Tom P. Theruvath

Mitochondrial Calcium and the Permeability Transition in Cell Death

Dysregulation of Ca(2+) has long been implicated to be important in cell injury. A Ca(2+)-linked process important in necrosis and apoptosis (or necrapoptosis) is the mitochondrial permeability transition (MPT). In the MPT, large conductance permeability transition (PT) pores open that make the mitochondrial inner membrane abruptly permeable to solutes up to 1500 Da. The importance of Ca(2+) in MPT induction varies with circumstance. Ca(2+) overload is sufficient to induce the MPT. By contrast after ischemia-reperfusion to cardiac myocytes, Ca(2+) overload is the consequence of bioenergetic failure after the MPT rather than its cause. In other models, such as cytotoxicity from Reye-related agents and storage-reperfusion injury to liver grafts, Ca(2+) appears to be permissive to MPT onset. Lastly in oxidative stress, increased mitochondrial Ca(2+) and ROS generation act synergistically to produce the MPT and cell death. Thus, the exact role of Ca(2+) for inducing the MPT and cell death depends on the particular biologic setting.

Supply of Pre- and Probiotics Reduces Bacterial Infection Rates After Liver Transplantation—A Randomized, Double-Blind Trial

Bacterial infections frequently occur early after liver transplantation. We recently reported significant progress with a synbiotic composition, consisting of one lactic acid bacteria (LAB) and one fiber, which reduced the infection rate from 48% (with selective bowel decontamination) to 13%. Now, our aim is to study if a combination of different LAB and fibers would further improve outcome.

Effect of Enteral Nutrition and Synbiotics on Bacterial Infection Rates After Pylorus-preserving Pancreatoduodenectomy A Randomized, Double-blind Trial

Objective:Patients undergoing pancreas resection carry several risk factors for nosocomial bacterial infections. Pre- and probiotics (synbiotics) are potentially useful for prevention of these infections. Summary Background Data:First trials in patients following major abdominal surgery including liver transplantation using one Lactobacillus (LAB) and one fiber showed significant reduction of infection rates and reduced length of antibiotic therapy compared with a control group. The present study was designed to analyze whether a combination of different LAB and fibers would further improve outcome. Methods:A prospective randomized monocentric double-blind trial was undertaken in 80 patients following pylorus-preserving pancreatoduodenectomy (PPPD). All patients received enteral nutrition immediately postoperatively. One group (A) received a composition of 4 LAB and 4 fibers, and another group (B) received placebo (fibers only) starting the day before surgery and continuing for 8 days. Thirty-day infection rate, length of hospital stay, duration of antibiotic therapy, noninfectious complications, and side effects were recorded. Results:The incidence of postoperative bacterial infections was significantly lower with LAB and fibers (12.5%) than with fibers only (40%). In addition, the duration of antibiotic therapy was significantly shorter in the latter group. Fibers and LAB were well tolerated. Conclusion:Early enteral nutrition supplemented with a mixture of LAB and fibers reduces bacterial infection rates and antibiotic therapy following PPPD.

Rodent models of partial hepatectomies

Small rodents are the most used experimental models in liver surgical research. Hepatic resections in rodents are commonly performed to study liver regeneration, acute liver failure, hepatic metastasis, hepatic function, ‘small‐for‐size’ transplantation and metabolic response to injury. Most resections require only basic skills, are fast, reliable and highly reproducible. The partial hepatectomy technique in rodents can be improved by microsurgical techniques, which permit individualized dissection and ligature of the vascular and biliary branches with minimal operative morbidity and mortality. This is particularly relevant for murine models of liver resection. However, it requires advanced microsurgical skills. Here, we review the models, surgical techniques, results and limitations of partial liver resections in rodent models. We also reported for the first time segmentectomies of the median lobe in rodent models.

Description of B lymphocytes and plasma cells, complement, and chemokines/receptors in acute liver allograft rejection.

