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*
Department of Medicine and Therapeutics, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom; and
Institut National de la Santé et de la Recherche National, Unité 437, Nantes, France
| Abstract |
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and TNF. Ad-IL4-transfected macrophages localized with enhanced
efficiency to inflamed glomeruli after renal artery injection in rats
with NTN compared with adenovirus expressing
-galactosidase
(Ad-
gal)-transfected macrophages and produced elevated levels of the
cytokine in glomeruli in vivo for up to 4 days. The delivery of
IL-4-expressing macrophages produced a marked reduction in the severity
of albuminuria (day 2 albuminuria, 61 ± 15 mg/24 h) compared with
unmodified NTN (day 2 albuminuria, 286 ± 40 mg/24 h;
p < 0.01), and this was matched by a reduction in
the number of ED1-positive macrophages infiltrating the glomeruli.
Interestingly, the injection of IL-4-expressing macrophages into single
kidney produced a marked reduction in the numbers of ED1-positive
macrophages in the contralateral noninjected kidney, an effect that
could not be mimicked by systemic delivery of IL-4-expressing
macrophages. This implies that the presence of IL-4-expressing
macrophages in a single kidney can alter the systemic development of
the inflammatory response. Macrophage transfection and delivery provide
a valuable system to study and modulate inflammatory disease and
highlight the feasibility of macrophage-based gene
therapy. | Introduction |
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We have previously shown that rat macrophages, both cell lines and
primary cultures, can be transfected with recombinant adenovirus and
that these modified macrophages preferentially localized to inflamed
glomeruli of rats with nephrotoxic nephritis
(NTN),3 an
experimental model of glomerulonephritis (10).
Surprisingly, localization did not worsen injury and actually caused a
small reduction in the level of albuminuria. Transfection of
macrophages using recombinant adenoviruses could be used to deliver
macrophages with specific functions to areas of injury and provide a
more physiological approach to study the effects of cytokines in
inflammation. The responses of macrophages to pro- and
anti-inflammatory cytokines are well established, and macrophages
can be programmed by exposure to specific cytokines. For example, prior
stimulation with the anti-inflammatory cytokine such as IL-4 makes
macrophages unresponsive to proinflammatory cytokines, including
IFN-
and TNF (11). Thus, transfecting macrophages to
express specific cytokines might not only alter the secretory profile
of but also, their responses to other signals, and when these
transfected macrophages infiltrate the focus of inflammation they will
be able to affect surrounding cells involved in injury
(12). In a number of autoimmune disease models the
administration of exogenous IL-4 has been shown to reduce the severity
of injury, including experimental glomerulonephritis (13, 14), collagen-induced arthritis (15), and
experimental allergic encephalomyelitis (16). This makes
IL-4 an ideal candidate molecule to assess the efficacy of
macrophage-mediated gene therapy.
The purpose of the experiments in this paper was 1) to characterize the effect of transfection with adenovirus expressing rat IL-4 (Ad-IL4) on macrophage function and responses to proinflammatory cytokines; 2) to determine whether, after injection into the renal artery, Ad-IL4-transfected macrophages localize to inflamed glomeruli and synthesize IL-4 there; and 3) to analyze the effect of injection of these macrophages on glomerular injury in nephrotoxic nephritis in rats. The results show not only that macrophages transfected with Ad-IL4 localize to inflamed glomeruli, but that they reduce the severity of injury in rats with experimental glomerulonephritis. Surprisingly, the injury is reduced not only in the kidney into which the IL-4-expressing macrophages have been injected, but also in the contralateral kidney. This result cannot be explained by systemic leakage of IL-4 and suggests that cells transiting through glomerular inflammation in the context of high concentrations of IL-4 are able to down-modulate glomerular inflammation at a distant site. If confirmed, this would have profound implications for understanding the control of inflammation in general.
