Acute inhibition of PMCA4, but not global ablation,reduces blood pressure and arterial contractility via a nNOS‐dependent mechanism

Cardiovascular disease is the world's leading cause of morbidity and mortality, with high blood pressure (BP) contributing to increased severity and number of adverse outcomes. Plasma membrane calcium ATPase 4 (PMCA4) has been previously shown to modulate systemic BP. However, published data are conflicting, with both overexpression and inhibition of PMCA4 in vivo shown to increase arterial contractility. Hence, our objective was to determine the role of PMCA4 in the regulation of BP and to further understand how PMCA4 functionally regulates BP using a novel specific inhibitor to PMCA4, aurintricarboxylic acid (ATA). Our approach assessed conscious BP and contractility of resistance arteries from PMCA4 global knockout (PMCA4KO) mice compared to wild‐type animals. Global ablation of PMCA4 had no significant effect on BP, arterial structure or isolated arterial contractility. ATA treatment significantly reduced BP and arterial contractility in wild‐type mice but had no significant effect in PMCA4KO mice. The effect of ATAin vivo and ex vivo was abolished by the neuronal nitric oxide synthase (nNOS) inhibitor Vinyl‐l ‐NIO. Thus, this highlights differences in the effects of PMCA4 ablation and acute inhibition on the vasculature. Importantly, for doses here used, we show the vascular effects of ATA to be specific for PMCA4 and that ATA may be a further experimental tool for elucidating the role of PMCA4.     

Mammary gland involution is associated with rapid down regulation of major mammary Ca-ATPases

Sixty percent of calcium in milk is transported across the mammary cells apical membrane by the plasma membrane Ca²⁺-ATPase 2 (PMCA2). The effect of abrupt cessation of milk production on the Ca²⁺-ATPases and mammary calcium transport is unknown. We found that 24 h after stopping milk production, PMCA2 and secretory pathway Ca²⁺-ATPases 1 and 2 (SPCA1 and 2) expression decreased 80-95%. PMCA4 and Sarco/Endoplasmic Reticulum Ca²⁺-ATPase 2 (SERCA2) expression increased with the loss of PMCA2, SPCA1, and SPCA2 but did not increase until 72-96 h of involution. The rapid loss of these Ca²⁺-ATPases occurs at a time of high mammary tissue calcium. These results suggest that the abrupt loss of Ca²⁺-ATPases, required by the mammary gland to regulate the large amount of calcium associated with milk production, could lead to accumulation of cell calcium, mitochondria Ca²⁺ overload, calcium mediated cell death and thus play a part in early signaling of mammary involution.     

Vasodilation and blood pressure-lowering effect mediated by 5,6-EEQ lactone in 5/6 nephrectomy hypertensive rats

Microvascular dysfunction is a key contributor to vascular hypertension, one of the most common chronic diseases in the world. Microvascular dysfunction leads to the loss of nitric oxide-mediated endothelial dilation and the subsequent compensatory function of endothelium-derived hyperpolarizing (EDH) factors in the regulation of vascular tone. Previously, we showed that lactone metabolite derived from arachidonic acid induces endothelial-dependent vasodilation in isolated human microvessels. Based on structural similarities, we hypothesize that additional lactone metabolites formed from eicosapentaenoic fatty acid (EPA) may bear EDH properties.AimTo elucidate the vasodilatory and blood pressure (BP)-reducing characteristics of the 5,6-EEQ (5,6-epoxyeicosatetraenoic acids) lactone (EPA-L) in hypertensive 5/6 nephrectomy (5/6Nx) rats.Methods5/6Nx hypertensive rats intravenously administrated with EPA-L for five days. BP, blood and urine chemistry, and kidney function were detected and analyzed. Vascular dilation was detected using a pressure myograph with or without Ca²⁺ − activated K⁺ (K_Ca) endothelial channel inhibitors. KCNN3 and KCNN4 gene expression (mRNA) detected in mesenteric arteries from 5/6Nx and NT rats.ResultsEPA-L administration to 5/6Nx rats significantly (p < 0.05) reduced BP and heart rate without affecting kidney function. 5/6Nx rat mesenteric arterioles exhibited a lower dilation response to acetylcholine (10^-7 mol/l) than normotensive (NT) vessels, while EPA-L administration restored the vessel relaxation response. The EPA-L-driven relaxation of mesenteric arteries was significantly reduced by pretreatment with TRAM-34 and apamin. However, K_Ca channel expression did not significantly differ between 5/6Nx and NT mesenteric arteries.ConclusionEPA-L reduces BP by improving microvessel dilation involving calcium-dependent potassium endothelial channels.     

