| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Institute of Human Nutrition, University of Southampton, United Kingdom
Correspondence: Philip C. Calder, Institute of Human Nutrition, University of Southampton, Basset Crescent East, Southampton SO16 7PX, UK. E-mail: pcc{at}soton.ac.uk
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
production was
decreased by safflower oil or fish oil feeding. IL-4 production was not
significantly affected by diet, although production was lowest by
lymphocytes from fish oil-fed mice. The ratio of production of Th1- to
Th2-type cytokines (determined as the IFN-/IL-4 ratio) was lower for
lymphocytes from mice fed the safflower oil or fish oil diets. After
4 h of culture, IL-2 mRNA levels were higher in cells from mice
fed coconut oil, and IFN- mRNA levels were higher in cells from mice
fed coconut oil or safflower oil. After 8 h of culture, IL-2,
IFN-, and IL-4 mRNA levels were lowest in cells from mice fed fish
oil. The ratio of the relative levels of IFN- mRNA to IL-4 mRNA was
highest in cells from mice fed coconut oil and was lowest in cells of
mice fed fish oil. The influence of individual fatty acids on IL-2
production by murine spleen lymphocytes was examined in
vitro. Although all fatty acids decreased IL-2 production in a
concentration-dependent manner, saturated fatty acids were the least
potent and n-3 PUFAs the most potent inhibitors, with
n-6 PUFAs falling in between in terms of potency. It is
concluded that saturated fatty acids have minimal effects on cytokine
production. In contrast, PUFAs act to inhibit production of Th1-type
cytokines with little effect on Th2-type cytokines; n-3
PUFAs are particularly potent. The effects of fatty acids on cytokine
production appear to be exerted at the level of gene expression.
Key Words: interleukin • interferon • lymphocyte • T-helper cell • fish oil • polyunsaturated fatty acid • mouse
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
-linolenic acid and di-homo--linolenic acid.
The structures of the fatty acids mentioned in this article are shown
in Table 1 , while their metabolic relationships are shown in Figure 1
. A second reason for the interest in the immunological effects of
fatty acids is that epidemiological studies have found that populations
such as Greenland Eskimos, whose diets contain significant quantities
of the long-chain n-3 PUFAs eicosapentaenoic and
docosahexaenoic acids, have a very low incidence of inflammatory and
autoimmune disorders [3
]. Fish oil (FO) is rich in these
long-chain n-3 PUFAs, and thus it is suggested that FO is
anti-inflammatory and immunomodulatory. In the absence of intake of the
long-chain n-3 PUFAs, they can be formed from a shorter
chain precursor, 
-linolenic acid (Fig. 1)
.
|
|
-linolenic, eicosapentaenoic,
and docosahexaenoic acids were also potent inhibitors of the
mitogen-stimulated proliferation of rodent [8
9
10
] and
human lymphocytes [10
11
12
13
14
15
]. Given the potent effects of
PUFAs on T lymphocyte proliferation, it would be expected that they
would alter production of T cell-derived cytokines. Indeed linoleic,
-linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acids
were found to have roughly equipotent inhibitory effects on the
production of interleukin (IL)-2 by concanavalin A (Con A)-stimulated
rat and human lymphocytes [9
, 12
];
saturated fatty acids had little effect on IL-2 production. More
recently, Purasiri et al. [14
] have confirmed that
eicosapentaenoic and docosahexaenoic acids inhibit IL-2 production by
cultured human lymphocytes.
The effects of fatty acids on lymphocyte proliferation that have been
observed in vitro have been confirmed in feeding
experiments, although these are often difficult to compare because of
the levels of fat used and the exact comparison being made. Several
studies show that feeding rats or mice diets rich in saturated fat has
little effect on lymphocyte proliferation compared with feeding a
low-fat diet [16
17
18
], although some studies do show a
suppressive effect of high saturated fat feeding, but this is less
pronounced than the effect of feeding high levels of PUFAs
[19
20
21
22
23
]. Feeding laboratory rodents diets rich in
linoleic acid, -linolenic acid, or FO leads to decreased
mitogen-stimulated lymphocyte proliferation examined ex vivo
[10
, 16
, 19
, 20
,
22
23
24
25
26
27
]. It appears that FO is more potent than
-linolenic acid-rich oils which are, in turn, more potent than
linoleic acid-rich oils. Increasing the amount of -linolenic acid or
FO in the human diet has been shown to lead to a decreased
proliferative response of blood lymphocytes [28
29
30
].
