Senescent Vascular Smooth Muscle Cells Drive Inflammation Through an Interleukin-1α-Dependent Senescence-Associated Secretory Phenotype.
Bottom Line: Consequently, the VSMC senescence-associated secretory phenotype promotes chemotaxis of mononuclear cells in vitro and in vivo.Importantly, maintaining the senescence-associated secretory phenotype places a large metabolic burden on senescent VSMCs, such that they can be selectively killed by inhibiting glucose utilization.Senescent VSMCs may actively contribute toward the chronic inflammation associated with atherosclerosis through the interleukin-1α-driven senescence-associated secretory phenotype and the priming of adjacent cells to a proatherosclerotic state.
Affiliation: From the Department of Medicine, Division of Cardiovascular Medicine, University of Cambridge, Cambridge, United Kingdom.Show MeSH
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Mentions: As senescent VSMCs secrete IL-1α, and the classic inflammasome priming toll-like receptor ligands (eg, lipopolysaccharide) induce equivalent downstream signaling as IL-1, we investigated whether IL-1α could also prime local control VSMCs or macrophages to a proinflammasome phenotype. Treatment of control VSMCs with IL-1α led to an upregulation of inflammasome components comparable with that seen in senescent VSMCs (Figure XIII in the online-only Data Supplement), although macrophages showed no response to IL-1α (not shown). Importantly, given that the SASP is a complex mixture of cytokines, we determined whether conditioned media from senescent VSMCs could activate normal VSMCs and ECs. As this conditioned media already contains SASP factors, we treated target cells with bafilomycin A to block protein secretion, and assayed factors within cell lysates after exposure to conditioned media from control or senescent VSMCs. Conditioned media from senescent VSMCs led to IL-1α–dependent production of IL-6, IL-8 (Figure 5A and 5B), and MCP-1 (Figures XIV and XV in the online-only Data Supplement) in both VSMCs and ECs, whereas media from control VSMCs did not. Furthermore, senescent VSMC conditioned media caused the IL-1α–dependent upregulation of the adhesion molecules vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1), and E-selectin in ECs (Figure 5C and 5D). This suggests that in addition to the direct release of inflammatory factors, senescent VSMCs can cause normal cells to release cytokines and upregulate adhesion molecules.
Affiliation: From the Department of Medicine, Division of Cardiovascular Medicine, University of Cambridge, Cambridge, United Kingdom.