Ethyl pyruvate protects against hypoxic-ischemic brain injury via anti-cell death and anti-inflammatory mechanisms
Introduction
Perinatal hypoxic-ischemic (H-I) brain injury is a common cause of neurological deficits in children (Chang and Huang, 2006). The mechanisms of H-I-induced brain damage are heterogeneous. A complex series of pathological events including apoptosis, inflammation, oxidative stress and excitotoxicity after H-I injury are known to precipitate neuronal demise and subsequent neurological dysfunction (Benjelloun, 1999, Blomgren and Hagberg, 2006, Johnston, 2005, Northington, 2001). H-I lesion to the brain has been shown to result in earlier acute necrotic neuronal death in the core of the infarction, followed by a delayed but prolonged apoptotic-like neuronal death in the surrounding zone (Nakajima, 2000, Northington, 2001). A rapidly expanding body of evidence also indicates that cerebral inflammation, characterized by activation of microglia and macrophages, leukocyte infiltration, release of pro-inflammatory cytokines, and increased expression of endothelial adhesion molecules (Barone and Feuerstein, 1999, del Zoppo, 2000), also contributes substantially to the pathogenesis of perinatal H-I brain injury (Benjelloun et al., 1999). The synergistic actions of these pathological processes exacerbate brain injury, leading to deterioration of neurological functions (Barone and Feuerstein, 1999). Therefore, therapeutic strategies that can target multiple mechanisms could be extremely useful in limiting post-H-I neuronal damage.
Ethyl pyruvate (EP) is a stable lipophilic ester derivative of pyruvate. EP was initially reported to ameliorate structural and functional damage associated with mesenteric ischemia and reperfusion in rats (Sims et al., 2001). Subsequent in vivo studies documented therapeutic benefits of EP in experimental models of many illnesses, such as coronary ischemia and reperfusion injury (Woo et al., 2004), hemorrhagic shock (Tawadrous, 2002, Yang, 2002), severe sepsis (Ulloa, 2002, Zhang, 2009), and acute pancreatitis (Yang et al., 2004b, 2008). The neuroprotective effect of EP was also observed in post-ischemic brain using an adult rat model of middle cerebral artery occlusion (MCAO) (Kim, 2005, Yu, 2005). The effect of EP in immature brain after H-I, however, is unknown. Multiple mechanisms such as metabolic augmentation, inflammatory response suppression and radical scavenging have been suggested to be involved in the protective effect of EP (Kim, 2008, Tokumaru, 2009). However, the specific molecular target of EP that produces neuroprotection remains to be elucidated.
In the current study, we explored the protective effect of EP in neonatal brain after H-I injury and investigated the molecular mechanisms underlying the action of EP. Using a rat model of neonatal H-I brain injury that induces considerable unilateral damage in cortical, hippocampal and striatal regions, we found that intraperitoneal injections of EP resulted in marked and prolonged neuroprotection. We further demonstrated that EP protects against H-I via dual mechanisms. On one hand, EP directly protects neurons against H-I by inhibiting calpain activation and subsequent pro-death pathways. On the other hand, EP offers indirect neuroprotection via suppression of microglial-mediated inflammatory response.
Section snippets
Rat model of H-I injury and EP administration
All animal protocols used in this study were approved by the Institutional Animal Care and Use Committee. Animals were treated humanely and with regard for alleviating suffering. Housing and breeding of animals were done in accordance with National Institutes of Health guidelines. The procedures for the modeling of neonatal H-I injury were based on the modification of the Levine method using Sprague–Dawley rat litters at postnatal day 7 (P7) (Levine, 1960, Rice, 1981). Pups were anesthetized
EP protects against brain tissue loss after neonatal H-I
To evaluate the neuroprotective effect of EP against neonatal H-I-induced brain injury, EP was administered intraperitoneally at different doses (10, 30, 50, 100, 250 and 500 mg/kg) 1 h after the left common carotid artery occlusion (CCAO) and 30 min before hypoxia (Fig. 1A). The extent of brain damage was determined 7 days after H-I by calculating the degree of tissue loss in each section. As shown in Fig. 1B, EP at concentrations ranging from 30 to 500 mg/kg significantly attenuated post-H-I
Discussion
Neonatal H-I brain injury is an important clinical problem associated with high morbidity and mortality. Current available therapies for this disease are rather limited. In this study, we demonstrated, for the first time, that EP significantly reduced brain damage and improved neurological outcomes evaluated up to 2 months after neonatal H-I injury. Brain tissue loss was ameliorated even when EP administration was delayed for up to 30 min following the H-I insult. Further mechanistic studies
Acknowledgments
H.S. and X.H. contributed equally to this manuscript. This project was supported by NIH/NINDS grants NS36736, NS43802, and NS45048 (to J.C.). Y.G. was supported by the Chinese Natural Science Foundation (grants 30470592, 30670642 and J0730860). C.L. was supported by the Chinese Natural Science Foundation (grant J0730860). We thank Carol Culver for excellent editorial assistance.
