Biomedical subjects

Wuding Zhou

Publications and source records attributed to Wuding Zhou.

16 recordsLinked to original sources

PubMed2006

Role of dendritic cell synthesis of complement in the allospecific T cell response.

Although extrahepatic synthesis of complement and particularly C3 has been widely studied in most cells and tissues, new information is emerging on dendritic cells (DCs). This research has shown that mouse bone marrow (BM) derived DCs are able to synthesise C3 and this synthesis has a substantial impact on DC activation, affecting the diverse range of DC functions relevant to the allospecific T cell response. Thus, local production of C3 appears to regulate the capacity of DCs to trigger the primary T cell response against donor alloantigen. Understanding of the key mechanisms by which complement activation modulates DC maturation could lead to the development of therapeutic strategies to down regulate DC activation thus reduce allograft rejection.

Animals↗

PubMed2006

Influence of donor C3 allotype on late renal-transplantation outcome.

BACKGROUND: The complement system has a critical role in both the innate and the adaptive immune responses. In humans, C3 exists as two main allotypes, F (fast) and S (slow), which are known to affect the incidence of inflammatory disease. We conducted a study to address the influence of these alleles on late renal-graft outcome. METHODS: We determined the C3 allotypes of 662 pairs of adult kidney donors and recipients from 1993 through 2002 and then related C3F/S polymorphism status to demographic and clinical outcome data. The median length of follow-up was 3.3 years. RESULTS: Analysis of 513 pairs of white donors and recipients identified 113 C3S/S recipients of a C3S/F or a C3F/F kidney and 179 C3S/S recipients of a C3S/S kidney. Graft survival was significantly better with a C3F/F or C3F/S donor allotype than a C3S/S allotype (P=0.05). The hazard ratio for graft loss of C3S/S kidneys, as compared with C3F/F or C3F/S kidneys, was 2.21 (95 percent confidence interval, 1.04 to 4.72; P=0.04). The graft function of C3F/F or C3F/S donor kidneys was significantly better than that of C3S/S donor kidneys (P<0.001). The effect of the C3F allele was specific to recipients who did not themselves possess this allele. Multivariate analysis excluded effects of other factors known to influence graft outcome. CONCLUSIONS: Expression of C3 alleles by donor renal cells appears to have a differential effect on late graft outcome. Among white C3S/S recipients, receipt of a C3F/F or C3F/S donor kidney, rather than a C3S/S donor kidney, is associated with a significantly better long-term outcome. These findings suggest that the two alleles have functional differences.

Adult↗

PubMed2006

Dendritic cell synthesis of C3 is required for full T cell activation and development of a Th1 phenotype.

Previous studies have found that deficiency of complement component C3 is associated with reduced T cell responses in several disease models including viral infection, autoimmune disease, and transplantation. However, the underlying mechanism is unclear. In this study, we demonstrate that dendritic cells (DCs) are able to synthesize C3 and this synthesis is required for the capacity of DCs to stimulate alloreactive T cell responses in vitro and in vivo. Compared with C3-producing DCs, C3-nonproducing DCs exhibit reduced potency to stimulate an alloreactive T cell response, favor the polarization of CD4(+) T cells toward Th2 phenotype, and have regulatory T cell-driving capacity. In addition, priming mice with C3-deficient DCs compared with wild-type DCs led to delayed skin allograft rejection. Our findings that nonproduction of C3 by DCs significantly reduced T cell stimulation and impaired allograft rejection provide a potentially important explanation of how C3-deficient mice develop reduced T cell responses and of how C3-deficient donor kidney is protected from T cell-mediated graft rejection.

Animals↗

PubMed2006

Therapeutic strategy with a membrane-localizing complement regulator to increase the number of usable donor organs after prolonged cold storage.

