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*
Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, Genova, Italy;
Institut National de la Santé et la Recherche Médicale, Unité 468, Service de Biochimie et Génétique, Hôpital Henri Mondor, Créteil, France; and
Laboratorio di Patologia Molecolare, Centro Regionale Fibrosi Cistica, Verona, Italy
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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. RT-PCR
experiments show that IL-4 elicits a 7-fold decrease in the level of
the 
amiloride-sensitive Na+ channel mRNA, one of the
subunits of the amiloride-sensitive Na+ channel, and an
increase in CFTR mRNA. Our data suggest that IL-4 may favor the
hydration of the airway surface by decreasing Na+
absorption and increasing Cl- secretion. This could be
required to fluidify the mucus, which is hypersecreted during
inflammatory conditions. On the other hand, the modifications of ion
transport could also affect the ion composition of airway surface
fluid. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, 
, and ), is
responsible for Na+ and consequently fluid
absorption. The important physiological role of ENaC is demonstrated by
the finding that -ENaC knockout mice die at birth because they are
unable to reabsorb the fluid that fills the airways (2).
Furthermore, patients affected by pseudohypoaldosteronism, due to
mutations impairing ENaC function, are affected by poor fluid
absorption in the airways (3). In the presence of a
favorable gradient, e.g., when ENaC is blocked with amiloride,
Cl- may be secreted through anion channels such
as cystic fibrosis transmembrane conductance regulator (CFTR) and
Ca2+-dependent Cl-
channels. Mutations to CFTR, which occur in cystic fibrosis (CF)
patients, result in defective Cl- transport and
increased Na+ absorption (4, 5).
These abnormalities cause impaired mucociliary clearance and eventually
lead to chronic colonization of the airways by bacteria resistant to
antibiotic treatment. The pathogenetic mechanism is controversial and
could involve excessive fluid absorption or increased salt
concentration in the airways surface fluid (6, 7, 8, 9).
Recent studies indicate that inflammatory cytokines may affect
transepithelial ion transport. We showed that IFN- causes marked
changes in Na+, Cl-, and
fluid transport in the bronchial epithelium (10).
Furthermore, the expression of CFTR is modulated by IFN-, TNF-,
and IL-1 in intestinal epithelial cells (11, 12, 13). These
findings suggest that the inflammatory state might affect the airway
ion transport in vivo. IL-4 has a particular pathogenetic role in the
lung. Actually, the pathology associated with asthma seems to be
mediated by CD4+ T lymphocytes, which produce the
type 2 cytokines IL-4 and IL-5. IL-4 is increased in the airways of
asthmatic subjects (14, 15), and mice deficient for
Stat-6, the transcription factor that mediates IL-4 effects, fail to
develop airway hyper-responsiveness upon Ag sensitization and challenge
(16). These animals also lack Th2 response and mucus
hypersecretion, all features found in asthma. In addition, the mucus
hypersecretion characteristic of the Th2 response requires an intact
IL-4R, the receptor for IL-4 and IL-13 (17). Finally,
IL-4 directly induces mucin gene expression and goblet cell metaplasia
(18, 19). Given its importance in lung pathology, we asked
whether IL-4 is also able to modify transepithelial ion transport as
found for IFN-. Indeed, in other studies it has been shown that
these two cytokines may have synergistic effects on important processes
in the airways (20, 21). In this study we show for the
first time that IL-4 markedly alters the ion transport properties of
the cultured bronchial epithelium. The effects only partially resemble
those produced by IFN- and suggest a role for IL-4 in increasing
Cl- and fluid secretion.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Human bronchial and nasal epithelial cells were subcultured as
previously described (22, 23). To obtain polarized
epithelia, cells were plated at high density on Transwell-CLEAR or
Snapwell permeable supports (Corning Costar, Cambridge, MA) that had
diameters of 24 and 12 mm, respectively. The medium under these
conditions contained 2% FBS (Fetal Clone II; HyClone, Logan, UT) and
various hormones and supplements as indicated previously (22, 23). With respect to previous studies we kept the cells on
permeable supports for more days (8–12 days) before performing ion
transport measurements. This allowed a more complete differentiation as
indicated by the development of larger short circuit currents and lower
resistance (1205 ± 31 
/cm2;
n = 49) and by the presence of cilia (not shown).
