Elevation Of Intraluminal Pressure Research Articles

Sphingosine-1-Phosphate Promotes Resiliency to External Stress in the Human Microvasculature

Exposure to external stress (e.g. high pressure, high glucose) promotes human microvascular endothelial dysfunction and reduces the overall magnitude of flow-induced dilation (FID). We have previously shown that treatment with sphingosine-1-phosphate (S1P), a sphingolipid known to activate pro-survival pathways in endothelial cells, restores nitric oxide (NO) as the primary mediator of flow-induced dilation (FID) in arterioles from patients with coronary artery disease. Whether pre-treatment with S1P can prevent stress-induced microvascular endothelial dysfunction remains unknown. Our hypothesis is that pre-conditioning with S1P will promote resiliency to external stress (high intraluminal pressure) and prevent stress-induced reduction of FID. Human resistance arterioles (100-250μm) from otherwise healthy adults (one risk factor or less for coronary artery disease) were dissected from discarded surgical adipose tissue and treated with S1P (1μM) or vehicle control for 16-20 hr prior to the flow experiment. Vessels were cannulated for videomicroscopy and stressed with elevated intraluminal pressure (150mmHg, 30 min) then pre-constricted with endothelin-1 prior to initiating flow to elicit dilation. Arterioles treated with vehicle and exposed to high intraluminal pressure exhibited an overall reduction in vasodilatory capacity to flow (37.3%±8.6) compared to non-stressed, vehicle treated microvessels (66.1%±5.5). However, the ability to dilate to flow was preserved in microvessels pre-treated with S1P and exposed to high pressure (74.8%±6.7) compared to vehicle and high pressure (37.3%±8.6). These data suggest that S1P-activated pathways may foster resilience by reversing stress-induced microvascular endothelial function. Targeting S1P signaling may offer a novel therapeutic strategy to prevent microvascular dysfunction and the myriad diseases it causes, such as large vessel atherosclerosis, and heart failure with preserved ejection fraction. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Death-associated protein kinase 3 regulates the myogenic reactivity of cerebral arteries.

What is the central question of this study? DAPK3 contributes to the Ca2+ -sensitization of vascular smooth muscle contraction: does this protein kinase participate in the myogenic response of cerebral arteries? What is the main finding and its importance? Small molecule inhibitors of DAPK3 effectively block the myogenic responses of cerebral arteries. HS38-dependent changes to vessel constriction occur independent of LC20 phosphorylation, and therefore DAPK3 appears to operate via the actin cytoskeleton. A role for DAPK3 in the myogenic response was not previously reported, and the results support a potential new therapeutic target in the cerebrovascular system. The vascular smooth muscle (VSM) of resistance blood vessels is a target of intrinsic autoregulatory responses to increased intraluminal pressure, the myogenic response. In the brain, the myogenic reactivity of cerebral arteries is critical to homeostatic blood flow regulation. Here we provide the first evidence to link the death-associated protein kinase 3 (DAPK3) to the myogenic response of rat and human cerebral arteries. DAPK3 is a Ser/Thr kinase involved in Ca2+ -sensitization mechanisms of smooth muscle contraction. Ex vivo administration of a specific DAPK3 inhibitor (i.e., HS38) could attenuate vessel constrictions invoked by serotonin as well as intraluminal pressure elevation. The HS38-dependent dilatation was not associated with any change in myosin light chain (LC20) phosphorylation. The results suggest that DAPK3 does not regulate Ca2+ sensitization pathways during the myogenic response of cerebral vessels but rather operates to control the actin cytoskeleton. A slow return of myogenic tone was observed during the sustained ex vivo exposure of cerebral arteries to HS38. Recovery of tone was associated with greater LC20 phosphorylation that suggests intrinsic signalling compensation in response to attenuation of DAPK3 activity. Additional experiments with VSM cells revealed HS38- and siDAPK-dependent effects on the actin cytoskeleton and focal adhesion kinase phosphorylation status. The translational importance of DAPK3 to the human cerebral vasculature was noted, with robust expression of the protein kinase and significant HS38-dependent attenuation of myogenic reactivity found for human pial vessels.

Novel Smooth Muscle Ca2+-Signaling Nanodomains in Blood Pressure Regulation.

