TGF-beta 1 protects hippocampal neurons against degeneration caused by transient global ischemia. Dose-response relationship and potential neuroprotective mechanisms

Deciphering the genetic basis of behavioral traits in dogs: Observed-trait GWAS and latent-trait GWAS analysis reveal key genes and variants

Dogs exhibit remarkable phenotypic diversity, particularly in behavioral traits, making them an excellent model for studying the genetic basis of complex behaviors. Behavioral traits such as aggression and fear are highly heritable among different dog breeds, but their genetic basis is largely unknown. We used the genome-wide association study (GWAS) to identify candidate genes associated with nine behavioral traits including; stranger-directed aggression (SDA), owner-directed aggression (ODA), dog-directed aggression (DDA), stranger-directed fear (SDF), nonsocial fear (NF), dog-directed fear (DDF), touch sensitivity (TS), separation-related behavior (SRB) and attachment attention-seeking (AAS). The observed behavioral traits were collected from 38,714 to 40,460 individuals across 108 modern dog breeds. We performed a GWAS based on a latent trait extracted using the confirmatory factor analysis (CFA) method with nine observable behavioral traits and compared the results with those from the GWAS of the observed traits. Using both observed-trait and latent-trait GWAS, we identified 41 significant SNPs that were common between both GWAS methods, of which 26 were pleiotropic, as well as 10 SNPs unique to the latent-trait GWAS, and 5 SNPs unique to the observed-trait GWAS discovered. These SNPs were associated with 21 genes in latent-trait GWAS and 22 genes in the observed-trait GWAS, with 19 genes shared by both. According to previous studies, some of the genes from this study have been reported to be related to behavioral and neurological functions in dogs. In the human population, these identified genes play a role in either the formation of the nervous system or are linked to various mental health conditions. Taken together, our findings suggest that latent-trait GWAS for behavioral traits in dogs identifies significant latent genes that are neurologically prioritized.

Transcriptome Sequencing Reveals Tgf-β-Mediated Noncoding RNA Regulatory Mechanisms Involved in DNA Damage in the 661W Photoreceptor Cell Line

Transforming growth factor β (Tgf-β), a pleiotropic cytokine, can enhance DNA repair in various cells, including cancer cells and neurons. The noncoding regulatory system plays an important role in Tgf-β-mediated biological activities, whereas few studies have explored its role in DNA damage and repair. In this study, we suggested that Tgf-β improved while its inhibitor LSKL impaired DNA repair and cell viability in UV-irradiated 661W cells. Moreover, RNA-seq was carried out, and a total of 106 differentially expressed (DE)-mRNAs and 7 DE-lncRNAs were identified between UV/LSKL and UV/ctrl 661W cells. Gene ontology and Reactome analysis confirmed that the DE-mRNAs were enriched in multiple DNA damaged- and repair-related biological functions and pathways. We then constructed a ceRNA network that included 3 lncRNAs, 19 miRNAs, and 29 mRNAs with a bioinformatics prediction. Through RT-qPCR and further functional verification, 2 Tgf-β-mediated ceRNA axes (Gm20559-miR-361-5p-Oas2/Gbp7) were further identified. Gm20559 knockout or miR-361-5p mimics markedly impaired DNA repair and cell viability in UV-irradiated 661W cells, which confirms the bioinformatics results. In summary, this study revealed that Tgf-β could reduce DNA damage in 661W cells, provided a Tgf-β-associated ceRNA network for DNA damage and repair, and suggested that the molecular signatures may be useful candidates as targets of treatment for photoreceptor pathology.

TGF-β1 in plasma and cerebrospinal fluid can be used as a biological indicator of chronic pain in patients with osteoarthritis

Introduction

Previous studies have demonstrated that cytokines, transforming growth factor (TGF-β1), and brain-derived neurotrophic factor (BDNF) can impact the intensity of pain in rodents. However, the roles of cytokines, TGF-β1 and BDNF in humans with chronic pain in osteoarthritis remains unclear, and no comparison between plasma and central cerebral spinal fluid (CSF) has been conducted.

Methods

Patients with osteoarthritis who were scheduled to receive spinal anesthesia were enrolled. The intensity of pain was evaluated with a visual analogue scale (VAS). In addition, patients with genitourinary system (GU) diseases and without obvious pain (VAS 0–1) were included as a comparison (control) group. The levels of TGF-β1, BDNF, tumor necrosis factor-α (TNF-α), and interleukin (IL)-8 within the CSF and plasma were collected and evaluated before surgery.

Results

The plasma and CSF TGF-β1 levels were significantly lower in the osteoarthritis patients with pain (VAS ≥ 3) than in the GU control patients. Downregulation of plasma BDNF was also found in osteoarthritis patients with pain. The Spearman correlation analysis showed that the VAS pain scores were significantly negatively correlated with the levels of TGF-β1 in the CSF of patients with osteoarthritis. However, there was no significant correlations between the pain scores and the levels of BDNF, TNF-α, and IL-8 in either the CSF or plasma.

Conclusions

TGF-β1 but not BDNF, TNF-α, or IL-8 may be an important biological indicator in the CSF of osteoarthritis patients with chronic pain.

TGFβ-Neurotrophin Interactions in Heart, Retina, and Brain

Ischemic insults to the heart and brain, i.e., myocardial and cerebral infarction, respectively, are amongst the leading causes of death worldwide. While there are therapeutic options to allow reperfusion of ischemic myocardial and brain tissue by reopening obstructed vessels, mitigating primary tissue damage, post-infarction inflammation and tissue remodeling can lead to secondary tissue damage. Similarly, ischemia in retinal tissue is the driving force in the progression of neovascular eye diseases such as diabetic retinopathy (DR) and age-related macular degeneration (AMD), which eventually lead to functional blindness, if left untreated. Intriguingly, the easily observable retinal blood vessels can be used as a window to the heart and brain to allow judgement of microvascular damages in diseases such as diabetes or hypertension. The complex neuronal and endocrine interactions between heart, retina and brain have also been appreciated in myocardial infarction, ischemic stroke, and retinal diseases. To describe the intimate relationship between the individual tissues, we use the terms heart-brain and brain-retina axis in this review and focus on the role of transforming growth factor β (TGFβ) and neurotrophins in regulation of these axes under physiologic and pathologic conditions. Moreover, we particularly discuss their roles in inflammation and repair following ischemic/neovascular insults. As there is evidence that TGFβ signaling has the potential to regulate expression of neurotrophins, it is tempting to speculate, and is discussed here, that cross-talk between TGFβ and neurotrophin signaling protects cells from harmful and/or damaging events in the heart, retina, and brain.

TGF-β Signaling: A Therapeutic Target to Reinstate Regenerative Plasticity in Vascular Dementia?

Vascular dementia (VaD) is the second leading form of memory loss after Alzheimer's disease (AD). Currently, there is no cure available. The etiology, pathophysiology and clinical manifestations of VaD are extremely heterogeneous, but the impaired cerebral blood flow (CBF) represents a common denominator of VaD. The latter might be the result of atherosclerosis, amyloid angiopathy, microbleeding and micro-strokes, together causing blood-brain barrier (BBB) dysfunction and vessel leakage, collectively originating from the consequence of hypertension, one of the main risk factors for VaD. At the histopathological level, VaD displays abnormal vascular remodeling, endothelial cell death, string vessel formation, pericyte responses, fibrosis, astrogliosis, sclerosis, microglia activation, neuroinflammation, demyelination, white matter lesions, deprivation of synapses and neuronal loss. The transforming growth factor (TGF) β has been identified as one of the key molecular factors involved in the aforementioned various pathological aspects. Thus, targeting TGF-β signaling in the brain might be a promising therapeutic strategy to mitigate vascular pathology and improve cognitive functions in patients with VaD. This review revisits the recent understanding of the role of TGF-β in VaD and associated pathological hallmarks. It further explores the potential to modulate certain aspects of VaD pathology by targeting TGF-β signaling.

Pre- and Neonatal Exposure to Lead (Pb) Induces Neuroinflammation in the Forebrain Cortex, Hippocampus and Cerebellum of Rat Pups

Lead (Pb) is a heavy metal with a proven neurotoxic effect. Exposure is particularly dangerous to the developing brain in the pre- and neonatal periods. One postulated mechanism of its neurotoxicity is induction of inflammation. This study analyzed the effect of exposure of rat pups to Pb during periods of brain development on the concentrations of selected cytokines and prostanoids in the forebrain cortex, hippocampus and cerebellum. Methods: Administration of 0.1% lead acetate (PbAc) in drinking water ad libitum, from the first day of gestation to postnatal day 21, resulted in blood Pb in rat pups reaching levels below the threshold considered safe for humans by the Centers for Disease Control and Prevention (10 µg/dL). Enzyme-linked immunosorbent assay (ELISA) method was used to determine the levels of interleukins IL-1β, IL-6, transforming growth factor-β (TGF-β), prostaglandin E2 (PGE2) and thromboxane B2 (TXB2). Western blot and quantitative real-time PCR were used to determine the expression levels of cyclooxygenases COX-1 and COX-2. Finally, Western blot was used to determine the level of nuclear factor kappa B (NF-κB). Results: In all studied brain structures (forebrain cortex, hippocampus and cerebellum), the administration of Pb caused a significant increase in all studied cytokines and prostanoids (IL-1β, IL-6, TGF-β, PGE2 and TXB2). The protein and mRNA expression of COX-1 and COX-2 increased in all studied brain structures, as did NF-κB expression. Conclusions: Chronic pre- and neonatal exposure to Pb induces neuroinflammation in the forebrain cortex, hippocampus and cerebellum of rat pups.

