Physiologic homeostasis after pig-to-human kidney xenotransplantation

Demand for kidney grafts outpaces supply, limiting kidney transplantation as a treatment for kidney failure. Xenotransplantation has the potential to make kidney transplantation available to many more patients with kidney failure, but the ability of xenografts to support human physiologic homeostasis has not been established. A brain-dead adult decedent underwent bilateral native nephrectomies followed by 10 gene-edited (four gene knockouts, six human transgenes) pig-to-human xenotransplantation. Physiologic parameters and laboratory values were measured for seven days in a critical care setting. Data collection aimed to assess homeostasis by measuring components of the renin-angiotensin-aldosterone system, parathyroid hormone signaling, glomerular filtration rate, and markers of salt and water balance. Mean arterial blood pressure was maintained above 60 mmHg throughout. Pig kidneys secreted renin (post-operative day three to seven mean and standard deviation: 47.3 ± 9 pg/mL). Aldosterone and angiotensin II levels were present (post-operative day three to seven, 57.0 ± 8 pg/mL and 5.4 ± 4.3 pg/mL, respectively) despite plasma renin activity under 0.6 ng/mL/hr. Parathyroid hormone levels followed ionized calcium. Urine output down trended from 37 L to 6 L per day with 4.5 L of electrolyte free water loss on post-operative day six. Aquaporin 2 channels were detected in the apical surface of principal cells, supporting pig kidney response to human vasopressin. Serum creatinine down trended to 0.9 mg/dL by day seven. Glomerular filtration rate ranged 90-240 mL/min by creatinine clearance and single-dose inulin clearance. Thus, in a human decedent model, xenotransplantation of 10 gene-edited pig kidneys provided physiologic balance for seven days. Hence, our in-human study paves the way for future clinical study of pig-to-human kidney xenotransplantation in living persons.

Passive antibody transfer from pregnant women to their fetus are maximized after SARS-CoV-2 vaccination irrespective of prior infection

Background

Pregnancy is associated with a higher risk of adverse symptoms and outcomes for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection for both mother and neonate. Antibodies can provide protection against SARS-CoV-2 infection and are induced in pregnant women after vaccination or infection. Passive transfer of these antibodies from mother to fetus in utero may provide protection to the neonate against infection. However, it is unclear whether the magnitude or quality and kinetics of maternally derived fetal antibodies differs in the context of maternal infection or vaccination.

Objective

We aimed to determine whether antibodies transferred from maternal to fetus differed in quality or quantity between infection- or vaccination-induced humoral immune responses.

Methods

We evaluated 93 paired maternal and neonatal umbilical cord blood plasma samples collected between October 2020 and February 2022 from a birth cohort of pregnant women from New Orleans, Louisiana, with histories of SARS-CoV-2 infection and/or vaccination. Plasma was profiled for the levels of spike-specific antibodies and induction of antiviral humoral immune functions, including neutralization and Fc-mediated innate immune effector functions. Responses were compared between 4 groups according to maternal infection and vaccination.

Results

We found that SARS-CoV-2 vaccination or infection during pregnancy increased the levels of antiviral antibodies compared to naive subjects. Vaccinated mothers and cord samples had the highest anti-spike antibody levels and antiviral function independent of the time of vaccination during pregnancy.

Conclusions

These results show that the most effective passive transfer of functional antibodies against SARS-CoV-2 in utero is achieved through vaccination, highlighting the importance of vaccination in pregnant women.

High-Fat Diet Modulates the Excitability of Neurons within the Brain-Liver Pathway

Stimulation of hepatic sympathetic nerves increases glucose production and glycogenolysis. Activity of pre-sympathetic neurons in the paraventricular nucleus (PVN) of the hypothalamus and in the ventrolateral and ventromedial medulla (VLM/VMM) largely influence the sympathetic output. Increased activity of the sympathetic nervous system (SNS) plays a role in the development and progression of metabolic diseases; however, despite the importance of the central circuits, the excitability of pre-sympathetic liver-related neurons remains to be determined. Here, we tested the hypothesis that the activity of liver-related neurons in the PVN and VLM/VMM is altered in diet-induced obese mice, as well as their response to insulin. Patch-clamp recordings were conducted from liver-related PVN neurons, VLM-projecting PVN neurons, and pre-sympathetic liver-related neurons in the ventral brainstem. Our data demonstrate that the excitability of liver-related PVN neurons increased in high-fat diet (HFD)-fed mice compared to mice fed with control diet. Insulin receptor expression was detected in a population of liver-related neurons, and insulin suppressed the firing activity of liver-related PVN and pre-sympathetic VLM/VMM neurons in HFD mice; however, it did not affect VLM-projecting liver-related PVN neurons. These findings further suggest that HFD alters the excitability of pre-autonomic neurons as well as their response to insulin.

The Renin-Angiotensin-Aldosterone System in Metabolic Diseases and Other Pathologies

It has been our pleasure to have been able to develop two special issues within the International Journal of Molecular Sciences: (1) Renin-Angiotensin-Aldosterone System in Pathologies and (2) Renin-Angiotensin-Aldosterone System in Metabolism & Disease [...].

Renin-angiotensin-aldosterone system function in the pig-to-baboon kidney xenotransplantation model

After pig-to-baboon kidney transplantation, episodes of hypovolemia and hypotension from an unexplained mechanism have been reported. This study evaluated the renin-angiotensin-aldosterone system post-kidney xenotransplantation. Kidneys from genetically-engineered pigs were transplanted into 5 immunosuppressed baboons after the excision of the native kidneys. Immunosuppressive therapy was based on the blockade of the CD40/CD154 costimulation pathway. Plasma renin, angiotensinogen (AGT), angiotensin II (Ang II), aldosterone levels, and urine osmolality and electrolytes were measured in healthy pigs, healthy nonimmunosuppressed baboons, and immunosuppressed baboons with life-supporting pig kidney grafts. After pig kidney transplantation, plasma renin and Ang II levels were not significantly different, although Ang II trended lower, even though plasma AGT and potassium were increased. Plasma aldosterone levels were unchanged. Urine osmolality and sodium concentration were decreased. Even in the presence of increasing AGT and potassium levels, lower plasma Ang II concentrations may be because of reduced, albeit not absent, the reactivity of pig renin to cleave baboon AGT, suggesting an impaired response of the renin-angiotensin-aldosterone system to hypovolemic and hypotensive episodes. The maintenance of aldosterone may be protective. The reduced urine osmolality and sodium concentration reflect the decreased ability of the pig kidney to concentrate urine. These considerations should not prohibit successful clinical pig kidney xenotransplantation.

Abstract 044: Stimulation Of Intrarenal Angiotensinogen Expression And The Development Of Hypertension And Kidney Injury In Angiotensin II-infused Hepatic Angiotensinogen Knockout Mice

Regulation of systemic and local angiotensinogen (AGT) levels is a key determinant of tissue angiotensin II (Ang II) levels and inappropriate AGT augmentation promotes the development of hypertension and tissue injury. Kidney and urinary AGT levels are increased in Ang II-mediated hypertension. Recent studies have demonstrated that circulating hepatocyte-derived AGT (hAGT) enters kidneys sustaining kidney and urinary AGT levels. However, roles of hAGT in blood pressure elevation and kidney injury in Ang II-mediated hypertension have not been delineated. This study tested if hAGT contributes to the development of the pathophysiological events in Ang II-infused mice. A low dose of Ang II (400 ng/kg/min) was infused to male wild type (WT) and hAGT gene knockout (KO) mice (N=9 and 13) for 4 weeks. The control group in each genotype received vehicle (Veh) infusion (N=5 and 6). Western blot confirmed non-detectable levels of hAGT in KO mice. hAGT KO markedly decreased plasma AGT levels (WT+Veh:12.2±0.6 vs. hAGT KO+Veh: 0.8±0.1 μg/ml). Ang II infusion did not elevate plasma AGT levels in either WT and hAGT KO mice. Although hAGT KO mice exhibited a lower baseline of systolic blood pressure (SBP) than WT mice, Ang II-mediated increases in SBP was not attenuated in hAGT KO mice (ΔSBP in WT+Ang II: 30.1±4.4 vs. hAGT KO+Ang II: 26.0±4.2 mmHg). Kidney AGT mRNA levels were increased by Ang II infusion to the same extent in both WT and hAGT mice (WT+Ang II: 1.30±0.04 vs. hAGT KO+Ang II: 1.34±0.06, ratio to control). Likewise, Ang II infusion increased IL-6 mRNA to the same magnitude in both WT and hAGT KO mice. Urinary AGT was sustained in hAGT KO+Veh mice (66±9%) compared to WT+Veh mice. Ang II infusion did not alter urinary AGT levels in both groups. Glomerular mesangial expansion and fibrosis by Ang II infusion were not observed. Ang II infusion developed tubulointerstitial fibrosis in renal cortex and medulla. hAGT KO prevented the fibrosis only in the medulla. These outcomes demonstrate that elevation of SBP, augmentation of intrarenal AGT and IL-6 expression, and the development of renal cortical fibrosis in Ang II-mediated hypertension do not require hAGT. In contrast, hAGT contributes to renal medullary fibrosis which may be due to the lower absolute levels of blood pressure.

