Hypercholesterolemia, hyperhomocysteinemia, hypertension, diabetes, smoking, sedentary behaviour, Chlamydia pneumonia, Helicobacter pylori, Cytomegalovirus, Herpes zoster virus or Bacteroides gingivalis infections cause oxidative stress, thereby activating the transcription factor nuclear factor-kappa B. Subsequently, proatherogenic cytokines like tumour necrosis factor α, interleukins (IL) IL-1 and IL-6, adhesion molecules and chemokines are produced and inhibit endothelial nitric oxide synthase (eNOS) activity and, thus, NO production [10]. This evidence concerns the gene NOS3 and chlamydia trachomatis infectious disease.