Mechanisms of U46619-induced contraction in mouse intrarenal artery

Thromboxane A₂ (TXA₂ ) has been implicated in the pathogenesis of vascular complications, but the underlying mechanism remains unclear. The contraction of renal arterial rings in mice was measured by a Multi Myograph System. The intracellular calcium concentration ([Ca²⁺ ]_i ) in vascular smooth muscle cells (VSMCs) was obtained by using a fluo-4/AM dye and a confocal laser scanning microscopy. The results show that the U46619-induced vasoconstriction of renal artery was completely blocked by a TXA₂ receptor antagonist GR32191, significantly inhibited by a selective phospholipase C (PI-PLC) inhibitor U73122 at 10 μmol/L and partially inhibited by a Phosphatidylcholine - specific phospholipase C (PC-PLC) inhibitor D609 at 50 μmol/L. Moreover, the U46619-induced vasoconstriction was inhibited by a general protein kinase C (PKC) inhibitor chelerythrine at 10 μmol/L, and a selective PKCδ inhibitor rottlerin at 10 μmol/L. In addition, the PKC-induced vasoconstriction was partially inhibited by a Rho-kinase inhibitor Y-27632 at 10 μmol/L and was further completely inhibited together with a putative IP₃ receptor antagonist and store-operated Ca²⁺ (SOC) entry inhibitor 2-APB at 100 μmol/L. On the other hand, U46619-induced vasoconstriction was partially inhibited by L-type calcium channel (Cav1.2) inhibitor nifedipine at 1 μmol/L and 2-APB at 50 and 100 μmol/L. Last, U46619-induced vasoconstriction was partially inhibited by a cell membrane Ca²⁺ activated C1^- channel blocker 5-Nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) at 50 and 100 μmol/L. Our results suggest that the U46619-induced contraction of mouse intrarenal arteries is mediated by Cav1.2 and SOC channel, through the activation of thromboxane-prostanoid receptors and its downstream signaling pathway.

Hepatorenal Syndrome

Hepatorenal syndrome is a severe complication of end-stage cirrhosis characterized by increased splanchnic blood flow, hyperdynamic state, a state of decreased central volume, activation of vasoconstrictor systems, and extreme kidney vasoconstriction leading to decreased GFR. The contribution of systemic inflammation, a key feature of cirrhosis, in the development of hepatorenal syndrome has been highlighted in recent years. The mechanisms by which systemic inflammation precipitates kidney circulatory changes during hepatorenal syndrome need to be clarified. Early diagnosis is central in the management and recent changes in the definition of hepatorenal syndrome help identify patients at an earlier stage. Vasoconstrictive agents (terlipressin in particular) and albumin are the first-line treatment option. Several controlled studies proved that terlipressin is effective at reversing hepatorenal syndrome and may improve short-term survival. Not all patients are responders, and even in responders, early mortality rates are very high in the absence of liver transplantation. Liver transplantation is the only curative treatment of hepatorenal syndrome. In the long term, patients transplanted with hepatorenal syndrome tend to have lower GFR compared with patients without hepatorenal syndrome. Differentiating hepatorenal syndrome from acute tubular necrosis (ATN) is often a challenging yet important step because vasoconstrictors are not justified for the treatment of ATN. Hepatorenal syndrome and ATN may be considered as a continuum rather than distinct entities. Emerging biomarkers may help differentiate these two conditions and provide prognostic information on kidney recovery after liver transplantation, and potentially affect the decision for simultaneous liver-kidney transplantation.

Preparation of Pulmonary Artery Myocytes and Rings to Study Vasoactive GPCRs

G protein-coupled receptors (GPCR) are crucial transducers of extracellular signals into changes in vascular tone. Vasoactive GPCR stimulation in the pulmonary circuit may be elicited by agonists released in acute tissue hypoxia or inflammation, as well as chronic disease. Acute responses involve activation of smooth muscle contraction or relaxation machinery causing changes in actomyosin interaction, thereby altering lumen diameter. Chronic responses may typically include activation of proliferation or fibrosis. Using pulmonary artery myocytes and pulmonary artery rings, we describe a general strategy for quantification of vasoconstrictor or vasodilator GPCR responses, and for comparison of signaling pathways in cultured cells and in contracted vessels using immunohistochemistry of contracting vessels.

The safety of one-per-mil tumescent infiltration into tissue that has survived ischemia

Background

The aim of this study was to assess the safety of one-per-mil tumescent injections into viable skin flaps that had survived an ischemic insult, in order to assess the potential suitability of one-per-mil tumescent injections in future secondary reconstructive procedures such as flap revision and refinements after replantation.