Immunosuppression by Mycophenolate Mofetil Mitigates Intrarenal Angiotensinogen Augmentation in Angiotensin II-Dependent Hypertension

Augmentation of intrarenal angiotensinogen (AGT) leads to further formation of intrarenal angiotensin II (Ang II) and the development of hypertensive kidney injury. Recent studies demonstrated that macrophages and the enhanced production of pro-inflammatory cytokines can be crucial mediators of renal AGT augmentation in hypertension. Accordingly, this study investigated the effects of immunosuppression by mycophenolate mofetil (MMF) on intrarenal AGT augmentation. Ang II (80 ng/min) was infused with or without daily administration of MMF (50 mg/kg) to Sprague-Dawley rats for 2 weeks. Mean arterial pressure (MAP) in Ang II infused rats was slightly higher (169.7 ± 6.1 mmHg) than the Ang II + MMF group (154.7 ± 2.0 mmHg), but was not statistically different from the Ang II + MMF group. MMF treatment suppressed Ang II-induced renal macrophages and IL-6 elevation. Augmentation of urinary AGT by Ang II infusion was attenuated by MMF treatment (control: 89.3 ± 25.2, Ang II: 1194 ± 305.1, and Ang II + MMF: 389 ± 192.0 ng/day). The augmentation of urinary AGT by Ang II infusion was observed before the onset of proteinuria. Elevated intrarenal AGT mRNA and protein levels in Ang II infused rats were also normalized by the MMF treatment (AGT mRNA, Ang II: 2.5 ± 0.2 and Ang II + MMF: 1.5 ± 0.1, ratio to control). Ang II-induced proteinuria, mesangial expansion and renal tubulointerstitial fibrosis were attenuated by MMF. Furthermore, MMF treatment attenuated the augmentation of intrarenal NLRP3 mRNA, a component of inflammasome. These results indicate that stimulated cytokine production in macrophages contributes to intrarenal AGT augmentation in Ang II-dependent hypertension, which leads to the development of kidney injury.

Angiotensin II biphasically regulates cell differentiation in human iPSC-derived kidney organoids

Human kidney organoid technology holds promise for novel kidney disease treatment strategies and utility in pharmacological and basic science. Given the crucial roles of the intrarenal renin-angiotensin system (RAS) and angiotensin II (ANG II) in the progression of kidney development and injury, we investigated the expression of RAS components and effects of ANG II on cell differentiation in human kidney organoids. Human induced pluripotent stem cell-derived kidney organoids were induced using a modified 18-day Takasato protocol. Gene expression analysis by digital PCR and immunostaining demonstrated the formation of renal compartments and expression of RAS components. The ANG II type 1 receptor (AT1R) was strongly expressed in the early phase of organoid development (around day 0), whereas ANG II type 2 receptor (AT2R) expression levels peaked on day 5. Thus, the organoids were treated with 100 nM ANG II in the early phase on days 0-5 (ANG II-E) or during the middle phase on days 5-10 (ANG II-M). ANG II-E was observed to decrease levels of marker genes for renal tubules and proximal tubules, and the downregulation of renal tubules was inhibited by an AT1R antagonist. In contrast, ANG II-M increased levels of markers for podocytes, the ureteric tip, and the nephrogenic mesenchyme, and an AT2R blocker attenuated the ANG II-M-induced augmentation of podocyte formation. These findings demonstrate RAS expression and ANG II exertion of biphasic effects on cell differentiation through distinct mediatory roles of AT1R and AT2R, providing a novel strategy to establish and further characterize the developmental potential of human induced pluripotent stem cell-derived kidney organoids.NEW & NOTEWORTHY This study demonstrates angiotensin II exertion of biphasic effects on cell differentiation through distinct mediatory roles of angiotensin II type 1 receptor and type 2 receptor in human induced pluripotent stem cell-derived kidney organoids, providing a novel strategy to establish and further characterize the developmental potential of the human kidney organoids.

Inflammation-frailty linkage and its long-term prognostic impact in patients with acute coronary syndrome

Introduction

Chronic inflammation has been receiving considerable attention as an emerging risk factor for cardiovascular disease. In contrast, with the aging of the population, frailty has been also attracting a great deal of attention as the residual risk for cardiovascular disease. Although inflammation and frailty exacerbate each other and have an adverse effect on many diseases, the relationship between chronic inflammation and frailty and the impact of these combination on long-term prognosis in patients with acute coronary syndrome (ACS) are not elucidated.

Purpose

The aims of this study were to determine the association between chronic inflammation and frailty and its impact on long-term cardiovascular outcomes in patients with ACS.

Methods

A total of 482 consecutive ACS patients with obstructive coronary artery disease (age 66±12 years, male 81%) were enrolled in this observational study. We evaluated patients' gait speed as a measure of frailty before discharge. C-reactive protein (CRP) levels at 1 month after discharge were also evaluated as inflammation in the chronic phase. According to commonly used criteria of the residual inflammation (CRP>0.2 mg/dL) and the definition of the European Working Group for Sarcopenia (gait speed ≤0.8 m/sec), patients were stratified by 4 subgroups: low/high CRP with slow/normal gait speed. The primary endpoint was composite outcomes of cardiovascular death, myocardial infarction and ischemic stroke.

Results

While there was no significant association between CRP levels and gait speed in all patients, a significant negative association between two variables was observed in the high CRP group (Spearman's ρ = −0.31, p=0.001). During the median follow-up of 6 years, primary endpoints have occurred in 82 patients. Overall, event-free rates differed significantly among the 4 groups, demonstrating the lowest event-free rate in the patients with high CRP and slow gait speed (p<0.0001; Figure). In the multivariate analysis, high CRP (adjusted HR 1.99, 95% CI 1.14–3.46, p=0.02) and slow gait speed (adjusted HR 1.82, 95% CI 1.09–3.04, p=0.02) were independently and significantly associated with the primary endpoint. Moreover, the patients with both high CRP and slow gait speed had a 2.6-fold higher risk of cardiovascular events compared to others (adjusted HR 2.62, 95% CI 1.36–5.05, p=0.004).

Conclusion

In the patients with ACS, CRP levels and gait speed were negatively associated in the high CRP group. Chronic inflammation and frailty were both associated with poor prognosis in ACS and in particular, the combination of these factors was strongly associated with poor prognosis.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Alterations in the estrogen receptor profile of cardiovascular tissues during aging

Estrogen exerts protective effects on the cardiovascular system via three known estrogen receptors: alpha (ERα), beta (ERß), and the G protein-coupled estrogen receptor (GPER). Our laboratory has previously showed the importance of GPER in the beneficial cardiovascular effects of estrogen. Since clinical studies indicate that the protective effects of exogenous estrogen on cardiovascular function are attenuated or reversed 10 years post-menopause, the hypothesis was that GPER expression may be reduced during aging. Vascular reactivity and GPER protein expression were assessed in female mice of varying ages. Physiological parameters, blood pressure, and estrogen receptor transcripts via droplet digital PCR (ddPCR) were assessed in the heart, kidney, and aorta of adult, middle-aged, and aged male and female C57BL/6 mice. Vasodilation to estrogen (E2) and the GPER agonist G-1 were reduced in aging female mice and were accompanied by downregulation of GPER protein. However, ERα and GPER were the predominant receptors in all tissues, whereas ERß was detectable only in the kidney. Female sex was associated with higher mRNA for both ERα and GPER in both the aorta and the heart. Aging impacted receptor transcript in a tissue-dependent manner. ERα transcript decreased in the heart with aging, while GPER expression increased in the heart. These data indicate that aging impacts estrogen receptor expression in the cardiovascular system in a tissue- and sex-specific manner. Understanding the impact of aging on estrogen receptor expression is critical for developing selective hormone therapies that protect from cardiovascular damage.

Low-density lipoprotein cholesterol levels on admission and long-term outcomes in statin-naive patients with acute coronary syndrome

Introduction

Dyslipidemia, especially an increase in the low-density lipoprotein cholesterol (LDL-C) has been established as one of the most important risk factors for atherosclerotic cardiovascular diseases. In contrast, some recent studies have shown that the low LDL-C level was associated with short-term poor prognosis in patients with cardiovascular disease, and this is so-called “cholesterol paradox”. However, there is few data evaluating the effects on long-term outcome of “cholesterol paradox” in patients with acute coronary syndrome (ACS).

Purpose

The purpose of this study was to examine whether the low LDL-C level on admission affect long-term prognosis in patients with ACS.

Methods

A total of 434 ACS patients who survived to hospital discharge were enrolled in this study. All patients were statin-naïve on admission, and were received statin therapy after hospitalization. Patients were divided into the low LDL-C (≤114 mg/dl) and high LDL-C (>114 mg/dl) groups using the first tertile of the LDL-C level on admission. The primary endpoint was composite outcomes of all-cause death, myocardial infarction, ischemic stroke, hospitalization for congestive heart failure and unplanned revascularization.

Results

During a median follow-up period of 5.5 years, primary endpoint occurred in 117 patients. Overall, event-free rates differed significantly between the low and high LDL-C groups, demonstrating the lower event-free rate in patients with the low LDL-C group (38.9% in low LDL-C group versus 20.7% in high LDL-C group, p=0.0002; Figure). Even after adjustment for age, sex, body mass index, and various classical risk factors, the low LDL-C group was significantly at higher risk for primary composite outcomes compared to the high LDL-C group (adjusted hazard ratio 1.65, 95%-confidence interval 1.10–2.49, p=0.02).

Conclusion

In patients with ACS, the low LDL-C level on admission was significantly associated with long-term worse prognosis, regardless of statin therapy at discharge. In ACS patients with low LDL-C level, it might be necessary for elucidating the residual risk for secondary adverse event to improve their prognosis.

