PARP-1 inhibitor alleviates cerebral ischemia/reperfusion injury by reducing PARylation of HK-1 and LDH in mice

Poly (ADP-ribose) polymerase-1 (PARP-1) activity significantly increases during cerebral ischemia/reperfusion. PARP-1 is an NAD+-consumption enzyme. PARP-1 hyperactivity causes intracellular NAD+ deficiency and bioenergetic collapse, contributing to neuronal death. Besides, the powerful trigger of PARP-1 causes the catalyzation of poly (ADP-ribosyl)ation (PARylation), a posttranslational modification of proteins. Here, we found that PARP-1 was activated in the ischemic brain tissue during middle-cerebral-artery occlusion and reperfusion (MCAO/R) for 24 h, and PAR accumulated in the neurons in mice. Using immunoprecipitation, Western blotting, liquid chromatography-mass spectrometry, and 3D-modeling analysis, we revealed that the activation of PARP-1 caused PARylation of hexokinase-1 and lactate dehydrogenase-B, which, therefore, caused the inhibition of these enzyme activities and the resulting cell energy metabolism collapse. PARP-1 inhibition significantly reversed the activity of hexokinase and lactate dehydrogenase, decreased infarct volume, and improved neuronal deficiency. PARP-1 inhibitor combined with pyruvate further alleviated MCAO/R-induced ischemic brain injury in mice. As such, we conclude that PARP-1 inhibitor alleviates neuronal death partly by inhibiting the PARylation of metabolic-related enzymes and reversing metabolism reprogramming during cerebral ischemia/reperfusion injury in mice. PARP-1 inhibitor combined with pyruvate might be a promising therapeutic approach against brain ischemia/reperfusion injury.

[Classification, diagnosis and treatment status of pulmonary hypertension from 2012 to 2019: a single center study in Yunnan province]

Objective: To analyze the classification, diagnosis and treatment status of patients with pulmonary hypertension (PH) in Yunnan province. Methods: This was a retrospective study. Hospitalized patients with PH at Yan'an Affiliated Hospital of Kunming Medical University from January 2012 to December 2019 were enrolled. The clinical data of enrolled patients, including demographic data, comorbidities, targeted drug therapy, echocardiography and right heart catheterization results, were obtained through the electronic medical record system. The composition ratio of PH, diagnosis and treatment were analyzed. Results: A total of 13 590 patients with PH were enrolled, accounting for 3.09% (13 590/440 056) of the total number of hospitalizations during the same period. The composition of PH was predominantly pulmonary arterial hypertension (PAH) (55.50% (7 542/13 590)), followed by pulmonary hypertension (PH) caused by left heart disease (24.16% (3 284/13 590)). Among them, PAH could be subdivided into four types: idiopathic pulmonary arterial hypertension (IPAH), PAH associated with connective tissue disease, PAH associated with portal hypertension, and PAH associated with congenital heart disease (CHD-PAH), with CHD-PAH as the predominating type (98.09% (7 398/7 542). Patients with PAH were predominantly adolescents. In hospitalized patients with PH, from 2012 to 2019, the proportion of children and adolescents showed a decreasing trend from year to year, and the proportion of middle-aged and older adults showed a significant increasing trend, and the proportion of female patients showed a gradual decreasing trend, and the proportion of patients with comorbid hypertension, diabetes mellitus, coronary artery disease, arrhythmia, and pneumonia showed an increasing trend. A total of 1 034 patients (7.61% (1 034/13 590)) underwent right heart catheterization. The concordance rate between echocardiographic and right heart catheterization findings was (86.98% (875/1 006)). A total of 2 574 (18.94%) of PH patients were treated with PAH targeted drugs, of which 58.16% (1 497/2 574) were treated with monotherapy. Among the PH patients treated with PAH targeted drugs, the majority of patients were PAH patients (86.44% (2 225/2 574)), and 83.53% (2 150/2 574) patients treated with PAH targeted drugs were CHD-PAH. Conclusions: Hospitalized PH patients in our center between 2012 and 2019 are predominantly CHD-PAH, and the proportion of patients receiving right heart catheterization and targeted drug therapy is relatively low. The percentage of middle-aged and elderly PH patients shows an increasing trend from year to year, as well as the percentage of those with concomitant comorbidities.

The Depletion of NAMPT Disturbs Mitochondrial Homeostasis and Causes Neuronal Degeneration in Mouse Hippocampus

Nicotinamide phosphoribosyltransferase (NAMPT) is the key enzyme in the salvaging synthesis pathway of the nicotinamide adenine dinucleotide (NAD). Both NAMPT and NAD progressively decline upon aging and neurodegenerative diseases. The depletion of NAMPT induces mitochondrial dysfunction in motor neurons and causes bioenergetic stress in neurons. However, the roles of NAMPT in hippocampus neurons need to be further studied. Using floxed Nampt (Nampt^flox/flox) mice, we knocked out Nampt specifically in the hippocampus CA1 neurons by injecting rAAV-hSyn-Cre-APRE-pA. The depletion of NAMPT in hippocampus neurons induced cognitive deficiency in mice. Nevertheless, no morphological change of hippocampus neurons was observed with immunofluorescent imaging. Under the transmission electron microscope, we observed mitochondrial swollen and mitochondrial number decreasing in the cell body and the neurites of hippocampus neurons. In addition, we found the intracellular Aβ (6E10) increased in the hippocampus CA1 region. The intensity of Aβ42 remained unchanged, but it tended to aggregate. The GFAP level, an astrocyte marker, and the Iba1 level, a microglia marker, significantly increased in the mouse hippocampus. In the primary cultured rat neurons, NAMPT inhibition by FK866 decreased the NAD level of neurons at > 10^-9 M. FK866 dropped the mitochondrial membrane potential in the cell body of neurons at > 10^-9 M and in the dendrite of neurons at > 10^-8 M. FK866 decreased the number and shortened the length of branches of neurons at > 10^-7 M. Together, likely due to the injury of mitochondria, the decline of NAMPT level can be a critical risk factor for neurodegeneration.

Ischemia-Reperfusion Injury in a Simulated Lung Transplant Setting Differentially Regulates Transcriptomic Profiles between Human Lung Endothelial and Epithelial Cells

Current understanding of mechanisms of ischemia-reperfusion-induced lung injury during lung preservation and transplantation is mainly based on clinical observations and animal studies. Herein, we used cell and systems biology approaches to explore these mechanisms at transcriptomics levels, especially by focusing on the differences between human lung endothelial and epithelial cells, which are crucial for maintaining essential lung structure and function. Human pulmonary microvascular endothelial cells and human lung epithelial cells were cultured to confluent, subjected to different cold ischemic times (CIT) to mimic static cold storage with preservation solution, and then subjected to warm reperfusion with a serum containing culture medium to simulate lung transplantation. Cell morphology, viability, and transcriptomic profiles were studied. Ischemia-reperfusion injury induced a CIT time-dependent cell death, which was associated with dramatic changes in gene expression. Under normal control conditions, endothelial cells showed gene clusters enriched in the vascular process and inflammation, while epithelial cells showed gene clusters enriched in protein biosynthesis and metabolism. CIT 6 h alone or after reperfusion had little effect on these phenotypic characteristics. After CIT 18 h, protein-biosynthesis-related gene clusters disappeared in epithelial cells; after reperfusion, metabolism-related gene clusters in epithelial cells and multiple gene clusters in the endothelial cells also disappeared. Human pulmonary endothelial and epithelial cells have distinct phenotypic transcriptomic signatures. Severe cellular injury reduces these gene expression signatures in a cell-type-dependent manner. Therapeutics that preserve these transcriptomic signatures may represent new treatment to prevent acute lung injury during lung transplantation.

Nicotinamide phosphoribosyltransferase inhibitor ameliorates mouse aging-induced cognitive impairment

Nicotinamide phosphoribosyltransferase (NAMPT) is the key enzyme for the synthesis of nicotinamide adenine dinucleotide (NAD) in the salvaging pathway. Though NAMPT inhibitors such as FK866 were originally developed as anti-cancer drugs, they also display neuroprotective effects. Here we show that the administration of FK866 at 0.5 mg/kg (ip, qod) for four weeks, i.e., ∼1% of the dose used for the treatment of cancer, significantly alleviates the aging-induced impairment of cognition and locomotor activity. Mechanistically, FK866 enhanced autophagy, reduced protein aggregation, and inhibited neuroinflammation indicated by decreasing TNFα, IL-6, GFAP, and Iba1 levels in the aged mouse brain. Though FK866 did not affect the total NAD and nicotinamide mononucleotide (NMN) levels in the mouse brain at the dose we used, FK866 increased nicotinamide (NAM) level in the young mouse brain and decreased NAM level in the aged mouse brain. On the other hand, FK866 did not affect the serum glucose, cholesterol, and triglyceride of young and aged mice and exhibited no effects on the various indices of young mice. Thus, the NAMPT inhibitor can be repurpose to counteract the cognitive impairment upon aging. We also envision that NAMPT inhibitor can be used for the treatment of age-related neurodegenerative diseases.

