Role of protein kinase C in alpha(1)-adrenergic regulation of a(Na)(i) in guinea pig ventricular myocytes

We investigated the role of protein kinase C (PKC) in alpha(1)-adrenergic regulation of intracellular Na(+) activity (a(Na)(i)) in single guinea pig ventricular myocytes. a(Na)(i) and membrane potentials were measured with the Na(+)-sensitive indicator sodium-binding benzofuran isophthalate and conventional microelectrodes, respectively, at room temperature (24-26 degrees C) while myocytes were stimulated at a rate of 0.25-0.3 Hz. The PKC activator 4beta-phorbol 12-myristate 13-acetate (PMA) decreased a(Na)(i) in a concentration-dependent manner. PMA (100 nM) produced a maximal decrease in a(Na)(i) of 1.5 mM from 6.5 +/- 0.4 to 5.0 +/- 0.4 mM (means +/- SE, n = 12, P < 0.01). The PMA concentration required for a half-maximal decrease in a(Na)(i) was 0.46 +/- 0.13 nM (n = 3, P < 0.01). An inactive phorbol, 4alpha-phorbol 12-myristate 13-acetate, did not decrease a(Na)(i). The decrease caused by PMA could be blocked by the PKC inhibitors staurosporine and bisindolylmaleimide I (GF-109203X). Stimulation of the alpha(1)-adrenoceptor with 50 microM phenylephrine decreased a(Na)(i) from 6.1 +/- 0.3 to 4.6 +/- 0.3 mM (n = 11, P < 0.01). The decrease in a(Na)(i) produced by phenylephrine was blocked by pretreatment with staurosporine, GF-109203X, or PMA. The decrease in a(Na)(i) produced by PMA was not prevented by pretreatment with tetrodotoxin but was blocked by pretreatment with strophanthidin or high extracellular K(+) concentration. The results suggest that alpha(1)-adrenergic receptor activation results in a decrease in a(Na)(i) via PKC-induced stimulation of the Na(+)-K(+) pump in cardiac myocytes.

Differential changes in the expression of cyclic nucleotide phosphodiesterase isoforms in rat brains by chronic treatment with electroconvulsive shock

Electroconvulsive shock (ECS) has been suggested to affect cAMP signaling pathways to exert therapeutic effects. ECS was recently reported to increase the expression of PDE4 isoforms in rat brain, however, these studies were limited to PDE4 family in the cerebral cortex and hippocampus. Thus, for comprehensive understanding of how ECS regulates PDE activity, the present study was performed to determine whether chronic ECS treatment induces differential changes in the expression of all the PDE isoforms in rat brains. We analyzed the mRNA expression of PDE isoforms in the rat hippocampus and striatum using reverse transcription polymerase chain reaction. We found chronic ECS treatment induced differential changes in the expression of PDE isoform 1, 2, 3, 4, 5 and 7 at the rat hippocampus and striatum. In the hippocampus, the expression of PDE1A/B (694%), PDE4A (158%), PDE4B (323 %), and PDE4D (181%) isoforms was increased from the controls, but the expression of PDE2 (62.8%) and PDE7 (37.8%) decreased by chronic ECS treatment. In the striatum, the expression of PDE1A/B (179%), PDE4A (223%), PDE4B (171%), and PDE4D (327%) was increased by chronic ECS treatment with the concomitant decrease in the expression of PDE2 (78.4%) and PDE3A (67.1%). In conclusion, chronic ECS treatment induces differential changes in the expression of most PDE isoforms including PDE1, PDE2, PDE3, PDE4, PDE5, and PDE7 in the rat hippocampus and striatum in an isoform- and brain region-specific manner. Such differential change is suggested to play an important role in regulation of the activity of PDE and cAMP system by ECS.

The role of polyamines in gastric mucus synthesis inhibited by cigarette smoke or its extract

BACKGROUND

Cigarette smoking was shown to delay gastric ulcer healing and reduce synthesis of mucus, which is important for gastric ulcer protection and healing. Polyamines are important in these processes.

AIMS

To study the effects of cigarette smoking on the synthesis of mucus and to investigate if such an effect is acting by interference with the polyamine pathway.

METHODS

Gastric mucosal ornithine decarboxylase activity, mucous secreting layer thickness, and ulcer size were determined after different concentrations of cigarette smoke exposure (0, 2, or 4%) in intact animals and animals with ulcers. Synthesis of mucus and ornithine decarboxylase activity and mRNA expression were also assessed in cigarette smoke extract treated MKN-28 cells.

