The Next Evolution of HemoDialysis eXpanded: From a Delphi Questionnaire-Based Approach to the Real Life of Italian Dialysis Units.

INTRODUCTION: Impact assessment of new technologies in chronic hemodialysis (HD) is challenging due to HD patient frailty, the complexity of HD clinical trials and practice variability among countries. Among the most recent HD innovations, medium cut-off (MCO) dialyzers present an optimized membrane geometry that provides enhanced clearances for middle and large molecular weight uremic toxins (UT). These toxins are poorly cleared by available HD techniques and largely contribute to patient morbidity and mortality. The aim of this paper is to assess the available clinical evidence about MCO membranes and to identify the next steps needed to generate conclusive data on their use in HD. METHODS: With this purpose, we first reviewed and compared the current HD technologies aimed to improve the clearance of middle and large UT; subsequently, we used a Delphi questionnaire to identify and discuss the consensus about MCO efficacy within a large sample of the Italian Nephrology community. RESULTS AND CONCLUSIONS: Our investigation gathered a significant degree of consensus on the beneficial role of MCO membrane and expanded HD. Finally, we used our results to propose future trial designs and clinical investigations aimed to improve evidence quality about the use of these membranes in the present clinical scenario of dialysis units.

Online Hemodiafiltration Inhibits Inflammation-Related Endothelial Dysfunction and Vascular Calcification of Uremic Patients Modulating miR-223 Expression in Plasma Extracellular Vesicles.

Decreased inflammation and cardiovascular mortality are evident in patients with end-stage chronic kidney disease treated by online hemodiafiltration. Extracellular vesicles (EV) are mediators of cell-to-cell communication and contain different RNA types. This study investigated whether mixed online hemodiafiltration (mOL-HDF) beneficial effects associate with changes in the RNA content of plasma EV in chronic kidney disease patients. Thirty bicarbonate hemodialysis (BHD) patients were randomized 1:1 to continue BHD or switch to mOL-HDF. Concentration, size, and microRNA content of plasma EV were evaluated for 9 mo; we then studied EV effects on inflammation, angiogenesis, and apoptosis of endothelial cells (HUVEC) and on osteoblast mineralization of vascular smooth muscle cells (VSMC). mOL-HDF treatment reduced different inflammatory markers, including circulating CRP, IL-6, and NGAL. All hemodialysis patients showed higher plasma levels of endothelial-derived EV than healthy subjects, with no significant differences between BHD and mOL-HDF. However, BHD-derived EV had an increased expression of the proatherogenic miR-223 with respect to healthy subjects or mOL-HDF. Compared with EV from healthy subjects, those from hemodialysis patients reduced angiogenesis and increased HUVEC apoptosis and VSMC calcification; however, all these detrimental effects were reduced with mOL-HDF with respect to BHD. Cell transfection with miR-223 mimic or antagomiR proved the role of this microRNA in EV-induced HUVEC and VSMC dysfunction. The switch from BHD to mOL-HDF significantly reduced systemic inflammation and miR-223 expression in plasma EV, thus improving HUVEC angiogenesis and reducing VSMC calcification.

A call to action to evaluate renal functional reserve in patients with COVID-19.

Coronavirus disease 2019 (COVID-19) poses an unprecedented challenge to world health systems, substantially increasing hospitalization and mortality rates in all affected countries. Being primarily a respiratory disease, COVID-19 is mainly associated with pneumonia or minor upper respiratory tract symptoms; however, different organs can sustain considerable (if not terminal) damage because of coronavirus. Acute kidney injury is the most common complication of COVID-19-related pneumonia, and more than 20% of patients requiring ventilatory support develop renal failure. Additionally, chronic kidney disease is a major risk factor for COVID-19 severity and mortality. All these data demonstrate the relevance of renal function assessment in patients with COVID-19 and the need of early kidney-directed diagnostic and therapeutic approaches. However, the sole assessment of renal function could be not entirely indicative of kidney tissue status. In this viewpoint, we discuss the clinical significance and potential relevance of renal functional reserve evaluation in patients with COVID-19.

Perfluorocarbon solutions limit tubular epithelial cell injury and promote CD133+ kidney progenitor differentiation: potential use in renal assist devices for sepsis-associated acute kidney injury and multiple organ failure.

