Disruption of p21 attenuates lung inflammation induced by cigarette smoke, LPS, and fMLP in mice

Research Progress on Micro (Nano)Plastics Exposure-Induced miRNA-Mediated Biotoxicity

Micro- and nano-plastics (MNPs) are ubiquitously distributed in the environment, infiltrate organisms through multiple pathways, and accumulate, thus posing potential threats to human health. MNP exposure elicits changes in microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), thereby precipitating immune, neurological, and other toxic effects. The investigation of MNP exposure and its effect on miRNA expression has garnered increasing attention. Following MNP exposure, circRNAs serve as miRNA sponges by modulating gene expression, while lncRNAs function as competing endogenous RNAs (ceRNAs) by fine-tuning target gene expression and consequently impacting protein translation and physiological processes in cells. Dysregulated miRNA expression mediates mitochondrial dysfunction, inflammation, and oxidative stress, thereby increasing the risk of neurodegenerative diseases, cardiovascular diseases, and cancer. This tract, blood, urine, feces, placenta, and review delves into the biotoxicity arising from dysregulated miRNA expression due to MNP exposure and addresses the challenges encountered in this field. This study provides novel insights into the connections between MNPs and disease risk.

The role of FPR2-mediated ferroptosis in formyl peptide-induced acute lung injury against endothelial barrier damage and protective effect of the mitochondria-derived peptide MOTS-c

BACKGROUND

Acute lung injury (ALI) has garnered significant attention in the field of respiratory and critical care due to its high mortality and morbidity, and limited treatment options. The role of the endothelial barrier in the development of ALI is crucial. Several bacterial pathogenic factors, including the bacteria-derived formyl peptide (fMLP), have been implicated in damaging the endothelial barrier and initiating ALI. However, the mechanism by which fMLP causes ALI remains unclear. In this study, we aim to explore the mechanisms of ALI caused by fMLP and evaluate the protective effects of MOTS-c, a mitochondrial-derived peptide.

METHODS

We established a rat model of ALI and a human pulmonary microvascular endothelial cell (HPMVEC) model of ALI by treatment with fMLP. In vivo experiments involved lung histopathology assays, assessments of inflammatory and oxidative stress factors, and measurements of ferroptosis-related proteins and barrier proteins to evaluate the severity of fMLP-induced ALI and the type of tissue damage in rats. In vitro experiments included evaluations of fMLP-induced damage on HPMVEC using cell activity assays, assessments of inflammatory and oxidative stress factors, measurements of ferroptosis-related proteins, endothelial barrier function assays, and examination of the key role of FPR2 in fMLP-induced ALI. We also assessed the protective effect of MOTS-c and investigated its mechanism on the fMLP-induced ALI in vivo and in vitro.

RESULTS

Results from both in vitro and in vivo experiments demonstrate that fMLP promotes the expression of inflammatory and oxidative stress factors, activates ferroptosis and disrupts the vascular endothelial barrier, ultimately contributing to the development and progression of ALI. Mechanistically, ferroptosis mediated by FPR2 plays a key role in fMLP-induced injury, and the Nrf2 and MAPK pathways are involved in this process. Knockdown of FPR2 and inhibition of ferroptosis can attenuate ALI induced by fMLP. Moreover, MOTS-c could protect the vascular endothelial barrier function by inhibiting ferroptosis and suppressing the expression of inflammatory and oxidative stress factors through Nrf2 and MAPK pathways, thereby alleviating fMLP-induced ALI.

CONCLUSION

Overall, fMLP disrupts the vascular endothelial barrier through FPR2-mediated ferroptosis, leading to the development and progression of ALI. MOTS-c demonstrates potential as a protective treatment against ALI by alleviating the damage induced by fMLP.

A novel role for the ROS-ATM-Chk2 axis mediated metabolic and cell cycle reprogramming in the M1 macrophage polarization

Reactive oxygen species (ROS) play a pivotal role in macrophage-mediated acute inflammation. However, the precise molecular mechanism by which ROS regulate macrophage polarization remains unclear. Here, we show that ROS function as signaling molecules that regulate M1 macrophage polarization through ataxia-telangiectasia mutated (ATM) and cell cycle checkpoint kinase 2 (Chk2), vital effector kinases in the DNA damage response (DDR) signaling pathway. We further demonstrate that Chk2 phosphorylates PKM2 at the T95 and T195 sites, promoting glycolysis and facilitating macrophage M1 polarization. In addition, Chk2 activation increases the Chk2-dependent expression of p21, inducing cell cycle arrest for subsequent macrophage M1 polarization. Finally, Chk2-deficient mice infected with lipopolysaccharides (LPS) display a significant decrease in lung inflammation and M1 macrophage counts. Taken together, these results suggest that inhibiting the ROS-Chk2 axis can prevent the excessive inflammatory activation of macrophages, and this pathway can be targeted to develop a novel therapy for inflammation-associated diseases and expand our understanding of the pathophysiological functions of DDR in innate immunity.

Club cell-specific telomere protection protein 1 (TPP1) protects against tobacco smoke-induced lung inflammation, xenobiotic metabolic dysregulation, and injurious responses

Inhaling xenobiotics, such as tobacco smoke is a major risk factor for pulmonary diseases, e.g., COPD/emphysema, interstitial lung disease, and pre-invasive diseases. Shelterin complex or telosome provides telomeric end protection during replication. Telomere protection protein 1 (TPP1) is one of the main six subunits of the shelterin complex supporting the telomere stability and genomic integrity. Dysfunctional telomeres and shelterin complex are associated as a disease mechanism of tobacco smoke-induced pulmonary damage and disease processes. The airway epithelium is critical to maintaining respiratory homeostasis and is implicated in lung diseases. Club cells (also known as clara cells) play an essential role in the immune response, surfactant production, and metabolism. Disrupted shelterin complex may lead to dysregulated cellular function, DNA damage, and disease progression. However, it is unknown if the conditional removal of TPP1 from Club cells can induce lung disease pathogenesis caused by tobacco smoke exposure. In this study, conditional knockout of Club-cell specific TPP1 demonstrated the instability of other shelterin protein subunits, such as TRF1, dysregulation of cell cycle checkpoint proteins, p53 and downstream targets, and dysregulation of telomeric genes. This was associated with age-dependent senescence-associated genes, increased DNA damage, and upregulated RANTES/IL13/IL33 mediated lung inflammation and injury network by cigarette smoke (CS). These phenomena are also associated with alterations in cytochrome P450 and glutathione transferases, upregulated molecular pathways promoting lung lesions, bronchial neoplasms, and adenocarcinomas. These findings suggest a pivotal role of TPP1 in maintaining lung homeostasis and injurious responses in response to CS. Thus, these data TPP1 may have therapeutic value in alleviating telomere-related chronic lung diseases.

FOXO3 Activation Prevents Cellular Senescence in Emphysema Induced by Cigarette Smoke

Because cigarette smoke can induce COPD/emphysema through accelerating senescence with or without an incomplete repair system. However, the pathogenesis of COPD following lung senescence induced by CS is not fully understood. Airspace enlargement and airway epithelial cell senescence are common finding during the COPD development. We investigated the lung tress response to CS and demonstrated that a stress-responsive transcription factor, FOXO3, was regulated by deacetylase. SIRT1 inhibited FOXO3 acetylation and FOXO3 degradation, leading to FOXO3 accumulation and activation in airway epithelial cells. CS exposure activated SIRT1 contributed to FOXO3 activation and functioned to protect lungs, as deletion of SIRT1 decreased CS-induced FOXO3 activation and resulted in more severe airway epithelial cells senescence airspace enlargement. Strikingly, deletion of FOXO3 during the development of COPD aggravated lung structural and functional damage, leading to a much more profound COPD phenotype. We show that deletion of FOXO3 resulted in decreased autophagic response and increased senescence, which may explain lung protection by FOXO3. Our study indicates that in the COPD, stress-responsive transcription factors can be activated for adaptions to counteract senescence insults, thus attenuating COPD development.

Mitochondrial damage-associated molecular patterns in chronic obstructive pulmonary disease: Pathogenetic mechanism and therapeutic target

Chronic obstructive pulmonary disease (COPD) is a common inflammatory airway disease characterized by enhanced inflammation. Recent studies suggest that mitochondrial damage-associated molecular patterns (DAMPs) may play an important role in the regulation of inflammation and are involved in a serial of inflammatory diseases, and they may also be involved in COPD. This review highlights the potential role of mitochondrial DAMPs during COPD pathogenesis and discusses the therapeutic potential of targeting mitochondrial DAMPs and their related signaling pathways and receptors for COPD. Research progress on mitochondrial DAMPs may enhance our understanding of COPD inflammation and provide novel therapeutic targets.

