High-Resolution NMR Structures of Intrastrand Hairpins Formed by CTG Trinucleotide Repeats.

The CAG and CTG trinucleotide repeat expansions cause more than 10 human neurodegenerative diseases. Intrastrand hairpins formed by trinucleotide repeats contribute to repeat expansions, establishing them as potential drug targets. High-resolution structural determination of CAG and CTG hairpins poses as a long-standing goal to aid drug development, yet it has not been realized due to the intrinsic conformational flexibility of repetitive sequences. We herein investigate the solution structures of CTG hairpins using nuclear magnetic resonance (NMR) spectroscopy and found that four CTG repeats with a clamping G-C base pair was able to form a stable hairpin structure. We determine the first solution NMR structure of dG(CTG)4C hairpin and decipher a type I folding geometry of the TGCT tetraloop, wherein the two thymine residues form a T·T loop-closing base pair and the first three loop residues continuously stack. We further reveal that the CTG hairpin can be bound and stabilized by a small-molecule ligand, and the binding interferes with replication of a DNA template containing CTG repeats. Our determined high-resolution structures lay an important foundation for studying molecular interactions between native CTG hairpins and ligands, and benefit drug development for trinucleotide repeat expansion diseases.

Photoprotective energy quenching in the red alga Porphyridium purpureum occurs at the core antenna of the photosystem II but not at its reaction center.

Photosynthetic organisms have evolved light-harvesting antennae over time. In cyanobacteria, external phycobilisomes (PBSs) are the dominant antennae, whereas in green algae and higher plants, PBSs have been replaced by proteins of the Lhc family that are integrated in the membrane. Red algae represent an evolutionary intermediate between these two systems, as they employ both PBSs and membrane LHCR proteins as light-harvesting units. Understanding how red algae cope with light is not only interesting for biotechnological applications, but is also of evolutionary interest. For example, energy-dependent quenching (qE) is an essential photoprotective mechanism widely used by species from cyanobacteria to higher plants to avoid light damage; however, the quenching mechanism in red algae remains largely unexplored. Here, we used both pulse amplitude-modulated (PAM) and time-resolved chlorophyll fluorescence to characterize qE kinetics in the red alga Porphyridium purpureum. PAM traces confirmed that qE in P. purpureum is activated by a decrease in the thylakoid lumen pH, whereas time-resolved fluorescence results further revealed the quenching site and ultrafast quenching kinetics. We found that quenching exclusively takes place in the photosystem II (PSII) complexes and preferentially occurs at PSII's core antenna rather than at its reaction center, with an overall quenching rate of 17.6 ± 3.0 ns-1. In conclusion, we propose that qE in red algae is not a reaction center type of quenching, and that there might be a membrane-bound protein that resembles PsbS of higher plants or LHCSR of green algae that senses low luminal pH and triggers qE in red algae.

Molecular Engineering of Aptamer Self-Assemblies Increases in Vivo Stability and Targeted Recognition.

Functionally modified aptamer conjugates are promising tools for targeted imaging or treatment of various diseases. However, broad applications of aptamer molecules are limited by their in vivo instability. To overcome this challenge, current strategies mostly rely on covalent chemical modification of aptamers, a complicated process that requires case-by-case sequence design, multiple-step synthesis, and purification. Herein, we report a covalent modification-free strategy to enhance the in vivo stability of aptamers. This strategy simply utilizes one-step molecular engineering of aptamers with gold nanoclusters (GNCs) to form GNCs@aptamer self-assemblies. Using Sgc8 as a representative aptamer, the resulting GNCs@Sgc8 assemblies enhance cancer-cell-specific binding and sequential internalization by a receptor-mediated endocytosis pathway. Importantly, the GNCs@aptamer self-assemblies resist nuclease degradation for as long as 48 h, compared to the degradation of aptamer alone at 3 h. In parallel, the tumor-targeted recognition and retention of GNCs@aptamer self-assemblies are dramatically enhanced, indicated by a 9-fold signal increase inside the tumor compared to the aptamer alone. This strategy is to avoid complicated chemical modification of aptamers and can be extended to all aptamers. Our work provides a simple, effective, and universal strategy for enhancing the in vivo stability of any aptamer or its conjugates, thus expanding their imaging and therapeutic applications.