Background: The renal assist device (RAD) is a blood purification system containing viable renal tubular epithelial cells (TECs) that has been proposed for the treatment of acute kidney injury (AKI) and multiple organ failure. Perfluorocarbons (PFCs) are oxygen carriers used for organ preservation in transplantation. The aim of this study was to investigate the effect of PFCs on hypoxia- and sepsis-induced TEC injury and on renal CD133+ progenitor differentiation in a microenvironment similar to the RAD. Methods: TECs were seeded in a polysulphone hollow fibre under hypoxia or cultured with plasma from 10 patients with sepsis-associated AKI in the presence or absence of PFCs and were tested for cytotoxicity (XTT assay), apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling assay, caspases, enzyme-linked immunosorbent assay, Fas/Fas Ligand pathway activation), mitochondrial activity, cell polarity [transepithelial electrical resistance (TEER)] and adenosine triphosphate production. The effect of PFCs on proliferation and differentiation of human CD133+ progenitors was also studied. Results: In the presence of PFCs, TECs seeded into the polysulphone hollow fibre showed increased viability and expression of insulin-like growth factor 1, hepatocyte growth factor and macrophage-stimulating protein. Plasma from septic patients induced TEC apoptosis, disruption of oxidative metabolism, alteration of cell polarity and albumin uptake, down-regulation of the tight junction protein ZO-1 and the endocytic receptor megalin on the TEC surface. These detrimental effects were significantly reduced by PFCs. Moreover, PFCs induced CD133+ renal progenitor cell proliferation and differentiation towards an epithelial/tubular-like phenotype. Conclusions: PFCs improved the viability and metabolic function of TECs seeded within a polysulphone hollow fibre and subjected to plasma from septic AKI patients. Additionally, PFCs promoted differentiation towards a tubular/epithelial phenotype of CD133+ renal progenitor cells.

Sodium glucose cotransporters inhibitors in type 1 diabetes.

Sodium glucose cotransporter inhibitors (SGLTi) are oral hypoglycemic drugs that reduce renal glucose re-uptake and induce glycosuria. SGLTi have been successfully tested in large randomized clinical trials for type 2 diabetes, and several molecules have been approved in this setting by the international pharmaceutical agencies. Additionally, recent evidence has shown that SGLTi may be useful also in type 1 diabetes (T1D). Indeed, these drugs can be used as an ancillary to insulin to improve glycemic control and reduce insulin dosage, and such regimens have been associated with a lower rate of hypoglycemic episodes. The pharmacological effects of SGLTi therapy are described herein, and we also discuss the future use of SGLTi in T1D.

ATP and T-cell-mediated rejection.

PURPOSE OF REVIEW: Purine nucleosides and nucleotides are released in the extracellular space following cell injury and act as paracrine mediators through a number of dedicated membrane receptors. In particular, extracellular ATP (eATP) significantly influences T-lymphocyte activation and phenotype. The purpose of this review is to discuss the role of ATP signaling in the T-cell-mediated alloimmune response. RECENT FINDINGS: In various animal models of solid transplantation, the purinergic axis has been targeted to prevent acute rejection and to promote long-term graft tolerance. The inhibition of ATP-gated P2X receptors has been shown to halt lymphocyte activation, to downregulate both Th1 and Th17 responses and to promote T-regulatory (Treg) cell differentiation. Similarly, the inhibition of ATP signaling attenuated graft-versus-host disease in mice undergoing hematopoietic cell transplantation. Significantly, different drugs targeting the purinergic system have been recently approved for human use and may be a viable therapeutic option for transplant patients. SUMMARY: The inhibition of eATP signaling downregulates the alloimmune response, expands Treg cells and promotes graft survival. This robust preclinical evidence and the recent advances in pharmacological research may lead to intriguing clinical applications.

Detrimental cross-talk between sepsis and acute kidney injury: new pathogenic mechanisms, early biomarkers and targeted therapies.

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency medicine 2016. Other selected articles can be found online at http://www.biomedcentral.com/collections/annualupdate2016. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Endothelial progenitor cell-derived extracellular vesicles protect from complement-mediated mesangial injury in experimental anti-Thy1.1 glomerulonephritis.

