Low concentrations of TNF-α in vitro transform the phenotype of vascular smooth muscle cells and enhance their survival in a three-dimensional culture system.

BACKGROUND: Vascular smooth muscle cells (VSMCs) are commonly used as seed cells in tissue-engineered vascular constructions. However, their variable phenotypes and difficult to control functions pose challenges. This study aimed to overcome these obstacles using a three-dimensional culture system. METHODS: Calf VSMCs were administered tumor necrosis factor-alpha (TNF-α) before culturing in two- and three-dimensional well plates and polyglycolic acid (PGA) scaffolds, respectively. The phenotypic markers of VSMCs were detected by immunofluorescence staining and western blotting, and the proliferation and migration abilities of VSMCs were detected by CCK-8, EDU, cell counting, scratch, and Transwell assays. RESULTS: TNF-α rapidly decreased the contractile phenotypic markers and elevated the synthetic phenotypic markers of VSMCs, as well as markedly increasing the proliferation and migration ability of VSMCs under two- and three-dimensional culture conditions. CONCLUSIONS: TNF-α can rapidly induce a phenotypic shift in VSMCs and change their viability on PGA scaffolds.

Carrageenan maintains the contractile phenotype of vascular smooth muscle cells by increasing macromolecular crowding in vitro.

BACKGROUND: The contractile phenotype of vascular smooth muscle cells (VSMCs) results in good diastolic and contractile capacities, and its altered function is the main pathophysiological basis for diseases such as hypertension. VSMCs exist as a synthetic phenotype in vitro, making it challenging to maintain a contractile phenotype for research. It is widely recognized that the common medium in vitro is significantly less crowded than in the in vivo environment. Additionally, VSMCs have a heightened sense for detecting changes in medium crowding. However, it is unclear whether macromolecular crowding (MMC) helps maintain the VSMCs contractile phenotype. PURPOSE: This study aimed to explore the phenotypic, behavioral and gene expression changes of VSMCs after increasing the crowding degree by adding carrageenan (CR). METHODS: The degree of medium crowding was examined by a dynamic light scattering assay; VSMCs survival and activity were examined by calcein/PI cell activity and toxicity and CCK-8 assays; VSMCs phenotypes and migration were examined by WB and wound healing assays; and gene expression was examined by transcriptomic analysis and RT-qPCR. RESULTS: Notably, 225 µg/mL CR significantly increased the crowding degree of the medium and did not affect cell survival. Simultaneously, CR significantly promoted the contraction phenotypic marker expression in VSMCs, shortened cell length, decreased cell proliferation, and inhibited cell migration. CR significantly altered gene expression in VSMCs. Specifically, 856 genes were upregulated and 1207 genes were downregulated. These alterations primarily affect the cellular ion channel transport, microtubule movement, respiratory metabolism, amino acid transport, and extracellular matrix synthesis. The upregulated genes were primarily involved in the cytoskeleton and contraction processes of VSMCs, whereas the downregulated genes were mainly involved in extracellular matrix synthesis. CONCLUSIONS: The in vitro study showed that VSMCs can maintain the contractile phenotype by sensing changes in the crowding of the culture environment, which can be maintained by adding CR.

Macromolecular Crowding Enhances Matrix Protein Deposition in Tissue-Engineered Vascular Grafts.

Successful in vitro culture of small-diameter tissue-engineered vascular grafts (TEVGs) requires rapid deposition of biomacromolecules secreted by vascular smooth muscle cells in a polyglycolic acid mesh scaffold's three-dimensional (3D) porous environment. However, common media have lower crowding conditions than in vivo tissue fluids. In addition, during the early stages of construction, most of the biomolecules secreted by the cells into the medium are lost, which negatively affects the TEVG culture process. In this study, we propose the use of macromolecular crowding (MMC) to enhance medium crowding to improve the deposition and self-assembly efficiency of major biomolecules in the early stages of TEVG culture. The addition of carrageenan significantly increased the degree of MMC in the culture medium without affecting cell viability, proliferation, and metabolic activity. Protein analysis demonstrated that the deposition of collagen types I and III and fibronectin increased significantly in the cell layers of two-dimensional and 3D smooth muscle cell cultures after the addition of a MMC agent. Collagen type I in the culture medium decreased significantly compared with that in the medium without a MMC agent. Scanning electron microscopy demonstrated that MMC agents considerably enhanced the formation of matrix protein structures during the early stages of 3D culture. Hence, MMC modifies the crowding degree of the culture medium, resulting in the rapid formation of numerous matrix proteins and fiber structures. Impact Statement Small-diameter tissue-engineered vascular grafts (TEVGs) are one of the most promising means of treating cardiovascular diseases; however, the in vitro construction of TEVGs has some limitations, such as slow deposition of extracellular matrix (ECM), long culture period, and poor mechanical properties. We hypothesized that macromolecular crowding can increase the crowding of the culture medium to construct a more bionic microenvironment, which enhances ECM deposition in the medium to the cell layer and reduces collagen loss, accelerating and enhancing TEVG culture and construction in vitro.