RESULTS

Exposure to cigarette smoke significantly reduced the thickness of the mucous secreting layer and gastric mucosal ornithine decarboxylase activity in animals with or without ulcers. Spermidine not only reversed inhibition of mucus synthesis in both intact and ulcer bearing animals but also reversed the delay in ulcer healing. Cigarette smoke extract significantly reduced mucus synthesis and ornithine decarboxylase activity but not its mRNA expression in MKN-28 cells. The reduction in mucus synthesis was restored by spermidine.

CONCLUSIONS

Cigarette smoke and its extract repress mucus synthesis in vivo and in vitro, respectively. Reduction of ornithine decarboxylase activity in gastric mucosa is closely associated with this effect.

Intragastric administration of heparin enhances gastric ulcer healing through a nitric oxide-dependent mechanism in rats

Our preliminary finding indicated that intravenous (i.v.) injection of heparin increased gastric ulcer healing in rats. However, the anticoagulant action of i.v. heparin could produce complications in ulcer patients if the drug was used as an anti-ulcer agent. The present study aimed to investigate whether intragastric (i.g.) administration of heparin, known to have no anticoagulant activity, would have the similar ulcer healing effect and the relationship of this effect, if any, with nitric oxide (NO), a substance suggested to be important for ulcer healing. Heparin (100, 500, 1000 U/kg, i.g. ) administered once daily for 4 days accelerated the healing of gastric ulcer induced by acetic acid in Sprague-Dawley rats, which was accompanied by an increase in mucosal proliferation and regeneration at the ulcer margin, microvessel number both at the ulcer margin and base, and the thickness of mucus layer. Both activity and content, but not the mRNA of constitutive nitric oxide synthase (cNOS) in the gastric mucosa were enhanced. L-N(G)-nitroarginine methyl ester (L-NAME), an inhibitor of NOS activity blocked the cNOS activity activated by heparin and reversed the beneficial effects of heparin on ulcer healing. The bleeding time was not altered by i.g. heparin. These findings demonstrate that i.g. heparin promotes the healing processes of gastric ulcer. Such effect is suggested to act through the stimulation of mucosal cNOS activity. In addition, i.g. heparin is better than i.v. heparin without the potential anticoagulation effect.

High prevalence of Helicobacter pylori infection with dual resistance to metronidazole and clarithromycin in Hong Kong

BACKGROUND

Metronidazole resistance is a common problem in most Asian countries, and clarithromycin has been widely used in Hong Kong.

AIM

To determine the prevalence of Helicobacter pylori strains resistant to metronidazole and clarithromycin in Hong Kong and to assess the effect on eradication rates. Also to determine the genetic mutation in relation to phenotypic divergence in clarithromycin-resistant strains.

METHODS

H. pylori were cultured from gastric biopsies obtained from 87 patients during upper endoscopy. Minimal inhibitory concentrations of metronidazole and clarithromycin were determined by Etest and agar dilution methods. Mutations in clarithromycin-resistant strains were identified by polymerase chain reaction and restriction analysis. Random amplified polymorphic DNA fingerprinting was performed on clarithromycin-resistant and susceptible isolates.

RESULTS

The prevalences of H. pylori strains resistant to metronidazole and clarithromycin were 49.4% and 10.8%, respectively, in Hong Kong. Dual resistance to metronidazole and clarithromycin were found in 7. 2% of patients. The agreement between E-test and agar dilution methods was determined by error-rate bound analysis as 95.4% for metronidazole and 100% for clarithromycin. Dual resistant strains reduced the eradication rate to 66.7%. Among clarithromycin-resistant strains tested, all were due to A2144G point mutation in 23S rRNA gene. Random amplified polymorphic DNA fingerprinting suggested various phenotypically mixed populations.

CONCLUSIONS

The prevalence of metronidazole-resistant H. pylori strains remained static whilst the prevalence of clarithromycin-resistant strains was not rare in Hong Kong. An alarming 7.2% of patients were resistant to both the antimicrobials, which had a definite impact on treatment success. All cases of resistance to clarithromycin were due to A2144G mutation in 23S rRNA of H. pylori.

