Inhibition of caspases in vivo protects the rat liver against alcohol-induced sensitization to bacterial lipopolysaccharide.

BACKGROUND: The mechanisms of liver sensitization by alcohol to Gram-negative bacterial lipopolysaccharide (LPS) remain elusive. The purpose of this study was two-fold: (1) to test the hypothesis that alcohol-enhanced liver apoptosis may be a sensitizing mechanism for LPS and (2) to further characterize the liver apoptotic response to alcohol. METHODS: Rats were fed a high-fat, alcohol-containing liquid diet for 14 weeks, treated with LPS (1.0 mg/kg of body weight, intravenously) or saline, followed by injection of a pan-caspase inhibitor IDN1965; N-[(1,3-dimethylindole-2-carbonyl)-valinyl]-3-amino-4-oxo-5-fluoropentanoic acid; 10 mg/kg of body weight, intraperitoneally or vehicle, and killed. The following parameters were assessed: plasma aspartate: 2-oxoglutarate aminotransferase activity (AST); liver histology and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) response; caspase-3, -8, and -9 activity; and mRNA and protein expression for two apoptosis-signaling molecules: Fas receptor and Fas ligand; and three apoptosis adaptors: Bax, Bcl-XL, and Bcl-2. RESULTS: Alcohol-feeding-induced liver steatosis, slightly increased caspases' activity, the number of TUNEL-positive nuclei, and facilitated the LPS necrotic effect without affecting mRNA expression of apoptosis signals and adaptors. LPS induced a significant increase in AST and the number of TUNEL-positive nuclei, both effects being more pronounced in alcohol-treated rats. LPS produced hepatic necrosis only in alcohol-treated rats. LPS effects were associated with up-regulation of mRNA expression for both apoptosis adaptors and signaling molecules. IDN1965 administration 3 hr after LPS injection strongly inhibited caspases' activity, particularly that of caspase-3. IDN1965 also abolished the increase in TUNEL-positive nuclei, reversed the effect of LPS on plasma AST in alcohol-treated rats, and prevented LPS-induced necrosis. CONCLUSIONS: (1) Alcohol-enhanced liver apoptosis may not involve regulatory steps at the transcriptional level. LPS-induced liver apoptosis seems to involve transcriptional regulation of several apoptosis adaptors. Therefore, alcohol and LPS may enhance liver apoptosis through different mechanisms. (2) Alcohol-enhanced liver apoptosis precedes and may facilitate the hepatic effects of LPS. LPS superimposed on alcohol further elevates the rate of apoptosis in the liver. This may exceed the phagocytosing capacity of the liver so that all the apoptotic cells are not phagocytosed, but rather die of necrosis.

Anti-goitrous effect of lecithin-bound iodine in propylthiouracil treated rats.

OBJECTIVE: Excess iodine and some iodine-containing compounds are known to affect various parameters of thyroid function. Lecithin-bound iodine (LBI) is a compound which induces involution of an enlarged thyroid. LBI was tested for its ability to affect thyroid ornithine decarboxylase (ODC) activity and apoptosis. METHODS: LBI was given orally to propylthiouracil-pretreated rats and the changes in ODC activity and apoptosis were observed. The thyroid apoptosis was detected by DNA laddering and flow cytometry. RESULTS: LBI suppressed the thyroid ODC activity within one hour after its administration and lowered slightly but significantly the thyroid putrescine levels at 3 h. The DNA cleavage ladder was evident at 3-6 h after LBI treatment. Propylthiouracil induced thyroid enlargement was reduced significantly at 3 days after chronic treatment with LBI. The thyroidal content of putrescine was also decreased after chronic treatment. These effects of LBI were essentially the same as those of excess iodide, while other iodinated compounds including amiodarone, iopanoic acid and erythrosine had no effect on the thyroid ODC activity. CONCLUSIONS: These results suggest that LBI may exert its anti-goitrous effects, consisting of the inhibition of ODC activity and apoptosis, in the form of inorganic iodide in vivo.

Excess iodine induces apoptosis in the thyroid of goitrogen-pretreated rats in vivo.

