Background/Purpose:

The extravasation and recruitment of leukocytes in damaged tissues is an essential component of the inflammatory response. Once in the inflammatory foci, neutrophils destroy invading microorganisms by bringing them into contact with chemicals, among which reactive oxygen species (ROS) are the most important. Correct cell extravasation requires the coordinated intervention of a number of adhesion molecules, including L-selectin, a molecule that plays a key role in the initial interaction between flowing neutrophils and endothelial cells. However, the mechanisms that control the regulation of the L-selectin ectodomain processing during the inflammatory response are still not well understood. Objectives: In this work we study the mechanisms involved in the intravascular ROS production by neutrophils, as well as the potential implication of these oxygen derivatives in the regulation of neutrophil/endothelial cell interactions during the early events of the inflammatory response

Methods:

The effect of ROS on L-selectin and CD11b basal surface expression on human neutrophils was studied by flow cytometry analysis. Neutrophil ROS production during neutrophil-HUVEC (human umbilical vein endothelial cells) interaction was assessed in dihydroethidium-preloaded neutrophils using a flow chamber. The role of Interleukin(IL)-8 in the neutrophil ROS production was studied using lL-8 blocking mAb or a synthetic CXCR1 inhibitor (SB225002). Physiologic antioxidants such as superoxide dismutase (SOD) and catalase, as well as the NADPH-oxidase complex inhibitor diphenyleniodonium chloride (DPI), were used to determine the role of ROS in the regulation of neutrophil rolling and extravasation.

Results:

Flow cytometry experiments showed that shedding of L-selectin can be triggered in response to ROS through an autocrine-paracrine TACE-dependent mechanism in neutrophils. Flow chamber experiments showed that intracellular ROS production by neutrophils: 1) is proportional to the distance a neutrophil travelled doing rolling; and 2) requires Interleukin (IL)-8/CXCR1 interaction. In accordance with this result, the preincubation of neutrophils with physiological antioxidants (SOD and catalase) and an inhibitor of NADPH oxidase complex (DPI) increased the number of rolling cells, reducing the transmigration capability of neutrophils through activated-HUVEC

Conclusion:

Our data indicate that, in response to IL-8, neutrophils initiate intracellular ROS production during the rolling phase of the inflammatory response. By inducing L-selectin shedding, ROS could participate in the regulation of inflammation, thereby reducing the extravasation capability of neutrophils. These data could help to define new therapeutic targets for control inflammation in diseases such as Rheumatoid Arthritis.

« Back to 2015 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/regulation-of-neutrophil-extravasation-by-interleukin-8-induced-intravascular-reactive-oxygen-species-production-during-the-inflammatory-response/