Calprotectin blockade inhibits long-term vascular pathology following peritoneal dialysis-associated bacterial infection

Bacterial infections and the concurrent inflammation have been associated with increased long-term cardiovascular (CV) risk. In patients receiving peritoneal dialysis (PD), bacterial peritonitis is a common occurrence, and each episode further increases late CV mortality risk. However, the underlying mechanism(s) remains to be elucidated before safe and efficient anti-inflammatory interventions can be developed. Damage-Associated Molecular Patterns (DAMPs) have been shown to contribute to the acute inflammatory response to infections, but a potential role for DAMPs in mediating long-term vascular inflammation and CV risk following infection resolution in PD, has not been investigated. We found that bacterial peritonitis in mice that resolved within 24h led to CV disease-promoting systemic and vascular immune-mediated inflammatory responses that were maintained up to 28 days. These included higher blood proportions of inflammatory leukocytes displaying increased adhesion molecule expression, higher plasma cytokines levels, and increased aortic inflammatory and atherosclerosis-associated gene expression. These effects were also observed in infected nephropathic mice and amplified in mice routinely exposed to PD fluids. A peritonitis episode resulted in elevated plasma levels of the DAMP Calprotectin, both in PD patients and mice, here the increase was maintained up to 28 days. In vitro, the ability of culture supernatants from infected cells to promote key inflammatory and atherosclerosis-associated cellular responses, such as monocyte chemotaxis, and foam cell formation, was Calprotectin-dependent. In vivo, Calprotectin blockade robustly inhibited the short and long-term peripheral and vascular consequences of peritonitis, thereby demonstrating that targeting of the DAMP Calprotectin is a promising therapeutic strategy to reduce the long-lasting vascular inflammatory aftermath of an infection, notably PD-associated peritonitis, ultimately lowering CV risk

Novel aspects of the immune response involved in the peritoneal damage in chronic Kkdney 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 KRTThis research was funded by grants from the Instituto de Salud Carlos III (ISCIII) and Fondos FEDER European Union (PI20/00140, PI19/00815, and DTS20/00083). Red de Investi gación Renal REDINREN: RD16/0009/0003 to M.R-O and RICORS2040; RD21/0005/0002 funded by European Union—NextGenerationEU, Sociedad Española de Nefrología. Innovation programme under the Marie Skłodowska-Curie grant of the European Union’s Horizon 2020 (IMPROVE-PD ID: 812699) to M.R-O. E.K. was supported by the grant from the Narodowe Centrum Nauki (NCN, Polish National Science Centre; 2018/29/N/NZ3/02504). R.S. was supported by Ministry for Health of Italy (Ricerca Corrente). This work was also supported by a grant (PID 2019-110132RB I00/AEI/10.13039/501100011033) from the Spanish Ministry of Science and Innovation/Fondo Europeo de Desarrollo Regional (MICINN/FEDER) to M.L.-C

Paricalcitol reduces peritoneal fibrosis in mice through the activation of regulatory T cells and reduction in IL-17 production

Fibrosis is a significant health problem associated with a chronic inflammatory reaction. The precise mechanisms involved in the fibrotic process are still poorly understood. However, given that inflammation is a major causative factor, immunomodulation is a possible therapeutic approach to reduce fibrosis. The vitamin D receptor (VDR) that is present in all hematopoietic cells has been associated with immunomodulation. We investigated whether the intraperitoneal administration of paricalcitol, a specific activator of the VDR, modulates peritoneal dialysis fluid (PDF)-induced peritoneal fibrosis. We characterized the inflammatory process in the peritoneal cavity of mice treated or not treated with paricalcitol and analyzed the ensuing fibrosis. The treatment reduced peritoneal IL-17 levels, which strongly correlated with a significantly lower peritoneal fibrotic response. In vitro studies demonstrate that both CD4+ and CD8+ regulatory T cells appear to impact the regulation of IL-17. Paricalcitol treatment resulted in a significantly increased frequency of CD8+ T cells showing a regulatory phenotype. The frequency of CD4+ Tregs tends to be increased, but it did not achieve statistical significance. However, paricalcitol treatment increased the number of CD4+ and CD8+ Treg cells in vivo. In conclusion, the activation of immunological regulatory mechanisms by VDR signaling could prevent or reduce fibrosis, as shown in peritoneal fibrosis induced by PDF exposure in mice.This study was supported by RETICS 06/0016 (VFM, RS) and FIS PI 09/0064 (RS) from the Fondo de Investigaciones Sanitarias (Health Research Fund). MLC was funded by SAF 2013-47611-R, SAF 2010-21249, and SAF 2007-61201 from the Ministerio de Economía y competitividad. MRO was supported by RETICS 12/0021,S2012DMD2321 from the Comunidad Autónoma de Madrid, PI 11/01854 from Fondo Investigaciones Sanitarias. GTGM was supported by Renal Foundation Íñigo Álvarez de Toledo, FIBHULP, and by Severo Ochoa FoundationPeer Reviewe

