Microinflammation in hemodialysis is related to a preactivated subset of monocytes

Premature Aging in Chronic Kidney Disease: The Outcome of Persistent Inflammation beyond the Bounds

Over the last hundred years, life expectancy in developed countries has increased because of healthier living habits and the treatment of chronic pathologies causing premature aging. Aging is an inexorable, time-dependent, multifactorial process characterized by a series of progressive and irreversible physiological changes associated with loss of functional, psychological, and social capabilities. Numerous factors, such as oxidative stress, inflammation, and cellular senescence, and an irreversible geriatric syndrome known as frailty, contribute to human body deterioration in aging. The speed of aging may differ between individuals depending on the presence or absence of multiple factors (genetic and/or environment) and the subsequent misbalance of homeostasis, together with the increase of frailty, which also plays a key role in developing chronic diseases. In addition, pathological circumstances have been reported to precipitate or accelerate the aging process. This review investigated the mechanisms involved in the developing pathologies, particularly chronic kidney disease, associated with aging.

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.

Interleukin 6 is a better predictor of 5-year cardiovascular mortality than high-sensitivity C-reactive protein in hemodialysis patients using reused low-flux dialyzers

PURPOSE

In this study, we focused on the role of elevated serum interleukin 6 (IL-6) concentration in predicting 5-year cardiovascular mortality in hemodialysis patients using low-flux dialyzer reuse.

MATERIALS AND METHODS

We measured serum IL-6 concentrations in 236 hemodialysis patients (138 males and 98 females) to predict 5-year cardiovascular mortality. We assessed the baseline demographics of all patients who had a mean age of 44 years and a median hemodialysis duration of 38.5 months. We divided all patients into two equal groups based on the serum IL-6 concentration: G1 (n = 118) with serum IL-6 concentration < 6.78 pg/L and G2 (n = 118) with serum IL-6 concentration ≥ 6.78 pg/L.

RESULTS

After the 5-year follow-up, 45 patients died due to cardiovascular causes (19.1%). Lipid disorder, hemoglobin, serum albumin, β2-M, and IL-6 concentration were independent risk factors for predicting cardiovascular mortality during the 60-month follow-up in hemodialysis patients. Based on the Kaplan-Meier analysis, we realized that patients with a higher interleukin 6 concentration (G2) had a significantly higher cardiovascular mortality rate than patients in G1 (log-rank test p < 0.001). Serum IL-6 concentration was a better predictor of 5-year cardiovascular mortality than high-sensitivity C-reactive protein in hemodialysis patients using low-flux dialyzer reuse (AUC = 0.818; p < 0.001; cut-off value: 8.055 pg/mL, Se = 77.8%, Sp = 78.5%).

CONCLUSION

Serum IL-6 concentration was a better predictor of 5-year cardiovascular mortality than high-sensitivity C-reactive protein in maintenance hemodialysis patients using low-flux dialysis reuse.

Mechanisms of Cardiovascular Disorders in Patients With Chronic Kidney Disease: A Process Related to Accelerated Senescence

Cardiovascular diseases (CVDs), especially those involving a systemic inflammatory process such as atherosclerosis, remain the leading cause of morbidity and mortality in patients with chronic kidney disease (CKD). CKD is a systemic condition affecting approximately 10% of the general population. The prevalence of CKD has increased over the past decades because of the aging of the population worldwide. Indeed, CVDs in patients with CKD constitute a premature form of CVD observed in the general population. Multiple studies indicate that patients with renal disease undergo accelerated aging, which precipitates the appearance of pathologies, including CVDs, usually associated with advanced age. In this review, we discuss several aspects that characterize CKD-associated CVDs, such as etiopathogenic elements that CKD patients share with the general population, changes in the cellular balance of reactive oxygen species (ROS), and the associated process of cellular senescence. Uremia-associated aging is linked with numerous changes at the cellular and molecular level. These changes are similar to those observed in the normal process of physiologic aging. We also discuss new perspectives in the study of CKD-associated CVDs and epigenetic alterations in intercellular signaling, mediated by microRNAs and/or extracellular vesicles (EVs), which promote vascular damage and subsequent development of CVD. Understanding the processes and factors involved in accelerated senescence and other abnormal intercellular signaling will identify new therapeutic targets and lead to improved methods of diagnosis and monitoring for patients with CKD-associated CVDs.

