EGFR-driven profibrotic signals in AKI-to-CKD transition are blocked by TNF inhibition: Opportunities for etanercept treatment

Abstract

Inflammation is a key driver of fibrosis and progression of human chronic kidney disease (CKD), often caused or worsened by acute kidney injury (AKI-to-CKD transition). Sustained epidermal-growth-factor-receptor (EGFR) activation in injured proximal-tubule-cells (PTC) is strongly pro-inflammatory and has emerged as a key paradigm in AKI-to-CKD transition and CKD progression. Whether the key Type 1 inflammatory cytokine tumor-necrosis-factor (TNF) has a role in CKD progression and how TNF relates to the PTC-EGFR pathway is unknown, but retrospective analysis of patients using TNF biologic inhibitors suggests that TNF inhibition reduces incident CKD and CKD progression in humans. Here, we compared mice treated with control, TNF inhibition (murine etanercept, soluble TNF-scavenger), EGFR inhibition (erlotinib, EGFR-kinase-inhibitor) or their combination in an AKI-to-CKD bilateral renal-ischemia-reperfusion model. TNF- or EGFR-inhibition did not affect initial kidney injury, but significantly overlapped in reducing kidney injury-upregulated cytokines and equally strongly reduced kidney fibrosis, while combination treatment had no additive effect, suggesting EGFR and TNF act in the same fibrosis pathway. TNF exerted its profibrotic effects downstream of PTC-EGFR, as TNF-inhibition did not affect tubular EGFR activation in vivo. Consistent with this, TNF PTC-KO did not reduce inflammation or fibrosis, suggesting that PTC-derived TNF does not contribute to profibrotic PTC-EGFR activation. Kidney single-cell RNAseq analysis identified macrophages, dendritic cells and T cells, but not PTC, as dominant TNF sources after AKI. Only EGFR inhibition, but not TNF inhibition significantly blocked injury-induced kidney ingress of chemokine-receptor-2 (CCR2) positive cells and accumulation of macrophages, however, macrophage numbers where equal one month after AKI independent of treatment. Thus EGFR inhibition reduces ingress and accumulation of TNF-producing proinflammatory and profibrotic immune cells whereas TNF inhibition mechanistically largely acts by neutralizing their proinflammatory and profibrotic activities. Our work provides mechanistic background to motivate examination of TNF pathway inhibition in human AKI or CKD.