Heme oxygenase-1 induction in islet cells results in protection from apoptosis and improved in vivo function after transplantation

Islet graft response to transplantation injury includes upregulation of protective as well as apoptotic genes

Pancreatic islets are particularly vulnerable in the initial days after transplantation when multiple factors converge to damage the islet graft. The aim of this study was to investigate the expression profile of genes involved in damage and protection of beta-cells in the initial days after syngeneic islet transplantation. We studied the expression of a set of selected genes involved in apoptosis (Bcl2, Bclx(L), Bax, Bad, Bid, and CHOP), cytokine defense, (SOCS-1 and SOCS-3), or free radical protection (Hmox1, Cu/Zn-SOD, Mn-SOD, and Hsp70). Because hyperglycemia has deleterious effects on islet transplantation outcome, we studied its effect on the expression of these genes. Five hundred islets were syngeneically transplanted under the kidney capsule of normoglycemic or streptozotocin-induced diabetic Lewis rats. Gene expression was analyzed by quantitative real-time RT-PCR in grafts 1, 3, and 7 days after transplantation, and in freshly isolated islets. The expression of proapoptotic genes Bid and CHOP, as well as protective genes Bclx(L), Socs1, Socs3, Hmox1, and MnSod, was maximally increased 1 day after transplantation, and in most cases it remained increased 7 days later, indicating the presence of a protective response against cell damage. In contrast, the expression of Bcl2, Bax, Bad, Cu/ZnSod, and Hsp70 genes did not change. Hyperglycemia did not modify the expression of most studied genes. However, MnSod and Ins2 expression was increased and reduced, respectively, on day 7 after transplantation to diabetic recipients, suggesting that hyperglycemia increased oxidative stress and deteriorated beta-cell function in transplanted islets.

Induction of antioxidant enzymes by curcumin and its analogues in human islets: implications in transplantation

OBJECTIVES

The survival of transplanted human islets is hampered by the quality of islets, which is affected by oxidative stress during isolation. The objective of this study was to determine if curcumin and its analogues could induce antioxidant enzymes in beta cells of human islets.

METHODS

The expression of antioxidant enzymes in isolated human islets exposed to curcuminoids was determined at the messenger RNA levels by real-time quantitative reverse transcription-polymerase chain reaction using Taqman probes and at the protein level by Western blot analysis. Double immunofluorescent staining of islets was carried out to determine the induction of antioxidant enzymes in beta cells.

RESULTS

Curcuminoids induced the expression of heme oxygenase 1; modulatory subunit of gamma-glutamyl-cysteine ligase; and NAD(P)H:quinone oxidoreductase 1 at the messenger RNA levels by 2- to 12-fold and at the protein levels by 2- to 6-fold in human islets. Increased expression of antioxidant enzymes was seen in beta cells of islets as shown by immunofluorescent staining. Curcuminoids also increased the islet content of glutathione (a product of the modulatory subunit of gamma-glutamyl-cysteine ligase) and the basal insulin secretion and protected them from oxidative stress.

CONCLUSIONS

Our observations suggest that curcumin or its analogues could be used to induce cellular defense against oxidative stress and improve islet transplantation outcomes.

Innate immunity and heat shock response in islet transplantation

Islet transplantation is an extremely effective therapy for patients with type I diabetes, providing tight control of blood glucose and persistent insulin release. Islet grafts struggle with various stress responses and immunity attacks, which contribute to loss of islet grafts in the long term. In this review we focus upon the innate immunity and heat shock responses, which are closely relevant to the outcome of islet grafts. Potential strategies provided by more comprehensive interventions to control innate immunity and by selective induction of heat shock proteins may ameliorate the outcome of islet transplantation.

Synergistic induction of heme oxygenase-1 by the components of the antioxidant supplement Protandim

Protandim is an antioxidant supplement that consists of five ingredients, namely, ashwagandha, bacopa extract, green tea extract, silymarin, and curcumin, each with known therapeutic properties. Protandim was formulated with the objective of combining multiple phytochemicals at low nontoxic doses to gain synergy among them. A recent clinical study demonstrated the in vivo antioxidant effects of Protandim (S.K. Nelson et al., 2006, Free Radic. Biol. Med. 40, 341-347). The objective of the present study was to determine if the components of Protandim induce heme oxygenase-1 (HO-1) in a synergistic manner in cultured MIN6 cells, a mouse beta-cell line, and in SK-N-MC cells, a human neuroblastoma cell line. When the components of Protandim were tested alone at low doses, curcumin showed minimal induction, whereas the others were unable to induce the HO-1 promoter, assayed by transient transfection. All components together, however, produced a strongly synergistic induction of around three- to ninefold in a dose-dependent manner, greatly exceeding the sum of the parts. Similar findings were obtained for the expression of HO-1 at the mRNA and protein levels. Protandim-mediated HO-1 induction involved the presence of ARE sites in the HO-1 promoter and nuclear translocalization of the transcription factor Nrf2, which binds to ARE sites. The involvement of multiple signaling pathways, including PI3-kinase/Akt, p38MAPK, and PKCdelta, in HO-1 induction seems to be the probable mechanism of synergy between the components of Protandim. There were significant increases in the levels of total glutathione in Protandim-treated cells. These findings suggest that the use of a combination of phytochemicals may be an efficient method for the induction of antioxidant enzymes.

The role of macrophage migration inhibitory factor in mouse islet transplantation

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by many tissues including pancreatic beta-cells.

METHODS

This study investigates the impact of MIF on islet transplantation using MIF knock-out (MIFko) mice.

RESULTS

Early islet function, assessed with a syngeneic marginal islet mass transplant model, was enhanced when using MIFko islets (P<0.05 compared with wild-type [WT] controls). This result was supported by increased in vitro resistance of MIFko islets to apoptosis (terminal deoxynucleotide tranferase-mediated dUTP nick-end labeling assay), and by improved glucose metabolism (lower blood glucose levels, reduced glucose areas under curve and higher insulin release during intraperitoneal glucose challenges, and in vitro in the absence of MIF, P<0.01). The beneficial impact of MIFko islets was insufficient to delay allogeneic islet rejection. However, the rejection of WT islet allografts was marginally delayed in MIFko recipients by 6 days when compared with WT recipient (P<0.05). This effect is supported by the lower activity of MIF-deficient macrophages, assessed in vitro and in vivo by cotransplantation of islet/macrophages. Leukocyte infiltration of the graft and donor-specific lymphocyte activity (mixed lymphocyte reaction, interferon gamma ELISPOT) were similar in both groups.

CONCLUSION

These data indicate that targeting MIF has the potential to improve early function after syngeneic islet transplantation, but has only a marginal impact on allogeneic rejection.

c-Jun N-terminal kinase 1 is deleterious to the function and survival of murine pancreatic islets

AIMS/HYPOTHESIS

Inhibition of c-jun N-terminal kinase (JNK) favours pancreatic islet function and survival. Since two JNK isoforms are present in the pancreas (JNK1 and JNK2), we addressed their specific roles in experimental islet transplantation.

METHODS

C57BL/6J (wild-type [WT]), Jnk1 (also known as Mapk8)(-/-) and Jnk2 (also known as Mapk9)(-/-) mice were used as donor/recipients in a syngeneic islet transplantation model. Islet cell composition, function, viability, production of cytokines and of vascular endothelial growth factor (VEGF) were also studied in vitro.

RESULTS

Jnk1 ( -/- ) islets secreted more insulin in response to glucose and were more resistant to cytokine-induced cell death compared with WT and Jnk2 (-/-) islets (p < 0.01). Cytokines reduced VEGF production in WT and Jnk2 (-/-) but not Jnk1 ( -/- ) islets; VEGF blockade restored Jnk1 ( -/- ) islet susceptibility to cytokine-induced cell death. Transplantation of Jnk1 ( -/- ) or WT islets into WT recipients made diabetic had similar outcomes. However, Jnk1 ( -/- ) recipients of WT islets had shorter time to diabetes reversal (17 vs 55 days in WT, p = 0.033), while none of the Jnk2 (-/-) recipients had diabetes reversal (0% vs 71% in WT, p = 0.0003). Co-culture of WT islets with macrophages from each strain revealed a discordant cytokine production.

