Engineering and characterization of an enhanced fluorescent protein voltage sensor

Background

Fluorescent proteins have been used to generate a variety of biosensors to optically monitor biological phenomena in living cells. Among this class of genetically encoded biosensors, reporters for membrane potential have been a particular challenge. The use of presently known voltage sensor proteins is limited by incorrect subcellular localization and small or absent voltage responses in mammalian cells.

Results

Here we report on a fluorescent protein voltage sensor with superior targeting to the mammalian plasma membrane and high responsiveness to membrane potential signaling in excitable cells.

Conclusions and Significance

This biosensor, which we termed VSFP2.1, is likely to lead to new methods of monitoring electrically active cells with cell type specificity, non-invasively and in large numbers, simultaneously.

Long-term depression at olfactory nerve synapses

The synapses formed by the olfactory nerve (ON) convey sensory information to olfactory glomeruli, the first stage of central odor processing. Morphological and behavioral studies suggest that glomerular odor processing is plastic in neonate rodents. However, long-term synaptic plasticity, a cellular correlate of functional and structural plasticity, has not yet been demonstrated in this system. Here, we report that ON-->mitral cell (MC) synapses of 5- to 8-d-old mice express long-term depression (LTD) after brief low-frequency ON stimulation. Pharmacological techniques and imaging of presynaptic calcium signals demonstrate that ON-MC LTD is expressed presynaptically and requires the activation of metabotropic glutamate receptors but does not require fast synaptic transmission. LTD at the ON--> MC synapse is potentially relevant for the establishment, maintenance, and experience-dependent refinement of odor maps in the olfactory bulb.

Helicobacter pylori eradication induces marked increase in H+/K+-adenosine triphosphatase expression without altering parietal cell number in human gastric mucosa

BACKGROUND AND AIMS

Gastric acid secretion is downregulated by Helicobacter pylori infection and upregulated after its eradication, but the mechanisms are still unclear. We examined the effects of H pylori eradication on the number of parietal cells and on expression of molecules functioning in acid secretion in the human gastric mucosa.

METHODS

We enrolled 111 consecutive men with chronic gastritis induced by H pylori. Biopsy specimens were endoscopically obtained before and 12 weeks after successful eradication of H pylori and parietal cell numbers were counted. mRNA expression levels of H+/K+-adenosine triphosphatase (H+/K+-ATPase), anion exchanger 2, M3 muscarinic receptor, intrinsic factor, and interleukin 1beta were determined with a real time reverse transcriptase-polymerase chain reaction method. The severity of gastric atrophy was evaluated using the serum pepsinogen I/II ratio.

RESULTS

No significant difference was observed in parietal cell numbers before and after H pylori eradication. Median mRNA expression levels of H+/K+-ATPase in the gastric mucosa increased 250-fold after H pylori eradication accompanied by attenuation of interleukin 1beta. A large increase in H+/K+-ATPase expression was observed even in patients with severe atrophic gastritis. In contrast, fold increases in mRNA expression levels, including intrinsic factor, anion exchanger 2, and M3 muscarinic receptor, after eradication therapy, were limited to 1.4, 2.3, and 2.5 times, respectively.

CONCLUSIONS

In the absence of alteration of parietal cell number, gastric H+/K+-ATPase mRNA expression was markedly restored after successful H pylori eradication, suggesting a central role for the restoration of H+/K+-ATPase expression in gastric acid secretion recovery after H pylori eradication.

