Dual effects of cigarette smoke extract on proliferation of endothelial progenitor cells and the protective effect of 5-aza-2'-deoxycytidine on EPCs against the damage caused by CSE

Cigarette smoke extract affects methylation status and attenuates Sca-1 expression of mouse endothelial progenitor cell in vitro

INTRODUCTION

Endothelial dysfunction appears in many smoking-related diseases, it is also an important pathophysiological feature. Endothelial progenitor cells (EPCs) are precursors of endothelial cells and have a crucial effect on the repair and maintenance of endothelial integrity. Sca-1 is not only common in bone marrow-derived hematopoietic stem cells (HSCs), but it is also expressed in nonhematopoietic organs by tissue-resident stem and progenitor cells. The aim of this study is to investigate the impact of cigarette smoke extract (CSE) on the function of bone marrow-derived EPCs and the expression level of Sca-1 in EPCs, and also whether the methylation of Sca-1 is involved in EPC dysfunction.

METHODS

We measured EPC capacities including adhesion, secretion and proliferation, the concentration of endothelial nitric oxide synthase (eNOS) and apoptosis-inducing factor (AIF) in cell culture supernatant, and also Sca-1 expression and promoter methylation in EPCs induced by CSE. Decitabine (Dec) was applied to test whether it could alter the impact caused by CSE.

RESULTS

The adhesion, proliferation and secretion ability of EPCs can be induced to be decreased by CSE in vitro, accompanied by decreased concentrations of AIF and eNOS in cell culture supernatant and decreased Sca-1 expression in EPCs. In addition, Dec could partly attenuate the impact described above. There were no significant differences in the quantitative analysis of Sca-1 promoter methylation among different groups.

CONCLUSIONS

The decreased Sca-1 expression was related to EPC dysfunction induced by CSE. EPC dysfunction resulting from CSE may be related to methylation mechanism, but not the methylation of Sca-1 promoter.

Inhibiting DNA methylation alleviates cigarette smoke extract-induced dysregulation of Bcl-2 and endothelial apoptosis

INTRODUCTION

There is evidence that cigarette smoking participates in disease progression through endothelial apoptosis. Bcl-2 family proteins are essential and critical regulators of apoptosis. We explored whether Bcl-2 plays a role in cigarette smoke extract induced (CSE-induced) endothelial apoptosis. Furthermore, given the involvement of epigenetics in apoptosis and Bcl-2 expression, we hypothesized that CSE-induced apoptosis might be caused by gene methylation.

METHODS

Human umbilical vascular endothelial cells (HUVECs) were treated with CSE, CSE plus 5-aza-2'-deoxycytidine (AZA, an inhibitor of DNA methylation), or AZA and phosphate-buffered saline (PBS). Endothelial apoptosis was determined by Annexin-V and propidium iodide staining. The expression levels of Bcl-2, Bax, and cytochrome C (cyt C) were assessed by immunoblotting and RT-PCR. The methylation status of the Bcl-2 promoter was observed by bisulfite sequencing PCR (BSP).

RESULTS

The apoptotic index of endothelial cells in the CSE-treated group increased. Decreased expression of Bcl-2 and high methylation of the Bcl-2 promoter were observed after CSE treatment. AZA alleviated the endothelial apoptosis caused by CSE. AZA treatment also increased Bcl-2 expression along with decreased Bcl-2 promoter methylation.

CONCLUSIONS

Inhibiting DNA methylation alleviates CSE-induced endothelial apoptosis and Bcl-2 promoter methylation. Bcl-2 promoter methylation might be involved in CES-induced endothelial apoptosis.

Notch promotes DNMT-mediated hypermethylation of Klotho leads to COPD-related inflammation

AIM

Klotho expression significantly declines in alveolar macrophages and airway epithelial cells in chronic obstructive pulmonary disease (COPD) patients, and cigarette smoke extract dramatically inhibits the expression and secretion of α-Klotho. This suggests that the silencing of Klotho is the major factor promoting COPD related inflammatory responses. This study aims to investigate the mechanism of Klotho downregulation and its effect on the inflammatory cytokines secretion and cell apoptosis.

METHODS

Expression of DNA methyltransferases (DNMTs) and Notch signaling activation were quantified in MH-S and 16HBE cells stimulated with cigarette smoke extract (CSE) solution. Specific inhibitors of DNMTs or Notch pathway were added together with CSE into treated and control cells. Inflammatory cytokines, cell viability and cell death were determined to explore the effect of Klotho on COPD related inflammation.