CONCLUSIONS/INTERPRETATION

We have shown a deleterious effect of JNK2 deficiency on islet graft outcome, most likely related to JNK1 activation, suggesting that specific JNK1 blockade may be superior to general JNK inhibition, particularly when administered to transplant recipients.

Hepatic ischemia reperfusion injury and calcium overload

Hepatic ischemia reperfusion injury is a common pathophysiologic process, whose basic mechanism is related to intracellular calcium overload. Calcium overload is related to cell membrane cranny, Na⁺/Ca²⁺ exchanger, the decreased activity of Ca²⁺-ATPase, mitochondrial dysfuncsion and oxygen free radicals. The prophylaxis and treatment options of calcium overload include: ATP-sensitive K⁺ channel openers, anesthesia, calcium channel entry blockers, mitochondrial permeability transition inhibitors, heme oxygenase 1 and so on.

Ductal injection of preservation solution increases islet yields in islet isolation and improves islet graft function

For islet transplantation, it is important to obtain an available islet mass adequate for diabetes reversal from a single donor pancreas. A recent report demonstrated that the use of M-Kyoto solution instead of UW solution improved islet yields in the two-layer method for pancreas preservation. The present study investigated whether the ductal injection of a large volume of preservation solution (UW and M-Kyoto solution) before pancreas storage improves islet yields. Islet yield both before and after purification was significantly higher in the ductal injection (+) group compared with the ductal injection (-) group. TUNEL-positive cells in the ductal injection (+) group were significantly decreased in comparison to the ductal injection (-) group. The ductal injection of preservation solution increased the ATP level in the pancreas tissue and reduced trypsin activity during the digestion step. Annexin V and PI assays showed that the ductal injection prevents islet apoptosis. In a transplant model, the ductal injection improved islet graft function. These findings suggest that the ductal injection of preservation solution, especially the M-Kyoto solution, leads to improved outcomes for pancreatic islet transplantation. Based on these data, this technique is now used for clinical islet transplantation from non-heart-beating donor pancreata or living donor pancreas.

Cobalt Protoporpyhrin Reduces Caspase-3,-7 Enzyme Activity in Neonatal Porcine Islets, But Does Not Inhibit Cell Death Induced by TNF-α

Apoptotic phenomena observed in vitro following isolation and following transplantation contribute significantly to islet graft loss. Strategies to reduce apoptosis of islet tissue prior to and posttransplantation may improve graft survival and function and reduce the amount of tissue necessary to achieve insulin independence. The expression of cytoprotective proteins is one such strategy that may prolong islet survival. In this light, heme-oxygenase 1 (HO-1) upregulation has been studied in both allo- and xenotransplantation models. In this study, the effect of HO-1 on apoptosis in neonatal porcine islet-like cell clusters (NPICC) was assessed. In in vitro assessments of NPICC apoptosis, NPICC showed a high sensitivity to apoptotic stimulation using a combination of TNF-α and cycloheximide. Stimulation with TNF-α alone was sufficient to induce reproducible apoptotic responses as demonstrated by caspase-3,-7 activation and subdiploid DNA analysis. Dose-dependent, high-level HO-1 protein expression was achieved following culture of NPICC in medium containing either cobalt protoporphyrin (CoPP) or cobalt mesoporphyrin (CoMP). CoPP treatment resulted in the reduction of caspase-3,-7 enzyme activity following TNF-α stimulation. However, such an effect was not associated with a reduction in the levels of cell death. Indeed, the inhibition of caspase enzyme activity resulted in decreased PARP-1 cleavage, which may lead to heightened levels of necrosis in treated NPICC cultures, possibly explaining the observed commitment of NPICC to the death pathway.

Protective effects of taurine on the islet viability and function in rats

AIM: To investigate the protective effect of taurine on the islets during culturing and its mechanism in rats.

METHODS: Wistar rats were divided into 2 groups: RPMI-1640 group and taurine group. The percentage of active Caspase-9-positive cells or phospho-Akt 473-positive cells was determined by flow cytometry. The mRNA levels of tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), nuclear factor-κB (NF-κB), and heme oxygenase-1 (HO-1) were evaluated by reverse transcription-polymerase chain reaction (RT-PCR) in the isolated rat islets of both groups.

RESULTS: After 1-wk culture, the percentage of Caspase-9-positive cells was significantly higher in the taurine group than that in the RPMI-1640 group (41.03% ± 4.46% vs 23.85% ± 3.09%, P < 0.05). The mRNAs of TNF-α, IL-1β, NF-κB and HO-1 were significantly expressed after the islets were isolated and purified. However, the mRNAs of TNF-α, IL-1β, NF-κB expression were decreased gradually while HO-1 expression was increased with the culturing time. After 6-h, 72-h and 1-wk culture, the mRNA levels of TNF-α, IL-1β, and NF-κB were significantly lower in the taurine group (TNF-α: 0.34 ± 0.02, 0.24 ± 0.01, 0.19 ± 0.02; IL-1β: 0.24 ± 0.09, 0.09 ± 0.01, 0.05 ± 0.01; NF-κB: 1.76 ± 0.30, 0.93 ± 0.15, 0.37 ± 0.02) than those in the RPMI-1640 group (TNF-α: 0.57 ± 0.1, 0.39 ± 0.02, 0.29 ± 0.02; IL-1β: 0.34 ± 0.02, 0.24 ± 0.01, 0.19 ± 0.02; NF-κB: 2.52 ± 0.24, 1.21 ± 0.14, 0.76 ± 0.07) (all P < 0.05), but the HO-1 mRNA level was markedly higher in the taurine group (3.74 ± 0.10, 4.33 ± 0.29, 5.28 ± 0.29 vs 2.46±0.30, 3.13 ± 0.07, 3.59 ± 0.22; all P < 0.05).

CONCLUSION: Taurine can protect the islet cells from apoptosis by inhibiting the transcription of TNF-α, IL-1β and NF-κB gene or by increasing phospho-Akt activity.

(GT)N dinucleotide repeat polymorphism of haem oxygenase-1 promotor region is not associated with inflammatory bowel disease risk or disease course

Haem oxygenase-1 (HO-1) up-regulation was suggested to reduce mucosal tissue damage in inflammatory bowel disease (IBD) and an up-regulation of HO-1 expression in patients with Crohn's disease (CD) and ulcerative colitis (UC) was demonstrated. A HO-1 gene promoter microsatellite (GT)(n) dinucleotide repeat polymorphism was associated with regulation of HO-1 in response to inflammatory stimuli. We therefore hypothesized that IBD patients might segregate into phenotypes with high or low HO-1 inducibility. Ethylenediamine tetraacetic acid blood samples were obtained from 179 CD patients, 110 UC patients and 56 control patients without inflammation. Genomic DNA was purified and the 5'-flanking region of the HO-1 gene containing the (GT)(n) dinucleotide repeat was amplified. Polymerase chain reaction (PCR) products were purified and the length of the PCR fragments was analysed. The number of (GT)(n) repeats in the population studied ranged from 13 to 42. The distribution of the allele frequencies was comparable in patients and controls for both the short and the long alleles. The frequencies of short-, middle- and long-sized alleles were not changed among the groups studied. No correlation was found between IBD and microsatellite instability detected in five individals. Our data indicate that (GT)(n) dinucleotide repeats of the HO-1 promotor region have no significance for the pathophysiology and disease course of IBD.

Pharmacological and clinical aspects of heme oxygenase

This review is intended to stimulate interest in the effect of increased expression of heme oxygenase-1 (HO-1) protein and increased levels of HO activity on normal and pathological states. The HO system includes the heme catabolic pathway, comprising HO and biliverdin reductase, and the products of heme degradation, carbon monoxide (CO), iron, and biliverdin/bilirubin. The role of the HO system in diabetes, inflammation, heart disease, hypertension, neurological disorders, transplantation, endotoxemia and other pathologies is a burgeoning area of research. This review focuses on the clinical potential of increased levels of HO-1 protein and HO activity to ameliorate tissue injury. The use of pharmacological and genetic probes to manipulate HO, leading to new insights into the complex relationship of the HO system with biological and pathological phenomena under investigation, is reviewed. This information is critical in both drug development and the implementation of clinical approaches to moderate and to alleviate the numerous chronic disorders in humans affected by perturbations in the HO system.

