Rat Aortic Tissue Research Articles

Effect of rapid cooling, frozen storage, and thawing on the passive viscoelastic properties and structure of the rat aorta

Biological tissues decay over time after harvesting, which alters their biomechanical properties. This poses logistical challenges for studies investigating passive arterial biomechanics as tissues need to be characterized shortly after excision. Freezing and cryopreservation methods can help alleviate the need for biomechanical testing of fresh tissue in human ex vivo studies. However, these methods tend to eliminate or reduce arterial cell functionality and affect passive biomechanics. Furthermore, their impact on dynamic arterial biomechanics remains unknown despite arterial viscoelastic properties being an integral component contributing to arterial stiffness under in vivo loading conditions. The present study aims to investigate the impact of rapid cooling and subsequent storage at −80 °C on the passive viscoelastic properties of arterial tissue and aid in ascertaining whether this is a suitable method to delay tissue analysis for studies investigating passive arterial biomechanics. Control and frozen abdominal rat aorta segments were quasi-statically and dynamically tested using a biaxial testing set-up. The results were modeled using a constituent-based quasi-linear viscoelastic modeling framework, yielding directional stiffness parameters, individual constituent biomechanical contributions, and a quantification of viscoelastic stiffening under dynamic pressurization conditions. Frozen samples displayed significantly decreased wall thickness, viscoelastic dissipation, viscoelastic stiffening, and significantly decreased circumferential deformation with changes in luminal pressure. Furthermore, frozen samples displayed significantly increased circumferential stiffness, pulse wave velocity, and collagen load bearing. Consequently, these changes should be considered when utilizing this tissue preservation method to delay biomechanical characterization of rat aortic tissue.

Astragalus polysaccharides attenuate rat aortic endothelial senescence via regulation of the SIRT-1/p53 signaling pathway

BackgroundAstragalus polysaccharides (APS) have been verified to have antioxidative and antiaging activities in the mouse liver and brain. However, the effect of APS on aortic endothelial senescence in old rats and its underlying mechanism are currently unclear. Here, we aimed to elucidate the effects of APS on rat aortic endothelial oxidative stress and senescence in vitro and in vivo and investigate the potential molecular targets.MethodsTwenty-month-old natural aging male rats were treated with APS (200 mg/kg, 400 mg/kg, 800 mg/kg daily) for 3 months. Serum parameters were tested using corresponding assay kits. Aortic morphology was observed by staining with hematoxylin and eosin (H&E) and Verhoeff Van Gieson (VVG). Aging-related protein levels were evaluated using immunofluorescence and western blot analysis. Primary rat aortic endothelial cells (RAECs) were isolated by tissue explant method. RAEC mitochondrial function was evaluated by the mitochondrial membrane potential (MMP) measured with the fluorescent lipophilic cationic dye JC‑1. Intracellular total antioxidant capacity (T-AOC) was detected by a commercial kit. Cellular senescence was assessed using senescence-associated-β-galactosidase (SA-β-Gal) staining.ResultsTreatment of APS for three months was found to lessen aortic wall thickness, renovate vascular elastic tissue, improve vascular endothelial function, and reduce oxidative stress levels in 20-month-old rats. Primary mechanism analysis showed that APS treatment enhanced Sirtuin 1 (SIRT-1) protein expression and decreased the levels of the aging marker proteins p53, p21 and p16 in rat aortic tissue. Furthermore, APS abated hydrogen peroxide (H2O2)-induced cell senescence and restored H2O2-induced impairment of the MMP and T-AOC in RAECs. Similarly, APS increased SIRT-1 and decreased p53, p21 and p16 protein levels in senescent RAECs isolated from old rats. Knockdown of SIRT-1 diminished the protective effect of APS against H2O2-induced RAEC senescence and T-AOC loss, increased the levels of the downstream proteins p53 and p21, and abolished the inhibitory effect of APS on the expression of these proteins in RAECs.ConclusionAPS may reduce rat aortic endothelial oxidative stress and senescence via the SIRT-1/p53 signaling pathway.

Astragaloside IV Mediates the PI3K/Akt/mTOR Pathway to Alleviate Injury and Modulate the Composition of Intestinal Flora in ApoE-/- Atherosclerosis Model Rats.

