Pleiotrophin regulates microglia-mediated neuroinflammation

Recurrent endothelin-1 mediated vascular insult leads to cognitive impairment protected by trophic factor pleiotrophin

Vascular dementia (VaD) is a complex neurodegenerative condition, with cerebral small vessel dysfunctions as the central role in its pathogenesis. Given the lack of suitable animal models to study the disease pathogenesis, we developed a mouse model to closely emulate the clinical scenarios of recurrent transient ischemic attacks (TIAs) leading to VaD using vasoconstricting peptide Endothelin-1(ET-1). We observed that administration of ET-1 led to blood-brain barrier (BBB) disruption and detrimental changes in its components, such as endothelial cells and pericytes, along with neuronal loss and synaptic dysfunction, resulting in irreversible memory loss. Further, in our pursuit of understanding potential interventions, we co-administered pleiotrophin (PTN) alongside ET-1 injections. PTN exhibited remarkable efficacy in preserving vital components of the BBB, including endothelial cells and pericytes, thereby restoring BBB integrity, preventing neuronal loss, and enhancing memory function. Our findings give a valuable framework for understanding the detrimental effects of multiple TIAs on brain health and provide a useful animal model to explore VaD's underlying mechanisms further and pave the way for promising therapies.

Constitutive Pleiotrophin Deletion Results in a Phenotype with an Altered Pancreatic Morphology and Function in Old Mice

Pleiotrophin (PTN) is crucial for embryonic development and pancreas organogenesis as it regulates metainflammation, metabolic homeostasis, thermogenesis, and glucose tolerance. Pleiotrophin deletion is associated with a lipodystrophic phenotype in which adipose tissue plasticity is altered in late life. This study explored the impact of pleiotrophin deletion on pancreatic morphology and function in later life. We analyzed glucose tolerance and circulating parameters on female wild-type (Ptn+/+) and knock-out (Ptn-/-) mice. At 9 and 15 months, we conducted morphometric analyses of pancreatic islets and evaluated the levels of insulin, glucagon, somatostatin, glucose transporter 2 (GLUT2), vesicle-associated membrane protein 2 (VAMP2), and synaptosome-associated protein 25 (SNAP25) via immunofluorescence. The effect of PTN on glucose-stimulated insulin secretion (GSIS) was evaluated in INS1E cells and isolated islets. Ptn-/- mice showed hyperinsulinemia, impaired glucose tolerance, and increased homeostatic model assessment for insulin resistance (HOMA-IR) with age. While Ptn+/+ islets enlarge with age, in Ptn-/- mice, the median size decreased, and insulin content increased. Vesicle transport and exocytosis proteins were significantly increased in 9-month-old Ptn-/- islets. Islets from Ptn-/- mice showed impaired GSIS and decreased cell membrane localization of GLUT2 whereas, PTN increased GSIS in INS1E cells. Ptn deletion accelerated age-related changes in the endocrine pancreas, affecting islet number and size, and altering VAMP2 and SNAP25 levels and GLUT2 localization leading to impaired GSIS and insulin accumulation in islets.

Pleiotrophin modulates acute and long-term LPS-induced neuroinflammatory responses and hippocampal neurogenesis

The hippocampus is one of the most vulnerable regions affected in disorders characterized by overt neuroinflammation such as neurodegenerative diseases. Pleiotrophin (PTN) is a neurotrophic factor that modulates acute neuroinflammation in different contexts. PTN is found highly upregulated in the brain in different chronic disorders characterized by neuroinflammation, suggesting an important role in the modulation of sustained neuroinflammation. To test this hypothesis, we studied the acute and long-term effects of a single lipopolysaccharide (LPS; 5 mg/kg) administration in Ptn+/+ and Ptn-/- mice, and in mice with Ptn-overexpression (Ptn-Tg). Endogenous PTN levels proportionally modulate LPS-induced increase in TNF-α plasma levels one hour after treatment. In the dentate gyrus (DG) of the hippocampus, a lower percentage of DCX+ cells were detected in saline-treated Ptn-/- mice compared to Ptn+/+ mice, suggesting a crucial role of PTN in the maintenance of hippocampal neuronal progenitors. The data show that PTN overexpression tends to potentiate acute microglial responses in the DG 16 hours after LPS treatment. Remarkably, a significant increase in the number of neuronal progenitors together with astrogliosis was detected 10 months after a single injection of LPS treatment in wild type mice. However, these LPS-induced long-term effects were prevented in Ptn-/- and Ptn-Tg mice, suggesting that PTN modulates LPS-induced long-term neurogenesis changes and astrocytic response in the hippocampus. The data presented here suggest that endogenous PTN levels are crucial in the regulation of acute LPS-induced systemic and hippocampal microglial responses in young mice. Furthermore, our findings provide evidence of the key role of PTN in the regulation of long-term LPS effects on astrocytic response and neurogenesis in the hippocampus.

αMI-domain of integrin Mac-1 binds the cytokine pleiotrophin using multiple mechanisms

The integrin Mac-1 (αMβ2, CD11b/CD18, CR3) is an adhesion receptor expressed on macrophages and neutrophils. Mac-1 is also a promiscuous integrin that binds a diverse set of ligands through its αMI-domain. However, the binding mechanism of most ligands remains unclear. We have characterized the interaction of αMI-domain with the cytokine pleiotrophin (PTN), a protein known to bind αMI-domain and induce Mac-1-mediated cell adhesion and migration. Our data show that PTN's N-terminal domain binds a unique site near the N- and C-termini of the αMI-domain using a metal-independent mechanism. However, a stronger interaction is achieved when an acidic amino acid in a zwitterionic motif in PTN's C-terminal domain chelates the divalent cation in the metal ion-dependent adhesion site of active αMI-domain. These results indicate that αMI-domain can bind ligands using multiple mechanisms and that the active αMI-domain has a preference for motifs containing both positively and negatively charged amino acids.

Secretome analysis of oligodendrocytes and precursors reveals their roles as contributors to the extracellular matrix and potential regulators of inflammation

Oligodendrocytes form myelin that ensheaths axons and accelerates the speed of action potential propagation. Oligodendrocyte progenitor cells (OPCs) proliferate and replenish oligodendrocytes. While the myelin-forming role of oligodendrocytes and OPCs is well-established, potential additional roles of these cells are yet to be fully explored. Here, we analyzed the secreted proteome of oligodendrocytes and OPCs in vitro to determine whether these cell types are major sources of secreted proteins in the central nervous system (CNS). Interestingly, we found that both oligodendrocytes and OPCs secret various extracellular matrix proteins. Considering the critical role of neuroinflammation in neurological disorders, we evaluated the responses and potential contributions of oligodendrocytes and OPCs to this process. By characterizing the secreted proteomes of these cells after pro-inflammatory cytokine treatment, we discovered the secretion of immunoregulators such as C2 and B2m. This finding sheds new light on the hitherto underappreciated role of oligodendrocytes and OPCs in actively modulating neuroinflammation. Our study provides a comprehensive and unbiased proteomic dataset of proteins secreted by oligodendrocyte and OPC under both physiological and inflammatory conditions. It revealed the potential of these cells to secrete matrix and signaling molecules, highlighting their multifaceted function beyond their conventional myelin-forming roles.

Brain Cell-based Genetic Subtyping and Drug Repositioning for Alzheimer Disease

Alzheimer's Disease (AD) is characterized by its complex and heterogeneous etiology and gradual progression, leading to high drug failure rates in late-stage clinical trials. In order to better stratify individuals at risk for AD and discern potential therapeutic targets we employed a novel procedure utilizing cell-based co-regulated gene networks and polygenic risk scores (cbPRSs). After defining genetic subtypes using extremes of cbPRS distributions, we evaluated correlations of the genetic subtypes with previously defined AD subtypes defined on the basis of domain-specific cognitive functioning and neuroimaging biomarkers. Employing a PageRank algorithm, we identified priority gene targets for the genetic subtypes. Pathway analysis of priority genes demonstrated associations with neurodegeneration and suggested candidate drugs currently utilized in diabetes, hypertension, and epilepsy for repositioning in AD. Experimental validation utilizing human induced pluripotent stem cell (hiPSC)-derived astrocytes demonstrated the modifying effects of estradiol, levetiracetam, and pioglitazone on expression of APOE and complement C4 genes, suggesting potential repositioning for AD.

