Conditional deletion of Notch1 and Notch2 genes in excitatory neurons of postnatal forebrain does not cause neurodegeneration or reduction of Notch mRNAs and proteins

Activation of Notch signaling requires intramembranous cleavage by γ-secretase to release the intracellular domain. We previously demonstrated that presenilin and nicastrin, components of the γ-secretase complex, are required for neuronal survival in the adult cerebral cortex. Here we investigate whether Notch1 and/or Notch2 are functional targets of presenilin/γ-secretase in promoting survival of excitatory neurons in the adult cerebral cortex by generating Notch1, Notch2, and Notch1/Notch2 conditional knock-out (cKO) mice. Unexpectedly, we did not detect any neuronal degeneration in the adult cerebral cortex of these Notch cKO mice up to ～2 years of age, whereas conditional inactivation of presenilin or nicastrin using the same αCaMKII-Cre transgenic mouse caused progressive, striking neuronal loss beginning at 4 months of age. More surprisingly, we failed to detect any reduction of Notch1 and Notch2 mRNAs and proteins in the cerebral cortex of Notch1 and Notch2 cKO mice, respectively, even though Cre-mediated genomic deletion of the floxed Notch1 and Notch2 exons clearly took place in the cerebral cortex of these cKO mice. Furthermore, introduction of Cre recombinase into primary cortical cultures prepared from postnatal floxed Notch1/Notch2 pups, where Notch1 and Notch2 are highly expressed, completely eliminated their expression, indicating that the floxed Notch1 and Notch2 alleles can be efficiently inactivated in the presence of Cre. Together, these results demonstrate that Notch1 and Notch2 are not involved in the age-related neurodegeneration caused by loss of presenilin or γ-secretase and suggest that there is no detectable expression of Notch1 and Notch2 in pyramidal neurons of the adult cerebral cortex.     

The endocannabinoid 2-arachidonoyl-glycerol activates human neutrophils: critical role of its hydrolysis and de novo leukotriene B4 biosynthesis

Although endocannabinoids are important players in nociception and obesity, their roles as immunomodulators remain elusive. The main endocannabinoids described to date, namely 2-arachidonoyl-glycerol (2-AG) and arachidonyl-ethanolamide (AEA), induce an intriguing profile of pro- and anti-inflammatory effects. This could relate to cell-specific cannabinoid receptor expression and/or the action of endocannabinoid-derived metabolites. Importantly, 2-AG and AEA comprise a molecule of arachidonic acid (AA) in their structure and are hydrolyzed rapidly. We postulated the following: 1) the released AA from endocannabinoid hydrolysis would be metabolized into eicosanoids; and 2) these eicosanoids would mediate some of the effects of endocannabinoids. To confirm these hypotheses, experiments were performed in which freshly isolated human neutrophils were treated with endocannabinoids. Unlike AEA, 2-AG stimulated myeloperoxidase release, kinase activation, and calcium mobilization by neutrophils. Although 2-AG did not induce the migration of neutrophils, it induced the release of a migrating activity for neutrophils. 2-AG also rapidly (1 min) induced a robust biosynthesis of leukotrienes, similar to that observed with AA. The effects of 2-AG were not mimicked nor prevented by cannabinoid receptor agonists or antagonists, respectively. Finally, the blockade of either 2-AG hydrolysis, leukotriene (LT) B(4) biosynthesis, or LTB(4) receptor 1 activation prevented all the effects of 2-AG on neutrophil functions. In conclusion, we demonstrated that 2-AG potently activates human neutrophils. This is the consequence of 2-AG hydrolysis, de novo LTB(4) biosynthesis, and an autocrine activation loop involving LTB(4) receptor 1.     

Rac1 changes the substrate specificity of gamma-secretase between amyloid precursor protein and Notch1

Beta amyloid peptide is generated from amyloid precursor protein (APP) by proteolytic cleavage of β- and γ-secretases, and plays a critical role in the pathogenesis of Alzheimer’s disease. Since γ-secretase cleaves several proteins including APP and Notch in a number of cell types, it is important to understand the conditions determining γ-secretase substrate specificity. In the present study, inhibition of Rac1 attenuated γ-secretase activity for APP, resulting in decreased production of the APP intracellular domain but accumulated C-terminal fragments (APP-CTF). In contrast, Rac1 inhibitor, NSC23766 increased production of the Notch1 intracellular domain but slightly decreased the ectodomain-shed form of Notch1 (NotchΔE). To elucidate the mechanism underlying these observations, we performed co-immunoprecipitation experiments to analyze the interaction between Rac1 and presenilin1 (PS1), a component of the γ-secretase complex. Inhibition of Rac1 enhanced its interaction with PS1. Under the same condition, PS1 interacted more strongly with NotchΔE than with APP-CTF. Our results suggested that PS1 determines the preferred substrate for γ-secretase between APP and Notch1, depending on the activation status of Rac1.     

