Testicular histomorphometric patterns and spermatogenesis dynamics of Oecomys bicolor tomes, 1860 (Rodentia: Cricetidae).

Although the order Rodentia does not present a high risk of extinction compared to mammals as a whole, several families demonstrate high levels of threat and/or data deficiency, therefore highlighting the need for targeted research and the application of ecological and reproductive data to the development of conservation actions. The order Rodentia, the largest among mammals, includes 9 families, and the family Cricetidae is the most diverse of the Brazilian rodents. In Brazil, 12 of the 16 genera of Oecomys are found. Oecomys bicolor is known in Brazil as the 'arboreal rat' and is, found in dry, deciduous and tropical forests. The mean body weight of Oecomys bicolor was 35.8 g and the gonadal, tubular and epithelial somatic indexes were, 0.53%, 0.47% and 0.37%, respectively. Seminiferous tubules volume density was 89.72% and the mitotic and meiotic indexes corresponded to 8.59 and 2.45 cells, respectively, and the yield of spermatogenesis was 23.83 cells. The intertubular compartment represented 10.28% of the testis parenchyma and around 5% of the interstitial space was occupied by Leydig cells, whose number per gram of testis was 11.10 × 107 cells. By evaluating the biometric and histomorphometric characteristics of the testis, there is evidence that this species has a high investment in reproduction. Due to the high contribution of the seminiferous epithelium and the intertubular compartment in this species, compared to the others of the same family, it is possible to infer that the species Oecomys bicolor has a promiscuous reproductive behaviour.

Mechanisms of heart failure and chronic kidney disease protection by SGLT2 inhibitors in nondiabetic conditions.

Sodium-glucose cotransporter 2 inhibitors (SGLT2is), initially developed for type 2 diabetes (T2D) treatment, have demonstrated significant cardiovascular and renal benefits in heart failure (HF) and chronic kidney disease (CKD), irrespective of T2D. This review provides an analysis of the multifaceted mechanisms underlying the cardiorenal benefits of SGLT2i in HF and CKD outside of the T2D context. Eight major aspects of the protective effects of SGLT2i beyond glycemic control are explored: 1) the impact on renal hemodynamics and tubuloglomerular feedback; 2) the natriuretic effects via proximal tubule Na+/H+ exchanger NHE3 inhibition; 3) the modulation of neurohumoral pathways with evidence of attenuated sympathetic activity; 4) the impact on erythropoiesis, not only in the context of local hypoxia but also systemic inflammation and iron regulation; 5) the uricosuria and mitigation of the hyperuricemic environment in cardiorenal syndromes; 6) the multiorgan metabolic reprogramming including the potential induction of a fasting-like state, improvement in glucose and insulin tolerance, and stimulation of lipolysis and ketogenesis; 7) the vascular endothelial growth factor A (VEGF-A) upregulation and angiogenesis, and 8) the direct cardiac effects. The intricate interplay between renal, neurohumoral, metabolic, and cardiac effects underscores the complexity of SGLT2i actions and provides valuable insights into their therapeutic implications for HF and CKD. Furthermore, this review sets the stage for future research to evaluate the individual contributions of these mechanisms in diverse clinical settings.

Tumor de los cordones sexuales con estructuras túbulo anulares. Presentación de un caso no asociado a síndrome de Peutz-Jeghers

El tumor de los cordones sexuales con estructuras túbulo anulares (TCSTA) es un tumor ovárico extremadamente infrecuente representando el 1%-2% de los tumores de los cordones sexuales. Cuando existe asociación con síndrome de Peutz-Jeghers (SPJ) el tumor generalmente tiene un comportamiento benigno, no así en la ausencia de esta asociación. Se presenta el caso de una paciente de 18 años con sus características clínicas e histopatológicas.

Sex cord tumor with tubule-annular structures (TCSTA) is a rare ovarian tumor, representing 1%-2% of sex-cord stromal tumors. When there is an association with Peutz-Jeghers syndrome (SPJ), the tumor generally behaves benignly, but not without this association. The case of an 18-year-old patient with its clinical and histopathological characteristics is presented.

Toll like receptor 4 mediates the inhibitory effect of SARS-CoV-2 spike protein on proximal tubule albumin endocytosis.

