Cerebral Resistance Arteries Research Articles

Evaluation of Vascular Control Mechanisms Utilizing Video Microscopy of Isolated Resistance Arteries of Rats.

This protocol describes the use of in vitro television microscopy to evaluate vascular function in isolated cerebral resistance arteries (and other vessels), and describes techniques for evaluating tissue perfusion using Laser Doppler Flowmetry (LDF) and microvessel density utilizing fluorescently labeled Griffonia simplicifolia (GS1) lectin. Current methods for studying isolated resistance arteries at transmural pressures encountered in vivo and in the absence of parenchymal cell influences provide a critical link between in vivo studies and information gained from molecular reductionist approaches that provide limited insight into integrative responses at the whole animal level. LDF and techniques to selectively identify arterioles and capillaries with fluorescently-labeled GS1 lectin provide practical solutions to enable investigators to extend the knowledge gained from studies of isolated resistance arteries. This paper describes the application of these techniques to gain fundamental knowledge of vascular physiology and pathology in the rat as a general experimental model, and in a variety of specialized genetically engineered "designer" rat strains that can provide important insight into the influence of specific genes on important vascular phenotypes. Utilizing these valuable experimental approaches in rat strains developed by selective breeding strategies and new technologies for producing gene knockout models in the rat, will expand the rigor of scientific premises developed in knockout mouse models and extend that knowledge to a more relevant animal model, with a well understood physiological background and suitability for physiological studies because of its larger size.

Terlipressin-induced modifications of Doppler ultrasound signals of systemic arteries in preterm infants with vasoactive-resistant patent ductus arteriosus: A pilot study.

To study the effects of terlipressin (TP) infusion on systemic perfusion, estimated with pulsed-wave Doppler ultrasonography of systemic arteries, in a population of extremely low birth-weight (ELBW) preterm infants with vasoactive-resistant ductus arteriosus. This prospective, observational cohort included, during five years, 12 ELBW infants with hemodynamically significant patent ductus arteriosus and absent or reversed diastolic flow at Doppler ultrasonography of systemic arteries, despite treatment and high-dose vasoactive support. We measured flow velocity of the anterior cerebral, right renal, and superior mesenteric arteries before and after TP infusion. Changes were evaluated by Spearman's rho coefficient analysis, Wilcoxon signed-rank, and Friedman test. Time-averaged mean velocity of the renal artery (P = .028) increased, while renal pulsatility (P = .010) and resistance (P = .004) indexes, and cerebral artery resistance index (P = .021) decreased after TP infusion. Time-averaged mean velocity of the anterior cerebral artery proportionately increased with dopamine dose (rho = 0.678; P = .015), but showed opposite shifts after TP (rho = -0.662; P = .024). These changes suggest that TP may improve systemic perfusion in the ELBW infants with vasoactive-resistant ductus arteriosus.

The prenatal ultrasonic study of cerebral sulci and gyrus development in fetuses with conotruncal defects at the second and third trimester

Objective To evaluate the development of cerebral sulci and gyrus in fetuses with conotruncal defect(CTD) at the second and third trimester by ultrasound, and to improve clinician′s understanding of the cerebral cortical development in fetuses with CTD. Methods The study was conducted at Shenzhen Maternity and Child Healthcare Hospital Affiliated to Southern Medicial University from December 2015 to January 2017, enrolled 180 women with single fetus, among whom 60 fetuses with CTD and gestational age between 20 weeks to 33+ 6 weeks were diagnosed by echocardiographic examination. CTD included persistent truncus arteriosous, tetralogy of fallot, transpofition of the great arteries and double outlet of right ventricle. Evaluation indexes of cerebral sulci and gyrus included depth and angle of parietooccipital sulcus, width and depth of sylvian fissure, uncovered width of insular, uncovered insular ratio, depth of calcarine sulcus, head circumference; evaluation indexes of hemodynamics included umbilical artery resistance index, umbilical artery pulsation index, middle cerebral artery resistance index, middle cerebral artery pulsation index, the cerebral-to-placental resistance ratio and the cerebroplacental pulsation ratio. Above indexes were measured for statistical analysis. Results At the whole gestational age in the study, depth of parietooccipital sulcus and width of sylvian fissure in CTD fetuses were smaller than those in the control group, uncovered insular ratio was larger than that in the normal group(P<0.05); middle cerebral artery resistance index, middle cerebral artery pulsation index and the cerebroplacental pulsation ratio in CTD fetuses were lower than those of the control group (P<0.05). Conclusions The change of hemodynamics in fetuses with CTD may be one of the reasons that fetuses with CTD have cerebral cortical hypoevolutism. Key words: Ultrasonography, prenatal; Fetus; Conotruncal defects; Sulci and gyrus

