178 research outputs found
Tissue-Protective Mechanisms of Bioactive Phytochemicals in Flap Surgery
Despite careful preoperative planning, surgical flaps are prone to ischemic tissue damage
and ischemiaâreperfusion injury. The resulting wound breakdown and flap necrosis
increase both treatment costs and patient morbidity. Hence, there is a need for
strategies to promote flap survival and prevent ischemia-induced tissue damage.
Phytochemicals, defined as non-essential, bioactive, and plant-derived molecules, are
attractive candidates for perioperative treatment as they have little to no side effects and
are well tolerated by most patients. Furthermore, they have been shown to exert beneficial
combinations of pro-angiogenic, anti-inflammatory, anti-oxidant, and anti-apoptotic
effects. This review provides an overview of bioactive phytochemicals that have been
used to increase flap survival in preclinical animal models and discusses the underlying
molecular and cellular mechanisms
Regulatory Mechanisms of Somatostatin Expression
Somatostatin is a peptide hormone, which most commonly is produced by endocrine cells and the central nervous system. In mammals, somatostatin originates from pre-prosomatostatin and is processed to a shorter form, i.e., somatostatin-14, and a longer form, i.e., somatostatin-28. The two peptides repress growth hormone secretion and are involved in the regulation of glucagon and insulin synthesis in the pancreas. In recent years, the processing and secretion of somatostatin have been studied intensively. However, little attention has been paid to the regulatory mechanisms that control its expression. This review provides an up-to-date overview of these mechanisms. In particular, it focuses on the role of enhancers and silencers within the promoter region as well as on the binding of modulatory transcription factors to these elements. Moreover, it addresses extracellular factors, which trigger key signaling pathways, leading to an enhanced somatostatin expression in health and disease
Maslinic acid alleviates ischemia/reperfusion-induced inflammation by downregulation of NFÎșB-mediated adhesion molecule expression
Ischemia/reperfusion (I/R)-induced inflammation is associated with enhanced leukocyte rolling, adhesion and transmigration within the microcirculation. These steps are mediated by hypoxia-triggered signaling pathways, which upregulate adhesion molecule expression on endothelial cells and pericytes. We analyzed whether these cellular events are affected by maslinic acid (MA). Mitochondrial activity and viability of MA-exposed endothelial cells and pericytes were assessed by water-soluble tetrazolium (WST)-1 and lactate dehydrogenase (LDH) assays as well as Annexin V/propidium iodide (PI) stainings. Effects of MA on hypoxia and reoxygenation-induced expression of E-selectin, intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 were determined by flow cytometry. The subcellular localization of the NFÎșB subunit p65 was analyzed by immunofluorescence and Western blot. I/R-induced leukocytic inflammation was studied in MA- and vehicle-treated mouse dorsal skinfold chambers by intravital fluorescence microscopy and immunohistochemistry. MA did not affect viability, but suppressed the mitochondrial activity of endothelial cells. Furthermore, MA reduced adhesion molecule expression on endothelial cells and pericytes due to an inhibitory action on NFÎșB signaling. Numbers of adherent and transmigrated leukocytes were lower in post-ischemic tissue of MA-treated mice when compared to vehicle-treated controls. In addition, MA affected reactive oxygen species (ROS) formation, resulting in a diminished oxidative DNA damage. Hence, MA represents an attractive compound for the establishment of novel therapeutic approaches against I/R-induced inflammation
The regulatory mechanisms of NG2/CSPG4 expression
Neuron-glial antigen 2 (NG2), also known as chondroitin sulphate proteoglycan 4 (CSPG4), is a surface type I transmembrane core proteoglycan that is crucially involved in cell survival, migration and angiogenesis. NG2 is frequently used as a marker for the identification and characterization of certain cell types, but little is known about the mechanisms regulating its expression. In this review, we provide evidence that the regulation of NG2 expression underlies inflammation and hypoxia and is mediated by methyltransferases, transcription factors, including Sp1, paired box (Pax) 3 and Egr-1, and the microRNA miR129-2. These regulatory factors crucially determine NG2-mediated cellular processes such as glial scar formation in the central nervous system (CNS) or tumor growth and metastasis. Therefore, they are potential targets for the establishment of novel NG2-based therapeutic strategies in the treatment of CNS injuries, cancer and other conditions of these types
