Lack of the transient receptor potential vanilloid 1 shifts cannabinoid-dependent excitatory synaptic plasticity in the dentate gyrus of the mouse brain hippocampus

[EN] The transient receptor potential vanilloid 1 (TRPV1) participates in synaptic functions in the brain. In the dentate gyrus, post-synaptic TRPV1 in the granule cell (GC) dendritic spines mediates a type of long-term depression (LTD) of the excitatory medial perforant path (MPP) synapses independent of pre-synaptic cannabinoid CB1 receptors. As CB1 receptors also mediate LTD at these synapses, both CB1 and TRPV1 might be influencing the activity of each other acting from opposite synaptic sites. We tested this hypothesis in the MPP–GC synapses of mice lacking TRPV1 (TRPV1-/-). Unlike wild-type (WT) mice, low-frequency stimulation (10min at 10Hz) of TRPV1-/- MPP fibers elicited a form of long-term potentiation (LTP) that was dependent on (1) CB1 receptors, (2) the endocannabinoid 2-arachidonoylglycerol (2-AG), (3) rearrangement of actin filaments, and (4) nitric oxide signaling. These functional changes were associated with an increase in the maximum binding efficacy of guanosine-5′-O-(3-[35S]thiotriphosphate) ([35S]GTPgS) stimulated by the CB1 receptor agonist CP 55,940, and a significant decrease in receptor basal activation in the TRPV1-/- hippocampus. Finally, TRPV1-/- hippocampal synaptosomes showed an augmented level of the guanine nucleotide-binding (G) Gai1, Gai2, and Gai3 protein alpha subunits. Altogether, the lack of TRPV1 modifies CB1 receptor signaling in the dentate gyrus and causes the shift from CB1 receptor-mediated LTD to LTP at the MPP–GC synapses.This work was supported by the Basque Government (IT1230- 19, to PG); MINECO/FEDER, UE (SAF2015-65034-R, to PG); Ministry of Science and Innovation (PID2019-107548RBI00, to PG); Red de Trastornos Adictivos, Instituto de Salud Carlos III (ISC-III); and European Regional Development Funds-European Union (ERDF-EU, Investing in your future; RD16/0017/0012, to PG); MINECO CTQ2017-85686-R (Spanish Ministry of Economy and Competitiveness, to JS); JE-H is a Postdoctoral Researcher contracted with funds of Red de Trastornos Adictivos, Instituto de Salud Carlos III (ISC-III), and European Regional Development Funds-European Union (ERDF-EU, Investing in your future; RD16/0017/0012), and the Basque Government (IT1230-19). IB-D holds a Postdoctoral Orientation Period contract (BES-2016-076766, BES-C-2016-0051). SA has a Ph.D. contract granted by University of the Basque Country (PIF 16/251). ES-G is funded by Ikerbasque and MINECO (PGC2018- 093990-A-I00; MICIU/AEI/FEDER, UE)

The Absence of the Transient Receptor Potential Vanilloid 1 Directly Impacts on the Expression and Localization of the Endocannabinoid System in the Mouse Hippocampus

The transient receptor potential vanilloid 1 (TRPV1) is a non-selective ligand-gated cation channel involved in synaptic transmission, plasticity, and brain pathology. In the hippocampal dentate gyrus, TRPV1 localizes to dendritic spines and dendrites postsynaptic to excitatory synapses in the molecular layer (ML). At these same synapses, the cannabinoid CB1 receptor (CB1R) activated by exogenous and endogenous cannabinoids localizes to the presynaptic terminals. Hence, as both receptors are activated by endogenous anandamide, co-localize, and mediate long-term depression of the excitatory synaptic transmission at the medial perforant path (MPP) excitatory synapses though by different mechanisms, it is plausible that they might be exerting a reciprocal influence from their opposite synaptic sites. In this anatomical scenario, we tested whether the absence of TRPV1 affects the endocannabinoid system. The results obtained using biochemical techniques and immunoelectron microscopy in a mouse with the genetic deletion of TRPV1 show that the expression and localization of components of the endocannabinoid system, included CB1R, change upon the constitutive absence of TRPV1. Thus, the expression of fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) drastically increased in TRPV1(-/-) whole homogenates. Furthermore, CB1R and MAGL decreased and the cannabinoid receptor interacting protein 1a (CRIP1a) increased in TRPV1(-/-) synaptosomes. Also, CB1R positive excitatory terminals increased, the number of excitatory terminals decreased, and CB1R particles dropped significantly in inhibitory terminals in the dentate ML of TRPV1(-/-) mice. In the outer 2/3 ML of the TRPV1(-/-) mutants, the proportion of CB1R particles decreased in dendrites, and increased in excitatory terminals and astrocytes. In the inner 1/3 ML, the proportion of labeling increased in excitatory terminals, neuronal mitochondria, and dendrites. Altogether, these observations indicate the existence of compensatory changes in the endocannabinoid system upon TRPV1 removal, and endorse the importance of the potential functional adaptations derived from the lack of TRPV1 in the mouse brain.This work was supported by the Basque Government (IT123019, to PG); MINECO/FEDER, UE (SAF2015-65034-R, to PG); Ministry of Science and Innovation (PID2019-107548RBI00, to PG); Red de Trastornos Adictivos, Instituto de Salud Carlos III (ISC-III) and European Regional Development Funds-European Union (ERDF-EU, Investing in your future; RD16/0017/0012, to PG); MINECO CTQ2017-85686-R (Spanish Ministry of Economy and Competitiviness, to JS); JE-H is a Postdoctoral Researcher contracted with funds of Red de Trastornos Adictivos, Instituto de Salud Carlos III (ISC-III) and European Regional Development Funds-European Union (ERDF-EU, Investing in your future; RD16/0017/0012), and the Basque Government (IT1230-19); IB-DR holds a Postdoctoral contract (BES2016-076766, BES-C-2016-0051); AM is the recipient of a PhD contract granted by the Department of Education of the Basque Governmen

