Neural Precursor-Derived Pleiotrophin Mediates Subventricular Zone Invasion by Glioma.

The lateral ventricle subventricular zone (SVZ) is a frequent and consequential site of pediatric and adult glioma spread, but the cellular and molecular mechanisms mediating this are poorly understood. We demonstrate that neural precursor cell (NPC):glioma cell communication underpins this propensity of glioma to colonize the SVZ through secretion of chemoattractant signals toward which glioma cells home. Biochemical, proteomic, and functional analyses of SVZ NPC-secreted factors revealed the neurite outgrowth-promoting factor pleiotrophin, along with required binding partners SPARC/SPARCL1 and HSP90B, as key mediators of this chemoattractant effect. Pleiotrophin expression is strongly enriched in the SVZ, and pleiotrophin knock down starkly reduced glioma invasion of the SVZ in the murine brain. Pleiotrophin, in complex with the binding partners, activated glioma Rho/ROCK signaling, and ROCK inhibition decreased invasion toward SVZ NPC-secreted factors. These findings demonstrate a pathogenic role for NPC:glioma interactions and potential therapeutic targets to limit glioma invasion. PAPERCLIP.

Pleiotrophin ameliorates white matter injury of neonatal rats by activating the mTOR/YY1/Id4 signaling pathway.

Brain white matter injury (WMI) is a serious disease of the central nervous system. Pleiotrophin (PTN) promotes the differentiation and myelination of oligodendrocytes (OLs) in vitro. However, the role of PTN in WMI remains unknown. Therefore, this study aimed to investigate the neuroprotective role and potential mechanisms of PTN function in neonatal rats with WMI. The PTN and mammalian target of rapamycin (mTOR) inhibitor everolimus was used to treat a WMI model in postnatal day 3 Sprague-Dawley rats, in which the right common carotid arteries of these rats were isolated, ligated, and exposed to a hypoxic environment (6% O2 + 94% N2 ) for 2 h. OL differentiation and myelination, as well as the spatial learning and memory abilities of the rats were evaluated to examine the effects of PTN. Two proteins of the mTOR signaling pathway, YingYang1 (YY1) and inhibitor of DNA binding 4 (Id4), were detected and were used to explore the potential mechanisms of PTN in rat WMI experiment and oxygen glucose deprivation (OGD) model. We found that the differentiation and myelination of OLs were impaired after WMI. PTN administration rescued this injury by activating mTOR/YY1 and inhibiting Id4. Everolimus administration inhibited mTOR/YY1 and activated Id4, which blocked the neuroprotective role of PTN in WMI. PTN plays a neuroprotective role in neonatal rats with WMI, which could be involved in the mTOR/YY1/Id4 signaling pathway.

The Combination of Quantitative Proteomics and Systems Genetics Analysis Reveals that PTN Is Associated with Sleep-Loss-Induced Cognitive Impairment.

Sleep loss is associated with cognitive dysfunction. However, the detailed mechanisms remain unclear. In this study, we established a para-chlorophenylalanine (PCPA)-induced insomniac mouse model with impaired cognitive function. Mass-spectrometry-based proteomics showed that the expression of 164 proteins was significantly altered in the hippocampus of the PCPA mice. To identify critical regulators among the potential markers, a transcriptome-wide association screening was performed in the BXD mice panel. Among the candidates, the expression of pleiotrophin (Ptn) was significantly associated with cognitive functions, indicating that Ptn-mediates sleep-loss-induced cognitive impairment. Gene co-expression analysis further revealed the potential mechanism by which Ptn mediates insomnia-induced cognitive impairment via the MAPK signaling pathway; that is, the decreased secretion of Ptn induced by insomnia leads to reduced binding to Ptprz1 on the postsynaptic membrane with the activation of the MAPK pathway via Fos and Nr4a1, further leading to the apoptosis of neurons. In addition, Ptn is genetically trans-regulated in the mouse hippocampus and implicated in neurodegenerative diseases in human genome-wide association studies. Our study provides a novel biomarker for insomnia-induced cognitive impairment and a new strategy for seeking neurological biomarkers by the integration of proteomics and systems genetics.

