Mechanics of living cells measured by laser tracking microrheology

To establish laser-tracking microrheology (LTM) as a new technique for quantifying cytoskeletal mechanics, we measure viscoelastic moduli with wide bandwidth (5 decades) within living cells. With the first subcellular measurements of viscoelastic phase angles, LTM provides estimates of solid versus liquid behavior at different frequencies. In LTM, the viscoelastic shear moduli are inferred from the Brownian motion of particles embedded in the cytoskeletal network. Custom laser optoelectronics provide sub-nanometer and near-microsecond resolution of particle trajectories. The kidney epithelial cell line, COS7, has numerous spherical lipid-storage granules that are ideal probes for noninvasive LTM. Although most granules are percolating through perinuclear spaces, a subset of perinuclear granules is embedded in dense viscoelastic cytoplasm. Over all time scales embedded particles exhibit subdiffusive behavior and are not merely tethered by molecular motors. At low frequencies, lamellar regions (820 +/- 520 dyne/cm(2)) are more rigid than viscoelastic perinuclear regions (330 +/- 250 dyne/cm(2), p < 0.0001), but spectra converge at high frequencies. Although the actin-disrupting agent, latrunculin A, softens and liquefies lamellae, physiological levels of F-actin, alone (11 +/- 1.2 dyne/cm(2)) are approximately 70-fold softer than lamellae. Therefore, F-actin is necessary for lamellae mechanics, but not sufficient. Furthermore, in time-lapse of apparently quiescent cells, individual lamellar granules can show approximately 4-fold changes in moduli that last >10 s. Over a broad range of frequencies (0.1-30, 000 rad/s), LTM provides a unique ability to noninvasively quantify dynamic, local changes in cell viscoelasticity.

Antitumor agents. 199. Three-dimensional quantitative structure-activity relationship study of the colchicine binding site ligands using comparative molecular field analysis

Inhibitors of tubulin polymerization interacting at the colchicine binding site are potential anticancer agents. We have been involved in the synthesis of a number of colchicine site agents, such as thiocolchicinoids and allocolchicinoids, which are colchicine analogues, and 2-phenyl-quinolones and 2-aryl-naphthyridinones, which are the amino analogues of cytotoxic antimitotic flavonoids. The most cytotoxic of the latter compounds strongly inhibit binding of radiolabeled colchicine to tubulin, and these agents therefore probably bind in the colchicine site of tubulin. We have applied conventional CoMFA and q(2)-GRS CoMFA to identify the essential structural requirements for increasing the ability of these compounds to form tubulin complexes. The CoMFA model for the training set of 51 compounds yielded cross-validated R(2) (q(2)) values of 0.637 for conventional CoMFA and 0.692 for q(2)-GRS CoMFA. The predictive power of this model was confirmed by successful activity prediction for a test set of 53 compounds with known potencies as inhibitors of tubulin polymerization. The activities of 88% of the compounds were predicted with absolute value of residuals of less than 0.5. The predictive q(2) values were 0.546 for conventional CoMFA and 0.426 for q(2)-GRS CoMFA. The conventional CoMFA model with the highest predictive q(2) (0.546) was analyzed in detail in terms of underlying structure-activity relationships.

An appliance to replace prematurely lost maxillary anterior teeth using double stainless steel crowns on abutment teeth

This paper describes an appliance to replace prematurely lost maxillary anterior teeth. The prosthesis is different from previous appliance designs, since it uses double stainless steel crowns on abutment teeth, and uses a donor cast to fabricate artificial teeth. A case is presented describing laboratory and office procedures.

Antitumor agents. 196. Substituted 2-thienyl-1,8-naphthyridin-4-ones: their synthesis, cytotoxicity, and inhibition of tubulin polymerization

As part of our continuing search for potential anticancer drug candidates in the 2-aryl-1,8-naphthyridin-4-one series, we have synthesized a series of substituted 2-thienyl-1, 8-naphthyridin-4-ones. Most compounds showed significant cytotoxic effects (log GI(50) < -4.0; log molar drug concentration required to cause 50% growth inhibition) against a variety of human tumor cell lines in the National Cancer Institute's in vitro screen, including cells derived from solid tumors such as non-small-cell lung, colon, central nervous system, melanoma, ovarian, prostate, and breast cancers. The most active compounds (31-33,40) demonstrated strong cytotoxic effects with ED(50) values in the micromolar or submicromolar range in most of the tumor cell lines. The most cytotoxic compounds inhibited tubulin polymerization at concentrations substoichiometric to the tubulin concentration. The most potent inhibitors of polymerization (40,42,43) had effects comparable to those of the potent antimitotic natural products podophyllotoxin and combretastatin A-4 and to that of NSC 664171, a particularly potent, structurally related analogue. Only compound 40 was a potent inhibitor of the binding of radiolabeled colchicine to tubulin, and it was both the most cytotoxic agent and the most effective inhibitor of polymerization among the newly synthesized compounds.

