Compared with males, females have lower BP before age 60, blunted hypertensive response to angiotensin II, and a leftward shift in pressure natriuresis. This study tested the concept that this female advantage associates with a distinct sexual dimorphic pattern of transporters along the nephron. We applied quantitative immunoblotting to generate profiles of transporters, channels, claudins, and selected regulators in both sexes and assessed the physiologic consequences of the differences. In rats, females excreted a saline load more rapidly than males did. Compared with the proximal tubule of males, the proximal tubule of females had greater phosphorylation of Na/H exchanger isoform 3 (NHE3), distribution of NHE3 at the base of the microvilli, and less abundant expression of Na/Pi cotransporter 2, claudin-2, and aquaporin 1. These changes associated with less bicarbonate reabsorption and higher lithium clearance in females. The distal nephrons of females had a higher abundance of total and phosphorylated Na/Cl cotransporter (NCC), claudin-7, and cleaved forms of epithelial Na channel (ENaC) and subunits, which associated with a lower baseline plasma K concentration. A K-rich meal increased the urinary K concentration and decreased the level of renal phosphorylated NCC in females. Notably, we observed similar abundance profiles in female versus male C57BL/6 mice. These results define sexual dimorphic phenotypes along the nephron and suggest that lower proximal reabsorption in female rats expedites excretion of a saline load and enhances NCC and ENaC abundance and activation, which may facilitate K secretion and set plasma K at a lower level.

The acute direct action of angiotensin-(1-7) [ANG-(1-7)] on bicarbonate reabsorption (JHCO(3)(-)) was evaluated by stationary microperfusions on in vivo middle proximal tubules in rats using H ion-sensitive microelectrodes. The control JHCO(3)(-) is 2.82 ± 0.078 nmol·cm(-2)·s(-1) (50). ANG-(1-7) (10(-12) or 10(-9) M) in luminally perfused tubules decreases JHCO(3)(-) (36 or 60%, respectively), but ANG-(1-7) (10(-6) M) increases it (80%). A779 increases JHCO(3)(-) (30%) and prevents both the inhibitory and the stimulatory effects of ANG-(1-7) on it. S3226 decreases JHCO(3)(-) (45%) and changes the stimulatory effect of ANG-(1-7) to an inhibitory effect (30%) but does not affect the inhibitory effect of ANG-(1-7). Our results indicate that in the basal condition endogenous ANG-(1-7) inhibits JHCO(3)(-) and that the biphasic dose-dependent effect of ANG-(1-7) on JHCO(3)(-) is mediated by the Mas receptors via the Na(+)/H(+) exchanger 3 (NHE3). The control value of intracellular Ca(2+) concentration ([Ca(2+)](i)), as monitored using fura-2 AM, is 101 ± 2 nM (6), and ANG-(1-7) (10(-12), 10(-9), or 10(-6)M) transiently (3 min) increases it (by 151, 102, or 52%, respectively). A779 increases the [Ca(2+)](i) (25%) but impairs the stimulatory effect of all doses of ANG-(1-7) on it. The use of BAPTA or thapsigargin suggests a correlation between the ANG-(1-7) dose-dependent effects on [Ca(2+)](i) and JHCO(3)(-). Therefore, the interaction of the opposing dose-dependent effects of ANG II and ANG-(1-7) on [Ca(2+)](i) and JHCO(3)(-) may represent an physiological regulatory mechanism of extracellular volume and/or pH changes. However, whether [Ca(2+)](i) modification is an important direct mechanism for NHE3 activation by these peptides or is a side effect of other signaling pathways will require additional studies.

