Integrated approach to the mechanisms of thyroid toxins: electron transfer, reactive oxygen species, oxidative stress, cell signaling, receptors, and antioxidants

Protective Effects of Melatonin against Carcinogen-Induced Oxidative Damage in the Thyroid

Melatonin, primarily synthesized in the pineal gland, plays a crucial role in regulating circadian rhythms and possesses significant antioxidative properties. By neutralizing free radicals and reducing oxidative stress, melatonin emerges as a promising agent for the prevention and therapy of many different disorders, including cancer. This paper reviews the relationship between the thyroid gland and melatonin, presenting experimental evidence on the protective effects of this indoleamine against oxidative damage to macromolecules in thyroid tissue caused by documented carcinogens (as classified by the International Agency for Research on Cancer, IARC) or caused by potential carcinogens. Furthermore, the possible influence on cancer therapy in humans and the overall well-being of cancer patients are discussed. The article highlights melatonin's essential role in maintaining thyroid health and its contribution to management strategies in patients with thyroid cancer and other thyroid diseases.

Iodine as a potential endocrine disruptor-a role of oxidative stress

PURPOSE

Iodine is an essential micronutrient required for thyroid hormone biosynthesis. However, overtreatment with iodine can unfavorably affect thyroid physiology. The aim of this review is to present the evidence that iodine-when in excess-can interfere with thyroid hormone synthesis and, therefore, can act as a potential endocrine-disrupting chemical (EDC), and that this action, as well as other abnormalities in the thyroid, occurs-at least partially-via oxidative stress.

METHODS

We reviewed published studies on iodine as a potential EDC, with particular emphasis on the phenomenon of oxidative stress.

RESULTS

This paper summarizes current knowledge on iodine excess in the context of its properties as an EDC and its effects on oxidative processes.

CONCLUSION

Iodine does fulfill the criteria of an EDC because it is an exogenous chemical that interferes-when in excess-with thyroid hormone synthesis. However, this statement cannot change general rules regarding iodine supply, which means that iodine deficiency should be still eliminated worldwide and, at the same time, iodine excess should be avoided. Universal awareness that iodine is a potential EDC would make consumers more careful regarding their diet and what they supplement in tablets, and-what is of great importance-it would make caregivers choose iodine-containing medications (or other chemicals) more prudently. It should be stressed that compared to iodine deficiency, iodine in excess (acting either as a potential EDC or via other mechanisms) is much less harmful in such a sense that it affects only a small percentage of sensitive individuals, whereas the former affects whole populations; therefore, it causes endemic consequences.

Effect of Nigella sativa and Foeniculum vulgare seeds extracts on male mice exposed to carbendazim

The increasing prevalence of environmental pollutants such as pesticides is a major global problem that affects living organisms. Exposure to environmental pollutants remains a major source of health risk throughout the world. The potential health benefits of various medicinal plants and natural products in relation to protect various diseases are currently receiving considerable attention. A current approach is to develop a new biological compound from natural products that inhibits pain. Ethnopharmacological surveys have been found to be one of the most reliable tools for the discovery of the natural and semi-synthetic drug. The present study was performed to investigate the hematological and biochemical changes induced by carbendazim (CBZ) and the potential protective effect of seeds extracts of Nigella sativa (NSSE) and Foeniculum vulgare (FVSE) against CBZ toxicity in male mice. Mice were distributed into 6 groups. Mice of group 1 were served as control. Group 2 was exposed to CBZ. Group 3 was supplemented with NSSE and exposed to CBZ. Group 4 was treated with FVSE and CBZ. Normal mice of group 5 and 6 were subjected to NSSE and FVSE respectively. Body weight gain was significantly decreased in mice of group 2. In mice of group 2, significant declines of RBC, HB, Hct, WBC, total protein, FSH, LH, testosterone, T4, T3, CAT and SOD were observed. Moreover, the levels of ALT, AST, ALP, total bilirubin, creatinine, BUN, uric acid, glucose, cholesterol, CK, LDH, MDA and GSH were significantly enhanced. Treatment with NSSE and FVSE showed attenuation effects against CBZ induced hematological and biochemical changes. The results suggest that the attenuation effects of NSSE and FVSE attributed to their antioxidant properties.

