Potentiation of ischemia-reperfusion liver injury by hyperthyroidism in the rat

Thyroid hormone in the frontier of cell protection, survival and functional recovery

Thyroid hormone (TH) exerts important actions on cellular energy metabolism, accelerating O2consumption with consequent reactive oxygen species (ROS) generation and redox signalling affording cell protection, a response that is contributed by redox-independent mechanisms. These processes underlie genomic and non-genomic pathways, which are integrated and exhibit hierarchical organisation. ROS production led to the activation of the redox-sensitive transcription factors nuclear factor-κB, signal transducer and activator of transcription 3, activating protein 1 and nuclear factor erythroid 2-related factor 2, promoting cell protection and survival by TH. These features involve enhancement in the homeostatic potential including antioxidant, antiapoptotic, antiinflammatory and cell proliferation responses, besides higher detoxification capabilities and energy supply through AMP-activated protein kinase upregulation. The above aspects constitute the molecular basis for TH-induced preconditioning of the liver that exerts protection against ischemia-reperfusion injury, a strategy also observed in extrahepatic organs of experimental animals and with other types of injury, which awaits application in the clinical setting. Noteworthy, re-adjusting TH to normal levels results in several beneficial effects; for example, it lengthens the cold storage time of organs for transplantation from brain-dead donors; allows a superior neurological outcome in infants of <28 weeks of gestation; reduces the cognitive side-effects of lithium and improves electroconvulsive therapy in patients with bipolar disorders.

Effects of dietary concentrations of methionine on growth performance and oxidative status of broiler chickens with different hatching weight

1. A study was conducted to evaluate the effects of two hatching weight (HW) levels and two dietary concentrations of methionine on the growth performance and oxidative status of broilers. Male Arbor Acres chickens were divided into two groups on their HW (low and high HW, H and L). Each HW group was then distributed into two subgroups, of similar HW, receiving either low or high dietary concentrations of methionine (4.9 g methionine/kg, LM; 5.9 g methionine/kg, HM). Thus, all day-old birds were distributed into 4 treatments (H-LM, H-HM, L-LM, L-HM) × 6 replicates × 10 birds for 21 d. 2. Broilers with high HW were heavier than those with low HW during the 21 d assay, which appeared to result from increased body weight gain rather than improved feed conversion efficiency. A higher dietary concentration of methionine (5.9 g/kg) improved growth performance of broilers with low HW in terms of body weight gain and feed conversion ratio. 3. Broilers with different HW had similar antioxidant status both in serum and liver. 4. Broilers given a diet containing 5.9 g/kg methionine had enhanced serum superoxide dismutase (SOD) activity and decreased hepatic malondialdehyde (MDA) content at day 7. 5. Broilers given a diet containing 5.9 g/kg methionine had a higher hepatic reduced glutathione (GSH):glutathione disulphide (GSSG) ratio than those given a diet containing 4.9 g/kg methionine at day 21. High dietary methionine concentration reduced hepatic GSH content and glutathione peroxidase (GPX) activity of broilers with high HW at day 7 and at day 21, respectively, but increased hepatic GSH content of broilers with low HW at day 7. 6. Although broilers with different HW had similar oxidative status as indicated by several parameters in blood and liver, HW can have positive effects on the subsequent growth performance of broilers, and a higher dietary methionine concentration (5.9 g/kg) can improve growth performance and antioxidant status in broilers exhibiting low HW.

Vitamin E management of oxidative damage-linked dysfunctions of hyperthyroid tissues

INTRODUCTION

Thyroid hormones affect growth, development, and metabolism of vertebrates, and are considered the major regulators of their homeostasis. On the other hand, elevated circulating levels of thyroid hormones are associated with modifications in the whole organism (weight loss and increased metabolism and temperature) and in several body regions. Indeed, tachycardia, atrial arrhythmias, heart failure, muscle weakness and wasting, bone mass loss, and hepatobiliary complications are commonly found in hyperthyroid animals and humans.

RESULTS

Most thyroid hormone actions result from influences on transcription of T3-responsive genes, which are mediated through nuclear receptors. However, there is significant evidence that tissue oxidative stress underlies some dysfunctions produced by hyperthyroidism.