FLIM-FRET-Based Structural Characterization of a Class-A GPCR Dimer in the Cell Membrane

Class-A G protein-coupled receptors (GPCRs) are known to homo-dimerize in the membrane. Yet, methods to characterize the structure of GPCR dimer in the native environment are lacking. Accordingly, the molecular basis and functional relevance of the class-A GPCR dimerization remain unclear. Here, we present the dimeric structural model of GPR17 in the cell membrane. The dimer mainly involves transmembrane helix 5 (TM5) at the interface, with F229 in TM5, a critical residue. An F229A mutation makes GPR17 monomeric regardless of the expression level of the receptor. Monomeric mutants of GPR17 display impaired ERK1/2 activation and cannot be properly internalized upon agonist treatment. Conversely, the F229C mutant is cross-linked as a dimer and behaves like wild-type. Importantly, the GPR17 dimer structure has been modeled using sparse inter-protomer FRET distance restraints obtained from fluorescence lifetime imaging microscopy. The same approach can be applied to characterizing the interactions of other important membrane proteins in the cell.

[Treatment of Chilomastix mesnili infection with traditional Chinese medicine: a case report]

This paper reports a case with Chilomastix mesnili infections, and summarizes the diagnosis and treatment with traditional Chinese medicine.

Physicochemical-property guided design of a highly sensitive probe to image nitrosative stress in the pathology of stroke

In vivo real-time imaging of nitrosative stress in the pathology of stroke has long been a formidable challenge due to both the presence of the blood–brain barrier (BBB) and the elusive nature of reactive nitrogen species, while this task is also informative to gain a molecular level understanding of neurovascular injury caused by nitrosative stress during the stroke episode. Herein, using a physicochemical property-guided probe design strategy in combination with the reaction-based probe design rationale, we have developed an ultrasensitive probe for imaging nitrosative stress evolved in the pathology of stroke. This probe demonstrates an almost zero background fluorescence signal but a maximum 1000-fold fluorescence enhancement in response to peroxynitrite, the nitrosative stress marker. Due to its good physicochemical properties, the probe readily penetrates the BBB after intravenous administration, and quickly accumulates in mice brain to sense local vascular injuries. After accomplishing its imaging mission, the probe is easily metabolized and therefore won't cause safety concerns. These desirable features make the probe competent for the straightforward visualization of nitrosative stress progression in stroke pathology.

A brain–blood barrier permeable probe was developed for fluorogenically sensing nitrosative stress caused by brain vascular injury.

Nicotinamide phosphoribosyltransferase secreted from microglia via exosome during ischemic injury

Nicotinamide phosphoribosyltransferase (NAMPT) is the key enzyme of the salvage pathway of nicotinamide adenine dinucleotide synthesis. NAMPT can also be secreted and functions as a cytokine. We have previously shown that in the brain, NAMPT expression and secretion can be induced in microglia upon neuroinflammation and injury. Yet the mechanism for NAMPT secretion remains unclear. Here we show that NAMPT can be actively secreted from microglia upon the treatment of ischemia-like injury - oxygen-glucose deprivation and recovery (OGD/R). We confirmed that classical ER-Golgi pathway is not involved in NAMPT secretion. NAMPT secretion was further enhanced by ATP, and the secretion was mediated by P2X₇ receptor and by intracellular Ca²⁺ . Importantly, we found that phospholipase D inhibitor, n-butanol, phospholipase D siRNA, and wortmannin significantly decreased OGD/R-induced and ATP-enhanced release of NAMPT in microglia. After excluding the mechanisms of involving secretory autophagy, endosomes, and secretory lysosome, we have concluded that microglial NAMPT is secreted mainly via exosome. Immune-electron microscopy identifies NAMPT in extracellular vesicles with the size and morphology characteristic of exosome. With the vesicles harvested by ultra-centrifugation, exosomal NAMPT is further confirmed by Western blotting analysis. Intriguingly, the amount of NAMPT relative to exosomal protein markers remains unchanged upon the treatment of OGD/R, suggesting a constant load of exosomal NAMPT in microglia. Taken together, we have identified NAMPT is actively secreted via exosome from microglia during neuroinflammation of ischemic injury.

Nicotinamide ribose ameliorates cognitive impairment of aged and Alzheimer's disease model mice

Nicotinamide adenine dinucleotide (NAD) supplementation to repair the disabled mitochondria is a promising strategy for the treatment of Alzheimer's disease (AD) and other dementia. Nicotinamide ribose (NR) is a safe NAD precursor with high oral bioavailability, and has beneficial effects on aging. Here, we applied NR supplied food (2.5 g/kg food) to APP/PS1 transgenic AD model mice and aged mice for 3 months. Cognitive function, locomotor activity and anxiety level were assessed by standard behavioral tests. The change of body weight, the activation of microglia and astrocytes, the accumulation of Aβ and the level of serum nicotinamide phosphoribosyltransferase (NAMPT) were determined for the evaluation of pathological processes. We found that NR supplementation improved the short-term spatial memory of aged mice, and the contextual fear memory of AD mice. Moreover, NR supplementation inhibited the activation of astrocytes and the elevation of serum NAMPT of aged mice. For AD model mice, NR supplementation inhibited the accumulation of Aβ and the migration of astrocyte to Aβ. In addition, NR supplementation inhibit the body weight gain of aged and APP/PS1 mice. Thus, NR has selective benefits for both AD and aged mice, and the oral uptake of NR can be used to prevent the progression of dementia.

Cangrelor alleviates pulmonary fibrosis by inhibiting GPR17-mediated inflammation in mice

Pulmonary fibrosis is a progressive and intractable lung disease. Macrophages play a critical role in the progression of pulmonary fibrosis. Cangrelor, an anti-platelet agent, is also a non-selective Gprotein-coupled receptor 17 (GPR17) antagonist. GPR17 mediates microglial inflammation in the chronic phase of cerebral ischemia and regulates allergic pulmonary inflammation. In this study, we observed the effects of cangrelor on bleomycin (BLM)-induced macrophage cellular inflammation and BLM-induced pulmonary fibrosis in C57BL/6J mice. We found that BLM significantly increased GPR17 expression, the mRNA synthesis and release of inflammatory cytokines including TNF-α, IL-6 and TGF-β1 in murine RAW 264.7 macrophage cells. Knockdown of GPR17 attenuated the BLM-induced inflammatory responses. Cangrelor (2.5 μM-10 μM) significantly alleviated BLM-induced inflammatory response in RAW 264.7 macrophage cells in concentration-dependent manner. In BLM-induced fibrotic mouse lungs, GPR17 expression and GPR17-positive macrophages were increased. Cangrelor (2.5 mg/kg-10 mg/kg) alleviated pulmonary fibrosis in dose-dependent manner. Cangrelor not only reduced the number of GPR17-positive macrophages, but also decreased BLM-induced mRNA synthesis and release of inflammatory cytokine. As such, we concluded that cangrelor alleviates BLM-induced pulmonary fibrosis by suppressing GPR17-mediated inflammation. Cangrelor could be a potential therapeutic drug for pulmonary fibrosis.