Atherosclerosis (AS) is a chronic inflammatory vascular disease with a complex pathogenesis. Astragaloside IV (AST IV), the primary active component of Astragalus, possesses anti-inflammatory, antioxidant, and immunomodulatory properties. This research aims to investigate the outcome of AST IV on AS and its potential molecular mechanism. A high-fat diet (21% fat, 50% carbohydrate, 20% protein, 0.15% cholesterol, and 34% sucrose) was utilized to feed Apolipoprotein E deficient (ApoE-/-) SD rats for 8 weeks, followed by continuous intragastric administration of AST IV for 8 weeks. Biochemical detection was conducted for serum lipid levels and changes in vasoactive substances. After Masson staining, aortic root oil red O staining, and Hematoxylin Eosin (HE) staining, the efficacy of AST IV was verified using quantitative reverse transcription polymerase chain reaction (qRT-PCR). The mRNA expression levels of inflammatory factors and endothelial dysfunction-related biomarkers in rat aortic root tissues were appraised. The changes in the composition of intestinal flora in rats after AST IV treatment were appraised using Image J (Multi-point Tool). Western blot was used to evaluate phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway-related protein levels in rat aortic root tissues. AST IV administration alleviated the pathological symptoms of AS rats. AST IV administration reduced serum total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), endothelin-1 (ET-1) and angiotensin (Ang)-II (Ang-II) levels, and augmented serum high-density lipoprotein cholesterol (HDL-C) and nitric oxide (NO) levels. At the same time, AST IV administration inhibited the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-1β, vascular cell adhesion molecule-1 (VCAM-1), matrix metalloproteinase-2 (MMP-2), macrophage inflammatory protein-1 (MCP-1), and intercellular adhesion molecule-1 (ICAM-1) in the aortic root tissue of AS rats. In addition, the intestinal flora changed significantly after AST IV administration. The number of Bifidobacterium, Lactobacillus, and Bacteroides augmented significantly, and Enterobacter, Enterococcus, Fusobacterium, and Clostridium significantly decreased. Mechanistically, AST IV administration inhibited the phosphorylation of PI3K, Akt, and mTOR in AS rats. When combined with Dactolisib (BEZ235) (a PI3K/Akt/mTOR pathway inhibitor), AST IV could further inhibit phosphorylation and reduce inflammation. AST IV has a potential anti-AS effect, which can improve the pathological changes of the aorta in ApoE-/- rats fed with a high-fat diet, reduce the level of inflammatory factors, and modulate the composition of intestinal flora via the PI3K/Akt/mTOR pathway.

Cellular microarrays for assessing single-cell phenotypic changes in vascular cell populations

Microengineering technologies provide bespoke tools for single-cell studies, including microarray approaches. There are many challenges when culturing adherent single cells in confined geometries for extended periods, including the ability of migratory cells to overcome confining cell-repellent surfaces with time. Following studies suggesting clonal expansion of only a few vascular smooth muscle cells (vSMCs) contributes to plaque formation, the investigation of vSMCs at the single-cell level is central to furthering our understanding of atherosclerosis. Herein, we present a medium throughput cellular microarray, for the tracking of single, freshly-isolated vSMCs as they undergo phenotypic modulation in vitro. Our solution facilitates long-term cell confinement (> 3 weeks) utilising novel application of surface functionalisation methods to define individual culture microwells. We demonstrate successful tracking of hundreds of native vSMCs isolated from rat aortic and carotid artery tissue, monitoring their proliferative capacity and uptake of oxidised low-density lipoprotein (oxLDL) by live-cell microscopy. After 7 days in vitro, the majority of viable SMCs remained as single non-proliferating cells (51% aorta, 78% carotid). However, a sub-population of vSMCs demonstrated high proliferative capacity (≥ 10 progeny; 18% aorta, 5% carotid), in line with reports that a limited number of medial SMCs selectively expand to populate atherosclerotic lesions. Furthermore, we show that, when exposed to oxLDL, proliferative cells uptake higher levels of lipoproteins, whilst also expressing greater levels of galectin-3. Our microwell array approach enables long-term characterisation of multiple phenotypic characteristics and the identification of new cellular sub-populations in migratory, proliferative adherent cell types.Graphical abstract

Biomechanical Properties of the Aortic Wall: Changes during Vascular Calcification.

Medial vascular calcification (MAC) is characterized by the deposition of hydroxyapatite (HAP) in the medial layer of the vessel wall, leading to disruption of vessel integrity and vascular stiffness. Because currently no direct therapeutic interventions for MAC are available, studying the MAC pathogenesis is of high research interest. Several methods exist to measure and describe the pathophysiological processes in the vessel wall, such as histological staining and gene expression. However, no method describing the physiological properties of the arterial wall is currently available. This study aims to close that gap and validate a method to measure the biomechanical properties of the arterial wall during vascular calcification. Therefore, a stress-stretch curve is monitored using small-vessel-myography upon ex vivo calcification of rat aortic tissue. The measurement of biomechanical properties could help to gain further insights into vessel integrity during calcification progression.

Inhibition of Endoplasmic Reticulum Stress Improves Acetylcholine-Mediated Relaxation in the Aorta of Type-2 Diabetic Rats.

