Potentiation by thyroid hormone of human IFN-gamma-induced HLA-DR expression.

We have investigated the mechanism by which thyroid hormone potentiates IFN-gamma-induced HLA-DR expression. IFN-gamma-induced HLA-DR expression requires activation of STAT1alpha and induction of the Class II trans-activator, CIITA. HeLa and CV-1 cells treated only with L-thyroxine (T4) demonstrated increased tyrosine phosphorylation and nuclear translocation (= activation) of STAT1alpha; this hormone effect on signal transduction, and T4 potentiation of IFN-gamma-induced HLA-DR expression, were blocked by the inhibitors CGP 41251 (PKC) and genistein (tyrosine kinase). Treatment of cells with T4-agarose also caused activation of STAT1alpha. In the presence of IFN-gamma, T4 enhanced cytokine-induced STAT1alpha activation. Potentiation by T4 of IFN-gamma action was associated with increased mRNA for both CIITA and HLA-DR, with peak enhancement at 16 h (CIITA), and 2 d (HLA-DR). T4 increased IFN-gamma-induced HLA-DR protein 2.2-fold and HLA-DR mRNA fourfold after 2 d. Treatment with actinomycin D after induction of HLA-DR mRNA with IFN-gamma, with or without T4, showed that thyroid hormone decreased the t(1/2) of mRNA from 2.4 to 1.1 h. HeLa and CV-1 cells lack functional nuclear thyroid hormone receptor. Tetraiodothyroacetic acid (tetrac) and 3,5,3'-triiodo-thyroacetic acid (triac) blocked T4 potentiation of IFN-gamma-induced HLA-DR expression and T4 activation of STAT1alpha. These studies define an early hormone recognition step at the cell surface that is novel, distinct from nuclear thyroid hormone receptor, and blocked by tetrac and triac. Thus, thyroid hormone potentiation of IFN-gamma-induced HLA-DR transcription is mediated by a cell membrane hormone binding site, enhanced activation of STAT1alpha, and increased CIITA induction.

Effects of thyroxine and its related compounds on cerebral GABA receptors: inhibitory action on benzodiazepine recognition site in GABAA receptor complex.

The effects of thyroxine and its related derivatives on gamma-aminobutyric acid (GABA) receptors in the rat brain were examined. D-Thyroxine strongly inhibited [3H]flunitrazepam binding to benzodiazepine receptor in crude synaptic membrane from the rat brain. The Scatchard analysis of the [3H]flunitrazepam binding in the presence of D-thyroxine indicated the decreases in the affinity and maximum number of binding site. Furthermore, D-thyroxine inhibited the enhancing effect of flunitrazepam on GABA-stimulated 36Cl- influx into membrane vesicles, although GABA-stimulated 36Cl- influx alone was not affected by D-thyroxine. On the other hand, the effects of thyroxine and its related derivatives on cerebral GABAB receptor binding were not noted. These results suggest that D-thyroxine may be a drug which is able to modulate the function of GABAA receptor complex via the inhibitory action on benzodiazepine recognition site.

Dextrothyroxine in the treatment of generalized thyroid hormone resistance in a boy homozygous for a defect in the T3 receptor.

The dextroisomer of thyroxine (D-T4) has been shown to have suppressive effects on pituitary TSH secretion in euthyroid individuals and patients with mild thyroid hormone resistance. We treated a 3-year-old boy with D-T4 who was homozygous for a T3 receptor defect, resulting in a complex clinical picture of tissue-specific hyperthyroidism and hypothyroidism. There was no evidence of significant alteration in thyroid physiology, including serum concentrations of basal and TRH stimulated TSH or echocardiographic parameters measuring systolic time interval. We conclude that D-T4 at a daily dose of 6 mg (0.65 mg/kg) was ineffective in this boy with homozygous dominant negative thyroid hormone resistance.

Steinernema feltiae (= Neoaplectana carpocapsae): effect of sterols and hypolipidemic agents on development.

