Lukas Margaritis

Electromagnetic fields (EMFs) disrupt the electrochemical balance of biological membranes, thereby causing abnormal cation movement and deterioration of the function of membrane voltage-gated ion channels. These can trigger an increase of oxidative stress (OS) and the impairment of all cellular functions, including DNA damage and subsequent carcinogenesis. In this review we focus on the main mechanisms of OS generation by EMF-sensitized NADPH oxidase (NOX), the involved OS biochemistry, and the associated key biological effects.

The dielectric properties of biological tissues can contribute non-invasively to a better characterization and understanding of the structural properties and physiology of living organisms. The question we asked, is whether these induced changes are effected by an endogenous or exogenous cellular stress, and can they be detected non-invasively in the form of a dielectric response, e.g., an AC conductivity switch in the broadband frequency spectrum. This study constitutes the first methodological approach for the detection of environmental stress-induced damage in mammalian tissues by the means of broadband dielectric spectroscopy (BDS) at the frequencies of 1–10⁶ Hz. Firstly, we used non-ionizing (NIR) and ionizing radiation (IR) as a typical environmental stress. Specifically, rats were exposed to either digital enhanced cordless telecommunication (DECT) radio frequency electromagnetic radiation or to γ-radiation, respectively. The other type of stress, characterized usually by high genomic instability, was the pathophysiological state of human cancer (lung and prostate). Analyzing the results of isothermal dielectric measurements provided information on the tissues’ water fraction. In most cases, our methodology proved sufficient in detecting structural changes, especially in the case of IR and malignancy. Useful specific dielectric response patterns are detected and correlated with each type of stress. Our results point towards the development of a dielectric-based methodology for better understanding and, in a relatively invasive way, the biological and structural changes effected by radiation and developing lung or prostate cancer often associated with genomic instability.

The daily use by people of wireless communication devices has increased exponentially in the last decade, begetting concerns regarding its potential health hazards. Drosophila melanogaster four days-old adult female flies were exposed for 30 min to radiation emitted by a commercial mobile phone at a SAR of 0.15 W/kg and a SAE of 270 J/kg. ROS levels and apoptotic follicles were assayed in parallel with a genome-wide microarrays analysis. ROS cellular contents were found to increase by 1.6-fold (x), immediately after the end of exposure, in follicles of pre-choriogenic stages (germarium - stage 10), while sporadically generated apoptotic follicles (germarium 2b and stages 7–9) presented with an averaged 2x upregulation in their sub-population mass, 4 h after fly's irradiation with mobile device. Microarray analysis revealed 168 genes being differentially expressed, 2 h post-exposure, in response to radiofrequency (RF) electromagnetic field-radiation exposure (≥1.25x, P < 0.05) and associated with multiple and critical biological processes, such as basic metabolism and cellular subroutines related to stress response and apoptotic death. Exposure of adult flies to mobile-phone radiation for 30 min has an immediate impact on ROS production in animal's ovary, which seems to cause a global, systemic and non-targeted transcriptional reprogramming of gene expression, 2 h post-exposure, being finally followed by induction of apoptosis 4 h after the end of exposure. Conclusively, this unique type of pulsed radiation, mainly being derived from daily used mobile phones, seems capable of mobilizing critical cytopathic mechanisms, and altering fundamental genetic programs and networks in D. melanogaster.

In eukaryotes, the ubiquitin–proteasome machinery regulates a number of fundamental cellular processes through accurate and tightly controlled protein degradation pathways. We have, herein, examined the effects of proteasome functional disruption in Dmp53 ^+/+ (wild-type) and Dmp53 ^−/− Drosophila melanogaster fly strains through utilization of Bortezomib, a proteasome-specific inhibitor. We report that proteasome inhibition drastically shortens fly life-span and impairs climbing performance, while it also causes larval lethality and activates developmentally irregular cell death programs during oogenesis. Interestingly, Dmp53 gene seems to play a role in fly longevity and climbing ability. Moreover, Bortezomib proved to induce endoplasmic reticulum (ER) stress that was able to result in the engagement of unfolded protein response (UPR) signaling pathway, as respectively indicated by fly Xbp1 activation and Ref(2)P-containing protein aggregate formation. Larva salivary gland and adult brain both underwent strong ER stress in response to Bortezomib, thus underscoring the detrimental role of proteasome inhibition in larval development and brain function. We also propose that the observed upregulation of autophagy operates as a protective mechanism to “counterbalance” Bortezomib-induced systemic toxicity, which is tightly associated, besides ER stress, with activation of apoptosis, mainly mediated by functional Drice caspase and deregulated dAkt kinase. The reduced life-span of exposed to Bortezomib flies overexpressing Atg1_RNAi or Atg18_RNAi supports the protective nature of autophagy against proteasome inhibition-induced stress. Our data reveal the in vivo significance of proteasome functional integrity as a major defensive system against cellular toxicity likely occurring during critical biological processes and morphogenetic courses.

