Endometrial carcinoma often arises from normal endometrial glandular cells via a precursor, atypical endometrial hyperplasia. However, the genetic changes involved in this carcinogenetic process are not fully understood. Differentially expressed genes were selected from glandular cells of normal proliferative-phase endometria, atypical endometrial hyperplasia, and endometrial carcinoma using laser-captured microdissection and microarray. The microarray analysis revealed a total of 51 genes to be up-regulated and 23 genes to be down-regulated in neoplastic endometrial epithelia. We focused on lipocalin2 (LCN2), which showed the largest magnitude of up-regulation. Immunostaining for lipocalin2 confirmed a stepwise increase in its expression in endometrial hyperplasia and carcinoma. In addition, elevated expression of lipocalin2 was correlated with the poor outcome of endometrial carcinoma patients. The subcellular distribution of lipocalin2 was both cytoplasmic and nuclear, despite reports that lipocalin2 is a secretory protein. Treatment of endometrial carcinoma cells with 5-azacytidine increased the expression of lipocalin2, suggesting the expression to be controlled by methylation of the promoter. The forced expression of lipocalin2 resulted in the enhanced cell proliferation and invasion in vitro. The expression of lipocalin2 increased with the endometrial carcinogenesis, and accumulation of the protein conferred biological aggressiveness to endometrial carcinoma cells. These results suggest lipocalin2 to be a novel target in the treatment of endometrial carcinoma.

Lipocalin 2 (LCN2) is a poor prognostic factor in esophageal squamous cell carcinoma (ESCC), however its functional roles and molecular mechanisms of action remain to be clarified. Here, we described the functions and signaling pathways for LCN2 in ESCC. Overexpression of LCN2 in ESCC cells accelerated cell migration and invasion in vitro, and promoted lung metastasis in vivo. Blocking LCN2 expression inhibited its pro-oncogenic effect. Either overexpression of LCN2 or treatment with recombinant human LCN2 protein enhanced the activation of MEK/ERK pathway, which in turn increases endogenous LCN2 to increase MMP-9 activity. The decreased p-cofilin and increased p-ERM induced by pERK1/2 cause the cytoskeleton F-actin rearrangement and alter the behavior of ESCC cells mediated by LCN2. As a consequence, activation of MMP-9 and the rearrangement of F-actin throw light on the mechanisms for LCN2 in ESCC. These results imply that LCN2 promotes the migration and invasion of ESCC cells through a novel positive feedback loop.

Alkaline phosphatase (AP) inactivates bacterial lipopolysaccharide and may therefore be protective. The small intestine and colon express intestinal (IAP) and tissue nonspecific enzyme (TNAP), respectively. The aim of this study was to assess the therapeutic potential of exogenous AP and its complementarity with endogenous enzyme protection in the intestine, as evidenced recently. IAP was given to rats by the oral or intrarectal route (700U/kgday). Oral budesonide (1mg/kgday) was used as a reference treatment. Treatment with intrarectal AP resulted in a 54.5% and 38.0% lower colonic weight and damage score, respectively, and an almost complete normalization of the expression of S100A8, LCN2 and IL-1β (p<0.05). Oral AP was less efficacious, while budesonide had a more pronounced effect on most parameters. Both oral and intrarectal AP counteracted bacterial translocation effectively (78 and 100%, respectively, p<0.05 for the latter), while budesonide failed to exert a positive effect. AP activity was increased in the feces of TNBS colitic animals, associated with augmented sensitivity to the inhibitor levamisole, suggesting enhanced luminal release of this enzyme. This was also observed in the mouse lymphocyte transfer model of chronic colitis. In a separate time course study, TNAP was shown to increase 2-3 days after colitis induction, while dextran sulfate sodium was a much weaker inducer of this isoform. We conclude that exogenous AP exerts beneficial effects on experimental colitis, which includes protection against bacterial translocation. AP of the tissue-nonspecific isoform is shed in higher amounts to the intestinal lumen in experimental colitis, possibly aiding in intestinal protection.