Intercellular crosstalk in adult dental pulp is mediated by heparin-binding growth factors Pleiotrophin and Midkine.

BACKGROUND: In-depth knowledge of the cellular and molecular composition of dental pulp (DP) and the crosstalk between DP cells that drive tissue homeostasis are not well understood. To address these questions, we performed a comparative analysis of publicly available single-cell transcriptomes of healthy adult human DP to 5 other reference tissues: peripheral blood mononuclear cells, bone marrow, adipose tissue, lung, and skin. RESULTS: Our analysis revealed that DP resident cells have a unique gene expression profile when compared to the reference tissues, and that DP fibroblasts are the main cell type contributing to this expression profile. Genes coding for pleiotrophin (PTN) and midkine (MDK), homologous heparin-binding growth-factors, possessed the highest differential expression levels in DP fibroblasts. In addition, we identified extensive crosstalk between DP fibroblasts and several other DP resident cells, including Schwann cells, mesenchymal stem cells and odontoblasts, mediated by PTN and MDK. CONCLUSIONS: DP fibroblasts emerge as unappreciated players in DP homeostasis, mainly through their crosstalk with glial cells. These findings suggest that fibroblast-derived growth factors possess major regulatory functions and thus have a potential role as dental therapeutic targets.

Genetic deletion or tyrosine phosphatase inhibition of PTPRZ1 activates c-Met to up-regulate angiogenesis and lung adenocarcinoma growth.

Protein tyrosine phosphatase receptor zeta 1 (PTPRZ1) is a transmembrane tyrosine phosphatase (TP) expressed in endothelial cells and required for stimulation of cell migration by vascular endothelial growth factor A165 (VEGFA165 ) and pleiotrophin (PTN). It is also over or under-expressed in various tumor types. In this study, we used genetically engineered Ptprz1-/- and Ptprz1+/+ mice to study mechanistic aspects of PTPRZ1 involvement in angiogenesis and investigate its role in lung adenocarcinoma (LUAD) growth. Ptprz1-/- lung microvascular endothelial cells (LMVEC) have increased angiogenic features compared with Ptprz1+/+ LMVEC, in line with the increased lung angiogenesis and the enhanced chemically induced LUAD growth in Ptprz1-/- compared with Ptprz1+/+ mice. In LUAD cells isolated from the lungs of urethane-treated mice, PTPRZ1 TP inhibition also enhanced proliferation and migration. Expression of beta 3 (ß3 ) integrin is decreased in Ptprz1-/- LMVEC, linked to enhanced VEGF receptor 2 (VEGFR2), c-Met tyrosine kinase (TK) and Akt kinase activities. However, only c-Met and Akt seem responsible for the enhanced endothelial cell activation in vitro and LUAD growth and angiogenesis in vivo in Ptprz1-/- mice. A selective PTPRZ1 TP inhibitor, VEGFA165 and PTN also activate c-Met and Akt in a PTPRZ1-dependent manner in endothelial cells, and their stimulatory effects are abolished by the c-Met TK inhibitor (TKI) crizotinib. Altogether, our data suggest that low PTPRZ1 expression is linked to worse LUAD prognosis and response to c-Met TKIs and uncover for the first time the role of PTPRZ1 in mediating c-Met activation by VEGFA and PTN.

Pleiotrophin attenuates the senescence of dental pulp stem cells.

