Up-regulation of cyclooxygenase-2-derived prostaglandin E2 in colon cancer cells resistant to 5-fluorouracil / 대한외과학회지

PURPOSE: It has been suggested that constitutive up-regulation of cyclooxygenase (COX)-2 is associated with resistance to apoptosis, increased angiogenesis, and increased tumor invasiveness in various cancers including colon cancer. There are many factors involved in the resistance to 5-fluorouracil (5-FU) in colon cancer. However, little is known about the role of COX-2 in acquired resistance to 5-FU in colon cancer. METHODS: Hence we investigated whether COX-2 contribute to acquired resistance to 5-FU in colon cancer cells, using cytotoxicity assay for cell survival, reverse transcription-polymerase chain reaction (RT-PCR) for vascular endothelial growth factor (VEGF), quantitative RT-PCR for COX-1 and COX-2, and enzyme-linked immunosorbent assay for PGE2. RESULTS: The 5-FU resistant colon cancer cells, SNU-C5/5FUR, showed increased expression of COX-2, prostaglandin E2 (PGE2), and VEGF, compared to its parental cell (SNU-C5). By treatment with meloxicam, the expression of PGE2 and VEGF was reduced significantly in the resistant cells, but not in the parent cells. CONCLUSION: These results demonstrate that COX-2 derived PGE2 is up-regulated and COX-2 inhibitor may have an anti-angiogenic effect in the colon cancer cells resistant to 5-FU.

Effect of Nebulized Bovine Surfactant for Experimental Otitis Media with Effusion

OBJECTIVES: In this study, we evaluated the efficacy of nebulized bovine pulmonary surfactant on experimentally induced otitis media with effusion (OME) in guinea pigs. METHODS: Twenty guinea pigs were divided into three groups. Four untreated animals served as normal controls. Experimental OME was established in both ears of the remaining 16 animals by a transbullar injection of 10 microL of Pseudomonas aeruginosa lipopolysaccharide in saline. Thereafter, the guinea pigs received nebulized phosphate buffered saline (n=8) or nebulized bovine pulmonary surfactant (n=8). Nebulization was given daily for 7 days. On day 8, all the animals' passive opening pressure (POP) of the Eustachian tube was measured and histopathological observations of the bulla were made by light microscopy. RESULTS: Nebulized bovine pulmonary surfactant significantly reduced the POP compared to that of saline nebulization. The bovine pulmonary surfactant improved the tubal patency and produced less histopathologcally-evident edematous bullar mucosa. CONCLUSION: Nebulization of bovine pulmonary surfactant plays an important role in treating otitis media with effusion in guinea pigs. Our results suggest that the chosen nebulized bovine pulmonary surfactant can be of good clinical benefit for treating OME in the future.

Impacts of Cytosolic Phospholipase A2, 15-Prostaglandin Dehydrogenase, and Cyclooxygenase-2 Expressions on Tumor Progression in Colorectal Cancer

PURPOSE: In addition to cyclooxygenase-2 (COX-2) which is related to prostaglandin E2 synthesis, other enzymes such as cytosolic phospholipase A2 (cPLA2), microsomal prostaglandin E2 synthase-1 (mPGES-1), and 15-prostaglandin dehydrogenase (15-PGDH) have been suggested to be related to carcinogenesis of colorectal cancer (CRC). The aim of this study was to investigate the roles of cPLA2, COX-2, mPGES-1, and 15-PGDH in tumor progression. MATERIALS AND METHODS: cPLA2, COX-2, mPGES-1, 15-PGDH, and vascular endothelial growth factor (VEGF) expressions were immunohistochemically examined in 89 CRC, and their expressions were compared with each other or clinicopathologic parameters as well as VEGF as tumor progression parameters. RESULTS: cPLA2 was expressed in 54.5%, COX-2 in 80.5%, mPGES-1 in 96.4%, 15-PGDH in 46.1%, and VEGF in 65.9%. The expression of cPLA2 correlated with VEGF expression. COX-2 expression was correlated with the depth of invasion, tumor stage, cPLA2, and VEGF expressions. Moreover, VEGF revealed the highest expression in the tissues positive for both cPLA2 and COX-2. Furthermore, 15-PGDH expression was inversely correlated with VEGF expression. CONCLUSION: The present study demonstrates that cPLA2 and mPGES-1, in addition to COX-2, are constitutively overexpressed, and that 15-PGDH might be attenuated in colorectal cancer. Furthermore, cPLA2 and 15-PGDH as well as COX-2 could have an important role in tumor progression.

