Human intrahepatic biliary epithelial cells engulf blebs from their apoptotic peers

The phagocytic clearance of apoptotic cells is critical for tissue homeostasis; a number of non-professional phagocytic cells, including epithelial cells, can both take up and process apoptotic bodies, including the release of anti-inflammatory mediators. These observations are particularly important in the case of human intrahepatic biliary cells (HiBEC), because such cells are themselves a target of destruction in primary biliary cirrhosis, the human autoimmune disease. To address the apoptotic ability of HiBECs, we have focused on their ability to phagocytize apoptotic blebs from autologous HiBECs. In this study we report that HiBEC cells demonstrate phagocytic function from autologous HiBEC peers accompanied by up-regulation of the chemokines CCL2 [monocyte chemotactic protein-1 (MCP-1)] and CXCL8 [interleukin (IL)-8]. In particular, HiBEC cells express the phagocytosis-related receptor phosphatidylserine receptors (PSR), implying that HiBECs function through the 'eat-me' signal phosphatidylserine expressed by apoptotic cells. Indeed, although HiBEC cells acquire antigen-presenting cell (APC) function, they do not change the expression of classic APC function surface markers after engulfment of blebs, both with and without the presence of Toll-like receptor (TLR) stimulation. These results are important not only for understanding of the normal physiological function of HiBECs, but also explain the inflammatory potential and reduced clearance of HiBEC cells following the inflammatory cascade in primary biliary cirrhosis.

Inflammatory myofibroblastic tumour of the maxillary sinus: CT and MRI findings

AIM

To characterize the computed tomography (CT) and magnetic resonance imaging (MRI) findings of inflammatory myofibroblastic tumours (IMTs) of the maxillary sinus.

MATERIALS AND METHODS

The imaging findings of eight patients with IMTs of the maxillary sinus were reviewed retrospectively. Of the eight patients, four patients underwent unenhanced and contrast-enhanced CT, and one patient underwent unenhanced CT only; three patients underwent unenhanced and contrast-enhanced MRI.

RESULTS

Five cases of IMTs occurred in the left maxillary sinus, while three cases were right-sided. Four cases occupied the entire sinus, and the other four cases only partially occupied the sinus. Unenhanced CT images showed heterogeneous masses in four cases and a homogeneous mass in one case. One of the tumours showed some areas of calcification. T1-weighted MRI images showed isointense lesions. T2-weighted images showed mixed isointense and mild hyperintense lesions. All cases showed bone destruction and had infiltrated into the nasal fossa, orbit, infratemporal fossa, and other adjacent tissues. Seven cases showed mild to moderate heterogeneous enhancement on contrast-enhanced CT or T1-weighted MRI images.

CONCLUSION

IMTs of the maxillary sinus can be characterized as a soft-tissue mass with bony destruction and infiltration of the adjacent tissues, with mild to moderate enhancement after the injection of contrast medium. CT and MRI can help to diagnose IMTs, determine the extent of the lesion and its relationship with adjacent tissues, and thus facilitate the prediction of surgical resectability.

Serum CA125 elevation is independently associated with serositis in SLE patients

OBJECTIVES

Some studies have reported that serum CA125 level is elevated in SLE patients, and elevated CA125 level may be associated with kidney involvement and disease activity in SLE. However, none of the previous studies controlled confounding variables and the results remained controversial. The present study was aimed to investigate whether elevated serum CA125 level is independently associated with clinical and laboratory features of SLE by excluding various confounders in Chinese patients.

METHODS

A total of 156 SLE patients, consisting of 139 women and 17 men, were included in the study. Some clinical and laboratory characteristics of the patients were obtained by medical record review. Serum CA125 levels were measured by electrochemiluminescence immunoassays.

