A20 attenuates vascular smooth muscle cell proliferation and migration through blocking PI3k/Akt singling in vitro and in vivo

Advancements in Omics and Breakthrough Gene Therapies: A Glimpse into the Future of Peripheral Artery Disease

Peripheral artery disease (PAD), a highly prevalent global disease, associates with significant morbidity and mortality in affected patients. Despite progress in endovascular and open revascularization techniques for advanced PAD, these interventions grapple with elevated rates of arterial restenosis and vein graft failure attributed to intimal hyperplasia (IH). Novel multiomics technologies, coupled with sophisticated analyses tools recently powered by advances in artificial intelligence, have enabled the study of atherosclerosis and IH with unprecedented single-cell and spatial precision. Numerous studies have pinpointed gene hubs regulating pivotal atherogenic and atheroprotective signaling pathways as potential therapeutic candidates. Leveraging advancements in viral and nonviral gene therapy (GT) platforms, gene editing technologies, and cutting-edge biomaterial reservoirs for delivery uniquely positions us to develop safe, efficient, and targeted GTs for PAD-related diseases. Gene therapies appear particularly fitting for ex vivo genetic engineering of IH-resistant vein grafts. This manuscript highlights currently available state-of-the-art multiomics approaches, explores promising GT-based candidates, and details GT delivery modalities employed by our laboratory and others to thwart mid-term vein graft failure caused by IH, as well as other PAD-related conditions. The potential clinical translation of these targeted GTs holds the promise to revolutionize PAD treatment, thereby enhancing patients' quality of life and life expectancy.

PI3Kγ (Phosphoinositide 3-Kinase γ) Regulates Vascular Smooth Muscle Cell Phenotypic Modulation and Neointimal Formation Through CREB (Cyclic AMP-Response Element Binding Protein)/YAP (Yes-Associated Protein) Signaling

Objective- Vascular smooth muscle cells (VSMCs) phenotype modulation is critical for the resolution of vascular injury. Genetic and pharmacological inhibition of PI3Kγ (phosphoinositide 3-kinase γ) exerts anti-inflammatory and protective effects in multiple cardiovascular diseases. This study investigated the role of PI3Kγ and its downstream effector molecules in the regulation of VSMC phenotypic modulation and neointimal formation in response to vascular injury. Approach and Results- Increased expression of PI3Kγ was found in injured vessel wall as well in cultured, serum-activated wild-type VSMCs, accompanied by a reduction in the expression of calponin and SM22α, 2 differentiation markers of VSMCs. However, the injury-induced downregulation of calponin and SM22α was profoundly attenuated in PI3Kγ^-/- mice. Pharmacological inhibition and short hairpin RNA knockdown of PI3Kγ (PI3Kγ-KD) markedly attenuated YAP (Yes-associated protein) expression and CREB (cyclic AMP-response element binding protein) activation but improved the downregulation of differentiation genes in cultured VSMCs accompanied by reduced cell proliferation and migration. Mechanistically, activated CREB upregulated YAP transcriptional expression through binding to its promoter. Ectopic expression of YAP strikingly repressed the expression of differentiation genes even in PI3Kγ-KD VSMCs. Moreover, established carotid artery ligation and chimeric mice models demonstrate that deletion of PI3Kγ in naïve PI3Kγ^-/- mice as well as in chimeric mice lacking PI3Kγ either in bone marrow or vascular wall significantly reduced neointimal formation after injury. Conclusions- PI3Kγ controls phenotypic modulation of VSMCs by regulating transcription factor CREB activation and YAP expression. Modulating PI3Kγ signaling on local vascular wall may represent a new therapeutic approach to treat proliferative vascular disease.

PI3Kγ promotes vascular smooth muscle cell phenotypic modulation and transplant arteriosclerosis via a SOX9-dependent mechanism

Background

Transplant arteriosclerosis (TA) remains the major cause of chronic graft failure in solid organ transplantation. The phenotypic modulation of vascular smooth muscle cells (VSMCs) is a key event for the initiation and progression of neointimal formation and TA. This study aims to explore the role and underlying mechanism of phosphoinositide 3-kinases γ (PI3Kγ) in VSMC phenotypic modulation and TA.

Methods

The rat model of aortic transplantation was established to detect PI3Kγ expression and its role in neointimal formation and vascular remodeling in vivo. PI3Kγ shRNA transfection was employed to knockdown PI3Kγ gene. Aortic VSMCs was cultured and treated with TNF-α to explore the role and molecular mechanism of PI3Kγ in VSMC phenotypic modulation.

