T cells in aorta, mesenteric vascular arcade and epididymal adipose tissue exhibit a heterogeneous inflammatory phenotype with advanced age
Authors: Trott Daniel 
Published: April 2020

T cells mediate vascular and metabolic dysfunction in rodent models of hypertension and obesity. It is less well known whether T cells contribute to chronic age‐related declines in vascular and metabolic dysfunction. We have previously shown that aging results in infiltration of T cells around the aorta and mesenteric vascular arcade. This study tested the hypothesis that in addition to increased infiltrating T cells in the aorta, mesenteric arcade and epididymal adipose tissue with age, a greater proportion of these T cells will exhibit proinflammatory cytokine production. The aorta, mesenteric vasculature (both including perivascular adipose) and epididymal white adipose tissue (eWAT) were excised from young (Y, 4–6 months, n = 7) and old (O, 22–24 months, n = 8) male C57Bl6 mice and digested to a single cell suspension. Cells were stimulated with phorbol 12‐myristate 13‐acetate and ionomycin to stimulate cytokine production and Brefeldin A to block protein transport to the Golgi. Cells were then labeled with antibodies against CD45 (total leukocytes), CD3 (pan T cells), CD4 (T helper cells), CD8 (cytotoxic T cells), interferon (IFN)‐γ and tumor necrosis factor (TNF)‐α and analyzed by flow cytometry. Data are expressed as mean ± standard error and differences are considered significant at p ≤ 0.05 as assessed by an independent samples T test. Aging resulted in a greater proportion of CD8+ IFN− γ+ cells in the aorta (Y 46 ± 6% vs. O 75 ± 3%) but not mesentery (Y 52.6 ± 4% vs. O 63 ± 9%) or eWAT (Y 63 ± 5% vs. O 69 ± 4%). Similarly, aging resulted in a greater proportion of CD8+ TNF‐α+ cells in aorta (Y 17 ± 3% vs. O 35 ± 5%) but not mesentery (Y 24 ± 6% vs. O 32 ± 8%) or eWAT (Y 23 ± 3% vs. O 28 ± 4%). Among CD4 cells, aging resulted in a greater proportion of IFN‐γ+ cells in the aorta (Y 34 ± 7% vs. O 56 ± 4%) but not mesentery (Y 27 ± 4% vs. O 36 ± 6%) or eWAT (Y 30 ± 3% vs. O 30 ± 4%). Aging did not alter the proportion of CD4+ TNF‐α+ CD4 cells in the aorta (Y 63 ± 4% vs. O 65 ± 4%), mesentery (Y 56 ± 5% vs. O 53 ± 5%), or eWAT (Y 47 ± 6% vs. O 40 ± 7%). Despite not changing the proportion of inflammatory cytokines in mesentery and eWAT, when normalized to adipose tissue mass (expressed as cells per gram), aging resulted in greater numbers of CD8+ IFN‐γ+ cells in mesentery (Y 733 ± 190 vs. O 19952 ± 7435), CD8+ TNF‐α+ cells (Y 410 ± 145 vs. O 5901 ± 3971), CD4+ IFN‐γ+ (Y 410 ± 145 vs. O 5901 ± 1776), and CD4+ TNF‐α+ cells (Y 760 ± 172 vs. O 11587 ± 4133). Similar results were observed in the eWAT: CD8+ IFN‐γ+ cells (Y 330 ± 156 vs. O 1185 ± 266), CD8+ TNF‐α+ cells (Y 112 ± 48 vs. O 502 ± 152), CD4+ IFN‐γ+ (Y 345 ± 166 vs. O 1090 ± 237) and CD4+ TNF‐α+ cells (Y 530 ± 212 vs. O 1399 ± 294). To begin to address the influence of exercise on T cell phenotype, a subset of old animals were provided with a running wheel (n = 3). Voluntary running (VR) resulted in attenuated proportions of CD8+ IFN‐γ+ cells (O 75 ± 3% vs. OVR 59 ± 10%) and CD4+ IFN‐γ+ cells (O 55 ± 4% vs. OVR 33 ± 7%) in aorta but not mesentery or eWAT when compared to sedentary mice. These data suggest that; 1) there is heterogeneity in the phenotype of perivascular and visceral adipose infiltrating T cells in advanced age; 2) that T cell trafficking, rather than inflammatory phenotype, may be responsible for age‐related increases in adipose tissue inflammation and subsequent vascular and metabolic disease risk.Support or Funding InformationSupported by NIH K01AG06127 and R01AG060395