Mengxiong Tang

The involvement of transforming growth factor-β1 secretion in Urotensin II-induced collagen synthesis in neonatal cardiac fibroblasts

As the most potent vasoconstrictor in mammals, urotensin II (U II) has recently been demonstrated to play an important role in adverse cardiac remodeling and fibrosis. However, the mechanisms of U II-induced myocardial fibrosis remain to be clarified. We postulated that U II alters transforming growth factor-beta1 (TGF-beta1) expression, and thereby modulates cardiac fibroblast collagen metabolism. Experiments were conducted using cardiac fibroblast from neonatal Wistar rats to determine the expression of TGF-beta1, and the role of U II receptor UT in this process. The functional role of TGF-beta1 and UT in modulating U II effects on type I, III collagen mRNA expression and 3H-proline incorporation was also analyzed. TGF-beta1 gene and protein expression were consistently identified in quiescent cardiac fibroblasts. U II increased the expression of TGF-beta1 mRNA and protein in a time-dependent manner. This effect was UT mediated, because UT antagonist urantide abolished U II-induced TGF-beta1 expression. U II-induced increase in type I, III collagen mRNA expression and 3H-proline incorporation were both inhibited by a specific TGF-beta1 neutralizing antibody and UT receptor antagonist urantide. Hence, our results indicate that TGF-beta1 is upregulated in cardiac fibroblasts by U II via UT and modulates profibrotic effects of U II. These findings provide novel insights into U II-induced cardiac remodeling.

Prostaglandin F2α facilitates collagen synthesis in cardiac fibroblasts via an F-prostanoid receptor/protein kinase C/Rho kinase pathway independent of transforming growth factor β1

Accumulation of collagen I and III in the myocardium is a prominent feature of interstitial fibrosis. Prostaglandin F(2α) (PGF(2α)) facilitates fibrosis by increasing collagen synthesis. However, the underlying mechanisms mediating the effect of PGF(2α) on collagen expression in cardiac fibroblasts are not yet fully elucidated. We measured the mRNA and protein levels of collagen I and III by quantitative real-time PCR and ELISA, respectively. Activation of signaling pathways was determined by western blot analysis. In primary rat cardiac fibroblasts, treatment with PGF(2α) stimulated both the mRNA and protein levels of collagen I and III, and pretreatment with the F-prostanoid (FP) receptor antagonist AL-8810, protein kinase C inhibitor LY-333531, and Rho kinase inhibitor Y-27632 significantly inhibited PGF(2α)-induced collagen I and III expression. FP receptor, protein kinase C, and Rho kinase were activated with PGF(2α) treatment. PGF(2α) may be an important regulator in the synthesis of collagen I and III via an FP receptor/protein kinase C/Rho kinase cascade in cardiac fibroblasts, which might be a new therapeutic target for myocardial fibrosis.

Elevated expression of urotensin II and its receptor in diabetic cardiomyopathy.

OBJECTIVE Urotensin II (UII) is a somatostatin-like peptide recently identified to have several cardiovascular effects, including potent vasoactive, cardiac inotropic and chronotropic properties. Our aim was to determine the degree of expression of UII and UII receptor (UT) in the myocardium of rats with streptozotocin (STZ)-induced diabetes. METHODS Real-time polymerase chain reaction, Western blot, and immunohistochemistry were used to determine the degree of expression and location of UII and UT in the myocardium of STZ-induced diabetic rats. RESULTS UII and UT expression were significantly enhanced in the myocardium of rats with diabetes compared with healthy controls on both messenger RNA and protein levels. Both UII and UT protein expression were mainly concentrated in the cardiomyocytes, endothelial cells, cardiac fibroblasts, and smooth muscle cells of diabetic cardiomyopathy (DCM). CONCLUSIONS Our results suggest a possible role for the UII/UT system in the pathophysiology of DCM.

