Role of the hemodialysis vascular access type in inflammation status and monocyte activation

What is the role of the neutrophil extracellular traps in the cardiovascular disease burden associated with hemodialysis bioincompatibility?

Despite significant progress in dialysis modalities, intermittent renal replacement therapy remains an "unphysiological" treatment that imperfectly corrects uremic disorders and may lead to low-grade chronic inflammation, neutrophil activation, and oxidative stress due to repetitive blood/membrane interactions contributing to the "remaining uremic syndrome" and cardiovascular disease burden of hemodialysis patients. Understanding dialysis bioincompatibility pathways still remains a clinical and biochemical challenge. Indeed, surrogate biomarkers of inflammation including C-reactive protein could not discriminate between all components involved in these complex pathways. A few examples may serve to illustrate the case. Cytokine release during dialysis sessions may be underestimated due to their removal using high-flux dialysis or hemodiafiltration modalities. Complement activation is recognized as a key event of bioincompatibility. However, it appears as an early and transient event with anaphylatoxin level normalization at the end of the dialysis session. Complement activation is generally assumed to trigger leukocyte stimulation leading to proinflammatory mediators' secretion and oxidative burst. In addition to being part of the innate immune response involved in eliminating physically and enzymatically microbes, the formation of Neutrophil Extracellular Traps (NETs), known as NETosis, has been recently identified as a major harmful component in a wide range of pathologies associated with inflammatory processes. NETs result from the neutrophil degranulation induced by reactive oxygen species overproduction via NADPH oxidase and consist of modified chromatin decorated with serine proteases, elastase, bactericidal proteins, and myeloperoxidase (MPO) that produces hypochlorite anion. Currently, NETosis remains poorly investigated as a sensitive and integrated marker of bioincompatibility in dialysis. Only scarce data could be found in the literature. Oxidative burst and NADPH oxidase activation are well-known events in the bioincompatibility phenomenon. NET byproducts such as elastase, MPO, and circulating DNA have been reported to be increased in dialysis patients more specifically during dialysis sessions, and were identified as predictors of poor outcomes. As NETs and MPO could be taken up by endothelium, NETs could be considered as a vascular memory of intermittent bioincompatibility phenomenon. In this working hypothesis article, we summarized the puzzle pieces showing the involvement of NET formation during hemodialysis and postulated that NETosis may act as a disease modifier and may contribute to the comorbid burden associated with dialysis bioincompatibility.

Oxidative stress: An essential factor in the process of arteriovenous fistula failure

For more than half a century, arteriovenous fistula (AVFs) has been recognized as a lifeline for patients requiring hemodialysis (HD). With its higher long-term patency rate and lower probability of complications, AVF is strongly recommended by guidelines in different areas as the first choice for vascular access for HD patients, and its proportion of application is gradually increasing. Despite technological improvements and advances in the standards of postoperative care, many deficiencies are still encountered in the use of AVF related to its high incidence of failure due to unsuccessful maturation to adequately support HD and the development of neointimal hyperplasia (NIH), which narrows the AVF lumen. AVF failure is linked to the activation and migration of vascular cells and the remodeling of the extracellular matrix, where complex interactions between cytokines, adhesion molecules, and inflammatory mediators lead to poor adaptive remodeling. Oxidative stress also plays a vital role in AVF failure, and a growing amount of data suggest a link between AVF failure and oxidative stress. In this review, we summarize the present understanding of the pathophysiology of AVF failure. Furthermore, we focus on the relation between oxidative stress and AVF dysfunction. Finally, we discuss potential therapies for addressing AVF failure based on targeting oxidative stress.

