PAF mediates cigarette smoke-induced goblet cell metaplasia in guinea pig airways

A comprehensive assessment of smokeless tobacco (Shammah) extract: unraveling the effects on hematological parameters, antioxidant defense mechanisms, and organ health in rats

Shammah, also known as smokeless tobacco, is a form of tobacco product consumed without combustion, commonly used in various cultures, particularly in the Middle East and parts of Africa. The experiment was conducted in four groups control male and female, also treated male and female. The administration of Shammah extract induced significant hematological, biochemical, and histopathological changes in both female and male rats. Treated females showed a decrease in total leukocyte count (TLC) to 9900, while treated males increased to 14,525. Lymphocyte percentage decreased by 9.5% in females and 6.02% in males, with neutrophil counts rising by 24.6% and 20.5%, respectively. Eosinophil levels surged by 240% in females and 50.3% in males. Hemoglobin levels decreased by 12.4-13.1% in females, while males showed a non-significant increase to 15.68. Malondialdehyde (MDA) levels increased to 1.57 in females (57% increase) and 1.93 in males (70.8% increase). Antioxidant enzymes decreased, with superoxide dismutase (SOD) at 3.53 (116.2% decrease) in females and 3.90 (45.8% decrease) in males. Kidney function assessments revealed elevated urea levels of 36.35 (84.8% increase) in females and 43.17 (131.2% increase) in males, alongside creatinine levels of 1.28 (75.3% increase) in females and 1.56 (90.2% increase) in males. Histopathological examinations showed untreated livers with a typical structure, while treated livers exhibited infiltrative cell aggregations, venous congestion, hemorrhage, and edema. Treated kidneys showed severe glomerular atrophy and degeneration. Spleens from treated groups had blending of white and red pulp, while brains displayed hemorrhage and distorted neurons in males, and ghost neurons in females. Treated testes exhibited dilated blood vessels, edema, and reduced spermatogenesis, while treated ovaries showed cyst formation and vacuolar degeneration. These findings indicate significant oxidative stress and organ damage associated with Shammah extract exposure.

Aberrant epithelial differentiation by cigarette smoke dysregulates respiratory host defence

It is currently unknown how cigarette smoke-induced airway remodelling affects highly expressed respiratory epithelial defence proteins and thereby mucosal host defence.

Localisation of a selected set of highly expressed respiratory epithelial host defence proteins was assessed in well-differentiated primary bronchial epithelial cell (PBEC) cultures. Next, PBEC were cultured at the air–liquid interface, and during differentiation for 2–3 weeks exposed daily to whole cigarette smoke. Gene expression, protein levels and epithelial cell markers were subsequently assessed. In addition, functional activities and persistence of the cigarette smoke-induced effects upon cessation were determined.

Expression of the polymeric immunoglobulin receptor, secretory leukocyte protease inhibitor and long and short PLUNC (palate, lung and nasal epithelium clone protein) was restricted to luminal cells and exposure of differentiating PBECs to cigarette smoke resulted in a selective reduction of the expression of these luminal cell-restricted respiratory host defence proteins compared to controls. This reduced expression was a consequence of cigarette smoke-impaired end-stage differentiation of epithelial cells, and accompanied by a significant decreased transepithelial transport of IgA and bacterial killing.

These findings shed new light on the importance of airway epithelial cell differentiation in respiratory host defence and could provide an additional explanation for the increased susceptibility of smokers and patients with chronic obstructive pulmonary disease to respiratory infections.

Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease

BACKGROUND

Bacteria expressing phosphorylcholine (ChoP) co-opt host-expressed platelet-activating factor receptor (PAFR) to adhere to lower airway cells. Cigarette smoke and rhinovirus (RV) infection upregulate PAFR-dependent bacterial adhesion to airway cells in vitro, and in healthy adults smoking increases the proportion of PAFR positive bronchial epithelial cells. To date the effect of chronic obstructive pulmonary disease (COPD) on smoke-induced PAFR is unknown. We therefore sought to test the hypothesis that bronchial PAFR mRNA expression is increased in smokers with chronic obstructive pulmonary disease (COPD), and further increases after RV infection.

