Regulation of shear-induced nuclear translocation of the Nrf2 transcription factor in endothelial cells.

BACKGROUND: Vascular endothelial cells (ECs) constantly experience fluid shear stresses generated by blood flow. Laminar flow is known to produce atheroprotective effects on ECs. Nrf2 is a transcription factor that is essential for the antioxidant response element (ARE)-mediated induction of genes such as heme-oxygenase 1 (HO-1). We previously showed that fluid shear stress increases intracellular reactive oxygen species (ROS) in ECs. Moreover, oxidants are known to stimulate Nrf2. We thus examined the regulation of Nrf2 in cultured human ECs by shear stress. RESULTS: Exposure of human umbilical vein endothelial cells (HUVECs) to laminar shear stress (12 dyne/cm2) induced Nrf2 nuclear translocation, which was inhibited by a phosphatidylinositol 3-kinase (PI3K) inhibitor, a protein kinase C (PKC) inhibitor, and an antioxidant agent N-acetyl cysteine (NAC), but not by other protein kinase inhibitors. Therefore, PI3K, PKC, and ROS are involved in the signaling pathway that leads to the shear-induced nuclear translocation of Nrf2. We also found that shear stress increased the ARE-binding activity of Nrf2 and the downstream expression of HO-1. CONCLUSION: Our data suggest that the atheroprotective effect of laminar flow is partially attributed to Nrf2 activation which results in ARE-mediated gene transcriptions, such as HO-1 expression, that are beneficial to the cardiovascular system.

Laminar flow attenuates interferon-induced inflammatory responses in endothelial cells.

OBJECTIVE: Atherosclerosis is a chronic disease that involves inflammation, in which cytokines, including interferon-gamma (IFNgamma), participate. Endothelial cells (ECs) exposed to IFNgamma increase the expression of CXC chemokines. ECs subjected to laminar flow (LF) are atheroprotective, despite an unclear mechanism. This study was conducted to analyze whether ECs under LF were protected from IFNgamma-induced responses. METHODS: IFNgamma-treated human umbilical cord ECs were subjected to LF in a well-defined flow chamber system. IFNgamma-induced STAT1 activation and downstream target genes were examined. RESULTS: ECs exposed to IFNgamma triggered STAT1 activation via the phosphorylation of Tyr701 and Ser727 in STAT1. ECs exposed to LF alone did not activate STAT1. LF exposure of IFNgamma-treated ECs significantly attenuated IFNgamma-induced Tyr701 phosphorylation in a shear-force- and time-dependent manner, whereas Ser727 phosphorylation was unaffected. Consistently, LF inhibited IFNgamma-induced STAT1 binding to DNA. ECs treated with IFNgamma induced the expression of three T-cell-specific CXC chemokines (CXCL9, CXCL10 and CXCL11) as well as CIITA, a transcriptional regulator of major histocompatibility complex class II (MHCII). Consistently, LF exposure of IFNgamma-treated ECs reduced the expression of CXC chemokines and CIITA. CONCLUSIONS: LF attenuates IFNgamma-induced responses via the suppression of STAT1 activation. Inhibition by LF of the interferon-induced ECs' response may explain some aspects of LF's atheroprotective effects on the endothelium.

Remodeling of carotid arteries is associated with increased expression of thrombomodulin in a mouse transverse aortic constriction model.

Thrombomodulin (TM) is an endothelial glycoprotein that functions as a thrombin cofactor in the activation of protein C. Recent evidence has revealed that TM has unique effects on cellular proliferation, adhesion, and inflammation. We examined TM expression in the arterial remodeling process with different shear conditions. Quantitative real-time reverse transcription-PCR (Q-PCR) revealed that shear stress (25 dyne/cm(2) for 6 hours) induced a 2.6 +/- 0.4-fold increase in TM mRNA levels in endothelial cell culture. Adult FVB (Friend leukemia virus B strain) mice underwent transverse aortic constriction (TAC) between the right (RCA) and left carotid artery (LCA). Doppler (n = 8), morphometric (n = 8), and Q-PCR (n = 8 or 10) studies were performed on carotid arteries at different time points. The RCA lumen and media area increased. The LCA wall shear stress decreased after TAC. RCA wall shear stress increased at day 7 followed by a decrease to the baseline at day 28. TM mRNA level in the LCA was decreased by 61% at day 7 after TAC (0.39 +/- 0.04; p < 0.05 vs. baseline). It progressively returned to the baseline at day 14 (0.85 +/- 0.12) and day 28 (1.48 +/- 0.05; all p = NS). TM appeared in the media of the RCA; TM mRNA level in the RCA was increased by 11-fold at day 14 after TAC (11.0 +/- 0.22) and progressively decreased at day 28 (5.34 +/- 0.25, all p < 0.05 vs. baseline). Our studies suggested that altered shear stress induced significant TM gene expression changes during the arterial remodeling process.

Nasal dissemination of a single-clone IgH-rearranged conjunctival MALT lymphoma through the nasolacrimal duct: A case report.

The aim of the present study was to report a rare case of single-clone, immunoglobulin heavy chain (IgH)-rearranged mucosa-associated lymphoid tissue (MALT) lymphoma in the conjunctiva, with nasal cavity dissemination through the nasolacrimal duct. A 24-year-old female was diagnosed with MALT lymphoma of the nasal cavity at the Department of Otolaryngology, Wan Fang Medical Center, Taipei Medical University (Tapei, Taiwan) in October 2008. A biopsy of the relapsing conjunctival lesion revealed a MALT lymphoma by pathological staining, while a single-clone, IgH-rearranged tumor lesion in the nasal cavity and conjunctiva was confirmed using continuous sinus computed tomography scans and polymerase chain reaction. Tumor lesions were negative for Helicobacter pylori and Chlamydia infection, but exhibited bilateral neck lymph node dissemination. A combination of radiation therapy (a total dosage of 46.8 Gray, in two phases covering the left lacrimal sac, nasal cavity and bilateral neck region) and topical ciprofloxacin plus steroid (0.3% ciprofloxacin 4 times a day and betamethasone eye ointment before sleep for 1 month) was provided as an effective therapeutic strategy, and no recurrence was found in the next 3 years. The nasolacrimal duct serves as a channel for conjunctival tumor spreading and is easily neglected. IgH-involved translocation in MALT lymphoma is a factor in the progression of the disease, and aggressive combination therapy is essential for a high-risk, disseminated IgH-rearranged MALT lymphoma.