RNA Sequencing Reveals Cancer-Associated Changes in Laryngeal Cells Exposed to Non-Acid Pepsin

OBJECTIVE

Laryngopharyngeal reflux (LPR) is a common affliction that contributes to laryngeal inflammation, symptoms that impact quality of life, and life-threatening illnesses such as cancer. Effective treatment strategies for LPR are lacking. Pepsin is a proinflammatory and carcinogenic element of refluxate. Investigation of molecular pathways involved in pepsin-mediated damage may lead to identification of novel biomarkers and therapeutic targets for LPR. In this study, RNA sequencing was used to examine changes in human laryngeal epithelial cells following brief pepsin insult. Cells were immortalized to generate a model to aid future study of laryngeal injury and therapeutics.

STUDY DESIGN

In vitro translational.

METHODS

Laryngeal epithelial cells were cultured from a patient without signs or symptoms of LPR or laryngeal cancer. Cells were treated with 0.1 mg/ml pepsin for 1 hour or normal growth media (control) prior to RNA sequencing. Cells were immortalized via HPV E6/7 and characterized by microscopy, immunohistochemistry, G-banding, and soft agar assay.

RESULTS

Three hundred ninety-seven genes exhibited differences in expression with pepsin treatment (P < .05). Pathway analysis revealed association with cancer and related signaling processes including dysregulation of cancer-associated molecules, Metastasis-Associated Lung Adenocarcinoma Transcript 1 and KRT82, and the long-noncoding RNA, lipoprotein receptor-related protein 1 (LRP1)-AS, which regulates the putative pepsin receptor LRP1.

CONCLUSIONS

A single, brief exposure to pepsin activated cancer-associated signaling pathways in laryngeal cells in vitro, revealing novel mechanisms by which chronic reflux may contribute to carcinogenesis. The cell line developed herein represents a novel tool in which to investigate pepsin-dysregulated pathways identified by RNA sequencing and disparities of tumor proneness of laryngeal subsites.

LEVEL OF EVIDENCE

N/A Laryngoscope, 131:121-129, 2021.

Assessment of cancer stem cell marker expression in primary head and neck squamous cell carcinoma shows prognostic value for aldehyde dehydrogenase (ALDH1A1)

Cancer stem cells (CSCs) play a key role in carcinogenesis and progression of head and neck squamous cell carcinomas (HNSCC). The most common markers indicating for CSCs are: CD44, CD24, CD133, ALDH1A1. Our objective was to evaluate the prognostic potential of CSC markers in HNSCC. The study included 49 patients treated for primary HNSCC, 11 patients with upper respiratory tract epithelial dysplasia and 12 subjects with the normal pharyngeal mucosa as a control group. The frequency and expression levels of the four CSC markers were assessed by immunohistochemistry. Univariate and multivariate analyses were used to correlate CSC expression levels with tumor stage, lymph node metastases or overall survival (OS). CD44, CD24, CD133, ALDH1A1 were widely expressed in tumors, whereas CD44 was found to be higher in cancer tissue (P = 0.001). ALDH1A1 expression levels were found to be significantly higher in T3-T4 tumors vs. T1-T2 tumors (P = 0.05). Lymph node metastases had significantly higher expression levels of CD24 (P = 0.01) and CD133 (P < 0.05) than primary tumors. Multifactorial analysis revealed that overall survival (OS) for patients with ALDH1A1 negative tumors was 5.25 times higher than for patients with ALDH1A1 positive (ALDH1A1+) tumors (P = 0.01). On univariate and multivariate analysis, only ALDH1A1 positivity had a significant effect on OS of HNSCC patients (HR = 2.47 for P = 0.02). Immunohistochemistry-based assessments of CSC marker expression in HNSCC has significant predictive implications for patients with HNSCC. The frequency of CSCs in the tumor, specifically of ALDH1A1+ cells correlated with five-year OS in these patients.

A Method to Administer Agents to the Larynx in an Awake Large Animal

PURPOSE

This research note describes an adapted experimental methodology to administer an exogenous agent to the larynx and upper airway of awake animals. The exogenous agent could be a perturbation. In the current study, the agent was isotonic saline. Isotonic saline was selected because it is safe, of similar composition to extracellular fluid, and used in voice studies. The described approach allowed large animals such as pigs to be comfortably restrained without chemical sedation or anesthesia for extended periods while receiving the agent.

