Selective histone deacetylase 6 inhibition prolongs survival in a lethal two-hit model.

BACKGROUND

Hemorrhagic shock (HS) followed by a subsequent insult ("second hit") often initiates an exaggerated systemic inflammatory response and multiple organ failure. We have previously demonstrated that valproic acid, a pan histone deacetylase inhibitor, could improve survival in a rodent "two-hit" model. In the present study, our goal was to determine whether selective inhibition of histone deacetylase 6 with Tubastatin A (Tub-A) could prolong survival in a two-hit model where HS was followed by sepsis from cecal ligation and puncture (CLP).

METHODS

C57Bl/6J mice were subjected to sublethal HS (30% blood loss) and then randomly divided into two groups (n = 13 per group) such as Tub-A group (treatment) and vehicle (VEH) group (control). The Tub-A group was given an intraperitoneal injection of Tub-A (70 mg/kg) dissolved in dimethyl sulfoxide (DMSO). The VEH group was injected with DMSO (1 μl/g body weight). After 24 h, all mice were subjected CLP followed immediately by another dose of Tub-A or DMSO. Survival was monitored for 10 d. In a parallel study, peritoneal irrigation fluid and liver tissue from Tub-A- or DMSO-treated mice were collected 3 h after CLP. Enzyme-linked immunosorbent assay was performed to quantify activity of the myeloperoxidase and concentrations of tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6) in the peritoneal irrigation fluid. RNA was isolated from the liver tissue, and real-time polymerase chain reaction was performed to measure relative messenger RNA levels of TNF-α and IL-6.

RESULTS

Treatment with Tub-A significantly improved survival compared with that of the control (69.2% versus 15.4%). In addition, Tub-A significantly suppressed myeloperoxidase activity (169.9 ± 8.4 ng/mL versus 70.4 ± 17.4 ng/mL; P < 0.01) and reduced levels of cytokines TNF-α and IL-6 in the peritoneal fluid (TNF-α: 105.7 ± 4.7 versus 7.4 ± 2.4 pg/mL; IL-6: 907.4 ± 2.3 versus 483.6 ± 1.6 pg/mL; P < 0.01) compared with those in the VEH control. Gene expression measured by real-time polymerase chain reaction confirmed that Tub-A inhibits transcription of TNF-α and IL-6.

CONCLUSIONS

Tub-A treatment significantly improves survival, attenuates inflammation, and downregulates TNF-α and IL-6 gene expression in a rodent two-hit model.