| Materials and Methods |
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The rat alveolar macrophage cell line NR8383 was obtained from American Type Culture Collection (Manassas, CA) and cultured in Hams F-12 (BioWhittaker, Walkersville, MD) with 100 U/ml penicillin, 100 µg/ml streptomycin, and 10% FCS (Sigma, Poole, U.K.). Rat bone marrow-derived cells were isolated and purified using our standard technique (11). All cells were cultured at 37°C with 5% CO2. Nephrotoxic serum was produced according to our standard protocol by immunizing rabbits with 1 mg of isolated rat glomeruli with CFA (Sigma) followed by four injections, each 2 wk apart, of 1 mg of glomerular Ags with IFA. Concentrations of IL-4 were assessed using a capture ELISA for IL-4 (PharMingen, San Diego, CA).
Recombinant adenoviruses and transfection
Ad-IL4 was constructed as previously described (17)
with control adenovirus provided by
-galactosidase expressing vector
(Ad-
gal) or Ad-dl312, a null adenovirus with no insert
(18). All adenoviruses were produced in 293 cells with
subsequent purification on cesium chloride gradient, dialysis against
10 mM Tris (pH 7.4) buffer with 10% (v/v) glycerol, and storage at
-70°C (19). Viral titer was determined by plaque assay
on 293 cells and expressed as PFUs, while the absence of replication
competent virus was confirmed by plaque assay on HeLa cells
(19). NR8383 rat alveolar macrophages were stimulated with
510% L929-conditioned medium containing M-CSF for 48 h before
transfection to up-regulate
v
3 integrins and
enhance transfection efficiency (20). Transfection was
performed in standard medium with 2% FCS as previously described
(10). Production of IL-4 by transfected macrophages into
tissue culture medium was assessed using a capture ELISA
(PharMingen).
Properties of transfected macrophages
The effect of transfection on generation of NO by NR8383 cells
and bone marrow-derived macrophages was assessed by nitrite
production, assayed using a Greiss reaction (11). In
brief, 48 h after transfection 200-µl aliquots of medium from
the cells were removed and incubated with 50 µl of Greiss reagent
(0.5% sulfanilamide and 0.05% N-(1-naphthyl)ethylendiamine
dihydrochloride in 2.5% phosphoric acid) in 96-well flat-bottom
culture plates for 10 min. The ODs of the assay samples were then
measured at 540 nm using a solution of phenol red-free DMEM. After
transfection macrophages were stimulated with 1020 ng/ml LPS (Sigma)
or IFN-
(Sigma; 1 U = 3 ng) and TNF (R&D Systems, Abingdon,
U.K.; 1 U = 3 ng), and the production of NO was assessed 24 h
later.
Nephrotoxic nephritis and in vivo delivery of macrophages
Male Sprague Dawley rats (weight, 200250 g) were purchased from Harlan (Bicester, U.K.). Rats were preimmunized with s.c. injection 1 mg of rabbit IgG (Sigma) in CFA. One week later the rats received an i.v. injection of 1 ml/200 g of rabbit nephrotoxic serum under halothane anesthesia (Zeneca, Macclesfield, U.K.). Transfected and nontransfected macrophages were labeled with red fluorescent membrane label, PKH-26GL (Sigma) as previously described (10) and harvested into serum-free medium immediately before injection. Labeled macrophages were injected directly into the renal artery 56 h after induction of NTN. This was performed by anesthetizing rats with fentanyl (Janssen-Cilag, High Wycombe, U.K.) and diazepam (Phoenix Pharmaceuticals, Gloucester, U.K.), performing a midline laparotomy, and isolating the left renal artery. A 27-gauge butterfly needle (Abbott, Dublin, Ireland) was inserted directly into the renal artery, the cells were injected over 12 min, and renal blood flow was re-established in <5 min. Animals were left for 17 days, and timed urine collections were made from metabolic cages. In specific experiments transfected NR8383 macrophages were injected into the tail vein or into the peritoneal space to compare the effect of route of delivery.
