Hongjing Guan

Tumor necrosis factor receptor-associated factor 5 is an essential mediator of ischemic brain infarction.

Tumor necrosis factor receptor‐associated factor 5 (TRAF5) is an adaptor protein of the tumor necrosis factor (TNF) receptor superfamily and the interleukin‐1 receptor/Toll‐like receptor superfamily and plays important roles in regulating multiple signaling pathways. This study was conducted to investigate the role of TRAF5 in the context of brain ischemia/reperfusion (I/R) injury. Transient occlusion of the middle cerebral artery was performed on TRAF5 knockout mice (KO), neuron‐specific TRAF5 transgene (TG), and the appropriate controls. Compared with the WT mice, the TRAF5 KO mice showed lower infarct volumes and better outcomes in the neurological tests. A low neuronal apoptosis level, an attenuated blood‐brain barrier (BBB) disruption and an inhibited inflammatory response were exhibited in TRAF5 KO mice. TRAF5 TG mice exhibited an opposite phenotype. Moreover, the Akt/FoxO1 signaling pathway was enhanced in the ischemic brains of the TRAF5 KO mice. These results provide the first demonstration that TRAF5 is a critical mediator of I/R injury in an experimental stroke model. The Akt /FoxO1 signaling pathway probably plays an important role in the biological function of TRAF5 in this model.

Mindin regulates vascular smooth muscle cell phenotype and prevents neointima formation.

Mindin/spondin 2, an extracellular matrix (ECM) component that belongs to the thrombospondin type 1 (TSR) class of molecules, plays prominent roles in the regulation of inflammatory responses, angiogenesis and metabolic disorders. Our most recent studies indicated that mindin is largely involved in the initiation and development of cardiac and cerebrovascular diseases [Zhu et al. (2014) J. Hepatol. 60, 1046-1054; Bian et al. (2012) J. Mol. Med. 90, 895-910; Wang et al. (2013) Exp. Neurol. 247, 506-516; Yan et al. (2011) Cardiovasc. Res. 92, 85-94]. However, the regulatory functions of mindin in neointima formation remain unclear. In the present study, mindin expression was significantly down-regulated in platelet-derived growth factor-BB (PDGF-BB)-stimulated vascular smooth muscle cells (VSMCs) and wire injury-stimulated vascular tissue. Using a gain-of-function approach, overexpression of mindin in VSMCs exhibited strong anti-proliferative and anti-migratory effects on VSMCs, whereas significant suppression of intimal hyperplasia was observed in transgenic (TG) mice expressing mindin specifically in smooth muscle cells (SMCs). These mice exhibited blunted VSMC proliferation, migration and phenotypic switching. Conversely, deletion of mindin dramatically exacerbated neointima formation in a wire-injury mouse model, which was further confirmed in a balloon injury-induced vascular lesion model using a novel mindin-KO (knockout) rat strain. From a mechanistic standpoint, the AKT (Protein Kinase B)-GSK3β (glycogen synthase kinase 3β)/mTOR (mammalian target of rapamycin)-FOXO3A (forkhead box O)-FOXO1 signalling axis is responsible for the regulation of mindin during intimal thickening. Interestingly, an AKT inhibitor largely reversed mindin-KO-induced aggravated hyperplasia, suggesting that mindin-mediated neointima formation is AKT-dependent. Taken together, our findings demonstrate that mindin protects against vascular hyperplasia by suppression of abnormal VSMC proliferation, migration and phenotypic switching in an AKT-dependent manner. Up-regulation of mindin might represent an effective therapy for vascular-remodelling-related diseases.

Gastrodin inhibits cell proliferation in vascular smooth muscle cells and attenuates neointima formation in vivo.