Activation of cerebellar parallel fibers monitored in transgenic mice expressing a fluorescent Ca2+indicator protein

Genetically encoded fluorescent Ca2+ indicator proteins (FCIPs) are promising tools to study Ca2+ signaling in large assemblies of nerve cells. Currently, there are few examples of stable transgenic mouse lines that functionally express such sensors in well-defined neuronal cell populations. Here we report the generation and characterization of transgenic mice expressing an FCIP under the 5' regulatory sequences of the Kv3.1 potassium channel promoter. In the cerebellar cortex, expression was restricted to granule cells. We first demonstrated reliable measurements of Ca2+ transients from beams of parallel fibers and compared the FCIP signals with intrinsic autofluorescence signals. We demonstrate that, in a transgenic line that exhibits a high expression level of the FCIP, autofluorescence signals are negligible and stimulation-induced fluorescence transients represent FCIP signals. Using frontal cerebellar slices we imaged antidromic activation of granule cells following electrical stimulation of parallel fibers and orthodromic activation of beams of parallel fibers following electrical stimulation of granule cells. We found that paired pulse-induced presynaptic Ca2+ transients of parallel fibers are not affected by blockade of N-methyl-D-aspartate receptors.

Histamine-2 receptor expression in gastric mucosa before and after Helicobacter pylori cure

BACKGROUND

Helicobacter pylori infection prevents the occurrence of the tolerance phenomenon of Histamine-2 (H2) receptor antagonists. Gastro-esophageal reflux disease develops in some cases with the restoration of acid secretion after H. pylori eradication therapy.

AIM

To clarify the mechanisms of H2 receptor restoration after the eradication of H. pylori on parietal cells.

METHODS

We enrolled 80 consecutive asymptomatic male patients with H. pylori infection, having chronic gastritis with or without the presence of peptic ulcers. Biopsy specimens from the greater curvatures at the mid-corpus of the stomach were obtained endoscopically from all subjects before and 12 weeks after the eradication of H. pylori. Degrees of gastric atrophy were evaluated by serum pepsinogen levels. The amounts of mRNA expression of H2 receptor were evaluated in each subject's gastric mucosa by real time reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

H2 receptor mRNA expression levels significantly correlated with serum pepsinogens I and II ratios. The expression level of H2 receptor mRNA was lower in subjects with hypergastrinemia. The median expression level of H2 receptor after H. pylori eradication was threefold greater than prior to treatment. In addition, its restoration became more pronounced in subjects with severe gastric atrophy. However, a comparatively low restoration of H2 receptor mRNA was found in subjects with hypergastrinemia.

CONCLUSIONS

H2 receptor mRNA levels decrease with the progression of gastric atrophy induced by H. pylori infection, and are restored after H. pylori eradication. Such expression levels of H2 receptor may explain a part of the tolerance phenomenon to H2 receptor antagonists.

Pericryptal fibroblast sheath in intestinal metaplasia and gastric carcinoma

BACKGROUND AND AIMS

In the progression of chronic gastritis, gastric mucosal cells deviate from the normal pathway of gastric differentiation to an intestinal phenotype which is closely related to gastric carcinoma. However, to date, it has not been elucidated whether the intestinal metaplasia is merely a change in the epithelium or whether the underlying mesenchyme also changes from gastric type to intestinal type. We have investigated the relationship between intestinal metaplasia and the pericryptal fibroblast sheath (PCFS) in the mesenchyme. In addition, we also examined PCFS in gastric carcinoma.

METHODS

We determined the existence of PCFS in the intestinal metaplastic mucosa and carcinoma of both human and Cdx2 transgenic mouse stomach. PCFS was determined using the antibody against alpha-smooth muscle actin and electron microscopic observations.

RESULTS

PCFS formed an almost complete layer around the small and large intestinal crypts while it did not exist around the normal gastric glands in both mice and humans. PCFS was seen around the glands of intestinal metaplastic mucosa in both Cdx2 transgenic mouse and human stomachs. However, PCFS was virtually absent in the intestinal-type gastric adenocarcinoma area.

CONCLUSION

We successfully demonstrated that the epithelium as well as the mesenchyme changed from the gastric type to the intestinal type in intestinal metaplasia and that PCFS disappeared in intestinal-type gastric carcinoma.

Cdx1 induced intestinal metaplasia in the transgenic mouse stomach: comparative study with Cdx2 transgenic mice

BACKGROUND AND AIMS

Gastric intestinal metaplasia, which is mainly induced by Helicobacter pylori infection, is thought to be a precancerous lesion of gastric adenocarcinoma. Intestinal metaplastic mucosa expresses intestine specific homeobox genes, Cdx1 and Cdx2, in the human gastric mucosa. We and others have reported that ectopic expression of Cdx2 in the gastric epithelium generates intestinal metaplasia in the transgenic mouse model.

