Control of sodium and potassium homeostasis by renal distal convoluted tubules.

Distal convoluted tubules (DCT), which contain the Na-Cl cotransporter (NCC) inhibited by thiazide diuretics, undergo complex modulation to preserve Na+ and K+ homeostasis. The lysine kinases 1 and 4 (WNK1 and WNK4), identified as hyperactive in the hereditary disease pseudohypoaldosteronism type 2, are responsible for activation of NCC and consequent hypokalemia and hypertension. WNK4, highly expressed in DCT, activates the SPAK/OSR1 kinases, which phosphorylate NCC and other regulatory proteins and transporters in the distal nephron.

Highlighting COVID-19: What the imaging exams show about the disease.

Coronavirus disease 2019 (COVID-19), a global emergency, is caused by severe acute respiratory syndrome coronavirus 2. The gold standard for its diagnosis is the reverse transcription polymerase chain reaction, but considering the high number of infected people, the low availability of this diagnostic tool in some contexts, and the limitations of the test, other tools that aid in the identification of the disease are necessary. In this scenario, imaging exams such as chest X-ray (CXR) and computed tomography (CT) have played important roles.

The Angiotensin II Type 1 Receptor-Associated Protein Attenuates Angiotensin II-Mediated Inhibition of the Renal Outer Medullary Potassium Channel in Collecting Duct Cells.

Adjustments in renal K excretion constitute a central mechanism for K homeostasis. The renal outer medullary potassium (ROMK) channel accounts for the major K secretory route in collecting ducts during basal conditions. Activation of the angiotensin II (Ang II) type 1 receptor (AT1R) by Ang II is known to inhibit ROMK activity under the setting of K dietary restriction, underscoring the role of the AT1R in K conservation.

Signaling pathways involved in the rapid biphasic effect of aldosterone on Na/H exchanger in rat proximal tubule cells.

The receptors and signaling pathways for nongenomic effects of aldosterone (Aldo) on the proximal Na/H exchanger are still unknown; therefore, the aim of this study was to investigate the mineralocorticoid receptor (MR) and/or glucocorticoid receptor (GR) participation in rapid Aldo effects on NHE1 (basolateral Na/H exchanger isoform) and cytosolic calcium concentration ([Ca]). In addition, phospholipase C (PLC), protein kinase C (PKC), and mitogen-activated protein kinase kinase (MEK) involvement in signaling pathways of such effects was evaluated, using immortalized proximal tubule cells of rat (IRPTC) as an experimental model. MR and GR expression was investigated using reverse transcription polymerase chain reaction and immunoblotting.

Atorvastatin attenuation of ABCB1 expression is mediated by microRNA miR-491-3p in Caco-2 cells.

Aim: Atorvastatin, a HMG-CoA reductase inhibitor, used in the treatment of hypercholesterolemia, has been previously shown to regulate ABCB1 expression in vivo and in vitro. We hypothesized that the statin could regulate gene expression of ABCB1 transporter via microRNAs.

Methods: Expression of microRNAs and ABCB1 mRNA was examined in atorvastatin-treated and control cells using real-time PCR.

Proximal tubule NHE3 activity is inhibited by beta-arrestin-biased angiotensin II type 1 receptor signaling.

Physiological concentrations of angiotensin II (ANG II) upregulate the activity of Na(+)/H(+) exchanger isoform 3 (NHE3) in the renal proximal tubule through activation of the ANG II type I (AT1) receptor/G protein-coupled signaling. This effect is key for maintenance of extracellular fluid volume homeostasis and blood pressure. Recent findings have shown that selective activation of the beta-arrestin-biased AT1 receptor signaling pathway induces diuresis and natriuresis independent of G protein-mediated signaling.

Parathyroid hormone inhibition of Na(+)/H(+) exchanger 3 transcription: Intracellular signaling pathways and transcription factor expression.

The main transport mechanism of reabsorption of sodium bicarbonate and fluid in the renal proximal tubules involves Na(+)/H(+) exchanger 3 (NHE3), which is acutely and chronically downregulated by parathyroid hormone (PTH). Although PTH is known to exert an inhibitory effect on NHE3 expression and transcription, the molecular mechanisms involved remain unclear. Here, we demonstrated that, in opossum kidney proximal tubule (OKP) cells, PTH-induced inhibition of Nhe3 gene promoter occurs even in the core promoter that controls expression of the reporter gene.

Identification of nuclear factor-κB sites in the Slc2a4 gene promoter.

Glucose transporter GLUT4 protein, codified by Slc2a4 gene plays a key role in glycemic homeostasis. Insulin resistance, as in obesity, has been associated to inflammatory state, in which decreased GLUT4 is a feature. Inflammatory NF-κB transcriptional factor has been proposed as a repressor of Slc2a4; although, the binding site(s) in Slc2a4 promoter and the direct repressor effect have never been reported yet.

Fructose acutely stimulates NHE3 activity in kidney proximal tubule.