A shortage of donor organs and increasing dependence on marginal grafts with prolonged ischemic times have meant that new methods are needed to prevent postischemic damage. Herein is reported a new strategy aimed to protect donor kidney from complement-mediated postischemic damage and therefore increase the number of successful transplants. Rat donor kidneys were perfused with a membrane-localizing complement regulator derived from human complement receptor type 1 (APT070) and then subjected to prolonged periods of cold storage (at 4 degrees C). A relationship was found between the duration of cold ischemia and the extent of complement-mediated tubule damage and loss of graft function. After 16 h of cold storage, APT070-treated kidneys that were transplanted into syngeneic recipients showed a significant increase in the number of surviving grafts, compared with control-treated grafts (63.6 versus 26.3%). Surviving grafts also displayed less acute tubular injury and better preservation of renal function. These results not only enhance the understanding of the mechanism by which prolonged cold ischemia reduces immediate graft survival but also provide essential information about the effectiveness of membrane-localizing complement regulator with prolonged cold storage. This could lead to more effective strategies for improving the use of severely ischemic donor organs.

Animals↗

PubMed2006

Local extravascular pool of C3 is a determinant of postischemic acute renal failure.

The third complement component (C3) is an acute phase protein that plays a central role in reperfusion injury in several organ models. To investigate the contribution of local synthesis of C3 and distinguish it from that of circulating complement mainly produced by hepatic synthesis, we employed a mouse renal isograft model. Our model demonstrated a close relationship between the extent of intrarenal expression of C3 and cold-ischemia induced injury. Ischemic C3-positive donor kidneys transplanted into C3-positive or C3-negative recipients developed widespread tissue damage and severe acute renal failure. In contrast, ischemic C3-negative isografts exhibited only mild degrees of functional and structural disturbance, even when transplanted into normal C3-positive recipients. Thus local synthesis of C3, mostly identified in the tubular epithelium, was essential for complement-mediated reperfusion damage, whereas circulating C3 had a negligible effect. Our results suggest a two-compartment model for the pathogenic function of C3, in which the extravascular compartment is the domain of local synthesis of C3, and where the role of circulating C3 is redundant. Our data cast new light on the mechanism of complement-mediated tissue injury in nonimmunological disorders, and challenges the longstanding dogma that circulating components are the main complement effectors of extravascular tissue damage.

Animals↗

PubMed2006

Deficiency of C4 from donor or recipient mouse fails to prevent renal allograft rejection.

Complement effector products generated in the transplanted kidney are known to mediate transplant rejection, but which of the three main activation pathways of complement trigger this response is unclear. Here we assessed the role of the classical and lectin pathways by studying the common component C4 in mouse kidney transplant rejection. We transplanted wild-type or C4-null H-2(b) donor kidneys into H-2(k) or H-2(d) recipients, or vice-versa, to assess the roles of donor kidney and recipient expression of complement. Intragraft C4 gene expression rose substantially during rejection. However, we found no significant association between graft acceptance and the presence of C4 in either the donor kidney or recipient mouse. At the time of rejection, we found no significant differences in alloantibody response in the different groups. Tubular deposition of C3 to C9 occurred regardless of the absence or presence of C4 in either the donor or recipient mouse, indicating that C4 was dispensable for complement activation at this site. These data suggest that complement activation and renal allograft rejection are independent of the classical and lectin pathways in these models, implying that in the absence of these pathways the alternative pathway is the main trigger for complement-mediated rejection.

Animals↗

PubMed2005

Macrophages from C3-deficient mice have impaired potency to stimulate alloreactive T cells.