Heme oxygenase 1: does it have a role in renal cytoprotection?

Heme oxygenase (HO) was first identified as the rate-limiting enzyme in the degradative pathway of heme, but is now recognized to be involved in diverse biological processes. Different isoforms of HO exist; HO-1 (HMOX1) is ubiquitously present in mammalian tissue with low constitutive expression under physiological conditions, but is upregulated in response to a variety of potentially noxious stimuli. HO-1, an integral component of an important cytoprotective mechanism, mediates its action through removal of heme, the generation of heme breakdown reaction products (biliverdin, free iron, and carbon monoxide), and modulation of key cellular molecules. Data from experimental models in which HO-1 was induced or inhibited, together with observations in genetically modified animals, showed a beneficial effect of HO-1 in several pathways leading to kidney injury. The discovery of a functional guanosine thymine tandem repeat polymorphism in the promoter region of the human HO-1 gene has stimulated clinical investigations in a variety of diseases. However, despite theoretical and experimental support for an important pathophysiological role for HO-1, the relevance of this polymorphism in native kidney or renal transplant function is equivocal. This article reviews the molecular genetics of HO-1, its myriad cytoprotective effects allied to how these are mediated, and relates these findings to experimental and clinical evidence of HO-1 involvement in renal disease.

Induction of heme oxygenase-1 improves the survival of pancreas grafts by prevention of pancreatitis after transplantation

BACKGROUND

Ischemia/reperfusion (I/R) injury after pancreas transplantation might result in graft pancreatitis. The role of heme oxygenase-1 (HO-1) in pancreas transplantation and prevention of graft pancreatitis is unknown.

METHOD

We studied the impact of HO-1 induction with cobalt protoporphyrin (CoPP) in experimental pancreas transplantation with moderate (6 hr) and prolonged (20 hr) cold ischemic time (CIT). Donor animals received CoPP 5 mg/kg intraperitoneal at 48 hr or intraperitoneal saline injections in the corresponding control groups before procurement. Harvested grafts were perfused with HTK solution and stored at 4 degrees C.

RESULTS

After prolonged CIT, graft survival was 100% with CoPP pretreatment in contrast to only 37.5% without pretreatment. CoPP-pretreated grafts demonstrated an unimpaired endocrine graft function at moderate and prolonged CIT. Serum lipase activity as a sign of exocrine preservation was significantly lower. In addition, morphological architecture was well preserved. CoPP pretreatment markedly increased HO-1 gene expression in donor pancreas (130-fold increase) by means of quantitative reverse transcriptase -polymerase chain reaction. Immunohistochemical examinations showed that the increase of HO-1 on the protein level was related to HO-1-positive donor macrophages in the pancreas grafts. HO-1 overexpression was accompanied by significant decrease of proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin (IL)-2, IL-6, interferon-y, and by significant increase of the anti-inflammatory cytokine IL-10 and less expression of adhesion molecules such as e- and p-selectins.

CONCLUSIONS

HO-1 is highly inducible in the allograft rat pancreas and associated with a survival benefit and good graft function after transplantation. This study contributes to the beneficial potentials of HO-1 for the prevention of graft pancreatitis.

Inhibition of c-jun N terminal kinase (JNK) improves functional beta cell mass in human islets and leads to AKT and glycogen synthase kinase-3 (GSK-3) phosphorylation

AIMS/HYPOTHESIS

Activation of c-jun N-terminal kinase (JNK) has been described in islet isolation and engraftment, making JNK a key target in islet transplantation. The objective of this study was to investigate if JNK inhibition with a cell-permeable TAT peptide inhibitor (L-JNKI) protects functional beta cell mass in human islets and affects AKT and its substrates in islet cells.

METHODS

The effect of L-JNKI (10 micromol/l) on islet count, mitochondrial membrane potential, glucose-stimulated insulin release and phosphorylation of both AKT and its substrates, as well as on reversal of diabetes in immunodeficient diabetic Nu/Nu mice was studied.

RESULTS

In vitro, L-JNKI reduced the islet loss in culture and protected from cell death caused by acute cytokine exposure. In vivo, treatment of freshly isolated human islets and diabetic Nu/Nu mice recipients of such islets resulted in improved functional beta cell mass. We showed that L-JNKI activates AKT and downregulates glycogen synthase kinase-3 beta (GSK-3B) in human islets exposed to cytokines, while other AKT substrates were unaffected, suggesting that a specific AKT/GSK-3B regulation by L-JNKI may represent one of its mechanisms of cytoprotection.

CONCLUSIONS/INTERPRETATION

In conclusion, we have demonstrated that targeting JNK in human pancreatic islets results in improved functional beta cell mass and in the regulation of AKT/GSK3B activity.

Induction of heme oxygenase-1 by plant extract KIOM-79 via Akt pathway and NF-E2 related factor 2 in pancreatic beta-cells

The objective of the present study was to determine the mechanism by which KIOM-79 induced heme oxygenase-1 (HO-1) in rat pancreatic beta-cells (RINm5F). A mixture of plant extracts (KIOM-79) was obtained from Magnolia officinalis, Pueraria lobata, Glycyrrhiza uralensis, and Euphorbia pekinensis. HO-1, an antioxidant phase 2 enzyme, was previously reported to possess cytoprotective properties in pancreatic beta-cells. KIOM-79 induced heme oxygenase-1 (HO-1) expression at the mRNA and protein levels, leading to increased HO-1 activity. The transcription factor, NF-E2 related factor 2 (Nrf2), regulates the antioxidant response element (ARE) of the phase 2 detoxifying and antioxidant enzymes, resulting in modulation of HO-1 expression. KIOM-79 increased nuclear translocation, ARE binding, and transcriptional activity of Nrf2. Furthermore, KIOM-79 also elicited activation of Akt (protein kinase B) and LY294004 (inhibitor of Akt)-suppressed KIOM-79-induced activation of Nrf2, which subsequently decreased HO-1 protein levels. Taken together, these data suggest that KIOM-79 augments the cellular antioxidant defense capacity through induction of HO-1 via the Akt-Nrf2-ARE signaling pathway, thereby protecting cells from streptozotocin-induced oxidative stress.

Therapeutic applications of bilirubin and biliverdin in transplantation

Bilirubin is the end product of heme catabolism by heme oxygenases. The inducible form of these enzymes is heme oxygenase-1 (HO-1), which is the rate-limiting enzyme that can degrade heme into equimolar quantities of carbon monoxide (CO), biliverdin, and free iron. Biliverdin is very rapidly converted to bilirubin by the enzyme biliverdin reductase, and free iron upregulates the expression of ferritin. HO-1 is a ubiquitous stress protein and is induced in many cell types by various stimuli. Induced HO-1 exerts antiinflammatory effects and modulates apoptosis. Expression of HO-1 in vivo suppresses the inflammatory responses in endotoxic shock, hyperoxia, acute pleurisy, and organ transplantation, as well as ischemia-reperfusion injury, and thereby provides salutary effects in these conditions. Accumulating evidence indicates that biliverdin/bilirubin can mediate the protective effects of HO-1 in many disease models, such as IRI and organ transplantation, via its antiinflammatory, antiapoptotic, antiproliferative, and antioxidant properties, as well as its effects on the immune response. This review attempts to summarize these protective roles as well as the molecular mechanisms by which biliverdin/bilirubin benefit IRI and solid-organ transplantation, including chronic rejection, and islet transplantation.