Targeting toll-like receptors with soluble toll-like receptor 2 prevents peritoneal dialysis solution-induced fibrosis

Peritoneal membrane failure due to fibrosis limits the use of peritoneal dialysis (PD). Peritoneal fibrosis may potentially be induced by sterile inflammation caused by ongoing cellular stress due to prolonged exposure to PD solutions (PDS). Effective therapies to prevent this process remain to be developed. Toll-like receptors (TLRs) mediate sterile inflammation by recognizing damage-associated molecular patterns (DAMPs) released by cellular stress. We evaluated the involvement of TLRs and DAMPs in PDS-induced fibrosis models and the therapeutic potential of TLR-DAMP targeting for preventing fibrosis. A range of PDS elicited pro-inflammatory and fibrotic responses from PD patient peritoneal leukocytes, mesothelial cells and mouse peritoneal leukocytes. TLR2/4 blockade of human peritoneal cells or TLR2/4 knockouts inhibited these effects. PDS did not induce rapid ERK phosphorylation or IκB-α degradation, suggesting that they do not contain components capable of direct TLR activation. However, PDS increased the release of Hsp70 and hyaluronan, both TLR2/4 DAMP ligands, by human and mouse peritoneal cells, and their blockade decreased PDS-driven inflammation. Soluble TLR2, a TLR inhibitor, reduced PDS-induced pro-inflammatory and fibrotic cytokine release ex vivo. Daily catheter infusion of PDS in mice caused peritoneal fibrosis, but co-administration of soluble TLR2 prevented fibrosis, suppressed pro-fibrotic gene expression and pro-inflammatory cytokine production, reduced leukocyte/neutrophil recruitment, recovered Treg cell levels and increased the Treg:Th17 ratio. Thus, TLR2/4, Hsp70 and hyaluronan showed major roles in PDS-induced peritoneal inflammation and fibrosis. The study demonstrates the therapeutic potential of a TLR-DAMP targeting strategy to prevent PDS-induced fibrosis

Alanyl-Glutamine Restores Tight Junction Organization after Disruption by a Conventional Peritoneal Dialysis Fluid

Understanding and targeting the molecular basis of peritoneal solute and protein transport is essential to improve peritoneal dialysis (PD) efficacy and patient outcome. Supplementation of PD fluids (PDF) with alanyl-glutamine (AlaGln) increased small solute transport and reduced peritoneal protein loss in a recent clinical trial. Transepithelial resistance and 10 kDa and 70 kDa dextran transport were measured in primary human endothelial cells (HUVEC) exposed to conventional acidic, glucose degradation products (GDP) containing PDF (CPDF) and to low GDP containing PDF (LPDF) with and without AlaGln. Zonula occludens-1 (ZO-1) and claudin-5 were quantified by Western blot and immunofluorescence and in mice exposed to saline and CPDF for 7 weeks by digital imaging analyses. Spatial clustering of ZO-1 molecules was assessed by single molecule localization microscopy. AlaGln increased transepithelial resistance, and in CPDF exposed HUVEC decreased dextran transport rates and preserved claudin-5 and ZO-1 abundance. Endothelial clustering of membrane bound ZO-1 was higher in CPDF supplemented with AlaGln. In mice, arteriolar endothelial claudin-5 was reduced in CPDF, but restored with AlaGln, while mesothelial claudin-5 abundance was unchanged. AlaGln supplementation seals the peritoneal endothelial barrier, and when supplemented to conventional PD fluid increases claudin-5 and ZO-1 abundance and clustering of ZO-1 in the endothelial cell membrane.This work is part of the IMPROVE-PD project that has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement number 812699. M.B. is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Projektnummer 419826430. R.H. was supported by a research fellowship of the European Renal Association and European Dialysis and Transplant Association (ERA-EDTA). E.L. was supported by the ÚNKP-18-2 New National Excellence Program of the Ministry of Human Capacities, Hungary. E.L. and H.J. were supported by Jellinek-Harry scholarship. S.G.Z. acknowledges the Alexander von Humboldt Stiftung/Foundation for an Experienced Researcher Fellowship (2019–2021) and the International Peritoneal Dialysis Society (ISPD) for an International Cooperation Research Grant (2019–2021). C.P.S. has obtained funding from European Nephrology and Dialysis Institute (ENDI).Peer reviewe