Alteration of calcium homeostasis in primary preeclamptic syncytiotrophoblasts: effect on calcium exchange in placenta

Preeclampsia (PE) is characterized by maternal hypertension, proteinuria, oedema and, in 30% of cases, by intrauterine growth retardation. Causes are still unknown; however, epidemiological and clinical studies have suggested alterations in maternal calcium metabolism. We suggested that in PE, calcium transport by the syncytiotrophoblast (ST) is disturbed. From total placental tissues, we studied the expression of: calcium channels (TRPV5, TRPV6 [transient receptor potential vanilloid]), calcium binding proteins (CaBP‐9K, CaBP‐28K), plasma membrane calcium ATPase (PMCA)1,2,3,4 pumps, ATP synthase, genes implicated in Ca²⁺ release [inositol‐1,4,5‐triphosphate receptor (IP3R)1,2,3; Ryanodine receptor (RyR)1,2,3] and replenishment (SERCA1,2,3 [sarcoendoplasmic reticulum Ca²⁺ ATPases]) from endoplasmic reticulum, channels implicated in mitochondrial Ca²⁺ accumulation (VDAC1,2,3 [voltage‐dependent anion channels]) and a marker of oxidative stress (hOGG1 [Human 8‐oxoguanine‐DNA glycosylase 1]), as well as the influence of these variations on calcium transport in primary ST cultures. The mRNA and protein levels were thereby examined by real‐time PCR and Western blot analysis, respectively, in two different groups of pregnant women with similar gestational age: a normal group (n= 16) and a PE group (n= 8), diagnosed by a clinician. Our study showed a significant decrease in calcium transport by the ST cultured from preeclamptic placentas. We found a significant (P < 0.05) decrease in mRNA levels of TRPV5, TRPV6, CaBP‐9K, CaBP‐28K, PMCA1, PMCA4, ATP synthase, IP3R1, IP3R2, RyR1, RyR2 and RyR3 in PE group compared to normal one. We also noted a significant decrease in protein levels of TRPV5, TRPV6, CaBP‐9K, CaBP‐28K and PMCA1/4 in PE group. In contrast, SERCA1, SERCA2, SERCA3, VDAC3 and hOGG1 mRNA expressions were significantly increased in PE placentas. Calcium homeostasis and transport through placenta is compromised in preeclamptic pregnancies and it appears to be affected by a lack of ATP and an excess of oxidative stress.     

Heterogeneity in Arterial Remodeling among Sublines of Spontaneously Hypertensive Rats

Objectives

Spontaneously hypertensive rats (SHR) have been used frequently as a model for human essential hypertension. However, both the SHR and its normotensive control, the Wistar Kyoto rat (WKY), consist of genetically different sublines. We tested the hypothesis that the pathophysiology of vascular remodeling in hypertension differs among rat sublines.

Methods and Results

We studied mesenteric resistance arteries of WKY and SHR from three different sources, at 6 weeks and 5 months of age. Sublines of WKY and SHR showed differences in blood pressure, body weight, vascular remodeling, endothelial function, and vessel ultrastructure. Common features in small mesenteric arteries from SHR were an increase in wall thickness, wall-to-lumen ratio, and internal elastic lamina thickness.