Allogeneic islet transplantation

Significant progress has been made in the field of beta-cell replacement therapies by islet transplantation in patients with unstable Type 1 diabetes mellitus (T1DM). Recent clinical trials have shown that islet transplantation can reproducibly lead to insulin independence when adequate islet numbers are implanted. Benefits include improvement of glycemic control, prevention of severe hypoglycemia and amelioration of quality of life. Numerous challenges still limit this therapeutic option from becoming the treatment of choice for T1DM. The limitations are primarily associated with the low islet yield of human pancreas isolations and the need for chronic immunosuppressive therapies. Herein the authors present an overview of the historical progress of islet transplantation and outline the recent advances of the field. Cellular therapies offer the potential for a cure for patients with T1DM. The progress in beta-cell replacement treatment by islet transplantation as well as those of emerging immune interventions for the restoration of self tolerance justify great optimism for years to come.

Interference with tissue factor prolongs intrahepatic islet allograft survival in a nonhuman primate marginal mass model

BACKGROUND

Tissue factor (TF) expression on islets can result in an instant blood-mediated inflammatory reaction (IBMIR) that contributes to early islet loss. We tested whether peritransplant protection of islets from IBMIR with a monoclonal anti-TF antibody (CNTO859) would enhance engraftment in our nonhuman primate marginal mass model.

METHODS

Each of six pairs of cynomolgus monkeys (CM) with streptozotocin-induced diabetes was closely matched for metabolic control and was transplanted with 5,000 IEQ/kg allogeneic, ABO-compatible islets from the same donor under the cover of steroid-free immunosuppression. For each pair, experimental animals received islets cultured with 20 microg/mL anti-TF and were dosed with 6 mg/kg anti-TF intravenously, 10-25 min before islet infusion; control monkeys received an equal number of islets from the same preparation cultured without anti-TF and no in vivo treatment.

RESULTS

Early fasting C-peptide (CP) values were different between (P<0.01), but not within, pairs and correlated with in vitro functional capacity of islets as assessed by perifusion (r=0.60; P=0.022). Compared to their matched controls, experimental animals had decreased posttransplant markers of coagulation, higher fasting CP levels (1 month posttransplant and end of study) and prolonged graft function.

CONCLUSIONS

These data suggest that pretreatment of islets and the recipient with anti-TF may limit the effects of IBMIR, thereby enhancing islet engraftment and survival.

Regulation of heme oxygenase-1 expression by demethoxy curcuminoids through Nrf2 by a PI3-kinase/Akt-mediated pathway in mouse beta-cells

Curcumin (diferuloylmethane), a component of turmeric, has been shown to have therapeutic properties. Induction of phase 2 detoxifying enzymes is a potential mechanism through which some of the actions of curcumin could proceed. Heme oxygenase-1 (HO-1), an antioxidant phase 2 enzyme, has been reported to have cytoprotective effects in pancreatic beta-cells. Curcumin on further purification yields demethoxy curcumin (DMC) and bisdemethoxy curcumin (BDMC). The objective of the present study was to determine the mechanism by which these purified curcuminoids induce HO-1 in MIN6 cells, a mouse beta-cell line. Demethoxy curcuminoids induced HO-1 promoter linked to the luciferase reporter gene more effectively than curcumin. The induction was dependent on the presence of antioxidant response element (ARE) sites containing enhancer regions (E1 and E2) in HO-1 promoter and nuclear translocation of nuclear factor-E2-related factor (Nrf2), the transcription factor that binds to ARE. Curcuminoids stimulated multiple signaling pathways that are known to induce HO-1. Inhibition of specific signaling pathways with pharmacological inhibitors and cotransfection experiments suggested the involvement of phosphotidylinositol 3-kinase and Akt. Real-time quantitative RT-PCR analysis showed significant elevation in the mRNA levels of HO-1 and two other phase 2 enzymes, the regulatory subunit of glutamyl cysteine ligase, which is needed for the synthesis of glutathione, and NAD(P)H:quinone oxidoreductase, which detoxifies quinones. DMC and BDMC induced the expression of HO-1 and translocated Nrf2 to nucleus in beta-cells of mouse islets. Our observations suggest that demethoxy curcuminoids could be used to induce a cellular defense mechanism in beta-cells under conditions of stress as seen in diabetes.

Rapid loss of intraportally transplanted islets: an overview of pathophysiology and preventive strategies

Islets isolated from multiple pancreas donors are often necessary to achieve euglycemia in type 1 diabetic patients treated by islet allotransplantation. This increases the burden on the limited pool of donor organs. After infusion into the portal vein, a substantial percentage of islets are lost in the immediate post-transplant period through an inflammatory response termed the instant blood-mediated inflammatory reaction (IBMIR). IBMIR is equally, if not more of a problem after islet xenotransplantation, e.g., using pig islets in non-human primates. Coagulation, platelet aggregation, complement activation, and neutrophil and monocyte infiltration play roles in this reaction. IBMIR is potentially triggered by islet surface molecules, such as tissue factor and collagen residues that are normally not in direct contact with the blood. Also, stress during the islet isolation process results in the expression and production of several inflammatory mediators by the islets themselves. The potential mechanisms involved in this rapid graft loss and treatment options to reduce this loss are reviewed. Preventive strategies for IBMIR can include systemic treatment of the recipient, pre-conditioning of the isolated islets, or, in the case of xenotransplantation, genetic modification of the organ-source pig. Pre-conditioning of islets in culture by exposure to anti-inflammatory agents or by genetic modification harbors fewer risks of systemic complications in the recipient. The future of clinical islet transplantation will, at least in part, depend on the success of efforts made to reduce rapid graft loss, and thus allow islet transplantation to become a more efficient therapy by the use of single donors.

Interdiction of the diabetic state in NOD mice by sustained induction of heme oxygenase: possible role of carbon monoxide and bilirubin

The aims of the present study were to assess whether sustained HO-1 expression could moderate or prevent diabetes in an animal model of the disease and, if so, to examine the possible mechanisms involved. Our results showed that HO-1 expression and HO activity were upregulated in the pancreas of non-obese diabetic (NOD) mice by the weekly administration of cobalt protoporphyrin (CoPP). Blood glucose levels in CoPPtreated mice decreased to normal, but continuously increased in untreated controls. Beta-cell numbers were preserved in the islets of CoPP-treated mice, whereas no beta cells were found in untreated diabetic mice. The number of CD11c(+) dendritic cells was significantly decreased in the pancreas of CoPP-treated NOD mice, but this effect was reversed by the inhibition of HO activity. Increased levels of HO-1 produced a new pancreatic phenotype, as reflected by increases in phosphorylated AKT, BcL-xL and RSK levels, and decreases in O(2)- and 3-NT levels. These novel findings provide a link between the increase in HO-1 activity, with its concurrent enhanced production of carbon monoxide (CO) and bilirubin, a decrease in infiltrated CD11c(+) dendritic cells and an increase in anti-apoptotic proteins, including RSK and BcL-xL, in the interdiction of the diabetic state.

Heme oxygenase-1, carbon monoxide, and bilirubin induce tolerance in recipients toward islet allografts by modulating T regulatory cells

Heme oxygenase-1 (HO-1) induction in, or carbon monoxide (CO), or bilirubin administration to, donors and/or recipients frequently lead to long-term survival (>100 days) of DBA/2 islets into B6AF1 recipients. We tested here whether similar treatments show value in a stronger immunogenetic combination, i.e., BALB/c to C57BL/6, and attempted to elucidate the mechanism accounting for tolerance. Induction of HO-1, administering CO or bilirubin to the donor, the islets or the recipient, prolonged islet allograft survival to different extents. Combining all the above treatments (the "combined" protocol) led to survival for >100 days and antigen-specific tolerance to 60% of the transplanted grafts. A high level of forkhead box P3 (Foxp3) and transforming growth factor beta (TGF-beta) expression was detected in the long-term surviving grafts. With the combined protocol, significantly more T regulatory cells (Tregs) were observed surrounding islets 7 days following transplantation. No prolongation of graft survival was observed using the combined protocol when CD4+ CD25+ T cells were predepleted from the recipients before transplantation. In conclusion, our combined protocol led to long-term survival and tolerance to islets in the BALB/c to C57BL/6 combination by promoting Foxp3+ Tregs; these cells played a critical role in the induction and maintenance of tolerance in the recipient.

