Louis Huang

Aldosterone Induces Kidney Fibroblast Proliferation via Activation of Growth Factor Receptors and PI3K/MAPK Signalling

Background/Aims: The mineralocorticoid hormone, aldosterone, has pro-fibrotic properties which can cause kidney damage. The severity of kidney interstitial fibrosis is dependent on the accumulation of fibroblasts, which result largely from local proliferation; however, it is unknown whether aldosterone stimulates kidney fibroblast proliferation. Therefore, we examined the effects of aldosterone on the proliferation of cultured kidney fibroblasts. Methods: Uptake of 3H-thymidine and cell number quantitation were used to determine the proliferative effects of aldosterone on a rat kidney fibroblast cell line (NRK49F cells) and interstitial fibroblasts extracted from mouse kidneys after unilateral ureter obstruction. The role of different mitogenic signalling pathways in aldosterone-induced proliferation was assessed using specific inhibitors of receptors and kinases. Results: Physiological levels of aldosterone induced a doubling of proliferation of kidney fibroblasts (p < 0.0001), which was inhibited by pre-treatment with the mineralocorticoid receptor antagonist, eplerenone. Aldosterone-induced fibroblast proliferation was dependent upon the kinase activity of growth factor receptors [platelet-derived growth factor receptor (PDGFR) and epidermal growth factor receptor]. Notably, PDGF ligands were not involved in aldosterone-induced PDGFR activation, indicating receptor transactivation. Aldosterone-induced fibroblast proliferation also required signalling via PI3K, JNK and ERK pathways, but not via the transforming growth factor-β1 receptor. Conclusion: Aldosterone ligation of the mineralocorticoid receptor in kidney fibroblasts results in rapid activation of growth factor receptors and induction of PI3K/MAPK signalling, which stimulates proliferation. This suggests that increased levels of aldosterone during disease may promote the severity of kidney fibrosis by inducing fibroblast proliferation.

Review: Membranes for haemodialysis

Haemodialysis, by design, uses a semipermeable membrane to separate blood from dialysate. The qualities of this membrane determine the nature of the ‘traffic’ between the blood and dialysate. In this sense, the qualities of the membrane determine what size molecules move from one compartment to the other, the amount and rate at which they might move and the amount and rate of water movement across the membrane. In addition, the nature of the membrane influences the biological response of the patient both in terms of what is or is not removed by the dialysis process and by way of the reaction to the biocompatibility of the membrane. This brief review will explore aspects of dialysis membrane characteristics.

Slow and steady. Reducing thrombotic events in renal transplant recipients treated with IVIg for antibody-mediated rejection.

Intravenous immunoglobulin (IVIg) therapy for antibody‐mediated rejection (AMR) is increasing and is associated with a small but significant incidence of thrombosis. We determined thrombosis rates in patients treated with high‐dose IVIg for AMR before and after alteration of an infusion protocol. The newer protocol introduced routine administration of aspirin 300 mg, enoxaparin 1 mg/kg, intravenous hydration and a maximum infusion rate of 100 mg/kg per hour (previously 200 mg/kg per hour). Nine thromboses in 275 infusions occurred before the protocol alteration (event rate 3.3%). Two were arterial thromboses including an acute myocardial infarct and a renal transplant artery thrombosis, which resulted in infarction of 2/3 of the graft. Seven venous thromboses occurred, six in arteriovenous fistulae and one case with bilateral above knee deep venous thromboses. Significant associations with thromboses were seen with higher IVIg dose and male sex. In the 6 months since the introduction of the new infusion protocol, 74 infusions have been administered with no thrombotic events. There have been no significant bleeding or fluid overload side‐effects. Infusion times, however, have been doubled. A slower rate of infusion combined with antiplatelet and anticoagulation has thus far eliminated the small but significant IVIg‐related thrombosis rate previously observed in our patients treated for AMR without resulting in significant side‐effects. Further study is now required to define which elements of this protocol are essential.

Myeloid Mineralocorticoid Receptor Activation Contributes to Progressive Kidney Disease

Clinical and experimental studies have shown that mineralocorticoid receptor (MR) antagonists substantially reduce kidney injury. However, the specific cellular targets and mechanisms by which MR antagonists protect against kidney injury must be identified. We used conditional gene deletion of MR signaling in myeloid cells (MR(flox/flox) LysM(Cre) mice; MyMRKO) or podocytes (MR(flox/flox) Pod(Cre) mice; PodMRKO) to establish the role of MR in these cell types in the development of mouse GN. Accelerated anti-glomerular basement membrane GN was examined in groups of mice: MyMRKO, PodMRKO, wild-type (WT) littermates, and WT mice receiving eplerenone (100 mg/kg twice a day; EPL-treated). At day 15 of disease, WT mice had glomerular crescents (37%±5%), severe proteinuria, and a 6-fold increase in serum cystatin-C. MyMRKO, PodMRKO, and EPL-treated mice with GN displayed proteinuria similar to that in these disease controls. However, MyMRKO and EPL-treated groups had a 35% reduction in serum cystatin-C levels and reduced crescent numbers compared with WT mice, whereas PodMRKO mice were not protected. The protection observed in MyMRKO mice appeared to result predominantly from reduced recruitment of macrophages and neutrophils into the inflamed kidney. Suppression of kidney leukocyte accumulation in MyMRKO mice correlated with reductions in gene expression of proinflammatory molecules (TNF-α, inducible nitric oxide synthase, chemokine (C-C motif) ligand 2, matrix metalloproteinase-12), tubular damage, and renal fibrosis and was similar in EPL-treated mice. In conclusion, MR signaling in myeloid cells, but not podocytes, contributes to the progression of renal injury in mouse GN, and myeloid deficiency of MR provides protection similar to eplerenone in this disease.

