DTIC ADA628189: Assessment of Oxidative Stress in Lungs from Sheep After Inhalation of Wood Smoke

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by  Defense Technical Information Center

Toxicology195(2004)97–112
Assessment of oxidative stress in lungs from sheep
after inhalation of wood smoke
Myung S. Park, Leopoldo C. Cancio, Bryan S. Jordan, William W. Brinkley,
∗
Victor R. Rivera, Michael A. Dubick
USArmyInstituteofSurgicalResearch,FortSamHouston,TX78234-6315,USA
Received10March2003;receivedinrevisedform12September2003;accepted15September2003
Abstract
Toelucidatepotentialdose-dependentmechanismsassociatedwithwoodsmokeinhalationinjury,thepresentstudyevaluated
antioxidantstatusandtheextentofpulmonaryinjuryinsheepaftergradedexposuretosmoke.Adult,malesheep(n = 4–5
pergroup)wereanesthetizedandreceived0,5,10or16unitsofcooledwesternpinebarksmoke,correspondingto0,175,
350and560s,respectively,ofsmokedwelltimeintheairwaysandlung.Smokewasmixedata1:1ratiowith100%O to
2
minimizehypoxia.Plasmaandexpiredbreathsampleswerecollectedpre-smoke,and6,12,18,24,36and48haftersmoke
exposure.Sheepwereeuthanatized48haftersmokeexposureandlungandairwaysectionswereevaluatedhistologicallyfor
injuryandbiochemicallyforindicesofoxidativestress.Plasmathiobarbituricacidreactivesubstances(TBARS)were66and69%
higherthancontrolsaftermoderateandseveresmokeexposureat48h,whereastotalantioxidantpotentialwasnotstatistically
differentamonggroupsatanytimeafterexposure.LungTBARSshowedadose-dependentresponsetosmokeinhalationand
wereapproximately2-,3-and4-foldhigher,respectively,thancontrolsafterexposureto5,10and16unitsofsmoke.Lung
myeloperoxidase (MPO) activity was also higher in smoke-exposed animals than controls, and MPO activity was markedly
elevated(19-and22-foldhigherthancontrolsinrightapicalandmediallobes)inresponsetoseveresmokeexposure.Smoke
exposurealsoinducedadose-dependentinjurytotracheobronchialepitheliumandlungparenchyma.Takentogetherthesedata
showthatfewindicesofoxidativestressrespondedinadose-dependentmannertogradeddosesofsmokeinhalation,although
mostoftheindicesmeasuredinlungwereaffectedbythehighestdoseofsmoke.Additionaltimecoursestudiesarenecessaryto
determinewhethertheseoxidantsareacauseoraconsequenceoftheairwayandlunginjuryassociatedwithexposuretowood
smoke.
©2003ElsevierIrelandLtd.Allrightsreserved.
Keywords Woodsmoke;Oxidantstress;Lipidperoxidation;Myeloperoxidase;Sheep
1. Introduction
Smoke inhalation injury is a major comorbid fac-
∗ Correspondingauthor.Tel.:[phone];
tor in patients with thermal injury, and has been
fax:[phone].
reported to occur in about 30% of patients with ma-
E-mailaddress [email protected]
(M.A.Dubick). jor burns (Herndon et al., 1985). Such patients with
0300-483X/$–seefrontmatter©2003ElsevierIrelandLtd.Allrightsreserved.
doi:10.1016/j.tox.2003.09.005
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4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER
Assessment of oxidative stress in lungs from sheep after inhalation of
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wood smoke.