Experiments were performed on bronchial cells obtained from two non-CF
subjects and from one F508del homozygous CF patient. Epithelial
monolayers were also prepared from nasal polyps of two non-CF subjects
and one F508del homozygous CF patient. Furthermore, we also conducted a
conventional primary culture (23) by directly plating the
cells obtained from a non-CF nasal polyp on Snapwell filters without
subculturing.
Ussing chamber experiments
The permeable supports were mounted in Ussing chamber-like systems: Trans-24 miniperfusion system (World Precision Instruments, Sarasota, FL) for Transwell cups and Vertical Diffusion Chamber (Corning Costar) for Snapwell inserts. The apical and basolateral chambers were filled with Krebs bicarbonate solution that contained: 126 mM NaCl, 0.38 mM KH2PO4, 2.13 mM K2HPO4, 1 mM MgSO4, 1 mM CaCl2, 24 mM NaHCO3, and 10 mM glucose. The solution was bubbled in each chamber with 5% CO2-95% air. Experiments were performed at 37°C. The transepithelial potential difference was short circuited with a voltage clamp (558-C5; Department of Bioengineering, University of Iowa, Iowa City, IA) connected to the apical and basolateral chambers via Ag-AgCl electrodes and agar bridges. The potential difference and fluid resistance between potential-sensing electrodes were compensated.
The data presented to show the effect of cytokines on short circuit current were essentially obtained using Snapwell inserts. Given their large surface, Transwell inserts were used to provide enough cells for RNA extraction. However, Ussing chamber experiments were also performed with Transwell filters to ensure that the effect of cytokine was the same as in Snapwell.
RNA extraction
Total RNA was isolated by lysing the cells onto filters with the
TRIzol reagent (Life Technologies, Gaithersburg, MD) following the
manufacturer’s instructions. RNA purity was checked by
spectrophotometer
(OD260/OD280 
1.7) and
electrophoresis and stored at -80°C until used. The RNA was
processed at the Gaslini Institute for the semiquantitative assay of
ENaC subunits or was sent to the other laboratories for the
quantitative RT-PCR determinations of CFTR (Créteil, France) or
EnaC (Verona, Italy).
Quantitation of ENaC subunits by semiquantitative RT-PCR
Total RNA was retrotranscribed using the Advantage RT for PCR
kit (Clontech, Palo Alto, CA). Two microliters of each cDNA were
serially diluted 1/1 in buffer to obtain dilutions down to 1/64. Then 2
µl of each dilution was amplified in a 25-µl reaction containing
0.625 U AmpliTaq Gold, 2 mM MgCl2, 15 pmol of
each primer, and 200 µM dNTPs. The forward primer was labeled with
fluorescent amidite (6FAM). The amplification conditions were 45 s
at 95°C, 45 s at 55°C, and 45 s at 72°C. The numbers of
cycles were 27, 30, 35, and 25 for ENaC, ENaC, ENaC, and
-actin, respectively. The primers used are shown in Table I
.
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-actin obtained for each sample.
Quantitation of ENaC mRNA by competitive RT-PCR
The single-tube competitive RT-PCR technique previously
described (24) was applied by using oligonucleotide
primers designed from the human ENaC gene sequence
(25), as reported in Table I
. The homologous competitor
for human ENaC mRNA (cEnaC) was obtained by RT of total RNA from
human bronchial epithelial cells with primer ENaC-R1, followed by
amplification with primers ENaC-D1 and ENaCD*, which generated
a 7-bp deletion with respect to the wild-type sequence.
RT of 200 ng total RNA was performed with primer ENaC-R1, followed
by two amplification runs in the presence of known amounts of cEnaC.
Primers for PCR-1 were ENAC-D2 and ENaC-R1 for PCR-2 ENaC-D2
and ENaC-R2. The amplification conditions for PCR-1 and PCR-2 were
85°C for 5 min, then 30 cycles at 94, 56, and 72°C for 30 s.