METHOD

Six Sinclair pigs were successfully trained with positive reinforcement to voluntarily enter and then be restrained in a Panepinto Sling. Once restrained, the pigs accepted a nose cone that delivered nebulized isotonic saline. This procedure was repeated 3 times per day for 20 days. At the end of the study, the larynx and airway tissues were excised and examined using histology and transmission electron microscopy.

RESULTS

Pathology related to the procedure (i.e., nebulized inhaled isotonic saline or stress) was not identified in any examined tissues.

CONCLUSIONS

This methodology allowed for repeated application of exogenous agents to awake, unstressed animals. This method can be used repeatedly in the laboratory to test various therapeutics for safety, toxicity, and dosage. Future studies will specifically manipulate the type of agent to further our understanding of laryngeal pathobiology.

Quantitative Analysis of OX62-Positive Dendritic Cell Distribution in the Rat Laryngeal Complex

Objectives:

Dendritic cells (DCs) are key instigators of rejection after transplantation. Their distribution has not been systematically characterized in all locations of the larynx and its surrounding tissues.

Methods:

Rat larynges were stained with monoclonal antibodies identifying DCs. These cells were then enumerated by a new combination of techniques including immunofluorescence, confocal microscopy, and imaging software.

Results:

The vast majority of DCs were located in the epithelium and subepithelium of the airway; the mean DC density ranged from 9 cells per square millimeter (0.2% of cells) to 645 cells per square millimeter (10.3% of cells). Their density in the epithelium was 3 to 11 times higher than that in the subepithelium. Non-airway sites (thyroid, parathyroid, muscle, fat) had mean DC densities varying from 3 cells per square millimeter (0.2%) to 57 cells per square millimeter (0.8%). No DCs were detected in cartilage.

Conclusions:

Dendritic cells are concentrated in the laryngotracheal epithelium and subepithelium and represent a much smaller proportion in the other sites studied. A baseline for laryngeal DC population studies has been established, and a computerized model for consistent quantitation using confocal microscopy has been developed. This unique method will serve as a foundation for investigating DC trafficking after rat laryngeal transplantation.

Age-Related Expression of α-Gustducin in the Rat Larynx

Objectives:

The age-related changes in distribution of α-gustducin–immunoreactive structures in the larynx of Sprague-Dawley rats were studied.

Methods:

For this purpose, tissues obtained from 12 male rats ranging in age from 5 to 21 weeks were compared with respect to the distribution and morphology of laryngeal taste buds immunoreactive for α-gustducin, the α-subunit of a taste cell–specific G protein.

Results:

Three different morphological types of α-gustducin–immunoreactive structures were seen: typical gemmal forms, clusters composed of 2 or 3 cells, and isolated immunoreactive cells not associated with taste buds. α-Gustducin–immunoreactive structures were most abundant in the epiglottis in all age groups. α-Gustducin–immunoreactive cells in rats seem to be located along the lateral food channels, in which they may come in contact with food. The total number of these α-gustducin–immunoreactive structures did not show any age-related changes, but the percentage of solitary immunoreactive cells in 5-week-old rats was significantly larger than the percentages in 8-, 14-, and 21-week-old animals.

Conclusions:

Solitary α-gustducin–immunoreactive cells, which are abundant in 5-week-old rats but are found in fewer numbers along the base of the epiglottis in mature rats, may be nociceptic in function, whereas the chemosensory clusters or buds that contain α-gustducin–positive cells and are distributed along the lateral food channels on the pharyngeal side of the larynx may have a role in gustatory reception.

Effect of Acid and Pepsin on Gene Expression in Laryngeal Fibroblasts

The aim of this study was to determine changes that momentary low pH with or without pepsin causes in gene expression in laryngeal fibroblasts. Cell cultures were established from human false vocal fold (FVF) and postcricoidal (PC) mucosae. Using a real-time polymerase chain reaction, we analyzed messenger RNA gene expression of growth factors (transforming growth factor β1, vascular endothelial growth factor, fibroblast growth factor 2), matrix metalloproteinases (MMP-1, MMP-2), and decorin in normal media, pH 4 media, and pH 5 media with and without pepsin. The FVF fibroblast gene expression differed substantially from the PC fibroblast gene expression. No significant interaction effects for acid and pepsin were found in the FVF culture, but in PC cultures we found a significant overexpression interaction effect for vascular endothelial growth factor, fibroblast growth factor 2, MMP-1, MMP-2, and decorin. These results imply that PC tissue is more sensitive than FVF tissue to the noxious effects of gastric contents. Furthermore, there appears to be a synergistic effect for acid and pepsin exposure in the posterior larynx.

