Alternating antineutrophil cytoplasmic antibody specificity: drug-induced vasculitis in a patient with Wegener's granulomatosis.
We describe a patient who presented with Wegener's granulomatosis associated with antineutrophil cytoplasmic antibodies (ANCA) directed against proteinase 3 (PR3) with a cytoplasmic immunofluorescence pattern (cANCA), whose ANCA type changed to antimyeloperoxidase antibodies with a perinuclear immunofluorescence pattern (pANCA) when treated with propylthiouracil, and changed back to anti-PR3 antibodies with cANCA after the medication was discontinued. The patient developed flares of vasculitis symptoms associated with rises in either type of ANCA. Tests for antimyeloperoxidase ANCA were repeatedly negative before the drug was started, strongly implicating the drug as the cause of the episode. This case demonstrates that patients with idiopathic ANCA-positive vasculitis may quickly develop a superimposed drug-associated ANCA-positive vasculitis. Iatrogenic vasculitis should be suspected when a patient with idiopathic vasculitis with one type of ANCA develops the other type of ANCA. (+info
Stimulation of Na,K-ATPase by hypothyroidism in the thyroid gland.
Although studies have documented the regulatory effects of thyroid hormones on the Na,K-ATPase in peripheral tissues, there is little information on the regulation of this transporter in the thyroid gland itself. Accordingly, we investigated the effects of thyroid status on Na,K-ATPase specific activity and the abundance of its constituent subunits in rat thyroid. Exogenous tri-iodothyronine (T3) was administered daily to produce hyperthyroidism. 6n-propyl-2-thiouracil (PTU), an inhibitor of thyroid hormone synthesis, was used to induce hypothyroidism. There was a four-fold increase in Na,K-ATPase specific activity in the follicular membranes from PTU-treated animals after 7 days. Enzymatic activities were not changed in the T3-treated glands. Immunoblotting of membranes from T3-treated rats revealed a 75% reduction in alpha1 subunit abundance and a slight, but nonsignificant reduction in beta1 abundance. On the other hand, the membranes from PTU-treated rats displayed 136 and 567% increases in the abundance of the alpha1 and beta1 subunits respectively. These data demonstrate that thyroid hormone status regulates Na,K-ATPase in the gland, but the effects are in direct contrast to those seen in the periphery. (+info
Na,K-ATPase mRNA beta 1 expression in rat myocardium--effect of thyroid status.
The abundance of Na,K-ATPase and its alpha and beta subunit mRNAs is upregulated in cardiac and other target tissue by thyroid hormone (T3). Multiple Na,K-ATPase mRNA beta 1 species encoding an identical beta 1 polypeptide are expressed in the heart. The different mRNA beta 1 species result from utilization of two transcription start-sites in the first exon and multiple (five) poly(A) signals in the terminal exon of the beta 1 gene. In the present study we identify the mRNA beta 1 species that are expressed in rat ventricular myocardium under basal conditions, and determine whether they are differentially regulated by T3. mRNA beta 1 species were identified by 3'-RACE followed by DNA sequencing, and by Northern blotting using probes derived from different regions of rat cDNA beta 1. Five mRNA beta 1 species are expressed in rat heart: mRNA beta 1 species that are initiated at the first transcription start-site and end at the first, second and fifth poly(A) sites (resulting in mRNAs of 1630, 1810, and 2780 nucleotides), and mRNA beta 1 species initiated at the second transcription start-site and ending at the second and fifth poly(A) sites (resulting in mRNAs of 1500 and 2490 nucleotides); in order of increasing length, the five mRNAs constitute 0.04, 0.15, 0.38, 0.11 and 0.32 of total mRNA beta 1 content. In hypothyroid rats (induced by addition of propyl-thiouracil to the drinking water for 3 weeks), total mRNA beta 1 content decreased to 0.18 euthyroid levels, which was associated with a disproportionate 7.5-fold decrease in the abundance of the longest transcript (P < 0.05); transcripts initiating at the first transcription start-site and ending at the second poly(A) signal in hypothyroid hearts were 0.26 euthyroid levels (P < 0.05). Hyperthyroidism induced by injection of normal rats with three doses of 100 micrograms T3/100 g body weight every 48 h resulted in an overall approximately 2-fold increase in mRNA beta 1 content with no change in the fractional contribution of any of the mRNA beta 1 species. The results indicate a complex heterogeneity in the expression of mRNA beta 1 in myocardium. (+info
In vivo regulation of beta-MHC gene in rodent heart: role of T3 and evidence for an upstream enhancer.
