Frequent STAT3 activation is associated with Mcl-1 expression in nasal NK-cell lymphoma.

Nasal natural killer (NK)-cell lymphoma was resistant to various antitumor agents. Although high expression of p-glycoprotein has been reported, other molecular mechanism of the chemo-resistance is largely unknown. Activation of STAT3 and expression of major apoptosis-related proteins Bcl-2, Bcl-x, and Mcl-1 were analyzed by immunohistochemistry. Effects of STAT3 inhibitor AG490 on NK-YS cell line were analyzed by Western blotting and flow cytometric apoptosis assay. STAT3 was activated in six of the nine nasal NK-cell lymphomas (67%). In contrast, STAT3 activation was detected in 35% of diffuse large B-cell lymphoma (DLBCL) and in 10% of follicular lymphoma (FL). Frequent activation of STAT3 was significantly correlated with Mcl-1 expression in nasal NK-cell lymphoma, i.e., Mcl-1 was positive in five of six STAT3-active cases and negative in all three STAT3-inactive ones. In DLBCL, not only six out of seven STAT3-active cases (86%) but also eight out of thirteen STAT3-inactive cases (62%) were positive for Mcl-1 expression. Latent membrane protein-1 was positive in four nasal NK-cell lymphomas, among which three cases showed intermediate STAT3 activation. Inhibition of STAT3 activation by JAK inhibitor AG490 decreased Mcl-1 expression and induced apoptosis in STAT3-active NK-YS cells. Serum starvation rather increased the Mcl-1 level in NK-YS cells, and this effect was also canceled by AG490. These results suggest that activation of STAT3-Mcl-1 axis may play a role in the chemotherapy resistance of nasal NK-cell lymphoma. The pathway may be one of the future therapeutic targets of this intractable disease.

Electron transmission characteristics of Au/1,4-benzenedithiol/Au junctions.

Electron transmission through individual 1,4-benzenedithiol molecules bridging between two gold electrodes (Au/BDT/Au junctions) has been studied by measuring the current-voltage (I-V) characteristics. Measurements were made at room temperature on three junction states of conductance 0.005G(0), 0.01G(0), and 0.1G(0), respectively, where G(0) is the quantum unit of conductance. All I-V curves are linear around zero bias and nonlinearly increase upward for biases above approximately 0.2 V. Absence of plateaus in the observed I-V characteristics up to +/- 1 V indicates that the electron transmission spectrum of Au/BDT/Au has no peaks within +/- 0.5 eV from the Fermi level.

Valacyclovir neurotoxicity: clinical experience and review of the literature.

Valacyclovir (VACV) is used increasingly to treat herpes zoster, although neuropsychiatric symptoms [VACV neurotoxicity (VAN) or acyclovir neurotoxicity], may accompany use of this drug. To promote awareness of this rare condition, we describe here two clinical cases of VAN we previously reported and review 20 cases from the literature. In all cases, chronic or acute renal failure preceded VAN. The symptoms of VAN varied, but disturbances of consciousness and hallucination occurred most commonly. When acute renal failure was due to the drug, recovery from both the disturbance of consciousness and renal failure followed within several days after discontinuation of VACV. Early recognition and diagnosis will ensure effective treatment of VAN.

Hsp90-inhibitor geldanamycin abrogates G2 arrest in p53-negative leukemia cell lines through the depletion of Chk1.

Checkpoint protein Chk1 has been identified as an Hsp90 client. Treatment with 100 nM geldanamycin (GM) for 24 h markedly reduced the Chk1 amount in Jurkat and ML-1 leukemia cell lines. Because Chk1 plays a central role in G2 checkpoint, we added GM to G2-arrested Jurkat and HL-60 cells pretreated with 50 nM doxorubicin for 24 h. GM slowly released both cell lines from doxorubicin-induced G2 arrest into G1 phase. GM also abrogated ICRF-193-induced decatenation G2 checkpoint in Jurkat and HL-60 cells. Western blot analysis showed that addition of GM attenuates doxorubicin- and ICRF-193-induced Chk1 phosphorylation at Ser345. GM, however, failed to abrogate G2 arrest in p53-positive ML-1 cells maybe due to the p21 induction. GM released HeLa cells from doxorubicin-induced G2 arrest but trapped them at M phase. Flow cytometric analysis showed that addition of GM converted doxorubicin-induced necrosis into apoptosis in Jurkat cells. Colony assay indicated that although GM has a weak cytotoxic effect as a single agent, it dramatically intensifies the cytotoxicity of doxorubicin and ICRF-193 in Jurkat and HL-60 cells. These results suggest that abrogation of G2 checkpoint by GM may play a central role in sensitizing p53-negative tumor cells to DNA-damaging and decatenation-inhibiting agents.

