Bile duct epithelial tight junctions and barrier function.

Bile ducts play a crucial role in the formation and secretion of bile as well as excretion of circulating xenobiotic substances. In addition to its secretory and excretory functions, bile duct epithelium plays an important role in the formation of a barrier to the diffusion of toxic substances from bile into the hepatic interstitial tissue. Disruption of barrier function and toxic injury to liver cells appear to be involved in the pathogenesis of a variety of liver diseases such as primary sclerosing cholangitis, primary biliary cirrhosis and cholangiocarcinoma. Although the investigations into understanding the structure and regulation of tight junctions in gut, renal and endothelial tissues have expanded rapidly, very little is known about the structure and regulation of tight junctions in the bile duct epithelium. In this article we summarize the current understanding of physiology and pathophysiology of bile duct epithelium, the structure and regulation of tight junctions in canaliculi and bile duct epithelia and different mechanisms involved in the regulation of disruption and protection of bile duct epithelial tight junctions. This article will make a case for the need of future investigations toward our understanding of molecular organization and regulation of canalicular and bile duct epithelial tight junctions.

c-Jun NH2-terminal kinase-2 mediates osmotic stress-induced tight junction disruption in the intestinal epithelium.

Gastrointestinal epithelium faces osmotic stress, both at physiological and pathophysiological conditions. JNK activation is an immediate cellular response to osmotic stress. We investigated the effect of osmotic stress on intestinal epithelial barrier function and delineated the role of JNK2 in osmotic stress-induced tight junction (TJ) regulation in Caco-2 cell monolayers and ileum of Jnk(-/-) and Jnk2(-/-) mice. The role of JNK activation in osmotic stress-induced TJ disruption was evaluated using JNK-specific inhibitor and antisense oligonucleotides. Furthermore, the effect of cold restraint stress in vivo on TJ integrity was determined in rats. Osmotic stress disrupted TJs and barrier function in Caco-2 cell monolayers without affecting cell viability. Osmotic stress activated JNK1 and JNK2 and the inhibition of JNK by SP600125 attenuated osmotic stress-induced TJ disruption. TJ disruption and barrier dysfunction by osmotic stress was associated with JNK-dependent remodeling of actin cytoskeleton. Knockdown of JNK2 accelerated TJ assembly and attenuated osmotic stress-induced TJ disruption in Caco-2 cell monolayers. In mouse ileum in vitro, osmotic stress increased paracellular permeability, which was attenuated by SP600125. Osmotic stress disrupted actin cytoskeleton and TJs and increased paracellular permeability in the ileum of wild-type and JNK1(-/-) mice, but not in JNK2(-/-) mouse ileum. Cold restraint stress activated JNK in rat ileum and caused JNK-dependent remodeling of actin cytoskeleton and redistribution of occludin and zona occluden-1 from the intercellular junctions. These results reveal the role of JNK2 in the mechanism of osmotic stress-induced TJ disruption in the intestinal epithelium.

Hydrogen peroxide activates focal adhesion kinase and c-Src by a phosphatidylinositol 3 kinase-dependent mechanism and promotes cell migration in Caco-2 cell monolayers.