Radiation properties of quantum emitters via a plasmonic waveguide integrated with a V-shaped traveling wave antenna.

We experimentally study the radiation direction and relaxation rate of quantum emitters (QEs) coupled with a plasmonic waveguide integrated with a V-shaped traveling wave antenna. The plasmonic waveguide couples the excitation energy of the nearby QEs into surface plasmons and the connected V-shaped traveling wave antenna converts them into highly directional radiation. The directivity of the radiation depends on the shape of the antenna. The half-power beam widths of the radiation with respect to the azimuthal and polar angles are as small as 15.1° and 13.1°, respectively, when the antenna has a 144° intersection angle. The relaxation rates of the QEs are enhanced up to 33.04 times relative to the intrinsic emission rate. The method to control the fluorescence of QEs is of great significance for optical devices, nanoscale light sources, and integrated optics.

Nanoscale Refractive Index Sensors with High Figures of Merit via Optical Slot Antennas.

Nanoscale refractive index (RI) sensors based on a single nanorod or nanoantenna typically suffer from a low figure of merit (FOM) due to the large full width at half-maximum of the plasmonic dipole resonance. Here, we demonstrate nanosensors with a high FOM and a sensing volume that is much smaller than λ3 using slot antennas. Two configurations, one based on a bowtie slot antenna (BSA) and one based on a slot antenna pair (SAP), are proposed. The RI information is obtained from the extinction dip that is due to the interference of surface plasmon polaritons (SPPs), which are launched at different nodes of a third-order resonant mode of the BSA or different antennas of the SAP. The high FOM is attributed to the dependence of the extinction spectrum on both the amplitude and the phase of the SPPs. There are important applications for these nanosensors, which can measure the local RI beyond the diffraction limit and can be flexibly integrated.

Prenatal hypoxia plus postnatal high-fat diet exacerbated vascular dysfunction via up-regulated vascular Cav1.2 channels in offspring rats.

BACKGROUND: This study aimed to examine whether and how postnatal high-fat diet had additional impact on promoting vascular dysfunction in the offspring exposed to prenatal hypoxia. METHODS AND RESULTS: Pregnant Sprague-Dawley rats were randomly assigned to hypoxia (10.5% oxygen) or normoxia (21% O2 ) groups from gestation days 5-21. A subset of male offspring was placed on a high-fat diet (HF, 45% fat) from 4-16 weeks of age. Prenatal hypoxia induced a decrease in birth weight. In offspring-fed HF diet, prenatal hypoxia was associated with increased fasting plasma triglyceride, total cholesterol, free fatty acids, and low-density lipoprotein-cholesterol. Compared with the other three groups, prenatal hypoxic offspring with high-fat diet showed a significant increase in blood pressure, phenylephrine-mediated vasoconstrictions, L-type voltage-gated Ca2+ (Cav1.2) channel currents, and elevated mRNA and protein expression of Cav1.2 α1 subunit in mesenteric arteries or myocytes. The large-conductance Ca2+-activated K+ (BK) channels currents and the BK channel units (ß1, not α-subunits) were significantly increased in mesenteric arteries or myocytes in HF offspring independent of prenatal hypoxia factor. CONCLUSION: The results demonstrated that prenatal hypoxia followed by postnatal HF caused vascular dysfunction through ion channel remodelling in myocytes.

Magnesium Sulfate-Mediated Vascular Relaxation and Calcium Channel Activity in Placental Vessels Different From Nonplacental Vessels.

