Collecting Duct Pro(Renin) Receptor Contributes to Unilateral Ureteral Obstruction-Induced Kidney Injury via Activation of the Intrarenal RAS.

BACKGROUND: Although the concept of the intrarenal renin-angiotensin system (RAS) in renal disease is well-described in the literature, the precise pathogenic role and mechanism of this local system have not been directly assessed in the absence of confounding influence from the systemic RAS. The present study used novel mouse models of collecting duct (CD)-specific deletion of (pro)renin receptor (PRR) or renin together with pharmacological inhibition of soluble PRR production to unravel the precise contribution of the intrarenal RAS to renal injury induced by unilateral ureteral obstruction. METHODS: We examined the impact of CD-specific deletion of PRR, CD-specific deletion of renin, and S1P (site-1 protease) inhibitor PF429242 treatment on renal fibrosis and inflammation and the indices of the intrarenal RAS in a mouse model of unilateral ureteral obstruction. RESULTS: After 3 days of unilateral ureteral obstruction, the indices of the intrarenal RAS including the renal medullary renin content, activity and mRNA expression, and Ang (angiotensin) II content in obstructed kidneys of floxed mice were all increased. That effect was reversed with CD-specific deletion of PRR, CD-specific deletion of renin, and PF429242 treatment, accompanied by consistent improvement in renal fibrosis and inflammation. On the other hand, renal cortical renin levels were unaffected by unilateral ureteral obstruction, irrespective of the genotype. Similar results were obtained via pharmacological inhibition of S1P, the key protease for the generation of soluble PRR. CONCLUSIONS: Our results reveal that PRR-dependent/soluble PRR-dependent activation of CD renin represents a key determinant of the intrarenal RAS and, thus, obstruction-induced renal inflammation and fibrosis.

Measurement and multiplexing of ultra-low duty cycle Nyquist pulse sequences.

In this paper, we propose a novel, to the best of our knowledge, method to our knowledge for generating and accurately measuring Nyquist pulse sequences with an ultra-low duty cycle of only 0.037, which breaks the limitations caused by the noise and bandwidth of the optical sampling oscilloscope (OSO) by using a narrow-bandwidth real-time oscilloscope (OSC) and an electrical spectrum analyzer (ESA). By this method, it is found that the bias point drift of the dual parallel Mach-Zehnder modulator (DPMZM) is the main cause of the distortion of the waveform. In addition, we increase the repetition rate of Nyquist pulse sequences by a factor of 16 by multiplexing the unmodulated Nyquist pulse sequences.

Soluble (Pro)Renin Receptor in Hypertension.

The (pro)renin receptor (PRR) was originally cloned as a specific single-transmembrane receptor for prorenin and renin and has now emerged as a multifunctional protein implicated in a wide variety of developmental and physiopathological processes. Activation of PRR in the kidney causes Na+ and water retention, contributing to elevation of blood pressure in response to various hypertensive stimuli. Part of the renal action of PRR depends on activation of intrarenal renin-angiotensin system. In recent years, accumulating evidence suggests that the prohypertensive action of renal PRR was largely mediated by production of the 28-kDa soluble (pro)renin receptor through protease-mediated cleavage of the extracellular domain of PRR. The generation of multiple isoforms of PRR due to the protease-mediated cleavage partially explains diversified actions of PRR. The current review will summarize recent advances in understanding the roles of sPPR in animal models of hypertension.

Mutagenesis of the cleavage site of (pro)renin receptor abrogates aldosterone-salt-induced hypertension and renal injury in mice.