Binding of angiotensin II (ANG II) to the AT receptor (ATR) in the proximal tubule stimulates Na/H exchanger isoform 3 (NHE3) activity through multiple signaling pathways. However, the effects of ANG II/ATR-induced inihibitory G protein (G) activation and subsequent decrease in cAMP accumulation on NHE3 regulation are not well established. We therefore tested the hypothesis that ANG II reduces cAMP/PKA-mediated phosphorylation of NHE3 on serine 552 and, in doing so, stimulates NHE3 activity. Under basal conditions, ANG II stimulated NHE3 activity but did not affect PKA-mediated NHE3 phosphorylation at serine 552 in opossum kidney (OKP) cells. However, in the presence of the cAMP-elevating agent forskolin (FSK), ANG II blocked FSK-induced NHE3 inhibition, reduced intracellular cAMP concentrations, lowered PKA activity, and prevented the FSK-mediated increase in NHE3 serine 552 phosphorylation. All effects of ANG II were blocked by pretreating OKP cells with the ATR antagonist losartan, highlighting the contribution of the ATR/G pathway in ANG II-mediated NHE3 upregulation under cAMP-elevating conditions. Accordingly, G inhibition by pertussis toxin treatment decreased NHE3 activity both in vitro and in vivo and, more importantly, prevented the stimulatory effect of ANG II on NHE3 activity in rat proximal tubules. Collectively, our results suggest that ANG II counteracts the effects of cAMP/PKA on NHE3 phosphorylation and inhibition by activating the ATR/G pathway. Moreover, these findings support the notion that NHE3 dephosphorylation at serine 552 may represent a key event in the regulation of renal proximal tubule sodium handling by ANG II in the presence of natriuretic hormones that promote cAMP accumulation and transporter phosphorylation.

The lack of effective pharmacological treatments for acute kidney injury (AKI) remains a significant public health problem. Given the involvement of apoptosis and regulated necrosis in the initiation and progression of AKI, the inhibition of cell death may contribute to AKI prevention/recovery. Curcuminoids are a family of plant polyphenols that exhibit attractive biological properties that make them potentially suitable for AKI treatment. Now, in cultured tubular cells, we demonstrated that a crosslinked self-assembled star-shaped polyglutamate (PGA) conjugate of bisdemethoxycurcumin (St-PGA-CL-BDMC) inhibits apoptosis and necroptosis induced by Tweak/TNFα/IFNγ alone or concomitant to caspase inhibition. St-PGA-CL-BDMC also reduced NF-κB activation and subsequent gene transcription. In vivo, St-PGA-CL-BDMC prevented renal cell loss and preserved renal function in mice with folic acid-induced AKI. Mechanistically, St-PGA-CL-BDMC inhibited AKI-induced apoptosis and expression of ferroptosis markers and also decreased the kidney expression of genes involved in tubular damage and inflammation, while preserving the kidney expression of the protective factor, Klotho. Thus, due to renal accumulation and attractive pharmacological properties, the application of PGAbased therapeutics may improve nephroprotective properties of current AKI treatments. Acute kidney injury (AKI) involves a sudden and generally transient loss of glomerular filtration leading to the retention of damaging nitrogenous byproducts normally excreted in the urine. Independently of its etiology, AKI usually implies extensive renal parenchymal injury, which, in the case of unsuccessful repair, favors the progression of AKI to chronic kidney disease (CKD). The mortality of AKI may be as high as 50%, and currently, there exist no specific therapies to attenuate AKI or accelerate recovery beyond dialysis 1. Thus, there is an unmet clinical need for novel AKI treatments. During the initial stages of AKI, proximal renal tubular cell death triggers a cascade of damaging events, including inflammation, that amplifies kidney injury 2,3. Thus, the control and execution of apoptosis and several kinds of regulated necrosis depend on environmental conditions as well as on the recruitment of intracellular cell death pathways. Distinct forms of cell death are amenable to pharmacological modulation. Strategies to specifically inhibit caspases, the final executioners of apoptosis, decrease apoptosis, inflammation, and improve renal function in experimental ischemia/reperfusion or septic AKI 4,5. However, the inhibition of overall caspase activity failed to improve nephrotoxic AKI 6. In this regard, caspase activation is involved in cellular events beyond cell death regulation, including, among others, cell cycle and the regulation of proliferation 7,8. Strategies that interfere with initial or intermediate regulators of caspase activity, like protein kinases, survival factors, cytokine death receptors, oxidative stress factors, apoptosome factors, and tumor-suppresso...

