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.

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.

Zebrafish as a Model of Cardiac Pathology and Toxicity: Spotlight on Uremic Toxins.

Chronic kidney disease (CKD) is an increasing health care problem. About 10% of the general population is affected by CKD, representing the sixth cause of death in the world. Cardiovascular events are the main mortality cause in CKD, with a cardiovascular risk 10 times higher in these patients than the rate observed in healthy subjects. The gradual decline of the kidney leads to the accumulation of uremic solutes with a negative effect on every organ, especially on the cardiovascular system. Mammalian models, sharing structural and functional similarities with humans, have been widely used to study cardiovascular disease mechanisms and test new therapies, but many of them are rather expensive and difficult to manipulate. Over the last few decades, zebrafish has become a powerful non-mammalian model to study alterations associated with human disease. The high conservation of gene function, low cost, small size, rapid growth, and easiness of genetic manipulation are just some of the features of this experimental model. More specifically, embryonic cardiac development and physiological responses to exposure to numerous toxin substances are similar to those observed in mammals, making zebrafish an ideal model to study cardiac development, toxicity, and cardiovascular disease.

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.

Multi-Omics Studies Unveil Extraciliary Functions of BBS10 and Show Metabolic Aberrations Underlying Renal Disease in Bardet-Biedl Syndrome.

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive ciliopathy resulting in multiple organ dysfunctions, including chronic kidney disease (CKD). Despite the recent progress in the 'ciliopathy' field, there is still little information on the mechanisms underlying renal disease. To elucidate these pathomechanisms, we conducted a translational study, including (i) the characterization of the urine metabolomic pattern of BBS patients and controls in a pilot and confirmation study and (ii) the proteomic analysis of the BBS10 interactome, one of the major mutated BBS genes in patients, in a renal-epithelial-derived cell culture model. The urine metabolomic fingerprinting of BBS patients differed from controls in both pilot and confirmation studies, demonstrating an increased urinary excretion of several monocarboxylates, including lactic acid (LA), at both early and late CKD stages. Increased urine LA was detected in the absence of both increased plasmatic LA levels and generalized proximal tubular dysfunction, suggesting a possible renal-specific defective handling. The inner medulla renal epithelial (IMCD3) cell line, where Bbs10 was stably invalidated, displayed an increased proliferative rate, increased ATP production, and an up-regulation of aerobic glycolysis. A mass spectrometry-based analysis detected several putative BBS10 interactors in vitro, indicating a potential role of BBS10 in several biological processes, including renal metabolism, RNA processing, and cell proliferation. The present study suggests that the urine metabolomic pattern of BBS patients may reflect intra-renal metabolic aberrations. The analysis of BBS10 interactors unveils possible novel functions, including cell metabolism.

Lanthionine, a Novel Uremic Toxin, in the Vascular Calcification of Chronic Kidney Disease: The Role of Proinflammatory Cytokines.

Vascular calcification (VC) is a risk factor for cardiovascular events and mortality in chronic kidney disease (CKD). Several components influence the occurrence of VC, among which inflammation. A novel uremic toxin, lanthionine, was shown to increase intracellular calcium in endothelial cells and may have a role in VC. A group of CKD patients was selected and divided into patients with a glomerular filtration rate (GFR) of <45 mL/min/1.73 m2 and ≥45 mL/min/1.73 m2. Total Calcium Score (TCS), based on the Agatston score, was assessed as circulating lanthionine and a panel of different cytokines. A hemodialysis patient group was also considered. Lanthionine was elevated in CKD patients, and levels increased significantly in hemodialysis patients with respect to the two CKD groups; in addition, lanthionine increased along with the increase in TCS, starting from one up to three. Interleukin IL-6, IL-8, and Eotaxin were significantly increased in patients with GFR < 45 mL/min/1.73 m2 with respect to those with GFR ≥ 45 mL/min/1.73 m2. IL-1b, IL-7, IL-8, IL-12, Eotaxin, and VEGF increased in calcified patients with respect to the non-calcified. IL-8 and Eotaxin were elevated both in the low GFR group and in the calcified group. We propose that lanthionine, but also IL-8 and Eotaxin, in particular, are a key feature of VC of CKD, with possible marker significance.

