Hypothyroidism-associated immunosuppression involves induction of galectin-1-producing regulatory T cells

Hypothyroidism exerts deleterious effects on immunity, but the precise role of the hypothalamic-pituitary-thyroid (HPT) axis in immunoregulatory and tolerogenic programs is barely understood. Here, we investigated the mechanisms underlying hypothyroid-related immunosuppression by examining the regulatory role of components of the HPT axis. We first analyzed lymphocyte activity in mice overexpressing the TRH gene (Tg-Trh). T cells from Tg-Trh showed increased proliferation than wild-type (WT) euthyroid mice in response to polyclonal activation. The release of Th1 pro-inflammatory cytokines was also increased in Tg-Trh and TSH levels correlated with T-cell proliferation. To gain further mechanistic insights into hypothyroidism-related immunosuppression, we evaluated T-cell subpopulations in lymphoid tissues of hypothyroid and control mice. No differences were observed in CD3/CD19 or CD4/CD8 ratios between these strains. However, the frequency of regulatory T cells (Tregs) was significantly increased in hypothyroid mice, and not in Tg-Trh mice. Accordingly, in vitro Tregs differentiation was more pronounced in naïve T cells isolated from hypothyroid mice. Since Tregs overexpress galectin-1 (Gal-1) and mice lacking this lectin (Lgals1^-/- ) show reduced Treg function, we investigated the involvement of this immunoregulatory lectin in the control of Tregs in settings of hypothyroidism. Increased T lymphocyte reactivity and reduced frequency of Tregs were found in hypothyroid Lgals1^-/- mice when compared to hypothyroid WT animals. This effect was rescued by the addition of recombinant Gal-1. Finally, increased expression of Gal-1 was found in Tregs purified from hypothyroid WT mice compared with their euthyroid counterpart. Thus, a substantial increase in the frequency and activity of Gal-1-expressing Tregs underlies immunosuppression associated with hypothyroid conditions, with critical implications in immunopathology, metabolic disorders, and cancer.

Cardiac Thyrotropin-releasing Hormone Inhibition Improves Ventricular Function and Reduces Hypertrophy and Fibrosis After Myocardial Infarction in Rats

BACKGROUND

Cardiac thyrotropin-releasing hormone (TRH) is a tripeptide with still unknown functions. We demonstrated that the left ventricle (LV) TRH system is hyperactivated in spontaneously hypertensive rats and its inhibition prevented cardiac hypertrophy and fibrosis. Therefore, we evaluated whether in vivo cardiac TRH inhibition could improve myocardial function and attenuate ventricular remodeling in a rat model of myocardial infarction (MI).

METHODS AND RESULTS

In Wistar rats, MI was induced by a permanent left anterior descending coronary artery ligation. A coronary injection of a specific small interfering RNA against TRH was applied simultaneously. The control group received a scrambled small interfering RNA. Cardiac remodeling variables were evaluated one week later. In MI rats, TRH inhibition decreased LV end-diastolic (1.049 ± 0.102 mL vs 1.339 ± 0.102 mL, P < .05), and end-systolic volumes (0.282 ± 0.043 mL vs 0.515 ± 0.037 mL, P < .001), and increased LV ejection fraction (71.89 ± 2.80% vs 65.69 ± 2.85%, P < .05). Although both MI groups presented similar infarct size, small interfering RNA against TRH treatment attenuated the cardiac hypertrophy index and myocardial interstitial collagen deposition in the peri-infarct myocardium. These effects were accompanied by attenuation in the rise of transforming growth factor-β, collagen I, and collagen III, as well as the fetal genes (atrial natriuretic peptide, B-type natriuretic peptide, and beta myosin heavy chain) expression in the peri-infarct region. In addition, the expression of Hif1α and vascular endothelial growth factor significantly increased compared with all groups.

CONCLUSIONS

Cardiac TRH inhibition improves LV systolic function and attenuates ventricular remodeling after MI. These novel findings support the idea that TRH inhibition may serve as a new therapeutic strategy against the progression of heart failure.

Abstract 091: Leptin-Thyroliberin Pathway in Left Ventricle Hypertrophy

Cardiac TRH (cTRH) induces LVH and fibrosis. The adiponectin Leptin induces TRH in CNS. We hypothesized that in obesity, the increase of cTRH induced by hyperleptinemia is responsible for the LVH, mostly attributed to pressure load. We studied obese hyperleptinemic with mild hypertension Agouti mice, and found LVH with higher (p<0.05) cTRH, fibrotic (I/III col,TGFβ) and hypertrophic (BNP,βMHC) marker genes vs lean (BL/6J). We normalized pressure in Agouti mice with hydroclorothiazide (20 mg/kg/day) since weaning (n=9) vs non treated mice. Still both developed (p<0.05) LVH, higher cTRH, fibrotic and hypertrophic marker genes expression, suggesting that LVH would not be due to hypertension. Opposite to Agouti model, we used obese normotensive ob/ob mice, lacking Leptin expression, and without LVH despite their obesity. We treated them with Leptin (80 ug/kg/day) or saline since weaning for 15 days. Only the treated group developed LVH (p< 0.05, n=7) demonstrating that it is Leptin dependant. Also we found increase (p<0.05) in cTRH, col III, TGFβ and BNP suggesting that leptin-TRH interaction is required in obesity-induced LVH. Finally, we evaluated whether Leptin administration, (n=6, 10 ug/kg/day) could induce hypertrophy in lean C57 mice with and withouth native cTRH system, by previous siRNA injection (5ug). Diuretic was given to Leptin groups, to avoid its hypertensive effect. Leptin induced cTRH expression, not observed in the groups with siRNA-TRH (p<0.05).This probably induce fibrotic and hypertrophic markers, demonstrating that the novel interaction is functional also in mildy hyperleptinemia at normal weight status. To confirm TRH's Leptin induction we used cardiomyocytes cell line H9C2 (n=6) stimulated with Leptin (10 and 100 ng/ml). TRH expression and precursor content increased (p<0.05) post Leptin treatment with both concentrations. Moreover in primary cardiomyocytes culture from neonate rats, Leptin stimulus (80 ng/ml, 24 hs) increased (p<0.05) TRH content vs controls, confirming the direct TRH-Leptin induction in heart cells. We described a novel Leptin-cTRH pathway which explains Leptin-induced LVH, highly likely since early stages.

