Aging, oxidative responses, and proliferative capacity in cultured mouse aortic smooth muscle cells

Abstract

The cellular mechanisms that contribute to the acceleration of atherosclerosis in aging populations are poorly understood, although it is hypothesized that changes in the proliferative capacity of vascular smooth muscle cells is contributory. We addressed the relationship among aging, generation of reactive oxygen species (ROS), and proliferation in primary culture smooth muscle cells (SMC) derived from the aortas of young (4 mo old) and aged (16 mo old) mice to understand the phenotypic modulation of these cells as aging occurs. SMC from aged mice had decreased proliferative capacity in response to alpha-thrombin stimulation, yet generated higher levels of ROS and had constitutively increased mitogen-activated protein kinase activity, in comparison with cells from younger mice. These effects may be explained by dysregulation of cell cycle-associated proteins such as cyclin D1 and p27Kip1 in SMC from aged mice. Increased ROS generation was associated with decreased endogenous antioxidant activity, increased lipid peroxidation, and mitochondrial DNA damage. Accrual of oxidant-induced damage and decreased proliferative capacity in SMC may explain, in part, the age-associated transition to plaque instability in humans with atherosclerosis.

Impact of Insulin-like Growth Factor-I on Migration, Proliferation and Akt-ERK Signaling in Early and Late-passages of Vascular Smooth Muscle Cells

“…3). This results suggest an enhanced oxidative stress in VSMCs from the late-passages which is consistent with the previous reports [21,35]. However, IGF-1 exposure (10 ng/ml) failed to enhance ROS formation in cells from either the early or late passages.…”

“…This is supported by in vitro observations that late-passage VSMCs exhibit greater proliferative capacity compared to the early-passage cells isolated from mice of the same age [20,21]. However, contrasting findings were reported earlier by the same group indicating that SMCs derived from aged mice show decreased proliferative capacity compared to VSMCs from young mice [20,21]. Chen and colleagues confirmed that late-passage cells showed low-to-undetectable levels of telomerase activity, indicating that late-passage cells may represent progression of the life cycle [22].…”

“…However, evidence from other groups has shown that SMCs from older animals possess a higher proliferative capacity than those from younger counterparts [17][18][19]. This is supported by in vitro observations that late-passage VSMCs exhibit greater proliferative capacity compared to the early-passage cells isolated from mice of the same age [20,21]. However, contrasting findings were reported earlier by the same group indicating that SMCs derived from aged mice show decreased proliferative capacity compared to VSMCs from young mice [20,21].…”

“…It has been demonstrated that late passage VSMCs possess a higher proliferative capacity in response to fetal bovine serum associated with enhanced matrix metalloprotein-9 expression in comparison with young cells [20]. Paradoxically, conflicting data from the same group indicate that cultured SMCs from aged mice display reduced proliferative capacity compared with cells from young mice [21].…”

Activation of oxidative stress-responsive signaling pathways in early splenotoxic response of aniline

“…Protein in the lysates was determined by Bio-Rad Protein Assay Kit (Bio-Rad Laboratories). Blots were quantitated by densitometry and normalized using the actin signal to correct for differences in loading of the proteins (Moon et al, 2001;Sunters et al, 2004). For the densitometric analysis, the protein bands on the blot were measured using Eagle Eye II software.…”