The regulation of endocannabinoids after neuronal damage and the neuroprotective impact of GPR55 in organotypic hippocampal slice cultures

Endocannabinoids (eCB) are signaling lipids and became known for their importance in the central nervous system as well as in immune defense. Beneficial effects of eCB are shown in processes of excitotoxic lesion, secondary damage and neuronal plasticity throughout the last years. Two canabinoid receptors, type 1 (CB1) and type 2 (CB2) as the respective endogenous ligands belong to the endocannabinoid system (eCBS). In 1990, the CB1 could be cloned and was localised mainly on neurons. Shortly thereafter in 1993, the CB2 was characterised and found primarily on cells belonging to the immune system. N-arachidonoylethanolamide (AEA), often called anandamide, and 2-arachidonoylglycerol (2-AG) are the best characterised eCB. N-palmitylethanolamide (PEA) and N-oleoylethanolamide (OEA) have no or only low affinity to CB1 but enhance the affinity of AEA significantly. This group is therefore often summarized as N-ethanolamides (NEA). ECB are derivates of arachidonic acid and are stored in membranes where they become hydrolysed on demand by specific enzymes. Traumatic brain injury altered the levels of eCB in the blood in vivo and when applied in vitro after neuronal damage, eCB could reduce the damaging burden. Further studies demonstrated that eCB are potent to down-regulate pro-inflammatory cytokines and most important to decrease neuronal excitation. In the present study, the intrinsic regulation of the endocannabinoid system after neuronal damage over time was investigated in rat Organotypic Hippocampal Slice Cultures (OHSC). Temporal and spatial dynamics of eCB levels were analysed after transection of the perforant pathway (PPT) in originating neurons (enthorhinal cortex, EC), areas of deafferentiation/anterograde axonal degeneration (dentate gyrus, DG) and of the synaptically linked cornu ammonis region 1 (CA1) as well as after excitotoxic lesion in the respective regions. A strong increase of all eCB was observed only in the denervation zone of the DG 24 hours post PPT. In excitotoxic lesioned OHSC all eCB were elevated, in the investigated regions up to 72 hours post lesion (hpl). The responsible enzyme for biosynthesis of the NEA, NAPE-PLD protein, was increased during the early timepoints of measurement (1-6 hpl). The responsible catabolizing enzyme, FAAH, and the CB1 receptor were up-regulated at a later timepoint, 48 hpl, explaining the eCB levels. In the present model, the inhibition of the enzyme responsible for 2-AG hydrolysis (MAGL) was neuroprotective as previously shown and a re-distribution within neurons and astrocytes during neuronal damage could be observed. In primary cell cultures microglia expressed the regulating enzymes of 2-AG and the enzyme responsible for NEA down-regulation, FAAH. Astrocytes expressed mainly the catalyzing enzymes, indicating the role for eCB break-down. All these findings together demonstrate the great capacity of the eCBS to control inflammatory processes and consequently neuronal cell death. All effects of the known eCB could not be clarified by CB1/CB2 deficient mice. Several G-protein coupled receptors (GPR) are recently in discussion whether they might and should belong to the endocannabinoid system. The GPR55, the not yet cloned abnormal cannabidiol receptor and further GPRs are candidates as potential endocannabinoid receptors. Recently GPR55 has been discussed as a putative cannabinoid receptor type 3 (CB3). Quantitative PCR revealed that Gpr55 is present in primary microglia and the brain, but the exact regional and cellular distribution and the physiological/pathological effects downstream of GPR55 activation in the CNS still remain open. Therefore, the excitotoxic rat OHSC model, previously used to investigate the neuroprotective potency of eCB, was now used to investigate the neuroprotective potency of GPR55. Activation of GPR55 protected dentate gyrus granule cells in vitro after excitotoxic lesion, induced by NMDA. In parallel, GPR55 activation was able to reduce the number of microglia in the dentate gyrus. These neuroprotective effects vanished however in microglia depleted OHSCs as well as in OHSC transfected with Gpr55 siRNA, indicating a strong involvement of microglia in GPR55 mediated neuroprotection. In summary, the present study found a strong time-dependent and anterograde mechanism of action of eCB after long-range projection damage and provided further evidence for the neuroprotective properties of eCB. The potential cannabinoid receptor 3 (GPR55) mediates neuronal protection on behalf of microglia

Intrinsic up-regulation of 2-AG favors an area specific neuronal survival in different in vitro models of neuronal damage