BACKGROUND: Endothelial progenitor cells (EPCs) are known to induce tissue repair by paracrine mechanisms including the release of growth factors and extracellular vesicles (EVs), nanoparticles able to carry proteins and genetic information to target cells. The aim of this study was to evaluate whether EVs derived from EPCs may protect from complement-mediated mesangial injury in experimental anti-Thy1.1 glomerulonephritis. METHODS: EVs were isolated by serial ultracentrifugation from supernatants of cultured human EPCs and characterized for their protein and RNA content. In vivo, EVs were injected i.v. in the experimental rat model of mesangiolytic anti-Thy1.1 glomerulonephritis evaluating renal function, proteinuria, complement activity and histological lesions. In vitro, the biological effects of EPC-derived EVs were studied in cultured rat mesangial cells incubated with anti-Thy1.1 antibody and rat or human serum as complement source. RESULTS: After i.v. injection in Thy1.1-treated rats, EVs localized within injured glomeruli and inhibited mesangial cell activation, leucocyte infiltration and apoptosis, decreased proteinuria, increased serum complement haemolytic activity (CH50) and ameliorated renal function. EV treatment decreased intraglomerular deposition of the membrane attack complex (MAC or C5b-9) and expression of smooth muscle cell actin and preserved the endothelial antigen RECA-1 and the podocyte marker synaptopodin. The protective effect of EVs was significantly reduced by pre-treatment with a high dose of RNase (1 U/mL), suggesting a key role for EV-carried RNAs in these mechanisms. Indeed, EPC-derived EVs contained different mRNAs coding for several anti-apoptotic molecules and for the complement inhibitors Factor H, CD55 and CD59 and the related proteins. The in vitro experiments aimed to investigate the mechanisms of EV protection indicated that EVs transferred to mesangial cell mRNAs coding for Factor H, CD55 and CD59 and inhibited anti-Thy1.1 antibody/complement-induced apoptosis and C5b-9/C3 mesangial cell deposition. CONCLUSIONS: EVs derived from EPCs exert a protective effect in Thy1.1 glomerulonephritis by inhibition of antibody- and complement-mediated injury of mesangial cells.

Interaction between systemic inflammation and renal tubular epithelial cells.

Systemic inflammation is known to target tubular epithelial cells (TECs), leading to acute kidney injury. Tubular cells have been implicated in the response to inflammatory mediators in ischaemic and septic renal damage. Moreover, loss of tubular cells by apoptosis or epithelial-to-mesenchymal transition may ingenerate conditions that lead to progression towards chronic kidney disease. On the other hand, TECs may actively contribute to the production of inflammatory mediators that may propagate the injury locally or in distant organs. In the present review, we discuss the tubular cell response and its contribution to systemic inflammation.

Detrimental role of humoral signalling in cardio-renal cross-talk.

In critically ill patients, any acute organ injury is associated with a sudden change of circulating factors that may play a role in distant organ dysfunction through a complex cross-talk. In this issue, Virzì and colleagues discuss the relevance of humoral signalling between heart and kidney, focusing on type 1 and type 3 cardio-renal syndrome. We herein review the mechanisms of heart-kidney cross-talk, discussing the role of circulating detrimental mediators in the pathogenetic mechanisms of cardio-renal syndrome.

Glycemic pattern in diabetic patients on hemodialysis: continuous glucose monitoring (CGM) analysis.

BACKGROUND/AIMS: Recent evidences suggest that hemodialysis (HD) induces glycemic variations in diabetic patients. Continuous glucose monitoring (CGM) devices measure interstitial glucose in a 'Holter-like' manner thereby improving the glycemic control assessment method. METHODS: A CGM device (Medtronic iPRO) was used on 12 diabetic patients with chronic HD for 6 days to assess intra- and extra-dialytic interstitial glucose. RESULTS: In all enrolled patients, HD was associated with a decrease of interstitial glucose values. Intradialytic glucose nadir was 79 mg/dl and it was reached at the third hour after the beginning of the session. At the end of HD, interstitial glucose increased in all patients and a glycemic peak (187 mg/dl) occurred after an average time of 2.5 h. No episodes of nocturnal hypoglycemia occurred. CONCLUSION: HD is associated with significant intradialytic reduction of glycemia and postdialytic hyperglycemia. CGM devices result in better monitoring of glycemic trends in diabetic patients on chronic HD and could improve insulin management.