Recent studies showed that c-Src and phosphatidylinositol 3 (PI3) kinase mediate the oxidative stress-induced disruption of tight junctions in Caco-2 cell monolayers. The present study evaluated the roles of PI3 kinase and Src kinase in the oxidative stress-induced activation of focal adhesion kinase (FAK) and acceleration of cell migration. Oxidative stress, induced by xanthine and xanthine oxidase system, rapidly increased phosphorylation of FAK on Y397, Y925, and Y577 in the detergent-insoluble and soluble fractions and increased its tyrosine kinase activity. The PI3 kinase inhibitors, wortmannin and LY294002, and the Src kinase inhibitor, 4-amino-5[chlorophyll]-7-[t-butyl]pyrazolo[3-4-d]pyrimidine, attenuated tyrosine phosphorylation of FAK. Oxidative stress induced phosphorylation of c-Src on Y418 by a PI3 kinase-dependent mechanism, whereas oxidative stress-induced activation of PI3 kinase was independent of Src kinase activity. Hydrogen peroxide accelerated Caco-2 cell migration in a concentration-dependent manner. Promotion of cell migration by hydrogen peroxide was attenuated by LY294002 and PP2. Reduced expression of FAK by siRNA attenuated hydrogen peroxide-induced acceleration of cell migration. The expression of constitutively active c-Src(Y527F) enhanced cell migration, whereas the expression of dominant negative c-Src(K296R/Y528F) attenuated hydrogen peroxide-induced stimulation of cell migration. Oxidative stress-induced activation of c-Src and FAK was associated with a rapid increase in the tyrosine phosphorylation and the levels of paxillin and p130(CAS) in actin-rich, detergent-insoluble fractions. This study shows that oxidative stress activates FAK and accelerates cell migration in an intestinal epithelium by a PI3 kinase- and Src kinase-dependent mechanism.

Acetaldehyde-induced barrier disruption and paracellular permeability in Caco-2 cell monolayer.

A significant body of evidence indicates that endotoxemia plays a crucial role in the pathogenesis of alcoholic liver disease. There are several possible factors that may be involved in inducing alcoholic endotoxemia, but increased intestinal permeability to enteric endotoxins appears to be the major contributing factor. In the normal gut, the epithelial barrier function prevents diffusion of toxins across the epithelium. However, the barrier is disrupted in patients with alcoholic liver disease. We showed that acetaldehyde disrupts intestinal epithelial tight junctions and increases paracellular permeability to endotoxins in Caco-2 cell monolayer, the extensively studied model of the differentiated intestinal epithelium. The mechanisms involved in acetaldehyde-induced increase in intestinal permeability to endotoxins can be elucidated in this model of the intestinal epithelium.

Lipopolysaccharide disrupts tight junctions in cholangiocyte monolayers by a c-Src-, TLR4-, and LBP-dependent mechanism.

Bile duct epithelium forms a barrier to the backflow of bile into the liver parenchyma. However, the structure and regulation of the tight junctions in bile duct epithelium is not well understood. In the present study, we evaluated the effect of lipopolysaccharide on tight junction integrity and barrier function in normal rat cholangiocyte monolayers. Lipopolysaccharide disrupts barrier function and increases paracellular permeability in a time- and dose-dependent manner. Lipopolysaccharide induced a redistribution of tight junction proteins, occludin, claudin-1, claudin-4, and zonula occludens (ZO)-1 from the intercellular junctions and reduced the level of ZO-1. Tyrosine kinase inhibitors (genistein and PP2) prevented lipopolysaccharide-induced increase in permeability and subcellular redistribution of ZO-1. Reduced expression of c-Src, TLR4, or LBP by specific small interfering RNA attenuated lipopolysaccharide-induced permeability and redistribution of ZO-1. ML-7, a myosin light chain kinase inhibitor, attenuated LPS-induced permeability. Lipopolysaccharide treatment rapidly increased the phosphorylation of occludin and ZO-1 on tyrosine residues, which was prevented by genistein and PP2. Occludin and ZO-1 were found to be highly phosphorylated on threonine residues in intact cell monolayers. Threonine-phosphorylation of occludin was rapidly reduced by lipopolysaccharide administration. Lipopolysaccharide-induced dephosphorylation of occludin on Thr residues was prevented by genistein and PP2. In conclusion, lipopolysaccharide disrupts the tight junction of a bile duct epithelial monolayer by a c-Src-, TLR4-, LBP-, and myosin light chain kinase-dependent mechanism.

Acetaldehyde disrupts tight junctions and adherens junctions in human colonic mucosa: protection by EGF and L-glutamine.

