TLR4 and pulmonary arterial hypertension: Single nucleotide polymorphisms (SNPs) in the NAMPT promoter influence NAMPT transcription and secretion and are linked to the susceptibility/severity of ARDS [16, 28], pulmonary hypertension [23], coronary artery disease [55], diabetes [56], and multiple cancers [57, 58], yet the exact mechanisms by which eNAMPT/TLR4 autocrine/paracrine signaling directly influences disease severity are incompletely understood.