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Glycyrrhizin protects against focal cerebral ischemia via inhibition of T cell activity and HMGB1-mediated mechanisms

View Article: PubMed Central - PubMed

ABSTRACT

Background: Glycyrrhizin (Gly) protects against brain injury induced by stroke. We studied whether Gly achieves its protection by inhibiting T cell activity and high-mobility group box 1 (HMGB1) release in the ischemic brain.

Methods: Stroke was induced by transient middle cerebral artery occlusion in rats and mice. Gly was injected intraperitoneally before or after stroke. We measured infarction, neuroinflammatory cells, gene expressions of interferon-γ (IFNγ), IL-4, and IL-10 in CD4 T cells, HMGB1 release, and T cell proliferation in cultured splenocytes.

Results: Gly treatment reduced infarctions and neuroinflammation characterized by the infiltration of CD68-positive macrophages and myeloperoxidase-positive neutrophils, which corresponds to a reduction in the number of T cells and their subsets, CD4 and CD8 T cells, in the ischemic brain, as measured by flow cytometry. Unlike in wild-type animals, Gly did not offer protection in nude rats and severe combined immunodeficient (SCID) mice who had no T cells, while Gly reduced infarction in both nude rats and SCID mice whose T cells were reconstituted, suggesting that T cells should be the target of Gly. In addition, Gly administration inhibited T cell proliferation stimulated by ConA in in vitro assays and inhibited HMGB1 release from the ischemic brain. Furthermore, Gly attenuated gene expression of IFNγ, but not IL-4 and IL-10 in CD4 T cells. Lastly, HMGB1 promoted T cell proliferation stimulated by ConA, which was inhibited by the addition of Gly.

Conclusions: Gly blocks infarction by inhibiting IFNγ-mediated T cell activity, which is at least partly modulated by HMGB1 activity.

No MeSH data available.


Related in: MedlinePlus

Gly injection did not reduce infarction in SCID mice and T cell-deficient nude rats. Infarct size in the ipsilateral hemisphere was measured 3 days after stroke onset using TTC staining, then normalized to the contralateral hemisphere and expressed as a percentage. a The effects of Gly injection on brain infarction in SCID mice with and without T cell reconstitution. n = 7 to 9/each group. *P < 0.05 between the two indicated groups. b Gly treatment did not reduce infarct size in focal ischemia with 100 min MCA suture occlusion in nude rats. The drug was injected i.p. immediately before stroke onset and 2 h after reperfusion. The animals were divided into four groups. Nude rats in the first two groups were injected with vehicle and Gly, while nude rats in the second two groups were reconstituted with wild-type splenocytes, thus T cells were reconstituted. ***P < 0.001 vs control ischemia with vehicle injection; #P < 0.05 between the two indicated groups. c The effects of Gly on neuronal death in the co-culture with splenocytes. Neurons were co-cultured with wild-type (WT) and SCID splenocytes. *P < 0.05 between the two indicated groups
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Fig4: Gly injection did not reduce infarction in SCID mice and T cell-deficient nude rats. Infarct size in the ipsilateral hemisphere was measured 3 days after stroke onset using TTC staining, then normalized to the contralateral hemisphere and expressed as a percentage. a The effects of Gly injection on brain infarction in SCID mice with and without T cell reconstitution. n = 7 to 9/each group. *P < 0.05 between the two indicated groups. b Gly treatment did not reduce infarct size in focal ischemia with 100 min MCA suture occlusion in nude rats. The drug was injected i.p. immediately before stroke onset and 2 h after reperfusion. The animals were divided into four groups. Nude rats in the first two groups were injected with vehicle and Gly, while nude rats in the second two groups were reconstituted with wild-type splenocytes, thus T cells were reconstituted. ***P < 0.001 vs control ischemia with vehicle injection; #P < 0.05 between the two indicated groups. c The effects of Gly on neuronal death in the co-culture with splenocytes. Neurons were co-cultured with wild-type (WT) and SCID splenocytes. *P < 0.05 between the two indicated groups

Mentions: We then test if T cells are the targets for the protective effects of Gly. As STAIR requires that multiple animal models should be used to confirm a drug’s protective effects against stroke, both mice and rats were used. We first examined whether Gly injection reduces infarction in SCID mice in which no T cells or B cells are present. The results showed that Gly injection significantly inhibited infarction in the wild-type mice but showed no protection in the SCID mice. Nevertheless, when T cells and B cells were reconstituted in SCID mice, Gly injection again reduced infarct sizes (Fig. 4a). These results suggest that T cells might be the essential target for the protective effect of Gly.Fig. 4


