Mucin-secreting Goblet Cells Research Articles

The effects of diet supplemented with Lactobacillus rhamnosus on tissue parameters of rainbow trout, Oncorhynchus mykiss (Walbaum)

This study was carried out in order to establish the effects of a 6-week treatment with the diet supplemented with L. rhamnosus in concentrations of 10*7 CFU g-1 (G1 group) and 10*8 CFU g-1 (G2 group) on the condition expressed by condition factors (Fulton’s, Clark’s and B), intestinal microbiology, haematological, histological, and selected antioxidative parameters of rainbow trout. A significantly higher condition factors was found in G1 group indicating that higher concentration of probiotic (10*8 CFU g-1) did not result in the better condition. Cholesterol and urea levels were significantly higher in both G1 and G2 groups, albumin in G1 and creatinine in G2 group with respect to control. A significantly higher liver TBARS level was observed in G2 group. The feeding with supplemented probiont apparently changed the resident microbiota. Three weeks after withdrawal of the supplemented feed, the microflora mostly reverted to the control composition, although L. rhamnosus in fecal matter of fish remained inherent. The epithelial structure of the proximal and distal intestine revealed the increased absorptive area in both treated groups, as well as the increase of the mucin-secreting goblet cells. The L. rhamnosus treated groups demonstrated the capacity for the augmentation of the innate host defense.

Lipoxin A4 activates ALX/FPR2 receptor to regulate conjunctival goblet cell secretion.

Conjunctival goblet cells play a major role in maintaining the mucous layer of the tear film under physiological conditions as well as in inflammatory diseases like dry eye and allergic conjunctivitis.. Resolution of inflammation is mediated by pro-resolution agonists such as lipoxin A4 (LXA4) that can also function under physiological conditions. The purpose of this study was to determine the actions of LXA4 on cultured rat conjunctival goblet cell mucin secretion, intracellular [Ca2+] ([Ca2+]i) and identify signaling pathways activated by LXA4. ALX/FPR was localized to goblet cells in rat conjunctiva and in cultured goblet cells. LXA4 significantly increased mucin secretion, [Ca2+]i, and ERK 1/2 activation. These functions were inhibited by ALX/FPR2 inhibitors. Stable analogs of LXA4 increased [Ca2+]i to the same extent as LXA4. Sequential addition of either LXA4 or resolvin D1 followed by the second compound decreased [Ca2+]i of the second compound compared to its initial response. LXA4 activated phospholipase C, -D, and A2 and downstream molecules protein kinase C, ERK 1/2, and Ca2+/calmodulin dependent kinase to increase mucin secretion and [Ca2+]i. We conclude that conjunctival goblet cells respond to LXA4 to maintain the homeostasis of the ocular surface and could be a novel treatment for dry eye diseases.

Subchronic exposure to acrylamide affects colon mucin secretion in juvenile wistar rats

Acrylamide (AA) is an important industrial chemical worldwide. AA also forms naturally in many high-carbohydrate foods (bread, French fries, coffee, etc.) when they are heated. Since AA is ubiquitous in the human diet, and more than one-third of the calories we take in each day come from foods with detectable levels of acrylamide, the aim of this study was to determine the effect of subchronic AA treatment on colon goblet cell mucin secretion. Male Wistar rats were gavaged with AA for 5 days a week for 21 days. The animals were divided into three groups that were gavaged with different AA concentrations (0, 25, 50 mg/kg/day). Colon samples were processed for histochemical (PAS-AB, HID-AB) and immunohistochemical (anti-rat MUC2 antibody) staining to visualize mucins in the goblet cells. AA treatment showed an alteration in mucin production and secretion in that the amount of all investigated mucin types dropped. More prominent changes were detected in the upper crypt part where a decreased number of goblet cell was observed. AA treatment elicited a significant reduction in neutral mucins, while acidic mucins showed linearly decreasing trend with respect to AA doses. Also, a linear reduction of MUC2 mucins was noticed. Sulfomucins were absent in the colon lower crypt in all experimental groups, while in the upper crypt both sulfo- and sialomucins were significantly decreased. The results of our study point to changes in the synthesis, differentiation and distribution of mucins after AA treatment, which can have adverse effect on colorectal health.

