Embryonic exposure to butylparaben and propylparaben induced developmental toxicity and triggered anxiety-like neurobehavioral response associated with oxidative stress and apoptosis in the head of zebrafish larvae

Parabens are synthetic antimicrobial compounds used as a preservative for extending the shelf life of food, pharmaceutical and cosmetic products. The alkyl chain length of the paraben esters positively correlates with their antimicrobial property. Hence, long-chain paraben esters, namely butylparaben and propylparaben, are used in combination as they have better solubility and antimicrobial efficacy. Extensive use of parabens has now resulted in the ubiquitous presence of these compounds in various human and environmental matrices. During early life, exposure to environmental contaminants is known to cause oxidative-stress mediated apoptosis in developing organs. The brain being one of the high oxygen-consuming, metabolically active and lipid-rich organ, it is primarily susceptible to reactive oxygen species (ROS) and lipid peroxidation (LP) induced neuronal cell death. The primary cause for the impairment in cognitive and emotional neurobehvioural outcomes in neurodegenerative disease was found to be associated with neuronal apoptosis. The present study aimed to study butylparaben and propylparaben's effect on zebrafish during early embryonic stages. Besides this, the association between alteration in anxiety-like neurobehavioral response with oxidative stress and antioxidant status in head region was also studied. The study results showed variation in the toxic signature left by butylparaben and propylparaben on developmental parameters such as hatching rate, survival and non-lethal malformations in a time-dependent manner. Data from the light-dark preference test showed embryonic exposure to butylparaben and propylparaben to trigger anxiety-like behavior in zebrafish larvae. In addition, a significant increase in intracellular ROS and LP levels correlated with suppressed antioxidant enzymes: superoxide dismutases (SOD), catalases (CAT), Glutathione peroxidase (GPx), glutathione S-transferase (GST), and Glutathione (GSH) activity in the head region of the zebrafish larvae. Acetylcholinesterase (AChE) activity was also suppressed in the exposed groups, along with increased nitric oxide production. The overall observations show increased oxidative stress indices correlating with upregulated expression of apoptotic cells in a dose-dependent manner. Collectively, our findings reveal butylparaben and propylparaben as an anxiogenic neuroactive compound capable of inducing anxiety-like behavior through a mechanism involving oxidative-stress-induced apoptosis in the head of zebrafish larvae, which suggests a potential hazard to the early life of zebrafish and this can be extrapolated to human health as well.

In utero exposure to endocrine-disrupting chemicals, maternal factors and alterations in the epigenetic landscape underlying later-life health effects

Widespread persistence of endocrine-disrupting chemicals (EDCs) in the environment has mandated the need to study their potential effects on an individual's long-term health after both acute and chronic exposure periods. In this review article a particular focus is given on in utero exposure to EDCs in rodent models which resulted in altered epigenetic programming and transgenerational effects in the offspring causing disrupted reproductive and metabolic phenotypes. The literature to date establishes the impact of transgenerational effects of EDCs potentially associated with epigenetic mediated mechanisms. Therefore, this review aims to provide a comprehensive overview of epigenetic programming and it's regulation in mammals, primarily focusing on the epigenetic plasticity and susceptibility to exogenous hormone active chemicals during the early developmental period. Further, we have also in depth discussed the epigenetic alterations associated with the exposure to selected EDCs such as Bisphenol A (BPA), di-2-ethylhexyl phthalate (DEHP) and vinclozlin upon in utero exposure especially in rodent models.

Functional role of piRNAs in animal models and its prospects in aquaculture

The recent advances in the field of aquaculture over the last decade has helped the cultured‐fish industry production sector to identify problems and choose the best approaches to achieve high‐volume production. Understanding the emerging roles of non‐coding RNA (ncRNA) in the regulation of fish physiology and health will assist in gaining knowledge on the possible applications of ncRNAs for the advancement of aquaculture. There is information available on the practical considerations of epigenetic mechanisms like DNA methylation, histone modification and ncRNAs, such as microRNA in aquaculture, for both fish and shellfish. Among the non‐coding RNAs, PIWI‐interacting RNA (piRNA) is 24–31 bp long transcripts, which is primarily involved in silencing the germline transposons. Besides, the burgeoning reports and studies establish piRNAs' role in various aspects of biology. Till date, there are no reviews that summarize the recent findings available on piRNAs in animal models, especially on piRNAs biogenesis and biological action. To gain a better understanding and get an overview on the process of piRNA genesis among the different animals, this work reviews the literature available on the processes of piRNA biogenesis in animal models with special reference to aquatic animal model zebrafish. This review also presents a short discussion and prospects of piRNA’s application in relevance to the aquaculture industry.