Psoriasis is characterized by resistance to infections, which is regulated by antimicrobial proteins. Whether antimicrobial proteins play a pathogenic role in psoriasis remains unclear. In this study, we aimed to elucidate the role of lipocalin-2 (Lcn2), an antimicrobial protein, in the pathogenesis of psoriasis. Our results showed that Lcn2 was highly expressed in the lesional skin of psoriatic patients. The neutralization of Lcn2 alleviated epidermal hyperplasia, inflammation, and especially neutrophil infiltration in an imiquimod-induced psoriasis-like murine model. In vitro, Lcn2 stimulated human neutrophils to produce vital proinflammatory mediators, such as IL-6, IL-8, tumor necrosis factor-α, and IL-1α via a specific receptor, 24p3R, on neutrophils, which consequently activated the downstream extracellular signal-regulated kinase-1/2 and p38-mitogen-activated protein kinase signaling pathways. Moreover, Lcn2-induced neutrophil chemotaxis was concentration dependent and mediated by the extracellular signal-regulated kinase-1/2 and p38-mitogen-activated protein kinase signaling pathways in vitro. Furthermore, we demonstrated that both keratinocytes and neutrophils were the sources of Lcn2 in the lesional skin of psoriatic patients. Taken together, these results suggest that Lcn2 is involved in the pathogenesis of psoriasis by modulating neutrophil function, and that it could serve as a potential target for treating psoriasis.

The tumor suppressor gene HIC1 is frequently deleted or epigenetically silenced in human cancer, where its restoration may improve cancer prognosis. Here, we report results illuminating how HIC1 silencing alters effect or signals in triple-negative breast cancer (TNBC), which are crucial for its pathogenesis. HIC1 expression was silenced only in TNBC compared with other molecular subtypes of breast cancer. Restoring HIC1 expression in TNBC cells reduced cell migration, invasion, and metastasis, whereas RNAi-mediated silencing of HIC1 in untransformed human breast cells increased their invasive capabilities. Mechanistic investigations identified the small-secreted protein lipocalin-2 (LCN2), as a critical downstream target of HIC1 in TNBC cells. Elevating LCN2 expression in cells expressing HIC1 partially rescued its suppression of cell invasion and metastasis. Notably, autocrine secretion of LCN2 induced by loss of HIC1 activated the AKT pathway through the neutrophil gelatinase-associated lipocalin receptor, which is associated with TNBC progression. Taken together, our findings revealed that the HIC1-LCN2 axis may serve as a subtype-specific prognostic biomarker, providing an appealing candidate target for TNBC therapy.

Head and neck cancers, including oral squamous cell carcinoma (OSCC), are the sixth most common malignancy in the world and are characterized by poor prognosis and a low survival rate. Saliva is oral fluid with intimate contact with OSCC. Besides non-invasive, simple, and rapid to collect, saliva is a potential source of biomarkers. In this study, we build an SRM assay that targets fourteen OSCC candidate biomarker proteins, which were evaluated in a set of clinically-derived saliva samples. Using Skyline software package, we demonstrated a statistically significant higher abundance of the C1R, LCN2, SLPI, FAM49B, TAGLN2, CFB, C3, C4B, LRG1, SERPINA1 candidate biomarkers in the saliva of OSCC patients. Furthermore, our study also demonstrated that CFB, C3, C4B, SERPINA1 and LRG1 are associated with the risk of developing OSCC. Overall, this study successfully used targeted proteomics to measure in saliva a panel of biomarker candidates for OSCC.

Lipocalin-2 (LCN2) is a member of the secreted lipocalin protein family. LCN2 is also a representative gliocalin that is primarily released by glial cells, as well as acts upon them. Astrocytes are one of the major cellular sources of LCN2 under brain injury conditions. Astrocytes secrete LCN2 to promote neuroinflammation. Studies using Lcn2 knockout animals and cultured neural cells suggest an important role of LCN2 in regulating the development of hemorrhagic and ischemic stroke as well as other brain injuries. The clinical relevance of LCN2 is supported by studies on patients with stroke. Mechanistic studies have revealed that LCN2 is a molecular switch for determining the phenotypic fate of astrocytes under inflammatory conditions. LCN2 gene expression is regulated at the multiple levels; mostly at the transcription level, post-transcription level by microRNAs, and protein level by minor post-translational modification. Recent advances in LCN2 research strongly indicate that astrocytic LCN2 is a promising drug target for the injured brain. Future research should focus on its translational aspects, such as developing small-molecule inhibitors or neutralizing antibodies to target LCN2 for the treatment of brain injury. However, spatiotemporally complex roles of LCN2, which are either beneficial or deleterious, should be considered when targeting LCN2. The potential use of LCN2 as a biomarker for the diagnosis and prognosis of various brain disorders is also discussed.

