HMGB1 Induced Oxidative Stress and Inflammation in Endothelial Cells Exposed to Impinging Flow.

Introduction: Oxidative stress and inflammation contribute to many aspects of the pathological processes involved in intracranial aneurysm (IA). However, the underlying mechanism for inducing oxidative stress and inflammation under impinging flow remains unclear. Accumulating evidence has shown that high mobility group box-1 (HMGB1) is associated with oxidative stress-related chronic diseases and inflammatory responses. Therefore, we aimed to investigate whether HMGB1 is involved in oxidative stress and inflammatory responses in endothelial cells (ECs) exposed to impinging flow. Methods: We used a modified T-chamber to simulate the in vitro situation of human umbilical vein ECs (HUVECs) subjected to impinging flow at the arterial bifurcation in order to analyze the effect of wall shear stress (WSS) on the ECs. To investigate the role of HMGB1 in this process, we transfected ECs with short hairpin RNA (shRNA) before conducting impinging flow experiments. Intracellular reactive oxygen species (ROS) were measured by flow cytometry, and malondialdehyde, glutathione, and superoxide dismutase levels were measured to assess oxidative stress. Inflammation was assessed by measuring the mRNA expression levels of IL-1β, IL-6, and IL-8 using reverse transcription-quantitative polymerase chain reaction. We also examined the cellular localization of HMGB1 by immunofluorescence. Results: Exposure of HUVECs to WSS can increase the level of oxidative stress and inflammatory response. WSS increased the expression of HMGB1 in ECs and promoted the translocation of HMGB1 from cytosol to cytoplasm. When we knocked down HMGB1, the level of oxidative stress and inflammatory response caused by WSS in ECs decreased, suggesting that HMGB1 can mediate the oxidative stress and inflammatory response in HUVECs exposed to WSS. Conclusions: HMGB1 induced oxidative stress and inflammatory response in ECs exposed to impinging flow. Plain Language Summary: Oxidative stress and inflammatory are two important factors that are involved in the formation and development of intracranial aneurysm (IA). Wall shear stress (WSS) produced by impinging flow can induce oxidative stress and inflammatory. However, the specific mechanisms remain unclear. Accumulating evidence has shown that high mobility group box-1 (HMGB1) is associated with oxidative stress-related chronic diseases and inflammatory. We used a modified T-chamber to simulate the in vitro situation of human umbilical vein ECs (HUVECs) subjected to impinging flow at the arterial bifurcation in order to analyze the effect of WSS on HUVECs. The levels of oxidative stress were determined by measuring ROS levels using flow cytometry. The inflammatory was examined using Western blot to measure IL-1β, IL-6, and IL-8 expression levels. Our results demonstrate that WSS can induce oxidative stress and inflammatory in HUVECs. Moreover, we used Western blot to find high expression of HMGB1 in response to impinging flow. We also found by immunofluorescence that HMGB1 undergoes nuclear to cytoplasmic translocation upon exposure to impinging flow. Subsequently, we knocked down HMGB1 using lentiviral transfection of HUVECs and found that the levels of inflammatory and oxidative stress in HUVECs were significantly reduced. This allows us to conclude that HMGB1 is indeed involved in mediating the inflammatory and oxidative stress in HUVECs exposed to WSS. Those findings provide a theoretical basis and a research direction for targeting IA disease through the regulation of oxidative stress and inflammatory response. [ABSTRACT FROM AUTHOR]