The role of allopurinol on oxidative stress in experimental hyperthyroidism

Role of thyroid hormones-induced oxidative stress on cardiovascular physiology

Thyroid hormones (THs) play an essential role in the maintenance of cardiovascular homeostasis and are involved in the modulation of cardiac contractility, heart rate, diastolic function, systemic vascular resistance, and vasodilation. THs have actions on cardiovascular physiology through the activation or repression of target genes or the activation of intracellular signals through non-genomic mechanisms. Hyperthyroidism alters certain intracellular pathways involved in the preservation of the structure and functionality of the heart, causing relevant cardiovascular disorders. Reactive oxygen species (ROS) play an important role in the cardiovascular system, but the exacerbated increase in ROS caused by chronic hyperthyroidism together with regulation on the antioxidant system have been associated with the development of cardiovascular dysfunction. In this review, we analyze the role of THs-induced oxidative stress in the cellular and molecular changes that lead to cardiac dysfunction, as well as the effectiveness of antioxidant treatments in attenuating cardiac abnormalities developed during hyperthyroidism.

Anti-Oxidative Therapy in Islet Cell Transplantation

Islet cell transplantation has become a favorable therapeutic approach in the treatment of Type 1 Diabetes due to the lower surgical risks and potential complications compared to conventional pancreas transplantation. Despite significant improvements in islet cell transplantation outcomes, several limitations hamper long-term graft survival due to tremendous damage and loss of islet cells during the islet cell transplantation process. Oxidative stress has been identified as an omnipresent stressor that negatively affects both the viability and function of isolated islets. Furthermore, it has been established that at baseline, pancreatic β cells exhibit reduced antioxidative capacity, rendering them even more susceptible to oxidative stress during metabolic stress. Thus, identifying antioxidants capable of conferring protection against oxidative stressors present throughout the islet transplantation process is a valuable approach to improving the overall outcomes of islet cell transplantation. In this review we discuss the potential application of antioxidative therapy during each step of islet cell transplantation.

Association between the use of allopurinol and risk of increased thyroid-stimulating hormone level

Allopurinol is the first-line agent for patients with gout, including those with moderate-to-severe chronic kidney disease. However, increased thyroid-stimulating hormone (TSH) levels are observed in patients with long-term allopurinol treatment. This large-scale, nested case-control, retrospective observational study analysed the association between allopurinol use and increased TSH levels. A common data model based on an electronic medical record database of 19,200,973 patients from seven hospitals between January 1997 and September 2020 was used. Individuals aged > 19 years in South Korea with at least one record of a blood TSH test were included. Data of 59,307 cases with TSH levels > 4.5 mIU/L and 236,508 controls matched for sex, age (± 5), and cohort registration date (± 30 days) were analysed. An association between the risk of increased TSH and allopurinol use in participants from five hospitals was observed. A meta-analysis (I² = 0) showed that the OR was 1.51 (95% confidence interval: 1.32-1.72) in both the fixed and random effects models. The allopurinol intake group demonstrated that increased TSH did not significantly affect free thyroxine and thyroxine levels. After the index date, some diseases were likely to occur in patients with subclinical hypothyroidism and hypothyroidism. Allopurinol administration may induce subclinical hypothyroidism.

Association between low thyroid-stimulating hormone, posterior cortical atrophy and nitro-oxidative stress in elderly patients with cognitive dysfunction

INTRODUCTION

Cortical atrophy is known to be a valuable sign of cognitive decline. The purpose of this study was to assess the association between low thyroid-stimulating hormone (TSH), posterior cortical atrophy (Koedam score - KS) and nitro-oxidative stress in elderly patients.

MATERIAL AND METHODS

A study (SG) and a control group (CG), each subdivided by gender, were investigated. Subjects older than 59 years with low serum TSH level and with mild cognitive impairment were included in the SG. The CG was formed by subjects free of significant cortical atrophy and free or thyroid dysfunction. Demographic and clinical characteristics of the patients (Mini Mental State Examination, MMSE), Koedam score on cranial magnetic resonance imaging, and blood parameters (TSH, FT4, and nitric oxide - NOx) were assessed.

