Kate Wyburn

TLR4 activation mediates kidney ischemia/reperfusion injury

Ischemia/reperfusion injury (IRI) may activate innate immunity through the engagement of TLRs by endogenous ligands. TLR4 expressed within the kidney is a potential mediator of innate activation and inflammation. Using a mouse model of kidney IRI, we demonstrated a significant increase in TLR4 expression by tubular epithelial cells (TECs) and infiltrating leukocytes within the kidney following ischemia. TLR4 signaling through the MyD88-dependent pathway was required for the full development of kidney IRI, as both TLR4(-/-) and MyD88(-/-) mice were protected against kidney dysfunction, tubular damage, neutrophil and macrophage accumulation, and expression of proinflammatory cytokines and chemokines. In vitro, WT kidney TECs produced proinflammatory cytokines and chemokines and underwent apoptosis after ischemia. These effects were attenuated in TLR4(-/-) and MyD88(-/-) TECs. In addition, we demonstrated upregulation of the endogenous ligands high-mobility group box 1 (HMGB1), hyaluronan, and biglycan, providing circumstantial evidence that one or more of these ligands may be the source of TLR4 activation. To determine the relative contribution of TLR4 expression by parenchymal cells or leukocytes to kidney damage during IRI, we generated chimeric mice. TLR4(-/-) mice engrafted with WT hematopoietic cells had significantly lower serum creatinine and less tubular damage than WT mice reconstituted with TLR4(-/-) BM, suggesting that TLR4 signaling in intrinsic kidney cells plays the dominant role in mediating kidney damage.

HMGB1 Contributes to Kidney Ischemia Reperfusion Injury

High-mobility group box 1 (HMGB1), a nuclear factor released extracellularly as an inflammatory cytokine, is an endogenous ligand for Toll-like receptor 4 (TLR4). TLR4 activation mediates kidney ischemia-reperfusion injury (IRI), but whether HMGB1 contributes to IRI is unknown. Here, treating wild-type mice with neutralizing anti-HMGB1 antibody protected them against kidney IRI, evidenced by lower serum creatinine and less tubular damage than untreated mice. Mice treated with anti-HMGB1 had significantly less tubulointerstitial infiltration by neutrophils (day 1) and macrophages (day 5) and markedly reduced apoptosis of tubular epithelial cells. Furthermore, anti-HMGB1 antibody-treated IRI kidneys had significantly lower levels of IL-6, TNFα, and monocyte chemoattractant protein 1 (MCP1). mRNA, which are downstream of HMGB1. Conversely, administration of rHMGB1 after reperfusion exacerbated kidney IRI in wild-type mice. TLR4 deficient (TLR4(-/-)) mice were protected against kidney IRI; administration of neither anti-HMGB1 antibody nor rHMGB1 affected this renoprotection. In conclusion, endogenous HMGB1 promotes kidney damage after IRI, possibly through the TLR4 pathway. Administration of a neutralizing antibody to HMGB1 either before or soon after ischemia-reperfusion affords significant protection, suggesting therapeutic potential for acute kidney injury.

The role of macrophages in allograft rejection.

Macrophage accumulation has long been recognized as a feature of allograft rejection, yet the role of macrophages in rejection remains underappreciated. Macrophages contribute to both the innate and acquired arms of the alloimmune response and thus may be involved in all aspects of acute and chronic allograft rejection. Recent advances in macrophage biology have allowed a better understanding of the mechanisms of macrophage accumulation, their state of activation and the pleuripotent roles they play in allograft rejection. Therapeutic attention to macrophages, in addition to T lymphocytes, may lead to improved outcomes in organ transplantation.

IL-18 Contributes to Renal Damage after Ischemia-Reperfusion

IL-18 is a proinflammatory cytokine produced by macrophages and other cell types present in the kidney during ischemia-reperfusion injury (IRI), but its role in this injury is unknown. Here, compared with wild-type mice, IL-18(-/-) mice subjected to kidney IRI demonstrated better kidney function, less tubular damage, reduced accumulation of neutrophils and macrophages, and decreased expression of proinflammatory molecules that are downstream of IL-18. For determination of the relative contributions of leukocytes and parenchymal cells to IL-18 production and subsequent kidney damage during IRI, bone marrow-chimeric mice were generated. Wild-type mice engrafted with IL-18(-/-) hemopoietic cells showed less kidney dysfunction and tubular damage than IL-18(-/-) mice engrafted with wild-type bone marrow. In vitro, macrophages produced IL-18 mRNA and protein in response to ischemia. These data suggest bone marrow-derived cells are the key contributors to IL-18-mediated effects of renal IRI. Finally, similar to IL-18(-/-) mice, pretreatment of wild-type mice with IL-18-binding protein was renoprotective in this model of IRI. In conclusion, IL-18, derived primarily from cells of bone marrow origin, contributes to the renal damage observed during IRI. IL-18-binding protein may have potential as a renoprotective therapy.