Glomerular visualization and culture
To enable visualization of the fluorescent macrophages within glomeruli, part of the renal tissue was sieved through 250- and 150-µm pore size sieves, and the glomeruli were collected on a 63-µm pore size filter. The isolated glomeruli were labeled with anti-rabbit IgG FITC (Sigma), which binds to rabbit IgG from the nephrotoxic serum deposited on the glomerular basement membrane. The whole glomeruli were visualized under fluorescent microscopy, and the number of PKH-26GL-positive fluorescent cells in 100 glomeruli was counted. Isolated glomeruli were also cultured in DMEM with 10% FCS, and the level of IL-4 produced over 48 h was measured.
Albuminuria and urinary IL-4
Timed urine collections were made, and the albumin concentration was determined using Rocket electrophoresis as previously described (10). Albuminuria was then calculated as the total albumin excreted over 24 h. In addition, the concentrations of IL-4 in urine and plasma were measured by ELISA.
Determination of alloreaction to transfected NR8383 cells
Although the NR8383 cell is derived from Sprague Dawley rats,
this is an outbred strain of rat, leading to the possibility of an
alloreaction. To assess this experimentally, MLR was performed with
splenocytes from rats immunized with transfected NR8383 cells. Rats
with NTN were injected with 6 x 106 NR8383
cells transfected with either Ad-
gal or Ad-IL4 (to assess whether
IL-4 expression altered any immune response). Rats were sacrificed 7
days later, and splenocytes were isolated and cultured in RPMI with 2%
FCS supplemented with 2-ME and L-glutamine (Life
Technologies, Paisley, Scotland). The MLR was set up against mitomycin
C (Sigma)-treated NR8383 cells transfected with Ad-dl312, and the
incorporation of [3H]thymidine was assessed on
days 25. Various dilutions of NR8383 cells were used (0.35 x
105 NR8383) with 1.5 x
106 splenocytes in 2 ml. A positive control was
provided by stimulation of splenocytes with 2 µg/ml Con A (Sigma),
and results were compared with splenocytes from rats that were not
injected with NR8383 cells.
Pathology
Sections of renal tissue were fixed in methyl carnoys and paraffin-embedded, and 3-µm sections were cut before hematoxylin-eosin staining. To assess the infiltration of glomerular tissue with macrophages, unstained sections were stained with ED1 Ab (Serotec, Kidlington, U.K.) and visualized using an alkaline phosphatase/anti-alkaline phosphatase technique with the slides counterstained with hematoxylin. The numbers of ED1-positive foci were counted in the glomeruli at x20 magnification using Leica Q-win software and were calculated per glomerular area (50,000 µm2). The slides were examined for histological markers of injury, including glomerular endothelial cell swelling and proliferation (scored 03), mesangial cell proliferation (scored 03), and necrosis (scored 02) by an observer blinded to the experimental protocol.
Statistics
Results are presented as the mean ± SE, and differences between groups of cells or animals were tested using paired t test.
| Results |
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Expression of IL-4.
The rat alveolar macrophage cell line NR8383 was transfected with
increasing doses of Ad-IL4 (0200 PFU/cell), and the concentration of
IL-4 in the medium was measured 48 h later by capture ELISA.
Macrophage viability, when assessed by trypan blue exclusion, was not
affected by the transfection procedure, but transfection with
increasing numbers of viral PFU resulted in a dose-dependent increase
in IL-4 secreted into the medium (Fig. 1
A). Similarly, large amounts
of IL-4 were secreted by rat bone marrow-derived macrophages
transfected with Ad-IL4 (data not shown). As expected, nontransfected
macrophages and macrophages transfected with Ad-
gal did not produce
IL-4. Thus macrophages can be transfected successfully with Ad-IL4, and
the next issue was to determine the effect of such transfection on
macrophage function, in particular their responses to proinflammatory
cytokines.
