Abstract-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. Key Words: angiotensin II Ⅲ antisense Ⅲ blood pressure Ⅲ hypertension Ⅲ SHR Ⅲ thyroid hormones Ⅲ TRH Ⅲ TSH I n addition to its endocrine function, thyrotropin-releasing hormone (TRH; pyro-Glu-His-Pro-amide) also serves as a neurotransmitter in the central nervous system. 1 TRH immunoreactivity is widely distributed throughout the central nervous system, including the brain and spinal cord. 2 Although the lack of antagonists to the TRH receptor has made difficult to determine the physiological role for the extrahypothalamic TRH system, its presence in brain nuclei involved in cardiovascular regulation, such as the periventricular region and the preoptic area, suggests that this tripeptide may modulate the cardiovascular function. 3 In fact, many groups have described that brain microinjections of TRH produce dose-dependent pressor effects. 4 Recently, we have reported that the overexpression of the TRH precursor in the third ventricle of the central nervous system of normal rats induces a long-lasting elevation of arterial blood pressure along with an increase in the diencephalic TRH content in a dose-dependent manner. These effects were specifically reversed by an antisense treatment, indicating that the extrahypothalamic TRH system effectively participates in cardiovascular regulation in the rat. 5 Spontaneously hypertensive rats (SHR) have been extensive...

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.

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 ICV 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 μg) 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 ICV transfection pro-duces hypertension in rats which is reversed by specific antisense treatment. This model may help in testing effective antisense oligodeoxynucleotides against other candidate genes.