摘要:

Background.Nonimmune renal injury plays an important role in acute and chronic rejection by triggering an injury response through cytokine and chemokine release. Bioflavonoids are agents with potential immunosuppressive and renoprotective properties. We studied the effects of quercetin and curcumin, two bioflavonoids, on ischemia-reperfusion in the rat.Methods.Rats underwent 30 min of left renal pedicle occlusion with simultaneous right nephrectomy and were pretreated with quercetin or curcumin. Serial serum creatinine was measured, and renal expression of the chemokines regulated upon activation, normal T-cell expressed and secreted (RANTES), monocyte chemoattractant protein-1 (MCP-1), and allograft inflammatory factor(AIF) was quantified by polymerase chain reaction.Results.Pretreatment with quercetin or curcumin resulted in preservation of histological integrity, with a decrease in tubular damage and interstitial inflammation. On day 2 after ischemia-reperfusion, quercetin pretreatment decreased the mean serum creatinine level from 6.5±1.4 to 3.3±0.5 mg/dl (P=0.06). On day 7, the creatinine level for control animals was 7.5±1.5 mg/dl, which was significantly decreased by pretreatment with quercetin, curcumin, or both together (creatinine levels: 1.6±1.3, 1.8±0.2, and 2.0±0.4 mg/dl, respectively; allP<0.05 vs. untreated). By semiquantitative polymerase chain reaction, RANTES, MCP-1, and AIF were detected at high levels in kidneys on day 2 but not in normal kidneys. Pretreatment with quercetin or curcumin strongly attenuated this expression.Conclusion.Quercetin and curcumin reduce ischemia-reperfusion injury and its inflammatory sequelae. The bioflavonoids hold promise as agents that can reduce immune and nonimmune renal injury, the key risk factors in chronic graft loss.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Background.Ischemic-preconditioning is a process whereby a brief ischemic episode confers a state of protection against subsequent long-term ischemia-reperfusion injury. Ischemic preconditioning has been studied in heart and liver ischemia-reperfusion injury; however, few studies have been performed in the model of preservation-reperfusion injury in liver transplantation. The current study was designed to evaluate the ability of ischemic preconditioning to protect liver grafts from long-term preservation-reperfusion injury.Methods.Male Sprague Dawley rats were used as donors and recipients of orthotopic liver transplantation. Ischemic preconditioning was done by interruption of the portal vein and hepatic artery for 5, 10, and 20 min (5-10, 10-10, and 20-10 groups). Reflow was initiated by removal of the clamp for another 10 min in all groups. The liver was removed and placed in a bath with Euro-Collins solution for different preservation times. Tolerance of the transplanted liver to cold ischemia was determined by survival time and liver function tests. Rat tumor necrosis factor was analyzed by a bioassay. Nω-Nitro-L-arginine methyl ester, L-arginine, or adenosine was administered to block or stimulate the synthesis of nitric oxide (NO) in the rats that received long-term-preserved liver grafts.Results.Twenty percent of syngeneic rats (n=10) that received a liver graft with a 16-hr cold ischemia time in Euro-Collins solution survived for more than 1 day and 10% survived for more than 5 days. In contrast, 87.5% of rats (n=8) that received a liver graft with ischemic preconditioning (10-10 group) and 16 hr of cold ischemia survived for more than 1 day and 75% for more than 5 days. Recipients of liver grafts with ischemic preconditioning had significantly reduced levels of serum aspartate transaminase and tumor necrosis factor-α, as well as increased bile flow, compared with recipients of liver grafts without ischemic preconditioning. Blockage of the NO pathway using Nω-nitro-L-arginine methyl ester, a stereospecific competitive inhibitor of NO formation, attenuated the protective effect of ischemic preconditioning. Administration of one of two precursors of NO synthesis, L-arginine or adenosine, prolonged the survival of rats that received 16-hr-preserved liver grafts. In addition, L-arginine synergized with short-term ischemic preconditioning (5-10 group) to increase the survival of rats that received a liver graft with a 16-hr cold ischemia time, and the survival rate was 83% after 5 days. Finally, prolonged ischemic preconditioning (≥20 min; 20-10 group) resulted in liver damage and loss of function.Conclusion.The current results show that ischemic preconditioning protects the liver graft from subsequent long-term cold preservation-reperfusion injury in a rat liver transplantation model. The protective role of ischemic preconditioning may be mediated by the endogenous production of NO.