Bioactive constituents of Verbena officinalis regulate killing efficiency of primary human natural killer cells by accelerating killing processes

Abstract

Background Natural killer (NK) cells play a key role in eliminating tumorigenic and pathogen-infected cells. Verbena officinalis (V. officinalis) has been used as a medical plant in traditional and modern medicine, exhibiting anti-tumor and anti-inflammation activity.Purpose The impact of bioactive constituents of V. officinalis on immune responses still remains largely elusive. In this work we investigated the potential targets of V. officinalis and focused on killing efficiency and related functions of NK cells regulated by bioactive constituents of V. officinalis.Study design/methods We used primary human NK cells from peripheral blood mononuclear cells. Potential regulatory roles of selected compounds were analyzed by network pharmacology approaches. Killing efficiency was determined with real-time killing assay and live-cell imaging in 3D. Proliferation was examined by CFSE staining. Expression of cytotoxic proteins was analyzed using flow cytometry. Lytic granule release was quantified by CD107a degranulation assay. Contact time required for killing and determination of serial killers were analyzed using live cell imaging results. Results: Using network pharmacology approaches, we analyzed potential regulatory roles of five compounds (Acteoside, Apigenin, Kaempferol, Verbenalin and Hastatoside) from V. officinalis on immune cell functions and revealed NK cells as a major target. The effect of these compounds on NK killing efficiency was examined with real-time killing assay, and Verbenalin enhanced NK killing efficiency significantly. Further investigation showed that Verbenalin did not affect proliferation, expression of cytotoxic proteins, or lytic granule degranulation, but rather reduced contact time required for killing therefore enhancing total killing events per NK cell, suggestively via inhibition of inhibitory receptors as determined by docking assay.Conclusions Our findings reveal the underlying mechanisms how V. officinalis regulates functions of immune cells, especially NK cells, suggesting Verbenalin from V. officinalis as a promising therapeutic reagent to fight cancer and infection.Competing Interest StatementThe authors have declared no competing interest.