Findings

Activated PI3Kγ/p-Akt signaling was observed in aortic allografts and in TNF-α-treated VSMCs. Lentivirus-mediated shRNA transfection effectively inhibited PI3Kγ expression in medial VSMCs while restoring the expression of VSMC contractile genes, associated with impaired neointimal formation in aortic allografts. In cultured VSMCs, PI3Kγ blockade with pharmacological inhibitor or genetic knockdown markedly abrogated TNF-α-induced downregulation of VSMC contractile genes and increase in cellular proliferation and migration. Moreover, SOX9 located in nucleus competitively inhibited the interaction of Myocardin and SRF, while PI3Kγ inhibition robustly reduced SOX9 expression and its nuclear translocation and repaired the Myocardin/SRF association.

Interpretation

These results suggest that PI3Kγ plays a critical role in VSMC phenotypic modulation via a SOX9-dependent mechanism. Therefore, PI3Kγ in VSMCs may represent a promising therapeutic target for the treatment of TA.

Fund

National Natural Science Foundation of China.

SRPK1 gene silencing promotes vascular smooth muscle cell proliferation and vascular remodeling via inhibition of the PI3K/Akt signaling pathway in a rat model of intracranial aneurysms

OBJECTIVE

Intracranial aneurysm (IA) is a life threatening cerebrovascular disease characterized by phenotypic modulation of vascular smooth muscle cells (VSMCs) and loss of vessel cells. In addition to environmental factors, genetic factors have been proposed to be a critical factor in the onset and progression of IA. The present study investigates the effects of serine-arginine protein kinase 1 (SRPK1) on VSMC proliferation and apoptosis both in vivo and in vitro, as well as its role in vascular remodeling in vivo through PI3 K/Akt signaling in IA.

METHODS

Differentially expressed genes related to IA were initially identified using microarray analysis. Immunohistochemistry was conducted to determine SRPK1 expression in the vascular walls in IA and normal cerebral vascular walls. TUNEL staining were applied to observe cell apoptosis patterns of VSMCs. VSMC proliferation and apoptosis in vitro were detected by cell counting kit-8 (CCK8) assay and flow cytometry. The expressions of SRPK1, PI3 K/Akt signaling pathway- and apoptosis-related genes were evaluated by RT-qPCR and Western blot analysis.

RESULTS

Microarray data of GSE36791 and GSE54083 were analyzed to determine the selection of SRPK1 gene. The vascular walls in IA rat models produced high levels of SRPK1 expression and an activated PI3 K/Akt signaling pathway. VSMCs treated with siRNA-SRPK1 exhibited enhanced cell proliferation, repressed cell apoptosis, and increased vascular remodeling, all of which suggest the inhibition of the PI3 K/AKT pathway. Notably, PI3 K/AKT pathway reversed the effect of SRPK1 silencing.

CONCLUSION

Our results show that siRNA-mediated silencing of SRPK1 gene inhibits VSMC apoptosis, and increases VSMCs proliferation and vascular remodeling in IA via the PI3 K/Akt signaling pathway. Our findings provide a novel intervention target for the molecular treatment of IA.

O-Linked β-N-Acetylglucosamine Modification of A20 Enhances the Inhibition of NF-κB (Nuclear Factor-κB) Activation and Elicits Vascular Protection After Acute Endoluminal Arterial Injury

OBJECTIVE

Recently, we have demonstrated that acute glucosamine-induced augmentation of protein O-linked β-N-acetylglucosamine (O-GlcNAc) levels inhibits inflammation in isolated vascular smooth muscle cells and neointimal formation in a rat model of carotid injury by interfering with NF-κB (nuclear factor-κB) signaling. However, the specific molecular target for O-GlcNAcylation that is responsible for glucosamine-induced vascular protection remains unclear. In this study, we test the hypothesis that increased A20 (also known as TNFAIP3 [tumor necrosis factor α-induced protein 3]) O-GlcNAcylation is required for glucosamine-mediated inhibition of inflammation and vascular protection.

APPROACH AND RESULTS

In cultured rat vascular smooth muscle cells, both glucosamine and the selective O-linked N-acetylglucosaminidase inhibitor thiamet G significantly increased A20 O-GlcNAcylation. Thiamet G treatment did not increase A20 protein expression but did significantly enhance binding to TAX1BP1 (Tax1-binding protein 1), a key regulatory protein for A20 activity. Adenovirus-mediated A20 overexpression further enhanced the effects of thiamet G on prevention of TNF-α (tumor necrosis factor-α)-induced IκB (inhibitor of κB) degradation, p65 phosphorylation, and increases in DNA-binding activity. A20 overexpression enhanced the inhibitory effects of thiamet G on TNF-α-induced proinflammatory cytokine expression and vascular smooth muscle cell migration and proliferation, whereas silencing endogenous A20 by transfection of specific A20 shRNA significantly attenuated these inhibitory effects. In balloon-injured rat carotid arteries, glucosamine treatment markedly inhibited neointimal formation and p65 activation compared with vehicle treatment. Adenoviral delivery of A20 shRNA to the injured arteries dramatically reduced balloon injury-induced A20 expression and inflammatory response compared with scramble shRNA and completely abolished the vascular protection of glucosamine.