Homocysteine Solution-Induced Response in Aerosol Jet Printed OECTs by Means of Gold and Platinum Gate Electrodes.

Homocysteine (Hcy) is a non-protein, sulfur-containing amino acid, which is recognized as a possible risk factor for coronary artery and other pathologies when its levels in the blood exceed the normal range of between 5 and 12 µmol/L (hyperhomocysteinemia). At present, standard procedures in laboratory medicine, such as high-performance liquid chromatography (HPLC), are commonly employed for the quantitation of total Hcy (tHcy), i.e., the sum of the protein-bound (oxidized) and free (homocystine plus reduced Hcy) forms, in biological fluids (particularly, serum or plasma). Here, the response of Aerosol Jet-printed organic electrochemical transistors (OECTs), in the presence of either reduced (free) and oxidized Hcy-based solutions, was analyzed. Two different experimental protocols were followed to this end: the former consisting of gold (Au) electrodes' biothiol-induced thiolation, while the latter simply used bare platinum (Pt) electrodes. Electrochemical impedance spectroscopy (EIS) analysis was performed both to validate the gold thiolation protocol and to gain insights into the reduced Hcy sensing mechanism by the Au-gated OECTs, which provided a final limit of detection (LoD) of 80 nM. For the OECT response based on Platinum gate electrodes, on the other hand, a LoD of 180 nM was found in the presence of albumin-bound Hcy, with this being the most abundant oxidized Hcy-form (i.e., the protein-bound form) in physiological fluids. Despite the lack of any biochemical functionalization supporting the response selectivity, the findings discussed in this work highlight the potential role of OECT in the development of low-cost point-of-care (POC) electronic platforms that are suitable for the evaluation, in humans, of Hcy levels within the physiological range and in cases of hyperhomocysteinemia.

Proteomics and metabolomics studies exploring the pathophysiology of renal dysfunction in autosomal dominant polycystic kidney disease and other ciliopathies.

The primary cilium (PC) was considered as a vestigial organelle with no significant physiological importance, until the discovery that PC perturbation disturbs several signalling pathways and results in the dysfunction of a variety of organs. Genetic studies have demonstrated that mutations affecting PC proteins or its anchoring structure, the basal body, underlie a class of human disorders (known as ciliopathies) characterized by a constellation of clinical signs. Further investigations have demonstrated that the PC is involved in a broad range of biological processes, in both developing and mature tissues. Kidney disease is a common clinical feature of cilia disorders, supporting the hypothesis of a crucial role of the PC in kidney homoeostasis. Clinical proteomics and metabolomics are an expanding research area. Interestingly, the application of these methodologies to the analysis of urine, a biological sample that can be collected in a non-invasive fashion and possibly in large amounts, makes these studies feasible also in patients. The present article describes the most recent proteomic and metabolomic studies exploring kidney dysfunction in the setting of ciliopathies, showing the potential of these methodologies in the elucidation of disease pathophysiology and in the discovery of biomarkers.

Uremic Toxin Lanthionine Interferes with the Transsulfuration Pathway, Angiogenetic Signaling and Increases Intracellular Calcium.