The run-off reaction (26) was conducted with the
fluorescent primer ENaC-R3-TAMRA (one cycle of 94, 56, and 72°C
for 30 s each). Run-off reaction product (2 µl) was run in a PE
Biosystems 373A DNA sequencer. The peak area of fluorescent PCR
fragments corresponding to competitor and endogenous ENaC mRNA was
measured using GeneScan 672 software (PE Applied Biosystems). The ratio
of competitor over endogenous areas was plotted vs the number of copies
of competitor and fitted to a quadratic equation. ENaC mRNA copies
were taken as those corresponding to the equivalence between the areas
of the competitor and the endogenous transcript.
Quantitative determination of CFTR transcript
The expression of CFTR was determined using the competitive multiplex RT-PCR employing the transcription factor IID (TF IID) as the endogenous mRNA. Total RNA (1 µg) was reverse transcribed using Superscript II reverse transcriptase and random hexamers (Life Technologies, Cergy-Pontoise, France). The internal standards (competitors) for both CFTR and TF IID mRNA, were generated by the QuikChange site-directed mutagenesis technique using the full-length CFTR and TF IID cDNA cloned in the pBluescript phagemid vector (Stratagene, Amsterdam Zwidoost, The Netherlands), as template. The competitor for CFTR (pCFTRIS) had a 21-bp deletion, whereas that for TF IID (pTF IIDIS) contained a 12-bp insertion with respect to the wild-type sequences. RNA competitors were produced by in vitro transcription of these mutant plasmids with T7 RNA polymerase (Megascript kit, Ambion, Austin, TX). The competitive PCR reactions were performed with two pairs of 21-mer oligonucleotide primers purchased from Genset (Paris, France). CFTR and TF IID 5' primers were labeled with 6-carboxyfluorescein and tetrachloro-6-carboxyfluorescein, respectively. The CFTR primer set generated exon products of 457 and 436 bp in length using target and competitor CFTR cDNA as template, respectively. The primer set for TF IID generated exon products of 260 and 272 bp from target and competitor TF IID cDNA.
An aliquot (1/20 vol) of RT reaction was amplified by competitive multiplex PCR in a 25-µl reaction volume of master mix PCR containing 0.2 µM of both CFTR and TF IID primers, 10 µl of serial dilutions (1/10) of a mixture of the competitors pCFTRIS (2 x 10-3 ng/µl) and pTF IIDIS (2 x 10-2 ng/µl), and Taq DNA polymerase (Life Technologies). PCR conditions were 94°C for 4 min; 34 cycles of 94°C for 30 s, 55°C for 45 s, and 72°C for 1.5 min; and a final extension cycle of 94°C for 30 s, 55°C for 45 s, and 72°C for 5 min. To determine the amounts of amplified products, assays were performed in triplicate using six serial dilutions of competitors against a constant amount of reverse transcribed RNA. Triplicates were pooled, and the fluorescent dye-labeled PCR products were analyzed on a 377A ABI DNA sequencer for peak color, fragment size, and peak area using GeneScan 672 Fragment Analysis software (PE Applied Biosystems). The ratio of CFTR area to its competitor provided the basis of CFTR mRNA quantification. The amount of competitor corresponding to a 1/1 ratio is equivalent to the amount of target mRNA. TF IID mRNA content was simultaneously measured in the same way. Quantification of CFTR message was expressed as the CFTR/TF IID ratio. For each RNA sample three or four independent RT reactions were performed, and two independent PCR reactions were performed for each RT.