PRP significantly promotes the adhesion and migration of vascular smooth muscle cells on stent material.

BACKGROUND: The adhesion and survival state of cells on scaffold material is a major problem in tissue-engineered blood vessel (TEBV) culture. Platelet-rich plasma (PRP) contains a large amount of biologically active factors and fibrin, which is expected to play an important role in TEBV culture. PURPOSE: To combine PRP with cells and scaffold material to promote cell adhesion and biological activity on the scaffold material. METHODS: The adhesion status and migration of SMCs under the optimal concentration suitable for SMC growth and the optimal concentration of PRP were examined by scanning electron microscopy, HE staining, CCK-8 assays, qPCR, WB, and other experimental methods and compared with those under the conventional culture (20% FBS); finally, the effect of PRP on the deposition of ECM in vascular tissue engineering culture was verified by three-dimensional culture. RESULTS: PRP at 20% is a suitable concentration for SMCs. Compared with the control group, the 20% PRP group had better migration, and the number of SMC adhesions was significantly higher than that of the control group. In addition, collagen deposition in the experimental group was significantly higher than that in the control group. CONCLUSION: PRP (20%) can promote SMC adhesion, migration, and collagen deposition on the scaffold material.

Using Bayesian Neural Networks to Select Features and Compute Credible Intervals for Personalized Survival Prediction.

An Individual Survival Distribution (ISD) models a patient's personalized survival probability at all future time points. Previously, ISD models have been shown to produce accurate and personalized survival estimates (for example, time to relapse or to death) in several clinical applications. However, off-the-shelf neural-network-based ISD models are usually opaque models due to their limited support for meaningful feature selection and uncertainty estimation, which hinders their wide clinical adoption. Here, we introduce a Bayesian-neural-network-based ISD (BNN-ISD) model that produces accurate survival estimates but also quantifies the uncertainty in model's parameter estimation, which can be used to (1) rank the importance of the input features to support feature selection and (2) compute credible intervals around ISDs for clinicians to assess the model's confidence in its prediction. Our BNN-ISD model utilized sparsity-inducing priors to learn a sparse set of weights to enable feature selection. We provide empirical evidence, on 2 synthetic and 3 real-world clinical datasets, that BNN-ISD system can effectively select meaningful features and compute trustworthy credible intervals of the survival distribution for each patient. We observed that our approach accurately recovers feature importance in the synthetic datasets and selects meaningful features for the real-world clinical data as well, while also achieving state-of-the-art survival prediction performance. We also show that these credible regions can aid in clinical decision-making by providing a gauge of the uncertainty of the estimated ISD curves.

Patterns and predictors of adherence to breast cancer screening recommendations in Alberta's Tomorrow Project.