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6. AUTHOR(S) 5d. PROJECT NUMBER
Park M. S., Cancio L. C., Jordan B. S., Brinkley W. W., Rivera V. R.,
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Dubick M. A.,
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United States Army Institute of Surgical Research, JBSA Fort Sam REPORT NUMBER
Houston, TX 78234
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98 M.S.Parketal./Toxicology195(2004)97–112
combined smoke inhalation and thermal injuries tend 2. Materialsandmethods
tobehemodynamicallyunstableandgenerallyrequire
about 50% more initial crystalloid fluid for resusci- 2.1. Animalpreparation
tation than estimated for the burn surface area alone
(Navar et al., 1985; Thompson et al., 1986; Demling Twenty1-to2-year-oldneuteredmalesheep(Ovis
et al., 1995). In addition, inhalation injury report- aeries,RambouilletX),weighing24to33kg,andfree
edly accounts for 20–84% of the mortality in burned ofantibodiestoCoxiellaburnetti,wereobtainedfrom
individuals, and is associated with higher mortality a commercial source and used in the study. Animals
rates for every age and burn size category (Herndon were observed for 1 week in temperature-controlled,
et al., 1985; Thompson et al., 1986; Shirani et al., indoor runs, were treated for potential parasites (1%
1987). ivermectin,1ml/75lb)andwerefedcommercialchow
Smoke associated with structural fires, arises from andwateradlibitum.Theywerefastedfor24hbefore
the combustion or pyrolysis of wood and the vari- tracheostomy and instrumentation. All animals were
ous natural and synthetic fabrics, plastics and other maintained in a facility approved by the Association
common materials available today (Wong et al., forAssessmentandAccreditationofLaboratoryAni-
1984; Alarie, 2002). Such acute lung injury resulting malCareInternational.
from inhalation of these products involves complex The day before smoke or sham-smoke exposure,
pathophysiologic processes that may not manifest sheep were sedated with ketamine (5mg/kg i.v.)
into clinically significant symptoms for 24–72h and midazolam (0.275mg/kg i.v.) and orotracheally
(Ruddy, 1994). Impairment of mucocilliary function, intubated with a 7mm i.d. cuffed tube. A chest ra-
inflammatory responses such as interstitial edema, diograph was taken to exclude animals with active
neutrophil infiltration, generation of oxygen free rad- lung disease. Under isoflurane anesthesia (2–4%),
icals and pseudomembrane formation have all been a femoral artery was catheterized with a Silastic
reported as potentially important consequences and cannula; an external jugular vein was catheterized
mechanisms of smoke inhalation injury (Hubbard with an introducer sheath (8.5Fr, American Edwards
etal.,1991;Younetal.,1992;FitzpatrickandCioffi, Laboratories Inc., Irvine, CA), followed by an 8-Fr
1994, Ruddy, 1994; Lalonde et al., 1995). Direct balloon-tipped pulmonary-artery catheter; and open
alveolar damage, including alveolar edema, may also cystostomy and insertion of a urinary catheter were
occurdependingonthedoseofsmoke,thetoxicityof performed. A tracheostomy was then performed,
the chemicals present in the smoke, and/or as a con- and a 9-mm, low-pressure, cuffed tracheostomy tube
sequence of surfactant denaturation (Herndon et al., (Shiley, Mallinckrodt Medical TPI, Irvine, CA) was
1985; Fitzpatrick and Cioffi, 1994; Nieman et al., inserted. The animals were recovered overnight in an
1995). animalintensive-careunit(ICU).