Identification and Validation of an Aging-Associated circRNA-miRNA-mRNA Network in Neovascular Age-Related Macular Degeneration

INTRODUCTION

Neovascular age-related macular degeneration (NVAMD) is a leading cause of severe vision impairment in the elderly. Aging is one of the most pivotal underlying molecular mechanisms of NVAMD.

METHODS

In this study, we identified the potential aging-related genes involved in NVAMD. Considering that noncoding RNAs are vital regulators of NVAMD progression, we further explored and constructed an aging-originated circRNA-miRNA-mRNA network of NVAMD. Differential expression of 23 aging-associated genes was identified based on sequencing data and the Human Aging Genomic Resources tool at a threshold of p < 0.05, and log2|fold change| > 1.

RESULTS

We screened 12 microRNAs (miRNAs) using public datasets and miRNet database. A total of 13 circRNAs were subsequently mined using the starBase tool. Merging these 13 circRNAs, 12 miRNAs, and 15 genes together, we obtained 281 pairs of circRNA-miRNA and 30 pairs of miRNA-mRNA.

CONCLUSION

We created an aging-related circRNA-miRNA-mRNA network, which could be a promising target for future AMD treatments.

Stromal and therapy-induced macrophage proliferation promotes PDAC progression and susceptibility to innate immunotherapy

Tumor-associated macrophages (TAMs) are abundant in pancreatic ductal adenocarcinomas (PDACs). While TAMs are known to proliferate in cancer tissues, the impact of this on macrophage phenotype and disease progression is poorly understood. We showed that in PDAC, proliferation of TAMs could be driven by colony stimulating factor-1 (CSF1) produced by cancer-associated fibroblasts. CSF1 induced high levels of p21 in macrophages, which regulated both TAM proliferation and phenotype. TAMs in human and mouse PDACs with high levels of p21 had more inflammatory and immunosuppressive phenotypes. p21 expression in TAMs was induced by both stromal interaction and/or chemotherapy treatment. Finally, by modeling p21 expression levels in TAMs, we found that p21-driven macrophage immunosuppression in vivo drove tumor progression. Serendipitously, the same p21-driven pathways that drive tumor progression also drove response to CD40 agonist. These data suggest that stromal or therapy-induced regulation of cell cycle machinery can regulate both macrophage-mediated immune suppression and susceptibility to innate immunotherapy.

p21 facilitates chronic lung inflammation via epithelial and endothelial cells

Cellular senescence is a stable state of cell cycle arrest that regulates tissue integrity and protects the organism from tumorigenesis. However, the accumulation of senescent cells during aging contributes to age-related pathologies. One such pathology is chronic lung inflammation. p21 (CDKN1A) regulates cellular senescence via inhibition of cyclin-dependent kinases (CDKs). However, its role in chronic lung inflammation and functional impact on chronic lung disease, where senescent cells accumulate, is less understood. To elucidate the role of p21 in chronic lung inflammation, we subjected p21 knockout (p21-/-) mice to repetitive inhalations of lipopolysaccharide (LPS), an exposure that leads to chronic bronchitis and accumulation of senescent cells. p21 knockout led to a reduced presence of senescent cells, alleviated the pathological manifestations of chronic lung inflammation, and improved the fitness of the mice. The expression profiling of the lung cells revealed that resident epithelial and endothelial cells, but not immune cells, play a significant role in mediating the p21-dependent inflammatory response following chronic LPS exposure. Our results implicate p21 as a critical regulator of chronic bronchitis and a driver of chronic airway inflammation and lung destruction.

Loss of p16 does not protect against premature ovarian insufficiency caused by alkylating agents

BACKGROUND

Chemical agents such as alkylating agents (AAs) that are commonly used for the treatment of cancer cause great damage to the ovaries, thereby significantly increasing the risk of premature ovarian insufficiency (POI). However, the exact molecules underlying AA-induced POI remain largely obscure. Upregulation of the p16 gene may contribute to the progression of POI. As yet, no in vivo data from p16-deficient (KO) mice are available to demonstrate a critical role of p16 in POI. In the present study, we employed p16 KO mice to investigate whether loss of p16 could protect against POI caused by AAs.

METHODS

WT mice and their p16 KO littermates received a single dose of BUL + CTX to establish an AA-induced POI mouse model. One month later, oestrous cycles were monitored. Three months later, some of the mice were sacrificed to collect sera for measurements of hormone levels and ovaries for measurements of follicle counts, the proliferation and apoptosis of granulosa cells, ovarian stromal fibrosis and vessels. The remaining mice were mated with fertile males for the fertility test.

RESULTS

Our results showed that treatment with BUL + CTX significantly disrupted the oestrous cycles, increased the levels of FSH and LH while decreasing the levels of E2 and AMH, decreased the counts of primordial follicles and growing follicles while increasing the counts of atretic follicles, reduced the vascularized area in the ovarian stroma, and decreased fertility. All of these results were comparable between WT and p16 KO mice treated with BUL + CTX. In addition, ovarian fibrosis was not increased significantly in WT and p16 KO mice treated with BUL + CTX. Growing follicles with normal appearance had normally proliferating granulosa cells (without apparent apoptosis).

CONCLUSION

We concluded that genetic ablation of the p16 gene did not attenuate ovarian damage or help preserve the fertility of mice challenged by AAs. This study demonstrated for the first time that p16 is dispensable for AA-induced POI. Our preliminary findings suggest that targeting p16 alone may not preserve the ovarian reserve and fertility of females treated with AAs.

Weighted gene co-expression identification of CDKN1A as a hub inflammation gene following cardiopulmonary bypass in children with congenital heart disease

Background

Congenital heart disease (CHD) is the most common type of birth defect. Most patients with CHD require surgery, and cardiopulmonary bypass (CPB) is the most common surgery performed.

Methods

The present study utilized weighted gene co-expression network analysis (WGCNA) to identify key inflammation genes after CPB for CHD. The GSE132176 dataset was downloaded from the Gene Expression Omnibus(GEO) database for WGCNA to identify the modules closely related to clinical traits. Disease enrichment, functional annotation and pathway enrichment were performed on genes in the module closely related to clinical traits using Enrichr and Metascape. Immune infiltration analysis was also performed on the training dataset using CIBERSORT. Finally, we identified hub genes using high gene significance (GS), high module members (MMs) and Cytoscape, and we verified the hub genes using an independent dataset and Western blot analysis.

Results

WGCNA showed that the brown module with 461 genes had the highest correlation to CHD after CPB. Functional annotation and pathway enrichment analysis were performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, which showed that genes in the brown module were enriched in inflammation-related pathways. In the disease enrichment analysis, genes in the brown module were enriched for inflammatory diseases. After the 30 most highly associated brown intramodular genes were screened, a protein-protein interaction network was constructed using the STRING online analysis website. The protein-protein interaction results were then calculated using 12 algorithms in the cytoHubba plugin of Cytoscape software. The final result showed that CDKN1A was the fundamental gene of post-CPB for CHD. Using another independent validation dataset (GSE12486), we confirmed that CDKN1A was significantly differentially expressed between preoperative and postoperative CPB (Wilcoxon, P = 0.0079; T-test, P = 0.006). In addition, CDKN1A expression was elevated in eosinophils, neutrophils, memory CD4 T cells and activated mast cells. Western blot analysis showed that the expression of CDKN1A protein was significantly higher postoperative CPB than preoperative CPB. Moreover, CDKN1A was mainly related to inflammation.

Conclusion

In summary, we found a relationship between CDKN1A and inflammation after CPB for congenital heart disease by WGCNA, experiments and various bioinformatics methods. Thus, CDKN1A maybe serve as a biomarker or therapeutic target for accurate diagnosis and treatment of inflammation after CPB in the future.

Revealing the pathogenic and ageing-related mechanisms of the enigmatic idiopathic pulmonary fibrosis (and chronic obstructive pulmonary disease)

PURPOSE OF REVIEW

Growing evidence suggests that ageing-associated alterations occur in both idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD). Here, we review the most recent literature on dysregulated ageing pathways in IPF and COPD and discuss how they may contribute to disease pathogenesis.