RM12 similar to substance P from tachykinin of freshwater murrel Channa striatus influence intracellular ROS in vitro fish erythrocytes and developmental toxicity and antioxidant enzymes in vivo zebrafish embryo

In this study, substance P, an antioxidant peptide of tachykinin, was identified using bioinformatics tools from the earlier established muscle transcriptome of a freshwater murrel Channa striatus and the peptide was named RM12. The antioxidant properties of RM12 were screened using various colorimetric assays. The toxicity of RM12 was experimented using fish erythrocytes, and it is observed that the maximum concentration (320 μM) of RM12 was found to have 15 or 20% of hemolytic activity; however, it was not significant with other tested concentrations (10, 20, 40, 80, and 160 μM). Further, the in vivo antioxidant properties of RM12 were experimented on zebrafish embryo, the intracellular ROS level was estimated by 5 mM H₂O₂ stress in the zebrafish embryo, and inhibition of apoptosis was evaluated. The antioxidant enzymes were extracted from the H₂O₂-stressed zebrafish embryo, and the intracellular ROS was eliminated due to RM12. Collectively, the experiment showed that the substance P from the freshwater murrel C. striatus possessed potent antioxidant properties; thus, it can further be focused to develop it as antioxidant molecule in aquaculture organisms.

NV14 from serine O-acetyltransferase of cyanobacteria influences the antioxidant enzymes in vitro cells, gene expression against H2 O2 and other responses in vivo zebrafish larval model

In this study, we have identified a novel peptide NV14 with antioxidative functions from serine O-acetyltransferase (SAT) of Artrospira platensis (Ap). The full sequence of ApSAT and its derived NV14 peptide "NVRIGAGSVVLRDV" (141-154) was characterized using bioinformatics tools. To address the transcriptional activity of ApSAT in response to induce generic oxidative stress, the spirulina culture was exposed to H₂ O₂ (10 mM). The ApSAT expression was studied using RT-PCR across various time points and it was found that the expression of the ApSAT was significantly upregulated on Day 15. The in vitro cytotoxicity assay against NV14 was performed in human dermal fibroblast cells and human blood leukocytes. Results showed that NV14 treatment was non-cytotoxic to the cells. Besides, in vivo treatment of NV14 in zebrafish larvae did not exhibit the signs of developmental toxicity. Further, the in vitro antioxidant assays enhanced the activity of the antioxidant enzymes, such as SOD and CAT, due to NV14 treatment; and also significantly reduced the MDA levels, while increasing the superoxide radical and H₂ O₂ scavenging activity. The expression of antioxidant enzyme genes glutathione peroxidase, γ-glutamyl cysteine synthase, and glutathione S-transferase were found to be upregulated in the NV14 peptide pretreated zebrafish larvae when induced with generic oxidative stress, H₂ O₂ . Overall, the study showed that NV14 peptide possessed potent antioxidant properties, which were demonstrated over both in vitro and in vivo assays. NV14 enhanced the expression of antioxidant enzyme genes at the molecular level, thereby modulating and reversing the cellular antioxidant balance disrupted due to the H₂ O₂ -induced oxidative stress.

Tryptophan-tagged peptide from serine threonine-protein kinase of Channa striatus improves antioxidant defence in L6 myotubes and attenuates caspase 3-dependent apoptotic response in zebrafish larvae

