Novel Aspects of the Immune Response Involved in the Peritoneal Damage in Chronic Kidney Disease Patients under Dialysis

Chronic kidney disease (CKD) incidence is growing worldwide, with a significant percentage of CKD patients reaching end-stage renal disease (ESRD) and requiring kidney replacement therapies (KRT). Peritoneal dialysis (PD) is a convenient KRT presenting benefices as home therapy. In PD patients, the peritoneum is chronically exposed to PD fluids containing supraphysiologic concentrations of glucose or other osmotic agents, leading to the activation of cellular and molecular processes of damage, including inflammation and fibrosis. Importantly, peritonitis episodes enhance peritoneum inflammation status and accelerate peritoneal injury. Here, we review the role of immune cells in the damage of the peritoneal membrane (PM) by repeated exposure to PD fluids during KRT as well as by bacterial or viral infections. We also discuss the anti-inflammatory properties of current clinical treatments of CKD patients in KRT and their potential effect on preserving PM integrity. Finally, given the current importance of coronavirus disease 2019 (COVID-19) disease, we also analyze here the implications of this disease in CKD and KRT.

Effect of the one-day fasting on cortisol and DHEA daily rhythm regarding sex, chronotype, and age among obese adults

Introduction

Physiological and biochemical processes in the human body occur in a specific order and show rhythmic variability. Time dependence characterizes the secretion of cortisol and dehydroepiandrosterone (DHEA). One-day fasting implies alternating fasting days and eating days. The study aimed to determine how 24-h fasting affects the daily rhythm of cortisol and DHEA levels in obese people while taking into account gender and chronotype.

Methods

Forty-nine obese patients (BMI 32.2-67.1 kg/m²; 25 women and 24 men) underwent a 3-week hospital-controlled calorie restriction diet to reduce body weight. During hospitalization, patients fasted for 1 day, during which only water could be consumed. Samples of whole mixed unstimulated saliva were collected at 2-3-h intervals over a 64-h period and analyzed for cortisol and DHEA by immunoassays. The individual chronotypes were assessed by the morning and evening questionnaire, according to Horne and Östberg. Three components of daily rhythm were evaluated: amplitude, acrophase, and the so-called MESOR.

Results

Cortisol rhythm showed differences in amplitude (p = 0.0127) and acrophase (p = 0.0005). The amplitude on the fasting day was 11% higher (p = 0.224) than the day after. The acrophase advanced on the day of fasting, 48 min earlier than the day before (p = 0.0064), and by 39 min to the day after fasting (p = 0.0005). In the rhythm of DHEA, differences were found in the MESOR (p = 0.0381). The MESOR on the fasting day increased.

Discussion

Our results obtained during 64 consecutive hours of saliva sampling suggest that one-day fasting may affect three components of cortisol and DHEA daily rhythm. Additionally, no differences were found in the daily rhythm between the morning and evening chronotypes and between females and males. Although aging did not influence daily cortisol rhythm, DHEA amplitude, MESOR, and acrophase changed with age. To the best of our knowledge, this is the first presentation of changes in DHEA rhythm during one-day fasting.

Angiogenic Role of Mesothelium-Derived Chemokine CXCL1 During Unfavorable Peritoneal Tissue Remodeling in Patients Receiving Peritoneal Dialysis as Renal Replacement Therapy

Peritoneal dialysis (PD) is a valuable ‘home treatment’ option, even more so during the ongoing Coronavirus pandemic. However, the long-term use of PD is limited by unfavourable tissue remodelling in the peritoneal membrane, which is associated with inflammation-induced angiogenesis. This appears to be driven primarily through vascular endothelial growth factor (VEGF), while the involvement of other angiogenic signaling pathways is still poorly understood. Here, we have identified the crucial contribution of mesothelial cell-derived angiogenic CXC chemokine ligand 1 (CXCL1) to peritoneal angiogenesis in PD. CXCL1 expression and peritoneal microvessel density were analysed in biopsies obtained by the International Peritoneal Biobank (NCT01893710 at www.clinicaltrials.gov), comparing 13 children with end-stage kidney disease before initiating PD to 43 children on chronic PD. The angiogenic potential of mesothelial cell-derived CXCL1 was assessed in vitro by measuring endothelial tube formation of human microvascular endothelial cells (HMECs) treated with conditioned medium from human peritoneal mesothelial cells (HPMCs) stimulated to release CXCL1 by treatment with either recombinant IL-17 or PD effluent. We found that the capillary density in the human peritoneum correlated with local CXCL1 expression. Both CXCL1 expression and microvessel density were higher in PD patients than in the age-matched patients prior to initiation of PD. Exposure of HMECs to recombinant CXCL1 or conditioned medium from IL-17-stimulated HPMCs resulted in increased endothelial tube formation, while selective inhibition of mesothelial CXCL1 production by specific antibodies or through silencing of relevant transcription factors abolished the proangiogenic effect of HPMC-conditioned medium. In conclusion, peritoneal mesothelium-derived CXCL1 promotes endothelial tube formation in vitro and associates with peritoneal microvessel density in uremic patients undergoing PD, thus providing novel targets for therapeutic intervention to prolong PD therapy.

