Adenosine diphosphate-ribosylation factor-like 15 can regulate glycolysis and lipogenesis related genes in colon cancer.

This study was designed to investigate the potential key genes of ADP-ribosylation factor-like 15 (ARL15) regulating glycolysis and lipogenesis in colon cancer. Hematoxylin-eosin (HE) staining and immunohistochemistry were used to observe the expression of ARL15 in 10 normal colon tissues and 10 colon cancer tissues. Immunofluorescence staining was used to observe the expression position of ARL15 in normal human colorectal mucosa cells (FHC) and colon cancer cells (HCT116 and SW620) with a confocal microscope. The ARL15 plasmid and small interfering RNA (siRNA) were constructed. After transfection, the expression levels of glycolysis and lipogenesis regulatory enzymes and messenger RNA (mRNA) transcription of ARL15 in over-expressed and silenced colon cancer cells were detected by Western blotting and real-time quantitative PCR (qRT-PCR). High expression of ARL15 in colon cancer tissue and low expression in normal colon tissue, and all expression are in the cytosol. The expression position of ARL15 in the FHC, HCT116, and SW620 cells was consistent and mainly distributed in the cytosol. After the pCMV-3Tag-2-ARL15 plasmid was transfected in HCT116, the protein expressions of FASN, AKT, P-AKT, P-GSK, SREBP-1 (p125) (p<0.01), and AMPK (p<0.001) were higher than those in the control group. The mRNA transcription level of FASN, GSK, AMPKa1, and SREBP-1 gene was higher than control group after the over-expression of ARL15. After the ARL15-siRNA was transfected in HCT116, the protein expression levels of PKM2, PFK, FASN, AKT, P-AKT, P-GSK, and AMPK decreased compared with the control group, (p<0.05). The mRNA transcription level of FASN, GSK, AMPKα1 gene was lower than control group after the low-expression of ARL15 (p<0.05). After adding 2 µM JIB-04, ARL15 in HCT116 showed statistical differences compared with the control group at 12 h, 24 h and 36 h (p<0.05). After adding 2 µM JIB-04, the protein expression levels of AKT, p-GSK, FASN, AMPK and SREBP-1 in HCT116 cells decreased significantly after 24 h. It was also found that the expression levels of AKT, P-GSK, FASN, AMPK and SREBP-1 genes in the dose-adding group were significantly lower than those in the control group. In summary, ARL15 may promote the occurrence of colon cancer by increasing the expression of protein kinase B/AMP-activated protein kinase (AKT/AMPK) downstream regulatory enzymes for glycogenesis and lipogenesis. JIB-04 can target ARL15 and affect its expression as well as the expressions of glucose and lipid metabolity-related proteins in AKT and AMPK signaling pathways.

Del-1 enhances therapeutic efficacy of bacterial cancer immunotherapy by blocking recruitment of tumor-infiltrating neutrophils

BackgroundBacterial-mediated cancer immunotherapy (BCI) elicits a more robust initial immune response than conventional immunotherapy, but does not prevent tumor recurrence and metastasis. BCI is associated with recruitment of tumor-infiltrating neutrophils, which could suppress the therapeutic efficacy of this modality. Development endothelial locus 1 (Del-1), a potent inhibitor of neutrophil recruitment, antagonizes lymphocyte function-associated antigen-1 on the vascular endothelium. Here, we aimed to determine the effect of Del-1-secreting S.t△ppGpp on anti-tumor activity and tumor-infiltrating neutrophil recruitment in a mouse model of colon cancer.MethodsWe investigated the anti-cancer activity of Del-1-secreting engineered Salmonella (△ppGpp S. Typhimurium) in the mice colon cancer models.ResultsIn the present study, we identified that Del-1-secreting engineered Salmonella had more potent anti-cancer activity compared with normal S.t△ppGpp without Del-1 secretion. We postulated that Del-1 expression increased M1 macrophage recruitment to tumors by decreasing tumor-infiltrating neutrophils. This approach could enhance the anti-cancer effects of S.t△ppGpp.ConclusionsCollectively, the approach of using engineered bacteria that deliver Del-1 to block tumor-infiltrating neutrophil recruitment is a potential therapeutic approach.

