RESUMO
Emerging evidence suggests that immune receptors may participate in many aging-related processes such as energy metabolism, inflammation, and cognitive decline. CD300f, a TREM2-like lipid-sensing immune receptor, is an exceptional receptor as it integrates activating and inhibitory cell-signaling pathways that modulate inflammation, efferocytosis, and microglial metabolic fitness. We hypothesize that CD300f can regulate systemic aging-related processes and ultimately healthy lifespan. We closely followed several cohorts of two strains of CD300f-/- and WT mice of both sexes for 30 months and observed an important reduction in lifespan and healthspan in knockout mice. This was associated with systemic inflammaging, increased cognitive decline, reduced brain glucose uptake observed by 18FDG PET scans, enrichment in microglial aging/neurodegeneration phenotypes, proteostasis alterations, senescence, increased frailty, and sex-dependent systemic metabolic changes. Moreover, the absence of CD300f altered macrophage immunometabolic phenotype. Taken together, we provide strong evidence suggesting that myeloid cell CD300f immune receptor contributes to healthy aging.
Assuntos
Disfunção Cognitiva , Envelhecimento Saudável , Masculino , Feminino , Camundongos , Animais , Macrófagos/metabolismo , Inflamação/metabolismo , Microglia/metabolismo , Camundongos Knockout , Disfunção Cognitiva/metabolismoRESUMO
Acute and chronic inflammations are key homeostatic events in health and disease. Sirtuins (SIRTs), a family of NAD-dependent protein deacylases, play a pivotal role in the regulation of these inflammatory responses. Indeed, SIRTs have anti-inflammatory effects through a myriad of signaling cascades, including histone deacetylation and gene silencing, p65/RelA deacetylation and inactivation, and nucleotidebinding oligomerization domain, leucine rich repeat, and pyrin domaincontaining protein 3 inflammasome inhibition. Nevertheless, recent findings show that SIRTs, specifically SIRT6, are also necessary for mounting an active inflammatory response in macrophages. SIRT6 has been shown to positively regulate tumor necrosis factor alpha (TNFα) secretion by demyristoylating pro-TNFα in the cytoplasm. However, how SIRT6, a nuclear chromatin-binding protein, fulfills this function in the cytoplasm is currently unknown. Herein, we show by Western blot and immunofluorescence that in macrophages and fibroblasts there is a subpopulation of SIRT6 that is highly unstable and quickly degraded via the proteasome. Upon lipopolysaccharide stimulation in Raw 264.7, bone marrow, and peritoneal macrophages, this population of SIRT6 is rapidly stabilized and localizes in the cytoplasm, specifically in the vicinity of the endoplasmic reticulum, promoting TNFα secretion. Furthermore, we also found that acute SIRT6 inhibition dampens TNFα secretion both in vitro and in vivo, decreasing lipopolysaccharide-induced septic shock. Finally, we tested SIRT6 relevance in systemic inflammation using an obesity-induced chronic inflammatory in vivo model, where TNFα plays a key role, and we show that short-term genetic deletion of SIRT6 in macrophages of obese mice ameliorated systemic inflammation and hyperglycemia, suggesting that SIRT6 plays an active role in inflammation-mediated glucose intolerance during obesity.
Assuntos
Inflamação , Macrófagos , Sirtuínas , Animais , Citoplasma/metabolismo , Inflamação/genética , Inflamação/metabolismo , Lipopolissacarídeos/farmacologia , Macrófagos/metabolismo , Camundongos , Obesidade/metabolismo , Sirtuínas/genética , Sirtuínas/metabolismo , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Gramicidin is a thoroughly studied cation ionophore widely used to experimentally manipulate the plasma membrane potential (PMP). In addition, it has been established that the drug, due to its hydrophobic nature, is capable of affecting the organization of membrane lipids. We have previously shown that modifications in the plasma membrane potential of epithelial cells in culture determine reorganizations of the cytoskeleton. To elucidate the molecular mechanisms involved, we explored the effects of PMP depolarization on some putative signaling intermediates. In the course of these studies, we came across some results that could not be interpreted in terms of the properties of gramicidin as an ionic channel. The purpose of the present work is to communicate these results and, in general, to draw attention to the fact that gramicidin effects can be misleadingly attributed to its ionic or electrical properties. In addition, this work also contributes with some novel findings of the modifications provoked on the signaling intermediates by PMP depolarization and hyperpolarization.
