Isoflurane Decreases Self-renewal Capacity of Rat Cultured Neural Stem Cells

Abstract

Background Isoflurane produces neural and behavioral deficits in in-vitro and in-vivo models. This study tested the hypothesis that neural stem cells are adversely affected by isoflurane such that it inhibits proliferation and kills these cells. Methods Sprague Dawley rat embryonic neural stem cells were plated onto 96 well plates and treated with 0.7%, 1.4% or 2.8% isoflurane in 21% oxygen for 6 hours and fixed either at the end of treatment or 6 or 24 hours later. Control plates received 21% oxygen under identical conditions. Cell proliferation was assessed immunocytochemically using 5-ethynyl-2’-deoxyuridine incorporation and death by propidium iodide staining, lactate dehydrogenase release, and nuclear expression of cleaved caspase 3. Data were analyzed at each concentration using an ANOVA; P < 0.05 was considered significant. Results Isoflurane did not kill neural stem cells by any measure at any time. Isoflurane 1.4% and 2.8% reduced cell proliferation based upon 5-ethynyl-2’-deoxyuridine incorporation whereas 0.7 % had no effect. At 24 h after treatment, the net effect was a 20–30% decrease in the number of cells in culture. Conclusions Isoflurane does not kill neural stem cells in vitro. However, at concentrations at and above the minimum alveolar concentrations required for general anesthesia (1.4 and 2.8%), isoflurane inhibits proliferation of these cells but has no such effect at a sub-minimum alveolar concentrations (0.7%). These data imply that dosages of isoflurane at and above minimum alveolar concentrations may reduce the pool of neural stem cells in vivo but that lower dosages may be devoid of such adverse effects.

Dual Effects of Isoflurane on Neuronal Proliferation/Differentiation

“…First, the results obtained from an immortalized neuronal progenitor cell line may not necessarily be extrapolable to normal human neurons, given the paucity of data on the biochemical and electrophysiological characterization of these cells. In agreement with Zhao et al's findings., other recent studies using cultured neural stem cells found inhibition of cell proliferation at high (1.4-3.7%) isoflurane concentrations and no cytotoxic effect when isoflurane was administered for 4-6 h. 6,7 In contrast to the study by Zhao et al's, however, there was no effect on proliferation at a low isoflurane concentration (0.7%). stratmann et al found that one minimum-alveolar concentration isoflurane for 4 h did not affect brain cell death, hippocampal neurogenesis, or long-term cognitive outcome in aged rats.…”

Simvastatin Attenuates Neurogenetic Damage and Improves Neurocongnitive Deficits Induced by Isoflurane in Neonatal Rats

“…reports that isoflurane inhibited neurogenesis by promoting the apoptosis of NSCs [10,15,17,46,49], these results indicated that simvastatin protected neurogenesis by reducing NSC apoptosis.…”

Developmental Disability in the Young and Postoperative Cognitive Dysfunction in the Elderly After Anesthesia and Surgery: Do Data Justify Changing Clinical Practice?

“…18,19 Neurogenesis, of course, requires neural stem cells, and Culley et al have presented evidence that 1 minimum alveolar concentration (MAC) isoflurane reduces the production of neural stem cells by 20% in vitro 24 hours after exposure. 32 Decreased neurogenesis and decreased neural stem cell proliferation notwithstanding, using 16-day-old rats, Briner and coauthors found that sevoflurane, desflurane, and isoflurane rapidly increase dendritic spine density, which ''could interfere with physiologic patterns of synaptogenesis and thus might impair appropriate circuit assembly in the developing cerebral cortex.'' 25,26 In Humans Since 1945, investigators have observed an association between impaired neuro-cognitive-behavioral development and postnatal exposure to surgery and anesthesia prior to 3 or 4 years of age, 33 -52 with Levy 33 having found a statistically significant association between near-term emotional sequelae and younger age at anesthetic exposure (P < 0.0004, data not statistically analyzed in original article).…”

“…If so, this raises concern about the effect of all anesthetics on neural stem cell proliferation ''at critical periods of brain development as well as in adulthood.'' 32 …”