Polystyrene microplastics induce anxiety via HRAS derived PERK-NF-κB pathway

Exposure to environmentally hazardous substances is recognized as a significant risk factor for neurological associated disorders. Among these substances, polystyrene microplastics (PS-MPs), widely utilized in various consumer products, have been reported to exhibit neurotoxicity. However, the potential association of PS-MPs with abnormal anxiety behaviors, along with the underlying molecular mechanisms and key proteins involved, remains insufficiently explored. Here, we delineated the potential mechanisms of PS-MPs-induced anxiety through proteomics and molecular investigations. We characterized the PS-MPs, observed their accumulation in the brain, leading to anxiety-like behavior in mice, which is correlated with microglia activation and pro-inflammatory response. Consistent with these findings, our studies on BV2 microglia cells showed that PS-MPs activated NF-κB-mediated inflammation resulting in the upregulation of pro-inflammatory cytokines such as TNFα and IL-1β. Of particular significance, HRAS was identified as a key factor in the PS-MPs induced pro-inflammatory response through whole proteomics analysis, and knockdown of H-ras effectively inhibited PS-MPs induced PERK-NF-κB activation and associated pro-inflammatory response in microglia cells. Collectively, our findings highlight that PS-MPs induce anxiety of mice via the activation of the HRAS-derived PERK-NF-κB pathway in microlglia. Our results contribute valuable insights into the molecular mechanisms of PS-MPs-induced anxiety, and may offer implications for addressing neurotoxicity and prevention the adverse effects of environmentally hazardous substances, including microplastics.

αMI-domain of Integrin Mac-1 Binds the Cytokine Pleiotrophin Using Multiple Mechanisms

The integrin Mac-1 (αMβ2, CD11b/CD18, CR3) is an important adhesion receptor expressed on macrophages and neutrophils. Mac-1 is also the most promiscuous member of the integrin family that binds a diverse set of ligands through its αMI-domain. However, the binding mechanism of most ligands is not clear. We have determined the interaction of αMI-domain with the cytokine pleiotrophin (PTN), a cationic protein known to bind αMI-domain and induce Mac-1-mediated cell adhesion and migration. Our data show that PTN's N-terminal domain binds a unique site near the N- and C-termini of the αMI-domain using a metal-independent mechanism. However, stronger interaction is achieved when an acidic amino acid in a zwitterionic motif in PTN's C-terminal domain chelates the divalent cation in the metal ion-dependent adhesion site of the active αMI-domain. These results indicate that αMI-domain can bind ligands using multiple mechanisms, and suggest that active αMI-domain prefers acidic amino acids in zwitterionic motifs.

Knockdown and inhibition of hippocampal GPR17 attenuates lipopolysaccharide-induced cognitive impairment in mice

BACKGROUND

Previously we reported that inhibition of GPR17 prevents amyloid β 1-42 (Aβ1-42)-induced cognitive impairment in mice. However, the role of GPR17 on cognition is still largely unknown.

METHODS

Herein, we used a mouse model of cognitive impairment induced by lipopolysaccharide (LPS) to further investigate the role of GPR17 in cognition and its potential mechanism. The mice were pretreated with GPR17 shRNA lentivirus and cangrelor by microinjection into the dentate gyrus (DG) region of the hippocampus. After 21 days, LPS (0.25 mg/kg, i.p.) was administered for 7 days. Animal behavioral tests as well as pathological and biochemical assays were performed to evaluate the cognitive function in mice.

RESULTS

LPS exposure resulted in a significant increase in GPR17 expression at both protein and mRNA levels in the hippocampus. Gene reduction and pharmacological blockade of GPR17 improved cognitive impairment in both the Morris water maze and novel object recognition tests. Knockdown and inhibition of GPR17 inhibited Aβ production, decreased the expression of NF-κB p65, increased CREB phosphorylation and elevated BDNF expression, suppressed the accumulation of pro-inflammatory cytokines, inhibited Glial cells (microglia and astrocytes) activation, and increased Bcl-2, PSD-95, and SYN expression, reduced Bax expression as well as decreased caspase-3 activity and TUNEL-positive cells in the hippocampus of LPS-treated mice. Notably, knockdown and inhibition of GPR17 not only provided protective effects against cholinergic dysfunction but also facilitated the regulation of oxidative stress. In addition, cangrelor pretreatment can effectively inhibit the expression of inflammatory cytokines by suppressing NF-κB/CREB/BDNF signaling in BV-2 cells stimulated by LPS. However, activation of hippocampal GPR17 with MDL-29951 induced cognitive impairment in normal mice.

CONCLUSIONS

These observations indicate that GPR17 may possess a neuroprotective effect against LPS-induced cognition deficits, and neuroinflammation by modulation of NF-κB/CREB/BDNF signaling in mice, indicating that GPR17 may be a promising new target for the prevention and treatment of AD.

Single-cell RNA-sequencing analysis reveals enhanced non-canonical neurotrophic factor signaling in the subacute phase of traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of long-term disability in young adults and induces complex neuropathological processes. Cellular autonomous and intercellular changes during the subacute phase contribute substantially to the neuropathology of TBI. However, the underlying mechanisms remain elusive. In this study, we explored the dysregulated cellular signaling during the subacute phase of TBI.

METHODS

Single-cell RNA-sequencing data (GSE160763) of TBI were analyzed to explore the cell-cell communication in the subacute phase of TBI. Upregulated neurotrophic factor signaling was validated in a mouse model of TBI. Primary cell cultures and cell lines were used as in vitro models to examine the potential mechanisms affecting signaling.

RESULTS

Single-cell RNA-sequencing analysis revealed that microglia and astrocytes were the most affected cells during the subacute phase of TBI. Cell-cell communication analysis demonstrated that signaling mediated by the non-canonical neurotrophic factors midkine (MDK), pleiotrophin (PTN), and prosaposin (PSAP) in the microglia/astrocytes was upregulated in the subacute phase of TBI. Time-course profiling showed that MDK, PTN, and PSAP expression was primarily upregulated in the subacute phase of TBI, and astrocytes were the major source of MDK and PTN after TBI. In vitro studies revealed that the expression of MDK, PTN, and PSAP in astrocytes was enhanced by activated microglia. Moreover, MDK and PTN promoted the proliferation of neural progenitors derived from human-induced pluripotent stem cells (iPSCs) and neurite growth in iPSC-derived neurons, whereas PSAP exclusively stimulated neurite growth.

CONCLUSION

The non-canonical neurotrophic factors MDK, PTN, and PSAP were upregulated in the subacute phase of TBI and played a crucial role in neuroregeneration.

The functional impact of rare variation across the regulatory cascade

Each human genome has tens of thousands of rare genetic variants; however, identifying impactful rare variants remains a major challenge. We demonstrate how use of personal multi-omics can enable identification of impactful rare variants by using the Multi-Ethnic Study of Atherosclerosis, which included several hundred individuals, with whole-genome sequencing, transcriptomes, methylomes, and proteomes collected across two time points, 10 years apart. We evaluated each multi-omics phenotype's ability to separately and jointly inform functional rare variation. By combining expression and protein data, we observed rare stop variants 62 times and rare frameshift variants 216 times as frequently as controls, compared to 13-27 times as frequently for expression or protein effects alone. We extended a Bayesian hierarchical model, "Watershed," to prioritize specific rare variants underlying multi-omics signals across the regulatory cascade. With this approach, we identified rare variants that exhibited large effect sizes on multiple complex traits including height, schizophrenia, and Alzheimer's disease.

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.

Pleiotrophin and metabolic disorders: insights into its role in metabolism

Pleiotrophin (PTN) is a cytokine which has been for long studied at the level of the central nervous system, however few studies focus on its role in the peripheral organs. The main aim of this review is to summarize the state of the art of what is known up to date about pleiotrophin and its implications in the main metabolic organs. In summary, pleiotrophin promotes the proliferation of preadipocytes, pancreatic β cells, as well as cells during the mammary gland development. Moreover, this cytokine is important for the structural integrity of the liver and the neuromuscular junction in the skeletal muscle. From a metabolic point of view, pleiotrophin plays a key role in the maintenance of glucose and lipid as well as whole-body insulin homeostasis and favors oxidative metabolism in the skeletal muscle. All in all, this review proposes pleiotrophin as a druggable target to prevent from the development of insulin-resistance-related pathologies.

Bilirubin-Induced Transcriptomic Imprinting in Neonatal Hyperbilirubinemia

Recent findings indicated aberrant epigenetic control of the central nervous system (CNS) development in hyperbilirubinemic Gunn rats as an additional cause of cerebellar hypoplasia, the landmark of bilirubin neurotoxicity in rodents. Because the symptoms in severely hyperbilirubinemic human neonates suggest other regions as privileged targets of bilirubin neurotoxicity, we expanded the study of the potential impact of bilirubin on the control of postnatal brain development to regions correlating with human symptoms. Histology, transcriptomic, gene correlation, and behavioral studies were performed. The histology revealed widespread perturbation 9 days after birth, restoring in adulthood. At the genetic level, regional differences were noticed. Bilirubin affected synaptogenesis, repair, differentiation, energy, extracellular matrix development, etc., with transient alterations in the hippocampus (memory, learning, and cognition) and inferior colliculi (auditory functions) but permanent changes in the parietal cortex. Behavioral tests confirmed the presence of a permanent motor disability. The data correlate well both with the clinic description of neonatal bilirubin-induced neurotoxicity, as well as with the neurologic syndromes reported in adults that suffered neonatal hyperbilirubinemia. The results pave the way for better deciphering the neurotoxic features of bilirubin and evaluating deeply the efficacy of new therapeutic approaches against the acute and long-lasting sequels of bilirubin neurotoxicity.