Background. Although antibody mechanisms play a pathogenetic role in liver allograft rejection, no data exist on B lymphocytes, plasma cells, complement, and chemokines in rejected liver tissue. Methods. Liver biopsy specimens from 25 patients with acute allograft rejection (AR) (rejection activity index, RAI score: 1–9) were analyzed by immunohistochemistry (IH) and reverse transcriptase-polymerase chain reaction (RT-PCR) and compared with biopsy specimens taken prior to implantation (PI). The number of CD20+ and CD138+ cells was evaluated, and the presence and abundance of the chemokines macrophage inflammatory protein (MIP)-3&agr;, CXCL9, CXCL10, CXCL11, CXCL12, and their receptors CCR-6, CXCR3, and CXCR4 were examined. Complement depositions were visualized by C4d IH. Results. The numbers of B lymphocytes (P=0.002) and plasma cells (P=0.022) were significantly higher in AR biopsy specimens compared with PI biopsy specimens. MIP-3&agr;+ and CCR-6+ cells were detected in the portal fields of all AR biopsy specimens. IH double staining revealed a colocalization of MIP-3&agr;+/CD20+ cells; C4d deposits could be demonstrated along the portal capillaries. All examined chemokines and receptors could be detected in normal liver tissue and in AR biopsy specimens by RT-PCR and semiquantitative RT-PCR, demonstrating an overexpression of CXCL10 and -11. Conclusions. The significant increase of B lymphocytes and plasma cells during acute rejection, together with the lack of a significant increase of proliferating cells, indicates that the migration of B lymphocytes and plasma cells—promoted by the expression of B-cell activating chemokines/receptors—plays a key role in acute liver rejection. The C4d deposits along the portal capillaries indicate a humorally mediated alloresponse caused by the accumulated B and plasma cells.

Activation of the oxygen-sensing signal cascade prevents mitochondrial injury after mouse liver ischemia-reperfusion

The mitochondrial permeability transition (MPT) plays an important role in hepatocyte death caused by ischemia-reperfusion (IR). This study investigated whether activation of the cellular oxygen-sensing signal cascade by prolyl hydroxylase inhibitors (PHI) protects against the MPT after hepatic IR. Ethyl 3,4-dihyroxybenzoate (EDHB, 100 mg/kg ip), a PHI, increased mouse hepatic hypoxia-inducible factor-1alpha and heme oxygenase-1 (HO-1). EDHB-treated and untreated mice were subjected to 1 h of warm ischemia to approximately 70% of the liver followed by reperfusion. Mitochondrial polarization, cell death, and the MPT were assessed by intravital confocal/multiphoton microscopy of rhodamine 123, propidium iodide, and calcein. EDHB largely blunted alanine aminotransferase (ALT) release and necrosis after reperfusion. In vehicle-treated mice at 2 h after reperfusion, viable cells with depolarized mitochondria were 72%, and dead cells were 2%, indicating that depolarization preceded necrosis. Mitochondrial voids excluding calcein disappeared, indicating MPT onset in vivo. NIM811, a specific inhibitor of the MPT, blocked mitochondrial depolarization after IR, further confirming that mitochondrial depolarization was due to MPT onset. EDHB decreased mitochondrial depolarization to 16% and prevented the MPT. Tin protoporphyrin (10 micromol/kg sc), an HO-1 inhibitor, partially abrogated protection by EDHB against ALT release, necrosis, and mitochondrial depolarization. In conclusion, IR causes the MPT and mitochondrial dysfunction, leading to hepatocellular death. PHI prevents MPT onset and liver damage through an effect mediated partially by HO-1.

Mitochondrial Permeability Transition in Liver Ischemia and Reperfusion: Role of c-Jun N-Terminal Kinase 2

The mitochondrial permeability transition (MPT) mediates hepatic necrosis after ischemia and reperfusion (I/R). Here, we studied the role of c-Jun N-terminal kinase 2 (JNK2) in MPT-induced liver injury. Wildtype (WT) and JNK2 knockout (KO) mice underwent 70% liver ischemia for 1 hr followed by reperfusion for 8 hr, after which hepatocyte injury and animal survival was assessed. Compared with WT, JNK2 KO mice had 38% less alanine transaminase release and 39% less necrosis by histology. Survival out to 14 days was also greater in JNK2 KO mice (57% vs. 11%), and overall Kaplan-Meier survival was improved. No difference in apoptosis was observed. Intravital multiphoton microscopy of potential-indicating rhodamine 123 after reperfusion revealed depolarized mitochondria in 82% of WT hepatocytes, which decreased to 43% in JNK2 KO hepatocytes. In conclusion, JNK2 contributes to hepatocellular injury and death after I/R in association with increased mitochondrial dysfunction via the MPT.