Expression of Cyclooxygenase-2 and its Relationship to p53 Accumulation in Colorectal Cancers

PURPOSE: Cyclooxygenase (COX)-2 is an inducible isoform responsive to cytokines, mitogens, and growth factors, and is believed to be an important enzyme related to colorectal cancer (CRC). Existing evidence suggests that COX-2 expression is normally suppressed by wild-type p53 but not mutant p53, suggesting that loss of p53 function may result in the induction of COX-2 expression. The aim of this study was to determine the relationship between COX-2 expression and p53 levels in CRC. MATERIALS AND METHODS: Patients with sporadic colorectal adenocarcinoma (n=161) who underwent curative surgery in Chosun University Hospital were enrolled in this study. Expression of COX-2 and p53 proteins was examined by immunohistochemistry in paraffin-embedded cancer tissue blocks, and the relationship between COX-2 and/or p53 expression with clinicopathologic parameters was analyzed. RESUTLS: Expression of COX- 2 was positive in 47.8% of colorectal cancers, and significantly associated with the depth of tumor invasion (p= 0.042). In contrast, p53 was positive in 50.3% of the cases, and was associated with both age (p=0.025) and the depth of tumor invasion (p=0.014). There was no correlation between COX-2 expression and p53 expression (p=0.118). CONCLUSION: These results suggest that COX-2 expression might play an important role in the progression of colorectal cancer. However, COX-2 expression was not associated with mutational p53. Further studies are needed to clarify the regulatory mechanisms governing COX-2 overexpression in colorectal cancers.

Role of Gallic Acid in Inflammatory Allergic Process

The aim of the present study was to elucidate whether gallic acid could modulate the inflammatory allergic reaction and to study its mechanism of action Gallic acid inhibited compound 48/80- or immunoglobulin E (IgE)-induced histamine release from mast cells. The inhibitory effect of gallic acid on the histamine release was mediated by modulation of cAMP and intracellular calcium. Gallic acid decreased the phorbol 12-myristate 13-acetate plus calcium ionophore A23187-stimulated pro-inflammatory cytokine gene expression and production such as TNF-alpha and IL-6 in human mast cells, and the inhibitory effect of gallic acid was on dependent nuclear factor-kappa B and p38 mitogen-activated protein kinase. Our findings provide evidence that gallic acid inhibits mast cell-derived inflammatory allergic reaction by blocking histamine release and pro-inflammatory cytokine expression.

p38 Mitogen-Activated Protein Kinase and Extracellular Signal-Regulated Kinase Regulate Nitric Oxide Production and Inflammatory Cytokine Expression in Raw Cells

BACKGROUND: p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) signaling are thought to have critical role in lipopolysaccharide (LPS)-induced immune response but the molecular mechanism underlying the induction of these signaling are not clear. METHODS: Specific inhibitors for p38, SB203580, and for ERK, PD98059 were used. Cells were stimulated by LPS with or without specific MAPK inhibitors. RESULTS: LPS activated inducible nitric oxide synthase (iNOS), subsequent NO productions, and pro-inflammatory cytokine gene expressions (TNF-alpha, IL-1beta, IL-6, and IL-12). Treatment of both SB203580 and PD98059 decreased LPS-induced NO productions. Concomitant decreases in the expression of iNOS mRNA and protein were detected. SB203580 and PD98059 decreased LPS-induced gene expression of IL-1beta and IL-6. SB203580 increased LPS-induced expression of TNF-alpha and IL-12, and reactive oxygen species production, but PD98059 had no effect. CONCLUSION: These results indicate that both p38 and ERK pathways are involved in LPS-stimulated NO synthesis, and expression of IL-1beta and IL-6. p38 signaling pathways are involved in LPS-induced TNF-alpha and IL-12, and reactive oxygen species plays an important role in these signaling in macrophage.