Regulation of interleukin 6 production in a human gastric epithelial cell line MKN-28

Interleukin (IL-) 6 is closely related to gastrointestinal diseases. The question of whether gastric epithelial cell contributes to IL-6 production remains undefined. We aim to evaluate the regulatory pathway of IL-6 expression in gastric epithelial cells, by using different inflammatory cytokines, endotoxin, or protein kinase modulators. IL-6 was measured by ELISA. Phorbol-12-myristate-13-acetate (PMA), calcium ionophore A23187, TNF-alpha, IL-1beta, oncostatin M (OSM) but not lipopolysaccharide stimulated IL-6 production from gastric epithelial cell line MKN-28. Blocking protein tyrosine kinase (PTK) activation by herbimycin A or genistein, or blocking NF-kappaB activation by pyrrolidinedithiocarbamate, reduced the IL-6 expression induced by TNF-alpha, IL-1beta and OSM. Dexamethasone mimicked this effect. Protein kinase (PK) C inhibitor only reduced the PMA and OSM induced IL-6 production. Both inhibitors and activators for PKA and G-protein as well as IL-10 had no effects on IL-6 expression. These results indicate that inflammatory cytokines are crucial for IL-6 regulation in gastric epithelial cells. The IL-6 signal pathway is mediated through PTK, NF-kappaB, and also involve PKC, intracellular calcium and sensitive to dexamethasone, but is not related to PKA, G-protein and IL-10.

Study of the gastrointestinal protective effects of polysaccharides from Angelica sinensis in rats

We studied the protective effects of polysaccharides isolated from the root of Angelica sinensis (Oliv.) (Danggui) on gastrointestinal damage induced by ethanol or indomethacin in rats. Oral administration of ethanol provoked a marked hemorrhagic damage in the glandular mucosa, which was accompanied with a significant increase of myeloperoxidase (MPO) activity, a marker enzyme for inflammation and neutrophil infiltration. An extract from Angelica, which mainly consisted of polysaccharides (95%) (AP), dose-dependently prevented gastric mucosal damage. This ulcer protective effect could last at least 12 h after administration. Prostaglandin E2 produced a similar anti-lesion effect. AP and prostaglandin E2 also reduced mucosal MPO activity. Indomethacin-induced gastrointestinal damage, another neutrophil-dependent lesion model in the gastrointestinal tract, was also prevented by AP pretreatment. The present findings suggest that polysaccharides from Angelica possess an anti-inflammatory action, perhaps through the inhibitory action on neutrophil infiltration in the gastrointestinal mucosa. AP could potentially be useful to prevent any neutrophil-dependent mucosal injury in the gastrointestinal tract.

Exposure to cigarette smoke increases apoptosis in the rat gastric mucosa through a reactive oxygen species-mediated and p53-independent pathway

Cigarette smoking is a major risk factor for gastric cancer and peptic ulcer. The aim of our study was to investigate the relationship between exposure to cigarette smoke and apoptosis in the rat gastric mucosa and the mechanism involved. Rats were exposed to different concentrations of cigarette smoke (0, 2, and 4%) once daily for a different number of 1 h periods (1, 3, 6, and 9 d). Apoptosis was identified by the terminal deoxy-transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) method and caspase-3 activity. The mucosal xanthine oxidase (XO) activity and p53 level were also measured. The results showed that exposure to cigarette smoke produced a time- and concentration-dependent increase in apoptosis in the rat gastric mucosa that was accompanied by an increase in XO activity. The increased apoptosis and XO activity could be detected after even a single exposure. In contrast, the level of p53 was elevated only in the later stage of cigarette smoke exposure. The apoptotic effect could be blocked by pretreatment with an XO inhibitor (allopurinol, 20 mg/kg intraperitoneally) or a hydroxyl free radical scavenger (DMSO, 0.2%, 1 ml/kg intravenously). However, neither of these treatments had any effect on the p53 level of the mucosa. In summary, we conclude that exposure to cigarette smoke can increase apoptosis in the rat gastric mucosa through a reactive oxygen species- (ROS) mediated and a p53-independent pathway.