Long-term Graft Survival in Patients with Chronic Antibody Mediated Rejection with Persistent Peritubular Capillaritis Treated with Intravenous Immunoglobulin and Rituximab

Chronic antibody‐mediated rejection (cAMR) is the major cause of premature renal allograft loss and is resistant to therapy with 12‐month graft failure of up to 50% reported. We examined the duration of graft survival and associates of graft failure in patients with donor‐specific antibody‐positive cAMR and treatment‐resistant peritubular capillaritis between June 2007 and October 2010. Those with advanced interstitial fibrosis (n=5) were excluded. Included patients (n=24) received treatment with high‐dose intravenous immunoglobulin and fixed‐dose rituximab (500 mg). Compared with previous reports, the study group experienced prolonged graft survival (median 82.1 months). Graft loss was predicted by eGFR and degree of proteinuria at diagnosis but not by donor‐specific HLA antibody class or intensity, nor individual or summed Banff scores. Allograft biopsies were further examined for infiltrating leukocyte subtypes and location with high numbers of glomerular leukocytes, particularly macrophages, independently associated with an increased risk of graft failure. This study suggests that patients with cAMR and persistent microcirculatory inflammation, excluding those with advanced histological damage, can expect prolonged graft survival when treated with IVIg and rituximab. Trial level evidence is required to validate this observation. Further examination of the role of macrophages in cAMR is warranted.

Multifaceted Assessment of Health Literacy in People Receiving Dialysis: Associations With Psychological Stress and Quality of Life

Health literacy (HL) refers to a person’s ability to engage effectively with health information and services. We aimed to describe the HL of people receiving dialysis and the factors associated with it. A cross-sectional design was used, with demographic and clinical data as predictors. Participants were people receiving dialysis at a metropolitan health service in Melbourne, Australia. Health consumers with conditions not requiring dialysis were included for comparison. The Health Literacy Questionnaire, Kidney Disease Quality of Life–36, and Depression Anxiety Stress Scales–21 were administered. Participants (M age = 68.2 ± 13.7 years; n = 57 males) were 76 people receiving hemodialysis within a dialysis unit, 16 people receiving home peritoneal dialysis, and 8 people receiving home hemodialysis. Participants scored higher on the HL domains social support for health and engagement with health care providers but lower on active management of health than the comparison group (n = 813). Hierarchical cluster analysis revealed 2 clusters within the dialysis sample representing higher (n = 43) and lower (n = 57) profiles of HL. The higher HL cluster reported better quality of life across 4 of 5 domains of the Kidney Disease Quality of Life–36, fewer symptoms of depression and anxiety, and higher serum albumin (mean difference = 2.06 g/L, p = .04) than the lower HL cluster. These results show that people receiving dialysis feel better supported and informed about their health than other health consumers but are less active in managing it. Higher HL is associated with better mental health and quality of life. Identifying HL characteristics may help direct specific interventions to improve patient education and support.

Acute polyarthritis immediately after kidney transplantation: A medication-induced rheumatoid arthritis flare?

A patient with known steroid‐dependent rheumatoid arthritis (RA) developed an acute symmetrical polyarthropathy of small and medium‐sized joints associated with markedly elevated inflammatory markers suggestive of RA flare, on day 4 after deceased‐donor renal transplantation. The patient received standard induction immunosuppression with methylprednisolone and basiliximab, and had commenced prednisolone, tacrolimus and mycophenolate mofetil. Serological investigations and joint aspirate to exclude infective causes and crystal arthropathy were unremarkable. High‐dose prednisolone (50 mg daily) resulted in partial but unsustained symptomatic improvement. On suspicion of a medication‐related adverse event, tacrolimus and mycophenolate mofetil were changed to cyclosporine A and azathioprine on day 16. This was followed by rapid improvement in symptoms and normalization of inflammatory markers. Unexpected sequelae in the early post‐transplantation period create diagnostic and management challenges. Medication‐related adverse events are not uncommon, and we speculate in this case on the potential for medication‐induced immune system dysregulation stimulating disease activity in a chronic autoimmune condition after introduction of new immunosuppressants.