Statistics
Results are presented as the raw data or the arithmetic mean ± SEM. Statistical significance was determined with Student t test for unpaired data.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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). Under resting
conditions, this process is largely accounted for by the activity of
ENaC. Therefore, we applied 10 µM amiloride in the apical solution to
evaluate the activity of the Na+ channel in
control and cytokine-treated cells. As expected, amiloride caused a
fast reduction of short circuit current. However, there was a clear
quantitative difference between control and treated cells (Fig. 1, A and B). Indeed, the amiloride-sensitive current
(Iamil) underwent a 84% decrease upon cell
incubation with IL-4 (from 21.0 ± 1.2 (n = 39) to
3.1 ± 0.6 µA/cm2 (n =
12); p < 0.001). Amiloride-treated airway epithelia
can secrete Cl- if stimulated with cAMP- or
Ca2+-elevating agents. We asked whether
Cl- transport was also affected by IL-4
incubation. Therefore, we acutely stimulated bronchial epithelia with
8-(4-chlorophenylthio)adenosine (CPT)-cAMP, a
membrane-permeable cAMP analog that activates CFTR. CPT-cAMP was
applied simultaneously in the apical and basolateral solutions at 500
µM. Previous studies showed that this is the concentration that
produces maximal CFTR activation. In control cells CPT-cAMP elicited a
stable increase in short circuit current that reached a value of
13.7 ± 1.5 µA/cm2 (n =
28; Fig. 1, A and D). Cells treated with IL-4 (10
ng/ml) for 48 h showed a cAMP-dependent current
(IcAMP) that was more than twice that measured in
untreated cells (33.5 ± 5.2 µA/cm2;
n = 9; p < 0.001; Fig. 1, B
and D). This finding suggested that IL-4 leads to increased
CFTR activity. However, we wondered whether IL-4 was eliciting the
appearance of another cAMP-dependent ion transport distinct from CFTR.
Therefore, we used IL-4 to treat bronchial cells obtained from a CF
patient homozygote for F508del, a mutation that prevents most of CFTR
protein to be correctly targeted to the plasma membrane. As expected
for a process dependent on functional CFTR, the
IcAMP measured in CF cells was very small even
after IL-4 treatment (compare Fig. 1 and Fig. 2). Cytokine-treated CF cells showed an
IcAMP of only 1.02 ± 0.21
µA/cm2 (n = 9). Although this
value was small, it was significantly higher (p
< 0.01) than the current measured in untreated CF cells (0.18 ±
0.03 µA/cm2; n = 8). IL-4 also
inhibited Na+ transport in CF cells; the
Iamil was only 12.6 ± 4.9% of that in
untreated cells (n = 12; p <
0.01).
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). This current
(IUTP) peaked after 1 min of UTP application and
then returned to prestimulation levels in 15–20 min. Cells treated
with IL-4 (10 ng/ml for 48 h) responded to UTP with a higher
current amplitude (Fig. 3); the peak was 31.1 ± 1.8
µA/cm2 (n = 8;
p < 0.001). Despite this large response, the current
deactivated in a way similar to that of untreated cells. CF cells also
showed an increased response to UTP when treated with IL-4; the
amplitude of IUTP was up-regulated by >10-fold
(1245 ± 151% with respect to untreated cells; n
= 9; p < 0.001). It is interesting to note that
IUTP up-regulation was significantly stronger
than that in non-CF cells (p < 0.05). A
similar difference was previously observed for IFN-
(10).
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We asked whether the effects of IL-4 were a result of the subculture procedure that we used for nasal and bronchial cells. Therefore, we studied nasal epithelial cells using a conventional primary culture protocol in which the cells are directly plated on permeable supports after proteolytic dissociation (23). Although this procedure usually gives short circuit currents larger than those in subcultured cells, IL-4 had the same effect in relative terms. Iamil decreased from 40.3 ± 8.3 to 2.5 ± 0.85 µA/cm2 (p < 0.01), IcAMP increased from 52.5 ± 2.3 to 94.5 ± 3.5 µA/cm2 (p < 0.01), and IUTP increased from 3.9 ± 1.1 to 17.5 ± 1.4 µA/cm2 (p < 0.01; n = 3 for all conditions).
We tested IL-4 at different concentrations. The usual concentrations
that have been used in vitro range from 10 to 100 ng/ml (18, 20, 21). Our results show that 1 ng/ml was sufficient to produce
maximal effects on Iamil,
IcAMP, and IUTP (Fig. 4). A steep change was observed at
concentrations between 0.1 and 1 ng/ml. This behavior of the
dose-response curve could reflect positive cooperativity of IL-4. We
also determined the time dependence. Interestingly, at 6 h,
Iamil and IUTP, but not
IcAMP, showed a significant change. However,
nearly maximal effects were observed for the three types of currents
after 24 h of treatment and remained stable for 48 h (Fig. 5).