Impaired T-cell reactivity is a feature of C3-deficient mice in several disease models. The mechanism behind the reduced T-cell response is, however, poorly understood. We explored the hypothesis that antigen-presenting cells (APCs) from C3-/- mice have impaired potency to stimulate antigen-specific T cells, in an alloantigen-dependent model. Our results show that C3-/- macrophages have reduced ability to elicit alloreactive T-cell responses in vitro and in vivo, affecting both the primary and secondary responses. The C3 status of donor macrophages had a major impact on the CD4 T-cell response. The impaired CD4 T-cell response was associated with reduced expression of MHC class II on the surface of C3-/- macrophages, without loss of class II gene expression. Furthermore, inhibition of C3 gene expression in C3+/+ macrophages reduced their ability to stimulate alloreactive T cells, suggesting that endogenous production of C3 could in part contribute to the potency of APCs. Our data provide compelling evidence that C3 deficiency modulates the potency of APCs to stimulate the T-cell response, suggesting a critical role for complement in the maintenance of APC function. This could offer a partial explanation as to why the T-cell response is impaired in C3-/- mice.

Animals↗

PubMed2005

Allograft rejection: effect of local synthesis of complement.

The complement system is known for its ability to participate in non-specific inflammation and membrane injury as well as contributing to antigen-specific immune stimulation. In renal transplantation, the complement cascade behaves true to form in that both non-immune- and immune-mediated destruction of the renal tubules are complement dependent. What is remarkable, however, is the extent of involvement of local synthesis of complement in both of these injuries, suggesting that the extravascular tissue compartment is the domain of local synthesis, whereas the effect of circulating complement is much less. This creates a new paradigm for studying the influence of local synthesis of complement in other organ-based diseases and underlines the need for tissue-targeting strategies in successful therapeutic development.

Animals↗

PubMed2004

Independent pathways of P-selectin and complement-mediated renal ischemia/reperfusion injury.

Evidence from in vitro studies indicates that complement activation regulates the expression of P-selectin on endothelial cells. This suggests that in disorders such as ischemia/reperfusion injury, in which both complement and P-selectin have been shown to play a role, complement activation is a primary event and the effects of P-selectin are secondary. To test this hypothesis in vivo, we examined a mouse kidney model of ischemia/reperfusion injury. Surprisingly, the time course and extent of expression of P-selectin was unaltered in C3-deficient mice compared with wild-type mice, in which there was rapid but transient up-regulation of P-selectin on capillary walls and slower accumulation of complement split product on the tubular epithelium. In addition, treatment with anti-P-selectin antibody to reduce the neutrophil-mediated reperfusion damage was equally effective in the absence of C3. These data imply that complement and P-selectin-mediated pathways of renal reperfusion injury are mutually independent, a conclusion that is possibly explained by the differences in the location and time kinetics of complement activation and P-selectin expression. We conclude that in vivo interaction between complement and P-selectin is limited because of time and spatial considerations. Consequently, complement and P-selectin pose distinct targets for therapy.

Animals↗

PubMed2004

CD59a deficiency exacerbates ischemia-reperfusion injury in mice.

The terminal complement components C5a and the membrane attack complex are involved in the pathogenesis of ischemia-reperfusion injury in many organs. CD59 is the major regulator of membrane attack complex formation. Mice deficient in the Cd59a gene (mCd59a-/-) were used to investigate the role of CD59 in renal ischemia-reperfusion injury. Unilateral ischemia-reperfusion injury was induced by clamping the left renal pedicle for 30 minutes under general anesthetic. Mice were studied at 72 hours and 2 weeks after ischemia-reperfusion injury. mCd59a-/- mice developed significantly greater tubular injury (P = 0.01), tubulointerstitial apoptosis (P = 0.02), and neutrophil influx (P = 0.04) than controls at 72 hours after ischemia-reperfusion. Two weeks after ischemia-reperfusion, mCd59a-/- mice exhibited more severe tubular damage predominantly in a corticomedullary distribution than controls (P = 0.02). Quantification of interstitial leukocytes revealed significantly greater numbers of infiltrating lymphocytes (but not macrophages) in mCd59a-/- mice than controls (P = 0.04) at 2 weeks. At both time points, significantly more C9 (as a marker of membrane attack complex) deposition occurred in a peritubular distribution in mCd59a-/- mice than controls. In conclusion, these results demonstrate that the lack of CD59a, by allowing unregulated membrane attack complex deposition, exacerbates both the tubular injury and the interstitial leukocyte infiltrate after ischemia-reperfusion injury in mice.