Naltrexone Inhibits Catecholamine Secretion Evoked by Nicotinic Receptor Stimulation in the Perfused Rat Adrenal Medulla

The purpose of the present study was to examine the effect of naltrexone, an opioid antagonist, on secretion of catecholamines (CA) evoked by cholinergic nicotinic stimulation and membrane-depolarization from the isolated perfused rat adrenal gland and to establish the mechanism of its action. Naltrexone (3x10 (-6) M) perfused into an adrenal vein for 60 min produced time-dependent inhibition in CA secretory responses evoked by ACh (5.32x10 (-3) M), high K+ (5.6x10 (-2) M), DMPP (10 (-4) M) and McN-A-343 (10 (-4) M). Naltrexone itself did also fail to affect basal CA output. In adrenal glands loaded with naltrexone (3x10 (-6) M), the CA secretory responses evoked by Bay-K-8644, an activator of L-type Ca2+ channels and cyclopiazonic acid, an inhibitor of cytoplasmic Ca2+-ATPase, were also inhibited. However, in the presence of met-enkephalin (5x10 (-6) M), a well-known opioid agonist, the CA secretory responses evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were also significantly inhibited. Collectively, these experimental results demonstrate that naltrexone inhibits greatly CA secretion evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as that by membrane depolarization. It seems that this inhibitory effect of naltrexone does not involve opioid receptors, but might be mediated by blocking both the calcium influx into the rat adrenal medullary chromaffin cells and the uptake of Ca2+ into the cytoplasmic calcium store, which are at least partly relevant to the direct interaction with the nicotinic receptor itself.

Expression and Function of ABC Transporters as Multidrug Resistance Mechansims in Gastric Cancer Cells

PURPOSE: Multidrug resistance (MDR) is a phenomenon whereby tumor cell acquire resistance to a broad range of structurally and functionally diverse chemotherapeutic drugs. The most widely implicated mechanism of MDR is that of altered membrane transporter in tumor cells. P-glycoprotein (Pgp), multidrug resistance protein (MRP), and breast cancer-resistance protein (BCRP) are well known membrane transporters, which pump out antitumor agents via an ATP-dependent process, the so called ATP-binding cassette (ABC) superfamily or transporter. This study was undertaken to test the prevalence of each ABC transporter, and which of then exhibit functional activity in various gastric cancer cells. METHODS: The expressions of Pgp, MRP, and BCRP mRNA were determined by RT-PCR assay on 10 gastric cancer cells. The sensitivity to anticancer agents, substrates for each ABC transporter in the gastric cancer cells was determined using the MTT assay. The intracellular accumulation of fluorescent compounds for the functional detection of each ABC transporter was determined using flow cytometry. RESULTS: The Pgp mRNA was expressed at various levels in 9 out of the 10 gastric cancer cells tested, but significantly low. MRP mRNA was constitutively expressed in all the cells. BCRP mRNA was differentially expressed in 5 of the gastric cancer cells. There was no relation between the expressions of Pgp and MRP and the cytotoxicity to each substrate. It was observed that the accumulations of paclitaxel and VP-16 were significantly increased on the additions of PSC833 and probenecid, respectively, in all tested cells. The reversal effect of drug accumulation by each inhibitor was much higher in the MRP than Pgp. With BCRP, the observed cytotoxic effect and amount of mitoxanthrone accumulation were less than in the cells expressing the highest levels of BCRP compared to those that did not. However the mitoxanthrone accumulation was not increased on the addition of FTC in the either cell type. CONCLUSION: This study suggests that of the ABC transporters, MRP has primarily functional activity, whereas that of Pgp is only slight, in the gastric cancer cells. Other possible MDR mechanisms involved will have to be explored in further studies.

Expression and Function of ABC Transporters as Multidrug Resistance Mechansims in Colon Cancer Cells

PURPOSE: Multidrug resistance (MDR) is a phenomenon whereby tumor cells acquire resistance to a broad range of structurally and functionally diverse chemotherapeutic drugs. The most widely implicated mechanism of MDR is that concerned with altered membrane transporters in tumor cells. P-glycoprotein (Pgp), multidrug resistance protein (MRP), and breast-cancer-resistance protein (BCRP) are well-known membrane transporters that pump out antitumor agents by using an ATP-dependent process, the so-called ATP-binding cassette (ABC) superfamily or transporter. This study was undertaken to test the prevalence of each ABC transporter and to determine which transporter has functional acitivity in various colon cancer cells. METHODS: Expressions of Pgp, MRP, and BCRP mRNA were determined in 9 colon-cancer cell lines by using an RT-PCR assay. The sensitivity to anticancer agents substrate for each ABC transporter in the colon cancer cells determined using an MTT assay. The accumulation of fluorescent compounds for functional detection of each ABC transporter was determined by using flow cytometry. RESULTS: Pgp mRNA was variably expressed in 6 of 9 colon cancer cells lines. MRP and BCRP mRNA were expressed in all the 9 cell lines. A smaller cytotoxic effect to paclitaxel and a smaller amount of rhodamine123 accumulation were observed in Colo 320HSR expressing the highest levels of Pgp than in SNU-C5 not expressing Pgp. These effects in Colo320HSR were reversed with the addition of various Pgp inhibitors, but such a reversal did not occur in SNU-C5. The cytotoxic effect to VP-16 was not related to the expression levels of MRP in Colo320HSR and SNU-C, but the amount of calcein-AM accumulation was reversed with addition of probenecid, MRP inhibitor. The cytotoxic effect and the drug accumulation of mitoxantrone were not related to the expression levels of BCRP. CONCLUSIONS: This study suggests that of the ABC transporters, primarily Pgp and MRP have functional activity in colon cancer cell lines.

