH model by injection of autologous whole blood into the right basal ganglia in rats. RNA-sequencing and bioinformatics analyses were performed to identify the DEGs between ICH and sham rats, and some important ones were confirmed using quantitative real-time PCR (qRT-PCR). LCN shRNA was used to knockdown of LCN2 in ICH rats. Pathological examination was carried out using 2,3,5-triphenyltetrazolium chloride (TTC) staining and Hematoxylin-eosin (HE) staining. Immunohistochemistry detected Caspase-3, and co-staining of Terminal dUTP nick end labeling (TUNEL) and NEUN staining were performed for neuron apoptosis assessment. Western blot analysis was performed to quantify pyroptosis-related proteins. Enzyme-linked immunosorbent assay (ELISA) was used to measure inflammatory cytokine levels.

Results

ICH rats exhibited significant hematomas, higher brain water content, obvious interstitial edema, and inflammatory infiltration, as well as more apoptotic cells in brain tissues. RNA-seq analysis identified 103 upregulated and 81 downregulated DEGs. The expression of LCN2, HSPB1, CXCL10, and MEF2B were upregulated in ICH rats. ICH triggered the release of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), and IL-18, and promoted the expression of pyroptosis-related proteins Caspase-1, GSDMD, NLRP3, and ASC. LCN2 knockdown attenuated the pathological characteristics of ICH, and also reduced pyroptosis in brain tissues.

Conclusion

Inhibition of LCN2 attenuates brain injury after ICH via suppressing pyroptosis, which provide guidance for ICH management.

Association between lipocalin-2 levels and diabetic retinopathy in patients with overweight/obese type 2 diabetes mellitus

AIMS

The study aimed to investigate the association between lipocalin-2 (LCN-2) levels and diabetic retinopathy (DR) in patients with overweight/obese type 2 diabetes mellitus(T2DM), and to explore the mechanism of LCN-2 in overweight/obese DR.

METHODS

The study involved 237 T2DM inpatients divided into the normal group and overweight/obese group, and the two groups were further divided into two subgroups according to the presence or absence of DR. The demographic data and biochemical parameters were measured.

RESULTS

LCN-2 levels in overweight/obese groups were higher than those in normal groups (P < 0.001 for all), and patients with DR had higher levels of LCN-2 than those without DR(P < 0.05 for all) in normal groups and overweight/obese groups. Binary logistic regression analysis showed that no significant significance was observed for LCN-2 levels compared to those below the median in the normal group, but individuals with LCN-2 levels above the median had 4.198 times higher risk of developing DR than those below the median (OR = 4.198, 95% CI = 1.676-10.516) after adjustment for potential confounding factors in the overweight/obese group. In the total, normal and overweight/obese groups, the prediction capacity of LCN-2 for DR was 1.56, 1.58 and 1.65 times, respectively. Conclusionsː In conclusion, our study found that LCN-2 levels were higher in overweight/obese patients with DR, and LCN-2 was an independent predictor of DR in T2DM patients with overweight/obese. In addition, LCN-2 may be a valuable predictor of DR-like factors such as the duration of diabetes and hypertension.

Characteristics of activation of monocyte-derived macrophages versus microglia after mouse experimental intracerebral hemorrhage

Both monocyte-derived macrophages (MDMs) and brain resident microglia participate in hematoma resolution after intracerebral hemorrhage (ICH). Here, we utilized a transgenic mouse line with enhanced green fluorescent protein (EGFP) labeled microglia (Tmem119-EGFP mice) combined with a F4/80 immunohistochemistry (a pan-macrophage marker) to visualize changes in MDMs and microglia after ICH. A murine model of ICH was used in which autologous blood was stereotactically injected into the right basal ganglia. The autologous blood was co-injected with CD47 blocking antibodies to enhance phagocytosis or clodronate liposomes for phagocyte depletion. In addition, Tmem119-EGFP mice were injected with the blood components peroxiredoxin 2 (Prx2) or thrombin. MDMs entered the brain and formed a peri-hematoma cell layer by day 3 after ICH and giant phagocytes engulfed red blood cells were found. CD47 blocking antibody increased the number of MDMs around and inside the hematoma and extended MDM phagocytic activity to day 7. Both MDMs and microglia could be diminished by clodronate liposomes. Intracerebral injection of Prx2 but not thrombin attracted MDMs into brain parenchyma. In conclusion, MDMs play an important role in phagocytosis after ICH which can be enhanced by CD47 blocking antibody, suggesting the modulation of MDMs after ICH could be a future therapeutic target.