The distribution of mucous secreting cells in the gastrointestinal tracts of three small rodents from Saudi Arabia: Acomys dimidiatus, Meriones rex and Meriones libycus

The proportion of mucin phenotypes (which form the protective biofilm of the gastrointestinal tract) differs between intestinal regions. This study examines the distribution of mucin secreting cells in the gastrointestinal tracts of the Eastern spiny mouse (Acomys dimidiatus), King jird (Meriones rex) and Libyan jird (Meriones libycus), which inhabit the dry and hot deserts of Saudi Arabia. Intestinal tract samples were processed to wax and tissue sections stained with Alcian Blue-Periodic Acid Schiff (AB-PAS) and High Iron Diamine-Alcian Blue (HID-AB) in order to determine different mucin phenotypes by quantitative analysis. Mixed mucin secreting cells (combined neutral and acid) was the predominant mucin secreting cell type observed throughout the gastrointestinal tract in all species. Acid mucin secreting goblet cells were mainly located in the colon. A. dimidiatus presented with significantly more total sialo than sulfomucin secreting cells while the opposite was true for both Meriones species. The distribution of mucin secreting cells is therefore similar to previously reported results for small mammals not living under arid conditions.

McKittrick-Wheelock Syndrome: A Rare Cause of Diarrhea in a Young Woman

Tubulovillous adenomas account for 5% of all adenomas and have a higher incidence of becoming malignant than tubular adenomas. Larger lesions can also lead to obstruction and hypersecretory complications. McKittrick-Wheelock Syndrome is a rare cause of secretory diarrhea from a rectosigmoid villous adenoma generally >4 cm in size that can lead to severe electrolyte derangements, dehydration, renal failure, and even death. We present a rare case of McKittrick-Wheelock Syndrome in a young, pregnant woman. A 26 year old Hispanic woman in her first trimester of pregnancy presented to outside hospital with diarrhea and weight loss, initially treated conservatively. Over the next month she developed large volume mucoid diarrhea with hypotension and electrolyte abnormalities (Na 120 mmol/L, K 1.8 mmol/L) requiring IV hydration and up to 300 mEq/L of KCl supplementation per day. Sigmoidoscopy revealed a large obstructing rectal mass 8 cm from the anal verge. Cold forcep biopsies showed villous adenoma. Due to the obstructive nature of the mass, at week 19 of her pregnancy she underwent an open diverting transverse colostomy and was transferred to our institution for definitive management. MRI showed a large pedunculated mass extending from the anal verge, filling the lumen to 11 cm proximally with rectal thickening (figure 1, 2). Repeat colonoscopy showed a friable circumferential gelatinous mass from the anal verge to 15 cm (figure 3) with biopsies consistent with villous adenoma with low grade dysplasia; there were no synchronous lesions. She was diagnosed with McKittrick-Wheelock Syndrome with plan for definitive surgical resection post-partum. She remained hospitalized throughout her pregnancy and delivered successfully via C-section at 37 weeks. At 5 weeks post-partum she underwent low anterior resection of the rectal tumor which revealed a 13.2 cm secretory villous adenoma without high grade dysplasia. Within 1 week her mucoid rectal discharge ceased and her electrolytes stabilized. McKittrick-Wheelock Syndrome is a rare cause of secretory diarrhea. These lesions consist primarily of mucin-secreting goblet cells that secrete water and electrolytes; larger lesions entail a greater surface area that when in the distal-most portion of the colon limit the ability to absorb fluid. Hypersecretory rectosigmoid villous adenoma should be in the differential in patients with unexplained secretory diarrhea, and prompt diagnosis and early resection is prudent.Figure 1Figure 2Figure 3

Baseline Goblet Cell Mucin Secretion in the Airways Exceeds Stimulated Secretion over Extended Time Periods, and Is Sensitive to Shear Stress and Intracellular Mucin Stores.

