The leukotriene B4/BLT1‐dependent neutrophil accumulation exacerbates immune complex‐mediated glomerulonephritis

Crescent formation is the most important pathological finding that defines the prognosis of nephritis. Although neutrophils are known to play an important role in the progression of crescentic glomerulonephritis, such as anti‐neutrophil cytoplasmic antibody (ANCA)‐associated glomerulonephritis, the key chemoattractant for neutrophils in ANCA‐associated glomerulonephritis has not been identified. Here, we demonstrate that a lipid chemoattractant, leukotriene B4 (LTB4), and its receptor BLT1 are primarily involved in disease pathogenesis in a mouse model of immune complex‐mediated crescentic glomerulonephritis. Circulating neutrophils accumulated into glomeruli within 1 h after disease onset, which was accompanied by LTB4 accumulation in the kidney cortex, leading to kidney injury. LTB4 was produced by cross‐linking of Fc gamma receptors on neutrophils. Mice deficient in BLT1 or LTB4 biosynthesis exhibited suppressed initial neutrophil infiltration and subsequent thrombotic glomerulonephritis and renal fibrosis. Depletion of neutrophils before, but not after, disease onset prevented proteinuria and kidney injury, indicating the essential role of neutrophils in the early phase of glomerulonephritis. Administration of a BLT1 antagonist before and after disease onset almost completely suppressed induction of glomerulonephritis. Finally, we found that the glomeruli from patients with ANCA‐associated glomerulonephritis contained more BLT1‐positive cells than glomeruli from patients with other etiologies. Taken together, the LTB4‐BLT1 axis is the key driver of neutrophilic glomerular inflammation, and will be a novel therapeutic target for the crescentic glomerulonephritis.