Soluble (pro)renin receptor (sPRR), the extracellular domain of (pro)renin receptor (PRR), is primarily generated by site-1 protease and furin. It has been reported that sPRR functions as an important regulator of intrarenal renin contributing to angiotensin II (ANG II)-induced hypertension. Relatively, less is known for the function of sPRR in ANG II-independent hypertension such as mineralocorticoid excess. In the present study, we used a novel mouse model with mutagenesis of the cleavage site in PRR (termed as PRRR279V/L282V or mutant) to examine the phenotype during aldosterone (Aldo)-salt treatment. The hypertensive response of mutant mice to Aldo-salt treatment was blunted in parallel with the attenuated response of plasma volume expansion and renal medullary α-epithelial Na+ channel expression. Moreover, Aldo-salt-induced hypertrophy in the heart and kidney as well as proteinuria were improved, accompanied by blunted polydipsia and polyuria. Together, these results represent strong evidence favoring endogenous sPRR as a mediator of Aldo-salt-induced hypertension and renal injury.NEW & NOTEWORTHY We used a novel mouse model with mutagenesis of the cleavage site of PRR to support soluble PRR as an essential mediator of aldosterone-salt-induced hypertension and also as a potential therapeutic target for patients with mineralocorticoid excess. We firstly report that soluble PRR-dependent pathway medicates the Na+-retaining action of aldosterone in the distal nephron, which opens up a new area for a better understanding of the molecular basis of renal handling of Na+ balance and blood pressure.

Activating P2Y1 receptors improves function in arteries with repressed autophagy.

AIM: The importance of endothelial cell (EC) autophagy to vascular homeostasis in the context of health and disease is evolving. Earlier, we reported that intact EC autophagy is requisite to maintain shear-stress-induced nitric oxide (NO) generation via glycolysis-dependent purinergic signalling to endothelial NO synthase (eNOS). Here, we illustrate the translational and functional significance of these findings. METHODS AND RESULTS: First, we assessed translational relevance using older male humans and mice that exhibit blunted EC autophagy and impaired arterial function vs. adult controls. Active hyperaemia evoked by rhythmic handgrip exercise-elevated radial artery shear-rate similarly from baseline in adult and older subjects for 60 min. Compared with baseline, indexes of autophagy initiation, p-eNOSS1177 activation, and NO generation, occurred in radial artery ECs obtained from adult but not older volunteers. Regarding mice, indexes of autophagy and p-eNOSS1177 activation were robust in ECs from adult but not older animals that completed 60-min treadmill-running. Furthermore, 20 dyne • cm2 laminar shear stress × 45-min increased autophagic flux, glycolysis, ATP production, and p-eNOSS1177 in primary arterial ECs obtained from adult but not older mice. Concerning functional relevance, we next questioned whether the inability to initiate EC autophagy, glycolysis, and p-eNOSS1177in vitro precipitates arterial dysfunction ex vivo. Compromised intraluminal flow-mediated vasodilation displayed by arteries from older vs. adult mice was recapitulated in vessels from adult mice by (i) NO synthase inhibition; (ii) acute autophagy impairment using 3-methyladenine (3-MA); (iii) EC Atg3 depletion (iecAtg3KO mice); (iv) purinergic 2Y1-receptor (P2Y1-R) blockade; and (v) germline depletion of P2Y1-Rs. Importantly, P2Y1-R activation using 2-methylthio-ADP (2-Me-ADP) improved vasodilatory capacity in arteries from (i) adult mice treated with 3-MA; (ii) adult iecAtg3KO mice; and (iii) older animals with repressed EC autophagy. CONCLUSIONS: Arterial dysfunction concurrent with pharmacological, genetic, and age-associated EC autophagy compromise is improved by activating P2Y1-Rs.

Collecting duct renin regulates potassium homeostasis in mice.

