Free radicals and Graves' disease: the effects of therapy

Selenium supplementation in thyroid eye disease: an updated review from a clinical ophthalmic perspective

Thyroid eye disease (TED) consists of a spectrum of autoimmune orbital pathology that threatens patients' quality of life and vision. Research suggests that oxidative stress plays a role in both the thyroid gland and orbit. Selenium has been proposed as a potential therapeutic adjunct given its role in thyroid physiology and antioxidant metabolism. Furthermore, selenium status has been linked to multiple pathological thyroid states. Despite the preponderance of evidence demonstrating a role for selenium in thyroid disease, limited research exists highlighting its role in TED specifically. This review summarizes the pathophysiology and role of selenium in thyroid eye disease (TED) and the current body of evidence including in vitro and in vivo studies highlighting the role for supplementation in clinical ophthalmic practice. Notably, relatively lower selenium levels have been shown to have a modest correlation with severity of thyroid eye disease. Selenium supplementation has shown some benefit in patients with mild Graves' Orbitopathy in European populations presumed deficient. Despite the preponderance of evidence demonstrating a role for selenium in thyroid disease, limited data is available to conclusively expand its role in TED outside of a 6-month course of supplementation in selenium deficient or relatively deficient populations. Data subject to geographic and population differences in selenium levels limits the generalizability of supplementation in TED. Despite mechanistic evidence of its antioxidant effects in TED beyond the advantages of thyroid disease in general, the benefits of selenium supplementation should be interrogated further and contextually tailored in both clinical and research formats for ophthalmic practice.

Selenium in the Treatment of Graves' Hyperthyroidism and Eye Disease

Based on the role of oxidative stress in the pathogenesis of Graves' hyperthyroidism (GH) and Graves' Orbitopathy (GO), a therapy with the antioxidant agent selenium has been proposed and a number of studies have been performed, both in vitro and in vivo. In GH, reactive oxygen species (ROS) contribute to the thyroid and peripheral tissues damage. In GO, tissue hypoxia, as well as ROS, are involved in the typical changes that occur in fibroadipose orbital tissue and the perimysium of extraocular muscles. Antioxidants have been proposed to improve the effects of antithyroid drugs in GH patients, as well as the remodeling of orbital tissues in patients with GO. Here, we reviewed the literature on the possible beneficial effects and clinical use of selenium in the management of patients with GH and GO. A randomized clinical trial on the use of selenium in patients with mild GO provided evidence for a beneficial effect; no data are available on more severe forms of GO. Although the real effectiveness of selenium in patients with GH remains questionable, its use in the management of mild GO is generally believed to be beneficial, and selenium administration has been included in the clinical practice for the patients with mild eye disease.

Oxidative Stress in Graves Disease and Graves Orbitopathy

Oxidative stress is involved in the pathogenesis of Graves hyperthyroidism (GH) and Graves orbitopathy (GO) and an antioxidant approach has been proposed for both. In GH, a disbalance of the cell redox state is associated with thyroid hyperfunction and antithyroid medications may reduce oxidative stress. Tissue hypoxia participates in the pathogenesis of GO, and oxygen free radicals are involved in the typical changes of orbital tissues as reported by in vitro and clinical studies. Antioxidant agents, especially selenium, have been proposed as a therapeutic option for GH and GO. A clinical study regarding the use of selenium in mild GO has provided evidence for a beneficial effect in the short term, even though its beneficial effects in the long term are still to be investigated. In addition to selenium, a protective role of other antioxidant agents, i.e., quercetin, enalapril, vitamin C, N-acetyl-L-cysteine and melatonin has been suggested by in vitro studies, although clinical studies are lacking. Here, we review the role of oxidative stress and antioxidant agents in GH and GO.

The Effect of Immunosuppression on Selected Antioxidant Parameters in Patients with Graves' Disease with Active Thyroid-Associated Orbitopathy

BACKGROUND AND STUDY AIMS

Thyroid-associated orbitopathy, the most common extrathyroidal manifestation of Graves' disease, is an autoimmune inflammation of orbital soft tissue. We report the study assessing the effect of immunosuppressive treatment with methylprednisolone on selected antioxidant parameters in patients with Graves' disease with active thyroid-associated orbitopathy.

PATIENTS AND METHODS

Activity and serum levels of selected antioxidant parameters as well as lipid peroxidation products were determined in a group of 56 patients with active thyroid-associated orbitopathy at three time-points: at baseline, after the discontinuation of intravenous methylprednisolone treatment and at 3 months after the discontinuation of additional oral methylprednisolone treatment. A control group consisted of 20 healthy age- and sex-matched volunteers.

RESULTS

We found an increased activity of superoxide dismutase and glutathione peroxidase and increased serum levels of uric acid, malondialdehyde and conjugated dienes, as well as a reduced activity of paraoxonase-1 and reduced serum vitamin C level in the study group at baseline. Systemic intravenous and oral methylprednisolone therapy led to normalization of activity and concentration of the most studied parameters.

CONCLUSION

Results of our study confirmed that oxidative stress is one of the factors involved in the pathogenesis of thyroid-associated orbitopathy and the methyloprednisolone treatment is effective in reducing both clinical symptoms and oxidative stress in patients with this disease.

Thyroid hormones mediate metabolic rate and oxidative, anti-oxidative balance at different temperatures in Mongolian gerbils (Meriones unguiculatus)

Oxidative damage is a potential physiological cost of thermoregulation during seasonal adjustments to air temperature (T_a) in small mammals. Here, we hypothesized that T_a affects serum thyroid hormone levels and these hormones can mediate the changes in metabolic rate and oxidative damage. Mongolian gerbils (Meriones unguiculatus) were acclimated at different T_as (5 °C, 23 °C and 37 °C) for 3 weeks. Serum tri-iodothyronine (T3) levels increased at 5 °C but decreased at 37 °C compared to the control (23 °C). Protein carbonyls increased in liver at 37 °C compared with control, however, lipid damage (malonaldehyde, MDA) in both serum and liver was unrelated to T_a. After the effects of different T_as on thyroid hormone levels and oxidative damage markers were determined, we further investigate whether thyroid hormones mediated metabolic rate and oxidative damage. Another set of gerbils received 0.0036% L-thyroxin (hyperthyroid), 0.04% Methylimazol (hypothyroid) or water (control). Hypothyroid group showed a 34% reduction in resting metabolic rate (RMR) also 42% and 26% increases in MDA and liver protein carbonyl respectively, whereas hyperthyroid group had higher RMR, liver mass and superoxide dismutase (SOD) compared to control. Serum T3 or T3/T4 levels were correlated positively with RMR, liver mass, and SOD, but negatively with MDA and uncoupling protein 2 (UCP2). We concluded that high T_a induced hypothyroidism, decreased RMR and increased oxidative damage, whereas low T_a induced hyperthyroidism, increased RMR and unchanged oxidative damage. These data supported our hypothesis that thyroid hormones can be a cue to mediate metabolic rate and different aspects of oxidative and antioxidant activities at different T_as.