Breast cancer screening is an important prevention component as it can reduce cancer mortality and improve survival. Understanding patterns of adherence to screening recommendations is essential to guide health promotion strategies and policy implementation efforts. The 1999 Alberta screening guidelines were used to determine screening status for eligible female participants in Alberta's Tomorrow Project (n = 4,972), a longitudinal province-based cohort. Screening patterns were derived based on screening status assessed at enrollment (2001-2008) and follow-up (2008-2011). Information on reason for screening was also collected at each time point. Multinomial logistic regression was used to assess potential predictors of adherence to screening recommendations. The majority of participants were up-to-date with screening at enrollment (79.3 %), and follow-up (75.2 %). Among all participants, 66.3 % were up-to-date at both time points (considered 'regular screeners'), 8.9 % were not up-to-date or never at enrollment but up-to-date at follow-up (considered 'new screeners'), 21.6 % were not up-to-date at follow-up (considered 'episodic screeners') and 3.2 % had never participated in screening (considered 'non-screeners'). Having a family doctor was the strongest factor associated with being a regular screener (OR (95 % CI): 0.37 (0.24 0.57) when compared with new screeners. Current smokers were more likely to be non-regular screeners. The primary reason for screening was routine screening or age. In conclusions, non-regular screening patterns were more prevalent among women without a family doctor. This finding suggests having a family doctor is an important mechanism to encourage screening. Further work is required to raise awareness of current recommendations and to understand and address reasons for non-adherence.

Personalized breast cancer onset prediction from lifestyle and health history information.

We propose a method to predict when a woman will develop breast cancer (BCa) from her lifestyle and health history features. To address this objective, we use data from the Alberta's Tomorrow Project of 18,288 women to train Individual Survival Distribution (ISD) models to predict an individual's Breast-Cancer-Onset (BCaO) probability curve. We show that our three-step approach-(1) filling missing data with multiple imputations by chained equations, followed by (2) feature selection with the multivariate Cox method, and finally, (3) using MTLR to learn an ISD model-produced the model with the smallest L1-Hinge loss among all calibrated models with comparable C-index. We also identified 7 actionable lifestyle features that a woman can modify and illustrate how this model can predict the quantitative effects of those changes-suggesting how much each will potentially extend her BCa-free time. We anticipate this approach could be used to identify appropriate interventions for individuals with a higher likelihood of developing BCa in their lifetime.

Anthropometric changes and risk of diabetes: are there sex differences? A longitudinal study of Alberta's Tomorrow Project.

OBJECTIVES: To characterise the sex-specific difference in the association between anthropometric changes and risk of diabetes in the general population in Canada. SETTING AND PARTICIPANTS: From 2000 to 2008, Alberta's Tomorrow Project (ATP) invited Alberta's residents aged 35-69 years to a prospective cohort study. A total of 19 655 diabetes-free ATP participants having anthropometrics measured at the baseline and follow-ups were included. DESIGN AND OUTCOME MEASURES: A longitudinal study design was used to examine the association between anthropometric changes and risk of diabetes and the sex difference in this association. Changes in weight, body mass index (BMI), waist circumference (WC) and waist-hip-ratio (WHR) were calculated as the difference between baseline and follow-up measures. Diabetes cases were identified using the Canadian National Diabetes Surveillance System algorithm with administrative healthcare data (2000-2015) linked to the ATP cohort. The sex-specific association between anthropometric changes and incidence of diabetes were examined by multivariable Cox regression models. RESULTS: Changes in weight, BMI, WC and WHR over time were positively associated with incidence of diabetes in both men and women. The sex difference in risk of diabetes associated with 1 standard deviation (SD) increase in anthropometrics was 0.07 (95% CI -0.02 to 0.14) for weight, 0.08 (95% CI -0.03 to 0.17) for BMI, 0.07 (95% CI -0.02 to 0.15) for WC and 0.09 (95% CI 0.03 to 0.13) for WHR. Similar results were found in sex difference in the associations with changes per 5% and changes per categories (5% loss, ±5%, 5% gain). CONCLUSIONS: The positive association between anthropometric changes and risk of diabetes was generally stronger in men than in women. However, this sex-specific difference of approximately 10% of the total risk associated with anthropometric changes had limited significance. For population-based public health programmes aiming to control obesity and incidence of diabetes, it may not be necessary to set up sex-specific goals for anthropometric reduction.

Validation of drug prescription records for senior patients in Alberta's Tomorrow Project: Assessing agreement between two population-level administrative pharmaceutical databases in Alberta, Canada.

