Natural variation of GmFATA1B regulates seed oil content and composition in soybean.

Soybean (Glycine max) produces seeds that are rich in unsaturated fatty acids and is an important oilseed crop worldwide. Seed oil content and composition largely determine the economic value of soybean. Due to natural genetic variation, seed oil content varies substantially across soybean cultivars. Although much progress has been made in elucidating the genetic trajectory underlying fatty acid metabolism and oil biosynthesis in plants, the causal genes for many quantitative trait loci (QTLs) regulating seed oil content in soybean remain to be revealed. In this study, we identified GmFATA1B as the gene underlying a QTL that regulates seed oil content and composition, as well as seed size in soybean. Nine extra amino acids in the conserved region of GmFATA1B impair its function as a fatty acyl-acyl carrier protein thioesterase, thereby affecting seed oil content and composition. Heterogeneously overexpressing the functional GmFATA1B allele in Arabidopsis thaliana increased both the total oil content and the oleic acid and linoleic acid contents of seeds. Our findings uncover a previously unknown locus underlying variation in seed oil content in soybean and lay the foundation for improving seed oil content and composition in soybean.

Photoredox-catalyzed trifluoromethylation of 2H-indazoles using TT-CF3+OTf- in ionic liquids.

A protocol for metal and oxidant free photoredox catalyzed trifluoromethylation of 2H-indazoles was developed by using Eosin Y as the photocatalyst and recoverable ionic liquids as the solvents. A series of trifluoromethylated products were obtained in moderate to good yields in this protocol under mild conditions. The reaction proceeded via a free-radical mechanism with a broad substrate range, excellent regioselectivity, and good functional group tolerance. Furthermore, the utility of this protocol was demonstrated by the synthesis of a highly selective ligand for estrogen receptor beta (ERß) and the drug granisetron. The protocol provides a mild and environmentally friendly solution for trifluoromethylation reaction.

The Preoperative Diagnostic Performance of Multi-Parametric Quantitative Assessment in Rectal Carcinoma: A Preliminary Study Using Synthetic Magnetic Resonance Imaging.

Objective: Synthetic MRI (SyMRI) can reconstruct different contrast-weighted images(T1, T2, PD) and has shorter scan time, easier post-processing and better reproducibility. Some studies have shown splendid correlation with conventional mapping techniques and no degradation in the quality of syMRI images compared with conventional MRI. It is crucial to select an individualized treatment plan based on the preoperative images of rectal carcinoma (RC). We tried to explore the feasibility of syMRI on T, N stage and extramural vascular invasion (EMVI) of rectal cancer. Materials and Methods: A total of 100 patients (37 females and 63 males) diagnosed with rectal carcinoma were enrolled. All the patients underwent preoperative pelvic MR examinations including conventional MR sequence and synthetic MRI. Two radiologists evaluated the MRI findings of each rectal carcinoma and EMVI score in consensus. The values for T1, T2 relaxation times and PD value were measured in tumor(ROI-1) and pararectal fat space(ROI-2) and analyzed independently. A receiver operating characteristic (ROC) analysis was performed. Correlations between the T1, T2 and PD values and EMVI score were also evaluated. Results: Compared with the normal rectal wall, the values of T1 and T2 relaxation times of the tumor were significantly higher (P <0.001). There was no statistically significant difference in the PD value (P >0.05). As for ROI, the ROI of pararectal fat space(ROI-2) had better significance than rectal cancer lesion (ROI-1). T2 value of ROI-1 and T1 value of ROI-2 were higher in the pEMVI positive group than in the negative group (P=0.002 and 0.001) and T1 value of ROI-2 had better performance with an AUC of 0.787, (95% CI:0.693- 0.882). T1 value, T2 value and PD value from ROI-2 were effective for both T and N stage of rectal cancer. High-grade pathological stage had showed higher T1 value (PT stage=0.013,PN stage=0.035), lower T2 value (PT stage=0.025,PN stage=0.034) and lower PD value (PT stage=0.017). We also enrolled the characteristics with P < 0.05 in the combined model which had better diagnostic efficacy. A significant positive correlation was found between the T1 value of pararectal fat space(ROI-2) and EMVI score (r value = 0.519, P<0.001). The T2 value(r=0.213,P=0.049) and PD value(r=0.354,P=0.001) from ROI-1 was correlated with EMVI score. Correlation analysis did not show any significant associations between T2 value of tumor, T2, PD values of pararectal fat space and EMVI scores. Conclusion: Synthetic MRI can provide multi-parameter quantitative image maps with a easier measurement and slightly shorter acquisition time compared with conventional MRI. The measurement of multi-parametric quantitative values contributes to diagnosing the tumor and evaluating T stage, N stage and EMVI. It has the potential to be used as a preoperative diagnostic and grading technique in rectal carcinoma.

