Extract
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Introduction
Diabetic nephropathy is the main cause of end-stage
renal disease requiring dialysis. A basic mechanism
underlying diabetic nephropathy appears to be the high glucose
(HG)-induced overexpression of transforming growth
factor-β (TGf-β) and the accumulation of extracellular matrix
(ECM) molecules, such as collagen IV and
fibronectin[1,2]. For example, glomerular mesangial cells (GMC) showed
increased levels of TGf-β and ECM when cultured in the
presence of HG[1,2]. Recent studies suggest that
Janus
kinase (JAK)/signal transducers and activators of
transcription (STAT) signaling cascades may contribute to diabetic
nephropathy[3]. This pathway is mainly related to renal cell
growth, production of the cytokine TGf-β, as well as the
ECM proteins collagen IV and
fibronectin[4].
JAK/STAT is an important signaling pathway, which is
known to mediate the signaling of numerous cytokines and
growth factors and is implicated in the regulation of a wide
range of cellular processes, such as proliferation,
differen-tiation, and apoptosis[5]. The JAK enzymes, JAK1, JAK2,
JAK3, and tyrosine kinase-2 (TYK2), are responsible for the
activation of the STAT (STAT1, STAT2, STAT3, STAT4,
STAT5A/B, and STAT6), which are latent cytoplasmic
transcription factors. STAT, when activated by tyrosine and/or
serine phosphorylation, form homo- and heterodimers and
translocate to the nucleus where they regulate the
expression of various genes involved in cellular
proliferation[6].
It was reported that activation of JAK/STAT was induced
by HG and angiotensin II (Ang II) in rat GMC cultured
in vitro[7]. That is, the exposure of GMC to hyperglycemia
induces the tyrosine phosphorylation of JAK2, which was
accompanied by the tyrosine and/or serine phosphorylation of
STAT1, STAT3, and STAT5[7]. In addition, studies have also
shown that the activation of JAK2 was essential for both
Ang II- and hyperglycemia-induced collagen
IV production and GMC growth[7]. Wang
et al[4] reported that the
activation of JAK2 and STAT1 proteins was a requirement for the
hyperglycemia-induced production of TGf-β and fibronectin
in GMC. The exposure of vascular smooth muscle cells
(VSMC) to HG induced tyrosine phosphorylation of JAK2,
which was accompanied by the tyrosine and/or serine
phosphorylation of STAT1 and STAT3 and increased VSMC
proliferation[8]. In addition, the activation of JAK/STAT also
detected in diabetic rat glomeruli, and treatment with JAK2
inhibitor AG490 lowered systolic blood pressure and
significantly reduced urinary protein
excretion[9]. Therefore, it
appears that the activation of JAK2 and
STAT proteins by hyperglycemia might play an important
role in both promoting cell proliferation and the synthesis of ECM molecules.
The activation of JAK/STAT may be one of the major
mechanisms involved in high glucose-induced glomerular
injury[4].
Accumulating evidence has suggested that
3-hydroxy-3-methylglutanyl coenzyme A (HMG-CoA) reductase
inhibitors (statins) have anti-inflammatory and endothelial
cell-protective actions that are independent of the
cholesterol-lowering effect[10]. Statins may
influence intracellular pathways that are involved in the
inflammatory and fibrogenic responses in progressive renal
injury[10]. Fluvastatin is
effective in improved renal function in streptozotocin
(STZ)-induced diabetic rats[11]. Fluvastatin
significantly suppressed proteinuria
and serum creatinine in rats with puromycin
aminonucleoside (PAN )
nephrosis[12]. Fluvastatin could
inhibit the Ang II-induced activation of JAK/STAT in
VSMC[13]. A recent study demonstrated that simvastatin
blocked the HG- and Ang II-induced activation of the
JAK/STAT pathway in GMC[14]. Does fluvastatin show a similar
physiological role? In the present study, we used both
in vivo and in vitro methods to examine the effects of fluvastatin
on the HG-induced activation of JAK2 and STAT proteins.