Peripheral and Cerebral Resistance Arteries in the Spontaneously Hypertensive Heart Failure Rat: Effects of Stilbenoid Polyphenols

Hypertension is associated with aberrant structure and mechanical properties of resistance arteries. We determined the effects of resveratrol, a non-flavonoid polyphenol found in foods such as red grapes, and structurally-similar analogues (pterostilbene and gnetol) on systolic blood pressure (SBP) and resistance arteries from the spontaneously hypertensive heart failure (SHHF) rat. SBP was elevated in 17-week-old SHHF vs. Sprague-Dawley rats (normotensive control; 194 ± 3 vs. 142 ± 6 mmHg, p < 0.01) and was unaffected by resveratrol, pterostilbene, or gnetol (2.5 mg/kg/d). Geometry and mechanical properties of pressurized mesenteric resistance arteries and middle cerebral arteries were calculated from media and lumen dimensions measured at incremental intraluminal pressures. SHHF arteries exhibited remodeling which consisted of augmented media-to-lumen ratios, and this was attenuated by stilbenoid treatment. Compliance was significantly reduced in SHHF middle cerebral arteries but not mesenteric arteries vis-à-vis increased wall component stiffness; stilbenoid treatment failed to normalize compliance and wall component stiffness. Our data suggest that neither AMPK nor ERK mediate stilbenoid effects. In conclusion, we observed arterial bed-specific abnormalities, where mesenteric resistance arteries exhibited remodeling and cerebral arteries exhibited remodeling and stiffening. Resveratrol, pterostilbene, and gnetol exhibited similar abilities to attenuate vascular alterations.

The augmentation of BK channel activity by nitric oxide signaling in rat cerebral arteries involves co-localized regulatory elements

Large conductance, Ca2+-activated K+ (BK) channels control cerebrovascular tone; however, the regulatory processes influencing these channels remain poorly understood. Here, we investigate the cellular mechanisms underlying the enhancement of BK current in rat cerebral arteries by nitric oxide (NO) signaling. In isolated cerebral myocytes, BK current magnitude was reversibly increased by sodium nitroprusside (SNP, 100 μM) and sensitive to the BK channel inhibitor, penitrem-A (100 nM). Fostriecin (30 nM), a protein phosphatase type 2A (PP2A) inhibitor, significantly prolonged the SNP-induced augmentation of BK current and a similar effect was produced by sildenafil (30 nM), a phosphodiesterase 5 (PDE5) inhibitor. Using proximity ligation assay (PLA)-based co-immunostaining, BK channels were observed to co-localize with PP2A, PDE5, and cGMP-dependent protein kinase (cGKI) (spatial restriction < 40 nm); cGKI co-localization increased following SNP exposure. SNP (10 μM) reversibly inhibited myogenic tone in cannulated cerebral arteries, which was augmented by either fostriecin or sildenafil and inhibited by penitrem-A. Collectively, these data suggest that (1) cGKI, PDE5, and PP2A are compartmentalized with cerebrovascular BK channels and determine the extent of BK current augmentation by NO/cGMP signaling, and (2) the dynamic regulation of BK activity by co-localized signaling enzymes modulates NO-evoked dilation of cerebral resistance arteries.

Evaluation of fetal middle cerebral artery Doppler indices in pregnancies with intrauterine growth restriction: A cross-sectional study

