Clusterin (apolipoprotein J) facilitates NF-κB and Bax degradation and prevents I/R injury in heart transplantation.

ABSTRACT

BACKGROUND AND AIM: Ischemia-reperfusion (I/R) injury is an unavoidable event occurring during heart transplantation and is a key factor in graft failure and long-term survival rate of recipients. Therefore, there is an urgent need for the development of new therapies to prevent I/R injury. Clusterin is a hetero-dimeric glycoprotein with an antiapoptotic function. In this study, we investigated whether clusterin was cardioprotective in heart transplantation against I/R injury using an in vivo rat model and an in vitro cell culture system and we examined the underlying mechanisms of I/R injury. METHODS: Heart grafts from wild-type C57BL/6 mice were preserved in UW solution (control) or UW solution containing recombinant human apolipoprotein J (hr clusterin) for 24 hours. The preserved hearts were implanted into recipient mice of the same strain as the donors for 72 hours. The heart grafts were then taken for histopathological and gene expression analyses. An in vitro ischemia reperfusion model using H9C2 cells or H9C2/clusterin cDNA cells was constructed. The expression of clusterin, p65, Bax, Bcl-xL, IL-1ß, and TNF-α protein and mRNA in heart tissue and H9C2 cells was detected by Western blot, reverse transcription-polymerase chain reaction (RT-PCR), and quantitative RT-PCR assays. IL-1ß and TNF-α protein was detected by enzyme-linked immunosorbent assays. NF-kB activity was detected by an electrophoretic mobility shift assay and cell apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and flow cytometric analyses. RESULTS: Cold I/R caused severe morphologic myocardial injury to heart grafts from wild-type C57BL/6 mice whereas grafts from hr clusterin preservation showed less damage, as demonstrated by decreased cell apoptosis/death, decreased neutrophil infiltration, and the preservation of the normal structure of the heart. Clusterin reduced expression of p65, pre-inflammatory IL-1ß, TNF-α, and the pro-apoptotic gene Bax while it enhanced expression of the anti-apoptotic gene Bcl-xL in vitro and in vivo. Clusterin inhibited cell apoptosis/death and reduced pre-inflammation. CONCLUSION: Clusterin is a promising target for preventing cold I/R injury in heart transplantation. This study also shows that the resultant protective effects of clusterin are mediated by NF-κB signaling and Bax/Bcl-xL expression.