Palytoxin-Containing Aquarium Soft Corals as an Emerging Sanitary Problem

22 Pages·2016·0.53 MB·English

marine drugs
Review
Palytoxin-Containing Aquarium Soft Corals as
an Emerging Sanitary Problem
MarcoPelin,ValentinaBrovedani,SilvioSosaandAureliaTubaro*
DepartmentofLifeSciences,UniversityofTrieste,ViaValerio6,34127Trieste,Italy;[email protected](M.P.);
[email protected](V.B.);[email protected](S.S.)
* Correspondence:[email protected];Tel.:[phone]
AcademicEditor:PeerB.Jacobson
Received:1December2015;Accepted:27January2016;Published:4February2016
Abstract: Palytoxin (PLTX), one the most potent marine toxins, and/or its analogs, have been
identifiedindifferentmarineorganisms,suchasPalythoasoftcorals,Ostreopsisdinoflagellates,and
Trichodesmium cyanobacteria. Although the main concern for human health is PLTXs entrance in
the human food chain, there is growing evidence of adverse effects associated with inhalational,
cutaneous,and/orocularexposuretoaquariumsoftcoralscontaminatedbyPLTXsoraquariawaters.
Indeed,thenumberofcasereportsdescribinghumanpoisoningsafterhandlingthesecnidariansis
continuouslyincreasing.Ingeneral,thesignsandsymptomsinvolvemainlytherespiratory(rhinorrhea
and coughing), skeletomuscular (myalgia, weakness, spasms), cardiovascular (electrocardiogram
alterations),gastrointestinal(nausea),andnervous(paresthesia,ataxia,tremors)systemsorapparates.
The widespread phenomenon, the entity of the signs and symptoms of poisoning and the lack
of control in the trade of corals as aquaria decorative elements led to consider these poisonings
anemergingsanitaryproblem. Thisreviewsummarizesliteraturedataonhumanpoisoningsdueto,
orascribedto,PLTX-containingsoftcorals,focusingonthedifferentPLTXcongenersidentifiedin
theseorganismsandtheirtoxicpotential.
Keywords: palytoxins;Palythoa;Zoanthus;dermotoxicity;inhalationaltoxicity;aquarium
1. Introduction
Thehistoryofpalytoxin(PLTX)iscloselyconnectedtosoftcoralssincethetimeoftheHawaiian
Limu-make-o-Hanalegend,whichliterallymeans“ThetoxicseaweedofHana”. Thislegendtellsof
amancarryingasharkmouthonhisback,usedtokillfishermenenteringinhisfishingarea. Theman
waskilledbyonefishermenthat, afterburninghisbody, threwhisashesintoatidepoolnearthe
harborofHanawhere,shortlyafter,startedtogrowa“toxicalgae”. Thewarriorsusedtodipthetips
oftheirspearsinthiswatertomakethemfatal. Atthebeginningof1960s,Prof. Helfrichdiscovered
theexactlocationofthisplace,aswellasthe“toxicalgae”,foundtobeasoftcoralbelongingtothe
genusPalythoa(P.toxica). Thus,thetoxinidentifiedinthiszoanthidtenyearslaterbyProf. Scheuer
wascalledpalytoxin[1]. Overthedecades,chemical,biological,andtoxicologicalstudiesonPLTX
haveelucidatedthepeculiarpropertiesofthisfascinatingmarinetoxinthatnowadaysisconsidered
oneofthemosttoxicnon-proteinaceousnaturalcompounds.
Afterthebeginningofitshistory,theinterconnectionsbetweenPLTXandsoftcoralshaveprogressively
losttheirstrengthsincethetoxinandaseriesofitsanalogshavebeensubsequentlyidentifiedinother
marineorganisms,phylogeneticallyverydifferentfromcnidaria,suchasdinoflagellates,cyanobacteria,
andediblevertebratesandinvertebrates[2].Inparticular,consumptionofPLTX-contaminatedseafood
wasassociatedwithhumancasesofsevere,andevenlethal,adverseeffectsintropicalandsubtropical
areas. Subsequently,differenttoxicologicalimplicationsforhumanhealthwereascribedtoPLTXs
Mar.Drugs2016,14,33;doi:10.3390/md14020033 www.mdpi.com/journal/marinedrugs
Mar.Drugs2016,14,33 2of22
in temperate areas: the signs and symptoms ascribed to these toxins involved mainly the upper
respiratory tract and the skin, after inhalational, and/or cutaneous exposure to seawater and/or
Ostreopsiscellsconcomitantlytothesedinoflagellateblooms. Moreover,epidemiologicaldatashowed
that the majority of the poisonings certainly ascribed to PLTXs could be linked to dinoflagellates,
shiftingtheinterestfromsoftcoralstomicroalgaeortomarineedibleorganismsthatcouldaccumulate
thesetoxinsthroughthefoodchain[2]. However, inrecentyearsthetoxicologicalimplicationsof
PLTXsforhumanhealthgraduallyrecurredtotheexposurethroughsoftcorals. Indeed,thenumberof
casereportsonhumanpoisoningsaftermanipulationofPLTX-contaminatedsoftcorals,widelyused
asaquariadecorativeelementsbyaquariumhobbyists,iscontinuouslyincreasing. Thewidespread
phenomenon,alsoduetothelackofcoraltradecontrols,andtheentityoftheadverseeffectsledto
considerthesepoisoningsanemergingsanitaryproblem,eventhoughstillunderestimated.