Conclusions

Endothelial dysfunction, vascular stiffening, and inward remodeling of small mesenteric arteries are not common features of hypertension, but are subline-dependent. Differences in genetic background associate with different types of vascular remodeling in hypertensive rats.     

Intracellular renin increases the inward calcium current in smooth muscle cells of mesenteric artery of SHR. Implications for hypertension and vascular remodeling

The influence of intracellular renin on the inward calcium current in isolated smooth muscle cells from SHR mesenteric arteries was investigated. Measurements of calcium current were performed using the whole cell configuration of pCLAMP. The results indicated that: 1) renin (100 nM) dialyzed into smooth muscle cells, increased the inward calcium current; 2) verapamil (10–9 M) administered to the bath inhibited the effect of renin on the inward calcium current; 3) concurrently with the increase of calcium current a depolarization of 6.8 +/− 2.1 mV (n = 16)(P < 0.05) was found in cells dialyzed with renin; 4) intracellular dialysis of renin (100 nM) into smooth muscle cells isolated from mesenteric arteries of normal Wystar Kyoto rats showed no significant change on calcium current; 5) aliskiren (10–9 M) dialyzed into the cell together with renin (100 nM) abolished the effect of the enzyme on the calcium current in SHR; 6) Ang II (100 nM) dialyzed into the smooth muscle cell from mesenteric artery of SHR in absence of renin, decreased the calcium current-an effect greatly reduced by valsartan (10–9 M) added to the cytosol; 7) administration of renin (100 nM) plus angiotensinogen (100 nM) into the cytosol of muscles cells from SHR rats reduced the inward calcium current; 8) extracellular administration of Ang II (100 nM) increased the inward calcium current in mesenteric arteries of SHR. Conclusions: intracellular renin in vascular resistance vessels from SHR due to internalization or expression, contributes to the regulation of vascular tone and control of peripheral resistance-an effect independently of Ang II. Implications for hypertension and vascular remodeling are discussed.     

Plasma membrane calcium pump activity is affected by the membrane protein concentration: Evidence for the involvement of the actin cytoskeleton

Plasma membrane calcium pumps (PMCAs) are integral membrane proteins that actively expel Ca²⁺ from the cell. Specific Ca²⁺-ATPase activity of erythrocyte membranes increased steeply up to 1.5-5 times when the membrane protein concentration decreased from 50 μg/ml to 1 μg/ml. The activation by dilution was also observed for ATP-dependent Ca²⁺ uptake into vesicles from Sf9 cells over-expressing the PMCA 4b isoform, confirming that it is a property of the PMCA. Dilution of the protein did not modify the activation by ATP, Ca²⁺ or Ca²⁺-calmodulin. Treatment with non-ionic detergents did not abolish the dilution effect, suggesting that it was not due to resealing of the membrane vesicles. Pre-incubation of erythrocyte membranes with Cytochalasin D under conditions that promote actin polymerization abolished the dilution effect. Highly-purified, micellar PMCA showed no dilution effect and was not affected by Cytochalasin D. Taken together, these results suggest that the concentration-dependent behavior of the PMCA activity was due to interactions with cytoskeletal proteins. The dilution effect was also observed with different PMCA isoforms, indicating that this is a general phenomenon for all PMCAs.     

Activation of DNA demethylases attenuates aging‐associated arterial stiffening and hypertension

