Weakly acidic pH reduces inflammatory cytokine expression in airway epithelial cells

Low Antioxidant Enzyme Levels and Oxidative Stress in Laryngopharyngeal Reflux (LPR) Patients

OBJECTIVE

Laryngopharyngeal reflux disease (LPR) is a characterized by symptoms different from gastroesophageal reflux disease (GERD). LPR can causes chronic mucosal inflammation which may lead to an increase in cytokine production, and a systemic decrease in antioxidant enzyme levels. Our aim in this study is to evaluate antioxidant enzyme levels in patients with LPR.

METHODS

Reflux Symptom Index (RSI) questionnaire, extraesophageal symptom questionnaire which is included in RSI and Reflux Finding Score (RFS) evaluation with 70° rigid laryngoscope were performed to patients who applied to the otolaryngology clinic with a typical LPR complaint, and 60 patients who had an RSI score above 13 and an RFS score above 7 were included in the study. Thirty people consisting of healthy volunteers were included in the control group. Antioxidant enzyme SOD, GSH-Px and CAT levels were measured in the blood serum of the patients and compared with the control group. Results obtained from biochemical tests were expressed as mean ± SE. Descriptive statistical methods (mean ± standard error) were used for the independent t test for the control and study group. P < 0.05 was considered statistically significant.

RESULTS

In the LPR group, 28 (46%) were women, 32 (53%) were men, and age range was 21-60, average age was 36.45 ± 1.147.There was no significant difference between LPR and control group in terms of age, gender and Body Mass Index (BMI). In the LPR group, the lowest score for RSI was 14 and the highest score was 39. The average RSI was 23.67. RFS ranges from 8-22. The mean RFS was 13.50. A highly significant statistical correlation was observed between RSI and total RFS (P < 0.001). There was a significant difference between the antioxidant enzyme levels of the control group and the LPR group. Antioxidant enzyme levels of the control group were SOD 274.10 ± 26.836 U / L, GSH-Px 174.20 ± 20.699 µU / mL and CAT 42.2898 ± 20.699 KU / L. Antioxidant enzyme level results of the LPR group were SOD 147 ± 14.022 U / L (P < 0.01), GSH-Px 88.28 ± 9.113 µU / mL (P < 0.01) and CAT 12.67 ± 0.799 KU / L (P < 0.001). The RSI results ranges from 4 to 39 and the RFS from 8 to 22. Antioxidant enzyme levels demonstrated fairly consistent reliability with individual variables from both RFS and RFS. There was also a highly significant statistical correlation between RSI and RFS.

CONCLUSION

We found that the antioxidant enzymes SOD, GPX and catalase enzyme levels were significantly lower in LPR patients. Treatment modalities to reduce oxidative stress (OS) in LPR should be investigated.

Inflammation and Dry Eye-like Symptoms as Concomitant Manifestations of Laryngo-Pharyngeal Reflux

PURPOSE

Laryngo-pharyngeal reflux (LPR) is a common worldwide disease. LPR symptoms may involve distant organs and tissues including the ocular surface with manifestations of a Dry Eye-like disease. We evaluated the concomitant involvement of the ocular surface in patients with LPR. We also defined the clinical signs and the roles of chemical and neuro-inflammatory mediators in the tears of LPR patients.

METHODS

Seventy-seven patients with LPR (mean age 65.8 ± 16.8 SD) and 25 healthy controls (mean age 56.5 ± 16.3 SD) were recruited from the otorhinolaryngology unit. Each subject was evaluated for the presence of concomitant ocular surface disease through clinical examination, including the measurement of tear break-up time (TBUT) and the Ocular Surface Disease Index (OSDI) questionnaire. Tears and conjunctival imprints were collected. The presence of pepsin in tears was detected by ELISA. HLA-DR in conjunctival imprints were imaged by immunofluorescence microscopy. RT-PCR quantified conjunctival mRNA transcripts of HLA-DR, IL-8, MUC5AC, NADPH, VIP, and NPY.

RESULTS

Patients with LPR had significantly increased OSDI and reduced TBUT scores compared to control subjects (p < 0.05 each). Pepsin was detected in 51% of patient tears while it was not measurable in the controls (p < 0.01). Immunoreactivity for HLA-DR in the conjunctival impressions was greater than for the controls with an increased mRNA expression (p < 0.05). mRNA transcripts for IL-8, NADPH, and VIP were significantly increased in LPR patients (p < 0.05 each), but neither MUC5AC nor NPY were different from controls.