Methods

Forty groin flaps harvested from 20 healthy Wistar rats weighing 220 to 270 g were subjected to acute ischemia by clamping the pedicle for 15 minutes. All flaps showing total survival on the 7th postoperative day were randomly divided into group A (one-per-mil tumescent infiltration; n=14), group B (normal saline infiltration; n=13), and group C (control, with no infiltration; n=13) before being re-elevated. Transcutaneous oxygen tension (TcPO₂) was measured before and after infiltration, and changes in TcPO₂ were statistically analyzed using analysis of variance, the paired t-test, and the independent t-test. The viability of flaps was also assessed using the Analyzing Digital Images software at 7 days after the second elevation.

Results

Thirty-nine flaps survived to the final assessment, with the sole exception of a flap from group A that did not survive the first elevation. TcPO₂ readings showed significant decreases (P<0.05) following both one-per-mil tumescent (99.9±5.7 mmHg vs. 37.2±6.3 mmHg) and normal saline (103±8.5 mmHg vs. 48.7±5.9 mmHg) infiltration. Moreover, all groin flaps survived with no signs of tissue necrosis.

Conclusions

One-per-mil tumescent infiltration into groin flap tissue that had survived ischemia did not result in tissue necrosis, although the flaps experienced a significant decrease of cutaneous oxygenation.

Human umbilical cord and its vessels: a histomorphometric study in difference severity of hypertensive disorders of pregnancy

The umbilical cord (UC) is a platform for fetal nourishment and growth. The fetus, mother and placenta with UC form a triad, which contributes to pregnancy outcome. When pregnancy is complicated by a medical condition like hypertension, affects both maternal and fetal health. Being a fetal structure it can be used as a window to know the maternal dysfunctions and their impacts on fetal wellbeing. The present study is to explore the histomorphometric changes of the UC and its vessels involved in the development of hypertension during pregnancy. Sixty UCs were used and the following parameters, total UC area; total vessel area; jelly area; wall area, luminal area and wall thickness of umbilical arteries 1 and 2 and vein were studied using ImageJ software. From the results, the mean differences of above parameters of hypertensive UCs were found to be lesser than control and it was significantly higher in cases of severe preeclampsia (P≤0.05). From the present study, we conclude hypertensive cords and its vessels are associated with significant structural changes. Since it is a global health issue it is important to know the factors contributing it to diagnose and prevent.

Regulation of Smooth Muscle Myosin Light Chain Phosphatase by Multisite Phosphorylation of the Myosin Targeting Subunit, MYPT1

BACKGROUND

Smooth muscle contraction is triggered primarily by activation of Ca2+/calmodulin-dependent myosin light chain kinase leading to phosphorylation of the regulatory light chains of myosin II. Numerous contractile stimuli also induce inhibition of myosin light chain phosphatase thereby prolonging the contractile response. The phosphatase is a trimeric enzyme containing a catalytic subunit, a regulatory, myosin-binding subunit (MYPT1) and a third subunit of uncertain function. MYPT1 is phosphorylated at multiple sites by several kinases, which regulate phosphatase activity, protein-protein interactions and subcellular localization. The best-characterized phosphorylation events involve phosphorylation by Rho-associated coiled-coil kinase (ROCK) at T697 and T855, which inhibits phosphatase activity, and phosphorylation by cAMP- or cGMPdependent protein kinases (PKA and PKG, respectively) at S696, T697, S854 and T855, which has no effect on phosphatase activity. Furthermore, phosphorylation by ROCK at T697 and T855 prevents phosphorylation by PKA or PKG at the neighboring serine residues. Some 30 phosphorylation sites have been identified in MYPT1 with many more suggested by large-scale phosphoproteomic studies. It is important to gain as complete understanding as possible of the complex phosphorylation-mediated mechanisms of regulation of MYPT1 functions in part because of their involvement in pathological processes. For example, dysfunctional MYPT1 phosphorylation has been implicated in the pathogenesis of several vascular disorders, including type 2 diabetes.

CONCLUSION

Much effort is now being devoted to the development of novel therapeutics targeting MYPT1 and specific kinases involved in the phosphorylation of MYPT1.