Endoplasmic reticulum (ER) stress contributes to insulin resistance and macro- and microvascular complications associated with diabetes. This study aimed to evaluate the effect of ER stress inhibition on endothelial function in the aorta of type-2 diabetic rats. Type-2 diabetes was developed in male Sprague–Dawley rats using a high-fat diet and low-dose streptozotocin. Rat aortic tissues were harvested to study endothelial-dependent relaxation. The mechanisms for acetylcholine-mediated relaxation were investigated using pharmacological blockers, Western blotting, oxidative stress, and inflammatory markers. Acetylcholine-mediated relaxation was diminished in the aorta of diabetic rats compared to control rats; supplementation with TUDCA improved relaxation. In the aortas of control and diabetic rats receiving TUDCA, the relaxation was mediated via eNOS/PI3K/Akt, NAD(P)H, and the KATP channel. In diabetic rats, acetylcholine-mediated relaxation involved eNOS/PI3K/Akt and NAD(P)H, but not the KATP channel. The expression of ER stress markers was upregulated in the aorta of diabetic rats and reduced with TUDCA supplementation. The expression of eNOS and Akt were lower in diabetic rats but were upregulated after supplementation with TUDCA. The levels of MDA, IL-6, and SOD activity were higher in the aorta of the diabetic rats compared to control rats. This study demonstrated that endothelial function was impaired in diabetes, however, supplementation with TUDCA improved the function via eNOS/Akt/PI3K, NAD(P)H, and the KATP channel. The improvement of endothelial function was associated with increased expressions of eNOS and Akt. Thus, ER stress plays a crucial role in the impairment of endothelial-dependent relaxation. Mitigating ER stress could be a potential strategy for improving endothelial dysfunction in type-2 diabetes.

Linear ubiquitination modification of NR6A1 by LUBAC inhibits RIPK3 kinase activity and attenuates apoptosis of vascular smooth muscle cells

Nuclear receptor subfamily 6 group A member 1 (NR6A1) is involved in promoting the apoptotic process of vascular smooth muscle cells (VSMCs) which is a critical process involved in atherosclerosis, but the action mechanism remains to be determined. Therefore, we studied the underlying mechanisms by which NR6A1 accelerated VSMC apoptosis in atherosclerosis. An atherosclerosis model has been established in apolipoprotein E-deficient rats with a high-fat diet for 12 weeks, which was characterized by pathological aortic plaques, increased lipid depositionand collagen content in aortic tissues, and high cholesterol and triglycerides levels in the serum. NR6A1 was experimentally shown to increase at protein level rather than messenger RNA level in atherosclerotic rats. Immunofluorescence exhibited the main location of NR6A1 in the cell nucleus of rat aortic tissues. By performing ectopic expression experiments, NR6A1 was demonstrated to suppress the viability and expedite the apoptosis of VSMCs, corresponding to augmented caspase-3, caspase-8, and caspase-9 activities. It was further unraveled that NR6A1 could activate receptor-interacting serine/threonine-protein kinase 3 (RIPK3) by inducing its phosphorylation. Conversely, RIPK3 inhibitor GSK872 undermined the proapoptotic effect of NR6A1 on VSMCs. The co-immunoprecipitationassay identified that linear ubiquitin chain assembly complex (LUBAC) can be pulled down by NR6A1. Furthermore. LUBAC inhibited the expression of NR6A1 by promoting its linear ubiquitination, thereby dephosphorylating RIPK3 and consequently inhibiting the VSMC apoptosis. Overall, LUBAC-induced linear ubiquitination of NR6A1 can potentially arrest the apoptosis of VSMCs in atherosclerosis by downregulating RIPK3 and attenuating caspase activity. This finding suggests promising athero-protective targets by limiting VSMC apoptosis.

A Cell Permeant Phosphopeptide Mimetic Of Niban Restores Endothelial Function And Inhibits p38 MAPK Activation After IL‐1β Induced Vascular Injury

Activation and dysfunction of the vascular endothelium play a significant role in the pathogenesis of many viral infections such as COVID‐19. The cytokine storm (systemic inflammation) present in COVID‐19 causes organ failure by inflaming the vascular endothelium, leading to endothelial dysfunction and eventually death. Previous studies in the laboratory show that vascular injury leads to endothelial dysfunction that is associated with activation of p38 MAPK signaling and altered phosphorylation of Niban. Based on these findings, a cell permeant phosphomimetic peptide of Niban (NiPp) was developed and shows inhibitory activities on p38 MAPK and restores endothelial dysfunction after vascular injury. The effects of NiPp on endothelial dysfunction induced by interleukin‐1β (IL‐1β), a cytokine that is increased during infections, were examined ex‐vivo using intact rat aortic tissue (RA) and primary human endothelial cells (HCAEC). IL‐1β treatment led to a reduction in endothelial‐dependent relaxation (EDR) in RA, and inhibition of p38 MAPK by NiPp or BIRB796, a potent p38 MAPK inhibitor, improved EDR in IL‐1β treated RA (Figure 1). Treatment of HCAEC with NiPp or BIRB reduced IL‐1β induced activation of p38 MAPK and its downstream substrate, CREB (Figure 2). These data show that p38 MAPK and Niban signaling play a role in endothelial function, especially in response to inflammatory injury. Niban may be an endogenous regulator of p38 MAPK activation. NiPp may serve as a potential therapeutic to ameliorate inflammation of vascular endothelium.

