A natural small molecule-mediated inhibition of alpha-synuclein aggregation leads to neuroprotection in Caenorhabditis elegans.

Small molecules are being explored intensively for their applications as therapeutic molecules in the management of metabolic and neurological disorders. The natural small molecules can inhibit protein aggregation and underlying cellular pathogenesis of neurodegenerative diseases involving multi-factorial mechanisms of action. Certain natural small molecular inhibitors of pathogenic protein aggregation are highly efficient and have shown promising therapeutic potential. In the present study, Shikonin (SHK), a natural plant-based naphthoquinone has been investigated for its aggregation inhibition activity against α-synuclein (α-syn) and the neuroprotective potential in Caenorhabditis elegans (C. elegans). SHK significantly inhibited aggregation of α-syn at sub-stochiometric concentrations, delayed the linear lag phase and growth kinetics of seeded and unseeded α-syn aggregation. The binding of SHK to the C-terminus of α-syn maintained α-helical and disordered secondary structures with reduced beta-sheet content and complexity of aggregates. Further, in C. elegans transgenic PD models, SHK significantly reduced α-syn aggregation, improved locomotor activity and prevented dopaminergic (DA) neuronal degeneration, indicating the neuroprotective role of SHK. The present study highlights the potential of natural small molecules in the prevention of protein aggregation that may further be explored for their therapeutic efficacy in the management of protein aggregation and neurodegenerative diseases.

ß-triketone herbicide exposure cause tyrosine and fat accumulation in Caenorhabditis elegans.

ß-triketone herbicides have been efficiently employed as an alternate to atrazine. Triketones are 4-hydroxyphenylpyruvate dioxygenase (HPPD) enzyme inhibitors and exposure is reported to cause significant increase in plasma tyrosine levels. In this study, we have employed a non-target organism Caenorhabditis elegans to determine the impact of ß-triketone exposures at recommended field doses (RfD). Our results indicate sulcotrione and mesotrione, negatively influence the survival, behavior, and reproduction of the organism at RfD. Additionally, we have traced the parallels regarding the impact of triketones on the tyrosine metabolism pathway, in C. elegans to those in mammalian models, wherein the expression of the tyrosine metabolism pathway genes are altered, directly influencing tyrosine catabolism leading to significant tyrosine accumulation in exposed organism. Further, we investigated the impact of sulcotrione and mesotrione exposure on fat deposition (triglyceride levels, Oil-Red-O staining and lipidomics) and the fatty acid metabolism pathway. In the exposed worms, the expression of enlongases and fatty acid desaturases were up-regulated along with an increase in the levels of triglycerides. Thus, the data indicates a positive association of ß-triketone exposure to mis-regulation of the fatty acid metabolism pathway genes leading to fat accumulation in worms. Therefore, ß-triketone might be a potential obesogen.

Toxicity assessment of parabens in Caenorhabditis elegans.

Parabens, the alkyl esters of p-hydroxybenzoic acid such as methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), butylparaben (BuP) are used as a preservative in food, personal care products (PCPs), and pharmaceuticals, due to their antimicrobial properties. Parabens are continuously released into the environment, during washout of PCPs, disposal of industrial waste from the pharmaceutical and paper industries. Parabens have been detected in the indoor dust, wastewater stream, surface water of rivers, and the marine system. Recent eco-toxicological data and the environmental presence of parabens, has raised concerns regarding the safety and health of environment/humans. Thus, to further understand the toxicity of parabens, the present study was carried out in the soil nematode and well established biological model organism Caenorhabditis elegans. In the present study, LC50 of MeP, EtP, PrP and BuP for 72 h exposures from L1 larva to adult stage was found to be 278.1, 217.8, 169.2, and 131.88 µg/ml, respectively. Further exposure to 1/5th of LC50 of parabens yielded an internal concentration ranging from 1.67 to 2.83 µg/g dry weight of the organism. The toxicity of parabens on the survival, growth, behavior, and reproduction of the C. elegans was found in the order of BuP > PrP > EtP > MeP. Worms exposed to parabens show significant down-regulation of vitellogenin genes, high levels of reactive oxygen species and anti-oxidant transcripts, the latter being concordant with nuclear localization of DAF-16 and up-regulation of HSF-1 and SKN-1/Nrf. Hence, parabens caused endocrine disruption, oxidative stress and toxicity in C. elegans at environment relevant internal concentration of parabens.

Bioaccumulation, biotransformation and toxic effect of fipronil in Escherichia coli.

Fipronil is a highly effective, broad-spectrum insecticide used to control pests, globally. The increased usage has led to contamination of soil, water, fruits, and vegetables. The wide and frequent usage of fipronil across the globe calls for attention regarding risk assessment of undesirable effects on non-target microorganisms. In this context, the present study was carried to understand the impact of fipronil on non-pathogenic Escherichia coli. The non-pathogenic E. coli are important commensal of the intestinal tract of humans and animals and are also indicator organisms in the environment. Our study indicates that exposure of E. coli to fipronil (100 µM concentration) leads to significant reactive oxygen species production, loss of membrane potential and viability. Further, we have witnessed the bioaccumulation and biotransformation of fipronil by E. coli at non-lethal concentrations. The bio-transformed products (fipronil sulfone and fipronil sulfide) are also the major metabolites (along with amide) reported in the feces of the mammals when exposed to fipronil. Thus, there is a possibility that the gut E. coli might play a role in the degradation and thereby removal of fipronil. In addition, the bioaccumulation of fipronil in bacteria is of concern and need to be further explored because it can lead to biomagnification in the higher trophic level and can disturb the ecological balance. In our knowledge, this is the first report on the determination of fipronil and its metabolites in bacteria through GC-MS/MS.

