Synergism of non-thermal plasma and low concentration RSL3 triggers ferroptosis via promoting xCT lysosomal degradation through ROS/AMPK/mTOR axis in lung cancer cells.

BACKGROUND: Though (1S, 3R)-RSL3 has been used widely in basic research as a small molecular inducer of ferroptosis, the toxicity on normal cells and poor pharmacokinetic properties of RSL3 limited its clinical application. Here, we investigated the synergism of non-thermal plasma (NTP) and low-concentration RSL3 and attempted to rise the sensitivity of NSCLC cells on RSL3. METHODS: CCK-8 assay was employed to detect the change of cell viability. Microscopy and flowcytometry were applied to identify lipid peroxidation, cell death and reactive oxygen species (ROS) level respectively. The molecular mechanism was inspected with western blot and RT-qPCR. A xenograft mice model was adopted to investigate the effect of NTP and RSL3. RESULTS: We found the synergism of NTP and low-concentration RSL3 triggered severe mitochondria damage, more cell death and rapid ferroptosis occurrence in vitro and in vivo. NTP and RSL3 synergistically induced xCT lysosomal degradation through ROS/AMPK/mTOR signaling. Furthermore, we revealed mitochondrial ROS was the main executor for ferroptosis induced by the combined treatment. CONCLUSION: Our research shows NTP treatment promoted the toxic effect of RSL3 by inducing more ferroptosis rapidly and provided possibility of RSL3 clinical application.

Hemin enhances radiosensitivity of lung cancer cells through ferroptosis.

The principle underlying radiotherapy is to kill cancer cells while minimizing the harmful effects on non-cancer cells, which has still remained as a major challenge. In relation, ferroptosis has recently been proposed as a novel mechanism of radiation-induced cell death. In this study, we investigated and demonstrated the role of Hemin as an iron overloading agent in the generation of reactive oxygen species (ROS) induced by ionizing radiation in lung cancer and non-cancer cells. It was found that the presence of Hemin in irradiated lung cancer cells enhanced the productivity of initial ROS, resulting in lipid peroxidation and subsequent ferroptosis. We observed that application of Hemin as a co-treatment increased the activity of GPx4 degradation in both cancer and normal lung cells. Furthermore, Hemin protected normal lung cells against radiation-induced cell death, in that it suppressed ROS after radiation, and boosted the production of bilirubin which was a lipophilic ROS antioxidant. In addition, we demonstrated significant FTH1 expression in normal lung cells when compared to lung cancer cells, which prevented iron from playing a role in increasing IR-induced cell death. Our findings demonstrated that Hemin had a dual function in enhancing the radiosensitivity of ferroptosis in lung cancer cells while promoting cell survival in normal lung cells.

Micheliolide Enhances Radiosensitivities of p53-Deficient Non-Small-Cell Lung Cancer via Promoting HIF-1α Degradation.

Micheliolide (MCL) has shown promising anti-inflammatory and anti-tumor efficacy. However, whether and how MCL enhances the sensitivity of non-small-cell lung cancer (NSCLC) to radiotherapy are still unknown. In the present paper, we found that MCL exerted a tumor cell killing effect on NSCLC cells in a dose-dependent manner, and MCL strongly sensitized p53-deficient NSCLC cells, but not the cells with wild-type p53 to irradiation (IR). Meanwhile, MCL markedly inhibited the expression of hypoxia-inducible factor-1α (HIF-1α) after IR and hypoxic exposure in H1299 and Calu-1 cells rather than in H460 cells. Consistently, radiation- or hypoxia-induced expression of vascular endothelial growth factor (VEGF) was also significantly inhibited by MCL in H1299 and Calu-1 cells, but not in H460 cells. Therefore, inhibition of the HIF-1α pathway might, at least in part, contribute to the radiosensitizing effect of MCL. Further study showed that MCL could accelerate the degradation of HIF-1α through the ubiquitin-proteosome system. In addition, the transfection of wild-type p53 into p53-null cells (H1299) attenuated the effect of MCL on inhibiting HIF-1α expression. These results suggest MCL effectively sensitizes p53-deficient NSCLC cells to IR in a manner of inhibiting the HIF-1α pathway via promoting HIF-1α degradation, and p53 played a negative role in MCL-induced HIF-1α degradation.

