Sodium Reabsorption Research Articles

Cab39 is the major scaffolding protein for SPAK-mediated NCC activation in the mouse kidney

STE20/SPS1-related proline/alanine-rich kinase (SPAK) phosphorylates the sodium-chloride cotransporter (NCC) to stimulate sodium reabsorption in the Distal Convoluted Tubule (DCT) for K+ homeostasis and blood pressure. The scaffold proteins, Calcium-binding protein 39 (Cab39) and Cab39-like (Cab39l) activate SPAK in a Xenopus oocyte expression system. Still, it has not been determined whether Cab39 or Cab39-like are required for NCC phosphorylation in the DCT. Here, we developed DCT-specific Cab39 knockout (KO), global Cab39l-KO, and Cab39/Cab39l double knockout (DKO) mice to assess the role of the two adaptor proteins in the Kidney. The SPAK-NCC signaling axis was evaluated by Western Blot and immunofluorescence microscopy. Physiological consequences of altered signaling were evaluated with blood and urine electrolyte measurements. Cab39-KO mice had significantly lower total NCC (tNCC) and phosphorylated NCC (pNCC) abundance than wild-type mice. Phospho-activation of NCC with low K+ diet was also blunted in the Cab39 KO mice. By contrast, the Cab39l-KO mice did not show differences in total or phosphorylated NCC signals. However, when Cab39 was eliminated on the Cab39l KO background (DKO), pNCC abundance further decreased to almost undetectable levels. Remarkably, the DKO did not affect the phospho-activation of SPAK. Instead, SPAK failed to move to the apical membrane and accumulated into cytoplasmic puncta in the DKO mice. In summary, these data indicate that Cab39 and Cab39l act as major and minor regulators of SPAK-NCC signaling, providing an adaptor for translocating SPAK to the apical membrane for NCC interaction and phosphorylation. NIH grant R01DK093501 to Professor Eric Delpire and Professor Paul Welling, The Leducq Foundation grant 17CVD05 to Professor Eric Delpire and Professor Paul Welling, and a Crawford Long Innovation grant to Professor Eric Delpire. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Renal upregulation of NCC counteracts empagliflozin-mediated NHE3 inhibition in normotensive but not in hypertensive rats

Sodium-glucose cotransporter-2 inhibitors (SGLT2i) reduce blood pressure (BP) in hypertensive patients. However, the underlying molecular mechanisms remain largely unknown. Proximal tubule (PT) NHE3-mediated sodium reabsorption is inhibited by SGLT2i in normotensive rodents, yet no BP-lowering effect is observed under this scenario. This study examined the effect of empagliflozin (EMPA) on renal tubular sodium transport in normotensive and spontaneously hypertensive rats (SHRs). It also tested the hypothesis that EMPA-mediated PT NHE3 inhibition in normotensive rats is associated with upregulation of distal nephron apical sodium transporters. Administration of EMPA for 14 days reduced BP in 12-week-old SHRs but not in age-matched Wistar rats. PT NHE3 was inhibited by EMPA treatment in both Wistar and SHRs. EMPA increased NCC expression and phosphorylation levels in Wistar but not SHRs. SHRs exhibited higher cortical and medullary NKCC2 and β-ENaC subunit mRNA and higher medullary α-ENaC expression levels than Wistar rats, none of which were affected by EMPA. Another set of male Wistar rats was treated with EMPA, the NCC inhibitor hydrochlorothiazide (HCTZ), EMPA combined with HCTZ or vehicle for 14 days. In these rats, BP was reduced in response to EMPA and HCTZ combined but not by EMPA or HCTZ alone. Altogether, these data suggest that upregulation of NCC counteracts EMPA-mediated inhibition of PT NHE3 in male normotensive rats, thereby maintaining their baseline BP. Moreover, reducing NHE3 activity without further upregulation of the main apical sodium transporters beyond the PT may contribute to the BP-lowering effect of SGLT2i in experimental models and patients with hypertension. FAPESP 2016/22140-7 and 2021/14534-3. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