RECENT FINDINGS

Recent studies have shown that alveolar epithelial type II (ATII) cells undergo premature senescence under stress and that senescent ATII cells promote lung fibrogenesis. Some studies have explored the role of mitochondrial dysfunction in IPF. They have provided evidence that dysfunctional mitochondria are important contributors to fibrogenesis through release of damaged DNA and excessive formation of reactive oxygen species, whereas restoration of mitochondrial homeostasis may attenuate lung fibrosis. Insufficient autophagy has been shown to promote epithelial-to-mesenchymal transition and aberrant epithelial-fibroblast crosstalk, suggesting that autophagy augmentation may represent a potential therapeutic strategy. A number of studies have also explored the role of cellular senescence, mitochondrial homeostasis and autophagy in COPD.

SUMMARY

Several ageing mechanisms are dysregulated in the lungs of patients with IPF and COPD, although how they contribute to disease development and progression remains elusive. Genetic or pharmacologic attenuation of senescence-related pathways and elimination of senescent cells may represent a promising therapeutic strategy.

Senescence: Pathogenic Driver in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is recognized as a disease of accelerated lung aging. Over the past two decades, mounting evidence suggests an accumulation of senescent cells within the lungs of patients with COPD that contributes to dysregulated tissue repair and the secretion of multiple inflammatory proteins, termed the senescence-associated secretory phenotype (SASP). Cellular senescence in COPD is linked to telomere dysfunction, DNA damage, and oxidative stress. This review gives an overview of the mechanistic contributions and pathologic consequences of cellular senescence in COPD and discusses potential therapeutic approaches targeting senescence-associated signaling in COPD.

Identification and validation of aging-related genes in COPD based on bioinformatics analysis

Chronic obstructive pulmonary disease (COPD) is a serious chronic respiratory disorder. One of the major risk factors for COPD progression is aging. Therefore, we investigated aging-related genes in COPD using bioinformatic analyses. Firstly, the Aging Atlas database containing 500 aging-related genes and the Gene Expression Omnibus database (GSE38974) were utilized to screen candidates. A total of 24 candidate genes were identified related to both COPD and aging. Using gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses, we found that this list of 24 genes was enriched in genes associated with cytokine activity, cell apoptosis, NF-κB and IL-17 signaling. Four of these genes (CDKN1A, HIF1A, MXD1 and SOD2) were determined to be significantly upregulated in clinical COPD samples and in cigarette smoke extract-exposed Beas-2B cells in vitro, and their expression was negatively correlated with predicted forced expiratory volume and forced vital capacity. In addition, the combination of expression levels of these four genes had a good discriminative ability for COPD patients (AUC = 0.794, 95% CI 0.743-0.845). All four were identified as target genes of hsa-miR-519d-3p, which was significantly down-regulated in COPD patients. The results from this study proposed that regulatory network of hsa-miR-519d-3p/CDKN1A, HIF1A, MXD1, and SOD2 closely associated with the progression of COPD, which provides a theoretical basis to link aging effectors with COPD progression, and may suggest new diagnostic and therapeutic targets of this disease.

Involvement of miRNA-34a regulated Krüppel-like factor 4 expression in hyperoxia-induced senescence in lung epithelial cells

BACKGROUND

Premature infants, subjected to supplemental oxygen and mechanical ventilation, may develop bronchopulmonary dysplasia, a chronic lung disease characterized by alveolar dysplasia and impaired vascularization. We and others have shown that hyperoxia causes senescence in cultured lung epithelial cells and fibroblasts. Although miR-34a modulates senescence, it is unclear whether it contributes to hyperoxia-induced senescence. We hypothesized that hyperoxia increases miR-34a levels, leading to cellular senescence.

METHODS

We exposed mouse lung epithelial (MLE-12) cells and primary human small airway epithelial cells to hyperoxia (95% O₂/5% CO₂) or air (21% O₂/5% CO₂) for 24 h. Newborn mice (< 12 h old) were exposed to hyperoxia (> 95% O₂) for 3 days and allowed to recover in room air until postnatal day 7. Lung samples from premature human infants requiring mechanical ventilation and control subjects who were not mechanically ventilated were employed.

RESULTS

Hyperoxia caused senescence as indicated by loss of nuclear lamin B1, increased p21 gene expression, and senescence-associated secretory phenotype factors. Expression of miR-34a-5p was increased in epithelial cells and newborn mice exposed to hyperoxia, and in premature infants requiring mechanical ventilation. Transfection with a miR-34a-5p inhibitor reduced hyperoxia-induced senescence in MLE-12 cells. Additionally, hyperoxia increased protein levels of the oncogene and tumor-suppressor Krüppel-like factor 4 (KLF4), which were inhibited by a miR-34a-5p inhibitor. Furthermore, KLF4 knockdown by siRNA transfection reduced hyperoxia-induced senescence.

CONCLUSION

Hyperoxia increases miR-34a-5p, leading to senescence in lung epithelial cells. This is dictated in part by upregulation of KLF4 signaling. Therefore, inhibiting hyperoxia-induced senescence via miR-34a-5p or KLF4 suppression may provide a novel therapeutic strategy to mitigate the detrimental consequences of hyperoxia in the neonatal lung.

Non-coding RNAs as Regulators of Cellular Senescence in Idiopathic Pulmonary Fibrosis and Chronic Obstructive Pulmonary Disease

Cellular senescence is a cell fate implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD). Cellular senescence occurs in response to cellular stressors such as oxidative stress, DNA damage, telomere shortening, and mitochondrial dysfunction. Whether these stresses induce cellular senescence or an alternative cell fate depends on the type and magnitude of cellular stress, but also on intrinsic factors regulating the cellular stress response. Non-coding RNAs, including both microRNAs and long non-coding RNAs, are key regulators of cellular stress responses and susceptibility to cellular senescence. In this review, we will discuss cellular mechanisms that contribute to senescence in IPF and COPD and highlight recent advances in our understanding of how these processes are influenced by non-coding RNAs. We will also discuss the potential therapeutic role for targeting non-coding RNAs to treat these chronic lung diseases.

Age-Dependent Assessment of Genes Involved in Cellular Senescence, Telomere, and Mitochondrial Pathways in Human Lung Tissue of Smokers, COPD, and IPF: Associations With SARS-CoV-2 COVID-19 ACE2-TMPRSS2-Furin-DPP4 Axis

BACKGROUND

Aging is one of the key contributing factors for chronic obstructive pulmonary diseases (COPD) and other chronic inflammatory lung diseases. Here, we determined how aging contributes to the altered gene expression related to mitochondrial function, cellular senescence, and telomeric length processes that play an important role in the progression of COPD and idiopathic pulmonary fibrosis (IPF).

METHODS

Total RNA from the human lung tissues of non-smokers, smokers, and patients with COPD and IPF were processed and analyzed using a Nanostring platform based on their ages (younger: <55 years and older: >55 years).

RESULTS

Several genes were differentially expressed in younger and older smokers, and patients with COPD and IPF compared to non-smokers which were part of the mitochondrial biogenesis/function (HSPD1, FEN1, COX18, COX10, UCP2 & 3), cellular senescence (PCNA, PTEN, KLOTHO, CDKN1C, TNKS2, NFATC1 & 2, GADD45A), and telomere replication/maintenance (PARP1, SIRT6, NBN, TERT, RAD17, SLX4, HAT1) target genes. Interestingly, NOX4 and TNKS2 were increased in the young IPF as compared to the young COPD patients. Genes in the mitochondrial dynamics and quality control mechanisms like FIS1 and RHOT2 were decreased in young IPF compared to their age matched COPD subjects. ERCC1 and GADD45B were higher in young COPD as compared to IPF. Aging plays an important role in various infectious diseases including the SARS-CoV-2 infection. Lung immunoblot analysis of smokers, COPD and IPF subjects revealed increased abundance of proteases and receptor/spike protein like TMPRSS2, furin, and DPP4 in association with a slight increase in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor ACE2 levels.

CONCLUSIONS

Overall, these findings suggest that altered transcription of target genes that regulate mitochondrial function, cellular senescence, and telomere attrition in the pathobiology of lung aging in COPD and IPF is associated with alterations in SARS-CoV-2 ACE2-TMPRSS2-Furin-DPP4 axis as pharmacological targets for COVID-19.

