Mechanism of lncRNA-ANRIL/miR-181b in autophagy of cardiomyocytes in mice with uremia by targeting ATG5

OBJECTIVES

This study is to investigate whether the cardiac microvascular endothelial cells (CMECs) can regulate the autophagy of cardiomyocytes (CMs) by secreting lncRNA-ANRIL/miR-181b exosomes, thus participating in the occurrence of uremic cardiovascular disease (CVD).

METHODS

A 5/6 nephrectomy uremia model was established, with the mice injected with ANRIL-shRNA lentivirus vector, miR-181b agomir, and related control reagents, containing the serum creatinine and urea nitrogen measured. The renal tissue sections of mice were stained with Periodic Acid-Schiff (PAS), TUNEL, and Hematoxylin-Eosin (HE) performed on myocardial tissue sections of mice. ANRIL-shRNA, miR-181b mimics, and related control reagents were transfected into CMECs, in which the exosomes were extracted and co-cultured with CMs. The expressions of ANRIL, miR-181b and ATG5 were detected by qRT-PCR, and the expressions of autophagy related proteins by Western blot, as well as the binding of ANRIL and miR-181b by the double luciferase reporter gene experiment.

RESULTS

ANRIL down-regulation or miR-181b up-regulation can increase the weight of mice with uremia, as well as the expressions of p62 and miR-181b, and reduce the content of serum creatinine and urea nitrogen, the damage of kidney and myocardial tissues, the number of apoptotic cells in myocardial tissues, as well as the expressions of ANRIL, ATG5, Beclin1, and LC3. CMs can absorb the exosomes of CMECs. Compared with IS+ CMEC-Exo group, the expressions of ANRIL and ATG5 in CMs of IS+ CMEC-Exo + sh lncRNA ANRIL and IS+CMEC-Exo+miR-181b mimics groups was down-regulated, as well as the expressions of ATG5, Beclin1, and LC3, while miR-181b expression was up-regulated as well as P62 expression.

CONCLUSIONS

CMECs can regulate autophagy of CMs by releasing exosomes containing ANRIL and miR-181b.

Human CD16+ monocytes promote a pro-atherosclerotic endothelial cell phenotype via CX3CR1-CX3CL1 interaction

AIMS

Monocytes are central for atherosclerotic vascular inflammation. The human non-classical, patrolling subtype, which expresses high levels of CD16 and fractalkine receptor CX3CR1, strongly associates with cardiovascular events. This is most marked in renal failure, a condition with excess atherosclerosis morbidity. The underlying mechanism is not understood. This study investigated how human CD16+ monocytes modulate endothelial cell function.

METHODS AND RESULTS

In patients with kidney failure, CD16+ monocyte counts were elevated and dynamically decreased within a year after transplantation, chiefly due to a drop in CD14+CD16+ cells. The CX3CR1 ligand CX3CL1 was similarly elevated in the circulation of humans and mice with renal impairment. CX3CL1 up-regulation was also observed close to macrophage rich human coronary artery plaques. To investigate a mechanistic basis of this association, CD16+CX3CR1HIGH monocytes were co-incubated with primary human endothelium in vitro. Compared to classical CD14+ monocytes or transwell cocultures, CD16+ monocytes enhanced endothelial STAT1 and NF-κB p65 phosphorylation, up-regulated expression of CX3CL1 and interleukin-1β, numerous CCL and CXCL chemokines and molecules promoting leucocyte patrolling and adhesion such as ICAM1 and VCAM1. Genes required for vasodilatation including endothelial nitric oxide synthase decreased while endothelial collagen production increased. Uraemic patients' monocytes enhanced endothelial CX3CL1 even more markedly. Their receptor CX3CR1 was required for enhanced aortic endothelial stiffness in murine atherosclerosis with renal impairment. CX3CR1 dose-dependently modulated monocyte-contact-dependent gene expression in human endothelium.

CONCLUSION

By demonstrating endothelial proatherosclerotic gene regulation in direct contact with CD16+ monocytes, in part via cellular CX3CR1-CX3CL1 interaction, our data delineate a mechanism how this celltype can increase cardiovascular risk.

[SARS-CoV-2 vaccines - what the nephrologist should know]

Only fifteen months after the beginning of the COVID-19 pandemic, several vaccines are already available for clinical use. While the spike protein of SARS-CoV-2 constitutes the main target of all predominant SARS-CoV-2 vaccines, they work by different mechanisms (mRNA-based vaccines vs. vector-based vaccines vs. protein-based vaccines).Though there are slight differences regarding the level of protection against mild COVID-19, all five vaccines that have been through phase 3 trials were nearly 100 % effective in preventing severe or fatal cases of COVID-19. The side effects were of short duration.Patients with chronic kidney disease (or other significant comorbidities) were largely excluded from Phase 3 trials, which makes definite recommendations concerning their vaccination difficult. The vaccine's effectiveness may be reduced in that population due to a uremic immune defect and/or immunosuppressive medication. However, these patients have an increased risk for severe or fatal COVID-19, so that they may particularly benefit from the vaccine.

Protein-Bound Uremic Toxins and Immunity

Protein-bound uremic toxins (PBUTs) are bioactive microbiota metabolites originated exclusively from protein fermentation of the bacterial community resident within the gut microbiota, whose composition and function is profoundly different in the chronic kidney disease (CKD) population. PBUTs accumulate in the later stages of CKD because they cannot be efficiently removed by conventional hemodialysis due to their high binding affinity for albumin, worsening their toxic effects, especially at the cardiovascular level. The accumulation of uremic toxins, along with oxidative stress products and pro-inflammatory cytokines, characterizes the uremic status of CKD patients which is increasingly associated to a state of immune dysfunction including both immune activation and immunodepression. Furthermore, the links between immune activation and cardiovascular disease (CVD), and between immunodepression and infection diseases, which are the two major complications of CKD, are becoming more and more evident. This review summarizes and discusses the current state of knowledge on the role of the main PBUTs, namely indoxyl sulfate and p-cresyl sulfate, as regulators of immune response in CKD, in order to understand whether a microbiota modulation may be useful in the management of its main complications, CVD, and infections. Summarizing the direct effects of PBUT on immune system we may conclude that PCS seemed to be associated to an immune deficiency status of CKD mainly related to the adaptative immune response, while IS seemed to reflect the activation of both innate and adaptative immune systems likely responsible of the CKD-associated inflammation. However, the exact role of IS and PCS on immunity modulation in physiological and pathological state still needs in-depth investigation, particularly in vivo studies.

Indoxyl Sulfate-Mediated Metabolic Alteration of Transcriptome Signatures in Monocytes of Patients with End-Stage Renal Disease (ESRD)

End-stage renal disease (ESRD) is the final stage of chronic kidney disease, which is increasingly prevalent worldwide and is associated with the progression of cardiovascular disease (CVD). Indoxyl sulfate (IS), a major uremic toxin, plays a key role in the pathology of CVD via adverse effects in endothelial and immune cells. Thus, there is a need for a transcriptomic overview of IS responsive genes in immune cells of ESRD patients. Here, we investigated IS-mediated alterations in gene expression in monocytes from ESRD patients. Transcriptomic analysis of ESRD patient-derived monocytes and IS-stimulated monocytes from healthy controls was performed, followed by analysis of differentially expressed genes (DEGs) and gene ontology (GO). We found that 148 upregulated and 139 downregulated genes were shared between ESRD patient-derived and IS-stimulated monocytes. Interaction network analysis using STRING and ClueGo suggests that mainly metabolic pathways, such as the pentose phosphate pathway, are modified by IS in ESRD patient-derived monocytes. These findings were confirmed in IS-stimulated monocytes by the increased mRNA expression of genes including G6PD, PGD, and TALDO1. Our data suggest that IS causes alteration of metabolic pathways in monocytes of ESRD patients and, thus, these altered genes may be therapeutic targets.

