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

Association between DIO2 Thr92Ala polymorphism and hypertension in patients with hypothyroidism: Korean Genome and Epidemiology Study

BACKGROUND/AIMS

Recent evidence has identified the significance of type 2 iodothyronine deiodinase (DIO2) in various diseases. However, the role of DIO2 polymorphism in metabolic parameters in patients with hypothyroidism is not fully understood.

METHODS

We assessed the polymorphism of the DIO2 gene and various clinical parameters in 118 patients who were diagnosed with hypothyroidism from the Ansan-Anseong cohort of the Korean Genome and Epidemiology Study. Furthermore, we systematically analyzed Genotype-Tissue Expression (GTEx) data.

RESULTS

A total of 118 participants with hypothyroidism were recruited; 32 (27.1%) were homozygous for the Thr allele, 86 (73.9%) were homozygous for the Ala allele or heterozygous. Patients with hypothyroidism with DIO2 polymorphism without hypertension at baseline had higher incidence of hypertension compared to patients without DIO2 polymorphism. Analysis of the GTEx database revealed that elevation of DIO2 expression is associated with enhancement of genes involved in blood vessel regulation and angiogenesis.

CONCLUSION

Commonly inherited variation in the DIO2 gene is associated with high blood pressure and prevalence of hypertension in patients with hypothyroidism. Our results suggest that genetic variation in the hypothalamic-pituitary-thyroid pathway in influencing susceptibility to hypertension.

Maternal blood pressure associates with placental DNA methylation both directly and through alterations in cell-type composition

BACKGROUND

Maternal blood pressure levels reflect cardiovascular adaptation to pregnancy and proper maternal-fetal exchanges through the placenta and are very sensitive to numerous environmental stressors. Maternal hypertension during pregnancy has been associated with impaired placental functions and with an increased risk for children to suffer from cardiovascular and respiratory diseases later on. Investigating changes in placental DNA methylation levels and cell-type composition in association with maternal blood pressure could help elucidate its relationships with placental and fetal development.

METHODS

Taking advantage of a large cohort of 666 participants, we investigated the association between epigenome-wide DNA methylation patterns in the placenta, measured using the Infinium HumanMethylation450 BeadChip, placental cell-type composition, estimated in silico, and repeated measurements of maternal steady and pulsatile blood pressure indicators during pregnancy.

RESULTS

At the site-specific level, no significant association was found between maternal blood pressure and DNA methylation levels after correction for multiple testing (false discovery rate < 0.05), but 5 out of 24 previously found CpG associations were replicated (p-value < 0.05). At the regional level, our analyses highlighted 64 differentially methylated regions significantly associated with at least one blood pressure component, including 35 regions associated with mean arterial pressure levels during late pregnancy. These regions were found enriched for genes implicated in lung development and diseases. Further mediation analyses show that a significant part of the association between steady blood pressure-but not pulsatile pressure-and placental methylation can be explained by alterations in placental cell-type composition. In particular, elevated blood pressure levels are associated with a decrease in the ratio between mesenchymal stromal cells and syncytiotrophoblasts, even in the absence of preeclampsia.

CONCLUSIONS

This study provides the first evidence that the association between maternal steady blood pressure during pregnancy and placental DNA methylation is both direct and partly explained by changes in cell-type composition. These results could hint at molecular mechanisms linking maternal hypertension to lung development and early origins of childhood respiratory problems and at the importance of controlling maternal blood pressure during pregnancy.