Effect of TGF-beta1 on long-term synaptic plasticity and distribution of AMPA receptors in the CA1 field of the hippocampus

Using the methods of electrophysiology and immunohistochemistry, the effect of the transforming factor beta-1(TGF-β1), an anti-inflammatory cytokine, on the long-term post-tetanic potentiation (LTP) in CA1 field hippocampal slices and the distribution of the GluR1 subunit of the AMPA receptor has been studied. It was shown that TGF-β1 at a concentration of 10 ng/ml did not significantly affect the initial stage of LTP and substantially changed the distribution of synaptic AMPA receptors in response to tetanic stimulation. Twenty five minutes after the tetanization, the main pool of AMPA receptors (90%) was due to the postsynaptic density (PSD). By contrast, LTP in the presence of TGF-β1 was accompanied by less pronounced changes in the distribution of AMPA receptors. Their localization in both pre- and postsynaptic regions remained nearly the same as that in the control. It may be suggested that the normal distribution of AMPA receptors in spinous synapses promotes the stabilization of potentiated synapses, thereby retaining LTP for longer terms.

Aquaporin-4 deficiency reduces TGF-β1 in mouse midbrains and exacerbates pathology in experimental Parkinson's disease

Aquaporin-4 (AQP4), the main water-selective membrane transport protein in the brain, is localized to the astrocyte plasma membrane. Following the establishment of a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) model, AQP4-deficient (AQP4^-/- ) mice displayed significantly stronger microglial inflammatory responses and remarkably greater losses of tyrosine hydroxylase (TH⁺ )-positive neurons than did wild-type AQP4 (AQP4^+/+ ) controls. Microglia are the most important immune cells that mediate immune inflammation in PD. However, recently, few studies have reported why AQP4 deficiency results in more severe hypermicrogliosis and neuronal damage after MPTP treatment. In this study, transforming growth factor-β1 (TGF-β1), a key suppressive cytokine in PD onset and development, failed to increase in the midbrain and peripheral blood of AQP4^-/- mice after MPTP treatment. Furthermore, the lower level of TGF-β1 in AQP4^-/- mice partially resulted from impairment of its generation by astrocytes; reduced TGF-β1 may partially contribute to the uncontrolled microglial inflammatory responses and subsequent severe loss of TH⁺ neurons in AQP4^-/- mice after MPTP treatment. Our study provides not only a better understanding of both aetiological and pathogenical factors implicated in the neurodegenerative mechanism of PD but also a possible approach to developing new treatments for PD via intervention in AQP4-mediated immune regulation.

TGF-β1 Regulation of P-JNK and L-Type Calcium Channel Cav1.2 in Cortical Neurons

Central nervous system (CNS) diseases can cause a series of neuronal lesions, which may be improved by the anti-apoptotic neuroprotection of transforming growth factor-beta 1 (TGF-β1). In neurons, L-type Ca²⁺ channels (LTCC) are mainly composed of Cav1.2 subunits. Given the implication of TGF-β1 in numerous CNS diseases, we examined the neuroprotective effects of TGF-β1 on the Cav1.2 channel in the CNS. To simulate acute mechanical traumatic brain injury (TBI), we used a needle to create parallel scratches across plates, which were cultured for 9 h. Meanwhile, Fluo4-AM-loaded laser scanning confocal microscopy with a dual wavelength of 488 nm/530 nm was employed to determine intracellular calcium concentrations ([Ca²⁺]_i). We found that MAPK inhibitors impede TGF-β1-induced cell viability and that TGF-β1 recovered from the trauma-induced cell viability in neurons. Cav1.2 production was significantly decreased in the TGF-β1-treated (10 ng/mL) neurons. At this TGF-β1 concentration, Cav1.2 was significantly down-regulated in a time-dependent manner after 12 h. Moreover, TGF-β1 partially recovered the protein levels of Cav1.2 that were reduced by TBI. TGF-β1 significantly inhibited the fluorescence intensity of [Ca²⁺]_i increased by KCl and delayed the time of the peak [Ca²⁺]_i. The observed effects of TGF-β1 on Cav1.2 were regulated by MAPK inhibitors. The observed effects of TGF-β1 on P-JNK were also impeded by pre-incubation with the LTCC inhibitor (10 μM) nimodipine in trauma-injured neurons. Altogether, TGF-β1 regulated LTCCs through a mechanism dependent on MEK, JNK1/2 and p38 MAPK signal pathways in cortical neurons. Thus, we suggest the involvement of this mechanism in cell viability.

Long-term heroin use was associated with the downregulation of systemic platelets, BDNF, and TGF-β1, and it contributed to the disruption of executive function in Taiwanese Han Chinese

BACKGROUND

Long-term heroin addicts have low plasma brain-derived neurotrophic factor (BDNF) levels. However, the mechanisms and effects of systemic disturbances of BDNF caused by heroin remain unclear.

OBJECTIVE

Blood platelet might be a source of neurotrophic factors like BDNF and transforming growth factor (TGF)-β1. Thus, we investigated the effects of heroin on platelets, BDNF and TGF-β1, the association between blood platelets, BDNF, TGF-β1, and executive function in long-term heroin addicts.

METHODS

We enrolled 170 heroin addicts and 141 healthy controls. We measured their plasma BDNF and TGF-β1 levels and counted their platelets, red and white blood cells. The Wisconsin Card Sorting Test (WCST) was used to assess their executive function.

RESULTS

Plasma BDNF and TGF-β1 levels were significantly downregulated in long-term heroin addicts. BDNF, TGF-β1, and platelet levels were lower in patients who had used heroin for more than 6 years than in those who had used it for less than 6 years. Lower plasma BDNF and TGF-β1 levels were highly correlated with the changes in platelet counts. In the WCST, the number of trials needed to complete the first category were negatively associated with platelet counts and BDNF levels.

CONCLUSIONS

In long-term heroin addicts, lower platelet counts contributed to lower plasma BDNF and TGF-β1 levels, which, in turn, contributed to the disruption of executive function after long-term heroin use. Neurotrophic- and platelet-protective agents might provide a useful research focus for heroin addiction therapy.

Loss of Gas6 and Axl signaling results in extensive axonal damage, motor deficits, prolonged neuroinflammation, and less remyelination following cuprizone exposure

The TAM (Tyro3, Axl, and MerTK) family of receptor tyrosine kinases (RTKs) and their ligands, Gas6 and ProS1, are important for innate immune responses and central nervous system (CNS) homeostasis. While only Gas6 directly activates Axl, ProS1 activation of Tyro3/MerTK can indirectly activate Axl through receptor heterodimerization. Therefore, we generated Gas6^-/- Axl^-/- double knockout (DKO) mice to specifically examine the contribution of this signaling axis while retaining ProS1 signaling through Tyro3 and MerTK. We found that naïve young adult DKO and WT mice have comparable myelination and equal numbers of axons and oligodendrocytes in the corpus callosum. Using the cuprizone model of demyelination/remyelination, transmission electron microscopy revealed extensive axonal swellings containing autophagolysosomes and multivesicular bodies, and fewer myelinated axons in brains of DKO mice at 3-weeks recovery from a 6-week cuprizone diet. Analysis of immunofluorescent staining demonstrated more SMI32+ and APP+ axons and less myelin in the DKO mice. There were no significant differences in the number of GFAP+ astrocytes or Iba1+ microglia/macrophages between the groups of mice. However, at 6-weeks cuprizone and recovery, DKO mice had increased proinflammatory cytokine and altered suppressor of cytokine signaling (SOCS) mRNA expression supporting a role for Gas6-Axl signaling in proinflammatory cytokine suppression. Significant motor deficits in DKO mice relative to WT mice on cuprizone were also observed. These data suggest that Gas6-Axl signaling plays an important role in maintaining axonal integrity and regulating and reducing CNS inflammation that cannot be compensated for by ProS1/Tyro3/MerTK signaling.