DISCUSSION

During the last decades, increasing interest has been turned to the use of antioxidants as therapeutic agents in various diseases and pathophysiological disorders believed to be mediated by oxidative stress. In particular, because elevated circulating levels of thyroid hormones are associated with tissue oxidative injury, more attention has been paid to explore the application of antioxidants as therapeutic agents in thyroid related disorders.

CONCLUSIONS

At present, vitamin E is among the most commonly consumed dietary supplements due to the belief that it, as an antioxidant, may attenuate morbidity and mortality. This is due to the results of numerous scientific studies, which demonstrate that vitamin E has a primary function to destroy peroxyl radicals, thus protecting polyunsaturated fatty acids biological membranes from oxidative damage. However, results are also available indicating that protective vitamin E effects against oxidative damage can be obtained even through different mechanisms.

Hepatic failure resulting from thyroid storm with normal serum thyroxine and triiodothyronine concentrations

A 63-year-old male presented with productive cough, fever, palpitation, shortness of breath, and mental confusion. Fulminant hepatic failure occurred with high aminotransferase and severe jaundice. Thyroid function tests showed thyroid-stimulating hormone level of 0.7 microU/mL (normal range, < 6.2 microU/mL), with normal serum thyroxine and triiodothyronine levels. He died on post-admission day 5. Autopsy revealed diffuse hyperplasia of the thyroid gland, centrilobular necrosis of the liver, and congestion of the gastrointestinal tract, spleen, and adrenal glands. These pathological findings were compatible with decompensated hyperthyroidism. Thyroid storm may present with normal serum triiodothyronine, thyroxine, and hepatic failure. Such presentation is rare.

Investigation of lipid peroxide and glutathione redox status of chicken concerning on high dietary selenium intake

This study was designed to investigate the effects of excess (24.5 mg Se/kg feed) inorganic and organic dietary selenium supplementation on 3-week-old broilers. The experiments lasted 4 days. Intensity of lipid peroxidation processes (malondialdehyde, MDA) and the amount (reduced glutathione, GSH) and activity (glutathione peroxidase activity, GSHPx) of gluathione redox system were measured in blood plasma, red blood cell hemolysate and liver. Voluntary feed intake in the selenium-treated groups reduced remarkably. Elevated GSH concentration and GSHPx activity were measured in plasma and liver of both selenium-treated groups compared to the untreated control and the 'pair-fed' controls. The lipid peroxidation processes in the liver showed higher intensity than the control due to both selenium treatment. The applied dose of selenite and selenomethionine does not inhibit, but even improves the activity of glutathione redox system in the liver during the early period of selenium exposure.

Role of mitochondria in exercise-induced oxidative stress in skeletal muscle from hyperthyroid rats

Previous study showed that exercise induces higher oxidative damage and respiratory capacity reduction in hyperthyroid than in euthyroid skeletal muscle. Because impaired cell function can result from mitochondrial dysfunction, we evaluated the changes induced by exercise in oxygen consumption of skeletal muscle mitochondria from euthyroid and hyperthyroid rats. The mitochondrial function was related with indices of oxidative damage and nitric oxide production, scavenger levels and mitochondrial ROS production rates. Our results show that exercise increased state 4 and decreased state 3 respiration, and the highest changes happened in hyperthyroid preparations. This was consistent with the observation that oxidative damage and NO(*) derivative content were increased by T(3) administration and exercise, reaching the highest levels in hyperthyroid exercised rats. Our results also indicate that the high mitochondrial oxidative damage induced by T(3) and exercise is due to enhanced ROS production, which is dependent on increases in mitochondrial content and reduction degree, respectively, of autoxidizable electron carriers.

Thyroid hormone preconditioning: protection against ischemia-reperfusion liver injury in the rat