Compared with the large number of studies of the influence of dietary
fat on lymphocyte proliferation there are relatively few studies of the
influence on T cell-derived cytokines. Turek et al. [31
]
reported decreased IL-2 production by alveolar lymphocytes after
feeding pigs diets rich in -linolenic acid or FO. More recently,
eicosapentaenoic and docosahexaenoic acids were shown to be equipotent
in their ability to decrease IL-2 production when included in the mouse
diet at very high levels [32
]. Increasing the amount of
FO in the human diet decreased ex vivo IL-2 production by
blood lymphocytes [29
, 30
, 33
,
34
]. There are few studies of dietary fatty acids and
lymphocyte-derived cytokines other than IL-2. Gallai et al.
[34
] reported decreased interferon (IFN)- production
by Con A-stimulated blood lymphocytes after FO supplementation of the
human diet. In contrast to these studies, there were no differences in
the ex vivo production of IL-2, IFN-, IL-4, or IL-10
among spleen lymphocytes from mice fed diets rich in saturated fatty
acids, n-6 PUFAs, and n-3 PUFAs
[24
]. There are few other studies investigating dietary
fatty acids and T cell-derived cytokine production.
Given the key role of T helper (Th)1-type and Th2-type cytokines in mounting appropriate immune responses to pathogens and also in human disease [35 , 36 ], it seems important to understand more fully the influence of dietary fatty acids in modulating the production of both Th1-type and Th2-type cytokines. Therefore, in the current study we investigated the production of Th1- and Th2-type cytokines and their mRNAs by murine spleen lymphocytes taken from mice fed diets rich in saturated fatty acids, n-6 PUFA and n-3 PUFA. In addition, we made a detailed comparison of the in vitro effects of fatty acids on IL-2 production by these cells.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
20 g) were
purchased from Charles River (Margate, Kent, UK). They were housed in
plastic cages in controlled environmental conditions (21.5 ±
0.5°C, 45 ± 2% humidity; 14 h light/10 h dark cycle).
Mice used for preliminary studies and as a source of cells for in
vitro experiments were fed on standard laboratory chow (Rat and
Mouse No. 1 pellets; Special Diet Services, Witham, Essex, UK). For the
dietary studies mice were randomly allocated to receive one of four
diets on which they were maintained for 6 weeks until they were killed.
The diets used were a low-fat (LF) diet and three high-fat (HF) diets
(all prepared by ICN Biomedicals, High Wycombe, Bucks., UK); the LF
diet most closely resembled standard mouse chow and contained 25 g
maize oil/kg. The HF diets contained 200 g/kg of the lipid under study
[coconut oil (CO), safflower oil (SO), or FO], plus 10 g maize
oil/kg to prevent essential fatty acid deficiency. All diets contained
200 g protein, 200 g starch, 296 g sucrose, and 1.2 g vitamin E (250 IU/g) per kg and all diets were in pelleted form. In
the HF diets the additional fat was accompanied by a decrease in the
amount of fiber compared with the amount in the LF diet (50 g/kg in the
HF diets vs. 225 g/kg in the LF diet). The fatty acid composition of
the diets is shown in Table 2
. The CO diet was rich in the medium-chain saturated fatty acids
capric, lauric, and myristic acid. The chow, LF, and SO diets were rich
in the n-6 PUFA linoleic acid. The FO diet contained the
long-chain n-3 PUFA eicosapentaenoic and docosahexaenoic
acid. Apart from the FO diet, which was stored frozen, all diets were
stored at 20°C. Diets were provided fresh to the animals every 2
days. Mice were killed between 0800 and 0930 h by a rising
concentration of CO2. All procedures involving experimental
animals were approved under the Animals (Scientific Procedures) Act
1986 by the Home Office.
