Hypertonic saline resuscitation attenuates pulmonary apoptosis in rats through a PI3K-Akt independent pathway

Abstract

Introduction. Resuscitation with racemic lactated Ringer’s solution (LR) induces pulmonary apoptosis by increasing the levels of pro-apoptotic protein called bad protein. Paradoxically, phosphorylation of bad protein (p-bad) creates a prosurvival environment. The PI3K-Akt pathway is known to be responsible for phosphorylation of multiple proteins such as bad and eNOS. Hypertonic saline (HTS) resuscitation attenuates posthemorrhagic shock pulmonary apoptosis through an unknown mechanism. This study was designed to investigate whether the effects of HTS are meditated through the PI3k-Akt pathway. Methods. Sprague-Dawley rats ( n = 20, 5/g) were subjected to a modified volume controlled hemorrhagic shock and randomized as follows: (1) sham hemorrhage (SH), (2) hemorrhage and no resuscitation (NR), (3) resuscitation with racemic LR, three times the volume of shed blood (LR), (4) resuscitation with 7.5% HTS (HTS, 9.7 ml/kg). Lung tissue was obtained 2 h postresuscitation and Western blotting was used to measure the expression of total and phosphorylated Akt, bad, and eNOS proteins. Results. The expression of total bad protein (pro-apoptotic) increased and phosphorylated bad (prosurvival) decreased significantly following resuscitation with LR ( P < 0.05). Resuscitation with HTS was associated with normal levels of total bad, and decreased bad phosphorylation. Furthermore, HTS resuscitation also decreased the phosphorylation (activation) of Akt and eNOS proteins. Conclusions. Resuscitation with racemic lactated Ringer’s promotes pulmonary apoptosis by restricting PI3K-Akt pathway-dependent phosphorylation of bad protein. Hypertonic saline, on the other hand, attenuates pulmonary apoptosis through a PI3K-Akt-independent mechanism.