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, , and subunit
expression. IL-4 acts mainly on the ENaC, causing a 7-fold decrease
in its mRNA (Fig. 6). The amount of
subunit is also significantly decreased by 50%. On the contrary,
subunit expression is not affected by IL-4. To confirm the effect of
IL-4 on ENaC we performed a quantitative competitive RT-PCR. In
control cells we found 5040 ± 226 copies of ENaC mRNA/µg
total RNA (n = 3). In IL-4-treated cells the content of
this mRNA decreased to 700 ± 141 copies/µg (n =
3; p < 0.01). We also determined the effect of
IFN-, since we previously showed that this cytokine inhibits ENaC
activity in bronchial epithelial cells (10). In contrast
to IL-4, IFN- does not significantly affect the expression of any of
the ENaC subunits (Fig. 6).
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),
which is consistent with the increase in IcAMP
measured in treated cells (Fig. 1). The effect of TNF-, another
cytokine found to markedly increase CFTR protein expression
(10), was also evaluated. Our RT-PCR data confirm previous
results obtained at the protein level by showing a 12-fold increase in
CFTR mRNA in TNF--treated cells (Fig. 7).
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A). The
receptor for IL-4 has a subunit (IL-4R) that is also shared by a
receptor for IL-13 (27). We tested the involvement of
IL-4R using a mutated IL-4 (R121D, Y124D), which retains binding to
the receptor but has lost its ability to induce the signal
(28). This antagonist was used at 1 µg/ml in the
presence of 1 ng/ml IL-4. As shown in Fig. 8B, the activity
of IL-4 was significantly inhibited by the IL-4R antagonist.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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down-regulates CFTR and ENaC activity
in human bronchial epithelial cells, whereas, on the other hand, it
significantly up-regulates Ca2+-dependent
Cl- secretion (10). Down-regulation
of Na+ absorption may eventually favor hydration
of mucous secretions. However, the physiological meaning of CFTR
inhibition is less clear. In this study we have investigated the
effects of another cytokine, IL-4, which is involved in the humoral Th2
immune response. In a way similar to IFN-, IL-4 also decreases ENaC
activity. However, the mechanism seems markedly different. Indeed, IL-4
strongly decreases the mRNA levels of ENaC and, to a lesser extent,
that of the subunit. On the contrary, IFN- does not seem to
affect ENaC expression. Therefore, its inhibitory effect on
Na+ absorption has to involve another mechanism.
ENaC activity is controlled by several mechanisms, such as the
ubiquitination by Nedd4 (29), carboxylmethylation
(30), and proteolysis (31). Any of these
processes could be the one that is affected by IFN-. It is not
surprising to find that only one of the ENaC subunits is markedly
down-regulated by IL-4. There are already examples of independent
regulation of ENaC subunits in a tissue-specific way. For example, in
mouse kidney aldosterone increases by 2- to 3-fold the expression of
ENaC, while changes in and subunits are small
(32). On the contrary, in rat distal colon aldosterone
enhances the expression of - and ENaC, whereas the subunit is
unchanged or decreased (33).
In contrast to IFN-, IL-4 up-regulates the cAMP-dependent current.
According to RT-PCR data this effect can be explained by an increase in
the level of CFTR mRNA. The involvement of CFTR in the IL-4 effect is
also confirmed by the fact that cells obtained from a F508del CF
patient do not show a similar increase in cAMP-dependent current in
absolute terms. Therefore, we can exclude an up-regulation of an
alternative cAMP-activated channel. However, on a relative basis, CF
cells showed a more than a doubling of the cAMP-dependent current upon
treatment with IL-4. It is possible that this effect is due to the
increase in the mutant CFTR that reaches the membrane. Actually,
F508del is a mutation that causes CFTR to be trapped in the endoplasmic
reticulum, but it is believed that a small fraction of the mutant
protein may escape cell quality control systems (34, 35).
Although statistically significant, the CFTR-dependent current measured
in IL-4-treated CF cells is quite small and at the limit of the
threshold estimated to be required for a normal phenotype (i.e.,
5–10% of wild-type function) (36). However, elucidation
of regulatory mechanisms underlying the IL-4 effect may reveal novel
ways to up-regulate CFTR in CF cells to therapeutic levels. In this
respect it is worth noting that TNF- promotes a larger increase in
CFTR mRNA levels. This effect is consistent with the 9-fold increase in
CFTR protein observed previously in our laboratory (10).