CONCLUSIONS

These results suggest that O-GlcNAcylation of A20 plays a key role in the negative regulation of NF-κB signaling cascades in TNF-α-treated vascular smooth muscle cells in culture and in acutely injured arteries, thus protecting against inflammation-induced vascular injury.

A20 Haploinsufficiency Aggravates Transplant Arteriosclerosis in Mouse Vascular Allografts: Implications for Clinical Transplantation

BACKGROUND

Inflammation is central to the pathogenesis of transplant arteriosclerosis (TA). We questioned whether physiologic levels of anti-inflammatory A20 influence TA severity.

METHODS

We performed major histocompatibility complex mismatched aorta to carotid artery interposition grafts, using wild type (WT) or A20 heterozygote (HET) C57BL/6 (H-2) donors and BALB/c (H-2) recipients, and conversely BALB/c donors and WT/HET recipients. We analyzed aortic allografts by histology, immunohistochemistry, immunofluorescence, and gene profiling (quantitative real-time reverse-transcriptase polymerase chain reaction). We validated select in vivo A20 targets in human and mouse smooth muscle cell (SMC) cultures.

RESULTS

We noted significantly greater intimal hyperplasia in HET versus WT allografts, indicating aggravated TA. Inadequate upregulation of A20 in HET allografts after transplantation was associated with excessive NF-кB activation, gauged by higher levels of IkBα, p65, VCAM-1, ICAM-1, CXCL10, CCL2, TNF, and IL-6 (mostly localized to SMC). Correspondingly, cytokine-induced upregulation of TNF and IL-6 in human and mouse SMC cultures inversely correlated with A20 expression. Aggravated TA in HET versus WT allografts correlated with increased intimal SMC proliferation, and a higher number of infiltrating IFNγ and Granzyme B CD4 T cells and natural killer cells, and lower number of FoxP3 regulatory T cells. A20 haploinsufficiency in allograft recipients did not influence TA.

CONCLUSIONS

A20 haploinsufficiency in vascular allografts aggravates lesions of TA by exacerbating inflammation, SMC proliferation, and infiltration of pathogenic T cells. A20 single nucleotide polymorphisms associating with lower A20 expression or function in donors of vascularized allografts may inform risk and severity of TA, highlighting the clinical implications of our findings.

A20 deficiency leads to angiogenesis of pulmonary artery endothelial cells through stronger NF-κB activation under hypoxia

A20 is a zinc finger protein associated with hypoxia. As chronic hypoxia is responsible for intimal hyperplasia and disordered angiogenesis of pulmonary artery, which are histological hallmarks of pulmonary artery hypertension, we intended to explore the role of A20 in angiogenesis of pulmonary artery endothelial cells (ECs). Here, we found a transient elevation of A20 expression in the lung tissues from hypoxic rats compared with normoxic controls. This rapid enhancement was mainly detected in the endothelium, and similar results were reproduced in vitro. During early hypoxia, genetic inhibition of A20 increased proliferation in pulmonary artery ECs, linking to advanced cell cycle progression as well as microtubule polymerization, and aggravated angiogenic effects including tube formation, cell migration and adhesion molecules expression. In addition, a negative feedback loop between nuclear factor-kappa B and A20 was confirmed. Our findings provide evidence for an adaptive role of A20 against pulmonary artery ECs angiogenesis via nuclear factor-kappa B activation.

Emerging roles for A20 in islet biology and pathology

A20 is most characteristically described in terms relating to inflammation and inflammatory pathologies. The emerging understanding of inflammation in the etiology of diabetes mellitus lays the framework for considering a central role for A20 in this disease process. Diabetes mellitus is considered a major health issue, and describes a group of common metabolic disorders pathophysiologically characterized by hyperglycemia. Within islets of Langherhans, the endocrine powerhouse of the pancreas, are the insulin-producing pancreatic beta-cells. Loss of beta-cell mass and function to inflammation and apoptosis is a major contributing factor to diabetes. Consequently, restoring functional beta-cell mass via transplantation represents a therapeutic option for diabetes. Unfortunately, transplanted islets also suffers from loss of beta-cell function and mass fueled by a multifactorial inflammatory cycle triggered by islet isolation prior to transplantation, the ischemic environment at transplantation as well as allogeneic or recurrent auto-immune responses. Activation of the transcription factor NF-kappaB is a central mediator of inflammatory mediated beta-cell dysfunction and loss. Accordingly, a plethora of strategies to block NF-kappaB activation in islets and hence limit beta-cell loss have been explored, with mixed success. We propose that the relatively poor efficacy of NF-kappaB blockade in beta-cells is due to concommittant loss of the important, NF-kappaB regulated anti-apoptotic and anti-inflammatory protein A20. A20 has been identified as a beta-cell expressed gene, raising questions about its role in beta-cell development and function, and in beta-cell related pathologies. Involvement of apoptosis, inflammation and NF-kappaB activation as beta-cell factors contributing to the pathophysiology of diabetes, coupled with the knowledge that beta-cells express the A20 gene, implies an important role for A20 in both normal beta-cell biology as well as beta-cell related pathology. Genome wide association studies (GWAS) linking single nucleotide polymorphisms in the A20 gene with the occurrence of diabetes and its complications support this hypothesis. In this chapter we review data supporting the role of A20 in beta-cell health and disease. Furthermore, by way of their specialized function in metabolism, pancreatic beta-cells also provide opportunities to explore the biology of A20 in scenarios beyond inflammation.