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and TNF-
. NR8383 macrophages were transfected with 200 PFU/cell of
Ad-IL4 or with a null adenovirus (Ad-dl312) at the same dose, and the
transduced cells were stimulated with either 20 pg/ml LPS or 20 U/ml of
both IFN-
and TNF 24 h after transfection. The quantity of NO
was assayed 24 h after stimulation and compared with that in
nontransfected macrophages. Stimulation of both nontransfected and
null-transfected NR8383 macrophages with LPS (20 ng/ml) or IFN-
(20
U/ml) and TNF-
(20 U/ml) greatly increased NO generation. However,
in NR8383 macrophages expressing IL-4 the NO response to both sets of
stimuli was significantly reduced (Fig. 1
alone (data not shown)
IL-4-expressing NR8383 macrophages have properties similar to
those of macrophages treated with exogenous IL-4; in particular, they
generated lower levels of NO when activated with LPS or IFN-
. This
is important because macrophages infiltrating inflamed glomeruli in
nephrotoxic nephritis behave operationally as though programmed by
IFN-
and TNF-
(21), and this provides the rationale
for examining the effect of Ad-IL4-transfected macrophages on injury in
this macrophage-dependent model of nephritis.
Ad-IL4-transfected macrophages localize efficiently to inflamed glomeruli
First it was important to determine how well IL-4-expressing
macrophages localize to inflamed glomeruli. NR8383 macrophages were
used for these experiments because the efficiency of transfection
exceeds 95% (10). Between 24 x
106 Ad-IL4-transfected IL4 NR8383 macrophages
were labeled with the red fluorescent membrane label PKH-26GL and
injected into the renal artery. Large numbers of fluorescent
IL-4-expressing NR8383 macrophages were identified within the glomeruli
24 h after injection of cells (Fig. 2
A). More than 90% of
glomeruli contained at least one transfected macrophage, and the median
number was 10. Ad-IL4-transfected NR8383 macrophages localized more
efficiently than Ad-
gal-transfected macrophages, with almost 34
times as many transfected cells within the glomeruli 24 h after
injection when the same numbers of transfected macrophages were
injected (Fig. 3
A). Labeled
IL-4-expressing macrophages were seen only exceptionally in the right
kidney after injection into the left renal artery and were never
observed after injection of untransfected or Ad-
gal-transfected
cells. The increased ability of Ad-IL4-transfected macrophages to
localize to inflamed glomeruli was confirmed by studies in which they
were injected into the renal artery of healthy rats. Far fewer
localized to noninflamed glomeruli, and there was no difference in the
numbers of Ad-IL4- or Ad-
gal-transfected macrophages present within
the glomeruli (Fig. 3
A).
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gal-
and Ad-IL4-transfected NR8383 macrophages had a similar
duration of residence within inflamed glomeruli, with a half-time of
approximately 2 days estimated from measurements taken at 1, 4, and 7
days (Figs. 2
gal-transfected macrophages produced no detectable IL-4 in vitro.
Similarly, the urine from rats injected with IL-4-expressing
macrophages contained IL-4 on days 1, 2, and 4 after injection (Fig. 3
To assess the potential alloreaction against NR8383 cells, rats with
NTN were injected with 6 x 106 NR8383 cells
transfected with either Ad-
gal or Ad-IL4 or were unimmunized and
splenocytes were isolated 7 days later. The MLR was then set up against
various dilutions of NR8383 cells, with Con A acting as a positive
control. Proliferation was assessed by measuring uptake of
[3H]thymidine on days 25. Results were
similar at all dilutions of NR8383 cells used and on days 25 of the
assay, with the data for day 4 presented in Table I
being representative. There was the
expected proliferation in Con A-treated splenocytes, but no evidence of
proliferation on exposure to mitomycin C-treated adenovirus-transfected
NR8383 cells at various dilutions of cells. Thus, an alloreaction was
unlikely to be responsible for the disappearance of transfected
macrophages or altering the course of disease.