The Type of Fat in the Diet Influences Regulatory Aminopeptidases of the Renin-Angiotensin System and Stress in the Hypothalamic-Pituitary-Adrenal Axis in Adult Wistar Rats

(1) Background: Prolonged feeding with a high-fat diet (HFD) acts as a stressor by activating the functions of the hypothalamic-pituitary-adrenal gland (HPA) stress axis, accompanied of hypertension by inducing the renin-angiotensin-aldosterone system. Angiotensinases enzymes are regulatory aminopeptidases of angiotensin metabolism, which together with the dipeptidyl peptidase IV (DPP-IV), pyroglutamyl- and tyrosyl-aminopeptidase (pGluAP, TyrAP), participate in cognitive, stress, metabolic and cardiovascular functions. These functions appear to be modulated by the type of fat used in the diet. (2) Methods: To analyze a possible coordinated response of aminopeptidases, their activities were simultaneously determined in the hypothalamus, adenohypophysis and adrenal gland of adult male rats fed diets enriched with monounsaturated (standard diet (S diet) supplemented with 20% virgin olive oil; VOO diet) or saturated fatty acids (diet S supplemented with 20% butter and 0.1% cholesterol; Bch diet). Aminopeptidase activities were measured by fluorimetry using 2-Naphthylamine as substrates. (3) Results: the hypothalamus did not show differences in any of the experimental diets. In the pituitary, the Bch diet stimulated the renin-angiotensin system (RAS) by increasing certain angiotensinase activities (alanyl-, arginyl- and cystinyl-aminopeptidase) with respect to the S and VOO diets. DPP-IV activity was increased with the Bch diet, and TyrAP activity decrease with the VOO diet, having both a crucial role on stress and eating behavior. In the adrenal gland, both HFDs showed an increase in angiotensinase aspartyl-aminopeptidase. The interrelation of angiotensinases activities in the tissues were depending on the type of diet. In addition, correlations were shown between angiotensinases and aminopeptidases that regulate stress and eating behavior. (4) Conclusions: Taken together, these results support that the source of fat in the diet affects several peptidases activities in the HPA axis, which could be related to alterations in RAS, stress and feeding behavior.

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.

Cardiovascular and body weight regulation changes in transgenic mice overexpressing thyrotropin-releasing hormone (TRH)

Thyrotropin-releasing hormone (TRH) plays several roles as a hormone/neuropeptide. Diencephalic TRH (dTRH) participates in the regulation of blood pressure in diverse animal models, independently of the thyroid status. The present study aimed to evaluate whether chronic overexpression of TRH in mice affects cardiovascular and metabolic variables. We developed a transgenic (TG) mouse model that overexpresses dTrh. Despite having higher food consumption and water intake, TG mice showed significantly lower body weight respect to controls. Also, TG mice presented higher blood pressure, heart rate, and locomotor activity independently of thyroid hormone levels. These results and the higher urine noradrenaline excretion observed in TG mice suggest a higher metabolic rate mediated by sympathetic overflow. Cardiovascular changes were impeded by siRNA inhibition of the diencephalic Trh overexpression. Also, the silencing of dTRH in the TG mice normalized urine noradrenaline excretion, supporting the view that the cardiovascular effects of TRH involve the sympathetic system. Overall, we show that congenital dTrh overexpression leads to an increase in blood pressure accompanied by changes in body weight and food consumption mediated by a higher sympathetic overflow. These results provide new evidence confirming the participation of TRH in cardiovascular and body weight regulation.

Knockdown of Inhibitory Guanine Nucleotide Binding Protein Giα-2 by Antisense Oligodeoxynucleotides Attenuates the Development of Hypertension and Tachycardia in Spontaneously Hypertensive Rats

BACKGROUND

We previously showed that the levels of both Giα-2 and Giα-3 proteins were augmented in spontaneously hypertensive rats (SHRs) before the onset of hypertension. In addition, intraperitoneal injection of pertussis toxin, which inactivates both Giα proteins, prevented the development of hypertension in SHRs. The aim of the present study was to determine the specific contributions of Giα-2 and Giα-3 proteins to the development of hypertension.