Glucagon-like peptide 1 receptor is a T cell-negative costimulatory molecule.

Glucagon-like peptide-1 receptor (GLP-1R) is a key regulator of glucose metabolism known to be expressed by pancreatic ß cells. We herein investigated the role of GLP-1R on T lymphocytes during immune response. Our data showed that a subset of T lymphocytes expresses GLP-1R, which is upregulated during alloimmune response, similarly to PD-1. When mice received islet or cardiac allotransplantation, an expansion of GLP-1Rpos T cells occurred in the spleen and was found to infiltrate the graft. Additional single-cell RNA sequencing (scRNA-seq) analysis conducted on GLP-1Rpos and GLP-1Rneg CD3+ T cells unveiled the existence of molecular and functional dissimilarities between both subpopulations, as the GLP-1Rpos are mainly composed of exhausted CD8 T cells. GLP-1R acts as a T cell-negative costimulatory molecule, and GLP-1R signaling prolongs allograft survival, mitigates alloimmune response, and reduces T lymphocyte graft infiltration. Notably, GLP-1R antagonism triggered anti-tumor immunity when tested in a preclinical mouse model of colorectal cancer.

Cannabis Use and CKD: Epidemiological Associations and Mendelian Randomization.

Rationale & Objective: The association between cannabis use and chronic kidney disease (CKD) is controversial. We aimed to assess association of CKD with cannabis use in a large cohort study and then assess causality using Mendelian randomization with a genome-wide association study (GWAS). Study Design: Retrospective cohort study and genome-wide association study. Setting & Participants: The retrospective study was conducted on the All of Us cohort (N=223,354). Genetic instruments for cannabis use disorder were identified from 3 GWAS: the Psychiatric Genomics Consortium Substance Use Disorders, iPSYCH, and deCODE (N=384,032). Association between genetic instruments and CKD was investigated in the CKDGen GWAS (N > 1.2 million). Exposure: Cannabis consumption. Outcomes: CKD outcomes included: cystatin-C and creatinine-based kidney function, proteinuria, and blood urea nitrogen. Analytical Approach: We conducted association analyses to test for frequency of cannabis use and CKD. To evaluate causality, we performed a 2-sample Mendelian randomization. Results: In the retrospective study, compared to former users, less than monthly (OR, 1.01; 95% CI, 0.87-1.18; P = 0.87) and monthly cannabis users (OR, 1.15; 95% CI, 0.86-1.52; P = 0.33) did not have higher CKD odds. Conversely, weekly (OR, 1.28; 95% CI, 1.01-1.60; P = 0.04) and daily use (OR, 1.25; 95% CI, 1.04-1.50; P = 0.02) was significantly associated with CKD, adjusted for multiple confounders. In Mendelian randomization, genetic liability to cannabis use disorder was not associated with increased odds for CKD (OR, 1.00; 95% CI, 0.99-1.01; P = 0.96). These results were robust across different Mendelian randomization techniques and multiple kidney traits. Limitations: Likely underreporting of cannabis use. In Mendelian randomization, genetic instruments were identified in the GWAS that included individuals primarily of European ancestry. Conclusions: Despite the epidemiological association between cannabis use and CKD, there was no evidence of a causal effect, indicating confounding in observational studies.

Inhibition of RIP1 improves immune reconstitution and reduces GVHD mortality while preserving graft-versus-leukemia effects.

Graft-versus-host disease (GVHD) remains the major cause of morbidity and nonrelapse mortality (NRM) after hematopoietic cell transplantation (HCT). Inflammatory cytokines mediate damage to key GVHD targets such as intestinal stem cells (ISCs) and also activate receptor interacting protein kinase 1 (RIP1; RIPK1), a critical regulator of apoptosis and necroptosis. We therefore investigated the role of RIP1 in acute GVHD using samples from HCT patients, modeling GVHD damage in vitro with both human and mouse gastrointestinal (GI) organoids, and blocking RIP1 activation in vivo using several well-characterized mouse HCT models. Increased phospho-RIP1 expression in GI biopsies from patients with acute GVHD correlated with tissue damage and predicted NRM. Both the genetic inactivation of RIP1 and the RIP1 inhibitor GNE684 prevented GVHD-induced apoptosis of ISCs in vivo and in vitro. Daily administration of GNE684 for 14 days reduced inflammatory infiltrates in three GVHD target organs (intestine, liver, and spleen) in mice. Unexpectedly, GNE684 administration also reversed the marked loss of regulatory T cells in the intestines and liver during GVHD and reduced splenic T cell exhaustion, thus improving immune reconstitution. Pharmacological and genetic inhibition of RIP1 improved long-term survival without compromising the graft-versus-leukemia (GVL) effect in lymphocytic and myeloid leukemia mouse models. Thus, RIP1inhibition may represent a nonimmunosuppressive treatment for GVHD.