Tubular proteinuria is a common feature in COVID-19 patients, even in the absence of established acute kidney injury. SARS-CoV-2 spike protein (S protein) was shown to inhibit megalin-mediated albumin endocytosis in proximal tubule epithelial cells (PTECs). Angiotensin-converting enzyme type 2 (ACE2) was not directly involved. Since Toll-like receptor 4 (TLR4) mediates S protein effects in various cell types, we hypothesized that TLR4 could be participating in the inhibition of PTECs albumin endocytosis elicited by S protein. Two different models of PTECs were used: porcine proximal tubule cells (LLC-PK1) and human embryonic kidney cells (HEK-293). S protein reduced Akt activity by specifically inhibiting of threonine 308 (Thr308) phosphorylation, a process mediated by phosphoinositide-dependent kinase 1 (PDK1). GSK2334470, a PDK1 inhibitor, decreased albumin endocytosis and megalin expression mimicking S protein effect. S protein did not change total TLR4 expression but decreased its surface expression. LPS-RS, a TLR4 antagonist, also counteracted the effects of the S protein on Akt phosphorylation at Thr308, albumin endocytosis, and megalin expression. Conversely, these effects of the S protein were replicated by LPS, an agonist of TLR4. Incubation of PTECs with a pseudovirus containing S protein inhibited albumin endocytosis. Null or VSV-G pseudovirus, used as control, had no effect. LPS-RS prevented the inhibitory impact of pseudovirus containing the S protein on albumin endocytosis but had no influence on virus internalization. Our findings demonstrate that the inhibitory effect of the S protein on albumin endocytosis in PTECs is mediated through TLR4, resulting from a reduction in megalin expression.

Renal proximal tubule-on-a-chip in PDMS: fabrication, functionalization, and RPTEC:HUVEC co-culture evaluation.

'On-a-chip' technology advances the development of physiologically relevant organ-mimicking architecture by integrating human cells into three-dimensional microfluidic devices. This method also establishes discrete functional units, faciliting focused research on specific organ components. In this study, we detail the development and assessment of a convoluted renal proximal tubule-on-a-chip (PT-on-a-chip). This platform involves co-culturing Renal Proximal Tubule Epithelial Cells (RPTEC) and Human Umbilical Vein Endothelial Cells (HUVEC) within a polydimethylsiloxane microfluidic device, crafted through a combination of 3D printing and molding techniques. Our PT-on-a-chip significantly reduced high glucose level, exhibited albumin uptake, and simulated tubulopathy induced by amphotericin B. Remarkably, the RPTEC:HUVEC co-culture exhibited efficient cell adhesion within 30 min on microchannels functionalized with plasma, 3-aminopropyltriethoxysilane, and type-I collagen. This approach significantly reduced the required incubation time for medium perfusion. In comparison, alternative methods such as plasma and plasma plus polyvinyl alcohol were only effective in promoting cell attachment to flat surfaces. The PT-on-a-chip holds great promise as a valuable tool for assessing the nephrotoxic potential of new drug candidates, enhancing our understanding of drug interactions with co-cultured renal cells, and reducing the need for animal experimentation, promoting the safe and ethical development of new pharmaceuticals.

KS-WNK1 is required for the renal response to extreme changes in potassium intake.

Kidney-specific with-no-lysine kinase 1 (KS-WNK1) is an isoform of WNK1 kinase that is predominantly found in the distal convoluted tubule of the kidney. The precise physiological function of KS-WNK1 remains unclear. Some studies have suggested that it could play a role in regulating potassium renal excretion by modulating the activity of the Na+-Cl- cotransporter (NCC). However, changes in the potassium diet from normal to high failed to reveal a role for KS-WNK1, but under a normal-potassium diet, the expression of KS-WNK1 is negligible. It is only detectable when mice are exposed to a low-potassium diet. In this study, we investigated the role of KS-WNK1 in regulating potassium excretion under extreme changes in potassium intake. After following a zero-potassium diet (0KD) for 10 days, KS-WNK1-/- mice had lower plasma levels of K+ and Cl- while exhibiting higher urinary excretion of Na+, Cl-, and K+ compared with KS-WNK1+/+ mice. After 10 days of 0KD or normal-potassium diet (NKD), all mice were challenged with a high-potassium diet (HKD). Plasma K+ levels markedly increased after the HKD challenge only in mice previously fed with 0KD, regardless of genotype. KSWNK1+/+ mice adapt better to HKD challenge than KS-WNK1-/- mice after a potassium-retaining state. The difference in the phosphorylated NCC-to-NCC ratio between KS-WNK1+/+ and KS-WNK1-/- mice after 0KD and HKD indicates a role for KS-WNK1 in both NCC phosphorylation and dephosphorylation. These observations show that KS-WNK1 helps the distal convoluted tubule to respond to extreme changes in potassium intake, such as those occurring in wildlife.NEW & NOTEWORTHY The findings of this study demonstrate that kidney-specific with-no-lysine kinase 1 plays a role in regulating urinary electrolyte excretion during extreme changes in potassium intake, such as those occurring in wildlife. .

