Regulation of BTB (POZ) Structural Domain 6b by MicroRNA-222b in Zebrafish Embryos after Exposure to Di(2-ethylhexyl)phthalate at Low Concentrations.

Di-(2-ethylhexyl) phthalate (DEHP) is a sort of endocrine disruptor that induces abnormal physiological and biochemical activities such as epigenetic alterations, apoptosis, and oxidative stress. MicroRNAs (miRNAs) are a class of short noncoding RNAs that may regulate the expression of many protein-coding genes when organisms are exposed to environmental chemicals. miR-222b is a differentially expressed miRNA after DEHP exposure. miRNA-mRNA prediction suggested that BTB (POZ) structural domain 6b (BTBD6B) might be a target mRNA of miR-222b, and DEHP exposure altered its expression. However, the correlation between miR-222b and BTBD6B has not been experimentally confirmed. The aim of this study was to investigate the regulation of BTBD6B by miR-222b in zebrafish embryos under the effect of low concentration of DEHP. Dual fluorescent protein assays and dual luciferase reporter gene assays confirmed the interaction between miR-222b and the 3'-untranslated region (3'-UTR) of BTBD6B. Ectopic expression assays showed that miR-222b could negatively regulate BTBD6B in ZF4 cells. However, the relative expression of miR-222b and BTBD6B was significantly higher at both transcriptional and post-transcriptional levels in zebrafish embryos exposed to low concentrations of DEHP. The results of this study improved our understanding of the molecular mechanism of DEHP exposure toxicity. It identified that the aberrant expression of miR-222b/BTBD6B may be one of the mechanisms of DEHP toxicity, which can provide a theoretical reference and scientific basis for environmental management and biological health risk assessment.

In situ monitoring of mechanochemical MOF formation by NMR relaxation time correlation.

In this paper, we present a new approach to monitoring mechanochemical transformations, based on a magnetic resonance (MR) method in which relaxation time correlation maps are used to track the formation of the popular metal-organic framework (MOF) materials Zn-MOF-74 and ZIF-8. The two-dimensional (2D) relaxation correlation measurement employed yields a spectrum which visually and analytically identifies different 1H environments in the sample of interest. The measurement is well-suited to analyzing solid mixtures, and liquids, in complex systems. Application in this work to monitoring MOF formation shows changes in signal amplitudes, and their MR lifetime coordinates, within the 2D plots as the reaction progresses, confirming reaction completion. This new measurement provides a simple way to analyse solid-state reactions without dissolution, and there is a logical pathway to benchtop measurement with a new generation of permanent magnet-based MR instruments. The methodology described permits measurement in an MR compatible milling container, which may be directly transferred from the shaker assembly to the MR magnet for in situ measurement of the entire reaction mixture.

Imidacloprid Induces Neurotoxicity in Albino Male Rats by Inhibiting Acetylcholinesterase Activity, Altering Antioxidant Status, and Primary DNA Damage.

Imidacloprid (IMI) is a neonicotinoid insecticide used worldwide, either alone or in combination with other pesticides. The goal of this study was to assess the effects of IMI on the central nervous system of rats and its mechanism of oxidative stress-induced DNA damage by oxidant/antioxidant parameters. Fifteen male rats, divided into three groups, were used: the first group received 5 ml/kg body weight corn oil as a control, the second received a high oral dose of IMI (45 mg/kg body weight), while the third received a low dose (22 mg/kg body weight). After 28 days, acetylcholinesterase (AChE) activity, oxidative stress markers, histopathological alterations, and DNA damage were examined in the brains of these rats. The AChE activities decreased significantly after IMI exposure, reaching 2.45 and 2.75 nmol/min/mg protein in high dose and low dose, respectively, compared to the control group (3.75 nmol/g tissues), while the concentration of malondialdehyde MDA increased significantly (29.28 and 23.92 nmol/g tissues) vs. the control group (19.28 nmol/g tissues). The antioxidant status parameters such as reduced glutathione (GSH) content was 13.77 and 17.63 nmol/g, catalase (CAT) activity was 22.56 and 26.65 µmol/min/g, and superoxide dismutase (SOD) activity was 6.66 and 7.23 µmol/min/g in both doses against the control group (21.37 nmol/g, 30.67 µmol/min/g, 11.76 µmol/min/g), respectively, and histopathological changes in the brain tissues were observed. More in vivo research using epigenetic methods is needed to determine the ability of IMI and its metabolites to cause neurotoxicity and DNA lesions in mammalian brains.

