Oxidative Stress Potentiates a STAT1-APOL1 Feedforward Loop and Governs Disease Severity in APOL1-Mediated Kidney Disease.

Abstract

Introduction: Apolipoprotein L1 (APOL1) risk variants (G1 and G2) confer immunity against Trypanosoma infection but markedly increase susceptibility to progressive kidney disease. However, only a subset of biallelic risk-variant carriers develops disease progression, distinct from murine models. Here, we evaluated molecular drivers of progressive kidney disease using a model that reflected the low human disease penetrance.

Methods: To investigate the heterogeneity of APOL1-mediated kidney disease, we generated novel APOL1 bacterial artificial chromosome transgenic mice with doxycycline-inducible systemic interferon-γ expression (G0- or G1-IFNγ mice). Podocyte-specific transcriptomics using translating ribosome affinity purification (TRAP-seq) and single-cell spatial transcriptomics via 10x Genomics Xenium In Situ platform was performed. Mechanistic validation and analysis of factors regulating APOL1 upregulation were conducted in primary podocytes and subsequently validated in mouse kidney and in human kidney biopsy specimens via immunofluorescence.

Results: A subset of G1-IFNγ mice developed severe albuminuria and focal segmental glomerulosclerosis, which strongly correlated with the magnitude of APOL1 upregulation. By pairing TRAP-seq with single-cell spatial transcriptomic data, we identified mitochondrial dysfunction and JAK-STAT signaling as a central mediator of podocyte injury. In primary podocytes, APOL1 risk variants triggered mitochondrial-derived oxidative stress, establishing a self-amplifying STAT1-APOL1 feedforward loop that further enhances APOL1 expression and APOL1 oligomerization. This pathogenic loop was consistently enriched in podocytes from both G1-IFNγ mice and in kidney biopsy specimens from patients with APOL1-mediated focal segmental glomerulosclerosis, demonstrating translational relevance.

Conclusions: Our findings suggest that biallelic risk variants initiate an oxidative stress-induced positive feedforward loop which promotes and sustains APOL1 upregulation and STAT1 phosphorylation, thereby contributing to disease susceptibility, severity and outcome.