Heme Oxygenase-1 Restores Impaired GARP+CD4+CD25+ Regulatory T Cells from Patients with Acute Coronary Syndrome by Upregulating LAP and GARP Expression on Activated T Lymphocytes

Abstract

Background: Accumulating evidence shows that the pathological autoreactive immune response is responsible for plaque rupture and the subsequent onset of acute coronary syndrome (ACS). Naturally occurring CD4⁺CD25⁺regulatory T cells (nTregs) are indispensable in suppressing the pathological autoreactive immune response and maintaining immune homeostasis. However, the number and the suppressive function of glycoprotein-A repetitions predominant (GARP) ⁺ CD4⁺ CD25⁺ activated nTregs were impaired in patients with ACS. Recent evidence suggests that heme oxygenase-1 (HO-1) can regulate the adaptive immune response by promoting the expression of Foxp3. We therefore hypothesized that HO-1 may enhance the function of GARP⁺ CD4⁺ CD25⁺Tregs in patients with ACS and thus regulate immune imbalance. Methods: T lymphocytes were isolated from healthy volunteers (control, n=30) and patients with stable angina (SA, n=40) or ACS (n=51). Half of these cells were treated with an HO-1 inducer (hemin) for 48 h, and the other half were incubated with complete RPMI-1640 medium. The frequencies of T-helper 1 (Th1), Th2, Th17 and latency-associated peptide (LAP) ⁺CD4⁺ T cells and the expression of Foxp3 and GARP by CD4⁺CD25⁺T cells were then assessed by measuring flow cytometry after stimulation in vitro. The suppressive function of activated Tregs was measured by thymidine uptake. The levels of transforming growth factor-1 (TGF-β1) in the plasma were measured using enzyme-linked immunosorbent assay (ELISA). The expression levels of the genes encoding these proteins were analyzed by real-time polymerase chain reaction. Results: Patients with ACS exhibited an impaired number and suppressive function of GARP⁺ CD4⁺ CD25⁺Tregs and a mixed Th1/Th17-dominant T cell response when compared with the SA and control groups. The expression of LAP in T cells was also lower in patients with ACS compared to patients with SA and the control individuals. Treatment with an HO-1 inducer enhanced the biological activity of GARP⁺ CD4⁺ CD25⁺Tregs and resulted in increased expression of LAP and GARP by activated T cells. Conclusions: The reduced number and impaired suppressive function of GARP⁺ CD4⁺ CD25⁺Tregs result in excess effector T cell proliferation, leading to plaque instability and the onset of ACS. HO-1 can effectively restore impaired GARP⁺ CD4⁺ CD25⁺Tregs from patients with ACS by promoting LAP and GARP expression on activated T cells.

Angiotensin II Regulates Th1 T Cell Differentiation Through Angiotensin II Type 1 Receptor-PKA-Mediated Activation of Proteasome

“…Naive CD4 + T cells can differentiate into different Th cell lineages that are essential for efficient immune responses against different types of pathogens [4, 10]. Many factors are known to regulate Th1 and Th2 differentiation, especially renin-angiotensin system (RAS).…”

“…Jurkat cells (Clone E6-1), a Th0-like human T lymphoblastoid cell line (ATCC), were grown in suspension at 37°C in 5% CO 2 , in RPMI 1640 medium supplemented with glutamine (2 mM), 10% fetal bovine serum, and penicillin (100 units/ml) and streptomycin (100 µg/ml) as described [10]. The cells were passed at a dilution of 1: 15 once or twice a week to maintain the maximal density of 2-3 × 10 6 cells/ml.…”

Targeting heme oxygenase-1 and carbon monoxide for therapeutic modulation of inflammation

“…224 Stimulation of HO-1 induction ex vivo restored GARP + CD4 + CD25 + Tregs populations in isolated T lymphocyte samples from patients with acute coronary syndrome, and promoted the expression of effector molecules ( i.e., LAP and GARP) on activated T cells. 225 HO-1 may be important for the functioning of DCs in antigen-presentation and adaptive immune responses. Targeted up-regulation of HO-1 can influence the maturation and cell-specific functions of DCs in humans and mice.…”

Intracellular and extracellular TGF-β signaling in cancer: some recent topics

“…GARP is expressed on megakaryocytes/platelets, and may be important for platelet-endothelium interactions [220]. Impaired immunosuppressive functions of GARP + Tregs have also been reported to be involved in acute coronary syndrome [221,222].…”