Many earlier pieces of research on this that obviously your doctors and hospital did no followup on to create stroke protocols for this. Our stroke associations also did nothing with this, they need to be destroyed and run by survivors.
growth hormone (15 posts to March 2013)
Growth Hormone (GH) Enhances Endogenous Mechanisms of Neuroprotection and Neuroplasticity after Oxygen and Glucose Deprivation Injury (OGD) and Reoxygenation (OGD/R) in Chicken Hippocampal Cell Cultures
Juan David Olivares-Hernández
,1 Jerusa Elienai Balderas-Márquez,1 Martha Carranza,1 Maricela Luna,1 Carlos G. Martínez-Moreno,1 and Carlos Arámburo11Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, Qro., 76230, Mexico
Abstract
As a classical growth promoter and metabolic regulator, growth hormone (GH) is involved in development of the central nervous system (CNS). This hormone might also act as a neurotrophin, since GH is able to induce neuroprotection, neurite growth, and synaptogenesis during the repair process that occurs in response to neural injury. After an ischemic insult, the neural tissue activates endogenous neuroprotective mechanisms regulated by local neurotrophins that promote tissue recovery. In this work, we investigated the neuroprotective effects of GH in cultured hippocampal neurons exposed to hypoxia-ischemia injury and further reoxygenation. Hippocampal cell cultures obtained from chick embryos were incubated under oxygen-glucose deprivation (OGD, <5% O2, 1 g/L glucose) conditions for 24 h and simultaneously treated with GH. Then, cells were either collected for analysis or submitted to reoxygenation and normal glucose incubation conditions (OGD/R) for another 24 h, in the presence of GH. Results showed that OGD injury significantly reduced cell survival, the number of cells, dendritic length, and number of neurites, whereas OGD/R stage restored most of those adverse effects. Also, OGD/R increased the mRNA expression of several synaptogenic markers (i.e., NRXN1, NRXN3, NLG1, and GAP43), as well as the growth hormone receptor (GHR). The expression of BDNF, IGF-1, and BMP4 mRNAs was augmented in response to OGD injury, and exposure to OGD/R returned it to normoxic control levels, while the expression of NT-3 increased in both conditions. The addition of GH (10 nM) to hippocampal cultures during OGD reduced apoptosis and induced a significant increase in cell survival, number of cells, and doublecortin immunoreactivity (DCX-IR), above that observed in the OGD/R stage. GH treatment also protected dendrites and neurites during OGD, inducing plastic changes reflected in an increase and complexity of their outgrowths during OGD/R. Furthermore, GH increased the expression of NRXN1, NRXN3, NLG1, and GAP43 after OGD injury. GH also increased the BDNF expression after OGD, but reduced it after OGD/R. Conversely, BMP4 was upregulated by GH after OGD/R. Overall, these results indicate that GH protective actions in the neural tissue may be explained by a synergic combination between its own effect and that of other local neurotrophins regulated by autocrine/paracrine mechanisms, which together accelerate the recovery of tissue damaged by hypoxia-ischemia.
1. Introduction
Ischemic stroke is a serious cerebrovascular event caused by a blockage of blood supply and oxygen to the brain, leading to damage or death of brain cells, which produces a severe neurological impairment, or even decease [1]. It is well established that cerebral ischemia induces a pathophysiological response in the neural tissue that leads to apoptotic and necrotic cell death [2], neural structural damage, and synaptic loss, which then contribute to the drastic deficiency of neurological functions [3].
In addition to its classical actions on growth and metabolism, growth hormone (GH) has been reported to play a relevant role, as a neurotrophic factor, on brain repair after traumatic brain injury (TBI) and stroke [4–6]. The neurotrophic actions of GH in the central nervous system (CNS) include prosurvival effects during embryonic development [7, 8], neurogenesis in the adult brain [9], structural plasticity [10, 11], and synaptogenesis [12], among others. These effects could be associated with the cognitive and motor improvement observed in TBI patients, with or without growth hormone deficiency (GHD), who received GH therapy [6, 13–15].
It has been reported that after neural injury, there is an activation of local mechanisms that induce neuroprotection and neuroplasticity which, in some cases, also promote proliferation of newly born neurons and migration of neural precursor cells into the lesioned peri-infarct region [16, 17]. The cellular and molecular mechanisms behind the brain capacity to repair an infarcted region are still largely undetermined; although, the expression and release of endogenous neurotrophic factors have been shown to be significantly increased during ischemic events [18–21]. Interestingly, GH is also synthesized by cells surrounding the peri-infarcted area suggesting that local autocrine/paracrine mechanisms are triggered after a neural injury [22]. Moreover, it has been shown that the expression of growth hormone receptor (GHR) is increased in the injured tissue, facilitating the neuroprotective action of this hormone [23].
Neuroprotective actions of GH treatments on either brain ischemia in vivo or oxygen-glucose deprivation (OGD) injury in vitro have been previously documented [24–26]. In the hippocampus, GH significantly reduced apoptotic cell death rate after an experimental stroke [25], decreased loss of neural tissue, and increased the expression of neurotrophic factors, synaptogenesis, and myelination biomarkers, as well as the formation of new blood vessels within the peri-infarct area, and provoked an improvement in cognitive function in experimentally stroked mice [26]. Recent studies showed that the administration of GH after experimental stroke promoted neurogenesis and stimulated synaptic plasticity and angiogenesis within the peri-infarct region, which were associated with an improvement in the motor function [27]. Furthermore, GH treatment promoted remote hippocampal plasticity and enhanced cognitive recovery after cortical injury [28]. Relevantly, GH addition also increased the expression of neurotrophic factors, such as BDNF and IGF-1, which in turn could participate in the endogenous neuroprotective response that occurs after ischemic injury [4, 25, 29].
Given the increasing number of reports regarding the beneficial effects of GH treatment in patients with brain injury and stroke [4, 5, 14, 30–32], as well as its therapeutic potential to treat neurodegenerative diseases [33, 34], it is pertinent to further investigate the interactions between the administration of GH and the expression of endogenous neurotrophic factors that may be involved in local neuroprotection mechanisms. Thus, the aim of the present study was to evaluate the neuroprotective role of GH in cultured hippocampal neurons that were injured by exposition to OGD and then submitted to an additional reoxygenation (OGD/R) period.
This work shows that OGD injury (24 h) significantly affects cell survival, reduces neurite outgrowth, and alters the expression of several synaptogenic markers, such as neurexins (NRXN1, NRXN3), neuroligins (NLG1), and growth associated protein 43 (GAP43), in hippocampal neurons. Interestingly, exposure of the harmed cultures to reoxygenation and normal glucose incubation conditions (OGD/R), for another 24 h, reverses most of the adverse effects of OGD. Additionally, it is shown that the expression of several neurotrophic factors (i.e., BDNF, NT-3, IGF-1, and BMP4) is significantly increased after OGD, whereas the GHR expression was upregulated only in the OGD/R condition. Furthermore, it was found that administration of GH treatments, both under OGD and OGD/R conditions, clearly stimulated significant plastic changes by promoting cell survival, enabling an increase of neurite outgrowth, and inducing a rise of synapse formation markers, in levels above those observed in the OGD/R condition. These protective neurotrophic actions of GH are probably mediated through a synergistic mechanism between GH and other endogenous neurotrophins.