RESULTS

Subjects in the study group had fewer years of education above the 8th grade compared with the control group (p < 0.0001). A significantly higher percentage of subjects in the study group had a Koedam score of 2 or 3 compared with controls, who had in the majority of cases a Koedam score of zero (p < 0.02). Significantly higher NOx levels were observed when study groups of both genders were compared with corresponding controls (p < 0.001). No significant differences were observed with regard to FT4 (p > 0.70). Nitric oxide was found to be significantly associated with TSH (p < 0.03) and KS (p < 0.002) when the whole study group was considered as well as when just the non-smoker study group was investigated.

CONCLUSIONS

Our study revealed an association between subclinical thyroid hypofunction, nitro-oxidative stress, and posterior cortical atrophy as an early stage of global atrophy.

Therapeutic Effects of Blue Honeysuckle on Lesions of Hyperthyroidism in Rats

Hyperthyroidism is a hypermetabolic syndrome characterized by an overproduction of thyroid hormones, which enhances the hormone-induced oxidative stress responsible for some complications in the liver, heart and muscle. Blue honeysuckle (BH) is an edible berry, rich in polyphenols, especially flavonoids or anthocyanins, known as strong antioxidants. The chemo-protective activities of the berry have been connected to the improvement of symptoms in cancer, diabetes mellitus, tumor or cardiovascular diseases. Therefore, the therapeutic effects of BH were examined in hyperthyroidism rat model. The hyperthyroidism was induced by injection with levothyroxine (LT4), and the model was treated with distilled water (LT4 control), propylthiouracil (PTU) or BH at 3 dosages of 500, 250 and 125[Formula: see text]mg/kg. The treatment was performed once a day for 15 days. Compared to LT4 control, the oral administration of BH dose-dependently ameliorated the hyperthyroidism, reducing thyroid hormones and increasing thyroid stimulating hormones. These effects were accompanied by improvement of body weight loss and atrophy in the thyroid gland, liver and epididymal fat pads. BH treatments also reduced the levels of hepatic enzymes (AST and ALT), which suggests BH exerts protective effects on hepatocytes. BH might also be involved in the augmentation of the anti-oxidant activities, supported by increased endogenous antioxidant (glutathione). In addition, the histopathological analyses revealed the beneficial effects of BH on the atrophic changes and cellular injuries in the thyroid gland, liver and epididymal fat pads. The therapeutic potentials of BH were either similar or more effective than PTU. These results provide valuable information that will guide more detailed studies to use the BH as a complementary and alternative medicine.

Increase in thyroid stimulating hormone levels in patients with gout treated with inhibitors of xanthine oxidoreductase

Increase in thyroid stimulating hormone (TSH) levels over the upper normal limit has been reported in a small percentage of patients treated with febuxostat in clinical trials, but a mechanistic explanation is not yet available. In an observational parallel longitudinal cohort study, we evaluated changes in TSH levels in patients with gout at baseline and during urate-lowering treatment with febuxostat. Patients to be started on allopurinol who had a measurement of TSH in the 6-month period prior to baseline evaluation were used for comparison. TSH levels and change in TSH levels at 12-month follow-up were compared between groups. Patients with abnormal TSH levels or previous thyroid disease or on amiodarone were not included for analysis. Eighty-eight patients treated with febuxostat and 87 with allopurinol were available for comparisons. Patients to be treated with febuxostat had higher urate levels and TSH levels, more severe gout, and poorer renal function, but were similar regarding other characteristics. A similar rise in TSH levels was observed in both groups (0.4 and 0.5 µUI/mL for febuxostat and allopurinol, respectively); at 12-mo, 7/88 (7.9 %) of patients on febuxostat and 4/87 (3.4 %) of patients on allopurinol showed TSH levels over 0.5 µUI/mL. Doses prescribed (corrected for estimated glomerular filtration rate in the case if patients on allopurinol) and baseline TSH levels were determinants of TSH levels at 12-month follow-up. No impact on free T4 (fT4) levels was observed. Febuxostat, but also allopurinol, increased TSH levels in a dose-dependent way, thus suggesting rather a class effect than a drug effect, but with no apparent impact on either clinical or fT4 levels.