Ultrasonic activation of the endodontic sealer enhances its intratubular penetration and bond strength to irradiated root dentin.

To evaluate the effect of ultrasonic activation of the endodontic sealer on its intratubular penetration and bond strength to irradiated root dentin. Forty human teeth were distributed into 4 groups (n = 10), according to the radiation therapy (RT) exposure-70 Gy-and ultrasonic activation (UA) of the endodontic sealer: RT/UA-irradiated teeth and sealer UA; RT/no-UA-irradiated teeth and no sealer UA; no-RT/UA-non-irradiated teeth and sealer UA and no-RT/no-UA-non-irradiated teeth and no sealer UA. Push-out bond strength test was performed in a Universal Testing Machine. Failure modes and adhesive interface were analyzed under Scanning Electron Microscopy. The data were statistically compared (two-way-ANOVA and posthoc Games-Howell test; Fisher's exact test - α = 5%). The different experimental conditions (radiation and UA) and the root third had a significant effect on push-out bond strength, and the interaction of these factors was significant (p < 0.05). UA of the sealer significantly increased its bond strength to both irradiated and non-irradiated dentin (p < 0.05). The irradiated groups mostly presented adhesive-type failure of the sealer (p < 0.01). Regardless of the irradiation, the ultrasonically activated groups showed a more homogeneous adhesive interface, with the presence of sealer tags in greater density and depth. Ultrasonic activation enhanced the intratubular penetration and the bond strength of the endodontic sealer to irradiated dentin. The impact of ultrasonic activation of the endodontic sealer on teeth undergoing radiotherapy is a gap in the scientific literature that needs to be bridged.

Arginine vasopressin regulates the renal Na+-Cl- and Na+-K+-Cl- cotransporters through with-no-lysine kinase 4 and inhibitor 1 phosphorylation.

Vasopressin regulates water homeostasis via the V2 receptor in the kidney at least in part through protein kinase A (PKA) activation. Vasopressin, through an unknown pathway, upregulates the activity and phosphorylation of Na+-Cl- cotransporter (NCC) and Na+-K+-2Cl- cotransporter 2 (NKCC2) by Ste20-related proline/alanine-rich kinase (SPAK) and oxidative stress-responsive kinase 1 (OSR1), which are regulated by the with-no-lysine kinase (WNK) family. Phosphorylation of WNK4 at PKA consensus motifs may be involved. Inhibitor 1 (I1), a protein phosphatase 1 (PP1) inhibitor, may also play a role. In human embryonic kidney (HEK)-293 cells, we assessed the phosphorylation of WNK4, SPAK, NCC, or NKCC2 in response to forskolin or desmopressin. WNK4 and cotransporter phosphorylation were studied in desmopressin-infused WNK4-/- mice and in tubule suspensions. In HEK-293 cells, only wild-type WNK4 but not WNK1, WNK3, or a WNK4 mutant lacking PKA phosphorylation motifs could upregulate SPAK or cotransporter phosphorylation in response to forskolin or desmopressin. I1 transfection maximized SPAK phosphorylation in response to forskolin in the presence of WNK4 but not of mutant WNK4 lacking PP1 regulation. We observed direct PP1 regulation of NKCC2 dephosphorylation but not of NCC or SPAK in the absence of WNK4. WNK4-/- mice with desmopressin treatment did not increase SPAK/OSR1, NCC, or NKCC2 phosphorylation. In stimulated tubule suspensions from WNK4-/- mice, upregulation of pNKCC2 was reduced, whereas upregulation of SPAK phosphorylation was absent. These findings suggest that WNK4 is a central node in which kinase and phosphatase signaling converge to connect cAMP signaling to the SPAK/OSR1-NCC/NKCC2 pathway.NEW & NOTEWORTHY With-no-lysine kinases regulate the phosphorylation and activity of the Na+-Cl- and Na+-K+-2Cl- cotransporters. This pathway is modulated by arginine vasopressin (AVP). However, the link between AVP and WNK signaling remains unknown. Here, we show that AVP activates WNK4 through increased phosphorylation at putative protein kinase A-regulated sites and decreases its dephosphorylation by protein phosphatase 1. This work increases our understanding of the signaling pathways mediating AVP actions in the kidney.

