1 Department of Pathology, Seoul National University College of Medicine, Seoul 110-799, Korea
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Lipid
abnormalities and dysregulation of the plasminogen activator
(PA)/plasmin system may be involved in the development of
glomerulosclerosis. We investigated the effects of low-density lipoprotein (LDL) on PA inhibitor-1 (PAI-1), urokinase-type PA (uPA),
and tissue-type PA (tPA) in relationship to protein kinase C (PKC) in
cultured human mesangial cells (HMC). LDL (200 µg/ml) induced two
peaks of PKC activation at hours 0.25 and 6, with translocation of PKC-, -
1, and -
from cytosol to
the membrane. The second increase in PKC activity gradually decreased
to the control value by hour 18. LDL
downregulated 2.4-kb PAI-1, uPA, and tPA mRNA expression within 6 h of incubation with HMC. On the other hand, after 12-48 h,
LDL-treated cells showed a significant increase in PAI-1, tPA, and uPA
mRNA levels. LDL induced up to a twofold increase in PAI-1 antigen
levels in the extracellular matrix of HMC after 24-48 h as well as
increased PA inhibitory activity in the culture medium. Analysis of the
adhesion plaques from cells incubated with LDL for 48 h by
zymography showed increased intensity of lysis near molecular weights
of ~55,000 and 100,000. LDL slightly increased tPA release at
hours 24 and 48 but did not increase
PA activity in culture medium. The stimulatory effects of LDL on PAI-1,
tPA, and uPA gene regulation in HMC were blocked by the inhibition of
PKC using GF-109203X 12 h after treatment with LDL or
downregulation of PKC using phorbol myristate acetate. In summary, LDL
regulates PAI-1, uPA, and tPA in biphasic patterns in HMC, and the
upregulation of PAI-1, uPA, and tPA after long-term LDL exposure seems
to be mediated by a delayed PKC activation associated with an increased
PA inhibitory activity. These results suggest that LDL, after prolonged
incubations with HMC, causes a PA/inhibitor imbalance favoring
accumulation of matrix.
glomerulosclerosis; lipids; extracellular matrix; plasmin; protein kinase C; low-density lipoprotein
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
ACCUMULATION OF EXTRACELLULAR MATRIX (ECM) in the glomerular mesangium leading to glomerulosclerosis is an important feature of progressive glomerular injury. Glomerular mesangial cells, which are often compared with vascular smooth muscle cells (VSMC), are a major site of ECM synthesis in chronic glomerular disease. Hypercholesterolemia in nephrosis may play a role in the progression of original glomerular injury to progressive glomerulosclerosis (9, 19). Hypercholesterolemia is mainly due to the increased level of low-density lipoprotein (LDL). LDL stimulates the synthesis of ECM in cultured human mesangial cells (HMC) (14, 15).
The ECM can be degraded, and a distortion of the balance between ECM synthesis and turnover may result in an abnormal ECM accumulation in renal disease. Matrix metalloproteinases and the plasminogen activator (PA)/plasmin system are known to play a key role in matrix degradation (2, 18, 24, 29). Cultured HMC produce urokinase-type PA (uPA) (2, 6), tissue-type PA (tPA), and PA inhibitor-1 (PAI-1) (7, 13, 23). Plasminogen is activated to plasmin by the enzymatic activity of uPA and tPA, and plasmin mediates the degradation of ECM by cultured mesangial cells (2, 32). The rate of plasmin production is primarily regulated by PAI-1 (28), which also inhibits the plasmin-dependent activation of matrix metalloproteinases (20).
Protein kinase C (PKC) is activated by the physiological second messenger diacylglycerol (DAG), a product of phosphatidylinositol. On stimulation of cell surface receptors, there is an immediate and transient increase in DAG levels, often followed by the second phase of sustained DAG elevation (21). Tumor-promoting phorbol esters, such as 12-phorbol 13-myristate acetate (PMA), possess a molecular structure that is similar to that of DAG, cause a prolonged activation of PKC, and downregulate the enzyme. Oxidized LDL stimulated phosphoinositide turnover in cultured VSMC, which was inhibited by pretreatment of cells with PMA (25). In cultured HMC, PMA induced a marked increase in PAI-1 and tPA release over a period of 24 h (8, 23).
