Dexamethasone Inhibits Repair of Human Airway Epithelial Cells Mediated by Glucocorticoid-Induced Leucine Zipper (GILZ)
et al. (2013) Dexamethasone Inhibits Repair of Human Airway Epithelial Cells Mediated by Glucocorticoid-Induced
Leucine Zipper (GILZ). PLoS ONE 8(4): e60705. doi:10.1371/journal.pone.0060705
Dexamethasone Inhibits Repair of Human Airway Epithelial Cells Mediated by Glucocorticoid-Induced Leucine Zipper (GILZ)
Jingyue Liu 0
Mingxiang Zhang 0
Chao Niu 0
Zhengxiu Luo 0
Jihong Dai 0
Lijia Wang 0
Enmei Liu 0
Zhou Fu 0
Peter Chen, University of Washington, United States of America
0 1 Department of Respiratory Medicine, Children's Hospital of Chongqing Medical University , Chongqing , China , 2 Respiratory Research Laboratory, Ministry of Education Key Laboratory of Child Development and Disorders, Children's Hospital of Chongqing Medical University , Chongqing , China
Background: Glucocorticoids (GCs) are a first-line treatment for asthma for their anti-inflammatory effects, but they also hinder the repair of airway epithelial injury. The anti-inflammatory protein GC-induced leucine zipper (GILZ) is reported to inhibit the activation of the mitogen-activated protein kinase (MAPK)-extracellular-signal-regulated kinase (ERK) signaling pathway, which promotes the repair of airway epithelial cells around the damaged areas. We investigated whether the inhibition of airway epithelial repair imposed by the GC dexamethasone (DEX) is mediated by GILZ. Methods: We tested the effect of DEX on the expressions of GILZ mRNA and GILZ protein and the MAPK-ERK signaling pathway in human airway epithelial cells, via RT-PCR and Western blot. We further evaluated the role of GILZ in mediating the effect of DEX on the MAPK-ERK signaling pathway and in airway epithelium repair by utilizing small-interfering RNAs, MTT, CFSE labeling, wound-healing and cell migration assays. Results: DEX increased GILZ mRNA and GILZ protein levels in a human airway epithelial cell line. Furthermore, DEX inhibited the phosphorylation of Raf-1, Mek1/2, Erk1/2 (components of the MAPK-ERK signaling pathway), proliferation and migration. However, the inhibitory effect of DEX was mitigated in cells when the GILZ gene was silenced. Conclusions: The inhibition of epithelial injury repair by DEX is mediated in part by activation of GILZ, which suppressed activation of the MAPK-ERK signaling pathway, proliferation and migration. Our study implicates the involvement of DEX in this process, and furthers our understanding of the dual role of GCs.
Asthma is a chronic inflammatory airway disorder accompanied
by airway epithelial cell damage. The airway epithelium acts as a
barrier between the internal and external environment, and has a
crucial role in maintaining normal airway structure and function,
from the trachea to the alveoli. Thus, the airway epithelium is the
first to contact inhaled allergens, physical stimuli, pollution,
viruses, bacteria, and respiratory drugs . If the airway
epithelium undergoes prolonged and repeated damage, and there
is no appropriate repair process, the integrity of the airway is
destroyed and repair is further delayed. There is evidence that in
asthma the repair process is fundamentally flawed, and is
associated with activation of the epithelial-mesenchymal trophic
unit and growth factors that cause pathological airway remodeling
. Studies have also revealed that patients with asthma have
abnormal airway epithelial shedding, and almost all asthma
patients show on endobronchial biopsy a variable degree of airway
epithelial damage [3,4].
Inhaled glucocorticoids (GCs) have anti-allergy,
anti-inflammatory, and immunosuppressive properties, in addition to regulating
the biosynthesis and metabolism of key nutrients such as sugars,
fats, and proteins. GCs have been widely used in the treatment of
asthma, rheumatoid arthritis, and chronic obstructive pulmonary
disease, among other disorders [5,6]. As one of the most effective
medications to prevent and treat asthma, GCs primarily act on
airway epithelium to inhibit airway inflammation. However,
studies have shown that GCs also adversely affect the repair
process by suppressing early-stage migration and proliferation of
airway epithelial cells [7,8]. The molecular mechanisms
underlying the dual effects of GCs in these processes remain unclear.