Bupivacaine-induced contraction is attenuated by endothelial nitric oxide release modulated by activation of both stimulatory and inhibitory phosphorylation (Ser1177 and Thr495) of endothelial nitric oxide synthase

This study examined the mechanism associated with the endothelium-dependent attenuation of vasoconstriction induced by bupivacaine (BPV), with a particular focus on the upstream cellular signaling pathway of endothelial nitric oxide synthase (eNOS) phosphorylation induced by BPV in human umbilical vein endothelial cells (HUVECs). BPV concentration-response curves were investigated in the isolated rat aorta. The effects of Nω-nitro-L-arginine methyl ester (L-NAME), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), methylene blue, calmidazolium, the Src kinase inhibitor 4-amino-3-(4-chlorophenyl)-1-(t-butyl)-1H-pyrazolo[3,4-d]pyrimidine, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) and the combination of L-arginine and L-NAME on BPV-induced contraction in endothelium-intact aorta preparations were examined. The effects of BPV alone and in combination with PP2 on the phosphorylation of eNOS (at Ser1177 or Thr495), caveolin-1 and Src kinase were examined in HUVECs. BPV-induced contraction was lower in endothelium-intact aortae than in endothelium-denuded aortae. L-NAME, ODQ, methylene blue and calmidazolium increased BPV-induced contraction in endothelium-intact aortae, whereas PP2 alone and combined treatment with L-arginine and L-NAME inhibited BPV-induced contraction. Low-concentration BPV (30 µM) induced both stimulatory (Ser1177) and inhibitory (Thr495) phosphorylation of eNOS in HUVECs. However, high-concentration BPV (150 µM) induced only stimulatory (Ser1177) eNOS phosphorylation. Additionally, phosphorylation of Src kinase, caveolin-1 and inhibitory eNOS (Thr495) induced by low-concentration BPV was inhibited by PP2. These results suggest that contraction induced by low-concentration BPV is attenuated by endothelial nitric oxide release, which is modulated both stimulatory (Ser1177) and inhibitory eNOS phosphorylation (Thr495). BPV-induced phosphorylation of eNOS (Thr495) is indirectly mediated by an upstream cellular signaling pathway involving Src kinase (Tyr416) and caveolin-1 (Tyr14).

Vaginal dryness: individualised patient profiles, risks and mitigating measures

Vaginal dryness (VD) affects both pre- and postmenopausal women at any age. Since the hormonal regulation changes during the climacteric period are considered as being the main course of the VD, affected women prefer not to talk about the problem. However, the problem does exist, and unfortunately if any, relatively minor group in the population possesses the health literacy at sufficient level to understand that VD is a suboptimal health condition which carries a multi-factorial character. Thereby, some of the contributing factors are clearly preventable and, therefore, if treated properly, have a potential to milden the VD. Current chapter demonstrates specific signs and symptoms of Flammer syndrome in women suffering from vaginal dryness, although individualised patient profiles clearly discriminate between pre- and postmenopausal women regarding the subgroup-specific symptoms. Noteworthy, about 20% of the VD patients involved in the study notify a delayed or even impaired wound healing observed for themselves over a couple of years. Optimising modifiable risk factors accompanying FS phenotype at the level of primary prevention is strongly recommended. Individualised patient profiles provide important information for VD mitigating measures tailored to the person. Further, future projects should essentially deal with the complexity of vulvar-vaginal dryness as part of the Sicca syndrome in individuals with FS phenotype, in order to prevent genital female cancers which may occur at any age. In contrast to the human papilloma virus as possible trigger of the disease, the role of the vulvar-vaginal dryness as an important risk factor is strongly underestimated in currently applied diagnostic and treatment approaches.

Optimal Time Delay of Epinephrine in One-Per-Mil Solution to Visualize Operation Field

BACKGROUND

This study aimed to find out the optimal time delay of epinephrine in one-per-mil tumescent solution containing 1:1,000,000 epinephrine and 0.2% lidocaine to achieve optimal visualization in hand surgery.

MATERIALS AND METHODS

Twelve healthy male subjects who volunteered to join this prospective, randomized, double blind study were selected with convenient sampling technique. The subject's hand and the solution, either the one-per-mil or normal saline solution, were randomly selected. Injections were given to the ring finger's pulp, whereas the oxygen saturation (SpO₂) of each finger was measured with Masimo's Radical-7 Pulse Oximeter at 5 min before injection and continuously up to 45 min after injection. The device showed the SpO₂ every 2 s. Any value of SpO₂ was noted if it stayed the same point for at least 30 s in a row without interruption. The time of the lowest SpO₂ was recorded and analyzed.

RESULTS

The average of SpO₂ after injection in the epinephrine group was 96.5 (95-97), P = 0.002, whereas the normal saline group was 97.5 ± 1.168, P = 0.003. Both were statistically significant compared with their respective baseline values. The average delta SpO₂ of the epinephrine group was 3.42 ± 0.996, whereas the normal saline group was 1.50 ± 1.567 (P = 0.001; CI 0.923-2.911). The time to achieve the lowest SpO₂ in the epinephrine group was obtained at the average time of 13.90 ± 5.38 min after injection.

CONCLUSIONS

The optimal time delay of the epinephrine in the one-per-mil tumescent solution was 13.90 ± 5.38 min after injection.

