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

Hexose-6-phosphate Dehydrogenase Modulates 11β-Hydroxysteroid Dehydrogenase Type 1-Dependent Metabolism of 7-keto- and 7β-hydroxy-neurosteroids

BACKGROUND: The role of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in the regulation of energy metabolism and immune system by locally reactivating glucocorticoids has been extensively studied. Experiments determining initial rates of enzyme activity revealed that 11beta-HSD1 can catalyze both the reductase and the dehydrogenase reaction in cell lysates, whereas it predominantly catalyzes the reduction of cortisone to cortisol in intact cells that also express hexose-6-phosphate dehydrogenase (H6PDH), which provides cofactor NADPH. Besides its role in glucocorticoid metabolism, there is evidence that 11beta-HSD1 is involved in the metabolism of 7-keto- and 7-hydroxy-steroids; however the impact of H6PDH on this alternative function of 11beta-HSD1 has not been assessed. METHODOLOGY: We investigated the 11beta-HSD1-dependent metabolism of the neurosteroids 7-keto-, 7alpha-hydroxy- and 7beta-hydroxy-dehydroepiandrosterone (DHEA) and 7-keto- and 7beta-hydroxy-pregnenolone, respectively, in the absence or presence of H6PDH in intact cells. 3D-structural modeling was applied to study the binding of ligands in 11beta-HSD1. PRINCIPAL FINDINGS: We demonstrated that 11beta-HSD1 functions in a reversible way and efficiently catalyzed the interconversion of these 7-keto- and 7-hydroxy-neurosteroids in intact cells. In the presence of H6PDH, 11beta-HSD1 predominantly converted 7-keto-DHEA and 7-ketopregnenolone into their corresponding 7beta-hydroxy metabolites, indicating a role for H6PDH and 11beta-HSD1 in the local generation of 7beta-hydroxy-neurosteroids. 3D-structural modeling offered an explanation for the preferred formation of 7beta-hydroxy-neurosteroids. CONCLUSIONS: Our results from experiments determining the steady state concentrations of glucocorticoids or 7-oxygenated neurosteroids suggested that the equilibrium between cortisone and cortisol and between 7-keto- and 7-hydroxy-neurosteroids is regulated by 11beta-HSD1 and greatly depends on the coexpression with H6PDH. Thus, the impact of H6PDH on 11beta-HSD1 activity has to be considered for understanding both glucocorticoid and neurosteroid action in different tissues

A luteinizing hormone receptor intronic variant is significantly associated with decreased risk of Alzheimer's disease in males carrying an apolipoprotein E ε4 allele

Genetic and biochemical studies support the apolipoprotein E (APOE) ε4 allele as a major risk factor for late-onset Alzheimer's disease (AD), though ~50% of AD patients do not carry the allele. APOE transports cholesterol for luteinizing hormone (LH)-regulated steroidogenesis, and both LH and neurosteroids have been implicated in the etiology of AD. Since polymorphisms of LH beta-subunit (LHB) and its receptor (LHCGR) have not been tested for their association with AD, we scored AD and age-matched control samples for APOE genotype and 14 polymorphisms of LHB and LHCGR. Thirteen gene-gene interactions between the loci of LHB, LHCGR, and APOE were associated with AD. The most strongly supported of these interactions was between an LHCGR intronic polymorphism (rs4073366; lhcgr2) and APOE in males, which was detected using all three interaction analyses: linkage disequilibrium, multi-dimensionality reduction, and logistic regression. While the APOE ε4 allele carried significant risk of AD in males [p = 0.007, odds ratio (OR) = 3.08(95%confidence interval: 1.37, 6.91)], ε4-positive males carrying 1 or 2 C-alleles at lhcgr2 exhibited significantly decreased risk of AD [OR = 0.06(0.01, 0.38); p = 0.003]. This suggests that the lhcgr2 C-allele or a closely linked locus greatly reduces the risk of AD in males carrying an APOE ε4 allele. The reversal of risk embodied in this interaction powerfully supports the importance of considering the role gene-gene interactions play in the etiology of complex biological diseases and demonstrates the importance of using multiple analytic methods to detect well-supported gene-gene interactions

[Lung cancer in the elderly subject]

