Lethality of inappropriate plasma exposure on chicken embryonic development.

In this study, we examined the effects of non-thermal dielectric barrier discharge plasma on embryonic development in chicken eggs in order to determine the optimal level of plasma exposure for the promotion of embryonic growth. We exposed developing chicken embryos at either Hamburger-Hamilton (HH) stage 04 or HH 20 to plasma at voltages of 11.7 kV to 27.6 kV. Our results show exposure at 11.7 kV for 1 min promoted chicken embryonic development, but exposure to more duration and intensity of plasma resulted in dose-dependent embryonic death and HH 20 stage embryos survive longer than those at stage HH 04. Furthermore, plasma exposure for 4 min increased the production of reactive oxygen species (ROS) and inactivated the nuclear factor erythroid 2-related factor 2 (NRF2)-antioxidant response signaling pathway, resulting in suppression of antioxidant enzymes in the skeletal muscle tissue of the dead embryos. We also found decreased levels of adenosine triphosphate production and reductions in the expression levels of several growth-related genes and proteins. These findings indicate that inappropriate plasma exposure causes dose-dependent embryonic death via excessive accumulation of ROS, NRF2-antioxidant signaling pathway disruption, and decreased growth factor expression.

Exposure of keratinocytes to non­thermal dielectric barrier discharge plasma increases the level of 8­oxoguanine via inhibition of its repair enzyme.

Oxidative stress enhances cellular DNA oxidation and may cause mutations in DNA bases, including 8­oxoguanine (8­oxoG). Our recent study reported that exposure of cells to non­thermal dielectric barrier discharge (DBD) plasma generates reactive oxygen species and damages DNA. The present study investigated the effect of non­thermal DBD plasma exposure on the formation of 8­oxoG in HaCaT human keratinocytes. Cells exposed to DBD plasma exhibited increased level of 8­oxoG. In addition, mRNA and protein expression levels of 8­oxoguanine glycosylase 1 (OGG1), an 8­oxoG repair enzyme, were reduced in plasma­exposed cells. Furthermore, the expression level of nuclear factor erythroid 2­related factor 2 (Nrf2), a transcription factor that regulates OGG1 gene expression, was reduced following exposure to DBD plasma. Pretreatment of cells with an antioxidant, N­acetyl cysteine (NAC), prior to plasma exposure suppressed the formation of 8­oxoG and restored the expression levels of OGG1 and Nrf2. In addition, phosphorylation of protein kinase B (Akt), which regulates the activation of Nrf2, was reduced following plasma exposure. However, phosphorylation was restored by pretreatment with NAC. These findings suggested that non­thermal DBD plasma exposure generates 8­oxoG via inhibition of the Akt­Nrf2­OGG1 signaling pathway in HaCaT cells.

Growth-inducing effects of argon plasma on soybean sprouts via the regulation of demethylation levels of energy metabolism-related genes.

This study was conducted to determine the effects of argon plasma on the growth of soybean [Glycine max (L.) Merr.] sprouts and investigate the regulation mechanism of energy metabolism. The germination and growth characteristics were modified by argon plasma at different potentials and exposure durations. Upon investigation, plasma treatment at 22.1 kV for 12 s maximized the germination and seedling growth of soybean, increasing the concentrations of soluble protein, antioxidant enzymes, and adenosine triphosphate (ATP) as well as up-regulating ATP a1, ATP a2, ATP b1, ATP b2, ATP b3, target of rapamycin (TOR), growth-regulating factor (GRF) 1-6, down-regulating ATP MI25 mRNA expression, and increasing the demethylation levels of the sequenced region of ATP a1, ATP b1, TOR, GRF 5, and GRF 6 of 6-day-old soybean sprouts. These observations indicate that argon plasma promotes soybean seed germination and sprout growth by regulating the demethylation levels of ATP, TOR, and GRF.

Non-thermal gas plasma-induced endoplasmic reticulum stress mediates apoptosis in human colon cancer cells.

Colorectal cancer is a common type of tumor among both men and women worldwide. Conventional remedies such as chemotherapies pose the risk of side­effects, and in many cases cancer cells develop chemoresistance to these treatments. Non­thermal gas plasma (NTGP) was recently identified as a potential tool for cancer treatment. In this study, we investigated the potential use of NTGP to control SNUC5 human colon carcinoma cells. We hypothesized that NTGP would generate reactive oxygen species (ROS) in these cells, resulting in induction of endoplasmic reticulum (ER) stress. ROS generation, expression of ER stress­related proteins and mitochondrial calcium levels were analyzed. Our results confirmed that plasma­generated ROS induce apoptosis in SNUC5 cells. Furthermore, we found that plasma exposure resulted in mitochondrial calcium accumulation and expression of unfolded protein response (UPR) proteins such as glucose­related protein 78 (GRP78), protein kinase R (PKR)­like ER kinase (PERK), and inositol­requiring enzyme 1 (IRE1). Elevated expression of spliced X­box binding protein 1 (XBP1) and CCAAT/enhancer­binding protein homologous protein (CHOP) further confirmed that ROS generated by NTGP induces apoptosis through the ER stress signaling pathway.

Non-thermal dielectric-barrier discharge plasma damages human keratinocytes by inducing oxidative stress.

The aim of this study was to identify the mechanisms through which dielectric-barrier discharge plasma damages human keratinocytes (HaCaT cells) through the induction of oxidative stress. For this purpose, the cells were exposed to surface dielectric-barrier discharge plasma in 70% oxygen and 30% argon. We noted that cell viability was decreased following exposure of the cells to plasma in a time-dependent manner, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The levels of intracellular reactive oxygen species (ROS) were determined using 2',7'-dichlorodihydrofluorescein diacetate and dihydroethidium was used to monitor superoxide anion production. Plasma induced the generation of ROS, including superoxide anions, hydrogen peroxide and hydroxyl radicals. N-acetyl cysteine, which is an antioxidant, prevented the decrease in cell viability caused by exposure to plasma. ROS generated by exposure to plasma resulted in damage to various cellular components, including lipid membrane peroxidation, DNA breaks and protein carbonylation, which was detected by measuring the levels of 8-isoprostane and diphenyl-1-pyrenylphosphine assay, comet assay and protein carbonyl formation. These results suggest that plasma exerts cytotoxic effects by causing oxidative stress-induced damage to cellular components.