RESULTS

CSE treatment statistically increased the level of DNMTs expression, Klotho promoter methylation, and activated the Notch signaling pathway. Notch signal activation played a critical role in the process of modification of Klotho promoter methylation. The inhibition of DNMTs and Notch pathway rescued Klotho levels and inhibited inflammation and cell apoptosis after CSE treatment.

CONCLUSION

Notch-mediated Klotho hypermethylation inhibited Klotho expression, which promoted inflammatory response and cell apoptosis that were associated with the development of COPD.

5-Aza-2'-deoxycytidine protects against emphysema in mice via suppressing p16Ink4a expression in lung tissue

Background

There is a growing realization that COPD, or at least emphysema, involves several processes presenting in aging and cellular senescence. Endothelial progenitor cells (EPCs) contribute to neovascularization and play an important role in the development of COPD. The gene for p16^Ink4a is a major dominant senescence one. The aim of the present study was to observe changes in lung function, histomorphology of lung tissue, and expression of p16^Ink4a in lung tissue and bone marrow-derived EPCs in emphysematous mice induced by cigarette-smoke extract (CSE), and further to search for a potential candidate agent protecting against emphysema induced by CSE.

Materials and methods

An animal emphysema model was induced by intraperitoneal injection of CSE. 5-Aza-2′-deoxycytidine (5-Aza-CdR) was administered to the emphysematous mice. Lung function and histomorphology of lung tissue were measured. The p16^Ink4a protein and mRNA in EPCs and lung tissues were detected using Western blotting and quantitative reverse-transcription polymerase chain reaction, respectively.

Results

CSE induced emphysema with increased p16^Ink4a expression in lung tissue and bone marrow-derived EPCs. 5-Aza-CdR partly protected against emphysema, especially in the lung-morphology profile, and partly protest against the overexpression of p16^Ink4a in EPCs and lung tissue induced by CSE.

Conclusion

5-Aza-CdR partly protected against emphysema in mice via suppressing p16^Ink4a expression in EPCs and lung tissue.

Cigarette Smoke Extract Changes Expression of Endothelial Nitric Oxide Synthase (eNOS) and p16(INK4a) and is Related to Endothelial Progenitor Cell Dysfunction

BACKGROUND Endothelial dysfunction is an important pathophysiologic feature in many smoke-related diseases. Endothelial progenitor cells (EPCs) are the precursors of endothelial cells and play a fundamental role in the maintenance of endothelial integrity and function. Endothelial nitric oxide synthase (eNOS) is the dominant NOS isoform in the vasculature and plays a central role in the maintenance of endothelial homeostasis. p16(INK4a) is a cyclin-dependent kinase inhibitor and could be regarded as a major dominant senescence gene. The present study aimed to determine whether the expression of eNOS and p16(INK4a) in EPCs is related to EPCs function and the possible epigenetic mechanism, if any. MATERIAL AND METHODS We investigated EPCs capacity for proliferation, adhesion, and secretion, and the expression of eNOS and p16(INK4a) in EPCs which were altered by cigarette smoke extract (CSE) in vitro. Furthermore, Decitabine (Dec), an agent of demethylation, was used to examine whether it could alter the changes induced by CSE. RESULTS The present study demonstrated that EPCs altered by CSE in vitro displayed decreased capacities of proliferation, adhesion, and secretion, which was accompanied by decreased eNOS expression and increased p16(INK4a) expression in EPCs. Furthermore, Dec could alleviate the changes in the expression of eNOS and p16(INK4a), and protect against the EPCs dysfunction caused by CSE. CONCLUSIONS The decreased eNOS expression and increased p16(INK4a) expression was associated with dysfunction of EPCs caused by CSE. The mechanism of methylation, one of the most common epigenetic mechanism, may be involved in the EPCs dysfunction caused by CSE.

Cigarette smoke extracts induced the colon cancer migration via regulating epithelial mesenchymal transition and metastatic genes in human colon cancer cells

There was considerable evidence that exposure to cigarette smoke is associated with an increased risk for colon cancer. Nevertheless, the mechanism underlying the relationship between cigarette smoking and colon cancer remains unclear. Moreover, there were only a few studies on effects of complexing substance contained in cigarette smoke on colon cancer. Thus, we further investigated whether cigarette smoke extract (CSE) affects the cell cycle, apoptosis and migration of human metastatic colon cancer cells, SW-620. MTT assay revealed that SW-620 cell proliferation was significantly inhibited following treatments with all CSEs, 3R4F, and two-domestic cigarettes, for 9 days in a concentration-dependent manner. Moreover, CSE treatments decreased cyclin D1 and E1, and increased p21 and p27 proteins by Western blot analysis in SW-620 cells. Additionally, the treatment of the cells with CSE contributed to these effects expressing by apoptosis-related proteins. An increased migration or invasion ability of SW-620 cells following CSE treatment was also confirmed by a scratch or fibronectin invasion assay in vitro. In addition, the protein levels of E-cadherin as an epithelial maker were down-regulated, while the mesenchymal markers, N-cadherin, snail, and slug, were up-regulated in a time-dependent manner. A metastatic marker, cathepsin D, was also down-regulated by CSE treatment. Taken together, these results indicate that CSE exposure in colon cancer cells may deregulate the cell growth by altering the expression of cell cycle-related proteins and pro-apoptotic protein, and stimulate cell metastatic ability by altering epithelial-mesenchymal transition (EMT) markers and cathepsin D expression. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 690-704, 2017.