Type-1 diabetes mellitus down-regulated local cerebral glial fibrillary acidic protein expression in experimental toxoplasmosis

Cerebral toxoplasmosis is an opportunistic infection, occurring mostly in immunosuppressed patients due to the reactivation of latent Toxoplasma cysts. The cerebral comorbidity in diabetic patients tends to intensify the burden of pathogenic infection within the brain. The aim of this work was to study the effect of cerebral toxoplasmosis in experimentally infected hyperglycemic mice, on histopathology and glial fibrillary acidic protein (GFAP) expression, compared to normoglycemic mice at different time intervals. Vasculopathy was exclusively observed in diabetic groups, with features of increased severity during Toxoplasma infection. Gliosis was observed in diabetic groups, while hyperactive astroglial activity was detected in normoglycemic groups, especially at 6 weeks of infection. GFAP expression showed significant up-regulation in normoglycemic mice at 6 weeks of infection (40.03 ± 1.41) afterwards, it decreased to 22.22 ± 3.14 at 12 weeks which was statistically insignificant to the normal level, possibly indicating the successful Toxoplasma stage transformation (to bradyzoite), thereby limiting the infection within the brain. In hyperglycemic infected groups, GFAP was significantly down-regulated, in both acute and chronic phases of infection, most likely indicating failure of stage transformation and infection limitation. This may expose those vulnerable groups to the risk of dissemination, resulting in life-threatening diffuse encephalitis. The current study emphasized the importance of rapid diagnosis of Toxoplasma infection in diabetic subjects, and highlighted the value of using GFAP as a neurological indicator of disease progression in those comorbid cases.

Adiponectin Attenuates Splenectomy-Induced Cognitive Deficits by Neuroinflammation and Oxidative Stress via TLR4/MyD88/NF-κb Signaling Pathway in Aged Rats

Perioperative neurocognitive disorder (PND) is a common adverse event after surgical trauma in elderly patients. The pathogenesis of PND is still unclear. Adiponectin (APN) is a plasma protein secreted by adipose tissue. We have reported that a decreased APN expression is associated with PND patients. APN may be a promising therapeutic agent for PND. However, the neuroprotective mechanism of APN in PND is still unclear. In this study, 18 month old male Sprague-Dawley rats were assigned to six groups: the sham, sham + APN (intragastric (i.g.) administration of 10 μg/kg/day for 20 days before splenectomy), PND (splenectomy), PND + APN, PND + TAK-242 (intraperitoneal (i.p.) administration of 3 mg/kg TAK-242), and PND + APN + lipopolysaccharide (LPS) (i.p. administration of 2 mg/kg LPS). We first found that APN gastric infusion significantly improved learning and cognitive function in the Morris water maze (MWM) test after surgical trauma. Further experiments indicated that APN could inhibit the Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear factor kappa B (NF-κb) p65 pathway to decrease the degree of oxidative damage (malondialdehyde (MDA) and superoxide dismutase (SOD)), microglia-mediated neuroinflammation (ionized calcium binding adapter molecule 1 (IBA1), caspase-1, tumor necrosis factor (TNF)-α, interleukin-1β (IL-1β), and interleukin-6 (IL-6)), and apoptosis (p53, Bcl2, Bax, and caspase 3) in hippocampus. By using LPS-specific agonist and TAK-242-specific inhibitor, the involvement of TLR4 engagement was confirmed. APN intragastric administration exerts a neuroprotective effect against cognitive deficits induced by peripheral trauma, and the possible mechanisms include the inhibition of neuroinflammation, oxidative stress, and apoptosis, mediated by the suppression of the TLR4/MyD88/NF-κb signaling pathway. We propose that oral APN may be a promising candidate for PND treatment.

Implication of the PTN/RPTPβ/ζ Signaling Pathway in Acute Ethanol Neuroinflammation in Both Sexes: A Comparative Study with LPS

Binge drinking during adolescence increases the risk of alcohol use disorder, possibly by involving alterations of neuroimmune responses. Pleiotrophin (PTN) is a cytokine that inhibits Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ. PTN and MY10, an RPTPβ/ζ pharmacological inhibitor, modulate ethanol behavioral and microglial responses in adult mice. Now, to study the contribution of endogenous PTN and the implication of its receptor RPTPβ/ζ in the neuroinflammatory response in the prefrontal cortex (PFC) after acute ethanol exposure in adolescence, we used MY10 (60 mg/kg) treatment and mice with transgenic PTN overexpression in the brain. Cytokine levels by X-MAP technology and gene expression of neuroinflammatory markers were determined 18 h after ethanol administration (6 g/kg) and compared with determinations performed 18 h after LPS administration (5 g/kg). Our data indicate that Ccl2, Il6, and Tnfa play important roles as mediators of PTN modulatory actions on the effects of ethanol in the adolescent PFC. The data suggest PTN and RPTPβ/ζ as targets to differentially modulate neuroinflammation in different contexts. In this regard, we identified for the first time important sex differences that affect the ability of the PTN/RPTPβ/ζ signaling pathway to modulate ethanol and LPS actions in the adolescent mouse brain.

Inhibition of RPTPβ/ζ reduces chronic ethanol intake in adolescent mice and modulates ethanol effects on hippocampal neurogenesis and glial responses in a sex-dependent manner

Pleiotrophin (PTN) is a cytokine that modulates ethanol drinking and reward and regulates glial responses in different contexts. PTN is an inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ. Inhibition of RPTPβ/ζ reduces binge-like drinking in adult male mice. Whether inhibition of RPTPβ/ζ is effective in reducing ethanol consumption during adolescence and in both sexes remained to be studied. In this work, male and female adolescent mice underwent an intermittent access to ethanol (IAE) 2-bottle choice protocol. Treatment with MY10 (60 mg/kg, i.g.), a small-molecule RPTPβ/ζ inhibitor, reduced chronic 3-week ethanol consumption only in male mice. We detected an ethanol-induced overall decrease in hippocampal GFAPir and Iba1ir, independently of the treatment received, suggesting that RPTPβ/ζ is not key in the regulation of IAE-induced glial responses. However, we found a significant negative correlation between the size of microglial cells and the number of hippocampal neuronal progenitors only in male mice after IAE. This correlation was disrupted by treatment with MY10 before each drinking session, which may be related to the ability of MY10 to regulate the intensity of the perineuronal nets (PNNs) in the hippocampus in a sex-dependent manner. The data show for the first time that inhibition of RPTPβ/ζ reduces chronic voluntary ethanol consumption in adolescent mice in a sex-dependent manner. In addition, we show evidence for sex-specific differences in the effects of IAE on glial responses and hippocampal neurogenesis, which may be related to different actions of the RPTPβ/ζ signalling pathway in the brains of male and female mice.

Hsp22 pretreatment protection against LPS-induced hippocampal injury by alleviating neuroinflammation and apoptosis by regulating the NLRP3/Caspase1/IL-1β signaling pathway in mice

Neuroinflammation is an important reason for the occurrence and development of cognitive impairment. The Lentiviral vector Hsp22 was constructed for intracerebroventricular injection pretreatment, LPS was used to induce the cognitive impairment model in mice, and the Morris water maze was used to examine the changes in cognitive behavior in mice. LPS was used to induce BV-2 microglial cells, and plasmid pretreatment was used to overexpress Hsp22. HE staining, Nissl staining, immunohistochemistry, immunofluorescence, ELISA and protein blotting were used to examine microglial activation, changes in inflammatory factors, changes in pathway proteins and apoptosis. The results showed that LPS induced microglial expression of NLRP3/Caspase-1/IL-1β signaling pathway protein Iba1, and the inflammatory protein and inflammatory factors IL-1β, IL-6 and TNF-α, the expression of Bax increased significantly, Bcl2 expression decreased, and the learning and memory abilities of mice decreased significantly. Preconditioning with the Hsp22-overexpressing lentivirus attenuated LPS-induced activation of hippocampal microglia, the expression of inflammatory factors and pathway proteins, and apoptosis, and improved cognitive impairment in mice. In addition, plasmid-mediated Hsp22 overexpression reversed LPS-induced inflammation. These findings suggest that Hsp22 overexpression is a promising method for the treatment of cognitive impairment.

KDM4A, involved in the inflammatory and oxidative stress caused by traumatic brain injury-hemorrhagic shock, partly through the regulation of the microglia M1 polarization

BACKGROUND

Microglial polarization and the subsequent neuroinflammatory response and oxidative stress are contributing factors for traumatic brain injury (TBI) plus hemorrhagic shock (HS) induced brain injury. In the present work, we have explored whether Lysine (K)-specific demethylase 4 A (KDM4A) modulates microglia M1 polarization in the TBI and HS mice.

