Angiotensin II regulates brain (pro)renin receptor expression through activation of cAMP response element-binding protein

Graphene Oxide Enhances Biogenesis and Release of Exosomes in Human Ovarian Cancer Cells

BACKGROUND

Exosomes, which are nanovesicles secreted by almost all the cells, mediate intercellular communication and are involved in various physiological and pathological processes. We aimed to investigate the effects of graphene oxide (GO) on the biogenesis and release of exosomes in human ovarian cancer (SKOV3) cells.

METHODS

Exosomes were isolated using ultracentrifugation and ExoQuick and characterized by various analytical techniques. The expression levels of exosome markers were analyzed via quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

Graphene oxide (10-50 μg/mL), cisplatin (2-10 μg/mL), and C6-ceramide (5-25 μM) inhibited the cell viability, proliferation, and cytotoxicity in a dose-dependent manner. We observed that graphene oxide (GO), cisplatin (CIS), and C6-Ceramide (C6-Cer) stimulated acetylcholine esterase and neutral sphingomyelinase activity, total exosome protein concentration, and exosome counts associated with increased level of apoptosis, oxidative stress and endoplasmic reticulum stress. In contrast, GW4869 treatment inhibits biogenesis and release of exosomes. We observed that the human ovarian cancer cells secreted exosomes with typical cup-shaped morphology and surface protein biomarkers. The expression levels of TSG101, CD9, CD63, and CD81 were significantly higher in GO-treated cells than in control cells. Further, cytokine and chemokine levels were significantly higher in exosomes isolated from GO-treated SKOV3 cells than in those isolated from control cells. SKOV3 cells pre-treated with N-acetylcysteine or GW4869 displayed a significant reduction in GO-induced exosome biogenesis and release. Furthermore, endocytic inhibitors decrease exosome biogenesis and release by impairing endocytic pathways.

CONCLUSION

This study identifies GO as a potential tool for targeting the exosome pathway and stimulating exosome biogenesis and release. We believe that the knowledge acquired in this study can be potentially extended to other exosome-dominated pathologies and model systems. Furthermore, these nanoparticles can provide a promising means to enhance exosome production in SKOV3 cells.

Inhibitory effect of (pro)renin receptor decoy inhibitor PRO20 on endoplasmic reticulum stress during cardiac remodeling

Background: Ectopic activation of renin-angiotensin-system contributes to cardiovascular and renal diseases. (Pro)renin receptor (PRR) binds to renin and prorenin, participating in the progression of nephrology. However, whether PRR could be considered as a therapeutic target for cardiac remodeling and heart failure remains unknown.

Materials and methods: Transverse aortic constriction (TAC) surgery was performed to establish a mouse model of chronic pressure overload-induced cardiac remodeling. Neonatal rat cardiomyocytes (CMs) and cardiac fibroblasts (CFs) were isolated and stimulated by Angiotensin II (Ang II). PRR decoy inhibitor PRO20 was synthesized and used to evaluate its effect on cardiac remodeling.

Results: Soluble PRR and PRR were significantly upregulated in TAC-induced cardiac remodeling and Ang II-treated CMs and CFs. Results of In vivo experiments showed that suppression of PRR by PRO20 significantly retarded cardiac remodeling and heart failure indicated by morphological and echocardiographic analyses. In vitro experiments, PRO20 inhibited CM hypertrophy, and also alleviated CF activation, proliferation and extracellular matrix synthesis. Mechanically, PRO20 enhanced intracellular cAMP levels, but not affected cGMP levels in CMs and CFs. Moreover, treatment of PRO20 in CFs markedly attenuated the production of reactive oxygen species and phosphorylation of IRE1 and PERK, two well-identified markers of endoplasmic reticulum (ER) stress. Accordingly, administration of PRO20 reversed ER stressor thapsigargin-induced CM hypertrophy and CF activation/migration.

Conclusion: Taken together, these findings suggest that inhibition of PRR by PRO20 attenuates cardiac remodeling through increasing cAMP levels and reducing ER stress in both CMs and CFs.