Predictors of Early-Recurrence Atrial Fibrillation after Catheter Ablation in Women and Men with Abnormal Body Weight

Our study aimed to select factors that affect the rate of early recurrence (up to 3 months) of atrial fibrillation (AF) (ERAF) following pulmonary veins isolation (PVI) in obese women and men. The study comprised 114 patients: 54 women (age: 63.8 ± 6.3, BMI 31 ± 4 kg/m²), and 60 men (age: 60.7 ± 6.7; BMI 31 ± 3 kg/m²) with paroxysmal, persistent and long-standing persistent AF. They had been scheduled to undergo cryoballoon (men n = 30; women n = 30) and radiofrequency (RF) ablation (men n = 30; women n = 24) using the CARTO-mapping. The blood was collected at baseline and 24 h after ablation. The rate of ERAF was comparable after cryoballoon and RF ablation and constituted 18% in women and 22% in men. Almost 70 parameters were selected to perform univariate and multivariate analysis and to create a multivariate logistic regression (MLR) model of ERAF in the obese men and women. The MLR analysis was performed by forward stepwise logistic regression with three variables. It was only possible to create the MLR model for the group of obese men. It revealed a poor predictive value with an unsatisfactory sensitivity of 31%. Men with ERAF: smokers (OR 39.25, 95% CI 1.050-1467.8, p = 0.0021), with a higher ST2 elevation (OR 1.68, 95% CI 1.115-2.536, p = 0.0021) who received dihydropyridine calcium channel blockers (OR 0.042, 95% CI 0.002-1.071, p = 0.0021) less frequently. Our results indicate a complex pathogenesis of ERAF dependent on the patients' gender.

Control of neutrophil influx during peritonitis by transcriptional cross-regulation of chemokine CXCL1 by IL-17 and IFN-γ

Neutrophil infiltration is a hallmark of peritoneal inflammation, but mechanisms regulating neutrophil recruitment in patients with peritoneal dialysis (PD)-related peritonitis are not fully defined. We examined 104 samples of PD effluent collected during acute peritonitis for correspondence between a broad range of soluble parameters and neutrophil counts. We observed an association between peritoneal IL-17 and neutrophil levels. This relationship was evident in effluent samples with low but not high IFN-γ levels, suggesting a differential effect of IFN-γ concentration on neutrophil infiltration. Surprisingly, there was no association of neutrophil numbers with the level of CXCL1, a key IL-17-induced neutrophil chemoattractant. We investigated therefore the production of CXCL1 by human peritoneal mesothelial cells (HPMCs) under in vitro conditions mimicking clinical peritonitis. Stimulation of HPMCs with IL-17 increased CXCL1 production through induction of transcription factor SP1 and activation of the SP1-binding region of the CXCL1 promoter. These effects were amplified by TNFα. In contrast, IFN-γ dose-dependently suppressed IL-17-induced SP1 activation and CXCL1 production through a transcriptional mechanism involving STAT1. The SP1-mediated induction of CXCL1 was also observed in HPMCs exposed to PD effluent collected during peritonitis and containing IL-17 and TNFα, but not IFN-γ. Supplementation of the effluent with IFN-γ led to a dose-dependent activation of STAT1 and a resultant inhibition of SP1-induced CXCL1 expression. Transmesothelial migration of neutrophils in vitro increased upon stimulation of HPMCs with IL-17 and was reduced by IFN-γ. In addition, HPMCs were capable of binding CXCL1 at their apical cell surface. These observations indicate that changes in relative peritoneal concentrations of IL-17 and IFN-γ can differently engage SP1-STAT1, impacting on mesothelial cell transcription of CXCL1, whose release and binding to HPMC surface may determine optimal neutrophil recruitment and retention during peritonitis. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

The intensity of joint pain in relation to changes in serum TNFα during therapy with anti-TNFα inhibitors

Introduction

Tumor necrosis factor-alpha (TNFα) inhibitors have significantly improved the outcomes of treatment for rheumatoid arthritis (RA). In the present study, we aimed to determine whether serum levels of TNFα during therapy with TNFα inhibitors do really reflect the disease activity and correspond to the intensity of pain experienced.