Vitamin B12 and chronic kidney disease

Chronic Kidney Disease (CKD) is an emerging public health issue with a fast-growing global prevalence. Impairment in vitamin B12 metabolism is considered a nontraditional risk factor of poor outcomes associated with CKD, and there is greater interest from the scientific community than ever before to explore the role and influence of vitamin B12 in CKD. Homocysteine metabolism forms an important component of the vitamin B12 metabolic pathway. Hyperhomocysteinemia is frequently observed in CKD and End-Stage Kidney Disease (ESKD), but its representation as a prognostic marker for CKD outcomes is still not fully clear. This chapter reviews the vitamin B12 and homocysteine metabolic pathways and their dysfunction in CKD states. Biochemical factors and the MTHFR genetic polymorphisms which disrupt vitamin B12 and homocysteine metabolism are explored. The mechanisms of homocysteine-mediated and vitamin B12-mediated tissue damage in CKD are discussed. This chapter reviews current perspective on definition and measurement of plasma vitamin B12 levels in the CKD population. Updated evidence investigating the prognostic role of vitamin B12 for CKD outcomes is presented. Findings from major clinical trials conducted relating to outcomes from multivitamin (including folic acid and vitamin B12) supplementation in nondialysis and dialysis-dependent CKD are highlighted. The prognostic value of vitamin B12 and effects of vitamin B12 supplementation in the context of kidney transplantation and acute kidney injury is also reviewed. Future research considerations are summarized based on evidence gaps in our knowledge base of this topic. Greater abundance of high-level evidence to guide an approach toward vitamin B12 measurement, monitoring and supplementation in CKD may contribute to improved clinical outcomes.

Influence of Tunneled Hemodialysis-Catheters on Inflammation and Mortality in Dialyzed Patients

Older age and comorbidities in hemodialysis patients determines the use of tunneled catheters as vascular access despite their reported clinical and mortality disadvantages. This prospective matched study analyzes the impact of permanent catheters on inflammation and mortality in hemodialysis patients; We studied 108 patients, 54 with AV-fistula (AVF) and 54 with indwelling hemodialysis catheters (HDC) matched by sex, age, diabetes and time under renal-replacement therapy comparing dialysis efficacy, inflammation and micro-inflammation parameters as well as mortality. Cox-regression analysis was applied to determine predictors of mortality, HDC patients presented higher C-reactive-protein (CRP) blood levels and percentage of pro-inflammatory lymphocytes CD14+/CD16+ with worse dialysis-efficacy parameters. Thirty-six-months mortality appeared higher in the HDC group although statistical significance was not reached. Age with a Hazard Ratio (HR) = 1.06, hypoalbuminemia (HR = 0.43), hypophosphatemia (HR = 0.75) and the increase in CD14+/CD16+ monocyte count (HR = 1.02) were predictors of mortality; elder patients dialyzing through HDC show increased inflammation parameters as compared with nAVF bearing patients, although they do not present a significant increase in mortality when matched by covariates. Increasing age and percentage of pro-inflammatory monocytes as well as decreased phosphate and serum-albumin were predictors of mortality and indicate the main conclusions or interpretations.

Intravenous Iron Replacement Therapy Improves Cardiovascular Outcomes in Hemodialysis Patients

BACKGROUND/AIM

More than half of deaths among hemodialysis patients are due to cardiovascular disease. This study examined whether intravenous administration of ferric carboxymaltose (FCM) has an impact on cardiovascular events in iron-deficient hemodialysis patients.

PATIENTS AND METHODS

We performed a retrospective study concerning patients undergoing hemodialysis in our center from September 2016 to December 2019. We identified those who began FCM therapy (FCM group) during this period and those who did not (control group). We analyzed clinical, echocardiographic and laboratory parameters at the beginning (t0) and after one year (t1), to detect differences between the two groups.

RESULTS

We identified 53 patients for the FCM group and 19 for the control group. Median follow-up was 1 year±3 months for both groups. In the FCM group, we observed a reduction in the doses of erythropoiesis-stimulating agents (ESA) (p<0.001) and a significative difference in cardiovascular events (p<0.01), but no differences in echocardiographic parameters.

CONCLUSION

Patients who received FCM reached satisfactory values of transferrin saturation and ferritin, presented fewer coronary artery events and cardiovascular events, and could reduce doses of ESA.

