Perfluorooctane sulfonate (PFOS) and its selected analogs induce various cell death types in peripheral blood mononuclear cells

The perfluoalkyl substance (PFASs) perfluorooctane sulfonate (PFOS) has been widely used in industry. However, PFOS is a persistent organic pollutant and has been gradually replaced by its short-chain analogs, perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS). PFASs are extremely persistent and are very frequently detected among the general population. The aim of the study was to determine the effect of selected PFASs on peripheral blood mononuclear cells (PBMCs) and the mechanisms of their action. PBMCs were exposed to PFOS, PFBS and PFHxS at concentrations ranging from 0.02 to 400 μM for 24 h, they were then tested for viability, apoptosis (changes in cytosolic calcium ions level and caspase-3, -8 and -9 activation), ferroptosis (changes in chelatable iron ions level and lipid peroxidation), and autophagy (LC3-II and Raptor level assay). PFOS exposure decreased cell viability, increased calcium ion level and caspase-8 activation; it also enhanced lipid peroxidation and increased the intracellular pool of chelatable iron ions as well as LC3-II protein content. In contrast, short-chain PFBS and PFHxS induced significant changes in the markers of apoptosis but had no substantial impact on ferroptosis or autophagy markers over a wide range of concentrations. Our results indicate that only PFOS demonstrated pro-ferroptotic and pro-autophagic potential but observed changes occurred at relatively high exposure. A short-chain substitute (PFBS) exhibited strong pro-apoptotic potential at concentrations related to occupational exposure. While the short-chain PFASs strongly affected the mitochondrial pathway of apoptosis, apoptosis itself was only induced by PFBS via the intrinsic and extrinsic pathways. It seems that the length of the carbon chain in PFASs appears to determine the cell death mechanisms activated in human PBMCs following exposure. Our findings provide a new insight into the immune toxicity mechanism induced by these compounds.

Alveus, gen. nov. (Bacillariaceae, Bacillariophyta), a heavily silicified diatom found in warm water oceans

Scanning electron microscope images of complete and damaged frustules of Nitzschia marina Grun. revealed an unusual chambered structure of the valve. This structure is not present in any existing nitzschioid genus and warrants an independent generic status for this taxon, which is therefore separated into Alveus gen. nov. Generic and emended specific definitions are provided and presented in the context of their relationship to other genera within the family Bacillariaceae. Deep relief of the inner surface of Alveus valves is similar to that of genera Fragilariopsis, Denticulopsis, Neodenticula, and Crucidenticula. It differs from all these diatoms in the alveolar striation. This heavily silicified diatom was found in samples from the US Joint Global Oceanographic Flux Studies cruise TT007 stations 2 and 4, (9 degrees and 5 degrees N respectively, 140 degrees W) in the equatorial Pacific. Presently, this uncommon species is restricted to warm waters. It is very common in the surface sediments of the equatorial Pacific and Indian Ocean and in the tropical and subtropical Atlantic. The sedimentary record of Alveus marinus goes back to the Middle Late Miocene (approximately 8 Ma years).