Neurochemical alterations following the exposure to di-n-butyl phthalate in rats

Due to its ability to cross blood brain barrier and placenta, dibutyl phthalate (di-n-butyl phthalate, DBP) is expected to cause severe side effects to the central nervous system of animals and humans. A little data is available about the potential DBP neurotoxicity; therefore, this work was designed to investigate the brain tissue injury induced by DBP exposure. Forty Wister albino rats were allocated randomly into 4 groups (10 rats each). Group 1 served as control and the rats administered with physiological saline (0.9% NaCl) orally for 12 weeks. Groups 2, 3 and 4 were orally treated with DPB (100, 250 and 500 mg/kg) respectively for 12 weeks. DBP-intoxicated rats showed a disturbance in the oxidative status in cerebral cortex, striatum and brainstem, as represented by the elevated oxidants [malondialdehyde (MDA), nitric oxide (NO), 8-hydroxy-2-deoxyguanosine (8-OHdG)] and the decreased antioxidant molecules [reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR)]. DBP also enhanced a pro-inflammatory state through increasing the release of tumor necrosis factor- α (TNF-α) and interleukin-1β (IL-1β). The increase of these cytokines was associated with the increase of pro-apoptotic proteins [Bcl-2 associated X protein (Bax) and caspase-3] and the decrease of the anti-apoptotic protein, B cell lymphoma 2 (Bcl-2). In addition, the levels of norepinephrine (NE), dopamine (DA) and acetylcholine esterase (AChE) activity were decreased. This was accompanied by the alterations in the major excitatory and inhibitory amino acids neurotransmitters levels. The present findings indicated that DBP could exert its neuronal damage through oxidative stress, DNA oxidation, neuroinflammation, activation of apoptotic proteins and altering the monoaminergic, cholinergic and amino acids transmission.

The possible ameliorative effect of Olea europaea L. oil against deltamethrin-induced oxidative stress and alterations of serum concentrations of thyroid and reproductive hormones in adult female rats

This study aimed to verify whether Olea europaea L. (olive) oil (OEO) exerted a protective effect against oxidative stress induced by deltamethrin (DM) and alterations of pituitary, thyroid and gonadal hormones in adult female rats. DM (0,00256 g/kg body weight),OEO (0,6 g/kg body weight) and DM with OEO were administered to rats orally for 28 days. Volatile compounds present in olive oil were analysed by GC-MS. Estradiol (E₂), Thyroxine (T4),Thyroid Stimulating Hormone (TSH), Triiodothyronine (T3), Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Progesterone (Pg) were measured in serum using Chemiluminescent Microparticle Immunoassay (CMIA). Lipid peroxidation (LPO), protein carbonyls (PCs), reduced glutathione (GSH) levels along with superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and glutathione peroxidase (GPx) activities were determined in thyroid and ovarian tissues. Sesquiterpenes, (E,E)-α-farnesene (16.45%) and α-copaene (9,86%), were analysed as the main volatile compounds of OEO. The relative weight of ovaries and thyroid and body weight significantly decreased in rats treated with DM. DM caused significant alterations in TSH, T4, FSH, Pg and E₂ levels while T3 and LH concentrations remained unchanged when compared to control. DM also increased significantly LPO and PCs levels. In addition, GSH reserves as well as CAT, GPx, SOD and GST activities were suppressed in DM-received rats. The presence of OEO with DM returned the levels of oxidative stress markers, thyroid and reproductive hormones at the control values. Our results indicate that OEO is a powerful agent able to protect against DM oxidative stress and endocrine changes.

Relationship between urine lipid peroxidation, anthropometric parameters and parameters associated with goitre formation in school-age children

INTRODUCTION

Oxidative stress has been implicated in the normal ageing process and the pathogenesis of several diseases, including goitre. The aim of the study was to evaluate the relationship between urine lipid peroxidation (LPO) and anthropometric parameters as well as the parameters associated with goitre formation in children.

MATERIAL AND METHODS

The subjects included 172 healthy children (93 girls and 79 boys) aged 8-15, divided into 4 age groups - group I (8-9 years), group II (10-11 years), group III (12-13 years) and group IV (14-15 years) - and into 2 groups based on the BSA: the BSA-1 group (≤ 0.55 m²) and the BSA-2 group (> 0.55 m²).

RESULTS

The value of LPO was the highest in group I but the difference between the groups was not statistically significant (p = 0.074). In the BSA-1 group, the LPO was higher than in the BSA-2 group (12.75 ±6.90 nmol/ml and 10.79 ±4.86 nmol/ml, respectively; p = 0.023). We found a weak, negative linear correlation between LPO and age (r = -0.216; p < 0.005), body mass (r = -0.153; p < 0.05), height (r = -0.152; p < 0.05) and BSA (r = -0.151; p < 0.05).

