Palytoxin and an Ostreopsis toxin extract increase the levels of mRNAs encoding inflammation-related proteins in human macrophages via p38 MAPK and NF-κB.
BACKGROUND
Palytoxin and, likely, its analogues produced by the dinoflagellate genus Ostreopsis, represent a class of non-proteinaceous compounds displaying high toxicity in animals. Owing to the wide distribution and the poisonous effects of these toxins in humans, their chemistry and mechanism of action have generated a growing scientific interest. Depending on the exposure route, palytoxin and its Ostreopsis analogues may cause several adverse effects on human health, including acute inflammatory reactions which seem more typical of cutaneous and inhalation contact. These observations have led us to hypothesize that these toxins may activate pro-inflammatory signalling cascades.


RESULTS
Here we demonstrate that palytoxin and a semi-purified Ostreopsis cf. ovata toxin extract obtained from a cultured strain isolated in the NW Adriatic Sea and containing a putative palytoxin and all the ovatoxins so far known--including the recently identified ovatoxin-f--significantly increase the levels of mRNAs encoding inflammation-related proteins in immune cells, i.e. monocyte-derived human macrophages, as assessed by Real-Time PCR analysis. Western immunoblot and electrophoretic mobility shift assays revealed that nuclear transcription factor -κB (NF-κB) is activated in cells exposed to toxins in coincidence with reduced levels of the inhibitory protein IκB-α. Moreover, Mitogen-Activated Protein Kinases (MAPK) were phosphorylated in response to palytoxin, as also reported by others, and to the Ostreopsis toxin extract, as shown here for the first time. By using specific chemical inhibitors, the involvement of NF-κB and p38 MAPK in the toxin-induced transcription and accumulation of Cycloxigenase-2, Tumor Necrosis Factor-α, and Interleukin-8 transcripts has been demonstrated.


CONCLUSIONS
The identification of specific molecular targets of palytoxin and its Ostreopsis analogues, besides contributing to expand the still limited knowledge of the intracellular signalling cascades affected by these toxins, may have important implications in setting up focused pharmacological interventions, replacing currently used symptomatic treatments.
Section of Biochemistry and Molecular Biology, Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, PU, Italy. rita.crinelli@uniurb.it
Rita
R
Crinelli
Elisa
E
Carloni
Elisa
E
Giacomini
Antonella
A
Penna
Sabrina
S
Dominici
Cecilia
C
Battocchi
Patrizia
P
Ciminiello
Carmela
C
Dell'Aversano
Ernesto
E
Fattorusso
Martino
M
Forino
Luciana
L
Tartaglione
Mauro
M
Magnani
D000178:Acrylamides / Q000737:chemistry / Q000633:toxicity*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002853:Chromatography, Liquid; D003064:Cnidarian Venoms; D045424:Complex Mixtures / Q000633:toxicity; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D007249:Inflammation / Q000235:genetics*; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000201:enzymology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology*; D008387:Marine Toxins / Q000633:toxicity*; D013058:Mass Spectrometry; D009000:Monocytes / Q000166:cytology; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000095702:Polyether Toxins
D000178:Acrylamides; D003064:Cnidarian Venoms; D045424:Complex Mixtures; D051546:Cyclooxygenase 2; D020672:I-kappa B Proteins; D016209:Interleukin-8; D008387:Marine Toxins; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B; D010447:Peptide Hydrolases; D012333:RNA, Messenger; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; C000606204:NFKBIA protein, human; C496540:PTGS2 protein, human; C010272:palytoxin; D000095702:Polyether Toxins