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In this paper, the chronotoxicity of radiofrequency fields (RF) in the pubertal testis development and the involved molecular pathways were investigated by exposing four-week-old mice to RF (1800 MHz, SAR, 0.50 W/kg) in the morning and evening of each day for three weeks. Then, pathological changes and functional indices within the testis were determined. We also used a long non-coding RNA (lncRNA) microarray and GO/KEGG pathway analyses to determine lncRNA expression profiles and predict their potential functions. The cis and trans regulation of lncRNAs were investigated, and an interaction network was constructed using Cytoscape software. RF exposure led to a range of pathological changes in the testes of adolescent mice, as testicular weights and daily sperm productions decreased, and the testosterone secretion reduced. Furthermore, RF induced dysregulation in the expression of testicular lncRNAs. We identified 615 and 183 differentially expressed lncRNAs that were associated with morning and evening exposure to RF, respectively. From 15 differential expression lncRNAs both in morning RF group and evening RF group, we selected 6 lncRNAs to be validated by quantitative reverse transcription PCR (qRT-PCR). The differentially expressed lncRNAs induced by morning RF exposure were highly correlated with many different pathways, including Fanconi syndrome, metabolic processes, cell cycle, DNA damage, and DNA replication. Trans-regulation analyses further showed that differentially expressed lncRNAs were involved in multiple transcription factor-regulated pathways, such as TCFAP4, NFkB, HINFP, TFDP2, FoxN1, and PAX5. These transcription factors have all been shown to be involved in the modulation of testis development, cell cycle progression, and spermatogenesis. These findings suggest that the extent to which 1800 MHz RF induced toxicity in the testes and changed the expression of lncRNAs showed differences between morning exposure and evening exposure. These data indicate that differentially expressed lncRNAs play crucial roles in the RF exposure damage to the developing pubertal testis. Collectively, our findings provide a better understanding of the mechanisms underlying the toxic effects of RF exposure on testicular development.

Introduction: The ratio of Ce3+/Ce4+ in their structure confers unique functions on cerium oxide nanoparticles (CeO2NPs) containing rare earth elements in scavenging free radicals and protecting against oxidative damage. The potential of CeO2NPs to protect testosterone synthesis in primary mouse Leydig cells during exposure to 1,800 MHz radiofrequency (RF) radiation was examined in vitro. Methods: Leydig cells were treated with different concentrations of CeO2NPs to identify the optimum concentration for cell proliferation. The cells were pretreated with the optimum dose of CeO2NPs for 24 hrs and then exposed to 1,800 MHz RF at a power density of 200.27 µW/cm2 (specific absorption rate (SAR), 0.116 W/kg) for 1 hr, 2 hrs, or 4 hrs. The medium was used to measure the testosterone concentration. The cells were collected to determine the antioxidant indices (catalase [CAT], malondialdehyde [MDA], and total antioxidant capacity [T-AOC]), and the mRNA expression of the testosterone synthase genes (Star, Cyp11a1, and Hsd-3β) and clock genes (Clock, Bmal1, and Rorα). Results: Our preliminary result showed that 128 μg/mL CeO2NPs was the optimum dose for cell proliferation. Cells exposed to RF alone showed reduced levels of testosterone, T-AOC, and CAT activities, increased MDA content, and the downregulated genes expression of Star, Cyp11a1, Hsd-3β, Clock, Bmal1, and Rorα. Pretreatment of the cells with 128 μg/mL CeO2NPs for 24 hrs followed by RF exposure significantly increased testosterone synthesis, upregulated the expression of the testosterone synthase and clock genes, and increased the resistance to oxidative damage in Leydig cells compared with those in cells exposed to RF alone. Conclusion: Exposure to 1,800 MHz RF had adverse effects on testosterone synthesis, antioxidant levels, and clock gene expression in primary Leydig cells. Pretreatment with CeO2NPs prevented the adverse effects on testosterone synthesis induced by RF exposure by regulating their antioxidant capacity and clock gene expression in vitro. Further studies of the mechanism underlying the protective function of CeO2NPs against RF in the male reproductive system are required.

