Prevention of trauma/hemorrhagic shock-induced lung apoptosis by IL-6-mediated activation of Stat3.

Acute lung injury (ALI) occurs in up to 37% of patients following trauma/hemorrhagic shock (T/HS) and, in other settings, is due to alveolar epithelial cell (AEC) apoptosis. To determine if AEC apoptosis is a key contributor to ALI following T/HS and whether or not signal transducer and activator of translation (Stat)3 activation can prevent it, rats were pretreated with a Stat3 inhibitor or placebo and subjected to T/HS or sham protocol and resuscitated without or with interleukin (IL)-6. T/HS induced apoptosis in up to 15% of lung cells, 82% of which were AEC. Apoptosis increased with increasing duration of shock and required resuscitation. IL-6 treatment stimulated lung Stat3 activation and prevented AEC apoptosis. Pretreatment of rats with a Stat3 inhibitor blocked the antiapoptotic effect of IL-6. Mice deficient in Stat3 beta, a naturally occurring dominant negative isoform of Stat3, were resistant to T/HS-induced lung apoptosis. T/HS altered the expression of 87% of apoptosis-related genes. IL-6 treatment normalized expression of 75% of the genes altered by T/HS; Stat3 inhibition prevented normalization of 65% of the gene whose expression was normalized by IL-6. Thus, T/HS-induced AEC apoptosis, which depended on the duration of hypotension, required resuscitation and was prevented by IL-6-mediated activation of Stat3, which acted to normalize the apoptosis transcriptome.