Effects of acrylamide on creatine kinase from rabbit muscle

Molecular determinants of acrylamide neurotoxicity through covalent docking

Acrylamide (ACR) is formed during food processing by Maillard reaction between sugars and proteins at high temperatures. It is also used in many industries, from water waste treatment to manufacture of paper, fabrics, dyes and cosmetics. Unfortunately, cumulative exposure to acrylamide, either from diet or at the workplace, may result in neurotoxicity. Such adverse effects arise from covalent adducts formed between acrylamide and cysteine residues of several neuronal proteins via a Michael addition reaction. The molecular determinants of acrylamide reactivity and its impact on protein function are not completely understood. Here we have compiled a list of acrylamide protein targets reported so far in the literature in connection with neurotoxicity and performed a systematic covalent docking study. Our results indicate that acrylamide binding to cysteine is favored in the presence of nearby positively charged amino acids, such as lysines and arginines. For proteins with more than one reactive Cys, docking scores were able to discriminate between the primary ACR modification site and secondary sites modified only at high ACR concentrations. Therefore, docking scores emerge as a potential filter to predict Cys reactivity against acrylamide. Inspection of the ACR-protein complex structures provides insights into the putative functional consequences of ACR modification, especially for non-enzyme proteins. Based on our study, covalent docking is a promising computational tool to predict other potential protein targets mediating acrylamide neurotoxicity.

Redesigning food protein formulations with empirical phase diagrams: A case study on glycerol-poor and glycerol-free formulations

Redesigning existing food protein formulations is necessary in situations where food authorities propose dose adjustments or removal of currently employed additives. Redesigning formulations involves evaluating substitute additives to obtain similar long-term physical stability as the original formulation. Such formulation screening experiments benefit from comprehensive data visualization, understanding the effects of substitute additives on long-term physical stability, and identification of short-term optimization targets. This work employs empirical phase diagrams to reach these benefits by combining multidimensional long-term protein physical stability data with short-term empirical protein properties. A case study was performed where multidimensional protein phase diagrams (1152 formulations) allowed for identification of stabilizing effects as a result of pH, methionine, sugars, salt, and minimized glycerol content. Corresponding empirical protein property diagrams (144 formulations) resulted in the identification of normalized surface tension as a short-term empirical protein property to reach long-term physical stability presumably similar to the original product, namely via preferential hydration. Additionally, changes in pH and salt were identified as environmental optimization targets to reach stability via repulsive electrostatic forces. This case study shows the applicability of the empirical phase diagram method to rationally perform formulation redesign screenings, while simultaneously expanding knowledge on protein long-term physical stability.

Functional attributes of evolutionary conserved Arg45 of Wolbachia (Brugia malayi) translation initiation factor-1

AIM

Wolbachia is a promising antifilarial chemotherapeutic target. Translation initiation factor-1 (Tl IF-1) is an essential factor in prokaryotes. Functional characterization of Wolbachia's novel proteins/enzymes is necessary for the development of adulticidal drugs.

MATERIALS & METHODS

Mutant, Wol Tl IF-1 R45D was constructed by site directed mutagenesis. Fluorimetry and size exclusion chromatography were used to determine the biophysical characteristics. Mobility shift assay and fluorescence resonance energy transfer were used to investigate the functional aspect of Wol Tl IF-1 with its mutant.

RESULTS

Both wild and mutant were in monomeric native conformations. Wild exhibits nonspecific binding with ssRNA/ssDNA fragments under electrostatic conditions and showed annealing and displacement of RNA strands in comparison to mutant.

CONCLUSION

Point mutation impaired RNA chaperone activity of the mutant and its interaction with nucleotides.

The effect of lipoic acid on acrylamide-induced neuropathy in rats with reference to biochemical, hematological, and behavioral alterations

CONTEXT

Acrylamide (ACR) is a well-known neurotoxicant and carcinogenic agent which poses a greater risk for human and animal health.

OBJECTIVE

The present study evaluates the beneficial effects of α-lipoic acid (LA) on ACR-induced neuropathy.