Targeting Nrf2-mediated heme oxygenase-1 enhances non-thermal plasma-induced cell death in non-small-cell lung cancer A549 cells.

Non-thermal plasma (NTP) treatment has been proposed as a potential approach for cancer therapy for killing cancer cells via generation of reactive oxygen species (ROS). As an antioxidant protein, Heme oxygenase-1 (HO-1) has been known to protect cells against oxidative stress. In this paper, we investigated the role of HO-1 activation in NTP-induced apoptosis in A549 cells. Distinctly increased ROS production and apoptosis were observed after NTP exposure. NTP exposure induced HO-1 expression in a dose- and time-dependent manner via activating the translocation of Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) from cytoplasm to nucleus. Furthermore, inhibiting HO-1 activation with its specific inhibitor, ZnPP, increased "killing" effect of NTP. Knocking down HO-1 or Nrf2 with the special siRNA also led to elevated ROS level and enhanced NTP-induced cell death. In addition, the c-JUN N-terminal kinase (JNK) signaling pathway was shown to be involved in NTP-induced HO-1 expression. Interestingly, a higher resistance to NTP exposure of A549 cell compared to H1299 and H322 cells was found to be linked to its higher basal level of HO-1 expression. These findings revealed that HO-1 could be considered as a potential target to improve the effect of NTP in cancer therapy.

Non-thermal plasma induces mitochondria-mediated apoptotic signaling pathway via ROS generation in HeLa cells.

Non-thermal plasma (NTP) has been proposed as a novel therapeutic method for anticancer treatment. Although increasing evidence suggests that NTP selectively induces apoptosis in some types of tumor cells, the molecular mechanisms underlying this phenomenon remain unclear. In this study, we further investigated possible molecular mechanisms for NTP-induced apoptosis of HeLa cells. The results showed that NTP exposure significantly inhibited the growth and viability of HeLa cells. Morphological observation and flow cytometry analysis demonstrated that NTP exposure induced HeLa cell apoptosis. NTP exposure also activated caspase-9 and caspase-3, which subsequently cleaved poly (ADP- ribose) polymerase. Furthermore, NTP exposure suppressed Bcl-2 expression, enhanced Bax expression and translocation to mitochondria, activated mitochondria-mediated apoptotic pathway, followed by the release of cytochrome c. Further studies showed that NTP treatment led to ROS generation, whereas blockade of ROS generation by N-acetyl-l-cysteine (NAC, ROS scavengers) significantly prevented NTP-induced mitochondrial alteration and subsequent apoptosis of HeLa cells via suppressing Bax translocation, cytochrome c and caspase-3 activation. Taken together, our results indicated that NTP exposure induced mitochondria-mediated intrinsic apoptosis of HeLa cells was activated by ROS generation. These findings provide insights to the therapeutic potential and clinical research of NTP as a novel tool in cervical cancer treatment.

Exogenous Nitric Oxide Suppresses in Vivo X-ray-Induced Targeted and Non-Targeted Effects in Zebrafish Embryos.

The present paper studied the X-ray-induced targeted effect in irradiated zebrafish embryos (Danio rerio), as well as a non-targeted effect in bystander naïve embryos partnered with irradiated embryos, and examined the influence of exogenous nitric oxide (NO) on these targeted and non-targeted effects. The exogenous NO was generated using an NO donor, S-nitroso-N-acetylpenicillamine (SNAP). The targeted and non-targeted effects, as well as the toxicity of the SNAP, were assessed using the number of apoptotic events in the zebrafish embryos at 24 h post fertilization (hpf) revealed through acridine orange (AO) staining. SNAP with concentrations of 20 and 100 µM were first confirmed to have no significant toxicity on zebrafish embryos. The targeted effect was mitigated in zebrafish embryos if they were pretreated with 100 µM SNAP prior to irradiation with an X-ray dose of 75 mGy but was not alleviated in zebrafish embryos if they were pretreated with 20 µM SNAP. On the other hand, the non-targeted effect was eliminated in the bystander naïve zebrafish embryos if they were pretreated with 20 or 100 µM SNAP prior to partnering with zebrafish embryos having been subjected to irradiation with an X-ray dose of 75 mGy. These findings revealed the importance of NO in the protection against damages induced by ionizing radiations or by radiation-induced bystander signals, and could have important impacts on development of advanced cancer treatment strategies.

