A self-sustaining hypoxia inducible factor-1α-creatine kinase B feedforward circuit drives macrophage-mediated kidney fibrosis.

INTRODUCTION A fundamental challenge in treating chronic kidney disease (CKD) is the lack of therapies to reverse established fibrosis. While systemic hypoxia sensors like erythrocyte sphingosine kinase 1 (eSPHK1) can initiate fibrotic signaling, the mechanisms driving self-perpetuating and progressive fibrosis remain unknown.

Methods

eSphk1 specific deficient mice underwent four-week angiotensin-II infusion, unilateral ureteral obstruction or ischemia reperfusion injury. Untargeted metabolomics profiled purified kidney macrophages, and [13C615N4]-arginine fluxomic tracked arginine-creatine metabolism in hypoxia treated macrophages. Multi-color immunofluorescent images of kidney tissues were scanned and scored. Preclinical studies by hypoxia inducible factor-1α (HIF-1α) inhibitor or knockdown macrophage creatine kinase B (Ckb) were performed. Clinical relevance was evaluated by measuring CKB mRNA level in peripheral blood mononuclear cells obtained from 131 patients with CKD and determining its correlation with disease severity.

Results

We identify a HIF-1α-CKB feedforward loop within profibrotic macrophages that functions as an autonomous engine of kidney fibrosis. This circuit, which can be triggered by established pathways such as eSphk1 dysfunction, is characterized by its capacity for self-renewal. Specifically, HIF-1α drives Ckb expression, reprogramming arginine metabolism toward creatine phosphate shunt (CPS) to generate an ATP surge that synergizes with an S1PR3-PKC signaling cascade to phosphorylate and stabilize HIF-1α, effectively bypassing the need for continued hypoxic input. This metabolic rewiring drives macrophage profibrotic polarization and leads to kidney fibrosis. Preclinically, pharmacologic HIF 1α inhibition or knockdown macrophage Ckb collapses this autonomous loop and halts fibrosis. Translationally, CKB mRNA in peripheral blood mononuclear cells rises in parallel with estimated glomerular filtration rate decline and histologic fibrosis score in patients with CKD.

Conclusions

Our work identifies a novel HIF-1α-CKB feedforward circuit in macrophages that sustains HIF-1α induction, channeling arginine metabolism toward CPS and thus promoting kidney fibrosis. These findings highlight that fibrosis is conceptualized from a passive end-stage outcome to an actively maintained process driven by the macrophage metabolic-polarization circuit, suggesting that breaking this malicious loop, in addition to initiating triggers, is critical to halt kidney fibrosis.