Background/aims: Fructose causes a sodium-sensitive hypertension and acutely reduces the urinary Na+ excretion, suggesting that it may regulate the activity of renal tubular sodium transporters. NHE3 is highly expressed in proximal tubule (PT), along with proteins that mediate fructose transport and metabolism. The present work was outlined to investigate whether fructose modulates proximal NHE3 activity and to elucidate the molecular mechanisms underlying this modulation.

Neuromuscular efficiency of the vastus medialis obliquus and postural balance in professional soccer athletes after anterior cruciate ligament reconstruction.

The purpose of this study was to evaluate the neuromuscular efficiency of the vastus medialis obliquus and postural balance in high-performance soccer athletes after anterior cruciate ligament (ACL) reconstruction, compared to the uninvolved leg. A cross-sectional study was conducted with 22 male professional soccer players after ACL reconstruction (4-12 months postoperatively). The athletes were submitted to functional rehabilitation with an accelerated protocol on the soccer team.

Distinct mechanisms underlie adaptation of proximal tubule Na+/H+ exchanger isoform 3 in response to chronic metabolic and respiratory acidosis.

The Na(+/)H(+) exchanger isoform 3 (NHE3) is essential for HCO(3)(-) reabsorption in renal proximal tubules. The expression and function of NHE3 must adapt to acid-base conditions. The goal of this study was to elucidate the mechanisms responsible for higher proton secretion in proximal tubules during acidosis and to evaluate whether there are differences between metabolic and respiratory acidosis with regard to NHE3 modulation and, if so, to identify the relevant parameters that may trigger these distinct adaptive responses.

Transcriptional regulation of the Na⁺/H⁺ exchanger NHE3 by chronic exposure to angiotensin II in renal epithelial cells.

Angiotensin II (Ang II) exerts an acute bimodal effect on proximal tubule NHE3: while low doses stimulate the exchanger, high doses inhibit it. In the present study, we have investigated the chronic effects of Ang II on NHE3 expression and transcriptional regulation. Treatment of a tubular epithelial cell line, OKP, with Ang II 10(-11)M significantly increased NHE protein expression and mRNA levels, without evidence of bimodal effect.

Essential regulatory elements for NHE3 gene transcription in renal proximal tubule cells.

The objectives of the present study were to identify the cis-elements of the promoter absolutely required for the efficient rat NHE3 gene transcription and to locate positive and negative regulatory elements in the 5'-flanking sequence (5'FS), which might modulate the gene expression in proximal tubules, and to compare this result to those reported for intestinal cell lines. We analyzed the promoter activity of different 5'FS segments of the rat NHE3 gene, in the OKP renal proximal tubule cell line by measuring the activity of the reporter gene luciferase. Because the segment spanning the first 157 bp of 5'FS was the most active it was studied in more detail by sequential deletions, point mutations, and gel shift assays.

[Laparoscopic cholecystectomy training on plastic mannequins].

Objective: The objective of this project is to offer for any Medical Education Institution an effective method of learning and developing the skills on this new surgery procedure that is necessary to improve the ability as consequence of technological innovations.

Methods: Simple and low cost materials were used for doing and carrying on the laparoscopic cholecystectomy on plastic mannequins as if it were done in vivo.

Results: The results were shown through illustrated photographs from the surgery procedures.

Mechanisms underlying the long-term regulation of NHE3 by parathyroid hormone.

The activity of the Na(+)/H(+) exchanger NHE3 is regulated by a number of factors including parathyroid hormone (PTH). In the current study, we used a renal epithelial cell line, the opossum kidney (OKP) cell, to elucidate the mechanisms underlying the long-term effects of PTH on NHE3 transport activity and expression. We observed that NHE3 activity was reduced 6 h after addition of PTH, and this reduction persisted almost unaltered after 24 h.

Dipeptidyl peptidase IV inhibition downregulates Na+ - H+ exchanger NHE3 in rat renal proximal tubule.

In the microvillar microdomain of the kidney brush border, sodium hydrogen exchanger type 3 (NHE3) exists in physical complexes with the serine protease dipeptidyl peptidase IV (DPPIV). The purpose of this study was to explore the functional relationship between NHE3 and DPPIV in the intact proximal tubule in vivo. To this end, male Wistar rats were treated with an injection of the reversible DPPIV inhibitor Lys [Z(NO2)]-pyrrolidide (I40; 60 mg.

NHE1, NHE2, and NHE4 contribute to regulation of cell pH in T84 colon cancer cells.

The isoforms of the Na+/H+ exchanger present in T84 human colon cells were identified by functional and molecular methods. Cell pH was measured by fluorescence microscopy using the probe BCECF. Based on the pH recovery after an ammonium pulse and determination of buffering capacity of these cells, the rate of H+ extrusion (JH) was 3.

Long-term effects of intrauterine malnutrition on vascular function in female offspring: implications of oxidative stress.

