Endothelial dysfunction and claudin 5 regulation during acrolein-induced lung injury.

An integral membrane protein, Claudin 5 (CLDN5), is a critical component of endothelial tight junctions that control pericellular permeability. Breaching of endothelial barriers is a key event in the development of pulmonary edema during acute lung injury (ALI). A major irritant in smoke, acrolein can induce ALI possibly by altering CLDN5 expression. This study sought to determine the cell signaling mechanism controlling endothelial CLDN5 expression during ALI. To assess susceptibility, 12 mouse strains were exposed to acrolein (10 ppm, 24 h), and survival monitored. Histology, lavage protein, and CLDN5 transcripts were measured in the lung of the most sensitive and resistant strains. CLDN5 transcripts and phosphorylation status of forkhead box O1 (FOXO1) and catenin (cadherin-associated protein) beta 1 (CTNNB1) proteins were determined in control and acrolein-treated human endothelial cells. Mean survival time (MST) varied more than 2-fold among strains with the susceptible (BALB/cByJ) and resistant (129X1/SvJ) strains (MST, 17.3 ± 1.9 h vs. 41.4 ± 5.1 h, respectively). Histological analysis revealed earlier perivascular enlargement in the BALB/cByJ than in 129X1/SvJ mouse lung. Lung CLDN5 transcript and protein increased more in the resistant strain than in the susceptible strain. In human endothelial cells, 30 nM acrolein increased CLDN5 transcripts and increased p-FOXO1 protein levels. The phosphatidylinositol 3-kinase inhibitor LY294002 diminished the acrolein-induced increased CLDN5 transcript. Acrolein (300 nM) decreased CLDN5 transcripts, which were accompanied by increased FOXO1 and CTNNB1. The phosphorylation status of these transcription factors was consistent with the observed CLDN5 alteration. Preservation of endothelial CLDN5 may be a novel clinical approach for ALI therapy.

Peroxisome proliferator-activated receptor delta agonists attenuated the C-reactive protein-induced pro-inflammation in cardiomyocytes and H9c2 cardiomyoblasts.

C-reactive protein (CRP) has emerged as a new marker for cardiovascular diseases. Activation of peroxisome proliferator-activated receptor delta (PPARdelta) plays beneficial roles in cardiac disorders. However, the relationship between CRP and PPARdelta in cardiac cells remains unclear. This study focused on the underlying molecular mechanisms of CRP and PPARdeltaagonists. Cardiomyocytes and cardiomyoblast cell line (H9c2) were used in different groups: Untreated; 15 microg/ml CRP with or without 1 microM PPARdelta agonists (L-165041). CRP increased PPARdelta and interleukin-6 expression in cardiomyocytes and H9c2 cardiomyoblasts. NF-kappaB inducing kinase (NIK) and NF-kappaB pathway also activated by CRP stimulation. These changes could be inhibited by L-165041 through p38MAPK and c-JNK pathways. However, transfection with siRNA of CD32 CRP receptor did not decrease CRP signaling or reverse the effects of L-165041 in CRP-treated cardiomyocytes and H9c2. Pretreatment with L-165041 attenuated apoptosis induced by hypoxia with or without CRP in H9c2 cardiomyoblasts. CRP up-regulated PPARdelta expression in cardiomyocytes and H9c2. L-165041 attenuated CRP-induced pro-inflammatory signaling through p38MAPK and c-JNK in H9c2 cardiomyoblasts. However, PPARdelta activation attenuated CRP-induced NF-kappaB pathway may be independent of CD32. These results may provide new evidence of PPARdelta beneficial effects for inflammatory cardiomyopathy.