The regenerative potential of mesenchymal stem cells (MSCs) is impaired by cellular senescence, a multi factorial process that has various functions. However, pathways and molecules involved in senescence have not been fully identified. Lipocalin 2 (Lcn2) has been the subject of intensive research, due to its contribution to many physiological and pathophysiological conditions. The implication of Lcn2 has been reported in many conditions where senescence also occurs. In the present study, we evaluated the role of Lcn2 in the occurrence of senescence in human bone marrow-derived mesenchymal stem cells (hB-MSCs) under oxidative conditions. When hB-MSCs were genetically engineered to over-express Lcn2 (MSC-Lcn2) and exposed to H2O2, the proliferation rate of the cells increased. However, the number of colonies and the number of cells that made up each colony in both MSC-V and MSC-Lcn2 cells decreased compared to those cultivated under normal conditions. Our results revealed that over-expression of recombinant Lcn2 in hB-MSCs decreases senescence induced by H2O2 treatment. Senescent cells were observed in aged hB-MSCs; however, no alteration in the expression level of Lcn2 was detected compared to earlier passages. Finally, a higher amount of Lcn2 protein was detected in the plasma of the elderly than in young people. Our findings suggest that Lcn2 might restore the health and regeneration potential of MSCs by decreasing senescence.

The oncofetal isoform of the extracellular matrix protein fibronectin (Fn), which carries the extra-domain B (ED-B) and is exclusively expressed in neovasculature, has gained interest for tumor diagnosis and therapy using engineered antibody fragments. We have employed the human lipocalin 2 (Lcn2) as a small and robust non-immunoglobulin scaffold to select ED-B-specific Anticalins from a new advanced random library using bacterial phage display and ELISA screening against appropriately engineered Fn fragments. As a result, we have isolated and biochemically characterized four different Anticalins that all show low nanomolar affinities for ED-B, right in the range between the monomeric and dimeric forms of the single-chain variable antibody fragment L19 that has been widely applied in this area before. All Anticalins can be readily expressed in Escherichia coli as soluble and strictly monomeric proteins, and they show specific staining of ED-B-positive tumor cells in immunofluorescence microscopy while BIAcore affinity analyses indicate recognition of distinct ED-B epitopes. The crystal structure for one Anticalin, N7A, in complex with the Fn7B8 fragment, was solved at 2.6Å resolution and reveals binding to the gfcc' sheet and cc' loop on ED-B. This is the second example of a protein-specific Lcn2-based Anticalin, which illustrates the remarkable plasticity of the calyx-like ligand pocket of lipocalins with their four structurally hypervariable loops supported by a highly conserved β-barrel. The ED-B-specific Anticalins resulting from this study should provide useful reagents in research and biomedical drug development, both for in vivo imaging and for directed cancer therapy.

OBJECTIVE

To determine the relationship between selected cytokines and diabetes in Chinese subjects.

METHODS

Adult patients with recent-onset type 1 diabetes (n=53), latent autoimmune diabetes in adults (LADA) (n=250), and type 2 diabetes (n=285) from multiple centers were compared with normal subjects (n=196). We centrally tested serum GAD antibodies (GADAs), interleukin-6 (IL-6), lipocalin 2 (LCN2), high-sensitivity C-reactive protein (hs-CRP), and adiponectin.

RESULTS

After adjustment for age, sex, and BMI, all diabetes types had increased IL-6 and LCN2 (P<0.01), and all four cytokines were increased in LADA (P<0.01). In type 1 diabetes, adiponectin but not hs-CRP was increased (P<0.01), whereas in type 2 diabetes, hs-CRP but not adiponectin was increased (P<0.01). Adiponectin was correlated positively with GADA titer and negatively with hs-CRP (P<0.01 for both).

CONCLUSIONS

In China, inflammatory markers are increased in all three major types of diabetes, but probably for different reasons, even in autoimmune diabetes.