RESULTS

Male C57BL/6J mice were used to investigate the microglia polarization in the TBI + HS model in vivo. Lipopolysaccharide (LPS)-induced BV2 cells were used to examine the mechanism of KDM4A in regulating microglia polarization in vitro. We found that TBI + HS resulted in neuronal loss and microglia M1 polarization in vivo, reflected by the increased level of Iba1, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, malondialdehyde (MDA) and the decreased level of reduced glutathione (GSH). Additionally, KDM4A was upregulated in response to TBI + HS and microglia were among the cell types showing the increased level of KDM4A. Similar to the results in vivo, KDM4A also highly expressed in LPS-induced BV2 cells. LPS-induced BV2 cells exhibited enhanced microglia M1 polarization, and enhanced level of pro-inflammatory cytokines, oxidative stress and reactive oxygen species (ROS), while this enhancement was abolished by the suppression of KDM4A.

CONCLUSION

Accordingly, our findings indicated that KDM4A was upregulated in response to TBI + HS and microglia were among the cell types showing the increased level of KDM4A. The important role of KDM4A in TBI + HS-induced inflammatory response and oxidative stress was at least partially realized through regulating microglia M1 polarization.

Relationship between Hypoxic and Immune Pathways Activation in the Progression of Neuroinflammation: Role of HIF-1α and Th17 Cells

Neuroinflammation is a common event in degenerative diseases of the central and peripheral nervous system, triggered by alterations in the immune system or inflammatory cascade. The pathophysiology of these disorders is multifactorial, whereby the therapy available has low clinical efficacy. This review propounds the relationship between the deregulation of T helper cells and hypoxia, mainly Th17 and HIF-1α molecular pathways, events that are involved in the occurrence of the neuroinflammation. The clinical expression of neuroinflammation is included in prevalent pathologies such as multiple sclerosis, Guillain-Barré syndrome, and Alzheimer's disease, among others. In addition, therapeutic targets are analyzed in relation to the pathways that induced neuroinflammation.

BDNF-induced phrenic motor facilitation shifts from PKCθ to ERK dependence with mild systemic inflammation

Moderate acute intermittent hypoxia (mAIH) elicits a form of phrenic motor plasticity known as phrenic long-term facilitation (pLTF), which requires spinal 5-HT2 receptor activation, ERK/MAP kinase signaling, and new brain-derived neurotrophic factor (BDNF) synthesis. New BDNF protein activates TrkB receptors that normally signal through PKCθ to elicit pLTF. Phrenic motor plasticity elicited by spinal drug administration (e.g., BDNF) is referred to by a more general term: phrenic motor facilitation (pMF). Although mild systemic inflammation elicited by a low lipopolysaccharide (LPS) dose (100 µg/kg; 24 h prior) undermines mAIH-induced pLTF upstream from BDNF protein synthesis, it augments pMF induced by spinal BDNF administration through unknown mechanisms. Here, we tested the hypothesis that mild inflammation shifts BDNF/TrkB signaling from PKCθ to alternative pathways that enhance pMF. We examined the role of three known signaling pathways associated with TrkB (MEK/ERK MAP kinase, PI3 kinase/Akt, and PKCθ) in BDNF-induced pMF in anesthetized, paralyzed, and ventilated Sprague Dawley rats 24 h post-LPS. Spinal PKCθ inhibitor (TIP) attenuated early BDNF-induced pMF (≤30 min), with minimal effect 60-90 min post-BDNF injection. In contrast, MEK inhibition (U0126) abolished BDNF-induced pMF at 60 and 90 min. PI3K/Akt inhibition (PI-828) had no effect on BDNF-induced pMF at any time. Thus, whereas BDNF-induced pMF is exclusively PKCθ-dependent in normal rats, MEK/ERK is recruited by neuroinflammation to sustain, and even augment downstream plasticity. Because AIH is being developed as a therapeutic modality to restore breathing in people living with multiple neurological disorders, it is important to understand how inflammation, a common comorbidity in many traumatic or degenerative central nervous system disorders, impacts phrenic motor plasticity.NEW & NOTEWORTHY We demonstrate that even mild systemic inflammation shifts signaling mechanisms giving rise to BDNF-induced phrenic motor plasticity. This finding has important experimental, biological, and translational implications, particularly since BDNF-dependent spinal plasticity is being translated to restore breathing and nonrespiratory movements in diverse clinical disorders, such as spinal cord injury (SCI) and amyotrophic lateral sclerosis (ALS).

Is an MRI-derived anatomical measure of dementia risk also a measure of brain aging?

Machine learning methods have been applied to estimate measures of brain aging from neuroimages. However, only rarely have these measures been examined in the context of biologic age. Here, we investigated associations of an MRI-based measure of dementia risk, the Alzheimer's disease pattern similarity (AD-PS) scores, with measures used to calculate biological age. Participants were those from visit 5 of the Atherosclerosis Risk in Communities Study with cognitive status adjudication, proteomic data, and AD-PS scores available. The AD-PS score estimation is based on previously reported machine learning methods. We evaluated associations of the AD-PS score with all-cause mortality. Sensitivity analyses using only cognitively normal (CN) individuals were performed treating CNS-related causes of death as competing risk. AD-PS score was examined in association with 32 proteins measured, using a Somalogic platform, previously reported to be associated with age. Finally, associations with a deficit accumulation index (DAI) based on a count of 38 health conditions were investigated. All analyses were adjusted for age, race, sex, education, smoking, hypertension, and diabetes. The AD-PS score was significantly associated with all-cause mortality and with levels of 9 of the 32 proteins. Growth/differentiation factor 15 (GDF-15) and pleiotrophin remained significant after accounting for multiple-testing and when restricting the analysis to CN participants. A linear regression model showed a significant association between DAI and AD-PS scores overall. While the AD-PS scores were created as a measure of dementia risk, our analyses suggest that they could also be capturing brain aging.

Pleiotrophin deficiency protects against high-fat diet-induced neuroinflammation: Implications for brain mitochondrial dysfunction and aberrant protein aggregation

Metabolic Syndrome (MetS) is a risk factor for the development of neurodegenerative diseases. Neuroinflammation associated with MetS may contribute significantly to neurodegeneration. Pleiotrophin (PTN) is a neurotrophic factor that modulates neuroinflammation and is a key player in regulating energy metabolism and thermogenesis, suggesting that PTN could be important in the connection between MetS and neuroinflammation. We have now used a high-fat diet (HFD)-induced obesity model in Ptn^-/- mice. HFD and Ptn deletion caused alterations in circulating hormones including GIP, leptin and resistin. HFD produced in Ptn^+/+ mice a neuroinflammatory state as observed in cerebral quantifications of proinflammatory markers, including Il1β, Tnfα and Ccl2. The upregulation of neuroinflammatory markers was prevented in Ptn^-/- mice. Changes induced by HFD in genes related to mitochondrial biogenesis and dynamics were less pronounced in the brain of Ptn^-/- mice and were accompanied by significant increases in the protein expression of mitochondrial oxidative phosphorylation (OXPHOS) complexes I and IV. HFD-induced changes in genes related to the elimination of protein aggregates were also less pronounced in the brain of Ptn^-/- mice. This study provides substantial evidence that Ptn deletion protects against HFD-induced neuroinflammation, mitochondrial dysfunction, and aberrant protein aggregation, prominent features in neurodegenerative diseases.

Receptor protein tyrosine phosphatase β/ζ regulates loss of neurogenesis in the mouse hippocampus following adolescent acute ethanol exposure

Adolescence is a critical period for brain maturation in which this organ is more vulnerable to the damaging effects of ethanol. Administration of ethanol in mice induces a rapid cerebral upregulation of pleiotrophin (PTN), a cytokine that regulates the neuroinflammatory processes induced by different insults and the behavioral effects of ethanol. PTN binds Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ and inhibits its phosphatase activity, suggesting that RPTPβ/ζ may be involved in the regulation of ethanol effects. To test this hypothesis, we have treated adolescent mice with the RPTPβ/ζ inhibitor MY10 (60 mg/kg) before an acute ethanol (6 g/kg) administration. Treatment with MY10 completely prevented the ethanol-induced neurogenic loss in the hippocampus of both male and female mice. In flow cytometry studies, ethanol tended to increase the number of NeuN+/activated Caspase-3+ cells particularly in female mice, but no significant effects were found. Ethanol increased Iba1+ cell area and the total marked area in the hippocampus of female mice, suggesting sex differences in ethanol-induced microgliosis. In addition, ethanol reduced the circulating levels of IL-6 and IL-10 in both sexes, although this reduction was only found significant in males and not affected by MY10 treatment. Interestingly, MY10 alone increased the total marked area and the number of Iba1+ cells only in the female hippocampus, but tended to reduce the circulating levels of TNF-α only in male mice. In summary, the data identify a novel modulatory role of RPTPβ/ζ on ethanol-induced loss of hippocampal neurogenesis, which seems unrelated to glial and inflammatory responses. The data also suggest sex differences in RPTPβ/ζ function that may be relevant to immune responses and ethanol-induced microglial responses.