Cardiac ischemia/reperfusion injury is inversely affected by thyroid hormones excess or deficiency in male Wistar rats

AIM

Thyroid dysfunctions can increase the risk of myocardial ischemia and infarction. However, the repercussions on cardiac ischemia/reperfusion (IR) injury remain unclear so far. We report here the effects of hypothyroidism and thyrotoxicosis in the susceptibility to IR injury in isolated rat hearts compared to euthyroid condition and the potential role of antioxidant enzymes.

METHODS

Hypothyroidism and thyrotoxicosis were induced by administration of methimazole (MMZ, 300 mg/L) and thyroxine (T4, 12 mg/L), respectively in drinking water for 35 days. Isolated hearts were submitted to IR and evaluated for mechanical dysfunctions and infarct size. Superoxide dismutase types 1 and 2 (SOD1 and SOD2), glutathione peroxidase types 1 and 3 (GPX 1 and GPX3) and catalase mRNA levels were assessed by quantitative RT-PCR to investigate the potential role of antioxidant enzymes.

RESULTS

Thyrotoxicosis elicited cardiac hypertrophy and increased baseline mechanical performance, including increased left ventricle (LV) systolic pressure, LV developed pressure and derivatives of pressure (dP/dt), whereas in hypothyroid hearts exhibited decreased dP/dt. Post-ischemic recovery of LV end-diastolic pressure (LVEDP), LVDP and dP/dt was impaired in thyrotoxic rat hearts, whereas hypothyroid hearts exhibited improved LVEDP and decreased infarct size. Catalase expression was decreased by thyrotoxicosis.

CONCLUSION

Thyrotoxicosis was correlated, at least in part, to cardiac remodeling and increased susceptibility to IR injury possibly due to down-regulation of antioxidant enzymes, whereas hypothyroid hearts were less vulnerable to IR injury.

Protective and antigenotoxic effect of Ulva rigida C. Agardh in experimental hypothyroid

The presence of chromosomal damage in bone marrow cells affected by several diseases such as thyroid, cancer etc., was detected by the micronucleus (MN) assay. The present study was designed to evaluate: i) volatile components of Ulva rigida, ii) effects of hypothyroidism on bone marrow MN frequency, iii) effects of oral administration of Ulva rigida ethanolic extract (URE) on MN frequency produced by hypothyroidism, and iv) thyroid hormone levels in normal and 6-n-Propylthiouracil (PTU)-induced hypothyroid rats. The volatile components of Ulva rigida was studied using a direct thermal desorption (DTD) technique with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOF/MS). URE administration was of no significant impact on thyroid hormone levels in control group, while PTU administration decreased thyroid hormone levels compared to control group (p < 0.001). Moreover, URE supplementation resulted in a significant decrease in MN frequency in each thyroid group (p < 0.0001). This is the first in vivo study that shows the strong antigenotoxic and protective effect of URE against the genotoxicity produced by hypothyroidism.

Oxidative stress and the ageing endocrine system

Ageing is a process characterized by a progressive decline in cellular function, organismal fitness and increased risk of age-related diseases and death. Several hundred theories have attempted to explain this phenomenon. One of the most popular is the 'oxidative stress theory', originally termed the 'free radical theory'. The endocrine system seems to have a role in the modulation of oxidative stress; however, much less is known about the role that oxidative stress might have in the ageing of the endocrine system and the induction of age-related endocrine diseases. This Review outlines the interactions between hormones and oxidative metabolism and the potential effects of oxidative stress on ageing of endocrine organs. Many different mechanisms that link oxidative stress and ageing are discussed, all of which converge on the induction or regulation of inflammation. All these mechanisms, including cell senescence, mitochondrial dysfunction and microRNA dysregulation, as well as inflammation itself, could be targets of future studies aimed at clarifying the effects of oxidative stress on ageing of endocrine glands.

Radioiodine therapy in benign thyroid diseases: effects, side effects, and factors affecting therapeutic outcome

Radioiodine ((131)I) therapy of benign thyroid diseases was introduced 70 yr ago, and the patients treated since then are probably numbered in the millions. Fifty to 90% of hyperthyroid patients are cured within 1 yr after (131)I therapy. With longer follow-up, permanent hypothyroidism seems inevitable in Graves' disease, whereas this risk is much lower when treating toxic nodular goiter. The side effect causing most concern is the potential induction of ophthalmopathy in predisposed individuals. The response to (131)I therapy is to some extent related to the radiation dose. However, calculation of an exact thyroid dose is error-prone due to imprecise measurement of the (131)I biokinetics, and the importance of internal dosimetric factors, such as the thyroid follicle size, is probably underestimated. Besides these obstacles, several potential confounders interfere with the efficacy of (131)I therapy, and they may even interact mutually and counteract each other. Numerous studies have evaluated the effect of (131)I therapy, but results have been conflicting due to differences in design, sample size, patient selection, and dose calculation. It seems clear that no single factor reliably predicts the outcome from (131)I therapy. The individual radiosensitivity, still poorly defined and impossible to quantify, may be a major determinant of the outcome from (131)I therapy. Above all, the impact of (131)I therapy relies on the iodine-concentrating ability of the thyroid gland. The thyroid (131)I uptake (or retention) can be stimulated in several ways, including dietary iodine restriction and use of lithium. In particular, recombinant human thyrotropin has gained interest because this compound significantly amplifies the effect of (131)I therapy in patients with nontoxic nodular goiter.