Del-1 enhances therapeutic efficacy of bacterial cancer immunotherapy by blocking recruitment of tumor-infiltrating neutrophils.

BACKGROUND: Bacterial-mediated cancer immunotherapy (BCI) elicits a more robust initial immune response than conventional immunotherapy, but does not prevent tumor recurrence and metastasis. BCI is associated with recruitment of tumor-infiltrating neutrophils, which could suppress the therapeutic efficacy of this modality. Development endothelial locus 1 (Del-1), a potent inhibitor of neutrophil recruitment, antagonizes lymphocyte function-associated antigen-1 on the vascular endothelium. Here, we aimed to determine the effect of Del-1-secreting S.t△ppGpp on anti-tumor activity and tumor-infiltrating neutrophil recruitment in a mouse model of colon cancer. METHODS: We investigated the anti-cancer activity of Del-1-secreting engineered Salmonella (△ppGpp S. Typhimurium) in the mice colon cancer models. RESULTS: In the present study, we identified that Del-1-secreting engineered Salmonella had more potent anti-cancer activity compared with normal S.t△ppGpp without Del-1 secretion. We postulated that Del-1 expression increased M1 macrophage recruitment to tumors by decreasing tumor-infiltrating neutrophils. This approach could enhance the anti-cancer effects of S.t△ppGpp. CONCLUSIONS: Collectively, the approach of using engineered bacteria that deliver Del-1 to block tumor-infiltrating neutrophil recruitment is a potential therapeutic approach.

Long non-coding RNA plasmacytoma variant translocation 1 (PVT1) promotes glioblastoma multiforme progression via regulating miR-1301-3p/TMBIM6 axis.

OBJECTIVE: To explore whether plasmacytoma variant translocation 1 (PVT1) could regulate glioblastoma multiforme (GBM) progression via microRNA-1301-3p (miR-1301-3p) and transmembrane BAX inhibitor motif containing 6 (TMBIM6) axis. MATERIALS AND METHODS: Expression patterns of PVT1 and RMBIM6 in GBM patients were analyzed using GEPIA, an online gene expression analysis tool. Levels of PVT1 in GBM cells and normal cells were analyzed with quantitative real-time PCR method. Cell Counting Kit-8 (CCK-8), transwell invasion assay, and flow cytometry assay were applied to detect cell viability and apoptosis. Connections of PVT1 or TMBIM6 with miR-1301-3p were validated with bioinformatic tool and luciferase activity reporter assay. RESULTS: PVT1 was significantly expressed in GBM tissues and cells. PVT1 promotes GBM cell proliferation and invasion but inhibits apoptosis in vitro. TMBIM6 was significantly expressed in GBM tissues. The knockdown of TMBIM6 reversed the stimulation effects of PVT1 on GBM cell malignancy behaviors with miR-1301-3p as a bridge. CONCLUSIONS: Collectively, we showed PVT1 elevated TMBIM6 expression mediated by miR-1301-3p and thus to promote GBM progression.

Chinese herbal medicine for miscarriage affects decidual micro-environment and fetal growth.

INTRODUCTION: Intrauterine growth restriction complicates 5-10% of pregnancies. This study aims to test the hypothesis that Chinese herbal formula, JLFC01, affects pregnancy and fetal development by modulating the pro-inflammatory decidual micro-environment. METHODS: Human decidua from gestational age-matched elective terminations or incomplete/missed abortion was immunostained using anti-CD68 + anti-CD86 or anti-CD163 antibodies. qRT-PCR and Luminex assay measured the effects of JLFC01 on IL-1ß- or TNF-α-induced cytokine expression in first trimester decidual cells and on an established spontaneous abortion/intrauterine growth restriction (SA/IUGR)-prone mouse placentae. The effect of JLFC01 on human endometrial endothelial cell angiogenesis was evaluated by average area, length and numbers of branching points of tube formation. Food intake, litter size, fetal weight, placental weight and resorption rate were recorded in SA/IUGR-prone mouse treated with JLFC01. qRT-PCR, Western blot and immunohistochemistry assessed the expression of mouse placental IGF-I and IGF-IR. RESULTS: In spontaneous abortion, numbers of decidual macrophages expressing CD86 and CD163 are increased and decreased, respectively. JLFC01 reduces IL-1ß- or TNF-α-induced GM-CSF, M-CSF, C-C motif ligand 2 (CCL2), interferon-γ-inducible protein-10 (IP-10), CCL5 and IL-8 production in first trimester decidual cells. JLFC01 suppresses the activity of IL-1ß- or TNF-α-treated first trimester decidual cells in enhancing macrophage-inhibited angiogenesis. In SA/IUGR-prone mice, JLFC01 increases maternal food intake, litter size, fetal and placental weight, and reduces fetal resorption rate. JLFC01 induces IGF-I and IGF-IR expression and inhibits M-CSF, CCL2, CCL5, CCL11, CCL3 and G-CSF expression in the placentae. DISCUSSION: JLFC01 improves gestation by inhibiting decidual inflammation, enhancing angiogenesis and promoting fetal growth.

