Early-onset tufting enteropathy in HAI-2-deficient mice is independent of matriptase-mediated cleavage of EpCAM.

Congenital tufting enteropathy (CTE) is a life-threatening intestinal disorder resulting from loss-of-function mutations in EPCAM and SPINT2. Mice deficient in Spint2, encoding the protease inhibitor HAI-2, develop CTE-like intestinal failure associated with a progressive loss of the EpCAM protein, which is caused by unchecked activity of the serine protease matriptase (ST14). Here, we show that loss of HAI-2 leads to increased proteolytic processing of EpCAM. Elimination of the reported matriptase cleavage site strongly suppressed proteolytic processing of EpCAM in vitro and in vivo. Unexpectedly, expression of cleavage-resistant EpCAM failed to prevent intestinal failure and postnatal lethality in Spint2-deficient mice. In addition, genetic inactivation of intestinal matriptase (St14) counteracted the effect of Spint2 deficiency in mice expressing cleavage-resistant EpCAM, indicating that matriptase does not drive intestinal dysfunction by excessive proteolysis of EpCAM. Interestingly, mice expressing cleavage-resistant EpCAM developed late-onset intestinal defects and exhibited a shortened lifespan even in the presence of HAI-2, suggesting that EpCAM cleavage is indispensable for EpCAM function. Our findings provide new insights into the role of EpCAM and the etiology of the enteropathies driven by Spint2 deficiency.

Matriptase-2 regulates iron homeostasis primarily by setting the basal levels of hepatic hepcidin expression through a nonproteolytic mechanism.

Matriptase-2 (MT2), encoded by TMPRSS6, is a membrane-anchored serine protease. It plays a key role in iron homeostasis by suppressing the iron-regulatory hormone, hepcidin. Lack of functional MT2 results in an inappropriately high hepcidin and iron-refractory iron-deficiency anemia. Mt2 cleaves multiple components of the hepcidin-induction pathway in vitro. It is inhibited by the membrane-anchored serine protease inhibitor, Hai-2. Earlier in vivo studies show that Mt2 can suppress hepcidin expression independently of its proteolytic activity. In this study, our data indicate that hepatic Mt2 was a limiting factor in suppressing hepcidin. Studies in Tmprss6-/- mice revealed that increases in dietary iron to ∼0.5% were sufficient to overcome the high hepcidin barrier and to correct iron-deficiency anemia. Interestingly, the increased iron in Tmprss6-/- mice was able to further upregulate hepcidin expression to a similar magnitude as in wild-type mice. These results suggest that a lack of Mt2 does not impact the iron induction of hepcidin. Additional studies of wild-type Mt2 and the proteolytic-dead form, fMt2S762A, indicated that the function of Mt2 is to lower the basal levels of hepcidin expression in a manner that primarily relies on its nonproteolytic role. This idea is supported by the studies in mice with the hepatocyte-specific ablation of Hai-2, which showed a marginal impact on iron homeostasis and no significant effects on iron regulation of hepcidin. Together, these observations suggest that the function of Mt2 is to set the basal levels of hepcidin expression and that this process is primarily accomplished through a nonproteolytic mechanism.

Insufficiency of hepatocyte growth factor activator inhibitor-1 confers lymphatic invasion of tongue carcinoma cells.

Hepatocyte growth factor (HGF) activator inhibitor type-1 (HAI-1), encoded by the SPINT1 gene, is a transmembrane protease inhibitor that regulates membrane-anchored serine proteases, particularly matriptase. Here, we explored the role of HAI-1 in tongue squamous cell carcinoma (TSCC) cells. An immunohistochemical study of HAI-1 in surgically resected TSCC revealed the cell surface immunoreactivity of HAI-1 in the main portion of the tumor. The immunoreactivity decreased in the infiltrative front, and this decrease correlated with enhanced lymphatic invasion as judged by podoplanin immunostaining. In vitro homozygous deletion of SPINT1 (HAI-1KO) in TSCC cell lines (HSC3 and SAS) suppressed the cell growth rate but significantly enhanced invasion in vitro. The loss of HAI-1 resulted in enhanced pericellular activities of proteases, such as matriptase and urokinase-type plasminogen activator, which induced activation of HGF/MET signaling in the co-culture with pro-HGF-expressing fibroblasts and plasminogen-dependent plasmin generation, respectively. The enhanced plasminogen-dependent plasmin generation was abrogated partly by matriptase silencing. Culture supernatants of HAI-1KO cells had enhanced potency for converting the proform of vascular endothelial growth factor-C (VEGF-C), a lymphangiogenesis factor, into the mature form in a plasminogen-dependent manner. Furthermore, HGF significantly stimulated VEGF-C expression in TSCC cells. Orthotopic xenotransplantation into nude mouse tongue revealed enhanced lymphatic invasion of HAI-1KO TSCC cells compared to control cells. Our results suggest that HAI-1 insufficiency leads to dysregulated pericellular protease activity, which eventually orchestrates robust activation of protease-dependent growth factors, such as HGF and VEGF-C, in a tumor microenvironment to contribute to TSCC progression.

