Objective  To explore the action mechanism of Bruton's tyrosine kinase (BTK) inhibitor zanubrutinib on renal fibrosis after renal ischemia-reperfusion injury (RIRI).

Methods  C57BL/6 mice were randomly divided into sham operation group, modeling group and modeling + zanubrutinib treatment group (zanubrutinib group), with 5 mice in each group. The groups underwent sham operation, RIRI modeling and RIRI modeling + zanubrutinib (5 mg/kg) treatment, respectively. Tissues were collected after 21 days. The morphological changes of the kidneys, histopathological changes, levels of M1 macrophages in the kidneys, inflammatory responses in the kidneys, and the expression of related inflammatory signaling pathways of macrophages induced by lipopolysaccharide(LPS) + interferon(IFN)-γ in vitro after lentivirus transfection were observed.

Results  Compared with the sham operation group, the kidneys of the modeling group mice shrank, the ratio of unilateral kidney weight to mouse body weight decreased, renal tubular interstitial fibrosis worsened, and the expression of α-smooth muscle actin (α-SMA) and type I collagen in the kidneys increased. The expression of F4/80 and CD86 in the kidneys increased, the lumen of the renal proximal convoluted tubules was significantly dilated, cellular debris accumulated in the lumen and inflammatory cell infiltration occurred, and the messenger RNA (mRNA) levels of CD86, tumor necrosis factor (TNF)-α, interleukin (IL)-6, inducible nitric oxide synthase (iNOS) and IL-1β in the kidneys increased. Compared with the modeling group, the kidneys of the zanubrutinib group mice enlarged after RIRI, the ratio of unilateral kidney weight to mouse body weight decreased, renal tubular interstitial fibrosis was alleviated, and the expression of α-SMA and type I collagen in the kidneys decreased. The expression of F4/80 and CD86 in the kidneys decreased, the number of CD45⁺ lymphocytes and CD11b⁺ F4/80⁺ macrophages in the kidneys decreased, the infiltration of CD11b⁺ F4/80⁺ and CD86⁺ macrophages in the damaged tissue decreased, the degree of renal inflammatory pathological changes was milder, and the mRNA levels of CD86, TNF-α, IL-6, iNOS and IL-1β in the kidneys decreased. In vitro experiments using LPS+IFN-γ to induce M1-type macrophages found that the phosphorylation levels of phosphatidylinositol-3-kinase (PI3K), protein kinase B (Akt), and nuclear factor (NF)-κB increased, while the phosphorylation levels decreased after BTK knockdown, indicating that BTK knockdown may inhibit the PI3K/Akt and NF-κB related inflammatory signaling pathways, thereby reducing the pro-inflammatory effects of LPS+IFN-γ induced M1-type macrophages.

Conclusions  Zanubrutinib may alleviate renal fibrosis after RIRI by inhibiting the PI3K/Akt and NF-κB related inflammatory signaling pathways, reducing the infiltration of M1 macrophages and the expression of related inflammatory factors, providing potential evidence for its clinical application.