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Dyslipidemia inhibits Toll-like receptor-induced activation of CD8alpha-negative dendritic cells and protective Th1 type immunity.

Shamshiev AT, Ampenberger F, Ernst B, Rohrer L, Marsland BJ, Kopf M - J. Exp. Med. (2007)

Bottom Line: Decreased DC activation profoundly influenced T helper (Th) cell responses, leading to impaired Th1 and enhanced Th2 responses.We found that oxidized low-density lipoprotein (oxLDL) was the key active component responsible for this effect, as it could directly uncouple TLR-mediated signaling on CD8alpha(-) myeloid DCs and inhibit NF-kappaB nuclear translocation.These results show that a dyslipidemic microenvironment can directly interfere with DC responses to pathogen-derived signals and skew the development of T cell-mediated immunity.

View Article: PubMed Central - PubMed

Affiliation: Molecular Biomedicine, Institute of Integrative Biology, Swiss Federal Institute of Technology Zürich, 8952 Zürich, Switzerland.

ABSTRACT
Environmental factors, including diet, play a central role in influencing the balance of normal immune homeostasis; however, many of the cellular mechanisms maintaining this balance remain to be elucidated. Using mouse models of genetic and high-fat/cholesterol diet-induced dyslipidemia, we examined the influence of dyslipidemia on T cell and dendritic cell (DC) responses in vivo and in vitro. We show that dyslipidemia inhibited Toll-like receptor (TLR)-induced production of proinflammatory cytokines, including interleukin (IL)-12, IL-6, and tumor necrosis factor-alpha, as well as up-regulation of costimulatory molecules by CD8alpha(-) DCs, but not by CD8alpha(+) DCs, in vivo. Decreased DC activation profoundly influenced T helper (Th) cell responses, leading to impaired Th1 and enhanced Th2 responses. As a consequence of this immune modulation, host resistance to Leishmania major was compromised. We found that oxidized low-density lipoprotein (oxLDL) was the key active component responsible for this effect, as it could directly uncouple TLR-mediated signaling on CD8alpha(-) myeloid DCs and inhibit NF-kappaB nuclear translocation. These results show that a dyslipidemic microenvironment can directly interfere with DC responses to pathogen-derived signals and skew the development of T cell-mediated immunity.

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Impaired production of IL-12, -6, and TNF-α in dyslipidemic mice is restricted to the CD8α− myeloid DC subset. Splenic DCs were isolated from HFCD-fed C57BL/6 (B6) or apoE−/− mice and stimulated with CpG for 6 h. (A) Representative dot plots from cells stimulated with 100 nM CpG are shown. (B) The proportion of IL-12p40–producing cells in CD8α− and CD8α+ DC subsets after stimulation with the indicated doses of CpG. (C) Splenic CD8α− DCs and (D) CD8α+ DCs were sorted by flow cytometry from C57BL/6 and apoE−/− mice were fed either a chow or HFCD for 10 wk and stimulated with CpG and anti-CD40. Supernatants were collected after 20 h of culture and assayed for IL-12p40, -12p35, -6, and TNF-α by ELISA. Error bars represent the mean ± the SD.
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fig4: Impaired production of IL-12, -6, and TNF-α in dyslipidemic mice is restricted to the CD8α− myeloid DC subset. Splenic DCs were isolated from HFCD-fed C57BL/6 (B6) or apoE−/− mice and stimulated with CpG for 6 h. (A) Representative dot plots from cells stimulated with 100 nM CpG are shown. (B) The proportion of IL-12p40–producing cells in CD8α− and CD8α+ DC subsets after stimulation with the indicated doses of CpG. (C) Splenic CD8α− DCs and (D) CD8α+ DCs were sorted by flow cytometry from C57BL/6 and apoE−/− mice were fed either a chow or HFCD for 10 wk and stimulated with CpG and anti-CD40. Supernatants were collected after 20 h of culture and assayed for IL-12p40, -12p35, -6, and TNF-α by ELISA. Error bars represent the mean ± the SD.

Mentions: Splenic CD11c+ DCs can be classified into CD8α− (∼80% of total) and CD8α+ (∼20% of total) subsets that originate from myeloid and lymphoid precursors, respectively (21). Interestingly, impaired IL-12p40 production by apoE−/− DCs was only found in the CD8α−, but not in the CD8α+, DC subset (Fig. 4, A and B). DCs require both microbial stimuli and CD40 ligation for optimal production of IL-12p70 (22). Therefore, we stimulated purified CD8α− and CD8α+ DCs with both CpG and agonistic anti-CD40 mAb and measured cytokine production in the supernatant. HFCD strikingly inhibited the capacity of DCs to produce IL-12p40, -12p70, -6, and TNF-α from both C57BL/6 and apoE−/− mice with the most severe defect in the latter (Fig. 4 C). In contrast, CD8α+ DCs secreted comparable amounts of IL-12p70 and -12p40 (Fig. 4 D). To assess whether dyslipidemia affected the DC response to TLR stimulation in vivo, we injected HFCD-fed apoE−/− or C57BL/6 mice with CpG or LPS, and 5 h later we isolated splenic DCs and analyzed expression of costimulatory molecules and IL-12p40 production. Consistent with the in vitro results, we observed a reduced expression of the costimulatory molecules CD80, CD86, and CD40 (Fig. 5 A), and a reduced number of IL-12p40–producing CD8α− DCs isolated from HFCD-fed apoE−/− mice (4.6 ± 1.1%) compared with HFCD-fed C57BL/6 controls (15.3 ± 2.4%; Fig. 5 B). Collectively, these results demonstrate that dyslipidemia inhibits TLR-mediated maturation and proinflammatory cytokine production in CD8α− DCs, but not in CD8α+ DCs.


