Ca2+-RhoA signaling pathway required for polyamine-dependent intestinal epithelial cell migration

Protective role of fruits of Rosa odorata var. gigantea against WIRS-induced gastric mucosal injury in rats by modulating pathway related to inflammation, oxidative stress and apoptosis

Objective

Rosa odorata var. gigantea is a popular medicinal plant. Some studies have demonstrated that ethanolic extract of the fruits of R. odorata var. gigantea (FOE) has gastroprotective properties. The aim of this study was to investigate the gastroprotective activity of FOE on water immersion restrained stress (WIRS)-induced gastric mucosal injury in a rat model and elucidate the possible molecular mechanisms involved.

Methods

A rat stress ulcer model was established in this study using WIRS. After rats were treated with FOE orally for 7 d, the effect of FOE treatment was analyzed by hematoxylin and eosin (H&E) staining, and the changes of inflammatory factors, oxidative stress factors, and gastric-specific regulatory factors and pepsin in the blood and gastric tissues of rats were examined by ELISA assay. Molecular mechanism of FOE was investigated by immunohistochemical assay and Western blot.

Results

Compared with the WIRS group, FOE could diminish both the macroscopic and microscopic pathological morphology of gastric mucosa. FOE significantly preserved the antioxidants glutathione peroxidase (GSH-PX), superoxide dismutase (SOD) and catalase (CAT) contents; anti-inflammatory cytokines interleukin-10 (IL-10) and prostaglandin E2 (PGE2) levels as well as regulatory factors tumor necrosis factor-α (TGF-α) and somatostatin (SS) contents, while decreasing malondialdehyde (MDA), nitric oxide synthase (iNOS), tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), gastrin (GAS) and endothelin (ET) levels. Moreover, FOE distinctly upregulated the expression of Nrf2, HO-1, Bcl2 and proliferating cell nuclear antigen (PCNA). In addition, FOE activated the expression of p-EGFR and downregulated the expression of NF-κB, Bax, Cleaved-caspase-3, Cyto-C and Cleaved-PARP1, thus promoting gastric mucosal cell survival.

Conclusion

The current work demonstrated that FOE exerted a gastroprotective activity against gastric mucosal injury induced by WIRS. The underlying mechanism might be associated with the improvement of anti-inflammatory, anti-oxidation and anti-apoptosis systems.

Circular RNA Cdr1as inhibits proliferation and delays injury-induced regeneration of the intestinal epithelium

Circular RNAs (circRNAs) are highly expressed in the mammalian intestinal epithelium, but their functions remain largely unknown. Here, we identified the circRNA Cdr1as as a repressor of intestinal epithelial regeneration and defense. Cdr1as levels increased in mouse intestinal mucosa after colitis and septic stress, as well as in human intestinal mucosa from patients with inflammatory bowel disease and sepsis. Ablation of the Cdr1as locus from the mouse genome enhanced renewal of the intestinal mucosa, promoted injury-induced epithelial regeneration, and protected the mucosa against colitis. We found approximately 40 microRNAs, including miR-195, differentially expressed between intestinal mucosa of Cdr1as-knockout (Cdr1as-/-) versus littermate mice. Increasing the levels of Cdr1as inhibited intestinal epithelial repair after wounding in cultured cells and repressed growth of intestinal organoids cultured ex vivo, but this inhibition was abolished by miR-195 silencing. The reduction in miR-195 levels in the Cdr1as-/- intestinal epithelium was the result of reduced stability and processing of the precursor miR-195. These findings indicate that Cdr1as reduces proliferation and repair of the intestinal epithelium at least in part via interaction with miR-195 and highlight a role for induced Cdr1as in the pathogenesis of unhealed wounds and disrupted renewal of the intestinal mucosa.

Tormentic acid, a triterpenoid isolated from the fruits of Chaenomeles speciose, protected indomethacin-induced gastric mucosal lesion via modulating miR-139 and the CXCR4/CXCL12/PLC/PKC/Rho a/MLC pathway

CONTEXT

Tormentic acid (TA), an effective triterpenoid isolated from Chaenomeles speciosa (Sweet) Nakai (Rosaceae) fruits, exerts an effective treatment for gastric damage.

OBJECTIVE

To investigate the gastroprotective effect of TA on indomethacin (IND) damaged GES-1 cells and rats, and explore potential mechanisms.

MATERIALS AND METHODS

TA concentrations of 1.563-25 µM were used. Cell proliferation, apoptosis and migration were performed using MTT, colony formation, wound healing, migration, Hoechst staining assays. SD rats were divided into control, IND, TA (1, 2 and 4 mg/kg) + IND groups, once a day for 21 continuous days. Twenty-four hours after the last administration, all groups except the control group were given IND (100 mg/kg) by gavage. Gastric juice parameters, gastric ulcer, gastric blood flow (GBF), blood biochemical parameters and cytokine analysis and gastric mucosal histopathology were detected for 2 h and 6 h after IND oral administration. The mRNA and protein expression of miR-139 and the CXCR4/CXCL12/PLC/PKC/Rho A/MLC pathway were analyzed in the IND-damaged GES-1 cells and gastric tissue of rats.

RESULTS

TA might ameliorate the gastric mucosal injury by accelerating the IND-damaged GES-1 cell proliferation and migration, ameliorating GBF, ulcer area and pathologic changes, the redox system and cytokine levels, the gastric juice parameters, elevating the gastric pH in IND damaged rats; suppressed miR-139 mRNA expression, elevated CXCR4 and CXCL12 mRNA and protein expression, p-PLC, p-PKC, Rho A, MLCK and p-MLC protein expression.

DISCUSSION AND CONCLUSIONS

TA may have potential use as a clinical drug candidate for gastric mucosal lesion treatment.

Polysaccharides from Panax ginseng promote intestinal epithelial cell migration through affecting the Ca2+ related regulators

Background and aim

Panax ginseng, a key herbal medicine of replenishing Qi and tonifying Spleen, is widely used in the treatment of gastrointestinal diseases in East Asia. In this study, we aim to investigate the potential effects and mechanisms of polysaccharides from P. ginseng (PGP) on intestinal mucosal restitution which is one of the crucial repair modalities during the recovery of mucosal injury controlled by the Ca²⁺ signaling.

Methods

Rat model of intestinal mucosal injury was induced by indomethacin. The fractional cell migration was carried out by immunohistochemistry staining with BrdU. The morphological observations on intestinal mucosal injury were also performed. Intestinal epithelial cell (IEC-6) migration in vitro was conducted by scratch method. Western-blot was adopted to determine the expressions of PLC-γ1, Rac1, TRPC1, RhoA and Cav-1. Immunoprecipitation was used to evaluate the levels of Rac1/PLC-γ1, RhoA/TRPC1 and Cav-1/TRPC1.

Results

The results showed that PGP effectively reduced the assessment of intestinal mucosal injury, reversed the inhibition of epithelial cell migration induced by Indomethacin, and increased the level of Ca²⁺ in intestinal mucosa in vivo. Moreover, PGP dramatically promoted IEC-6 cell migration, the expression of Ca²⁺ regulators (PLC-γ1, Rac1, TRPC1, Cav-1 and RhoA) as well as protein complexes (Rac1/PLC-γ1, Cav-1/TRPC1 and RhoA/TRPC1) in vitro.

Conclusion

PGP increases the Ca²⁺ content in intestinal mucosa partly through controlling the regulators of Ca²⁺ mobilization, subsequently promotes intestinal epithelial cell migration, and then prevents intestinal mucosal injury induced by indomethacin.

STIM1 promotes IPEC-J2 porcine epithelial cell restitution by TRPC1 signaling

Intestinal epithelial restitution is partly dependent on cell migration, which reseals superficial wounding after injury. Here, we tested the hypothesis that stromal interaction molecule 1(STIM1) regulates porcine intestinal epithelial cell migration by activating transient receptor potential canonical 1 (TRPC1) signaling. Results showed that the knockdown of STIM1 repressed cell migration after wounding, reduced the protein concentration of STIM1 and TRPC1, and decreased the inositol trisphosphate (IP3) content in IPEC-J2 cells (p < 0.05). However, overexpression of STIM1 obtained opposite results (p < 0.05). The inhibition of TRPC1 activity by treatment with SKF96365 in cells overexpressing wild-type and mutant STIM1 attenuated the STIM1 overexpression-induced increase of cell migration, STIM1, TRPC1 and IP3 (p < 0.05). In addition, polyamine depletion caused by α-difluoromethylornithine (DFMO) resulted in the decrease of above-mentioned parameters, and exogenous polyamine could attenuate the negative effects of DFMO on IPEC-J2 cells (p < 0.05). Moreover, the overexpression of STIM1 could rescue cell migration, the protein level of STIM1 and TRPC1, and IP3 content in polyamine-deficient IPEC-J2 cells (p < 0.05). These results indicated that STIM1 could enhance porcine intestinal epithelial cell migration via the TRPC1 signaling pathway. Inhibition of cell migration by polyamine depletion resulted from the reduction of STIM1 activity.

Selenoprotein K Is Essential for the Migration and Phagocytosis of Immature Dendritic Cells

Selenoprotein K (SELENOK) is an endoplasmic reticulum stress (ERS)-regulated protein required for the calcium (Ca²⁺) flux-mediated migration of T cells and neutrophils, and the migration and phagocytosis of macrophages and microglia. However, the effect of SELENOK on the regulation of the immune function of dendritic cells (DCs), including immature DCs (imDCs) and mature DCs (mDCs), is still unclear. In this study, imDCs prepared from SELENOK knockout mice were used to evaluate the effect of SELENOK on the migration and phagocytosis of imDCs. The results showed that ERS-induced downregulation of imDCs phenotypic markers led to a reduction in Ras homolog gene family member A (RhoA)-dependent migration and enhanced Ca²⁺/CD205-mediated phagocytosis. SELENOK deficiency-induced upregulation of selenoprotein S (SELENOS) attenuated ERS levels in imDCs. An increase in Ca²⁺ levels resulted in increased migration and decreased phagocytosis with or without ERS conditions. The migration was RhoA-dependent, and Ca²⁺ or CD205 was associated with regulating phagocytosis in imDCs. Our study found that SELENOK is required for imDC migration and phagocytosis.

