| Background:Cardiopulmonary bypass is routinely used to repair the congenital heart defects in cardiovascular surgery. Ischemia-reperfusion(IR) is well known to result in severe damage to important organs such as heart and lung during the non-physiological process. Acute lung injury due to ischemia-reperfusion is believed to cause a pulmonary dysfunction with morbidity of15%-30%in adult patients and over60%in infant patients, especially in children with complicated CHD and pulmonary artery hypertension. It has long been recognized by cardiac surgeons, anesthetists, and intensive-care physicians since the early days of cardiac surgery. Lung is unique organ which not gains enough blood supply and is not cooled effectively during CPB. And lung is subjected to the damage from inflammatory factors and microthrombu except for heart. Compared to adult, infant lung has more danger to ischemia-reperfusion injury.Acute lung injury after CPB is induced by ischemia-reperfusion directly. CPB can activate numerous biologic pathways, which evokes an acute system inflammatory response syndrome with activation of cellular and humoral cascades. In reperfusion period, when many oxygen and blood come into lung, oxygen species and inflammatory factors are generated. IR induces a production of reactive oxygen species(ROS) in excess of the endogenous cellular capacity, referred to as the so-called oxidative stress, causing mitochondria dysfunction, together with inflammation factors, cause lung damage and cell death. During CPB, macrophage cell and endothelial cell produce many inflammatory factors such as TNF-α、IL-1and IL-8. TNF-α and IL-1are the main proinflammatory cytokines that secreted by activated monocytes during ischemia-reperfusion injury. It is reported that the stimulation of IR induces the production of intracellular ROS, which appear to act as "a second messenger" in the signal transduction pathways leading to degranulation and releases of calcium and cytokines such as TNF-a and NF-κB". Free radicals activates redoxsensitive transcription factors, including nuclear factor-KB, myeloid differentiation factor-88, and trigger the expression of interleukin-1,tumor necrosis factor-a, and other inflammatory mediators, while IL-1and TNF-a themselves are also potent inducers of NF-κB and MyD88.Mitochondria play an important role in cell death and ischemia-reperfuison. During ischemia, when ATP is progressively deleted, ion pumps cannot function resulting in a rise in calcium (Ca2+),which further accelerates ATP depletion. The rise in Ca2+during ischemia and reperfusion leads to mitochondrial Ca2+accumulation, particularly during reperfusion when oxygen is reintroduced.Myocardial cell death due to ischemia-reperfusion is a major cause of morbidity and mortality in western nations. In the past few decades, it has become clear that the myocardial response to ischemia-reperfusion can be manipulated to delay injury.Infant has a lower antioxidant capacity than adult, probably leading to a high susceptibility to the oxidative stress. It has been speculated that ischemia-reperfusion injury and total inflammatory reaction are the main mechanism of lung injury during CPB. How to relieve the ischemia-reperfusion injury and inflammatory reaction? It is the key for lung protection during CPB.Asiatic acid (AA) is one of the triterpenoid components of Terminalia catappa L. Previous studies showed that AA has numerous pharmacological actions, including antioxidant, anti-inflammatory, neuro-protective anti-cancer effects and hepatoprotective activity. Gao et al. found that the mechanisms of hepatoprotective activity may be related to regulation of the VDAC level and its protein conformational change. Some study demonstrate that AA shows neuroprotective effects against rotenone and H2O2-induced cellular injury. And that the mechanism underlying its protective effects may be related to prevent the mitochondrial dysfunction by reducing ROS, inhibited GSH decrease. It was also confirmed that AA also has hydroxyl radicals scavenging activity.In our study, we established ischemia-reperfusion lung injury of infant rabbits, and observed AA protection to ischemia-reperfusion lung injury. Furthermore, we maybe explore a new, more effective protective method to ischemia-reperfusion lung injury.Part I Ischemia-reperfusion lung