Endothelial Damage, Inflammation and Immunity in Chronic Kidney Disease

Chronic kidney disease (CKD) patients have an accelerated atherosclerosis, increased risk of thrombotic-ischemic complications, and excessive mortality rates when compared with the general population. There is also evidence of an endothelial damage in which the proinflammatory state, the enhanced oxidative stress, or the accumulation of toxins due to their reduced renal clearance in uremia play a role. Further, there is evidence that uremic endothelial cells are both involved in and victims of the activation of the innate immunity. Uremic endothelial cells produce danger associated molecular patterns (DAMPS), which by binding to specific pattern recognition receptors expressed in multiple cells, including endothelial cells, induce the expression of adhesion molecules, the production of proinflammatory cytokines and an enhanced production of reactive oxygen species in endothelial cells, which constitute a link between immunity and inflammation. The connection between endothelial damage, inflammation and defective immunity in uremia will be reviewed here.

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.

Chronic Kidney Disease-Associated Immune Dysfunctions: Impact of Protein-Bound Uremic Retention Solutes on Immune Cells

Regardless of the primary disease responsible for kidney failure, patients suffering from chronic kidney disease (CKD) have in common multiple impairments of both the innate and adaptive immune systems, the pathophysiology of which has long remained enigmatic. CKD-associated immune dysfunction includes chronic low-grade activation of monocytes and neutrophils, which induces endothelial damage and increases cardiovascular risk. Although innate immune effectors are activated during CKD, their anti-bacterial capacity is impaired, leading to increased susceptibility to extracellular bacterial infections. Finally, CKD patients are also characterized by profound alterations of cellular and humoral adaptive immune responses, which account for an increased risk for malignancies and viral infections. This review summarizes the recent emerging data that link the pathophysiology of CKD-associated immune dysfunctions with the accumulation of microbiota-derived metabolites, including indoxyl sulfate and p-cresyl sulfate, the two best characterized protein-bound uremic retention solutes.

Gut-Derived Metabolites and Their Role in Immune Dysfunction in Chronic Kidney Disease

Several of the uremic toxins, which are difficult to remove by dialysis, originate from the gut bacterial metabolism. This opens opportunities for novel targets trying to decrease circulating levels of these toxins and their pathophysiological effects. The current review focuses on immunomodulatory effects of these toxins both at their side of origin and in the circulation. In the gut end products of the bacterial metabolism such as p-cresol, trimethylamine and H₂S affect the intestinal barrier structure and function while in the circulation the related uremic toxins stimulate cells of the immune system. Both conditions contribute to the pro-inflammatory status of patients with chronic kidney disease (CKD). Generation and/or absorption of these toxin precursors could be targeted to decrease plasma levels of their respective uremic toxins and to reduce micro-inflammation in CKD.

Imbalance of Th22/Treg cells causes microinflammation in uremic patients undergoing hemodialysis

BACKGROUND

Regulatory T (Treg) cells are of critical functionality in immune activation and inflammation in uremic patients undergoing hemodialysis (HD). A disruption in balance of Treg cells has potency to elicit infectious disease progression. Here, we examined possible association between ratio imbalance of Th22/Treg cells and microinflammation in uremic patients undergoing HD.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated to allow measurement of the percentage of Th22 cells and Treg cells using flow cytometry. Subsequently, serum levels of related cytokines, interleukin (IL) 22 (IL-22) and IL-10 and inflammatory factors, C-reactive protein (CRP), (TNF-α), IL-6 were determined via enzyme-linked immunosorbent assay (ELISA). Then relationships among dialysis time, microinflammation status (CRP) and dialysis adequacy (immunoreactive parathyroid hormone (iPTH), urea clearance index (Kt/V), β2-MG, serum calcium, and serum phosphorus) were evaluated. Finally, correlation between microinflammation status and dialysis adequacy was analyzed with Pearson's correlation coefficient.

RESULTS

An increased percentage of Th22 and a decreased percentage of Treg cells were evident in uremic patients undergoing HD. Serum levels of IL-22, CRP, TNF-α, and IL-6 were increased, while IL-10 serum level was reduced. An imbalance of Th22/Treg cells was associated with microinflammation status in uremic patients undergoing HD. Furthermore, prolongation of the dialysis time, the microinflammation status and dialysis adequacy were changed. Increased dialysis adequacy was observed to correlate with alleviated microinflammation of uremic patients undergoing HD.

CONCLUSIONS

Conjointly, an imbalance of Th22/Treg cells may be a potential cause responsible for uremia occurrence, which in turn indicates that uremia could be effectively alleviated by altering the ratio of Th22/Treg cells.

Citrate dialysate does not induce oxidative stress or inflammation in vitro as compared to acetate dialysate

Increased acetataemia during haemodialysis sessions has been associated with a number of abnormalities, including increased oxidative stress, pro-inflammatory cytokines and nitric oxide synthesis. However, citric acid may play an alternative role to acetate as a dialysate stabiliser given that the effect of citrate on complement and leukocyte activation is different to that of acetate. The purpose of this study was to compare the inflammatory effect in immunocompetent blood cells of acetate dialysate and citrate dialysate.

MATERIAL AND METHODS

The effect of acetate and/or citrate was investigated in the whole blood of uraemic patients and in healthy in vitro samples. Four types of dialysate were tested: dialysate 1, acetate-free with 1mmol/L of citrate; dialysate 2, with 0.8mmol/L of citrate and 0.3mmol/L of acetate; dialysate 3, citrate-free with 3mmol/L of acetate; and dialysate 4, citrate-free with 4mmol/L of acetate. The cell types used were: human monocyte culture (THP-1); and peripheral blood mononuclear cells (PBMCs) from healthy subjects and uraemic patients on haemodialysis. ICAM-1 was determined and levels of reactive oxygen species and total microvesicles were quantified.

RESULTS

Unlike the citrate dialysates, the dialysates with acetate (dialysate 3 and dialysate 4) induced increased ICAM-1 expression density in THP-1 cells; an increase in ICAM-1 expression was observed in the immunocompetent cells of healthy subjects with acetate dialysate (dialysate 3 and dialysate 4) but not with citrate dialysate (dialysate 1 and dialysate 2). No significant ICAM-1 differences were found between the different dialysates in the cells of haemodialysed patients. Reactive oxygen species expression and the number of microvesicles increased significantly with acetate dialysate but not with citrate dialysate in the cells of both healthy subjects and haemodialysed patients.

CONCLUSIONS

At the concentrations in which it is generally used in clinical practice, acetate-based dialysate increases oxidative stress and the total number of microvesicles and may induce other pro-inflammatory stimuli typical of uraemic patients on haemodialysis. Citrate dialysates do not induce this activation, which could make them a suitable alternative in clinical practice.

Liraglutide Reduces Both Atherosclerosis and Kidney Inflammation in Moderately Uremic LDLr-/- Mice

Chronic kidney disease (CKD) leads to uremia. CKD is characterized by a gradual increase in kidney fibrosis and loss of kidney function, which is associated with a progressive increase in risk of atherosclerosis and cardiovascular death. To prevent progression of both kidney fibrosis and atherosclerosis in uremic settings, insight into new treatment options with effects on both parameters is warranted. The GLP-1 analogue liraglutide improves glucose homeostasis, and is approved for treatment of type 2 diabetes. Animal studies suggest that GLP-1 also dampens inflammation and atherosclerosis. Our aim was to examine effects of liraglutide on kidney fibrosis and atherosclerosis in a mouse model of moderate uremia (5/6 nephrectomy (NX)). Uremic (n = 29) and sham-operated (n = 14) atherosclerosis-prone low density lipoprotein receptor knockout mice were treated with liraglutide (1000 μg/kg, s.c. once daily) or vehicle for 13 weeks. As expected, uremia increased aortic atherosclerosis. In the remnant kidneys from NX mice, flow cytometry revealed an increase in the number of monocyte-like cells (CD68⁺F4/80^-), CD4⁺, and CD8⁺ T-cells, suggesting that moderate uremia induced kidney inflammation. Furthermore, markers of fibrosis (i.e. Col1a1 and Col3a1) were upregulated, and histological examinations showed increased glomerular diameter in NX mice. Importantly, liraglutide treatment attenuated atherosclerosis (~40%, p < 0.05) and reduced kidney inflammation in NX mice. There was no effect of liraglutide on expression of fibrosis markers and/or kidney histology. This study suggests that liraglutide has beneficial effects in a mouse model of moderate uremia by reducing atherosclerosis and attenuating kidney inflammation.