Background: Doppler velocimetry studies of placental and fetal circulation can provide important information regarding fetal well-being providing an opportunity to improve fetal outcome. Aims and Objective: The aim of this study to evaluate the role of color Doppler velocimetry of the fetal middle cerebral artery (MCA) velocity waveforms, systolic/diastolic ratio (S/D), pulsatility index (PI), and resistance index (RI) in intrauterine growth restriction (IUGR) pregnancies in II and III trimesters. Materials and Methods: This was a cross-sectional study. The control and study groups were studied in II and III trimesters. They were first subjected to ultrasonography biometry and then to MCA Doppler sonography. The statistical analysis was performed by “unpaired” and “paired” t-test. Results: In both control and study groups, the values of S/D ratio, PI, and RI in MCA decline during II to III trimester. The values were lower in the study group as compared to the control group. Thus that the present study predicts were; (a) lower PI values were suggestive of fetal hypoxia, (b) The lower values are due to vasodilatation due to hypoxia to supply more blood to the brain to protect it from the damaging effects of hypoxia. Thus, the brain is spared from damage. Conclusion: Doppler can be considered as one of the important non-invasive techniques to assess the fetomaternal and uteroplacental circulations. The MCA indices were valuable for predicting the outcome of IUGR pregnancies.

Association of biochemical markers with the severity of pre-eclampsia.

To assess the association between pre-eclampsia severity and biochemical and ultrasonography markers. A retrospective study was undertaken of women with severe pre-eclampsia (group 1, n=90), mild pre-eclampsia (group 2, n=90), or a normal pregnancy (group 3, n=90) who attended a hospital in Egypt in October 2013-April 2015. Associations between pre-eclampsia and biochemical, cardiotocography, and ultrasonography markers were investigated. There were significant differences between the groups in C-reactive protein (331.44±112.38, 251.43±59.05, and 23.81±16.19nmol/L; P≤0.05 for all), platelet count (113.40±36.72, 172.93±57.60, and 212.68±70.00×109 /L; P≤0.05 for group 1 comparisons), alanine transaminase (52.24±14.83, 38.34±13.12, and 23.11±6.92U/L; P≤0.05 for group 1 comparisons), and serum uric acid (600.80±117.19, 481.83±118.97, and 243.89±53.54μmol/L; P=0.050 for group 3 comparisons). Cardiotocography score was worse among women with severe pre-eclampsia than among those in the other two groups (P=0.039 for both comparisons). Biophysical profile score and umbilical artery resistance index differed by group (P≤0.05 for all). Middle cerebral artery resistance index was lower among women with severe pre-eclampsia (P≤0.05). The levels of C-reactive protein, blood urea nitrogen, serum uric acid, and alanine transaminase, and the platelet count were linked with the presence and severity of pre-eclampsia.

Brain Volume and Doppler Velocimetry in Growth-Restricted, Small-for-Gestational-Age, and Appropriate-for-Gestational-Age Fetuses.

Objective This study aims to detect possible differences in fetal brain volumes between growth-restricted fetuses (FGR), small-for-gestational-age (SGA) fetuses with normal Doppler indices, and appropriate-for-gestational-age fetuses (AGA). Study Design Three-dimensional measurements of fetal brain volume and umbilical artery and middle cerebral artery (MCA) pulsatility index (PI) and resistance index (RI) were made in 80 AGA fetuses, 68 SGA fetuses with normal Doppler indices, and 68 FGR with brain-sparing effect between 32 and 36 weeks of gestation. Results MCA-PI and MCA-RI were significantly lower in FGR group compared with the other two groups (p < 0.001). Brain volume was significantly lower in SGA and FGR groups compared with AGA group (p < 0.001). Conclusion Brain volume is significantly lower in SGA and FGR groups compared with AGA group.

Age decreases mitochondrial motility and increases mitochondrial size in vascular smooth muscle.