[Association between fatty liver and type 2 diabetes in the baseline population of Jinchang Cohort]

Objective: To explore the association between fatty liver and type 2 diabetes mellitus (T2DM) in the baseline-population of Jinchang cohort study. Methods: Data from all the participants involved in the baseline-population of Jinchang cohort study was used, to compare the risks of T2DM in fatty liver and non fatty liver groups and to explore the interaction between family history or fatty liver of diabetes and the prevalence of T2DM. Results: Among all the 46 861 participants, 10 574 were diagnosed as having fatty liver (22.56%), with the standardized rate as 20.66%. Another 3 818 participants were diagnosed as having T2DM (8.15%) with standardized rate as 6.90%. The prevalence of T2DM increased in parallel with the increase of age (trend χ(2)=2 833.671, trend P<0.001). The prevalence of T2DM in the fatty liver group was significantly higher than that in the non-fatty liver group, both in men or women and in the overall population. Compared with the group of non-fatty liver, the risks of T2DM in fatty liver group were seen 1.78 times higher in males, 2.33 times in women and 2.10 times in the overall population, after adjustment for factors as age, levels of education, smoking, drinking, physical exercise, BMI, family history of diabetes and some metabolic indicators (pressure, TC, TG, uric acid, ALT, AST, gamma-glutamyl transferase). Date from the interaction model showed that fatty liver and family history of diabetes present a positive additive interaction on T2DM (RERI=1.18, 95%CI: 0.59-1.78; AP=0.24, 95%CI: 0.14-0.34; S=1.43, 95%CI: 1.21-1.69). Conclusions: Fatty liver could significantly increase the risk of T2DM and a positive additive interaction was also observed between fatty liver and family history of diabetes on T2DM. It was important to strengthen the prevention program on T2DM, in order to effectively control the development of fatty liver.

Characterizing Protein Dynamics with Integrative Use of Bulk and Single-Molecule Techniques

A protein dynamically samples multiple conformations, and the conformational dynamics enables protein function. Most biophysical measurements are ensemble-based, with the observables averaged over all members of the ensemble. Though attainable, the decomposition of the observables to the constituent conformational states can be computationally expensive and ambiguous. Here we show that the incorporation of single-molecule fluorescence resonance energy transfer (smFRET) data resolves the ambiguity and affords protein ensemble structures that are more precise and accurate. Using K63-linked diubiquitin, we characterize the dynamic domain arrangements of the model system, with the use of chemical cross-linking coupled with mass spectrometry (CXMS), small-angle X-ray scattering (SAXS), and smFRET techniques. CXMS allows the modeling of protein conformational states that are alternatives to the crystal structure. SAXS provides ensemble-averaged low-resolution shape information. Importantly, smFRET affords state-specific populations, and the FRET distances validate the ensemble structures obtained by refining against CXMS and SAXS restraints. Together, the integrative use of bulk and single-molecule techniques affords better insight into protein dynamics and shall be widely implemented in structural biology.

Prognostic value of miR-141 downregulation in gastric cancer

Previous research has shown that microRNA-141 (miR-141) expression levels are associated with survival in several types of cancer. In the present study, we investigated the clinical significance and prognostic value of miR-141 in gastric cancer. Paired tissue specimens (tumor and adjacent normal mucosa) from 95 patients with gastric cancer were obtained at the Department of General Surgery, Xiangya Hospital, Central South University from March 2009 to February 2014. The levels of miR-141 in cancerous and corresponding non-cancerous tissues were detected by quantitative reverse transcription-polymerase chain reaction. Associations between clinicopathological parameters and miR-141 expression were evaluated using chi-square tests. Overall survival was calculated and survival curves were plotted using the Kaplan-Meier method; differences between groups were compared using log-rank tests. Compared to the matched normal gastric mucosa, gastric cancer tissues had significantly lower miR-141 expression levels (P < 0.001). This decreased miR-141 expression was significantly associated with tumor differentiation (P = 0.044), positive lymph node metastasis (P = 0.010), distant metastasis (P < 0.001), and advanced tumor-node-metastasis (TNM) stage (P < 0.001). Furthermore, a significant relationship was found between miR-141 expression and overall survival (P = 0.012, log-rank test). Cox regression analysis revealed that lymph node metastasis (P = 0.003), distant metastasis (P = 0.001), TNM stage (P < 0.001), and miR- 141 expression (P = 0.007) were independent prognostic factors in patients with gastric cancer. Our data provide evidence that the downregulation of miR-141 may contribute to the aggressive progression and poor prognosis of human gastric cancer.

Nicotinamide phosphoribosyltransferase inhibitor APO866 induces C6 glioblastoma cell death via autophagy

APO866 is a potent inhibitor of nicotinamide phosphoribosyltransferase (NAMPT), and inhibits nicotinamide adenine dinucleotide (NAD) synthesis. Our previous study showed that APO866 inhibits the proliferation of C6 glioblastoma cells, but failed to induce apoptosis. Since APO866 inhibits cellular metabolism and such metabolic stress is closely related with autophagy, thus we determined whether APO866 can induce autophagy in C6 glioblastoma cells and whether the autophagy induced by APO866 is pro-death or pro-survival. Using LC3 immunofluorescence imaging and transmission electron microscopy detection, we found that APO866 at 1-100 nM induced autophagy in C6 glioblastoma cells. APO866 at 1 nM mainly induced initial autophagic vacuoles. Whereas APO866 at 100 nM induced degrading autophagic vacuoles, as well as induced nuclei malformation and mitochondria swelling. In addition, APO866 concentration-dependently decreased the cell viability of C6 glioblastoma cells, and this effect was attenuated by autophagy inhibitors, including 3-methyladenine and LY294002. APO866 concentration-dependently decreased intracellular NAD level. Interestingly, APO866 at 1 nM slightly decreased intracellular NAD level, but dramatically increased autophagy-positive cells. The dramatical cell viability decreasing required the decreasing of intracellular NAD level to a very low threshold. Thus, our results indicated that APO866 induced pro-death autophagy in C6 glioblastoma cells by decreasing intracellular NAD, and low concentration of APO866 can be used as an autophagy inducer in autophagic-death sensitive glioblastoma.

HAMI 3379, a CysLT2R antagonist, dose- and time-dependently attenuates brain injury and inhibits microglial inflammation after focal cerebral ischemia in rats

Cysteinyl leukotrienes (CysLTs) induce inflammatory responses by activating their receptors, CysLT1R and CysLT2R. We have reported that CysLT2R is involved in neuronal injury, astrocytosis, and microgliosis, and that intracerebroventricular (i.c.v.) injection of the selective CysLT2R antagonist HAMI 3379 protects against acute brain injury after focal cerebral ischemia in rats. In the present study, we clarified features of the protective effect of intraperitoneally-injected HAMI 3379 in rats. We found that HAMI 3379 attenuated the acute brain injury 24 h after middle cerebral artery occlusion (MCAO) with effective doses of 0.1-0.4 mg/kg and a therapeutic window of ∼1h. It attenuated the neurological deficits, and reduced infarct volume, brain edema, and neuronal loss and degeneration 24 and 72h after MCAO. RNA interference with i.c.v. injection of CysLT2R short hairpin RNA (shRNA) attenuated the acute injury as well. Also, HAMI 3379 inhibited release of the cytokines IL-1β, interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α) into the serum and cerebrospinal fluid 24h after MCAO. Moreover, HAMI 3379 ameliorated the microglial activation and neutrophil accumulation in the ischemic regions, but did not affect astrocyte proliferation 72h after MCAO. In comparison, the CysLT1R antagonist pranlukast did not affect microglial activation and IFN-γ release, but inhibited astrocyte proliferation and reduced serum IL-4. Thus, we conclude that HAMI 3379 has a protective effect on acute and subacute ischemic brain injury, and attenuates microglia-related inflammation. CysLT2R antagonist(s) alone or in combination with CysLT1R antagonists may be a novel class of therapeutic agents in the treatment of ischemic stroke.

Cerebral ischemia is exacerbated by extracellular nicotinamide phosphoribosyltransferase via a non-enzymatic mechanism

Intracellular nicotinamide phosphoribosyltransferase (iNAMPT) in neuron has been known as a protective factor against cerebral ischemia through its enzymatic activity, but the role of central extracellular NAMPT (eNAMPT) is not clear. Here we show that eNAMPT protein level was elevated in the ischemic rat brain after middle-cerebral-artery occlusion (MCAO) and reperfusion, which can be traced to at least in part from blood circulation. Administration of recombinant NAMPT protein exacerbated MCAO-induced neuronal injury in rat brain, while exacerbated oxygen-glucose-deprivation (OGD) induced neuronal injury only in neuron-glial mixed culture, but not in neuron culture. In the mixed culture, NAMPT protein promoted TNF-α release in a time- and concentration-dependent fashion, while TNF-α neutralizing antibody protected OGD-induced, NAMPT-enhanced neuronal injury. Importantly, H247A mutant of NAMPT with essentially no enzymatic activity exerted similar effects on ischemic neuronal injury and TNF-α release as the wild type protein. Thus, eNAMPT is an injurious and inflammatory factor in cerebral ischemia and aggravates ischemic neuronal injury by triggering TNF-α release from glia cells, via a mechanism not related to NAMPT enzymatic activity.