Deep learning on electronic medical records identifies distinct subphenotypes of diabetic kidney disease driven by genetic variations in the Rho pathway.

Kidney disease affects 50% of all diabetic patients; however, prediction of disease progression has been challenging due to inherent disease heterogeneity. We use deep learning to identify novel genetic signatures prognostically associated with outcomes. Using autoencoders and unsupervised clustering of electronic health record data on 1,372 diabetic kidney disease patients, we establish two clusters with differential prevalence of end-stage kidney disease. Exome-wide associations identify a novel variant in ARHGEF18, a Rho guanine exchange factor specifically expressed in glomeruli. Overexpression of ARHGEF18 in human podocytes leads to impairments in focal adhesion architecture, cytoskeletal dynamics, cellular motility, and RhoA/Rac1 activation. Mutant GEF18 is resistant to ubiquitin mediated degradation leading to pathologically increased protein levels. Our findings uncover the first known disease-causing genetic variant that affects protein stability of a cytoskeletal regulator through impaired degradation, a potentially novel class of expression quantitative trait loci that can be therapeutically targeted.

Proteomic Characterization of Acute Kidney Injury in Patients Hospitalized with SARS-CoV2 Infection.

Background Acute kidney injury (AKI) is a known complication of COVID-19 and is associated with an increased risk of in-hospital mortality. Unbiased proteomics using biological specimens can lead to improved risk stratification and discover pathophysiological mechanisms. Methods Using measurements of ~4000 plasma proteins in two cohorts of patients hospitalized with COVID-19, we discovered and validated markers of COVID-associated AKI (stage 2 or 3) and long-term kidney dysfunction. In the discovery cohort (N= 437), we identified 413 higher plasma abundances of protein targets and 40 lower plasma abundances of protein targets associated with COVID-AKI (adjusted p <0.05). Of these, 62 proteins were validated in an external cohort (p <0.05, N =261). Results We demonstrate that COVID-AKI is associated with increased markers of tubular injury ( NGAL ) and myocardial injury. Using estimated glomerular filtration (eGFR) measurements taken after discharge, we also find that 25 of the 62 AKI-associated proteins are significantly associated with decreased post-discharge eGFR (adjusted p <0.05). Proteins most strongly associated with decreased post-discharge eGFR included desmocollin-2 , trefoil factor 3 , transmembrane emp24 domain-containing protein 10 , and cystatin-C indicating tubular dysfunction and injury. Conclusions Using clinical and proteomic data, our results suggest that while both acute and long-term COVID-associated kidney dysfunction are associated with markers of tubular dysfunction, AKI is driven by a largely multifactorial process involving hemodynamic instability and myocardial damage.

Peripheral Transcriptomics in Acute and Long-Term Kidney Dysfunction in SARS-CoV2 Infection.