Genetic polymorphism of pleiotrophin is associated with pain experience in Japanese adults: Case-control study

Genetic factors play a role in individual differences in pain experience. Here, we performed a genome-wide association study (GWAS) to identify novel loci regulating pain processing. We conducted a 2-stage GWAS and the candidate single-nucleotide polymorphisms (SNPs) association study on pain experience using an exploratory cohort of patients with cancer pain. The confirmatory cohort comprised of participants from the general population with and without habitual use of analgesic medication. In the exploratory cohort, we evaluated pain intensity using a numerical rating scale, recorded daily opioid dosages, and calculated pain reduction rate. In the confirmatory cohort, pain experience was defined as habitual nonsteroidal anti-inflammatory drug usage. Using linear regression models, we identified candidate SNP in the exploratory samples, and tested the association between phenotype and experienced pain in the confirmatory samples. We found 1 novel SNP (rs11764598)-located on the gene encoding for pleiotrophin on chromosome 7-that passed the genome-wide suggestive significance at 20% false discovery rate (FDR) correction in the exploratory samples of patients with cancer pain (P = 1.31 × 10-7, FDR = 0.101). We confirmed its significant association with daily analgesic usage in the confirmatory cohort (P = .028), although the minor allele affected pain experience in an opposite manner. We identified a novel genetic variant associated with pain experience. Further studies are required to validate the role of pleiotrophin in pain processing.

Metabolomics and biochemical alterations caused by pleiotrophin in the 6-hydroxydopamine mouse model of Parkinson's disease

Pleiotrophin (PTN) is a cytokine involved in nerve tissue repair processes, neuroinflammation and neuronal survival. PTN expression levels are upregulated in the nigrostriatal pathway of Parkinson's Disease (PD) patients. We aimed to characterize the dopaminergic injury and glial responses in the nigrostriatal pathway of mice with transgenic Ptn overexpression in the brain (Ptn-Tg) after intrastriatal injection of the catecholaminergic toxic 6-hydroxydopamine (6-OHDA) at a low dose (5 µg). Ten days after surgery, the injection of 6-OHDA induced a significant decrease of the number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra and of the striatal TH contents in Wild type (Wt) mice. In contrast, these effects of 6-OHDA were absent in Ptn-Tg mice. When the striatal Iba1 and GFAP immunoreactivity was studied, no statistical differences were found between vehicle-injected Wt and Ptn-Tg mice. Furthermore, 6-OHDA did not cause robust glial responses neither on Wt or Ptn-Tg mice 10 days after injections. In metabolomics studies, we detected interesting metabolites that significantly discriminate the more injured 6-OHDA-injected Wt striatum and the more protected 6-OHDA-injected Ptn-Tg striatum. Particularly, we detected groups of metabolites, mostly corresponding to phospholipids, whose trends were opposite in both groups. In summary, the data confirm lower 6-OHDA-induced decreases of TH contents in the nigrostriatal pathway of Ptn-Tg mice, suggesting a neuroprotective effect of brain PTN overexpression in this mouse model of PD. New lipid-related PD drug candidates emerge from this study and the data presented here support the increasingly recognized "lipid cascade" in PD.

Astrocyte-Derived Pleiotrophin Mitigates Late-Stage Autoimmune CNS Inflammation

Astrocytes are the most abundant glial cells in the central nervous system (CNS) with the capacity to sense and react to injury and inflammatory events. While it has been widely documented that astrocytes can exert tissue-degenerative functions, less is known about their protective and disease-limiting roles. Here, we report the upregulation of pleiotrophin (PTN) by mouse and human astrocytes in multiple sclerosis (MS) and its preclinical model experimental autoimmune encephalomyelitis (EAE). Using CRISPR-Cas9-based genetic perturbation systems, we demonstrate in vivo that astrocyte-derived PTN is critical for the recovery phase of EAE and limits chronic CNS inflammation. PTN reduces pro-inflammatory signaling in astrocytes and microglia and promotes neuronal survival following inflammatory challenge. Finally, we show that intranasal administration of PTN during the late phase of EAE successfully reduces disease severity, making it a potential therapeutic candidate for the treatment of progressive MS, for which existing therapies are limited.

Heparin-Binding Growth-Associated Molecule (Pleiotrophin) Affects Sensory Signaling and Selected Motor Functions in Mouse Model of Anatomically Incomplete Cervical Spinal Cord Injury

Heparin-binding growth-associated molecule (pleiotrophin) is a neurite outgrowth-promoting secretory protein that lines developing fiber tracts in juvenile CNS (central nervous system). Previously, we have shown that heparin-binding growth-associated molecule (HB-GAM) reverses the CSPG (chondroitin sulfate proteoglycan) inhibition on neurite outgrowth in the culture medium of primary CNS neurons and enhances axon growth through the injured spinal cord in mice demonstrated by two-photon imaging. In this study, we have started studies on the possible role of HB-GAM in enhancing functional recovery after incomplete spinal cord injury (SCI) using cervical lateral hemisection and hemicontusion mouse models. In vivo imaging of blood-oxygen-level-dependent (BOLD) signals associated with functional activity in the somatosensory cortex was used to assess the sensory functions during vibrotactile hind paw stimulation. The signal displays an exaggerated response in animals with lateral hemisection that recovers to the level seen in the sham-operated mice by injection of HB-GAM to the trauma site. The effect of HB-GAM treatment on sensory-motor functions was assessed by performance in demanding behavioral tests requiring integration of afferent and efferent signaling with central coordination. Administration of HB-GAM either by direct injection into the trauma site or by intrathecal injection improves the climbing abilities in animals with cervical hemisection and in addition enhances the grip strength in animals with lateral hemicontusion without affecting the spontaneous locomotor activity. Recovery of sensory signaling in the sensorimotor cortex by HB-GAM to the level of sham-operated mice may contribute to the improvement of skilled locomotion requiring integration of spatiotemporal signals in the somatosensory cortex.

Autophagy of Spinal Microglia Affects the Activation of Microglia through the PI3K/AKT/mTOR Signaling Pathway

Delayed paralysis occurs within some patients suffered from ischemic spinal cord injury (ISCI) due to the aorta occlusion during the repair surgery of thoracic and thoracoabdominal aortic aneurysms. Although mild hypothermia has been reported to improve ISCI and prolong the tolerance of rats to ISCI without inducing immediate paralysis, the mechanism remains unclear. Herein, the study revealed that the mild hypothermia treatment indeed partially improved the ISCI in rats caused by cross-clamping at the descending aorta. ISCI induced the excessive activation of microglia and moderate autophagy in the spinal cord tissues of rats, while mild hypothermia significantly induced autophagy and reversed the excessive activation of microglia in the spinal cord tissues of rats. In OGD-stimulated mouse microglia BV-2 cells, the excessive activation of microglia and moderate autophagy were also observed; in the rapamycin-treated OGD model in BV-2 cells, autophagy was significantly enhanced whereas the excessive activation of microglia was reversed. In both in vivo ISCI model in rats and in vitro OGD model in BV-2 cells, the PI3K/AKT/mTOR pathway showed to be inhibited, whereas the PI3K/AKT/mTOR pathway was further inhibited by mild hypothermia in ISCI rats or rapamycin treatment in OGD-stimulated BV-2 cells. In conclusion, enhanced autophagy might be the mechanism of inhibited microglia activation by hypothermia treatment in ISCI rats and by rapamycin treatment in OGD-stimulated BV-2 cells. Autophagy could be enhanced through inhibiting the PI3K/AKT/mTOR pathway.

LINCS Dataset-Based Repositioning of Dutasteride as an Anti-Neuroinflammation Agent

Neuroinflammation is often accompanied by central nervous system (CNS) injury seen in various CNS diseases, with no specific treatment. Drug repurposing is a strategy of finding new uses for approved or investigational drugs, and can be enabled by the Library of Integrated Network-based Cellular Signatures (LINCS), a large drug perturbation database. In this study, the signatures of Lipopolysaccharide (LPS) were compared with the signatures of compounds contained in the LINCS dataset. To the top 100 compounds obtained, the Quantitative Structure-Activity Relationship (QSAR)-based tool admetSAR was used to identify the top 10 candidate compounds with relatively high blood-brain barrier (BBB) penetration. Furthermore, the seventh-ranked compound, dutasteride, a 5-α-reductase inhibitor, was selected for in vitro and in vivo validation of its anti-neuroinflammation activity. The results showed that dutasteride significantly reduced the levels of IL-6 and TNF-α in the supernatants of LPS-stimulated BV2 cells, and decreased the levels of IL-6 in the hippocampus and plasma, and the number of activated microglia in the brain of LPS administration mice. Furthermore, dutasteride also attenuated the cognitive impairment caused by LPS stimulation in mice. Taken together, this study demonstrates that the LINCS dataset-based drug repurposing strategy is an effective approach, and the predicted candidate, dutasteride, has the potential to ameliorate LPS-induced neuroinflammation and cognitive impairment.

Estrogen Receptor α Agonist is Beneficial for Young Female Rats Against Chronic Unpredicted Mild Stress-Induced Depressive Behavior and Cognitive Deficits

BACKGROUND

Women are reported more likely to develop depression and dementia. However, the involved mechanism is poorly understood.