Materials and methods
Reagents Fluvastatin sodium was provided by Beijing
Novartis (Beijing, China). D-glucose,
D-mannitol and STZ were obtained from Sigma (St Louis, MO, USA). AG490 was
purchased from Calbiochem-Novabiochem (La Jolla, CA,
USA). The antibodies against SHP-1, JAK2, STAT1, STAT3,
phospho-STAT1 (A-2), phospho-STAT3 (B-7), phospho-Tyr
(PY99), protein A/G-agarose, and the enhanced
chemiluminescence detection kit were purchased from Santa Cruz
Biotechnology (Santa Cruz, CA, USA). SHP-2 and
phospho-SHP-2 (Tyr580) were purchased from Cell Signaling
Technology (Beverly, MA, USA). All culture media was purchased
from Gibco-BRL (Grand Island, NY, USA). TRIzol reagent
was obtained from Invitrogen Life Technologies
(Carlsbad, CA, USA). The RT-PCR system was obtained from Promega
(Madison, WI, USA). TGf-β1 and the fibronectin ELISA
systems were purchased from R&D Systems (Minneapolis,
MN, USA), and the polyvinylidene difluoride
(PVDF) membrane was purchased from Millipore (Billerica, MA, USA).
STZ-induced diabetes Five-week-old male
Sprague_Dawley rats (Grade II, Certificate
No 607089, Hebei Provincial Experimental Animal Center, Shijiazhuang, China) were
divided into 3 groups: (i) non-diabetic
control rats (non-DM, n=12); (ii) STZ-induced diabetic rats
received vehicle alone (DM, n=12); and (iii) diabetic rats
treated with fluvastatin (DM+Flu,
n=12). The DM and DM+Flu groups were intravenously injected with a single dose of 60 mg/kg STZ in
citrate buffer at pH 4.5. Hyperglycemia (>16.7 mmol/L) was
confirmed 48 h after STZ administration. The animals in the
DM+Flu group received a dose of fluvastatin (4 mg/kg) daily
by gavage from the next day of the induction of diabetes;
the animals in the non-DM and DM groups received vehicle
alone. Blood glucose was measured weekly, and only
rats with blood glucose at a concentration more than 16.7
mmol/L were included in the study. Four weeks later, systolic blood
pressure was measured by the tail-cuff method; urine and
blood samples were collected, and the animals were killed.
Both kidneys were dissected and weighed. The left kidney
was perfused with chilled saline solution and used to isolate
glomeruli. The right kidney was perfused with chilled saline
solution and fixed in 4% formaldehyde for histological
examination.
Isolation of glomeruli The renal cortex was minced with
a razor blade and pressed against a 0.3 mm stainless steel
grid. Large fibrous tissues were retained on the
grid surface, whereas glomeruli and tubular segments passed
through. The glomeruli were then isolated by filtration through a 75
µm nylon mesh using an ice-cold 0.9% NaCl
solution[15]. Those retained
on the sieve were collected, washed by centrifugation (4
°C, 2000×g), and suspended in 50 mmol/L
Tris-HCl (pH 7.4). The tissues were maintained at 4 °C during the
entire isolation procedure. The purity of the glomerular
suspensions was then assessed by light microscopy and
estimated to be at least 95% glomeruli at the end of each
prepara-tion. The glomerular suspensions
were then centrifuged at
4000×g for 5 min and used to extract total protein and RNA.
Histology The kidneys were fixed in 4% formaldehyde
and embedded in paraffin; 4 µm sections were prepared and
stained with hematoxylin_eosin and periodic acid-Schiff. The
renal cortex sections were observed under light microscopy
using the computer image analysis system. At least 50
glomeruli per animal were examined. Glomerular diameter was
measured using TD2000 image analysis software
(Tiandi-bainian, Beijing, China).
Cell culture The GMC were obtained from intact
glomeruli of 5-week-old Sprague-Dawley rats and characterized
according to published methods[16]. The GMC were plated
on plastic tissue culture flasks in RPMI-1640 medium with
20% fetal bovine serum, 100 U/mL penicillin, 100 µg/mL
streptomycin, and 0.6 U/mL insulin. GMC of passages 5_10
were grown to 75%_85% confluence, washed once with
serum-free RPMI-1640 medium, and then growth-arrested in
serum-free RPMI-1640 medium for 24 h to synchronize the
cell growth. The GMC were divided into 5 groups: (i) normal
glucose (NG, 5.5 mmol/L); (ii) NG+mannitol (24.5 mmol/L);
(iii) HG (30 mmol/L); (iv) HG+AG490 (10 µmol/L); and (v)
HG+fluvastatin (1 µmol/L).