METHODS AND RESULTS

Antisense oligodeoxynucleotide of Giα-2 and Giα-3 encapsulated in PEG/DOTAP/DOPE cationic liposomes were administrated intravenously into 3-week-old prehypertensive SHRs and Wistar Kyoto rats, whereas the control Wistar Kyoto rats and SHRs received PBS, empty liposomes, or sense. The knockdown of Giα-2 but not Giα-3 protein attenuated tachycardia and prevented the development of hypertension up to age 6 weeks; thereafter, blood pressure started increasing and reached the same level as that of untreated SHRs at 9 weeks. Furthermore, Giα-2 and Giα-3 antisense oligodeoxynucleotide treatments significantly decreased the enhanced levels of Giα-2 and Giα-3 proteins, respectively, and enhanced levels of superoxide anion and NADPH oxidase activity in heart, aorta, and kidney and hyperproliferation of vascular smooth muscle cells from SHRs aged 6 weeks. In addition, antisense oligodeoxynucleotide treatment with Giα-2 but not Giα-3 restored enhanced inhibition of adenylyl cyclase by oxotremorine to WKY levels.

CONCLUSIONS

These results suggested that the enhanced expression of Giα-2 but not Giα-3 protein plays an important role in the pathogenesis of hypertension and tachycardia in SHRs.

Cardiac microvascular rarefaction in hyperthyroidism-induced left ventricle dysfunction

OBJECTIVE

The pathophysiology underlying hyperthyroidism-induced left ventricle (LV) dysfunction and hypertrophy directly involves the heart and indirectly involves the neuroendocrine systems. The effects of hyperthyroidism on the microcirculation are still controversial in experimental models. We investigated the effects of hyperthyroidism on the cardiac function and microcirculation of an experimental rat model.

METHODS

Male Wistar rats (170-250 g) were divided into two groups: the euthyroid group (n = 10), which was treated with 0.9% saline solution, and the hyperthyroid group (n = 10), which was treated with l-thyroxine (600 μg/kg/day, i.p.) during 14 days. An echocardiographic study was performed to evaluate the alterations in cardiac function, structure and geometry. The structural capillary density and the expression of angiotensin II AT1 receptor in the LV were analyzed using histochemistry and immunohistochemistry, respectively.

RESULTS

Hyperthyroidism was found to induce profound cardiovascular alterations, such as systolic hypertension, tachycardia, LV dysfunction, cardiac hypertrophy, and myocardial fibrosis. This study demonstrates the existence of structural capillary rarefaction and the down-regulation of the cardiac angiotensin II AT1 receptor in the myocardium of hyperthyroid rats in comparison with euthyroid rats.

CONCLUSIONS

Microvascular rarefaction may be involved in the pathophysiology of hyperthyroidism-induced cardiovascular alterations.

Dipper and non-dipper blood pressure 24-hour patterns: circadian rhythm-dependent physiologic and pathophysiologic mechanisms

Neuroendocrine mechanisms are major determinants of the normal 24-h blood pressure (BP) pattern. At the central level, integration of the major driving factors of this temporal variability is mediated by circadian rhythms of monoaminergic systems in conjunction with those of the hypothalamic-pituitary-adrenal, hypothalamic-pituitary-thyroid, opioid, renin-angiotensin-aldosterone, plus endothelial systems and specific vasoactive peptides. Humoral secretions are typically episodic, coupled either to sleep and/or the circadian endogenous (suprachiasmatic nucleus) central pacemaker clock, but exhibiting also weekly, monthly, seasonal, and annual periodicities. Sleep induction and arousal are influenced also by many hormones and chemical substances that exhibit 24-h variation, e.g., arginine vasopressin, vasoactive intestinal peptide, melatonin, somatotropin, insulin, steroids, serotonin, corticotropin-releasing factor, adrenocorticotropic hormone, thyrotropin-releasing hormone, endogenous opioids, and prostaglandin E2, all with established effects on the cardiovascular system. As a consequence, physical, mental, and pathologic stimuli that activate or inhibit neuroendocrine effectors of biological rhythmicity may also interfere with, or modify, the temporal BP structure. Moreover, immediate adjustment to exogenous components/environment demands by BP rhythms is modulated by the circadian-time-dependent responsiveness of biological oscillators and their neuroendocrine effectors. This knowledge contributes to a better understanding of the pathophysiology of abnormalities of the 24-h BP pattern and level and their correction through circadian rhythm-based chronotherapeutic strategies.