Protective Effect of Tubotaiwine on Cadmium-Induced Hypertension in Rats through Reduction in Arterial Stiffness and Vascular Remodeling.

Humans are adversely affected by exposure to cadmium (Cd) as it induces oxidative stress which damages kidneys, bones pulmonary tissues, liver, cardiovascular, immune, reproductive systems and influences endocrine secretions. In the present study tubotaiwine treatment regulated systolic, diastolic and mean arterial blood pressure of the Cd exposed rats. Tubotaiwine significantly promoted vascular responsiveness to Phe, ACh and SNP and reversed Cd mediated decrease in eNOS and increase in iNOS expression. Treatment of the Cd exposed rats with tubotaiwine reduced number of smooth muscle cells, decreased collagen content and promoted content of elastin in aortic artery walls. Tubotaiwine treatment significantly suppressed Cd-induced increase in MMP-2 and MMP-9 in rat aortic artery tissues. Increase in O2-, urinary nitrate/nitrite, MDA, carbonyl level and decrease in GSH production in rat blood and thoracic aorta tissues were effectively reversed by tubotaiwine treatment. Tubotaiwine treatment of the rats significantly reduced Cd-induced increase in blood, liver, heart and kidney tissue Cd content in dose dependent manner. Thus, tubotaiwine suppresses Cd induced hypertension in rats by reducing arterial stiffness, inhibition of oxidative stress and increasing vascular remodeling. Therefore, tubotaiwine has beneficial effect on Cd induced hypertension in rats and may be developed as a potential candidate for treatment of hypertension.

Effect of the traditional Chinese medicine Pinggan-Qianyang decoction on SIRT1\u2013PTEN signaling in vascular aging in spontaneously hypertensive rats

Age-related functional decline is a physiological phenomenon that occurs in all organ systems. However, the acceleration and early occurrence of this process are observed in cardiovascular pathologies, including hypertension. This study aimed to investigate SIRT1–PTEN signaling in aortic tissue from spontaneously hypertensive rats (SHRs) and changes in SIRT1 and PTEN expression following treatment with Pinggan-Qianyang decoction (PGQYD) and explore the mechanism involved in the treatment of hypertensive vascular aging with traditional Chinese medicine. In this study, we used two rat models: spontaneously hypertensive rats (SHRs) at 14 and 64 weeks of age and WKY rats at 64 weeks of age. The degree of irritability and rotation tolerance time were evaluated to determine the effects of PGQYD on animal behavior. The morphology of the thoracic aorta was examined by hematoxylin-eosin (HE) and Masson staining and electron microscopy. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and superoxide dismutase (SOD) and anti-superoxide anion content were detected. Senescence-associated β-galactosidase (SA-β-Gal) staining was used to observe the thoracic aorta during vascular aging. RT-qPCR, immunofluorescence, and Western blot analysis were performed to detect changes in the mRNA and protein expression of p53, p21, SIRT1, and PTEN in rat aortic tissues. Behavioral tests and histological and morphological analyses showed the remarkable amelioration of vascular aging after PGQYD treatment compared with that in the older SHRs. Moreover, PGQYD significantly decreased vascular aging in SHRs, as indicated by reduced SA-β-Gal staining, NADPH oxidase activity, and p53 and p21 expression, and increased anti-superoxide anion and SOD content. Furthermore, PGQYD increased SIRT1 and PTEN expression, but the downregulated expression of SIRT1 induced by a SIRT1 inhibitor abolished the PGQYD-induced antiaging effects on gene expression and antioxidant activity and enhanced PTEN expression. PGQYD could ameliorate vascular aging effects in SHRs, which may have been mediated via the regulation of SIRT1–PTEN signaling in aortic tissue.