Protein extraction Isolated glomeruli or GMC were
washed twice with ice-cold PBS with 1 mmol/L
Na3VO4, and then treated for 60 min with ice-cold lysis buffer [20 mmol/L
Tris-HCl, pH 7.4, 2.5 mmol/L EDTA, 1% Triton X-100,
10% glycerol, 1% deoxycholate, 0.1% SDS, 10 mmol/L
Na4P2O7, 50 mmol/L NaF, 1 mmol/L
Na3VO4 and 1 mmol/L phenyl-methanesulfonyl fluoride (PMSF)]. The cell lysates
were centrifuged at 14 000×g for 25 min at 4 °C and the
supernatants were collected. The protein concentration was
measured by Bradford's method.
Immunoprecipitation and Western blotting study of
JAK2 and SHP-1 The cell lysates were incubated with 10
µg/mL of either anti-JAK2 or anti-SHP-1 antibody at 4 °C for
2 h and precipitated by an addition of 20 µL protein A/G
agarose beads at 4 °C overnight. The immunoprecipitates
were washed 3 times with ice-cold wash buffer (10 mmol/L
Tris-HCl, pH 7.4, 150 mmol/L NaCl, 0.1% Triton X-100,
1 mmol/L PMSF, and 1 mmol/L
Na3VO4). The immunoprecipitated proteins were subjected to SDS-PAGE and then
transferred to a PVDF membrane. After blocking in 5%
non-fat milk for 2 h at 37 °C, the membrane was incubated with
anti-phosphotyrosine antibody (1:1000) overnight at 4 °C,
followed by incubation with the secondary antibodies
conjugated with horseradish peroxidase (1:10000) for 2 h at room
temperature. After extensive washing, the membrane was
exposed to X-ray film using an enhanced chemiluminescence
detection kit. The intensity of the bands was measured
using LabWorks 4.5 (UVP, Upland, CA, USA).
Western blotting studies of SHP-2 and STAT proteins
The cell samples were resolved by SDS_PAGE, transferred
to a PVDF membrane, and blocked with 5% non-fat milk for
2 h at 37 °C. The membrane was incubated overnight at 4 °C
with anti-SHP-2 (1:500) and anti-STAT (1:400) antibodies,
respectively. Subsequently, the membranes were washed 3
times for 10 min each with TBS-T (10 mmol/L Tris-HCl, 150
mmol/L NaCl, 0.05% Tween 20) and incubated for 90 min with
goat anti-rabbit IgG or goat anti-mouse IgG horseradish
peroxidase conjugate. After extensive washing, the membranes
were exposed to X-ray film and results were analyzed as
described previously.
TGf-β1 RT-PCR analysis Total RNA and then cDNA
were prepared from rat glomeruli and cultured
cells using TRIzol reagent and RT-PCR kits. PCR was carried out for 30
cycles according to the following procedure: 95 °C for 60 s,
57 °C for 50 s, and 72 °C for 60 s; The primers for
TGf-β1 and GAPDH were 5'-CCA TGA CAT GAA CCG ACC CT-3',
5'-CCG GGT TGT GTT GGT TGT AG -3' and 5'-TAT CGG ACG CCT GGT TAC-3', 5'-CTG TGC CGT TGA ACT TGC-3',
respectively. The PCR products were subjected to 2%
agarose gel electrophoresis and analyzed with a GDS-8000
Bioimaging system (UVP, upland, CA, USA) and LabWorks
4.5 software. RNA expression was quantified by
comparison with internal-control GAPDH.
TGf-β1 and fibronectin ELISA After the cells were
cultured in 6-well plates with or without different stimuli for
48 h, the supernatants were collected and TGf-β1 and
fibronectin levels were measured by an ELISA kit,
according to the manufacturer's instruction. The
TGf-β1 protein was quantified using the commercial Quantikine
TGf-β1 ELISA kit. Briefly, the cell supernatants were activated with
1 mol/L HCl for 10 min, followed by neutralization with
1.2 mol/L NaOH. The activated samples were applied to
the plate precoated with soluble type II receptor and
incubated at room temperature for 3 h. After extensive washing,
horseradish peroxidase-conjugated anti-TGf-β1 antibody
was added and incubated for another 1.5 h. Then the
chromogen was added and the plate was read at 450 nm. The
fibronectin protein was quantified by competitive sandwich
ELISA. Briefly, the samples were diluted and applied to the
plate coated with the anti-fibronectin antibody, and the same
amount of biotin-labeled fibronectin was immediately added
to the wells. After incubation for 1.5 h and extensive washing,
the horseradish peroxidase-conjugated streptavidin was
added to the wells and incubated for 30 min. Then the
chromogen was added and the plate was read at 450 nm.