Inflammatory Macrophage Expansion in Pulmonary Hypertension Depends upon Mobilization of Blood-Borne Monocytes

Pulmonary inflammation, which is characterized by the presence of perivascular macrophages, has been proposed as a key pathogenic driver of pulmonary hypertension (PH), a vascular disease with increasing global significance. However, the mechanisms of expansion of lung macrophages and the role of blood-borne monocytes in PH are poorly understood. Using multicolor flow cytometric analysis of blood in mouse and rat models of PH and patients with PH, an increase in blood monocytes was observed. In parallel, lung tissue displayed increased chemokine transcript expression, including those responsible for monocyte recruitment, such as Ccl2 and Cx₃cl1, accompanied by an expansion of interstitial lung macrophages. These data indicate that blood monocytes are recruited to lung perivascular spaces and differentiate into inflammatory macrophages. Correspondingly, parabiosis between congenically different hypoxic mice demonstrated that most interstitial macrophages originated from blood monocytes. To define the actions of these cells in PH in vivo, we reduced blood monocyte numbers via genetic deficiency of cx₃cr1 or ccr2 in chronically hypoxic male mice and by pharmacologic inhibition of Cx₃cl1 in monocrotaline-exposed rats. Both models exhibited decreased inflammatory blood monocytes, as well as interstitial macrophages, leading to a substantial decrease in arteriolar remodeling but with a less robust hemodynamic effect. This study defines a direct mechanism by which interstitial macrophages expand in PH. It also demonstrates a pathway for pulmonary vascular remodeling in PH that depends upon interstitial macrophage-dependent inflammation yet is dissociated, at least in part, from hemodynamic consequences, thus offering guidance on future anti-inflammatory therapeutic strategies in this disease.

Origin and production of inflammatory perivascular macrophages in pulmonary hypertension

Myeloid cells, including monocytes and macrophages participate in steady state immune homeostasis and help mount the adaptive immune response during infection. The function and production of these cells in sterile inflammation, such as pulmonary hypertension (PH), is understudied. Emerging data indicate that pulmonary inflammation mediated by lung perivascular macrophages is a key pathogenic driver of pulmonary remodeling leading to increased right ventricular systolic pressure (RVSP). However, the origin of these macrophages in pulmonary inflammation is unknown. Inflammatory monocytes, the precursors of pathogenic macrophages, are derived from hematopoietic stem and progenitor cells (HSPC) in the bone marrow and spleen during acute and chronic inflammation. Understanding the role of these organs in monocytopoiesis, and the mechanisms of HSPC proliferation and differentiation in PH are important to discover therapeutic targets curbing inflammation. This review will summarize the current limited knowledge of the origin of lung macrophage subsets and over-production of inflammatory monocytes in PH.

Targeting Immunity in End-Stage Renal Disease

BACKGROUND

Despite the stable incidence of end-stage renal disease (ESRD), it continues to be associated with an unacceptably high cardiovascular risk.

SUMMARY

ESRD is characterized by enhanced oxidative stress and severe inflammation, which boost cardiovascular risk, thus increasing cardiovascular-associated mortality rate. While substantial effort has been made in the technological innovation of dialytic techniques, few significant advances have been made to reduce inflammation in patients with ESRD. Indeed, this contrasts with the extensive scientific breakthroughs made in the basic field of science in targeting inflammation. There is thus a pressing need for clinical trials to test the effect of reducing inflammation in patients with ESRD. Here, we will revisit the negative effect of ESRD on inflammation and explore the impact of enhanced inflammation on cardiovascular outcomes and survival in patients with ESRD. Finally, we will discuss the need for clinical trials that target inflammation in ESRD, as well as weigh potential disadvantages and offer novel innovative approaches. Key Message: We will try to understand why the issue of inflammation has not been successfully addressed thus far in patients with ESRD, while at the same time weighing the potential disadvantages and offering novel innovative approaches for targeting inflammation in patients with ESRD.

