Obesity-Induced Metabolic Stress Leads to Biased Effector Memory CD4+ T Cell Differentiation via PI3K p110δ-Akt-Mediated Signals

Abstract

Low-grade systemic inflammation associated to obesity leads to cardiovascular complications, caused partly by infiltration of adipose and vascular tissue by effector T cells. The signals leading to T cell differentiation and tissue infiltration during obesity are poorly understood. We tested whether saturated fatty acid-induced metabolic stress affects differentiation and trafficking patterns of CD4+ T cells. Memory CD4+ T cells primed in high-fat diet-fed donors preferentially migrated to non-lymphoid, inflammatory sites, independent of the metabolic status of the hosts. This was due to biased CD4+ T cell differentiation into CD44hi-CCR7lo-CD62Llo-CXCR3+-LFA1+ effector memory-like T cells upon priming in high-fat diet-fed animals. Similar phenotype was observed in obese subjects in a cohort of free-living people. This developmental bias was independent of any crosstalk between CD4+ T cells and dendritic cells and was mediated via direct exposure of CD4+ T cells to palmitate, leading to increased activation of a PI3K p110δ-Akt-dependent pathway upon priming.

Keywords: Akt; CD4; T lymphocyte; differentiation; effector memory; high-fat diet; inflammation; obesity; palmitate; saturated fatty acid.

Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Figures

Graphical abstract

Figure 1

Priming following HFD Induces Differentiation of a CD4+ T Cell Population that Readily Migrates to Inflamed, Non-lymphoid Tissues Independent of the Metabolic Status of the Host In vivo-primed CD4+ T cells isolated from pooled lymph nodes of HFD or CD Marilyn female donor mice, fluorescently labeled with CFSE or PKH26, respectively, in different tissue compartments (as described) of HFD or CD C57BL/6 male recipient mice 48 hr post-i.v. injection of donor cells. The male recipients were previously i.p. injected with zymosan (1 mg/mouse) and IFNγ (600 U/mouse). (A) Dot plots and quantification of donor cells in the blood circulation of CD recipient mice; 2 hr, 24 hr, and 48 hr post-i.v. injection of donor cells. (B–D) Dot plots and quantification of the localization of donor cells, fluorescently labeled with CFSE (HFD) or PKH26 (CD) in the peritoneal cavity (B), mesenteric lymph nodes (C), and spleen (D) of HFD or CD recipient mice. (E) Survival curve of C57BL/6 male skin grafts on HFD or CD Marilyn female recipient mice up to 28 days post-transplantation. (A–D) n = 4–6 independent recipients. (E) n = 7 HFD, n = 9 CD independent recipients. (A–D) The values denote mean ± SEM. ∗p < 0.05; ∗∗p < 0.01; and ∗∗∗p < 0.001. Mantel-Cox test, ∗p < 0.05.

Figure 2

HFD-Induced Metabolic Stress Promotes the Differentiation of Primed CD4+ T Cells to a CXCR3+-LFA1+ Effector Memory-like Phenotype in Mice (A–F) Cell surface staining of CCR7 (A), CD62L (B), CXCR3 (C), LFA1 (D), CD25 (E), and CD44 (F) in in vivo-primed CD4+ T cells isolated from pooled lymph nodes of the HFD or CD Marilyn female donor mice used in Figures 1A–1D (absolute numbers). (G) Ex vivo chemotaxis (3 hr, 6 hr, and 24 hr time points) of in vivo-primed CD4+ T cells isolated from pooled lymph nodes of the HFD or CD Marilyn female donor mice used in Figures 1A–1D in response to CXCL10 (300 ng/mL), CCL19/21 (200 ng/mL of each chemokine), or media only. (H and I) Intracellular staining of IFNγ (H) and IL4 (I) in in vivo-primed CD4+ T cells isolated from mesenteric lymph nodes of HFD or CD mice. (A–F) n = 3–6 independent donors. (G) n = 3 independent donors (each donor was tested in duplicate). (H and I) n = 5 independent mice. The values denote mean ± SEM. ∗p < 0.05; ∗∗p < 0.01; and ∗∗∗p < 0.001.

Figure 3

Obesity and Body Fat Distribution in Humans Positively Associates with an Increase in CXCR3+ Effector Memory T Cells (A–D) Number of total lymphocytes (A) and % of helper, naïve, and effector memory T cells (B–D) purified from the peripheral blood of lean, overweight, and obese subjects stratified according to BMI. (E) % of effector memory T cells purified from the peripheral blood of obese subjects stratified according to BMI either + (H) T cells with android/gynoid ratio. (A) n = 1,172. (B–D and F–H) n = 187. (E) n = 21 BMI ∗p < 0.05.

Figure 4

Antigen Presentation by DC from Metabolically Stressed Donors Does Not Affect T Cell Differentiation to a Pro-inflammatory Effector Memory-like Phenotype (A) Dot plots and quantification of in vitro proliferation of CFSE-labeled CD4+ T cells isolated from pooled lymph nodes of HFD or CD Marilyn female mice incubated for 3 days with CD11c+ DC isolated from the spleen of HFD or CD C57BL/6 male mice. The undivided and fourth division populations are quantified by dilution of the CFSE-label. (B) Cell surface staining of CD44, CCR7, CD62L, and CXCR3 in the undivided population of CFSE-labeled CD4+ T cells shown in (A). (C) Cell surface staining of CD40, CD80, and CD86 in CD11c+ DC used in (A). (A and B) n = 3 independent mice (each mouse was tested in triplicate). (C) n = 3 independent mice. The values denote mean ± SEM. ∗∗p < 0.01 and ∗∗∗p < 0.001.