The role of Astragalus polysaccharides in promoting IEC-6 cell migration from polyamine-mediated Ca2+ regulation

Astragalus polysaccharide (APS) has a protective effect on injured intestinal mucosa by promoting intestinal cell migration, but the specific mechanism is unclear. The polyamine-mediated calcium signaling pathway is an important mechanism of cell migration, generally, and we tested the hypothesis that APS can protect damaged intestinal mucosa through the polyamine-mediated calcium signaling pathway. High-performance liquid chromatography (HPLC), infrared chromatography, cell scratch test, Western blot, co-immunoprecipitation, polyamine inhibitor (DFMO), si-Cav1, RhoA inhibitor (Rhosin) and Rac1 inhibitor (NSC23766) were used to detect the pharmacodynamic of APS. The results show that APS can promote cell migration. In addition, APS increased the formations of RhoA/TRPC1, Cav1/TRPC1, and Rac1/PLCγ-1 complexes as well as the expressions of TRPC1, PLCγ-1, RhoA, Cav1, and Rac1, and it reversed the inhibitory effect of DFMO on the above factors. APS also reversed the inhibitory effect of si-Cav1 on Cav1 expression, cytoplasmic Ca²⁺ concentrations ([Ca²⁺]cyt), and cell migration. Moreover, APS removed the inhibition of NSC23766 and Rhosin on [Ca²⁺]cyt and cell migration. In vivo study, the water extract of Astragalus membranaceus (WEA) (15 g/kg) reduced the indomethacin-induced injury of intestinal mucosa as well. These observations suggest that APS can treat gastrointestinal mucosal injury through the polyamine calcium signaling pathway.

miR-195 Regulates Intestinal Epithelial Restitution after Wounding by altering Actin-Related Protein-2 Translation

Early gut epithelial restitution reseals superficial wounds after acute injury, but the exact mechanism underlying this rapid mucosal repair remains largely unknown. MicroRNA-195 (miR-195) is highly expressed in the gut epithelium and involved in many aspects of mucosal pathobiology. Actin-related proteins (ARPs) are key components essential for stimulation of actin polymerization and regulate cell motility. Here we reported that miR-195 modulates early intestinal epithelial restitution by altering ARP-2 expression at the translation level. MiR-195 directly interacted with the ARP-2 mRNA, and ectopically overexpressed miR-195 decreased ARP-2 protein without effect on its mRNA content. In contrast, miR-195 silencing by transfection with the anti-miR-195 increased ARP-2 protein expression. Decreased ARP-2 levels by miR-195 were associated with an inhibition of early epithelial restitution, as indicated by a decrease in cell migration over the wounded area. Elevation of cellular ARP-2 levels by transfection with its transgene restored cell migration after wounding in cells overexpressing miR-195. Polyamines were found to decrease miR-195 abundance and enhanced ARP-2 translation, thus promoting epithelial restitution after wounding. Moreover, increasing the levels of miR-195 disrupted F-actin cytoskeleton organization, which was prevented by ARP2 overexpression. These results indicate that miR-195 inhibits early epithelial restitution by decreasing ARP-2 translation and that miR-195 expression is negatively regulated by cellular polyamines.

Discovering the Triad between Nav1.5, Breast Cancer, and the Immune System: A Fundamental Review and Future Perspectives

Nav1.5 is one of the nine voltage-gated sodium channel-alpha subunit (VGSC-α) family members. The Nav1.5 channel typically carries an inward sodium ion current that depolarises the membrane potential during the upstroke of the cardiac action potential. The neonatal isoform of Nav1.5, nNav1.5, is produced via VGSC-α alternative splicing. nNav1.5 is known to potentiate breast cancer metastasis. Despite their well-known biological functions, the immunological perspectives of these channels are poorly explored. The current review has attempted to summarise the triad between Nav1.5 (nNav1.5), breast cancer, and the immune system. To date, there is no such review available that encompasses these three components as most reviews focus on the molecular and pharmacological prospects of Nav1.5. This review is divided into three major subsections: (1) the review highlights the roles of Nav1.5 and nNav1.5 in potentiating the progression of breast cancer, (2) focuses on the general connection between breast cancer and the immune system, and finally (3) the review emphasises the involvements of Nav1.5 and nNav1.5 in the functionality of the immune system and the immunogenicity. Compared to the other subsections, section three is pretty unexploited; it would be interesting to study this subsection as it completes the triad.

Deciphering cell signaling networks with massively multiplexed biosensor barcoding

Genetically encoded fluorescent biosensors are powerful tools for monitoring biochemical activities in live cells, but their multiplexing capacity is limited by the available spectral space. We overcome this problem by developing a set of barcoding proteins that can generate over 100 barcodes and are spectrally separable from commonly used biosensors. Mixtures of barcoded cells expressing different biosensors are simultaneously imaged and analyzed by deep learning models to achieve massively multiplexed tracking of signaling events. Importantly, different biosensors in cell mixtures show highly coordinated activities, thus facilitating the delineation of their temporal relationship. Simultaneous tracking of multiple biosensors in the receptor tyrosine kinase signaling network reveals distinct mechanisms of effector adaptation, cell autonomous and non-autonomous effects of KRAS mutations, as well as complex interactions in the network. Biosensor barcoding presents a scalable method to expand multiplexing capabilities for deciphering the complexity of signaling networks and their interactions between cells.

Circular RNA CircHIPK3 Promotes Homeostasis of the Intestinal Epithelium by Reducing MicroRNA 29b Function

BACKGROUND & AIMS

Circular RNAs (circRNAs) are a class of endogenous noncoding RNAs that form covalently closed circles. Although circRNAs influence many biological processes, little is known about their role in intestinal epithelium homeostasis. We surveyed circRNAs required to maintain intestinal epithelial integrity and identified circular homeodomain-interacting protein kinase 3 (circHIPK3) as a major regulator of intestinal epithelial repair after acute injury.

METHODS

Intestinal mucosal tissues were collected from mice exposed to cecal ligation and puncture for 48 hours and patients with inflammatory bowel diseases and sepsis. We isolated primary enterocytes from the small intestine of mice and derived intestinal organoids. The levels of circHIPK3 were silenced in intestinal epithelial cells (IECs) by transfection with small interfering RNAs targeting the circularization junction of circHIPK3 or elevated using a plasmid vector that overexpressed circHIPK3. Intestinal epithelial repair was examined in an in vitro injury model by removing part of the monolayer. The association of circHIPK3 with microRNA 29b (miR-29b) was determined by biotinylated RNA pull-down assays.

RESULTS

Genome-wide profile analyses identified ∼300 circRNAs, including circHIPK3, differentially expressed in the intestinal mucosa of mice after cecal ligation and puncture relative to sham mice. Intestinal mucosa from patients with inflammatory bowel diseases and sepsis had reduced levels of circHIPK3. Increasing the levels of circHIPK3 enhanced intestinal epithelium repair after wounding, whereas circHIPK3 silencing repressed epithelial recovery. CircHIPK3 silencing also inhibited growth of IECs and intestinal organoids, and circHIPK3 overexpression promoted intestinal epithelium renewal in mice. Mechanistic studies revealed that circHIPK3 directly bound to miR-29b and inhibited miR-29 activity, thus increasing expression of Rac1, Cdc42, and cyclin B1 in IECs after wounding.

CONCLUSIONS

In studies of mice, IECs, and human tissues, our results indicate that circHIPK3 improves repair of the intestinal epithelium at least in part by reducing miR-29b availability.

Effects of spermine on the proliferation and migration of porcine intestinal epithelial cells

Whether spermine promotes the repair of porcine intestinal epithelium damage through Ras-related C3 botulinum toxin substrate 1 (Rac1)/phospholipase C-γ1 (PLC-γ1) signaling remains unclear. The current study investigated the effects of spermine addition on the proliferation and migration of IPEC-J2 cells and the effects of Rac1/PLC-γ1 signaling on cell migration. We showed that the inhibitors of Rac1 (NSC-23766) and PLC-γ1 (U73122) reduced cell migration and decreased the protein levels of Rac1 and PLC-γ1 in the cells. Moreover, spermine promoted the proliferation and migration of the IPEC-J2 cells, that is, 1 µM spermine exhibited the best effect, and spermine treatment increased the protein levels of Rac1 and PLC-γ1. Further experiments showed that spermine treatment increased cell migration and enhanced Rac1 and PLC-γ1 protein levels, compared with NSC-23766 and U73122 treatments with spermine. In conclusion, spermine treatment promoted the repair of damaged porcine intestinal epithelium by accelerating cell proliferation and migration mediated by Rac1/PLC-γ1 signaling.

