Palytoxin and an Ostreopsis Toxin Extract Increase the Levels of mRNAs Encoding Inflammation-Related Proteins in Human Macrophages via p38 MAPK and NF-κB

Abstract

BackgroundPalytoxin 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.Methodology and Principal FindingsHere 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 and SignificanceThe 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.

The novel ovatoxin-g and isobaric palytoxin (so far referred to as putative palytoxin) from Ostreopsis cf. ovata (NW Mediterranean Sea): structural insights by LC-high resolution MSn

“…Although little is known on their toxicity [7], ovatoxins have been frequently involved in several Ostreopsis-related toxic outbreaks following inhalation of marine aerosols in the Mediterranean basin [8][9][10]. The presence of ovatoxins and O. cf.…”

Molecules Altering the Intracellular Thiol Content Modulate NF-kB and STAT-1/IRF-1 Signalling Pathways and IL-12 p40 and IL-27 p28 Production in Murine Macrophages

“…Cytosolic and nuclear extracts were obtained by low salt/detergent cell lysis followed by high salt extraction of nuclei as previously described [51]. After treatment, cells were extensively washed with cold PBS and lysed with Buffer A [10 mM Hepes/KOH pH 7.9, 1.5 mM MgCl 2 , 10 mM KCl, 1 mM dithiothreitol (DTT), 0.2 mM EDTA, 0.1% Nonidet-P40, supplemented with a cocktail of protease (Roche Applied Science) and phosphatase inhibitors (1 mM NaF, 1 mM Na 3 VO 4 )].…”

Ribosomal Alteration-Derived Signals for Cytokine Induction in Mucosal and Systemic Inflammation: Noncanonical Pathways by Ribosomal Inactivation

“…Ribosome-inactivating palytoxin interacts with high affinity cell-surface receptors, including the Na + , K + -ATPase, or Na + /H + antiporter [ 35 – 37 ]. These ribosomal inactivation-linked surface receptors (EGFR and Na + , K + -ATPase) can also trigger their downstream kinase signaling pathways, leading to proinflammatory cytokine production [ 38 , 39 ]. Although surface receptors may be activated by ribosomal inactivation, most signaling sentinels that respond to ribosome-inactivating stressors are associated with organelles themselves, including the ribosome and endoplasmic reticulum (ER).…”