Despite the possible relationship between plasmin system and LDL-induced mesangial matrix accumulation, no study has explored the effects of LDL on the PA/plasmin system in HMC. Enhanced effects of oxidized LDL on PAI-1 synthesis have only been described in cultured VSMC (5). Prolonged incubation of native LDL with cultured HMC has been shown to result in oxidative modification (14). Here, we have attempted to determine whether LDL regulates PAI-1, tPA, and uPA according to incubation times in HMC and whether PKC activation could be involved in LDL-induced PA/PAI-1 imbalance.
![]() |
MATERIALS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Reagents. Human tPA was obtained from Calbiochem (La Jolla, CA). PAI-1 and tPA ELISA kits were obtained from Biopool (Umea, Sweden). Purified human fibrinogen and plasminogen, bovine thrombin, synthetic substrate D-Val-Leu-Lys pNA (S2251), and amiloride were purchased from Sigma (St. Louis, MO). Other reagents came from the sources previously reported (14, 15).
Culture of HMC. HMC were obtained from adult nephrectomy specimens, as previously described (11, 16). The culture medium that was used was made of DMEM supplemented with 20% fetal calf serum, 200 mM L-glutamine, and antibiotics. For the present experiments, cells between passages 5 and 7 were used.
LDL isolation. Human LDL (density: 1.019-1.063) and lipoprotein-deficient serum (density >1.215) were isolated from the plasma of normal volunteers by the method of sequential ultracentrifugation, as previously described (16). Isolated LDL was dialyzed for 24 h at 4°C against buffer A, which contained 0.15 M NaCl and 0.24 mM EDTA at pH 7.4. After dialysis, LDL was stored at 4°C under nitrogen and was used within 14 days.
Experimental conditions. HMC were grown to confluency. The cells were synchronized to quiescence in serum-free DMEM containing 5 µg insulin-transferrin-selenite/ml for 48 h. After synchronization, cells were treated with 50-200 µg/ml LDL for a time period varying from 15 min to 48 h. In a particular experiment, simultaneous control monolayers were treated with serum-free DMEM alone. The possibility that prolonged treatment with GF-109203X (GFX) could be toxic to cells was excluded by trypan blue exclusion.
Assay of PKC activity.
Quiescent HMC in six-well plates were exposed to 200 µg/ml LDL for 15 min to 24 h, and the PKC activity was assayed by using QKRPSQRSKYL
as a specific substrate peptide. In brief, the cell homogenates were
centrifuged and the pellets (membrane) were resuspended. Samples were
added to a microcentrifuge tube containing a substrate cocktail,
inhibitor cocktail, and lipid activator. After the addition of an
[-32P]ATP mixture, the tube was incubated at 30°C
for 10 min, and an aliquot was transferred onto the phosphocellulose
paper. The radioactivity was determined, and the PKC-specific activity
(pmol phosphate incorporated into substrate peptide/min) was calculated as described (15).
Cell fractionation and PKC immunoblots.
Quiescent HMC in 100-mm plates were stimulated with 200 µg/ml LDL for
6 h. Cells were harvested, sonicated, and centrifuged as described
(15). The supernatants were then retained as the cytosolic
fraction. The pellets were resuspended, sonicated, and centrifuged. The
supernatants were collected and used as the membrane fraction. Aliquots
were then electrophoretically resolved by using a 10% polyacrylamide
gel in an SDS buffer and then transferred onto nitrocellulose
membranes. The blots were incubated with rabbit anti-PKC- (1:1,000)
or -
1 (1:200), or mouse anti-PKC-
(1:250) at 4°C
overnight. Bound primary antibody was visualized after incubation with
horseradish peroxidase-conjugated secondary antibody using an enhanced
chemiluminescence system kit (Amersham).
Quantification of ECM-associated PAI-1 by ELISA.
At the end of the incubation period, conditioned medium was collected,
centrifuged, and stored at 70°C until it was assayed. The cell
monolayer was washed twice with culture medium and then treated with
0.5 ml of 0.02 M Tris, 0.15 M NaCl, at pH 7.4, containing 0.5% Triton
X-100. After incubation for 45 min at room temperature on a rotating
plate, the resulting cell extract was removed by aspiration, and the
Triton X-100-insoluble ECM was washed twice with Tris buffer.