Online Haemodiafiltration Improves Inflammatory State in Dialysis Patients: A Longitudinal Study

Background

Patients undergoing conventional hemodialysis (C-HD) present a greater immuno-inflammatory state probably related to uremia, sympathetic nervous system (SNS) activation and /or membrane bioincompatibility, which could improve with a technique-switching to online hemodiafiltration (OL-HD). The antigen-independent pathway activation of this modified immunologic state turns dendritic cells (DC) into an accurate cell model to study these patients. The aim of this study is to further evaluate the immune-inflammatory state of patients in C-HD assessed by DC maturation.

Methods

31 patients were submitted to C-HD and after 4 months switched to the OL-HD technique. Monocytes-derived DCs from HD patients were cultured in the presence of IL-4/GM-CSF. DC-maturation was evaluated by assessing the maturation phenotype by flow cytometry (FACs). DCs-functional capacity to elicit T-cell alloresponse was studied by mixed leucocyte reaction. Cytokine release was assessed by FACs and SNS was evaluated measuring renalase levels by ELISA.

Results

An up-regulation of maturation markers was observed in C-HD DCs which induced two fold more T cells proliferation than OL-HD DCs. Also, C-HD-mDCs presented with over-production of pro-inflammatory cytokines (IL-6, IL-1β, IL-8, IL-10 and TNF-α) compared with OL-HD-mDC (P<0·05). Results were correlated with clinical data. When SNS was evaluated, hypotension events and blood pressure were significantly lower and renalase levels were significantly higher after conversion to OL-HD. Diabetes mellitus type 2 patients also found beneficial reduction of mDC when converted to OL-HD compared to non-diabetics.

Conclusions

OL-HD could interfere with immuno-inflammatory state in HD patients with an improvement of renalase levels as potential key mediators in the mechanistic pathway of down-regulation of DC maturation.

Effect of Chronic Uremia on the Cell Surface Expression of B7 Family Costimulatory Molecules in an HLA-A2 Transgenic Mouse Model of Chronic Kidney Disease

Uremia due to chronic kidney disease (CKD) in humans is associated with immune dysfunction, increased susceptibility to infections, immune-activation-associated inflammation, and poor responses to vaccines. The pathophysiologic basis of these immune defects is hypothesized to be associated with a wide range of immunologic abnormalities, including an inability to sufficiently express the B7 family (B7-1, CD80; B7-2, CD86) of T-cell costimulatory molecules. However, testing the hypothesis that a state of chronic uremia contributes to attenuated expression of CD80 or CD86 has been difficult because few animal models faithfully recapitulate the immune defects observed in human CKD patients. We used a humanized mouse in a model of surgically induced renal failure and secondary chronic uremia to evaluate the effect of uremia on the expression of these markers. In a manner that resembles the changes observed in CKD patients, surgically induced CKD in mice resulted in decreased costimulatory CD86 expression compared with that in sham-operated controls. Immunodeficiency was functionally demonstrated in this mouse model by documenting an attenuated immune response to a cholera-toxin-based hepatitis B vaccine. This model will be useful for investigating the mechanisms involved in chronic uremia-associated immunodeficiency, poor response to vaccination, and problems associated with immunization of CKD patients.

Oxidative stress in chronic kidney disease

Patients with chronic kidney disease (CKD) have high incidence rates of cardiovascular disease and malignancy. Several factors contribute to these conditions. Structural characteristics in CKD, loss of renal energy, and uremia result in an imbalance between free radical production and antioxidant defenses. Also, CKD patients usually have multiple cardiovascular risk factors like diabetes mellitus, dyslipidemia, and hypertension. These conditions are associated with oxidative stress, which can trigger the inflammatory process and accelerate renal injury progression. There are some clinical biomarkers to detect oxidative stress and antioxidant status in CKD patients. Antioxidant therapies may be beneficial in reducing oxidative stress, lowering uremic cardiovascular toxicity, and improving survival. Therefore, their roles in CKD patients have been evaluated in several studies as a new target for therapeutic intervention. This review provides an overview of oxidative stress mechanisms, clinical squeals, biomarkers, and possible antioxidant therapies in CKD patients.

High hepatitis B virus surface antigen levels and favorable interleukin 28B genotype predict spontaneous hepatitis C virus clearance in uremic patients

BACKGROUND & AIMS

Host and viral factors interplay in the spontaneous clearance of hepatitis C virus (HCV) infection. We aimed to explore the roles of IL28B genotypes and hepatitis B virus (HBV) infections in spontaneous HCV seroclearance.

METHODS

IL28B rs8099917 genotypes, HCV and HBV markers were determined in 290 patients who were seropositive for HCV antibodies from 1681 total uremic patients on maintenance hemodialysis.

RESULTS

Persistent HCV viremia was observed in 74.6% (214/287) of patients. Logistic regression revealed that the strongest factors associated with spontaneous HCV seroclearance were carriage of rs8099917 TT-type (odds ratio/95% confidence intervals [OR/CI]: 6.22/1.41-27.35, p=0.016), followed by concurrent hepatitis B surface antigen (HBsAg) seropositivity (OR/CI: 2.37/1.06-5.26, p=0.035). The clearance rate was highest among patients with both positive HBsAg/rs8099917 TT-type (44.8%, OR/CI: 20.88/3.5-402.5), followed by positive HBsAg/rs8099917 non-TT-type (28.6%, OR/CI: 8.86/1.8-160.8), and negative HBsAg/rs8099917 TT-type (26.7%, OR/CI: 12.75/1.0-319.4), compared to 4% of negative HBsAg/rs8099917 non-TT-type (trend p=0.0002). HBsAg levels, but not HBV DNA levels, were significantly associated with spontaneous HCV seroclearance. Spontaneous HCV seroclearance rate was 58.3% in patients with HBsAg>200IU/ml/rs8099917 TT-type (OR/CI: 42.54/5.7-908.4), 28.0% in patients with HBsAg<200IU/ml/rs8099917 TT-type or HBsAg>200IU/ml/rs8099917 non-TT-type (OR/CI: 11.12/2.3-201.0), compared to only 3.3% in those with HBsAg<200IU/ml/rs8099917 non-TT-type (trend p=0.0004). Five of 214 (2.3%) HCV viremic patients at enrollment had spontaneous HCV seroclearance during one-year follow-up, which was associated with baseline HCV RNA and HBsAg levels.

CONCLUSIONS

High HBsAg levels and favorable IL28B genotype were additively associated with spontaneous HCV seroclearance in uremic patients.

Protein-bound uremic toxins stimulate crosstalk between leukocytes and vessel wall

Leukocyte activation and endothelial damage both contribute to cardiovascular disease, a major cause of morbidity and mortality in CKD. Experimental in vitro data link several protein-bound uremic retention solutes to the modulation of inflammatory stimuli, including endothelium and leukocyte responses and cardiovascular damage, corroborating observational in vivo data. However, the impact of these uremic toxins on the crosstalk between endothelium and leukocytes has not been assessed. This study evaluated the effects of acute and continuous exposure to uremic levels of indoxylsulfate (IS), p-cresylsulfate (pCS), and p-cresylglucuronide (pCG) on the recruitment of circulating leukocytes in the rat peritoneal vascular bed using intravital microscopy. Superfusion with IS induced strong leukocyte adhesion, enhanced extravasation, and interrupted blood flow, whereas pCS caused a rapid increase in leukocyte rolling. Superfusion with pCS and pCG combined caused impaired blood flow and vascular leakage but did not further enhance leukocyte rolling over pCS alone. Intravenous infusion with IS confirmed the superfusion results and caused shedding of heparan sulfate, pointing to disruption of the glycocalyx as the mechanism likely mediating IS-induced flow stagnation. These results provide the first clear in vivo evidence that IS, pCS, and pCG exert proinflammatory effects that contribute to vascular damage by stimulating crosstalk between leukocytes and vessels.