CONCLUSIONS

LPR can adversely affect the ocular surface, leading to moderate signs and symptoms of dry eye. This study provides evidence that the presence of pepsin, HLA-DR immunoreactivity, and increased mRNA expression of neuro-inflammatory markers in the tears and conjunctival imprints of LPR patients suggests a potential link between LPR inflammation and ocular surface disease.

The effect of acute acid exposure on immunomodulatory protein secretion, cell survival, and cell cycle progression in tumour cell lines

Cancer develops when multiple systems fail to suppress uncontrolled cell proliferation. Breast cancers and oesophageal squamous cell carcinoma (OSCC) are common cancers prone to genetic instability. They typically occur in acidic microenvironments which impacts on cell proliferation, apoptosis, and their influence on surrounding cells to support tumour growth and immune evasion. This study aimed to evaluate the impact of the acidic tumour microenvironment on the production of pro-tumorigenic and immunomodulatory factors in cancer cell lines. Multiple factors that may mediate immune evasion were secreted including IL-6, IL-8, G-CSF, IP-10, GDF-15, Lipocalin-2, sICAM-1, and myoglobin. Others, such as VEGF, FGF, and EGF that are essential for tumour cell survival were also detected. Treatment with moderate acidity did not significantly affect secretion of most proteins, whereas very low pH did. Distinct differences in apoptosis were noted between the cell lines, with WHCO6 being better adapted to survive at moderate acid levels. Conditioned medium from acid-treated cells stimulated increased cell viability and proliferation in WHCO6, but increased cell death in MCF-7. This study highlights the importance of acidic tumour microenvironment in controlling apoptosis, cell proliferation, and immune evasion which may be different at different anatomical sites. Immunomodulatory molecules and growth factors provide therapeutic targets to improve the prognosis of individuals with cancer.

Investigating Potential TRPV1 Positive Feedback to Explain TRPV1 Upregulation in Airway Disease States

OBJECTIVE

The airway epithelium is a potential source of pathophysiology through activation of transient potential receptor vallinoid type 1 (TRPV1) channel. A positive feedback cycle caused by TRPV1 activity is hypothesised to induce upregulation and production of inflammatory cytokines, leading to exacerbations of chronic airway diseases. These cytokine and protein regulation effects were investigated in this study.

METHODS

Healthy (BEAS-2B) and cancer-derived (Calu-3) airway epithelial cell lines were assessed for changes to TRPV1 protein expression and mRNA expression following exposure to capsaicin (5 µM to 50 µM), and TRPV1 modulators including heat (43 °C), and hydrochloric acid (pH 3.4 to pH 6.4). Cytotoxicity was measured to determine the working concentration ranges of treatment. Subsequent bronchoconstriction by TRPV1 activation with capsaicin was measured on guinea pig airway tissue to confirm locally mediated activity without the action of known neuronal inputs.

RESULTS

TRPV1 protein expression was not different for all capsaicin, acidity, and heat exposures (P > 0.05), and was replicated in mRNA protein expression (P > 0.05). IL-6 and IL-8 expression were lower in BEAS-2B and Calu-3 cell lines exposed with acidity and heat (P < 0.05), but not consistently with capsaicin exposure, with potential cytotoxic effects possible.

CONCLUSIONS

TRPV1 expression was present in airway epithelial cells but its expression was not changed after activation by TRPV1 activators. Thus, it was not apparent the reason for reported TRPV1 upregulation in patients with airway disease states. More complex mechanisms are likely involved and will require further investigation.

Aspiration syndromes and associated lung injury: incidence, pathophysiology and management

Aspiration is a common condition affecting healthy or sick patients which could create an acute or chronic inflammatory reaction in the lungs. Aspiration syndromes could be categorized according to a content entering the respiratory system into bacterial aspiration pneumonia with the gastric or oropharyngeal bacteria entering, aspiration chemical pneumonitis with bacteria-freegastric acid aspiration, or aspiration of a foreign body which causes an acute pulmonary emergency. There are differences in the clinical presentation of volume-dependent aspirations (microaspiration and macroaspiration): the higher is the volume of aspiration, the greater is the injury to the patient and more serious are the health consequences (with 70 % mortality rate for hospitalized patients). Aspiration syndromes can affect both the airways and pulmonary parenchyma, leading to acute lung injury, increased hospitalization rate and worse outcomes in critically ill patients. Impaired alveolar-capillary permeability, oedema formation, neutrophilic inflammatory response and pulmonary surfactant inactivation lead to reduced lung compliance and loss of aerated lung tissue and give rise to hypoxemia and respiratory failure. This review discusses the effect of aspiration events on the pulmonary tissue. The main focus is to distinguish the differences between bacterial and chemical pneumonia, their clinical presentation and symptoms, risk factors of developing the changes, possibilities of diagnostics and management as well as prevention of aspirations. Because of a risk of serious lung damage after the aspiration, pathophysiology and processes leading to lung tissue injury are discussed in detail. Data sources represent a systematic literature search using relevant medical subject headings.