Background: Acute kidney injury (AKI) is common in hospitalized patients with SARS-CoV2 infection despite vaccination and leads to long-term kidney dysfunction. However, peripheral blood molecular signatures in AKI from COVID-19 and their association with long-term kidney dysfunction are yet unexplored. Methods: In patients hospitalized with SARS-CoV2, we performed bulk RNA sequencing using peripheral blood mononuclear cells(PBMCs). We applied linear models accounting for technical and biological variability on RNA-Seq data accounting for false discovery rate (FDR) and compared functional enrichment and pathway results to a historical sepsis-AKI cohort. Finally, we evaluated the association of these signatures with long-term trends in kidney function. Results: Of 283 patients, 106 had AKI. After adjustment for sex, age, mechanical ventilation, and chronic kidney disease (CKD), we identified 2635 significant differential gene expressions at FDR<0.05. Top canonical pathways were EIF2 signaling, oxidative phosphorylation, mTOR signaling, and Th17 signaling, indicating mitochondrial dysfunction and endoplasmic reticulum (ER) stress. Comparison with sepsis associated AKI showed considerable overlap of key pathways (48.14%). Using follow-up estimated glomerular filtration rate (eGFR) measurements from 115 patients, we identified 164/2635 (6.2%) of the significantly differentiated genes associated with overall decrease in long-term kidney function. The strongest associations were 'autophagy', 'renal impairment via fibrosis', and 'cardiac structure and function'. Conclusions: We show that AKI in SARS-CoV2 is a multifactorial process with mitochondrial dysfunction driven by ER stress whereas long-term kidney function decline is associated with cardiac structure and function and immune dysregulation. Functional overlap with sepsis-AKI also highlights common signatures, indicating generalizability in therapeutic approaches. SIGNIFICANCE STATEMENT: Peripheral transcriptomic findings in acute and long-term kidney dysfunction after hospitalization for SARS-CoV2 infection are unclear. We evaluated peripheral blood molecular signatures in AKI from COVID-19 (COVID-AKI) and their association with long-term kidney dysfunction using the largest hospitalized cohort with transcriptomic data. Analysis of 283 hospitalized patients of whom 37% had AKI, highlighted the contribution of mitochondrial dysfunction driven by endoplasmic reticulum stress in the acute stages. Subsequently, long-term kidney function decline exhibits significant associations with markers of cardiac structure and function and immune mediated dysregulation. There were similar biomolecular signatures in other inflammatory states, such as sepsis. This enhances the potential for repurposing and generalizability in therapeutic approaches.

Proteomic characterization of acute kidney injury in patients hospitalized with SARS-CoV2 infection.

BACKGROUND: Acute kidney injury (AKI) is a known complication of COVID-19 and is associated with an increased risk of in-hospital mortality. Unbiased proteomics using biological specimens can lead to improved risk stratification and discover pathophysiological mechanisms. METHODS: Using measurements of ~4000 plasma proteins in two cohorts of patients hospitalized with COVID-19, we discovered and validated markers of COVID-associated AKI (stage 2 or 3) and long-term kidney dysfunction. In the discovery cohort (N = 437), we identified 413 higher plasma abundances of protein targets and 30 lower plasma abundances of protein targets associated with COVID-AKI (adjusted p < 0.05). Of these, 62 proteins were validated in an external cohort (p < 0.05, N = 261). RESULTS: We demonstrate that COVID-AKI is associated with increased markers of tubular injury (NGAL) and myocardial injury. Using estimated glomerular filtration (eGFR) measurements taken after discharge, we also find that 25 of the 62 AKI-associated proteins are significantly associated with decreased post-discharge eGFR (adjusted p < 0.05). Proteins most strongly associated with decreased post-discharge eGFR included desmocollin-2, trefoil factor 3, transmembrane emp24 domain-containing protein 10, and cystatin-C indicating tubular dysfunction and injury. CONCLUSIONS: Using clinical and proteomic data, our results suggest that while both acute and long-term COVID-associated kidney dysfunction are associated with markers of tubular dysfunction, AKI is driven by a largely multifactorial process involving hemodynamic instability and myocardial damage.

Acute kidney injury (AKI) is a sudden, sometimes fatal, episode of kidney failure or damage. It is a known complication of COVID-19, albeit through unclear mechanisms. COVID-19 is also associated with kidney dysfunction in the long term, or chronic kidney disease (CKD). There is a need to better understand which patients with COVID-19 are at risk of AKI or CKD. We measure levels of several thousand proteins in the blood of hospitalized COVID-19 patients. We discover and validate sets of proteins associated with severe AKI and CKD in these patients. The markers identified suggest that kidney injury in COVID-19 patients involves damage to kidney cells that reabsorb fluid from urine and reduced blood flow to the heart, causing damage to heart muscles. Our findings might help clinicians to predict kidney injury in patients with COVID-19, and to understand its mechanisms.

[New mechanisms and recent insights in the pathogenesis of acute kidney injury (AKI)]. / Nuovi meccanismi e recenti acquisizioni nella patogenesi del danno renale acuto.