Glucocorticoid-induced leucine zipper (GILZ) was first described
in 1997 as a dexamethasone (DEX)-responsive gene . GILZ is a
member of the TSC-22 (transforming growth factorb-stimulated
clone 22) family. Members of this family are widely expressed and
they affect multiple biological processes. These molecules contain
three domains: a high degree of homology in the dimerization
domain (TSC-22 box and LZ pattern), and different N-terminal
and C-terminal domains . GILZ is expressed in the liver,
kidney, lung, and brain as well as other tissues or cells. GCs,
ethanol, interleukin (IL)10, and even certain bacterial species such
as Yersinia enterocolitica and Clostridium difficile further induce the
expression of GILZ . GILZ has been reported to be
involved in cellular proliferation and apoptosis, control of T-cell
activation and development, modulation of IL2 production, and
increase of epithelial sodium channel-mediated sodium transport
GILZ is involved in GC-induced anti-inflammatory and
immunosuppressive responses ; it inhibits the activation of
transcription factors, including nuclear factor-kappaB (NF-kB) and
activator protein 1 (AP-1) [21,22]. GILZ also inhibits the
mitogenactivated protein kinase (MAPK)-extracellular-signal-regulated
kinase (ERK) signaling pathway, by binding directly to the
upstream regulator V-raf-1 murine leukemia viral oncogene
homolog 1 (RAF1) to prevent phosphorylation . The
MAPK-ERK signaling pathway is involved in airway epithelial
repair after injury and promotes the proliferation and migration of
neighboring cells around the injury site [7,8,24].
In the present study we determined whether DEX induces the
expression of GILZ in human airway epithelial cells, using the cell
line 9HTE. We investigated whether the inhibition of airway
epithelial repair imposed by the GC dexamethasone (DEX) is
mediated by GILZ, and associated changes in the MAPK-ERK
signaling pathway and cellular proliferation and migration.
Materials and Methods
Cells of the cell line 9HTE (a Simian virus 40
[SV40]immortalized line of human tracheal epithelial cells) , provided
by Respiratory Research Laboratory, Ministry of Education Key
Laboratory of Child Development and Disorders, Childrens
Hospital, Chongqing, China, were grown in Dulbeccos modified
Eagles medium (DMEM) supplemented with 10% fetal bovine
serum (FBS; Gibco, USA). The cells were incubated at 37uC in a
5% CO2 atmosphere, and growth status was observed under an
inverted microscope. Upon reaching 80%90% confluence, cells
were digested with trypsin and subcultured.
Reverse transcription PCR (RT-PCR)
9HTE cells (56105/well) were cultured in 6-well plates and
stimulated with control or 10 mM dexamethasone (DEX; D1756,
Sigma, USA) for up to 24 h. Total RNA was then extracted from
the 9HTE cells using lysis buffer (Bioteke, Beijing, China) and
reversed transcribed with a PrimeScriptRT reagent kit (TaKaRa,
Shiga, Japan) as suggested by the manufacturers. The mRNA
expression level of GILZ was measured by semiquantitative reverse
transcription PCR (RT-PCR). Two microliters of cDNA were
amplified in a total of 25 mL volume reaction, containing 12.5 mL
26 Master Mix, 0.5 mL each of sense and antisense primers
(10 mM), and 9.5 mL ddH2O. The sequences of the primers were
GILZ forward: 59-TGGTGGTTCTGCGGTGTAAGTG-39,
reverse: 59-CTCCTCGTGAGATGATGCTTGG-39; b-actin
forward: 59-GTGGACATCCGCAAAGAC-39, reverse:
59GAAAGGGTGTAACGCAACT-39. The amplification of GILZ
was performed at 94uC for 4 min; followed by 35 cycles of 94uC
for 30 s, 64uC for 30 s, 72uC for 45 s; and then an extension at
72uC for 5 min. The expected product size was 115 bp. The
bactin conditions for amplification were: 94uC for 4 min; 30 cycles
of 94uC for 30 s, 60uC for 30 s, 72uC for 45 s, and an extension at
72uC for 5 min. The expected product size was 303 bp. PCR
products were resolved by electrophoresis in 1.5% agarose gels
and visualized with ethidium bromide staining. The ratio of the
PCR products GILZ-to-b-actin was measured by densitometry.
bactin was used as an internal reference.
The preparation of total RNA and cDNA was obtained as
described above. The reaction was performed using
RealMasterMix (SYBR Green; Tiangen, Beijing, China) in a total 20 mL
volume containing 2 mL cDNA, 9 mL SYBR solution, 0.5 mL each
of sense and antisense primers (10 mM), and up to 8 mL ddH2O.