Endocannabinoids and Inflammatory Response in Periodontal Ligament Cells

Endocannabinoids are associated with multiple regulatory functions in several tissues. The main endocannabinoids, anandamide (AEA) and 2-arachidonylglycerol (2-AG), have been detected in the gingival crevicular fluid of periodontitis patients, but the association between periodontal disease or human periodontal ligament cells (hPdLCs) and endocannabinoids still remain unclear. The aim of the present study was to examine the effects of AEA and 2-AG on the proliferation/viability and cytokine/chemokine production of hPdLCs in the presence/absence of Porphyromonas gingivalis lipopolysaccharide (P. gingivalis LPS). The proliferation/viability of hPdLCs was measured using 3,4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide (MTT)-assay. Interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemotactic protein-1 (MCP-1) levels were examined at gene expression and protein level by real-time PCR and ELISA, respectively. AEA and 2-AG did not reveal any significant effects on proliferation/viability of hPdLCs in the absence of P. gingivalis LPS. However, hPdLCs viability was significantly increased by 10–20 µM AEA in the presence of P. gingivalis LPS (1 µg/ml). In the absence of P. gingivalis LPS, AEA and 2-AG did not exhibit any significant effect on the expression of IL-8 and MCP-1 expression in hPdLCs, whereas IL-6 expression was slightly enhanced by 10 µM 2-AG and not affected by AEA. In P.gingivalis LPS stimulated hPdLCs, 10 µM AEA down-regulated gene-expression and protein production of IL-6, IL-8, and MCP-1. In contrast, 10 µM 2-AG had an opposite effect and induced a significant up-regulation of gene and protein expression of IL-6 and IL-8 (P<0.05) as well as gene-expression of MCP-1 in P. gingivalis LPS stimulated hPdLCs. Our data suggest that AEA appears to have an anti-inflammatory and immune suppressive effect on hPdLCs’ host response to P.gingivalis LPS, whereas 2-AG appears to promote detrimental inflammatory processes. In conclusion, AEA and 2-AG might play an important role in the modulation of periodontal inflammation.     

The Endocannabinoid,Anandamide, Augments Notch-1 Signaling in Cultured Cortical Neurons Exposed to Amyloid-β and in the Cortex of Aged Rats

Aberrant Notch signaling has recently emerged as a possible mechanism for the altered neurogenesis, cognitive impairment, and learning and memory deficits associated with Alzheimer disease (AD). Recently, targeting the endocannabinoid system in models of AD has emerged as a potential approach to slow the progression of the disease process. Although studies have identified neuroprotective roles for endocannabinoids, there is a paucity of information on modulation of the pro-survival Notch pathway by endocannabinoids. In this study the influence of the endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol, on the Notch-1 pathway and on its endogenous regulators were investigated in an in vitro model of AD. We report that AEA up-regulates Notch-1 signaling in cultured neurons. We also provide evidence that although Aβ_1–42 increases expression of the endogenous inhibitor of Notch-1, numb (Nb), this can be prevented by AEA and 2-arachidonoylglycerol. Interestingly, AEA up-regulated Nct expression, a component of γ-secretase, and this was found to play a crucial role in the enhanced Notch-1 signaling mediated by AEA. The stimulatory effects of AEA on Notch-1 signaling persisted in the presence of Aβ_1–42. AEA was found to induce a preferential processing of Notch-1 over amyloid precursor protein to generate Aβ_1–40. Aging, a natural process of neurodegeneration, was associated with a reduction in Notch-1 signaling in rat cortex and hippocampus, and this was restored with chronic treatment with URB 597. In summary, AEA has the proclivity to enhance Notch-1 signaling in an in vitro model of AD, which may have relevance for restoring neurogenesis and cognition in AD.     