MATERIALS AND METHODS

A total of 40 male rats were divided into four groups: a placebo group; LA-treated group, administered orally 1% (w/w) LA mixed with diet; ACR-treated group, given 0.05% (w/v) ACR dissolved in drinking water; and LA + ACR-treated group, given LA 1% 7 d before and along with ACR 0.05% for 21 d. After 28 d, blood samples were collected, the rats were decapitated, and the tissues were excised for the measurement of brain biomarkers, antioxidant status, and hematological analysis. Also, the gait score of rats was evaluated.

RESULTS

ACR-exposed rats exhibited abnormal gait deficits with significant (p < 0.05) decline in acetylcholine esterase (AChE) and creatine kinase in serum and brain tissues, respectively. However, the lactate dehydrogenase activity was increased in serum by 123%, although it decreased in brain tissues by -74%. ACR significantly (p < 0.05) increased the malondialdehyde level by 273% with subsequent depletion of glutathione S-transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR) activities and reduced the glutathione (GSH) level in brain tissue. Interestingly, LA significantly (p < 0.05) improved brain enzymatic biomarkers, attenuated lipid peroxidation (LPO), and increased antioxidant activities compared with the ACR-treated group.

DISCUSSION AND CONCLUSION

These results suggested that LA may have a role in the management of ACR-induced oxidative stress in brain tissues through its antioxidant activity, attenuation of LPO, and improvement of brain biomarkers.

A novel interaction mode between acrylamide and its specific antibody

Since the discovery of high-level acrylamide (Acr) contamination in food, extensive international studies have focused on its toxicity and detection. By using a novel antigen synthetic strategy, we have successfully obtained a specific antibody towards acrylamide (Acr-Ab). Herein, the Acr-Ab and its interactions with Acr were characterized. Enzyme-linked immunosorbent assay (ELISA) and dynamic light scattering (DLS) investigations revealed that the conformational structure of Acr-Ab was sensitive to buffers. It showed a satisfied immunoreactivity in phosphate buffered saline (PBS), but denatured in water. In natural state, Acr-Ab had a trend of getting aggregation through their complementarity determining regions (CDRs). Adding Acr leaded to their disassembling. While mixed with Acr, Acr-Ab exhibits not only a fast, high-specific, and reversible non covalent binding (by surface plasmon resonance, SPR), but also a covalent alkylation with Acr through cysteine and histidine residues on its surface, as demonstrated by high-performance liquid chromatography (HPLC). Neither of the two reactions involves conformational change in secondary or tertiary structures as shown in circular dichroism spectra (CD). These special properties of Acr-Ab and the entirely new interaction mode with Acr will extend our knowledge of Acr related biosystem and facilitate the development of new detection strategies for Acr.

Effect of sub-acute exposure to acrylamide on GABAergic neurons and astrocytes in weaning rat cerebellum

Occupational exposure and experimental intoxication of acrylamide (ACR) can produce skeletal muscle weakness and ataxia. In this study, we tested whether ACR would affect cerebellar function through the regulation of gamma-aminobutyric acid (GABA) and glial fibrillary acidic protein (GFAP) expression in cerebellum. Weaning male Sprague-Dawley rats were gavaged with ACR (5, 15, 30 mg/kg, 5 days per week) or saline for 4 weeks. Effects of ACR on the cerebellum were observed. For the 5 mg/kg group, no obvious change was observed, whereas moderate and severe ataxia were observed in the 15 mg/kg and 30 mg/kg groups, respectively. For the 15 mg/kg and 30 mg/kg groups, cerebellum concentrations of glutamate and GABA were dose-dependently decreased and increased, respectively. Moreover, the expression of GABA, the GABAergic presynaptic marker glutamate acid decarboxylase-65 (GAD65) and GFAP were significantly increased in those 2 groups. The results suggested that weaning rats were sensitive to ACR and that the toxic effects of ACR on the cerebellum may be associated with the increased expression of GABA and reactive astrocytes hypertrophy.

Effects of acrylamide on the activity and structure of human brain creatine kinase

Acrylamide is widely used worldwide in industry and it can also be produced by the cooking and processing of foods. It is harmful to human beings, and human brain CK (HBCK) has been proposed to be one of the important targets of acrylamide. In this research, we studied the effects of acrylamide on HBCK activity, structure and the potential binding sites. Compared to CKs from rabbit, HBCK was fully inactivated at several-fold lower concentrations of acrylamide, and exhibited distinct properties upon acrylamide-induced inactivation and structural changes. The binding sites of acrylamide were located at the cleft between the N- and C-terminal domains of CK, and Glu232 was one of the key binding residues. The effects of acrylamide on CK were proposed to be isoenzyme- and species-specific, and the underlying molecular mechanisms were discussed.

