Elephantopus scaber suppresses ConA-induced T cell activation by inhibiting NF-κB and Ca2+/NFAT signaling

Ethnopharmacological relevance: Elephantopus scaber L. (E. scaber) is a heat-clearing and detoxifying traditional Chinese medicine. Clinically, it is used for treating some immuno-inflammatory diseases associated with excessive T cell activation. However, its action and mechanism on T cells are still ambiguous.

Aim of the study: This study aims to investigate the molecular mechanism of the ethanol extract of E.scaber (ESE) in ConA-induced T cell activation models.

Materials and methods: IL-2 transcription and translation levels were determined by RT-qPCR and ELISA. CD4⁺ naïve T cells were sorted using the flow cytometer. Western blot assay was used for determining intracellular protein levels. Cytoplasmic and mitochondrial CA²⁺ concentrations were measured by fluorometric assays.

Results: ESE not only dampened the proliferation of splenic lymphocytes, but also decreased IL-2 production in ConA-activated T cells without affecting its mRNA stability. It could inhibit the activation of NFAT and NF-κB pathways, showed as impeding the nuclear translocation of NFAT and p65. Regarding the upstream signaling, ESE significantly decreased cytoplasmic CA²⁺ (CA²⁺_[c]) level in a model-independent manner. Although it failed to affect plasma membrane CA²⁺-ATPase, Na⁺/CA²⁺ exchanger, and mitochondrial CA²⁺ uptake, it affected sarco/endoplasmic CA²⁺-ATPase (SERCA) pathway. It also hindered IκBα phosphorylation and subsequent degradation. In vivo, ESE reduced IL-2 levels in local and systemic T cell activation models.

Conclusion: Through inhibiting the activation of SERCA/CA²⁺_[c]/NFAT and NF-κB pathways, ESE markedly decreased ConA-induced IL-2 production in vitro and in vivo. This study provides not only a modern explanation for the traditional uses of E. scaber, but also a scientific guidance for clinical practice.