ECM-associated PAI-1 was then brought into solution by the addition of
0.3 ml of 1 µg/ml tPA and incubated for 2 h at 37°C. This
treatment resulted in a >80% release of PAI-1 as a PAI-1/tPA complex
(27). A quantitative measurement of PAI-1 antigen was
carried out utilizing ELISA kits according to the manufacturer's instructions.
Preparation of adhesion plaques. After the experiments, adhesion plaques (composed of ventral membranes and ECM) were prepared as previously described (1). Briefly, cells were rinsed in 50 mM HEPES buffer containing 3 mM EGTA and 5 mM MgCl2, pH 7.2, and exposed for 2 min to the above buffer containing 1 mM ZnCl2. Then adhesion plaques were prepared by shearing with vigorously pipetted buffer (25 mM HEPES containing 3 mM MgCl2, pH 7.3).
Fibrinolytic activity and inhibitor activity assay. Fibrinolytic activity was measured by a chromogenic assay as previously described (13). Culture supernatants or adhesion plaques (80 µl) were added to 20 µl of Tris · HCl buffer, pH 7.4, containing 0.4 µM plasminogen and 2 mM S2251, which is a synthetic chromogenic substrate of plasmin. The optical density at 405 nm was measured in a microELISA reader after 1 h incubation at 37°C. Inhibitor activity using a conditioned medium was assayed as follows. The medium was incubated with the same volume of Tris buffer, pH 7.4, 0.02% SDS, and 0.2% Triton X-100 for 15 min. Exogenous tPA (2.5-5 U/ml) was incubated for 15 min at 37°C with the sample. Twenty microliters of plasminogen and S2251 were then added to measure the residual tPA activity.
Zymographic analysis. PAs in culture supernatants and adherent plaques were analyzed on gels as described (10). In brief, 11% SDS-polyacrylamide gels were prepared containing 0.12% fibrinogen, thrombin (1 NIH unit/ml), and plasminogen (1 U/ml). N,N,N',N'-tetramethylethylenediamine was added to the gel solution to a final concentration of 0.028%. Samples, which were dissolved in electrophoresis sample buffer without mercaptoethanol, were applied to the gel and separated electrophoretically. The gels were washed in 2.5% Triton X-100, incubated overnight at 37°C, and then stained with Coomassie blue.
Northern blot analysis.
Isolated RNA samples were transferred onto nylon filters as previously
described (14). A cDNA probe for human uPA detected a
transcript of a 1.5-kb PstI fragment (31). A
cDNA probe for the human tPA detected a transcript of a 1.6-kb
EcoRI fragment (4), and one for the human PAI-1
detected a 2.9-kb EcoRI fragment (22). The cDNA
probes for uPA and tPA were obtained from the American Type Culture
Collection (Manassas, VA). The PAI-1 cDNA probe was kindly donated by
Dr. D. J. Loskutoff (Scripps Clinic, La Jolla, CA). The blotted
membranes were incubated with the specific 32P-labeled cDNA
probes. The filters were dried and exposed at 70°C using Agfa film
(Agfa-Gevaert, Hortsel, Belgium). The mRNA levels for uPA, tPA, and
PAI-1 were expressed as a ratio of the optical density units for uPA,
tPA, or PAI-1 to
-actin.
Statistical analyses. Results were expressed as means ± SD. Results were analyzed by two-way analysis of variance for three groups or by Wilcoxon rank sum test between two groups. A P value of <0.05 was considered to be significant.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
LDL modulates PAI-1, uPA, and tPA mRNA expression according to
incubation times.
Starting 1 h after incubation with HMC, LDL at concentrations of
200 µg/ml significantly decreased 2.4-kb PAI-1, uPA, and tPA mRNA
synthesis until hour 6. No significant difference
in the levels of 3.4-kb PAI-1 mRNA was found between LDL-treated cells
and controls. At hour 12, LDL caused a slight but
significant increase in both 2.4- and 3.4-kb PAI-1 mRNA levels in HMC.
LDL also stimulated uPA and tPA mRNA synthesis at this incubation time.
At hours 24 and 48, LDL induced a more than
twofold increase in PAI-1, uPA, and tPA mRNA levels in HMC (Fig.
1).
|
LDL increases ECM-associated PAI-1 antigen and fibrinolytic
inhibitory activity in culture medium after prolonged incubation times.