Anumberofstudieshavelinkedantioxidants,both
endogenousanddietary,asplayingimportantrolesin 2.2. Smokeinhalation
preventing lung injury from exposure to various en-
vironmental toxicants (Cross et al., 2002; Ho, 2002). The following day, animals were anesthetized
In our further characterization of the effects of wood with sodium pentobarbital (25mg/kg i.v.). Once
smoke inhalation on antioxidant status, the present general anesthesia was confirmed, a neuromuscu-
study evaluated whether indices of an oxidant stress lar blocking agent was given (pancuronium bromide
in plasma and lung from sheep exposed to graded 0.03–0.04mg/kgi.v.).Thesedrugswereredosed,and
doses of smoke followed a dose-dependent pattern. anintravenousanalgesic(buprenorphine0.005mg/kg)
Sheephavelongbeenemployedtoinvestigatesmoke was administered, whenever necessary. All animals
inhalation injury. This injury is reproducible, dose remained anesthetized and mechanically ventilated,
dependent (Hubbard et al., 1988; Kimura et al., using a pressure control mode, for the remainder of
1988; Shimazu et al., 1996) and mimics that ob- the study (Siemens 900C ventilator, Siemens-Elema,
servedinhumans(Traberetal.,1985;Hubbardetal., Solna, Sweden). The animals were fasted, and main-
1991). tenance intravenous fluid (5% dextrose in lactated
M.S.Parketal./Toxicology195(2004)97–112 99
Ringer’s solution at 2ml/kgh) was given throughout smoke exposure, similar to other studies of smoke
the48-hexperimentalperiod. inhalation in sheep (Sakurai et al., 1999; Tasaki
On the day of injury, each animal was randomized et al., 2002), and were moved back to the animal
tooneoffourgroupsdescribedbelow.Smokeinhala- ICU,wheretheywerehousedinindividualmetabolic
tioninjurywasinducedusingthetechniqueemployed cages.Arterialbloodpressure,heartrate,andperiph-
at our Institute over the past 10 years (Ogura et al., eral oxygen saturation were continuously monitored.
1994; Harrington et al., 2001; Tasaki et al., 2002). Arumentubewasplacedfortherestofthestudy.
Fifty grams of pine wood bark (Decorative Western
Bark, Far West Forests Inc., Tempe, AZ) were cut 2.3. Serumoxidantstressmarkers
into1cm2chipsandwereplacedinacruciblefurnace
(Lindberg/BlueM laboratory furnace, model 56622, Blood samples were drawn at preinjury, 6, 12, 18,
Asheville,NC).Thefiringchamberofthefurnacewas 24,36and48haftersmokeexposureintoheparinized
◦
heatedto400 C.Thechamberwassuppliedwithdes- tubes. The blood was centrifuged in a clinical cen-
iccated air at 6.0l/min, to support combustion and to trifuge, and resultant plasma samples were stored at
facilitate flow of the smoke from the chamber into a −70◦Cforlessthan3monthsuntilanalyzed.Thiobar-
5.5lPlexiglasmixingboxandreservoir.Thisreservoir bituric acid reactive substances (TBARS), expressed
alsoreceived100%oxygenat6l/min,ataratioof1:1, as nanomoles of malondialdehyde per milliliter of
to permit the smoke to cool to ambient temperature plasma, were determined in the butanol phase as de-
◦
(approximately25.5 C)toeliminatethermalinjuryto scribed by Naito et al. (1993). Ferric reducing ability
the airway, to facilitate mixing, and to minimize hy- of plasma (FRAP), as an index of its antioxidant
poxiaintheanimal.Thetemperatureofthesmokewas status, was determined spectrophotometrically by the
measuredjustproximaltothetracheostomytubeusing methodofBenzieandStrain(1996).
a thermistor-tipped pulmonary-artery catheter. Three
minutes after initiation of pyrolysis, the smoke was 2.4. Lungtissueanalysis
drawn from the reservoir into a hand-operated piston
and was delivered to the animal via its tracheostomy Sheep were euthanatized 48h after smoke expo-
using modified ventilator circuit tubing with a man- sure using a standard veterinary euthanasia solution
ualbreath-holdvalve.Thetidalvolumeofeachsmoke that provided an overdose of pentobarbital, and lung
breathwascontrolledbyanadjustablestoponthepis- parenchymafromrightandleftapical,medialanddi-
tonsetat30ml/kg(Shimazuetal.,1987).Oneunitof aphragmaticlobeswerecollectedandstoredat−70◦C
smoke was defined as 5 such breaths; each breath in- for later assays. Oxidized and reduced glutathione
cluded a 7-s inspiratory hold as previously described weredeterminedspectrophotometricallyusingtheen-
(Harrington et al., 2001). Group I (control, n = 5) zymaticassaydescribedbyAnderson(1985).Briefly,
received no smoke, group II (mild, n = 5) received total glutathione concentration in 5-sulfosalicylic
5 units of smoke, group III (moderate, n = 5) re- acid-precipitated supernatants was determined by a
ceived10units,andgroupIV(severe,n=5)received 5,5(cid:6)-dithiobis(2-nitrobenzoic acid)-glutathione reduc-
16 units. All animals received the same number of tase recycling assay. Oxidized glutathione was deter-
piston-driven tidal volumes regardless of the smoke mined by the same assay after reduced glutathione
dose over a period of 17min. Based on this regimen, was derivatized by incubating the 5-sulfosalicylic
the mild, moderate and severe exposure groups were acid-precipitated supernatants with 2-vinylpyridine
subjected to 175, 350 and 560s of smoke dwell time for 1h at room temperature. Reduced glutathione
intheairwaysandlungs,respectively.Thecontrolan- concentrations were determined by subtracting the
imals received the same number of breaths via the concentration of oxidized glutathione from the total
sameapparatus,butwithoutsmoke. concentration (Anderson, 1985). TBARS and FRAP
Immediately following smoke exposure, arterial- in lung tissue were determined as described above.