Twist angle-dependent work functions in CVD-grown twisted bilayer graphene probed by Kelvin probe force microscopy.

Tailoring the interlayer twist angle of bilayer graphene (BLG) significantly affects its electronic properties, including its superconductivity, topological transitions, ferromagnetic states, and correlated insulating states. These exotic electronic properties are sensitive to the work functions of BLG samples. In this study, the twist angle-dependent work functions of chemical vapour deposition-grown twisted bilayer graphene (tBLG) were investigated in detail using Kelvin probe force microscopy (KPFM) in combination with Raman spectroscopy. The thickness-dependent surface potentials of Bernal-stacked multilayer graphene were measured. It is found that with the increase in the number of layers, the work function decreases and tends to saturate. Bernal-stacked BLG and tBLG were determined via KPFM due to their twist angle-specific surface potentials. The detailed relationship between the twist angle and surface potential was determined via in situ KPFM and Raman spectral measurements. With the increase in the twist angle, the work function of tBLG will increase rapidly and then increase slowly when it is greater than 5°. The thermal stability of tBLG was investigated through a controlled annealing process. tBLG will become Bernal-stacked BLG after annealing at 350 °C. Our work provides the twist angle-dependent surface potentials of tBLG and provides the relevant conditions for the stability of the twist angle, which lays the foundation for further exploration of its twist angle-dependent electronic properties.

Maximizing Electric Power through Spectral-Splitting Photovoltaic-Thermoelectric Hybrid System Integrated with Radiative Cooling.

As zero-emission technologies, a daytime radiative cooling (RC) strategy developed recently, and photovoltaic (PV) and thermoelectric (TE) technologies have aroused great interest to reduce fossil fuel consumption and carbon emissions. How to integrate these state-of-the-art technologies to maximise clean electricity from the sun and space remains a huge challenge, and the limit efficiency is still unclear. In this study, a spectral-splitting PV-TE hybrid system integrated with RC is proposed to maximise clean electricity from the sun and space without any emissions. For the sun acting as a typical constant heat-flux heat source, the current thermoelectric theory overestimates the thermoelectric efficiency highly since the theory is based on constant temperature-difference conditions. A new theory based on heat-flux conditions is employed to achieve maximum thermoelectric efficiency. The PV-TE hybrid system with RC is superior to the conventional hybrid system, not only in terms of higher efficiency but also in its 24-h operation capacity. In a system with a single-junction cell, the total efficiency with 30 suns (39.4%) is higher than the theoretical PV efficiency at 500 suns (38.2%). In a hybrid system with four-junction cells, total efficiency is over 65% which is superior to most current photoelectric and thermal power systems.

Research status, challenges and future prospects of renewable synthetic fuel catalysts for CO2 photocatalytic reduction conversion.

In recent years, with global climate change, the utilization of carbon dioxide as a resource has become an important goal of human society to achieve carbon peaking and carbon neutrality. Among them, the catalytic conversion of carbon dioxide to generate renewable fuels has received great attention. As one of these methods, photocatalysis has its unique properties and mechanism, which can only rely on sunlight without inputting other energy. It is an emerging discipline with great development prospects. The core of photocatalysis lies in the development of photocatalysts with high activity, high selectivity, low cost, and high durability. This review first introduces the background and mechanism of photocatalysis, then introduces various types of photocatalysts based on different substrates, and analyzes the methods and mechanisms to improve the activity and selectivity of photocatalysts. Finally, combining the plasmon effect with photocatalysis, the review analyzes the promoting effect of the plasmon effect on the photocatalytic carbon dioxide synthesis of renewable fuels, which provides a new idea for it.