Key points Age is proposed to be associated with altered structure and function of mitochondria; however, in fully‐differentiated cells, determining the structure of more than a few mitochondria at a time is challenging. In the present study, the structures of the entire mitochondrial complements of cells were resolved from a pixel‐by‐pixel covariance analysis of fluctuations in potentiometric fluorophore intensity during ‘flickers’ of mitochondrial membrane potential.Mitochondria are larger in vascular myocytes from aged rats compared to those in younger adult rats.A subpopulation of mitochondria in myocytes from aged, but not younger, animals is highly‐elongated.Some mitochondria in myocytes from younger, but not aged, animals are highly‐motile.Mitochondria that are motile are located more peripherally in the cell than non‐motile mitochondria. Mitochondrial function, motility and architecture are each central to cell function. Age‐associated mitochondrial dysfunction may contribute to vascular disease. However, mitochondrial changes in ageing remain ill‐defined because of the challenges of imaging in native cells. We determined the structure of mitochondria in live native cells, demarcating boundaries of individual organelles by inducing stochastic ‘flickers’ of membrane potential, recorded as fluctuations in potentiometric fluorophore intensity (flicker‐assisted localization microscopy; FaLM). In freshly‐isolated myocytes from rat cerebral resistance arteries, FaLM showed a range of mitochondrial X‐Y areas in both young adult (3 months; 0.05–6.58 μm2) and aged rats (18 months; 0.05–13.4 μm2). In cells from young animals, most mitochondria were small (mode area 0.051 μm2) compared to aged animals (0.710 μm2). Cells from older animals contained a subpopulation of highly‐elongated mitochondria (5.3% were >2 μm long, 4.2% had a length:width ratio >3) that was rare in younger animals (0.15% of mitochondria >2 μm long, 0.4% had length:width ratio >3). The extent of mitochondrial motility also varied. 1/811 mitochondria observed moved slightly (∼0.5 μm) in myocytes from older animals, whereas, in the younger animals, directed and Brownian‐like motility occurred regularly (215 of 1135 mitochondria moved within 10 min, up to distance of 12 μm). Mitochondria positioned closer to the cell periphery showed a greater tendency to move. In conclusion, cerebral vascular myocytes from young rats contained small, motile mitochondria. In aged rats, mitochondria were larger, immobile and could be highly‐elongated. These age‐associated alterations in mitochondrial behaviour may contribute to alterations in cell signalling, energy supply or the onset of proliferation.

Enhanced Mobilization of Endothelial Ca2+ by SKA‐31 Contributes to the Restoration of Agonist‐mediated Vasorelaxation in Resistance Arteries from Type 2 Diabetic Rats

Endothelial dysfunction is a common early pathogenic event in patients with type 2 diabetes (T2D). In isolated hearts from T2D Goto‐Kakizaki (GK) rats, we have observed that SKA‐31, a positive modulator of the endothelial Ca2+‐activated K+ (KCa) channels KCa2.3 and KCa3.1, increases total coronary flow and restores agonist‐evoked elevations in flow to the levels observed in Wistar control hearts. The goal of the current study was to investigate the cellular mechanisms by which SKA‐31 restores vascular responsiveness in T2D vessels. In cannulated, myogenically active cremaster and cerebral resistance arteries from 24 week old, male T2D GK rats, and small intra‐thoracic arteries from T2D patients, a threshold concentration of SKA‐31 (0.3 μM) enhanced the ability of 0.3 μM acetylcholine and 0.1 μM bradykinin to inhibit developed tone at 70 mmHg. This effect of SKA‐31 was not disrupted by treatment with L‐NAME (0.1 mM) and indomethacin (10 μM), demonstrating that endothelial nitric oxide synthase and cyclooxygenase activities do not contribute to SKA‐31 mediated enhancement of agonist‐evoked vasorelaxation in T2D arteries. Using single cell Fura‐2 fluorescence imaging, we observed that Ca2+ mobilization evoked by the muscarinic agonist carbachol (1 μM) was significantly impaired in acutely isolated endothelial cells from GK arteries compared with Wistar controls and that treatment with 0.3 μM SKA‐31 was able to reverse this defect in response. Ca2+ mobilization evoked by the SERCA inhibitor cyclopiazonic acid (20 μM) was not different in endothelial cells from Wistar and T2D GK arteries, suggesting that the internal Ca2+ store, per se, is not dysfunctional in GK endothelial cells. In summary, we have identified a novel cellular mechanism to restore agonist‐mediated inhibition of myogenic tone in T2D resistance arteries that involves “priming” of endothelial KCa channels by a small molecule activator (e.g. SKA‐31). Our data further reveal that SKA‐31 is able to augment agonist‐evoked Ca2+ mobilization in T2D endothelial cells, which likely contributes to the functional restoration of agonist‐evoked vasorelaxation in T2D arteries.Support or Funding InformationThis study was supported by research funding to APB from the CIHR.

Rebuttal from Ryan L. Hoiland and Philip N. Ainslie.