This review will summarize and discuss the documented cases of human poisonings due, or
ascribed, to PLTX-contaminated aquarium soft corals, considering the different PLTX congeners
currentlyidentifiedinthesecnidariansandtherelevanttoxicologicalpotential.
1.1. Palytoxin: ProducingOrganisms
PLTXhasbeenidentifiedinavarietyofmarineorganismsintropical,subtropical,andtemperate
regions. TheoriginalsourceofPLTXwasasoftcoral,Palythoatoxica,collectedinHawaii. Throughout
theyears,ithasalsobeenidentifiedinotherspeciesbelongingtothegeneraPalythoaandZoanthus[3].
MoredetailswillbegiveninSection3.1,describingPLTXanalogsidentifiedinPalythoaandZoanthus
softcorals.
In1995,aPLTX-likemoleculewasidentifiedinbenthicdinoflagellatesofthegenusOstreopsis.
Thiscompound,isolatedformO.siamensis,wasnamedostreocin-D(Ost-D;seeSection1.2)[4].Interestingly,
onlyO.siamensisoftheJapanesestrainwasshowntoproduceOst-D,andthetoxinhasneverbeen
identifiedinO.siamensisoftheMediterraneanarea,sofar[5]. OtherOstreopsisspecieswerelaterfound
to contain PLTX-like compounds: O. mascarenenesis, containing mascarenotoxins [6], and O. ovata,
asourceofovatoxins(seeSection1.2)[7].
ToexplainPLTX’spresenceinphylogenetically-differentspecies,someauthorsproposedbacteria
asproducingorganismsandapossiblecommonsourceofthesetoxins.Withthisrespect,Frolovaetal.[8],
using anti-PLTX antibodies, detected PLTX-like compounds in Gram-negative Aeromonas sp. and
Vibrio sp. bacteria. Similarly, bacteria isolated from Palythoa caribaeorum were found to display
aPLTX-likehemolyticactivity[9]. Inaddition,PLTXand42-hydroxy-PLTXwereisolatedfrommarine
Trichodesmiumspp. cyanobacteria[10]. However,acleardefinitionoftheactualproducingorganismof
PLTXisstillamatterofdebate.
1.2. Palytoxin: MolecularStructure
ThechemicalstructureofPLTXwaselucidatedin1981,almostadecadeafteritsfirstidentification
in Palythoa toxica, by two independent research groups [11,12]. The chemical formula of PLTX is
C H N O ,withamolecularweightof2680.13Da. PLTXisconsideredoneofthemostcomplex
129 223 3 54
and large non-polymeric natural molecules: it contains 129 aliphatic carbon atoms, 40 secondary
hydroxylgroups,twodienemotifs,aconjugateacrylamide-enamidesystem,threeunsaturatedbonds,
twohydrophobichydrocarbonchains,cyclicethersystems,andbicyclicacetals(Figure1).Thestructure
contains64chiralcentres,leadingtoahugenumberofpossibleconformationalstereoisomers[12].
StructuralstudiesdemonstratedthatPLTXassumesadimericforminaqueoussolution,acquiring
aformof8,measuring52.3ˆ22.0ˆ15.1Å[13]. ThePLTXmoietiesinvolvedinthedimerformation
havenotbeenidentified,sofar,althoughthehydrophobicregion(C21–C40)andtheregionaroundthe
conjugateddoublebonds(C60–C84)arethoughttobetentativelyinvolved. Moreover,theterminal
aminogroupisprobablyinvolvedintheinteractionbetweenthetwoPLTXmolecules: itsacetylation
preventsthedimerformationandreducestheinvitrobiologicalactivity(smoothmusclecontraction)
byabout100timeswithrespecttoPLTX[13].
Mar.Drugs2016,14,33 3of22
Figure1.ChemicalstructureofPLTXanditsmainanalogs.
InadditiontoPLTX,aseriesofitsanalogshasbeenidentified,sofar. TheydifferfromPLTXfor
additionaland/ormissinghydroxyland/ormethylgroups,orforchiralities,whichsometimesinfluence
their toxic potency. Only few PLTX analogs have been studied under a chemical and/or biological
pointofview. Amongthem,twoisomershadbeenisolatedfromsoftcorals: 42-hydroxy-palytoxin
(42S-OH-50S-PLTX), isolated from Palythoa toxica [14], and its stereoisomer with a conformational
inversionatC50(42S-OH-50R-PLTX),extractedfromPalythoatuberculosa[15]. Foracompletelistof
PLTXanalogsidentifiedinsoftcoralsandtherelevanttoxicologicalproperties,refertoSection3.1.
ThelimitedstudiesonPLTXanalogsidentifiedindinoflagellatesinvolvedostreocin-D(Ost-D),
isolatedfromOstreopsissiamensisinJapan[16],andovatoxin-a(OVTX-a),themajortoxinproduced
byOstreopsiscf. ovataintheMediterraneanSea[7]. RecentinvestigationsidentifiedseveralOVTX-a
analogs(OVTX-bto-h)inOstreopsiscf.ovata,atconcentrationslowerthanthoseofOVTX-a.Intriguingly,
indifferentpartsoftheMediterraneanSea,OVTX-ahasbeenalwaysdetectedasthemajorO.cf. ovata
toxin,withisobaricPLTXbeingfrequentlydetectedonlyintraces[7,17–23]. Veryrecently,aninvitro
studydemonstratedthatOVTX-acytotoxicityandbindingaffinitytowardsskinkeratinocytesare
morethantwoordersofmagnitudelowerthanthoseofPLTX.Accordinlgy,alsoOVTX-ahemolytic
effectseemstobelowerthanthatofPLTX[24].