YC-1 potentiates the antiplatelet effect of hydrogen peroxide via sensitization of soluble guanylate cyclase

In the present study, we showed that 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), a nitric oxide (NO)-independent activator of soluble guanylate cyclase, could potentiate H2O2-induced inhibition of platelet aggregation and increase of platelet cGMP levels. The synergistic effect of YC-1 and H2O2 on platelet aggregation and increases of cGMP were almost completely prevented by catalase and a selective soluble guanylate cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), or partially attenuated by the hydroxyl radical scavenger mannitol. In contrast, superoxide dismutase failed to influence H2O2/YC-1-induced inhibition of aggregation. Furthermore, YC-1 could enhance the activation of soluble guanylate cyclase caused by FeSO4/H2O2 and, this effect was prevented markedly by mannitol. These results suggest that YC-1 may enhance the antiaggregatory effect of H2O2 via the sensitization of platelet soluble guanylate cyclase. In addition, this phenomenon is, at least in part, dependent on H2O2-derived hydroxyl radical.

Additive effect of Sp1 and Sp3 in regulation of the ED-L1E promoter of the EBV LMP 1 gene in human epithelial cells

The ED-L1E promoter of the LMP 1 gene is a GC box-containing promoter. To test if Sp1/Sp3 are important for modulating ED-L1E promoter activity through the GC box, site-specific mutation and deletion constructs carrying a reporter gene were transfected into NPCTW076 and C33A cells. Results showed that deletion or mutation of the GC box abolished ED-L1E activity. Association of Sp1/Sp3 with the GC box was confirmed by electrophoretic mobility shift and supershift assays using Sp1- and Sp3-specific antibodies. Transfection of Sp1- and Sp3-expressing vectors into NPCTW076 and Sp-deficient Drosophila SL2 cells activated ED-L1E in a dose-dependent fashion and showed an additive effect. Data suggest that both factors may function as transcriptional activators and regulate the ED-L1E promoter in human epithelial cells.

Synthesis and cytotoxicity of methyl-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dione derivatives

2- and 3-Methyl-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dione and related derivatives were synthesized and evaluated in vitro by NCI against eight cancer types. Compounds 12-15 showed significant activity against melanoma, NCI-H23 non-small cell lung cancer, and MDA-MB-435 and MDA-N breast cancer cell lines; 2-hydroxymethyl-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dion e (13) showed the highest activity against melanoma (mean log GI50 = -7.74) and the highest overall potency (mean log GI50 = -6.99).

Motile properties of the kinesin-related Cin8p spindle motor extracted from Saccharomyces cerevisiae cells

We have developed microtubule binding and motility assays for Cin8p, a kinesin-related mitotic spindle motor protein from Saccharomyces cerevisiae. The methods examine Cin8p rapidly purified from crude yeast cell extracts. We created a recombinant form of CIN8 that fused the biotin carrying polypeptide from yeast pyruvate carboxylase to the carboxyl terminus of Cin8p. This form was biotinated in yeast cells and provided Cin8p activity in vivo. Avidin-coated glass surfaces were used to specifically bind biotinated Cin8p from crude extracts. Microtubules bound to the Cin8p-coated surfaces and moved at 3.4 +/- 0.5 micrometer/min in the presence of ATP. Force production by Cin8p was directed toward the plus ends of microtubules. A mutation affecting the microtubule-binding site within the motor domain (cin8-F467A) decreased Cin8p's ability to bind microtubules to the glass surface by >10-fold, but reduced gliding velocity by only 35%. The cin8-3 mutant form, affecting the alpha2 helix of the motor domain, caused a moderate defect in microtubule binding, but motility was severely affected. cin8-F467A cells, but not cin8-3 cells, were greatly impaired in bipolar spindle forming ability. We conclude that microtubule binding by Cin8p is more important than motility for proper spindle formation.