(1) The beneficial effects of hydrogen sulfide (H2S) on the cardiovascular and nervous system have recently been re-evaluated. It has been shown that lanthionine, a side product of H2S biosynthesis, previously used as a marker for H2S production, is dramatically increased in circulation in uremia, while H2S release is impaired. Thus, lanthionine could be classified as a novel uremic toxin. Our research was aimed at defining the mechanism(s) for lanthionine toxicity. (2) The effect of lanthionine on H2S release was tested by a novel lead acetate strip test (LAST) in EA.hy926 cell cultures. Effects of glutathione, as a redox agent, were assayed. Levels of sulfane sulfur were evaluated using the SSP4 probe and flow cytometry. Protein content and glutathionylation were analyzed by Western Blotting and immunoprecipitation, respectively. Gene expression and miRNA levels were assessed by qPCR. (3) We demonstrated that, in endothelial cells, lanthionine hampers H2S release; reduces protein content and glutathionylation of transsulfuration enzyme cystathionine-ß-synthase; modifies the expression of miR-200c and miR-423; lowers expression of vascular endothelial growth factor VEGF; increases Ca2+ levels. (4) Lanthionine-induced alterations in cell cultures, which involve both sulfur amino acid metabolism and calcium homeostasis, are consistent with uremic dysfunctional characteristics and further support the uremic toxin role of this amino acid.

Zebrafish, a Novel Model System to Study Uremic Toxins: The Case for the Sulfur Amino Acid Lanthionine.

The non-proteinogenic amino acid lanthionine is a byproduct of hydrogen sulfide biosynthesis: the third endogenous vasodilator gas, after nitric oxide and carbon monoxide. While hydrogen sulfide is decreased in uremic patients on hemodialysis, lanthionine is increased and has been proposed as a new uremic toxin, since it is able to impair hydrogen sulfide production in hepatoma cells. To characterize lanthionine as a uremic toxin, we explored its effects during the early development of the zebrafish (Danio rerio), a widely used model to study the organ and tissue alterations induced by xenobiotics. Lanthionine was employed at concentrations reproducing those previously detected in uremia. Light-induced visual motor response was also studied by means of the DanioVision system. Treatment of zebrafish embryos with lanthionine determined acute phenotypical alterations, on heart organogenesis (disproportion in cardiac chambers), increased heart beating, and arrhythmia. Lanthionine also induced locomotor alterations in zebrafish embryos. Some of these effects could be counteracted by glutathione. Lanthionine exerted acute effects on transsulfuration enzymes and the expression of genes involved in inflammation and metabolic regulation, and modified microRNA expression in a way comparable with some alterations detected in uremia. Lanthionine meets the criteria for classification as a uremic toxin. Zebrafish can be successfully used to explore uremic toxin effects.

Cross-cultural validation of Lupus Impact Tracker in five European clinical practice settings.

Objectives: The aim was to evaluate the cross-cultural validity of the Lupus Impact Tracker (LIT) in five European countries and to assess its acceptability and feasibility from the patient and physician perspectives. Methods: A prospective, observational, cross-sectional and multicentre validation study was conducted in clinical settings. Before the visit, patients completed LIT, Short Form 36 (SF-36) and care satisfaction questionnaires. During the visit, physicians assessed disease activity [Safety of Estrogens in Lupus Erythematosus National Assessment (SELENA)-SLEDAI], organ damage [SLICC/ACR damage index (SDI)] and flare occurrence. Cross-cultural validity was assessed using the Differential Item Functioning method. Results: Five hundred and sixty-nine SLE patients were included by 25 specialists; 91.7% were outpatients and 89.9% female, with mean age 43.5 (13.0) years. Disease profile was as follows: 18.3% experienced flares; mean SELENA-SLEDAI score 3.4 (4.5); mean SDI score 0.8 (1.4); and SF-36 mean physical and mental component summary scores: physical component summary 42.8 (10.8) and mental component summary 43.0 (12.3). Mean LIT score was 34.2 (22.3) (median: 32.5), indicating that lupus moderately impacted patients' daily life. A cultural Differential Item Functioning of negligible magnitude was detected across countries (pseudo- R 2 difference of 0.01-0.04). Differences were observed between LIT scores and Physician Global Assessment, SELENA-SLEDAI, SDI scores = 0 (P < 0.035) and absence of flares (P = 0.004). The LIT showed a strong association with SF-36 physical and social role functioning, vitality, bodily pain and mental health (P < 0.001). The LIT was well accepted by patients and physicians. It was reliable, with Cronbach α coefficients ranging from 0.89 to 0.92 among countries. Conclusion: The LIT is validated in the five participating European countries. The results show its reliability and cultural invariability across countries. They suggest that LIT can be used in routine clinical practice to evaluate and follow patient-reported outcomes in order to improve patient-physician interaction.