blood-gasanalysiswasperformedandthecarboxyhe- Myeloperoxidaseactivitywasdeterminedbyamodi-
moglobin(COHb)levelwasmeasuredbycooximetry. fication of the method of Trush et al. (1994). Briefly,
Animals were ventilated with 100% O for 2h after tissues were homogenized in 50mM potassium
2
100 M.S.Parketal./Toxicology195(2004)97–112
phosphate buffer pH 6.0 containing 0.5% hexade- croscopicexamination.Histologicgradingoftracheal,
cyltrimethylammonium bromide. The homogenates bronchialandpulmonaryinjurywasperformedusing
then underwent three freeze–thaw cycles and soni- thepreviouslydescribedscoringsystem(Tasakietal.,
◦
fication, followed by incubation at 60 C in a water 1997). The tracheal/bronchial injury score is as fol-
bath for 2h to extract myeloperoxidase and reduce lows:
interfering substances. Samples were centrifuged at
10,000×g for 30min at 4◦C. Myeloperoxidase ac- Injury Description
score
tivity was determined in the resultant supernatant
using o-dianisidine as substrate. Protein concentra- 0 Normal
tionsweredeterminedwithacommercialkit(BioRad 1 Somelossofcilia,and/orapical
Laboratories,Richmond,CA). respiratoryepithelium
2 Markedattenuationofpseudostratified
2.5. Exhaledbreathanalysis epitheliumorasinglelayerofepithelium
3 <50%segmental/focalulcerationof
Before injury and 6, 12, 18, 24, 36, and 48h af- epithelium
ter injury, exhaled nitric oxide (NO) was assayed by 4 >50%ulcerationofepithelium
a chemiluminescence method using a Sievers model
Parenchymal damage was evaluated at the apical,
NOA 280 nitric oxide analyzer (Sievers Instruments,
medial and diaphragmatic lobes of both lungs. The
Boulder,CO).Basically,exhaledgaswassampledvia
pulmonaryinjuryscoreisasfollows:
asidestreamportaccordingtothemanufacturer’sstan-
dard protocol. Two-point calibration of the analyzer Injury Description
wasperformeddaily.BecauseNOwaspresentinvari- score
ableconcentrationsininspiredair,animalswereven-
0 Normal
tilatedbeforeandduringNOcollectionwithamixture
1 Minimaltomildlythickenedalveolar
ofnitrogenandoxygenknowntobefreeofNO.