Toward the structure of presenilin/γ-secretase and presenilin homologs

Presenilin is the catalytic component of the γ-secretase complex, a membrane-embedded aspartyl protease that plays a central role in biology and in the pathogenesis of Alzheimer’s disease. Upon assembly with its three protein cofactors (nicastrin, Aph-1 and Pen-2), presenilin undergoes autoproteolysis into two subunits, each of which contributes one of the catalytic aspartates to the active site. A family of presenilin homologs, including signal peptide peptidase, possess proteolytic activity without the need for other protein factors, and these simpler intramembane aspartyl proteases have given insight into the action of presenilin within the γ-secretase complex. Cellular and molecular studies support a nine-transmembrane topology for presenilins and their homologs, and small-molecule inhibitors and cysteine scanning with crosslinking have suggested certain presenilin residues and regions that contribute to substrate recognition and handling. Identification of partial complexes has also offered clues to protein–protein interactions within the γ-secretase complex. Biophysical methods have allowed 3D views of the γ-secretase complex and presenilins. Most recently, the crystal structure of a microbial presenilin homolog has confirmed a nine-transmembrane topology and intramembranous location and proximity of the two conserved and essential aspartates. The crystal structure also provides a platform for the formulation of specific hypotheses regarding substrate interaction and catalysis as well as the pathogenic mechanism of Alzheimer-causing presenilin mutations. This article is part of a Special Issue entitled: Intramembrane Proteases.     

Presenilin is the molecular target of acidic γ-secretase modulators in living cells

The intramembrane-cleaving protease γ-secretase catalyzes the last step in the generation of toxic amyloid-β (Aβ) peptides and is a principal therapeutic target in Alzheimer's disease. Both preclinical and clinical studies have demonstrated that inhibition of γ-secretase is associated with prohibitive side effects due to suppression of Notch processing and signaling. Potentially safer are γ-secretase modulators (GSMs), which are small molecules that selectively lower generation of the highly amyloidogenic Aβ42 peptides but spare Notch processing. GSMs with nanomolar potency and favorable pharmacological properties have been described, but the molecular mechanism of GSMs remains uncertain and both the substrate amyloid precursor protein (APP) and subunits of the γ-secretase complex have been proposed as the molecular target of GSMs. We have generated a potent photo-probe based on an acidic GSM that lowers Aβ42 generation with an IC(50) of 290 nM in cellular assays. By combining in vivo photo-crosslinking with affinity purification, we demonstrated that this probe binds the N-terminal fragment of presenilin (PSEN), the catalytic subunit of the γ-secretase complex, in living cells. Labeling was not observed for APP or any of the other γ-secretase subunits. Binding was readily competed by structurally divergent acidic and non-acidic GSMs suggesting a shared mode of action. These findings indicate that potent acidic GSMs target presenilin to modulate the enzymatic activity of the γ-secretase complex.     

基于液相色谱-串联质谱技术（LC-MS/MS）检测癫痫小鼠毛发中内源性大麻素（2-AG、AEA）的含量

摘要 目的：基于液相色谱-串联质谱技术（LC-MS/MS）对癫痫小鼠毛发中内源性大麻素（2-AG、AEA）进行含量检测。方法：匹鲁卡品腹腔注射方法建立小鼠癫痫模型,采用LC-MS/MS检测毛发中2-AG、AEA的含量,对比分析不同癫痫发作分级小鼠2-AG、AEA含量差异。结果：标准品溶液中AEA、2-AG的保留时间分别为14.3 min,18.1 min,毛发样品中AEA、2-AG的保留时间分别为14.0 min,17.7 min。毛发样品中AEA的检测限、定量限、回收率为0.7 pg/mg、2.1 pg/mg和97.9%,毛发样品中2-AG的检测限、定量限、回收率为3.2 pg/mg、10.9 pg/mg和99.3%,且二者的日内、日间变异系数均低于15%。癫痫发作1级、2级、3级、4级、5级这五个分级癫痫小鼠的AEA含量和2-AG含量依次升高,不同癫痫发作分级小鼠毛发样品中AEA含量和2-AG含量比较（P均<0.05）。结论：LC-MS/MS测定癫痫小鼠毛发中2-AG、AEA的表达量,具有灵敏度更高,样品使用量更少等优点,可大规模样本研究。     

Familial Alzheimer disease presenilin-1 mutations alter the active site conformation of γ-secretase

Presenilin-1 (PS1) is the catalytic subunit of γ-secretase, and mutations in this protein cause familial Alzheimer Disease (FAD). However, little is known about how these mutations affect the active site of γ-secretase. Here, we show that PS1 mutations alter the S2 subsite within the active site of γ-secretase using a multiple photoaffinity probe approach called "photophore walking." Moreover, we developed a unique in vitro assay with a biotinylated recombinant Notch1 substrate and demonstrated that PS1 FAD mutations directly and significantly reduced γ-secretase activity for Notch1 cleavage. Substitution of the Notch Cys-1752 residue, which interacts with the S2 subsite, with Val, Met, or Ile has little effect on wild-type PS1 but leads to more efficient substrates for mutant PS1s. This study indicates that alteration of this S2 subsite plays an important role in determining the activity and specificity of γ-secretase for APP and Notch1 processing, which provides structural basis and insights on how certain PS1 FAD mutations lead to AD pathogenesis.     

