Prenatal exposure to glucocorticoids (GCs) programs for hypertension later in life. The aim of the current study was to examine the impact of prenatal GC exposure on the postnatal regulation of the gene encoding for phenylethanolamine N-methyltransferase (PNMT), the enzyme involved in the biosynthesis of the catecholamine, epinephrine. PNMT has been linked to hypertension and is elevated in animal models of hypertension. Male offspring of Wistar-Kyoto dams treated with dexamethasone (DEX) developed elevated systolic, diastolic and mean arterial blood pressure compared to saline-treated controls. Plasma epinephrine levels were also elevated in adult rats exposed to DEX in utero. RT-PCR analysis revealed adrenal PNMT mRNA was higher in DEX exposed adult rats. This was associated with increased mRNA levels of transcriptional regulators of the PNMT gene: Egr-1, AP-2, and GR. Western blot analyses showed increased expression of PNMT protein, along with increased Egr-1 and GR in adult rats exposed to DEX in utero. Furthermore, gel mobility shift assays showed increased binding of Egr-1 and GR to DNA. These results suggest that increased PNMT gene expression via altered transcriptional activity is a possible mechanism by which prenatal exposure to elevated levels of GCs may program for hypertension later in life.

No abstract

https://mc06.manuscriptcentral.com/cjpp-pubs ABSTRACTPhenylethanolamine N-methyltransferase (PNMT) is the terminal enzyme in the catecholamine biosynthetic pathway responsible for adrenaline biosynthesis. Adrenaline is involved in the sympathetic control of blood pressure; it augments cardiac function by increasing stroke volume and cardiac output. Genetic mapping studies have linked the PNMT gene to hypertension. This study examined the expression of cardiac PNMT and changes in its transcriptional regulators in the spontaneously hypertensive (SHR) and wild type Wistar-Kyoto (WKY) rats. SHR exhibit elevated levels of corticosterone, and lower levels of the cytokine IL-1 β, revealing systemic differences between SHR and WKY. PNMT mRNA was significantly increased in all chambers of the heart in the SHR, with the greatest increase in the right atrium. Transcriptional regulators of the PNMT promoter show elevated expression of Egr-1, Sp1, AP-2 and GR mRNA in all chambers of the SHR heart, while protein levels of Sp1, Egr-1 and GR were elevated only in the RA. Interestingly, only AP-2 protein-DNA binding was increased, suggesting it may be a key regulator of cardiac PNMT in SHR. This study provides the first insights into the molecular mechanisms involved in the dysregulation of cardiac PNMT in a genetic model of hypertension.

Catecholamines, neurohormones with extensive functions in the sympathetic regulation of blood pressure, have a well‐established role in cardiovascular disease and hypertension. Epidemiological data has shown that, in addition to elevations in the catecholamine adrenaline, hypertensive patients demonstrate altered plasma cytokine profiles, suggesting that hypertension entails a complex interplay of the neuroendocrine and immune systems. From preliminary work, we have found that spontaneously hypertensive rats (SHR) exhibit higher plasma levels of the cytokine CCL2, and decreased levels of interleukin (IL)‐1β and interferon (IFN)‐δ, compared to their normotensive counterparts. To delineate the relationship between cytokine‐mediated signalling and catecholamine synthesis, we tested a panel of cytokines for their ability to affect the expression of tyrosine hydroxylase (TH), dopamine beta hydroxylase (DBH) and phenylethanolamine N‐methyltransferase (PNMT), key enzymes for catecholamine biosynthesis. Adrenal medulla derived PC12 cells were treated with the cytokines IL‐1β, IL‐2, IL‐6, IL‐10, tumor necrosis factor‐α, IFN‐α, transforming growth factor‐β1, or CCL2, and transcriptional changes were analyzed using RT‐PCR. Alterations in the transcripts of TH, DBH and PNMT upon cytokine treatments were observed illustrating cytokine‐mediated regulation of catecholamine biosynthesis. Grant Funding Source: Supported by NSERC and CIHR