Acute lung injury (ALI) is a life-threatening complication of sepsis. Tetramethylpyrazine (TMP) has been used in the clinical treatment of vascular diseases. The aim of this study was to investigate the therapeutic effects and possible involved mechanisms on ALI. Material/Methods: Cecal ligation and puncture (CLP) was used to establish a sepsis model in rats. TMP at various dosages were administrated to rats using a intragastric method. Animal survival rate was calculated. The lung functions

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... e evaluated by lung weight/dry weight ratio (W/D), PaO 2 , dynamic compliance (DC), and airway resistance index (ARI). Pulmonary microvascular endothelial cells (PMVECs) were isolated from lungs harvested from rats with sepsis. TUNEL assay was used to detect apoptosis. Protein expression and phosphorylation levels were assessed by western blotting. Results: TMP administration increased the survival rate of septic rats. TMP also decreased W/D and DC, but increased PaO 2 and ARI in septic rats. Moreover, PMVECs apoptosis was inhibited in septic rats that received TMP treatment. The expression levels of GRP78, ATF4, caspase-12, active caspase-3, as well as the phosphorylation levels of PERK and eIF2a were suppressed in PMVECs isolated from TMP-treated septic rats. Conclusions: TMP alleviated sepsis-induced ALI by suppressing PMVECs apoptosis via PERK/eIF2a/ATF4/CHOP apoptotic signaling in endoplasmic reticulum stress.