OBJECTIVES: Pleiotrophin (PTN), a secreted extracellular matrix-associated protein, plays an important role in regulating the osteo/dentinogenic differentiation potential of dental pulp stem cells (DPSCs). Our previous study has demonstrated that PTN expression in young DPSCs was is 10-fold higher than that in aged DPSCs. However, the role of PTN on the in maintaining the stemness of senescent DPSCs remains unclear. The present study aimed to investigate the effect of PTN on senescent DPSCs in vitro. MATERIALS AND METHODS: Dental pulp stem cells were isolated from human third molars. PTN was knocked down using short hairpin RNAs to study the role of PTN on the senescence of DPSCs. DPSCs with aging performance were obtained by a replicative senescence cell model was obtained by the long-term culture of DPSCs to the 15th passage in vitro (P15). We then investigated the effect of PTN on senescent DPSCs (P15 DPSCs). Real-time RT-PCR, western blotting, alizarin red staining, quantitative calcium analysis, SA-ß-Gal staining, CFSE, and cell-counting kit-8 (CCK8) assays were used to study cellular senescence and function. RESULTS: The depletion of PTN increased the ratio of SA-ß-gal-positive cells, upregulated the expression of p16, and down-regulated the expression of TERT and p-p38. Furthermore, 50 pg/ml of PTN recombinant protein rescued these changes the altered ratio of SA-ß-gal-positive cells, decreased the expression of p16, enhanced TERT and p-p38 expression, as well as telomere activity, caused by PTN depletion and long-term culture. The15th passage cells displayed typical aging characteristic, including high ratio of SA-ß-gal-positive cells, increased aging-related gene expression, decreased proliferation rate, high level of Cyclin D expression, and impaired osteo/dentinogenic differentiation potential. However, 50 pg/ml of PTN recombinant protein could partially reverse these alteration rescue these changes. CONCLUSIONS: The present study demonstrated that PTN could protect DPSCs from senescence by improving the proliferation and osteo/dentinogenic differentiation ability, probably through the p38 MAPK pathway.

Pleiotrophin inhibited chondrogenic differentiation potential of dental pulp stem cells.

OBJECTIVE: Studies have shown that the levels of pleiotrophin (PTN) are greatly elevated in the synovial fluid and cartilage in osteoarthritis. Therefore, the purpose of this study was to investigate the effect and mechanism of PTN on the chondrogenic differentiation of DPSCs in inflammatory and normal microenvironments. MATERIALS AND METHODS: A lentiviral vector was used to deplete or overexpress PTN in DPSCs. The inflammatory microenvironment was simulated in vitro by the addition of IL-1ß to the culture medium. The chondrogenic differentiation potential was assessed using Alcian Blue staining and the main chondrogenic markers. A dual-luciferase reporter assay was used to explore the relationship between miR-137 and PTN. RESULTS: The results showed that 0.1 ng/mL IL-1ß treatment during chondrogenic induction greatly impaired the chondrogenic differentiation of DPSCs. Supplementation with PTN and PTN overexpression inhibited chondrogenic differentiation of DPSCs, while PTN depletion promoted chondrogenic differentiation. MiR-137 negatively regulated the expression of PTN by binding to the 3'UTR of its mRNA. Moreover, miR-137 promoted chondrogenic differentiation of DPSCs in normal and inflammatory microenvironments. CONCLUSION: Our results suggest that PTN may play an inhibitory role in the chondrogenic differentiation of DPSCs in normal and inflammatory microenvironments, which is regulated by miR-137.

Total synthesis of chondroitin sulfate E oligosaccharides and biological study.

A total synthesis approach of CS-E oligosaccharides was established and a series of derivatives were synthesized. These oligosaccharides were evaluated for a glycosaminoglycan (GAG)-binding protein interaction against cytokines, midkine, and pleiotrophin, by surface-plasmon resonance (SPR) assay. The binding epitopes of oligosaccharides to midkine were mapped using a saturation transfer difference (STD) NMR technique. The groups on the reducing end contributed to binding affinity, and should not be ignored in biological assays. These findings contribute to the structure and activity relationship research and a foundation of understanding that will underpin potential future optimization of this class of oligosaccharides as pharmaceutical agents.

The link between menin and pleiotrophin in the tumor biology of pancreatic neuroendocrine neoplasms.