DNA methylation increases with age. The objective of this study was to investigate whether compound H, a potential activator of DNA demethylases, attenuates aging‐related arterial stiffness and hypertension. Aged mice (24–27 months) and adult mice (12 months) were used. Pulse wave velocity (PWV), a direct measure of arterial stiffness, and blood pressure (BP) were increased significantly in aged mice. Notably, daily treatments with compound H (15 mg/kg, IP) for 2 weeks significantly attenuated the aging‐related increases in PWV and BP. Compound H abolished aging‐associated downregulation of secreted Klotho (SKL) levels in both kidneys and serum likely by enhancing DNA demethylase activity and decreasing DNA methylation. Aging‐related arterial stiffness was associated with accumulation of stiffer collagen and degradation of compliant elastin which are accompanied by increased expression of MMP2, MMP9, TGF‐β1, and TGF‐β3. These changes were effectively attenuated by compound H, suggesting rejuvenation of aged arteries. Compound H also rescued downregulation of Sirt1 deacetylase, AMPKα, and eNOS activities in aortas of aged mice. In cultured smooth muscle cells (SMCc) Klotho‐deficient serum upregulated expression of MMPs and TGFβ which, however, was not affected by compound H. In conclusion, compound H attenuates aging‐associated arterial stiffness and hypertension by activation of DNA demethylase which increases renal SKL expression and consequently circulating SKL levels leading to activation of the Sirt1‐AMPK‐eNOS pathway in aortas of aged mice.     

Decreases in plasma membrane Ca2+‐ATPase in brain synaptic membrane rafts from aged rats

Precise regulation of free intracellular Ca²⁺ concentrations [Ca²⁺]_i is critical for normal neuronal function, and alterations in Ca²⁺ homeostasis are associated with brain aging and neurodegenerative diseases. One of the most important proteins controlling [Ca²⁺]_i is the plasma membrane Ca²⁺‐ATPase (PMCA), the high‐affinity transporter that fine tunes the cytosolic nanomolar levels of Ca²⁺. We previously found that PMCA protein in synaptic plasma membranes (SPMs) is decreased with advancing age and the decrease in enzyme activity is much greater than that in protein levels. In this study, we isolated raft and non‐raft fractions from rat brain SPMs and used quantitative mass spectrometry to show that the specialized lipid microdomains in SPMs, the rafts, contain 60% of total PMCA, comprised all four isoforms. The raft PMCA pool had the highest specific activity and this decreased progressively with age. The reduction in PMCA protein could not account for the dramatic activity loss. Addition of excess calmodulin to the assay did not restore PMCA activity to that in young brains. Analysis of the major raft lipids revealed a slight age‐related increase in cholesterol levels and such increases might enhance membrane lipid order and prevent further loss of PMCA activity.     

Caloxin 1b3: A novel plasma membrane Ca2+-pump isoform 1 selective inhibitor that increases cytosolic Ca2+ in endothelial cells

The purpose of this study was to invent an extracellular inhibitor selective for the plasma membrane Ca²⁺ pump(s) (PMCA) isoform 1. PMCA extrude Ca²⁺ from cells during signalling and homeostasis. PMCA isoforms are encoded by 4 genes (PMCA1–4). Pig coronary artery endothelium and smooth muscle express the genes PMCA1 and 4. We showed that the endothelial cells contained mostly PMCA1 protein while smooth muscle cells had mostly PMCA4. A random peptide phage display library was screened for binding to synthetic extracellular domain 1 of PMCA1. The selected phage population was screened further by affinity chromatography using PMCA from rabbit duodenal mucosa which expressed mostly PMCA1. The peptide displayed by the selected phage was termed caloxin 1b3. Caloxin 1b3 inhibited PMCA Ca²⁺–Mg²⁺-ATPase in the rabbit duodenal mucosa (PMCA1) with a greater affinity (inhibition constant = 17 ± 2 μM) than the PMCA in the human erythrocyte ghosts (PMCA4, inhibition constant = 45 ± 4 μM). The affinity of caloxin 1b3 was also higher for PMCA1 than for PMCA2 and 3 indicating its selectivity for PMCA1. Consistent with an inhibition of PMCA1, caloxin 1b3 addition to the medium increased cytosolic Ca²⁺ concentration in endothelial cells. Caloxin 1b3 is the first known PMCA1 selective inhibitor. We anticipate caloxin 1b3 to aid in understanding PMCA physiology in endothelium and other tissues.     