Dendritic cell co-stimulatory and co-inhibitory markers in chronic HCV: an Egyptian study

AIM

To assess co-stimulatory and co-inhibitory markers of dendritic cells (DCs) in hepatitis C virus (HCV) infected subjects with and without uremia.

METHODS

Three subject groups were included in the study: group 1 involved 50 control subjects, group 2 involved 50 patients with chronic HCV infection and group 3 involved 50 HCV uremic subjects undergoing hemodialysis. CD83, CD86 and CD40 as co-stimulatory markers and PD-L1 as a co-inhibitory marker were assessed in peripheral blood mononuclear cells by real-time polymerase chain reaction. Interleukin-10 (IL-10) and hyaluronic acid (HA) levels were also assessed. All findings were correlated with disease activity, viral load and fibrogenesis.

RESULTS

There was a significant decrease in co-stimulatory markers; CD83, CD86 and CD40 in groups 2 and 3 vs the control group. Co-stimulatory markers were significantly higher in group 3 vs group 2. There was a significant elevation in PD-L1 in both HCV groups vs the control group. PD-L1 was significantly lower in group 3 vs group 2. There was a significant elevation in IL-10 and HA levels in groups 2 and 3, where IL-10 was higher in group 3 and HA was lower in group 3 vs group 2. HA level was significantly correlated with disease activity and fibrosis grade in group 2. IL-10 was significantly correlated with fibrosis grade in group 2. There were significant negative correlations between co-stimulatory markers and viral load in groups 2 and 3, except CD83 in dialysis patients. There was a significant positive correlation between PD-L1 and viral load in both HCV groups.

CONCLUSION

A significant decrease in DC co-stimulatory markers and a significant increase in a DC co-inhibitory marker were observed in HCV subjects and to a lesser extent in dialysis patients.

Uremia suppresses immune signal-induced CYP27B1 expression in human monocytes

BACKGROUND

Local production of 1,25-dihydroxyvitamin D (1,25(OH)(2)D) regulated by the CYP27B1 enzyme in monocytes contributes to the immunomodulatory effects of vitamin D. Uremia suppresses renal CYP27B1, but its impact on monocytic CYP27B1 is incompletely understood. The present study aimed to elucidate this issue and to define the pathogenic role of p-cresyl sulfate (PCS), indoxyl sulfate (IndS), and fibroblast growth factor 23 (FGF23).

METHODS

Resting or immune (interferon-γ + lipopolysaccharide)-stimulated THP1 cells and monocytes, isolated from healthy donors, were cultured in the presence of either healthy serum, uremic serum, PCS, IndS or FGF23. RNA expression levels for CYP27B1 and cytokines were quantified by RT-PCR and enzymatic CYP27B1 activity was measured 24 h after incubation.

RESULTS

Culturing THP1 cells or human monocytes in the presence of uremic serum led to higher inflammatory cytokine and CYP27B1 expression. Immune signal-induced CYP27B1 expression and activity, conversely, was impaired in the presence of uremic serum. Similar effects were observed in the presence of FGF23, although significance was reached in immune-stimulated cells only. PCS and IndS failed to show any effect.

CONCLUSIONS

Monocytic baseline CYP27B1 expression is increased in uremia, probably reflecting the microinflammatory state. Immune signal-induced CYP27B1 expression, conversely, is impaired in uremic conditions. Elevated FGF23 levels, but not PCS and IndS, may account, at least partly, for the dysregulation of monocytic CYP27B1 in uremia and, as such, may contribute to the high cardiovascular and infectious burden in chronic kidney disease.

Stat3 contributes to indoxyl sulfate-induced inflammatory and fibrotic gene expression and cellular senescence

BACKGROUND/AIM

Increased phosphorylation (activation) of signal transducer and activator of transcription 3 (Stat3) on tyrosine 705 leads to renal fibrosis. Indoxyl sulfate, a uremic toxin, induces renal fibrosis through expression of transforming growth factor-β(1) (TGF-β(1)) in proximal tubular cells. The present study aimed to determine whether Stat3 is involved in indoxyl sulfate-induced dysfunction of proximal tubular cells.

METHODS

Localization of phosphorylated Stat3 in the kidneys of normal, subtotally nephrectomized, and AST-120-treated subtotally nephrectomized rats was examined by immunohistochemistry. The effect of indoxyl sulfate on phosphorylation of Stat3 and the role of Stat3 on indoxyl sulfate-induced cellular effects were examined using human proximal tubular cells (HK-2 cells).

RESULTS

Subtotally nephrectomized rats showed increased immunostaining of phosphorylated Stat3 in the renal tubules compared with normal rats. Administration of AST-120, which reduces serum level of indoxyl sulfate, to subtotally nephrectomized rats reduced the immunostaining of phosphorylated Stat3 in the renal tubules. Indoxyl sulfate induced phosphorylation of Stat3 in HK-2 cells. Stat3 small interfering RNA suppressed indoxyl sulfate-induced expression of an inflammation marker gene (monocyte chemotactic protein-1), fibrosis marker genes (TGF-β(1), α-smooth muscle actin) and a subunit of nuclear factor-ĸB (p65), and attenuated a cellular senescence marker, senescence-associated β-galactosidase activity.

CONCLUSIONS

Stat3 is involved in indoxyl sulfate-induced inflammatory and fibrotic gene expression and cellular senescence in proximal tubular cells.

[Anti-MICA antibodies: risk factors for sensitization and the impact on renal transplantation outcomes]

OBJECTIVE

To investigate the risk factors for sensitization of anti-MICA antibodies and their impact on the outcomes of renal transplantation.

METHODS

Luminex flow cytometry were used to identify 10 MICA antibodies and evaluate the antibody specificity in 98 uremic patients positive or negative for anti-MICA antibodies undergoing kidney transplantation. The factors contributing to MICA sensitization were analyzed, and the incidence of acute rejection and graft function recovery time were compared between the positive and negative cases for anti-MICA antibodies.

RESULTS

Of the 98 uremic patients, 16 (16.3%) were positive for anti-MICA antibodies. The positive and negative cases showed significant differences in the history of blood transfusion, pregnancy, transplantation, and PRA status (P<0.05). In the 38 renal transplant recipients, 6 experienced acute graft rejection, which was reversed by methylprednisolone pulse therapy; of the 10 recipients positive for anti-MICA antibodies, 4 showed acute graft rejection as compared to 2 out of the 28 recipients negative for anti-MICA antibodies (P=0.031). The cases positive for anti-MICA antibodies showed a significantly longer graft function recovery time than the negative cases (14.6∓4.7 vs 8.2∓4.5 days, P=0.001).

CONCLUSIONS

Blood transfusion, pregnancy, and transplantation all contribute to the production of anti-MICA antibodies. Patients positive for anti-MICA antibodies may require strict HLA matching and more potent immunosuppressive drugs to prevent renal graft rejection and improve graft survival.

[Relationship between accelerated artherosclerosis and Treg/Teff balance in uremic apoE-/- mice]

OBJECTIVE

To establish a uremic apolipoprotein E knockout (apoE-/-) mouse model and explore the relationship between accelerated atherosclerosis and Treg/Teff balance.

