Veronica austriaca L. Extract and Arbutin Expand Mature Double TNF-α/IFN-γ Neutrophils in Murine Bone Marrow Pool

Plants from the Veronica genus are used across the world as traditional remedies. In the present study, extracts from the aerial part of the scarcely investigated Veronica austriaca L., collected from two habitats in Bulgaria-the Balkan Mountains (Vau-1) and the Rhodopi Mountains (Vau-2), were analyzed by nuclear magnetic resonance (NMR) spectroscopy. The secondary metabolite, arbutin, was identified as a major constituent in both extracts, and further quantified by high-performance liquid chromatography (HPLC), while catalpol, aucubin and verbascoside were detected at lower amounts. The effect of the extracts and of pure arbutin on the survival of neutrophils isolated from murine bone marrow (BM) were determined by colorimetric assay. The production of cytokines-tumor necrosis factor (TNF)-α and interferon (IFN)-γ was evaluated by flowcytometry. While Vau-1 inhibited neutrophil vitality in a dose-dependent manner, arbutin stimulated the survival of neutrophils at lower concentrations, and inhibited cell density at higher concentrations. The Vau-1 increased the level of intracellular TNF-α, while Vau-2 and arbutin failed to do so, and expanded the frequency of mature double TNF-α⁺/IFN-γ^hi neutrophils within the BM pool.