Differential effects of IL-2 and IL-15 on the death and survival of activated TCR gamma delta+ intestinal intraepithelial lymphocytes

TCR gamma delta+ cells are enriched in the intestine mucosa and constitute approximately half of the intestinal intraepithelial lymphocytes (iIEL) in mice. They are likely activated by self and foreign Ags in situ, but little is known about how the activated gamma delta iIEL are regulated. In the iIEL compartment, IL-2 is produced by activated TCR alpha beta+ iIEL, and IL-15 message is detected in iIEL and in the epithelial cells. We found surface expression of IL-2 as well as IL-15Rs on activated gamma delta iIEL, and examined the effects of IL-2 and IL-15 on the survival and death of gamma delta iIEL during secondary stimulation through TCR. We found that both cytokines supported growth of the restimulated gamma delta iIEL, but exerted different effects on their survival. A significant higher number of live cells were recovered from the gamma delta iIEL cultures restimulated in IL-15 than in IL-2. Quantitation of apoptotic cells showed more cell death in the IL-2 group than in the IL-15 group. The cell death was associated with restimulation through TCR and was not caused by insufficient growth factor, thus representing activation-induced cell death. Western blot analyses found no difference in the levels of Bcl-2 and Bax proteins between the two groups. However, the level of Bcl-xL protein diminished with time in the IL-2 group whereas the level was sustained in the IL-15 group, which may contribute to the pro-survival effect of IL-15. These results demonstrated that the survival of activated gamma delta iIEL is differentially regulated by IL-2 and IL-15.

Diffusing wave spectroscopy microrheology of actin filament networks

Filamentous actin (F-actin), one of the constituents of the cytoskeleton, is believed to be the most important participant in the motion and mechanical integrity of eukaryotic cells. Traditionally, the viscoelastic moduli of F-actin networks have been measured by imposing a small mechanical strain and quantifying the resulting stress. The magnitude of the viscoelastic moduli, their concentration dependence and strain dependence, as well as the viscoelastic nature (solid-like or liquid-like) of networks of uncross-linked F-actin, have been the subjects of debate. Although this paper helps to resolve the debate and establishes the extent of the linear regime of F-actin networks' rheology, we report novel measurements of the high-frequency behavior of networks of F-actin, using a noninvasive light-scattering based technique, diffusing wave spectroscopy (DWS). Because no external strain is applied, our optical assay generates measurements of the mechanical properties of F-actin networks that avoid many ambiguities inherent in mechanical measurements. We observe that the elastic modulus has a small magnitude, no strain dependence, and a weak concentration dependence. Therefore, F-actin alone is not sufficient to generate the elastic modulus necessary to sustain the structural rigidity of most cells or support new cellular protrusions. Unlike previous studies, our measurements show that the mechanical properties of F-actin are highly dependent on the frequency content of the deformation. We show that the loss modulus unexpectedly dominates the elastic modulus at high frequencies, which are key for fast transitions. Finally, the measured mean square displacement of the optical probes, which is also generated by DWS measurements, offers new insight into the local bending fluctuations of the individual actin filaments and shows how they generate enhanced dissipation at short time scales.

Terpenoids of Syzygium formosanum

A new natural product, 4-epifriedelin (1), and 12 known terpenoids have been isolated from the leaves of Syzygium formosanum. The known compounds include caryophyllene oxide, friedelin, canophyllal, glutinol, alpha-terpineol, phytol, betulinic acid, uvaol, lupeol, betulin, ursolic acid, and oleanolic acid. All of these compounds are reported for the first time from S. formosanum.

Synthesis and antiplatelet, antiinflammatory, and antiallergic activities of substituted 3-chloro-5,8-dimethoxy-1,4-naphthoquinone and related compounds

2-Amino (6), 2-alkylamino (7-8), 2-methoxy (9), 2-acetamido (10), and 5,8-diacetoxy (11) derivatives of the lead compound 2,3-dichloro-5,8-dimethoxy-1,4-naphthoquinone (4) were synthesized, together with 6,7-dichloro-5,8dimethoxy-1,4-naphthoquinone (5), a positional isomer of 4. Antiplatelet, antiinflammatory, and antiallergic activities were evaluated, and most compounds were quite potent in all assays. Compounds 5 and 9-11 were especially active; however, 5 was ineffective against neutrophil superoxide formation, and 10 was ineffective against mast cell degranulation.

