Licochalcone A improves the cognitive ability of mice by regulating T- and B-cell proliferation

Abstract

Licochalcone A (LA), a flavonoid found in licorice, has anticancer, antioxidant, anti-inflammatory, and neuroprotective properties. Here, we explored the effect of injecting LA into the tail vein of middle-aged C57BL/6 mice on their cognitive ability as measured by the Morris water maze (MWM) test and cerebral blood flow (CBF). The related mechanisms were assessed via RNA-seq, and T (CD3e⁺) and B (CD45R/B220⁺) cells in the spleen and whole blood were quantified via flow cytometry. LA improved the cognitive ability, according to the MWM test results, and upregulated the CBF level of treated mice. The RNA-seq results indicate that LA affected the interleukin (IL)-17 signaling pathway, which is related to T- and B-cell proliferation, and the flow cytometry data suggest that LA promoted T- and B-cell proliferation in the spleen and whole blood. We also performed immune reconstruction via a tail vein injection of lymphocytes into B-NDG (NOD-Prkdc^scidIl2rg^tm1/Bcge) mice before treating them with LA. We tested cognitive ability by subjecting these animals to new object recognition tests and quantified the splenic and whole blood T and B cells. Cognitive ability improved after immune reconstruction and LA treatment, and LA promoted T- and B-cell proliferation in the spleen and whole blood. This study demonstrates that LA, by activating the IL-17 signaling pathway, promotes T- and B-cell proliferation in the spleen and whole blood of mice and improves cognitive ability. Thus, LA may have immune-modulating therapeutic potential for improving cognition.

Keywords: B cells; T cells; cognitive ability; licochalcone A.

Figure 1

Effect of LA treatment on the cognitive ability of middle-aged C57BL/6 mice. (A) The chemical structure of LA. (B) Time taken by LA-treated or control (Ctrl)-treated mice to reach the platform in the MWM test over a 6-day experiment. (C) First latency to the platform in the MWM test. (D) In zone target duration in the MWM test. (E) Frequency in zone in the MWM test. (F) Cerebral blood flow level in LA- or Ctrl-treated mice. The data are presented as the mean±SD of three independent experiments. Statistical significance was determined using unpaired t-tests. *p < 0.05, **p < 0.01 compared with the Ctrl group; “n” indicates the number of animals in each experimental group.

Figure 2

Analysis of the mechanism by which LA regulates the immune system conducted using RNA-seq in the hippocampus. (A) Kegg pathway classification map. (B) Bubble diagram showing the pathways regulated by LA. (C) Heatmap showing the differentially expressed genes related to the IL-17 signaling pathway. The data are presented as the mean±SD of three independent experiments. Statistical significance was determined using unpaired t-tests. *p < 0.05, **p < 0.01 compared with the Ctrl group.

Figure 3

LA effect on lymphocyte proliferation in C57BL/6 mice. (A–D) T-cell and B-cell (A, C) or NK-cell (B, D) proliferation in the spleen (A, B) or whole blood (C, D) of LA- or control (Ctrl)-treated mice. The data are presented as the mean±SD of three independent experiments. Statistical significance was determined using unpaired t-tests. *p < 0.05, **p < 0.01 compared with the Ctrl group.

Figure 4

Effect of LA on T- and B-cell proliferation in B-NDG mice. (A) New object recognition results for the IR+LA, IR and non-IR groups. (B) Statistical analysis of the results shown in (A). (C, D) T- and B-cell proliferation in the spleen (C) and whole blood (D). The data are presented as the mean±SD of three independent experiments. Statistical significance was determined using unpaired t-tests. *p < 0.05, **p < 0.01 compared with the non-IR group; “n” indicates the number of animals for each experimental group.