TRPC1-mediated Ca2+ signaling enhances intestinal epithelial restitution by increasing α4 association with PP2Ac after wounding

Gut epithelial restitution after superficial wounding is an important repair modality regulated by numerous factors including Ca²⁺ signaling and cellular polyamines. Transient receptor potential canonical-1 (TRPC1) functions as a store-operated Ca²⁺ channel in intestinal epithelial cells (IECs) and its activation increases epithelial restitution by inducing Ca²⁺ influx after acute injury. α4 is a multiple functional protein and implicated in many aspects of cell functions by modulating protein phosphatase 2A (PP2A) stability and activity. Here we show that the clonal populations of IECs stably expressing TRPC1 (IEC-TRPC1) exhibited increased levels of α4 and PP2A catalytic subunit (PP2Ac) and that TRPC1 promoted intestinal epithelial restitution by increasing α4/PP2Ac association. The levels of α4 and PP2Ac proteins increased significantly in stable IEC-TRPC1 cells and this induction in α4/PP2Ac complexes was accompanied by an increase in IEC migration after wounding. α4 silencing by transfection with siRNA targeting α4 (siα4) or PP2Ac silencing destabilized α4/PP2Ac complexes in stable IEC-TRPC1 cells and repressed cell migration over the wounded area. Increasing the levels of cellular polyamines by stable transfection with the Odc gene stimulated α4 and PP2Ac expression and enhanced their association, thus also promoting epithelial restitution after wounding. In contrast, depletion of cellular polyamines by treatment with α-difluoromethylornithine reduced α4/PP2Ac complexes and repressed cell migration. Ectopic overexpression of α4 partially rescued rapid epithelial repair in polyamine-deficient cells. These results indicate that activation of TRPC1-mediated Ca²⁺ signaling enhances cell migration primarily by increasing α4/PP2Ac associations after wounding and this pathway is tightly regulated by cellular polyamines.

The Functional Role of Voltage-Gated Sodium Channel Nav1.5 in Metastatic Breast Cancer

Voltage-gated sodium channels (VGSCs), which are abnormally expressed in various types of cancers such as breast cancer, prostate cancer, lung cancer, and cervical cancer, are involved in the metastatic process of invasion and migration. Nav1.5 is a pore-forming α subunit of VGSC encoded by SCN5A. Various studies have demonstrated that Nav1.5, often as its neonatal splice form, is highly expressed in metastatic breast cancer cells. Abnormal activation and expression of Nav1.5 trigger a variety of cellular mechanisms, including changing H+ efflux, promoting epithelial-to-mesenchymal transition (EMT) and the expression of cysteine cathepsin, to potentiate the metastasis and invasiveness of breast cancer cells in vitro and in vivo. Here, we systematically review the latest available data on the pro-metastatic effect of Nav1.5 and its underlying mechanisms in breast cancer. We summarize the factors affecting Nav1.5 expression in breast cancer cells, and discuss the potential of Nav1.5 blockers serving as candidates for breast cancer treatment.

Regulatory role of l-proline in fetal pig growth and intestinal epithelial cell proliferation

l-proline (Pro) is a precursor of ornithine, which is converted into polyamines via ornithine decarboxylase (ODC). Polyamines plays a key role in the proliferation of intestinal epithelial cells. The study investigated the effect of Pro on polyamine metabolism and cell proliferation on porcine enterocytes in vivo and in vitro. Twenty-four Huanjiang mini-pigs were randomly assigned into 1 of 3 groups and fed a basal diet that contained 0.77% alanine (Ala, iso-nitrogenous control), 1% Pro or 1% Pro + 0.0167% α-difluoromethylornithine (DFMO) from d 15 to 70 of gestation. The fetal body weight and number of fetuses per litter were determined, and the small and large intestines were obtained on d 70 ± 1.78 of gestation. The in vitro study was performed in intestinal porcine epithelial (IPEC-J2) cells cultured in Dulbecco's modified Eagle medium-high glucose (DMEM-H) containing 0 μmol/L Pro, 400 μmol/L Pro, or 400 μmol/L Pro + 10 mmol/L DFMO for 4 d. The results showed that maternal dietary supplementation with 1% Pro increased fetal weight; the protein and DNA concentrations of the fetal small intestine; and mRNA levels for potassium voltage-gated channel, shaker-related subfamily, member 1 (Kv1.1) in the fetal small and large intestines (P < 0.05). Supplementing Pro to either gilts or IPEC-J2 cells increased ODC protein abundances and polyamine concentrations in the fetal intestines and IPEC-J2 cells (P < 0.05). In comparison with the Pro group, the combined administration of Pro and DFMO reduced the expression of ODC protein and spermine concentration in the fetal intestine, as well as the concentrations of putrescine, spermidine and spermine in IPEC-J2 cells (P < 0.05). Meanwhile, the percentage of cells in the S-phase and the mRNA levels of proto-oncogenes c-fos and c-myc were increased in response to Pro supplementation, whereas depletion of cellular polyamines with DFMO increased tumor protein p53 (p53) mRNA levels (P < 0.05). Taken together, dietary supplementation with Pro improved fetal pig growth and intestinal epithelial cell proliferation via enhancing polyamine synthesis.

Total triterpenes from the fruits of Chaenomeles speciosa (Sweet) Nakai protects against indomethacin-induced gastric mucosal injury: involvement of TFF1-mediated EGF/EGFR and apoptotic pathways

OBJECTIVES

Our previous studies indicated that the triterpenes from the fruits of Chaenomeles speciosa (Sweet) Nakai (TCS) owned effectively therapeutic effects on gastric ulcer patients and animals, but its mechanisms have not been fully understood. The current study was to further investigate its protective effect on indomethacin (IND)-damaged RGM-1 cells and rats, as well as its mechanisms involved.

METHODS

The gastroprotection of TCS was evaluated with IND-induced gastric lesions model in RGM-1 cells and rats. In vitro, the proliferation, migration, mitochondrial viability and apoptosis were assessed. In vivo, ulcer index, ulcer inhibition rate, gastric juice acidity, gastric wall mucus (GWM) and histopathology of gastric mucosa were detected. The gastroprotective effects of TCS through the TFF1-mediated EGF/EGFR and apoptotic pathways were measured by qRT-PCR and Western blot assays.

KEY FINDINGS

The results demonstrated that TCS had gastroprotective function, which was related to the amelioration in promoting IND-damaged RGM-1 cell proliferation and migration, hoisting gastric juice acidity and GWM, improving ulcer index and ulcer inhibition rate, attenuating the haemorrhage, oedema, epithelial cell loss and inflammatory cell infiltration of gastric mucosa, upregulating PCNA, Bcl-2, Bcl-xl mRNA and TFF1, EGF, p-EGFR, p-Src, pro-caspase-3, pro-caspase-9 protein expressions, mitochondrial viability, mitochondrial cytochrome c concentration and p-EGFR/EGFR, p-Src/Src, Bcl-2/Bax, Bcl-xl/Bad ratioes, downregulating Bax, Bad, Apaf-1 mRNA and cleaved-caspase-3, cleaved-caspase-9, cleaved PARP-1 protein expressions and cytosol cytochrome c concentration.

CONCLUSIONS

Our present study demonstrated that TCS's gastroprotective effect was closely connected with boosting TFF1 expression, activating TFF1-mediated EGF/EGFR pathway, thus restraining mitochondrial-dependent apoptosis, which provided new insights into interpreting its underlying mechanism and promised to act as a candidate drug to treat gastric mucosal injury.

Mechanistic insights into Nav1.7-dependent regulation of rat prostate cancer cell invasiveness revealed by toxin probes and proteomic analysis

Voltage-gated sodium channels are involved in tumor metastasis, as potentiating or attenuating their activities affects the migration and invasion process of tumor cells. In the present study, we tested the effect of two peptide toxins, JZTX-I and HNTX-III which function as Nav1.7 activator and inhibitor, respectively, on the migration and invasion ability of prostate cancer (PCa) cell line Mat-LyLu. These two peptides showed opposite effects, and subsequently a comparative proteomic analysis characterized 64 differentially expressed membrane proteins from the JZTX-I- and HNTX-III-treated groups. Among these, 15 proteins were down-regulated and 49 proteins were up-regulated in the HNTX-III group. Bioinformatic analysis showed eight proteins are cytoskeleton proteins or related regulators, which might play important roles in the metastasis of Mat-LyLu cells. The altered expressions of four of these proteins, fascin, muskelin, annexin A2, and cofilin-1, were validated by western blot analysis. Further function network analysis of these proteins revealed that the Rho family GTPases RhoA and Rac1 might be of particular importance for the rat PCa cell invasion. Pharmacological data revealed that JZTX-I and HNTX-III could modulate the Rho signaling pathway in a Nav1.7-dependent manner. In summary, this study suggests that the Nav1.7-dependent regulation of Rho GTPase activity plays a vital role in Mat-LyLu cell migration and invasion and provides new insights into the treatment of PCa.

Systems Pharmacology Dissection of Multi-Scale Mechanisms of Action of Huo-Xiang-Zheng-Qi Formula for the Treatment of Gastrointestinal Diseases

Multi-components Traditional Chinese Medicine (TCM) treats various complex diseases (multi-etiologies and multi-symptoms) via herbs interactions to exert curative efficacy with less adverse effects. However, the ancient Chinese compatibility theory of herbs formula still remains ambiguous. Presently, this combination principle is dissected through a systems pharmacology study on the mechanism of action of a representative TCM formula, Huo-xiang-zheng-qi (HXZQ) prescription, on the treatment of functional dyspepsia (FD), a chronic or recurrent clinical disorder of digestive system, as typical gastrointestinal (GI) diseases which burden human physical and mental health heavily and widely. In approach, a systems pharmacology platform which incorporates the pharmacokinetic and pharmaco-dynamics evaluation, target fishing and network pharmacological analyses is employed. As a result, 132 chemicals and 48 proteins are identified as active compounds and FD-related targets, and the mechanism of HXZQ formula for the treatment of GI diseases is based on its three function modules of anti-inflammation, immune protection and gastrointestinal motility regulation mainly through four, i.e., PIK-AKT, JAK-STAT, Toll-like as well as Calcium signaling pathways. In addition, HXZQ formula conforms to the ancient compatibility rule of "Jun-Chen-Zuo-Shi" due to the different, while cooperative roles that herbs possess, specifically, the direct FD curative effects of GHX (serving as Jun drug), the anti-bacterial efficacy and major accompanying symptoms-reliving bioactivities of ZS and BZ (as Chen), the detoxication and ADME regulation capacities of GC (as Shi), as well as the minor symptoms-treating efficacy of the rest 7 herbs (as Zuo). This work not only provides an insight of the therapeutic mechanism of TCMs on treating GI diseases from a multi-scale perspective, but also may offer an efficient way for drug discovery and development from herbal medicine as complementary drugs.

