Anti‐Inflammatory Effects of Rhamnetin on Bradykinin‐Induced Matrix Metalloproteinase‐9 Expression and Cell Migration in Rat Brain Astrocytes

Abstract

Bradykinin (BK) has been shown to induce matrix metalloproteinase (MMP)‐9 expression and participate in neuroinflammation. The BK/MMP‐9 axis can be a target for managing neuroin-flammation. Our previous reports have indicated that reactive oxygen species (ROS)‐mediated nu-clear factor‐kappaB (NF‐κB) activity is involved in BK‐induced MMP‐9 expression in rat brain as-trocytes (RBA‐1). Rhamnetin (RNT), a flavonoid compound, possesses antioxidant and anti‐inflam-matory effects. Thus, we proposed RNT could attenuate BK‐induced response in RBA‐1. This study aims to approach mechanisms underlying RNT regulating BK‐stimulated MMP‐9 expression, especially ROS and NF‐κB. We used pharmacological inhibitors and siRNAs to dissect molecular mech-anisms. Western blotting and gelatin zymography were used to evaluate protein and MMP‐9 ex-pression. Real‐time PCR was used for gene expression. Wound healing assay was applied for cell migration. 2ʹ,7ʹ‐dichlorodihydrofluorescein diacetate (H2DCF‐DA) and nicotinamide adenine dinu-cleotide phosphate (NADPH) oxidase (NOX) were used for ROS generation and NOX activity, re-spectively. Promoter luciferase assay and chromatin immunoprecipitation (ChIP) assay were applied to detect gene transcription. Our results showed that RNT inhibits BK‐induced MMP‐9 protein and mRNA expression, promoter activity, and cell migration in RBA‐1 cells. Besides, the levels of phospho‐PKCδ, NOX activity, ROS, phospho‐ERK1/2, phospho‐p65, and NF‐κB p65 binding to MMP‐9 promoter were attenuated by RNT. In summary, RNT attenuates BK‐enhanced MMP‐9 up-regulation through inhibiting PKCδ/NOX/ROS/ERK1/2‐dependent NF‐κB activity in RBA‐1.