Renal cystinuria and immune cells (T lymphocytes) dysfunction, what we know about?

Cystinuria (CYS) is the most common monogenic kidney stone disease. Starting from an unusual case of CYS associated to Primary Sclerosing Cholangitis, inflammatory bowel disease (IBD) and autoimmune hepatitis in a young male, we carefully review the literature and propose here a working hypothesis regarding the potential risk of cystinuric patients to develop conditions due to immune system dysregulation. To corroborate this hypothesis, we retrospectively evaluate the frequency of dysimmunity in a cohort of cystinuric patients compared to healthy and disease controls. Further studies are needed to define the relationship between proximal tubular transport defect of CYS and dysregulated immunity.

Animal models to study cognitive impairment of chronic kidney disease

Mild cognitive impairment (MCI) is common in people with chronic kidney disease (CKD) and its prevalence increases with progressive loss of kidney function. MCI is characterized by a decline in cognitive performance greater than expected for an individual age and education level but with minimal impairment of instrumental activities of daily living. Deterioration can affect one or several cognitive domains (attention, memory, executive functions, language, and perceptual motor or social cognition). Given the increasing prevalence of kidney disease, more and more people with CKD will also develop MCI causing an enormous disease burden for these individuals, their relatives and society. However, the underlying pathomechanisms are poorly understood and current therapies mostly aim at supporting patients in their daily life. This illustrates the urgent need to elucidate the pathogenesis, and potential therapeutic targets and test novel therapies in appropriate preclinical models. Here, we will outline the necessary criteria for experimental modelling of cognitive disorders in CKD. We discuss the use of mice, rats and zebrafish as model systems and present valuable techniques through which kidney function and cognitive impairment can be assessed in this setting. Our objective is to enable researchers to overcome hurdles and accelerate preclinical research aimed at improving therapy of people with CKD and MCI.

Efficacy of erythropoietin as a neuroprotective agent in CKD-associated cognitive dysfunction: A literature systematic review

Patients with chronic kidney disease (CKD) often experience mild cognitive impairment and other neurocognitive disorders. Studies have shown that erythropoietin (EPO) and its receptor have neuroprotective effects in cell and animal models of nervous system disorders. Recombinant human EPO (rHuEPO), commonly used to treat anemia in CKD patients, could be a neuroprotective agent. In this systematic review, we aimed to assess the published studies investigating the cognitive benefits of rHuEPO treatment in individuals with reduced kidney function. We comprehensively searched Pubmed, Cochrane Library, Scopus, and Web of Science databases from 1990 to 2023. After selection, 24 studies were analyzed, considering study design, sample size, participant characteristics, intervention, and main findings. The collective results of these studies in CKD patients indicated that rHuEPO enhances brain function, improves performance on neuropsychological tests, and positively affects electroencephalography measurements. These findings suggest that rHuEPO could be a promising neuroprotective agent for managing CKD-related cognitive impairment.

Neuropeptide Y gene polymorphisms and chronic kidney disease progression

BACKGROUND

Neuropeptide Y (NPY) is a neurotransmitter expressed in both the central and peripheral nervous systems, which is involved in regulating a multitude of physiological processes ranging from arterial pressure, energy balance, the immune response and inflammation and renal electrolyte transport. In a cohort of chronic kidney disease (CKD) patients, we recently showed that high plasma NPY levels predict renal disease progression independently of hypertension and other risk factors but the causal nature of this association remains unproven.

METHODS

In the same cohort of the previous study, we tested the relationship of NPY gene variability, as assessed by five single nucleotide polymorphisms (SNPs) that explained the whole gene variability, with the incidence rate of a predefined combined renal endpoint (dialysis/transplantation/estimated glomerular filtration rate reduction >30%) over a median follow up of 36 months (inter-quartile range 35-37 months) in 735 ethnically homogeneous patients with stage 2-5 CKD.

RESULTS

Two variants [rs16131 (recessive model for the T risk allele: TT, n  = 563; CT + CC, n  = 172) and rs16140 (dominant model for the G risk allele: GG + CG, n  = 413; CC, n  = 322)] were coherently associated with the incidence rate of renal events [hazard ratio (HR) ranging from 1.39 to 1.57, P  ≤ 0.015] and this was also true when the two SNPs were jointly introduced into the same Cox model ( P  ≤ 0.043). The analysis of the biological interaction showed a significant synergism between the NPY rs16131 and rs16140 variants. Indeed, patients harboring NPY rs16131 TT and NPY rs16140 GG + CG risk genotypes had a much higher HR of renal events [HR: 1.80, 95% confidence interval (CI):1.16-2.79, P  = 0.009] than that expected in the absence of biological interaction under both the additive and multiplicative models and the attributable proportion due to interaction (AP) was 25% and 38% on crude and adjusted analyses, respectively.

CONCLUSION

This study, based on the Mendelian randomization approach and using NPY gene variants as instrumental variables to test the link between NPY and CKD progression, is in line with findings indicating that high plasma NPY levels predict an increased risk for renal events and lend support to the hypothesis that NPY is causally involved in renal disease progression.

Cyclosporin-induced hypertension is associated with the up-regulation of Na+-K+-2Cl- cotransporter (NKCC2)

BACKGROUND

The use of cyclosporin A (CsA) is hampered by the development of nephrotoxicity including hypertension, which is partially dependent on renal sodium retention. To address this issue, we have investigated in vivo sodium reabsorption in different nephron segments of CsA-treated rats through micropuncture study coupled to expression analyses of sodium transporters. To translate the findings in rats to human, kidney-transplanted patients having CsA treatment were enrolled in the study.

METHODS

Adult male Sprague-Dawley rats were treated with CsA (15 mg/kg/day) for 21 days, followed by micropuncture study and expression analyses of sodium transporters. CsA-treated kidney-transplanted patients with resistant hypertension were challenged with 50 mg furosemide.

RESULTS

CsA-treated rats developed hypertension associated with reduced glomerular filtration rate. In vivo microperfusion study demonstrated a significant decrease in rate of absolute fluid reabsorption in the proximal tubule but enhanced sodium reabsorption in the thick ascending limb of Henle's loop (TAL). Expression analyses of sodium transporters at the same nephron segments further revealed a reduction in Na+-H+ exchanger isoform 3 (NHE3) in the renal cortex, while TAL-specific, furosemide-sensitive Na+-K+-2Cl- cotransporter (NKCC2) and NHE3 were significantly upregulated in the inner stripe of outer medulla. CsA-treated patients had a larger excretion of urinary NKCC2 protein at basal condition, and higher diuretic response to furosemide, showing increased FeNa+, FeCl- and FeCa2+ compared with both healthy controls and FK506-treated transplanted patients.

CONCLUSION

Altogether, these findings suggest that up-regulation of NKCC2 along the TAL facilitates sodium retention and contributes to the development of CsA-induced hypertension.

Fabry Disease in Women: Genetic Basis, Available Biomarkers, and Clinical Manifestations

Fabry Disease (FD) is a rare lysosomal storage disorder caused by mutations in the GLA gene on the X chromosome, leading to a deficiency in α-galactosidase A (AGAL) enzyme activity. This leads to the accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3), in vital organs such as the kidneys, heart, and nervous system. While FD was initially considered predominantly affecting males, recent studies have uncovered that heterozygous Fabry women, carrying a single mutated GLA gene, can manifest a wide array of clinical symptoms, challenging the notion of asymptomatic carriers. The mechanisms underlying the diverse clinical manifestations in females remain not fully understood due to X-chromosome inactivation (XCI). XCI also known as "lyonization", involves the random inactivation of one of the two X chromosomes. This process is considered a potential factor influencing phenotypic variation. This review delves into the complex landscape of FD in women, discussing its genetic basis, the available biomarkers, clinical manifestations, and the potential impact of XCI on disease severity. Additionally, it highlights the challenges faced by heterozygous Fabry women, both in terms of their disease burden and interactions with healthcare professionals. Current treatment options, including enzyme replacement therapy, are discussed, along with the need for healthcare providers to be well-informed about FD in women, ultimately contributing to improved patient care and quality of life.

Drugs with a negative impact on cognitive functions (Part 2): drug classes to consider while prescribing in CKD patients

There is growing evidence that chronic kidney disease (CKD) is an independent risk factor for cognitive impairment, especially due to vascular damage, blood-brain barrier disruption and uremic toxins. Given the presence of multiple comorbidities, the medication regimen of CKD patients often becomes very complex. Several medications such as psychotropic agents, drugs with anticholinergic properties, GABAergic drugs, opioids, corticosteroids, antibiotics and others have been linked to negative effects on cognition. These drugs are frequently included in the treatment regimen of CKD patients. The first review of this series described how CKD could represent a risk factor for adverse drug reactions affecting the central nervous system. This second review will describe some of the most common medications associated with cognitive impairment (in the general population and in CKD) and describe their effects.