Effect of Different Dialysis Methods on Cellular Immunity Function of Maintenance Haemodialysis Patients

Background

The study of the effect of different dialysis methods on cellular immune function of maintenance haemodialysis (MHD) patients should provide theoretical support for deciding on the best method of blood purification that effectively improves cellular immune function of haemodialysis patients.

Subjects and Method

Sixty MHD patients were randomly divided into three groups that respectively received treatment of haemodialysis (HD), high flux haemodialysis (HFHD) and haemodiafiltration (HDF). Peripheral blood T lymphocyte subsets [CD4+, CD8+, CD25+ (mIL-2R) and CD4+/CD8+ ratio] and serum interleukin (IL)-2 and soluble IL-2 receptor (sIL-2R) levels were detected before dialysis and 4, 24 and 48 hours after dialysis in all cases.

Results

Compared with the HD group, CD4+ and CD25+ cells, CD4+/CD8+ ratio and IL-2 level increased but sIL-2R level decreased in the HFHD and HDF groups at four hours without statistical significance (p > 0.05) and at 24 and 48 hours after dialysis with statistical significance (p < 0.05), while CD8+ cells had no change after dialysis (p > 0.05). Compared with the HFHD group, CD4+ and CD25+ cells, CD4+/CD8+ ratio, and IL-2 level increased but sIL-2R level decreased in the HDF group at four and 24 hours without statistical significance (p > 0.05) and at 48 hours after dialysis with statistical significance (p < 0.05), while CD8+ cells had no change after dialysis (p > 0.05).

Conclusion

The results indicate that HD can briefly improve the cellular immune function of MHD patients, while MHD and HFHD can improve it continuously, with HDF having the best effect.

Increased Expression of CD169 on Blood Monocytes and Its Regulation by Virus and CD8 T Cells in Macaque Models of HIV Infection and AIDS

Increased expression of CD169 on monocytes has been reported in HIV-1-infected humans. Using rhesus macaque models of HIV infection, we sought to investigate whether simian immunodeficiency virus (SIV) infection upregulates CD169 expression on monocytes/macrophages. We also sought to determine whether CD8 T cells and plasma viral load directly impact the expression of CD169 on monocytes during SIV infection. We longitudinally assessed monocyte expression of CD169 during the course of SIV infection by flow cytometry, and examined the expression of CD169 on macrophages by immunohistochemistry in the spleen and lymph nodes of uninfected and infected macaques. CD169 expression on monocytes was substantially upregulated as early as 4 days during the hyperacute phase and peaked by 5-15 days after infection. After a transient decrease following the peak, its expression continued to increase during progression to AIDS. Monocyte CD169 expression was directly associated with plasma viral loads. To determine the contribution of CD8(+) T lymphocytes and virus to the control of monocyte CD169 expression, we used experimental CD8(+) lymphocyte depletion and antiretroviral therapy (ART) in SIV-infected macaques. Rapid depletion of CD8 T cells during acute infection of rhesus macaques induced an abrupt increase in CD169 expression. Importantly, levels of CD169 expression plummeted following initiation of ART and rebounded upon cessation of therapy. Taken together, our data reveal independent roles for virus and CD8(+) T lymphocytes in controlling monocyte CD169 expression, which may be an important link in further investigating the host response to viral infection.