RESULTS

Compared with patients with normal CA125, those with elevated CA125 had significantly more serositis (37.5% vs. 1.9%, p<0.001) and lung involvement (37.5% vs. 12%, p=<0.001), higher SLEDAI scores (p<0.007). Furthermore, disease duration was significantly longer in those with elevated CA125. Univariate logistic regression analysis showed that elevated serum CA125 level was closely associated with disease duration (OR, 95%CI:1.005, 1.001-1.010; p=0.014), serositis (OR, 95%CI: 32.258, 6.993-142.857; p<0.001), renal involvement (OR, 95%CI: 2.283, 1.114-4.673; p=0.024), lung involvement (OR, 95%CI: 4.386, 1.927-10.000; p<0.001) and SLEDAI scores (OR, 95%CI: 1.098, 1.027-1.174; p=0.006). After controlling for various confounding variables, serositis and disease duration were the only two clinical variables significantly associated with elevation of serum CA125 level. The best cut-off value for CA125 using the ROC curve was 38 kU/L (sensitivity 85%, specificity 75%) and the area under the ROC curve was 0.777 with 95%CI of 0.685-0.868 (p<0.001). Furthermore, the serum CA125 levels can fall into the normal range again with the improvement of serositis.

CONCLUSIONS

Of various clinical and laboratory variables of SLE, only serositis is independently associated with serum CA125 elevation.

Imbalance between T helper type 17 and T regulatory cells in patients with primary biliary cirrhosis: the serum cytokine profile and peripheral cell population

Primary biliary cirrhosis (PBC) is an organ-specific autoimmune liver disease characterized by progressive loss of intrahepatic small bile ducts. Cellular immune mechanisms involving T cell reaction are thought to be involved significantly in the pathogenesis of PBC. Recent studies have independently revealed enhanced T helper type 17 (Th17) response and weakened T regulatory cell (T(reg)) response in some autoimmune diseases, indicating a role of Th17/T(reg) imbalance in the pathogenesis of autoimmunity. This prompted us to investigate whether the Th17/T(reg) balance was broken in the peripheral blood of patients with PBC and, if it was, what cytokine circumstances might contribute to this imbalance. The expression of 11 Th17/T(reg) differentiation-related genes and serum concentrations of the corresponding cytokines in 36 patients with PBC, 28 patients with chronic hepatitis B and 28 healthy controls were measured by real-time quantitative-polymerase chain reaction and enzyme-linked immunosorbent assay respectively. Peripheral Th17 and T(reg) cells were analysed by flow cytometry. Th17-related cytokines were increased significantly in patients with PBC. Consistent with the cytokine profile, the Th17 cell population and retinoid-related orphan receptor gammat expression were increased markedly. In contrast, the T(reg) cell population and forkhead box P3 expression were decreased dramatically in the peripheral blood of patients with PBC. Our study revealed that the Th17/T(reg) imbalance, both cytokine profile and cell numbers, exists in patients with PBC, suggesting its potential role in the breakdown of immune self-tolerance in PBC. Interleukin-23, which characterized the imbalanced cytokine profile, may play an essential role in Th17-related human autoimmunity.

Identification of site(s) of insulin nitration by peroxynitrite and characterization of its structural change

Insulin nitration mediated by peroxynitrite (ONOO(-)) has been implicated in diabetes and diabetic cardiovascular complications. In this study, we identified the nitration sites of porcine insulin by infusion of ONOO(-) and quantified its secondary structural change. Insulin was cleaved with V8 protease to six peptides (four of them contained each tyrosine residue), then analyzed by HPLC-MS and further confirmed the nitration sites by HPLC-MS/MS. At low accumulated doses of peroxynitrite, the main products were two different mono-nitrated insulin species at Tyr-A19 and Tyr-B26 with Tyr-A19 being predominant as shown by peptide mapping. Also, the content of alpha-helix structure of insulin reduced to 22.9 % and random-coil structure increased to 30.2 % (compare with native insulin of 41.7 % and 13.7 %, respectively) as determined by FTIR spectra.

RIP2 is required for NOD signaling but not for Th1 cell differentiation and cellular allograft rejection

Two previous reports that receptor-interacting protein (RIP)-2 knockout (RIP2-/-) mice had defective nuclear factor-kappa B (NF-kappaB) signaling and T helper (Th)1 immune responses had led us to believe that this putative serine-threonine kinase might be a possible target for transplant immunosuppression. Thus, we tested whether RIP2-/- mice were able to reject vascularized allografts. Surprisingly, we found that T cells from RIP2-/- mice proliferated and produced interferon (IFN)-gamma after allostimulation in vitro. Moreover, naïve RIP2-/- CD4+ T cells differentiated normally into Th1 or Th2 cells under appropriate cytokine microenvironments. Consistent with these findings, no difference in allograft survival was observed between wild-type and RIP2-/- recipient mice, and rejection had similar pathology and cytokine profiles in both types of recipients. RIP2 deficiency was associated with defective NOD signaling, but this did not affect T-cell receptor (TCR)-dependent activation of the canonical NF-kappaB signaling or expression of NF-kappaB genes in rejecting allografts. Our data demonstrate that RIP2-deficient mice have intact canonical NF-kappaB signaling and can mount Th1-mediated alloresponses and reject vascularized allografts as efficiently as wild-type mice, thus arguing against RIP2 as a primary target for immunosuppression.

