Roseli Golfetti

Baroreceptor reflex and integrative stress responses in chronic fatigue syndrome.

Objective Altered cardiovascular responses to mental and postural stressors have been reported in chronic fatigue syndrome (CFS). This study examined whether those findings may involve changes in baroreceptor reflex functioning. Methods Chronotropic baroreceptor reflex (by sequential analysis) and cardiovascular stress responses were recorded during postural (5-minute of active standing) and cognitive (speech task) stress testing in patients with CFS grouped into cases with severe (N = 21) or less severe (N = 22) illness, and in 29 matched control subjects. Results Patients with CFS had a greater decline in baroreceptor reflex sensitivity (BRS) during standing, although only those with severe CFS were significantly different from the controls. Systolic blood pressure declined during standing in the control group but was maintained in the CFS patients. In contrast, the patients with less severe CFS had blunted increases in blood pressure during the speech task, which could not, however, be explained by inadequate inhibition of the baroreceptor reflex, with all groups showing an appropriate reduction in BRS during the task. Conclusions These results indicate that in CFS, deficiencies in orthostatic regulation, but not in centrally mediated stress responses, may involve the baroreceptor reflex. This study also suggests that classifying patients with CFS on illness severity may discriminate between patients with abnormalities in peripheral vs. central mechanisms of cardiovascular stress responses.

Acetaminophen in the Post-ischemia Reperfused Myocardium

Acetaminophen was administered acutely at the onset of reperfusion after 20 min of low-flow, global myocardial ischemia in isolated, perfused guinea pig hearts (Langendorff) to evaluate its influence in the postischemia, reperfused myocardium. Similarly prepared hearts were treated with vehicle or with uric acid (another phenol for comparison). Functionally, acetaminophen-treated hearts (0.35 mM) achieved significantly greater recovery during reperfusion. For example, left ventricular developed pressures at 40 min reperfusion were 38 ± 3, 27 ± 3, and 20 ± 2 in the presence of acetaminophen (P < 0.05, relative to the other two groups), vehicle, and uric acid, respectively. Coronary perfusion pressures and calculated coronary vascular resistances, in the acetaminophen-treated hearts, were significantly lower at the same time (e.g., coronary perfusion pressures in the three groups, respectively, were 40 ± 2 [P < 0.05], 51 ± 3, and 65 ± 12 mm Hg). Under baseline, control conditions, creatine kinase ranged from 12–15 units/liter in the three groups. It increased to 35–40 units/liter (P < 0.05) during ischemia but was significantly reduced by acetaminophen during reperfusion (e.g., 5.3 ± 0.8 units/liter at 40 min). Oxidant-mediated chemiluminescence in all three treatment groups during baseline conditions and ischemia was similar (i.e., approximately 1.5–2.0 min for peak luminescence to reach its half maximal value). It took significantly more time during reperfusion for the oxidation of luminol in the presence of acetaminophen (>20 min, P < 0.05) than in its absence (3–8 min in uric acid- and vehicle-treated hearts). These results suggest that administration of acetaminophen (0.35 mM), at the onset of reperfusion, provides anti-oxidant–mediated cardioprotection in the postischemia, reperfused myocardium.

Acetaminophen reduces mitochondrial dysfunction during early cerebral postischemic reperfusion in rats

Acetaminophen, a popular analgesic and antipyretic, has been found to be effective against neuronal cell death in in vivo and in vitro models of neurological disorders. Acute neuronal death has been attributed to loss of mitochondrial permeability transition coupled with mitochondrial dysfunction. The potential impact of acetaminophen on acute injury from cerebral ischemia-reperfusion has not been studied. We investigated the effects of acetaminophen on cerebral ischemia-reperfusion-induced injury using a transient global forebrain ischemia model. Male Sprague-Dawley rats received 15mg/kg of acetaminophen intravenously during ischemia induced by hypovolemic hypotension and bilateral common carotid arterial occlusion, which was followed by reperfusion. Acetaminophen reduced tissue damage, degree of mitochondrial swelling, and loss of mitochondrial membrane potential. Acetaminophen maintained mitochondrial cytochrome c content and reduced activation of caspase-9 and incidence of apoptosis. Our data show that acetaminophen reduces apoptosis via a mitochondrial-mediated mechanism in an in vivo model of cerebral ischemia-reperfusion. These findings suggest a novel role for acetaminophen as a potential stroke therapeutic.

