NOS2 and brain aneurysm: NO produced by iNOS plays a pivotal role in the pathogenesis of inflammation and aneurysm.40–41 Increased iNOS expression has been implicated in rodent and human aortic aneurysms.28–29 Inhibition of iNOS has yielded positive outcomes in limiting aneurysm expansion in an elastase‐induced aneurysm model and in the prevention of cerebral aneurysm formation in a hypertensive rat model.25,40–41 In agreement with these findings, we revealed that iNOS‐derived NO has a detrimental effect on aortic structural integrity in S3KO mice.