Adult toxicity and dominant lethals induced by ozone at specific stages in spermatogenesis in Drosophila virilis

Episodic ozone exposure in Long-Evans rats has limited effects on cauda sperm motility and non-coding RNA populations

Epidemiological evidence suggests the potential for air pollutants to induce male reproductive toxicity. In experimental studies, exposure to ozone during sensitive windows in the sperm lifecycle has been associated with impaired sperm motility. Subsequently, we sought to investigate the effects of episodic exposure to ozone during sperm maturation in the rat. Long-Evans rats were exposed to either filtered air or ozone (0.4 or 0.8 ppm) for five non-consecutive days over two weeks. Ozone exposure did not impact male reproductive organ weights or sperm motility ~24hours following the final exposure. Furthermore, circulating sex hormones remained unchanged despite increased T3 and T4 in the 0.8 ppm group. While there was indication of altered adrenergic signaling attributable to ozone exposure in the testis, there were minimal impacts on small non-coding RNAs detected in cauda sperm. Only two piwi-interacting RNAs (piRNAs) were altered in the mature sperm of ozone-exposed rats (piR-rno-346434 and piR-rno-227431). Then data across all rats were analyzed to identify any non-coding RNAs that may be correlated with reduced sperm motility. A total of 7 microRNAs (miRNAs), 8 RNA fragments, and 1,682 piRNAs correlated well with sperm motility. Utilizing our exposure paradigm herein, we were unable to substantiate the relationship between ozone exposure during maturation with sperm motility. However, these approaches served to identify a suite of non-coding RNAs that were associated with sperm motility in rats. With additional investigation, these RNAs may prove to have functional roles in the acquisition of motility or be unique biomarkers for male reproductive toxicity.

An Ozonolysis Based Method and Applications for the Non-Lethal Modification of Insect Cuticular Hydrocarbons

Cuticular hydrocarbons (CHCs) are important, multi-function components of the insect epicuticle. In Drosophila spp., CHCs provide protection from desiccation and serve as semiochemicals for both intra- and interspecific communication. We developed a non-lethal method for the modification of Drosophila CHCs profiles through the exposure of live insects to a high dose of ozone gas (~ 45,000 ppm). Drosophila suzukii that were treated with ozone showed a 1.63-3.10 fold reduction in unsaturated hydrocarbons with these CHCs shown to regenerate over 108 h. Changes in CHCs were correlated with significantly reduced desiccation resistance in both male and female D. suzukii at one h after ozone treatment. Interestingly, individuals treated with ozone showed increased desiccation resistance in comparison to controls at 108 h after ozone treatment. The methodology reported in this paper provides a novel approach to investigate the biosynthesis and functions of CHCs during the lifespan of an insect.

Are Drosophila a useful model for understanding the toxicity of inhaled oxidative pollutants: a review

Oxidative atmospheric pollutants represent a significant stress and cause injury to both vertebrate and invertebrate species. In both, the biosurfaces of their respiratory apparatus are directly exposed to oxidizing pollutant-induced stresses. Respiratory-tract surfaces contain integrated antioxidant systems that appear to provide a primary defense against environmental insults caused by inhaled atmospheric reactive oxygen species (ROS) and reactive nitrogen species (RNS), whether gaseous or particulate. When the biosurface antioxidant defenses are overwhelmed, oxidative and nitrosative stress to the acellular and cellular components of the exposed biosurfaces can ensue via direct chemical reactions that lead to the induction of inflammatory, adaptive, injurious, and reparative processes. The study of model invertebrates (e.g., Drosophila) has a long history of yielding valuable insights into both fundamental biology and pathobiology. Mutants and/or transgenic insects, with specific alterations in key components of innate and/or adaptive antioxidant defense systems and immune genes, offer opportunities to dissect the complex systems that maintain respiratory tract surface defenses against environmental oxidants and the ensuing host responses. In this article, we use a comparative absfont approach to consider interactions of atmospheric oxidant pollutants with selected biosystems. We focused primarily on ozone (O(3)) as the pollutant, vertebrate and invertebrate respiratory tracts as the exposed biosystems, and nonenzymatic micronutrient antioxidants as significant contributors to overall antioxidant defense strategies. We present parallels among these diverse organisms with regard to their protective strategies against environmental atmospheric oxidants, with particular focus given to using the invertebrate Drosophila as a potentially useful model for vertebrate respiratory-tract responses to inhaled oxidants specifically and pollutants in general. We conclude that the insect respiratory system has considerable promise toward understanding novel aspects of vertebrate respiratory tract responses to inhaled oxidative environmental challenges.