Protective effect of clusterin on rod photoreceptor in rat model of retinitis pigmentosa

Retinitis Pigmentosa (RP) begins with the death of rod photoreceptors and is slowly followed by a gradual loss of cones and a rearrangement of the remaining retinal neurons. Clusterin is a chaperone protein that protects cells and is involved in various pathophysiological stresses, including retinal degeneration. Using a well-established transgenic rat model of RP (rhodopsin S334ter), we investigated the effects of clusterin on rod photoreceptor survival. To investigate the role of clusterin in S334ter-line3 retinas, Voronoi analysis and immunohistochemistry were used to evaluate the geometry of rod distribution. Additionally, immunoblot analysis, Bax activation, STAT3 and Akt phosphorylation were used to evaluate the pathway involved in rod cell protection. In this study, clusterin (10μg/ml) intravitreal treatment produced robust preservation of rod photoreceptors in S334ter-line3 retina. The mean number of rods in 1mm² was significantly greater in clusterin injected RP retinas (postnatal (P) 30, P45, P60, & P75) than in age-matched saline injected RP retinas (P<0.01). Clusterin activated Akt, STAT3 and significantly reduced Bax activity; in addition to inducing phosphorylated STAT3 in Müller cells, which suggests it may indirectly acts on photoreceptors. Thus, clusterin treatment may interferes with mechanisms leading to rod death by suppressing cell death through activation of Akt and STAT3, followed by Bax suppression. Novel insights into the pathway of how clusterin promotes the rod cell survival suggest this treatment may be a potential therapeutic strategy to slow progression of vision loss in human RP.

TGF-β Family Signaling in Neural and Neuronal Differentiation, Development, and Function

Signaling by the transforming growth factor β (TGF-β) family is necessary for proper neural development and function throughout life. Sequential waves of activation, inhibition, and reactivation of TGF-β family members regulate numerous elements of the nervous system from the earliest stages of embryogenesis through adulthood. This review discusses the expression, regulation, and function of TGF-β family members in the central nervous system at various developmental stages, beginning with induction and patterning of the nervous system to their importance in the adult as modulators of inflammatory response and involvement in degenerative diseases.

Smad4 is essential for directional progression from committed neural progenitor cells through neuronal differentiation in the postnatal mouse brain

Signaling by the TGFβ super-family, consisting of TGFβ/activin- and bone morphogenetic protein (BMP) branch pathways, is involved in the central nervous system patterning, growth, and differentiation during embryogenesis. Neural progenitor cells are implicated in various pathological conditions, such as brain injury, infarction, Parkinson's disease and Alzheimer's disease. However, the roles of TGFβ/BMP signaling in the postnatal neural progenitor cells in the brain are still poorly understood. We examined the functional contribution of Smad4, a key integrator of TGFβ/BMP signaling pathways, to the regulation of neural progenitor cells in the subventricular zone (SVZ). Conditional loss of Smad4 in neural progenitor cells caused an increase in the number of neural stem like cells in the SVZ. Smad4 conditional mutants also exhibited attenuation in neuronal lineage differentiation in the adult brain that led to a deficit in olfactory bulb neurons as well as to a reduction of brain parenchymal volume. SVZ-derived neural stem/progenitor cells from the Smad4 mutant brains yielded increased growth of neurospheres, elevated self-renewal capacity and resistance to differentiation. These results indicate that loss of Smad4 in neural progenitor cells causes defects in progression of neural progenitor cell commitment within the SVZ and subsequent neuronal differentiation in the postnatal mouse brain.

Effects of Acute Confinement Stress-induced Hypothalamic-Pituitary Adrenal Axis Activation and Concomitant Peripheral and Central Transforming Growth Factor-β1 Measures in Nonhuman Primates

Transforming growth factor-β1 (TGF-β1) is a multifunctional cytokine with anti-inflammatory, immunosuppressive, and neuroprotective properties. The hypothalamic-pituitary-adrenal axis and immune system exert bidirectional influences on each other, via cortisol and TGF-β1, but the exact nature of the interaction is not well characterized. The current study examined the effects, in bonnet macaques (Macaca radiata), of two consecutive acute confinement stress periods in an unfamiliar room while mildly restrained, first without and then with dexamethasone pretreatment (0.01 mg/kg intramuscular). Preceding the confinement studies, a non-stress control condition obtained contemporaneous levels of cortisol and TGF-β1 in both plasma and cerebrospinal fluid to match the confinement stress studies. Subjects were reared under either normative or variable foraging demand conditions. Since there were no rearing effects at baseline or for any of the conditions tested—either for cortisol or TGF-β—the study analyses were conducted on the combined rearing groups. The stress condition increased both plasma and cerebrospinal fluid cortisol levels whereas dexamethasone pretreatment decreased cortisol concentrations to below baseline levels despite stress. The stress condition decreased TGF-β1 concentrations only in cerebrospinal fluid but not in serum. Together, the data suggested that stress-induced reductions of a centrally active neuroprotective cytokine occur in the face of hypothalamic-pituitary-adrenal axis activation, potentially facilitating glucocortoid-induced neurotoxicity. Stress-induced reductions of neuroprotective cytokines prompt exploration of protective measures against glucocorticoid-induced neurotoxicity.

A positive correlation exists between neurotrauma and TGF-β1-containing microglia in rats

BACKGROUND

Transforming growth factor-beta 1 (TGF-β1) regulates many processes after traumatic brain injury (TBI). Both Neuro AiD™ (MLC601) and astragaloside (AST) attenuate microglia activation in rats with TBI. The purpose of this study was to investigate whether MLC601 or AST improves output of TBI by affecting microglial expression of TGF-β1.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats (120 in number) were used to investigate the contribution of TGF-β1-containing microglia in the MLC601-mediated or the AST-mediated neuroprotection in the brain trauma condition using lateral fluid percussion injury.

RESULTS

Pearson correlation analysis revealed that there was a positive correlation between brain injury (evidenced by both brain contused volume and neurological severity score) and the cortical numbers of TGF-β1-containing microglia for the rats (n = 12) 4 days post-TBI. MLC601 or AST significantly (P < 0·05) attenuated TBI-induced brain contused volume (119 ± 14 mm³ or 108 ± 11 mm³ vs. 160 ± 21 mm³ ), neurological severity score (7·8 ± 0·3 or 8·1 ± 0·4 vs. 10·2 ± 0·5) and numbers of TGF-β1-containing microglia (6% ± 2% or 11% ± 3% vs. 79% ± 7%) for the rats 4 days post-TBI.

CONCLUSIONS

There was a positive correlation between TBI and cortical numbers of TGF-β1-containing microglia which could be significantly attenuated by astragaloside or NeuroAiD™ (MLC601) in rats.

Maternal inflammation leads to impaired glutamate homeostasis and up-regulation of glutamate carboxypeptidase II in activated microglia in the fetal/newborn rabbit brain

Astrocyte dysfunction and excessive activation of glutamatergic systems have been implicated in a number of neurologic disorders, including periventricular leukomalacia (PVL) and cerebral palsy (CP). However, the role of chorioamnionitis on glutamate homeostasis in the fetal and neonatal brains is not clearly understood. We have previously shown that intrauterine endotoxin administration results in intense microglial 'activation' and increased pro-inflammatory cytokines in the periventricular region (PVR) of the neonatal rabbit brain. In this study, we assessed the effect of maternal inflammation on key components of the glutamate pathway and its relationship to astrocyte and microglial activation in the fetal and neonatal New Zealand white rabbit brain. We found that intrauterine endotoxin exposure at gestational day 28 (G28) induced acute and prolonged glutamate elevation in the PVR of fetal (G29, 1day post-injury) and postnatal day 1 (PND1, 3days post-injury) brains along with prominent morphological changes in the astrocytes (soma hypertrophy and retracted processes) in the white matter tracts. There was a significant increase in glutaminase and N-Methyl-d-Aspartate receptor (NMDAR) NR2 subunit expression along with decreased glial L-glutamate transporter 1 (GLT-1) in the PVR at G29, that would promote acute dysregulation of glutamate homeostasis. This was accompanied with significantly decreased TGF-β1 at PND1 in CP kits indicating ongoing neuroinflammation. We also show for the first time that glutamate carboxypeptidase II (GCPII) was significantly increased in the activated microglia at the periventricular white matter area in both G29 and PND1 CP kits. This was confirmed by in vitro studies demonstrating that LPS activated primary microglia markedly upregulate GCPII enzymatic activity. These results suggest that maternal intrauterine endotoxin exposure results in early onset and long-lasting dysregulation of glutamate homeostasis, which may be mediated by impaired astrocyte function and GCPII upregulation in activated microglia.