Airway mucin secretion studies have focused on goblet cell responses to exogenous agonists almost to the exclusion of baseline mucin secretion (BLMS). In human bronchial epithelial cell cultures (HBECCs), maximal agonist-stimulated secretion exceeds baseline by ~3-fold as measured over hour-long periods, but mucin stores are discharged completely and require 24 h for full restoration. Hence, over 24 h, total baseline exceeds agonist-induced secretion by several-fold. Studies with HBECCs and mouse tracheas showed that BLMS is highly sensitive to mechanical stresses. Harvesting three consecutive 1 h baseline luminal incubations with HBECCs yielded equal rates of BLMS; however, lengthening the middle period to 72 h decreased the respective rate significantly, suggesting a stimulation of BLMS by the gentle washes of HBECC luminal surfaces. BLMS declined exponentially after washing HBECCs (t1/2 = 2.75 h), to rates approaching zero. HBECCs exposed to low perfusion rates exhibited spike-like increases in BLMS when flow was jumped 5-fold: BLMS increased >4 fold, then decreased within 5 min to a stable plateau at 1.5–2-fold over control. Higher flow jumps induced proportionally higher BLMS increases. Inducing mucous hyperplasia in HBECCs increased mucin production, BLMS and agonist-induced secretion. Mouse tracheal BLMS was ~6-fold higher during perfusion, than when flow was stopped. Munc13-2 null mouse tracheas, with their defect of accumulated cellular mucins, exhibited similar BLMS as WT, contrary to predictions of lower values. Graded mucous metaplasia induced in WT and Munc13-2 null tracheas with IL-13, caused proportional increases in BLMS, suggesting that naïve Munc13-2 mouse BLMS is elevated by increased mucin stores. We conclude that BLMS is, [i] a major component of mucin secretion in the lung, [ii] sustained by the mechanical activity of a dynamic lung, [iii] proportional to levels of mucin stores, and [iv] regulated differentially from agonist-induced mucin secretion.

Lipoxin A4 Inhibits Histamine‐stimulated Increase in [Ca2+] and Mucin Secretion in Cultured Rat and Human Goblet Cells

In allergic conjunctivitis histamine levels are elevated and goblet cell mucin secretion stimulated. The purpose of this study was to determine if the effects of histamine can be blocked by the pro‐resolution compound lipoxin A4 (LXA4) in cultured conjunctival goblet cells (GCs), similar to pro‐resolution effects of resolvin D1 (RvD1). First passage GCs from rat and human were used. Intracellular [Ca2+] ([Ca2+]i) was measured using fura2. LXA4 (10‐11‐10‐8M) was added alone or 0.5h prior to histamine (10‐5M). In rat GCs, LXA4 alone increased [Ca2+]i a maximum of 116.4±21.5 nM above basal which was significantly inhibited by the ALX receptor inhibitor BOC‐2. In human GCs, LXA4 increased [Ca2+]i a maximum of 762.0±259.4nM above basal which was inhibited by BOC‐2. LXA4 inhibited histamine‐stimulated increase in [Ca2+]i by 63.7±10.2% and 71.0±7.7% in rat and human CGs, respectively. In rat GCs, stimulation with the specific H1 receptor agonist histamine dimaleate stimulated [Ca2+]i by 751.7±216.1 nM. This was inhibited by LXA4 by 70.5±8.9%. Preincubation with an inhibitor to b‐adrenergic receptor kinase 1 (βARK1), but not inhibition of protein kinase C by Ro31754, reversed LAX4 inhibition of histamine dimaleate response. We conclude that similarly to RvD1, LXA4 functions as a pro‐resolution mediator as it inhibits histamine‐stimulated responses by counter‐regulation of the H1 histamine receptor through βARK1. LXA4 could play a role in the return of GCs to homeostasis in allergic conjunctivitis.