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Injection of Ad-
gal-transfected or nontransfected NR8383
macrophages into the renal artery causes a small and transient
reduction in proteinuria (10). By contrast, injection of
similar numbers of Ad-IL4-transfected macrophages produced a profound
reduction in albuminuria on days 1, 2, and 4 after injection (Fig. 3
D). On days 1 and 2 after injection of IL-4-expressing
macrophages, the level of albuminuria was reduced to 1520% of that
in untreated nephritic rats with NTN. The reduction of albuminuria was
less on day 4, but still statistically significant, and had returned
toward control values by day 7. Attenuation of the effect over time
paralleled both the reduced numbers of transfected NR8383 macrophages
and the decreased production of IL-4 within the glomeruli.
To correct for the enhanced localization of IL-4-transfected
macrophages, 810 x 106
Ad-
gal-transfected NR8383 cells were injected compared with
24 x 106 Ad-IL4-transfected cells, which
resulted in similar numbers of transfected cells within the glomeruli
after processing on day 2 (Fig. 4
A). Renal artery injection of
IL-4-expressing macrophages caused a similar profound reduction in
albuminuria (Fig. 4B
) on both days 1 and 2 compared with that in
unmodified disease and Ad-
gal-injected rats. The fact that
IL-4-expressing macrophages reduce injury to a greater extent than
Ad-
gal-transfected macrophages despite similar numbers of cells
localizing to glomeruli indicates that IL-4 expression is essential for
the effect. Thus, the delivery of IL-4-expressing macrophages to the
left kidney caused a marked reduction in albuminuria, but only for the
time that IL-4-expressing macrophages were resident in nephritic
glomeruli.
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IL-4-expressing macrophages had only been injected into the left
kidney, and labeled cells were rarely detected in the right kidney. Yet
albuminuria was reduced by 80%, which suggests that the treatment also
affected injury in the contralateral kidney. NTN is a
macrophage-dependent form of glomerular inflammation (1);
therefore, we compared the number of macrophages infiltrating the right
and left kidneys of nephritic rats in whom IL-4-expressing NR8383 cells
were injected into the left kidney. Injection of IL-4-expressing
macrophages markedly reduced the total number of ED1-positive
macrophages within glomeruli from the left kidney on day 1 compared
with both unmodified NTN and NTN injected with Ad-
gal-expressing
cells (Fig. 5
). The effect was seen even
without subtracting the Ad-IL4-transfected NR8383 cells that are ED1
positive from the total number of glomerular macrophages. Macrophage
numbers were still reduced on day 4 compared with NTN disease controls,
but were not significantly different from those of nephritic rats
injected with Ad-
gal-transfected macrophages, a time point at which
the level of IL4 had been markedly reduced. By day 7 there was no
difference in glomerular ED1-positive macrophages numbers between any
of the groups (data not shown); however, on day 7 there were
differences in the light microscopic appearances. In control rats there
was evidence of increased glomerular endothelial cell swelling and
proliferation (control, 1.8 ± 0.3; IL-4 treated, 0.7 ± 0.2,
scoring out of 3), mesangial cell proliferation (control, 2.5 ±
0.2; IL-4, 0.7 ± 0.3, scoring out of 3), and necrosis (control,
1.1 ± 0.2; IL-4, 0, scoring out of 2) compared with IL-4-treated
rats, with all these differences significant (p
< 0.01). The most important finding was that the number of
ED1-positive macrophages was also reduced in the noninjected right
kidney. Thus, injection of IL-4-expressing macrophages into one kidney
can reduce inflammation at a distant focus. It is unlikely that this
effect could be due to IL-4-expressing macrophages in the contralateral
kidney, because only small numbers appeared there (<5% of glomeruli
contained cells, with only one or two cells seen in these
glomeruli).