Mapping genetic variants associated with beta-adrenergic responses in inbred mice

β-blockers and β-agonists are primarily used to treat cardiovascular diseases. Inter-individual variability in response to both drug classes is well recognized, yet the identity and relative contribution of the genetic players involved are poorly understood. This work is the first genome-wide association study (GWAS) addressing the values and susceptibility of cardiovascular-related traits to a selective β₁-blocker, Atenolol (ate), and a β-agonist, Isoproterenol (iso). The phenotypic dataset consisted of 27 highly heritable traits, each measured across 22 inbred mouse strains and four pharmacological conditions. The genotypic panel comprised 79922 informative SNPs of the mouse HapMap resource. Associations were mapped by Efficient Mixed Model Association (EMMA), a method that corrects for the population structure and genetic relatedness of the various strains. A total of 205 separate genome-wide scans were analyzed. The most significant hits include three candidate loci related to cardiac and body weight, three loci for electrocardiographic (ECG) values, two loci for the susceptibility of atrial weight index to iso, four loci for the susceptibility of systolic blood pressure (SBP) to perturbations of the β-adrenergic system, and one locus for the responsiveness of QTc (p<10⁻⁸). An additional 60 loci were suggestive for one or the other of the 27 traits, while 46 others were suggestive for one or the other drug effects (p<10⁻⁶). Most hits tagged unexpected regions, yet at least two loci for the susceptibility of SBP to β-adrenergic drugs pointed at members of the hypothalamic-pituitary-thyroid axis. Loci for cardiac-related traits were preferentially enriched in genes expressed in the heart, while 23% of the testable loci were replicated with datasets of the Mouse Phenome Database (MPD). Altogether these data and validation tests indicate that the mapped loci are relevant to the traits and responses studied.

Association of thyroid function with arterial pressure in normotensive and hypertensive euthyroid individuals: A cross-sectional study

Background

Overt hypothyroidism has been associated with arterial hypertension and increased arterial stiffness. Results in euthyroid individuals have been conflicting. We investigated associations of thyroid function with systolic (SAP) and diastolic (DAP) arterial pressure in euthyroid subjects.

Methods

311 euthyroid individuals (185 women, mean age 43.9 ± 9) without a history of diabetes attending a preventive medicine program were examined. Subjects receiving thyroxine (10.6%) were excluded; 19.3% had hypertension, 43% had a family history for hypertension. TSH, fT4, thyroid autoantibodies, insulin, glucose were measured. The "fT4.TSH product", which has been suggested as a T4 resistance-index, was calculated.

Results

TSH range was 0.1–8, median 1.4 mU/L, fT4 range was 11.5–25.2 pmol/L, median 17.4. TSH and the "fT4.TSH product" were positively associated with DAP (p < 0.03, for both associations). In the subgroup of individuals with TSH levels 0.36–2.5 mU/L, both TSH and the "fT4.TSH product" were positively correlated with SAP (r = +0.133 p = 0.044, r = +0.152 p = 0.026) and DAP (r = +0.243 p < 0.001, r = +0.252 p < 0.001 respectively); in multivariate analysis the "fT4.TSH product" was a significant predictor of DAP independently of HOMA-IR and BMI (p < 0.001). Similar associations were found when only the non-hypertensive subjects were analysed (p = 0.004). Hypertensive patients had higher TSH levels (p = 0.02) and belonged more frequently to the subgroup with TSH > 2 mU/L (35.3% vs 21.3%, p = 0.045).

Conclusion

In euthyroid individuals the association of thyroid function with diastolic arterial pressure remains significant even when a stricter "normal range" for TSH levels is considered. The "freeT4.TSH" product appears to be an even stronger predictor of DAP, independently of HOMA insulin resistance index and obesity.

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.

