A Novel Role of Peripheral Corticotropin-Releasing Hormone (CRH) on Dermal Fibroblasts

Corticotropin-releasing hormone, or factor, (CRH or CRF) exerts important biological effects in multiple peripheral tissues via paracrine/autocrine actions. The aim of our study was to assess the effects of endogenous CRH in the biology of mouse and human skin fibroblasts, the primary cell type involved in wound healing. We show expression of CRH and its receptors in primary fibroblasts, and we demonstrate the functionality of fibroblast CRH receptors by induction of cAMP. Fibroblasts genetically deficient in Crh (Crh−/−) had higher proliferation and migration rates and compromised production of IL-6 and TGF-β1 compared to the wildtype (Crh+/+) cells. Human primary cultures of foreskin fibroblasts exposed to the CRF1 antagonist antalarmin recapitulated the findings in the Crh−/− cells, exhibiting altered proliferative and migratory behavior and suppressed production of IL-6. In conclusion, our findings show an important role of fibroblast-expressed CRH in the proliferation, migration, and cytokine production of these cells, processes associated with the skin response to injury. Our data suggest that the immunomodulatory effects of CRH may include an important, albeit not explored yet, role in epidermal tissue remodeling and regeneration and maintenance of tissue homeostasis

Neurosteroid Dehydroepiandrosterone Interacts with Nerve Growth Factor (NGF) Receptors, Preventing Neuronal Apoptosis

The neurosteroid dehydroepiandrosterone (DHEA), produced by neurons and glia, affects multiple processes in the brain, including neuronal survival and neurogenesis during development and in aging. We provide evidence that DHEA interacts with pro-survival TrkA and pro-death p75NTR membrane receptors of neurotrophin nerve growth factor (NGF), acting as a neurotrophic factor: (1) the anti-apoptotic effects of DHEA were reversed by siRNA against TrkA or by a specific TrkA inhibitor; (2) [3H]-DHEA binding assays showed that it bound to membranes isolated from HEK293 cells transfected with the cDNAs of TrkA and p75NTR receptors (KD: 7.4±1.75 nM and 5.6±0.55 nM, respectively); (3) immobilized DHEA pulled down recombinant and naturally expressed TrkA and p75NTR receptors; (4) DHEA induced TrkA phosphorylation and NGF receptor-mediated signaling; Shc, Akt, and ERK1/2 kinases down-stream to TrkA receptors and TRAF6, RIP2, and RhoGDI interactors of p75NTR receptors; and (5) DHEA rescued from apoptosis TrkA receptor positive sensory neurons of dorsal root ganglia in NGF null embryos and compensated NGF in rescuing from apoptosis NGF receptor positive sympathetic neurons of embryonic superior cervical ganglia. Phylogenetic findings on the evolution of neurotrophins, their receptors, and CYP17, the enzyme responsible for DHEA biosynthesis, combined with our data support the hypothesis that DHEA served as a phylogenetically ancient neurotrophic factor

Νευροστεροειδή με νευροπροστατευτκές ιδιότητες: αξιολόγηση των βιολογικών και φαρμακολογικών ιδιοτήτων τους σε in vivo μοντέλα νευροεκφυλιστικών ασθενειών