The primer sequences of GILZ were as above, and the primer
sequences for the housekeeping gene glyceraldehyde 3 phosphate
dehydrogenase (GADPH) were forward:
59-AAGAAGGTGGTGAAGCAGGC-39 and reverse:
59-TCCACCACCCTGTTGCTGTA-39. The PCR amplification conditions
for GAPDH were 95uC for 3 min; and 40 cycles of 95uC for 10 s
and 60uC for 30 s. The expected product size was 203 bp. The
amplification conditions for GILZ were 95uC for 3 min, then 40
cycles of 95uC for 10 s, and 64uC for 30 s.
9HTE cells were seeded in culture plates in serum-free DMEM
without antibiotics. Three small-interfering RNAs (siRNAs) were
designed and synthesized targeting GILZ (GILZ123 siRNAs), as
well as a non-specific si-RNA (si-negative control), and a GAPDH
si-RNA (si-positive control) (Benefit and Invitrogen, Shanghai,
China). These were transfected into separate groups of 9HTE cells
using Lipofectamine 2000 (Invitrogen, Carlsbad, CA, USA) in
accordance with the manufacturers instructions. The GILZ13
siRNAs were evaluated for the most effective GILZ si-RNA. The
sequences of the three GILZ siRNAs were GILZ1 si-RNA:
59GGAUCUGGUGAAGAAUCAUTT-39, GILZ2 si-RNA:
59GAACUCCCAGCUAGAGCGUTT-39, and GILZ3 si-RNA:
59GUUCCAGUCCUGUCUGAGCTT-39. After 6 h of
transfection, fresh medium was added to the transfected cells to culture for
up to 24 h, and were then stimulated with DEX (10 mM) for an
additional 24 h. The cells were collected to verify gene silence by
determining the expression of GILZ mRNA and GILZ protein
using real-time PCR and Western blot, respectively.
9HTE cells (56104 cells/well) were cultured in 24-well plates, in
which the glass slides were placed in the bottom. The treated cells
were fixed with 4% paraformaldehyde for 30 min. After washing
with phosphate-buffered saline (PBS), slides were incubated with
0.1% TritonX-100 for 10 min to penetrate the membrane, and
blocked with 5% bovine serum albumin for 30 min at room
temperature. The slides were incubated with GILZ monoclonal
antibody (Santa Cruz Bio, CA, USA) at 1:50 dilution overnight at
4uC, followed by incubating with DyLightTM 488 conjugated
secondary antibody at 37uC for 45 min. Finally the slides were
washed and dyed with 49,6-diamidino-2-phenylindole (DAPI),
mounted, and examined by fluorescence microscopy. The
negative control was incubated with PBS instead of GILZ
The protein from 9HTE cells was collected and protein
concentration was determined by bicinchoninic acid assay. Equal
amounts of protein from whole cell lysates were solubilized in 56
sodium dodecyl sulfate (SDS)-sample buffer and separated on 10
15% SDS polyacrylamide gels (KeyGEN, Nanjing, China)
according to molecular weight. Separated proteins were
transferred onto a polyvinylidene fluoride membrane. After blocking,
the membrane was incubated with anti-GILZ antibody (1:100
dilution, Santa Cruz Bio, CA, USA)and sequentially with
antiRaf-1, p-Raf-1, Mek1/2, p-Mek1/2, Erk1/2, p-Erk1/2 antibodies
(1:1000 dilution, Cell Signaling, Danvers, MA, USA) overnight at
4uC. Afterwards, horseradish peroxidase-conjugated anti-mouse/
rabbit secondary antibodies (MultiSciences, Hangzhou, China)
were used. Blots were visualized using an enhanced
chemiluminescence kit (KeyGEN, Nanjing, China).
Cell proliferation was analyzed using a
methyl-thiazolyltetrazolium (MTT) bromide assay (Amresco, USA). Briefly, the
cells were seeded in 96-well plates at a density of 10 000 cells/well,
and transfected with non-specific si-RNA or GILZ si-RNA for up
to 48 h. Afterwards 10 mL MTT (5 mg/mL) was added and
incubated for an additional 4 h. The supernatants were removed
and 150 mL dimethyl sulfoxide (Amresco, USA) was added to each
well. There were five duplicate wells in each group and the
experiment was repeated three times. The absorbance value
(optical density) of each well was measured at 490 nm.