Ca2+ signals in smooth muscle cells (SMCs) contribute to vascular resistance and control blood pressure. Increased vascular resistance in hypertension has been attributed to impaired SMC Ca2+ signaling mechanisms. In this regard, transient receptor potential vanilloid 4 (TRPV4SMC) ion channels are a crucial Ca2+ entry pathway in SMCs. However, their role in blood pressure regulation has not been identified. We used SMC-specific TRPV4-/- (TRPV4SMC-/-) mice to assess the role of TRPV4SMC channels in blood pressure regulation. We determined the contribution of TRPV4SMC channels to the constrictor effect of α1 adrenergic receptor (α1AR) stimulation and elevated intraluminal pressure: 2 main physiologic stimuli that constrict resistance-sized arteries. The contribution of spatially separated TRPV4SMC channel subpopulations to elevated blood pressure in hypertension was evaluated in angiotensin II-infused mice and patients with hypertension. We provide first evidence that TRPV4SMC channel activity elevates resting blood pressure in normal mice. α1AR stimulation activated TRPV4SMC channels through PKCα (protein kinase Cα) signaling, which contributed significantly to vasoconstriction and blood pressure elevation. Intraluminal pressure-induced TRPV4SMC channel activity opposed vasoconstriction through activation of Ca2+-sensitive K+ (BK) channels, indicating functionally opposite pools of TRPV4SMC channels. Superresolution imaging of SMCs revealed spatially separated α1AR:TRPV4 and TRPV4:BK nanodomains in SMCs. These data suggest that spatially separated α1AR-TRPV4SMC and intraluminal pressure-TRPV4SMC-BK channel signaling have opposite effects on blood pressure, with α1AR-TRPV4SMC signaling dominating under resting conditions. Furthermore, in patients with hypertension and a mouse model of hypertension, constrictor α1AR-PKCα-TRPV4 signaling was upregulated, whereas dilator pressure-TRPV4-BK channel signaling was disrupted, thereby increasing vasoconstriction and elevating blood pressure. Our data identify novel smooth muscle Ca2+-signaling nanodomains that regulate blood pressure and demonstrate their impairment in hypertension.

Dynamic Remodeling of Human Arteriovenous Fistula Wall Obtained From Magnetic Resonance Imaging During the First 6 Months After Creation

The nonmaturation rate of arteriovenous fistulas (AVFs) is high.1 The direct connection of the AVF vein and artery creates a short path that bypasses the distal high-resistance vasculature, resulting in an immediate increase in the flow rate and venous pressure. With the endothelium-dependent flow dilation and increased distention by elevated intraluminal pressure for the vein, the AVF lumen diameter increases immediately, resulting in a thinner wall and increased hoop stress within the wall immediately after AVF creation.

Differential responses of resistance arterioles to elevated intraluminal pressure in blacks and whites.

Black Americans have an earlier onset, higher average blood pressure, and higher rates of hypertension-related mortality and morbidity, compared to whites. The racial difference may be related to microvasculature, the major regulatory site of blood pressure. The goal of this study was to compare the response of resistance vessels to high intraluminal pressure between black and white participants. A total of 38 vessels were obtained from human fat samples [21 black, 17 white; mean age 32 ± 12 yr and body mass index (BMI) 26.9 ± 4.9; between-group P ≥ 0.05] and included in this study. Internal diameter was measured in response to the flow induced by various pressure gradients (Δ10, Δ20, Δ40, Δ60, and Δ100 cmH2O), and flow-induced dilation (FID) was calculated before and after high intraluminal pressure (150 cmH2O). Before high intraluminal pressure, FID was not different between blacks and whites (P = 0.112). After exposure to high intraluminal pressure, FID was reduced at every pressure gradient in vessels from blacks (P < 0.001), whereas FID did not change in white participants except at Δ100 cmH2O. When incubated with the hydrogen peroxide (H2O2) scavenger polyethylene glycol-catalase (PEG-catalase), the FID response in vessels from black, but not white, individuals was significantly reduced and the magnitude was higher at normal pressure relative to high pressure. Our findings suggest that the vessels from self-identified black individuals are more susceptible to microvascular dysfunction following transient periods of high intraluminal pressure compared to whites and show greater dependence on H2O2 as a main contributor to FID at normal pressures.NEW & NOTEWORTHY Microvascular function regulates blood pressure and may contribute to racial differences in the incidence and prevalence of hypertension and other cardiovascular diseases. Here, we show that using an ex vivo model of resistance arterioles isolated from human gluteal fat tissue, flow-induced dilation is not different between black and white participants. However, when exposed to transient increases in intraluminal pressure, the flow-induced dilation in resistance arterioles from black participants demonstrated greater reductions relative to their white counterparts, indicating a higher sensitivity to pressure change in the microvasculature.