Deconstructing the physical processes of digestion: reductionist approaches may provide greater understanding

I provide a broad overview of the physical factors that govern intestinal digestion i.e. the admixture of food particles in digesta with secreted enzymes and the subsequent mass transfer of liberated nutrients from the surfaces of particles to the gut wall, with a view to outlining the quantitative work that is required to determine the relative importance of these factors in the digestion of particular foods. I first discuss what is known of the mechanical forces generated by contraction of the walls of the various segments of the gut and the level of diffusive, and advective mixing that it generates within the lumen. I then discuss the particular physical effects that may limit the digestion of solid, physically and/or chemically homogenous and heterogeneous food particles, notably capillarity, porosity, poro-elastic flow and compaction and their likely effects on diffusive and convective mass transfer at particulate surfaces. Similarly, I discuss mucins and morphology on mass transfer of nutrients to the gut wall i.e. the mucosa.

Spermidine/spermine N1-acetyltransferase regulates cell growth and metastasis via AKT/β-catenin signaling pathways in hepatocellular and colorectal carcinoma cells

Hepatocellular carcinoma (HCC) and colorectal cancer (CRC) are among the most common cancers across the world. Therefore, identifying the potential molecular mechanisms that promote HCC and CRC progression and metastasis are urgently needed. Spermidine/spermine N¹-acetyltransferase (SSAT) is a catabolic enzyme that acetylates the high-order polyamines spermine and spermidine, thus decreasing the cellular content of polyamines. Several publications have suggested that depletion of intracellular polyamines inhibited tumor progression and metastasis in various cancer cells. However, whether and how SSAT regulates cell growth, migration and invasion in hepatocellular and colorectal carcinoma cells remains unclear. In this study, depletion of polyamines mediated by SSAT not only attenuated the tumor cell proliferation but also dramatically inhibited cell migration and invasion in hepatocellular and colorectal carcinoma cells. Subsequent investigations revealed introduction of SSAT into HepG2, SMMC7721 hepatocellular carcinoma cells and HCT116 colorectal carcinoma cells significantly suppressed p-AKT, p-GSK3β expression as well as β-catenin nuclear translocation, while inhibition of GSK3β activity or exogenous polyamines could restore SSAT-induced decreases in the protein expression of p-AKT, p-GSK3β and β-catenin. Conversely, knockdown of SSAT in Bel7402 hepatocellular carcinoma cells and HT-29 colorectal carcinoma cells which expressed high levels of SSAT endogenously significantly promoted the expression of p-AKT, p-GSK3β as well as β-catenin nuclear translocation. Taken together, our results indicated depletion of polyamines by SSAT significantly inhibited cell proliferation, migration and invasion through AKT/GSK3β/β-catenin signaling pathway in hepatocellular carcinoma and colorectal cancer cells.

β-PIX plays an important role in regulation of intestinal epithelial restitution by interacting with GIT1 and Rac1 after wounding

Early gut mucosal restitution is a process by which intestinal epithelial cells (IECs) migrate over the wounded area, and its defective regulation occurs commonly in various critical pathological conditions. This rapid reepithelialization is mediated by different activating small GTP-binding proteins, but the exact mechanism underlying this process remains largely unknown. Recently, it has been reported that interaction between p21-activated kinase-interacting exchange factor (β-PIX) and G protein-coupled receptor kinase-interacting protein 1 (GIT1) activates small GTPases and plays an important role in the regulation of cell motility. Here, we show that induced association of β-PIX with GIT1 is essential for the stimulation of IEC migration after wounding by activating Rac1. Levels of β-PIX and GIT1 proteins and their association in differentiated IECs (line of IEC-Cdx2L1) were much higher than those observed in undifferentiated IECs (line of IEC-6), which was associated with an increase in IEC migration after wounding. Decreased levels of endogenous β-PIX by its gene-silencing destabilized β-PIX/GIT1 complexes, repressed Rac1 activity and inhibited cell migration over the wounded area. In contrast, ectopic overexpression of β-PIX increased the levels of β-PIX/GIT1 complexes, stimulated Rac1 activity, and enhanced intestinal epithelial restitution. Increased levels of cellular polyamines also stimulated β-PIX/GIT1 association, increased Rac1 activity, and promoted the epithelial restitution. Moreover, polyamine depletion decreased cellular abundances of β-PIX/GIT1 complex and repressed IEC migration after wounding, which was rescued by ectopic overexpression of β-PIX or GIT1. These results indicate that β-PIX/GIT1/Rac1 association is necessary for stimulation of IEC migration after wounding and that this signaling pathway is tightly regulated by cellular polyamines. NEW & NOTEWORTHY Our current study demonstrates that induced association of β-PIX with GIT1 is essential for the stimulation of intestinal epithelial restitution by activating Rac1, and this signaling pathway is tightly regulated by cellular polyamines.

Effects of probiotic bacteria on mucosal polyamines levels in dogs with IBD and colonic polyps: a preliminary study

Spermine (SPM) and its precursor putrescine (PUT), regulated by ornithine decarboxylase (ODC) and diamino-oxidase (DAO), are polyamines required for cell growth and proliferation. Only a few studies have investigated the anti-inflammatory and tumour inhibitory properties of probiotics on mucosal polyamine levels. We investigated the effects of a high concentration multistrain probiotic for human use on colonic polyamine biosynthesis in dogs. Histological sections (inflammatory bowel disease, n=10; polyposis, n=5) were assessed after receiving 112 to 225×10⁹ lyophilised bacteria daily for 60 days at baseline (T0) and 30 days after treatment end (T90). Histology scores, expression of PUT, SPM, ODC and DAO, and a clinical activity index (CIBDAI) were compared at T0 and T90. In polyps, cellular proliferation (Ki-67 expression), and apoptosis (caspase-3 protein expression) were also evaluated. After treatment, in inflammatory bowel disease significant decreases were observed for CIBDAI (P=0.006) and histology scores (P<0.001); PUT, SPM and ODC expression increased (P<0.01). In polyps, a significant decrease in polyamine levels, ODC activity, and Ki-67, and a significant increase in caspase-3 positivity and DAO expression (P=0.005) was noted. Our results suggest potential anti-proliferative and anti-inflammatory effects of the probiotic mixture in polyps and inflammation, associated with reduced mucosal infiltration and up-regulation of PUT, SPM, and ODC levels.

Directional migration of mesenchymal stem cells under an SDF-1α gradient on a microfluidic device

Homing of peripheral stem cells is regulated by one of the most representative homing factors, stromal cell-derived factor 1 alpha (SDF-1α), which specifically binds to the plasma membrane receptor CXCR4 of mesenchymal stem cells (MSCs) in order to initiate the signaling pathways that lead to directional migration and homing of stem cells. This complex homing process and directional migration of stem cells have been mimicked on a microfluidic device that is capable of generating a chemokine gradient within the collagen matrix and embedding endothelial cell (EC) monolayers to mimic blood vessels. On the microfluidic device, stem cells showed directional migration toward the higher concentration of SDF-1α, whereas treatment with the CXCR4 antagonist AMD3100 caused loss of directionality of stem cells. Furthermore, inhibition of stem cell's main migratory signaling pathways, Rho-ROCK and Rac pathways, caused blockage of actomyosin and lamellipodia formation, decreasing the migration distance but maintaining directionality. Stem cell homing regulated by SDF-1α caused directional migration of stem cells, while the migratory ability was affected by the activation of migration-related signaling pathways.

ASIC1 and ASIC3 contribute to acidity-induced EMT of pancreatic cancer through activating Ca2+/RhoA pathway

Extracellular acid can have important effects on cancer cells. Acid-sensing ion channels (ASICs), which emerged as key receptors for extracellular acidic pH, are differently expressed during various diseases and have been implicated in underlying pathogenesis. This study reports that ASIC1 and ASIC3 are mainly expressed on membrane of pancreatic cancer cells and upregulated in pancreatic cancer tissues. ASIC1 and ASIC3 are responsible for an acidity-induced inward current, which is required for elevation of intracellular Ca²⁺ concentration ([Ca²⁺]i). Inhibition of ASIC1 and ASIC3 with siRNA or pharmacological inhibitor significantly decreased [Ca²⁺]i and its downstream RhoA during acidity and, thus, suppressed acidity-induced epithelial–mesenchymal transition (EMT) of pancreatic cancer cells. Meanwhile, downregulating [Ca²⁺]i with calcium chelating agent BAPTA-AM or knockdown of RhoA with siRNA also significantly repressed acidity-induced EMT of pancreatic cancer cells. Significantly, although without obvious effect on proliferation, knockdown of ASIC1 and ASIC3 in pancreatic cancer cells significantly suppresses liver and lung metastasis in xenograft model. In addition, ASIC1 and ASIC3 are positively correlated with expression of mesenchymal marker vimentin, but inversely correlated with epithelial marker E-cadherin in pancreatic cancer cells. In conclusion, this study indicates that ASICs are master regulator of acidity-induced EMT. In addition, the data demonstrate a functional link between ASICs and [Ca²⁺]i/RhoA pathway, which contributes to the acidity-induced EMT.

Atractylenolide I stimulates intestinal epithelial repair through polyamine-mediated Ca2+ signaling pathway

BACKGROUND

An impairment of the integrity of the mucosal epithelial barrier can be observed in the course of various gastrointestinal diseases. The migration and proliferation of the intestinal epithelial (IEC-6) cells are essential repair modalities to the healing of mucosal ulcers and wounds. Atractylenolide I (AT-I), one of the major bioactive components in the rhizome of Atractylodes macrocephala Koidz. (AMR), possesses multiple pharmacological activities. This study was designed to investigate the therapeutic effects and the underlying molecular mechanisms of AT-I on gastrointestinal mucosal injury.