The Role of K+, Ca2+ channels and Endothelial Hyperpolarizing Factors in Vasorelaxation Induced by Tribulus terrestris

The present study focused on the relaxant effect of themethanolic extract (ME) of Tribulus terristris on rats’ thoracic aortae and included the study of underlying vasorelaxation mechanisms. The methanolic extract produced concentration-dependent relaxation in rats’ aorta. The methanolic extract produced concentration-dependent relaxation in the aortic rings. The use of different K+ channel blockers (BaCl2, 4-AP, GLIB, and TEA) indicated that Kv, KATP, KIR, and KCa and L-type Ca channels played no role in the methanolic extractinduced relaxation. However, with respect to endothelium-derived hyperpolarizing factors, PGI2 and sGC produced a mild inhibition in the relaxation response to ME while NO produced no effect at all.
 Based on the novel results of the current study, it can be concluded that T. terrestris methanolic extract (ME) mediated relaxation in isolated rat aortic tissues in a concentration-dependent manner. Moreover, we discovered that ME-mediated relaxation is endothelium-dependent and that potassium and calcium ion channels play no role in this relaxation with a limited role of PGI2 and sGC.

Immunomodulatory and antiangiogenic mechanisms of polymolecular botanical drug extract C5OSEW5050ESA OS derived from Orthosiphon stamineus

NuvastaticTM is a polymolecular botanical drug formulation containing a proprietary extract of a selected cultivar of Orthosiphon stamineus (OS) code name, C5OSEW5050ESA OS. The anti-angiogenic activity of C5OSEW5050ESA OS was explored by evaluating its activity towards a variety of angiogenesis modulators in vitro and in vivo. Multiplex immunoassays reveals that C5OSEW5050ESA OS inhibits Vascular Endothelial Growth factor (VEGF), Epidermal Growth Factor (EGF), Fibroblast Growth Factor (FGF), Interleukin 2 ( IL-2) & Interleukin 7 (IL-7), Nerve Growth Factor β (NGF-β) , Transforming Growth Factor -α (TGF-α) and Tumor Necrosis Factor- β (TNF-β). C5OSEW5050ESA OS also caused significant upregulation of interferon α (IFN-α), interferon β (IFN-β), interferon γ (IFN-γ) and Granulocyte-macrophage colony-stimulating factor (GM-CSF). C5OSEW5050ESA OS was found to inhibit endothelial cell proliferation and migration (92.6%) and disrupts the tube assembly (98.26%) for new blood vessel formation. The compound also inhibits neovascularisation in isolated rat aortic ring tissues (IC50 18.2 ± 2 µg/mL) and in chick chorioallantoic membrane assays (CAM) by 82.7%. In vivo matrigel plug assay treated with C5OSEW5050ESA OS shows inhibition of neovascularisation by 91.4± 3%. In conclusion, the study reveals that C5OSEW5050ESA OS has strong anti-angiogenic and immunomodulatory properties which may have significant clinical benefits in cancer therapy.

Metformin attenuates hyperlipidaemia-associated vascular calcification through anti-ferroptotic effects

Ferroptosis is a form of regulated cell death that involves metabolic dysfunction resulting from iron-dependent excessive lipid peroxidation. Elevated plasma levels of free fatty acids are tightly associated with cardiometabolic risk factors in patients with obesity, diabetes mellitus, and metabolic syndrome. Metformin (Met) is an antidiabetic drug with beneficial cardiovascular disease effects. The aim of this study was to determine the effects of Met on ferroptosis induced by lipid overload and the effects of these changes on vascular smooth muscle cells (VSMCs) calcification. We developed a hyperlipidaemia-related vascular calcification in vivo model with rats fed a high-fat diet combined with vitamin D3 plus nicotine, and palmitic acid (PA), the most abundant long-chain saturated fatty acid in plasma, was used to induce lipid overload and develop an oxidative stress-related calcification model in vitro. The results showed that Met inhibits hyperlipidaemia-associated calcium deposition in the rat aortic tissue. In vitro, treatment of VSMCs with PA stimulates ferroptosis concomitant with increased calcium deposition in VSMCs, while pretreatment with Met attenuates these effects. Furthermore, PA also promotes the protein expression of the extracellular matrix protein periostin (POSTN) and its secretion into the extracellular environment. More importantly, upregulation of POSTN increased the sensitivity of cells to ferroptosis. Mechanistically, upregulation of POSTN suppresses SLC7A11 expression through the inhibition of p53 in VSMCs, which contributes to a decrease in glutathione synthesis and therefore triggers ferroptosis. Interestingly, overexpression of p53 attenuates the inhibitory effect of POSTN on SLC7A11 expression, accompanied by increased Gpx4 expression. Furthermore, p53 knockdown suppresses Met-mediated anti-ferroptosis effects in PA-treated VSMCs, which may be related to the downregulation of SLC7A11 expression. In addition, supplementation of VSMCs with Met enhances the antioxidative capacity of VSMCs through Nrf2 signalling activation. Collectively, targeting POSTN in VSMCs may provide a new strategy for vascular calcification prevention or treatment.

A cell permeant phosphopeptide mimetic of Niban inhibits p38 MAPK and restores endothelial function after injury.

