Dose and time effect of CdTe quantum dots on antioxidant capacities of the liver and kidneys in mice

Abstract

Although quantum dot (QD)-induced toxicity occurs due to free radicals, generation of oxidative stress mediated by reactive oxygen species (ROS) formation is considered an important mechanism. However, free radical mechanisms are essentially difficult to elucidate at the molecular level because most biologically relevant free radicals are highly reactive and short-lived, making them difficult to directly detect, especially in vivo. Antioxidants play an important role in preventing or, in most cases, limiting the damage caused by ROS. Healthy people and animals possess many endogenous antioxidative substances that scavenge free radicals in vivo to maintain the redox balance and genome integrity. The antioxidant capacity of an organism is highly important but seldom studied. In this study, the dose and time effects of CdTe QDs on the antioxidant capacities of the liver and kidneys were investigated in mice using the electron paramagnetic resonance (EPR) spin-trapping technique. We found that the liver and kidneys of healthy mice contain specific antioxidant capacities that scavenge ·OH and ·O 2 − . Furthermore, oxidative stress markers (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPx], glutathione [GSH] and malondialdehyde [MDA]) were examined. In dose course studies, the free radical scavenging efficiencies of the liver and kidneys were found to gradually decrease with increasing concentration of CdTe QD exposure. The activities and levels of SOD, CAT, GPx and MDA were observed to increase in treated groups, whereas those of GSH were reduced. The time course studies revealed that the QD-induced antioxidant efficiency reduction was time dependent with GSH decrease and could recover after a period of time. These experimental results offer new information on QD toxicity in vivo. Specifically, CdTe QDs can deplete GSH to reduce the elimination ability of the liver and kidneys for ·OH and ·O 2 − , thus inducing oxidative damage to tissues.

Nephrotoxicity Evaluation of Indium Phosphide Quantum Dots with Different Surface Modifications in BALB/c Mice

“…In the physiological state, ROS are always in a dynamic balance between production and elimination, which is maintained by the antioxidant system in the body. If ROS cannot be removed normally and thus accumulate in the tissues, lipids in cells are oxidized to produce peroxides, which eventually leads to tissue damage and dysfunction [ 35 , 36 ]. MDA can directly reflect the severity of the free radical attack.…”

Denitrase activity of Debaryomyces�hansenii reduces the oxidized compound 3‑nitrotyrosine in mice liver with colitis

“…There is also an atypical response of T helper cells (Th) in patients with ulcerative colitis, specifically Th2, which exerts a cytotoxic response against epithelial cells (10)(11)(12). In addition, the recruitment of leukocytes is affected, because UC increases the release of the chemo attractant molecule CXCL8, this activates the leukocytes recruiting from the systemic circulation to the intestinal mucosa, its entrance triggers an inflammatory response with a high production of ROS, which is a defense response to phagocytosis of bacteria, also the granular material or soluble irritating compounds increase ROS levels (13).…”

“…The cells overcome the oxidative stress condition mainly by neutralization systems such as superoxide dismutase, catalase and oxide-reductase enzymes that react with ROS and in consequence diminish ROS and RNS (13). The cellular mechanisms to repair oxidative damage are scarce or null, such as the case of protein 3-NT elimination, which has been proposed as irreversible, and although an enzymatic like activity of denitrase for histone 3 to detoxify 3-NT has been demonstrated in humans (20), there are no data that clearly demonstrate the presence of denitrase enzyme in higher eukaryotic organisms.…”

The effect of PEG functionalization on the in vivo behavior and toxicity of CdTe quantum dots

“…5 The QDs studied to date are usually quickly taken up by the liver and spleen, and, to a minor degree, by bone. 6,7 It has not been shown that whether the QDs leave these organs once inside or they are ultimately cleared from the organs. Most QDs are made of toxic materials such as cadmium, indium, and arsenide.…”