Oxidative stress in graves' disease

Increased reactive oxygen species (ROS) generation and the consequent oxidative damage are involved in the development of several diseases, including autoimmune diseases. Graves' disease is an autoimmune disorder characterized by hyperthyroidism and, less frequently, orbitopathy. Hyperthyroidism is characterized by increased oxidative stress. Untreated hyperthyroidism is associated with an increase of several parameters of oxidative stress and in most studies (but not all) by an increase of antioxidant defense enzymes. Restoration of euthyroidism with antithyroid drug is associated with a reversal of the biochemical abnormalities associated with oxidative stress. Animal and human studies suggest that increased ROS may directly contribute to some clinical manifestation of the disease, including orbitopathy. Antioxidants administered alone improve some clinical signs and symptoms of hyperthyroidism and, when associated with antithyroid drugs, induce a more rapid control of clinical manifestations and a faster achievement of euthyroidism. A large randomized clinical trial has shown that antioxidant supplementation (selenium) may also be beneficial for mild Graves' orbitopathy.

Evaluation of oxidative status in patients with hyperthyroidism

Data on the antioxidant levels enzyme in patients with hyperthyroidism are limited and conflicting. Therefore, the objective of this study was to evaluate the oxidative status using an automated method in patients with hyperthyroidism. Thirty-six subjects with hyperthyroidism and 30 healthy controls were enrolled in this study. Serum oxidative status was determined via measurement of total antioxidant capacity (TAC) and total oxidant status (TOS) and calculation of oxidative stress index (OSI). Serum TAC levels were significantly lower in patients with hyperthyroidism than controls (P=0.002), while serum TOS levels and OSI values were significantly higher (P=0.008, 0.004; respectively). Serum TAC levels were correlated with TSH levels (rho=0.223, P=0.032), FT3 levels (rho=-0.434, P=0.002) and FT4 levels (rho=-0.363, P=0.003) in patients. Further, TOS levels and OSI values were correlated with TSH levels (rho=-0.245, P=0.037; rho=-0.312, P=0.011, respectively), FT3 levels (rho=0.293, P=0.017, rho=0.505, P=0.002, respectively), and FT4 levels (rho=0.302, P=0.006, rho=0.321, P=0.008, respectively) in patients. Duration of disease was significantly correlated with OSI values in patients (rho=0.420, P=0.011), while no correlation with serum TAC levels and TOS levels (P>0.05). Oxidants are increased and antioxidants are decreased in patients with hyperthyroidism; as a result, the oxidative-antioxidative balance is shifted to the oxidative side. Increased oxidative stress may play a role in the pathogenesis of hyperthyroidism. It is believed that supplementation of antioxidant vitamins such as vitamins C and E may be helpful for these patients.

A randomized trial evaluating a block-replacement regimen during radioiodine therapy

BACKGROUND

Lack of consensus regarding the antithyroid drug regimen in relation to radioiodine ((131) I) therapy of hyperthyroidism prompted this randomized trial comparing two strategies.

DESIGN

Patients with Graves' disease (GD, n = 51) or toxic nodular goitre (TNG, n = 49) were randomized to (131) I either 8 days following discontinuation of methimazole (-BRT, n = 52, median dose: 5 mg) or while on a continuous block-replacement regimen (+BRT, n = 48, median dose 15 mg methimazole and 100 μg levothyroxine). results: Patients in the +BRT group required more radioactivity. In this group, thyroid function did not change in the early post (131) I period, while serum-free T3 index was higher in the -BRT group (P < 0·05). One year posttherapy, the fraction of cured patients (euthyroid or hypothyroid) was 48% and 61% in the +BRT and -BRT group, respectively (P = 0·014 unadjusted; P = 0·004 adjusted), but the outcome depended on the type of disease. In GD, treatment failure in the +BRT group correlated positively with the 24-h thyroid (131) I uptake (P = 0·017), while no correlations existed in the -BRT group. In addition to +BRT allocation, patients with TNG were at higher risk of treatment failure with lower thyroid radiation doses (P = 0·048), higher doses of methimazole (P = 0·026) and lower levels of serum TSH (P = 0·009).

CONCLUSIONS

A continuous block-replacement regimen results in a stable thyroid function during (131) I therapy but is hampered by the higher amounts of radioactivity required. The study demonstrates that the outcome in GD is highly unpredictable, while treatment failure in patients with TNG is correlated with a number of factors.

Effects of pulse methylprednisolone and oral methylprednisolone treatments on serum levels of oxidative stress markers in Graves' ophthalmopathy

BACKGROUND

Recent evidence has shown that oxidative stress may play a role in the pathogenesis of autoimmune diseases, and this is an issue of considerable research interest in the field of infiltrative ophthalmopathy. Therefore, we evaluated both the relationship between Graves' ophthalmopathy (GO) and serum levels of certain indicators of oxidative stress, and the effects of methylprednisolone treatment on serum malondialdehyde (MDA) and glutathione (GSH) levels in patients with euthyroid GO.

MATERIALS AND METHODS

We compared GO patients to both Graves' patients without ophthalmopathy and healthy controls. Ultimately, we assessed four subject groups. Graves' patients with ophthalmopathy (GO) were subcategorized into two groups: Group A subjects (n = 18) were given intravenous glucocorticoid and Group B patients (n = 15) were given oral glucocorticoid. Graves' patients without ophthalmopathy comprised Group C (n = 20), and healthy controls comprised Group D (n = 15). Serum levels of MDA and GSH were measured at baseline and after 4 and 24 weeks of observation via spectrophotometric methods.

RESULTS

We found that serum MDA levels were significantly higher in the two GO groups (Groups A and B) than in GO patients without ophthalmopathy or healthy controls. Conversely, GSH levels were significantly lower in the two GO groups than in Groups C and D. MDA and GSH levels were not different between the latter two groups. MDA levels were strongly and positively correlated with a clinical activity score (CAS). In Group A, MDA levels and the CAS were significantly lower than in Group B at 4 weeks. After 24 weeks, however, MDA levels and the CAS were similar in these two groups.

CONCLUSION

Oxidative stress appears to be involved in the pathophysiology of GO. Relative to oral dosing, the intravenous administration of a glucocorticoid seems to yield more rapid improvement in disease activity. MDA might be useful as an indicator of clinical activity.

