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Nicole Morin

Publications and source records attributed to Nicole Morin.

4 recordsLinked to original sources
PubMed2006

Transforming growth factor-beta1-induced endothelial barrier dysfunction involves Smad2-dependent p38 activation and subsequent RhoA activation.

Lung edema due to increased vascular permeability is a hallmark of acute lung injury and acute respiratory distress syndrome. Both p38 and RhoA signaling events are involved in transforming growth factor (TGF)-beta1-increased endothelial permeability; however, the mechanism by which these pathways cooperate is not clear. In this study, we hypothesized that TGF-beta1-induced changes in endothelial monolayer permeability and in p38 and RhoA activation are dependent on Smad2 signaling. We assessed the role of Smad2 in p38 activation and the role of p38 in RhoA activation by TGF-beta1. We found that TGF-beta1 caused Smad2 phosphorylation between 0.5 and 1 h of exposure in endothelial cells. Knockdown of Smad2 protein prevented TGF-beta1-induced p38 activation and endothelial barrier dysfunction. Furthermore, TGF-beta1-enhanced RhoA activation was dependent on p38 activation. Inhibition of the RhoA-Rho kinase signaling pathway blunted TGF-beta1-induced adherens junction disruption and focal adhesion complex formation. In addition, depletion of heat shock protein 27, a downstream signaling molecule of p38, did not prevent TGF-beta1-induced endothelial barrier dysfunction. Finally, inhibition of de novo protein expression blunted TGF-beta1-induced RhoA activation and endothelial barrier dysfunction. Our data indicate that TGF-beta1 induces endothelial barrier dysfunction involving Smad2-dependent p38 activation, resulting in RhoA activation by possible transcriptional regulation.

Animals↗
PubMed2005

PKCdelta regulates endothelial basal barrier function through modulation of RhoA GTPase activity.

We have shown that PKCdelta enhanced microvascular endothelial basal barrier function, correlating with elevated RhoA GTPase activity and increased focal contact formation. In the current study, we investigated signaling pathways important in PKCdelta modulation of barrier function in unstimulated endothelial cell monolayers by assessing the effects of PKCdelta inhibition in endothelial cells (EC) derived from rat pulmonary artery (PAEC) and epididymus (FPEC). Rottlerin exposure or Ad PKCdeltadn infection significantly enhanced monolayer permeability in both EC. Immunofluorescence analyses demonstrated fewer stress fibers and focal contacts in rottlerin-treated or Ad PKCdeltadn-infected EC; yet, PKCdelta inhibition caused no significant changes in microtubule structures. These changes correlated with a reduction in both focal adhesion kinase (FAK) and RhoA GTPase activities. Microfilament stabilization significantly attenuated the focal contact and barrier disruptive effects of rottlerin. FAK overexpression did not blunt the effects of rottlerin-induced barrier dysfunction or stress fiber and focal contact disruption. Conversely, GFP-linked dominant active RhoA overexpression protected EC from stress fiber and focal contact disruption induced by both rottlerin exposure and overexpression of PKCdelta dominant negative protein. Additionally, PKCdelta immunoprecipitated with p190RhoGAP and p120RasGAP, modulators of RhoA activity. Thus, PKCdelta may regulate basal endothelial barrier function by stabilizing microfilaments and focal contacts by regulating RhoA GTPase activity through upstream modulators, p190RhoGAP and p120RasGAP.

Actin Cytoskeleton↗
PubMed2004

Barrier dysfunction and RhoA activation are blunted by homocysteine and adenosine in pulmonary endothelium.

RhoA GTPases modulate endothelial permeability. We have previously shown that adenosine and homocysteine enhance basal barrier function in pulmonary artery endothelial cells by a mechanism involving diminution of RhoA carboxyl methylation and activity. In the current study, we investigated the effects of adenosine and homocysteine on endothelial monolayer permeability in cultured monolayers. Adenosine and homocysteine significantly attenuated thrombin-induced endothelial barrier dysfunction and intercellular gap formation. We found significantly diminished RhoA associated with the membrane subcellular fraction in endothelial cells pretreated with adenosine and homocysteine, compared with vehicle-treated endothelial cells. Additionally, adenosine and homocysteine significantly blunted RhoA activation following thrombin exposure. Incubation with adenosine and homocysteine also enhanced in vitro interactions between RhoA and RhoGDI, as well as subcellular translocation of p190RhoGAP to the cytosol. These data demonstrate that elevated intracellular concentrations of homocysteine and adenosine enhance endothelial barrier function in cultured endothelial cells isolated from the main pulmonary artery and lung microvasculature, suggesting a potentially protective effect against pulmonary edema in response to lung injury. We speculate that homocysteine and adenosine modulate the level of endothelial barrier dysfunction through modulation of RhoA posttranslational processing resulting in diminished GTPase activity through altered interactions with modulators of RhoA activation.

Adenosine↗