PURPOSE: To assess agreement between the Pharmaceutical Information Network (PIN), a newly implemented medication data repository in Alberta, Canada, and the Alberta Blue Cross (ABC) database, a long established database with medication records of all senior patients in Alberta. METHODS: PIN data (2008-2015) were cross-validated with ABC medication records for senior participants (older than 65 years old) in Alberta's Tomorrow Project (ATP), a longitudinal cohort study in Alberta. The completeness and accuracy of PIN were respectively calculated as the percentage of ABC records coexisting (concordant) in PIN and the percentage of concordant records having mutually agreeable information on drug quantity. Generalized linear models were used to examine potential association of PIN completeness and accuracy with sociodemographic factors. RESULTS: A total of 1 218 191 drug prescription records from 13 143 ATP participants were captured by PIN and ABC in 2008-2015, among which 91.6% were from PIN, 82.5% from ABC, and 74.2% coexisted in PIN and ABC. The overall completeness of PIN in capturing ABC medication records was 89.9%, with small variations (less than ±5%) across types of drugs. The completeness of PIN was improved on average by 1.3% annually over time (P < .001). PIN had 100% accuracy as defined by drug quantity data agreeable with ABC records. No significant associations were observed with age, sex, ethnicity, rural/urban areas, and socioeconomic status of the participants. CONCLUSIONS: Cross-validated with the ABC dataset, our study showed that irrespective of drug type, PIN has a fairly good completeness (approximately 90%) and accuracy (100%) in capturing the ABC claimed medications for senior patients in Alberta.

Impact of adherence to cancer-specific prevention recommendations on subsequent risk of cancer in participants in Alberta's Tomorrow Project.

OBJECTIVE: The World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) publish recommendations for cancer prevention. The present study aimed to estimate the association between adherence to these cancer-specific prevention recommendations and subsequent development of cancer in a prospective cohort. DESIGN: A composite adherence score was constructed based on questionnaire data to reflect overall adherence to WCRF/AICR lifestyle-related recommendations on body fatness, physical activity, diet and alcoholic drinks. Multivariable Cox proportional hazard regression models were used to assess the association (hazard ratio; 95 % CI) between the adherence score and risk of developing cancer. SETTING: Alberta's Tomorrow Project, a prospective cohort study.ParticipantsMen and women (n 25 100, mean age at enrolment 50·5 years) recruited between 2001 and 2009 with no previous cancer diagnosis were included in analyses. RESULTS: Cancer cases (n 2066) were identified during a mean follow-up of 11·7 years. Participants who were most adherent to the selected WCRF/AICR recommendations (composite score: 4-6) were 13 % (0·87; 0·78, 0·98) less likely to develop cancer compared with those who were least adherent (composite score: 0-2). Each additional recommendation met corresponded to a 5 % (0·95; 0·91, 0·99) reduction in risk of developing cancer. When stratified by sex, the associations remained significant for women, but not for men. CONCLUSIONS: Adherence to lifestyle-related cancer prevention recommendations was associated with reduced risk of developing cancer over the follow-up term in this Canadian cohort.

Microwave assisted extraction for the determination of chlorogenic acid in Flos Lonicerae by direct analysis in real time mass spectrometry (DART-MS).

Flos Lonicerae was an important Chinese medicine. In this research, a microwave assisted extraction method was applied for the extraction of chlorogenic acid from Flos Lonicerae. The operating conditions were optimized using a Box-Behnken design test. Under the optimal conditions, the extraction yield of chlorogenic acid reached 32.52 ±â€¯1.31 mg/g. Next, a direct analysis in real time mass spectrometry (DART-MS) method was utilized to quantify of chlorogenic acid in Flos Lonicerae extracts. The primary parameters were optimized to obtain maximum signal intensity. In the detection process of the actual samples, the results obtained by DART-MS are consistent with those obtained by HPLC method with short detection time and acceptable repeatability and precision (<15%). In addition, the DART-MS/MS method has several advantages, such as speed, low cost and simplicity. Therefore, the DART-MS method is an efficient method that can be applied in the quantification of chlorogenic acid in Flos Lonicerae.

Patterns and predictors of adherence to colorectal cancer screening recommendations in Alberta's Tomorrow Project participants stratified by risk.