Laryngopharyngeal Reflux and Inflammatory Responses in Mucosal Barrier Dysfunction of the Upper Aerodigestive Tract

The upper aerodigestive tract (UAT) is the first line of defense against environmental stresses such as antigens, microbes, inhalants, foods, etc., and mucins, intracellular junctions, epithelial cells, and immune cells are the major constituents of this defensive mucosal barrier. Laryngopharyngeal reflux (LPR) is recognized as an independent risk factor for UAT mucosal disorders, and in this review, we describe the components and functions of the mucosal barrier and the results of LPR-induced mucosal inflammation in the UAT. We discuss the interactions between the refluxate and the mucosal components and the mechanisms through which these damaging events disrupt and alter the mucosal barriers. In addition, we discuss the dynamic alterations in the mucosal barrier that might be potential therapeutic targets for LPR-induced disorders.

The proton-sensing receptor ovarian cancer G-protein coupled receptor 1 (OGR1) in airway physiology and disease

Numerous G protein-coupled receptors (GPCRs) regulate multiple airway functions and play fundamental roles in normal and aberrant airway and lung physiology. Thus, GPCRs are prime candidates of targeting by disease therapeutics. The intriguing proton-sensing GPCR Ovarian cancer G-protein coupled receptor 1 (OGR1; aka GPR68) has recently been shown capable of regulating airway smooth muscle (ASM) contraction and proliferation. Although the study of OGR1 has been confounded by the fact that the proton is the presumed cognate ligand of OGR1, recent studies have begun to identify novel ligands and modulators capable of regulating the diverse signaling, and functional role of OGR1. Such studies offer hope for OGR1-targeting drugs as therapeutics for obstructive lung diseases such as asthma. Herein, we review the literature to date detailing the receptor biology and pharmacology of OGR1, receptor function in the airway, and describe the potential clinical utility of OGR1-modulating drugs.

VISTA: a novel immunotherapy target for normalizing innate and adaptive immunity

V-domain Ig suppressor of T cell activation (VISTA) is a novel checkpoint regulator with limited homology to other B7 family members. The constitutive expression of VISTA on both the myeloid and T lymphocyte lineages coupled to its important role in regulating innate and adaptive immune responses, qualifies VISTA to be a promising target for immunotherapeutic intervention. Studies have shown differential impact of agonistic and antagonistic targeting of VISTA, providing a unique landscape for influencing the outcome of cancer and inflammatory diseases.

Perioperative gastroesophageal regurgitation in patients with elevated abdominal pressure with nasogastric tubes? A simulation model based on esophageal multichannel intraluminal impedance and pH monitoring

Increased abdominal pressure is common in obese patients and predisposes them to gastroesophageal regurgitation (GER). To drain GER and prevent aspiration, nasogastric (NG) tubes are frequently inserted in obese patients undergoing general anesthesia. However, whether gastric drainage actually decreases the occurrence of GER remains to be elucidated. In this study, increased abdominal pressure was simulated with laparoscopic pneumoperitoneum and Trendelenburg (LPT) positioning, while the retained NG tube was replaced by a pre-inserted esophageal multichannel intraluminal and pH (MII-pH) monitoring. Fifteen patients undergoing elective gynecologic laparoscopy were enrolled in this study. Thirteen patients (86%) developed GER while in the LPT position. With the high occurrence of GER, pre-inserted NG tubes under general anesthesia are not likely to be protective in obese patients.

