Alanyl-glutamine protects the intestinal barrier function in trained rats against the impact of acute exhaustive exercise

Strenuous exercise triggers deleterious effects on the intestinal epithelium, but their mechanisms are still uncertain. Here, we investigated whether a prolonged training and an additional exhaustive training protocol alter intestinal permeability and the putative effect of alanyl-glutamine (AG) pretreatment in this condition. Rats were allocated into 5 different groups: 1) sedentary; 2 and 3) trained (50 min per day, 5 days per week for 12 weeks) with or without 6 weeks oral (1.5 g/kg) AG supplementation; 4 and 5) trained and subjected to an additional exhaustive test protocol with or without oral AG supplementation. Venous blood samples were collected to determine gasometrical indices at the end of the 12-week protocol or after exhaustive test. Lactate and glucose levels were determined before, during, and after the exhaustive test. Ileum tissue collected after all experimental procedures was used for gene expression analysis of Zonula occludens 1 (ZO-1), occludin, claudin-2, and oligopeptide transporter 1 (PepT-1). Intestinal permeability was assessed by urinary lactulose/mannitol test collected after the 12-week protocol or the exhaustive test. The exhaustive test decreased pH and base excess and increased pCO2. Training sessions delayed exhaustion time and reduced the changes in blood glucose and lactate levels. Trained rats exhibited upregulation of PEPT-1, ZO-1, and occludin mRNA, which were partially protected by AG. Exhaustive exercise induced intestinal paracellular leakage associated with the upregulation of claudin-2, a phenomenon protected by AG treatment. Thus, AG partially prevented intestinal training adaptations but also blocked paracellular leakage during exhaustive exercise involving claudin-2 and occludin gene expression.

Sildenafil decreases rat tracheal hyperresponsiveness to carbachol and changes canonical transient receptor potential gene expression after antigen challenge

Inhibition of type-5 phosphodiesterase by sildenafil decreases capacitative Ca2+ entry mediated by transient receptor potential proteins (TRPs) in the pulmonary artery. These families of channels, especially the canonical TRP (TRPC) subfamily, may be involved in the development of bronchial hyperresponsiveness, a hallmark of asthma. In the present study, we evaluated i) the effects of sildenafil on tracheal rings of rats subjected to antigen challenge, ii) whether the extent of TRPC gene expression may be modified by antigen challenge, and iii) whether inhibition of type-5 phosphodiesterase (PDE5) may alter TRPC gene expression after antigen challenge. Sildenafil (0.1 µM to 0.6 mM) fully relaxed carbachol-induced contractions in isolated tracheal rings prepared from naive male Wistar rats (250-300 g) by activating the NO-cGMP-K+ channel pathway. Rats sensitized to antigen by intraperitoneal injections of ovalbumin were subjected to antigen challenge by ovalbumin inhalation, and their tracheal rings were used to study the effects of sildenafil, which more effectively inhibited contractions induced by either carbachol (10 µM) or extracellular Ca2+ restoration after thapsigargin (1 µM) treatment. Antigen challenge increased the expression of the TRPC1 and TRPC4 genes but not the expression of the TRPC5 and TRPC6 genes. Applied before the antigen challenge, sildenafil increased the gene expression, which was evaluated by RT-PCR, of TRPC1 and TRPC6, decreased TRPC5 expression, and was inert against TRPC4. Thus, we conclude that PDE5 inhibition is involved in the development of an airway hyperresponsive phenotype in rats after antigen challenge by altering TRPC gene expression.