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IL-4 could not be detected in the circulation of rats after
injection of Ad-IL4 NR8383 cells into the renal artery, but leakage of
IL-4 into the circulation still provides the simplest explanation for
the reduced injury in the contralateral kidney, because systemic
injection of IL-4 reduces injury in this model of glomerulonephritis
(14). This possibility was examined by comparing the
results after injecting IL-4-expressing NR8383 cells into different
sites. Nephritic rats were injected with 24 x
106 Ad-IL4-transfected macrophages via the tail
vein (i.v.), the left renal artery, or the peritoneal space (i.p.).
Intraperitoneal injection of IL-4-expressing macrophages had no effect
on albuminuria, while injection into the tail vein caused a very
transient reduction despite localization of small numbers of labeled
macrophages to both glomeruli (510% of glomeruli contained
transfected cells, with one or two cells per glomerulus). By contrast,
injection into the left kidney again reduced albuminuria significantly
(Fig. 6
A) as well as
glomerular macrophage infiltration into both kidneys compared with all
control groups (Fig. 6
B). This demonstrates that the impact
of IL-4-expressing macrophages on injury is most profound when they
localize to the focus of inflammation, and this effect cannot be
mimicked by systemic delivery of macrophages.
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| Discussion |
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Our data highlight the fact that macrophage transfection provides an
effective method to deliver genes to and express biologically active
molecules in glomeruli, a target that has proved difficult using
conventional viral and nonviral methods (22). The Sendai
virus method (23) has been used to transfect and express
TGF-
1 in approximately 50% of glomeruli (24),
resulting in glomerulosclerosis. Recently the same approach has been
used to express 15-lipoxygenase in glomeruli of rats with NTN,
resulting in a reduction in albuminuria but no effect on macrophage
infiltration (25). Cell-based systems have proven more
successful to deliver genes to glomeruli using either mesangial cells
(26) or macrophages (10, 27, 28), with
macrophages of particular value in the modification of inflammatory
disease (10, 29) due to their ability to infiltrate a
focus of injury. Injection of adenovirus-transfected macrophages
provides a highly effective method for glomerular gene transfer, with
nearly 100% of glomeruli containing transfected macrophages.
Adenoviruses have a number of advantages over retroviral transformation
of macrophages, including higher levels of expression due to
transfection with more than one copy of cDNA, transfection of primary
cultures of macrophages (10), and a single-step
transfection without need for selection before injection. In addition
by transfecting macrophages to express anti-inflammatory cytokines
such as IL-4, it prevents macrophages from responding to
proinflammatory cytokines including IFN-
, which is important, as
macrophages from inflamed glomeruli behave as if stimulated with
IFN-
(21).
Macrophages are important in the development of many forms of
inflammation including nephrotoxic nephritis (1, 30) and
infiltrate glomeruli within 24 h of the onset of disease. In our
experiments large numbers of NR8383 macrophages localize to inflamed
glomeruli when injected 6 h after the induction of nephritis. This
property was enhanced in IL-4-transfected macrophages, with 34 times
as many cells localized compared with either Ad-
gal-transfected
macrophages or nontransfected macrophages (data not shown). The reasons
for enhanced localization of IL-4-expressing macrophages is unclear,
but was specific to inflamed glomeruli as similar numbers of Ad-IL4-
and Ad-
gal-transfected NR8383 macrophages localized to nondiseased
glomeruli. Similarly, IL-4 transfection did not change macrophage
morphology or adhesiveness in vitro. This suggests that increased
adhesiveness is mediated specifically by up-regulation (or activation)
of receptors involved in binding to glomerular endothelium during the
course of NTN.
