Brain death (BD) has been associated with an immunological priming of donor organs and is thought to exacerbate ischemia reperfusion injury (IRI). Recently we showed that the essential nitric oxide synthase co-factor tetrahydrobiopterin (BH4) abrogates IRI following pancreas transplantation. We therefore studied the effects of donor BD on IRI in a murine model of pancreas transplantation and tested the therapeutic potential of BH4 in this clinically relevant setting. Male C57BL6 mice were used as donors and recipients and cervical pancreas transplantation was performed using. Animals underwent BD induction and were followed for 3h under continuous ventilation. Experimental groups included (n=5): non-treated BD donors (1), pre-treatment of BD donors with 50mg/kg b.w. i.m BH4 prior to organ retrieval (2), ventilated non-treated donors (no BD, sham group) (3), and non brain death non-treated donors (4). Following 2 hours of reperfusion, microcirculation (functional capillary density, FCD; capillary diameter, CD) and cell viability was assessed by intravital fluorescence microscopy. Parenchymal damage was assessed by histology, BH4 levels were determined by HPLC and mRNA expression of inflammatory candidate markers were measured by real-time RT-PCR. Compared with controls, BD significantly exacerbated IRI reflected by reduced FCD and CD values (p<0.05) and induced IL-1ß, TNFa, IL-6 and ICAM-1 mRNA expression levels. Pancreatic grafts treated with BH4 displayed higher tissue levels of BH4 (p<0.01) and showed improved microcirculation reflected by increased FCD and CD values (p<0.05, respectively). Moreover, BD had devastating impact on cell viability, whereas BH4 treated grafts showed a significant higher percentage of viable cells (p<0.001, group 1 versus group 2). Early parenchymal damage was significantly more pronounced in organs from BD donors when compared to sham or non brain death donors (p<0.05), treatment with BH4 however significantly ameliorated necrotic lesions in organs from BD donors (p<0.05). In summary, our data gain new insights into the impact of BD on pancreatic isografts and that donor treatment with BH4 offers a therapeutical option for preventing BD exacerbated IRI in this transplant setting.

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