CFSE (5(6)-carboxyfluorescein diacetate succinimidyl
9HTE cells were suspended in pre-warmed PBS at a final
concentration of 16106 cells/mL, and 5 mM CFSE (Invitrogen,
Carlsbad, CA, USA) was added to the cell suspension, and the cells
were incubated at 37uC for 10 min. The labeling process was
quenched by the addition of 10 volumes of ice-cold culture
medium (10% FBS), and the cell suspension was incubated 5 min
on ice and subsequently centrifuged. CFSE-labeled cells were
washed twice with medium, and were seeded in 24-well plates at a
density of 16105 cells per well. Cultured cells from each well were
harvested after transfection and treated with DEX, and the CFSE
fluorescence intensity was measured by flow cytometry.
9HTE cells were seeded in 24-well plates at a density of 16105
cells per well. After the cells were transfected with non-specific
siRNA or GILZ si-RNA for 24 h and reached approximately
80%90% confluence, the cells were scratched with a 10 mL pipette tip
and cultured in the presence of 10 mM DEX for an additional
24 h. Images of the wound were recorded using a fluorescence
microscope, immediately after wounding (0 h) and after culturing
(24 h). The cells of both sides around the damaged area migrated
toward the cell-free area. The wound widths of three different
wound surfaces in each group were noted and subsequently
measured using image J analysis software. The experiment was
repeated three times.
Cell migration assay
9HTE cells were transfected with non-specific si-RNA or GILZ
si-RNA for 24 h, followed by digesting, counting, and suspension
in serum-free DMEM. One hundred-microliter cell suspensions
(26105cells) were seeded in the upper chamber of a transwell unit
with an 8.0 mm polycarbonate membrane (Millipore, Boston,
USA) inserted in a 24-well plate, and 600 mL culture medium with
10% FBS was placed in the lower chamber where DEX (10 mM)
was added. After the cells were incubated for 24 h at 37uC, the
cells on the top surface of the transwell chamber were removed
with a cotton swab. The cells adhering to the lower surface were
fixed with 4% paraformaldehyde for 30 min, stained with
Figure 2. GILZ expression in 9HTE cells transfected with GILZ siRNAs. (A) Real time-PCR was performed to show transcriptional levels of the
GILZ gene 48 h after transfection with GILZ123 siRNAs of cells treated with DEX for 24 h. Non-specific si-RNA was the negative control, and GAPDH
siRNA was the positive control (n = 3). (B) Cellular GILZ protein was collected from 9HTE cells transfected with non-specific si-RNA or GILZ3 si-RNA for
48 h. Afterwards, GILZ protein levels were detected by Western blot (0.87360.109 in the non-specific si-RNA group compared with 0.30560.065 in
the GILZ3 si-RNA group, **P,0.001, n = 3), b-actin was used as a loading control. (C) The expression of GILZ protein was detected by
immunofluorescence (2006) after 9HTE cells were transfected with non-specific si-RNA or GILZ si-RNA, separately for 48 h.
Experimental differences were assessed for statistical significance
using analysis of variance (ANOVA) and SPSS 16.0 software. Data
were expressed as mean6standard deviation and P-values ,0.05
were considered significant (P,0.05).
Expression of GILZ mRNA and GILZ protein in 9HTE cells
We tested the effect of DEX on the expression of GILZ mRNA
and GILZ protein in cells of the SV40-immortalized line of human
tracheal epithelial cells 9HTE. We found that DEX (10 mM)
significantly induced mRNA levels of GILZ starting at 6 h, and
levels continued to increase 24 h after treatment compared to the
untreated control cells (P ,0.05), as determined by RT-PCR
(Figure 1A). The results from the immunofluorescence assays
showed that GILZ protein was mainly located in the cytoplasm,
and DEX significantly increased the expression of GILZ protein at
6 h compared with the untreated control group (Figure 1B).
Similar results showing increased GILZ protein levels were also
found via Western blot analysis (Figure 1C). However, no further
induction was observed at longer treatment times. Thus, GILZ
was capable of being induced rapidly and obviously by DEX in
airway epithelial cells in vitro.
Identification of the most effective GILZ si-RNA
Three GILZ siRNAs (GILZ123 siRNAs) that targeted different
mRNA sequences were transfected into 9HTE cells. We
determined the relative silencing efficiency of these siRNAs by
real-time PCR to select the best for subsequent experiments
(Figure 2A). There was no statistical difference between the ratios
of GILZ-to-GAPDH in the untreated control group and
nonspecific group (P .0.05). However, the ratio of GILZ-to-GAPDH in
the GILZ1-, GILZ2-, and GILZ3 si-RNA groups were 0.2760.06,
0.3660.12, and 0.2260.04, respectively. These results revealed
that GILZ3 si-RNA had the highest silencing efficiency, and the
expression of GILZ in the group transfected with GILZ3 si-RNA
was 55.8% that of the non-specific si-RNA group.
