Association between GDF15, poverty and mortality in urban middle-aged African American and white adults.

Mortality disparities are influenced by race and poverty. There is limited information about whether poverty influences biologic markers of mortality risk. Emerging data suggests that growth differentiation factor 15 (GDF15) is associated with mortality; however, the interplay between GDF15, sociodemographic factors and mortality is not known. We sought to evaluate the interactions between GDF15 and sex, race and poverty status on mortality. Serum GDF15 was measured in 1036 African American and white middle-aged men and women above and below 125% of the Federal poverty status from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study. Multivariable adjusted Cox regression models were used to assess the association between log-transformed GDF15 (logGDF15) and 12-year mortality outcomes (all-cause, cardiovascular- and cancer-specific outcomes) and interactions with sex, race and poverty status. Likelihood ratio tests were used to assess significance of the interaction terms. Median GDF15 was 655.2 pg/mL (IQR = 575.1). During 12.2 years of follow-up, 331 died of which 94 cardiovascular- and 87 were cancer-specific deaths. One unit of increase in logGDF15 was associated with a hazard ratio for all-cause mortality, cardiovascular- and cancer-specific mortality of 2.26 (95% confidence interval [CI], 1.94-2.64), 2.74 (95%CI, 2.06-3.63) and 1.41 (95%CI, 1.00-2.00), respectively. There was an interaction between logGDF15 and poverty status on all-cause mortality (p<0.05). The GDF15×poverty status interaction term improved model calibration for all-cause mortality. Our study provides the first evidence that the effect of elevated GDF15 on all-cause mortality is modified by poverty status.

CRP Stimulates GDF15 Expression in Endothelial Cells through p53.

Growth differentiation factor 15 (GDF15) is a multifunctional, secreted protein that is a direct target gene of p53. GDF15 is a prospective biomarker of cardiovascular disease (CVD). C-reactive protein (CRP), like GDF15, is implicated in inflammation and an independent biomarker of CVD. However, the molecular interactions between GDF15 and CRP remain unexplored. In women, we found a significant relationship between hsCRP and GDF15 serum and mRNA levels. In vitro treatment of cultured human aortic endothelial cells (HAECs) with purified CRP or transfection of a CRP plasmid into HAECs induced GDF15 expression. Dual-luciferase reporter assays confirmed that CRP significantly increased the levels of GDF15 promoter luciferase activity, indicating that CRP induces GDF15 transcription. Chromatin immunoprecipitation (ChIP) assays confirmed that p53 was recruited to both p53 binding sites 1 and 2 in the GDF15 promoter in response to CRP. We have uncovered a linkage between CRP and GDF15, a new clue that could be important in the pathogenesis of endothelial inflammation.

Racial differences in microRNA and gene expression in hypertensive women.

Systemic arterial hypertension is an important cause of cardiovascular disease morbidity and mortality. African Americans are disproportionately affected by hypertension, in fact the incidence, prevalence, and severity of hypertension is highest among African American (AA) women. Previous data suggests that differential gene expression influences individual susceptibility to selected diseases and we hypothesized that this phenomena may affect health disparities in hypertension. Transcriptional profiling of peripheral blood mononuclear cells from AA or white, normotensive or hypertensive females identified thousands of mRNAs differentially-expressed by race and/or hypertension. Predominant gene expression differences were observed in AA hypertensive females compared to AA normotensives or white hypertensives. Since microRNAs play important roles in regulating gene expression, we profiled global microRNA expression and observed differentially-expressed microRNAs by race and/or hypertension. We identified novel mRNA-microRNA pairs potentially involved in hypertension-related pathways and differently-expressed, including MCL1/miR-20a-5p, APOL3/miR-4763-5p, PLD1/miR-4717-3p, and PLD1/miR-4709-3p. We validated gene expression levels via RT-qPCR and microRNA target validation was performed in primary endothelial cells. Altogether, we identified significant gene expression differences between AA and white female hypertensives and pinpointed novel mRNA-microRNA pairs differentially-expressed by hypertension and race. These differences may contribute to the known disparities in hypertension and may be potential targets for intervention.

Posttranscriptional Regulation of the Inflammatory Marker C-Reactive Protein by the RNA-Binding Protein HuR and MicroRNA 637.

C-reactive protein (CRP), an acute-phase plasma protein, is a major component of inflammatory reactions functioning as a mediator of innate immunity. It has been widely used as a validated clinical biomarker of the inflammatory state in trauma, infection, and age-associated chronic diseases, including cancer and cardiovascular disease (CVD). Despite this, the molecular mechanisms that regulate CRP expression are not well understood. Given that the CRP 3' untranslated region (UTR) is long and AU rich, we hypothesized that CRP may be regulated posttranscriptionally by RNA-binding proteins (RBPs) and by microRNAs. Here, we found that the RBP HuR bound directly to the CRP 3' UTR and affected CRP mRNA levels. Through this interaction, HuR selectively increased CRP mRNA stability and promoted CRP translation. Interestingly, treatment with the age-associated inflammatory cytokine interleukin-6 (IL-6) increased binding of HuR to CRP mRNA, and conversely, HuR was required for IL-6-mediated upregulation of CRP expression. In addition, we identified microRNA 637 (miR-637) as a microRNA that potently inhibited CRP expression in competition with HuR. Taken together, we have uncovered an important posttranscriptional mechanism that modulates the expression of the inflammatory marker CRP, which may be utilized in the development of treatments for inflammatory processes that cause CVD and age-related diseases.

N-acetyl cysteine suppresses the foam cell formation that is induced by oxidized low density lipoprotein via regulation of gene expression.