Effect of obturation technique on dentinal tubule penetration of two tricalcium silicate-based sealers: Ex vivo study.

The aim of this study was to assess by confocal laser microscope the depth of dentinal tubule penetration of two tricalcium silicate-based sealers promoted by two obturation techniques in curved canals compared with AHPlus. One hundred and twenty canals were divided into six groups (n = 20): BCSC-Bio-C Sealer (BC) and single-cone technique (SC); BCCW-BC and continuous condensation wave (CW); TFSC-Total Fill (TF) and SC; TFCW-TF and CW; AHSC-AH Plus (AH) and SC; AHCW-AH and CW. Data were analysed using the three-way ANOVA and Tukey's test (α = 5%). Penetration depth was significantly greater for TFCW than TFSC and greater for AHCW than AHSC (p < 0.05). There was no significant difference between BCCW and BCSC (p > 0.05). The penetration of TF was significantly greater (p < 0.05). The CW technique promoted greater intratubular penetration, except for the BC sealer.

O-Linked GlcNAcylation mediates the inhibition of proximal tubule (Na++K+)ATPase activity in the early stage of diabetes mellitus.

BACKGROUND: Diabetic kidney disease (DKD) is a severe complication of diabetes mellitus (DM). It has been proposed that modifications in the function of proximal tubule epithelial cells (PTECs) precede glomerular damage during the onset of DKD. This study aimed to identify modifications in renal sodium handling in the early stage of DM and its molecular mechanism. METHODS: Streptozotocin (STZ)-induced diabetic BALB/c mice (STZ group) and LLC-PK1 cells, a model of PTECs, were used. All parameters were assessed in the 4th week after an initial injection of STZ. RESULTS: Early stage of DKD was characterized by hyperfiltration and PTEC dysfunction. STZ group exhibited increased urinary sodium excretion due to impairment of tubular sodium reabsorption. This was correlated to a decrease in cortical (Na++K+)ATPase (NKA) α1 subunit expression and enzyme activity and an increase in O-GlcNAcylation. RNAseq analysis of patients with DKD revealed an increase in expression of the glutamine-fructose aminotransferase (GFAT) gene, a rate-limiting step of hexosamine biosynthetic pathway, and a decrease in NKA expression. Incubation of LLC-PK1 cells with 10 µM thiamet G, an inhibitor of O-GlcNAcase, reduced the expression and activity of NKA and increased O-GlcNAcylation. Furthermore, 6-diazo-5-oxo-L-norleucine (DON), a GFAT inhibitor, or dapagliflozin, an SGLT2 inhibitor, avoided the inhibitory effect of HG on expression and activity of NKA associated with the decrease in O-GlcNAcylation. CONCLUSION: Our results show that the impairment of tubular sodium reabsorption, in the early stage of DM, is due to SGLT2-mediated HG influx in PTECs, increase in O-GlcNAcylation and reduction in NKA expression and activity.

Effect of different obturation techniques on sealer penetration into dentinal tubules after final irrigation with XP-Endo finisher file

The first objective of this research was to evaluate the effectiveness of XP-Endo Finisher on dentinal tubule penetration of irrigation solution using confocal laser scanning microscopy. The main purpose of this research was to compare the effect of cold lateral condensation, continuous wave obturation and core-carrier based techniques on sealer penetration. Sixty mandibular premolars were prepared and allocated into two experimental groups (n=30) as the final irrigation technique and obturation technique experiment. In the final irrigation technique experiment, final irrigation was performed with XP-Endo Finisher, passive ultrasonic irrigation (PUI) and conventional needle irrigation (CNI) (n=10). The roots in the obturation technique experiment were also assigned into 3 groups and obturated with cold lateral condensation, continuous-wave obturation and core-carrier techniques (n=10). The most effective activation method, which emerged as a result of the first part of this study, was used as the final irrigation method in the obturation technique experiment. Then, all roots were sectioned in 1-mm-thick slices at 3mm from the apex for scanning. In terms of depth and percentage of material penetration, CNI exhibited significantly the lowest values and no significant difference was found between others. Also, there was no significant difference among obturation methods. In conclusion, XP-Endo Finisher and PUI are more effective than CNI on irrigant penetration. Sealer penetration into dentinal tubules is independent of obturation techniques.