|
Spleen lymphocyte preparation
Spleens were removed immediately after death and were placed in
RPMI culture medium. The cells were released by teasing apart the
spleens through a wire mesh strainer with the end of a 10-mL plastic
syringe plunger. Cell preparations were filtered through lens tissue to
remove debris and the cells collected by centrifugation (500
g, 5 min). The pelleted cells were resuspended and
mononuclear cells isolated by centrifugation on Histopaque (1000
g, 20 min). Mononuclear cells were collected from the
interface and were washed in RPMI culture medium. Finally, they were
resuspended at a concentration of 2 x 106 cells/mL in
RPMI culture medium containing 2 mM glutamine, 5% (vol/vol) FCS, and
antibiotics (50 µg/mL penicillin plus 50 µg/mL streptomycin).
Lymphocyte proliferation
Spleen lymphocytes (2 x 105) were cultured at
37°C in an atmosphere of 19:1 air/CO2 in RPMI culture
medium containing 2 mM glutamine, 5% (vol/vol) FCS, antibiotics and,
for stimulated cells, 2.5 µg/mL Con A [preliminary experiments
indicated that this was the concentration of Con A that induced maximal
proliferation of spleen lymphocytes from C57Bl6 mice of this age (data
not shown)]; the final volume of the culture was 200 µL. After
48 h 20 µL [3H]thymidine (0.1 µCi) was added to
each well and the cells were cultured for a further 18 h. Then the
contents of the wells were transferred to glass fiber filters and
washed and dried using a Skatron Cell Harvester (Skatron, Lier,
Norway). The filters were transferred to counting vials and 100 µL
scintillant (Wallac Optiphase Hisafe purchased from Fisher Scientific,
Loughborough, Leics., UK) added to each; radioactive incorporation was
measured using a Beckman LS6500 liquid scintillation counter.
Lymphocyte proliferation data are expressed as
[3H]thymidine incorporation in cpm/well.
Lymphocyte culture for cytokine analysis
Spleen lymphocytes (2 x 106) were cultured at
37°C in an atmosphere of 19:1 air/CO2 in RPMI culture
medium containing 2 mM glutamine, 5% (vol/vol) FCS, antibiotics, and
2.5 µg/mL Con A; the final volume of the culture was 2 mL.
Preliminary experiments indicated that a Con A concentration of 2.5
µg/mL induced maximal production of each of the cytokines studied
(data not shown). Cells from dietary experiments were cultured for 4
and 8 h (for cytokine mRNA analysis) and for 24 h (for
measurements of cytokine concentrations in the culture medium). For
in vitro studies of the effects of individual fatty acids,
spleen lymphocytes were cultured in the same conditions except that the
medium also contained fatty acids at final concentrations of 5, 10, 25,
or 50 µM. For these experiments cells were cultured for 48 h. At
the end of the culture period the culture plates were centrifuged to
separate the cells from the medium. Aliquots of the medium were frozen
at -70°C for cytokine analysis. The concentrations of the cytokines
in the culture medium were measured by commercially available ELISA
kits; all measurements were made according to the instructions given by
the manufacturers of the ELISA kits.
Extraction of RNA, reverse transcription, and DNA amplification and
visualization
Total RNA was extracted using TRIzol in accordance with the
manufacturer’s instructions. mRNA was then selectively reverse
transcribed from 4.5 µg of total RNA using an oligo(dT) primer.
Reverse transcription was achieved with 7.5 U of avian myeloblastosis
virus reverse transcriptase in the presence of 1 mM dNTPs, 5 mM
magnesium chloride, and 0.5 µg poly(dT)15; the reaction
was buffered by 10 mM Tris, 50 mM potassium chloride, 0.1% (v/v)
Triton X-100, pH 8.8, and the total volume was 20 µL. Reverse
transcription was carried out for 1 h at 42°C followed by
heating at 94°C for 3 min to inactivate the transcriptase. The
resulting cDNA was diluted with DEPC-treated water to a final volume of
35 µL and used as a polymerase chain reaction (PCR) substrate.