Drugs with a negative impact on cognitive function (Part 1): chronic kidney disease as a risk factor

People living with chronic kidney disease (CKD) frequently suffer from mild cognitive impairment and/or other neurocognitive disorders. This review in two parts will focus on adverse drug reactions resulting in cognitive impairment as a potentially modifiable risk factor in CKD patients. Many patients with CKD have a substantial burden of comorbidities leading to polypharmacy. A recent study found that patients seen by nephrologists were the most complex to treat because of their high number of comorbidities and medications. Due to polypharmacy, these patients may experience a wide range of adverse drug reactions. Along with CKD progression, the accumulation of uremic toxins may lead to blood-brain barrier (BBB) disruption and pharmacokinetic alterations, increasing the risk of adverse reactions affecting the central nervous system (CNS). In patients on dialysis, the excretion of drugs that depend on kidney function is severely reduced such that adverse and toxic levels of a drug or its metabolites may be reached at relatively low doses, unless dosing is adjusted. This first review will discuss how CKD represents a risk factor for adverse drug reactions affecting the CNS via (i) BBB disruption associated with CKD and (ii) the impact of reduced kidney function and dialysis itself on drug pharmacokinetics.

The SGLT2 inhibitor dapagliflozin improves kidney function in glycogen storage disease XI

Glycogen storage disease XI, also known as Fanconi-Bickel syndrome (FBS), is a rare autosomal recessive disorder caused by mutations in the SLC2A2 gene that encodes the glucose-facilitated transporter type 2 (GLUT2). Patients develop a life-threatening renal proximal tubule dysfunction for which no treatment is available apart from electrolyte replacement. To investigate the renal pathogenesis of FBS, SLC2A2 expression was ablated in mouse kidney and HK-2 proximal tubule cells. GLUT2Pax8Cre+ mice developed time-dependent glycogen accumulation in proximal tubule cells and recapitulated the renal Fanconi phenotype seen in patients. In vitro suppression of GLUT2 impaired lysosomal autophagy as shown by transcriptomic and biochemical analysis. However, this effect was reversed by exposure to a low glucose concentration, suggesting that GLUT2 facilitates the homeostasis of key cellular pathways in proximal tubule cells by preventing glucose toxicity. To investigate whether targeting proximal tubule glucose influx can limit glycogen accumulation and correct symptoms in vivo, we treated mice with the selective SGLT2 inhibitor dapagliflozin. Dapagliflozin reduced glycogen accumulation and improved metabolic acidosis and phosphaturia in the animals by normalizing the expression of Napi2a and NHE3 transporters. In addition, in a patient with FBS, dapagliflozin was safe, improved serum potassium and phosphate concentrations, and reduced glycogen content in urinary shed cells. Overall, this study provides proof of concept for dapagliflozin as a potentially suitable therapy for FBS.

Cognitive disorders in patients with chronic kidney disease: Approaches to prevention and treatment

BACKGROUND

Cognitive impairment is common in patients with chronic kidney disease (CKD), and early intervention may prevent the progression of this condition.

METHODS

Here, we review interventions for the complications of CKD (anemia, secondary hyperparathyroidism, metabolic acidosis, harmful effects of dialysis, the accumulation of uremic toxins) and for prevention of vascular events, interventions that may potentially be protective against cognitive impairment. Furthermore, we discuss nonpharmacological and pharmacological methods to prevent cognitive impairment and/or minimize the latter's impact on CKD patients' daily lives.

RESULTS

A particular attention on kidney function assessment is suggested during work-up for cognitive impairment. Different approaches are promising to reduce cognitive burden in patients with CKD but the availabe dedicated data are scarce.

CONCLUSIONS

There is a need for studies assessing the effect of interventions on the cognitive function of patients with CKD.

Methodological challenges and biases in the field of cognitive function among patients with chronic kidney disease

Chronic kidney disease (CKD) affects approximately 850 million people globally and is associated with an increased risk of cognitive impairment. The prevalence of cognitive impairment among CKD patients ranges from 30 to 60%, and the link between CKD and cognitive impairment is partially understood. Methodological challenges and biases in studying cognitive function in CKD patients need to be addressed to improve diagnosis, treatment, and management of cognitive impairment in this population. Here, we review the methodological challenges and study design issues, including observational studies' limitations, internal validity, and different types of bias that can impact the validity of research findings. Understanding the unique challenges and biases associated with studying cognitive function in CKD patients can help to identify potential sources of error and improve the quality of future research, leading to more accurate diagnoses and better treatment plans for CKD patients.

Possible Effects of Uremic Toxins p-Cresol, Indoxyl Sulfate, p-Cresyl Sulfate on the Development and Progression of Colon Cancer in Patients with Chronic Renal Failure

Chronic kidney disease (CKD) induces several systemic effects, including the accumulation and production of uremic toxins responsible for the activation of various harmful processes. Gut dysbiosis has been widely described in CKD patients, even in the early stages of the disease. The abundant discharge of urea and other waste substances into the gut favors the selection of an altered intestinal microbiota in CKD patients. The prevalence of bacteria with fermentative activity leads to the release and accumulation in the gut and in the blood of several substances, such as p-Cresol (p-C), Indoxyl Sulfate (IS) and p-Cresyl Sulfate (p-CS). Since these metabolites are normally eliminated in the urine, they tend to accumulate in the blood of CKD patients proportionally to renal impairment. P-CS, IS and p-C play a fundamental role in the activation of various pro-tumorigenic processes, such as chronic systemic inflammation, the increase in the production of free radicals and immune dysfunction. An up to two-fold increase in the incidence of colon cancer development in CKD has been reported in several studies, although the pathogenic mechanisms explaining this compelling association have not yet been described. Based on our literature review, it appears likely the hypothesis of a role of p-C, IS and p-CS in colon cancer development and progression in CKD patients.

Impact of Thyroid Cancer Treatment on Renal Function: A Relevant Issue to Be Addressed

Thyroid cancers require complex and heterogeneous therapies with different impacts on renal function. In our systematic literature review, we analyzed several aspects: renal function assessment, the impact of radiotherapy and thyroid surgery on kidney functioning, and mechanisms of nephrotoxicity of different chemotherapy, targeted and immunologic drugs. Our study revealed that the renal impact of thyroid cancer therapy can be a limiting factor in all radiotherapy, surgery, and pharmacological approaches. It is advisable to conduct a careful nephrological follow-up imposing the application of body surface based estimated Glomerular Filtration Rate (eGFR) formulas for the purpose of an early diagnosis and treatment of renal failure, guaranteeing the therapy continuation to thyroid cancer patients.

Next-Generation Sequencing (NGS) Analysis Illustrates the Phenotypic Variability of Collagen Type IV Nephropathies

Mutations in COL4A3-A5 cause a spectrum of glomerular disorders, including thin basement membrane nephropathy (TBMN) and Alport syndrome (AS). The wide application of next-generation sequencing (NGS) in the last few years has revealed that mutations in these genes are not limited to these clinical entities. In this study, 176 individuals with a clinical diagnosis of inherited kidney disorders underwent an NGS-based analysis to address the underlying cause; those who changed or perfected the clinical diagnosis after molecular analysis were selected. In 5 out of 83 individuals reaching a molecular diagnosis, the genetic result was unexpected: three individuals showed mutations in collagen type IV genes. These patients showed the following clinical pictures: (1) familial focal segmental glomerulosclerosis; (2) end-stage renal disease (ESRD) diagnosed incidentally in a 49-year-old man, with diffuse cortical calcifications on renal imaging; and (3) dysmorphic and asymmetric kidneys with multiple cysts and signs of tubule-interstitial defects. Genetic analysis revealed rare heterozygote/compound heterozygote COL4A4-A5 variants. Our study highlights the key role of NGS in the diagnosis of inherited renal disorders and shows the phenotype variability in patients carrying mutations in collagen type IV genes.

miRNA-23a modulates sodium-hydrogen exchanger 1 expression: studies in medullary thick ascending limb of salt-induced hypertensive rats

BACKGROUND

The kidney is the main organ in the pathophysiology of essential hypertension. Although most bicarbonate reabsorption occurs in the proximal tubule, the medullary thick ascending limb (mTAL) of the nephron also maintains acid-base balance by contributing to 25% of bicarbonate reabsorption. A crucial element in this regulation is the sodium-hydrogen exchanger 1 (NHE1), a ubiquitous membrane protein controlling intracellular pH, where proton extrusion is driven by the inward sodium flux. MicroRNA (miRNA) expression of hypertensive patients significantly differs from that of normotensive subjects. The aim of this study was to determine the functional role of miRNA alterations at the mTAL level.

METHODS

By miRNA microarray analysis, we identified miRNA expression profiles in isolated mTALs from high sodium intake-induced hypertensive rats (HSD) versus their normotensive counterparts (NSD). In vitro validation was carried out in rat mTAL cells.

RESULTS

Five miRNAs involved in the onset of salt-sensitive hypertension were identified, including miR-23a, which was bioinformatically predicted to target NHE1 mRNA. Data demonstrated that miRNA-23a is downregulated in the mTAL of HSD rats while NHE1 is upregulated. Consistently, transfection of an miRNA-23a mimic in an mTAL cell line, using a viral vector, resulted in NHE1 downregulation.

CONCLUSION

NHE1, a protein involved in sodium reabsorption at the mTAL level and blood pressure regulation, is upregulated in our model. This was due to a downregulation of miRNA-23a. Expression levels of this miRNA are influenced by high sodium intake in the mTALs of rats. The downregulation of miRNA-23a in humans affected by essential hypertension corroborate our data and point to the potential role of miRNA-23a in the regulation of mTAL function following high salt intake.