ADAM17, a New Player in the Pathogenesis of Chronic Kidney Disease-Mineral and Bone Disorder.

The triad composed by α-Klotho, fibroblast growth factor-23, and its receptor are involved in the pathogenesis of chronic kidney disease-mineral and bone disorder. A disintegrin and metalloproteinase 17 (ADAM17) is a metalloproteinase causing the proteolytic shedding of α-Klotho from the cell membrane, and its role in chronic kidney disease-mineral and bone disorder is not yet known. We studied the circulating levels of the above-mentioned mediators in patients with secondary hyperparathyroidism due to uremia, compared to control subjects, as well as in patients with primary hyperparathyroidism. We also measured the immunofluorescence pattern of the relevant tissue proteins in specimens obtained from patients undergoing parathyroid surgery for secondary compared to primary hyperparathyroidism. Results showed that α-Klotho tissue levels are reduced, in the presence of increased ADAM17 tissue levels. In addition, we showed increased serum levels of the main product of ADAM17 proteolytic activity, tumor necrosis factor-α. Thus, we found a paradoxical situation, in secondary compared to primary hyperparathyroidism, that is, that in the face of increased tumor necrosis factor-α in circulation, both soluble and tissue α-Klotho are reduced significantly, despite increased tissue ADAM17. In conclusion, tissue and serum levels of α-Klotho seem to have become independent from the regulation induced by ADAM17, which constitutes therefore another tassel in the impaired α-Klotho-FGF23 receptor axis present in uremia.

Renal phenotype in Bardet-Biedl syndrome: a combined defect of urinary concentration and dilution is associated with defective urinary AQP2 and UMOD excretion.

The renal phenotype in Bardet-Biedl syndrome (BBS) is highly variable. The present study describes renal findings in 41 BBS patients and analyzes the pathogenesis of hyposthenuria, the most common renal dysfunction. Five of 41 patients (12%) showed an estimated glomerular filtration rate < 60 ml·min-1·1.73 m-2 Urine protein and urine albumin-to-creatinine ratio were over 200 and 30 mg/g in 9/24 and 7/23 patients, respectively. Four of 41 patients showed no renal anomalies on ultrasound. Twenty of 34 patients had hyposthenuria in the absence of renal insufficiency. In all 8 of the hyposthenuric patients studied, dDAVP failed to elevate urine osmolality (Uosm), suggesting a nephrogenic origin. Interestingly, water loading (WL) did not result in a significant reduction of Uosm, indicating combined concentrating and diluting defects. dDAVP infusion induced a significant increase of plasma Factor VIII and von Willebrand Factor levels, supporting normal function of the type 2 vasopressin receptor at least in endothelial cells. While urinary aquaporin 2 (u-AQP2) abundance was not different between patients and controls at baseline, the dDAVP-induced increased u-AQP2 and the WL-induced reduction of u-AQP2 were blunted in patients with a combined concentrating and diluting defect, suggesting a potential role of AQP2 in the defective regulation of water absorption. Urine Uromodulin excretion was reduced in all hyposthenuric patients, suggesting a thick ascending limb defect. Interestingly, renal Na, Cl, Ca, but not K handling was impaired after acute WL but not at basal. In summary, BBS patients show combined urinary concentration and dilution defects; a thick ascending limb and collecting duct tubulopathy may underlie impaired water handling.

Clinical profile and direct medical cost of care of adults presenting with systemic lupus erythematosus in Italy.