Anti-CD45RB monoclonal antibody prolongs renal allograft survival in cynomolgus monkeys

Previously, an anti-CD45RB monoclonal antibody (mAb) has been shown to induce murine allograft tolerance. The present study was performed to assess the ability of an anti-human CD45RB mAb to prevent rejection in a monkey MHC-mismatched kidney transplant model. The recipients were allocated into the following treatment groups: (1) isotype control IgG; (2) mouse anti-human CD45RB IgG1 (6G3); (3) human-mouse chimeric anti-CD45RB-IgG1 (C6G3-IgG1); (4) human-mouse chimeric anti-CD45RB-IgG2 (C6G3-IgG2); (5) tacrolimus at a subtherapeutic dose and (6) tacrolimus and C6G3-IgG1 in combination. Monotherapy with anti-CD45RB mAb significantly prolonged renal allograft survival to a median survival of 21 days. Adding a subtherapeutic dose of tacrolimus improved the efficacy of the anti-CD45RB mAb, achieving a median survival of 85 days, whereas a subtherapeutic dose of tacrolimus alone only moderately prolonged survival to 27 days. Treatment with anti-CD45RB mAb resulted in an alteration of the CD45RB(hi) : CD45RB(lo) cell ratio in the peripheral blood. We have, for the first time, demonstrated that an anti-human CD45RB mAb (6G3) can prolong graft survival. Induction with an anti-CD45RB mAb improves the efficacy of tacrolimus in the prevention of rejection. These encouraging results indicate that an anti-CD45RB mAb may be valuable in future clinical transplantation.

Gal knockout and beyond

Recently, Galalpha1-3Galbeta1-4GlcNAc (Gal) knockout (k/o) pigs have been developed using genetic cloning technologies. This remarkable achievement has generated great enthusiasm in xenotransplantation studies. This review summarizes the current status of nonhuman primate experiments using Gal k/o pig organs. Briefly, when Gal k/o pig organs are transplanted into primates, hyperacute rejection does not occur. Although graft survival has been prolonged up to a few months in some cases, the overall results were not better than those using Gal-positive pig organs with human complement regulatory protein transgenes. Gal k/o pig kidneys rapidly developed rejection which was associated with increased anti-non-Gal antibodies. Although the precise mechanisms of Gal k/o pig organ rejection are not clear, it could result from incomplete deletion of Gal, up-regulation of new antigen (non-Gal antigen) and/or production of non-Gal antibodies. Future work in xenotransplantation should place emphasis on further modification of donors, such as combining human complement regulatory genes with Gal k/o, deleting non-Gal antigens and adding protective/surviving genes or a gene that inhibits coagulation. Induction of donor-specific T- and B-cell tolerance and promotion of accommodation are also warranted.

NOS2 (iNOS) deficiency in kidney donor accelerates allograft loss in a murine model

Renal NOS2 is expressed and produces abundant nitric oxide (NO) in various renal cells in response to proinflammatory cytokines. However, the role of this enzyme in renal allograft survival remains unknown. Kidney allotransplantation was performed in the murine model of C57BL/6J (H-2(d)) to nephrectomized Balb/c (H-2(b)) mice. Here we show that deficiency in NOS2 expression in kidney donors significantly advanced allograft failure, indicated by decreasing mean survival of recipients receiving NOS2 null grafts (15.4 +/- 6.4 days) as compared to those with wild type grafts (65.4 +/- 28.1 days) (p = 0.0005). Consistent with survival results, NOS2 null grafts had more severe renal tubule injury and decreased renal function compared to wild type grafts. In vitro NOS2 expressing TEC had greater resistance to allogeneic lymphocyte-mediated apoptosis. The addition of exogenous NO inhibited Fas-mediated TEC apoptosis and reduced proliferation of allogeneic lymphocytes. These data suggest that endogenous production of NO through renal NOS2 activity can play a protective role in kidney grafts through attenuating Fas-mediated donor cell apoptosis as well as by inhibiting proliferation of inflammatory infiltrating lymphocytes. Enhanced donor NOS2 expression may be a useful strategy to improve kidney transplant survival.