Maternal malnutrition is known to impair fetal growth and predispose to the development of hypertension and type 2 diabetes. Recently, studies have demonstrated that intrauterine malnutrition is followed later in male offspring by oxidative stress characterized by increased superoxide generation due to activation of NADPH oxidase and reduced antioxidant defenses. However, few studies have investigated the mechanisms involved in endothelial dysfunction in female offspring.

Increased NHE1 expression is associated with serum deprivation-induced differentiation in immortalized rat proximal tubule cells.

We studied the proton secretion mechanisms involved with pHi regulation in immortalized rat proximal tubule cells (IRPTC), a SV40-immortalized cell line derived from rat proximal tubule, and characterized the effects of serum deprivation on them. Using pHi measurements with the fluorescent probe BCECF, we demonstrated that the IRPTC express both Na+/H+ exchanger and H+-ATPase, but only NHE1 is modulated by serum deprivation. In these cells, 24 h of serum starvation increased pHi from 7.

Clonally rearranged T-cell receptor beta chain genes in HTLV-I carriers with abnormal, non-flower-like, lymphocytes.

Background: The diagnosis of Adult T-cell leukemia/lymphoma ATLL subtypes in human T-lymphotropic virus type I (HTLV-I) carriers based in morphology and immunophenotype of lymphocytes can be challenger. We propose that polymerase chain reaction (PCR) amplification of the rearranged TCR gene in HTLV-I healthy carriers would be a convenient method for establishing the nature of the circulating T lymphocytes in asymptomatic HTLV-I carriers, presenting only mild and inconclusive signals of deviation from normality.

Methods: Using PCR, we analyzed the genetic recombination pattern of the T-cell beta-chain receptor gene (TCR-beta) in order to identify clonal expansion of peripheral blood T lymphocytes in 17 HTLV-I-positive healthy carriers and in nine normal HTLV-I-negative blood donors.

Identification of clonally rearranged T-cell receptor beta chain genes in HTLV-I carriers as a potential instrument for early detection of neoplasia.

We analyzed the genetic recombination pattern of the T-cell receptor beta-chain gene (TCR-beta) in order to identify clonal expansion of T-lymphocytes in 17 human T-lymphotropic virus type I (HTLV-I)-positive healthy carriers, 7 of them with abnormal features in the peripheral blood lymphocytes. Monoclonal or oligoclonal expansion of T-cells was detected in 5 of 7 HTLV-I-positive patients with abnormal lymphocytes and unconfirmed diagnosis by using PCR amplification of segments of TCR-beta gene, in a set of reactions that target 102 different variable (V) segments, covering all members of the 24 V families available in the gene bank, including the more recently identified segments of the Vbeta-5 and Vbeta-8 family and the two diversity beta segments. Southern blots, the gold standard method to detect T-lymphocyte clonality, were negative for all of these 7 patients, what highlights the low sensitivity of this method that requires a large amount of very high quality DNA.

Real-time PCR quantitation of glucocorticoid receptor alpha isoform.

Background: The expression of glucocorticoid-receptor (GR) seems to be a key mechanism in the regulation of glucocorticoid (GC) sensitivity and is potentially involved in cases of GC resistance or hypersensitivity. The aim of this study is to describe a method for quantitation of GR alpha isoform (GRalpha) expression using real-time PCR (qrt-PCR) with analytical capabilities to monitor patients, offering standard-curve reproducibility as well as intra- and inter-assay precision.

Results: Standard-curves were constructed by employing standardized Jurkat cell culture procedures, both for GRalpha and BCR (breakpoint cluster region), as a normalizing gene.

Identification of genes regulated by oleic acid in Jurkat cells by suppressive subtractive hybridization analysis.

In this study, the effect of oleic acid (50 microM) on gene expression of Jurkat cells (human T lymphocytes cell line) was examined using the suppressive subtractive hybridization approach. This technique allowed us to identify genes with higher or lower expression after cell treatment with oleic acid as compared to untreated cells. Oleic acid upregulated the expression of the translation elongation factor alpha 1 and ATP synthase 8 and downregulated gp96 (human tumor rejection antigen gp96), heat-shock protein 60 and subtilisin-like protein 4.

Mechanisms of action of melanin-concentrating hormone in the teleost fish erythrophoroma cell line (GEM-81).

Melanin-concentrating hormone (MCH) evokes an increase of GEM-81 cell proliferation. This action of 10(-6)M MCH was inhibited in the presence of the following blockers: U-73122 (phospholipase C), Ro-31-8220 (PKC) or KN-93 (Ca(2+)/calmodulin-dependent kinase). The more selective PKC inhibitors, HBDDE and Go-6983, which block, respectively, PKC alpha/gamma isoform and beta1 isoform, were used.

Down-regulation of Na+ transporters and AQP2 is responsible for acyclovir-induced polyuria and hypophosphatemia.

Background: Acyclovir (ACY) is a useful therapeutic agent for the systemic treatment of herpes virus infection. An increase in urinary phosphate excretion and polyuria has been described. The objective of this study was to analyze the exact mechanism of the urinary-concentrating dysfunction and the increase in phosphaturia associated with ACY.