Hormetic responses of thyroid hormone calorigenesis in the liver: Association with oxidative stress

Thyroid hormone (L-3,3',5-triiodothyronine, T(3)) exerts calorigenic effects by accelerating mitochondrial O(2) consumption through transcriptional activation of respiratory genes, with consequent increased reactive oxygen species (ROS) production. In the liver, ROS generation occurs at different sites of hepatocytes and in the respiratory burst of Kupffer cells, triggering the activation of the transcription factors nuclear factor-kappaB, signal transducer and activator of transcription 3, and activating protein 1. Under these conditions, the redox upregulation of Kupffer cell-dependent expression of cytokines [tumor necrosis factor-alpha, interleukin (IL)-1, and IL-6] is achieved, which upon interaction with specific receptors in hepatocytes trigger the expression of antioxidant enzymes (manganese superoxide dismutase, inducible nitric oxide synthase), antiapoptotic proteins (Bcl-2), and acute-phase proteins (haptoglobin, beta-fibrinogen). These responses and the promotion of hepatocyte and Kupffer cell proliferation observed represent hormetic effects re-establishing redox homeostasis, promoting cell survival, and protecting the liver against ischemia-reperfusion (IR) injury. It is proposed that hormesis underlying T(3) action may constitute a novel preconditioning strategy for IR injury during liver surgery in man or in liver transplantation using reduced-size grafts from living donors, considering that (i) with the exception of the controversial ischemic preconditioning, all other studied strategies have failed to reach the clinical setting and (ii) T(3) is a well-tolerated therapeutic agent that either lacks major adverse effects or has minimal and controlled side effects.

Erythrocyte osmotic fragility and lipid peroxidation in experimental hyperthyroidism

This study investigated the relation between erythrocyte osmotic fragility and oxidative stress and antioxidant state in primary hyperthyroidism induced experimental rats. Twenty-four Spraque-Dawley-type female rats weighing between 160 and 200 g were divided into two, as control (n = 10) and experimental (n = 12), groups. The experimental group animals have received tap water and L-Tiroksin (0.4 mg/100 g fodder) added standard fodder for 30 days to induce hyperthyroidism. Control group animals were fed tap water and standard fodder for the same period. Blood samples were drawn from the abdominal aorta of the rats under ether anesthesia. T₃, T₄, and TSH levels, osmotic fragility, malondialdehyde (MDA), superoxide dismutase, and glutathione levels were measured in the blood. There was a statistically significant deviation found in maximum and minimum osmotic hemolysis limit values of experimental group when compared to controls. The standard hemolytic increment curve of the hyperthyroid group shifted to the right when compared to control group's curve. There was a statistically significant increase found in MDA and superoxide dismutase, but statistically a significant decrease was detected in glutathione levels in hyperthyroid group when compared to controls. As a result of our study, it may be concluded that hyperthyroidism may led to an increase in osmotic fragility of erythrocytes and this situation may possibly originate from the increased lipid peroxidation in hyperthyroidism.

Continuous methimazole therapy and its effect on the cure rate of hyperthyroidism using radioactive iodine: an evaluation by a randomized trial

BACKGROUND

A randomized clinical trial was performed to clarify whether continuous use of methimazole (MTZ) during radioiodine ((131)I) therapy influences the final outcome of this therapy.

DESIGN

Consecutive patients with Graves' disease (n = 30) or a toxic nodular goiter (n = 45) were rendered euthyroid by MTZ and randomized to stop MTZ 8 d before (131)I (-MTZ; n = 36) or to continue MTZ until 4 wk after (131)I (+MTZ; n = 39). Calculation of the (131)I activity included an assessment of the (131)I half-life and the thyroid volume.

RESULTS

The 24-h thyroid (131)I uptake was lower in the +MTZ group than in the -MTZ group (44.8 +/- 15.6% vs. 62.1 +/- 9.9%, respectively; P < 0.001). At 3 wk after therapy, no significant change in serum free T(4) index was observed in the +MTZ group (109 +/- 106 vs. 83 +/- 28 nmol/liter at baseline; P = 0.26), contrasting an increase in the -MTZ group (180 +/- 110 vs. 82 +/- 26 nmol/liter; P < 0.001). The number of cured patients was 17 (44%) and 22 (61%) in the +MTZ and -MTZ groups, respectively (P = 0.17). Cured patients tended to have a lower 24-h thyroid (131)I uptake (50.1 +/- 13.8% vs. 56.4 +/- 17.1%; P = 0.09). By adjusting for a possible interfactorial relationship through a regression analysis (variables: randomization, 24- and 96-h thyroid (131)I uptake, type and duration of disease, age, gender, presence of antithyroid peroxidase antibodies, thyroid volume, dose of MTZ), only the continuous use of MTZ correlated with treatment failure (P = 0.006), whereas a low 24-h thyroid (131)I uptake predicted a better outcome (P = 0.006).

CONCLUSION

Continuous use of MTZ hinders an excessive increase of the thyroid hormones during (131)I therapy of hyperthyroid diseases. However, such a strategy seems to reduce the final cure rate, although this adverse effect paradoxically is attenuated by the concomitant reduction of the thyroid (131)I uptake.

Effects of melatonin on lipid peroxidation and anti-oxidant enzyme activity in rats with experimentally induced hyperthyroidism

1. The present study was designed to investigate the effects of high-dose melatonin on lipid peroxidation and anti-oxidant enzyme activity in rats with experimentally induced hyperthyroidism. 2. Twenty-four albino male rats, weighing 240-260 g, were randomly allotted into one of three experimental groups (control, hyperthyroid and hyperthyroid + melatonin treatment), with each group containing eight animals. Hyperthyroidism was induced by a daily with i.p. injection of 200 microg l-thyroxine for 30 days. In addition to l-thyroxin treatment, rats in the hyperthyroid + melatonin treatment group were also given daily i.p. injections of 10 mg/kg melatonin on the last 10 days of l-thyroxine treatment. Control animals received injections of an equivalent volume of saline solution. Rats received the last injection 24 h before being killed. 3. At the end of the experiment, rats in all three groups were fasted for 12 h and killed by cardiac puncture under ether anaesthesia. Blood samples were taken for the determination of malondialdehyde (MDA), glutathione (GSH) and superoxide dismutase (SOD) levels and concentrations of tri-iodothyronine (T(3)) and thyroxine (T(4)). 4. It was found that MDA and SOD levels and concentrations of T(3) and T(4) were higher and the GSH level was lower in rats with hyperthyroidism compared with controls. Melatonin treatment decreased the elevated MDA and SOD levels and increased the lowered GSH level to control levels in rats with hyperthyroidism, but did not ameliorate the concentrations of T(3) and T(4). 5. It was concluded that high-dose melatonin treatment may decrease the hyperthyroidism-induced disturbances of lipid peroxidation and anti-oxidant enzyme activity and oxidative damage.