Non-Touch Aseptic Technique Maintains Sterility of Antibiotic-Admixed Peritoneal Dialysis Fluid

There is a paucity of data on the sterility of peritoneal dialysis fluid (PDF) after drug admixture. International Society for Peritoneal Dialysis (ISPD) guidelines suggest using sterile technique when admixing antibiotics; however, the degree of sterility remains unclear. This issue is most pertinent when preparing take-home PDF for outpatient treatment of peritonitis. This study compares the sterility of PDF admixed with antibiotics using a non-touch aseptic technique (NTAT) versus sterile technique. Groups of 8 PDF mixtures (1.5% Dianeal or Icodextrin [Baxter International Inc., Spring Grove, IL, USA]) were admixed with 1 g/L ceftazidime and vancomycin, or 20 mL saline, either by a pharmacist using sterile technique in a sterile suite, or a nurse in a clinical room using NTAT. Dianeal inoculated with 1 × 106 colony-forming units (CFU)/L of coagulase-negative Staphylococcus (CNS), with and without antibiotics, served as positive controls. Admixed PDFs were left at room temperature for 72 hours, then cultured using the BacT/ALERT system. A positive culture by day 5 constituted a contamination. Differences in proportion of contamination between groups were assessed using the Chi-squared test. Eighty PDF bags underwent microbiological testing. Sterility was maintained in all bags, independent of technique (NTAT versus sterile technique), type of PDF (Dianeal versus Icodextrin), or whether antibiotics were admixed. Of the positive controls, CNS-inoculated PDFs without antibiotics were all culture positive; however, when inoculated into antibiotic-admixed PDFs, only S. haemolyticus remained culture-positive (p < 0.0001). In conclusion, PDF sterility can be maintained using NTAT for up to 3 days at room temperature. Currently, there is insufficient evidence to adopt sterile technique in sterile suites when admixing take-home PDF.

CALCIPROTEIN PARTICLE FORMATION IN PERITONEAL DIALYSIS EFFLUENT IS DEPENDENT ON DIALYSATE CALCIUM CONCENTRATION

Background: The accumulation of fetuin-A-containing calciprotein particles (CPP) in the serum of patients with renal disease and those with chronic inflammation may be involved in driving sterile inflammation and extraosseous mineral deposition. We previously showed that both fetuin-A and CPP were present in the peritoneal dialysis (PD) effluent of stable PD patients. It is unknown whether different PD fluids might affect the formation of CPP in vivo. Method: Peritoneal effluent from 12 patients was collected after a 6-hour dwell with 7 different commercial PD fluids. Calciprotein particles and inflammatory cytokines were measured by flow cytometry. Results: High inter-subject variability in CPP concentration was observed. Peritoneal dialysis fluids containing 1.75 mmol/L calcium were associated with enhanced formation of CPP in vivo, compared with fluids containing 1.25 mmol/L calcium. Osmotic agent, fluid pH, and glucose concentration did not affect CPP formation. Peritoneal dialysis effluent CPP levels were not associated with changes in inflammatory cytokines. Conclusion: High calcium-containing PD fluids favor intraperitoneal CPP formation. This finding may have relevance for future PD fluid design.

PRACTICE OF PERITONEAL DIALYSIS CATHETER FLUSHING IN AUSTRALIA AND NEW ZEALAND: MULTI-CENTER CROSS-SECTIONAL SURVEY

Background: Evidence of effective interventions to prevent peritoneal dialysis (PD) catheter malfunction before first use is presently insufficient to guide clinical care. Regular flushing of the PD catheter (e.g. before PD commencement) has been adopted by some practitioners in the belief that it will prevent catheter obstruction and/or malfunction. The aim of this study was to characterize and evaluate PD catheter flushing practices across Australian and New Zealand PD units. Methods: An on-line survey was distributed to all 62 PD units in Australia (12 August 2016; n = 51) and New Zealand (2 February 2017; n = 11), with questions relating to PD catheter flushing practices, audit, and outcomes. Results: Forty-nine units of variable size (< 16 to > 100 patients) completed the survey (79% response rate). All centers flushed PD catheters at some stage after insertion as routine unit practice. Forty-one units (84%) routinely flushed during periods of PD rest at varying intervals ranging from alternate daily to monthly. The type and volume of solution used to flush varied between units. Units that practised routine flushing of PD catheters were almost twice as likely to audit their catheter-related outcomes (66% vs 38%, p = 0.23) and more likely to have reported blocked catheters in the preceding 12 months (84% vs 0%, p = 0.01) compared with those units that did not routinely flush PD catheters. Thirty units (61%) regularly audited and monitored catheter-related outcomes. Conclusions: This study identified a wide variation in center practices relating to PD catheter flushing. Drawing conclusions about any relationship between flushing practices and clinical outcomes was impeded by the relatively low uptake of regular auditing and monitoring of catheter-related outcomes across surveyed units. Evaluation of the benefits and harms of standardized PD catheter flushing practices on patient outcomes in a randomized trial is needed to guide practice.