Neurosteroid DHEA is biosynthesized in neurons and glia, regulating neuronal survival and neurogenesis during development and aging. We provide evidence that DHEA acts as a neurotrophic factor, protecting neuronal cells against apoptosis via activation of TrkA and p75NTR, membrane receptors of neurotrophin NGF. Specifically, we have shown that siRNA against prosurvival TrkA receptors blocked the anti-apoptotic effect of DHEA. Radiolabeled [3H]DHEA bound with high affinity to membranes isolated from HEK293 cells transfected with the cDNAs of TrkA and p75NTR receptors. DHEA-polyethylene-glycol beads effectively pulled down recombinant TrkA and p75NTR proteins, and precipitated both proteins from extracts prepared from cells expressing both receptors. DHEA effectively activated NGF receptor-mediated signaling; Shc, Akt, and ERK1/2 kinases down-stream to TrkA receptors and TRAF6, RIP2 and RhoGDI effectors of p75NTR receptor. Finally, DHEA rescued sensory neurons of dorsal root ganglia from apoptosis in NGF null embryos and compensated NGF in rescuing sympathetic neurons of embryonic superior cervical ganglia. Our findings suggest that DHEA and NGF crosstalk via their activation of NGF receptors to afford brain shaping and maintenance. Phylogenetic findings on the evolution of neurotrophins, their receptors and CYP17, the enzyme responsible for DHEA biosynthesis, combined with our data support the hypothesis that DHEA served as a phylogenetically ancient neurotrophic factor.Το νευροστεροειδές Διϋδροεπιανδροστερόνη (DHEA) συντίθεται στον εγκέφαλο απο νευρώνες και μικρογλιακά κύτταρα και ρυθμίζει την νευρική επιβίωση και νευρογένεση κατά τη διάρκεια της ανάπτυξης και της γήρανσης. Στη παρούσα μελέτη δείχνουμε ότι η DHEA ενεργεί ως νευροτροφικός παράγοντας, προστατεύοντας νευρικά κυττάρα από αποπτωτικό θάνατο μέσω της ενεργοποίησης των υποδοχέων TrkA και p75NTR, π ου ε ίναι ο ι υ ποδοχέις τ ου NGF. Συγκεκριμένα, έχουμε δείξει ότι siRNAs εναντίον του TrkA αναστέλλουν την αντι-αποπτωτική δράση της DHEA. Ραδιοσημασμένη [3H]DHEA προσδένεται με υψηλή συνάφεια σε μεμβράνες απομονωμένες από HEK293 κύτταρα διαμολυσμένα με cDNA’s των υποδοχέων TrkA και p75NTR. DHEA-polyethylene-glycol beads κατακρημνίζουν αποτελεσματικά απομονωμένους υποδοχείς ΤrkΑ και p75NTR. Επίσης, η DHEA όπως και ο NGF φωσφορυλιώνει τον TrkA και ενεργοποιεί το ενδοκυττάριο σηματοδοτικό μονοπάτι του (Shc, Αkt και Erk1/2) και οδηγεί στην αλληλεπίδραση του p75NTR με τους τελεστές του (TRAF6, RIP2 και RhoGDI). Τ έλος, η DHEA φάνηκε να αναστρέφει τον αποπτωτικό θάνατο λόγω έλλειψης NGF τοσο σε πρωτογενείς καλλιέργειες συμπαθητικών νευρώνων, όσο και των αισθητικών νεύρων των γαγγλίων της ραχιαίας ρίζας σε έμβρυα ngf-/- διαγονιδιακών ποντικών , in vivo. Τα ευρήματά μας δείχνουν ότι η DHEA και ο NGF αλληλεπιδρούν μέσω των υποδοχέων του NGF συμβάλλοντας στην διαμόρφωση και διατήρηση του ΝΣ. Φυλογενετική ανάλυση της εξέλιξης των νευροτροφινών των υποδοχέων τ ους κ αι τ ου υ πεύθυνου ε νζύμου γ ια τ η σ ύνθεση τ ης DHEA (CYP17) σε συνδυασμό με τα αποτελέσματα της παρούσας μελέτης στηρίζουν την υπόθεση ότι η DHEA πιθανόν να κατείχε το ρόλο ενός φυλογενετικά αρχέγονου νευροτροφικού παράγοντα

Complete representation of action space and value in all dorsal striatal pathways

The dorsal striatum plays a central role in the selection, execution, and evaluation of actions. An emerging model attributes action selection to the matrix and evaluation to the striosome compartment. Here, we use large-scale cell-type-specific calcium imaging to determine the activity of striatal projection neurons (SPNs) during motor and decision behaviors in the three major outputs of the dorsomedial striatum: Oprm1+ striosome versus D1+ direct and A2A+ indirect pathway SPNs. We find that Oprm1+ SPNs show complex tunings to simple movements and value-guided actions, which are conserved across many sessions in a single task but remap between contexts. During decision making, the SPN tuning profiles form a complete representation in which sequential SPN activity jointly encodes task progress and value. We propose that the three major output pathways in the dorsomedial striatum share a similarly complete representation of the entire action space, including task- and phase-specific signals of action value and choice.QC 20231101</p