(Pro)renin Receptor and Blood Pressure Regulation: A Focus on the Central Nervous System

The renin-angiotensin system (RAS) is classically described as a hormonal system in which angiotensin II (Ang II) is one of the main active peptides. The action of circulating Ang II on its cognate Ang II type-1 receptor (AT1R) in circumventricular organs has important roles in regulating the autonomic nervous system, blood pressure (BP) and body fluid homeostasis, and has more recently been implicated in cardiovascular metabolism. The presence of a local or tissue RAS in various tissues, including the central nervous system (CNS), is well established. However, because the level of renin, the rate-limiting enzyme in the systemic RAS, is very low in the brain, how endogenous angiotensin peptides are generated in the CNS-the focus of this review-has been the subject of considerable debate. Notable in this context is the identification of the (pro)renin receptor (PRR) as a key component of the brain RAS in the production of Ang II in the CNS. In this review, we highlight cellular and anatomical locations of the PRR in the CNS. We also summarize studies using gain- and loss-of function approaches to elucidate the functional importance of brain PRR-mediated Ang II formation and brain RAS activation, as well as PRR-mediated Ang II-independent signaling pathways, in regulating BP. We further discuss recent developments in PRR involvement in cardiovascular and metabolic diseases and present perspectives for future directions.

Increased (Pro)renin Receptor Expression in the Hypertensive Human Brain

Overactivation of the renin-angiotensin system (RAS) – a central physiological pathway involved in controlling blood pressure (BP) – leads to hypertension. It is now well-recognized that the central nervous system (CNS) has its own local RAS, and the majority of its components are known to be expressed in the brain. In physiological and pathological states, the (pro)renin receptor (PRR), a novel component of the brain RAS, plays a key role in the formation of angiotensin II (Ang II) and also mediates Ang II-independent PRR signaling. A recent study reported that neuronal PRR activation is a novel mechanism for cardiovascular and metabolic regulation in obesity and diabetes. Expression of the PRR is increased in cardiovascular regulatory nuclei in hypertensive (HTN) animal models and plays an important role in BP regulation in the CNS. To determine the clinical significance of the brain PRR in human hypertension, we investigated whether the PRR is expressed and regulated in the paraventricular nucleus of the hypothalamus (PVN) and rostral ventrolateral medulla (RVLM) – two key cardiovascular regulatory nuclei – in postmortem brain samples of normotensive (NTN) and HTN humans. Here, we report that the PRR is expressed in neurons, but not astrocytes, of the human PVN and RVLM. Notably, PRR immunoreactivity was significantly increased in both the PVN and RVLM of HTN subjects. In addition, PVN-PRR immunoreactivity was positively correlated with systolic BP (sBP) and showed a tendency toward correlation with age but not body mass index (BMI). Collectively, our data provide clinical evidence that the PRR in the PVN and RVLM may be a key molecular player in the neural regulation of BP and cardiovascular and metabolic function in humans.

The interaction partners of (pro)renin receptor in the distal nephron

The (pro)renin receptor (PRR), a key regulator of intrarenal renin-angiotensin system (RAS), is predominantly presented in podocytes, proximal tubules, distal convoluted tubules, and the apical membrane of collecting duct A-type intercalated cells, and plays a crucial role in hypertension, cardiovascular disease, kidney disease, and fluid homeostasis. In addition to its well-known renin-regulatory function, increasing evidence suggests PRR can also act in a variety of intracellular signaling cascades independently of RAS in the renal medulla, including Wnt/β-catenin signaling, cyclooxygenase-2 (COX-2)/prostaglandin E₂ (PGE₂ ) signaling, and the apelinergic system, and work as a component of the vacuolar H⁺ -ATPase. PRR and these pathways regulate the expression/activity of each other that controlling blood pressure and renal functions. In this review, we highlight recent findings regarding the antagonistic interaction between PRR and ELABELA/apelin, the mutually stimulatory relationship between PRR and COX-2/PGE₂ or Wnt/β-catenin signaling in the renal medulla, and their involvement in the regulation of intrarenal RAS thereby control blood pressure, renal injury, and urine concentrating ability in health and patho-physiological conditions. We also highlight the latest progress in the involvement of PRR for the vacuolar H⁺ -ATPase activity.