METHODS

Endobronchial biopsies were obtained by fibreoptic bronchoscopy from healthy non-smokers, smokers without airway obstruction, and smokers with COPD, before and after infection with rhinovirus (RV) serotype 16. Endobronchial PAFR mRNA expression was assessed by quantitative PCR and expressed as a ratio of glyceraldehyde-3-phosphate dehydrogenase. The distribution of PAFR was assessed by immunohistochemistry.

RESULTS

Baseline PAFR mRNA expression was increased (p < 0.05) in smokers (n = 16), and smokers with COPD (n = 14) compared with non-smokers (n = 18). In RV16 infected subjects there was no increase in PAFR mRNA expression in either non-smokers (n = 9), smokers (n = 8), or smokers with COPD (n = 7). PAFR immunoreactivity in all 3 groups was predominately restricted to the bronchial epithelium and submucosal glands.

CONCLUSIONS

Endobronchial PAFR mRNA is increased in both smokers without airway obstruction and smokers with COPD. We found preliminary evidence that RV16 infection does not increase PAFR mRNA expression in either smokers or smokers with COPD.

Susceptibility to viral infections in chronic obstructive pulmonary disease: role of epithelial cells

PURPOSE OF REVIEW

The aim is to understand how airway epithelial cells with compromised innate defense mechanisms enhance susceptibility to respiratory virus infections in chronic obstructive pulmonary disease (COPD).

RECENT FINDINGS

Exacerbations associated with respiratory viruses are more severe and increase disease severity in COPD. Airway epithelial cells cultured from COPD patients show excessive innate immune response to viral infection and higher viral load compared with normal cells.

SUMMARY

Airway epithelial cells are the first line of defense in the lung and are equipped with several lines of innate defense mechanisms to fight against invading pathogens including viruses. Under normal conditions, mucociliary and barrier functions of airway epithelial cells prevent virus binding and entry into the cells. Virus-infected airway epithelial cells also express various cytokines, which recruit and activate innate and adaptive immune cells ultimately controlling the infection and tissue damage. In COPD however, compromised mucociliary and barrier functions may increase virus binding and allow virus entry into airway epithelial cells. Virus-infected COPD airway epithelial cells also show disproportionate cytokine expression leading to inappropriate recruitment and activation of innate and adaptive immune cells. COPD airway epithelial cells also show defective antiviral responses. Such defects in innate defense mechanisms may increase susceptibility to viral infections and disease severity in COPD.

Endogenous and exogenous thioredoxin 1 prevents goblet cell hyperplasia in a chronic antigen exposure asthma model

BACKGROUND

Goblet cell hyperplasia with mucus hypersecretion contribute to increased morbidity and mortality in bronchial asthma. We have reported that thioredoxin 1 (TRX1), a redox (reduction/oxidation)-active protein acting as a strong antioxidant, inhibits pulmonary eosinophilic inflammation and production of chemokines and Th2 cytokines in the lungs, thus decreasing airway hyperresponsiveness (AHR) and airway remodeling in mouse asthma models. In the present study, we investigated whether endogenous or exogenous TRX1 inhibits goblet cell hyperplasia in a mouse asthma model involving chronic exposure to antigen.

METHODS

We used wild-type Balb/c mice and Balb/c background human TRX1-transgenic mice constitutively overproducing human TRX1 protein in the lungs. Mice were sensitized 7 times (days 0 to 12) and then challenged 9 times with ovalbumin (OVA) (days 19 to 45). Every second day from days 18 to 44 (14 times) or days 35 to 45 (6 times), Balb/c mice were treated with 40 microg recombinant human TRX1 (rhTRX1) protein. Goblet cells in the lungs were examined quantitatively on day 34 or 45.

RESULTS

Goblet cell hyperplasia was significantly prevented in TRX1-transgenic mice in comparison with TRX1 transgene-negative mice. rhTRX1 administration during OVA challenge (days 18 to 44) significantly inhibited goblet cell hyperplasia in OVA-sensitized and -challenged wild-type mice. Moreover, rhTRX1 administration after the establishment of goblet cell hyperplasia (days 35 to 45) also significantly ameliorated goblet cell hyperplasia in OVA-sensitized and -challenged wild-type mice.