Cardiac beta-myosin heavy chain (beta-MHC) gene expression is mainly regulated through transcriptional processes. Although these results are based primarily on in vitro cell culture models, relatively little information is available concerning the interaction of key regulatory factors thought to modulate MHC expression in the intact rodent heart. Using a direct gene transfer approach, we studied the in vivo transcriptional activity of different-length beta-MHC promoter fragments in normal control and in altered thyroid states. The test beta-MHC promoter was fused to a firefly luciferase reporter gene, whereas the control alpha-MHC promoter was fused to the Renilla luciferase reporter gene and was used to account for variations in transfection efficiency. Absolute reporter gene activities showed that beta- and alpha-MHC genes were individually and reciprocally regulated by thyroid hormone. The beta-to-alpha ratios of reporter gene expression demonstrated an almost threefold larger beta-MHC gene expression in the longest than in the shorter promoter fragments in normal control animals, implying the existence of an upstream enhancer. A mutation in the putative thyroid response element of the -408-bp beta-MHC promoter construct caused transcriptional activity to drop to null. When studied in the -3, 500-bp beta-MHC promoter, construct activity was reduced ( approximately 100-fold) while thyroid hormone responsiveness was retained. These findings suggest that, even though the bulk of the thyroid hormone responsiveness of the gene is contained within the first 215 bp of the beta-MHC promoter sequence, the exact mechanism of triiodothyronine (T3) action remains to be elucidated. (+info
Clinical study on early changes in thyroid function of hyperthyroidism treated with propylthiouracil and a relatively small dose of iodide.
In order to compare the acute effects of three kinds of antithyroid agents of iodide (I-), propylthiouracil (PTU) and PTU combined with iodide (PTU+I-) on thyroid function in hyperthyroid patients with diffuse goiter, serum concentrations of thyroxine (T4), triiodothyronine (T3), T3-resin sponge uptake (T3-RU) and free thyroxine index (FT4I) were employed as thyroid function parameters. In the group given iodine (1 mg/day) as iodinated-lecithine, the initial values of T4, T3, T3-RU and FT4I were 20.9 +/- 1.6 microng/100 ml (T4), greater than 740 ng/100 ml (T3), 49.5 +/- 2.3% (T3-RU) and 14.7 +/- 1.8 (FT4I). At the end of one week of therapy, they decreased clearly to 15.6 +/- 2.2 microng/100 ml, 457 +/- 87 ng/100 ml, 42.2 +/- 4.0% and 9.7 +/- 2.4. The so-called "escape phenomenon" from iodide inhibition was observed in serum T4, T3-RU and FT4I values at the end of two weeks of iodide therapy, while serum T3 continued to decrease but the value of T3 was far outside of the normal range. In the PTU group (300 mg/day), thyroid function parameters were 22.5 +/- 0.8 microng/100 ml (T4), greater than 592 ng/100 ml (T3), 54.9 +/- 1.0% (T3-RU) and 18.7 +/- 1.0 (FT4I) before treatment. They decreased continually week by week. At the end of four-week treatment with PTU, the value of each thyroid function parameter was 11.1 +/- 1.9 microng/100 ml, 229 +/- 56 ng/100 ml, 36.6 +/- 4.4% and 5.7 +/- 1.7. In the group of hyperthyroidism simultaneously given both PTU and iodide (300 mg/PTU and 1 mg/iodine), these thyroid function parameters decreased as well as in the group treated with PTU alone for more than two weeks. More rapid or significant decrease of T4, T3, T3-RU and ft4i in PTU+I- group than in PTU group was observed in the present study. These results suggested strongly that iodide alone was not an adequate therapy for hyperthyroidism as well known and they were also compatible with the idea that the concomitant administration of PTU and iodide was more effective in the early phase of therapy of hyperthyroidism than PTU alone. (+info
Tri-iodothyronine increases insulin-like growth factor binding protein-2 expression in cultured hepatocytes from hypothyroid rats.