Phospholipase D participates in H(2)O(2)-induced A549 alveolar epithelial cell migration

To investigate the effects of phospholipase D (PLD) on low-concentration hydrogen peroxide (H(2)O(2))-induced growth and migration in alveolar epithelial A549 cells, the cells were exposed to H(2)O(2) (3-100 μM) for 12-48 hours, cell proliferation was determined by MTT assay and cell migration was tested by a modified epithelial wound healing assay. We found that one bolus of H(2)O(2) (10-100 μM) did not affect proliferation, but significantly stimulated migration (143-161% of control) after a 12-hour exposure. Pretreatment with the antioxidants catalase (1000 U/ml), N-acetyl-cysteine (2 mM), or edaravone (10 μM) abolished the migration induced by 30 μM H(2)O(2); the PLD inhibitor 1-butanol (0.5%) also attenuated H(2)O(2)-induced migration to the control level; while exogenous phosphatidic acid (PA) (10(-7)-10(-4) M) mimicked the effects of PLD activation and induced migration in a dose-dependent manner. We suggest that the alveolar epithelial cell migration induced by exposure to low concentrations of H(2)O(2) benefits tissue repair during acute lung injury (ALI) and PLD is involved in the underlying mechanism.

Nicotinamide phosphoribosyltransferase may be involved in age-related brain diseases

Nicotinamide phosphoribosyltransferase (NAMPT) is a key enzyme for nicotinamide adenine dinucleotide (NAD) biosynthesis, and can be found either intracellularly (iNAMPT) or extracellularly (eNAMPT). Studies have shown that both iNAMPT and eNAMPT are implicated in aging and age-related diseases/disorders in the peripheral system. However, their functional roles in aged brain remain to be established. Here we showed that upon aging, NAMPT level increased in serum but decreased in brain, decreased in cortex and hippocampus but remained unchanged in cerebellum and striatum in brain, and increased in microglia but likely decreased in neuron. Accordingly, total NAD (tNAD) level significantly decreased in hippocampus, cerebellum and striatum in aged brain. Application of recombinant NAMPT, mimicking the elevated serum NAMPT level, enhanced the susceptibility of cerebral endothelial cells to ischemic injury, while inhibition of iNAMPT by FK866, a specific inhibitor, reduced intracellular NAD level and induced neuronal death. Taken together, we have revealed a region- and cell-specific change of NAMPT level in brain and serum upon aging, deduced its potential consequences, which suggests that NAMPT is a regulatory factor in aging and age-related brain diseases.

Intracerebroventricular injection of HAMI 3379, a selective cysteinyl leukotriene receptor 2 antagonist, protects against acute brain injury after focal cerebral ischemia in rats

Cysteinyl leukotrienes (CysLTs) induce inflammatory responses by activating their receptors, CysLT(1)R and CysLT(2)R. We recently reported that CysLT(2)R is involved in neuronal injury, astrocytosis and microgliosis after focal cerebral ischemia in rats. Here, we determined whether HAMI 3379, a selective CysLT(2)R antagonist, protects against acute brain injury after focal cerebral ischemia in rats. We induced transient focal cerebral ischemia by 30 min of middle cerebral artery occlusion (MCAO), followed by 24h of reperfusion. HAMI 3379 (1, 10 or 100 ng) was injected intracerebroventricularly (i.c.v.) 30 min before MCAO, and the CysLT(1)R antagonist pranlukast (0.1mg/kg, i.p.) was used as a positive control. HAMI 3379 at 10 and 100 ng (but not at 1 ng) attenuated the neurological deficits, and reduced infarct volume, brain edema, IgG exudation, neuronal degeneration and neuronal loss. This protective effect was similar to that of pranlukast. Thus, HAMI 3339 at 10-100 ng i.c.v. is neuroprotective against acute brain injury after focal cerebral ischemia in rats. These findings suggest therapeutic potential for CysLT(2)R antagonists in the treatment of ischemic stroke.

Transforming growth factor β1-induced astrocyte migration is mediated in part by activating 5-lipoxygenase and cysteinyl leukotriene receptor 1

BACKGROUND

Transforming growth factor-β 1 (TGF-β 1) is an important regulator of cell migration and plays a role in the scarring response in injured brain. It is also reported that 5-lipoxygenase (5-LOX) and its products, cysteinyl leukotrienes (CysLTs, namely LTC₄, LTD₄ and LTE₄), as well as cysteinyl leukotriene receptor 1 (CysLT₁R) are closely associated with astrocyte proliferation and glial scar formation after brain injury. However, how these molecules act on astrocyte migration, an initial step of the scarring response, is unknown. To clarify this, we determined the roles of 5-LOX and CysLT₁R in TGF-β 1-induced astrocyte migration.

METHODS

In primary cultures of rat astrocytes, the effects of TGF-β 1 and CysLT receptor agonists on migration and proliferation were assayed, and the expression of 5-LOX, CysLT receptors and TGF-β1 was detected. 5-LOX activation was analyzed by measuring its products (CysLTs) and applying its inhibitor. The role of CysLT₁R was investigated by applying CysLT receptor antagonists and CysLT₁R knockdown by small interfering RNA (siRNA). TGF-β 1 release was assayed as well.

RESULTS

TGF-β 1-induced astrocyte migration was potentiated by LTD₄, but attenuated by the 5-LOX inhibitor zileuton and the CysLT₁R antagonist montelukast. The non-selective agonist LTD₄ at 0.1 to 10 nM also induced a mild migration; however, the selective agonist N-methyl-LTC₄ and the selective antagonist Bay cysLT2 for CysLT₂R had no effects. Moreover, CysLT₁R siRNA inhibited TGF-β 1- and LTD₄-induced astrocyte migration by down-regulating the expression of this receptor. However, TGF-β 1 and LTD4 at various concentrations did not affect astrocyte proliferation 24 h after exposure. On the other hand, TGF-β 1 increased 5-LOX expression and the production of CysLTs, and up-regulated CysLT1R (not CysLT₂R), while LTD4 and N-methyl-LTC4 did not affect TGF-β 1 expression and release.

CONCLUSIONS

TGF-β 1-induced astrocyte migration is, at least in part, mediated by enhanced endogenous CysLTs through activating CysLT₁R. These findings indicate that the interaction between the cytokine TGF-β 1 and the pro-inflammatory mediators CysLTs in the regulation of astrocyte function is relevant to glial scar formation.

Aggravated chronic brain injury after focal cerebral ischemia in aquaporin-4-deficient mice

The water channel aquaporin-4 (AQP4) is important in brain water homeostasis, and is also involved in astrocyte growth and glial scar formation. It has been reported that AQP4 deficiency attenuates acute ischemic brain injury as a result of reducing cytotoxic edema. Here, we determined whether AQP4 deficiency influences chronic brain injury after focal cerebral ischemia induced by 30 min of middle cerebral artery occlusion (MCAO). AQP4(-/-) mice exhibited a lower survival rate and less body weight gain than wild-type mice, but their neurological deficits were similar to wild-type mice during 35 days after MCAO. At 35 days after MCAO, AQP4(-/-) mice showed more severe brain atrophy and cavity formation in the ischemic hemisphere as well as more neuronal loss in the hippocampus. Furthermore, astrocyte proliferation and glial scar formation were impaired in AQP4(-/-) mice. Therefore, AQP4 deficiency complicated by astrocyte dysfunction aggravates chronic brain injury after focal cerebral ischemia, suggesting that AQP4 may be important in the chronic phase of the post-ischemic recovery process.

Aquaporin-4 deficiency attenuates acute lesions but aggravates delayed lesions and microgliosis after cryoinjury to mouse brain

OBJECTIVE

To determine whether aquaporin-4 (AQP4) regulates acute lesions, delayed lesions, and the associated microglial activation after cryoinjury to the brain.

METHODS

Brain cryoinjury was applied to AQP4 knockout (KO) and wild-type mice. At 24 h and on days 7 and 14 after cryoinjury, lesion volume, neuronal loss, and densities of microglia and astrocytes were determined, and their changes were compared between AQP4 KO and wild-type mice.