Novel synthesis of cerium oxide nanoparticles for free radical scavenging

Aims: The aim of this article is to present a novel synthetic route to form CeO2 nanoparticles that protects against the detrimental influence of oxidative stress in mammalian cells. Methods: The noncytotoxic surfactant lecithin was used to synthesize CeO2 nanoparticles and the products were colloidally stabilized in a biocompatible tri-sodium citrate buffer. These nanoparticles were delivered into murine insulinoma βTC-tet cells, and intracellular free radical concentrations responding to exposure to hydroquinone were measured in a variety of extracellular CeO2 concentrations. Results: Well-dispersed, highly crystallized CeO2 nanoparticles of 3.7 nm in size were achieved that are chemically and colloidally stable in Dulbecco’s modified Eagle’s medium for extended periods of time. Treating βTC-tet cells with these nanoparticles alleviated detrimental intracellular free radical levels down to the primary level. Conclusion: CeO2 nanoparticles synthesized from this route are demonstrated to be effective free radical scavengers within βTC-tet cells. Furthermore, it is shown that CeO2 nanoparticles provide an effective means to improve cellular survival in settings wherein cell loss due to oxidative stress limits native function.

Could heme-oxygenase-1 have a role in modulating the recipient immune response to embryonic stem cells?

Pluripotent human embryonic stem cells (hESCs) may provide a potential source of cellular therapies, but as allogeneic cells may require evading the recipient's immune response. Using an NIH-registry hESC line, it was found that undifferentiated hESCs induce a reduced proliferative response compared to PBMC and demonstrate that this diminished response correlates with the activity of heme oxygenase-1 (HO-1). Inhibition of HO-1 significantly increases T cell proliferation against hESC, indicating the potential suppression of these cells during transplantation of allogeneic hESC. These data suggest the hypothesis that HO-1 provides a mechanism for protecting hESCs in vivo.

Long-term treatment with the apolipoprotein A1 mimetic peptide increases antioxidants and vascular repair in type I diabetic rats

Apolipoprotein A1 mimetic peptide (D-4F), synthesized from D-amino acid, enhances the ability of high-density lipoprotein to protect low-density lipoprotein (LDL) against oxidation in atherosclerotic disease. Using a rat model of type I diabetes, we investigated whether chronic use of D-4F would lead to up-regulation of heme oxygenase (HO)-1, endothelial cell marker (CD31(+)), and thrombomodulin (TM) expression and increase the number of endothelial progenitor cells (EPCs). Sprague-Dawley rats were rendered diabetic with streptozotocin (STZ) and either D-4F or vehicle was administered, by i.p. injection, daily for 6 weeks (100 microg/100 g b.wt.). HO activity was measured in liver, kidney, heart, and aorta. After 6 weeks of D-4F treatment, HO activity significantly increased in the heart and aorta by 29 and 31% (p < 0.05 and p < 0.49), respectively. Long-term D-4F treatment also caused a significant increase in TM and CD31(+) expression. D-4F administration increased antioxidant capacity, as reflected by the decrease in oxidized protein and oxidized LDL, and enhanced EPC function and/or repair, as evidenced by the increase in EPC endothelial nitric-oxide synthase (eNOS) and prevention of vascular TM and CD31(+) loss. In conclusion, HO-1 and eNOS are relevant targets for D-4F and may contribute to the D-4F-mediated increase in TM and CD31(+), the antioxidant and anti-inflammatory properties, and confers robust vascular protection in this animal model of type 1 diabetes.

Toll‐like receptor 4 suppression leads to islet allograft survival

Carbon monoxide (CO) exposure of an islet donor frequently leads to islet allograft long-term survival and tolerance in recipients. We show here that CO confers its protective effects at least in part by suppressing Toll-like receptor 4 (TLR4) up-regulation in pancreatic beta cells. TLR4 is normally up-regulated in islets during the isolation procedure; donor treatment with CO suppresses TLR4 expression in isolated islets as well as in transplanted grafts. TLR4 up-regulation allows initiation of inflammation, which leads to islet allograft rejection; islet grafts from TLR4-deficient mice survive indefinitely in BALB/c recipients and show significantly less inflammation at various days after transplantation compared with grafts from a control donor. Isolated islets preinfected with a TLR4 dominant negative virus before transplantation demonstrated prolonged survival in recipients. Despite the salutary effects of TLR4 suppression, HO-1 expression is still needed in the recipient for islet survival: TLR4-deficient islets were rejected promptly after being transplanted into recipients in which HO-1 activity was blocked. In addition, incubation of an insulinoma cell line, betaTC3, with an anti-TLR4 antibody protects those cells from cytokine-induced apoptosis. Our data suggest that TLR4 induction in beta cells is involved in beta cell death and graft rejection after transplantation. CO exposure protects islets from rejection by blocking TLR4 up-regulation.

Systemic expression of heme oxygenase-1 ameliorates type 1 diabetes in NOD mice

Heme oxygenase-1 (HO-1) is an enzyme with potent immunoregulatory capacity. To evaluate the effect of HO-1 on autoimmune diabetes, female NOD mice at 9 weeks of age received a single intravenous injection of a recombinant adeno-associated virus bearing HO-1 gene (AAV-HO-1; 0.5 x 10(10)-2.5 x 10(10) viruses/mouse). In a dose-dependent manner, HO-1 transduction reduced destructive insulitis and the incidence of overt diabetes examined over a 15-week period. HO-1-mediated protection was associated with a lower type 1 T-helper cell (Th1)-mediated response. Adaptive transfer experiments in NOD.scid mice demonstrated that splenocytes isolated from AAV-HO-1-treated mice were less diabetogenic. Flow cytometry analysis revealed no significant difference in the percentages of CD4(+)CD25(+) regulatory T-cells between saline-treated and AAV-HO-1-treated groups. However, the CD11c(+) major histocompatibility complex II(+) dendritic cell population was much lower in the AAV-HO-1-treated group. A similar protective effect against diabetes was observed in NOD mice subjected to carbon monoxide (CO) gas (250 ppm CO for 2 h, twice per week). These data suggest that HO-1 slows the progression to overt diabetes in pre-diabetic NOD mice by downregulating the phenotypic maturity of dendritic cells and Th1 effector function. CO appears to mediate at least partly the beneficial effect of HO-1 in this disease setting.

Induction of heme oxygenase-1 improves cold preservation effect of liver graft

We have examined the protective effect and mechanisms of heme oxygenase-1 (HO-1) induction in rat liver model of ex vivo cold ischemia preservation using cobalt protoporphyrin (CoPP) as HO-1 inducer and zinc protoporphyrin (ZnPP) as HO-1 inhibitor. There was a decrease in both aspartate transaminase and lactate dehydrogenase activities and in malondialdehyde level in liver of the CoPP-treated group compared with controls (p < 0.05). In the CoPP-treated rats, the histological signs of reperfusion injury were much lower than in control. Up-regulation of HO-1 expression was also associated with reduced levels of tumor necrosis factor alpha and interleukin-6. Markedly fewer apoptotic liver cells (determined by TUNEL assay) could be detected in CoPP-treated group compared with the control group. These protective effects were prevented by administration of ZnPP. In conclusion, induction of HO-1 provides protection against liver injury during cold ischemia preservation and improves the preservation of liver graft. The mechanisms underlying these beneficial effects include reduction of oxidative injury and of inflammatory response and prevention of apoptosis.

Impact of silencing HO-2 on EC-SOD and the mitochondrial signaling pathway

The contribution of heme oxygenase HO-2, the primary source of bilirubin and carbon monoxide (CO) under physiological conditions, to the regulation of vascular function has remained largely unexplored. Using siRNA HO-2, we examined the effect of suppressed levels of HO-2 on vascular antioxidant and survival proteins. In vivo HO-2 siRNA treatment decreased the basal levels of EC-SOD, pAKT proteins (serine-473 and threonine-308), without changing Akt protein expression. HO-2 siRNA treatment increased 3-nitrotyrosine (3-NT) and apoptotic signaling kinase-1 (ASK-1) (P < 0.01). HO activity was decreased by the use of siRNA HO-2. We extended these studies to the mitochondria, examining for the presence of HO-1 and its role in the regulation of pro- and anti-apoptotic proteins. HO activity was increased by the administration of CoPP resulting in the translocation of HO-1 into the mitochondria, mainly to the inner face of the mitochondrial inner membrane. These findings suggest that HO-2 is critical in the maintenance of heme homeostasis and also the regulation of apoptosis by controlling levels of EC-SOD, Akt, 3-NT, and ASK-1. In addition, localization of HO-1 in the mitochondrial compartment plays a critical role in mitochondria-mediated apoptosis.