septae,afewinflammatorycellsora
At these same timepoints, exhaled breath conden-
small,singlefocusofinflammatorycells
sate was collected for the measurement of H O . A
2 2
2 Thickenedalveolarseptaewithmultifocal
segment of sterile ventilator tubing was connected
areasofincreasedinflammatorycells
to the existing ventilator circuit, and was submerged
3 Diffuseinflammationand/oredemathat
in bucket of dry ice for 40min. The ice precipitate
affects<50%ofthesection
in the tubing was then collected, placed in a sterile
vial, and stored at −70◦C until analysis. Measure- 4 Diffuseinflammationand/oredemathat
affects>50%ofthesection
ment of H O in expired air condensate was deter-
2 2
minedspectrophotometricallyasdescribedbyGallati Parenchymal samples from right and left lung
and Pracht (1985), using horseradish peroxidase were also excised for the determination of blood-free
(HRPP)-catalyzed oxidation of tetramethylbenzidine. wet-to-drylungratiousingthemethoddescribedpre-
Briefly, 100(cid:1)l of 420(cid:1)M of tetramethylbenzidine viously (Drake et al., 1980) as modified by Ogura
and 10(cid:1)l of HRPP were mixed with 100(cid:1)l of ex- et al. (1994). Bilateral apical, medial and diaphrag-
pired air condensate. The reaction product was mea- matictissuesampleswereweighedandhomogenized
sured spectrophotometrically (Abs 450nm) using an with an identical weight of distilled water. Duplicate
automated plate reader. The absorbance is directly samples of the homogenate and venous blood were
◦
proportional to the amount of H O with a detection weighed and dried at 80 C for 48h. Dry weights
2 2
limitofapproximately0.1(cid:1)MH O . were measured and the wet-to-dry ratios of the ho-
2 2
mogenate and blood were calculated. To determine
2.6. Histology the hemoglobin levels in the homogenate and blood,
20(cid:1)l of the homogenate supernatant or the diluted
Atthetimeofeuthanasia,sectionsoflungandtra- blood was added to 2.5ml of Drabkin’s solution
chea were excised for H&E staining and light mi- and the absorbance of both solutions was measured
M.S.Parketal./Toxicology195(2004)97–112 101
spectrophotometrically at 540nm. From these data, Table1
thefractionofbloodinthewetanddrylungsections Effectsofsmokeinhalationinsheeponbloodcarboxyhemoglobin
andlungwet:dryweightsa
could be calculated and subtracted from the total wet
and dry weights. Blood-free wet-to-dry weight ratio Carboxyhemoglobin Lungwet:dryweight
wasthencalculatedasdescribed(Drakeetal.,1980). concentrations(%) ratio
Control 6.3±0.64 4.5±0.2
Mild 42.3±5.1∗ 5.1±0.3
2.7. Statisticalanalysis
Moderate 78.0±8.8∗ 5.5±0.4
Severe 91.9±1.3∗ 6.9±0.3∗
Data analysis employed SPSS v. 10.1 (SPSS,
a Data expressed as mean±S.E. for four to five animals per
Inc., Chicago, IL). As appropriate, one-way or
group.Seetextfordefinitionsofsmokedoses.
repeated-measures analysis of variance was per- ∗ P<0.05fromcontrol.
formed,withseverityofinjuryasthebetween-groups
factor. Post-hoc tests corrected for multiple compar-
in the mild group died at 36h, because of airway ob-
isons were performed to compare each injured group
struction.Therestoftheanimalsliveduntilthecom-
to the control group at various time points. Correla-
pletionofthe48-hstudy.
tions were run within a lobe to determine Pearson
Arterial COHb levels measured immediately after
correlation coefficients among the doses of smoke
smokeinhalationcorrespondedinstepwisefashionto
andthevariablesofoxidativestress.AP<0.05was
the dose of smoke, showing a significant difference
consideredstatisticallysignificant.
amonggroups(P<0.001)andbetweeneachinjured
groupandthecontrolgroup(P<0.001)(Table1).In
3. Results addition, lung wet:dry weight ratios were correlated
tothedoseofsmoke,butonlythehighestsmokedose
Twoanimalsintheseveregroupwereeuthanatized resultedinawet:dryweightratiosignificantlyhigher
at 29 and 36h, because of terminal pulmonary fail- thancontrols(Table1).
ure(inabilitytomaintainaPaO2of60mmHg,despite Plasma protein concentrations were significantly
FiO = 100% and PEEP = 15cmH O). One animal lower in the severe smoke exposure group at 24, 36
2 2
Fig. 1. Plasma protein concentrations in smoke-exposed sheep. Data represent mean±S.E. from four to five animals per group. (∗)
P<0.05fromcontrols.