Statistical analysis All data were presented as mean±SD.
Statistical analysis was performed by one-way ANOVA
using SPSS 11.0 (SPSS, Chicago, IL, USA).
P<0.05 was considered statistically significant.
Results
Changes of basic parameters Blood glucose levels of
both the DM and DM+Flu groups maintained at a high level
of >16.7 mmol/L during the 4 weeks. Treatment with
fluva-statin had no effect on the elevated blood glucose level.
There was no significant difference in systolic blood
pressure, total cholesterol, and triglyceride levels among the
3 groups. Urinary albumin excretion (UAE)was about
2.5-fold higher in the DM group than that of the non-DM group,
and fluvastatin treatment significantly alleviated proteinuria.
The kidney/body weight ratio was increased in DM group
compared with that of the non-DM group; the treatment with
fluvastatin was associated with a significant reduction in
the kidney/body weight ratio. In addition, we measured the
glomerular diameter (MGD). The MGD increased in the DM
group compared with that of the non-DM group
(P<0.01); fluvastatin treatment significantly inhibited glomerular
hypertrophy (P<0.05; Table 1).
Effect of fluvastatin on the transcription of
TGf-β1 mRNA The RT-PCR analysis indicated that the
mRNA level of TGf-β1 was increased significantly in diabetic glomeruli
when compared with that of non-diabetic glomeruli. The
treatment of fluvastatin downregulated glomerular
TGf-β1 mRNA expression in the diabetic kidney (Figure 1). We
cultured GMC under NG or HG conditions and treated them
with fluvastatin or AG490. TGf-β1 mRNA expression was
upregulated by HG stimulation in the mesangial cells, and
the treatment of AG490 or fluvastatin effectively inhibited
the HG-induced upregulation of the TGf-β1
mRNA level (Figure 2).
Effect of fluvastatin on the production of
TGf-β1 and fibronectin We examined the concentration of the
TGf-β1 protein and fibronectin in the culture medium of the GMC
with ELISA analysis. We found that the GMC exposed to
HG for 48 h showed higher levels of the TGf-β1 protein and
fibronectin than those cultured under NG condition. When
GMC were treated with AG490 or fluvastatin, the secretion
of TGf-β1 and fibronectin decreased (Table 2).
Effect of fluvastatin on the activation of the JAK2 and
STAT proteins To determine the effect of fluvastatin on the
activation of the JAK2 and STAT proteins, we first examined
the phosphorylation of JAK2, STAT1, and STAT3 in
diabetic glomeruli by Western blot analysis. The result
demonstrated that the expression levels of tyrosine
phosphorylation of JAK2, STAT1, and STAT3 obviously increased in the
DM group compared with the non-DM group. Fluvastatin
treatment significantly reduced glomerular tyrosine
phosphorylation of JAK2, STAT1, and STAT3 in diabetic kidneys
(P<0.05, Figures 3, 4). We further confirmed the effect of
fluvastatin on the activation of JAK2 and STAT proteins
using GMC cultured under HG condition. In accordance
with the in vivo data, the expression levels of the tyrosine
phosphorylation of JAK2, STAT1, and STAT3 significantly
increased under HG conditions, compared with of the NG
and NG+mannitol groups (P<0.01). The JAK2 inhibitor AG490
significantly inhibited the phosphorylation of JAK2, STAT1,
and STAT3 in GMC cultured in medium with HG
(P<0.05). Meanwhile, the tyrosine phosphorylation of JAK2, STAT1,
and STAT3 significantly reduced (P<0.05) with the addition
of fluvastatin to the culture medium (Figures 5, 6).