However, for reasons that are currently unclear, this dramatic increase
is not paralleled by a significant up-regulation of chloride transport.
One may speculate that TNF-, besides increasing CFTR levels, is also
evoking post-transcriptional or post-translational changes that limit
its activity. We have no data to determine whether the lack of
increased Cl- transport is due to altered CFTR
channel at the plasma membrane or to intracellular localization of the
channels. Future subcellular localization studies could help to clarify
this point.
As also observed for IFN-, IL-4 up-regulates the activity of
Ca2+-dependent Cl-
channels, as revealed by the strong increase in the current elicited by
apical UTP. However, there are important differences between the two
cytokines. Besides increasing the peak, IFN- also prolongs the
UTP-evoked current (10). This effect is not observed in
IL-4-treated cells. Furthermore, 48 h of IFN- treatment are
required to observe the increase in the UTP-dependent response, whereas
IL-4 begins to be effective after only 6 h. The molecular basis of
UTP-dependent current up-regulation is unknown and could involve the
hyperexpression of Ca2+-activated
Cl- channels, changes in channel regulators, or
up-regulation of purinergic receptors.
We found that IL-13 has the same effects as IL-4 on
Na+ and Cl- transport in
bronchial epithelium. This is not surprising, since these two cytokines
often share signaling cascades and receptor subunits such as IL-4R
(27). Indeed, this chain combines with the common
-chain protein to form a specific IL-4 receptor or with IL-13R1
to generate a receptor common to IL-4 and IL-13. The inhibitory effect
of a specific antagonist (28) suggests that the IL-4R
subunit is involved in the modulation of ion transport by IL-4 and
possibly IL-13 in airway epithelial cells. However, we cannot exclude
that IL-13 could also be acting through a specific IL-13R
(27). The regulatory steps downstream from the receptor
have not been elucidated. This cascade could be restricted to the
intracellular milieu and involve protein kinases, transcription
factors, and other regulatory proteins. Additionally, it could be based
on the release of soluble factors (e.g., chemokines) that would act in
an autocrine fashion.
Our study shows that IL-4 is able in vitro to down-regulate Na+ transport and, on the other hand, to increase the activity of Cl- channels. However, it has to be considered that the response in vivo can be modified by the presence of other cytokines and soluble mediators and by the interactions of epithelial cells with recruited leukocytes. We can speculate that in vivo IL-4 may favor Cl- and fluid secretion, thus leading to increased hydration of mucous secretions and improved clearance of airway surface. It is worth noting that IL-4 is responsible for mucus hypersecretion from goblet cells (18, 19). Therefore, the changes in ion transport observed in our study could be instrumental to help mucus clearance. However, it has to be considered that another model proposed to explain the role of ion transport in the airway epithelium postulates that a low salt concentration is required to maintain the defensin activity (8). Considering this model, IL-4 could alter the bactericidal properties of periciliary fluid.
The elucidation of the mechanisms underlying cytokine-dependent ion transport modification may help to design novel strategies for the fluidification of mucus secretions and the treatment of chronic pulmonary diseases.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Luis J. V. Galietta, Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, 16148 Genova, Italy. E-mail: galietta{at}unige.it
3 Abbreviations used in this paper: ENaC, amiloride-sensitive Na+ channel; CF, cystic fibrosis; CPT, 8-(4-chlorophenylthio)adenosine; CFTR, cystic fibrosis transmembrane conductance regulator; IcAMP, cAMP-dependent current; TF IID, transcription factor IID.
Received for publication April 30, 2001. Accepted for publication October 22, 2001.