Role of capsaicin sensory nerves and EGF in the healing of gastric ulcer in rats

Accumulating evidence indicates that capsaicin sensitive afferent fibers play a pivotal role not only in gastroprotection but also in ulcer healing. Denervation of capsaicin sensitive afferent fibers exerts an adverse action on these effects. However, whether such an action is mediated through a depression on epidermal growth factor (EGF) is undefined. In this study, the effects of denervation of sensory neurons with capsaicin (100 mg/kg, s.c.) on acetic acid-induced chronic gastric ulcers and their relationship with the EGF expression in salivary glands, serum and gastric mucosa were investigated. Capsaicin significantly increased ulcer size, decreased gastric mucosal cell proliferation at the ulcer margin, angiogenesis in the granulation tissue and also gastric mucus content. Ulcer induction by itself dramatically elevated EGF levels in salivary glands and serum on day 1 and 4, and also in the gastric mucosa on day 4. However, capsaicin completely abolished these effects. It is concluded that stimulation of EGF expression in salivary glands and serum may be one of the mechanisms by which capsaicin sensitive nerves contribute to the gastroprotective and ulcer healing actions in the stomach.

p53 codon 72 polymorphism and risk of cervical carcinoma in Korean women

A common polymorphism of the wild type p53 is known at codon 72 of exon 4, with 2 alleles encoding either arginine (CGC, p53Arg) or proline (CCC, p53Pro). A recent study suggested that this polymorphism affects the susceptibility of p53 protein to human papillomavirus E6 oncoprotein mediated degradation and that individuals homozygous for p53Arg are seven times more susceptible to HPV-associated carcinogenesis of the cervix than heterozygotes. To examine whether the p53Arg genotype could be a risk factor for HPV-associated cervical carcinomas in the Korean population, we analyzed the p53 codon 72 polymorphism status of HPV-positive invasive cervical carcinomas from 52 Korean women and 103 healthy control samples. The proportion of individuals homozygous for p53Arg, homozygous for p53Pro, and heterozygous for the two alleles were 40%, 19%, and 41% in normal healthy controls; 42%, 17%, and 40% in women with HPV-positive invasive cervical carcinoma. There were no significant differences in the distribution of p53 genotypes between controls and cervical carcinomas. This finding indicates that the p53Arg genotype is not associated with an increased susceptibility to cervical carcinoma in Korean women.

Reduction of EGF is associated with the delay of ulcer healing by cigarette smoking

Cigarette smoking is associated with peptic ulcer diseases. Smokers have lower levels of salivary epidermal growth factor (EGF) than nonsmokers. We investigated whether reduction of EGF is involved in the delay of gastric ulcer healing by cigarette smoking. Rats with acetic acid-induced ulcers were exposed to cigarette smoke (0, 2, or 4% vol/vol) 1 day after ulcer induction. EGF level was elevated 1 day after ulcer induction in salivary glands and serum, and 4 days after ulcer induction in the gastric mucosa. However, cigarette smoke depressed these beneficial effects and EGF mRNA expression in salivary glands and gastric mucosa. Cigarette smoke delayed gastric ulcer healing and reduced cell proliferation, angiogenesis, and mucus synthesis. Exogenous EGF (10 and 20 microg/kg i.v.) before smoke exposure reversed the adverse effects of cigarette smoke, whereas vascular endothelial growth factor level and nitric oxide synthase activity were unaffected. It is concluded that the detrimental effect of cigarette smoke on ulcer healing is a consequence of reduction of angiogenesis, cell proliferation, and mucus secretion through the depressive action on EGF biosynthesis and its mRNA expression in salivary glands and gastric mucosa.

Increased expression of Galphaq protein in the heart of streptozotocin-induced diabetic rats

Heart disease is one of the major cause of death in diabetic patients, but the pathogenesis of diabetic cardio-myopathy remains unclear. In this experiment, to assess the significance of G protein signaling pathways in the pathogenesis of diabetic cardiomyopathy, we analyzed the expression of G proteins and the activities of second messenger dependent protein kinases: cAMP-dependent protein kinase (PKA), DAG-mediated protein kinase C (PKC), and calmodulin dependent protein kinase II (CaM kinase II) in the streptozotocin induced diabetic rat heart. The expression of Galphaq was increased by slightly over 10% (P<0.05) in diabetic rat heart, while Galphas, Galphai, and Gbeta remained unchanged. The PKA activity in the heart did not change significantly but increased by 27% (P<0.01) in the liver. Insulin treatment did not restore the increased activity in the liver. Total PKC activity in the heart was increased by 56% (P<0.01), and insulin treatment did not restore such increase. The CaM kinase II activity in the heart remained at the same level but was slightly increased in the liver (14% increase, P<0.05). These findings of increased expression of Galphaq in the streptozotocin-diabetic rat heart that are reflected by the increased level of PKC activity and insensitivity to insulin demonstrate that alteration of Galphaq may underlie, at least partly, the cardiac dysfunction that is associated with diabetes.