1.3. MechanismofAction
ThemoleculartargetofPLTXisNa+/K+ATPase,atransmembranepumpbelongingtothefamily
of P-type ATPases, essential for maintaining cellular ion homeostasis. Na+/K+ ATPase transfers
threeNa+ ionsoutofthecellintradefortwoK+ ions,exploitingATPhydrolysis. PLTXbindingto
theα-βATPaseheterodimerchangesthetransmembranepumpintoanonspecificmonovalentcation
channel,leadingtoaconsistentionicimbalanceatthecellularlevel[25,26]. Thechannelformedby
PLTXbindingseemstobeaconsequenceofATPaseconformationalchangesleadingtoalossofpump
gatecontrolanduncouplingoftheiontransport. Inaddition,PLTXbindingreducestherateofthe
pumpde-phosphorylation,protractingthechannelopening[25,26].
Mar.Drugs2016,14,33 4of22
Thecardioactiveglycosideouabain(OUA),knowntoinhibitNa+/K+ATPase,hasbeenreportedto
inhibitPLTXinvitroeffects[27–31]. However,theincompleteabolishmentofPLTXbiologicalactivities
by OUA suggests that the latter does not completely compete with PLTX for the same molecular
target [32]. In fact, Artigas and Gadsby demonstrated that PLTX and OUA can simultaneously
bindtoNa+/K+-ATPase,suggestingtwobindingsitesonthepump[25].Accordingly,thepresence
of a high-affinity binding site for PLTX on skin HaCaT keratinocytes was subsequently reported.
ThisbindingsiteappearstobepartiallyinsensitivetoOUAandpartiallymodulatedbyOUAinacomplex
manner:asanegativeallostericmodulatoragainsthighPLTXconcentrations(0.3–1.0ˆ10´7M)andas
anon-competitiveantagonistagainstlowPLTXconcentrations(0.1–3.0ˆ10´9M).Thishypothesiscould
explaintheinabilityofOUAtototallypreventPLTX-inducedcytotoxiceffectsinHaCaTcells[32].
ThetransformationofNa+/K+-ATPaseintoanon-selectivecationicchannelbyPLTXresultsina
sustained cellular ion homeostasis imbalance, as previously reviewed by Rossini and Bigiani [33].
ThefirsteventconsistsofanintracellularoverloadofNa+ causingacellmembranedepolarization,
accompanied by a massive efflux of K+ and influx of Ca2+. Ca2+ influx seems to be mediated by
reverse functioning of the Na+/Ca2+ exchanger (NCE) caused by the increased intracellular Na+
concentrations. Althoughnotyetcompletelyclear,theincreasedintracellularCa2+levelsmightinduce
theopeningofK+orCl´channels,furtherimpairingthecellionicbalance. Moreover,theintracellular
Na+increaseappearstoinduceacytoplasmacidification,probablyduetothereversefunctioningof
theNa+/H+exchanger(NHE)[33]. ItiswidelyacceptedthatthecytotoxiceffectsofPLTXarestrictly
dependentonthisionicimbalance. Dependingonthecellulartype(i.e., non-excitableorexcitable
cells),Na+-orCa2+-dependentcytotoxiceffectshavebeenreported. Na+ overloadseemstobethe
firststepinmediatingPLTX-inducedearlycelldamage,asrecentlydemonstratedonhumanHaCaT
keratinocytes[28]. Moreover,theintracellularH+increase,consequenttotheabnormalintracellular
Na+concentrationinducedbythetoxin,seemstobethedrivingforceforO ´productionbyreversing
2
themitochondrialelectrontransport[34],ultimatelyleadingtoanirreversiblenecroticcelldeath[35].
ThisfindingisconsistentwithpreviousobservationssupportingNa+dependencyofPLTXeffects[14,36–38].
On the contrary, in excitable cells, where intracellular signalling is highly dependent on Ca2+
concentrationswithrespecttonon-excitablecells,PLTXeffectsarestrictlydependentonCa2+ ions.
Indeed,theincreasedintracellularCa2+concentrationsinducedbyNa+overloadwereshowntotrigger
aseriesofCa2+-dependentcytotoxiceffects,suchasneurotransmitterrelease,uncontrolledmusclecell
contraction,uptoCa2+-dependentcelldeath[30,39,40]. Asasecondaryeventtothesustainedionic
imbalance,damagesatthecytoskeletonlevelinducedbyPLTX,suchasdepolymerizationofactin
filamentsinintestinal[38]andneuroblastomacells[41,42],werealsoreported.
1.4. HumanRiskAssociatedwithPalytoxinExposure
CasesofhumanpoisoningsascribedtoPLTXshavebeengenerallyassociatedwithfourexposure
routes: (i)oralexposure;(ii)cutaneousexposure;(iii)inhalationalexposure;and(iv)ocularexposure.