Adjuvant Effect of NSAIDs on the Cytotoxicity of Colon Cancer Cells to 5-FU

PURPOSE: Cyclooxygenase (COX)-2, an inducible enzyme that catalyzes the conversion of arachidonic acid to prostaglandins, is believed to be an important enzyme related to colorectal cancer. A large number of studies have supported the concept that non-steroidal anti-inflammatory drugs (NSAIDs) targeting COX alter the biologic processes of colon carcinogenesis. Although COX-2 inhibitors generally reduce the growth rate of established tumors, tumor regression is rarely observed. Hence, it is reasonable that COX-2 inhibitors be given in conjunction with standard anti-cancer therapy in treating cancer. We investigated whether aspirin and meloxicam not only are cytotoxic but also potentiate the antitumor effect of 5-Fluorouracil (5-FU) against colon cancer cells. METHODS: Expressions of COX-1 and COX-2 were determined by using the reverse transcriptase-polymerase chain reaction (RT-PCR) & Western blotting assay in 9 colon cancer cell lines. The cytotoxicities of NSAIDs and/or 5-FU were determined by using a microculture tetrazolium dye (MTT) assay. RESULTS: COX-1 mRNA and protein, as well as COX-2 mRNA, were variably expressed in all the cell lines tested whereas COX-2 protein was expressed in HT-29 and to a lesser extent in HCT-8, but not in the other cell lines. We selected two representative cell lines, HT-29 expressing COX-2 protein and SNU-C1 not expressing it. The dose-dependent cytotoxicity was observed in both cell lines treated with aspirin and with meloxicam. A combination treatment of aspirin or meloxicam with 5-FU revealed some additive effect, rather than a synergistic effect, for both cells lines. This additive effect was remarkable even for low concentrations of the drugs. Furthermore, the additive effect was highest when the combination was adminstered sequentially, 5-FU followed by aspirin or meloxicam, in both cell lines. CONCLUSIONS: These results suggest that a combination therapy using NSAIDs and 5-FU might be useful in the treatment of colon cancer cells not expressing COX-2, as well as in colon cancer cells expressing COX-2.

Role of Inducibility of Superoxide Dismutases and Metallothionein of Mouse Lungs by Paraquat in Aging / 결핵

BACKGROUND: The aging process may be induced, at least in part, by reactive oxygen species(ROS). It has been though that the lung could be a good source of ROS because it has a high oxygen tension. In the present study, we invetigated the inducibility of the first and last lines against oxidative stress, superoxide dismutases (Cu/Zn-SOD and Mn-SOD) as a scavenger of O2- and metallothionein(MT) as a scavenger of OH·, respectively, in mouse lungs with age. METHODS: Oxidative stress was induced by paraquat, an intracellular superoxide generator, at 1, 4, 8, and 12 months of age and then SODs and MT mRNAs were determined by RT-PCR method. RESULTS: The steady-state level of Mn-SOD mRNA increased from 1 to 8 months but decreased thereafter. However, Mn-SOD mRNA was not induced by paraquat after 1 month. On the other hand, there was no change in the steady-state level of Cu/Zn/-SOD mRNA, which decrease abruptly at 12 months of age. Additionally, Cu/Zn/-SOD mRNA was not induced by paraquat at any age. There was no change in the steady-state level of MT mRNA with age whereas its inducibility by paraquat was intact at all ages. CONCLUSION: These results indicate that lack of induction of SODs with age may be one of the causative factors in the aging process while induction of MT may play an important role in the defense against oxidative stress. It is therefore implicated that the tissue antioxidant/proxidant balance could be one determinants of meal life span.