HYPERBILIRUBINEMIA AS AN INDICATOR IN PERFORATED APPENDICITIS

Introduction: Acute appendicitis is one of the most common causes of urgent admission to the hospital.In appendicitis, elevated intra-luminal pressure and ischemic necrosis of mucosa causes tissue gangrene or perforation. This leads to cytotoxin facilitated progressive bacterial invasion or translocation into the hepatic parenchyma through portal system. This phenomenon interferes with the bilirubin excretion into the bile canaliculi. The rate of misdiagnosis of appendicitis and the rate of appendicular perforation has remained constant, inspite of increased use of ultrasonography, computed tomography scanning and laparoscopy. Among commonly used inammation markers of Acute appendicitis, bilirubin concentration is not well studied and thus is rarely applied. Every investigation that can contribute towards a diagnosis of appendicitis is valuable to the emergency general surgeon Aim: 1. To study the relationship between hyperbilirubinemia and acute appendicitis; and to evaluate its credibility as a diagnostic marker for acute appendicitis. 2. To evaluate whether elevated bilirubin levels have a predictive potential for the diagnosis of Appendicular perforation. Material and methods: The study was conducted in the Department of General Surgery, Navodaya Medical College &amp; Research centre, Raichur during the period of January 2020 to December 2020.Patients admitted with clinical diagnosis of acute appendicitis or appendicular perforation under the Department of Surgery, Navodaya Medical College &amp; Research centre, Raichur during the study period. A total of 100 patients with clinical diagnosis of acute appendicitis or appendicular perforation were studied. Results: .Normal bilirubin values were seen in 26% patients while, 74% had raised bilirubin levels (Hyperbilirubinemia). Of 81 patients with acute appendicitis, 71.6% had raised bilirubin levels, while 28.4% had normal levels. 19 patients were diagnosed as Appendicular perforation, 16 patients (84.21%) had raised bilirubin levels, while the remaining 03 patients (15.79%) had normal levels.Amongst the patients diagnosed with Acute appendicitis without perforation (n=81), 58 patients (71.6%) were found to have elevated bilirubin (&gt;1.0 mg/dL) while only 23 patients (28.4%) had normal bilirubin levels (≤1.0 mg/dL). In patients diagnosed with Appendicular perforation (n=19), 16 patients (84.21%) had bilirubin elevated (&gt;1.0 mg/dL), while only 3 patients (15.79%) had normal levels (&gt;1.0 mg/dL). Thus, Hyperbilirubinemia was found in most of the patients diagnosed with acute appendicitis (71.6%) or Appendicular perforation (84.21%). Conclusion: The present study suggests- Serum bilirubin levels appears to be a promising new laboratory marker for diagnosing acute appendicitis, however diagnosis of appendicitis remains essentially still - clinical. Its level come out to be a credible aid in diagnosis of acute appendicitis and would be helpful investigation in decision making. Patients with clinical signs and symptoms of appendicitis and with hyperbilirubinemia higher than the normal range should be identied as having a higher probability of Appendicular perforation suggesting, serum bilirubin levels have a predictive potential for the diagnosis of Appendicular perforation.

Evaluation of role of hyperbilirubinemia as a new diagnostic marker of complicated appendicitis

BackgroundIn appendicitis, elevated intra-luminal pressure and ischemic necrosis of mucosa causes tissue gangrene or perforation. This leads to cytotoxin facilitated progressive bacterial invasion or translocation into the hepatic parenchyma through portal system. This phenomenon interferes with the bilirubin excretion into the bile canaliculi. In the present study, establishment of a possible role of hyperbilirubinemia as a marker of gangrenous/perforated appendicitis has been studied.MethodsAfter matching the inclusion and exclusion criteria, all cases of clinically diagnosed acute appendicitis were taken for this prospective, single center, observational study. Per-operative diagnosis was confirmed by histopathological examination.ResultsOut of 110 subjects of acute appendicitis 41 subjects (37.27%) had hyperbilirubinemia. Out of 35 subjects diagnosed as complicated appendicitis 32 subjects (91.42%) had raised total bilirubin levels, while the remaining 03 (8.58%) had normal levels. Among 75 subjects diagnosed as acute simple appendicitis 09 subjects (12%) had raised total bilirubin level, while the remaining 66 subjects (88%) had normal levels. It was Mixed Type of Hyperbilirubinemia in gangrenous/perforated appendicitis. The sensitivity of Total serum bilirubin in predicting complicated appendicitis was found 91.43% (76.942% to 98.196%), where as the specificity of this test was 88.00% (78.439% to 94.363%). positive predictive value and negative predictive value were 78.03% and 95.65% respectively. Positive likelihood ratio and negative likelihood ratio were found to be 7.619 and 0.097 respectively taking prevalence of complicated appendicitis be 31.80%. Receiver Operating Characteristic curve was obtained which shows optimal criterion at Total Bilirubin Level 1.06 mg/dl where sensitivity was 91.43% and specificity was 97.33% at 95% confidence interval with 31.8% disease prevalence.ConclusionsThis is to conclude that Serum bilirubin level estimation, which is a simple, cheap and easily available laboratory test, can be added to the routine investigations in clinically suspected cases of acute appendicitis for early diagnosis of complications.Trial registration Registered with Clinical Trials Registry-India (ICMR-NIMS) with Registration number CTRI/2019/05/018879 Dated 01/05/2019. This was a prospective trial. Trial URL: http://ctri.nic.in/Clinicaltrials/pdf_generate.php?trialid=33113&EncHid=99780.32960&modid=1&compid=19%27,%2733113det%27.

