Effects of oxygen concentration and pressure on Drosophila melanogaster: oxidative stress, mitochondrial activity, and survivorship

Neurotoxic and behavioral deficit in Drosophila melanogaster exposed to photocatalytic products of Paraquat

The Advanced Oxidative Processes have demonstrated potential for application in the degradation of organic pollutants, such as Paraquat (PQ) from water and wastewater, due to their low price, high efficiency, and non-toxic properties. In this study, we investigated whether the photodegradation of PQ with TiO2 nanotubes reduced its toxicity in Drosophila melanogaster. However, dietary ingestion of degradation products PQ for larvae resulted in a low axial ratio (pupal volume). In the adults, products of photodegradation of PQ exposure markedly diminished climbing ability in a time-dependent manner after 10 days of feeding. In addition, exposure of D. melanogaster to photodegradation of PQ reduced acetylcholinesterase and citrate synthase activities but improved oxidative stress, as evidenced by oxide nitric, protein carbonyl, and lactate production. These results suggest that the photodegradation of PQ with TiO2 nanotubes produced PQ fragments with higher toxicity than PQ, while the precise mechanism of its action needs further investigation.

Chronic changes in developmental oxygen have little effect on mitochondria and tracheal density in the endothermic moth Manduca sexta

Oxygen availability during development is known to impact the development of insect respiratory and metabolic systems. Drosophila adult tracheal density exhibits developmental plasticity in response to hypoxic or hyperoxic oxygen levels during larval development. Respiratory systems of insects with higher aerobic demands, such as those that are facultative endotherms, may be even more responsive to oxygen levels above or below normoxia during development. The moth Manduca sexta is a large endothermic flying insect that serves as a good study system to start answering questions about developmental plasticity. In this study, we examined the effect of developmental oxygen levels (hypoxia: 10% oxygen, and hyperoxia: 30% oxygen) on the respiratory and metabolic phenotype of adult moths, focusing on morphological and physiological cellular and intercellular changes in phenotype. Mitochondrial respiration rate in permeabilized and isolated flight muscle was measured in adults. We found that permeabilized flight muscle fibers from the hypoxic group had increased mitochondrial oxygen consumption, but this was not replicated in isolated flight muscle mitochondria. Morphological changes in the trachea were examined using confocal imaging. We used transmission electron microscopy to quantify muscle and mitochondrial density in the flight muscle. The respiratory morphology was not significantly different between developmental oxygen groups. These results suggest that the developing M. sexta trachea and mitochondrial respiration have limited developmental plasticity when faced with rearing at 10% or 30% oxygen.

Piranhea trifoliata extracts ameliorate muscular decline in Drosophila melanogaster exposed to Paraquat

In this study, we have demonstrated, for the first time, the muscular protective effects of Piranhea trifoliata bark extract against Paraquat (PQ)-induced oxidative stress in Drosophila melanogaster. Exposure of D. melanogaster (Canton Special) to PQ caused oxidative stress, as evidenced by protein carbonyl and elevated acetylcholinesterase (AChE) activity levels. However, a diet supplemented with the P. trifoliata extracts (0.1 mg/ml) for 10 days ameliorates protein carbonyl levels and enzymatic activities of AChE and citrate synthase to prevent PQ damage. Also, P. trifoliata bark extracts showed in phytochemical assays the presence of phenols, at 46.06 mg EAG/g extract of total phenolic compounds, and a 40% 2,2-diphenyl-1-picryl-hydrazyl scavenging effect. The study showed the muscular protective function of the P. trifoliata extracts in D. melanogaster exposed to PQ. On the basis of the results, we contemplate that the bark of P. trifoliata might prevent and ameliorate human diseases caused by oxidative stress. The muscular action of the P. trifoliata extract can be attributed to the antioxidant constituents, while the precise mechanism of its action needs further investigation.