Effect of fluvastatin on the activation of SHP-1 and
SHP-2 The expression ratio of tyrosine phosphorylated
SHP-1/total SHP-1 significantly decreased in DM group compared
with the non-DM group; whereas, SHP-2 tyrosine
phosphorylation increased in the DM group. Fluvastatin significantly
inhibited the tyrosine phosphorylation of SHP-2, but no
significant effect was seen on the dephosphorylation of SHP-1
(Figure 7). We also investigated the effects of fluvastatin on
the activation of SHP-1 and SHP-2 in GMC by examining
their tyrosine phosphorylation levels. The ratio of
phosphorylated SHP-1/total SHP-1 was lower in the HG group
than in the NG and NG+M groups; whereas the GMC in HG
group showed increased SHP-2 phosphorylation. Fluvastatin
significantly inhibited the HG-induced tyrosine
phosphorylation of SHP-2, but it had no effect on SHP-1
phosphorylation in GMC under HG conditions (Figure 8).
Discussion
Statins are lipid-lowering agents that specifically,
competitively, and reversibly inhibit the HMG-CoA reductase, the enzyme that catalyzes the conversion of
HMG-CoA to mevalonic acid, which is the rate-limiting step in the
formation of cholesterol. Cardiovascular benefits of statins
have been conventionally attributed to the reduction in
levels of low-density lipoprotein cholesterol. More recently,
subanalyses of large clinical trials suggest that statins may
also prove beneficial in ameliorating the progression of
kidney disease through their cholesterol-dependent and/or
cholesterol-independent effects[17]. In the hypertensive model
of diabetic nephropathy, cerivastatin decreased albuminuria
through the suppression of glomerular hyperfiltration,
mesangial expansion, and the loss of charge barrier
independently of a cholesterol-lowering
effect[18].
In the present study, untreated STZ-induced diabetic rats
exhibited significantly increased
urinary albumin excretion (UAE), kidney weight/body weight ratio, and mean
glomerular diameter. Fluvastatin treatment resulted in the
amelioration of albuminuria and glomerular
hypertrophy, without altering serum total cholesterol and triglyceride levels.
Our findings suggest that these renoprotective effects are
independent of the cholesterol-lowering effect.
Diabetic nephropathy is characterized by excessive
deposition of ECM in the kidney, leading to
glomerular mesangial expansion and tubulointerstitial fibrosis. Recent studies have
demonstrated that early renal hypertrophy is detrimental to
the kidney in the long term and is a precursor of
development of renal fibrosis[19,20]. Although the exact mechanisms
of renal hypertrophy are still unclear, several growth factors,
cytokines, chemokines, and vasoactive agents have been
implicated in the development of renal hypertrophy, which
include TGf-β, insulin like growth factor-1 (IGF-1), and
platelet derived growth factor
(PDGF)[21_23]. Among them, TGf-β is an effecter molecule studied extensively as a major
mediator of the hypertrophic and prosclerotic changes in diabetic
kidney disease[24]. Our result demonstrated that the
transcription level of TGf-β1 was increased in diabetic glomeruli
and this increase was suppressed by fluvastatin. To confirm
the fluvastatin effect on the glomerular TGf-β1
expression in diabetic rats, cultured rat GMC
were also examined. Our study showed
that GMC cultured under HG conditions produce
TGf-β1 and ECM fibronectin at a significantly faster rate
than those cultured under NG conditions, and the
transcription level of TGf-β1 increased in the HG group. After
treatment with fluvastatin, the transcription level of
TGf-β1 and the secretion of TGf-β1 and fibronectin were decreased.
This result suggests that fluvastatin may
prevent diabetic nephropathy by the suppression of glomerular
TGf-β1 expression.
The JAK/STAT pathway is an important link between
cell surface receptors and nuclear transcriptional events
leading to cell growth[3]. The JAK/STAT pathway, especially the
JAK2-STAT1-dependent pathway, contributes to HG-induced
overproduction of TGf-β and fibronectin in
GMC[4]. Treatment with JAK2 inhibitor AG490 lowered systolic blood
pressure and significantly reduced urinary protein excretion
in diabetic rats[9]. In our present study, the STZ-induced
diabetic rats revealed increased phosphorylation of JAK2,
STAT1, and STAT3, and fluvastatin resulted in the
inhibition of JAK2, STAT1, and STAT3 phosphorylation. Our
result also demonstrated that fluvastatin significantly
inhibited the increased phosphorylation of JAK2, STAT1, and
STAT3 in GMC cultured under HG conditions. Meanwhile,
AG490 blocked HG-induced JAK2, STAT1, and STAT3
phosphorylation and production of TGf-β1 and fibronectin.
