Abstract
Diatoms are an important class of unicellular algae that produce bioactive polyunsaturated aldehydes (PUAs) that induce abortions or malformations in the offspring of invertebrates exposed to them during gestation. Here we compare the effects of the PUAs 2-trans,4-trans-decadienal (DD), 2-trans,4-trans-octadienal (OD) and 2-trans,4-trans-heptadienal (HD) on the adenocarcinoma cell lines lung A549 and colon COLO 205, and the normal lung/brunch epithelial BEAS-2B cell line. Using the viability MTT/Trypan blue assays, we show that PUAs have a toxic effect on both A549 and COLO 205 tumor cells but not BEAS-2B normal cells. DD was the strongest of the three PUAs tested, at all time-intervals considered, but HD was as strong as DD after 48 h. OD was the least active of the three PUAs. The effect of the three PUAs was somewhat stronger for A549 cells. We therefore studied the death signaling pathway activated in A549 showing that cells treated with DD activated Tumor Necrosis Factor Receptor 1 (TNFR1) and Fas Associated Death Domain (FADD) leading to necroptosis via caspase-3 without activating the survival pathway Receptor-Interacting Protein (RIP). The TNFR1/FADD/caspase pathway was also observed with OD, but only after 48 h. This was the only PUA that activated RIP, consistent with the finding that OD causes less damage to the cell compared to DD and HD. In contrast, cells treated with HD activated the Fas/FADD/caspase pathway. This is the first report that PUAs activate an extrinsic apoptotic machinery in contrast to other anticancer drugs that promote an intrinsic death pathway, without affecting the viability of normal cells from the same tissue type. These findings have interesting implications also from the ecological viewpoint considering that HD is one of the most common PUAs produced by diatoms.
Highlights
Diatoms are microscopic, unicellular algae that represent dominant photosynthetic organisms in the world’s oceans
Cell cultures and treatment The A549 (ATCC CCL185) human lung adenocarcinoma and COLO 205 (ATCC CCL-222) colon adenocarcinoma metastatic ascites-deriving cell lines were maintained in DMEM (Dulbecco’s modified Eagle’s medium) supplemented with 10% fetal bovine serum (FBS), 100 units ml21 penicillin and 100 mg ml21 streptomycin
After 72 h, A549 cell viability decreased to 0% with 5 and 10 mM DD and to 26% with 2 mM DD; COLO-205 cell viability was 30%, 21% and 13% with 2, 5 and 10 mM DD, respectively
Summary
Unicellular algae that represent dominant photosynthetic organisms in the world’s oceans. Their beneficial role as food for grazers was challenged over a decade ago after the discovery that some diatom species produce teratogenic compounds such as polyunsaturated aldehydes (PUAs) that induce abortions, birth defects, poor development and high offspring mortality in predatory planktonic and benthic invertebrates [1,2,3]. Numerous functions have been proposed for PUAs such as: grazer defense [6,7]; allelopathy [8,9], cell to cell signaling [10], antibacterial activity [11,12], and bloom termination [13,14]. The same secondary metabolites have multiple functions from grazing defense to signal molecules mediating several plankton interactions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