Theoralexposureafteringestionofcontaminatedfishorcrustaceansisthemostharmfulforhuman
health, althoughalimitednumberoffoodbornepoisoningshavebeendocumentedonlyintropical
and subtropical regions, so far [43–47]. Among the foodborne poisonings ascribed to PLTX, only
a few of them were certainly attributed to these toxins by their direct detection in the leftovers
through biological and/or chemical methods of analysis. The vectors of PLTX were mainly crabs
(Demaniareynaudii;Alcalaetal. 1988),parrotfish(Scarusovifrons)[43],goldspotherring(Herklotsichthys
quadrimaculatus) [45–47], and serranid fish (Epinephelus sp.) [46]. The symptoms of poisoning
initiallyinvolvedthegastro-intestinaltract(nausea,diarrhea,andvomiting)andthenervoussystem
(convulsions,dizziness,numbness,andrestlessness),withsubsequentinvolvementofotherexcitable
tissues,suchasthoseofskeletalmuscle(weakness,musclecramps,myalgia,andrhabdomyolysis)
andcardiovascularsystem(bradycardia,tachycardia). Theclinicalpictureusuallyworsened,with
symptomsinvolvingtherespiratorytract(rapidandshallowbreathing,cyanosis,anddyspnea)leading,
insomecases,torespiratoryfailureanddeath. OtherdocumentedcaseswereattributedtoPLTXsby
Mar.Drugs2016,14,33 5of22
anindirecttoxindetectioninthecausativespeciescollectedafterorbeforethepoisoning,sometimes
evenindifferentareas.Somecaseswereattributedtothetoxinonlyonthebasisoftheclinicalsignsand
symptomsassociatedwithseafoodingestion.ForacompletelistrefertoTubaroetal.[2]andWuetal.[47].
Intemperateareas,humanpoisoningsascribedtoPLTXwereoftenassociatedwithinhalationof
marineaerosoland/orcutaneousexposurestoseawaterduringOstreopsisblooms. Themostcommon
signs and symptoms were respiratory distress, rhinorrhea, cough, fever, and dermatitis [48–51].
SeveralcasesofadverseeffectsafterexposuretoseawaterduringOstreopsisbloomsoccurredalong
theItaliancoasts[48,51–53]andsomeepisodesalsoalongotherMediterraneancoasts[49,50]. Inthese
cases,thetoxinsdetectionand/orquantitationareoftenincompleteormissing,andtheyhavebeen
frequentlyascribedtoPLTXonlyonthebasisofsymptoms,anamnesis,and/orenvironmentaldata.
Notwithstanding,thedocumentedepisodescouldrepresentonlythetipoftheicebergsincethese
poisonings could be significantly underestimated. In fact, the symptoms do not always require
hospitalizationandcouldbefrequentlyascribedtoadifferentetiology[2].
Inrecentyears,thereisgrowingevidencethatinhalationaland/orcutaneousexposuretoPLTXs
couldalsooccurafterhandlingPLTX-contaminatedsoftcoralsduringmaintenanceofhomemarine
aquaria. ThetoxicpotentialofPLTXsidentifiedinsoftcorals,togetherwiththeuncontrolledtradeof
thesezoanthids,raiseaseriousconcernforhumanhealth. Duetothegrowingnumberofdocumented
cases,thesepoisoningscanbeconsideredanemergingsanitaryproblem.
2. HumanPoisoningsPostulatedtoPLTXExposurethroughHandlingofSoftCorals
2.1. ExposureRoutes
Asreportedabove,adverseeffectsinhumansascribedtoPLTXshavebeengenerallyassociated
with exposure to contaminated marine organisms and/or seawater through: (i) oral exposure;
(ii)cutaneousexposure;(iii)inhalationalexposure;and(iv)ocularexposure. Poisoningsassociated
with handling of PLTX-contaminated soft corals are no exception, although ingestion of corals or
surrounding seawater can be regarded as improbable, but not impossible, events. On the other
hand,inhalationofvaporsfromhomemarineaquariaduringtheeradicationofPLTX-contaminated
zoanthids appears to be the most frequent route of exposure to PLTXs associated with soft corals.
Indeed,sincethesecoralsrapidlycolonizetheaquariaduetotheoptimalgrowingconditions,they
havetobefrequentlyeradicated,usuallybypouringboilingwaterand/orbrushingtherockscarrying
thesecnidarians. Thesubsequentsteaminhalationcaninduceaseriesofadverseeffectsinvolving
the respiratory tract (i.e., rhinorrhea, cough, dyspnea) but also other symptoms, such as myalgia,
paresthesias,tachycardia,hypotension,fever,andgastrointestinalsymptoms[1,54–57].
Similarly,accidentalcutaneousexposuretoPLTX-contaminatedcoralsbyaquariumhobbyistswhile
cleaningmarineaquariahasbeenassociatedwithadverseeffects. Inadditiontolocalinflammatory
signs,suchasedemaanderythema,systemicsymptomsofpoisoningwereexperiencedafterhandling
thecorals,bothbyintactordamagedskin. Amongthem,perioralparesthesiaanddysgeusiawerethe
mostcommononesand,inthemostseverecases,transitoryalterationsofcardiacfunctionswerealso
recorded[1,54,58].
AlthoughocularexposureisoneofthelesspredictableexposureroutesforPLTX,casesofeye
irritation,mainlykeratoconjunctivitis,occurredafterthecontactwithmucoussecretionsfromsoft
corals[59,60].
2.2. HumanPoisoningsAscribedtoPalytoxins-ContaminatedSoftCorals: DirectIdentificationofPLTXsin
theCorals
SimilarlytothehumanpoisoningsassociatedwithconsumptionofPLTX-contaminatedseafood,
documentedcasesofPLTXadverseeffectsbyexposuretosoftcoralssupportedbythetoxin’sidentification
inthecausativespecimens,areverylimited(Tables1–3). Thesecaseswillbegroupedandreviewedon
thebasisoftheexposureroutes.
Mar.Drugs2016,14,33 6of22
Table1.HumanpoisoningsdueorascribedtoinhalationalexposuretovaporsordustfromPLTX-contaminatedsoftcorals.