Acetaldehyde, a toxic metabolite of ethanol oxidation, is suggested to play a role in the increased risk for gastrointestinal cancers in alcoholics. In the present study, the effect of acetaldehyde on tyrosine phosphorylation, immunofluorescence localization, and detergent-insoluble fractions of the tight junction and the adherens junction proteins was determined in the human colonic mucosa. The role of EGF and L-glutamine in prevention of acetaldehyde-induced effects was also evaluated. Acetaldehyde reduced the protein tyrosine phosphatase activity, thereby increasing the tyrosine phosphorylation of occludin, E-cadherin, and beta-catenin. The levels of occludin, zonula occludens-1, E-cadherin, and beta-catenin in detergent-insoluble fractions were reduced by acetaldehyde, while it increased their levels in detergent-soluble fractions. Pretreatment with EGF or L-glutamine prevented acetaldehyde-induced protein tyrosine phosphorylation, redistribution from intercellular junctions, and reduction in the levels of detergent-insoluble fractions of occludin, zonula occludens-1, E-cadherin, and beta-catenin. These results demonstrate that acetaldehyde induces tyrosine phosphorylation and disrupts tight junction and adherens junction in human colonic mucosa, which can be prevented by EGF and glutamine.

L-Glutamine ameliorates acetaldehyde-induced increase in paracellular permeability in Caco-2 cell monolayer.

Role of L-glutamine in the protection of intestinal epithelium from acetaldehyde-induced disruption of barrier function was evaluated in Caco-2 cell monolayer. L-Glutamine reduced the acetaldehyde-induced decrease in transepithelilal electrical resistance and increase in permeability to inulin and lipopolysaccharide in a time- and dose-dependent manner; d-glutamine, L-aspargine, L-arginine, L-lysine, or L-alanine produced no significant protection. The glutaminase inhibitor 6-diazo-5-oxo-L-norleucine failed to affect the L-glutamine-mediated protection of barrier function. L-Glutamine reduced the acetaldehyde-induced redistribution of occludin, zonula occludens-1 (ZO-1), E-cadherin, and beta-catenin from the intercellular junctions. Acetaldehyde dissociates occludin, ZO-1, E-cadherin, and beta-catenin from the actin cytoskeleton, and this effect was reduced by L-glutamine. L-Glutamine induced a rapid increase in the tyrosine phosphorylation of EGF receptor, and the protective effect of L-glutamine was prevented by AG1478, the EGF-receptor tyrosine kinase inhibitor. These results indicate that L-glutamine prevents acetaldehyde-induced disruption of the tight junction and increase in the paracellular permeability in Caco-2 cell monolayer by an EGF receptor-dependent mechanism.

A potential role for nuclear factor of activated T-cells in receptor tyrosine kinase and G-protein-coupled receptor agonist-induced cell proliferation.

We have studied the role of nuclear factor of activated T-cells (NFAT) transcription factors in the induction of vascular smooth muscle cell (VSMC) growth by platelet-derived growth factor-BB (PDGF-BB) and thrombin, the receptor tyrosine kinase (RTK) and G-protein-coupled receptor (GPCR) agonists, respectively. NFATc1 but not NFATc2 or NFATc3 was translocated from the cytoplasm to the nucleus upon treatment of VSMCs with PDGF-BB or thrombin. Translocation of NFATc1 was followed by an increase in NFAT-DNA binding activity and NFAT-dependent reporter gene expression. Cyclosporin A (CsA), a potent and specific inhibitor of calcineurin, a calcium/calmodulin-dependent serine phosphatase involved in the dephosphorylation and activation of NFATs, blocked NFAT-DNA binding activity and NFAT-dependent reporter gene expression induced by PDGF-BB and thrombin. CsA also completely inhibited PDGF-BB- and thrombin-induced VSMC growth, as measured by DNA synthesis and cell number. In addition, forced expression of the NFAT-competing peptide VIVIT for calcineurin binding significantly attenuated the DNA synthesis induced by PDGF-BB and thrombin in VSMCs. Together, these findings for the first time demonstrate a role for NFATs in RTK and GPCR agonist-induced growth in VSMCs.

