We have identified as a novel protective gene against TAA formation and define an additional target for the future development of treatments to limit TAA pathogenesis.

Monocyte chemoattractant protein (MCP)-1 is expressed by astrocytes in diverse inflammatory states and is a key regulator of monocyte recruitment to the central nervous system (CNS). In the current study, we addressed mechanisms by which transcription of the human MCP-1 gene (hMCP-1) was terminated, after induction by interferon (IFN)-gamma. Our results demonstrated that IFN-gamma-induced transcription of hMCP-1 was followed by a refractory state, during which hMCP-1 was resistant to restimulation by either IFN-gamma or heterologous activators such as TNF-alpha. This refractory state affected the hMCP-1 gene selectively, as other IFN-gamma-inducible genes remained responsive to restimulation. The IFN-gamma-induced hMCP-1 refractory state was governed at the transcriptional level and was sensitive to protein synthesis inhibitors, suggesting a requirement for newly expressed components. A minimal 213 base pair hMCP-1 regulatory element directed both IFN-gamma-mediated transcription and the subsequent refractory state. We previously demonstrated that IFN-gamma treatment resulted in coordinate protein occupancy in vivo of two hMCP-1 promoter elements, a gamma-activated site (GAS) and a GC-rich element. During the refractory state, IFN-gamma treatment failed to induce protection of either the hMCP-1 GAS element or the GC box. These results furnish insight into the expression of hMCP-1 during CNS inflammation and provide the first delineation of an IFN-gamma-induced transcriptional refractory state.

This study was undertaken to determine the in vitro effect of lentivirus-mediated siPin1 on cell cycle and apoptosis of vascular smooth muscle cells (VSMCs). Further we sought to provide insight into the mechanisms behind these processes. Human umbilical artery smooth muscle cells (HUASMCs) were transfected with lentiviral siPin1. Real-time RT-PCR and Western blotting were used to examine Pin1 mRNA and protein expression. MTT and [(3)H]thymidine incorporation assays were employed to observe cell proliferation status. The apoptotic rate and cell cycle were analyzed by Hoechst33258 staining and flow cytometry. Finally we measured the expression of cyclin D1, beta-catenin, CDK4, cytochrome c, procaspase-3, cleaved caspase-3, procaspase-9, cleaved caspase-9, Bcl-2, Bax, STAT3, phosphorylated STAT3 and VEGF in lentiviral siPin1 infected VSMCs. Lentivirus-mediated siPin1 effectively diminished endogenous Pin1 expression in VSMCs resulting in cell cycle arrest and enhancement of apoptosis. This was accompanied by downregulation of cyclin D1, beta-catenin, CDK4, increase of Bax/Bcl-2 ratio, release of cytochrome c, and activation of caspase-3 and -9. We concluded that this effect was mediated, at least in part, via the beta-catenin/cyclin D1/CDK4 cascade, and that the mitochondrial pathway was responsible for VSMC apoptosis in the absence of Pin1. Our observations raised the possibility that Pin1 might be a potential therapeutic target to prevent stenosis.

Chemokine receptors dictate the cellular responses to chemokines on target cells. Therefore, the regulation of expression of chemokine receptors is likely a crucial point for the regulation of chemokine action. Here we show that CC chemokine receptor 1 (CCR1) expression by primary mouse astrocytes is increased after transforming growth factor beta1 (TGFbeta1) stimulation. TGFbeta1 caused a pronounced up-regulation of CCR1 mRNA in a concentration- and time-dependent manner. TGFbeta1-mediated increase of CCR1 mRNA accumulation resulted in increased CCR1 protein expression and augmented cell migration to a physiological ligand, macrophage inflammatory protein-1alpha (MIP-1alpha). The half life of CCR1 mRNA in the presence and absence of TGFbeta1 stimulation was comparable, suggesting that TGFbeta1-induced CCR1 mRNA accumulation occurred at the transcriptional level. TGFbeta1 did not affect CCR1 mRNA expression in hematopoietic cells, indicating that TGFbeta1 effect on CCR1 expression in primary astrocytes is cell-type specific. This is the first evidence that TGFbeta1 may modulate central nervous system (CNS) inflammation in part by affecting chemokine receptor expression on astrocytes.

Altogether this work supports a role for Pin1 as a vital modulator of VSMC senescence, thereby providing a novel target for regulation and control of atherosclerosis.