Increasing resistance of tubular epithelial cells to apoptosis by shRNA therapy ameliorates renal ischemia-reperfusion injury

Renal tubular epithelial cells (TEC) die by apoptosis or necrosis in renal ischemia-reperfusion injury (IRI). Fas/Fas ligand-dependent fratricide is critical in TEC apoptosis, and Fas promotes renal IRI. Therefore, targeting Fas or caspase-8 may have therapeutic potential for renal injury in kidney transplant or failure. RNA silencing by short hairpin RNA (shRNA) is a novel strategy to down-regulate protein expression. Using this approach, silencing of Fas or caspase-8 by shRNA to prevent TEC apoptosis and IRI was evaluated. IRI was induced by renal artery clamping for 45 or 60 min at 32 degrees C in uninephrectomized C57BL/6 mice. Here, we showed that Fas or pro-caspase-8 expression was significantly knocked down in TEC by stable expression of shRNA, resulting in resistance to apoptosis induced by superoxide, IFN-gamma/TNF-alpha and anti-Fas antibody. Inferior vena cava delivery of pHEX-small interfering RNA targeting Fas or pro-caspase-8 resulted in protection of kidney from IRI, indicated by reduction of renal tubular injury (necrosis and apoptosis) and serum creatinine or blood urea nitrogen. Our data suggest that shRNA-based therapy targeting Fas and caspase-8 in renal cells can lead to protection of kidney from IRI. Attenuation of pro-apoptotic proteins using genetic manipulation strategies such as shRNA might represent a novel strategy to promote kidney allograft survival from rejection or failure.

Preventing renal ischemia-reperfusion injury using small interfering RNA by targeting complement 3 gene

The complement system is one of the important mediators of renal ischemia-reperfusion injury (IRI). We hypothesized that efficient silencing of C3, which is the central component on which all complement activation pathways converge, could be achieved using small interfering RNA (siRNA), and that this would result in overall inhibition of complement activation, thereby preventing IRI in kidneys. A series of experiments was conducted, using a mouse model of IRI and vector-delivered C3-specific siRNA. We demonstrated the following: (1) renal expression of C3 increases as a result of IRI; (2) by incorporation into a pRNAT U6.1 vector, siRNA can be delivered to renal cells in vivo; (3) systemically delivered siRNA is effective in reducing the expression of C3 in an experimentally induced mouse kidney model of IRI; (4) similarly, siRNA reduces complement-mediated IRI-related effects, both in terms of renal injury (as evidenced by renal function and histopathology examination) and mouse mortality and (5) silencing the production of C3 diminishes in vivo production of TNF-alpha. This study implies that siRNA represents a novel approach to preventing IRI in kidneys and might be used in a variety of clinical settings, including transplantation and acute tubular necrosis.

Prolongation of allograft survival by administration of anti-CD45RB monoclonal antibody is due to alteration of CD45RBhi: CD45RBlo T-cell proportions

CD45RB monoclonal antibody (mAb) therapy is capable of prolonging allograft survival. We have previously shown that CD45RB mAb enriches the CD45RBlo T-cell population in vitro and in vivo by preferentially depleting CD45RBhi T cells. The present study assessed the importance of CD45RBhi T-cell depletion in murine cardiac allograft survival by infusion of naive CD45RB T-cell subsets. Here we show that naturally occurring CD45RBloCD4+ T cells express regulatory transcription factor Foxp3 and have regulatory function, whereas CD45RBhiCD4+ T cells express low levels of Foxp3 and have effector function. Infusion of syngeneic CD45RBhi T cells significantly reduced graft survival after depletion of CD45RBhi T cells by CD45RB mAb. Reduction of graft survival also occurred when syngeneic CD45RBhi T cells were infused into rapamycin-treated mice, whereas survival was prolonged when CD45RBlo T cells were added. This indicates that an alteration in the balance between regulatory CD45RBlo and effector CD45RBhi T cells is critical to the immunologic function of CD45RB mAb. A strategy to eliminate effector T cells with consequent enrichment of the regulatory T-cell compartment may be an important new strategy in the prevention of rejection.

