Glycyrrhizic acid improves cognitive levels of aging mice by regulating T/B cell proliferation

Abstract

Dear Editor,Licorice is the root of Glycyrrhiza glabra L. (Leguminosae), which grows in various warm climates such as the Middle East, Asia, and Southern Europe. It is one of the oldest known medicinal herbs and is referred to as "the father of herbal medicine." Glycyrrhizic acid (GA) (Fig. 1A), a triterpenoid saponin, is a major component of licorice. It has a variety of pharmacological activities such as anti-inflammatory, antioxidant, anticancer, neuroprotective, and immune effects, among others.[1]. Previous studies indicated that GA produces robust neuroprotection via the modulation of anti-apoptotic and pro-apoptotic factors, primarily through the ERK signaling pathway and its anti-inflammatory properties against high-mobility group box 1 phosphorylation and the suppression of inflammatory cytokine induction [2-4]. These results were based on pathological models. Although numerous pathways have been implicated in the neuroprotective effects of GA, the molecular mechanisms are not yet completely understood. In this study, we aimed to investigate the effects of GA in preventing age-related immune involution and cognitive disorders, the relationship between immune involution and cognition, and the underlying molecular mechanisms. O_FIG O_LINKSMALLFIG WIDTH=141 HEIGHT=200 SRC="FIGDIR/small/008821v1_fig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@5a123dorg.highwire.dtl.DTLVardef@163a085org.highwire.dtl.DTLVardef@1bfadb6org.highwire.dtl.DTLVardef@125b2ae_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO Glycyrrhizic acid ameliorated cognitive declines in aged mice, improved CBF and increased T and B cell numbers. A. The chemical structure of glycyrrhizic acid (GA). B. Escape latencies from six consecutive daily tests. C. The first platform-finding latencies in the probe trial. D. The time spent in the target quadrant in the probe trial. E. The target platform crossing times in the probe trial. F. Images of CBF in C57BL/6 mice. G. Quantification of blood perfusion in the ipsilateral hemisphere. H. Bubble diagram showing GA treatment influence on hematopoietic cell lineage. I. Heatmap showing actively expressed genes related to T cells in the hematopoietic cell lineage of control and GA-treated C57BL/6 mice. J. Representative FACS plots showing CD3e+ T and CD45R/B220+ B cells in the spleens of C57BL mice; bar graphs showing the statistical analysis of T and B cells in the spleens of C57BL mice. K. Representative FACS plots showing CD3e+ T and CD45R/B220+ B cells in the blood of C57BL mice; Bar graphs showing the statistical results of T and B cell analyses in the blood of C57BL mice. GA (5mg/kg, once every other day); Data represent mean {+/-} SEM (n = 8 per group). *P < 0.05, **P < 0.01, ***P < 0.001 vs. Ctrl. C_FIG