Lipopolysaccharide induces anandamide synthesis in macrophages via CD14/MAPK/phosphoinositide 3-kinase/NF-kappaB independently of platelet-activating factor

Macrophage-derived endocannabinoids have been implicated in endotoxin (lipopolysaccharide (LPS))-induced hypotension, but the endocannabinoid involved and the mechanism of its regulation by LPS are unknown. In RAW264.7 mouse macrophages, LPS (10 ng/ml) increases anandamide (AEA) levels >10-fold via CD14-, NF-kappaB-, and p44/42-dependent, platelet-activating factor-independent activation of the AEA biosynthetic enzymes, N-acyltransferase and phospholipase D. LPS also induces the AEA-degrading enzyme fatty acid amidohydrolase (FAAH), and inhibition of FAAH activity potentiates, whereas actinomycin D or cycloheximide blocks the LPS-induced increase in AEA levels and N-acyltransferase and phospholipase D activities. In contrast, cellular levels of the endocannabinoid 2-arachidonoylglycerol (2-AG) are unaffected by LPS but increased by platelet-activating factor. LPS similarly induces AEA, but not 2-AG, in mouse peritoneal macrophages where basal AEA levels are higher, and the LPS-stimulated increase in AEA is potentiated in cells from FAAH-/- as compared with FAAH+/+ mice. Intravenous administration of 107 LPS-treated mouse macrophages to anesthetized rats elicits hypotension, which is much greater in response to FAAH-/- than FAAH+/+ cells and is susceptible to inhibition by SR141716, a cannabinoid CB1 receptor antagonist. We conclude that AEA and 2-AG synthesis are differentially regulated in macrophages, and AEA rather than 2-AG is a major contributor to LPS-induced hypotension.     

The endocannabinoid system in neurodegeneration

Endocannabinoids are bioactive lipids, that comprise amides, esters and ethers of long chain polyunsaturated fatty acids. Anandamide (N-arachidonoylethanolamine; AEA) and 2-arachidonoylglycerol (2-AG) are the best studied endocannabinoids, and act as agonists of cannabinoid receptors. Thus, AEA and 2-AG mimic several pharmacological effects of the exogenous cannabinoid delta9-tetrahydrocannabinol, the psychoactive principle of hashish and marijuana. It is known that the activity of endocannabinoids at their receptors is limited by cellular uptake through specific membrane transporters, followed by intracellular degradation by a fatty acid amide hydrolase (for AEA and partly 2-AG) or by a monoacylglycerol lipase (for 2-AG). Together with AEA, 2-AG and congeners, the proteins that bind, transport and metabolize these lipids form the "endocannabinoid system". This new system will be briefly presented in this review, in order to put in a better perspective the role of the endocannabinoid pathway in neurodegenerative disorders, like Parkinson's disease, Huntington's disease, and multiple sclerosis. In addition, the potential exploitation of antagonists of endocannabinoid receptors, or of inhibitors of endocannabinoid metabolism, as next-generation therapeutics will be discussed.     

Hydrogen Sulfide Selectively Inhibits γ-Secretase Activity and Decreases Mitochondrial Aβ Production in Neurons from APP/PS1 Transgenic Mice