Association Between Microglia, Inflammatory Factors, and Complement with Loss of Hippocampal Mossy Fiber Synapses Induced by Trimethyltin

Complement-associated factors are implicated in pathogen presentation, neurodegeneration, and microglia resolution of tissue injury. To characterize complement activation with microglial clearance of degenerating mossy fiber boutons, hippocampal dentate granule neurons were ablated in CD-1 mice with trimethyltin (TMT; 2.2 mg/kg, i.p.). Neuronal apoptosis was accompanied by amoeboid microglia and elevations in tumor necrosis factor [Tnfa], interleukin 1β [Il1b], and Il6 mRNA and C1q protein. Inos mRNA levels were unaltered. Silver degeneration and synaptophysin staining indicated loss of synaptic innervation to CA3 pyramidal neurons. Reactive microglia with thickened bushy morphology showed co-localization of synaptophysin+ fragments. The initial response at 2 days post-TMT included transient elevations in Tnfa, Il1b, Il6, and Inos mRNA levels. A concurrent increase at 2 days was observed in arginase-1 [Arg1], Il10, transforming growth factor β1 [Tgfb1], and chitinase 3 like-3 [Ym1] mRNA levels. At 2 days, C1q protein was evident in the CA3 with elevated C1qa, C1qb, C3, Cr3a, and Cr3b mRNA levels. mRNA levels remained elevated at 5 days, returning to control by 14 days, corresponding to silver degeneration. mRNA levels for pentraxin3 (Ptx3) were elevated on day 2 and Ptx1 was not altered. Our data suggest an association between microglia reactivity, the induction of anti-inflammatory genes concurrent with pro-inflammatory genes and the expression of complement-associated factors with the degeneration of synapses following apoptotic neuronal loss.

Increased levels of tumour necrosis factor alpha (TNFα) but not transforming growth factor-beta 1 (TGFβ1) are associated with the severity of congenital hydrocephalus in the hyh mouse

AIMS

Here, we tested the hypothesis that glial responses via the production of cytokines such as transforming growth factor-beta 1 (TGFβ1) and tumour necrosis factor alpha (TNFα), which play important roles in neurodegenerative diseases, are correlated with the severity of congenital hydrocephalus in the hyh mouse model. We also searched for evidence of this association in human cases of primary hydrocephalus.

METHODS

Hyh mice, which exhibit either severe or compensated long-lasting forms of hydrocephalus, were examined and compared with wild-type mice. TGFβ1, TNFα and TNFαR1 mRNA levels were quantified using real-time PCR. TNFα and TNFαR1 were immunolocalized in the brain tissues of hyh mice and four hydrocephalic human foetuses relative to astroglial and microglial reactions.

RESULTS

The TGFβ1 mRNA levels were not significantly different between hyh mice exhibiting severe or compensated hydrocephalus and normal mice. In contrast, severely hydrocephalic mice exhibited four- and two-fold increases in the mean levels of TNFα and TNFαR1, respectively, compared with normal mice. In the hyh mouse, TNFα and TNFαR1 immunoreactivity was preferentially detected in astrocytes that form a particular periventricular reaction characteristic of hydrocephalus. However, these proteins were rarely detected in microglia, which did not appear to be activated. TNFα immunoreactivity was also detected in the glial reaction in the small group of human foetuses exhibiting hydrocephalus that were examined.

CONCLUSIONS

In the hyh mouse model of congenital hydrocephalus, TNFα and TNFαR1 appear to be associated with the severity of the disease, probably mediating the astrocyte reaction, neurodegenerative processes and ischaemia.

TGF-β improves myocardial function and prevents apoptosis induced by anoxia-reoxygenation, through the reduction of endoplasmic reticulum stress

BACKGROUND

Transforming growth factor-β (TGF-β) is known for its role in ventricular remodeling, inflammatory response, cell survival, and apoptosis. However, its role in improving myocardial function in rat hearts subjected to ischemia-reperfusion (I/R) and protecting against apoptosis induced in cardiomyocytes by anoxia-reoxygenation (A/R) has not been elucidated. This study investigated the protective effects and molecular mechanisms of TGF-β on myocardial function and cardiomyocyte apoptosis.

METHODS AND RESULTS

We used TUNEL staining, we tested cell viability, and we measured mitochondrial membrane potential and levels of mitochondrial ROS after 6 h of simulated anoxia together with various durations of simulated reoxygenation in H9c2 cells. We further observed the contractile function in rat hearts after they were subjected to 30 min global ischemia and 180 min reperfusion. Pretreatment with TGF-β markedly inhibited apoptosis in H9c2 cells, as evidenced by increased cell viability and decreased numbers of TUNEL-positive cells, maintained mitochondrial membrane potential, and diminished mitochondrial production of reactive oxygen species (ROS). These changes were associated with the inhibition of endoplasmic reticulum (ER) stress-dependent markers of apoptosis (GRP78, CHOP, caspase-12, and JNK), and the modulation of the expression of Bcl2/Bax. Furthermore, TGF-β improved I/R-induced myocardial contractile dysfunction. All of these protective effects were concentration-dependent.

CONCLUSION

Our results show that TGF-β prevents A/R-induced apoptosis of cardiomyocytes and improves myocardial function in rat hearts injured by I/R.

Protection of TGF-β1 against neuroinflammation and neurodegeneration in Aβ1-42-induced Alzheimer's disease model rats

Neuroinflammation has been reported to be associated with Alzheimer’s disease (AD) pathogenesis. Neuroinflammation is generally considered as an outcome of glial activation; however, we recently demonstrated that T helper (Th)17 cells, a subpopulation of proinflammatory CD4+ T cells, are also involved in AD pathogenesis. Transforming growth factor (TGF)-β1, a cytokine that can be expressed in the brain, can be immunosuppressive, but its effects on lymphocyte-mediated neuroinflammation in AD pathogenesis have not been well addressed. In the current study we administered TGF-β1 via intracerebroventricle (ICV) and intranasal (IN) routes in AD model rats to investigate its antiinflammatory and neuroprotective effects. The AD rat model was prepared by bilateral hippocampal injection of amyloid-β (Aβ)_1–42. TGF-β1 was administered via ICV one hour prior to Aβ_1–42 injection or via both nares seven days after Aβ_1–42 injection. ICV administration of TGF-β1 before Aβ_1–42 injection remarkably ameliorated Aβ_1–42-induced neurodegeneration and prevented Aβ_1–42-induced increases in glia-derived proinflammatory mediators (TNF-α, IL-1β and iNOS), as well as T cell-derived proinflammatory cytokines (IFN-γ, IL-2, IL-17 and IL-22), in the hypothalamus, serum or cerebrospinal fluid (CSF) in a concentration-dependent manner. TGF-β1 pretreatment also prevented Aβ_1–42-induced decreases in the neurotrophic factors, IGF-1, GDNF and BDNF, and in the antiinflammatory cytokine, IL-10. Similarly, IN administration of TGF-β1 after Aβ_1–42 injection reduced neurodegeneration, elevation of proinflammatory mediators and cytokines, and reduction of neurotrophic and antiinflammatory factors, in the hypothalamus, serum or CSF. These findings suggest that TGF-β1 suppresses glial and T cell-mediated neuroinflammation and thereby alleviates AD-related neurodegeneration. The effectiveness of IN administered TGF-β1 in reducing Aβ_1–42 neurotoxicity suggests a possible therapeutic approach in patients with AD.

The use of microRNAs to modulate redox and immune response to stroke

SIGNIFICANCE

Cerebral ischemia is a major cause of death and disability throughout the world, yet therapeutic options remain limited. The interplay between the cellular redox state and the immune response plays a critical role in determining the extent of neural cell injury after ischemia and reperfusion. Excessive amounts of reactive oxygen species (ROS) generated by mitochondria and other sources act both as triggers and effectors of inflammation. This review will focus on the interplay between these two mechanisms.

RECENT ADVANCES

MicroRNAs (miRNAs) are important post-transcriptional regulators that interact with multiple target messenger RNAs coordinately regulating target genes, including those involved in controlling mitochondrial function, redox state, and inflammatory pathways. This review will focus on the regulation of mitochondria, ROS, and inflammation by miRNAs in the chain of deleterious intra- and intercellular events that lead to brain cell death after cerebral ischemia.

CRITICAL ISSUES

Although pretreatment using miRNAs was effective in cerebral ischemia in rodents, testing treatment after the onset of ischemia is an essential next step in the development of acute stroke treatment. In addition, miRNA formulation and delivery into the CNS remain a challenge in the clinical translation of miRNA therapy.

FUTURE DIRECTIONS

Future research should focus on post-treatment and potential clinical use of miRNAs.