Identification of cholinergic chemosensory cells in mouse tracheal and laryngeal glandular ducts

Specialized epithelial cells in the respiratory tract such as solitary chemosensory cells and brush cells sense the luminal content and initiate protective reflexes in response to the detection of potentially harmful substances. The majority of these cells are cholinergic and utilize the canonical taste signal transduction cascade to detect "bitter" substances such as bacterial quorum sensing molecules. Utilizing two different mouse strains reporting expression of choline acetyltransferase (ChAT), the synthesizing enzyme of acetylcholine (ACh), we detected cholinergic cells in the submucosal glands of the murine larynx and trachea. These cells were localized in the ciliated glandular ducts and were neither found in the collecting ducts nor in alveolar or tubular segments of the glands. ChAT expression in tracheal gland ducts was confirmed by in situ hybridization. The cholinergic duct cells expressed the brush cell marker proteins, villin and cytokeratin-18, and were immunoreactive for components of the taste signal transduction cascade (Gα-gustducin, transient receptor potential melastatin-like subtype 5 channel = TRPM5, phospholipase C(β2)), but not for carbonic anhydrase IV. Furthermore, these cells expressed the bitter taste receptor Tas2r131, as demonstrated utilizing an appropriate reporter mouse strain. Our study identified a previously unrecognized presumptive chemosensory cell type in the duct of the airway submucosal glands that likely utilizes ACh for paracrine signaling. We propose that these cells participate in infection-sensing mechanisms and initiate responses assisting bacterial clearance from the lower airways.

A flexible wide-field FLIM endoscope utilising blue excitation light for label-free contrast of tissue

Fluorescence lifetime imaging (FLIM) has previously been shown to provide contrast between normal and diseased tissue. Here we present progress towards clinical and preclinical FLIM endoscopy of tissue autofluorescence, demonstrating a flexible wide-field endoscope that utilised a low average power blue picosecond laser diode excitation source and was able to acquire ∼mm-scale spatial maps of autofluorescence lifetimes from fresh ex vivo diseased human larynx biopsies in ∼8 seconds using an average excitation power of ∼0.5 mW at the specimen. To illustrate its potential for FLIM at higher acquisition rates, a higher power mode-locked frequency doubled Ti:Sapphire laser was used to demonstrate FLIM of ex vivo mouse bowel at up to 2.5 Hz using 10 mW of average excitation power at the specimen.

Automated labeling of cancer textures in larynx histopathology slides using quasi-supervised learning

OBJECTIVE

To evaluate the performance of a quasi-supervised statistical learning algorithm, operating on datasets having normal and neoplastic tissues, to identify larynx squamous cell carcinomas. Furthermore, cancer texture separability measures against normal tissues are to be developed and compared either for colorectal or larynx tissues.

STUDY DESIGN

Light microscopic digital images from histopathological sections were obtained from laryngectomy materials including squamous cell carcinoma and nonneoplastic regions. The texture features were calculated by using co-occurrence matrices and local histograms. The texture features were input to the quasi-supervised learning algorithm.

RESULTS

Larynx regions containing squamous cell carcinomas were accurately identified, having false and true positive rates up to 21% and 87%, respectively.

CONCLUSION

Larynx squamous cell carcinoma versus normal tissue texture separability measures were higher than colorectal adenocarcinoma versus normal textures for the colorectal database. Furthermore, the resultant labeling performances for all larynx datasets are higher than or equal to that of colorectal datasets. The results in larynx datasets, in comparison with the former colorectal study, suggested that quasi-supervised texture classification is to be a helpful method in histopathological image classification and analysis.

Localization of label-retaining cells in murine vocal fold epithelium

PURPOSE

Epithelial homeostasis is critical for vocal fold health, yet little is known about the cells that support epithelial self-renewal. As a known characteristic of stem cells is that they are slow-cycling in vivo, the purpose of this prospective controlled study was to identify and quantify slow-cycling cells or putative stem cells in murine vocal fold epithelium.