BACKGROUND: The endocannabinoid 2-arachidonoyl glycerol (2-AG) acts as a retrograde messenger and modulates synaptic signaling e. g. in the hippocampus. 2-AG also exerts neuroprotective effects under pathological situations. To better understand the mechanism beyond physiological signaling we used Organotypic Entorhino-Hippocampal Slice Cultures (OHSC) and investigated the temporal regulation of 2-AG in different cell subsets during excitotoxic lesion and dendritic lesion of long range projections in the enthorhinal cortex (EC), dentate gyrus (DG) and the cornu ammonis region 1 (CA1). RESULTS: 2-AG levels were elevated 24 h after excitotoxic lesion in CA1 and DG (but not EC) and 24 h after perforant pathway transection (PPT) in the DG only. After PPT diacylglycerol lipase alpha (DAGL) protein, the synthesizing enzyme of 2-AG was decreased when Dagl mRNA expression and 2-AG levels were enhanced. In contrast to DAGL, the 2-AG hydrolyzing enzyme monoacylglycerol lipase (MAGL) showed no alterations in total protein and mRNA expression after PPT in OHSC. MAGL immunoreaction underwent a redistribution after PPT and excitotoxic lesion since MAGL IR disappeared in astrocytes of lesioned OHSC. DAGL and MAGL immunoreactions were not detectable in microglia at all investigated time points. Thus, induction of the neuroprotective endocannabinoid 2-AG might be generally accomplished by down-regulation of MAGL in astrocytes after neuronal lesions. CONCLUSION: Increase in 2-AG levels during secondary neuronal damage reflects a general neuroprotective mechanism since it occurred independently in both different lesion models. This intrinsic up-regulation of 2-AG is synergistically controlled by DAGL and MAGL in neurons and astrocytes and thus represents a protective system for neurons that is involved in dendritic reorganisation

A Human Pan-Cancer System Analysis of Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase 3 (PLOD3)

The overexpression of the enzymes involved in the degradation of procollagen lysine is correlated with various tumor entities. Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 3 (PLOD3) expression was found to be correlated to the progression and migration of cancer cells in gastric, lung and prostate cancer. Here, we analyzed the gene expression, protein expression, and the clinical parameters of survival across 33 cancers based on the Clinical Proteomic Tumor Analysis Consortium (CPTAC), function annotation of the mammalian genome 5 (FANTOM5), Gene Expression Omnibus (GEO), Genotype-Tissue Expression (GTEx), Human Protein Atlas (HPA) and The Cancer Genome Atlas (TCGA) databases. Genetic alteration, immune infiltration and relevant cellular pathways were analyzed in detail. PLOD3 expression negatively correlated with survival periods and the infiltration level of CD8+ T cells, but positively correlated to the infiltration of cancer associated fibroblasts in diverse cancers. Immunohistochemistry in colon carcinomas, glioblastomas, and soft tissue sarcomas further confirm PLOD 3 expression in human cancer tissue. Moreover, amplification and mutation accounted for the largest proportion in esophageal adenocarcinoma and uterine corpus endometrial carcinoma, respectively; the copy number alteration of PLOD3 appeared in all cancers from TCGA; and molecular mechanisms further proved the effect of PLOD3 on tumorigenesis. In particular, PLOD3 expression appears to have a tumor immunological effect, and is related to multiple immune cells. Furthermore, it is also associated with tumor mutation burden and microsatellite instability in various tumors. PLOD3 acts as an inducer of various cancers, and it could be a potential biomarker for prognosis and targeted treatment

Site-Specific and Time-Dependent Activation of the Endocannabinoid System after Transection of Long-Range Projections

Background: After focal neuronal injury the endocannabinioid system becomes activated and protects or harms neurons depending on cannabinoid derivates and receptor subtypes. Endocannabinoids (eCBs) play a central role in controlling local responses and influencing neural plasticity and survival. However, little is known about the functional relevance of eCBs in long-range projection damage as observed in stroke or spinal cord injury (SCI). Methods: In rat organotypic entorhino-hippocampal slice cultures (OHSC) as a relevant and suitable model for investigating projection fibers in the CNS we performed perforant pathway transection (PPT) and subsequently analyzed the spatial and temporal dynamics of eCB levels. This approach allows proper distinction of responses in originating neurons (entorhinal cortex), areas of deafferentiation/anterograde axonal degeneration (dentate gyrus) and putative changes in more distant but synaptically connected subfields (cornu ammonis (CA) 1 region). Results: Using LC-MS/MS, we measured a strong increase in arachidonoylethanolamide (AEA), oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) levels in the denervation zone (dentate gyrus) 24 hours post lesion (hpl), whereas entorhinal cortex and CA1 region exhibited little if any changes. NAPE-PLD, responsible for biosynthesis of eCBs, was increased early, whereas FAAH, a catabolizing enzyme, was up-regulated 48hpl. Conclusion: Neuronal damage as assessed by transection of long-range projections apparently provides a strong time-dependent and area-confined signal for de novo synthesis of eCB, presumably to restrict neuronal damage. The present data underlines the importance of activation of the eCB system in CNS pathologies and identifies a novel site-specific intrinsic regulation of eCBs after long-range projection damage

