Anna Serrano-Mollar

Cardiac Arrhythmogenic Remodeling in a Rat Model of Long-Term Intensive Exercise Training

Background— Recent clinical studies suggest that endurance sports may promote cardiac arrhythmias. The aim of this study was to use an animal model to evaluate whether sustained intensive exercise training induces potentially adverse myocardial remodeling and thus creates a potential substrate for arrhythmias. Methods and Results— Male Wistar rats were conditioned to run vigorously for 4, 8, and 16 weeks; time-matched sedentary rats served as controls. Serial echocardiograms and in vivo electrophysiological studies at 16 weeks were obtained in both groups. After euthanasia, ventricular collagen deposition was quantified by histological and biochemical studies, and messenger RNA and protein expression of transforming growth factor-&bgr;1, fibronectin-1, matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-1, procollagen-I, and procollagen-III was evaluated in all 4 cardiac chambers. At 16 weeks, exercise rats developed eccentric hypertrophy and diastolic dysfunction, together with atrial dilation. In addition, collagen deposition in the right ventricle and messenger RNA and protein expression of fibrosis markers in both atria and right ventricle were significantly greater in exercise than in sedentary rats at 16 weeks. Ventricular tachycardia could be induced in 5 of 12 exercise rats (42%) and only 1 of 16 sedentary rats (6%; P=0.05). The fibrotic changes caused by 16 weeks of intensive exercise were reversed after an 8-week exercise cessation. Conclusions— In this animal model, we documented cardiac fibrosis after long-term intensive exercise training, together with changes in ventricular function and increased arrhythmia inducibility. If our findings are confirmed in humans, the results would support the notion that long-term vigorous endurance exercise training may in some cases promote adverse remodeling and produce a substrate for cardiac arrhythmias.

In vivo antioxidant treatment protects against bleomycin-induced lung damage in rats

This study examines the activity of the antioxidant N‐acetylcysteine on bleomycin‐induced pulmonary fibrosis in rats with emphasis on the early inflammatory phase. Rats receiving N‐acetylcysteine (300 mg kg−1 day−1, intraperitoneal) had less augmented lung wet weight, and lower levels of proteins, lactate dehydrogenase, neutrophil and macrophage counts in bronchoalveolar lavage fluid and lung myeloperoxidase activity with a betterment of histological score at 3 days postbleomycin. A diminished lung GSH/GSSG ratio and augmented lipid hydroperoxides were observed 3 days postbleomycin. These changes were attenuated by N‐acetylcysteine. Alveolar macrophages from bleomycin‐exposed rats released augmented amounts of superoxide anion and nitric oxide. N‐Acetylcysteine did not modify superoxide anion generation but reduced the increased production of nitric oxide. N‐Acetylcysteine suppressed the bleomycin‐induced increased activation of lung NF‐κB (shift assay and immunohistochemistry), and decreased the augmented levels of the early inflammatory cytokines, tumour necrosis factor‐α, interleukin‐β, interleukin‐6 and macrophage inflammatory protein‐2 observed in bronchoalveolar lavage fluid at 1 and 3 days postbleomycin exposure. At 15 days postbleomycin, N‐acetylcysteine decreased collagen deposition in bleomycin‐exposed rats (hydroxyproline content: 6351±669 and 4626±288 μg per lung in drug vehicle‐ and N‐acetylcysteine‐treated rats, respectively; P<0.05). Semiquantitative histological assessment at this stage showed less collagen deposition in N‐acetylcysteine‐treated rats compared to those receiving bleomycin alone. These results indicate that N‐acetylcysteine reduces the primary inflammatory events, thus preventing cellular damage and the subsequent development of pulmonary fibrosis in the bleomycin rat model.

La célula epitelial como factor etiopatogénico de la fibrosis pulmonar

Idiopathic pulmonary fibrosis (IPF) is characterized by a progressive accumulation of extracellular matrix and an imbalance between profibrotic and antifibrotic mediators. In the last few years, understanding of the mechanisms of the biology of IPF has increased. One of the most significant discoveries is the finding that alveolar epithelial cell injury plays an important role in the pathogenesis of this disease. In this review, we describe some of the mechanisms involved in alveolar cell injury and their contribution to the development of IPF.Resumen La fibrosis pulmonar idiopatica se caracteriza por una acumulacion progresiva de matriz extracelular y un desequilibrio entre mediadores profibroticos y antifibroticos. Durante los ultimos anos se ha avanzado mucho en el conocimiento de los mecanismos de la biologia de la fibrosis pulmonar idiopatica. En este sentido, uno de los hallazgos mas significativo es el descubrimiento de que la lesion de las celulas del epitelio alveolar juega un papel importante en la patogenesis de esta enfermedad. En la presente revision se describen algunos de los mecanismos por los cuales las lesiones en las celulas alveolares pueden contribuir al desarrollo de la fibrosis pulmonar idiopatica.