102 M.S.Parketal./Toxicology195(2004)97–112
and 48h compared with controls (Fig. 1). Plasma but the differences were not statistically significant
protein concentrations in the mild and moderate (Fig. 2). Generally, these values remained elevated
smoke-exposedanimalsgenerallyremainedsimilarto throughout the 48-h experimental period, particularly
controllevelsthroughouttheexperimentalperiod. in the moderate smoke-exposed group. Overall, the
response to smoke inhalation was variable and no
3.1. Serum, breath and tissue oxidative dose-dependent effect of smoke exposure on plasma
stressmarkers TBARS concentrations was observed (Fig. 2). At
48haftersmokeexposure,plasmaTBARSwere66%
PlasmaTBARSappearedtoriseinanimalsexposed and 69% higher in the moderate and severe smoke
tosmokecomparedwithcontrolsat6hafterexposure, exposed groups than controls. In contrast to TBARS
Fig.2.Top-PlasmaThiobarbituricacidreactivesubstances(TBARSs)concentrationsinsmoke-exposedsheep.Bottom-Totalantioxidant
potential in plasma from smoke-exposed sheep. Data represent mean±S.E. from four to five animals per group. (∗) P < 0.05 from
controls.
M.S.Parketal./Toxicology195(2004)97–112 103
levels, plasma antioxidant potential was not signif- Inlungtissuespecimenscollected48haftersmoke
icantly affected by smoke exposure in any group exposure, a dose-dependent increase in TBARS con-
(Fig. 2). Although, plasma antioxidant potential centrations were observed in both left and right
was consistently lower in the mild smoke ex- lung lobes (Fig. 3). In all lobes from moderate and
posure group compared with the other groups, severe smoke exposed animals, TBARS were sig-
the baseline level was also low, suggesting that nificantly higher than controls, with levels about
smoke exposure induced no significant effect in this 3- and 4-fold higher than controls (Fig. 3). Lung
group. antioxidant potential appeared to be generally af-
In addition, expired hydrogen peroxide or NO lev- fected by all doses of smoke, but only the severe
els measured in expired air were not significantly groupachievedstatisticalsignificancecomparedwith
affected by smoke exposure at any time during the controls, with values 20–25% lower than controls
experimentalperiod(datanotshown). (Fig.4).
Fig.3.TBARSconcentrationsinlunglobes(apical(upper),medial(middle)anddiaphragmatic(lower))fromsmoke-exposedsheep.Data
representmean±S.E.fromfourtofiveanimalspergroup.(∗)P<0.05fromcontrols.
104 M.S.Parketal./Toxicology195(2004)97–112
Fig. 4. Total antioxidant potential in lung lobes from smoke-exposed sheep. Data represent mean±S.E. from four to five animals per
group.(∗)P<0.05fromcontrols.