El objetivo principal de esta investigación fue evaluar la eficacia de XP- Endo Finisher en la penetración de la solución de irrigación en los túbulos dentinarios mediante microscopía de láser confocal. Se prepararon sesenta premolares mandibulares y se distribuyeron en dos grupos experimentales (n=30) según el tipo de método de evaluación utilizado. En el experimento de la técnica de irrigación final, la irrigación final se realizó con XP-Endo Finisher, irrigación ultrasónica pasiva (PUI) e irrigación con aguja convencional (CNI) (n=10). Las raíces en el experimento de la técnica de obturación también se asignaron en 3 grupos y se obturaron con técnicas de condensación lateral fría, obturación de onda continua y portador de núcleo (n=10). El método de activación más eficaz, que surgió como resultado de la primera parte de este estudio, se utilizó como método de irrigación final en el experimento de la técnica de obturación. Luego, todas las raíces se seccionaron en muestras de 1mm de espesor. En términos de profundidad y porcentaje de penetración del material, CNI exhibió significativamente los valores más bajos y no se encontraron diferencias significativas entre los demás. Además, no hubo diferencias significativas entre los métodos de obturación. En conclusión, XP-Endo Finisher y PUI son más efectivos que CNI en la penetración del irrigante. La penetración del sellador en los túbulos dentinarios es independiente de las técnicas de obturación.

Rapamycin treatment induces tubular proteinuria: role of megalin-mediated protein reabsorption.

Introduction: Rapamycin is an immunosuppressor that acts by inhibiting the serine/threonine kinase mechanistic target of rapamycin complex 1. Therapeutic use of rapamycin is limited by its adverse effects. Proteinuria is an important marker of kidney damage and a risk factor for kidney diseases progression and has been reported in patients and animal models treated with rapamycin. However, the mechanism underlying proteinuria induced by rapamycin is still an open matter. In this work, we investigated the effects of rapamycin on parameters of renal function and structure and on protein handling by proximal tubule epithelial cells (PTECs). Methods: Healthy BALB/c mice were treated with 1.5 mg/kg rapamycin by oral gavage for 1, 3, or 7 days. At the end of each treatment, the animals were kept in metabolic cages and renal function and structural parameters were analyzed. LLC-PK1 cell line was used as a model of PTECs to test specific effect of rapamycin. Results: Rapamycin treatment did not change parameters of glomerular structure and function. Conversely, there was a transient increase in 24-h proteinuria, urinary protein to creatinine ratio (UPCr), and albuminuria in the groups treated with rapamycin. In accordance with these findings, rapamycin treatment decreased albumin-fluorescein isothiocyanate uptake in the renal cortex. This effect was associated with reduced brush border expression and impaired subcellular distribution of megalin in PTECs. The effect of rapamycin seems to be specific for albumin endocytosis machinery because it did not modify renal sodium handling or (Na++K+)ATPase activity in BALB/c mice and in the LLC-PK1 cell line. A positive Pearson correlation was found between megalin expression and albumin uptake while an inverse correlation was shown between albumin uptake and UPCr or 24-h proteinuria. Despite its effect on albumin handling in PTECs, rapamycin treatment did not induce tubular injury measured by interstitial space and collagen deposition. Conclusion: These findings suggest that proteinuria induced by rapamycin could have a tubular rather than a glomerular origin. This effect involves a specific change in protein endocytosis machinery. Our results open new perspectives on understanding the undesired effect of proteinuria generated by rapamycin.

Localization of Diacylglycerol Kinase ζ in the Kidney of Adult Rats: Its Dominant Expression in Collecting Tubules and its Selective Lack in Proximal Tubules / Localización de Diacilglicerol Quinasa ζ en el Riñón de Ratas Adultas: su Expresión Dominante en Túbulos Colectores y su Carencia Selectiva en Túbulos Proximales