AIM: The kaliuretic action of the renin-angiotensin-aldosterone system (RAAS) is well established as highlighted by hyperkalemia side effect of RAAS inhibitors but such action is usually ascribed to systemic RAAS. The present study addresses the involvement of intrarenal RAAS in K+ homeostasis with emphasis on locally generated renin within the collecting duct (CD). METHODS: Wild-type (Floxed) and CD-specific deletion of renin (CD renin KO) mice were treated for 7 days with a high K+ (HK) diet to investigate the role of CD renin in kaliuresis regulation and further define the underlying mechanism with emphasis on analysis of intrarenal aldosterone biosynthesis. RESULTS: In floxed mice, renin levels were elevated in the renal medulla and urine following a 1-week HK diet, indicating activation of the intrarenal renin. CD renin KO mice had blunted HK-induced intrarenal renin response and developed impaired kaliuresis and elevated plasma K+ level (4.45 ± 0.14 vs. 3.89 ± 0.04 mM, p < 0.01). In parallel, HK-induced intrarenal aldosterone and CYP11B2 expression along with expression of renal outer medullary K+ channel (ROMK), calcium-activated potassium channel subunit alpha-1 (α-BK), α-Na+ -K+ -ATPase, and epithelial sodium channel (ß-ENaC and cleaved-γ-ENaC) expression were all significantly blunted in CD renin KO mice in contrast to the unaltered responses of plasma aldosterone and adrenal CYP11B2. CONCLUSION: Taken together, these results support a kaliuretic action of CD renin during HK intake.

Potential of soluble (pro)renin receptor in kidney disease: can it go beyond a biomarker?

(Pro)renin receptor (PRR), also termed ATPase H+-transporting accessory protein 2 (ATP6AP2), is a type I transmembrane receptor and is capable of binding and activating prorenin and renin. Apart from its association with the renin-angiotensin system, PRR has been implicated in diverse developmental, physiological, and pathophysiological processes. Within the kidney, PRR is predominantly expressed in the distal nephron, particularly the intercalated cells, and activation of renal PRR contributes to renal injury in various rodent models of chronic kidney disease. Moreover, recent evidence demonstrates that PRR is primarily cleaved by site-1 protease to produce 28-kDa soluble PRR (sPRR). sPRR seems to mediate most of the known pathophysiological functions of renal PRR through modulating the activity of the intrarenal renin-angiotensin system and provoking proinflammatory and profibrotic responses. Not only does sPRR activate renin, but it also directly binds and activates the angiotensin II type 1 receptor. This review summarizes recent advances in understanding the roles and mechanisms of sPRR in the context of renal pathophysiology.

Revisiting the relationship between (Pro)Renin receptor and the intrarenal RAS: focus on the soluble receptor.

PURPOSE OF REVIEW: The (pro)renin receptor (PRR), also termed as ATPase H+ transporting accessory protein 2 (ATP6AP2), was originally cloned as a specific receptor for prorenin and renin [together called (pro)renin]. Given the wide tissue distribution of PRR, PRR was further postulated to act as a regulator of tissue renin. However, assigning a physiological role of PRR within the renin-angiotensin system (RAS) has been challenging largely due to its pleotropic functions in regulation of embryogenesis, autophagy, and H+ transport. The current review will summarize recent advances in understanding the roles of sPPR within the intrarenal RAS as well as those outside this local system. RECENT FINDINGS: Site-1 protease (S1P) is a predominant source of sPPR at least in the kidney. So far most of the known physiological functions of PRR including renal handling of electrolytes and fluid and blood pressure are mediated by sPRR. In particular, sPRR serves as a positive regulator of collecting duct renin to activate the intrarenal RAS during water deprivation or angiotensin-II (AngII) infusion. However, PRR/sPRR can act in renin-independent manner under other circumstances. SUMMARY: S1P-derived sPRR has emerged as a key regulator of kidney function and blood pressure and its relationship with the intrarenal RAS depends on the physiological context.

EPA-enriched plasmalogen attenuates the cytotoxic effects of LPS-stimulated microglia on the SH-SY5Y neuronal cell line.