Bardet-Biedl Syndrome: Current Perspectives and Clinical Outlook

The Bardet Biedl syndrome (BBS) is a rare inherited disorder considered a model of non-motile ciliopathy. It is in fact caused by mutations of genes encoding for proteins mainly localized to the base of the cilium. Clinical features of BBS patients are widely shared with patients suffering from other ciliopathies, especially autosomal recessive syndromic disorders; moreover, mutations in cilia-related genes can cause different clinical ciliopathy entities. Besides the best-known clinical features, as retinal degeneration, learning disabilities, polydactyly, obesity and renal defects, several additional clinical signs have been reported in BBS, expanding our understanding of the complexity of its clinical spectrum. The present review aims to describe the current knowledge of BBS i) pathophysiology, ii) clinical manifestations, highlighting both the most common and the less described features, iii) current and future perspective for treatment.

Therapeutic Plasmapheresis: A Revision of Literature

BACKGROUND

Therapeutic plasmapheresis (TP) is an extracorporeal therapy that allows the removal of pathogens from plasma. The role of TP in immuno-mediated diseases and toxic conditions has been of interest for decades.

SUMMARY

We reviewed the recent literature on the application and the optimal choice of TP technique ranging from plasma exchange, double filtration plasmapheresis, rheopheresis, immunoadsorptions, plasma adsorption perfusion and lipidoapheresis. In addition, we report our experience in the application of TP for various diseases ranging in different medical specialties, following the American Society for Apheresis (ASFA) recommendations.

KEY MESSAGES

Overall patients receiving TP showed an improvement in clinical and laboratory parameters. Our review and single-center experience suggest a benefit of the application of TP in multiple clinical disciplines.

Computational and Structural Analysis to Assess the Pathogenicity of Bardet-Biedl Syndrome Related Missense Variants Identified in Bardet-Biedl Syndrome 10 Gene (BBS10)

Bardet-Biedl Syndrome (BBS) is a rare inherited disorder resulting in multiple organ dysfunctions, whose cardinal clinical features include cognitive impairment, obesity, and renal dysfunction. Although it is highly heterogeneous at genetic levels, BBS10 is one of the major causative genes worldwide. The BBS10 protein is part of a multiprotein complex localized at the basal body of the primary cilium. With the advancement of sequencing technologies, novel missense mutations are regularly reported in BBS10. However, prioritizing missense variants and conducting further in-depth analysis are key challenges in addressing their pathogenic effect. This study aims to characterize the known missense mutations of BBS10 by combining nine different in silico tools (SIFT, SNAP2, PROVEAN, Align-GVGD, ConSurf, I Mutant, MuPro, PremPS, and Dynamut) and molecular dynamics (MD) simulations. A total of 101 BBS10 missense variants have been analyzed. Our results showed that six BBS10 missense variants (Ser191Leu, Cys19Gly, Ile342Thr, Cys371Ser, Ala417Glu, and Tyr613Cys) were potentially deleterious. Overall, this study provides a comprehensive workflow for screening BBS10 missense mutations to identify pathogenic variants effectively.

[Italian Society of Cardiology-Italian Society of Nephrology Consensus document: The cardio-renal interaction in the prevention and treatment of cardiovascular diseases - Part II: From preventive strategies to treatment of patients with cardio-renal damage]

Chronic kidney disease and cardiovascular disease are strictly connected each other with a bidirectional interaction. Thus, the prevention of cardio-renal damage, as its appropriate treatment, are essential steps for a correct management of long-term patients' prognosis. Several preventive and therapeutic strategies, pharmacological and not, are now available for cardio-renal damage prevention and treatment, and for the management of its complications. The second part of this consensus document focuses on the management and treatment of cardio-renal damage, directing the attention on the correct use of drugs that may slow renal disease progression, on the application of preventive strategies in case of invasive cardiac procedures with the use of contrast agents, and on the accurate use of cardiological drugs in patients with chronic kidney disease.

Dapagliflozin Prevents Kidney Glycogen Accumulation and Improves Renal Proximal Tubule Cell Functions in a Mouse Model of Glycogen Storage Disease Type 1b

BACKGROUND

Mutations in SLC37A4, which encodes the intracellular glucose transporter G6PT, cause the rare glycogen storage disease type 1b (GSD1b). A long-term consequence of GSD1b is kidney failure, which requires KRT. The main protein markers of proximal tubule function, including NaPi2A, NHE3, SGLT2, GLUT2, and AQP1, are downregulated as part of the disease phenotype.

METHODS

We utilized an inducible mouse model of GSD1b, TM-G6PT-/-, to show that glycogen accumulation plays a crucial role in altering proximal tubule morphology and function. To limit glucose entry into proximal tubule cells and thus to prevent glycogen accumulation, we administered an SGLT2-inhibitor, dapagliflozin, to TM-G6PT-/- mice.

RESULTS

In proximal tubule cells, G6PT suppression stimulates the upregulation and activity of hexokinase-I, which increases availability of the reabsorbed glucose for intracellular metabolism. Dapagliflozin prevented glycogen accumulation and improved kidney morphology by promoting a metabolic switch from glycogen synthesis toward lysis and by restoring expression levels of the main proximal tubule functional markers.

CONCLUSION

We provide proof of concept for the efficacy of dapagliflozin in preserving kidney function in GSD1b mice. Our findings could represent the basis for repurposing this drug to treat patients with GSD1b.

[Italian Society of Cardiology-Italian Society of Nephrology Consensus document: The cardio-renal interaction in the prevention and treatment of cardiovascular diseases - Part I: From cardiovascular risk factors to the mechanisms of cardio-renal syndrome]

Chronic kidney disease (CKD) and cardiovascular (CV) disease are highly prevalent conditions in the general population and are strictly connected to each other with a bidirectional interaction. In patients affected by CKD, the leading cause of morbidity and mortality is represented by CV disease, since CKD promotes the atherosclerotic process increasing inflammation, and modifying lipid and bone mineral metabolism. On the other side, a strict relationship exists between CKD and CV risk factors, which are prevalent in nephropathic patients and impose a stringent assessment of the risk of CV events in this population together with an optimized pharmacological approach, complicated by the coexistence of the two pathological conditions. The first part of this consensus document focuses on the mechanisms of cardio-renal damage and on the impact, as well as the management, of the main CV risk factors in the context of CKD.

Phosphate in the Context of Cognitive Impairment and Other Neurological Disorders Occurrence in Chronic Kidney Disease

The nervous system and the kidneys are linked under physiological states to maintain normal body homeostasis. In chronic kidney disease (CKD), damaged kidneys can impair the central nervous system, including cerebrovascular disease and cognitive impairment (CI). Recently, kidney disease has been proposed as a new modifiable risk factor for dementia. It is reported that uremic toxins may have direct neurotoxic (astrocyte activation and neuronal death) and/or indirect action through vascular effects (cerebral endothelial dysfunction, calcification, and inflammation). This review summarizes the evidence from research investigating the pathophysiological effects of phosphate toxicity in the nervous system, raising the question of whether the control of hyperphosphatemia in CKD would lower patients’ risk of developing cognitive impairment and dementia.

MO675: A New in Vivo Multi-Photon Microscopy Based Approach to Study the Peritoneal Membrane Changes Induced by Peritoneal Dialysis

BACKGROUND AND AIMS

Peritoneal dialysis (PD) is a renal replacement therapy that allows the elimination of metabolic waste products and excess body fluid through the peritoneal membrane. The exposure to PD solution contributes to membrane aging and fibrosis resulting in ultrafiltration and clearance failure.

The glucose, used as an osmotic factor, in PD dialysate triggers several processes involved in the pathogenesis of peritoneal fibrosis, angiogenesis and epithelial to mesenchymal transition.

Studies on natural extracts, such as Oleuropein (Ole), a powerful antioxidant with remarkable antifibrotic and protective effects on the peritoneal membrane, are currently being validated.

This study aims to develop a method based on multi-photon microscopy to study the physiology of the peritoneal membrane during dialysis exchange and to validate in vivo the effects of the Ole in animal models of fibrosis undergoing dialysis treatment.

METHOD

Multi-photon microscopy allows in vivo evaluation of the microcirculation that supply the peritoneum and also to study the framework of mesothelial cells and their underlying layer of collagen fibers that contributes to the sub-mesothelial space.

We have implemented the surgical procedure in order to optimize the stability of a flap of parietal peritoneum to directly observe at the scope. With this approach the peritoneal membrane is evaluable at baseline condition and during exposure to dialysate solutions.

RESULTS

Our method allows building a three-dimensional render of the peritoneal membrane, with the evaluation of all the single layers without the use of specific markers. In this way we could assess specifically the phenomena induced by the fibrotic process: the thickening of the sub-mesothelial interstitium and the greater density of the vascular network.

Furthermore, in vivo measurements of flow in the vessels of microcirculation (arterioles, capillaries, post-capillary venules) determine that exposure to hypotonic solutions increases significantly the flow in large-diameter vessels due to better permeability and hemodilution.

Finally in order to evaluate the possibility to detect morphological and functional changes in pathogenic model we have used the well-established model of peritoneal fibrosis derived by 15 days’ long exposure of the peritoneal membrane with 3.86% glucose dialysate. Whth this approach we could detect the significant increase in the parameters of cellularity, vascularization, fibrosis and thickening of collagen fibers.

