Elevations of Extracellular Vesicles and Inflammatory Biomarkers in Closed Circuit SCUBA Divers

Abstract

Blood-borne extracellular vesicles and inflammatory mediators were evaluated in divers using a closed circuit rebreathing apparatus and custom-mixed gases to diminish some diving risks. “Deep” divers (n = 8) dove once to mean (±SD) 102.5 ± 1.2 m of sea water (msw) for 167.3 ± 11.5 min. “Shallow” divers (n = 6) dove 3 times on day 1, and then repetitively over 7 days to 16.4 ± 3.7 msw, for 49.9 ± 11.9 min. There were statistically significant elevations of microparticles (MPs) in deep divers (day 1) and shallow divers at day 7 that expressed proteins specific to microglia, neutrophils, platelets, and endothelial cells, as well as thrombospondin (TSP)-1 and filamentous (F-) actin. Intra-MP IL-1β increased by 7.5-fold (p < 0.001) after day 1 and 41-fold (p = 0.003) at day 7. Intra-MP nitric oxide synthase-2 (NOS2) increased 17-fold (p < 0.001) after day 1 and 19-fold (p = 0.002) at day 7. Plasma gelsolin (pGSN) levels decreased by 73% (p < 0.001) in deep divers (day 1) and 37% in shallow divers by day 7. Plasma samples containing exosomes and other lipophilic particles increased from 186% to 490% among the divers but contained no IL-1β or NOS2. We conclude that diving triggers inflammatory events, even when controlling for hyperoxia, and many are not proportional to the depth of diving.

Endurance Exercise Performance Is Reduced after 6-h Dives at 1.35 ATA When Breathing 100% Oxygen Compared with Air

“…Previous data do suggest that a 20-min hyperoxic (PO 2 of ~142 kPa) dive in warm water (31–32°C) with mild exercise can significantly increase oxidative stress (24). Further, single and repeated (9–12 dives) hyperoxic (PO 2 of ~120 kPa) dives can elevate inflammatory markers and may also influence physical performance (25). Therefore, prolonged exposure to ROS from hyperoxia may precondition skeletal muscle to a state of fatigue thereby reducing performance.…”

Physiology of deep closed circuit rebreather mixed gas diving: vascular gas emboli and biological changes during a week-long liveaboard safari

“…These discrepancies have also prompted investigations focused on inflammatory pathways ( Francis et al, 1988 ; Martin and Thom, 2002 ; Bigley et al, 2008 ; Mitchell et al, 2022 ). Also, our previous data after 1 week of diving using closed circuit rebreather (CCR) apparatus ( Balestra et al, 2022b ; Arya et al, 2023 ; Gouin et al, 2023 ) mandated investigating the inflammatory bubble production hypothesis (see Figure 1 ). This latter hypothesis is based on a “first and second hit” mechanism that cannot be considered fully subordinate to gas supersaturation.…”

“…This latter hypothesis is based on a “first and second hit” mechanism that cannot be considered fully subordinate to gas supersaturation. Indeed, this second mechanism is thought to be related to a pro-inflammatory/oxidative response following diving, probably mediated by the presence/generation of microparticles (MPs) ( Arya et al, 2023 ). These MPs which are increased by repetitive and deep dives, may enlarge on decompression as any of micronuclei.…”

“…These MPs which are increased by repetitive and deep dives, may enlarge on decompression as any of micronuclei. More, actual data suggest that some of them possess enzyme activity, which provides a nucleation site for bubble formation (second generation micronuclei) ( Thom et al, 2018 ; Bhopale et al, 2021 ; Arya et al, 2023 ). Because MPs are more numerous and possess higher NOS2 concentrations post-dive, somewhat in proportion to dive repetition and probably depth.…”

“…It should be noted that, given the micro-dimensions of MPs, these “second-generation” bubbles related to MPs would still be below the detection limits of current ultrasound technology and may go beyond the pulmonary filter. Nevertheless, this mechanism could be at the root of some adverse effects of repetitive deep diving since these non-visible bubbles can be fed by inert gas accumulation and form measurable VGE (Vascular Gas Emboli) ( Arya et al, 2023 ).…”