METHODS

Scratch method with a gel-loading microtip was used to detect IEC-6 cell migration. The real-time cell analyzer (RTCA) system was adopted to evaluate IEC-6 cell proliferation. Intracellular polyamines content was determined using high performance liquid chromatography (HPLC). Flow cytometry was used to measure cytosolic free Ca²⁺ concentration ([Ca²⁺]_c). mRNA and protein expression of TRPC1 and PLC-γ₁ were determined by real-time PCR and Western blotting assay respectively.

RESULTS

Treatment of IEC-6 cells with AT-I promoted cell migration and proliferation, increased polyamines content, raised cytosolic free Ca²⁺ concentration ([Ca²⁺]_c), and enhanced TRPC1 and PLC-γ₁ mRNA and protein expression. Depletion of cellular polyamines by DL-a-difluoromethylornithine (DFMO, an inhibitor of polyamine synthesis) suppressed cell migration and proliferation, decreased polyamines content, and reduced [Ca²⁺]_c, which was paralleled by a decrease in TRPC1 and PLC-γ₁ mRNA and protein expression in IEC-6 cells. AT-I reversed the effects of DFMO on polyamines content, [Ca²⁺]_c, TRPC1 and PLC-γ₁ mRNA and protein expression, and restored IEC-6 cell migration and proliferation to near normal levels.

CONCLUSION

Our data demonstrate that AT-I stimulates intestinal epithelial cell migration and proliferation via the polyamine-mediated Ca²⁺ signaling pathway. Therefore, AT-I may have the potential to be further developed as a promising therapeutic agent to treat diseases associated with gastrointestinal mucosal injury, such as inflammatory bowel disease and peptic ulcer.

HuR Enhances Early Restitution of the Intestinal Epithelium by Increasing Cdc42 Translation

The mammalian intestinal mucosa exhibits a spectrum of responses after acute injury and repairs itself rapidly to restore the epithelial integrity. The RNA-binding protein HuR regulates the stability and translation of target mRNAs and is involved in many aspects of gut epithelium homeostasis, but its exact role in the regulation of mucosal repair after injury remains unknown. We show here that HuR is essential for early intestinal epithelial restitution by increasing the expression of cell division control protein 42 (Cdc42) at the posttranscriptional level. HuR bound to the Cdc42 mRNA via its 3' untranslated region, and this association specifically enhanced Cdc42 translation without an effect on the Cdc42 mRNA level. Intestinal epithelium-specific HuR knockout not only decreased Cdc42 levels in mucosal tissues, but it also inhibited repair of damaged mucosa induced by mesenteric ischemia/reperfusion in the small intestine and by dextran sulfate sodium in the colon. Furthermore, Cdc42 silencing prevented HuR-mediated stimulation of cell migration over the wounded area by altering the subcellular distribution of F-actin. These results indicate that HuR promotes early intestinal mucosal repair after injury by increasing Cdc42 translation and demonstrate the importance of HuR deficiency in the pathogenesis of delayed mucosal healing in certain pathological conditions.

c-Jun enhances intestinal epithelial restitution after wounding by increasing phospholipase C-γ1 transcription

c-Jun is an activating protein 1 (AP-1) transcription factor and implicated in many aspects of cellular functions, but its exact role in the regulation of early intestinal epithelial restitution after injury remains largely unknown. Phospholipase C-γ1 (PLCγ1) catalyzes hydrolysis of phosphatidylinositol 4,5 biphosphate into the second messenger diacylglycerol and inositol 1,4,5 triphosphate, coordinates Ca²⁺ store mobilization, and regulates cell migration and proliferation in response to stress. Here we reported that c-Jun upregulates PLCγ1 expression and enhances PLCγ1-induced Ca²⁺ signaling, thus promoting intestinal epithelial restitution after wounding. Ectopically expressed c-Jun increased PLCγ1 expression at the transcription level, and this stimulation is mediated by directly interacting with AP-1 and CCAAT-enhancer-binding protein (C/EBP) binding sites that are located at the proximal region of the rat PLCγ1 promoter. Increased levels of PLCγ1 by c-Jun elevated cytosolic free Ca²⁺ concentration and stimulated intestinal epithelial cell migration over the denuded area after wounding. The c-Jun-mediated PLCγ1/Ca²⁺ signal also plays an important role in polyamine-induced cell migration after wounding because increased c-Jun rescued Ca²⁺ influx and cell migration in polyamine-deficient cells. These findings indicate that c-Jun induces PLCγ1 expression transcriptionally and enhances rapid epithelial restitution after injury by activating Ca²⁺ signal.

Oral administration of putrescine and proline during the suckling period improves epithelial restitution after early weaning in piglets

Polyamines are necessary for normal integrity and the restitution after injury of the gastrointestinal epithelium. The objective of this study was to investigate the effects of oral administration of putrescine and proline during the suckling period on epithelial restitution after early weaning in piglets. Eighteen neonatal piglets (Duroc × Landrace × Large Yorkshire) from 3 litters (6 piglets per litter) were assigned to 3 groups, representing oral administration with an equal volume of saline (control), putrescine (5 mg/kg BW), and proline (25 mg/kg BW) twice daily from d 1 to weaning at 14 d of age. Plasma and intestinal samples were obtained 3 d after weaning. The results showed that oral administration of putrescine or proline increased the final BW and ADG of piglets compared with the control (P < 0.05). Proline treatment decreased plasma D-lactate concentration but increased the villus height in the jejunum and ileum, as well as the percentage of proliferating cell nuclear antigen (PCNA) positive cells and alkaline phosphatase (AKP) activity in the jejunal mucosa (P < 0.05). The protein expressions for zonula occludens (ZO-1), occludin, and claudin-3 (P < 0.05) but not mRNA were increased in the jejunum of putrescine- and proline-treated piglets compared with those of control piglets. The voltage-gated K+ channel (Kv) 1.1 protein expression in the jejunum of piglets administrated with putrescine and the Kv1.5 mRNA and Kv1.1 protein levels in the ileum of piglets administrated with proline were greater than those in control piglets (P < 0.05). These findings indicate that polyamine or its precursor could improve mucosal proliferation, intestinal morphology, as well as tight junction and potassium channel protein expressions in early-weaned piglets, with implications for epithelial restitution and barrier function after stress injury.

Inhibition of Kv channel expression by NSAIDs depolarizes membrane potential and inhibits cell migration by disrupting calpain signaling

Clinical use of non-steroidal anti-inflammatory drugs (NSAIDs) is well known to cause gastrointestinal ulcer formation via several mechanisms that include inhibiting epithelial cell migration and mucosal restitution. The drug-affected signaling pathways that contribute to inhibition of migration by NSAIDs are poorly understood, though previous studies have shown that NSAIDs depolarize membrane potential and suppress expression of calpain proteases and voltage-gated potassium (Kv) channel subunits. Kv channels play significant roles in cell migration and are targets of NSAID activity in white blood cells, but the specific functional effects of NSAID-induced changes in Kv channel expression, particularly on cell migration, are unknown in intestinal epithelial cells. Accordingly, we investigated the effects of NSAIDs on expression of Kv1.3, 1.4, and 1.6 in vitro and/or in vivo and evaluated the functional significance of loss of Kv subunit expression. Indomethacin or NS-398 reduced total and plasma membrane protein expression of Kv1.3 in cultured intestinal epithelial cells (IEC-6). Additionally, depolarization of membrane potential with margatoxin (MgTx), 40mM K(+), or silencing of Kv channel expression with siRNA significantly reduced IEC-6 cell migration and disrupted calpain activity. Furthermore, in rat small intestinal epithelia, indomethacin and NS-398 had significant, yet distinct, effects on gene and protein expression of Kv1.3, 1.4, or 1.6, suggesting that these may be clinically relevant targets. Our results show that inhibition of epithelial cell migration by NSAIDs is associated with decreased expression of Kv channel subunits, and provide a mechanism through which NSAIDs inhibit cell migration and may contribute to NSAID-induced gastrointestinal (GI) toxicity.

RhoA enhances store-operated Ca2+ entry and intestinal epithelial restitution by interacting with TRPC1 after wounding

Early mucosal restitution occurs as a consequence of epithelial cell migration to resealing of superficial wounds after injury. Our previous studies show that canonical transient receptor potential-1 (TRPC1) functions as a store-operated Ca(2+) channel (SOC) in intestinal epithelial cells (IECs) and plays an important role in early epithelial restitution by increasing Ca(2+) influx. Here we further reported that RhoA, a small GTP-binding protein, interacts with and regulates TRPC1, thus enhancing SOC-mediated Ca(2+) entry (SOCE) and epithelial restitution after wounding. RhoA physically associated with TRPC1 and formed the RhoA/TRPC1 complexes, and this interaction increased in stable TRPC1-transfected IEC-6 cells (IEC-TRPC1). Inactivation of RhoA by treating IEC-TRPC1 cells with exoenzyme C3 transferase (C3) or ectopic expression of dominant negative RhoA (DNMRhoA) reduced RhoA/TRPC1 complexes and inhibited Ca(2+) influx after store depletion, which was paralleled by an inhibition of cell migration over the wounded area. In contrast, ectopic expression of wild-type (WT)-RhoA increased the levels of RhoA/TRPC1 complexes, induced Ca(2+) influx through activation of SOCE, and promoted cell migration after wounding. TRPC1 silencing by transfecting stable WT RhoA-transfected cells with siRNA targeting TRPC1 (siTRPC1) reduced SOCE and repressed epithelial restitution. Moreover, ectopic overexpression of WT-RhoA in polyamine-deficient cells rescued the inhibition of Ca(2+) influx and cell migration induced by polyamine depletion. These findings indicate that RhoA interacts with and activates TRPC1 and thus stimulates rapid epithelial restitution after injury by inducing Ca(2+) signaling.