In order to test the sensibility of our approach to the evaluation of the peritoneal membrane senescence parameters, we tested the effect of Ole in preventing the damage induced by high glucose–containing dialysate. Ole reduced both the thickness and the organization of the collagen fibers and the vascular network, including the number of branch points.

CONCLUSION

The developed method has potential for a dynamic and reliable in vivo approach. Studies are ongoing to validate the effects of drugs and dialysates with different osmotic and electrolytic compositions on the dialysis capacities of the peritoneal membrane and on the blood flow in peritoneal capillaries.

This method offers great potential for testing new pharmacological approaches aimed at preserving the structural and functional integrity of the peritoneum and for the validation of substances, such as natural extracts with beneficial effects against the damage induced in the long term by conventional dialysis solutions.

MO068: Paraoxonase 2 Protects the Kidney Tissue from Aldosterone-Promoted Oxidative Stress in Milan Normotensive Rats Strain

BACKGROUND AND AIMS

Kidney plays a pivotal role on the maintenance of blood pressure by the regulation of sodium reabsorption. Aldosterone sensitive distal nephron finely tunes salt reabsorption through several transporters, including the epithelial sodium channel (ENaC). Alteration in ENaC function leads to clinical relevant conditions associated with high or low blood pressure when gain or loss of function mutations occur, respectively.

Recently, accumulating evidence suggests the putative role of renal Paraoxonase 2 (PON2) as regulator of ENaC function. PON2 is a membrane-associated enzyme showing hydrolytic activity against 3-oxo-C12 homoserine lactone, a signaling molecule produced by bacteria and mainly Pseudomonas aeruginosa. PON2 also exhibits antioxidant property. In the distal nephron, PON2 is expressed in principal cells, and in vitro it physically interacts with ENaC subunits and inhibits ENaC channel activity in Xenopus oocytes likely by modulating channel assembly in the endoplasmic reticulum. However, the role of PON2 in the kidney is still not known.

In the present study, we investigate whether PON2 is regulated by changes in aldosterone state and its role in aldosterone-induced oxidative stress in the kidneys.

METHOD

We addressed these issues utilizing both in vivo and in vitro approaches, such as

RESULTS

We first demonstrated that in Milan normotensive rats strain, PON2 is upregulated by low-salt state according with α-ENaC activation. This regulation is aldosterone sensitive since pretreatment with mineralocorticoid receptor antagonist spironolactone prevented the stimulatory effects of sodium restricted diet. Furthermore, low-sodium diet inducing PON2 upregulation was associated with reduced ROS levels, more specifically superoxide levels, but treatment with spironolactone prevented this beneficial effect, by increasing ROS level in kidney cortex.

Since antihypertensive drugs spironolactone and canrenone contain a lactone residue in their molecular structure, we tested whether they could directly interact with PON2. We demonstrated in vitro that spironolactone and canrenone were able to inhibit PON2 lactonase activity and so to directly interfere with PON2 function. Finally, Milan hypertensive rats, carrying a mutation of α-adducin as determinant of their hypertensive phenotype, presented with higher level of ROS while PON2 was upregulated.

CONCLUSION

These results demonstrate PON2 as a novel target of steroid hormone aldosterone. PON2 may serve as a potential ROS scavenger mechanism protecting the kidneys from aldosterone-promoted oxidative stress.

Single nephron glomerular filtration rate measured by linescan multiphoton microscopy compared to conventional micropuncture

Renal micropuncture, which requires the direct access to the renal tubules, has for long time been the technique of choice to measure the single nephron glomerular filtration rate (SNGFR) in animal models. This approach is challenging by virtue of complex animal preparation and numerous technically difficult steps. The introduction of intravital multiphoton microscopy (MPM) offers another approach to the measure of the SNGFR by mean of the high laser-tissue penetration and the optical sectioning capacity. Previous MPM studies measuring SNGFR in vivo relied on fast full-frame acquisition during the filtration process obtainable with high performance resonant scanners. In this study, we describe an innovative linescan–based MPM method. The new method can discriminate SNGFR variations both in conditions of low and high glomerular filtration, and shows results comparable to conventional micropuncture both for rats and mice. Moreover, this novel approach has improved spatial and time resolution and is faster than previous methods, thus enabling the investigation of SNGFR from more tubules and improving options for data-analysis.

A Shared Nephroprotective Mechanism for Renin-Angiotensin-System Inhibitors, Sodium-Glucose Co-Transporter 2 Inhibitors, and Vasopressin Receptor Antagonists: Immunology Meets Hemodynamics

A major paradigm in nephrology states that the loss of filtration function over a long time is driven by a persistent hyperfiltration state of surviving nephrons. This hyperfiltration may derive from circulating immunological factors. However, some clue about the hemodynamic effects of these factors derives from the effects of so-called nephroprotective drugs. Thirty years after the introduction of Renin-Angiotensin-system inhibitors (RASi) into clinical practice, two new families of nephroprotective drugs have been identified: the sodium-glucose cotransporter 2 inhibitors (SGLT2i) and the vasopressin receptor antagonists (VRA). Even though the molecular targets of the three-drug classes are very different, they share the reduction in the glomerular filtration rate (GFR) at the beginning of the therapy, which is usually considered an adverse effect. Therefore, we hypothesize that acute GFR decline is a prerequisite to obtaining nephroprotection with all these drugs. In this study, we reanalyze evidence that RASi, SGLT2i, and VRA reduce the eGFR at the onset of therapy. Afterward, we evaluate whether the extent of eGFR reduction correlates with their long-term efficacy. The results suggest that the extent of initial eGFR decline predicts the nephroprotective efficacy in the long run. Therefore, we propose that RASi, SGLT2i, and VRA delay kidney disease progression by controlling maladaptive glomerular hyperfiltration resulting from circulating immunological factors. Further studies are needed to verify their combined effects.

The DiaCoVAb study in South Italy: immune response to Sars-CoV-2 vaccination in dialysis patients

INTRODUCTION

Since the pandemic of Coronavirus Disease 2019 (COVID-19) started from December 2019, remarkable numbers of infections and deaths associated with COVID-19 have been recorded worldwide. End-Stage Renal Disease (ESRD) patients on dialysis are particularly at high risk of infections due to impairments in the innate and adaptive immune system. Vaccination on dialysis patients (DP) still remains challenging, because of the variable response and low seroconversion rate compared with healthy controls (HC). Therefore, it is urgently necessary to establish a different vaccination strategy for DP, in terms of dose and administration time.

METHODS

Here, we report an observational prospective cohort study in which the immunogenic efficacies of SARS-CoV-2 vaccine BNT162b2 on DP and HC were evaluated by absolute quantification of IgG levels in the blood.

RESULTS

DP showed a delayed seroconversion after two vaccine doses, with a low absolute IgG levels compared to HC. While healthy populations reached complete seroconversion within 10 days from the administration of second dose, only 76% of DP were seropositive. After booster dose, DP strongly improved seroconversion rate as well as antibody levels, reaching 97% seropositivity and 50 times enhancement on antibody levels.

DISCUSSION/CONCLUSION

These results prompt to suggest an additional vaccine dose in DP, reducing the interval of time from the second dose. Since few data are available on immune response in DP overtime after three vaccine doses currently, our study is among the first reports demonstrating the improved seropositivity and IgG levels in DP after booster vaccine dose.

Bardet-Biedl syndrome: The pleiotropic role of the chaperonin-like BBS6, 10, and 12 proteins

Bardet–Biedl syndrome (BBS) is a rare pleiotropic disorder known as a ciliopathy. Despite significant genetic heterogeneity, BBS1 and BBS10 are responsible for major diagnosis in western countries. It is well established that eight BBS proteins, namely BBS1, 2, 4, 5, 7, 8, 9, and 18, form the BBSome, a multiprotein complex serving as a regulator of ciliary membrane protein composition. Less information is available for BBS6, BBS10, and BBS12, three proteins showing sequence homology with the CCT/TRiC family of group II chaperonins. Even though their chaperonin function is debated, scientific evidence demonstrated that they are required for initial BBSome assembly in vitro. Recent studies suggest that genotype may partially predict clinical outcomes. Indeed, patients carrying truncating mutations in any gene show the most severe phenotype; moreover, mutations in chaperonin‐like BBS proteins correlated with severe kidney impairment. This study is a critical review of the literature on genetics, expression level, cellular localization and function of BBS proteins, focusing primarily on the chaperonin‐like BBS proteins, and aiming to provide some clues to understand the pathomechanisms of disease in this setting.

Albuminuria as a risk factor for mild cognitive impairment and dementia-what is the evidence?