Abstract P141: Cardiac TRH Partly Mediates Angiotensin II-induced Fibrotic and Hypertrophy Effects in "in vivo" and "in vitro" Models

Cardiac TRH (cTRH) is overexpressed in the hypertrophied ventricle (LV) of the SHR. Additionally in vivo siRNA-TRH treatment induced downregulation of LV-TRH preventing cardiac hypertrophy and fibrosis demonstrating that TRH is involved in hypertrophic and fibrotic processes. Moreover, in a normal heart, the increase of LV TRH expression alone could induce structural changes where fibrosis and hypertrophy could be involved, independently of any other system alterations.

Is well-known the cardiac hypertrophy/ fibrotic effects induced by AII, raising the question of whether specific LV cTRH inhibition might attenuates AII induced cardiac hypertrophy and fibrosis in mice.

We challenged C57 mice with AII (osmotic pumps,14 days; 2 mg/kg) to induce cardiac hypertrophy vs saline. Groups were divided and , simultaneously to pump surgery, injected intracardiac with siRNA-TRH and siRNA-Con as its control. Body weight, water consume and SABP were measured daily.

As expected, AII significantly increased SABP (p<0.05) in both groups treated , although cardiac hypertrophy (heart weight/body weight) was only evident in the group with the cardiac TRH system undamaged, suggesting that the cardiac TRH system function as a necessary mediator of the AII-induced hypertrophic effect.

As hypothesized, we found an AII-induced increase of TRH (p<0.05) gene expression (real-t PCR) confirmed by immunofluorescence that was not observed in the group AII+siRNA-TRH demonstrating the specific siRNA treatment efficiency.

Furthermore, AII significantly increase (p<0.05) BNP (hypertrophic marker), III collagen and TGFB (fibrosis markers) expressions only in the group with AII with the cardiac TRH system intact. On the contrary, the group with AII and the cTRH system inhibited, shows genes expressions similar to the saline control group. We confirmed these results by immunofluorescence.

Similar fibrotic results were observed with NIH3T3 cell culture where we demonstrated that AII induced TRH gene expression (p<0.05) and its inhibition impedes AII-induced increase of TGFB and III/I collagens expressions telling us about the role of the cTRH in the AII fibrosis effects.

Our results point out that the cardiac TRH is involved in the AII-induced hypertrophic and fibrotic effects.

Thyrotropin-releasing hormone overexpression induces structural changes of the left ventricle in the normal rat heart

Thyrotropin-releasing hormone (TRH) hyperactivity has been observed in the left ventricle of spontaneously hypertensive rats. Its long-term inhibition suppresses the development of hypertrophy, specifically preventing fibrosis. The presence of diverse systemic abnormalities in spontaneously hypertensive rat hearts has raised the question of whether specific TRH overexpression might be capable of inducing structural changes in favor of the hypertrophic phenotype in normal rat hearts. We produced TRH overexpression in normal rats by injecting into their left ventricular wall a plasmid driving expression of the preproTRH gene (PCMV-TRH). TRH content and expression of preproTRH, collagen type III, brain natriuretic peptide, β-myosin heavy chain, Bax-to-Bcl-2 ratio, and caspase-3 were measured. The overexpression maneuver was a success, as we found a significant increase in both tripeptide and preproTRH mRNA levels in the PCMV-TRH group compared with the control group. Immunohistochemical staining against TRH showed markedly positive brown signals only in the PCMV-TRH group. TRH overexpression induced a significant increase in fibrosis, evident in the increase of collagen type III expression accompanied by a significant increase in extracellular matrix expansion. We found a significant increase in brain natriuretic peptide and β-myosin heavy chain expression (recognized markers of hypertrophy). Moreover, TRH overexpression induced a slight but significant increase in myocyte diameter, indicating the onset of cell hypertrophy. We confirmed the data “in vitro” using primary cardiac cell cultures (fibroblasts and myocytes). In conclusion, these results show that a specific TRH increase in the left ventricle induced structural changes in the normal heart, thus making the cardiac TRH system a promising therapeutic target.

Detection and structural characterization of oxo-chromium(V)-sugar complexes by electron paramagnetic resonance

This article describes the detection and characterization of oxo-Cr(V)-saccharide coordination compounds, produced during chromic oxidation of carbohydrates by Cr(VI) and Cr(V), using electron paramagnetic resonance (EPR) spectroscopy. After an introduction into the main importance of chromium (bio)chemistry, and more specifically the oxo-chromium(V)-sugar complexes, a general overview is given of the current state-of-the-art EPR techniques. The next step reviews which types of EPR spectroscopy are currently applied to oxo-Cr(V) complexes, and what information about these systems can be gained from such experiments. The advantages and pitfalls of the different approaches are discussed, and it is shown that the potential of high-field and pulsed EPR techniques is as yet still largely unexploited in the field of oxo-Cr(V) complexes. Subsequently, the discussion focuses on the analysis of oxo-Cr(V) complexes of different types of sugars and the implications of the results in terms of understanding chromium (bio)chemistry.