DCT Transcriptional and Structural Remodeling: Impacts on Magnesium Handling

Loss of activity of the NaCl Cotransporter (NCC) in Gitelman syndrome and with chronic thiazide treatment results in hypomagnesemia but the underlying mechanism remains unresolved. The prevailing hypothesis is that it results indirectly from distal convoluted tubule (DCT) atrophy lowering magnesium (Mg)-reabsorbing capacity by this segment. We tested the hypothesis that NCC inhibition directly disrupts a cellular mechanism related to Mg handling independent of DCT atrophy. We used the NCC-Cre+−/−- INTACT+/- mouse line to allow enrichment of DCT nuclei via Cre-dependent GFP expression in DCT nuclei. Eight- to 10-week-old male mice were given 50 mg/kg/day metolazone (MTZ) orally in food for 4 days; littermate controls receiving only vehicle. After nuclei isolation, GFP+ events (DCT nuclei) were sorted by fluorescence assisted nuclei sorting. Purified DCT nuclei were sequenced using 10X Chromium controller. Reads were then analyzed using a standard transcriptomic bioinformatics pipeline with Seurat. Tubule morphometrics using optical tissue clearing was performed on kidneys from animals receiving the same treatment. MTZ-treated mice had lower plasma Mg compared to controls recapitulating thiazide-induced hypomagnesemia. Our snRNAseq dataset containing 45,953 cells from 3 MTZ-treated and 3 control mice showed clear separation into early DCT (DCT1) and late DCT (DCT2) based on canonical segment markers. Gene expression analysis showed the DCT1 contained a magnesium cassette consisting of known magnesiotropic genes Trpm6, Trpm7, Egf, Umod, Prox1, Fxyd2, Cnnm2, and Slc41a3 so we focused subsequent analyses on DCT1. NCC inhibition caused DCT1 degeneration as indicated by lower mean DCT1 score of DCT1 cells and a greater proportion of DCT1 cells with low differentiation state in the MTZ group. Similarly, MTZ-treated samples had lower DCT1/DCT2 cell proportion in our snRNAseq dataset and morphometrics revelead significantly shorter DCT1 tubules implying that the degeneration process eventually leads to DCT1 atrophy. Using the aggregate expression of the magnesium cassette genes, we computationally defined a Mg score as a surrogate marker for Mg reabsorption capacity for each individual cells. The average Mg score was lower in the MTZ-treated group compared to the controls. Our data supports the long-standing hypothesis that hypomagnesemia is a secondary consequence of the loss of effective surface area for Mg reabsorption. Additionally, we uncovered that even at the single cell level, the Mg handling capacity of the cell decreases as a result of NCC inhibition implying that a disruption in sodium reabsorption disrupts expression of the Mg reabsorption machinery. NIH DK51496, NIH DK054983, NIDDK DK132066, VA 1I01BX002228, LeDucq Foundation, DOST-PCHRD-ASTHRDP. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Deletion of dipeptidyl peptidase 4 attenuates angiotensin II-induced blood pressure rise and enhances NHE3 phosphorylation at serine 552 in the kidneys of male and female mice

Dipeptidyl peptidase 4 (DPP4) physically associates with the Na+/H+ exchanger isoform3 (NHE3), and DPP4 inhibitors reduce NHE3-dependent sodium reabsorption in the renal proximal tubule. Angiotensin II (Ang II) is a key mediator of sodium and water retention by the kidneys, partly through the activation of proximal tubule NHE3. Recent studies from our group reveled that Ang II activates DPP4 by, both in vivo and in vitro, and that inhibition of several canonical and non-canonical pathways can suppress this activation. However, the impact of this interaction on renal sodium handling and blood pressure remains unclear. This study aimed to test the hypothesis that DPP4 deletion mitigates the blood pressure elevation induced by Ang II in male and female mice, at least partly due to the downregulation of NHE3 in the renal proximal tubule. Male and female mice with global DPP4 deletion or wild-type controls were acutely administered either a pressor dose of Ang II (1000 ng/kg/minute) or saline. Blood pressure was measured before and one hour after the administration of Ang II or saline by tail-cuff plethysmography. Kidneys were subsequently collected for protein homogenate preparation. Increased DPP4 activity was observed in response to acute Ang II stimulation in both male and female wild-type mice, with female mice exhibiting higher basal DPP4 activity. As expected, DPP4 knockout mice exhibited minimal DPP4 activity. Baseline blood pressure did not differ significantly between male wild-type and DPP4 knockout mice or between females. In line with our hypothesis, both male and female DPP4 knockout mice displayed a reduced increase in blood pressure in response to acute Ang II administration compared to their wild-type counterparts. Furthermore, the phosphorylation of NHE3 at serine 552 (pS552-NHE3), a surrogate marker of NHE3 inhibition, was higher in wild-type females than males. Interestingly, pS552-NHE3 was fivefold higher in male DPP4 knockout mice and threefold higher in female DPP4 knockout mice compared to their wild-type counterparts. Additionally, the increase in pS552-NHE3 one hour after Ang II administration was higher in males (1208 ± 119 vs. 544 ± 54 %, P < 0.01) and females (385 ± 18 vs. 271 ± 27%, P < 0.01) DPP4 knockout mice compared to wild-type animals. Moreover, ERK, a well-known effector of the AT1R signaling cascade, was phosphorylated in a similar manner as NHE3 in response to Ang II in males but not in females. In conclusion, our data demonstrate that the absence of DPP4 reduces the rise in blood pressure induced by acute Ang II stimulation, possibly through Ang II/AT1R signaling pathways influencing phosphorylation of downstream effectors such as NHE3. Furthermore, we observe significant sex differences in Ang II effects on DPP4 activity, and AT1R signaling cascades. FAPESP 2021/14524-3 NIDDKD - K08DK115886. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