Protease-activated receptor-2 accelerates intestinal tumor formation through activation of nuclear factor-κB signaling and tumor angiogenesis in ApcMin/+ mice.

Hepatocyte growth factor activator inhibitor-1 (HAI-1), encoded by the SPINT1 gene, is a membrane-bound protease inhibitor expressed on the surface of epithelial cells. Hepatocyte growth factor activator inhibitor-1 regulates type II transmembrane serine proteases that activate protease-activated receptor-2 (PAR-2). We previously reported that deletion of Spint1 in ApcMin/+ mice resulted in accelerated formation of intestinal tumors, possibly through enhanced nuclear factor-κB signaling. In this study, we examined the role of PAR-2 in accelerating tumor formation in the ApcMin/+ model in the presence or absence of Spint1. We observed that knockout of the F2rl1 gene, encoding PAR-2, not only eliminated the enhanced formation of intestinal tumors caused by Spint1 deletion, but also reduced tumor formation in the presence of Spint1. Exacerbation of anemia and weight loss associated with HAI-1 deficiency was also normalized by compound deficiency of PAR-2. Mechanistically, signaling triggered by deregulated protease activities increased nuclear translocation of RelA/p65, vascular endothelial growth factor expression, and vascular density in ApcMin/+ -induced intestinal tumors. These results suggest that serine proteases promote intestinal carcinogenesis through activation of PAR-2, and that HAI-1 plays a critical tumor suppressor role as an inhibitor of matriptase, kallikreins, and other PAR-2 activating proteases.

HAI-2 stabilizes, inhibits and regulates SEA-cleavage-dependent secretory transport of matriptase.

It has recently been shown that hepatocyte growth factor activator inhibitor-2 (HAI-2) is able to suppress carcinogenesis induced by overexpression of matriptase, as well as cause regression of individual established tumors in a mouse model system. However, the role of HAI-2 is poorly understood. In this study, we describe 3 mutations in the binding loop of the HAI-2 Kunitz domain 1 (K42N, C47F and R48L) that cause a delay in the SEA domain cleavage of matriptase, leading to accumulation of non-SEA domain cleaved matriptase in the endoplasmic reticulum (ER). We suggest that, like other known SEA domains, the matriptase SEA domain auto-cleaves and reflects that correct oligomerization, maturation, and/or folding has been obtained. Our results suggest that the HAI-2 Kunitz domain 1 mutants influence the flux of matriptase to the plasma membrane by affecting the oligomerization, maturation and/or folding of matriptase, and as a result the SEA domain cleavage of matriptase. Two of the HAI-2 Kunitz domain 1 mutants investigated (C47F, R48L and C47F/R48L) also displayed a reduced ability to proteolytically silence matriptase. Hence, HAI-2 separately stabilizes matriptase, regulates the secretory transport, possibly via maturation/oligomerization and inhibits the proteolytic activity of matriptase in the ER, and possible throughout the secretory pathway.

A Nucleoside Derivative 5-Vinyluridine (VrU) for Imaging RNA in Cells and Animals.

In the present study, we used a nucleoside derivative 5-vinyluridine (VrU) for labeling during cell division and for tumor imaging in living mice. We demonstrated that the functional nucleoside bearing a 5-vinyl group is metabolically incorporated into cellular RNA and can be used to image RNA using a Diels-Alder reaction. The reagent allows for simultaneous and clear imaging of DNA and RNA in mammalian cells at single-cell resolution. We extended this approach to observe DNA and RNA behaviors in several basic stages of cell division. We further demonstrated that the derivative can be used for fluorescence imaging of tumor in live mice.

Aberrant methylation and silencing of the SPINT2 gene in high-grade gliomas.