Baseline Goblet Cell Mucin Secretion in the Airways Exceeds Stimulated Secretion over Extended Time Periods, and Is Sensitive to Shear Stress and Intracellular Mucin Stores

Baseline Goblet Cell Mucin Secretion in the Airways Exceeds Stimulated Secretion over Extended Time Periods, and Is Sensitive to Shear Stress and Intracellular Mucin Stores

Conjunctival epithelial and goblet cell function in chronic inflammation and ocular allergic inflammation.

Although conjunctival goblet cells are a major cell type in ocular mucosa, their responses during ocular allergy are largely unexplored. This review summarizes the recent findings that provide key insights into the mechanisms by which their function and survival are altered during chronic inflammatory responses, including ocular allergy. Conjunctiva represents a major component of the ocular mucosa that harbors specialized lymphoid tissue. Exposure of mucin-secreting goblet cells to allergic and inflammatory mediators released by the local innate and adaptive immune cells modulates proliferation, secretory function, and cell survival. Allergic mediators like histamine, leukotrienes, and prostaglandins directly stimulate goblet cell mucin secretion and consistently increase goblet cell proliferation. Goblet cell mucin secretion is also detectable in a murine model of allergic conjunctivitis. Additionally, primary goblet cell cultures allow evaluation of various inflammatory cytokines with respect to changes in goblet cell mucin secretion, proliferation, and apoptosis. These findings in combination with the preclinical mouse models help understand the goblet cell responses and their modulation during chronic inflammatory diseases, including ocular allergy. Recent findings related to conjunctival goblet cells provide the basis for novel therapeutic approaches, involving modulation of goblet cell mucin production, to improve treatment of ocular allergies.

Loss of Sonic hedgehog leads to alterations in intestinal secretory cell maturation and autophagy.

BackgroundIntestinal epithelial cells express the Sonic and Indian hedgehog ligands. Despite the strong interest in gut hedgehog signaling in GI diseases, no studies have specifically addressed the singular role of intestinal epithelial cell Sonic hedgehog signaling. The aim of this study was to investigate the specific role of Sonic hedgehog in adult ileal epithelial homeostasis.Methodology/Principal FindingsA Sonic hedgehog intestinal epithelial conditional knockout mouse model was generated. Assessment of ileal histological abnormalities, crypt epithelial cell proliferation, epithelial cell fate, junctional proteins, signaling pathways, as well as ultrastructural analysis of intracellular organelles were performed in control and mutant mice. Mice lacking intestinal epithelial Sonic Hedgehog displayed decreased ileal crypt/villus length, decreased crypt proliferation as well as a decrease in the number of ileal mucin-secreting goblet cells and antimicrobial peptide-secreting Paneth cells during adult life. These secretory cells also exhibited disruption of their secretory products in mutant mice. Ultrastructural microscopy analysis revealed a dilated ER lumen in secretory cells. This phenotype was also associated with a decrease in autophagy.Conclusions/SignificanceAltogether, these findings indicate that the loss of Sonic hedgehog can lead to ileal secretory cell modifications indicative of endoplasmic reticulum stress, accompanied by a significant reduction in autophagy.

Ostrich oil failed to improve intestinal barrier function following 5‐fluorouracil‐induced mucositis in rats (1111.5)