Role of hydration water in protein unfolding

In this paper, following our work on the two-state outer neighbor mixed bonding model of water, it is proposed that polar groups promote the formation of the low density ice Ih-type bonding in their neighborhood, whereas nonpolar groups tend to promote the higher density ice II-type structure. In a protein, because of the large numbers of exposed polar and nonpolar groups, large changes in the neighboring water structure can occur. These changes, of course, depend on whether the protein is in its native or its unfolded state and will be shown here to have a direct impact on the thermodynamics of protein unfolding at both high and low temperatures. For example, it is known that the polar hydration entropies become rapidly more negative with increasing temperature. This very unusual behavior can be directly related to the promotion in the outer bulk liquid of the more stable Ih-type bonding at the expense of II-type bonding by polar groups of the protein. In contrast, nonpolar groups have an opposite effect on the thermodynamics. It is the delicate balance created by these outer hydration contributions, mixed with ordinary thermodynamic contributions from the inner hydration shell and those from hydrogen-bond and van der Waals forces within the protein molecule itself that is responsible for both heat and cold denaturation of proteins.

The ulcer healing effect of protamine sulphate in rat stomach

BACKGROUND

Protamine sulphate has been reported to stimulate nitric oxide production from blood vessels, which is a pivotal factor for gastric ulcer healing. Our preliminary study also showed that protamine sulphate potentiated the ulcer healing effect of heparin.

METHODS

Male SD rats with acetic acid-induced gastric ulcers were given protamine sulphate (40-80 mg/kg, s.c.) twice daily for 4 or 7 days. L-NG-nitroarginine methyl ester (L-NAME, 5 mg/kg), an inhibitor of nitric oxide synthase (NOS), was given s.c. prior to protamine sulphate (80 mg/kg) treatment. Ulcer healing, angiogenesis, mucosal histological changes, NOS activity and growth factors were determined.

RESULTS

Protamine sulphate dose-dependently accelerated gastric ulcer healing, which was accompanied by a significant increase in angiogenesis, mucosal regeneration and constitutive NOS activity. Inhibition of gastric secretion was observed. Epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), tumour necrosis factor-alpha (TNF-alpha) or inducible NOS activity was also affected. L-NAME completely blocked the beneficial effects of protamine sulphate.

CONCLUSIONS

Protamine sulphate accelerates gastric ulcer healing through a mucosal nitric oxide-dependent and possibly also the EGF-and bFGF-associated pathways, which are followed by an increase of angiogenesis and mucosal regeneration. Acid inhibition contributes in part to the ulcer healing action of protamine sulphate.

Involvement of neutrophils and free radicals in the potentiating effects of passive cigarette smoking on inflammatory bowel disease in rats

BACKGROUND & AIMS

Cigarette smoking is associated with inflammatory bowel diseases (IBDs), particularly Crohn's disease, in humans. The aim of this study was to examine whether passive cigarette smoking aggravates experimental IBD in rats and to clarify the underlying mechanisms.

METHODS

Rats were exposed to cigarette smoke (CS) for 1 hour once daily for 4 days before induction of IBD by 2,4, 6-trinitrobenzene sulfonic acid (TNBS)-ethanol enema and were then killed at 2, 6, or 24 hours later.

RESULTS

Preexposure to CS significantly potentiated colonic damage induced by TNBS. TNBS-ethanol enema caused a pronounced increase in colonic myeloperoxidase activity, leukotriene B(4) level, and also inducible nitric oxide synthase activity, its protein, and messenger RNA expression. These parameters were all significantly increased further by exposure to CS. In contrast, increased colonic superoxide dismutase activity after TNBS-ethanol enema was attenuated by CS exposure. The potentiating effects of CS exposure on TNBS-induced IBD were significantly alleviated after pretreatment with cyclosporin A (an immunosuppressant), N (G)-nitro-L-arginine methylester (a nitric oxide synthase inhibitor), and dimethyl sulfoxide (a hydroxyl radical scavenger).

CONCLUSIONS

The results show that promotion of neutrophil infiltration and free radical production contributed significantly to the potentiating effect of passive cigarette smoking on experimental IBD.