BACKGROUND: Magnesium sulfate (MgSO4) has been used as a common therapy for preeclampsia and eclampsia for many years. MgSO4 decreases peripheral vascular resistance so as to reduce maternal blood pressure. Whether placental blood vessels react to MgSO4 in the same patterns as that in maternal vessels is largely unknown. METHODS AND RESULTS: This study compared placental vessels (PV) versus nonplacental vessels (non-PV) in human and animal models. MgSO4-caused vascular dilation was significantly weaker in PV than that in non-PV. Prostaglandin I2 synthetase affected MgSO4-mediated vasodilatation in PV, not in umbilical vessels, while cyclooxygenase did not influence MgSO4-induced relaxation in both PV and non-PV. Mg2+-caused vasodilatation was mainly through calcium channels. In PV, calcium channel activities were significantly weaker in PV than that in non-PV. Relative mRNA expression of CACNA1D, CACNB2, and CACNB3 was significantly higher in PV than those in umbilical vessels, despite the fact that the expression of CACNA1F was less in PV. The contractile phenotype of smooth muscle cell marker (CALD1) was less and the synthetic phenotype (MYH10) was more in PV than that in UV. CONCLUSIONS: These results demonstrated that PV were characterized by much weaker responses to MgSO4 compared with nonplacental vessels. The difference was related to weaker calcium channel activity and minor contractile phenotype smooth muscle cells in PV, providing important information for further understanding treatments with MgSO4 in preeclampsia.

Methylation-reprogrammed Wnt/ß-catenin signalling mediated prenatal hypoxia-induced brain injury in foetal and offspring rats.

Prenatal hypoxia (PH) is a common pregnancy complication, harmful to brain development. This study investigated whether and how PH affected Wnt pathway in the brain. Pregnant rats were exposed to hypoxia (10.5% O2 ) or normoxia (21% O2 ; Control). Foetal brain weight and body weight were decreased in the PH group, the ratio of brain weight to body weight was increased significantly. Prenatal hypoxia increased mRNA expression of Wnt3a, Wnt7a, Wnt7b and Fzd4, but not Lrp6. Activated ß-catenin protein and Fosl1 expression were also significantly up-regulated. Increased Hif1a expression was found in the PH group associated with the higher Wnt signalling. Among 5 members of the Sfrp family, Sfrp4 was down-regulated. In the methylation-regulating genes, higher mRNA expressions of Dnmt1 and Dnmt3b were found in the PH group. Sodium bisulphite and sequencing revealed hyper-methylation in the promoter region of Sfrp4 gene in the foetal brain, accounting for its decreased expression and contributing to the activation of the Wnt-Catenin signalling. The study of PC12 cells treated with 5-aza further approved that decreased methylation could result in the higher Sfrp4 expression. In the offspring hippocampus, protein levels of Hif1a and mRNA expression of Sfrp4 were unchanged, whereas Wnt signal pathway was inhibited. The data demonstrated that PH activated the Wnt pathway in the foetal brain, related to the hyper-methylation of Sfrp4 as well as Hif1a signalling. Activated Wnt signalling might play acute protective roles to the foetal brain in response to hypoxia, also would result in disadvantageous influence on the offspring in long-term.

Regulation of cerebral arterial BKCa channels by angiotensin II signaling in adult offspring exposed to prenatal high sucrose diets.

Prenatal insults have been shown to affect vascular functions, leading to increased risks of cardiovascular diseases in offspring. The present study determined whether high sucrose (HS) intake in pregnancy affected central vascular functions in middle cerebral artery (MCA) of offspring. Sprague-Dawley rats were fed a standard food and tap water with normal or high (20%) sucrose content during pregnancy. Offspring were maintained with normal diets and tap water. Central vascular functions and related ion channels were assessed in male offspring at 5 months old. Compared with the control, angiotensin II (AII)-induced vasoconstrictions were significantly higher in the MCA of the offspring exposed to prenatal HS. In the MCA, large conductance Ca2+-activated K+ channels (BKCa) currents were decreased with a reduction of opening frequency, sensitivity to intracellular Ca2+/membrane voltage, and BKß1 expression. mRNA levels of AT1α and AT2, as well as AT1/AT2 ratio, were significantly increased in the MCA of offspring following exposure to prenatal HS diets. The data suggested that prenatal HS diets could alter microvascular activities in the MCA, probably via changes of BKCa channels in the brain.

Prenatal high sucrose intake affected learning and memory of aged rat offspring with abnormal oxidative stress and NMDARs/Wnt signaling in the hippocampus.