ß-Amyloid discordance of cerebrospinal fluid and positron emission tomography imaging shows distinct spatial tau patterns.

Extracellular ß-amyloid plaques and intracellular neurofibrillary tau tangles are the primary hallmarks of Alzheimer's disease. ß-Amyloid pathology can be directly quantified by positron emission tomography imaging or indirectly by measuring the decrease of cerebrospinal fluid ß-amyloid42/ß-amyloid40 ratio. Although these two ß-amyloid biomarkers may be considered interchangeable, they sometimes show discordance, particularly in early stage of Alzheimer's disease. Individuals with cerebrospinal fluid ß-amyloid positive only or ß-amyloid positron emission tomography positive only may be at early amyloidosis stage compared to those who are cerebrospinal fluid ß-amyloid negative and ß-amyloid positron emission tomography negative orcerebrospinal fluid ß-amyloid positive and ß-amyloid positron emission tomography positive. Besides, ß-amyloid pathology may play an initiating role in Alzheimer's disease onset, leading to subsequent tau increases. However, it is still unclear whether individuals with different ß-amyloid pathways have distinct spatial patterns of cortical tau tangles in early amyloidosis stage. In this study, we analyzed 238 cognitively unimpaired and 77 mild cognitive impairment individuals with concurrent (interval of acquisition <1 year) 18F-flortaucipir tau positron emission tomography, ß-amyloid (18F-florbetapir or 18F-florbetaben) positron emission tomography and cerebrospinal fluid ß-amyloid42 and ß-amyloid40 and cerebrospinal fluid p-Tau181 and divided them into four different cerebrospinal fluid/positron emission tomography groups based on the abnormal status of cerebrospinal fluid ß-amyloid42/ß-amyloid40 (cerebrospinal fluid±) and ß-amyloid positron emission tomography (±). We determined the cortical regions with significant tau elevations of different cerebrospinal fluid/positron emission tomography groups and investigated the region-wise and voxel-wise associations of tau positron emission tomography images with cerebrospinal fluid ß-amyloid42/ß-amyloid40, ß-amyloid positron emission tomography and cerebrospinal fluid p-Tau/ß-amyloid40 in early (cerebrospinal fluid positive/positron emission tomography negative and cerebrospinal fluid negative/positron emission tomography positive) and late (cerebrospinal fluid positive/positron emission tomography positive) amyloidosis stages. By compared to the cerebrospinal fluid negative/positron emission tomography negative individuals (Ref) without evidence of tau increase measured by cerebrospinal fluid or positron emission tomography, cerebrospinal fluid positive/positron emission tomography negative individuals showed higher tau in entorhinal but not in BraakIII/IV and BraakV/VI, whereas cerebrospinal fluid negative/positron emission tomography positive individuals had significant tau elevations in BraakV/VI but not in entorhinal and BraakIII/IV. In contrast, cerebrospinal fluid positive/positron emission tomography positive individuals showed significant tau increases in all the cortical regions than the Ref group. The voxel-wise analyses provided further evidence that lower cerebrospinal fluid ß-amyloid42/ß-amyloid40 was associated with higher tau in entorhinal, whilst higher ß-amyloid positron emission tomography was related to higher tau in BraakV/VI regions in early amyloidosis stage. Both lower cerebrospinal fluid ß-amyloid42/ß-amyloid40 and higher ß-amyloid positron emission tomography were correlated with tau aggregation in all the Braak stages regions in late amyloidosis stage. These findings provide novel insights into the spatial patterns of cortical tau tangles in different amyloidosis stages of Alzheimer's disease, suggesting cerebrospinal fluid ß-amyloid and ß-amyloid positron emission tomography discordant groups may have distinct characteristics of cortical tau tangles in early amyloidosis stage.