Hepatocyte growth factor activator inhibitor type 2 (HAI-2), encoded by the SPINT2 gene, is a membrane-anchored protein that inhibits proteases involved in the activation of hepatocyte growth factor (HGF), a ligand of MET receptor. Epigenetic silencing of the SPINT2 gene has been reported in a human glioblastoma cell line (U87) and glioblastoma-derived cancer stem cells. However, the incidence of SPINT2 methylation in tumor tissues obtained from glioma patients is unknown. In this study, we analyzed the methylation status of the SPINT2 gene of eight human glioblastoma cell lines and surgically resected glioma tissues of different grades (II, III, and IV) by bisulfite sequence analysis and methylation-specific PCR. Most glioblastoma lines (7/8) showed methylation of the SPINT2 gene with a significantly reduced level of SPINT2mRNA compared to cultured astrocytes and normal brain tissues. However, all glioblastoma lines expressed mRNA for HGF activator (HGFAC), a target protease of HAI-2/SPINT2. Forced expression of SPINT2 reduced MET phosphorylation of U87 glioblastoma cells both in vitro and in intracranial xenografts in nude mice. Methylation-specific PCR analysis of the resected glioma tissues indicated notable methylation of the SPINT2 gene in 33.3% (2/6), 71.4% (10/14), and 74.3% (26/35) of grade II, III, and IV gliomas, respectively. Analysis of RNA sequencing data in a public database indicated an increased HGFAC/SPINT2 expression ratio in high-grade compared to low-grade gliomas (P = .01). In summary, aberrant methylation of the SPINT2 gene is frequently observed in high-grade gliomas and might confer MET signaling in the glioma cells.

Hepatocyte growth factor activator inhibitors (HAI-1 and HAI-2): Emerging key players in epithelial integrity and cancer.

The growth, survival, and metabolic activities of multicellular organisms at the cellular level are regulated by intracellular signaling, systemic homeostasis and the pericellular microenvironment. Pericellular proteolysis has a crucial role in processing bioactive molecules in the microenvironment and thereby has profound effects on cellular functions. Hepatocyte growth factor activator inhibitor type 1 (HAI-1) and HAI-2 are type I transmembrane serine protease inhibitors expressed by most epithelial cells. They regulate the pericellular activities of circulating hepatocyte growth factor activator and cellular type II transmembrane serine proteases (TTSPs), proteases required for the activation of hepatocyte growth factor (HGF)/scatter factor (SF). Activated HGF/SF transduces pleiotropic signals through its receptor tyrosine kinase, MET (coded by the proto-oncogene MET), which are necessary for cellular migration, survival, growth and triggering stem cells for accelerated healing. HAI-1 and HAI-2 are also required for normal epithelial functions through regulation of TTSP-mediated activation of other proteases and protease-activated receptor 2, and also through suppressing excess degradation of epithelial junctional proteins. This review summarizes current knowledge regarding the mechanism of pericellular HGF/SF activation and highlights emerging roles of HAIs in epithelial development and integrity, as well as tumorigenesis and progression of transformed epithelial cells.

Deregulated matriptase activity in oral squamous cell carcinoma promotes the infiltration of cancer-associated fibroblasts by paracrine activation of protease-activated receptor 2.

Cancer-associated fibroblasts (CAFs) are known to contribute to cancer progression. We have reported that cell surface expression of hepatocyte growth factor activator inhibitor 1 (HAI-1) is decreased in invasive oral squamous cell carcinoma (OSCC) cells. This study examined if HAI-1-insufficiency contributes to CAF recruitment in OSCC. Serum-free conditioned medium (SFCM) from a human OSCC line (SAS) stimulated the migration of 3 human fibroblast cell lines, NB1RGB, MRC5 and KD. SFCM from HAI-1-knockdown SAS showed an additive effect on the migration of NB1RGB and MRC5, but not KD. SAS SFCM induced protease-activated receptor-2 (PAR-2) expression in NB1RGB and MRC5, but not in KD, and a PAR-2 antagonist blocked the stimulatory effect of HAI-1 knockdown on migration of the PAR-2 expressing cell lines. Moreover, HAI-1-deficient SFCM showed additive stimulatory effects on the migration of wild-type but not PAR-2-deficient mouse fibroblasts. Therefore, the enhanced migration induced by HAI-1-insufficiency was mediated by PAR-2 activation in fibroblasts. This activation resulted from the deregulation of the activity of matriptase, a PAR-2 agonist protease. HAI-1 may thus prevent CAF recruitment to OSCC by controlling matriptase activity. When HAI-1 expression is reduced on OSCC, matriptase may contribute to CAF accumulation by paracrine activation of fibroblast PAR-2. Immunohistochemical analysis of resected OSCC revealed increased PAR2-positive CAFs in 35% (33/95) of the cases studied. The increased PAR-2 positive CAFs tended to correlate with infiltrative histology of the invasion front and shorter disease-free survival of the patients.