Funding Acknowledgement

Type of funding source: None

Chymase inhibition retards albuminuria in type 2 diabetes

Chymase released from mast cells produces pro‐fibrotic, inflammatory, and vasoconstrictor agents. Studies were performed to test the hypothesis that chronic chymase inhibition provides a renal protective effect in type 2 diabetes. Diabetic (db/db) and control mice (db/m) were chronically infused with a chymase‐specific inhibitor or vehicle for 8 weeks. Baseline urinary albumin excretion (UalbV) averaged 42 ± 3 and 442 ± 32 microg/d in control (n = 22) and diabetic mice (n = 27), respectively (p < .05). After administration of chymase inhibitor to diabetic mice, the change in UalbV was significantly lower (459 ± 57 microg/d) than in vehicle‐treated diabetic mice (645 ± 108 microg/d). U_NGALV was not different at baseline between diabetic mice that would receive the chymase inhibitor (349 ± 56 ng/d, n = 6) and vehicle (373 ± 99 ng/d, n = 6) infusions, but increased significantly only in the vehicle‐treated diabetic mice (p < .05). Glomeruli of diabetic kidneys treated chronically with chymase inhibition demonstrated reduced mesangial matrix expansion compared to glomeruli from untreated diabetic mice. Plasma angiotensin II levels were not altered by chymase inhibitor treatment. In summary, chronic chymase inhibition slowed the progression of urinary albumin excretion in diabetic mice. In conclusion, renal chymase may contribute to the progression of albuminuria in type 2 diabetes renal disease.

Abstract P141: Immunosuppressant Treatment Attenuates Augmentation Of Intrarenal NLRP-3 Inflammasome In Angiotensin II-dependent Hypertension

Activated inflammasomes enhance maturation of pro-inflammatory cytokines, which facilitates the development of kidney injury. NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3), one of major subunits in the inflammasome complex, plays a crucial role in innate immunity and inflammation. Although NLRP3 inflammasome is activated by ATP-P2Y7 axis and reactive oxygen species, the expression of pro-NLRP3 is promoted by NF-κB activated by cytokines or PAMPs/DAMPs. Thus, we hypothesized that mycophenolate mofetil (MMF), an immunosuppressant, attenuates augmentation of intrarenal NLRP3 and consequent progression of kidney injury in angiotensin II (Ang II)-dependent hypertension. Ang II (80 ng/min) was infused with/without daily MMF administration (50 ng/kg) to Sprague-Dawley rats for 2 weeks. mRNA levels of intrarenal NLRP3 and AIM2, which forms another type of inflammasome complex by viral or bacterial infections, were measured by droplet digital PCR. Furthermore, kidney injury was evaluated. MMF treatment mitigated Ang II-induced macrophage infiltration into kidneys, suggesting immunosuppression by the drug. Ang II infusion significantly increased intrarenal NLRP3 mRNA levels (normotensive control group: 4.12±1.1 copies/ng RNA vs. Ang II-infused group: 9.96±1.8 copies, N=5). The elevated NLRP3 expression in kidneys of Ang II-infused rats was attenuated by MMF treatment (6.24±1.4 copies). In contrast, intrarenal AIM2 levels were lower than NLRP3 in the control group and the levels were not altered by Ang II infusion or MMF treatment (normotensive control group: 0.42±0.1 copies, Ang II-infused group: 0.35±0.06 copies and Ang II+MMF group: 0.35±0.08 copies). Urinary protein and angiotensinogen levels were elevated in Ang II-infused rats and MMF treatment suppressed the augmentations. Histological analyses also showed the development of kidney injury including mesangial expansion and tubulointerstitial fibrosis observed in the hypertensive rats, but these injury markers were mitigated by MMF. These results demonstrate activation of the NLRP3 inflammasome in Ang II dependent hypertension and indicate that immunosuppression by MMF mitigates the inflammasome activation, which contributes to attenuation of the kidney injury.

STAT1 regulates interferon-γ-induced angiotensinogen and MCP-1 expression in a bidirectional manner in primary cultured mesangial cells

Objective:

Intrarenal interferon-γ significantly contributes to the development of glomerular injury in which angiotensinogen and monocyte chemoattractant protein 1 levels are elevated. However, the exact nature of the role that interferon-γ plays in regulating angiotensinogen and monocyte chemoattractant protein 1 expression has not been fully delineated. Therefore, the aim of this study was to investigate the role that interferon-γ plays in angiotensinogen and monocyte chemoattractant protein 1 expression.

Methods:

Primary cultured rat mesangial cells were treated with 0–20 ng/mL interferon-γ for 2, 8 or 24 hours. Expression levels of angiotensinogen, monocyte chemoattractant protein 1, suppressors of cytokine signaling 1, an intracellular suppressor of Janus kinase-signal transducers and activators of transcription signaling and activity of the Janus kinase-signal transducers and activators of transcription pathway were evaluated by reverse transcriptase polymerase chain reaction and western blot analysis.

Results:

Interferon-γ increased angiotensinogen expression in mesangial cells with maximal augmentation observed following 5 ng/mL interferon-γ at 8 hours of treatment (1.87 ± 0.05, mRNA, relative ratio). Further increases were reduced or absent using higher concentrations of interferon-γ. Following treatments, monocyte chemoattractant protein 1 expression was induced in a linear dose-dependent manner (6.85 ± 0.62-fold by 20 ng/mL interferon-γ at 24 hours). In addition, interferon-γ induced STAT1 phosphorylation and suppressors of cytokine signaling 1 expression in a linear dose-dependent manner. The suppression of STAT1 and suppressors of cytokine signaling 1 expression by small interference RNAs facilitated an increase in interferon-γ-induced angiotensinogen expression, indicating that these two factors negatively regulate angiotensinogen expression. In contrast, the increase in interferon-γ-induced monocyte chemoattractant protein 1 expression was attenuated in STAT1-deficient mesangial cells, suggesting that STAT1 positively regulates monocyte chemoattractant protein 1 expression in mesangial cells.

Conclusion:

These results demonstrate that while interferon-γ increases both angiotensinogen and monocyte chemoattractant protein 1 expression, STAT1 plays an opposing role in the regulation of each factor in mesangial cells.

Elevated cerebrospinal fluid sodium in hypertensive human subjects with a family history of Alzheimer's disease

High salt (sodium) intake leads to the development of hypertension despite the fact that plasma sodium concentration ([Na⁺]) is usually normal in hypertensive human patients. Increased cerebrospinal fluid (CSF) sodium contributes to elevated sympathetic activity and high blood pressure (BP) in rodent models of hypertension. However, whether there is an increased accumulation of sodium in the CSF of humans with chronic hypertension is not well defined. Here, we investigated CSF [Na⁺] from hypertensive and normotensive human subjects with family histories of Alzheimer's disease in samples collected in a clinical trial, as spinal tap is not a routine clinical procedure for hypertensive patients. The [Na⁺] and osmolality in plasma and CSF were measured by flame photometry. Daytime ambulatory BP was monitored while individuals were awake. Participants were deidentified and data were analyzed in conjunction with a retrospective analysis of patient history and diagnosis. We found that CSF [Na⁺] was significantly higher in participants with high BP compared with normotensive participants; there was no difference in plasma [Na⁺], or plasma and CSF osmolality between groups. Subsequent multiple linear regression analyses controlling for age, sex, race, and body mass index revealed a significant positive correlation between CSF [Na⁺] and BP but showed no correlation between plasma [Na⁺] and BP. In sum, CSF [Na⁺] was higher in chronic hypertensive individuals and may play a key role in the pathogenesis of human hypertension. Collectively, our findings provide evidence for the clinical significance of CSF [Na⁺] in chronic hypertension in humans.

Nitric oxide synthase inhibitors negatively regulate respiration in isolated rodent cardiac and brain mitochondria

Nitric oxide (NO) is known to exert inhibitory control on mitochondrial respiration in the heart and brain. Evidence supports the presence of NO synthase (NOS) in the mitochondria (mtNOS) of cells; however, the functional role of mtNOS in the regulation of mitochondrial respiration is unclear. Our objective was to examine the effect of NOS inhibitors on mitochondrial respiration and protein S-nitrosylation. Freshly isolated cardiac and brain nonsynaptosomal mitochondria were incubated with selective inhibitors of neuronal (nNOS; ARL-17477, 1 µmol/L) or endothelial [eNOS; N⁵-(1-iminoethyl)-l-ornithine, NIO, 1 µmol/L] NOS isoforms. Mitochondrial respiratory parameters were calculated from the oxygen consumption rates measured using Agilent Seahorse XFe24 analyzer. Expression of NOS isoforms in the mitochondria was confirmed by immunoprecipitation and Western blot analysis. In addition, we determined the protein S-nitrosylation by biotin-switch method followed by immunoblotting. nNOS inhibitor decreased the state IIIu respiration in cardiac mitochondria and both state III and state IIIu respiration in brain mitochondria. In contrast, eNOS inhibitor had no effect on the respiration in the mitochondria from both heart and brain. Interestingly, NOS inhibitors reduced the levels of protein S-nitrosylation only in brain mitochondria, but nNOS and eNOS immunoreactivity was observed in the cardiac and brain mitochondrial lysates. Thus, the effects of NOS inhibitors on S-nitrosylation of mitochondrial proteins and mitochondrial respiration confirm the existence of functionally active NOS isoforms in the mitochondria. Notably, our study presents first evidence of the positive regulation of mitochondrial respiration by mitochondrial nNOS contrary to the current dogma representing the inhibitory role attributed to NOS isoforms.NEW & NOTEWORTHY Existence and the role of nitric oxide synthases in the mitochondria are controversial. We report for the first time that mitochondrial nNOS positively regulates respiration in isolated heart and brain mitochondria, thus challenging the existing dogma that NO is inhibitory to mitochondrial respiration. We have also demonstrated reduced protein S-nitrosylation by NOS inhibition in isolated mitochondria, supporting the presence of functional mitochondrial NOS.