SUMMARY: Diacylglycerol kinase (DGK) exerts balancing the intracellular level between two-second messengers, diacylglycerol and phosphatidic acid, by its phosphorylation activity. DGK ζ is often localized in cell nuclei, suggesting its involvement in the regulation of intranuclear activities, including mitosis and apoptosis. The present immunohistochemical study of rat kidneys first revealed no detection levels of DGK ζ -immunoreactivity in nuclei of most proximal tubule epithelia in contrast to its distinct occurrence in cell nuclei of collecting and distal tubules with the former more dominant. This finding suggests that DGK ζ is a key factor regulating vulnerability to acute kidney injury in various renal tubules: its low expression represents the high vulnerability of proximal tubule cells, and its distinct expression does the resistance of collecting and distal tubule cells. In addition, this isozyme was more or less localized in nuclei of cells forming glomeruli as well as in endothelial nuclei of peritubular capillaries and other intrarenal blood vessels, and epithelial nuclei of glomerular capsules (Bowman's capsules) and renal calyces, including intrarenal interstitial cells.

La diacilglicerol quinasa (DGK) ejerce el equilibrio del nivel intracelular entre dos segundos mensajeros, diacilglicerol y ácido fosfatídico, por su actividad de fosforilación. La DGK ζ a menudo se localiza en los núcleos celulares, lo que sugiere su participación en la regulación de las actividades intranucleares, incluidas la mitosis y la apoptosis. El presente estudio inmunohistoquímico en riñones de rata no reveló niveles de detección de inmunorreactividad de DGK ζ en los núcleos de la mayoría de los epitelios de los túbulos proximales, en contraste a la detección en los núcleos celulares de los túbulos colectores y distales, siendo el primero más dominante. Este hallazgo sugiere que DGK ζ es un factor clave que regula la vulnerabilidad a la lesión renal aguda en varios túbulos renales: su baja expresión representa la alta vulnerabilidad de las células del túbulo proximal, y su expresión distinta hace a la resistencia de las células del túbulo colector y distal. Además, esta isoenzima estaba más o menos localizada en los núcleos de las células que forman los glomérulos, así como en los núcleos endoteliales de los capilares peritubulares y otros vasos sanguíneos intrarrenales, y en los núcleos epiteliales de las cápsulas glomerulares (cápsulas de Bowman) y los cálices renales, incluidas las células intersticiales intrarrenales.

The serine-threonine protein phosphatases that regulate the thiazide-sensitive NaCl cotransporter.

The activity of the Na+-Cl- cotransporter (NCC) in the distal convoluted tubule (DCT) is finely tuned by phosphorylation networks involving serine/threonine kinases and phosphatases. While much attention has been paid to the With-No-lysine (K) kinase (WNK)- STE20-related Proline Alanine rich Kinase (SPAK)/Oxidative Stress Responsive kinase 1 (OSR1) signaling pathway, there remain many unanswered questions regarding phosphatase-mediated modulation of NCC and its interactors. The phosphatases shown to regulate NCC's activity, directly or indirectly, are protein phosphatase 1 (PP1), protein phosphatase 2A (PP2A), calcineurin (CN), and protein phosphatase 4 (PP4). PP1 has been suggested to directly dephosphorylate WNK4, SPAK, and NCC. This phosphatase increases its abundance and activity when extracellular K+ is increased, which leads to distinct inhibitory mechanisms towards NCC. Inhibitor-1 (I1), oppositely, inhibits PP1 when phosphorylated by protein kinase A (PKA). CN inhibitors, like tacrolimus and cyclosporin A, increase NCC phosphorylation, giving an explanation to the Familial Hyperkalemic Hypertension-like syndrome that affects some patients treated with these drugs. CN inhibitors can prevent high K+-induced dephosphorylation of NCC. CN can also dephosphorylate and activate Kelch-like protein 3 (KLHL3), thus decreasing WNK abundance. PP2A and PP4 have been shown in in vitro models to regulate NCC or its upstream activators. However, no studies in native kidneys or tubules have been performed to test their physiological role in NCC regulation. This review focuses on these dephosphorylation mediators and the transduction mechanisms possibly involved in physiological states that require of the modulation of the dephosphorylation rate of NCC.

Physiology of a Forgotten Electrolyte-Magnesium Disorders.