CONCLUSIONS

Our results suggest that TRX1 prevents the development of goblet cell hyperplasia, and also ameliorates established goblet cell hyperplasia.

Asthma induction in mice leads to appearance of alpha2-3- and alpha2-6-linked sialic acid residues in respiratory goblet-like cells

Allergic asthmatic inflammation in mice was induced by sensitization with ovalbumin and lipopolysaccharide from Escherichia coli and visualized in the airways of asthmatic mice by spatial and temporal changes of carbohydrates containing sialic acid residues. Immunohistochemistry was used to demonstrate binding of lectins and antibodies that detect alpha2-3- and alpha2-6-linked sialic acid residues. After sensitization and challenge, the histology of the lung changed markedly, and goblet-like cells appeared, most likely caused by Clara cell metaplasia. Normal Clara cells showed no reaction after incubation with the sialic acid detecting agents, while the goblet-like cells expressed both alpha2-3- and alpha2-6-linked sialic acid residues in the asthmatic animals. The lectins but not the antibodies reacted with intestinal goblet cells. Instead, an antibody recognizing a disialoganglioside, stained large mononuclear cells in the submucosa, indicating a difference in sialylation between goblet cells in the intestine and goblet-like cells developed from Clara cells.

Using guinea pigs in studies relevant to asthma and COPD

The guinea pig has been the most commonly used small animal species in preclinical studies related to asthma and COPD. The primary advantages of the guinea pig are the similar potencies and efficacies of agonists and antagonists in human and guinea pig airways and the many similarities in physiological processes, especially airway autonomic control and the response to allergen. The primary disadvantages to using guinea pigs are the lack of transgenic methods, limited numbers of guinea pig strains for comparative studies and a prominent axon reflex that is unlikely to be present in human airways. These attributes and various models developed in guinea pigs are discussed.

Mechanisms of cigarette smoke-induced COPD: insights from animal models

Cigarette smoke-induced animal models of chronic obstructive pulmonary disease support the protease-antiprotease hypothesis of emphysema, although which cells and proteases are the crucial actors remains controversial. Inhibition of either serine or metalloproteases produces significant protection against emphysema, but inhibition is invariably accompanied by decreases in the inflammatory response to cigarette smoke, suggesting that these inhibitors do more than just prevent matrix degradation. Direct anti-inflammatory interventions are also effective against the development of emphysema, as are antioxidant strategies; the latter again decrease smoke-induced inflammation. There is increasing evidence for autoimmunity, perhaps directed against matrix components, as a driving force in emphysema. There is intriguing but controversial animal model evidence that failure to repair/failure of lung maintenance also plays a role in the pathogenesis of emphysema. Cigarette smoke produces small airway remodeling in laboratory animals, possibly by direct induction of fibrogenic growth factors in the airway wall, and also produces pulmonary hypertension, at least in part through direct upregulation of vasoactive mediators in the intrapulmonary arteries. Smoke exposure causes goblet cell metaplasia and excess mucus production in the small airways and proximal trachea, but these changes are not good models of either chronic bronchitis or acute exacerbations. Emphysema, small airway remodeling, pulmonary hypertension, and mucus production appear to be at least partially independent processes that may require different therapeutic approaches.

The Epithelial Cell in Lung Health and Emphysema Pathogenesis

Cigarette smoking is the primary cause of the irreversible lung disease emphysema. Historically, inflammatory cells such as macrophages and neutrophils have been studied for their role in emphysema pathology. However, recent studies indicate that the lung epithelium is an active participant in emphysema pathogenesis and plays a critical role in the lung's response to cigarette smoke. Tobacco smoke increases protease production and alters cytokine expression in isolated epithelial cells, suggesting that these cells respond potently even in the absence of a complete inflammatory program. Tobacco smoke also acts as an immunosuppressant, reducing the defense function of airway epithelial cells and enhancing colonization of the lower airways. Thus, the paradigm that emphysema is strictly an inflammatory-cell based disease is shifting to consider the involvement of resident epithelial cells. Here we review the role of epithelial cells in lung development and emphysema. To better understand tobacco-epithelial interactions we performed microarray analyses of RNA from human airway epithelial cells exposed to smoke extract for 24 hours. These studies identified differential regulation of 425 genes involved in diverse biological processes, such as apoptosis, immune function, cell cycle, signal transduction, proliferation, and antioxidants. Some of these genes, including VEGF, glutathione peroxidase, IL-13 receptor, and cytochrome P450, have been previously reported to be altered in the lungs of smokers. Others, such as pirin, cathepsin L, STAT1, and BMP2, are shown here for the first time to have a potential role in smoke-associated injury. These data broaden our understanding of the importance of epithelial cells in lung health and cigarette smoke-induced emphysema.