Dyslipidemia inhibits Toll-like receptor-induced activation of CD8alpha-negative dendritic cells and protective Th1 type immunity.

Shamshiev AT, Ampenberger F, Ernst B, Rohrer L, Marsland BJ, Kopf M - J. Exp. Med. (2007)

Impaired production of IL-12, -6, and TNF-α in dyslipidemic mice is restricted to the CD8α− myeloid DC subset. Splenic DCs were isolated from HFCD-fed C57BL/6 (B6) or apoE−/− mice and stimulated with CpG for 6 h. (A) Representative dot plots from cells stimulated with 100 nM CpG are shown. (B) The proportion of IL-12p40–producing cells in CD8α− and CD8α+ DC subsets after stimulation with the indicated doses of CpG. (C) Splenic CD8α− DCs and (D) CD8α+ DCs were sorted by flow cytometry from C57BL/6 and apoE−/− mice were fed either a chow or HFCD for 10 wk and stimulated with CpG and anti-CD40. Supernatants were collected after 20 h of culture and assayed for IL-12p40, -12p35, -6, and TNF-α by ELISA. Error bars represent the mean ± the SD.
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Related In: Results  -  Collection

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fig4: Impaired production of IL-12, -6, and TNF-α in dyslipidemic mice is restricted to the CD8α− myeloid DC subset. Splenic DCs were isolated from HFCD-fed C57BL/6 (B6) or apoE−/− mice and stimulated with CpG for 6 h. (A) Representative dot plots from cells stimulated with 100 nM CpG are shown. (B) The proportion of IL-12p40–producing cells in CD8α− and CD8α+ DC subsets after stimulation with the indicated doses of CpG. (C) Splenic CD8α− DCs and (D) CD8α+ DCs were sorted by flow cytometry from C57BL/6 and apoE−/− mice were fed either a chow or HFCD for 10 wk and stimulated with CpG and anti-CD40. Supernatants were collected after 20 h of culture and assayed for IL-12p40, -12p35, -6, and TNF-α by ELISA. Error bars represent the mean ± the SD.
Mentions: Splenic CD11c+ DCs can be classified into CD8α− (∼80% of total) and CD8α+ (∼20% of total) subsets that originate from myeloid and lymphoid precursors, respectively (21). Interestingly, impaired IL-12p40 production by apoE−/− DCs was only found in the CD8α−, but not in the CD8α+, DC subset (Fig. 4, A and B). DCs require both microbial stimuli and CD40 ligation for optimal production of IL-12p70 (22). Therefore, we stimulated purified CD8α− and CD8α+ DCs with both CpG and agonistic anti-CD40 mAb and measured cytokine production in the supernatant. HFCD strikingly inhibited the capacity of DCs to produce IL-12p40, -12p70, -6, and TNF-α from both C57BL/6 and apoE−/− mice with the most severe defect in the latter (Fig. 4 C). In contrast, CD8α+ DCs secreted comparable amounts of IL-12p70 and -12p40 (Fig. 4 D). To assess whether dyslipidemia affected the DC response to TLR stimulation in vivo, we injected HFCD-fed apoE−/− or C57BL/6 mice with CpG or LPS, and 5 h later we isolated splenic DCs and analyzed expression of costimulatory molecules and IL-12p40 production. Consistent with the in vitro results, we observed a reduced expression of the costimulatory molecules CD80, CD86, and CD40 (Fig. 5 A), and a reduced number of IL-12p40–producing CD8α− DCs isolated from HFCD-fed apoE−/− mice (4.6 ± 1.1%) compared with HFCD-fed C57BL/6 controls (15.3 ± 2.4%; Fig. 5 B). Collectively, these results demonstrate that dyslipidemia inhibits TLR-mediated maturation and proinflammatory cytokine production in CD8α− DCs, but not in CD8α+ DCs.

Bottom Line: Decreased DC activation profoundly influenced T helper (Th) cell responses, leading to impaired Th1 and enhanced Th2 responses.We found that oxidized low-density lipoprotein (oxLDL) was the key active component responsible for this effect, as it could directly uncouple TLR-mediated signaling on CD8alpha(-) myeloid DCs and inhibit NF-kappaB nuclear translocation.These results show that a dyslipidemic microenvironment can directly interfere with DC responses to pathogen-derived signals and skew the development of T cell-mediated immunity.

View Article: PubMed Central - PubMed

Affiliation: Molecular Biomedicine, Institute of Integrative Biology, Swiss Federal Institute of Technology Zürich, 8952 Zürich, Switzerland.

ABSTRACT
Environmental factors, including diet, play a central role in influencing the balance of normal immune homeostasis; however, many of the cellular mechanisms maintaining this balance remain to be elucidated. Using mouse models of genetic and high-fat/cholesterol diet-induced dyslipidemia, we examined the influence of dyslipidemia on T cell and dendritic cell (DC) responses in vivo and in vitro. We show that dyslipidemia inhibited Toll-like receptor (TLR)-induced production of proinflammatory cytokines, including interleukin (IL)-12, IL-6, and tumor necrosis factor-alpha, as well as up-regulation of costimulatory molecules by CD8alpha(-) DCs, but not by CD8alpha(+) DCs, in vivo. Decreased DC activation profoundly influenced T helper (Th) cell responses, leading to impaired Th1 and enhanced Th2 responses. As a consequence of this immune modulation, host resistance to Leishmania major was compromised. We found that oxidized low-density lipoprotein (oxLDL) was the key active component responsible for this effect, as it could directly uncouple TLR-mediated signaling on CD8alpha(-) myeloid DCs and inhibit NF-kappaB nuclear translocation. These results show that a dyslipidemic microenvironment can directly interfere with DC responses to pathogen-derived signals and skew the development of T cell-mediated immunity.

Show MeSH
Related in: MedlinePlus