3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors increase the binding activity and nuclear level of Oct-1 in mononuclear cells

An integrative approach to characterize disease-specific pathways and their coordination: a case study in cancer

Background

The most common application of microarray technology in disease research is to identify genes differentially expressed in disease versus normal tissues. However, it is known that, in complex diseases, phenotypes are determined not only by genes, but also by the underlying structure of genetic networks. Often, it is the interaction of many genes that causes phenotypic variations.

Results

In this work, using cancer as an example, we develop graph-based methods to integrate multiple microarray datasets to discover disease-related co-expression network modules. We propose an unsupervised method that take into account both co-expression dynamics and network topological information to simultaneously infer network modules and phenotype conditions in which they are activated or de-activated. Using our method, we have discovered network modules specific to cancer or subtypes of cancers. Many of these modules are consistent with or supported by their functional annotations or their previously known involvement in cancer. In particular, we identified a module that is predominately activated in breast cancer and is involved in tumor suppression. While individual components of this module have been suggested to be associated with tumor suppression, their coordinated function has never been elucidated. Here by adopting a network perspective, we have identified their interrelationships and, particularly, a hub gene PDGFRL that may play an important role in this tumor suppressor network.

Conclusion

Using a network-based approach, our method provides new insights into the complex cellular mechanisms that characterize cancer and cancer subtypes. By incorporating co-expression dynamics information, our approach can not only extract more functionally homogeneous modules than those based solely on network topology, but also reveal pathway coordination beyond co-expression.

Simvastatin modulates chemokine and chemokine receptor expression by geranylgeranyl isoprenoid pathway in human endothelial cells and macrophages

OBJECTIVE

Atherosclerosis is a chronic immuno-inflammatory disease involving the recruitment of monocytes and T lymphocytes to the vascular wall of arteries. Chemokines and their receptors, known to induce leukocyte migration, have recently been implicated in atherogenesis. Recent in vitro and in vivo studies have suggested that statins (3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors) have anti-inflammatory properties beyond their lipid-lowering effects. Thus, the aim of the present study was to investigate whether simvastatin reduces the expression of chemokines and chemokine receptors in two major cell types implicated in atherogenesis and to test isoprenoid intermediates involved in their regulation.

METHODS AND RESULTS

We performed in vitro experiments on human vascular endothelial cells and human primary macrophages. First, we have shown by ELISA that 1 microM simvastatin significantly reduced MCP-1 in endothelial cells (ECs) and macrophages stimulated with TNF-alpha or IFN-gamma, respectively. Messenger RNA analysis revealed that expression of the chemokines MCP-1, MIP-1alpha and MIP-1beta, as well as the chemokine receptors CCR1, CCR2, CCR4 and CCR5, was decreased by simvastatin, both in ECs and macrophages. Furthermore, the statin effects were reversed by mevalonate and mimicked by the geranylgeranyl transferase inhibitor (GGTI), whereas the farnesyl transeferase inhibitor (FTI) had no effect. These results suggests that statins act via inhibition of the geranylgeranylation of proteins.

CONCLUSIONS

Our results demonstrate that statins reduce chemokine and chemokine receptor expressions in human ECs and macrophages via inhibition of the geranylgeranylpyrophosphate pathway. Thus, our data provide further evidence that statins have anti-inflammatory properties beyond their lipid-lowering effects. These findings highlight specific novel therapeutic targets for cardiovascular diseases to reduce inflammation mediated by chemokines and their receptors.

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) transcriptional regulation by Oct-1 in human endothelial cells: implications for atherosclerosis

LOX-1, a receptor for ox-LDL (oxidized low-density lipoprotein), has recently been determined to play a critical role in the progression of atherosclerosis. LOX-1 expression (mRNA and protein) has been shown to be up-regulated by pro-atherogenic stimuli, such as ox-LDL and Ang II (angiotensin II). However, the molecular mechanisms of these up-regulations are unclear. In the present study, we explored LOX-1 transcriptional promoter activation in response to ox-LDL and Ang II. Under basal states, LOX-1 core promoter (LOX-1 -35/+36) was found to be sufficient for its basal activity in HCAECs (human coronary artery endothelial cells). More importantly, we found that ox-LDL (60 microg/ml for 24 h) induced LOX-1 promoter activity significantly and that a 105 bp fragment (between nt -1599 and -1494) was required for this activation. Within this 106 bp fragment, there is a potential binding motif for the transcription factor Oct-1 (octamer-1). By electrophoretic mobility-shift assay, we observed the activation of Oct-1 by ox-LDL. The critical role of Oct-1 in ox-LDL-induced LOX-1 promoter activation was further confirmed by mutagenesis assay. For comparison, we also examined LOX-1 promoter activation in response to Ang II (1 micromol/l for 24 h). Interestingly, another promoter region, between nt -2336 and -1990, was required for Ang II-induced LOX-1 promoter activation. In conclusion, the present study strongly suggests that ox-LDL, by activating Oct-1, induces LOX-1 promoter activation. Furthermore, this study suggests that while ox-LDL and Ang II both induce LOX-1 expression in HCAECs, the underlying mechanisms of promoter activation are different from each other.