Maternal high-fructose intake induces hypertension through activating histone codes on the (pro)renin receptor promoter

High-fructose intake induces hypertension via the renal expression of (pro)renin receptor (PRR) that stimulates the expression of sodium/hydrogen exchanger 3, Na/K/2Cl cotransporter 2, and genes of the intrarenal renin-angiotensin system. We hypothesize that maternal high-fructose intake induces hypertension in subsequent generation offspring through activating histone codes on the PRR promoter. Mice dams were offered 20% fructose solution during pregnancy and lactation, while the subsequent 1st to 4th generation offspring were raised without fructose. Blood pressure was measured via tail-cuff method. The mRNA and protein expression were determined using quantitative real-time polymerase chain reaction and western blotting, respectively. Histone modification was evaluated using a chromatin immunoprecipitation assay. Maternal high-fructose intake statistically significantly increased blood pressure in the 1st and 2nd generations of offspring compared to the control group. Expression levels of sodium transporters and PRR were increased in the kidneys of the 1st to 3rd generation offspring. Increased enrichment of active histone codes such as H3Ac and H3K4me2 but decreased enrichment of repressive histone codes such as H3K9me3 and H3K27me3 on the PRR promoter were observed in the 1st to 3rd not the 4th generation. Moreover, there was increased the mRNA expression for histone acetyltransferase and methyl transferases for H3K4 in the 1st and 2nd generation offspring compared to the control group. This study implicates that maternal high-fructose intake induces hypertension in multigenerational offspring through activating histone codes on the PRR promoter.

Angiotensin II represses Npr1 expression and receptor function by recruitment of transcription factors CREB and HSF-4a and activation of HDACs

The two vasoactive hormones, angiotensin II (ANG II; vasoconstrictive) and atrial natriuretic peptide (ANP; vasodilatory) antagonize the biological actions of each other. ANP acting through natriuretic peptide receptor-A (NPRA) lowers blood pressure and blood volume. We tested hypothesis that ANG II plays critical roles in the transcriptional repression of Npr1 (encoding NPRA) and receptor function. ANG II significantly decreased NPRA mRNA and protein levels and cGMP accumulation in cultured mesangial cells and attenuated ANP-mediated relaxation of aortic rings ex vivo. The transcription factors, cAMP-response element-binding protein (CREB) and heat-shock factor-4a (HSF-4a) facilitated the ANG II-mediated repressive effects on Npr1 transcription. Tyrosine kinase (TK) inhibitor, genistein and phosphatidylinositol 3-kinase (PI-3K) inhibitor, wortmannin reversed the ANG II-dependent repression of Npr1 transcription and receptor function. ANG II enhanced the activities of Class I histone deacetylases (HDACs 1/2), thereby decreased histone acetylation of H3K9/14ac and H4K8ac. The repressive effect of ANG II on Npr1 transcription and receptor signaling seems to be transduced by TK and PI-3K pathways and modulated by CREB, HSF-4a, HDACs, and modified histones. The current findings suggest that ANG II-mediated repressive mechanisms of Npr1 transcription and receptor function may provide new molecular targets for treatment and prevention of hypertension and cardiovascular diseases.

The (pro)renin receptor in health and disease

The (pro)renin receptor ((P)RR) was first identified as a single-transmembrane receptor in human kidneys and initially attracted attention owing to its potential role as a regulator of the tissue renin-angiotensin system (RAS). Subsequent studies found that the (P)RR is widely distributed in organs throughout the body, including the kidneys, heart, brain, eyes, placenta and the immune system, and has multifaceted functions in vivo. The (P)RR has roles in various physiological processes, such as the cell cycle, autophagy, acid-base balance, energy metabolism, embryonic development, T cell homeostasis, water balance, blood pressure regulation, cardiac remodelling and maintenance of podocyte structure. These roles of the (P)RR are mediated by its effects on important biological systems and pathways including the tissue RAS, vacuolar H⁺-ATPase, Wnt, partitioning defective homologue (Par) and tyrosine phosphorylation. In addition, the (P)RR has been reported to contribute to the pathogenesis of diseases such as fibrosis, hypertension, pre-eclampsia, diabetic microangiopathy, acute kidney injury, cardiovascular disease, cancer and obesity. Current evidence suggests that the (P)RR has key roles in the normal development and maintenance of vital organs and that dysfunction of the (P)RR is associated with diseases that are characterized by a disruption of the homeostasis of physiological functions.