Atractylodes macrocephala Koidz stimulates intestinal epithelial cell migration through a polyamine dependent mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Atractylodes macrocephala Koidz (AMK), a valuable traditional Chinese herbal medicine, has been widely used in clinical practice for treating patients with disorders of the digestive system. AMK has shown noteworthy promoting effect on improving gastrointestinal function and immunity, which might represent a promising candidate for the treatment of intestinal mucosa injury. The aim of this study was to investigate the efficacy of AMK on intestinal mucosal restitution and the underlying mechanisms via intestinal epithelial (IEC-6) cell migration model.

MATERIALS AND METHODS

A cell migration model of IEC-6 cells was induced by a single-edge razor blade along the diameter of the cell layers in six-well polystyrene plates. After wounding, the cells were grown in control cultures and in cultures containing spermidine (5μM, SPD, reference drug), alpha-difluoromethylornithine (2.5mM, DFMO, polyamine inhibitor), AMK (50, 100, and 200mg/L), DFMO plus SPD and DFMO plus AMK for 12h. The polyamines content was detected by high-performance liquid chromatography (HPLC) with pre-column derivatization. The Rho mRNAs expression levels were assessed by Q-RT-PCR. The Rho and non-muscle myosin II proteins expression levels were analyzed by Western blot. The formation and distribution of non-muscle myosin II stress fibers were monitored with immunostaining techniques using specific antibodies and observed by confocal microscopy. Cell migration assay was carried out using inverted microscope and the Image-Pro Plus software. All of these indexes were used to evaluate the effectiveness of AMK.

RESULTS

(1) Treatment with AMK caused significant increases in cellular polyamines content and Rho mRNAs and proteins expression levels, as compared to control group. Furthermore, AMK exposure increased non-muscle myosin II protein expression levels and formation of non-muscle myosin II stress fibers, and resulted in an acceleration of cell migration in IEC-6 cells. (2) Depletion of cellular polyamines by DFMO resulted in a decrease of cellular polyamines levels, Rho mRNAs and proteins expression, non-muscle myosin II protein formation and distribution, thereby inhibiting IEC-6 cell migration. AMK not only reversed the inhibitory effects of DFMO on the polyamines content, Rho mRNAs and proteins expression, non-muscle myosin II protein formation and distribution, but also restored cell migration to control levels.

CONCLUSIONS

The results obtained from this study revealed that AMK significantly stimulates the migration of IEC-6 cells through a polyamine dependent mechanism, which could accelerate the healing of intestinal injury. These findings suggest the potential value of AMK in curing intestinal diseases characterized by injury and ineffective repair of the intestinal mucosa in clinical practice.

Differential activation of receptors and signal pathways upon stimulation by different doses of sphingosine-1-phosphate in endothelial cells

NEW FINDINGS

What is the central question of this study? Why do different doses of sphingosine-1-phosphate (S1P) induce distinct biological effects in endothelial cells? What is the main finding and its importance? S1P at physiological concentrations preserved endothelial barrier function by binding to S1P receptor 1, then triggering Ca(2+) release from endoplasmic reticulum through phosphoinositide phospholipase C and inositol triphosphate, and consequently strengthening tight junction and F-actin assembly through Rac1 activation. Excessive S1P induced endothelial malfunction by activating S1P receptor 2 and RhoA/ROCK pathway, causing F-actin and tight junction disorganisation. Extracellular Ca(2+) influx was involved in this process. Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid in plasma, and its plasma concentration can be adjusted through a complex metabolic process. The alterations in S1P levels and the activation of receptors collaboratively regulate distinct biological effects. This study was performed to investigate comparatively the effect of different concentrations of S1P on endothelial barrier function and to explore the roles of S1P receptors (S1PRs), Rho GTPases and calcium in S1P-induced endothelial responses. Endothelial barrier function was studied using transendothelial electric resistance and a resistance meter in human umbilical vein endothelial cells. Specific agonists or antagonists were applied to control the activation of S1P receptors and the release of calcium from different cellular compartments. The results indicated that at physiological concentrations, S1P preserved endothelial barrier function by binding with S1PR1. The activation of S1PR1 triggered the release of intracellular Ca(2+) from the endoplasmic reticulum through the PI-phospholipase C and inositol trisphosphate pathways. Consequently, the Rho GTPase Rac1 was activated, strengthening the assembly of tight junction proteins and F-actin. However, excessive S1P induced endothelial barrier dysfunction by activating S1PR2 followed by the RhoA/RhoA kinase pathway, causing the disorganization of F-actin and the disassembly of the tight junction protein ZO-1. An influx of extracellular Ca(2+) was involved in this process. These data suggest that physiological and excessive amounts of S1P induce different responses in human umbilical vein endothelial cells; the activation of the 1PR1-PLC-IP3 R-Ca(2+) -Rac1 pathway governs the low-dose S1P-enhanced endothelial barrier integrity, and the activation of S1PR2-calcium influx-RhoA/ROCK dominates the high-dose S1P-induced endothelial monolayer hyperpermeability response.

Caveolin-1 enhances rapid mucosal restitution by activating TRPC1-mediated Ca2+ signaling

Early rapid mucosal restitution occurs as a consequence of epithelial cell migration to reseal superficial wounds, a process independent of cell proliferation. Our previous studies revealed that the canonical transient receptor potential-1 (TRPC1) functions as a store-operated Ca(2+) channel (SOCs) in intestinal epithelial cells (IECs) and regulates epithelial restitution after wounding, but the exact mechanism underlying TRPC1 activation remains elusive. Caveolin-1 (Cav1) is a major component protein that is associated with caveolar lipid rafts in the plasma membrane and was recently identified as a regulator of store-operated Ca(2+) entry (SOCE). Here, we showed that Cav1 plays an important role in the regulation of mucosal restitution by activating TRPC1-mediated Ca(2+) signaling. Target deletion of Cav1 delayed gastric mucosal repair after exposure to hypertonic NaCl in mice, although it did not affect total levels of TRPC1 protein. In cultured IECs, Cav1 directly interacted with TRPC1 and formed Cav1/TRPC1 complex as measured by immunoprecipitation assays. Cav1 silencing in stable TRPC1-transfected cells by transfection with siCav1 reduced SOCE without effect on the level of resting [Ca(2+)]cyt. Inhibition of Cav1 expression by siCav1 and subsequent decrease in Ca(2+) influx repressed epithelial restitution, as indicated by a decrease in cell migration over the wounded area, whereas stable ectopic overexpression of Cav1 increased Cav1/TRPC1 complex, induced SOCE, and enhanced cell migration after wounding. These results indicate that Cav1 physically interacts with and activates TRPC1, thus stimulating TRPC1-mediated Ca(2+) signaling and rapid mucosal restitution after injury.

Src-mediated caveolin-1 phosphorylation regulates intestinal epithelial restitution by altering Ca(2+) influx after wounding

Early mucosal restitution occurs as a consequence of intestinal epithelial cell (IEC) migration to reseal superficial wounds, but its exact mechanism remains largely unknown. Caveolin-1 (Cav1), a major component associated with caveolar lipid rafts in the plasma membrane, is implicated in many aspects of cellular functions. This study determined if c-Src kinase (Src)-induced Cav1 phosphorylation promotes intestinal epithelial restitution after wounding by activating Cav1-mediated Ca(2+) signaling. Src directly interacted with Cav1, formed Cav1-Src complexes, and phosphorylated Cav1 in IECs. Inhibition of Src activity by its chemical inhibitor PP2 or suppression of the functional caveolin scaffolding domain by caveolin-scaffolding domain peptides prevented Cav1-Src interaction, reduced Cav1 phosphorylation, decreased Ca(2+) influx, and inhibited cell migration after wounding. Disruption of caveolar lipid raft microdomains by methyl-β-cyclodextrin reduced Cav1-mediated Ca(2+) influx and repressed epithelial restitution. Moreover, Src silencing prevented subcellular redistribution of phosphorylated Cav1 in migrating IECs. These results indicate that Src-induced Cav1 phosphorylation stimulates epithelial restitution by increasing Cav1-mediated Ca(2+) signaling after wounding, thus contributing to the maintenance of gut mucosal integrity under various pathological conditions.

Ethanol disrupts intestinal epithelial tight junction integrity through intracellular calcium-mediated Rho/ROCK activation

Evidence indicates that ethanol-induced intestinal barrier dysfunction and subsequent endotoxemia plays a key role in the pathogenesis of alcoholic liver disease. Recently, it has been demonstrated that ethanol induces RhoA kinase activation in intestinal epithelium, thereby disrupting barrier integrity. In this study, the role of a rise in intracellular calcium concentration ([Ca(2+)]i) in ethanol-induced Rho-associated coiled coil-forming kinase (Rho/ROCK) activation and barrier disruption was investigated in Caco-2 cell monolayers. Treatment of Caco-2 monolayers with 40 mmol/l ethanol induced [Ca(2+)]i release as indicated by increased relative fluorescent units of Fluo-3 from 0.06 ± 0.02 to 2.27 ± 1.96 (P < 0.0001). Pretreatment with 1,2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM) completely inhibited the release, whereas the inositol 1,4,5-triphosphate receptor (IP3R)-antagonist, Xestospongin C, partially inhibited the ethanol-induced [Ca(2+)]i release (from 2.27 ± 1.96 to 0.03 ± 0.01; P < 0.0001 and from 2.27 ± 1.96 to 1.19 ± 1.80; P < 0.001, respectively). The rise in [Ca(2+)]i was paralleled with increased intestinal permeability, which could be attenuated by either BAPTA-AM or Xestospongin C. Furthermore, ethanol induced Rho/ROCK activation, as indicated by increased phosphorylation of myosin-binding subunit, which could be prevented either by BAPTA, Xestospongin C, or the specific Rho/ROCK inhibitor Y27632. Finally, inhibition of Rho/ROCK kinase by Y27632 ameliorated the ethanol-induced redistribution of zonula occluden-1, adherens junction proteins including E-cadherin and β-catenin, and also disorganization of F-actin. These findings suggest that ethanol-induced [Ca(2+)]i release, mediated by stimulating IP3R-gated Ca(2+) channel, activates Rho/ROCK in Caco-2 cells, thereby contributing to ethanol-induced intestinal barrier dysfunction.