OBJECTIVE

Here, we clarified the role of estrogen receptor α (ERα) in depression and cognitive deficit in young female rats.

METHODS

After being exposed to 7-weeks' chronic unpredicted mild stress (CUMS), the depression resilient rats (Res rats) and depressed rats (Dep rats) were selected according to their records in sucrose preference test, forced swimming test, and open field test. Their cognition abilities were tested by Morris water maze. Proteomic assay, immunoprecipitation, western blotting, immunohistochemical, and Nissl staining were also used to understand the involved mechanism.

RESULTS

Compared with control rats and Res rats, Dep rats showed cognitive deficits and hippocampal impairments revealed by proteomic data, neuron losses, increased cleaved caspase-3, β-catenin phosphorylation, and glycogen synthase kinase3β (GSK3β) activation. As ERα, but not ERβ, was found declined in hippocampi of Dep rats, 4,4k,4a-(4-propyl-[1H]-pyrazole-1,3,5-triyl) trisphenol (PPT, an ERα agonist, 1 mg/kg/day), was used to treat Dep rats (Dep + PPT). Twenty days later, the depressive behaviors, cognition deficits, and hippocampal neuron loss were rescued in Dep + PPT rats. Furthermore, Res and Dep + PPT rats had higher levels of β-catenin combined with ERα and lower levels of β-catenin combined with GSK3β than Dep rats in hippocampi.

CONCLUSION

These results demonstrated hippocampal ERα is an important pro-resilient factor in CUMS-induced depressive behaviors and cognitive deficits. It was also given that the neuroprotection afforded by hippocampal ERα/Wnt interactions have significant implications for cognition and emotion in young females.

Ultrasound-Mediated Blood-Brain Barrier Opening Improves Whole Brain Gene Delivery in Mice

Gene therapy represents a powerful therapeutic tool to treat diseased tissues and provide a durable and effective correction. The central nervous system (CNS) is the target of many gene therapy protocols, but its high complexity makes it one of the most difficult organs to reach, in part due to the blood-brain barrier that protects it from external threats. Focused ultrasound (FUS) coupled with microbubbles appears as a technological breakthrough to deliver therapeutic agents into the CNS. While most studies focus on a specific targeted area of the brain, the present work proposes to permeabilize the entire brain for gene therapy in several pathologies. Our results show that, after i.v. administration and FUS sonication in a raster scan manner, a self-complementary AAV9-CMV-GFP vector strongly and safely infected the whole brain of mice. An increase in vector DNA (19.8 times), GFP mRNA (16.4 times), and GFP protein levels (17.4 times) was measured in whole brain extracts of FUS-treated GFP injected mice compared to non-FUS GFP injected mice. In addition to this increase in GFP levels, on average, a 7.3-fold increase of infected cells in the cortex, hippocampus, and striatum was observed. No side effects were detected in the brain of treated mice. The combining of FUS and AAV-based gene delivery represents a significant improvement in the treatment of neurological genetic diseases.

Aging biomarkers and the brain

Quantifying biological aging is critical for understanding why aging is the primary driver of morbidity and mortality and for assessing novel therapies to counter pathological aging. In the past decade, many biomarkers relevant to brain aging have been developed using various data types and modeling techniques. Aging involves numerous interconnected processes, and thus many complementary biomarkers are needed, each capturing a different slice of aging biology. Here we present a hierarchical framework highlighting how these biomarkers are related to each other and the underlying biological processes. We review those measures most studied in the context of brain aging: epigenetic clocks, proteomic clocks, and neuroimaging age predictors. Many studies have linked these biomarkers to cognition, mental health, brain structure, and pathology during aging. We also delve into the challenges and complexities in interpreting these biomarkers and suggest areas for further innovation. Ultimately, a robust mechanistic understanding of these biomarkers will be needed to effectively intervene in the aging process to prevent and treat age-related disease.

Stimulation of astrocytic sigma-1 receptor is sufficient to ameliorate inflammation- induced depression

Astrocytes play important roles in the development of depression. As a promising target for antidepressant development, sigma-1 receptor (Sig-1R) is reported to promote activation of astrocyte in chronic stress-induced depression in our previous study. However, astrocytes are hyper-activated in inflammation-induced depression, raising concerns of whether stimulation of astrocytic Sig-1R would exert antidepressant-like effect in inflammation-induced depression. Here we reported that specific stimulation of astrocytic Sig-1R using adeno-associated virus (AAV) significantly attenuated lipopolysaccharide (LPS)- induced depressive-like behavior in the forced swim test (FST), tail suspension test (TST), sucrose preference test, and improved the memory function in novel object recognition test. Besides, specific stimulation of astrocytic Sig-1R decreased the activation of astrocyte and microglia, as well as increased brain-derived neurotrophic factor (BDNF) in LPS-induced depression. In primary cultured astrocytes, overexpression of Sig-1R also reduced the expression of IL-1β, TNF-α, iNOS during inflammation-treated astrocyte. Taken together, the results suggest that specific stimulation of astrocytic Sig-1R ameliorates inflammation-induced depressive-like behavior, providing the evidence that astrocytic Sig-1R could represent a reliable therapeutic target for depression.

Pleiotrophin serum level is increased in Relapsing-Remitting Multiple Sclerosis and correlates with sex, BMI and treatment

BACKGROUND

Multiple Sclerosis (MS) is an immune-mediated demyelinating disease mainly affecting the Central Nervous System (CNS). 80% of MS patients present the Relapsing-Remitting form (RRMS). Pleiotrophin (PTN), a cytokine previously associated with other autoimmune and neurological diseases, could play a role in the pathophysiology of RRMS due to its neuro and immunomodulatory effect. However, PTN has never been explored in RRMS patients.

AIM OF THE STUDY

To determine PTN serum levels in patients with RRMS, treated with Glatiramer acetate (GA) or Interferon-beta (IFN-β), as well as in non-treated patients and healthy controls as a first attempt to explore PTN in RRMS.

METHODS

PTN serum levels were quantified by ELISA in 57 patients and 18 controls.

RESULTS

We demonstrated that PTN serum levels are significantly higher in RRMS patients. In IFN-β treated patients alone, PTN correlated positively with time of disease evolution and time of IFN-β use and correlated negatively with the MS severity score (MSSS). When comparing groups according to weight status, we observed that PTN is statistically increased in overweight female patients and that weight does not affect male patients. The Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve analysis was higher for males compared to females.

CONCLUSION

PTN serum level is higher in RRMS patients and that is associated with sex, BMI and IFN-β treatment. Therefore, we propose that PTN could be playing a role in MS. Further studies must be performed to identify the exact role of PTN in this pathology.

Role of Receptor Protein Tyrosine Phosphatase β/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) β/ζ, which is abundantly expressed in the CNS. Using a specific inhibitor of RPTPβ/ζ (MY10), we aimed to assess whether the PTN/RPTPβ/ζ axis is involved in neuronal and glial injury induced by the toxin MPP+. Treatment with the RPTPβ/ζ inhibitor MY10 alone decreased the viability of both SH-SY5Y neuroblastoma cells and BV2 microglial cultures, suggesting that normal RPTPβ/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.

Role of RPTPβ/ζ in neuroinflammation and microglia-neuron communication

Pleiotrophin (PTN) is a cytokine that is upregulated in different neuroinflammatory disorders. Using mice with transgenic PTN overexpression in the brain (Ptn-Tg), we have found a positive correlation between iNos and Tnfα mRNA and Ptn mRNA levels in the prefrontal cortex (PFC) of LPS-treated mice. PTN is an inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ, which is mainly expressed in the central nervous system. We aimed to test if RPTPβ/ζ is involved in the modulation of neuroinflammatory responses using specific inhibitors of RPTPβ/ζ (MY10 and MY33-3). Treatment with MY10 potentiated LPS-induced microglial responses in the mouse PFC. Surprisingly, MY10 caused a decrease in LPS-induced NF-κB p65 expression, suggesting that RPTPβ/ζ may be involved in a novel mechanism of potentiation of microglial activation independent of the NF-κB p65 pathway. MY33-3 and MY10 limited LPS-induced nitrites production and iNos increases in BV2 microglial cells. SH-SY5Y neuronal cells were treated with the conditioned media from MY10/LPS-treated BV2 cells. Conditioned media from non-stimulated and from LPS-stimulated BV2 cells increased the viability of SH-SY5Y cultures. RPTPβ/ζ inhibition in microglial cells disrupted this neurotrophic effect of microglia, suggesting that RPTPβ/ζ plays a role in the neurotrophic phenotype of microglia and in microglia-neuron communication.