Murine models of cardiovascular comorbidity in chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) have an increased risk for cardiovascular disease (CVD). Currently, COPD patients with atherosclerosis (i.e., the most important underlying cause of CVD) receive COPD therapy complemented with standard CVD therapy. This may, however, not be the most optimal treatment. To investigate the link between COPD and atherosclerosis and to develop specific therapeutic strategies for COPD patients with atherosclerosis, a substantial number of preclinical studies using murine models have been performed. In this review, we summarize the currently used murine models of COPD and atherosclerosis, both individually and combined, and discuss the relevance of these models for studying the pathogenesis and development of new treatments for COPD patients with atherosclerosis. Murine and clinical studies have provided complementary information showing a prominent role for systemic inflammation and oxidative stress in the link between COPD and atherosclerosis. These and other studies showed that murine models for COPD and atherosclerosis are useful tools and can provide important insights relevant to understanding the link between COPD and CVD. More importantly, murine studies provide good platforms for studying the potential of promising (new) therapeutic strategies for COPD patients with CVD.

Decitabine enhances stem cell antigen-1 expression in cigarette smoke extract-induced emphysema in animal model

Stem cell antigen-1 (Sca-1) is a mouse glycosyl phosphatidylinositol-anchored protein and a cell surface marker found on hematopoietic stem cells (HSCs). Despite decades of study, its biological functions remain little known. Sca-1 is a typical marker of bone marrow-derived HSCs, it is also expressed by a mixture of tissue-resident stem, progenitor cells in nonhematopoietic organs. Endothelial progenitor cell (EPC) is a subtype of HSC and contributes to endothelial repair by homing in on locations of injury. Abnormal genetic methylation has been detected in smoking-related diseases. The present study aimed to investigate the lung function and histomorphology, the expression of Sca-1 gene in lung tissues, and bone marrow-derived EPCs in cigarette smoke extract (CSE)-induced emphysema mice, and to further determine whether Decitabine (Dec), the most widely used inhibitor of DNA methylation, could protect against the damages caused by CSE. The results of the present study demonstrated that Dec could partly protect against CSE-induced emphysema in mice, enhance Sca-1 expression in lung tissue, and bone marrow-derived EPCs. The results suggested that the depletion of the progenitor cell pool and DNA methylation of Sca-1 gene may be involved in the progression of emphysema in mice.

Comparison between cigarette smoke-induced emphysema and cigarette smoke extract-induced emphysema

Background and objective

Emphysema is the main pathological feature of COPD and also is the focus of the related research. Although several emphysema animal models have been established, exact comparison of findings is seldom. The present study aimed to compare cigarette smoke (CS) exposure-induced emphysema model and intraperitoneal injection of cigarette smoke extract (CSE)-induced emphysema model to evaluate the effectiveness of the two different modeling methods.

Methods

Six-week-old male C57BL/6 J mice were used and randomly divided into two groups: CS exposure and intraperitoneal injection of CSE. Each group was subdivided into two subgroups: control and CS or CSE. Lung function, mean linear intercept (MLI), destructive index (DI), apoptotic index (AI), total and differential cells count in broncholavolar lavage fluid (BALF), SOD and IL-6 concentration in serum were measured.

Results

Compared with their respective controls, lung function was significantly decreased in CS and CSE groups (P < 0.01); MLI, DI, and AI of lung tissue were significantly higher in CS and CSE groups (P < 0.01); total number of leukocytes, the number and percentage of neutrophils (NEUs), and the number of macrophages (MAC) in BALF were significantly higher in CS and CSE groups (P < 0.01); SOD concentration in serum was significantly decreased in CS and CSE groups (P < 0.01); IL-6 concentration in serum was significantly increased in in CS and CSE groups (P < 0.01). There was no significant difference between CS group and CSE group in any of the parameters described above.

Conclusions

Both CS exposure and intraperitoneal injection of CSE could induce emphysema and the effectiveness of the two different modeling methods were equal.