These results suggest that the renoprotective effects of HMG-CoA
reductase inhibitor fluvastatin may be partly through the
inhibitory activation of the JAK/STAT signaling pathway.
SHP-1 and SHP-2 are 2 Src homology 2
domain-containing tyrosine phosphatases with major pathological
implications in cell growth-regulating signaling. The
phosphorylation state of JAK2 is tightly
regulated by SHP-1 and SHP-2 in
GMC[7]. SHP-1 and SHP-2 have opposite roles in Ang
II-induced JAK2 phosphorylation[25]. SHP-1 appears to act as
a conventional phosphatase, promoting JAK2
dephosphorylation and the termination of the Ang II-induced JAK/STAT
signaling[25]. On the other hand, SHP-2 seems to play an
essential role in promoting JAK2 phosphorylation and the
initiation of the Ang II-induced JAK/STAT cascade, leading
to cell proliferation[25]. In this study, we investigated the
phosphorylation of 2 cytosolic tyrosine
phosphatases, SHP-1 and SHP-2, in diabetic rat glomeruli and GMC under HG
condition. Our results demonstrated that SHP-1
phosphorylation was decreased and
SHP-2 phosphorylation was increased under hyperglycemic conditions. These findings
are consistent with a previous study[9]. These results
provide further support for the hypothesis that
sustained JAK2 activation under hyperglycemic conditions might be
partly due to decreased SHP-1 and increased SHP-2
phosphoryla-tion. We also found that fluvastatin significantly reduced
the hyperglycemia-induced tyrosine phosphorylation of
SHP-2. This result suggested that the inhibitory effect of
fluvastatin on JAK2 phosphorylation might be partly due to
decreased SHP-2 phosphorylation.
The mechanism by which HG promotes JAK2 activation
may relate to an interaction of JAK2 with reactive oxygen
species (ROS) induced by HG[4]. Recent studies have shown
that ROS regulates the activity of the protein-tyrosine
phosphatases SHP-1 and SHP-2[26,27]. Amiri
et al[8] demonstrated that HG augmented Ang II-induced ROS production, VSMC
proliferation, and tyrosine phosphorylation
of JAK2 via the polyol pathway activation of protein kinase
C-b2, which in turn activated NADPH oxidase to produce ROS.
ROS regulate the activity of the protein tyrosine phosphatases SHP-1
and SHP-2, and SHP-1 and SHP-2 in turn regulated the
activation of JAK2. HG, advanced glycation end products,
Ang II, and TGf-β1 all increase intracellular ROS in renal
cells and contribute to the development and
progression of diabetic renal
injury[28]. Recent studies have demonstrated
that statins may prevent the production of
ROS[29,30]. Fluvastatin could increase renal intrinsic antioxidant enzyme
activities and improve renal function in STZ-induced diabetic rats[11]. Therefore, the fluvastatin-regulated
activation of the JAK/STAT pathway may be partly via reducing
ROS production in GMC and diabetic kidneys.
In VSMC, Ang II has been shown to stimulate tyrosine
phosphorylation and the activation of SHP-2, and HG
appears to enhance the effects of Ang II on both SHP-2
tyrosine phosphorylation and SHP-2
activity[31]. Ang II type 1
(AT1)-receptor antagonist
candesartan significantly reduced the hyperglycemia-induced tyrosine
phosphorylation of SHP-2 in diabetic
glomeruli[9]. This result demonstrated that tyrosine
phosphorylation of SHP-2 was probably via the
AT1 receptor. A previous study suggested that SHP-2 functions as an
adaptor protein for the JAK2 association with the
AT1 receptor[25]. Recent evidence revealed that treatment with statins
decreased AT1 receptor expression in VSMC
in vitro and in vivo. Fluvastatin reduced
AT1 receptor protein and mRNA expression with a time-course in
VSMC[30,32]. There-fore, the possible mechanism by which fluvastatin regulated SHP-2
phosphorylation was partly due to decreasing
AT1 receptor expression.
In summary, our data demonstrate that fluvastatin exerts
an inhibitory effect on the activation of the JAK/STAT
pathway in diabetic rat glomeruli and GMC under HG conditions.
The results provide further evidence that inhibiting
JAK/STAT signaling might be an effective therapeutic strategy
for diabetic nephropathy.
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