NIM811, a Mitochondrial Permeability Transition Inhibitor, Prevents Mitochondrial Depolarization in Small-for-Size Rat Liver Grafts

ATP decreases markedly in small‐for‐size liver grafts. This study tested if the mitochondrial permeability transition (MPT) underlies dysfunction of small‐for‐size livers. Half‐size livers were implanted into recipients of about twice the donor weight, resulting in quarter‐size liver grafts. NIM811 (5 μM), a nonimmunosuppressive MPT inhibitor was added to the storage solutions. Mitochondrial polarization and cell death were assessed by confocal microscopy of rhodamine 123 (Rh123) and propidium iodide (PI), respectively. After quarter‐size transplantation, alanine aminotransferase (ALT), serum bilirubin and necrosis all increased. NIM811 blocked these increases by >70%. After 38 h, BrdU labeling, a marker of cell proliferation and graft weight increase were 3% and 5%, respectively, which NIM811 increased to 30% and 42%. NIM811 also increased survival of quarter‐size grafts. In sham‐operated livers, hepatocytes exhibited punctate Rh123 fluorescence. By contrast, in quarter‐size grafts at 18 h after implantation, mitochondria of most hepatocytes did not take up Rh123, indicating mitochondrial depolarization. Nearly all hepatocytes not taking up Rh123 continued to exclude PI at 18 h, indicating that depolarization preceded cell death. NIM811 and free radical‐scavenging polyphenols strongly attenuated mitochondrial depolarization. In conclusion, mitochondria depolarized after quarter‐size liver transplantation. NIM811 decreased injury and stimulated regeneration, probably by inhibiting free radical‐dependent MPT onset.

NIM811 (N-Methyl-4-isoleucine Cyclosporine), a Mitochondrial Permeability Transition Inhibitor, Attenuates Cholestatic Liver Injury but Not Fibrosis in Mice

Cholestasis causes hepatocyte death, possibly because of mitochondrial injury. This study investigated whether NIM811 (N-methyl-4-isoleucine cyclosporine), an inhibitor of the mitochondrial permeability transition (MPT), attenuates cholestatic liver injury in vivo. Cholestasis was induced in mice by bile duct ligation (BDL). NIM811 was gavaged (20 mg/kg) before BDL and daily (10 mg/kg) afterward. Mitochondrial depolarization, cell death, and MPT onset were assessed by intravital confocal/multiphoton microscopy of rhodamine 123, propidium iodide, and calcein. After BDL, serum alanine aminotransferase (ALT), hepatic necrosis, and apoptosis all increased. NIM811 decreased ALT, necrosis, and apoptosis by 60 to 86%. In vehicle-treated mice at 6 h after BDL, viable hepatocytes with depolarized mitochondria were 18/high-power field (hpf), and nonviable cells were ∼1/hpf, showing that depolarization preceded necrosis. Calcein entered mitochondria after BDL, indicating MPT onset in vivo. NIM811 decreased depolarization by 72%, prevented calcein entry into mitochondria, and blocked release of cytochrome c. Hepatic tumor necrosis factor α, transforming growth factor-β1, procollagen α1(I) mRNA, α-smooth muscle actin, and Sirius red staining for collagen increased after BDL but were not different in vehicle- and NIM811-treated mice. Taken together, NIM811 decreased cholestatic necrosis and apoptosis but did not block fibrosis, indicating that the MPT plays an important role in cholestatic cell death in vivo.

C-Jun N-terminal kinase 2 promotes graft injury via the mitochondrial permeability transition after mouse liver transplantation.

The c‐Jun N‐terminal kinase (JNK) pathway enhances graft injury after liver transplantation (LT). We hypothesized that the JNK2 isoform promotes graft injury via the mitochondrial permeability transition (MPT). Livers of C57BL/6J (wild‐type, WT) and JNK2 knockout (KO) mice were transplanted into WT recipients after 30 h of cold storage in UW solution. Injury after implantation was assessed by serum ALT, histological necrosis, TUNEL, Caspase 3 activity, 30‐day survival, and cytochrome c and 4‐hydroxynonenal immunostaining. Multiphoton microscopy after LT monitored mitochondrial membrane potential in vivo. After LT, ALT increased three times more in WT compared to KO (p < 0.05). Necrosis and TUNEL were more than two times greater in WT than KO (p < 0.05). Immunostaining showed a >80% decrease of mitochondrial cytochrome c release in KO compared to WT (p < 0.01). Lipid peroxidation was similarly decreased. Every KO graft but one survived longer than all WT grafts (p < 0.05, Kaplan‐Meier). After LT, depolarization of mitochondria occurred in 73% of WT hepatocytes, which decreased to 28% in KO (p < 0.05). In conclusion, donor JNK2 promotes injury after mouse LT via the MPT. MPT inhibition using specific JNK2 inhibitors may be useful in protecting grafts against adverse outcomes from ischemia/reperfusion injury.