TGF-β1 protection against Aβ1-42-induced neuroinflammation and neurodegeneration in rats

Transforming growth factor (TGF)-β1, a cytokine that can be expressed in the brain, is a key regulator of the brain's responses to injury and inflammation. Alzheimer's disease (AD), the most common neurodegenerative disorder, involves inflammatory processes in the brain in addition to the hallmarks, amyloid-β (Aβ) plaques and neurofibrillary tangles. Recently, we have shown that T-helper (Th) 17 cells, a subpopulation of CD4+ T-cells with high proinflammation, also participate in the brain inflammatory process of AD. However, it is poorly known whether TGF-β1 ameliorates the lymphocyte-mediated neuroinflammation and, thereby, alleviates neurodegeneration in AD. Herein, we administered TGF-β1 via the intracerebroventricle (ICV) in AD model rats, by Aβ1-42 injection in both sides of the hippocampus, to show the neuroprotection of TGF-β1. The TGF-β1 administration after the Aβ1-42 injection ameliorated cognitive deficit and neuronal loss and apoptosis, reduced amyloid precursor protein (APP) expression, elevated protein phosphatase (PP)2A expression, attenuated glial activation and alleviated the imbalance of the pro-inflammatory/anti-inflammatory responses of T-lymphocytes, compared to the Aβ1-42 injection alone. These findings demonstrate that TGF-β1 provides protection against AD neurodegeneration and suggest that the TGF-β1 neuroprotection is implemented by the alleviation of glial and T-cell-mediated neuroinflammation.

The blood-brain barrier-gatekeeper to neuronal homeostasis: clinical implications in the setting of stroke

The blood-brain barrier is part of the neurovascular unit and serves as a functional and anatomical barrier between the blood and the extracellular space. It controls the flow of solutes in and out of the brain thereby providing an optimal environment for neuronal functioning. Paracellular transport between endothelial cells is restricted by tight junctions and transendothelial transport is reduced and more selective compared to capillaries of other organs. Further, the blood-brain barrier is involved in controlling blood flow and it is the site for signaling damage of the nervous system to the peripheral immune system. As an important player in brain homeostasis, blood-brain barrier dysfunction has been implicated in the pathophysiology of many brain diseases including stroke, traumatic brain injury, brain tumors, epilepsy and neurodegenerative disorders. In this article - highlighting recent advances in basic science - we review the features of the blood-brain barrier and their significance for neuronal homeostasis to discuss clinical implications for neurological complications following cerebral ischemia.

Neurogenesis and inflammation after ischemic stroke: what is known and where we go from here

This review covers the pathogenesis of ischemic stroke and future directions regarding therapeutic options after injury. Ischemic stroke is a devastating disease process affecting millions of people worldwide every year. The mechanisms underlying the pathophysiology of stroke are not fully understood but there is increasing evidence demonstrating the contribution of inflammation to the drastic changes after cerebral ischemia. This inflammation not only immediately affects the infarcted tissue but also causes long-term damage in the ischemic penumbra. Furthermore, the interaction between inflammation and subsequent neurogenesis is not well understood but the close relationship between these two processes has garnered significant interest in the last decade or so. Current approved therapy for stroke involving pharmacological thrombolysis is limited in its efficacy and new treatment strategies need to be investigated. Research aimed at new therapies is largely about transplantation of neural stem cells and using endogenous progenitor cells to promote brain repair. By understanding the interaction between inflammation and neurogenesis, new potential therapies could be developed to further establish brain repair mechanisms.

TGF-beta signalling in the adult neurogenic niche promotes stem cell quiescence as well as generation of new neurons

Members of the transforming growth factor (TGF)-β family govern a wide range of mechanisms in brain development and in the adult, in particular neuronal/glial differentiation and survival, but also cell cycle regulation and neural stem cell maintenance. This clearly created some discrepancies in the field with some studies favouring neuronal differentiation/survival of progenitors and others favouring cell cycle exit and neural stem cell quiescence/maintenance. Here, we provide a unifying hypothesis claiming that through its regulation of neural progenitor cell (NPC) proliferation, TGF-β signalling might be responsible for (i) maintaining stem cells in a quiescent stage, and (ii) promoting survival of newly generated neurons and their functional differentiation. Therefore, we performed a detailed histological analysis of TGF-β1 signalling in the hippocampal neural stem cell niche of a transgenic mouse that was previously generated to express TGF-β1 under a tetracycline regulatable Ca-Calmodulin kinase promoter. We also analysed NPC proliferation, quiescence, neuronal survival and differentiation in relation to elevated levels of TGF-β1 in vitro and in vivo conditions. Finally, we performed a gene expression profiling to identify the targets of TGF-β1 signalling in adult NPCs. The results demonstrate that TGF-β1 promotes stem cell quiescence on one side, but also neuronal survival on the other side. Thus, considering the elevated levels of TGF-β1 in ageing and neurodegenerative diseases, TGF-β1 signalling presents a molecular target for future interventions in such conditions.

Potential neuroprotective role of transforming growth factor β1 (TGFβ1) in the brain

TGFβ1 is a growth factor that is known to be expressed in most neurodegenerative diseases and after vascular accidents in the brain. TGFβ1 downregulates the activity of activated microglia and promotes astrogliosis. It also prevents cell death by a known mechanism dependant on astrocytes and the secretion of the plasminogen activator inhibitor 1 (PAI-1). This mechanism can provide light on what is the mechanism of action of TGFβ1 as a protective factor and it can provide the pharmacological principles in which this pathway could be used with therapeutic purposes. TGFβ1 is upregulated in most neurodegenerative diseases, however, its expression appears dramatically blocked in Huntington's disease, the fastest of those diseases in progress after the onset. This fact suggests that TGFβ1 slows down the neurodegenerative process, preventing tissue damage and neural apoptotic death. However, the exact details of TGFβ1 action are still unknown and the physiological roles on the diseases are still mysterious. Interestingly, all the data regarding the roles of TGFβ1 in health and disease have been also confirmed with the use of transgenic knockouts and TGFβ1 overexpressing mice. What possibly came as a surprise from the study of TGFβ1 overexpressing models is that combining its neuroprotective and antiproliferative effects, this cytokine generates a significant disruption in the hippocampal circuitry with its consequent learning and memory deficit.

Herbal medicines for ischemic stroke: combating inflammation as therapeutic targets

Stroke is a debilitating disease for which limited therapeutic approaches are available currently. Thus, there is an urgent need for developing novel therapies for stroke. Astrocytes, endothelial cells and pericytes constitute a neurovascular network for metabolic requirement of neurons. During ischemic stroke, these cells contribute to post-ischemic inflammation at multiple stages of ischemic cascades. Upon ischemia onset, activated resident microglia and astrocytes, and infiltrated immune cells release multiple inflammation factors including cytokines, chemokines, enzymes, free radicals and other small molecules, not only inducing brain damage but affecting brain repair. Recent progress indicates that anti-inflammation is an important therapeutic strategy for stroke. Given a long history with direct experience in the treatment of human subjects, Traditional Chinese Medicine and its related natural compounds are recognized as important sources for drug discovery. Last decade, a great progress has been made to identify active compounds from herbal medicines with the properties of modulating post-ischemic inflammation for neuroprotection. Herein, we discuss the inflammatory pathway in early stage and secondary response to injured tissues after stroke from initial artery occlusion to brain repair, and review the active ingredients from natural products with anti-inflammation and neuroprotection effects as therapeutic agents for ischemic stroke. Further studies on the post-ischemic inflammatory mechanisms and corresponding drug candidates from herbal medicine may lead to the development of novel therapeutic strategies in stroke treatment.

Identification of a unique TGF-β-dependent molecular and functional signature in microglia

Microglia are myeloid cells of the central nervous system (CNS) that participate both in normal CNS function and disease. We investigated the molecular signature of microglia and identified 239 genes and 8 microRNAs that were uniquely or highly expressed in microglia vs. myeloid and other immune cells. Out of 239 genes, 106 were enriched in microglia as compared to astrocytes, oligodendrocytes and neurons. This microglia signature was not observed in microglial lines or in monocytes recruited to the CNS and was also observed in human microglia. Based on this signature, we found a crucial role for TGF-β in microglial biology that included: 1) the requirement of TGF-β for the in vitro development of microglia that express the microglial molecular signature characteristic of adult microglia; and 2) the absence of microglia in CNS TGF-β1 deficient mice. Our results identify a unique microglial signature that is dependent on TGF-β signaling which provides insights into microglial biology and the possibility of targeting microglia for the treatment of CNS disease.

Neuroprotective effects of Nigella sativa extract on cell death in hippocampal neurons following experimental global cerebral ischemia-reperfusion injury in rats

BACKGROUND

Global cerebral ischemia followed by reperfusion, leads to extensive neuronal damage, particularly the neurons in the hippocampal CA region. Recent studies have demonstrated that pharmacological agents, such as Nigella sativa L. (Ranunculaceae) that is an annual herbaceous flowering plant, given at the time of reperfusion afforded protection against ischemia, which is referred to as pharmacological post conditioning.

OBJECTIVES

The aim of this study was to evaluate the neuroprotective effects of Nigella sativa in the hippocampus neurons of rats exposed to global ischemia/reperfusion.