Myocardial antioxidant enzyme activities and concentration and glutathione metabolism in experimental hyperthyroidism

Hyperthyroidism was induced in rats by l-thyroxine administration (12 mg/L in drinking water, 4 weeks). Animals were assessed hemodynamically, and heart, lung, and liver morphometry were performed. Lipid peroxidation (LPO) and protein oxidation (carbonyls) were measured in heart homogenates. It was quantified glutathione (GSH) metabolism, and antioxidant enzyme activities its and protein expression (by Western blot). At the end of treatment, it was observed cardiac hypertrophy, elevation of left ventricular systolic and end diastolic pressures, lung and liver congestion. LPO and carbonyls were increased in the hyperthyroid group, and GSH was decreased by 46% in the fourth week. Myocardial oxidative stress time course analysis revealed that it was increased in the second week of treatment. Antioxidant enzyme activities elevation was accompanied by protein expression induction in the hyperthyroid group in the fourth week. These results imply that hyperthyroidism generates myocardial dysfunction associated with oxidative stress inducing antioxidant enzyme activities and protein expression.

Sister chromatid exchange and micronuclei in human peripheral blood lymphocytes treated with thyroxine in vitro

Thyroid hormones enhance the metabolic rate and the aerobic metabolism favoring oxidative stress, which is accompanied by induction of damage to cellular macromolecules including the DNA. The aim of the present study was to investigate the ability of thyroxine to induce sister chromatid exchange and micronuclei, and to modulate cell-cycle kinetics in cultured human lymphocytes. Eight experimental concentrations of thyroxine were used, ranging from 2 x 10(-9) to 0.5 x 10(-4)M. Treatment with thyroxine increased the frequency of SCE per cell at the higher concentrations (1.5 x 10(-6), 0.5 x 10(-5), 1.5 x 10(-5) and 0.5 x 10(-4)M). On the other hand, there were no significant aneugenic and/or clastogenic effects observed in the cytokinesis-block micronucleus assay. The results show that thyroxine acted as a relatively weak clastogen compared with the positive control N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). In addition to the genotoxic effects, two high concentrations of thyroxine decreased the mitotic index and caused cell-cycle delay. In conclusion, thyroxine exhibited weak clastogenic effects only at high concentrations. Therefore, effects in humans might appear in cases of acute thyroxine overdose.

Thyroid hormone-induced oxidative stress in rodents and humans: a comparative view and relation to redox regulation of gene expression

Thyroid hormone (3,3',5-triiodothyronine, T(3)) exerts significant actions on energy metabolism, with mitochondria being the major target for its calorigenic effects. Acceleration of O(2) consumption by T(3) leads to an enhanced generation of reactive oxygen and nitrogen species in target tissues, with a higher consumption of cellular antioxidants and inactivation of antioxidant enzymes, thus inducing oxidative stress. This redox imbalance occurring in rodent liver and extrahepatic tissues with a calorigenic response, as well as in hyperthyroid patients, is further enhanced by an increased respiratory burst activity in Kupffer cells, which may activate redox-sensitive transcription factors such as NF-kappaB thus up-regulating gene expression. T(3) elicits an 80-fold increase in the serum levels of tumor necrosis factor-alpha (TNF-alpha), which is abolished by pretreatment with the antioxidants alpha-tocopherol and N-acetylcysteine, the Kupffer-cell inactivator GdCl(3), or an antisense oligonucleotide against TNF-alpha. In addition, T(3) treatment activates hepatic NF-kappaB, a response that is (i) inhibited by antioxidants and GdCl(3) and (ii) accompanied by induced mRNA expression of the NF-kappaB-responsive genes for TNF-alpha and interleukin (IL)-10. T(3) also increases the hepatic levels of mRNA for IL-1alpha and those of IL-1alpha in serum. Up-regulation of liver iNOS expression is also achieved by T(3), through a cascade initiated by TNF-alpha and involving IkappaB-alpha phosphorylation and NF-kappaB activation. In conclusion, T(3)-induced oxidative stress in the liver enhances the DNA-binding of NF-kappaB and the NF-kappaB-dependent expression of cytokines and iNOS by actions primarily exerted at the Kupffer cell level.

Thyroid disease and increased cardiovascular risk

The effects of thyroid dysfunction are thought to be reversible on restoration of euthyroidism, but postmortem and epidemiologic data suggest that subclinical or treated thyroid disease is associated with increased vascular risk. In order to determine the extent of this risk, and to explore whether the nature and/or treatment of thyroid disease are critical in this relationship, we used medical record linkage to match patients with treated thyroid disease of various etiologies with routinely collected national inpatient and daycase hospital discharge records and death records, and assessed the number of hospitalizations from cardiovascular or cerebrovascular disease or death in patients with thyroid disease and control patients. Patients treated for Graves' disease had more hospitalizations from cardiovascular disease than controls (relative risk, 1.42; 95% confidence interval, 1.20 to 1.67; p < 0.001). Toxic multinodular goiter was also associated with significantly higher rates of cardiovascular disease (relative risk, 1.50; 95% confidence interval, 1.11 to 2.02; p = 0.008). Patients with Hashimoto's thyroiditis aged over 50 years had a threefold increase in cardiovascular admissions compared to controls (23.5% and 6.5%, respectively; 95% confidence interval for difference, 6.0% to 27.9%; p = 0.003). Thus, different forms of thyroid disease were associated with increased long-term vascular risk despite restoration of euthyroidism. The mechanisms that mediate this risk are unclear but may not involve thyroid hormone abnormality.

Propylthiouracil and thiamazole do not alter in vitro neutrophil oxidative burst

Propylthiouracil and thiamazole are thionamides used in the treatment of hyperthyroidism. In addition to reducing thyroid hormone synthesis, these drugs have other activities that improve the hypermetabolic state of the patients as well as adverse and toxic effects. The capacity of these 2 drugs to interfere with the production of reactive oxygen species of human neutrophils exposed in vitro to these drugs was evaluated. The production of reactive oxygen species was assessed by chemiluminescence assays and the cells were stimulated with zymosan particles opsonized with a pool of normal human serum. No alteration was found in the chemiluminescence response of treated human neutrophils when compared to controls. The results show that these drugs, at the studied concentrations and with the experimental approach used, have no direct effect on the production of oxidative burst of neutrophils. We conclude that if these drugs have any action on the oxidative metabolism of neutrophils these might include some metabolization steps that do not take place in this in vitro model.

