Immunosuppressive effects of voclosporin in inflammatory bowel disease through targeted inhibition of SLP-76 and metabolic reprogramming.

Abstract

The adaptor protein SLP-76 plays a critical role in T-cell receptor signaling and immune activation, yet its relevance in inflammatory bowel disease (IBD) remains unclear. Although calcineurin inhibitors such as cyclosporine A (CsA) are used in severe ulcerative colitis, voclosporin (VCS), a novel calcineurin inhibitor approved for lupus nephritis, has not been systematically evaluated in IBD. We investigated whether SLP-76 is dysregulated in IBD and can be modulated by calcineurin inhibitors. Expression of SLP-76 was analyzed in intestinal biopsy specimens of patients with ulcerative colitis and Crohn's disease using quantitative PCR (qPCR) and immunofluorescence. PBMCs from patients with IBD and healthy control participants were stimulated with anti-CD3/CD28 in the presence or absence of CsA or VCS. Downstream effects were analyzed by qPCR, flow cytometry, cytokine, and metabolic profiling. SLP-76 was significantly upregulated in inflamed intestinal tissue and correlated significantly with histological inflammation. No differences were observed in PBMCs between control participants and patients with IBD. Both calcineurin inhibitors reduced phosphorylation of SLP-76 and impaired downstream signaling in CD4+ and CD8+ T cells. However, only VCS significantly decreased total SLP-76 protein and suppressed expression of the early activation marker CD69 and Ras-MAPL signaling. Metabolomic profiling showed that VCS induced distinct metabolic changes compared with CsA. Our findings highlight SLP-76 as a potential immunoregulatory target in IBD and suggest that VCS exerts broader immunosuppressive effects than CsA, supporting its repurposing as a therapeutic strategy.