RESUMO
Cellular senescence is a stress response program characterized by a robust cell cycle arrest and the induction of a proinflammatory senescence-associated secretory phenotype (SASP) that is triggered through an unknown mechanism. Here, we show that, during oncogene-induced senescence (OIS), the Toll-like receptor 2 (TLR2) and its partner TLR10 are key mediators of senescence in vitro and in murine models. TLR2 promotes cell cycle arrest by regulating the tumor suppressors p53-p21CIP1, p16INK4a, and p15INK4b and regulates the SASP through the induction of the acute-phase serum amyloids A1 and A2 (A-SAAs) that, in turn, function as the damage-associated molecular patterns (DAMPs) signaling through TLR2 in OIS. Last, we found evidence that the cGAS-STING cytosolic DNA sensing pathway primes TLR2 and A-SAAs expression in OIS. In summary, we report that innate immune sensing of senescence-associated DAMPs by TLR2 controls the SASP and reinforces the cell cycle arrest program in OIS.
Assuntos
Senescência Celular , Imunidade Inata , Receptor 2 Toll-Like/metabolismo , Alarminas/metabolismo , Animais , Senescência Celular/efeitos dos fármacos , Fibroblastos/citologia , Fibroblastos/metabolismo , Humanos , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , NF-kappa B/metabolismo , Nucleotidiltransferases/metabolismo , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Proteína Amiloide A Sérica/genética , Proteína Amiloide A Sérica/metabolismo , Transdução de Sinais , Tamoxifeno/análogos & derivados , Tamoxifeno/farmacologia , Receptor 10 Toll-Like/antagonistas & inibidores , Receptor 10 Toll-Like/genética , Receptor 10 Toll-Like/metabolismo , Receptor 2 Toll-Like/antagonistas & inibidores , Receptor 2 Toll-Like/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Proteínas ras/genética , Proteínas ras/metabolismoRESUMO
Listeria monocytogenes is a Gram-positive bacterium that can cause a serious infection. Intestinal microorganisms have been demonstrated to contribute to intestinal physiology not only through immunological responses but also by modulating the intestinal serotonergic system. Serotonin (5-HT) is a neuromodulator that is synthesized in the intestinal epithelium and regulates the whole intestinal physiology. The serotonin transporter (SERT), located in enterocytes, controls intestinal 5-HT availability and therefore serotonin's effects. Infections caused by L. monocytogenes are well described as being due to the invasion of intestinal epithelial cells; however, the effect of L. monocytogenes on the intestinal epithelium remains unknown. The main aim of this work, therefore, was to study the effect of L. monocytogenes on SERT. Caco2/TC7 cell line was used as an enterocyte-like in vitro model, and SERT functional and molecular expression assays were performed. Our results demonstrate that living L. monocytogenes inhibits serotonin uptake by reducing SERT expression at the brush border membrane. However, neither inactivated L. monocytogenes nor soluble metabolites were able to affect SERT. The results also demonstrate that L. monocytogenes yields TLR2 and TLR10 transcriptional changes in intestinal epithelial cells and suggest that TLR10 is potentially involved in the inhibitory effect observed on SERT. Therefore, L. monocytogenes, through TLR10-mediated SERT inhibition, may induce increased intestinal serotonin availability and potentially contributing to intestinal physiological changes and the initiation of the inflammatory response.
Assuntos
Células CACO-2/efeitos dos fármacos , Intestinos/microbiologia , Listeria monocytogenes/metabolismo , Listeria monocytogenes/patogenicidade , Inibidores Seletivos de Recaptação de Serotonina/antagonistas & inibidores , Proteínas da Membrana Plasmática de Transporte de Serotonina/efeitos dos fármacos , Técnicas de Cultura de Células , Células Epiteliais/metabolismo , Humanos , Mucosa Intestinal/metabolismo , Mucosa Intestinal/microbiologia , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/crescimento & desenvolvimento , Listeriose , Técnicas Microbiológicas , Fator 88 de Diferenciação Mieloide , Serotonina/biossíntese , Serotonina/metabolismo , Serotonina/farmacologia , Proteínas da Membrana Plasmática de Transporte de Serotonina/biossíntese , Receptor 10 Toll-Like/antagonistas & inibidores , Receptor 10 Toll-Like/metabolismo , Receptor 2 Toll-Like/metabolismoRESUMO
Listeria monocytogenes is a Gram-positive bacterium that can cause septicemia and meningitis. TLRs are central receptors of the innate immune system that drive inflammatory responses to invading microbes such as L. monocytogenes. Although intestinal epithelial cells (IECs) represent the initial point of entry used by L. monocytogenes for infection, the innate immune response to L. monocytogenes in these cells has been poorly characterized to date. The aim of this study was to determine which TLRs are involved in mediating the immune response to L. monocytogenes in IECs. We performed an RNA interference screen of TLRs 1-10 in the HT-29 IEC cell line and observed the most significant reduction in chemokine output following silencing of TLR10. This effect was also observed in the macrophage cell line THP-1. The chemokines CCL20, CCL1, and IL-8 were reduced following knockdown of TLR10. Silencing of TLR10 resulted in increased viability of L. monocytogenes in both HT-29 and THP-1 cells. TLR10 was found to be predominantly expressed intracellularly in epithelia, and activation required viable L. monocytogenes. NF-κB activation was seen to require TLR2 in addition to TLR10. Taken together, these data indicate novel roles for TLR10 in sensing pathogenic infection in both the epithelium and macrophages and have identified L. monocytogenes as a source of ligand for the orphan receptor TLR10.