Monocyte infiltration has been extensively studied and shown to be dependent on selectins, VCAM, and ICAM (31); however, in the glomerulus different molecules appear to be involved. Selectins are poorly expressed and do not play an important role in glomerular leukocyte recruitment (32, 33). ICAM-1 is up-regulated on glomerular endothelium in NTN; however, the evidence for its involvement in localization of macrophages to inflamed glomeruli is contradictory depending on the species of rat used (34, 35). IL-4 has been well characterized to increase endothelial expression of VCAM-1 and subsequent monocyte adhesion (36, 37); however, there is little evidence that VCAM is expressed on glomerular endothelium during NTN or that it is involved in macrophage adhesion in NTN (34, 38). In addition there is no evidence that IL-4 alters the expression of or activates integrins including CD18/CD11 (counter-receptor to ICAM1 and ICAM2) or very late Ag-4 (counter-receptor to VCAM) or alters the expression of selectins. Thus, the standard integrin adhesion molecules are unlikely to be responsible for enhanced localization of IL-4-expressing macrophages.
Recent evidence has implicated both fractalkine (39) and
Gro-
4 in the localization of
macrophages in NTN. IL-4 has been shown to increase the expression of
chemokine receptors CXCR1 and CXCR2, which are counter-receptors
to IL-8 and Gro-
, thus making monocyte/macrophages responsive to
IL-8 (40). In addition we have recently demonstrated that
blockade of Gro-
receptor on the macrophage surface reduces their
ability to localize to inflamed glomeruli with NTN within 24 h of
the onset of disease (4). Thus, IL-4 transfection gives
macrophages a unique ability to localize to inflamed glomeruli, and
altered expression of chemoadhesin receptors is the prime candidate for
mediating this effect.
Once within the inflamed glomerulus, the transfected NR8383 macrophages
produce large quantities of the cytokine, as detected both in urine and
in isolated glomeruli containing transfected macrophages. The
transfected macrophages remain within the glomerulus with a half-life
of approximately 2 days for both the number of cells present and the
production of IL-4. The fate of the transfected macrophages is
unclear; they may die within the glomerulus, migrate to regional lymph
nodes (41, 42), or reverse migrate across the endothelium
(43). Clearly migration to local lymph nodes may be
crucial in altering the course of the disease and in particular in
affecting inflammation in the contralateral kidney. The NR8383
macrophages are from Sprague Dawley rats, and the experiments have used
an outbred strain of Sprague Dawley rats, which raises the possibility
that an alloreaction may be induced. This was made unlikely by the
short time course we studied (<7 days) before an alloreaction
developed and was confirmed by showing the absence of proliferation of
splenocytes isolated from rats immunized for 7 days with either
Ad-
gal- or Ad-IL4-transfected NR8383 cells on re-exposure to
adenovirus-transfected NR8383 cells.
The injection of IL-4-expressing macrophages into a single renal artery
has a profound effect on the severity of injury, with a 75% reduction
in the level of albuminuria, which is a sensitive indicator of
glomerular damage. In addition there was a marked reduction in the
number of ED1-positive macrophages. ED1 is pan-macrophage marker, and
at this stage of disease they are the principal inflammatory cell and
thus represent a sensitive marker of glomerular inflammation before
more severe histological injury. Interestingly on day 7 there were
histological differences between control and IL-4-treated rats with
reduced necrosis and capillary and mesangial cell proliferation. Thus,
reduction of macrophage infiltration early on prevents subsequent
histological changes. This effect is dependent on the production of
IL-4 by the transfected macrophages, as injection of
Ad-
gal-transfected macrophages did not have the same impact. IL-4 is
capable of reducing the expression of a number of proinflammatory
cytokines, particularly in macrophages, including TNF, IL-1
,
IFN-
, and IL-12, which have been implicated in glomerular
inflammation (44, 45, 46), and increasing expression of
antagonists to proinflammatory cytokines such as IL-1R
antagonist and IL-1 decoy receptor (reviewed in Ref.
47). Intraperitoneal injection of high doses of IL-4 in
this model from before the onset of disease caused a less pronounced
reduction in both albuminuria and numbers of ED1-positive macrophages.
Thus, IL-4 expression by transfected macrophages is more effective at
modifying inflammation than repeated systemic injections.
