Ivabradine restores tonic cardiovascular autonomic control and reduces tachycardia, hypertension and left ventricular inflammation in post-weaning protein malnourished rats.

Malnutrition results in autonomic imbalance and heart hypertrophy. Overexpression of hyperpolarization-activated cyclic nucleotide-gated channels (HCN) in the left ventricles (LV) is linked to hypertrophied hearts and abnormal myocardium automaticity. Given that ivabradine (IVA) has emerging pleiotropic effects, in addition to the widely known bradycardic response, this study evaluated if IVA treatment could repair the autonomic control and cardiac damages in malnourished rats. AIM: Assess the impact of IVA on tonic cardiovascular autonomic control and its relationship with hemodynamics regulation, LV inflammation, and HCN gene expression in post-weaning protein malnutrition condition. MAIN METHODS: After weaning, male rats were divided into control (CG; 22 % protein) and malnourished (MG; 6 % protein) groups. At 35 days, groups were subdivided into CG-PBS, CG-IVA, MG-PBS and MG-IVA (PBS 1 ml/kg or IVA 1 mg/kg) received during 8 days. We performed jugular vein cannulation and electrode implant for drug delivery and ECG registration to assess tonic cardiovascular autonomic control; femoral cannulation for blood pressure (BP) and heart rate (HR) assessment; and LV collection to evaluate ventricular remodeling and HCN gene expression investigation. KEY FINDINGS: Malnutrition induced BP and HR increases, sympathetic system dominance, and LV remodeling without affecting HCN gene expression. IVA reversed the cardiovascular autonomic imbalance; prevented hypertension and tachycardia; and inhibited the LV inflammatory process and fiber thickening caused by malnutrition. SIGNIFICANCE: Our findings suggest that ivabradine protects against malnutrition-mediated cardiovascular damage. Moreover, our results propose these effects were not attributed to HCN expression changes, but rather to IVA pleiotropic effects on autonomic control and inflammation.

Preventive effects of hesperidin in an experimental model ofs acute lung inflammation.

In this study, we hypothesized that long-term administration of hesperidin can modulate the inflammatory response and oxidative stress in animals submitted to mechanical ventilation (MV). Twenty-five C57BL/6 male mice were divided into 5 groups: control, MV, animals receiving hesperidin in three doses 10, 25 and 50 mg/kg. The animals received the doses of hesperidin for 30 days via orogastric gavage, and at the end of the period the animals were submitted to MV. In animals submitted to MV, increased lymphocyte, neutrophil and monocyte/macrophage cell counts were observed in the blood and airways. Associated to this, MV promoted an increase in inflammatory cytokine levels such as CCL2, IL-12 and TNFα. The daily administration of hesperidin in the three doses prevented the effects caused by MV, which was observed by a lower influx of inflammatory cells into the airways, a reduction in inflammatory markers and less oxidative damage.

Chronic Oral Administration of Aluminum Hydroxide Stimulates Systemic Inflammation and Redox Imbalance in BALB/c Mice.

The present study is aimed at investigating the long-term effects of the aluminum hydroxide administration in the small intestine, lung, liver, and kidney of male BALB/c mice. The mice received via orogastric gavage phosphate buffered or 10 mg/kg aluminum hydroxide 3 times a week for 6 months. Administration of aluminum hydroxide decreased hemoglobin, hematocrit, and erythrocyte. In the blood, kidney and liver function markers were evaluated, and long-term administration of aluminum hydroxide led to an increase in AST levels and a decrease in urea levels. The animals exposed to aluminum showed higher lipid and protein oxidation in all the organs analyzed. In relation to the enzymes involved in antioxidant defense, the lungs showed lower superoxide dismutase (SOD) and catalase activity and a lower reduced and oxidized glutathione (GSH/GSSG) ratio. In the liver, aluminum administration led to a decrease in catalase activity and the GSH/GSSG ratio. Lower catalase activity was observed in the small intestine, as well as in the lungs and liver. In addition to alterations in antioxidant defense, increased levels of the chemokine CCL-2 were observed in the lungs, lower levels of IL-10 in the liver and small intestine, and decreased levels of IL-6 in the intestine of the animals that received aluminum hydroxide for 6 months. Long-term exposure to aluminum promoted steatosis in the liver. In the kidneys, mice treated with aluminum presented a decreased glomerular density than in the naive control group. In the small intestine, exposure caused villi shortening. Our results indicate that long-term oral administration of aluminum hydroxide provokes systemic histological damage, inflammation, and redox imbalance.