Involvement of cyclic AMP generation in the inhibition of respiratory burst by 2-phenyl-4-quinolone (YT-1) in rat neutrophils

The inhibitory effect of 2-phenyl-4-quinolone (YT-1) on respiratory burst in rat neutrophils was investigated, and the underlying mechanism of action was assessed. YT-1 caused a concentration-dependent inhibition of the rate of O2.- release from rat neutrophils in response to formylmethionyl-leucyl-phenylalanine (fMLP), but not to phorbol 12-myristate 13-acetate (PMA), with an IC50 value of 60.7+/-8.2 microM. A comparable effect was also demonstrated in the inhibition of O2 consumption. Unlike superoxide dismutase, YT-1 had no effect on O2.- generation in the xanthine-xanthine oxidase system and during dihydroxyfumaric acid autoxidation. The fMLP-induced inositol trisphosphate (IP3) formation was unaffected by YT-1. In addition, YT-1 did not affect the initial spike of [Ca2+]i, but it accelerated the rate of [Ca2+]i decline in cells in response to fMLP. YT-1 was found to have little effect on the activity of neutrophil cytosolic protein kinase C (PKC). YT-1 increased the cellular cyclic AMP level, while having no effect on the cyclic GMP level. In addition, YT-1 increased neutrophil cytosolic protein kinase A (PKA) activity, but had no direct effect on the enzyme activity of pure porcine heart PKA. When neutrophils were treated with (8R,9S,11S)-(-)-9-hydroxy-9-hexoxycarbonyl-8-methyl-2,3,9,10-tetra hydro-8,11-epoxy- 1H,8H,11H-2,7b,11a-triazadibenzo[a,g]cycloocta[cde]trinde n-1-one, (KT 5720), a PKA inhibitor, the inhibition of O2.- generation by YT-1, as well as by prostaglandin E1 (PGE1) and dibutyryl cyclic AMP, was attenuated effectively. YT-1 did not activate the adenylate cyclase associated with neutrophil particulate fraction but inhibited the cytosolic phosphodiesterase (PDE) activity in a concentration-dependent manner. Neutrophils treated with YT-1 had a more pronounced increase in cellular cyclic AMP level by PGE1. Moreover, the ability of PGE1 to inhibit the respiratory burst in neutrophils was greatly enhanced by YT-1. These results suggest that the increase in cellular cyclic AMP levels by YT-1 through the inhibition of PDE (probably PDE4 isoenzyme) activity is involved in its inhibition of fMLP-induced respiratory burst in rat neutrophils.

Synthesis and cytotoxicity of 2-acetyl-4,8-dihydrobenzodithiophene-4, 8-dione derivatives

2-Acetyl-4,8-dihydrobenzo[1,2-b:4,5-b']dithiophene-4,8-dione (9) and 2-acetyl-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dione (19), together with 10 related mono- and disubstituted derivatives, were synthesized and evaluated in vitro by NCI against eight cancer types. All compounds showed significant activity against melanoma, HL-60 leukemia, NCI-H23 non-small-cell lung cancer, OVCAR-3 ovarian cancer, and MDA-MB-435 and MDA-N breast cancer cell lines. Compound 11, 2-(1'-acetoxyethyl)-4,8-dihydrobenzo[1,2-b:4,5-b']dithiophene-4, 8-dione, showed the highest overall potency (mean GI50 = 40 nM).

Constituents and bioactive principles of Polygonum chinensis

Isolation and characterization of the chemical constituents of Polygonum chinensis L. gave the new 25R-spirost-4-ene-3,12-dione. The known compounds stigmast-4-ene-3,6-dione, stigmastane-3,6-dione, hecogenin and aurantiamide acetate were also isolated from for the first time from this species. Their anti-inflammatory and anti-allergic properties are described.

Synthesis and cytotoxicity of acetyl-4H,9H-naphtho[2,3-b]thiophene-4,9-diones

Several new acetyl-4H,9H-naphtho[2,3-b]thiophene-4,9-diones were synthesized and evaluated for in vitro cytotoxicity by NCI against seven cancer cell types. 2,7-Diacetyl naphtho[2,3-b]thiophene-4,9-dione (9) showed significant cytotoxicity against leukemia cells with log GI50 values of -7.61 against SR cells and -7.18 against MOLT-4 cells. 3-Acetyl-naphtho[2,3-b]thiophene-4,9-dione (6) also demonstrated potent cytotoxicity in the latter cell line with log GI50 < -8.