Maternal over-nutrition may predispose offspring to obesity, type 2 diabetes and other adult diseases. The present study investigated long-term impact of prenatal high sucrose (HS) diets on cognitive capabilities in aged rat offspring. The fasting plasma glucose concentration did not differ between the control and HS groups. However, the fasting plasma insulin and insulin resistance index values were significantly increased in HS offspring that showed abnormal glucose tolerance test. HS offspring exhibited increased escape latency and swimming path length to the platform, and reduced time in the target quadrant and the number of crossing the platform, as compared with the control group. The expression of Grin2b/NR2B, Wnt2, Wnt3a and active form of ß-catenin protein were decreased, and Dickkopf-related protein 1 was increased in the HS group. In addition, the levels of lipid peroxidation biomarker thiobarbituricacid reactive substance, nicotinamide adenine dinucleotide phosphate oxidases 2 and superoxide dismutase 1 were significantly increased, and the activity of catalase was decreased in the hippocampus in the HS group. The results demonstrate that prenatal HS-induced metabolic changes cause cognitive deficits in aged rat offspring, probably due to altered N-methyl-d-aspartate receptors/Wnt signaling and oxidative stress in the hippocampus.

Prenatal exposure to the Great Chinese Famine and mid-age hypertension.

BACKGROUND: One of the most terrible famines last century was Great Chinese Famine (GCF) in 1959~1961 when millions of people died from starving. Under-nutrition during famine between the Western and Eastern (Dutch Hungry vs. GCF) was similar, while cardiovascular consequences might not be the same. Addressing such questions may gain new insight into prevention of cardiovascular diseases. METHODS: A retrospective cohort of 18,593 participants aged 43-49 years of old, was from Suzhou, China. Logistic regression model was used to calculate the relative risk (RR) of hypertension and corresponding 95% confidence interval (CI). The multivariate RRs were adjusted for age, plasma glucose, triglyceride, and cholesterol. RESULTS: The multivariate RRs of systolic and diastolic pressure were not significantly elevated in the rural subgroups, but was higher in the urban population born in the famine (systolic pressure adjust RR 1.382, 95% CI 1.235-1.545, diastolic pressure adjust RR 1.569, 95% CI 1.415-1.740). The risks of hypertension were significantly higher among the urban subjects than that in the rural subgroups (systolic hypertension adjust RR 2.915, 95% CI 2.616-3.249, diastolic hypertension adjust RR 4.568, 95% CI 4.079-5.116). Percentile of optimal diastolic pressure at mid-age was significantly lower in the urban population prenatally exposed to the famine regardless of sexes. However, a similar reduction of percentage of optimal systolic pressure was only seen in the female, not the male population in the urban region. CONCLUSION: The data suggest Asian genetic basis was not able to block famine-programmed vascular diseases as that happened in Europe, and the programmed problems due to under-nutrition could be reversed after birth. Protective mechanisms may be related to diet habits before age of 30 years old, which is important contribution to early prevention of hypertension.

A novel mechanism of angiotensin II-regulated placental vascular tone in the development of hypertension in preeclampsia.

The present study tested the hypothesis that angiotensin II plays a role in the regulation of placental vascular tone, which contributes to hypertension in preeclampsia. Functional and molecular assays were performed in large and micro placental and non-placental vessels from humans and animals. In human placental vessels, angiotensin II induced vasoconstrictions in 78.7% vessels in 155 tests, as referenced to KCl-induced contractions. In contrast, phenylephrine only produced contractions in 3.0% of 133 tests. In non-placental vessels, phenylephrine induced contractions in 76.0% of 67 tests, whereas angiotensin II failed to produce contractions in 75 tests. Similar results were obtained in animal placental and non-placental vessels. Compared with non-placental vessels, angiotensin II receptors and ß-adrenoceptors were significantly increased in placental vessels. Compared to the vessels from normal pregnancy, angiotensin II-induced vasoconstrictions were significantly reduced in preeclamptic placentas, which was associated with a decrease in angiotensin II receptors. In addition, angiotensin II and angiotensin converting enzyme in the maternal-placenta circulation in preeclampsia were increased, whereas angiotensin I and angiotensin1-7 concentrations were unchanged. The study demonstrates a selective effect of angiotensin II in maintaining placental vessel tension, which may play an important role in development of hypertension in preeclampsia.