P2X7 receptor knockout does not alter renal function or prevent angiotensin II-induced kidney injury in F344 rats

P2X7 receptors (P2X7) mediate immune and endothelial cell responses to extracellular ATP. Acute pharmacological blockade increases renal blood flow (RBF) and glomerular filtration rate (GFR), suggesting that P2X7 receptor activation promotes tonic vasoconstriction. P2X7 expression is increased in kidney disease and blockade/knockout is renoprotective. Here, we generated a novel P2X7 global knockout (KO) rat on the F344 background, hypothesising enhanced RBF and protection from chronic angiotensin II (ANG II)-induced injury. CRISPR/Cas9 technology introduced an early stop codon into exon 2 of P2rx7. In male and female KO and WT rats, renal P2X7 expression was measured by RTqPCR (n=4-5/group) and western blotting (n=3/group). Bone marrow-derived macrophages (BMDM) were used to assess P2X7 function by measuring interleukin (IL)-1β release (ELISA) after stimulation with lipopolysaccharide (LPS) (1μg/mL, 4h) and ATP (3mM, 1h) (n=5-6/group). In vivo kidney function was assessed in anesthetized rats (thiopental, 50mg/kg, i.p.) at baseline and following serial arterial ligation to induce acute pressure natriuresis (n=9-10/group). Arterial blood pressure (BP) was measured directly, and urine was collected via tube cystotomy. RBF was measured using a Transonic Doppler flow probe placed around the main renal artery, and cortical and medullary flux by laser Doppler needle probes. GFR was determined by FITC-inulin clearance. Urinary sodium was measured by sodium-selective electrode analysis. In a separate experiment, BP was recorded over five consecutive days in conscious male KO and WT rats via implanted radiotelemetry devices (n=7-8/group). Finally, male KO and WT rats (n=9-10/group) were infused with ANG II (250ng/kg/min, s.c.) for 6 weeks. At end, one renal artery was isolated and vascular reactivity to phenylephrine, acetylcholine and sodium nitroprusside determined by wire myography. Bladder urine was collected to measure albumin/creatinine ratio (n=4-7/group), and kidneys were harvested for histological analyses (n=6/group). Data were analysed with unpaired t-test (two groups compared) or two-way ANOVA (two variables), with p<0.05 statistically significant. P2rx7 mutation was confirmed by genome sequencing (Sanger). P2rx7 mRNA abundance was partially decreased in kidney from male (-54%) and female (-25%) KO vs WT. P2X7 protein was detected in kidneys from WT but not from KO rats. In BMDM from WT rats, LPS+ATP stimulation induced IL-1β release; this response was markedly suppressed in KO BMDM (males: 2577±140 vs 413±175pg/mL, p<0.0001; females: 1889±394 vs 265±121pg/mL, p<0.0001). In vivo BP, renal haemodynamics and tubular sodium handling were not different between genotypes for either sex (P>0.05). Radiotelemetry confirmed no difference in BP between KO and WT rats. Following chronic ANG II infusion, KO and WT rats had no renal artery dysfunction but showed similar increases in albuminuria (P=0.3587), renal perivascular fibrosis (Picrosirius Red, P=0.5393), cortical interstitium CD68-positive area (p=0.6546) and tubular casts (Periodic acid-Schiff, P=0.8803), compared with naïve controls. Contrary to our hypothesis, global genetic deletion of P2X7 did not affect renal hemodynamics and we found no significant role for P2X7 in the modulation of tubular sodium reabsorption. Our data do not support a major role of P2X7 in causing renal vascular and tubular injury. This work was supported by Diabetes UK grant 17/0005685, The British Heart Foundation(FS/15/60/31510; RE/18/5/34216), the Medical Research Council (MR/S01053X), and the University of Edinburgh College of Medicine & Veterinary Medicine PhD Studentship. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Proximal Tubule Response to Low Potassium Is Mediated by mTOR/AKT Activation via Kir4.2