Photoplethysmographic characterization of vascular tone mediated changes in arterial pressure: an observational study

To determine whether a classification based on the contour of the photoplethysmography signal (PPGc) can detect changes in systolic arterial blood pressure (SAP) and vascular tone. Episodes of normotension (SAP 90-140 mmHg), hypertension (SAP > 140 mmHg) and hypotension (SAP < 90 mmHg) were analyzed in 15 cardiac surgery patients. SAP and two surrogates of the vascular tone, systemic vascular resistance (SVR) and vascular compliance (Cvasc = stroke volume/pulse pressure) were compared with PPGc. Changes in PPG amplitude (foot-to-peak distance) and dicrotic notch position were used to define 6 classes taking class III as a normal vascular tone with a notch placed between 20 and 50% of the PPG amplitude. Class I-to-II represented vasoconstriction with notch placed > 50% in a small PPG, while class IV-to-VI described vasodilation with a notch placed < 20% in a tall PPG wave. 190 datasets were analyzed including 61 episodes of hypertension [SAP = 159 (151-170) mmHg (median 1st-3rd quartiles)], 84 of normotension, SAP = 124 (113-131) mmHg and 45 of hypotension SAP = 85(80-87) mmHg. SAP were well correlated with SVR (r = 0.78, p < 0.0001) and Cvasc (r = 0.84, p < 0.0001). The PPG-based classification correlated well with SAP (r = - 0.90, p < 0.0001), SVR (r = - 0.72, p < 0.0001) and Cvasc (r = 0.82, p < 0.0001). The PPGc misclassified 7 out of the 190 episodes, presenting good accuracy (98.4% and 97.8%), sensitivity (100% and 94.9%) and specificity (97.9% and 99.2%) for detecting episodes of hypotension and hypertension, respectively. Changes in arterial pressure and vascular tone were closely related to the proposed classification based on PPG waveform.Clinical Trial Registration NTC02854852.

Hemodynamic and neuronal responses to cocaine differ in awake versus anesthetized animals: Optical brain imaging study

Cocaine is a highly addictive drug with complex pharmacological effects. Most preclinical imaging studies investigating the effects of cocaine in the brain have been performed under anesthesia, which confounds findings. To tackle this problem, we used optical imaging to compare the effects of cocaine in the awake versus the anesthetized states. For this purpose, we customized an air floating mobile cage to fit the multi-wavelength spectral and laser speckle optical imaging system and implanted a multi-layer cranial window over the mouse somatosensory cortex. Results showed significant differences in neuronal activity and hemodynamics at baseline and in response to cocaine between the awake and the anesthetized states (isoflurane anesthesia). Specifically, 1) at baseline isoflurane dilated cerebral vessels, increased cerebral blood flow and depressed neuronal Ca²⁺ activity compared to the awake state; 2) acute cocaine (1 mg/kg iv) vasoconstricted blood vessels (arteries and veins) and decreased cerebral blood flow and oxygenated hemoglobin in the anesthetized state but not in the awake condition; 3) cocaine increased the accumulation of mean intracellular Ca²⁺ in neurons in the anesthetized state but not in the awake condition; and 4) in the awake state acute cocaine increased neuronal activities (increased the frequency of Ca²⁺ transients) and increased neuronal synchronization. We also corroborated that in the awake state cocaine also disrupted neurovascular coupling. These findings indicate that both vascular and neuronal responses to cocaine are influenced by isoflurane anesthesia, which highlights the importance of imaging awake animals when studying the effects of cocaine or other drugs in the brain.

Prostaglandin E2 Receptor EP4 Inhibition Contracts Rat Ductus Arteriosus

BACKGROUND

Patent ductus arteriosus (PDA) is common in premature infants. Cyclooxygenase inhibitors such as indomethacin, which inhibit prostaglandin E₂(PGE₂) synthesis, are currently the sole treatments for patients with PDA. Their efficacy are, however, frequently limited, and adverse effects are problematic. Because the PGE₂-specific receptor EP4 selectively expresses in rat ductus arteriosus (DA), it is hypothesized that EP4 inhibition would promote DA closure with fewer side-effects.Methods and Results:A new chemical compound EP4 antagonist, RQ-15986 (renamed from CJ-042794), was used. Whether RQ-15986 selectively contracted the DA was examined by measuring the isometric tension of rat DA ex vivo at embryonic day 19 (e19) and e21. RQ-15986 at a dose of 10^-6mol/L increased the isometric tension of the DA up to 44.8±6.2% and 69.1±12.9% to the maximal KCl-induced tension at e19 and e21 respectively. The effect of RQ-15986 on rat DA in vivo was also tested by using a rapid whole-body freezing method. RQ-15986 inhibited PGE₁-induced DA dilatation in neonatal rats. Furthermore, RQ-15986 contracted the DA in a dose-dependent manner, and the constriction was greater at e21 than at e19. Moreover, RQ-15986 did not contract the aorta or the marginal artery of the colon.

