Lactate programs PBX1 lactylation and mesangial proliferation in lupus nephritis

Lupus nephritis (LN) constitutes the most common organ-threatening manifestation of systemic lupus erythematosus (SLE), with the pathological proliferation of mesangial cells (MCs) recognized as a critical factor in its pathogenesis and progression. Self-DNA-containing immune complex (DNA-IC) represents a prime pathogenic factor in SLE, yet its pathological effect on MCs remains unclear. In the present study, we elucidated the mechanism underlying the excessive proliferation of MCs following the recognition of DNA-IC in patients with LN. Here, we pinpointed that the excessive proliferation of MCs was attributed to an anomalous transition from the G1 to the S phase of the cell cycle in patients with LN. Mechanically, the dysfunction of P27 protein resulted in the aberrant G1-S phase transition, and the phenomenon was closely related to the ubiquitin-mediated degradation of its key transcription factor, PBX1. This degradation was regulated by lactylation of PBX1 in the site of Lys40 residue. The elevated lactylation level of PBX1 protein was caused by the upregulation of glycolysis levels induced by DNA-IC. Accordingly, targeting lactate production in MCs from patients with LN effectively alleviated their renal inflammation and fibrosis progression. Elevated lactate resulted in PBX1 lactylation, leading to excessive proliferation of MCs and, thus, serving as a promising therapeutic target for LN.