Regulation of protein phosphatase 2A by hydrogen peroxide and glutathionylation.

The regulation of protein phosphatase 2A (PP2A) and protein threonine phosphorylation by H(2)O(2) was determined in Caco-2 cell monolayer. Incubation with H(2)O(2) (20 microM) resulted in threonine phosphorylation of a cluster of proteins at the molecular mass range of 170-250 kDa. PKC activity and plasma membrane localization of several isoforms of PKC were not affected by H(2)O(2). However, H(2)O(2) reduced 80-85% of okadaic acid-sensitive protein phosphatase activity. Immunocomplex protein phosphatase assay demonstrated that H(2)O(2) reduced the activity of PP2A, but not that of PP2C or PP1. Oxidized glutathione inhibited PP2A activity in plasma membranes prepared from Caco-2 cells and the phosphatase activity of an isolated PP2A. PP2A activity was also inhibited by N-ethylmaleimide, iodoacetamide, and p-chloromercuribenzoate. Inhibition of PP2A by oxidized glutathione was reversed by reduced glutathione. Glutathione also restored the PP2A activity in plasma membranes isolated from H(2)O(2)-treated Caco-2 cell monolayer. These results indicate that PP2A activity can be regulated by glutathionylation, and that H(2)O(2) inhibits PP2A in Caco-2 cells, which may involve glutathionylation of PP2A.

Inducible expression of mutant alpha-synuclein decreases proteasome activity and increases sensitivity to mitochondria-dependent apoptosis.

Parkinson's disease (PD) is a common progressive neurodegenerative disorder caused by the loss of dopaminergic neurons in the substantia nigra. Although mutations in alpha-synuclein have been identified in autosomal dominant PD, the mechanism by which dopaminergic neural cell death occurs remains unknown. Proteins encoded by two other genes in which mutations cause familial PD, parkin and UCH-L1, are involved in regulation of the ubiquitin-proteasome pathway, suggesting that dysregulation of the ubiquitin-proteasome pathway is involved in the mechanism by which these mutations cause PD. We established inducible PC12 cell lines in which wild-type or mutant alpha-synuclein can be de-repressed by removing doxycycline. Differentiated PC12 cell lines expressing mutant alpha-synuclein showed decreased activity of proteasomes without direct toxicity. Cells expressing mutant alpha-synuclein showed increased sensitivity to apoptotic cell death when treated with sub-toxic concentrations of an exogenous proteasome inhibitor. Apoptosis was accompanied by mitochondrial depolarization and elevation of caspase-3 and -9, and was blocked by cyclosporin A. These data suggest that expression of mutant alpha-synuclein results in sensitivity to impairment of proteasome activity, leading to mitochondrial abnormalities and neuronal cell death.

Glutathione oxidation and PTPase inhibition by hydrogen peroxide in Caco-2 cell monolayer.

The role of H(2)O(2) and protein thiol oxidation in oxidative stress-induced epithelial paracellular permeability was investigated in Caco-2 cell monolayers. Treatment with a H(2)O(2) generating system (xanthine oxidase + xanthine) or H(2)O(2) (20 microM) increased the paracellular permeability. Xanthine oxidase-induced permeability was potentiated by superoxide dismutase and prevented by catalase. H(2)O(2)-induced permeability was prevented by ferrous sulfate and potentiated by deferoxamine and 1,10-phenanthroline. GSH, N-acetyl-L-cysteine, dithiothreitol, mercaptosuccinate, and diethylmaleate inhibited H(2)O(2)-induced permeability, but it was potentiated by 1,3-bis(2-chloroethyl)-1-nitrosourea. H(2)O(2) reduced cellular GSH and protein thiols and increased GSSG. H(2)O(2)-mediated reduction of GSH-to-GSSG ratio was prevented by ferrous sulfate, GSH, N-acetyl-L-cysteine, diethylmaleate, and mercaptosuccinate and potentiated by 1,10-phenanthroline and 1, 3-bis(2-chloroethyl)-1-nitrosourea. Incubation of soluble fraction of cells with GSSG reduced protein tyrosine phosphatase (PTPase) activity, which was prevented by coincubation with GSH. PTPase activity was also lower in H(2)O(2)-treated cells. This study indicates that H(2)O(2), but not O(2)(-). or.OH, increases paracellular permeability of Caco-2 cell monolayer by a mechanism that involves oxidation of GSH and inhibition of PTPases.

