Antimicrobial Peptides Increase Tolerance to Oxidant Stress in Drosophila melanogaster

Abstract

It is well appreciated that reactive oxygen species (ROS) are deleterious to mammals, including humans, especially when generated in abnormally large quantities from cellular metabolism. Whereas the mechanisms leading to the production of ROS are rather well delineated, the mechanisms underlying tissue susceptibility or tolerance to oxidant stress remain elusive. Through an experimental selection over many generations, we have previously generated Drosophila melanogaster flies that tolerate tremendous oxidant stress and have shown that the family of antimicrobial peptides (AMPs) is over-represented in these tolerant flies. Furthermore, we have also demonstrated that overexpression of even one AMP at a time (e.g. Diptericin) allows wild-type flies to survive much better in hyperoxia. In this study, we used a number of experimental approaches to investigate the potential mechanisms underlying hyperoxia tolerance in flies with AMP overexpression. We demonstrate that flies with Diptericin overexpression resist oxidative stress by increasing antioxidant enzyme activities and preventing an increase in ROS levels after hyperoxia. Depleting the GSH pool using buthionine sulfoximine limits fly survival, thus confirming that enhanced survival observed in these flies is related to improved redox homeostasis. We conclude that 1) AMPs play an important role in tolerance to oxidant stress, 2) overexpression of Diptericin changes the cellular redox balance between oxidant and antioxidant, and 3) this change in redox balance plays an important role in survival in hyperoxia.Oxygen is essential for aerobic life. However, except for the beneficial role in wound healing, too little or too much oxygen can induce morbidity and mortality (1, 2). Mammalian aging and numerous diseases such as neurodegenerative diseases and chronic inflammatory diseases, as well as injury to the heart, lungs, retina, brain, and other organs due to ischemia and reperfusion states, result, by and large, from oxidant injury (3-6). High O 2 -induced oxidant injury could occur in cells in every organ, especially in the lungs, retina, heart, and brain (7,8). Prolonged exposure to high O 2 generates excessive reactive oxygen species (ROS), 2 induces cell death and oxidative stress responses, affects the immune response and DNA integrity, and modulates cell growth (5, 9 -11).Drosophila melanogaster has similar O 2 response pathways as mammals, and research on flies has enhanced our understanding of oxidant stress (12)(13)(14). In the past, through an experimental selection design over many generations, we have successfully generated D. melanogaster flies that tolerate tremendously high O 2 -induced oxidative stress. Microarray analysis has revealed that the family of antimicrobial peptides (AMPs) is over-represented among the up-regulated genes in these tolerant flies. We have further demonstrated that overexpression of even one AMP gene at a time (e.g. Diptericin (Dpt)) allows wild-type flies to survive much better in hyperoxia (15). To our knowledge, this is t...

The bacteriumWolbachiaexploits host innate immunity to establish a symbiotic relationship with the dengue vector mosquitoAedes aegypti

“…One example could be antioxidants, the expression of which was previously shown to be induced or suppressed by activation or silencing, respectively, of the Toll pathway in A. aegypti . In Drosophila, overexpression of antimicrobial peptides increases antioxidant enzyme activities and changes the cellular redox balance, facilitating fly survival in hyperoxia (Zhao et al, 2011). Consistent with our observation in both WB1 and MGYP2 mosquitoes, previous studies also showed that antioxidant treatment resulted in increased Wolbachia density in Drosophila (Brennan et al, 2012).…”

“…Antioxidants, as potential effector molecules of boosted immunity, enhance Wolbachia infection in A. aegypti Overexpression of antimicrobial peptides was reported to increase tolerance to oxidant stress in Drosophila melanogaster (Zhao et al, 2011), and both wAlbB and boosting mosquito immunity were observed to induce the expression of antioxidants and antimicrobial peptides in A. aegypti . We speculated that boosting immunity enhances Wolbachia infection through alterations Figure 3 Boosted basal immunity promotes the growth of wAlbB in A. aegypti.…”

Long-term dietary exposure to low concentration of dichloroacetic acid promoted longevity and attenuated cellular and functional declines in aged Drosophila melanogaster

“…Assay was performed as described by Zhao et al (2010). In brief, 100 μl of fly homogenate was incubated with 10 μM DCFH-DA (in dimethyl sulfoxide) and fluorescence was measured using a microplate reader at an excitation and emission wavelength of 485 and 535 nm, respectively.…”

Efficacy of methuselah gene mutation toward tolerance of dichlorvos exposure in Drosophila melanogaster

“…Oxidation of DCFH-DA (in terms of DCF fluorescence) was assayed as a measure of the general index of oxidative stress as described previously by Zhao et al [31]. In brief, 100 ml of fly homogenate (homogenization was performed for 30 s) was incubated with 10 μM dye (in dimethyl sulfoxide) for 30 min in the dark at 2471 1C and fluorescence was measured (60 s intervals) using a Varioskan Flash spectrofluorometer (Thermo Fisher Scientific, Waltham, MA, USA) at excitation/emission wavelengths of 485/535 nm.…”