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Effect of preconditioning on propofol-induced neurotoxicity during the developmental period. PLoS One 2022; 17:e0273219. [PMID: 35984772 PMCID: PMC9390907 DOI: 10.1371/journal.pone.0273219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 08/04/2022] [Indexed: 11/19/2022] Open
Abstract
At therapeutic concentrations, propofol (PPF), an anesthetic agent, significantly elevates intracellular calcium concentration ([Ca2 +]i) and induces neural death during the developmental period. Preconditioning enables specialized tissues to tolerate major insults better compared with tissues that have already been exposed to sublethal insults. Here, we investigated whether the neurotoxicity induced by clinical concentrations of PPF could be alleviated by prior exposure to sublethal amounts of PPF. Cortical neurons from embryonic day (E) 17 Wistar rat fetuses were cultured in vitro, and on day in vitro (DIV) 2, the cells were preconditioned by exposure to PPF (PPF-PC) at either 100 nM or 1 μM for 24 h. For morphological observations, cells were exposed to clinical concentrations of PPF (10 μM or 100 μM) for 24 h and the survival ratio (SR) was calculated. Calcium imaging revealed significant PPF-induced [Ca2+]i elevation in cells on DIV 4 regardless of PPF-PC. Additionally, PPF-PC did not alleviate neural cell death induced by PPF under any condition. Our findings indicate that PPF-PC does not alleviate PPF-induced neurotoxicity during the developmental period.
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Shibuta S, Morita T, Kosaka J. Intravenous anesthetic-induced calcium dysregulation and neurotoxic shift with age during development in primary cultured neurons. Neurotoxicology 2018; 69:320-329. [PMID: 30107222 DOI: 10.1016/j.neuro.2018.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Revised: 07/29/2018] [Accepted: 08/08/2018] [Indexed: 10/28/2022]
Abstract
Anesthetic-induced neurotoxicity in the developing brain is a concern. This neurotoxicity is closely related to anesthetic exposure time, dose, and developmental stages. Using calcium imaging and morphological examinations in vitro, we sought to determine whether intravenous anesthetic-induced direct neurotoxicity varies according to different stages of the days in vitro (DIV) of neurons in primary culture. Cortical neurons from E17 Wistar rats were prepared. On DIV 3, 7, and 13, cells were exposed to the intravenous anesthetics thiopental sodium (TPS), midazolam (MDZ), or propofol (PPF), to investigate direct neurotoxicity using morphological experiments. Furthermore, using calcium imaging, the anesthetic-induced intracellular calcium concentration ([Ca2+]i) elevation was monitored in cells on DIV 4, 8, and 13. All anesthetics elicited significant [Ca2+]i increases on DIV 4. While TPS (100 μM) and MDZ (10 μM) did not alter neuronal death, PPF (10 μM and 100 μM) decreased the survival ratio (SR) significantly. On DIV 8, TPS and MDZ did not elicit [Ca2+]i elevation or SR decrease, while PPF still induced [Ca2+]i elevation (both at 10 μM and 100 μM) and significant SR decrease at 100 μM (0.76 ± 0.03; P < 0.05), but not at 10 μM (0.91 ± 0.03). Such anesthetic-induced [Ca2+]i elevation and SR decrease were not observed on DIV 13-14 for any of the anesthetic drugs. Our study indicates that more caution may be exercised when using PPF compared to TPS or MDZ during development.
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Affiliation(s)
- Satoshi Shibuta
- Department of Anesthesiology and Intensive Care Medicine, International University of Health and Welfare, Narita, Chiba, Japan; Department of Anesthesiology and Intensive Care Medicine, Osaka University, Suita, Osaka, Japan.
| | - Tomotaka Morita
- Department of Anesthesiology and Intensive Care Medicine, Osaka University, Suita, Osaka, Japan.
| | - Jun Kosaka
- Department of Anatomy, International University of Health and Welfare, Narita, Chiba, Japan.
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Zhang Z, Zhang L, Ding Y, Han Z, Ji X. Effects of Therapeutic Hypothermia Combined with Other Neuroprotective Strategies on Ischemic Stroke: Review of Evidence. Aging Dis 2018; 9:507-522. [PMID: 29896438 PMCID: PMC5988605 DOI: 10.14336/ad.2017.0628] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Accepted: 06/28/2017] [Indexed: 12/19/2022] Open
Abstract
Ischemic stroke is a major cause of death and disability globally, and its incidence is increasing. The only treatment approved by the US Food and Drug Administration for acute ischemic stroke is thrombolytic treatment with recombinant tissue plasminogen activator. As an alternative, therapeutic hypothermia has shown excellent potential in preclinical and small clinical studies, but it has largely failed in large clinical studies. This has led clinicians to explore the combination of therapeutic hypothermia with other neuroprotective strategies. This review examines preclinical and clinical progress towards developing highly effective combination therapy involving hypothermia for stroke patients.