Phosphorylation of Nanog is essential to regulate Bmi1 and promote tumorigenesis.

Emerging evidence indicates that Nanog is intimately involved in tumorigenesis, in part, through regulation of the cancer-initiating cell (CIC) population. However, the regulation and role of Nanog in tumorigenesis are still poorly understood. In this study, human Nanog was identified to be phosphorylated by human protein kinase Cɛ at multiple residues, including T200 and T280. Our work indicated that phosphorylation at T200 and T280 modulates Nanog function through several regulatory mechanisms. Results with phosphorylation-insensitive and phosphorylation-mimetic mutant Nanog revealed that phosphorylation at T200 and T280 enhance Nanog protein stability. Moreover, phosphorylation-insensitive T200A and T280A mutant Nanog had a dominant-negative function to inhibit endogenous Nanog transcriptional activity. Inactivation of Nanog was due to impaired homodimerization, DNA binding, promoter occupancy and p300, a transcriptional co-activator, recruitment resulting in a defect in target gene-promoter activation. Ectopic expression of phosphorylation-insensitive T200A or T280A mutant Nanog reduced cell proliferation, colony formation, invasion, migration and the CIC population in head and neck squamous cell carcinoma (HNSCC) cells. The in vivo cancer-initiating ability was severely compromised in HNSCC cells expressing phosphorylation-insensitive T200A or T280A mutant Nanog; 87.5% (14/16), 12.5% (1/8), and 0% (0/8) for control, T200A, and T280A, respectively. Nanog occupied the Bmi1 promoter to directly transactivate and regulate Bmi1. Genetic ablation and rescue experiments demonstrated that Bmi1 is a critical downstream signaling node for the pleiotropic, pro-oncogenic effects of Nanog. Taken together, our study revealed, for the first time, that post-translational phosphorylation of Nanog is essential to regulate Bmi1 and promote tumorigenesis.

Targeting HPV16 E6-p300 interaction reactivates p53 and inhibits the tumorigenicity of HPV-positive head and neck squamous cell carcinoma.

The incidence of human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) has rapidly increased over the past 30 years, prompting the suggestion that an epidemic maybe on the horizon. Therefore, there is a clinical need to develop alternate therapeutic strategies to manage the growing number of HPV-positive HNSCC patients. High-risk HPV E6 inactivates p53 through two distinct mechanisms; association with E6AP to degrade p53 and association with p300 to block p300-mediated p53 acetylation and activation. In this study, we determined if targeting the E6-p300 interaction is an effective approach to reactivate p53 in HPV-positive HNSCC. Ectopic expression of the CH1 domain of p300 in HPV-positive HNSCC blocks the association between E6 and p300, increases total and acetylated p53 levels and enhances p53 transcriptional activity. Moreover, expression of p21, miR-34a and miR-200c are increased, demonstrating functional p53 reactivation. CH1 overexpression in HPV-positive HNSCC has a global anticancer effect resulting in a decrease in cell proliferation and clonogenic survival and an increase in apoptosis. The in vivo tumor-initiating ability of HPV-positive HNSCC is severely compromised with CH1 overexpression, in part through a reduction in the cancer-initiating cell population. A novel small-molecule CH1 inhibitor, CH1iB, reactivates p53 and potentiates the anticancer activity of cis-platinum in HPV-positive HNSCC cells. Our work shows that CH1-domain inhibitors represent a novel class of p53-reactivation therapeutics for managing HPV-positive HNSCC patients.

