Eosinophilic oesophagitis: a common cause of food bolus obstruction.

BACKGROUND: Eosinophilic oesophagitis (EOE) is a known cause of food bolus obstruction (FBO) with rising incidence and prevalence. AIMS: To assess the rates of EOE in adult cases presenting with an FBO via prospective biopsy collection during index endoscopy. METHODS: Oesophageal FBO cases requiring gastroscopy between February 2014 and January 2021 at a single institution with a unified policy to perform biopsies on FBO cases were analysed using medical records, endoscopy and histology. Statistical analysis was undertaken to compare those with and without EOE as their final diagnosis, including the timing of oesophageal biopsy and the season that cases presented. RESULTS: One hundred ninety FBO presentations were analysed, 15 patients presented twice and one patient presented four times within the 7-year study period. Men represented 72% of cases. A total of 78% of cases had biopsies collected at an index or scheduled follow-up endoscopy. EOE was the cause of the FBO in 28% (53/190) of presentations. FBO secondary to EOE was more likely to occur in the spring and summer months (Australian September to March), with 39% (19 of 49) of cases presenting in spring attributable to EOE. CONCLUSION: EOE affects a significant proportion of patients presenting with FBO (28%); a high biopsy rate of 78% in FBO cases provides an opportunity for prompt diagnosis and treatment.

Toll-Interacting Protein, Tollip, Inhibits IL-13-Mediated Pulmonary Eosinophilic Inflammation in Mice.

Toll-interacting protein (Tollip) is a key negative regulator of innate immunity by preventing excessive proinflammatory responses. Tollip genetic variation has been associated with airflow limitation in asthma subjects and Tollip expression. Whether Tollip regulates lung inflammation in a type 2 cytokine milieu (e.g., IL-13) is unclear. Our goal was to determine the in vivo role of Tollip in IL-13-mediated lung eosinophilic inflammation and the underlying mechanisms. Tollip-knockout (KO) and wild-type (WT) mice were inoculated intranasally with recombinant mouse IL-13 protein to examine lung inflammation. To determine how Tollip regulates inflammation, alveolar macrophages and bone marrow-derived macrophages from Tollip KO and WT mice were cultured with or without IL-13 and/or IL-33. IL-13-treated Tollip KO mice significantly increased lung eosinophilic inflammation and eotaxin-2 (CCL24) levels compared with the WT mice. IL-13- treated Tollip KO (vs. WT) macrophages, in the absence and particularly in the presence of IL-33, increased expression of the IL-33 receptor ST2L and CCL24, which was in part dependent on enhanced activation of interleukin (IL)-1 receptor-associated kinase 1 (IRAK1) and signal transducer and activator of transcription 6 (STAT6). Our results suggest that Tollip downregulates IL-13-mediated pulmonary eosinophilia in part through inhibiting the activity of the ST2L/IL-33/IRAK1 axis and STAT6.

MUC18 regulates IL-13-mediated airway inflammatory response.

OBJECTIVE: To evaluate the effects of MUC18 on IL-13-mediated airway inflammatory responses in human airway epithelial cells and in mice. MATERIALS: Primary normal human tracheobronchial epithelial (HTBE) cells, wild-type (WT) and Muc18 knockout (KO) mice, and mouse tracheal epithelial cells (mTECs) were utilized. TREATMENT: Cultured HTBE cells treated with MUC18 siRNA or MUC18 expressing lentivirus were incubated with IL-13 (10 ng/mL) for 24 h. Mice were intranasally instilled with 500 ng of IL-13 for 3 days. mTECs were treated with IL-13 (10 ng/mL) for 3 days. METHODS: PCR was used to measure mRNA expression. Western Blot and ELISAs were used to quantify protein expression. Cytospins of bronchoalveolar lavage (BAL) cells were used to obtain leukocyte differentials. RESULTS: MUC18 siRNA reduced IL-13-mediated eotaxin-3 (183 ± 44 vs. 380 ± 59 pg/mL, p < 0.05), while MUC18 overexpression increased IL-13-mediated eotaxin-3 (95 ± 3 vs. 58 ± 3 pg/mL, p < 0.05) in HTBE cells. IL-13-treated Muc18 KO mice had a lower percentage of neutrophils in BAL than WT mice (25 ± 3 vs. 35 ± 3%, p = 0.0565). CONCLUSIONS: These results implicate MUC18 as a potential enhancer of airway inflammation in a type 2 cytokine (e.g., IL-13) milieu.

A novel mouse model of conditional IRAK-M deficiency in myeloid cells: application in lung Pseudomonas aeruginosa infection.