Distinct Immune Responses Elicited From Cervicovaginal Epithelial Cells by Lactic Acid and Short Chain Fatty Acids Associated With Optimal and Non-optimal Vaginal Microbiota

Non-optimal vaginal microbiota, as observed in bacterial vaginosis (BV), is typically characterized by a depletion of beneficial lactobacilli and an abundance of numerous anaerobes. These non-optimal conditions are associated with subclinical cervicovaginal inflammation and an increased risk of HIV infection compared to women colonized with optimal vaginal microbiota dominated by lactobacilli. Lactic acid (LA) is a major organic acid metabolite produced by vaginal lactobacilli that elicits anti-inflammatory effects from cervicovaginal epithelial cells and is dramatically depleted during BV. However, it is unclear if LA retains its anti-inflammatory activity in the presence of vaginal microbiota metabolites comprising short chain fatty acids (SCFAs) and succinic acid, which are also produced by an optimal vaginal microbiota. Furthermore, the immunomodulatory effect of SCFAs and succinic acid on cervicovaginal epithelial cells at higher concentrations present during BV is unknown. Here we report that in the presence of physiologically relevant concentrations of SCFAs and succinic acid at pH 3.9 (as found in women with lactobacillus-dominated microbiota) LA induced an anti-inflammatory state in cervicovaginal epithelial cells and inhibited inflammation elicited by the toll-like receptor (TLR) agonists polyinosinic:polycytidylic acid and Pam3CSK4. When cervicovaginal epithelial cells were treated with a vaginal microbiota metabolite mixture representative of BV, containing a lower concentration of LA but higher concentrations of SCFA/succinic acid at pH 7, no anti-inflammatory was observed. Rather, the vaginal microbiota metabolite mixture representative of BV dysregulated the immune response of cervicovaginal epithelial cells during prolonged and sustained treatments. This was evidenced by increased basal and TLR-induced production of pro-inflammatory cytokines including tumor necrosis factor-α, but decreased basal production of chemokines including RANTES and IP-10. Further characterization of individual components of the BV vaginal microbiota mixture suggested that acetic acid is an important vaginal microbiota metabolite capable of eliciting diverse immunomodulatory effects on a range of cervicovaginal epithelial cell targets. These findings indicate that elevated levels of SCFAs are a potential source of cervicovaginal inflammation in women experiencing BV, and support the unique anti-inflammatory properties of LA on cervicovaginal epithelial cells as well as a role for LA or LA-producing lactobacilli to reverse genital inflammation associated with increased HIV risk.

Suppression of Intestinal Epithelial Cell Chemokine Production by Lactobacillus rhamnosus R0011 and Lactobacillus helveticus R0389 Is Mediated by Secreted Bioactive Molecules

Host intestinal epithelial cells (IEC) present at the gastrointestinal interface are exposed to pathogenic and non-pathogenic bacteria and their products. Certain probiotic lactic acid bacteria (LAB) have been associated with a range of host-immune modulatory activities including down-regulation of pro-inflammatory gene expression and cytokine production by IEC, with growing evidence suggesting that these bacteria secrete bioactive molecules with immunomodulatory activity. The aim of this study was to determine whether two lactobacilli with immunomodulatory activity [Lactobacillus rhamnosus R0011 (Lr) and Lactobacillus helveticus R0389 (Lh)], produce soluble mediators able to influence IEC responses to Pattern Recognition Receptor (PRR) ligands and pro-inflammatory cytokines [Tumor Necrosis Factor α (TNFα), Interleukin-1β (IL-1β)], signals inducing IEC chemokine production during infection. To this end, the effects of cell-free supernatants (CFS) from Lr and Lh on IEC production of the pro-inflammatory chemokines interleukin (IL)-8 and cytokine-induced neutrophil chemoattractant 1 (CINC-1) induced by a range of host- or pathogen-derived pro-inflammatory stimuli were determined, and the impact on human HT-29 IEC and a primary IEC line (rat IEC-6) was compared. The Lr-CFS and Lh-CFS did not significantly modulate basal IL-8 production from HT-29 IECs or CINC-1 production from IEC-6 cells. However, both Lr-CFS and Lh-CFS significantly down-regulated IL-8 production from HT-29 IECs challenged with varied PRR ligands. Lr-CFS and Lh-CFS had differential effects on PRR-induced CINC-1 production by rat IEC-6 IECs, with no significant down-regulation of CINC-1 observed from IEC-6 IECs cultured with Lh-CFS. Further analysis of the Lr-CFS revealed down-regulation of IL-8 production induced by the pro-inflammatory cytokines IL-1β and TNFα Preliminary characterization of the bioactive constituent(s) of the Lr-CFS indicates that it is resistant to treatment with DNase, RNase, and an acidic protease, but is sensitive to alterations in pH. Taken together, these results indicate that these lactobacilli secrete bioactive molecules of low molecular weight that may modulate host innate immune activity through interactions with IEC.