INTRODUCTION. Mucositis is characterized by intestinal barrier disruption following chemotherapy. Emu Oil promoted small intestinal repair in a rat model of mucositis (Mashtoub, 2013). However, the effects of Ostrich Oil (OO) remain unexplored. We investigated the effects of OO on mucin‐secreting goblet cells (GC) during the recovery phase of mucositis. METHODS. Female Dark Agouti rats were allocated to groups (n=8/group): Saline+Water; Saline+OO; 5‐Fluorouracil (5‐FU)+Water; 5‐FU+OO. Mucositis was induced on day 5 by 5‐FU injection and rats were euthanized on day 10. Intestinal villus height (VH), crypt depth (CD) and GC were quantified. p<0.05 was considered significant. RESULTS. Compared to water controls, VH was increased 15% by OO (p<0.05), however, VH was unaffected by 5‐FU. 5‐FU tended to decrease GC count in the villi, relative to water controls (p=0.069). GC count was unaffected by OO in 5‐FU‐treated rats compared to 5‐FU controls. CD was increased 24% by 5‐FU (p<0.01); an effect that was not altered by OO. 5‐FU reduced GC count in crypts (33%; p<0.01) compared to water controls. However, OO did not attenuate the decrease in GC count in 5‐FU‐treated rats. CONCLUSIONS. Ostrich Oil treatment failed to improve intestinal barrier function indicated by mucin‐secreting goblet cells. As this is the first report of Ostrich Oil in bowel disease, further studies are required to explore dosage and timing regimens.Grant Funding Source: Supported by The Rural Industries Research and Development Corporation Australia

Amphisomes: out of the autophagosome shadow?

Amphisomes are intermediate organelles, formed during autophagy through the fusion between autophagosomes and endosomes. Complex multivesicular vacuoles that resemble amphisomes have been observed in various cell types, but whether they have cellular roles other than being a precursor structure is still enigmatic. While autophagy-related (ATG) proteins interact with the endocytic pathways in other processes different from autophagy, Patel and colleagues now report that these factors come together to generate amphisome-like compartments that regulate mucin secretion in goblet cells.

Emu oil expedites small intestinal repair following 5-fluorouracil-induced mucositis in rats

Mucositis resulting from cancer chemotherapy is characterized by intestinal inflammation and ulceration. Previously, emu oil (EO) improved intestinal architecture (Br J Nutr, 2010) in a rat model of chemotherapy-induced mucositis. We investigated EO for its further potential to promote intestinal repair in this mucositis model. Female Dark Agouti rats (n = 8/group) were gavaged with water, olive oil (OO) or EO once daily (1 mL), injected with 5-fluorouracil (5-FU) or saline on day 5 and euthanized on day 8, 9, 10 or 11. Intestinal villus height (VH) and crypt depth (CD), neutral mucin-secreting goblet cell (GC) count, myeloperoxidase (MPO) activity and selected cytokines were quantified; P < 0.05 was considered significant. In 5-FU-injected rats, only EO administration significantly increased VH in the ileum (day 8), jejunum and jejunum-ileum junction (days 8 and 9) compared to 5-FU controls (P < 0.05). GC count was significantly reduced by 5-FU (jejunum: days 8 and 9; ileum: day 8; P < 0.05) and EO increased ileal GC on days 10 and 11 compared to 5-FU controls. MPO activity was significantly increased in jejunum (days 8 and 9) and ileum (day 8) following 5-FU injection, compared to normal controls (P < 0.05). Both EO and OO significantly reduced jejunal MPO on days 8 and 9; however, only EO decreased ileal MPO on day 8. Cytokine levels were not significantly affected by either oil or 5-FU administration at the day 8 time point. Promotion of repair from injury could represent a new mechanism of action for EO, suggesting potential as an adjunct to conventional treatment approaches for cancer management.

Otitis media in the Tgif knockout mouse implicates TGFβ signalling in chronic middle ear inflammatory disease.

Otitis media with effusion (OME) is the most common cause of hearing loss in children and tympanostomy to alleviate the condition remains the commonest surgical intervention in children in the developed world. Chronic and recurrent forms of OM are known to have a very significant genetic component, however, until recently little was known of the underlying genes involved. The identification of mouse models of chronic OM has indicated a role of transforming growth factor beta (TGFβ) signalling and its impact on responses to hypoxia in the inflamed middle ear. We have, therefore, investigated the role of TGFβ signalling and identified and characterized a new model of chronic OM carrying a mutation in the gene for transforming growth interacting factor 1 (Tgif1). Tgif1 homozygous mutant mice have significantly raised auditory thresholds due to a conductive deafness arising from a chronic effusion starting at around 3 weeks of age. The OM is accompanied by a significant thickening of the middle ear mucosa lining, expansion of mucin-secreting goblet cell populations and raised levels of vascular endothelial growth factor, TNF-α and IL-1β in ear fluids. We also identified downstream effects on TGFβ signalling in middle ear epithelia at the time of development of chronic OM. Both phosphorylated SMAD2 and p21 levels were lowered in the homozygous mutant, demonstrating a suppression of the TGFβ pathway. The identification and characterization of the Tgif mutant supports the role of TGFβ signalling in the development of chronic OM and provides an important candidate gene for genetic studies in the human population.