The role of antioxidants in attenuation of Caenorhabditis elegans lethality on exposure to TiO2 and ZnO nanoparticles.

The exponential increase in the usage of engineered nanoparticles (ENPs) has raised global concerns due to their potential toxicity and environmental impacts. Nano-TiO2 and nano-ZnO have been extensively used in various applications. Thus, there is a need for determining the toxic potentials of ENPs as well as, to develop the possible attenuation method for ENPs toxicity. Both in the in vitro and in vivo systems, exposure to the majority of ENPs have shown Reactive Oxygen Species (ROS) generation, which leads to oxidative stress mediated inflammation, genotoxicity, and cytotoxicity. Hence, with the rationale of determining easy and economical protection against ENPs exposure, the amelioration effect of the antioxidants (curcumin and vitamin-C) against the nano-TiO2 and nano-ZnO induced ROS and lethality were investigated in Caenorhabditis elegans. We not only employed pre-treatment and along with treatment approach, but also determined the effect of antioxidants at different time points of treatment. Our study revealed that both the antioxidants efficiently ameliorate nanoparticles induced ROS as well as lethality in worms. Further, the pretreatment approach was more effective than the along with treatment. Therefore, our study indicates the possibility of evading the nanotoxicity by incorporating curcumin and vitamin-C in everyday diet.

Metabolomics reveals the perturbations in the metabolome of Caenorhabditis elegans exposed to titanium dioxide nanoparticles.

The increasing use of nanotechnology in our daily life can have many unintended effects and pose adverse impact on human health, environment and ecosystems. Wider application of engineered nanoparticles, especially TiO2 nanoparticles (TiO2 NP) necessitates the understanding of toxicity and mechanism of action. Metabolomics provides a unique opportunity to find out biomarkers of nanoparticles exposure, which leads to the identification of cellular pathways and their biological mechanisms. Gas chromatography mass spectrometry (GC-MS)-based metabolomics approach was used in the present study to understand the toxicity of sub-lethal concentrations (7.7 and 38.5 µg/ml) of TiO2 NP (<25 nm) in well-known, soil nematode Caenorhabditis elegans (C. elegans). Multivariate pattern recognition analysis reflected the perturbations in the metabolism (amino acids, organic acids, sugars) of C. elegans on exposure to TiO2 NP. The biological pathways affected due to the exposure of TiO2 NP were identified, among them mainly affected pathways are tricarboxylic acid (TCA) cycle, arachidonic acid metabolism and glyoxalate dicarobxylate metabolism. The manifestation of differential metabolic profile in organism exposed to TiO2 (NP or bulk particle) was witnessed as an effect on reproduction. The present study demonstrates that metabolomics can be employed as a tool to understand the potential toxicity of nanoparticles in terms of organism-environment interactions as well as in assessing the organism function at the molecular level.

Size dependent toxicity of zinc oxide nano-particles in soil nematode Caenorhabditis elegans.

Zinc oxide nano-particles (ZnO NPs), with their unique physico-chemical properties conferred by various size formulations, are extensively used in consumer products. The enormous usage coupled with their release to the environment demands risk assessment of ZnO NPs on health and the environment. Toxicity of ZnO NPs is well understood in comparison to the bulk ZnO. However, toxicity in relation to the NP size is poorly understood. In this context, we examined the adverse effects of different sizes (35 nm, 50 nm and 100 nm) of ZnO NPs in soil nematode C. elegans along with bulk ZnO and ZnCl2. Here, we show that growth, reproduction and behavior of worms were adversely affected by ZnO NPs in a size dependent manner. Further, exposure to ZnO NPs caused modulation of expression/function of genes associated with Insulin/IGF-like signaling pathway and/or stress response pathway in a size dependent manner in exposed worms. The expression of pro-apoptotic gene and suppression of anti-apoptotic genes, together with increased numbers of cell corpses in the germ line, indicated that apoptosis was also dependent on the size of the ZnO NP. Taken together, our study provides evidence that exposure to ZnO NPs disrupts various physiological processes and causes apoptosis in the germ-line even at very low concentration in a size dependent manner. Our finding suggests the inclusion of size as an additional measure for the cautious monitoring of ZnO NP disposal into the environment.

Adverse effects of TiO2 and ZnO nanoparticles in soil nematode, Caenorhabditis elegans.

During the last decade, advancement of nanotechnology has revolutionized various fields such as electronics, optics, materials science as well as architecture, and medicine. However, their health and environmental impact is not fully understood. TiO2 and ZnO nanoparticles (NPs), which are abundantly used for commercial purposes, pose a great risk to environment. In this context, we examined the adverse effects of TiO2 and ZnO NPs of < 25 nm and < 100 nm sizes to nematode Caenorhabditis elegans. < 25 nm TiO2 and ZnO NPs showed LC50 of 77 mg/L and 0.32 mg/L respectively, while < 100 nm TiO2 NPs were non-toxic and LC50 of 2 mg/L was obtained for < 100 nm ZnO NPs. Our studies indicate that in both cases, smaller particle sizes are more toxic than larger NPs and ZnO NPs are more toxic than TiO2 NPs. Further, we observed low LC50 values for ZnO NPs, probably reflecting the sensitivity of C. elegans as a model for eco-toxicity studies of NPs.