Characterization of donor dendritic cells and enhancement of dendritic cell efflux with CC-chemokine ligand 21: a novel strategy to prolong islet allograft survival

Dendritic cells (DCs) are the most potent antigen-presenting cells, yet little data are available on the differential characteristics of donor and recipient DCs (dDCs and rDCs, respectively) during the process of islet allograft rejection. DTR-GFP-DC mice provide a novel tool to monitor DC trafficking and characteristics during allograft rejection. We show rapid migration of dDCs to recipient lymphoid tissues as early as 3 h post-islet allotransplantation. Compared with rDCs, dDCs express different patterns of chemokine receptors, display differential proliferative capacity, and exhibit a higher level of maturity; these findings could be attributed to the effects of injury that dDCs undergo during islet cell preparation and engraftment. Intriguingly, we detected dDCs in the spleen of recipients long after rejection of islet allografts. Given that dDCs express high levels of CCR7, islets were cultured before transplant with the ligand for CCR7 (CCL21). This novel method, which enabled us to enhance the efflux of dDCs from islet preparations, resulted in a prolongation of islet allograft survival in immunocompetent recipients. This study introduces dDCs and rDCs as two distinct types of DCs and provides novel data with clinical implications to use chemokine-based DC-depleting strategies to prolong islet allograft survival.

A natural sweetener, Momordica grosvenori, attenuates the imbalance of cellular immune functions in alloxan-induced diabetic mice

Momordica grosvenori (MG), a traditional medicinal herb in China used as a substitute sugar for obese and diabetic patients, exhibited an enhancement of immunity. Heme oxygenase-1 (HO-1) is among the acute phase proteins that play an important role in the inflammatory process and have antiinflammatory activities with their antioxidant properties. The hypothesis that MG could modulate an imbalance of the cellular immune system and prevent the progression of diabetes mellitus, via induction of HO-1 protein expression was investigated. Diabetes was induced in male Balb/c mice by intraperitoneal injection of alloxan (200 mg/kg). The mice were randomly assigned to non-diabetic and diabetic groups, and further subdivided according to their treatments: control (distilled water), low dose MG (150 mg/kg) and high dose MG (300 mg/kg), which were administered by gavage in 24 h cycles over a 30 day period. MG administration effectively regulated the immune imbalance in diabetic mice, principally by upregulating the CD4(+) T lymphocyte subsets, and remodeling the intracellular cytokine profiles (reducing the expression of pro-inflammatory Th1 cytokines towards a beneficial Th2 pattern), ascribed to its induction and upregulation of HO-1. In conclusion, MG exhibited antidiabetic effects and may be used as a new natural drug for the treatment of diabetes.

Influence of heme oxygenase-1 gene transfer on the viability and function of rat islets in in vitro culture

AIM: To investigate the influence of heme oxygenase-1 (HO-1) gene transfer on the viability and function of cultured rat islets in vitro.

METHODS: Islets were isolated from the pancreata of Sprague-Dawley rats by intraductal collagenase digestion, and purified by discontinuous Ficoll density gradient centrifugation. Purified rat islets were transfected with adenoviral vectors containing human HO-1 gene (Ad-HO-1) or enhanced green fluorescent protein gene (Ad-EGFP), and then cultured for seven days. Transfection was confirmed by fluorescence microscopy and Western blot. Islet viability was evaluated by acridine orange/ propidium iodide fluorescent staining. Glucose-stimulated insulin release was detected using insulin radioimmunoassay kits and was used to assess the function of islets. Stimulation index (SI) was calculated by dividing the insulin release upon high glucose stimulation by the insulin release upon low glucose stimulation.

RESULTS: After seven days culture, the viability of cultured rat islets decreased significantly (92% ± 6% vs 52% ± 13%, P < 0.05), and glucose-stimulated insulin release also decreased significantly (6.47 ± 0.55 mIU/L/30IEQ vs 4.57 ± 0.40 mIU/L/30IEQ, 14.93 ± 1.17 mIU/L/30IEQ vs 9.63 ± 0.71 mIU/L/30IEQ, P < 0.05). Transfection of rat islets with adenoviral vectors at an MOI of 20 was efficient, and did not impair islet function. At 7 d post-transfection, the viability of Ad-HO-1 transfected islets was higher than that of control islets (71% ± 15% vs 52% ± 13%, P < 0.05). There was no significant difference in insulin release upon low glucose stimulation (2.8 mmol/L) among Ad-HO-1 transfected group, Ad-EGFP transfected group, and control group (P > 0.05), while when stimulated by high glucose (16.7 mmol/L) solution, insulin release in Ad-HO-1 transfected group was significantly higher than that in Ad-EGFP transfected group and control group, respectively (12.50 ± 2.17 mIU/L/30IEQ vs 8.87 ± 0.65 mIU/L/30IEQ; 12.50 ± 2.17 mIU/L/30IEQ vs 9.63 ± 0.71 mIU/L/30IEQ, P < 0.05). The SI of Ad-HO-1 transfected group was also significantly higher than that of Ad-EGFP transfected group and control group, respectively (2.21 ± 0.02 vs 2.08 ± 0.05; 2.21 ± 0.02 vs 2.11 ± 0.03, P < 0.05).

CONCLUSION: The viability and function of rat islets decrease over time in in vitro culture, and heme oxygenase-1 gene transfer could improve the viability and function of cultured rat islets.

MnSOD mimic compounds can counteract mechanical stress and islet β cell apoptosis, although at appropriate concentration ranges

Pancreatic islets are commonly isolated for research and transplantation without taking into consideration that they undergo mechanical or chemical stress during this process. In order to counteract both types of injuries, the compound AEOL10150, a novel MnSOD mimic, was added during isolation of islet at concentrations ranging from 18 to 100 microM. Mechanical or chemical stress-related pro-apoptotic signals were then studied. We demonstrate that this MnSOD mimic diminishes the negative effects of mechanical stress by blocking insulin impairment, production of non-specific islet beta-cell proteins, transcription of iNOS and FAS, activation of caspase-3 and -9 and, ultimately, apoptosis. Moreover, the effects of the MnSOD mimic on isolated islets were greatly influenced by dosage: the best dose able to fully counteract mechanical stress was found to be 100 microM; doses > or =150 microM were themselves highly toxic for islet cells. On the other hand, rIL-1beta-induced chemical stress is rather complex, and there was no protection in this scenario. Therefore, contrarily to what has been previously reported, MnSOD mimic administration is only capable of counteracting mechanical stress, and not cytokine-induced cytotoxicity, and that this drug acts within a limited concentration range.

Changes in gene expression in beta cells after islet isolation and transplantation using laser-capture microdissection

AIMS/HYPOTHESIS

The process of islet isolation can cause chemical and mechanical injury to beta cells. In addition, hyperglycaemia after islet transplantation can compromise beta cell function. The aim of this experiment was to evaluate changes in gene expression in endogenous islets using laser-capture microdissection (LCM).

MATERIALS AND METHODS

Islets from B6AF1 mice were studied in situ in the pancreas as well as those freshly isolated or cultured for 24 h. Fresh islets were transplanted under the kidney capsule of syngeneic diabetic (streptozocin-induced) and non-diabetic mice. Frozen sections from all the samples were prepared for LCM to obtain beta cell-enriched tissue; RNA was extracted and amplified using T7 polymerase. RT-PCR was used to assess expression of selected genes critical for beta cell function (Ins, Ipf1 [previously known as Pdx1], Slc2a2 [previously known as GLUT2] and Ldha) and the stress response (Hmox1 [previously known as HO-1], Gpx1, Tnfaip3 [previously known as A20] and Fas). Immunostaining was also performed.