Vascular injury leads to membrane disruption, ATP release, and endothelial dysfunction. Increases in the phosphorylation of p38 mitogen‐activated protein kinase (p38 MAPK) and decreases in the phosphorylation of Niban, a protein implicated in ER stress and apoptosis, are associated with vascular injury. A cell permeant phosphopeptide mimetic of Niban (NiPp) was generated. The effects of NiPp in restoring endothelial function were determined ex vivo using intact rat aortic tissue (RA) after pharmacological activation of p38 MAPK and also in multiple clinically relevant injury models. Anisomycin (Aniso) increased p38 MAPK phosphorylation and reduced endothelial‐dependent relaxation in RA. Treatment with NiPp prevented Ansio‐induced reduction in endothelial function and increases in p38 MAPK phosphorylation. NiPp treatment also restored endothelial function after stretch injury (subfailure stretch), treatment with acidic Normal Saline (NS), and P2X7R activation with 2′(3′)‐O‐(4‐Benzoylbenzoyl)adenosine 5′‐triphosphate (BzATP). Aged, diseased, human saphenous vein (HSV) remnants obtained from patients undergoing coronary bypass surgical procedures have impaired endothelial function. Treatment of these HSV segments with NiPp improved endothelial‐dependent relaxation. Kinome screening experiments indicated that NiPp inhibits p38 MAPK. These data demonstrate that p38 MAPK and Niban signaling have a role in endothelial function, particularly in response to injury. Niban may represent an endogenous regulator of p38 MAPK activation. The NiPp peptide may serve as an experimental tool to further elucidate p38 MAPK regulation and as a potential therapeutic for endothelial dysfunction.

The Effects of Novel Myristoylated PKC Epsilon Peptide Modulators on Real‐Time Nitric Oxide Release in Human Umbilical Vein Endothelial Cells

Endothelial dysfunction is a major consequence of ischemia‐reperfusion (I/R) injury, such as during the re‐establishment of blood flow after endovascular thrombus removal. It is characterized by limited nitric oxide (NO) bioavailability and production of superoxide (SO) instead of NO, in part from uncoupled endothelial NO synthase (eNOS) activity when the dihydrobiopterin (BH2) to tetrahydrobiopterin (BH4) ratio is elevated during reperfusion following prolonged ischemia. The protein kinase C epsilon (PKCɛ) isoform is known to participate in pre‐conditioning (PKCɛ activation treatment prior to ischemia) and post‐conditioning (PKCɛ inhibition treatment during reperfusion) to attenuate rat myocardial I/R injury. Normally following diacylglycerol‐dependent activation, PKCɛ binds to isoform‐specific receptors for activated C‐kinase (RACK) and translocates from the cytosol to the cell membrane to phosphorylate its targets, such as eNOS at Ser‐1177 to augment NO release when the BH2 to BH4 ratio is reduced to promote coupled eNOS activity that is normally seen prior to prolonged ischemia. Cell permeable myristic acid conjugated PKCɛ peptide activator (myr‐HDAPIGYD; myr‐PKCɛ+) and inhibitor (N‐myr‐EAVSLKPT; myr‐PKCɛ‐) has been shown to increase and decrease NO release, respectively, in rat aortic tissue by regulating PKCɛ translocation to eNOS. However, modulation of PKCɛ‐mediated NO release with these peptides in human cells remains undetermined. We hypothesize that myr‐PKCɛ+ will augment and myr‐PKCɛ‐ will attenuate NO release in cultured human umbilical vein endothelial cells (HUVECs). Real‐time HUVEC NO release (pmol) was measured using a calibrated NO electrode following administration of myr‐PKCɛ+ or myr‐PKCɛ‐ ± acetylcholine (Ach; positive control). Data were analyzed by ANOVA using Fishers post‐hoc analysis. Basal NO levels (66±6; n=35) were determined as the pmol difference between cell‐populated (106 cells/well) and reagent only wells. Control Ach (10 μM) enhanced NO release (102±7; n=37), myr‐PKCɛ+ (10 μM) enhanced NO release with Ach (107±16; n=8) and without Ach (107±13; n=7), and myr‐PKCɛ‐ (10 μM) attenuated NO release with Ach (37±9; n=13) and without Ach (7±29; n=9) compared to basal levels (all p<0.05). Results suggest that myr‐PKCɛ +/− effects on NO release is translational across mammalian species, presumably through activation and inhibition of PKCɛ‐mediated phosphorylation of eNOS. Thus, therapeutic intervention that targets inhibition of PKCɛ to reduce uncoupled eNOS activity during reperfusion may yield protective effects via attenuating the extent of I/R injury seen in clinical myocardial infarction, coronary bypass, coronary angioplasty, and organ transplantation.Support or Funding InformationThis research was supported by the Division of Research, Department of Biomedical Sciences, and the Center for Chronic Disorders of Aging at Philadelphia College of Osteopathic Medicine. Current research license is supported by Young Therapeutics, LLC.

