Effect Of Nebulization Of NO Donors On Acute Hypoxic Myocardial Impairment And Lung Injury In Newborn Piglets

Multiple organ disfunction syndrome (MODS) induced by perinatal asphyxia is one of the major causes of neonatal death, and the myocardial impairment and lung injury occur commonly. Nowadays, inhaled nitric oxide (iNO) has been used successfully in persistent pulmonary hypertension of newborn (PPHN). Unfortunately, the technology required to support iNO needs mechanical ventilation and strict monitor system and the cost of treatment with iNO is very expensive. Therefore, iNO is not universally available for clinical application. Furthermore, rebound pulmonary hypertension occurs on acute withdrawal of iNO because of the short half-life of NO. Given these together, the search for new selectively pulmonary vasolators is of value. In recent years some reports showed that nebulization of NO donors can selectively reduce pulmonary hypertension. However, there is no report about the effect of nebulization of NO donors on hypoxic myocardial impairment. On the other hand, iNO has been shown to inhibit neutrophil congregate in the lung, yet the influence of nebulization of NO donors on hypoxic lung injury is unknown. In this study we studied the effects of nebulization of nitroglycerin (NTG) and sodium nitroprusside (SNP), two widely used NO donors, on myocardial impairment and lung injury induced by hypoxia in newborn piglets.Part â…  Effect of nebulized NO donors on acute hypoxic myocardial impairment in newborn pigletsObjectiveTo investigate the effect of nebulized NO donors on pulmonary and systemic hemodynamics and myocardial impairment induced by hypoxia in newborn piglets.Materials and methodsPulmonary hypertension and myocardial impairment was induced by inspiring 10% O₂ for 1h. Thirty piglets (5～7 days old) were randomly divided into five groups as following: â‘  group S, which did not expose to hypoxia; â‘¡ group C, which received nebulization of saline at 1h of hypoxia for 0.5h; â‘¢ group N1, which received nebulization of NTG at 1h of hypoxia for 0.5h; â‘£ group N2, whichreceived nebulization of NTG at 0.5h of hypoxia for 0.5h; (5) group SNP, which received nebulization of SNP at 1h of hypoxia for 0.5h. Mean artery pressure (MAP) and mean pulmonary artery pressure (MPAP) were monitored continuously. Arterial blood gas was analysed at baseline, at 0.5h and 1h of hypoxia, at 0.5h, 1h, 3h and 5h after termination of hypoxia. Serum CK-MB and cTnI level were measured at baseline, at 1h of hypoxia and at 5h after termination of hypoxia. Cardiac functions were evaluated by echocardiography at 5h after termination of hypoxia. Apoptotic cells were detected with TUNEL method and myoglobin (Mb) and connexin 43 (Cx43) staining were studied by immunohistochemistry method. Mb mRNA and Cx43 mRNA were calculated by real-time fluorescence quantitative RT-PCR.Results1. After nebulization, MPAP in group N1 and N2 were both significantly lower than that in group C (P<0.05 and P <0.01, respectively) and MPAP in group SNP was also significantly lower than that in group C (P<0.05).2. Serum CK-MB in group SNP was significantly lower than that in Group C at 5h after termination of hypoxia (P <0.05). Serum cTnI in group N1,N2 and SNP were all significantly lower than that in Group C at 5h after termination of hypoxia (P<0.01).3. Echocardiography showed the ratio of isovolumic relaxation time of left ventricle and R-R interval (LIRTc) in group N1,N2 and SNP were all significantly lower than that in Group C (P <0.05).4. Sporadic hemorrhage was observed in hypoxic myocardium by HE staining of myocardial tissue. BFP staining showed normal myocardium appeared yellow and hypoxic myocardium appeared red.5. The percentage of apoptotic cell in group N1,N2 and SNP were all significantly lower than that in Group C (P <0.05). Immunohistochemistry method showed the expression of Mb in Group N1,N2 and SNP were all significantly stronger