METHODS

In the present study 30 Wister rats (200-250 g) were divided into 5 groups namely sham (operated without treatment), control (operation with normal saline treatment), and 3 treatment groups with Nigella sativa 1mg/kg, 10mg/kg and 50mg/kg. Firstly, the animals were anesthetized by ketamin and xylazine, and then the right carotid artery was operated upon dissection of the soft tissues around it and ligation by a clamp for 20 min. The Nigella sativa extraction was used during surgery through IP route and after 72 h the animals were euthanized and their brain removed, fixed and prepared for histopathological examinations.

RESULTS

In treatment group (1mg/kg) the interstitial neuron frequency which contains cytoplasmic edema, along with CA, was 28 cells, whereas the edematous astrocyte number along with CA in this group was 115 cells. In the treatment group (10mg/kg) the interstitial neurons of cornua ammonis (CA) were 15 and the edematous astrocytes were 122 cells and in the treatment group (50mg/kg) the number of edematous interstitial neurons was 7 cells in distance of 2900 μ of CA. In such group the number of edematous interstitial neurons was less as well. In this group the appearance of CA cells was more similar to control group, not only the edema decreased in interstitial and astrocyte cells, but it dramatically decreased in pyramidal cells. Our study revealed that the Nigella sativa extraction could prevent intracellular edema of interneurons in 50mg/kg group significantly compared to sham group (91.6%) and the extraction (50mg/kg) decreased edematous astrocytes 67.1% dramatically compared to sham group. Furthermore there was no significant difference between control and two treatment groups (1 and 10mg/kg) (P>0.05), CONCLUSION: Our finding suggested that the N. sativa extraction could prevent the cerebral edema which the best result was obtained in 50mg/kg group; consequently such extraction is able to prevent ischemia/reperfusion in the hippocampus tissue of the brain.

Temporal and regional patterns of Smad activation in the rat hippocampus following global ischemia

In this study, we examined the temporal and regional patterns of Smad activation in the rat hippocampus following global ischemia. We also examined the association between Smad activation and ischemia-induced pathology in the hippocampus. We found that 1) Smad1, -2, -3, and -5 proteins were detected in the rat hippocampus by means of western blot and immunohistochemistry; 2) after 5 min of ischemia, Smad2 and Smad3 proteins accumulated in the nuclei of pyramidal cells in the CA1 region, which is vulnerable to ischemia; 3) after 3 min of ischemia, which was non-lethal, there was no such nuclear accumulation of Smad2 and Smad3 in the CA1 region; 4) following injection of activin A, nuclear accumulation of Smad2 and Smad3 was induced not only in pyramidal cells of the CA1 region, but also in pyramidal cells of the CA3 region as well as in granule cells of the DG region; 5) activin A-induced nuclear accumulation of Smad2 and Smad3 neither caused degeneration of hippocampal neurons nor prevented degeneration induced by ischemia. These results suggest that in the hippocampus, ischemia-induced activation of Smad2 and Smad3 is associated with the response to stress but is not related to neuronal survival or death.

Chronic over-expression of TGFβ1 alters hippocampal structure and causes learning deficits

The cytokine transforming growth factor β1 (TGFβ1) is chronically upregulated in several neurodegenerative conditions, including Alzheimer's disease, Parkinson's disease, Creutzfeldt-Jacob disease, amyotrophic lateral sclerosis and multiple sclerosis, and following stroke. Although previous studies have shown that TGFβ1 may be neuroprotective, chronic exposure to elevated levels of this cytokine may contribute to disease pathology on its own. In order to study the effects of chronic exposure to TGFβ1 in isolation, we used transgenic mice that over-express a constitutively active porcine TGFβ1 in astrocytes. We found that TGFβ1 over-expression altered brain structure, with the most pronounced volumetric increases localized to the hippocampus. Within the dentate gyrus (DG) of the hippocampus, increases in granule cell number and astrocyte size were responsible for volumetric expansion, with the increased granule cell number primarily related to a marked reduction in death of new granule cells generated in adulthood. Finally, these cumulative changes in DG microstructure and macrostructure were associated with the age-dependent emergence of spatial learning deficits in TGFβ1 over-expressing mice. Together, our data indicate that chronic upregulation of TGFβ1 negatively impacts hippocampal structure and, even in the absence of disease, impairs hippocampus-dependent learning.

Impaired glutamate recycling and GluN2B-mediated neuronal calcium overload in mice lacking TGF-β1 in the CNS

Transforming growth factor β1 (TGF-β1) is a pleiotropic cytokine expressed throughout the CNS. Previous studies demonstrated that TGF-β1 contributes to maintain neuronal survival, but mechanistically this effect is not well understood. We generated a CNS-specific TGF-β1-deficient mouse model to investigate the functional consequences of TGF-β1-deficiency in the adult mouse brain. We found that depletion of TGF-β1 in the CNS resulted in a loss of the astrocyte glutamate transporter (GluT) proteins GLT-1 (EAAT2) and GLAST (EAAT1) and decreased glutamate uptake in the mouse hippocampus. Treatment with TGF-β1 induced the expression of GLAST and GLT-1 in cultured astrocytes and enhanced astroglial glutamate uptake. Similar to GLT-1-deficient mice, CNS-TGF-β1-deficient mice had reduced brain weight and neuronal loss in the CA1 hippocampal region. CNS-TGF-β1-deficient mice showed GluN2B-dependent aberrant synaptic plasticity in the CA1 area of the hippocampus similar to the glutamate transport inhibitor DL-TBOA and these mice were highly sensitive to excitotoxic injury. In addition, hippocampal neurons from TGF-β1-deficient mice had elevated GluN2B-mediated calcium signals in response to extrasynaptic glutamate receptor stimulation, whereas cells treated with TGF-β1 exhibited reduced GluN2B-mediated calcium signals. In summary, our study demonstrates a previously unrecognized function of TGF-β1 in the CNS to control extracellular glutamate homeostasis and GluN2B-mediated calcium responses in the mouse hippocampus.

Thrombin-induced TGF-β1 pathway: a cause of communicating hydrocephalus post subarachnoid hemorrhage

The mechanism of communicating hydrocephalus after subarachnoid hemorrhage (SAH) remains unclear. Revealing a signaling cascade may provide significant insights into the molecular etiology of the accumulation of cerebrospinal fluid (CSF) in cerebral compartments during SAH. To investigate the mechanism of the communicating hydrocephalus following SAH, we infused CSF with thrombin (TH), resulting in proinflammatory and proliferative responses in rat meninges of SAH. The effect of TH could be completely blocked by a transforming growth factor β1 (TGF-β1) inhibitor, SB-431542, suggesting that TH-stimulated proliferation of meninges is through the TGF-β1 signaling pathway. The cascade of TGF β1-Smad3 was significantly upregulated by TH, which, in turn, stimulated the proliferation of subarachnoid meninges. TH-induced overexpression of TGF-β1 and activation of its downstream factors might be a mechanism of communicating hydrocephalus after SAH.

Macrophages prevent hemorrhagic infarct transformation in murine stroke models

OBJECTIVE

Inflammation is increasingly viewed as a new therapeutic target in subacute stages of brain infarction. However, apart from causing secondary damage, inflammation could equally promote beneficial lesion remodeling and repair. Distinct subpopulations of monocytes/macrophages (MOs/MPs) may critically determine the outcome of lesion-associated inflammation.

METHODS

We addressed the role of bone marrow-derived MOs/MPs in 2 different mouse models of ischemic stroke using a combined cell-specific depletion, chemokine receptor knockout, bone marrow chimeric, and pharmacological approach.

RESULTS

Starting within 24 hours of stroke onset, immature Ly6c(hi) monocytes infiltrated into the infarct border zone and differentiated into mature Ly6c(lo) phagocytes within the lesion compartment. MO/MP infiltration was CCR2-dependent, whereas we did not obtain evidence for additional recruitment via CX3CR1. Depletion of circulating MOs/MPs or selective targeting of CCR2 in bone marrow-derived cells caused delayed clinical deterioration and hemorrhagic conversion of the infarctions. Bleeding frequently occurred around thin-walled, dilated neovessels in the infarct border zone and was accompanied by decreased expression of transforming growth factor (TGF)-β1 and collagen-4, along with diminished activation of Smad2. Injection of TGF-β1 into the lesion border zone greatly reduced infarct bleeding in MO/MP-depleted mice.

INTERPRETATION

Bone marrow-derived MOs/MPs recruited via CCR2 and acting via TGF-β1 are essential for maintaining integrity of the neurovascular unit following brain ischemia. Future therapies should be aimed at enhancing physiological repair functions of CCR2(+) MOs/MPs rather than blocking their hematogenous recruitment.