Placental Growth Factor and Vascular Endothelial Growth Factor Together Regulate Tumour Progression via Increased Vasculature in Cutaneous T-cell Lymphoma.

Angiogenesis is regarded as an essential step in supporting tumour growth and metastasis. In haematological malignancies, including cutaneous T-cell lymphoma (CTCL), angiogenesis is increased and serum levels of some pro-angiogenic markers are elevated. The aim of this study was to investigate expression levels of placental growth factor (PlGF) and vascular endothelial growth factor (VEGF)-A in lesional skin and sera in patients with CTCL, and to assess the association of these factors with development of CTCL. A further aim was to investigate the effect of PlGF on lymphoma cell growth in vivo using a tumour inoculation model. Expression of PlGF and VEGF-A were significantly elevated in CTCL skin. Tumour cells expressed PlGF in some cases. Serum PlGF levels were increased in patients with advanced CTCL and correlated with disease markers. Moreover, PlGF enhanced lymphoma cell growth in vivo through increasing tumour vasculature. These findings suggest that angiogenesis plays a role in the progression of CTCL and raises the possibility of using inhibitors of PlGF in CTCL therapy.

Hepatocyte growth factor activator inhibitor type 1 maintains the assembly of keratin into desmosomes in keratinocytes by regulating protease-activated receptor 2-dependent p38 signaling.

Hepatocyte growth factor activator inhibitor type 1 (HAI-1; official symbol SPINT1) is a membrane-associated serine proteinase inhibitor abundantly expressed in epithelial tissues. Genetically engineered mouse models demonstrated that HAI-1 is critical for epidermal function, possibly through direct and indirect regulation of cell surface proteases, such as matriptase and prostasin. To obtain a better understanding of the role of HAI-1 in maintaining epidermal integrity, we performed ultrastructural analysis of Spint1-deleted mouse epidermis and organotypic culture of an HAI-1 knockdown (KD) human keratinocyte cell line, HaCaT. We found that the aggregation of tonofilaments to desmosomes was significantly reduced in HAI-1-deficient mouse epidermis with decreased desmosome number. Similar findings were observed in HAI-1 KD HaCaT organotypic cultures. Immunoblot and immunohistochemical analyses revealed that p38 mitogen-activated protein kinase was activated in response to HAI-1 insufficiency. Treatment of HAI-1 KD HaCaT cells with a p38 inhibitor abrogated the above-observed ultrastructural abnormalities. The activation of p38 induced by the loss of HAI-1 likely resulted from enhanced signaling of protease-activated receptor-2 (PAR-2), because its silencing abrogated the enhanced activation of p38. Consequently, treatment of HAI-1 KD HaCaT cells with a serine protease inhibitor, aprotinin, or PAR-2 antagonist alleviated the abnormal ultrastructural phenotype in organotypic culture. These results suggest that HAI-1 may have a critical role in maintaining normal keratinocyte morphology through regulation of PAR-2-dependent p38 mitogen-activated protein kinase signaling.

Ghrelin administration suppresses inflammation-associated colorectal carcinogenesis in mice.

Ghrelin is a 28-amino-acid peptide that stimulates the release of pituitary growth hormone. Because of its orexigenic effects, ghrelin is being developed as a therapeutic option for postoperative support and treatment of anorexia-cachexia syndrome of cancer patients. However, ghrelin has a multiplicity of physiological functions, and it also affects cell proliferation. Therefore, the effects of ghrelin administration on carcinogenesis and cancer progression in patients susceptible to cancer should be clarified. In this study, we examined the effects of ghrelin on cancer promotion in vivo using murine intestinal carcinogenesis models. Intestinal tumorigenesis was examined to determine the effects of either exogenous ghrelin administration or ghrelin deficiency following deletion of the Ghrl gene. Two murine intestinal tumorigenesis models were used. The first was the azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced inflammation-associated colon carcinogenesis model and the second was the Apc(Min/+) genetic cancer susceptibility model. In AOM/DSS-treated mice, administration of ghrelin significantly suppressed tumor formation in the colon. In contrast, ghrelin administration did not affect the number of intestinal tumors formed in Apc(Min/+) mice. The absence of endogenous ghrelin did not affect the incidence of intestinal tumors in either AOM/DSS-treated mice or Apc(Min/+) mice, though tumor size tended to be larger in Ghrl(-/-) colons in the AOM/DSS model. No tumor-promoting effect was observed by ghrelin administration in either tumorigenesis model. In summary, this study provides in vivo experimental evidence for the usefulness of ghrelin administration in the chemoprevention of inflammation-associated colorectal carcinogenesis and may suggest its safety in patients under colitis-associated cancer susceptibility conditions.