METHODS

To clarify the differences in the roles of Cdx1 and Cdx2 in intestinal metaplasia, we generated transgenic mice expressing Cdx1 in the gastric mucosa and compared Cdx1 induced gastric mucosal morphological changes with Cdx2 induced intestinal metaplasia.

RESULTS

The gastric mucosa in Cdx1 transgenic mice was completely replaced by intestinal metaplastic mucosa, consisting of all four intestinal epithelial cell types: absorptive enterocytes, goblet, enteroendocrine, and Paneth cells. Paneth cells, which were not recognised in Cdx2 transgenic mice, were in the upper portion of the intestinal metaplastic mucosa. Pseudopyloric gland metaplasia, which was induced in Cdx2 transgenic mice, was not recognised in Cdx1 transgenic mice. Proliferating cell nuclear antigen (PCNA) positive cells were diffusely scattered in Cdx1 induced intestinal metaplastic mucosa while PCNA positive cells in Cdx2 induced intestinal metaplastic mucosa were in the base of the metaplastic mucosa. Intestinal metaplastic mucosa of Cdx1 transgenic mouse stomach was significantly thicker than that of wild-type or Cdx2 transgenic mouse stomach.

CONCLUSIONS

We have confirmed that Cdx1 induced gastric intestinal metaplasia but that it differed from Cdx2 induced intestinal metaplasia in differentiation, structure, and proliferation.

Calcium signaling in mitral cell dendrites of olfactory bulbs of neonatal rats and mice during olfactory nerve Stimulation and beta-adrenoceptor activation

Synapses formed by the olfactory nerve (ON) provide the source of excitatory synaptic input onto mitral cells (MC) in the olfactory bulb. These synapses, which relay odor-specific inputs, are confined to the distally tufted single primary dendrites of MCs, the first stage of central olfactory processing. beta-adrenergic modulation of electrical and chemical signaling at these synapses may be involved in early odor preference learning. To investigate this possibility, we combined electrophysiological recordings with calcium imaging in olfactory bulb slices prepared from neonatal rats and mice. Activation of ON-MC synapses induced postsynaptic potentials, which were associated with large postsynaptic calcium transients. Neither electrical nor calcium responses were affected by beta-adrenergic agonists or antagonist. Immunocytochemical analysis of MCs and their tufted dendrites revealed clear immunoreactivity with antibodies against alpha1A (Cav2.1, P/Q-type) and alpha1B (Cav2.2, N-type), but not against alpha1C (Cav1.2, L-type) or alpha1D (Cav1.3, L-type) calcium channel subunits. Moreover, nimodipine, a blocker of L-type calcium channels, had no effect on either electrical or calcium signaling at ON-MC synapses. In contrast to previous evidence, we concluded that in neonatal rats and mice (P5-P8), mitral cells do not express significant amounts of L-type calcium channels, the calcium channel type that is often targeted by beta-adrenergic modulation. The absence of beta-adrenergic modulation on either electrical or calcium signaling at ON-MC synapses of neonatal rats and mice excludes the involvement of this mechanism in early odor preference learning.

Functional topology of the mossy fibre-granule cell--Purkinje cell system revealed by imaging of intrinsic fluorescence in mouse cerebellum