CONCLUSIONS

EP4 inhibition contracts rat DA with fewer side-effects. EP4 inhibition is a promising alternative strategy to treat patients with PDA.

Angiographic Characteristics of Hemorrhagic and Ischemic Phases of Reversible Cerebral Vasoconstriction Syndrome

PURPOSE

This study aimed to assess the evolution of imaging patterns over time in patients with neurological complications caused by reversible cerebral vasoconstriction syndrome.

METHODS

A total of 24 consecutive patients with reversible cerebral vasoconstriction syndrome presenting between 2009 and 2016 were included, whose disease course was complicated by intracranial hemorrhage and/or ischemic events. In total 55 angiographic studies were carried out. The nature of the intracranial complication and location of vasoconstriction on the angiograms in relation to the time interval since symptom-onset were assessed.

RESULTS

Complications included subarachnoid hemorrhage (n = 19, 79%), intracerebral hemorrhage (n = 7, 29%), ischemic stroke (n = 6, 25%), and transient ischemic attack (n = 4, 17%). Hemorrhagic complications mainly occurred within 7 days after symptom onset (18/19 patients, 95%), whereas ischemic events only occurred after the first week (10/10 patients, 100%, p < 0.00001). Distal vasospasm was predominantly observed within 7 days (26/28 angiograms, 93%) and proximal vasospasm ≥7 days (23/27 angiograms, 85%, p < 0.00001).

CONCLUSION

In reversible cerebral vasoconstriction syndrome causing neurological complications, an early hemorrhagic phase with distal vasospasm and a delayed ischemic phase with proximal vasospasm can be discriminated.

(-)-Epicatechin inhibits development of dilated cardiomyopathy in δ sarcoglycan null mouse

BACKGROUND AND AIMS

Several studies propose that (-)-epicatechin, a flavonol present in high concentration in the cocoa, has cardioprotective effects. This study aimed to evaluate the impact of (-)-epicatechin on the development of dilated cardiomyopathy in a δ sarcoglycan null mouse model.

METHODS AND RESULTS

δ Sarcoglycan null mice were treated for 15 days with (-)-epicatechin. Histological and morphometric analysis of the hearts treated mutant mice showed significant reduction of the vasoconstrictions in the coronary arteries as well as fewer areas with fibrosis and a reduction in the loss of the ventricular wall. On the contrary, it was observed a thickening of this region. By Western blot analysis, it was shown, and increment in the phosphorylation level of eNOS and PI3K/AKT/mTOR/p70S6K proteins in the heart of the (-)-epicatechin treated animals. On the other hand, we observed a significantly decreased level of the atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) heart failure markers.

CONCLUSION

All the results indicate that (-)-epicatechin has the potential to prevent the development of dilated cardiomyopathy of genetic origin and encourages the use of this flavonol as a pharmacological therapy for dilated cardiomyopathy and heart failure diseases.

CO2-related vasoconstriction superimposed on ischemic medullary brain autonomic nuclei may contribute to sudden death

INTRODUCTION

In 2015, a multinational randomized controlled phase IV clinical trial of adaptive servoventilation for the management of heart failure with central sleep apnea was halted in progress because more patients in the study group were dying than in the control group. One year later, another large clinical trial reported results on the effectiveness of continuous positive airway pressure (CPAP) in preventing sudden death and other cardiovascular events such as heart attack and stroke in patients with preexisting vascular disease as well as obstructive sleep apnea.

BACKGROUND

Sudden unexpected death has been associated with many types of small and nonmalignant medullary brain lesions, like demyelination plaques - largely asymptomatic until they caused sudden death. Many such medullary lesions, typically without hemorrhage or mass effect, have in themselves been previously considered relatively harmless - in cases where they have been known to be present.

DISCUSSION

Why did not the improved pulmonary ventilation and subsequently improved gas exchange provided during the CPAP and servoventilation clinical trials help to resolve any ischemic lesions that may have been present both in the heart and in the medulla, thereby tending to normalize interactions between the vagal neural structures and the heart? CO₂ is a potent dilator of brain vasculature, thereby increasing blood flow to the brain. When ventilation is increased, even if only to improve it back toward normal from a depressed steady-state level, the alveolar partial pressure of carbon dioxide is decreased, likely resulting in a converse relative vasoconstriction in the brain, thereby reducing blood flow in the brain, especially in watershed areas like the solitary tract nucleus. In normal physiology, this is demonstrated impressively by the ability of hyperventilation to induce loss of consciousness.