Translational studies of A20 in atherosclerosis and cardiovascular disease

Cardiovascular disease (CVD) is the biggest killer in the Western World despite significant advances in understanding its molecular underpinnings. Chronic inflammation, the classical hallmark of atherogenesis is thought to play a key pathogenic role in the development of atherosclerotic lesions from initiation of fatty streaks to plaque rupture. Over-representation of mostly pro-inflammatory nuclear factor kappa B (NF-kappaB) target genes within atherosclerotic lesions has led to the common-held belief that excessive NF-kappaB activity promotes and aggravates atherogenesis. However, mouse models lacking various proteins involved in NF-kappaB signaling have often resulted in conflicting findings, fueling additional investigations to uncover the molecular involvement of NF-kappaB and its target genes in atherogenesis. In this chapter we will review the role of the NF-kappaB-regulated, yet potent NF-kappaB inhibitory and anti-inflammatory gene A20/TNFAIP3 in atherogenesis, and highlight the potential use of its atheroprotective properties for the prevention and treatment of cardiovascular diseases.

Flank sequences of miR-145/143 and their aberrant expression in vascular disease: mechanism and therapeutic application

BACKGROUND

Many microRNAs (miRNAs) are downregulated in proliferative vascular disease. Thus, upregulation of these miRNAs has become a major focus of research activity. However, there is a critical barrier in gene therapy to upregulate some miRNAs such as miR-145 and miR-143 because of their significant downregulation by the unclear endogenous mechanisms under disease conditions. The purpose of this study was to determine the molecular mechanisms responsible for their downregulation and to overcome the therapeutic barrier.

METHODS AND RESULTS

In cultured proliferative rat vascular smooth muscle cells (VSMCs) in vitro and in diseased rat and mouse arteries in vivo, we have identified that the impairment of pri-miR-145 into pre-miR-145 is the critical step related to the downregulation of miR-145, in which the PI3-kinase/Akt/p53 pathway is involved. We further identified that the flank sequences of pri-miR-145 are the critical structural components responsible for the aberrant miR-145 expression. Switching of the flank sequence of downregulated miR-145 and miR-143 to the flank sequence of miR-31 confers resistance to their downregulation. The genetically engineered miR-145 (smart miR-145) restored the downregulated miR-145 in proliferative rat VSMCs and in rat carotid arteries with balloon injury and mouse atherosclerotic aortas and demonstrated much better therapeutic effects on the abnormal growth of VSMCs, expression of its target gene, KLF5 expression, VSMC marker gene expression, and vascular neointimal growth.

CONCLUSIONS

The flank sequences of miR-145 and miR-143 play a critical role in their aberrant expression in VSMCs and vascular walls. The genetically engineered "smart" miRNAs based on their flank sequences may have broadly therapeutic applications for many vascular diseases.

Insulin modulates the inflammatory granulocyte response to streptococci via phosphatidylinositol 3-kinase

Group B streptococci (GBS; Streptococcus agalactiae) are a major cause of invasive infections in newborn infants and in patients with type 2 diabetes. Both patient groups exhibit peripheral insulin resistance and alterations in polymorphonuclear leukocyte (PML) function. In this investigation, we studied the PML response repertoire to GBS with a focus on TLR signaling and the modulation of this response by insulin in mice and humans. We found that GBS-induced, MyD88-dependent chemokine formation of PML was specifically downmodulated by insulin via insulin receptor-mediated induction of PI3K. PI3K inhibited transcription of chemokine genes on the level of NF-κB activation and binding. Insulin specifically modulated the chemokine response of PML to whole bacteria, but affected neither activation by purified TLR agonists nor antimicrobial properties, such as migration, phagocytosis, bacterial killing, and formation of reactive oxygen species. The targeted modulation of bacteria-induced chemokine formation by insulin via PI3K may form a basis for the development of novel targets of adjunctive sepsis therapy.