Background: The renal epithelium is highly sensitive to changes in blood potassium (K+) levels. We have a detailed understanding of distal K+-sensitive signaling pathways, yet proximal mechanisms are less well-defined. Results: Mice lacking the basolateral proximal tubule inwardly rectifying K+ channel, Kir4.2, (Kir4.2−/−) demonstrated normal blood and urine electrolytes at baseline. Upon removal of K+ from their diet, Kir4.2−/− animals decompensated as evidenced by increased urinary K+ excretion and development of a proximal renal tubular acidosis compared to control animals (Kir4.2+/+). Potassium wasting in Kir4.2−/− mice was not proximal in origin, but was dependent upon increased ENaC activity along the connecting segment. This was demonstrated by the correction of K+ wasting in knockouts treated with the ENaC inhibitor, amiloride. Using lithium clearance studies, we further demonstrated increased distal sodium delivery in Kir4.2−/− animals due to reduced proximal tubule sodium reabsorption. Optical clearing and three-dimensional confocal imaging reveal Kir4.2−/− mice failed to undergo proximal tubule hypertrophy when fed a low K+ diet, while the distal convoluted tubule response was exaggerated in knockouts compared to control animals. A phosphoproteomics mass spectrometry analysis identified increased mTOR/AKT signaling as mediating the proximal dietary response to K+ depletion in control animals, and changes to mTOR/AKT signaling was blunted in Kir4.2 knockouts. Lastly, we demonstrated in isolated renal tubules that AKT phosphorylation in response to low K+ depended upon mTORC2 activation by secondary reductions in intracellular Cl−. Conclusions: In this work we identify the basolateral inwardly rectifying K+ channel, Kir4.2, as a mediator of the proximal tubule response to K+ deficiency. Kir4.2 knockout mice increase their distal nephron transport burden to maintain electrolyte homeostasis in the face of deficient proximal tubule cell function. Data identify a conserved proximal role for cell Cl− which, as it does along the distal convoluted tubule, responds to extracellular K+ changes to activate intracellular kinase signaling. Along the proximal tubule, mTOR/AKT signaling is essential for the cell response to low K+. Proximal and distal nephron cell Cl− responses work in concert to preserve K+ homeostasis. These studies were supported by NIH grants DP5-OD033412 (AST), DK51265, DK95785, DK62794, DK7569, P30DK114809 (RCH, MZZ), and the Vanderbilt Center for Kidney Disease and Vanderbilt Diabetes Research and Training Center (DK020593) pilot and feasibility grant (JSD). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

SGLT-2 Inhibitors: Focus on Dapagliflozin.

Dapagliflozin (trade name FARXIGA) is a sodium-glucose cotransporter-2 (SGLT-2) inhibitor that has transcended its initial antidiabetic application to demonstrate benefits in cardiac and renal diseases. It was first approved by the food and department administration for type 2 diabetes in 2014. Since then, it has gained food and department administration approval for chronic kidney disease in 2021, heart failure with reduced ejection fraction in 2020, and heart failure with preserved ejection fraction in 2023. Thus, dapagliflozin plays a pivotal role in improving patient outcomes. By competitive binding to renal SGLT-2 cotransporters, dapagliflozin effectively prevents glucose and sodium reabsorption, leading to glucosuria. Its pharmacokinetic profile involves minimal cytochrome P450-induced metabolism, rapid absorption with an 18-hour duration of action, and stable effects. Clinical trials have revealed dapagliflozin's efficacy in glycemic control without the risk of hypoglycemia, making it an advantageous choice for patients insufficiently managed on other antidiabetic drugs. Comparative analysis with other SGLT-2 inhibitors suggests dapagliflozin's potential superiority in preventing heart failure. Compared to empagliflozin, it has more extended effects, contributing to stable sodium diuresis, reduced blood pressure fluctuations, and potentially lower cardiovascular disease risks. However, it leads to less urinary glucose excretion compared with canagliflozin. Dapagliflozin has specific contraindications, such as type 1 diabetes and end-stage chronic kidney disease. Adverse effects include an increased risk of genital infections, urinary tract infections, and Fournier's gangrene. A nuanced understanding of dapagliflozin's benefits and limitations is imperative for informed clinical decision-making in the management of diabetes and its complications.

CCNA2 and KIF23 are molecular targets for the prognosis of adenoid cystic carcinoma.

Adenoid cystic carcinoma (ACC) is a tumor type derived from glands. However, relationship between CCNA2 and KIF23, and adenoid cystic carcinoma remains unclear. GSE36820 and GSE88804 profiles for ACC were obtained from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were identified, and Weighted Gene Co-expression Network Analysis (WGCNA) was conducted. Subsequently, the construction and analysis of protein-protein interaction (PPI) network, functional enrichment analysis, and Gene Set Enrichment Analysis (GSEA) were performed. A gene expression heat map was generated to visually depict the expression difference of core genes between adenoid cystic carcinoma and normal samples. TargetScan was employed to identify miRNAs that regulated central DEGs. Western blotting (WB) was conducted for cell verification. A total of 885 DEGs were identified. GO and KEGG analyses revealed their main enrichment in responses to chemical stimuli, cell proliferation, tissue development, and regulation of cell proliferation. The GO and KEGG results indicated significant enrichment in aldosterone-regulated sodium reabsorption, the cell cycle, and the PPAR signaling pathway. Notably, core genes (CCNA2 and KIF23) were found to be highly expressed in Adenoid Cystic Carcinoma samples and expressed at low levels in normal samples. WB validated the overexpression of CCNA2 and KIF23 in the Adenoid Cystic Carcinoma group, confirming the protein-level changes associated with cell cycle, metastasis, apoptosis, and inflammatory factors in Adenoid Cystic Carcinoma groups with gene overexpression and knockout. CCNA2 and KIF23 exhibit high expression levels in ACC, suggesting their potential role as molecular targets for this malignancy.

Renal upregulation of NCC counteracts empagliflozin-mediated NHE3 inhibition in normotensive but not in hypertensive male rat.