injury of infant rabbitsObjectives:The aim of the study was to compare ischemia-reperfusion-induced lung injury between adult and infant rabbits and summarized the character and the mechanism of ischemia-reperfusion lung injury of infant rabbitsMethods:Both24infant(15-21days old) and24adult (5-6months old) rabbits were randomly divided into either ischemia-reperfusion or sham operation. Under anesthesia ischemia-reperfusion model was induced by clamping the right pulmonary hilum for1hour and then removal of the clamp for4hours. The lung tissue was collected for histological examination by light and electron microcopies and for extracting mitochondrial. The evaluation of mitochondrial alteration, including swelling rate, membrane potential difference and intramitochondrial Ca2+concentration were measued. Production and expression of free radical species-hydroxyl radical (ROS-HR), malondialdehyde (MDA), superoxide dismutase(SOD), glutathione peroxidase(GSH-PX), myeloid differentiation factor-88(MyD-88), and muclear factors-κB(NF-κB) in the lung tissue were also examined.In addition, serum levels of interleukin-1β and tumor necrosis factor-a were measured during the ischemia-reperfusion process.Results:The infant lungs had more injury after ischemia-reperfusion. In comparison to adult lungs, the infant lungs had more increase neutrophil infiltration, edema, swelled alveolar epithelial and endothelial cells, and severe mitochondrial impairment reflected by damage of the inner membrane as well as decrease in the membrane potential after ischemia-reperfusion. The lungs in infants with ischemia-reperfusion were found to futher produce more ROS-HR, intramitochondrial Ca2+and MDA, and less SOD and GSH-PX than the ischemia-reperfusion adult lungs. The serum levels of interleukin-1β and tumor necrosis factor-a were elevated during the period of reperfusion2hours, particularly in the infant animals, as well as the expression of MyD88and NF-κB in the lungs.Conclusions:Ischemia-reperfusion causes more severe lung damage in infants than in adults, probably due to combination of low antioxidant capacity, overproduction of ROS and high inflammatory reaction in infants.Part II Asiatic acid protects the infant lung injury induced by ischemia-reperfusionObjectives:AA has numerous pharmacological actions, including antioxidant, anti-inflammatory. The aim of the study was to examine whether AA could attenuate ischemia-reperfusion induced lung injury in infant rabbits.Methods:60New Zealand White rabbits at age from15to21days were subjected to sham operation, IR, low dose AA plus IR, medium dose AA puls IR, and high dose AA puls IR. IR was induced by clamping the right pulmonary hilum for1hour an then removal of the clamp for4hours. AA was given3days before operation according7.5mg/kg、15mg/kg、30mg/kg respectively. The evaluation of mitochondrial alteration, including swelling rate, membrane potential difference and intramitochondrial Ca2+concentration were measued. Production and expression of free radical species-hydroxyl radical (ROS-HR), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase(GSH-PX), myeloid differentiation factor-88(MyD-88), and muclear factors-κB(NF-KB) in the lung tissue were also was evaluated. And temperature, hemodynamics, blood gases and neutrophil count were measured after reperfusing2hours. In addition, serum levels of interleukin-1β and tumor necrosis factor-a were measured during the ischemia-reperfusion process.Results:Asiatic acid can attenuate the ischemia-reperfusion lung injury in infant. The infant lungs in AA group had less neutrophil infiltration by electron and light microscopies, edema, swelled alveolar epithelial and endothelial cells, and mitochondrial impairment got better as well as increase in the membrane potential. AA reduced the production of ROS-HR and MDA and improved the activities of GSH-PX and SOD markedly. A near-minimum or minimum swelled mitochondria were observed in AA rabbits. AA pretreatment decreased the serum levels of interleukin-1β and tumor necrosis factor-a were measured during the ischemia-reperfusion process. As well as the great development of hemodynamics and blood gases in AA pretreatment rabbits compared IR rabbits.Conclusions:AA pretreatment reduces the lung mitochondrial damage induced by IR in the infant rabbits... |
PDF Full Text Request