Acute kidney injury (AKI) is a frequent complication in hospitalized patients often associated with multiple organ failure, increased mortality and progression toward chronic kidney disease. The identification of new cellular and molecular targets involved in AKI may lead to an improvement of diagnostic and therapeutic approaches. In recent years, the pathogenetic mechanisms of AKI have been fully elucidated: tubular epithelial cells and endothelial cells present in the microvasculature have been identified as the main targets of ischemia and of nephrotoxic drugs. Indeed, endothelial cell injury is associated with an extension phase of AKI, whereas tubular cells are subjected to an alteration of cell polarity, mislocalization of tight junction proteins and membrane transporters, and finally to the development of necrosis or apotosis. Apoptosis, or programmed cell death, is also a key component of sepsis-associated AKI in which the mechanisms of tissue damage are associated not only with hypoperfusion but also with a direct detrimental effect of bacterial products and inflammatory mediators on resident kidney cells. Endothelial and tubular epithelial cells also represent the main targets in the immunological mechanisms of AKI in kidney transplantation during cell-mediated and antibody-mediated rejection. Recent studies evidenced new molecules as early biomarkers of AKI. Among these molecules, NGAL and KIM-1 play a possible role in the progression toward chronic kidney disease. Lastly, the new frontier of AKI therapy is represented by the use of bone marrow-derived mesenchymal stem cells able to induce a regenerative program in the damaged kidney.

Mannan-Binding Lectin Promotes Murine Graft-versus-Host Disease by Amplifying Lipopolysaccharide-Initiated Inflammation.

Conditioning regimens used for hematopoietic stem cell transplantation (HCT) can escalate the severity of acute T cell-mediated graft-versus-host disease (GVHD) by disrupting gastrointestinal integrity and initiating lipopolysaccharide (LPS)-dependent innate immune cell activation. Activation of the complement cascade has been associated with murine GVHD, and previous work has shown that alternative pathway complement activation can amplify T cell immunity. Whether and how mannan-binding lectin (MBL), a component of the complement system that binds mannose as well as oligosaccharide components of LPS and lipoteichoic acid, affects GVHD is unknown. In this study, we tested the hypothesis that MBL modulates murine GVHD and examined the mechanisms by which it does so. We adoptively transferred C3.SW bone marrow (BM) cells ± T cells into irradiated wild type (WT) or MBL-deficient C57Bl/6 (B6) recipients with or without inhibiting MBL-initiated complement activation using C1-esterase inhibitor (C1-INH). We analyzed the clinical severity of disease expression and analyzed intestinal gene and cell infiltration. In vitro studies assessed MBL expression on antigen-presenting cells (APCs) and compared LPS-induced responses of WT and MBL-deficient APCs. MBL-deficient recipients of donor BM ± T cells exhibited significantly less weight loss over the first 2 weeks post-transplantation weeks compared with B6 controls (P < .05), with similar donor engraftment in the 2 groups. In recipients of C3.SW BM + T cells, the clinical expression of GVHD was less severe (P < .05) and overall survival was better (P < .05) in MBL-deficient mice compared with WT mice. On day-7 post-transplantation, analyses showed that the MBL-deficient recipients exhibited less intestinal IL1b, IL17, and IL12 p40 gene expression (P < .05 for each) and fewer infiltrating intestinal CD11c+, CD11b+, and F4/80+ cells and TCRß+, CD4+, CD4+IL17+, and CD8+ T cells (P < .05 for each). Ovalbumin or allogeneic cell immunizations induced equivalent T cell responses in MBL-deficient and WT mice, demonstrating that MBL-deficiency does not directly impact T cell immunity in the absence of irradiation conditioning. Administration of C1-INH did not alter the clinical expression of GVHD in preconditioned WT B6 recipients, suggesting that MBL amplifies clinical expression of GVHD via a complement-independent mechanism. WT, but not MBL-deficient, APCs express MBL on their surfaces. LPS-stimulated APCs from MBL-deficient mice produced less proinflammatory cytokines (P < .05) and induced weaker alloreactive T cell responses (P < .05) compared with WT APCs. Together, our data show that MBL modulates murine GVHD, likely by amplifying complement-independent, LPS-initiated gastrointestinal inflammation. The results suggest that devising strategies to block LPS/MBL ligation on APCs has the potential to reduce the clinical expression of GVHD.