We have identified some unique triterpenoids isolated from the fruiting bodies of Ac and As and evaluated their biological effects 23, 35–38. However, their immunomodulatory activity is not known. DC play a central role in immune system. Thus, DC are selected for evaluating the immunomodulatory effect of these compounds. We tested some reported triterpenoid compounds, including eburicoic acid, dehydroeburicoic acid, sulphurenic acid, dehydrosulphurenic acid, 3-keto-dehydrosulphurenic acid, 15α-acetyl-dehydrosulphurenic acid, versisponic acid D, zhankuic acid A, B, C, antcin A, C, K, and me-Ant K. In addition, we included two newly identified triterpenoids from Ac, antcin N (3α, 7β, 12α-trihydroxy-4α-methylergosta-8, 24(29)-dien-11-on-26-oic acid) and me-Ant N (unpublished data), which have the same molecular weight as antcin K (3α, 4β, 7β-trihydroxy-4α-methylergosta-8, 24(29)-dien-11-on-26-oic acid) and me-Ant K, respectively (Fig. 1A). To determine the effect of these triterpenoids on DC, we first examined the BMDC cultures by microscopy after treatment of these compounds for 16 h. All compounds had >90–95% purity and were used at 50 μM as the maximal bioactivity was shown at this concentration for some compounds 23, 36, 38. In addition, all compounds had no significant cytotoxicity at this dose as measured by PI staining (data not shown). DC aggregation was observed after the compound me-Ant K treatment (data not shown), indicating that me-Ant K can potentially activate DC. Using flow cytometry, we found that me-Ant K, and to a lesser extent me-Ant N, induced upregulation of MHC class II and CD86 on DC while other triterpernoids had no effect (Fig. 1B). The degree of MHC class II and CD86 upregulation with me-Ant K approximates, but is less than, that seen with LPS stimulation.
Figure 1. The structures of four triterpenoid compounds and their effects on BMDC activation. (A) The structure of antcin K, antcin N, me-Ant K, and me-Ant N. Antcin N and me-Ant N are newly identified triterpenoids from Ac. (B) BMDC were incubated with compounds (50 μM) (black line) or DMSO (control, gray line) for 16 h. LPS (100 ng/mL) treated cells (black line) or untreated cells are shown in the right panels. Dotted lines represent staining with an isotype-matched control Ab. DC activation was determined by flow cytometry after staining with mAb specific for MHC class II and CD86. The change of MFI from control to treatment was indicated. Data are representative of three independent experiments.
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