Effect of heme oxygenase 1 and renin/prorenin receptor on oxidized low-density lipoprotein-induced human umbilical vein endothelial cells

The incidence of depression has previously been correlated to hypertension. The aim of the present study was to explore the mechanisms of depression and hypertension by examining the expression and interaction of renin/prorenin receptor (PRR) and heme oxygenase 1 (HO-1) in vascular endothelial cells. A case-control study was conducted, and general data and serum factors were compared between hypertension patients complicated with depression and patients with hypertension alone. Logistic regression analysis was used to detect risk factors associated with hypertension complicated with depression. In addition, human umbilical vein endothelial cells (HUVECs) were treated with oxidized low-density lipoprotein (ox-LDL) and/or PRR gene silencing, and a Cell Counting Kit-8 (CCK-8) assay was performed to test their proliferation. The concentrations of inflammatory factors and oxidative stress factor were also detected using enzyme-linked immunosorbent assay and chemical colorimetry. Western blot analysis and reverse transcription-quantitative polymerase chain reaction were applied to detect protein and mRNA expression levels, respectively. The results revealed that HO-1 and renin precursor (Rep) were independent factors that affected hypertension complicated with depression. Serum HO-1 levels in patients with hypertension complicated with depression were significantly lower than that in hypertensive patients without depression, while Rep levels in patients with hypertension complicated with depression were significantly higher than that in hypertensive patients without depression. In HUVECs, ox-LDL reduced the cell proliferation in a dose-dependent manner, upregulated the expression of PRR gene and downregulated the expression of HO-1 gene. It was also observed that silencing of the PRR gene promoted the expression of the HO-1 gene. Furthermore, ox-LDL upregulated the inflammatory response and oxidative stress levels, while PRR gene silencing inhibited the ox-LDL-induced inflammatory factor and oxidative stress levels in HUVECs. Thus, regulating the expression levels of HO-1 and PRR to inhibit the oxidative stress and pro-inflammatory effect of ox-LDL may provide new insight for the treatment of hypertension patients with depression.

(Pro)renin receptor knockdown in the paraventricular nucleus of the hypothalamus attenuates hypertension development and AT1 receptor-mediated calcium events

Activation of the brain renin-angiotensin system (RAS) is a pivotal step in the pathogenesis of hypertension. The paraventricular nucleus (PVN) of the hypothalamus is a critical part of the angiotensinergic sympatho-excitatory neuronal network involved in neural control of blood pressure and hypertension. However, the importance of the PVN (pro)renin receptor (PVN-PRR)-a key component of the brain RAS-in hypertension development has not been examined. In this study, we investigated the involvement and mechanisms of the PVN-PRR in DOCA-salt-induced hypertension, a mouse model of hypertension. Using nanoinjection of adeno-associated virus-mediated Cre recombinase expression to knock down the PRR specifically in the PVN, we report here that PVN-PRR knockdown attenuated the enhanced blood pressure and sympathetic tone associated with hypertension. Mechanistically, we found that PVN-PRR knockdown was associated with reduced activation of ERK (extracellular signal-regulated kinase)-1/2 in the PVN and rostral ventrolateral medulla during hypertension. In addition, using the genetically encoded Ca²⁺ biosensor GCaMP6 to monitor Ca²⁺-signaling events in the neurons of PVN brain slices, we identified a reduction in angiotensin II type 1 receptor-mediated Ca²⁺ activity as part of the mechanism by which PVN-PRR knockdown attenuates hypertension. Our study demonstrates an essential role of the PRR in PVN neurons in hypertension through regulation of ERK1/2 activation and angiotensin II type 1 receptor-mediated Ca²⁺ activity. NEW & NOTEWORTHY PRR knockdown in PVN neurons attenuates the development of DOCA-salt hypertension and autonomic dysfunction through a decrease in ERK1/2 activation in the PVN and RVLM during hypertension. In addition, PRR knockdown reduced AT_1aR expression and AT₁R-mediated calcium activity during hypertension. Furthermore, we characterized the neuronal targeting specificity of AAV serotype 2 in the mouse PVN and validated the advantages of the genetically encoded calcium biosensor GCaMP6 in visualizing neuronal calcium activity in the PVN.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Glial-neuronal signaling mechanisms underlying the neuroinflammatory effects of manganese

