Regulatory Effect of the HMGB1-TLR4 Signaling Pathway in Pulmonary Ischemia/Reperfusion.

Objective: To determine the molecular mechanism of pulmonary ischemia-reperfusion (I/R) injury and seek effective therapeutic targets to reduce the incidence and mortality of pulmonary I/R injury.

Methods: Two models were established to explore the expression of the HMGB1-TLR4 pathway in a pulmonary I/R injury, its correlation with downstream inflammatory factors, and the effects of HMGB1-neutralizing antibodies on inflammation.

Results: IL-6 and TNF-α levels in the three mouse models showed a rapid increase, IL-1β, IL-6, and TNF-α were up-regulated in alveolar macrophages after LPS stimulation, TNF-α and HMGB1 were up-regulated in TLR4+/+ cells and peaked at 48 h but was not up-regulated in TLR4-/- cells. Western blot assays revealed that in TLR4+/+ cells, TLR4 was up-regulated after stimulation by LPS and was rapidly down-regulated after treatment with the HMGB1-neutralizing antibody. In contrast, TLR4-/- cells did not respond to LPS stimulation, and the HMGB1-neutralizing antibody did not significantly alter the TLR4 concentration.

Conclusions: HMGB1-TLR4 pathway plays an important role in the regulation of inflammation in pulmonary I/R injury. Furthermore, HMGB1 up-regulated downstream inflammatory factors via TLR4. HMGB1-neutralizing antibodies had a protective effect against lung injury by down-regulating the inflammatory response.