METHODS

Using apoE-/- mice with C57BL/6J background, uremic apoE-/- mice were created by electrocautery of the right kidney and nephrectomy of the left, and the control apoE-/- mice received a sham-operation. Two weeks after inducing uremia, the renal function of the mice were evaluated to assess the validity of the model. Ten weeks after the operation, blood samples were obtained from the mice to assess the renal function and serum total cholesterol (TCH); the serum concentrations of transforming growth factor-beta(1) (TGF-beta(1)) and interferon-gamma (IFN-gamma) were detected by ELISA, and CD4(+)CD25(+)Foxp3(+)Treg ratio in the spleen was determined by flow cytometry. RT-PCR was used to detect the expression of Foxp3 and IFN-gamma mRNA in the aorta, and oil red O staining used to investigate the relative atherosclerotic area on the frozen sections of the aortic root. The correlation between the renal function parameters and Treg quantity was analyzed.

RESULTS

Renal function detection confirmed successful establishment of the uremic apoE-/- mouse model. Ten weeks after the operation, the relative atherosclerotic plaque area in the aortic root plaque increased significantly, the spleen Treg ratio decreased, the serum concentrations of TGF-beta(1) decreased and IFN-gamma and TCH increased, the expression of aortic Foxp3 mRNA decreased and IFN-gamma mRNA increased as compared with those in the control apoE-/- mice. A significant inverse correlation was found between the renal function parameters and Treg quantity in uremic apoE-/- mice.

CONCLUSION

In uremic apoE-/- mice, accelerated aortic atherosclerosis is correlated to the T cell subset (Treg/Teff) imbalance shown by decreased quantity and impaired function of Treg and enhanced activity of Teff.

Oxidized LDL modulates apoptosis of regulatory T cells in patients with ESRD

Increased levels of oxidized low-density lipoproteins (oxLDL) contribute to the increased risk for atherosclerosis, which persists even after adjusting for traditional risk factors, among patients with ESRD. Regulatory T cells (CD4+/CD25+ Tregs), which down-regulate T cell responses to foreign and self-antigens, are protective in murine atherogenesis, but whether similar immunoregulation occurs in humans with ESRD is unknown. Because cellular defense systems against oxLDL involve proteolytic degradation, the authors investigated the role of oxLDL on proteasome activity of CD4+/CD25+ Tregs in patients with ESRD. CD4+/CD25+ Tregs isolated from uremic patients' peripheral blood, especially that of chronically hemodialyzed patients, failed to suppress cell proliferation, exhibited cell-cycle arrest, and entered apoptosis by altering proteasome activity. Treating CD4+/CD25+ Tregs with oxLDL or uremic serum ex vivo decreased the number and suppressive capacity of CD4+/CD25+ Tregs. In vitro, oxLDL promoted the accumulation of p27Kip1, the cyclin-dependent kinase inhibitor responsible for G1 cell cycle arrest, and increased apoptosis in a time- and concentration-dependent manner. In summary, proteasome inhibition by oxLDL leads to cell cycle arrest and apoptosis, dramatically affecting the number and suppressive capacity of CD4+/CD25+ Tregs in chronically hemodialyzed patients. This response may contribute to the immune dysfunction, microinflammation, and atherogenesis observed in patients with ESRD.

Frequency of Anti-Heparin-PF4 Complex Antibodies (HIT Antibodies) in Uremic Patients on Chronic Intermittent Hemodialysis

The aim of this study was to determine the frequency of heparin/platelet factor (PF) 4 complex antibodies in 305 uremic patients treated with chronic intermittent hemodialysis using unfractionated heparin or low-molecular-weight heparin for 3 months. Heparin-induced thrombocytopenia (HIT) antibodies were detected by ELISA in 7 patients (2.3%) who had no history of HIT. Two patients abruptly developed HIT associated with the formation of clots in the extracorporeal circuit after they were found to be carrying HIT antibodies. These patients were suspected to have a similar trigger: an increased dose of recombinant human erythropoietin (rHuEPO). The drug might induce parallel changes in hematocrit (Ht) levels and platelet counts until the onset of HIT. After the onset of HIT, a parallel phenomenon between Ht and platelet counts was not found because of the thrombocytopenia due to HIT. Although HIT onset has been reported during the initial phase of dialysis sessions, there have been few reports on the onset of HIT in uremic patients on dialysis with long-term heparin anticoagulation. In this study, HIT was observed in 2 uremic patients on chronic dialysis with intermittent use of heparin. In some patients on chronic intermittent dialysis carrying HIT antibodies, HIT may occur following rHuEPO treatment. The presence of HIT should be borne in mind in chronic dialysis patients carrying HIT antibodies for 3 months or more.

Lymphocytes from multitransfused uremic patients have poor MLC reactivity

Lymphocytes from uremic patients showed statistically significantly lower (P less than 0.01) MLC reactivity against pooled stimulator cells as compared with lymphocytes from age matched controls. A consistently low MLC reactivity was recorded in lymphocytes from patients who had received more than 20 units of blood and the lowest responses were seen with cells from patients with multispecific anti-HLA-antibodies. Removal of B cells and removal of phagocytic cells from the responder cells resulted in a significant (P less than 0.05) increase in MLC reactivity in the uremic but not in the control group. Both addition of enriched B cells to autologous enriched T cells and addition of adherent cells to non-adherent autologous cells caused a slight supression of MLC reactivity. PHA reactivity was lower (P less than 0.001) in lymphocytes from the multitransfused patients compared to cells from age matched controls. However, no difference in PHA responses were recorded between lymphocytes from uremic patients who had received less than 20 units of blood and controls.

Chronic viral hepatitis and iron affect the plasma levels of LIGHT--a new member of the TNF superfamily in uraemic haemodialyzed patients

LIGHT (lymphotoxin-like inducible protein that competes with glycoprotein D for binding herpesvirus entry mediator on T cells) is a recently identified of the tumor necrosis factor alpha (TNF-alpha) ligand superfamily. We wanted to establish whether the presence of chronic viral hepatitis could be implicated in enhanced inflammation as well as the elevation of plasma LIGHT levels in haemodialyzed (HD) patients. The plasma levels of LIGHT, high sensitivity C-reactive protein (hs CRP) and TNF-alpha were measured in HD patients with hepatitis in comparison to subjects without hepatitis and to healthy volunteers. The values of hs CRP and TNF-alpha were significantly elevated in HD patients when compared to the controls. TNF-alpha levels were significantly higher in the hepatitis-positive relative to the hepatitis-negative group (p <0.01). LIGHT levels were significantly decreased in hepatitis-negative patients as compared to controls (p <0.001) and hepatitis-positive group (p < 0.01). Both LIGHT and TNF-alpha were directly associated with the presence of hepatitis. Multiple stepwise regression analysis identified increased iron levels as the only independent variable significantly associated with increased LIGHT (beta=0.475, p=0.003). These results suggest the presence of chronic viral hepatitis and iron levels are novel determinants of the increased LIGHT in the plasma of HD patients.

Enhanced susceptibility to immune nephritis in DBA/1 mice is contingent upon IL-1 expression

The DBA/1 mouse strain is particularly sensitive to experimental immune-mediated nephritis. Previous studies have indicated that various chemokines/cytokines are elevated in strains of mice susceptible to immune-mediated glomerulonephritis. One of the many elevated cytokines is IL-1. This study was designed to determine if IL-1 is essential for the development of immune-mediated nephritis in the DBA/1 mouse strain that is particularly sensitive to this disease. Both male and female DBA/1 mice and DBA/1.IL-1R1(-/-) mice were challenged with anti-GBM sera. We then compared DBA/1 mice to DBA/1.IL-1R1(-/-) mice to determine the influence of IL-1 on immune-mediated nephritis. Compared to DBA/1 mice, DBA/1.IL-1R1(-/-) mice excreted significantly less protein post anti-GBM serum challenge. None of the DBA/1.IL-1R1(-/-) mice, male or female, had a BUN higher than 22 mg/dl post-challenge whereas wild-type DBA/1 mice had significantly elevated BUN. Wild-type DBA/1 mice exhibited pronounced glomerulonephritis, with crescent formation, as well as tubulo-interstitial disease compared to DBA/1.IL1R1(-/-) mice. These findings indicate that IL-1 is necessary for the development of nephritis in DBA/1 mice and suggest that the elevated IL-1 levels in these mice may be one reason why the DBA/1 strain is particularly sensitive to multiple end organ diseases.