The structure and concentration of sterol in a lipid-defined artificial medium affected the development of the entomogenous nematode, Steinernema feltiae (= Neoaplectana carpocapsae). The nematode grew normally in vitro when the medium was supplemented with delta 5-desalkylsterol (cholesterol) or delta 5-desalkylsteryl ester (cholesterol oleate). The minimum amount of cholesterol in the medium that was necessary to support the development of S. feltiae to the climax population (i.e., dauer stage) was 0.0025%. The nematode also completed its life cycle normally when delta 0- or delta 7-desalkylsterols (cholestanol and lathosterol) were substituted for cholesterol. In contrast, development was inhibited when the medium contained delta 5,7-desalkylsterol (7-dehydrocholesterol); however, the nematode population reached the climax stage, in medium containing this sterol, when cholesterol was also present. S. feltiae was able to utilize delta 5- and delta 0-24 alpha-ethylsterols (sitosterol and sitostanol) as dietary sterols; however, when a delta 22-bond was introduced into the side chain (stigmasterol) the rate of development of the nematode slowed significantly. The growth of the nematode was also retarded when the medium contained delta 5,7,22-24 beta-methylsterol (ergosterol). The nematode population reached the climax stage in medium containing delta 8,24-4,14 alpha-trimethylsterol (lanosterol) only when cholesterol was also present. When S. feltiae was exposed to certain hypolipidemic agents, which are known to lower the level of lipids in human plasma (clofibrate, cholestyramine resin, niacin, and D-thyroxine), all but D-thyroxine affected the growth and development of the nematode in vivo (in Heliothis zea) and/or in vitro. Therefore further studies are warranted to determine how these drugs affect the lipid biochemistry of this nematode.

Acute and chronic effects of dextro-thyroxine on pituitary thyroid axis and on reverse triiodothyronine production in euthyroid subjects.

Serum levels of thyroxine (T4), triiodothyronine (T3), reverse triiodothyronine (rT3) and TSH were measured in euthyroid subjects after a single dose of 4 mg D-thyroxine (DT4) or of 0.25 mg L-thyroxine (LT4). The same parameters and TSH response to TRH were also evaluated in 7 dyslipidemic patients before and after one month of treatment with 6 mg DT4. T4 levels increased about 165% at h 4 after DT4 and only 47% after LT4; T3 levels remained unchanged until h 10 both after DT4 and after LT4; rT3 levels increased almost 179% after DT4 and only 32% after LT4. TSH levels decreased about 30% after both DT4 and LT4. In the long term study similar variations of the same parameters were observed: basal TSH levels decreased and TSH response to TRH was inhibited in all patients but one; T4 levels increased 62%, T3 levels increased 35%, while rT3 levels increased 545%. Our results show that: both acute and long-term treatment with DT4 suppress TSH secretion; DT4 both in acute and in long-term administration, is preferentially dealogenated in the alaninic ring with production of rDT3, instead of in the phenolic ring with production of DT3. This may contribute to explain its lower metabolic activity.

The effect of D- and L-thyroxine on sex hormone-binding globulin in rabbits.