Low Concentration of Exogenous Carbon Monoxide Modulates Radiation-Induced Bystander Effect in Mammalian Cell Cluster Model.

During radiotherapy procedures, radiation-induced bystander effect (RIBE) can potentially lead to genetic hazards to normal tissues surrounding the targeted regions. Previous studies showed that RIBE intensities in cell cluster models were much higher than those in monolayer cultured cell models. On the other hand, low-concentration carbon monoxide (CO) was previously shown to exert biological functions via binding to the heme domain of proteins and then modulating various signaling pathways. In relation, our previous studies showed that exogenous CO generated by the CO releasing molecule, tricarbonyldichlororuthenium (CORM-2), at a relatively low concentration (20 µM), effectively attenuated the formation of RIBE-induced DNA double-strand breaks (DSB) and micronucleus (MN). In the present work, we further investigated the capability of a low concentration of exogenous CO (CORM-2) of attenuating or inhibiting RIBE in a mixed-cell cluster model. Our results showed that CO (CORM-2) with a low concentration of 30 µM could effectively suppress RIBE-induced DSB (p53 binding protein 1, p53BP1), MN formation and cell proliferation in bystander cells but not irradiated cells via modulating the inducible nitric oxide synthase (iNOS) andcyclooxygenase-2 (COX-2). The results can help mitigate RIBE-induced hazards during radiotherapy procedures.

Non-thermal plasma treatment altered gene expression profiling in non-small-cell lung cancer A549 cells.

BACKGROUND: Recent technological advances in atmospheric plasmas have made the creation of non-thermal atmospheric pressure plasma (NTP) possible for utilization in the medical field. Although accumulated evidence suggests that NTP induces cell death in various cancer cell types thus offering a promising alternative treatment strategy, the mechanism underlying its therapeutic effect is not fully understood. RESULTS: We analyzed relevant signaling cascades associated with the tumor protein p53, in particular the cell cycle arrest, DNA damage as well as the underlying apoptosis pathways. Based on our results, the major effect from plasma exposure was found to be the activation of MAPK and p53 signaling pathways, resulting in changes in gene expression of MEKK, GADD, FOS and JUN. Finally, a significant modulation in expression of genes related to cellular proliferation and differentiation was observed. CONCLUSION: Overall, the presented data of the tumor transcriptome helped identify the key players in modulated gene expression following exposure to plasma at the molecular level, and also helped interpret the downstream processes. The present work laid the foundation for further studies to clarify the roles of multiple pathways in plasma-induced biological processes. Further investigation of these genes in other cell lines may reveal comprehensive mechanisms of plasma induced effects.

Rescue effects: irradiated cells helped by unirradiated bystander cells.

The rescue effect describes the phenomenon where irradiated cells or organisms derive benefits from the feedback signals sent from the bystander unirradiated cells or organisms. An example of the benefit is the mitigation of radiation-induced DNA damages in the irradiated cells. The rescue effect can compromise the efficacy of radioimmunotherapy (RIT) (and actually all radiotherapy). In this paper, the discovery and subsequent confirmation studies on the rescue effect were reviewed. The mechanisms and the chemical messengers responsible for the rescue effect studied to date were summarized. The rescue effect between irradiated and bystander unirradiated zebrafish embryos in vivo sharing the same medium was also described. In the discussion section, the mechanism proposed for the rescue effect involving activation of the nuclear factor κB (NF-κB) pathway was scrutinized. This mechanism could explain the promotion of cellular survival and correct repair of DNA damage, dependence on cyclic adenosine monophosphate (cAMP) and modulation of intracellular reactive oxygen species (ROS) level in irradiated cells. Exploitation of the NF-κB pathway to improve the effectiveness of RIT was proposed. Finally, the possibility of using zebrafish embryos as the model to study the efficacy of RIT in treating solid tumors was also discussed.