PCR was performed for a housekeeping gene (cyclophilin), IL-2, IFN-,
and IL-4. Amplification of 2.5 µL of cDNA was achieved using 1 U of
Taq polymerase in the presence of 15 pmol of primer (primer sequences
are shown in Table 3
), magnesium-free buffer [19 mM Tris, 50 mM potassium chloride,
0.1% (v/v) Triton X-100, pH 9], 2 mM magnesium chloride (1.5 mM for
PCR of cyclophilin) and 0.2 mM dNTPs. The reaction mix was incubated at
93°C for 1 min. The reaction was cycled at 94°C for 30 s, the
annealing temperature (see Table 3
) for 30 s, and 72°C for 1 min
in a Hybaid Touchdown Thermocycler (Hybaid, Teddington, Middlesex, UK).
The optimized number of cycles used (reflecting the exponential phase
of the reaction) is shown in Table 3
.
|
Fatty acid composition analysis
Total lipid was extracted from lymphocytes with
chloroform/methanol (2:1 v/v) as previously described
[37
]. Fatty acids were prepared by saponification for
3 h at 80°C in methanolic 0.5 M sodium hydroxide; after cooling
the samples were neutralized by addition of 5 M sulfuric acid. Then,
fatty acids were extracted with chloroform/methanol (2:1 v/v) and fatty
acid methyl esters prepared by incubation with diazomethane in ether.
Fatty acid methyl esters were isolated by solvent extraction, dried,
and separated by gas chromatography in a Hewlett-Packard 6890 gas
chromatograph (Hewlett Packard, Avondale, PA) fitted with a 30 m
x 0.32 mm BPX70 capillary column, film thickness 0.25 µm. Helium at
2.0 mL/min was used as the carrier gas and the split/splitless injector
was used with a split:splitless ratio of 10:1. Injector and detector
temperatures were 170 and 250°C, respectively. The column oven
temperature was maintained at 170°C for 12 min after sample injection
and was programmed to then increase from 170 to 200°C at 5°C/min
before being maintained at 200°C for 15 min. The separation was
recorded with Hewlett Packard gas chromatography Chem Station software
(Hewlett Packard, Avondale, PA). Fatty acid methyl esters were
identified by comparison with standards run previously.
Statistical analysis
All data are presented as means ± SE. Statistically
significant differences between dietary groups or between cultures
containing different fatty acids were determined by one-way analysis of
variance and a post-hoc least-significant difference test.
All analyses were performed using SPSS version 6.0 (SPSS, Chicago, IL)
and a value for P < 0.05 was taken to indicate a
statistically significant difference.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
|
|
production was decreased by SO or FO feeding compared
with LF or CO feeding (Table 5)
. IL-4 production was not significantly
affected by diet, although production was lowest by lymphocytes from
FO-fed mice (Table 5)
. The ratio of production of Th1- to Th2-type
cytokines was determined as the IFN-/IL-4 ratio. This ratio was
significantly lower for lymphocytes from mice fed the SO or FO diets
compared with those from mice fed the LF or CO diets (Table 5)
.
|
|
mRNA levels increased between 4 and 8 h of culture (Fig. 3B) . After 4 h of culture, IFN- mRNA levels tended to be higher
in cells from mice fed CO or SO (Fig. 3B)
. After 8 h of culture
IFN- mRNA levels were lowest in cells from mice fed FO; in these
cells IFN- mRNA levels were not increased at 8 h compared with
4 h (Fig. 3B)
. IL-4 mRNA levels were similar after 4 and 8 h of culture (Fig. 3C) . After 4 h of culture IL-4 mRNA levels tended to be higher in cells from mice fed SO (Fig. 3C) . After 8 h of culture IL-4 mRNA levels were lowest in cells from mice fed FO (Fig. 3C) .
The ratio of the relative levels of IFN- mRNA to IL-4 mRNA was
higher at 4 h of culture in cells from mice fed CO (approximately
0.5) than in those from mice fed the other three diets (approximately
0.2 to 0.3). At 8 h of culture this ratio was lower in cells of
mice fed FO (approximately 0.3) compared with those fed the other three
diets (approximately 0.6–0.8).
