Guadalupe Bravo

Cardiovascular Alterations After Spinal Cord Injury: An Overview

The recent developments in the management of spinal cord injury (SCI) have led to a reduction in mortality and in the consequences, resulting from incomplete spinal cord damage in those who survive. In this respect, it is noteworthy that SCI not only results in paraplegia or tetraplegia, but also in systemic, cardiovascular and metabolic alterations secondary to autonomic dysfunction. After SCI there is a decrease in sympathetic discharge and an increase in parasympathetic drive, resulting in profound changes in arterial blood pressure and heart rate. When SCI is induced in experimental animals, an immediate hypotension occurs (acute phase) which has been attributed to an autonomic imbalance involving a predominance of parasympathetic activity. Subsequently, an episodic hypertension may develop (chronic phase) as a part of a condition denominated autonomic dysreflexia. This hypertension is caused by afferent stimulation below the level of injury and can be so severe that sometimes may lead to cerebral haemorrhage, seizures, and death. In the light of the above lines of evidence, experimental SCI may provide an ideal model to study the nature of cardiovascular mechanisms following traumatic injury. Thus, the present review will deal with an update of the possible cardiovascular complications associated to SCI (including spinal shock, autonomic dysreflexia, deep venous thrombosis, and risk for coronary heart disease). This will be discussed within the context of the development of drugs with potential therapeutic usefulness in the acute and chronic stages of SCI.

Oxidative stress in cardiomyocytes contributes to decreased SERCA2a activity in rats with metabolic syndrome

Ca(+) mishandling due to impaired activity of cardiac sarco(endo)plasmic reticulum Ca(2+) ATPase (SERCA2a) has been associated with the development of left ventricular diastolic dysfunction in insulin-resistant cardiomyopathy. However, the molecular causes underlying SERCA2a alterations induced by insulin resistance and related metabolic disorders, such as metabolic syndrome (MetS), are not completely understood. In this study, we used a sucrose-fed rat model of MetS to test the hypothesis that decreased SERCA2a activity is mediated by elevated oxidative stress produced in the MetS heart. Production of ROS and cytosolic Ca(2+) concentration were recorded in left ventricular myocytes using confocal imaging. The level of SERCA2a oxidation was determined in left ventricular homogenates by biotinylated iodoacetamide labeling. Compared with control rats, sucrose-fed rats exhibited several characteristics of MetS, including central obesity, insulin resistance, hyperinsulinemia, and hypertriglyceridemia. Moreover, relative to myocytes from control rats, myocytes from MetS rats exhibited elevated basal production of ROS accompanied by slowed cytosolic Ca(2+) removal, reflected by prolonged Ca(2+) transients. The slowed cytosolic Ca(2+) removal was associated with a significant decrease in SERCA2a-mediated Ca(2+) reuptake and increased SERCA2a oxidation. Importantly, myocytes from MetS rats treated with the antioxidant N-acetylcysteine showed normal ROS levels and SERCA2a-mediated Ca(2+) reuptake as well as accelerated cytosolic Ca(2+) removal. These data suggest that elevated oxidative stress may induce oxidative modifications on SERCA2a leading to abnormal function of this protein in the MetS heart.

Effect of losartan on vascular function in fructose-fed rats: the role of perivascular adipose tissue.

Recent studies have shown the effect of perivascular adipose tissue (PVAT) on the regulation of vascular function; however, its role in the model of metabolic syndrome remains unclear. The aim of this study was to examine the effect of losartan on PVAT-derived vascular dysfunction in fructose-induced hypertensive rats. Rats were fed with either water, 10% fructose, or 10% fructose with 10mg/kg losartan for 8 weeks. In the isolated aorta with PVAT and endothelium, contraction induced by norepinephrine (NE) was more potent in fructose-fed rats compared to control rats. Losartan normalized blood pressure, insulin resistance, and NE-induced vasoconstriction in fructose-fed rats. In the aortic rings with/without endothelium and with/without PVAT, losartan could not improve the acetylcholine-induced relaxation in fructose-fed rats. The observation suggested that losartan partly improved the PVAT-associated vascular regulation in fructose-induced hypertensive rats.