Simvastatin protection against acute immune-mediated glomerulonephritis in mice

In addition to cholesterol lowering, 3-hydroxy-3-nethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors limit inflammatory changes associated with atherosclerosis. There is also support for their use as inhibitors of progression in chronic renal disease, irrespective of cause. In this study, their capacity to limit acute renal inflammation was evaluated. For this purpose, mice were treated with Simvastatin either prior to, at the time of, or shortly after induction of nephrotoxic nephritis. The severity of disease was determined by evaluation of blood urea nitrogen (BUN), proteinuria, and renal histologic changes. The reversibility of benefit was evaluated by the administration of mevalonic acid along with nephrotoxic serum (NTS) and Simvastatin The severity of the acute nephritis, including proteinuria, elevated BUN, and histologic changes, was ameliorated in a dose-dependent manner, when Simvastatin was administered either prior to NTS injection or at the time of NTS injection. By contrast, Simvastatin did not alter the course of established nephritis. Coadministration of mevalonic acid, the immediate substrate following HMG-CoA reductase, abolished Simvastatin's renoprotective effect, indicating that the benefit is, at least in part, due to interference with HMG-CoA reductase and biosynthetic substrates downstream from the enzyme. These findings provide the rationale for the evaluation of the efficacy of HMG-CoA reductase inhibitors in patients with recurrent forms of renal inflammation, to limit the severity of acute exacerbations of disease, prevent renal scarring and slow the rate of progression.

Statins downregulate myeloperoxidase gene expression in macrophages

Statins, inhibitors of HMG-CoA reductase, have pleiotropic benefits independent of cholesterol levels, including anti-oxidant and anti-inflammatory effects. Here, we investigate the effect of statins on myeloperoxidase (MPO) expression. MPO, expressed in foam cell macrophages, was recently shown to oxidize the ApoA-1 component of HDL, impairing ABCA-1 mediated cholesterol efflux. High levels of serum MPO correlate with increased risk of CAD events. Findings here show that statins strongly inhibit MPO mRNA expression in human and murine monocyte-macrophages. Suppression was reversed by downstream intermediates of HMG-CoA reductase, mevalonate, and geranylgeranylpyrophosphate, but not farnesylpyrophosphate. An inhibitor of geranylgeranyltransferase, GGTI-286, mimics the effects of statins, indicating geranylgeranylation is key to MPO expression. Reduction of MPO mRNA levels was observed in vivo in leukocytes from statin-fed mice, correlating with reductions in MPO protein and enzyme activity. These findings suggest that the pleiotropic protections afforded by statins may be due in part to suppression of MPO expression.

p38 MAPK-dependent and YY1-mediated chemokine receptors CCR5 and CXCR4 up-regulation in U937 cell line infected by Mycobacterium tuberculosis or Actinobacillus actinomycetemcomitans

We have found previously that the chemokine receptors CCR5 and CXCR4, which are the coreceptors of HIV, are up-regulated in human macrophage cell line U937 infected by Mycobacterium tuberculosis (MTB). This suggests another possibility to explain the co-infection of MTB and HIV. In order to detect the up-regulation of CCR5 and CXCR4 as a unique phenomenon of MTB infection or a ubiquitous phenomenon of pathogenic bacteria, we investigated the expression changes of these two chemokine receptors in macrophages attacked by another bacterium Actinobacillus actinomycetemcomitans (AA) (from mRNA level and protein level). To reveal the molecular mechanism of these expression changes, p38 MAPK special inhibitor SB203580 was used and the expression of CCR5 and CXCR4 negative regulator YY1 transfactor was analyzed. Finally, we conclude that the up-regulation of CCR5 and CXCR4 can at least partially contribute to the down-regulation of transfactor YY1 which is p38 MAPK pathway-dependent and this up-regulation has little relationship with MTB and HIV co-infection.

