ABSTRACT
Proteasome inhibitors are considered to have anti-inflammatory therapeutic potential. However, recent reports addressing proteasome inhibition in the vascular system are controversial, ranging from beneficial anti-inflammatory and anti-oxidative effects to potentiation of inflammation and oxidative stress. This study was based on the hypothesis that the divergent effects might be a result of a differential and dose-dependent responsiveness of vascular cells to proteasome inhibitors. We tested whether low doses of proteasome inhibitors would favor anti-inflammatory effects in vascular cells in vitro and in vivo. Human umbilical vein endothelial cells (HUVEC) were preincubated with proteasome inhibitors MG132 and MG262 at concentrations that did not affect cell viability during a 24-h treatment. Upon addition of tumor necrosis factor alpha (TNF-alpha) the induced expression of adhesion molecules and the adhesion of monocytic THP-1 cells to HUVECs was significantly lowered. However, nuclear translocation of NF-kappaB was only slightly diminished. Low-dose pretreatment with proteasome inhibitors decreased TNF-alpha-induced generation of reactive oxygen species in HUVEC. Bortezomib was administered at a dose of 50 microg/kg body weight to Dahl salt-sensitive rats (DSSR) on high-salt diet. This low-dose proteasome inhibition led to decreased hypertension-induced oxidative stress and reduced expression of vascular cell adhesion molecule 1 (VCAM-1) in the aortae.
Subject(s)
Anti-Inflammatory Agents/pharmacology , Boronic Acids/pharmacology , Enzyme Inhibitors/pharmacology , Leupeptins/pharmacology , Proteasome Inhibitors , Vascular Cell Adhesion Molecule-1/metabolism , Animals , Bortezomib , Cell Adhesion/drug effects , Cell Adhesion Molecules/genetics , Cell Adhesion Molecules/metabolism , Cells, Cultured , Endothelial Cells/cytology , Endothelial Cells/drug effects , Endothelial Cells/metabolism , Gene Expression Regulation/drug effects , Humans , Male , Monocytes/cytology , Monocytes/drug effects , NF-kappa B/metabolism , Oxidative Stress/drug effects , Pyrazines/pharmacology , Rats , Rats, Inbred Dahl , Reactive Oxygen Species/metabolism , Tumor Necrosis Factor-alpha/metabolism , Vascular Cell Adhesion Molecule-1/geneticsABSTRACT
Atherosclerosis is a chronic inflammatory disease accompanied by the expression of endothelial adhesion molecules. Phloretin is a plant-derived phytochemical that is mainly present in apples. Because phloretin is reported to promote antioxidative activities, we investigated the effects of phloretin on cytokine-induced expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and endothelial leukocyte adhesion molecule-1 (E-selectin) in human umbilical vein endothelial cells (HUVECs). Phloretin prevented TNF-alpha-stimulated upregulation of VCAM-1, ICAM-1, and E-selectin expression in a concentration-dependent manner. To the same extent as for TNF-alpha, phloretin also inhibited IL-1beta-induced upregulation in expression of all 3 adhesion molecules. Inhibition of cytokine-induced adhesion molecule expression for VCAM-1, ICAM-1, and E-selectin was detected already at the level of mRNA. Preincubation with phloretin dose-dependently attenuated TNF-alpha-stimulated adhesion of monocytic THP-1 cells to HUVECs and human aortic endothelial cells. Phloretin did not affect TNF-alpha-stimulated activation of nuclear factor kappaB (NF-kappaB) but inhibited activation of interferon regulatory factor 1, a transcription factor involved in the regulation of endothelial cell adhesion molecule expression. In human platelets, phloretin diminished adenosine diphosphate (ADP) and thrombin receptor-activating peptide-stimulated expression of the activated form of the GPIIb/IIIa complex and reduced platelet aggregation stimulated by ADP. Thus phloretin may have beneficial effects in the onset and progression of cardiovascular diseases.
Subject(s)
Blood Platelets/physiology , Cell Adhesion Molecules/genetics , Endothelium, Vascular/physiology , Phloretin/pharmacology , Platelet Aggregation/drug effects , Blood Platelets/drug effects , E-Selectin/genetics , Endothelium, Vascular/drug effects , Flavonoids/pharmacology , Humans , Intercellular Adhesion Molecule-1/genetics , Interleukin-1/pharmacology , Kinetics , Reverse Transcriptase Polymerase Chain Reaction , Transcription Factors/metabolism , Umbilical Veins , Vascular Cell Adhesion Molecule-1/drug effectsABSTRACT
Attachment of leukocytes to the vascular endothelium and the subsequent migration of cells into the vessel wall are early events in atherogenesis. This process requires the expression of endothelial adhesion molecules. Since tea catechins are reputed to promote antiatherogenic activities, we investigated the effects of various tea catechins-i.e., epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG)-on cytokine-induced expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and endothelial leukocyte adhesion molecule-1 (E-selectin) in HUVECs by ELISA. EGCG and to a lesser extent ECG prevented the induction of VCAM-1 expression in a concentration-dependent manner after stimulation with TNF-alpha, whereas EC and EGC were without effect. EGCG also inhibited the IL-1beta-induced induction of VCAM-1 expression. Inhibition of cytokine-induced VCAM-1 expression was manifested already on the transcriptional level. Furthermore, EGCG reduced the TNF-alpha-induced adhesion of THP-1 cells to HUVECs. EGCG did not influence TNF-alpha-stimulated NF-kappaB activation.