Glycyrrhizin protects against focal cerebral ischemia via inhibition of T cell activity and HMGB1-mediated mechanisms
Gly injection did not reduce infarction in SCID mice and T cell-deficient nude rats. Infarct size in the ipsilateral hemisphere was measured 3 days after stroke onset using TTC staining, then normalized to the contralateral hemisphere and expressed as a percentage. a The effects of Gly injection on brain infarction in SCID mice with and without T cell reconstitution. n = 7 to 9/each group. *P < 0.05 between the two indicated groups. b Gly treatment did not reduce infarct size in focal ischemia with 100 min MCA suture occlusion in nude rats. The drug was injected i.p. immediately before stroke onset and 2 h after reperfusion. The animals were divided into four groups. Nude rats in the first two groups were injected with vehicle and Gly, while nude rats in the second two groups were reconstituted with wild-type splenocytes, thus T cells were reconstituted. ***P < 0.001 vs control ischemia with vehicle injection; #P < 0.05 between the two indicated groups. c The effects of Gly on neuronal death in the co-culture with splenocytes. Neurons were co-cultured with wild-type (WT) and SCID splenocytes. *P < 0.05 between the two indicated groups
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5016958&req=5

Fig4: Gly injection did not reduce infarction in SCID mice and T cell-deficient nude rats. Infarct size in the ipsilateral hemisphere was measured 3 days after stroke onset using TTC staining, then normalized to the contralateral hemisphere and expressed as a percentage. a The effects of Gly injection on brain infarction in SCID mice with and without T cell reconstitution. n = 7 to 9/each group. *P < 0.05 between the two indicated groups. b Gly treatment did not reduce infarct size in focal ischemia with 100 min MCA suture occlusion in nude rats. The drug was injected i.p. immediately before stroke onset and 2 h after reperfusion. The animals were divided into four groups. Nude rats in the first two groups were injected with vehicle and Gly, while nude rats in the second two groups were reconstituted with wild-type splenocytes, thus T cells were reconstituted. ***P < 0.001 vs control ischemia with vehicle injection; #P < 0.05 between the two indicated groups. c The effects of Gly on neuronal death in the co-culture with splenocytes. Neurons were co-cultured with wild-type (WT) and SCID splenocytes. *P < 0.05 between the two indicated groups
Mentions: We then test if T cells are the targets for the protective effects of Gly. As STAIR requires that multiple animal models should be used to confirm a drug’s protective effects against stroke, both mice and rats were used. We first examined whether Gly injection reduces infarction in SCID mice in which no T cells or B cells are present. The results showed that Gly injection significantly inhibited infarction in the wild-type mice but showed no protection in the SCID mice. Nevertheless, when T cells and B cells were reconstituted in SCID mice, Gly injection again reduced infarct sizes (Fig. 4a). These results suggest that T cells might be the essential target for the protective effect of Gly.Fig. 4

View Article: PubMed Central - PubMed

ABSTRACT

Background: Glycyrrhizin (Gly) protects against brain injury induced by stroke. We studied whether Gly achieves its protection by inhibiting T cell activity and high-mobility group box 1 (HMGB1) release in the ischemic brain.

Methods: Stroke was induced by transient middle cerebral artery occlusion in rats and mice. Gly was injected intraperitoneally before or after stroke. We measured infarction, neuroinflammatory cells, gene expressions of interferon-&gamma; (IFN&gamma;), IL-4, and IL-10 in CD4 T cells, HMGB1 release, and T cell proliferation in cultured splenocytes.

Results: Gly treatment reduced infarctions and neuroinflammation characterized by the infiltration of CD68-positive macrophages and myeloperoxidase-positive neutrophils, which corresponds to a reduction in the number of T cells and their subsets, CD4 and CD8 T cells, in the ischemic brain, as measured by flow cytometry. Unlike in wild-type animals, Gly did not offer protection in nude rats and severe combined immunodeficient (SCID) mice who had no T cells, while Gly reduced infarction in both nude rats and SCID mice whose T cells were reconstituted, suggesting that T cells should be the target of Gly. In addition, Gly administration inhibited T cell proliferation stimulated by ConA in in vitro assays and inhibited HMGB1 release from the ischemic brain. Furthermore, Gly attenuated gene expression of IFN&gamma;, but not IL-4 and IL-10 in CD4 T cells. Lastly, HMGB1 promoted T cell proliferation stimulated by ConA, which was inhibited by the addition of Gly.

Conclusions: Gly blocks infarction by inhibiting IFN&gamma;-mediated T cell activity, which is at least partly modulated by HMGB1 activity.

No MeSH data available.


Related in: MedlinePlus