Increased serum levels of microvesicles in nonvalvular atrial fibrillation determinated by ELISA using a specific monoclonal antibody AD-1

BACKGROUND Microvesicles are involved in different pathological processes such as inflammation, coagulation and tumor progression. We intended to establish an immunoaffinity capture method for detecting microvesicles and bioactive effectors carried on them using a specific homemade monoclonal antibody AD-1. By this method we investigated the association of inflammation with platelet activation in patients with nonvalvular atrial fibrillation (NVAF). METHODS A case-control study of 90 Chinese subjects selected in 3 groups: control, paroxysmal AF, and persistent AF. After capturing the microvesicles of serum using a specific monoclonal antibody AD-1, the amounts of LAP, IL-1β and P-selectin loaded on these microvesicles were quantified by either enzyme activity assay (LAP) or ELISA respectively. RESULTS Compared with normal controls, the patients with persistent AF showed significantly increased serum levels of microvesicles (P<0.001), microvesicle-bound IL-1 β (P=0.019) and microvesicle-bound P-selectin (P=0.001). The latter two were significantly correlated with each other (r(2)=0.371, r=0.616, P<0.001). The microvesicle-bound IL-1β (β=0.570, P<0.001) and body weight (β=0.427, P=0.002) were as independent predictors of platelet activation. CONCLUSIONS The method was easy and reproducible. Inflammation may be involved in the activation of platelets in NVAF.

Apolipoprotein E-knockout mice show increased titers of serum anti-nuclear and anti-dsDNA antibodies.

Apolipoprotein E-knockout (ApoE(-/-)) mice, atherosclerosis-prone mice, show an autoimmune response, but the pathogenesis is not fully understood. We investigated the pathogenesis in female and male ApoE(-/-) mice. The spleens of all ApoE(-/-) and C57BL/6 (B6) mice were weighed. The serum IgG level and titers of anti-nuclear antibody (ANA) and anti-double-stranded DNA (anti-dsDNA) antibody were assayed by ELISA. Apoptosis of spleen tissue was evaluated by TUNEL. TLR4 level in spleen tissue was tested by immunohistochemistry and Western blot analysis. Levels of MyD88, p38, phosphorylated p38 (pp38), interferon regulatory factor 3 (IRF3) and Bcl-2-associated X protein (Bax) in spleen tissue were detected by Western blot analysis. We also survey the changes of serum autoantibodies, spleen weight, splenocyte apoptosis and the expressions of TLR4, MyD88, pp38, IRF3 and Bax in spleen tissue in male ApoE(-/-) mice after 4weeks of lipopolysaccharide (LPS), Toll-like receptor 4 ligand, administration. ApoE(-/-) mice showed splenomegaly and significantly increased serum level of IgG and titers of ANA and anti-dsDNA antibody as compared with B6 mice. Splenocyte apoptosis and the expression of TLR4, MyD88, pp38, IRF3 and Bax in spleen tissue were significantly lower in ApoE(-/-) than B6 mice. The expression of TLR4, MyD88, IRF3, pp38, and Bax differed by sex in ApoE(-/-) spleen tissue. The down-regulation of TLR4 signal molecules induced by LPS led to decreased expression of Bax and increased serum titers of ANA and anti-dsDNA antibody. Therefore, the TLR4 signal pathway may participate in maintaining the balance of splenocyte apoptosis and autoantibody production in ApoE(-/-) mice.

Apolipoprotein E-knockout mice on high-fat diet show autoimmune injury on kidney and aorta