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Background.Two important processes in the preservation of the function of donor hearts are the maintenance of ATP-sensitive potassium channel activity during myocardial ischemia and the scavenging of reactive oxygen species formed during reperfusion. The aim of this study was to compare the effect of three protocols on the preservation of hemodynamic function in isolated rat hearts after hypothermic storage. These protocols were: (1) pretreatment of the heart with a potassium channel opener (200 µM pinacidil); (2) storage of the heart in an aspartate-enriched extracellular cardioplegic solution containing the lazaroid antioxidant, U74500A (30 µM); and(3) a combination of protocols 1 and 2.Methods.Hearts from Wistar rats were perfused on a Langendorff apparatus. After stabilization in working mode, baseline measurements of heart rate, coronary and aortic flow, and cardiac output were performed. Hearts (n=6 in each group) were then randomized to protocols 1-3, untreated controls, or vehicle-treated controls. Hearts were stored in extracellular-based preservation solution for 12 hr at 2-3°C, remounted on the perfusion apparatus, and stabilized as before; hemodynamic measurements were then repeated.Results.Recovery of hemodynamic function was enhanced by pinacidil pretreatment or incorporation of lazaroid in the storage solution, but the combination of these two treatments produced the best results.Conclusions.Combined pharmacological activation of ATP-sensitive potassium channels before cardioplegia and the addition of U74500A to the preservation solution is associated with significantly enhanced hemodynamic function in the isolated rat heart after 12 hr of hypothermic storage. These data suggest a novel use for these agents in the transplantation context.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Background.Unlike in kidney and heart transplantation, the role of pretransplant donor-specific blood transfusion (DST) has not been studied prospectively in a large animal model of bowel transplantation. We investigated the impact of portal versus systemic DST on overall survival, rejection, graft-versus-host disease (GVHD), and infection after total (small and large) bowel transplantation in pigs.Methods.Mixed lymphocyte culture-reactive, outbred pigs underwent total enterectomy and orthotopic total bowel transplantation with portal vein graft drainage. One unit of donor blood was transfused via the portal or systemic circulation (according to a randomization protocol) before graft implantation was begun. We studied six groups, all of which underwent at least a total bowel transplant: group 1 (n=5) comprised nonimmunosuppressed control pigs with portal DST; group 2 (n=6), nonimmunosuppressed control pigs with systemic DST; group 3 (n=5), cyclosporine (CsA)-treated pigs with portal DST; group 4 (n=5), CsA-treated pigs with systemic DST; group 5 (n=5), tacrolimus-treated pigs with portal DST; and group 6 (n=5), tacrolimus-treated pigs with systemic DST. All immunosuppressed pigs received prednisone (2 mg/kg/day) and either CsA (to maintain levels between 250 and 350 ng/ml) or tacrolimus (to maintain levels between 10 and 30 ng/ml). Stomal biopsies and autopsies were obtained to study the incidence of rejection, GVHD, and infection.Results.Portal DST and tacrolimus-based immunosuppression resulted in the highest survival rates. At 7, 14, and 28 days after transplantation, survival rates in group 5 were 100%, 100%, and 80%; in group 6, 100%, 60%, and 40%; and in group 3, 100%, 0%, and 0%, respectively. Only the combination of portal DST and tacrolimus prevented the occurrence of, and death from, rejection. Death from rejection at 7, 14, and 28 days in group 5 was 0%, 0%, and 0%; in group 6, 0%, 33%, and 67%; and in group 3, 0%, 100%, and 100%, respectively. Of note, if immunosuppression was used, the groups with portal (versus systemic) DST had a higher risk of death from infection but a lower risk of death from GVHD. Simultaneous immunologic events were noted more frequently in groups with systemic (versus portal) DST. Long-term survival was noted only in groups with tacrolimus-based immunosuppression and was more common for those with portal (versus systemic) DST.Conclusions.Portal DST at the time of total bowel transplantation and posttransplant immunosuppression with tacrolimus prevent rejection and significantly increase graft survival. The combination of portal antigen presentation and tacrolimus needs to be studied in clinical bowel transplantation.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Background.Our aim was to evaluate the hepatic blood flows and oxygen metabolism of non-heart-beating donor (NHBD) pigs, with the use of cardiopulmonary bypass(CPB) and normothermic recirculation (NR) before total body cooling, and its relationship with recipient survival.Methods.Thirty-five pigs were transplanted with an allograft from NHBDs. After warm ischemia (WI) time (20, 30, or 40 min), CPB and NR were run for 30 min. After this period, the animals were cooled to 15°C. In the control group(20 min of WI), the period of NR was excluded. Liver procurement was then performed.Results.Survival rate was 100% in the 20WI, 70% in the 30WI, and 50% in the 40WI. Control group survival rate was 0%. Hepatic artery blood flow and portal blood flow recovered during NR. Pump blood flow during CPB increased rapidly during NR and was significantly higher in the 20WI. When donors of the livers transplanted in "surviving pigs" (DSP) were compared with donors of the livers transplanted in "nonsurviving pigs" (DNSP), hepatic artery blood flow, portal blood flow, and pump blood flow were higher in the DSP. Hepatic oxygen extraction ratio increased in the three groups with respect to baseline values. Hepatic oxygen extraction ratio was lower in the 20WI than in the other groups and was lower in the DSP than in the DNSP.Conclusions.The use of a NR period before total body cooling improves survival of liver transplantation in NHBDs. Portal blood flow and pump blood flow measurements can predict the viability of the grafts.