CONCLUSIONS

The findings of several clinical trials recently reported, taken together with neuropathology case studies reported elsewhere, suggest that additional research is warranted in regard to the mechanisms by which focal medullary autonomic brain ischemia may be related to sudden death in general medical illnesses - and how it may additionally be influenced by changes in arterial CO₂ levels.

Distinct roles of angiotensin receptors in autonomic dysreflexia following high-level spinal cord injury in mice

Autonomic dysreflexia (AD), a syndrome caused by loss of supraspinal control over sympathetic activity and amplified vascular reflex upon sensory stimuli below injury level, is a major health problem in high-level spinal cord injury (SCI). After supraspinal sympathetic control of the vasculature below the lesion is lost, the renin-angiotensin system (RAS) is thought to be involved in AD by regulating blood pressure and vascular reactivity. In this study, we aimed to assess the role of different RAS receptors during AD following SCI. Therefore, we induced AD by colorectal distention (CRD) in wild-type mice and mice deficient in the RAS components angiotensin (Ang) II type 1a receptor (AT1a) (Agtr1a^-/-) and Ang-(1-7) receptor Mas (Mas^-/-) four weeks after complete transection of spinal cord at thoracic level 4 (T4). Systemic blood pressure measurements and wire myography technique were performed to assess hemodynamics and the reactivity of peripheral arteries, respectively. CRD increased mean arterial blood pressure (MAP) and decreased heart rate (HR) in all three animal groups. However, we found less increases in MAP in Mas^-/- mice compared to control mice after CRD, whereas AT1a deficiency did not affect the hemodynamic response. We found that the reactivity of wild-type and Mas^-/- mesenteric arteries, which are innervated from ganglia distal but close to thoracic level T4, was diminished in response to Ang II in AD after T4-SCI, but this difference was not observed in the absence of AT1a receptors. CRD did not influence the reactivity of femoral arteries which are innervated from ganglia more distal to thoracic level T4, in response to Ang II in AD. In conclusion, we identified a specific role of the Ang-(1-7) receptor Mas in regulating the systemic blood pressure increase in AD in T4-SCI mice. Furthermore, AT1a signaling is not involved in this hemodynamic response, but underlies increased vascular reactivity in mesenteric arteries in response to Ang II, where it may contribute to adaptive changes in regional blood flow.

Role of Urotensin-2 in 5-Fluorouracil-Related Arterial Vasoconstriction in Cancer Patients

BACKGROUND

The aim of this study was to identify the possible relationship of 5-fluorouracil (5-FU)-related arterial vasoconstriction with urotensin-2 (UT-2), which has a high potential as an endogenic vasoconstrictor.

METHODS

We assigned the patients to 1 of 3 groups. Patients in group 1 received a bolus of 5-FU, those in group 2 a continuous infusion (CI) of 5-FU, and those in group 3 no 5-FU, which was also a control group. Pre- and post-treatment UT-2 levels and brachial arterial diameters were measured and recorded in all patients.

RESULTS

132 patients were included in the study. Pre- and post-treatment brachial artery diameters were similar in all groups: in group 1 (3.28 ± 0.52 vs. 3.25 ± 0.44 mm, p = 0.740), in group 2 (3.57 ± 0.47 vs. 3.46 ± 0.45 mm, p = 0.441) and in the control group (3.51 ± 0.52 vs. 3.25 ± 0.44 mm, p = 0.818). Pre- and post-treatment UT-2 levels were significantly different in each group: in group 1 (39.5 ± 30.9 vs. 56.7 ± 27.1 ng/ml, p = 0.0001), in group 2 (37.7 ± 33.7 vs. 62.5 ± 37.7 ng/ml, p = 0.0001) and in the control group (52.9 ± 40.2 vs. 60.8 ± 40.7 ng/ml, p = 0.006).

CONCLUSION

Our findings suggest that UT-2 has a high potential as a vasoconstrictor agent in our bodies and its level increases through a bolus or CI 5-FU. Increased UT-2 levels are likely to play a role in 5-FU-related cardiac toxicity pathogenesis.

Effects of hyperoxia on vascular tone in animal models: systematic review and meta-analysis

BACKGROUND

Arterial hyperoxia may induce vasoconstriction and reduce cardiac output, which is particularly undesirable in patients who already have compromised perfusion of vital organs. Due to the inaccessibility of vital organs in humans, vasoconstrictive effects of hyperoxia have primarily been studied in animal models. However, the results of these studies vary substantially. Here, we investigate the variation in magnitude of the hyperoxia effect among studies and explore possible sources of heterogeneity, such as vascular region and animal species.