KHA‐CARI guideline: KHA‐CARI adaptation of the KDIGO Clinical Practice Guideline for the Care of Kidney Transplant Recipients

The latest Caring for Australians with Renal Impairment (CARI) guideline detailing renal transplant care, developed as a local modification of the Kidney Disease Improving Global Outcomes (KDIGO) guidelines.

Interleukin-18 affects local cytokine expression but does not impact on the development of kidney allograft rejection.

Interleukin‐18 is predominantly a macrophage‐derived cytokine with a key role in inflammation and cell‐mediated immunity. Having previously demonstrated IL‐18 upregulation in a rat model of kidney rejection, here we examined IL‐18 in a fully MHC‐mismatched murine model of acute kidney rejection using IL‐18‐deficient recipients (IL‐18−/−) and animals administered neutralizing IL‐18 binding protein (IL‐18BP). Gene expression of IL‐18 and its receptor were significantly upregulated in allografts compared to isografts, as was the cellular infiltrate (T cells and macrophages) (p < 0.001). Allografts developed kidney dysfunction (p < 0.05) and tubulitis (p < 0.01) not observed in controls. There was a significant reduction in gene expression of IL‐18 downstream pro‐inflammatory molecules (iNOS, TNFα and IFNγ) in IL‐18−/− recipients (p < 0.01), and IL‐18BP‐treated animals. The CD4+ infiltrate and IL‐4 mRNA expression was greater in the IL‐18−/− recipients than wild‐type (WT) allografts and IL‐18BP‐treated animals (p < 0.05), suggesting a Th2‐bias which was supported by IFNγ and IL‐4 ELISPOT data and an increased eosinophil accumulation (p < 0.001). Neither IL‐18 deficiency nor neutralization prevented renal dysfunction or tubulitis. This study demonstrates increased production of IL‐18 in murine kidney allograft rejection and provides evidence that IL‐18‐induced pathways of inflammation are active. However, neither IL‐18 deficiency nor neutralization was protective against the development of allograft rejection.

Photopheresis therapy for problematic renal allograft rejection.

Background: Photopheresis is an immunomodulatory therapy for the treatment of T cell‐mediated disorders. It has been used for rejection prophylaxis in cardiac transplantation, adjuvant treatment of bronchiolitis obliterans in lung transplantation, treatment of graft verse host disease, and in a small number of cases, for treatment of acute rejection in renal transplantation. Little is known of long‐term outcomes following the use of photopheresis in solid organ transplantation. Methods: We report prospective follow‐up of our consecutive experience of the use of photopheresis as adjuvant/salvage therapy for problematic rejection in patients undergoing renal transplantation. Transplant graft survival, infective and malignant outcomes were reported. Results: A cohort of 10 renal transplants recipients received photopheresis therapy for therapy‐resistant rejection. Conventional therapy included an average of 6.2 g pulse methyl‐prednisolone and 17.1 days antilymphocyte therapy. The cohort received additional photopheresis therapy when the unresponsive nature of their rejections raised concerns of graft loss. Median follow‐up censored for patient loss was 66.7 months following photopheresis commencement. Rejection resolved in association with photopheresis use in all 10 patients. Six patients continued to have stable graft function (median serum creatinine: 191.5 μmol/L) at a median follow‐up of 71.0 months. There has been one patient death from sepsis and two from malignancy with functioning grafts while one graft has been lost to disease recurrence. Conclusion: Photopheresis may have a role as an adjuvant or salvage antirejection therapy in solid organ transplantation. Furthermore, evaluation in randomized controlled clinical trials is required to evaluate its potential. J. Clin. Apheresis, 2009.