Western blot was then used to detect the GILZ protein
expression in 9HTE cells transfected with GILZ3 si-RNA. We
found that GILZ3 si-RNA significantly silenced GILZ protein
expression (P ,0.001, compared with the non-specific si-RNA
group), and there was no statistical difference between the control
and non-specific groups (Figure 2B). We further confirmed the
expression of GILZ protein by immunofluorescence, which was
significantly decreased in cells where GILZ gene was silenced by
the si-RNA (Figure 2C). Therefore, GILZ3 si-RNA was used for
Increased expression of GILZ induced by DEX inhibited
activation of the MAPK-ERK signaling pathway
The MAPK-ERK signaling pathway is a key factor in the
regulation of cell survival, apoptosis, proliferation, migration, and
differentiation to promote airway epithelial repair ; GILZ
induced by DEX inhibited the activation of the MAPK-ERK
signaling pathway . We investigated via Western blot whether
increased DEX-induced GILZ inhibited the activation of several
members of the MAPK-ERK pathway. We found that DEX
inhibited the phosphorylation of Raf-1, Mek1/2, and Erk1/2 (P
,0.05, compared with the non-specific si-RNA group), which was
not observed in cells in which GILZ expression was silenced (P
.0.05, compared with the non-specific si-RNA group), and the
amount of total Raf-1, Mek1/2, and Erk1/2 proteins was
unchanged (Figure 3). These data indicated that expression of
GILZ is involved in the activation of the MAPK-ERK signaling
GILZ mediated DEX to inhibit proliferation and migration
of 9HTE cells
We examined the effect of DEX on cell proliferation using an
MTT assay. We found that DEX inhibited cell proliferation (P
,0.05, compared with the non-specific si-RNA group), which was
overcome by downregulation of GILZ using GILZ si-RNA (P
.0.05, compared with the non-specific si-RNA group; Figure 4A).
We labeled cells using CFSE and found that when treated with
DEX, cells exhibited less proliferation compared with those in the
non-specific si-RNA group. However, the percentage of cell
proliferation was higher in those cells in which the GILZ gene was
silenced (Figure 4B).
The wound-healing assay showed that 24 h after wounding
DEX treatment inhibited wound closure relative to the
nonspecific si-RNA group (P ,0.05; Figure 5A), and the wound width
decreased in cells where the GILZ gene was silenced.
We further detected cell migration using transwell assays. We
found that, compared with the non-specific si-RNA group, fewer
cells migrated in the DEX group (P ,0.001; Figure 5B), but
migration was recovered in GILZ si-RNA-transfected cells. The
GILZ si-RNA group overcame the inhibitory effect of DEX and
there was no statistical difference compared to the non-specific
siRNA group (Figure 5B). The results suggested that DEX, acting
through its effect on GILZ, inhibited proliferation and migration
of 9HTE cells.
Although GCs are one of the most effective therapies for
asthma, in vitro studies indicate that GCs inhibit repair of airway
epithelial cells. GCs, which are involved in a variety of
physiological processes, have proved highly effective in gaining a
therapeutic response from most asthmatics, by suppressing
inflammation and relieving or preventing symptoms [27,28].
Despite these effects GCs are still not able to fully reverse the
damage done to airway epithelium. The failure of appropriate
growth and differentiation of airway epithelial cells will cause
persistent injury .
The repair of airway epithelium is mainly regulated through the
proliferation and migration of neighboring cells around the
damaged area. Currently, details of the mechanisms by which
GCs inhibit the repair of airway epithelial cells remain unclear.
Figure 3. Differential expressions of components of the MAPK-ERK pathway in non-specific si-RNA, DEX-treated/non-specific
siRNA, and DEX-treated/GILZ si-RNA-transfected 9HTE cells. Cellular proteins were collected from 9HTE cells transfected with non-specific
siRNA or GILZ si-RNA in the absence or presence of DEX for 24 h. Western blot was performed to detect levels of the phosphorylated forms of Raf-1,
Mek1/2, and Erk1/2, and the respective total proteins (p-Raf-1, p-Mek1/2, p-Erk1/2: 0.93560.056, 0.96560.042, 0.95960.052 in the non-specific si-RNA
group compared with 0.57460.143, 0.69460.145, 0.71260.066 in the DEX-treated/non-specific si-RNA group, compared with 0.86160.087,
0.84960.067, 0.84060.061 in the DEX-treated/GILZ si-RNA group, n = 3). *Indicates a significant difference (P,0.05), b-actin was used as the loading
RNA group, *P,0.05, n = 3). (B) 9HTE cells were labeling with CFSE and the CFSE fluorescence intensity was measured by flow cytometry
(6.46861.463 in the non-specific si-RNA group and 5.23360.970 in the DEX-treated/GILZ si-RNA group compared with 2.76560.539 in the
DEXtreated/non-specific si-RNA group, *P,0.05, n = 4).