Toxin Removal and Inflammatory State Modulation during Online Hemodiafiltration Using Two Different Dialyzers (TRIAD2 Study)

Uremic toxins play a pathological role in atherosclerosis and represent an important risk factor in dialysis patients. Online hemodiafiltration (HDF) has been introduced to improve the clearance of middle- and large-molecular-weight solutes (>500 Da) and has been associated with reduced cardiovascular mortality compared to standard hemodialysis. This non-randomized, open-label observational study will explore the efficacy of two dialyzers currently used for online HDF, a polysulfone-based high-flux membrane, and a cellulose triacetate membrane, in hemodialysis patients with signs of middle-molecule intoxication or intradialytic hypotension. In particular, the two filters will be evaluated for their ability in uremic toxin removal and modulation of inflammatory status. Sixteen subjects in standard chronic bicarbonate hemodialysis requiring a switch to online HDF in view of their clinical status will be enrolled and divided into two treatment arms, according to the previous history of hypersensitivity to polysulfone/polyethersulfone dialysis filters and hypersensitivity to drugs or other allergens. Group A will consist of 16 patients without a previous history of hypersensitivity and will be treated with a polysulfone filter (Helixone FX100), and group B, also consisting of 16 patients, with a previous history of hypersensitivity and will be treated with asymmetric triacetate (ATA; SOLACEA 21-H) dialyzer. Each patient will be followed for a period of 24 months, with monthly assessments of circulating middle-weight toxins and protein-bound toxins, markers of inflammation and oxidative stress, lymphocyte subsets, activated lymphocytes, and monocytes, cell apoptosis, the accumulation of advanced glycation end-products (AGEs), variations in arterial stiffens measured by pulse wave velocity (PWV), and mortality rate. The in vitro effect on endothelial cells of uremic serum collected from patients treated with the two different dialyzers will also be investigated to examine the changes in angiogenesis, cell migration, differentiation, apoptosis and proliferative potential, and gene and protein expression profile. The expected results will be a better awareness of the different effects of polysulfone gold-standard membrane for online HDF and the new ATA membrane on the removal of uremic toxins removal and inflammation due to blood-membrane interaction.

Monocytes in Uremia

Monocytes play an important role in both innate immunity and antigen presentation for specific cellular immune defense. In patients with chronic renal failure, as well as those treated with maintenance hemodialysis, these cells are largely dysregulated. There is a large body of literature on monocyte alterations in such patients. However, most of the publications report on small series, there is a vast spectrum of different methods and the heterogeneity of the data prevents any meta-analytic approach. Thus, a narrative review was performed to describe the current knowledge. Monocytes from patients with chronic renal failure differ from those of healthy individuals in the pattern of surface molecule expression, cytokine and mediator production, and function. If these findings can be summarized at all, they might be subsumed as showing chronic inflammation in resting cells together with limited activation upon immunologic challenge. The picture is complicated by the fact that monocytes fall into morphologically and functionally different populations and population shifts interact heavily with dysregulation of the individual cells. Severe complications of chronic renal failure such as impaired immune defense, inflammation, and atherosclerosis can be related to several aspects of monocyte dysfunction. Therefore, this review aims to provide an overview about the impairment and activation of monocytes by uremia and the resulting clinical consequences for renal failure patients.

Association between initial dialytic modalities and the risks of mortality, infection death, and cardiovascular events: A nationwide population-based cohort study

To date, few studies have been conducted to pairwise compare the prognosis of peritoneal dialysis (PD), unplanned PD, and unplanned hemodialysis (HD). We analyzed longitudinal data from Taiwan’s National Health Insurance Research Database. We included 45,165 patients whose initial dialytic modality was PD or unplanned HD between January 1, 2001 and December 31, 2013. We divided the patients into three groups according to their initial dialytic modalities. The primary outcomes were all-cause mortality and death from infection during 1-year follow up. The risks of all-cause mortality and infection death were higher in the unplanned PD group than in the planned PD group (hazard ratio [HR] 1.43, 95% confidence interval [CI] 1.28–1.60; HR 1.54, 95% CI 1.32–1.80). Likewise, the risks of all-cause mortality and infection death were higher in the unplanned HD group (HR 1.64, 95% CI 1.48–1.82; HR 1.85, 95% CI 1.61–2.13). Furthermore, the risks of all-cause mortality and infection death were also higher in the unplanned HD group than in the unplanned PD group (HR 1.15, 95% CI 1.07–1.23; HR 1.20, 95% CI 1.09–1.32). In conclusion, our study demonstrates that patients whose initial modality was planned PD or unplanned PD may have better clinical outcomes than those whose initial modality was unplanned HD.