Dopamine stabilizes milrinone-induced changes in heart rate and arterial pressure during anaesthesia with isoflurane.

BACKGROUND AND OBJECTIVE: Phosphodiesterase-III inhibitors and dobutamine effectively improve cardiac function in patients with cardiac failure, but they are limited by possible hypotensive effects. We tested the hypothesis that dopamine contributes to stabilizing milrinone-induced haemodynamic changes. METHODS: Nine patients undergoing major surgery were anaesthetized using nitrous oxide and oxygen supplemented with isoflurane 1-2%. After baseline haemodynamics were recorded, milrinone (25 or 50 microg kg(-1)) was administered over 10min, followed by a continuous infusion (0.5 microg kg(-1) min(-1). The second set of haemodynamic values was measured 50 min after beginning the continuous infusion of milrinone. Dopamine (4 microg kg(-1) min(-1)) was then administered with milrinone. RESULTS: Milrinone significantly increased the heart rate from 81 +/- 8 to 102 +/- 16beats min(-1), but it decreased the mean arterial pressure from 83 +/- 10 to 66 +/- 10 mmHg and systemic vascular resistance (P < 0.05 for each). The pulmonary capillary wedge pressure, cardiac index and pulmonary vascular resistance did not change significantly. The addition of dopamine to the milrinone infusion significantly decreased the heart rate (94 +/- 12 beats min(-1)) and increased the mean arterial pressure (82 +/- 11 mmHg). Dopamine and milrinone, but not milrinone alone, significantly increased the cardiac index and the rate-pressure product. CONCLUSIONS: The combination regimen of milrinone and dopamine improved cardiac function, and changes in heart rate and mean arterial pressure induced by milrinone were attenuated by dopamine. The results suggest that a combination regimen of milrinone and dopamine rather than milrinone alone should be used to maintain arterial pressure.

Overexpression of EC-SOD suppresses endothelial-cell-mediated LDL oxidation.

Reactive oxygen species have been proposed to play important roles in atherosclerosis. To investigate the protective role of extracellular superoxide dismutase (EC-SOD), its inhibition of endothelial-cell-mediated LDL oxidation was examined. We constructed the recombinant adenovirus AxCAEC-SOD expressing human EC-SOD by CAG promoter. Infection of endothelial cells with AxCAEC-SOD resulted in EC-SOD protein secretion in a dose-dependent manner and a decrease of endothelial-cell-derived superoxide production. Moreover, it was proven to coexist with heparan sulfate by immunohistochemical staining. Endothelial-cell-mediated LDL oxidation enhanced by ferric-sodium EDTA was inhibited by 47% in TBARS formation by AxCAEC-SOD infection. In agarose gel electrophoresis, AxCAEC-SOD decreased the negative charge of oxidized LDL by 50% and suppressed fragmentation of apolipoprotein B. These results suggested that human EC-SOD localized in the extracellular space and reduced endothelial-cell-mediated LDL oxidation. In subendothelial space, EC-SOD bound on heparan sulfate might suppress LDL oxidation through reduction of superoxide anion.

Inhibition of drug-metabolizing enzyme activity in human hepatic cytochrome P450s by bisphenol A.

Effect of bisphenol A on drug-metabolizing enzyme activities by human hepatic cytochrome P450s (CYP) was investigated. We measured aminopyrine N-demethylation by eleven kinds of cDNA-expressed CYPs. CYP2C19 and CYP2B6 catalyzed most efficiently the aminopyrine N-demethylation, followed by CYP2C8 and CYP2D6. Bisphenol A (1 mM) most efficiently inhibited aminopyrine N-demethylation by CYP2C8 and CYP2C19 by 82% and 85%, respectively, whereas inhibition of the activities by CYP 2B6 and 2D6 was less than 40%. Bisphenol A exhibited a noncompetitive-type inhibition of aminopyrine N-demethylase activity by CYP2C8 with Ki value of 97 microM. Additionally, we investigated the inhibitory effect of bisphenol A on CYP2C19-mediated S-mephenytoin 4-hydroxylation. Bisphenol A exhibited a mixed-type inhibition with Ki value of 113 microM. These results suggest that bisphenol A inhibits human hepatic CYP activities, especially CYP2C8 and CYP2C19.