In vitro effects of fatty acids on cytokine production
by spleen lymphocytes
All fatty acids decreased IL-2 production in a
concentration-dependent manner, although the effect of palmitic acid
did not reach statistical significance (Table 6
). Saturated fatty acids were relatively poor inhibitors of IL-2
production (Table 6)
. The shorter-chain n-6 PUFAs, linoleic
and -linolenic acids, were also relatively poor inhibitors causing
55% inhibition at a concentration of 50 µM (Table 6)
, with an
IC50 value of approximately 47 µM. The long-chain
n-6 PUFAs, di-homo--linolenic and arachidonic acids, were
more potent, causing 75% inhibition at a concentration of 50 µM
(Table 6)
with an IC50 of approximately 22 µM. Oleic and
docosahexaenoic acids had IC50 values of approximately 32
to 35 µM, although docosahexaenoic acid caused greater inhibition
(95%) than oleic acid (70%) at a concentration of 50 µM (Table 6)
.
-Linolenic acid was the most potent inhibitor, causing 96%
inhibition at a concentration of 50 µM (Table 6)
with an
IC50 of approximately 16 µM. Eicosapentaenoic acid
exhibited a unique pattern of effects: this fatty acid tended to
enhance IL-2 production at the lowest concentrations tested (5 and 10
µM) and only became inhibitory at the highest concentration tested
(50 µM), at which it caused almost 80% inhibition of IL-2 production
(Table 6)
.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
The pattern of effects of the diets on spleen lymphocyte proliferation
stimulated by Con A is consistent with that previously shown for spleen
lymphocytes from MF1 strain mice fed these diets [24
].
In that study the proliferation of lymphocytes from mice fed on CO was
greater than that of those from mice fed on the LF and SO diets, which
were, in turn, greater than that of lymphocytes from mice fed on FO
[24
]. Spleen lymphocytes from rats fed the SO or FO
diets proliferated less well than those from rats fed the LF or CO
diets (when the cells were cultured in FCS, as in the current study),
although CO did not enhance rat lymphocyte proliferation compared with
the LF diet [22
]. Taking these studies together, it
appears that, in comparison with saturated fatty acids and as
components of a HF diet, long-chain n-3 PUFAs at the levels
present in the FO diet (i.e., about 20% of dietary fatty acids) are
approximately as effective at inhibiting lymphocyte proliferation as is
linoleic acid at the level at which it is present in SO (i.e., about
60% of dietary fatty acids). The differences in the proportions of the
n-3 PUFAs and linoleic acid in these diets suggest that
long-chain n-3 PUFAs are about three times more potent at
inhibiting lymphocyte proliferation than is linoleic acid. This potency
of long-chain n-3 PUFAs is consistent with the inhibition of
lymphocyte proliferation observed when humans supplement their diet
with FO [29
, 30
]. The similar effects of SO
and FO upon lymphocyte proliferation reported in the current study and
previously [22
, 24
], appear to contrast
with the observations of Jolly et al. [32
]. Those
authors reported that feeding C57Bl6 mice on diets rich in either
eicosapentaenoic acid or docosahexaenoic acid significantly decreased
Con A-stimulated spleen lymphocyte proliferation (by 80%) compared
with feeding SO. However, in the study by Jolly et al.
[32
] the long-chain n-3 PUFAs contributed
32% of dietary fatty acids, which is a 50% increase compared with
their proportion in the FO diet used in the current study.
The pattern of effects of the diets on IL-2 production in response to
Con A was similar to the effects on lymphocyte proliferation: the CO
diet increased IL-2 production compared with the other diets. There was
a strong positive correlation between IL-2 production and thymidine
incorporation (r = 0.85), as might be expected given
the regulatory role of IL-2 in lymphocyte proliferation
[41
], and suggesting that the effect of dietary fatty
acids on lymphocyte proliferation is mediated via changes in IL-2
production. Several studies in humans have reported that increased
consumption of FO leads to decreased ex vivo IL-2 production
by blood lymphocytes [29
, 30
,
33
, 34
]. However, to our knowledge there are
only two animal studies demonstrating this, one in pigs
[31
] and one in mice [32
]. The similar
effects of SO and FO upon IL-2 production observed in the current study
appear to contrast with those of Jolly et al. [32
] who
reported that feeding C57Bl6 mice on diets rich in either
eicosapentaenoic acid or docosahexaenoic acid significantly decreased
IL-2 production by Con A-stimulated spleen lymphocytes (by 50%)
compared with feeding SO. However, as described above, this difference
might relate to the difference in the contribution of long-chain
n-3 PUFAs to the diet between the studies. One other animal
study reported IL-2 production by murine spleen lymphocytes after
feeding the diets used in the current study [24
]. That
study found no significant effects of diet. The reason for the
difference between the earlier study [24
] and the
current study is not clear, although it might relate to the strain of
mouse used: the earlier study used MF1 mice.
