TLR4 and pulmonary embolism: 2) In this acute pulmonary embolism combined with shock model, SNP (0.35 mg/kg) treatment enhances NO release, and therefore reduces pulmonary vasospasm in the embolism area and non-embolism area, possibly through inhibiting the expression of TLR4/NF-κB/HIF-1α signaling pathway, thus breaking the vicious cycle of circulatory failure, relieving shock.