B(1) and B(2) bradykinin receptors on adventitial fibroblasts of cerebral arteries are coupled to recombinant eNOS.

Our previous ex vivo and in vivo studies reported that expression of the recombinant endothelial nitric oxide (NO) synthase (eNOS) gene in adventitial fibroblasts recovers NO production in arteries without endothelium in response to bradykinin. The present study was designed to characterize subtypes of bradykinin receptors on adventitial fibroblasts coupled to the activation of recombinant eNOS. Endothelium-denuded segments of canine basilar arteries were transduced with beta-galactosidase (beta-Gal) gene or eNOS gene ex vivo, using a replication-defective adenoviral vector (10(10) plaque-forming units/ml) for 30 min at 37 degrees C. Twenty-four hours later, isometric force recording or cGMP measurement was carried out. B(1) bradykinin receptor agonist (des-Arg(9)-bradykinin, 10(-10)-10(-8) mol/l) did not significantly affect vascular tone in control or beta-Gal gene-transduced canine basilar arteries without endothelium. In contrast, this agonist caused concentration-dependent relaxations in recombinant eNOS gene-transduced arteries without endothelium. Relaxations to B(1) receptor agonist in the eNOS arteries were abolished by B(1) receptor antagonist (des-Arg(9)-[Leu(8)]bradykinin, 6 x 10(-9) mol/l) but not by B(2) receptor antagonist (Hoe-140, 5 x 10(-8) mol/l). Bradykinin did not significantly alter vascular tone in control or beta-gal arteries without endothelium, whereas this peptide (10(-11)-10(-8) mol/l) induced concentration-dependent relaxations, as well as an increase in cGMP formation in endothelium-denuded eNOS-transduced arteries. Stimulatory effects of bradykinin were prevented in the presence of a B(2) receptor antagonist but not in the presence of a B(1) receptor antagonist. B(1) and B(2) receptor antagonists had no effect on relaxations to substance P, confirming the selectivity of the compounds. Our results suggest that B(1) and B(2) bradykinin receptors are coupled to activation of recombinant eNOS expressed in adventitial fibroblasts.

Effects of recombinant eNOS gene expression on reactivity of small cerebral arteries.

Resistance arteries are an important target for vascular gene therapy because they play a key role in the regulation of tissue blood flow. The present study was designed to determine the effects of recombinant endothelial (e) nitric oxide synthase (NOS) gene expression on vasomotor reactivity of small brain stem arteries (internal diameter, 253 +/- 2.5 microm). Arterial rings were exposed ex vivo to an adenoviral vector (10(9) and 10(10) plaque-forming units/ml) encoding eNOS gene or beta-galactosidase gene. Twenty-four hours after transduction, vascular function was examined by isometric force studies. Transgene expression was evident mainly in adventitia. In arteries with endothelium transduced with eNOS gene but not with control beta-galactosidase gene, relaxations to bradykinin and substance P were significantly augmented. Removal of endothelium abolished relaxations to bradykinin and substance P in control and beta-galactosidase arteries. However, in endothelium-denuded arteries transduced with recombinant eNOS, bradykinin and substance P caused relaxations that were abolished in the presence of the NOS inhibitor N(G)-nitro-L-arginine methyl ester. In control arteries, endothelium removal augmented relaxations to the nitric oxide donors sodium nitroprusside and diethylamine NONOate. This augmentation was absent in eNOS gene-transduced arteries without endothelium. Our results suggest that, in small brain stem arteries, expression of recombinant eNOS increases biosynthesis of nitric oxide. Adventitia of small arteries is a good target for expression of recombinant eNOS. Genetically engineered adventitial cells may serve as a substitute source of nitric oxide in cerebral arteries with dysfunctional endothelium.

[A late phase II study of raltitrexed (ZD 1694) in chemotherapy-naive patients with advanced colorectal cancer].