METHOD

Pubmed and Embase were searched for eligible studies up to November 2017. In vivo and ex vivo animal studies reporting on vascular tone changes induced by local or systemic normobaric hyperoxia were included. Experiments with co-interventions (e.g. disease or endothelium removal) or studies focusing on lung, brain or fetal vasculature or the ductus arteriosus were not included. We extracted data pertaining to species, vascular region, blood vessel characteristics and method of hyperoxia induction. Overall effect sizes were estimated with a standardized mean difference (SMD) random effects model.

RESULTS

We identified a total of 60 studies, which reported data on 67 in vivo and 18 ex vivo experiments. In the in vivo studies, hyperoxia caused vasoconstriction with an SMD of - 1.42 (95% CI - 1.65 to - 1.19). Ex vivo, the overall effect size was SMD - 0.56 (95% CI - 1.09 to - 0.03). Between-study heterogeneity (I2) was high for in vivo (72%, 95% CI 62 to 85%) and ex vivo studies (86%, 95% CI 78 to 98%). In vivo, in comparison to the overall effect size, hyperoxic vasoconstriction was less pronounced in the intestines and skin (P = 0.03) but enhanced in the cremaster muscle region (P < 0.001). Increased constriction was seen in vessels 15-25 μm in diameter. Hyperoxic constriction appeared to be directly proportional to oxygen concentration. For ex vivo studies, heterogeneity could not be explained with subgroup analysis.

CONCLUSION

The effect of hyperoxia on vascular tone is substantially higher in vivo than ex vivo. The magnitude of the constriction is most pronounced in vessels ~ 15-25 μm in diameter and is proportional to the level of hyperoxia. Relatively increased constriction was seen in muscle vasculature, while reduced constriction was seen in the skin and intestines.

Large-conductance Ca2+-activated potassium channels are potently involved in the inverse neurovascular response to spreading depolarization

Recurrent spreading depolarizations occur in the cerebral cortex from minutes up to weeks following acute brain injury. Clinical evidence suggests that the immediate reduction of cerebral blood flow in response to spreading depolarization importantly contributes to lesion progression as the wave propagates over vulnerable tissue zones, characterized by potassium concentration already elevated prior to the passage of spreading depolarization. Here we demonstrate with two-photon microscopy in anesthetized mice that initial vasoconstriction in response to SD triggered experimentally with 1 M KCl is coincident in space and time with the large extracellular accumulation of potassium, as shown with a potassium indicator fluorescent dye. Moreover, pharmacological manipulations in combination with the use of potassium-sensitive microelectrodes suggest that large-conductance Ca²⁺-activated potassium (BK) channels and L-type voltage-gated calcium channels play significant roles in the marked initial vasoconstriction under elevated baseline potassium. We propose that potassium efflux through BK channels is a central component in the devastating neurovascular effects of spreading depolarizations in tissue at risk.

Endocannabinoid-mediated modulation of Gq protein-coupled receptor mediates vascular hyporeactivity to nor-adrenaline during polymicrobial sepsis

BACKGROUND

Endocannabinoids level are reported to increase in sepsis, however, the role of vascular cannabinoid receptor-1 (CB1R) in sepsis-induced vascular hyporeactivity is yet to be unravelled.

METHODS

Polymicrobial sepsis was induced by caecal ligation and puncture in mice. Isometric tension in isolated aortic rings during early (6 h) and late (20 h) phases of sepsis was recorded and expression of mRNA of monoacylglycerol lipase (MAGL) and cannabinoid receptor-1 (CB1R) was investigated.

RESULTS

Sepsis significantly (p < 0.001) reduced the mean survival time in mice along with increase in bacterial load in blood and peritoneal lavage. Compared to Sham-operated (SO) mice, vascular reactivity to nor-adrenaline (NA) was significantly (p < 0.05) attenuated in both early and late phases of sepsis. NA-induced vasoconstriction was significantly (p < 0.05) potentiated by inhibition of diacylglycerol lipase (DAGL) and attenuated by inhibition of MAGL in SO mice. Pre-incubation with KT 109, a DAGL inhibitor, significantly (p < 0.05) improved the vascular hypo-reactivity to NA during both the phases of sepsis. mRNA expression of MAGL in aorta was significantly (p < 0.05) attenuated during both the phases of sepsis. But in the presence of AM 251, specific antagonist of CB1R, vascular reactivity to NA was significantly (p < 0.05) restored along with significant (p < 0.05) increase in mRNA expression of CB1R in aortic rings from both early and late phases of septic mice.

CONCLUSION

2-AG regulates vascular response to NA and increased aortic expression of CB1R is responsible for vascular hyporeactivity to NA in sepsis, and in vitro inhibition of this receptor by AM 251 restored the vascular reactivity.