OBJECTIVES: To determine the clinical profile and estimate the annual direct medical cost of care of adult patients with active, autoantibody positive systemic lupus erythematosus (SLE) in Italy. METHODS: A two-year, retrospective, multicentre, observational study was conducted from January to May 2011. Patients' characteristics, SLE disease activity and severity, rate of flares, healthcare consumption (e.g. medications, etc.) were evaluated. Medical costs were assessed from the Italian National Health Insurance perspective. RESULTS: Four centres enrolled 96 eligible patients, including 85.4% women. Patients were equally stratified per disease severity (severe SLE: 51%). The mean (SD) age was 42.9 (13.8) years. At baseline, SLE duration was 12.6 (7.2) years. The mean (SD) SELENA-SLEDAI score was higher in severe than in non-severe patients 9.2 (6.4) vs. 3.3 (3.1) (p<0.001). The mean (SD) SLICC/ACR index score was similar in the two subgroups: 0.4 (0.8) vs. 0.3 (0.8). Over the study period, severe patients experienced on average 0.73 (0.56) flares/year and non-severe patients 0.57 (0.63). The annual medical cost was 1.6 times higher in severe than in non-severe patients (€2,101 vs. €1,320; p=0.031). The cost of medications was also 2.5 times higher in severe patients (€1101 vs. €445, p=0.007). Low C3/C4 complement levels and each severe flare incremented the annual cost of €550 (p=0.011) and €465 (p=0.02), respectively. CONCLUSIONS: The medical cost of SLE in Italy is related to disease severity and flares. Medications identified as the main cost drivers, and low C3/C4 complement levels and severe flares as the main cost predictors, increased significantly the cost of SLE management.

Annual direct medical cost of active systemic lupus erythematosus in five European countries.

OBJECTIVES: To evaluate the annual direct medical cost of managing adult systemic lupus erythematosus (SLE) patients with active autoantibody positive disease in Europe. METHODS: A 2-year, retrospective, multicentre, observational study was conducted in five countries (France, Germany, Italy, Spain and the UK). Data included patients' characteristics, disease activity and severity, flare assessments and health resource use (eg, laboratory tests, medications, specialist visits and hospitalisations). Costs were assessed from the public payers' perspective. Cost predictors were estimated by multivariate regression models. RESULTS: Thirty-one centres enrolled 427 consecutive eligible patients stratified equally by disease severity. At baseline, mean (SD) age was 44.5 (13.8) years, 90.5% were women and mean (SD) SLE duration was 10.7 (8.0) years. The SELENA-SLEDAI (11.2 vs 5.3) and SLICC/ACR index (1.0 vs 0.7) scores were higher in severe patients. Over the study period, patients experienced on average 1.02 (0.71) flares/year. The mean annual direct medical cost was higher in severe compared to non-severe patients (€4748 vs €2650, p<0.001). Medication costs were €2518 in severe versus €1251 in non-severe patients (p<0.001). Medications represented 53% and 47% of the total cost for severe and non-severe patients, respectively, primarily due to immunosuppressants and biologics. Flares, especially severe flares, were identified as the major cost predictor, with each flare increasing the annual total cost by about €1002 (p<0.001). CONCLUSIONS: The annual direct medical cost of SLE patients in Europe is related to disease severity and flares. Medical treatments were the main cost drivers. Severe flares and major organ involvement were identified as important cost predictors.

Bone mineral density assessment in patients with cystinuria.

BACKGROUND: Cystinuria is a rare genetic disease characterized by impaired tubular transport of cystine. Clinical features of cystinuria mainly include nephrolithiasis and its complications, although cystinuric patients may present with other comorbidities. There are currently no data on bone features of patients with cystinuria. Our aim is to characterize bone mineral density (BMD) in cystinuria. METHODS: Our study included adult cystinuric patients with estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m2 followed at 3 specialized outpatient clinics in Italy (Rome, Naples and Verona). Markers of bone turnover were analyzed in a centralized laboratory. Clinical, biochemical and dual-energy X-ray absorptiometry (DEXA) data were collected from September 2021 to December 2022. Linear regression models were used to evaluate statistically significant deviations from zero of Z-scores. RESULTS: Twenty-seven patients were included in the study. Mean (SD) age was 37 (15) years, 41% were women. Mean estimated glomerular filtration rate was 99 mL/min/1.73 m2. Serum parameters associated with bone turnover (parathyroid hormone, FGF23, calcium and phosphate) were all in the normal range, with only 4 patients showing mild hypophosphatemia. Prevalence of low bone mineral density, defined as Z-score ≤ - 2 at any site, was 15%. Average Z-scores were negative across most sites. CONCLUSIONS: Our study suggests that cystinuric patients have lower bone mineral density compared with individuals of the same sex and age, even when their kidney function is normal.