Vascular smooth muscle cell (VSMC) proliferation plays a critical role in the development of vascular diseases. In the present study, we tested the efficacy and the mechanisms of action of gastrodin, a bioactive component of the Chinese herb Gastrodia elata Bl, in relation to platelet-derived growth factor-BB (PDGF-BB)-dependent cell proliferation and neointima formation after acute vascular injury. Cell experiments were performed with VSMCs isolated from rat aortas. WST and BrdU incorporation assays were used to evaluate VSMC proliferation. Eight-week-old C57BL/6 mice were used for the animal experiments. Gastrodin (150 mg/kg/day) was administered in the animal chow for 14 days, and the mice were subjected to wire injury of the left carotid artery. Our data demonstrated that gastrodin attenuated the VSMC proliferation induced by PDGF-BB, as assessed by WST assay and BrdU incorporation. Gastrodin influenced the S-phase entry of VSMCs and stabilised p27Kip1 expression. In addition, pre-incubation with sinomenine prior to PDGF-BB stimulation led to increased smooth muscle-specific gene expression, thereby inhibiting VSMC dedifferentiation. Gastrodin treatment also reduced the intimal area and the number of PCNA-positive cells. Furthermore, PDGF-BB-induced phosphorylation of ERK1/2, p38 MAPK, Akt and GSK3β was suppressed by gastrodin. Our results suggest that gastrodin can inhibit VSMC proliferation and attenuate neointimal hyperplasia in response to vascular injury. Furthermore, the ERK1/2, p38 MAPK and Akt/GSK3β signalling pathways were found to be involved in the effects of gastrodin.

Disruption of Tumor Necrosis Factor Receptor Associated Factor 5 Exacerbates Pressure Overload Cardiac Hypertrophy and Fibrosis

The cytoplasmic signaling protein tumor necrosis factor (TNF) receptor‐associated factor 5 (TRAF5), which was identified as a signal transducer for members of the TNF receptor super‐family, has been implicated in several biological functions in T/B lymphocytes and the innate immune response against viral infection. However, the role of TRAF5 in cardiac hypertrophy has not been reported. In the present study, we investigated the effect of TRAF5 on the development of pathological cardiac hypertrophy induced by transthoracic aorta constriction (TAC) and further explored the underlying molecular mechanisms. Cardiac hypertrophy and function were evaluated with echocardiography, hemodynamic measurements, pathological and molecular analyses. For the first time, we found that TRAF5 deficiency substantially aggravated cardiac hypertrophy, cardiac dysfunction and fibrosis in response to pressure overload after 4 weeks of TAC compared to wild‐type (WT) mice. Moreover, the mitogen‐activated protein/extracellular signal‐regulated kinase kinase (MEK)‐extracellular signal‐regulated kinases 1/2 (ERK1/2) signaling pathway was more activated in TRAF5‐deficient mice than WT mice. In conclusion, our results suggest that as an intrinsic cardioprotective factor, TRAF5 plays a crucial role in the development of cardiac hypertrophy through the negative regulation of the MEK‐ERK1/2 pathway. J. Cell. Biochem. 115: 349–358, 2014.

Interferon regulatory factor 3 protects against adverse neo-intima formation

AIMS Vascular smooth muscle cell (VSMC) proliferation is central to the pathophysiology of neo-intima formation. Interferon regulatory factor 3 (IRF3) inhibits the growth of cancer cells and fibroblasts. However, the role of IRF3 in vascular neo-intima formation is unknown. We evaluated the protective role of IRF3 against neo-intima formation in mice and the underlying mechanisms. METHODS AND RESULTS IRF3 expression was down-regulated in VSMCs after carotid wire injury in vivo, and in SMCs after platelet-derived growth factor (PDGF)-BB challenge in vitro. Global knockout of IRF3 (IRF3-KO) led to accelerated neo-intima formation and proliferation of VSMCs, whereas the opposite was seen in SMC-specific IRF3 transgenic mice. Mechanistically, we identified IRF3 as a novel regulator of peroxisome proliferator-activated receptor γ (PPARγ), a negative regulator of SMC proliferation after vascular injury. Binding of IRF3 to the AB domain of PPARγ in the nucleus of SMCs facilitated PPARγ transactivation, resulting in decreased proliferation cell nuclear antigen expression and suppressed proliferation. Overexpression of wild-type, but not truncated, IRF3 with a mutated IRF association domain (IAD) retained the ability to exert anti-proliferative effect. CONCLUSIONS IRF3 inhibits VSMC proliferation and neo-intima formation after vascular injury through PPARγ activation.

