Abstract 382: Reduced Mitochondrial Function and Metabolic Dysregulation in Aneurysmal Fibulin-4 Mice.

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Ingrid van der Pluijm ◽  
P.M. van Heijningen ◽  
A. IJpma ◽  
N. van Vliet ◽  
W Sluiter ◽  
...  

Thoracic aortic aneurysms are a life-threatening condition often diagnosed too late. The underlying mechanism is largely unknown. An accurate and early predictive biomarker for aneurysm formation has not yet been identified, although some molecular processes, such as disturbed TGF-β signalling, have been implicated. To discover novel robust biomarkers, we aimed to better understand the molecular mechanisms involved in aneurysm initiation and progression. In Fibulin-4 R/R mice, the extracellular matrix protein Fibulin-4 is 4-fold reduced, resulting in progressive ascending aneurysm formation and early death around 3 months of age. We performed LC-MS/MS proteomics and transcriptomics analyses on the aortas of Fibulin-4 R/R and Fibulin-4 +/+ mice. Protein and gene data sets were separately analysed for genotype specific differences with Ingenuity Pathway analysis tools. Intriguingly, we observed alterations in mitochondrial composition in aortas from Fibulin-4 R/R mice. Consistently, functional studies in Fibulin-4 R/R vascular smooth muscle cells (VSMCs) revealed lower oxygen consumption rates, but increased acidification rates compared to Fibulin-4 +/+ . The mitochondria in VSMCs of Fibulin-4 R/R mice were reduced in size and had increased complex I-IV levels. Furthermore, aortas of aneurysmal Fibulin-4 R/R mice displayed increased levels of ROS. Consistent with these findings, gene expression analyses revealed the dysregulation of metabolic pathways. In accordance, ketone levels in the blood of Fibulin-4 R/R mice were reduced and liver fatty acids were decreased, while liver glycogen was increased. As predicted by these findings, activity of PGC1α, a key regulator between mitochondrial function and organismal metabolism, was downregulated in Fibulin-4 R/R VSMCs. In conclusion, our data indicate altered mitochondrial function and metabolic dysregulation, leading to increased ROS levels and altered energy production, as a novel mechanism, which may contribute to thoracic aortic aneurysm formation. This discovery will not only provide new biomarkers that can be validated in human aortas, but they will also provide the rational for new interventions such as alterations in diet to prevent aneurysm formation.

2016 ◽  
Vol 310 (11) ◽  
pp. H1486-H1493 ◽  
Author(s):  
Teresa Palao ◽  
Catarina Rippe ◽  
Henk van Veen ◽  
Ed VanBavel ◽  
Karl Swärd ◽  
...  

Thrombospondin-4 (TSP-4) is a multidomain calcium-binding protein that has both intracellular and extracellular functions. As an extracellular matrix protein, it is involved in remodeling processes. Previous work showed that, in the cardiovascular system, TSP-4 expression is induced in the heart in response to experimental pressure overload and infarction injury. Intracellularly, it mediates the endoplasmic reticulum stress response in the heart. In this study, we explored the role of TSP-4 in hypertension. For this purpose, wild-type and TSP-4 knockout ( Thbs4 −/−) mice were treated with angiotensin II (ANG II). Hearts from ANG II-treated Thbs4 −/− mice showed an exaggerated hypertrophic response. Interestingly, aortas from Thbs4 −/− mice treated with ANG II showed a high incidence of aneurysms. In resistance arteries, ANG II-treated wild-type mice showed impaired endothelial-dependent relaxation. This was not observed in ANG II-treated Thbs4 −/− mice or in untreated controls. No differences were found in the passive pressure-diameter curves or stress-strain relationships, although ANG II-treated Thbs4 −/− mice showed a tendency to be less stiff, associated with thicker diameters of the collagen fibers as revealed by electron microscopy. We conclude that TSP-4 plays a role in hypertension, affecting cardiac hypertrophy, aortic aneurysm formation, as well as endothelial-dependent relaxation in resistance arteries.