This study reports the antioxidant property and molecular mechanism of a tryptophan-tagged peptide derived from a teleost fish Channa striatus of serine threonine-protein kinase (STPK). The peptide was tagged with tryptophan to enhance the antioxidant property of STPK and named as IW13. The antioxidant activity of IW13 peptide was investigated using in vitro methods such as DPPH, ABTS, superoxide anion radical scavenging and hydrogen peroxide scavenging assay. Furthermore, to investigate the toxicity and dose response of IW13 peptide on antioxidant defence in vitro, L6 myotubes were induced with generic oxidative stress due to exposure of hydrogen peroxide (H₂O₂). IW13 peptide exposure was found to be non-cytotoxic to L6 cells in the tested concentration (10, 20, 30, 40 and 50 μM). Also, the pre-treatment of IW13 peptide decreased the lipid peroxidation level and increased glutathione enzyme activity. IW13 peptide treatment upregulated the antioxidant enzyme genes: GPx (glutathione peroxidase), GST (glutathione S transferase) and GCS (glutamine cysteine synthase), in vitro in L6 myotubes and in vivo in zebrafish larvae against the H₂O₂-induced oxidative stress. The results demonstrated that IW13 renders protection against the H₂O₂-induced oxidative stress through a cellular antioxidant defence mechanism by upregulating the gene expression, thus enhancing the antioxidant activity in the cellular or organismal level. The findings exhibited that the tryptophan-tagged IW13 peptide from STPK of C. striatus could be a promising candidate for the treatment of oxidative stress-associated diseases.

SARS-CoV-2/human interactome reveals ACE2 locus crosstalk with the immune regulatory network in the host

Severe acute respiratory syndrome, coronavirus 2 (SARS-CoV-2), remains to be a threat across the globe. SARS-CoV-2 entry into the host is mediated by binding of viral spike protein to the Human angiotensin-converting enzyme 2 (ACE2) receptor. ACE2 is an essential member of the Renin–Angiotensin system (RAS) involved in maintaining the blood pressure and vascular remodelling. Although ACE2 receptor is the entry point to the host, recent studies show activation of ACE2 to modulate the host to develop a suitable environment for its replication. However, the ACE2 activating the immune signals on SARS-CoV-2 attachment is still under investigation. We have used systems biological approach to construct the host regulatory network upon SARS-CoV-2 attachment to the ACE2 receptor. Since lungs are the primary infection site, we integrate human lung gene expression profile along with the host regulatory network to demonstrate the altered host signalling mechanism in viral infection. Further, the network was functionally enriched to determine immune modulation in the network. We also used the proteomic database to assess the occurrence of similar signalling events in other human tissues that exhibit lineage of infection across different organs. The constructed network contains 133 host proteins with 298 interactions that directly or indirectly connect to the ACE2 receptor. Among 133 proteins, 29 were found to be differentially regulated in the host lungs on SARS-CoV-2 infection. Altered proteins connect multiple proteins in a network that modulates kinase, carboxypeptidase and cytokine activity, leading to changes in the host immune system, cell cycle and signal transduction mechanisms. Further investigation showed the presence of similar signalling events in the kidneys, placenta, pancreas, testis, small intestine and adrenal gland as well. Overall, our results will help in understanding the immune molecular regulatory networks influenced by the ACE2 mediated interaction in other body tissues, which may aid in identifying the secondary health complications associated with SARS-CoV-2 infection.

Intracellular ROS scavenging and antioxidant regulation of WL15 from cysteine and glycine-rich protein 2 demonstrated in zebrafish in vivo model

Antioxidant peptides are naturally present in food, especially in fishes, and are considered to contain rich source of various bioactive compounds that are structurally heterogeneous. This study aims to identify and characterize the antioxidant property of the WL15 peptide, derived from Cysteine and glycine-rich protein 2 (CSRP2) identified from the transcriptome of a freshwater food fish, Channa striatus. C. striatus is already studied to contain high levels of amino acids and fatty acids, besides traditionally known for its pharmacological benefits in the Southeast Asian region. In our study, in vitro analysis of WL15 peptide exhibited strong free radical scavenging activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), superoxide anion radical and hydrogen peroxide (H2O2) scavenging assay. Further, to evaluate the cytotoxicity and dose-response, the Human dermal fibroblast (HDF) cells were used. Results showed that the treatment of HDF cells with varying concentrations (10, 20, 30, 40 and 50 μM) of WL15 peptide was not cytotoxic. However, the treatment concentrations showed enhanced antioxidant properties by significantly inhibiting the levels of free radicals. For in vivo assessment, we have used zebrafish larvae for evaluating the developmental toxicity and for determining the antioxidant property of the WL15 peptide. Zebrafish embryos were treated with the WL15 peptide from 4 h of post-fertilization (hpf) to 96 hpf covering the embryo-larval developmental period. At the end of the exposure period, the larvae were exposed to H2O2 (1 mM) for inducing generic oxidative stress. The exposure of WL15 peptide during the embryo-larval period showed no developmental toxicity even in higher concentrations of the peptide. Besides, the WL15 peptide considerably decreased the intracellular reactive oxygen species (ROS) levels induced by H2O2 exposure. WL15 peptide also inhibited the H2O2-induced caspase 3-dependent apoptotic response in zebrafish larvae was observed using the whole-mount immunofluorescence staining. Overall results from our study showed that the pre-treatment of WL15 (50 μM) in the H2O2-exposed zebrafish larvae, attenuated the expression of activated caspase 3 expressions, reduced Malondialdehyde (MDA) levels, and enhanced antioxidant enzymes, including superoxide dismutase (SOD) and catalase (CAT). The gene expression of antioxidant enzymes such as glutathione S-transferase (GST), glutathione peroxide (GPx) and γ-glutamyl cysteine synthetase (GCS) was found to be upregulated. In conclusion, it can be conceived that pre-treatment with WL15 could mitigate H2O2-induced oxidative injury by elevating the activity and expression of antioxidant enzymes, thereby decreasing MDA levels and cellular apoptosis by enhancing the antioxidant response, demonstrated by the in vitro and in vivo experiments.

