Gitelman and Bartter syndromes are rare inherited diseases that belong to the category of renal tubulopathies. The genes associated with these pathologies encode electrolyte transport proteins located in the nephron, particularly in the Distal Convoluted Tubule and Ascending Loop of Henle. Therefore, both syndromes are characterized by alterations in the secretion and reabsorption processes that occur in these regions. Patients suffer from deficiencies in the concentration of electrolytes in the blood and urine, which leads to different systemic consequences related to these salt-wasting processes. The main clinical features of both syndromes are hypokalemia, hypochloremia, metabolic alkalosis, hyperreninemia and hyperaldosteronism. Despite having a different molecular etiology, Gitelman and Bartter syndromes share a relevant number of clinical symptoms, and they have similar therapeutic approaches. The main basis of their treatment consists of electrolytes supplements accompanied by dietary changes. Specifically for Bartter syndrome, the use of non-steroidal anti-inflammatory drugs is also strongly supported. This review aims to address the latest diagnostic challenges and therapeutic approaches, as well as relevant recent research on the biology of the proteins involved in disease. Finally, we highlight several objectives to continue advancing in the characterization of both etiologies.

Significance Statement: In autosomal dominant polycystic kidney disease (ADPKD), interstitial inflammation promotes cyst progression. TWEAK is a TNF superfamily cytokine that regulates inflammatory responses, and its receptor, Fn14, is expressed in nephron epithelium. This paper describes TWEAK’s role in ADPKD and its potential as a therapeutic target. The Fn14/TWEAK axis is upregulated in human and mouse polycystic kidneys, and TWEAK administration in mice accelerates cyst progression, whereas anti-TWEAK treatment slows cyst growth, improving kidney function and survival. Anti-TWEAK antibodies restore several ADPKD-related pathways, such as proliferation and NF-κB; slightly reduces fibrosis and apoptosis; and indirectly decreases macrophage recruitment. These findings identify the TWEAK signaling pathway as a new disease mechanism in ADPKD and a new possible therapeutic approach. Background: In autosomal dominant polycystic kidney disease (ADPKD), cyst development and enlargement lead to ESKD. Macrophage recruitment and interstitial inflammation promote cyst growth. TWEAK is a TNF superfamily (TNFSF) cytokine that regulates inflammatory responses, cell proliferation, and cell death, and its receptor Fn14 (TNFRSF12a) is expressed in macrophage and nephron epithelia. Methods: To evaluate the role of the TWEAK signaling pathway in cystic disease, we evaluated Fn14 expression in human and in an orthologous murine model of ADPKD. We also explored the cystic response to TWEAK signaling pathway activation and inhibition by peritoneal injection. Results: Meta-analysis of published animal-model data of cystic disease reveals mRNA upregulation of several components of the TWEAK signaling pathway. We also observed that TWEAK and Fn14 were overexpressed in mouse ADPKD kidney cysts, and TWEAK was significantly high in urine and cystic fluid from patients with ADPKD. TWEAK administration induced cystogenesis and increased cystic growth, worsening the phenotype in a murine ADPKD model. Anti-TWEAK antibodies significantly slowed the progression of ADPKD, preserved renal function, and improved survival. Furthermore, the anti-TWEAK cystogenesis reduction is related to decreased cell proliferation–related MAPK signaling, decreased NF-κB pathway activation, a slight reduction of fibrosis and apoptosis, and an indirect decrease in macrophage recruitment. Conclusions: This study identifies the TWEAK signaling pathway as a new disease mechanism involved in cystogenesis and cystic growth and may lead to a new therapeutic approach in ADPKD.

Human milk (HM) is the first form of communication between mothers and newborns and it is implicated in the infant growth and protection. We recently showed a functional characterization of HM, unmasking the molecular mechanisms related to EVs signaling and its functional role in prematurity. In that study, we identified the need to establish and optimize a standard isolation protocol for human milk extracellular vesicles (mEVs). Four mEVs isolation methods were compared: ultracentrifugation (UC), size exclusion chromatography (SEC), immunoprecipitation with tetraspanin CD9 (IP_CD9) and ExoGAG. Three pools of human milk (each composed of samples from ten donor mothers) were used and isolation of mEVs was performed starting from the same volume for each method. The proteomic, transcriptomic and glycomic composition of the extracellular vesicles obtained after isolation was then analyzed for each method. The sensitivity, specificity and quality of the results were also determined. A comparative analysis of results common across all isolation methods was performed to identify potential signaling pathways associated with mEVs. ExoGAG and UC proved to be the most efficient of the four techniques compared for mEVs isolation. However, ExoGAG compared to UC provided a higher concentration of total and vesicle-related proteins and peptides and a higher glycoprotein count keeping all the glycan subgroups. Despite ExoGAG and UC show similar vesicle profiles in terms of size, concentration, tetraspanin subpopulations and EVs markers, ExoGAG was the most efficient technique in terms of accuracy, consistency and reproducibility for omics studies. Furthermore, results allowed us to identify that mEVs components are involved in the signaling pathways of infant biological development, immune system maturation and protein metabolism. This study establishes UC and ExoGAG as reliable methods for mEVs isolation and describes its protocol, being ExoGAG the most efficient. Also, the omics analysis show that biomolecules conforming those mEVs are linked to the defense system against external agents (specific role in the immune system pathway) and in the correct establishment of the neural structure (developmental pathway), while providing all the nutritional requirements for the correct growth of the newborn (metabolic pathway).

(1) Background: Polycystic liver disease (PLD) is a heterogeneous group of congenital disorders characterized by bile duct dilatation and cyst development derived from cholangiocytes. Nevertheless, the cystogenesis mechanism is currently unknown and the PLD treatment is limited to liver transplantation. Novel and efficient therapeutic approaches are th6us needed. In this context, the present work has a principal aim to find novel molecular pathways, as well as new therapeutic targets, involved in the hepatic cystogenesis process. (2) Methods: Quantitative proteomics based on SWATH–MS technology were performed comparing hepatic proteomes of Wild Type and mutant/polycystic livers in a polycystic kidney disease (PKD) murine model (Pkd1^cond/cond;Tam-Cre^−/+). (3) Results: We identified several proteins altered in abundance, with two-fold cut-off up-regulation or down-regulation and an adjusted p-value significantly related to hepatic cystogenesis. Then, we performed enrichment and a protein–protein analysis identifying a cluster focused on hepatic fibrinogens. Finally, we validated a selection of targets by RT-qPCR, Western blotting and immunohistochemistry, finding a high correlation with quantitative proteomics data and validating the fibrinogen complex. (4) Conclusions: This work identified a novel molecular pathway in cystic liver disease, highlighting the fibrinogen complex as a possible new therapeutic target for PLD.