Hydrogen sulfide reduces cell adhesion and relevant inflammatory triggering by preventing ADAM17-dependent TNF-α activation.

H2S is the third endogenous gaseous mediator, after nitric oxide and carbon monoxide, possessing pleiotropic effects, including cytoprotection and anti-inflammatory action. We analyzed, in an in vitro model entailing monocyte adhesion to an endothelial monolayer, the changes induced by H2S on various potential targets, including cytokines, chemokines, and proteases, playing a crucial role in inflammation and cell adhesion. Results show that H2S prevents the increase in monocyte adhesion induced by tumor necrosis factor-α (TNF-α). Under these conditions, downregulation of monocyte chemoattractant protein-1 (MCP-1), chemokine C-C motif receptor 2, and increase of cluster of differentiation 36 could be detected in monocytes. In endothelial cells, H2 S treatment reduces the increase in MCP-1, inter-cellular adhesion molecule-1, vascular cell adhesion molecule-1, and of a disintegrin and metalloproteinase metallopeptidase domain 17 (ADAM17), both at the gene expression and protein levels. Cystathionine γ-lyase and 3-mercaptopyruvate sulfurtransferase, the major H2S forming enzymes, are downregulated in endothelial cells. In addition, H2S significantly reduces activation of ADAM17 by PMA in endothelial cells, with consequent reduction of both ADAM17-dependent TNF-α ectodomain shedding and MCP-1 release. In conclusion, H2S is able to prevent endothelial activation by hampering endothelial activation, triggered by TNF-α. The mechanism of this protective effect is mainly mediated by down-modulation of ADAM17-dependent TNF-converting enzyme (TACE) activity with consequent inhibition of soluble TNF-α shedding and its relevant MCP-1 release in the medium. These results are discussed in the light of the potential protective role of H2S in pro-inflammatory and pro-atherogenic processes, such as chronic renal failure.

Altered folate receptor 2 expression in uraemic patients on haemodialysis: implications for folate resistance.

BACKGROUND: Folate therapy reduces, but does not normalize homocysteine (Hcy) levels, frequently elevated in chronic kidney disease (CKD). The mechanisms of this folate resistance are unknown. Cellular acquisition of folate is mediated by folate receptors (FRs), whose expression is also modulated by folate status, through an Hcy-dependent regulation mechanism involving heterogeneous nuclear ribonucleoprotein-E1 (hnRNP-E1). Our objective was to evaluate whether an alteration of the FR2 (the form present in nucleated blood cells) expression is present in CKD patients on haemodialysis (HD), and its susceptibility to folate treatment. METHODS: A population of chronic uraemic patients on HD was enrolled, along with a control group, and studies on FR2 receptor expression and related items were performed in plasma and mononuclear cells from peripheral blood. A subgroup of patients was treated with methyltetrahydrofolate for 1 month. RESULTS: In HD, there was a significant reduction in FR2 protein expression compared with controls, not correlated with Hcy concentrations, while its mRNA levels were significantly increased. After folate treatment, there was a significant mRNA decrease, in the absence of significant changes in receptor protein expression. hnRNP-E1 gene and protein expression levels increased pre-treatment, while decreased post-treatment. CONCLUSIONS: In HD, FR2 expression is altered in peripheral mononuclear cells, since its levels are decreased and are not responsive to variations in Hcy concentration, while the intracellular machinery (receptor mRNA and hnRNP-E1), possibly triggering its regulation, is conserved. These findings provide insight into the mechanisms of folate resistance in uraemia.