Recently, we reported that oxidative stress due to 3,3',5-triiodothyronine (T(3))-induced calorigenesis up-regulates the hepatic expression of mediators promoting cell protection. In this study, T(3) administration in rats (single dose of 0.1 mg/kg intraperitoneally) induced significant depletion of reduced liver glutathione (GSH), with higher protein oxidation, O(2) consumption, and Kupffer cell function (carbon phagocytosis and carbon-induced O(2) uptake). These changes occurred within a period of 36 hours of T(3) treatment in animals showing normal liver histology and lack of alteration in serum AST and ALT levels. Partial hepatic ischemia-reperfusion (IR) (1 h of ischemia via vascular clamping and 20 h reperfusion) led to 11-fold and 42-fold increases in serum AST and ALT levels, respectively, and significant changes in liver histology, with a 36% decrease in liver GSH content and a 133% increase in that of protein carbonyls. T(3) administration in a time window of 48 hours was substantially protective against hepatic IR injury, with a net 60% and 90% reduction in liver GSH depletion and protein oxidation induced by IR, respectively. Liver IR led to decreased DNA binding of nuclear factor-kappaB (NF-kappaB) (54%) and signal transducer and activator of transcription 3 (STAT3) (53%) (electromobility shift assay), with 50% diminution in the protein expression of haptoglobin (Western blot), changes that were normalized by T(3) preconditioning.

CONCLUSION

T(3) administration involving transient oxidative stress in the liver exerts significant protection against IR injury, a novel preconditioning maneuver that is associated with NF-kappaB and STAT3 activation and acute-phase response.

Effects of triiodothyronine-induced hyperthyroidism on lipid peroxidation, erythrocyte resistance and iron-binding and iron-oxidizing antioxidant properties of plasma in the rabbit

The effect of hyperthyroidism on some oxidative stress parameters is reported. The hyperthyroid state was induced by intraperitoneal injection of triiodothyronine (T3)(10 microg/kg body weight) for 14 days in two groups of female rabbits (3 and 12 months old). The T3 injection caused increase by 1.5-fold to 1.7-fold in T3 serum level, and 2-fold to 3-fold decrease (age-dependent) in body weight gain at the end of experimental period. The induced hyperthyroidism caused a significant increase in the serum concentration of the lipid peroxidation end-product malondialdehyde and lowered erythrocyte resistance to oxidative stress when subjected to the free radical generator 2,2'-azobis(2-amidinopropane) hydrochloride in vitro. The half maximum haemolysis time (HT50) decreased in the both experimental groups of rabbits, by about 12 min in the 3-month-old animals and 27 min in the 12-month-old animals. The study showed for the first time that hyperthyroidism enhances the ability of plasma to protect against iron-binding and iron oxidizing organic radicals. The scavenging property and antioxidant capacity of plasma against iron-binding inorganic radicals also increased. Measurement of erythrocyte resistance to oxidative stress and the protective ability of plasma against oxygen radicals discriminates the thyroid hormone modulatory effects in defence mechanisms against lipid peroxidation.

Effect of supplementation with methionine and different fat sources on the glutathione redox system of growing chickens

The effect of supplementary methionine and fats of different saturation levels on the glutathione redox system of growing broiler cockerels was studied. The diet of three groups of chicks was supplemented with corn germ oil, beef tallow and fish oil at the levels of 30 g/kg and 50 g/kg of feed, respectively. The diet of further three groups was supplemented with methionine (5 g/kg of feed) in addition to the different fat sources. Control chicks were fed with a compound feed without methionine and fat supplementation. Reduced glutathione (GSH) and glutathione disulphide (GSSG) content as well as glutathione peroxidase activity in the liver were determined and GSH/GSSG ratio was calculated at day old and then at one and three weeks of age. Our results indicate that supplementary methionine stimulates both the synthesis of the glutathione redox system and glutathione peroxidase activity in growing chickens in the first period of postnatal life, when the risk of lipid peroxidation is high due to feeding unsaturated fats in the diet.

Elevated urinary 8-isoprostaglandin F(2alpha) in females with Graves' hyperthyroidism

In this study, we investigate how oxidative stress alters the urinary F2-isoprostanes' level and we examine the correlation between 8-isoPGF(2alpha) and thyroid hormones in female patients with Graves' hyperthyroidism. We quantitatively determined the concentrations of urinary F2-isoprostanes using gas chromatography-mass spectrometry in the selected ion-monitoring mode. We recruited individuals in the following three groups of subjects for this study: (1) female hyperthyroidism patients (n = 14, 21-71 years), (2) female hypothyroidism patients (n = 16, 16-66 years), and (3) female age-matched normal controls (n = 10, 20-61 years). The average concentration of 8-iso prostaglandin F(2alpha) (8-isoPGF(2alpha)) in hyperthyroidism patients was significantly higher than that in the healthy controls (P < 0.05). The concentration of 8-isoPGF(2alpha) in hypothyroidism patients was similar to that in normal controls. Although the level of 8-isoPGF(2alpha) in two of the patients was slightly elevated, the P value was not significant (NS). Our data suggest that the increased level of urinary 8-isoPGF(2alpha) may reflect possible oxidation injuries in hyperthyroidism patients due to the high level of thyroid hormones. Therefore, the elevated 8-isoPGF(2alpha) in patients could be used as an important biomarker for hyperthyroidism disease.

