HMGB1 mediates hyperglycaemia-induced cardiomyocyte apoptosis via ERK/Ets-1 signalling pathway.

Apoptosis is a key event involved in diabetic cardiomyopathy. The expression of high mobility group box 1 protein (HMGB1) is up-regulated in diabetic mice. However, the molecular mechanism of high glucose (HG)-induced cardiomyocyte apoptosis remains obscure. We aimed to determine the role of HMGB1 in HG-induced apoptosis of cardiomyocytes. Treating neonatal primary cardiomyocytes with HG increased cell apoptosis, which was accompanied by elevated levels of HMGB1. Inhibition of HMGB1 by short-hairpin RNA significantly decreased HG-induced cell apoptosis by reducing caspase-3 activation and ratio of Bcl2-associated X protein to B-cell lymphoma/leukemia-2 (bax/bcl-2). Furthermore, HG activated E26 transformation-specific sequence-1 (Ets-1), and HMGB1 inhibition attenuated HG-induced activation of Ets-1 via extracellular signal-regulated kinase 1/2 (ERK1/2) signalling. In addition, inhibition of Ets-1 significantly decreased HG-induced cardiomyocyte apoptosis. Similar results were observed in streptozotocin-treated diabetic mice. Inhibition of HMGB1 by short-hairpin RNA markedly decreased myocardial cell apoptosis and activation of ERK and Ets-1 in diabetic mice. In conclusion, inhibition of HMGB1 may protect against hyperglycaemia-induced cardiomyocyte apoptosis by down-regulating ERK-dependent activation of Ets-1.

Arginase I attenuates inflammatory cytokine secretion induced by lipopolysaccharide in vascular smooth muscle cells.

OBJECTIVE: Inflammation plays an important role in atherosclerosis. Arginase I (Arg I) promotes the proliferation of vascular smooth muscle cells; however, the effect of Arg I on inflammation remains unknown. The present study investigated the role of Arg I in inflammation in vitro and in vivo. METHODS AND RESULTS: Quantitative reverse transcription-polymerase chain reaction and Western blot analysis demonstrated that Arg I inhibited tumor necrosis factor-α production induced by lipopolysaccharide in human aortic smooth muscle cells. Inducible nitric oxide synthase substrate competition and nuclear factor-κB activation were main contributors to lipopolysaccharide-mediated inflammatory cytokine generation. However, Arg I could attenuate the function of inducible nitric oxide synthase and inhibit the subsequent nuclear factor-κB activation, leading to inhibition of tumor necrosis factor-α generation. Furthermore, upregulation of Arg I significantly decreased macrophage infiltration and inflammation in atherosclerotic plaque of rabbits, whereas downregulation of Arg I aggravated these adverse effects. CONCLUSIONS: The results indicate the antiinflammatory effects of Arg I and suggest an unexpected beneficial role of Arg I in inflammatory disease.

Inhibition of c-Jun N-terminal kinase attenuates low shear stress-induced atherogenesis in apolipoprotein E-deficient mice.

Atherosclerosis begins as local inflammation of arterial walls at sites of disturbed flow, such as vessel curvatures and bifurcations with low shear stress. c-Jun NH2-terminal kinase (JNK) is a major regulator of flow-dependent gene expression in endothelial cells in atherosclerosis. However, little is known about the in vivo role of JNK in low shear stress in atherosclerosis. We aimed to observe the effect of JNK on low shear stress-induced atherogenesis in apolipoprotein E-deficient (ApoE(-/-)) mice and investigate the potential mechanism in human umbilical vein endothelial cells (HUVECs). We divided 84 male ApoE(-/-) mice into two groups for treatment with normal saline (NS) (n = 42) and JNK inhibitor SP600125 (JNK-I) (n = 42). Perivascular shear stress modifiers were placed around the right carotid arteries, and plaque formation was studied at low shear stress regions. The left carotid arteries without modifiers represented undisturbed shear stress as a control. The NS group showed atherosclerotic lesions in arterial regions with low shear stress, whereas the JNK-I group showed almost no atherosclerotic lesions. Corresponding to the expression of proatherogenic vascular cell adhesion molecule 1 (VCAM-1), phospho-JNK (p-JNK) level was higher in low shear stress regions with NS than with JNK-I inhibitor. In HUVECs under low shear stress, siRNA knockdown and SP600125 inhibition of JNK attenuated nuclear factor (NF)-κB activity and VCAM-1 expression. Furthermore, siRNA knockdown of platelet endothelial cell adhesion molecule 1 (PECAM-1) (CD31) reduced p-JNK and VCAM-1 levels after low shear stress stimulation. JNK may play a critical role in low shear stress-induced atherogenesis by a PECAM-1-dependent mechanosensory pathway and modulating NF-κB activity and VCAM-1 expression.