Methylation of TFAM gene promoter in peripheral white blood cells is associated with insulin resistance in adolescents

PURPOSE

To explore whether DNA methylation of the mitochondrial transcription factor A (TFAM) promoter is associated with insulin resistance in a sample of adolescents with features of metabolic syndrome.

METHODS

The data and blood samples were collected from 122 adolescents out of a cross-sectional study of 934 high-school students. The population was divided into two groups: noninsulin resistance (NIR) and insulin resistance (IR). After bisulfite treatment of genomic DNA from peripheral leukocytes, we used methylation-specific polymerase chain reaction (PCR) to assess DNA methylation of three putative methylation target sites (CpG) in the TFAM promoter.

RESULTS

The ratio of the promoter methylated DNA/unmethylated DNA was 0.012+/-0.0009 (1.2% of alleles), and inversely correlated with the biochemical features of insulin resistance (plasma fasting insulin R: -0.26, p<0.004 and homeostasis model assessment (HOMA) index R: -0.27, p<0.002), and obesity (R: -0.27, p<0.002). Multiple regression analysis showed that the log-transformed HOMA index correlated with the status of promoter methylation of TFAM, independently of body mass index (BMI) Z score (beta: -0.33+/-0.094, p=0.00094). Finally, the TFAM promoter methylated DNA/unmethylated DNA ratio was found to be significantly associated with insulin resistance as dichotomous variable (NIR n=45, 0.014+/-0.002 and IR n=77, 0.011+/-0.001, respectively, p<0.016).

CONCLUSION

Our findings suggest a potential role of promoter TFAM methylation in the pathogenesis of insulin resistance in adolescents.

Maternal pregestational BMI is associated with methylation of the PPARGC1A promoter in newborns

We explored peroxisome proliferator-activated receptor-gamma co-activator 1alpha gene (PPARGC1A), peroxisome proliferator-activated receptor-gamma gene (PPARG), and transcription factor A mitochondrial gene (Tfam) promoter DNA methylation in newborns between both extremes of abnormal fetal growth: Small (SGA) and large for gestational age (LGA) in relation to the mother's characteristics. We further sought for the association of rs9930506 variant at FTO gene and the promoter patterns of DNA methylation in the aforementioned genes, in relation to the offspring's birth weight. In a cross-sectional study, 88 healthy pregnant women and their babies were included. According to the offspring birth weight, there were 57 newborns with appropriate weight for gestational age (AGA), 17 SGA, and 14 LGA. After bisulphite treatment of umbilical cord genomic DNA, a real-time methylation-specific PCR was used to determine the promoter methylation status in selected CpGs. Promoter methylated DNA/unmethylated DNA ratio, expressed as mean +/- s.e., was 0.82 +/- 0.15 (45% of alleles) for PPARGC1A, and 0.0044 +/- 0.0006 (0.4% of alleles) for Tfam. PPARG promoter was almost 100% methylated in all samples. In univariate analysis, there was no association among characteristics of the newborn and gene promoter methylation. None of the maternal features were related with the status of promoter methylation, except for a positive correlation between maternal BMI and PPARGC1A promoter methylation in umbilical cord (Pearson correlation coefficient r = 0.41, P = 0.0007). Finally, FTO rs9930506 AA homozygous in the LGA group showed decreased levels of methylated PPARGC1A in comparison with AG + GG genotypes and AGA and SGA infants. In conclusion, our findings suggest a potential role of promoter PPARGC1A methylation in metabolic programming.

A decreased mitochondrial DNA content is related to insulin resistance in adolescents

The aim of this study was to investigate whether mitochondrial DNA (mtDNA) content is associated with insulin resistance (IR) in a sample of adolescents with features of metabolic syndrome. We further studied the link between polymorphisms in three genes involved in mitochondrial biogenesis and the presence of deleted mtDNA and mtDNA content. Data and blood samples were collected from 175 adolescents out of a cross-sectional, population-based study of 934 high school students. On the basis of the median value of homeostasis model assessment of IR (HOMA-IR) of the whole sample (2.2), the population was divided into two groups: noninsulin resistance (NIR) and IR. mtDNA quantification using nuclear DNA (nDNA) as a reference was carried out using a real-time quantitative PCR method. Genotyping for peroxisome proliferator-activated receptor-gamma (PPAR-gamma) (pro12Ala), PPAR- gamma coactivator-1alpha (PGC-1alpha) (Gly482Ser), and Tfam (rs1937 and rs12247015) polymorphisms was performed by PCR-based restriction fragment length polymorphism. Long-extension PCR was performed to amplify the whole mitochondrial genome. The mtDNA/nDNA ratio was significantly lower in the IR group (median: 9.08, range: 68.94) in comparison with the NIR group (12.24, 71.92) (P<0.03). Besides, the mtDNA/nDNA ratio was inversely correlated with HOMA (R: -0.18, P<0.02), glucose (R: -0.21, P<0.008), and uric acid (R: -0.18, P<0.03). Genotypes for the PPAR- gamma, PGC-1alpha, and Tfam variants were not associated with the mtDNA/nDNA ratio. Long-extension PCR did not show significant levels of mtDNA deletions. In conclusion, our findings indicate that reduced mtDNA content in peripheral leukocytes is associated with IR. This result seems not to be related with the previously mentioned variants in genes involved in the regulation of mitochondrial biogenesis.

