ALOX5 and pulmonary arterial hypertension: Subsequently, this chain of events leads to increased production of ALOX5 which catalyzes the metabolism of arachidonic acid to produce potent chemotactic agents LTB4 and cysteinyl LT group (LTC4, LTD4, and LTE4), all of which increase vascular permeability and vasoconstriction and are broadly associated with PAH.