The acute effects of angiotensin-1-7 [ANG-(1-7)] on the reabsorptive bicarbonate flow (J[Formula: see text]) were evaluated using stationary microperfusion in vivo in the proximal tubules of spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar-Kyoto (WKY) rats, using a microelectrode sensitive to H In WKY rats, the control J[Formula: see text] was 2.40 ± 0.10 nmol·cm·s ( = 120); losartan (10 M) or A779 (10 M, a specific Mas antagonist), alone or in combination with losartan, decreased the J[Formula: see text] ANG-(1-7) had biphasic effects on J[Formula: see text]: at 10 M, it inhibited, and at 10, it stimulated the flow. S3226 [10 M, a specific Na-H exchanger 3 (NHE3) antagonist] decreased J[Formula: see text] and changed the stimulatory effect of ANG-(1-7) to an inhibitory one but did not alter the inhibitory action of ANG-(1-7). In SHR, the control J[Formula: see text] was 2.04 ± 0.13 nmol·cm·s ( = 56), and A779 and/or losartan reduced the flow. ANG-(1-7) at 10 M increased J[Formula: see text], and ANG-(1-7) at 10 M reduced it. The effects of A779, losartan, and S3226 on the J[Formula: see text] were similar to those found in WKY rats, which indicated that in SHR, the ANG-(1-7) action on the NHE3 was via Mas and ANG II type 1. The cytosolic calcium in the WKY or SHR rats was ~100 nM and was increased by ANG-(1-7) at 10 or 10 M. In hypertensive animals, a high plasma level of ANG-(1-7) inhibited NHE3 in the proximal tubule, which mitigated the hypertension caused by the high plasma level of ANG II.

BackgroundA growing body of evidence suggests an interplay between extracellular volume and glucose homeostasis. NHE3 is the main pathway for Na reabsorption in the proximal tubule (PT). The sodium glucose cotransporter SGLT2 reabsorbs most of the glucose filtered by the kidneys and colocalizes with NHE3 in the apical membrane of PT. Thus, we tested the hypothesis that SGLT2 and NHE3 functionally interact. Given that SGLT2 inhibitors confer blood‐pressure lowering effects in T2DM patients, we also tested the hypothesis that the antihypertensive effects of SGLT2 inhibitors may be associated with PT NHE3 inhibition.MethodsThe acute and long‐term effects of the SGLT2 inhibitor empagliflozin on PT NHE3 activity were determined by in vivo stationary microperfusion in fourteen‐week‐old male Wistar rats and SHR‐treated rats. Additionally, twelve‐week‐old SHRs were treated with empagliflozin (10 mg/kg/day) or vehicle (control) for two weeks. Tail‐cuff blood pressure and renal function were measured before (baseline) and after treatment (post‐treatment). NHE3 expression and phosphorylation levels were evaluated by immunoblotting.ResultsEmpagliflozin acutely inhibited PT NHE3 activity in both Wistar (1.73 ± 0.07 vs. 2.55 ± 0.14 nmol/cm2.s, P < 0.001) and SHR (0.82 ± 0.07 vs. 1.21 ± 0.10 nmol/cm2.s, P < 0.01). Blood pressure (BP) of empagliflozin‐treated SHR was lower than baseline levels (176 ± 4 vs. 194 ± 4 mm Hg, P < 0.01) whereas no change in BP was observed in vehicle‐treated SHR (194 ± 6 vs. 192 ± 5 mm Hg). Compared to baseline, empagliflozin‐treatment enhanced cumulative urinary flow, calcium, sodium and glucose excretion whereas in vehicle‐treated SHR these parameters remained unchanged. Lower BP in empagliflozin‐treated SHR was associated with lower PT NHE3 activity (0.67 ± 0.10 vs. 1.18 ± 0.10 nmol/cm2.s, P < 0.001). No differences were observed on renal cortical NHE3 protein expression or NHE3 phosphorylation levels between the two groups of rats.ConclusionThese results suggest that NHE3 and SGLT2 functionally interact in the PT. Inhibition of NHE3 by SGLT2 inhibitors may underlie, at least in part, the antihypertensive effect of empagliflozin.Support or Funding InformationFAPESPThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The type I interferon (TI-IFN) pathway regulates innate immunity, inflammation, and apoptosis during infection. However, the contribution of the TI-IFN pathway or upstream signaling pathways to tubular injury in kidney disease is poorly understood. Upon observing evidence of activation of upstream regulators of the TI-IFN pathway in a transcriptomics analysis of murine kidney tubulointerstitial injury, we have now addressed the impact of the TI-IFN and upstream signaling pathways on kidney tubulointerstitial injury. In cultured tubular