RESULTS

Lesion volume and neuronal loss in AQP4 KO mice were milder at 24 h following cryoinjury, but worsened on days 7 and 14, compared to those in wild-type mice. Besides, microglial density increased more, and astrocyte proliferation and glial scar formation were attenuated on days 7 and 14 in AQP4 KO mice.

CONCLUSION

AQP4 deficiency ameliorates acute lesions, but worsens delayed lesions, perhaps due to the microgliosis in the late phase.

The new P2Y-like receptor G protein-coupled receptor 17 mediates acute neuronal injury and late microgliosis after focal cerebral ischemia in rats

G protein-coupled receptor 17 (GPR17), the new P2Y-like receptor, is phylogenetically related to the P2Y and cysteinyl leukotriene receptors, and responds to both uracil nucleotides and cysteinyl leukotrienes. GPR17 has been proposed to be a damage sensor in ischemic stroke; however, its role in brain inflammation needs further detailed investigation. Here, we extended previous studies on the spatiotemporal profiles of GPR17 expression and localization, and their implications for brain injury after focal cerebral ischemia. We found that in the ischemic core, GPR17 mRNA and protein levels were upregulated at both 12-24 h and 7-14 days, but in the boundary zone the levels increased 7-14 days after reperfusion. The spatiotemporal pattern of GPR17 expression well matched the acute and late (subacute/chronic) responses in the ischemic brain. According to previous findings, in the acute phase, after ischemia (24 h), upregulated GPR17 was localized in injured neurons in the ischemic core and in a few microglia in the ischemic core and boundary zone. In the late phase (14 days), it was localized in microglia, especially in activated (ED1-positive) microglia in the ischemic core, but weakly in most microglia in the boundary zone. No GPR17 was detectable in astrocytes. GPR17 knockdown by a small interfering RNA attenuated the neurological dysfunction, infarction, and neuron loss at 24 h, and brain atrophy, neuron loss, and microglial activation at 14 days after reperfusion. Thus, GPR17 might mediate acute neuronal injury and late microgliosis after focal cerebral ischemia.

Anti-proliferation effect of APO866 on C6 glioblastoma cells by inhibiting nicotinamide phosphoribosyltransferase

Nicotinamide phosphoribosyltransferase (NAMPT) is a key enzyme in the salvaging pathway for the synthesis of nicotinamide adenine dinucleotide (NAD) that is involved in cell metabolism and proliferation. NAMPT is normally absent in astrocyte but highly expressed in glioblastoma, suggesting that it may promote cell survival through synthesizing more NAD. In this report, we evaluated the effect of APO866, a potent inhibitor of NAMPT against C6 glioblastoma. We found that APO866 inhibited the growth of C6 glioblastoma cells with IC(50) in nano-molar range. APO866 depleted intracellular NAD, caused marked inhibition of ERK activation and induced G2/M cell-cycle arrest. The effects by APO866 were abrogated by nicotinamide mononucleotide (NMN), the direct product of NAMPT. Administration of U0126, an ERK1/2 inhibitor, inhibited cell growth but displayed no synergistic effect with APO866. Taken together, our results indicated that APO866 is a potent growth inhibitor against glioblastoma through targeting NAMPT.

[Deficiency of water channel AQP4 aggravates NMDA-induced brain injury in mice]

OBJECTIVE

To evaluate the role of water channel AQP4 in NMDA-induced brain injury in mice.

METHODS

In AQP4 gene knockout (AQP4(-/-)) mice, brain injury was induced by microinjection of NMDA into the cortex. The injured area was determined by toluidine blue staining, degenerated neurons were detected by Fluro-Jade B staining, and increased blood-brain barrier (BBB) permeability was evaluated by IgG immunostaining.

RESULT

Compared with wild-type mice, AQP4(-/-) mice exhibited increased cortical lesion area, aggravated neuron degeneration, and increased BBB disruption after NMDA microinjection.

CONCLUSION

AQP4 may play a protective role in NMDA-induced brain injury in mice.

[Effects of agonist and antagonist of cysteinyl leukotriene receptors on differentiation of rat glioma C6 cells]

OBJECTIVE

To investigate the role of cysteinyl leukotriene (CysLT) receptors in the differentiation of rat glioma C6 cells.

METHODS

Rat glioma C6 cells were treated with the agonist LTD(4), the CysLT(1) receptor antagonist montelukast and the differentiation inducer forskolin. Cell morphology and GFAP protein expression were determined after treatments.

RESULT

Forskolin (10 μmol/L) induced morphological changes and GFAP protein expression (cell differentiation) in C6 cells, but LTD(4) (0.1-100 nmol/L) did not induce these changes. Montelukast (1 μmol/L) alone did not affect C6 cell differentiation, while it induced the differentiation when combined with the LTD(4) (100 nmol/L).

CONCLUSION

The CysLT(2) receptor may modulate the differentiation of rat glioma C6 cells.

[Rotenone-induced changes of cysteinyl leukotriene receptor 1 expression in BV2 microglial cells]

OBJECTIVE

To prepare and identify a polyclonal antibody (pAb) against (mouse) cysteinyl leukotriene receptor 1 (CysLT(1)) and to investigate the changes of CysLT(1) receptor expression in BV2 microglial cells after rotenone treatment.

METHODS

Rabbits were immunized with KLH-coupled CysLT(1) peptide to prepare the pAb. The titer of the pAb in rabbit plasma was detected by ELISA method, and the specificity of the pAb was tested by antigen blockade. After BV2 cells were treated with rotenone (0.01-1 μmol/L) for 24 h, the expression of CysLT(1) was determined by immunostaining, Western blotting and RT-PCR.

RESULT

The pAb showed a titer of 1/32728, and was not cross-reacted with antigens of CysLT(2) receptor and GPR17. Immunostaining, Western blotting and RT-PCR analysis showed the expression of CysLT(1) receptor in BV2 microglia. Rotenone at 1μmol/L significantly induced an increased expression of CysLT(1) receptor.

CONCLUSION

The prepared CysLT(1) receptor polyclonal antibody has a high titer and high specificity to meet testing requirements of Western blotting and immunostaining; CysLT(1) is associated with rotenone-induced injury of BV2 microglial cells.

[Enzymatic activities of recombinant human NAMPT and NAMPT (H247A) proteins]

OBJECTIVE

To prepare and purify recombinant human NAMPT and NAMPT (H247A) proteins and to detect their enzymatic activity.

METHODS

Using pcDNA3.1-hnampt as template, full-length hnampt was sub-cloned into pET-11a(+) plasmid. The hnampt (H247A) mutant was obtained by site-directed mutagenesis. The plasmids were introduced in Escherichia coli BL21star for protein expression. The recombined NAMPT and NAMPT (H247A) proteins were purified by flowing through nickel column and size-exclusion column. The target proteins were confirmed by SDS-PAGE and mass spectrometry detection. The enzymatic activities of recombinant proteins were assessed by solution NMR.

RESULT

The DNA sequences showed that hnampt (wild type) and hnampt (H247A) (mutation) were cloned into pET-11a(+). The recombinant proteins were expressed in Escherichia coli BL21star in soluble form. The purified protein was confirmed to be NAMPT with a molecular weight of 56 KD. The enzyme activity of NAMPT (H247A) was dramatically decreased compared to wild-type NAMPT.

CONCLUSION

The recombinant hNAMPT and hNAMPT (H247A) proteins have been successful prepared and purified. The H247A mutation dramatically decreases the enzymatic activity of NAMPT.

[Construction of HEK293 cell lines expressing hCysLT₂ receptor and its application in screening of antagonists]

OBJECTIVE

To construct HEK293 cell lines stably expressing hCysLT(2) receptor, and to evaluate its application in screening of synthetic compounds with antagonist activity.

METHODS

The recombinant plasmid pcDNA3.1(+)-hCysLT(2) was transfected into HEK293 cells using Lipofectamin 2000. The transfected HEK293 cells were selected in 96 well plates by limiting dilution with 600 μg/ml C418 for 8 weeks. The expression of human CysLT(2) receptor was detected by RT-PCR and immunofluorescence staining. In HEK293 cells stably transfected with hCysLT(2), the agonist LTD(4)-induced elevation of intracellular calcium concentration ([Ca2(+)]i) was measured as the index for screening compounds with antagonist activity.

