Diammonium Glycyrrhizinate Mitigates Liver Injury Via Inhibiting Proliferation Of NKT Cells And Promoting Proliferation Of Tregs.
Purpose
Diammonium glycyrrhizinate (DG) is a replacement for glycyrrhizic acid, which is used as a hepatic protector in clinical practice for most liver diseases. The potential role of immune response during autoimmune hepatitis-induced by concanavalin A (Con A)-remains to be elucidated.


Methods
C57BL/6J mice were treated with two different doses of DG (75 and 200 mg/kg) 2 hrs before administering Con A. The mice were sacrificed after administering Con A for 0, 6, and 24 hrs. Liver damage grade and serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin levels were evaluated. The expression level of cleaved-caspase 3 in liver was detected by Western blotting. Inflammatory cytokines such as tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), and interferon γ (IFN-γ) in liver were detected by RT-PCR. Thymus, peripheral blood, spleen, and liver tissues were collected to analyze the percentages of NKT cells, subsets of CD4+CD25-CD69+ and CD8+CD69+ T cells, and subsets of regulatory T cells (Tregs).


Results
Our results revealed that DG pre-treatment significantly decreased the serum ALT and AST levels and improved the histological damage in Con A-induced autoimmune liver injury. Pre-treatment with DG down-regulated the inflammatory cytokines upon challenge with Con A. The DG pre-treatment inhibited the apoptosis of T lymphocytes in the thymus. Further, it effectively suppressed the proliferation of CD4+CD25-CD69+ and CD8+CD69+ subsets in the peripheral blood and spleen. In addition, the DG pretreatment significantly downregulated the frequency of NKT cells, while upregulating the frequency of Tregs in the liver.


Conclusion
We believe that the potential protective effect of DG against Con A-induced hepatitis may be partially attributed to its inhibitory activities on inflammatory cytokines in the livers, lymphocyte apoptosis in the thymus, NKT cells proliferation, and activation of CD8+T cells; further, there may also be a possibility of DC promoting Tregs proliferation.
['Gao|Meixin|M|0000-0002-5385-9703', 'Li|Xiulan|X|', 'He|Lingling|L|0000-0001-8082-8788', 'Yang|Junru|J|0000-0003-4030-7560', 'Ye|Xiaohui|X|0000-0002-4161-4389', 'Xiao|Fan|F|', 'Wei|Hongshan|H|']
D000818:Animals D000893:Anti-Inflammatory Agents D049109:Cell Proliferation D056486:Chemical and Drug Induced Liver Injury D003208:Concanavalin A D004195:Disease Models, Animal D004305:Dose-Response Relationship, Drug D019695:Glycyrrhizic Acid D019693:Hepatitis, Autoimmune D008297:Male D051379:Mice D008810:Mice, Inbred C57BL D015394:Molecular Structure D055611:Natural Killer T-Cells D013329:Structure-Activity Relationship D050378:T-Lymphocytes, Regulatory
diammonium glycyrrhizinate NKT cells concanavalin A autoimmune hepatitis regulatory T-cell