Immunological Effects of a Single Hemodialysis Treatment

Immune disorders, involving both innate and adaptive response, are common in patients with end-stage renal disease under chronic hemodialysis. Endogenous and exogenous factors, such as uremic toxins and the extracorporeal treatment itself, alter the immune balance, leading to chronic inflammation and higher risk of cardiovascular events. Several studies have previously described the immune effects of chronic hemodialysis and the possibility to modulate inflammation through more biocompatible dialyzers and innovative techniques. On the other hand, very limited data are available on the possible immunological effects of a single hemodialysis treatment. In spite of the lacking information about the immunological reactivity related to a single session, there is evidence to indicate that mediators of innate and adaptive response, above all complement cascade and T cells, are implicated in immune system modulation during hemodialysis treatment. Expanding our understanding of these modulations represents a necessary basis to develop pro-tolerogenic strategies in specific conditions, like hemodialysis in septic patients or the last session prior to kidney transplant in candidates for receiving a graft.

Folic Acid and Vitamin B12 Administration in CKD, Why Not?

Patients affected by chronic kidney disease (CKD) or end-stage renal disease (ESRD) experience a huge cardiovascular risk and cardiovascular events represent the leading causes of death. Since traditional risk factors cannot fully explain such increased cardiovascular risk, interest in non-traditional risk factors, such as hyperhomocysteinemia and folic acid and vitamin B12 metabolism impairment, is growing. Although elevated homocysteine blood levels are often seen in patients with CKD and ESRD, whether hyperhomocysteinemia represents a reliable cardiovascular and mortality risk marker or a therapeutic target in this population is still unclear. In addition, folic acid and vitamin B12 could not only be mere cofactors in the homocysteine metabolism; they may have a direct action in determining tissue damage and cardiovascular risk. The purpose of this review was to highlight homocysteine, folic acid and vitamin B12 metabolism impairment in CKD and ESRD and to summarize available evidences on hyperhomocysteinemia, folic acid and vitamin B12 as cardiovascular risk markers, therapeutic target and risk factors for CKD progression.

Folic Acid and Homocysteine in Chronic Kidney Disease and Cardiovascular Disease Progression: Which Comes First?

Background

Hyperhomocysteinemia (Hhcy) occurs in about 85% of chronic kidney disease (CKD) patients because of impaired renal metabolism and reduced renal excretion. Folic acid (FA), the synthetic form of vitamin B₉, is critical in the conversion of homocysteine (Hcy) to methionine. If there is not enough intake of FA, there is not enough conversion, and Hcy levels are raised.

Summary

Hhcy is regarded as an independent predictor of cardiovascular morbidity and mortality in end-stage renal disease. Hhcy exerts its pathogenic action on the main processes involved in the progression of vascular damage. Research has shown Hhcy suggests enhanced risks for inflammation and endothelial injury which lead to cardiovascular disease (CVD), stroke, and CKD. FA has also been shown to improve endothelial function without lowering Hcy, suggesting an alternative explanation for the effect of FA on endothelial function. Recently, the role of FA and Hhcy in CVD and in CKD progression was renewed in some randomized trials.

Key Messages

In the general population and in CKD patients, it remains a topic of discussion whether any beneficial effects of FA therapy are to be referred to its direct effect or to a reduction of Hhcy. While waiting for the results of confirmatory trials, it is reasonable to consider FA with or without methylcobalamin supplementation as appropriate adjunctive therapy in patients with CKD.

Vascular access type, inflammatory markers, and mortality in incident hemodialysis patients: the Choices for Healthy Outcomes in Caring for End-Stage Renal Disease (CHOICE) Study

BACKGROUND

Few reports have shown an association between access type and inflammatory marker levels in a longitudinal cohort. We investigated the role of access type on serial levels of inflammatory markers and the role of inflammatory markers in mediating the association of access type and risk of mortality in a prospective study of incident dialysis patients.

STUDY DESIGN

Cohort study, post hoc analysis of the CHOICE (Choices for Healthy Outcomes in Caring for ESRD) Study.