References (77)
calcium elevation in mitochondria is the main Ca2+ requirement for mitochondrial permeability transition pore (mPTP) opening
J. Biol. Chem.
(2009)Glial activation in white matter following ischemia in the neonatal P7 rat brain
Exp. Neurol.
(2006)- et al.
Free radicals, mitochondria, and hypoxia-ischemia in the developing brain
Free Radic. Biol. Med.
(2006) Calpastatin is up-regulated in response to hypoxia and is a suicide substrate to calpain after neonatal cerebral hypoxia-ischemia
J. Biol. Chem.
(1999)Synergistic activation of caspase-3 by m-calpain after neonatal hypoxia-ischemia: a mechanism of “pathological apoptosis”?
J. Biol. Chem.
(2001)Minocycline alleviates hypoxic-ischemic injury to developing oligodendrocytes in the neonatal rat brain
Neuroscience
(2006)Post-insult minocycline treatment attenuates hypoxia-ischemia-induced neuroinflammation and white matter injury in the neonatal rat: a comparison of two different dose regimens
Int. J. Dev. Neurosci.
(2008)Calcium: still center-stage in hypoxic-ischemic neuronal death
Trends Neurosci.
(1995)Clinical trials with neuroprotective drugs in acute ischaemic stroke: are we doing the right thing?
Trends Neurosci.
(1999)Diazoxide prevents mitochondrial swelling and Ca2+ accumulation in CA1 pyramidal cells after cerebral ischemia in newborn pigs
Brain Res.
(2004)
Novel anti-inflammatory therapy for Parkinson's disease
Trends Pharmacol. Sci.
Ethyl pyruvate modulates adhesive and secretory reactions in human lung epithelial cells
Life Sci.
Anti-inflammatory mechanism is involved in ethyl pyruvate-mediated efficacious neuroprotection in the postischemic brain
Brain Res.
Ethyl pyruvate has an anti-inflammatory effect by inhibiting ROS-dependent STAT signaling in activated microglia
Free Radic. Biol. Med.
Neurological reflexes and early motor behavior in rats subjected to neonatal hypoxic-ischemic injury
Behav. Brain Res.
Early neurodegeneration after hypoxia-ischemia in neonatal rat is necrosis while delayed neuronal death is apoptosis
Neurobiol. Dis.
Apoptosis in perinatal hypoxic-ischemic brain injury: how important is it and should it be inhibited?
Brain Res. Brain Res. Rev.
Calpain I induces cleavage and release of apoptosis-inducing factor from isolated mitochondria
J. Biol. Chem.
NADPH oxidase mediates lipopolysaccharide-induced neurotoxicity and proinflammatory gene expression in activated microglia
J. Biol. Chem.
Mitochondrial calcium and oxidative stress as mediators of ischemic brain injury
Cell Calcium
Ethyl pyruvate enhances ATP levels, reduces oxidative stress and preserves cardiac function in a rat model of off-pump coronary bypass
Heart Lung Circ.
Calcium dysregulation induces apoptosis-inducing factor release: cross-talk between PARP-1- and calpain-signaling pathways
Exp. Neurol.
Ethyl pyruvate protects PC12 cells from dopamine-induced apoptosis
Eur. J. Pharmacol.
Ethyl pyruvate preserves cardiac function and attenuates oxidative injury after prolonged myocardial ischemia
J. Thorac. Cardiovasc. Surg.
Ethyl pyruvate ameliorates acute alcohol-induced liver injury and inflammation in mice
J. Lab. Clin. Med.
Surviving the kiss of death
Biochem. Pharmacol.
TAT-mediated delivery of Bcl-xL protein is neuroprotective against neonatal hypoxic-ischemic brain injury via inhibition of caspases and AIF
Neurobiol. Dis.
Critical role of PTEN in the coupling between PI3K/Akt and JNK1/2 signaling in ischemic brain injury
FEBS Lett.
Inflammatory mediators and stroke: new opportunities for novel therapeutics
J. Cereb. Blood Flow Metab.
Inflammatory responses in the cerebral cortex after ischemia in the P7 neonatal Rat
Stroke
AIF-mediated programmed necrosis: a highly regulated way to die
Cell Cycle
In vivo delivery of a Bcl-xL fusion protein containing the TAT protein transduction domain protects against ischemic brain injury and neuronal apoptosis
J. Neurosci.
Translocation of apoptosis-inducing factor in vulnerable neurons after transient cerebral ischemia and in neuronal cultures after oxygen-glucose deprivation
J. Cereb. Blood Flow Metab.
Critical role of calpain I in mitochondrial release of apoptosis-inducing factor in ischemic neuronal injury
J. Neurosci.
Perinatal brain injury and regulation of transcription
Curr. Opin. Neurol.
Dissociating the dual roles of apoptosis-inducing factor in maintaining mitochondrial structure and apoptosis
EMBO J.
Targeting Bid to prevent programmed cell death in neurons
Biochem. Soc. Trans.
Ethyl pyruvate decreases HMGB1 release and ameliorates murine colitis
J. Leukoc. Biol.
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