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M-J Hébert

Publications and source records attributed to M-J Hébert.

5 recordsLinked to original sources
PubMed2006

Reactive oxygen species and nuclear factor-kappa B pathway mediate high glucose-induced Pax-2 gene expression in mouse embryonic mesenchymal epithelial cells and kidney explants.

Diabetic mellitus confers a major risk of congenital malformations, and is associated with diabetic embryopathy, affecting multiple organs including the kidney. The DNA paired box-2 (Pax-2) gene is essential in nephrogenesis. We investigated whether high glucose alters Pax-2 gene expression and aimed to delineate its underlying mechanism(s) of action using both in vitro (mouse embryonic mesenchymal epithelial cells (MK4) and ex vivo (kidney explant from Hoxb7-green florescent protein (GFP) mice) approaches. Pax-2 gene expression was determined by reverse transcriptase-polymerase chain reaction, Western blotting, and immunofluorescent staining. A fusion gene containing the full-length 5'-flanking region of the human Pax-2 promoter linked to a luciferase reporter gene, pGL-2/hPax-2, was transfected into MK4 cells with or without dominant negative IkappaBalpha (DN IkappaBalpha) cotransfection. Fusion gene expression level was quantified by cellular luciferase activity. Reactive oxygen species (ROS) generation was measured by lucigenin assay. Embryonic kidneys from Hoxb7-GFP mice were cultured ex vivo. High D(+) glucose (25 mM), compared to normal glucose (5 mM), specifically induced Pax-2 gene expression in MK4 cells and kidney explants. High glucose-induced Pax-2 gene expression is mediated, at least in part, via ROS generation and activation of the nuclear factor kappa B signaling pathway, but not via protein kinase C, p38 mitogen-activated protein kinase (MAPK), and p44/42 MAPK signaling.

Animals↗
PubMed2006

Transforming growth factor-beta 1 stimulates angiotensinogen gene expression in kidney proximal tubular cells.

The present study investigated whether transforming growth factor-beta 1 (TGF-beta1) exerts an autocrine positive effect on angiotensinogen (ANG) gene expression in rat kidney proximal tubular cells, and delineates its underlying mechanism(s) of action. Rat immortalized renal proximal tubular cells (IRPTCs) and freshly isolated mouse renal proximal tubules were incubated in the absence or presence of active human TGF-beta1. IRPTCs were also stably transfected with rat TGF-beta1 or p53 tumor suppressor protein (p53) cDNA in sense (S) and antisense (AS) orientations. ANG mRNA and p53 protein expression were assessed by reverse transcription-polymerase chain reaction and Western blotting, respectively. Reactive oxygen species (ROS) generation was quantified by lucigenin assay. Active TGF-beta1 evoked ROS generation and stimulated ANG mRNA and p53 protein expression, whereas a superoxide scavenger and inhibitors of nicotinamide adenine dinucleotide oxidase and p38 mitogen-activated protein kinase (p38 MAPK) abolished the TGF-beta1 effect. Stable transfer of p53 cDNA (S) enhanced and p53 cDNA (AS) abolished the stimulatory effect of TGF-beta1 on ANG mRNA expression in IRPTCs. Our results demonstrate that TGF-beta1 stimulates ANG gene expression and its action is mediated, at least in part, via ROS generation, p38 MAPK activation, and p53 expression, suggesting that angiotensin II and TGF-beta1 may form a positive feedback loop to enhance their respective gene expression, leading to renal injury.

Angiotensinogen↗
PubMed2006

Endothelial apoptosis and chronic transplant vasculopathy: recent results, novel mechanisms.

Chronic transplant vasculopathy (CTV) is a progressive form of vascular obliteration affecting the arteries, arterioles and capillaries of solid organ transplants. It is characterized by intimal accumulation of mononuclear cells, vascular smooth muscle cells (VSMC), myofibroblasts and connective tissue. Mounting evidence, based on animal models and human biopsy results, suggests that acute and persistent rejection triggering apoptosis of endothelial cells (EC) plays a pivotal role in CTV. The precise mechanisms that underlie the induction of fibroproliferative changes in association with endothelial apoptosis have yet to be clearly delineated. Recent observations in the field of apoptosis research provide some important mechanistic clues. First, endothelial apoptosis creates a state of hyperadhesiveness for mononuclear cells, thus facilitating sustained leukocyte infiltration. Second, phosphatidylserine-dependent engulfment of apoptotic cells by infiltrating mononuclear leukocytes promotes transforming growth factor-beta1 production. Third, apoptosis of EC triggers extracellular matrix (ECM) proteolysis thus initiating the production of fibroproliferative/fibrogenic ECM fragments. The relative importance of these mechanisms in the pathophysiology of CTV will need to be addressed in vivo. Yet, these recent developments provide a new mechanistic framework that will help better define the importance of immune-mediated EC apoptosis in the regulation of vascular repair.

Apoptosis↗