Phosphatidylinositol 3-kinase (PI3K) is required for smooth muscle cell (SMC) proliferation. This study reports that inhibitors of PI3K also prevent SMC migration and block neointimal hyperplasia in an organ culture model of restenosis. Inhibition of neointimal formation by LY-294002 was concentration and time dependent, with 10 muM yielding the maximal effect. Continuous exposure for at least the first 4-7 days of culture was essential for significant inhibition. To assess the role of matrix metalloproteinases (MMPs) in this process, we monitored MMP secretion by injured vessels in culture. Treatment with LY-294002 selectively reduced active MMP-2 in media samples according to zymography and Western blot analysis without concomitant changes in latent MMP-2. Parallel results with wortmannin indicate that MMP-2 activation is PI3K dependent. Previous research has shown a role for both furin and membrane-type 1 (MT1)-MMP (MMP-14) in the activation of MMP-2. The furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone did not prevent MMP-2 activation after balloon angioplasty. In contrast, balloon angioplasty induced a significant increase in the levels of MT1-MMP, which was suppressed by LY-294002. No change in MT1-MMP mRNA was observed with LY-294002, because equivalent amounts of this mRNA were present in both injured and noninjured vessels. These results implicate PI3K-dependent regulation of MT1-MMP protein synthesis and subsequent activation of latent MMP-2 as critical events in neointimal hyperplasia after vascular injury.
"This rapid response to cell stress was consistent with the role of vimentin in protection against cytotoxic effects (Figure 1B). Also, the membrane type 1-matrix metalloproteases MMP14 and MMP2, which are functional partners during skeletal development  and stress response in the context of vascular injury , were robustly co-regulated at the transcriptional level in response to heat shock of C2C12 skeletal myotubes. Their expression level rose within 2–4 hours of insult, followed by a repression of expression levels at 8 and 24 hours (Figure 1C). "
[Show abstract][Hide abstract] ABSTRACT: Using a gene clustering strategy we determined intracellular pathway relationships within skeletal myotubes in response to an acute heat stress stimuli. Following heat shock, the transcriptome was analyzed by microarray in a temporal fashion to characterize the dynamic relationship of signaling pathways.
Bioinformatics analyses exposed coordination of functionally-related gene sets, depicting mechanism-based responses to heat shock. Protein turnover-related pathways were significantly affected including protein folding, pre-mRNA processing, mRNA splicing, proteolysis and proteasome-related pathways. Many responses were transient, tending to normalize within 24 hours.
In summary, we show that the transcriptional response to acute cell stress is largely transient and proteosome-centric.
"Furthermore, signaling pathways involved in the mechanism of preconditioning influence the expression or activation of MMPs; e.g., activation of protein kinase C- and - subtypes increases expression of MMP-2 in rat cardiac fibroblast culture (Xie et al., 2004). Phosphatidylinositol 3-ki- nase-dependent up-regulation of membrane-type 1-MMP expression modulates MMP-2 activity in injured pig coronary arteries (Zahradka et al., 2004). We have previously shown that preconditioning inhibits ischemia-induced activation and release of MMP-2 into the perfusate in rat hearts (Lalu et al., 2002); however, it is not known if MMPs and their endogenous inhibitors, the tissue inhibitors of matrix metalloproteinases (TIMPs), play a role in cardioprotection produced by preconditioning. "
[Show abstract][Hide abstract] ABSTRACT: Hyperlipidemia attenuates the cardioprotective effect of preconditioning via unknown mechanisms. We have reported previously that in normolipidemic rats, preconditioning decreased ischemia-induced activation and release of myocardial matrix metalloproteinase (MMP)-2 into the coronary perfusate. Here, we investigated whether hyperlipidemia interferes with the cardioprotective effect of preconditioning through modulation of MMP-2. Hearts isolated from male Wistar rats fed 2% cholesterol-enriched or control chow for 9 weeks were subjected to a preconditioning protocol (three intermittent periods of ischemia/reperfusion of 5-min duration each) or a time-matched nonpreconditioning protocol. This was followed by a test ischemia/reperfusion (30-min ischemia and 120-min reperfusion) in both groups. Preconditioning decreased infarct size in the control but not the cholesterol-fed group. Cardioprotection in the preconditioned control group but not in the cholesterol-fed group was associated with an 18 +/- 3% (p < 0.05) inhibition of test ischemia/reperfusion-induced activation and release of myocardial MMP-2 into the perfusate. Myocardial protein levels of tissue inhibitors of MMPs [tissue inhibitor of metalloproteinases (TIMP)-2 and TIMP-4] were not changed in either group. A reduction of infarct size in nonpreconditioned hearts from both control and cholesterol-fed group was produced by the MMP inhibitor ilomastat at 0.25 microM, a concentration producing MMP-2 inhibition comparable with that of preconditioning in the control group. We conclude that hyperlipidemia blocks preconditioning-induced cardioprotection, hyperlipidemia abolishes preconditioning-induced inhibition of myocardial MMP-2 activation and release, preconditioning-induced inhibition of MMP-2 activation and release is not mediated by TIMPs, and pharmacological inhibition of MMPs produces cardioprotection in both normal and hyperlipidemic rats.
Journal of Pharmacology and Experimental Therapeutics 02/2006; 316(1):154-61. DOI:10.1124/jpet.105.091140 · 3.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Venous neointimal hyperplasia (VNH) lesions are prone to localized development within the vascular access junction (VAJ) and
efferent vein of arteriovenous (AV) fistulae and grafts. The creation of VAJ dramatically alters the local venous hemodynamics
with high pulsatile flow velocities enter the vein resulting in blood-flow separation, recirculation and flow reversal. This
study conducted a computational hemodynamic investigation of an idealized AV graft and realistic AV fistula which demonstrated
a complex hemodynamic environment within the VAJ, producing elevated wall shear stress (WSS) magnitudes and significant spatial
and temporal WSS gradients in the VAJ. These hemodynamic patterns and non-physiological WSSs are postulated to initiate VNH
development at the transcriptional level. Human umbilical vein endothelial cells (HUVEC) were exposed to elevated temporal
WSS waveforms obtained from the aforementioned computational analysis, using a cone-and-plate bioreactor. Using real-time
RT-PCR, early induction of MMP-2 and delayed transcriptional upregulation of MCP-1 was observed following EC exposure to VAJ
high wall shear forces. These results indicate that MMP-2 and MCP-1 may be induced by high WSS present in the VAJ, suggesting
a link between elevated WSS magnitudes and temporal gradients, extracellular matrix decomposition, smooth muscle cell migration
and proliferation, and the subsequent VNH development in AV VAJs.
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