Previous evidence suggests the existence of a thyroid hormone-IGF axis in the liver and changes in hepatic insulin-like growth factor binding protein (IGFBP) expression in rats with altered thyroid status have been previously reported. The aim of this study was to check if the higher IGFBP-2 mRNA levels observed in liver of hypothyroid rats could be due to a direct effect of thyroid hormone on the IGFBP-2 gene. In our experiments, cultured hepatocytes isolated from normal and hypothyroid adult rats were used. Northern blot analysis revealed barely detectable IGFBP-2 mRNA in normal rat hepatocytes, but easily detectable signal in hypothyroid rat cells. Therefore, the effect of tri-iodothyronine (T3) was investigated using cultured hepatocytes from hypothyroid rats as an in vitro model. The IGFBP-2 message was increased in a dose-dependent manner in hepatocytes cultured for 12-24 h in the presence of T3. A similar increase occurred in accumulation of IGFBP-2 in the culture medium, as measured by RIA. The effect of T3 on IGFBP-2 transcript levels appeared to consist of enhanced gene transcription and was independent of ongoing protein synthesis, but it was completely abolished by the incubation of hepatocytes with insulin. The latter result confirmed the dominant role of insulin in regulating IGFBP-2 expression by cultured hepatocytes. In vivo experiments confirmed an increase in hepatic IGFBP-2 mRNA and serum IGFBP-2 levels in hypothyroid rats and demonstrated, in addition, a significant increase in these measures in T3-treated rats. Taken together, our in vitro and in vivo results support a role for a thyroid hormone-IGF axis in the liver and suggest that other factors, such as insulin, interact in vivo with thryoid hormone in regulating hepatic IGFBP-2 expression. (+info
Improved suppression by dietary taurine of the fecal excretion of bile acids from hypothyroid rats.
The effect of dietary taurine, 2-aminoethanesulfonic acid, on hypercholesterolemia caused by thiouracil-induced hypothyroidism was investigated in hypothyroid rats. Serum total- and HDL-cholesterol were significantly increased, and the excretion of fecal bile acids was significantly decreased. Taurine did not change the hypercholesterolemia, but significantly recovered the excretion of bile acids. (+info
Effects of oral propylthiouracil treatment on nitric oxide production in rat aorta.
The effects of oral propylthiouracil (PTU) treatment on vascular nitric oxide (NO) production were studied in the rat aorta. Rats were fed a standard low fat diet with or without 0.1% PTU, for 2 or 4 weeks, or for 2 weeks with additional thyroxine injections. Concentration response curves were then constructed to phenylephrine (PE) in both endothelium-intact and denuded aortic rings from these animals and after incubation with 0.1 mM L-N(G)nitroarginine (L-NOARG). In addition, expression of nitric oxide synthase (NOS) was analysed in sections of aorta from PTU-treated and control rats using rabbit polyclonal antibodies to both inducible NOS (iNOS) and endothelial NOS (eNOS). Oral PTU treatment resulted in a significant reduction in both the maximum response (control, 0.53+/-0.02; 2 week PTU, 0.20+/-0.07; 4 week PTU, 0.07+/-0.02 g mg(-1)) and vessel sensitivity (EC50 values: control, 9.10x10(-8)+/-0.67; 2 week PTU, 7.45x10(-7)+/-1.15; 4 week PTU, 9.73x10(-7)+/-0.45 M) to PE in endothelium-intact vessel rings, as compared to controls (P<0.05). Both endothelial removal and incubation with L-NOARG restored the maximum response after 2, but not 4 weeks, although, in general, vessel sensitivity was not altered by either treatment. Vessels from PTU-treated rats given thyroxine injections showed no significant differences between any of the dose response curve parameters. Immunohistochemical analysis suggested that labelling for eNOS may be increased after PTU treatment as compared to control animals, whereas iNOS antibody immunoreactivity was not different between the two groups. These results suggest that the hyporesponsiveness to PE observed after oral PTU treatment is, in part, due to enhanced nitric oxide (NO) production by the endothelium, and demonstrate for the first time that thyroid hormones may play a role in the regulation of eNOS activity in the rat aorta. (+info