Antisense inhibition at the beta-secretase-site of beta-amyloid precursor protein reduces cerebral amyloid and acetyl cholinesterase activity in Tg2576

Misprocessing of beta-amyloid precursor protein (APP) leading to the formation of elevated quantities of beta-amyloid peptide (Abeta), derived by a cleavage at the beta-secretase site (N-671/673aa) and by a cleavage at the gamma-secretase site (C-711/713aa) of APP, is considered a key event in the pathogenesis of Alzheimer disease (AD). Point mutations near the beta-secretase site in the human gene for APP, such as in the Swedish mutation-KM670/671NL, lead to a form of dominantly inherited AD. These mutations are known to promote beta-site cleavage and to increase levels of Abeta. Abeta has been shown previously to increase acetyl cholinesterase (AChE) activity in vitro. We wished to test whether translational blocking of APP-mRNA at the mutated beta-site by antisense (AS) oligodeoxynucleotides (ODNs) directed to the mutated site will reduce cerebral amyloid in the Swedish transgenic mouse model (Tg2576). Mice were injected i.c.v. with AS-ODNs directed at the mutated beta-site (AS-beta site) or with AS-ODNs directed at the normal gamma-site (AS-gamma site) of human APP-mRNA, and compared with procedural controls that received i.c.v. injections of sense ODNs at the beta-site (S-beta site), sense ODNs at the gamma-site (S-gamma site) or mismatched ODNs, and with untreated littermates (Lt) and untreated transgenic mice (Tgs). ODNs were injected into the 3rd ventricle once a week for 4 weeks. Brains were processed for enzyme-linked immunosorbent assay analysis of beta- and gamma-cleaved soluble Abeta40 (sAbeta40), beta- and gamma-cleaved soluble Abeta42 (sAbeta42) and alpha-cleaved soluble beta-amyloid precursor protein (sAPPalpha). The physiological relevance of AS ODNs was tested by evaluating the cerebral distribution of AChE before and after the treatment. AChE was found increased about fivefold in Tg cortex as compared with control brain. Results show that compared with untreated and procedural controls, AS-beta increased cerebral levels of sAPPalpha by 43% and reduced sAbeta40/42 by approximately 39%; while simultaneously reducing the cortical density of AChE by approximately fourfold in the treated Tg animals, almost to the level found in the control brain (all values P<0.0001, analysis of variance, unpaired two-tailed Student's t-test), while AS-gamma did not have any effect. These results indicate that AS directed to the mutated beta-site may be an effective approach to treat familial AD.

Gene-based therapy for hypertension--do preclinical data suggest a promising future?

Many experimental studies have obtained a prolonged control of blood pressure through gene treatment. This consists in the administration of genes coding for vasodilator proteins (the 'sense' approach), or of nucleotide sequences that are complementary to the mRNA of vasoconstrictor proteins, which are consequently synthesized in smaller amounts (the 'antisense' approach). Examples of the sense approach include the genes encoding endothelial nitric oxide synthase and kallikrein. Examples of the second type of approach are the antisense oligodeoxynucleotides to angiotensin-converting enzyme and endothelin-1. Also, RNA molecules, such as ribozymes and small interfering RNAs, are capable to inhibit RNA function. Whole sense genes are usually administered through viral vectors, while antisense oligonucleotides may be administered with plasmids or liposomes. Both viral and non-viral vectors have advantages and disadvantages. Despite the still persisting limitations, the possibility exists that in the future some forms of genetic treatment will be extended to the clinical setting, allowing a prolonged control of essential hypertension and its end-organ sequelae.