Serum sex hormone-binding globulin (SHBG) concentration is increased in patients with thyrotoxicosis. SHBG is also present in rabbit serum, although it does not bind estradiol-17 beta (E2). Studies were carried out in female rabbits to determine the effects of thyroid hormone on SHBG. Serum concentrations of L-T4 cholesterol, E2, progesterone, free and total testosterone (T), and SHBG were measured in immature female rabbits (8-10 weeks of age). Rabbits were ovariectomized or subjected to sham surgery at puberty (age, 14-16 weeks) and restudied 6 weeks later. Values for serum T4, T, percent free T, free T, E2, progesterone and cholesterol were similar in ovariectomized and sham treated rabbits. Serum SHBG concentration progressively decreased in all rabbits from immaturity to age 20-22 weeks and values remained constant thereafter. Ovariectomy did not affect this age-related decrease in serum SHBG concentration. The 20- to 22-week-old ovariectomized and sham-operated rabbits were treated daily with either 30 micrograms/kg L-T4 or 150 micrograms/kg D-T4 for 2 weeks. This dose of L-T4 induced a 10-25% loss of BW, whereas D-T4 treatment did not, strongly suggesting that the L-T4 but not the D-T4-treated rabbits were hypermetabolic. D-T4 and L-T4 induced similar increases in serum SHBG (D-T4, delta 132 nM; L-T4, delta 146 nM). The increase in serum SHBG activity in response to D-T4 or L-T4 was reversible, since serum SHBG concentration returned to pretreatment values 5 weeks after thyroid hormone therapy was discontinued. The 27- to 29-week-old rabbits were then treated for 2 weeks with D-T4 (150 micrograms kg-1 day-1). Serum SHBG concentration significantly increased, and there were negative correlations between the thyroid hormone-induced increase in SHBG activity and both the percent free T and free T (P less than 0.01). D-T4 administration significantly lowered the serum cholesterol concentration without altering BW.

Effects of dextro-thyroxine, a preparation almost free of levo-thyroxine, on thyroid function, serum lipids and apolipoprotein A-I in "double pre-beta lipoproteinemia".

Eight subjects, belonging to a large family kindred repeatedly showing the electrophoretic pattern of the "double pre-beta lipoproteinemia", were studied. In seven of them thyroid function, serum lipids and apolipoprotein A-I were determined before and after treatment with dextro-thyroxine, preparation almost free of levo-thyroxine. In most of the patients, total-T4 levels and free-T4 Index were in the lower normal range, but basal TSH levels and the TSH response to TRH were normal. Dextro-thyroxine was effective in reducing both serum total cholesterol and triglycerides, but the percentage decrease in serum triglycerides was definitely greater than that of serum total cholesterol. This marked, unexpected hypotriglyceridemic effect is similar to that observed in a group of obese, hypertriglyceridemic hypothyroid patients treated with levo-thyroxine. Besides serum total cholesterol and triglycerides, the VLDL cholesterol/triglycerides ratio and the electrophoretic "slow moving" pre-beta component were also significantly reduced after treatment, suggesting that dextro-thyroxine can remove efficiently "remnant" VLDL particles from the plasma. Following dextro-thyroxine therapy, the relatively low pretreatment values of apolipoprotein A-I were significantly increased, being restored to normal.

Inhibition of insulin secretion by L-thyroxine and D-thyroxine treatment in rats under the influence of drugs affecting the adrenergic nervous system.

Both L-thyroxine and D-thyroxine induced an inhibition of glucose-induced insulin secretion with comparable time- and dose-dependent characteristics. L-thyroxine was ten times more potent than D-thyroxine. While L-thyroxine and a ten times higher dose of D-thyroxine had a similar potency in inducing hyperthermia and hypocholesterolaemia, hyperglycaemia in response to D-thyroxine was less pronounced than in response to L-thyroxine. This difference may be explained by a greater depletion of liver glycogen stores and consequently more limited capacity for provision of glucose for the circulation. The results support the view that the differences between L-thyroxine and D-thyroxine are quantitative. Adrenergic contribution to L-thyroxine- and D-thyroxine-induced inhibition of insulin secretion by rat pancreas is apparently of minor importance. Treatment of the rats with propranolol as well as with reserpine or 6-hydroxydopamine did not alleviate L-thyroxine- or D-thyroxine-induced inhibition of insulin secretion by rat pancreas.

The effect of D-thyroxine on lipoprotein lipids and apolipoproteins in primary type IIa hyperlipoproteinemia.

