Preclinical analyses of the therapeutic potential of allopregnanolone to promote neurogenesis in vitro and in vivo in transgenic mouse model of Alzheimer's disease.
ABSTRACT Herein, we present data to support a preclinical proof of concept for the therapeutic potential of allopregnanolone to promote neurogenesis. Our recent work has demonstrated that the neuroactive progesterone metabolite, allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one), (APalpha) induced, in a dose dependent manner, a significant increase in proliferation of neuroprogenitor cells (NPCs) derived from the rat hippocampus and human neural stem cells (hNSM) derived from the cerebral cortex . Proliferative efficacy was determined by incorporation of BrdU and (3)H-thymidine, FACS analysis of MuLV-GFP-labeled mitotic NPCs and quantification of total cell number. Allopregnanolone-induced proliferation was isomer and steroid specific, in that the stereoisomer 3beta-hydroxy-5beta-pregnan-20-one and related steroids did not increase (3)H-thymidine uptake. Immunofluorescent analyses for the NPC markers, nestin and Tuj1, indicated that newly formed cells were of neuronal lineage. Furthermore, microarray analysis of cell cycle genes and real time RT-PCR and western blot validation revealed that allopregnanolone increased the expression of genes which promote mitosis and inhibited the expression of genes that repress cell proliferation. Allopregnanolone-induced proliferation was antagonized by the voltage gated L-type calcium channel blocker nifedipine consistent with the finding that allopregnanolone induces a rapid increase in intracellular calcium in hippocampal neurons via a GABA type A receptor activated L-type calcium channel. Preliminary in vivo data indicate that APalpha for 24 hrs significantly increased neurogenesis in dentate gyrus, as determined by unbiased stereological analysis of BrdU positive cells, of 3-month-old male triple transgenic Alzheimer's disease mice. The in vitro and in vivo neurogenic properties of APalpha coupled with a low molecular weight, easy penetration of the blood brain barrier and lack of toxicity, are key elements required for developing APalpha as a neurogenic / regenerative therapeutic for restoration of neurons in victims of Alzheimer's disease.
- SourceAvailable from: Liisa A M Galea
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- "Depending on the outcome variable of interest, allopregnanolone may be a more potent inducer of neuroprotection than progesterone (Djebaili et al., 2005; Sayeed and Stein, 2009). Interestingly, allopregnanolone also increases progenitor cell proliferation (Brinton and Wang, 2006; Wang et al., 2008). Importantly these two neurosteroids do not work through the same receptor. "
ABSTRACT: Traumatic brain injury (TBI) increases cell death in the hippocampus and impairs hippocampus-dependent cognition. The hippocampus is also the site of ongoing neurogenesis throughout the lifespan. Progesterone treatment improves behavioral recovery and reduces inflammation, apoptosis, lesion volume, and edema, when given after TBI. The aim of the present study was to determine whether progesterone altered cell proliferation and short-term survival in the dentate gyrus after TBI. Male Sprague-Dawley rats with bilateral contusions of the frontal cortex or sham operations received progesterone or vehicle at 1 and 6 h post-surgery and daily through post-surgery Day 7, and a single injection of bromodeoxyuridine (BrdU) 48 h after injury. Brains were then processed for Ki67 (endogenous marker of cell proliferation), BrdU (short-term cell survival), doublecortin (endogenous marker of immature neurons), and Fluoro-Jade B (marker of degenerating neurons). TBI increased cell proliferation compared to shams and progesterone normalized cell proliferation in injured rats. Progesterone alone increased cell proliferation in intact rats. Interestingly, injury and/or progesterone treatment did not influence short-term cell survival of BrdU-ir cells. All treatments increased the percentage of BrdU-ir cells that were co-labeled with doublecortin (an immature neuronal marker in this case labeling new neurons that survived 5 days), indicating that cell fate is influenced independently by TBI and progesterone treatment. The number of immature neurons that survived 5 days was increased following TBI, but progesterone treatment reduced this effect. Furthermore, TBI increased cell death and progesterone treatment reduced cell death to levels seen in intact rats. Together these findings suggest that progesterone treatment after TBI normalizes the levels of cell proliferation and cell death in the dentate gyrus of the hippocampus.Experimental Neurology 06/2011; 231(1):72-81. DOI:10.1016/j.expneurol.2011.05.016 · 4.62 Impact Factor