Astrocytes as a source for extracellular matrix molecules and cytokines

Research of the past 25 years has shown that astrocytes do more than participating and building up the blood-brain barrier and detoxify the active synapse by reuptake of neurotransmitters and ions. Indeed, astrocytes express neurotransmitter receptors and, as a consequence, respond to stimuli. Within the tripartite synapse, the astrocytes owe more and more importance. Besides the functional aspects the differentiation of astrocytes has gained a more intensive focus. Deeper knowledge of the differentiation processes during development of the central nervous system might help explaining and even help treating neurological diseases like Alzheimer’s disease, Amyotrophic lateral sclerosis, Parkinsons disease, and psychiatric disorders in which astrocytes have been shown to play a role. Specific differentiation of neural stem cells toward the astroglial lineage is performed as a multi-step process. Astrocytes and oligodendrocytes develop from a multipotent stem cell that prior to this has produced primarily neuronal precursor cells. This switch toward the more astroglial differentiation is regulated by a change in receptor composition on the cell surface and responsiveness to Fibroblast growth factor and Epidermal growth factor (EGF). The glial precursor cell is driven into the astroglial direction by signaling molecules like Ciliary neurotrophic factor, Bone Morphogenetic Proteins, and EGF. However, the early astrocytes influence their environment not only by releasing and responding to diverse soluble factors but also express a wide range of extracellular matrix (ECM) molecules, in particular proteoglycans of the lectican family and tenascins. Lately these ECM molecules have been shown to participate in glial development. In this regard, especially the matrix protein Tenascin C (Tnc) proved to be an important regulator of astrocyte precursor cell proliferation and migration during spinal cord development. Nevertheless, ECM molecules expressed by reactive astrocytes are also known to act mostly in an inhibitory fashion under pathophysiological conditions. Thus, we further summarize resent data concerning the role of chondroitin sulfate proteoglycans and Tnc under pathological conditions.

Common variants at 12q14 and 12q24 are associated with hippocampal volume

Aging is associated with reductions in hippocampal volume (HV) that are accelerated by Alzheimer’s disease and vascular risk factors. Our genome-wide association study of dementia-free persons (n=9,232) identified 46 SNPs at four loci with p-values <4.0×10^-7. Two additional samples (n=2,318) replicated associations at 12q24 within MSRB3/WIF1 (discovery + replication, rs17178006; p=5.3×10^-11) and at 12q14 near HRK/FBXW8 (rs7294919; p=2.9×10^-11). Remaining associations included one 2q24 SNP within DPP4 (rs6741949; p=2.9×10^-7) and nine 9p33 SNPs within ASTN2 (rs7852872; p=1.0×10^-7) that were also associated with HV (p<0.05) in a third younger, more heterogeneous sample (n=7,794). The ASTN2 SNP was also associated with decline in cognition in a largely independent sample (n=1,563). These associations implicate genes related to apoptosis (HRK), development (WIF1), oxidative stress (MSR3B), ubiquitination (FBXW8), enzymes targeted by new diabetes medications (DPP4), and neuronal migration (ASTN2), indicating novel genetic influences that influence hippocampal size and possibly the risk of cognitive decline and dementia.

High serum levels of transforming growth factor β1 are associated with increased cortical thickness in cingulate and right frontal areas in healthy subjects

BACKGROUND

Transforming growth factor β (TGF-β) is a cytokine having multiple functions in the central nervous system such as promoting repair mechanisms in degenerative diseases and stroke. To date, however, its neuroprotective effects in non-disease conditions have not been studied

METHODS

With the aim of exploring the relationship between peripheral TGF-β1 expression and brain structural integrity, 70 healthy participants underwent high-resolution structural T1-weighted magnetic resonance imaging scans and blood sampling. Data were processed to obtain brain cortical thickness and serum concentrations of TGF-β1. We investigated the correlation between TGF-β1 and cortical thickness using both region-of-interest- and vertex-based approaches.

FINDINGS

Region-of-interest-based analysis of the cortical mantle showed a correlation between TGF-β1 serum concentrations and cortical thickness bilaterally in cingulate and right frontal and temporal areas. Similar results emerged in the vertex-based analysis, where significant correlations were found bilaterally in cingulate and right frontal cortices.

CONCLUSIONS

These results suggest that TGF-β1, through its role in down-regulating inflammatory processes, might have a beneficial effect on the structural integrity of the brain in physiological states.

Enhanced functional recovery in MRL/MpJ mice after spinal cord dorsal hemisection

Adult MRL/MpJ mice have been shown to possess unique regeneration capabilities. They are able to heal an ear-punched hole or an injured heart with normal tissue architecture and without scar formation. Here we present functional and histological evidence for enhanced recovery following spinal cord injury (SCI) in MRL/MpJ mice. A control group (C57BL/6 mice) and MRL/MpJ mice underwent a dorsal hemisection at T9 (thoracic vertebra 9). Our data show that MRL/MpJ mice recovered motor function significantly faster and more completely. We observed enhanced regeneration of the corticospinal tract (CST). Furthermore, we observed a reduced astrocytic response and fewer micro-cavities at the injury site, which appear to create a more growth-permissive environment for the injured axons. Our data suggest that the reduced astrocytic response is in part due to a lower lesion-induced increase of cell proliferation post-SCI, and a reduced astrocytic differentiation of the proliferating cells. Interestingly, we also found an increased number of proliferating microglia, which could be involved in the MRL/MpJ spinal cord repair mechanisms. Finally, to evaluate the molecular basis of faster spinal cord repair, we examined the difference in gene expression changes in MRL/MpJ and C57BL/6 mice after SCI. Our microarray data support our histological findings and reveal a transcriptional profile associated with a more efficient spinal cord repair in MRL/MpJ mice.

Anti-inflammatory cytokines, TGF-β1 and IL-10, exert anti-hypoxic action and abolish posthypoxic hyperexcitability in hippocampal slice neurons: comparative aspects

The aim of this study was to investigate the comparative effects of transforming growth factor β1 (TGF-β1) and interleukin-10 (IL-10) on the repeated brief hypoxia-induced alterations in the activity of hippocampal slice CA1 pyramidal neurons. The method of field potentials measurement in CA1 region of hippocampal slices was used. The principal results of our work are summarized as follow. 1. TGF-β1 reduces the depressive effect of brief hypoxia on the population spike amplitude more effectively than IL-10. 2. During TGF-β1 exposure (in contrast to IL-10), three 3-min hypoxic episodes do not induce the rapid hypoxic preconditioning. 3. TGF-β1 and IL-10 equally abolish posthypoxic hyperexcitability induced by repeated brief episodes of hypoxia in CA1 pyramidal neurons. These findings indicated that TGF-β1 and IL-10 are able to evoke anti-hypoxic effect and abolish the development of posthypoxic hyperexcitability induced by repeated brief hypoxic episodes in hippocampal CA1 pyramidal neurons. Our results also demonstrated that TGF-β1 reduced the effectiveness of hypoxia to depress neuronal activity more effectively than IL-10. We suggest that the present findings allow to explain the certain neuroprotective mechanisms of IL-10 and TGF-beta1 in the early phase of hypoxia and indicate that a therapeutic anti-inflammatory approach using these substances can provide neuroprotection in the brain hypoxic conditions.

Vascular damage in the central nervous system: a multifaceted role for vascular-derived TGF-β

The brain function depends on a continuous supply of blood. The blood-brain barrier (BBB), which is formed by vascular cells and glia, separates components of the circulating blood from neurons and maintains the precisely regulated brain milieu required for proper neuronal function. A compromised BBB alters the transport of molecules between the blood and brain and has been associated with or shown to precede neurodegenerative disease. Blood components immediately leak into the brain after mechanical damage or as a consequence of a compromised BBB in brain disease changing the extracellular environment at sites of vascular damage. It is intriguing how blood-derived components alter the cellular and molecular constituents of the neurovascular interface after BBB opening. We recently identified an unexpected role for the blood protein fibrinogen, which is deposited in the nervous system promptly after vascular damage, as an initial scar inducer by promoting the availability of active TGF-β. Fibrinogen-bound latent TGF-β interacts with astrocytes, leading to active TGF-β formation and activation of the TGF-β/Smad signaling pathway. Here, we discuss the pleiotropic effects of potentially vascular-derived TGF-β on cells at the neurovascular interface and we speculate how these biological effects might contribute to degeneration and regeneration processes. Summarizing the effects of the components derived from the brain vascular system on nervous system regeneration might support the development of new therapeutic approaches.