Low concentration of exogenous carbon monoxide protects mammalian cells against proliferation induced by radiation-induced bystander effect.

Radiation-induced bystander effect (RIBE) has been proposed to have tight relationship with the irradiation-caused secondary cancers beyond the irradiation-treated area after radiotherapy. Our previous studies demonstrated a protective effect of low concentration carbon monoxide (CO) on the genotoxicity of RIBE after α-particle irradiation. In the present work, a significant inhibitory effect of low-dose exogenous CO, generated by tricarbonyldichlororuthenium (II) dimer [CO-releasing molecule (CORM-2)], on both RIBE-induced proliferation and chromosome aberration was observed. Further studies on the mechanism revealed that the transforming growth factor ß1/nitric oxide (NO) signaling pathway, which mediated RIBE signaling transduction, could be modulated by CO involved in the protective effects. Considering the potential of exogenous CO in clinical applications and its protective effect on RIBE, the present work aims to provide a foundation for potential application of CO in radiotherapy.

Exogenous carbon monoxide promotes GPX4-dependent ferroptosis through ROS/GSK3ß axis in non-small cell lung cancer.

The gas therapy is drawing increasing attention in the treatment of many diseases including cancer. As one of gas signaling molecules, carbon monoxide (CO) has been proved to exert anti-cancer effects via triggering multiple cell death types, such as autophagy, apoptosis and necrosis. Here, we showed that low concentration CO delivered from CO-releasing molecule 3 (CORM-3) effectively induced ferroptosis, known as a novel proinflammatory programmed cell death, in vitro and in vivo. Mechanistically, we found that CO triggered ferroptosis by modulating the ROS/GSK3ß/GPX4 signaling pathway, resulting in the accumulation of lipid hydroperoxides and the occurrence of ferroptosis. We think our findings provide novel insights into the anti-cancer mechanisms of CO, and suggest that CO could potentially be exploited as a novel ferroptosis inducer for cancer treatment in the future.

Bystander effect between zebrafish embryos in vivo induced by high-dose X-rays.

We employed embryos of the zebrafish, Danio rerio, for our studies on the in vivo bystander effect between embryos irradiated with high-dose X-rays and naive unirradiated embryos. The effects on the naive whole embryos were studied through quantification of apoptotic signals at 25 h post fertilization (hpf) through the terminal dUTP transferase-mediated nick end-labeling (TUNEL) assay followed by counting the stained cells under a microscope. We report data showing that embryos at 5 hpf subjected to a 4-Gy X-ray irradiation could release a stress signal into the medium, which could induce a bystander effect in partnered naive embryos sharing the same medium. We further demonstrated that this bystander effect (induced through partnering) could be successfully suppressed through the addition of the nitric oxide (NO) scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) into the medium but not through the addition of the CO liberator tricarbonylchloro(glycinato)ruthenium(II) (CORM-3). This shows that NO was involved in the bystander response between zebrafish embryos induced through X-ray irradiation. We also report data showing that the bystander effect could be successfully induced in naive embryos by introducing them into the irradiated embryo conditioned medium (IECM) alone, i.e., without partnering with the irradiated embryos. The IECM was harvested from the medium that had conditioned the zebrafish embryos irradiated at 5 hpf with 4-Gy X-ray until the irradiated embryos developed into 29 hpf. NO released from the irradiated embryos was unlikely to be involved in the bystander effect induced through the IECM because of the short life of NO. We further revealed that this bystander effect (induced through IECM) was rapidly abolished through diluting the IECM by a factor of 2× or greater, which agreed with the proposal that the bystander effect was an on/off response with a threshold.

