Responses of Antioxidant Enzymes in Catfish Exposed to Liquid Crystals from E-Waste

Abstract

Liquid crystals (LCs) are typically elongated organic molecules with a non-uniform distribution of electrical charges leading to a dipole. LCs are widely used in displays of computers and other electronic devices. The rapid obsolescence rate of electronics results in large amounts of liquid crystal displays (LCDs) entering the environment. Data on health effects of LCs on living creatures are currently limited to some acute toxicity tests by a few major LC manufacturers. These tests concluded that the vast majority of LCs are not acutely toxic. Since the amount of LCs in electronic devices is very small, the health effects of LCs at low concentrations or doses become important. Catfish were used as the test animals in this study. Four major enzymes of the fish’s antioxidant defense system catalase (CAT), superoxide dismutase (SOD), selenium-dependent glutathione peroxidase (Se-GPx), and glutathione-S-transferase (GST) were chosen as biomarkers to examine effects of LCs, which were taken from obsolete laptop personal computers made in the early 1990s. The catfish were fed with food containing different contents of LCs for 40 days. Activities of the four chosen enzymes in fish livers were assayed. The results showed that there were significant inductions of CAT, SOD, and Se-GPx activities in response to the LC doses. The plots of the enzyme activities versus LC doses suggested an occurrence of oxidative stress when the dose reached about 20 μg LC/g fish·d. It was concluded that LCs can cause pollutant-induced stress to catfish at low doses. CAT, SOD and Se-GPx are effective biomarkers to give early warning on potential health effects of LCs on some aquatic lives including catfish.

Persistent, bioaccumulative, and toxic properties of liquid crystal monomers and their detection in indoor residential dust

“…commercially were not harmful to fish during short-term exposures to relatively high concentrations, relative to what would be expected to occur in surface waters (10). However, the absence of acute effects does not necessarily mean that LCMs have no persistent, bioaccumulative, and/or chronic toxic (T) properties (10,12).…”

“…To the best of our knowledge, current research and legislation/ regulations on handling and disposal of e-waste focuses primarily on metals or metalloids, flame retardants, and ozone-depleting substances, but no regulations exist for LCM materials (9). Even though key materials in LCDs are mixed LCMs, there are essentially no published reports on occurrences or hazards posed by LCMs (10,11). Information regarding structures of LCMs is normally kept confidential among manufacturers of LCs or LCDs.…”

“…Information regarding structures of LCMs is normally kept confidential among manufacturers of LCs or LCDs. Thus, studies of effects of LCMs on biota are relatively rare (10). A large producer of LCMs once claimed that those used Significance Liquid crystal devices, such as smartphones, televisions, and tablet computers, have become integral tools of modern society; however, people do not know the environmental effects of liquid crystal monomers (LCMs).…”

Suppression of miR-26a attenuates physiological disturbances arising from exposure of Nile tilapia (Oreochromis niloticus) to ammonia

“…SOD, GPX and CAT activities in brain were determined using the Total Superoxide Dismutase Assay Kit (Beyotime, Shanghai, China), commercial Detection Kit A005 and Kit A007-1 (Jiancheng, Nanjing, China), respectively ( Ran et al, 2008 ). SOD analysis was performed based on the ability of SOD to inhibit the reduction of WST-8 Formazan dye by the xanthine oxidase/xanthine reaction.…”

Assessment of Biomarkers of Oxidative Stress and Antioxidant in Wild and Farmed Çoruh trout (Salmo coruhensis) Spermatozoa

“…They can inactive the harmful effects of ROS. The body produces more antioxidant enzymes in order to eliminate of ROS damage (Frei, 1999;An et al, 2008;Aksu et al, 2016;2017).…”