Exogenous surfactant reduces inflammation and redox imbalance in rats under prone or supine mechanical ventilation.

Mechanical ventilation (MV) is a lifesaving therapy for patients with acute or chronic respiratory failure. Despite, it can also cause lung injury by inducing or worsening inflammatory responses and oxidative stress. Several clinical approaches have protective effects on the lungs, including the prone position and exogenous surfactant; however, few studies have evaluated the association between the two strategies, especially in individuals without previous lung injury. We tested the hypothesis that the effects of the homogenization in lung aeration caused by the prone position in association with the anti-inflammatory properties of exogenous surfactant pre-treatment could have a cumulative protective effect against ventilator-induced lung injury. Therefore, Wistar rats were divided into four experimental groups: Mechanical Ventilation in Supine Position (MVSP), Mechanical Ventilation in Prone position (MVPP), Mechanical Ventilation in Supine Position + surfactant (MVSPS), and Mechanical Ventilation in Prone Position + Surfactant (MVPPS). The intranasal instillation of a porcine surfactant (Curosurf®) was performed in the animals of MVSPS and MVPPS 1 h before the MV, all the rats were subjected to MV for 1 h. The prone position in association with surfactant decreased mRNA expression levels of pro-inflammatory cytokines in ventilated animals compared to the supine position; in addition, the NfκB was lower in MVPP, MVSPS and MVPPS when compared to MVSP. However, it had no effects on oxidative stress caused by MV. Pre-treatment with exogenous surfactant was more efficient in promoting lung protection than the prone position, as it also reduced oxidative damage in the lung parenchyma. Nevertheless, the surfactant did not cause additional improvements in most parameters that were also improved by the prone position. Our results indicate that the pre-treatment with exogenous surfactant, regardless of the position adopted in mechanical ventilation, preserves the original lung histoarchitecture, reduces redox imbalance, and reduces acute inflammatory responses caused by mechanical ventilation in healthy adult Wistar rats.

Thermoregulatory responses, heart rate, and the susceptibility to anxiety in obese animals subjected to stress.

Obesity and stress are related to cardiovascular diseases. Rats fed a high-fat diet (HFD) show increased cardiovascular reactivity to emotional stress and altered defensive behavioral responses. Indeed, changes in thermoregulatory responses in an aversive environment are observed in these animals. However, studies aimed at clarifying the physiological mechanisms linking obesity, stress hyperreactivity and behavioral changes are needed. The aim of this study was to evaluate the changes in thermoregulatory responses, heart rate, and the susceptibility to anxiety in obese animals subjected to stress. Nine-week high-fat diet protocol was effective in inducing obesity by increasing weight gain, fat mass, adiposity index, white epididymal, retroperitoneal, inguinal and brown adipose tissue. Animals induced to obesity and subjected to stress (HFDS group) by the intruder animal method showed increases in heart rate (HR), core body temperature and tail temperature. HFDS showed an increase in the first exposure to the closed arm (anxiety-like behavior) in elevated T-Maze (ETM). The groups did not differ with respect to panic behavior assessed in the ETM and locomotor activity in the open field test. Our study shows that HFDS animals presented increased reactivity to stress with higher stress hyperthermia and anxious behavior. Thus, our results present relevant information regarding stress responsiveness and behavioral changes in obese animals.

Protein restriction during pregnancy affects lung development and promotes oxidative stress and inflammation in C57 BL/6 mice offspring.