Role of lipocalin 2 in stroke

Stroke is the second leading cause of death worldwide; however, the treatment choices available to neurologists are limited in clinical practice. Lipocalin 2 (LCN2) is a secreted protein, belonging to the lipocalin superfamily, with multiple biological functions in mediating innate immune response, inflammatory response, iron-homeostasis, cell migration and differentiation, energy metabolism, and other processes in the body. LCN2 is expressed at low levels in the brain under normal physiological conditions, but its expression is significantly up-regulated in multiple acute stimulations and chronic pathologies. An up-regulation of LCN2 has been found in the blood/cerebrospinal fluid of patients with ischemic/hemorrhagic stroke, and could serve as a potential biomarker for the prediction of the severity of acute stroke. LCN2 activates reactive astrocytes and microglia, promotes neutrophil infiltration, amplifies post-stroke inflammation, promotes blood-brain barrier disruption, white matter injury, and neuronal death. Moreover, LCN2 is involved in brain injury induced by thrombin and erythrocyte lysates, as well as microvascular thrombosis after hemorrhage. In this paper, we review the role of LCN2 in the pathological processes of ischemic stroke; intracerebral hemorrhage; subarachnoid hemorrhage; and stroke-related brain diseases, such as vascular dementia and post-stroke depression, and their underlying mechanisms. We hope that this review will help elucidate the value of LCN2 as a therapeutic target in stroke.

Iron-Induced Hydrocephalus: the Role of Choroid Plexus Stromal Macrophages

Evidence indicates that erythrocyte-derived iron and inflammation both play a role in intraventricular hemorrhage-induced brain injury including hydrocephalus. Many immune-associated cells, primarily stromal macrophages, reside at the choroid plexus where they are involved in inflammatory responses and antigen presentation. However, whether intraventricular iron impacts those stromal cells is unknown. The aim of this study was to evaluate the relationship between choroid plexus stromal macrophages and iron-induced hydrocephalus in rats and the impact of minocycline and clodronate liposomes on those changes. Aged (18-month-old) and young (3-month-old) male Fischer 344 rats were used to study choroid plexus stromal macrophages. Rats underwent intraventricular iron injection to induce hydrocephalus and treated with either minocycline, a microglia/macrophage inhibitor, or clodronate liposomes, a macrophage depleting agent. Ventricular volume was measured using magnetic resonance imaging, and stromal macrophages were quantified by immunofluorescence staining. We found that stromal macrophages accounted for about 10% of the total choroid plexus cells with more in aged rats. In both aged and young rats, intraventricular iron injection resulted in hydrocephalus and increased stromal macrophage number. Minocycline or clodronate liposomes ameliorated iron-induced hydrocephalus and the increase in stromal macrophages. In conclusion, stromal macrophages account for ~10% of all choroid plexus cells, with more in aged rats. Treatments targeting macrophages (minocycline and clodronate liposomes) are associated with reduced iron-induced hydrocephalus.