BACKGROUND: Colorectal cancer (CRC) screening is an important modifiable behaviour for cancer control. Regular screening, following recommendations for the type, timing and frequency based on personal CRC risk, contributes to earlier detection and increases likelihood of successful treatment. METHODS: To determine adherence to screening recommendations in a large provincial cohort of adults, participants in Alberta's Tomorrow Project (n = 9641) were stratified based on increasing level of CRC risk: age (Age-only), family history of CRC (FamilyHx), personal history of bowel conditions (PersonalHx), or both (Family/PersonalHx) using self-reported information from questionnaires. Provincial and national guidelines for timing and frequency of screening tests were used to determine if participants were up-to-date based on their CRC risk. Screening status was compared between enrollment (2000-2006) and follow-up (2008) to determine screening pattern over time. RESULTS: The majority of participants (77%) fell into the average risk Age-only strata. Only a third of this strata were up-to-date for screening at baseline, but the proportion increased across the higher risk strata, with > 90% of the highest risk Family/PersonalHx strata up-to-date at baseline. There was also a lower proportion (< 25%) of the Age-only group who were regular screeners over time compared to the higher risk strata, though age, higher income and uptake of other screening tests (e.g. mammography) were associated with a greater likelihood of regular screening in multinomial logistic regression. CONCLUSIONS: The low (< 50%) adherence to regular CRC screening in average and moderate risk strata highlights the need to further explore barriers to uptake of screening across different risk profiles.

Changes in body mass index and incidence of diabetes: A longitudinal study of Alberta's Tomorrow Project Cohort.

Although obesity is a known risk factor for diabetes, the impact of body mass index (BMI) changes over time, especially BMI reduction, on diabetes development is less than clear. The objective of this study is to characterize the association between BMI changes over time and incidence of diabetes in a cohort of adults in Alberta. From 2000 to 2008, Alberta's Tomorrow Project (ATP) enrolled participants aged 35-69 to a population-based prospective cohort study. BMI was calculated from self-reported height and weight; change in BMI (∆BMI) was calculated as the difference between baseline and follow-up measurements. Diabetes cases were identified using the Canadian National Diabetes Surveillance System algorithm applied to linked administrative data (2000-2015). Multivariable Cox regression was used to examine the association between ∆BMI and incidence of diabetes. In a subset of the ATP cohort (n=19,164), 1168 incident cases of diabetes were identified during 198,853person-years of follow-up. Overall, BMI increase was associated with increased risk and BMI reduction was associated with reduced risk of diabetes. Particularly, compared to minimal BMI change (±5%), moderate (5%-10%) reduction in BMI was associated with 34% (95% CI: 12%-51%) reduction in risk of diabetes in participants with obesity; whereas 10% or greater increase in BMI was associated with an increased risk of diabetes of 64% or more in participants with overweight and obesity; in participants with normal and underweight, BMI changes was not apparently associated with risk of diabetes. Public health programs promoting weight loss, even at a moderate extent, would reduce risk of diabetes.

Systemic use of antibiotics and risk of diabetes in adults: A nested case-control study of Alberta's Tomorrow Project.

AIMS: Previous observational studies using administrative health records have suggested an increased risk of diabetes with use of antibiotics. However, unmeasured confounding factors may explain these results. This study characterized the association between systemic use of antibiotics and risk of diabetes in a cohort of adults in Canada, accounting for both clinical and self-reported disease risk factors. MATERIALS AND METHODS: In this nested case-control study, we used data from Alberta's Tomorrow Project (ATP), a longitudinal cohort study in Canada, and the linked administrative health records (2000-2015). Incident cases of diabetes were matched with up to 8 age and sex-matched controls per case. Conditional logistic regression was used to examine the association between antibiotic exposures and incident diabetes after sequentially adjusting for important clinical and lifestyle factors. RESULTS: This study included 1676 cases of diabetes and 13 401 controls. Although 17.9% of cases received more than 5 courses of antibiotics, compared to 13.8% of controls (P < .0001), the association between antibiotic use and risk of diabetes was progressively reduced as important clinical and lifestyle factors were accounted for. In fully adjusted models, compared to participants with 0 to 1 courses of antibiotics, participants receiving more antibiotics had no increased risk of diabetes [Odds Ratio, 0.97 (0.83-1.13) for 2 to 4 courses and 0.98 (0.82-1.18) for ≥5 courses]. CONCLUSIONS: After adjustment for clinical and difficult-to-capture lifestyle data, we found no association between systemic use of antibiotics and risk of diabetes. Our results suggest that those positive associations observed in previous studies using only administrative records might have been confounded.