Endometriosis is an estrogen-dependent inflammatory disorder among reproductive-aged women associated with pelvic pain, anxiety, and depression. Pain is characterized by central sensitization; however, it is not clear if endometriosis leads to increased pain perception or if women with the disease are more sensitive to pain, increasing the detection of endometriosis. Endometriosis was induced in mice and changes in behavior including pain perception, brain electrophysiology, and gene expression were characterized. Behavioral tests revealed that mice with endometriosis were more depressed, anxious and sensitive to pain compared to sham controls. Microarray analyses confirmed by qPCR identified differential gene expression in several regions of brain in mice with endometriosis. In these mice, genes such as Gpr88, Glra3 in insula, Chrnb4, Npas4 in the hippocampus, and Lcn2 in the amygdala were upregulated while Lct, Serpina3n (insula), and Nptx2 (amygdala) were downregulated. These genes are involved in anxiety, locomotion, and pain. Patch clamp recordings in the amygdala were altered in endometriosis mice demonstrating an effect of endometriosis on brain electrophysiology. Endometriosis induced pain sensitization, anxiety, and depression by modulating brain gene expression and electrophysiology; the effect of endometriosis on the brain may underlie pain sensitization and mood disorders reported in women with the disease.

Mutation in TAR DNA binding protein 43 (TDP-43) is a causative factor of amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Neurodegeneration may not require the presence of pathogenic TDP-43 in all types of relevant cells. Rather, expression of pathogenic TDP-43 in neurons or astrocytes alone is sufficient to cause cell-autonomous or non-cell-autonomous neuron death in transgenic rats. How pathogenic TDP-43 in astrocytes causes non-cell-autonomous neuron death, however, is not clear. Here, we examined the effect of pathogenic TDP-43 on gene expression in astrocytes. Microarray assay revealed that pathogenic TDP-43 in astrocytes preferentially altered expression of the genes encoding secretory proteins. Whereas neurotrophic genes were down-regulated, neurotoxic genes were up-regulated. Representative genes Lcn2 and chitinase-3-like protein 1 were markedly up-regulated in astrocytes from primary culture and intact transgenic rats. Furthermore, synthetic chitinase-3-like protein 1 induced neuron death in a dose-dependent manner. Our results suggest that TDP-43 pathogenesis is associated with the simultaneous induction of multiple neurotoxic genes in astrocytes, which may synergistically produce adverse effects on neuronal survival and contribute to non-cell-autonomous neuron death. Restricted expression of pathogenic TDP-43 in astrocytes causes non-cell-autonomous motor neuron death in transgenic rats. As revealed by microarray assay, pathogenic TDP-43 in astrocytes preferentially altered expression of the genes encoding secretory proteins. Whereas neurotrophic genes were down-regulated, neurotoxic genes were up-regulated. Therefore, TDP-43 pathogenesis is associated with simultaneous induction of neurotoxic genes and repression of neurotrophic genes in astrocytes.

Lipocalin-2 (LCN2) is an acute phase protein induced in response to injury, infection or other inflammatory stimuli. Based on the previously reported involvement of LCN2 in chemokine induction and in the recruitment of neutrophils at the sites of infection or tissue injury, we investigated the role of LCN2 in the pathogenesis of chronic/persistent inflammatory pain hypersensitivity. In the complete Freund's adjuvant (CFA)-induced chronic inflammatory pain model, LCN2 expression was strongly induced in the ipsilateral hindpaws, peaking at 12h after CFA injection and then gradually subsiding. In CFA-injected hindpaw tissues, LCN2 and its receptor 24p3R were mainly expressed in infiltrating neutrophils and macrophages. CFA-induced thermal hyperalgesia and mechanical allodynia were significantly diminished in Lcn2-deficient mice compared to wild-type animals. Furthermore, neutrophil infiltration, myeloperoxidase activity, expression of TNF-α, IL-1β and MIP-2 in CFA-injected hindpaws, and spinal glial activation were markedly reduced by Lcn2 deficiency. An intraplantar injection of recombinant LCN2 protein induced thermal and mechanical hypersensitivities in naïve mice, and this was accompanied by neutrophil and macrophage infiltration into the hindpaws and glial activation in the dorsal horn of the spinal cord. Taken together, our results show that inflammatory cell-derived LCN2 at the sites of inflammation plays important roles in central sensitization and the subsequent nociceptive behavior in the rodent model of chronic inflammatory pain.