Protein transduction domain-hA20 fusion protein protects endothelial cells against high glucose-induced injury

We constructed a plasmid containing a protein transduction domain (PTD) and a human A20 (hA20) gene fragment; the fusion protein was obtained by highly expressing this plasmid in the yeast Pichia pastoris GS115. The plasmid was obtained by adding 9xArg and EcoRІ recognition sites to the end of the primer, and 6xHis-Tag and NotІ recognition sites to its end. After sequencing, the hA20 gene fragment was inserted into plasmid pPIC9k to construct expression vector pPIC9k-PTD-hA20; then, we transfected GS115 with the vector and induced PTD-hA20 protein expression. We purified protein from the yeast fermentation supernatant using a nickel column. Human umbilical vein endothelial cells (HUVECs) were cultured in high glucose medium (30 mM glucose) and in high glucose medium containing different concentrations of protein. Apoptosis of HUVECs was assayed by TUNEL 72 h later. The biological activity tests indicated that the fusion protein not only passed through the cell membrane freely, but also inhibited apoptosis of HUVECs induced by high glucose levels. We conclude that the fusion protein PTD-hA20 has potential for clinical use.

3,3'Diindolylmethane suppresses vascular smooth muscle cell phenotypic modulation and inhibits neointima formation after carotid injury

BACKGROUND

3,3'Diindolylmethane (DIM), a natural phytochemical, has shown inhibitory effects on the growth and migration of a variety of cancer cells; however, whether DIM has similar effects on vascular smooth muscle cells (VSMCs) remains unknown. The purpose of this study was to assess the effects of DIM on the proliferation and migration of cultured VSMCs and neointima formation in a carotid injury model, as well as the related cell signaling mechanisms.

METHODOLOGY/PRINCIPAL FINDINGS

DIM dose-dependently inhibited the platelet-derived growth factor (PDGF)-BB-induced proliferation of VSMCs without cell cytotoxicity. This inhibition was caused by a G0/G1 phase cell cycle arrest demonstrated by fluorescence-activated cell-sorting analysis. We also showed that DIM-induced growth inhibition was associated with the inhibition of the expression of cyclin D1 and cyclin-dependent kinase (CDK) 4/6 as well as an increase in p27(Kip1) levels in PDGF-stimulated VSMCs. Moreover, DIM was also found to modulate migration of VSMCs and smooth muscle-specific contractile marker expression. Mechanistically, DIM negatively modulated PDGF-BB-induced phosphorylation of PDGF-recptorβ (PDGF-Rβ) and the activities of downstream signaling molecules including Akt/glycogen synthase kinase(GSK)3β, extracellular signal-regulated kinase1/2 (ERK1/2), and signal transducers and activators of transcription 3 (STAT3). Our in vivo studies using a mouse carotid arterial injury model revealed that treatment with 150 mg/kg DIM resulted in significant reduction of the neointima/media ratio and proliferating cell nuclear antigen (PCNA)-positive cells, without affecting apoptosis of vascular cells and reendothelialization. Infiltration of inflammatory cells was also inhibited by DIM administration.

CONCLUSION

These results demonstrate that DIM can suppress the phenotypic modulation of VSMCs and neointima hyperplasia after vascular injury. These beneficial effects on VSMCs were at least partly mediated by the inhibition of PDGF-Rβ and the activities of downstream signaling pathways. The results suggest that DIM has the potential to be a candidate for the prevention of restenosis.

Zinc finger protein A20 overexpression inhibits monocyte homing and protects endothelial cells from injury induced by high glucose

Diabetes mellitus causes vascular lesions and may ultimately lead to atherosclerosis. One of the earliest steps in the development of atherosclerotic lesions is the adhesion of monocytes to endothelial cells of the vessel wall. It is currently unknown whether zinc finger protein A20 is able to protect endothelial cells from injury caused by high levels of glucose and monocyte homing. In our study, adhesion of monocytes to the vessel wall endothelium was detected by measuring the rolling velocity of monocytes along human umbilical vein endothelial cells (HUVECs). Activation of NF-κB was analyzed through Western blot. HUVEC apoptosis was monitored by TUNEL in situ end-labeling and flow cytometry. High glucose concentrations (25 mM) stimulated monocytes, reducing the velocity at which they roll along HUVECs. Stimulation of monocytes with high levels of glucose also induced HUVEC apoptosis. Overexpression of the zinc finger protein A20 inhibited monocyte recruitment, NF-κB activation, P-selectin expression, and HUVEC apoptosis induced by high glucose levels. We conclude that zinc finger protein A20 can protect HUVECs from injury induced by high levels of glucose and potentially could be used to develop treatments against diabetic vascular lesions.