BACKGROUND

Exposure to increased manganese (Mn) causes inflammation and neuronal injury in the cortex and basal ganglia, resulting in neurological symptoms resembling Parkinson's disease. The mechanisms underlying neuronal death from exposure to Mn are not well understood but involve inflammatory activation of microglia and astrocytes. Expression of neurotoxic inflammatory genes in glia is highly regulated through the NF-κB pathway, but factors modulating neurotoxic glial-glial and glial-neuronal signaling by Mn are not well understood.

METHODS

We examined the role of NF-κB in Mn-induced neurotoxicity by exposing purified microglia, astrocytes (from wild-type and astrocyte-specific IKK knockout mice), and mixed glial cultures to varying Mn concentrations and then treating neurons with the conditioned media (GCM) of each cell type. We hypothesized that mixed glial cultures exposed to Mn (0-100 μM) would enhance glial activation and neuronal death compared to microglia, wild-type astrocytes, or IKK-knockout astrocytes alone or in mixed cultures.

RESULTS

Mixed glial cultures treated with 0-100 μM Mn for 24 h showed the most pronounced effect of increased expression of inflammatory genes including inducible nitric oxide synthase (Nos2), Tnf, Ccl5, Il6, Ccr2, Il1b, and the astrocyte-specific genes, C3 and Ccl2. Gene deletion of IKK2 in astrocytes dramatically reduced cytokine release in Mn-treated mixed glial cultures. Measurement of neuronal viability and apoptosis following exposure to Mn-GCM demonstrated that mixed glial cultures induced greater neuronal death than either cell type alone. Loss of IKK in astrocytes also decreased neuronal death compared to microglia alone, wild-type astrocytes, or mixed glia.

CONCLUSIONS

This suggests that astrocytes are a critical mediator of Mn neurotoxicity through enhanced expression of inflammatory cytokines and chemokines, including those most associated with a reactive phenotype such as CCL2 but not C3.

DOCA-Salt Hypertension: an Update

Hypertension is a multifaceted disease that is involved in ∼40% of cardiovascular mortalities and is the result of both genetic and environmental factors. Because of its complexity, hypertension has been studied by using various models and approaches, each of which tends to focus on individual organs or tissues to isolate the most critical and treatable causes of hypertension and the related damage to end-organs. Animal models of hypertension have ranged from Goldblatt's kidney clip models in which the origin of the disease is clearly renal to animals that spontaneously develop hypertension either through targeted genetic manipulations, such as the TGR(mRen2)27, or selective breeding resulting in more enigmatic origins, as exemplified by the spontaneously hypertensive rat (SHR). These two genetically derived models simulate the less-common human primary hypertension in which research has been able to define a Mendelian linkage. Several models are more neurogenic or endocrine in nature and illustrate that crosstalk between the nervous system and hormones can cause a significant rise in blood pressure (BP). This review will examine one of these neurogenic models of hypertension, i.e., the deoxycorticosterone acetate (DOCA), reduced renal mass, and high-salt diet (DOCA-salt) rodent model, one of the most common experimental models used today. Although the DOCA-salt model is mainly believed to be neurogenic and has been shown to impact the central and peripheral nervous systems, it also significantly involves many other body organs.