2017 ◽  
Vol 114 (22) ◽  
pp. E4408-E4415 ◽  
Author(s):  
Sean E. Reichheld ◽  
Lisa D. Muiznieks ◽  
Fred W. Keeley ◽  
Simon Sharpe

Despite its growing importance in biology and in biomaterials development, liquid–liquid phase separation of proteins remains poorly understood. In particular, the molecular mechanisms underlying simple coacervation of proteins, such as the extracellular matrix protein elastin, have not been reported. Coacervation of the elastin monomer, tropoelastin, in response to heat and salt is a critical step in the assembly of elastic fibers in vivo, preceding chemical cross-linking. Elastin-like polypeptides (ELPs) derived from the tropoelastin sequence have been shown to undergo a similar phase separation, allowing formation of biomaterials that closely mimic the material properties of native elastin. We have used NMR spectroscopy to obtain site-specific structure and dynamics of a self-assembling elastin-like polypeptide along its entire self-assembly pathway, from monomer through coacervation and into a cross-linked elastic material. Our data reveal that elastin-like hydrophobic domains are composed of transient β-turns in a highly dynamic and disordered chain, and that this disorder is retained both after phase separation and in elastic materials. Cross-linking domains are also highly disordered in monomeric and coacervated ELP3 and form stable helices only after chemical cross-linking. Detailed structural analysis combined with dynamic measurements from NMR relaxation and diffusion data provides direct evidence for an entropy-driven mechanism of simple coacervation of a protein in which transient and nonspecific intermolecular hydrophobic contacts are formed by disordered chains, whereas bulk water and salt are excluded.


Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Ashley Dawson ◽  
Yanming Li ◽  
Pingping Ren ◽  
Hernan Vasquez ◽  
Chen Zhang ◽  
...  

Background: Thoracic aortic aneurysms associated with Marfan syndrome (MFS) carry a high risk of mortality; however, the molecular and cellular processes leading to aortopathy in this population remain poorly understood. We aimed to use single-cell RNA (scRNA) sequencing to define the non-immune cell populations present within the aortic wall in MFS, hypothesizing that these would differ from those of non-aneurysmal control tissue. Methods: We performed scRNA sequencing of ascending aortic aneurysm tissues from MFS patients (n=3) undergoing aneurysm repair and of age-matched, non-aneurysmal control tissue from cardiac transplant donors and recipients (n=4). The Seurat package in R was used for analysis. Differentially expressed genes were identified using edgeR. Results: Eighteen non-immune cell clusters were identified, with conserved gene expression of the largest of the clusters consistent with smooth muscle cells (SMCs; n=6), fibroblasts (n=3), and endothelial cells (n=3). The SMCs and fibroblasts exhibited graded changes in their expression of contractile and extracellular matrix protein genes, supportive of a phenotypic continuum. Additionally, we identified differences in the proportions of non-immune cells in MFS tissues compared to controls. In control tissues, the most common non-immune cells expressed markers of contractile SMC maturity including CNN1 , MYH11 , and SMTN . In contrast, the largest clusters in MFS tissue were most closely related to SMCs on correlation analysis, but displayed increased expression of cyclin genes as well as immune, endothelial, and fibroblast genes indicative of de-differentiated, proliferative SMCs. Additionally, expression of genes associated with SMC phenotypic maturity, including MYH11 and MYOCD , were significantly downregulated in several of the MFS SMC clusters. Conclusion: Our data demonstrate a phenotypic continuum between fibroblasts and SMCs, with aortas from patients with MFS exhibiting an increased proportion of de-differentiated, proliferative SMCs compared to controls. Additionally, markers of SMC maturity were downregulated in SMCs in MFS compared to controls. This may be due to disruption of signaling pathways that promote differentiation.