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

During recent decades, model organisms such as Drosophila melanogaster have made it possible to study the effects of different environmental oxygen conditions on lifespan and oxidative stress. However, many studies have often yielded controversial results usually assigned to variations in Drosophila genetic background and differences in study design. In this study, we compared longevity and ROS levels in young, unmated males of three laboratory wild-type lines (Canton-S, Oregon-R and Berlin-K) and one mutant line (Sod1ⁿ¹) as a positive control of redox imbalance, under both normoxic and hypoxic (2% oxygen for 24 h) conditions. Lifespan was used to detect the effects of hypoxic treatment and differences were analysed by means of Kaplan–Meier survival curves and log-rank tests. Electron paramagnetic resonance spectroscopy was used to measure ROS levels and analysis of variance was used to estimate the effects of hypoxic treatment and to assess ROS differences between strains. We observed that the genetic background is a relevant factor involved in D. melanogaster longevity and ROS levels. Indeed, as expected, in normoxia Sod1ⁿ¹ are the shortest-lived, while the wild-type strains, despite a longer lifespan, show some differences, with the Canton-S line displaying the lowest mortality rate. After hypoxic stress these variances are amplified, with Berlin-K flies showing the highest mortality rate and most evident reduction of lifespan. Moreover, our analysis highlighted differential effects of hypoxia on redox balance/unbalance. Canton-S flies had the lowest increase of ROS level compared to all the other strains, confirming it to be the less sensitive to hypoxic stress. Sod1ⁿ¹ flies displayed the highest ROS levels in normoxia and after hypoxia. These results should be used to further standardize future Drosophila research models designed to investigate genes and pathways that may be involved in lifespan and/or ROS, as well as comparative studies on specific mutant strains.

Summary: In our study Drosophila melanogaster was used to evaluate the effects of different environmental oxygen conditions on survival and ROS levels in three wild-type and one mutant strain.

A Link between Atmospheric Pressure and Fertility of Drosophila Laboratory Strains

Simple Summary

The researchers usually keep insects under study under thoroughly controlled conditions. However, sometimes they encounter a situation where the data they obtained under such conditions demonstrate an obvious side effect of some unaccounted factor. Here we provide evidence that changes in atmospheric pressure could be responsible for some such cases.

Abstract

Standardization of conditions under which insects are kept is of great importance when studying their physiology and researchers do their best to maintain it. Nevertheless, sometimes an obvious side effect of some unaccounted factor affecting insects’ reproduction can be revealed even under thoroughly controlled laboratory conditions. We faced such a phenomenon when studying the fertility level in two wild type Drosophila melanogaster strains. For fertility analysis, 50 newly emerged females and 50 males of each strain under study were transferred to fresh medium daily within 10 days. We found out that fertility of both strains was stable on days 2–10 after the oviposition onset in one experiment, while in another one it was significantly decreased during days 5–10. When compared to publicly available meteorological data, these changes in the fertility level demonstrated a strong association with one weather factor: barometric pressure. Thus, we conclude that changes in atmospheric pressure can be considered a factor affecting insects reproduction and discuss a possible mechanism of their influence on fertility.

Inhibition of mitochondrial respiration under hypoxia and increased antioxidant activity after reoxygenation of Tribolium castaneum

Regulating the air in low-oxygen environments protects hermetically stored grains from storage pests damage. However, pests that can tolerate hypoxic stress pose a huge challenge in terms of grain storage. We used various biological approaches to determine the fundamental mechanisms of Tribolium castaneum to cope with hypoxia. Our results indicated that limiting the available oxygen to T. castaneum increased glycolysis and inhibited the Krebs cycle, and that accumulated pyruvic acid was preferentially converted to lactic acid via anaerobic metabolism. Mitochondrial aerobic respiration was markedly suppressed for beetles under hypoxia, which also might have led to mitochondrial autophagy. The enzymatic activity of citrate synthase decreased in insects under hypoxia but recovered within 12 h, which suggested that the beetles recovered from the hypoxia. Moreover, hypoxia-reperfusion resulted in severe oxidative damage to insects, and antioxidant levels increased to defend against the high level of reactive oxygen species. In conclusion, our findings show that mitochondria were the main target in T. castaneum in response to low oxygen. The beetles under hypoxia inhibited mitochondrial respiration and increased antioxidant activity after reoxygenation. Our research advances the field of pest control and makes it possible to develop more efficient strategies for hermetic storage.