Sodium-glucose cotransporter-2 inhibitors (SGLT2i) reduce blood pressure (BP) in patients with hypertension, yet the precise molecular mechanisms remain elusive. SGLT2i inhibits proximal tubule (PT) NHE3-mediated sodium reabsorption in normotensive rodents, yet no hypotensive effect is observed under this scenario. This study examined the effect of empagliflozin (EMPA) on renal tubular sodium transport in normotensive and spontaneously hypertensive rats (SHRs). It also tested the hypothesis that EMPA-mediated PT NHE3 inhibition in normotensive rats is associated with upregulation of distal nephron apical sodium transporters. EMPA administration for 14 days reduced BP in 12-wk-old SHRs but not in age-matched Wistar rats. PT NHE3 activity was inhibited by EMPA treatment in both Wistar and SHRs. In Wistar rats, EMPA increased NCC activity, mRNA expression, protein abundance, and phosphorylation levels, but not in SHRs. SHRs showed higher NKCC2 activity and an abundance of cleaved ENaC α and γ subunits compared with Wistar rats, none of which were affected by EMPA. Another set of male Wistar rats was treated with EMPA, the NCC inhibitor hydrochlorothiazide (HCTZ), and EMPA combined with HCTZ or vehicle for 14 days. In these rats, BP reduction was observed only with combined EMPA and HCTZ treatment, not with either drug alone. These findings suggest that NCC upregulation counteracts EMPA-mediated inhibition of PT NHE3 in male normotensive rats, maintaining their baseline BP. Moreover, the reduction of NHE3 activity without further upregulation of major apical sodium transporters beyond the PT may contribute to the BP-lowering effect of SGLT2i in experimental models and patients with hypertension.NEW & NOTEWORTHY This study suggests that reduced NHE3-mediated sodium reabsorption in the renal proximal tubule may account, at least in part, for the BP-lowering effect of SGLT2 inhibitors in the setting of hypertension. It also demonstrates that chronic treatment with SGLT2 inhibitors upregulates NCC activity, phosphorylation, and expression in the distal tubule of normotensive but not hypertensive rats. SGLT2 inhibitor-mediated upregulation of NCC seems crucial to counteract proximal tubule natriuresis in subjects with normal BP.

Primary aldosteronism and cardiovascular risk. Review

Primary aldosteronism (PA), a significant and curable cause of secondary hypertension, occurs in 5—10% of hypertensive patients, with prevalence dependent on the severity of hypertension. The main etiologies of PA include bilateral idiopathic hypertrophy (BIH) and aldosterone‑producing adenoma (APA), while less common causes include unilateral hyperplasia, familial hyperaldosteronism (FH) types I—IV, aldosterone‑producing carcinoma, and ectopic aldosterone synthesis. This condition, characterized by excessive secretion of aldosterone, leads to increased reabsorption of sodium and water along with potassium loss, culminating in the distinct clinical signs of elevated aldosterone, suppressed renin, and hypertension. It should be noted that hypokalemia is present in only 28% of patients with PA and is not the main indicator. The association of PA with an increased risk profile for cardiovascular disease, regardless of blood pressure level, is notable. Patients with PA show an increased rate of cardiovascular events compared to patients with essential hypertension, adjusted for age, sex, and blood pressure level. Despite its prevalence, PA often remains undiagnosed, highlighting the need for enhanced screening protocols. The diagnostic process for PA involves a three‑pronged assessment: the aldosterone/renin ratio (ARR) as the initial screening tool, followed by confirmatory and subtype tests. A positive ARR requires confirmatory testing to rule out false positives. Examination to detect PA should be carried out in patients with arterial hypertension: moderate (> 160—179/100—109 mm Hg) or severe (> 180/110 mm Hg); resistant to treatment; with idiopathic or diuretic‑induced hypokalemia; with an accidentally diagnosed tumor of the adrenal glands; if first‑generation relatives are diagnosed with PA, or family history indicates early onset of arterial hypertension, or cerebrovascular disorders at a young age (< 40 years); with accompanying obstructive sleep apnea.

Effects of furosemide, acetazolamide and amiloride on renal cortical and medullary tissue oxygenation in non-anaesthetised healthy sheep.