Recurrent obstructive apneas trigger early systemic inflammation in a rat model of sleep apnea.

Obstructive sleep apnea (OSA) is associated with vascular disorders possibly due to systemic inflammation. To determine whether repeated episodes of OSA in a rat model lead to endothelial cell activation and systemic leukocyte recruitment in the microcirculation. Three experimental groups (apnea, sham and naive) were studied. The apnea group was instrumented and subjected to repeated obstruction for 3h (rate 60/h, length 5s) using a special device. The sham group was only instrumented and the naive group was used as a control. Leukocyte-endothelial cell interactions (intravital microscopy) and expression of P-selectin (immunohistochemistry) were determined in colonic venules. The apnea group induced a significant increase in the flux of leukocytes rolling, number of rolling leukocytes and number of adherent leukocytes when compared with the sham or naive groups. P-selectin was up-regulated only in the apnea group. This experimental model of recurrent obstruction demonstrates rapid endothelial cell activation, suggesting the onset of an inflammatory response.

P-selectin upregulation in bleomycin induced lung injury in rats: effect of N-acetyl-L-cysteine

Background: A number of adhesion molecules are involved in the process of neutrophil infiltration into the lung. P-selectin is one of these neutrophil-endothelial cell adhesion molecules. A study was undertaken to examine the involvement of P-selectin in the development of bleomycin induced inflammation and the ability of N-acetyl-l-cysteine to reduce the potential expression of this selectin in rats. Methods:N-acetyl-l-cysteine (3 mmol/kg po) was administered daily for seven days prior to bleomycin administration (2.5 U/kg). The kinetics of P-selectin expression and the effect of N-acetyl-l-cysteine after bleomycin treatment were measured using radiolabelled antibodies. P-selectin localisation was evaluated by immunohistochemistry and neutrophil infiltration was assessed by myeloperoxidase activity. Results: Bleomycin administration resulted in an upregulation of P-selectin at 1 hour, returning to baseline at 3 hours. Myeloperoxidase activity showed a significant increase at 6 hours after bleomycin administration that lasted for 3 days. N-acetyl-l-cysteine treatment completely prevented these increases. Conclusion: Upregulation of P-selectin in the lung is associated with neutrophil recruitment in response to bleomycin. The beneficial effect of N-acetyl-l-cysteine on bleomycin induced lung injury may be explained in part by the prevention of neutrophil recruitment in the inflammatory stage of the disease.

Activation of lung macrophage subpopulations in experimental acute pancreatitis

Pulmonary macrophages exist in two different anatomical compartments in the lower respiratory tract: alveolar macrophages in the alveoli and interstitial macrophages in the interstitium. Depending on the micro‐environmental stimulation, macrophages follow different activation pathways. According to their inflammatory response pattern, activated macrophages have been characterized as pro‐inflammatory (M1), wound‐healing (M2a) and regulatory (M2b). Since acute pancreatitis occurs in parallel with acute lung injury, the profile of the different macrophage subpopulations could be relevant in the progression of the disease. The activation of lung alveolar and interstitial macrophages was assessed in an experimental model of severe acute pancreatitis induced in rats by intraductal infusion of 3.5% sodium taurocholate. Alveolar and interstitial macrophages were obtained and the expression of markers of different activations was evaluated. Activation of nuclear factors PPARγ and NF‐κB, which are involved in the acquisition of different phenoytpes, was also measured. Alveolar macrophages acquired an early M1 phenotype characterized by the expression of inflammatory cytokines and NF‐κB activation. In contrast, interstitial macrophages followed the inhibitory M2b pathway. In these macrophages, PPARγ became activated and the anti‐inflammatory cytokine IL‐10 was expressed. These results suggest that alveolar and interstitial macrophages play different roles in acute lung injury associated with acute pancreatitis. Alveolar macrophages promote an early inflammatory response, whereas interstitial macrophages help resolve inflammation. Copyright

Biological consequences of oxygen desaturation and respiratory effort in an acute animal model of obstructive sleep apnea (OSA)

BACKGROUND An animal model mimicking all the factors involved in obstructive sleep apnea (OSA) is useful for investigating mechanisms because the associated comorbidity usually present in such patients is an important limitation. AIM To test the hypothesis that hypoxia/normoxia and respiratory effort have different effects on the induction of inflammatory response and endothelial dysfunction in an acute rat model of OSA. METHODS Four groups of anesthetized rats were studied (n=8): (1) sham; (2) apnea: obstructions (15s each, 60/h, for 3h); (3) apnea+O(2): obstructions and breathing oxygen-enriched air to avoid hypoxia and (4) intermittent hypoxia/normoxia. Inflammatory and endothelial mediators were measured as outcomes along with NF-kappaB in the lung and diaphragm. RESULTS TNF-alpha and IL-1beta significantly increased in all groups compared with sham. NF-kappaB in the lung was increased in apnea and hypoxia/normoxia groups, but not in apnea+O(2) group. In diaphragm tissue, NF-kappaB was only significant in apnea compared to sham. Significant differences were found in the ratio thromboxane-B2/6-keto-Prostaglandin-F1alpha between apnea and hypoxia/normoxia compared to sham but not in apnea+O(2). CONCLUSIONS Oxygen desaturations and respiratory efforts play a role in the induction of systemic inflammation but only hypoxia/normoxia induces endothelial dysfunction. These data suggest a potential role for oxygen therapy in patients with OSA.

