PTGS2 and endothelial dysfunction: Regarding endothelial dysfunction, C. pneumoniae has been shown to significantly enhance the superoxide anion production in endothelial cells through the upregulation of NOX (NOX-1, NOX-4, and p22phox), and cyclooxygenase-2 (COX-2) as well as through the downregulation of antioxidant enzyme systems such as catalase, SOD-1, and thioredoxin-1 [32].