MicroRNA-375 Mediated Regulation on Pre-mRNA Processing Factor 3 in Zebrafish Embryos Exposed to Di-(2-ethylhexyl)phthalate at Low Concentrations.

Di-(2-ethylhexyl)phthalate (DEHP) is an endocrine-disrupting chemical (EDC) that induces epigenetic alterations, apoptosis, and oxidative stress after biological exposure. MicroRNAs (miRNAs) are a class of small noncoding RNAs with many regulatory functions and play a role in organisms exposed to environmental chemicals. miRNA-mRNA prediction indicated that pre-mRNA processing factor 3 (PRPF3) is a likely target mRNA for miR-375 whose expression is altered by DEHP exposure. However, the interrelation between miR-375 and PRPF3 has not yet been confirmed experimentally. This study aimed to investigate the effects of DEHP on miR-375 and PRPF3 in zebrafish. The expression of miR-375 was downregulated, whereas PRPF3 was upregulated at both transcriptional and post-transcriptional levels upon stimulation with DEHP. The interaction between miR-375 and the 3'-untranslated region (3'-UTR) of PRPF3 was confirmed by a dual fluorescent protein assay and a dual luciferase reporter gene assay. The expression of PRPF3 at both transcriptional and post-transcriptional levels was reduced in ZF4 cells when transfected with a miR-375 mimic but increased when transfected with a miR-375 inhibitor. The results improved our understanding of molecular mechanisms of toxicity upon DEHP exposure and presented miR-375 as a potential novel toxicological biomarker for chemical exposure.

Protective action of polysaccharides from Laurencia papillose (Rhodophyta) against imidacloprid induced genotoxicity and oxidative stress in male albino rats.

Imidacloprid (IMI), the main component of neonicotinoid insecticides, promotes oxidative stress and genotoxicity in mammals. The aim of this experiment is to assess oxidative stress in liver cells and genotoxicity of erythrocytes for rats exposed to sub-lethal doses of IMI and the protective effects for Rhodophyta as antioxidant material versus imidacloprid. A total of 30 adult male albino rats (average body weight, 190-200 g) were divided into six groups (n=5) as follows: group 1 served as the control, group 2 received 200 mg/kg red algae, group 3 received 45 mg/kg IMI (high-dose group), group 4 received 22.5 mg/kg IMI (low-dose group), group 5 received 200 mg/kg red algae +45 mg/kg IMI, and group 6 received 200 mg/kg red algae +22.5 mg/kg IMI. After 28 d of treatment, the antioxidant activity of the crude extract of red algae was assessed in terms of free radical scavenging activity and found to be higher in TCA (75.57%) followed by DPPH (50.08%) at concentration 100 µg extract and a significant increase in lipid peroxidation and reductions in glutathione were observed in liver cells were intoxicated with high and low doses of IMI. Moreover decreases in catalase and glutathione peroxidase parameters in same previous groups which indicated oxidative stress. In addition significant increases in micronucleus frequency (MN) in the bone marrow of the rats as a genotoxicity marker which indicated DNA damage in erythrocytes cells with alterations in the histopathology of liver cells were also noted such as necrosis, inflammatory cells, infiltration, and necrobiotic changes. Whereas Rhodophyta succeeded in alleviation the oxidative damage and genotoxicity induced by the insecticide. In conclusion, IMI demonstrates hazardous effects, such as alterations in antioxidant status and mutagenicity of erythrocytes and polysaccharides from Rhodophyta has good antioxidant activity in vivo model systems against imidacloprid.

Rapid measurement of T1*-T2* relaxation correlation with a Look-Locker sequence.

