Ligustilide prevents thymic immune senescence by regulating Thymosin β15-dependent spatial distribution of thymic epithelial cells

BACKGROUND

Thymus is the most crucial organ connecting immunity and aging. The progressive senescence of thymic epithelial cells (TECs) leads to the involution of thymus under aging, chronic stress and other factors. Ligustilide (LIG) is a major active component of the anti-aging Chinese herbal medicine Angelica sinensis (Oliv.) Diels, but its role in preventing TEC-based thymic aging remains elusive.

PURPOSE

This study explored the protective role of Ligustilide in alleviating ADM (adriamycin) -induced thymic immune senescence and its underlying molecular mechanisms.

METHOD

The protective effect of Ligustilide on ADM-induced thymic atrophy was examined by mouse and organotypic models, and conformed by SA-β-gal staining in TECs. The abnormal spatial distribution of TECs in the senescent thymus was analyzed using H&E, immunofluorescence and flow cytometry. The possible mechanisms of Ligustilide in ADM-induced thymic aging were elucidated by qPCR, fluorescence labeling and Western blot. The mechanism of Ligustilide was subsequently validated through actin polymerization inhibitor, genetic engineering to regulate Thymosin β15 (Tβ15) and Tβ4 expression, molecular docking and β Thymosin-G-actin cross-linking assay.

RESULTS

At a 5 mg/kg dose, Ligustilide markedly ameliorated ADM-induced weight loss and limb grip weakness in mice. It also reversed thymic damage and restored positive selection impaired by ADM. In vitro, ADM disrupted thymic structure, reduced TECs number and hindered double negative (DN) T cell differentiation. Ligustilide counteracted these effects, promoted TEC proliferation and reticular differentiation, leading to an increase in CD4+ single positive (CD4SP) T cell proportion. Mechanistically, ADM diminished the microfilament quantity in immortalized TECs (iTECs), and lowered the expression of cytoskeletal marker proteins. Molecular docking and cross-linking assay revealed that Ligustilide inhibited the protein binding between G-actin and Tβ15 by inhibiting the formation of the Tβ15-G-actin complex, thus enhancing the microfilament assembly capacity in TECs.

CONCLUSION

This study, for the first time, reveals that Ligustilide can attenuate actin depolymerization, protects TECs from ADM-induced acute aging by inhibiting the binding of Tβ15 to G-actin, thereby improving thymic immune function. Moreover, it underscores the interesting role of Ligustilide in maintaining cytoskeletal assembly and network structure of TECs, offering a novel perspective for deeper understanding of anti thymic aging.