Adiponectin Reduces Angiotensin II‐Induced Vascular Hypertrophy by Targeting ROS Formation and Actin Cytoskeleton Remodeling

Background and aimsAdiponectin (APN), an adipocytokine, exerts cardioprotective effects, while angiotensin II (Ang II) plays a critical role in the pathogenesis of hypertrophy of vascular smooth muscle cells (VSMCs) induces hypertension and vascular remodeling. Ang II induces VSMC hypertrophy in part via activation of RhoA/ROCK pathway. In this study, we investigated the molecular mechanisms associated with Ang II‐induced RhoA activation and translocation and the ability of ANP to counteract Ang II‐hypertrophic effect through inhibition of RhoA activation, actin cytoskeleton remolding and reactive oxygen species (ROS) formation.MethodsStudies were carried out using rat aortic tissues and VSMCs. The effect of APN on Ang II‐induced RhoA translocation was assessed by Western blotting (WB) and Immunohistochemistry. Leucine incorporation was used to examine NO effect on Ang II induced hypertrophy. The phosphorylation of cofilin‐2 and ERK1/2 was detected by WB. Moreover, immunohistochemistry was performed on aortic frozen sections to detect ROS, F‐actin and G‐actin levels, RhoA‐Cav 1 co‐localization and eNOS translocation.ResultsAng II‐induced VSMCs hypertrophy was prevented by supplementing APN. The hypertrophic response to Ang II was associated with RhoA translocation to caveolae‐rich membrane, cofilin‐2 and ERK1/2 phosphorylation, in addition to a significant decrease in G/F actin ratio. Moreover, ROS production significantly increased with Ang II treatment as revealed by confocal microscopy. However, these effects were inhibited by APN and caveolae disruption. Taken together, these results suggest that Ang II hypertrophic effect is due, in part, to RhoA translocation to caveolae rich micro‐domains and its downstream effectors which is counteracted by APN.ConclusionThese findings suggest the ability of APN to attenuate Angiotensin II‐induced vascular hypertrophy.

A cell permeant phosphopeptide mimetic of Niban restores endothelial function and inhibits p38 MAPK activation after vascular injury

Vascular injury leads to membrane disruption, ATP release, and endothelial dysfunction. Increases in the phosphorylation of p38 MAPK and decreases in the phosphorylation of Niban, a protein implicated in ER stress and apoptosis, are associated with vascular injury. A cell‐permeant phospho‐peptide mimetic of Niban (NiPp) was generated. The effects of NiPp in restoring endothelial function were determined ex vivo using intact rat aortic tissue (RA) after pharmacological activation of p38 MAPK and a clinically relevant stretch injury model. Anisomycin increased p38 MAPK phosphorylation and reduced endothelial‐dependent relaxation in RA. Treatment with NiPp prevented anisomycin‐induced reduction in endothelial function and increase in p38 MAPK phosphorylation (Figure 1). NiPp treatment also restored endothelial function after subfailure overstretch injury (Figure 2). Kinome screening experiments indicated that NiPp inhibits p38 MAPK. These data demonstrate that p38 MAPK and Niban signaling have a role in endothelial function, particularly in response to injury. Niban may represent an endogenous regulator of p38 MAPK activation. NiPp may serve as an experimental tool to further elucidate p38 MAPK regulation and as a potential therapeutic for endothelial dysfunction.Support or Funding InformationThis work was supported by the National Institutes of Health grants R01HL70715‐09 to CB and R01HL105731‐01 to JC.NiPp prevented anisomycin‐induced phosphorylation of p38 MAPK and endothelial dysfunction in rat aorta (RA).RA rings were treated with anisomycin (200μM) in the absence or presence of NiPp (500μM) pretreatment and endothelial function was determined in a muscle bath. A) Representative muscle bath tracings. B) Percent relaxation induced by 0.5μM CCH. C, D) Phosphorylation of p38 MAPK in RA after treatment as determined by Western blot analysis. n=10,*p<.05 in one‐way ANOVA with Tukey post‐test.Figure 1NiPp restored endothelial function and reduced p38MAPK phosphorylation in RA after subfailure stretch injury.RA was subjected to subfailure stretch and incubated in the absence or presence of NiPp (500μM) for 1 h. A) Endothelial‐dependent relaxation was determined in the muscle bath. n=5 rats; #p<.05, two‐way ANOVA. B, C) Phosphorylation of p38 MAPK in RA after stretch injury and NiPp treatment as determined by Western blot analysis n= 10. *p<.05, in one‐way ANOVA with Tukey post‐test.Figure 2

CCR2 Positron Emission Tomography for the Assessment of Abdominal Aortic Aneurysm Inflammation and Rupture Prediction.