It has been proposed that diuretics can improve renal tissue oxygenation through inhibition of tubular sodium reabsorption and reduced metabolic demand. However, the impact of clinically used diuretic drugs on the renal cortical and medullary microcirculation is unclear. Therefore, we examined the effects of three commonly used diuretics, at clinically relevant doses, on renal cortical and medullary perfusion and oxygenation in non-anaesthetised healthy sheep. Merino ewes received acetazolamide (250mg; n=9), furosemide (20mg; n=10) or amiloride (10mg; n=7) intravenously. Systemic and renal haemodynamics, renal cortical and medullary tissue perfusion and , and renal function were then monitored for up to 8h post-treatment. The peak diuretic response occurred 2h (99.4±14.8mL/h) after acetazolamide, at which stage cortical and medullary tissue perfusion and were not significantly different from their baseline levels. The peak diuretic response to furosemide occurred at 1h (196.5±12.3mL/h) post-treatment but there were no significant changes in cortical and medullary tissue oxygenation during this period. However, cortical tissue fell from 40.1±3.8mmHg at baseline to 17.2±4.4mmHg at 3h and to 20.5±5.3mmHg at 6h after furosemide administration. Amiloride did not produce a diuretic response and was not associated with significant changes in cortical or medullary tissue oxygenation. In conclusion, clinically relevant doses of diuretic agents did not improve regional renal tissue oxygenation in healthy animals during the 8h experimentation period. On the contrary, rebound renal cortical hypoxia may develop after dissipation of furosemide-induced diuresis.

Сравнительная характеристика эффективности профилактики прогрессирования ХПН с использованием терапии секретомом эмбриональных клеток и трансплантации неонатальных тканей.

Introduction. Literature data and our own research indicate that therapy with immature cell secretion products (secretome) has a pronounced nephroprotective effect both in acute kidney injury and in chronic renal failure (CRF). Considering that the source of the complex of signaling molecules stimulating reparative processes in organs are low-differentiated cells of functionally and anatomically immature organs in a state of deveopment, the question arises to what extent tissue transplantation of these organs reproduces the effect of therapy with a secretome of stem cells in relation to the progression of CRF. Material and methods. The experiments were carried out on 40 outbred male rats weighing 260-290 g, in which CRF was modeled by resection of 4/5 functionally active renal parenchyma. In the 1st series (control), no therapeutic actions were performed. In the 2nd series, after modeling CRF, a course of therapy with Cellex, the active component of which is the secretome of pig embryonic brain cells, was carried out in the form of 2 10-day courses with a 10-day break between them. In the 3rd and 4th series, immediately after CRF modeling, kidney or testicle tissue obtained from newborn baby rats (1-2 days after birth) was injected under the capsule of the resected kidney as a source of immature cells. Tissues of different organs were used to assess the severity of the tissue-specific effect of therapy. Results. 7 days after the modeling of CRF in all series, a deterioration of more than 2 times of all functional parameters was revealed. After 1 month, in the control and in the 2nd and 3rd series, a tendency to an increase in GFR was revealed, which did not reach statistical significance, whereas in the 4th series, the increase in GFR turned out to be statistically significant. After 2 months in the control series, there was a repeated decrease in the GFR index, whereas in all experimental series, GFR continued to increase or remained at subnormal values. The activity of tubular reabsorption of sodium and calcium after a significant decrease after 7 days to 1 month in the control series increased slightly (but unreliably), and after 2 months they again decreased to values 2 times lower than normal. In all experimental series, after 1 and 2 months, the reabsorption of these electrolytes was at values close to normal. The improvement was especially pronounced in groups 2 and 4. After 7 days, the activity of intracellular enzymes (aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH)) in the blood increased in all series with a gradual decrease in hyperfermentemia after 2 months, more pronounced in group 4, as well as in all experimental groups with respect to LDH. Histological examination of the condition of neonatal transplants revealed the destruction of transplanted kidney tissue and a viable testicular graft. Conclusion. Transplantation of neonatal organ tissue under a kidney capsule to rats with CRF has a comparable nephroprotective effect with therapy with the secretome of embryonic cells (Cellex drug). A more pronounced improvement in functional parameters during testicular tissue transplantation is explained by the preservation of the viability of the graft.

The Human Gut and Dietary Salt: The Bacteroides/Prevotella Ratio as a Potential Marker of Sodium Intake and Beyond.

The gut microbiota is a dynamic ecosystem that plays a pivotal role in maintaining host health. The perturbation of these microbes has been linked to several health conditions. Hence, they have emerged as promising targets for understanding and promoting good health. Despite the growing body of research on the role of sodium in health, its effects on the human gut microbiome remain under-explored. Here, using nutrition and metagenomics methods, we investigate the influence of dietary sodium intake and alterations of the human gut microbiota. We found that a high-sodium diet (HSD) altered the gut microbiota composition with a significant reduction in Bacteroides and inverse increase in Prevotella compared to a low-sodium diet (LSD). However, there is no clear distinction in the Firmicutes/Bacteroidetes (F/B) ratio between the two diet types. Metabolic pathway reconstruction revealed the presence of sodium reabsorption genes in the HSD, but not LSD. Since it is currently difficult in microbiome studies to confidently associate the F/B ratio with what is considered healthy (e.g., low sodium) or unhealthy (e.g., high sodium), we suggest that the use of a genus-based ratio such as the Bacteroides/Prevotella (B/P) ratio may be more beneficial for the application of microbiome studies in health.

Nephrotic Syndrome: From Pathophysiology to Novel Therapeutic Approaches.

