The neuroactive steroids dehydroepiandrosterone (DHEA), its sulfate ester DHEA sulfate (DHEAS), and allopregnanolone (Allo), produced by the CNS and the adrenals, appear to exert a protective effect in hippocampal and cortical neuron ischemia- and excitotoxicity-induced injury. We hypothesized that they may also play a protective role on the adrenal medulla, an important part of the sympathetic nervous system, and the tissue adjacent to their primary site of production. DHEA, DHEAS, and Allo protected rat chromaffin cells and the rat pheochromocytoma PC12 cell line, an established model for the study of adrenomedullary cell apoptosis and survival, against serum deprivation-induced apoptosis. Their effects were time- and dose-dependent, with EC ₅₀ 1.8, 1.1, and 1.5 nM, respectively. The antiapoptotic effect of DHEA DHEAS and Allo was compared to that of a long list of structurally related compounds and was found to be structure-specific, confined mainly to conformation 3β-OH-Δ ⁵ for androstenes and 3α-OH for pregnanes. Indeed, 3-keto, Δ ⁴ , or C7 hydroxylated androstenes and 3β pregnanes were ineffective. The prosurvival effect of DHEA(S) and Allo was N -methyl-D-aspartate-, GABA _A -, sigma1-, or estrogen receptor-independent. It involved the antiapoptotic Bcl-2 proteins, their role being sine qua non for their action because Bcl-2 antisense oligonucleotides reversed their effects. Finally, DHEA(S) and Allo activated cAMP response element-binding protein and NF-κB, upstream effectors of antiapoptotic Bcl-2 protein expression. They also activated the antiapoptotic kinase PKCα/β, a posttranslational activator of Bcl-2 protein. Our findings suggest that decline of DHEA(S) and Allo during aging or stress may leave the adrenal medulla unprotected against proapoptotic challenges.

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 p75^NTR 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 p75^NTR receptors (K_D: 7.4±1.75 nM and 5.6±0.55 nM, respectively); (3) immobilized DHEA pulled down recombinant and naturally expressed TrkA and p75^NTR 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 p75^NTR 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. Dehydroepiandrosterone (DHEA) and its sulphate ester are the most abundant steroid hormones in humans, and DHEA was described as the first neurosteroid produced in the brain. DHEA is known to participate in multiple events in the brain, including neuronal survival and neurogenesis. However, to date no specific cellular receptor has been described for this important neurosteroid. In this study, we provide evidence that DHEA exerts its neurotrophic effects by directly interacting with the TrkA and p75^NTR membrane receptors of nerve growth factor (NGF), and efficiently activates their downstream signaling pathways. This activation prevents the apoptotic loss of NGF receptor positive sensory and sympathetic neurons. The interaction of DHEA with NGF receptors may also offer a mechanistic explanation for the multiple actions of DHEA in other peripheral biological systems expressing NGF receptors, such as the immune, reproductive, and cardiovascular systems.

Neural stem cell (NSC) grafts have demonstrated significant effects in animal models of spinal cord injury (SCI), yet their clinical translation remains challenging. Significant evidence suggests that the supporting matrix of NSC grafts has a crucial role in regulating NSC effects. Here we demonstrate that grafts based on porous collagen-based scaffolds (PCSs), similar to biomaterials utilized clinically in induced regeneration, can deliver and protect embryonic NSCs at SCI sites, leading to significant improvement in locomotion recovery in an experimental mouse SCI model, so that 12 weeks post-injury locomotion performance of implanted animals does not statistically differ from that of uninjured control animals. NSC-seeded PCS grafts can modulate key processes required to induce regeneration in SCI lesions including enhancing NSC neuronal differentiation and functional integration in vivo, enabling robust axonal elongation, and reducing astrogliosis. Our findings suggest that the efficacy and translational potential of emerging NSC-based SCI therapies could be enhanced by delivering NSC via scaffolds derived from well-characterized clinically proven PCS.

Abstract: Hypothalamic CRF plays a central role in the coordination of endocrine and behavioral responses to stress and it is also involved in the pathophysiology of several neuropsychiatric diseases including depression, anxiety and addiction. In the mammals, the CRF family of peptides includes CRF, urocortin (Ucn), Ucn I, and Ucn II while was enriched with new members, the urocortins. Their biological effects are mediated by the CRF1 and CRF2 receptors, which belong to the G-protein-coupled receptor super family. Multiple research groups have demonstrated during the last decade the expression of the CRF peptides and their receptors in several components of the immune system and their participation in the ad hoc regulation of inflammatory phenomena. Non-peptide CRF1 antagonists have been recently synthesized for the treatment of CNS related diseases, such as anxiety, depression and drug abuse. In the gastrointestinal tract, these compounds open new therapeutic options in the treatment of lower-GI inflammatory diseases associated to CRF, such as the chronic inflammatory bowel syndromes, irritable bowel disease and ulcerative colitis while Ucn, Ucn I, Ucn II or synthetic non-peptide CRF2 agonists may be useful in the treatment of upper-GI inflammatory diseases. In human endometrium, CRF1 antagonists may be used as abortive agents interfering with the inflammatory phenomena taking place during the implantation of the conceptus. They thus may represent a new class of nonsteroidal inhibitors of implantation. These two examples illustrate the potential therapeutic significance of the CRH in regulating inflammatory phenomena in an ad hoc approach without affecting the rest of the immune system.

Background: Recently we have reported membrane androgen receptors-induced apoptotic regression of prostate cancer cells regulated by Rho/ROCK/actin signaling. In the present study we explored the specificity of these receptors and we analyzed downstream effectors controlling survival and apoptosis in hormone refractory DU145-prostate cancer cells stimulated with membrane androgen receptor-selective agonists. Results: Using membrane impermeable conjugates of serum albumin covalently linked to testosterone, we show here down-regulation of the activity of pro-survival gene products, namely PI-3K/Akt and NF-κB, in DU145 cells. Testosterone-albumin conjugates further induced FasL expression. A FasL blocking peptide abrogated membrane androgen receptors-dependent apoptosis. In addition, testosterone-albumin conjugates increased caspase-3 and Bad protein activity. The actin cytoskeleton drug cytochalasin B and the ROCK inhibitor Y-27632 inhibited FasL induction and caspase-3 activation, indicating that the newly identified Rho/Rock/actin signaling may regulate the downstream pro-apoptotic effectors in DU145 cells. Finally, other steroids or steroid-albumin conjugates did not interfere with these receptors indicating testosterone specificity. Conclusion: Collectively, our results provide novel mechanistic insights pointing to specific pro-apoptotic molecules controlling membrane androgen receptors-induced apoptotic regression of prostate cancer cells and corroborate previously published observations on the potential use of membrane androgen receptor-agonists as novel anti-tumor agents in prostate cancer.