Figure 6.

Schematic of Hb α expression in pulmonary endothelium and its potential effect on NO signaling. Normal lungs express low levels of Hb α, allowing for abundant NO bioavailability, contributing to low basal pulmonary vascular resistance. However, in the setting of PH, Hb α is up-regulated at the protein level, which leads to increased NO scavenging, promoting PA endothelial dysfunction and vasoconstriction. Hb α X peptide inhibits coupling between Hb α and eNOS, increasing NO diffusion across the MEJ.