Association between diencephalic thyroliberin and arterial blood pressure in agouti-yellow and ob/ob mice may be mediated by leptin

Leptin, a hormone secreted by the adipose tissue, stimulates anorexigenic peptides and also inhibits orexigenic peptides in hypothalamic arcuate nuclei-located neurons. It also counteracts the starvation-induced suppression of thyroid hormones by up-regulating the expression of preproTRH gene. On the other hand, in addition to its role as a modulator of the thyroid-hypothalamic-hypophysial axis, thyrotropin-releasing hormone (TRH) acts as a modulator of the cardiovascular system. In fact, we reported that overexpression of diencephalic TRH (dTRH) induces hypertension. We have recently shown that, in rats with obesity-induced hypertension, hyperleptinemia may produce an increase of dTRH together with an elevation of arterial blood pressure (ABP) through an increase of sympathetic activity and that these alterations were reversed by antisense oligonucleotide and small interfering RNA against preproTRH treatments. Here we explore the possible role of dTRH as a mediator involved in leptin-induced hypertension in 2 obesity mouse models: agouti-yellow mice, which are hyperleptinemic and hypertensive, and ob/ob mice, which lack functional circulating leptin. These 2 models share some characteristics, but ob/ob mice show lower ABP and plasma catecholamines levels. Then, for the first time, we report that there is a clear association between ABP and dTRH levels in both mouse models, as we have found that dTRH content was elevated in agouti-yellow mice and diminished in ob/ob mice compared with their controls. We also show that, after 3 days of subcutaneous leptin injections (10 microg/12 hours), ABP and dTRH increased significantly in ob/ob mice with no alterations of thyroid hormone levels. These results add evidence to the putative molecular mechanisms for the strong association between obesity and hypertension.

Knocking down the diencephalic thyrotropin-releasing hormone precursor gene normalizes obesity-induced hypertension in the rat

We recently showed that diencephalic TRH may mediate the central leptin-induced pressor effect. Here, to study the role of TRH in obesity-induced hypertension (OIH), we used a model of OIH produced by a high-fat diet (HFD, 45 days) in male Wistar rats. After 4 wk, body weight and systolic arterial blood pressure (SABP) increased in HFD animals. Plasma leptin was correlated with peritoneal adipose tissue. Then, we treated OIH animals with an antisense oligodeoxynucleotide and small interfering (si)RNA against the prepro-TRH. Antisense significantly decreased diencephalic TRH content and SABP at 24 and 48 h posttreatment. Similar effects were observed with siRNA against prepro-TRH but for up to 4 wk. Conversely, vehicle, an inverted antisense sequence and siRNA against green fluorescence protein, produced no changes. SABP decrease seems to be owing to an inhibition of the obesity-enhanced sympathetic outflow but not to an alteration in thyroid status. Using a simple OIH model we demonstrated, for the first time, that central TRH participates in the hypertension induced by body weight gain probably through its well-known action on sympathetic activity. Thus the TRH-leptin interaction may contribute to the strong association between hypertension and obesity.

Short allele of serotonin transporter gene promoter is a risk factor for obesity in adolescents

Obesity and hypertension are increasing medical problems in adolescents. Serotonin transporter (5-HTT) is involved in mood and eating disturbances. Encoded by the gene SLC6A4, the promoter shows functional insertion/deletion alleles: long (L) and short (S). Because individuals who are carriers for the short version are known to be at risk for higher levels of anxiety, we hypothesized that this variant may be associated with overweight. Data and blood samples were collected from 172 adolescents out of a cross-sectional, population-based study of 934 high school students. To replicate the findings, we also included 119 outpatients from the Nutrition and Diabetes Section of the Children's County Hospital. We found that the S allele was associated with overweight (BMI > 85th percentile), being a risk factor for overweight independently of sex, age, and hypertension [odds ratio (OR): 1.85; 95% confidence interval (CI): 1.13, 3.05; p < 0.02]. Additionally, in the outpatient study, compared with the homozygous LL subjects, S allele carriers showed a higher BMI z-score (1.47 +/- 1.09 vs. 0.51 +/- 1.4; p < 0.002) and were more frequent in overweight children. In conclusion, the S allele of the SLC6A4 promoter variant is associated with overweight being an independent genetic risk factor for obesity.

Mitochondrial DNA depletion in small- and large-for-gestational-age newborns

OBJECTIVE

To investigate whether mitochondrial DNA (mtDNA) content may be associated with clinical features, anthropometric variables, and laboratory findings in both extremes of abnormal fetal growth: small and large size for gestational age.

RESEARCH METHODS AND PROCEDURES

Eighty-eight pregnant women and their infants were included in a cross-sectional study. According to the offspring birthweight, normalized by sex and gestational age, there were 57 newborns with appropriate weight for gestational age (AGA) and 31 with abnormal weight for gestational age: 17 small for gestational age (SGA) and 14 large for gestational age (LGA). mtDNA quantification using nuclear DNA as a reference was measured by a real-time quantitative polymerase chain reaction method.