A synergistic effect between PG490-88 and tacrolimus prolongs renal allograft survival in monkeys

This study was undertaken to determine if PG490-88 and tacrolimus (Tac) act synergistically to prevent renal allograft rejection in monkeys and to explore possible mechanisms of synergy between these agents. MHC-mismatched renal allografts were transplanted into cynomolgus monkeys after bilateral nephrectomy. Recipients were divided into the following groups: (i) no treatment; (ii) PG490-88 (0.03 mg/kg); (iii) Tac (1 mg/kg); (iv) PG490-88 (0.01 mg/kg) + Tac (1 mg/kg) and (v) PG490-88 (0.03 mg/kg) + Tac (1 mg/kg). Through synergy PG490-88 and Tac inhibited anti-CD3/PMA-induced T-cell proliferation and IFN-gamma expression in vitro. Tac monotherapy only marginally prolonged survival (27 +/- 3.2 days), while the combination of PG490-88 and Tac significantly prolonged graft survival to a median of 99 days (PG490-88 at 0.03 mg) and 38.5 days (PG490-88 at 0.01 mg/kg). Prolonged survival correlated with inhibited IgM production as well as reduced T-cell infiltration, IL-2 protein expression and NF-AT/NF-kappaB activity. We conclude that PG490-88 and a subtherapeutic dose of Tac significantly prolong renal allograft survival in monkeys through the synergistic inhibition of T-cell activation and a decrease in IFN-gamma production and NF-AT/NF-kappaB activity.

Xenotransplantation of human decay accelerating factor transgenic porcine kidney to non-human primates: 4 years experience at a Canadian center

From July 1999 to December 2002, a total of 27 baboons underwent transplantation with human decay accelerating factor (hDAF) transgenic porcine kidneys. The immunosuppressive protocol included combinations of 1 or more of the following immunosuppressive agents: cyclosporine, TPC, cyclosphophamide, methylprednisolone, GAS914 (a polymeric alpha-Gal), rabbit antithymocyte serum (RATS), and rapamycin derivative (RAD). The animals were followed up clinically with monitoring of renal function based on daily creatinine and urinary output. Histopathological examination of the tissue samples was performed after paraffin embedding. Electron microscopy was performed on occasion. All pathology was read blindly with a semiquantitative scoring method to assess the presence or absence of histological features of xenotransplant rejection. Mean survival time was 20.7 days (range, 4-75 days) with 15 animals dying of classic humoral rejection and 12 dying of complications unrelated to rejection. The most frequent complications were as follows: chronic diarrhea with malabsorption, bleeding diathesis, infections, and drug toxicity. Irrespective of the immunosuppressive regimen, a significant number of baboons (10) developed untreatable diarrhea and gastrointestinal bleeding. Samples of their gastrointestinal tracts showed evidence of varying degrees of necrotizing vasculitis with immunoglobulin (Ig)G,IgM, and fibrin deposition. The survival in pig-to-baboon kidney xenotransplantation continues to be limited by acute xenograft rejection and complications of immunosuppression. Although significantly increased survivals have been obtained, an ideal protocol has not yet been achieved. Efforts will continue in an attempt to develop a protocol with minimal complications and long-term survival beyond 90 days.

Renal tubular epithelial cell apoptosis by Fas-FasL–dependent self-injury can augment renal allograft injury