Neutrophils from Brazilian patients with Graves' disease: some biochemical and functional aspects

Graves' disease shows important systemic inflammatory complications and has been considered to be systemic autoimmune thyroid, skeletal muscle and connective tissue syndrome. Neutrophils participate in the pathophysiology of the two major immune and inflammatory manifestations of the disease, ophthalmopathy and myxedema, and may worsen the inflammatory picture. In this study we analysed some biochemical and functional aspects of neutrophils in Graves' disease patients to assess their participation in these processes. The results show that the complement and/or Fcgamma receptor-mediated oxygen radical production by neutrophils was increased when patient cells were compared with controls. However the percentage of cells expressing complement and IgG receptors and the per-cell fluorescence, were similar, indicating that the increased oxidative burst was not due to an abnormal expression of mediating receptors. The production of hydrogen peroxide was also increased in hyperthyroid patient neutrophils as compared to controls. Conversely, antioxidant defences (superoxide dismutase activity and reduced glutathione content) in neutrophils from patients were not significantly different from healthy controls. The liberation of potent oxidative compounds together with the absence of adequate quenching of them by antioxidant mechanisms could be responsible for greater tissue damage in inflammatory conditions, as is the case in ophthalmopathy and myxedema patients. Considering our results and those of other workers, we encourage and suggest an associated antioxidant therapy to complement the conventional anti-thyroid therapy, especially in obvious inflammatory cases and in individuals who smoke.

The effect of the antioxidant catalase on oestrogens, triiodothyronine, and noradrenaline in the Comet assay

Metabolic changes in the phenolic groups of steroidal oestrogens accompanied by the generation of quinones and reactive oxygen species underlie their mutagenic effects. Although nonsteroidal hormones and related compounds have not been thoroughly investigated for genotoxicity, some of them also contain phenolic groups that could be involved in redox cycling. Therefore, the aim of the present study was to evaluate the possible DNA damaging effects of the thyroid hormone, triiodothyronine (T3), and the neurotransmitter, noradrenaline (NA), in human lymphocytes using the Comet assay. After dose-response investigations, doses of 100 microM T3 and 550 microM of NA, producing clear DNA damaging effects and good cell viability, were chosen for further experiments with the antioxidant, catalase. Since the scavenging enzyme catalase reduced the DNA damaging effects of T3 and NA, it can be concluded that T3 and NA induced DNA damage mainly via the production of reactive oxygen species. Therefore, the mechanism of mutagenic action of both steroidal hormones and nonsteroidal compounds, T3 and NA, imply the creation of oxidative stress and subsequent DNA damage with reactive oxygen species and, possibly, with reactive hormone derivatives created during their redox cycling.

Peripheral parameters of oxidative stress in Graves' disease: the effects of methimazole and 131 iodine treatments

BACKGROUND

Increased oxidative stress, with elevated levels of free radicals, together with diminished antioxidation have been described previously in models of hyperthyroidism and in patients with Graves' disease. However, controversial results have been found about the antioxidant status and its response to treatment.

AIM

To evaluate the antioxidant/oxidant balance in active Graves' disease and the effects of treatment with methimazole (MMI) and 131 iodine (131I).

PATIENTS AND METHODS

We studied 69 hyperthyroid (H) patients, 58 female and 11 male, 16-50 years old; total T3: 8 +/- 2 nmol/l, total T4: 264 +/- 65 nmol/l (all mean +/- SD), TSH: 0.1 +/- 0.1 mIU/l, TSH receptor antibody 41 +/- 21%, highest 131Iodine uptake: 67 +/- 16%. As a control group (C), 19 normal adults were studied.

DESIGN

Parameters evaluated were: tert-butyl hydroperoxide initiated chemiluminiscence (CL), superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GPx) and total reactive antioxidant potential (TRAP).

RESULTS

In patients vs. controls there was an increase in CL levels (6207 +/- 1434 vs. 3000 +/- 851 cpm/mg of haemoglobin, P < 0.001), decrease in SOD (0.4 +/- 0.1 vs. 0.7 +/- 0.2 U/mg prot, P < 0.05; corresponding to 0.15 micro g/ml), CAT (2.8 +/- 0.6 vs. 3.8 +/- 0.7 pmol/mg prot, P < 0.001) and GSH (1.2 +/- 0.4 vs. 2 +/- 0.7 mmol/l erythrocytes, P < 0.05). The decrease in GPx and TRAP did not show significant differences. The parameters were also recorded in 30 patients who became euthyroid after treatment: 20 of them under MMI therapy (2-12 months) and the rest 3-6 months after 131Iodine administration. All the parameters evaluated were normalized after MMI; however, CL levels stayed high after 131I and only CAT and GSH levels returned to normal values.

CONCLUSION

Our results confirm the imbalance of the antioxidant/oxidant status in hyperthyroid patients. MMI treatment was more effective than 131I therapy to improve that balance. We speculate on the benefits of antioxidant therapy administrated together with the habitual treatment of hyperthyroidism, especially in patients after 131I therapy.

Free radical activity and antioxidant defense mechanisms in patients with hyperthyroidism due to Graves' disease during therapy

Free radical-mediated oxidative stress has been implicated in the etiopathogenesis of several autoimmune disorders. We investigated the prooxidant-antioxidant status in order to evaluate the possible deleterious role of oxidative phenomena in patients with Graves' disease. Thirty patients with hyperthyroidism due to Graves' disease were investigated. Thirty age-matched healthy subjects were studied as a control group. Free radical activity indices, antioxidant defense systems, and thyroid and pituitary hormone levels were measured in fasting blood samples. Blood samples were taken before initiation of therapy and after attainment of euthyroid state. A significant increase in lipid peroxidation activity indices, i.e., conjugated dienes and thiobarbituric acid-reacting substances, was found in blood serum of the patients with untreated Graves' disease. These changes were accompanied by a decrease in plasma thiol and erythrocyte lysate thiol groups concentrations. Hyperthyroidism resulted in a marked increase in intracellular antioxidant enzymes, i.e., superoxide dismutase, catalase and glutathione peroxidase activities as compared to the controls. Extracellular anti-free radical scavenging systems potential, measured by glutathione reductase activity and total antioxidant status level, was found to be significantly decreased in untreated Graves' patients. Treatment with thiamazole resulted in normalization of the free radical and antioxidant activity indices. The obtained results indicate an enhanced generation of reactive oxygen species and impairment of cellular and extracellular antioxidant systems potential in patients with Graves' disease. The attainment of euthyroid state led to an improvement in oxidative stress indices and antioxidant potential parameters.