Measurement of longitudinal-transverse (T1-T2*) relaxation may be time-consuming for samples with a long T1 lifetime. In this work, a fast measurement method of T1*-T2* relaxation correlation was presented based on a saturation recovery Look-Locker sequence. T1* is the effective T1 lifetime. The T1 lifetime can be calculated from the measured T1* lifetime and acquisition parameters. The new measurement method was verified by numerical simulation. Three representative samples, corn starch, Advil caplets, and shale in the fields of food, pharmaceutics, and energy, were employed as test samples. Comparisons of T1*-T2* and T1-T2* relaxation correlations show that the new two-dimensional magnetic resonance pulse sequence works well, with a high collection efficiency and good accuracy.

Regulation of TRAF6 by MicroRNA-146a in Zebrafish Embryos after Exposure to Di(2-Ethylhexyl) Phthalate at Different Concentrations.

As an endocrine disruptor, di(2-ethylhexyl) phthalate (DEHP) is ubiquitous in multiple environmental media, causing long-term toxic effects on organisms. MicroRNAs are a class of noncoding RNAs with only 20-24 nucleotides in length, which regulate the expression of many protein-coding genes when organisms are exposed to environmental chemicals. MiR-146a, a differentially expressed miRNA after DEHP exposure, was screened by miRNA sequencing. As its target, TRAF6 was predicted and identified by double fluorescent protein assay and double fluorescent gene reporting assay. It shows the contrary expression pattern with miR-146a when mimics and inhibitors were transfected into ZF4 cells. MiR-146a and TRAF6 were downregulated and upregulated, respectively, in zebrafish embryos exposed to a low-dose concentration gradient of DEHP. These results deepen our understanding of the molecular mechanisms of DEHP toxicity and suggest that miR-146a can serve as a potential biomarker for DEHP exposure.

Magnetic resonance T1-T2* and T1ρ-T2* relaxation correlation measurements in solid-like materials with non-exponential decays.

Magnetic resonance T1-T2* relaxation correlation is a newly emerging and powerful tool to study the structure and dynamics of materials. However, the T1-T2* of solid-like materials may consist of a linear combination of exponential decays and non-exponential decays, and the traditional methods for processing T1-T2 data would be not applicable. In this paper, a method of processing T1-T2* data with non-exponential decays was proposed. The critical idea is to decompose the data into two sub-datasets, exponential decays and non-exponential decays, employing a non-linear fitting method, and then to invert the sub-datasets and to combine the inversion results. We also introduce a related relaxation correlation measurement, T1ρ-T2*, for examination of solid-like materials. The same data processing strategy as for T1-T2* was implemented. The effectiveness of the proposed method for processing non-exponential data, Sinc Gaussian and Gaussian decay, was validated with simulation and experiment. The results showed that the proposed method recovers T1-T2* and T1ρ-T2* spectra with accurate relative signal intensities. The proposed method provides a platform for further development of MR methods applied to solid-like materials. These relaxation correlations are well suited to measuring composition of mixtures, with solid components in the mixture.

T1-T2* relaxation correlation measurements.