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Background:Mixed lymphohematopoietic chimerism can provide an effective means of inducing long-term immunological tolerance and has been documented in a monkey allograft model. A conditioning regimen including nonmyeloablative or myeloablative irradiation and splenectomy has been used to induce chimerism in a pig-to-primate transplantation model. Since the presence of anti-Galα1-3Gal (αGal) natural antibodies leads to the hyperacute rejection of pig organs transplanted into primates, extracorporeal immunoaffinity adsorption (EIA) of anti-αGal antibodies is also included in the regimen. The effect of the tolerance induction protocol on the anti-αGal antibody response has been assessed.Methods:Anti-αGal antibody was measured after the EIA of plasma through anαGal immunoaffinity column in baseline studies involving two unmodified baboons, one splenectomized baboon, and one baboon that received a challenge with porcine bone marrow (BM), and in three groups of baboons (n=2 in each group) that received different conditioning regimens for tolerance induction. Group 1 received a nonmyeloablative conditioning regimen without porcine BM transplantation. Group 2 received nonmyeloablative conditioning with pig BM transplantation and pig cytokine therapy. Group 3 received myeloablative conditioning, and autologous BM transplant (with BM depleted of CD2+or CD2+/CD20+cells), and pig BM transplantation.Results:In the baseline studies, a single EIA of anti-αGal antibodies in an unmodified animal initially depleted anti-αGal antibody, followed by a mild rebound. Nonmyeloablative conditioning (group 1) in the absence of pig cell exposure reduced the rate of anti-αGal antibody return. Pig BM cells markedly stimulated anti-αGal antibody production in an unmodified baboon (αGal IgM and IgG levels increased 40- and 220-fold, respectively). This response was significantly reduced (to an only 2- to 5.5-fold increase of IgM and IgG) in baboons undergoing nonmyeloablative conditioning (group 2). A myeloablative conditioning regimen (group 3) prevented the antibody response to pig BM, with the reduction in response being greater in the baboon that received autologous BM depleted of both CD2+and CD20+cells. No new antibody directed against pig non-αGal antigens was detected in any baboon during the 1 month follow-up period.Conclusions.(i) EIA of anti-αGal antibody in unmodified baboons results in a transient depletion followed by a mild rebound of antibody; (ii) exposure to pig BM cells results in a substantial increase in anti-αGal antibody production; (iii) a nonmyeloablative conditioning regimen reduces the rate of antibody return and (iv) markedly reduces the response to pig BM cells; (v) the anti-αGal response is completely suppressed by a myeloablative regimen if CD2+and CD20+cells are eliminated from the autologous BM inoculum. Furthermore, (vi) challenge with pig BM cells appears to stimulate only an anti-αGal antibody response without the development of other (non-αGal) anti-pig antibodies. We conclude that regimens used for T-cell tolerance induction can be beneficial in reducing the anti-αGal antibody response to porcine BM.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Background.Selected esters of succinic acid were recently proposed as novel nutrients to support ATP generation in cells endangered by an imbalance between the formation and breakdown of this adenine nucleotide. In the present study, a new ester, glycerol-1,2,3-trimethylsuccinate, was examined for its potential beneficial effect in the procedures preceding liver transplantation.Methods.The viability and metabolic behavior of hepatocytes were examined after perfusion and storage of rat livers for 20 hr at 4°C with a Belzer UW-CSS solution in the absence or presence or 2 mM glycerol-1,2,3-trimethylsuccinate.Results.Although it failed to affect significantly the release of cellular enzymes during storage and the protein or glycogen content of the liver, and was unable to prevent the storage-induced decrease in both biosynthetic activity and D-[U-14C]glucose incorporation into glycogen in isolated hepatocytes, the ester restored to a close-to-normal value the viability of the hepatocytes and opposed the starvation-like effects of liver storage upon both the conversion of D-[U-14C]glucose to14CO2and radioactive amino acids and the de novo generation of14C-labeled D-glucose from [2-14C]pyruvate.Conclusions.Because succinic acid esters are efficiently metabolized in several cell types, the present results suggest that such esters may have a wide field of application in transplantation procedures.