Stability of SARS-CoV-2 spike antigens against mutations

Modern health care needs preventive vaccines and therapeutic treatments with stability against pathogen mutations to cope with current and future viral infections. At the beginning of the COVID-19 pandemic, our analytic and predictive tool identified a set of eight short SARS-CoV-2 S-spike protein epitopes that had the potential to persistently avoid mutation. Here a combination of genetic, Systems Biology and protein structure analyses confirm the stability of our identified epitopes against viral mutations. Remarkably, this research spans the whole period of the pandemic, during which 93.9% of the eight peptides remained invariable in the globally predominant 43 circulating variants, including Omicron. Likewise, the selected epitopes are conserved in 97% of all 1,514 known SARS-CoV-2 lineages. Finally, experimental analyses performed with these short peptides showed their specific immunoreactivity. This work opens a new perspective on the design of next-generation vaccines and antibody therapies that will remain reliable against future pathogen mutations.Dr. Lozano-Perez acknowledges the European Commission ERDF/FEDER Operational Program 'Murcia' CCI No. 2007ES161PO001 (Project No. 14-20/20). Miodrag Grbic acknowledges support from the NSERC Discovery grant (Canada). This work also has received funding from the Department of Education of the Basque Government via the Consolidated Research Group MATH MODE (IT1456-22). Besides, Ildefonso Martinez De la Fuente and Iker Malaina were supported by the UPV/EHU and Basque Center of Applied Mathematics, grant US21/27N

Adjuvant Biological Therapies in Chronic Leg Ulcers

Current biological treatments for non-healing wounds aim to address the common deviations in healing mechanisms, mainly inflammation, inadequate angiogenesis and reduced synthesis of extracellular matrix. In this context, regenerative medicine strategies, i.e., platelet rich plasmas and mesenchymal stromal cell products, may form part of adjuvant interventions in an integral patient management. We synthesized the clinical experience on ulcer management using these two categories of biological adjuvants. The results of ten controlled trials that are included in this systematic review favor the use of mesenchymal stromal cell based-adjuvants for impaired wound healing, but the number and quality of studies is moderate-low and are complicated by the diversity of biological products. Regarding platelet-derived products, 18 controlled studies investigated their efficacy in chronic wounds in the lower limb, but the heterogeneity of products and protocols hinders clinically meaningful quantitative synthesis. Most patients were diabetic, emphasizing an unmet medical need in this condition. Overall, there is not sufficient evidence to inform routine care, and further clinical research is necessary to realize the full potential of adjuvant regenerative medicine strategies in the management of chronic leg ulcers

Intermittent ethanol exposure during adolescence impairs cannabinoid type 1 receptor-dependent long-term depression and recognition memory in adult mice.

Binge drinking is a significant problem in adolescent populations, and because of the reciprocal interactions between ethanol (EtOH) consumption and the endocannabinoid (eCB) system, we sought to determine if adolescent EtOH intake altered the localization and function of the cannabinoid 1 (CB1) receptors in the adult brain. Adolescent mice were exposed to a 4-day-per week drinking in the dark (DID) procedure for a total of 4 weeks and then tested after a 2-week withdrawal period. Field excitatory postsynaptic potentials (fEPSPs), evoked by medial perforant path (MPP) stimulation in the dentate gyrus molecular layer (DGML), were significantly smaller. Furthermore, unlike control animals, CB1 receptor activation did not depress fEPSPs in the EtOH-exposed animals. We also examined a form of excitatory long-term depression that is dependent on CB1 receptors (eCB-eLTD) and found that it was completely lacking in the animals that consumed EtOH during adolescence. Histological analyses indicated that adolescent EtOH intake significantly reduced the CB1 receptor distribution and proportion of immunopositive excitatory synaptic terminals in the medial DGML. Furthermore, there was decreased binding of [35S]guanosine-5*-O-(3-thiotriphosphate) ([35S] GTPγS) and the guanine nucleotide-binding (G) protein Gαi2 subunit in the EtOH-exposed animals. Associated with this, there was a significant increase in monoacylglycerol lipase (MAGL) mRNA and protein in the hippocampus of EtOH-exposed animals. Conversely, deficits in eCB-eLTD and recognition memory could be rescued by inhibiting MAGL with JZL184. These findings indicate that repeated exposure to EtOH during adolescence leads to long-term deficits in CB1 receptor expression, eCB-eLTD, and reduced recognition memory, but that these functional deficits can be restored by treatments that increase endogenous 2-arachidonoylglycerol