Project description:Cell senescence has recently emerged as a potentially relevant pathogenic mechanism in fibrosing interstitial lung diseases (f-ILDs), particularly in idiopathic pulmonary fibrosis. We hypothesized that senescent human fibroblasts may suffice to trigger a progressive fibrogenic reaction in the lung. To address this, senescent human lung fibroblasts, or their secretome (SASP), were instilled into the lungs of immunodeficient mice. We found that: (1) human senescent fibroblasts engraft in the lungs of immunodeficient mice and trigger progressive lung fibrosis associated to increasing levels of mouse senescent cells, whereas non-senescent fibroblasts do not trigger fibrosis; (2) the SASP of human senescent fibroblasts is pro-senescence and pro-fibrotic both in vitro when added to mouse recipient cells and in vivo when delivered into the lungs of mice, whereas the conditioned medium (CM) from non-senescent fibroblasts lacks these activities; and, (3) navitoclax, nintedanib and pirfenidone ameliorate lung fibrosis induced by senescent human fibroblasts in mice, albeit only navitoclax displayed senolytic activity. We conclude that human senescent fibroblasts, through their bioactive secretome, trigger a progressive fibrogenic reaction in the lungs of immunodeficient mice that includes the induction of paracrine senescence in the cells of the host, supporting the concept that senescent cells actively contribute to disease progression in patients with f-ILDs.
Project description:Accumulation of senescent cells is associated with the progression of pulmonary fibrosis, but mechanisms accounting for this linkage are not well understood. To explore this issue, we investigated whether a class of biologically active profibrotic lipids, the leukotrienes (LT), is part of the senescence-associated secretory phenotype. The analysis of conditioned medium (CM), lipid extracts, and gene expression of LT biosynthesis enzymes revealed that senescent cells secreted LT, regardless of the origin of the cells or the modality of senescence induction. The synthesis of LT was biphasic and followed by antifibrotic prostaglandin (PG) secretion. The LT-rich CM of senescent lung fibroblasts (IMR-90) induced profibrotic signaling in naive fibroblasts, which were abrogated by inhibitors of ALOX5, the principal enzyme in LT biosynthesis. The bleomycin-induced expression of genes encoding LT and PG synthases, level of cysteinyl LT in the bronchoalveolar lavage, and overall fibrosis were reduced upon senescent cell removal either in a genetic mouse model or after senolytic treatment. Quantification of ALOX5+ cells in lung explants obtained from idiopathic pulmonary fibrosis (IPF) patients indicated that half of these cells were also senescent (p16Ink4a+). Unlike human fibroblasts from unused donor lungs made senescent by irradiation, senescent IPF fibroblasts secreted LTs but failed to synthesize PGs. This study demonstrates for the first time to our knowledge that senescent cells secrete functional LTs, significantly contributing to the LT pool known to cause or exacerbate IPF.
Project description:Cellular senescence is crucial in the progression of idiopathic pulmonary fibrosis (IPF), but it is not evident whether the standard-of-care (SOC) drugs, nintedanib and pirfenidone, have senolytic properties. To address this question, we performed colorimetric and fluorimetric assays, qRT-PCR, and western blotting to evaluate the effect of SOC drugs and D + Q on senescent normal and IPF lung fibroblasts. In this study, we found that SOC drugs did not provoke apoptosis in the absence of death ligand in normal or IPF senescent lung fibroblasts. Nintedanib increased caspase-3 activity in the presence of Fas Ligand in normal but not in IPF senescent fibroblasts. Conversely, nintedanib enhanced B cell lymphoma 2 expression in senescent IPF lung fibroblasts. Moreover, in senescent IPF cells, pirfenidone induced mixed lineage kinase domain-like pseudokinase phosphorylation, provoking necroptosis. Furthermore, pirfenidone increased transcript levels of FN1 and COL1A1 in senescent IPF fibroblasts. Lastly, D + Q augmented growth differentiation factor 15 (GDF15) transcript and protein levels in both normal and IPF senescent fibroblasts. Taken together, these results establish that SOC drugs failed to trigger apoptosis in senescent primary human lung fibroblasts, possibly due to enhanced Bcl-2 levels by nintedanib and the activation of the necroptosis pathway by pirfenidone. Together, these data revealed the inefficacy of SOC drugs to target senescent cells in IPF.