RESULT

After selection in 96 well plates by limiting dilution, 12 monoclones were obtained and 11 of them highly expressed hCysLT(2) receptor. The positive control ATP at 50 μmol/L and LTD(4) at 100 nmol/L elevated [Ca2(+)]i in hCysLT(2)-HEK293 cells. AP-2100984 inhibited LTD(4)-induced [Ca2(+)]i elevation, but selective CysLT(1) receptor antagonists did not exert such an effect. The newly synthesized compounds DXW2, DXW3, DXW4, DXW5, DXW9, DXW25, DXW26, DXW29 and DXW35 at 1 μmol/L significantly inhibited LTD(4)-induced [Ca2(+)]i elevation. The IC(50) values of DXW4 and DXW5 were 0.25 μmol/L and 7.5 μmol/L.

CONCLUSION

HEK293 cell lines stably expressing hCysLT(2) receptor have been successfully constructed, and can be used to screen compounds with CysLT(2) receptor antagonist activity.

CysLT2 receptor-mediated AQP4 up-regulation is involved in ischemic-like injury through activation of ERK and p38 MAPK in rat astrocytes

AIMS

We previously reported that cysteinyl leukotriene receptor 2 (CysLT(2)) mediates ischemic astrocyte injury, and leukotriene D(4)-activated CysLT(2) receptor up-regulates the water channel aquaporin 4 (AQP4). Here we investigated the mechanism underlying CysLT(2) receptor-mediated ischemic astrocyte injury induced by 4-h oxygen-glucose deprivation and 24-h recovery (OGD/R).

MAIN METHODS

Primary cultures of rat astrocytes were treated by OGD/R to construct the cell injury model. AQP4 expression was inhibited by small interfering RNA (siRNA). The expressions of AQP4 and CysLTs receptors, and the MAPK signaling pathway were determined.

KEY FINDINGS

OGD/R induced astrocyte injury, and increased expression of the CysLT(2) (but not CysLT(1)) receptor and AQP4. OGD/R-induced cell injury and AQP4 up-regulation were inhibited by a CysLT(2) receptor antagonist (Bay cysLT2) and a non-selective CysLT receptor antagonist (Bay u9773), but not by a CysLT(1) receptor antagonist (montelukast). Knockdown of AQP4 by siRNA attenuated OGD/R injury. Furthermore, OGD/R increased phosphorylation of ERK1/2 and p38, whose inhibitors relieved the cell injury and AQP4 up-regulation.

SIGNIFICANCE

The CysLT(2) receptor mediates AQP4 up-regulation in astrocytes, and up-regulated AQP4 leads to OGD/R-induced injury, which results from activation of the ERK1/2 and p38 MAPK pathways.

Activation of phospholipase D involved in both injury and survival in A549 alveolar epithelial cells exposed to H2O2

To determine the role of the phospholipase D (PLD) pathway in injury and survival of alveolar epithelial cells, A549 cells were exposed to H(2)O(2) (500 microM) which resulted in time-dependent injury and bi-phasic increase of PLD activity at 5 min and at 3 h, respectively. n-Butanol (0.5%) inhibited PLD activation, attenuated cell injury at 5 min of H(2)O(2) exposure, but enhanced injury at 3h of exposure. This activation was inhibited by treatment with catalase (500 units/ml). Exogenous phosphatidic acid mimicked the effects of PLD activation, and diphenyliodonium (NADPH oxidase inhibitor) reversed the decline in cell viability induced by H(2)O(2) exposure. Propranolol (phosphatidic acid phospholydrolase inhibitor) and quinacrine (phospholipase A2 inhibitor) had weak effects on H(2)O(2)-induced PLD activation but reversed H(2)O(2)-induced injury. We speculate that PLD activation at the initiation of H(2)O(2) exposure predominantly results in NAPDH oxidase activation, which mediates A549 cell injury, but turns to mediating cell survival as the H(2)O(2) attack continues, which might be mainly due to the accumulation of intracellular phosphatidic acid.

[Method for screening cysteinyl leukotriene receptor 2 antagonists and preliminary screening of compounds]

OBJECTIVE

To establish a method for screening cysteinyl leukotriene receptor 2 (CysLT(2)) antagonists and to preliminarily screen a series of synthetic compounds.

METHODS

Rat glioma cell line (C6 cells) highly expressing CysLT(2) receptor was used. Intracellular calcium concentration was measured after stimulation with the agonist LTD(4),which was used to screen compounds with antagonist activity for CysLT(2) receptor. Bay u9773, a CysLT1/CysLT(2) receptor non-selective antagonist, and AP-100984, a CysLT(2) receptor antagonist, were used as control.

RESULT

PT-PCR showed a higher expression of CysLT(2) receptor in C6 cells. LTD(4) at 1 mumol/L significantly increased intracellular calcium in C6 cells; the maximal effect was about 37.5% of ATP, a positive stimulus.LTD(4)-induced increase of intracellular calcium was blocked by CysLT(2) receptor antagonists, but not by CysLT(1) receptor antagonists. Among the synthetic compounds, D(XW-)1,2,13,23,29 and 30 inhibited LTD(4)-induced increase of intracellular calcium.

CONCLUSION

LTD(4)-induced change in intracellular calcium in C6 cells can be used as a screening method for CysLT(2) receptor antagonists. The compounds, D(XW-)1,2,13,23,29 and 30, possess antagonist activity for CysLT(2) receptor.

[Preparation and identification of polyclonal antibody against cysteinyl leukotriene receptor 2]

OBJECTIVE

To prepare and identify a polyclonal antibody against cysteinyl leukotriene receptor (CysLT(2)receptor).

METHODS

Rabbits were immunized with KLH-coupled CysLT(2) receptor peptide to prepare the polyclonal antibody (pAb). The titer of the pAb in rabbit plasma was detected by indirect ELISA, and the specificity of the pAb was tested by antigen blockade. The tissue distribution of CysLT(2) receptor was detected by Western blot and immunohistochemistry with the prepared pAb.

RESULT

The pAb showed a titer higher than 1/1047296, and was specific to CysLT(2) receptor, without cross-reaction with the antigens of CysLT(1) receptor and GPR17. A higher expression of CysLT(2) receptor in kidney, brain and lung of rats and mice was detected by Western blot analysis using the prepared pAb. The molecular weight of CysLT(2) receptor protein was about 40 kD. Immunohistochemical examination showed that CysLT(2) receptor was expressed mainly in the neuron, and partly in astrocytes in rat brain.

CONCLUSION

The prepared CysLT(2) receptor pAb has high sensitivity and specificity, and can be used in Western blot and immunohistochemistry.

[Construction and identification of eukaryotic expression vector of rat GPR17 gene]

OBJECTIVE

To construct the eukaryotic expression vector of rat GPR17 (rGPR17) cDNA,and to identify its function in HEK293 cells.

METHODS

Total RNA was extracted from rat brain tissue; full-length GPR17 cDNA was prepared by RT-PCR, and cloned into pcDNA3.1(+) plasmid. The recombinant plasmid was converted into E.coli DH5alpha and confirmed by PCR, double enzyme digestion analysis and DNA sequencing. The recombinant plasmid pcDNA3.1(+)-rGPR17 was transiently transfected into HEK293 cells using Lipofectamin 2000. Expression of rGPR17 gene was confirmed by RT-PCR and immunofluorescence staining. The exogenous LTD(4) enhanced intracellular calcium was measured using Fluo-4.

RESULT

RT-PCR, double enzyme digestion analysis and sequencing showed that the rGPR17 gene was cloned into recombinant vector, and the recombinant rGPR17 was expressed after transfection in HKE293 cells. LTD(4) increased intracellular calcium release in the transfected HEK293 cells.

CONCLUSION

The eukaryotic expression vector of rGPR17 cDNA has been constructed; it is functionally expressed in HEK293 cells. This work provides a basis for further research of the GPR17 receptor and its antagonists.

Leukotriene D4 stimulates the migration but not proliferation of endothelial cells mediated by the cysteinyl leukotriene cyslt(1) receptor via the extracellular signal-regulated kinase pathway

The actions of cysteinyl leukotrienes (CysLTs) are mediated by activating CysLT receptors, CysLT(1), and CysLT(2). The CysLT(1) receptor mediates vascular responses to CysLTs; however, its effect on the proliferation and migration of endothelial cells is not clarified. To determine this effect, we observed proliferation and migration in EA.hy926 cells, a human endothelial cell line, and the involvement of activation of mitogen-activated protein kinases (MAPKs). We found that LTD(4) did not affect the proliferation, but significantly stimulated the migration of endothelial cells. LTD(4) also induced the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, but not those of p38 or JNK. The LTD(4)-induced migration and ERK1/2 phosphorylation were blocked by the CysLT(1)-receptor antagonist montelukast and the dual antagonist Bay u9773, but not by the CysLT(2)-receptor antagonist Bay cysLT2; the migration was also inhibited by the ERK1/2 inhibitor U0126. Our findings indicate that LTD(4) stimulates the CysLT(1) receptor-mediated migration of endothelial cells; this may be regulated by the ERK1/2 pathway.

