The Effect Of Sodium Cyanide On Environmental Hypoxia-induced Brain Injury In Mice And The Improvement Effect Of Acetazolamide

Objective:Hypoxia is an important factor causing neurological dysfunction.Hypoxia includes external hypoxia and internal hypoxia,with external hypoxia referring to environmental hypoxia and internal hypoxia referring to tissue hypoxia.Both internal and external environmental hypoxia often coexist,for example,when a fire occurs,internal hypoxia and external hypoxia may occur due to insufficient oxygen supply and oxygen utilization barriers.Both internal and external environmental hypoxia can lead to brain damage,especially external hypoxia combined with internal hypoxia may further exacerbate brain damage,but its specific injury characteristics and mechanism of action have not been elucidated.Sodium cyanide（Na CN）can block the electron transfer of the respiratory chain within cells,leading to oxygen utilization disorders and tissue hypoxia,which occurs at this time.To investigate the effects of external hypoxia combined with internal hypoxia on brain tissue function,this study used Na CN simulation to establish an internal hypoxia model to observe the effect of internal hypoxia on brain damage caused by environmental hypoxia and explore the relevant mechanisms of action.Acetazolamide（ACZ）is a carbonic anhydrase inhibitor commonly used to prevent low-pressure hypoxia in high-altitude environments.This study also observed the protective effect of ACZ on brain injury caused by internal hypoxia combined with external hypoxia.The aim is to elucidate the effect of sodium cyanide on brain tissue damage caused by environmental hypoxia in mice,reveal the protective effect of ACZ on internal and external composite hypoxia damage,and provide experimental basis for the prevention and treatment of brain damage caused by internal and external composite hypoxia.Methods:Male Male Kunming mice were randomly divided into 11 groups:normal control group,Na CN 2.56 mg/kg group,Na CN 3.8 mg/kg group,Na CN 5.1 mg/kg group,ACZ group,external hypoxia 30 minutes group,external hypoxia 60 minutes group,Na CN composite hypoxia 30 minutes group,Na CN composite hypoxia 60 minutes group,ACZ+Na CN composite hypoxia 30 minutes group,and ACZ+Na CN composite hypoxia60 minutes group.The control group received intraperitoneal injection of equal volume physiological saline.The Na CN combined hypoxia group received i.p.3.8 mg/kg Na CN,the ACZ group received i.g.61.65 mg/kg ACZ,and the ACZ+Na CN combined hypoxia group received i.g.61.65 mg/kg ACZ+i.p.3.8 mg/kg Na CN.After intraperitoneal injection of different doses of Na CN（0,2.56,3.8,5.1 mg/kg）,the changes of Time to live after Na CN combined with hypoxia environment were observed.Spontaneous experiments and rod rotation experiments were used to observe changes in mouse activity levels and balance abilities;Evaluate whether mouse brain edema occurs by detecting the water content of mouse brain tissue;The changes of cerebral blood flow in mice were studied by laser Speckle imaging;Evaluate changes in mouse blood routine by detecting the blood gas value of the abdominal aorta;The contents of total Superoxide dismutase（T-SOD）and Malondialdehyde（MDA）in the hippocampus were detected with the kit to evaluate the changes of oxidative stress in the hippocampus of mice;After staining with Haematoxylin and eosin（HE）,the morphological changes of brain tissue in mice were observed under light microscope;The degree of apoptosis damage in mouse brain tissue was observed by terminal deoxynucleotidyl transferase mediated d UTP nick end labeling（Tunel）staining.Results:1.After intraperitoneal injection of different doses of Na CN（0,2.56,3.8,5.1mg/kg）and hypoxia treatment,compared with the control group（intraperitoneal injection of equal volume physiological saline.0 mg/kg dose group）,Na CN can prolong the survival time of mice under hypoxia conditions.2.The results of behavioral experiments indicate that external hypoxia can cause a downregulation of spontaneous activity and balance ability in mice,and Na CN treatment can further reduce the changes in spontaneous activity and balance ability caused by external hypoxia in mice;Pre-treatment with ACZ can significantly improve the downregulation of spontaneous activity and balance ability in mice caused by hypoxia combined with Na CN.3.The results of brain tissue water content showed that simple hypoxia did not cause an increase in brain tissue water content in mice.Compared with the control group,the Na CN（3.8 mg/kg）group and the Na CN combined hypoxia group both increased brain tissue water content.After ACZ treatment,the increase in brain tissue water content caused by hypoxia combined with Na CN could be significantly improved.4.The results of cerebral blood flow showed that external hypoxia can lead to a decrease in cerebral blood flow in mice.After Na CN treatment,it further reduces cerebral blood flow in mice.When ACZ treatment is applied,it can improve the decrease in cerebral blood flow caused by hypoxia combined with Na CN.5.The results of blood gas analysis showed that hypoxia would cause the increase of arterial blood partial pressure（Pa CO₂）in mice.Na CN would delay the increase of Pa CO₂ and the decrease of arterial partial pressure of oxygen（Pa O₂）within 30 minutes of hypoxia,and significantly increase the oxygen saturation（Sa O₂）in mice.6.Compared with the control group,the T-SOD activity and MDA content in the hippocampus of mice in the Na CN 3.8 mg/kg group and the 60 minute external hypoxia group were significantly upregulated;Compared with the external hypoxia group,the T-SOD activity and MDA content in the hippocampus of mice in the Na CN combined hypoxia group were further upregulated;ACZ treatment can significantly downregulate the T-SOD activity and MDA upregulation in mouse hippocampal tissue caused by Na CN combined hypoxia.7.HE staining results showed that hypoxia could lead to sparse and vacuolated arrangement of hippocampal histiocyte in mice;In Na CN combined hypoxia group,the volume of hippocampal histiocyte became larger,with obvious swelling and vacuolization,and the number of cells decreased significantly;ACZ treatment can significantly improve the disorder of hippocampal tissue arrangement caused by Na CN combined hypoxia.8.The results of Tunel staining showed that hypoxia can cause significant apoptosis of hippocampal neurons in mice,and Na CN can further exacerbate the apoptosis of hippocampal neurons caused by external hypoxia.Treatment with ACZ can significantly improve the apoptosis of hippocampal neurons caused by hypoxia combined with Na CN,playing a protective role.Conclusions:1.Na CN combined environment hypoxia can lead to a decrease in cerebral blood flow in hypoxic mice,leading to significant oxidative stress response and neuronal apoptosis in the hippocampus,leading to brain edema and serious damage to the brain tissue of mice,resulting in changes in spontaneous activity and balance ability.2.ACZ improves oxidative stress,reduces tissue apoptosis,and alleviates behavioral changes in mice caused by hypoxia combined with Na CN.This suggests that ACZ pretreatment can alleviate brain tissue damage caused by hypoxia combined with Na CN,playing a certain improvement role.