Blockade of sodium-glucose cotransporter 2 suppresses high glucose-induced angiotensinogen augmentation in renal proximal tubular cells

Renal proximal tubular angiotensinogen (AGT) is increased by hyperglycemia (HG) in diabetes mellitus, which augments intrarenal angiotensin II formation, contributing to the development of hypertension and kidney injury. Sodium-glucose cotransporter 2 (SGLT2) is abundantly expressed in proximal tubular cells (PTCs). The present study investigated the effects of canagliflozin (CANA), a SGLT2 inhibitor, on HG-induced AGT elevation in cultured PTCs. Mouse PTCs were treated with 5-25 mM glucose. CANA (0-10 µM) was applied 1 h before glucose treatment. Glucose (10 mM) increased AGT mRNA and protein levels at 12 h (3.06 ± 0.48-fold in protein), and 1 and 10 µM CANA as well as SGLT2 shRNA attenuated the AGT augmentation. CANA did not suppress the elevated AGT levels induced by 25 mM glucose. Increased AGT expression induced by treatment with pyruvate, a glucose metabolite that does not require SGLT2 for uptake, was not attenuated by CANA. In HG-treated PTCs, intracellular reactive oxygen species levels were elevated compared with baseline (4.24 ± 0.23-fold), and these were also inhibited by CANA. Furthermore, tempol, an antioxidant, attenuated AGT upregulation in HG-treated PTCs. HG-induced AGT upregulation was not inhibited by an angiotensin II receptor antagonist, indicating that HG stimulates AGT expression in an angiotensin II-independent manner. These results indicate that enhanced glucose entry via SGLT2 into PTCs elevates intracellular reactive oxygen species generation by stimulation of glycolysis and consequent AGT augmentation. SGLT2 blockade limits HG-induced AGT stimulation, thus reducing the development of kidney injury in diabetes mellitus.

P5483Prognostic impact of skeletal muscle, fat, and bone mass in male patients with ST-segment elevation myocardial infarction

Introduction

Muscle, fat and bone mass may play some roles to keep physical activity and favorable outcome in patients with cardiovascular diseases. However, there is a paucity of data regarding the effects on the prognosis of skeletal muscle, fat, and bone mass in patients with ST-segment elevation myocardial infarction (STEMI).

Purpose

Our purpose was to examine whether skeletal muscle, fat, and bone mass each affect the prognosis after STEMI.

Methods

A total of 354 male patients with STEMI were enrolled in this study. Dual-energy X-ray absorptiometry scan was performed before discharge. All patients were followed up for the primary composite outcome of all-cause death, nonfatal myocardial infarction, nonfatal ischemic stroke, hospitalization for congestive heart failure, and unplanned revascularization.

Results

During a median follow-up of 32 months, 57 patients experienced primary composite outcome. Each of skeletal muscle, fat, and bone mass were indexed by height squared (kg/m2) and divided into two groups using the cut-off value obtained from the maximum Youden index to predict the primary composite outcome. The event rate was significantly higher in patients with low appendicular skeletal muscle mass index (ASMI) (29.2% vs 11.7%, p<0.001), low fat mass index (FMI) (22.9% vs 13.3%, p=0.030), and low bone mass index (23.8% vs 11.6%, p=0.002). After adjustment for age, renal function, diabetes mellitus, infarct size, Killip classification, and body mass index, low ASMI but not FMI (p=0.150) and bone mass index (p=0.159) was independently and significantly associated with the primary composite outcome (adjusted hazard ratio 2.12, 95%-confidence interval 1.05–4.31, p=0.035).

Conclusions

Index about muscle mass rather than fat and bone mass have prognostic impact in male patients with STEMI.

P2657Prognostic impact of skeletal muscle mass in upper and lower extremities in patients with ST-segment elevation myocardial infarction

Introduction

Sarcopenia, characterized by the loss of skeletal muscle mass and muscle strength, has been demonstrated the importance in cardiovascular diseases including ST-segment elevation myocardial infarction (STEMI). However, there is few data comparing the effects on the prognosis of skeletal muscle mass of upper and lower extremities in STEMI patients.

Purpose

Our purpose was to examine whether skeletal muscle mass of upper and lower extremities affect the prognosis after STEMI.

Methods

A total of 432 patients with STEMI were enrolled in this study. Dual-energy X-ray absorptiometry scan was performed before discharge. Each of upper and lower extremity skeletal muscle masses was indexed by height squared (kg/m2), and divided into two groups using the first quartile value for each sex. All patients were followed up for the primary composite outcome of all-cause death, nonfatal myocardial infarction, nonfatal ischemic stroke, hospitalization for congestive heart failure, and unplanned revascularization.

Results

During a median follow-up of 32 months, 68 patients experienced primary composite outcome. The event rate was significantly higher in patients with low-lower extremity skeletal muscle mass index (LESMI) than in those with high-LESMI (24.3% vs 12.9%, log-rank p<0.001), as well as in those with low-upper extremity muscle mass index than in those with high-upper extremity muscle mass index (UESMI) (19.6% vs 14.5%, log-rank p=0.047). However, after adjustment for age, gender, renal function, diabetes mellitus, infarct size, body mass index, and body fat percentage, only low-LESMI was independently and significantly associated with the primary composite outcome (adjusted hazard ratio for LESMI 2.11, 95%-confidence interval 1.06–4.14, p=0.034, adjusted hazard ratio for UESMI 1.04, 95%-confidence interval 0.52–2.08, p=0.906,).

Conclusions

Decreased muscle mass of lower extremity, rather than upper extremity, might have prognostic impact in patients with STEMI.

Abstract 062: Elevated Cerebrospinal Fluid Sodium Concentration in Hypertensive Humans

High salt intake has been linked to the pathogenesis of hypertension and increased sympathetic activity, considered a hallmark of human hypertension. Recent studies showed that high-salt diets may lead to sequestration of sodium into interstitial tissues. Increased CSF sodium contributes to elevated sympathetic activity and high blood pressure (BP) in rodent models of hypertension. However, it is not known if there is an enhanced sequestration of sodium into cerebrospinal fluid (CSF) of chronic hypertensive humans. To address this question, we obtained CSF and plasma samples from 43 middle-aged, normotensive (n=26) and hypertensive (n=17) individuals. The sodium concentration ([Na + ]) in plasma and CSF were measured using flame photometer. Ambulatory BP was monitored every 20 minutes while the participant was awake and once per hour while the participant was asleep over 24-hour period. Participants were deidentified and data were analyzed in conjunction with a retrospective analysis of patient history and diagnosis. Participants with uncontrolled hypertension had higher BP levels compared with the normotensive participants (systolic BP: 135.5±2.7 mmHg vs. 114.3±1.5 mmHg; diastolic BP: 81.9±2.1 mmHg vs. 71.6±1.2 mmHg, P <0.0001). Importantly, we found that CSF [Na+] was significantly higher in participants with uncontrolled hypertension (149.3±3.5 mM) compared with those of normotensive (139.5±2.12 mM, P =0.0156); while there was no difference in plasma [Na+] between groups (136±0.76 mM vs. 135.5±1 mM, P =0.73). Further multiple linear regressions analysis controlling for age, sex, race and body mass index revealed a significant positive correlation between CSF [Na + ] and blood pressure levels (sBP: R 2 =0.4189, P= 0.0007; dBP: R 2 =0.205, P =0.032), but showed no correlation between plasma [Na + ] and BP. Furthermore, we found that plasma and CSF [Na + ] were not correlated with each other (R 2 =0.0002174, P =0.9252), suggesting that increases in CSF [Na + ] in hypertensive humans do not reflect simple passive diffusion from the circulation. In sum, CSF [Na + ] was higher in chronic hypertensive humans and CSF sodium may play a key role in the pathogenesis of human hypertension.

Canagliflozin Prevents Intrarenal Angiotensinogen Augmentation and Mitigates Kidney Injury and Hypertension in Mouse Model of Type 2 Diabetes Mellitus

BACKGROUND

Hypertension and renal injury are common complications of type 2 diabetes mellitus (T2DM). Hyperglycemia stimulates renal proximal tubular angiotensinogen (AGT) expression via elevated oxidative stress contributing to the development of high blood pressure and diabetic nephropathy. The sodium glucose cotransporter 2 (SGLT2) in proximal tubules is responsible for the majority of glucose reabsorption by renal tubules. We tested the hypothesis that SGLT2 inhibition with canagliflozin (CANA) prevents intrarenal AGT augmentation and ameliorates kidney injury and hypertension in T2DM.

METHODS

We induced T2DM in New Zealand obese mice with a high fat diet (DM, 30% fat) with control mice receiving regular fat diet (ND, 4% fat). When DM mice exhibited > 350 mg/dL blood glucose levels, both DM- and ND-fed mice were treated with 10 mg/kg/day CANA or vehicle by oral gavage for 6 weeks. We evaluated intrarenal AGT, blood pressure, and the development of kidney injury.

RESULTS

Systolic blood pressure in DM mice (133.9 ± 2.0 mm Hg) was normalized by CANA (113.9 ± 4.0 mm Hg). CANA treatment ameliorated hyperglycemia-associated augmentation of renal AGT mRNA (148 ± 21 copies/ng RNA in DM, and 90 ± 16 copies/ng RNA in DM + CANA) and protein levels as well as elevation of urinary 8-isoprostane levels. Tubular fibrosis in DM mice (3.4 ± 0.9-fold, fibrotic score, ratio to ND) was suppressed by CANA (0.9 ± 0.3-fold). Furthermore, CANA attenuated DM associated increased macrophage infiltration and cell proliferation in kidneys of DM mice.