A multicenter co-operative late phase II study of raltitrexed (ZD1694), a specific thymidylate synthase (TS) inhibitor, was conducted in chemotherapy-naive patients with advanced colorectal cancer. Raltitrexed was infused intravenously over 15 minutes once every three weeks. Between April 1996 and September 1998, 61 patients were enrolled and 58 were eligible. Fourteen patients experienced a partial response (PR), 22 no change (NC), 20 progressive disease (PD) and 2 no evaluable (NE). The overall response rate was 24.1% (95% CI: 13.9-37.2%). Responses were seen in lung (22.7%), liver (22.9%) and deep lymph nodes (10.0%). Median survival was 11.6 months. Grade 3 or 4 toxicities were: leukopenia (13.8%), neutropenia (24.1%), hemoglobin decrease (15.5%), FBC decrease (6.9%), hematocrit decrease (6.9%), thrombocytopenia (6.9%), transient SGPT increase (6.9%), nausea/vomiting (20.7%), anorexia (15.5%), and asthenia (6.9%). These adverse reactions were considered to be manageable. Only one death was associated with drug treatment. These results suggest that raltitrexed provides an effective and convenient treatment for patients with advanced and previously untreated colorectal cancer.

[A case of advanced gastric cancer with abdominal para-aortic lymph node metastasis successfully treated with FLP therapy].

A 73-year-old woman was admitted to our hospital in June 1998, suffering from upper abdominal pain. The upper G-I series and endoscopic examination revealed stenosis of the pylorus and antrum by a type 2 cancer, and a poorly differentiated adenocarcinoma and a signet-ring cell carcinoma were confirmed on endoscopic biopsy. A CT scan showed the enlargement of many regional and abdominal para-aortic lymph nodes. FLP therapy combined with cisplatin (50 mg/m2 drip i.v., day 1-8), 5-fluorouracil (333 mg/m2 drip i.v.) and leucovorin (30 mg/body i.v., day 1-8) was planned for neoadjuvant chemotherapy (NAC) in order to reduce or eliminate the tumor and increase curability. After two cycles of the FLP therapy, the tumor size shrunk remarkably and the enlargement of the para-aortic lymph nodes disappeared. Distal gastrectomy with extended lymphadenectomy and cholecystectomy was performed. The histological findings of the primary tumor and metastatic lymph nodes demonstrated massive cancer cell degeneration such as pycnosis and vacuolation, xanthogranulomatous inflammation and dense fibrosis. The effect of NAC was judged to be grade 2 histologically. FLP therapy is an effective and safe regimen for NAC.

Adventitial expression of recombinant endothelial nitric oxide synthase gene reverses vasoconstrictor effect of endothelin-1.

The present study was designed to determine the effect of recombinant endothelial nitric oxide synthase (eNOS) gene expression on reactivity of canine basilar arteries to endothelin-1 (ET-1). Experiments were performed ex vivo. The arteries were exposed (30 minutes at 37 degrees C) to adenoviral vectors encoding eNOS gene (AdCMVeNOS) or beta-galactosidase reporter gene (AdCMVbeta-Gal). Twenty-four hours after transduction, transgene expression was evident mainly in the vascular adventitia. Rings of control (nontransduced), AdCMVbeta-Gal- and AdCMVeNOS-transduced arteries with and without endothelium were suspended for isometric tension recording. Levels of guanosine 3',5'-cyclic monophosphate (cGMP) were measured by radioimmunoassay. During contractions to uridine 5'-triphosphate, ET-1 (10(-10) to 3x10(-9) mol/L) caused further increase in tension in control and AdCMVbeta-Gal-transduced arteries. In contrast, ET-1 caused concentration-dependent relaxations of AdCMVeNOS-transduced arteries. The relaxations to ET-1 in AdCMVeNOS-transduced arteries were endothelium-independent. They were abolished by N(G)-nitro-L-arginine methyl ester or by chemical treatment of adventitia with paraformaldehyde before gene transfer. ET-1 (10(-9) mol/L) significantly increased intracellular cGMP levels in AdCMVeNOS-transduced arteries without endothelium. In arteries transduced with AdCMVeNOS, higher concentrations (10(-9) to 3x10(-8) mol/L) of ET-2 also caused relaxations, whereas ET-3 and sarafotoxin, a selective ET(B) receptor agonist, did not produce any relaxations. The relaxations to ET-1 in AdCMVeNOS-transduced arteries were strongly reduced by BQ-123 (10(-7) mol/L), an ET(A) receptor antagonist, but were not affected by BQ-788 (3x10(-7) mol/L), an ET(B) receptor antagonist. These results suggest that genetically modified adventitia can produce nitric oxide and cause relaxations in response to ET-1 via activation of ET(A) receptors. Our findings support a novel concept that successful transfer and expression of recombinant eNOS gene can lead to a qualitative change in responsiveness to vasoconstrictor substances.