Loss‐ and Gain‐of‐Function Mutations in the Type 1 IP3 Receptor (IP3R1) Affect Myogenic Constriction of Cerebral Resistance Arteries in Response to Intraluminal Pressure

The constriction and relaxation of resistance arteries/arterioles in response to changes in intraluminal pressure, referred to as the myogenic response, is a key physiological mechanism for the regulation of blood pressure and flow. Despite the recognized contribution of phospholipase C activity and IP3‐mediated intracellular Ca2+ release to the myogenic response, a lack of selective pharmacological agents to target the predominant IP3R1 Ca2+ release channel has prevented interrogation of this key mechanism. Mutations in the IP3R1 are known to produce either loss‐of‐function (LOF) or gain‐of‐function (GOF) phenotypes in humans that impact cerebellar activity (e.g. ataxia), yet the effect of these mutations on the cardiovascular system is not established. Here, we employed a novel genetic knock‐in mouse model with a single point mutation in the transmembrane S6 helix of IP3R1 that confers either a LOF (D2594A) or GOF (D2594K) phenotype. In preliminary experiments, the LOF and GOF mutations shifted IP3‐mediated ER Ca2+ release ~2‐fold to the right and left, respectively, compared to wild‐type (WT) IP3R1 in permeabilized HEK293 cells. In endothelium‐denuded posterior cerebral arteries of 3–4 month old WT mice, myogenic vasoconstriction was evident at ≥40 mmHg, maximal at ~120 mmHg, and declined at &gt;120 mmHg (n=7). In contrast, myogenic constriction was initiated at a higher pressure (≥50 mmHg) and was smaller in amplitude in arteries of heterozygous IP3R1 LOF mice (n=8). In IP3R1 GOF vessels (n=7), myogenic tone developed at a lower pressure (≥20 mmHg), was maximal at ~80 mmHg, and declined at &gt;90 mmHg. Relative levels of phosphorylation of myosin regulatory light chain (LC20) and myosin phosphatase targeting subunit (MYPT1) at 10, 40, 80 and 120 mmHg, and of globular (G‐) actin content at 10, 60 and 120 mmHg, in arteries from WT, LOF and GOF mice were assessed by ultra‐high sensitivity immunoblotting. An identical pressure‐dependent increase in phospho‐LC20 content was detected in WT, LOF and GOF vessels (n=5 each). Although phospho‐MYPT1‐T855 content increased with intraluminal pressure in arteries of WT and LOF mice, it did not change in vessels of GOF mice. Elevation of intraluminal pressure decreased in G‐actin content in arteries of WT mice, did not affect G‐actin content in LOF vessels, and caused a significantly greater decrease in GOF arteries. Taken together, these data demonstrate that genetic modification of IP3R1‐mediated Ca2+ mobilization affects the myogenic response of cerebral arteries to intraluminal pressure, a vascular impairment that may contribute to neurological dysfunction in patients with LOF and GOF IP3R1 mutations.Support or Funding InformationThis work was funded by the following research grants from the Canadian Institutes of Health Research: MOP‐97988 (WCC) MOP‐142467 (APB) and PJT‐155963 (APB, WC and WCC).

Isometric Exercise with Large Muscle Mass Improves Redox Balance and Blood Pressure in Hypertensive Adults.