Glycogen synthase kinase 3 beta positively regulates Notch signaling in vascular smooth muscle cells: role in cell proliferation and survival

The role of glycogen synthase kinase 3 beta (GSK-3β) in modulating Notch control of vascular smooth muscle cell (vSMC) growth (proliferation and apoptosis) was examined in vitro under varying conditions of cyclic strain and validated in vivo following changes in medial tension and stress. Modulation of GSK-3β in vSMC following ectopic expression of constitutively active GSK-3β, siRNA knockdown and pharmacological inhibition with SB-216763 demonstrated that GSK-3β positively regulates Notch intracellular domain expression, CBF-1/RBP-Jκ transactivation and downstream target gene mRNA levels, while concomitantly promoting vSMC proliferation and inhibiting apoptosis. In contrast, inhibition of GSK-3β attenuated Notch signaling and decreased vSMC proliferation and survival. Exposure of vSMC to cyclic strain environments in vitro using both a Flexercell™ Tension system and a novel Sylgard™ phantom vessel following bare metal stent implantation revealed that cyclic strain inhibits GSK-3β activity independent of p42/p44 MAPK and p38 activation concomitant with reduced Notch signaling and decreased vSMC proliferation and survival. Exposure of vSMC to changes in medial strain microenvironments in vivo following carotid artery ligation revealed that enhanced GSK-3β activity was predominantly localized to medial and neointimal vSMC concomitant with increased Notch signaling, proliferating nuclear antigen and decreased Bax expression, respectively, as vascular remodeling progressed. GSK-3β is an important modulator of Notch signaling leading to altered vSMC cell growth where low strain/tension microenvironments prevail.

Overexpression of miR-200c induces chemoresistance in esophageal cancers mediated through activation of the Akt signaling pathway

PURPOSE

To determine the relationship between resistance to chemotherapy and microRNA (miRNA) expression in esophageal cancer, we focused on miRNAs known to be associated with maintenance of stem cell function.

EXPERIMENTAL DESIGN

Using 98 formalin-fixed, paraffin-embedded samples obtained from patients with esophageal cancer who had received preoperative chemotherapy followed by surgery, we measured expression levels of several miRNAs that are considered to be involved in the regulation of stem cell function (e.g., let-7a, let-7g, miR-21, miR-134, miR-145, miR-155, miR-200c, miR-203, and miR-296) by real-time reverse transcriptase PCR. Then, we examined the relationship between miRNA expression and prognosis or response to chemotherapy. To investigate the mechanism of miRNA-induced chemoresistance, in vitro assays were carried out using esophageal cancer cells.

RESULTS

Analyses of the 9 miRNAs expression showed that overexpression of miR-200c (P = 0.037), underexpression of miR-145 (P = 0.023), and overexpression of miR-21 (P = 0.048) correlated significantly with shortened overall duration of survival. In particular, miR-200c expression correlated significantly with response to chemotherapy (P = 0.009 for clinical response; P = 0.007 for pathologic response). In vitro assay showed significantly increased miR-200c expression in cisplatin-resistant cells compared with their parent cells (∼1.7-fold). In anti-miR-200c-transfected cells, chemosensitivity to cisplatin and apoptosis after exposure to cisplatin was found to increase as compared with the negative control. Western blotting showed that knockdown of miR-200c expression was associated with increased expression of PPP2R1B, a subunit of protein phosphatase 2A, which resulted in reduced expression of phospho-Akt.

CONCLUSIONS

Results of this study emphasized the involvement of miR-200c in resistance to chemotherapy among esophageal cancers and that this effect was mediated through the Akt pathway.

Effect of S-adenosylmethionine on neointimal formation after balloon injury in obese diabetic rats

AIMS

The association between hyperhomocysteinaemia and cardiovascular disease has been attributed to low levels of S-adenosylmethionine (SAM), a metabolic intermediate of homocysteine. However, the role of SAM in the development of restenosis has not been explored. Therefore, we investigated the effects of SAM on neointimal formation after balloon injury in obese diabetic rats and cultured cells.

METHODS AND RESULTS

Otsuka Long-Evans Tokushima fatty rats were divided into the following three groups: control (normal saline); SAM15; and SAM30 (15 and 30 mg/kg per day, respectively; n = 10 per group). SAM was administered orally from 1 week before carotid injury to 2 weeks thereafter. SAM treatment for 3 weeks caused a significant dose-dependent reduction in the intima-to-media ratio. SAM treatment significantly reduced the proliferation of vascular smooth muscle cells (VSMCs) and induced more apoptosis than was observed in the control group. This effect was accompanied by reduced circulating levels of high-sensitivity C-reactive protein and monocyte chemoattractant protein-1, reduced urine 8-hydroxy-2'-deoxyguanosine (8-OHdG), and increased adiponectin. Intima-to-media ratio correlated significantly with the levels of inflammatory markers, adiponectin, and 8-OHdG. In vitro experiments demonstrated that VSMC proliferation and migration and the adhesion of monocytes decreased in response to SAM. SAM treatment also reduced tumour necrosis factor-α-induced reactive oxygen species and tunicamycin-induced GRP78 expression in VSMCs.

CONCLUSION

These findings suggest that SAM exerts protective effects against restenosis after balloon injury in a rat model of type 2 diabetes by reducing the proliferation and inducing the apoptosis of VSMCs, modifying the inflammatory processes and reducing oxidative and endoplasmic reticulum stresses.