We reported previously that subarachnoid hemorrhage (SAH) causes acute white matter injury in mice. In this study, we investigated lipocalin 2 (LCN2) mediated blood-brain barrier (BBB) disruption in white matter, which may lead to subsequent injury. SAH was induced by endovascular perforation in wild-type (WT) and LCN2-knockout (LCN2(-/-)) mice. Sham mice underwent the same procedure without perforation. Mice underwent magnetic resonance imaging (MRI) 24 h after SAH to confirm the development of T2-hyperintensity in white matter. Western blotting and immunohistochemistry were performed to elucidate the mechanisms of LCN2-mediated white matter injury and BBB disruption. It was confirmed that LCN2 expression was significantly increased in white matter of WT mice after SAH by Western blotting (versus sham; p < 0.05). Immunohistochemistry showed that LCN2 receptor 24p3R was expressed in oligodendrocytes, astrocytes, endothelial cells, and pericytes in the white matter. In WT mice with SAH, albumin leakage along the white matter was prominently observed and was consistent with T2-hyperintensity on MRI. As with our previous report, LCN2(-/-) mice scarcely developed T2-hyperintensity on MRI or albumin leakage in white matter. Our results suggest that BBB leakage occurs in white matter after SAH and that LCN2 contributes to SAH-induced BBB disruption.

Endothelial cells are spatially close to osteoblasts and regulate osteogenesis. Moreover, they are sensitive to mechanical stimuli, therefore we hypothesized that they are implicated in the regulation of bone metabolism during unloading. Conditioned media from endothelial cells (EC-CM) subjected to simulated microgravity (0.08g and 0.008g) increased osteoblast proliferation and decreased their differentiation compared to unit gravity (1g) EC-CM. Microgravity-EC-CM increased the expression of osteoblast Rankl and subsequent osteoclastogenesis, and induced the osteoblast de-differentiating factor, Lipocalin 2 (Lcn2), whose downregulation recovered osteoblast activity, decreased Rankl expression and reduced osteoclastogenesis. Microgravity-EC-CM enhanced osteoblast NO-Synthase2 (NOS2) and CycloOXygenase2 (COX2) expression. Inhibition of NOS2 or NO signaling reduced osteoblast proliferation and rescued their differentiation. Nuclear translocation of the Lcn2/NOS2 transcription factor, NF-κB, occurred in microgravity-EC-CM-treated osteoblasts and in microgravity-treated endothelial cells, alongside high expression of the NF-κB activator, IL-1β. IL-1β depletion and NF-κB inhibition reduced osteoblast proliferation and rescued differentiation. Lcn2 and NOS2 were incremented in ex vivo calvarias cultured in microgravity-EC-CM, and in vivo tibias and calvarias injected with microgravity-EC-CM. Furthermore, tibias of botulin A toxin-treated and tail-suspended mice, which featured unloading and decreased bone mass, showed higher expression of IL-1β, Lcn2 and Nos2, suggesting their pathophysiologic involvement in endothelial cell-osteoblast crosstalk.

Cancer cells exhibit an increasing iron demand associated with the tumor progression. But the mechanism of iron accumulation in the tumor microenvironment is still unclear. Tumor associated macrophages (TAMs) in the tumor microenvironment may act as extra iron source. However, evidence is still lacking in TAMs as iron donors. In the present study, we found that iron concentration was significantly increased at tumor metastatic stage, which could be attributed to up-regulated expression of lipocalin2 (Lcn2). TAMs in the microenvironment secreted Lcn2. Moreover, TAMs increased intracellular iron concentration in tumor cells via Lcn2 as transporter, which could be restored by Lcn2 antibody neutralization. In conclusion, TAMs increased intracellular iron concentration of the tumor cells via Lcn2 which acted as an iron transporter. Targeting Lcn2 secretion in TAMs to "starve cancer cells" could act as alternative option for tumor therapy.

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.