Salivary epidermal growth factor plays a role in protection of ileal mucosal integrity.

The role of salivary epidermal growth factor (EGF) in the maintenance of ileal mucosal integrity was studied by evaluating the effects of sialoadenectomy on luminal EGF levels, ileal tissue resistance (Rt), and unidirectional flux of [51Cr]EDTA. Mice in groups 1 (SLX) and 2 (SLX + EGF) were subjected to sialoadenectomy, while mice in groups 3 (Sham) and 4 (Sham + EGF) underwent a sham procedure. All animals received normal diet and water, except that EGF (100 ng/ml) was added to water for SLX + EGF and Sham + EGF mice. At seven days after surgery, luminal EGF levels in gastrointestinal segments and ileal Rt were significantly reduced by sialoadenectomy, which was prevented by EGF supplementation. Unidirectional flux of [51Cr]EDTA was 6- to 22-fold greater in the ileum of sialoadenectomized mice, which was prevented by EGF administration. Results suggest that salivary EGF may be the major source of intestinal EGF, and it may play a role in maintenance of ileal mucosal integrity.

Oxidant-induced disruption of intestinal epithelial barrier function: role of protein tyrosine phosphorylation.

The effect of hydrogen peroxide (H2O2) on intestinal epithelial barrier function was examined in Caco-2 and T84 cell monolayers. H2O2 reduced transepithelial electrical resistance (TER) of Caco-2 and T84 cell monolayers. This decrease in TER was associated with a decrease in dilution potential and an increase in [3H]mannitol permeability, suggesting an H2O2-induced disruption of the paracellular junctional complexes. H2O2 administration also induced tyrosine phosphorylation of several proteins (at the molecular mass ranges of 50-90, 100-130, and 150-180 kDa) in Caco-2 cell monolayers. Phenylarsine oxide and sodium orthovanadate, inhibitors of protein tyrosine phosphatase, decreased TER and increased mannitol permeability and protein tyrosine phosphorylation (PTP). A low concentration of sodium orthovanadate also potentiated the effect of H2O2 on TER, dilution potential, mannitol permeability, and PTP. Pretreatment with genistein (30-300 microM) and tyrphostin (100 microM) inhibited the effect of H2O2 on TER, dilution potential, mannitol permeability, and PTP. These studies show that H2O2 increases the epithelial permeability by disrupting paracellular junctional complexes, most likely by a PTP-dependent mechanism.

Molecular variants of epidermal growth factor in malignant astrocytoma.

The present study has measured EGF levels in primary brain tumor tissues. EGF levels were measured by specific radioimmunoassay (RIA) and further analyzed by reversed-phase high performance liquid chromatography (RP-HPLC) followed by RIA and radioreceptor binding. The levels of EGF-like immunoreactivity (EGF-LI) in astrocytoma-IV tumors were fourfold greater than those in normal brain tissues. In astrocytoma-II and astrocytoma-III tumors, however, levels of EGF-LI were not different from those in normal brain. HPLC analysis of extracts from normal brain tissue and astrocytoma-II showed one peak of EGF-LI that coeluted with standard human EGF (retention time 22 min). Interestingly, EGF-LI in extracts of astrocytoma-IV tumors eluted in two distinct peaks with retention times of 24 and 26 min (Astro-A and Astro-B, respectively). Materials in both Astro-A and Astro-B peaks reduced the specific binding of [125I]hEGF to EGF receptors in human placental membranes. These studies demonstrate elevated levels of EGF-LI in malignant astrocytoma, but not in benign tumors. Furthermore, two different EGF-like molecules that are different from native EGF are present in malignant astrocytoma.

