TY - JOUR T1 - Inflammation in pulmonary arterial hypertension: is it time to quell the fire? JF - European Respiratory Journal JO - Eur Respir J SP - 685 LP - 688 DO - 10.1183/09031936.00006014 VL - 43 IS - 3 AU - Paul M. Hassoun Y1 - 2014/03/01 UR - http://erj.ersjournals.com/content/43/3/685.abstract N2 - Inflammare, or to set ablaze, is the Latin origin of the word inflammation, a physical condition that was undoubtedly already familiar to the ancient Egyptians and Greeks. It is, however, the Roman Aulus Celsus who is credited with describing, in the first century AD, the four cardinal signs of inflammation consisting of rubor et tumor cum calore et dolore (redness and swelling with heat and pain). Two centuries later, Galen promoted the humoral view of inflammation as a potential part of the healing process rather than a pure pathological process, and may have proposed the fifth cardinal sign (functio laesa or loss of function) [1], although this is also attributed to Virchow in the 19th century [2]. And while we now know that, in many pathologies characterised by inflammation, the initial four cardinal signs can be subclinical and silent, it is clear that for Virchow inflammation was ultimately pathologic since it lead to loss of function.What is then going on in pulmonary arterial hypertension (PAH)? Over the past 120 years since the first pathologic description of “pulmonary vascular sclerosis” by Romberg, our understanding of the remodelling process underlying what we now call PAH has greatly changed from a mere description of the thickening of the three components of the pulmonary vascular wall leading to narrowing of the lumen, to aberrant cellular proliferation (e.g. endothelial and smooth muscle cells and fibroblasts) and influx of inflammatory cells in and around the various components of the vascular wall. Tuder et al. [3] were among the first to describe a significant influx of inflammatory cells, including macrophages and lymphocytes, into the plexiform lesions of hypertensive pulmonary vessels. Within a few years, other markers of inflammation, including macrophage inflammatory protein-1α, interleukin (IL)-1β and IL-6 [ … ER -