17-Allylamino-17-demethoxygeldanamycin (17-AAG), a benzoquinone ansamycin antibiotic, specifically targets heat shock protein 90 (Hsp90) and interferes with its function as a molecular chaperone that maintains the structural and functional integrity of various protein clients involved in cellular signaling. In this study, we have investigated the effect of 17-AAG on the regulation of Hsp90-dependent signaling pathways directly implicated in cell cycle progression, survival and motility of human urinary bladder cancer cell lines.

Cigarette smoke (CS) is the main cause in the development of chronic obstructive pulmonary disease (COPD), the pathogenesis of which is related to an extended inflammatory response. In this study, we investigated the effect of low and high doses of gas phase cigarette smoke (GPS) on cultured lymphocyte progenitor cells, using techniques to assess cell viability and to elucidate whether cells die of apoptosis or necrosis upon exposure to different doses of GPS.

Modern molecular approaches on the genome of enteroviruses’ circulating strains have established new data about the mechanism and significance of its evolution. In the present study, 46 enteroviruses isolates, belonging to HEV-B species and exhibiting distinct origin in geographical or chronological terms, were investigated concerning their primary structure and phylogeny. Two regions of the aforementioned strains genome, which have not been thoroughly investigated (2B and 5′ extreme of 2C) were amplified and sequenced for the first time. Phylogenetic and nucleotide analysis of the isolates’ fragments, along with representative prototype sequences, demonstrate that the classification scheme of monophyly and accordance with the genotype, which characterizes VP1 region, is seriously disturbed. Moreover, the phylogenetic trees constructed from adjacent regions of the genome appear radically incongruent suggesting that the parameters that affect these portions are different or act in a different extent. Our study results an additional step in the study of enteroviruses evolution and inheritance, by investigating unstudied regions of newly sequenced strains and revealing that the primary structure and phylogeny of them is different not only comparably to the structural genome but also from one to another.

In the present study, we demonstrate the apoptotic events of the ovarian follicle cells during the late stages of oogenesis in Drosophila melanogaster. Follicle cell morphology appears normal from stage 10 up to stage 14, exhibiting a euchromatic nucleus and a well-organized cytoplasm. First signs of apoptosis appear at the anterior pole of the egg chamber at stage 14A. They are characterized by loss of microvilli at the apical cell membrane, alterations in nuclear morphology, such as chromatin condensation and convolution of the nuclear membrane, and also by condensation and vacuolization of the cytoplasm. During the following stage 14B, the follicle cell nuclei contain fragmented DNA as is demonstrated by acridine orange staining and TUNEL (TdT-mediated dUTP nick end-labeling) assay. Finally, the apoptotic follicle cells seem to detach from the eggshell when the mature egg chamber exits the ovariole. The detached follicle cells exhibit condensed nuclear chromatin, a disorganized cytoplasm with crowded organelles and are surrounded by epithelial cells. The above results seem to be associated with the abundant phagocytosis that we observed at the entry of the lateral oviducts, where the epithelial cells contain apoptotic cell bodies. Additionally, we tested the effect of etoposide treatment in the follicular epithelium and found that it induces apoptosis in a stage- and site-specific manner. These observations suggest a possible method of absorption of the apoptotic follicle cells that prevents the blockage of the ovarioles and helps the regular production of mature eggs.

In the present study, we demonstrate the actin cytoskeleton reorganization during nurse cells apoptosis of the olive fruit fly Dacus oleae. At the developmental stage 9A of oogenesis, the actin microfilaments are assembled in numerous ring canals and subcortically support all the nurse cells, as is shown by phalloidin‐FITC staining. During the following stages, 9B and 10A, this structural pattern remains the same. The developmental stage 10B is characterized by actin microfilament rearrangement and formation of actin cables that are symmetrically organized around the nurse cell nuclei. At stage 11, when the dumping process begins, these actin cables seem to retain each nurse cell nucleus in the cell center, away from blocking the ring canals. The early stage 12 is characterized by an asynchronous nurse cell nuclear chromatin condensation, while at late stage 12 the actin cables become very thick, as adjacent ones overlap one another and traverse the disorganized apoptotic nurse cell nuclei that already have fragmented DNA, as is demonstrated by acridine orange staining and TUNEL assay. Finally, during stage 13, the apoptotic nuclear remnants are phagocytosed by the neighboring follicle cells. The data presented herein compared to previous reported results in Drosophila [Nezis et al., 2000: Eur J Cell Biol 79:610–620], demonstrate that actin cytoskeleton reorganization during nurse cell apoptosis is a developmentally regulated physiological mechanism, phylogenetically conserved in higher Dipteran. Cell Motil. Cytoskeleton 48:224–233, 2001.