Maternal high-sucrose diets altered vascular large-conductance Ca2+-activated K+ channels via reactive oxygen species in offspring rats.

Overnutrition during pregnancy could increase risks of cardiovascular diseases in late life. This study investigated whether and how reactive oxygen species (ROS) may influence functions of large-conductance Ca2+-activated K+ channels (BKCa) in the offspring exposed to prenatal high sucrose (HS). We found that prenatal HS diets significantly increased phenylephrine (PE)-induced vessel contractions in mesenteric arteries of the adult offspring. Pretreatment with iberiotoxin (BKCa blocker, IBTX) significantly increased PE-mediated vascular contractions in the control, not in the HS group. Electrophysiological studies demonstrated that BKCa current density and single-channel current were reduced in the vascular smooth muscle cells (VSMCs) of the HS offspring. The expression of BKCa alpha, beta1 subunits in mesenteric arteries was decreased in the HS offspring, indicating that both activity and number of BKCa channels in HS offspring were reduced. Superoxide production and NADPH oxidase (NOX)4 of the HS offspring were elevated. Following inhibiting NOX by apocynin, vasoconstriction in the HS offspring was weakened and the reduced currents in the VSMCs were improved with altered protein kinase B (AKT) pathway. The results suggested that NOX4-derived ROS might inhibit the offspring vascular BKCa channel activity via AKT pathway.

Maternal high salt diet altered Adenosine-mediated vasodilatation via PKA/BK channel pathway in offspring rats.

SCOPE: High salt (HS) diets are related to cardiovascular diseases, and prenatal HS was suggested to increase risks of coronary artery diseases in the offspring. This study tested the hypothesis that prenatal HS may influence Adenosine-induced vasodilatation via protein kinase A (PKA) pathway in coronary arteries. METHODS AND RESULTS: Sprague-Dawley rats were fed with 8% salt diet for gestation, the control was fed with 0.3% salt diet. Coronary arteries from male adult offspring were tested for K+ channels and Adenosine signal pathways. Adenosine-mediated vasodilatation was reduced in coronary arteries in HS. There was no difference in gene expression of A2A receptors between the two groups. After pretreatment with PKA inhibitor, vasodilatation to Adenosine was decreased to a smaller extent in HS than that in control. Forskolin (activator of adenylate cyclase)-mediated vasodilatation was decreased in HS. Iberiotoxin (large-conductance Ca2+ -activated K+ channel [BK channel] inhibitor) attenuated Forskolin-induced vasodilatation in control, not in HS group. Currents of BK channels decreased in coronary artery smooth muscle cells, and PKA-modulated BK channel functions were declined. Protein levels of BK ß1 and PKA C-subunits in coronary arteries of HS offspring were reduced. CONCLUSIONS: Prenatal HS diets altered Adenosine-mediated coronary artery vasodilatation in the offspring, which was linked to downregulation of cAMP/PKA/BK channel pathway.

Maternal high-salt diet altered PKC/MLC20 pathway and increased ANG II receptor-mediated vasoconstriction in adult male rat offspring.