Figure 5

Direct Exposure of CD4+ T Cells to Saturated FA Causes Enhanced Activation of a PI3K p110δ-Akt-Dependent Pathway upon Priming (A) Levels and densitometric quantification of p-Akt (S473), Akt, p-S6 (S235/236), and β-actin protein expression in in vivo-primed CD4+ T cells isolated from mesenteric lymph nodes of CD and HFD mice i.p. injected with the PI3K inhibitor IC87114 or left untreated. (B) Levels and densitometric quantification of p-Akt (S473) and Akt protein expression in CD4+ T cells purified from the peripheral blood of lean and obese human subjects. (C) Membrane fluidity index in in vivo-primed CD4+ T cells isolated from mesenteric lymph nodes of CD and HFD mice, calculated as the ratio of oleic acid (C18:1) to linoleic acid (C18:2). (D) Cell surface staining of CTxB in in vitro activated (Act) CD4+ T cells isolated from the lymph nodes of CD and HFD mice. The quantification of aggregation of CTxB is measured by bright detail intensity of the signal. (E–H) Cell surface staining of CD44 with CCR7 (E), CD62L (F), CXCR3 (G), and LFA1 (H) in in vivo-primed CD4+ T cells isolated from mesenteric lymph nodes of PED and PCD mice. (I and J) Protein levels and densitometric quantification of p-Akt (S473), Akt, p-S6 (S235/236), and S6 protein expression (I), and gene expression of CCR7 and CD62L (J) in CD4+ T cells isolated from pooled lymph nodes of mice and cultured overnight with IL-7 (1 ng/mL) in the presence or absence of palmitic, linoleic, or stearic acid (200 μM), followed by activation with plate bound anti-CD3 (0.5 μg/mL) and anti-CD28 (2.5 μg/mL) for the indicated time points. (K and L) Levels of CCR7 and CD62L gene expression (K) and CCR7 protein (L) in CD4+ T cells isolated from pooled lymph nodes of mice, then activated with plate bound anti-CD3 (0.5 μg/mL) and anti-CD28 (2.5 μg/mL) for the indicated time points in the presence or absence of the Akt activator SC79 (500 nM). (A and B) Each lane shows data from independent mouse/human samples. (C–H) n = 3–6 independent mice. (I) Representative data of n = 3 independent mice. (J–L) 3–6 pooled mice. The values denote mean ± SEM. ∗p < 0.05; ∗∗p < 0.01; and ∗∗∗p < 0.001.

Figure 6

The PI3K, Akt Pathway Is Key for the Differentiation of CXCR3+ Effector Memory T Cells (A–D) Cell surface staining of CD44 with CCR7 (A), CD62L (B), CXCR3 (C), and LFA1 (D) in in vivo-primed CD4+ T cells isolated from mesenteric lymph nodes of HFD P110δD910A or WT C57BL/6 mice. (E) Levels and densitometric quantification of p-Akt (S473), Akt, p-S6 (S235/236), and S6 protein expression in in vivo-primed CD4+ T cells from (A)–(D). (F) Ex vivo chemotaxis (3 hr, 6 hr, and 24 hr time points) of in vivo-primed CD4+ T cells isolated from mesenteric lymph nodes of HFD or CD OT-II P110δD910A mice in response to CXCL10 (300 ng/mL), CCL19/21 (200 ng/mL of each chemokine), or media only. (G–J) Cell surface staining of CD44 with CCR7 (G), CD62L (H), CXCR3 (I), and LFA1 (J) in in vivo-primed CD4+ T cells isolated from mesenteric lymph nodes of CD and HFD mice i.p. injected with the PI3K inhibitor IC87114, the Akt activator SC79, or left untreated. (A–E and G–J) n = 5 independent mice. (F) n = 4 independent mice (each mouse was tested in duplicate). The values denote mean ± SEM. ∗p < 0.05; ∗∗p < 0.01; and ∗∗∗p < 0.001.

Figure 7

Inhibition of FAO Prevents Enhanced Effector Memory Differentiation in Saturated Fatty Acid-Enriched Diet (A) OCR of naive CD4+ T cells isolated from pooled lymph nodes of mice and cultured overnight with IL-7 (1 ng/mL) in the presence or absence of palmitic or stearic acid (200 μM). (B–E) Cell surface staining of CD44 with CCR7 (B), CD62L (C), CXCR3 (D), and LFA1 (E) in in vivo-primed CD4+ T cells isolated from mesenteric lymph nodes of PED or PCD mice i.p. injected with etomoxir or left untreated. (A) Six pooled mice tested in 6–10 replicates per treatment. (B–E) n = 5 independent mice. The values denote mean ± SEM. ∗p < 0.05 and ∗∗p < 0.01.