Numberof PLTXsDetectionMethod
Location,Year Corals SignsandSymptoms TreatmentandOutcome Reference
Patients andConcentration
Foulodor.Difficultbreathing, Anti-inflammatorycorticosteroids Hemolysisneutralization
Palythoa/
Virginia(USA),2007 1 lightheadedness,chestpain, andcoughsuppressant. assay(309µgPLTXeq./g); [54]
Protopalythoasp.
bronchoconstriction. Recoveryafter1month HPLC(613µgPLTXeq./g)
Cough,dyspnea,chestpain,tachycardia, Oxygentherapy,non-steroidal LC/MS(1018µgPLTX/g
Palythoa
TheNetherlands,2014* 4 nausea.Leukocytosiswithelevated anti-inflammatorydrugs. wetcoral;46µg [56]
heliodiscus
neutrophils,CPK,CRP Recoveryaftermorethan3months 42-OH-PLTX/gwetcoral)
Dyspnea,scratchythroat,paresthesia,
Palythoa Supportivetherapy. HPLC,LC/MS(7.3mg
Alaska(USA),2014 3 myalgia,spasms,ataxia,weakness, [57]
heliodiscus Recoverywithin2days PLTX/gwetcoral)
tremors,nausea,tachycardia,fever
Noexperimentaldetails
Palythoa
Oklahoma(USA),1961 3 Chills,nausea,headache Recoverywithin1day (acompoundidenticalto [1]
caribaeorum
PLTXfromP.toxica)
Foulodor,shortnessofbreath,chest Inhaledalbuterol.
NewYork(USA),2008* 1 Palythoasp. Noanalysis [61]
pain,sinustachycardia Recoveryafter48h
Fever,hypotension,nausea,headache,
Supportivetherapy.
TheNetherlands,2012* 4 Zoanthids shivering,musclecramps.Leukocytosis, Noanalysis [62]
Recoverywithin48h
elevatedCRP
Dyspnea,drycough,nausea,headache,
fever,chills,tachycardia,hypoxemia.
Leukocytosis,slightlyelevatedLDH, Treatmentnotreported.
Switzerland,2012* 3 Palythoasp. Noanalysis [63]
CRPandprocalcitonin.Restrictive Recoverywithin2weeks
ventilatorpattern,diffusebronchial
swellingandsecretion.
Albuterol,levoflaxic,
Shortnessofbreath,fever,drycough,
acetaminophen,hydrationand
NewYork(USA),2013* 5 Palythoasp. chills,myalgia,emesis.Leukocytosis, Noanalysis [64,65]
supportivetherapy.
slightlyelevatedLDH,CPK,CKMB
Recoverywithin48h
Bittermetallictaste,fever,tremors, Treatmentnotreported.Recovery
Alaska,(USA),
9 Zoanthids weakness,ataxia,cough,jointand within24h,butsometimeswith Noanalysis [57]
2012–2014
musclepain,pulmonarysymptoms pulmonarysymptomsafter2years
Fever,chills,myalgia,tachycardia, Albuterol,acetaminophen,
NewYork(USA),2015* 3 Zoanthidcorals wheezes,hemoptysis,dyspnea, supplementaloxygen,prednisone. Noanalysis [66]
leukocytosis,bibasilaropacities Completerecoveryafter1month
*Yearofpublication;CPK=creatinephosphokinase;CKMB=creatinekinaseMBisoenzyme;CRP=C-reactiveprotein;LDH=lactatedehydrogenase;eq.=equivalents.
Mar.Drugs2016,14,33 7of22
Table2.HumanpoisoningsdueorascribedtocutaneousexposuretoPLTX-contaminatedsoftcorals.
Numberof PLTXsDetectionand
Location,Year Corals SignsandSymptoms TreatmentandOutcome Reference
Patients Concentration
Supportivepharmacological
Hawaii(USA), Dizziness,nausea,headache,malaise,discomfortto NMR(280µgPLTX/g
1 Palythoatoxica treatment.Recovery [1]
1962 thehands wetweight)
after1week
Shivering,myalgia,weaknessoftheextremities,
Infusionofintra-venous Hemolysisneutralization
Palythoasp.and speechdisturbance.Swellinganderythemaatcut
Germany,2008* 1 physiologicalfluids.Recovery assay(2–3mgPLTXeq./g [58]
Parazoanthussp. finger,numbness,andparesthesiasofthearm.
after48h wetweight)
SlightlyelevatedCPK,LDH,CRP.AbnormalECG
Metallictaste,perioralparesthesia,hivesontorso Intravenousdiphenhydramine,
California
1 Zoanthidcorals andextremities,edemaanderythemaathands. methylprednisolineand Noanalysis [67]
(USA),2009*
Urticarialrashonarms,things,abdomen,andback. lorazepam.Recoveryafter24h
Patientserum:haemolytic
Chestpain,lightheadedness,weakness,and activity,noneutralizationby
Georgia(USA), Supportivetreatment.
1 Palythoasp. numbnessoftheleftarm,tachycardia. anti-PLTXantibody;no [54]
2006 Recoveryafter48h
ElevatedCPK PLTX-likecompound
detectionbyHPLC,LC/MS
*Yearofpublication;CPK=creatinephosphokinase;CRP=C-reactiveprotein;LDH=lactatedehydrogenase;ECG=electrocardiogram;eq.=equivalents.
Table3.HumanpoisoningsascribedtoocularexposuretoPLTX-contaminatedsoftcorals.
