The effect of intravenous and intrathecal morphine preconditioning on hepatic ischaemia-reperfusion injury in normal and cirrhotic livers

Abstract

Hepatic ischaemia-reperfusion injury occurs when patients undergoing liver

operations such as liver transplantation, tumour resection and shock. Intravenous and

intrathecal administration of morphine can be used to provide analgesia prior or after

liver surgery. It has been reported that systemically administered morphine conferred

protective effect on numerous organs, including heart, brain and kidney. The focus of

my research is to investigate the effect of intravenous and intrathecal morphine

preconditioning on normal and cirrhotic livers. Further, PI3K/Akt, STAT3 and

HO-1/iNOS pathways had been shown to ameliorate hepatic ischemia-reperfusion

injury. Hence, we aim to investigate these possible signaling pathways associated with

morphine mediated hepato-protection.

A partial hepatic ischaemia reperfusion injury model in rats was used. The

experiments were divided into two series: one involved in normal livers and the other

one involved in cirrhotic livers. For the normal livers, morphine at different doses

were administrated intravenously or intrathecally prior the onset of ischaemia, and the

experiments were repeated with previous intravenous administration of naloxone

methiodide (opioid receptor antagonist), or wortmannin (Akt inhibitor), respectively.

For the cirrhotic livers, morphine at optimal doses were injected intravenously or

intrathecally prior the onset of ischaemia. Those rats with only induced hepatic

ischaemia-reperfusion injury only were marked as control groups. The effect of

morphine preconditioning on hepatic architecture, apoptosis and liver function were

evaluated respectively by hematoxylin-eosin (H&E) staining, Terminal

deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) staining, the

expression of cleaved Caspase-3, and serum levels of alanine aminotransferase (ALT)

and aspartate aminotransferase (AST). Meanwhile, the expression of phosphorylated

Akt, phosphorylated JAK2, phosphorylated STAT3, HO-1 and iNOS were detected by

Western Blot to determine the signaling pathways involved by intravenous and

intrathecal morphine preconditioning.

The normal livers series presented intravenous and intrathecal morphine

preconditioning at the 100μg/kg, 10μg/kg, respectively, better persevered hepatic

architecture when compared with control groups. The degree of liver cell apoptosis

and expression of cleaved caspase-3 were also reduced by intravenous and intrathecal

morphine preconditioning. In additional, intravenous and intrathecal morphine

preconditioning ameliorated hepatocellular damage by reducing ALT&AST release.

Moreover, the expressions of phosphorylated Akt and its downstream protein STAT3

were significantly increased by intravenous and intrathecal morphine preconditioning,

compared with their respective control groups. The hepato-protective effect of

intravenous and intrathecal morphine preconditioning was reversed by naloxone

methiodide or wortmannin pretreatment. The similar pattern of protection was

observed in cirrhotic livers. Both intravenous and intrathecal morphine

preconditioning protected hepatic architecture much better than control groups. They

also attenuated hepatic apoptosis degree and hepatocellular enzyme release.

Furthermore, the expression of HO-1 was up-regulated, whereas the expression of

iNOS was down-regulated by intravenous and intrathecal morphine preconditioning.

In summary, this study provided evidence that intravenous and intrathecal

morphine preconditioning could attenuate hepatic ischaemia-reperfusion injury in

normal and cirrhotic livers. The involvement of opioid receptors, Akt/STAT3 pathway

and HO-1 pathway might be the underlying mechanisms of morphine

hepato-protection. Finally, the protective effect of morphine preconditioning might

provide a potential therapeutic approach for clinical usage.