Chemical Characterization of Chinese Perilla Seed Oil.

Physicochemical properties and chemical composition of Chinese perilla seed oil has been characterized in this study. The result showed that both the cold press oil and the solvent extracted oil possessed low acid value and peroxide value. The fatty acid composition result showed that the oil has high content of linolenic acid (C18:3) up to 66.4 g/100 g, followed by linoleic acid (C18:2) of 15.3 g/100 g. The total triacylglycerol (TAG) profiles results showed that the oil contained 20 TAGs including 17 regioisomers, including LnLnLn (35.8 g/100 g), LLnLn (20.2 g/100 g), LLLn (17.7 g/100 g) and PLnLn (14.9 g/100 g) (Ln, linolenic acid; L, linoleic acid; P, palmitic acid). With content of only 0.57 g/100 g oil, the unsaponifiable matters were mainly composed of phytosterols, squalene, tocopherol, alcohols and hydrocarbons. The total phytosterols content was 0.39 g/100 g oil, in which ß-sitosterol has high content of 0.31 g/100 g oil.

[Effect of warm-needle moxibustion intervention on immune function and intestinal flora in patients after colorectal cancer radical operation].

OBJECTIVE: To explore the effect of warm-needle moxibustion (WNM) on the levels of T cell subgroups and serum inflammatory factors, intestinal microecological balance and postoperative adverse reactions in patients with colorectal cancer. METHODS: Eighty-four patients who underwent elective radical resection of colorectal cancer were randomly and equally divided into control (medication) group (23 men and 19 women) and WNM group (24 men and 18 women). Patients of the control group received conventional medication treatment (such as postoperative anti-infection and fluid supplementation), and those of the WNM group received conventional medication plus WNM stimulation (the acupuncture needle handle warmed by ignited moxa stick) of bilateral Zusanli(ST36), Sanyinjiao(SP6), Yinlingquan(SP9), Shangjuxu(ST37), and Zhaohai(KI6). The acupuncture needles were retained for 45 minutes every time, starting on the first day after surgery, once a day for 15 days. The number of T cell subsets (CD3+, CD4+, CD8+) positive cells was counted under fluorescence microscope, and the contents of serum tumor necrosis factor α(TNF-α) and interleukin-6 (IL-6) were detected by using ELISA, and the level of C-reactive protein (CRP) was detected by using immunoturbidimetry. The levels (logarithm of colony-forming units per gram of wet fecal weight) of Bifidobacterium, Lactobacillus, Escherichia coli and Enterococcus were determined. The adverse reactions (leukocyte decline, nausea and vomiting, peripheral phlebitis, cold stimulation sensitivity) were recorded after surgery. RESULTS: Before treatment, there were no significant differences between the two groups in the number of T cell subgroups, TNF-α and IL-6 contents, and intestinal flora numbers (P>0.05). After the treatment, self-comparison showed that the numbers of CD3+ and CD4+ positive cells, the ratio of CD4+/CD8+ and the intestinal Bifidobacterium and Lactobacillus levels in the WNM group were significantly increased (P<0.05), whereas the number of CD8+positive cells, intestinal Escherichia coli and Enterococcus levels in the WNM group, and the levels of TNF-α, IL-6 and CRP in both groups were obviously decreased in comparison with their own pretreatment (P<0.05), but no significant changes were found in the levels of CD3+ and CD4+ positive cells, CD4+/CD8+ and intestinal Bifidobacterium, Lactobacillus, Escherichia coli and Enterococcus in the control group (P>0.05). Comparison between two groups displayed that after the treatment, the numbers of CD3+ and CD4+ positive cells, the ratio of CD4+/CD8+, as well as the levels of Bifidobacterium and Lactobacillus were significantly higher in the WNM group than in the control group (P<0.05), whereas the number of CD8+ positive cells， TNF-a, IL-6 and CRP, and the levels of Escherichia coli and Enterococcus were obviously lower in the WNM group than in the control group (P<0.05). The incidence of adverse reactions including leukopenia, nausea and vomiting, peripheral phlebitis, and sensitivity to cold stimulation in the WNM group were markedly lower than those of the control group (P<0.05). CONCLUSION: WNM intervention can significantly improve the immune function, reduce the level of inflammatory factors, regulate the level of beneficial intestinal flora, and also reduce the incidence of postoperative adverse reactions in patients experiencing radical resection of colorectal cancer.