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Affiliation(s)
- Zheng Zhang
- Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
- Department of Neurology, the First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Linlei Zhang
- Department of Neurology, the Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Yuchuan Ding
- Department of Neurological Surgery, Wayne State University School of Medicine, Detroit, MI, USA
| | - Zhao Han
- Department of Neurology, the Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Xunming Ji
- Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
- China-America Institute of Neuroscience, Xuanwu Hospital, Capital Medical University, Beijing, China
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Morita T, Shibuta S, Kosaka J, Fujino Y. Thiopental sodium preserves the responsiveness to glutamate but not acetylcholine in rat primary cultured neurons exposed to hypoxia. J Neurol Sci 2016; 365:126-31. [PMID: 27206889 DOI: 10.1016/j.jns.2016.04.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 03/17/2016] [Accepted: 04/15/2016] [Indexed: 10/21/2022]
Abstract
Although many in vitro studies demonstrated that thiopental sodium (TPS) is a promising neuroprotective agent, clinical attempts to use TPS showed mainly unsatisfactory results. We investigated the neuroprotective effects of TPS against hypoxic insults (HI), and the responses of the neurons to l-glutamate and acetylcholine application. Neurons prepared from E17 Wistar rats were used after 2weeks in culture. The neurons were exposed to 12-h HI with or without TPS. HI-induced neurotoxicity was evaluated morphologically. Moreover, we investigated the dynamics of the free intracellular calcium ([Ca(2+)]i) in the surviving neurons after HI with or without TPS pretreatment following the application of neurotransmitters. TPS was neuroprotective against HI according to the morphological examinations (0.73±0.06 vs. 0.52±0.07, P=0.04). While the response to l-glutamate was maintained (0.89±0.08 vs. 1.02±0.09, P=0.60), the [Ca(2+)]i response to acetylcholine was notably impaired (0.59±0.02 vs. 0.94±0.04, P<0.01). Though TPS to cortical cultures was neuroprotective against HI morphologically, the [Ca(2+)]i response not to l-glutamate but to acetylcholine was impaired. This may partially explain the inconsistent results regarding the neuroprotective effects of TPS between experimental studies and clinical settings.
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Affiliation(s)
- Tomotaka Morita
- Department of Anesthesiology and Intensive Care Medicine, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Satoshi Shibuta
- Department of Anesthesiology and Intensive Care Medicine, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Jun Kosaka
- Center for Medical Science, International University of Health and Welfare, 2600-1 Kita-Kanemaru, Ohtawara, Tochigi 324-8501, Japan.
| | - Yuji Fujino
- Department of Anesthesiology and Intensive Care Medicine, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
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Shibuta S, Morita T, Kosaka J, Kamibayashi T, Fujino Y. Only extra-high dose of ketamine affects l-glutamate-induced intracellular Ca2+ elevation and neurotoxicity. Neurosci Res 2015; 98:9-16. [DOI: 10.1016/j.neures.2015.04.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Revised: 04/18/2015] [Accepted: 04/21/2015] [Indexed: 11/25/2022]
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Hirsch S, Dickenson A, Corradini L. Anesthesia influences neuronal activity and drug effectiveness in neuropathic rats. Pain 2014; 155:2583-2590. [DOI: 10.1016/j.pain.2014.09.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 09/16/2014] [Accepted: 09/16/2014] [Indexed: 01/16/2023]
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Schifilliti D, Grasso G, Conti A, Fodale V. Anaesthetic-related neuroprotection: intravenous or inhalational agents? CNS Drugs 2010; 24:893-907. [PMID: 20932063 DOI: 10.2165/11584760-000000000-00000] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
In designing the anaesthetic plan for patients undergoing surgery, the choice of anaesthetic agent may often appear irrelevant and the best results obtained by the use of a technique or a drug with which the anaesthesia care provider is familiar. Nevertheless, in those surgical procedures (cardiopulmonary bypass, carotid surgery and cerebral aneurysm surgery) and clinical situations (subarachnoid haemorrhage, stroke, brain trauma and post-cardiac arrest resuscitation) where protecting the CNS is a priority, the choice of anaesthetic drug assumes a fundamental role. Treating patients with a neuroprotective agent may be a consideration in improving overall neurological outcome. Therefore, a clear understanding of the relative degree of protection provided by various agents becomes essential in deciding on the most appropriate anaesthetic treatment geared to these objectives. This article surveys the current literature on the effects of the most commonly used anaesthetic drugs (volatile