Is overall blockade superior to selective blockade of adrenergic receptor subtypes in suppressing left ventricular remodeling in spontaneously hypertensive rats?

Chinese Classical Music Lowers Blood Pressure and Improves Left Ventricular Hypertrophy in Spontaneously Hypertensive Rats

High blood pressure (BP) plays an important role in the pathogenesis and development of cardiovascular diseases and multi-organ damages. Music has been well known to elicit emotional changes, such as anxiolytic effects. However, whether music therapy lowers BP in spontaneously hypertensive rats (SHR) and the potential mechanism remains unknown. SHRs were, respectively exposed to white noise (WN), Western classical music (WM), Chinese classical music (CCM), rock music (RM), and bisoprolol treatment. WN and WM did not lower systemic BP, but CCM and RM significantly lowered BPs in SHRs. The effects of CCM therapy on lowering systemic BPs is comparable to that of bisoprolol at the dose of low to medium. Combination of CCM treatment with bisoprolol further improved systemic BPs and myocardial hypertrophy in SHRs, compared to CCM treatment or bisoprolol alone. Furthermore, IHC and WB analysis indicated that CCM therapy inhibited the β1/cAMP/PKA and α1/PLC/PKC signalings, but didn’t alter the β2/PI3K/Akt signaling. Above all, CCM therapy lowers systemic BPs and alleviates myocardial hypertrophy in hypertensive rats, which may be caused by the inhibitions of β1/cAMP/PKA and α1/PLC/PKC signalings.

Cardiac α1A-adrenergic receptors: emerging protective roles in cardiovascular diseases

α1-Adrenergic receptors (ARs) are catecholamine-activated G protein-coupled receptors (GPCRs) that are expressed in mouse and human myocardium and vasculature, and play essential roles in the regulation of cardiovascular physiology. Though α1-ARs are less abundant in the heart than β1-ARs, activation of cardiac α1-ARs results in important biologic processes such as hypertrophy, positive inotropy, ischemic preconditioning, and protection from cell death. Data from the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) indicate that nonselectively blocking α1-ARs is associated with a twofold increase in adverse cardiac events, including heart failure and angina, suggesting that α1-AR activation might also be cardioprotective in humans. Mounting evidence implicates the α1A-AR subtype in these adaptive effects, including prevention and reversal of heart failure in animal models by α1A agonists. In this review, we summarize recent advances in our understanding of cardiac α1A-ARs.

Postmenopausal hypertension: role of the sympathetic nervous system in an animal model

In postmenopausal women the mechanisms responsible for hypertension have not been completely elucidated, and there are no gender-specific guidelines for women despite studies showing that blood pressure is not as well controlled to goal in women as in men. In the present study we tested the hypotheses that the sympathetic nervous system and the renal sympathetic nerves contribute to hypertension in aging female rats, that sympathetic activation may be mediated by the melanocortin 3/4 receptor (MC3/4R), and that MC3/4R activation may be due to increases in leptin. α-1, β-1,2-Adrenergic blockade reduced blood pressure in both young (3-4 mo) and old (18-19 mo) female spontaneously hypertensive rats (SHR). Renal denervation attenuated the hypertension more in old females than young females. MC3/4R antagonism with SHU-9119 given intracerebroventricularly had no effect on blood pressure in either young or old females but significantly reduced blood pressure in old males. Plasma leptin levels were similar in old male and female SHR and in old versus young females. These data suggest that the hypertension in old female SHR is in part due to activation of the sympathetic nervous system, that the renal nerves contribute to the hypertension, and that the mechanism responsible for sympathetic activation in old females is independent of the MC3/4R.

Prenatal exposure to lipopolysaccharide results in myocardial remodelling in adult murine offspring

BACKGROUND

The epigenetic plasticity hypothesis indicates that pregnancy exposure may result in adult-onset diseases, including hypertension, diabetes and cardiovascular disease, in offspring. In a previous study, we discovered that prenatal exposure to inflammatory stimulants, such as lipopolysaccharides (LPS), could lead to hypertension in adult rat offspring. In the present study, we further demonstrate that maternal inflammation induces cardiac hypertrophy and dysfunction via ectopic over-expression of nuclear transcription factor κB (NF- κB), and pyrrolidine dithiocarbamate (PDTC) can protect cardiac function by reducing maternal inflammation.

METHODS

Pregnant SD rats were randomly divided into three groups and intraperitoneally injected with a vehicle, LPS (0.79 mg/kg), or LPS (0.79 mg/kg) plus PDTC (100 mg/kg) at 8 to 12 days of gestation. The offspring were raised until 4 and 8 months old, at which point an echocardiographic study was performed. The left ventricular (LV) mass index and apoptosis were examined.

RESULTS

At 4 months of age, the LPS offspring exhibited augmented posterior wall thickness. These rats displayed left ventricle (LV) hypertrophy and LV diastolic dysfunction as well as a higher apoptotic index, a higher level of Bax and a lower level of Bcl-2 at 8 months of age. The protein levels of NF-κB (p65) in the myocardium of the offspring were measured at this time. NF-κB protein levels were higher in the myocardium of LPS offspring. The offspring that were prenatally treated with PDTC displayed improved signs of blood pressure (BP) and LV hypertrophy.

CONCLUSIONS

Maternal inflammation can induce cardiac hypertrophy in offspring during aging accompanied with hypertension emergence and can be rescued by the maternal administration of PDTC (the inhibitor of NF-κB).