Cigarette smoke and its extract delays ulcer healing and reduces nitric oxide synthase activity and angiogenesis in rat stomach

1. The purpose of the present study was to examine whether cigarette smoke and its extract could affect ulcer healing, angiogenesis and nitric oxide synthase (NOS) activity in the gastric mucosa. 2. Ulcerated rats were either exposed to cigarette smoke or given smoke extract once daily for 3 days. Rats were killed and stomachs were removed for the measurement of ulcer size, angiogenesis and NOS activity. 3. Angiogenesis and constitutive NOS activity were concomitantly and dose-dependently reduced by cigarette smoke or its extract. The same treatments also delayed ulcer healing. 4. These results indicate that cigarette smoke and its extract repress the processes of new blood vessel formation and NOS activity during tissue repair in the gastric mucosa. These could, in turn, retard the healing process in the gastric mucosa.

Interactions of EGF and ornithine decarboxylase activity in the regulation of gastric mucus synthesis in cigarette smoke exposed rats

Cigarette smoking has been shown to aggravate ulceration and delay ulcer healing. Smokers had a lower level of mucus in their stomachs. In the present study, we examined whether cigarette smoke or its extract reduced mucus production through the suppression of epidermal growth factor (EGF) associated with the reduction of polyamine biosynthesis both in vivo and in vitro. Ornithine decarboxylase (ODC) activities and mucus synthesis were determined in rat gastric mucosa and in human MKN-28 cells. Incubation of MKN-28 cells with EGF (0.01-1.00 ng/mL) significantly increased mucus synthesis in vitro, which was accompanied by an increase of ODC activity. Removal of salivary glands decreased the circulated EGF level and induced a significant reduction of mucus-secreting layer thickness in the gastric mucosa. Cigarette smoke or its extract markedly decreased mucus synthesis in vivo and in vitro, both of which could be completely reversed by intravenous administration of EGF (20 microg/kg) in rats or co-incubation with EGF (1 and 2 ng/mL) in MKN-28 cells. However, ODC activities, which were suppressed by cigarette smoke or its extract, were unaffected by intravenous administration of EGF in rats, or only partially reversed by co-incubation with EGF in MKN-28 cells. These findings indicate that both EGF and ODC activity represent two different entities in the modulation of cigarette smoking on gastric mucus synthesis. The action of EGF on mucus synthesis may only be partially if not dependent on ODC activity in the stomach.

Co-regulation of mucosal nitric oxide and prostaglandin in gastric adaptive cytoprotection

OBJECTIVE

The correlation between mucosal generation of nitric oxide (NO) and prostaglandin E2 (PGE2) in gastric adaptive cytoprotection was investigated.

MATERIALS AND TREATMENT

Male Sprague-Dawley rats were pretreated with either N(w)-nitro-L-arginine methyl ester (L-NAME, 12.5 mg/kg i.v.) or indomethacin (5 mg/kg s.c.). Following that, mild irritant 20% ethanol was administered, 15 min prior to 100% ethanol challenge.

METHODS

Macroscopic gastric mucosal damage, NO synthase activity, mucosal PGE2 and leukotriene C4 (LTC4) levels were measured.

RESULTS

Administration of L-NAME and indomethacin significantly reduced the protective action of 20% ethanol against 100% ethanol-induced gastric mucosal damage. Besides, mucosal activity of constitutive NO (cNO) synthase, but not of the inducible isozyme (iNO synthase), was elevated following 20% ethanol treatment. This was accompanied by a reduction in mucosal leukotriene C4 level. Indomethacin significantly inhibited mucosal PGE2 biosynthesis but increased cNO synthase activity. Nevertheless, L-NAME reduced both cNO and iNO formation and prevented the increase in cNO formation caused by 20% ethanol, while enhancing mucosal PGE2 production. Combined L-NAME and indomethacin treatment markedly potentiated ethanol-induced mucosal damage, and completely prevented the increase in cNO or PGE2 biosynthesis when either compound was given alone.

CONCLUSIONS

These findings suggest a co-regulatory relationship between mucosal NO and PG in the gastric defense system, which will be released after activation by the mild irritants to induce cytoprotection.