Lipid peroxidation by nitric oxide supplements after spinal cord injury: effect of antioxidants in rats

To determine the extent to which exogenous nitric oxide (NO) might affect hemodynamics and/or increase oxidative damage after acute spinal cord (SC) injury, rats were submitted to SC contusion, and given a NO donor or NO precursor. Intravenous isosorbide dinitrate (10 microg/kg per min) or L-arginine (300 mg/kg per 23 h) showed a tendency to increase lipid peroxidation (LP), although without reaching significance compared to non-treated injured rats 24 h post-injury, and without affecting mean arterial pressure and heart rate importantly. LP due to injury and exogenous NO was significantly inhibited by the co-administration of a cocktail of antioxidants (12 mg/kg superoxide dismutase mimetic, 27000 U/kg catalase, and 12 mg/kg glutathione), but less effectively for the injury-L-arginine condition. These results demonstrate that in order to further test the potential neuroprotective effect of NO enhancing reagents after SC injury, antioxidants must be included in the treatment scheme.

Mechanisms involved in the cardiovascular alterations immediately after spinal cord injury.

The early cardiovascular effects resulting from an acute spinal cord injury (SCI) produced by a contusion procedure at T5-T6 were evaluated in anaesthetized rats. The mean arterial pressure (MAP) and heart rate (HR) were measured during one hour after the injury. A marked decrease in MAP and HR was observed immediately after injury, followed by an abrupt increase in MAP. These changes were observed between 3 and 9 min and the basal values were recovered after 20 min. Fall in the MAP and HR and increase in MAP induced by SCI were abolished by atropine. The interruption of the parasympathetic outflow by vagotomy also significantly diminished the fall and increase in MAP and the fall in HR. Likewise, pre-treatment with nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) completely abolished the effects produced by SCI. These data suggest that after SCI the decrement in MAP and HR was probably due to acetylcholine release from parasympathetic fibers and NO from endothelial source probably by a cholinergic stimulation. Additionally, the MAP increase observed was probably due to a reflex compensatory vasoconstriction.

Antinociceptive effects of tramadol in co-administration with metamizol after single and repeated administrations in rats

Combinations of two analgesic drugs of the same or different class are widely used in clinical therapy to enhance its antinociceptive effects and reduce the side effects. In order to evaluate a possible antinociceptive synergistic interaction of metamizol s.c., a nonsteroidal antiinflammatory drug (NSAID), and tramadol s.c., an atypical opioid (opioid receptor agonist), were administered alone or in combination. In the present study, the antinociceptive efficacy and the possible development of pharmacological tolerance produced by the combination tramadol plus metamizol during a 4-day treatment in rats using the plantar test was evaluated. Male Wistar rats were s.c. injected with tramadol (17.8 mg/kg), metamizol (177.8 mg/kg) or the combination tramadol plus metamizol three times a day for 4 days. Both metamizol and tramadol produced antinociceptive effects with a low rate trend towards tolerance development at the end of the treatment. The antinociceptive efficacy of tramadol and metamizol co-administration gradually decreased after the second injection. These data suggest that when the combination is given in a unique administration it results in an important potentiation of their individual antinociceptive effects. But, the repeated coadministration of tramadol plus metamizol results in a development of tolerance.

Sympathetic blockade significantly improves cardiovascular alterations immediately after spinal cord injury in rats.

Immediately after an experimental spinal cord injury (SCI) in rats, there is a large fall in mean arterial pressure (MAP) and heart rate (HR), followed by an abrupt increase in MAP. To better understand the mechanism involved in these early cardiovascular alterations, we tested the effect of treatment with ganglionic and sympathetic blockers in anesthetized rats subjected to T-5 SCI. Fall in MAP was partially diminished by propranolol and pentolinium, while increase in MAP was abolished by propranolol and pentolinium. Adrenalectomy did not diminish the fall in MAP and HR, however, the increase in MAP was significantly reduced. Likewise, propranolol and pentolinium completely abolished the effects in HR. These data suggest that the early cardiovascular alterations secondary to SCI results from an increased parasympathetic activity and a sympathetic withdrawal.