Overexpression of the neuronal human (pro)renin receptor mediates angiotensin II-independent blood pressure regulation in the central nervous system

Despite advances in antihypertensive therapeutics, at least 15-20% of hypertensive patients have resistant hypertension through mechanisms that remain poorly understood. In this study, we provide a new mechanism for the regulation of blood pressure (BP) in the central nervous system (CNS) by the (pro)renin receptor (PRR), a recently identified component of the renin-angiotensin system that mediates ANG II formation in the CNS. Although PRR also mediates ANG II-independent signaling, the importance of these pathways in BP regulation is unknown. Here, we developed a unique transgenic mouse model overexpressing human PRR (hPRR) specifically in neurons (Syn-hPRR). Intracerebroventricular infusion of human prorenin caused increased BP in Syn-hPRR mice. This BP response was attenuated by a NADPH oxidase (NOX) inhibitor but not by antihypertensive agents that target the renin-angiotensin system. Using a brain-targeted genetic knockdown approach, we found that NOX4 was the key isoform responsible for the prorenin-induced elevation of BP in Syn-hPRR mice. Moreover, inhibition of ERK significantly attenuated the increase in NOX activity and BP induced by human prorenin. Collectively, our findings indicate that an ANG II-independent, PRR-mediated signaling pathway regulates BP in the CNS by a PRR-ERK-NOX4 mechanism. NEW & NOTEWORTHY This study characterizes a new transgenic mouse model with overexpression of the human (pro)renin receptor in neurons and demonstrated a novel angiotensin II-independent mechanism mediated by human prorenin and the (pro)renin receptor in the central regulation of blood pressure.

Increased (pro)renin receptor expression in the subfornical organ of hypertensive humans

The central nervous system plays an important role in essential hypertension in humans and in animal models of hypertension through modulation of sympathetic activity and Na⁺ and body fluid homeostasis. Data from animal models of hypertension suggest that the renin-angiotensin system in the subfornical organ (SFO) of the brain is critical for hypertension development. We recently reported that the brain (pro)renin receptor (PRR) is a novel component of the brain renin-angiotensin system and could be a key initiator of the pathogenesis of hypertension. Here, we examined the expression level and cellular distribution of PRR in the SFO of postmortem human brains to assess its association with the pathogenesis of human hypertension. Postmortem SFO tissues were collected from hypertensive and normotensive human subjects. Immunolabeling for the PRR and a retrospective analysis of clinical data were performed. We found that human PRR was prominently expressed in most neurons and microglia, but not in astrocytes, in the SFO. Importantly, PRR levels in the SFO were elevated in hypertensive subjects. Moreover, PRR immunoreactivity was significantly correlated with systolic blood pressure but not body weight, age, or diastolic blood pressure. Interestingly, this correlation was independent of antihypertensive drug therapy. Our data indicate that PRR in the SFO may be a key molecular player in the pathogenesis of human hypertension and, as such, could be an important focus of efforts to understand the neurogenic origin of hypertension. NEW & NOTEWORTHY This study provides evidence that, in the subfornical organ of the human brain, the (pro)renin receptor is expressed in neurons and microglia cells but not in astrocytes. More importantly, (pro)renin receptor immunoreactivity in the subfornical organ is increased in hypertensive humans and is significantly correlated with systolic blood pressure.

Cellular selectivity of AAV serotypes for gene delivery in neurons and astrocytes by neonatal intracerebroventricular injection