Preconditioning Therapy in ABO-Incompatible Living Kidney Transplantation: A Systematic Review and Meta-Analysis.

Background ABO-incompatible (ABOi) kidney transplantation is now an established form of renal replacement therapy, but the efficacy and safety of the different types of preconditioning therapies are unclear. We aimed to synthesize the totality of the published evidence about the effects of any form of preconditioning therapies in living donor ABOi kidney transplantation on graft and patient outcomes. Methods We searched MEDLINE, Embase, and Clinicaltrial.gov databases (inception through June 2015) to identify all studies that described the outcomes of adult living donor ABOi kidney transplantations using any form of preconditioning therapies. Two independent reviewers identified studies, extracted data, and assessed the risk of bias. Data were summarized using the random effects model, and heterogeneity was explored using subgroup analyses. We assessed confidence in the evidence using the Grading of Recommendations Assessment, Development, and Evaluation framework. Results Eighty-three studies (54 case reports and case series, 25 cohort, 2 case-control, and 2 registry studies) involving 4810 ABOi transplant recipients were identified. Overall, confidence in the available evidence was low. During a mean follow-up time of 28 (standard deviation [SD], 26.6) months, the overall graft survival for recipients who received immunoadsorption or apheresis was 94.1% (95% confidence interval [95%CI], 88.2%-97.1%) and 88.0% (95% CI, 82.6%-91.8%), respectively. For those who received rituximab or underwent splenectomy, the overall graft survival was 94.5% (95% CI, 91.6%-96.5%) and 79.7% (95% CI, 72.9%-85.1%), respectively. Data on other longer-term outcomes, including malignancy, were sparse. Conclusions Rituximab or immunoadsorption appeared to be promising preconditioning strategies before ABOi kidney transplantation. However, the overall quality of evidence and the confidence in the observed treatment effects are low. The increased use of ABOi kidney transplantation needs to be matched with randomized trials of different types, dosing, and frequency of preconditioning therapies so that this scarce resource can be used most effectively and efficiently.

Peritoneal dialysis in pregnancy: A case series

SUMMARY:  Patients with significant renal impairment have difficulties maintaining a viable pregnancy due to maternal and fetal complications. Both peritoneal dialysis and hemodialysis support throughout pregnancy has been reported to assist in these pregnancies. We report our experience with the use of peritoneal dialysis in five cases leading to successful deliveries with minimal complications.

Sirolimus reduces vasculopathy but exacerbates proteinuria in association with inhibition of VEGF and VEGFR in a rat kidney model of chronic allograft dysfunction

BACKGROUND Use of the mTOR inhibitor (mTORi) sirolimus to replace calcineurin inhibitors in kidney transplantation has been associated with improved renal function but, in a proportion of cases, also with de novo or exacerbated proteinuria. Experimental deficiency of vascular endothelial growth factor (VEGF) induces proteinuria and mTOR is required for VEGF production and signalling. We therefore explored the impact of sirolimus on the development of chronic allograft dysfunction (CAD) in the rat, with a focus on VEGF biology. METHODS Lewis rats received F344 kidney allografts and were treated with 24 weeks of cyclosporine or sirolimus. Controls included allografts treated with cyclosporine for 10 days only and isografts treated with cyclosporine or sirolimus for 24 weeks. Kidney injury (proteinuria and histology) and expression of VEGF and VEGF-receptor (VEGFR; immunohistochemistry, laser capture micro-dissection and quantitative RT-PCR) were assessed. RESULTS Allograft controls developed proteinuria, tubulointerstitial fibrosis and atrophy, glomerulosclerosis, vasculopathy and leucocyte accumulation. Proteinuria was significantly reduced in both treatment groups but significantly more in cyclosporine treated animals. Tubulointerstitial damage, glomerulosclerosis and leucocyte accumulation were significantly attenuated in both treatment groups; however, vasculopathy was reduced only by sirolimus. Significantly diminished expression of VEGF and VEGFR mRNA and protein was evident in the sirolimus group. In vitro, sirolimus reduced VEGF production by podocytes (P < 0.05) and inhibited VEGF-induced proliferation of podocytes, endothelial and mesangial cells. CONCLUSIONS Cyclosporine and sirolimus retard development of CAD in this rat model. Sirolimus exhibits greater protection against vasculopathy but induces proteinuria; effects are likely to be related to inhibition of VEGF signalling.