The threshold number of protons to induce an adaptive response in zebrafish embryos.

In this study, microbeam protons were used to provide the priming dose to induce an in vivo radioadaptive response (RAR) in the embryos of zebrafish, Danio rerio, against subsequent challenging doses provided by x-ray photons. The microbeam irradiation system (Single-Particle Irradiation System to Cell, acronym SPICE) at the National Institute of Radiological Sciences (NIRS), Japan, was employed. The embryos were dechorionated at 4 h post fertilisation (hpf) and irradiated at 5 hpf by microbeam protons. For each embryo, one irradiation point was chosen, to which 5, 10, 20, 30, 40, 50, 100, 200, 300 and 500 protons each with an energy of 3.4 MeV were delivered. The embryos were returned to the incubator until 10 hpf to further receive the challenging exposure, which was achieved using 2 Gy of x-ray irradiation, and then again returned to the incubator until 24 hpf for analyses. The levels of apoptosis in zebrafish embryos at 25 hpf were quantified through terminal dUTP transferase-mediated nick end-labelling (TUNEL) assay. The results revealed that at least 200 protons (with average radiation doses of about 300 and 650 mGy absorbed by an irradiated epithelial and deep cell, respectively) would be required to induce RAR in the zebrafish embryos in vivo. Our previous investigation showed that 5 protons delivered at 10 points on an embryo would already be sufficient to induce RAR in the zebrafish embryos. The difference was explained in terms of the radiation-induced bystander effect as well as the rescue effect.

Adaptive response to ionising radiation induced by cadmium in zebrafish embryos.

An adaptive response is a biological response where the exposure of cells or animals to a low priming exposure induces mechanisms that protect the cells or animals against the detrimental effects of a subsequent larger challenging exposure. In realistic environmental situations, living organisms can be exposed to a mixture of stressors, and the resultant effects due to such exposures are referred to as multiple stressor effects. In the present work we demonstrated, via quantification of apoptosis in the embryos, that embryos of the zebrafish (Danio rerio) subjected to a priming exposure provided by one environmental stressor (cadmium in micromolar concentrations) could undergo an adaptive response against a subsequent challenging exposure provided by another environmental stressor (alpha particles). We concluded that zebrafish embryos treated with 1 to 10 µM Cd at 5 h postfertilisation (hpf) for both 1 and 5 h could undergo an adaptive response against subsequent ~4.4 mGy alpha-particle irradiation at 10 hpf, which could be interpreted as an antagonistic multiple stressor effect between Cd and ionising radiation. The zebrafish has become a popular vertebrate model for studying the in vivo response to ionising radiation. As such, our results suggested that multiple stressor effects should be carefully considered for human radiation risk assessment since the risk may be perturbed by another environmental stressor such as a heavy metal.

The multiple stressor effect in zebrafish embryos from simultaneous exposure to ionising radiation and cadmium.

Living organisms are exposed to a mixture of environmental stressors, and the resultant effects are referred to as multiple stressor effects. In the present work, we studied the multiple stressor effect in embryos of the zebrafish (Danio rerio) from simultaneous exposure to ionising radiation (alpha particles) and cadmium through quantification of apoptotic signals at 24 h postfertilisation (hpf) revealed by vital dye acridine orange staining. For each set of experiments, 32-40 dechorionated embryos were deployed, which were divided into four groups each having 8-10 embryos. The four groups of embryos were referred to as (1) the control group (C), which received no further treatments after dechorionation; (2) the Cd-dosed and irradiated group (CdIr), which was exposed to 100 µM Cd from 5 to 24 hpf, and also received about 4.4 mGy from alpha particles at 5 hpf; (3) the irradiated group (Ir), which received about 4.4 mGy from alpha particles at 5 hpf; and (4) the Cd-dosed group (Cd), which was exposed to 100 µM Cd from 5 to 24 hpf. In general, the CdIr, Ir and Cd groups had more apoptotic signals than the C group. Within the 12 sets of experimental results, two showed significant synergistic effects, one showed a weakly synergistic effect and nine showed additive effects. The multiple stressor effect of 100 µM Cd with ~4.4 mGy alpha-particle radiation resulted in an additive or synergistic effect, but no antagonistic effect. The failure to identify significant synergistic effects for some sets of data, and thus their subsequent classification as additive effects, might be a result of the relatively small magnitude of the synergistic effects. The results showed that the radiation risk could be perturbed by another environmental stressor such as a heavy metal, and as such a realistic human radiation risk assessment should in general take into account the multiple stressor effects.