cells and kidney tissue, IFNα/β binding to IFNAR activated the TI-IFN pathway and recruited antiviral interferon-stimulated genes (ISG) and NF-κB-associated proinflammatory responses. TWEAK and lipopolysaccharide (LPS) signaled through TBK1/IKKε and IRF3 to activate both ISGs and NF-κB. In addition, TWEAK recruited TLR4 to stimulate TBK1/IKKε-dependent ISG and inflammatory responses. Dual pharmacological inhibition of TBK1/IKKε with amlexanox decreased TWEAK- or LPS-induced ISG and cytokine responses, as well as cell death induced by a complex inflammatory milieu that included TWEAK. TBK1 or IRF3 siRNA prevented the TWEAK-induced ISG and inflammatory gene expression while IKKε siRNA did not. In vivo, kidney IFNAR and IFNβ were increased in murine LPS and folic acid nephrotoxicity while IFNAR was increased in human kidney biopsies with tubulointerstitial damage. Inhibition of TBK1/IKKε with amlexanox or IFNAR neutralization decreased TI-IFN pathway activation and protected from kidney injury induced by folic acid or LPS. In conclusion, TI-IFNs, TWEAK, and LPS engage interrelated proinflammatory and antiviral responses in tubular cells. Moreover, inhibition of TBK1/IKKε with amlexanox, and IFNAR targeting, may protect from tubulointerstitial kidney injury.

* Autor para correspondência: viniciuscooper@usp.br RESUMO O ensino de fisiologia endócrina faz parte do currículo dos estudantes da área de Ciências Biomédicas. Contudo, em função da necessidade de um conjunto de conhecimentos bem fundamentados de Biologia Celular, Molecular e Bioquímica, há dificuldade na assimilação desse tópico, principalmente por alunos dos primeiros dois anos de graduação, o que cria a necessidade do uso de diferentes estratégias de ensino-aprendizagem para a apropriação desses conhecimentos. Quando empregado de forma coerente com a proposta pedagógica, o vídeo em sala de aula pode ser uma ferramenta útil para a superação dessa dificuldade. Com esse intuito nos propusemos a utilizar essa estratégia junto aos alunos do primeiro semestre de graduação da Escola de Educação Física e Esporte da Universidade de São Paulo, como uma atividade em grupo em sala de aula, a fim de motivá-los a desenvolver uma leitura crítica da mídia em relação ao conteúdo de Fisiologia Endócrina, mais especificamente de fisiologia das glândulas adrenais e do metabolismo do cálcio e do fósforo. Com a introdução dos vídeos em sala de aula, tornaram-se notórios o maior interesse e o envolvimento dos alunos na realização das atividades propostas, possibilitando: (a) melhor aproveitamento do conteúdo previamente trabalhado em sala de aula, o que certamente facilitou o aprendizado; e (b) o estabelecimento de correlações entre fatos do cotidiano e a liberação e ação de hormônios naquele contexto determinado.Palavras-chave: Vídeo; Ensino de Fisiologia Endócrina; Educação; Graduação; Contextualização. ABSTRACTThe endocrine physiology teaching is part of the curriculum of the students of the Biomedical Sciences area. However, the need of a set of well-founded knowledge of Cell and Molecular Biology, as well as Biochemistry subjects, turns this topic very difficult to be understandable, mainly for the students of the first semesters. This creates the need of using different teaching and learning strategies for the appropriation of these knowledges. When applied in a coherent way in conjunction with the pedagogical proposal, the use of videos in the classrooms could be a useful tool to help to overcome this difficulty. In this context, we have used this strategy as a group activity in the classroom, with undergraduate students of the first semester of the Faculty of Physical Education and Sport of the Universidade de São Paulo. We aimed to lead them to develop a critical evaluation of the media in relation to Endocrine Physiology content, specifically the physiology of the adrenal glands and the calcium and phosphorus metabolism. With the introduction of videos in the classroom, it became notorious the great interest and involvement of the students in carrying out the proposed activities. This allowed: (a) a better comprehension of the content previously taught in the classroom, which certainly facilitated the learning process and (b) the ability to make correlations between routine events and the release of hormones and their a...