Ganoderic acid Me induces the apoptosis of competent T cells and increases the proportion of Treg cells through enhancing the expression and activation of indoleamine 2,3-dioxygenase in mouse lewis lung cancer cells.

Abstract

The indoleamine 2,3-dioxygenase-(IDO-) mediated microenvironment plays an important role in tumor immune escape. It is known that ganoderic acid Me can enhance IFN-γ expression and IDO is preferentially induced by IFN-γ. However, whether GA-Me can induce IDO expression has not been clarified yet. We established stable clones of IDO-overexpressing 2 LL cells (2LL-EGFP-IDO). After co-culturing with IDO expressing or control vector-transfected 2LL-EGFP cells, T cell apoptosis was determined and the proportion of the regulatory T cells (Tregs) and CD8+ T cell subset was measured. The total cellular protein samples of 2 LL-EGFP-IDO cells were isolated for detecting JAK-STAT1 signalling pathway. Co-culture supernatants were used to detect amino acids and cytokines. IDO transfected 2 LL cells yielded high level of IDO enzymatic activity, resulting in complete depletion of tryptophan from the culture medium. We found that apoptosis occurred in T cells after cocultured with IDO+2LL cells and the proportion of CD4+CD25+ cells and FoxP3+ cells increased while CD8+ cells decreased. The specific inhibitor of IDO, 1-D-MT and GA-Me efficiently enhanced T cell apoptosis, increased Tregs, and reduced CD8+ T cells in vitro. Increased expression of IDO, p-JAK1 and p-STAT1 were confirmed by Western blot analysis. The levels of IFN-γ, IL-10, LDH and kynurenine in co-culture supernatant correspondingly increased, while tryptophan reduced. These results suggest that GA-Me contributing to IDO helps to create a tolerogenic milieu in lung tumors by directly inducing T cell apoptosis, restraining CD8+ T cell activation, and enhancing Treg-mediated immunosuppression.

• Authors: Zujun Que, Fangyuan Zou, Anle Zhang, Yuanhong Zheng, Ling Bi, Jianjiang Zhong, Jianhui Tian, Jianwen Liu
• Journal: International immunopharmacology (Int Immunopharmacol) Vol. 23 Issue 1 Pg. 192-204 (Nov 2014) ISSN: 1878-1705 [Electronic] Netherlands
• PMID: 25138378 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier B.V. All rights reserved.

Chemical References

• Indoleamine-Pyrrole 2,3,-Dioxygenase
• Interleukin-1
• STAT1 Transcription Factor
• Triterpenes
• ganoderic acid Me
• Interferon-gamma
• Janus Kinases

Topics

• Animals
• Apoptosis (drug effects)
• CD8-Positive T-Lymphocytes (drug effects, immunology)
• Carcinoma, Lewis Lung (drug therapy, immunology)
• Clone Cells
• Coculture Techniques
• Humans
• Indoleamine-Pyrrole 2,3,-Dioxygenase (genetics, metabolism)
• Interferon-gamma (metabolism)
• Interleukin-1 (metabolism)
• Janus Kinases (metabolism)
• Mice
• Mice, Inbred C57BL
• Phytotherapy (methods)
• Reishi (immunology)
• STAT1 Transcription Factor (metabolism)
• Signal Transduction (drug effects)
• T-Lymphocytes, Regulatory (drug effects, immunology)
• Triterpenes (pharmacology)
• Tumor Escape