Hydrogen sulfide (H₂S) is now considered to be a gasotransmitter and may be involved in the pathological process of Alzheimer’s disease (AD). A majority of APP is associated with mitochondria and is a substrate for the mitochondrial γ-secretase. The mitochondria-associated APP metabolism where APP intracellular domains (AICD) and Aβ are generated locally and may contribute to mitochondrial dysfunction in AD. Here, we aimed to investigate the ability of H₂S to mediate APP processing in mitochondria and assessed the possible mechanisms underlying H₂S-mediated AD development. We treated neurons from APP/PS1 transgenic mice with a range of sodium hydrosulfide (NaHS) concentrations. NaHS attenuated APP processing and decreased Aβ production in mitochondria. Meanwhile, NaHS did not changed BACE-1 and ADAM10 (a disintegrin and metalloprotease 10) protein levels, but NaHS (30 μM) significantly increased the levels of presenilin 1(PS1), PEN-2, and NCT, as well as improved the γ-secretase activity, while NaHS (50 μM) exhibits the opposing effects. Furthermore, the intracellular ATP and the COX IV activity of APP/PS1 neurons were increased after 30 μM NaHS treatment, while the ROS level was decreased and the MMP was stabilized. The effect of NaHS differs from DAPT (a non-selective γ-secretase inhibitor), and it selectively inhibited γ-secretase in vitro, without interacting with Notch and modulating its cleavage. The results indicated that NaHS decreases Aβ accumulation in mitochondria by selectively inhibiting γ-secretase. Thus, we provide a mechanistic view of NaHS is a potential anti-AD drug candidate and it may decrease Aβ deposition in mitochondria by selectively inhibiting γ-secretase activity and therefore protecting the mitochondrial function during AD conditions.

     

Identification of two novel synaptic γ-secretase associated proteins that affect amyloid β-peptide levels without altering Notch processing

Synaptic degeneration is one of the earliest hallmarks of Alzheimer disease (AD) and results in loss of cognitive function. One of the causative agents for the synaptic degeneration is the amyloid β-peptide (Aβ), which is formed from its precursor protein by two sequential cleavages mediated by β- and γ-secretase. We have earlier shown that γ-secretase activity is enriched in synaptic compartments, suggesting that the synaptotoxic Aβ is produced locally. Proteins that interact with γ-secretase at the synapse and regulate the production of Aβ can therefore be potential therapeutic targets. We used a recently developed affinity purification approach to identify γ-secretase associated proteins (GSAPs) in synaptic membranes and synaptic vesicles prepared from rat brain. Liquid chromatography-tandem mass spectrometry analysis of the affinity purified samples revealed the known γ-secretase components presenilin-1, nicastrin and Aph-1b along with a number of novel potential GSAPs. To investigate the effect of these GSAPs on APP processing, we performed siRNA experiments to knock down the expression of the GSAPs and measured the Aβ levels. Silencing of NADH dehydrogenase [ubiquinone] iron-sulfur protein 7 (NDUFS7) resulted in a decrease in Aβ levels whereas silencing of tubulin polymerization promoting protein (TPPP) resulted in an increase in Aβ levels. Treatment with γ-secretase inhibitors often results in Notch-related side effects and therefore we also studied the effect of the siRNAs on Notch processing. Interestingly, silencing of TPPP or NDUFS7 did not affect cleavage of Notch. We also studied the expression of TPPP and NDUFS7 in control and AD brain and found NDUFS7 to be highly expressed in vulnerable neurons such as pyramidal neurons in the hippocampus, whereas TPPP was found to accumulate in intraneuronal granules and fibrous structures in hippocampus from AD cases. In summary, we here report on two proteins, TPPP and NDUFS7, which interact with γ-secretase and alter the Aβ levels without affecting Notch cleavage.     

Identification of presenilin 1-selective γ-secretase inhibitors with reconstituted γ-secretase complexes

Accumulation of the β-amyloid (Aβ) peptides is one of the major pathologic hallmarks in the brains of Alzheimer's disease (AD) patients. Aβ is generated by sequential proteolytic cleavage of the amyloid precursor protein (APP) catalyzed by β- and γ-secretases. Inhibition of Aβ production by γ-secretase inhibitors (GSIs) is thus being pursued as a target for treatment of AD. In addition to processing APP, γ-secretase also catalyzes proteolytic cleavage of other transmembrane substrates, with the best characterized one being the cell surface receptor Notch. GSIs reduce Aβ production in animals and humans but also cause significant side effects because of the inhibition of Notch processing. The development of GSIs that reduce Aβ production and have less Notch-mediated side effect liability is therefore an important goal. γ-Secretase is a large membrane protein complex with four components, two of which have multiple isoforms: presenilin (PS1 or PS2), aph-1 (aph-1a or aph-1b), nicastrin, and pen-2. Here we describe the reconstitution of four γ-secretase complexes in Sf9 cells containing PS1--aph-1a, PS1--aph-1b, PS2--aph-1a, and PS2--aph-1b complexes. While PS1--aph-1a, PS1--aph-1b, and PS2--aph-1a complexes displayed robust γ-secretase activity, the reconstituted PS2--aph-1b complex was devoid of detectable γ-secretase activity. γ-Secretase complexes containing PS1 produced a higher proportion of the toxic species Aβ42 than γ-secretase complexes containing PS2. Using the reconstitution system, we identified MRK-560 and SCH 1500022 as highly selective inhibitors of PS1 γ-secretase activity. These findings may provide important insights into developing a new generation of γ-secretase inhibitors with improved side effect profiles.     