Negative feedback by IRE1β optimizes mucin production in goblet cells

In mammals, the prototypical endoplasmic reticulum (ER) stress sensor inositol-requiring enzyme 1 (IRE1) has diverged into two paralogs. IRE1α is broadly expressed and mediates the unconventional splicing of X-box binding protein 1 (XBP1) mRNA during ER stress. By contrast, IRE1β is expressed selectively in the digestive tract, and its function remains unclear. Here, we report that IRE1β plays a distinctive role in mucin-secreting goblet cells. In IRE1β(-/-) mice, aberrant mucin 2 (MUC2) accumulated in the ER of goblet cells, accompanied by ER distension and elevated ER stress signaling such as increased XBP1 mRNA splicing. In contrast, conditional IRE1α(-/-) mice showed no such ER distension but a marked decrease in spliced XBP1 mRNA. mRNA stability assay revealed that MUC2 mRNA was greatly stabilized in IRE1β(-/-) mice. These findings suggest that in goblet cells, IRE1β, but not IRE1α, promotes efficient protein folding and secretion in the ER by optimizing the level of mRNA encoding their major secretory product, MUC2.

Modulation of conjunctival goblet cell function by inflammatory cytokines.

Ocular surface inflammation associated with Sjögren's syndrome is characterized by a loss of secretory function and alteration in numbers of mucin secreting goblet cells. Such changes are a prominent feature of ocular surface inflammatory diseases and are attributed to inflammation; however, the exact effect of the inflammatory cytokines on conjunctival goblet cell function remains largely unknown. In this study, we developed a primary culture of mouse goblet cells from conjunctival tissue and evaluated the effects on their function by inflammatory cytokines detected in the conjunctiva of mouse model of Sjögren's syndrome (Thrombospondin-1 deficient mice). We found that apoptosis of goblet cells was primarily induced by TNF-α and IFN-γ. These two cytokines also inhibited mucin secretion by goblet cells in response to cholinergic stimulation, whereas IL-6 enhanced such secretion. No changes in secretory response were detected in the presence of IL-13 or IL-17. Goblet cells proliferated to varying degrees in response to all the tested cytokines with the greatest response to IL-13 followed by IL-6. Our results therefore reveal that inflammatory cytokines expressed in the conjunctiva during an ocular surface disease directly disrupt conjunctival goblet cell functions, compromising the protective function of tears, thereby contributing to ocular surface damage.

Effect of β-lactoglobulin hydrolysate and β-lactorphin on intestinal mucin secretion and gene expression in human goblet cells

A hydrolysate obtained from a whey protein concentrate rich in β-lactoglobulin has been shown to stimulate mucin secretion and mucin 5AC gene expression in human intestinal goblet cells HT29-MTX. Mass spectrometry-based peptidomic analysis allowed the identification of the peptides contained in the hydrolysate. None of them had the required structure to bind opioid receptors, except for the sequence YLLF, corresponding to β-lactorphin. The exposure of the cells to synthetic β-lactorphin evoked a mucin secretory effect although no change in the mucin gene expression was observed. The amidated homolog of this peptide, which has been reported as a more potent opioid, induced mucin gene expression after incubation for 4h. This supports the hypothesis that induction of the mucin secretory response can be mediated by μ-opioid receptors in HT29-MTX cells, although other mechanisms responsible for the hydrolysate activity cannot be excluded. Protein hydrolysates with the ability to induce mucin secretion could be promising for improving gastrointestinal protection.

