A single air dive induces apoptotic gene regulation but no increase in nucleosomes

Oxidative stress caused by elevated partial pressure of oxygen during diving is a major contributor of inflammation and apoptosis. The underlying molecular mechanisms are poorly understood. The aim of the study was to describe apoptotic gene regulation induced by a single air dive.

19 healthy volunteers were exposed to a 30-minute dive at 2.8 atmospheres (ATA) absolute in a pressure chamber in ambient air. Blood samples were obtained before, directly after and 24 hours after exposure. Gene expressions of Bcl-2, Bcl-xL and Bax were analyzed in mononuclear cell extracts by real-time polymerase chain reaction (PCR). Circulating nucleosomes were measured in serum before exposure and 24 hours afterward.

The pro-apoptotic Bax expression was not significantly increased (p=0.74) directly after the dive but was induced (2.22 ± 0.85-fold) after 24 hours (p ≤ 0.01). Bcl-2 expression was not changed significantly directly after (p = 0.11) but was 1.88 ± 1.08-fold higher after 24 hours (p ≤ 0.01). Bcl-xL expression was not elevated significantly (p = 0.54) but was 2.04 ± 1.02-fold higher after 24 hours (p ≤ 0.01). The level of nucleosomes did not change after 24 hours compared to baseline.

A single air dive at 2.8 ATA for 30 minutes causes an upregulation of pro- and anti-apoptotic genes but did not elevate circulating nucleosomes. In a single air dive the upregulation of anti-apoptotic Bcl-2 family members may counteract the pro-apoptotic potential of Bax.