Protective impact of landiolol against acute lung injury following hemorrhagic shock and resuscitation in rats.

Hemorrhagic shock and resuscitation (HSR) induces pulmonary inflammation, leading to acute lung injury (ALI). Notably, blocking β1 receptors can lead to organ protection through anti‑inflammatory and anti‑apoptotic effects. Additionally, although the β1 receptor pathway is blocked by the β1 blocker, the β2 receptor pathway may be preserved and activate the 5' adenosine monophosphate‑activated protein kinase (AMPK) pathway. The present study aimed to examine whether administration of the β1 blocker landiolol could achieve lung protection in a model of HSR‑ALI, alongside improvements in inflammation and apoptosis. Male Sprague‑Dawley rats underwent hemorrhage keeping their mean arterial pressure at 30 mmHg for 1 h. Resuscitation by reinfusion was initiated to restore blood pressure to pre‑hemorrhage levels for >15 min, followed by a 45‑min stabilization period to create the HSR‑ALI model. Landiolol (100 mg/kg/min) or saline was continuously administered after resuscitation. The lung tissues, which were collected for assessing inflammation and apoptosis‑related damage, underwent analyses, including histological examination, neutrophil count, assessment of lung wet/dry weight ratio, detection of the mRNA levels of tumor necrosis factor‑α (TNF‑α) and inducible nitric oxide synthase (iNOS), identification of terminal deoxynucleotidyl transferase dUTP nick‑end labeling (TUNEL)‑positive cells, and evaluation of caspase‑3 expression. In addition, phosphorylated AMPKα (pAMPKα) expression was tested via western blotting. Compared with the HSR/saline group, the HSR/landiolol group demonstrated a reduction in lung tissue damage score, and significant reductions in neutrophil count, lung wet/dry weight ratio, lung TNF‑α and iNOS mRNA levels, TUNEL‑positive cells and cleaved caspase‑3 expression. Furthermore, landiolol administration following HSR treatment increased pAMPKα expression. No significant hypotension occurred between the HSR/landiolol and HSR/saline groups; and blood loss did not differ significantly between the groups. In conclusion, landiolol administration after HSR reduced lung inflammation and apoptosis, suggesting a potential improvement in tissue damage. Furthermore, pAMPKα activation in the HSR/landiolol group may be the mechanism underlying the pulmonary protective effects of landiolol.