MEN1, which encodes menin protein, is the most frequently mutated gene in pancreatic neuroendocrine neoplasms (pNEN). Pleiotrophin (PTN) has been reported as a downstream factor of menin that promotes metastasis in different tumor entities. In this study, the effect of menin and its link to PTN were assessed using features of pNEN cells and the outcome of patients with pNEN. The expression levels of menin and PTN in tissues from patients with pNEN were examined using qRT-PCR and western blot and compared with their metastasis status. Functional assays, including transwell migration/invasion and scratch wound-healing assays, were performed on specifically designed CRISPR/Cas9-mediated MEN1-knockout (MEN1-KO) pNEN cell lines (BON1MEN1-KO and QGP1MEN1-KO ) to study the metastasis of pNEN. Among 30 patients with menin-negative pNEN, 21 revealed a strong protein expression of PTN. This combination was associated with metastasis and shorter disease-free survival. Accordingly, in BON1MEN1-KO and QGP1MEN1-KO cells, PTN protein expression was positively associated with enhanced cell migration and invasion, which could be reversed using PTN silencing. PTN is a predicting factor of metastatic behavior of menin-deficient-pNEN. In vitro, menin is able to both promote and suppress the metastasis of pNEN by regulating PTN expression depending on the tumoral origin of pNEN cells.

Deletion of pleiotrophin impairs glucose tolerance and liver metabolism in pregnant mice: Moonlighting role of glycerol kinase.

Pleiotrophin is a pleiotropic cytokine that has been demonstrated to have a critical role in regulating energy metabolism, lipid turnover and plasticity of adipose tissue. Here, we hypothesize that this cytokine can be involved in regulatory processes of glucose and lipid homeostasis in the liver during pregnancy. Using 18-days pregnant Ptn-deficient mice, we evaluated the biochemical profile (circulating variables), tissue mRNA expression (qPCR) and protein levels of key enzymes and transcription factors involved in main metabolic pathways. Ptn deletion was associated with a reduction in body weight gain, hyperglycemia and glucose intolerance. Moreover, we observed an impairment in glucose synthesis and degradation during late pregnancy in Ptn-/- mice. Hepatic lipid content was significantly lower (73.6%) in Ptn-/- mice and was associated with a clear reduction in fatty acid, triacylglycerides and cholesterol synthesis. Ptn deletion was accompanying with a diabetogenic state in the mother and a decreased expression of key proteins involved in glucose and lipid uptake and metabolism. Moreover, Ptn-/- pregnant mice have a decreased expression of transcription factors, such as PPAR-α, regulating lipid uptake and glucose and lipid utilization. Furthermore, the augmented expression and nuclear translocation of glycerol kinase, and the decrease in NUR77 protein levels in the knock-out animals can further explain the alterations observed in hepatic glucose metabolism. Our results point out for the first time that pleiotrophin is an important player in maintaining hepatic metabolic homeostasis during late gestation, and further highlighted the moonlighting role of glycerol kinase in the regulation of maternal glucose homeostasis during pregnancy.

The Interaction between Chondroitin Sulfate and Dermatan Sulfate Tetrasaccharides and Pleiotrophin.

Pleiotrophin (PTN) is a neurotrophic factor that participates in the development of the embryonic central nervous system (CNS) and neural stem cell regulation by means of an interaction with sulfated glycosaminoglycans (GAGs). Chondroitin sulfate (CS) is the natural ligand in the CNS. We have previously studied the complexes between the tetrasaccharides used here and MK (Midkine) by ligand-observed NMR techniques. The present work describes the interactions between a tetrasaccharide library of synthetic models of CS-types and mimetics thereof with PTN using the same NMR transient techniques. We have concluded that: (1) global ligand structures do not change upon binding, (2) the introduction of lipophilic substituents in the structure of the ligand improves the strength of binding, (3) binding is weaker than for MK, (4) STD-NMR results are compatible with multiple binding modes, and (5) the replacement of GlcA for IdoA is not relevant for binding. Then we can conclude that the binding of CS derivatives to PTN and MK are similar and compatible with multiple binding modes of the same basic conformation.