Age-dependent assessment of genes involved in cellular senescence, telomere and mitochondrial pathways in human lung tissue of smokers, COPD and IPF: Associations with SARS-CoV-2 COVID-19 ACE2-TMPRSS2-Furin-DPP4 axis

Aging is one of the key contributing factors for chronic obstructive pulmonary diseases (COPD) and other chronic inflammatory lung diseases. Cigarette smoke is a major etiological risk factor that has been shown to alter cellular processes involving mitochondrial function, cellular senescence and telomeric length. Here we determined how aging contribute to the alteration in the gene expression of above mentioned cellular processes that play an important role in the progression of COPD and IPF. We hypothesized that aging may differentially alter the expression of mitochondrial, cellular senescence and telomere genes in smokers and patients with COPD and IPF compared to non-smokers. Total RNA from human lung tissues from non-smokers, smokers, and patients with COPD and IPF were processed and analyzed based on their ages (younger: <55 yrs and older: >55 yrs). NanoString nCounter panel was used to analyze the gene expression profiles using a custom designed codeset containing 112 genes including 6 housekeeping controls (mitochondrial biogenesis and function, cellular senescence, telomere replication and maintenance). mRNA counts were normalized, log2 transformed for differential expression analysis using linear models in the limma package (R/Bioconductor). Data from non-smokers, smokers and patients with COPD and IPF were analyzed based on the age groups (pairwise comparisons between younger vs. older groups). Several genes were differentially expressed in younger and older smokers, and patients with COPD and IPF compared to non-smokers which were part of the mitochondrial biogenesis/function (HSPD1, FEN1, COX18, COX10, UCP2 & 3), cellular senescence (PCNA, PTEN, KLOTHO, CDKN1C, TNKS2, NFATC1 & 2, GADD45A) and telomere replication/maintenance (PARP1, SIRT6, NBN, TERT, RAD17, SLX4, HAT1) target genes. Interestingly, NOX4 and TNKS2 were increased in the young IPF as compared to the young COPD patients. Genes in the mitochondrial dynamics and other quality control mechanisms like FIS1 and RHOT2 were decreased in young IPF compared to their age matched COPD subjects. ERCC1 (Excision Repair Cross-Complementation Group 1) and GADD45B were higher in young COPD as compared to IPF. Aging plays an important role in various infectious diseases. Elderly patients with chronic lung disease and smokers were found to have high incidence and mortality rates in the current pandemic of SARS-CoV-2 infection. Immunoblot analysis in the lung homogenates of smokers, COPD and IPF subjects revealed increased protein abundance of important proteases and spike proteins like TMPRSS2, furin and DPP4 in association with a slight increase in SARS-CoV-2 receptor ACE2 levels. This may further strengthen the observation that smokers, COPD and IPF subjects are more prone to COVID-19 infection. Overall, these findings suggest that altered transcription of target genes that regulate mitochondrial function, cellular senescence, and telomere attrition add to the pathobiology of lung aging in COPD and IPF and other smoking-related chronic lung disease in associated with alterations in SARS-CoV-2 ACE2-TMPRSS2-Furin-DPP4 axis for COVID-19 infection.

Age-dependent assessment of genes involved in cellular senescence, telomere and mitochondrial pathways in human lung tissue of smokers, COPD and IPF: Associations with SARS-CoV-2 COVID-19 ACE2-TMPRSS2-Furin-DPP4 axis

Aging is one of the key contributing factors for chronic obstructive pulmonary diseases (COPD) and other chronic inflammatory lung diseases. Cigarette smoke is a major etiological risk factor that has been shown to alter cellular processes involving mitochondrial function, cellular senescence and telomeric length. Here we determined how aging contribute to the alteration in the gene expression of above mentioned cellular processes that play an important role in the progression of COPD and IPF. We hypothesized that aging may differentially alter the expression of mitochondrial, cellular senescence and telomere genes in smokers and patients with COPD and IPF compared to non-smokers. Total RNA from human lung tissues from non-smokers, smokers, and patients with COPD and IPF were processed and analyzed based on their ages (younger: <55 yrs and older: >55 yrs). NanoString nCounter panel was used to analyze the gene expression profiles using a custom designed codeset containing 112 genes including 6 housekeeping controls (mitochondrial biogenesis and function, cellular senescence, telomere replication and maintenance). mRNA counts were normalized, log2 transformed for differential expression analysis using linear models in the limma package (R/Bioconductor). Data from non-smokers, smokers and patients with COPD and IPF were analyzed based on the age groups (pairwise comparisons between younger vs. older groups). Several genes were differentially expressed in younger and older smokers, and patients with COPD and IPF compared to non-smokers which were part of the mitochondrial biogenesis/function (HSPD1, FEN1, COX18, COX10, UCP2 & 3), cellular senescence (PCNA, PTEN, KLOTHO, CDKN1C, TNKS2, NFATC1 & 2, GADD45A) and telomere replication/maintenance (PARP1, SIRT6, NBN, TERT, RAD17, SLX4, HAT1) target genes. Interestingly, NOX4 and TNKS2 were increased in the young IPF as compared to the young COPD patients. Genes in the mitochondrial dynamics and other quality control mechanisms like FIS1 and RHOT2 were decreased in young IPF compared to their age matched COPD subjects. ERCC1 (Excision Repair Cross-Complementation Group 1) and GADD45B were higher in young COPD as compared to IPF. Aging plays an important role in various infectious diseases. Elderly patients with chronic lung disease and smokers were found to have high incidence and mortality rates in the current pandemic of SARS-CoV-2 infection. Immunoblot analysis in the lung homogenates of smokers, COPD and IPF subjects revealed increased protein abundance of important proteases and spike proteins like TMPRSS2, furin and DPP4 in association with a slight increase in SARS-CoV-2 receptor ACE2 levels. This may further strengthen the observation that smokers, COPD and IPF subjects are more prone to COVID-19 infection. Overall, these findings suggest that altered transcription of target genes that regulate mitochondrial function, cellular senescence, and telomere attrition add to the pathobiology of lung aging in COPD and IPF and other smoking-related chronic lung disease in associated with alterations in SARS-CoV-2 ACE2-TMPRSS2-Furin-DPP4 axis for COVID-19 infection.

Innate Immunity and Cell Surface Receptors in the Pathogenesis of COPD: Insights from Mouse Smoking Models

Chronic obstructive pulmonary disease (COPD) is mainly associated with smoking habit. Inflammation is the major initiating process whereby neutrophils and monocytes are attracted into the lung microenvironment by external stimuli present in tobacco leaves and in cigarette smoke, which promote chemotaxis, adhesion, phagocytosis, release of superoxide anions and enzyme granule contents. A minority of smokers develops COPD and different molecular factors, which contribute to the onset of the disease, have been put forward. After many years of research, the pathogenesis of COPD is still an object of debate. In vivo models of cigarette smoke-induced COPD may help to unravel cellular and molecular mechanisms underlying the pathogenesis of COPD. The mouse represents the most favored animal choice with regard to the study of immune mechanisms due to its genetic and physiological similarities to humans, the availability of a large variability of inbred strains, the presence in the species of several genetic disorders analogous to those in man, and finally on the possibility to create models “made-to-measure” by genetic manipulation. The review outlines the different response of mouse strains to cigarette smoke used in COPD studies while retaining a strong focus on their relatability to human patients. These studies reveal the importance of innate immunity and cell surface receptors in the pathogenesis of pulmonary injury induced by cigarette smoking. They further advance the way in which we use wild type or genetically manipulated strains to improve our overall understanding of a multifaceted disease such as COPD. The structural and functional features, which have been found in the different strains of mice after chronic exposure to cigarette smoke, can be used in preclinical studies to develop effective new therapeutic agents for the different phenotypes in human COPD.

The Role of the Cyclin Dependent Kinase Inhibitor p21cip1/waf1 in Targeting Cancer: Molecular Mechanisms and Novel Therapeutics

p21^cip1/waf1 mediates various biological activities by sensing and responding to multiple stimuli, via p53-dependent and independent pathways. p21 is known to act as a tumor suppressor mainly by inhibiting cell cycle progression and allowing DNA repair. Significant advances have been made in elucidating the potential role of p21 in promoting tumorigenesis. Here, we discuss the involvement of p21 in multiple signaling pathways, its dual role in cancer, and the importance of understanding its paradoxical functions for effectively designing therapeutic strategies that could selectively inhibit its oncogenic activities, override resistance to therapy and yet preserve its tumor suppressive functions.

