Gene Transduction of an Active Mutant of Akt Exerts Cytoprotection and Reduces Graft Injury After Liver Transplantation

Abstract

Akt is expected to be an effective target for the treatment of ischemia-reperfusion injury (I/R) due to its anti-apoptotic properties and its ability to activate the endothelial nitric oxide synthase (eNOS) enzyme. Therefore, this study was aimed to determine the efficacy of an active mutant of Akt (myr-Akt) to decrease I/R injury in a model of orthotopic liver transplantation in pigs. In addition, we analyzed the contribution of nitric oxide in the Akt-mediated effects by using an eNOS mutant (S1179DeNOS) that mimics the phosphorylation promoted by Akt in the eNOS sequence. Donors were treated with adenoviruses codifying for myr-Akt, S1179DeNOS or b -galactosidase 24 h before liver harvesting. Then, liver grafts were orthotopically transplanted into their corresponding recipients. Levels of transaminases and lactate dehydrogenase (LDH) increased in all recipients after 24 h of transplant. However, transaminases and LDH levels were significantly lower in the myr-Akt group compared with vehicle. The percentage of apoptotic cells and the amount of activated-caspase 3 protein were also markedly reduced in myr-Akt-treated grafts after 4 days of liver transplant compared with vehicle and S1179DeNOS groups. In conclusion, myr-Akt gene therapy effectively exerts cytoprotection against hepatic I/R injury regardless of the Akt-dependent eNOS activation.

Impact of Cell Cycle Disruption on Impaired Hepatic Regeneration in Aged Livers with Ischemic Insult

“…In contrast, the old rats subjected to hepatic ischemia showed sustained caspase-3 activation and delayed Akt activation, resulting in prolonged apoptosis. It was found in recent studies that adenoviral gene transfer of the active mutant of Akt exerted anti-apoptotic effects against hepatic I/R injury, which supports our interpretation of our results [19,21]. In addition, the suppression of Akt activity by phosphatidylinositol 3-kinase (PI3K) inhibitor contributed to apoptotic damage and liver injury in mice after TNF-a administration [20], suggesting that Akt plays a crucial role in cell survival by inhibiting apoptosis.…”

“…In addition, the suppression of Akt activity by phosphatidylinositol 3-kinase (PI3K) inhibitor contributed to apoptotic damage and liver injury in mice after TNF-a administration [20], suggesting that Akt plays a crucial role in cell survival by inhibiting apoptosis. The PI3K/ Akt pathway is a 'survival signaling pathway', the downstream targets of which are involved in antiapoptosis, anti-oxidative defense, and protein synthesis [18][19][20][21]. As for the effect of aging on the PI3K/Akt pathway, our results suggested that delayed Akt activation; i.e., delayed protection against apoptosis, may affect the recovery from liver injury after hepatectomy in old rats that have been subjected to ischemic insult.…”

“…Akt has anti-apoptotic properties and acts hepatoprotectively [18][19][20][21]. However, no report has investigated the age-dependent profile of Akt expression after hepatectomy.…”

“…We next examined the expression profiles of p-Akt and NF-kB activation, which are known to exhibit anti-apoptotic effects against some forms of liver injury [18][19][20][21][22]. In the rats that were not subjected to hepatic ischemia, the increased p-Akt levels observed 1 h after hepatectomy were sustained until 48 h in both the young and old rats (Fig.…”

Step-by-Step Guide for a Simplified Model of Porcine Orthotopic Liver Transplant

“…Since the mid 1990s, our group has used a simplified technique to perform hundreds of liver transplants in pigs with consistent success [15][16][17][18][19][20]. The purpose of this work is to communicate, in detail, how to reproduce this technically straightforward model, from the induction of anesthesia to the postoperative follow-up.…”