Diet quality is associated with reduced incidence of cancer and self-reported chronic disease: Observations from Alberta's Tomorrow Project.

The objective of this study was to assess diet quality using the Healthy Eating Index-2005 Canada (HEI-2005-Canada) and its association with risk of cancer and chronic disease in a sample of Alberta's Tomorrow Project (ATP) participants. Food frequency questionnaires completed by 25,169 participants (38% men; mean age 50.3 (9.2)) enrolled between 2000 and 2008 were used to calculate HEI-2005-Canada scores. Data from a subset of participants (n=10,735) who reported no chronic disease at enrollment were used to investigate the association between HEI-2005-Canada score and development of self-reported chronic disease at follow-up (2008). Participants were divided into HEI-2005-Canada score quartiles. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for cancer and chronic disease incidence. In this cohort, mean HEI-2005-Canada scores for men and women were 50.9 and 55.5 (maximum range 0-100), respectively. In men, higher HEI-2005-Canada score (Q4 vs. Q1) was associated with lower cancer risk (HR (95% CI) 0.63 (0.49-0.83)) over the course of follow-up (mean (SD)=10.4 (2.3) years); the same was not observed in women. In contrast, higher overall HEI-2005-Canada score (Q4 vs. Q1) was associated with lower risk of self-reported chronic disease (0.85 (0.75-0.97)) in both men and women over follow-up (4.2 (2.3) years). In conclusion, in this cohort better diet quality was associated with a lower risk of cancer in men and lower risk of chronic disease in both sexes. Future studies with longer follow-up and repeated measures of diet may be helpful to elucidate sex-specific associations between dietary quality and disease outcomes.

Alberta's Tomorrow Project: adherence to cancer prevention recommendations pertaining to diet, physical activity and body size.

OBJECTIVE: To explore cross-sectional adherence to cancer prevention recommendations by adults enrolled in a prospective cohort in Alberta, Canada. DESIGN: Questionnaire data were used to construct a composite cancer prevention adherence score for each participant, based on selected personal recommendations published by the World Cancer Research Fund/American Institute for Cancer Research (2007). Data were self-reported on health and lifestyle, past-year physical activity and past-year FFQ. The scores accounted for physical activity, dietary supplement use, body size, and intakes of alcohol, fruit, vegetables and red meat. Tobacco exposure was also included. Scores ranged from 0 (least adherent) to 7 (most adherent). SETTING: Alberta's Tomorrow Project; a research platform based on a prospective cohort. SUBJECTS: Adult men and women (n 24 988) aged 35-69 years recruited by random digit dialling and enrolled in Alberta's Tomorrow Project between 2001 and 2009. RESULTS: Of the cohort, 14 % achieved adherence scores ≥5 and 60 % had scores ≤3. Overall adherence scores were higher in women (mean (sd): 3·4 (1·1)) than in men (3·0 (1·2)). The extent of overall adherence was also associated with level of education, employment status, annual household income, personal history of chronic disease, family history of chronic disease and age. CONCLUSIONS: Reported adherence to selected personal recommendations for cancer prevention was low in this cohort of adults. In the short to medium term, these results suggest that more work is required to identify behaviours to target with cancer prevention strategies at a population level. Future work will explore the associations between adherence scores and cancer risk in this cohort.

Ultrasound extraction of polysaccharides from mulberry leaves and their effect on enhancing antioxidant activity.

A Box-Behnken design (BBD) was applied to optimize the ultrasound-assisted extraction of polysaccharides from mulberry leaves. Under the optimum conditions of an extraction temperature of 57 °C, an extraction time of 80 min and a liquid/solid ratio of 53 mL/g, the mulberry leaf polysaccharide (MLP) yield was 6.92 ± 0.29%. Then, three fractions of MLPs were obtained by deproteinization, dialysis and decolorization. The carbohydrate content, FT-IR spectrum and monosaccharide composition of the MLPs were also investigated. The antioxidant activities of the three fractions were compared, and the results indicated that the antioxidant activities decreased with the increasing MLP purity. Therefore, highly concentrated MLPs were shown to have very little antioxidant activity. After quercetin (10 µg/mL) was added, the antioxidant activities were improved significantly. This result showed that MLPs and quercetin have a synergistic effect on the antioxidant activity. Although the MLPs have very little antioxidant activity alone, they greatly enhance the antioxidant activity of flavonoids. Thus, MLPs can be used as an antioxidant activity enhancer in the food industry.