Molecular process of glucose uptake and glycogen storage due to hamamelitannin via insulin signalling cascade in glucose metabolism

Understanding the mechanism by which the exogenous biomolecule modulates the GLUT-4 signalling cascade along with the information on glucose metabolism is essential for finding solutions to increasing cases of diabetes and metabolic disease. This study aimed at investigating the effect of hamamelitannin on glycogen synthesis in an insulin resistance model using L6 myotubes. Glucose uptake was determined using 2-deoxy-D-[1-³H] glucose and glycogen synthesis were also estimated in L6 myotubes. The expression levels of key genes and proteins involved in the insulin-signaling pathway were determined using real-time PCR and western blot techniques. The cells treated with various concentrations of hamamelitannin (20 µM to 100 µM) for 24 h showed that, the exposure of hamamelitannin was not cytotoxic to L6 myotubes. Further the 2-deoxy-D-[1-³H] glucose uptake assay was carried out in the presence of wortmannin and Genistein inhibitor for studying the GLUT-4 dependent cell surface recruitment. Hamamelitannin exhibited anti-diabetic activity by displaying a significant increase in glucose uptake (125.1%) and glycogen storage (8.7 mM) in a dose-dependent manner. The optimum concentration evincing maximum activity was found to be 100 µm. In addition, the expression of key genes and proteins involved in the insulin signaling pathway was studied to be upregulated by hamamelitannin treatment. Western blot analysis confirmed the translocation of GLUT-4 protein from an intracellular pool to the plasma membrane. Therefore, it can be conceived that hamamelitannin exhibited an insulinomimetic effect by enhancing the glucose uptake and its further conversion into glycogen by regulating glucose metabolism.

Transient exposure of methylparaben to zebrafish (Danio rerio) embryos altered cortisol level, acetylcholinesterase activity and induced anxiety-like behaviour

Parabens are widely used as antimicrobial preservatives. Recent studies have reported the endocrine disrupting effects of these chemicals, especially methylparaben. Previously, we have reported the alteration in Vtg gene expression upon exposure to environmentally relevant doses of methylparaben in zebrafish (Danio rerio) embryos. However, studies reporting neurobehavioural outcomes on exposure to methylparaben are limited. Therefore, this study was aimed at investigating the methylparaben-induced effects on developmental and neurobehavioural endpoints. Zebrafish embryos were exposed to sub-lethal concentrations of methylparaben: 0.1 ppb, 1 ppb, 10 ppb and 100 ppb. Alterations in developmental landmarks such as heart rate and hatching percentage were observed in embryos exposed to 10 ppb and 100 ppb of methylparaben. Results obtained from the novel tank diving test established that anxiety-like behaviour is induced in larvae exposed to 0.1 ppb and 1 ppb of methylparaben. A significant inhibition in the acetylcholinesterase (AChE) activity was also recorded in methylparaben-exposed groups. An increase in cortisol levels was observed in the exposed groups, which further supports the observations made in the novel tank diving test, establishing methylparaben as an anxiogenic agent even at sub-lethal concentrations. The underlying molecular mechanism needs further elucidation to investigate whether the behavioural effects are proximally or distally induced by early developmental exposure to methylparaben.