We report an activity-induced green fluorescence signal observed when mouse cerebellar slices were illuminated with blue light and parallel fibre-Purkinje cell synapses were activated. The optical signal consisted of an initial increase in fluorescence that peaked within 1-2 s after the onset of stimulation, followed by a long lasting (40 s) transient decrease in fluorescence. Single or tetanic electrical stimuli applied to the molecular layer elicited 'beam-shaped' fluorescence changes along the trajectory of parallel fibres. These signals reported activation of Purkinje cells as they were depressed by antagonists of ionotropic and metabotropic glutamate receptors at Purkinje cells and correlated with Purkinje cell spiking activity. Optical responses induced by direct pharmacological activation of glutamate receptors were reduced by a calcium-free extracellular medium, consistent with the hypothesis that they reflect metabolic activity due to an increased intracellular calcium load associated with neuronal activation. We used these intrinsic fluorescence signals to address the question of whether granule cells excite Purkinje cells only locally via the ascending branches of their axons, or more widespread along the parallel fibre trajectory. White matter stimulation of the mossy fibres also elicited a beam-like fluorescence change along the trajectory of parallel fibres. Simultaneous imaging and extracellular recording demonstrated the association between the beam-like fluorescence signal and Purkinje cell spiking. This non-invasive imaging technique supports the notion that parallel fibre activity, evoked either locally or through the mossy fibre-granule cell pathway, can activate postsynaptic Purkinje cells along more than 3 mm of the parallel fibre trajectory.

L-type Ca 2+ channel and Ca 2+ -permeable nonselective cation channel as a Ca 2+ conducting pathway in myocytes isolated from the cricket lateral oviduct

The Ca2+-conducting pathway of myocytes isolated from the cricket lateral oviduct was investigated by means of the whole-cell patch clamp technique. In voltage-clamp configuration, two types of whole cell inward currents were identified. One was voltage-dependent, initially activated at -40 mV and reaching a maximum at 10 mV with the use of 140 mM Cs2+-aspartate in the patch pipette and normal saline in the bath solution. Replacement of the external Ca2+ with Ba2+ slowed the current decay. Increasing the external Ca2+ or Ba2+ concentration increased the amplitude of the inward current and the current-voltage (I-V) relationship was shifted as expected from a screening effect on negative surface charges. The inward current could be carried by Na+ in the absence of extracellular Ca2+. Current carried by Na+ (INa) was almost completely blocked by the dihydropyridine Ca2+ channel antagonist, nifedipine, suggesting that the INa is through voltage-dependent L-type Ca2+ channels. The other inward current is voltage-independent and its I-V relationship was linear between -100 mV to 0 mV with a slight inward rectification at more hyperpolarizing membrane potentials when 140 mM Cs+-aspartate and 140 mM Na+-gluconate were used in the patch pipette and in the bath solution, respectively. A similar current was observed even when the external Na+ was replaced with an equimolar amount of K+ or Cs+, or 50 mM Ca2+ or Ba2+. When the osmolarity of the bath solution was reduced by removing mannitol from the bath solution, the inward current became larger at negative potentials. The I-V relationship for the current evoked by the hypotonic solution also showed a linear relationship between -100 mV to 0 mV. Bath application of Gd3+ (10 microM) decreased the inward current activated by membrane hyperpolarization. These results clearly indicate that the majority of current activated by a membrane hyperpolarization is through a stretch-activated Ca2+-permeable nonselective cation channel (NSCC). Here, for the first time, we have identified voltage-dependent L-type Ca2+ channel and stretch-activated Ca2+-permeable NSCCs from enzymatically isolated muscle cells of the cricket using the whole-cell patch clamp recording technique.

An efficient linkage analysis strategy for autosomal dominant polycystic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited renal disorders in the world. Mutations in PKD1 are responsible for 80-95% of all autosomal dominant polycystic kidney disease (ADPKD). Although the need for linkage analysis of ADPKD is decreasing after the success of mutation detection at whole exons of PKD1, linkage analysis still has some advantages in detecting non-PKD1 families, thereby avoiding hopeless mutation analysis.

METHODS

We evaluated ten microsatellite markers beside or inside PKD1 on chromosome 16p. Allele frequency and heterozygosity of each marker were calculated based on the 100 genotypes obtained from 50 normal Japanese. Automated microsatellite genotyping using ABI Prism 377 and GeneScan software was applied. Markers were mapped using radiation hybrid mapping. Finally, this strategy was applied in the linkage analysis of 6 independent Japanese ADPKD families.