Ferroptosis triggered by STAT1- IRF1-ACSL4 pathway was involved in radiation-induced intestinal injury.

Radiation-induced intestinal injury (RIII), a common gastrointestinal complication caused by radiotherapy on pelvic, abdominal and retroperitoneal tumors, seriously affects the life quality of patients and may result in termination of radiotherapy. At present, the pathogenesis of RIII has not been fully understood. Herein, we demonstrated that ferroptosis played a critical role in RIII occurrence. The RNA sequencing analysis strongly hinted ferroptosis was involved in RIII mice. In line with this, the levels of 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA), markers of lipid peroxidation, remarkably increased in RIII mice. And the ferroptosis inhibitor, Ferrostatin-1 (Fer-1), improved the mice survival and alleviated intestinal fibrosis in vivo. Moreover, our results revealed that arachidonic acid (AA) enhanced ferroptosis in cultured intestinal epithelial cells (IECs) and organoids in vitro after irradiation, and AA gavage aggravated RIII in mice. Mechanistic studies revealed the level of ACSL4 protein significantly increased in mouse jejunums and IECs after irradiation. Radiation-induced ferroptosis in IECs was also prevented following ACSL4 knockdown or with the function inhibitor of ACSL4. Furthermore, we found that transcription of ACSL4 induced by irradiation was regulated by STAT1/IRF1 axis, and AMPK activation triggered by AA negatively regulated radiation-induced ferroptosis. Taken together, our results suggest that ferroptosis mediates RIII and reducing dietary AA intake as well as targeting the STAT1-IRF1-ACSL4 axis or AMPK may be the potential approaches to alleviate RIII.

Ionizing Radiation Triggers the Antitumor Immunity by Inducing Gasdermin E-Mediated Pyroptosis in Tumor Cells.

PURPOSE: To understand pyroptosis induced by ionizing radiation and its implications for radiation therapy, we explored the involved factors, possible mechanisms of radiation-induced pyroptosis and consequent antitumor immunity. METHODS AND MATERIALS: The occurrence of pyroptosis was assessed by cell morphology, lactate dehydrogenase release, Annexin V/PI staining and the cleavage of Gasdermin E (GSDME). Cell radiosensitivity was tested with MTT and colony survival assays. Xenograft tumor volume, Ki-67, CD8+ lymphocytes, and ELISA were used to evaluate the effect of GSDME on tumor suppression after irradiation. RESULTS: Irradiation induced pyroptosis in GSDME high-expressing tumor cell lines covering lung, liver, breast, and glioma cancers. Cleavage of GSDME occurred in a dose- and time-dependent manner after irradiation, and pyroptosis could be induced by various kinds of irradiation. The combination of chemotherapy drugs for DNA damage (cisplatin or etoposide) or demethylation (decitabine or azacytidine) and irradiation significantly enhanced the occurrence of pyroptosis. Moreover, we revealed that the Caspase 9/Caspase 3/GSDME pathway was involved in irradiation-induced pyroptosis. Notably, enhanced tumor suppression was observed in Balb/c mice bearing GSDME-overexpressing 4T1 tumors compared with those bearing vector tumors for the promotion of antitumor immunity, which was manifested as distinctly elevated levels of cytotoxic T lymphocytes and release of the related cytokines rather than the direct effect of pyroptosis on tumor cell radiosensitivity. CONCLUSIONS: As an immunogenic cell death caused by radiation, pyroptosis promotes antitumor immunity after irradiation. Our findings may provide new insights to improve the efficacy of tumor radiation therapy.