2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Paulina Rudziak ◽  
Christopher G. Ellis ◽  
Paulina M. Kowalewska

Leukocyte recruitment is a hallmark of the inflammatory response. Migrating leukocytes breach the endothelium along with the vascular basement membrane and associated pericytes. While much is known about leukocyte-endothelial cell interactions, the mechanisms and role of pericytes in extravasation are poorly understood and the classical paradigm of leukocyte recruitment in the microvasculature seldom adequately discusses the involvement of pericytes. Emerging evidence shows that pericytes are essential players in the regulation of leukocyte extravasation in addition to their functions in blood vessel formation and blood-brain barrier maintenance. Junctions between venular endothelial cells are closely aligned with extracellular matrix protein low expression regions (LERs) in the basement membrane, which in turn are aligned with gaps between pericytes. This forms preferential paths for leukocyte extravasation. Breaching of the layer formed by pericytes and the basement membrane entails remodelling of LERs, leukocyte-pericyte adhesion, crawling of leukocytes on pericyte processes, and enlargement of gaps between pericytes to form channels for migrating leukocytes. Furthermore, inflamed arteriolar and capillary pericytes induce chemotactic migration of leukocytes that exit postcapillary venules, and through direct pericyte-leukocyte contact, they induce efficient interstitial migration to enhance the immunosurveillance capacity of leukocytes. Given their role as regulators of leukocyte extravasation, proper pericyte function is imperative in inflammatory disease contexts such as diabetic retinopathy and sepsis. This review summarizes research on the molecular mechanisms by which pericytes mediate leukocyte diapedesis in inflamed tissues.


2000 ◽  
Vol 150 (1) ◽  
pp. 27-40 ◽  
Author(s):  
Masahiro Iwamoto ◽  
Yoshinobu Higuchi ◽  
Eiki Koyama ◽  
Motomi Enomoto-Iwamoto ◽  
Kojiro Kurisu ◽  
...  

During limb development, chondrocytes located at the epiphyseal tip of long bone models give rise to articular tissue, whereas the more numerous chondrocytes in the shaft undergo maturation, hypertrophy, and mineralization and are replaced by bone cells. It is not understood how chondrocytes follow these alternative pathways to distinct fates and functions. In this study we describe the cloning of C-1-1, a novel variant of the ets transcription factor ch-ERG. C-1-1 lacks a short 27–amino acid segment located ∼80 amino acids upstream of the ets DNA binding domain. We found that in chick embryo long bone anlagen, C-1-1 expression characterizes developing articular chondrocytes, whereas ch-ERG expression is particularly prominent in prehypertrophic chondrocytes in the growth plate. To analyze the function of C-1-1 and ch-ERG, viral vectors were used to constitutively express each factor in developing chick leg buds and cultured chondrocytes. We found that virally driven expression of C-1-1 maintained chondrocytes in a stable and immature phenotype, blocked their maturation into hypertrophic cells, and prevented the replacement of cartilage with bone. It also induced synthesis of tenascin-C, an extracellular matrix protein that is a unique product of developing articular chondrocytes. In contrast, virally driven expression of ch-ERG significantly stimulated chondrocyte maturation in culture, as indicated by increases in alkaline phosphatase activity and deposition of a mineralized matrix; however, it had modest effects in vivo. The data show that C-1-1 and ch-ERG have diverse biological properties and distinct expression patterns during skeletogenesis, and are part of molecular mechanisms by which limb chondrocytes follow alternative developmental pathways. C-1-1 is the first transcription factor identified to date that appears to be instrumental in the genesis and function of epiphyseal articular chondrocytes.


2021 ◽  
Vol 8 ◽  
Author(s):  
Paul Thomas ◽  
Aparna Venugopalan ◽  
Siddharth Narayanan ◽  
Thomas Mathew ◽  
Lakshmi Parvathi Deepti Cherukuwada ◽  
...  

Aortic diseases requiring surgery in childhood are distinctive and rare. Very few reports in the literature account for the occurrence of multiple thoracic aortic aneurysms in the same pediatric patient because of a genetic cause. We report a rare occurrence of severe thoracic aortic aneurysms (involving the ascending, arch and descending aortic segments) with severe aortic insufficiency in a 7-year-old female child secondary to the extremely rare and often lethal genetic disorder, cutis laxa. She was eventually identified as a carrier of a homozygous EFEMP2 (alias FBLN4) mutation. This gene encodes the extracellular matrix protein fibulin-4, and its mutation is associated with autosomal recessive cutis laxa type 1B that leads to severe aortopathy with aneurysm formation and vascular tortuosity. Parents of the child were not known to be consanguineous. Significant symptomatic improvement in the patient could be discerned after timely intervention with the valve-sparing aortic root replacement (David V procedure) and a concomitant aortic arch replacement. This is a unique report with a successful outcome that highlights the occurrence of a rare hereditary aortopathy associated with a high morbidity and mortality, and the importance of an early diagnosis and timely management. It also offers insight to physicians in having a very broad differential and multimodal approach in handling rare pediatric cardio-pathologies with a genetic predisposition.