Kidney dysfunction can profoundly influence many organ systems, and recent evidence suggests a potential role for increased albuminuria in the development of mild cognitive impairment (MCI) or dementia. Epidemiological studies conducted in different populations have demonstrated that the presence of increased albuminuria is associated with a higher relative risk of MCI or dementia both in cross-sectional analyses and in studies with long-term follow-up. The underlying pathophysiological mechanisms of albuminuria's effect are as yet insufficiently studied, with several important knowledge gaps still present in a complex relationship with other MCI and dementia risk factors. Both the kidney and the brain have microvascular similarities that make them sensitive to endothelial dysfunction involving different mechanisms, including oxidative stress and inflammation. The exact substrate of MCI and dementia is still under investigation, however available experimental data indicate that elevated albuminuria and low glomerular filtration rate are associated with significant neuroanatomical declines in hippocampal function and grey matter volume. Thus, albuminuria may be critical in the development of cognitive impairment and its progression to dementia. In this review, we summarize the available evidence on albuminuria's link to MCI and dementia, point to existing gaps in our knowledge and suggest actions to overcome them. The major question of whether interventions that target increased albuminuria could prevent cognitive decline remains unanswered. Our recommendations for future research are aimed at helping to plan clinical trials and to solve the complex conundrum outlined in this review, with the ultimate goal of improving the lives of patients with chronic kidney disease.

An update on the use of tolvaptan for ADPKD: Consensus statement on behalf of the ERA Working Group on Inherited Kidney Disorders (WGIKD), the European Rare Kidney Disease Reference Network (ERKNet) and Polycystic Kidney Disease International (PKD-International)

Approval of the vasopressin V2 receptor antagonist tolvaptan—based on the landmark TEMPO 3:4 trial—marked a transformation in the management of autosomal dominant polycystic kidney disease (ADPKD). This development has advanced patient care in ADPKD from general measures to prevent progression of chronic kidney disease to targeting disease-specific mechanisms. However, considering the long-term nature of this treatment, as well as potential side effects, evidence-based approaches to initiate treatment only in patients with rapidly progressing disease are crucial. In 2016, the position statement issued by the European Renal Association (ERA) was the first society-based recommendation on the use of tolvaptan and has served as a widely used decision-making tool for nephrologists. Since then, considerable practical experience regarding the use of tolvaptan in ADPKD has accumulated. More importantly, additional data from REPRISE, a second randomized clinical trial (RCT) examining the use of tolvaptan in later-stage disease, have added important evidence to the field, as have post hoc studies of these RCTs. To incorporate this new knowledge, we provide an updated algorithm to guide patient selection for treatment with tolvaptan and add practical advice for its use.

Brain dysfunction in tubular and tubulointerstitial kidney diseases

Kidney function has two important elements: glomerular filtration and tubular function (secretion and reabsorption). A persistent decrease in glomerular filtration rate (GFR), with or without proteinuria, is diagnostic of chronic kidney disease (CKD). While glomerular injury or disease is a major cause of CKD and usually associated with proteinuria, predominant tubular injury, with or without tubulointerstitial disease, is typically non-proteinuric. CKD has been linked with cognitive impairment, but it is unclear how much this depends on a reduced GFR, altered tubular function or the presence of proteinuria. Since CKD is often accompanied by tubular and interstitial dysfunction, we explore here for the first time the potential role of the tubular and tubulointerstitial compartments in cognitive dysfunction. To help address this issue, we have selected a group of primary tubular diseases with preserved GFR, in which to review the evidence for any association with brain dysfunction. Cognition, mood, neurosensory, and motor disturbances are not well characterized in tubular diseases, possibly because they are subclinical and less prominent than other clinical manifestations. The available literature suggests that brain dysfunction in tubular and tubulointerstitial diseases is usually mild and is more often seen in disorders of water handling. Brain dysfunction may occur when severe electrolyte and water disorders in young children persist over a long period of time before the diagnosis is made. We have chosen as examples to highlight this topic, Bartter and Gitelman syndromes and nephrogenic diabetes insipidus. We discuss current published findings, some unanswered questions, and propose topics for future research.

Acidosis, cognitive dysfunction and motor impairments in patients with kidney disease

Metabolic acidosis, defined as a plasma or serum bicarbonate concentration <22 mmol/L, is a frequent consequence of chronic kidney disease (CKD) and occurs in ~10–30% of patients with advanced stages of CKD. Likewise, in patients with a kidney transplant, prevalence rates of metabolic acidosis range from 20% to 50%. CKD has recently been associated with cognitive dysfunction, including mild cognitive impairment with memory and attention deficits, reduced executive functions and morphological damage detectable with imaging. Also, impaired motor functions and loss of muscle strength are often found in patients with advanced CKD, which in part may be attributed to altered central nervous system (CNS) functions. While the exact mechanisms of how CKD may cause cognitive dysfunction and reduced motor functions are still debated, recent data point towards the possibility that acidosis is one modifiable contributor to cognitive dysfunction. This review summarizes recent evidence for an association between acidosis and cognitive dysfunction in patients with CKD and discusses potential mechanisms by which acidosis may impact CNS functions. The review also identifies important open questions to be answered to improve prevention and therapy of cognitive dysfunction in the setting of metabolic acidosis in patients with CKD.

Diffusion tensor imaging for the study of early renal dysfunction in patients affected by bardet-biedl syndrome

Kidney structural abnormalities are common features of Bardet-Biedl syndrome (BBS) patients that lead to a progressive decline in renal function. Magnetic resonance diffusion tensor imaging (DTI) provides useful information on renal microstructures but it has not been applied to these patients. This study investigated using DTI to detect renal abnormalities in BBS patients with no overt renal dysfunction. Ten BBS subjects with estimated glomerular filtration rates over 60 ml/min/1.73m² and 14 individuals matched for age, gender, body mass index and renal function were subjected to high-field DTI. Fractional anisotropy (FA), and mean, radial and axial diffusivity were evaluated from renal cortex and medulla. Moreover, the corticomedullary differentiation of each DTI parameter was compared between groups. Only cortical FA statistically differed between BBS patients and controls (p = 0.033), but all the medullary DTI parameters discriminated between the two groups with lower FA (p < 0.001) and axial diffusivity (p = 0.021) and higher mean diffusivity (p = 0.043) and radial diffusivity (p < 0.001) in BBS patients compared with controls. Corticomedullary differentiation values were significantly reduced in BBS patients. Thus, DTI is a valuable tool for investigating microstructural alterations in renal disorders when kidney functionality is preserved.

Efficacy of Unsupervised Self-Collected Mid-Turbinate FLOQSwabs for the Diagnosis of Coronavirus Disease 2019 (COVID-19)

CONTEXT

The Global Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) pandemic has resulted in explosive patterns of transmission in most countries. Nasopharyngeal swabs were the specimen's collection tools recommended for the diagnosis of SARS-CoV-2 infection, and for monitoring infection outbreaks in communities. Our objective was to report the quality and efficacy of unsupervised self-collected mid turbinate "dry FLOQSwabs" (MT FLOQSwabs) (56380CS01, Copan). There were 111 specimens collected for the study: 36 by health care personnel, from themselves, to verify the quality and efficacy of mid-turbinate swabs; 75 to compare and assess the diagnostic performance, among health care personnel, of nasopharyngeal swabs and self-collected mid-turbinate FLOQSwabs. A collection of 51 specimens was enrolled to define the efficacy of the Testami program (validation). Our analyses demonstrate that self-collected mid-turbinate dry swabs ensure an accuracy of 97.3%, as compared to the standard nasopharyngeal swabs collected by health care workers. Furthermore, the mid-turbinate FLOQSwabs can be stored without medium for six days at room temperature without affecting the molecular diagnosis of the SARS-CoV-2 virus infection. Self-collection of diagnostic specimens at home could offer an avenue to increase testing availability for SARS-CoV-2 infection without asking people to travel to a clinic or a laboratory, thus reducing people's exposure to infection. Our findings demonstrate that unsupervised self-collection swabs, transported dry, are sensitive, practical and easy-to-use tools and should be considered for diagnosis of SARS-COV-2 and coronavirus disease 2019 (COVID-19) surveillance.

The European Rare Kidney Disease Registry (ERKReg): objectives, design and initial results

BACKGROUND

The European Rare Kidney Disease Reference Network (ERKNet) recently established ERKReg, a Web-based registry for all patients with rare kidney diseases. The main objectives of this core registry are to generate epidemiological information, identify current patient cohort for clinical research, explore diagnostic and therapeutic management practices, and monitor treatment performance and patient's outcomes. The registry has a modular design that allows to integrate comprehensive disease-specific registries as extensions to the core database. The diagnosis (Orphacode) and diagnostic information (clinical, imaging, histopathological, biochemical, immunological and genetic) are recorded. Anthropometric, kidney function, and disease-specific management and outcome items informing a set of 61 key performance indicators (KPIs) are obtained annually. Data quality is ensured by automated plausibility checks upon data entry and regular offline database checks prompting queries. Centre KPI statistics and benchmarking are calculated automatically.

RESULTS

Within the first 24 months since its launch, 7607 patients were enrolled to the registry at 45 pediatric and 12 specialized adult nephrology units from 21 countries. A kidney disease diagnosis had been established in 97.1% of these patients at time of enrolment. While 199 individual disease entities were reported by Orphacode, 50% of the cohort could be classified with 11, 80% with 43 and 95% with 92 codes. Two kidney diagnoses were assigned in 6.5% of patients; 5.9% suffered from syndromic disease. Whereas glomerulopathies (54.8%) and ciliopathies including autosomal dominant polycystic kidney disease (ADPKD) (31.5%) were the predominant disease groups among adults, the pediatric disease spectrum encompassed congenital anomalies of the kidney and urinary tract (CAKUT) (33.7%), glomerulopathies (30.7%), ciliopathies (14.0%), tubulopathies (9.2%), thrombotic microangiopathies (5.6%), and metabolic nephropathies (4.1%). Genetically confirmed diagnoses were reported in 24% of all pediatric and 12% adult patients, whereas glomerulopathies had been confirmed by kidney biopsy in 80.4% adult versus 38.5% pediatric glomerulopathy cases.