METHOD

Twelve mice were administered daily intraperitoneal injections of a nucleotide dye, bromodeoxyuridine (BrdU), over 7 consecutive days. Under this pulse-chase paradigm, slow-cycling cells retain the dye (label-retaining cells; LRCs) while more rapidly cycling cells lose dye to dilution during multiple cell divisions. The percentage of label-retaining cells (%LRCs) was calculated following a chase period of 2, 4, and 8 weeks postinjections.

RESULTS

The %LRCs decreased significantly from 9.4% at 2 weeks to 3.1% at 8 weeks following injections (p < .05). No statistically significant differences in the quantity of BrdU-positive cells were measured between the anterior, mid-membranous, or cartilaginous regions of the vocal fold (p > .05).

CONCLUSION

These findings are consistent with the presence and first report of a small population of putative stem cells along the length of murine vocal fold epithelium.

Tissue-engineered larynx using perfusion-decellularized technique and mesenchymal stem cells in a rabbit model

CONCLUSION

Reseeding mesenchymal stem cells (MSCs) into the decellularized laryngeal muscle matrix for construction of a tissue-engineered larynx is feasible. This in vivo maturation in the omentum could be the first step before in situ implantation of the construct. This construct could facilitate a tissue-engineered method for laryngeal reconstruction.

OBJECTIVES

The extracellular matrix (ECM) and MSCs have been widely used for organ reconstruction. Our study aimed to prepare a soft tissue decellularized laryngeal scaffold with intact laryngeal cartilages utilizing a perfusion-decellularized technique, reseeding cells on it, and then construct a recellularized larynx.

METHODS

Perfusion-decellularized larynges were obtained from 20 rabbits by perfusion of the common carotid arteries with detergents. Twelve perfused larynges were observed by macroscopic visualization, histological examination, scanning electron microscopy (SEM), and cartilage viability. The remaining eight perfusion constructs were reseeded with induced MSCs aspirated from eight receptor rabbits. Composites were transferred into greater omentums of receptor rabbits after adherence for 1 day in vitro. Rabbit larynges were harvested after 4 weeks and 8 weeks, respectively. Macroscopic visualization, histological examination, and immunohistochemistry were performed.

RESULTS

Larynges perfused by sodium dodecyl sulfate became transparent after 2 h of perfusion. Histology and SEM indicated that the perfusion method showed a better decullularized effect. Almost no intact cells or nuclei were found, while more pores and collagen fibers were retained in the decellularized matrix. The chondrocyte vitality assay indicated that chondrocyte vitality was high. Vascularization was clearly seen by 4 weeks and relatively integrated cartilage frameworks remained by 8 weeks. Histological and immunohistochemical examinations clearly showed muscle bundles and vessels.

Immunohistochemical localization of glutathione s-transferase isoenzymes (gsta, Gstp, Gstm4, And Gstt1) and tumour marker p53 in matched tissue from normal larynx and laryngeal carcinoma: correlations with prognostic factors

OBJECTIVE

The immunohistochemical staining characteristics of glutathione S-transferase (GST) alpha (GSTA), pi (GSTP), mu (GSTM4), and theta (GSTT1) and P53 were investigated in laryngeal squamous cell carcinoma (LSCC) cases and normal laryngeal tissue from 46 patients. The relationships between expression of the GST isoenzymes and some clinicopathologic features were also examined.

PATIENTS AND METHODS

For immunohistochemical studies, tissues from 46 patients with LSCC at the Dr. Lütfi Kirdar Kartal Education and Research Hospital were used. The relationship between expression of the GST isoenzymes and P53 in normal and tumour tissue was analyzed using the Wilcoxon signed rank test. The correlation between GST isoenzymes and P53 and clinicopathologic data was also examined using the Spearman rank test.

RESULTS

When the normal and tumour tissues of these cases were compared according to their staining intensity and percentage of positive staining, GSTA expression in normal cells was significantly higher than in tumour cells, and GSTP and P53 expression was higher in tumour cells (p < .05). GSTM and GSTT1 expression was higher in normal cells; however, the statistical significance was low (p > .05). There was no correlation between P53 and GST expression in patients with LSCC. When the immunohistochemical results of GST isoenzymes and P53 were correlated with the clinical parameters, GSTA expression was increased in poorly differentiated laryngeal tumour, but GSTM4 and GSTT1 expression was decreased (p < .05).

CONCLUSION

According to these results, GST-A, -P, and T1 and P53 were important in the diagnosis of LSCC.