Brain edema formation and therapy after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) accounts for about 10% of all strokes in the United States of America causing a high degree of disability and mortality. There is initial (primary) brain injury due to the mechanical disruption caused by the hematoma. There is then secondary injury, triggered by the initial injury but also the release of various clot-derived factors (e.g., thrombin and hemoglobin). ICH alters brain fluid homeostasis. Apart from the initial hematoma mass, ICH causes blood-brain barrier disruption and parenchymal cell swelling, which result in brain edema and intracranial hypertension affecting patient prognosis. Reducing brain edema is a critical part of post-ICH care. However, there are limited effective treatment methods for reducing perihematomal cerebral edema and intracranial pressure in ICH. This review discusses the mechanisms underlying perihematomal brain edema formation, the effects of sex and age, as well as how edema is resolved. It examines progress in pharmacotherapy, particularly focusing on drugs which have been or are currently being investigated in clinical trials.

Identification of CD73 as a Novel Biomarker Encompassing the Tumor Microenvironment, Prognosis, and Therapeutic Responses in Various Cancers

CD73 is essential in promoting tumor growth by prohibiting anti-tumor immunity in many cancer types. While the mechanism remains largely unknown, our paper comprehensively confirmed the onco-immunological characteristics of CD73 in the tumor microenvironment (TME) of pan-cancer. This paper explored the expression pattern, mutational profile, prognostic value, tumor immune infiltration, and response to immunotherapy of CD73 in a continuous cohort of cancers through various computational tools. The co-expression of CD73 on cancer cells, immune cells, and stromal cells in the TME was also detected. Especially, we examined the correlation between CD73 and CD8+ (a marker of T cell), CD68+ (a marker of macrophage), and CD163+ (a marker of M2 macrophage) cells using multiplex immunofluorescence staining of tissue microarrays. CD73 expression is significantly associated with a patient's prognosis and could be a promising predictor of these cancers. High CD73 levels are strongly linked to immune infiltrations, neoantigens, and immune checkpoint expression in the TME. In particular, enrichment signaling pathway analysis demonstrated that CD73 was obviously related to activation pathways of immune cells, including T cells, macrophages, and cancer-associated fibroblasts (CAFs). Meanwhile, single-cell sequencing algorithms found that CD73 is predominantly co-expressed on cancer cells, CAFs, M2 macrophages, and T cells in several cancers. In addition, we explored the cellular communication among 14 cell types in glioblastoma (GBM) based on CD73 expression. Based on the expression of CD73 as well as macrophage and T cell markers, we predicted the methylation and enrichment pathways of these markers in pan-cancer. Furthermore, a lot of therapeutic molecules sensitive to these markers were predicted. Finally, potential anticancer inhibitors, immunotherapies, and gene therapy responses targeting CD73 were identified from a series of immunotherapy cohorts. CD73 is closely linked to clinical prognosis and immune infiltration in many cancers. Targeting CD73-dependent signaling pathways may be a promising therapeutic strategy for future tumor immunotherapy.

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.

Large-Scale Single-Cell and Bulk Sequencing Analyses Reveal the Prognostic Value and Immune Aspects of CD147 in Pan-Cancer

CD147 plays an important role in promoting tumor proliferation and inhibiting cancer cell apoptosis in the tumor microenvironment. However, the mechanisms by which CD147 is involved in tumorigenesis remains unclear. This study systematically analyzed the prognostic value and immune characteristics of CD147 in 31 cancer types. The expression levels and mutant landscapes of CD147 in pan-cancer were explored. The Kaplan-Meier (KM) analysis was applied to analyze the prognostic value of CD147. The immune characteristics of CD147 in the tumor microenvironment were evaluated via TIMER 2.0 and R package (immunedeconv). We also explored the expression of CD147 on tumor cells and stromal cells through Gene Set Variation Analysis and single-cell sequencing analysis. The co-expression of CD147 and macrophage markers CD68 and CD163 in pan-cancer was detected using multiplex immunofluorescence staining on tissue microarrays. CD147 was found to be overexpressed in almost all cancer types, which was related to poor outcome. CD147 expression exhibited a strong association with immune infiltrates, immune checkpoint molecules, and neoantigen levels in the tumor microenvironment. In addition, CD147 was expressed on various cell types in the tumor microenvironment, including tumor cells, macrophages, T cells, monocytes, fibroblasts, etc. Furthermore, multiplex immunofluorescence revealed the co-expression pattern of CD147 and macrophage markers CD68 and CD163 in many tumor types. Finally, the immunotherapy response and sensitive small molecule drugs based on CD147 expression were predicted. In sum, CD147 has a significant relationship with the clinical outcome and immune infiltrates in multiple cancer types. Inhibiting the CD147-dependent signaling pathways might be a promising therapeutic strategy for tumor immunotherapy.