RESULTS

The mothers' pregestational BMI was associated with the weight of their offspring: SGA infants had lean mothers (BMI, 21.4 +/- 0.7), and LGA infants had overweight mothers (BMI, 26.7 +/- 1.4) in comparison with AGA infants (BMI, 23.0 +/- 0.7) (p < 0.003). Newborn leptin levels were associated with birthweight after adjustment for sex and gestational age (SGA, 7.0 +/- 1.1 ng/mL; AGA, 15.2 +/- 1.6 ng/mL; and LGA, 25.6 +/- 4.1 ng/mL) (p < 0.002). Conversely, mtDNA/nuclear DNA ratio was significantly lower in both extremes of abnormal fetal growth, SGA (18 +/- 6) and LGA (9 +/- 2), at birth in comparison to AGA-weight infants (28 +/- 4) (p < 0.03).

DISCUSSION

Our findings show that mtDNA content is decreased in newborns with abnormal weight in comparison with AGA infants. On the basis of a cumulative body of evidence, we speculate that mtDNA depletion is one of the putative links between abnormal fetal growth and metabolic and cardiovascular complications in later life.

Peroxisome proliferator-activated receptor gamma and its coactivator-1 alpha may be associated with features of the metabolic syndrome in adolescents

Our objective was to search for differences in genotypes of peroxisome proliferator-activated receptor gamma (PPARgamma) (Pro12 Ala) and its coactivator PGC-1alpha (Gly482 Ser) in adolescents harboring features of metabolic syndrome. In a population-based study, we determined medical history, anthropometric variables, biochemical measurements and arterial blood pressures of 934 high-school students of Caucasian origin. We selected 220 adolescents who had systolic or diastolic blood pressures more than the 80th or less than the 20th percentiles based on the previous single set of measurements. One hundred and seventy-five adolescents completed the study and underwent two additional blood pressure measurements on different days, as well as biochemical analysis and genotyping. We found no association between insulin resistance, body mass index (BMI) and leptin levels and PPARgamma and PGC-1alpha genotypes. The 12 Ala PPARgamma allele was associated with increased waist-to-hip ratio (WHR) and carriers seemed to have higher diastolic blood pressure and lower pulse pressure than non-carriers, particularly in the hypertensive and overweight group. Although Ser482 Ser PGC-1alpha homozygotes had lower WHRs than other PGC-1alpha genotypes, they were more frequent in the hypertensive group than in the normotensive (44.4 vs 24.5%, P<0.03), so the 482 Ser PGC-1 allele was in our population a risk factor for hypertension independently of WHR, homeostasis model assessment of insulin resistance, BMI and Pro12 Ala PPARgamma variant (odds ratio=4.0, 95% confidence interval 1.5-10.6, P<0.01). Multiple regression analysis showed that age- and sex-adjusted systolic blood pressure correlated with the 482 Ser PGC-1 allele regardless of those covariates. In conclusion, the Gly482 Ser variant of the PGC-1alpha gene may be an independent genetic risk factor for young-onset hypertension.

The G-308A promoter variant of the tumor necrosis factor-alpha gene is associated with hypertension in adolescents harboring the metabolic syndrome

BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha) has been associated with obesity, obesity-related hypertension, and metabolic syndrome. We investigated the possible contribution of the G-308A TNF-alpha mutant to explain variables of the metabolic syndrome.

METHODS

Data and blood samples were used from the 175 adolescents that satisfied the criterion of having systolic or diastolic blood pressures (BP) more than the 80th or less than the 20th percentiles, out of a cross-sectional, population-based study of 934 high school students. Genotyping for the polymorphism was performed by polymerase chain reaction-based restriction fragment length polymorphism analysis.

RESULTS

In univariate analysis, we found that there was no difference between A allele carriers and noncarriers in most of the clinical characteristics of the metabolic syndrome such as body mass index (BMI), waist-to-hip ratio, plasma leptin levels, total cholesterol, HDL- and LDL-cholesterol, triglycerides, plasma fasting glucose, insulin, and homocysteine levels. However, we found a significantly (P = .015) higher age- and sex-adjusted systolic BP (Z score) in the A allele carriers, and A allele carriers also showed an elevated homeostasis model assessment of insulin resistance (HOMA) index with respect to noncarriers. Logistic regression analysis indicates that A allele carriers had a 2.8-fold higher probability of being hypertensive independent of BMI, waist-to-hip ratio, and HOMA index.

CONCLUSIONS

In this report we found a positive association between the G-308A TNF-alpha variant and systolic arterial BP Z score and HOMA index in adolescents harboring features of metabolic syndrome. Therefore, the A allele may predispose to hypertension and insulin resistance in youth.

Thyrotropin-releasing hormone in cardiovascular pathophysiology

Thyrotropin (TSH)-releasing hormone (TRH) also known as thyroliberin was the first of a number of peptides exerting several roles as a hormone and as a neuropeptide. Its ubiquitous distribution in the hypothalamus and in the extrahypothalamic regions and its diverse pharmacological and physiological effects are all features of its dual functions. For this reason, TRH has been the subject of much research throughout the past 20 years, work that has examined the structure, function, distribution, and regulation of the tripeptide and it has been extensively reviewed elsewhere [O'Leary R., O'Connor B. Thyrotropin-releasing hormone. J Neurochem. 1995;65:953-963.; Nillni E., Sevarino K. The biology of pro-thyrotropin-releasing hormone-derived peptides. Endocrine Reviews, 1999;20:599-664.]. After a brief overview of its distribution, hypothalamic and extrahypothalamic functions, and receptors involved, this review discusses efforts devoted to support TRH role in cardiovascular regulation with a main focus on hypertension pathophysiology in experimental models and humans.