Brothers & Zhang (2016) provide a relevant CrossTalk discussion on the measurement of middle cerebral artery (MCA) diameter during alterations in arterial blood pressure (ABP) and gases. While in support of a constant MCA diameter, they nonetheless judiciously acknowledge that several previous studies indicating a constant MCA diameter, specifically during alterations in arterial blood gases, are confounded by subject co-morbidities, anesthesia, and/or suffer from poor resolution (1.5 T MRI) (Schreiber et al. 2000; Serrador et al. 2000). They speculate that elevations in ABP and the associated autoregulatory response concurrent to hypercapnia may explain the increases in diameter reported by the more recent and higher resolution MRI studies (3 and 7 T) assessing MCA diameter (Verbree et al. 2014; Coverdale et al. 2014). The rationale for this hypothesis is unclear as the available data in humans indicate an increase in ABP will increase cerebral vascular resistance in large cerebral arteries (Liu et al. 2013; Warnert et al. 2016). Collectively, these findings indicate that any engagement of autoregulatory mechanisms would more likely lead to an underestimation of vasodilatation, not overestimation. In their discussion of arterial blood gases, Brothers & Zhang fail to discuss the potential for hypoxia-induced vasomotion of the MCA. Previous study has indicated MCA dilatation in hypoxia (Wilson et al. 2011), in addition to more recent evidence that continues to highlight a tendency for increased MCA diameter (Sagoo et al. 2016). Overall there is a strong body of data supporting hypoxia-induced dilatation at the level of the MCA. It is noted by Brothers & Zhang that the study by Serrador et al. (2000) provides insight into MCA diameter during mild hypotension; however, a statistical change in BP did not occur during their simulated orthostasis trial (see Table 2 in Serrador et al. 2000). This renders the study by Giller et al. (1993) the only one to date that has directly imaged MCA diameter during alterations in ABP. Thus, while it remains difficult to definitively conclude the effect of ABP on MCA diameter, a large body of evidence now supports the notion that MCA diameter does change during alterations in arterial blood gases. Although we acknowledge that much utility still exists in the employment of transcranial Doppler ultrasound, we encourage the complimentary addition of multi-modal imaging to provide important new insight into cerebrovascular regulation in humans. Readers are invited to give their views on this and the accompanying CrossTalk articles in this issue by submitting a brief (250 word) comment. Comments may be submitted up to 6 weeks after publication of the article, at which point the discussion will close and the CrossTalk authors will be invited to submit a ‘Last Word’. Please email your comment, including a title and a declaration of interest, to jphysiol@physoc.org. Comments will be moderated and accepted comments will be published online only as ‘supporting information’ to the original debate articles once discussion has closed. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. The authors declare no conflict of interest, financial or otherwise. Both authors have approved the final version of the manuscript and agree to be accountable for all aspects of the work. All persons designated as authors qualify for authorship, and all those who qualify for authorship are listed.

Prediction of perinatal outcome in preeclampsia using middle cerebral artery and umbilical artery pulsatility and resistance indices

ABSTRACTObjective: In preeclampsia, changes in fetal hemodynamics can be detected 2–3 weeks earlier than any changes in cardiotocogram. Thus, these Doppler changes can be used to predict perinatal outcome. The present study is planned to assess the accuracy of the middle cerebral artery to umbilical artery (UA) pulsatility index (PI) and resistance index (RI) in predicting adverse perinatal outcome in pregnancies complicated by preeclampsia. Methods: Total of 115 and 108 pregnant women were included in preeclampsia and control group, respectively. Weekly Doppler study was done in both groups starting from 30 weeks till 36 weeks or delivery, whichever is later. Results: Mean gestational age at delivery was 250 ± 13 and 273 ± 8 days, respectively, in preeclampsia and control group (p < 0.01). Thirty-four babies in preeclampsia group had been admitted to nursery; out of which three died (p < 0.01). On receiver operating characteristic analysis, MCA /UmA PI ratio and MCA /UmA RI ratio had sensitivity of 9% and 9.7% and specificity of 98% and 96.6%, respectively, for predicting adverse perinatal outcome. Conclusion: Doppler indices of MCA and Um A are significantly abnormal in preeclampsia. But on diagnostic statistical analysis they have good specificity but low sensitivity for detecting adverse perinatal outcome.

Fetal vascular adaptation before and after treatment of severe maternal anemia in pregnancy.