The aim of this study was to investigate the hemodynamic, oxidative stress (OS), and nitric oxide (NO) responses to a submaximal isometric exercise session (IES) involving large muscle mass. Fourteen hypertensive (HTG: age = 35.9 ± 8.1 yr, height = 1.73 ± 0.10 m, total body mass = 78.0 ± 15.8 kg) and 10 normotensive (NTG: age = 41.1 ± 9.4 yr, height = 1.71 ± 0.12 m, total body mass = 82.3 ± 22.4 kg) participants performed two experimental sessions in the leg press and bench press: (i) control session and (ii) 8 sets × 1 min contraction at 30% maximal voluntary isometric contraction with 2-min rest interval. Blood pressure (BP) was measured at rest and during 60 min postexercise. Blood samples were collected at rest, immediately after the session, and 60 min postexercise. NO was obtained through the Griess reaction method. OS parameters were analyzed using commercial kits. A repeated-measures ANOVA with Bonferroni post hoc test was used to analyze all dependent variables. A significant decrease in systolic BP was observed only for HTG at 45 and 60 min postexercise (baseline vs 45 min: P = 0.03, Δ% = 4.44%; vs 60 min: P = 0.018, Δ% = 5.58%). NO increased immediately postexercise only for HTG (P = 0.008, Δ% = 16.44%). Regarding OS parameters, thiobarbituric acid reactive substances presented a significant reduction 60 min after the IES for NTG and HTG; catalase increased in both groups. The data showed that only 8 min of IES with a large muscle mass elicits an elevated pro-oxidant activity leading to a greater NO bioavailability, increases antioxidant reaction, and consequently reduces BP in hypertensive patients.

Modest Static Pressure Suppresses Columnar Epithelial Cell Growth in Association with Cell Shape and Cytoskeletal Modifications.

Intraluminal pressure elevation can cause degenerative disorders, such as ileus and hydronephrosis, and the threshold is fairly low and constant, 20–30 cm H2O. We previously devised a novel two-chamber culture system subjecting cells cultured on a semipermeable membrane to increased culture medium height (water pressure up to 60 cm H2O). Here, we sought to determine how a continuous pressure load of ~30 cm H2O affects proliferating epithelial cells with special interest in the link with cell morphology. We cultured several different cell lines using the low static pressure-loadable two-chamber system, and examined cell growth, cell cycle, and cell morphology. Madin–Darby canine kidney (MDCK) columnar epithelial cells were growth-suppressed in a manner dependent on static water pressure ranging from 2 to 50 cm H2O, without cell cycle arrest at any specific phase. Two other types of columnar epithelial cells exhibited similar phenotypes. By contrast, spherical epithelial and mesenchymal cells were not growth-suppressed, even at 50 cm H2O. Phalloidin staining revealed that 50 cm H2O pressure load vertically flattened and laterally widened columnar epithelial cells and made actin fiber distribution sparse, without affecting total phalloidin intensity per cell. When the mucosal protectant irsogladine maleate (100 nM) was added to 50-cm-high culture medium, MDCK cells were reduced in volume and their doubling time shortened. Cell proliferation and morphology are known to be regulated by the Hippo signaling pathway. A pressure load of 50 cm H2O enhanced serine-127 phosphorylation and cytoplasmic retention of YAP, the major constituent of this pathway, suggesting that Hippo pathway was involved in the pressure-induced cell growth suppression. RNA sequencing of MDCK cells showed that a 50 cm H2O pressure load upregulated keratin 14, an intermediate filament, 12-fold. This upregulation was confirmed at the protein level by immunofluorescence, suggesting a role in cytoskeletal reinforcement. These results provide evidence that cell morphology and the cytoskeleton are closely linked to cell growth. Pathological intraluminal pressure elevation may cause mucosal degeneration by acting directly on this linkage and the Hippo pathway.

ROK and Arteriolar Myogenic Tone Generation: Molecular Evidence in Health and Disease.

The myogenic response is an inherent property of resistance arteries that warrants a relatively constant blood flow in response to changes in perfusion pressure and protect delicate organs from vascular insufficiencies and excessive blood flow. This fundamental phenomenon has been extensively studied aiming to elucidate the underlying mechanisms triggering smooth muscle contraction in response to intraluminal pressure elevation, particularly, Rho-associated kinase (ROK)-mediated Ca2+-independent mechanisms. The size of the resistance arteries limits the capacity to examine changes in protein phosphorylation/expression levels associated with ROK signaling. A highly sensitive biochemical detection approach was beneficial in examining the role of ROK in different force generation mechanisms along the course of myogenic constriction. In this mini review, we summarize recent results showing direct evidence for the contribution of ROK in development of myogenic response at the level of mechanotransduction, myosin light chain phosphatase inhibition and dynamic actin cytoskeleton reorganization. We will also present evidence that alterations in ROK signaling could underlie the progressive loss in myogenic response in a rat model of type 2 diabetes.

