Pre-Exposure to 50 Hz Magnetic Fields Modifies Menadione-Induced Genotoxic Effects in Human SH-SY5Y Neuroblastoma Cells

BACKGROUND: Extremely low frequency (ELF) magnetic fields (MF) are generated by power lines and various electric appliances. They have been classified as possibly carcinogenic by the International Agency for Research on Cancer, but a mechanistic explanation for carcinogenic effects is lacking. A previous study in our laboratory showed that pre-exposure to ELF MF altered cancer-relevant cellular responses (cell cycle arrest, apoptosis) to menadione-induced DNA damage, but it did not include endpoints measuring actual genetic damage. In the present study, we examined whether pre-exposure to ELF MF affects chemically induced DNA damage level, DNA repair rate, or micronucleus frequency in human SH-SY5Y neuroblastoma cells. METHODOLOGY/PRINCIPAL FINDINGS: Exposure to 50 Hz MF was conducted at 100 µT for 24 hours, followed by chemical exposure for 3 hours. The chemicals used for inducing DNA damage and subsequent micronucleus formation were menadione and methyl methanesulphonate (MMS). Pre-treatment with MF enhanced menadione-induced DNA damage, DNA repair rate, and micronucleus formation in human SH-SY5Y neuroblastoma cells. Although the results with MMS indicated similar effects, the differences were not statistically significant. No effects were observed after MF exposure alone. CONCLUSIONS: The results confirm our previous findings showing that pre-exposure to MFs as low as 100 µT alters cellular responses to menadione, and show that increased genotoxicity results from such interaction. The present findings also indicate that complementary data at several chronological points may be critical for understanding the MF effects on DNA damage, repair, and post-repair integrity of the genome

Aurinkosuojautuminen 16–20-vuotiaiden nuorten kokemana

Tutkimuksen tarkoituksena oli kuvata 16–20-vuotiaiden suomalaisnuorten aurinkosuojautumista. Tutkimus liittyy valtakunnalliseen nuorten aurinkosuojautumiskampanjaan, jota ovat yhteistyössä toteuttaneet Säteilyturvakeskus, Ilmatieteen laitos, Syöpäjärjestöt sekä Itä-Suomen yliopisto. Tutkimusaineisto muodostuu yhdentoista nuoren yksilöhaastatteluista (n=11) ja se kerättiin kaksivaiheisesti; nuorten aurinkosuojautumiskampanjan suunnitteluvaiheessa vuonna 2020 sekä kampanjan jatkuessa joulukuun 2021 ja tammikuun 2022 välisenä aikana. Tutkimuksen aineisto analysoitiin induktiivisella sisällönanalyysillä. Tulosten mukaan nuoret suojautuivat auringolta pääasiassa aurinkovoiteella, päähineellä ja olemalla varjossa. Nuorten aurinkosuojautumiseen vaikuttivat aurinkoon ja auringon ottamiseen liittyvät asenteet, aurinkoon ja auringon terveysvaikutuksiin liittyvät tiedot sekä muut tekijät, kuten esimerkiksi aikaan ja paikkaan liittyvät tekijät, sosiaalinen verkosto sekä käsitykset ihon palamisesta. Aurinkoon liittyvät tiedot vaikuttivat nuorten suojautumiseen, mutta varsin hyvätkään tiedot eivät taanneet riittävää aurinkosuojautumista, sillä nuorten oli vaikeaa nähdä ihosyövän koskettavan heitä itseään. Nuorten mukaan aurinkosuojautumista olisi mahdollista edistää puhumalla aiheesta enemmän ja lisäämällä nuorten auringon haittoihin ja aurinkosuojautumiseen liittyvää tietoa niin kouluissa kuin sosiaalisessa mediassakin. Tämän tutkimuksen tuloksia voidaan hyödyntää nuorten aurinkosuojautumiseen liittyvän tiedon lisäämisessä sekä suunniteltaessa valtakunnallisia kampanjoita, joilla on mahdollista edistää nuorten terveyden kannalta turvallisempaa aurinkosuojautumista

LED-valaistuksen mahdollisuudet metsäpuiden taimien kasvatuksessa

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Genomic instability induced by radiation-mimicking chemicals is not associated with persistent mitochondrial degeneration

Ionizing radiation has been shown to cause induced genomic instability (IGI), which is defined as a persistently increased rate of genomic damage in the progeny of the exposed cells. In this study, IGI was investigated by exposing human SH-SY5Y neuroblastoma cells to hydroxyurea and zeocin, two chemicals mimicking different DNA-damaging effects of ionizing radiation. The aim was to explore whether IGI was associated with persistent mitochondrial dysfunction. Changes to mitochondrial function were assessed by analyzing mitochondrial superoxide production, mitochondrial membrane potential, and mitochondrial activity. The formation of micronuclei was used to determine immediate genetic damage and IGI. Measurements were performed either immediately, 8 days, or 15 days following exposure. Both hydroxyurea and zeocin increased mitochondrial superoxide production and affected mitochondrial activity immediately after exposure, and mitochondrial membrane potential was affected by zeocin, but no persistent changes in mitochondrial function were observed. IGI became manifested 15 days after exposure in hydroxyurea-exposed cells. In conclusion, immediate responses in mitochondrial function did not cause persistent dysfunction of mitochondria, and this dysfunction was not required for IGI in human neuroblastoma cells

Effects of 50 Hz magnetic field (MF) and menadione (0.1, 1, 10, 15, and 20 µM) or methyl methanesulphonate (MMS; 10, 15, and 20 µg/ml) on relative survival in human SH-SY5Y neuroblastoma cells.

<p>Both menadione (15 and 20 µM) and MMS (20 µg/ml) resulted in statistically significantly decreases in relative survival (p<0.01, p<0.001, p<0.01, respectively). Error bars represent SEM from three experiments.</p

Effects of 50 Hz magnetic field (MF) and menadione (0.1, 1, 10, 15, and 20 µM) or methyl methanesulphonate (MMS; 10, 15, and 20 µg/ml) on micronucleus frequency in human SH-SY5Y neuroblastoma cells.

<p>The symbol ↔ represents MF + menadione exposed groups compared to groups exposed to menadione alone. Exposure to menadione (doses 15 and 20 µM) and MMS (15 and 20 µg/ml) caused statistically significant increase in micronucleus frequency (p<0.05, p<0.001, p<0.05 and p<0.01, respectively). Error bars represent SEM from three experiments, * =  p<0.05, and ** =  p<0.01.</p

Effects of 50 Hz magnetic field (MF) and (A) 20 µM menadione (MQ) or (B) 35 µg/ml methyl methanesulphonate (MMS) on DNA damage level and DNA repair rate in human SH-SY5Y neuroblastoma cells.

<p>Both 20 µM menadione and 35 µg/ml MMS produced a statistically significant increase in DNA damage (p<0.01 and p<0.001, respectively). The symbol ↔ presents the overall change (DNA repair rate, 0 to 15 min) between menadione and MF + menadione exposed groups. Error bars represent SEM from three experiments with 100 nuclei analyzed in each experiment (thus, a total of 300 nuclei were analyzed), * =  p<0.05.</p