Microglia plays an important role in the production of inflammation in the central nervous system. Excessive nerve inflammation can cause neuronal damage and neurodegenerative disease. It has been shown that EPA-enriched ethanolamine plasmalogen (EPA-PlsEtn) significantly inhibited the expressions of inflammatory factors and suppressed neuronal loss in a rat model of Alzheimer's disease. However, whether EPA-PlsEtn protects against neuronal loss by inhibiting the activation of microglia is still not clear. Therefore, we examined the effect of PlsEtn on SH-SY5Y cells incubated by conditioned medium from LPS-induced BV2 cells as a neuroinflammation model. Results showed that pre-incubation of LPS-induced BV2 cells with PlsEtn significantly improved the viability of SH-SY5Y cells by reducing the early apoptosis. The increasing production of NO and TNF-α in BV2 cells was reversed by PlsEtn treatment, while the decreasing level of IL-10 was raised. Polarization toward M1 phenotype and activation of NLRP3 inflammasome pathways are attenuated significantly by pre-treatment of PlsEtn in LPS-induced BV2 cells. The study provides evidence for a positive effect of PlsEtn on neuroprotection and the inhibition of neuroinflammation, and PlsEtn may be explored as a potential functional ingredient with neuroprotection effects.

Na+-Retaining Action of COX-2 (Cyclooxygenase-2)/EP1 Pathway in the Collecting Duct via Activation of Intrarenal Renin-Angiotensin-Aldosterone System and Epithelial Sodium Channel.

BACKGROUND: The collecting duct (CD) is a major site of both biosynthesis and action of prostaglandin E2 as highlighted by the predominant expression of COX-2 (cyclooxygenase-2) and some E-prostanoid (EP) subtypes at this nephron site. The purpose of this study was to determine the relevance and mechanism of CD COX-2/prostaglandin E2/EP1 signaling for the regulation of Na+ hemostasis during Na+ depletion. METHODS: Mice with Aqp2Cre-driven deletion of COX-2 (COX-2fl/flAqp2Cre+) or the EP1 subtype (EP1fl/flAqp2Cre+) were generated and the Na+-wasting phenotype of these mice during low-salt (LS) intake was examined. EP subtypes responsible for prostaglandin E2-induced local renin response were analyzed in primary cultured mouse inner medullary CD cells. RESULTS: Following 28-day LS intake, COX-2fl/flAqp2Cre+ mice exhibited a higher urinary Na+ excretion and lower cumulative Na+ balance, accompanied with suppressed intrarenal renin, AngII (angiotensin II), and aldosterone, expression of CYP11B2 (cytochrome P450 family 11 subfamily B member 2), and blunted expression of epithelial sodium channel subunits compared to floxed controls (COX-2fl/flAqp2Cre-), whereas no differences were observed for indices of systemic renin-angiotensin-aldosterone system. In cultured CD cells, exposure to prostaglandin E2 stimulated release of soluble (pro)renin receptor, prorenin/renin and aldosterone and the stimulation was more sensitive to antagonism of EP1 as compared other EP subtypes. Subsequently, EP1fl/flAqp2Cre+ mice largely recapitulated Na+-wasting phenotype seen in COX-2fl/flAqp2Cre+ mice. CONCLUSIONS: The study for the first time reports that CD COX-2/EP1 pathway might play a key role in maintenance of Na+ homeostasis in the face of Na+ depletion, at least in part, through activation of intrarenal renin-angiotensin-aldosterone-system and epithelial sodium channel.

New Approaches for Treatment of Advanced Extranodal NK/T-Cell Lymphoma.

Extranodal NK/T cell lymphoma (ENKL) is a rare subtype of lymphoma that shows a poor clinical outcome. The most common sites are the nasal cavity, nasopharynx, paranasal sinuses, tonsils and larynx. Because of P-glycoprotein expression on ENKL cells, ENKL is resistant to anthracycline-based chemotherapy. L-asparaginase-based chemotherapy with or without radiotherapy shows promising outcomes for advanced ENKL, but has limited efficacy in relapsed/refractory ENKL. immune-checkpoint inhibitors, histone deacetylase inhibitors, and monoclonal antibodies are being investigated. In this review, we summarize the new treatments for ENKL.

(Pro)renin Receptor Regulates Phosphate Homeostasis in Rats via Releasing Fibroblast Growth Factor-23.