This paper presents a new recursive identification method which can efficiently estimate time-varying parameters in discrete time systems and has significant advantages over standard recursive leas...

Our recent study showed that quiescent G0 cells are more resistant to ionizing radiation than G1 cells; however, the underlying mechanism for this increased radioresistance is unknown. Based on the relatively lower DNA damage induced in G0 cells, we hypothesize that these cells are exposed to less oxidative stress during exposure. As a catalytic subunit of NADPH oxidase, Ras-related C3 botulinum toxin substrate 2 (RAC2) may be involved in the cellular response to ionizing radiation. Here, we show that RAC2 was expressed at low levels in G0 cells but increased substantially in G1 cells. Relative to G1 cells, the total antioxidant capacity in G0 phase cells increased upon exposure to X-ray radiation, whereas the intracellular concentration of ROS and malondialdehyde increased only slightly. The induction of DNA single- and double-stranded breaks in G1 cells by X-ray radiation was inhibited by knockdown of RAC2. P38 MAPK interaction with RAC2 resulted in a decrease of functional RAC2. Increased phosphorylation of P38 MAPK in G0 cells also increased cellular radioresistance; however, excessive production of ROS caused P38 MAPK dephosphorylation. P38 MAPK, phosphorylated P38 MAPK, and RAC2 regulated in mutual feedback and negative feedback regulatory pathways, resulting in the radioresistance of G0 cells.

Radiation-induced bystander effects are well-established phenomena, in which DNA damage responses are induced not only in the directly irradiated cells but also in the non-irradiated bystander cells through intercellular signal transmission. Recent studies hint that bystander effects are possibly mediated via small non-coding RNAs, especially microRNAs. Thus, more details about the roles of microRNA in bystander effects are urgently needed to be elucidated. Here we demonstrated that bystander effects were induced in human fetal lung MRC-5 fibroblasts through medium-mediated way by different types of radiation. We identified a set of differentially expressed microRNAs in the cell culture medium after irradiation, among which the up-regulation of miR-21 was further verified with qRT-PCR. In addition, we found significant upregulation of miR-21 in both directly irradiated cells and bystander cells, which was confirmed by the expression of miR-21 precursor and its target genes. Transfection of miR-21 mimics into non-irradiated MRC-5 cells caused bystander-like effects. Taken together, our data reveals that miR-21 is involved in radiation-induced bystander effects. Elucidation of such a miRNA-mediated bystander effect is of utmost importance in understanding the biological processes related to ionizing radiation and cell-to-cell communication.

The mechanisms of radiation-induced bystander effects (RIBE) have been investigated intensively over the past two decades. Although quite a few reports demonstrated that cytokines such as TGF-β1 are induced within the directly irradiated cells and play critical roles in mediating the bystander effects, little is known about the signaling pathways that occur in bystander cells. The crucial question as to why RIBE signals cannot be infinitely transmitted, therefore, remains unclear. In the present study, we showed that miR-663, a radiosensitive microRNA, participates in the regulation of biological effects in both directly irradiated and bystander cells via its targeting of TGF-β1. MiR-663 was downregulated, while TGFB1 was upregulated in directly irradiated cells. The regulation profile of miR-663 and TGFB1, on the other hand, was reversed in bystander cells, in which an elevated miR-663 expression was exhibited and led to downregulation of TGF-β1. Further studies revealed that miR-663 interacts with TGFB1 directly and that through its binding to the core regulation sequence, miR-663 suppresses the expression of TGFB1. Based on the results, we propose that miR-663 inhibits the propagation of RIBE in a feedback mode, in which the induction of TGF-β1 by reduced miR-663 in directly irradiated cells leads to increased level of miR-663 in bystander cells. The upregulation of miR-663 in turn suppresses the expression of TGF-β1 and limits further transmission of the bystander signals.