Role of NonO-histone interaction in TNFalpha-suppressed prolyl-4-hydroxylase alpha1.

Inflammation is a key process in cardiovascular diseases. The extracellular matrix (ECM) of the vasculature is a major target of inflammatory cytokines, and TNFalpha regulates ECM metabolism by affecting collagen production. In this study, we have examined the pathways mediating TNFalpha-induced suppression of prolyl-4 hydroxylase alpha1 (P4Halpha1), the rate-limiting isoform of P4H responsible for procollagen hydroxylation, maturation, and organization. Using human aortic smooth muscle cells, we found that TNFalpha activated the MKK4-JNK1 pathway, which induced histone (H) 4 lysine 12 acetylation within the TNFalpha response element in the P4Halpha1 promoter. The acetylated-H4 then recruited a transcription factor, NonO, which, in turn, recruited HDACs and induced H3 lysine 9 deacetylation, thereby inhibiting transcription of the P4Halpha1 promoter. Furthermore, we found that TNFalpha oxidized DJ-1, which may be essential for the NonO-P4Halpha1 interaction because treatment with gene specific siRNA to knockout DJ-1 eliminated the TNFalpha-induced NonO-P4Halpha1 interaction and its suppression. Our findings may be relevant to aortic aneurysm and dissection and the stability of the fibrous cap of atherosclerotic plaque in which collagen metabolism is important in arterial remodeling. Defining this cytokine-mediated regulatory pathway may provide novel molecular targets for therapeutic intervention in preventing plaque rupture and acute coronary occlusion.

[Two novel mutations of GLA gene in Chinese patients with Fabry disease].

OBJECTIVE: To observe the disease-causing GLA gene mutations in Chinese patients with Fabry disease and the correlation between the genotype and phenotype. METHODS: DNA from 2 Chinese patients with Fabry disease and their relatives were collected. The seven exons and nonjunctional regions of GLA gene were amplified with polymerase chain reaction and the products were sequenced. The correlation between the genotype and phenotype was analyzed. RESULTS: Two mutations, G1168A and G1170A, located in 5' untranslated regions (5'UTR) were identified in the two probands and the two mutations were absent in normal controls. Three patients with the same genotype were found in the pedigree with G1168A mutation and there was no gene mutation carrier in the pedigree with G1170A mutation. Symptoms of the disease are less in female patients than that in male patients. CONCLUSION: GLA gene mutation in 5'UTR may also be involved in the disease process of patients with Fabry disease and the phenotype is partly affected by gender.

Serum amyloid A stimulates vascular endothelial growth factor receptor 2 expression and angiogenesis.

Serum amyloid A (SAA), a major acute-phase reactant, modulates angiogenesis in many diseases. Vascular endothelial growth factor receptor 2 (VEGFR2) is the primary angiogenic receptor for vascular endothelial growth factor (VEGF), but the possibility of an interaction between SAA and VEGFR2 has not yet been resolved. Here, we investigated if SAA stimulates the expression of VEGFR2 and promotes angiogenesis in vitro. Human umbilical vein endothelial cells (HUVECs) were stimulated with recombinant SAA (rSAA), and the messenger RNA (mRNA) and protein expression of VEGFR2 was detected by Western blot analysis and quantitative real-time PCR. Formyl peptide receptor-like 1 (FPRL1) agonist (WKYMVm) and antagonist (WRW(4)) and inhibitors of mitogen-activated protein kinases (MAPKs) were used to investigate the mechanism of regulation of VEGFR2.We show that SAA induces VEGFR2 expression in a time- and dose-dependent manner in HUVECs. In addition, SAA promotes tube formation in HUVECs. The effect of SAA on tube formation was shown to be the result of an increase in VEGFR2 expression, which was blocked by the multi-angiokinase receptor inhibitor BIBF1120. These activities of SAA appear to be mediated by FPRL1/MAPK signaling pathways, as they were mimicked by WKYMVm and abrogated by WRW(4) and inhibitors of MAPKs. These observations indicate that SAA induces VEGFR2 expression and promotes tube formation in HUVECs via the FPRL1/MAPK signaling pathway, thus providing a potential target for the control of angiogenesis.

[A novel missense mutation, K124N, in the troponin T gene of Chinese populations with hypertrophic cardiomyopathy].