LDL induced a slight decrease in the ECM-associated PAI-1 antigen
1-6 h after incubation with HMC. After 12 h of culture with LDL, a slight but significant increase in ECM-associated PAI-1 antigen
was found. LDL caused a 2.1- and 1.8-fold increase in the
ECM-associated PAI-1 antigen at hours 24 and
48 (Fig. 2).
|
|
LDL increases uPA activity in adhesion plaques and tPA release in
culture medium after prolonged incubation times.
Zymographic analysis of adhesion plaques prepared from control cells
and cells treated with LDL of 200 µg/ml for 48 h showed zones of
lysis near relative molecular weights (Mr) of
~55,000, 70,000, and 100,000. There was a significant increase in the
intensity of the ~100,000- and ~55,000-Mr
bands after LDL treatment (Fig. 4A). The
~55,000-Mr band appears to be a monomeric uPA,
whereas the ~100,000-Mr band may be a complex
of uPA with PAI-1 (6). In addition, the
~70,000-Mr band seems to be tPA. When
zymography was performed in the presence of amiloride, which blocks uPA
activity but not tPA (30), fibrinolytic activity near
Mr ~55,000 and 100,000 disappeared (Fig.
4B).
|
|
LDL induces two PKC peaks in HMC.
As previously shown by our laboratory (15), incubation of
HMC with LDL induced a rapid PKC activation by 15 min. This decreased to control values by hour 2. Total PKC activity
again increased to 2.9 ± 1.1 times the control level 6 h
after the addition of LDL. At hours 9,
12, and 15, PKC activity was still significantly higher in the LDL-treated group than in controls. After 18 h, this
effect had disappeared (Fig. 5).
|
|
PKC downregulation or inhibition attenuates the LDL-induced PAI-1,
uPA, and tPA mRNA expression.
The role played by PKC in causing an LDL-induced increase in PAI-1,
uPA, and tPA gene expression was assessed by analysis of the inhibiting
enzymatic activity of the kinase in HMC. Pretreatments of HMC with GFX
30 min before the start of the LDL stimulation blocked the LDL-induced
increases in PAI-1, uPA, and tPA mRNA expression. Prior exposure of HMC
to PMA for 24 h before exposure to LDL also blocked the
stimulatory effect of LDL on the mRNA expression (Fig.
7). Addition of GFX at 5 h, which
was 1 h before the second peak, and at 12 h also prevented
the PAI-1, uPA, and tPA mRNA overproduction induced by LDL (Fig.
8). On the other hand, the addition of
GFX at 18 h after the initiation of LDL treatment did not
significantly alter LDL-induced PAI-1, uPA, and tPA mRNA generation
(data not shown).
|
|
|
Antioxidant attenuates the LDL-induced PAI-1 mRNA expression.
The addition of vitamin E (50 µM) to HMC exposed to LDL for 48 h markedly reduced PAI-1 mRNA expression (Fig.
10).
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
These studies demonstrate that LDL either downregulated or upregulated PAI-1, uPA, and tPA in HMC according to incubation times. They also show that the upregulation of PAI-1, uPA, and tPA after long-term LDL exposure could be mediated by a delayed PKC activation and that LDL-induced PA inhibitory activity was greater than PA activity.
We show that LDL induced a second PKC activation at 6 h after the
start of LDL stimulation, in addition to the previously described first
peak at 15 min (15). In contrast to the transient first
PKC activation, the second one persisted for over 9 h and gradually decreased to basal level at hour 18 after the start of LDL administration. Translocation of PKC-,
-
1, and -
from cytosol to the membrane was induced by
LDL at hour 6. Lipid peroxidation products were
detected in culture medium even after a 3-h incubation of LDL with HMC
(14). Thus the second PKC activation by LDL in the present
study might be mediated through the scavenger receptor (16) rather than through the LDL receptor in HMC.
In this study, LDL promoted both 2.4- and 3.4-kb PAI-1 mRNA expression in HMC after prolonged incubation times, but short incubation times with LDL rather decreased 2.4-kb PAI-1 mRNA levels. In parallel with PAI-1 mRNA levels, LDL increased ECM-associated PAI-1 antigen levels over a 12- to 48-h incubation period. Moreover, PA inhibitory activity in culture medium was increased by LDL, as shown by chromogenic assay for residual tPA activity.