Parathyroid hormone-related protein overexpression decreases blood pressure in spontaneously hypertensive rats

We have recently demonstrated that arterial PTHrP expression and cardiovascular responses to this protein are altered in SHR compared with normotensive animals, Wistar Kyoto (WKY) and Sprague-Dawley (SD) rats. To investigate whether the slightly, but significantly decreased, aortic PTHrP gene expression observed in SHR, compared to that of normotensive animals, may play a causative role in the maintenance of the elevated arterial blood pressure (ABP) of the SHR, we transfected a hepatic lobe with a PTHrP expression vector in a sense and antisense orientation. At 24 and 48 hours, sense pSV2neo-ECE induced a significant five-fold increase in PTHrP mRNA abundance with respect to antisense pSV2neo-ECE and vehicle. This increment in the PTHrP mRNA induced by the sense PTHrP expression vector was totally inhibited by the co-administration of the antisense PTHrP expression vector. At the same time, we observed a significant decrease of mean ABP (MABP) in SHR transfected with the sense pSV2neo-ECE to similar values as those obtained in the normotensive strain. Neither antisense PTHrP expression vector nor vehicle had any significant effect in any strain. Again, the effect of the sense PTHrP expression vector on MABP was blocked by the simultaneous treatment with the antisense PTHrP expression vector. At 48 hours, the hypotensive effect of the sense pSV2neo-ECE in SHR was reverted by the i.v. bolus injection of a specific competitive PTHrP receptor antagonist such as Nle8,18,Tyr34-bPTH(3-34)amide. We propose that a defect of this potent local vasodilator may contribute to the development and/or maintenance of arterial hypertension in SHR. This defect can be ameliorated by transfecting tissues with protein-exporting capabilities, such as the liver. Finally, our work adds additional data to a cumulative body of evidence suggesting that it might be possible to design an effective gene therapy to treat the common polygenic and multifactorial form of hypertension by increasing the activity of potent and physiological vasodilators.

A1166C angiotensin II type 1 receptor gene polymorphism may predict hemodynamic response to losartan in patients with cirrhosis and portal hypertension

OBJECTIVE

Losartan, a dose of 25 mg/day, has been found to be effective in 50% of patients with portal hypertension without adverse effects. We evaluated the relationship between genetic polymorphisms of the renin-angiotensin system (A1166C angiotensin II type 1 receptor (AT1R), angiotensinogen T174M and M235T, and angiotensin-converting enzyme I/D) and the effects of losartan on portal and systemic hemodynamic in patients with cirrhosis and portal hypertension.

METHODS

We performed a longitudinal study that included 23 consecutive patients with cirrhosis and esophageal varices who received 25 mg/day of losartan during 12 wk. Hepatic venous pressure gradient (HVPG) and systemic hemodynamic were measured at baseline and after treatment. Genomic DNA was extracted from peripheral blood leukocytes; genetic polymorphisms of the renin-angiotensin system were investigated by polymerase chain reaction and restriction fragment length polymorphisms.

RESULTS

The homozygous patients for AT1R A allele showed higher pulmonary-wedged and free hepatic venous pressure on baseline. After treatment, they showed a higher decrease of HVPG (32.5%+/- 19.2) in comparison with patients with AC/CC genotype (2.4%+/-18.9), p < 0.01. Ten of 15 patients with AA genotype were responders, while only one of eight with AC/CC genotype (p < 0.002); genotype AA showed a positive predictive value of 66.6% and negative predictive value of 87.5%.

CONCLUSIONS

These results suggest that there is a relationship between the AT1R A1166C polymorphisms and the therapeutic response to losartan. The genetic testing may be used as a predictive factor of this response.

Renin-angiotensin-aldosterone system loci and multilocus interactions in young-onset essential hypertension

OBJECTIVE

Renin-angiotensin-aldosterone system component genes have been associated to essential hypertension. Thus, we studied the association of singe locus or multilocus interactions with young-onset essential hypertension.

SETTING AND DESIGN

This is a case-control study based on a population sample of adolescent at an inner city.

PARTICIPANTS

We studied 54 adolescents with hypertension and 121 age-matched normotensives, recruited from a high-school student population of 934 interviewed individuals.

METHODS

Resting blood pressure was measured on three different days and normalized (Z-score) by sex and age. Genotypes of ACE (I/D) angiotensinogen (T174M and M235T), ATIR (A1166C), and CYP11B2 (C-344T) were determined by PCR/RFLP or ASO.

RESULTS

Although genotype frequencies were not different in both groups, we found a significant dominant effect of ACE D and angiotensinogen 235T alleles on normalized systolic arterial blood pressure in males. This effect was confirmed by sib-pair linkage analysis taking normalized blood pressure as a quantitative trait. We independently analyzed multilocus interactions in normotensive and hypertensive adolescents searching for multiple locus deviation from Hardy-Weinberg or linkage equilibrium. We found that from 63 multilocus combinations, 4 deviated significantly from equilibrium in hypertensive adolescents but none in the normotensives. Deviations from equilibrium may indicate that the combination of alleles at different loci affects susceptibility or resistance to the disease.

CONCLUSION

In addition to the angiotensin-converting enzyme (ACE) and angiotensinogen (AGT) gene variants, gene-gene interactions may be important causative factors in a complex disease such as young-onset essential hypertension.