Cannabinoids Modulate Neuronal Activity and Cancer by CB1 and CB2 Receptor-Independent Mechanisms

Cannabinoids include the active constituents of Cannabis or are molecules that mimic the structure and/or function of these Cannabis-derived molecules. Cannabinoids produce many of their cellular and organ system effects by interacting with the well-characterized CB1 and CB2 receptors. However, it has become clear that not all effects of cannabinoid drugs are attributable to their interaction with CB1 and CB2 receptors. Evidence now demonstrates that cannabinoid agents produce effects by modulating activity of the entire array of cellular macromolecules targeted by other drug classes, including: other receptor types; ion channels; transporters; enzymes, and protein- and non-protein cellular structures. This review summarizes evidence for these interactions in the CNS and in cancer, and is organized according to the cellular targets involved. The CNS represents a well-studied area and cancer is emerging in terms of understanding mechanisms by which cannabinoids modulate their activity. Considering the CNS and cancer together allow identification of non-cannabinoid receptor targets that are shared and divergent in both systems. This comparative approach allows the identified targets to be compared and contrasted, suggesting potential new areas of investigation. It also provides insight into the diverse sources of efficacy employed by this interesting class of drugs. Obtaining a comprehensive understanding of the diverse mechanisms of cannabinoid action may lead to the design and development of therapeutic agents with greater efficacy and specificity for their cellular targets

A Human Pan-Cancer System Analysis of Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase 3 (PLOD3)

The overexpression of the enzymes involved in the degradation of procollagen lysine is correlated with various tumor entities. Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 3 (PLOD3) expression was found to be correlated to the progression and migration of cancer cells in gastric, lung and prostate cancer. Here, we analyzed the gene expression, protein expression, and the clinical parameters of survival across 33 cancers based on the Clinical Proteomic Tumor Analysis Consortium (CPTAC), function annotation of the mammalian genome 5 (FANTOM5), Gene Expression Omnibus (GEO), Genotype-Tissue Expression (GTEx), Human Protein Atlas (HPA) and The Cancer Genome Atlas (TCGA) databases. Genetic alteration, immune infiltration and relevant cellular pathways were analyzed in detail. PLOD3 expression negatively correlated with survival periods and the infiltration level of CD8+ T cells, but positively correlated to the infiltration of cancer associated fibroblasts in diverse cancers. Immunohistochemistry in colon carcinomas, glioblastomas, and soft tissue sarcomas further confirm PLOD 3 expression in human cancer tissue. Moreover, amplification and mutation accounted for the largest proportion in esophageal adenocarcinoma and uterine corpus endometrial carcinoma, respectively; the copy number alteration of PLOD3 appeared in all cancers from TCGA; and molecular mechanisms further proved the effect of PLOD3 on tumorigenesis. In particular, PLOD3 expression appears to have a tumor immunological effect, and is related to multiple immune cells. Furthermore, it is also associated with tumor mutation burden and microsatellite instability in various tumors. PLOD3 acts as an inducer of various cancers, and it could be a potential biomarker for prognosis and targeted treatment

PLOD Family: A Novel Biomarker for Prognosis and Personalized Treatment in Soft Tissue Sarcoma

Despite various treatment attempts, the heterogenous group of soft tissue sarcomata (STS) with more than 100 subtypes still shows poor outcomes. Therefore, effective biomarkers for prognosis prediction and personalized treatment are of high importance. The Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase (PLOD) gene family, which is related to multiple cancer entities, consists of three members which encode important enzymes for the formation of connective tissue. The relation to STS, however, has not yet been explored. In this study, data from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases were used to analyze the role of PLOD1–3 in STS. It was found that an overexpression of PLOD family members correlates with poor prognosis, which might be due to an increased infiltration of immune-related cells in the tumor microenvironment. In STS, the expression of PLOD genes could be a novel biomarker for prognosis and a personalized, more aggressive treatment in these patients