It is tempting to speculate that LDL's liability to peroxidation might be responsible for biphasic regulation of PAI-1 by LDL. Prolonged incubation of native LDL with cultured HMC has been shown to result in oxidative modification (14). In the present study, an antioxidant, vitamin E, attenuated the LDL-induced PAI-1 mRNA synthesis, suggesting that PAI-1 overproduction in HMC after long-term LDL exposure might be mediated by oxidation products. In contrast, initial downregulation of PAI-1 after short-term LDL exposure could be related to native LDL effect on PAI-1 expression and, therefore, may have physiological relevance. In support of our hypothesis, Dichtl et al. (5) demonstrated that the effect of native LDL on PAI-1 expression was not consistent in cultured VSMC and that augmentation of LDL levels in rats led to LDL oxidation at later time frames with increased vascular expression of PAI-1.
We also found that LDL-treated HMC showed a significant increase in uPA mRNA expression at late incubation times, despite a rapid and transient decrease in uPA mRNA at earlier time frames. Adhesion plaques from HMC treated with LDL for 48 h also exhibited an increase in the intensity of possible monomeric uPA and complex of uPA with PAI-1 compared with the controls. Furthermore, the zymography performed in the presence of amiloride showed no fibrinolytic activity, thus confirming the uPA nature of lysis.
The level of tPA mRNA was also markedly decreased by LDL in earlier time frames but increased after prolonged incubation times. Despite a distinctive increase in tPA mRNA expression at hours 24 and 48, LDL enhanced the tPA release only to a slight degree. Furthermore, increased tPA activity was not clearly demonstrated by zymography of the medium.
In our study, both the downregulation of PKC by PMA and inhibition of PKC by GFX resulted in the abolition of the stimulatory effects of LDL on PAI-1, uPA, and tPA gene expression. These results suggest that LDL after long-term incubation stimulates the expression of the PAI-1, uPA, and tPA mRNAs in HMC mediated by PKC. Early PKC activation may not mediate the LDL-induced overproduction of these mRNAs in HMC, because the addition of GFX at 12 h after the administration of LDL or 6 h after the second PKC peak still effectively prevented the mRNA synthesis. The addition of GFX at 18 h after initiation of LDL stimulation failed to inhibit the overexpression of these mRNAs. Thus the delayed activation of PKC occurring between 6 and 15 h after the administration of LDL may signal the upregulation of PAI-1, uPA, and tPA expression in HMC.
PAI-1 has been implicated in renal disease as being a mediator of ECM accumulation (24) and as a feedback mechanism to limit vascular fibrinolysis (17, 26). Our results describing the LDL-induced increase in PAI-1 synthesis as well as increased PA inhibitory activity at later time frames suggest that persistent hypercholesterolemia in chronic renal disease could lead to a mesangial ECM accumulation and to eventual renal fibrosis partly linked to an impaired matrix degradation.
Abnormal ECM accumulation is often preceded or combined with an increased expression of ECM-degrading enzymes (29), suggesting that increased proteolytic activity is required for the degradation of the normal ECM before its replacement by the abnormal ECM (24). Similarly, LDL-induced enhanced tPA or uPA synthesis, though minor, may help PAI-1 to be accumulated in ECM by degrading the normal mesangial matrix.
In the presence of fibrin, the fibrinolytic activity of tPA is much higher than that of uPA. Recent animal studies suggest that uPA may not have an important role in preventing glomerular fibrin deposition (12). uPA, after binding to the uPA receptor, can activate cell-signaling pathways involved in cell adhesion, cell migration, and chemotaxis, independently of its proteolytic activity (3). Whether an LDL-induced increase in uPA can also activate the mesangial cell-signaling pathways needs to be clarified further.
In summary, LDL regulates PAI-1, uPA, and tPA in biphasic patterns in HMC, and the upregulation of PAI-1, uPA, and tPA after long-term LDL exposure seems to be mediated by a delayed PKC activation associated with increased PA inhibitory activity. These results suggest that prolonged incubations of LDL with HMC lead to a PA/inhibitor imbalance that favors accumulation of matrix. This effect of LDL might have a pathophysiological function in the pathogenesis of glomerulosclerosis.
![]() |
ACKNOWLEDGEMENTS |
---|
We thank Dr. David J. Loskutoff (Department of Immunology, Scripps Clinic, La Jolla, CA) for providing the PAI-1 cDNA probe. We also thank Dr. Eric Rondeau (Hôpital Tenon, Paris, France) for helpful comments and discussion.