Lung GSH concentrations were not consistently moderate and severe smoke exposure. Severe smoke
different from controls in any smoke exposed group exposure resulted in 53% higher GSSG levels than
(Table 2). Only left medial (middle) GSH concen- controls in right diaphragmatic (lower) lung lobes
trations were significantly lower than controls after (Table2).Moderatesmokeexposureresultedinhigher
M.S.Parketal./Toxicology195(2004)97–112 105
Table2
Effectsofsmokeinhalationinsheeponlungreduced(GSH)andoxidized(GSSG)glutathioneconcentrationsa
Rightapical Rightmedial Rightdiaphragmatic Leftapical Leftmedial Leftdiaphragmatic
GSH
Control 10.8±1.7 12.8±1.1 12.2±2.2 12.2±1.5 14.1±0.9 9.5±1
Mild 11.8±1.7 11.6±1.1 9.3±0.7 13.2±2 13.9±1.5 14.2±1.2∗
Moderate 13.9±1.7 10.1±1.5 11±0.99 14.8±1.4 9.2±0.9∗ 7.6±0.4
Severe 7.8±0.7 8.6±1.8 10.9±1.54 13.4±1.1 9.8±0.4∗ 10.8±1
GSSG
Control 0.63±0.04 0.60±0.16 0.51±0.02 0.60±0.07 0.70±0.05 0.75±0.02
Mild 0.74±0.05 0.58±0.09 0.49±0.03 0.78±0.14 0.98±0.14 0.74±0.11
Moderate 0.91±0.05∗ 0.67±0.12 0.90±0.12∗ 1.08±0.15∗ 0.82±0.11 0.85±0.07
Severe 0.73±0.05 0.95±0.09 1.03±0.11∗ 1.00±0.13 0.83±0.08 0.91±0.12
a Dataexpressedasmean±S.E.nmol/mgproteinforfourtofiveanimalspergroup.
∗ P<0.05fromcontrol.
GSSG levels in right diaphragmatic and left apical 4. Discussion
(upper)lobescomparedwithcontrols(Table2).
Mild and moderate smoke exposure resulted in Thesmokegeneratedfromthepyrolysisofwoodis
slightly higher MPO activity in most lung lobes knowntocontainover200compounds,includingcar-
compared with controls, although few data achieved bonmonoxide,nitrogenoxides,sulfuroxides,aldehy-
statistical significance due to variability in the data des, polycyclic aromatic hydrocarbons and respirable
(Fig. 5). In contrast, severe smoke exposure ele- particulate matter (Pierson et al., 1989; Larson and
vated MPO activity in apical and medial lung lobes Koenig,1994;Zelikoffetal.,2002).Inaddition,wood
compared with controls (Fig. 5). For example, MPO smoke can generate stable carbon-centered radicals
activity in the right apical and medial lobes was 19- and hydroxyl radicals (Lachocki et al., 1989; Pryor,
and 22-fold higher, respectively, than controls. In 1992; Kou et al., 1997; Leonard et al., 2000). This
addition, MPO activity in the right upper lobe was information has generated much interest in determin-
significantlycorrelatedwiththedoseofsmoke. ingthehealtheffectsofsubchronicandchronicexpo-
sure to individuals exposed to smoke generated from
woodburning stoves (Tesfaigzi et al., 2002; Zelikoff
3.2. Histology et al., 2002). The present study, however, focused on
theacuteeffectsofwoodsmokeinhalationthatmight
Based on the criteria described in the Materials occur in a structural fire (Wong et al., 1984; Barillo
and Methods section, a dose-dependent increase in etal.,1994).
tracheal injury score was observed in response to In the present study a dose-related rise in blood
smoke inhalation, as confirmed by correlation analy- carboxyhemoglobin (COHb) concentrations was ob-
sis (Fig. 6). The predominant observations following served immediately after smoke exposure. It is well
moderate or severe smoke exposure in trachea, were recognized that carbon monoxide is one of the major
loss of cilia, epithelial attenuation, ulceration of res- toxicants of smoke in fires (Alarie, 2002). For exam-
piratory mucosa and serocellular/mucocellular cast ple, average blood COHb levels exceeding 50%, and
formation. Although correlation analysis also noted sometimes as high as 60–80% have been observed
thatlungparenchymalinjuryscoresweredoserelated, in victims of fires and blood COHb levels exceeding
onlytheseveresmokeexposureproducedstatistically 50% have often been cited as evidence for carbon
higher injury scores compared with controls (Fig. 6). monoxide related deaths in humans (Fitzpatrick and
Severe wood smoke exposure resulted in the largest Cioffi,1994;Alarie,2002).Asnoted,however,anum-
number of diffusely distributed inflammatory cells, beroffactorscancontributetofire-associateddeaths,
andedemainlung,comparedwiththeothergroups. and blood COHb levels can be higher or lower than