Phosphate (Pi) is one of the basic necessities required for sustenance of life and its metabolism largely relies on excretory function of the kidney, a process chiefly under the endocrine control of bone-derived fibroblast growth factor 23 (FGF23). However, knowledge gap exists in understanding the regulatory loop responsible for eliciting phophaturic response to Pi treatment. Here, we reported a novel role of (pro)renin receptor (PRR) in mediating phosphaturic response to Pi treatment via upregulation of FGF23 production. Male Sprague-Dawley rats were pretreated for 5 days via osmotic pump-driven infusion of a PRR antagonist PRO20 or vehicle, and then treated with high Pi (HP) solution as drinking fluid for the last 24 h. PRO20 reduced HP-induced Pi excretion by 42%, accompanied by blunted upregulation of circulating FGF23 and parathyroid hormone (PTH) and downregulation of renal Na/Pi-IIa expression. In cultured osteoblast cells, exposure to HP induced a 1.56-fold increase in FGF23 expression, which was blunted by PRO20 or siRNA against PRR. Together, these results suggest that activation of PRR promotes phosphaturic response through stimulation of FGF23 production and subsequent downregulation of renal Na/Pi-IIa expression.

Role of (pro)renin receptor in cyclosporin A-induced nephropathy.

Calcineurin inhibitors such as cyclosporin A (CsA) have been widely used to improve graft survival following solid-organ transplantation. However, the clinical use of CsA is often limited by its nephrotoxicity. The present study tested the hypothesis that activation of the (pro)renin receptor (PRR) contributes to CsA-induced nephropathy by activating the renin-angiotensin system (RAS). Renal injury in male Sprague-Dawley rats was induced by a low-salt diet combined with CsA as evidenced by elevated plasma creatinine and blood urea nitrogen levels, decreased creatinine clearance and induced renal inflammation, apoptosis and interstitial fibrosis, and elevated urinary N-acetyl-ß-d-glucosaminidase activity and urinary kidney injury molecule-1 content. Each index of renal injury was attenuated following 2 wk of treatment with the PRR decoy inhibitor PRO20. Although CsA-treated rats with kidney injury displayed increased renal soluble (s)PRR abundance, plasma sPRR, renin activity, angiotensin II, and heightened urinary total prorenin/renin content, RAS activation was attenuated by PRO20. Exposure of cultured human renal proximal tubular HK-2 cells to CsA induced expression of fibronectin and sPRR production, but the fibrotic response was attenuated by PRO20 and siRNA-mediated PRR knockdown. These findings support the hypothesis that activation of PRR contributes to CsA-induced nephropathy by activating the RAS in rats. Of importance, we provide strong proof of concept that targeting PRR offers a novel therapeutic strategy to limit nephrotoxic effects of immunosuppressant drugs.NEW & NOTEWORTHY The present study reports, for the first time, that activation of the (pro)renin receptor drives the renin-angiotensin system to induce renal injury during cyclosporin A administration. More importantly, our study has identified that antagonism with PRO20 offers a novel intervention in the management of side effects of cyclosporin A.

Temperature-dependent characteristics of infrared photodetectors based on surface-state absorption in silicon.

At various temperatures, ranging from 25°C to 50°C, we characterized two types of photodetectors based on surface-state absorption in silicon: (1) contactless integrated photonic probes (CLIPPs) and (2) normal-incidence photoconductors. Both types of photodetectors exhibited temperature-dependent AC admittance without illumination. With illumination at telecommunication wavelengths near 1550 nm, in the temperature range we measured, the photoresponse of CLIPPs, i.e., the variance of admittance due to illumination, was relatively insensitive to temperature changes; in comparison, the temperature dependence of the photoresponse of normal-incidence photoconductors was more pronounced-their responsivity increased as temperature raised.

Soluble (Pro)Renin Receptor as a Negative Regulator of NCC (Na+-Cl- Cotransporter) Activity.

[Figure: see text].

(Pro)renin receptor antagonist PRO20 attenuates nephrectomy-induced nephropathy in rats via inhibition of intrarenal RAS and Wnt/ß-catenin signaling.