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Background.During allograft rejection, cytokines and lipid mediators contribute to cell injury and organ failure. Peroxisomes play a crucial role in lipid metabolism, including the degradation of lipid mediators by peroxisomalβ-oxidation. Therefore, we investigated the alterations of hepatic peroxisomes after allogeneic rat liver transplantation.Methods.MHC-incompatible Dark Agouti (RT1a) donor rats and Lewis(RT11) recipient rats were used for allogeneic transplantation. For immunosuppression, a group of these animals received cyclosporine (CsA) intraperitoneally (1 mg/kg body weight per day). Lewis rats were used for isogeneic transplant combination. Ten days after transplantation, livers were investigated using morphometrical methods for determination of peroxisomal diameter and volume density. The activities of peroxisomal catalase (CAT) and acylcoenzyme A oxidase (AOX) were determined, and the corresponding proteins were evaluated by quantitative immunocytochemistry and immunoblotting. The expressions of mRNAs encoding CAT and AOX were investigated by Northern blotting.Results.The volume density and diameter of peroxisomes were significantly decreased in allogeneic transplanted livers but were unchanged in CsA-treated animals. Both the activities of CAT and AOX and their protein levels were significantly reduced in liver allografts. Moreover, the corresponding mRNA levels of CAT and AOX were decreased significantly in liver allografts, whereas CsA treatment led to an increase of those mRNAs. Isogeneic transplanted livers showed only a slight reduction of the corresponding enzyme values.Conclusions.Peroxisomes are severely affected both morphologically and functionally after allogeneic liver transplantation. These results suggest that impairment of peroxisomal lipid βoxidation could contribute to the pathogenesis of the rejection process by decreased catabolism of lipid mediators involved in the regulation of the inflammatory response. CsA, in addition to its immunosuppressive effects, may contribute to allograft survival by maintenance of those important peroxisomal functions.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Background.Pancreatic islet transplantation is limited because of immune rejection of the transplanted tissue. Long-term survival of allogeneic pancreatic islet grafts in the absence of systemic immunosuppressive agents should be possible by transfecting the islets directly with DNA encoding immunoregulatory molecules. Localized production of these molecules should affect only the immune cells that come into the vicinity of the foreign tissue. We investigated whether local expression of human CTLA4-Ig or soluble human Fas ligand from biolistically transfected mouse islets would have a protective effect on allograft survival.Methods.Isolated CBA (H2k) islets were biolistically transfected using the gene gun. The experimental groups were naked gold particles (n=6), empty vector DNA (n=5), DNA encoding human CTLA4-Ig (n=8), or soluble human Fas ligand (n=5). Secretion of the transfected gene product was confirmed by screening islet culture supernatants for protein production using a sandwich ELISA. The blasted islets were transplanted under the kidney capsule of alloxan-diabetic BALB/c (H2d) recipients.Results.Control grafts survived for 23 days, on average. CTLA4-Ig-transfected islets showed a bimodal distribution: 50% of cases survived ≥46 days and 50% were similar to the controls. In the soluble human Fas ligand group, 80% of grafts survived ≥50 days. There was no correlation between graft survival times and pretransplant levels of protein production.Conclusion.Our results indicate that local production of human CTLA4-Ig or soluble human Fas ligand by biolistically transfected islets can promote allograft survival. This approach should be valuable as a potential immunoprotective therapeutic strategy in tissue transplantation.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Background.Because of its anatomical and physiological similarities to humans, the pig appears to be a suitable large animal model for preclinical studies of islet transplantation. The aim of this study was to investigate islet auto- and allotransplantation in a pig model with diabetes induced by total pancreatectomy.Methods.Porcine islets were isolated by a continuous digestion-filtration device at 32°C and purified by a discontinuous iso-osmolar Ficoll-sodium-diatrizoate gradient on a Cobe 2991. The purified islets were autografted into the liver or the renal subcapsular space. The liver appears to be a more suitable site for the islet grafts than the renal subcapsular space, and the minimal amount of islets for reversal of diabetes is >5µl/kg of body weight.Results.Persistent normoglycemia (fasting blood glucose level: 72.4±44.38 mg/dl) with a normal insulin secretion response to glucose stimulation was successfully achieved in five of six diabetic pigs by implanting a sufficient islet mass into the liver. Triple-drug immunosuppressive therapy with cyclosporine, azathioprine, and prednisolone did not prevent porcine islet allografts from experiencing early failure. However, the addition of 15-deoxyspergualin to the triple-drug immunosuppressive regimen significantly prolonged the function of the islet allografts. When antithymocyte globulin was added to the above-mentioned immunosuppressive drug regimen, the normoglycemic period was prolonged to more than 1 month (fasting blood glucose level: 75.4±17 mg/dl).Conclusion.We conclude that autotransplantation with a sufficient islet mass can induce normoglycemia with a normal insulin secretion response to glucose stimulation in pancreatectomized diabetic pigs and that allotransplantation can be successfully achieved when 15-deoxyspergualin and antithymocyte globulin are combined with the triple-drug immunosuppression described above. However, this immunosuppressive protocol results in a high rate of infectious complications.

ISSN:0041-1337    

出版商:OVID    

年代:1998

数据来源: OVID