Respiratory tract mucin genes and mucin glycoproteins in health and disease

This review focuses on the role and regulation of mucin glycoproteins (mucins) in airway health and disease. Mucins are highly glycosylated macromolecules (> or =50% carbohydrate, wt/wt). MUC protein backbones are characterized by numerous tandem repeats that contain proline and are high in serine and/or threonine residues, the sites of O-glycosylation. Secretory and membrane-tethered mucins contribute to mucociliary defense, an innate immune defense system that protects the airways against pathogens and environmental toxins. Inflammatory/immune response mediators and the overproduction of mucus characterize chronic airway diseases: asthma, chronic obstructive pulmonary diseases (COPD), or cystic fibrosis (CF). Specific inflammatory/immune response mediators can activate mucin gene regulation and airway remodeling, including goblet cell hyperplasia (GCH). These processes sustain airway mucin overproduction and contribute to airway obstruction by mucus and therefore to the high morbidity and mortality associated with these diseases. Importantly, mucin overproduction and GCH, although linked, are not synonymous and may follow from different signaling and gene regulatory pathways. In section i, structure, expression, and localization of the 18 human MUC genes and MUC gene products having tandem repeat domains and the specificity and application of MUC-specific antibodies that identify mucin gene products in airway tissues, cells, and secretions are overviewed. Mucin overproduction in chronic airway diseases and secretory cell metaplasia in animal model systems are reviewed in section ii and addressed in disease-specific subsections on asthma, COPD, and CF. Information on regulation of mucin genes by inflammatory/immune response mediators is summarized in section iii. In section iv, deficiencies in understanding the functional roles of mucins at the molecular level are identified as areas for further investigations that will impact on airway health and disease. The underlying premise is that understanding the pathways and processes that lead to mucus overproduction in specific airway diseases will allow circumvention or amelioration of these processes.

Mucin secretion in the rat tracheal epithelial cells by epidermal growth factor and Pseudomonas aeruginosa extracts

BACKGROUND

Hypersecretion of mucin due to goblet cell hyperplasia is frequently encountered in many chronic airway diseases, such as chronic bronchitis, bronchiectasis, bronchial asthma and cystic fibrosis. Even in normal individuals, viral infection or bacterial pneumonia frequently provoke huge amounts of bronchial secretions which may cause airway obstruction. The production of mucin was regulated by epidermal growth factor (EGF) in vitro. To know whether this EGF system regulates mucin secretion in vivo and Pseudomonas also stimulates the mucin secretion by the same pathway, we studied these relationships in the cultured rat tracheal epithelial cells.

METHODS

Rat tracheal epithelial cells were obtained by pronase dissociation from the male Fisher 344 rats. When cells became confluent, they were divided into 6 groups and stimulated with either EGF for 24 hours or Pseudomonas extracts for 12 hours with or without selective EGF-R tyrosine kinase inhibitor tyrphostin AG1478.

RESULTS

We found that both EGF and Pseudomonas extracts phosphorylated the tyrosine residue in the EGF receptor from the rat tracheal epithelial cells and this tyrosine phosphorylation was nearly completely blocked by selective EGF-R tyrosine kinase inhibitor tyrphostin AG1478. The mucin secretion was also stimulated by either EGF or Pseudomonas extracts but more strong secretion of mucin and MUC5AC gene expression in the rat tracheal epithelial cell was done by Pseudomonas extracts.

CONCLUSION

These data suggest that Pseudomonas secretes the mucin by way of the EGF receptor and MUC5AC gene expression and the inhibitors of EGF receptor tyrosine phosphorylation would be useful to prevent the huge production of mucin due to Pseudomonas aeruginosa lung infection.