Location, Numberof PLTXsDetection
Corals SignsandSymptoms TreatmentandOutcome Reference
Year Patients andConcentration
Ocularirritationandredness,bittermetallictaste,eye
Moxifloxacin,artificialtears,topical
painphotophobia,blurryvision,purulentdischarge
N.D. 2 Zoanthids prednisoloneacetate,fluorometholone, Notperformed [59]
fromeyes,bilateralpunctateepithelialerosion,
moxifloxacin,cyclosporinedrops
conjuctivalhyperemia
Intravenousinfusionofbalancedcrystalloid
Eyesburning,dyspnea,nausea,shivering,conjunctival
solution,Diphoterine®,topicalantibioticsand
Switzerland, injection,superficialpunctuateepitheliopathy,multiple
1 Zoanthids steroid,amnioticmembranetransplantation, Notperformed [60]
2015* cornealDescemet’sfolds,cornealerosion.
scleracontactlenses(4months).Recovery
Leukocytosis,elevatedCRP,CPK,LDH
withinseveralweeks
*Yearofpublication;CPK=creatinephosphokinase;CRP=C-reactiveprotein;LDH=lactatedehydrogenase.
Mar.Drugs2016,14,33 8of22
2.2.1. InhalationalExposuretoVaporsfromPalytoxins-ContaminatedSoftCorals
CasesofhumanpoisoningassociatedtoinhalationofvaporsfromhotwaterpouredonPLTX-contaminated
zoanthids, supported by PLTX detection in the involved cnidarian, are summarized in Table 1.
Thefirstwell-documentedcaseofahumanpoisoningbyinhalationofsteamfromPLTX-contaminated
softcoralswasdescribedin2010[54]. ItinvolvedamaninVirginia(USA)whoeradicatedfromhis
aquariumacolonyofgreen/brownmedium-sizedzoanthids,growingonliverockforthreeyears.
Pouringboilingwaterontherock, thepatientinhaledthesteamandimmediatelyfeltafoulodor.
Symptomsofpoisoning,involvingmainlytheupperrespiratorytract(rhinorrheaandcough),appeared
within 20 min. The patient took an antihistamine agent, believing the symptoms could be caused
by seasonal allergy. Notwithstanding, the symptoms (dyspnea and lightheadedness up to severe
fitsofcoughingandchestpain)worsenedwithin4handthepatientwashospitalized.Uponadmission,
hiselectrocardiogram(ECG)wasregular,butitisunclearifhematochemicalanalyseswerecarried
out. Pharmacological treatment was symptomatic with an anti-inflammatory corticosteroid and
painmedications. After15hofhospitalization,thepatientwasdischargedwithprescribedinhaled
corticosteroidandcoughsuppressant. Afollow-uppulmonaryexamination,twoweekspost-exposure,
diagnosed asthma-like symptoms (bronchial inflammation and bronchoconstriction), so that
the pharmacological treatment continued up to the complete relapse, one month post-exposure.
Morphologicalanalysisofthesoftcoralscollectedfromtheinfestedrockshowedthemascompatible
withPalythoa/Protopalythoasp. zoanthids. Hemolysisneutralizationassayonthecoralethanolextract
and high-performance liquid chromatography (HPLC) analysis determined 309 and 613 µg PLTX
equivalents/g wet coral weight, respectively, whereas electrospray ionization-mass spectrometry
(ESI-MS) confirmed that the toxin was consistent with PLTX. Subsequent investigations in a local
Marylandaquariumstorefoundacolony,morphologicallyconsistentwiththePalythoasp. colony
involvedintheVirginiacase,containing515µgPLTXequivalents/g,asdeterminedbyHPLC[55].
Recently,apoisoningduetosteaminhalationfromboilingwaterpouredonasoftcoral(Palythoa
heliodiscus) involved four patients in The Netherlands. After patient 1 poured hot water over the
coral, all patients developed cough (after 1–2 min) and dyspnea (after 5–10 min). The estimated
exposure of patients 1–4 to vapors was 20, 15, 5, and 10 min, respectively, within six meters
from the coral. The patients were admitted to the emergency room 45 min after starting the coral
cleaning,withaseriesofsymptomsincludingdyspnea,cough,chestpain,tachycardia,andnausea.
Anamnesisshowedthatnoneofthemhadsignificantpre-existinghealthproblemsorsmokinghistory.
ECG and chest radiograph did not show any alteration, whereas hematological analyses revealed
leukocytosisinallpatients(15to34ˆ103cells/µL)withhighlevelsofneutrophils(patients3and4:
31and15ˆ103cells/µL),creatinephospho-kinase(CPK;patient1: 215IU/L)andC-reactiveprotein
(CRP;patients2,3,and4: 28–228mg/L).Thetreatmentwasonlysupportive,consistingofoxygen
therapyandnon-steroidalanti-inflammatorydrugs(acetaminophenanddiclofenac). Thesignsand
symptomsofpoisoningdisappearedwithin36hpostexposure,exceptfordyspneainpatients1and2.
Patientsweredischargedwithin72hfromthevapor’sexposure. Patients1and2stillshoweddyspnea
andfatigueevenafterthreemonths. Chemicalanalysis(liquidchromatographyassociatedwithmass
spectrometry,LC/MS)onaspecimencollectedfromtheaquariumofthepoisonedpatientsrevealed
highlevelsofPLTXand42-hydroxy-PLTX(1018µgand46µg/gwetcoral,respectively)[56].