Identification of thyroid hormone receptors in the human larynx

PURPOSE

Thyroid hormone is essential for normal development, growth, and function of the majority of tissues. Among the many clinical signs associated with hypothyroidism, alterations in the voice may occur even in cases of mild thyroid failure, suggesting that the larynx is a target tissue for thyroid hormone. The objective of our study is to further understand the effects of thyroid hormone on the larynx by first identifying the presence and locations of its receptors.

METHODS

Two human cadaveric larynges (one male and one female) were harvested, formalin-fixed, and paraffin-embedded. Sections were immunostained with antibodies reactive with the two identified thyroid hormone receptors, TR-alpha and TR-beta. The slides were examined under light microscopy.

RESULTS

Both male and female specimens revealed consistent patterns of staining for thyroid hormone receptors. The staining pattern for TR-alpha included the fibrous connective tissue of the lamina propria, the cartilage, and the glandular elements. The staining pattern for TR-beta included the fibrous connective tissue of the lamina propria only. No receptors were identified in the respiratory mucosa or muscle.

CONCLUSIONS

Thyroid hormone receptors are present in both the male and the female human larynx. These findings imply a role for thyroid hormone within the human larynx, through both TR-alpha and TR-beta.

Cough reflex is additively potentiated by inputs from the laryngeal and tracheobronchial [corrected] receptors and enhanced by stimulation of the central respiratory neurons

The cough is an essential airway defense reflex. In this study we investigated the coordination of inputs from the laryngeal and tracheobronchial receptors in the cough reflex. In 15 beagle dogs (7-9 kg) lightly anesthetized with intravenous profobol (20-30 mg/kg/h), the cough response was elicited with mechanical stimulation of either the vocal chord or tracheal bifurcation. Simultaneous stimulation of both sites increased all the parameters of cough strength, that is, mean pleural pressure (P (pl)), mean expiratory flow, number of cough bouts, and cough duration, in comparison with stimulation of the sites individually. The increases in mean P (pl) and cough duration reached statistical significance (13.3 vs. 18.4 cmH(2)O and 13.3 vs. 18.2 s, respectively). When the anesthetic level became deeper, the prolongation of cough duration almost disappeared, but the augmentation of mean P (pl) was much less affected. During stimulation of the central respiratory neurons by intravenous dimorphoramine or acute hyperoxic hypercapnia, the cough strength increased significantly. We concluded that inputs from the laryngeal and tracheobonchial cough receptors acted in concert and potentiated the cough reflex. Furthermore, stimulation of the central respiratory neurons may increase the intensity of a cough response.

Distribution and density of CD1a+ and CD83+ dendritic cells in HPV-associated laryngeal papillomas

BACKGROUND

Respiratory papillomatosis associated with human papilloma virus (HPV) infection is the most common benign laryngeal neoplasm. The age of patients at disease onset, HPV type, number of surgeries are well known prognostic factors of the disease course. The correlation between dendritic cell (DC) density in tumor tissue and clinical prognosis was established.

AIM

The aim of our study was to estimate the density of DC in laryngeal papillomas associated with HPV types 6/11 infection and to evaluate the relationship between the number of DC and the disease severity.

MATERIALS AND METHODS

Our study included 40 randomly selected biopsy specimens from patients with HPV-positive laryngeal papillomatosis aged from 1.7 to 20 year. DC were immunohistochemically labelled with anti-CD1a antibodies and anti-CD83 antibodies. The density of DC was analysed in epithelial layer and lamina propria.

RESULTS

In the epithelial layer of papillomas the number of CD1a+ and CD83+ DC was 86.2 (47.5-119.9) cells/mm(2) and 2.6 (0.6-7.9) cells/mm(2), respectively. In lamina propria - 15.3 (5.1-27.9) and 16.0 (6.7-33.2) cells/mm(2). For subgroups of patients with high number of operations (more than 3), early disease onset (children under 3 years of age) and lingering duration of disease (more than 1 year) we detected an increase of CD83+ DC in the epithelial layer. However, our data did not demonstrate a statistically significant difference in CD1a+ DC count neither in the epithelium nor in the lamina propria. Probably, the increase of CD83+ DC density in epithelial layer of patients with severe course of disease can be an evidence of impaired migration of matured DC.