The gene GILZ was originally discovered in studies aimed at
characterizing genes targeted by DEX. The persistence of the
GILZ gene and GILZ protein depends on the continuous presence
of DEX, which is induced in airway epithelial cells and has an
important regulatory role in the asthmatic airway .
Recently, detailed studies of the functions of GILZ have
revealed some features for this molecule: GILZ binds to Raf-1,
which is considered the most important prerequisite responsible
for the inhibition of the phosphorylation of downstream Mek1/2
and Erk1/2, and inhibits the activation of the MAPK-ERK
signaling pathway, which has an important role in controlling cell
survival, apoptosis, proliferation, migration, and differentiation
. Therefore, we hypothesized that the activities of GCs that
influence the repair of the airway epithelium may be mediated by
In the current study, we investigated the expression and
function of GILZ in human airway epithelial cells. Studies have
shown that GCs rapidly upregulated the expression of GILZ in T
lymphocytes, multiple myeloma cells, mesenchymal stem cells, and
human airway epithelial cells, among others [11,16,30,31]. Our
results suggested that GILZ was not only upregulated by DEX but
was also rapidly induced in airway epithelial cells. We also
demonstrated that DEX inhibited the phosphorylation of Raf-1
and the downstream Mek1/2 and Erk1/2, and inhibited
proliferation and migration. We used si-RNA technology to
knockdown GILZ levels and investigated whether the inhibition of
airway epithelial repair imposed by DEX was mediated by GILZ.
Interestingly, silencing GILZ blocked the inhibitory effect of DEX
on the MAPK-ERK signaling pathway. We also observed that the
DEX-mediated decrease in proliferation and migration was due in
part to the activation of GILZ in human airway epithelial cells.
Altogether, our findings imply that the expression of GILZ is
involved in the inhibitory effect that DEX exerts on the repair of
airway epithelium. Studies have reported that the asthmatic
airway epithelium showed evidence of damage, loss, and shedding
to various degrees even after GCs treatment. Our results suggest
that DEX, acting in part via GILZ, inhibited the repair of airway
epithelium by suppressing cell proliferation and migration.
Figure 5. GILZ mediated the inhibiting effect of DEX on migration of 9HTE cells. (A) Wound sites (area cleared of cells in the center of the
scraped area) were observed and photographed. Photographs showed the repair of the wound in the three groups. (0.82760.080 in the non-specific
si-RNA group compared with 0.91860.045 in the DEX-treated/non-specific si-RNA group, *P,0.05, n = 3). (B) 9HTE cell migration was examined by
transwell chamber and counted under a microscope in five randomly chosen fields of each group, three independent experiments (97.066615.448 in
the non-specific si-RNA group and 87.266612.876 in the DEX-treated/GILZ si-RNA group compared with 69.733612.572 in the
DEX-treated/nonspecific si-RNA group, **P,0.001 and *P,0.05, n = 3).
GILZ, a protein ubiquitously expressed and induced mainly by
GCs, regulates the cell cycle, apoptosis, proliferation, and
differentiation . GILZ has an anti-inflammatory function; it
modulates the activation of the MAPK-ERK signaling pathway
and inhibits proliferation and migration, thereby influencing the
repair of airway epithelium. GCs are widely prescribed
antiinflammatory drugs and most effective treatment available for
asthma, but the negative influence on airway epithelial repair
should not be ignored. In this study we found that one of the
effects of GCs on the airway epithelium was the induction of GILZ
expression, and that part of the reason for the inhibition of
epithelial repair by GCs was the suppression of the MAPK-ERK
signaling pathway and proliferation and migration. Together,
these results have important implications for understanding the
physiopathological role and function of GCs in the airway
Contributed to the idea and directed the research: CN ZXL JHD EML.
Conceived and designed the experiments: JYL MXZ ZF. Performed the
experiments: JYL LJW. Analyzed the data: JYL. Contributed reagents/
materials/analysis tools: ZF. Wrote the paper: JYL ZF.
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