Animals↗

PubMed2004

Complement activation regulates the capacity of proximal tubular epithelial cell to stimulate alloreactive T cell response.

Tissue expression of C3 is an unexpected regulator of the alloimmune response in mouse kidney transplantation. It is unclear, however, whether a direct or an indirect action of complement on the host immune response is involved. Also unknown is which of the complement effector products, cleaved C3, cleaved C5, or C5b-9, is responsible. Proximal tubular epithelial cells (PTEC) not only constitute a major target of the alloimmune response but also produce substantial amounts of C3. This study investigated the property of mouse PTEC to stimulate alloreactive T cells in a complement-dependent manner. The proliferative and cytokine responses of primed alloreactive T cells were measured after exposure to donor-specific PTEC that had been pretreated with normal mouse serum, heat-inactivated mouse serum, or complement- deficient (C3, C5, or C6) mouse sera to differentially deposit complement components. PTEC were able to stimulate alloreactive T cells in an antigen-specific manner. Complement activation leading to the deposition of cleaved C3 on PTEC enhanced the alloreactive T cell response. This complement-mediated stimulation of the T cell response was dependent on C3 but not on C5 or C6. The primary influence of tissue-bound complement was on CD4(+) T cells. Moreover, the effect of complement on alloreactive T cells was B7 dependent, shown by inhibition studies with CTLA4-Ig. These results suggest that donor epithelium-bound C3 can upregulate the alloimmune response. It is postulated that surface-bound C3 interacts with complement receptors on alloreactive T cells or on antigen presenting cells to increase allo-immune stimulation.

Animals↗

PubMed2003

The effect of locally synthesised complement on acute renal allograft rejection.

The complement system of components and receptors is one of the earliest forms of defence. Excessive or inappropriate activation can result in tissue damage, classically illustrated in immune-mediated nephritis. In addition, complement forms a bridge between innate and adaptive immunity, helping to prepare and focus T and B lymphocyte responses. More recent research in renal allograft models has shown that complement-inhibited and complement-deficient animals have reduced inflammatory injury and lowered antidonor immune responses. Furthermore, it is known that the transplanted kidney is a significant site of local synthesis of C3, although until recently the relative contribution of locally produced C3 to transplant injury was unknown. Current evidence indicates that defective local synthesis of C3 both reduces tissue injury and lowers the antidonor T cell response, substantially increasing graft survival. Among various possible explanations to account for these findings, the data favours a direct effect of complement on alloreactive T cell stimulation. Study of complement gene regulation by common immunosuppressive agents suggests that they do not influence local complement synthesis. Alternative approaches are therefore required to control the local effect of complement in the extravascular tissue compartment of the graft.

Acute Disease↗

PubMed2003

Nontransgenic hyperexpression of a complement regulator in donor kidney modulates transplant ischemia/reperfusion damage, acute rejection, and chronic nephropathy.

Complement activation during ischemia and reperfusion contributes to the development of tissue injury with severe negative impact on outcomes in transplantation. To counter the effect of complement, we present a strategy to deliver a novel complement regulator stabilized on cell surfaces within donor organs. The membrane-bound complement regulator is able to inhibit complement activation when the donor organ is revascularized and exposed to host-circulating complement. Application of this construct to donor kidneys protected transplanted tissues from ischemia/reperfusion injury and reduced the deposition of activated complement and histological signs of damage under conditions in which a nontargeted control construct was ineffective. Treatment of donor organs in this way improved graft performance in the short and long term. An analysis of the immune response in allograft recipients showed that reducing graft damage at the time of transplantation through complement regulation also modulated the alloresponse. Additionally, the results of perfusion studies with human kidneys demonstrated the feasibility of targeting endothelial and epithelial surfaces with this construct, to allow investigation in clinical transplantation.