Tonic suppression of gastric acid secretion by endogenous peptides in neonatal rats.

Stimulation of gastric acid secretion by secretagogues was measured in developing rats by in vivo and in vitro techniques. Basal acid outputs in vivo were very low in 8- and 14-day-old rats compared with those in 20- and 30-day-old rats. In 20-day-old rats, all secretagogues increased acid output in vivo, whereas only carbachol, pentagastrin, and sulfated cholecystokinin octapeptide (CCK-8S) were active in 14-day-old rats. In contrast, basal acid output in vitro and stimulation by secretagogues did not differ significantly with age. CCK-8S-stimulated acid output in vitro in 14-day-old rats was blocked by L-365,260, L-364,718, tetrodotoxin, and atropine, but not by hexamethonium, whereas gastrin-stimulated acid output was blocked only by L-365,260. Furthermore, acid output in vivo was elevated three- to fourfold by subcutaneous naloxone-methiodide or L-364,718, but not by L-365,260, in 14-day-old rats; none of these antagonists produced an effect in 20-day-old rats. These studies show that low basal gastric acid output in neonatal rats is caused by tonic inhibitory regulation by endogenous regulatory peptides.

A randomized clinical trial in bronchogenic small-cell carcinoma evaluating alternating maintenance therapy of vincristine, adriamycin, procarbazine, and etoposide (VAPE) with cyclophosphamide, CCNU, and methotrexate (CCM) versus CCM maintenance alone in complete responders following VAPE induction and late intensification.

Initially, 109 evaluable patients with locally advanced or metastatic small cell lung cancer (SCLC) were treated with vincristine, Adriamycin, procarbazine, and etoposide (VAPE). Partial (PR) or nonresponders (NR) were crossed to CCM (cyclophosphamide, CCNU, and methotrexate) and then to HMiVe (hexamethylmelamine, mitomycin C, vinblastine) sequentially at maximum response. Complete responders (CR) were intensified by 50% with VAPE primarily and randomized to VAPE, alternating with CCM or CCM alone during maintenance. CR patients with limited disease received local thoracic irradiation and prophylactic cranial irradiation (PCI), whereas those with extensive disease received PCI alone. There were 45 patients (41%) who achieved a CR to chemotherapy, and 27 patients were eligible for randomization. Of 12 CR patients randomized to alternating therapy (VAPE/CCM), the median survival was 25.9 months compared to 12.9 months for 15 CR patients randomized to continuous CCM (P = .049). In addition, 35 patients achieved a PR (32%) and 29 were NR (27%). Overall median survivals were significantly different for the CR patients (13.0 months) as compared to PR (7.6 months) and NR patients (6.4 months). Late intensification did not appear to add substantially to survival while contributing to toxicity. In summary, VAPE is a new outpatient regimen for SCLC, which is highly effective as an induction regimen with moderate hematologic toxicity and predominantly gastrointestinal nonhematologic toxicity.

Ontogenic differences in the inhibition of gastric acid secretion by epidermal growth factor.

