CXCL12 and pulmonary arterial hypertension: NOX1 siRNA-treatment for 16 h prior to hypoxia abolished elevated CXCL12 expression measured by Western blot and flow cytometry (Figure 1D,E, respectively); NOX1 siRNA had no effect on basal CXCL12 under normoxic conditions (Figure 1D) but markedly attenuated the hypoxia-induced elevation in CXCL12 (Figure 1D,E) With respect to ROS, our previous data from PAH vs. non-PAH human subjects demonstrated increased ROS levels in PAH that were NOX1-mediated [8,15].