CONCLUSIONS

ERKReg is a rapidly growing source of epidemiological information and patient cohorts for clinical research, and an innovative tool to monitor management quality and patient outcomes.

Urine concentrating defect as presenting sign of progressive renal failure in Bardet-Biedl syndrome patients

BACKGROUND

Urine concentrating defect is a common dysfunction in ciliopathies, even though its underlying mechanism and its prognostic meaning are largely unknown. This study assesses renal function in a cohort of 54 Bardet-Biedl syndrome (BBS) individuals and analyses whether renal hyposthenuria is the result of specific tubule dysfunction and predicts renal disease progression.

METHODS

The estimated glomerular filtration rate (eGFR), urine albumin:creatinine ratio (ACR) and maximum urine osmolality (max-Uosm) were measured in all patients. Genetic analysis was conducted in 43 patients. Annual eGFR decline (ΔeGFR) was measured in patients with a median follow-up period of 6.5 years. Urine aquaporin-2 (uAQP2) excretion was measured and the furosemide test was performed in patients and controls.

RESULTS

At baseline, 33 (61.1%), 12 (22.2%) and 9 (16.7%) patients showed an eGFR >90, 60-90 and <60 mL/min/1.73 m2, respectively; 27.3% showed an ACR >30 mg/g and 55.8% of patients showed urine concentrating defect in the absence of renal insufficiency. Baseline eGFR, but not max-Uosm, correlated negatively with age. Conversely, truncating mutations affected max-Uosm and showed a trend towards a reduction in eGFR. Max-Uosm correlated with ΔeGFR (P < 0.005), suggesting that urine concentrating defect may predict disease progression. uAQP2 excretion and Na+ and Cl- fractional excretion after furosemide did not differ between hyposthenuric patients and controls, suggesting that specific collecting duct and thick ascending limb dysfunctions are unlikely to play a central role in the pathogenesis of hyposthenuria.

CONCLUSIONS

Hyposthenuria is a warning sign predicting poor renal outcome in BBS. The pathophysiology of this defect is most likely beyond defective tubular function.

Dysregulation of Principal Cell miRNAs Facilitates Epigenetic Regulation of AQP2 and Results in Nephrogenic Diabetes Insipidus

BACKGROUND

MicroRNAs (miRNAs), formed by cleavage of pre-microRNA by the endoribonuclease Dicer, are critical modulators of cell function by post-transcriptionally regulating gene expression.

METHODS

Selective ablation of Dicer in AQP2-expressing cells (Dicer^AQP2Cre+ mice) was used to investigate the role of miRNAs in the kidney collecting duct of mice.

RESULTS

The mice had severe polyuria and nephrogenic diabetes insipidus, potentially due to greatly reduced AQP2 and AQP4 levels. Although epithelial sodium channel levels were decreased in cortex and increased in inner medulla, amiloride-sensitive sodium reabsorption was equivalent in Dicer^AQP2Cre+ mice and controls. Small-RNA sequencing and proteomic analysis revealed 31 and 178 significantly regulated miRNAs and proteins, respectively. Integrated bioinformatic analysis of the miRNAome and proteome suggested alterations in the epigenetic machinery and various transcription factors regulating AQP2 expression in Dicer^AQP2Cre+ mice. The expression profile and function of three miRNAs (miR-7688-5p, miR-8114, and miR-409-3p) whose predicted targets were involved in epigenetic control (Phf2, Kdm5c, and Kdm4a) or transcriptional regulation (GATA3, GATA2, and ELF3) of AQP2 were validated. Luciferase assays could not demonstrate direct interaction of AQP2 or the three potential transcription factors with miR-7688-5p, miR-8114, and miR-409-3p. However, transfection of respective miRNA mimics reduced AQP2 expression. Chromatin immunoprecipitation assays demonstrated decreased Phf2 and significantly increased Kdm5c interactions at the Aqp2 gene promoter in Dicer^AQP2Cre+ mice, resulting in decreased RNA Pol II association.

CONCLUSIONS

Novel evidence indicates miRNA-mediated epigenetic regulation of AQP2 expression.

MO354PRELIMINARY EVIDENCE OF RIVASTIGMINE EFFICACY IN CKD RELATED MILD COGNITIVE IMPAIRMENT

Background and Aims

Mild Cognitive Impairment (MCI) is a common finding in chronic kidney disease (CKD) patients. Indeed, CKD represents a relevant risk factor for developing dementia and MCI. Cholinesterase inhibitors, such as rivastigmine, are among the few drugs approved for the treatment of dementia and MCI. Rivastigmine is also used to treat vascular dementia because it protects subcortical brain structures. Data are scanty regarding the use of rivastigmine in CKD patients with MCI and are much needed to guide the therapy for MCI in this cohort of patients.

Method

This retrospective case-control study compared the effects of rivastigmine on cognitive functions in MCI patients with CKD (stage III-IV; n= 20) and without CKD (n=21, control group), comparable for the extent of cognitive impairment (indexed by Montreal Cognitive Assessment, MoCA), age (range 18-65 years), gender, weight, and comorbidities. Patients under treatment with rivastigmine and with a baseline MoCA score available were included in the study. Exclusion criteria were ictus, psychiatric or other neurological conditions, heart failure, liver failure, severe obesity, anemia, electrolyte disorders, cancer, dialysis, and other severe comorbidities. Laboratory test data (glycemia, cholesterol, hemoglobin, proteinuria, creatinine) were used to characterize the two populations. MCI was defined as a MoCA score between 21-26. The cognitive screening was available at baseline (before treatment) and during a follow-up in a range of three-six months after the start of the treatment. CKD was defined by eGFR &lt; 60 mL/min/1.73m2.

Results

The follow-up timing for cognitive screening was not statistically different between the two cohorts. The control group (MCI without CKD) showed a small, significant improvement in the MoCA score after treatment (baseline MoCA: 22.9±0.5, follow-up MoCA: 23.5±0.5, p=0.02, t-test for paired data).

At variance, the MCI-CKD group showed a significant improvement in the MoCA score (baseline MoCA=23±0.4, follow-up MoCA=24.3±0.4, p&lt;0.05).

Accordingly, the extent of improvement of MoCA score after rivastigmine was inversely correlated to the eGFR (r = -0.23).

Conclusion

A significant improvement in MoCA score accompanied treatment with rivastigmine in the CKD group. More extensive population studies are needed to verify the greater efficacy of Acetylcholinesterase inhibitors in this population.

MO1032HISTORY OF THE PARADIGMS OF INFLAMMATION IN KIDNEY DISEASES

Background and Aims

The term "inflammation" is undoubtedly one of the oldest medical terms and yet in use. However, its meaning has changed over the centuries. This work gives a historical and critical view of the concept of inflammation, with particular reference to kidney diseases.

Method

The term "inflammation" was used in Galenic medicine to specify a collection of symptoms. Celsus (c. 25 BC – c. 50 AD) described "rubor et tumor cum calor et dolor", but the list became much longer in subsequent Galenic scholars. It is interesting to note that one of the inflammation symptoms, "tumor," was then used to indicate cancer (tumor=swelling due to a mass or due to edema). Virchow (1821 –1902) is often quoted for introducing a fifth symptom, "function Lasa", but his significant contribution relies on introducing the microscope to study diseases: thanks to this instrument, the paradigm of inflammation was undergoing a revolution. Thereby, the definition of inflammation shifted from a pure collection of symptoms to a histopathological classification, characterized by the tissue "inflammatory infiltrates" with subcategories according to the cell types involved. Numerous authors added their names to pathology textbooks when describing a new kind of cellular infiltration.

Overall, the tremendous success of the histopathologic paradigm of inflammation or "inflammatory infiltrates" was the possibility to contain and revert this phenomenon with corticosteroids (with few exceptions). Subsequently, specific drugs were proposed for each inflammatory infiltrate. This type of paradigm is still used today to define, e.g., tubulointerstitial nephritis or intra- and peri-glomerular inflammations. The subsequent classification of inflammatory infiltrates using immunohistochemistry did not modify our classification system (the distinction of, e.g., CD20 lymphocytes from CD4 T-cells is not used, unfortunately, in today's classification system).

Results

Towards the 1940s, Avery et al. recognize that some plasma proteins (specifically the famous C-reactive protein) increase during acute infection, which is a typical inflammatory state. This observation led to a new "molecular definition of inflammation". The idea to identify the presence of inflammatory infiltrates in tissues just by looking at plasma constituents had great success: after all, the histological processing of tissues was no longer needed. Even though many authors were alerting that these plasma constituents are often increased even in the absence of any "inflammatory infiltrate", the plasma proteins were so easily accessible that the new direction was not modifiable.

A modern generalization of this type of approach is called "liquid biopsy, " even though it is not limited to the inflammatory states, but to a larger number of identifiable diseases today only histologically.