RESULTS

In freshly isolated and cultured islets, insulin and Ipf1 mRNA levels were decreased by 40% (compared with islets in situ), while stress genes were upregulated. Comparison between in situ pancreatic islets and engrafted beta cells of cured mice showed declines in Ipf1 expression.

CONCLUSIONS/INTERPRETATION

Our experiment, the first report to investigate changes in gene expression in endogenous islets using LCM, indicate that beta cells following islet isolation and residing in a foreign graft environment have decreased expression of genes involved in insulin production and increased expression of stress genes. Our data suggest that an islet graft, even in successful transplantation, may be different from endogenous islets in gene expression.

Transplantation of rat islets transduced with human heme oxygenase-1 gene using adenovirus vector

OBJECTIVE

To investigate whether human heme oxygenase-1 (HO-1) gene has protective action on islets cultured in vitro, and to explore whether transduction of HO-1 gene to donor islets could enhance engrafted islets survival and suppress local lymphocytic infiltration in islet grafts.

METHODS

Newly isolated rat islets were isolated from the Sprague-Dawley rats and were divided into 3 groups in vitro study as follows: enhanced green fluorescent protein (EGFP) group, islets transduced with adenovirus vectors containing EGFP gene using multiplicities of infection (MOI) = 2, 5, 10, and 20 to determine the transduction efficacy; HO-1 group, islets transduced with adenovirus vectors containing human HO-1 gene using MOI = 20; and control group, mock transduced islets. Flow cytometry was used to detect apoptotic cells after induction by recombinant human tumor necrosis factor-alpha (rTNF-alpha) and cycloheximide (CHX) for 48 hours. Diabetic recipients were randomly divided into the following groups: HO-1 group (n = 9), receiving islets transduced with recombinant adenovirus-HO-1; control group (n = 9), receiving mock transduced islets; and phosphate buffer solution (PBS) group (n = 6), receiving only 0.8 mL PBS. About 1200 rat islet equivalents were transplanted into each recipient rendered by streptozotocin using the portal vein as transplant site. Allograft survival, apoptosis, and the state of lymphocytic infiltration were analyzed.

RESULTS

After treatment with rTNF-alpha and CHX, the apoptotic ratio of islet cells was 4.22% +/- 2.38% in the HO-1 group (MOI = 20), significantly lower than 23.81% +/- 8.51% in the control group (P < 0.05), and 28.76% +/- 14.76% in the EGFP group (MOI = 20; P < 0.05). Maintenance of normoglycemia was prolonged in the HO-1 group, indicated by results that islet survival time was 10.56 +/- 4.33 days significantly longer than that of untreated islets which was 5.33 +/- 4.18 days (P < 0.05). The lymphocytic infiltration degree in engrafted islets treated with HO-1 gene was lower than that in the control group.

CONCLUSIONS

HO-1 gene overexpression in rat islets by adenovirus transduction can protect cultured islets against rTNF-alpha and CHX-mediated cytotoxicity. HO-1 gene has cytoprotective effects on engrafted islets, which could prolong engrafted islets survival in allogenic transplantation model, and diminish the degree of lymphocytic infiltration in islet grafts. These findings suggest a potential therapeutic application for HO-1 gene in improving islet survival/function in human islet transplantation.

Overcoming the Challenges Now Limiting Islet Transplantation: A Sequential, Integrated Approach

Steady improvements in islet cell processing technology and immunosuppressive protocols have made pancreatic islet transplantation a clinical reality for the treatment of patients with Type 1 diabetes mellitus (T1DM). Recent trials are showing that improved glycemic metabolic control, prevention of severe hypoglycemia, and better quality of life can be reproducibly achieved after transplantation of allogeneic islets in patients with unstable T1DM. Despite these encouraging results, challenges ahead comprise obtaining adequate islet cells for transplant, enhancing islets engraftment, sustaining beta cell mass and function over time, and defining effective immune interventions, among others. In order to overcome the current hurdles to the widespread application of islet transplantation there is a need for implementation of integrated, sequential therapeutic approaches.

Minimization of immunosuppressive therapy after islet transplantation: combined action of heme oxygenase-1 and PEGylation to islet

We previously established a type of PEGylated islets to attenuate cellular immune reactions by immobilizing polyethylene glycol (PEG) molecules on islet surfaces, thereby synergistically reducing the dose of immunosuppressant cyclosporine A (CsA; 3 mg/kg/day) to protect transplanted islets. However, higher doses of immunosuppressants should be administered after islet transplantation due to nonspecific inflammation. This study documents that PEGylated islets can be cooperatively protected by the systemic overexpression of heme oxygenase-1 (HO-1), which has a potent cytoprotective function in preventing nonspecific inflammation during an early stage following islet transplantation. Under this scheme, the viability of PEGylated islets was improved; that is, PEG molecules could block cellular immunity and HO-1 could exert its cytoprotective property against inflammation. Interestingly, when employed with a low dose of CsA (1 mg/kg/day), a cooperative action of PEG molecules and HO-1 in immune reactions could result in the complete survival of transplanted islets for 100 days without islet function impairment. However, unmodified islets (control) were completely rejected within 2 weeks despite cotreatment with HO-1 expression and CsA. These results demonstrated that the combinatorial protocol of initial induction of HO-1 expression, followed by the daily administration of a low dose CsA after transplantation of PEGylated islets can be employed as a successful cell therapy in clinical islet transplantation.

Heme oxygenase-1 upregulation protects against intestinal ischemia/reperfusion injury: a laboratory based study

OBJECTIVES

Tissue damage caused by ischemia/reperfusion injury (IRI) of the intestine may lead to organ dysfunction in several clinical conditions, and is associated with increased incidence of chronic rejection after transplantation. Heme oxygenase-1 (HO-1) is a stress-inducible protein capable of modulating inflammation, oxidative stress, and cell death. The aim of the present study was to assess the effects of HO-1 upregulation on intestinal IRI.

METHODS

Lewis rats (seven groups, n=6 each) underwent intestinal warm ischemia induced by clamping the superior mesenteric artery and by ligating the inferior mesenteric artery for 60 min. After 120 or 240 min of reperfusion, tissue samples were collected for analysis. Cobalt protoporphyrin (CoPP) was administered IP at 10 or 20mg/kg 24h before IRI, to induce HO-1 upregulation. Control animals received vehicle alone. Tissue injury measurements included the following: histological changes, tissue myeloperoxidase (MPO) activity, nitrate/nitrite levels, and IL-6 levels.

RESULTS

A significant HO-1 upregulation was demonstrated in pre-treated animals (p<0.05, 95% CI: -0.84 to -0.05). Intestinal IL-6 mRNA expression levels were significantly reduced in animals treated with CoPP 20mg/kg after 240 min of IRI (p<0.05, 95% CI: 0.09-2.25). Significant reduction in MPO activity and NO products was observed in treated animals when compared to controls (p<0.01, 95% CI: 0.07-0.24 and p<0.01, 95% CI: 5.58-12.75, respectively).

CONCLUSIONS

Induction of HO-1 by CoPP administration before IRI was resulted in a significant reduction of intestinal tissue injury. Developing strategies to induce HO-1 upregulation before surgery will be important to reduce IRI in the clinical setting.

Microsatellite polymorphism in the heme oxygenase-1 gene promoter and cardiac allograft vasculopathy

BACKGROUND

The heme oxygenase-1 (HO-1) isoenzyme has recently been suggested to protect transplants from ischemia-reperfusion and immunologic injury. Inducibility of this enzyme is modulated by a (GT)n dinucleotide length polymorphism in the HO-1 gene promoter. Short (class S) repeats are associated with greater up-regulation of HO-1 than are long repeats. In the present study, we investigated the impact of the promoter polymorphism on the development of cardiac allograft vasculopathy (CAV) in human heart transplants.

METHODS

We enrolled 152 recipients of a heart allograft with at least 1 year survival post-transplantation in this retrospective study. The HO-1 genotype was assessed using genomic DNA isolated from paraffin-embedded allograft biopsy specimens. Patients were followed angiographically for CAV. Angiographic vessel-wall abnormalities were defined as CAV, and a stenosis of more than 50% in at least 1 vessel area was defined as severe CAV.