IL-2 mRNA was more rapidly induced in Con A-stimulated spleen lymphocytes from mice fed CO compared with those fed the LF or FO diets. This might account for the higher IL-2 production by cells from CO-fed mice compared with those from mice fed the LF or FO diets. Thus, the enhancing effect of CO on IL-2 production might relate to more rapid induction of gene transcription. IL-2 mRNA levels in lymphocytes from SO-fed mice were similar to those in cells from mice fed the LF or CO diets, and so the reason for decreased IL-2 production by these cells, in comparison to those from CO-fed mice, is not clear. SO feeding may affect some later component of IL-2 processing. Jolly et al. [42 ] studied IL-2 mRNA levels in Con-A-stimulated spleen lymphocytes from C57Bl6 mice fed on diets rich in SO or long-chain n-3 PUFAs. They stated that dietary n-3 PUFAs do not affect IL-2 gene expression [42 ]. However, the data shown indicate that IL-2 mRNA levels were significantly lower at 3 and 9 h of culture in cells from mice fed long-chain n-3 PUFAs [42 ].
Reports of dietary fats and production of cytokines other than IL-2 by
lymphocytes are rare. Gallai et al. [34
] reported
decreased IFN- production by blood lymphocytes from humans who
consumed FO. This ability of FO to decrease IFN- production by
lymphocytes, at least in comparison with the LF and CO diets, is
demonstrated in the current study. IFN- mRNA was slightly more
rapidly induced in Con A-stimulated spleen lymphocytes from mice fed CO
compared with those fed the LF diet. This might account for the
slightly higher IFN- production by cells from CO-fed mice compared
with those from mice fed the LF diet. IFN- mRNA was very poorly
expressed in cells from FO-fed mice. This most likely accounts for the
very low production of IFN- by these cells. Thus, the inhibiting
effect of FO on IFN- production might relate to markedly decreased
induction of gene transcription. IFN- mRNA levels in lymphocytes
from SO-fed mice were similar to those in cells from mice fed the LF or
CO diets, and so the reason for decreased IFN- production by these
cells, in comparison to those from LF or CO-fed mice, is not clear. SO
feeding may affect some later component of IFN- processing.
IL-4 production was not affected by the diets used here, which is in agreement with an earlier study in MF1 mice [24 ], although they tended to be highest in mice fed SO and lowest in mice fed FO. IL-4 mRNA was more rapidly induced in the cells of SO-fed mice and was relatively poorly induced in the cells of FO-fed mice. Thus, the moderate effects of dietary fatty acids on IL-4 production appear to be related to effects at the level of IL-4 gene expression.
The effects of dietary fats on the production of cytokines and their
mRNAs suggest that they are able to alter the Th1-/Th2-type cytokine
balance. FO appears to be particularly potent at skewing this balance
away from Th1 toward Th2. Compared with CO feeding, FO altered the
balance in production of cytokines away from Th1 and toward Th2 by a
factor of about 5; at the level of the cytokine mRNAs FO altered this
balance by a factor of about 2. These data can be compared with those
from a study in which the levels of mRNA for IFN- and IL-10 were
measured in the Peyer’s patches of diabetes-prone rats fed diets rich
in either saturated fat or FO [43
]. The FO diet
decreased the level of IFN- mRNA by about 65% and increased the
level of IL-10 mRNA by about 5.5-fold, so causing a shift in the
Th1/Th2 balance (defined as IFN- mRNA/IL-10 mRNA) away from Th1 by a
factor of about 15 [43
].