ApoisoningprobablyduetoinhalationalexposuretoPLTXsduringsoftcoralshandlinghasbeen
recentlydescribedinAlaska[57]. Thecaseinvolvedthreepersons: (i)patientAwhotransferred32kg
oflivecoralsintoa758Laquarium;(ii)patientBand(iii)patientCwhowereasleepinaroomadjacent
totheaquariumduringthecoraltransfer.Duringthisoperation,severalcoralfragmentsfeltonthefloor
causingthebreakingoffofsomesoftcorals.After7h,allthepatientsexperiencedrespiratory(dyspnea,
scratchythroat),muscular(myalgiaandspasms),neurological(paresthesia,ataxia,weakness,tremors),
andgastrointestinal(nausea)symptoms. PatientA,whosleptfor7hintheroomwiththeaquarium,
showedthemostserioussymptoms,includingcough,nausea,headache,muscle,andjointpain. Atthe
hospitaladmission,hewastachycardic,tachypneic,andfebrile(maximumtemperature: 39.4˝C),with
Mar.Drugs2016,14,33 9of22
leukocytosis(13.8ˆ103 cells/µLand86%neutrophils. Sincethehematochemicalparameters,the
renalfunctionandchestradiographywerewithinthenormalrange,thepharmacologicaltreatment
wasonlysupportive. ThepatientA’ssymptomsdisappearedwithintwodays,whereaspatientsBand
C,reportinglessseveresymptoms,relapsedin12h. Geneticanalysisonasoftcoralsample,collected
fromthesamehomeaquarium,identifiedthespeciesasPalythoaheliodiscus. HPLCanalysisofthe
samespecimenquantified7.3mgPLTXequivalents/gwetweightofzoanthidandLC/MSconfirmed
PLTXasthemaintoxin[57].
2.2.2. CutaneousExposuretoPalytoxins-ContaminatedSoftCorals
TwohumancasesofadverseeffectsassociatedtoskinexposuretoPLTX-contaminatedsoftcorals
aredocumented(Table2). Oneofthefirstreportsonadverseeffectsbycutaneousexposuretosoft
coralscontaminatedbyPLTXswasanecdotallyreportedintheearly1960sduringthesecondcollection
ofPalythoatoxicainHawaii,fromwhichPLTXwasfirstlypurified[1]. Collectingthezoanthidcolonies
withbarehandsandfeet,aresearcherexperienceddizziness,nausea,headache,increasingmalaise
anddiscomforttothehands. Thesesymptoms,probablyfacilitatedbysmallcutsandabrasionscaused
bythecoralcollection,lastedforoneweekandneededsupportivepharmacologicaltreatmentsand
medical attention to the feet. Nuclear magnetic resonance (NMR) analysis of P. toxica specimens
collectedduringthisepisodedeterminedaconcentrationof280µgPLTX/gzoanthid[1].
Anothercase,describedin2008byHoffmannandcoworkers[58],involvedamaninGermany
whocollapsed16hafterhandlingseveralzoanthidcolonies(Palythoasp. andParazoanthussp.) in
hishomeaquarium. Symptomsstarted2haftercontactwiththecnidariaandincludedshivering,
myalgia,andgeneralweaknessoftheextremities. Dizzinessandspeechdisturbancewereexperienced
atthetimeofcollapse. Attheadmissiontothehospital(20hpostexposure),themanshowedminor
cuts on three fingers, with local inflammatory signs (swelling and erythema). The numbness and
paresthesias of the fingers extended to the whole arm over the following 20 h. Hematochemical
analysesdemonstratedslightlyelevatedserumlevelsofCPK(198IU/L),lactatedehydrogenase(LDH,
304IU/L),andCRP(13.8mg/L),consistentwiththedevelopedmyalgiaandskeletomusculardamage.
Despitecardiovascularexaminationrevealedarhythmicheartbeat(83beats/min)withoutmurmurs
and a blood pressure within the normal range (100/70 mmHg), an abnormal electrocardiogram
(sinusrhythmoflefttypewithanincompleterightbundleblock)wasrecorded. Afterintravenous
physiologicalfluidsinfusion,cardiacsignsrecededwithinthenext24h,butparesthesia,weakness,
and myalgia persisted until discharge, 48 h later. Samples of two zoanthid colonies from the
aquarium,identifiedasPalythoasp.andParazoanthussp.,weresubsequentlyanalyzedbythehemolysis
neutralizationassay,detectinghighlevelsofPLTXonlyinParazoanthussp. (7700hemolyticunits/g,
correspondingto2–3mgPLTXequivalents/gwetweight).
2.3. HumanPoisoningsAscribedtoPalytoxins-ContaminatedSoftCorals: NoDirectIdentificationofPLTXsin
theCorals
Agreatnumberofcasesdescribinghumanpoisoningstentativelyassociatedwithzoanthidsknown
toproducePLTX-likecompoundsisreportedintheweb. Themajorityofthesecasesareanecdotally
describedinaquariumhobbyistforumsandblogs,sothatitseemsquitewellknownamongtheaquarists
thatsomecoralscouldbehighlytoxic.However,nospecimenfromtheinvolvedcoralswasanalyzedfor
PLTXs,whoseinvolvementhadbeenhypothesizedonlyonthebasisofsymptomsandthecoralspecies
ascausativeagentofpoisoning. Amongallthesecases,thosedocumentedbythescientificliterature
(datasources: electronicdatabasesPubMed,Scopus,ToxLine,andthereferencesofidentifiedarticles)
willbediscussed.