Corynebacterium diphtheriae employs specific minor pilins to target human pharyngeal epithelial cells

Adherence to host tissues mediated by pili is pivotal in the establishment of infection by many bacterial pathogens. Corynebacterium diphtheriae assembles on its surface three distinct pilus structures. The function and the mechanism of how various pili mediate adherence, however, have remained poorly understood. Here we show that the SpaA-type pilus is sufficient for the specific adherence of corynebacteria to human pharyngeal epithelial cells. The deletion of the spaA gene, which encodes the major pilin forming the pilus shaft, abolishes pilus assembly but not adherence to pharyngeal cells. In contrast, adherence is greatly diminished when either minor pilin SpaB or SpaC is absent. Antibodies directed against either SpaB or SpaC block bacterial adherence. Consistent with a direct role of the minor pilins, latex beads coated with SpaB or SpaC protein bind specifically to pharyngeal cells. Therefore, tissue tropism of corynebacteria for pharyngeal cells is governed by specific minor pilins. Importantly, immunoelectron microscopy and immunofluorescence studies reveal clusters of minor pilins that are anchored to cell surface in the absence of a pilus shaft. Thus, the minor pilins may also be cell wall anchored in addition to their incorporation into pilus structures that could facilitate tight binding to host cells during bacterial infection.

Homogeneity of intrinsic properties of sexually dimorphic vocal motoneurons in male and female zebra finches

Sex differences in behavioral repertoires are often reflected in the underlying electrophysiological and morphological properties of motor neurons. Male zebra finches produce long, spectrally complex, learned songs and short calls, whereas female finches only produce short, innate, and spectrally simple calls. In both sexes, vocalizations are produced by using syringeal muscles controlled by motoneurons within the tracheosyringeal part of the hypoglossal motor nucleus (XIIts). We asked whether the sexually dimorphic vocal repertoire of adult zebra finches is paralleled by structural and functional differences in syringeal motoneurons. By using immunohistochemical and intracellular staining methods, we describe sex differences in the morphology of XIIts and its surrounding neuropil (suprahypoglossal region; SH). Although the overall number of XIIts neurons and the proportions of somata/neuropil were not sexually dimorphic, the volumes of both XIIts and SH were larger in males, in part because male XIIts neurons had larger somata. In contrast, female XIIts motoneurons had a more complex dendritic structure than did male neurons, suggesting that the larger volume of the male XIIts is due in part to increased numbers of afferents. Intracellular recordings in brain slices revealed that the intrinsic electrophysiological properties of female XIIts neurons were similar to published values for male XIIts motoneurons. We also show that female neurons received glycinergic inputs from the brainstem respiratory premotor column, similar to those described in males. These findings indicate that male and female zebra finches produce their disparate vocal repertoires using physiologically similar motoneurons. Thus, sites upstream of the motoneuron pool may be the major determinants of sexually dimorphic vocal behaviors in this species.

Contributions of the active and passive components of the cytoskeletal prestress to stiffening of airway smooth muscle cells

Airway smooth muscle cells exhibit stiffening during contractile activation. This stiffening may be interpreted as a result of the stabilizing influence of the mechanical prestress stored within the cytoskeleton (CSK). However, in vivo, airway smooth muscle cells contract while simultaneously experiencing breathing-induced stretching. Excessive stretching of cells could cause actin-myosin crosslinks, and possibly other cytoskeletal filaments, to break, thereby leading to dissipation of the prestress and inhibition of further cell stiffening. The aim of this study is to investigate the stiffening behavior of individual human airway smooth muscle (HASM) cells exposed to a combination of substrate stretching, contractile activation and relaxation. We treated cultured HASM cells with either contractile (histamine) or relaxing (DBcAMP) pharmacological agonists and used magnetic cytometry technique to investigate the stiffening behavior of these cells during uniform substrate stretching (0-30%). Cells that were not treated, as well as those treated with histamine, exhibited increasing stiffening during stretching up to 20% of substrate strain, with additional stiffening becoming inhibited for substrate strains of 20-30%. In contrast, in cells treated with DBcAMP, stretching produced moderate but continuous stiffening with increasing substrate strain. These results indicate that both active and passive components of the prestress contribute to cell stiffening. We also observed that cells permeabilized with saponin exhibited stiffening at low levels (<10%) of substrate stretching, similar to non-permeabilized cells, but not at high levels (10-30%) of stretching, where stiffening was inhibited. These data suggest that at low levels of substrate strains the relative contributions of ion channel activation as well as actin and focal adhesion remodeling are less important for stiffening than passive distension of the CSK. Taken together, our results suggest that both the active and passive components of the cytoskeletal prestress contribute to the stiffening behavior of HASM cells under physiological conditions, but that at high levels of cellular distensions there is a possible tradeoff between these two components with the contribution from the passive component becoming increasingly more important.

