Abstract
The etiology of atherosclerosis and restenosis involves aberrant inflammation and proliferation, rendering compounds with both anti-inflammatory and anti-mitogenic properties as promising candidates for combatting vascular diseases. A recent study identified the iridoid plumericin as a new scaffold inhibitor of the pro-inflammatory NF-κB pathway in endothelial cells. We here examined the impact of plumericin on the proliferation of primary vascular smooth muscle cells (VSMC). Plumericin inhibited serum-stimulated proliferation of rat VSMC. It arrested VSMC in the G1/G0-phase of the cell cycle accompanied by abrogated cyclin D1 expression and hindered Ser 807/811-phosphorylation of retinoblastoma protein. Transient depletion of glutathione by the electrophilic plumericin led to S-glutathionylation as well as hampered Tyr705-phosphorylation and activation of the transcription factor signal transducer and activator of transcription 3 (Stat3). Exogenous addition of glutathione markedly prevented this inhibitory effect of plumericin on Stat3. It also overcame downregulation of cyclin D1 expression and the reduction of biomass increase upon serum exposure. This study revealed an anti-proliferative property of plumericin towards VSMC which depends on plumericin’s thiol reactivity and S-glutathionylation of Stat3. Hence, plumericin, by targeting at least two culprits of vascular dysfunction –inflammation and smooth muscle cell proliferation -might become a promising electrophilic lead compound for vascular disease therapy.
Highlights
Atherosclerosis is the underlying cause of the majority of cardiovascular diseases, which represent the leading cause of mortality worldwide[1,2] The pathology of atherosclerosis is from its early stages driven by a chronic ongoing inflammatory state causing leukocyte recruitment to the vessel wall, induced proliferation of vascular smooth muscle cells (VSMC) and generation of a collagen-rich matrix
This study investigated whether plumericin (Fig. 1a), already identified as inhibitor of the NF-κ B signaling pathway in endothelial cells[13], interferes with the proliferation of vascular smooth muscle cells (VSMC) and could, be further developed into a potential dual defense againststenosis
Plumericin concentration-dependently (IC50 value of 1.11 μ M) inhibited serum-induced incorporation of the thymidine analogue 5-bromo-2′ -deoxy-uridin (BrdU) in VSMC, which is indicative of impaired DNA replication during cell division (Fig. 1b)
Summary
Atherosclerosis is the underlying cause of the majority of cardiovascular diseases, which represent the leading cause of mortality worldwide[1,2] The pathology of atherosclerosis is from its early stages driven by a chronic ongoing inflammatory state causing leukocyte recruitment to the vessel wall, induced proliferation of vascular smooth muscle cells (VSMC) and generation of a collagen-rich matrix. These result in the formation of plaques in the intima, the inner-most layer of large and mid-sized arteries, causing their narrowing[3,4,5]. We investigated the influence of plumericin on VSMC proliferation in vitro and the underlying molecular mode of action
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