Increased sensitivity of serotonin on the voltage-dependent K channels in mesenteric arterial smooth muscle cells of OLETF rats

This study examined the mechanisms of hypertension in diabetes. We investigated the effects of serotonin (5-HT) on voltage-dependent K⁺ (Kv) channel activity, vasoconstriction, 5-HT receptor expression levels, and the involvement of protein kinase C (PKC) in mesenteric arteries of Otsuka Long-Evans Tokushima fatty (OLETF) rats compared with Long-Evans Tokushima Otsuka (LETO) rats. Blood pressure, body weight, blood glucose level, and mesenteric arterial wall thickness were greater in OLETF rats. The 5-HT-induced vasoconstriction of mesenteric arteries was greater in OLETF rats than in LETO rats and inhibited by the 5-HT_2A inhibitor inhibitor, ketanserin. The Kv currents in mesenteric arterial smooth muscle cells (MASMCs), determined using a perforated patch clamp technique, was inhibited by 1 mM 4-AP (42.5 ± 4.1% vs. 63.5 ± 2.3% in LETO vs. OLETF rats at +40 mV), but was insensitive to 1 mM TEA and 100 nM iberiotoxin. The inhibition of Kv current by 1 μM 5-HT in MASMCs was greater in OLETF rats than in LETO rats (17.1 ± 2.2% vs. 33.2 ± 2.7% in LETO vs. OLETF rats at +40 mV), and the inhibition was prevented by treatment with the PKCα- and β- selective inhibitor, Gö6976. The expression level of 5-HT_2A, but not 5-HT_2B, receptor and the expression levels of total PKC, PKCβ, and PKCε, but not PKCα, were higher in the mesenteric arteries of OLETF rats compared with LETO rats. The enhanced expression of 5-HT_2A receptor together with PKCβ may promote mesenteric vasoconstriction and increase vascular resistance in OLETF rats.     

Age attenuates the T‐type CaV3.2‐RyR axis in vascular smooth muscle

Caveolae position Ca_V3.2 (T‐type Ca²⁺ channel encoded by the α‐3.2 subunit) sufficiently close to RyR (ryanodine receptors) for extracellular Ca²⁺ influx to trigger Ca²⁺ sparks and large‐conductance Ca²⁺‐activated K⁺ channel feedback in vascular smooth muscle. We hypothesize that this mechanism of Ca²⁺ spark generation is affected by age. Using smooth muscle cells (VSMCs) from mouse mesenteric arteries, we found that both Ca_v3.2 channel inhibition by Ni²⁺ (50 µM) and caveolae disruption by methyl‐ß‐cyclodextrin or genetic abolition of Eps15 homology domain‐containing protein (EHD2) inhibited Ca²⁺ sparks in cells from young (4 months) but not old (12 months) mice. In accordance, expression of Ca_v3.2 channel was higher in mesenteric arteries from young than old mice. Similar effects were observed for caveolae density. Using SMAKO Ca_v1.2^?/? mice, caffeine (RyR activator) and thapsigargin (Ca²⁺ transport ATPase inhibitor), we found that sufficient SR Ca²⁺ load is a prerequisite for the Ca_V3.2‐RyR axis to generate Ca²⁺ sparks. We identified a fraction of Ca²⁺ sparks in aged VSMCs, which is sensitive to the TRP channel blocker Gd³⁺ (100 µM), but insensitive to Ca_V1.2 and Ca_V3.2 channel blockade. Our data demonstrate that the VSMC Ca_V3.2‐RyR axis is down‐regulated by aging. This defective Ca_V3.2‐RyR coupling is counterbalanced by a Gd³⁺ sensitive Ca²⁺ pathway providing compensatory Ca²⁺ influx for triggering Ca²⁺ sparks in aged VSMCs.     