Association of Sixty-One Non-Synonymous Polymorphisms in Forty-One Hypertension Candidate Genes with Blood Pressure Variation and Hypertension

We previously selected a group of hypertension candidate genes by a key word search using the OMIM database of NCBI and validated 525 coding single nucleotide polymorphisms (SNPs) in 179 hypertension candidate genes by DNA sequencing in a Japanese population. In the present study, we examined the association between 61 non-synonymous SNPs and blood pressure variations and hypertension. We used DNA samples taken from 1,880 subjects in the Suita study, a population-based study using randomly selected subjects. Analyses of covariance adjusting for age, body mass index, hyperlipidemia, diabetes, smoking, drinking, and antihypertensive medication revealed that 17 polymorphisms in 16 genes (APOB, CAST, CLCNKB, CTNS, GHR, GYS1, HF1, IKBKAP, KCNJ11, LIPC, LPL, P2RY2, PON2, SLC4A1, TRH, VWF) were significantly associated with blood pressure variations. Multivariate logistic regression analysis with adjustment for the same factors revealed that 11 polymorphisms in 11 genes (CAST, CTLA4, F5, GC, GHR, LIPC, PLA2G7, SLC4A1, SLCI8A1, TRH, VWF) showed significant associations with hypertension. Five polymorphisms in five genes, CAST(calpastatin), LIPC (hepatic lipase), SLC4A1 (band 3 anion transporter), TRH (thyrotropin-releasing hormone), and VWF (von Willebrand factor), were significantly associated with both blood pressure variation and hypertension. Thus, our study suggests that these five genes were susceptibility genes for essential hypertension in this Japanese population.

Central thyrotropin-releasing hormone infusion opposes cardiovascular and metabolic suppression during caloric restriction

Inhibition of hypothalamic thyrotropin-releasing hormone (TRH) neuronal activity is a well-established adaptation to caloric restriction (CR) that suppresses pituitary secretion of thyroid-stimulating hormone, but may also participate in modulation of autonomic function. Thus, we hypothesized that decreased hypothalamic TRH activity contributes to CR-induced bradycardia and decreased metabolic rate. To test this hypothesis, male Sprague-Dawley rats were instrumented with telemetry devices for measurement of heart rate (HR) and blood pressure (BP) and a lateral intracerebroventricular (i.c.v.) guide cannula for central infusions. After recovery, rats were housed in metabolic chambers and given either ad libitum(ad-lib) or CR treatments for 7 days; half of each diet group was then given continuous i.c.v. infusions of TRH (25 nmol/h) or saline (0.25 microl/h) for 7 days via osmotic pump. This dose of TRH did not significantly alter peripheral free T(4) levels. In ad-lib rats, TRH infusion produced small reductions in food intake and small increases in HR and BP over saline-infused controls. In CR rats, TRH infusion resulted in an increase in HR and also energy expenditure over saline-infused controls. These results support the hypothesis that suppression of central TRH activity contributes to the homeostatic suppression of energy expenditure and HR observed during CR.

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.

Effect of Aging on Rat Tissue Peptidase Activities

The process of aging is known to involve alterations in the activity of peptidases and proteases. However, the precise changes in the activity of many peptidases in aged tissues have not yet been fully characterized, and both decreases and increases in both peptidase activity and peptide levels have been reported to occur during the aging process. In the present study, we measured the activity of several peptidases in selected tissues (brain cortex, brain stem, liver, kidney, heart, and lung) of the young adult (3 months old) and aged (18 months old and 22 months old) rat. The activities of prolyl endopeptidase, pyroglutamyl peptidase I, puromycin sensitive aminopeptidase, and aminopeptidase N were assayed using beta-naphthylamine aminoacidic derivatives as substrates. The activity of the soluble fractions of prolyl endopeptidase was found to be reduced in the lungs of aged animals, while reduced activity of soluble pyroglutamyl peptidase I and also aminopeptidase N was measured in the aged kidney and heart, respectively. In contrast, increased activity of particulate prolyl endopeptidase was measured in the brain stem of older animals. Since most of these changes can be correlated with known alterations in the levels of peptides controlled by each enzyme, the results of the present study indicate that the studied peptidases may play an important role in regulating tissue peptide levels during aging.