Assuntos
Gramicidina/metabolismo , Potenciais da Membrana/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Animais , Bovinos , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Citoesqueleto/metabolismo , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Células Epiteliais/metabolismo , Gramicidina/efeitos adversos , Gramicidina/farmacologia , Canais Iônicos/metabolismo , Íons/metabolismo , Microtúbulos/metabolismo , Cultura Primária de Células , Transdução de Sinais/fisiologiaRESUMO
In previous work, we reported that plasma membrane potential depolarization (PMPD) provokes cortical F-actin remodeling in bovine corneal endothelial (BCE) cells in culture, which eventually leads to the appearance of intercellular gaps. In kidney epithelial cells it has been shown that PMPD determines an extracellular-signal-regulated kinase (ERK)/Rho-dependent increase in diphosphorylated myosin light chain (ppMLC). The present study investigated the signaling pathways involved in the response of BCE cells to PMPD. Differently to renal epithelial cells, we observed that PMPD leads to a decrease in monophosphorylated MLC (pMLC) without affecting diphosphorylated MLC. Also, that the pMLC reduction is a consequence of cyclic adenosine 3',5'-monophosphate (cAMP)/protein kinase A (PKA) activation. In addition, we found evidence that the cAMP increase mostly depends on soluble adenylyl cyclase activity. Inhibition of this enzyme reduces the effect of PMPD on the cAMP rise, F-actin remodeling, and pMLC decrease. No changes in phosho-ERK were observed, although we could determine that RhoA undergoes activation. Our results suggested that active RhoA is not involved in the intercellular gap formation. Overall, the findings of this study support the view that, differently to renal epithelial cells, in BCE cells PMPD determines cytoskeletal reorganization via activation of the cAMP/PKA pathway.
Assuntos
Membrana Celular/metabolismo , Citoesqueleto/metabolismo , Células Endoteliais/metabolismo , Transdução de Sinais/fisiologia , Actinas/metabolismo , Adenosina/metabolismo , Animais , Bovinos , Células Cultivadas , AMP Cíclico/metabolismo , Cadeias Leves de Miosina/metabolismo , Fosforilação/efeitos dos fármacos , Quinases Associadas a rho/metabolismoRESUMO
Tissue injury triggers a complex network of cellular and molecular responses. Although cell migration and proliferation are the most conspicuous, several other responses, such as apoptosis and increased protease activity, are necessary for a proper restitution of the tissue. In this work, we study the leukocyte elastase inhibitor (LEI) expression during wound healing of bovine corneal endothelial monolayers in culture. LEI is a multifunctional protein with anti-protease and anti-apoptotic activity. When properly cleaved, it is transformed into L-DNase II, a pro-apoptotic enzyme and translocated to the nucleus. We found that early after injury LEI increases its protein and mRNA expressions, without nuclear translocation and returns to basal levels immediately after wound closure. This increase is blocked by N-acetylcysteine, suggesting that production of reactive oxygen species immediately after wounding is involved in the LEI increase. Another finding of this work is that there is an acidification of the cells at the wound border which, in contrast to other cell types, does not determine nuclear translocation of the protein. Taken together, the results of this work suggest that the function of LEI during wound healing is related to its activity as a protease inhibitor and/or to its anti-apoptotic activity.
Assuntos
Células Endoteliais/metabolismo , Células Endoteliais/patologia , Endotélio Corneano/patologia , Elastase de Leucócito/antagonistas & inibidores , Serpinas/metabolismo , Cicatrização , Animais , Sinalização do Cálcio , Bovinos , Imunofluorescência , Concentração de Íons de Hidrogênio , Espaço Intracelular/metabolismo , Elastase de Leucócito/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Sus scrofaRESUMO
Previous work from our laboratory and others has shown that, in some epithelia, the epithelial sodium channel (ENaC) increases its expression during wound healing. In these cases, inhibition of the channel determines a decrease in the healing rate, a result suggesting a role for ENaC in the overall healing process. To understand further this role of ENaC in epithelia, we explored the participation of ENaC in wound healing in four cultured epithelial cell lines selected on the basis of their different embryonic origins, function and modality of healing, i.e., by lamellipodial cell crawling or by actin cable formation. Three of the cell lines (bovine corneal endothelial cells, rabbit corneal epithelial cells and Madin-Darby canine kidney cells) exhibited an increase in ENaC expression and consequent membrane potential depolarization and an increase in cytosolic sodium and calcium, whereas one line (bovine aortal endothelial cells, BAEC) did not exhibit any of these changes. In all of the cell lines, however, ENaC inhibition determined a similar decrease in the rate of wound healing. In BAEC monolayers, the increase in ENaC activity produced plasma membrane depolarization, increased cytosolic sodium and calcium, and augmented the velocity of healing. These novel findings contribute to the idea that ENaC plays a critical role in wound healing in various epithelia, independently of the modality of healing and of any increase in the expression of the channel.