BACKGROUND Apolipoprotein E-knockout (ApoE(-/-)) mice is a classic model of atherosclerosis. We have found that ApoE(-/-) mice showed splenomegaly, higher titers of serum anti-nuclear antibody (ANA) and anti-dsDNA antibody compared with C57B6/L (B6) mice. However, whether ApoE(-/-) mice show autoimmune injury remains unclear. METHODS AND RESULTS Six females and six males in each group, ApoE(-/)(-), Fas(-/-) and B6 mice, were used in this study. The titers of serum ANA, anti-dsDNA antibody and creatinine and urine protein were measured by ELISA after 4 months of high-fat diet. The spleen weight and the glomerular area were determined. The expressions of IgG, C3 and macrophage in kidney and atherosclerotic plaque were detected by immunostaining followed by morphometric analysis. Similar to the characteristics of Fas(-/-) mice, a model of systemic lupus erythematosus (SLE), ApoE(-/-) mice, especially female, displayed significant increases of spleen weight and glomerular area when compared to B6 mice. Also, elevated titers of serum ANA, anti-dsDNA antibody and creatinine and urine protein. Moreover, the expressions of IgG, C3 and macrophage in glomeruli and aortic plaques were found in ApoE(-/-) mice. In addition, the IgG and C3 expressions in glomeruli and plaques significantly increased (or a trend of increase) in female ApoE(-/-) mice compared with males. CONCLUSIONS Apolipoprotein E-knockout mice on high-fat diet show autoimmune injury on kidney and aorta.

An integrative view on the carotid artery alterations in metabolic syndrome

Eur J Clin Invest 2012; 42 (5): 496–502

Association of the six transmembrane protein of prostate 2 gene polymorphisms with metabolic syndrome in Han Chinese population

AIM The six-transmembrane protein of prostate 2 (STAMP2) has been demonstrated to play a potential role in the pathogenesis of metabolic syndrome (MetS). The present study was designed to investigate the association of STAMP2 gene polymorphisms with MetS in Han Chinese population. METHODS A case-control study enrolled 350 Han Chinese subjects in two groups: 182 MetS patients and 168 control subjects. The clinical and biochemical characteristics were determined. Three single nucleotide polymorphisms (SNPs), rs1981529, rs12386756 and rs10263111 in STAMP2 gene were genotyped. The association of STAMP2 gene polymorphisms with MetS was analyzed. RESULTS SNPs rs1981529 and rs10263111 were found to be significantly associated with MetS phenotype in male population (P=0.014 and 0.025). Moreover, SNP rs1981529 was found to be associated with high density lipoprotein-cholesterol in male cases and with body mass index in female cases (P=0.014 and 0.049). SNP rs10263111 was found to be associated with both waist circumference and diastolic blood pressure in total cases (P=0.044 and 0.033). Haplotype analysis yielded significant association of STAMP2 gene with MetS in total (global P=0.0109) and male population (global P=0.0004). CONCLUSION Our findings revealed that STAMP2 gene polymorphisms are likely to significantly contribute to the risk of MetS in male Han Chinese population.

Transmural Peak Systolic Strain and Strain Rate Predict Transmural Myocardial Blood Flow in a Pig Myocardial Infarction Model

Objective: To test the hypothesis that the transmural variation of the longitudinal myocardial peak systolic strain (Sp) and strain rate (SRp) can predict the transmural distribution of myocardial blood flow (MBF) in a pig model of acute myocardial infarction. Methods: The longitudinal Sp and SRp were measured by echocardiography in both subendocardium (Sp-endo, SRp-endo) and subepicardium (Sp-epi, SRp-epi) in the normal, ischemic and infarct segments, respectively. The MBF in corresponding sites was measured by colored microspheres technique. The subendocardial to subepicardial ratio of Sp (Sp-EER), SRp (SRp-EER) and MBF (MBF-EER) were calculated. Results: In the normal segments, Sp-endo and SRp-endo were significantly higher than Sp-epi and SRp-ep, respectively. In the ischemic segments, Sp-endo and SRp-endo decreased to a greater extent than Sp-epi and SRp-epi, respectively. In the infarct segments, Sp-endo, SRp-endo Sp-epi and SRp-epi were all remarkably reduced. High correlations were found between Sp and SRp measurements and MBF in both subendocardium and subepicardium (r = –0.75 to –0.84, p < 0.001). Conclusion: Strain and strain rate imaging provides a reliable approach to the noninvasive estimation of the transmural blood distribution across the normal, ischemic and infarct segments.