Dysregulated repair and inflammatory responses by e-cigarette-derived inhaled nicotine and humectant propylene glycol in a sex-dependent manner in mouse lung

Nicotine inhalation via electronic cigarettes (e‐cigs) is an emerging concern. However, little is known about the acute toxicity in the lungs following inhalation of nicotine‐containing e‐cig aerosols. We hypothesized that acute exposure to aerosolized nicotine causes lung toxicity by eliciting inflammatory and dysregulated repair responses. Adult C57BL/6J mice were exposed 2 hours daily for 3 days to e‐cig aerosols containing propylene glycol (PG) with or without nicotine. Acute exposure to nicotine‐containing e‐cig aerosols induced inflammatory cell influx (neutrophils and CD8a⁺ T lymphocytes), and release of pro‐inflammatory cytokines in bronchoalveolar lavage fluid in a sex‐dependent manner. Inhalation of e‐cig aerosol containing PG alone significantly augmented the lung levels of various homeostasis/repair mediators (PPARγ, ADRP, ACTA2, CTNNB1, LEF1, β‐catenin, E‐cadherin, and MMP2) in a sex‐dependent manner when compared to air controls. These findings were accompanied by an increase in protein abundance and altered gene expression of lipogenic markers (PPARγ, ADRP) and myogenic markers (fibronectin, α‐smooth muscle actin and β‐catenin), suggesting a dysregulated repair response in mouse lungs. Furthermore, exposure to nicotine‐containing e‐cig aerosols or PG alone differentially affected the release of pro‐inflammatory cytokines in healthy and COPD human 3D EpiAirway tissues. Overall, acute exposure to nicotine‐containing e‐cig aerosols was sufficient to elicit a pro‐inflammatory response and altered mRNA and protein levels of myogenic, lipogenic, and extracellular matrix markers in mouse lung in a sex‐dependent manner. Thus, acute exposure to inhaled nicotine via e‐cig leads to dysregulated repair and inflammatory responses, which may lead to airway remodeling in the lungs.

Cellular senescence in the lung across the age spectrum

Cellular senescence results in cell cycle arrest with secretion of cytokines, chemokines, growth factors, and remodeling proteins (senescence-associated secretory phenotype; SASP) that have autocrine and paracrine effects on the tissue microenvironment. SASP can promote remodeling, inflammation, infectious susceptibility, angiogenesis, and proliferation, while hindering tissue repair and regeneration. While the role of senescence and the contributions of senescent cells are increasingly recognized in the context of aging and a variety of disease states, relatively less is known regarding the portfolio and influences of senescent cells in normal lung growth and aging per se or in the induction or progression of lung diseases across the age spectrum such as bronchopulmonary dysplasia, asthma, chronic obstructive pulmonary disease, or pulmonary fibrosis. In this review, we introduce concepts of cellular senescence, the mechanisms involved in the induction of senescence, and the SASP portfolio that are relevant to lung cells, presenting the potential contribution of senescent cells and SASP to inflammation, hypercontractility, and remodeling/fibrosis: aspects critical to a range of lung diseases. The potential to blunt lung disease by targeting senescent cells using a novel class of drugs (senolytics) is discussed. Potential areas for future research on cellular senescence in the lung are identified.

Development of autoimmune pancreatitis is independent of CDKN1A/p21-mediated pancreatic inflammation

OBJECTIVE

Chronic pancreatitis (CP) and autoimmune pancreatitis (AIP) are characterised by different inflammatory processes. If pancreatic inflammation is a prerequisite for autoimmunity is still unclear. AIP is considered mostly a T cell-mediated disease; however, in induction of CP, macrophages play a pivotal role. p21-a member of cyclin-dependent kinase inhibitors-can influence inflammatory processes, in particular can regulate T cell activation and promote macrophage development. We therefore examined the role of p21-mediated inflammation in AIP.

DESIGN

We intercrossed lymphotoxin (LT) overexpressing mice (Tg(Ela1-LTa,b))-a model to study AIP development-with p21-deficient mice. Furthermore, we characterised p21 expression in human AIP and non-AIP specimens.

RESULTS

p21 deficiency in LT mice (LTp21^-/-) prevented early pancreatic injury and reduced inflammation. In acinar cells, diminished proliferation and abrogated activation of non-canonical nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) pathway was observed. In contrast, 12-month-old LT mice with and without p21 had similar inflammatory signatures and T-B cell infiltration. Interestingly, LT and LTp21^-/- mice had comparable tertiary lymphoid organs (TLOs), autoantibodies and elevated IgG levels. However, acinar cell proliferation, acinar-to-ductal metaplasia and acinar non-canonical NF-κB pathway activation remained impaired in LTp21^-/- pancreata.

CONCLUSIONS

Our findings indicate that p21 is crucial for pancreatic inflammation in LT-driven pancreatic injury. p21 is involved in early acinar secretion of inflammatory mediators that attract innate immune cells. However, p21 is not essential for humoral immune response, accountable for autoimmunity. Remarkably, p21 renders acinar cells less susceptible to proliferation and transdifferentiation. We therefore suggest that AIP can also develop independent of chronic inflammatory processes.

Genetic Ablation of p16INK4a Does Not Protect against Cellular Senescence in Mouse Models of Chronic Obstructive Pulmonary Disease/Emphysema

Cigarette smoke (CS) affects DNA damage and cellular senescence signaling pathways in the pathogenesis of chronic obstructive pulmonary disease (COPD). p16INK4a (p16: a cyclin-dependent kinase inhibitor) is a key marker of cellular senescence, which is induced by CS in lung cells. It is thought that removal of p16 attenuates premature aging by removing senesced cells. However, the role of p16 in CS-induced stress-induced premature senescence (SIPS) and senescence-associated secretory phenotype (SASP) during the development of COPD/emphysema is not known. We hypothesize that p16 regulates cellular senescence and DNA damage/repair molecular signaling targets during chronic CS-induced inflammation and airspace enlargement in mouse models of COPD. We used p16 global knockout (KO) and p16 lung epithelial cell-specific KO (p16CreCC10) mice to determine whether p16 removal in lung epithelium augments or protects against cellular senescence (SIPS and SASP) in chronic CS- and elastase-induced development of COPD/emphysema in mice. p16 KO mice exposed to chronic CS and p16 lung epithelial cell-specific KO mice exposed to elastase did not show attenuation of lung inflammation, altered lung function, or airspace enlargement. p16 KO and p16CreCC10 exposed to CS and elastase showed increases in lung senescence-associated β-galactosidase activity. Thus, removal of p16-positive cells did not protect against airspace enlargement and decline in lung function induced in COPD mouse models. Our findings suggest that p16 is not the only key player associated with CS-induced cellular senescence phenotypes (SIPS and SASP), decline in lung function, and airspace enlargement in COPD/emphysema.

Nrf2 attenuates inflammatory response in COPD/emphysema: Crosstalk with Wnt3a/β-catenin and AMPK pathways

Chronic obstructive pulmonary disease (COPD) is characterized by persistent airflow limitation and abnormal inflammatory response. Wnt/β-catenin and AMP-activated protein kinase (AMPK) have been shown to modulate lung inflammatory responses and injury. However, it remains elusive whether Wnt/β-catenin and AMPK modulate nuclear factor erythroid-2 related factor-2 (Nrf2)-mediated protective responses during the development of emphysema. Here we showed that treatment with a Wnt pathway activator (LiCl) reduced elastase-induced airspace enlargement and cigarette smoke extract (CSE)-induced lung inflammatory responses in WT mice, which was associated with increased activation of Nrf2 pathway. Interestingly, these effects of LiCl were not observed in Nrf2^-/- mice exposed to elastase. In normal human bronchial epithelial (NHBE) cells, Wnt3a overexpression up-regulated, whereas Wnt3a knockdown further down-regulated the levels of Nrf2 and its target proteins heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1) by CSE treatment. In contrast, Nrf2 deficiency did not have any effects on Wnt/β-catenin pathway in mouse lungs and NHBE cells. Both elastase and CSE exposures reduced AMPK phosphorylation. A specific AMPK activator metformin increased Wnt3a, β-catenin, Nrf2 phosphorylation and activation but reduced the levels of IL-6 and IL-8 in NHBE cells and mouse lungs exposed to CSE. Furthermore, Nrf2 deficiency abolished the protection of metformin against CSE-induced increase in IL-6 and IL-8 in NHBE cells. In conclusion, Nrf2 mediates the protective effects of both Wnt3a/β-catenin and AMPK on lung inflammatory responses during the development of COPD/emphysema. These findings provide potential therapeutic targets for the intervention of COPD/emphysema.