Materials and methods

Thirty RA patients were examined before and after 12 weeks of routine therapy with TNFα inhibitors. Serum levels of TNFα were measured with a high-sensitivity immunoassay and related to patients’ clinical and biochemical status. Disease activity was assessed by the modified disease activity score (DAS28).

Results

A median relative change in TNFα was 13%. The patients were stratified according to whether the relative change in serum TNFα after therapy was above or below this median value. The patients from both subgroups did not differ in baseline characteristics and response to therapy. However, the patients in whom serum TNFα increased after therapy above the median value had more tender joints after treatment than patients from the other group. Consequently, the number of tender joints after the treatment correlated with absolute TNFα concentrations at this time (r = 0.37; p = 0.049) and the magnitude of changes in serum TNFα correlated with a change in the number of tender joints (r = − 0.48; p = 0.008).

Conclusions

Circulating TNFα levels did not decrease in RA patients treated with TNFα inhibitors, despite clinical and biochemical improvement. It is possible, that circulating TNFα is responsible for the persistence of joint pain in this group of patients.

IL-17 in Peritoneal Dialysis-Associated Inflammation and Angiogenesis: Conclusions and Perspectives

Long-term peritoneal dialysis (PD) is associated with peritoneal membrane remodeling. This includes changes in peritoneal vasculature, which may ultimately lead to inadequate solute and water removal and treatment failure. The potential cause of such alterations is chronic inflammation induced by repeated episodes of infectious peritonitis and/or exposure to bioincompatible PD fluids. While these factors may jeopardize the peritoneal membrane integrity, it is not clear why adverse peritoneal remodeling develops only in some PD patients. Increasing evidence points to the differences that occur between patients in response to the same invading microorganism and/or the differences in the course of inflammatory reaction triggered by different species. Such differences may be related to the involvement of different inflammatory mediators. Here, we discuss the potential role of IL-17 in these processes with emphasis on its impact on peritoneal mesothelial cells and peritoneal vascularity.

Epithelial-to-Mesenchymal Transition and Migration of Human Peritoneal Mesothelial Cells Undergoing Senescence

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) of human peritoneal mesothelial cells (HPMCs) contributes to fibrotic thickening of the peritoneum that develops in patients on peritoneal dialysis (PD). The process is thought to be largely mediated by transforming growth factor-beta (TGF-β). As TGF-β has also been implicated in senescence of HPMCs, we have performed an exploratory study to examine if senescent HPMCs can undergo EMT.

METHODS

Omentum-derived HPMCs were rendered senescent by repeated passages in culture. Features of EMT were assessed by immunostaining and quantitative polymerase chain reaction (qPCR) at various stages of the HPMC lifespan and after treatment with or without TGF-β. The motility of HPMCs was assessed in a scratch wound migration assay.

RESULTS

Replicative senescence of HPMCs was associated with a gradual increase in the constitutive expression of EMT markers, including increased production of extracellular matrix proteins. However, senescent HPMCs also retained epithelial cell features such as cytokeratin, calretinin, and E-cadherin and showed decreased, rather than increased, motility. In contrast, exposure to TGF-β resulted in an up-regulation of mesenchymal markers and down-regulation of epithelial markers. Such effects of TGF-β occurred both in young and senescent cells, although they were less pronounced in senescence.

CONCLUSIONS

Senescence of HPMCs is associated with spontaneous development of several EMT features. At the same time, senescent HPMCs preserve epithelial cell-like characteristics and are less prone to develop a full EMT phenotype in response to TGF-β. These observations may support the concept of cellular senescence being antagonistically pleiotropic with regard to EMT.

Thy-1+/- fibroblast subsets in the human peritoneum

Fibrotic thickening of the peritoneum develops in patients receiving peritoneal dialysis (PD) for renal failure. For unknown reasons, however, in some patients it progresses to extensive fibrosis that compromises dialysis capacity of the peritoneum. It is increasingly clear that fibroblasts display large heterogeneity not only between but also within tissues. Differential surface expression of thymocyte differentiation antigen 1 (Thy-1) has been shown to identify functionally distinct fibroblast subsets in several organs. Here, we isolated Thy-1^+/- subsets of human peritoneal fibroblasts (HPFB) and analyzed them in terms of profibrotic myofibroblast features. In healthy individuals, Thy-1⁺ cells constituted ~45% of the HPFB population found in the greater omentum but were not detected in the parietal peritoneum. When propagated in culture and compared with Thy-1^- cells, omentum-derived Thy-1⁺ HPFB consistently displayed an increased expression of α-smooth muscle actin, collagen I, and transforming growth factor-β1. They also showed greater proliferation capacity and enhanced contractile properties. The number of Thy-1⁺ HPFB increased significantly in PD patients and made up more than 70 and 95% of all HPFB found in the omentum and parietal peritoneum, respectively. These data indicate that the expansion of Thy-1⁺ fibroblasts may contribute to fibrotic thickening of the peritoneal membrane during PD.