Prenatal exposure to bisphenol-A altered miRNA-224 and protein expression of aromatase in ovarian granulosa cells concomitant with elevated serum estradiol levels in F1 adult offspring

This study was aimed to predict bisphenol-A (BPA)-responsive miRNA's using an in silico approach and to study their expression in granulosa cells of animals exposed prenatally to BPA. Pregnant Wistar rats were exposed to BPA through water (25 μg/L, 250 μg/L, and 2.5 mg/L) during gestation. The expression of miRNA-133b, miRNA-378 and miRNA-224 were analyzed in ovarian granulosa cells. BPA affected the postnatal developmental landmarks such as weight of the pups at birth and reduced anogenital distance. BPA exposed animals showed elevated serum estradiol (E2) levels, while follicle-stimulating hormone levels were reduced. The expression of miRNA-224 and aromatase protein levels were found to be increased. This preliminary finding reveals the impact of early life exposure to BPA on the long-term ovarian functions that may be mediated through miRNA-based granulosa cell response. Besides, it is also a compelling indicator for the subclinical response that could have important consequences on female fertility.

Developmental toxicity and induction of vitellogenin in embryo-larval stages of zebrafish (Danio rerio) exposed to methyl Paraben

MethylParaben (MP), a methyl ester of p-hydroxybenzoic acid, is used as an anti-microbial preservative in foods, drugs and cosmetics for decades. It enters the aquatic environment, and can have toxic effects on aquatic organisms. Little is known on the developmental toxicity of MP exposure to zebrafish during early life stages. In this study, the developmental effects of MP were evaluated in embryo-larval zebrafish (at concentrations ranging from 100μM, 200μM, 400µM, 800μM and 1000μM for 96h post fertilization (hpf). The survival, hatching, heart beat rate and developmental abnormalities were observed in the embryos exposed to MP. MP exposure resulted in decreased heart rate and hatching rate. Defects including pericardial edema blood cell accumulation and bent spine were observed in all the treated concentration, except at 100μM. With increasing concentrations, the frequency of these defects increased. The 96 hpf LC₅₀ of MP was calculated to be 428μM (0.065mg/L). Furthermore, RT-PCR result showed that in larval zebrafish exposed to 100μM (0.015mg/L) of MP till 96 hpf, expression of vitellogenin I (Vtg -I) was significantly upregulated compared to the control group. This data suggest that even though lower concentrations of MP do not cause phenotypic malformations, it leads to dysregulated expression of estrogenic biomarker gene Vtg-I.

Detection of phenolic endocrine disrupting chemicals (EDCs) from maternal blood plasma and amniotic fluid in Indian population

There is a widespread exposure of general population, including pregnant women and developing fetuses, to the endocrine disrupting chemicals (EDCs). These chemicals have been reported to be present in urine, blood serum, breast milk and amniotic fluid. We aimed to investigate the association between the maternal exposure and in utero fetal exposure levels of these chemicals to study their transfer from maternal to fetal unit indicating prenatal exposure. Samples of maternal blood and amniotic fluid were collected as set from 53 pregnant women at full term. Nine phenolic EDCs, methyl paraben (MP; 20.92ng/mL and 18.92ng/mL), ethyl paraben (EP; 1.97ng/ mL and 1.89ng/mL), propyl paraben (PP; 19.22ng/mL and 18.82ng/mL), butyl paraben (BP; 1.11ng/mL and 1.37ng/mL), p-hydroxybenzoic acid (PHBA; 29.99ng/mL and 26.15ng/mL), bisphenol A (BPA; 7.43ng/mL and 7.75ng/mL), triclosan (TCS; 7.17ng/mL and 7.04ng/mL), octyl phenol (OP; 5.46ng/mL and 5.72ng/mL) and nonyl phenol (NP; 9.38ng/mL and 8.44ng/mL), were simultaneously detected in samples of maternal blood plasma and amniotic fluid respectively using Gas Chromatography-Mass Spectrometry (GC-MS). Highest positive correlation was found for total concentration of 4-nonyl phenol, NP (r=0.575, p<0.001), whereas the lowest positive correlation was found for free form of bisphenol A, BPA (r=0.343, p<0.05), when compared between the two matrices. Our results suggest that maternal exposure to several EDCs is positively associated with in utero exposure to the developing fetus. Future studies should focus on collection of amniotic fluid at different trimesters and the corresponding maternal samples to better characterize the pharmacokinetics and the associated disease etiologies of these EDCs during fetal development.