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.

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.

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.

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.

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.

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.

Kidney and blood pressure regulation-latest evidence for molecular mechanisms.

Hypertension is one of the major health problems leading to the development of cardiovascular diseases. Despite a rapid expansion in global hypertension prevalence, molecular mechanisms leading to hypertension are not fully understood largely due to the complexity of pathogenesis involving several factors. Salt intake is recognized as a leading determinant of blood pressure, since reduced dietary salt intake is related to lower morbidity and mortality, and hypertension in relation to cardiovascular events. Compared with salt-resistant populations, salt-sensitive individuals exhibit high sensitivity in blood pressure responses according to changes in salt intake. In this setting, the kidney plays a major role in the maintenance of blood pressure under the hormonal control of the renin-angiotensin-aldosterone system. In the present review, we summarize the current overview on the molecular mechanisms for modulation of blood pressure associated with renal ion channels/transporters including sodium-hydrogen exchanger isoform 3 (NHE3), Na+-K+-2Cl- cotransporter (NKCC2), sodium-chloride cotransporter (NCC), epithelial sodium channel (ENaC) and pendrin expressed in different nephron segments. In particular, recent studies on experimental animal models with deletion of renal ion channels led to the identification of several crucial physiological mechanisms and molecules involved in hypertension. These findings could further provide a potential for novel therapeutic approaches applicable on human patients with hypertension.

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.

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.

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.

Urinary epidermal growth factor/monocyte chemotactic peptide 1 ratio as non-invasive predictor of Mayo clinic imaging classes in autosomal dominant polycystic kidney disease.

BACKGROUND: Age- and height-adjusted total kidney volume is currently considered the best prognosticator in patients with autosomal dominant polycystic kidney disease. We tested the ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 for the prediction of the Mayo Clinic Imaging Classes. METHODS: Urinary epidermal growth factor and monocyte chemotactic peptide 1 levels were measured in two independent cohorts (discovery, n = 74 and validation set, n = 177) and healthy controls (n = 59) by immunological assay. Magnetic resonance imaging parameters were used for total kidney volume calculation and the Mayo Clinic Imaging Classification defined slow (1A-1B) and fast progressors (1C-1E). Microarray and quantitative gene expression analysis were used to test epidermal growth factor and monocyte chemotactic peptide 1 gene expression. RESULTS: Baseline ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 correlated with total kidney volume adjusted for height (r = - 0.6, p < 0.001), estimated glomerular filtration rate (r = 0.69 p < 0.001), discriminated between Mayo Clinic Imaging Classes (p < 0.001), and predicted the variation of estimated glomerular filtration rate at 10 years (r = - 0.51, p < 0.001). Conditional Inference Trees identified cut-off levels of the ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 for slow and fast progressors at > 132 (100% slow) and < 25.76 (89% and 86% fast, according to age), with 94% sensitivity and 66% specificity (p = 6.51E-16). Further, the ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 at baseline showed a positive correlation (p = 0.006, r = 0.36) with renal outcome (delta-estimated glomerular filtration rate per year, over a mean follow-up of 4.2 ± 1.2 years). Changes in the urinary epidermal growth factor and monocyte chemotactic peptide 1 were mirrored by gene expression levels in both human kidney cysts (epidermal growth factor: - 5.6-fold, fdr = 0.001; monocyte chemotactic peptide 1: 3.1-fold, fdr = 0.03) and Pkd1 knock-out mouse kidney (Egf: - 14.8-fold, fdr = 2.37E-20, Mcp1: 2.8-fold, fdr = 6.82E-15). CONCLUSION: The ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 is a non-invasive pathophysiological biomarker that can be used for clinical risk stratification in autosomal dominant polycystic kidney disease.

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.

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 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.