Nephrotic edema stands out as one of the most common complications of nephrotic syndrome. The effective management of hypervolemia is paramount in addressing this condition. Initially, "the underfill hypothesis" suggested that proteinuria and hypoalbuminemia led to fluid extravasation into the interstitial space, causing the intravascular hypovolemia and activation of neurohormonal compensatory mechanisms, which increased the retention of salt and water. Consequently, the recommended management involved diuretics and human-albumin infusion. However, recent findings from human and animal studies have unveiled a kidney-limited sodium-reabsorption mechanism, attributed to the presence of various serine proteases in the tubular lumen-activating ENaC channels, thereby causing sodium reabsorption. There is currently no standardized guideline for diuretic therapy. In clinical practice, loop diuretics continue to be the preferred initial choice. It is noteworthy that patients often exhibit diuretic resistance due to various factors such as high-sodium diets, poor drug compliance, changes in pharmacokinetics or pharmacodynamics, kidney dysfunction, decreased renal flow, nephron remodeling and proteasuria. Considering these challenges, combining diuretics may be a rational approach to overcoming diuretic resistance. Despite the limited data available on diuretic treatment in nephrotic syndrome complicated by hypervolemia, ENaC blockers emerge as a potential add-on treatment for nephrotic edema.

Kinin-kallikrein system: New perspectives in heart failure.

Heart failure (HF) is a pervasive clinical challenge characterized by compromised cardiac function and reduced quality of life. The kinin-kallikrein system (KSS), a multifaceted peptide cascade, has garnered substantial attention due to its potential role in HF. Through activation of B1 and/or B2 receptors and downstream signaling, kinins modulate various physiological processes, including inflammation, coagulation, pain, blood pressure control, and vascular permeability. Notably, aberrations in KKS components have been linked to HF risk. The elevation of vasodilatory bradykinin (BK) due to kallikrein activity reduces preload and afterload, while concurrently fostering sodium reabsorption inhibition. However, kallikrein's conversion of prorenin to renin leads to angiotensinsII upregulation, resulting in vasoconstriction and fluid retention, alongside increased immune cell activity that fuels inflammation and cardiac remodeling. Importantly, prolonged KKS activation resulting from volume overload and tissue stretch contributes to cardiac collagen loss. The conventional renin-angiotensin-aldosterone system (RAAS) inhibitors used in HF management may inadvertently intensify KKS activity, exacerbating collagen depletion and cardiac remodeling. It is crucial to balance the KKS's role in acute cardiac damage, which may temporarily enhance function and metabolic parameters against its detrimental long-term effects. Thus, KKS blockade emerges as a promising strategy to impede HF progression. By attenuating the link between immune system function and tissue damage, KKS inhibition can potentially reduce cardiac remodeling and alleviate HF symptoms. However, the nuanced roles of BK in various acute conditions necessitate further investigation into the sustained benefits of kallikrein inhibitors in patients with chronic HF.

Antihypertensive Effect of Sodium-Glucose Cotransporter 2 Inhibitors and Glucagon-like Peptide 1 Receptor Agonists

An increasing body of evidence shows that new antidiabetic drugs—particularly sodium-glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 (GLP-1) receptor agonists—have a beneficial effect on cardiovascular outcome. The majority of these studies have been performed in patients with heart failure and the results have shown first positive effect on blood pressure (BP) reduction. These effects are more pronounced with SGLT2 inhibitors than with GLP-1 receptor agonists. However, the reasons and mechanisms of action inducing BP reduction are still not sufficiently clear. Proposed mechanisms of SGLT2 inhibitors involve the natriuretic effect, modification of the renin-angiotensin-aldosterone system, and/or the reduction in the sympathetic nervous system. GLP-1 receptor agonists have several mechanisms that are related to glycemic, weight, and BP control. Current data show that SGLT2 inhibitors have a stronger antihypertensive effect than GLP-1 receptor agonists, which is mainly related to their renal effect. Briefly, SGLT2 inhibitors increase the response to diuretics and decrease the meal-related antinatriuretic pressure by lowering post-prandial hyperglycemia and hyperinsulinemia and prevent proximal sodium reabsorption. SGLT2 inhibitors can be used as second-line therapy in patients with diabetes mellitus or heart disease and concomitant hypertension. This article aims to summarize current knowledge regarding the antihypertensive effect of SGLT2 inhibitors and GLP-1 receptor agonists.

The Role of Sodium-Glucose Cotransporter-2 Inhibitors in the Treatment of Polycystic Ovary Syndrome: A Review.