The monocyte chemoattractant protein-1/CCR2 (chemokine receptor 2) axis plays an important role in abdominal aortic aneurysm (AAA) pathogenesis, with effects on disease progression and anatomic stability. We assessed the expression of CCR2 in a rodent model and human tissues, using a targeted positron emission tomography radiotracer (64Cu-DOTA-ECL1i). AAAs were generated in Sprague-Dawley rats by exposing the infrarenal, intraluminal aorta to PPE (porcine pancreatic elastase) under pressure to induce aneurysmal degeneration. Heat-inactivated PPE was used to generate a sham operative control. Rat AAA rupture was stimulated by the administration of β-aminopropionitrile, a lysyl oxidase inhibitor. Biodistribution was performed in wild-type rats at 1 hour post tail vein injection of 64Cu-DOTA-ECL1i. Dynamic positron emission tomography/computed tomography imaging was performed in rats to determine the in vivo distribution of radiotracer. Biodistribution showed fast renal clearance. The localization of radiotracer uptake in AAA was verified with high-resolution computed tomography. At day 7 post-AAA induction, the radiotracer uptake (standardized uptake value [SUV]=0.91±0.25) was approximately twice that of sham-controls (SUV=0.47±0.10; P<0.01). At 14 days post-AAA induction, radiotracer uptake by either group did not significantly change (AAA SUV=0.86±0.17 and sham-control SUV=0.46±0.10), independent of variations in aortic diameter. Competitive CCR2 receptor blocking significantly decreased AAA uptake (SUV=0.42±0.09). Tracer uptake in AAAs that subsequently ruptured (SUV=1.31±0.14; P<0.005) demonstrated uptake nearly twice that of nonruptured AAAs (SUV=0.73±0.11). Histopathologic characterization of rat and human AAA tissues obtained from surgery revealed increased expression of CCR2 that was co-localized with CD68+ macrophages. Ex vivo autoradiography demonstrated specific binding of 64Cu-DOTA-ECL1i to CCR2 in both rat and human aortic tissues. CCR2 positron emission tomography is a promising new biomarker for the noninvasive assessment of AAA inflammation that may aid in associated rupture prediction.

Denatonium enhanced the tone of denuded rat aorta via bitter taste receptor and phosphodiesterase activation

Bitter taste receptors (Tas2rs) initiate a bitter taste signaling involving the activation of taste-specific G protein gustducin and phosphodiesterases (PDEs); it leads to the decrease of cytosolic level of cyclic adenosine monophosphate (cAMP) in taste cells. Recent studies have identified the expression of Tas2rs in a variety of non-lingual tissues including vascular smooth muscle (VSM), pulmonary smooth muscle and airway smooth muscle. The current study aims to determine the expression of Tas2rs and gustducin in rat aortic smooth muscle tissue and to investigate the effect of Tas2rs agonist denatonium on the tone of isolated denuded aorta rings. Here we reported the expression of six subtypes of Tas2r mRNA and the taste receptor-associated G proteins in endothelium-denuded aorta. Immunostaining experiments showed that the protein of gustducin expressed in vascular smooth muscle cells (VSMCs). Furthermore, denatonium increased the tone of freshly isolated denuded aorta rings in a concentration-dependent manner, and the potentiation effect of denatonium was blocked by a Tas2rs antagonist adenosine 5′-monophosphate (5′-AMP), by the cAMP-hydrolyzing PDE inhibitors, and by a cAMP-synthesizing enzyme activator forskolin, respectively. The blockade of Gβγ signaling did not have a negative impact on the denatonium-induced tonic contractions. These findings suggested that the functional Tas2rs and gustducin are expressed in rat aortic smooth muscle and that denatonium might increase the smooth muscle tone through a Tas2rs signaling pathway involving the activation of PDEs.

A Novel Long-Term ex vivo Model for Studying Vascular Calcification Pathogenesis: The Rat Isolated-Perfused Aorta

The investigation of vascular calcification and its underlying cellular and molecular pathways is of great interest in current research efforts. Therefore, suitable assays are needed to allow examination of the complex calcification process under controlled conditions. The current study describes a new ex vivo model of isolated-perfused rat aortic tissue with subsequent quantification and vessel staining to analyze the calcium content of the aortic wall. A rat aorta was perfused ex vivo with control and calcification media for 14 days, respectively. The calcification medium was luminally perfused and induced a significant increase in calcium deposition within the media of the vessel wall detected alongside the elastic laminae. Perfusion with control medium induced no calcification. In addition, the mRNA expression of the osteogenic marker bone morphogenetic protein 2 (BMP-2) increased in aortic tissue after perfusion, while SM22α as smooth muscle marker decreased. This newly developed ex vivo model of isolated-perfused rat aorta is suitable for vascular calcification studies testing inducers and inhibitors of vessel calcification and studying signaling pathways within calcification progression.