Acute Disease↗

PubMed2003

Role of the complement system in rejection.

The complement system plays a complex role in transplantation, beginning with effects on reperfusion injury and continuing with stimulation of the adaptive immune response. Recent evidence has emphasised the importance of the late components of the complement cascade in the mediation of post-ischaemic damage, which are apparently triggered by the classical, alternative or lectin pathways of complement activation, depending on the organ affected. In studies of renal allograft rejection, the local synthesis of complement component C3 seems to influence the T-cell response more strongly than circulating complement protein, raising the possibility that there is co-operation between locally derived C3 and antigen presentation in the graft. Class switching of alloantibody to a high-affinity IgG response is also highly dependent on C3. In addition, the finding that capillary-bound C4d is a robust marker for humoral rejection has started a new investigation into the significance of alloantibodies in acute and chronic allograft rejection. There are several selective and nonselective inhibitors suitable for clinical development; clearly it is time for more concerted effort to evaluate their role in clinical transplantation.

Complement Activation↗

PubMed2003

Locally produced complement and its role in renal allograft rejection.

The role of innate immunity in allograft injury is just beginning to become clear, and complement is probably one of a number of factors that are activated very early in the course of transplantation. Kidney transplantation into complement-inhibited rats reduces subsequent inflammation of the graft, probably as a result of reduction of ischemia reperfusion damage as well as diminution of immune mediated damage. Closer analysis of the role of locally synthesised components in mice has suggested that regional synthesis of complement proteins, in particular by the renal tubule, may play a more important role than circulating components. A marked effect on the antidonor T cell response may be explained by the triggering of complement receptors present on antigen presenting cells or T cells infiltrating the graft, or by a more direct effect of complement on the liaison between proximal tubule cells and T cells. Therapeutic control is likely to require a shift to a more targeted approach, directed at complement components produced in the extravascular tissue compartment.

Animals↗

PubMed2002

Triptolide is a potent suppressant of C3, CD40 and B7h expression in activated human proximal tubular epithelial cells.

BACKGROUND: Previous studies have shown that triptolide possesses potent immunosuppressive and anti-inflammatory properties. Increasing recognition of the importance of the proximal tubular epithelial cells (PTEC) in renal disease and renal transplantation raises the question of whether triptolide suppresses the pro-inflammatory activity of PTEC. METHODS: Cultured human PTEC were exposed to tumor necrosis factor-alpha (TNF-alpha) and immunosuppressant (triptolide or CsA or FK506) for 24 hours, followed by RT-PCR, ELISA, flow cytometry and Western blotting analysis for complement C3, CD40, B7h expression. RESULTS: TNF-alpha up-regulated C3, CD40 and B7h production by PTEC. This up-regulation was inhibited by all three immunosuppressants with different intensity. Firstly, triptolide (4 to 8 ng/mL), CsA (4000 to 6000 ng/mL) and FK506 (2000 ng/mL) inhibited up-regulation of C3 mRNA, but CsA and FK506 had less of an effect than triptolide. Secondly, triptolide (4 to 8 ng/mL) completely inhibited C3 expression at both mRNA and protein levels. In contrast, CsA and FK506 had only slight effects on C3 expression at the protein level. Thirdly, triptolide (4 to 8 ng/mL), CsA (500 to 2500 ng/mL) and FK506 (1250 ng/mL) inhibited up-regulation of CD40 and B7h mRNA, the effect on B7h and CD40 mRNA expression by CsA and FK506 being greater than that on C3 mRNA expression. CONCLUSION: Triptolide effectively inhibited up-regulation of C3, CD40 and B7h on PTEC. Triptolide was more effective than CsA and FK506 at inhibiting C3 expression. This suggests that triptolide, at non-cytotoxic concentrations, has the potential to reduce the inflammatory and immunostimulatory properties of PTEC, in addition to any of the previously reported actions on T cell or B cell function.

Anti-Inflammatory Agents, Non-Steroidal↗