Angiotensin II activates plasminogen activator inhibitor-I promoter in renal tubular epithelial cells via the AT1receptor

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) regulates normal extracellular matrix (ECM) metabolism and it is a key regulator of the fibrotic process. Both angiotensin II (Ang II) and angiotensin IV (Ang IV) have been reported to stimulate PAI-1 expression. It is not known how PAI-1 expression is regulated by the renin-angiotensin system (RAS) in renal tubular cells.

METHODS

To dissect signaling mechanisms contributing to the up-regulation of the PAI-1 promoter, porcine proximal tubular cells stably expressing the rabbit AT1 receptor (LLC-PK/AT1) were transiently transfected with a luciferase reporter construct containing the PAI-1 promoter. Promoter activation was assessed by measuring luciferase activity from cell lysates.

RESULTS

Ang II dose-dependently stimulated the transcriptional activity of the PAI-1 promoter in renal proximal tubular cells whereas Ang IV had no consistent effect on the promoter activity. Neither inhibition of the Extracellular Signal Regulated Kinase (ERK) cascade nor inhibition of the c-Jun-N-terminal Kinase (JNK) pathway did reduce the stimulation of the PAI-1 promoter by Ang II. However, genistein, a tyrosine kinase inhibitor blocked the effect of Ang II.

CONCLUSION

Ang II but not Ang IV activates the PAI-1 promoter in renal proximal tubular cells and this effect is mediated by tyrosine kinases.

Comparative study of beta-tricalcium phosphate mixed with platelet-rich plasma versus beta-tricalcium phosphate, a bone substitute material in dentistry

Animal experiments were carried out with osteoconductive bone substitute beta-tricalcium phosphate (beta-TCP), with the aim of assessing the effects of the growth factors synthesised by thrombocytes on the speed of beta-TCP incorporation and on the quality of newly formed bone. The question to be answered was the extent to which platelet-rich plasma (PRP) accelerated the resorption of beta-TCP and the formation of new bone. Two teeth were removed symmetrically from each side of the mandible of 12 Beagle dogs; the resulting cavities were filled on one side with beta-TCP alone, and on the other side with a mixture of beta-TCP + PRP (obtained from autologous blood). The quality of the newly formed bone and the effects of this PRP were studied by histological and histomorphometric methods. In week 6, bone formation was already more effective when PRP was applied in comparison with beta-TCP alone, and in week 12 the growth was significantly greater. The results demonstrate that the use of PRP accelerates the remodelling of new bone created by beta-TCP.

The endosomal epsilon-coatomer protein is involved in human adenovirus type 5 internalisation

The effects of bafilomycin A1 and of the reduced level of endosomal epsilon-COP (coatomer protein) on the infectivity of human adenovirus type 5 were investigated in Coxsackie adenovirus receptor- (CAR-) transfected Chinese hamster ovary (CHO) cells. The endosomal proton pump inhibitor bafilomycin A1 was able to cause only partial inhibition. Using Id1F cells (an epsilon-COP thermosensitive mutant CHO cell line) the reduction of epsilon-COP level also had partial inhibitory effect. Based on these results and comparing them to existing models of the adenovirus entry, we propose a refined model in which there are two pathways of adenoviral entry: the first one involves the epsilon-COP as the downstream effector of the acidification and can be blocked by bafilomycin A1 and the second one is a pH-independent pathway.

The use of a second reporter plasmid as an internal standard to normalize luciferase activity in transient transfection experiments may lead to a systematic error

beta-galactosidase reporter plasmids containing different viral or minimal promoters are commonly used to correct variable transfection efficiencies in transient transfection experiments. The transcriptional activity of these promoters is thought to be stable under most circumstances. To determine if expression of beta-galactosidase from the commonly used beta-galactosidase plasmids remains stable upon stimulation of the cells with agonists we performed transient transfection experiments. CHO cells stably expressing the rat AT(1A) receptor were transfected with RSVbeta- or CMVbeta- or pTKbeta plasmids alone or together with a reporter construct in which luciferase transcription is driven by the c-fos promoter. Luciferase and/or beta-galactosidase activity was measured from the lysate of cells treated with angiotensin II or serum. We found that agonists increased the transcriptional activity of the different beta-galactosidase plasmids. The effect of angiotensin II and serum was different on the different promoters. Finally, cotransfection of other plasmids also modulated beta-galactosidase activity. These agonist induced variations of beta-galactosidase activity may influence the analysis and interpretation of the results in a systematic manner. Consequently we conclude that the use of a second reporter system to control for transfection efficiency in certain types of experiments may lead to a systematic error and is questionable as a general procedure.

Extracellular signal-regulated kinase and the small GTP-binding protein p21Rac1 are involved in the regulation of gene transcription by angiotensin II

To study the role of extracellular-signal-regulated kinase (ERK) cascade and the small GTP-ase proteins in the activation of the c-fos promoter by angiotensin II (AII), transient transfection experiments were performed in CHO cells stably expressing the rat AT(1A) receptor. In this system AII activated ERK in 1 min and also increased the transcriptional activity of the c-fos promoter-luciferase reporter gene construct. The activation of the promoter proved to be dependent on the Ras-Raf-ERK cascade as cotransfection of expression vectors known to specifically inhibit this cascade blocked the effect of AII. Dominant-negative p21Rac1 mutant partially blocked the activation of the c-fos promoter by AII. However, activation of the c-fos promoter was independent of protein kinase C (PKC) as bisindolylmaleimide I, a specific PKC inhibitor did not block the effect of AII. These results suggest that AII activates the transcription of the c-fos through the Ras-Raf-ERK cascade. Furthermore, p21Rac1 is involved in the modulation of the c-fos promoter by AII.

[Normal percentiles of kidney size in children as measured by ultrasonography]

The most anomaly of kidney development and urinary tract diseases have an effect on the size of the kidneys. Kidney size (renal length and parenchymal thickness) is readily measurable by ultrasonography, but the evaluation remains subjective without the use of appropriate standards. The aim of authors was, to produce a centile chart for normal kidney size based on US measurement in healthy Hungarian children. Renal length and renal parenchymal thickness (upper pole, middle part and lower pole) as well body weight and height were measured in 330 children. Normograms (centile charts) with 10th, 50th and 90th centiles were produced for body weight/height and renal length/parenchymal thickness. Renal length correlated strongly with both body weight (r = 0.93, p < 0.001) and height (r = 0.93, p < 0.001). The centile chart for renal size enables the objective evaluation of abnormal kidney size; it can help in the early recognition and follow up of urinary diseases.