Dihydroartemisinin potentiates the cytotoxic effect of temozolomide in rat C6 glioma cells

Gliomas are the most common primary brain tumor in adults, but the efficacy of chemotherapy is limited. Artemisinin and its analogs, such as dihydroartemisinin (DHA), can kill cancer cells via generating free radicals. In the present study, we determined whether DHA at low concentrations potentiates the cytotoxic effect of temozolomide in rat glioma C6 cells. We found that the IC50 values of DHA and temozolomide for cell viability were 23.4 and 560 micromol/l, respectively. The cytotoxic effect of temozolomide was enhanced by 177% at a nontoxic DHA concentration (1 micromol/l), and by 321% at a low-toxic DHA concentration (5 micromol/l). DHA substantially increased temozolomide-induced apoptosis and necrosis. The generation of intracellular reactive oxygen species (ROS) was increased by temozolomide combined with DHA at noneffective concentrations of both agents. Edaravone (20 micromol/l), a ROS scavenger, reversed the effects of temozolomide/DHA on both ROS generation and cell viability reduction. These results indicate that DHA at low concentrations potentiates the cytotoxic effects of temozolomide in C6 cells partly via generating ROS, suggesting a beneficial combination for the chemotherapy of gliomas.

Activation of CysLT receptors induces astrocyte proliferation and death after oxygen-glucose deprivation

We recently found that 5-lipoxygenase (5-LOX) is activated to produce cysteinyl leukotrienes (CysLTs), and CysLTs may cause neuronal injury and astrocytosis through activation of CysLT(1) and CysLT(2) receptors in the brain after focal cerebral ischemia. However, the property of astrocyte responses to in vitro ischemic injury is not clear; whether 5-LOX, CysLTs, and their receptors are also involved in the responses of ischemic astrocytes remains unknown. In the present study, we performed oxygen-glucose deprivation (OGD) followed by recovery to induce ischemic-like injury in the cultured rat astrocytes. We found that 1-h OGD did not injure astrocytes (sub-lethal OGD) but induced astrocyte proliferation 48 and 72 h after recovery; whereas 4-h OGD moderately injured the cells (moderate OGD) and led to death 24-72 h after recovery. Inhibition of phospholipase A(2) and 5-LOX attenuated both the proliferation and death. Sub-lethal and moderate OGD enhanced the production of CysLTs that was inhibited by 5-LOX inhibitors. Sub-lethal OGD increased the expressions of CysLT(1) receptor mRNA and protein, while moderate OGD induced the expression of CysLT(2) receptor mRNA. Exogenously applied leukotriene D(4) (LTD(4)) induced astrocyte proliferation at 1-10 nM and astrocyte death at 100-1,000 nM. The CysLT(1) receptor antagonist montelukast attenuated astrocyte proliferation, the CysLT(2) receptor antagonist BAY cysLT2 reversed astrocyte death, and the dual CysLT receptor antagonist BAY u9773 exhibited both effects. In addition, LTD(4) (100 nM) increased the expression of CysLT(2) receptor mRNA. Thus, in vitro ischemia activates astrocyte 5-LOX to produce CysLTs, and CysLTs result in CysLT(1) receptor-mediated proliferation and CysLT(2) receptor-mediated death.

Dihydroartemisinin exerts cytotoxic effects and inhibits hypoxia inducible factor-1alpha activation in C6 glioma cells

Artemisinin and its analogue dihydroartemisinin exert cytotoxic effects in some kinds of cancer cell lines. Here we determined whether dihydroartemisinin inhibits the growth and induces apoptosis of rat C6 glioma cells. We found dihydroartemisinin (5-25 microM) inhibited the growth and induced apoptosis of C6 cells in a concentration- and time-dependent manner; however, it was much less toxic to rat primary astrocytes. Dihydroartemisinin (5-25 microM) also increased the generation of reactive oxygen species in C6 cells. These effects of dihydroartemisinin were enhanced by ferrous ions (12.5-100 microM) and reduced by the iron chelator deferoxamine (25-200 microM). Immunoblotting analysis revealed that dihydroartemisinin (5-25 microM) significantly reduced hypoxia- and deferoxamine-induced expression of hypoxia inducible factor-1alpha and its target gene protein, vascular endothelial growth factor, in C6 cells. The results showed that dihydroartemisinin exerts a selective cytotoxic effect on C6 cells by increasing the reactive oxygen species and inhibiting hypoxia inducible factor-1alpha activation.

[Cysteinyl leukotriene receptor 1 antagonist pranlukast modulates differentiation of SK-N-SH cells]

OBJECTIVE

To determine whether cysteinyl leukotriene receptor agonist LTD(4) and cysteinyl leukotriene receptor 1 (CysLT(1)) antagonist pranlukast affect the differentiation of human neuroblastoma SK-N-SH cells.

METHODS

SK-N-SH cell morphological changes induced by LTD(4), pranlukast and LTD(4) + pranlukast were observed with retinoid acid (RA) as the positive control. The expressions of CysLT(1) and CysLT(2) receptors were detected by immunoblotting analysis, and the expression of microtubule-associated protein-2 (MAP-2), a neuron marker, was detected by fluorescent immunostaining.

RESULT

The immunoblotting results showed that SK-N-SH cells expressed CysLT(1) receptor moderately, and CysLT(2) receptor highly. The morphological results showed that RA, pranlukast and LTD(4) + pranlukast induced the compaction of the cell bodies and the outgrowth of neurites, while LTD(4) had no significant effect. The immunostaining results showed that MAP-2 was distributed in the cell bodies in control or pranlukast-treated cells; it was distributed in cell bodies and neuritis in RA-treated cells. Pranlukast increased the numbers of MAP-2-positive cells.

CONCLUSION

The CysLT(1)receptor antagonist pranlukast modulates the differentiation of SK-N-SH cells.

Viscoelastic properties of individual glial cells and neurons in the CNS

One hundred fifty years ago glial cells were discovered as a second, non-neuronal, cell type in the central nervous system. To ascribe a function to these new, enigmatic cells, it was suggested that they either glue the neurons together (the Greek word "gammalambdaiotaalpha" means "glue") or provide a robust scaffold for them ("support cells"). Although both speculations are still widely accepted, they would actually require quite different mechanical cell properties, and neither one has ever been confirmed experimentally. We investigated the biomechanics of CNS tissue and acutely isolated individual neurons and glial cells from mammalian brain (hippocampus) and retina. Scanning force microscopy, bulk rheology, and optically induced deformation were used to determine their viscoelastic characteristics. We found that (i) in all CNS cells the elastic behavior dominates over the viscous behavior, (ii) in distinct cell compartments, such as soma and cell processes, the mechanical properties differ, most likely because of the unequal local distribution of cell organelles, (iii) in comparison to most other eukaryotic cells, both neurons and glial cells are very soft ("rubber elastic"), and (iv) intriguingly, glial cells are even softer than their neighboring neurons. Our results indicate that glial cells can neither serve as structural support cells (as they are too soft) nor as glue (because restoring forces are dominant) for neurons. Nevertheless, from a structural perspective they might act as soft, compliant embedding for neurons, protecting them in case of mechanical trauma, and also as a soft substrate required for neurite growth and facilitating neuronal plasticity.

Changes of phospholipase D activity of rat peritoneal mast cells in degranulation

AIM

To study the changes of phospholipase D (PLD) activity of actively sensitized rat peritoneal mast cells (RPMC) in degranulation.

METHODS

Degranulation of RPMC was determined by measurement of beta-hexosaminidase release. PLD activity assay was carried out by measurement of PLD product, choline, with chemiluminescent oxidation of luminol.

