Diabetes-related Changes in cAMP Response Element-binding Protein Content Enhance Smooth Muscle Cell Proliferation and Migration

Abstract

We hypothesized that diabetes and glucose-induced reactive oxygen species lead to depletion of cAMP response element-binding protein (CREB) content in the vasculature. In primary cultures of smooth muscle cells (SMC) high medium glucose decreased CREB function but increased SMC chemokinesis and entry into the cell cycle. These effects were blocked by pretreatment with the antioxidants. High glucose increased intracellular reactive oxygen species detected by CM-H 2 DCFA. SMC exposed to oxidative stress (H 2 O 2 ) demonstrated a 3.5-fold increase in chemokinesis (p < 0.05) and accelerated entry into cell cycle, accompanied by a significant decrease in CREB content. Chronic oxidative challenge similar to the microenvironment in diabetes (glucose oxidase treatment) decreases CREB content (40 -50%). Adenoviral-mediated expression of constitutively active CREB abolished the increase in chemokinesis and cell cycle progression induced by either high glucose or oxidative stress. Analysis of vessels from insulin resistant or diabetic animals indicates that CREB content is decreased in the vascular stroma. Treatment of insulinresistant animals with the insulin sensitizer rosiglitazone restores vessel wall CREB content toward that observed in normal animals. In summary, high glucose and oxidative stress decrease SMC CREB content increase chemokinesis and entry into the cell cycle, which is blocked by antioxidants or restoration of CREB content. Thus, decreased vascular CREB content could be one of the molecular mechanisms leading to increased atherosclerosis in diabetes.

Molecular Mechanisms of High Glucose-Induced Cyclooxygenase-2 Expression in Monocytes

“…Another key difference between the actions of S100b and high glucose is our present observation for the first time that high glucoseinduced COX-2 also involves the proximal CRE site and activation of CREB. Whereas reports have shown the effects on high glucose on CREB in vascular smooth muscle cells (43) and mesangial cells (44), our results suggest a novel new role for CREB in monocytes. Thus, whereas both AGEs and high glucose can induce COX-2 expression in monocytes, they differ in the molecular mechanisms of regulation.…”

Contribution of Aldose Reductase to Diabetic Hyperproliferation of Vascular Smooth Muscle Cells

“…This is further supported by our data showing that high glucose increases SMC proliferation in culture. Although some previous studies show that high glucose increases SMC proliferation (38,39), in other studies, no mitogenic effects were observed (30 -32). Reasons for such discordance are unclear but may relate to the inability of high glucose to promote growth in the absence of serum or when supra-maximal growth is stimulated by high (5-10%) serum in the growth medium.…”

Activation of Sphingosine Kinase-1 Mediates Inhibition of Vascular Smooth Muscle Cell Apoptosis by Hyperglycemia

“…Specific primers used for RT-PCR analysis of S1P receptors and sphingosine kinase isoforms were designed essentially as previously described (25). The expected PCR products for S1P 1 , S1P 2 , S1P 3 , S1P 4 , S1P 5 , SK1, and SK2 were 647, 321, 321, 278, 306, 500, and 319 bp, respectively. RT-PCR was performed by using one-step RT-PCR kit (Invitrogen).…”

“…The pathogenesis of occlusive macrovascular disease involves an excessive accumulation of cells within the intima and media (3). Enhanced cell proliferation is believed to be a key feature of diabetic vasculopathy (4,5). However, recent studies clearly suggest that dysregulated cell apoptosis also contributes to the pathogenesis and progression of vascular disease (6,7).…”