Although there have been extensive in vitro studies of the influence of individual fatty acids on lymphocyte proliferation [4 5 6 7 8 9 10 11 12 13 14 15 ], there have been relatively few such studies on cytokines. In our previous studies we reported the effects of fatty acids at a concentration of 100 µM on IL-2 production by rat [9 ] or human [12 ] lymphocytes. This is a higher concentration of unesterified fatty acid than is likely to occur in the bloodstream or intracellularly. In the current study fatty acid concentrations of 5–50 µM were used. As a group, the n-3 PUFAs were the most potent inhibitors of IL-2 production in vitro, whereas, as a group, the n-6 PUFAs were more potent than the saturated fatty acids. Thus, the relative potencies of the fatty acid families as inhibitors of IL-2 production in vitro mirror the relative potencies observed when diets rich in those particular fatty acids are fed to mice.
Thus, n-3 PUFAs provided to spleen lymphocytes either
in vitro or in the diet result in decreased cytokine
production by lymphocytes, with the strongest effects being observed
upon Th1 cytokines. These effects occur at both the mRNA and the
secreted protein levels, and they contrast with the effects of
saturated fatty acids. The decreased induction of mRNA for all three
cytokines studied suggests that FO feeding results in a defect early in
the signaling pathway which links cellular activation to cytokine gene
induction. Con A binds to the T cell receptor/CD3 complex
[44
] activating lymphocytes largely via phospholipase
C-mediated events [45
]. Subsequently, the second
messengers inositol-1,4,5-trisphosphate and diacylglycerol are
generated, and then intracellular calcium concentrations become
elevated and protein kinase C becomes activated [45
]. FO
feeding has been shown to inhibit the activation of phospholipase
C-1 in rat lymphocytes with a concomitant decrease in
inositol-1,4,5-trisphosphate generation [46
] and to
decrease the generation of diacylglycerol and ceramide in Con
A-stimulated mouse lymphocytes [32
]. These actions would
serve to diminish the elevation in intracellular free calcium
concentrations and the activation of protein kinase C, thereby having
the general effect of decreasing cellular responses. In addition,
eicosapentaenoic and docosahexaenoic acids can directly inhibit the
activity of spleen lymphocyte protein kinase C [47
].
Thus, there are several potential early sites at which the inhibitory
effects of the components of FO could be exerted.
A FO-induced shift away from a Th1-type response may explain the low incidence of inflammatory and autoimmune disorders among Greenland Eskimos [3 ]. Furthermore, it could explain some of the benefits that have been observed following the administration of FO to patients with rheumatoid arthritis [see refs. 48 49 for reviews], ulcerative colitis [see 50 for a review], Crohn’s disease [see 51 for a review], and psoriasis [see 52 for a review]. FO also prolongs the survival of cardiac transplants in rats [53 54 55 ], and renal transplants survive and/or function better in patients who receive FO [56 57 58 59 ] and this effect might be due to a shift away from a Th1-type response.
In summary, the type of fatty acid in the diet can modulate lymphocyte proliferation and the production of cytokines by lymphocytes. Th1-type cytokines are more sensitive to the effects of fatty acids than are Th2-type cytokines and the long-chain n-3 PUFAs, as found in FO, appear to be the most potent fatty acids in this regard. The effects of fatty acids on cytokine production appear to be exerted through effects on cytokine gene expression.