OBJECTIVE: To study the cardiac troponin T (TNNT2) gene mutation in Chinese patients with hypertrophic cardiomyopathy (HCM) and to analyze the correlation between the genotype and phenotype. METHODS: Specimens of peripheral blood were collected from 71 unrelated Chinese probands with HCM, aged 40 +/- 18. The genome DNA was extracted. Single-strand conformation polymorphism gel analysis of the polymerase chain reaction-amplified products was conducted to search for mutations in the exons 8, 9, 10, 11, and 16 of the TNNT2 gene. Relevant clinical data were collected. One hundred normal persons, aged 44 +/- 14, were used as controls. RESULTS: A missense mutation, K124N, in the exon 9 of the TNNT2 gene was identified in a 41-year-old female patient with HCM and failed to be detected in the 100 normal controls, which suggested the disease-causing mutation. The patient began to have the symptoms of chest distress and palpitation since the age of 38, presented moderate hypertrophy of the intraventricular septum, and did not have a family history of sudden cardiac death. CONCLUSION: A novel missense mutation of troponin T gene has been identified. Mutation in tail part of cardiac troponin T, essential for it's binding function, causes the disease of HCM. Correlative analysis confirms the genetic heterogeneity of the disease.

Inhibition of high-mobility group box 1 improves myocardial fibrosis and dysfunction in diabetic cardiomyopathy.

BACKGROUND: High-mobility group box 1 (HMGB1) is an important mediator of the inflammatory response. Its expression is increased in diabetic cardiomyopathy (DCM), but its role is unclear. We investigated the potential role and mechanism of HMGB1 in diabetes-induced myocardial fibrosis and dysfunction in mice. METHODS: In vivo, type 1 diabetes was induced by streptozotocin (STZ) in mice. HMGB1 expression was knocked down by lentivirus-mediated short-hairpin RNA (shRNA). Cardiac function was assessed by echocardiography. Total collagen deposition was assessed by Masson's trichrome and Picrosirius red staining. HMGB1, collagen I and III, and transforming growth factor ß1 (TGF-ß1) expression was quantified by immunostaining and western bolt analysis. In vitro, isolated neonatal cardiac fibroblasts were treated with high glucose (HG) or recombinant HMGB1 (rHMGB1). Pharmacologic (neutralizing anti-HMGB1 antibody) or genetic (shRNA-HMGB1) inhibition of HMGB1 was used to investigate the role of HMGB1 in HG-induced functional changes of cardiac fibroblasts. RESULTS: In vivo, HMGB1 was diffusely expressed in the myocardium of diabetic mice. HMGB1 silencing ameliorated left ventricular dysfunction and remodeling and decreased collagen deposition in diabetic mice. In vitro, HG induced HMGB1 translocation and secretion in both viable cardiomyocytes and fibroblasts. Administration of rHMGB1 dose-dependently increased the expression of collagens I and III and TGF-ß1 in cardiac fibroblasts. HMGB1 inhibition reduced HG-induced collagen production, matrix metalloproteinase (MMP) activities, proliferation, and activated mitogen-activated protein kinase signaling in cardiac fibroblasts. CONCLUSIONS: HMGB1 inhibition could alleviate cardiac fibrosis and remodeling in diabetic cardiomyopathy. Inhibition of HMGB1 might have therapeutic potential in the treatment of the disease.

Serum amyloid A stimulates lipoprotein-associated phospholipase A2 expression in vitro and in vivo.

OBJECTIVES: Although lipoprotein-associated phospholipase A2 (Lp-PLA2) has been regarded as a biomarker and a causative agent for acute coronary events recently, the mechanism of the regulation of Lp-PLA2 has not been fully elucidated yet. This study was aimed to investigate the influence of serum amyloid A (SAA) on the expression of Lp-PLA2 in THP-1 cells and ApoE-deficient (ApoE(-/-)) mice. METHODS: THP-1 cells were stimulated by SAA and the mRNA and protein expression of Lp-PLA2 was detected. ApoE(-/-) mice were intravenously injected with murine SAA1 lentivirus. Formyl peptide receptor like-1 (FPRL1) agonist (WKYMVm) and inhibitor (WRW(4)), mitogen-activated protein kinases (MAPKs) inhibitors, and peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist and inhibitor were used to investigate the mechanism of regulation of Lp-PLA2. RESULTS: Recombinant SAA up-regulated Lp-PLA2 expression in a dose and time-dependent manner in THP-1 cells. Immunohistochemical analysis of aortic root of ApoE(-/-) mice also demonstrated that the expression of Lp-PLA2 was up-regulated significantly with SAA treatment. WRW(4) decreased SAA-induced Lp-PLA2 production; while WKYMVm could induce Lp-PLA2 expression. ERK1/2, JNK1/2, and p38 inhibition reduced SAA-induced Lp-PLA2 production. Furthermore, the results suggested the activation of PPAR-γ played a crucial role in this process. CONCLUSION: These results demonstrate that SAA up-regulates Lp-PLA2 production significantly via a FPRL1/MAPKs./PPAR-γ signaling pathway.