Camptothecin-nduced Apoptosis in Gastric Cancer Cell Lines: Involvement of Bcl-

BACKGROUND: Apoptosis can be induced by various anticancer agents. Resistance to apoptosis may play an important role in tumors refractory to chemotherapy. The authors investigated both the induction of apoptosis by camptothecin, a topoisomerase I inhibitor, in gastric cancer cell lines and the roles of apoptosis-elated gene products. METHODS: Two gastric cancer cell lines, SNU- and SNU-6, were examined for response to chemotherapeutic agents. Cytotoxicity was determined by a MTT assay. Apoptosis was measured by a DNA fragmentation assay using agarose gel electrophoresis and electron microscopy. Apoptosis-elated gene products were determined by western blot analysis. RESULTS: The two gastric cancer cell lines (SNU- and SNU-6) showed different sensitivities to camptothecin. Apoptosis of SNU-6 was easily induced by camptothecin, while SNU- was refractory to apoptosis, which was confirmed by DNA fragment assays and electron microscopy. Western blot analysis revealed that the amount of Bcl- in SNU- was 2.68-imes more than that in SNU-6. There were no differences in the levels of Bax, Bcl-L, Bcl-s, and p53 between the two cell lines. CONCLUSIONS: It is thought that Bcl- may play an important role in blocking cell death due to anticancer drugs in gastric cancer cell lines. Thus, chemosensitivity might be increased if this cell death-locking status were to be modified by new biologic therapies for gastric cancer.

Inducibility of superoxide dismutases and metallothionein in the liver and kidney of mice by paraquat with age / 대한내과학회지

BACKGROUND: A number of theories have been proposed to explain the nature of aging process. Unfortunately, there is so far no theory that can completely explain all aging processes. In the present study, to investigate roles of inducibility of defense mechanisms by oxidative stress, cellular mRNA level of superoxide dismutases (SODs) and metallothionein (MT) as well as their inducibility by paraquat, an intracellular superoxide generator, was examined in the liver and kidney of the mice of aging process. METHODS: The steady-state levels of SODs and MT mRNA and their induction by paraquat were determined by the RT-PCR assay in male mice of 4 ages, 1, 4, 8, and 12 months. RESULTS: In the liver, the steady-state levels of Mn-SOD, Cu/Zn-SOD and MT mRNA increased until 8 months with age and decreased significantly at 12 months. Cu/Zn-SOD and MT mRNA were induced well by paraquat at all ages but Mn-SOD mRNA not at 12 months. In the kidney, their mRNA levels of Mn-SOD, Cu/Zn-SOD and MT increased with age. Mn-SOD mRNA was induced by paraquat only at 1 month but Cu/Zn-SOD mRNA not at all ages. On the other hand, MT mRNA was significantly induced by paraquat at all ages. CONCLUSION: These results suggest that SODs and MT are differentially expressed and induced according to the age and organs. In addition, it is thought that the lack of induction of Mn-SOD by oxidative stress in both the liver and kidney may be one of causative factors in the aging process while Cu/Zn-SOD and MT in the liver and MT in the kidney may play protective roles in the aging process. It is therefore implicated that the tissue antioxidant/prooxidant balance could be one of determinants of mean life span.

Relationship between the Expression of Apoptosis-Related Proteins and Chemosensitivity in Gastric Cancer Cell Lines

BACKGROUND: There has been a growing realization that a variety of anticancer drugs can induce apoptotic cell death. In the present study, an attempt was made to investigate the responsiveness of gastric cancer cells to various anticancer drugs and to identify which apoptosis-related proteins could be correlated to chemosensitivity. METHODS: Nine human Korean gastric cancer cell lines (SNU-1, -5, -16, -484, -601, -620, -638, -668, and -719) were analyzed. The cytotoxicity of each cell line to camptothecin, cisplatin, mitomycin C, vincristine, 5-FU, epirubicin, and doxorubicin was determined by using a MTT (dimethylthiazole- diphenyltetrazolium-bromide) assay. Apoptosis-related proteins (p53, p21, Bcl-2, Bcl-x, and Bax) were detected using a Western blot assay. RESULTS: Of the nine gastric cancer cell lines, SNU-1 was resistant while SNU-5 was sensitive to anticancer drugs. Mutated p53 was detected in all the cell lines. The highest expression of Bcl-2 was observed in SNU-1 while less or no expression of Bcl-2 was observed in SNU-5, -484, and -601. Bcl-xL was less expressed in SNU-5 than in the other cell lines. CONCLUSIONS: Chemosensitivity in gastric cancer cell lines was correlated mainly with the level of Bcl-2 and partly with that of Bcl-xL. There was no correlation between the chemosensitivity and other apoptosis-related proteins, such as p21, p53, Bax, and Bcl-xS in the studied gastric cancer cell lines.

