ABSTRACT
Epidemiological studies have linked the consumption of phenolic acids with reduced risk of cardiovascular diseases. In the present study, we sought to investigate whether caffeic acid, a phenolic acid which is abundant in normal diet, can antagonize angiotensin II (Ang II)-induced vascular smooth muscle cell (VSMC) proliferation in stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto (WKY) rats, and if so, to elucidate the underlying cell signaling mechanisms. We exposed VSMCs to Ang II and caffeic acid and found that caffeic acid significantly inhibited intracellular superoxide anion generation (decreased from 127 +/- 6.3% to 100.3 +/- 6.6% of the control cells) and the cell proliferation induced by Ang II. Furthermore, caffeic acid significantly abolished the tyrosine phosphorylation of JAK2 (decreased from 7.4 +/- 0.6-fold to 2.4 +/- 0.6-fold at 2 min) and STAT1 (decreased from 1.8 +/- 0.2-fold to 0.5 +/- 0.1-fold at 2 min) and the phosphorylation of ERK1/2 (decreased from 99.2 +/- 10.2-fold to 49.8 +/- 10.9-fold at 2 min) that were induced by Ang II. These effects of caffeic acid were consistent with the inhibition of the proliferation of VSMCs by DPI, an NADPH oxidase inhibitor, and by AG-490, a JAK2 inhibitor. In conclusion, our findings suggest that caffeic acid attenuates the proliferative reaction of VSMCs to Ang II stimulation in both SHRSP and WKY rats by inhibiting the generation of reactive oxygen species and then partially blocking the JAK/STAT signaling cascade and the Ras/Raf-1/ERK1/2 cascade.
Subject(s)
Angiotensin II/pharmacology , Antioxidants/pharmacology , Caffeic Acids/pharmacology , Hypertension/drug therapy , Muscle, Smooth, Vascular/drug effects , Vasoconstrictor Agents/pharmacology , Animals , Cell Division/drug effects , DNA-Binding Proteins/metabolism , Drug Interactions , Enzyme Inhibitors/pharmacology , HSP90 Heat-Shock Proteins/metabolism , Hypertension/chemically induced , Janus Kinase 2 , Male , Mitogen-Activated Protein Kinase 1/metabolism , Mitogen-Activated Protein Kinase 3/metabolism , Muscle, Smooth, Vascular/cytology , Muscle, Smooth, Vascular/metabolism , Phosphorylation/drug effects , Protein-Tyrosine Kinases/antagonists & inhibitors , Protein-Tyrosine Kinases/metabolism , Proto-Oncogene Proteins/antagonists & inhibitors , Proto-Oncogene Proteins/metabolism , Rats , Rats, Inbred SHR , Rats, Inbred WKY , STAT1 Transcription Factor , Signal Transduction/drug effects , Stroke/prevention & control , Superoxides/metabolism , Trans-Activators/metabolism , Tyrosine/metabolism , Tyrphostins/pharmacologyABSTRACT
Caffeic acid, a dietary phenol from coffee, fruits and vegetables, is an efficient antioxidant. However, little is known about its anti-oxidative mechanism in the modulation of fundamental cellular processes. In this study, we investigated whether caffeic acid regulates Rac1 GTPase activity, a partner of NADPH oxidase. Our results showed that caffeic acid decrease Rac1 protein level under basal conditions and incubation with angiotensin II (ANG II) in vascular smooth muscle cells. In a Rac-bound-to-PAK pull down assay, caffeic acid clearly inhibited Rac1 activity. We also observed that caffeic acid suppressed the generation of superoxide anion stimulated by ANG II that activates NADPH oxidase. On the other hand, co-incubation with caffei caid and cycloheximide significantly accelerated the Rac1 degradation. In addition, pretreatment with caffeic acid for 24 hours was able to prevent phosphorylation of MLC and HSP27, when cells were challenged with ANG II through the redox sensitive pathway. These results support the hypothesis that caffeic acid reduces Rac1 GTPase protein and activity level, followed by a down-regulation of NADPH oxidase activity.