Genetic ablation of histone deacetylase 2 leads to lung cellular senescence and lymphoid follicle formation in COPD/emphysema

Histone deacetylase 2 (HDAC2), a critical determinant of chromatin remodeling, is reduced as a consequence of oxidative stress-mediated DNA damage and impaired repair. Cigarette smoke (CS) exposure causes DNA damage and cellular senescence. However, no information is available on the role of HDAC2 in CS-induced DNA damage, stress-induced premature senescence (SIPS), and senescence-associated secretory phenotype (SASP) during the pathogenesis of chronic obstructive pulmonary disease (COPD)/emphysema. We hypothesized that CS causes persistent DNA damage and cellular senescence via HDAC2-dependent mechanisms. We used HDAC2 global knockout (KO) and HDAC2 lung epithelial cell-specific KO [Clara cell-specific HDAC2 deletion (HDAC2 CreCC10)] mice to determine whether HDAC2 is a major player in CS-induced oxidative stress, SIPS, and SASP. HDAC2 KO mice exposed to CS show exaggerated DNA damage, inflammatory response, and decline in lung function leading to airspace enlargement. Chronic CS exposure augments lung senescence-associated β-galactosidase activity in HDAC2 KO, but not in HDAC2 CreCC10 mice. HDAC2 lung epithelial cell-specific KO did not further augment CS-induced inflammatory response and airspace enlargement but instead caused an increase in lymphoid aggregate formation. Our study reveals that HDAC2 is a key player regulating CS-induced DNA damage, inflammatory response, and cellular senescence leading to COPD/emphysema.-Sundar, I. K., Rashid, K., Gerloff, J., Rangel-Moreno, J., Li, D., Rahman, I. Genetic ablation of histone deacetylase 2 leads to lung cellular senescence and lymphoid follicle formation in COPD/emphysema.

4-Hydroxycinnamic acid protects mice from cigarette smoke-induced pulmonary inflammation via MAPK pathways

Cigarette smoke (CS) is the main etiological cause of chronic obstructive pulmonary disease, the prevalence of which has continuously increased in recent years. 4-Hydroxycinnamic acid (HA) is a plant phenolic acid that has anti-inflammatory activities. In this study, we explored the therapeutic effects of HA on airway inflammation caused by CS and lipopolysaccharide (LPS) in mice. The animals received 1 h of CS exposure for 7 days and intranasal instillation of LPS on day 4. HA (10 and 20 mg/kg) was administered to animals via oral gavage 1 h before CS exposure. HA treatment significantly decreased the accumulation of inflammatory cells and production of cytokines, including tumor necrosis factor-α, interleukin (IL)-6, and IL-1β, caused by CS and LPS exposure. After histological examination, we observed that HA treatment significantly reduced the infiltration of inflammatory cells into lung tissue caused by CS and LPS exposure. Furthermore, HA-treated groups showed significantly decreased phosphorylation of extracellular signal-regulated kinase, c-Jun N-terminal kinase, p38, and nuclear factor-κB, and activity of cytochrome c oxidase subunit-2 caused by CS and LPS. In conclusion, HA effectively suppresses the airway inflammatory response induced by CS and LPS exposure, and is closely associated with the downregulation of mitogen-activated protein kinases signaling.

Taraxasterol inhibits cigarette smoke-induced lung inflammation by inhibiting reactive oxygen species-induced TLR4 trafficking to lipid rafts

Taraxasterol, a pentacyclic-triterpene isolated from Taraxacum officinale, has been demonstrated to have anti-inflammatory effects. However, the protective effects of taraxasterol against cigarette smoke (CS)-induced lung inflammation have not been reported. This study aimed to investigate the protective effects and mechanism of taraxasterol on CS-induced lung inflammation in mice. CS-induced mouse lung inflammation model was used to investigate the protective effects of taraxasterol in vivo. Human bronchial epithelial cells (HBECs) were used to investigate the protective mechanism of taraxasterol in vitro. The results showed that taraxasterol attenuated CS-induced lung pathological changes, inflammatory cells infiltration, inflammatory cytokines TNF-α, IL-6 and IL-1β production. Taraxasterol also up-regulated CS-induced glutathione (GSH) production. In vitro, taraxasterol was found to inhibit CS-induced reactive oxygen species production, recruitment of TLR4 into lipid rafts, NF-κB activation, and IL-8 production. Furthermore, our results showed that antioxidant N-acetyl-L-cysteine (NAC) significantly inhibited CS-induced recruitment of TLR4 into lipid rafts as well as IL-8 production. In conclusion, our results suggested that taraxasterol had protective effects of CS-induced lung inflammation.

Phospholipase C-ε signaling mediates endothelial cell inflammation and barrier disruption in acute lung injury

Phospholipase C-ε (PLC-ε) is a unique PLC isoform that can be regulated by multiple signaling inputs from both Ras family GTPases and heterotrimeric G proteins and has primary sites of expression in the heart and lung. Whereas the role of PLC-ε in cardiac function and pathology has been documented, its relevance in acute lung injury (ALI) is unclear. We used PLC-ε(-/-) mice to address the role of PLC-ε in regulating lung vascular inflammation and injury in an aerosolized bacterial LPS inhalation mouse model of ALI. PLC-ε(-/-) mice showed a marked decrease in LPS-induced proinflammatory mediators (ICAM-1, VCAM-1, TNF-α, IL-1β, IL-6, macrophage inflammatory protein 2, keratinocyte-derived cytokine, monocyte chemoattractant protein 1, and granulocyte-macrophage colony-stimulating factor), lung neutrophil infiltration and microvascular leakage, and loss of VE-cadherin compared with PLC-ε(+/+) mice. These data identify PLC-ε as a critical determinant of proinflammatory and leaky phenotype of the lung. To test the possibility that PLC-ε activity in endothelial cells (EC) could contribute to ALI, we determined its role in EC inflammation and barrier disruption. RNAi knockdown of PLC-ε inhibited NF-κB activity in response to diverse proinflammatory stimuli, thrombin, LPS, TNF-α, and the nonreceptor agonist phorbol 13-myristate 12-acetate (phorbol esters) in EC. Depletion of PLC-ε also inhibited thrombin-induced expression of NF-κB target gene, VCAM-1. Importantly, PLC-ε knockdown also protected against thrombin-induced EC barrier disruption by inhibiting the loss of VE-cadherin at adherens junctions and formation of actin stress fibers. These data identify PLC-ε as a novel regulator of EC inflammation and permeability and show a hitherto unknown role of PLC-ε in the pathogenesis of ALI.

Lack of Transcription Factor p53 Exacerbates Elastase-Induced Emphysema in Mice

The transcription factor p53 is overexpressed in the lung of patients with emphysema, but it remains unclear if it has a deleterious or protective effect in disease progression. We investigated the role of p53 in the elastase-induced emphysema model and the molecular underlining mechanisms. Wild-type (WT) and p53(-/-) mice were instilled with pancreatic porcine elastase. We quantified emphysema (morphometric analysis), chemokine (C-C motif) ligand 2 (CCL2), and TNF-α in bronchoalveolar lavage (BAL) (ELISA), oxidative stress markers [heme oxygenase 1 (HO1), NAD(P)H dehydrogenase quinone 1 (NQO1), and quantitative RT-PCR], matrix metalloproteinase 12 (MMP12) expression, and macrophage apoptosis (cleaved caspase-3, immunofluorescence). p53 gene expression was up-regulated in the lung of elastase-instilled mice. p53 deletion aggravated elastase-induced emphysema severity, pulmonary inflammation (macrophage and neutrophil numbers and CCL2 and TNF-α levels in BAL), and lung oxidative stress. These findings, except for the increase in CCL2, were reproduced in WT mice transplanted with p53(-/-) bone marrow cells. The increased number of macrophages in p53(-/-) mice was not a consequence of reduced apoptosis or an excess of chemotaxis toward CCL2. Macrophage expression of MMP12 was higher in p53(-/-) mice compared with WT mice after elastase instillation. These findings provide evidence that p53(-/-) mice and WT mice grafted with p53(-/-) bone marrow cells are more prone to developing elastase-induced emphysema, supporting a protective role of p53, and more precisely p53 expressed in macrophages, against emphysema development. The pivotal role played by macrophages in this phenomenon may involve the MMP12-TNF-α pathway.

