Abstract
Production of blood-borne microparticles (MPs), 0.1–1 µm diameter vesicles, and interleukin (IL)-1β in response to high pressure is reported in lab animals and associated with pathological changes. It is unknown whether the responses occur in humans, and whether they are due to exposure to high pressure or to the process of decompression. Blood from research subjects exposed in hyperbaric chambers to air pressure equal to 18 meters of sea water (msw) for 60 minutes or 30 msw for 35 minutes were obtained prior to and during compression and 2 hours post-decompression. MPs and intra-particle IL-1β elevations occurred while at pressure in both groups. At 18 msw (n = 15) MPs increased by 1.8-fold, and IL-1β by 7.0-fold (p < 0.05, repeated measures ANOVA on ranks). At 30 msw (n = 16) MPs increased by 2.5-fold, and IL-1β by 4.6-fold (p < 0.05), and elevations persisted after decompression with MPs elevated by 2.0-fold, and IL-1β by 6.0-fold (p < 0.05). Whereas neutrophils incubated in ambient air pressure for up to 3 hours ex vivo did not generate MPs, those exposed to air pressure at 180 kPa for 1 hour generated 1.4 ± 0.1 MPs/cell (n = 8, p < 0.05 versus ambient air), and 1.7 ± 0.1 MPs/cell (p < 0.05 versus ambient air) when exposed to 300 kPa for 35 minutes. At both pressures IL-1β concentration tripled (p < 0.05 versus ambient air) during pressure exposure and increased 6-fold (p < 0.05 versus ambient air) over 2 hours post-decompression. Platelets also generated MPs but at a rate about 1/100 that seen with neutrophils. We conclude that production of MPs containing elevated concentrations of IL-1β occur in humans during exposure to high gas pressures, more so than as a response to decompression. While these events may pose adverse health threats, their contribution to decompression sickness development requires further study.
Highlights
Decompression sickness (DCS) presents a health risk for deep sea divers and a constraint to space exploration and provocative diving operations
MP and neutrophil activation analyses were performed on all samples
We evaluated whether the gas pressure profiles used with divers stimulated production of MPs by isolated neutrophils and platelets
Summary
Decompression sickness (DCS) presents a health risk for deep sea divers and a constraint to space exploration and provocative diving operations. Microparticles (MPs) are membrane vesicles with diameters of 0.1 to 1.0 μm generated by a variety of cells, and they are elevated in association with simulated as well as bona fide underwater diving[4,5,6,7,8,9,10,11]. Vascular injuries mediated by MPs following some insults can be directly linked to high concentrations of IL-1β in the particles[11,16,17,18]. This investigation was prompted because translation of findings from the murine decompression model to humans requires additional study. Data are mean ± SE, n is shown for each sample, * indicates significantly different from pre-exposure, p < 0.05, RM ANOVA
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