Effect of triiodothyronine on reactive oxygen species generation by leukocytes, indices of oxidative damage, and antioxidant reserve

We have examined the effect of short-term triiodothyronine (T3) administration on reactive oxygen species (ROS) generation by leukocytes in 9 euthyroid subjects. At a dose of 60 microg/d orally for 7 days, T3 induced a significant increase in ROS generation by mononuclear cells (MNCs) from 183 +/- 102 mV at baseline to 313 +/- 111 mV on the seventh day (P < .02), and by polymorphonuclear leukocytes (PMNLs) from 195 +/- 94 mV at baseline to 302 +/- 104 mV on the seventh day (P < .02). There was also a significant increase in meta-tyrosine (P < .001) and ortho-tyrosine (P < .001), known indices of oxidative damage to proteins and amino acids. However, there was no increase in plasma thiobarbituric acid-reactive substances (TBARS), an index of oxidative damage to lipids, and in the level of carbonylated proteins, a less sensitive index to assess protein oxidation. There was no decrease in the level of antioxidants such as alpha-tocopherol, vitamin A, beta-carotene, lycopene, and lutein/zeaxanthin. The stimulatory effect on ROS generation may reflect a generalized increase in metabolic activity or may be a specific effect on NADPH oxidase in leukocyte membranes. The absence of a significant change in TBARS, carbonylated proteins, alpha-tocopherol, vitamin A, beta-carotene, lycopene, and lutein/zeaxanthin may reflect the short duration of the increased ROS load.

Antioxidants: their role in pregnancy and miscarriage

The aim of this study was to examine the role of antioxidants within the normal menstrual cycle, in healthy pregnancy, and in women suffering first-trimester miscarriage. The antioxidants chosen comprised of two from peripheral blood-plasma thiol and ceruloplasmin-and two extracellular parameters-superoxide dismustase (SOD) and red cell lysate thiol. We found that antioxidant levels varied little throughout the menstrual cycle. Pregnancies that went successfully to term were associated with increased levels of ceruloplasmin and SOD early in the first trimester. These changes were thought to offer the cell protection from the damage caused by the increased oxidative stress associated with pregnancy. First-trimester miscarriage was associated with significantly reduced levels of SOD. A subgroup of patients who miscarried in their first pregnancy, but whose second pregnancies were successful, had higher levels of plasma thiol and significantly reduced levels of red cell lysate thiol in the on-going pregnancy compared to levels at the time of miscarriage. Miscarriage and pregnancy appear to be associated with increased oxidative stress. In a successful pregnancy, however, changes occurred within the peripheral blood that offered protection from oxidant attack.

Protein oxidation in thyroid hormone-induced liver oxidative stress: relation to lipid peroxidation

The influence of thyroid hormone administration (daily doses of 0.1 mg of 3,3',5-triiodothyranine (T3)/kg for 1-3 consecutive days) on rat liver protein oxidation was investigated in relation to the calorigenic and lipid peroxidative actions of the hormone. T3 treatment elicited a progressive enhancement in the serum levels of the hormone, the rectal temperature of the animals, and in the rate of O2 uptake of the liver, changes that are significantly correlated and evidence the development of thyroid calorigenesis. Liver lipid peroxidation was augmented by T3 administration as determined by the tissue content of thiobarbituric acid reactants, with a maximal effect (3.1-fold increase) being found at 2 days after treatment, whereas protein oxidation measured by the content of protein hydrazone derivatives exhibited a maximal 88% increase at 3 days. Maximal rates of lipid peroxidation occur at 1 day after the administration of T3, whereas those of protein oxidation are attained after treatment with three daily doses of T3, time at which the former levels off. It is concluded that T3 administration induces a substantial enhancement in hepatic protein oxidation, in addition to lipid peroxidation, that seems to be due to the higher oxidative stress status conditioned in the liver by thyroid calorigenesis. Both processes exhibit a differential time course of changes, that may represent differences in the susceptibility of target molecules to free radical attack and/or in the efficiency of repair mechanisms.

Evidence for carbimazole as an antioxidant?

There is evidence in the literature to support the view that antioxidants are involved in the pathogenesis of Graves disease and that antioxidants may act as free radical scavengers. This study has compared the effects of a 12 month course of conventional Carbimazole therapy on peripheral blood antioxidant levels with those of a 12 month course of a higher dose treatment regime. Fifty seven patients were enrolled into the study. Those in Group 1 (n = 23) received a 12 month course of 60 mg/day Carbimazole. Those in Group 2 (n = 34) received 45 mg/day for the first month, 30 mg/day for the second and 20 mg/day for the remaining 10 months of treatment. T3 was added in both groups after 2-4 months to maintain patients euthyroid. Baseline samples were also obtained from 30 control subjects. Blood samples were taken for the measurement of plasma thiol (PSH), lysate thiol (LSH), superoxide dismutase (SOD) and caeruloplasmin (CP) and for routine thyroid function tests (TT4, TT3 and TSH). In untreated Graves' patients, serum levels of PSH and SOD were reduced and levels of LSH increased compared to controls. Following 2 months high dose Carbimazole therapy there was a significant increase in PSH levels and a significant reduction in CP levels compared to presentation levels. In the more conventional dose Group 2 patients PSH levels also rose significantly during the first 2 months of treatment. Levels for both groups were still significantly lower than the control group. After 12 months high dose Carbimazole therapy PSH levels had decreased so that they no longer differed from untreated levels. LSH and SOD levels still remained abnormal. CP levels continued to fall. Similar findings were obtained in those patients receiving the more conventional course of treatment. At no point was their any significant difference in antioxidant levels between the two treatment groups. The abnormal levels of antioxidants in the serum of untreated Graves' patients confirm their involvement in the pathogenesis of Graves' disease. Carbimazole therapy appeared to have only short term effects on the peripheral blood levels of the antioxidants measured. Carbimazole appeared to act only on the extra cellular markers of antioxidant activity (PSH, CP) although the disease itself had marked intracellular effects (LSH, SOD). These findings suggest that Carbimazole does not act as a free radical scavenger.

