Posthypoxic behavioral impairment and mortality of Drosophila melanogaster are associated with high temperatures, enhanced predeath activity and oxidative stress

Abstract

Hypoxia is an underlying pathophysiological condition of a variety of devastating diseases, including acute ischemic stroke (AIS). We are faced with limited therapeutic options for AIS patients, and even after successful restoration of cerebral blood flow, the poststroke mortality is still high. More basic research is needed to explain mortality after reperfusion and to develop adjunct neuroprotective therapies. Drosophila melanogaster (D.m.) is a suitable model to analyze hypoxia; however, little is known about the impacts of hypoxia and especially of the subsequent reperfusion injury on the behavior and survival of D.m. To address this knowledge gap, we subjected two wild-type D.m. strains (Canton-S and Oregon-R) to severe hypoxia (<0.3% O2) under standardized environmental conditions in a well-constructed hypoxia chamber. During posthypoxic reperfusion (21% O2), we assessed fly activity (evoked and spontaneous) and analyzed molecular characteristics (oxidative stress marker abundance, reactive oxygen species (ROS) production, and metabolic activity) at various timepoints during reperfusion. First, we established standard conditions to induce hypoxia in D.m. to guarantee stable and reproducible experiments. Exposure to severe hypoxia under defined conditions impaired the climbing ability and reduced the overall activity of both D.m. strains. Furthermore, a majority of the flies died during the early reperfusion phase (up to 24 h). Interestingly, the flies that died early exhibited elevated activity before death compared to that of the flies that survived the entire reperfusion period. Additionally, we detected increases in ROS and stress marker (Catalase, Superoxide Dismutase and Heat Shock Protein 70) levels as well as reductions in metabolic activity in the reperfusion phase. Finally, we found that changes in environmental conditions impacted the mortality rate. In particular, decreasing the temperature during hypoxia or the reperfusion phase displayed a protective effect. In conclusion, our data suggest that reperfusion-dependent death might be associated with elevated temperatures, predeath activity, and oxidative stress.

Increased Post-Hypoxic Oxidative Stress and Activation of the PERK Branch of the UPR in Trap1-Deficient Drosophila melanogaster Is Abrogated by Metformin

“…As previously described [45] hypoxia was induced with nitrogen (N 2 ) in a selfconstructed hypoxia chamber, consisting of a heated water chamber, gas-flow regulator, humidifier, and an airtight acrylic glass compartment with a stainless-steel bottom plate and lid (Figure 1a). The chamber enables control and monitoring of oxygen levels (Greisinger GOX 100 T O 2 -Sensor, Greisinger, Regenstauf, Germany), humidity, temperature (Habor Thermo-Hygrometer, Habor, Deggenhausertal, Germany), and pressure (Fluke 700RG06 100 PSIG pressure gauge, Fluke, Glottertal, Germany).…”

“…The activity of each fly was assessed as previously reported [45]. After hypoxia, each fly was transferred into the Drosophila Activity Monitoring system (Model DAM2, Trikinetics Inc., Waltham, MA, USA).…”

“…D. melanogaster as a model species has many advantages such as a short life cycle, large numbers of progeny, limited need for resources, and a remarkably high degree of conservation compared to the human genome [42][43][44]. Our established hypoxia system for D. melanogaster with the ability to monitor and regulate parameters such as oxygen levels, temperature, humidity, and atmospheric pressure enabled us to induce reproducible and valid hypoxia during each experiment [45].…”

Drosophila Trachea as a Novel Model of COPD

“…The Drosophila functional homolog of HIF-1α is Similar [ 52 ]. Hypoxia-induced activation of Similar leads to over branching caused by elevated Drosophila FGF, Branchless (Bnl) [ 53 ] as well as increased ROS levels, similar to what was observed in COPD patients [ 54 ].…”

Lifespan and ROS levels in different Drosophila melanogaster strains after 24 h hypoxia exposure

“…Although adult fruit flies normally do not live at extremely low oxygen tensions, it has been shown that D. melanogaster effectively responds to variations in oxygen levels ( Zhao and Haddad, 2011 ). However, differently from mammals, fruit flies can tolerate short hypoxic or even anoxic treatments without apparent injury ( Zhao and Haddad, 2011 ; Azad and Haddad, 2009 ; Azad et al, 2009 ; Habib et al, 2021 ). Considering these features, the D. melanogaster organism is an ideal system to investigate the hypoxic response at its early stages, before the onset of major and irreversible damages to the organism.…”