Pleiotropic effects of the non-calcium phosphate binder sevelamer

The number of chronic kidney disease (CKD) patients and related adverse outcomes has dramatically increased worldwide in the past decade. Therefore, numerous experimental and clinical studies have recently addressed the underlying mechanisms, in particular the marked increase in cardiovascular mortality. Hyperphosphatemia is a major problem in these patients with advanced stage of CKD. Its control by calcium-containing phosphate binders is effective, but at the price of potentially noxious calcium overload. Sevelamer hydrochloride is a phosphate binder that offers an effective control of hyperphosphatemia as calcium-rich binders but without increase of calcium load. Beyond the control of phosphate, sevelamer seems to exert pleiotropic effects which include the correction of lipid abnormalities and the clearance of some uremic toxins.

Inhibition of the Renin-Angiotensin System Abolishes the Proatherogenic Effect of Uremia in Apolipoprotein E-Deficient Mice

Objective— Uremia accelerates atherosclerosis in apolipoprotein E-deficient (apoE −/− ) mice. We examined whether this effect may be preventable by pharmacological blockade of the renin-angiotensin system (RAS).

Methods and Results— Uremia was induced in apoE −/− mice by 5/6 nephrectomy (NX). Treatment with the angiotensin converting enzyme inhibitor enalapril (2 or 12 mg/kg/d) from week 4 to 36 after NX reduced the aortic plaque area fraction from 0.23±0.02 (n=20) in untreated mice to 0.11±0.01 (n=21) and 0.08±0.01 (n=23), respectively ( P <0.0001); the aortic plaque area fraction was 0.09±0.01 (n=22) in sham-operated controls. Enalapril from week 20 to 44 after NX also retarded the progression of atherosclerosis. Plasma levels of soluble intercellular adhesion molecule-1 (sICAM-1) and vascular cell adhesion molecule-1 (sVCAM-1) and concentrations of IgM antibodies against oxidized low density lipoprotein (OxLDL) increased after NX ( P <0.01). Enalapril (12 mg/kg/d) attenuated these increases ( P <0.05) and reduced aortic expression of vascular cell adhesion molecule (VCAM)-1 mRNA ( P <0.05). Atherosclerosis in NX mice was also reduced by losartan (an angiotensin II receptor-blocker), but not when blood pressure was lowered with hydralazine (a non-RAS-dependent vasodilator).

Conclusion— The results suggest that inhibition of RAS abolishes the proatherogenic effect of uremia independent of its blood pressure-lowering effect, possibly because of antiinflammatory and antioxidative mechanisms.

Vascular sources of oxidative stress: implications for uremia-related cardiovascular disease

Chronic oxidative stress that characterizes uremia has potentially devastating effects on the vasculature and has been advocated in the pathogenesis of accelerated atherosclerosis in this disease. Recent advances have been made in our understanding of the molecular mechanisms that regulate expression and activity of key enzymes of vascular oxidative stress (eg, nicotinamide adenine dinucleotide phosphate [NAD{P}H] oxidase) and that dissect their interactions with signalling pathways of inflammation. The finding that NAD(P)H oxidase is upregulated in experimental uremia has important consequences from a physiologic and a therapeutic standpoint. In addition, identification of novel proteins involved in systemic oxidative stress has shed some new light on the pathogenesis of vascular disease. p66(shc) is a cytoplasmic protein that is expressed in a wide range of cell types. Initially believed to be involved in signalling pathways that regulate cell growth and oxidative stress, it has now been shown to play a pivotal role in promoting endothelial dysfunction and atherosclerosis. Although a specific role in uremia-related vascular disease has not yet been shown, available data in humans suggest involvement of p66(shc) in clinical conditions associated with increased oxidative stress.

Inflammation but not oxidative stress is associated with beta-chemokine levels and prevalence of cardiovascular disease in uraemic patients

Inflammation and oxidative stress (SOX) have been reported in patients with chronic renal failure (CRF), but their influence on beta-chemokines levels and cardiovascular disease (CVD) prevalence remains unknown. We assessed beta-chemokines, SOX markers and high sensitivity C-reactive protein (hs CRP) as a marker of inflammation in 40 uraemic patients, both with as well as without CVD and 20 controls. Compared with the controls, the patients with CVD showed a significant increase in plasma concentrations of monocyte chemoattractant protein-1 (MCP-1), total peroxide (both p<0.05), macrophage inflammatory protein 1beta (MIP-1beta) and hs CRP (both p<0.01). The values of MCP-1 and hs CRP were more elevated in patients with CVD than without CVD (p<0.01 and p<0.05; respectively). Both subgroup of CRF patients were lower of regulated upon activation, normal T cell expressed and secreted (RANTES) levels than in the controls (both p<0.001). The positive relationships were between hs CRP and presence of CVD, MIP-1beta (both p<0.01) and MCP-1 levels (p<0.05). SOX markers did not show any significant correlation with beta-chemokines, hs CRP and presence of CVD. We documented that increased inflammation but not SOX were associated with significant elevation in plasma beta-chemokines levels and CVD prevalence in CRF patients not requiring dialysis.

Increased whole blood chemiluminescence in patients with chronic renal failure independent of hemodialysis treatment

INTRODUCTION

The luminol-enhanced whole blood chemiluminescence (LBCL) assay is a rapid assay for the measurement of reactive oxygen species (ROS) generation by circulating phagocytes. This study's aim was to determine if patients on maintenance hemodialysis (HD) and non-dialyzed patients with chronic renal failure (CRF) have altered LBCL and if dialysis itself affects ROS production in the blood.

MATERIALS AND METHODS

Twenty-six HD patients, 11 non-dialyzed patients with CRF, and 20 gender- and age-matched healthy controls were studied. Resting (rCl) and 2 x 10(-5) M n-formyl-methionyl-leucyl-phenylalanine-stimulated LBCL (peak chemiluminescence: pCl, total light emission after agonist addition: tCl) calculated per 10(4) phagocytes present in the 3-mul blood samples were measured with a Bio-Orbit 1251 luminometer at 37 degrees C for 11 min.

RESULTS

Prior to the HD session, median rCL, pCL, and tCL were 1.5, 3.0, and 2.8 times higher in HD patients than in healthy controls (p<0.01) and tended to increase at the end of the session. Significant increases in tCl were observed at 30 min and 240 min (end) of HD (1023.5 vs. 1810.6 vs. 2006.8 arbitrary units x s/10(4) phagocytes, n=9, p<0.05). Median pCl and tCl were 5.0 and 4.3 times higher in non-dialyzed patients with CRF than in healthy controls (p<0.001). However, no significant differences were found between pre- and post-HD LBCL of HD patients and the LBCL of non-dialyzed patients with renal failure.

CONCLUSIONS

Blood from patients with renal failure generates elevated amounts of oxidants independently of HD treatment. This may add to the understanding of the nature of oxidative stress and suggests the need of anti-oxidant treatment in these patients.

New flow cytometric technique for the evaluation of circulating endothelial progenitor cell levels in various disease groups

Circulating endothelial progenitor cells (EPC) localise to sites of ischaemia and play a role in vascular repair and re-endothelialisation of injured blood vessels. Low levels of EPCs are associated with cardiovascular disease (CVD) in the general population. It is not clear at present whether and how the numbers of circulating EPCs vary in diseases other than CVD. We have enumerated EPCs by the flow cytometric analysis of whole blood by using a novel cocktail of monoclonal antibodies. This consisted of CD2FITC, CD13FITC and CD22FITC to eliminate non-progenitor cells and VEGFR2PE and CD133-streptavidin-PeCy7 to include only EPCs. We analysed 250 patients with varying stages of uraemia, 36 patients with inflammatory bowel disease (IBD) and 9 patients with acute respiratory distress syndrome and compared this to 74 healthy controls. Using flow cytometry we were able to measure the circulating levels of EPCs, with a result available within hours of the sample being obtained. Circulating EPC numbers vary in different patient groups and healthy controls. In uraemic patients, irrespective of disease severity, there are lower numbers of circulating EPC numbers compared to normal controls (46.6+/-3.7 vs. 66.1+/-4.7; p=0.03). This new technique provides a means of monitoring patients and shows a reduction in circulating EPCs in uraemic patients; this abnormality may be a target of novel therapies.