Trafficking of intracerebroventricularly injected antisense oligonucleotides in the mouse brain

Intracerebroventricular (icv) delivery of therapeutic molecules directly into the brain parenchyma has attracted considerable attention because of the advantage of bypassing the blood-brain barrier. Exogenous icv administration of antisense oligodeoxynucleotides (AS-ODNs) has been implicated in modifying gene expression within the targeted brain area. The biodistribution, tissue penetration, and stability of exogenously administered AS-ODNs are the major determinants with regard to their potential utility as agents for modifying gene expression. This report examined the distribution and clearance of labeled AS-ODNs with the aim of exploring the feasibility of icv administration of AS-ODNs as a targeted treatment approach to Alzheimer's disease. A single icv injection of fluorescein-labeled 2'-O-(methoxy) ethyl (2'MOE) ribosyl-modified AS-ODNs directed at the beta-secretase cleavage site of beta-amyloid precursor protein (APP) mRNA into the mouse brain showed rapid uptake by 15 minutes, overall gradual spread and retention by 30 minutes to 3 hours, and complete clearance by 8 hours postinjection. Labeled AS-ODNs were observed to penetrate across the cell membrane and accumulate in both nuclear and cytoplasmic compartments of neuronal and nonneuronal cell populations. Current study provides a basic pattern of uptake, distribution, and stability of AS-ODNs in the mouse brain.

Harnessing the mouse to unravel the genetics of human disease

Complex traits, i.e. those with multiple genetic and environmental determinants, represent the greatest challenge for genetic analysis, largely due to the difficulty of isolating the effects of any one gene amid the noise of other genetic and environmental influences. Methods exist for detecting and mapping the Quantitative Trait Loci (QTLs) that influence complex traits. However, once mapped, gene identification commonly involves reduction of focus to single candidate genes or isolated chromosomal regions. To reach the next level in unraveling the genetics of human disease will require moving beyond the focus on one gene at a time, to explorations of pleiotropism, epistasis and environment-dependency of genetic effects. Genetic interactions and unique environmental features must be as carefully scrutinized as are single gene effects. No one genetic approach is likely to possess all the necessary features for comprehensive analysis of a complex disease. Rather, the entire arsenal of behavioral genomic and other approaches will be needed, such as random mutagenesis, QTL analyses, transgenic and knockout models, viral mediated gene transfer, pharmacological analyses, gene expression assays, antisense approaches and importantly, revitalization of classical genetic methods. In our view, classical breeding designs are currently underutilized, and will shorten the distance to the target of understanding the complex genetic and environmental interactions associated with disease. We assert that unique combinations of classical approaches with current behavioral and molecular genomic approaches will more rapidly advance the field.

The hypothalamus and hypertension

Most forms of hypertension are associated with a wide variety of functional changes in the hypothalamus. Alterations in the following substances are discussed: catecholamines, acetylcholine, angiotensin II, natriuretic peptides, vasopressin, nitric oxide, serotonin, GABA, ouabain, neuropeptide Y, opioids, bradykinin, thyrotropin-releasing factor, vasoactive intestinal polypeptide, tachykinins, histamine, and corticotropin-releasing factor. Functional changes in these substances occur throughout the hypothalamus but are particularly prominent rostrally; most lead to an increase in sympathetic nervous activity which is responsible for the rise in arterial pressure. A few appear to be depressor compensatory changes. The majority of the hypothalamic changes begin as the pressure rises and are particularly prominent in the young rat; subsequently they tend to fluctuate and overall to diminish with age. It is proposed that, with the possible exception of the Dahl salt-sensitive rat, the hypothalamic changes associated with hypertension are caused by renal and intrathoracic cardiopulmonary afferent stimulation. Renal afferent stimulation occurs as a result of renal ischemia and trauma as in the reduced renal mass rat. It is suggested that afferents from the chest arise, at least in part, from the observed increase in left auricular pressure which, it is submitted, is due to the associated documented impaired ability to excrete sodium. It is proposed, therefore, that the hypothalamic changes in hypertension are a link in an integrated compensatory natriuretic response to the kidney's impaired ability to excrete sodium.