Simvastatin inhibits MMP‐9 secretion from human saphenous vein smooth muscle cells by inhibiting the RhoA/ROCK pathway and reducing MMP‐9 mRNA levels

Increased matrix metalloproteinase-9 (MMP-9) expression is associated with intimal hyperplasia in saphenous vein (SV) bypass grafts. Recent evidence suggests that HMG-CoA reductase inhibitors (statins) can prevent the progression of vein graft failure. Here we investigated whether statins inhibited MMP-9 secretion from cultured human SV smooth muscle cells (SMC) and examined the underlying mechanisms. SV-SMC from different patients were exposed to phorbol ester (TPA) or PDGF-BB plus interleukin-1alpha (IL-1). MMP-9 secretion and mRNA expression were analyzed using gelatin zymography and RT-PCR, respectively. Specific signal transduction pathways were investigated by immunoblotting and pharmacological inhibition. Simvastatin reduced TPA- and PDGF/IL-1-induced MMP-9 secretion and mRNA levels, effects reversed by geranylgeranyl pyrophosphate and mimicked by inhibiting Rho geranylgeranylation or Rho-kinase (ROCK). MMP-9 secretion induced by PDGF/IL-1 was mediated via the ERK, p38 MAPK, and NFkappaB pathways, whereas that induced by TPA was mediated specifically via the ERK pathway. Simvastatin failed to inhibit activation of these signaling pathways. Moreover, simvastatin did not affect MMP-9 mRNA stability. Together these data suggest that simvastatin reduces MMP-9 secretion from human SV-SMC by inhibiting the RhoA/ROCK pathway and decreasing MMP-9 mRNA levels independently of effects on signaling pathways required for MMP-9 gene expression.

The impact of parietal cells on Helicobacter pylori tropism and host pathology: an analysis using gnotobiotic normal and transgenic mice

Helicobacter pylori infection of the human stomach is common and typically benign, although a subset of hosts develops severe pathology. Infection occurs in an organ with distinct microenvironments characterized by pronounced differences in the composition of acid-producing parietal cells. In this study, we examine determinants of bacterial tropism to various gastric niches by using germ-free normal and transgenic mice with an engineered parietal cell ablation. Mice were colonized for 8 weeks with a clinical isolate (Hp1) that expresses adhesins recognized by epithelial NeuAcalpha2,3Galbeta1,4 glycan receptors. In normal mice, Hp1 has tropism for a parietal cell-deficient niche where sialylated glycans are expressed by a narrow band of pit cells positioned at the boundary between the squamous epithelium (forestomach) and the proximal glandular epithelium. Lymphoid aggregates that develop in this niche, but not elsewhere in the stomach, were analyzed by GeneChip and quantitative RT-PCR studies of laser capture microdissected mucosa and yielded a series of biomarkers indicative of immune cell activation and maturation. Genetic ablation of parietal cells produced a new source of NeuAcalpha2,3Galbeta1,4 glycans in amplified gastric epithelial lineage progenitors, with accompanying expansion of Hp1 within the glandular epithelium. Lymphoid aggregates that develop in this formerly acid-protected epithelium have molecular features similar to those observed at the forestomach/glandular junction. These findings demonstrate the important roles played by parietal cells and glycan receptors in determining the positioning of H. pylori within the gastric ecosystem, and emphasize the need to consider the evolution of pathology within a given host in a niche-specific context.

Anti-inflammatory and immunomodulatory effects of statins

Anti-inflammatory and immunomodulatory effects of statins. 3-Hydroxy-3-methyl-gutaryl coenzyme A (HMG-CoA) reductase inhibitors or statins constitute the most powerful class of lipid-lowering drugs. Clinical trials have demonstrated a marked reduction in cardiovascular mortality in patients treated with statins. However, the benefits observed with statin therapy appear to be related, at least in part, with their cholesterol-lowering independent effects. Extensive research carried out mainly in the last decade suggests that the clinical benefits of these drugs could be related to an improvement in endothelial dysfunction, a reduction in blood thrombogenicity, anti-inflammatory properties, and, recently, immunomodulatory actions. In this sense, statins decrease T cell activation, the recruitment of monocytes and T cells into the arterial wall, and enhance the stability of atherosclerotic lesions. Many of these effects are related with the inhibition of isoprenoid synthesis, which serve as a lipid attachment for a variety of proteins implicated in intracellular signaling. In fact, small G proteins, whose proper membrane localization and function are dependent on isoprenylation, may play an important role in the lipid-lowering independent effects of HMG-CoA reductase inhibitors. This article summarizes the anti-inflammatory and immunomodulatory effects of statins and their participation in the different steps of atherosclerotic lesion formation.