CONCLUSIONS

CANA prevents intrarenal AGT upregulation and oxidative stress and which may mitigate high blood pressure, renal tubular fibrosis, and renal inflammation in T2DM.

Estrogen receptor profiles across tissues from male and female Rattus norvegicus

Background

Estrogen is formed by the enzyme aromatase (CYP19A1) and signals via three identified receptors ERα (ESR1), ERß (ESR2), and the G protein-coupled estrogen receptor (GPER). Understanding the relative contribution of each receptor to estrogenic signaling may elucidate the disparate effects of this sex hormone across tissues, and recent developments in PCR technology allow absolute quantification and direct comparison of multiple targets. We hypothesized that this approach would reveal tissue- and sex-specific differences in estrogen receptor mRNA.

Methods

ESR1, ESR2, GPER, and CYP19A1 were measured in four cardiovascular tissues (heart, aorta, kidney, and adrenal gland), three brain areas (somatosensory cortex, hippocampus, and prefrontal cortex), and reproductive tissues (ovaries, mammary gland, uterus, testes) from six male and six female adult Sprague-Dawley rats.

Results

GPER mRNA expression was relatively stable across all tissues in both sexes, ranging from 5.49 to 113 copies/ng RNA, a 21-fold difference. In contrast, ESR1/ESR2 were variable across tissues although similar within an organ system. ESR1 ranged from 4.46 to 614 copies/ng RNA (138-fold difference) while ESR2 ranged from 0.154 to 83.1 copies/ng RNA (540-fold). Significant sex differences were broadly absent except for renal ESR1 (female 206 vs. male 614 copies/ng RNA, P < 0.0001) and GPER (62.0 vs. 30.2 copies/ng RNA, P < 0.05) as well as gonadal GPER (5.49 vs. 47.5 copies/ng RNA, P < 0.01), ESR2 (83.1 vs. 0.299 copies/ng RNA, P < 0.01), and CYP19A1 (322 vs. 7.18 copies/ng RNA, P < 0.01). Cardiovascular tissues showed a predominance of ESR1, followed by GPER. In contrast, GPER was the predominant transcript in the brain with similarly low levels of ESR1 and ESR2. CYP19A1 was detected at very low levels except for reproductive tissues and the hippocampus.

Conclusion

While the data indicates a lack of sex differences in most tissues, significant differences were found in the range of receptor gene expression across tissues as well as in the receptor profile between organ systems. The data provide a guide for future studies by establishing estrogen receptor expression across multiple tissues using absolute PCR quantification. This knowledge on tissue-specific estrogen receptor profiles will aid the development of hormonal therapies that elicit beneficial effects in specific tissues.

Interaction between TRPV1-expressing neurons in the hypothalamus

Transient receptor potential vanilloid type 1 (TRPV1) is a ligand-gated ion channel expressed in the peripheral and central nervous systems. TRPV1-dependent mechanisms take part in a wide range of physiological and pathophysiological pathways including the regulation of homeostatic functions. TRPV1 expression in the hypothalamus has been described as well as evidence that TRPV1-dependent excitatory inputs to hypothalamic preautonomic neurons are diminished in diabetic conditions. Here we aimed to determine the functional expression of TRPV1 in two hypothalamic nuclei known to be involved in the central control of metabolism and to test the hypothesis that TRPV1-expressing neurons receive TRPV1-expressing inputs. A mouse model (TRPV1Cre/tdTom) was generated to identify TRPV1-expressing cells and determine the cellular properties of TRPV1-expressing neurons in adult mice. Our study demonstrated the functional expression of TRPV1 in the dorsomedial hypothalamic nucleus and paraventricular nucleus in adult mice. Our findings revealed that a subset of TRPV1Cre/tdTom neurons receive TRPV1-expressing excitatory inputs, indicating direct interaction between TRPV1-expressing neurons. In addition, astrocytes likely play a role in the modulation of TRPV1-expressing neurons. In summary, this study identified specific hypothalamic regions where TRPV1 is expressed and functional in adult mice and the existence of direct connections between TRPV1Cre/tdTom neurons. NEW & NOTEWORTHY Transient receptor potential vanilloid type 1 (TRPV1) is expressed in the hypothalamus, and TRPV1-dependent regulation of preautonomic neurons is decreased in hyperglycemic conditions. Our study demonstrated functional expression of TRPV1 in two hypothalamic nuclei involved in the control of energy homeostasis. Our results also revealed that a subset of TRPV1-expressing neurons receive TRPV1-expressing excitatory inputs. These findings suggest direct interaction between TRPV1-expressing neurons.

Inflammation as a Regulator of the Renin-Angiotensin System and Blood Pressure

PURPOSE OF REVIEW

Mechanisms facilitating progression of hypertension via cross stimulation of the renin-angiotensin system (RAS) and inflammation have been proposed. Accordingly, we review and update evidence for regulation of RAS components by pro-inflammatory factors.

RECENT FINDINGS

Angiotensin II (Ang II), which is produced by RAS, induces vasoconstriction and consequent blood pressure elevation. In addition to this direct action, chronically elevated Ang II stimulates several pathophysiological mechanisms including generation of oxidative stress, stimulation of the nervous system, alterations in renal hemodynamics, and activation of the immune system. In particular, an activated immune system has been shown to contribute to the development of hypertension. Recent studies have demonstrated that immune cell-derived pro-inflammatory cytokines regulate RAS components, further accelerating systemic and local Ang II formation. Specifically, regulation of angiotensinogen (AGT) production by pro-inflammatory cytokines in the liver and kidney is proposed as a key mechanism underlying the progression of Ang II-dependent hypertension.

Abstract P327: Real-Time Analysis of Blood Glucose Dynamics by a Glucose Telemetry System in Canagliflozin-Treated Diabetic Mice

SGLT2 inhibitors lower blood glucose (BG) levels and have the potential to reduce cardiovascular and renal complications of type 2 diabetes mellitus (T2DM). Since BG levels can vary significantly during a treatment regime, hemoglobin A1c is often utilized as a stable indicator of BG status but dynamic measurements of BG may provide greater insights. A blood glucose telemetry systems was used to investigate BG dynamics in canagliflozin (CANA, an SGLT inhibitor)-treated T2DM mice. Male New Zealand Obese mice were fed a high fat diet to induce diabetes. When the mice exhibited a BG of ~350 mg/dl, the mice were treated with vehicle for 5 days followed by 10 mg/kg/day CANA for 5 days by daily oral gavage (single dosing/day). BG levels were monitored continuously via implanted telemetry devices. Chronic treatment (6 weeks) was also performed to investigate blood pressure monitored by a telemetry system and to assess kidney injury. During vehicle treatment for 5 days, BG levels in the mice averaged 336.7 mg/dl. Lower BG levels during early morning compared to night time (active time) were observed during vehicle treatment. BG levels demonstrated a large variation over 24 hours during the vehicle treatment (maximum minus minimum BG: 368.5 mg/dl on day 5). CANA rapidly reduced BG levels within 3 hours following treatment (214.8±25.4 mg/dl), and the lowered BG was sustained until the next dosing. The average 24-hour BG was gradually suppressed during the CANA treatment reaching 170.1 mg/dl on the last day of CANA treatment. Moreover, CANA reduced the variation of BG (maximum minus minimum BG: 214.8 mg/dl on day 5 of CANA treatment). In mice receiving chronic treatment, CANA started lowering systolic blood pressure on week 2 and significant suppression was observed on week 6 (vehicle: 157.9±2.2 vs. CANA: 124.7±7.6 mmHg). The development of kidney injury, especially renal tubular fibrosis and inflammation, was attenuated by CANA. These findings demonstrate that CANA treatment results in rapid and sustained reductions of both BG levels and BG variability which precede the reduction of blood pressure. The temporal dissociation between the lowering of BG and of arterial pressure levels by CANA suggests hyperglycemia-induced factors mediate the development of hypertension in T2DM.

Abstract P410: Characterization of the Renin-angiotensin System in Induced Pluripotent Stem Cell-derived Human Kidney Organoids

Intrarenal renin-angiotensin system (RAS), including proximal tubular angiotensinogen (AGT), plays crucial roles in the progression of hypertension, kidney injury, and kidney development and has been investigated in vivo using animal models. For translational relevance, we sought to further our investigations in human tissue. This study investigated RAS expression and AGT regulation by histone deacetylase 9 (HDAC9), an epigenetic repressor of AGT, in human iPSC-derived kidney organoids. After pre-treatment of human iPSC with CHIR99201, a glycogen synthase kinase inhibitor, and fibroblast growth factor 9, cells were moved to transwell membranes. Cells were harvested on day 0, 5, 12 or 18 to determine mRNA copy numbers of developmental markers and RAS genes by digital PCR. Marker genes of renal structures were induced during the culture with concomitant decrease in progenitor markers including Cited1. Immunostaining revealed that the organoids contain podocytes, proximal tubules expressing AGT and distal tubules. Angiotensin II type 1 receptor (AT1R) levels were higher than other RAS components on day 0 and the expression was downregulated on day 5. AT2R induction peaked on day 5 and reduced until day 18. Renin expression was strongly induced on day 5 and sustained until day 18. Angiotensin-converting enzyme levels were moderately augmented during the culture. AGT levels were elevated on day 12 and remained until day 18 (7.6-fold, ratio to day 0). Conversely, HDAC9 levels decreased by day 18. On day 18, AGT and HDAC9 levels were inversely correlated in a CHIR99201 concentration-dependent manner. Moreover, an HDAC9 inhibitor increased AGT expression (2.25±0.21-fold, ratio to control). These results suggest that all RAS components are expressed and independently regulated during the development of iPSC-derived human kidney organoids. The existence of all RAS components including high renin expression, their regulation, and epigenetic regulation of AGT in the organoids support previous findings in rodent models. Concerted effort, including this study, to overcome technical challenges to generate complete nephrons will provide human kidney organoids to study development, pathophysiological mechanisms, novel drugs and clinical therapies.