Modification of low density lipoprotein potentiates its inhibitory effect on catecholamine secretion in cultured bovine adrenal medullary cells.

Low density lipoprotein (LDL) and lipoprotein(a) suppress catecholamine secretion in cultured adrenal medullary cells. Modification of LDL by oxidation or acetylation potentiates various atherogenic actions of LDL. In the present study, we investigated whether the modification of LDL influences catecholamine secretion in cultured bovine adrenal medullary cells. The exposure of LDL to CuSO4 caused a time-dependent oxidation of LDL. Maximal oxidation of LDL was observed after exposure to CuSO4 for 24 h. Native LDL inhibited catecholamine secretion induced by carbachol to 68.5% of control. Oxidized LDL caused further inhibition of carbachol-evoked secretion to 37.6% of control. Acetylated LDL inhibited it to 41.0% of control. There was a good correlation between the extent of LDL oxidation and the inhibition of catecholamine secretion. These results suggest that oxidation or acetylation of LDL augments its inhibitory effect on the secretion of catecholamines. Since catecholamines are a risk factor of atherosclerosis, the inhibitory effect by such modified LDL may be a mechanism inhibiting atherosclerotic progression.

Adventitia-dependent relaxations of canine basilar arteries transduced with recombinant eNOS gene.

We recently reported that expression of recombinant endothelial nitric oxide (NO) synthase (eNOS) gene in adventitial fibroblasts restores NO formation in canine cerebral arteries without endothelium in response to bradykinin ex vivo and in vivo. The present study was designed to further characterize the stimuli that can activate recombinant eNOS enzyme expressed in the adventitia of cerebral arteries. To stimulate recombinant eNOS, we used serum (0. 1-10%), substance P (10(-11)-3 x 10(-9) M), and ANG II (10(-7)-10(-5) M) because they increase intracellular calcium concentrations in fibroblasts. Endothelium-denuded segments of canine basilar arteries were incubated with an adenoviral vector encoding beta-galactosidase gene or eNOS gene for 30 min at 37 degrees C. After 24 h, vasomotor activity and cGMP formation in eNOS or beta-galactosidase arteries were examined by isometric force recording and by radioimmunoassay, respectively. In control arteries and beta-galactosidase gene-transduced arteries, serum caused concentration-dependent contractions, whereas in recombinant eNOS gene-transduced arteries, serum produced concentration-dependent relaxations. Substance P and ANG II had no effect on vascular tone in control and beta-galactosidase arteries but caused concentration-dependent relaxations as well as a significant increase in cGMP levels in eNOS arteries. These relaxations were blocked by the NOS inhibitor NG-nitro-L-arginine methyl ester. Chemical treatment or mechanical inactivation of adventitial function significantly attenuated substance P-induced relaxations and ANG II-induced relaxations. These findings demonstrate that serum, substance P, and ANG II cause adventitia-dependent relaxations in cerebral arteries expressing the recombinant eNOS gene. This mechanism of vasodilatation may have beneficial effects in the prevention and treatment of vascular disorders characterized by the diminished bioavailability of NO, such as cerebral vasospasm.

Visualization of prekinetochore locus on the centromeric region of highly extended chromatin fibers: does kinetochore autoantigen CENP-C constitute a kinetochore organizing center?

Kinetochore is morphologically defined as a trilaminated, highly differentiated structure at the primary constriction of mitotic chromosomes. This subcellular organella is assumed to be composed of DNA and proteins. Immunoelectron microscopy has shown that centromere autoantigens CENP-C and CENP-B localize to the kinetochore inner plate and the underlying centromeric region respectively. We previously indicated that both are DNA-binding proteins that constitute centromeric heterochromatin throughout the cell cycle. Here, we tried to elucidate how these molecules are involved in the kinetochore/centromere organization in vivo by analyzing their morphological behavior in nuclei. Using immunofluorescence microscopy, we found that CENP-C remained as round discrete dots, whereas CENP-B displayed larger surrounding materials. To examine the CENP-C-binding locus on the genome, we prepared highly extended chromatin fibers and performed simultaneous immunofluorescence and fluorescence in situ hybridization. We obsreved that centromeric alphoid DNA, targeted by CENP-B, was highly dispersed, whereas the CENP-C antigen persisted as small dots well situated on the fibers. These features reminded us of the 'ball and cup' structure that had been presented for 'prekinetochore'. We propose here that CENP-C constitutes a 'kinetochore organizing center' tightly associating with DNA, whereas CENP-B heterochromatin offers the solid support during kinetochore maturation.