Acidic pH promotes oxidation-induced dissociation of C-reactive protein

BACKGROUND

Circulating levels of the systemic inflammation marker C-reactive protein (CRP) have been associated with increased risk and poor outcomes of many diseases, such as cardiovascular events and cancer. Accumulating evidence has indicated that the conformational rearrangement of human pentameric CRP (pCRP) to monomeric CRP (mCRP) is a prerequisite for participation in the pathogenesis. Therefore, determining the mechanism of the dissociation of pCRP into pro-inflammatory mCRP under physiological/pathological circumstances has been intriguing.

METHODS

The effects of oxidative and acidic stress occurring in inflammation on pCRP were examined by electrophoresis, electron microscopy, protein fluorescence, neoepitope expression and endothelial cell responses.

RESULTS

Reactive oxygen species (ROS) generated by the copper-hydrogen peroxide system could rapidly induce the dissociation of CRP at mild acidic pH within four hours, but not at physiological pH of 7.4. Meanwhile, mannitol, a ROS scavenger, could not protect against dissociation, which implied that local ROS from accessible histidine residues may be crucially beneficial to the formation of mCRP in a redox-balanced microenvironment. Furthermore, mCRP generated by ROS could be reduced by DTT, which indicated the exposure of functional motif aa35-47, and showed potent proinflammatory actions on endothelial cells, comparable to mCRP generated by urea.

CONCLUSION

dissociation of pCRP to mCRP could be rapidly induced by ROS from copper- hydrogen peroxide system in dependence on mildly acidic stress regardless of a redox-balanced microenvironment.

Gastric Aspiration and Its Role in Airway Inflammation

Gastro-Oesophageal Reflux (GOR) has been associated with chronic airway diseases while the passage of foreign matter into airways and lungs through aspiration has the potential to initiate a wide spectrum of pulmonary disorders. The clinical syndrome resulting from such aspiration will depend both on the quantity and nature of the aspirate as well as the individual host response. Aspiration of gastric fluids may cause damage to airway epithelium, not only because acidity is toxic to bronchial epithelial cells but also due to the effect of digestive enzymes such as pepsin and bile salts. Experimental models have shown that direct instillation of these factors to airways epithelia cause damage with a consequential inflammatory response. The pathophysiology of these responses is gradually being dissected, with better understanding of acute gastric aspiration injury, a major cause of acute lung injury, providing opportunities for therapeutic intervention and potentially, ultimately, improved understanding of the chronic airway response to aspiration. Ultimately, clarification of the inflammatory pathways which are related to micro-aspiration via pepsin and bile acid salts may eventually progress to pharmacological intervention and surgical studies to assess the clinical benefits of such therapies in driving symptom improvement or reducing disease progression.

Mild intracellular acidification by dexamethasone attenuates mitochondrial dysfunction in a human inflammatory proximal tubule epithelial cell model

Septic acute kidney injury (AKI) associates with poor survival rates and often requires renal replacement therapy. Glucocorticoids may pose renal protective effects in sepsis via stimulation of mitochondrial function. Therefore, we studied the mitochondrial effects of dexamethasone in an experimental inflammatory proximal tubule epithelial cell model. Treatment of human proximal tubule epithelial cells with lipopolysaccharide (LPS) closely resembles pathophysiological processes during endotoxaemia, and led to increased cytokine excretion rates and cellular reactive oxygen species levels, combined with a reduced mitochondrial membrane potential and respiratory capacity. These effects were attenuated by dexamethasone. Dexamethasone specifically increased the expression and activity of mitochondrial complex V (CV), which could not be explained by an increase in mitochondrial mass. Finally, we demonstrated that dexamethasone acidified the intracellular milieu and consequently reversed LPS-induced alkalisation, leading to restoration of the mitochondrial function. This acidification also provides an explanation for the increase in CV expression, which is expected to compensate for the inhibitory effect of the acidified environment on this complex. Besides the mechanistic insights into the beneficial effects of dexamethasone during renal cellular inflammation, our work also supports a key role for mitochondria in this process and, hence, provides novel therapeutic avenues for the treatment of AKI.