Gastric secretions were studied in rats by pyloric ligation in vivo. The effects of epidermal growth factor (EGF) administered s.c. on gastric secretion were evaluated at different stages of development (8, 14, 20 and 30 postnatal days). The rates of fluid, protein and acid outputs were very low in developing rats but increased in maturing rats. The rate of acid output in 8- day-old rats (3.83 +/- 1.16) was not different from that in 14-day-old rats (4.84 +/- 0.99), whereas the rate of acid output in 20-day-old rats was 11-fold greater than that in 14-day-old rats, and it was 21-fold greater in 30-day-old rats. Subcutaneous administration of 30 micrograms/kg b.wt. of EGF significantly suppressed the gastric secretion of fluid, protein and acid in 20- and 30-day-old rats. In 30-day-old rats, acid output was 85% lower at 1 hr after EGF administration and in 20-day-old rats it was 85% lower at 2 hr and 50% lower at 3 hr. Interestingly, EGF had no effect on basal gastric secretions in 8- and 14-day-old rats; EGF also had no effect on the gastric acid output that was stimulated by pentagastrin administration in 14-day-old rats. In 20-day-old rats, inhibitory effects of EGF lasted for 3 hr before gastric secretions rebounded to normal levels, but inhibition lasted for only 1 hr in 30-day-old rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of neuropeptide Y, peptide YY and sigma ligands on ion transport in mouse jejunum.

The effects of putative sigma ligands and two neuropeptides on intestinal ion transport were evaluated in isolated sheets of whole mouse jejunum mounted in Ussing flux chambers. Serosal administration of neuropeptide Y (NPY), peptide YY (PYY), (+)-N-cyclopropylmethyl-N-methyl-1,4- diphenyl-1-ethyl-but-3-en-1-ylamine hydrochloride (JO 1784), di(ortho-tolyl)guanidine (DTG) and (+)- or (-)-N-allyl-normetazocine (NANM) produced concentration-related decreases in short-circuit current (Isc) without changes in tissue conductance. Although NPY and PYY were active in nanomolar concentrations, JO 1784, DTG and (+)- and (-)-NANM were active in micromolar concentrations; the rank order of potency in inhibiting Isc was PYY > NPY >> JO 1784 = (-)-N- cyclopropylmethyl-N-methyl-1,4-diphenyl-1-ethyl-but-3-en-1-ylamine hydrochloride > DTG > (+)-NANM = (-)-NANM. Serosal application of tetrodotoxin effectively blocked the decrease in Isc associated with all of the ligands tested. The activity of the serosally applied ligands was blocked by prior application of chlorisondamine, a ganglionic blocker. The effects of JO 1784 and NPY were evaluated using antagonists of several receptor types. Although application of serosal haloperidol had no effect alone up to concentrations of 1 microM, this compound produced a rightward displacement in both the NPY and JO 1784 concentration-effect curves. In contrast, sulpiride, SCH-23390, naloxone, yohimbine and prazosin failed to antagonize the effects of NPY or JO 1784.(ABSTRACT TRUNCATED AT 250 WORDS)

A phase II clinical trial evaluating the use of two sequential, four-drug combination chemotherapy regimens in ambulatory bronchogenic adenocarcinoma patients.

Forty-three ambulatory patients with locally advanced or metastatic bronchogenic adenocarcinoma were sequentially treated with two potentially mutually non-cross-resistant chemotherapy regimens. A new regimen, MVPF (mitomycin-c, vinblastine, procarbazine, and 5-fluorouracil), was given until progressive disease occurred. Then, a second regimen--MOCC (methotrexate, vincristine [Oncovin], cyclophosphamide, and CCNU)--was initiated. At further progression, regional disease patients received radiotherapy, whereas extensive disease patients received Phase II agents. Of the 43 patients entered on the study, 40 were evaluable. Three patients withdrew early due to poor tolerance of the regimen. The response rate for MVPF was 33% (12 of 40 PR, 1 of 40 CR) compared to a 4% (1 of 23 PR) response for MOCC (difference: p < or = .03), for a total response rate of 35%. Although there was an initial improvement in survival for responders (31.7 weeks) versus nonresponders (15.7 weeks) at the 75th percentile (p < or = .05), there was no significant difference in median survival. The hematologic toxicity was equivalent for both groups, whereas nonhematologic toxicity revealed a high incidence of nausea and vomiting in the MVPF group. It is concluded that this approach lent itself well to ambulatory care, and MVPF could be considered an alternative to cyclophosphamide-based regimens. However, the absence of a meaningful CR rate and lack of influence of response on median survival were factors limiting its effectiveness.