Atractylodes macrocephala Koidz promotes intestinal epithelial restitution via the polyamine--voltage-gated K+ channel pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Atractylodes macrocephala Koidz (AMK) has been used widely as a digestive and tonic in traditional Chinese medicine. AMK has shown noteworthy promoting effect on intestinal epithelial cell migration, which might represent a promising candidate for the treatment of intestinal mucosa injury. The aim of this study was to investigate the efficacy of AMK on intestinal mucosal restitution and the underlying mechanisms via IEC-6 cell migration model.

MATERIALS AND METHODS

A wounding model of IEC-6 cells was induced by a single-edge razor blade along the diameter of six-well polystyrene plates. The cells were grown in control cultures and in cultures containing spermidine (5 μmol/L, SPD, reference drug), alpha-difluoromethylornithine (2.5 mmol/L, DFMO, polyamine inhibitor), AMK (50, 100, and 200 μg/mL), DFMO plus SPD and DFMO plus AMK for 24h. The membrane potential (MP) and cytosolic free Ca(2+) concentration ([Ca(2+)]cyt) were detected by flow cytometry, and polyamines content was determined via high-performance liquid chromatography (HPLC). The expression of Kv1.1 mRNA and protein levels were assessed by RT-qPCR and Western blot analysis, respectively. Cell migration assay was carried out using the Image-Pro Plus software. All of these indexes were used to evaluate the effectiveness of AMK.

RESULTS

(1) Treatment with AMK caused significant increases in cellular polyamines content, membrane hyperpolarization, an elevation of [Ca(2+)]cyt and an acceleration of cell migration in IEC-6 cells, as compared to control group. (2) AMK not only reversed the inhibitory effects of DFMO on the polyamines content, MP, and [Ca(2+)]cyt but also restored IEC-6 cell migration to control levels. (3) The Kv1.1 mRNA and protein expression were significantly increased by AMK treatment in control and polyamine-deficient IEC-6 cells.

CONCLUSIONS

The results of our current studies revealed that treatment with AMK significantly stimulates the migration of intestinal epithelial cells through polyamine-Kv1.1 channel signaling pathway, which could promote the healing of intestinal injury. These results suggest the potential usefulness of AMK to cure intestinal disorders characterized by injury and ineffective repair of the intestinal mucosa.

The small GTPase RhoA regulates the expression and function of the sodium channel Nav1.5 in breast cancer cells

Voltage-gated Na+ channels (VGSCs) are highly expressed in several types of carcinomas including breast, prostate and lung cancers as well as in mesothelioma and cervical cancers. Although the VGSCs activity is considered crucial for the potentiation of cancer cell migration and invasion, the mechanisms responsible for their functional expression and regulation in cancer cells remain unclear. In the present study, the role of the small GTPase RhoA in the regulation of expression and function of the Nav1.5 channel in the breast cancer cell lines MDA-MB 231 and MCF-7 was investigated. RhoA silencing significantly reduced both Nav1.5 channel expression and sodium current indicating that RhoA exerts a stimulatory effect on the synthesis of an active form of Nav1.5 channel in cancer cells. The inhibition of Nav1.5 expression dramatically reduced both cell invasion and proliferation. In addition, a decrease of RhoA protein levels induced by Nav1.5 silencing was observed. Altogether, these findings revealed: i) the key role of the small GTPase RhoA in upregulation of Nav1.5 channel expression and tumor aggressiveness, and ii) the existence of a positive feedback of Nav1.5 channels on RhoA protein levels.

Polyamines regulate intestinal epithelial restitution through TRPC1-mediated Ca²+ signaling by differentially modulating STIM1 and STIM2

Early epithelial restitution occurs as a consequence of intestinal epithelial cell (IEC) migration after wounding, and its defective regulation is implicated in various critical pathological conditions. Polyamines stimulate intestinal epithelial restitution, but their exact mechanism remains unclear. Canonical transient receptor potential-1 (TRPC1)-mediated Ca(2+) signaling is crucial for stimulation of IEC migration after wounding, and induced translocation of stromal interaction molecule 1 (STIM1) to the plasma membrane activates TRPC1-mediated Ca(2+) influx and thus enhanced restitution. Here, we show that polyamines regulate intestinal epithelial restitution through TRPC1-mediated Ca(2+) signaling by altering the ratio of STIM1 to STIM2. Increasing cellular polyamines by ectopic overexpression of the ornithine decarboxylase (ODC) gene stimulated STIM1 but inhibited STIM2 expression, whereas depletion of cellular polyamines by inhibiting ODC activity decreased STIM1 but increased STIM2 levels. Induced STIM1/TRPC1 association by increasing polyamines enhanced Ca(2+) influx and stimulated epithelial restitution, while decreased formation of the STIM1/TRPC1 complex by polyamine depletion decreased Ca(2+) influx and repressed cell migration. Induced STIM1/STIM2 heteromers by polyamine depletion or STIM2 overexpression suppressed STIM1 membrane translocation and inhibited Ca(2+) influx and epithelial restitution. These results indicate that polyamines differentially modulate cellular STIM1 and STIM2 levels in IECs, in turn controlling TRPC1-mediated Ca(2+) signaling and influencing cell migration after wounding.

L-arginine supplementation improves responses to injury and inflammation in dextran sulfate sodium colitis

Inflammatory bowel disease (IBD), consisting of Crohn's disease and ulcerative colitis (UC), results in substantial morbidity and is difficult to treat. New strategies for adjunct therapies are needed. One candidate is the semi-essential amino acid, L-arginine (L-Arg), a complementary medicine purported to be an enhancer of immunity and vitality in the lay media. Using dextran sulfate sodium (DSS) as a murine colonic injury and repair model with similarities to human UC, we assessed the effect of L-Arg, as DSS induced increases in colonic expression of the y(+) cationic amino acid transporter 2 (CAT2) and L-Arg uptake. L-Arg supplementation improved the clinical parameters of survival, body weight loss, and colon weight, and reduced colonic permeability and the number of myeloperoxidase-positive neutrophils in DSS colitis. Luminex-based multi-analyte profiling demonstrated that there was a marked reduction in proinflammatory cytokine and chemokine expression with L-Arg treatment. Genomic analysis by microarray demonstrated that DSS-treated mice supplemented with L-Arg clustered more closely with mice not exposed to DSS than to those receiving DSS alone, and revealed that multiple genes that were upregulated or downregulated with DSS alone exhibited normalization of expression with L-Arg supplementation. Additionally, L-Arg treatment of mice with DSS colitis resulted in increased ex vivo migration of colonic epithelial cells, suggestive of increased capacity for wound repair. Because CAT2 induction was sustained during L-Arg treatment and inducible nitric oxide (NO) synthase (iNOS) requires uptake of L-Arg for generation of NO, we tested the effect of L-Arg in iNOS(-/-) mice and found that its benefits in DSS colitis were eliminated. These preclinical studies indicate that L-Arg supplementation could be a potential therapy for IBD, and that one mechanism of action may be functional enhancement of iNOS activity.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Role of myosin light chain kinase in cardiotrophin-1-induced cardiac myofibroblast cell migration

Chemotactic movement of myofibroblasts is recognized as a common means for their sequestration to the site of tissue injury. Following myocardial infarction (MI), recruitment of cardiac myofibroblasts to the infarct scar is a critical step in wound healing. Contractile myofibroblasts express embryonic smooth muscle myosin, α-smooth muscle actin, as well as collagens I and III. We examined the effects of cardiotrophin-1 (CT-1) in the induction of primary rat ventricular myofibroblast motility. Changes in membrane potential (Em) and Ca2+entry were studied to reveal the mechanisms for induction of myofibroblast migration. CT-1-induced cardiac myofibroblast cell migration, which was attenuated through the inhibition of JAK2 (25 μM AG490), and myosin light chain kinase (20 μM ML-7). Inhibition of K+channels (1 mM tetraethylammonium or 100 μM 4-aminopyridine) and nonselective cation channels by 10 μM gadolinium (Gd3+) significantly reduced migration in the presence of CT-1. CT-1 treatment caused a significant increase in myosin light chain phosphorylation, which could be inhibited by incubation in Ca2+-free conditions or by application of AG490, ML-7, and W7 (100 μM; calmodulin inhibitor). Monitoring myofibroblast membrane potential with potentiometric fluorescent DiBAC4( 3 ) dye revealed a biphasic response to CT-1 consisting of an initial depolarization followed by hyperpolarization. Increased intracellular Ca2+, as assessed by fluo 3, occurred immediately after membrane depolarization and attenuated at the time of maximal hyperpolarization. CT-1 exerts chemotactic effects via multiple parallel signaling modalities in ventricular myofibroblasts, including changes in membrane potential, alterations in intracellular calcium, and activation of a number of intracellular signaling pathways. Further study is warranted to determine the precise role of K+currents in this process.

Sphingosine-1-phosphate regulates the expression of adherens junction protein E-cadherin and enhances intestinal epithelial cell barrier function

BACKGROUND

The regulation of intestinal barrier permeability is important in the maintenance of normal intestinal physiology. Sphingosine-1-phosphate (S1P) has been shown to play a pivotal role in enhancing barrier function in several non-intestinal tissues. The current study determined whether S1P regulated function of the intestinal epithelial barrier by altering expression of E-cadherin, an important protein in adherens junctions.