Lysosomes involved in the cellular toxicity of nano-alumina: combined effects of particle size and chemical composition.

Nowadays, manufactured nano-particles of aluminum oxide (nano-alumina) have been widely used in many fields with the rapidly developed nano-technology, but their basic toxic data are scarce. It is believed that the smaller nano-particles are able to easily cross the bio-membrane and quickly reach cellular compartments rather than micro-size particles, thus showing more toxic effects. The aim of this study was to compare the toxicity of nano- and micro- particles of alumina for detecting particle size related toxicity, and to compare the toxicity of nano-alumina and nano-carbon with the same particle size for determining chemical composition related toxicity. The present study revealed that nano-particles of alumina were much toxic than micro-alumina particles, indicating a particle size related toxicity; and were much more toxic than nano-carbon particles as well, manifesting a chemical related toxicity. The mechanism might be concerned with the involvement of the lysosomes. In conclusion, toxicity of nano-alumina is a combination of the toxic effects of its particle size and chemical composition.

Effect of resiniferatoxin on glutamatergic spontaneous excitatory synaptic transmission in substantia gelatinosa neurons of the adult rat spinal cord.

The transient receptor potential (TRP) vanilloid type 1 (TRPV1) agonist, capsaicin, enhances glutamatergic spontaneous excitatory synaptic transmission in CNS neurons. Resiniferatoxin (RTX) has a much higher affinity for TRPV1 than capsaicin, but its ability to modulate excitatory transmission is unclear. We examined the effect of RTX on excitatory transmission using the whole-cell patch-clamp technique in substantia gelatinosa (SG) neurons of adult rat spinal cord slices. Bath-applied RTX dose-dependently increased the frequency, but not the amplitude, of spontaneous excitatory postsynaptic current (sEPSC), independent of its application time. In about a half of the neurons tested, this effect was accompanied by an inward current at -70 mV that was sensitive to glutamate-receptor antagonists. Repeated application of RTX did not affect excitatory transmission. RTX was more potent than capsaicin but showed similar efficacy. RTX activity could be blocked by capsazepine or SB-366791, a TRPV1 antagonist, but not tetrodotoxin, a Na(+)-channel blocker, and could be inhibited by pretreatment with capsaicin but not the TRPA1 agonist, allyl isothiocyanate. RTX enhances the spontaneous release of L-glutamate from nerve terminals with similar efficacy as capsaicin and produces a membrane depolarization by activating TRPV1 in the SG, with fast desensitization and slow recovery from desensitization. These results indicate a mechanism by which RTX can modulate excitatory transmission in SG neurons to regulate nociceptive transmission.

MAC-CCD system: a novel lymphocyte microwell-array chip system equipped with CCD scanner to generate human monoclonal antibodies against influenza virus.

We previously developed a lymphocyte microwell-array system, which effectively detects antigen-specific B-cells by monitoring intracellular Ca(2+) mobilization at the single-cell level with a fluorescent Ca(2+) indicator, fluo-4. However, it is difficult for the system to perform time-lapse monitoring. Here, we developed a novel method, a lymphocyte microwell-array chip system equipped with a charge-coupled device (CCD) time-lapse scanner (MAC-CCD system), for monitoring intracellular Ca(2+) mobilization. The MAC-CCD system is able to monitor intracellular Ca(2+) mobilization of more than 15,000-20,000 individual live B-cells every 10 s. In addition, we adopted a correlation method in a MAC-CCD system, which enabled us to detect B-cells with a frequency of as few as 0.046%. Furthermore, we succeeded in obtaining six influenza nucleoprotein-specific human monoclonal antibodies from the peripheral blood of influenza-vaccinated volunteers. These results demonstrate that the MAC-CCD system with a correlation method could detect very rare antigen-specific B-cells.

Caspase-8 has an essential role in resveratrol-induced apoptosis of rheumatoid fibroblast-like synoviocytes.