Relationship between time of exposure of laryngopharyngeal reflux and gene expression in laryngeal fibroblasts

OBJECTIVES

Acid reflux is damaging to the laryngeal mucosa; however, the significance of the duration of reflux episodes has not been evaluated. The purpose of this study was to determine whether varying the exposure times at low pH with or without pepsin alters gene expression in laryngeal fibroblasts.

METHODS

Human false vocal fold and postcricoidal cultures were exposed to pH 4 or pH 5 media with and without pepsin for 10, 30, 60, and 240 seconds. Using a real-time polymerase chain reaction, we determined the messenger RNA expression of TGFbeta-1, VEGF, FGF-2, EGR-1, ATF-3, CTGF, MMP-1, MMP-2, and decorin.

RESULTS

Molecular responses were initiated at pH 5. Postcricoidal fibroblasts were more sensitive than false vocal fold fibroblasts to the presence of pepsin. Changes in transcript levels were dependent on acid exposure time, and the most significant changes were measured during the first 60 seconds after exposure.

CONCLUSIONS

Time of exposure to acid and pepsin needs to be taken into consideration when determining limit of pathology in pharyngeal reflux. Genes are identified that are induced by low pH and that may be of potential importance in the pathogenesis of reflux laryngitis.

Airway nociceptors activated by pro-inflammatory cytokines

The present studies evaluate whether the vagus nerves link the lungs' immune and neural systems by transmitting information through pulmonary nociceptors. Single unit activities from pulmonary nociceptors [C fiber receptors (CFRs) and high threshold Adelta fiber receptors (HTARs)] were recorded from the cervical vagus nerve in anesthetized, open-chest, and mechanically ventilated rabbits. Interleukin1beta was then injected into the nociceptor field (IL-1beta, 10 microg/ml, 20 microl). Both CFRs and HTARs were stimulated by the local injection; their activities increased from 0.2+/-0.1 to 1.8+/-0.5 imp/s (n=10; p<0.01), and from 0.2+/-0.1 to 1.1+/-0.1 imp/s, respectively (n=6; p<0.01). These increases were greatly attenuated by simultaneous administration of IL-1beta with IL-1 ra, a natural IL-1 receptor antagonist. The nociceptors were not stimulated by local injection of normal saline. Our data demonstrate that nociceptors can be activated by pro-inflammatory cytokines and support the hypothesis that airway nociceptors transmit immune signals from the lung to the brain.

Adherence and internalization of Streptococcus gordonii by epithelial cells involves beta1 integrin recognition by SspA and SspB (antigen I/II family) polypeptides

Streptococcus gordonii is a commensal bacterium that colonizes the hard and soft tissues present in the human mouth and nasopharynx. The cell wall-anchored polypeptides SspA and SspB expressed by S. gordonii mediate a wide range of interactions with host proteins and other bacteria. In this article we have determined the role of SspA and SspB proteins, which are members of the streptococcal antigen I/II (AgI/II) adhesin family, in S. gordonii adherence and internalization by epithelial cells. Wild-type S. gordonii DL1 expressing AgI/II polypeptides attached to and was internalized by HEp-2 cells, whereas an isogenic AgI/II- mutant was reduced in adherence and was not internalized. Association of S. gordonii DL1 with HEp-2 cells triggered protein tyrosine phosphorylation but no significant actin rearrangement. By contrast, Streptococcus pyogenes A40 showed 50-fold higher levels of internalization and this was associated with actin polymerization and interleukin-8 upregulation. Adherence and internalization of S. gordonii by HEp-2 cells involved beta1 integrin recognition but was not fibronectin-dependent. Recombinant SspA and SspB polypeptides bound to purified human alpha5beta1 integrin through sequences present within the NAV (N-terminal) region of AgI/II polypeptide. AgI/II polypeptides blocked interactions of S. gordonii and S. pyogenes with HEp-2 cells, and S. gordonii DL1 cells expressing AgI/II proteins inhibited adherence and internalization of S. pyogenes by HEp-2 cells. Conversely, S. gordonii AgI/II- mutant cells did not inhibit internalization of S. pyogenes. The results suggest that AgI/II proteins not only promote integrin-mediated internalization of oral commensal streptococci by host cells, but also potentially influence susceptibility of host tissues to more pathogenic bacteria.