The role of mTOR inhibitors and HMG-CoA reductase inhibitors on young and old endothelial cell functions, critical for re-endothelialisation after percutaneous coronary intervention: an in vitro study

Percutaneous coronary intervention (PCI) has become a standard treatment in patients with acute coronary syndrome. However, it is associated with endothelial cell denudation, which may predispose to in-stent thrombosis and restenosis. Pharmacological methods which prevent restenosis can delay post-PCI re-endothelialisation. We have therefore examined how atorvastatin (HMG-CoA reductase inhibitor), sirolimus and everolimus (mTOR inhibitors) affect young and old endothelial cell functions which are responsible for wound healing after PCI. Replicative senescence was induced by serial passages of human umbilical vein endothelial cells (HUVECs). The cells which were examined at their first passages and last passages were designated as 'young' and 'old' respectively. Young and old endothelium were grown to confluence and were wounded by scraping. Scratch healing in the presence or absence of atorvastatin (AT), rapamycin (SR) and everolimus (EV) was monitored by time-lapse microscopy. In addition cells were assessed for viability (MTT assay), migration (chemotaxis chamber), proliferation (³H-thymidine), and cytokine production (immunoassays). Senescent endothelial cells produce more proinflammatory cytokines, angiogenic VEGF and extracellular matrix proteins. They stop proliferating and have diminished migration. When compared to young endothelium, they have similar viability and can regenerate wounds in comparable time. The drugs that have been tested have anti-inflammatory properties but even after pretreatment old cells still produced significantly higher concentration of tested mediators in comparison with young ones. In the concentration obtained in serum after stent implantation, mTOR inhibitors in dose-dependent manner reduced cell proliferation, migration and wound healing. Reduced healing is more pronounced in young endothelium. Atorvastatin, at clinically relevant concentration, is safe for young and old cells. Atorvastatin, sirolimus and everolimus inhibited the secretion of pro-inflammatory mediators in young and old endothelium. In concentrations seen in serum during standard therapy, rapalogs impair endothelial cell regeneration after injuries mimicking those occurring during PCI, while atorvastatin does not affect the healing.

Activation of nuclear factor of activated T cells 5 in the peritoneal membrane of uremic patients

Peritoneal inflammation and fibrosis are responses to the uremic milieu and exposure to hyperosmolar dialysis fluids in patients on peritoneal dialysis. Cells respond to high osmolarity via the transcription factor nuclear factor of activated T cells (NFAT5). In the present study, the response of human peritoneal fibroblasts to glucose was analyzed in vitro. Expression levels of NFAT5 and chemokine (C-C motif) ligand (CCL2) mRNA were quantified in peritoneal biopsies of five nonuremic control patients, five uremic patients before PD (pPD), and eight patients on PD (oPD) using real-time PCR. Biopsies from 5 control patients, 25 pPD patients, and 25 oPD patients were investigated using immunohistochemistry to detect the expression of NFAT5, CCL2, NF-κB p50, NF-κB p65, and CD68. High glucose concentrations led to an early, dose-dependent induction of NFAT5 mRNA in human peritoneal fibroblasts. CCL2 mRNA expression was upregulated by high concentrations of glucose after 6 h, but, most notably, a concentration-dependent induction of CCL2 was present after 96 h. In human peritoneal biopsies, NFAT5 mRNA levels were increased in uremic patients compared with nonuremic control patients. No significant difference was found between the pPD group and oPD group. CCL2 mRNA expression was higher in the oPD group. Immunohistochemistry analysis was consistent with the results of mRNA analysis. CD68-positive cells were significantly increased in the oPD group. In conclusion, uremia results in NFAT5 induction, which might promote early changes of the peritoneum. Upregulation of NFAT5 in PD patients is associated with NFκB induction, potentially resulting in the recruitment of macrophages.