Effects of long-acting somatostatin analogue (Sandostatin) on manifest diabetic ketoacidosis

Insulin deficiency and counterregulatory hormone excess are the basic process in the development of diabetic ketoacidosis (DKA). Somatostatin, which suppresses the secretion of glucagon and growth hormone, has been known to attenuate the rate of gluconeogesis and ketogenesis in insulin-dependent diabetes mellitus patients. However, the therapeutic efficacy of somatostatin has not been approved to be practical in the treatment of manifest DKA. To examine the additive effect of octreotide, the synthetic long-acting somatostatin analogue SMS 201-995, to conventional treatment of manifest DKA, we compared the correction time of acidosis, ketonuria, and hyperglycemia of patients treated with an intravenous infusion of low-dose insulin (4 units per hour) plus subcutaneous injection of octreotide (50 microg every 6 hours) by low-dose insulin alone. The correction time for hyperglycemia and acidosis did not show any difference between groups (p = 0.089, p = 0.82). However, the time for disappearance of ketonuria of the octreotide-treated group (38.0 +/- 32.0 h) was reduced significantly compared to other group (68.3 +/- 26.0 h) (p = 0.048). These results indicated that the addition of octreotide to conventional treatment of DKA might improve the correction of ketosis, but would not allow more rapid control of acidosis and hyperglycemia in manifest DKA.

Cigarette smoke increases apoptosis in the gastric mucosa: role of epidermal growth factor

BACKGROUND/AIMS

Apoptosis is a common mechanism for the regulation of cell loss. It is associated with both tissue atrophy and metaplasia. Cigarette smoking has tremendous adverse effects on the stomach and also increases the risk of gastric cancer. This action may be through the change in apoptosis in the stomach. The aim of this study was to examine the effect of cigarette smoking on apoptosis in the gastric mucosa and the possible role of epidermal growth factor (EGF) in this action.

METHODS

Gastric blood flow was assessed by the laser Doppler technique. Serum and gastric mucosal EGF levels were measured by RIA. Gastric mucosal apoptosis was determined using TdT-mediated dUTP-biotin nick end labeling (TUNEL).

RESULTS

Cigarette smoke exposure decreased serum EGF which was accompanied by a reduction in gastric blood flow. Meanwhile, gastric mucosal cell apoptosis was increased. Administration of EGF (20 microg/kg i.v.) before each cigarette smoke exposure reversed these actions. Removal of salivary glands induced similar effects on the gastric blood flow, apoptosis, and serum EGF level as with cigarette smoke exposure.

CONCLUSION

A reduction in serum EGF was involved in the decrease in gastric blood flow and increase in gastric mucosal apoptosis caused by cigarette smoking.

Association of heparin with basic fibroblast growth factor, epidermal growth factor, and constitutive nitric oxide synthase on healing of gastric ulcer in rats

The healing effect of heparin on gastric ulcer and its underlying mechanisms were studied. The influences of protamine on these effects were also investigated. Gastric ulcer was induced by acetic acid in rats. Heparin (100-1000 U/kg i.v.) was given once daily for 4 or 7 days. Ulcer area was measured; gastric mucosal regeneration, proliferation, and angiogenesis were determined by histological or immunohistochemical methods. Gastric mucosal basic fibroblast growth factor (bFGF) level was assessed by an enzyme-linked immunosorbent assay, and the mucosal epidermal growth factor (EGF) level and nitric oxide synthase (NOS) activity were measured by radioimmunoassay. The anticoagulant action of heparin was determined by the duration of bleeding time. The results showed that heparin given for 4 or 7 days significantly accelerated gastric ulcer healing in a dose-dependent manner. The three doses of heparin significantly stimulated mucosal regeneration and proliferation as well as angiogenesis but not the contraction of ulcer base. Similar effects were observed in gastric mucosal bFGF and EGF levels and constitutive NOS activity. Protamine not only abolished the anticoagulant action of heparin but also significantly potentiated its effects on ulcer healing, gastric mucosal proliferation, angiogenesis, and constitutive NOS activity. These findings indicate that heparin can accelerate gastric ulcer healing, which is associated with mucosal regeneration, proliferation, and angiogenesis. These actions are likely to be stimulated by bFGF, EGF, and constitutive NOS activity in the gastric mucosa. Protamine potentiates the ulcer-healing effect of heparin, which is probably acting through constitutive NOS activation.