Magnesium (Mg2+) is the second most common intracellular cation and the fourth most abundant element on earth. However, Mg2+ is a frequently overlooked electrolyte and often not measured in patients. While hypomagnesemia is common in 15% of the general population, hypermagnesemia is typically only found in preeclamptic women after Mg2+ therapy and in patients with ESRD. Mild to moderate hypomagnesemia has been associated with hypertension, metabolic syndrome, type 2 diabetes mellitus, CKD, and cancer. Nutritional Mg2+ intake and enteral Mg2+ absorption are important for Mg2+ homeostasis, but the kidneys are the key regulators of Mg2+ homeostasis by limiting urinary excretion to less than 4% while the gastrointestinal tract loses over 50% of the Mg2+ intake in the feces. Here, we review the physiological relevance of Mg2+, the current knowledge of Mg2+ absorption in the kidneys and the gut, the different causes of hypomagnesemia, and a diagnostic approach on how to assess Mg2+ status. We highlight the latest discoveries of monogenetic conditions causing hypomagnesemia, which have enhanced our understanding of tubular Mg2+ absorption. We will also discuss external and iatrogenic causes of hypomagnesemia and advances in the treatment of hypomagnesemia.

Prolonged Ca2+ release refractoriness and T-tubule disruption as determinants of increased propensity to cardiac alternans in the hypertensive heart disease.

AIM: Cardiac alternans is a dynamical phenomenon linked to the genesis of severe arrhythmias and sudden cardiac death. It has been proposed that alternans is caused by alterations in Ca2+ handling by the sarcoplasmic reticulum (SR), in both the SR Ca2+ uptake and release processes. The hypertrophic myocardium is particularly prone to alternans, but the precise mechanisms underlying its increased vulnerability are not known. METHODS: Mechanical alternans (intact hearts) and Ca2+ alternans (cardiac myocytes) were studied in spontaneously hypertensive rats (SHR) during the first year of age after the onset of hypertension and compared with age-matched normotensive rats. Subcellular Ca2+ alternans, T-tubule organization, SR Ca2+ uptake, and Ca2+ release refractoriness were measured. RESULTS: The increased susceptibility of SHR to high-frequency-induced mechanical and Ca2+ alternans appeared when the hypertrophy developed, associated with an adverse remodeling of the T-tubule network (6 mo). At the subcellular level, Ca2+ discordant alternans was also observed. From 6 mo of age, SHR myocytes showed a prolongation of Ca2+ release refractoriness without alterations in the capacity of SR Ca2+ removal, measured by the frequency-dependent acceleration of relaxation. Sensitizing SR Ca2+ release channels (RyR2) by a low dose of caffeine or by an increase in extracellular Ca2+ concentration, shortened refractoriness of SR Ca2+ release, and reduced alternans in SHR hearts. CONCLUSIONS: The tuning of SR Ca2+ release refractoriness is a crucial target to prevent cardiac alternans in a hypertrophic myocardium with an adverse T-tubule remodeling.

Inherited Fanconi syndrome.

BACKGROUND: Fanconi-Debré-de Toni syndrome (also known as Fanconi renotubular syndrome, or FRST) profoundly increased the understanding of the functions of the proximal convoluted tubule (PCT) and provided important insights into the pathophysiology of several kidney diseases and drug toxicities. DATA SOURCES: We searched Pubmed and Scopus databases to find relevant articles about FRST. This review article focuses on the physiology of the PCT, as well as on the physiopathology of FRST in children, its diagnosis, and treatment. RESULTS: FRST encompasses a wide variety of inherited and acquired PCT alterations that lead to impairment of PCT reabsorption. In children, FRST often presents as a secondary feature of systemic disorders that impair energy supply, such as Lowe's syndrome, Dent's disease, cystinosis, hereditary fructose intolerance, galactosemia, tyrosinemia, Alport syndrome, and Wilson's disease. Although rare, congenital causes of FRST greatly impact the morbidity and mortality of patients and impose diagnostic challenges. Furthermore, its treatment is diverse and considers the ability of the clinician to identify the correct etiology of the disease. CONCLUSION: The early diagnosis and treatment of pediatric patients with FRST improve the prognosis and the quality of life.

Gold nanoparticles reduce tubule-interstitial injury and proteinuria in a murine model of subclinical acute kidney injury.