Loss of hepatocyte growth factor activator inhibitor type 1 participates in metastatic spreading of human pancreatic cancer cells in a mouse orthotopic transplantation model.

Hepatocyte growth factor activator inhibitor type 1 (HAI-1) is a membrane-bound serine protease inhibitor that is expressed on the surface of epithelial and carcinoma cells. On the cell surface, HAI-1 regulates membrane-anchored serine proteases, with matriptase being the most critical target. Matriptase is involved in pericellular processing of biologically active molecules, including protease-activated receptor-2 (PAR-2). Previously we reported that S2-CP8 cells, a metastatic variant of the SUIT-2 human pancreatic adenocarcinoma cell line, showed markedly decreased HAI-1 expression. To assess the significance of HAI-1 loss in invasion and spontaneous metastasis of S2-CP8 cells, we established stable S2-CP8 sublines that expressed HAI-1 under the control of a tetracycline-regulated promoter. In vitro migration and invasion assays revealed inhibitory effects of HAI-1 on S2-CP8 cell migration and invasion. Matriptase activity was suppressed by the expression of HAI-1. As the enhanced invasiveness in the absence of HAI-1 was alleviated by knockdown of matriptase by 81% and of PAR-2 completely, and PAR-2 antagonist also suppressed the invasion, matriptase-mediated PAR-2 activation is involved in HAI-1 loss-induced invasion of S2-CP8 cells. We then analyzed the effect of HAI-1 expression on metastasis of S2-CP8 cells in vivo using a nude mouse orthotopic xenograft model. Although approximately 50% of the control mice developed distant metastasis, mice treated with doxycycline to induce HAI-1 expression did not develop metastasis. These data indicate that HAI-1 loss contributes to invasion and dissemination of a highly metastatic subline of SUIT-2, suggesting crucial roles for the balance of pericellular serine proteases/inhibitors in pancreatic cancer progression.

Aberrant expression of monocarboxylate transporter 4 in tumour cells predicts an unfavourable outcome in patients with hepatocellular carcinoma.

BACKGROUND & AIMS: The tumour cell microenvironment, which includes local oxygen saturation, pericellular pH and stromal cells, can modulate tumour progression. This study determined the prognostic impact of infiltrating tumour-associated macrophages and the expression of monocarboxylate transporter 4 (MCT4) and glypican 3 (GPC3) in hepatocellular carcinoma (HCC) clinical specimens. METHODS: A total of 225 cases of resected HCC were subjected to immunohistochemical analyses of CD68, CD204, MCT4 and GPC3. Immunoreactivities and other common clinicopathological parameters were subjected to univariate prognostic analyses for overall survival (OS, n = 225) and disease-free survival (DFS, n = 222). All variables with prognostic impact were further analysed in multivariate analysis. RESULTS: Increased intratumoural infiltration of CD204-positive or MCT4-positive macrophages suggested shorter OS (P = 0.015 or P = 0.001 respectively), but DFS was not altered. The GPC3 score (with an emphasis on circumferential immunoreactivity) was correlated with shorter OS and DFS. Aberrant expression of MCT4 in HCC cells was observed in a subset of HCC cases (21%, 47/225). In those cases, significantly poorer OS (P < 0.0001) and DFS (P = 0.0003) were observed, and there was a positive correlation with the intratumoural infiltration of CD204- or MCT4-positive macrophages and the GPC3 score. Multivariate analysis showed that aberrant MCT4 expression in HCC cells was an independent prognostic factor for shorter OS (P = 0.018) and DFS (P = 0.006) after resection of HCC. CONCLUSION: Aberrant expression of MCT4 in carcinoma cells serves as a novel, independent prognostic factor for HCC, indicating a poorer patient outcome.