and gaseous inhalation, and intravenous agents) with regard to their role in neuroprotection. A systematic search was performed in the MEDLINE, Cumulative Index to Nursing and Allied Health Literature (CINHAL®) and Cochrane Library databases using the following keywords: 'brain' (with the limits 'newborn' or 'infant' or 'child' or 'neonate' or 'neonatal' or 'animals') AND 'neurodegeneration' or 'apoptosis' or 'toxicity' or 'neuroprotection' in combination with individual drug names ('halothane', 'isoflurane', 'desflurane', 'sevoflurane', 'nitrous oxide', 'xenon', 'barbiturates', 'thiopental', 'propofol', 'ketamine'). Over 600 abstracts for articles published from January 1980 to April 2010, including studies in animals, humans and in vitro, were examined, but just over 100 of them were considered and reviewed for quality. Taken as a whole, the available data appear to indicate that anaesthetic drugs such as barbiturates, propofol, xenon and most volatile anaesthetics (halothane, isoflurane, desflurane, sevoflurane) show neuroprotective effects that protect cerebral tissue from adverse events--such as apoptosis, degeneration, inflammation and energy failure--caused by chronic neurodegenerative diseases, ischaemia, stroke or nervous system trauma. Nevertheless, in several studies, the administration of gaseous, volatile and intravenous anaesthetics (especially isoflurane and ketamine) was also associated with dose-dependent and exposure time-dependent neurodegenerative effects in the developing animal brain. At present, available experimental data do not support the selection of any one anaesthetic agent over the others. Furthermore, the relative benefit of one anaesthetic versus another, with regard to neuroprotective potential, is unlikely to form a rational basis for choice. Each drug has some undesirable adverse effects that, together with the patient's medical and surgical history, appear to be decisive in choosing the most suitable anaesthetic agent for a specific situation. Moreover, it is important to highlight that many of the studies in the literature have been conducted in animals or in vitro; hence, results and conclusions of most of them may not be directly applied to the clinical setting. For these reasons, and given the serious implications for public health, we believe that further investigation--geared mainly to clarifying the complex interactions between anaesthetic drug actions and specific mechanisms involved in brain injury, within a setting as close as possible to the clinical situation--is imperative.
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Affiliation(s)
- Daniela Schifilliti
- Department of Neuroscience Psychiatric and Anesthesiological Sciences, University of Messina, Messina, Italy
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Shibuta S, Varathan S, Kamibayashi T, Mashimo T. Small temperature variations alter edaravone-induced neuroprotection of cortical cultures exposed to prolonged hypoxic episodes. Br J Anaesth 2010; 104:52-8. [PMID: 19923134 DOI: 10.1093/bja/aep320] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Edaravone, a free radical scavenger, has been shown to be neuroprotective in vivo and in vitro. However, the impact of small temperature variations on its neuroprotective actions remains unknown. METHODS We examined the degree of neuroprotection conferred by various concentrations of edaravone on cortical cultures exposed to prolonged hypoxia (24 h) under three conditions: mild hypothermia (32 degrees C), normothermia (37 degrees C), and mild hyperthermia (39 degrees C). The survival of cortical neurones from E16 Wistar rats (SR) was evaluated using photomicrographs taken before and after exposure to hypoxia. RESULTS The mean survival of neurones exposed to hypoxia at normothermia was 14.7 (sem 1.8)%. The addition of 50 microM edaravone significantly improved the mean survival to 40.5 (4.7)%. This improvement was noted at higher doses of edaravone (5 microM < or =) but not at lower doses (< or =500 nM). With mild hypothermia and prolonged hypoxia without edaravone, neuroprotection was significantly improved with a mean survival of 63.0 (5.2)%. This neuroprotective effect was not enhanced with the addition of edaravone, even at the highest dose. Hypoxia-induced neurotoxicity was aggravated by mild hyperthermia as reflected by a mean survival of 9.1 (2.1)%. However, higher concentrations of edaravone inhibited the deleterious effect of mild hyperthermia, thereby demonstrating a significant neuroprotective effect. The survival of neurones subjected to both hyperthermia and edaravone was the same as that of neurones exposed to normothermia and edaravone. CONCLUSIONS Temperature is a potential factor in determining whether edaravone confers a neuroprotective effect when applied during prolonged hypoxic insults.
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Affiliation(s)
- S Shibuta
- Department of Anaesthesiology and Intensive Care Medicine, Graduate School of Medicine D7, Osaka University, 2-2, Yamadaoka, Suita 565-0871, Japan.