Role of Oxidative Stress in Thyroid Hormone-Induced Cardiomyocyte Hypertrophy and Associated Cardiac Dysfunction: An Undisclosed Story

Cardiac hypertrophy is the most documented cardiomyopathy following hyperthyroidism in experimental animals. Thyroid hormone-induced cardiac hypertrophy is described as a relative ventricular hypertrophy that encompasses the whole heart and is linked with contractile abnormalities in both right and left ventricles. The increase in oxidative stress that takes place in experimental hyperthyroidism proposes that reactive oxygen species are key players in the cardiomyopathy frequently reported in this endocrine disorder. The goal of this review is to shed light on the effects of thyroid hormones on the development of oxidative stress in the heart along with the subsequent cellular and molecular changes. In particular, we will review the role of thyroid hormone-induced oxidative stress in the development of cardiomyocyte hypertrophy and associated cardiac dysfunction, as well as the potential effectiveness of antioxidant treatments in attenuating these hyperthyroidism-induced abnormalities in experimental animal models.

Effect of amlodipine, lisinopril and allopurinol on acetaminophen-induced hepatotoxicity in rats

Background

Exposure to chemotherapeutic agents such as acetaminophen may lead to serious liver injury. Calcium deregulation, angiotensin II production and xanthine oxidase activity are suggested to play mechanistic roles in such injury.

Objective

This study evaluates the possible protective effects of the calcium channel blocker amlodipine, the angiotensin converting enzyme inhibitor lisinopril, and the xanthine oxidase inhibitor allopurinol against experimental acetaminophen-induced hepatotoxicity, aiming to understand its underlying hepatotoxic mechanisms.

Material and methods

Animals were allocated into a normal control group, a acetaminophen hepatotoxicity control group (receiving a single oral dose of acetaminophen; 750 mg/kg/day), and four treatment groups receive N-acetylcysteine (300 mg/kg/day; a reference standard), amlodipine (10 mg/kg/day), lisinopril (20 mg/kg/day) and allopurinol (50 mg/kg/day) orally for 14 consecutive days prior to acetaminophen administration. Evaluation of hepatotoxicity was performed by the assessment of hepatocyte integrity markers (serum transaminases), oxidative stress markers (hepatic malondialdehyde, glutathione and catalase), and inflammatory markers (hepatic myeloperoxidase and nitrate/nitrite), in addition to a histopathological study.

Results

Rats pre-treated with amlodipine, lisinopril or allopurinol showed significantly lower serum transaminases, significantly lower hepatic malondialdehyde, myeloperoxidase and nitrate/nitrite, as well as significantly higher hepatic glutathione and catalase levels, compared with acetaminophen control rats. Serum transaminases were normalized in the lisinopril treatment group, while hepatic myeloperoxidase was normalized in the all treatment groups. Histopathological evaluation strongly supported the results of biochemical estimations.

Conclusion

Amlodipine, lisinopril or allopurinol can protect against acetaminophen-induced hepatotoxicity, showing mechanistic roles of calcium channels, angiotensin converting enzyme and xanthine oxidase enzyme in the pathogenesis of hepatotoxicity induced by acetaminophen.

Antioxidant and Protective Effects of Bupleurum falcatum on the L-Thyroxine-Induced Hyperthyroidism in Rats

Bupleuri Radix (BR), the dried roots of Bupleurum falcatum L., has been used in folk medicine as an antiinflammatory and antioxidative agent. The aqueous extract of BR was evaluated for its possible ameliorative effect in the regulation of hyperthyroidism in l-thyroxine- (LT4-) induced rat model. After oral administration of 300, 150, and 75 mg/kg of BR extracts, once a day for 15 days from 12th LT4 treatments, changes on the body, thyroid gland, liver, and epididymal fat pad weights, serum triiodothyronine, thyroxine, thyroid-stimulating hormone, asparte aminotransferase and alanine aminotransferase concentrations, hepatic lipid peroxidation, glutathione contents, superoxide dismutase, and catalase activities were investigated with thyroid gland, liver, and epididymal fat histopathological changes. The effects of BR extracts were compared with that of propylthiouracil, a standard antithyroid drug 10 mg/kg (intraperitoneally). In this experiment, BR extracts dose dependently reversed LT4-induced hyperthyroidisms, and these effects indicating their potential in the regulation of hyperthyroidism. Further, the BR extract normalized LT4-induced liver oxidative stresses, and also reduced liver and epididymal fat pad changes. BR extracts 150 mg/kg showed comparable effects on the LT4-induced rat hyperthyroidism as compared with PTU 10 mg/kg. These effects of BR may help the improvement of hyperthyroidisms and accompanied various organ damages.