Pleiotropin enhances the osteo/dentinogenic differentiation potential of dental pulp stem cells.

Purpose: Pleiotrophin (PTN) is a heparin-binding growth-associated molecule and expressed in ameloblasts and odontoblasts throughout tooth maturation. Our previous study has shown that PTN expressed more than 20-fold higher in dental tissue than dental stem cells. However, the role of PTN on proliferation and osteo/dentinogenesis of dental pulp stem cells (DPSCs) is unclear. The purpose of the present study was to investigate the role of PTN on the DPSCs' function.Methods: DPSCs were isolated from human third molars. Short hairpin RNAs (shRNAs) was used to knock down the PTN expression in DPSCs. Real-time RT-PCR, alizarin red staining, quantitative calcium analysis, in vivo transplantation and cell counting kit-8 (CCK8) assay were used to study the function of DPSCs. Possible mechanism was studied by RNA sequencing.Results: After PTN depletion, ALP activity and mineralization ability of DPSCs decreased. Expression of DMP-1 and BSP weakened. Proliferation of DPSCs at 48 h and 72 h was inhibited. Furthermore, 50 pg/mL PTN recombinant protein rescued the impaired osteo/dentinogenic differentiation potential and proliferation ability caused by PTN depletion. In addition, RNA sequencing showed 221 genes were downregulated and 233 genes upregulated in PTN depleted DPSCs. Several genes including BMP2 and IGFBP5 might be associated with PTN function on the DPSCs. P53 and the AMPK signaling pathways were involved. LncRNA analysis displayed 47 significantly upregulated lncRNA and 31 downregulated lncRNA comparing PTN depleted DPSCs with the control.Conclusion: Our research demonstrated that PTN has a positive role in maintaining DPSCs proliferation and osteo/dentinogenic differentiation potential.

Role of Receptor Protein Tyrosine Phosphatase ß/ζ in Neuron-Microglia Communication in a Cellular Model of Parkinson's Disease.

Pleiotrophin (PTN) is a neurotrophic factor that regulates glial responses in animal models of different types of central nervous system (CNS) injuries. PTN is upregulated in the brain in different pathologies characterized by exacerbated neuroinflammation, including Parkinson's disease. PTN is an endogenous inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) ß/ζ, which is abundantly expressed in the CNS. Using a specific inhibitor of RPTPß/ζ (MY10), we aimed to assess whether the PTN/RPTPß/ζ axis is involved in neuronal and glial injury induced by the toxin MPP+. Treatment with the RPTPß/ζ inhibitor MY10 alone decreased the viability of both SH-SY5Y neuroblastoma cells and BV2 microglial cultures, suggesting that normal RPTPß/ζ function is involved in neuronal and microglial viability. We observed that PTN partially decreased the cytotoxicity induced by MPP+ in SH-SY5Y cells underpinning the neuroprotective function of PTN. However, MY10 did not seem to modulate the SH-SY5Y cell loss induced by MPP+. Interestingly, we observed that media from SH-SY5Y cells treated with MPP+ and MY10 decreases microglial viability but may elicit a neuroprotective response of microglia by upregulating Ptn expression. The data suggest a neurotrophic role of microglia in response to neuronal injury through upregulation of Ptn levels.

Pleiotrophin Deficiency Induces Browning of Periovarian Adipose Tissue and Protects against High-Fat Diet-Induced Hepatic Steatosis.