To use color Doppler ultrasonography indices to study the effects on fetal circulation of treating severe maternal anemia. A prospective cohort study enrolled patients who were at 30-34weeks of pregnancy and had hemoglobin levels below 70g/L between November 1, 2011 and March 31, 2013 at a hospital in New Delhi, India. A control group consisting of patients with the same duration of pregnancy and with hemoglobin levels above 110g/L was included. Umbilical artery and middle cerebral artery velocimetry were performed using color Doppler ultrasonography at admission and after 4weeks and 6weeks of treatment. The maternal anemia cohort demonstrated a significantly lower middle cerebral artery resistance index and middle cerebral/umbilical artery resistance ratio (P<0.001) at admission. Following 4weeks of treatment for maternal anemia, significant increases in these parameters were observed (P<0.001). Fetuses of individuals with severe maternal anemia demonstrated altered cerebral and umbilical artery flows. Normal flows were restored following treatment of maternal anemia.

Predicting success of labor induction in singleton term pregnancies by combining maternal and ultrasound variables

Objective: To assess pre-induction maternal and ultrasonographic factors in the prediction of the onset of labor within 12 h, and vaginal delivery (VD) irrespective of the induction-to-delivery interval in term pregnancies.Methods: We performed a prospective cohort study with 204 singleton pregnant women between 37 and 42 weeks of gestation. The following maternal and ultrasonographic variables were assessed: parity, marital status, height, body mass index (BMI), previous cesarean section (Cs), Bishop score, variety of fetal position, single deepest pocket (SDP), fetal middle cerebral and umbilical artery resistance indices, cervical length (CL) measurement, posterior cervical angle (PCA), head circumference (HC) and estimated fetal weight (EFW). χ2 test and logistic regression analysis were applied to compare the groups. Receiver operating characteristics (ROC) curves were determined.Results: VD occurred in 116 (56.9%) women. Prediction of the onset of labor within 12 h was provided by the BMI and resistance index of the fetal middle cerebral artery. Prediction of the VD irrespective of the induction-to-delivery interval was provided by height, BMI, parity, number of prenatal visits, consistency, effacement and dilation of uterine cervix, PCA, oligohydramnios, HC and EFW. Area under ROC curve for PCA and EFW were 63.5 (sensibility: 66.4%, specificity: 59.1%) and 60.2 (sensibility: 54.3%, specificity: 70.4%), respectively.Conclusions: Several pre-induction maternal and ultrasonographic factors can increase the chance of achieving a successful VD. PCA and EFW were the best ultrasonographic predictors for the success of induction of labor; however, with limited potential to be used in the clinical practice.

Early functional and morphological brain disturbances in late-onset intrauterine growth restriction

AimsTo determine whether the brain disturbances develop in late-onset intrauterine growth restriction (IUGR) before blood flow redistribution towards the fetal brain (detected by Doppler measurements in the middle cerebral artery and umbilical artery). Further, to evaluate predictive values of Doppler arterial indices and umbilical cord blood gases and pH for early functional and/or morphological brain disturbances in late-onset IUGR. Study designThis cohort study included 60 singleton term pregnancies with placental insufficiency caused late-onset IUGR (IUGR occurring after 34 gestational weeks). Umbilical artery resistance index (URI), middle cerebral artery resistance index (CRI), and cerebroumbilical (C/U) ratio (CRI/URI) were monitored once weekly. Umbilical blood cord samples (arterial and venous) were collected for the analysis of pO2, pCO2 and pH. Morphological neurological outcome was evaluated by cranial ultrasound (cUS), whereas functional neurological outcome by Amiel-Tison Neurological Assessment at Term (ATNAT). Results50 fetuses had C/U ratio>1, and 10 had C/U ratio≤1; among these 10 fetuses, 9 had abnormal neonatal cUS findings and all 10 had non-optimal ATNAT. However, the total number of abnormal neurological findings was much higher. 32 neonates had abnormal cUS (53.37%), and 42 (70.00%) had non-optimal ATNAT. Furthermore, Doppler indices had higher predictive validity for early brain disturbances than umbilical cord blood gases and pH. C/U ratio had the highest predictive validity with threshold for adverse neurological outcome at value 1.13 (ROC analysis), i.e., 1.18 (party machine learning algorithm). ConclusionAdverse neurological outcome at average values of C/U ratios>1 confirmed that early functional and/or structural brain disturbances in late-onset IUGR develop even before activation of fetal cardiovascular compensatory mechanisms, i.e., before Doppler signs of blood flow redistribution between the fetal brain and the placenta.

Metabolic syndrome impairs reactivity and wall mechanics of cerebral resistance arteries in obese Zucker rats.