CONCLUSIONS

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

Periodontal disease is a bacterial infection that destroys the gingiva and surrounding tissues of the oral cavity. Gingival crevicular fluid (GCF) is extracted from the gingival sulcus and pocket. Analysis of biochemical markers in GCF, which predict the progression of periodontal disease, may facilitate disease diagnosis. However, no useful GCF biochemical markers with high sensitivity for detecting periodontal disease have been identified. Thus, the search for biochemical markers of periodontal disease is of continued interest in experimental and clinical periodontal disease research. Using tandem mass tag (TMT) labeling, we analyzed GCF samples from healthy subjects and patients with periodontal disease, and identified a total of 619 GCF proteins based on proteomic analysis. Of these, we focused on two proteins, matrix metalloproteinase (MMP)-9 and neutrophil gelatinase-associated lipocalin (LCN2), which are involved in the progression of periodontal disease. Western blot analysis revealed that the levels of MMP-9 and LCN2 were significantly higher in patients with periodontal disease than in healthy subjects. In addition, ELISA also detected significantly higher levels of LCN2 in patients with periodontal disease than in healthy subjects. Thus, LC-MS/MS analyses of GCF using TMT labeling led to the identification of LCN2, which may be a promising GCF biomarker for the detection of periodontal disease.

Genetic instability is strongly involved in cancer development and progression, and elucidating the mechanism could lead to novel therapeutics for preventing carcinogenesis. Philadelphia-negative myeloproliferative neoplasms (MPNs) are clonal myeloid disorders with a high prevalence of JAK2V617F mutation, and transformation to acute myeloid leukemia through accumulation of additional mutations is a major complication in MPNs. Here, we showed that JAK2V617F(+) cells conferred paracrine DNA damage to neighboring normal cells as well as to themselves through increased reactive oxygen species (ROS). We screened candidate factors responsible for the effect and found that lipocalin-2 (Lcn2) is overexpressed in JAK2V617F(+) cells and that short hairpin RNA-mediated knockdown of Lcn2 significantly alleviated the paracrine DNA damage. Normal hematopoietic cells showed elevated ROS levels through increased intracellular iron levels when treated with lipocalin-2, which led to p53 pathway activation, increased apoptosis, and decreased cellular proliferation. In contrast, JAK2V617F(+) cells did not suffer from lipocalin-2-induced growth suppression resulting from attenuated p53 pathway activation, which conferred a relative growth advantage to JAK2V617F(+) clones. In summary, we demonstrated that JAK2V617F-harboring cells cause paracrine DNA damage accumulation through secretion of lipocalin-2, which gives proliferative advantage to themselves and an increased risk for leukemic transformation to both JAK2V617F(+) and JAK2V617F(-) clones.

Traumatic brain injury (TBI) produces axotomy, deafferentation and reactive synaptogenesis. Inflammation influences synaptic repair, and the novel brain cytokine osteopontin (OPN) has potential to support axon regeneration through exposure of its integrin receptor binding sites. This study explored whether OPN secretion and proteolysis by matrix metalloproteinases (MMPs) mediate the initial degenerative phase of synaptogenesis, targeting reactive neuroglia to affect successful repair. Adult rats received unilateral entorhinal cortex lesion (UEC) modeling adaptive synaptic plasticity. Over the first week postinjury, hippocampal OPN protein and mRNA were assayed and histology was performed. At 1-2d, OPN protein increased up to 51 fold, and was localized within activated, mobilized glia. OPN transcript also increased over 50 fold, predominantly within reactive microglia. OPN fragments known to be derived from MMP proteolysis were elevated at 1d, consistent with prior reports of UEC glial activation and enzyme production. Postinjury minocycline immunosuppression attenuated MMP-9 gelatinase activity, which was correlated with the reduction of neutrophil gelatinase-associated lipocalin (LCN2) expression, and reduced OPN fragment generation. The antibiotic also attenuated removal of synapsin-1 positive axons from the deafferented zone. OPN KO mice subjected to UEC had similar reduction of hippocampal MMP-9 activity, as well as lower synapsin-1 breakdown over the deafferented zone. MAP1B and N-cadherin, surrogates of cytoarchitecture and synaptic adhesion, were not affected. OPN KO mice with UEC exhibited time dependent cognitive deficits during the synaptogenic phase of recovery. This study demonstrates that OPN can mediate immune response during TBI synaptic repair, positively influencing synapse reorganization and functional recovery.

