While TNF dramatically enhanced UCH-L1 protein expression in vehicle treated RASMCs over-expressed with UCH-L1, it could not up-regulate UCH-L1 protein expression in cycloheximide treated cells (Fig. in the United States, and the majority of cardiovascular disorders results from complications of vascular diseases [1]. While it is still far from a comprehensive understanding of molecular and cellular mechanisms leading to vascular diseases, a preponderance of evidence supports a notion that inflammation plays a critical role in a wide range of vascular complications Chrysophanic acid (Chrysophanol) and dysfunctions [26]. Vascular inflammation has been characterized as a complex process involving endothelial dysfunction, leukocyte recruitment, VSMC activation, and malfunction of inflammatory mediators including both anti-inflammatory and pro-inflammatory cytokines [27]. Recently, TNF, a pro-inflammatory cytokine, has emerged as a key factor in the pathogenesis of vascular diseases [7,8]. TNF triggers myriads of pro-inflammatory effects on vascular cells such as VSMC migration and proliferation, thereby contributing to maladaptive vascular modeling. It has been demonstrated that nuclear factor (NF)-B and mitogen-activated protein kinase (MAPK) cascades are major component of TNF signal transduction [9]; however, the precise signaling mechanisms responsible for the pathological TNF activity in vasculature remain to be defined. We have recently demonstrated that a DUB of ubiquitin carboxyl terminal hydrolyase L1 (UCH-L1) inhibits vascular lesion formation via suppressing inflammatory responses in vasculature [10]. However, cellular and signaling mechanisms by which UCH-L1 suppresses vascular inflammatory responses remain to be further investigated. In the present study, we explored role of UCH-L1 in the regulation of TNF-mediated VSMC proliferationin vitro. Our results uncovered for the first time that UCH-L1 Chrysophanic acid (Chrysophanol) negatively regulates TNF-mediated VSMC proliferation via suppressing ERK activity. == Material and methods == == Cell culture and adenoviral infection == Vascular smooth muscle cells (VSMCs) were isolated from thoracic aorta of adult Spague-Dawley rats as previously described [11], and cultured in low glucose (1 g/L) Dulbeccos Modified Eagles Medium (DMEM) (Invitrogen) supplemented with 10% fetal bovine serum. Sub-confluent rat aortic smooth muscle cells (RASMCs) were infected with adenovirus of control beta-galactoside (Ad-Gal) and human UCH-L1 (Ad-hUCH-L1) (Welgen Inc.) in serum free DMEM for 48 hours. == [3H]thymidine Chrysophanic acid (Chrysophanol) uptake == RASMCs were cultured in serum free DMEM for 24 hours to induce a quiescent status, and then stimulated with or without TNF (Sigma-Aldrich) for 40 hours. [3H]thymidine (MP Biomedicals) was added to the media (final concentration 1 Ci/ml) during the last 24 hours. [3H]thymidine uptake was measured by a Beckman LS6000 scintillation counter (Beckman Coulter, Inc.) Chrysophanic acid (Chrysophanol) as previously described [11]. [3H]thymidine incorporation was normalized by the amount of cellular protein counted. == Reverse transcription-polymerase chain reaction (RT-PCR) and quantitative real time (Q-PCR) == Total RNA purification, RT reaction, and Q-PCR were performed as described previously [12]. Expression levels of target genes were normalized by concurrent measurement of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA levels. Primers that were used for Q-PCR are as Chrysophanic acid (Chrysophanol) follows: Forward primer (5′-CCCCGAGATGCTGAACAAAGT-3′) and reverse primer (5′-ATGGTCTGCTTCATGAAGTA-3′) were used for PCR amplification of rat UCH-L1 (NM_017237). Forward primer (5′-ACCACAGTCCATGCCATCAC-3′) and reverse primer (5′-TCCACCACCCTGTTGCTGTA-3′) were Akt2 used for PCR amplification of rat GAPDH (NM_017008). == UCH-L1 mRNA stability assessment == Quiescent RASMCs were pretreated with or without actinomysin D, an inhibitor of gene transcription, for 1 hour, and then stimulated with or without TNF (5 ng/ml) as indicated. As actinomysin D at a dose of 1 1 g/ml has been demonstrated not to inhibit GAPDH but other genes transcription in RASMCs [13], we applied actinomysin D (1 g/ml) in the present study. UCH-L1 mRNA expression was quantified by Q-PCR as described above. Expression UCH-L1 mRNA levels in RASMCs treated with vehicle alone was considered as 100%. == Western blot == Cell lysates were subjected to immunoblot analysis as previously describe [11] using antibodies of phosphor-ERK (Cat# 9101, Cell Signaling Technology), anti-UCH-L1 (AB1761, Millipore) and anti-GAPDH (FL-335, sc-25778, Santa Cruz.