SETTING & PARTICIPANTS

In 583 participants, inflammation was assessed by measuring serum C-reactive protein (CRP) and interleukin 6 (IL-6) after access placement and at multiple times during 3 years' follow-up. Type of access was categorized as central venous catheter (CVC), arteriovenous graft (AVG), and arteriovenous fistula (AVF), and changes over time were recorded.

PREDICTOR

Access type, age, sex, race, body mass index, diabetes, cardiovascular disease, and serum albumin level.

OUTCOMES

CRP level, IL-6 level, and mortality.

MEASUREMENTS

We used mixed-effects pattern mixture models to study the association between access type and repeated measurements of inflammation and survival analysis to investigate the association of access type and mortality, adjusting for predictors.

RESULTS

In a mixed-effects pattern mixture model, compared with AVFs, the presence of CVCs and AVGs was associated with 62% (P=0.02) and 30% (P=0.05) increases in average CRP levels, respectively. A Cox proportional hazards model yielded nonsignificant associations of CVC and AVG use (vs AVFs) with risk of mortality when adjusted for inflammatory marker levels. Higher CRP levels were associated with increased risk of CVC failure than lower CRP levels.

LIMITATIONS

CRP and IL-6 measurements not performed for all hemodialysis patients.

CONCLUSIONS

CVCs, compared with AVFs, are associated with a greater state of inflammation in incident hemodialysis patients, and the association of catheter use and mortality may be mediated by access-induced inflammation. Our findings support recommendations for the early removal or avoidance of CVC placements.

The impact of inflammatory factors associated with primary arteriovenous failure

PURPOSE

Very scarce data exist regarding the relationship between differential white blood cell (WBC) counts and primary arteriovenous fistula (AVF) failure. Thus, the current study aimed to investigate the specific relationship between primary AVF failure and differential WBC counts.


METHODS

Sociodemographic, clinical, and laboratory parameters including automatically determined complete blood counts of the patients (from medical records and hospital charts) prior to AVF fistula surgery were recorded. Primary AVF failure was described as a complication of the AVF before the first successful cannulation for HD treatment.


RESULTS

In total 94 patients (Male/Female: 49/45, Aged: 50.9 ± 15.0 years) were included. Ferritin, high sensitive C-reactive protein (hs-crp), total WBC count, neutrophil count, red cell distribution width (RDW) were higher in patients with primary AVF failure compared to patients without primary AVF failure. Logistic regression analysis showed that presence of diabetes (OR = 3.654, p = 0.035), RDW (OR = 0.449, p = 0.033) and ferritin (OR = 1.097, p = 0.021) were independently related with primary AVF failure.


CONCLUSIONS

Neither total WBC counts nor WBC subtypes were related with primary AVF failure. Higher RDW and ferritin levels had a prognostic value for development of primary AVF failure.

Incidence and Prevalence of Cancer in Kidney Transplantation Waiting List Patients: An Italian Experience

Introduction

Evaluation of kidney transplant candidates is based on strict exclusion of major pathologies, such as neoplastic disease. The aim of this study is to evaluate epidemiological and clinical impact of tumor disease in an Italian renal transplant waiting list and to propose a screening schedule for neoplastic detection.

Materials and methods

We retrospectively observed data of patients enrolled on the Emilia-Romagna kidney transplant waiting list between 1st August 2008 and 31st December 2010, evaluating the different causes of getting out from the list, the histologic type and incidence of cancer and the correlation between cancer onset and clinical features. The ratio of observed to expected cancer numbers (standardized incidence ratio, SIR), was estimated.

Results

We observed 2345 patients; 1297 got out from the waiting list; 57 of them (4,4%) got out because the onset of tumor. The overall incidence rate of cancer was 1354.8 (x 100000 person-year) (1045.9 person-year in patients awaiting for first transplant(FT), 1851.5 person-year in patients awaiting for second transplant(ST)). The overall prevalence of cancer was 2,43% (2.2% in FT, 3.4% in ST) with a SIR of 1.8; In our population the prevalence of cancers related to ESKD was 52.6% with a SIR of 15.8.

Conclusion

Kidney transplant waiting list patients present a higher incidence and prevalence of cancer compared to general population; it could be important to evaluate them for ESKD related malignancies because of their high incidence.