The metabolic syndrome (MetS) is highly prevalent in the North American population and is associated with increased risk for development of cerebrovascular disease. This study determined the structural and functional changes in the middle cerebral arteries (MCA) during the progression of MetS and the effects of chronic pharmacological interventions on mitigating vascular alterations in obese Zucker rats (OZR), a translationally relevant model of MetS. The reactivity and wall mechanics of ex vivo pressurized MCA from lean Zucker rats (LZR) and OZR were determined at 7-8, 12-13, and 16-17 wk of age under control conditions and following chronic treatment with pharmacological agents targeting specific systemic pathologies. With increasing age, control OZR demonstrated reduced nitric oxide bioavailability, impaired dilator (acetylcholine) reactivity, elevated myogenic properties, structural narrowing, and wall stiffening compared with LZR. Antihypertensive therapy (e.g., captopril or hydralazine) starting at 7-8 wk of age blunted the progression of arterial stiffening compared with OZR controls, while treatments that reduced inflammation and oxidative stress (e.g., atorvastatin, rosiglitazone, and captopril) improved NO bioavailability and vascular reactivity compared with OZR controls and had mixed effects on structural remodeling. These data identify specific functional and structural cerebral adaptations that limit cerebrovascular blood flow in MetS patients, contributing to increased risk of cognitive decline, cerebral hypoperfusion, and ischemic stroke; however, these pathological adaptations could potentially be blunted if treated early in the progression of MetS.

α5-Integrin-mediated cellular signaling contributes to the myogenic response of cerebral resistance arteries

The myogenic response of resistance arterioles and small arteries involving constriction in response to intraluminal pressure elevation and dilation on pressure reduction is fundamental to local blood flow regulation in the microcirculation. Integrins have garnered considerable attention in the context of initiating the myogenic response, but evidence indicative of mechanotransduction by integrin adhesions, for example established changes in tyrosine phosphorylation of key adhesion proteins, has not been obtained to substantiate this interpretation. Here, we evaluated the role of integrin adhesions and associated cellular signaling in the rat cerebral arterial myogenic response using function-blocking antibodies against α5β1-integrins, pharmacological inhibitors of focal adhesion kinase (FAK) and Src family kinase (SFK), an ultra-high-sensitivity western blotting technique, site-specific phosphoprotein antibodies to quantify adhesion and contractile filament protein phosphorylation, and differential centrifugation to determine G-actin levels in rat cerebral arteries at varied intraluminal pressures. Pressure-dependent increases in the levels of phosphorylation of FAK (FAK-Y397, Y576/Y577), SFK (SFK-Y416; Y527 phosphorylation was reduced), vinculin-Y1065, paxillin-Y118 and phosphoinositide-specific phospholipase C-γ1 (PLCγ1)-Y783 were detected. Treatment with α5-integrin function-blocking antibodies, FAK inhibitor FI-14 or SFK inhibitor SU6656 suppressed the changes in adhesion protein phosphorylation, and prevented pressure-dependent phosphorylation of the myosin targeting subunit of myosin light chain phosphatase (MYPT1) at T855 and 20kDa myosin regulatory light chains (LC20) at S19, as well as actin polymerization that are necessary for myogenic constriction. We conclude that mechanotransduction by integrin adhesions and subsequent cellular signaling play a fundamental role in the cerebral arterial myogenic response.

Therapeutically Targeting Tumor Necrosis Factor-α/Sphingosine-1-Phosphate Signaling Corrects Myogenic Reactivity in Subarachnoid Hemorrhage.

Subarachnoid hemorrhage (SAH) is a complex stroke subtype characterized by an initial brain injury, followed by delayed cerebrovascular constriction and ischemia. Current therapeutic strategies nonselectively curtail exacerbated cerebrovascular constriction, which necessarily disrupts the essential and protective process of cerebral blood flow autoregulation. This study identifies a smooth muscle cell autocrine/paracrine signaling network that augments myogenic tone in a murine model of experimental SAH: it links tumor necrosis factor-α (TNFα), the cystic fibrosis transmembrane conductance regulator, and sphingosine-1-phosphate signaling. Mouse olfactory cerebral resistance arteries were isolated, cannulated, and pressurized for in vitro vascular reactivity assessments. Cerebral blood flow was measured by speckle flowmetry and magnetic resonance imaging. Standard Western blot, immunohistochemical techniques, and neurobehavioral assessments were also used. We demonstrate that targeting TNFα and sphingosine-1-phosphate signaling in vivo has potential therapeutic application in SAH. Both interventions (1) eliminate the SAH-induced myogenic tone enhancement, but otherwise leave vascular reactivity intact; (2) ameliorate SAH-induced neuronal degeneration and apoptosis; and (3) improve neurobehavioral performance in mice with SAH. Furthermore, TNFα sequestration with etanercept normalizes cerebral perfusion in SAH. Vascular smooth muscle cell TNFα and sphingosine-1-phosphate signaling significantly enhance cerebral artery tone in SAH; anti-TNFα and anti-sphingosine-1-phosphate treatment may significantly improve clinical outcome.