The majority of low field Magnetic Resonance (MR) analyses rely on T2 lifetime measurements. Modification of the T2 measurement to include a T1 dimension has made the T1-T2 measurement a very powerful analytical technique. The T1-T2 measurement is uniquely well suited to characterization of different spin populations in porous materials, such as fluid bearing reservoir rocks, and in soft biopolymer materials, for example foods. However, the T1-T2 measurement is challenging or impossible if the T2 relaxation lifetime, or a component lifetime, is short-lived and the signal unobservable in an echo measurement. This occurs in many important classes of materials. A short lifetime T2 will not however, in general, preclude observation of a free induction decay with signal decay governed by T2*. As outlined in this paper a T1-T2* measurement is a useful analog to the T1-T2 experiment. T1-T2* measurement enables one to differentiate species as a function of T2* in one dimension and T1 in the other dimension. Monitoring changes of the T1-T2* coordinate, and associated signal intensity changes, has the potential to reveal structural changes in materials evolving in time. These methods may also be employed to discriminate and identify solid-like species present in static samples. The T1-T2* measurement is very general in application, but in this paper we focus on cement-based mortars to develop and illustrate the essential ideas. T1-T2* results show a multi-modal behaviour of the MR signal lifetimes, T1 and T2*, in mortar samples under study, indicating at least two different water populations. The short T2* lifetime was assigned to interlayer water (water between C-S-H layers) where the associated T1 is also short lived. The longer T2* lifetime was assigned to water in the pore space, where T1 is also longer lived. In addition to mortar samples we also show application of the method to a crystalline organic species, o-phenylenediamine, which features Sinc Gaussian and exponential decays of transverse magnetization.

Screening of metal-organic frameworks for water adsorption heat transformation using structure-property relationships.

It is of great importance to correlate the water adsorption performance of MOFs to their physicochemical features in order to design and prepare MOFs for applications in adsorption heat transformation. In this work, both data analysis from existing studies and Grand Canonical Monte Carlo molecular simulation investigations were carried out. The results indicated that the highest water adsorption capacity was determined by the pore volume of MOF adsorbents, while there was a linear correlation interrelationship between isosteric heats of adsorption and the water adsorption performance at a low relative pressure. More detailed analysis showed that the charge distribution framework and pore size of MOFs contributed together to the hydrophilicity. Electrostatic interaction between water molecules and the framework atoms played a key role at low relative water pressure. A quantitative structure-property relationship model that can correlate the hydrophilicity of MOFs to their pore size and atomic partial charge was established. Along with some qualitative considerations, the screening methodology is proposed and is used to screen proper MOFs in the CoRE database. Seven MOFs were detected, and four of them were synthesized to validate the screening principle. The results indicated that these four MOFs possessed outstanding water adsorption performance and could be considered as promising candidates in applications for adsorption heating and cooling.

A novel two-dimensional NMR relaxometry pulse sequence for petrophysical characterization of shale at low field.

Low field two-dimensional nuclear magnetic resonance (2D-NMR) relaxometry is a powerful probe for the characterization of heterogenous, porous media and provides geometrical, physical and chemical information about samples at a molecular level and has been widely used in shale studies. However, NMR signals of shale decay so rapidly, dry sample for particular, that the conventional two-dimensional pulse sequence is either not sensitive enough to short relaxation components or takes too much measurement time. In this paper, 2D-NMR relaxometry correlation based on partial inversion recovery CPMG (PIR-CPMG) pulse sequence is proposed and illustrated to improve the contrast over saturation recovery CPMG (SR-CPMG) and reduces the T1 encoding time of inversion recovery CPMG (IR-CPMG) for petrophysical characterization of shale. Subsequently, the kernel function and inversion method of this sequence are presented and the reliability of the inversion method is testified by numerical simulation. Next, theoretical analysis is conducted to validate the advantages of PIR-CPMG. Ultimately, experiments on copper sulfate solution, artificial sandstone, and shale samples are performed, respectively, to verify the feasibility and effectiveness of the proposed pulse sequence. The results demonstrate that the PIR-CPMG sequence is time-saving and high-contrast, especially for the short relaxation components. This pulse sequence can be utilized in bench-top NMR core analyzer and downhole well logging, potentially, to achieve integrated petrophysical characterization of shale.

MicroRNAs as Potential Biomarkers of Insecticide Exposure: A Review.