The effect of the new "molecular" definition of inflammation was that a large number of diseases without significant inflammatory infiltrates (such as obesity, atherosclerosis, aging, dialysis, and chronic kidney disease) are notwithstanding accompanied by the increase of plasma proteins labeled as "inflammatory". Therefore, the list of "inflammatory" diseases (in the new terms) is now much more extensive. The price for such enlargement of conditions is that most new entries do not respond to steroids or other anti-inflammatory drugs.

Conclusion

The new definition of" inflammatory disease" comprises classical steroid-dependent disorders characterized by inflammatory infiltrates and new conditions with minimal inflammatory infiltrates plus the presence of "inflammatory" plasma proteins plus little response to steroids. It might be beneficial to distinguish these types of inflammation.

MO221ONLY A SIMPLE CASE OF AKI IN AN ONCOLOGIC PATIENT?

Background

Nivolumab is a drug belonging to the class of Immune Checkpoint Inhibitors (ICPI), the use of which has improved the prognosis for patients with various advanced malignancies. These agents are associated with several "immune-mediated" adverse effects, although the literature on Nivolumab renal toxicity is poor and anecdotal. A rare immune-mediated renal adverse event is acute interstitial nephritis (AIN) that often imposes Nivolumab suspension.

Case report

We present the case of a 75-year-old woman with stage IV melanoma (inguinal and external iliac lymph node metastases without localization of the primitive lesion). At diagnosis, renal function was normal by age (Creatinine 0.89 mg/dl; CKD EPI eGFR 71 ml/min/1.73 m2). After lymphadenectomy, an adjuvant treatment with Nivolumab was initiated.

At 4-month follow-up, the patient was hospitalized for AKI (creatinine 2.6 mg/dl; eGFR 17,3 ml/min/1.73 m2). Although, renal function decline was not accompanied by signs of systemic immunoactivation, Nivolumab was suspended. In the following weeks, only a partial renal function recovery was observed, still limiting immunotherapy reintroduction. Thus, the patient was referred to our Onconephrology Outpatient Unit for a multidisciplinary approach. We performed a urinalysis with microscopy study of the sediment and observed rare dysmorphic red blood cells and leukocytes. To exclude a glomerulopathy, a comprehensive screening for autoimmune diseases and 24 hours proteinuria were also measured and found not significant (Table 1). Renal ultrasound did not show any relevant alteration.

Based on our original suspicion of AIN, although in absence of an history of fever, rush or eosinophilia, we introduced Prednisone 25 mg/day. In the following weeks, blood and urine tests showed a significant improvement in renal function (serum creatinine 1.06 mg/dL, eGFR CKD-EPI 51 mL/min/1.73m2) and the absence of red blood cells, leukocytes and proteinuria in the urinalysis.

Based on nephrologist advice, the patient was then able to resume the cancer treatment with a maintenance dose of prednisone equal to 5 mg/day.

Conclusion

AIN is a rare adverse effect of ICPIs that mandates the close monitoring of renal function in patients under immunotherapy with these agents.

AKI occurrence in patients treated with ICPIs should always lead to investigate a possible AIN, even in the absence of the classic symptom set of fever, rush and eosinophilia and with minimal changes in urinalysis. Based on our single observation, and after an accurate literature review, we suggest the initiation of a corticosteroid treatment in oncologic patients on an ICPI complicated with AKI and with suspicion of AIN at urinalysis.

Moreover, this case report thickens the importance of a multidisciplinary approach to oncologic patients not only when a conventional nephrotoxic chemotherapy has to be started, but also in case of ICIPs use. The nephrologist advice, in fact, could be useful in both preventing and treating severe renal complications such as AIN, also allowing the oncologic therapy maintenance.

MO234LIFE THREATENING MALIGNANT HYPERCALCEMIA IN BREAST CANCER: CAN THE NEPHROLOGIST CHANGE THE PATIENT DESTINY?

Background

Malignant hypercalcemia is a common complication in cancer patients and can be predictive of poor prognosis and advanced malignancy. Cancer-related mechanisms of hypercalcemia depends either on ectopic hypersecretion of humoral factors (PTH, PTH-like molecules, Vit D) by the tumoral mass, or on osteolysis due to bone invasion. In consideration of the high renal and cardiac impact of severe hypercalcemia, its prompt recognition and treatment can be lifesaving. AKI is frequently associated with malignant hypercalcemia and recognizes a multifactorial pathogenesis (direct renal vasoconstriction, volume depletion, tubule-interstitial damage, etc.). Substitutive renal treatment can be necessary, but not always viable in patients with poor physical performance and is a difficult choice in cancer patients with advanced malignancies.

Case report

We present the case of a 46 years old woman with an infiltrating non special type (NST) carcinoma of the right breast (luminal B, ER 70%, PgR 60%, Ki67 35%, HER2 1+). Unfortunately, she quickly progressed after a neoadjuvant treatment with Epirubicin/Cyclophosfamide (4 cycles) followed by Paclitaxel (10 cycles). A first line hormonal treatment (Palbociclib, Letrozole and LHRH analogous) was then started, but a further rapid disease progression was observed. A new biopsy showed a muted and more aggressive cancer phenotype (high grade triple negative carcinoma with no PDL1 expression). Due to a rapid worsening of general conditions with cognitive impairment, the patient was admitted to the Oncology department. Blood test showed severe hypercalcemia (corrected calcium: 23.26 mg/dl) and severe hypokalemic metabolic alkalosis (blood pH 7.57; HCO-3 32 mmol/l; K+ 2.6 mmol/l) associated to AKI (creatinine doubled to 1.42 mg/dl; eGFR 45 ml/min/1,73 mq). Alkaline phosphatase and Vitamin D were normal and iPTH was &lt; 2 pg/ml. ECG showed a significant QTc prolongation to 550 msec. Imaging exams revealed lung metastasis, lung carcinomatous lymphangitis and bilateral pleural effusion, while Bone Scan showed a low caption limited to right ribs. Oncologists and Intensive Care Physicians referred to our Nephrology and Dialysis Unit proposing Hemodialysis support. In consideration of the preserved diuresis, the advanced disease stage and the unstable hemodynamics, our advice was instead for a conservative medical approach. An i.v. infusion of 4000 ml NaCl 0.9% + KCl 60 mEq/24h; a continuous i.v. infusion of Furosemide 5mg/h were started and maintained for several days, leading to a progressive and full renal function recovery (creatinine decreased to 0.7 mg/dl) and metabolic alkalosis correction. However, corrected calcium remained largely over target, being 16.3 mg/dl. Sodium bicarbonate 80 mEq, Zoledronic acid 4 mg and Desametasone 4mg/day were administered and at day 16 even calcium was in normal range. We realized that this was a favourable window for acting on the underlaying cause of malignant hypercalcemia, that likely was the aberrant secretion of non-dosable PTH-like molecule(s). Thus, we suggested the Oncologist to start chemotherapy, and they were allowed to treat the patient with Carboplatin/Gemcitabine. The patient was successfully treated with stabilization of normocalcemia and is still alive.

Conclusion

Malignant hypercalcemia is a life-threatening complication in advanced malignancies. Our case report highlights the key role of the nephrologist in treating a complex and fragile oncologic patient, achieving the full correction of several severe renal disorders, hemodialysis avoidance and survival improvement.

MO429A NOVEL METHOD LINESCAN-DRIVEN FOR SNGFR MEASUREMENTS AS ALTERNATIVE TO HIGH FULL FRAME MULTIPHOTON MICROSCOPY ACQUISITION

Background and Aims

Renal micropuncture, which requires the direct access to the renal tubules, has been for long time the technique of choice to measure the single nephron glomerular filtration rate (SNGFR) in animal models, but this approach is challenging by virtue of complex animal preparation and numerous careful steps. The introduction of intravital multiphoton microscopy (MPM) permitted to improve the study of renal functions exploiting the high laser penetration and the optical sectioning capacity. Previous MPM studies measuring in vivo the SNGFR relied on fast full frame acquisition during the filtration process obtainable with microscope resonant scanners, which represent optional expensive equipment able to reach very high acquisition speed. In this work we propose an innovative linescan-based MPM method to calculate SNGFR in rodents doable without using the fast acquisition rate offered by resonant scanners.

Method

An in vivo MPM approach was used to measure the SNGFR in control Munich Wistar Frömter rats (MWF) and to test the feasibility of the innovative linescan approach. In order to validate this method in conditions known for reduced and increased SNGFR, it was applied to ischemia reperfusion injury (IRI) and low-dose dopamine treated conditions, respectively.

Results

The glomeruli connected to S1 proximal tubules extending at least 100 μm from the exit of the Bowman’s space were chosen for the measurement. A linescan path starting from the urinary pole and crossing many times the tubular lumen orthogonally to the cellular wall was hand drawn. The linescan was acquired soon after a i.v. bolus of low-molecular weight fluorescent marker was injected. The tubular length, the mean diameter and the transit time of the fluorescent marker within two lines of interest (called cross1 and cross2) were measured to obtain the SNGFR. SNGFR measured in control rats was comparable with previous reported data both at MPM and micropuncture. Significantly higher values compared to control were obtained in 3 μg/kg/min dopamine-treated rats. In IRI-treated rats the SNGFR was reduced about 35% compared to the controls.