Radial primary percutaneous coronary intervention is independently associated with decreased long-term mortality in high-risk ST-elevation myocardial infarction patients.

To compare long-term clinical outcomes in patients with ST-elevation myocardial infarction (STEMI) treated by primary percutaneous coronary intervention (PPCI) using radial and femoral arterial access. The present study was an observational cohort study of patients with STEMI treated consecutively with PPCI between 2004 and 2011 at a single centre. The primary end point was all-cause mortality at a median follow-up of 3 years.Among 2727 patients, 1600 (58.7%) underwent PPCI via the femoral route. The femoral group was older (64.7 vs. 61.7 years; P < 0.0001), and had higher rates of diabetes (18.6% vs. 16.0%; P < 0.0001), previous PCI (11.2 vs. 7.8%; P = 0.004), previous myocardial infarction (15.3 vs. 8.3%; P < 0.0001) and cardiogenic shock (9.8 vs. 1.3%; P < 0.0001). Bleeding complications were more frequent in the femoral group (4.7 vs. 1.2%; P < 0.0001). The 5-year death rate was significantly higher in the femoral group than in the radial group (10.4 vs. 3.0%; P < 0.0001). After adjustment for confounding variables, bleeding complications [heart rate 2.07 (95% confidence interval 1.05-4.08)] and femoral access [heart rate 1.60 (95% confidence interval 1.02-2.53)] were independent predictors of all-cause mortality. After stratification using the propensity score, excess long-term mortality in patients treated via the femoral approach was predominantly in patients with a high baseline risk of death. Patients undergoing PPCI via the femoral route are at a higher risk of adverse short-term and long-term outcomes than patients undergoing PPCI via the radial route. Patients with a high baseline risk may benefit most from radial access, and future outcome studies should focus on the most at-risk patients.

PKC-mediated cerebral vasoconstriction: Role of myosin light chain phosphorylation versus actin cytoskeleton reorganization

Defective protein kinase C (PKC) signaling has been suggested to contribute to abnormal vascular contraction in disease conditions including hypertension and diabetes. Our previous work on agonist and pressure-induced cerebral vasoconstriction implicated PKC as a major contributor to force production in a myosin light chain (LC20) phosphorylation-independent manner. Here, we used phorbol dibutyrate to selectively induce a PKC-dependent constriction in rat middle cerebral arteries and delineate the relative contribution of different contractile mechanisms involved. Specifically, we employed an ultra-sensitive 3-step western blotting approach to detect changes in the content of phosphoproteins that regulate myosin light chain phosphatase (MLCP) activity, thin filament activation, and actin cytoskeleton reorganization. Data indicate that PKC activation evoked a greater constriction at a similar level of LC20 phosphorylation achieved by 5-HT. PDBu-evoked constriction persisted in the presence of Gö6976, a selective inhibitor of Ca2+-dependent PKC, and in the absence of extracellular Ca2+. Biochemical evidence indicates that either + or − extracellular Ca2+, PDBu (i) inhibits MLCP activity via the phosphorylation of myosin targeting subunit of myosin phosphatase (MYPT1) and C-kinase potentiated protein phosphatase-1 inhibitor (CPI-17), (ii) increases the phosphorylation of paxillin and heat shock protein 27 (HSP27), and reduces G-actin content, and (iii) does not change the phospho-content of the thin filament proteins, calponin and caldesmon. PDBu-induced constriction was more sensitive to disruption of actin cytoskeleton compared to inhibition of cross-bridge cycling. In conclusion, this study provided evidence for the pivotal contribution of cytoskeletal actin polymerization in force generation following PKC activation in cerebral resistance arteries.