Suxiao Jiuxin Pill Promotes Post-Myocardial Infarction Cardiac Repair by Enhancing Regulatory T Cell Function via the ST2L Signaling Pathway

Background: Clinical evidence suggests that extended treatment with Suxiao Jiuxin Pill (SJP) significantly reduces the recurrence rates of myocardial infarction (MI), primarily through its modulation of cardiac immune-fibrotic responses. Nonetheless, the precise molecular mechanisms underlying this effect remain to be fully elucidated. Methods: Male C57BL/6J mice were randomly assigned to six groups: sham-operated control, MI + saline (vehicle control), MI + SJP (39, 78, and 156 mg/kg), and MI + dapagliflozin (1.5 mg/kg, positive control). Cardiac function and infarct size were assessed using echocardiography and Masson’s trichrome staining. Serum levels of lactate dehydrogenase (LDH), creatine kinase (CK), and creatine kinase-MB (CK-MB) were measured with a Hitachi 7020 automatic biochemical analyzer, while cardiac troponin T (cTnT) levels were quantified via enzyme-linked immunosorbent assay (ELISA). Gene expression analysis was conducted using reverse transcription polymerase chain reaction (RT-PCR). Immune cell populations within the ischemic heart were analyzed through flow cytometry. Naïve CD4 + T cells were isolated and differentiated into regulatory T cells (Tregs) to assess their immunosuppressive function. Results: The administration of SJP treatment resulted in a significant reduction in infarct size and enhancement of cardiac function in mice with MI. Additionally, SJP modulated the immune profile of the infarcted myocardium by reducing neutrophil infiltration and increasing the presence of CD4 + T cells and CD206 + macrophages. Importantly, SJP markedly expanded the population of regulatory T cells (Tregs) and augmented their immunosuppressive capabilities, as evidenced by the upregulated expression of IL-10, Ctla-4, and Sparc. The cardioprotective effects of SJP were found to be dependent on Tregs, as their depletion negated the therapeutic benefits of SJP. Mechanistically, SJP facilitated Treg expansion within the infarcted myocardium by activating the ST2L/Foxp3 signaling pathway and restoring the balance between Treg and Th17 cytokines. In vitro analyses identified senkyunolide I and levistolide A as the predominant active compounds responsible for these effects. Conclusion: This study elucidates the cardioprotective effects of SJP, which are mediated through the expansion of the Treg population and enhancement of their immunosuppressive function via activation of the ST2L/Foxp3 signaling pathway, with senkyunolide I and levistolide A identified as primary drivers behind the enhanced Treg function.