Exploring the Mechanism on the Medullary Visceral Zone Inhibiting the Cholinergic Anti-inflammatory Pathway Induced by Sepsis

Inflammatory storm is an important pathological mechanism of multiple organ dysfunction, and it is associated with most deaths in septic patients, deserving to be studied. Recent findings have confirmed that the Medullary Visceral Zone (MVZ) regulates inflammation and immunity through the cholinergic anti-inflammatory pathway (CAP), but how sepsis affects the MVZ and leads to uncontrolled inflammation remain unclear. The current study reported that sepsis induced MVZ to inhibit CAP which underlies the inflammation storm. Our studies have shown that the rat models of sepsis prepared by cecal ligation and puncture had a higher inflammatory level, higher mortality, and higher Murine Sepsis Score. In septic rats, some indicators of heart rate variability (HRV) such as SDNN, HF band, RMSSD, SD1, and SD2 significantly reduced. In MVZ of septic rats, many cholinergic and catecholaminergic neurons showed apoptotic, with low expressions of tyrosine hydroxylase and choline acetyltransferase. The α7nAChR agonist GTS-21 can improve these pathologies, while the α7nAChR antagonist MLA is the opposite. Our study demonstrates for the first time that cholinergic and catecholaminergic neurons in MVZ went through significant apoptosis and inactiveness in sepsis, which contributes to the inhibition of CAP and acceleration of the inflammation storm in early sepsis. Intervening with CAP has a significant effect on the activity and apoptosis of MVZ neurons while altering systemic inflammation and immunity; in addition, for the first time, we confirmed that some indicators of HRV such as SDNN, HF band, RMSSD, SD1, and SD2 can reflect the activity of CAP, but the CAP interference had little effect on these indicators.

Age-related changes in cerebral congenital toxoplasmosis: Histopathological and immunohistochemical evaluation

Congenital toxoplasmosis is a widespread worldwide disease producing varying degrees of damage to the fetus including ocular and neurological impairment. However, the underlying mechanisms are not yet clear. Therefore, the current study aimed to investigate the progress of congenital cerebral toxoplasmosis in experimentally infected offspring animal model at different age groups till become adults. To fulfill this aim, the offspring of Me49 T. gondii infected pregnant mice were divided into groups; embryo, infant, young and adult phases. Blood and brain samples were collected for further hormonal and histopathological studies and immunohistochemical staining of glial fibrillary acidic protein (GFAP) and synaptophysin (SYN). Our results showed several encephalitic changes in the infected groups ranging from gliosis to reduced cortical cell number and fibrinoid degeneration of the brain. We showed increased expression of GFAP and SYN indicating activation of astrocytes and modification of the synaptic function, respectively. These changes started intrauterine following congenital infection and increased progressively afterward. Moreover, infected mice had elevated corticosterone levels. In conclusion, the current study provided new evidences for the cellular changes especially in the infected embryo and highlighted the role of GFAP and SYN that may be used as indicators for T. gondii-related neuropathy.

Molecular alterations in the extracellular matrix in the brains of newborns with congenital Zika syndrome

Zika virus (ZIKV) infection during pregnancy can cause a set of severe abnormalities in the fetus known as congenital Zika syndrome (CZS). Experiments with animal models and in vitro systems have substantially contributed to our understanding of the pathophysiology of ZIKV infection. Here, to investigate the molecular basis of CZS in humans, we used a systems biology approach to integrate transcriptomic, proteomic, and genomic data from the postmortem brains of neonates with CZS. We observed that collagens were greatly reduced in expression in CZS brains at both the RNA and protein levels and that neonates with CZS had several single-nucleotide polymorphisms in collagen-encoding genes that are associated with osteogenesis imperfecta and arthrogryposis. These findings were validated by immunohistochemistry and comparative analysis of collagen abundance in ZIKV-infected and uninfected samples. In addition, we showed a ZIKV-dependent increase in the expression of cell adhesion factors that are essential for neurite outgrowth and axon guidance, findings that are consistent with the neuronal migration defects observed in CZS. Together, these findings provide insights into the underlying molecular alterations in the ZIKV-infected brain and reveal host genes associated with CZS susceptibility.

Synthetic PreImplantation Factor (sPIF) reduces inflammation and prevents preterm birth

Preterm birth (PTB) is the leading cause of neonatal morbidity and mortality and spontaneous PTB is a major contributor. The preceding inflammation/infection contributes not only to spontaneous PTB but is associated with neonatal morbidities including impaired brain development. Therefore, control of exaggerated immune response during pregnancy is an attractive strategy. A potential candidate is synthetic PreImplantation Factor (sPIF) as sPIF prevents inflammatory induced fetal loss and has neuroprotective properties. Here, we tested maternal sPIF prophylaxis in pregnant mice subjected to a lipopolysaccharides (LPS) insult, which results in PTB. Additionally, we evaluated sPIF effects in placental and microglial cell lines. Maternal sPIF application reduced the LPS induced PTB rate significantly. Consequently, sPIF reduced microglial activation (Iba-1 positive cells) and preserved neuronal migration (Cux-2 positive cells) in fetal brains. In fetal brain lysates sPIF decreased IL-6 and INFγ concentrations. In-vitro, sPIF reduced Iba1 and TNFα expression in microglial cells and reduced the expression of pro-apoptotic (Bad and Bax) and inflammatory (IL-6 and NLRP4) genes in placental cell lines. Together, maternal sPIF prophylaxis prevents PTB in part by controlling exaggerated immune response. Given the sPIF`FDA Fast Track approval in non-pregnant subjects, we envision sPIF therapy in pregnancy.

Pleiotrophin: Activity and mechanism

Pleiotrophin (PTN) is a potent mitogenic cytokine with a high affinity for the polysaccharide glycosaminoglycan (GAG). Although it is most strongly associated with neural development during embryogenesis and the neonatal period, its expression has also been linked to a plethora of other physiological events including cancer metastasis, angiogenesis, bone development, and inflammation. A considerable amount of research has been carried out to understand the mechanisms by which PTN regulates these events. In particular, PTN has now been shown to bind a diverse collection of receptors including many GAG-containing proteoglycans. These interactions lead to the activation of many intracellular kinases and, ultimately, activation and transformation of cells. Structural studies of PTN in complex with both GAG and domains from its non-proteoglycan receptors reveal a binding mechanism that relies on electrostatic interactions and points to PTN-induced receptor oligomerization as one of the possible ways PTN uses to control cellular functions.

Immune response mediates the cardiac damage after subarachnoid hemorrhage

Cardiac dysfunction is a common adverse effect of subarachnoid hemorrhage (SAH). Autopsy of SAH patients shows immunocyte infiltration into the heart. In this study, a SAH model of endovascular perforation was performed in adult male mice in order to test whether SAH causes cardiac dysfunction in non-primary cardiac disease young adult male mice and whether immune response mediates SAH induced cardiac and neurological deficit. Splenectomy was performed on a subpopulation of mice one week prior to induction of the SAH. Neurological functional tests, transthoracic Doppler echocardiography, immunofluorescent staining, and flow cytometry were performed to investigate neurological and cardiac function and immune/inflammatory effects of SAH in mice with or without splenectomy. We found that SAH significantly induces ventricular fibrillation and cardiac dysfunction identified by significantly reduced left ventricular ejection fraction, left ventricular fractional shortening, decreased heart rate, as well as increased macrophage and neutrophil infiltration into heart and inflammatory factor expression in the heart compared to sham control mice. SAH also induces neurological deficit, increases astrocyte and microglial activity, and inflammatory cell infiltration into brain as well as up-regulates inflammatory factor expression in the brain tissue. Splenectomy not only significantly improves neurological function, but also reduces cardiac dysfunction compared to SAH alone mice. Splenectomy in SAH mice significantly reduces inflammatory cell infiltration, and decreases NADPH oxidase-2 and macrophage chemokine protein-1 expression in heart and brain when compared to non-splenectomy SAH mice. Our data suggest that, SAH induces acute cardiac dysfunction in non-primary cardiac disease mice. Secondary immune response may play an important role in mediating brain-heart damage after SAH.

Neuroinflammation in the NTS is associated with changes in cardiovascular reflexes during systemic inflammation

BACKGROUND

Lipopolysaccharide (LPS)-induced systemic inflammation (SI) is associated with neuroinflammation in the brain, hypotension, tachycardia, and multiple organs dysfunctions. Considering that during SI these important cardiovascular and inflammatory changes take place, we measured the sensitivity of the cardiovascular reflexes baroreflex, chemoreflex, and Bezold-Jarisch that are key regulators of hemodynamic function. We also evaluated neuroinflammation in the nucleus tractus solitarius (NTS), the first synaptic station that integrates peripheral signals arising from the cardiovascular and inflammatory status.

METHODS

We combined cardiovascular recordings, immunofluorescence, and assays of inflammatory markers in male Wistar rats that receive iv administration of LPS (1.5 or 2.5 mg kg-1) to investigate putative interactions of the neuroinflammation in the NTS and in the anteroventral preoptic region of the hypothalamus (AVPO) with the short-term regulation of blood pressure and heart rate.

RESULTS

LPS induced hypotension, tachycardia, autonomic disbalance, hypothermia followed by fever, and reduction in spontaneous baroreflex gain. On the other hand, during SI, the bradycardic component of Bezold-Jarisch and chemoreflex activation was increased. These changes were associated with a higher number of activated microglia and interleukin (IL)-1β levels in the NTS.