Adenosine Signaling and Clathrin-Mediated Endocytosis of Glutamate AMPA Receptors in Delayed Hypoxic Injury in Rat Hippocampus: Role of Casein Kinase 2.

Chronic adenosine A1R stimulation in hypoxia leads to persistent hippocampal synaptic depression, while unopposed adenosine A2AR receptor stimulation during hypoxia/reperfusion triggers adenosine-induced post-hypoxia synaptic potentiation (APSP) and increased neuronal death. Still, the mechanisms responsible for this adenosine-mediated neuronal damage following hypoxia need to be fully elucidated. We tested the hypothesis that A1R and A2AR regulation by protein kinase casein kinase 2 (CK2) and clathrin-dependent endocytosis of AMPARs both contribute to APSPs and neuronal damage. The APSPs following a 20-min hypoxia recorded from CA1 layer of rat hippocampal slices were abolished by A1R and A2AR antagonists and by broad-spectrum AMPAR antagonists. The inhibitor of GluA2 clathrin-mediated endocytosis Tat-GluA2-3Y peptide and the dynamin-dependent endocytosis inhibitor dynasore both significantly inhibited APSPs. The CK2 antagonist DRB also inhibited APSPs and, like hypoxic treatment, caused opposite regulation of A1R and A2AR surface expression. APSPs were abolished when calcium-permeable AMPAR (CP-AMPAR) antagonist (IEM or philanthotoxin) or non-competitive AMPAR antagonist perampanel was applied 5 min after hypoxia. In contrast, perampanel, but not CP-AMPAR antagonists, abolished APSPs when applied during hypoxia/reperfusion. To test for neuronal viability after hypoxia, propidium iodide staining revealed significant neuroprotection of hippocampal CA1 pyramidal neurons when pretreated with Tat-GluA2-3Y peptide, CK2 inhibitors, dynamin inhibitor, CP-AMPAR antagonists (applied 5 min after hypoxia), and perampanel (either at 5 min hypoxia onset or during APSP). These results suggest that the A1R-CK2-A2AR signaling pathway in hypoxia/reperfusion injury model mediates increased hippocampal synaptic transmission and neuronal damage via calcium-permeable AMPARs that can be targeted by perampanel for neuroprotective stroke therapy.

Nutritional Component and Chemical Characterization of Chinese Highland Barley Bran Oil.

The nutritional composition and chemical properties of the Chinese highland barley bran oil were characterized in this study. The barley bran oil extracted with solvent possessed relatively high acid value and peroxide value, indicating that the oil should be further refined before using. The fatty acid composition of the oil showed that the content of unsaturated fatty acids was 80.12 g/100 g, in which the content of polyunsaturated fatty acids was as high as 60.41 g/100 g. The overall triacylglycerol profile showed that the oil contained 27 TAGs including 21 regioisomers. Major TAGs included LLL (21.08 g/100 g), PLL (19.27 g/100 g), LLO (12.24 g/100 g), and LLLn (12.17 g/100 g). The total unsaponifiable matter of the oil reached up to 10.74 g/100 g oil. The total phytosterol content reached 7.90 g/100 g oil, in which ß-sitosterol was the most predominant, with the content of 5.69 g/100 g oil. Other important sterols included campesterol (1.32 g/100 g oil), lanosterol (0.70 g/100 g oil) and stigmasterol (0.19 g/100 g oil).

Paeonol exerts anti­tumor activity against colorectal cancer cells by inducing G0/G1 phase arrest and cell apoptosis via inhibiting the Wnt/ß­catenin signaling pathway.