2.3.1. InhalationalExposuretoDustorVaporsfromSoftCorals
Differentcasesofadverseeffectsafterinhalationofsteamordustfromsoftcoralswerereported,
withoutconfirmationofPLTXpresenceinthesecnidarian(Table1). Thefirstcasetentativelyascribed
Mar.Drugs2016,14,33 10of22
toPLTXinhalationfromsoftcoralswasanecdotallyreportedbyMooreetal.[1]. In1961,investigating
asoftcoralidentifiedasPalythoacarribaeorumattheUniversityofOklahoma,threestudentsexperienced
chills, nausea, and headache after pulverizing the sun-dried coral in a mixer. The symptoms,
probablyduetothecoraldustleakedoutintotheatmosphere,resolvedwithinoneday. Althoughno
experimentaldetailsweregiven,subsequentcoralanalysisidentifiedacompoundidenticaltoPLTX
foundinP.toxicaandP.tuberculosa[1].
In2008,a32-years-oldman,withoutanypreviousmedicalhistoryincludingasthmaorother
respiratory diseases, recurred to the Emergency Department in New York (USA) after attempting
to eradicate an infesting Palythoa coral from his aquarium with boiling water. The coral secreted
amucous-likesubstanceand,immediatelyafterinhalingthefoulodorsteam,themanexperienced
shortnessofbreathandchestpain. Attheadmissiontothehospital,despitenormalvitalsigns,hehad
wheezinginalllungfieldsandECGshowedsinustachycardia(110beats/min),withnoST-Twave
changesandnormalQRSandQTcintervals. Hisrespiratorysymptomsimprovedwiththreedoses
ofthenebulizedbronchodilatoralbuterol,butthechestpainpersisted. Sincethesubsequentclinical
analysesdidnotshowelevatedcardiacenzymes, dysrhythmia, orothersequelae, thepatientwas
discharged24hlater. NochemicalanalyseswereperformedtoidentifyPLTXsinthecoral[61].
Fouryearslater,apoisoninginvolvingfourmembersofafamily(a37-years-oldman,his35-years-old
wife,andtheirtwo10-years-oldtwins)wasdescribedinTheNetherlands.Afterattemptingtoeradicate
azoanthidcolonybyboilingwater,allthepatientsdevelopedalmostthesamesymptoms(fever,hypotension,
nausea,headache,shivering,andseveremusclecramps).Aftertheadmissiontotheemergencyroom,all
ofthemshowedlowbloodpressure,fever>38.5˝C,leukocytosis,andelevatedbloodlevelsofCRP.
Allthefamilymembersrecoveredwithin48h,aftersupportivetherapy. Althoughnoanalyseswere
carried out to identify the zoanthid species or the presence of PLTX-like compounds, the authors
hypothesizedaPLTXpoisoning[62].
Inthesameperiod,apoisoninginvolvingthreepersons(twomenandonewomanagedbetween
21and23years)wasdescribedinSwitzerland. Withinafewminutesaftersoftcoralintroduction
intheiraquarium, theydevelopeddyspneaatrest, drycough, nausea, headache, fever, andchills.
Thepatientswereadmittedtothehospital2hlaterand,consideringtheiroverlappingsymptoms,the
clinicalpictureofthe23-years-oldmanwasdescribedasrepresentativeforthecasereport. Hisblood
pressure was normal and heart and respiratory rates were 121beats/min and 25 breaths/min,
respectively. Arterial oxygen saturation breathing room air was 93% and body temperature
was 40 ˝C. The patient showed a severe hypoxemia (pH 7.36, PaO 5.6 kPa, PaCO 6.4kPa),
2 2
leukocytosis and mild increase of LDH, CRP, and procalcitonin serum levels. Two days post
exposure,feverpersisted,andbloodinflammatoryparametersfurtherincreased(CRP=193.3mg/L;
procalcitonin=12.82ng/m; leukocytes = 27.6 ˆ 103 cells/µL). Since the respiratory symptoms
worsenedondaytwo,high-resolutioncomputedtomographyofthechestwasperformed,showing
zonesofpatchyandpleural-basedconsolidationatbothlungbases. Apulmonaryfunctiontestcarried
outthreedaysafterexposureshowedarestrictiveventilatorypatternwithanormaldiffusioncapacity,
while flexible bronchoscopy revealed a diffuse bronchial swelling with clear bronchial secretion.
Thebroncho-alveolarlavagewasslightlyturbid,withanelevatedcellscount(705ˆ103 cells/µL),
andapredominantgranulocyticinfiltrationpattern(alveolarmacrophages=46%;neutrophils=49%;
lymphocytes=2%;eosinophils=3%). Allthepatientsweredischargedfourdaysafterthepoisoning
butlungfunctiontestsreturnedwithinthenormalrangeonlyatthefollow-upvisittwoweekslater.
ThesoftcoraltentativelyresponsibleofthepoisoningbelongedtothegenusPalythoa,butnochemical
analyseswereperformedtoconfirmthepresenceofPLTX-likecompounds[63].
Anothercaseofpoisoningascribedtoinhalationalexposuretovaporsfromsoftcoralswasreported
by Sud and co-workers [64] and subsequently deepened by Rumore and Houst [65]. It involved
fivepersons: aprofessionalfishtankcleaner,theownerofafishtank,hiswife,andtheirtwochildren.
Immediatelyaftercleaningthefishtank(probablycontainingPalythoacorals)byboilingwater,the
42-years-old fish tank cleaner experienced shortness of breath and a body temperature of 38 ˝C.