Exenatide mitigated diet-induced vascular aging and atherosclerotic plaque growth in ApoE-deficient mice under chronic stress

GLP-1 Receptor Agonist Exendin-4 Attenuates NR4A Orphan Nuclear Receptor NOR1 Expression in Vascular Smooth Muscle Cells

AIMS

Recently, incretin therapy has attracted increasing attention because of its potential use in tissue-protective therapy. Neuron-derived orphan receptor 1 (NOR1) is a nuclear orphan receptor that regulates vascular smooth muscle cell (VSMC) proliferation. In the present study, we investigated the vascular-protective effect of Exendin-4 (Ex-4), a glucagon-like peptide-1 receptor agonist, by inhibiting NOR1 expression in VSMCs.

METHODS

We classified 7-week-old male 129X1/SvJ mice into control group and Ex-4 low- and high-dose-treated groups fed normal or high-fat diets, respectively. Endothelial denudation injuries were induced in the femoral artery at 8 weeks of age, followed by the evaluation of neointima formation at 12 weeks of age. To evaluate VSMC proliferation, bromodeoxyuridine incorporation assay and cell cycle distribution analysis were performed. NOR1 and cell cycle regulators were detected using immunohistochemistry, western blotting, quantitative reverse-transcription polymerase chain reaction, and luciferase assays.

RESULTS

Ex-4 treatment reduced vascular injury-induced neointima formation compared with controls. In terms of VSMCs occupying the neointima area, VSMC numbers and NOR1-expressing proliferative cells were significantly decreased by Ex-4 in a dose-dependent manner in both diabetic and non-diabetic mice. In vitro experiments using primary cultured VSMCs revealed that Ex-4 attenuated NOR1 expression by reducing extracellular signal-regulated kinase-mitogen-activated protein kinase and cAMP-responsive element-binding protein phosphorylations. Furthermore, in the cell cycle distribution analysis, serum-induced G1-S phase entry was significantly attenuated by Ex-4 treatment of VSMCs by inhibiting the induction of S-phase kinase-associated protein 2.

CONCLUSION

Ex-4 attenuates neointima formation after vascular injury and VSMC proliferation possibly by inhibiting NOR1 expression.

Vascular Senescence in Cardiovascular and Metabolic Diseases

In mammals, aging is associated with accumulation of senescent cells. Stresses such as telomere shortening and reactive oxygen species induce “cellular senescence”, which is characterized by growth arrest and alteration of the gene expression profile. Chronological aging is associated with development of age-related diseases, including heart failure, diabetes, and atherosclerotic disease, and studies have shown that accumulation of senescent cells has a causative role in the pathology of these age-related disorders. Endothelial cell senescence has been reported to develop in heart failure and promotes pathologic changes in the failing heart. Senescent endothelial cells and vascular smooth muscle cells are found in atherosclerotic plaque, and studies indicate that these cells are involved in progression of plaque. Diabetes is also linked to accumulation of senescent vascular endothelial cells, while endothelial cell senescence per se induces systemic glucose intolerance by inhibiting skeletal muscle metabolism. A close connection between derangement of systemic metabolism and cellular senescence is also well recognized. Aging is a complex phenomenon, and there is no simple approach to understanding the whole process. However, there is accumulating evidence that cellular senescence has a central role in the development and progression of various undesirable aspects of aging. Suppression of cellular senescence or elimination of senescent cells reverses phenotypic changes of aging in several models, and proof-of-concept has been established that inhibiting accumulation of senescent cells could become a next generation therapy for age-related disorders. It is clear that cellular senescence drives various pathological changes associated with aging. Accordingly, further investigation into the role of this biological process in age-related disorders and discovery of senolytic compounds are important fields for future exploration.

Matrine suppresses AGE-induced HAEC injury by inhibiting ROS-mediated NRLP3 inflammasome activation

Diabetes is characterized by a high level of advanced glycation end products (AGEs), which induce damage in the arterial endothelium. Matrine has been shown to have cardioprotective effects. This study's aim was to investigate the protective effects and possible molecular mechanisms of matrine in AGE-induced human aortic endothelial cell (HAEC) injury. Cultured HAECs were treated with AGEs and/or serially diluted matrine. Cell viability was evaluated by MTT assay. Intracellular reactive oxygen species production was determined by flow cytometry. The expression levels of nucleotide-binding, leucine-rich repeat, and pyrin-domain-containing 3 (NLRP3), adaptor molecule apoptosis-associated speck-like protein, cleaved caspase-1 and interleukin-1β (IL-1β) were assessed by Western blotting; the concentration of IL-1β in culture supernatants was determined by enzyme-linked immunosorbent assay (ELISA). In a concentration-dependent manner, matrine co-treatment with AGEs substantially inhibited the reduction in cell viability and the increase in intracellular reactive oxygen species induced by AGEs. Co-treatment with matrine significantly inhibited the AGE-induced increase in NLRP3, ASC, caspase-1, p20 and IL-1β expression in HAECs in a concentration-dependent manner. Moreover, the AGE-mediated increase in IL-1β expression in cell culture supernatants was also reduced by co-treatment with matrine in a concentration-dependent manner. AGEs induced HAEC injury by inducing reactive oxygen species -mediated NLRP3 inflammasome activation. Matrine recovered HAEC viability by inhibiting reactive oxygen species -mediated NLRP3 inflammasome activation.

Dose rectification of an imbalance between DPP4 and GLP-1 ameliorates chronic stress-related vascular aging and atherosclerosis?

Exposure to psychosocial stress is a risk factor for cardiovascular disease, including vascular aging and regeneration. Dipeptidyl peptidase-4 (DPP-4) exerts many physiological and pharmacological functions by regulating its extremely abundant substrates [eg., glucagon-like peptide-1 (GLP-1), stromal cell-derived factor-1α/C-X-C chemokine receptor type-4, etc.]. Over the past decade, emerging data has revealed unexpected roles for DPP-4 and GLP-1 in intracellular signaling, oxidative stress production, lipid metabolism, cell apoptosis, immune activation, insulin resistance, and inflammation. This mini review focuses on recent findings in this field, highlighting an imbalance between DPP4 and GLP-1 as a potential therapeutic target in the management of vascular aging and atherosclerosis in animals under experimental stress conditions.