Foam cells derived from macrophages have been implicated as markers of early stage atherosclerosis development. In this study, we found that N-acetyl cysteine (NAC), a well-known inhibitor of reactive oxygen species (ROS), decreased the generation of ROS and suppressed foam cell formation in the presence of oxidized low density lipoprotein through down-regulation of cluster of differentiation 36 expression. We investigated gene expression profiles in order to determine the effects of NAC on foam cell formation using a microarray analysis. The level of apolipoprotein E, which is involved in lipid efflux, was increased and the levels of the antioxidant genes glutathione peroxidase 1 and 3 were also increased. The expression levels of the oxidative stress response and the DNA repair genes were decreased. These results were confirmed using quantitative real-time PCR. Our results indicate that oxidative stress plays an important role in foam cell formation, and that regulation of oxidation using antioxidants is a potential therapeutic method for blocking atherosclerosis development.

Inhibitory effect of Trolox on the migration and invasion of human lung and cervical cancer cells.

The antioxidant 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) is implicated in migration and invasion of metastatic tumors. However, the molecular mechanism underlying the effect of Trolox on metastatic cancer cells is not known. We found that a non-cytotoxic dose of Trolox decreased phorbol 12-myristate 13-acetate (PMA)-induced invasion and migration of both A549 and HeLa cancer cells. We also found that Trolox suppressed both the expression and the proteolytic activity of matrix metalloproteinase-9 (MMP-9), and that the promoter activity of PMA-induced MMP-9 was inhibited by Trolox. Our results show that Trolox inhibits the transcriptional activity of MMP-9 by suppression of NF-κB transactivation. These results indicate that Trolox inhibits NF-κB-mediated MMP-9 expression, leading to the suppression of migration and invasion in lung and cervical cancer cells. Trolox is a potential agent for clinical use in preventing the invasion and metastasis of human malignant lung and cervical cancers.

The role of 14-3-3ß in transcriptional activation of estrogen receptor α and its involvement in proliferation of breast cancer cells.

The estrogen receptor (ER) functions as a transcription factor that mediates the effects of estrogen. ERα, which plays a crucial role in the development and progression of breast cancer, is activated by estrogen binding, leading to receptor phosphorylation, dimerization, and recruitment of co-activators and chaperons to the estrogen-bound receptor complex. The 14-3-3 proteins bind to target proteins via phosphorylation and influence many cellular events by altering their subcellular localization or acting as a chaperone. However, regulation of ERα expression and transactivation by the 14-3-3 proteins has not been reported. We demonstrate that 14-3-3ß functions as a positive regulator of ERα through a direct protein-protein interaction in an estrogen-dependent manner. Ectopic expression of 14-3-3ß stimulated ERα-mediated transcriptional activity in MCF-7 breast cancer cells. Enhanced ERα transcriptional activity due to 14-3-3ß increased the expressions of the endogenous ERα target genes, leading to proliferation of breast cancer cells. We suggest that 14-3-3ß has oncogenic potential in breast cancer via binding to ERα and activation of the transcriptional activity of ERα.

Celastrol inhibits breast cancer cell invasion via suppression of NF-ĸB-mediated matrix metalloproteinase-9 expression.

BACKGROUND/AIMS: Metastasis is one of the main causes of death for patients with malignant tumors. Induction of matrix metalloproteinase (MMP)-9 is particularly important for the invasiveness of various cancer cells. Celastrol, a triterpenoid isolated from the traditional Chinese medicine, is known to inhibit the proliferation of a variety of tumor cells, including leukemia, glioma, prostate and breast cancer cells. In this study, we investigated the effect of celastrol on the migration and invasion of human breast carcinoma cells. RESULTS: We observed that celastrol suppressed phorbol 12-myristate 13-acetate (PMA)-induced invasion and migration of MCF-7 cells. We also found that celastrol inhibited PMA-induced MMP-9 expression at both the mRNA and the protein levels, and the proteolytic activity of MMP-9 in MCF-7 cells. Our results revealed that celastrol inhibited the transcriptional activity of MMP-9 by suppression of the DNA binding activity of NF-κB in the MMP-9 promoter, and inhibited degradation of IκBα and nuclear translocation of NF-κB. CONCLUSION: These results indicate that celastrol inhibits NF-κB-mediated MMP-9 expression, resulting in suppression of breast cancer cell invasion and migration that is induced by PMA. Celastrol is a potential agent for clinical use in preventing the invasion and metastasis of human malignant breast tumors.

The role of calpains in ligand-induced degradation of the glucocorticoid receptor.

The glucocorticoid receptor (GR) is a ligand-activated transcription factor that mediates the effects of glucocorticoids in diverse cellular processes, including homeostasis, stress response, and inflammation. Glucocorticoids induce down-regulation of GR at both the mRNA and protein levels, causing reduced hormone responsiveness in response to long-term treatment with glucocorticoid. However, the mechanism involved in this process is still obscure. In this study, we examined whether calpain, a calcium-activated cysteine protease, is involved in ligand-stimulated degradation of GR. In COS-7 cells expressing the human GR, treatment with a calpain inhibitor abolished glucocorticoid-induced down-regulation of GR in a dose dependent manner. The protein level of endogenous GR was also elevated by inhibition of the calpain activity in HeLa cells treated with glucocorticoid. Furthermore, glucocorticoid-induced transcriptional activation of GR was enhanced in cells treated with a calpain inhibitor. These results indicate that calpain is involved in ligand-dependent degradation of GR, thus causing reduced hormone responsiveness.