Probucol attenuates oxidative stress, energy starvation, and nitric acid production following transient forebrain ischemia in the rat hippocampus

Oxidative stress and energy depletion are believed to participate in hippocampal neuronal damage after forebrain ischemia. This study has been initiated to investigate the potential neuroprotective effects of probucol, a lipid-lowering drug with strong antioxidant properties, against transient forebrain ischemia-induced neuronal damage and biochemical abnormalities in rat hippocampal CA1 region. Adult male Wistar albino rats were subjected to forebrain ischemia and injected with probucol for the next 7 successive days, and compared to controls. Forebrain ischemia resulted in a significant decrease in the number of intact neurons (77%), glutathione (GSH), and adenosine triphosphate (ATP), and a significant increase in thiobarbituric acid reactive substances (TBARS) and total nitrate/nitrite, (NO_x) production in hippocampal tissues. The administration of probucol attenuated forebrain ischemia-induced neuronal damage, manifested as a complete reversal of the decrease in the number of intact neurons, ATP and GSH and the increase in TBARS and NO_x in hippocampal tissues. This study demonstrates that probucol treatment abates forebrain ischemia-induced hippocampal neuronal loss, energy depletion, and oxidative stress in hippocampal CA1 region. Thus, probucol could be a promising neuroprotective agent in the treatment of forebrain ischemia.

Susceptible gene single nucleotide polymorphism and hemorrhage risk in patients with brain arteriovenous malformation

The relationship between single nucleotide polymorphism (SNP) of interleukin-17 (IL-17A), transforming growth factor β (TGF-β), as well as its receptor (TGFR-β2) and susceptibility to intracerebral hemorrhage in patients with brain arteriovenous malformation (BAVM) was investigated in the present study. A total of 53 patients with BAVM and 120 healthy controls were recruited, all of whom were Han Chinese from South China. There were no statistically significant differences in the IL-17A-197 guanine/adenine (G/A) or TGF-β1-509 cytosine/thymine (C/T) genotypes or gene frequencies between BAVM patients and controls (p>0.05), but the gene frequency of the TGFR-β2-875 A/G genotype in patients with BAVM was significantly higher (p<0.05). Furthermore, the frequencies of the G allele of IL-17A-197 G/A and TGFR-β2-875 A/G in BAVM patients with hemorrhage were higher than those without hemorrhage. TGFR-β2-875 G/G genotype is a risk factor for BAVM, and the IL-17A-197 G/A and TGFR-β2-875 A/G genotype is closely related to hemorrhage risk for patients with BAVM.

Developmental regulation of the neuroinflammatory responses to LPS and/or hypoxia-ischemia between preterm and term neonates: An experimental study

Background

Preterm and term newborns are at high risk of brain damage as well as subsequent cerebral palsy and learning disabilities. Indeed, hypoxia-ischemia (HI), pathogen exposures, and associated intracerebral increase of pro-inflammatory cytokines have all been linked to perinatal brain damage. However, the developmental effects of potential variations of pro- and anti-inflammatory cytokine ratios remain unknown.

Methods

Using rat models of perinatal brain damage induced by exposures to lipopolysaccharide (LPS) and/or HI at distinct levels of maturity, we compared cytokine expression at stages of cerebral development equivalent to either preterm (postnatal day 1, P1) or term (P12) newborns.

Results

At P1, expression of anti-inflammatory cytokine within the brain was either not modulated (IL-6, IL-10) or down-regulated (IL-1ra, TGF-β1) by HI, LPS or LPS+HI. In contrast, there was at P12 an up-regulation of all anti-inflammatory cytokines studied in HI or LPS+HI condition, but not after LPS exposure. Interestingly, IL-1β was the main pro-inflammatory cytokine up-regulated moderately at P1, and strongly at P12, with a weak co-expression of TNF-α observed mainly at P12. These age-dependant inflammatory reactions were also accompanied, under HI and LPS+HI conditions, at P12 only, by combined: (i) expression of chemokines CINC-1 and MCP-1, (ii) blood-brain barrier (BBB) leakage, and (iii) intracerebral recruitment of systemic immune cells such as neutrophils. In contrast, sole LPS induced IL-1β responses mainly within white matter at P1 and mainly within gray matter at P12, that were only associated with early MCP-1 (but no CINC-1) induction at both ages, without any recruitment of neutrophils and CD68+ cells.

Conclusion

HI and LPS+HI induce pro-inflammatory oriented immune responses in both preterm and term like brains, with a maximal inflammatory response triggered by the combination of LPS+HI. The profile of these neuroinflammatory responses presented striking variations according to age: no or down-regulated anti-inflammatory responses associated with mainly IL-1β release in preterm-like brains (P1), in sharp contrast to term-like brains (P12) presenting stronger anti-and pro-inflammatory responses, including both IL-1β and TNF-α releases, and BBB leakage. These developmental-dependant variations of neuroinflammatory response could contribute to the differential pattern of brain lesions observed across gestational ages in humans. This also highlights the necessity to take into consideration the maturation stage, of both brain and immune systems, in order to develop new anti-inflammatory neuroprotective strategies.

Reactive astrocytes as therapeutic targets for CNS disorders

Reactive astrogliosis has long been recognized as a ubiquitous feature of CNS pathologies. Although its roles in CNS pathology are only beginning to be defined, genetic tools are enabling molecular dissection of the functions and mechanisms of reactive astrogliosis in vivo. It is now clear that reactive astrogliosis is not simply an all-or-nothing phenomenon but, rather, is a finely gradated continuum of molecular, cellular, and functional changes that range from subtle alterations in gene expression to scar formation. These changes can exert both beneficial and detrimental effects in a context-dependent manner determined by specific molecular signaling cascades. Dysfunction of either astrocytes or the process of reactive astrogliosis is emerging as an important potential source of mechanisms that might contribute to, or play primary roles in, a host of CNS disorders via loss of normal or gain of abnormal astrocyte activities. A rapidly growing understanding of the mechanisms underlying astrocyte signaling and reactive astrogliosis has the potential to open doors to identifying many molecules that might serve as novel therapeutic targets for a wide range of neurological disorders. This review considers general principles and examines selected examples regarding the potential of targeting specific molecular aspects of reactive astrogliosis for therapeutic manipulations, including regulation of glutamate, reactive oxygen species, and cytokines.

Neuroinflammation is a key player in Parkinson's disease and a prime target for therapy

Parkinson's disease (PD) is a neurodegenerative movement disorder characterized by the progressive loss of dopaminergic neurons in the substantia nigra and depletion of dopamine in the striatum, which lead to pathological and clinical abnormalities. Increasing evidence has demonstrated that inflammation is the fundamental process contributing to neuron death in PD. Neuroinflammation, which is characterized by activated microglia and infiltrating T cells at sites of neuronal injury, is a prominent contributor to the pathogenesis of progressive PD. Microglia play a critical role in forming a self-propelling cycle leading to sustained chronic neuroinflammation and driving the progressive neurodegeneration in PD. This activation depends heavily on the respiratory burst within the microglia, which in turn regulates a number of downstream pro-inflammatory activities. On the other hand, the adaptive immune responses, most notably T cells, are now emerging as important components of the inflammatory response that contribute to the pathogenesis of PD. This review paper focus on the understanding of the inflammatory etiology of PD, as well as the molecular signaling involved in this inflammatory response, with the aim to provide more effective treatments to slow down or halt the progression of chronic inflammation-induced CNS disorders, such as PD.

The role of astroglia in neuroprotection

Astrocytes are the main neural cell type responsible for the maintenance of brain homeostasis. They form highly organized anatomical domains that are interconnected into extensive networks. These features, along with the expression of a wide array of receptors, transporters, and ion channels, ideally position them to sense and dynamically modulate neuronal activity. Astrocytes cooperate with neurons on several levels, including neurotransmitter trafficking and recycling, ion homeostasis, energy metabolism, and defense against oxidative stress. The critical dependence of neurons upon their constant support confers astrocytes with intrinsic neuroprotective properties which are discussed here. Conversely, pathogenic stimuli may disturb astrocytic function, thus compromising neuronal functionality and viability. Using neuroinflammation, Alzheimer's disease, and hepatic encephalopathy as examples, we discuss how astrocytic defense mechanisms may be overwhelmed in pathological conditions, contributing to disease progression.

Transcriptome profiling reveals TGF-beta signaling involvement in epileptogenesis

Brain injury may result in the development of epilepsy, one of the most common neurological disorders. We previously demonstrated that albumin is critical in the generation of epilepsy after blood-brain barrier (BBB) compromise. Here, we identify TGF-beta pathway activation as the underlying mechanism. We demonstrate that direct activation of the TGF-beta pathway by TGF-beta1 results in epileptiform activity similar to that after exposure to albumin. Coimmunoprecipitation revealed binding of albumin to TGF-beta receptor II, and Smad2 phosphorylation confirmed downstream activation of this pathway. Transcriptome profiling demonstrated similar expression patterns after BBB breakdown, albumin, and TGF-beta1 exposure, including modulation of genes associated with the TGF-beta pathway, early astrocytic activation, inflammation, and reduced inhibitory transmission. Importantly, TGF-beta pathway blockers suppressed most albumin-induced transcriptional changes and prevented the generation of epileptiform activity. Our present data identifies the TGF-beta pathway as a novel putative epileptogenic signaling cascade and therapeutic target for the prevention of injury-induced epilepsy.