PTGIS and Sepsis: Prostacyclin synthase (PGIS) is oxidatively inhibited via nitration of tyrosine 430 by ONOO ̄, whereas peroxide-driven activation of cyclooxygenase-1/2 (COX-1/2) leads to higher prostaglandin endoperoxide (PGH2) levels and cyclooxygenase-2 (COX-2) is oxidatively inhibited via tyrosine nitration, all of which contributes to redox regulation of prostanoid synthesis and vascular tone with relevance for atherosclerosis, diabetes, nitrate tolerance, and sepsis [8,49,209,210,211,212,213,214,215].