Insecticides are key weapons for the control of pests. Large scale use of insecticides is harmful to the ecosystem, which is made up of a wide range of species and environments. MicroRNAs (miRNAs) are a class of endogenous single-stranded noncoding small RNAs in length of 20-24 nucleotides (nt), which extensively regulate expression of genes at transcriptional and post-transcriptional levels. The current research on miRNA-induced insecticide resistance reveals that dysregulated miRNAs cause significant changes in detoxification genes, particularly cytochrome P450s. Meanwhile, insecticide-induced changes in miRNAs are related to the decline of honeybees and threatened the development of zebrafish and other animals. Additionally, miRNAs are involved in insecticide-induced cytotoxicity, and dysregulated miRNAs are associated with human occupational and environmental exposure to insecticides. Therefore, miRNAs are valuable novel biomarkers of insecticide exposure, and they are potential factors to explain the toxicological effects of insecticides.

Nuclear magnetic resonance T1-T2 inversion with double objective functions.

We report an effective and robust method for nuclear magnetic resonance (NMR) longitudinal relaxation time-transverse relaxation time (T1-T2) inversion with double objective functions. First, we develop the first objective function based on L1 regularization, proposed an effective method to choose the optimum L1 regularization parameter, and solve the objective function employing a two-step iterative shrinkage/thresholding algorithm. Subsequently, we update the kernel matrix based on the solution of the first objective function, and then develop the second objective function using the measured data and updated kernel matrix based on the least-squares principle, and we use the conjugate gradient algorithm for the first time to solve the objective function about NMR data inversion. To improve the speed of NMR T1-T2 inversion, we present a Gaussian-based random SVD method. Finally, numerical and experimental examples are done to test the robustness of the proposed inversion method. The results indicate that the proposed inversion method can effectively achieve NMR T1-T2 inversion at a low data SNR.

Triazophos-induced toxicity in zebrafish: miRNA-217 inhibits nup43.

Triazophos is a highly toxic organophosphorus pesticide, causing acute toxicity to brain tissue, and neurotoxicity and embryotoxicity to animals. Therefore, triazophos is considered as a public health problem due to its acute hazard index. MicroRNAs (miRNAs), a class of endogenous noncoding RNAs, can regulate the expression of target gene(s) by mediating mRNA cleavage or translational repression in organisms exposed to environmental chemicals. We found that nup43 is targeted by miR-217, which was significantly regulated in adult zebrafish (Danio rerio) exposed to triazophos (phenyl-1,2,4-triazolyl-3-(o,o-diethyl thionophosphate)). The expression of nup43 in both mRNA and protein levels was downregulated in a dose-dependent manner upon stimulation with triazophos. A dual luciferase reporter assay demonstrated that miR-217 interacted with the 3'-untranslated regions (3'-UTR) of nup43. The expression of nup43 in both mRNA and protein level was reduced in ZF4 cells when transfected with an miR-217 mimic, but increased when transfected with an miR-217 inhibitor. As a result, nup43 is targeted by miR-217 upon triazophos exposure. We suggest that miR-217 could be a potential toxicological biomarker for triazophos.

Transcriptome sequencing analysis of novel sRNAs of Kineococcus radiotolerans in response to ionizing radiation.

Kineococcus radiotolerans is a Gram-positive, radio-resistant bacterium isolated from a radioactive environment. The small noncoding RNAs (sRNAs) in bacteria are reported to play roles in the immediate response to stress and/or the recovery from stress. The analysis of K. radiotolerans transcriptome sequencing results can identify these sRNAs in a genome-wide detection, using RNA sequencing (RNA-seq) by the deep sequencing technique. In this study, the raw data of radiation-exposed samples (RS) and control samples (CS) were acquired separately from the sequencing platform. There were 217 common sRNA candidates in the two samples screened in the genome-wide scale by bioinformatics analysis. There were 43 differentially expressed sRNA candidates, including 28 up-regulated and 15 down-regulated ones. The down-regulated sRNAs were selected for the sRNA target prediction, of which 12 sRNAs that may modulate the genes related to the transcription regulation and DNA repair were considered as the candidates involved in the radio-resistance regulation system.

miRNA-216 and miRNA-499 target cyb561d2 in zebrafish in response to fipronil exposure.