Subclinical acute kidney injury (subAKI) is characterized by tubule-interstitial injury without significant changes in glomerular function. SubAKI is associated with the pathogenesis and progression of acute and chronic kidney diseases. Currently, therapeutic strategies to treat subAKI are limited. The use of gold nanoparticles (AuNPs) has shown promising benefits in different models of diseases. However, their possible effects on subAKI are still unknown. Here, we investigated the effects of AuNPs on a mouse model of subAKI. Animals with subAKI showed increased functional and histopathologic markers of tubular injury. There were no changes in glomerular function and structure. The animals with subAKI also presented an inflammatory profile demonstrated by activation of Th1 and Th17 cells in the renal cortex. This phenotype was associated with decreased megalin-mediated albumin endocytosis and expression of proximal tubular megalin. AuNP treatment prevented tubule-interstitial injury induced by subAKI. This effect was associated with a shift to an anti-inflammatory Th2 response. Furthermore, AuNP treatment preserved megalin-mediated albumin endocytosis in vivo and in vitro. AuNPs were not nephrotoxic in healthy mice. These results suggest that AuNPs have a protective effect in the tubule-interstitial injury observed in subAKI, highlighting a promising strategy as a future antiproteinuric treatment.

Inhibition of SGLT2 co-transporter by dapagliflozin ameliorates tubular proteinuria and tubule-interstitial injury at the early stage of diabetic kidney disease.

Diabetic kidney disease (DKD) is characterized by progressive impairment of kidney function. It has been postulated that tubule-interstitial injury, associated with tubular albuminuria, precedes glomerular damage in the early stage of DKD. Here, we wanted to determine if the development of tubule-interstitial injury at the early stage of DKD implies modulation of megalin-mediated protein reabsorption in proximal tubule epithelial cells (PTECs) by SGLT2-dependent high glucose influx. Rats with streptozotocin (STZ)-induced diabetes were treated or not with dapagliflozin (DAPA) for 8 weeks. Four experimental groups were generated: (1) CONT, control; (2) DAPA, rats treated with DAPA; (3) STZ, diabetic rats; (4) STZ + DAPA, diabetic rats treated with DAPA. No changes in glomerular structure and function were observed. The STZ group presented proteinuria and albuminuria associated with an increase in the fractional excretion of proteins. A positive correlation between glycemia and proteinuria was found. These phenomena were linked to a decrease in luminal and total megalin expression and, consequently, in albumin reabsorption in PTECs. We also observed tubule-interstitial injury characterized by an increase in urinary tubular injury biomarkers and changes in tubular histomorphometry parameters. In addition, inverse correlations were found between cortical albumin uptake and tubule-interstitial injury or glycemia. All these modifications were attenuated in the STZ + DAPA group. These results suggest that SGLT2-dependent high glucose influx into PTECs promotes a harmful effect on the PTECs, leading to the development of tubular albuminuria and tubule-interstitial injury preceding glomerular damage. These results expand current knowledge on the renoprotective effects of gliflozins.

In vitro dentin permeability and tubule occlusion of experimental in-office desensitizing materials.

OBJECTIVES: This study investigates the dentin permeability (by hydraulic conductance) and tubule occlusion (by confocal and scanning electron microscopies) of in-office desensitizing materials. MATERIALS AND METHODS: Bovine dentin blocks were immersed in EDTA to open dentinal tubules. Placebo varnish (PLA), fluoride varnish (FLU), NaF 5% + 5% nanoparticulate sodium trimetaphosphate varnish (TMP), universal adhesive system (SBU), S-PRG filler varnish (SPRG), Biosilicate (BIOS), and amelotin (AMTN) solution were the materials tested. After application, the specimens underwent an erosive-abrasive challenge. Dentin permeability was evaluated at T0 (initial), T1 (after treatment), and T2 (after challenge). Confocal and scanning electron microscopy (SEM) were used to evaluate, respectively, length and number of dentinal tubule occlusions and opened dentinal tubules, after challenge. Permeability and SEM data were analyzed by two-way repeated measures ANOVA and Tukey's tests. Confocal data were analyzed by one-way ANOVA, Tukey's test, and Kruskal-Wallis and Dunn's tests. Spearman and Pearson's correlation tests were also used. Significance level was set at 5%. RESULTS: At T1, the AMTN group showed the lowest permeability value, following the increasing order at T2: AMTN = SBU < BIOS = SPRG < TMP < FLU < PLA. The SBU group had the highest value of occluded dentinal tubule length. The AMTN group presented more occluded dentinal tubules compared to PLA and FLU. AMTN and SBU had the lowest values of opened dentin tubules. Results showed a negative correlation between the analyses. CONCLUSION: The SBU and AMTN solution were more effective in reducing dentin permeability by occluding dentin tubules. CLINICAL RELEVANCE: All materials reduced permeability after challenge, except fluoride varnish.