LPS Induces Hyper-Permeability of Intestinal Epithelial Cells

Necrotizing Enterocolitis (NEC) is a severe inflammatory disorder leading to high morbidity and mortality rates. A growing body of evidence demonstrate the key role of the Toll like receptor 4 (TLR4) in NEC. This membranal receptor recognizes lipopolysaccharides (LPS) from the bacterial wall and triggers an inflammatory response. The aim of the present study was to elucidate the effect of LPS on paracellular permeability known to be severely affected in NEC. IEC-18 cells were treated with LPS and the effects on morphology, paracellular permeability and their associated gene and protein expressions were measured. Our results show that LPS down regulated the expression of occludin and ZO-1 mRNAs while up regulating Cdkn1a. In addition LPS caused a significant increase in paracellular permeability and epithelial barrier damage. Finally ZO-1 protein was found to be spatially disarrayed in the intercellular junctions in response to LPS. We conclude that LPS adversely affected the functionality of the intestinal epithelial barrier suggesting a new mechanism by which bacterial infection may contribute to the development of NEC. J. Cell. Physiol. 232: 381-390, 2017. © 2016 Wiley Periodicals, Inc.

Mitochondrial N-formyl peptides cause airway contraction and lung neutrophil infiltration via formyl peptide receptor activation

Respiratory failure is a common characteristic of systemic inflammatory response syndrome (SIRS) and sepsis. Trauma and severe blood loss cause the release of endogenous molecules known as damage-associated molecular patterns (DAMPs). Mitochondrial N-formyl peptides (F-MITs) are DAMPs that share similarities with bacterial N-formylated peptides, and are potent immune system activators. Recently, we observed that hemorrhagic shock-induced increases in plasma levels of F-MITs associated with lung damage, and that antagonism of formyl peptide receptors (FPR) ameliorated hemorrhagic shock-induced lung injury in rats. Corroborating these data, in the present study, it was observed that F-MITs expression is higher in plasma samples from trauma patients with SIRS or sepsis when compared to control trauma group. Therefore, to better understand the role of F-MITs in the regulation of lung and airway function, we studied the hypothesis that F-MITs lead to airway contraction and lung inflammation. We observed that F-MITs induced concentration-dependent contraction in trachea, bronchi and bronchioles. However, pre-treatment with mast cells degranulator or FPR antagonist decreased this response. Finally, intratracheal challenge with F-MITs increased neutrophil elastase expression in lung and inducible nitric oxide synthase and cell division control protein 42 expression in all airway segments. These data suggest that F-MITs could be a putative target to treat respiratory failure in trauma patients.

Soluble extracellular Klotho decreases sensitivity to cigarette smoke induced cell death in human lung epithelial cells

Chronic obstructive pulmonary disease (COPD) is currently the third leading cause of death in the US and is associated with an abnormal inflammatory response to cigarette smoke (CS). Exposure to CS induces oxidative stress and can result in cellular senescence in the lung. Cellular senescence can then lead to decreased proliferation of epithelial cells, the destruction of alveolar structure and pulmonary emphysema. The anti-aging gene, klotho, encodes a membrane bound protein that has been shown to be a key regulator of oxidative stress and cellular senescence. In this study the role of Klotho (KL) with regard to oxidative stress and cellular senescence was investigated in human pulmonary epithelial cells exposed to cigarette smoke. Individual clones that stably overexpress Klotho were generated through retroviral transfection and geneticin selection. Klotho overexpression was confirmed through RT-qPCR, Western blotting and ELISA. Compared to control cells, constitutive Klotho overexpression resulted in decreased sensitivity to cigarette smoke induced cell death in vitro via a reduction of reactive oxygen species and a decrease in the expression of p21. Our results suggest that increasing Klotho level in pulmonary epithelial cells may be a promising strategy to reduce cellular senescence and mitigate the risk for the development of COPD.

DNA damage response at telomeres contributes to lung aging and chronic obstructive pulmonary disease

Cellular senescence has been associated with the structural and functional decline observed during physiological lung aging and in chronic obstructive pulmonary disease (COPD). Airway epithelial cells are the first line of defense in the lungs and are important to COPD pathogenesis. However, the mechanisms underlying airway epithelial cell senescence, and particularly the role of telomere dysfunction in this process, are poorly understood. We aimed to investigate telomere dysfunction in airway epithelial cells from patients with COPD, in the aging murine lung and following cigarette smoke exposure. We evaluated colocalization of γ-histone protein 2A.X and telomeres and telomere length in small airway epithelial cells from patients with COPD, during murine lung aging, and following cigarette smoke exposure in vivo and in vitro. We found that telomere-associated DNA damage foci increase in small airway epithelial cells from patients with COPD, without significant telomere shortening detected. With age, telomere-associated foci increase in small airway epithelial cells of the murine lung, which is accelerated by cigarette smoke exposure. Moreover, telomere-associated foci predict age-dependent emphysema, and late-generation Terc null mice, which harbor dysfunctional telomeres, show early-onset emphysema. We found that cigarette smoke accelerates telomere dysfunction via reactive oxygen species in vitro and may be associated with ataxia telangiectasia mutated-dependent secretion of inflammatory cytokines interleukin-6 and -8. We propose that telomeres are highly sensitive to cigarette smoke-induced damage, and telomere dysfunction may underlie decline of lung function observed during aging and in COPD.

Sulindac reversal of 15-PGDH-mediated resistance to colon tumor chemoprevention with NSAIDs

Non-steroidal anti-inflammatory drugs prevent colorectal cancer by inhibiting cyclooxygenase (COX) enzymes that synthesize tumor-promoting prostaglandins. 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a tumor suppressor that degrades tumor-promoting prostaglandins. Murine knockout of 15-PGDH increases susceptibility to azoxymethane-induced colon tumors. It also renders these mice resistant to celecoxib, a selective inhibitor of inducible COX-2 during colon neoplasia. Similarly, humans with low colonic 15-PGDH are also resistant to colon adenoma prevention with celecoxib. Here, we used aspirin and sulindac, which inhibit both COX-1 and COX-2, in order to determine if these broader COX inhibitors can prevent colon tumors in 15-PGDH knockout (KO) mice. Unlike celecoxib, sulindac proved highly effective in colon tumor prevention of 15-PGDH KO mice. Significantly, however, aspirin demonstrated no effect on colon tumor incidence in either 15-PGDH wild-type or KO mice, despite a comparable reduction in colonic mucosal Prostaglandin E₂ (PGE₂) levels by both sulindac and aspirin. Notably, colon tumor prevention activity by sulindac was accompanied by a marked induction of lymphoid aggregates and proximal colonic inflammatory mass lesions, a side effect seen to a lesser degree with celecoxib, but not with aspirin. These findings suggest that sulindac may be the most effective agent for colon cancer prevention in humans with low 15-PGDH, but its use may also be associated with inflammatory lesions in the colon.

P21-PARP-1 pathway is involved in cigarette smoke-induced lung DNA damage and cellular senescence

Persistent DNA damage triggers cellular senescence, which may play an important role in the pathogenesis of cigarette smoke (CS)-induced lung diseases. Both p21^CDKN1A (p21) and poly(ADP-ribose) polymerase-1 (PARP-1) are involved in DNA damage and repair. However, the role of p21-PARP-1 axis in regulating CS-induced lung DNA damage and cellular senescence remains unknown. We hypothesized that CS causes DNA damage and cellular senescence through a p21-PARP-1 axis. To test this hypothesis, we determined the levels of γH2AX (a marker for DNA double-strand breaks) as well as non-homologous end joining proteins (Ku70 and Ku80) in lungs of mice exposed to CS. We found that the level of γH2AX was increased, whereas the level of Ku70 was reduced in lungs of CS-exposed mice. Furthermore, p21 deletion reduced the level of γH2AX, but augmented the levels of Ku70, Ku80, and PAR in lungs by CS. Administration of PARP-1 inhibitor 3-aminobenzamide increased CS-induced DNA damage, but lowered the levels of Ku70 and Ku80, in lungs of p21 knockout mice. Moreover, 3-aminobenzamide increased senescence-associated β-galactosidase activity, but decreased the expression of proliferating cell nuclear antigen in mouse lungs in response to CS. Interestingly, 3-aminobenzamide treatment had no effect on neutrophil influx into bronchoalveolar lavage fluid by CS. These results demonstrate that the p21-PARP-1 pathway is involved in CS-induced DNA damage and cellular senescence.