Changes in intestinal morphology and amino acid catabolism in common carp at mildly elevated temperature as affected by dietary mannanoligosaccharides

A study was conducted to evaluate whether dietary mannanoligosaccharides (MOS) modulate the effect of mildly elevated water temperature on intestinal morphology and some selected whole blood amino acids and acylcarnitines in common carp (Cyprinus carpio carpio). Twenty fish in 10 aquaria were randomly assigned to either a control diet or the same diet with 4g/kg MOS. A 35-day period at ideal temperature (23.2°C) was followed by 14 days at elevated temperature (26.1°C). After both temperature periods, one fish per aquarium was euthanized for the intestinal morphology and whole blood analysis on free amino acids and carnitine esters. The elevated temperature period decreased the number of neutral (P=0.031) and acid (P=0.004) mucin-secreting goblet cells and tended to reduce (P=0.056) the fold height in the midgut, irrespective of MOS supplementation. In both periods, supplementation of MOS increased (P=0.035) the number of goblet cells in the hindgut, but other histomorphometries were unaffected. Free concentrations of whole blood amino acids were increased after the mildly elevated temperature period: valine (P=0.002), leucine (P=0.001), methionine (P<0.001), phenylalanine (P=0.001) and tyrosine (P=0.001), but not affected by MOS supplementation. None of the carnitine esters were altered by the elevated temperature except propionyl carnitine that was higher (P=0.003) after the mildly elevated temperature of 14 days. Supplementation of MOS only tended to reduce the tiglyl carnitine (P=0.069) and methylmalonyl carnitine (P=0.078) concentrations. The analysis of free amino acids and carnitine esters could not support the hypothesis that MOS counteracts depressing effects of elevated temperature on amino acid catabolism. In conclusion, moderate elevation of water temperature could lead to considerable changes in gut histology and metabolism.

VAMP8 is a vesicle SNARE that regulates mucin secretion in airway goblet cells

Mucin secretion is an innate defence mechanism, which is noxiously upregulated in obstructive lung diseases (e.g. chronic obstructive pulmonary disease (COPD), cystic fibrosis and asthma). Mucin granule exocytosis is regulated by specific protein complexes, but the SNARE exocytotic core has not been defined in airway goblet cells. In this study, we identify VAMP8 as one of the SNAREs regulating mucin granule exocytosis. VAMP8 mRNA was present in human airway and lung epithelial cells, and deep-sequencing and expression analyses of airway epithelial cells revealed that VAMP8 transcripts were expressed at 10 times higher levels than other VAMP mRNAs. In human airway epithelial cell cultures and freshly excised tissues, VAMP8 immunolocalised mainly to goblet cell mucin granules. The function of VAMP8 in airway mucin secretion was tested by RNA interference techniques. Both VAMP8 short interfering RNAs (siRNAs) and short hairpin RNAs (shRNAs) reduced mucin secretion induced by PAR agonists, neutrophil elastase and ATP in two airway epithelial cell culture models. Notably, basal (non-agonist elicited) mucin secretion was also reduced in these experiments. VAMP8 knockdown was also effective in decreasing mucin secretion in airway epithelial cell cultures with induced mucous metaplasia/mucin hypersecretion. Unlike VAMP8 silencing, knockdown of VAMP2 or VAMP3 did not affect mucin secretion. Importantly, in VAMP8 knock-out (KO) mice with IL-13-induced mucous metaplasia, mucin content in the bronchoalveolar lavage (BAL) and ATP-stimulated mucin secretion in the trachea were reduced compared to WT-matched littermates. Our data indicate that VAMP8 is an essential SNARE in airway mucin granule exocytosis. Reduction of VAMP8 activity/expression may provide a novel therapeutic target to ameliorate airway mucus obstruction in lung diseases.

VAMP8 is a vesicle SNARE that regulates mucin secretion in airway goblet cells

VAMP8 is a vesicle SNARE that regulates mucin secretion in airway goblet cells