Previously, we observed that excess iodide rapidly suppressed the elevated ornithine decarboxylase activity in the thyroid of propylthiouracil (PTU)-pretreated rats. Excess iodide also induces involution of goitrous thyroids. These findings led us to study effects of excess iodide on apoptosis of rat thyroids. When given to PTU-pretreated rats, excess potassium iodide (KI) (13 mg/kg body weight, 10 mg as iodine) induced DNA fragmentation in the thyroid at the first 3 hours after its treatment. The percentage of DNA fragmentation was also maximal at 3 hours after KI treatment. In methimazole-pretreated rats, the kinetic of DNA fragmentation was nearly the same; apoptosis increased for the first 6 hours and then decreased at 12 hours after KI administration. Other iodinated compounds such as amiodarone and diiodotyrosine have also shown apoptosis-inducing activity, but their effect was observed later than KI. Iopanoic acid had no such effect. Apoptotic changes were also observed with the use of flow cytometry. PTU or methimazole alone had some stimulatory effect on thyroid apoptosis. Iodine effect was not observed in rats treated with either perchlorate or thiocyanate. These results suggest that excess iodine induces thyroid involution in goitrogen-treated rats at least partially by apoptosis.

Suppressive effect of active hexose correlated compound (AHCC) on thymic apoptosis induced by dexamethasone in the rat.

OBJECTIVE: Mushroom extracts are known to have immunomodulating and antitumor effects in humans as well as in animals. In the present study Active Hexose Correlated Compound (AHCC), an extract obtained from several kinds of basidiomycetes was examined for its suppressive effect on thymocyte apoptosis induced by dexamethasone. METHOD: Thymic apoptosis was evaluated by gel electrophoresis and by flow cytometry at 3 h after injection of dexamethasone to rats. RESULTS: When given to rats at 4 % concentration in drinking water for more than 4 days, AHCC suppressed the internucleosomal DNA fragmentation in the thymus induced by dexamethasone. Flow cytometry also revealed that thymic apoptosis induced by dexamethasone was prevented by pretreatment with AHCC. Dexamethasone increased the caspase 3-like activity within 3 h after its treatment and AHCC pretreatment suppressed the increased enzyme activity only slightly. No apparent increase in serum levels of melatonin and interleukin 1beta was observed after AHCC treatment. CONCLUSIONS: These results suggest that AHCC exhibits immuno-modulating effects at least partially by regulating thymic apoptosis.

Thyrotropin via cyclic AMP induces insulin receptor expression and insulin Co-stimulation of growth and amplifies insulin and insulin-like growth factor signaling pathways in dog thyroid epithelial cells.

Despite the similarity of their receptors and signal transduction pathways, insulin is regarded as a regulator of glucose, protein, and lipid metabolism, whereas insulin-like growth factors (IGF-I and IGF-II) mainly act as mitogenic hormones. In the dog thyroid primary culture model, the triggering of DNA synthesis by thyrotropin (TSH) through cAMP, or by cAMP-independent factors including epidermal growth factor, hepatocyte growth factor and phorbol esters, requires insulin or IGFs as comitogenic factors. In the present study, in TSH-treated cells, IGF-I receptors and insulin receptors were paradoxically equivalent in their capacity to elicit the comitogenic pathway, which, however, was mediated only by IGF-I receptors in dog thyroid cells stimulated by cAMP-independent mitogens. Moreover, prior cell exposure to TSH or forskolin increased their responsiveness to insulin, IGF-I, and IGF-II, as seen on DNA synthesis and activation of a common insulin/IGF signaling pathway. To understand these observations, binding characteristics and expression of insulin and IGF-I receptors were examined. To analyze IGF-I receptor characteristics, the unexpected interference of a huge presence of IGF-binding proteins at the cell membrane was avoided using labeled Long R3 IGF-I instead of IGF-I. Strikingly, TSH, through cAMP, time-dependently induced insulin binding and insulin receptor mRNA and protein accumulation without any effect on IGF-I receptors. These findings constitute a first example of an induction of insulin receptor gene expression by a cAMP-mediated hormone. In dog thyroid cells, this allows low physiological insulin concentrations to act as a comitogenic factor and might explain in part the enhanced responsiveness to IGFs in response to TSH. This raises the possibility that TSH-insulin interactions may play a role in the regulation of thyroid growth and function in vivo.

[Effect of immobilization stress on the level of thyroid hormone secretion]. / Vliianie immobilizatsionnogo stressa na uroven' sekretsii tireoidnykh gormonov.

Analysis of blood flowing from the rat thyroid has shown that an acute immobilization stress enhanced thyroid hormone secretion with an increase of the T3/T4 x 100 index. The most marked response to stress was observed after repeated 2 min immobilization with a 3 min interval. Such increase of secretion was arrested by injection of prazosin, an alpha-adrenoblocker. Propylthiouracil injected an hour before the experiment reduced T4 thyroid conversion index. These results permit a conclusion that short-term repeated immobilization enhanced thyroid hormone secretion via alpha-adrenergic system stimulation, this being paralleled by increased production of hormonally more active T3.