Radiation-Induced Apoptosis of Lymphocytes in Peripheral Blood / 대한방사선종양학회지

PURPOSE: This study quantitatively evaluated the apoptosis in human peripheral blood lymphocytes using flow cytometry, and investigated the possibility of using this method, with a small amount of blood, and the time and dose dependence of radiation-induced apoptosis. MATERIALS AND METHODS: Peripheral blood lymphocytes were isolated from the heparinized venous blood of 11 healthy volunteers, 8 men and 3 women, with each 10 ml of blood being divided into 15 samples. The blood lymphocytes were irradiated using a linear accelerator at a dose rate of 2.4 Gy/min, to deliver doses of 0.5, 1, 2 and 5 Gy. The control samples, and irradiated cells, were maintained in culture medium for 24, 48 and 72 hours following the irradiation. The number of apoptotic cells after the in vitro X-irradiation was measured by flow cytometry after incubation periods of 24, 48 and 72 hours. We also observed the apoptotic cells using a DNA fragmentation assay and electron microscopy. RESULTS: The rate of spontaneous apoptosis increased in relation to the time interval following irradiation (1.761+/-0.161, 3.563+/-0.564, 11.098+/-2.849, at 24, 48, and 72 hours). The apoptotic cells also increased in the samples irradiated with 0.5, 1, 2 and 5 Gy, in a radiation dose and time interval after irradiation manner, with the apoptosis being too great at 72 hours after irradiation. The dose-response curves were characterized by an initial steep increase in the number of apoptotic cells for irradiation doses below 2 Gy, with a flattening of the curves as the dose approached towards 5 Gy. CONCLUSION: The flow cytometric assay technique yielded adequate data, and required less than 1 mL of blood. The time and dose dependence of the radiation-induced apoptosis, was also shown. It is suggested that the adequate time interval required for the evaluation of apoptosis would be 24 to 48 hours after blood sampling.

Influence of staurosporine on catecholamine release evoked by cholinergic stimulation and membrane depolarization from the rat adrenal gland

The present study was attempted to examine the effect of staurosporine (STS) on secretion of catecholamines (CA) evoked by cholinergic stimulation and membrane depolarization from the isolated perfused rat adrenal gland and to establish its mechanism of action. The perfusion of STS (3 X 10(-7) ~3 X 10(-8) M) into an adrenal vein for 20 min produced a dose-dependent inhibition in CA secretion evoked by ACh (5.32 X 10(-3) M), high K+ (5.6 X 10(-2) M), DMPP (10(-4) M for 2 min), McN-A-343 (10(-4) M for 2 min), cyclopiazonic acid (10(-5) M for 4 min) and Bay-K-8644 (10(-5) M for 4 min). Also, in the presence of tamoxifen (2 X 10(-6) M), which is known to be a protein kinase inhibitor, CA secretory responses evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were also significantly depressed. However, in adrenal glands preloaded with STS (10(-7) M) under the presence of phorbol-12,13-dibutyrate (10(-7) M), a specific activator of protein kinases (for 20 min), the inhibitory effect of STS on CA secretory responses evoked by ACh, high K+, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid was greatly recovered to the extent of the control release as compared to those in the presence of STS only. These results demonstrate that STS causes the marked inhibition of CA secretion evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as by membrane depolarization, indicating strongly that this effect may be mediated by inhibiting influx of extracellular calcium and release in intracellular calcium in the rat adrenomedullary chromaffin cells through preventing activation of protein kinases. Furthermore, these findings also suggest that these STS-sensitive protein kinases play a modulatory role partly in regulating the rat adrenomedullary CA secretion.