Expression, biological activities and mechanisms of action of A20 (TNFAIP3)

A20 (also known as TNFAIP3) is a cytoplasmic protein that plays a key role in the negative regulation of inflammation and immunity. Polymorphisms in the A20 gene locus have been identified as risk alleles for multiple human autoimmune diseases, and A20 has also been proposed to function as a tumor suppressor in several human B-cell lymphomas. A20 expression is strongly induced by multiple stimuli, including the proinflammatory cytokines TNF and IL-1, and microbial products that trigger pathogen recognition receptors, such as Toll-like receptors. A20 functions in a negative feedback loop, which mediates its inhibitory functions by downregulating key proinflammatory signaling pathways, including those controlling NF-κB- and IRF3-dependent gene expression. Activation of these transcription factors is controlled by both K48- and K63- polyubiquitination of upstream signaling proteins, respectively triggering proteasome-mediated degradation or interaction with other signaling proteins. A20 turns off NF-κB and IRF3 activation by modulating both types of ubiquitination. Induction of K48-polyubiquitination by A20 involves its C-terminal zinc-finger ubiquitin-binding domain, which may promote interaction with E3 ligases, such as Itch and RNF11 that are involved in mediating A20 inhibitory functions. A20 is thought to promote de-ubiquitination of K63-polyubiquitin chains either directly, due to its N-terminal deubiquitinase domain, or by disrupting the interaction between E3 and E2 enzymes that catalyze K63-polyubiquitination. A20 is subject to different mechanisms of regulation, including phosphorylation, proteolytic processing, and association with ubiquitin binding proteins. Here we review the expression and biological activities of A20, as well as the underlying molecular mechanisms.

Tumor suppressor A20 protects against cardiac hypertrophy and fibrosis by blocking transforming growth factor-beta-activated kinase 1-dependent signaling

A20 or tumor necrosis factor-induced protein 3 is a negative regulator of nuclear factor kappaB signaling. A20 has been shown previously to attenuate cardiac hypertrophy in vitro and postmyocardial infarction remodeling in vivo. In the present study, we tested the hypothesis that overexpression of A20 in the murine heart would protect against cardiac hypertrophy in vivo. The effects of constitutive human A20 expression on cardiac hypertrophy were investigated using in vitro and in vivo models. Cardiac hypertrophy was produced by aortic banding in A20 transgenic mice and control animals. The extent of cardiac hypertrophy was quantitated by echocardiography, as well as by pathological and molecular analyses of heart samples. Constitutive overexpression of human A20 in the murine heart attenuated the hypertrophic response and markedly reduced inflammation, apoptosis, and fibrosis. Cardiac function was also preserved in hearts with increased A20 levels in response to hypertrophic stimuli. Western blot experiments further showed A20 expression markedly blocked transforming growth factor-beta-activated kinase 1-dependent c-Jun N-terminal kinase/p38 signaling cascade but with no difference in either extracellular signal-regulated kinase 1/2 or AKT activation in vivo and in vitro. In cultured neonatal rat cardiac myocytes, [3H]proline incorporation and Western blot assays revealed that A20 expression suppressed transforming growth factor-beta-induced collagen synthesis and transforming growth factor-beta-activated kinase 1-dependent Smad 2/3/4 activation. In conclusion, A20 improves cardiac functions and inhibits cardiac hypertrophy, inflammation, apoptosis, and fibrosis by blocking transforming growth factor-beta-activated kinase 1-dependent signaling.

Grape seed proanthocyanidins attenuate vascular smooth muscle cell proliferation via blocking phosphatidylinositol 3-kinase-dependent signaling pathways

The excess generation of reactive oxygen species (ROS) play important role in the development and progression of diabetes and related vascular complications. Therefore, blocking the production of ROS will be able to improve hyperglycemia-induced vascular dysfunction. The objective of this study was to determine whether a novel IH636 grape seed proanthocyanidins (GSPs) could protect against hyperproliferation of cultured rat vascular smooth muscle cells (VSMCs) induced by high glucose (HG) and determine the related molecular mechanisms. Our data demonstrated that GSPs markedly inhibited rat VSMCs proliferation as well as ROS generation and NAPDH oxidase activity induced by HG treatment. Further studies revealed that HG treatment resulted in phosphorylation and membrane translocation of Rac1, p47phox, and p67phox subunits leading to NADPH oxidase activation. GSPs treatment remarkably disrupted the phosphorylation and membrane translocation of Rac1, p47phox, and p67phox subunits. More importantly, our data further revealed that GSPs significantly disrupted HG-induced activation of ERK1/2, JNK1/2, and PI3K/AKT/GSK3beta as well as NF-kappaB signalings, which were dependent on reactive oxygen species (ROS) generation and Rac1 activation. In addition, our results also demonstrated that HG-induced cell proliferation and excess ROS production was dependent on the activation of PI3 kinase subunit p110alpha. Collectively, these results suggest that HG-induced VSMC growth was attenuated by grape seed proanthocyanidin (GSPs) treatment through blocking PI3 kinase-dependent signaling pathway, indicating that GSPs may be useful in retarding intimal hyperplasia and restenosis in diabetic vessels.