RESULTS

Eighty-seven patients (57%) had received a heart from a donor with at least 1 class S allele. Within the mean follow-up period of 9 years, 95 patients (63%) showed signs of CAV, among which 60 patients (40%) developed severe CAV. The frequency of CAV and severe CAV was not significantly different between class S allele recipients and non-recipients (CAV, 57/87 vs 38/65, p = 0.12; severe CAV, 35/87 vs 25/65, p = 0.30).

CONCLUSION

In contrast to recent findings in renal allografts and vascular injury, the HO-1 gene promoter polymorphism does not show an association with the development of CAV in heart transplants.

Interventional strategies to prevent beta-cell apoptosis in islet transplantation

A substantial proportion of the transplanted islet mass fails to engraft due to death by apoptosis, and a number of strategies have been explored to inhibit beta-cell loss. Inhibition of extrinsic signals of apoptosis (i.e., cFLIP or A20) have been explored in experimental islet transplantation but have only shown limited impact. Similarly, strategies targeted at intrinsic signal inhibition (i.e., BCL-2) have not yet provided substantial improvement in islet engraftment. Recently, investigation of downstream apoptosis inhibitors that block the final common pathway (i.e., X-linked inhibitor of apoptosis protein [XIAP]) have demonstrated promise in both human and rodent models of engraftment. In addition, XIAP has enhanced long-term murine islet allograft survival. The complexities of both intrinsic and extrinsic apoptotic pathway inhibition are discussed in depth.

Carbon monoxide and biliverdin prevent endothelial cell sloughing in rats with type I diabetes

Hyperglycemia has been linked to increased oxidative stress, a resultant endothelial cell dysfunction, and, ultimately, apoptosis. Heme oxygenases (HO-1/HO-2) and the products of their activity, biliverdin/bilirubin and carbon monoxide (CO), play a physiological role in the vascular system. The effects of heme-mediated HO-1 induction, CO, and biliverdin on urinary 8-epi-isoprostane PGF(2alpha) and endothelial cell sloughing were examined in an animal model of streptozotocin (STZ)-induced diabetes. Hyperglycemia itself did not affect HO-1 and HO-2 protein levels, but caused a net decrease in HO activity. Weekly heme administration induced HO-1 protein, as demonstrated by immunohistochemistry and Western blot analyses. Administration of biliverdin or the CO donor, CORM-3, decreased urinary 8-epi-isoprostane PGF(2alpha), P < 0.5 compared to diabetes. Hyperglycemia increased endothelial cell sloughing; 8.2 +/- 0.8 cells/ml blood in control rats vs. 48 +/- 4.8 cells/ml blood in diabetic rats (P < 0.05). Heme administration significantly increased endothelial cell sloughing in diabetic rats (98 +/- 8.1 cells/ml blood, P < 0.0007) whereas biliverdin modestly decreased endothelial cell sloughing (26 +/- 3.5 cells/ml blood, P < 0.003). Administration of CORM-3 to diabetic rats resulted in a significant decrease in endothelial cell sloughing to 21.3 +/- 2.3 (P < 0.001). Administration of SnMP to CORM-3 diabetic rats only partially reversed the protective effects of CORM-3 on endothelial cell sloughing from 21.3 +/- 2.3 to 29 +/- 2.1 cells/ml, thus confirming a direct protective of CO, in addition to the ability of CORM-3 to induce HO-1 protein. These results demonstrate that exogenously administered CO or bilirubin can prevent endothelial cell sloughing in diabetic rats, likely via a decrease in oxidative stress, and thus represents a novel approach to prophylactic vascular protection in diabetes.

A protective role for heme oxygenase-1 in INS-1 cells and rat islets that are exposed to high glucose conditions

Heme oxygenase-1 (HO-1) has been described as an inducible protein that is capable of cytoprotection via radical scavenging and the prevention of apoptosis. Chronic exposure to hyperglycemia can lead to cellular dysfunction that may become irreversible over time, and this process has been termed glucose toxicity. Yet little is known about the relation between glucose toxicity and HO-1 in the islets. The purposes of the present study were to determine whether prolonged exposure of pancreatic islets to a supraphysiologic glucose concentration disrupts the intracellular balance between reactive oxygen species (ROS) and HO-1, and so this causes defective insulin secretion; we also wanted to evaluate a protective role for HO-1 in pancreatic islets against high glucose levels. The intracellular peroxide levels of the pancreatic islets (INS-1 cell, rat islet) were increased in the high glucose media (30 mM glucose or 50 mM ribose). The HO-1 expression was induced in the INS-1 cells by the high glucose levels. Both the HO-1 expression and glucose stimulated insulin secretion (GSIS) was decreased simultaneously in the islets by treatment of the HO-1 antisense. The HO-1 was upregulated in the INS-1 cells by hemin, an inducer of HO-1. And, HO-1 upregulation induced by hemin reversed the GSIS in the islets at a high glucose condition. These results suggest HO-1 seems to mediate the protective response of pancreatic islets against the oxidative stress that is due to high glucose conditions.

Biological and Biomaterial Approaches for Improved Islet Transplantation

Islet transplantation may be used to treat type I diabetes. Despite tremendous progress in islet isolation, culture, and preservation, the clinical use of this modality of treatment is limited due to post-transplantation challenges to the islets such as the failure to revascularize and immune destruction of the islet graft. In addition, the need for lifelong strong immunosuppressing agents restricts the use of this option to a limited subset of patients, which is further restricted by the unmet need for large numbers of islets. Inadequate islet supply issues are being addressed by regeneration therapy and xenotransplantation. Various strategies are being tried to prevent beta-cell death, including immunoisolation using semipermeable biocompatible polymeric capsules and induction of immune tolerance. Genetic modification of islets promises to complement all these strategies toward the success of islet transplantation. Furthermore, synergistic application of more than one strategy is required for improving the success of islet transplantation. This review will critically address various insights developed in each individual strategy and for multipronged approaches, which will be helpful in achieving better outcomes.

Pancreatic islet transplantation for treating diabetes

Pancreatic islet transplantation is one of the options for treating diabetes and has been shown to improve the quality of life of severe diabetic patients. Since the Edmonton protocol was announced, islet transplantation have advanced considerably, including islet after kidney transplantation, utilisation of non-heart-beating donors, single-donor islet transplantation and living-donor islet transplantation. These advances were based on revised immunosuppression protocols, improved pancreas procurement and islet isolation methods, and enhanced islet engraftment. Further improvements are necessary to make islet transplantation a routine clinical treatment. To synergise efforts towards a cure for type 1 diabetes, a Diabetes Research Institute (DRI) Federation is currently being established to include leading diabetes research centres worldwide, including DRIs in Miami, Edmonton and Kyoto among others.

Heme oxygenase-1/carbon monoxide: from basic science to therapeutic applications

The heme oxygenases, which consist of constitutive and inducible isozymes (HO-1, HO-2), catalyze the rate-limiting step in the metabolic conversion of heme to the bile pigments (i.e., biliverdin and bilirubin) and thus constitute a major intracellular source of iron and carbon monoxide (CO). In recent years, endogenously produced CO has been shown to possess intriguing signaling properties affecting numerous critical cellular functions including but not limited to inflammation, cellular proliferation, and apoptotic cell death. The era of gaseous molecules in biomedical research and human diseases initiated with the discovery that the endothelial cell-derived relaxing factor was identical to the gaseous molecule nitric oxide (NO). The discovery that endogenously produced gaseous molecules such as NO and now CO can impart potent physiological and biological effector functions truly represented a paradigm shift and unraveled new avenues of intense investigations. This review covers the molecular and biochemical characterization of HOs, with a discussion on the mechanisms of signal transduction and gene regulation that mediate the induction of HO-1 by environmental stress. Furthermore, the current understanding of the functional significance of HO shall be discussed from the perspective of each of the metabolic by-products, with a special emphasis on CO. Finally, this presentation aspires to lay a foundation for potential future clinical applications of these systems.