Potentiating effect of passive cigarette smoking on gastrointestinal damage induced by indomethacin in rats

Cigarette smoking and nonsteroidal antiinflammatory drugs (NSAIDs) have been associated with gastroduodenal ulcers. The present study aimed to clarify the ulcerogenic mechanisms of passive cigarette smoking on gastrointestinal damage induced by indomethacin in fasted or in fasted and refed rats. Rats were exposed to cigarette smoke (0%, 1%, 2%, or 4%, v/v) before and/or after indomethacin administration. Cigarette smoke dose-dependently potentiated indomethacin-induced gastric mucosal lesions in the fasted animals and further lowered gastric blood flow. The gastric myeloperoxidase activity (a marker enzyme for neutrophils) was also potentiated. In addition, passive cigarette smoking increased the mortality and aggravated duodenal ulceration and also the reduction of duodenal blood flow in the fasted and refed rats after indomethacin treatment. The results indicated that the potentiating effect of passive cigarette smoking on indomethacin-induced gastroduodenal lesions is probably due to the depression of blood flow in the gastroduodenal mucosa and to the aggravation of neutrophil infiltration in the gastric mucosa.

Monophosphoryl lipid A (MPL) upregulates major histocompatibility complex (MHC) class I expression by increasing interferon-gamma (IFN-gamma)

Tumor immunity is primarily mediated by cells as CD8+ cytotoxic T lymphocytes (CTL) recognize tumor antigen by MHC class I molecules. But most tumors are associated with a decreased expression of MHC class I to escape the antitumor immunity of the host. Our previous data have demonstrated that MPL has an antitumor effect on metastatic lung cancer of B16 melanoma with enhancing cytotoxicity due to increase of IFN-gamma and IL-2, and decrease of IL-4, which indicates the stimulation of type 1 helper T cells (Th1). To determine the effects of MPL, IFN-gamma, TNF-alpha, and IL-1 alpha on MHC class I expression of B16 melanoma cells, we evaluated the expression of MHC class I molecules with treatments of MPL, IFN-gamma, TNF-alpha, and IL-1 alpha by flow cytometry. The supernatant of MPL-treated spleen cells in vitro upregulated the expression of MHC class I molecules of B16 melanoma cells compared to the control supernatant of spleen cells. The MHC class I expression of B16 melanoma cells treated with IFN-gamma, but not TNF-alpha or IL-1 alpha, increased in a time-dependent manner. In conclusion, MPL upregulated MHC class I expression of B16 melanoma cells by activating spleen cells via IFN-gamma. These data suggest that increased IFN-gamma by MPL is responsible for the upregulation of MHC class I expression to augment cytotoxicity. Therefore, we suggest that MPL could play an important role in immunotherapy.

Study of propranolol and its related adrenoceptor antagonists on changes of gastric electrical parameters induced by ethanol in rats

The actions of different adrenoceptor antagonists on gastric potential difference (PD), electrical current (I) and resistance (R) were studied, using the voltage clamp technique. In an isolated gastric mucosal tissue, 5% ethanol was able to reduce the PD and I across the gastric mucosa. Direct incubation with propranolol 10(-4) mol/l either from the mucosal or submucosal sides attenuated such effects. Intraperitoneal administration of propranolol (2.5-10 mg/kg), a nonselective beta-adrenoceptor blocker with significant membrane-stabilizing activity, given 30 min before the preparation of the gastric tissue, not only alleviated the fall in PD and I across the gastric mucosa, but also increased the R of the stomach tissue. Butoxamine, a selective beta2-antagonist, produced the similar but less significant effects in the same experimental setting. Metroprolol, a beta1-adrenoceptor blocker, given by the similar doses did not produce significant effects. Nonselective beta-adrenoceptor blocker, nadolol but not the beta- and alpha-adrenoceptor blocker, labetalol, also significantly preserved the decrease of PD induced by ethanol, but to a lesser extent. These findings suggest that blockade of the beta2-receptors in the gastric mucosa together with membrane-stabilizing activity could improve the integrity of the gastric mucosa, and these effects are probably acting through its direct action on the tissue.

Effects of cigarette smoking on gastric ulcer formation and healing: possible mechanisms of action

Epidemiologic studies have shown that cigarette smoking is closely related to peptic ulcer disease. The mechanisms by which cigarette smoking adversely affects gastric mucosa have been suggested and elucidated. This article reviews some of the mechanisms involved in cigarette smoking-related gastric ulceration and healing. Experimental findings suggest that cigarette smoking increases xanthine oxidase activity, leukotrienes, and nitric oxide production and also neutrophil infiltration in the gastric mucosa. On the other hand, it reduces blood flow, prostaglandin production, epithelial cell proliferation, and formation of blood vessels in the tissue. These actions are important for ulcer formation and healing. The evidence thus far available strengthens the hypothesis that cigarette smoke is indeed harmful to gastric mucosa through defined mechanisms.