INTRODUCTION: (Pro)renin receptor has emerged as a new member of the renin-angiotensin system implicated in the pathogenesis of chronic kidney disease (CKD). Herein we report characterization of the therapeutic potential of (pro)renin receptor (PRR) antagonist PRO20 in 5/6 nephrectomy (5/6Nx) rats. METHODS: Male Wistar rats underwent 5/6Nx followed by treatment with vehicle or received daily injections of a PRR inhibitor PRO20 (700 µg/kg) via the 3 s.c. Sham group served as a control. RESULTS: As compared with the sham control, the 5/6Nx rats exhibited significant increases in proteinuria, glomerulosclerosis, tubular injury, and interstitial inflammation in the remnant kidneys. Treatment with PRO20 significantly attenuated these abnormalities, as evidenced by reduced expression of fibronectin, α-SMA, collagen 1, TGF-ß1, IL-6, IL-8, IL-1ß, MCP-1 and increased expression of E-cadherin. Increased urinary/renal levels of renin activity, angiotensinogen (AGT), and Angiotensin II (Ang II) by 5/6Nx, which were all ameliorated by PRO20. Renal PRR, the secreted proteolytic fragment of PRR (sPRR) in renal and urinary, were all elevated in 5/6Nx rats. Moreover, our results revealed that renal Wnt3A and ß-catenin expression were upregulated during 5/6Nx, which were all attenuated by PRO20. CONCLUSIONS: Overall we conclude that in vivo antagonism of PRR with PRO20 will improve 5/6Nx-induced CKD mainly through inhibition of intrarenal RAS and Wnt/ß-catenin signaling pathway.

Mutagenesis of the Cleavage Site of Pro Renin Receptor Abrogates Angiotensin II-Induced Hypertension in Mice.

[Figure: see text].

Serine Protease HTRA1 as a Novel Target Antigen in Primary Membranous Nephropathy.

BACKGROUND: Identification of target antigens PLA2R, THSD7A, NELL1, or Semaphorin-3B can explain the majority of cases of primary membranous nephropathy (MN). However, target antigens remain unidentified in 15%-20% of patients. METHODS: A multipronged approach, using traditional and modern technologies, converged on a novel target antigen, and capitalized on the temporal variation in autoantibody titer for biomarker discovery. Immunoblotting of human glomerular proteins followed by differential immunoprecipitation and mass spectrometric analysis was complemented by laser-capture microdissection followed by mass spectrometry, elution of immune complexes from renal biopsy specimen tissue, and autoimmune profiling on a protein fragment microarray. RESULTS: These approaches identified serine protease HTRA1 as a novel podocyte antigen in a subset of patients with primary MN. Sera from two patients reacted by immunoblotting with a 51-kD protein within glomerular extract and with recombinant human HTRA1, under reducing and nonreducing conditions. Longitudinal serum samples from these patients seemed to correlate with clinical disease activity. As in PLA2R- and THSD7A- associated MN, anti-HTRA1 antibodies were predominantly IgG4, suggesting a primary etiology. Analysis of sera collected during active disease versus remission on protein fragment microarrays detected significantly higher titers of anti-HTRA1 antibody in active disease. HTRA1 was specifically detected within immune deposits of HTRA1-associated MN in 14 patients identified among three cohorts. Screening of 118 "quadruple-negative" (PLA2R-, THSD7A-, NELL1-, EXT2-negative) patients in a large repository of MN biopsy specimens revealed a prevalence of 4.2%. CONCLUSIONS: Conventional and more modern techniques converged to identify serine protease HTRA1 as a target antigen in MN.

Observation of square- and h-shaped pulse from a mode-locked erbium-doped fiber laser.

We demonstrate the generation of a type of square-shaped pulse in a passively mode-locked erbium-doped fiber laser based on the nonlinear optical loop mirror technique. Through adjusting the pump power and polarization state, square-shaped pulses are generated. Furthermore, we investigate the pulse profile in relation to the optical spectrum. By filtering out short-wavelength spectrum components gradually, pulse shaping is achieved, and the top of the square-shaped pulse becomes flat. Subsequently, by filtering out long-wavelength spectrum components, a type of h-shaped pulse is obtained and the formation reason is also investigated.