The Role Of Sulfur Dioxide In Regulating Cardiovascular And Mechanism In The Pathogenesis Of Septic

Objective:1. The present work was designed to determine the cardiovascular functions and mechanisms of sulfur dioxide (SO2) within the nucleus tractus solitarii (NTS) and rostral caudal ventrolateral medulla (RVLM) of rats.2. To investigate the distribution and content of endogenous SO2in Septic rats.3. To determine the potential role and mechanism of sulfur dioxide SO2in regulating areterial baroreflex (ABR) in septic rats.Methods:1. Cardiovascular effects of SO2in the NTS and RVLM:Fifty adult male Spargue-Dawley (SD) rats were enrolled in this study. Twenty five of them received different doses of SO2(2pmol,20pmol, and200pmol, respectively) or artificial cerebrospinal fluid (aCSF) in unilateral RVLM. The others received different doses of SO2(2pmol,20pmol, and200pmol, respectively) or aCSF in unilateral NTS. And the effects of SO2on blood pressure and heart rate of these rats were observed.2. Mechanism of SO2produce cardiovascular effects in RVLM:Forty-three adult male SD rats were enrolled in this study. In eleven rats, Glutamate inotropic of non-selective receptors antagonist kynurenic acid (KYN,15nmol) was applied into RVLM of rats10min before SO2(20pmol) was microinjected. The other thirty-two rats, aCSF, ATP-sensitive potassium channels (KATP) blocker glibenclamide (Gli,40μmol). L-type calcium channels blocker nicardipine (Nic,200pmol), a non-specific nitric-oxide synthase inhibitor NG-nitro-L-arginine-methylester (L-NAME,15nmol) or soluble guanylyl cyclase (sGC) inhibitors1-H-[1,2,4]oxadiaolo[4,3-a]quinoxalin-l-one (ODQ,250pmol) were prior applied before SO2(20pmol) was microinjected to explore the signal transduction pathway of sulfur dioxide.3. The distribution of SO2in various tissues and serum levels:The rat model of cecal ligation and puncture (CLP) induced sepsis was established.40Spargue-Dawley rats were randomly divided into sham operation group (n=8) and sepsis model group (n=32) using the random table method. The model group rats were sacrificed after3h,6h,12h and24h of surgery. Take the liver, kidney, heart, brain and serum specimens, using enzyme-linked immunosorbent assay (ELISA) for detection of serum SO2levels.4. The effect of SO2on sepsis rats ABR function:Sixty six male Spargue-Dawley rats were randomly divided into11groups of random table method:①Sham operation(sO)+saline+intravenous inJection(iv)group:②CLP+Saline+iv group:③SO+SO2+iv group:④CLIP+SO2+iv group;⑤SO+artiificial cerebrospinal fluid(aCSF)+bilater nucleus tractus solitarii(NTS)microinjection group;⑥SO+SO2+NTS group;⑦CLP+aCSF+NTS group;⑧CLP+SO2+NTS group；⑨CLP+kynurenic acid(KYN)+NTS group:⑩SO+aCSF+SO2+NTS group(Pre-micinjection of aCSF in the bilater NTS.then injected SO2at the same site):11SO+KYN+SO2+NTS group(Pre-micinjection of KYN in the bilater NTS,then injected SO2at the same site).The ABR function was measured before administration and5min and30min after administration.ResuIts:1. Cardiovascular effects of SO2in the NTS and RVLM:Unilateral microinjection of SO2into the NTS produced dose-dependent hypotension and bradycardia(P<0.05).Unilateral microinjection of SO2into the RVLM produced dose-dependent hyperpiesia and tachycardia(P<0.05).2.Mechanism of SO2produce cardiovascular effects in RVLM:Pretreatment with KYN within the RVLM partially blocks the hyperpiesia and tachycardia evoked by intra-RVLM H2SO3(P<0.05).Prior application of Gli Nic L-NAME or ODQ into the RVLM partially abolished the hyperpiesia and tachycardia evoked by intra-RVLM H2SO3(P<0.05).3. The distribution of SO2in various tissues and serum levels:SO2was endogenously generated in various rat tissues including liver,kidney,heart,brain and serum.The SO2content was higher in heart than in other tissues；Compared with the control group,The SO2levels began to increase at3h after CLP,then showed gradual increasing tendency to24h.4.The effect of SO2on sepsis rats ABR function:①The ABR value of rats at different time in the same groups:Compared with the ABR value before administration in the SO+SO2+iv group,CLP+SO2+iv group,SO+SO2+NTS group,CLP+SO2+NTS group,SO+aCSF+S02+NTS group,the ABR values of rats significantly decreased at5min and30min after administration(P<0.05),which significantly increased in the CLP+KYN+NTS group(P<0.05).②The ABR value of rats at the same time in the different groups:Before administration,the ABR value of rat in the CLP+Saline+iv group was significantly lower than that in the SO+Saline+iv group or SO+S02+iv group(P<0.05),CLP+aCSF+NTS group was significantly lowet than that in the SO+aCSF+NTS group or SO+S02+NTS group(P)<0.05).At5min and30min after administration,the ABR value of rat in the CLP+SO2+iv group was significantly lower than that in the CLP+Saline+iv group(P<0.05)or SO+Saline+iv(P<0.05),CLP+S02+NTS group was significantly lower than that in the CLP+aCSF+NTS group(P<0.05)or SO+aCSF+NTS group(P<0.05),CLP+KYN+NTS group was significantly higher than that in the CLP+aCSF+NTS group(P<0.05),SO+KYN+SO2+NTS group was significantly higher than that in the SO+aCSF:+SO2+NTS group(P<0.05).Conclusion: 1. SO2in NTS can cause dose-dependent hypotension and bradycardia. SO2in RVLM can cause dose-dependent hyperpiesia and tachycardia.2. Hyperpiesia and tachycardia induced by SO2in the RVLM is mediated by part of Glu receptors, and the mechanism may be related to KATP and L-type calcium channels open. The cardiovascular effects of sulfur dioxide are mainly associated with NO/cGMP signal transduction pathway.3. SO2is endogenously generated in sham operation rats, and the SO2content in heart is higher than that in other organs; SO2in sepsis rats than in normal level, may be involved in the pathogenesis of septic rats.4. SO2plays an adverse role in septic ABR function, and activating glutamate inotropic non-selective receptor at the pathway of ABR, may be the mechanism involved in the down-regulation of ABR function in septic rat. Notably, the NTS may be also responsible for reduction of ABR value.