The Marine-Derived Triterpenoid Frondoside A Inhibits Thrombus Formation
Background: The marine-derived triterpenoid frondoside A inhibits the phosphatidylinositol-3-kinase (PI3K) pathway in cancer cells. Because this pathway is also crucially involved in platelet activation, we studied the effect of frondoside A on thrombus formation. Methods: Frondoside A effects on platelet viability, surface adhesion molecule expression, and intracellular signaling were analyzed by flow cytometry and Western blot. The effect of frondoside A was analyzed by photochemically induced thrombus formation in the mouse dorsal skinfold chamber model and by tail vein bleeding. Results: Concentrations of up to 15 ”M frondoside A did not affect the viability of platelets, but reduced their surface expression of P-selectin (CD62P) and the activation of glycoprotein (GP)IIb/IIIa after agonist stimulation. Additional mechanistic analyses revealed that this was mediated by downregulation of PI3K-dependent Akt and extracellular-stimuli-responsive kinase (ERK) phosphorylation. Frondoside A significantly prolonged the complete vessel occlusion time in the mouse dorsal skinfold chamber model of photochemically induced thrombus formation and also the tail vein bleeding time when compared to vehicle-treated controls. Conclusion: Our findings demonstrated that frondoside A inhibits agonist-induced CD62P expression and activation of GPIIb/IIIa. Moreover, frondoside A suppresses thrombus formation. Therefore, this marine-derived triterpenoid may serve as a lead compound for the development of novel antithrombotic drugs
Improved Vascularization and Survival of White Compared to Brown Adipose Tissue Grafts in the Dorsal Skinfold Chamber
Fat grafting is a frequently applied procedure in plastic surgery for volume reconstruction.
Moreover, the transplantation of white adipose tissue (WAT) and brown adipose tissue (BAT) in creasingly gains interest in preclinical research for the treatment of obesity-related metabolic defects.
Therefore, we herein directly compared the vascularization capacity and survival of WAT and BAT
grafts. For this purpose, size-matched grafts isolated from the inguinal WAT pad and the interscapu lar BAT depot of C57BL/6N donor mice were syngeneically transplanted into the dorsal skinfold
chamber of recipient animals. The vascularization and survival of the grafts were analyzed by means
of intravital fluorescence microscopy, histology, and immunohistochemistry over an observation
period of 14 days. WAT grafts showed an identical microvascular architecture and functional mi crovessel density as native WAT. In contrast, BAT grafts developed an erratic microvasculature with
a significantly lower functional microvessel density when compared to native BAT. Accordingly, they
also contained a markedly lower number of CD31-positive microvessels, which was associated with
a massive loss of perilipin-positive adipocytes. These findings indicate that in contrast to WAT grafts,
BAT grafts exhibit an impaired vascularization capacity and survival, which may be due to their
higher metabolic demand. Hence, future studies should focus on the establishment of strategies to
improve the engraftment of transplanted BAT
Absent in Melanoma (AIM)2 Promotes the Outcome of Islet Transplantation by Repressing Ischemia-Induced Interferon (IFN) Signaling
Clinical islet transplantation is limited by ischemia-induced islet cell death. Recently, it
has been reported that the absent in melanoma (AIM)2 inflammasome is upregulated by ischemic
cell death due to recognition of aberrant cytoplasmic self-dsDNA. However, it is unknown whether
AIM2 determines the outcome of islet transplantation. To investigate this, isolated wild type (WT)
and AIM2-deficient (AIM2â/â) islets were exposed to oxygen-glucose deprivation to mimic ischemia,
and their viability, endocrine function, and interferon (IFN) signaling were assessed. Moreover,
the revascularization and endocrine function of grafted WT and AIM2â/â islets were analyzed in
the mouse dorsal skinfold chamber model and the diabetic kidney capsule model. Ischemic WT
and AIM2â/â islets did not differ in their viability. However, AIM2â/â islets exhibited a higher
protein level of p202, a transcriptional regulator of IFN-ÎČ and IFN-Îł gene expression. Accordingly,
these cytokines were upregulated in AIM2â/â islets, resulting in a suppressed gene expression and
secretion of insulin. Moreover, the revascularization of AIM2â/â islet grafts was deteriorated when
compared to WT controls. Furthermore, transplantation of AIM2â/â islets in diabetic mice failed to
restore physiological blood glucose levels. These findings indicate that AIM2 crucially determines
the engraftment and endocrine function of transplanted islets by repressing IFN signaling
The Marine-Derived Kinase Inhibitor Fascaplysin Exerts Anti-Thrombotic Activity