Selective vitamin D receptor activation as anti-inflammatory target in chronic kidney disease

Paricalcitol, a selective vitamin D receptor (VDR) activator used for treatment of secondary hyperparathyroidism in chronic kidney disease (CKD), has been associated with survival advantages, suggesting that this drug, beyond its ability to suppress parathyroid hormone, may have additional beneficial actions. In this prospective, nonrandomised, open-label, proof-of-concept study, we evaluated the hypothesis that selective vitamin D receptor activation with paricalcitol is an effective target to modulate inflammation in CKD patients. Eight patients with an estimated glomerular filtration rate between 15 and 44 mL/min/1.73 m² and an intact parathyroid hormone (PTH) level higher than 110 pg/mL received oral paricalcitol (1 μg/48 hours) as therapy for secondary hyperparathyroidism. Nine patients matched by age, sex, and stage of CKD, but a PTH level <110 pg/mL, were enrolled as a control group. Our results show that five months of paricalcitol administration were associated with a reduction in serum concentrations of hs-CRP (13.9%, P < 0.01), TNF-α (11.9%, P = 0.01), and IL-6 (7%, P < 0.05), with a nonsignificant increase of IL-10 by 16%. In addition, mRNA expression levels of the TNFα and IL-6 genes in peripheral blood mononuclear cells decreased significantly by 30.8% (P = 0.01) and 35.4% (P = 0.01), respectively. In conclusion, selective VDR activation is an effective target to modulate inflammation in CKD.

Anti-inflammatory profile of paricalcitol in hemodialysis patients: a prospective, open-label, pilot study

Inflammation is a strong predictor of increased morbidity and mortality in hemodialysis (HD) patients. Paricalcitol, a selective vitamin D receptor activator used for prevention and treatment of secondary hyperparathyroidism, has shown anti-inflammatory properties in experimental studies, although clinical data are scarce. In an open-label, prospective, single center, pilot study, 25 stable HD patients, previously receiving calcitriol, completed 12 weeks of therapy with oral paricalcitol. Serum and peripheral blood mononuclear cell (PBMC) expression profiles of inflammatory cytokines were analyzed. Serum interleukin (IL)-1, IL-10, and IL-18 did not change, unlike high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α), and IL-6, which experienced a significant mean percent decrease of 14.3%, 4.7%, and 5%, respectively. There was a significant reduction in the TNF-α/IL-10 and the IL-6/IL-10 ratios (P < .05). Serum intact parathyroid hormone concentration experienced a mild but significant reduction. In addition, expression levels of TNF-α and IL-6 decreased by 19.1% (P < .01) and 17.5% (P < .001), respectively, whereas expression of IL-10 increased by 17.7% (P < .01) after treatment. In conclusion, paricalcitol administration to HD patients is associated with a beneficial effect on the inflammatory cytokine serum and gene expression profile of PBMC. This effect may contribute to the survival benefits of paricalcitol observed in clinical studies.

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

PURPOSE

The aim of this study was to ascertain the role of different vascular access types in inflammatory status, monocyte activation, and senescence in hemodialysis patients.

METHODS

We recruited 126 hemodialysis patients, including 51 with arterovenous fistula (AVF), 32 with arterovenous graft (AVG), and 43 with tunneled cuffed catheters (TCC). In dialysis patients enrolled in the study and in a control group of 40 healthy subjects, we measured the serum levels of albumin, CRP, IL-6, and TNF-a, the expression of CD14, CD44, and CD32 on monocyte surface, and the percentage of monocytes exhibiting a senescent phenotype (CD14+CD32+).

RESULTS

The patients with AVG compared to those with AVF had: a) higher levels of CRP and TNF-a; b) increased expression of CD14 and CD32 on monocyte surface, with no difference in CD44 expression; c) no difference in the percentage of CD14+CD32+ monocytes. In the comparison of TCC vs. AVF group, we observed significantly higher values of: a) circulating inflammatory markers (CRP, IL-6, TNF-a); b) monocyte surface expression of cellular activation markers (CD14, CD44 and CD32); c) relative count of CD14+CD32+ monocytes. When comparing TCC vs. AVG group, we found: a) no difference in serum levels of CRP, IL-6, and TNF-a; b) no difference in the expression of CD14, CD44, and CD32 on monocyte surface; c) no difference in the percentage of CD14+CD32+ monocytes.