Influence of Phenilamine on Pressor Responses of Norepinephrine and Tyramine

The effect of Pheniramine(Avil), a histaminergic-1 receptor blocking agent presently employed in treating various allergic diseases on pressor actions of norepinephring(NE) and tyramine (TR) was studied in the rabbit. Pheniramine, when given into a femoral vein with a dose(3mg/kg) enough to block H1-receptor, potentiated markedly the pressor responses of NE and TR. The pressor action of NE augmented by pheniramine was not affected by additional adminstration of debrisoquin (Drenergic neuron blocker) or phenelzine(monoamine oxidase inhibitor) or desipramine(U1-uptake blocker), or while potentiated by additional treatment with chlorisondamine(ganglionic blocker)or reserpine(catecholamine depleter). The hypertensive response of NE to phenelzine or desipramine was reinforced significantly by addition of pheniramine, but the response of NE in rabbits treated with reserpine or chlorisondamine or debrisoquin was not influenced by pheniramine-addition. Elevation of blood pressure to TR potentiated by pheniramine was attenuated significantly by reserpine treatment with chlorisondamine made the significant augmentation of pressor action to TR after pheniramine. Tyramine-induced response of blood pressure after pheniramine, but the response of blood pressure to TR caused by phenelzine or desipramine was enhanced markedly by pheniramine-treatment. From the above experimental results, it is thought that the pressor effect of NE and TR potentiated by pheniramine is similar to that of debrisoquin, i.e. the sensitization of effector cell, and that central action of pheniramine can not ruled out.

Relationship between Expression of Thy- midylate Synthase mRNA and Resistance of Colon and Gastric Cancer Cells to 5-FU

PURPOSE: Thymidylate synthase (TS) is an important target for chemotherapeutic drugs such as 5-fluorouracil (5-FU). Overexpression of TS has been linked to chemotherapy resistance, but their relationship was not completely understood. We compared the expression level of TS with resistance of colon and gastric cancer cell lines to 5-FU. METHODS: Expression of TS mRNA was determined by RT-PCR assay in 9 colon and 10 gastric cancer cell lines. Cytotoxicity of 5-FU was determined by MTT assay. Apoptosis was determined using propidium iodide staining by flow cytometry. RESULTS: All cancer cell lines tested showed differential levels of TS mRNA expression. Colon cancer cell Colo320 (the highest expression of TS) was more resistant to 5-FU than SNU-C1 (the lowest expression of TS) was. Flow cytometry also showed that 5-FU induced apoptosis less in Colo320 than SNU-C1. But in gastric cancer cells SNU-1 (the highest expression of TS) was not resistant to 5-FU than SNU-16 (the lowest expression of TS) was. CONCLUSIONS: The high level of expression of TS was correlated with resistance of colon cancer cells to 5-FU, but not in gastric cancer cells. Thus, TS may be differently involved in the resistance of gastric and colon cancer cells to 5-FU, which may depend on the origin of cancer cells and status of apoptosis related genes.

Influence of Metoclopramide on the Response of Blood Pressure in Rabbits

No abstract available.

The Expression of Multidrug Resistance-Associated Protein (MRP) and the Chemosensitivity in Gastric Cancer Cell Lines

PURPOSE: Gastric cancer cells may show resistance to various chemotherapeutic agents. The ability of cancer cells to become drug resistant is thought to be a cause of chemotherapy failure. Recent studies showed that multidrug resistance-associated protein (MRP) might confer resistance to a wide spectrum of natural product drugs. However, the clinical relevance of MRP-mediated multidrug resistance in human gastric cancer remains unknown. To determine the significance of MRP expression in gastric cancer, we investigated the relationship between MRP expression and chemosensitivity in gastric cancer cell lines. METHODS: In 8 gastric cancer cell lines (SNU-1, 5, 16, 484, 601, 620, 638 and 668), the expression of MRP and MRP mRNA was detected by using Western blot and reverse transcription-polymerase chain reaction (RT-PCR) analyses, respectively. Sensitivity to the anticancer agents (cisplatin, doxorubicin, 5-fluorouracil, camptothecin, epirubicin, and vincristine) was examined using a dimethylthiazole- diphenyltetrazolium-bromide (MTT) assay. RESULTS: All 8 cell lines expressed MRP and MRP mRNA in various degrees. There was no significant correlation between the expression of MRP and MRP mRNA. Sensitivity to anticancer agents had no significant correlation with the level of MRP expression. CONCLUSION: There was no general correlation between the expression of MRP and chemosensitivity in the various gastric cancer cell lines used in this study. In addition to MRP, another mechanism might be involved in the chemosensitivity of gastric cancer cell lines.