CONCLUSIONS

Anthropometric parameters of school-age children independently of age are negatively associated with oxidative damage to membrane lipids, whereas factors promoting goitrogenesis do not contribute to this process.

Papillary Thyroid Carcinoma: A Malignant Tumor with Increased Antioxidant Defense Capacity

Papillary thyroid carcinoma (PTC) is the commonest thyroid malignancy worldwide for which the radiation exposure is the most influential risk factor. The levels of oxidative stress in PTC are not well characterized on the tissue level. The objective of this study was to evaluate total oxidant status (TOS) and total antioxidant status (TAS) in PTC and benign goiter (BG) tissues and to examine their association with clinicopathological characteristics. Tumor and normal thyroid tissue samples were collected from 59 PTC patients, and goiter tissues were collected from 50 BG patients. TOS and TAS were quantified in the tissue homogenates by spectrophotometric assays. TOS values in tumor tissues did not differ significantly from normal and goiter tissues; however, PTC tissues have significantly higher TAS values than normal and goiter tissues. TOS values correlated with retrosternal growth in BG patients. The significant correlations were found between TOS and TAS values and thyroid function parameters. In 17 PTC patients with multiple tumor foci (multicentric phenotype), TAS values were significantly lower, compared to 42 patients with unicentric PTC. TAS and TOS are the most useful predictors of thyroid capsular invasion by PTC. The age, sex, body mass index, smoking, familial history of thyroid disease and nodule size did not influence TOS and TAS in PTC or BG patients. In conclusion, we show the profiles of TOS and TAS in PTC and BG tissues. Importantly, PTC tissues possess increased antioxidant capacity. The redox status influences the parameters of the thyroid function and tumor's biological behavior.

Effects of electromagnetic radiation exposure on stress-related behaviors and stress hormones in male wistar rats

Studies have demonstrated that electromagnetic waves, as the one of the most important physical factors, may alter cognitive and non-cognitive behaviors, depending on the frequency and energy. Moreover, non-ionizing radiation of low energy waves e.g. very low frequency waves could alter this phenomenon via alterations in neurotransmitters and neurohormones. In this study, short, medium, and long-term exposure to the extremely low frequency electromagnetic field (ELF-EMF) (1 and 5 Hz radiation) on behavioral, hormonal, and metabolic changes in male Wistar rats (250 g) were studied. In addition, changes in plasma concentrations for two main stress hormones, noradrenaline and adrenocorticotropic hormone (ACTH) were evaluated. ELF-EMF exposure did not alter body weight, and food and water intake. Plasma glucose level was increased and decreased in the groups which exposed to the 5 and 1Hz wave, respectively. Plasma ACTH concentration increased in both using frequencies, whereas nor-adrenaline concentration showed overall reduction. At last, numbers of rearing, sniffing, locomotor activity was increased in group receiving 5 Hz wave over the time. In conclusions, these data showed that the effects of 1 and 5 Hz on the hormonal, metabolic and stress-like behaviors may be different. Moreover, the influence of waves on stress system is depending on time of exposure.

Nitroaromatic compounds: Environmental toxicity, carcinogenicity, mutagenicity, therapy and mechanism

Vehicle pollution is an increasing problem in the industrial world. Aromatic nitro compounds comprise a significant portion of the threat. In this review, the class includes nitro derivatives of benzene, biphenyls, naphthalenes, benzanthrone and polycyclic aromatic hydrocarbons, plus nitroheteroaromatic compounds. The numerous toxic manifestations are discussed. An appreciable number of drugs incorporate the nitroaromatic structure. The mechanistic aspects of both toxicity and therapy are addressed in the context of a unifying mechanism involving electron transfer, reactive oxygen species, oxidative stress and antioxidants.

Nanoparticles: toxicity, radicals, electron transfer, and antioxidants

In recent years, nanoparticles have received increasing attention in research and technology, including a variety of practical applications. The bioactivity appears to be related to the small particle size, in addition to inherent chemical activity as electron transfer (ET) agents, generators of reactive oxygen species (ROS) with subsequent oxidative stress (OS), and as antioxidants (AOs). The mechanism of toxicity, therapeutic action, and AO property is addressed based on the ET-ROS-OS approach. There are several main classes of ET functionalities, namely, quinones (or phenolic precursors), metal compounds, aromatic nitro compounds (or reduction products), and imine or iminium species. Most of the nanospecies fall within the metal category. Cell signaling is also discussed. This review discusses recent developments based on ET-ROS-OS-AO framework.