Thyrotropin-releasing hormone decreases leptin and mediates the leptin-induced pressor effect

Leptin, an adipocyte-released hormone, modifies food intake and energy expenditure regulating hypothalamic-pituitary-thyroid axis function. We previously reported that thyrotropin-releasing hormone (TRH) precursor gene overexpression induces hypertension in the normal rat and that spontaneously hypertensive rats have central TRH hyperactivity with increased TRH synthesis and release and an elevated TRH receptor number. In both models, intracerebroventricular antisense (AS) treatment against the TRH precursor produced a dose-dependent reduction of the increased diencephalic TRH content while normalizing high arterial blood pressure. In this article, we report that male Wistar rats that were made hypertensive by intracerebroventricular injection of a eucaryotic expression plasmid containing the pre-TRH cDNA showed decreased leptin plasma levels and that pre-TRH AS treatment reversed this phenomenon. In addition, male and female spontaneously hypertensive rats showed lower levels of circulating leptin than did sex-matched Wistar-Kyoto control rats. This difference also was abated by the pre-TRH AS treatment. Conversely, 20 microg ICV leptin induced a long-lasting pressor effect (18 +/- 5 mm Hg, n=6, P<0.01, >60 minutes) that was not observed in pre-TRH AS pretreated rats (2 +/- 3 mm Hg, n=6) but persisted in rats used as controls that were treated with inverted oligonucleotide (20 +/- 6 mm Hg, n=4, P<0.01). These data suggest that in rats with TRH-induced hypertension, leptin is decreased, inducing compensatory adiposity. We propose that because leptin produces central TRH synthesis and release, obesity may induce hypertension through TRH system activation and that the TRH-leptin interaction may thus contribute to the strong association between hypertension and obesity.

Thyrotropin-releasing hormone receptor (TRHR) gene is associated with essential hypertension

In essential hypertension, a polygenic and multifactorial syndrome, several genes interact with the environment to produce high blood pressure. Thyrotropin-releasing hormone (TRH) plays an important role in central cardiovascular regulation. We have described that TRH overexpression induces hypertension in a normal rat, which was reversed by TRH antisense treatment. This treatment also reduces the central TRH hyperactivity in spontaneously hypertensive rats and normalizes blood pressure. Human TRH receptor (TRHR) belongs to the G protein-coupled seven-transmembrane domain receptor superfamily. Mutations of these receptors may result in constitutive activation. As it has been demonstrated that hypertensive patients have a blunted TSH response to TRH injection, suggesting a defect in the TRHR, we postulate that the TRHR gene is involved in human hypertension. We studied 2 independent populations from different geographic regions of our country: a sample of adult subjects from a referral clinic and a population-based sample of high school students. In search of molecular variants of TRHR, we disclosed that a polymorphic TG dinucleotide repeat (STR) at -68 bp and a novel single nucleotide polymorphism, a G-->C conversion at -221 located in the promoter of the TRHR are associated with essential hypertension. As STRs detected in gene promoters are potential Z-DNA-forming sequences and seem to affect gene expression, we studied the potentially different transcriptional activity of these TRHR promoter variants and found that the S/-221C allele has a higher affinity than does the L/G-221 allele to nuclear protein factor(s). Our findings support the hypothesis that the TRHR gene participates in the etiopathogenesis of essential hypertension.

Antisense inhibition of thyrotropin-releasing hormone reduces arterial blood pressure in spontaneously hypertensive rats

Thyrotropin-releasing hormone (TRH) plays an important role in central cardiovascular regulation. Recently, we described that the TRH precursor gene overexpression induces hypertension in the normal rat. In addition, we published that spontaneously hypertensive rats (SHR) have central extrahypothalamic TRH hyperactivity with increased TRH synthesis and release and an elevated TRH receptor number. In the present study, we report that intracerebroventricular antisense (AS) treatment with a phosphorothioate oligonucleotide against the TRH precursor gene significantly diminished up to 72 hours and in a dose-dependent manner the increased diencephalic TRH content, whereas normalized systolic blood pressure (SABP) was present in the SHR compared with Wistar-Kyoto (WKY) rats. Although basal thyrotropin was higher in SHR compared with WKY rats and this difference disappeared after antisense treatment, no differences were observed in plasma T4 or T3 between strains with or without AS treatment, indicating that the effect of the AS on SABP was independent of the thyroid status. Because the encephalic renin-angiotensin system seems to be crucial in the development and/or maintenance of hypertension in SHR, we investigated the effect of antisense inhibition of TRH on that system and found that TRH antisense treatment significantly diminished the elevated diencephalic angiotensin II (Ang II) content in the SHR without any effect in control animals, suggesting that the Ang II system is involved in the TRH cardiovascular effects. To summarize, the central TRH system seems to be involved in the etiopathogenesis of hypertension in this model of essential hypertension.

Expression of TRH and TRH-like peptides in a human glioblastoma-astrocytoma cell line (U-373-MG)

The human glioblastoma-astrocytoma cell line U-373-MG shows morphological features typical of its neuroectodermal origin. Cells showed positive immunostaining for the glial fibrillary acidic protein. We used this cell culture for studying the putative production of TRH and TRH-related peptides. In a cell extract and conditioned medium, cation and anion exchange chromatography and HPLC revealed the presence of TRH and acidic TRH-like peptides which were identified, at least in part, as pGlu-Glu-ProNH(2). These findings demonstrated that U-373-MG cells are able to produce and release these peptides. Further evidence of TRH synthesis was obtained by amplification using RT-PCR of a 396 bp fragment that corresponds to the TRH precursor mRNA. Our results therefore suggest that the U-373-MG cell line may be a useful model for studying the regulation of TRH and TRH-related peptide production and the interaction of these peptides with other classical neurotransmitter systems. In fact, pilocarpine (a muscarinic cholinergic agonist) enhanced and nicotine (a nicotinic cholinergic agonist) decreased TRH and TRH-related compound production by this cell line. These data also point out that glia may produce substances with neuromodulatory action.