OBJECTIVES: The present study aimed to evaluate the effects of maternal protein restriction during pregnancy on the lungs of 1-d and 31-d old offspring of C57BL/6 mice. METHODS: The C57BL/6 mice (8-10 wk) were used for breeding. After pregnancy confirmation, female mice were randomly divided into a control group (CG) receiving a standard diet (22% protein) and a protein-restriction group (PRG) receiving a low-protein diet (6% protein). In the low-protein diet, protein was replaced by carbohydrate. After parturition, female mice that received the low-protein diet were fed the standard diet. Male offspring were euthanized 1 d and 31 d after birth for subsequent analysis. We evaluated the effects of a protein-restricted diet during gestation in pulmonary organogenesis, lung oxidative stress, and pulmonary inflammatory response of the offspring. RESULTS: PRG mice 1 d after birth showed lower body and lung mass, length, relative mass, lung density, and erythrocyte count compared with CG mice. There was an increase in alveolar airspace density and a higher mean linear intercept (Lm), greater oxidative damage, and inflammation in PRG mice compared with CG mice. At 31 d after birth, PRG mice had lower body mass, length, and lung mass values compared with CG mice. PRG mice showed greater recruitment of inflammatory cells to the airways. In addition, there was increased collagen deposition in the lungs, altered inflammatory mediators, and greater oxidative damage compared with CG mice. CONCLUSIONS: Protein restriction during pregnancy reduces the body weight of offspring and promotes inflammation and oxidative stress, resulting in a simplification of the lung structure.

Quercetin Improves Pulmonary Function and Prevents Emphysema Caused by Exposure to Cigarette Smoke in Male Mice.

Chronic obstructive pulmonary disease (COPD) is the major cause of morbidity and mortality worldwide, and cigarette smoke is a key factor in the development of COPD. Thus, the development of effective therapies to prevent the advancement of COPD has become increasingly essential. We hypothesized that quercetin protects lungs in mice exposed to long-term cigarette smoke. Thirty-five C57BL/6 mice were exposed to cigarette smoke (12 cigarettes per day) for 60 days and pretreated with 10 mg/kg/day of quercetin via orogastric gavage. After the experimental protocol, the animals were euthanized and samples were collected for histopathological, antioxidant defense, oxidative stress and inflammatory analysis. The animals exposed to cigarette smoke showed an increase in respiratory rate and hematological parameters, cell influx into the airways, oxidative damage and inflammatory mediators, besides presenting with alterations in the pulmonary histoarchitecture. The animals receiving 10 mg/kg/day of quercetin that were exposed to cigarette smoke presented a reduction in cellular influx, less oxidative damage, reduction in cytokine levels, improvement in the histological pattern and improvement in pulmonary emphysema compared to the group that was only exposed to cigarette smoke. These results suggest that quercetin may be an agent in preventing pulmonary emphysema induced by cigarette smoke.

Effects in vitro and in vivo of hesperidin administration in an experimental model of acute lung inflammation.

Mechanical ventilation (MV) is a tool used in critical patient care. However, it can trigger inflammatory and oxidative processes capable of causing or aggravating lung injuries, which is known as ventilator-induced lung injury (VILI). Hesperidin is a flavonoid with antioxidant and anti-inflammatory properties in various diseases. The role of hesperidin in the process triggered by MV is poorly studied. Thus, we hypothesize hesperidin could protect the lung of mice submitted to mechanical ventilation. For that, we evaluated cell viability and reactive oxygen species (ROS) formation in macrophages using different hesperidin concentrations. We observed hesperidin did not reduce cell viability, however; it attenuated the production of intracellular ROS in cells stimulated with lipopolysaccharide (LPS). We further evaluated the effects of hesperidin in vivo in animals submitted to MV. In the bronchoalveolar lavage fluid, there were higher levels of macrophage, lymphocyte and neutrophil counts in animals submitted to MV, indicating an inflammatory process. In the lung tissue, MV induced oxidative damage and increased myeloperoxidase activity, though the antioxidant enzyme activity decreased. MV also induced the production of the inflammatory mediators CCL-2, TNF-α and IL-12. Pretreatment with hesperidin resulted in less recruitment of inflammatory cells to the airways and less oxidative damage. Also, it reduced the formation of CCL-2 and IL-12. Our results show pretreatment with hesperidin can protect the lungs of mice submitted to mechanical ventilation by modulating the inflammatory response and redox imbalance and may act to prevent MV injury.

Lasting effects of ketamine and isoflurane administration on anxiety- and panic-like behavioral responses in Wistar rats.