A20 inhibits post-angioplasty restenosis by blocking macrophage trafficking and decreasing adventitial neovascularization

OBJECTIVE

Neointimal hyperplasia is an inflammatory and proliferative process that occurs as a result of injury to the vessel wall. We have shown that the homeostatic protein A20 prevents neointimal hyperplasia by affecting endothelial cell (EC) and smooth muscle cell (SMC) responses to injury. In this work, we questioned whether A20 impacts other pathogenic effectors of neointimal hyperplasia including homing of monocyte/macrophages and EC/SMC precursors to the site of vascular injury, vascular endothelial growth factor (VEGF) secretion, and adventitial neovascularization.

METHODS AND RESULTS

Carotid balloon angioplasty was performed on rat recipients of a bone marrow transplant from green fluorescent rats. Adenoviral delivery of A20 prevented neointimal hyperplasia and decreased macrophage infiltration. This was associated with decreased ICAM-1 and MCP-1 expression in vitro. Additionally, A20 reduced neovascularization in the adventitia of balloon injured carotid arteries, which correlated with fewer VEGF positive cells.

CONCLUSIONS

A20 downregulates adhesion markers, chemokine production, and adventitial angiogenesis, all of which are required for macrophage trafficking to sites of vascular injury. This, in turn, diminishes the inflammatory milieu to prevent neointimal hyperplasia.

A differential role for endocytosis in receptor-mediated activation of Nox1

Internalization of activated receptors to a compartment enriched with NAPDH oxidase and associated signaling molecules is expected to facilitate regulation of redox-mediated signal transduction. The aim of this study was to test the hypothesis that endocytosis is necessary for generation of reactive oxygen species (ROS) by Nox1 and for redox-dependent signaling in smooth muscle cells (SMCs). Within minutes of treatment with tumor necrosis factor (TNF)-alpha or thrombin, SMCs increased cellular levels of ROS that was inhibited by shRNA to Nox1. Treatment of SMC with TNF-alpha induced a dynamin-dependent endosomal generation of ROS, whereas thrombin-mediated ROS production did not occur within endosomes and was not prevented by dominant-negative dynamin (dn-dynamin), but instead required transactivation of the epidermal growth factor receptor (EGFR). Activation of the phosphatidylinositol 3-kinase (PI3K)-Akt-activating transcription factor-1 (ATF-1) pathway by TNF-alpha and thrombin were both Nox1- and dynamin-dependent. In conclusion, we show that formation of specific ligand-receptor complexes results in spatially distinct mechanisms of Nox1 activation and generation of ROS. These findings provide novel insights into the role of compartmentalization for integrating redox-dependent cell signaling.

CB2 cannabinoid receptor agonists attenuate TNF-alpha-induced human vascular smooth muscle cell proliferation and migration

BACKGROUND AND PURPOSE

Vascular smooth muscle proliferation and migration triggered by inflammatory stimuli are involved in the development and progression of atherosclerosis and restenosis. Cannabinoids may modulate cell proliferation in various cell types through cannabinoid 2 (CB2) receptors. Here, we investigated the effects of CB2 receptor agonists on TNF-alpha-induced proliferation, migration and signal transduction in human coronary artery smooth muscle cells (HCASMCs).

EXPERIMENTAL APPROACH

HCASMCs were stimulated with TNF-alpha. Smooth muscle proliferation was determined by the extent of BrdU incorporation and the migration was assayed by modified Boyden chamber. CB2 and/or CB1 receptor expressions were determined by immunofluorescence staining, western blotting, RT-PCR, real-time PCR and flow cytometry.

KEY RESULTS

Low levels of CB2 and CB1 receptors were detectable in HCASMCs compared to the high levels of CB2 receptors expressed in THP-1 monocytes. TNF-alpha triggered up to approximately 80% increase (depending on the method used) in CB2 receptor mRNA and/or protein expression in HCASMCs, and induced Ras, p38 MAPK, ERK 1/2, SAPK/JNK and Akt activation, while increasing proliferation and migration. The CB2 agonists, JWH-133 and HU-308, dose-dependently attenuated these effects of TNF-alpha.

CONCLUSIONS AND IMPLICATIONS

Since the above-mentioned TNF-alpha-induced phenotypic changes are critical in the initiation and progression of atherosclerosis and restenosis, our findings suggest that CB2 agonists may offer a novel approach in the treatment of these pathologies by decreasing vascular smooth muscle proliferation and migration.