Abstract P414: Blockade of Sodium Glucose Cotransporter 2 by Canagliflozin Suppresses High Glucose-induced Angiotensinogen Augmentation in Renal Proximal Tubular Cells

Intrarenal angiotensinogen (AGT) is mainly expressed in proximal tubular cells (PTC). AGT is increased by hyperglycemia (HG) in type 1 and 2 diabetes mellitus, which causes elevated intrarenal angiotensin formation contributing to the development of hypertension and kidney injury. Sodium glucose co-transporter 2 (SGLT2) is abundantly expressed in early PTC and may promote increased intrarenal AGT by increasing intracellular glucose levels. This study tested the effects of canagliflozin (CANA), an SGLT2 inhibitor, on HG-induced AGT elevation in cultured PTC. Mouse PTC were treated with 5, 10 or 25 mM glucose. 0-10 μM CANA was applied one hour before glucose treatment. AGT mRNA and protein levels were measured by digital PCR and western blot analysis. Levels of intracellular reactive oxygen species (ROS) were determined with H 2 DCF-DA. Tempol, an antioxidant, was used to test if elevated ROS is involved in HG-induced AGT upregulation. 10 mM glucose increased AGT protein levels at 12 hours (3.06±0.48-fold compared with 5 mM glucose) and treatment with 10 μM CANA attenuated the AGT augmentation (1.68±0.05-fold). AGT protein levels were also increased by 25 mM glucose; but CANA did not suppress the AGT levels caused by this glucose concentration. In PTC treated with 10 mM glucose for 12 hours, the suppressing effect on AGT upregulation was observed with 1 and 10 μM CANA. Lower concentrations of CANA (0.01 and 0.1 μM) did not lower AGT protein levels significantly. Elevated AGT mRNA expression by glucose was also attenuated by CANA. Treatment of PTC with 1 mM pyruvate also increased AGT expression levels, indicating that glycolysis is involved in HG-induced AGT upregulation. After incubation of PTC with 10 mM glucose for 12 hours, intracellular ROS levels were elevated compared to baseline (4.24±0.23-fold) and these were also inhibited by CANA (0.2±0.08-fold). Furthermore, tempol attenuated AGT upregulation in HG-treated PTC. These results indicate that enhanced glucose entry via SGLT2 into PTC elevates intracellular ROS generation by stimulation of glycolysis and consequent AGT augmentation. Thus, SGLT2 inhibition by CANA may limit HG-induced AGT stimulation which suppress intrarenal angiotensin formation and reduce kidney injury in diabetes mellitus.

Regulation of Nephron Progenitor Cell Self-Renewal by Intermediary Metabolism

Nephron progenitor cells (NPCs) show an age-dependent capacity to balance self-renewal with differentiation. Older NPCs (postnatal day 0) exit the progenitor niche at a higher rate than younger (embryonic day 13.5) NPCs do. This behavior is reflected in the transcript profiles of young and old NPCs. Bioenergetic pathways have emerged as important regulators of stem cell fate. Here, we investigated the mechanisms underlying this regulation in murine NPCs. Upon isolation and culture in NPC renewal medium, younger NPCs displayed a higher glycolysis rate than older NPCs. Inhibition of glycolysis enhanced nephrogenesis in cultured embryonic kidneys, without increasing ureteric tree branching, and promoted mesenchymal-to-epithelial transition in cultured isolated metanephric mesenchyme. Cotreatment with a canonical Wnt signaling inhibitor attenuated but did not entirely block the increase in nephrogenesis observed after glycolysis inhibition. Furthermore, inhibition of the phosphatidylinositol 3-kinase/Akt self-renewal signaling pathway or stimulation of differentiation pathways in the NPC decreased glycolytic flux. Our findings suggest that glycolysis is a pivotal, cell-intrinsic determinant of NPC fate, with a high glycolytic flux supporting self-renewal and inhibition of glycolysis stimulating differentiation.

HDAC9 is an epigenetic repressor of kidney angiotensinogen establishing a sex difference

Background

Sexual difference has been shown in the pathogenesis of chronic kidney disease induced by hypertension. Females are protected from hypertension and related end-organ damage. Augmentation of renal proximal tubular angiotensinogen (AGT) expression can promote intrarenal angiotensin formation and the development of associated hypertension and kidney injury. Female rodents exhibit lower intrarenal AGT levels than males under normal conditions, suggesting that the suppressed intrarenal AGT production by programmed mechanisms in females may provide protection from these diseases. This study was performed to examine whether epigenetic mechanisms serve as repressors of AGT.

Methods

Male and female Sprague Dawley rats were used to investigate sex differences of systemic, hepatic, and intrarenal AGT levels. All histone deacetylase (HDAC) mRNA levels in the kidneys were determined using a PCR array. HDAC9 protein expression in the kidneys and cultured renal proximal tubular cells (PTC) was analyzed by Western blot analysis and immunohistochemistry. The effects of HDAC9 on AGT expression were evaluated by using an inhibitor and siRNA. ChIP assay was performed to investigate the interaction between the AGT promoter and HDAC9.

Results

Plasma and liver AGT levels did not show differences between male and female Sprague-Dawley rats. In contrast, females exhibited lower AGT levels than males in the renal cortex and urine. In the absence of supplemented sex hormones, primary cultured renal cortical cells isolated from female rats sustained lower AGT levels than those from males, suggesting that the kidneys have a unique mechanism of AGT regulation controlled by epigenetic factors rather than sex hormones. HDAC9 mRNA and protein levels were higher in the renal cortex of female rats versus male rats (7.09 ± 0.88, ratio to male) while other HDACs did not exhibit a sex difference. HDAC9 expression was localized in PTC which are the primary source of intrarenal AGT. Importantly, HDAC9 knockdown augmented AGT mRNA (1.92 ± 0.35-fold) and protein (2.25 ± 0.50-fold) levels, similar to an HDAC9 inhibitor. Furthermore, an interaction between HDAC9 and a distal 5’ flanking region of AGT via a histone complex containing H3 and H4 was demonstrated.

Conclusions

These results indicate that HDAC9 is a novel suppressing factor involved in AGT regulation in PTC, leading to low levels of intrarenal AGT in females. These findings will help to delineate mechanisms underlying sex differences in the development of hypertension and renin-angiotensin system (RAS) associated kidney injury.

Abstract P613: Absolute Gene Quantification Of Intrarenal Renin-angiotensin System Components Using Droplet Digital PCR Analysis

The intrarenal renin-angiotensin system (RAS) has been shown to play crucial roles in the development of hypertension and RAS associated kidney injury including diabetic nephropathy. Although some circulating RAS components are filtered into kidneys and contribute to the regulation of intrarenal RAS activity, evaluating expression levels of RAS components in the kidney is important to elucidate the mechanisms underlying intrarenal RAS activation. Digital PCR is a new technique that has been established to quantify absolute target gene levels, which allows for comparisons of different gene levels. Thus, this study was performed to establish profiles of absolute gene copy numbers for intrarenal RAS components in wild-type (WT) rats, WT and streptozotocin (STZ)-induced diabetic mice. Male Sprague-Dawley rats (N=5) and male C57BL/6J mice were used in this study. The mice were subjected to either control (N=5) or STZ (200 mg/kg, N=4) injection. Seven days after STZ injection, copy numbers of renal cortical angiotensinogen (AGT), angiotensin-converting enzyme (ACE), ACE2, angiotensin type 1 receptor a (AT1a), and AT2 mRNA were determined by a droplet digital PCR. Since (pro)renin proteins produced by juxtaglomerular cells are secreted to circulating system, analysis of renin mRNA was excluded from this evaluation. In the renal cortex of WT rats, the copy number of AGT was higher than other measured RAS components (AGT: 719.2±46.6, ACE: 116.0±14.9, ACE2: 183.6±21.5, AT1a: 196.0±25.2 copies in 1 ng total RNA). AT2 levels were lower than other components (0.068±0.01 copies). In WT mice, ACE exhibited the highest copy number in the components (AGT: 447.2±29.0, ACE: 1662.4±61.2, ACE2: 676.8±41.5, AT1a: 867.0±16.8, AT2: 0.049±0.01 copies). Although STZ-induced diabetes did not change ACE2 and AT1a, ACE levels were reduced (765.5±98.1 copies) and AT2 levels were augmented (0.10±0.01 copies) as previously demonstrated. Accordingly, the absolute quantification by digital PCR established precise gene profiles of intrarenal RAS components, which will provide rationales for targeting the each component in future studies. Furthermore, the results indicate that the high sensitive assay accurately quantifies rare target genes including intrarenal AT2.