![]() |
FOOTNOTES |
---|
This study was supported by grants from the Ministry of Health and Welfare (Korea).
Address for reprint requests and other correspondence: H. S. Lee, Dept. of Pathology, Seoul National Univ. College of Medicine, Chongno-gu, Yongon-dong 28, Seoul 110-799, Korea (E-mail: hyunsoon{at}plaza.snu.ac.kr).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
10.1152/ajprenal.00304.2001
Received 25 September 2001; accepted in final form 19 March 2002.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Avnur, Z,
and
Geiger B.
Substrate-attached membranes of cultured cells. Isolation and characterization of ventral cell membranes and the associated cytoskeleton.
J Mol Biol
153:
361-379,
1981[ISI][Medline].
2.
Baricos, WH,
Cortez SL,
El-Dahr SS,
and
Schnaper HW.
ECM degradation by cultured human mesangial cells is mediated by a PA/plasmin/MMP-2 cascade.
Kidney Int
47:
1039-1047,
1995[ISI][Medline].
3.
Chapman, HA.
Plaminogen activators, integrins, and the coordinated regulation of cell adhesion and migration.
Curr Opin Cell Biol
9:
714-724,
1997[ISI][Medline].
4.
Degen, SJF,
Rajput B,
and
Reich E.
The human tissue plasminogen activator gene.
J Biol Chem
261:
6972-6985,
1986
5.
Dichtl, W,
Stiko A,
Eriksson P,
Goncalves I,
Calara F,
Banfi C,
Ares MPS,
Hamsten A,
and
Nilsson J.
Oxidized LDL and lysophosphatidylcholine stimulate plasminogen activator inhibitor-1 expression in vascular smooth muscle cells.
Arterioscler Thromb Vasc Biol
19:
3025-3032,
1999
6.
Glass, WF, II,
Kreisberg JI,
and
Troyer DA.
Two-chain urokinase, receptor, and type I inhibitor in cultured human mesangial cells.
Am J Physiol Renal Fluid Electrolyte Physiol
264:
F532-F539,
1993
7.
Hagege, J,
Peraldi MN,
Rondeau E,
Adida C,
Delarue F,
Medcalf R,
Schleuning WD,
and
Sraer JD.
Plasminogen activator inhibitor 1 deposition in the extracellular matrix of cultured mesangial cells.
Am J Pathol
141:
117-128,
1992[Abstract].
8.
Hagege, J,
Delarue F,
Peraldi MN,
Sraer JD,
and
Rondeau E.
Heparin selectively inhibits synthesis of tissue type plasminogen activator and matrix deposition of plasminogen activator inhibitor 1 by human mesangial cells.
Lab Invest
71:
828-837,
1994[ISI][Medline].
9.
Keane, WF.
Lipids and the kidney.
Kidney Int
46:
910-920,
1994[ISI][Medline].
10.
Kim, SH,
Choi NS,
and
Lee WY.
Fibrin zymography: a direct analysis of fibrinolytic enzymes on gels.
Anal Biochem
263:
115-116,
1998[ISI][Medline].
11.
Kim, YS,
Kim BC,
Song CY,
Hong HK,
Moon KC,
and
Lee HS.
Advanced glycosylation end products stimulate collagen mRNA synthesis in mesangial cells mediated by protein kinase C and transforming growth factor-beta.
J Lab Clin Med
138:
59-68,
2001[ISI][Medline].
12.
Kitching, AR,
Holdsworth SR,
Ploplis VA,
Plow EF,
Collen D,
Carmeliet P,
and
Tipping PG.
Plasminogen and plasminogen activators protect against renal injury in crescentic glomerulonephritis.
J Exp Med
185:
963-968,
1997
13.
Lacave, R,
Rondeau E,
Ochi S,
Delarue F,
Schleuning WD,
and
Sraer JD.
Characterization of a plasminogen activator and its inhibitor in human mesangial cells.
Kidney Int
35:
806-811,
1989[ISI][Medline].
14.
Lee, HS,
Kim BC,
Kim YS,
Choi KH,
and
Chung HK.
Involvement of oxidation in LDL-induced collagen gene regulation in mesangial cells.
Kidney Int
50:
1582-1590,
1996[ISI][Medline].
15.
Lee, HS,
Kim BC,
Hong HK,
and
Kim YS.
LDL stimulates collagen mRNA synthesis in mesangial cells through induction of PKC and TGF- expression.