Coexpression and estrogen-mediated regulation of TRPV6 and PMCA1 in the human endometrium during the menstrual cycle

Maintenance of calcium balance in the uterus is essential for many of its functions, including embryo implantation. The plasma membrane Ca²⁺‐pumping ATPase proteins are encoded by four genes designated PMCA1‐4, and PMCA1 is expressed in the uterus of rats during the estrous cycle. Although transient receptor potential cation channel subfamily V, member 6 (TRPV6), has been detected in the human placenta, pancreas and the prostate gland, expression patterns of uterine TRPV6 and PMCA1 and their potential roles in the human endometrium remain to be elucidated. In the present study, the expression patterns of TRPV6 and PMCA1 were examined to predict their potential roles in the human endometrium during the menstrual cycle. Human classified endometrial tissues (total n = 40) were separated into three groups according to menstrual cycle phase: menstrual, proliferative (early‐, mid‐, late), and secretory phase (early‐, mid‐, late). The expression of TRPV6 and PMCA1 mRNA and protein in the uterine endometrium during the menstrual cycle increased by 1.5‐ to 1.8‐fold at the proliferative phase (early‐, mid‐, and late‐) in comparison to the other phases. Estrogen treatment caused a significant increase in TRPV6 and PMCA1 mRNA expression. Immunohistochemical analysis of the distribution of TRPV6 and PMCA1 in the uterus revealed that both proteins are abundantly expressed in the cytoplasm of endometrial and glandular epithelial cells during menstrual phases. Taken together, these results suggest that uterine expression of TRPV6 and PMCA1 may be involved in human reproductive function. Mol. Reprod. Dev. 78:274–282, 2011. © 2011 Wiley‐Liss, Inc.     

Irradiated stem cells and ageing of the haematopoietic system

In the work presented here, changes in haematopoiesis of mice (B6129SF2/J) were studied 1 year after their whole-body exposure to a dose of 7 Gy (72% of mice survived). The irradiated mice were compared with non-irradiated younger (4 months of age) and older (16 months of age) mice. There was a significant increase in the relative abundance of primitive stem cells with long-term capability of the haematopoiesis recovery lin⁻/Sca-1⁺/CD117⁺/CD34⁻ in the bone marrow of mice aged 16 months (irradiated and non-irradiated) compared with those aged 4 months. In terms of the ability to respond to further whole-body irradiation at a dose of 1 Gy, the presence of γH2A.X foci was studied in lin⁻ bone marrow cells. There was a considerable number of persisting foci in lin⁻ stem cells isolated from the bone marrow of the older irradiated mice. In the blood count from the peripheral blood of the older mice (both non-irradiated and irradiated at 7 Gy), there was a significant increase in granulocytes. In the group exposed to 7 Gy, the numbers of thrombocytes significantly increased, and on the contrary, the numbers of erythrocytes, the amount of haemoglobin, and haematocrit significantly decreased.     

Ca<Superscript>2+</Superscript> signalling in cardiovascular disease: the role of the plasma membrane calcium pumps

The plasma membrane calcium ATPases (PMCA) are a family of genes which extrude Ca²⁺ from the cell and are involved in the maintenance of intracellular free calcium levels and/or with Ca²⁺ signalling, depending on the cell type. In the cardiovascular system, Ca²⁺ is not only essential for contraction and relaxation but also has a vital role as a second messenger in signal transduction pathways. A complex array of mechanisms regulate intracellular free calcium levels in the heart and vasculature and a failure in these systems to maintain normal Ca²⁺ homeostasis has been linked to both heart failure and hypertension. This article focuses on the functions of PMCA, in particular isoform 4 (PMCA4), in the heart and vasculature and the reported links between PMCAs and contractile function, cardiac hypertrophy, cardiac rhythm and sudden cardiac death, and blood pressure control and hypertension. It is becoming clear that this family of calcium extrusion pumps have essential roles in both cardiovascular health and disease.     