MicroRNA (miRNA) can regulate the expression of its target gene by mediating mRNA cleavage or by translational repression at a post-transcriptional level. Usually, one miRNA may regulate many genes as its targets, while one gene may also be targeted by many miRNAs. We previously demonstrated that cyb561d2, whose protein product is involved in cell defense, and chemical stress, is targeted by miR-155 in adult zebrafish (Danio rerio) when exposed to fipronil (5-amino-1-[2,6-dichloro-4-(trifluoromethyl) phenyl]-4-[(trifluoromethyl) sulphinyl]-1H-pyrazole-3-carbonitrile). Microcosm Targets prediction showed that the cyb561d2 gene is also highly possibly targeted by miR-194a, miR-216b, miR-429, and miR-499. These interactions need to be further validated experimentally. In this study, we evaluated the effects of fipronil on miR-194a, miR-216b, miR-429, miR-499 and cyb561d2 in zebrafish and investigated whether these four miRNAs could regulate the expression of cyb561d2 in both mRNA and protein levels. The expression of cyb561d2 was upregulated in both mRNA and protein level in a dose-dependent manner upon stimulation of fipronil, and miR-216b and miR-499 were downregulated concurrently, whereas there was no significant changes were observed in the expression level of miR-194a and miR-429. The dual luciferase report assay demonstrated that miR-216b and miR-499 interacted with cyb561d2 3'-untranslated regions (3'-UTR), miR-194a and miR-429 did not stimulate degradation of cyb561d2 mRNA. The expression of cyb561d2 was reduced in both mRNA and protein level when ZF4 cells were transfected with miR-499 mimic, whereas expression level of both mRNA and protein was increased when endogenous miR-499 was inhibited by transfection with miR-499 inhibitor. Likewise, the mRNA and protein level of cyb561d2 was affected by treatment with the mimics and the inhibitor of miR-216b. In contrast, when ZF4 cells were transfected with a mimic of miR-194a or miR-429, the expression of cyb561d2 mRNA was not significantly changed. As a result, cyb561d2 is targeted by miR-155, miR-216b and miR-499 upon fipronil exposure, and miR-194a and miR-429 can not target cyb561d2. The expression pattern of these 3 miRNAs presents novel fipronil responses that could be used as a toxicological biomarker.

MicroRNA-155 targets cyb561d2 in zebrafish in response to fipronil exposure.

MicroRNAs (miRNAs), which are a class of small noncoding RNAs, can modulate the expression of many protein-coding genes when an organism is exposed to an environmental chemical. We previously demonstrated that miR-155 was significantly downregulated in adult zebrafish (Danio rerio) in response to fipronil (5-amino-1-[2,6-dichloro-4-(trifluoromethyl) phenyl]-4-[(trifluoromethyl) sulphinyl]-1H-pyrazole-3-carbonitrile) exposure. However, the regulation of this miRNA's predicted target gene cyb561d2, which is a member of the cytochrome b561 (cyt b561) family involved in electron transfer, cell defence, and chemical stress, has not been experimentally validated to date. In this study, we evaluated the effects of fipronil on miR-155 and cyb561d2 in zebrafish. The expression of miR-155 was downregulated, whereas cyb561d2 was upregulated in both mRNA and protein level in a dose-dependent manner upon stimulation of fipronil. The dual luciferase report assay demonstrated that miR-155 interacted with cyb561d2 3'-untranslated regions (3'-UTR). The expression of cyb561d2 was reduced in both mRNA and protein levels when ZF4 cells were transfected with an miR-155 mimic, whereas its expression levels of both mRNA and protein were increased when endogenous miR-155 was inhibited by transfection with an miR-155 inhibitor. The results improved our understanding of molecular mechanism of toxicity upon fipronil exposure, and presents miR-155 as a potential novel toxicological biomarker for chemical exposure. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 877-886, 2016.