Endocannabinoids in synaptic plasticity and neuroprotection.

Endocannabinoids (eCBs) are endogenous lipid mediators involved in a variety of physiological, pharmacological, and pathological processes. While activation of the eCB system primarily induces inhibitory effects on both GABAergic and glutamatergic synaptic transmission and plasticity through acting on presynaptically expressed CB1 receptors in the brain, accumulated information suggests that eCB signaling is also capable of facilitating or potentiating excitatory synaptic transmission in the hippocampus. Recent studies show that a long-lasting potentiation of excitatory synaptic transmission at Schaffer collateral (SC)-CA1 synapses is induced by spatiotemporally primed inputs, accompanying with a long-term depression of inhibitory synaptic transmission (I-LTD) in hippocampal CA1 pyramidal neurons. This input timing-dependent long-lasting synaptic potentiation at SC-CA1 synapses is mediated by 2-arachidonoylglycerol (2-AG) signaling triggered by activation of postsynaptic N-methyl-D-aspartate receptors, group I metabotropic glutamate receptors (mGluRs), and a concurrent rise in intracellular Ca(2+). Emerging evidence now also indicates that 2-AG is an important signaling mediator keeping brain homeostasis by exerting its anti-inflammatory and neuroprotective effects in response to harmful insults through CB1/2 receptor-dependent and/or -independent mechanisms. Activation of the nuclear receptor protein peroxisome proliferator-activated receptor-γ apparently is one of the important mechanisms in resolving neuroinflammation and protecting neurons produced by 2-AG signaling. Thus, the information summarized in this review suggests that the role of eCB signaling in maintaining integrity of brain function is greater than what we thought previously.

Long-lasting potentiation of hippocampal synaptic transmission by direct cortical input is mediated via endocannabinoids.

Hippocampal CA1 pyramidal neurons receive sensory inputs from the entorhinal cortex directly through the perforant path (PP) and indirectly through Schaffer collaterals (SC). Direct cortical inputs to CA1 pyramidal neurons through the PP provide instructive signals for hippocampal long-term synaptic plasticity. However, the molecules conveying synaptic signalling in this new form of heterosynaptic plasticity remain unclear. Endocannabinoids, important endogenous signalling mediators, modulate synaptic efficacy primarily through inhibition of GABAergic or glutamatergic synaptic transmission via presynaptically expressed CB1 receptors. Here, we report that pairing of direct and indirect cortical inputs to CA1 pyramidal neurons resulted in a long-lasting potentiation of synaptic responses at SC synapses, but not at the PP. The pairing-potentiated synaptic transmission at the SC was accompanied by a reduced ratio of paired-pulse facilitation (PPR). Enhanced synaptic response at the SC by pairing of PP­SC stimuli is Ca(2+) dependent and requires the presence of functional GABAergic and glutamatergic synaptic transmissions and activation of group I metabotropic glutamate receptors. Pharmacological inhibition or genetic deletion of the CB1 receptor eliminated the pairing-induced long-term synaptic plasticity and decreased PPR at the SC. The potentiation induced by pairing of PP­SC stimuli primarily is the glutamatergic synaptic transmission. While the pairing-induced long-lasting potentiation of synaptic response was blocked by inhibitors for diacylglycerol lipase (DGL), which biosynthesizes 2-AG, inhibition of monoacylglycerol lipase (MAGL), which metabolizes 2-AG, facilitated the potentiation at SC synapses by pairing of weak PP­SC stimuli. Our results suggest that 2-AG functions as a signalling mediator tuning synaptic efficacy at the proximal synapses of hippocampal CA1 pyramidal neurons while direct and indirect cortical inputs to the same neurons are spatiotemporally primed.