The Study Of Neuronal Apoptosis Aggravated By Hypercapnia Via Increasing Oxygen Metabolism Of Hypoxic Astrocyte

BackgroundAcute respiratory distress syndrome(ARDS)is a common complication of the hospital intensive care unit(ICU),which seriously affects the quality of life of patients.In the treatment of patients with ARDS,in order to correct hypoxia and avoid lung injury,a small tidal volume mechanical ventilation strategy is often used,but the strategy often leads to hypercapnia.For a long time,it has always been clinically concerned only about the benefits of small tidal volume mechanical ventilation strategies for the lungs,while ignoring the effects of hypercapnia on the brain.Astrocytes are the largest and largest group of cells that make up the brain,which play an important role in regulating neuronal synaptic function,repairing and protecting neurons.Our previous studies showed that hypercapnia can aggravate the cognitive impairment of hypoxic-induced SD rats,and short-term exposure to hypoxia combined with high concentrations of CO2 can significantly increase brain oxygen consumption in SD rats.Therefore,for patients with ARDS under hypoxic conditions,whether hypercapnia can aggravate hypoxia-induced neuronal apoptosis by regulating astrocyte oxygen metabolism,and its related molecular mechanism remains to be studied.Methods:In this study,we investigated the molecular mechanisms of hypercapnia aggravating neuronal apoptosis in hypoxia.1.Establish an animal model of hypoxemia and hypercapnia in SD rats,simulate the clinical status of ARDS with permissive hypercapnia.And detect the expression of apoptosis-related protein Cleved-caspase-3 in the cerebral neurons.2.Detect the changes in cerebral oxygen extraction rate of SD rats and expression of metabolic proteins PDK1 and p-PDH in cerebral astrocytes.3.Culture astrocytes in vitro by hypoxia and high CO2 conditions,detect astrocyte oxygen consumption rate,metabolic related proteins PDK1 and p-PDH,and ROS changes.And the astrocytes were treated with hypoxia and high concentration of CO2,and its conditioned medium was used to intervene the primary neurons to detect the expression of neuronal apoptosis-related protein Cleved-caspase-3.Culture astrocytes in vitro by hypoxia and high CO2 conditions,detect astrocyte oxygen consumption rate,metabolic related proteins PDK1 and p-PDH,and ROS changes;low oxygen and high concentration CO2 treatment Astrocytes were treated with conditioned medium to interfere with primary neurons,and the expression of neuronal apoptosis-related protein Cleved-caspase-3 was detected.4.Finally,pretreatment of astrocytes with ROS inhibitor NAC,followed by hypoxia and high concentration of CO2,conditioned medium was used to culture primary neurons,and express changes of neuronal apoptosis-related protein Cleved-caspase-3 was detected again.Results:1.Hypercapnia could increase the expression of apoptosis-related protein Cleved-caspase-3 in rat cortical neurons under hypoxia.2.Hypercapnia could increase the cerebral oxygen extraction rate of SD rats under hypoxia.And it may reduce the expression of metabolic related proteins PDK1 and p-PDH in the cortical astrocytes of SD rats under hypoxia.3.High concentration of CO2 can increase the oxygen consumption of astrocytes under hypoxia.And it could reduce the expression of astrocyte metabolism-related proteins PDK1 and p-PDH under hypoxia.What’s more,it can increase the production of reactive oxygen species(ROS)induced by astrocytes under hypoxia.4.Pretreatment of astrocytes with hypoxia and high concentration of CO2,and the conditioned medium was used to intervene the primary neurons,which could significantly express the expression of Cleved-caspase-3,a neuronal apoptosis-related protein.Conclusions:1.Hypercapnia could aggravate the apoptosis of rat cortical neurons under hypoxia.2.Hypercapnia might increase the cerebral oxygen extraction rate of SD rats under hypoxic conditions by regulating metabolic related proteins.3.High concentration of CO2 may increase the oxygen consumption of astrocytes in hypoxia by regulating oxygen metabolism-related enzymes,leading to cellular oxidative stress and induction of excessive production of reactive oxygen species(ROS).4.High concentration of CO2 interfered with astrocytes under hypoxic conditions,and the conditioned medium was used to interfere with primary neurons,which significantly aggravated the apoptosis of primary neurons.