Abnormal myosin phosphatase targeting subunit 1 phosphorylation and actin polymerization contribute to impaired myogenic regulation of cerebral arterial diameter in the type 2 diabetic Goto-Kakizaki rat

The myogenic response of cerebral resistance arterial smooth muscle to intraluminal pressure elevation is a key physiological mechanism regulating blood flow to the brain. Rho-associated kinase plays a critical role in the myogenic response by activating Ca2+ sensitization mechanisms: (i) Rho-associated kinase inhibits myosin light chain phosphatase by phosphorylating its targeting subunit myosin phosphatase targeting subunit 1 (at T855), augmenting 20 kDa myosin regulatory light chain (LC20) phosphorylation and force generation; and (ii) Rho-associated kinase stimulates cytoskeletal actin polymerization, enhancing force transmission to the cell membrane. Here, we tested the hypothesis that abnormal Rho-associated kinase-mediated myosin light chain phosphatase regulation underlies the dysfunctional cerebral myogenic response of the Goto-Kakizaki rat model of type 2 diabetes. Basal levels of myogenic tone, LC20, and MYPT1-T855 phosphorylation were elevated and G-actin content was reduced in arteries of pre-diabetic 8–10 weeks Goto-Kakizaki rats with normal serum insulin and glucose levels. Pressure-dependent myogenic constriction, LC20, and myosin phosphatase targeting subunit 1 phosphorylation and actin polymerization were suppressed in both pre-diabetic Goto-Kakizaki and diabetic (18–20 weeks) Goto-Kakizaki rats, whereas RhoA, ROK2, and MYPT1 expression were unaffected. We conclude that abnormal Rho-associated kinase-mediated Ca2+ sensitization contributes to the dysfunctional cerebral myogenic response in the Goto-Kakizaki model of type 2 diabetes.

Anti-VEGF Therapy for Retinal Vein Occlusions.

Retinal vein occlusion (RVO) is the second most common cause of visual loss in the Western World. RVO is usually classified into branch RVO (BRVO) and central RVO (CRVO) according to the anatomical site of the vascular occlusion. The pathogenesis of RVO is not yet fully understood, however an important event is the intraluminal thrombus formation, which is usually secondary to several conditions such as hypertension, hyperlipidemia, diabetes and thrombophilia. The blockage of venous circulation causes an elevation of intraluminal pressure in the capillaries, leading to hemorrhages and leakage of fluid within the retina, increase of interstitial pressure and a consequent reduction of retinal perfusion. Ischemia may develop resulting in secretion of vascular endothelial growth factor (VEGF) that causes further vascular leakage and retinal oedema. VEGF has therefore a leading role in RVO pathogenesis and symptoms. As a consequence use of anti-VEGF agents by intravitreal injections has become very common with the aim to improve the clinical outcomes in these patients. Currently 2 anti-VEGF agents (ranimizumab and aflibercept) have been FDA (Food and Drug Administration) and EMA (European Medicine Agency) approved for the treatment of RVO, while another VEGF inhibitor (bevacizumab) is often used "off-label" in clinical practice. Many treatment regimens have been suggested in the clinical trials with these drugs, as monthly injections or injections when needed, however the ideal regimen has not been defined yet. We conducted a systematic review searching MEDLINE for the following terms: retinal vein occlusion, ranibizumab, bevacizumab, aflibercept, vascular endothelial growth factor, macular oedema. Data were extracted by one author (AG and BE) and checked by a second (BPM, CC). Aim of this article was to review available data for each drug, focusing on their efficacy and safety trying to compare their advantages and limits.

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.

Segmental type of gallbladder adenomyomatosis – Case report and literature review

Abstract Introduction Adenomyomatosis of the gallbladder is a benign mural disorder characterized by a thickened wall, proliferation and distention of Rokitansky–Aschoff sinuses surrounded by proliferated fibromuscular tissue. Aim Overview of radiological imaging methods used to evaluate the segmental type of adenomyomatosis of the gallbladder. Case report The patient was admitted to the Emergency Department with typical symptoms of hepatic colic. Ultrasonography did not allow the exclusion of gallbladder cancer and diagnosis required clarification in Multidetector CT and MR with MR cholangiopancreatography. The surgical pathological specimen revealed segmental form of adenomyomatosis with cholelithiasis and chronic inflammation. Results and discussion Adenomyomatosis is not considered a pre-cancerous condition, but elevated intraluminal pressure, gallstones and chronic inflammation are risk factors for gallbladder cancer. The most common imaging methods used to diagnose adenomyomatosis of gallbladder are US and MRI with MRCP. Conclusions The segmental type of gallbladder adenomyomatosis with a tendency of cholelithiasis, and higher risk of gallbladder malignancies, is a direct recommendation for cholecystectomy. Despite improvements of diagnostic imaging methods differentiation of segmental adenomyomatosis from early gallbladder cancer still remains challenging.