Project description:Although cellular senescence may be a protective mechanism in modulating proliferative capacity, fibroblast senescence is now recognized as a key pathogenic mechanism in idiopathic pulmonary fibrosis (IPF). In aged mice, abundance and persistence of apoptosis-resistant senescent fibroblasts play a central role in nonresolving lung fibrosis after bleomycin challenge. Therefore, we investigated whether quercetin can restore the susceptibility of senescent IPF fibroblasts to proapoptotic stimuli and mitigate bleomycin-induced pulmonary fibrosis in aged mice. Unlike senescent normal lung fibroblasts, IPF lung fibroblasts from patients with stable and rapidly progressing disease were highly resistant to Fas ligand (FasL)-induced and TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Senescent IPF fibroblasts exhibited decreased expression of FasL and TRAIL receptors and caveolin-1, as well as increased AKT activation, compared with senescent normal lung fibroblasts. Although quercetin alone was not proapoptotic, it abolished the resistance to FasL- or TRAIL-induced apoptosis in IPF fibroblasts. Mechanistically, quercetin upregulated FasL receptor and caveolin-1 expression and modulated AKT activation. In vivo quercetin reversed bleomycin-induced pulmonary fibrosis and attenuated lethality, weight loss, and the expression of pulmonary senescence markers p21 and p19-ARF and senescence-associated secretory phenotype in aged mice. Collectively, these data indicate that quercetin reverses the resistance to death ligand-induced apoptosis by promoting FasL receptor and caveolin-1 expression and inhibiting AKT activation, thus mitigating the progression of established pulmonary fibrosis in aged mice. Therefore, quercetin may be a viable therapeutic option for IPF and other age-related diseases that progress with the accumulation of senescent fibroblasts.
Project description:Lung cancer is a fatal complication of idiopathic pulmonary fibrosis (IPF) with a poor prognosis. Current treatments are insufficient in improving the prognosis of lung cancer patients with comorbid idiopathic pulmonary fibrosis (IPF-LC). Senescent fibroblasts, as stromal cells in the tumor microenvironment, influence tumor progression via exosomes. With evidence that fibroblast senescence is an important mechanism of IPF, we investigated the impact of senescent IPF lung fibroblast (diseased human lung fibroblasts, DHLF)-derived exosomes on non-small cell lung cancer (NSCLC). We found DHLF expressed significant senescence markers, and promoted NSCLC proliferation, invasion, and epithelial-mesenchymal transition. Specifically, senescent DHLF showed strong secretion of exosomes, and these exosomes enhanced the proliferation and colony-forming ability of cancer cells. Proteomic analysis showed DHLF-derived exosomes exhibited upregulated senescence-associated secretory phenotype (SASP) factors, notably MMP1, which activates the surface receptor PAR1. Knocking down MMP1 or using PAR1 inhibitors reduced the tumor-promoting effects of DHLF-derived exosomes in vivo and in vitro. Mechanistically, MMP1 acted by activating the PI3K-AKT-mTOR pathway. In conclusion, our results suggest that exosomal MMP1 derived from senescent IPF fibroblasts promotes NSCLC proliferation and colony formation by targeting PAR1 and activating the PI3K-AKT-mTOR pathway. These findings provide a novel therapeutic approach for patients with IPF-LC.
Project description:BackgroundAging is characterized by a low-grade systemic inflammation that contributes to the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD). However, little knowledge is currently available on the molecular processes leading to chronic neuroinflammation. In this context, recent studies have described the role of chromatin regulators in inflammation and longevity including the REST corepressor (Rcor)-2 factor, which seems to be involved in an inflammatory suppressive program.MethodsTo assess the impact of Rcor2 in age-related inflammation, gene expression levels were quantified in different tissues and ages of the spontaneous senescence-accelerated P8 mouse (P8) using the SAMR1 mouse (R1) as a control. Specific siRNA transfection in P8 and R1 astrocyte cultures was used to determine Rcor2 involvement in the modulation of neuroinflammation. The effect of lipopolysaccharide (LPS) treatment on Rcor2 levels and neuroinflammation was analyzed both in vivo and in vitro.ResultsP8 mice presented a dramatic decrease in Rcor2 gene expression compared with R1 controls in splenocytes, an alteration also observed in the brain cortex, hippocampus and primary astrocytes of these mice. Rcor2 reduction in astrocytes was accompanied by an increased basal expression of the interleukin (Il)-6 gene. Strikingly, intraperitoneal LPS injection in R1 mice downregulated Rcor2 in the hippocampus, with a concomitant upregulation of tumor necrosis factor (Tnf-?), Il1-? and Il6 genes. A negative correlation between Rcor2 and Il6 gene expression was also verified in LPS-treated C6 glioma cells. Knock down of Rcor2 by siRNA transfection (siRcor2) in R1 astrocytes upregulated Il6 gene expression while siRcor2 further increased Il6 expression in P8 astrocytes. Moreover, LPS activation provoked a further downregulation of Rcor2 and an amplified induction of Il6 in siRcor2-tranfected astrocytes.ConclusionsData presented here show interplay between Rcor2 downregulation and increased inflammation and suggest that Rcor2 may be a key regulator of inflammaging.