The proto-oncogene c-Fos transcriptionally regulates VEGF production during peritoneal inflammation

Vascular endothelial growth factor (VEGF) and transforming growth factor-β1 (TGF-β1) are key mediators of adverse peritoneal membrane remodeling in peritoneal dialysis eventually leading to ultrafiltration failure. Both are pleiotropic growth factors with cell type-dependent regulation of expression and biological effects. Here we studied regulation of TGF-β1-induced VEGF expression in human peritoneal mesothelial cells in the absence or presence of proinflammatory stimuli, tumor necrosis factor-α (TNF-α) or interleukin-1β (IL-1β). Quiescent human peritoneal mesothelial cells secreted only trace amounts of VEGF. Stimulation with TGF-β1 resulted in time- and dose-dependent increases in VEGF mRNA expression and protein release. TNF-α and IL-1β alone had minimal effects but acted in synergy with TGF-β1. Combined stimulation led to induction of transcription factor c-Fos and activation of the VEGF promoter region with high-affinity binding sites for c-Fos. Inhibition of c-Fos by small interfering RNA interference or by pharmacological blockade with SR-11302 decreased VEGF promoter activity and downregulated its expression and release. Exposure of human peritoneal mesothelial cells to dialysate effluent containing increased levels of TGF-β1, TNF-α, and IL-1β obtained during peritonitis resulted in a dose-dependent VEGF induction that was significantly attenuated by SR-11302. Thus, dialysate TGF-β1, IL-1β, and TNF-α act through c-Fos to synergistically upregulate VEGF production in peritoneal mesothelium and may represent an important regulatory link between inflammation and angiogenesis in the peritoneal membrane.

Atorvastatin does not impair endothelial cell wound healing in an in vitro model of vascular injury

Percutaneous coronary intervention (PCI) became standard treatment modality for coronary revascularization. However, it is associated with endothelial cell denudation, which may predispose to in-stent thrombosis and restenosis. Since statins may inhibit vascular cell proliferation, one may fear that their early administration will delay post-PCI re-endothelialization. We have therefore employed an in vitro scratch assay to examine how atorvastatin affects endothelial cell wound healing. Human umbilical vein endothelial cells (HUVEC) were grown to confluence and wounded by scraping. Scratch healing in the presence or absence of atorvastatin was monitored by time-lapse photo-microscopy. In addition cells were assessed for viability (MTT assay), migration (chemotaxis chamber), proliferation ((3)H-thymidine and bromodeoxyuridine incorporation), and cytokine production (immunoassays). The exposure of HUVEC to atorvastatin resulted in a dose-dependent decrease in cell viability and proliferation. However, this effect was observed only at doses ≥1 μM, which is well above the concentrations seen in vivo. At clinically relevant doses (≤0.1 μM) atorvastatin did not impair wound closure, nor did it inhibit cell viability, proliferation, and migration. It did however reduce the constitutive and the stimulated release of cytokines (IL-6, IL-8, MCP-1), adhesion molecules (sICAM-1) and matrix proteins (fibronectin). We conclude that atorvastatin at doses corresponding to concentrations seen in serum during standard therapy does not impair endothelial cell regeneration after injuries mimicking those occurring during PCI. It does, however, inhibits the secretion of pro-inflammatory mediators.

Relation of salivary antioxidant status and cytokine levels to clinical parameters of oral health in pregnant women with diabetes

OBJECTIVE

Both pregnancy and diabetes are thought to predispose to the impairment of oral health. As saliva contributes to oral homeostasis, we have characterised its properties and flow rate in pregnant women with or without diabetes.

DESIGN

Unstimulated whole mixed saliva was collected from 63 women in the first trimester of pregnancy and analysed for the concentration of selected antioxidants, cytokines, and growth factors.

RESULTS

Pregnant women with diabetes were found to have markedly increased indexes of caries activity, plaque formation, gingival and periodontal status, as well as increased salivary antioxidant capacity and pro-inflammatory cytokine levels. These changes were more pronounced in patients with long-term disease and systemic diabetic complications, but only partly correlated with the level of blood glycated haemoglobin. Of the cytokines examined, salivary VEGF and HGF concentrations in diabetic pregnant women correlated in a positive and negative manner, respectively, with the prevalence of caries. Moreover, VEGF levels in this group correlated inversely with the probing depth and clinical attachment levels. All such associations did not occur in healthy individuals. In contrast, the salivary pH and flow rate correlated inversely with several parameters of caries and plaque formation irrespectively of whether the pregnant women were diabetic or not.

CONCLUSIONS

Diabetes in pregnant women significantly changes saliva properties, which may contribute to accelerated deterioration of the oral status in this population.