Lipocalin-2 and Cerebral Stroke

Stroke is a common and devastating disease with an escalating prevalence worldwide. The known secondary injuries after stroke include cell death, neuroinflammation, blood-brain barrier disruption, oxidative stress, iron dysregulation, and neurovascular unit dysfunction. Lipocalin-2 (LCN-2) is a neutrophil gelatinase-associated protein that influences diverse cellular processes during a stroke. The role of LCN-2 has been widely recognized in the peripheral system; however, recent findings have revealed that there are links between LCN-2 and secondary injury and diseases in the central nervous system. Novel roles of LCN-2 in neurons, microglia, astrocytes, and endothelial cells have also been demonstrated. Here, we review the evidence on the regulatory roles of LCN-2 in secondary injuries following a stroke from various perspectives and the pathological mechanisms involved in the modulation of stroke. Overall, our review suggests that LCN-2 is a promising target to promote a better understanding of the neuropathology of stroke.

Lipocalin-2 silencing suppresses inflammation and oxidative stress of acute respiratory distress syndrome by ferroptosis via inhibition of MAPK/ERK pathway in neonatal mice

Neonatal acute respiratory distress syndrome (ARDS) has high morbidity and mortality rates worldwide, but there is a lack of pharmacologic treatment and clinical targeted therapies. In this study, we aimed to explore the effects of Lipocalin-2 (LCN2) on ferroptosis-mediated inflammation and oxidative stress in neonatal ARDS and the potential mechanism. In this study, we established an in vivo ARDS mouse model and an in vitro ARDS cell model by LPS (Lipopolysaccharide) stimulation. Lung tissue injury was evaluated by wet/dry ratios and histopathological examination. LCN2 expression was detected by qRT-PCR and Western blot. Inflammatory factors, oxidative stress and apoptosis were also detected. Ferroptosis was identified by detection of Fe²⁺ level and ferroptosis-associated protein expressions. Mitogen-activated protein kinases (MAPK)/extracellular signal-regulated kinase (ERK) pathway signaling was examined by Western blot analysis. The data revealed that LCN2 expression was significantly upregulated in neonatal mice with ARDS. Interference with LCN2 protected LPS-induced lung in neonatal mouse by reducing the radio of wet/dry and alleviating pathological damages. In addition, LCN2 silencing repressed LPS-induced inflammation, oxidative stress in vivo and in vitro, as well as apoptosis. Meanwhile, decreased level of Fe²⁺ and transferrin while increased levels of ferritin heavy chain 1 (FTH1) and glutathione peroxidase 4 (GPX4) were observed. The expression MAPK/ERK pathway was inhibited by depletion of LCN2. The present results suggest that LCN2 knockdown protected LPS-induced ARDS model via inhibition of ferroptosis-related inflammation and oxidative stress by inhibiting the MAPK/ERK pathway, thereby presenting a novel target for the treatment of ARDS.

Lipocalin-2 Regulates Hippocampal Microglial Activation in Poststroke Depression

Background and Purpose: Microglia play important role in poststroke depression (PSD), however, the exact mechanism was still unclear. The purpose of the study was to study the mechanism of microglial activation in PSD.

Methods: 24 rats were randomly divided into three groups: the PSD group (n = 10), the poststroke (PS) group (n = 7), and the sham group (n = 7). Primary hippocampal microglia were isolated and cultured, and recombined LCN2 protein was used to stimulate the cultured microglia. The protein expression of Iba1, P38 MAPK and PP38 MAPK was analyzed by western blotting; the LCN2 expression was measured by RT-qPCR, the serum LCN2 level and the NO level were analyzed by ELISA.

