NOX5 variants are functionally active in endothelial cells.

Area of Science:

• Vascular Biology
• Cell Signaling
• Biochemistry

Background:

• NADPH oxidases (NOX) generate reactive oxygen species (ROS) in vascular cells.
• While NOX1, NOX2, and NOX4 are known in endothelial cells, the role of NOX5 in these cells was unclear.
• NOX5 possesses unique N-terminal calcium-binding domains.

Purpose of the Study:

• To investigate the expression and function of NOX5 variants in human microvascular endothelial cells (HMEC-1).
• To determine the role of NOX5 in ROS production, endothelial cell proliferation, and angiogenesis.
• To elucidate NOX5's contribution to endothelial responses to thrombin.

Main Methods:

• Detection of NOX5 protein in HMEC-1 cells and the vascular wall.
• Expression analysis of NOX5 variants (NOX5beta, NOX5delta, NOX5S).
• Assessment of ROS production, cell proliferation, and capillary-like structure formation.
• siRNA-mediated depletion of NOX5 to evaluate functional consequences.

Main Results:

• NOX5 protein and its variants (NOX5beta, NOX5delta, NOX5S) were identified in HMEC-1 cells.
• NOX5beta and NOX5S increased basal ROS levels; ionomycin specifically enhanced NOX5beta-driven ROS.
• NOX5 stimulated endothelial cell proliferation and capillary-like structure formation; NOX5 depletion inhibited thrombin-induced responses.

Conclusions:

• Endothelial cells express diverse NOX5 variants, including NOX5S lacking calcium-binding domains.
• NOX5 proteins are functional, driving ROS production, proliferation, and angiogenesis in endothelial cells.
• NOX5 variants play a significant role in vascular ROS-dependent processes and thrombin signaling.