Dynamic article: steady pressure CO2 colonoscopy; its feasibility and underlying mechanism.

Steady pressure automatically controlled endoscopy is a new insufflation concept, achieving a laparoscopy-like steady environment in the upper GI tract, recently reported in the esophagus. The purpose of this work was to validate the feasibility and safety of steady pressure automatically controlled endoscopy in the lower GI tract and to identify major factors that enable it. This was a nonsurvival animal study using canine models. The study was conducted in an academic center. Canine models were used in this study. In experiment 1, steady pressure automatically controlled endoscopy was attempted in the cecum with insufflation pressures of 4, 8, and 12 mm Hg. We assessed performance by video review and continuous intracecal pressure monitoring. Next, steady pressure automatically controlled endoscopy was performed for 20 minutes under optimal pressure, 8 mm Hg (n = 10). In experiment 2, steady pressure automatically controlled endoscopy was attempted in the rectum with or without artificial colonic flexure and with either low (8 mm Hg) or high (16 mm Hg) insufflation pressure to assess the effects of anatomic flexure and insufflation pressure on the establishment of steady pressure automatically controlled endoscopy (n = 6). We measured multipoint intraluminal pressure monitoring in the upstream bowel, as well as cardiopulmonary parameters. For experiment 1, steady pressure automatically controlled endoscopy in cecum was successful at all of the tested insufflation pressures; 8 mm Hg provided the optimal result. Steady pressure automatically controlled endoscopy was safely performed for 20 minutes at 8 mm Hg without any cardiopulmonary parameter changes or intraluminal pressure elevation in the upstream bowel. For experiment 2, confinement of the steady pressure environment to the rectum was achieved only with the assistance of colonic flexure and at 8 mm Hg insufflation pressure. In other conditions, the insufflated gas extended throughout the entire colon. This study was limited by being an animal study. Steady pressure automatically controlled endoscopy is feasible and safe in the lower GI tract under the optimized insufflation pressure and in the presence of anatomical flexure (see Video, Supplemental Digital Content 1, http://links.lww.com/DCR/A150).

Altered wall mechanics of conduit arteries of obese Zucker rats with progression of metabolic syndrome (867.8)

The metabolic syndrome (MetSyn) in obese Zucker rats (OZR) comes with a wide array of distinct vasculopathies including impaired endothelium‐dependent dilation and more modest alterations to VSM‐dependent responses (constrictor or dilator). While OZR do not develop atherosclerotic plaques, the presence of these alterations to wall mechanics in conduit arteries would have significant implications for pulse wave propagation, thrombo‐embolytic events, and responses to cardiovascular events such as stroke. To address this, we studied the mechanics of ex vivo carotid arteries (CA) from 17 week old OZR, where vascular tone was abolished. OZR exhibited obesity, severe insulin resistance, moderate hypertension and dyslipidemia. In response to elevated intraluminal pressure, CA from OZR exhibited a smaller expansion than CA from LZR. However, wall thickness and cross‐sectional area was reduced in CA from OZR vs. LZR. At low intraluminal pressures, incremental distensibility of CA from OZR was reduced vs. LZR. The circumferential stress vs. strain relation for CA from OZR was left‐shifted vs. LZR, with an increased β (slope) coefficient (p&lt;0.01). These results suggest that CA stiffness in OZR is increased over that in LZR and that this loss of arterial distensibility could contribute to poor cardiovascular outcomes in MetSyn.Grant Funding Source: Supported by National Institutes of Health and American Heart Association

Hydrogen peroxide via thromboxane A2 receptors mediates myogenic response of small skeletal muscle veins in rats