The effect of 3 months' treatment with D-thyroxine on the lipoprotein lipids and apolipoproteins AI and B was investigated in 12 patients with type IIa hyperlipoproteinemia. VLDL, LDL and HDL were separated by preparative ultracentrifugation. Both apolipoproteins were measured in serum by electroimmunoassay procedures with monospecific antisera. There was a significant decrease of cholesterol, phospholipids and apolipoprotein B in serum and of all lipids in the LDL class. VLDL and HDL lipids and apolipoprotein AI showed no significant alterations. The atherogenic ratios LDL/HDL lipids and apolipoprotein B/apolipoprotein AI were lowered with the most pronounced effect on the ratio between the two apoliopoproteins. It is concluded that there is an effective reduction of LDL particles by D-thyroxine. Further investigations are necessary to evaluate whether lipoprotein lipids or apolipoproteins are a better discriminator of the influence on atherosclerotic risk in type IIa hyperlipoproteinemia.

Reactions of hypothalamic ascorbic acid, serum ceruloplasmin and the adenohypophysis to oestradiol: inhibition by L-thyroxine.

Four weeks' administration of oestradiol benzoate to male and female rats in doses of 1 mg twice a week leads to adenohypophyseal hyperplasia and to an increase in the thyroxine-binding capacity of the adenohypophyseal proteins in vitro. At the same time, serum polyphenol oxidase (ceruloplasmin) activity rises and the hypothalamic ascorbic acid concentration falls. The simultaneous administration of L-thyroxine (0.1 mg/rat/per day) or dried thyroid (but not D-thyroxine) significantly inhibits these changes (adenohypophysis, ceruloplasmin) or completely suppresses them (hypothalamic ascorbic acid). L-thyroxine evidently blocks the action of oestradiol in the adenohypophysis, the liver and the hypothalamus; the significance of this inhibition is discussed in relation to dopaminergic modulation of the adenohypophyseal reaction to oestradiol.

Fetal hemoglobin: in vivo stimulation by D-thyroxine in adult marmosets.

Reactivation of fetal hemoglobin gene expressions was studied in new-world monkeys (marmosets). After a series of intraperitoneal injections of D-thyroxine, fetal hemoglobin production was increased in three experimental animals. Control animals were unaffected by the injection of the solvent. Because the percentage of cells containing fetal hemoglobin exceeded the total percentage of fetal hemoglobin, it was concluded that thyroid hormone influenced the synthesis of fetal hemoglobin rather than the development of a population of fetal cells.

[Expeimental studies in animals on a new lipid lowering compound: etiroxate hydrochloride (author's transl)]. / Tierexperimentelle Untersuchungen mit einer neuen lipidsenkenden Substanz: Etiroxat-hydrochlorid.

D,L-alpha-Methyl-thyroxin-ethylester hydrochloride (etiroxate hydrochloride, CG 635, Skleronorm) has been proved to be highly effective in lowering serum lipids in rats. Even daily oral doses of 3.3 mumol etiroxate hydrochloride/kg (2.8 mg/kg) decrease serum cholesterol significantly in hypercholesterolemic rats. From a dose of 10 mg/kg upwards etiroxate hydrochloride also significantly reduces serum triglycerides. Etiroxate hydrochloride has much less effect on oxygen consumption, heart rate and heart weight of rats than have L-thyroxin and D-thyroxin, and its antigoitrogenic effect is also much slighter. As calculated from the ratio between relative effect on basal metabolism and relative effect on serum cholesterol, the relative therapeutic index of the compound is 10--35 in comparison to a relative therapeutic index of 1 for L-thyroxin and D-thyroxin.

The influence of thyroid and testicular hormones on globule leucocytes in the rat duodenal crypt epithelium.