Paeonol is a simple phenolic compound isolated from herbal root bark, which has been reported to possess numerous biological and pharmacological characteristics, including a desirable anti­tumor effect. To date, the effect of paeonol against colorectal cancer (CRC) cells is yet to be fully elucidated. Therefore, the present study aimed to identify the underlying mechanism via which paeonol exerts its anti­tumor activity on HCT116 cells. After incubation with various concentrations of paeonol (7.8125, 15.625, 31.25, 62.5, 125, 250 and 500 µg/ml), the inhibitory effect of paeonol on cell viability was assessed using a Cell Counting Kit­8 assay. Cell apoptosis and cell cycle distribution were measured using flow cytometry. Moreover, caspase activity was measured using a colorimetric caspase assay. Luciferase assay was also used to determine the ß­catenin­mediated transcriptional activity of T­cell specific transcription factor/lymphoid­enhancer binding factor (TCF/LEF), and western blotting analysis was performed to measure the related expression of proteins. The results indicated that paeonol exhibited a notable effect against HCT116 cells by inducing G0/G1­phase arrest, as demonstrated by downregulation of the cell cycle regulators cyclin­dependent kinase 4 and cyclin D1 and upregulation of p21Cip1 in a dose­dependent manner. Furthermore, paeonol dose­dependently induced cell apoptosis, accompanied by an increase in the Bax/Bcl­2 ratio, release of cytochrome c and further activation of caspases. Paeonol also dose­dependently blocked the activation of the Wnt/ß­catenin signaling pathway by suppressing the expression of ß­catenin, resulting in a decrease in ß­catenin­mediated activity of TCF/LEF and downregulation of downstream target genes, including cyclin D1, survivin and c­Myc. Therefore, the present results suggested that paeonol exerted its anti­tumor effects on CRC cells, including the inhibition of cell proliferation, induction of cell cycle arrest and initiation of apoptosis, at least partly by suppressing the Wnt/ß­catenin pathway, which may offer a promising therapeutic strategy for CRC.

Fatty Acid, Triacylglycerol and Unsaponifiable Matters Profiles and Physicochemical Properties of Chinese Evening Primrose Oil.

This work focused on physicochemical property assaying, fatty acid composition, triacylglycerol (TAG) profiles, and unsaponifiable matters composition of the Chinese evening primrose oil. The cold press oil possessed very low acid value and peroxide value, and relatively high iodine value. Fatty acid composition results indicated that this oil was especially high in linoleic acid and linolenic acid. Characterization of TAG composition was achieved by a two-dimensional HPLC coupling of nonaqueous reverse-phase and silver ion HPLC with atmospheric pressure chemical ionization MS method. There was a total of 38 TAGs including 27 regioisomers which had been determined. Unsaponifiable matters composition results revealed that this oil possessed a number of phytosterols, in which ß-sitosterol and stigmasterol were most predominant.

Modulation of G2/M cell cycle arrest and apoptosis by luteolin in human colon cancer cells and xenografts.

The aim of the present study was to investigate the underlying molecular mechanisms of the potent cell cycle inhibition and apoptotic effect of luteolin on LoVo human colon cancer cells. In the present study, Cell Counting kit-8 assay revealed that luteolin exerted notable cytotoxicity on LoVo cells in a dose- and time-dependent manner, with a 50% inhibitory concentration value of 66.70 and 30.47 µmol/l at the time points of 24 and 72 h, respectively. Flow cytometric analysis confirmed that luteolin promoted cell cycle arrest at the G2/M phase, and subsequently induced cell apoptosis. Western blot analysis further revealed that luteolin exhibited an inhibitory effect on the proliferation of LoVo cells by inhibiting cell cycle arrest at the G2/M phase transition, with an inactivation of cyclin B1/cell division cycle 2 and induction of cell apoptosis, in part via cytochrome c- and deoxyadenosine triphosphate-mediated activation of apoptotic protease activating factor 1. In vivo studies revealed that luteolin effectively decreased the colon tumor body weight of mice. Therefore, the evidence suggests that luteolin may be a potential chemopreventive and chemotherapeutic agent against human colon cancer.

Columnaristerol A, a novel 19-norsterol from the Formosan octocoral Nephthea columnaris.