2021 ◽  
Vol 12 ◽  
Author(s):  
Zhang’an Dai ◽  
Lin Cai ◽  
Yingyu Chen ◽  
Silu Wang ◽  
Qian Zhang ◽  
...  

Brusatol (Bru), a Chinese herbal extract, has a variety of anti-tumor effects. However, little is known regarding its role and underlying mechanism in glioblastoma cells. Here, we found that Bru could inhibit the proliferation of glioblastoma cells in vivo and in vitro. Besides, it also had an inhibitory effect on human primary glioblastoma cells. RNA-seq analysis indicated that Bru possibly achieved these effects through inhibiting the expression of extracellular matrix protein 1 (ECM1). Down-regulating the expression of ECM1 via transfecting siRNA could weaken the proliferation and invasion of glioblastoma cells and promote the inhibitory effect of Bru treatment. Lentivirus-mediated overexpression of ECM1 could effectively reverse this weakening effect. Our findings indicated that Bru could inhibit the proliferation and invasion of glioblastoma cells by suppressing the expression of ECM1, and Bru might be a novel effective anticancer drug for glioblastoma cells.


Hypertension ◽  
2017 ◽  
Vol 70 (suppl_1) ◽  
Author(s):  
Daniela Carnevale ◽  
Raimondo Carnevale ◽  
Francesco Da Ros ◽  
Roberta Iacobucci ◽  
Manuel Casaburo ◽  
...  

Aortic aneurysms represent a life-threatening condition because of the current lack of effective treatments. Aneurysm formation is typically associated with extracellular matrix remodeling and persistent inflammation. Although the molecular mechanisms underlying aortic pathology remain largely unclear, TGFβ signaling is unquestionably implied and its downstream target Smad4 showed protective functions for maintenance of aortic walls’ integrity. Using mice with smooth muscle cells (SMCs) specific deletion of Smad4 in the adult ( Smad4 -SMC iko ), developing spontaneous aneurysms (Ascending Aorta Diameter: Smad4 -SMC iko 2.15±0.03; Smad4 -SMC wt 1.7±0.03;***p< 0.001), we investigated the molecular mechanisms activated by dysregulation of TGFβ signaling. Structural disarrangement of ascending aorta in Smad4 -SMC iko mice was clearly appreciated early after Smad4 deletion as discrete breaks of elastic lamellae (breaks/section: Smad4 -SMC iko 2.05±0.5; Smad4 -SMC wt 0.83±0.4;***p< 0.001). Interestingly, the islands of damage in the aorta of Smad4 -SMC iko were enriched of immune infiltrate, mainly monocytes/macrophages, as indicated by FACS and immunofluorescence. We then analyzed several pathways downstream to Smad4 inhibition, finding a selective activation of NF-kB/IL-1β in SMCs. To test the relevance of this pathway in the formation of aneurysms, we deleted Smad4 in SMCs of mice with Il1r1 null background ( Smad4 -SMC iko ; Il1r1 -/- ). Ultrasonographic analyses revealed that ablation of IL1 receptor1 protected Smad4 -SMC iko mice from the progression of pathology and improved their overall survival. In the end, to test the translational potential of our findings, we neutralized IL-1β signaling with the clinically relevant murine version of the FDA-approved clinical drug canakinumab. During a time course of 16 weeks, while a weekly administration of control immunoglobulins did not change aneurysm progression in Smad4 -SMC iko mice, treatment with anti-IL-1β antibody significantly hampered aneurysm formation in the aorta ( Smad4 -SMC iko +anti- IL-1β 1.85±0.02; Smad4 -SMC iko +anti-IgG 2.09±0.03; ***p< 0.001) These findings identify a mechanistic target for controlling aneurysms progression induced by disrupted TGFβ signaling.