(1) Background: Pleiotrophin preserves insulin sensitivity, regulates adipose tissue lipid turnover and plasticity, energy metabolism and thermogenesis. The aim of this study was to determine the role of pleiotrophin in hepatic lipid metabolism and in the metabolic crosstalk between the liver and brown and white adipose tissue (AT) in a high-fat diet-induced (HFD) obesity mice model. (2) Methods: We analyzed circulating variables, lipid metabolism (hepatic lipid content and mRNA expression), brown AT thermogenesis (UCP-1 expression) and periovarian AT browning (brown adipocyte markers mRNA and immunodetection) in Ptn-/- mice either fed with standard-chow diet or with HFD and in their corresponding Ptn+/+ counterparts. (3) Results: HFD-Ptn-/- mice are protected against the development of HFD-induced insulin resistance, had lower liver lipid content and lower expression of the key enzymes involved in triacylglycerides and fatty acid synthesis in liver. HFD-Ptn-/- mice showed higher UCP-1 expression in brown AT. Moreover, Ptn deletion increased the expression of specific markers of brown/beige adipocytes and was associated with the immunodetection of UCP-1 enriched multilocular adipocytes in periovarian AT. (4) Conclusions: Ptn deletion protects against the development of HFD-induced insulin resistance and liver steatosis, by increasing UCP-1 expression in brown AT and promoting periovarian AT browning.

A head-to-toe dimerization has physiological relevance for ligand-induced inactivation of protein tyrosine receptor type Z.

Protein-tyrosine phosphatase (PTPase) receptor type Z (PTPRZ) has two receptor isoforms, PTPRZ-A and -B, containing tandem intracellular PTP-D1 and -D2 domains, with only D1 being active. Pleiotrophin (PTN) binding to the extracellular PTPRZ region leads to inactivation of its PTPase activity, thereby facilitating oligodendrocyte precursor cell (OPC) differentiation and myelination in the central nervous system. However, the mechanisms responsible for PTN-induced PTPRZ inactivation remain unclear. We herein report that the crystal structure of the intracellular region of PTPRZ (PTPRZ-ICR) shows a "head-to-toe"-type dimer conformation, with D2 masking the catalytic site of D1. MS analyses revealed that PTPRZ-ICR proteins remain in monomer-dimer equilibrium in aqueous solution and that a substrate-derived inhibitory peptide or competitive inhibitor (SCB4380) specifically bind to the monomer form in a 1:1 ratio. A D2 deletion (ΔD2) or dimer interface mutation (DDKK) disrupted dimer formation, but SCB4380 binding was maintained. Similar to WT PTPRZ-B, monomer-biased PTPRZ-B-ΔD2 and PTPRZ-B-DDKK variants efficiently dephosphorylated p190RhoGAP at Tyr-1105 when co-expressed in BHK-21 cells. The catalytic activities of these variants were not suppressed by PTN treatment, but were inhibited by the cell-permeable PTPase inhibitor NAZ2329. Of note, the PTN treatment did not enhance OPC differentiation in primary cultured glial cells from ΔD2 or PTPase-inactive PTPRZ-B (CS) mutant knock-in mice. Our results thus indicate that PTN-induced PTPRZ inactivation results from dimer formation of the intracellular tandem PTP domains in a head-to-toe configuration, which is physiologically relevant to the control of OPC differentiation in vivo.

Inhibition of Receptor Protein Tyrosine Phosphatase ß/ζ Reduces Alcohol Intake in Rats.

BACKGROUND: Pleiotrophin (PTN) and midkine (MK) are cytokines that are up-regulated in the prefrontal cortex (PFC) after alcohol administration and have been shown to reduce alcohol intake and reward. Both cytokines are endogenous inhibitors of receptor protein tyrosine phosphatase (RPTP) ß/ζ (a.k.a. PTPRZ1). Recently, a new compound named MY10 was designed with the aim of mimicking the activity of PTN and MK. MY10 has already shown promising results regulating alcohol-related behaviors in mice. METHODS: We have now tested the effects of MY10 on alcohol operant self-administration and Drinking In the Dark-Multiple Scheduled Access (DID-MSA) paradigms in rats. Gene expression of relevant genes in the PTN/MK signaling pathway in the PFC was analyzed by real-time PCR. RESULTS: MY10, at the highest dose tested (100 mg/kg), reduced alcohol consumption in the alcohol operant self-administration paradigm (p = 0.040). In the DID-MSA paradigm, rats drank significantly less alcohol (p = 0.019) and showed a significant decrease in alcohol preference (p = 0.002). We observed that the longer the exposure to alcohol, the greater the suppressing effects of MY10 on alcohol consumption. It was demonstrated that the effects of MY10 were specific to alcohol since saccharin intake was not affected by MY10 (p = 0.804). MY10 prevented the alcohol-induced down-regulation of Ptprz1 (p = 0.004) and anaplastic lymphoma kinase (Alk; p = 0.013) expression. CONCLUSIONS: Our results support and provide further evidence regarding the efficacy of MY10 on alcohol-related behaviors and suggest the consideration of the blockade of RPTPß/ζ as a target for reducing excessive alcohol consumption.