The uremic solute p-cresol decreases leukocyte transendothelial migration in vitro

Chronic renal failure (CRF) patients display an immunodeficiency state, and uremic solutes that accumulate during CRF may be involved in this immunodeficiency. In this study, we examined whether the uremic solute para-cresol (p-cresol), at concentrations similar to those found in patients, alters leukocyte transmigration in vitro. We found that p-cresol significantly inhibited monocyte THP-1 cell line and PBMCs transmigration across IL-1beta-stimulated human umbilical vein endothelial cell (HUVEC) in a static two-compartment model. This inhibitory effect of p-cresol persisted in the presence of a physiologic concentration of human serum albumin. In order to investigate the mechanism involved, expression of endothelial chemokines, fractalkine, monocyte chemoattractant protein 1 (MCP-1) and IL-8 and membrane expression of junctional adhesion molecule A (JAM-A or JAM-1) were studied. We found that p-cresol decreased mRNA expression of the chemokine fractalkine in IL-1beta-stimulated HUVEC, without modifying mRNA expression of MCP-1 and IL-8. In addition, p-cresol decreased IL-1beta-induced expression of membrane-bound and soluble forms of fractalkine and impaired the membrane expression of JAM-A. Taken together, these results suggest that p-cresol, by impairing leukocyte transendothelial migration, plays a role in the immune dysfunction of uremic patients.

Peripheral tissue release of interleukin-6 in patients with chronic kidney diseases: effects of end-stage renal disease and microinflammatory state

To examine if uremia influences muscle interleukin-6 (IL-6) metabolism we studied the exchange of IL-6 across the forearm in 16 patients with chronic kidney disease (CKD) (stages 3 and 4), in 15 hemodialysis (HD)-treated end-stage renal disease (ESRD) patients (n=15), and in six healthy controls. In addition, we performed an analysis of both IL-6 protein and IL-6 mRNA expression in muscle of CKD (stage 4) patients showing evidence of inflammation and in controls. A release of IL-6 from the forearm was observed in patients with elevated IL-6 plasma levels. Arterial IL-6 was directly related to released IL-6 (r=0.69; P<0.004) in HD patients. Both IL-6 protein and IL-6 mRNA expression were increased in muscle of inflamed CKD patients vs controls (P<0.05). Although muscle net protein balance was similar in all patients, it was significantly more negative in HD patients with high than in those with low IL-6 plasma levels (P<0.05). In addition, net protein balance was related to the forearm release of IL-6 in HD patients only (r=0.47; P<0.038). These data demonstrate that IL-6 expression is upregulated in muscle, and that muscle tissue, by releasing this cytokine, may contribute to the inflammatory response in HD patients. The release of IL-6 from peripheral tissues is associated with an increase in muscle protein loss in HD patients, suggesting that muscle release of IL-6 is linked to protein catabolism in these patients. The release of IL-6 from peripheral tissues may act as a signal for the inflammatory response and contribute to functional dysregulation in uremia.

Naïve and central memory T-cell lymphopenia in end-stage renal disease

End-stage renal disease (ESRD) is associated with increased propensity to infections, diminished response to vaccination, impaired cell-mediated immunity, and reduced CD4+/CD8+ T-lymphocyte ratio. Four subsets of CD4+ and CD8+ T cells have been recently identified: naïve cells (as yet uncommitted), central memory (CM) cells (previously programmed), and CD45RA-positive and CD45RA-negative effector memory (EM) cells (programmed to perform specific effector functions). The effect of ESRD on subpopulations of T lymphocytes is unclear and was studied here. Twenty-one hemodialysis patients and 21 age-matched controls were studied. Pre- and post-dialysis blood samples were obtained and analyzed by three-color flow cytometry. CD4+/CD8+ ratio and the numbers of the naïve and CM CD4+ and CD8+ T cells were significantly reduced, whereas the numbers of EM CD4+ and CD8+ T cells were unchanged in the ESRD group. The reduction of the naïve and CM T-cell counts in the ESRD group was associated with increased apoptosis of these cells. Negative correlations were found between severity of azotemia, oxidative stress, and hyperphosphatemia with the number of naïve T cells. Comparison of diabetic with non-diabetic ESRD patients revealed higher numbers of total CD8+ cells and EM CD8+ T cells in the diabetic group. Dialysis did not significantly change the naïve and CM CD4+ or CD8+ cell counts, but significantly lowered CD8+ EM cell count. Thus, ESRD results in increased apoptosis and diminished populations of naïve and CM T lymphocytes. This phenomenon may, in part, contribute to the impaired immune response in this population.

Reduced expression of Toll-like receptor 4 contributes to impaired cytokine response of monocytes in uremic patients

Toll-like receptors (TLRs) play a pivotal role in pathogen recognition and subsequent cytokine synthesis by immune cells. Uremic patients have a high infectious morbidity, but it remains unclear if this arises from the defective innate immune responses related to TLRs. We studied TLR4 expression in monocytes and their intracellular cytokine synthesis in response to lipopolysaccharide (LPS) stimulation in 35 predialysis patients with chronic kidney disease (CKD) with or without predisposition to bacterial infections and 16 age-matched controls. Expression of TLR4 in unstimulated peripheral monocytes was determined by staining with anti-TLR4 antibody and analysis with flow cytometry. Monocytes were then stimulated by LPS, labeled with anti-CD14 antibody, and subjected to intracellular cytokine staining and flow cytometry. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, and IL-8 synthesis was examined in CD14(+) monocytes. TLR4 expression was constitutively diminished in CKD patients with reduced expression being more severe in those CKD patients who were predisposed to infections. Monocytes from these infection prone CKD patients exhibited significantly reduced synthesis of TNF-alpha, IL-1beta, IL-6, and IL-8 in response to LPS challenge compared with those from control subjects. The intensity of synthesis of each cytokine significantly correlated with TLR4 expression levels in monocytes (P<0.01). The capacity of monocytes to synthesize proinflammatory cytokines was significantly reduced in infection prone CKD patients, and this may possibly be due to the reduced monocyte expression of TLR4. Abnormal TLR4 expression by monocytes may play a role in the susceptibility of such patients to bacterial infections.

TNF-alpha priming effect on polymorphonuclear leukocyte reactive oxygen species generation and adhesion molecule expression in hemodialyzed patients

INTRODUCTION

The study aimed to assess reactive oxygen species generation and the expressions of some surface antigens on polymorphonuclear leukocytes (PMNs) in patients on regular hemodialysis (HD) treatment.

MATERIALS AND METHODS

The respiratory burst of PMNs was determined with luminol-dependent chemiluminescence (CL) in resting cells and following N-formyl-methionyl-leucyl-phenylalanine (fMLP), phorbol 12-myristate 13-acetate (PMA), or opsonized zymosan (OZ) stimulation and expressed in arbitrary CL units times assay-time (aU x min). The expressions of CD11b/CD18, CD10, and CD13 receptors were determined with flow cytometry.

RESULTS

Basal PMN CL was increased in HD patients to up to 1285 +/- 129 aU x min compared with 895 +/- 88 aU x min in healthy controls (p < 0.05). The CL of unprimed PMNs increased after fMLP stimulation from 3085 +/- 746 to 4529 +/- 808 aU x min, and after OZ stimulation from 12945 +/- 1296 to 14678 +/- 1355 aU x min. PMA-stimulated CL of PMNs was similar to control values. The oxidative burst in PMNs from HD patients and healthy controls was similar in response to TNF-alpha alone. The CL of TNF-alpha-primed PMNs in HD patients was significantly lower than CL measured in healthy controls (p < 0.05). The expressions of CD10 and CD13 metalloproteinase receptors were also increased (p < 0.05). Although CD11b expression was significantly increased at rest and after fMLP stimulation, the expression of another beta-integrin heterodimer compound, CD18, was not increased.