2003 ◽  
Vol 285 (1) ◽  
pp. E1-E9 ◽  
Author(s):  
L. Darryl Quarles

There is evidence for a hormone/enzyme/extracellular matrix protein cascade involving fibroblastic growth factor 23 (FGF23), a phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX), and a matrix extracellular phosphoglycoprotein (MEPE) that regulates systemic phosphate homeostasis and mineralization. Genetic studies of autosomal dominant hypophosphatemic rickets (ADHR) and X-linked hypophosphatemia (XLH) identified the phosphaturic hormone FGF23 and the membrane metalloprotease PHEX, and investigations of tumor-induced osteomalacia (TIO) discovered the extracellular matrix protein MEPE. Similarities between ADHR, XLH, and TIO suggest a model to explain the common pathogenesis of renal phosphate wasting and defective mineralization in these disorders. In this model, increments in FGF23 and MEPE, respectively, cause renal phosphate wasting and intrinsic mineralization abnormalities. FGF23 elevations in ADHR are due to mutations of FGF23 that block its degradation, in XLH from indirect actions of inactivating mutations of PHEX to modify the expression and/or degradation of FGF23 and MEPE, and in TIO because of increased production of FGF23 and MEPE. Although this model is attractive, several aspects need to be validated. First, the enzymes responsible for metabolizing FGF23 and MEPE need to be established. Second, the physiologically relevant PHEX substrates and the mechanisms whereby PHEX controls FGF23 and MEPE metabolism need to be elucidated. Finally, additional studies are required to establish the molecular mechanisms of FGF23 and MEPE actions on kidney and bone, as well as to confirm the role of these and other potential “phosphatonins,” such as frizzled related protein-4, in the pathogenesis of the renal and skeletal phenotypes in XLH and TIO. Unraveling the components of this hormone/enzyme/extracellular matrix pathway will not only lead to a better understanding of phosphate homeostasis and mineralization but may also improve the diagnosis and treatment of hypo- and hyperphosphatemic disorders.


2015 ◽  
Vol 309 (1) ◽  
pp. H103-H113 ◽  
Author(s):  
Jungsil Kim ◽  
Jesse D. Procknow ◽  
Hiromi Yanagisawa ◽  
Jessica E. Wagenseil

Fibulin-4 is an extracellular matrix protein that is essential for proper assembly of arterial elastic fibers. Mutations in fibulin-4 cause cutis laxa with thoracic aortic aneurysms (TAAs). Sixty percent of TAAs occur in the ascending aorta (AA). Newborn mice lacking fibulin-4 ( Fbln4−/−) have aneurysms in the AA, but narrowing in the descending aorta (DA), and are a unique model to investigate locational differences in aneurysm susceptibility. We measured mechanical behavior and gene expression of AA and DA segments in newborn Fbln4−/− and Fbln4+/+ mice. Fbln4−/− AA has increased diameters compared with Fbln4+/+ AA and Fbln4−/− DA at most applied pressures, confirming genotypic and locational specificity of the aneurysm phenotype. When diameter compliance and tangent modulus were calculated from the mechanical data, we found few significant differences between genotypes, suggesting that the mechanical response to incremental diameter changes is similar, despite the fragmented elastic fibers in Fbln4−/− aortas. Fbln4−/− aortas showed a trend toward increased circumferential stretch, which may be transmitted to smooth muscle cells (SMCs) in the wall. Gene expression data suggest activation of pathways for SMC proliferation and inflammation in Fbln4−/− aortas compared with Fbln4+/+. Additional genes in both pathways, as well as matrix metalloprotease-8 ( Mmp8), are upregulated specifically in Fbln4−/− AA compared with Fbln4+/+ AA and Fbln4−/− DA. Mmp8 is a neutrophil collagenase that targets type 1 collagen, and upregulation may be necessary to allow diameter expansion in Fbln4−/− AA. Our results provide molecular and mechanical targets for further investigation in aneurysm pathogenesis.


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