METHODS

Studies were performed upon cultured differentiated IECs (IEC-Cdx2L1 line) using standard techniques.

RESULTS

S1P treatment significantly increased levels of E-cadherin protein and mRNA in intestinal epithelial cells (IECs) and also led to E-cadherin localizing strongly to the cell-cell border. S1P also improved the barrier function as indicated by a decrease in 14C-mannitol paracellular permeability and an increase in transepithelial electrical resistance (TEER) in vitro.

CONCLUSIONS

These results indicate that S1P increases levels of E-cadherin, both in cellular amounts and at the cell-cell junctions, and leads to improved barrier integrity in cultured intestinal epithelial cells.

STIM1 translocation to the plasma membrane enhances intestinal epithelial restitution by inducing TRPC1-mediated Ca2+ signaling after wounding

Early epithelial restitution is an important repair modality in the gut mucosa and occurs as a consequence of epithelial cell migration. Canonical transient receptor potential-1 (TRPC1) functions as a store-operated Ca2+ channel (SOCs) in intestinal epithelial cells (IECs) and regulates intestinal restitution, but the exact upstream signals initiating TRPC1 activation after mucosal injury remain elusive. Stromal interaction molecule 1 (STIM1) is a single membrane-spanning protein and is recently identified as essential components of SOC activation. The current study was performed to determine whether STIM1 plays a role in the regulation of intestinal epithelial restitution by activating TRPC1 channels. STIM1 translocation to the plasma membrane increased after wounding, which was followed by an increase in IEC migration to reseal wounds. Increased STIM1 levels at the plasma membrane by overexpressing EF-hand mutant STIM1 enhanced Ca2+ influx through SOCs and stimulated IEC migration after wounding. STIM1 interacted with TRPC1 and formed STIM1/TRPC1 complex, whereas inactivation of STIM1 by STIM1 silencing decreased SOC-mediated Ca2+ influx and inhibited epithelial restitution. In cells overexpressing EF-hand mutant STIM1, TRPC1 silencing also decreased STIM1/TRPC1 complex, reduced SOC-mediated Ca2+ influx, and repressed cell migration after wounding. Our findings demonstrate that induced STIM1 translocation to the plasma membrane promotes IEC migration after wounding by enhancing TRPC1-mediated Ca2+ signaling and provide new insight into the mechanism of intestinal epithelial restitution.

Calcium mobilization triggered by the chemokine CXCL12 regulates migration in wounded intestinal epithelial monolayers

Restitution of intestinal epithelial barrier damage involves the coordinated remodeling of focal adhesions in actively migrating enterocytes. Defining the extracellular mediators and the intracellular signaling pathways regulating those dynamic processes is a key step in developing restitution-targeted therapies. Previously we have determined that activation of the chemokine receptor CXCR4 by the cognate ligand CXCL12 enhances intestinal epithelial restitution through reorganization of the actin cytoskeleton. The aim of these studies was to investigate the role of calcium effectors in CXCL12-mediated restitution. CXCL12 stimulated release of intracellular calcium in a dose-dependent manner. Inhibition of intracellular calcium flux impaired CXCL12-mediated migration of IEC-6 and CaCo2 cells. Pharmacological blockade and specific shRNA depletion of the phospholipase-C (PLCbeta3) isoform attenuated CXCL12-enhanced migration, linking receptor activation with intracellular calcium flux. Immunoblot analyses demonstrated CXCL12 activated the calcium-regulated focal adhesion protein proline-rich tyrosine kinase-2 (Pyk2) and the effector proteins paxillin and p130(Cas). Interruption of Pyk2 signaling potently blocked CXCL12-induced wound closure. CXCL12-stimulated epithelial cell migration was enhanced on laminin and abrogated by intracellular calcium chelation. These results suggest CXCL12 regulates restitution through calcium-activated Pyk2 localized to active focal adhesions. Calcium signaling pathways may therefore provide a novel avenue for enhancing barrier repair.

Increased serum levels of L-arginine in ulcerative colitis and correlation with disease severity

BACKGROUND

L-arginine (L-Arg) is a semi-essential amino acid that is the substrate for both nitric oxide and polyamine synthesis. Cellular uptake of L-Arg is an active transport process that is subject to competitive inhibition by L-ornithine (L-Orn) and L-lysine (L-Lys). We investigated L-Arg utilization in patients with ulcerative colitis (UC).

METHODS

Serum was collected from 14 normal controls and 22 UC patients with pancolitis of moderate or severe activity by histopathology score. The Mayo Disease Activity Index (DAI) and endoscopy subscore were assessed. Serum amino acid levels were measured by high-performance liquid chromatography. Arginine availability index (AAI) was defined as [L-Arg]/([L-Orn] + [L-Lys]).

RESULTS

Serum L-Arg levels were significantly associated with histopathologic grade (P = 0.001). L-Arg levels were increased in subjects with severe colitis when compared to those with moderate colitis or normal mucosa. L-Orn + L-Lys levels were also increased in severe colitis, so that AAI was not significantly increased. L-Arg levels were also strongly associated with the endoscopy subscore (P < 0.001). There was a strong correlation between DAI and L-Arg levels (r = 0.656, P < 0.001).

CONCLUSIONS

Serum L-Arg levels correlate with UC disease severity but availability is not increased due to competitive inhibition by L-Orn and L-Lys. Our findings suggest that L-Arg uptake by cells in the inflamed colon is defective, which may contribute to the pathogenesis of UC. Studies delineating the mechanism of uptake inhibition could enhance our understanding of UC or lead to novel treatment options.

Sphingosine-1-phosphate protects intestinal epithelial cells from apoptosis through the Akt signaling pathway

OBJECTIVE

The regulation of apoptosis of intestinal mucosal cells is important in maintenance of normal intestinal physiology.

SUMMARY

Sphingosine-1-phosphate (S1P) has been shown to play a critical role in cellular protection to otherwise lethal stimuli in several nonintestinal tissues.

METHODS

The current study determines whether S1P protected normal intestinal epithelial cells (IECs) from apoptosis and whether Akt activation was the central pathway for this effect.

RESULTS

S1P demonstrated significantly reduced levels of apoptosis induced by tumor necrosis factor-alpha (TNF-alpha)/cycloheximide (CHX). S1P induced increased levels of phosphorylated Akt and increased Akt activity, but did not affect total amounts of Akt. This activation of Akt was associated with decreased levels of both caspase-3 protein levels and of caspase-3 activity. Inactivation of Akt by treatment with the PI3K chemical inhibitor LY294002 or by overexpression of the dominant negative mutant of Akt (DNMAkt) prevented the protective effect of S1P on apoptosis. Additionally, silencing of the S1P-1 receptor by specific siRNA demonstrated a lesser decrease in apoptosis to S1P exposure.

CONCLUSION

These results indicate that S1P protects intestinal epithelial cells from apoptosis via an Akt-dependent pathway.

Rac1 promotes intestinal epithelial restitution by increasing Ca2+ influx through interaction with phospholipase C-(gamma)1 after wounding

Intestinal mucosal restitution occurs as a consequence of epithelial cell migration and reseals superficial wounds after injury. This rapid reepithelialization is mediated in part by a phospholipase C-gamma1 (PLC-gamma1)-induced Ca(2+) signaling, but the exact mechanism underlying such signaling and its regulation remains elusive. The small GTP-binding protein Rac1 functions as a pivotal regulator of several signaling networks and plays an important role in regulating cell motility. The current study tests the hypothesis that Rac1 modulates intestinal epithelial cell migration after wounding by altering PLC-gamma1-induced Ca(2+) signaling. Inhibition of Rac1 activity by treatment with its inhibitor NSC-23766 or Rac1 silencing with small interfering RNA decreased store depletion-induced Ca(2+) influx and suppressed cell migration during restitution, whereas ectopic overexpression of Rac1 increased Ca(2+) influx and promoted cell migration. Rac1 physically interacted with PLC-gamma1 and formed Rac1/PLC-gamma1 complex in intestinal epithelial cells. PLC-gamma1 silencing in cells overexpressing Rac1 prevented stimulation of store depletion-induced Ca(2+) influx and cell migration after wounding. Polyamine depletion inhibited expression of both Rac1 and PLC-gamma1, decreased Rac1/PLC-gamma1 complex levels, reduced Ca(2+) influx, and repressed cell migration. Overexpression of Rac1 alone failed to rescue Ca(2+) influx after store depletion and cell migration in polyamine-deficient cells, because it did not alter PLC-gamma1 levels. These results indicate that Rac1 promotes intestinal epithelial cell migration after wounding by increasing Ca(2+) influx as a result of its interaction with PLC-gamma1.

The alpha9beta1 integrin enhances cell migration by polyamine-mediated modulation of an inward-rectifier potassium channel

The alpha9beta1 integrin accelerates cell migration through binding of spermidine/spermine acetyltransferase (SSAT) to the alpha9 cytoplasmic domain. We now show that SSAT enhances alpha9-mediated migration specifically through catabolism of spermidine and/or spermine. Because spermine and spermidine are effective blockers of K(+) ion efflux through inward-rectifier K(+) (Kir) channels, we examined the involvement of Kir channels in this pathway. The Kir channel inhibitor, barium, or knockdown of a single subunit, Kir4.2, specifically inhibited alpha9-dependent cell migration. alpha9beta1 and Kir4.2 colocalized in focal adhesions at the leading edge of migrating cells and inhibition or knockdown of Kir4.2 caused reduced persistence and an increased number of lamellipodial extensions in cells migrating on an alpha9beta1 ligand. These results identify a pathway through which the alpha9 integrin subunit stimulates cell migration by localized polyamine catabolism and modulation of Kir channel function.