Am J Physiol Renal Physiol
277:
F369-F376,
1999
16.
Lee, HS,
and
Koh HI.
Visualization of binding and uptake of oxidized low density lipoproteins by cultured mesangial cells.
Lab Invest
71:
200-208,
1994[ISI][Medline].
17.
Lee, HS,
Park SY,
Moon KC,
Hong HK,
Song CY,
and
Hong SY.
mRNA expression of urokinase and plasminogen activator inhibitor-1 in human crescentic glomerulonephritis.
Histopathology
39:
182-188,
2001.
18.
Martin, J,
Eynstone L,
Davies M,
and
Steadman R.
Induction of metalloproteinases by glomerular mesangial cells stimulated by proteins of the extracellular matrix.
J Am Soc Nephrol
12:
88-96,
2001
19.
Moorhead, JF.
Lipids and progressive kidney disease.
Kidney Int
39, Suppl31:
S35-S40,
1991[ISI].
20.
Murphy, G,
Ward R,
Gavrilovic J,
and
Atkinson S.
Physiological mechanisms for metalloproteinase activation.
Matrix Suppl
1:
224-230,
1992[Medline].
21.
Nishizuka, Y.
Protein kinase C and lipid signaling for sustained cellular responses.
FASEB J
9:
484-496,
1995
22.
Ny, T,
Sawdey M,
Lawrence D,
Millan JL,
and
Loskutoff DJ.
Cloning and sequence of a cDNA coding for the human -migrating endothelial-cell-type plasminogen activator inhibitor.
Proc Natl Acad Sci USA
83:
6776-6780,
1986[Abstract].
23.
Peraldi, MN,
Rondeau E,
Medcalf RL,
Hagege J,
Lacave R,
Delarue F,
Schleuning WD,
and
Sraer JD.
Cell-specific regulation of plasminogen activator inhibitor 1 and tissue type plasminogen activator release by human kidney mesangial cells.
Biochim Biophys Acta
1134:
189-196,
1992[ISI][Medline].
24.
Rerolle, JP,
Hertig A,
Nguyen G,
Sraer JD,
and
Rondeau EP.
Plasminogen activator inhibitor type I is a potential target in renal fibrogenesis.
Kidney Int
58:
1841-1850,
2000[ISI][Medline].
25.
Resink, TJ,
Tkachuk VA,
Bernhardt J,
and
Bühler FR.
Oxidized low density lipoproteins stimulate phosphoinositide turnover in cultured vascular smooth muscle cells.
Arterioscler Thromb
12:
278-285,
1992[Abstract].
26.
Rondeau, E,
Mougenot B,
Lacave R,
Peraldi MN,
Kruithof EKO,
and
Sraer JD.
Plaminogen activator inhibitor I in renal fibrin deposits of human nephropathies.
Clin Nephrol
33:
55-60,
1990[ISI][Medline].
27.
Schleef, RR,
Podor TJ,
Dunne E,
Mimuro J,
and
Loskutoff DJ.
The majority of type I plasminogen activator inhibitor associated with cultured human endothelial cells is located under the cells and is accessible to solution-phase tissue-type plasminogen activator.
J Cell Biol
110:
155-163,
1990[Abstract].
28.
Sprengers, ED,
and
Kluft C.
Plasminogen activator inhibitors.
Blood
69:
381-387,
1987[ISI][Medline].
29.
Stetler-Stevenson, WG.
Dynamics of matrix turnover during pathologic remodeling of the extracellular matrix.
Am J Pathol
148:
1345-1350,
1996[ISI][Medline].
30.
Vassalli, JD,
and
Belin D.
Amiloride selectively inhibits the urokinase-type plasminogen activator.
FEBS Lett
214:
187-191,
1987[ISI][Medline].
31.
Verde, P,
Stoppelli MP,
Galeffi P,
Di Nocera P,
and
Blasi F.
Identification and primary sequence of an unspliced human urokinase poly(A)+ RNA.
Proc Natl Acad Sci USA
81:
4727-4731,
1984[Abstract].
32.
Wong, AP,
Cortez SL,
and
Baricos WH.
Role of plasmin and gelatinase in extracellular matrix degradation by cultured rat mesangial cells.
Am J Physiol Renal Fluid Electrolyte Physiol
263:
F1112-F1118,
1992