In clinical and laboratory practice, the use of anesthetics is essential in order to perform surgeries. Anesthetics, besides causing sedation and muscle relaxation, promote several physiological outcomes, such as psychotomimetic alterations, increased heart rate, and blood pressure. However, studies depicting the behavioral effect induced by ketamine and isoflurane are conflicting. In the present study, we assessed the behavioral effects precipitated by ketamine and isoflurane administration. We have also evaluated the ketamine effect on cell cytotoxicity and viability in an amygdalar neuronal primary cell culture. Ketamine (80 mg/kg) caused an anxiogenic effect in rats exposed to the elevated T-maze test (ETM) 2 and 7 days after ketamine administration. Ketamine (40 and 80 mg/kg) administration also decreased panic-like behavior in the ETM. In the light/dark test, ketamine had an anxiogenic effect. Isoflurane did not change animal behavior on the ETM. Neither ketamine nor isoflurane changed the spontaneous locomotor activity in the open field test. However, isoflurane-treated animals explored less frequently the OF central area seven days after treatment. Neither anesthetic caused oxidative damage in the liver. Ketamine also reduced cellular metabolism and led to neuronal death in amygdalar primary cell cultures. Thus, our work provides evidence that ketamine and isoflurane induce pronounced long lasting anxiety-related behaviors in male rats.

Role of the Renin Angiotensin System in Blood Pressure Allostasis-induced by Severe Food Restriction in Female Fischer rats.

Severe food restriction (FR) is associated with blood pressure (BP) and cardiovascular dysfunction. The renin-angiotensin system (RAS) regulates BP and its dysregulation contributes to impaired cardiovascular function. Female Fischer rats were maintained on a control (CT) or severe FR (40% of CT) diet for 14 days. In response to severe FR, BP allostasis was achieved by up-regulating circulating Ang-[1-8] by 1.3-fold through increased angiotensin converting enzyme (ACE) activity and by increasing the expression of AT1Rs 1.7-fold in mesenteric vessels. Activation of the RAS countered the depressor effect of the severe plasma volume reduction (≥30%). The RAS, however, still underperformed as evidenced by reduced pressor responses to Ang-[1-8] even though AT1Rs were still responsive to the depressor effects of an AT1R antagonist. The aldosterone (ALDO) response was also inadequate as no changes in plasma ALDO were observed after the large fall in plasma volume. These findings have implications for individuals who have experienced a period(s) of severe FR (e.g., anorexia nervosa, dieters, natural disasters) and suggests increased activity of the RAS in order to achieve allostasis contributes to the cardiovascular dysfunction associated with inadequate food intake.

High-Fat Diet Increases HMGB1 Expression and Promotes Lung Inflammation in Mice Subjected to Mechanical Ventilation.

This study aims to evaluate the effects of a high-fat diet and mechanical ventilation on the pulmonary and systemic inflammatory response in C57BL/6 mice. Male C57BL/6 mice were divided into two groups: one received a standard diet, and the other received a high-fat diet. After 10 weeks, the groups were further divided into two groups each: control group (CG), mechanical ventilation group (MVG), diet group (DG), and diet mechanical ventilation group (DMVG). MVG and DMVG underwent mechanical ventilation for 60 minutes. All animals were euthanized for subsequent analysis. Animals receiving a high-fat diet presented higher body mass, adipose index, and greater adipocyte area. In the lung, the expression of HMGB1 was greater in DG and DMVG than in CG and MVG. CCL2 and IL-22 levels in MVG and DMVG were increased compared to those in CG and DG, whereas IL-10 and IL-17 were decreased. Superoxide dismutase activity was higher in MVG and DMVG than in CG. Catalase activity was lower in DG than in CG, and in MV groups, it was lower than that in CG and DG. MV and obesity promote inflammation and pulmonary oxidative stress in adult C57BL/6 mice.

Bezold-Jarisch reflex in sino-aortic denervated malnourished rats.