Environmental induction models for the investigation of activity: changes in glutathione peroxidase, a crucial factor of the antioxidant defence

Glutathione peroxidase enzyme superfamily plays significant role in the elimination of reactive oxygen free radicals in the animals. Many characteristics of these proteins have been revealed already, but their regulation is still not known. Several data suggest that some environmental factors have certain regulatory effect, while others propose strict genetic regulation. In this report we present four different environmental induction models in which New Zealand white rabbits were used as experimental animals. In three models, free radical load of different origin, lipidperoxide load, application of a glutathione depletor or a prooxidant agent, was introduced. Beside these negative models a positive model was also constructed in which additive selenium was supplied. Glutathione peroxidase activity was measured in blood serum, erythrocyte haemolysate and liver. Reduced glutathione, and malondialdehyde concentration in the liver were also determined. According to the results, the established models are capable for analysing the enzyme activity x environmental interactions.

Plasma isocitrate dehydrogenase as a marker of centrilobular hepatic necrosis in patients with hyperthyroidism

Isocitrate dehydrogenase (ICDH) may be useful for differentiating centrilobular from periportal necrosis in rats with liver injury. In this study, we assessed the usefulness of ICDH as a marker of centrilobular necrosis in patients with hyperthyroidism. Isocitrate dehydrogenase and alanine aminotransferase (ALT) activities were measured in the plasma of 56 patients with hyperthyroidism, 16 patients with chronic viral hepatitis (CVH), and 17 controls. Isocitrate dehydrogenase levels were higher in patients with hyperthyroidism than in those with CVH or in the controls (p < 0.01 and p < 0.001, respectively), even though ALT levels were higher in patients with CVH than in patients with hyperthyroidism (p < 0.01). Isocitrate dehydrogenase/ALT ratios were also higher in patients with hyperthyroidism than in those with CVH (p < 0.0001). Isocitrate dehydrogenase correlated to ALT levels in patients with hyperthyroidism or CVH (p < 0.05). In a patient with hyperthyroidism, ICDH levels decreased progressively to normal, and the ALT level and thyroid function were normalized. Thus, the plasma ICDH or ICDH/ALT ratio might be useful for differentiating centrilobular from periportal necrosis and for monitoring the degree of hepatic necrosis in patients with hyperthyroidism.

Effects of iron overload and lindane intoxication in relation to oxidative stress, Kupffer cell function, and liver injury in the rat

Parameters related to liver oxidative stress, Kupffer cell function, and hepatocellular injury were assessed in control rats and in animals subjected to lindane (40 mg/kg; 24 h) and/or iron (200 mg/kg; 4 h) administration. Independently of lindane treatment, iron overload enhanced the levels of iron in serum and liver. Biliary efflux of glutathione disulfide increased by 140, 160, or 335% by lindane, iron, or their combined administration, respectively, and the hepatic content of protein carbonyls was elevated by 5.84-, 2.95-, and 10-fold. Colloidal carbon uptake by perfused livers was not modified by lindane and/or iron, whereas gadolinium chloride (GdCl(3)) pretreatment diminished uptake by 60-72%. Carbon-induced liver O(2) uptake was not altered by lindane, whereas iron produced a 61% increase and the combined treatment led to a 72% decrease over control values. Pretreatment with GdCl(3) abolished these effects in all groups. Lindane-treated rats showed acidophilic hepatocytes in periportal areas and some hepatic cells with nuclear pyknosis, whereas iron overload led to moderate hyperplasia and hypertrophy of Kupffer cells and moderate inflammatory cell infiltration. Combined lindane-iron treatment led to hepatocytes with pyknotic nuclei, significant acidophilia, and extensive lymphatic and neutrophil infiltration in the portal space. Hepatic myeloperoxidase activity increased by 1.1-, 2.1-, or 6.7-fold by lindane, iron, or their combined administration, respectively. Liver sinusoidal lactate dehydrogenase efflux increased by 2.2-fold (basal conditions) and 9.7-fold (carbon infusion) in the lindane-iron treated rats, effects that were diminished by 35 and 78% by GdCl(3) pretreatment, respectively. These data support the contention that lindane sensitizes the liver to the damaging effects of iron overload by providing an added enhancement to the oxidative stress status in the tissue, and this may contribute to the alteration of the respiratory activity of Kupffer cells and the development of an inflammatory response.