Serum levels of angiopoietin-2, but not angiopoietin-1, are elevated in patients with erythrodermic cutaneous T-cell lymphoma.

Angiogenesis is a crucial process in the growth and progression of cancer, correlating with the metastatic potential of tumour cells. Angiopoietins are ligands for the endothelium-specific tyrosine kinase Tie2 receptor, which comprise 4 structurally related proteins, termed angiopoietin (Ang)-1, Ang-2, Ang-3 and Ang-4. The roles of Ang-1 and Ang-2 have recently been clarified as crucial in angiogenesis. In this report, we measured serum Ang-1 and Ang-2 levels in patients with cutaneous T-cell lymphoma (CTCL). Serum levels of Ang-2, but not Ang-1, in patients with Sézary syndrome were significantly higher than those in patch mycosis fungoides (MF), plaque/tumour MF, and healthy controls. In patients with CTCL, serum Ang-2 correlated with disease activity. Moreover, the numbers of Ang-2+ cells in lesional skin of CTCL were significantly larger than those in normal skin. These results suggest that Ang-2 may have important roles in the development of CTCL.

Loss of membrane-bound serine protease inhibitor HAI-1 induces oral squamous cell carcinoma cells' invasiveness.

A loss of balance between cell membrane-associated proteases and their inhibitors may underlie cancer invasion and metastasis. We analysed the roles of a membrane- associated serine protease inhibitor, HAI-1, in oral squamous cell carcinoma (OSCC). While membranous HAI-1 was widely observed in cancer cells of human OSCC tissues, this was significantly reduced at the infiltrative invasion front. In vitro, HAI-1 was detected in all eight OSCC cell lines examined, in which its cognate membrane protease, matriptase was also expressed. HAI-1 expression knock-down (KD) in OSCC lines, SAS and HSC-3, reduced the growth of both lines in vitro but significantly enhanced SAS tumourigenicity in vivo, which was accompanied by histological changes suggestive of the epithelial-mesenchymal transition. Both HAI-1-KD lines also exhibited significantly enhanced migratory capability, and membrane-associated but not truncated HAI-1 was required to rescue this phenotype. Other OSCC lines (HSC-2, Sa3, Ca9-22) also showed enhanced migration in response to HAI-1 KD. The enhanced migration is partly attributed to dysregulation of matriptase, as simultaneous matriptase KD alleviated the migration of HAI-1-KD cells. HAI-1 deficiency also altered the expression of CD24, S100A4, CCND2 and DUSP6, all of which are involved in tumour progression. While matriptase was involved in the increased CD24 expression associated with HAI-1 deficiency, the protease appeared to be not responsible for the altered expression of other genes. Therefore, a matriptase-independent mechanism for the invasiveness associated with HAI-1 KD is also present. Together, these observations suggest that HAI-1 has a crucial suppressive role in OSCC cell invasiveness.

Adrenomedullin alleviates mucosal injury in experimental colitis and increases claudin-4 expression in the colonic epithelium.

Adrenomedullin (AM) is a peptide with pleiotropic physiological functions that attenuates intestinal mucosal inflammation. However, the mechanism underpinning mucosal protection by AM is not fully understood, and its effect on intestinal epithelial cells remains unclear. Here, we investigated the effects of AM on junctional molecules in primary-cultured murine intestinal epithelial cells and discovered that AM upregulates claudin-4 expression. In a mouse model of dextran sulfate sodium-induced colitis, AM administration also enhanced claudin-4 expression and accelerated mucosal regeneration. Furthermore, AM reversed TNFα-mediated downregulation of claudin-4 and loss of cell-cell adhesion of the HCT116 human intestinal epithelial cell line in vitro. These results indicate that AM may enhance intestinal epithelial integrity by upregulating claudin-4 expression.

Blueberry Leaf Extract Prevents Lacrimal Hyposecretion in Sjögren's Syndrome-like Model of Non-obese Diabetic Mice.