than those in Group C (P <0.01), and the expression of Cx43 in Group N1, N2 and SNP were all significantly stronger than those in Group C (P <0.05).6. There was no significant difference in the expression of Mb mRNA and Cx43 mRNA between the five groups (P >0.05).Conclusion1. Pulmonary hypertension and myocardial impairment can be induced by inhalationof 10% O₂ for 1h in newborn piglets.2. Nebulization of NTG or SNP produces a selective pulmonary vasodilation in hypoxic newborn piglets.3. Nebulization of NTG or SNP can alleviate hypoxic myocardial impairment.4. The expression of Mb and Cx43 decline obviously in myocardium after hypoxia without the decreased level of mRNA, which indicate hypoxia influence the expression or the location rather than the transcription of Mb and Cx43.Part â…¡ Effect of nebulization of NO donors on acute hypoxic lung injury in newborn pigletsObjectiveTo evaluate the effect of nebulized NO donors on acute hypoxic lung injury in newborn piglets.Materials and methodsThe animal groups were the same as those in Part â…  . Rrespiratory dynamic compliance (Cdyn) and resistance of respiratory system (Rrs) were recorded at baseline, at 0.5h and 1h of hypoxia, at 0.5h, 1h, 3h and 5h after termination of hypoxia. After nebulization, arterial blood was collected for measuring methemoglobin (MetHb) and nitrate/nitrite (NO₂^-/NO₃^-) level. Right mid-lobe lung tissues were used for determining wet-dry ratio (W/D) and myeloperoxidase (MPO) level. The remainders of right lungs were lavaged to get the bronchoalveolar lavage fluid (BALF) for the analysis of total phospholipids (TPL), disaturated phosphatidylcholine (DSPC) and total protein (TP). Left lungs were used for examining pathologic changes.Results1. No significant difference was observed in Cdyn and Rrs among the five groups at the same time points (P >0.05).2. There was no significant difference in W/D among the five groups (P >0.05).3. WCC in BALF in group C, N1 and N2 significantly increased as compared with group S (P <0.05). MPO level in lung tissue in group N1, N2 and SNP significantly decreased as compared with group C (P <0.05).4. No significant difference was observed in TPL and DSPC/TPL in BALF amongthe five groups. TP in BALF in group C increased significantly than that in group S (P<0.05). DSPC/TP in BALF in group C decreased significantly than that in group S (P<0.05).5. Pathological analysis of lungs showed that edema, infiltration of neutrophils and hemorrhage occurred after hypoxia. Edema score in group C and N2 was significantly higher than that in group S (P<0.05). Infiltration of neutrophils in group N1,N2 and SNP decreased significantly than that in group C (P <0.05). Hemorrhage score in group C was significantly higher than that in group S (P <0.01), while hemorrhage score in group N1,N2 and SNP was significantly higher than that in group S (P <0.05).6. No significant difference was observed in the concentration of MetHb and NO₂^-/NO₃^- level among the groups after nebulization as compared with group S (P>0.05).Conclusion1. Inhalation of 10% O₂ for 1h could induce inflammatory lung injury in newborn piglets.2. Nebulization of either NTG or SNP could reduce MPO content in the lung tissue and relieve the infiltration of neutrophils.3. Nebulization of NTG or SNP has no effect on the metabolism of phospholipids and the water content in the lungs.4. Nebulization of NTG or SNP doesn't cause methemoglobinemia.SummaryNebulization of NTG or SNP can selectively reduce acute hypoxic pulmonary hypertension. It can also decrease the apoptotic myocardial cells and relieve the loss of CK-MB, cTnI, Mb and Cx43 of myocardial tissue to protect the myocardial function after hypoxia. Nebulization of NTG or SNP can alleviate the infiltration of neutrophils in the lungs without effects on the content of phospholipids and the water content. This method has potential value of clinical application since it can be easier used and the cost is cheaper.