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Bassin SL, Bleck TP. Barbiturates for the treatment of intracranial hypertension after traumatic brain injury. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2008; 12:185. [PMID: 18983702 PMCID: PMC2592754 DOI: 10.1186/cc7020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In their article on the use of barbiturates for the treatment of intracranial hypertension after traumatic brain injury, Perez-Barcena and colleagues conclude that thiopental was more effective than pentobarbital in decreasing intracranial pressure. Here we discuss the limitations of this study and review areas of controversy surrounding barbiturate use in neurocritical care.
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Affiliation(s)
- Sarice L Bassin
- Department of Neurology, Northwestern University Feinberg School of Medicine, N Lake Shore Drive, Chicago, Illinois 60611, USA.
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. HE, . KAG, . MM, . HZ, . VS, . NAG. The Effects of Morphine on Cerebral Blood Flow and its Neuroprotective or Cell Damage Before and after Brain Ischemia Reperfusion in Rabbits. INT J PHARMACOL 2006. [DOI: 10.3923/ijp.2006.613.617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Shibuta S, Varathan S, Mashimo T. Ketamine and thiopental sodium: individual and combined neuroprotective effects on cortical cultures exposed to NMDA or nitric oxide. Br J Anaesth 2006; 97:517-24. [PMID: 16928698 DOI: 10.1093/bja/ael192] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND An N-methyl-D-aspartate (NMDA) blocker, ketamine, has been shown to be neuroprotective both in vivo and in vitro. However, ketamine is not commonly recommended for use in patients suffering from cerebral ischaemia because of its adverse neurological effects. We hypothesized that combined administration of ketamine and thiopental sodium (TPS) would be highly effective in protecting cerebral cortical neurones from ischaemia, with possibly reduced dosages. METHODS We examined the degree of neuroprotection provided by various concentrations of ketamine and TPS, alone and in combination, in cortical cultures exposed to NMDA or a nitric oxide-releasing compound (NOC-5) for 24 h. The survival rate (SR) of E16 Wistar rat cortical neurones was evaluated using photomicrographs before and after exposure to these compounds. RESULTS The SRs of cortical neurones exposed to 30 microM NMDA or NOC-5 were 15.0 (3.8)%, 12.8 (3.1)%, respectively. Higher doses (5, 10 and 50 microM) but not lower doses (<1 microM) of ketamine improved SRs [57.9 (2.2)%, 61.1 (5.4)%, 76.7 (3.0)%, respectively] against NMDA but not NOC. Enhanced survival was observed with combined administration of 5 or 10 microM ketamine and 50 microM TPS [SR 71.3 (4.8)%, 74.7 (3.7)%, respectively, P<0.05 if ketamine alone, P<0.01 if TPS alone], against NMDA-induced neurotoxicity in vitro. Only the highest dose of TPS (50 microM) improved survival after NOC exposure. This neuroprotection was not influenced by ketamine. CONCLUSIONS These data indicate that a low, clinically relevant dose of ketamine offer significant neuroprotection during prolonged exposure to NMDA but not to NOC. Combinations of reduced doses of ketamine and TPS exhibited enhanced neuroprotection against NMDA-induced neurotoxicity. Hence, combinations of these two common i.v. anaesthetics agents could be developed to protect the brain from ischaemia.
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Affiliation(s)
- S Shibuta
- Department of Anaesthesiology and Intensive Care Medicine, Graduate School of Medicine D7, Osaka University 2-2, Yamadaoka, Suita 565-0871, Japan.
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Sasaki R, Hirota K, Roth SH, Yamazaki M. Anoxic depolarization of rat hippocampal slices is prevented by thiopental but not by propofol or isoflurane. Br J Anaesth 2005; 94:486-91. [PMID: 15708869 DOI: 10.1093/bja/aei077] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND There is strong evidence to suggest that anoxic depolarization (AD) is an important factor in hypoxia/ischaemia-induced neural damage. Treatments that prevent the occurrence of AD may be useful in providing neuronal protection against hypoxia. The current study was designed to determine whether general anaesthetics which have been suggested to 'induce prophylaxis' against hypoxia can attenuate the incidence of AD. METHODS The effects of anoxia (3 min) on evoked extracellularly recorded field potentials of CA1 neurons in rat hippocampal slices were assessed in the absence and presence of the i.v. general anaesthetics thiopental and propofol and the volatile anaesthetic isoflurane. RESULTS In the absence of anaesthetics, AD occurred in 81% of the preparations tested. Thiopental (2 x 10(-4) M) significantly reduced the incidence of AD (16%, P=0.0006). In comparison, propofol (2 x 10(-4) M) and isoflurane (1.5 vol%) were ineffective (69% and 60%, respectively). Furthermore, in the presence of thiopental, the population spike amplitude recovered with and without AD (90% and 94% of pre-anoxic value, respectively) following 3 min anoxia. CONCLUSION The prophylactic effect of thiopental against hypoxia might be induced, in part, by preventing the generation of AD.
