Extensive Simulated Diving Aggravates Endothelial Dysfunction in Male Pro-atherosclerotic ApoE Knockout Rats

Abstract

IntroductionThe average age of the diving population is rising, and the risk of atherosclerosis and cardiovascular disease in divers are accordingly increasing. It is an open question whether this risk is altered by diving per se. In this study, we examined the effect of 7-weeks simulated diving on endothelial function and mitochondrial respiration in atherosclerosis-prone rats.MethodsTwenty-four male ApoE knockout (KO) rats (9-weeks-old) were fed a Western diet for 8 weeks before 12 rats were exposed to simulated heliox dry-diving in a pressure chamber (600 kPa for 60 min, decompression of 50 kPa/min). The rats were dived twice-weekly for 7 weeks, resulting in a total of 14 dives. The remaining 12 non-diving rats served as controls. Endothelial function of the pulmonary and mesenteric arteries was examined in vitro using an isometric myograph. Mitochondrial respiration in cardiac muscle tissues was measured using high-resolution respirometry.Results and ConclusionBoth ApoE KO diving and non-diving rats showed changes in endothelial function at the end of the intervention, but the extent of these changes was larger in the diving group. Altered nitric oxide signaling was primarily involved in these changes. Mitochondrial respiration was unaltered. In this pro-atherosclerotic rat model of cardiovascular changes, extensive diving appeared to aggravate endothelial dysfunction rather than promote adaptation to oxidative stress.

Effects of Cold Decompression on Hemodynamic Function and Decompression Sickness Risk in a Dry Diving Rat Model

“…While the cardiovascular system of humans and rats are largely similar structurally and functionally ( Buetow and Laflamme, 2018 ), the rodents’ relatively larger body surface area and higher metabolic rate cause them to respond differently from humans to changes in ambient temperature ( Maloney et al, 2014 ). Also, dry diving affects cardiovascular function to a lesser degree than water immersion does ( Gaustad et al, 2010 ), and diving-naïve rats, as the ones in the present study, display different vascular responses than rats that have been exposed to diving regularly ( Berenji Ardestani et al, 2019 , 2020 ). Finally, epidemiological data from human divers as well as pre-clinical models show that DCS development is dictated by more factors than bubbles ( Cialoni et al, 2017 ; Lautridou et al, 2017 ).…”

Hyperbaric exposure in rodents with non-invasive imaging assessment of decompression bubbles: A scoping review protocol

“…Results from this review will identify significant gaps in the field, while also reducing the need for duplicate in vivo experimentation, and be utilized for designing future experimentation. This information is anticipated to be useful for researchers in the decompression field that are studying rodents as a model for diving physiology or those using rodents for demonstration of new technologies prior to human translation [11,14,[19][20][21]. Further, due to the size and physiological differences between humans and rodents, it is not always practical to apply the same methods for imaging these different subjects.…”