Abstract
Platycodongrandiflorus (PG) root extract has been widely used as an oriental herbal medicine. Red PG root extract (RPGE), which is made by steaming and drying PG several times, contains more saponin than raw (white) PG. Although RPGE has been known to have anti-inflammatory activity, the effects of RPGE on the immune-enhancing response remain unclear. In this study, we aimed to investigate the immune-enhancing effects of RPGE and its mechanism in macrophage cells and splenocytes. Our results revealed that cell proliferation of both macrophages and splenocytes correlate positively with the concentration of RPGE. Moreover, RPGE treatment increased the phagocytic activity of macrophage cells, as well as nitric oxide and cytokines production. Furthermore, RPGE induced phosphorylation of the p38 mitogen-activated protein kinase, which contributed to nuclear factor-kappa B activation. Thus, our findings suggest that RPGE may be a potential functional food for improving immune function.
Highlights
Herbal immunostimulants are generally categorized as natural compounds that can enhance immune responses by activating immune cells, such as macrophages [1,2]
We aimed to evaluate the immune-enhancing effects of red PG extract (RPGE) in RAW 264.7 macrophage cells and mouse splenocytes
We investigated its effects on the NF-κB and mitogen-activated protein kinase (MAPK) signaling pathways to determine the underlying mechanisms of the immune-enhancing effects of RPGE in immune cells
Summary
Herbal immunostimulants are generally categorized as natural compounds that can enhance immune responses by activating immune cells, such as macrophages [1,2]. Nuclear factor-kappa B (NF-κB)-mediated cellular changes are known to be closely associated with both the innate and adaptive immune responses [4,5]. In innate immune cells, such as macrophages, NF-κB activation is initiated by the degradation of inhibitory kappa B alpha (IκB) proteins, following which the free NF-κB enters the nucleus to perform various downstream functions, including immune regulation and proliferation [4,6]. Immunostimulants activate the immune cell function through specific binding with receptors [7]. Immunostimulants trigger several downstream signals, such as the NF-κB pathway, p38 mitogen-activated protein kinase (MAPK), and the c-Jun
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