OBJECTIVE: Resveratrol is a naturally occurring polyphenol, which possesses chemotherapeutic potential through its ability to trigger apoptosis. The objective of this study was to investigate the major determinant for the apoptotic cell death induction by resveratrol in fibroblast-like synoviocytes (FLS) derived from patients with RA. METHODS: The effect of resveratrol on apoptotic cell death was quantified in a population of subG1 in RA FLS by flow cytometry. The underlying signalling mechanism for apoptotic death was examined by analysing mitochondrial membrane potential, activation of the caspase cascade and translocation of Bid. RESULTS: We show that activation of caspase-8 is essential for triggering resveratrol-induced apoptotic signalling via the involvement of the mitochondrial pathway in RA FLS. Our findings also suggest that this enhanced apoptosis caused by resveratrol occurred in RA FLS irrespective of p53 status. Exposure to resveratrol caused extensive apoptotic cell death, along with a caspase-dependent (activation of caspase-9 and -3, poly ADPribose polymerase (PARP) cleavage and mitochondrial cytochrome c release) or caspase-independent [translocation of apoptosis-inducing factor (AIF) to the nucleus] signalling pathway. Analysis of upstream signalling events affected by resveratrol revealed that the activated caspase-8 triggered mitochondrial apoptotic events by inducing Bid cleavage without any alteration in the levels of Bax, Bcl-xL or Bcl2. The caspase-8 inhibitor or over-expression of crmA abrogated cell death induced by resveratrol and prevented processing of the downstream cascade. CONCLUSION: The results suggest that resveratrol causes activation of caspase-8, which in turn results in modulation of mitochondrial apoptotic machinery to promote apoptosis of RA FLS.

The effect of C-type natriuretic peptide on delayed rectifier potassium currents in gastric antral circular myocytes of the guinea-pig.

C-type natriuretic peptides (CNP) play an inhibitory role in smooth muscle motility of the gastrointestinal tract, but the effect of CNP on delayed rectifier potassium currents is still unclear. This study was designed to investigate the effect of CNP on delayed rectifier potassium currents and its mechanism by using conventional whole-cell patch-clamp technique in guinea-pig gastric myocytes isolated by collagenase. CNP significantly inhibited delayed rectifier potassium currents [I(K (V))] in dose-dependent manner, and CNP inhibited the peak current elicited by depolarized step pulse to 86.1+/-1.6 % (n=7, P<0.05), 78.4+/-2.6 % (n=10, P<0.01) and 67.7+/-2.3 % (n=14, P<0.01), at concentrations of 0.01 micromol/l, 0.1 micromol/l and 1 micromol/l, respectively, at +60 mV. When the cells were preincubated with 0.1 micromol/l LY83583, a guanylate cyclase inhibitor, the 1 ?micromol/l CNP-induced inhibition of I(K (V)) was significantly impaired but when the cells were preincubated with 0.1 micromol/l zaprinast, a cGMP-sensitive phosphodiesterase inhibitor, the 0.01 micromol/l CNP-induced inhibition of I(K (V)) was significantly potentiated. 8-Br-cGMP, a membrane permeable cGMP analogue mimicked inhibitory effect of CNP on I(K (V)). CNP-induced inhibition of I(K (V)) was completely blocked by KT5823, an inhibitor of cGMP-dependent protein kinase (PKG). The results suggest that CNP inhibits the delayed rectifier potassium currents via cGMP-PKG signal pathway in the gastric antral circular myocytes of the guinea-pig.

Lentivirus-mediated carboxyl-terminal modulator protein gene transfection via aerosol in lungs of K-ras null mice.

The low efficiency of conventional therapies in achieving long-term survival of lung cancer patients calls for development of novel options. Aerosol gene delivery may provide the alternative for safe and effective treatment for lung cancer. Therefore, current study was performed to elucidate the potential effects of C-terminal modulator protein (CTMP) via aerosol on lung tumorigenesis. Lentiviral vector-CTMP was delivered into K-ras null lung cancer mice through the nose-only inhalation system for 30 min. After 48 h, the potential effects of CTMP on Akt1-related signals and cell cycle regulation in the lungs were evaluated by western blot, immunohistochemistry and zymography. Lentivirus-based CTMP delivery inhibited the Akt1 activity through selective suppression of Akt1 phosphorylation at Ser473. Aerosol delivery of CTMP inhibited proteins important for Akt1 signals, cell cycle and tumor metastasis in lungs of K-ras null mice. Together, our results suggest that lentivirus-mediated aerosol delivery of CTMP may be compatible with noninvasive in vivo gene therapy. Our results emphasize the importance of noninvasive-targeted delivery of CTMP for lung cancer therapy in the future. While the studies are conducted in mice, it is envisioned that noninvasive targeting the specific genes responsible for cancer progression is an attractive strategy for effective anticancer therapeutics.