Has the use of antithyroid drugs for Graves' disease become obsolete?

In spite of an experience of almost 50 years of use of antithyroid drugs and radioiodine for the treatment of Graves' disease, the rationale for choice is often obscure. Early reports of high remission rates during thiourea therapy were followed by less optimistic ones, which along with other factors may have fueled the current major shift toward use of radioiodine. This review examines whether or not the use of antithyroid drugs indeed may have become obsolete. The intrathyroidal and extrathyroidal mechanisms of action of the drugs are reviewed with emphasis on their potential immunosuppressive effects. The latter may involve a direct effect on thyroid follicular cells, a direct suppression of TSH receptor antibody formation, or indirect effects mediated via heat shock proteins, oxygen free radicals, and the immune system. Potential factors associated with success or failure with antithyroid drug therapy are discussed, such as the effects of dose and duration of treatment, iodine milieu, and concomitant L-thyroxine therapy. The risks inherent to radioiodine therapy are only briefly described with emphasis on the possible aggravation by radioiodine of preexistent ophthalmopathy. The reader must decide whether the evidence marshalled convincingly indicates that the use of the thiourea compounds should be abandoned. The author thinks not, and is optimistic that imminent discovery of the yet elusive and enigmatic pathogenesis of Graves' disease will permit new and innovative treatment or more effective use of currently available therapies.

Studies of oxidative stress in cellular systems. The interaction of monocytes and erythrocytes

1H spin echo NMR spectroscopy is used to follow the interaction of intact and viable erythrocytes and monocytes obtained from different sources in mixed cultures. After a lag time (270 min) erythrocyte glutathione is observed to become more oxidised. This result is believed to occur as a consequence of monocyte activation generating hydrogen peroxide or hypochlorous acid, which is targeted at the erythrocyte. The red cell in turn employs its sulphydryl system as an anti-oxidant defence.

Spin echo nuclear magnetic resonance studies on intact erythrocytes: changes in cellular metabolism as a consequence of carbimazole therapy

OBJECTIVE

Because the exact mechanism of action of carbimazole is uncertain, nuclear magnetic resonance (NMR) spectroscopy was used to investigate cellular changes in erythrocytes from Graves' patients following a course of carbimazole therapy.

DESIGN

NMR spectroscopy was carried out using intact erythrocytes obtained from Graves' patients prior to and at 2 and 12 months after carbimazole treatment. The data were correlated with thyroid hormone and antibody levels.

PATIENTS

Twenty patients (four males; 16 females) with newly diagnosed and previously untreated Graves' disease were enrolled into the study. Assessments were made prior to the commencement of therapy and after 2 and 12 months on treatment. Of the 20 patients assessed at 0 and 2 months only 12 completed the study.

MEASUREMENTS

The oxidation-reduction balance of erythrocyte glutathione was measured directly using 1H spin echo NMR spectroscopy of intact cells. Thyroid hormone and antibody levels were measured using reported methods.

RESULTS

At 2 and 12 months a significant (P < 0.01) oxidation of the erythrocyte glutathione was observed. Of the four thyroid related markers (T3, T4, TRAb and TSH) assessed in this study both T3 (P < 0.001) and TRAb (P < 0.001) were observed to correlate with the NMR observed changes in glutathione. However, in-vitro experiments indicated that carbimazole does not affect red cell glutathione directly.

CONCLUSIONS

A model is presented which uses the hydrated iodium cation (I+), the natural product of T4 conversion to T3, as a chemical oxidant which can produce the observed clinical alteration in intracellular glutathione in ex-vivo erythrocytes. It is suggested that a major factor in the action of carbimazole in Graves' disease may be to stimulate the function of the deiodinase enzymes.

Antioxidant systems in normal pregnancy and in pregnancy-induced hypertension

Increased free radical activity has been implicated in the pathogenesis of pregnancy-induced hypertension. This article investigates whether changes in antioxidant systems contribute to this condition. Two extracellular (plasma thiols and ceruloplasmin) and two intracellular (red blood cell lysate thiols and red blood cell superoxide dismutase) antioxidant markers were assayed in 25 nonpregnant women, 16 pregnant women with normal blood pressure, 19 women with pregnancy-induced hypertension, and 13 women with proteinuric pregnancy-induced hypertension. In the normotensive pregnant group (in comparison with the nonpregnant group) the plasma thiol level was reduced (p less than 0.001) and the ceruloplasmin level raised (p less than 0.005), suggesting increased free radical activity. The lysate thiol level increased (p less than 0.005), which may reflect a compensatory protective response. In the hypertensive pregnant groups the lysate thiol rise was not present. These red blood cells may be more prone to oxidative stress. Whether this situation is a cause or an effect of oxidative stress in pregnancy-induced hypertension has yet to be elucidated.

Clinical analysis in intact erythrocytes using 1H spin echo NMR

A new method of clinical analysis based on 1H spin echo NMR spectroscopy is presented. It is capable of providing information on six metabolites within viable erythrocytes, directly and without any preparative procedures prior to analysis except for cell separation and washing. Erythrocytes from patients with rheumatoid arthritis and Graves' disease are compared with cells obtained from healthy volunteers. The NMR detectable species in the cytosol of the cells are glutathione, ergothioneine, choline, creatine, glycine, lactate and to a lesser extent alanine and valine. Significant differences are observed between the ergothioneine pools in the rheumatoid group (P less than 0.01) compared to the control group. The glutathione: di-glutathione ratio can be assessed from the ratio, g2 to g4, taken from different signals in the glutathione molecule. The total concentration of glutathione present is easily assessed qualitatively but is more difficult to quantitate.

The effect of carbimazole therapy on interleukin 2, interleukin 2 receptors and free radicals

Levels of Interleukin 2 (IL2), IL2 receptors (IL2R) and free radical scavengers were measured in 25 Graves' disease patients prior to and following an 8 week course of Carbimazole therapy in an attempt to understand the mechanism by which the drug acts on the immune system. In untreated Graves' patients IL2R levels were elevated and IL2 levels reduced. Free radical scavengers were also reduced in these patients. Following treatment IL2R levels fell and IL2 levels rose. Levels of the free radical scanvengers also rose. It is not clear whether it is the fall in IL2R levels or the rise in the level of free radical scavengers (implying a reduction in free radical activity) which is responsible for the rise in IL2.