Columnaristerol A (1), a rare natural 19-norsterol possessing a 10ß-hydroxy group was isolated from the Formosan octocoral Nephthea columnaris, and its structure was elucidated by spectroscopic methods. Sterol 1 was found to be a cytotoxic agent that exhibited in vitro moderate cytotoxic activity against MOLT-4 and SUP-T1 human leukemia-lymphoma cell lines.

Development and evaluation of a double antibody sandwich ELISA for the detection of human sDC-SIGN.

sDC-SIGN is the soluble form of dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN, CD209), which is a molecule involved with pathogen recognition and immune regulation. However, there is no commercially available ELISA kit for detecting human sDC-SIGN, and the normal range of this molecule is unknown. Here, we describe an ELISA for detecting human sDC-SIGN with high specificity. First, sDC-SIGN protein was expressed and purified. Monoclonal and polyclonal antibodies were then raised against the purified protein and subsequently characterized. A sandwich ELISA was developed using polyclonal antibodies specific for sDC-SIGN for capture and a biotin-labeled monoclonal antibody specific for sDC-SIGN for detection of protein. This method has sensitivity up to 0.2 ng/ml. Using this ELISA, we found that the concentration of sDC-SIGN in sera of healthy volunteers ranges from 0-319 ng/ml with a mean concentration of 27.14 ng/ml. Interestingly, the concentration of sDC-SIGN in sera from patients with cancer or chronic hepatitis B virus (CHB) infection was lower than that of health controls. The mean concentrations of sDC-SIGN in cancer patients and chronic hepatitis B virus infection patients were 3.2 ng/ml and 3.8 ng/ml, respectively. We developed a sandwich ELISA for detecting human sDC-SIGN and demonstrated its use by assessing sera concentrations of sDC-SIGN in patients with cancer and chronic CHB infection compared to that of healthy controls.

Protein phosphatase role in adenosine A1 receptor-induced AMPA receptor trafficking and rat hippocampal neuronal damage in hypoxia/reperfusion injury.

Adenosine signaling via A1 receptor (A1R) and A2A receptor (A2AR) has shown promise in revealing potential targets for neuroprotection in cerebral ischemia. We recently showed a novel mechanism by which A1R activation with N(6)-cyclopentyl adenosine (CPA) induced GluA1 and GluA2 AMPA receptor (AMPAR) endocytosis and adenosine-induced persistent synaptic depression (APSD) in rat hippocampus. This study further investigates the mechanism of A1R-mediated AMPAR internalization and hippocampal slice neuronal damage through activation of protein phosphatase 1 (PP1), 2A (PP2A), and 2B (PP2B) using electrophysiological, biochemical and imaging techniques. Following prolonged A1R activation, GluA2 internalization was selectively blocked by PP2A inhibitors (okadaic acid and fostriecin), whereas inhibitors of PP2A, PP1 (tautomycetin), and PP2B (FK506) all prevented GluA1 internalization. Additionally, GluA1 phosphorylation at Ser831 and Ser845 was reduced after prolonged A1R activation in hippocampal slices. PP2A inhibitors nullified A1R-mediated downregulation of pSer845-GluA1, while PP1 and PP2B inhibitors prevented pSer831-GluA1 downregulation. Each protein phosphatase inhibitor also blunted CPA-induced synaptic depression and APSD. We then tested whether A1R-mediated changes in AMPAR trafficking and APSD contribute to hypoxia-induced neuronal injury. Hypoxia (20 min) induced A1R-mediated internalization of both AMPAR subunits, and subsequent normoxic reperfusion (45 min) increased GluA1 but persistently reduced GluA2 surface expression. Neuronal damage after hypoxia-reperfusion injury was significantly blunted by pre-incubation with the above protein phosphatase inhibitors. Together, these data suggest that A1R-mediated protein phosphatase activation causes persistent synaptic depression by downregulating GluA2-containing AMPARs; this previously undefined role of A1R stimulation in hippocampal neuronal damage represents a novel therapeutic target in cerebral ischemic damage.

Adenosine A1 Receptor-Mediated Endocytosis of AMPA Receptors Contributes to Impairments in Long-Term Potentiation (LTP) in the Middle-Aged Rat Hippocampus.