Cell-free production and stable-isotope labeling of milligram quantities of proteins.

We have improved the productivity of an Escherichia coli cell-free protein synthesis system. First, creatine phosphate and creatine kinase were used as the energy source regeneration system, and the other components of the reaction mixture were optimized. Second, the E. coli S30 cell extract was condensed by dialysis against a polyethylene glycol solution to increase the rate of synthesis. Third, during the protein synthesis, the reaction mixture was dialyzed against a low-molecular-weight substrate solution to prolong the reaction. Thus, the yield of chloramphenicol acetyltransferase was raised to 6 mg/ml of reaction mixture. Stable-isotope labeling of a protein with 13C/15N-labeled amino acids for NMR spectroscopy was achieved by this method.

Enantioselectivity of bunitrolol 4-hydroxylation is reversed by the change of an amino acid residue from valine to methionine at position 374 of cytochrome P450-2D6.

The enantioselectivity of 4-hydroxylation of bunitrolol (BTL), a beta-adrenoceptor blocking drug, was studied in microsomes from human liver, human hepatoma (Hep G2) cells expressing CYP2D6, and lymphoblastoid cells expressing CYP2D6. Kinetics in human liver microsomes showed that the Vmax value for (+)-BTL was 2.1-fold that of (-)-BTL, and that the Km value for (+)-BTL was lower than that for the (-)-antipode, resulting in the intrinsic clearance (Vmax/Km) of (+)-BTL being 2.1-fold over its (-)-antipode. CYP2D6 (CYP2D6-met) expressed in Hep G2 cells had a methionine residue at position 373 of the amino acid sequence and a rat-type N-terminal peptide (MELLNGTGLWSM) instead of the human-type (MGLEALVPLAVIV), and showed enantioselectivity of [(+)-BTL < (-)-BTL] for the rate of BTL 4-hydroxylation. In contrast, enantioselectivity [(+)-BTL > (-)-BTL] for Hep G2-CYP2D6 (CYP2D6-val) with a human-type N-terminal peptide that had a valine residue at 374, which corresponds to the methionine of the CYP2D6-met variant, was the same as that for human liver microsomes. We further confirmed that CYP2D6-met and CYP2D6-val expressed in human lymphoblastoid cells, both of which have methionine and valine, respectively, at position 374 and a human-type N-terminal peptide, exhibited the same enantioselectivities as those obtained from CYP2D6-met and CYP2D6-val expressed in the Hep G2 cell system. These results indicate that the amino acid at 374 of CYP2D6 is one of the key factors influencing the enantioselectivity of BTL 4-hydroxylation.

Atherogenic lipoproteins inhibit catecholamine secretion in cultured bovine adrenal medullary cells.

The effects of lipoproteins on ion channel-mediated catecholamine secretion were investigated in cultured bovine adrenal medullary cells. Low density lipoprotein (LDL: 20-80 mg/dl) and lipoprotein(a) [Lp(a); 10-80 mg/dl] inhibited catecholamine secretion induced by carbachol, an activator of nicotinic acetylcholine receptor-ion channels. LDL and Lp(a) suppressed carbachol-induced 22Na+ influx as well as 45Ca2+ influx in a concentration-dependent manner similar to that of catecholamine secretion. The inhibition of catecholamine secretion by Lp(a) was not overcome by increasing the concentration of carbachol. On the other hand, high density lipoprotein (HDL; < 150 mg/dl) had no effect on 22Na+ influx, 45Ca2+ influx, and catecholamine secretion. Like LDL and Lp(a), a synthetic peptide homologous to human plasma apolipoprotein B (apoB), apoB fragment(3358-3372)-amide (3-60 microM), attenuated 22Na+ influx, 45Ca2+ influx, and catecholamine secretion caused by carbachol. The apoB fragment also suppressed 22Na+ influx induced by veratridine (an activator of voltage-dependent Na+ channels) and 45Ca2+ influx induced by 56 mM K+ (an indirect activator of voltage-dependent Ca2+ channels). These findings suggest that atherogenic lipoproteins such as LDL and Lp(a) suppress catecholamine secretion by interfering with Na+ influx through nicotinic acetylcholine receptor-ion channels, in which apoB, a structural component common to both LDL and Lp(a), plays an important role. The inhibition by atherogenic lipoproteins of catecholamine secretion may influence the progression of atherosclerosis induced by these lipoproteins.