Deletion of p21/Cdkn1a confers protective effect against prostate tumorigenesis in transgenic adenocarcinoma of the mouse prostate model

Cyclin-dependent kinase inhibitors (CDKIs) p21(Cip1/Waf1) (p21) and p27(Kip1) (p27) play a determining role in cell cycle progression by regulating CDK activity; however, p21 role in prostate cancer (PCa) is controversial. Whereas p21 upregulation by anticancer agents causes cell cycle arrest in various PCa cell lines, elevated p21 levels have been associated with higher Gleason score, poor survival and increased PCa recurrence. These conflicting findings suggest that more studies are needed to examine p21 role in PCa. Herein, employing genetic approach, transgenic mice harboring p21/Cdkn1a homozygous deletion (p21(-/-)) were crossed with the transgenic adenocarcinoma of the mouse prostate (TRAMP) mice to characterize in vivo consequences of p21 deletion on prostate tumorigenesis. Lower urogenital tract weight of p21(-/-)/TRAMP mice was significantly lower than those of p21(+/-)/TRAMP and TRAMP mice. Histopathology further supported these observations, showing less aggressiveness in prostates of p21(-/-)/TRAMP. Furthermore, a significantly higher incidence of low-grade prostatic intraepithelial lesions (PIN) with a concomitant reduction in adenocarcinoma incidence was observed in p21(-/-)/TRAMP mice compared with TRAMP mice. In addition, whereas TRAMP mice showed the presence of poorly differentiated adenocarcinoma lesions, no such lesions were observed in p21/TRAMP transgenic mice. Specifically, there was a significant reduction in the severity of lesions in both p21(-/-)/TRAMP and p21(+/-)/TRAMP mice compared with TRAMP mice. Together, our data showed that p21 deletion reduces prostate tumorigenesis by slowing-down progression of PIN (pre-malignant) to adenocarcinoma (malignant), suggesting that intact p21 expression is associated with PCa aggressiveness, while its decreased levels may in fact confer protection against prostate tumorigenesis.

Senescence in chronic obstructive pulmonary disease

There is a growing realization that chronic obstructive pulmonary disease involves several processes present in aging and cellular senescence. The impact of these processes in the pathogenesis of the main manifestations is multiple, particularly in the propagation of a proinflammatory phenotype, loss of reparative potential, and amplification of oxidative stress, all ultimately leading to tissue damage. This review highlights salient aspects related to senescence discussed in the 2011 Aspen Lung Conference.

Suppressed expression of T-box transcription factors is involved in senescence in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major global health problem. The etiology of COPD has been associated with apoptosis, oxidative stress, and inflammation. However, understanding of the molecular interactions that modulate COPD pathogenesis remains only partly resolved. We conducted an exploratory study on COPD etiology to identify the key molecular participants. We used information-theoretic algorithms including Context Likelihood of Relatedness (CLR), Algorithm for the Reconstruction of Accurate Cellular Networks (ARACNE), and Inferelator. We captured direct functional associations among genes, given a compendium of gene expression profiles of human lung epithelial cells. A set of genes differentially expressed in COPD, as reported in a previous study were superposed with the resulting transcriptional regulatory networks. After factoring in the properties of the networks, an established COPD susceptibility locus and domain-domain interactions involving protein products of genes in the generated networks, several molecular candidates were predicted to be involved in the etiology of COPD. These include COL4A3, CFLAR, GULP1, PDCD1, CASP10, PAX3, BOK, HSPD1, PITX2, and PML. Furthermore, T-box (TBX) genes and cyclin-dependent kinase inhibitor 2A (CDKN2A), which are in a direct transcriptional regulatory relationship, emerged as preeminent participants in the etiology of COPD by means of senescence. Contrary to observations in neoplasms, our study reveals that the expression of genes and proteins in the lung samples from patients with COPD indicate an increased tendency towards cellular senescence. The expression of the anti-senescence mediators TBX transcription factors, chromatin modifiers histone deacetylases, and sirtuins was suppressed; while the expression of TBX-regulated cellular senescence markers such as CDKN2A, CDKN1A, and CAV1 was elevated in the peripheral lung tissue samples from patients with COPD. The critical balance between senescence and anti-senescence factors is disrupted towards senescence in COPD lungs.

Perspectives on translational and therapeutic aspects of SIRT1 in inflammaging and senescence

Sirtuin1 (SIRT1), a type III protein deacetylase, is considered as a novel anti-aging protein involved in regulation of cellular senescence/aging and inflammation. SIRT1 level and activity are decreased during lung inflammaging caused by oxidative stress. The mechanism of SIRT1-mediated protection against inflammaging is associated with the regulation of inflammation, premature senescence, telomere attrition, senescence associated secretory phenotype, and DNA damage response. A variety of dietary polyphenols and pharmacological activators are shown to regulate SIRT1 so as to intervene the progression of type 2 diabetes, cancer, cardiovascular diseases, and chronic obstructive pulmonary disease associated with inflammaging. However, recent studies have shown the non-specific regulation of SIRT1 by the aforementioned pharmacological activators and polyphenols. In this perspective, we have briefly discussed the role of SIRT1 in regulation of cellular senescence and its associated secretory phenotype, DNA damage response, particularly in lung inflammaging and during the development of chronic obstructive pulmonary diseases. We have also discussed the potential directions for future translational therapeutic avenues for SIRT1 in modulating lung inflammaging associated with senescence in chronic lung diseases associated with increased oxidative stress.

Mesenchymal stem cell-conditioned media recovers lung fibroblasts from cigarette smoke-induced damage

Cigarette smoking causes apoptotic death, senescence, and impairment of repair functions in lung fibroblasts, which maintain the integrity of alveolar structure by producing extracellular matrix (ECM) proteins. Therefore, recovery of lung fibroblasts from cigarette smoke-induced damage may be crucial in regeneration of emphysematous lung resulting from degradation of ECM proteins and subsequent loss of alveolar cells. Recently, we reported that bone marrow-derived mesenchymal stem cell-conditioned media (MSC-CM) led to angiogenesis and regeneration of lung damaged by cigarette smoke. In this study, to further investigate reparative mechanisms for MSC-CM-mediated lung repair, we attempted to determine whether MSC-CM can recover lung fibroblasts from cigarette smoke-induced damage. In lung fibroblasts exposed to cigarette smoke extract (CSE), MSC-CM, not only inhibited apoptotic death, but also induced cell proliferation and reversed CSE-induced changes in the levels of caspase-3, p53, p21, p27, Akt, and p-Akt. MSC-CM also restored expression of ECM proteins and collagen gel contraction while suppressing CSE-induced expression of cyclooxygenase-2 and microsomal PGE(2) synthase-2. The CSE-opposing effects of MSC-CM on cell fate, expression of ECM proteins, and collagen gel contraction were partially inhibited by LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor. In rats, MSC-CM administration also resulted in elevation of p-Akt and restored proliferation of lung fibroblasts, which was suppressed by exposure to cigarette smoke. Taken together, these data suggest that MSC-CM may recover lung fibroblasts from cigarette smoke-induced damage, possibly through inhibition of apoptosis, induction of proliferation, and restoration of lung fibroblast repair function, which are mediated in part by the PI3K/Akt pathway.

SIRT1 as a therapeutic target in inflammaging of the pulmonary disease

OBJECTIVE

Chronic inflammation and cellular senescence are intertwined in the pathogenesis of premature aging, which is considered as an important contributing factor in driving chronic obstructive pulmonary disease (COPD). Sirtuin1 (SIRT1), a nicotinamide adenine dinucleotide (NAD(+))-dependent protein/histone deacetylase, regulates inflammation, senescence/aging, stress resistance, and deoxyribonucleic acid (DNA) damage repair via deacetylating intracellular signaling molecules and chromatin histones. The present review describes the mechanism and regulation of SIRT1 by environmental agents/oxidants/reactive aldehydes and pro-inflammatory stimuli in lung inflammation and aging. The role of dietary polyphenols in regulation of SIRT1 in inflammaging is also discussed.

METHODS

Analysis of current research findings on the mechanism of inflammation and senescence/aging (i.e., inflammaging) and their regulation by SIRT1 in premature aging of the lung.

RESULTS

COPD is a disease of the lung inflammaging, which is associated with the DNA damage response, transcription activation and chromatin modifications. SIRT1 regulates inflammaging via regulating forkhead box class O 3, p53, nuclear factor kappa B, histones and various proteins involved in DNA damage and repair. Polyphenols and its analogs have been shown to activate SIRT1 although they have anti-inflammatory and antioxidant properties.

CONCLUSIONS

Targeting lung inflammation and cellular senescence as well as premature lung aging using pharmacological SIRT1 activators or polyphenols would be a promising therapeutic intervention for COPD/emphysema.