In vitro reconstitution of gamma-secretase activity using yeast microsomes

γ-Secretase is composed of at least four transmembrane proteins, presenilin (PS) 1/2, nicastrin, anterior pharynx-1 (Aph-1) and presenilin enhancer-2 (Pen-2), and cleaves amyloid precursor protein (APP) to produce amyloid β peptides (Aβ) that is deposited in the brains of Alzheimer disease. However, the mechanism of γ-secretase-mediated cleavage remains unclear. To examine the enzymatic properties of γ-secretase, we established an in vitro assay system using Saccharomyces cerevisiae, which does not possess homologs of human PS1/2, nicastrin, Aph-1, or Pen-2. We transformed these subunits and the substrate in pep4Δ cells with vacuole proteases inactivated, and microsome was isolated for in vitro assay. In the assay, Aβ40, Aβ42, and Aβ43 were produced with an optimal pH of ∼7.0. We also detected Aβ-production by yeast endogenous protease(s), which was abolished by the addition of phosphatidyl choline. This novel system will facilitate the analysis of substrate recognition by γ-secretase.     

Opposing actions of Notch1 and VEGF in post-natal cardiac valve endothelial cells

The endothelium of the cardiac valves is unique compared the rest of the vasculature in its ability to undergo an endothelial-to-mesenchymal transformation (EMT) in vitro in response to transforming growth factor-β (TGF-β). EMT is a critical event during embryonic valve development, and both VEGF-A and Notch1 have been shown to function in this process. Here we investigate the effects of VEGF-A and Notch1 on EMT in clonal endothelial cell (EC) populations isolated from adult aortic valve leaflets. VEGF-A inhibited TGF-β-induced EMT. Endothelial growth, however, was not affected by VEGF-A or TGF-β. A positive role for Notch1 was revealed in three experiments: (1) TGF-β induced Notch1 mRNA in valve ECs, (2) a γ-secretase inhibitor of Notch1 signaling blocked EMT, and (3) overexpression of a ligand-independent form of Notch1 induced EMT. These results demonstrate, for the first time, that VEGF-A and Notch1 play opposing roles in regulating EMT in post-natal valve endothelium.     

Biochemistry and pharmacology of the endocannabinoids arachidonylethanolamide and 2-arachidonylglycerol

The purpose of this review is to discuss the cellular synthesis and inactivation of two putative endogenous ligands of the cannabinoid receptor, N-arachidonylethanolamine (AEA) and 2-arachidonylglycerol (2-AG). Both ligands are synthesized by neurons and brain tissue in response to increased intracellular calcium concentrations. Both ligands are substrates for fatty acid amide hydrolase (FAAH). Both AEA and 2-AG bind to the neuronal form of the cannabinoid receptor (CB1). AEA binds the receptor with moderate affinity and has the characteristics of a partial agonist, whereas, 2-AG binds with low affinity but exhibits full efficacy. Two possible physiological roles of the endocannabinoids and the CB1 receptor are discussed: the regulation of gestation and the regulation of gastrointestinal motility.     

Notch Signaling Regulates Microglial Activation and Inflammatory Reactions in a Rat Model of Temporal Lobe Epilepsy

The inflammatory response mediated by microglia in the central nervous system is closely related to epilepsy. Notch signaling plays an important role in the microglial activation during hypoxia. This study aimed to investigate whether Notch signaling is involved in microglial activation and subsequent inflammation-related neuronal injury during the process of epileptogenesis in a rat model of temporal lobe epilepsy. By using western blotting, real-time quantitative PCR, immunohistochemistry and immunofluorescence labeling, we found that the expression of Notch signaling increased after status epilepticus and that a γ-secretase inhibitor could significantly inhibit the upregulation of Notch signaling, the activation of microglia, and the release of proinflammatory cytokines. Likewise, the neuronal apoptosis and loss in the hippocampus after SE were attenuated by the γ-secretase inhibitor. These results suggest that Notch signaling plays a key role in neuroinflammation and inflammation-related neuronal damage in epilepsy, and γ-secretase inhibitors may become a novel prospective therapeutic agent for epilepsy.