CONCLUSIONS

These results provide evidence that TNF-alpha priming of PMNs is down-regulated in HD patients despite constitutive up-regulation of resting cytotoxicity and enhanced expression of adhesion and metalloproteinase receptors.

Reduced Capacity of Mononuclear Cells to Synthesize Cytokines against an Inflammatory Stimulus in Uremic Patients

BACKGROUND

The local production of cytokines and phagocytosis is pivotal in innate immunity. Uremic patients have a high infectious morbidity, but it remains unclear if this arises from incompetence of these local cellular functions.

METHODS

In 30 predialysis uremic patients and 20 controls, we studied the intracellular cytokine synthesis by mononuclear cells in response to stimulation. Moreover, phagocytic activity by leukocytes was tested. Lipopolysaccharide- or mitogen-stimulated peripheral blood cells were labeled with anti-CD14 and -CD4 antibodies, respectively and subjected to intracellular cytokine staining and flow cytometry. Tumor necrosis factor (TNF)-alpha, IL-1beta, IL-6, and IL-8 synthesis was examined in CD14(+) monocytes. IFN-gamma and IL-4 synthesis was examined in CD4(+) helper T cells to determine their Th1 or Th2 phenotype. The flow cytometric analysis of phagocytosis of opsonized bacteria was performed in whole blood.

RESULTS

Uremic patients exhibited a significantly reduced monokine response and inhibited development of helper T cells into Th1 or Th2 phenotypes compared with control subjects. Their phagocytic activity was comparable to control subjects. No clinical parameters were linked to in vitro cytokine production and phagocytic activity.

CONCLUSIONS

Mononuclear cells in uremic patients are hyporeactive to inflammatory challenge and this may be one reason why uremic patients are vulnerable to infections.

Aberrant activation of the TNF-alpha system and production of Fas and scavenger receptors on monocytes in patients with end-stage renal disease

Ten patients with nondialyzed chronic renal failure (CRF), 14 receiving continuous ambulatory peritoneal dialysis (CAPD), 16 receiving hemodialysis (HD), and 10 normal controls (NC), were evaluated. Levels of Fas antigen (CD95), scavenger receptors (CD36 and CD68), and tumor necrosis factor-receptor 2 (CD120b) on monocytes were measured using flow cytometry. All patients showed lymphocytopenia, and monocyte counts were decreased in those with CRF. Fas levels were higher in patients receiving HD than the others, and were higher in the CRF and CAPD groups than in controls. CD120b levels were similar to those of Fas. Monocyte CD36 levels in the dialysis groups were significantly higher than in the CRF and NC groups. CD68 was also significantly elevated in HD patients. Fas levels were positively correlated with those of CD120b and CD68. The patient groups showed higher levels of apoptotic markers and scavenger receptors, combined with activation of the TNF-alpha system, especially in patients receiving HD.

Replicative senescence in patients with chronic kidney failure

BACKGROUND

Chronic activation of immunocompetent cells may lead to stress-induced premature senescence (SIPS); these senescent cells are characterized by a decrease in telomere length. The present study evaluates SIPS in circulating immunocompetent cells from predialysis patients, patients on hemodialysis, and in renal transplant patients with normal renal function.

METHODS

Determination of telomere length by flow-fluorescence in situ hybridization (FISH), expression of surface molecules, and evaluation of apoptosis was performed by flow cytometry.

RESULTS

In uremic predialysis patients, we observed a subpopulation of lymphocytes with short telomeres. However, in this population of patients we did not observe SIPS mononuclear cells. In hemodialysis patients, we found a subpopulation of SIPS mononuclear cells that also showed phenotypic changes of proinflammatory activity. Finally, transplant patients with normal renal function also exhibited a subpopulation of SIPS lymphocytes, which can be attributed to chronic lymphocyte activation induced by the major histocompatibility complex.

CONCLUSION

In chronic kidney disease patients, immunocompetent cells undergo SIPS, a process associated with chronic cell activation and induced by numerous stimuli including uremia, hemodialysis membranes, and bacterial products. Because SIPS immunocompetent cells are activated cells with proinflammatory features and live longer in peripheral blood, it is likely that SIPS cells contribute significantly to the chronic inflammatory state of patients with advanced renal failure.

IL-10, IL-6, and TNF-alpha: central factors in the altered cytokine network of uremia--the good, the bad, and the ugly

It has been increasingly apparent that wasting and cardiovascular disease (CVD) is associated with a persistent systemic inflammatory response in end-stage renal disease (ESRD) patients. The reasons for the increased risk of inflammation in ESRD patients appear to be complex, including non-dialysis as well as dialysis-related factors. The combination of an impaired immune response coupled with persistent immune stimulation may have a role in the low-grade systemic inflammation and altered cytokine balance that characterizes the uremic state and which may translate into increased risk for vascular disease. The accelerated atherosclerotic process of ESRD may involve several interrelated processes, such as oxidative stress, endothelial dysfunction, and vascular calcification, in a milieu of constant low-grade inflammation with impaired function of neutrophils and T cells, as well as a dysregulated cytokine network. Although a large number of pro- and anti-inflammatory cytokines are of importance, available data suggest that the anti-inflammatory cytokine interleukin (IL)-10 and the mainly proinflammatory cytokines IL-6 and tumor necrosis factor-alpha (TNF-alpha) may play important roles in the development of Th imbalance, CVD and wasting in the uremic milieu. Given the strong association between proinflammatory cytokines and complications common in ESRD, such as vascular calcification and wasting, the potential role of both general and targeted anticytokine treatment strategies in ESRD patients needs further evaluation.

In uremia, plasma levels of anti-protein C and anti-protein S antibodies are associated with thrombosis

BACKGROUND

Vascular access thrombosis is an important cause of morbidity in patients with end-stage renal failure on maintenance hemodialysis (MHD). However, little is known about its risk factors. The present study was undertaken to evaluate the role of coagulation factors, fibrinolytic factors, and anti-phospholipid antibodies (aPL). In particular, we have evaluated the role of anti-protein C and anti-protein S antibodies in patients on MHD with and without thrombosis because no data are available in the literature.

METHODS

The study group comprised 30 patients with thrombotic complications (TC), 40 patients matched for age, sex, and dialytic age with no thrombotic complications (NTC) and 400 controls. We have measured: anti-protein C antibodies, anti-protein S antibodies, anticardiolipin antibodies (ACA), anti-beta2-glycoprotein antibodies (beta2-GPI), and anti-prothrombin antibodies (aPT), along with prothrombin time, fibrinogen, plasminogen, protein C, protein S, anti-thrombin III, APC-resistance test, D-dimer, tissue-type plasminogen's activator, plasminogen activator inhibitor-1 (PAI-1), prothrombin fragment 1+2, factors of the intrinsic and extrinsic pathway, C-reactive protein, and homocysteine.

RESULTS

There were no significant differences between groups for prothrombin time, fibrinogen, plasminogen, protein C, protein S, anti-thrombin III, activated protein C (APC) resistance, D-dimer, tPA, C-reactive protein, Factors II, X, and VII. The anti-beta2-GP1 and aPT were elevated in both TC and NTC patients, compared to the control group. Significant differences between TC and NTC groups were found for anti-protein C and anti-protein S antibodies, ACA-IgM, PAI-1, Factor VIII, prothrombin fragments 1+2, and homocysteine.

CONCLUSION

The most novel finding was a significant elevation of anti-protein C antibodies and anti-protein S antibodies in the TC group (i.e., in patients on MHD with thrombosis of vascular access). It indicates that other pathogenetic mechanisms in addition to endothelial damage may cause hypercoagulability in uremia.