Iron Sulfur and Molybdenum Cofactor Enzymes Regulate the Drosophila Life Cycle by Controlling Cell Metabolism

Iron sulfur (Fe-S) clusters and the molybdenum cofactor (Moco) are present at enzyme sites, where the active metal facilitates electron transfer. Such enzyme systems are soluble in the mitochondrial matrix, cytosol and nucleus, or embedded in the inner mitochondrial membrane, but virtually absent from the cell secretory pathway. They are of ancient evolutionary origin supporting respiration, DNA replication, transcription, translation, the biosynthesis of steroids, heme, catabolism of purines, hydroxylation of xenobiotics, and cellular sulfur metabolism. Here, Fe-S cluster and Moco biosynthesis in Drosophila melanogaster is reviewed and the multiple biochemical and physiological functions of known Fe-S and Moco enzymes are described. We show that RNA interference of Mocs3 disrupts Moco biosynthesis and the circadian clock. Fe-S-dependent mitochondrial respiration is discussed in the context of germ line and somatic development, stem cell differentiation and aging. The subcellular compartmentalization of the Fe-S and Moco assembly machinery components and their connections to iron sensing mechanisms and intermediary metabolism are emphasized. A biochemically active Fe-S core complex of heterologously expressed fly Nfs1, Isd11, IscU, and human frataxin is presented. Based on the recent demonstration that copper displaces the Fe-S cluster of yeast and human ferredoxin, an explanation for why high dietary copper leads to cytoplasmic iron deficiency in flies is proposed. Another proposal that exosomes contribute to the transport of xanthine dehydrogenase from peripheral tissues to the eye pigment cells is put forward, where the Vps16a subunit of the HOPS complex may have a specialized role in concentrating this enzyme within pigment granules. Finally, we formulate a hypothesis that (i) mitochondrial superoxide mobilizes iron from the Fe-S clusters in aconitase and succinate dehydrogenase; (ii) increased iron transiently displaces manganese on superoxide dismutase, which may function as a mitochondrial iron sensor since it is inactivated by iron; (iii) with the Krebs cycle thus disrupted, citrate is exported to the cytosol for fatty acid synthesis, while succinyl-CoA and the iron are used for heme biosynthesis; (iv) as iron is used for heme biosynthesis its concentration in the matrix drops allowing for manganese to reactivate superoxide dismutase and Fe-S cluster biosynthesis to reestablish the Krebs cycle.

Protective action of Omega-3 on paraquat intoxication in Drosophila melanogaster

Paraquat (PQ) (1,1'-dimethyl-4-4'-bipyridinium dichloride) is the second most widely used herbicide worldwide; however, in countries different sales and distribution remain restricted. Chronic exposure to PQ leads to several diseases related to oxidative stress and mitochondrial dysfunctions including myocardial failure, cancer, and neurodegeneration and subsequently death depending upon the dose level. The aim of this study was to examine if diet supplementation with eicosapentaenoic and docosahexaenoic acids (EPA and DHA, omega-3 long-chain fatty acids) serves a protective mechanism against neuromuscular dysfunctions mediated by PQ using Drosophila melanogaster as a model with focus on mitochondrial metabolism. PQ ingestion (170 mg/kg b.w. for 3 d) resulted in a decreased life span and climbing ability in D. melanogaster. In the brain, PQ increased thioflavin fluorescence and reduced either 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) nuclei staining and neuronal nuclei protein (NeuN) positive neurons, indicating amyloid formation and neurodegenetation, respectively. In the thorax, PQ ingestion lowered citrate synthase activity and respiratory functions indicating a reduction in mitochondrial content. PQ elevated Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) mRNA expression levels, indicative of high calcium influx from cytosol to mitochondrial matrix. In brain and thorax, PQ also increased hydrogen peroxide (H2O2) production and impaired acetylcholinesterase (AChE) activity. Concomitant EPA/DHA ingestion (0.31/0.19 mg/kg b.w.) protected D. melanogaster against PQ-induced toxicity preserving neuromuscular function and slowing down the rate of aging. In brain and thorax, these omega-3 fatty acids inhibited excess H2O2 production and restored AChE activity. EPA/DHA delayed amyloid deposition in the brain, and restored low citrate synthase activity and respiratory functions in the thorax. The effects in the thorax were attributed to stimulated mRNA expression level of genes involved either in mitochondrial dynamics or biogenesis promoted by EPA/DHA: dynamin-related protein (DRP1), mitochondrial assembly regulatory factor (MARF), mitochondrial dynamin like GTPase (OPA1), and peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α). In conclusion, diet supplementation with EPA/DHA appears to protect D. melanogaster muscular and neuronal tissues against PQ intoxication.