Aging causes multiple changes in the mammalian brain, including changes in synaptic signaling. Previous reports have shown increased extracellular adenosine in the aging brain, and we recently reported that activation of adenosine A1 receptors (A1Rs) induces AMPA receptor (AMPAR) internalization in rat hippocampus. This study investigated whether aging-related changes in the rat hippocampus include altered surface expression of adenosine A1 and A2A receptors, and whether these changes correspond to changes in AMPAR surface expression and altered synaptic plasticity. We found reduced A1R surface expression in middle-aged rat hippocampus, and also reduced GluA1 and GluA2 AMPAR subunit surface expression. Using a chemically-induced LTP (cLTP) experimental protocol, we recorded fEPSPs in young (1 month old) and middle-aged (7-12 month old) rat hippocampal slices. There were significant impairments in cLTP in middle-aged slices, suggesting impaired synaptic plasticity. Since we previously showed that the A1R agonist N(6)-cyclopentyladenosine (CPA) reduced both A1Rs and GluA2/GluA1 AMPARs, we hypothesized that the observed impaired synaptic plasticity in middle-aged brains is regulated by A1R-mediated AMPAR internalization by clathrin-mediated endocytosis. Following cLTP, we found a significant increase in GluA1 and GluA2 surface expression in young rats, which was blunted in middle-aged brains or in young brains pretreated with CPA. Blocking A1Rs with 8-cyclopentyl-1,3-dipropylxanthine or AMPAR endocytosis with either Tat-GluA2-3Y peptide or dynasore (dynamin inhibitor) similarly enhanced AMPAR surface expression following cLTP. These data suggest that age-dependent alteration in adenosine receptor expression contributes to increased AMPAR endocytosis and impaired synaptic plasticity in aged brains.

Prolonged adenosine A1 receptor activation in hypoxia and pial vessel disruption focal cortical ischemia facilitates clathrin-mediated AMPA receptor endocytosis and long-lasting synaptic inhibition in rat hippocampal CA3-CA1 synapses: differential regulation of GluA2 and GluA1 subunits by p38 MAPK and JNK.

Activation of presynaptic adenosine A1 receptors (A1Rs) causes substantial synaptic depression during hypoxia/cerebral ischemia, but postsynaptic actions of A1Rs are less clear. We found that A1Rs and GluA2-containing AMPA receptors (AMPARs) form stable protein complexes from hippocampal brain homogenates and cultured hippocampal neurons from Sprague Dawley rats. In contrast, adenosine A2A receptors (A2ARs) did not coprecipitate or colocalize with GluA2-containing AMPARs. Prolonged stimulation of A1Rs with the agonist N(6)-cyclopentyladenosine (CPA) caused adenosine-induced persistent synaptic depression (APSD) in hippocampal brain slices, and APSD levels were blunted by inhibiting clathrin-mediated endocytosis of GluA2 subunits with the Tat-GluA2-3Y peptide. Using biotinylation and membrane fractionation assays, prolonged CPA incubation showed significant depletion of GluA2/GluA1 surface expression from hippocampal brain slices and cultured neurons. Tat-GluA2-3Y peptide or dynamin inhibitor Dynasore prevented CPA-induced GluA2/GluA1 internalization. Confocal imaging analysis confirmed that functional A1Rs, but not A2ARs, are required for clathrin-mediated AMPAR endocytosis in hippocampal neurons. Pharmacological inhibitors or shRNA knockdown of p38 MAPK and JNK prevented A1R-mediated internalization of GluA2 but not GluA1 subunits. Tat-GluA2-3Y peptide or A1R antagonist 8-cyclopentyl-1,3-dipropylxanthine also prevented hypoxia-mediated GluA2/GluA1 internalization. Finally, in a pial vessel disruption cortical stroke model, a unilateral cortical lesion compared with sham surgery reduced hippocampal GluA2, GluA1, and A1R surface expression and also caused synaptic depression in hippocampal slices that was consistent with AMPAR downregulation and decreased probability of transmitter release. Together, these results indicate a previously unknown mechanism for A1R-induced persistent synaptic depression involving clathrin-mediated GluA2 and GluA1 internalization that leads to hippocampal neurodegeneration after hypoxia/cerebral ischemia.