ABSTRACT
AIM:To investigate the role of specific binding of precursor form of nerve growth factor(proNGF) to p75NTR(proNGF-p75NTR)in isoflurane-induced cognitive impairment in aging mice.METHODS: Aging C57BL/6J male mice were randomly divided into 3 groups:control group,isoflurane(Iso)group and p75NTR specific inhibitor 2-ami-no-3-methyl-pentanoic acid amide(LM11A-31,LM)+isoflurane(LM+Iso)group.Aging C57BL/6J mice in Iso group and LM+Iso group were exposed to isoflurane,and the mice in control group were exposed to air.The mice in LM+Iso group were treated with LM,which dissolved in normal saline water and was administered daily by oral gavage at 50 mg· kg-1· d-1for 1 month.The mice in control group and Iso group received an equivalent volume of normal saline by the same route.Arterial blood gas analysis was conducted to detect the physiological state of the mice after isoflurane exposure. Morris water maze was performed to evaluate the cognitive function.The protein levels of proNGF,p75NTR,phosphorylated p38 MAPK and cleaved caspase-3 were determined by Western blot.RESULTS: Compared with the control group, the protein expression of proNGF and p75NTR in the hippocampus of Iso group was significantly elevated(P<0.05).The phos-phorylation level of p38 MAPK was higher in Iso group than that in control group(P<0.05),which was reduced in LM +Iso group significantly(P<0.05).A significant increase in the protein level of cleaved caspase-3 was observed in Iso group as compared with control group(P<0.05), while LM11A-31 treatment reversed this elevation significantly(P<0.05).The escape latency prolonged and the number of crossing the original platform location reduced in Iso group com -pared with control group(P<0.05), which were reversed by LM11A-31 in LM+Iso group(P<0.05).CONCLU-SION:ProNGF-p75NTR probably plays an vital role in the apoptotic pathway activation and the cognitive dysfunction in ag -ing mice exposure to isoflurane,which provides a potential target for clinical intervention.
ABSTRACT
<p><b>BACKGROUND</b>Isoflurane, a commonly used inhaled anesthetic, induces apoptosis in primary rat cortical neurons of rat in a concentration- and time-dependent manner by an unknown mechanism. We hypothesized that isoflurane induced apoptosis by causing abnormal calcium release from the endoplasmic reticulum (ER) via activation of inositol 1, 4, 5-trisphosphate (IP(3)) receptors. Sevoflurane has a reduced ability to disrupt intracellular calcium homeostasis and is a less potent cytotoxic agent. This study examined and compared the cytotoxic effects of isoflurane and sevoflurane on rat primary cortical neurons and their relationship with disruption of intracellular calcium homeostasis and production of reactive oxygen species (ROS).</p><p><b>METHODS</b>Primary rat cortical neurons were treated with the equivalent of 1 minimal alveolar concentration (MAC) of isoflurane and sevoflurane for 12 hours. MTT reduction and LDH release assays were performed to evaluate cell viability. Changes of calcium concentration in the cytosolic space, [Ca(2+)](c), and production of ROS were determined after exposing primary rat cortical neurons to isoflurane and sevoflurane. We also determined the effects of IP(3) receptor antagonist xestospongin C on isoflurane-induced cytotoxicity and calcium release from the ER in primary rat cortical neurons.</p><p><b>RESULTS</b>Isoflurane at 1 MAC for 12 hours induced cytotoxicity in primary rat cortical neurons, which was also associated with a high and fast elevation of peak [Ca(2+)](c). Xestospongin C significantly ameliorated isoflurane cytotoxicity in primary cortical neurons, as well as inhibited the calcium release from the ER in primary cortical neurons. Isoflurane did not induce significant changes of ROS production in primary rat cortical neurons. Sevoflurane, at equivalent exposure to isoflurane, did not induce similar cytotoxicity or elevation of peak [Ca(2+)](c) in primary rat cortical neurons.</p><p><b>CONCLUSION</b>These results suggested that isoflurane induced elevation in [Ca(2+)](c), partially via elevated activity of IP(3) receptors, which rendered cells vulnerable to isoflurane neurotoxicity. ROS production was not involved in isoflurane-induced neurotoxicity. Sevoflurane, at an equivalent exposure to isoflurane, did not induce similar elevations of [Ca(2+)](c) or neurotoxicity in primary cortical neurons of rat.</p>