Review of the genotoxicity of ozone

Ozone is a powerful oxidant, reactive to biomolecules. In aqueous solution it decomposes to give hydrogen peroxide, superoxide and hydroxy radicals which can take part in secondary reactions. Ozone is a disinfectant that inactivates both viruses and bacteria. Although other reactions are primarily responsible for the inactivation, cellular DNA is also damaged. Ozone is genotoxic to microorganisms, plants and cell cultures in vitro. The results from in vivo cytogenetic studies with laboratory animals after inhalation exposure are contradictory. Chromosome aberrations in lymphocytes, but not SCEs, have been demonstrated in Chinese hamsters but not in mice. Chromatid deletions were induced in pulmonary macrophages in rats. No cytogenetic effects have been reported for bone marrow cells or spermatocytes. The few experimental and epidemiological studies with human subjects do not allow a conclusion on the cytogenetic effects of ozone in lymphocytes in humans. No life-long cancer studies have been performed with ozone. However, after 4 and 6 months of inhalation exposure, lung adenomas were induced in strain A/J mice, but not in Swiss-Webster mice.

Preneoplastic transformation of rat tracheal epithelial cells by ozone

The transforming potency of ozone for rat tracheal epithelial (RTE) cells exposed in vivo or in vitro was determined. RTE cells isolated from rats exposed to ozone (0, 0.14, 0.6, or 1.2 ppm, 6 hr/day, 5 days/week for 1, 2, or 4 weeks) showed no increase in the frequency of preneoplastic transformation compared to cells isolated from unexposed rats, although ozone-induced morphologic changes were observed in exposed tracheas. In contrast, preneoplastic variants of RTE cells were induced by multiple, but not single, exposures of RTE cells to ozone in culture. RTE cells exposed biweekly to ozone (approximately 0.7 ppm for 40 min, nine total exposures) had approximately twofold increases in the frequency of preneoplastic transformation compared to that of concurrent controls exposed to air. Single, 40-min exposures to ozone (approximately 1 or approximately 10 ppm) did not induce preneoplastic variants. However, single, 40-min exposures of RTE cells to approximately 10 ppm ozone did result in approximately 40% decreases in colony-forming efficiency. In addition, single, 40-min exposures of RTE cells to approximately 1 ppm ozone reduced the transforming potency of a subsequent exposure to the direct-acting chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). When multiple ozone exposures followed exposure to MNNG (approximately 0.7 ppm ozone for 40 min, nine biweekly exposures), an additive (or possibly a multiplicative) effect of ozone on MNNG-induced preneoplastic transformation was seen. These results demonstrate that ozone can, under some conditions, induce preneoplastic variants of RTE cells. In addition, depending on the sequence or combinations of exposures, ozone can reduce or, possibly, increase, the transforming potency of the carcinogen MNNG for rat tracheal cells in culture.

Inhalation exposure in Drosophila mutagenesis assays: experiments with aliphatic halogenated hydrocarbons, with emphasis on the genetic activity profile of 1,2-dichloroethane

A series of mutation experiments was carried out with Drosophila melanogaster using inhalation exposure. 1,2-Dichloroethane (DCE) and 1,2-dibromoethane (DBE) were active in the sex-linked recessive lethal assay (SLRLT), whereas dichloromethane, dibromomethane, 1,2-dichloropropane and 1,3-dichloropropane were not. Compared to DBE, DCE is a less potent mutagen in the SLRL system. For both compounds, there is no evidence of a clear-cut dose-rate effect. DCE and dichloromethane were also investigated in the somatic mutation and recombination test (SMART), with results similar to those from the SLRLT. For DCE the genetic activity profile was further analyzed by carrying out a sex-chromosome loss assay and a complementation analysis of a series of induced recessive lethal mutations. A review of the use of inhalation in mutagenicity assays with Drosophila shows that this route of exposure is an effective one. Especially with chronic exposure times, rather low exposure concentrations can be detected. With compounds of intermediate volatility inhalation is not superior to other modes of administration; nor is it likely to be sensitive enough for in situ monitoring.