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A. Dagenais, R. Frechette, M.-E. Clermont, C. Masse, A. Prive, E. Brochiero, and Y. Berthiaume Dexamethasone inhibits the action of TNF on ENaC expression and activity Am J Physiol Lung Cell Mol Physiol, December 1, 2006; 291(6): L1220 - L1231. [Abstract] [Full Text] [PDF]
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 I. C. Davis, E. R. Lazarowski, J. M. Hickman-Davis, J. A. Fortenberry, F.-P. Chen, X. Zhao, E. Sorscher, L. M. Graves, W. M. Sullender, and S. Matalon Leflunomide Prevents Alveolar Fluid Clearance Inhibition by Respiratory Syncytial Virus Am. J. Respir. Crit. Care Med., March 15, 2006; 173(6): 673 - 682. [Abstract] [Full Text] [PDF]
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G. Candiano, M. Bruschi, N. Pedemonte, E. Caci, S. Liberatori, L. Bini, C. Pellegrini, M. Vigano, B. J. O'Connor, T. H. Lee, et al. Gelsolin Secretion in Interleukin-4-treated Bronchial Epithelia and in Asthmatic Airways Am. J. Respir. Crit. Care Med., November 1, 2005; 172(9): 1090 - 1096. [Abstract] [Full Text] [PDF]
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 J. Roux, H. Kawakatsu, B. Gartland, M. Pespeni, D. Sheppard, M. A. Matthay, C. M. Canessa, and J.-F. Pittet Interleukin-1{beta} Decreases Expression of the Epithelial Sodium Channel {alpha}-Subunit in Alveolar Epithelial Cells via a p38 MAPK-dependent Signaling Pathway J. Biol. Chem., May 13, 2005; 280(19): 18579 - 18589. [Abstract] [Full Text] [PDF]
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A. Dagenais, R. Frechette, Y. Yamagata, T. Yamagata, J.-F. Carmel, M.-E. Clermont, E. Brochiero, C. Masse, and Y. Berthiaume Downregulation of ENaC activity and expression by TNF-{alpha} in alveolar epithelial cells Am J Physiol Lung Cell Mol Physiol, February 1, 2004; 286(2): L301 - L311. [Abstract] [Full Text] [PDF]
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 L. J. V. Galietta, C. Folli, E. Caci, N. Pedemonte, A. Taddei, R. Ravazzolo, and O. Zegarra-Moran Effect of Inflammatory Stimuli on Airway Ion Transport Proceedings of the ATS, January 1, 2004; 1(1): 62 - 65. [Abstract] [Full Text] [PDF]
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 D. Miotto, M.P. Ruggieri, P. Boschetto, G. Cavallesco, A. Papi, I. Bononi, C. Piola, B. Murer, L.M. Fabbri, and C.E. Mapp Interleukin-13 and -4 expression in the central airways of smokers with chronic bronchitis Eur. Respir. J., October 1, 2003; 22(4): 602 - 608. [Abstract] [Full Text] [PDF]
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H. C. Atherton, G. Jones, and H. Danahay IL-13-induced changes in the goblet cell density of human bronchial epithelial cell cultures: MAP kinase and phosphatidylinositol 3-kinase regulation Am J Physiol Lung Cell Mol Physiol, September 1, 2003; 285(3): L730 - L739. [Abstract] [Full Text] [PDF]
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R. Schafer, F. Sedehizade, T. Welte, and G. Reiser ATP- and UTP-activated P2Y receptors differently regulate proliferation of human lung epithelial tumor cells Am J Physiol Lung Cell Mol Physiol, August 1, 2003; 285(2): L376 - L385. [Abstract] [Full Text] [PDF]
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E. Caci, C. Folli, O. Zegarra-Moran, T. Ma, M. F. Springsteel, R. E. Sammelson, M. H. Nantz, M. J. Kurth, A. S. Verkman, and L. J. V. Galietta CFTR activation in human bronchial epithelial cells by novel benzoflavone and benzimidazolone compounds Am J Physiol Lung Cell Mol Physiol, July 1, 2003; 285(1): L180 - L188. [Abstract] [Full Text] [PDF]
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K. B. Madden, L. Whitman, C. Sullivan, W. C. Gause, J. F. Urban Jr., I. M. Katona, F. D. Finkelman, and T. Shea-Donohue Role of STAT6 and Mast Cells in IL-4- and IL-13-Induced Alterations in Murine Intestinal Epithelial Cell Function J. Immunol., October 15, 2002; 169(8): 4417 - 4422. [Abstract] [Full Text] [PDF]
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