Derangement of Kupffer cell functioning and hepatotoxicity in hyperthyroid rats subjected to acute iron overload

Liver oxidative stress, Kupffer cell functioning, and cell injury were studied in control rats and in animals subjected to L-3,3',5-tri-iodothyronine (T3) and/or acute iron overload. Thyroid calorigenesis with increased rates of hepatic O2 uptake was not altered by iron treatment, whereas iron enhanced serum and liver iron levels independently of T3. Liver thiobarbituric acid reactants formation increased by 5.8-, 5.7-, or 11.0-fold by T3, iron, or their combined treatment, respectively. Iron enhanced the content of protein carbonyls independently of T3 administration, whereas glutathione levels decreased in T3- and iron-treated rats (54%) and in T3Fe-treated animals (71%). Colloidal carbon infusion into perfused livers elicited a 109% and 68% increase in O2 uptake in T3 and iron-treated rats over controls. This parameter was decreased (78%) by the joint T3Fe administration and abolished by gadolinium chloride (GdCl3) pretreatment in all experimental groups. Hyperthyroidism and iron overload did not modify the sinusoidal efflux of lactate dehydrogenase, whereas T3Fe-treated rats exhibited a 35-fold increase over control values, with a 54% reduction by GdCl3 pretreatment. Histological studies showed a slight increase in the number or size of Kupffer cells in hyperthyroid rats or in iron overloaded animals, respectively. Kupffer cell hypertrophy and hyperplasia with presence of inflammatory cells and increased hepatic myeloperoxidase activity were found in T3Fe-treated rats. It is concluded that hyperthyroidism increases the susceptibility of the liver to the toxic effects of iron, which seems to be related to the development of a severe oxidative stress status in the tissue, thus contributing to the concomitant liver injury and impairment of Kupffer cell phagocytosis and particle-induced respiratory burst activity.

Liver microsomal parameters related to oxidative stress and antioxidant systems in hyperthyroid rats subjected to acute lindane treatment

Liver microsomal functions related to xenobiotic biotransformation and free radical production were studied in control rats and in animals subjected to L-3,3',5-triiodothyronine (T3) and/or lindane administration as possible mechanisms contributing to oxidative stress, in relation to the activity of enzymes (superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), and glucose-6-phosphate dehydrogenase (G-6PDH)) and content of lipid-soluble vitamins (alpha-tocopherol, beta-carotene, and lycopene) affording antioxidant protection. Lindane treatment in euthyroid rats at a dosage of 20mg/kg did not modify the content of liver microsomal cytochromes P450 and b5, the activity of NADPH-cytochrome P450 reductase and NADH-cytochrome b5 reductase, and the production of superoxide radical (O2.-), as well as antioxidant systems, except for the reduction in lycopene levels. Hyperthyroidism elicited a calorigenic response and increased specific and molecular activities of NADPH-cytochrome P450 reductase, O2.- generation, and G-6PDH activity, concomitantly with diminution in liver SOD and catalase activities and in alpha-tocopherol, beta-carotene, and lycopene levels. The administration of lindane to hyperthyroid animals led to a further increase in the molecular activity of NADPH-cytochrome P450 reductase and in the O2.- production/SOD activity ratio, and decrease of hepatic alpha-tocopherol content, in a magnitude exceeding the sum of effects elicited by the separate treatments, as previously reported for reduced glutathione depletion. Collectively, these data support the contention that the increased susceptibility of the liver to the toxic effects of acute lindane treatment in hyperthyroid state is conditioned by potentiation of the hepatic oxidative stress status.