CONCLUSIONS

The present data are consistent with the notion that during SI and neuroinflammation in the NTS, rats have a reduced baroreflex gain, combined with an enhancement of the bradycardic component of Bezold-Jarisch and chemoreflex despite the important cardiovascular impairments (hypotension and tachycardia). These changes in the cardiac component of Bezold-Jarisch and chemoreflex may be beneficial during SI and indicate that the improvement of theses reflexes responsiveness though specific nerve stimulations may be useful in the management of sepsis.

Baicalin ameliorates neuroinflammation-induced depressive-like behavior through inhibition of toll-like receptor 4 expression via the PI3K/AKT/FoxO1 pathway

Background

Baicalin, which is isolated from Radix Scutellariae, possesses strong biological activities including an anti-inflammation property. Recent studies have shown that the anti-inflammatory effect of baicalin is linked to toll-like receptor 4 (TLR4), which participates in pathological changes of central nervous system diseases such as depression. In this study, we explored whether baicalin could produce antidepressant effects via regulation of TLR4 signaling in mice and attempted to elucidate the underlying mechanisms.

Methods

A chronic unpredictable mild stress (CUMS) mice model was performed to explore whether baicalin could produce antidepressant effects via the inhibition of neuroinflammation. To clarify the role of TLR4 in the anti-neuroinflammatory efficacy of baicalin, a lipopolysaccharide (LPS) was employed in mice to specially activate TLR4 and the behavioral changes were determined. Furthermore, we used LY294002 to examine the molecular mechanisms of baicalin in regulating the expression of TLR4 in vivo and in vitro using western blot, ELISA kits, and immunostaining. In the in vitro tests, the BV2 microglia cell lines and primary microglia cultures were pretreated with baicalin and LY292002 for 1 h and then stimulated 24 h with LPS. The primary microglial cells were transfected with the forkhead transcription factor forkhead box protein O 1 (FoxO1)-specific siRNA for 5 h and then co-stimulated with baicalin and LPS to investigate whether FoxO1 participated in the effect of baicalin on TLR4 expression.

Results

The administration of baicalin (especially 60 mg/kg) dramatically ameliorated CUMS-induced depressive-like symptoms; substantially decreased the levels of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) in the hippocampus; and significantly decreased the expression of TLR4. The activation of TLR4 by the LPS triggered neuroinflammation and evoked depressive-like behaviors in mice, which were also alleviated by the treatment with baicalin (60 mg/kg). Furthermore, the application of baicalin significantly increased the phosphorylation of phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), and FoxO1. The application of baicalin also promoted FoxO1 nuclear exclusion and contributed to the inhibition of the FoxO1 transactivation potential, which led to the downregulation of the expression of TLR4 in CUMS mice or LPS-treated BV2 cells and primary microglia cells. However, prophylactic treatment of LY294002 abolished the above effects of baicalin. In addition, we found that FoxO1 played a vital role in baicalin by regulating the TLR4 and TLR4-mediating neuroinflammation triggered by the LPS via knocking down the expression of FoxO1 in the primary microglia.

Conclusion

Collectively, these results demonstrate that baicalin ameliorated neuroinflammation-induced depressive-like behaviors through the inhibition of TLR4 expression via the PI3K/AKT/FoxO1 pathway.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1474-8) contains supplementary material, which is available to authorized users.

Connecting Metainflammation and Neuroinflammation Through the PTN-MK-RPTPβ/ζ Axis: Relevance in Therapeutic Development

Inflammation is a common factor of pathologies such as obesity, type 2 diabetes or neurodegenerative diseases. Chronic inflammation is considered part of the pathogenic mechanisms of different disorders associated with aging. Interestingly, peripheral inflammation and the associated metabolic alterations not only facilitate insulin resistance and diabetes but also neurodegenerative disorders. Therefore, the identification of novel pathways, common to the development of these diseases, which modulate the immune response and signaling is key. It will provide highly relevant information to advance our knowledge of the multifactorial process of aging, and to establish new biomarkers and/or therapeutic targets to counteract the underlying chronic inflammatory processes. One novel pathway that regulates peripheral and central immune responses is triggered by the cytokines pleiotrophin (PTN) and midkine (MK), which bind its receptor, Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ, and inactivate its phosphatase activity. In this review, we compile a growing body of knowledge suggesting that PTN and MK modulate the immune response and/or inflammation in different pathologies characterized by peripheral inflammation associated with insulin resistance, such as aging, and in central disorders characterized by overt neuroinflammation, such as neurodegenerative diseases and endotoxemia. Evidence strongly suggests that regulation of the PTN and MK signaling pathways may provide new therapeutic opportunities particularly in those neurological disorders characterized by increased PTN and/or MK cerebral levels and neuroinflammation. Importantly, we discuss existing therapeutics, and others being developed, that modulate these signaling pathways, and their potential use in pathologies characterized by overt neuroinflammation.

Dcf1 Deficiency Attenuates the Role of Activated Microglia During Neuroinflammation

Microglia serve as the principal immune cells and play crucial roles in the central nervous system, responding to neuroinflammation via migration and the execution of phagocytosis. Dendritic cell-derived factor 1 (Dcf1) is known to play an important role in neural stem cell differentiation, glioma apoptosis, dendritic spine formation, and Alzheimer’s disease (AD), nevertheless, the involvement of the Dcf1 gene in the brain immune response has not yet been reported. In the present paper, the RNA-sequencing and function enrichment analysis suggested that the majority of the down-regulated genes in Dcf1^-/- (Dcf1-KO) mice are immune-related. In vivo experiments showed that Dcf1 deletion produced profound effects on microglial function, increased the expression of microglial activation markers, such as ionized calcium binding adaptor molecule 1 (Iba1), Cluster of Differentiation 68 (CD68) and translocator protein (TSPO), as well as certain proinflammatory cytokines (Cxcl1, Ccl7, and IL17D), but decreased the migratory and phagocytic abilities of microglial cells, and reduced the expression levels of some other proinflammatory cytokines (Cox-2, IL-1β, IL-6, TNF-α, and Csf1) in the mouse hippocampus. Furthermore, in vitro experiments revealed that in the absence of lipopolysaccharide (LPS), the majority of microglia were ramified and existed in a resting state, with only approximately 10% of cells exhibiting an amoeboid-like morphology, indicative of an activated state. LPS treatment dramatically increased the ratio of activated to resting cells, and Dcf1 downregulation further increased this ratio. These data indicated that Dcf1 deletion mediates neuroinflammation and induces dysfunction of activated microglia, preventing migration and the execution of phagocytosis. These findings support further investigation into the biological mechanisms underlying microglia-related neuroinflammatory diseases, and the role of Dcf1 in the immune response.

IL-33/ST2 plays a critical role in endothelial cell activation and microglia-mediated neuroinflammation modulation

Background

Interleukin-33 (IL-33) is increasingly being recognized as a key immunomodulatory cytokine in many neurological diseases.

Methods

In the present study, wild-type (WT) and IL-33^−/− mice received intracerebroventricular (i.c.v.) injection of lipopolysaccharide (LPS) to induce neuroinflammation. Intravital microscopy was employed to examine leukocyte–endothelial interactions in the brain vasculature. The degree of neutrophil infiltration was determined by myeloperoxidase (MPO) staining. Real-time PCR and western blotting were used to detect endothelial activation. Enzyme-linked immunosorbent assay and quantitative PCR were conducted to detect pro-inflammatory cytokine levels in the brain.

Results

In IL-33^−/− mice, neutrophil infiltration in the brain cortex and leukocyte–endothelial cell interactions in the cerebral microvessels were significantly decreased as compared to WT mice after LPS injection. In addition, IL-33^−/− mice showed reduced activation of microglia and cerebral endothelial cells. In vitro results indicated that IL-33 directly activated cerebral endothelial cells and promoted pro-inflammatory cytokine production in LPS-stimulated microglia.

Conclusions

Our study indicated that IL-33/ST2 signaling plays an important role in the activation of microglia and cerebral endothelial cells and, therefore, is essential in leukocyte recruitment in brain inflammation.

Graphical abstract

The role of IL-33/ST2 in LPS induced neuroinflammation

ALK is required for NLRP3 inflammasome activation in macrophages

The NLRP3 inflammasome is a key mediator of host immune responses through the induction of pyroptosis and the release of cytokines. Although the pathologic role of inflammasome in infection and sterile inflammation is well known, the mechanism and regulation of NLRP3 inflammasome activation remains obscure. Here, we report that anaplastic lymphoma kinase (ALK) is a novel regulator of NLRP3 inflammasome activation in macrophages. Pharmacologic or genetic inhibition of ALK through targeted drugs (ceritinib and lorlatinib) or RNAi blocked extracellular ATP-induced NLRP3 inflammasome activation in macrophages. Mechanically, ALK-mediated NF-κB activation was required for the priming step of NLRP3 upregulation, whereas ALK-mediated lipid peroxidation contributed to the sensing step of NLRP3-NEK7 complex formation. These studies indicate that inhibition of ALK could be utilized to treat NLRP3-related inflammatory diseases.