Abstract 015: Immunosuppression Attenuates Intrarenal Angiotensinogen Augmentation in Angiotensin II Dependent Hypertension

Augmented intrarenal angiotensinogen (AGT) is a critical contributor to activation of intrarenal renin-angiotensin system (RAS) leading to the development of hypertension and associated kidney injury. It has been shown that treatment with mycophenolate mofetil (MMF), an immunosuppressive drug, mitigates the increased intrarenal angiotensin (Ang) II levels and blood pressure in hypertensive animal models, suggesting that an activated immune system mediates intrarenal RAS activation and consequent hypertension. Associated macrophage (MΦ) infiltration augments pro-inflammatory cytokine levels including interleukin-6 (IL-6), which plays a crucial role in augmentation of AGT expression in cultured renal proximal tubular cells. Accordingly, this study was performed to establish pathophysiological relevance for the effects of stimulated MΦ and IL-6 on intrarenal AGT augmentation in Ang II-dependent hypertension. Ang II (80 ng/min) was infused with/without daily MMF administration (50 ng/kg) to Sprague-Dawley rats for 2 weeks. Mean arterial pressure (MAP) in Ang II infused rats was slightly higher (169.7±6.1 mmHg) than MAP in Ang II+MMF group (154.7±2.0 mmHg) which was not statistically different than in control group. The augmentation of urinary AGT and urinary protein by Ang II infusion was attenuated by MMF treatment (AGT, control: 89.3±25.2, Ang II: 1,194±305.1, and Ang II+MMF: 389±192.0 ng/day). Importantly, the augmentation of urinary AGT by Ang II infusion was observed before the onset of proteinuria. Urinary 8-isoprostane levels were not altered by Ang II and/or MMF during the 2-week treatments. MMF treatment suppressed Ang II-induced renal MΦ infiltration and IL-6 elevation (IL-6 mRNA, Ang II: 32.4±7.5 and Ang II+MMF: 3.6±1.7, ratio to control). qRT-PCR, western blot and immunohistochemistry revealed elevated intrarenal AGT mRNA and protein levels in Ang II infused rats which were normalized by the MMF treatment (AGT mRNA, Ang II: 2.5±0.2 and Ang II+MMF: 1.5±0.1, ratio to control). These results indicate that stimulated IL-6 production in infiltrated MΦ contributes to intrarenal AGT augmentation in early stages of Ang II-dependent hypertension, which contributes to the development of kidney injury.

Quantification of intact plasma AGT consisting of oxidized and reduced conformations using a modified ELISA

The pleiotropic actions of the renin-angiotensin system (RAS) depend on the availability of angiotensinogen (AGT) which generates angiotensin I (ANG I) when cleaved by renin. Thus, quantification of the intact AGT (iAGT) concentrations is important to evaluate the actual renin substrate available. The iAGT conformation exists as oxidized AGT (oxi-AGT) and reduced AGT (red-AGT) in a disulfide bond, and oxi-AGT has a higher affinity for renin, which may exacerbate RAS-associated diseases. Accordingly, we determined iAGT, oxi-AGT, and red-AGT levels in plasma from rats and mice. Blood samples were obtained by cardiac puncture and then immediately mixed with an inhibitor solution containing a renin inhibitor. Total AGT (tAGT) levels were measured by tAGT ELISA which detects both cleaved and iAGT. iAGT levels were determined by iAGT ELISA which was found to only detect red-AGT. Thus, it was necessary to treat samples with dithiothreitol, a reducing agent, to quantify total iAGT concentration. tAGT levels in rat and mouse plasma were 1,839 ± 139 and 1,082 ± 77 ng/ml, respectively. iAGT levels were 53% of tAGT in rat plasma but only 22% in mouse plasma, probably reflecting the greater plasma renin activity in mice. The ratios of oxi-AGT and red-AGT were ∼4:1 (rat) and 16:1 (mouse). Plasma iAGT consists of oxi-AGT and red-AGT, suggesting that oxidative stress can influence ANG I generation by the AGT conformation switch. Furthermore, the lower availability of plasma iAGT in mice suggests that it may serve as a limiting factor in ANG I formation in this species.

Increased angiotensinogen expression, urinary angiotensinogen excretion, and tissue injury in nonclipped kidneys of two-kidney, one-clip hypertensive rats

In angiotensin II (ANG II)-dependent hypertension, there is an angiotensin type 1 receptor-dependent amplification mechanism enhancing intrarenal angiotensinogen (AGT) formation and secretion in the tubular fluid. To evaluate the role of increased arterial pressure, AGT mRNA, protein expression, and urinary AGT (uAGT) excretion and tissue injury were assessed in both kidneys of two-kidney, one-clip Sprague-Dawley hypertensive rats subjected to left renal arterial clipping (0.25-mm gap). By 18-21 days, systolic arterial pressure increased to 180 ± 3 mmHg, and uAGT increased. Water intake, body weights, 24-h urine volumes, and sodium excretion were similar. In separate measurements of renal function in anesthetized rats, renal plasma flow and glomerular filtration rate were similar in clipped and nonclipped kidneys and not different from those in sham rats, indicating that the perfusion pressure to the clipped kidneys remained within the autoregulatory range. The nonclipped kidneys exhibited increased urine flow and sodium excretion. The uAGT excretion was significantly greater in nonclipped kidneys compared with clipped and sham kidneys. AGT mRNA was 2.15-fold greater in the nonclipped kidneys compared with sham (1.0 ± 0.1) or clipped (0.98 ± 0.15) kidneys. AGT protein levels were also greater in the nonclipped kidneys. The nonclipped kidneys exhibited greater glomerular expansion and immune cell infiltration, medullary fibrosis, and cellular proliferation than the clipped kidneys. Because both kidneys have elevated ANG II levels, the greater tissue injury in the nonclipped kidneys indicates that an increased arterial pressure synergizes with increased intrarenal ANG II to stimulate AGT production and exert greater renal injury.

Macrophage-derived IL-6 contributes to ANG II-mediated angiotensinogen stimulation in renal proximal tubular cells

The development of ANG II-dependent hypertension involves increased infiltration of macrophages (MΦ) and T cells into the kidney and the consequent elevation of intrarenal cytokines including IL-6, which facilitates the progression of hypertension and associated kidney injury. Intrarenal renin-angiotensin system (RAS) activation, including proximal tubular angiotensinogen (AGT) stimulation, has also been regarded as a cardinal mechanism contributing to these diseases. However, the interaction between immune cells and intrarenal RAS activation has not been fully delineated. Therefore, the present study investigated whether ANG II-treated MΦ induce AGT upregulation in renal proximal tubular cells (PTCs). MΦ were treated with 0-10(-6) M ANG II for up to 48 h. PTCs were incubated with the collected medium from MΦ. In ANG II-treated MΦ, IL-6 mRNA and protein levels were increased (1.86 ± 0.14, protein level, ratio to control); moreover, IL-6 levels were higher than TNF-α and IL-1β in culture medium isolated from ANG II-treated MΦ. Elevated AGT expression (1.69 ± 0.04, ratio to control) accompanied by phosphorylated STAT3 were observed in PTCs that received culture medium from ANG II-treated MΦ. The addition of a neutralizing IL-6 antibody to the collected medium attenuated phosphorylation of STAT3 and AGT augmentation in PTCs. Furthermore, a JAK2 inhibitor also suppressed STAT3 phosphorylation and AGT augmentation in PTCs. These results demonstrate that ANG II-induced IL-6 elevation in MΦ enhances activation of the JAK-STAT pathway and consequent AGT upregulation in PTCs, suggesting involvement of an immune response in driving intrarenal RAS activity.

Augmentation of angiotensinogen expression in the proximal tubule by intracellular angiotensin II via AT1a/MAPK/NF-кB signaling pathways

Long-term angiotensin II (ANG II) infusion significantly increases ANG II levels in the kidney through two major mechanisms: AT1 receptor-mediated augmentation of angiotensinogen (AGT) expression and uptake of circulating ANG II by the proximal tubules. However, it is not known whether intracellular ANG II stimulates AGT expression in the proximal tubule. In the present study, we overexpressed an intracellular cyan fluorescent ANG II fusion protein (Ad-sglt2-ECFP/ANG II) selectively in the proximal tubule of rats and mice using the sodium and glucose cotransporter 2 (sglt2) promoter. AGT mRNA and protein expression in the renal cortex and 24-h urinary AGT excretion were determined 4 wk following overexpression of ECFP/ANG II in the proximal tubule. Systolic blood pressure was significantly increased with a small antinatriuretic effect in rats and mice with proximal tubule-selective expression of ECFP/ANG II (P < 0.01). AGT mRNA and protein expression in the cortex were increased by >1.5-fold and 61 ± 16% (P < 0.05), whereas urinary AGT excretion was increased from 48.7 ± 5.7 (n = 13) to 102 ± 13.5 (n = 13) ng/24 h (P < 0.05). However, plasma AGT, renin activity, and ANG II levels remained unaltered by ECFP/ANG II. The increased AGT mRNA and protein expressions in the cortex by ECFP/ANG II were blocked in AT1a-knockout (KO) mice. Studies in cultured mouse proximal tubule cells demonstrated involvement of AT1a receptor/MAP kinases/NF-кB signaling pathways. These results indicate that intracellular ANG II stimulates AGT expression in the proximal tubules, leading to increased AGT formation and secretion into the tubular fluid, which contributes to ANG II-dependent hypertension.

