Amphiregulin Aggravates Glomerulonephritis via Recruitment and Activation of Myeloid Cells

Significance Statement The EGF receptor (EGFR) ligand amphiregulin (AREG) has emerged as a potent mediator of inflammation. AREG’s tissue-protective and immunosuppressive properties have recently received much attention, but the ligand has another function. In a mouse model of GN, AREG plays an unexpectedly strong proinflammatory rather than protective role. Renal resident cells that secrete AREG enhance the recruitment, proliferation, and activation of tissue-destructive myeloid cells. Importantly, studies in human crescentic GN also revealed strong upregulation of renal AREG expression, indicating clinical relevance of the murine model. These findings contribute to a more balanced understanding of AREG’s biology and help with the selection of patients and timing of AREG/EGFR-directed therapies. Background Recent studies have identified the EGF receptor (EGFR) ligand amphiregulin (AREG) as an important mediator of inflammatory diseases. Both pro- and anti-inflammatory functions have been described, but the role of AREG in GN remains unknown. Methods The nephrotoxic nephritis model of GN was studied in AREG −/− mice after bone marrow transplantation, and in mice with myeloid cell–specific EGFR deficiency. Therapeutic utility of AREG neutralization was assessed. Furthermore, AREG's effects on renal cells and monocytes/macrophages (M/M) were analyzed. Finally, we evaluated AREG expression in human renal biopsies. Results Renal AREG mRNA was strongly upregulated in murine GN. Renal resident cells were the most functionally relevant source of AREG. Importantly, the observation that knockout mice showed significant amelioration of disease indicates that AREG is pathogenic in GN. AREG enhanced myeloid cell responses via inducing chemokine and colony stimulating factor 2 (CSF2) expression in kidney resident cells. Furthermore, AREG directly skewed M/M to a proinflammatory M1 phenotype and protected them from apoptosis. Consequently, anti-AREG antibody treatment dose-dependently ameliorated GN. Notably, selective abrogation of EGFR signaling in myeloid cells was sufficient to protect against nephritis. Finally, strong upregulation of AREG expression was also detected in kidneys of patients with two forms of crescentic GN. Conclusions AREG is a proinflammatory mediator of GN via ( 1 ) enhancing renal pathogenic myeloid cell infiltration and ( 2 ) direct effects on M/M polarization, proliferation, and cytokine secretion. The AREG/EGFR axis is a potential therapeutic target for acute GN.