Project description:Elevated arginases including type-I (Arg-I) and type-II isoenzyme (Arg-II) are reported to play a role in aging, age-associated organ inflammaging, and fibrosis. A role of arginase in pulmonary aging and underlying mechanisms are not explored. Our present study shows increased Arg-II levels in aging lung of female mice, which is detected in bronchial ciliated epithelium, club cells, alveolar type 2 (AT2) pneumocytes, and fibroblasts (but not vascular endothelial and smooth muscle cells). Similar cellular localization of Arg-II is also observed in human lung biopsies. The age-associated increase in lung fibrosis and inflammatory cytokines, including IL-1β and TGF-β1 that are highly expressed in bronchial epithelium, AT2 cells, and fibroblasts, are ameliorated in arg-ii deficient (arg-ii-/- ) mice. The effects of arg-ii-/- on lung inflammaging are weaker in male as compared to female animals. Conditioned medium (CM) from human Arg-II-positive bronchial and alveolar epithelial cells, but not that from arg-ii-/- cells, activates fibroblasts to produce various cytokines including TGF-β1 and collagen, which is abolished by IL-1β receptor antagonist or TGF-β type I receptor blocker. Conversely, TGF-β1 or IL-1β also increases Arg-II expression. In the mouse models, we confirmed the age-associated increase in IL-1β and TGF-β1 in epithelial cells and activation of fibroblasts, which is inhibited in arg-ii-/- mice. Taken together, our study demonstrates a critical role of epithelial Arg-II in activation of pulmonary fibroblasts via paracrine release of IL-1β and TGF-β1, contributing to pulmonary inflammaging and fibrosis. The results provide a novel mechanistic insight in the role of Arg-II in pulmonary aging.
Project description:With the coming of the "silver tsunami," expanding the knowledge about how various intrinsic and extrinsic factors affect the immune system in the elderly is timely and of immediate clinical need. The global population is increasing in age. By the year 2030, more than 20% of the population of the United States will be older than 65 years of age. This article focuses on how advanced age alters the immune systems and how this, in turn, modulates the ability of the aging lung to deal with infectious challenges from the outside world and from within the host.
Project description:Increasing evidence highlights that senescence plays an important role in idiopathic pulmonary fibrosis (IPF). This study delineates the specific contribution of mitochondria and the superoxide they form to the senescent phenotype of lung fibroblasts from IPF patients (IPF-LFs). Primary cultures of IPF-LFs exhibited an intensified DNA damage response (DDR) and were more senescent than age-matched fibroblasts from control donors (Ctrl-LFs). Furthermore, IPF-LFs exhibited mitochondrial dysfunction, exemplified by increases in mitochondrial superoxide, DNA, stress and activation of mTORC1. The DNA damaging agent etoposide elicited a DDR and augmented senescence in Ctrl-LFs, which were accompanied by disturbances in mitochondrial homoeostasis including heightened superoxide production. However, etoposide had no effect on IPF-LFs. Mitochondrial perturbation by rotenone involving sharp increases in superoxide production also evoked a DDR and senescence in Ctrl-LFs, but not IPF-LFs. Inhibition of mTORC1, antioxidant treatment and a mitochondrial targeting antioxidant decelerated IPF-LF senescence and/or attenuated pharmacologically induced Ctrl-LF senescence. In conclusion, increased superoxide production by dysfunctional mitochondria reinforces lung fibroblast senescence via prolongation of the DDR. As part of an auto-amplifying loop, mTORC1 is activated, altering mitochondrial homoeostasis and increasing superoxide production. Deeper understanding the mechanisms by which mitochondria contribute to fibroblast senescence in IPF has potentially important therapeutic implications.
Project description:The pathogenesis and development of chronic obstructive pulmonary disease (COPD) are significantly related to cellular senescence. Strategies to eliminate senescent cells have been confirmed to benefit several senescence-related diseases. However, there are few reports of senolytic drugs in COPD management. In this study, we demonstrated elevated FOXO4 expression in cigarette smoke-induced senescent lung fibroblasts both in vitro and in vivo. Additionally, self-assembled DNA nanotubes loaded with single-stranded FOXO4 siRNA (siFOXO4-NT) were designed and synthesized to knockdown FOXO4 in senescent fibroblasts. We found that siFOXO4-NT can concentration- and time-dependently enter human lung fibroblasts (HFL-1 cells), thereby reducing FOXO4 levels in vitro. Most importantly, siFOXO4-NT selectively cleared senescent HFL-1 cells by reducing BCLXL expression and the BCL2/BAX ratio, which were increased in CSE-induced senescent HFL-1 cells. The findings from our work present a novel strategy for senolytic drug development for COPD therapy.