The role of Fas-FasL interactions in kidney allograft injury may be complex as renal tubular epithelial cells (TEC) express both Fas and FasL. The role and regulation of TEC self-injury has not been investigated. In co-cultures of TEC, FasL-bearing, Fas-null TEC was demonstrated to induce apoptosis of TEC-bearing Fas. Co-culturing effector lpr-TEC (M3.1-lpr) with target WT-TEC (CS3.7) at a ratio of 10:1 (E/T) induced 15.2 +/- 2.4% of target apoptosis as compared to its basal level of 2.6 +/- 0.3%. Similarly lpr-TEC induced apoptosis in gld-TEC (MRM-gld) from a basal level of 3.7 +/- 0.2% to 6.4 +/- 0.3%. Expression of kidney Fas-FasL on injury was tested in a renal transplant model. C57BL/6 (B6) mice were transplanted with Fas-deficient C3H-lpr/lpr or FasL mutation C3H-gld/gld kidneys as compared to normal (wild-type [WT]) C3H/Hej donors. Survival of both lpr and gld recipient was improved compared to WT donors (P <.05) as was function of lpr and gld kidneys indicated by a lower serum creatinine (LPR: 41 +/- 8 micromol/L; GLD: 52 +/- 7 micromol/L) as compared to the WT donors (84 +/- 8 micromol/L, P <.001). These results demonstrate that activated TEC may commit a novel and previously unreported form of self-injury (fractricide) through Fas-FasL. These results suggest that inhibition of renal Fas or FasL might be a useful strategy to prevent TEC loss during rejection.

Development of an XTT tetrazolium salt-based assay for detection of specific hyperthermia sensitizers in a high-flux screening programme

It is now possible to search for new drugs using high-throughput screening of chemical libraries accumulated over the past few years. To detect potential new hyperthermia sensitizers, we are screening for chemical inhibitors of thermotolerance. For the screening of a large chemical library, a rapid and simple assay based on the XTT-tetrazolium salt with the addition of intermediate electron acceptor, phenazine methosulphate (PMS) as a promoter, was developed. It was found that the sensitivity of the XTT/PMS assay is sufficient for assessing thermal cell killing and thermotolerance, although it was highly dependent on cell number and type. When the formazan assay system was challenged with the bioflavonoid drug quercetin (up to 25mm) and validated against the clonogenic cell survival assay, significant decreases in thermotolerant cell viability were observed, directly reflecting inhibition of thermotolerance. Although short-term assays can, in some instances, underestimate overall cell killing, the dose dependency of inhibition of thermotolerance by quercetin recorded in this study by clonogenic and XTT/PMS assays was similar. Application of the XTT/PMS assay in chemical library screening was highly effective in differentiating potential thermotolerance inhibitors from both chemicals with lack of efficacy and from toxic compounds. Taken together, these results show that the XTT/PMS assay, when carried out under careful conditions, is well suited for primary high-flux screen of many thousands of compounds, thus opening up new areas for discovery of hyperthermia sensitizers.

Thymic re-entry of mature activated T cells and increased negative selection in vascularized allograft recipients

Transplantation tolerance is a dynamic state that involves several homeostatic mechanisms intrinsic to the host. One of these mechanisms is activation-induced T cell death (AICD). However, it is unclear where AICD takes place during alloreactive responses. Since activated T cells can re-enter the thymus, we hypothesized that mature T cells activated by an allograft could be deleted upon re-entry into the thymus. To test this hypothesis, we used wild-type or 2C TCR transgenic mice receiving syngeneic or allogeneic heterotopic, vascularized heart grafts. First, we demonstrated that ex vivo CFSE-labelled T cells re-entered the thymus when transferred into allograft recipients but not when transferred into isograft recipients. Next, we compared the changes in cell subset numbers and incidence of apoptosis in the thymi and spleens of allograft or isograft recipients. Seven days after transplantation, at a time in which all the allografts were undergoing rejection, cells expressing donor-MHC class II molecules had migrated to the thymus and to the spleen. In the thymus of allograft recipients, overall cellularity was significantly reduced by 40% and associated with an increase in the number of double negative (CD4-CD8-) thymocytes and a decrease in double positive (CD4+CD8+) thymocytes, consistent with increased negative selection of thymocytes. Additionally, thymi of allograft recipients showed an increase in the number of recently activated, mature T cells (TCRhi, CD25+, CD44+) and a significant increase in the number of apoptotic cells, especially in the thymic medulla, that involved mature T cells as indicated by the TCRhi, CD44+, CD4 or CD8 single positive phenotype. Spleens of allograft recipients were increased in size and cellularity but did not show any of the changes in cell subsets seen in the thymi. Our data show that after allografting there is an increase in apoptotic cell death that is associated with negative selection of developing thymocytes as well as of alloreactive mature T cells that have re-entered the thymus upon activation in the periphery. This may occur upon migration of graft-derived antigen-presenting cells to the thymus.