Conclusion

The results achieved with our linescan method were quite similar to those obtained with conventional micropuncture, suggesting that the two methods overlap for the normal, dopamine and IRI treatment. Our results show that linescan approach is a promising and cheap alternative to the fast full frame acquisition for the investigation of SNGFR in health and disease, offering results comparable to conventional micropuncture with unprecedent temporal resolution.

MO036DAPAGLIFLOZIN RESCUES THE RENAL PHENOTYPE OF GLYCOGEN STORAGE DISEASE TYPE IB

Background and Aims

Glycogenosis I type b (GsdI-b) is a rare metabolic disease and immune disorder characterized by hepato-renal glycogen accumulation caused by a deficiency in the Glucose-6-phosphate transporter (G6PT). G6PT transports glucose-6-phosphate (G6P) from cytoplasm to endoplasmic reticulum (ER) where a G6Pase catalyses the hydrolysis of G6P in glucose and phosphate. G6PT deficiency lead to impaired glucose homeostasis, myeloid disfunction and long-term risk of hepatocellular adenomas. No causal therapy is so far available for GSDI-b patients besides a dietary approach to control glycemia and the use of Granulocyte Colony-Stimulating Factor (GCSF) to improve neutropenia. Over time, these supports increase the chronicity of GSDI-b with some complications. A mouse model recapitulating the GDSI-b has been recently generated by inducing G6PT suppression after tamoxifen injection. Here, we characterized the renal phenotype of TM-G6PT-/- mice model focusing on the molecular mechanisms that lead to renal dysfunction. Finally, we evaluated the efficiency of Dapagliflozin, a selective inhibitor of SGLT2, on kidney functions in terms of therapeutic effect.

Method

Machine learning approach to computer based evaluation of renal morphology was used to analyze the renal sections from TM-G6PT-/- treated with or without dapagliflozin.

Results: G6PT is expressed in all renal zones and a severe downregulation of G6PT mRNA expression in whole kidney of TM-G6PT-/- mice can be observed. TM-G6PT-/- mice show tubular vacuolization and overall cellular dysfunction of PT due to a high glycogen accumulation. TM-G6PT-/- mice manifest glycosuria, phosphaturia and polyuria associated with a down regulation of main transporters of PT cells. The urine concentrating defect is due to a primarily role of G6PT in CNT/CD cells confirmed by a downregulation of AQP2, main water channel along CD segments. This mouse model recapitulates the human GSD-Ib renal phenotype characterized by a disfunction of PT but also CNT/CD cells. In order to evaluate whether targeting the glucose metabolism would improve the renal phenotype of these mice we limited glucose flux across the apical membrane of PT cells, applying the SGLT2-inhibitor dapagliflozin to reduce new glycogen formation. After one month of treatment, Dapagliflozin prevents glycogen accumulation in TM-G6PT-/- mice and ameliorates the main dysregulated markers of PT function. This finding was paralleled by an improvement of the histological features of kidney morphology in dapagliflozin treated TM-G6PT-/- mice.

Conclusion

Our data provide evidence that treatment with dapagliflozin ameliorates intracellular glycogen storage and improves the renal functions in TM-G6PT-/- mice.

MO030IDENTIFICATION OF REGULATED MRNAS AND MIRNAS IN GLOMERULI ISOLATED FROM AN FSGS-LIKE ZEBRAFISH MODEL

Background and Aims

The zebrafish (Danio rerio) is a powerful animal model to study glomerular morphology and the function of the permselectivity of the glomerular filtration barrier.

Since zebrafish larvae develop quickly and can be bred to become transparent, in vivo observation of these animals is possible. At 48 hours post fertilization, zebrafish larvae develop a single glomerulus which is attached to a pair of tubules. Like in mammals, the glomerular filtration barrier consists of a fenestrated endothelium, the glomerular basement membrane and interdigitating podocyte foot processes bridged by a slit diaphragm. By using genetically modified zebrafish strains with fluorescently labeled podocytes, it is possible to study alterations of the glomerulus during the development of renal disease like focal segmental glomerulosclerosis (FSGS) directly in vivo. FSGS is characterized by podocyte loss, the effacement of their foot processes as well as scarring of the glomerulus. To study FSGS in zebrafish larvae, we induced podocyte detachment by the use of a zebrafish strain expressing the enzyme nitroreductase converting metronidazole into a toxic substance specifically in podocytes. The aim of our study was to collect glomeruli for the identification of mRNAs as well as miRNAs by RNA_Seq that are up- and down-regulated in the glomeruli of this FSGS-like disease model.

Method

The transgenic zebrafish strain Cherry (Tg(nphs2:GAL4); Tg(UAS:Eco.nfsB-mCherry); mitfaw2/w2; mpv17a9/a9) which expresses the prokaryotic enzyme nitroreductase (NTR) fused to mCherry, a red fluorescent protein, under the control of the podocyte-specific podocin (nphs2) promoter in a transparent zebrafish strain, was utilized. After addition of metronidazole (MTZ) into the tank water, MTZ is converted into a cytotoxin by NTR leading to dose-dependent apoptosis exclusively in podocytes. Cherry larvae were treated at 4 days post fertilization (dpf) for 48 h with 80 µM MTZ. MTZ-treated and control larvae were homogenized at 6 dpf. The cell suspension was diluted, and red-fluorescent glomeruli were collected using a micropipette and a microscope. Total RNA was isolated, and integrity was checked by a Bioanalyzer. Libraries were generated with a MACE kit and True Quant small RNA seq kit by GenXPro. Constructs were amplified by PCR and sequenced on an Illumina Hiseq 2000. Normalization and statistical analysis for differential gene expression were done using DESeq2.

Results

Zebrafish larvae showed severe whole-body edema, proteinuria, loss of podocytes and an increased mortality rate after MTZ-treatment. The glomerular histology resembled mammalian FSGS. We found that only the RNA of manually collected glomeruli had an excellent quality. Using RNA_Seq, we identified a total of 16941 genes. DESeq2 analysis showed 494 up-regulated and 473 down-regulated genes. Gene ontology (GO) enrichment analysis of up-regulated genes revealed a total of 167 that are significantly enriched in GO terms (e.g. metabolic processes, immune response and ion transport). Down-regulated genes were enriched in 14 GO terms and most of them are linked to normal glomerular function and the slit diaphragm. DESeq2 analysis identified 200 miRNAs of 777 small RNAs. Some of these miRNA are already described to be regulated in different glomerular diseases like FSGS, lupus nephritis, IgA nephropathy and diabetic nephropathy.

Conclusion

We analyzed isolated glomeruli from transgenic zebrafish larvae that developed a FSGS-like disease. By sequencing, we have found mRNAs and miRNAs that were significantly regulated after the onset of disease. Detailed knowledge of these mRNAs and miRNA-based gene regulation will help to uncover the pathomechanism as well as to develop therapeutics for the treatment of FSGS.

MO045THE APPLICATION OF A NGS KIDNEY PANEL REVEALED KEY CHALLENGES OF PKD1-2 ANALYSIS: INTERPRETATION OF MISSENSE VARIANTS, SIGNIFICANCE OF VARIANTS IN DUPLICATED REGIONS AND HIGH ALLELIC HETEROGENEITY

Background and Aims

Genetic testing has changed the clinical management of inherited kidney diseases patients, improving prognosis, surveillance and therapy. On the other hand, it has put geneticists and clinicians in front of new challenges, as the heterogeneity of these disorders and the high number of variants, with no clear genotype-phenotype correlation.

Method

108 patients underwent genetic analysis through a kidney focused NGS panel, named Nephroplex, containing 119 genetic loci associated with inherited kidney disorders. The study aimed to addressed the genetic landscape of cystic individuals and to analyze PKD1 and PKD2 variants in non-cystic individuals.

Results

Following diagnostic criteria, patients were divided as cystic kidney diseases (n=36) and non-cystic kidney diseases (n=72). Among the group of cystic patients, a causative mutation was detected in 51% of cases. We found thirty-seven PKD1 and PKD2 variants in 26 out of 35 individuals. In particular, 12 variants were shown to be damaging and nine of that were reported in public database, as CLINVAR and Mayo Clinic databases. Among pathogenic variants, twelve were truncating and the remaining were missense variants. Of note, 7 out of 12 damaging PKD1 mutations were located in duplicated regions. Moreover, in three cystic patients, we found a (i) a frameshift hemizygote OFD1 mutation (ii) compound heterozygote PKHD1 variants and (iii) a frameshift MUC1 variant, framing the diagnosis of oro-facio-digital type 1, autosomal recessive polycystic kidney disease and autosomal dominant tubulointerstitial disease, respectively. Interestingly, we detected 28 PKD1-2 rare variants in 21 out of 75 adult non cystic patients (28%). The most were observed in PKD1 genes (82% vs 18% in PKD2). Eighteen of 28 variants were described in the literature as likely benign or as mutations of uncertain significance, while we found 10 novel variants. In silico analysis revealed as pathogenic a frameshift mutation located in exon 15. Of note, the great part of these variations reside into the duplicated PKD1 regions.

Conclusion

Our data showed that genetic analysis of ADPKD retains unique challenges, given the high degree of homology of PKD1 with his pseudogenes and the high allelic heterogeneity in non-cystic individuals.