C-X-C-Chemokine-Receptor-Type-4 Inhibitor AMD3100 Attenuates Pulmonary Inflammation and Fibrosis in Silicotic Mice

Abstract

Background Silicosis is a severe pulmonary disease caused by inhaling dust containing crystalline silica. The progression of silicosis to pulmonary fibrosis is usually unavoidable. Recent studies have revealed positivity for the overexpression of C-X-C chemokine receptor type 4 (CXCR4) in pulmonary fibrosis and shown that the CXCR4 inhibitor AMD3100 attenuated pulmonary fibrosis after bleomycin challenge and paraquat exposure. However, it is unclear whether AMD3100 reduces crystalline silica-induced pulmonary fibrosis. Methods C57BL/6 male mice were instilled intranasally with a single dose of crystalline silica (12 mg/60 μL) to establish an acute silicosis mouse model. Twelve hours later, the mice were injected intraperitoneally with 5 mg/kg AMD3100 or control solution. Then, the mice were weighed daily and sacrificed on day 7, 14, or 28 to collect lung tissue and peripheral blood. Western blotting was also applied to determine the level of CXCR4, while different histological techniques were used to assess pulmonary inflammation and fibrosis. In addition, the level of B cells in peripheral blood was measured by flow cytometry. Results CXCR4 and its ligand CXCL12 were upregulated in the lung tissues of crystalline silica-exposed mice. Blocking CXCR4 with AMD3100 suppressed the upregulation of CXCR4/CXCL12, reduced the severity of lung injury, and prevented weight loss. It also inhibited neutrophil infiltration at inflammatory sites and neutrophil extracellular trap formation, as well as reduced B-lymphocyte aggregates in the lung. Additionally, it decreased the recruitment of circulating fibrocytes (CD45 + collagen I + CXCR4 + ) to the lung and the deposition of collagen I and α-smooth muscle actin in lung tissue. AMD3100 also increased the level of B cells in peripheral blood, preventing circulating B cells from migrating to the injured lungs. Conclusion Blocking CXCR4 with AMD3100 delays pulmonary inflammation and fibrosis in a silicosis mouse model, suggesting the potential of AMD3100 as a drug for treating silicosis.

CXCR4/CXCL12 axis: “old” pathway as “novel” target for anti‐inflammatory drug discovery

“…After treatment with AMD3100, the increase in neutrophils caused by CS exposure was reversed, the number of lymphatic aggregates around blood vessels decreased, and pulmonary fibrosis improved. At the same time, blocking the CXCR4/CXCL12 axis also effectively reduced the number of B cells in peripheral blood and inhibited the migration of B cells to the lungs 117 …”

“…116 CXCR4 also plays a vital role in pulmonary fibrosis. Sun et al 117 reported that the infiltration of neutrophils, lymphocytes, and B cells in the lungs increased and the expression of the CXCR4/CXCL12 axis was upregulated in mice with crystalline silica (CS)-induced pulmonary fibrosis, resulting in alveolar damage and abnormal thickening of the bronchial wall. After treatment with AMD3100, the increase in neutrophils caused by CS exposure was reversed, the number of lymphatic aggregates around blood vessels decreased, and pulmonary fibrosis improved.…”

“…At the same time, blocking the CXCR4/CXCL12 axis also effectively reduced the number of B cells in peripheral blood and inhibited the migration of B cells to the lungs. 117 Currently, various CXCR4 antagonists are widely used in the study of lung injury. As expected, AMD3100 is the most frequently used antagonist.…”

“…118,119 Furthermore, AMD3100 effectively reduced collagen deposition in the lungs and improved the progression of CS-induced pulmonary fibrosis. 117 Chow et al 120 showed that the administration of AMD070, an oral CXCR4 antagonist derived from AMD3100, significantly reduced the mortality rate of bleomycin (BLM)-induced pulmonary fibrosis in mice and prolonged the survival cycle. 120 Additionally, 4-fluorobenzoyl-TE14011, an analog of CXCR4 antagonistic peptide T140, with a 4-fluorobenzoyl moiety at the N-terminus, also improved lung injury by antagonizing the recruitment effect of the CXCR4/CXCL12 axis on neutrophils.…”

“…In animals with LPS‐induced lung injury, the mRNA levels of CXCR4 and CXCL12 on the surface of neutrophils decreased after AMD3100 administration, preventing the migration of polymorphonuclear neutrophils (PMNs) to lung epithelium and significantly reducing the number of PMNs in the alveoli, thereby effectively reducing the inflammatory response 118,119 . Furthermore, AMD3100 effectively reduced collagen deposition in the lungs and improved the progression of CS‐induced pulmonary fibrosis 117 . Chow et al 120 showed that the administration of AMD070, an oral CXCR4 antagonist derived from AMD3100, significantly reduced the mortality rate of bleomycin (BLM)‐induced pulmonary fibrosis in mice and prolonged the survival cycle 120 .…”