Pleiotrophin deletion alters glucose homeostasis, energy metabolism and brown fat thermogenic function in mice.

AIMS/HYPOTHESIS: Pleiotrophin, a developmentally regulated and highly conserved cytokine, exerts different functions including regulation of cell growth and survival. Here, we hypothesise that this cytokine can play a regulatory role in glucose and lipid homeostasis. METHODS: To test this hypothesis, we performed a longitudinal study characterising the metabolic profile (circulating variables and tissue mRNA expression) of gene-targeted Ptn-deficient female mice and their corresponding wild-type counterparts at different ages from young adulthood (3 months) to older age (15 months). Metabolic cages were used to investigate the respiratory exchange ratio and energy expenditure, at both 24°C and 30°C. Undifferentiated immortalised mouse brown adipocytes (mBAs) were treated with 0.1 µg/ml pleiotrophin until day 6 of differentiation, and markers of mBA differentiation were analysed by quantitative real-time PCR (qPCR). RESULTS: Ptn deletion was associated with a reduction in total body fat (20.2% in Ptn+/+ vs 13.9% in Ptn-/- mice) and an enhanced lipolytic response to isoprenaline in isolated adipocytes from 15-month-old mice (189% in Ptn+/+ vs 273% in Ptn-/- mice). We found that Ptn-/- mice exhibited a significantly lower QUICKI value and an altered lipid profile; plasma triacylglycerols and NEFA did not increase with age, as happens in Ptn+/+ mice. Furthermore, the contribution of cold-induced thermogenesis to energy expenditure was greater in Ptn-/- than Ptn+/+ mice (42.6% and 33.6%, respectively). Body temperature and the activity and expression of deiodinase, T3 and mitochondrial uncoupling protein-1 in the brown adipose tissue of Ptn-/- mice were higher than in wild-type controls. Finally, supplementing brown pre-adipocytes with pleiotrophin decreased the expression of the brown adipocyte markers Cidea (20% reduction), Prdm16 (21% reduction), and Pgc1-α (also known as Ppargc1a, 11% reduction). CONCLUSIONS/INTERPRETATION: Our results reveal for the first time that pleiotrophin is a key player in preserving insulin sensitivity, driving the dynamics of adipose tissue lipid turnover and plasticity, and regulating energy metabolism and thermogenesis. These findings open therapeutic avenues for the treatment of metabolic disorders by targeting pleiotrophin in the crosstalk between white and brown adipose tissue.

Serum pleiotrophin as a diagnostic and prognostic marker for small cell lung cancer.

Pleiotrophin (PTN) is involved in tumour progression, angiogenesis and metastasis. The purpose of this study was to investigate the expression level of PTN in the serum of patients with small cell lung cancer (SCLC) and to explore the clinical significance of PTN. Serum samples from 128 patients with SCLC, 120 healthy volunteers (HV) and 60 patients with benign lung disease (BLD) were collected. The levels of serum PTN were determined with ELISA and its correlation with the clinical data was examined. The serum PTN levels in SCLC patients were significantly higher than that in BLD patients (P < 0.05) or HV (P < 0.05). With a cutoff value of 258.18 ng/mL, the sensitivity and specificity of PTN to SCLC patients and BLD patients, SCLC patients and HV were 79.2% and 91.7%, 86.7% and 95.8% respectively. An area under the curve for all stages of SCLC resulting from PTN, which was significantly better than the other tumour markers tested including progastrin-releasing peptide and neuron-specific enolase. High serum PTN levels appear to correlate with poor survival in patients with SCLC. These results suggest that PTN levels in the serum could be a new effective biomarker for the diagnosis and prognosis of SCLC.