In this study we assessed the role of Bezold-Jarisch reflex (BJR) in the regulation of blood pressure (BP) of malnourished (MN) and control rats (CN) with sino-aortic denervation (SAD). Fischer rats were fed diets containing either 6% (MN) or 15% (CN) protein for 35 days after weaning. These rats underwent sham or SAD and catheterization of femoral artery and vein for BP measurements and drug injection. Phenylbiguanide (PBG 5 µg/kg, i.v.) for activation BJR, produced bradycardia (-317±22 bpm for CN vs. -372±16 bpm for MN) and hypotension (-57±4 mm Hg for CN vs. -54±6 mm Hg for MN. After SAD, MN rats had reduced hypotensive (-37±7 mm Hg for MN vs. -82±6 mm Hg for CN) and bradycardic (-124±17 for MN vs. -414±20 bpm CN) responses to BJR activation. To evaluate the contribution of the parasympathetic component due to BJR for the fall in BP, methyl atropine bromide, was given between two injections of PBG (5 µg/kg) separated by 10 min each other. Both bradycardic (-216±21 bpm before and -4±3 bpm after for CN -226±43 bpm before and -9±20 bpm after for MN) and hypotensive (-42±4 mm Hg before and -6±1 mm Hg after for CN -33±9 mm Hg before and -5±2 mm Hg after for MN) responses were abolished in CN and MN groups. These data indicate that dietary protein malnutrition changes the relation between baroreflex and BJR required for maintenance of the BP during malnourishment.

Sympathetic cutaneous vasomotor alerting responses (SCVARs) are associated with hippocampal theta rhythm in non-moving conscious rats.

Alerting stimuli that cause sympathetic cutaneous vasomotor alerting responses ("SCVARs") in the thermoregulatory vascular bed of the rabbit ear pinna also induce theta (5-8 Hz) rhythm in the hippocampal EEG, a marker that the animal is engaged with the environment. The present study determines the relation between SCVARs in the thermoregulatory tail artery vascular bed and hippocampal EEG theta rhythm in Sprague-Dawley rats. A Doppler ultrasonic flow probe chronically implanted around the base of the tail artery was used to measure SCVARs. Unipolar electrodes were implanted in the hippocampus (CA1 region) to measure EEG. Six standard non-noxious brief alerting stimuli were administered during continuous recording of tail blood flow and EEG. The SCVAR index was calculated as the percentage fall from pre-alerting blood flow values. After stimuli the SCVAR index for the tail artery blood flow was 84+/-2% of the pre-alerting control. In contrast, the same stimuli caused little fall in blood flow within the superior mesenteric bed (SCVAR index=18+/-2%). The proportion of theta power in the total frequency range (0-20 Hz) increased significantly after alerting stimuli (46+/-2% vs. 29+/-1% before stimuli, p<0.05). Theta proportion began to increase approximately 0.5 s after the stimuli and preceded SCVARs by approximately 1 s. The SCVAR index was correlated with the magnitude of the increment in theta power. Our study demonstrates that alerting responses resulting in selective vasoconstriction of the tail vascular bed are associated with hippocampal theta rhythm in conscious rats.

Role of periaqueductal gray on the cardiovascular response evoked by disinhibition of the dorsomedial hypothalamus.

Activation of neurons in the region of the dorsomedial hypothalamus (DMH), by microinjection of the GABA(A) receptor antagonist bicuculline methiodide (BMI) results in increases in arterial pressure, heart rate as well as behavioral changes similar to those evoked by acute emotional stress. Previous anatomic studies clearly demonstrated projections from the DMH to the midbrain periaqueductal gray (PAG), a brain region implicated in the organization of behavioral strategies associated with specific cardiovascular responses. In this study, physiological experiments in conscious rats were used to investigate the functional significance of this pathway. Unilateral inhibition of the lateral dorsolateral region of the PAG (l/dlPAG) with the GABA(A) receptor agonist, muscimol (1 nmol/100 nl) largely reduced the tachycardia and the pressor response produced by microinjection of BMI (10 pmol/100 nl) into the ipsilateral DMH. In contrast, inhibition of the ventrolateral PAG (vlPAG) region had no significant effect on the cardiovascular response evoked from disinhibition of the ipsilateral DMH. Our present results indicate that the l/dlPAG region is an important synaptic relay in the descending cardiovascular pathways from the DMH.