RESULTS

D16S3024, D16S3082, D16S3027 and D16S423 showed high heterozygosity (> 0.80) in a normal Japanese population and sufficient proximity to the PKD1 gene for linkage analysis. We could successfully analyze 144 genotypes within 7 hours. This strategy produced theoretically near-maximum LOD scores in 4 independent Japanese families inheriting ADPKD.

CONCLUSIONS

Automated genotyping using microsatellite markers, D16S3024, D16S3082, D16S3027 and D16S423 are very useful in the linkage analysis of ADPKD.

Change in apoptosis in the gastric surface epithelium and glands after eradication of Helicobacter pylori

BACKGROUND

Change in apoptosis in gastric glands after eradication of Helicobacter pylori has never been reported.

AIMS

The purpose of this paper is to investigate the change in apoptosis in gastric glands after eradication of Heliobacter pylori.

PATIENTS AND METHODS

We studied 23 Heliobacter pylori-positive patients with duodenal and gastric ulcers, who were monitored for 6-12 months after eradication, and eight controls. Biopsies were taken from the antrum and body. Apoptosis was evaluated immunohistochemically using anti-single stranded DNA antibody. Apoptotic index was calculated by counting immunostained cells in surface epithelial and glandular cells.

RESULTS

In the surface epithelium, Apoptotic indexes were significantly higher in patients than in controls. In the upper portion of fundic glands, apoptotic indexes were significantly higher in patients with gastric ulcers (14.2% (9.3, 17.8)) (median (1st quartile, 3rd quartile)) than in controls (8.0% (2.0, 9.0), p < 0.01) and decreased significantly after eradication (3.4% (2.0, 5.3)), p < 0.01). In pyloric glands, apoptotic indexes were no different between patients and controls. In the lower portion of fundic glands, apoptotic indexes were very low, both in patients and in controls.

CONCLUSIONS

Our results showed that apoptosis, not only of surface epithelial cells but also of glandular cells in the upper portion of fundic glands, increased in Heliobacter pylori-positive patients with gastric ulcers and decreased to normal levels after eradication of Heliobacter pylori.

Association between nasal allergy and a coding variant of the Fc epsilon RI beta gene Glu237Gly in a Japanese population

The gene for the beta-chain of the high-affinity receptor for IgE (Fc epsilon RI beta) has been proposed as a candidate gene for atopy. A coding variant Glu237Gly has been studied in various populations with asthma and atopy, and the results were controversial for association of the variant with atopy/asthma. Because nasal allergy is a more common atopic disease and shows less remission than asthma, we analyzed whether the Glu237Gly variant is correlated with nasal allergy. The study enrolled 233 patients with nasal allergy and 100 control subjects. Further, three subgroups were selected: patients with perennial nasal allergy (n=149), Japanese cedar pollinosis (n=189), and allergy to multiple allergens (n=45). The allele frequency of Gly237 in the controls and patients was 0.14 and 0.20, and the frequency of Gly237-positive subjects was 0.23 and 0.356, respectively. There was a significant association between Gly237-positivity and nasal allergy, perennial nasal allergy, Japanese cedar pollinosis, and allergy to multiple allergens. Among all 333 subjects we observed a significant relationship between Gly237 and elevated levels of serum total IgE (>250 IU/ml) and very high IgE (>1000 IU/ml). Among patients positive for a specific IgE, Gly237 was significantly associated with high IgE for house dust, mite, and Japanese cedar pollen. These results suggest that the Glu237Gly variant of the Fc epsilon RI beta gene is involved in the development of nasal allergy through the process for the production of both specific and nonspecific IgE antibodies.

