Senescent RAW264.7 cells exhibit increased production of nitric oxide and release inducible nitric oxide synthase in exosomes

Abstract

Aging cells not only cease growing, but also secrete various proteins such as inflammatory cytokines. This secretory phenomenon is known as the senescence-associated secretory phenotype (SASP). The aim of the present study was to elucidate the effects of senescence on the differentiation of osteoclast precursors (OCPs) and corresponding SASP. RAW264.7 cells were used as OCPs and were cultured to passage (P)5, P10 and P20. Cell proliferation assays, senescence-associated β-galactosidase staining and telomere length quantification were subsequently performed, and it was revealed that replicative senescence was induced at P20. In addition, the level of tartrate-resistant acid phosphatase activity in P20 cells treated with receptor activator of nuclear factor-κB ligand was significantly lower than that in P5 and P10 cells. The SASP factors interleukin-6, tumour necrosis factor-α and nitric oxide were significantly increased in P20 culture supernatants compared with those in P5 and P10 supernatants. Furthermore, the number of exosomes at P20 was increased compared with that at P5 and P10, and inducible nitric oxide synthase (iNOS) was expressed in exosomes at P20, but not in exosomes at P5. In conclusion, the present study revealed that senescent RAW264.7 cells exhibit increased expression of SASP factors and release iNOS in exosomes.

Exploring the Communication of the SASP: Dynamic, Interactive, and Adaptive Effects on the Microenvironment

“…Hemostasis-related factors, another class of bioactive compounds, show a marked increase in secretion into the extracellular medium by senescent human primary fibroblasts when exposed to different inducers (IR, doxorubicin (DOX), and MiDAS) [ 61 ]. Non-protein signaling molecules, including various bioactive oxidized lipid metabolites, prostaglandins, and nitric oxide can also be found enriched in the sSASP of senescent cells [ 62 , 63 , 64 , 65 ]. While empirical research has focused on soluble factors secreted by senescent cells, new studies show evidence that EVs are also a substantial and effective part of SASP [ 66 ].…”

Regulation of Extracellular Vesicle-Mediated Immune Responses against Antigen-Specific Presentation

“…For this strategy, a fusion protein is prepared in which Gag, an EV inner-membrane tropic protein, is fused with NBD. The addition of Gag-NBD-loaded EVs to LPS-stimulated macrophages significantly suppressed macrophage inflammatory responses, that is, inflammatory cytokine production, nitric oxide (NO) synthase induction, and subsequent NO production [ 355 , 356 ]. Therefore, EVs-mediated immune responses are essential factors for tumour progression.…”