Inhibition of acrylamide toxicity in mice by three dietary constituents

The inhibitory effects of three dietary constituents, tea polyphenols, resveratrol, and diallyl trisulfide, on acrylamide-biomacromolecule (liver DNA, protamine, and hemoglobin) adduct formation at human exposure level were studied by accelerator mass spectrometry. The results demonstrated that the three dietary constituents all significantly inhibited the formation of acrylamide adducts with liver DNA, whereas tea polyphenols and diallyl trisulfide reduced protamine and hemoglobin adducts, respectively. Further biochemical studies showed that acrylamide could significantly inactivate creatine kinase and glutathione S-transferase and deplete glutathione. When the inhibitors were cotreated with acrylamide, all of them could effectively recover the activities of creatine kinase. In addition, tea polyphenols and diallyl trisulfide could increase glutathione S-transferase activity remarkably. On the basis of these results, mechanisms of the effects are discussed. This study might provide a beneficial guide to people's diet for the purpose of reducing the harmful effect of acrylamide.

Review of methods for the reduction of dietary content and toxicity of acrylamide

Potentially toxic acrylamide is largely derived from heat-induced reactions between the amino group of the free amino acid asparagine and carbonyl groups of glucose and fructose in cereals, potatoes, and other plant-derived foods. This overview surveys and consolidates the following dietary aspects of acrylamide: distribution in food originating from different sources; consumption by diverse populations; reduction of the acrylamide content in the diet; and suppression of adverse effects in vivo. Methods to reduce adverse effects of dietary acrylamide include (a) selecting potato, cereal, and other plant varieties for dietary use that contain low levels of the acrylamide precursors, namely, asparagine and glucose; (b) removing precursors before processing; (c) using the enzyme asparaginase to hydrolyze asparagine to aspartic acid; (d) selecting processing conditions (pH, temperature, time, processing and storage atmosphere) that minimize acrylamide formation; (e) adding food ingredients (acidulants, amino acids, antioxidants, nonreducing carbohydrates, chitosan, garlic compounds, protein hydrolysates, proteins, metal salts) that have been reported to prevent acrylamide formation; (f) removing/trapping acrylamide after it is formed with the aid of chromatography, evaporation, polymerization, or reaction with other food ingredients; and (g) reducing in vivo toxicity. Research needs are suggested that may further facilitate reducing the acrylamide burden of the diet. Researchers are challenged to (a) apply the available methods and to minimize the acrylamide content of the diet without adversely affecting the nutritional quality, safety, and sensory attributes, including color and flavor, while maintaining consumer acceptance; and (b) educate commercial and home food processors and the public about available approaches to mitigating undesirable effects of dietary acrylamide.

Acrylamide-induced oxidative stress and biochemical perturbations in rats

Acrylamide is neurotoxic to experimental animals and humans. Also, it has mutagenic and carcinogenic effects. The present study was carried out to investigate the effects of different doses of acrylamide on some enzyme activities and lipid peroxidation in male rats. Animals were assigned at random to one of the following treatments: group 1 served as control, while groups 2, 3, 4, 5, 6 and 7 were treated with 0.5, 5, 25, 50, 250 and 500 microg/kg body weight of acrylamide, respectively in drinking water for 10 weeks. Acrylamide significantly decreased plasma protein levels and the activity of creatine kinase, while increased plasma phosphatases. The activities of transaminases and phosphatases were significantly decreased in liver and testes, while lactate dehydrogenase did not change compared to control group. Plasma and brain acetylcholinesterase activity was significantly decreased. The concentration of thiobarbituric acid reactive substances, and the activities of glutathione S-transferase and superoxide dismutase in plasma, liver, testes, brain, and kidney were increased in acrylamide-treated rats. On the other hand, results obtained showed that acrylamide significantly reduced the content of sulfhydryl groups and protein in different tissues. The present results showed that different doses of acrylamide exerted deterioration effects on enzyme activities and lipid peroxidation in a dose-dependent manner.