Exogenously administered B-type natriuretic peptide (BNP) has been shown to offer cardioprotection through activation of particulate guanylyl cyclase (pGC), protein kinase G (PKG) and KATP channel opening. The current study explores if cardioprotection afforded by short intermittent BNP administration involves PI3K/Akt/p70s6k dependent signaling, and whether this signaling pathway may participate in regulation of BNP mRNA expression at early reperfusion. Isolated Langendorff perfused rat hearts were subjected to 30min of regional ischemia and 120min of reperfusion (IR). Applying intermittent 3×30s infusion of BNP peptide in a postconditioning like manner (BNPPost) reduced infarct size by >50% compared to controls (BNPPost 17±2% vs. control 42±4%, p<0.001). Co-treatment with inhibitors of the PI3K/Akt/p70s6k pathway (wortmannin, SH-6 and rapamycin) completely abolished the infarct-limiting effect of BNP postconditioning (BNPPost+Wi 36±5%, BNPPost+SH-6 41±4%, BNPPost+Rap 37±6% vs. BNPPost 17±2%, p<0.001). Inhibition of natriuretic peptide receptors (NPR) by isatin also abrogated BNPPost cardioprotection (BNPPost+isatin 46±2% vs. BNPPost 17±2%, p<0.001). BNPPost also significantly phosphorylated Akt and p70s6k at early reperfusion, and Akt phosphorylation was inhibited by SH-6 and isatin. Myocardial BNP mRNA levels in the area at risk (AA) were significantly elevated at early reperfusion as compared to the non-ischemic area (ANA) (Ctr(AA) 2.7±0.5 vs. Ctr(ANA) 1.2±0.2, p<0.05) and the ischemic control tissue (Ctr(AA) 2.7±0.5 vs. ischemia 1.0±0.1, p<0.05). Additional experiments also revealed a significant higher BNP mRNA level in ischemic postconditioned (IPost) hearts as compared to ischemic controls (IPost 6.7±1.3 vs. ischemia 1.0±0.2, p<0.05), but showed no difference from controls run in parallel (Ctr 5.4±0.8). Akt inhibition by SH-6 completely abrogated this elevation (IPost 6.7±1.3 vs. IPost+SH-6 1.8±0.7, p<0.05) (Ctr 5.4±0.8 vs. SH-6 1.5±0.9, p<0.05). In conclusion, Akt dependent signaling is involved in mediating the cardioprotection afforded by intermittent BNP infusion at early reperfusion, and may also participate in regulation of reperfusion induced BNP expression.

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Purpose To evaluate the long-term outcomes of percutaneous transhepatic stent placement for portal vein (PV) stenosis after liver transplantation (LT) and hepato-pancreato-biliary (HPB) surgery. Methods Retrospective study of 455 patients who underwent LT and 522 patients who underwent resection of the pancreatic head between June 2011 and February 2016. Technical success, clinical success, patency, and complications were evaluated for both groups. Results A total of 23 patients were confirmed to have postoperative PV stenosis and were treated with percutaneous transhepatic PV stent placement. The technical success rate was 100%, the clinical success rate was 80%, and the long-term stent patency was 91.3% for the entire study population. Two procedure-related hemorrhages and two early stent thromboses occurred in the HPB group while no complications occurred in the LT group. A literature review of selected studies reporting PV stent placement for the treatment of PV stenosis after HPB surgery and LT showed a technical success rate of 78-100%, a clinical success rate of 72-100%, and a long-term patency of 57-100%, whereas the procedure-related complication rate varied from 0-33.3%. Conclusions Percutaneous transhepatic PV stent is a safe and effective treatment for postoperative PV stenosis/occlusion in patients undergoing LT regardless of symptoms. Due to increased risk of complications, the indication for percutaneous PV stent placement after HPB surgery should be limited to patients with clinical symptoms after an individual assessment.

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