Gene delivery using IL-4 has been shown previously to alter
inflammatory disease. In collagen-induced arthritis in mice adenoviral
transfection with IL-4 into the joint appeared to enhance synovial
inflammation, but reduce cartilage destruction, with suppression of
TNF, IL-1
, IL-12, and IL-17 expression (48) and
inhibition of osteoclast formation (49). While in a model
of inflammatory bowel disease i.p. injections of adenovirus-expressing
IL-4 reduced tissue damage, with an increase in systemic IL-4 rather
than clear local expression (50). Also delivery of
retrovirus-transduced T cells expressing IL-4 reduces the severity of
inflammation in EAE in mice (51). Our results further
demonstrate the immune modulation achieved by local IL-4 delivery and
its anti-inflammatory potential. Ad-
gal-transfected macrophages
also resulted in a small reduction in albuminuria as noted in our
previous work (10). The most likely mechanisms for this
are blockade of entry of endogenous macrophages by NR8383 cells
occupying endothelial adhesion molecules or transfected macrophages
developing anti-inflammatory properties.
The most surprising observation was that injection of IL-4-expressing NR8383 macrophages into a single kidney reduced the number of infiltrating ED1-positive macrophages in both the injected and noninjected glomeruli. This implies that the presence of disease-modifying macrophages in one inflammatory site can alter inflammation at a distant site. The most obvious explanations are leakage of cells or leakage of cytokine; however, our control experiments effectively exclude both these possibilities. Very few cells leak across to the contralateral, although theoretically these small numbers could be effective. This is made unlikely by the i.v. experiments in which small numbers of IL-4-expressing macrophages were found in both glomeruli and resulted in no sustained reduction in albuminuria or reduction in ED1-positive cells. IL-4 was not detected in the circulation after intra-arterial injection of IL-4-expressing NR8383 macrophages. Similarly, IL-4 was not detected after injection of comparable numbers of NR8383 macrophages either i.p. or i.v., and delivery of cells by either route did not affect glomerular inflammation. Thus, large numbers of IL-4-expressing macrophages in inflamed glomeruli are necessary to reduce inflammation in the contralateral glomeruli. There is a precedent for this from transfection of rabbit knee joints with experimental arthritis. Here transfection with adenovirus-expressing soluble IL-1 and TNF receptors reduced inflammation in both the transfected and nontransfected contralateral knee (52), with similarly no evidence of systemic leakage. The most probable explanation is trafficking to regional lymph nodes of either the transfected macrophages themselves (41) or other mononuclear cells that have been exposed to IL-4 in the glomeruli and had their phenotype altered (11). Technically these possibilities are difficult to resolve with tracking of transfected and/or infiltrating macrophages not yet possible.
These observations have profound implications, as they suggest that local delivery of IL-4-expressing macrophages could reduce similar inflammation at a distant site. In addition these experiments establish the precedent of macrophage gene therapy for inflammatory disease.
| Footnotes |
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2 Address correspondence and reprint requests to Dr. David Kluth, Department of Medicine and Therapeutics, IMS Building, University of Aberdeen, Foresterhill, Aberdeen, U.K. AB25 2ZD. ![]()
3 Abbreviations used in this paper: NTN, nephrotoxic nephritis; Ad-IL4, adenovirus expressing rat IL-4; Ad-
gal, adenovirus expressing
-galactosidase. ![]()
4 A. Zernecke, K. S. C. Weber, L. P. Erwig, D. C. Kluth, B. Schroppel, A. J. Rees, and C. Weber. Combinatorial model of chemokine involvement in glomerular monocyte infiltration. Submitted for publication. ![]()
5 A. Zernecke, K. S. C. Weber, L. P. Erwig, D. C. Kluth, B. Schroppel, A. J. Rees, and C. Weber. Combinatorial model of chemokine involvement in glomerular monocyte infiltration. Submitted of publication. ![]()
Received for publication August 11, 2000. Accepted for publication January 24, 2001.
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