Impact of COVID-19 on the sleep-wake patterns of preschool children.

OBJECTIVE: To explore the impact of the COVID-19 pandemic on the sleep-wake patterns of preschool children. METHODS: A cohort of preschoolers established before the COVID-19 pandemic was invited to participate in this study. Data including children's demographics, their own and parental sleep-wake patterns, physical activities, and screen time were collected through an online questionnaire from August to September 2020. A comparison was made on the collected data from the same cohort of children before and during the pandemic. RESULTS: The cohort which was established before the pandemic consisted of 3720 preschoolers. For this current study, 642 (17%) participated, and 497 (13%) children who fulfilled the eligibility criteria were included in the final analysis. They showed a delay in their bedtime and wake time on both weekdays and weekends with a 15-30 min increase in nocturnal sleep duration. However, with a reduction in nap time, the average daily sleep duration was shortened by 16.3 ± 64.3 min (p < 0.001) and 27.5 ± 72.9 min (p < 0.001) during weekdays and weekends, respectively. Screen time was increased while outdoor activity duration was decreased. Parental sleep/wake times were also delayed with an increase in sleep duration. Children's sleep habits were associated with screen time and parental sleep/wake patterns. CONCLUSION: Despite school suspension during the COVID-19 pandemic, preschoolers were not sleeping longer. Screen time and parental sleep/wake patterns were the major factors driving the preschoolers' sleep habits. Health education is required to control screen time in children and to promote sleep hygiene among all family members.

Hormetic effect induced by alpha-particle-induced stress communicated in vivo between zebrafish embryos.

We report data showing that embryos of the zebrafish, Danio rerio, at 1.5 h post fertilization (hpf) subjected to a low-dose alpha-particle irradiation can release a stress signal into the water, which can be communicated to unirradiated bystander zebrafish embryos sharing the same water medium to induce a hormetic effect in the bystander embryos. Hormetic responses are characterized as biphasic dose-response relationships exhibiting a low-dose stimulation and a high-dose inhibition. The effects on the whole embryos were studied through quantification of apoptotic signals at 24 hpf through staining with the vital dye acridine orange, followed by counting the stained cells under a microscope. The results show that, for low alpha-particle dose, the number of apoptotic signals decreases in the irradiated embryos and also in the unirradiated bystander embryos having partnered with the irradiated embryos. These suggested that alpha-particle-irradiated zebrafish embryos could release a stress signal into the water, which could be communicated to unirradiated bystander zebrafish embryos sharing the same water medium to induce a hormetic effect in the bystander embryos.

α-Particle irradiated zebrafish embryos rescued by bystander unirradiated zebrafish embryos.

We report data demonstrating that zebrafish embryos irradiated by α-particles can release a stress signal into the water, which can be communicated to the unirradiated zebrafish embryos sharing the same water medium, and then these unirradiated zebrafish embryos can release a feedback stress signal back to the irradiated embryos. The effects of radiation on the whole embryos were studied through quantification of apoptotic signals at 24 h post fertilization through staining with the vital dye acridine orange, followed by counting the stained cells under a microscope. We refer to this phenomenon as the "rescue effect", where the unirradiated embryos successfully helped the irradiated embryos mitigate the radiation induced DNA damages. The results showed that the number of apoptotic signals in the irradiated embryos was smaller when they were partnered with bystander unirradiated embryos in the same medium. The results also showed significantly fewer apoptotic signals in the irradiated embryos when the population of bystander embryos increased from 10 to 30, while keeping the population of irradiated embryos at 10. These data suggest that the stress communicated between the unirradiated zebrafish embryos and the irradiated embryos sharing the same medium will help "rescue" the irradiated embryos, and that the strength of the rescue effect depends on the number of rescuing bystander unirradiated embryos.