Increased expression of magnocellular vasopressin mRNA in rats with deoxycorticosterone-acetate induced salt appetite

The neuropeptides arginine vasopressin (AVP) and oxytocin (OT) have been implicated in the genesis of hypertension due to deoxycorticosterone acetate (DOCA)-salt treatment of uninephrectomized rats. In this work, we studied if DOCA treatment of intact rats in doses arousing a salt appetite (a prehypertensive state), modulated mRNA for AVP and OT in the hypothalamus. Male Sprague-Dawley rats were offered both tap water and 3% NaCl in separate bottles and received vehicle or subcutaneous injections of 10 mg DOCA on alternate days for 7 days (4 injections) or 17 days (9 injections). They developed a preference for 3% NaCl solutions 24-48 h after treatment. Brain slices from rats killed on the 8th or 18th day were exposed to 35S-labeled probes encoding prepro-AVP mRNA or OT mRNA, respectively. Expression of these mRNAs was measured in the magnocellular and parvocellular divisions of the paraventricular nucleus (PVN) and magnocellular cells of the supraoptic nucleus (SON). No changes were obtained in neuropeptide mRNA levels in the parvocellular division of the PVN between control and the two groups of DOCA-treated rats. However, DOCA-treated animals presented an increased number of grains per cell for AVP mRNA in the magnocellular division of the PVN and in magnocellular cells of the SON, as shown by group mean comparisons and frequency histograms. No changes were detected for OT mRNA. In a second series of studies, control or DOCA-treated rats were offered 3% NaCl or water as the only choice. Animals drinking 3% NaCl showed increased AVP and OT mRNA levels, whether they received DOCA or not. However, AVP mRNA levels in both nuclei were higher in DOCA-treated rats drinking 3% NaCl than in controls drinking salt solution. In comparison, control and DOCA-treated rats drinking water showed lower levels of AVP mRNA. OT mRNA levels in the SON remained unchanged in the same groups. The results suggest that in the magnocellular cells of the PVN and SON, increments in AVP mRNA are obtained following increments in salt intake produced by either mineralocorticoid treatment or exclusive salt drinking. In rats offered salt solution and water to drink, DOCA effects on AVP mRNA developed before changes occurred in serum sodium levels. Because combined DOCA + salt treatment induced a higher response in terms of AVP mRNA expression, we suggest that AVP could be a target of the central effects of the mineralocorticoid.

Central overexpression of the TRH precursor gene induces hypertension in rats: antisense reversal

Extrahypothalamic TRH participates in cardiovascular regulation and spontaneous hypertension of the rat. To investigate whether an increase in central TRH activity produces hypertension we studied the effect of the preTRH overproduction induced by I.C.V. transfection with a naked eukaryotic expression plasmid vector which encodes preTRH (pCMV-TRH). Northern blot analysis and RT-PCR showed that pCMV-TRH was transcribed in vitro and in vivo. At 24, 48, and 72 hours, pCMV-TRH (100 microg) in a significant and dose-dependent manner increased 37%, 84%, and 49%, respectively, the diencephalic TRH content and SABP (42+/-3, 50+/-2, and 22+/-2 mm Hg, respectively) with respect to the vector without the preTRH cDNA insert (V[TRH(-)]) as measured by RIA and the plethysmographic method, respectively, in awake animals. In addition, using immunohistochemistry we found that the increase of TRH was produced in circumventricular areas where the tripeptide is normally located. To further analyze the specificity of these effects we studied the actions of 23-mer sense (S), antisense (AS), and 3'self-stabilized sense (Ss) and antisense (ASs) phosphorothioate oligonucleotides against the initiation codon region. Only ASs inhibited the increase of TRH content and SABP induced by pCMV-TRH treatment. In addition, pCMV-TRH-induced hypertension seems not to be mediated by central Ang II or serum TSH. To summarize, central TRH overproduction in periventricular areas induced by I.C.V. transfection produces hypertension in rats which is reversed by specific antisense treatment. This model may help in testing effective antisense oligodeoxynucleotides against other candidate genes.

Brain amines in glucocorticoid-induced hypertension in the rat

A two week administration of the glucocorticoid betametasone to male Wistar rats produced a mild hypertensive state. The brain of these rats showed some significant changes in amine and metabolite content with respect to normotensive controls. Epinephrine and metanephrine were increased in the rostral ventrolateral medulla and in the preoptic area. Epinephrine also increased in the septal area. Normetanephrine decreased in the rostral ventrolateral medulla. Dopamine and homovanillic acid increased in septal and preoptic areas. Dopamine alone increased in rostral ventrolateral medulla. Serotonin and 5-hydroxyindole-3-acetic acid increased in the septal area and dorsal medulla. These changes suggest significant alterations in the aminergic activity of the brain circuitry known to regulate cardiovascular functions; the changes may play a basic role in the development and maintenance of glucocorticoid-induced hypertension.