The non-pathogenic parvovirus, adeno-associated virus (AAV), is an efficient vector for transgene expression in vivo and shows promise for treatment of brain disorders in clinical trials. Currently, there are more than 100 AAV serotypes identified that differ in the binding capacity of capsid proteins to specific cell surface receptors that can transduce different cell types and brain regions in the CNS. In the current study, multiple AAV serotypes expressing a GFP reporter (AAV1, AAV2/1, AAVDJ, AAV8, AAVDJ8, AAV9, AAVDJ9) were screened for their infectivity in both primary murine astrocyte and neuronal cell cultures. AAV2/1, AAVDJ8 and AAV9 were selected for further investigation of their tropism throughout different brain regions and cell types. Each AAV was administered to P0-neonatal mice via intracerebroventricular injections (ICV). Brains were then systematically analyzed for GFP expression at 3 or 6 weeks post-infection in various regions, including the olfactory bulb, striatum, cortex, hippocampus, substantia nigra (SN) and cerebellum. Cell counting data revealed that AAV2/1 infections were more prevalent in the cortical layers but penetrated to the midbrain less than AAVDJ8 and AAV9. Additionally, there were differences in the persistence of viral transgene expression amongst the three serotypes examined in vivo at 3 and 6 weeks post-infection. Because AAV-mediated transgene expression is of interest in neurodegenerative diseases such as Parkinson's Disease, we examined the SN with microscopy techniques, such as CLARITY tissue transmutation, to identify AAV serotypes that resulted in optimal transgene expression in either astrocytes or dopaminergic neurons. AAVDJ8 displayed more tropism in astrocytes compared to AAV9 in the SN region. We conclude that ICV injection results in lasting expression of virally encoded transgene when using AAV vectors and that specific AAV serotypes are required to selectively deliver transgenes of interest to different brain regions in both astrocytes and neurons.

(Pro)renin receptor as a therapeutic target for the treatment of cardiovascular diseases?

The discovery of the (pro)renin receptor [(P)RR] 15years ago stimulated ideas on prorenin being more than renin's inactive precursor. Indeed, binding of prorenin to the (P)RR induces a conformational change in the prorenin molecule, allowing it to display angiotensin-generating activity, and additionally results in intracellular signaling in an angiotensin-independent manner. However, the prorenin levels required to observe these angiotensin-dependent and -independent effects of the (P)RR are many orders above its in vivo concentrations, both under normal and pathological conditions. Given this requirement, the idea that the (P)RR has a function within the renin-angiotensin system (RAS) is now being abandoned. Instead, research is now focused on the (P)RR as an accessory protein of vacuolar H⁺-ATPase (V-ATPase), potentially determining its integrity. Acting as an adaptor between Frizzled co-receptor LRP6 and V-ATPase, the (P)RR appears to be indispensable for Wnt/β-catenin signaling, thus explaining why (P)RR deletion (unlike renin deletion) is lethal even when restricted to specific cells, such as cardiomyocytes, podocytes and smooth muscle cells. Furthermore, recent studies suggest that the (P)RR may play important roles in lipoprotein metabolism and overall energy metabolism. In this review, we summarize the controversial RAS-related effects of the (P)RR, and critically review the novel non-RAS-related functions of the (P)RR, ending with a discussion on the potential of targeting the (P)RR to treat cardiovascular diseases.

(Pro)renin Receptor Is an Amplifier of Wnt/β-Catenin Signaling in Kidney Injury and Fibrosis

The (pro)renin receptor (PRR) is a transmembrane protein with multiple functions. However, its regulation and role in the pathogenesis of CKD remain poorly defined. Here, we report that PRR is a downstream target and an essential component of Wnt/β-catenin signaling. In mouse models, induction of CKD by ischemia-reperfusion injury (IRI), adriamycin, or angiotensin II infusion upregulated PRR expression in kidney tubular epithelium. Immunohistochemical staining of kidney biopsy specimens also revealed induction of renal PRR in human CKD. Overexpression of either Wnt1 or β-catenin induced PRR mRNA and protein expression in vitro Notably, forced expression of PRR potentiated Wnt1-mediated β-catenin activation and augmented the expression of downstream targets such as fibronectin, plasminogen activator inhibitor 1, and α-smooth muscle actin (α-SMA). Conversely, knockdown of PRR by siRNA abolished β-catenin activation. PRR potentiation of Wnt/β-catenin signaling did not require renin, but required vacuolar H⁺ ATPase activity. In the mouse model of IRI, transfection with PRR or Wnt1 expression vectors promoted β-catenin activation, aggravated kidney dysfunction, and worsened renal inflammation and fibrotic lesions. Coexpression of PRR and Wnt1 had a synergistic effect. In contrast, knockdown of PRR expression ameliorated kidney injury and fibrosis after IRI. These results indicate that PRR is both a downstream target and a crucial element in Wnt signal transmission. We conclude that PRR can promote kidney injury and fibrosis by amplifying Wnt/β-catenin signaling.