We aimed to test two hypotheses: (1) isolated small veins develop substantial myogenic tone in response to elevation of intraluminal pressure, (2) H2O2 contributes to the mediation of myogenic response via activation of arachidonic acid (AA) cascade and release constrictor prostaglandins. Small veins were isolated from gracilis muscle of male rats, then cannulated. Changes of diameter to increases in intraluminal pressure, H2O2 and arachidonic acid in the presence and absence of various inhibitors were measured by videomicroscope and microangiometer. At the end of experiments the passive diameter were obtained in Ca2+ -free PSS solution. Isolated rat gracilis muscle small veins developed a substantial myogenic tone in response to increases in intraluminal pressure (1-12 mmHg). Calculated maximum myogenic tone was 70 ± 5% at 10 mmHg. Presence of catalase or indomethacin or SQ 29,548 reduced significantly the pressure-induced myogenic response. Also, H2O2 (10-9-10-5 M) and arachidonic acid (10-7-10-4 M) elicited concentration dependent constrictions, which were inhibited by the presence of indomethacin or SQ 29,548. We propose that both myogenic response and pressure-induced release of H2O2 play important roles in regulating the vasomotor function of venules both in physiological and pathological conditions.

Esophageal submucosal dissection under steady pressure automatically controlled endoscopy (SPACE): a randomized preclinical trial

A new overtube system has been developed for steady pressure automatically controlled endoscopy (SPACE) in the gastrointestinal tract. The objectives of this study were to validate the feasibility and safety of SPACE in the esophagus, and to evaluate its potential advantages over conventional (manually insufflating) endoscopy in endoscopic submucosal dissection (ESD). This was a multicenter preclinical trial using acute porcine models (n = 20). In Experiment 1 (feasibility/safety study), SPACE was attempted in the esophagus with continuous monitoring of cardiopulmonary parameters and intraluminal pressures in the downstream bowel. Different insufflation pressures were tested to optimize the insufflation condition. Each session was video-recorded and scored by blinded reviewers. In Experiment 2 (randomized trial), esophageal ESD was attempted using either SPACE or conventional endoscopy, and results were compared. In Experiment 1, SPACE was performed safely without intraluminal pressure elevation in the downstream bowel. According to video review, SPACE provided more stable, reproducible, and rapid visualization than conventional endoscopy. The insufflation pressure was optimized at 14 mmHg for esophageal SPACE. In Experiment 2, ESD was completed in all animals. The ESD time was significantly shorter with SPACE compared with conventional endoscopy (1326 vs. 1616 seconds; P = 0.009). Responses to questionnaires showed that 94 % - 100 % of participants considered SPACE to provide improved exposure and more uniform tissue tension than conventional endoscopy. Other data were comparable. SPACE is feasible, safe, and potentially effective for complicated endoscopic procedures, such as ESD. SPACE improves and standardizes endoscopic exposure and tissue tension. A clinical study is required to further confirm its safety and clinical effectiveness.

Flow-Evoked Vasodilation is Blunted in Penile Arteries from Zucker Diabetic Fatty Rats

Endothelium-derived relaxing factors such as nitric oxide (NO), prostanoids, and endothelium-derived hyperpolarizing factor (EDHF) are thought to play an important role in vasodilation of penile arteries. The present study investigated the mechanisms involved in flow- and acetylcholine-induced vasodilation in penile arteries, and whether acetylcholine- and flow-mediated vasodilation is altered in Zucker diabetic fatty (ZDF) rats, a model of type 2 diabetes. Moreover, it was addressed whether enhanced myogenic tone may explain impaired flow-evoked vasodilation in arteries from ZDF rats. Penile dorsal arteries obtained from lean control and ZDF rats were suspended in a pressure myograph, and flow- and acetylcholine-evoked vasodilation was measured as changes in arterial diameter. Changes in penile arterial diameter. Incubation with an inhibitor of NO synthase, asymmetric dimethyl-L-arginine (ADMA), and of cyclooxygenase, indomethacin, reduced acetylcholine but not flow-evoked vasodilation in penile arteries, while both responses were abolished by endothelial cell removal. Iberiotoxin, a blocker of large-conductance calcium-activated K+ (BK(Ca) ) channels, inhibited flow-evoked vasodilation. Flow-evoked vasodilation was reduced in arteries from ZDF rats in the absence, but not in the presence, of indomethacin plus ADMA. Elevation of intraluminal pressure increased myogenic tone, which was reduced in arteries from ZDF rats. The present findings show that flow evokes endothelium-dependent EDHF-type vasodilation involving BK(Ca) channels in penile arteries. Flow-evoked vasodilation is reduced and only of EDHF-type in penile arteries from type 2 diabetic rats suggesting modulation of this pathway may restore endothelial function and preserve erection in diabetes.