[Role of norepinephrine in the regulation of thyroid gland functional activity in rabbits]. / Uchastie noradrenalina v reguliatsii funktsional'noi aktivnosti shchitovidnoi zhelezy krolikov.

By collecting in situ the blood flowing from the thyroid, the authors have demonstrated that noradrenaline injected in a dose 1 microgram/kg into rabbit thyroid artery enhanced triiodothyronine secretion without changing thyroxin secretion. This process was inhibited by prazosin, an alpha-adrenoblocker, in a dose 1 microgram/kg, injected 5 min before noradrenaline, but not by propranolol, a beta-adrenoblocker. Phenylephrine, an alpha-adrenergic agonist, in a dose 1 microgram/kg, injected into the thyroid artery, influenced thyroid hormone secretion similarly as noradrenaline. The T3/T4.100 ratio taken as an indicator of T4 thyroid conversion increased under the effect of noradrenaline injection after prazosin. Thus, in our experiment noradrenaline activated thyroid function via stimulation of alpha-adrenoceptor system. Hence, catecholamines are capable of directly influencing thyroid functional activity.

[The effect of cryopreservation and transplantation factors on the morphofunctional state of the thyroid in dogs]. / Vliianie kriokonservatsii i faktorov transplantatsii na morfofunktsional'noe sostoianie shchitovidnoi zhelezy sobak.

Influence of transplantation of non-specific factors (denervation, delymphatization, surgical trauma, ischemia, changes in blood supply conditions) as well as the effect of cryopreservation (-196 degrees C) on morphological structure and ability for secretion of thyroid hormones and response to TS stimulation were studied using the model of extracorporal biological perfusion in isolated thyroid of dogs. The results of biochemical and morphological investigations of thyroid in different conditions of perfusion showed, that it had preserved its main functional and morphological characteristics under the action of transplantation of nonspecific factors and extremely low temperatures.

[Changes in the ratio of secreted thyroid hormones under the action of adrenaline, propranolol and thyrotropic hormone]. / Izmenenie sootnosheniia sekretiruemykh tireoidnykh gormonov pod deistviem adrenalina, propranolola i tireotropnogo gormona.

The injection of 0.5 mM of adrenalin and 3.3 X 10(-3) M of propranolol in the thyroid artery of the thyroid lobe perfused in a thermostatic chamber (37 degrees C) 1h after the beginning of perfusion caused a decrease in the index of thyroid deiodination by 48 and 37%, respectively. Adrenalin injection 2 h after TSH lowered the stimulating effect of the latter on thyroxine thyroid conversion. A conclusion is made that adrenalin testing can suppress the activity of thyroid conversion of T4 into T3 and decrease the activity of TSH-stimulated deiodination.

[Extracorporeal biological perfusion of isolated canine thyroid glands]. / Ekstrakorporal'naia biologicheskaia perfuziia isolirovannoi shchitovidnoi zhelezy sobak.

A model of extracorporeal biological perfusion of the isolated thyroid gland in dogs has been developed. The experiments on dogs were performed to analyse the functional state of the perfused gland. It has been shown that the functional state parameters in 6-hour perfusion were comparable to the control values. It is concluded that the model suggested creates physiologic conditions and can be employed as a model for studying the influence of various factors on the isolated thyroid gland, as well as for investigating problems related to thyroid gland transplantation.

[Intrathyroid deiodination of thyroxine: the effect of thyrotropic hormone and denervation of the thyroid]. / Vnutritireoidnoe deiodirovanie tiroksina: vliianie tireotropnogo gormona i denervatsii shchitovidnoi zhelezy.

Intrathyroid transformation of thyroxin (T4) into triiodothyronine (T3) and the role of thyrotropic hormone and denervation in this process were studied with in vivo blood perfusion of dog thyroid gland in situ and at 37 degrees C. Both labelled 125I-T4 (200,000 imp/min) and nonlabeled T4 (1000 ng) were administrated in the arteries of thyroid lobules in situ and in a constant-temperature cabinet. Enhanced excretion of triiodothyronine (both labeled and nonlabeled) observed two hours after the injection in the thyroid blood output was suggested as an evidence of denervation-independent deiodination occurring in the thyroid tissue. Without T4 load the proportion of T3 in the thyroid venous blood was significantly increasing under the thyroid denervation thus attesting inhibitory effect of nervous impulse on T4 deiodination in the thyroid gland. TTH being administrated into thyroid arteries in a dose of 20 I.U. produced a pronounced elevation of T4 thyroid conversion in T3 which was less manifest in the process of denervation thus evidencing the high sensitivity of the process to TTH.