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in reproductive-age women impacting their reproductive, mental, and metabolic health. Insulin resistance is a major driver of the pathophysiology of PCOS. There are several challenges with the management of this complex disorder including insufficient treatment options. Over the past 88 years, multiple hormonal and non-hormonal medications have been tried to treat the various components of this syndrome and there is no FDA (Food and Drug Administration)-approved medication specifically for PCOS yet. Sodium-glucose cotransporter-2 (SGLT-2) inhibitors have a unique mechanism of inhibiting the coupled reabsorption of sodium and glucose in renal proximal convoluted tubules. This review aims to examine the efficacy and side-effect profile of SGLT-2 inhibitors in patients with PCOS. In a limited number of studies, SGLT-2 inhibitors appear to be effective in improving menstrual frequency, reducing body weight and total fat mass, lowering total testosterone and DHEAS levels, and improving some glycemic indices in women with PCOS. SGLT2 inhibitors are generally well tolerated. With future research, it is possible that SGLT-2 inhibitors could become a key therapeutic option for PCOS.

Thyroid Heart Disease Was Successfully Treated With Acetazolamide

Introduction: Loop diuretics are currently the first-choice treatment for acutely decompensated HF therapy and for maintaining euvolemia, but the addition of other diuretic agents, such as the carbonic anhydrase inhibitor acetazolamide might be effective for patients with refractory heart failure. Case: A 35-year-old woman referred from a private hospital came to the emergency unit at Sanjiwani Regional Hospital with complaints of shortness of breath and palpitations, and both legs were swollen. The patient has risk factors for hyperthyroidism and a family history of coronary heart disease. On physical examination, he was conscious of compost mentis with blood pressure 85/50 mmHg, heart rate 79 times/minute, respiratory rate 45 times/minute with saturation 93%, rales (+), oedema in both legs, cold acral; laboratory examination showed TsHs 0.22 uIU/ml, FT4 26.29 pmol/L. Discussion: Acetazolamide is a carbonic anhydrase inhibitor that reduces proximal tubular sodium reabsorption and may improve diuretic efficiency when added to loop diuretics, thereby potentially facilitating decongestion, was not associated with an increased incidence of adverse events, and associated with a shorter duration of hospital stay. Conclusion: Acetazolamide is a carbonic anhydrase inhibitor that may improve diuretic efficiency when added to loop diuretics.

Deciphering molecular basis of pesticide-induced recurrent pregnancy loss: insights from transcriptomics analysis

Recent studies have revealed a notable connection between pesticide exposure and Recurrent Pregnancy Loss (RPL), yet the precise molecular underpinning of this toxicity remains elusive. Through the alignment of Differentially Expressed Genes (DEGs) of healthy and RPL patients with the target genes of 9 pesticide components, we identified a set of 12 genes responsible for RPL etiology. Interestingly, biological process showed that besides RPL, those 12 genes also associated with preeclampsia and cardiovascular disease. Enrichment analysis showed the engagement of these genes associated with essential roles in the molecular transport of small molecules, as well as the aldosterone-regulated sodium reabsorption, endocrine and other factor-regulated calcium reabsorption, mineral absorption, ion homeostasis, and ion transport by P-type ATPases. Notably, the crosstalk targets between pesticide components played crucial roles in influencing RPL results, suggesting a role in attenuating pesticide agents that contribute to RPL. It is important to note that non-significant concentration of the pesticide components observed in both control and RPL samples should not prematurely undermine the potential for pesticides to induce RPL in humans. This study emphasizes the complexity of pesticide induced RPL and highlights avenues for further research and precautionary measures.

Primary Role of the Kidney in Pathogenesis of Hypertension.

Previous transplantation studies and the concept of 'nephron underdosing' support the idea that the kidney plays a crucial role in the development of essential hypertension. This suggests that there are genetic factors in the kidney that can either elevate or decrease blood pressure. The kidney normally maintains arterial pressure within a narrow range by employing the mechanism of pressure-natriuresis. Hypertension is induced when the pressure-natriuresis mechanism fails due to both subtle and overt kidney abnormalities. The inheritance of hypertension is believed to be polygenic, and essential hypertension may result from a combination of genetic variants that code for renal tubular sodium transporters or proteins involved in regulatory pathways. The renin-angiotensin-aldosterone system (RAAS) and sympathetic nervous system (SNS) are the major regulators of renal sodium reabsorption. Hyperactivity of either the RAAS or SNS leads to a rightward shift in the pressure-natriuresis curve. In other words, hypertension is induced when the activity of RAAS and SNS is not suppressed despite increased salt intake. Sodium overload, caused by increased intake and/or reduced renal excretion, not only leads to an expansion of plasma volume but also to an increase in systemic vascular resistance. Endothelial dysfunction is caused by an increased intracellular Na+ concentration, which inhibits endothelial nitric oxide (NO) synthase and reduces NO production. The stiffness of vascular smooth muscle cells is increased by the accumulation of intracellular Na+ and subsequent elevation of cytoplasmic Ca++ concentration. In contrast to the hemodynamic effects of osmotically active Na+, osmotically inactive Na+ stimulates immune cells and produces proinflammatory cytokines, which contribute to hypertension. When this occurs in the gut, the microbiota may become imbalanced, leading to intestinal inflammation and systemic hypertension. In conclusion, the primary cause of hypertension is sodium overload resulting from kidney dysregulation.