Pacemaker currents modulated by C-type natriuretic peptide in interstitial cells of Cajal from murine small intestine

Although the presence of C-type natriuretic peptide (CNP) in gastrointestinal tract has been demonstrated, the effect of CNP on interstitial cells of Cajal (ICC), pacemaker cells in gastrointestinal tract, is still unclear. This study was designed to investigate the effect of CNP on pacemaker currents of ICC and possible mechanisms. We used immunocytochemistry techniques to exhibit natriuretic peptide receptors (NPR) and recorded membrane currents by using whole-cell patch clamp technique on cultured ICC. Our experiment showed that NPR-A and NPR-B were expressed in ICC from murine small intestine. Whole cell recordings further showed that the amplitude of pacemaker currents in intestinal small networks of ICC was 322±22pA and the frequency was 16.25±0.95 Hz. CNP significantly reduced the amplitude of pacemaker currents in small networks of ICC in a dose-dependent manner, and the amplitude was inhibited by 23.95%, 61.76% and 81.67%, the amplitude values in 329±28.0pA, 311.2±14.8pA and 295±26.5pA before treatment with CNP and 237.9±27.5pA, 119.6±18.5pA and 57.2±13.5pA after treatment with 0.01μmol•L−1, 0.1μmol•L−1 and 1μmol•L−1 CNP, respectively. The frequencies of pacemaker currents were also significantly reduced from 16.25±0.95Hz of control to 13±0.9Hz, 12±0.8Hz and 3±0.2Hz by 0.01μmol•L−1, 0.1μmol•L−1 and 1μmol•L−1 CNP, respectively. CNP also inhibited the amplitude of pacemaker currents in single ICC. The inhibitory effect of CNP was mimicked by 8-Br-cGMP, a membrane permeable cGMP analogue, which suggests that CNP could inhibit pacemaker currents via NPR-B-particulate guanylate cyclase (pGC)-cGMP signal pathway (AU)

Se ha demostrado la presencia del péptido natriurético de tipo C (CNP) en tracto gastrointestinal. En el presente trabajo se investiga acerca del efecto del CNP sobre la actividad marcapaso en las células intersticiales de Cajal (ICC). Se utilizan técnicas de inmunohistoquímica para detectar receptores del péptido natriurético y se registran corrientes de membrana mediante la técnica de voltaje impuesto. Los resultados muestran la presencia de receptores NPR-A y NPR-B en ICC de intestino delgado de ratón. La amplitud de las corrientes marcapasos en pequeñas redes de ICC en intestino es de 322±22 pA y la frecuencia, de 16,25±0,95 Hz. El péptido CNP reduce la amplitud de la corriente marcapasos de ICC de modo dependiente de la concentración (en un 23,9%, 61,76% y 81,67% para concentraciones de CNP 0,01 μmol L−1, 0,1 μmol L−1 y 1 μmol L−1 respectivamente). También disminuyeron las frecuencias (desde el valor control 16,25±0,95 a 13±0,9 Hz, 12±08 Hz y 3±0,2 Hz para CNP 0,01 μmol L−1, 0,1 μmol L−1 y 1 μmol L−1 respectivamente). También se observa inhibición de la amplitud de las corrientes marcapaso por CNP en células ICC aisladas. El efecto inhibitorio del CNP es mimetizado por 8-Br-GMPc, un análogo permeable del GMPc, lo que sugiere que el CNP podría inhibir las corrientes marcapaso por interacción con NPR-B vía GMPc (AU)

Pacemaker currents modulated by C-type natriuretic peptide in interstitial cells of cajal from murine small intestine.