Age‐related variation in the trophic characteristics of a marsupial carnivore,the Tasmanian devil Sarcophilus harrisii

Age‐related changes in diet have implications for competitive interactions and for predator–prey dynamics, affecting individuals and groups at different life stages. To quantify patterns of variation and ontogenetic change in the diets of Tasmanian devils Sarcophilus harrisii, a threatened marsupial carnivore, we analyzed variation in the stable isotope composition of whisker tissue samples taken from 91 individual devils from Wilmot, Tasmania from December 2014 to February 2017. Both δ¹³C and δ¹⁵N decreased with increasing age in weaned Tasmanian devils, indicating that as they age devils rely less on small mammals and birds, and more on large herbivores. Devils <12 months old had broader group isotopic niches, as estimated by Bayesian standard ellipses (SEA_B mode = 1.042) than devils from 12 to 23 months old (mode = 0.541) and devils ≥24 months old (mode = 0.532). Devils <24 months old had broader individual isotopic niches (SEA_B mode range 0.492–1.083) than devils ≥24 months old (mode range 0.092–0.240). A decrease in δ¹⁵N from the older whisker sections to the more recently grown sections in devils <24 months old likely reflects the period of weaning in this species, as this pattern was not observed in devils ≥24 months old. Our data reveal changes in the isotopic composition of devil whiskers with increasing age, accompanied by a reduction in isotopic variation both among population age classes and within individuals, reflecting the effect of weaning in early life, and a likely shift from an initially diverse diet of small mammals, birds, and invertebrates towards increasing consumption of larger herbivores in adulthood.     

Identification of novel proteins and mechanistic pathways associated with early-onset hypertension by deep proteomic mapping of resistance arteries

Resistance arteries are small blood vessels that create resistance to blood flow. In hypertension, resistance arteries undergo remodeling, affecting their ability to contract and relax appropriately. To date, no study has mapped the hypertension-related proteomic changes in resistance arteries. Using a novel data-independent acquisition–mass spectrometry (DIA-MS) approach, we determined the proteomic changes in small mesenteric and renal arteries in pre- and early-onset hypertension from the spontaneously hypertensive rat (SHR) model, which represents human primary hypertension. Compared with normotensive controls, mesenteric arteries from 12-week-old SHRs had 286 proteins that were significantly up- or downregulated, whereas 52 proteins were identified as up- or downregulated in mesenteric arteries from 6-week-old SHRs. Of these proteins, 18 were also similarly regulated in SHR renal arteries. Our pathway analyses reveal several novel pathways in the pathogenesis of hypertension. Finally, using a matrisome database, we identified 38 altered extracellular-matrix-associated proteins, many of which have never previously been associated with hypertension. Taken together, this study reveals novel proteins and mechanisms that are associated with early-onset hypertension, thereby providing novel insights into disease progression.     

Altered neurochemical profile in the McGill‐R‐Thy1‐APP rat model of Alzheimer's disease: a longitudinal in vivo 1H MRS study

We investigated metabolite levels during the progression of pathology in McGill‐R‐Thy1‐APP rats, a transgenic animal model of Alzheimer's disease, and in healthy age‐matched controls. Rats were subjected to in vivo ¹H magnetic resonance spectroscopy (MRS) of the dorsal hippocampus at age 3, 9 and 12 months and of frontal cortex at 9 and 12 months. At 3 months, a stage in which only Aβ oligomers are present, lower glutamate, myo‐inositol and total choline content were apparent in McGill‐R‐Thy1‐APP rats. At age 9 months, lower levels of glutamate, GABA, N‐acetylaspartate and total choline and elevated myo‐inositol and taurine were found in dorsal hippocampus, whereas lower levels of glutamate, GABA, glutamine and N‐acetylaspartate were found in frontal cortex. At age 12 months, only the taurine level was significantly different in dorsal hippocampus, whereas taurine, myo‐inositol, N‐acetylaspartate and total creatine levels were significantly higher in frontal cortex. McGill‐R‐Thy1‐APP rats did not show the same changes in metabolite levels with age as displayed in the controls, and overall, prominent and complex metabolite differences were evident in this transgenic rat model of Alzheimer's disease. The findings also demonstrate that in vivo ¹H MRS is a powerful tool to investigate disease‐related metabolite changes in the brain.