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- "(4) Involving the transcription factor cyclic AMP response element binding protein (CREB) signaling pathway, APα up-regulates the expression of cell cycle genes that promote neural progenitor mitosis while simultaneously down regulating genes that repress cell division. (5) The mechanism of APα-induced neurogenesis takes advantage of the developmentally regulated direction of Cl − flux to induce neurogenesis in those cells that are phenotypically competent to divide while not activating those mechanisms in mature neurons (Wang et al., 2005; Brinton and Wang, 2006). Adult hippocampal neural progenitor cells (BrdU+ cells immunolabeled green; NeuN+ cells are colored red; coronal section of mouse hippocampal dentate gyrus; scale bar = 50 μm) in the image above are shown as an illustrative example of neurogenesis within the mouse dentate gyrus subgranular zone (SGZ). "
ABSTRACT: The proliferative pool and regenerative potential of neural stem cells diminishes with age, a phenomenon that may be exacerbated in prodromal and mild Alzheimer's disease (AD) brains. In parallel, the neuroactive progesterone metabolite, allopregnanolone (APα), along with a host of other factors, is decreased in the AD brain. Results of preclinical analyses demonstrate that APα is a potent inducer of neural progenitor proliferation of both rodent and human derived neural progenitor cells in vitro. In vivo, APα significantly increased neurogenesis within the subgranular zone of the dentate gyrus and subventricular zone of the 3xTgAD mouse model. Functionally, APα reversed the learning and memory deficits of 3xTgAD mice prior to and following the onset of AD pathology and was comparably efficacious in aged normal mice. In addition to inducing regenerative responses in mouse models of AD, APα significantly reduced beta-amyloid burden, beta-amyloid binding alcohol dehydrogenase load, and microglial activation. In parallel, APα increased markers of white matter generation and cholesterol homeostasis. Analyses to determine the optimal treatment regimen in the 3xTgAD mouse brain indicated that a treatment regimen of APα once per week was optimal for both inducing neurogenesis and reducing AD pathology. Pharmacokinetic analyses indicated that APα is rapidly increased in both plasma and brain following a single dose. APα is most efficacious when administered once per week which will contribute to its margin of safety. Further, analyses in both animals and humans have provided parameters for safe APα dosage exposure in humans. From a translational perspective, APα is a small molecular weight, blood brain barrier penetrant molecule with substantial preclinical efficacy data as a potential Alzheimer's therapeutic with existing safety data in animals and humans. To our knowledge, APα is the only small molecule that both promotes neural progenitor regeneration in brain and simultaneously reduces AD pathology burden.Frontiers in Endocrinology 01/2011; 2:117. DOI:10.3389/fendo.2011.00117
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- "While prevention is preferable, there will always be a need to treat the already damaged brains of symptomatic AD patients, and manipulating neurosteroid biology is still a potential therapeutic opportunity to slow disease progress or mitigate particular disease features such as mood disorders. The use of native neuroactive steroids such as allopregnanolone to stimulate regeneration of neurological damage has been suggested   . It may however be necessary to look at strategies to boost neurosteroid synthesis in situ rather than by manipulating circulating steroids; to find ways to raise neurosteroid levels within the relevant areas of the brain or to augment the specific desired actions of neurosteroids (for example on sigma 1 receptors) by means of synthetic analogues. "
ABSTRACT: A reduction of neurosteroids in the brain may initiate sporadic Alzheimer's disease (AD) which comprises >99% of all AD cases. AD research is currently focused on aberrant amyloid precursor protein (APP) processing and the hyper-phosphorylation of tau protein. This is based on early-onset genetic and pathological observations clearly showing that these markers are involved in the progression of the disease. However, there is still ongoing debate as to the key pathological events in the sporadic form of AD where the Abeta and tau genes are not usually mutated. The vulnerability of the transentorhinal cortex, which displays the first architectural signs of AD, may be related to its role as the entry point for an enormous amount of excitatory information, the majority from the neocortex, which passes through the hippocampal formation. Neurosteroids provide a layer of protection from excessive excitation, and their age-related decrease may expose the vulnerability required to allow neuronal death by excitotoxicity and thereby initiate the disease.Current Alzheimer Research 08/2008; 5(4):367-374. DOI:10.2174/156720508785132325 · 3.80 Impact Factor