The critical role of the central nervous system (pro)renin receptor in regulating systemic blood pressure

The systemic renin-angiotensin system (RAS) has long been recognized as a critically important system in blood pressure (BP) regulation. However, extensive evidence has shown that a majority of RAS components are also present in many tissues and play indispensable roles in BP regulation. Here, we review evidence that RAS components, notably including the newly identified (pro)renin receptor (PRR), are present in the brain and are essential for the central regulation of BP. Binding of the PRR to its ligand, prorenin or renin, increases BP and promotes progression of cardiovascular diseases in an angiotensin II-dependent and -independent manner, establishing the PRR a promising antihypertensive drug target. We also review the existing PRR blockers, including handle region peptide and PRO20, and propose a rationale for blocking prorenin/PRR activation as a therapeutic approach that does not affect the actions of the PRR in vacuolar H(+)-ATPase and development. Finally, we summarize categories of currently available antihypertensive drugs and consider future perspectives.

A novel synthetic activator of Nurr1 induces dopaminergic gene expression and protects against 6-hydroxydopamine neurotoxicity in vitro

Degeneration of dopaminergic neurons in Parkinson's disease (PD) is associated with decreased expression of the orphan nuclear receptor Nurr1 (NR4A2), which is critical for both homeostasis and development of dopamine (DA) neurons. The synthetic, phytochemical-based compound, 1,1-bis (3'-indolyl)-1-(p-chlorophenyl) methane (C-DIM12) activates Nurr1 in cancer cells and prevents loss of dopaminergic neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of PD in mice. In the present study, we examined the capacity of C-DIM12 to induce expression of Nurr1-regulated genes in two dopaminergic neuronal cell lines (N2A, N27) and to protect against 6-hydroxydopamine (6-OHDA) neurotoxicity. C-DIM12 induced expression of Nurr1-regulated genes that was abolished by Nurr1 knockdown. C-DIM12 increased expression of transfected human Nurr1, induced Nurr1 protein expression in primary dopaminergic neurons and enhanced neuronal survival from exposure to 6-OHDA. These data indicate that C-DIM12 stimulates neuroprotective expression Nurr1-regulated genes in DA neurons.

Trichostatin A Modulates Angiotensin II-induced Vasoconstriction and Blood Pressure Via Inhibition of p66shc Activation

Histone deacetylase (HDAC) has been recognized as a potentially useful therapeutic target for cardiovascular disorders. However, the effect of the HDAC inhibitor, trichostatin A (TSA), on vasoreactivity and hypertension remains unknown. We performed aortic coarctation at the inter-renal level in rats in order to create a hypertensive rat model. Hypertension induced by abdominal aortic coarctation was significantly suppressed by chronic treatment with TSA (0.5 mg/kg/day for 7 days). Nicotinamide adenine dinucleotide phosphate-driven reactive oxygen species production was also reduced in the aortas of TSA-treated aortic coarctation rats. The vasoconstriction induced by angiotensin II (Ang II, 100 nM) was inhibited by TSA in both endothelium-intact and endothelium-denuded rat aortas, suggesting that TSA has mainly acted in vascular smooth muscle cells (VSMCs). In cultured rat aortic VSMCs, Ang II increased p66shc phosphorylation, which was inhibited by the Ang II receptor type I (AT1R) inhibitor, valsartan (10 µM), but not by the AT2R inhibitor, PD123319. TSA (1~10 µM) inhibited Ang II-induced p66shc phosphorylation in VSMCs and in HEK293T cells expressing AT1R. Taken together, these results suggest that TSA treatment inhibited vasoconstriction and hypertension via inhibition of Ang II-induced phosphorylation of p66shc through AT1R.