Background: The marine-derived kinase inhibitor fascaplysin down-regulates the PI3K pathway in cancer cells. Since this pathway also plays an essential role in platelet signaling, we herein investigated the effect of fascaplysin on thrombosis. Methods: Fascaplysin effects on platelet activation, platelet aggregation and platelet-leukocyte aggregates (PLA) formation were analyzed by flow cytometry. Mouse dorsal skinfold chambers were used to determine in vivo the effect of fascaplysin on photochemically induced thrombus formation and tail-vein bleeding time. Results: Pre-treatment of platelets with fascaplysin reduced the activation of glycoprotein (GP)IIb/IIIa after protease-activated receptor-1-activating peptide (PAR-1-AP), adenosine diphosphate (ADP) and phorbol-12-myristate-13-acetate (PMA) stimulation, but did not markedly affect the expression of P-selectin. This was associated with a decreased platelet aggregation. Fascaplysin also decreased PLA formation after PMA but not PAR-1-AP and ADP stimulation. This may be explained by an increased expression of CD11b on leukocytes in PAR-1-AP- and ADP-treated whole blood. In the dorsal skinfold chamber model of photochemically induced thrombus formation, fascaplysin-treated mice revealed a significantly extended complete vessel occlusion time when compared to controls. Furthermore, fascaplysin increased the tail-vein bleeding time. Conclusion: Fascaplysin exerts anti-thrombotic activity, which represents a novel mode of action in the pleiotropic activity spectrum of this compound
Erythropoietin exposure of isolated pancreatic islets accelerates their revascularization after transplantation
Aims
The exposure of isolated pancreatic islets to pro-angiogenic factors prior to their transplantation represents a promising strategy to accelerate the revascularization of the grafts. It has been shown that erythropoietin (EPO), a glycoprotein regulating erythropoiesis, also induces angiogenesis. Therefore, we hypothesized that EPO exposure of isolated islets improves their posttransplant revascularization.
Methods
Flow cytometric, immunohistochemical and quantitative real-time (qRT)-PCR analyses were performed to study the effect of EPO on the viability, cellular composition and gene expression of isolated islets. Moreover, islets expressing a mitochondrial or cytosolic H2O2 sensor were used to determine reactive oxygen species (ROS) levels. The dorsal skinfold chamber model in combination with intravital fluorescence microscopy was used to analyze the revascularization of transplanted islets.
Results
We found that the exposure of isolated islets to EPO (3 units/mL) for 24 h does not affect the viability and the production of ROS when compared to vehicle-treated and freshly isolated islets. However, the exposure of islets to EPO increased the number of CD31-positive cells and enhanced the gene expression of insulin and vascular endothelial growth factor (VEGF)-A. The revascularization of the EPO-cultivated islets was accelerated within the initial phase after transplantation when compared to both controls.
Conclusion
These findings indicate that the exposure of isolated islets to EPO may be a promising approach to improve clinical islet transplantation
Brassinin Promotes the Degradation of Tie2 and FGFR1 in Endothelial Cells and Inhibits Triple-Negative Breast Cancer Angiogenesis
Brassinin, a phytoalexin derived from cruciferous vegetables, has been reported to exhibit
anti-cancer activity in multiple cancer types. However, its effects on triple-negative breast cancer
(TNBC) development and the underlying mechanisms have not been elucidated so far. In this
study, we demonstrated in vitro that brassinin preferentially reduces the viability of endothelial cells
(ECs) when compared to other cell types of the tumor microenvironment, including TNBC cells,
pericytes, and fibroblasts. Moreover, brassinin at non-cytotoxic doses significantly suppressed the
proliferation, migration, tube formation, and spheroid sprouting of ECs. It also efficiently inhibited
angiogenesis in an ex-vivo aortic ring assay and an in-vivo Matrigel plug assay. Daily intraperitoneal
injection of brassinin significantly reduced tumor size, microvessel density, as well as the perfusion
of tumor microvessels in a dorsal skinfold chamber model of TNBC. Mechanistic analyses showed
that brassinin selectively stimulates the degradation of Tie2 and fibroblast growth factor receptor 1 in
ECs, leading to the down-regulation of the AKT and extracellular signal-regulated kinase pathways.
These findings demonstrate a preferential and potent anti-angiogenic activity of brassinin, which
may be the main mechanism of its anti-tumor action. Accordingly, this phytochemical represents a
promising candidate for the future anti-angiogenic treatment of TNBC
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