SCOPE: High-salt diet (HSD) is associated with cardiovascular diseases. This study aims at ascertaining the influence of maternal HSD on offspring's angiotensin II (ANG II)-mediated vasoconstriction and the underlying mechanisms. METHODS AND RESULTS: In comparison to a normal-salt diet, HSD used in pregnancy in rats changed the ultrastructures of the coronary artery (CA) in 5-month-old male offspring, and increased ANG II-mediated CA contractility. Measurement of [Ca(2+) ]i in CA using fluorescent fura-2, a Ca(2+) indicator, showed that ANG II-mediated increases in [Ca(2+) ]i were the same between HSD and normal-salt diet groups, but the ratio of diameter change/[Ca(2+) ]i induced by ANG II were significantly higher in HSD groups. Angiotensin II receptor type 1, not angiotensin II receptor type 2, caused ANG II-mediated vasoconstriction. Protein kinase C (PKC) inhibitor GF109203X attenuated the ANG II-mediated vasoconstriction, PKC agonist phorbol12,13-dibutyrate produced a greater contraction. There was an increase in PKCß mRNA and the corresponding protein abundance in the offspring, whereas other PKC subunits PKCα, PKCδ, and PKCε did not change. Moreover, 20 kDa myosin light chain phosphorylation levels were increased in HSD group. CONCLUSION: Maternal HSD affected the developmental programing for the offspring CA, with increased ANG II-mediated vasoconstrictions. The angiotensin II receptor type 1-PKC-20 kDa myosin light chain phosphorylation pathway was the possible mediated cellular mechanism.

High-salt diets during pregnancy increases renal vascular reactivity due to altered soluble guanylyl cyclase-related pathways in rat offspring.

Adverse prenatal factors such as overtake of salt or fat food are potential risks for cardiovascular diseases in offspring. This study tested the hypothesis that prenatal high-salt (HS) diets may influence renal vascular tone and attenuates signaling pathways related to soluble guanylyl cyclase (sGC) or/and large-conductance Ca(2+)-activated K(+) (BKCa) channels in the offspring. Pregnant rats were fed either normal salt (NS) (1% NaCl) or HS (8% NaCl) diet for the whole gestation. Offspring were maintained on NS diets. Renal interlobar arteries in offspring were tested for vascular responses to phenylephrine (Phe), K(+) channels and signal pathways related to sGC. Phe induced higher vessel tension in interlobar arteries of the HS offspring. Following pretreatment with BKCa channel inhibitor iberiotoxin, Phe-mediated vasoconstrictions were decreased in HS offspring compared to NS. Phe-mediated constrictions following pretreatment with NO synthase inhibitor N(G)-nitro-l-arginine methyl ester or sGC inhibitor 1H-1,2,4-oxadiazolo-4,3-quinoxalin-1-one in the HS offspring were less sensitive than NS. The whole-cell K(+) currents and the component of BKCa channels were not changed in smooth muscle cells from interlobar arteries, whereas the K(+) currents stimulated by sGC activator BAY41-2272 were reduced in the HS offspring. The protein expressions of sGC ß1 and ß2 in the interlobar arteries of HS offspring were reduced. The results showed that chronic overintake of salt during pregnancy could increase renal vascular tone in the offspring. The affected signal pathways included down-regulation of sGC function and expression.

Hippocampal NMDAR-Wnt-Catenin signaling disrupted with cognitive deficits in adolescent offspring exposed to prenatal hypoxia.

Prenatal hypoxia (PH) is one of the most common stresses on fetuses, and might lead to abnormal brain development. This work investigates whether PH affects behavioral development of the learning/memory ability in the adolescent offspring rats and the underlying molecular basis in the brain. In this study, pregnant rats used to generate PH offspring were treated with hypoxia (10.5% oxygen) from gestational day 4 to 21. Brain weights of either the fetuses or the 6-week old offspring in the PH group were found to be significantly lower compared with the control group. Morris water maze tests showed longer escape latency and swimming distance during navigation testing in the PH offspring; retention tests demonstrated less frequency of crossing target areas indicating impaired learning and memory ability in the PH offspring. The expressions of subunits of N-methyl-D-aspartate receptors (NMDARs), Grin1/NR1, Grin2a/NR2A, and Grin2b/NR2B, were significantly decreased in the hippocampus of adolescent offspring in the PH group. Wnt3a as well as active form of ß-catenin protein were also significantly down-regulated. Furthermore, the expression of early response gene, Fosl1, was significantly reduced. The results above provide new evidence that PH might result in the spatial acquisition and retrieval deficits in the adolescent offspring, associated with dysregulation of NMDARs-Wnt-Catenin signaling in the hippocampus. This study result deepens the knowledge of the long-term influence of prenatal insults on the neuro-behavioral development.