Analysis of the p53 gene in parotid gland cancers: a relatively high frequency of mutations in low-grade mucoepidermoid carcinomas

Mutations and overexpression of the p53 gene and protein were analyzed in 40 cases with various types of parotid gland cancers. Mutations were found in 12 cases (30%), and low-grade mucoepidermoid carcinomas (43%) and highly malignant carcinomas including adenocarcinoma, salivary duct carcinoma, and undifferentiated carcinoma (56%) showed a relatively high frequency of mutations. Overexpression of the protein was observed in 11 cases (28%) and 4 of the 11 cases also had p53 mutations. These results suggest that mutations of the p53 gene have significance in certain types of parotid cancers irrespective of the aggressiveness of a tumor type.

p53 expression in the gastric mucosa before and after eradication of Helicobacter pylori

BACKGROUND

Accumulation of p53 has been recognized in the gastric mucosa infected with Helicobacter pylori. We investigated the prevalence of p53-positive cells in the gastric mucosa before and one month after eradication of H. pylori and the relationship between p53 positivity and inflammation and cell proliferation.

METHODS

The subjects included 24 H. pylori-positive patients. They achieved eradication one month after anti-H. pylori therapy. Biopsies were taken from the greater curvatures of the antrum and middle body. H. pylori status was assessed using culture and tissue section (Giemsa stain). Serial sections were used for examination of gastritis (hematoxylin and eosin stain) and for immunostaining of p53, Ki-67 and myeloperoxidase (MPO). p53 index and Ki-67 labeling index (LI) were calculated by counting p53-positive and Ki-67-positive cells in the entire gastric pits longitudinally sectioned and expressing them as a percentage of the total cells in a gastric pit. In the neck regions with and without p53-positive cells, polymorphonuclear leukocytes (PMNs) were counted in the corresponding area (/50 x 50 microm2) of the sections stained both with p53 and MPO.

RESULTS

p53-positive cells decreased significantly after eradication of H. pylori. Before eradication, the number of PMNs was significantly higher in the neck regions with p53-positive cells than in those without.

CONCLUSIONS

In the gastric mucosa infected with H. pylori, p53-positive cells were found in the neck region infiltrated with PMNs. p53 expression decreased significantly one month after eradication of H. pylori.

A missense mutation, A156T, in the alpha-galactosidase A gene causes typical Fabry disease

AIMS

Fabry disease is a rare but important cause of end-stage renal disease. Recent molecular investigations on alpha-galactosidase A (alpha-Gal A) have proven the existence of atypical variants in Fabry disease, making genotype assessment of each phenotype indispensable. We report here a missense mutation, which causes a typical form of Fabry disease.

MATERIAL AND METHODS

The proband, a 45-year-old man, presented with acroparesthesias, hypohidrosis, left ventricular hypertrophy, renal involvement (proteinuria and renal insufficiency) with typical microscopic findings and extremely reduced plasma alpha-Gal A activity, indicating the typical form of the disease. Total RNA was isolated from the proband's cultured fibroblasts, reverse-transcribed and amplified for direct sequencing of alpha-Gal A. Genomic DNA of the proband's mother and 75 controls (50 males and 25 females) living in the same area as the proband was also examined.

RESULTS

Sequencing of the cDNA revealed a substitution of G to A in codon 156 of alpha-Gal A, resulting in a single amino acid change from alanine to threonine (A156T). The mutation can be detected with PCR-RFLP with SfaNI digestion. This technique revealed that the mother was a heterozygote of A156T with no A156T noted in the 100 haplotypes of the controls. With a vigorous search of the same mutation in the literature, no previous description was found other than one case listed in several review papers as a classic phenotype without any other information. In our study, we examined A156T in a pedigree and demonstrated that the mutation was not a polymorphic variant in our area.

CONCLUSION

Taken together, the present results strongly suggest that the missense mutation, A156T, in the alpha-Gal A gene causes typical Fabry disease.