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Affiliation(s)
- R Sasaki
- Department of Anaesthesiology, Toyama Medical and Pharmaceutical University of Medicine, 2630 Sugitani, Toyama, 930-0194, Japan
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Shibuta S, Varathan S, Mashimo T. The neuroprotective effect of ONO-1714 on NMDA-mediated cytotoxicity in vitro. J Neurol Sci 2003; 215:31-6. [PMID: 14568125 DOI: 10.1016/s0022-510x(03)00180-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We report the effects of a newly developed NOS inhibitor on the neurotoxicity induced by NMDA on cultured fetal rat cortical neurons. To date, three different isoforms of NOS have been characterized. It has been considered that both neuronal NOS and inducible NOS activities are detrimental to the ischemic brain, whereas endothelial NOS plays a prominent role in maintaining cerebral blood flow and prevents neuronal injury during ischemia. ONO-1714 is a newly developed competitive NOS inhibitor that has selective inhibitory potency for iNOS than eNOS. However, its effect on nNOS has not been investigated yet. In this study, we investigated the neuroprotective effect of ONO-1714 on NMDA-induced neurotoxicity in our established model of primary cultured cortical neurons of rat foetus. Cortical neurons (prepared from E16 rat foetuses) were used after 13-14 days in culture. The cells were exposed to 30 muM NMDA for 24 h in the culture. To evaluate the neuroprotective effects of NOS inhibitors, ONO-1714 and L-NAME, neurons were exposed to various concentrations of an NOS inhibitor with 30 muM NMDA. The NMDA induced neurotoxicity was significantly attenuated by ONO-1714 in all concentrations, but not in low to moderate concentrations of L-NAME. These findings demonstrate that the neuroprotective effect of ONO-1714 was more potent than L-NAME. Moreover, ONO-1714 has a strong inhibitory effect on nNOS and would be a powerful tool for the protection of neurons against cerebral ischemia.
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Affiliation(s)
- Satoshi Shibuta
- Department of Anesthesiology and Acute Critical Medicine, Graduate School of Medicine, Osaka University (D7), 2-2 Yamadaoka, Osaka 565-0871, Suita, Japan.
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Varathan S, Shibuta S, Varathan V, Takemura M, Yonehara N, Mashimo T. Effects of deep hypothermia on nitric oxide-induced cytotoxicity in primary cultures of cortical neurons. J Neurosci Res 2003; 72:613-21. [PMID: 12749026 DOI: 10.1002/jnr.10608] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Nitric oxide (NO) is thought to play a major role during cerebral ischemia. However, the protective efficacy of hypothermia against NO-induced neurotoxicity remains to be examined. In the present study, the degree of neurotoxicity induced by NO was analyzed in two temperature groups (normothermia, 37 degrees C; deep hypothermia, 22 degrees C) of cultured E16 Wistar rat cortical neurons. Two different NO donors, 1-hydroxy-2-oxo-3-(N-ethyl-2-aminoethyl)-3-ethyl-1-triazene (NOC-12) and 1-hydroxy-2-oxo-3-(3-amynopropyl)-3-isopropyl-1-triazene (NOC-5), that have equal half-lives at 37 degrees C and 22 degrees C, respectively, were used. Cultured neurons in each temperature group were exposed to 30 and 100 micro M NOC for three different time courses, 6 hr, 12 hr, and 24 hr. The survival rates of neurons were evaluated by assessing viable neurons on photomicrographs before and after the experiments. The highest survival rate (approximately 93%) was seen in both temperature groups when neurons were exposed to 30 micro M NOC for 6 hr and 12 hr, and there was no significant difference observed between these two groups (P > 0.05). Almost equal survival rates were observed in both temperature groups following exposure to 30 micro M NOC for 24 hr (at 37 degrees C, 80.4% +/- 2.6%; at 22 degrees C, 83.2% +/- 1.6%; P > 0.05). During exposure to 100 micro M NOC, although the survival rate linearly decreased (approximately from 70% to 5%) in both temperature groups when exposed for 6-24 hr, there were no significant intergroup differences observed (P > 0.05). In conclusion, hypothermia does not provide adequate protection to the neurons by acting on the mechanisms evoked by NO, so we speculate that hypothermia may not confer neuroprotetcion once NO is released during ischemia.
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