Since inflammatory processes are involved in the pathophysiology of PAH and since HO activity has potent anti-inflammatory properties (28), we also measured monocyte chemo attractant protein-1 (MCP-1) levels, a major inflammatory marker, in order to study the effects of modulation of HO activity using EPO and SnMP on inflammatory processes in PAH. This evidence concerns the gene EPO and pulmonary arterial hypertension.