International audienceINTRODUCTION: In France, the average age for the diagnosis of bronchial carcinoma is 64. It is 76 in the population of over 70. In fact, its incidence increases with age linked intrinsic risk of developing a cancer and with general ageing of the population. Diagnosis tools are the same for elderlies than for younger patients, and positive diagnosis mainly depends on fibreoptic bronchoscopy, complications of which being comparable to those observed in younger patients. STATE OF THE ART: The assessment of dissemination has been modified in recent years by the availability of PET scanning which is increasingly becoming the examination of choice for preventing unnecessary surgical intervention, a fortiori in elderly subjects. Cerebral imaging by tomodensitometry and nuclear magnetic resonance should systematically be obtained before proposing chirurgical treatment. An assessment of the general state of health of the elderly subject is an essential step before the therapeutic decision is made. This depends on the concept of geriatric evaluation: Geriatric Multidimensional Assessment, and the Comprehensive Geriatric Assessment which concerns overall competence of the elderly. PERSPECTIVES: This is a global approach that allows precise definition and ranking of the patient's problems and their impact on daily life and social environment. Certain geriatric variables (IADL, BADL, MMSE, IMC etc) may be predictive of survival rates after chemotherapy or the incidence of complications following thoracic surgery. The main therapeutic principles for the management of bronchial carcinoma are applicable to the elderly subject; long term survival without relapse after surgical resection is independent of age. Whether the oncological strategy is curative or palliative, the elderly patient with bronchial carcinoma should receive supportive treatments. They should be integrated into a palliative programme if such is the case. In fact, age alone is not a factor that should detract from optimal oncological management. CONCLUSIONS: The development of an individual management programme for an elderly patient suffering from bronchial carcinoma should be based on the combination of oncological investigation and comprehensive geriatric assessment

[Lung cancer in the elderly subject]

International audienceINTRODUCTION: In France, the average age for the diagnosis of bronchial carcinoma is 64. It is 76 in the population of over 70. In fact, its incidence increases with age linked intrinsic risk of developing a cancer and with general ageing of the population. Diagnosis tools are the same for elderlies than for younger patients, and positive diagnosis mainly depends on fibreoptic bronchoscopy, complications of which being comparable to those observed in younger patients. STATE OF THE ART: The assessment of dissemination has been modified in recent years by the availability of PET scanning which is increasingly becoming the examination of choice for preventing unnecessary surgical intervention, a fortiori in elderly subjects. Cerebral imaging by tomodensitometry and nuclear magnetic resonance should systematically be obtained before proposing chirurgical treatment. An assessment of the general state of health of the elderly subject is an essential step before the therapeutic decision is made. This depends on the concept of geriatric evaluation: Geriatric Multidimensional Assessment, and the Comprehensive Geriatric Assessment which concerns overall competence of the elderly. PERSPECTIVES: This is a global approach that allows precise definition and ranking of the patient's problems and their impact on daily life and social environment. Certain geriatric variables (IADL, BADL, MMSE, IMC etc) may be predictive of survival rates after chemotherapy or the incidence of complications following thoracic surgery. The main therapeutic principles for the management of bronchial carcinoma are applicable to the elderly subject; long term survival without relapse after surgical resection is independent of age. Whether the oncological strategy is curative or palliative, the elderly patient with bronchial carcinoma should receive supportive treatments. They should be integrated into a palliative programme if such is the case. In fact, age alone is not a factor that should detract from optimal oncological management. CONCLUSIONS: The development of an individual management programme for an elderly patient suffering from bronchial carcinoma should be based on the combination of oncological investigation and comprehensive geriatric assessment

Allopregnanolone reverses neurogenic and cognitive deficits in mouse model of Alzheimer's disease

Our previous analyses showed that allopregnanolone (APα) significantly increased proliferation of rodent and human neural progenitor cells in vitro. In this study, we investigated the efficacy of APα to promote neurogenesis in the hippocampal subgranular zone (SGZ), to reverse learning and memory deficits in 3-month-old male triple transgenic mouse model of Alzheimer's (3xTgAD) and the correlation between APα-induced neural progenitor cell survival and memory function in 3xTgAD mice. Neural progenitor cell proliferation was determined by unbiased stereological analysis of BrdU incorporation and survival determined by FACS for BrdU+ cells. Learning and memory function was assessed using the hippocampal-dependent trace eye-blink conditioning paradigm. At 3 months, basal level of BrdU+ cells in the SGZ of 3xTgAD mice was significantly lower relative to non-Tg mice, despite the lack of evident AD pathology. APα significantly increased, in a dose-dependent manner, BrdU+ cells in SGZ in 3xTgAD mice and restored SGZ proliferation to normal magnitude. As with the deficit in proliferation, 3xTgAD mice exhibited deficits in learning and memory. APα reversed the cognitive deficits to restore learning and memory performance to the level of normal non-Tg mice. In 3xTgAD mice, APα-induced survival of neural progenitors was significantly correlated with APα-induced memory performance. These findings suggest that early neurogenic deficits, which were evident before immunodetectable Aβ, may contribute to the cognitive phenotype of AD, and that APα could serve as a regenerative therapeutic to prevent or delay neurogenic and cognitive deficits associated with mild cognitive impairment and Alzheimer's disease