Enhancement in cellular Na+K+ATPase activity by low doses of peroxynitrite in mouse renal tissue and in cultured HK2 cells

In the normal condition, endogenous formation of peroxynitrite (ONOOˉ) from the interaction of nitric oxide and superoxide has been suggested to play a renoprotective role. However, the exact mechanism associated with renoprotection by this radical compound is not yet clearly defined. Although ONOOˉ usually inhibits renal tubular Na⁺K⁺ATPase (NKA) activity at high concentrations (micromolar to millimolar range [μM–mM], achieved in pathophysiological conditions), the effects at lower concentrations (nanomolar range [nM], relevant in normal condition) remain unknown. To examine the direct effect of ONOOˉ on NKA activity, preparations of cellular membrane fraction from mouse renal tissue and from cultured HK2 cells (human proximal tubular epithelial cell lines) were incubated for 10 and 30 min each with different concentrations of ONOOˉ (10 nmol/L–200 μmol/L). NKA activity in these samples (n = 5 in each case) was measured via a colorimetric assay capable of detecting inorganic phosphate. At high concentrations (1–200 μmol/L), ONOOˉ caused dose‐dependent inhibition of NKA activity (−3.0 ± 0.6% and −36.4 ± 1.4%). However, NKA activity remained unchanged at 100 and 500 nmol/L ONOOˉ concentration, but interestingly, at lower concentrations (10 and 50 nmol/L), ONOOˉ caused small but significant increases in the NKA activity (3.3 ± 1.1% and 3.1 ± 0.6%). Pretreatment with a ONOOˉ scavenger, mercaptoethylguanidine (MEG; 200 μmol/L), prevented these biphasic responses to ONOOˉ. This dose‐dependent biphasic action of ONOO⁻ on NKA activity may implicate that this radical compound helps to maintain sodium homeostasis either by enhancing tubular sodium reabsorption under normal conditions or by inhibiting it during oxidative stress conditions.

Abstract P021: The Combined Effects of Elevated Intrarenal Ang Ii and Blood Pressure Causes Greater Renal Injury in the Non-clipped Kidneys in 2k1c Rats

In 2-kidney 1-clip (2K1C) hypertension, intrarenal angiotensin II (Ang II) levels are increased in both kidneys, which are often implicated in the further augmentation of the intrarenal renin-angiotensin system and the development of hypertension and kidney injury. We recently reported that angiotensinogen (AGT) expression and secretion are increased only in the non-clipped kidneys (NCK). These findings provide the basis for the hypothesis that elevated Ang II levels, augmented AGT, and high arteriolar pressure in NCK synergistically cause greater kidney injury. Accordingly, we compared the degrees of kidney injury between clipped kidneys (CK) and NCK using a 2K1C model that maintains normal renal blood flow and GFR in the CK. Left kidneys of male rats were clipped for 21 days. Histological and immunohistological analyses were performed on both the CK and NCK. Twenty glomeruli and 20 microscope fields in the cortex and the medulla were examined for each group. The PAS-positive area in the glomeruli was higher in NCK compared with sham (33.9 ± 0.89 vs. 12.4 ± 0.51%) and CK (vs. 15.1 ± 0.58%). Similarly, the Masson's trichrome-positive area in the medullary region was greater in NCK compared with sham (2.21 ± 0.10 vs. 1.32 ± 0.05%) and CK (vs. 1.67 ± 0.10%), but the changes were not observed in the interstitial tissue of the cortex. Immunoreactivity for CD68, a marker of the macrophage and monocyte levels, was higher in NCK compared with sham (0.72 ± 0.07 vs. 0.36 ± 0.04%), but similar to that in CK. In contrast, accumulation of the immune cells in the glomeruli was greater in NCK compared with sham (8.99 ± 0.69 vs. 3.46 ± 0.46%) and CK (vs. 3.08 ± 0.24%). The proliferating cell nuclear antigen levels, a marker of cell proliferation, were greater in NCK (3.49 ± 0.09 %) but not in the CK. Levels of vimentin, a cell transformation and regeneration marker, were also higher in NCK compared with CK and sham. Increased vascular wall thickness (α-SMA) was observed in both kidneys. These results indicate that pathological factors associated with the high blood pressure are required for the development of renal injury in the 2K1C model including glomerular expansion, medullary fibrosis, immune cell infiltration in glomeruli and cell proliferation/transformation.

Role of stimulated intrarenal angiotensinogen in hypertension

Experimental models of hypertension and patients with inappropriately increased renin formation due to a stenotic kidney, arteriosclerotic narrowing of the renal arterioles or a rare juxtaglomerular cell tumor have shown a progressive augmentation of the intrarenal/intratubular renin-angiotensin system (RAS). The increased intrarenal angiotensin II (Ang II) elicits renal vasoconstriction and enhanced tubular sodium reabsorption in proximal and distal nephron segments. The enhanced intrarenal Ang II levels are due to both increased Ang II type 1 (AT1) receptor mediated Ang II uptake and AT1 receptor dependent stimulation of renal angiotensinogen (AGT) mRNA and augmented AGT production. The increased AGT formation and secretion into the proximal tubular lumen leads to local formation of Ang II, which stimulates proximal transporters such as the sodium/hydrogen exchanger. Enhanced AGT production also leads to spillover of AGT into the distal nephron segments as reflected by AGT in the urine, which provides an index of intrarenal RAS activity. There is also increased Ang II concentration in distal nephron with stimulation of distal sodium transport. Increased urinary excretion of AGT has been demonstrated in patients with hypertension, type 1 and type 2 diabetes mellitus, and several types of chronic kidney diseases indicating an upregulation of intrarenal RAS activity.

Abstract 408: Hyperglycemia Increases the Prorenin Receptor in the Plasma Membrane of Collecting Duct Cells in Rats with Type 1 Diabetes Mellitus

In type 1 diabetes mellitus (T1DM) there is increased prorenin secretion by the principal cells of the collecting duct. Binding of prorenin to prorenin receptor (PRR) on intercalated cells increases its catalytic activity, increases local angiotensin (Ang) II formation, and stimulates intracellular MAPK signaling responsible for inflammation and tissue fibrosis. Thus, changes in the amount of membrane bound PRR may be a key factor in stimulating these pathways. However, it has not been established that activation of PRR in the collecting duct contributes to increased intrarenal Ang II and tubulointerstitial inflammation via stimulation of inflammatory pathways including transforming growth factor-beta (TGF-β). This study tested the hypothesis that hyperglycemia increases the PRR abundance at the plasma membrane (PM) in the collecting duct cells, thus allowing greater capability to be activated by locally produced prorenin. Streptozotocin (STZ; 60 mg/kg; ip single dose) was used to induce T1DM in Sprague-Dawley rats (N=10) and compared to control rats (N=8). After 7-days induction, STZ-rats showed plasma glucose levels of 428±13 vs. 138±9 mg/dL and insulin of 0.05±0.02 vs. 2.4±0.6 ng/mL, compared to control. Although PRR transcript in the renal medulla were not different between groups; PRR localized predominantly on the apical aspects of collecting duct cells in STZ-induced rats; while in controls it was primarily found intracellularlly. These changes were accompanied by greater levels of active renin and Ang II in the urine and increased TGF-β mRNA levels in the renal medulla of STZ-rats (Renin: 186± 34 vs. 6± 3 ng Ang I/mL/h; P<0.01; Ang II: 884± 147 vs. 42± 14 fmol/h; P<0.05; TGF-β: 1.22 ± 0.06 vs. 0.97 ± 0.03 mRNA ratio; P<0.01). To further assess if hyperglycemia induced in vitro PRR trafficking alterations, collecting duct M-1 cells were treated with normal glucose (NG; 1mM glucose + 1 mM mannitol) and high glucose (HG; 4mM) for 5, 60, and 360 min. PRR protein levels were higher in the PM fractions in cells treated with HG, compared to cells treated with NG. Thus, hyperglycemia increases PRR abundance in the PM of the collecting duct and stimulates TGF-β synthesis in the renal medulla which may underlie the development of tubulointerstitial inflammation.

Abstract 519: Increased Renal Angiotensinogen Expression in Non-clipped Kidneys of 2-Kidney 1-Clip Hypertensive Rats

In 2-kidney 1-clip (2K1C) hypertension, intrarenal angiotensin II (Ang II) levels are increased in both kidneys but the mechanisms for augmentation of Ang II may be different. We recently reported that urinary angiotensinogen (AGT) is increased only in the non-clipped kidneys. However, it has not been determined if these changes are accompanied by augmentation of intrarenal AGT mRNA synthesis in the non-clipped kidneys of 2K1C hypertensive rats. Experiments were performed on male Sprague-Dawley rats (n=11) subjected to left renal arterial clipping (.25 mm gap) and followed for 18-21 days prior to anesthesia and separate measurements of renal function. Systolic arterial pressure increased to 180±3 mmHg compared to 126±4 mmHg in sham operated rats. There were no significant differences in water intake, body weights, and 24 hour urine volume and sodium excretion in awake rats. Separate measurements of renal function showed that renal plasma flow and glomerular filtration rate were similar in clipped and non-clipped kidneys and not different from those in sham rats. However, urine flow, sodium excretion and urinary AGT (uAGT) excretion were significantly greater in non-clipped kidneys compared to clipped and sham kidneys. While kidney AGT protein levels were not increased significantly, AGT transcript measured by real time RT-PCR revealed that the AGT mRNA levels in the cortex were 2.15 fold significantly greater in the non-clipped kidneys than in sham (1.0±.1) or clipped kidneys (.98±.15). The results support the hypothesis that in the non-clipped kidneys of 2K1C rats there is an augmentation of intrarenal AGT mRNA synthesis which explains increased uAGT excretion rates and intrarenal Ang II levels.

JAK-STAT and the renin-angiotensin system: The role of the JAK-STAT pathway in blood pressure and intrarenal renin-angiotensin system regulation

The renin-angiotensin system (RAS) plays important roles in blood pressure control and tissue disease. An inappropriate local angiotensin II elevation in the kidneys leads to the development of hypertension, tissue damage and chronic injury. Studies have demonstrated that the JAK-STAT pathway mediates angiotensin II-triggered gene transcription. The JAK-STAT pathway in turn, acting as an amplifying system, contributes to further intrarenal RAS activation. These observations prompt the suggestion that the JAK-STAT pathway may be of importance in elucidating the mechanisms RAS-associated tissue injury. Accordingly, this review provides a brief overview of the interactions between the JAK-STAT pathway and the RAS, specifically the RAS expressed in the kidneys.