Estrogens attenuate neuronal injury due to hemoglobin, chemical hypoxia, and excitatory amino acids in murine cortical cultures
Introduction
Epidemiologic evidence suggests that estrogen replacement therapy is associated with a decreased incidence of Alzheimer's disease in postmenopausal women 25, 29, 40. Although a number of factors may account for this observation, recent studies support the hypothesis that estrogens have a direct protective action on neurons. Estrogens attenuated neuronal death due to amyloid β-peptide, glutamate and other oxidants in a hippocampal cell line [1]and in primary hippocampal cultures [12]. Relatively high concentrations (10−5 M) were required for maximal benefit, but macromolecular synthesis was not; a mechanism that is at least partly independent of nuclear estrogen receptor binding therefore seems likely.
Estrogens have a number of non-genomic effects that may promote the survival of the stressed neuron. Their antioxidant properties have been intensely investigated in atherosclerosis research. In cell free systems, both natural and synthetic estrogens inhibit oxidation of lipids, lipoproteins, and nucleic acids with an efficacy that exceeds that of α-tocopherol 14, 19, 26, 43, 44. Estrogens also directly block vascular and neuronal l-type voltage-gated calcium channels 5, 23, 41. This action may account for their vasodilatory effect, and may attenuate cellular injury associated with calcium influx via these channels. High concentrations (10−5 M) of estrogens decrease the activity of neuronal nitric oxide synthase (nNOS) in brain homogenates via a direct interaction with calmodulin; however, at low concentrations (10−10 M), nNOS activity is enhanced [16]. Other potentially beneficial effects on neurons, which may involve nuclear estrogen receptors, include increased expression of neurotrophins and their high-affinity receptors [45], induction of calcium binding proteins [6], and stabilization of microtubules [10].
Traumatic and ischemic neuronal death is likely a consequence of a complex autodestructive cascade involving multiple injury mechanisms occurring both in series and in parallel 2, 9, 22, 39. Glutamate release, excessive activation of calcium-dependent lipases and proteases, free radical formation, oxidation of cellular constituents, cytoskeletal disruption, and induction of apoptosis are likely key components. Although monotherapy with an agent acting selectively on one mechanism has been protective in experimental models, demonstration of clinical efficacy has been problematic. A therapeutic `cocktail' of several agents acting at different sites may prove more successful, but may be limited by additive toxicities and adverse drug interactions. Furthermore, the rapid administration of several drugs to an unstable patient will likely be logistically difficult if not impossible in the prehospital or emergency department settings. A single agent with several beneficial actions, if clinically tolerated, may be preferable. Studies to date suggest that estrogens may be well suited to such a role. We therefore assessed the efficacy of selected estrogens in injury paradigms that may be relevant to CNS ischemia and trauma. An abstract has already appeared [32].
Section snippets
Cell cultures
Murine cortical cell cultures were prepared as previously described [31]. Under halothane anesthesia, gravid Swiss-Webster mice (15–16 days gestation) were euthanized by cervical dislocation. After removal of brains from embryos, cortices were isolated and incubated in 0.075% acetylated trypsin at 37°C for 1 h. Tissue was then collected by low-speed centrifugation and was resuspended in plating medium consisting of Eagle's minimal essential medium (MEM) supplemented with 5% horse serum, 5%
Estrogens attenuate hemoglobin neurotoxicity
In this culture system, prolonged Hb exposure produces an iron-dependent, oxidative injury to neurons without injuring glia [33]. Concomitant treatment with 17β-estradiol (E2) attenuated Hb neurotoxicity in a concentration-dependent fashion, with complete protection at 10 μM (Fig. 1A). This cytoprotective effect was quantitatively correlated with inhibition of Hb-mediated oxidation of cellular constituents, as determined by the thiobarbituric acid test. Consistent with prior observations [33],
Discussion
The results of this study are in general agreement with recent reports. Behl et al. observed that 17β-estradiol (E2) attenuated the toxicity of amyloid-β peptide, hydrogen peroxide, and glutamate in a hippocampal cell line [1]. In primary rat hippocampal cultures, Goodman et al. reported that E2 and estriol likewise attenuated the neurotoxicity of amyloid-β peptide and glutamate, and also reduced neuronal death induced by iron salts and glucose deprivation [12]. In addition to confirming the
References (49)
- et al.
17-β estradiol protects neurons from oxidative stress-induced cell death in vitro
Biochem. Biophys. Res. Commun.
(1995) - et al.
Trolox attenuates cortical neuronal injury induced by iron, ultraviolet light, glucose deprivation, or AMPA
Brain Res.