The globule leucocyte is a cell with a wide distribution in the digestive, respiratory, biliary, urinary and genital tract epithelia of homeotherms. It occurs in the crypts of the rat small intestine and within the epithelium on the villous bases but not on the remainder of the villi. A characteristic feature of this cell is the presence of acidophilic cytoplasmic granules, 0.5 to a few micrometers in diameter. The nucleus resembles that of intraepithelial intestinal lymphocytes. In this investigation, a quantitative study was made of the effect of thyroidectomy and/or castration on the number of globule leucocytes in the duodenal crypts of immature and adult rats. In sham-operated rats, globule leucocytes were rare, occurring with a frequency of 1 or 2 per 1,000 epithelial cells. After thyroidectomy, they increased to 14--20 per 1,000 epithelial cells. Castration did not influence the number of globule leucocytes but resulted in an increase in the number, size and acidophilia of their cytoplasmic granules. In immature rats, but not in adults, castration combined with thyroidectomy enhanced the effect of thyroidectomy, increasing globule leucocyte number to 32 per 1,000 epithelial cells. Treatment of thyroidectomized-castrates with thyroxine, initiated 38 days after operation, reduced the crypt globule leucocyte population to normal, whereas treatment with testosterone did not. Growth hormone failed to influence the elevated number of globule leucocytes in thyroidectomized rats, suggesting that this action of thyroxine was not mediated via an influence on growth hormone release. Because of their similar nuclear morphology, intraepithelial crypt lymphocytes were also counted and there was no obvious relationship in the fluctuations of these two cell populations. It is suggested that the greater number of crypt globule leucocytes in thyroid deficiency may reflect changes in the intestinal secretory immunoglobulin system and this is being investigated, beginning with a study of the distribution of IgE.

Influence of D-thyroxine on plasma thyroid hormone levels and TSH secretion.

Triiodothyronine (T3), thyroxine (T4), basal TSH and TSH after stimulation with TRH were determined in healthy subjects and patients treated with D-thyroxine (DT4). After a dosage of 6 mg DT4 the D/L T4 plasma concentration rose about 4-fold 4 hours after application and was only moderately elevated 14 hours later. To achieve constantly elevated T4 levels 3 mg DT4 were applied in the further experiment every 12 hours. The D/L T4 plasma concentration rose 2.5-4-fold and there was a small but significant increase of the D/L T3 plasma concentration. 74 hours after onset of treatment basal TSH was below detectable limits and the increase of TSH 30 min after injection of 200 mug TRH (TRH test) was only about 15% compared to zero time. The time course of TSH suppression was investigated after treatment with DT4 and LT4 (single dosage of 3 mg). TRH-tests were performed before, 10, 26, 50 and 74 hours after the first dosage of D or LT4. There was no difference in the time course of basal TSH and TSH stimulated by TRH. In 10 patients on DT4 long-term therapy, basal and stimulated TSH were found to be below the detectable limits of 0.4 mug/ml. Our results show that (1) plasma half-life of DT4 is less than 1 day, (2) TSH suppression after D and LT4 treatment is very similar, and (3) in patients on long-term DT4 treatment, TSH plasma concentration is below detectable limits even after stimulation with TRH.

Treatment of generalized scleroderma with inhibitors of connective tissue formation.

103 patients suffering from generalized scleroderma were studied in order to assess the effect of treatment with inhibitors of connective tissue formation. 93 patients with generalized scleroderma were given D-penicillamine, benzyl-penicillin-diethylamino-ethyl-ester hydroiodide, adrenal glucocorticoids, dextro-thyroxine, hydralazine, and "mixed treatment" (one or several of the drugs in consecutive courses, or concurrently). The effect of dextrothyroxine could not be evaluated in this study. No improvement could be seen after adrenocortical steroid therapy. Hydralazine seemed to be effective. D-penicillamine improved 25 of 34 treated patients; penicillin hydroiodide 12 out of 16. The dermal sclerosis of 6 patients regressed completely; in 16, sclerosis regressed with the exception of finger sclerosis; in 32, partial regression was registered; 20 had their progression arrested, but there was no regression; in 19 cases, there was no effect whatsoever. The prognosis seemed to be better for young than for old people. The age at onset was lower in the better groups. The higher the total dose, the better the results. The length of the treatment course is probably of some significance. The short-lasting cases had better prospects than the longer lasting. Ten untreated patients of this material and 11 patients seen earlier showed continued progression. Side effects leading to discontinuation of the drugs were seen in a substantial number of patients, especially after D-penicillamine. Twelve deaths could not be related to the treatments.