Tribbles homolog 3 is induced by high glucose and associated with apoptosis in human endothelial cells.

Tribbles homolog 3 (TRIB3) is an intracellular kinase-like molecule that modifies cellular survival and metabolism. The present study aimed to investigate the function of TRIB3 regulation in the process of high glucose-induced apoptosis in endothelial cells, with the aim of identifying a novel intervention target for the prevention and treatment of diabetes mellitus. Human umbilical vein endothelial cells (HUVECs) grown in medium with various concentrations of glucose (5.5, 10, 20, 30 and 40 mmol/l) were assessed for mRNA expression of TRIB1, TRIB2 and TRIB3 using reverse transcription quantitative polymerase chain reaction. In addition, protein expression of TRIB3 was examined using western blot analysis. Immunofluorescence staining was performed in order to determine the distribution and localization of TRIB3 in HUVECs. Furthermore, cells grown in normal (5.5 mmol/l) or high glucose (HG; 30 mmol/l) medium were subjected to TRIB3 inhibition through small interfering (si)RNA knockdown. These cells were then examined in order to determine whether TRIB3 upregulation was associated with endothelial cell apoptosis. HUVECs treated with 30 and 40 mmol/l glucose for 48 h and 72 h showed significantly lower survival rates compared with those treated with normal glucose levels. In addition, slight but not significant increases in TRIB1 and TRIB2 mRNA expression were observed in HUVECs incubated with various concentrations of glucose for different durations. By contrast, TRIB3 mRNA expression was increased 7.2-fold following incubation with HG. Western blot analysis revealed a 5.44-fold increase in TRIB3 protein levels in cells grown in HG medium for 24 h compared with those grown in normal medium. Immunostaining assays revealed a markedly higher and well-defined nucleolar fluorescence intensity for TRIB3 expression at 24 h in HG medium compared with that of the control group. Furthermore, the apoptotic rate of HG-treated TRIB3 siRNA-transfected HUVECs was significantly increased compared with that of those transfected with control siRNA In conclusion, the results of the present study suggested that TRIB3 was associated with high glucose-induced HUVECs apoptosis, which was attenuated following transfection with TRIB3 siRNA.

Expression of STAMP2 in monocytes associates with cardiovascular alterations.

BACKGROUND: Metabolic and inflammatory pathways crosstalk at many levels. In this study, we aimed to investigate the expression of six-transmembrane protein of prostate 2 (STAMP2) in macrophages and tried to search for the association between the decreased STAMP2 expression, if any, and carotid atherosclerosis as well as cardiac adaptations. MATERIALS AND METHODS: A total of 97 unrelated Chinese subjects were recruited including 48 subjects with metabolic syndrome (MetS) and 49 controls. Clinical and biochemical characteristics were collected from subjects, with quantification of STAMP2 in monocyte/macrophages. All subjects underwent ultrasonography. RESULTS: STAMP2 expression in macrophages was significantly decreased in MetS as compared with the control group (10.25 +/- 9.20 vs. 15.20 +/- 9.18, P = 0.009), especially in women patients. Partial correlation analysis showed that STAMP2 expression in macrophages correlated with BMI (r = -0.375, P = 0.045), age (r = 0.414, P = 0.026) and HDL (r = 0.377, P = 0.044) after controlling for systolic blood pressure (SBP). Furthermore, STAMP2 expression was correlated with PI (r = -0.454, P = 0.013), LVEF (r = -0.503, P = 0.005), LA-ESR (r = -0.424, P = 0.022), LA-S (r = 0.469, P = 0.010) and mitral E/A ratio (r = 0.492, P = 0.005) after controlling for SBP. Still, in multivariable analysis, STAMP2 expression was independently associated with IMT(mean), PI and mitral E/A ratio. CONCLUSIONS: In MetS patients, especially women patients, STAMP2 expression was down-regulated in peripheral blood mononuclear cell, which was correlated with carotid atherosclerosis and cardiac adaptation.

Tribble 3, a novel oxidized low-density lipoprotein-inducible gene, is induced via the activating transcription factor 4-C/EBP homologous protein pathway.

1. C/EBP homologueueueous protein (CHOP), an endoplasmic reticulum (ER) stress-inducible protein, has a critical role in regulation of the cell cycle and apoptosis by forming heterodimers with other C/EBP proteins. However, how CHOP function is regulated remains to be determined. The human homologue of Drosophila tribbles (TRIB3) is associated with CHOP and is upregulated by oxidized low-density lipoprotein (ox-LDL). The aim of the present study was to investigate the role of CHOP in ox-LDL-induced TRIB3 expression in macrophages. 2. Human monocyte-derived macrophages were treated with various concentrations of ox-LDL (0, 2.5, 5, 10, 25 and 50 microg/mL) or 2 microg/mL tunicamycin for 0, 4, 8, 16, 24 and 48 h or were transfected with CHOP or TRIB3 expression plasmid and TRIB3 targeting short interference RNA (siRNA). The expression of CHOP and activating transcription factor 4 (ATF4) mRNA in treated cells was detected by quantitative real-time polymerase chain reaction (PCR). 3. The expression of CHOP and ATF4 mRNA increased with increasing concentrations of ox-LDL and duration of time. The ox-LDL-induced expression of TRIB3 mRNA was upregulated later than the expression of CHOP and ATF4 mRNA. Overexpression of CHOP increased the mRNA expression of TRIB3, which was further increased in CHOP-overexpressing macrophages treated with ox-LDL. Overexpression of TRIB3 suppressed the expression of CHOP, whereas TRIB3 silencing increased CHOP expression following ox-LDL stimulation by a negative feedback mechanism. 4. In conclusion, the expression of ATF4 and CHOP is upregulated by ox-LDL in a dose- and time-dependent manner in naturally differentiated human macrophages. Oxidized LDL induces TRIB3 expression via an ATF4/CHOP-dependent ER stress pathway.