Effects Of Inhaled Hydrogen Sulfide Gas On Cotton Smoke Inhalation-induced Lung Injury In Rats

BackgroundSmoke inhalation injury is the main reason people died in a fire. And smokeinhalation, which is present in30%of burn patients, increases burn-related mortality by20%, making the mortality of combined smoke/burn injury30%–90%. Severe smokeinhalation injury can cause toxic pneumonia or pulmonary edema, and grave injury mayresult in acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Despite recentadvances in intensive care, smoke inhalation injury mortality remains high. It’s also theproblem in the department of respiratory and critical care medicine, as well as one of thehotspots in war injury research.In recent studies, endogenous hydrogen sulfide (H2S), which changes the past imageof rotten egg smell waste gas, is known as the third gas signal molecule following nitricoxide (NO) and carbon monoxide (CO), with the function of anti-oxidative stress,regulating inflammation, vasodilation, anti-fibrotic and regulating endocrine andreproductive system function and so on. Exogenous H2S of low dose can attenuate lunginjury and play a role of lung protection in various animal models of lung injury, but thestudy of inhalation of H2S gas in smoke inhalation injury animal model hasn’t beenreported. Therefore, this study is designed to observe the effect of inhaled H2S gas used inthe cotton smoke inhalation-induced lung injury in a rat model, and to explore the relatedmechanism.Objective1. To design a cotton smoke inhalation-induced lung injury model of rat.2. To observe the interventional effect of inhalation of H2S gas80ppm for6hours oncotton smoke inhalation-induced lung injury in rats, and to improve the detection ofrelevant indicators.3. To observe the difference of the interventional effect of inhalation of H2S gas80ppm on cotton smoke inhalation-induced lung injury in rats beween3hours time courseand6hours, as well as to explore the molecular mechanism underlying this process. Methods1. The cotton smoke inhalation-induced lung injury model of rat was designed andproduced by consulting previous literature. Blood gas analysis, gross observation in lungand lung histopathology, ELISA assay of levels of total protein, interleukin-1β (IL-1β),interleukin-8(IL-8) in rat bronchoalveolar lavage fluid (BALF), concentrations ofmalondialdehyde (MDA), myeloperoxidase (MPO) in lung tissue were investigated.2. The rat model of cotton smoke inhalation injury was copied and the rats inhaled80ppm H2S gas for6hours. The detection mentioned aboved were operated. Theconcentration of inducible nitric oxide synthase (iNOS) and the p65subunit of nuclearfactor kappaB (NF-κBp65) in lung tissue were detected by ELISA. Using the method offluorescence quantitative PCR the expression of iNOS mRNA in homogenized lung tissuewas detected.3. The rat model of cotton smoke inhalation injury was copied and the rats inhaled80ppm H2S gas for3hours or6hours. The detection mentioned aboved were operated.Lung wet/dry weight ratio was detected, while the concentrations in lung tissue of NO,glutathione (GSH), γ-glutamyl cysteine synthetase (γ-GCS) were dected by ELISA assay.Using the method of fluorescence quantitative PCR the expression of iNOS mRNA orγ-GCS mRNA in homogenized lung tissue was detected, and the relative expression ofNF-κBp65or nuclear factor-E2related factor (Nrf2) was immunohistochemically detectedand calculated with Image Pro Plus6.0software.Results1. Compared with the control group, after smoke inhalation a typical performance oflung injury occured by gross observation as severe edema, most of the lung surface area ofbleeding bright red to dark red and histopathological observation as the diffuse damage ofalveolar structure, hyaline membrane, red blood cells leakage, alveolar septal thickening,inflammatory cell infiltration. Concentrations of total protein, IL-1β, IL-8in BALF weresignificantly elevated, as well as the MDA and MPO levels in lung tissue, those alsosupports lung injury diagnosis.2. Compared with the smoke group, lung injury performance in smoke+H2S grouprats significantly reduced, oxygenation index increased, total protein, IL-1β, IL-8in BALF decreased, concentrations of MDA, MPO, iNOS, NF-κBp65and relative expression ofiNOS mRNA in lung tissue decreased. The rats in H2S group inhaled hydrogen suldife80ppm for6hours with mild lung injury performance.3. In smoke+H2S3h group or smoke+H2S6h group, sum integrated optical density ofNF-kBp65or Nrf2, relative expression of iNOS mRNA or γ-GCS mRNA, concentrationsof NF-kBp65, iNOS, NO, GSH in rat lung tissues were decreased. The concentration ofγ-GCS has no significant difference between them. There were no significant differencebetween smoke+H2S3h group and smoke+H2S6h group in lung tissue biopsy pathology，blood oxygen analysis, lung wet-dry weight ratio, MDA and other indicators. Neverthelessrats in H2S6h group appered mild lung injury, while rats in H2S3h group didn’t.Conclusion1. Cotton smoke inhalation can cause acute lung injury in rats, and the performance ofrat lung gross and histopathological observation, indicators of oxygenation index, lungwet/dry weight ratio, BALF total protein, IL-1β, IL-8concentrations, MDA, MPOconcentration in lung tissue detected at the6hours after inhalation like those in humanacute lung injury.2. Inhaled hydrogen sulfide shows a good protective effect on cotton smokeinhalation-induced lung injury, that it can ameliorate oxidative stress and tissueinflammation. But inhaled H2S80ppm for6hours may also cause mild lung injury, thatcan not be excluded.3. The mechanism of inhaled80ppm hydrogen sulfide protecting against cottonsmoke inhalation-induced ALI in rats potentially is inhaled hydrogen sulfide inhibiting theactivation of NF-κBp65, so the expression of iNOS mRNA, iNOS and NO growsdownwards, as a result, it relieves oxidative stress and reduces pathological damage to lungtissue. The inhalation of H2S80ppm for3hours can avoid additional damage to lung tissueand is a superior way of inhalation of H2S80ppm than for a long time.