CONCLUSIONS

These results suggest that the use of AVG and TCC for dialysis vascular access is associated with serological and cellular indexes of inflammatory reaction, also resulting in a higher degree of monocyte activation and senescence.

Bio-incompatibility and Th2 polarization during regular dialysis treatment

Long-term hemodialysis treatment results in chronic monocyte activation with cytokine release. It generates Treg induction with potential immune dysfunction and associated clinical complications. Recent immunological data and preliminary clinical evidence suggest that synthetic polymers and vitamin E coated membranes are associated with a significant improvement in hemodialysis tolerance when compared to cellulose membranes. The aim of this review is to update cytokine release, T-cell polarization, and its clinical impact in patients under extracorporeal hemodialysis comparing traditional cellulose to synthetic/vitamin E coated membranes.

Cholecalciferol supplementation alters calcitriol-responsive monocyte proteins and decreases inflammatory cytokines in ESRD

In vitro, monocyte 1alpha-hydroxylase converts 25-hydroxyvitamin D [25(OH)D] to 1,25-dihydroxyvitamin D to regulate local innate immune responses, but whether 25(OH)D repletion affects vitamin D-responsive monocyte pathways in vivo is unknown. Here, we identified seven patients who had 25(OH)D insufficiency and were undergoing long-term hemodialysis and assessed changes after cholecalciferol and paricalcitol therapies in both vitamin D-responsive proteins in circulating monocytes and serum levels of inflammatory cytokines. Cholecalciferol therapy increased serum 25(OH)D levels four-fold, monocyte vitamin D receptor expression three-fold, and 24-hydroxylase expression; therapy decreased monocyte 1alpha-hydroxylase levels. The CD16(+) "inflammatory" monocyte subset responded to 25(OH)D repletion the most, demonstrating the greatest increase in vitamin D receptor expression after cholecalciferol. Cholecalciferol therapy reduced circulating levels of inflammatory cytokines, including IL-8, IL-6, and TNF. These data suggest that nutritional vitamin D therapy has a biologic effect on circulating monocytes and associated inflammatory markers in patients with ESRD.

Oxidative stress, lipid rafts, and macrophage reprogramming

Oxidant stress, induced under a variety of conditions, is known to lead to the molecular reprogramming of the tissue-fixed macrophage. This reprogramming is associated with an altered response to subsequent inflammatory stimuli, such as lipopolysaccharide (LPS), leading to enhanced liberation of proinflammatory chemokines and cytokines. Due to this altered response, dysregulated immunity ensues, leading to the development of clinical syndromes such as multiple organ dysfunction syndrome (MODS). Although the mechanisms responsible for this altered macrophage activity by oxidant stress remains complex and poorly elucidated, it appears, based on recent research, that early and direct alterations within lipid rafts are responsible. This early and direct interaction with lipid rafts by oxidants leads to the mobilization of annexin VI from lipid raft constructs, leading to the release of calcium. This increased cytosolic concentration of this secondary messenger, in turn, results in the activation of calcium-dependent kinases, leading to further alterations in lipid raft lipids and eventually lipid raft proteins. Due to these lipid raft compositional changes, preassembly of receptor complexes occur, leading to enhanced proinflammatory activation. Within this review, the complexity of oxidant-induced reprogramming within the tissue fixed macrophage as currently understood is explained.

Clinical effects of online dialysate and infusion fluids

Online hemodiafiltration appears to be the most effective technique of renal replacement therapy in many respects. Removal of small and high-molecular weight substances is enhanced. Modern technology ensures a safe, online production of reinfusion fluids. Nonetheless, stringent maintenance rules are required for the production of sterile and nonpyrogenic-dialysate solutions. In this review, we will critically review the state of the art of the clinical effects derived from the use of ultrapure dialysate and the online production of dialysate fluids in high-flux hemodiafiltration.