BACKGROUND/AIM: This study evaluated the effect of blueberry leaf hot water extract (BLEx) on Sjögren's syndrome (SS)-like lacrimal hyposecretion in male non-obese diabetic (NOD) mice. MATERIALS AND METHODS: NOD or BALB/c mice were fed 1% BLEx or control (AIN-93G) for 2 weeks from the age of 4 to 6 weeks. Pilocarpine-induced tear volume was measured using a phenol red-impregnated thread. The lacrimal glands were evaluated histologically by H&E staining. The IL-1ß and TNF-α levels in the lacrimal gland tissue were measured by ELISA. The mRNA expression levels of secretion-related proteins were measured by real-time PCR. LC3 I/II and arginase 1 expression levels were measured by western blot. RESULTS: After feeding with BLEx, pilocarpine-induced tear secretion in NOD mice was increased. In contrast, the mRNA expression levels of the cholinergic muscarinic M3 receptor, aquaporin 5, and ion channels related to lacrimal secretion were not changed by BLEx administration. In addition, the protein expression of arginase 1, which was recently reported to be involved in tear hyposecretion in NOD mice, was also not improved by BLEx administration. Although infiltration in the lacrimal gland of NOD mice was not decreased, the levels of TNF-α and the autophagy-related protein LC3 were significantly suppressed by BLEx treatment. CONCLUSION: BLEx treatment may ameliorate lacrimal hyposecretion in NOD mice by delaying the progression of autoimmune disease by suppressing autophagy in lacrimal glands.

Membrane-bound serine protease inhibitor HAI-1 is required for maintenance of intestinal epithelial integrity.

Hepatocyte growth factor activator inhibitor type 1 (HAI-1), encoded by the serine protease inhibitor Kunitz type 1 (SPINT1) gene, is a membrane-bound serine protease inhibitor expressed in epithelial tissues. Mutant mouse models revealed that HAI-1/SPINT1 is essential for placental labyrinth formation and is critically involved in regulating epidermal keratinization through interaction with its cognate cell surface protease, matriptase. HAI-1/SPINT1 is abundantly expressed in both human and mouse intestinal epithelium; therefore, we analyzed its role in intestinal function using mice with intestinal epithelial cell-specific deletion of Spint1 generated by interbreeding mice carrying Spint1(LoxP) homozygous alleles with transgenic mice carrying the Cre recombinase gene controlled by the intestine-specific Villin promoter. Although the resulting mice had normal development and appearance, crypts in the proximal aspect of the colon, including the cecum, exhibited histologic abnormalities and increased apoptosis and epithelial cell turnover accompanied by increased intestinal permeability. Distended endoplasmic reticula were observed ultrastructurally in some crypt epithelial cells, indicative of endoplasmic reticular stress. To study the role of HAI-1/SPINT1 in mucosal injury, we induced colitis by adding dextran sodium sulfate to the drinking water. After dextran sodium sulfate treatment, intestine-specific HAI-1/SPINT1-deficient mice had more severe symptoms and a significantly lower survival rate relative to control mice. These results suggest that HAI-1/SPINT1 plays an important role in maintaining colonic epithelium integrity.

Role of the polycystic kidney disease domain in matriptase chaperone activity and localization of hepatocyte growth factor activator inhibitor-1.

Hepatocyte growth factor activator inhibitor-1 (HAI-1, also known as SPINT1) is an inhibitor of matriptase, a type-2 transmembrane protease widely expressed in epithelial cells. HAI-1 also functions as a chaperone to maintain the processing and localization of matriptase required for epithelial integrity. However, mechanisms underpinning the chaperone function remain to be elucidated. Here, we show that the first Kunitz domain (KD1) and the adjacent polycystic kidney disease (PKD) domain-like internal domain of HAI-1 are essential for the chaperone function. In HEK293T cells, which do not express endogenous HAI-1 or matriptase, forced matriptase overexpression was unsuccessful unless sufficient HAI-1 was co-expressed. Among mutant HAI-1 constructs, HAI-1 with inactivation mutation in KD1 (HAI-1mKD1) or HAI-1 lacking the PKD domain (HAI-1dPKD) was unable to support matriptase expression, and neither mutant formed a complex with activated matriptase. Matriptase did not localize to the cell surface when co-expressed with HAI-1dPKD. Moreover, HAI-1dPKD accumulated in the cytoplasm of HEK293T and HaCaT cells rather than localizing to the cell surface, presumably due to misfolding as judged by altered antibody recognition. On the other hand, activationlocked and activity-incompetent matriptase were stable and readily overexpressed and localized to the cell surface without HAI-1. Therefore, the observed matriptase instability was caused by its own catalytic activity in the absence of inhibitory HAI-1. The matriptase chaperone function of HAI-1 is thus mediated primarily by the inhibition of undesired intracellular matriptase activity, and the PKD domain is essential for the proper folding and trafficking of inhibitory HAI-1 and its chaperone function.