The PTN-PTPRZ signal activates the AFAP1L2-dependent PI3K-AKT pathway for oligodendrocyte differentiation: Targeted inactivation of PTPRZ activity in mice.

Protein tyrosine phosphatase receptor type Z (PTPRZ) maintains oligodendrocyte precursor cells (OPCs) in an undifferentiated state. The inhibition of PTPase by its ligand pleiotrophin (PTN) promotes OPC differentiation; however, the substrate molecules of PTPRZ involved in the differentiation have not yet been elucidated in detail. We herein demonstrated that the tyrosine phosphorylation of AFAP1L2, paxillin, ERBB4, GIT1, p190RhoGAP, and NYAP2 was enhanced in OPC-like OL1 cells by a treatment with PTN. AFAP1L2, an adaptor protein involved in the PI3K-AKT pathway, exhibited the strongest response to PTN. PTPRZ dephosphorylated AFAP1L2 at tyrosine residues in vitro and in HEK293T cells. In OL1 cells, the knockdown of AFAP1L2 or application of a PI3K inhibitor suppressed cell differentiation as well as the PTN-induced phosphorylation of AKT and mTOR. We generated a knock-in mouse harboring a catalytically inactive Cys to Ser (CS) mutation in the PTPase domain. The phosphorylation levels of AFAP1L2, AKT, and mTOR were higher, and the expression of oligodendrocyte markers, including myelin basic protein (MBP) and myelin regulatory factor (MYRF), was stronger in CS knock-in brains than in wild-type brains on postnatal day 10; however, these differences mostly disappeared in the adult stage. Adult CS knock-in mice exhibited earlier remyelination after cuprizone-induced demyelination through the accelerated differentiation of OPCs. These phenotypes in CS knock-in mice were similar to those in Ptprz-deficient mice. Therefore, we conclude that the PTN-PTPRZ signal stimulates OPC differentiation partly by enhancing the tyrosine phosphorylation of AFAP1L2 in order to activate the PI3K-AKT pathway.

Hepatitis B virus promotes proliferation and metastasis in male Chinese hepatocellular carcinoma patients through the LEF-1/miR-371a-5p/SRCIN1/pleiotrophin/Slug pathway.

Hepatocellular carcinoma (HCC) is a male-dominant cancer. Several factors may contribute to the gender difference. Recent investigations have reported that miRNAs are involved in sex-linked signaling pathways and play a critical role in the molecular pathogenesis of hepatitis B virus (HBV)-related HCC. Therefore, we speculated that some of these miRNAs might contribute to the gender differences observed in HBV-related HCC. Our results showed that miR-371a-5p was significantly upregulated in tumor tissue and serum from HCC patients and that the expression level of miR-371a-5p was related to HBV infection, sexuality, TNM stage, adjacent organ invasion and microvascular invasion. Moreover, a high level of miR-371a-5p expression predicted poor overall survival of HCC patients, and in vitro and in vivo studies revealed that the overexpression of miR-371a-5p promoted proliferation and metastasis. Mechanistic investigations suggested that miR-371a-5p was upregulated by HBV and testosterone through LEF-1. SRCIN1 was a direct target of miR-371a-5p and reversed the effects of miR-371a-5p on HCC tumorigenesis. Our results also revealed that SRCIN1 negatively regulated the expression of PTN by inhibiting the activity of NF-κB. As a hepatocyte growth factor, PTN promoted EMT-induced metastasis in vitro and in vivo through the AKT/Slug pathway. These data strongly suggested that the upregulation of miR-371a-5p played an important role in HBV-related HCC. Through the LEF-1/miR-371a-5p/SRCIN1/PTN/Slug pathway, HBV and testosterone promote the proliferation and metastasis of hepatoma cells, especially in male patients with HBV-related HCC.