Chronically Administered Acetaminophen and the Ischemia/Reperfused Myocardium

Male and female Hartley strain guinea pigs weighing 280 ± 10 g were given acetaminophen-treated water ad libitum for 10 days. Sham-treated control animals were given similar quantities of untreated tap water (vehicle-treated control group). On Day 10, hearts were extracted, instrumented, and exposed to an ischemia (low-flow, 20 min)/reperfusion protocol. Our objective was to compare and contrast ventricular function, coronary circulation, and selected biochemical and histological indices in the two treatment groups. Left ventricular developed pressure in the early minutes of reperfusion was significantly greater in the presence of acetaminophen, e.g., at 1 min, 40 ± 4 vs 21 ± 3 mmHg (P < 0.05). Coronary perfusion pressure was significantly less from 3 to 40 min of reperfusion in the presence of acetaminophen. Creatine kinase release in vehicle-treated hearts rose from 42 ± 14 (baseline) to 78 ± 25 units/liter by the end of ischemia. Corresponding values in acetaminophen-treated hearts were 36 ± 8 and 44 ± 14 units/liter. Acetaminophen significantly (P < 0.05) attenuated release of creatine kinase. Chemiluminescence, an indicator of the in vitro production of peroxynitrite via the in vivo release of superoxide and nitric oxide, was also significantly attenuated by acetaminophen. Electron microscopy indicated a well-preserved myofibrillar ultrastructure in the postischemic myocardium of acetaminophen-treated hearts relative to vehicle-treated hearts (e.g., few signs of contraction bands, little or no evidence of swollen mitochondria, and well-defined light and dark bands in sarcomeres with acetaminophen; opposite with vehicle). We conclude that chronic administration of acetaminophen provides cardioprotection to the postischemic, reperfused rodent myocardium.

Acetaminophen is cardioprotective against H2O2-induced injury in vivo.

Here we report our ongoing investigation of the cardiovascular effects of acetaminophen, with emphasis on oxidation-induced canine myocardial dysfunction. The objective of the current study was to investigate whether acetaminophen could attenuate exogenous H2O2-mediated myocardial dysfunction in vivo. Respiratory, metabolic, and hemodynamic indices such as left ventricular function (LVDP and ±dP/dtmax), and percent ectopy were measured in anesthetized, open-chest dogs during intravenous administration of 0.88 mM, 2.2 mM, 6.6 mM H2O2. Following 6.6 mM H2O2, tissue from the left ventricle was harvested for electron microscopy. Left ventricular function did not vary significantly between vehicle and acetaminophen groups under baseline conditions. Acetaminophen-treated dogs regained a significantly greater fraction of baseline function after high concentrations of H2O2 than vehicle-treated dogs. Moreover, the incidence of H2O2-induced ventricular arrhythmias was significantly reduced in the acetaminophen-treated group. Percent ectopy following 6.6 mM concentrations of H2O2 was 1 ± 0.3 vs. 0.3 ± 0.1 (P < 0.05) for vehicle- and acetaminophen-treated dogs, respectively. Additionally, electron micrograph images of left ventricular tissue confirmed preservation of tissue ultrastructure in acetaminophen-treated hearts when compared to vehicle. We conclude that, in the canine myocardium, acetaminophen is both functionally cardioprotective and antiarrhythmic against H2O2-induced oxidative injury.

Antiarrhythmic Properties of Acetaminophen in the Dog

Mongrel dogs bred for research and weighing 25 ± 3 kg were used to test the hypothesis that acetaminophen has antiar-rhythmic properties. Only ventricular arrhythmias defined by the Lambeth Conventions were investigated. Dogs were exposed either to 60 mins of regional myocardial ischemia followed by 180 mins of reperfusion (n = 14) or were administered a high dose of ouabain (n = 14). Both groups of 14 dogs were further divided into vehicle and acetaminophen treatment groups (n = 7 in each). During selected 10-min intervals, we recorded the numbers of ventricular premature beats, ventricular salvos, ventricular bigeminy, ventricular tachycardia (nonsustained and sustained), and we recorded the heart rate, systemic arterial blood pressure, and left ventricular function. Neither heart rate nor the number of ventricular arrhythmias differed significantly under baseline conditions. Conversely, the combined average number of ventricular ectopic beats during ischemia and reperfusion was significantly less in the presence of acetaminophen (28 ± 4 vs. 6 ± 1; P < 0.05). Similarly, percent ectopy during reperfusion in vehicle- and acetaminophen-treated dogs was 1.4 ± 0.4 and 0.4 ± 0.2, respectively (P < 0.05). The number of all ventricular ectopic beats except ventricular salvos was also significantly reduced in the presence of acetaminophen. Similar results were obtained with ouabain. Our results reveal that systemic administration of a therapeutic dose of acetaminophen has previously unreported antiarrhythmic effects in the dog.

New Perspectives on Acetaminophen

Acetaminophen (paracetamol) continues to be one of the leading, international over-the-counter analgesics. Unlike the COX-2 inhibitors, no adverse cardiovascular effects have been associated with acetaminophen usage in safe, therapeutic dosages. There are few rigorous physiological investigations of its actions/mechanisms of action. Several investigations, in recent years, have questioned its potential activity in the mammalian cardiovascular system. Our laboratory has found some positive salutary effects in myocardial ischemia/reperfusion injury and during myocardial infarction. In addition, another laboratory found concomitant cardioprotective effects during the acute phase of myocardial infarction. They report similar effects of the ability of acetaminophen to reduce the severity of myocardial infarction and ultimately result in improved mortality rates. They also postulate that this attenuation in myocardial damage is mediated through antioxidant means. Others have not found similar results but have reported no detrimental cardiovascular actions of acetaminophen in experimental animals. The inconsistency in results probably reflects multiple differences in experimental approaches, including use of different species, different experimental preparations, different drug concentrations, and different routes/modes of administering/preparing the drug. The current review focuses on this recent research and tries to provide new perspectives for future investigations. In particular, we have identified new cellular/subcellular targets at which acetaminophen might be acting. These include matrix metalloproteinases and the mitochondrial permeability transition pore. Future work will help identify additional tissue/organ actions of acetaminophen and its as-yet-unknown mechanisms of action.