RESULTS

Actively sensitized RPMC challenged with ovalbumin (0.5-8 mg/L for 120 s, 4 mg/L for 15-120 s) resulted in significant activation of PLD accompanied with the increment of beta-hexosaminidase release. PLD activity of sensitized RPMC was increased by more than 2-fold compared with that of unsensitized RPMC which contained low levels of PLD activity [(35+/-13) pmol choline/min in 10(6)cells], but beta-hexosaminidase releases of the sensitized cells were as low as spontaneous releases. After challenge with ovalbumin 4 mg/L for 120 s, PLD activity of sensitized RPMC was increased to (155+/-43) pmol choline/min in 10(6)cells and beta-hexosaminidase release was also elevated significantly (4.5-fold of spontaneous release, n=6, P<0.05). When unsensitized RPMC were stimulated with antigen, PLD activity and beta-hexosaminidase release of the cells were hardly changed. Sensitized RPMC were treated with 1 % 1-butanol or 2,3- disphosphoglycerate 10 mmol/L before challenge with ovalbumin, these drugs induced an inhibition of PLD activity and a reduction of beta-hexosaminidase release to basal level. 1-Butanol 0.1 % also worked.

CONCLUSION

Phospholipase D plays an important role in the regulation of beta-hexosaminidase release in actively sensitized rat peritoneal mast cells.

Acetamide-45 inhibits histamine-and methacholine-induced contraction of isolated guinea pig trachea

AIM

To investigate the effects of the new antiallergic agent N-(pyridin-4-yl)-(indol-3-yl) acetamide-45 (acetamide-45) on histamine- and methacholine-induced contraction of the isolated guinea pig trachea.

METHODS

Cumulative histamine or methacholine concentration-contraction studies were carried out in the absence or presence of acetamide-45. Changes in isometric force were measured by force transducers and recorded on a multi-channel polygraph recorder.

RESULTS

Acetamide-45 (1 - 30 micromol/L) concentration-dependently inhibited histamine- or methacholine-induced contractile response of isolated guinea pig trachea. At concentrations of 3, 10, 30 mumol/L, acetamide-45 significantly decreased maximum contractile response to histamine by 21 % - 51 %, and EC50 values (95 % confidence limits) were 31.1 (24.4 - 39.8), 34.7(26.8 - 45.0), and 134.4 (82.2 - 220.0) micromol/L, respectively. Similarly, acetamide-45 also inhibited the contraction induced by methacholine in isolated guinea pig trachea.

CONCLUSION

Acetamide-45 inhibited histamine- or methacholine-induced contraction of isolated guinea pig trachea, and these effects might be non-specific for either histamine receptor or cholinoceptor.

Effects of methylprednisolone and aprotinin on phospholipase D activity of leukocytes in systemic inflammatory response induced by cardiopulmonary bypass

AIM

To investigate the role of leukocyte phospholipase D (PLD) in systemic inflammatory response induced by cardiopulmonary bypass (CPB) and the effects of methylprednisolone and aprotinin on leukocyte PLD activity.

METHODS

Forty-two patients who received CPB open heart surgery were divided into 3 groups: methylprednisolone group, aprotinin group, and control group. Arterial blood (10 mL) was collected for assay of leukocyte PLD activity, myeloperoxidase (MPO) activity, and CD11b expression at 8 different time points in perioperative period. Plasma IL-6, IL-8, and C-reactive protein levels were also determined.

RESULTS

At the time point of ascending aorta declamped, leukocyte PLD activity for control group was (18 +/- 8) nmol choline . h-1 . mg-1, which was higher than that of pre-CPB (P < 0.01); the PLD activity for methylprednisolone group was (10 +/- 6) nmol choline . h-1 . mg-1 that was lower than control (P < 0.05), while it had no statistical difference compared with that of pre-CPB. In methylprednisolone group, PLD activity elevation was postponed to the time point of CPB stopped. There was no statistical difference in PLD activity between aprotinin group and control (P > 0.05). After administration of methylprednisolone or aprotinin, leukocyte CD11b expression, plasma IL-6, IL-8, C-reactive protein levels, and MPO activity decreased by different extent.

CONCLUSION

Leukocyte PLD activity was elevated significantly in systemic inflammatory response induced by CPB and methylprednisolone partially blunted the CPB-induced inflammatory response by inhibiting PLD activity.

[Role of phospholipase D in phagocytosis and exocytosis]

Mammalian phospholipase D(PLD) is a very important enzyme in the cellular signalling pathways. More and more lines of evidences suggest that PLD may be pivotal on multiple specialized steps in receptor-mediated phagocytosis and exocytosis. In this review, we will explore the recent advances on the role and the mechanism of PLD in phagocytosis and exocytosis.

MyoD-dependent induction during myoblast differentiation of p204, a protein also inducible by interferon

p204, an interferon-inducible p200 family protein, inhibits rRNA synthesis in fibroblasts by blocking the binding of the upstream binding factor transcription factor to DNA. Here we report that among 10 adult mouse tissues tested, the level of p204 was highest in heart and skeletal muscles. In cultured C2C12 skeletal muscle myoblasts, p204 was nucleoplasmic and its level was low. During myoblast fusion this level strongly increased, p204 became phosphorylated, and the bulk of p204 appeared in the cytoplasm of the myotubes. Leptomycin B, an inhibitor of nuclear export that blocked myoblast fusion, inhibited the nuclear export signal-dependent translocation of p204 to the cytoplasm. The increase in the p204 level during myoblast fusion was a consequence of MyoD transcription factor binding to several MyoD-specific sequences in the gene encoding p204, followed by transcription. Overexpression of p204 (in C2C12 myoblasts carrying an inducible p204 expression plasmid) accelerated the fusion of myoblasts to myotubes in differentiation medium and induced the fusion even in growth medium. The level of p204 in mouse heart muscle strongly increased during differentiation; it was barely detectable in 10. 5-day-old embryos, reached the peak level in 16.5-day-old embryos, and remained high thereafter. p204 is the second p200 family protein (after p202a) found to be involved in muscle differentiation. (p202a was formerly designated p202. The new designation is due to the identification of a highly similar protein-p202b [H. Wang, G. Chatterjee, J. J. Meyer, C. J. Liu, N. A. Manjunath, P. Bray-Ward, and P. Lengyel, Genomics 60:281-294, 1999].) These results reveal that p204 and p202a function in both muscle differentiation and interferon action.

Bronchodilating effects of bambuterol on bronchoconstriction in guinea pigs

AIM

To study the effects of bambuterol (Bam) on bronchoconstriction in guinea pigs.

METHODS

Bronchospasm induced by histamine aerosol, lung resistance (RL) and dynamic lung compliance (Cdyn) changes induced by ovalbumin aerosol in vivo, isolated resting lung parenchyma strips, and carbamylcholine-induced tracheal constriction in vitro in guinea pig were investigated.

RESULTS

Bam dose-dependently prolonged the time to histamine-induced collapse, ED50 values (95% confidence limits) of Bam intragastric gavage (i.g.) after 1 h, 4 h, and 24 h were 0.74 (0.60-0.91), 0.75 (0.61-0.91) and 1.00 (0.77-1.30) mg.kg-1, respectively. Bam 2 or 10 mg.kg-1 i.g. 2 h before ovalbumin aerosol partly or almost completely inhibited bronchial challenge of ovalbumin-induced change of RL and Cdyn. Bam 0.1-1.0 mumol.L-1 gave a weak relaxation on isolated tracheal strips induced by carbamylcholine and failed to relax the isolated resting lung parenchyma strips in guinea pig.

CONCLUSION

Bam showed a long-acting bronchodilation by its slow metabolism in vivo.

Mechanistic studies of initiator-initiator interaction and replication initiation

Unlike the chromosome of Escherichia coli that needs only one replication initiator protein (origin recognition protein) called DnaA, many plasmid replicons require dual initiators: host-encoded DnaA and a plasmid-encoded origin recognition protein, which is believed to be the major determinant of replication control. Hitherto, the relative mechanistic roles of dual initiators in DNA replication were unclear. Here, we present the first evidence that DnaA communicates with the plasmid-encoded pi initiator of R6K and contacts the latter at a specific N-terminal region. Without this specific contact, productive unwinding of plasmid ori gamma and replication is abrogated. The results also show that DnaA performs different roles in host and plasmid replication as revealed by the finding that the ATP-activated form of DnaA, while indispensable for oriC replication, was not required for R6K replication. We have analyzed the accessory role of the DNA bending protein, integration host factor (IHF), in promoting initiator-origin interaction and have found that IHF significantly enhances the binding of DnaA to its cognate site. Collectively, the results further advance our understanding of replication initiation.