Apigenin attenuates neointima formation via suppression of vascular smooth muscle cell phenotypic transformation.

Abnormal proliferation, migration, and phenotypic modulation of vascular smooth muscle cells (VSMCs) are critical factors in neointima formation during restenosis. The purpose of this study is to determine the efficacy and possible cell signaling mechanisms of apigenin in VSMC activation induced by platelet‐derived growth factor (PDGF)‐BB and injury‐induced neointima formation. Our data revealed a dose‐dependent apigenin inhibition of PDGF‐BB‐induced proliferation of VSMCs by arresting cells in G0/G1‐phase of the cell cycle as determined using 5‐bromo‐2′‐deoxyuridine incorporation and flow cytometry. This was associated with the inhibition of cyclin‐dependent kinase (CDK) 4,6 expression and an increase in p27Kip1 levels in PDGF‐stimulated VSMCs. Moreover, apigenin was also found to regulate PDGF‐induced migration and expression of smooth‐muscle‐specific contractile markers. Mechanistically, the PDGF‐BB‐induced phosphorylation of PDGF‐receptor β (PDGF‐Rβ), Akt/glycogen synthase kinase(GSK)3β, extracellular signal‐regulated kinase1/2 (ERK1/2), and signal transducers and activators of transcription 3 (STAT3) is negatively modulated by apigenin. For the in vivo studies using a mouse carotid arterial injury model, the administration of apigenin resulted in a significant inhibition of the neointima/media ratio and proliferating cell nuclear antigen (PCNA)‐positive cells. These results demonstrate that apigenin can suppress PDGF‐induced VSMC activation and neointima hyperplasia after vascular injury; these beneficial effects are probably the result of the blockade of PDGF‐Rβ phosphorylation and its downstream signal transduction, including the Akt/GSK‐3β, ERK1/2, and STAT3 pathways. The results suggest that apigenin may be a potential therapeutic candidate for the prevention of restenosis. J. Cell. Biochem. 113: 1198–1207, 2012.

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 p27Kip1 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.

Vinexin β Ablation Inhibits Atherosclerosis in Apolipoprotein E–Deficient Mice by Inactivating the Akt–Nuclear Factor κB Inflammatory Axis

Background Vinexin β is a novel adaptor protein that regulates cellular adhesion, cytoskeletal reorganization, signal transduction, and transcription; however, the exact role that vinexin β plays in atherosclerosis remains unknown. Methods and Results Immunoblot analysis showed that vinexin β expression is upregulated in the atherosclerotic lesions of both patients with coronary heart disease and hyperlipemic apolipoprotein E–deficient mice and is primarily localized in macrophages indicated by immunofluorescence staining. The high‐fat diet–induced double‐knockout mice exhibited lower aortic plaque burdens than apolipoprotein E−/− littermates and decreased macrophage content. Vinexin β deficiency improved plaque stability by attenuating lipid accumulation and increasing smooth muscle cell content and collagen. Moreover, the bone marrow transplant experiment demonstrated that vinexin β deficiency exerts atheroprotective effects in hematopoietic cells. Consistent with these changes, the mRNA expression of proinflammatory cytokines were downregulated in vinexin β−/− apolipoprotein E−/− mice, whereas the anti‐inflammatory M2 macrophage markers were upregulated. The immunohistochemical staining and in vitro experiments showed that deficiency of vinexin β inhibited the accumulation of monocytes and the migration of macrophages induced by tumor necrosis factor α–stimulated human umbilical vein endothelial cells as well as macrophage proliferation. Finally, the inhibitory effects exerted by vinexin β deficiency on foam cell formation, nuclear factor κB activation, and inflammatory cytokine expression were largely reversed by constitutive Akt activation, whereas the increased expression of the nuclear factor κB subset promoted by adenoviral vinexin β was dramatically suppressed by inhibition of AKT. Conclusions Vinexin β deficiency attenuates atherogenesis primarily by suppressing vascular inflammation and inactivating Akt–nuclear factor κB signaling. Our data suggest that vinexin β could be a therapeutic target for the treatment of atherosclerosis.