Myeloid cells such as macrophages are critical to innate defense against infection. IL-1 receptor-associated kinase M (IRAK-M) is a negative regulator of TLR signaling during bacterial infection, but the role of myeloid cell IRAK-M in bacterial infection is unclear. Our goal was to generate a novel conditional knockout mouse model to define the role of myeloid cell IRAK-M during bacterial infection. Myeloid cell-specific IRAK-M knockout mice were generated by crossing IRAK-M floxed mice with LysM-Cre knock-in mice. The resulting LysM-Cre+/IRAK-Mfl/wt and control (LysM-Cre-/IRAK-Mfl/wt) mice were intranasally infected with Pseudomonas aeruginosa (PA). IRAK-M deletion, inflammation, myeloperoxidase (MPO) activity and PA load were measured in leukocytes, bronchoalveolar lavage (BAL) fluid and lungs. PA killing assay with BAL fluid was performed to determine mechanisms of IRAK-M-mediated host defense. IRAK-M mRNA and protein levels in alveolar and lung macrophages were significantly reduced in LysM-Cre+/IRAK-Mfl/wt mice compared with control mice. Following PA infection, LysM-Cre+/IRAK-Mfl/wt mice have enhanced lung neutrophilic inflammation, including MPO activity, but reduced PA load. The increased lung MPO activity in LysM-Cre+/IRAK-Mfl/wt mouse BAL fluid reduced PA load. Generation of IRAK-M conditional knockout mice will enable investigators to determine precisely the function of IRAK-M in myeloid cells and other types of cells during infection and inflammation.

MUC18 Regulates Lung Rhinovirus Infection and Inflammation.

BACKGROUND: MUC18 is upregulated in the lungs of asthma and COPD patients. It has been shown to have pro-inflammatory functions in cultured human airway epithelial cells during viral infections and in mice during lung bacterial infections. However, the in vivo role of MUC18 in the context of viral infections remains poorly understood. The goal of this study is to define the in vivo function of MUC18 during respiratory rhinovirus infection. METHODS: Muc18 wild-type (WT) and knockout (KO) mice were infected with human rhinovirus 1B (HRV-1B) and sacrificed after 1 day to determine the inflammatory and antiviral responses. To examine the direct effects of Muc18 on viral infection, tracheal epithelial cells isolated from WT and KO mice were grown under air-liquid interface and infected with HRV-1B. Finally, siRNA mediated knockdown of MUC18 was performed in human airway epithelial cells (AECs) to define the impact of MUC18 on human airway response to HRV-1B. RESULTS: Both viral load and neutrophilic inflammation were significantly decreased in Muc18 KO mice compared to WT mice. In the in vitro setting, viral load was significantly lower and antiviral gene expression was higher in airway epithelial cells of Muc18 KO mice than the WT mice. Furthermore, in MUC18 knockdown human AECs, viral load was decreased and antiviral gene expression was increased compared to controls. CONCLUSIONS: Our study is the first to demonstrate MUC18's pro-inflammatory and pro-viral function in an in vivo mouse model of rhinovirus infection.

The Anti-inflammatory Effect of Alpha-1 Antitrypsin in Rhinovirus-infected Human Airway Epithelial Cells.

OBJECTIVE: Excessive airway inflammation is seen in chronic obstructive pulmonary disease (COPD) patients experiencing acute exacerbations, which are often associated with human rhinovirus (HRV) infection. Alpha-1 antitrypsin (A1AT) has anti-inflammatory function in endothelial cells and monocytes, but its anti-inflammatory effect has not been investigated in COPD airway epithelial cells. We determined A1AT's anti-inflammatory function in COPD airway epithelial cells and the underlying mechanisms such as the role of caspase-1. METHODS: Brushed bronchial epithelial cells from COPD and normal subjects were cultured at air-liquid interface and treated with A1AT or bovine serum albumin (BSA, control) two hours prior to whole cigarette smoke (WCS) or air exposure, followed by HRV-16 infection. After 24 hours of viral infection, cell supernatants were collected for measuring IL-8, and cells were examined for caspase-1. The in vivo anti-inflammatory function of A1AT was determined by infecting mice intranasally with HRV-1B followed by aerosolized A1AT or BSA. RESULTS: A1AT significantly reduced WCS and HRV-16-induced IL-8 production in normal and COPD airway epithelial cells. COPD cells are less sensitive to A1AT's anti-inflammatory effect than normal cells. A1AT exerted the anti-inflammatory function in part via reducing caspase-1 in normal cells, but not in COPD cells. In mice, A1AT significantly reduced HRV-1B induced lung neutrophilic inflammation. CONCLUSIONS: A1AT exerts an anti-inflammatory effect in cigarette smoke-exposed and HRV-infected human airway epithelial cells, which may be related to its inhibitory effect on caspase-1 activity.

SRC-2 is an essential coactivator for orchestrating metabolism and circadian rhythm.

Synchrony of the mammalian circadian clock is achieved by complex transcriptional and translational feedback loops centered on the BMAL1:CLOCK heterodimer. Modulation of circadian feedback loops is essential for maintaining rhythmicity, yet the role of transcriptional coactivators in driving BMAL1:CLOCK transcriptional networks is largely unexplored. Here, we show diurnal hepatic steroid receptor coactivator 2 (SRC-2) recruitment to the genome that extensively overlaps with the BMAL1 cistrome during the light phase, targeting genes that enrich for circadian and metabolic processes. Notably, SRC-2 ablation impairs wheel-running behavior, alters circadian gene expression in several peripheral tissues, alters the rhythmicity of the hepatic metabolome, and deregulates the synchronization of cell-autonomous metabolites. We identify SRC-2 as a potent coregulator of BMAL1:CLOCK and find that SRC-2 targets itself with BMAL1:CLOCK in a feedforward loop. Collectively, our data suggest that SRC-2 is a transcriptional coactivator of the BMAL1:CLOCK oscillators and establish SRC-2 as a critical positive regulator of the mammalian circadian clock.