Impact of dexmedetomidine on the tissue distribution, anesthetic action, and hemodynamic effects of mepivacaine

The present study investigated the regional blood flow, tissue distribution, local anesthetic action, and hemodynamic effects of mepivacaine containing dexmedetomidine hydrochloride (DEX) in rats. Blood flow was measured after injection of 0.5% mepivacaine (M group), 12.5 µg/ml DEX (D group), or 0.5% mepivacaine containing 12.5 µg/ml DEX (DM group) into the upper lip. Mepivacaine distribution was autoradiographically observed in maxillary bone resected after injection of 0.5% ³H-mepivacaine (HM group) or 0.5% ³H-mepivacaine containing 12.5 µg/ml DEX (DHM group) into the palatal mucosa adjacent to the right maxillary first molar. Radioactivity was also measured using a liquid scintillation counter. SEP were measured to analyze anesthetic action. Blood pressure and heart rate were measured to compare hemodynamic effect. The addition of DEX significantly decreased blood flow compared to M group from 10 to 60 min after injection. The addition of DEX significantly increased the amount of radioactivity compared to HM group in the palatal mucosa from 5 to 60 min after injection and in the body of the maxilla from 2 to 60 min after injection. Maximum blood radioactivity was measured at 5 min after injection in HM group and 50 min after injection in DHM group. The addition of DEX significantly decreased peak-to-peak amplitudes compared to M group until 60 min after injection. No significant hemodynamic differences were observed. DEX enhances the action of mepivacaine in reducing regional blood flow prolongs its tissue retention, and increases the local anesthetic action without affecting hemodynamics on local administration.

Mechanisms of electrical vasoconstriction

BACKGROUND

Electrical vasoconstriction is a promising approach to control blood pressure or restrict bleeding in non-compressible wounds. We explore the neural and non-neural pathways of electrical vasoconstriction in-vivo.

METHODS

Charge-balanced, asymmetric pulses were delivered through a pair of metal disc electrodes. Vasoconstriction was assessed by measuring the diameter of rat saphenous vessels stimulated with low-voltage (20 V, 1 ms) and high-voltage (150 V, 10 μs) stimuli at 10 Hz for 5 min. Activation pathways were explored by topical application of a specific neural agonist (phenylephrine, alpha-1 receptor), a non-specific agonist (KCl) and neural inhibitors (phenoxybenzamine, 25 mg/ml; guanethidine, 1 mg/ml). Acute tissue damage was assessed with a membrane permeability (live-dead) fluorescent assay. The Joule heating in tissue was estimated using COMSOL Multiphysics modeling.

RESULTS

During stimulation, arteries constricted to 41 ± 8% and 37 ± 6% of their pre-stimulus diameter with low- and high-voltage stimuli, while veins constricted to 80 ± 18% and 40 ± 11%, respectively. In arteries, despite similar extent of constriction, the recovery time was very different: about 30 s for low-voltage and 10 min for high-voltage stimuli. Neural inhibitors significantly reduced low-voltage arterial constriction, but did not affect high-voltage arterial or venous constriction, indicating that high-voltage stimuli activate non-neural vasoconstriction pathways. Adrenergic pathways predominantly controlled low-voltage arterial but not venous constriction, which may involve a purinergic pathway. Viability staining confirmed that stimuli were below the electroporation threshold. Modeling indicates that heating of the blood vessels during stimulation (< 0.2 °C) is too low to cause vasoconstriction.

CONCLUSIONS

We demonstrate that low-voltage stimuli induce reversible vasoconstriction through neural pathways, while high-voltage stimuli activate non-neural pathways, likely in addition to neural stimulation. Different stimuli providing precise control over the extent of arterial and venous constriction as well as relaxation rate could be used to control bleeding, perfusion or blood pressure.

Vascular effects of apelin: Mechanisms and therapeutic potential

Apelin is a vasoactive peptide and is an endogenous ligand for APJ receptors, which are widely expressed in blood vessels, heart, and cardiovascular regulatory regions of the brain. A growing body of evidence now demonstrates a regulatory role for the apelin/APJ receptor system in cardiovascular physiology and pathophysiology, thus making it a potential target for cardiovascular drug discovery and development. Indeed, ongoing studies are investigating the potential benefits of apelin and apelin-mimetics for disorders such as heart failure and pulmonary arterial hypertension. Apelin causes relaxation of isolated arteries, and systemic administration of apelin typically results in a reduction in systolic and diastolic blood pressure and an increase in blood flow. Nonetheless, vasopressor responses and contraction of vascular smooth muscle in response to apelin have also been observed under certain conditions. The goal of the current review is to summarize major findings regarding the apelin/APJ receptor system in blood vessels, with an emphasis on regulation of vascular tone, and to identify areas of investigation that may provide guidance for the development of novel therapeutic agents that target this system.