The sympathetic nervous system not only regulates cardiovascular and metabolic responses to stress but also is altered by stress. The sympathoneural and sympathoadrenomedullary systems are modified by different metabolic pathways and have different responses to short- and to long-term stressors. Stress also induces nonneuronal catecholamine enzymes, primarily through corticosteroids. Catecholamine synthetic enzymes are induced by different pathways in response to short- and long-term acting stressors, like cold exposure or immobilization, and differently in the sympathetic ganglia and the adrenal medulla. However, a long-term exposure to one stressor can increase the response to a second, different stressor. Tyrosine hydroxylase gene transcription increases after only 5min of immobilization through phosphorylation of CREB, but this response is short lived. However, repeated stress gives a longer-lived response utilizing transcription factors such as Egr-1 and Fra-2. Glucocorticoids and ACTH also induce sympathoneural enzymes leading to distinct patterns of short-term and long-lived activation of the sympathetic nervous system. Nonneuronal phenylethanolamine N-methyltransferase (PNMT) develops early in the heart and then diminishes. However, intrinsic cardiac adrenergic cells remain and nonneuronal PNMT is present in many cells of the adult organism and increases in response to glucocorticoids. Both stress-induced and administered glucocorticoids induce fetal PNMT and hypertension. Human stressors such as caring for an ill spouse or sleep apnea cause a persistent increase in blood norepinephrine, increased blood pressure, and downregulated catecholamine receptors. Hypertension is associated with a loss of slow-wave sleep, when sympathetic nerve activity is lowest. These findings indicate that stress-induced alteration of the sympathetic nervous system occurs in man as in experimental animals.

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Mitochondria play a central role in the integration and execution of a wide variety of apoptotic signals. In the present study, we examined the deleterious effects of burn injury on heart tissue. We explored the effects of vagal nerve stimulation (VNS) on cardiac injury in a murine burn injury model, with a focus on the protective effect of VNS on mitochondrial dysfunction in heart tissue. Mice were subjected to a 30% total body surface area, full-thickness steam burn followed by right cervical VNS for 10 min. and compared to burn alone. A separate group of mice were treated with the M3-muscarinic acetylcholine receptor (M3-AchR) antagonist 4-DAMP or phosphatidylinositol 3 Kinase (PI3K) inhibitor LY294002 prior to burn and VNS. Heart tissue samples were collected at 6 and 24 hrs after injury to measure changes in apoptotic signalling pathways. Burn injury caused significant cardiac pathological changes, cardiomyocyte apoptosis, mitochondrial swelling and decrease in myocardial ATP content at 6 and 24 hrs after injury. These changes were significantly attenuated by VNS. VNS inhibited release of pro-apoptotic protein cytochrome C and apoptosis-inducing factor from mitochondria to cytosol by increasing the expression of Bcl-2, and the phosphorylation level of Bad (pBad136) and Akt (pAkt308). These protective changes were blocked by 4-DAMP or LY294002. We demonstrated that VNS protected against burn injury–induced cardiac injury by attenuating mitochondria dysfunction, likely through the M3-AchR and the PI3K/Akt signalling pathways.

To compare the therapeutic effects of intensive versus moderate dosage of atorvastatin regimens in new-onset unstable angina with borderline lesions, 100 patients were randomized to receive either 80 mg/d or 20 mg/d atorvastatin for 9 months. Clinical symptoms, lipid profiles, and coronary stenosis (evaluated by coronary angiography and intravascular ultrasound) were compared to their corresponding baselines within each group and between the 2 groups after 9 months of treatment. The results showed that (1) when compared to their corresponding baselines, both groups exhibited improvement in clinical symptoms, a significant decrease in total cholesterol, triglyceride, low-density lipoprotein cholesterol (LDL-C), and high-sensitivity C-reactive protein (hs-CRP; P < .01) and a significant increase in high-density lipoprotein cholesterol (HDL-C); (2) the improvement in clinical symptoms and the decrease in LDL-C and hs-CRP were significantly greater (P < .01) in the intensive-dose group than in the moderate-dose group; (3) the mean plaque volume did not progress in the intensive-dose group but increased significantly (P < .05) in the moderate-dose group. We conclude that compared to the moderate dose, the intensive-dose regimen significantly improves clinical symptoms, lowers LDL-C and hs-CRP, and halts the progression of borderline atherosclerotic plaques in patients with new-onset unstable angina.