Although the presence of C-type natriuretic peptide (CNP) in gastrointestinal tract has been demonstrated, the effect of CNP on interstitial cells of Cajal (ICC), pacemaker cells in gastrointestinal tract, is still unclear. This study was designed to investigate the effect of CNP on pacemaker currents of ICC and possible mechanisms. We used immunocytochemistry techniques to exhibit natriuretic peptide receptors (NPR) and recorded membrane currents by using whole-cell patch clamp technique on cultured ICC. Our experiment showed that NPR-A and NPR-B were expressed in ICC from murine small intestine. Whole cell recordings further showed that the amplitude of pacemaker currents in intestinal small networks of ICC was 322+/-22pA and the frequency was 16.25+/-0.95Hz. CNP significantly reduced the amplitude of pacemaker currents in small networks of ICC in a dose-dependent manner, and the amplitude was inhibited by 23.95%, 61.76% and 81.67%, the amplitude values in 329+/-28.0pA, 311.2+/-14.8pA and 295+/-26.5pA before treatment with CNP and 237.9+/-27.5pA, 119.6+/-18.5pA and 57.2+/-13.5pA after treatment with 0.01 micromolxL(-1), 0.1 micromolxL(-1) and 1pmolxL(-1) CNP, respectively. The frequencies of pacemaker currents were also significantly reduced from 16.25+/-0.95Hz of control to 13+/-0.9Hz, 12+/-0.8Hz and 3+/-0.2Hz by 0.01micromolxL 1, 0.1micromolxL(-1) and 1 micromol x L(-1) CNP, respectively. CNP also inhibited the amplitude of pacemaker currents in single ICC. The inhibitory effect of CNP was mimicked by 8-Br-cGMP, a membrane permeable cGMP analogue, which suggests that CNP could inhibit pacemaker currents via NPR-B-particulate guanylate cyclase (pGC)-cGMP signal pathway.

Increment of calcium-activated and delayed rectifier potassium current by hyposmotic swelling in gastric antral circular myocytes of guinea pig.

AIM: To observe the effect of hyposmotic swelling on calcium-activated potassium current [IKCa] and delayed rectifier potassium current [IKV] in gastric antral circular myocytes of guinea pig. METHODS: The whole cell patch-clamp technique was used, and the myocytes were isolated by collagenase. Cells were swelled by the hyposmotic solution (200 Osmmol/kg). RESULTS: The hyposmotic solution markedly increased IKCa and IKV. The increase of IKCa was markedly inhibited by tetrathylammonium (TEA) 4 mmol/L and charybdotoxin (ChTX) 200 nmol/L. The increase of IKV was incompletely blocked by TEA and completely blocked by 4-aminopyridine (4-AP) 10 mmol/L. There was no significant difference between the amplitudes of the increase of IKCa and IKV (P < 0.05). IKCa increased (17.0 +/- 4.8) s after the cells were perfused with the hyposmotic solution, whereas IKV increased (30.7 +/- 13.7) s after the cells exposed to the hyposmotic solution. There was significant difference between the latency of IKCa and IKV (P < 0.05). CONCLUSION: Hyposmotic swelling increased both IKCa and IKV, and the increment was likely related to the cell volume regulation.

The involvement of calcium mobilization in the calcium-activated potassium currents activated by hyposmotic swelling in gastric antral circular myocytes of the guinea-pig.

In our study of the effects of hyposmotic swelling on the Ca(2+)-activated potassium currents [I(K(Ca))] and its mechanism, we employed the whole-cell patch clamp technique using the gastric antral circular myocytes of the guinea-pig. Hyposmotic swelling efficiently increased I(K(Ca)), and the extent of changes in I(K(Ca)) was sharply dependent on the osmolarity of the perfusion solutions. When the calcium-free solution (EGTA 10 microM added in calcium-free solution) was superfused, I(K(Ca)) was not increased by the hyposmotic swelling. Gadolinium (Gd(3+)) 100 nM, a blocker of the stretch-activated nonselective cation channel, blocked the activation of I(K(Ca)) induced by hyposmotic swelling, but nicardipine 5 microM (the L-type calcium channel blocker) did not. Heparin 3 mg/ml, a potent inhibitor of inositol triphosphate receptor (InsP(3)R), did not inhibit the response, and caffeine 1 mM (the agonist for calcium-induced calcium release [CICR]) imitated the effect of hyposmotic swelling. Ryanodine (15 microM), markedly inhibited the effect. These results suggest that hyposmotic swelling activates I(K(Ca)), and the activation is associated with CICR, which is triggered by extracellular calcium influx through the stretch-activated channel (SA channel).