Oxidative damage to macromolecules in the thyroid - experimental evidence

Whereas oxidative reactions occur in all tissues and organs, the thyroid gland constitutes such an organ, in which oxidative processes are indispensable for thyroid hormone synthesis. It is estimated that huge amount of reactive oxygen species, especially of hydrogen peroxide (H₂O₂), are produced in the thyroid under physiological conditions, justifying the statement that the thyroid gland is an organ of “oxidative nature”. Apart from H₂O₂, also other free radicals or reactive species, formed from iodine or tyrosine residues, participate in thyroid hormone synthesis. Under physiological conditions, there is a balance between generation and detoxification of free radicals. Effective protective mechanisms, comprising antioxidative molecules and the process of compartmentalization of potentially toxic molecules, must have been developed in the thyroid to maintain this balance. However, with additional oxidative abuse caused by exogenous or endogenous prooxidants (ionizing radiation being the most spectacular), increased damage to macromolecules occurs, potentially leading to different thyroid diseases, cancer included.

Membrane lipids and nuclear DNA are differently susceptive to Fenton reaction substrates in porcine thyroid

Fenton reaction (Fe(2+)+H(2)O(2) → Fe(3+)+()OH+OH(-)) is of special significance in the thyroid, as both substrates are indispensable for thyroid hormone synthesis, therefore being available presumably at high concentrations under physiological conditions. The study aimed at evaluation if both Fenton reaction substrates are required to induce oxidative damage to membrane lipids and nuclear DNA in porcine thyroid homogenates, and if these macromolecules are vulnerable to the same extent. Thyroid homogenates and nuclear DNA were incubated in the presence of H(2)O(2) and/or Fe(2+). Malondialdehyde+4-hydroxyalkenals (MDA+4-HDA) concentration (lipid peroxidation index) was measured spectrophotometrically, and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) concentration (DNA damage index) by HPLC. Whereas Fenton reaction substrates, used separately, did not affect lipid peroxidation, they increased 8-oxodG level for the highest H(2)O(2) concentration (100mM) and in Fe(2+) concentration-dependent manner (300, 150, 30 and 15 μM). If Fe(2+) and H(2)O(2) were applied together, lipid peroxidation increased significantly, however without H(2)O(2) concentration- but with clear Fe(2+) concentration-dependent effect. Concerning DNA damage, Fe(2+) enhanced H(2)O(2) effect, whereas Fe(2+) concentration-dependent effect was not changed by H(2)O(2). Excess of exclusively one of Fenton reaction substrates is sufficient to induce oxidative DNA damage, but not lipid peroxidation, in porcine thyroid. Comparing to H(2)O(2), Fe(2+) seems to be a stronger damaging substrate.

Propoxur: a novel mechanism for insecticidal action and toxicity

Propoxur is a carbamate insecticide that has recently attracted considerable attention as a possible treatment option for addressing the bedbug epidemic. The generally accepted mechanism of toxicity for propoxur involves the inhibition of ChE, as is the case for many agents in the category. Considerable research supports the concept that most physiologically active substances induce their effects through multi-faceted action. In this review, we provide evidence that ET--ROS--OS participate mechanistically in both the action and in human toxicity of pesticides, including propoxur. Propoxur is a catechol derivative that contains carbamate and isopropyl groups on the oxygens in its moiety. Metabolic studies with propoxur reveal hydrolysis of the carbamate and dealkylation of the isopropyl group to yield the parent catechol. In addition, nuclear hydroxylation produces a hydroquinone derivative. Both the catechol and this hydroquinone derivative are potentially able to undergo redox cycling with the corresponding quinone to produce ROS. It is primarily for these reasons that we believe propoxur may be similar to other classes of physiologically active compounds in producing effects through ET-ROS-OS. Generally, reactive ROS are generated by metabolic processes that yield ET entities, and this occurs with propoxur as well. Although ROS are commonly associated with toxicity, there is little recognition in the literature that they can also play a role in therapeutic action.

Mechanism of Anesthetic Toxicity: Metabolism, Reactive Oxygen Species, Oxidative Stress, and Electron Transfer

There is much literature on the toxic effects of anesthetics. This paper deals with both the volatiles and locals. Adverse effects appear to be multifaceted, with the focus on radicals, oxidative stress (OS), and electron transfer (ET). ET functionalities involved are quinone, iminoquinone, conjugated iminium, and nitrone. The non-ET routes involving radicals and OS apparently pertain to haloalkanes and ethers. Beneficial effects of antioxidants, evidently countering OS, are reported. Knowledge at the molecular level should aid in devising strategies to combat the adverse effects.