(1994) - et al.
Preparation of human hemoglobin Ao for possible use as a blood substitute
Biochem. Biophys. Methods
(1988) - et al.
An estrogen-responsive element mediates the transcriptional regulation of calbindin D-9K gene in rat uterus
J. Biol. Chem.
(1991) - et al.
Estrogen improves biochemical and neurologic outcome following traumatic brain injury in male rats, but not in females
Brain Res.
(1993) - et al.
Biphasic effect of estrogen on neuronal constitutive nitric oxide synthase via Ca2+-calmodulin dependent mechanism
Biochem. Biophys. Res. Commun.
(1994) - et al.
Quantitative determination of glutamate mediated cortical neuronal injury in cell culture by lactate dehydrogenase efflux assay
J. Neurosci. Methods
(1987) - et al.
Distribution of 17β-hydroxysteroid dehydrogenase gene expression and activity in rat and human tissues
J. Steroid Biochem. Mol. Biol.
(1992) - et al.
21-aminosteroids attenuate excitotoxic neuronal injury in cortical cell cultures
Neuron
(1990) - et al.
Novel and potent biological antioxidants on membrane phospholipid peroxidation: 2-hydroxy estrone and 2-hydroxy estradiol
Biochem. Biophys. Res. Commun.
(1987)
Transient elevation of estrogen receptors in the neonatal rat hippocampus
Dev. Brain Res.
Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction
Anal. Biochem.
The effect of NMDA, AMPA/kainate, and calcium channel antagonists on traumatic cortical neuronal injury in culture
Brain Res.
Neurotoxicity of hemoglobin in cortical cell culture
Neurosci. Lett.
Traumatic neuronal injury in cortical cell culture is attenuated by 21-aminosteroids
Brain Res.
Estrogen receptors in the rhesus monkey brain during fetal development
Dev. Brain Res.
Mechanisms of estrogen-induced vasodilatation: in vivo studies in canine coronary conductance and resistance arteries
J. Am. Coll. Cardiol.
Astrocyte glutamate uptake during chemical hypoxia in vitro
Neurosci. Lett.
Estrogens protect against hydrogen peroxide and arachidonic acid induced DNA damage
Biochim. Biophys. Acta
Role of oxidants in ischemic brain damage
Stroke
Effect of 17β-estradiol and the nonsteroidal benzothiophene LY117018 on in vitro rat aortic responses to norepinephrine, serotonin, U46619, and BayK 8644
Drug Dev. Res.
Nitric oxide mediates glutamate neurotoxicity in primary cortical cultures
Proc. Natl. Acad. Sci. USA
Experimental neurobiology of central nervous system trauma
Crit. Rev. Neurobiol.
Estrogen-enhanced neurite outgrowth: evidence for a selective induction of Tau and stable microtubules
J. Neurosci.
Cited by (141)
Mechanisms of Damage After Cerebral Hemorrhage
2021, Stroke: Pathophysiology, Diagnosis, and ManagementMechanisms of Cerebral Hemorrhage
2015, Stroke: Pathophysiology, Diagnosis, and ManagementAstrocyte-derived growth factors and estrogen neuroprotection: Role of transforming growth factor-α in estrogen-induced upregulation of glutamate transporters in astrocytes
2014, Molecular and Cellular EndocrinologyCitation Excerpt :Thus, the goal of this review is to shed light on the role of astrocyte-derived growth factors in E2 neuroprotection with a particular focus on mechanisms involved in E2-induced upregulation of astrocytic glutamate transporters, GLAST and GLT-1. It is well-documented that E2 promotes neuronal survival (Sudo et al., 1997 #156) and offers neuroprotection against various stimuli including iron (Vedder et al., 1999 #157), glutamate (Singer et al., 1996 #158), kainate (Regan and Guo, 1997 #160) and H2O2 (Bonnefont et al., 1998 #159) in neurons. However, it should be emphasized that astrocytes also play a critical role in mediating E2-induced neuroprotection as E2 is capable of exerting neuroprotection against a neuronal toxic insult in the presence of astrocytes under condition in which it is unable to protect neurons in the absence of astrocytes (Dhandapani and Brann, 2002 #10; Park et al., 2001 #11; Platania et al., 2005 #12).
Inflammation in intracerebral hemorrhage: From mechanisms to clinical translation
2014, Progress in NeurobiologyEffect of sex differences and gonadal hormones on kainic acid-induced neurodegeneration in the bed nucleus of the stria terminalis of the rat
2012, Experimental and Toxicologic Pathology
- 1
Fax: +1 (215) 923-6225.