Effect of Serenoa Repens on Oxidative Stress, Inflammatory and Growth Factors in Obese Wistar Rats with Benign Prostatic Hyperplasia

Serenoa repens has been widely used to treat benign prostatic hyperplasia and lower urinary tract symptoms; however, most of the studies have been conducted in individuals with normal weight and not obese. In this study, the effects of a lipidic extract of S. repens, in markers of oxidative stress, inflammation, and growth factors, in obese rats with testosterone‐induced prostatic hyperplasia, were investigated. Total nitrites, malondialdehyde, total glutathione, superoxide dismutase (SOD), and catalase activity were measured; in addition, assays for inflammatory cytokines TNF‐α, IL‐1β, IL‐6 and the growth factors basic fibroblast growth factor (FGFb) and vascular endothelial growth factor (VEGF) were performed. The obese rats had a higher prostate weight compared with controls. S. repens significantly decreased prostate weight, total nitrites, and malondialdehyde; improved total glutathione, SOD, and catalase activity; and significantly reduced inflammatory (TNF‐α, IL‐1β and IL‐6) and growth factors (VEGF and FGFb). S. repens showed high antioxidant and antiinflammatory activity in obese rats, suggesting that their use could be beneficial in the treatment of benign prostatic hyperplasia. Copyright

Plasminogen Activator Inhibitor-1, Fibrinogen, and Lung Function in Adolescents with Asthma and Obesity

Background. Obesity promotes a low-grade systemic inflammatory state that may act on the lung to exacerbate asthma. There is little information on the relationship between systemic inflammation and lung function in children and adolescents. Objectives. To explore the relationship among fibrinogen, plasminogen activator inhibitor-1 (PAI-1), lung function in adolescents with the presence of asthma, and/or obesity. Methods. Totally 178 adolescents (boys and girls) were involved; four groups were divided according to their diagnosis: non-obese and non-asthmatic controls (n = 38), non-obese asthmatics (n = 31), obese non-asthmatics (n = 62), obese asthmatics (n = 47). The levels of PAI-1 and fibrinogen were determined in blood samples. The lung function was evaluated with spirometry by measuring forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and forced expiratory flows between 25 and75% (FEF25–75%). Results. Compared to healthy controls, obese adolescents with or without asthma show higher levels of fibrinogen (289.2 ± 61.5, 328.4 ± 54.9, and 324.9 ± 68.9 mg/dL, respectively), PAI-1 (36.0 ± 17.3, 53.2 ± 22.3, and 52.6 ± 24.7 ng/mL, respectively), and the reduced FEV1/FVC ratio (87.7 ± 7.7, 81.6 ± 8.6, and 81.7 ± 6.9, respectively). In the whole studied subjects, FEV1/FVC ratio shows significant inverse correlation with PAI-1 (r = −0.185), fibrinogen (r = −0.157), body mass index (BMI; r = −0.303), insulin(r = −0.198), and HOMA (r = −0.173). In the 78 asthmatic subjects, FVC correlates positively with BMI. Conclusion. Our data demonstrate that the degree of systemic inflammation and the degree of obesity in the whole studied adolescents groups correlate negatively with lung function, suggesting an obstructive pulmonary pattern. Further studies are needed to identify the pathophysiological mechanism for such association.

Effects of Honey Against the Accumulation of Adipose Tissue and the Increased Blood Pressure on Carbohydrate-Induced Obesity in Rat

This study was designed to assess the effect of honey supplementation and sugar-based hypercaloric regimen on weight gain and blood pressure (BP) in Wistar rats. Animals were fed for 8 weeks with standard diet (S-free) or a hypercaloric diet (standard chow and 30% sugar in drinking water), (SF), or standard chow supplemented with fat and honey and 10% sugar in drinking water (HF). Overall weight gain and body fat levels were significantly higher in SF and HF than in S-free. Fat cells were significantly larger in SF compared with HF. Compared with SF and S-free, HF had higher glucose, but triglycerides, and LDLc levels were not different. BP was significantly higher in SF but not in HF compared to S-free. These observations indicate that honey may afford a protection against increase in BP and in fat cell size resulting from a hypercaloric diet.