Potential therapeutic effects of natural plant compounds in kidney disease

Background: The blockade of the progression or onset of pathological events is essential for the homeostasis of an organism. Some common pathological mechanisms involving a wide range of diseases are the uncontrolled inflammatory reactions that promote fibrosis, oxidative reactions, and other alterations. Natural plant compounds (NPCs) are bioactive elements obtained from natural sources that can regulate physiological processes. Inflammation is recognized as an important factor in the development and evolution of chronic renal damage. Consequently, any compound able to modulate inflammation or inflammation-related processes can be thought of as a renal protective agent and/or a potential treatment tool for controlling renal damage. The objective of this research was to review the beneficial effects of bioactive natural compounds on kidney damage to reveal their efficacy as demonstrated in clinical studies. Methods: This systematic review is based on relevant studies focused on the impact of NPCs with therapeutic potential for kidney disease treatment in humans. Results: Clinical studies have evaluated NPCs as a different way to treat or prevent renal damage and appear to show some benefits in improving OS, inflammation, and antioxidant capacity, therefore making them promising therapeutic tools to reduce or prevent the onset and progression of KD pathogenesis. Conclusions: This review shows the promising clinical properties of NPC in KD therapy. However, more robust clinical trials are needed to establish their safety and therapeutic effects in the area of renal damage

Paricalcitol reduces peritoneal fibrosis in mice through the activation of regulatory T cells and reduction in IL-17 production.

Fibrosis is a significant health problem associated with a chronic inflammatory reaction. The precise mechanisms involved in the fibrotic process are still poorly understood. However, given that inflammation is a major causative factor, immunomodulation is a possible therapeutic approach to reduce fibrosis. The vitamin D receptor (VDR) that is present in all hematopoietic cells has been associated with immunomodulation. We investigated whether the intraperitoneal administration of paricalcitol, a specific activator of the VDR, modulates peritoneal dialysis fluid (PDF)-induced peritoneal fibrosis. We characterized the inflammatory process in the peritoneal cavity of mice treated or not treated with paricalcitol and analyzed the ensuing fibrosis. The treatment reduced peritoneal IL-17 levels, which strongly correlated with a significantly lower peritoneal fibrotic response. In vitro studies demonstrate that both CD4+ and CD8+ regulatory T cells appear to impact the regulation of IL-17. Paricalcitol treatment resulted in a significantly increased frequency of CD8+ T cells showing a regulatory phenotype. The frequency of CD4+ Tregs tends to be increased, but it did not achieve statistical significance. However, paricalcitol treatment increased the number of CD4+ and CD8+ Treg cells in vivo. In conclusion, the activation of immunological regulatory mechanisms by VDR signaling could prevent or reduce fibrosis, as shown in peritoneal fibrosis induced by PDF exposure in mice

Paricalcitol reduced peritoneal membrane fibrosis, inflammation and ultrafiltration failure in mice exposed to PDF.

<p>A) Paraffin sections of the peritoneal membrane from the 3 groups were stained with Masson's trichrome. B) Thickening of the peritoneal membrane was determined by morphometric analysis. C) Peritoneal permeability was determined by net ultrafiltration. D) The presence of inflammatory and mesothelial cells was determined by the expression of CD45 (green) and cytokeratin (red), respectively, in frozen sections of peritoneal membrane representative of each group. A green arrow indicates hematopoietic cells. A red arrow indicates mesothelial cells. E) The angiogenesis was determined by the expression of CD31 (green). Cytokeratin-positive cells are stained in red. The color balance was equally adjusted in immunofluorescence using Photoshop V10 for Mac (Abobe Systems Incorporated, US). n≥5 in each group. Statistical significance was determined using the Mann-Whitney test. *<i>P</i><.05; ***<i>P</i><.001.</p

Paricalcitol induced the recruitment of regulatory CD8+ T cells into the peritoneal cavity.

<p>Paricalcitol (dashed box) tended to increase the frequency of CD4⁺ T cells expressing Foxp-3 (A), but not CTLA-4 (B) or membrane TGF-β (C). Paricalcitol increased the frequency of CD8⁺ T cells expressing Foxp-3 (A), CTLA-4 (B) and membrane TGF-β (C) compared with the PDF-group (white box). n≥9 in each group. Paricalcitol treated group had higher number of CD4⁺ CD8⁺ T cells expressing Foxp-3 than PDF group (D). Statistical significance was determined using the Mann-Whitney test. *<i>P</i><.05; **<i>P</i><.01; ***<i>P</i><.001.</p

Chemokine concentrations in the peritoneal cavity were not affected by paricalcitol treatment.

<p>Concentrations of RANTES (A), MIP-1α (B) and MIP-1β (C) were determined in the peritoneal washing fluid. We observed no difference between the paricalcitol and the PDF group. n≥5 in each group.</p