Microglia polarization to the classical M1 activation state is characterized by elevated pro-inflammatory cytokines; however, a full profile has not been generated in the early stages of a sterile inflammatory response recruiting only resident microglia. We characterized the initial M1 state in a hippocampal injury model dependent upon tumor necrosis factor (TNF) receptor signaling for dentate granule cell death. Twenty-one-day-old CD1 male mice were injected with trimethyltin (TMT 2.3 mg/kg, i.p.) and the hippocampus was examined at an early stage (24-h post-dosing) of neuronal death. Glia activation was assessed using a custom quantitative nuclease protection assay. We report elevated mRNA levels for glia response such as ionizing calcium-binding adapter molecule-1 and glial fibrillary acidic protein (Gfap); Fas, hypoxia inducible factor alpha, complement component 1qb, TNF-related genes (Tnf, Tnfaip3, Tnfrsfla); interleukin-1 alpha, Cd44, chemokine (C-C motif) ligand (Ccl)2, Cc14, integrin alpha M, lipocalin (Lcn2), and secreted phosphoprotein 1 (Spp1). These changes occurred in the absence of changes in matrix metalloproteinase 9 and 12, neural cell adhesion molecule, metabotropic glutamate receptor (Grm)3, and Ly6/neurotoxin 1 (Lynx1), as well as, a decrease in neurotrophin 3, glutamate receptor subunit epsilon (Grin)-2b, and neurotrophic tyrosine kinase receptor, type 3. The M2 anti-inflammatory marker, transforming growth factor beta-1 (Tgfb1) was elevated. mRNAs associated with early stage of injury-induced neurogenesis including fibroblast growth factor 21 and Mki67 were elevated. In the "non-injured" temporal cortex receiving projections from the hippocampus, Lynx1, Grm3, and Grin2b were decreased and Gfap increased. Formalin fixed-paraffin-embedded tissue did not generate a comparable profile.

BACKGROUND

Studies in mice have shown that PPARα is an important regulator of lipid metabolism in liver and key transcription factor involved in the adaptive response to fasting. However, much less is known about the role of PPARα in human liver.

METHODS

Here we set out to study the function of PPARα in human liver via analysis of whole genome gene regulation in human liver slices treated with the PPARα agonist Wy14643.

RESULTS

Quantitative PCR indicated that PPARα is well expressed in human liver and human liver slices and that the classical PPARα targets PLIN2, VLDLR, ANGPTL4, CPT1A and PDK4 are robustly induced by PPARα activation. Transcriptomics analysis indicated that 617 genes were upregulated and 665 genes were downregulated by PPARα activation (q value < 0.05). Many genes induced by PPARα activation were involved in lipid metabolism (ACSL5, AGPAT9, FADS1, SLC27A4), xenobiotic metabolism (POR, ABCC2, CYP3A5) or the unfolded protein response, whereas most of the downregulated genes were involved in immune-related pathways. Among the most highly repressed genes upon PPARα activation were several chemokines (e.g. CXCL9-11, CCL8, CX3CL1, CXCL6), interferon γ-induced genes (e.g. IFITM1, IFIT1, IFIT2, IFIT3) and numerous other immune-related genes (e.g. TLR3, NOS2, and LCN2). Comparative analysis of gene regulation by Wy14643 between human liver slices and primary human hepatocytes showed that down-regulation of gene expression by PPARα is much better captured by liver slices as compared to primary hepatocytes. In particular, PPARα activation markedly suppressed immunity/inflammation-related genes in human liver slices but not in primary hepatocytes. Finally, several putative new target genes of PPARα were identified that were commonly induced by PPARα activation in the two human liver model systems, including TSKU, RHOF, CA12 and VSIG10L.

CONCLUSIONS

Our paper demonstrates the suitability and superiority of human liver slices over primary hepatocytes for studying the functional role of PPARα in human liver. Our data underscore the major role of PPARα in regulation of hepatic lipid and xenobiotic metabolism in human liver and reveal a marked immuno-suppressive/anti-inflammatory effect of PPARα in human liver slices that may be therapeutically relevant for non-alcoholic fatty liver disease.