Results: Open field test scores (horizontal score, vertical score, and self-grooming score) and the serum LCN2 level were significantly decreased in the PSD group compared with the other two groups (P < 0.05). The serum LCN2 level was positively correlated with the horizontal score and negatively correlated with the self-grooming score in the open field test (P < 0.05). The relative protein level of Iba1 and the LCN2 mRNA level were significantly increased in the hippocampal region compared with other brain regions (P < 0.05), while the relative protein level of Iba1 and the LCN2 mRNA level were significantly increased in the PSD group compared with the other two groups (P < 0.05). The length, supernatant NO level, phagocytic ability and migration ability of LCN2-treated microglia were significantly increased compared with those of untreated microglia (P < 0.05). The relative protein levels of P38 MAPK and the PP38 MAPK significantly increased in hippocampal region in the PSD group and LCN2-treated hippocampal microglia (P < 0.05).

Conclusion: Hippocampal microglia are activated during PSD; LCN2 may regulate hippocampal microglial activation by the P38 MAPK pathway in the process of PSD.

Lipocalin 2 as a link between ageing, risk factor conditions and age-related brain diseases

Chronic (neuro)inflammation plays an important role in many age-related central nervous system (CNS) diseases, including Alzheimer's disease, Parkinson's disease and vascular dementia. Inflammation also characterizes many conditions that form a risk factor for these CNS disorders, such as physical inactivity, obesity and cardiovascular disease. Lipocalin 2 (Lcn2) is an inflammatory protein shown to be involved in different age-related CNS diseases, as well as risk factor conditions thereof. Lcn2 expression is increased in the periphery and the brain in different age-related CNS diseases and also their risk factor conditions. Experimental studies indicate that Lcn2 contributes to various neuropathophysiological processes of age-related CNS diseases, including exacerbated neuroinflammation, cell death and iron dysregulation, which may negatively impact cognitive function. We hypothesize that increased Lcn2 levels as a result of age-related risk factor conditions may sensitize the brain and increase the risk to develop age-related CNS diseases. In this review we first provide a comprehensive overview of the known functions of Lcn2, and its effects in the CNS. Subsequently, this review explores Lcn2 as a potential (neuro)inflammatory link between different risk factor conditions and the development of age-related CNS disorders. Altogether, evidence convincingly indicates Lcn2 as a key constituent in ageing and age-related brain diseases.

Role of Complement Component 3 in Early Erythrolysis in the Hematoma After Experimental Intracerebral Hemorrhage

[Figure: see text].

Elevated Hydrostatic Pressure Causes Retinal Degeneration Through Upregulating Lipocalin-2

Elevation of intraocular pressure is a major risk factor for glaucoma development, which causes the loss of retinal ganglion cells (RGCs). Lipocalin 2 (Lcn2) is upregulated in glaucomatous retinae; however, whether Lcn2 is directly involved in glaucoma is debated. In this study, retinal explant cultures were subjected to increased water pressure using a two-chamber culture device, and Lcn2 protein levels were examined by immunoblotting. In situ TdT-mediated dUTP nick and labeling (TUNEL) and glial fibrillary acidic protein (GFAP) immunohistochemical assays were performed to assess apoptosis and gliosis, respectively. The neurotoxicity of Lcn2 in the retinal explant culture was determined with exogenous administration of recombinant Lcn2. The Lcn2 protein levels, percentage of TUNEL-positive cells, and GFAP-positive area were significantly higher in retinae cultured under 50 cm H₂O pressure loads compared to those cultured under 20 cm H₂O. We found that Lcn2 exhibited neurotoxicity in retinae at dose of 1 μg/ml. The negative effects of increased hydrostatic pressure were attenuated by the iron chelator deferoxamine. This is the first report demonstrating the direct upregulation of Lcn2 by elevating hydrostatic pressure. Modulating Lcn2 and iron levels may be a promising therapeutic approach for retinal degeneration.