Oxidative stress‐related PMK‐1 P38 MAPK activation as a mechanism for toxicity of silver nanoparticles to reproduction in the nematode Caenorhabditis elegans

Abstract

In the present study, a toxic mechanism of silver nanoparticles (AgNPs) was investigated in the nematode, Caenorhabditis elegans, focusing on the involvement of oxidative stress in reproduction toxicity. Initially, AgNPs were tested as potential oxidative stress inducers, and increased formation of reactive oxygen species (ROS) was observed in AgNP-exposed C. elegans. Subsequently, the potential upstream signaling pathway activated in response to AgNP exposure was investigated, paying special attention to the C. elegans PMK-1 p38 mitogen-activated protein kinase (MAPK). Increased PMK-1 p38 MAPK gene and protein expressions were observed in C. elegans exposed to AgNPs. Expression of the p38-dependent transcription factor genes and glutathione S-transferase (GST) enzyme activity was also investigated in wildtype (N2) and pmk-1 mutant (km25) C. elegans exposed to AgNPs. The results indicated that AgNP exposure led to increased ROS formation, increased expression of PMK-1 p38 MAPK and hypoxia-inducible factor (HIF-1), GST enzyme activity, and decreased reproductive potential in wildtype (N2) C. elegans; whereas in the AgNP-exposed pmk-1 (km25) mutant, ROS formation and HIF-1 and GST activation were not observed, and decreased reproductive potential was rescued. These results suggest that oxidative stress is an important mechanism of AgNP-induced reproduction toxicity in C. elegans, and that PMK-1 p38 MAPK plays an important role in it. The results also suggest that GST and HIF-1 activation by AgNP exposure are PMK-1 p38 MAPK-dependent, and that both play an important role in the PMK-1 p38 MAPK-mediated defense pathway to AgNP exposure in C. elegans.

Metal‐based nanoparticles in soil: Fate, behavior, and effects on soil invertebrates

“…Although specific functional coatings may be applied to metal-based NPs during manufacturing, sorption of ions such as humic substances may occur in the environment, potentially involving partial or complete replacement of any manufactured coating. Positively charged Al 2 O 3 NPs (50,80, and 120 nm) demonstrated relatively low mobility [74] because of sorption to negatively charged soil surfaces. Conversely, Al 2 O 3 NPs (50 nm) with adsorbed phosphate, producing a net negative charge, showed reduced sorption to soil and hence higher mobility [73].…”

“…Silver NPs cause the formation of reactive oxygen species (ROS) in the cells, although their toxicity also involves mechanisms other than ROS [79]. A recent study showed that the nematode C. elegans had increased ROS formation when exposed to 1 mg/L Ag NPs (20-30 nm in K-media), whereas no increase in ROS production was seen from the matching AgNO 3 exposure [80]. This confirms indications from previous studies in C. elegans by the same authors in which Ag NPs caused reproductive toxicity, which was related to oxidative stress, whereas no effects were seen on survival and growth (14-20 nm Ag NPs up to 0.5 mg/L in K-media) [81].…”

Caenorhabditis elegans locomotion is affected by internalized paramagnetic nanoparticles in the presence of magnetic field

“…Coating, size, developmental stage of the worm and duration of exposure to nanoparticles, regardless of their core material, have been shown to affect translocation of particles in various parts and tissues of the worm's body (38,57,60). The particles used in the present study are larger (38,(57)(58)(59) and worms have been exposed to them for a shorter period of time (18-20hrs) than in most other studies (38,61). These differences may explain why most of the nanoparticles detected with either bright field or fluorescent microscopy ( Fig.…”

“…elegans as the subject organism (38,(57)(58)(59). Coating, size, developmental stage of the worm and duration of exposure to nanoparticles, regardless of their core material, have been shown to affect translocation of particles in various parts and tissues of the worm's body (38,57,60).…”

Toxicogenomics of iron oxide nanoparticles in the nematodeC. elegans

“…(Roh et al, 2010b, Tsyusko et al, 2012, Ahn et al, 2014 These biological mechanisms have been previously reported in C. elegans for a range of inorganic NPs. (Kim et al, 2012, Li et al, 2012b, Lim et al, 2012, Wu et al, 2012, Rui et al, 2013, Ahn et al, 2014, Polak et al, 2014 The effects of the activated pathways might be of importance in the long term, hence further investigation is required to correlate the pathways identified in this work with the effects of chronic exposures in C. elegans.…”