Effect of ACE gene polymorphism on age at renal death in polycystic kidney disease in Japan

Polycystic kidney disease (PKD) is one of the most common genetic disorders and a major cause of renal death or end-stage renal disease (ESRD) requiring regular hemodialysis. The responsible genes recently have been cloned; however, genetic factors influencing the rate of progression to ESRD in patients with PKD have yet to be defined. Several studies have shown increased activity of the renin-angiotensin system (RAS) in patients with PKD. In addition, genetic polymorphisms of the RAS have been associated with the development of cardiovascular diseases. Therefore, these polymorphisms are good candidates for disease-modifying genetic factors or markers in PKD. In two previous reports of white subjects with a cumulative survival analysis, it was suggested that patients with P:KD1 homozygous for the deletion allele of the angiotensin-converting enzyme (ACE) gene are at increased risk for early renal death. To confirm this hypothesis in Japanese subjects, 103 individuals with PKD were genotyped for several components of the RAS, ie, ACE insertion/deletion (I/D) polymorphism, angiotensinogen (AGT) M235T, and angiotensin II type 1 receptor (AT1) A1166C. Seventy-six of the 103 patients (73.8%) reached ESRD at an average age of 52.1 +/- 11.3 years. The frequencies of each genotype of the genes were similar to those expected from Hardy-Weinberg equilibrium. There was a tendency to an excess of patients homozygous for the D allele in patients with ESRD (DD in patients with ESRD, 11.8%; DD in patients without ESRD, 3.7%; chi-square, 1.505; P: = 0.22). Cumulative renal survival was significantly less in those with the DD genotype compared with ID/II genotypes. Estimated mean renal survival was 46.4 years (95% confidence interval, 39.5 to 53.3) in subjects with the DD genotype and 57.2 years (95% confidence interval, 54.2 to 60.2) in ID/II genotypes (chi-square, 7.76; P: = 0.0053). There was no association between age at onset of ESRD and either M235T or A1166C polymorphism. These findings suggest that Japanese patients with PKD homozygous for the D allele of the ACE gene are at increased risk for developing ESRD at an early age.

Suppression by flavonoids of cyclooxygenase-2 promoter-dependent transcriptional activity in colon cancer cells: structure-activity relationship

Cyclooxygenase-2 (COX-2) plays an important role in carcinogenesis. Investigation of the suppressive action of twelve flavonoids of different chemical classes on the transcriptional activity of the COX-2 gene in human colon cancer DLD-1 cells using a reporter gene assay have revealed quercetin to be the most potent suppressor of COX-2 transcription (IC50 = 10.5 microM), while catechin and epicatechin showed weak activity (IC50 = 415.3 microM). Flavonoids have three heterocyclic rings as a common structure. A structure-activity study indicated that the number of hydroxyl groups on the B ring and an oxo group at the 4-position of the C ring are important in the suppression of COX-2 transcriptional activity. A low electron density of the oxygen atom in the hydroxyl group of the A ring was also important. Further examination of the role of the hydroxyl group in the A ring showed that bromination of resacetophenone to give 3,5-dibromo-2,4-dihydroxyacetophenone resulted in a 6.8-fold increase in potency for suppressing COX-2 promoter activity. These results provide a basis for the design of improved suppressors of COX-2 transcriptional activity.

Suppression of cyclooxygenase-2 promoter-dependent transcriptional activity in colon cancer cells by chemopreventive agents with a resorcin-type structure

Cyclooxygenase-2 (COX-2) is abundantly expressed in colon cancer cells. It has been reported that inhibition of COX-2 enzyme activity is shown to prevent colon carcinogenesis. Thus, suppression of COX-2 expression may also be an effective chemopreventive strategy. In the present study, we constructed a beta-galactosidase reporter gene system in human colon cancer DLD-1 cells, and measured COX-2 promoter-dependent transcriptional activity in the cells. Interferon gamma suppressed this COX-2 promoter activity, while 12-O-tetradecanoylphorbol-13-acetate and transforming growth factor alpha (TGFalpha) exerted enhancing effects. We then tested the influence of 14 candidate cancer chemopreventive compounds on COX-2 promoter activity. Chemopreventive agents such as quercetin, kaempferol, genistein, resveratrol and resorcinol, all having a common resorcin moiety, were found to effectively suppress the COX-2 promoter activity with and without TGFalpha-stimulation in DLD-1 cells. Since all these compounds have a resorcin moiety as a common structure, a resorcin-type structure may play an active role in the inhibition of COX-2 expression in colon cancer cells.