|
ACKNOWLEDGEMENTS |
|---|
|
FOOTNOTES |
|---|
Received July 27, 2000; revised October 17, 2000; accepted October 20, 2000.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
-tocopherol alters plasma phospholipid and mononuclear cell fatty acid compositions but not mononuclear cell functions Eur. J. Clin. Invest. 30,260-274[Medline]
expression in activated murine lymphocytes Prost. Leuk. Ess. Fatty Acids 58,289-293[Medline]
in lymphocytes Biochim. Biophys. Acta 1392,300-308[Medline]
This article has been cited by other articles:
|
|
 |
|
  C. T. McFarland, Y.-Y. Fan, R. S. Chapkin, B. R. Weeks, and D. N. McMurray Dietary Polyunsaturated Fatty Acids Modulate Resistance to Mycobacterium tuberculosis in Guinea Pigs J. Nutr., November 1, 2008; 138(11): 2123 - 2128. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Zhang, W. Kim, L. Zhou, N. Wang, L. H. Ly, D. N. McMurray, and R. S. Chapkin Dietary Fish Oil Inhibits Antigen-Specific Murine Th1 Cell Development by Suppression of Clonal Expansion J. Nutr., September 1, 2006; 136(9): 2391 - 2398. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. A. Puertollano, L. Cruz-Chamorro, E. Puertollano, M. T. Perez-Toscano, G. Alvarez de Cienfuegos, and M. A. de Pablo Assessment of Interleukin-12, Gamma Interferon, and Tumor Necrosis Factor Alpha Secretion in Sera from Mice Fed with Dietary Lipids during Different Stages of Listeria monocytogenes Infection Clin. Vaccine Immunol., September 1, 2005; 12(9): 1098 - 1103. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Zhang, R. Smith, R. S. Chapkin, and D. N. McMurray Dietary (n-3) Polyunsaturated Fatty Acids Modulate Murine Th1/Th2 Balance toward the Th2 Pole by Suppression of Th1 Development J. Nutr., July 1, 2005; 135(7): 1745 - 1751. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Zeyda, M. D. Saemann, K. M. Stuhlmeier, D. G. Mascher, P. N. Nowotny, G. J. Zlabinger, W. Waldhausl, and T. M. Stulnig Polyunsaturated Fatty Acids Block Dendritic Cell Activation and Function Independently of NF-{kappa}B Activation J. Biol. Chem., April 8, 2005; 280(14): 14293 - 14301. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. C. Switzer, Y.-Y. Fan, N. Wang, D. N. McMurray, and R. S. Chapkin Dietary n-3 polyunsaturated fatty acids promote activation-induced cell death in Th1-polarized murine CD4+ T-cells J. Lipid Res., August 1, 2004; 45(8): 1482 - 1492. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Lessard, N. Gagnon, D. L. Godson, and H. V. Petit Influence of Parturition and Diets Enriched in n-3 or n-6 Polyunsaturated Fatty Acids on Immune Response of Dairy Cows During the Transition Period J Dairy Sci, July 1, 2004; 87(7): 2197 - 2210. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. M Virtanen and M. Knip Nutritional risk predictors of {beta} cell autoimmunity and type 1 diabetes at a young age Am. J. Clinical Nutrition, December 1, 2003; 78(6): 1053 - 1067. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Kew, S. Wells, F. Thies, G. P. McNeill, P. T. Quinlan, G. T. Clark, H. Dombrowsky, A. D. Postle, and P. C. Calder The Effect of Eicosapentaenoic Acid on Rat Lymphocyte Proliferation Depends Upon Its Position in Dietary Triacylglycerols J. Nutr., December 1, 2003; 133(12): 4230 - 4238. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Zeyda, A. B. Szekeres, M. D. Saemann, R. Geyeregger, H. Stockinger, G. J. Zlabinger, W. Waldhausl, and T. M. Stulnig Suppression of T Cell Signaling by Polyunsaturated Fatty Acids: Selectivity in Inhibition of Mitogen-Activated Protein Kinase and Nuclear Factor Activation J. Immunol., June 15, 2003; 170(12): 6033 - 6039. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. A. de Pablo, M. A. Puertollano, and G. Alvarez de Cienfuegos Biological and Clinical Significance of Lipids as Modulators of Immune System Functions Clin. Vaccine Immunol., September 1, 2002; 9(5): 945 - 950. [Full Text] [PDF]
|
|
|
|
 |
|
 I.P. Crocker, N. Lawson, P.N. Baker, and J. Fletcher The anti-inflammatory effects of circulating fatty acids in obstructive jaundice: similarities with pregnancy-induced immunosuppression QJM, September 1, 2001; 94(9): 475 - 484. [Abstract] [Full Text] [PDF]
|
|
|