Expression of matrix metalloproteinase-9 (gelatinase B) in benign, premalignant and malignant laryngeal lesions

The matrix metalloproteinases (MMPs) are a family of proteolytic zinc-containing enzymes, which are responsible for the breakdown of the extracellular matrix components in pathological and physiological conditions. They are involved in basement membrane disruption, stroma and blood vessel penetration, metastasis and more recently there is evidence that they participate in tumor growth and angiogenic events. Matrix metalloproteinase 2 and 9 (MMP 2 and 9) belong to the gelatinases, a subgroup of MMPs, and have the capacity to degrade the triple helix type IV collagen of basal lamina of the basement membrane. With the present study, we tried to demonstrate the expression of MMP-9 immunohistochemically, comparatively in benign, premalignant and malignant lesions of the larynx. We studied 154 laryngeal lesions including 55 squamous cell carcinomas, 8 in situ carcinomas, 54 cases of dysplasia (of low and intermediate grade), 13 papillomas and 24 cases of keratosis. Overexpression of MMP 9 was observed in 74.4% and 50% in invasive and in situ squamous cell carcinomas respectively. In dysplastic cases, in papillomas and in keratoses the percentage of overexpression was 62.9%, 61.53% and 54.16% respectively and the expression of MMP-9 was significantly higher in invasive squamous cell carcinomas compared to dysplasias (p=0.000004). Also significantly higher was the expression of MMP-9 in dysplastic cases compared to papillomas (p=0.023). The MMP-9 expression was related neither to survival nor to the other available clinicopathological parameters (tumor size, grade, clinical stage, lymph node status and patient age). In conclusion, our study indicates that the expression of MMP-9 is up-regulated in a stepwise fashion, with two main steps, the first one, when a dysplastic lesion evolves and the next one, when the dysplasia progresses to invasive carcinoma.

In vitro and in vivo studies on CCR10 regulation by Annexin A1

The mode of action of annexin A1 (ANXA1) is poorly understood. By using rapid subtraction hybridization we studied the effects of human recombinant ANXA1 and the N-terminal ANXA1 peptide on gene expression in a human larynx cell line. Three genes showed strong downregulation after treatment with ANXA1. In contrast, expression of CCR10, a seven transmembrane G-protein coupled receptor for chemokine CCL27 involved in mucosal immunity, was increased. Moreover the reduction in CCR10 expression induced by ANXA1 gene deletion was rescued by intravenous treatment with low doses of ANXA1. These findings provide new evidence that ANXA1 modulates gene expression.

Phosphatidylinositol 3-kinase regulates early differentiation in human laryngeal keratinocytes

Epidermal growth factor receptor (EGFR) signaling regulates a variety of cellular functions, including proliferation, gene expression, and differentiation. Infection of laryngeal epithelial cells by human papillomaviruses causes recurrent respiratory papillomas, benign tumors characterized by an altered pattern of differentiation. Papilloma cells overexpress the EGFR and have constitutively active extracellular signal-regulated kinase (ERK) and enhanced phosphatidylinositol 3-kinase (PI3K) activity, but overexpression of the lipid phosphatase PTEN (Phosphatase and Tensin Homolog) reduces activation of Akt by PI3K. We hypothesized that the altered differentiation of papillomas reflects these changes in signaling from the EGFR-ERK and PI3K-Akt pathways and that one or both of these pathways is required for the normal differentiation process in mucosal epithelium. Inhibiting either the enzymatic activity or the synthesis of PI3K in uninfected laryngeal cells blocked expression of keratin-13 (K13), a protein induced during normal differentiation. In contrast, inhibiting activation of ERK had minimal effect. Using ribonucleic acid interference to reduce protein levels of integrin-linked kinase 1 or phosphoinositide-dependent protein kinase 1, intermediates in the activation of Akt by PI3K, or reducing levels of Akt-1 itself did not inhibit K13 expression by normal laryngeal keratinocytes. We conclude that PI3K activation is an important regulator of expression of K13, a marker for the normal differentiation process in human mucosal keratinocytes, that this function does not require activation of Akt-1, and that the failure to express K13 in papilloma cells is not because of reduction in activated Akt.