Review article: transcriptional events controlling the terminal differentiation of intestinal endocrine cells

Secretin-producing enteroendocrine cells arise from a multipotential endocrine progenitor in the crypts of the small intestine. As these cells migrate up the crypt-villus axis, they produce secretin and stop dividing as they terminally differentiate and die. Transcription of the secretin gene is controlled by a complex enhancer binding to multiple transcription factors. The basic helix-loop-helix protein, BETA2, binds to an E box sequence and associates with the p300 coactivator to activate transcription of the secretin gene. Basic helix-loop-helix proteins appear to play a pivotal role in the control of cellular differentiation. BETA2 induces cell cycle arrest and apoptosis in addition to activating secretin gene expression. Thus BETA2 may function as a master regulatory gene to coordinate terminal differentiation of secretin cells.

Pretreatment antimicrobial susceptibilities of paired gastric Helicobacter pylori isolates: antrum versus corpus

BACKGROUND

Antimicrobial susceptibility testing of Helicobacter pylori isolates is the most useful tool for guiding specific therapy, especially when primary resistance is suspected. However, the most informative gastric biopsy site for detection of resistant H. pylori isolates is uncertain. We sought to determine whether susceptibilities to commonly used antimicrobials (amoxicillin, clarithromycin, minocycline, and metronidazole) were related to biopsy site.

METHODS

H. pylori isolates were obtained from patients who had duodenal ulcer and had not received any therapy directed against H. pylori. Agar-dilution minimum inhibitory concentrations of each antimicrobial were compared between paired H. pylori isolates from the antrum and the proximal corpus.

RESULTS

Differences in minimum inhibitory concentrations exceeding twofold were observed within the pairs of H. pylori isolates in 5 of the 40 patients tested. In three patients with clarithromycin-resistant isolates and two with metronidazole-resistant isolates, both antral and corporeal specimens revealed resistance. However, no patient had pairs of isolates categorized as resistant at one site and sensitive at the other.

CONCLUSIONS

While we found that an individual may have a mixed H. pylori infection with respect to differing antimicrobial susceptibility in different parts of the stomach, a single biopsy specimen from either the antrum or the corpus should provide reliable detection of H. pylori isolates with primary resistance.

Polaprezinc, a mucosal protective agent, in combination with lansoprazole, amoxycillin and clarithromycin increases the cure rate of Helicobacter pylori infection

AIM

To evaluate the efficacy of polaprezinc, a mucosal protective agent, in combination with a 7-day triple therapy containing lansoprazole, amoxycillin and clarithromycin, as a treatment for Helicobacter pylori.

METHODS

Sixty-six consecutive patients suffering from dyspeptic symptoms with H. pylori infection were randomly allocated to one of two regimens: one group (LAC; n = 31) received lansoprazole 30 mg b.d., amoxycillin 500 mg b.d. and clarithromycin 400 mg b.d. for 7 days. The other group (LACP; n = 35) received the LAC regimen plus polaprezinc 150 mg b.d. for 7 days. H. pylori status was evaluated by rapid urease test, histology and culture at entry and 4 weeks after treatment.

RESULTS

Five patients did not complete the treatment: no follow-up endoscopy was performed on two patients in the LAC group; one patient in the LAC group and two in the LACP group had their treatment stopped due to severe diarrhoea. By per protocol analysis, H. pylori eradication was achieved in 24 of the 28 evaluable patients (86%; 95% CI: 72-100%) after LAC therapy, and in 33 of the 33 evaluable patients (100%) after LACP therapy (P < 0.05). On intention-to-treat analysis, the rates of eradication were 24 of 31 patients (77%; 95% CI: 62-93%) in the LAC group, and 33 of 35 patients (94%; 95% CI: 86-100%) in the LACP group (P < 0.05).

CONCLUSION

A 7-day triple therapy with lansoprazole, amoxycillin and clarithromycin is effective in H. pylori eradication, but this regimen is significantly improved by the addition of polaprezinc.