Losartan prevents heart fibrosis induced by long-term intensive exercise in an animal model

Rationale Recently it has been shown that long-term intensive exercise practice is able to induce myocardial fibrosis in an animal model. Angiotensin II is a profibrotic hormone that could be involved in the cardiac remodeling resulting from endurance exercise. Objective This study examined the antifibrotic effect of losartan, an angiotensin II type 1 receptor antagonist, in an animal model of heart fibrosis induced by long-term intense exercise. Methods and Results Male Wistar rats were randomly distributed into 4 experimental groups: Exercise, Exercise plus losartan, Sedentary and Sedentary plus losartan. Exercise groups were conditioned to run vigorously for 16 weeks. Losartan was orally administered daily before each training session (50 mg/kg/day). Time-matched sedentary rats served as controls. After euthanasia, heart hypertrophy was evaluated by histological studies; ventricular collagen deposition was quantified by histological and biochemical studies; and messenger RNA and protein expression of transforming growth factor-β1, fibronectin-1, matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-1, procollagen-I and procollagen-III was evaluated in all 4 cardiac chambers. Daily intensive exercise caused hypertrophy in the left ventricular heart wall and originated collagen deposition in the right ventricle. Additionally long-term intensive exercise induced a significant increase in messenger RNA expression and protein synthesis of the major fibrotic markers in both atria and in the right ventricle. Losartan treatment was able to reduce all increases in messenger RNA expression and protein levels caused by exercise, although it could not completely reverse the heart hypertrophy. Conclusions Losartan treatment prevents the heart fibrosis induced by endurance exercise in training animals.

Angiotensinogen gene G-6A polymorphism influences idiopathic pulmonary fibrosis disease progression

Angiotensin II is a growth factor that plays a key role in the physiopathology of idiopathic pulmonary fibrosis (IPF). A nucleotide substitution of an adenine instead of a guanine (G-6A) in the proximal promoter region of angiotensinogen (AGT), the precursor of angiotensin II, has been associated with an increased gene transcription rate. In order to investigate whether the G-6A polymorphism of the AGT gene is associated with IPF development, severity and progression, the present study utilised a case–control study design and genotyped G-6A in 219 patients with IPF and 224 control subjects. The distribution of G-6A genotypes and alleles did not significantly differ between cases and controls. The G-6A polymorphism of the AGT gene was not associated with disease severity at diagnosis. The presence of the A allele was strongly associated with increased alveolar arterial oxygen tension difference during follow-up, after controlling for the confounding factors. Higher alveolar arterial oxygen tension changes over time were observed in patients with the AA genotype (0.37±0.7 mmHg (0.049±0.093 kPa) per month) compared to GA genotype (0.12±1 mmHg (0.016±0.133 kPa) per month) and GG genotype (0.2±0.6 mmHg (0.027±0.080 kPa) per month). G-6A polymorphism of the angiotensinogen gene is associated with idiopathic pulmonary fibrosis progression but not with disease predisposition. This polymorphism could have a predictive significance in idiopathic pulmonary fibrosis patients.

Pirfenidone for the treatment of idiopathic pulmonary fibrosis

Introduction: Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and lethal fibrosing interstitial pneumonia. The median survival from the onset of the symptoms is 2.8 – 4.2 years and the 5-year survival rate is 20%. Its poor prognosis, combined with the scarcity of treatment options, provides a strong rationale for the development of novel therapeutic strategies. During the past decade there has been a huge rise in clinical trials with anti-fibrotic drugs, although only pirfenidone (Esbriet) has shown a beneficial effect. Areas covered: This article reviews the medical literature on the effectiveness and safety of pirfenidone in IPF, by means of a PubMed search from 1995 to present, completed with some data on file from the manufacturer. Expert opinion: Pirfenidone is the only anti-fibrotic drug approved for the treatment of IPF. Pirfenidone provides a meaningful clinical effect on reductions in the decrease in forced vital capacity (FVC), six-minute walk test (6MWT) distance and mortality, and it improves the progression-free survival in IPF patients with mild-to-moderate disease. Pirfenidone is well tolerated, with the most common side-effects being gastrointestinal discomfort and photosensitivity. Pirfenidone has a favorable benefit-risk profile and represents a suitable treatment option for patients with mild-to-moderate IPF.