Synthesis and antiplatelet activity of phenyl quinolones

In our search for novel antiplatelet agents, seven positional phenyl quinolone isomers were synthesized. Preliminary screening confirmed their inhibitory effects against arachidonic acid (AA)-induced platelet aggregation. Varying the substitutional position of the phenyl group had a profound effect on the antiplatelet activity of these isomers. 3-Phenyl-4-quinolone showed the greatest potency and was superior to indomethacin, although the two structures are quite different. The mechanism and pharmacological action of 3-phenyl-4-quinolone are currently under investigation.

Antioxidant properties of butein isolated from Dalbergia odorifera

The antioxidant properties of butein, isolated from Dalbergia odorifera T. Chen, were investigated in this study. Butein inhibited iron-induced lipid peroxidation in rat brain homogenate in a concentration-dependent manner with an IC50, 3.3+/-0.4 microM. It was as potent as alpha-tocopherol in reducing the stable free radical diphenyl-2-picrylhydrazyl (DPPH) with an IC0.200, 9.2+/-1.8 microM. It also inhibited the activity of xanthine oxidase with an IC50, 5.9+/-0.3 microM. Besides, butein scavenged the peroxyl radical derived from 2,2-azobis(2-amidinopropane) dihydrochloride (AAPH) in aqueous phase, but not that from 2,2-azobis(2, 4-dimethylvaleronitrile) (AMVN) in hexane. Furthermore, butein inhibited copper-catalyzed oxidation of human low-density lipoprotein (LDL), as measured by conjugated dienes and thiobarbituric acid-reactive substance (TBARS) formations, and electrophoretic mobility in a concentration-dependent manner. Spectral analysis revealed that butein was a chelator of ferrous and copper ions. It is proposed that butein serves as a powerful antioxidant against lipid and LDL peroxidation by its versatile free radical scavenging actions and metal ion chelation.

Ibuprofen affects arylamine N-acetyltransferase activity in Helicobacter pylori from peptic ulcer patients

Arylamine N-acetyltransferase (NAT) activities with 2-aminofluorene and p-aminobenzoic acid were determined in the bacterium Helicobacter pylori collected from peptic ulcer patients. Cytosols or suspensions of H. pylori with or without specific concentrations of ibuprofen co-treatment showed different percentages of 2-aminofluorene and p-aminobenzoic acid acetylation. The data indicate that there was decreased NAT activity associated with increased levels of ibuprofen in H. pylori cytosols. Inhibition of growth studies on H. pylori demonstrated that ibuprofen elicited a dose-dependent bactericide effect in H. pylori cultures, i.e. the greater the concentration of ibuprofen, the greater the inhibition of growth to H. pylori. For the cytosol and intact bacteria examinations, the apparent values of Km and Vmax were decreased after co-treatment with 40 microM ibuprofen. This report is the first demonstration of ibuprofen inhibition of arylamine N-acetyltransferase activity and ibuprofen inhibition of growth in the bacterium H. pylori.

Antitumor agents. 181. Synthesis and biological evaluation of 6,7,2',3',4'-substituted-1,2,3,4-tetrahydro-2-phenyl-4-quinolones as a new class of antimitotic antitumor agents

A novel series of 6,7,2',3',4'-substituted-1,2,3,4-tetrahydro-2-phenyl- 4-quinolones were synthesized and evaluated for interactions with tubulin and for cytotoxic activity against a panel of human tumor cell lines, including ileocecal carcinoma (HCT-8), breast cancer (MCF-7), lung carcinoma (A-549), epidermoid carcinoma of the nasopharynx (KB), renal cancer (CAKI-1), and melanoma cancer (SKMEL-2). Most compounds (18, 20, 22-27) showed potent cytotoxic and antitubulin effects. The most active compounds (23, 26, 27) demonstrated strong cytotoxic effects with ED50 values in the nanomolar or subnanomolar range in almost all tumor cell lines. Three active racemates (20, 22, 25) were separated into the enantiomers, and generally, the optically pure (-)-isomers (20a, 22a, 25a) exhibited greater biological activity than the racemates or (+)-isomers. Cytotoxicity and antitubulin activity were closely correlated, with the most active compounds (23, 26, 27) having effects comparable to those of colchicine, podophyllotoxin, and combretastatin A-4.

Three new flavonoids and antiallergic, anti-inflammatory constituents from the heartwood of Dalbergia odorifera

Three new flavonoids, (3R)-4'-methoxy-2',3,7-trihydroxyisoflavanone (11), 7-methoxy-3,3',4',6-tetrahydroxyflavone (18), and 2',7-dihydroxy-4',5'-dimethoxyisoflavone (22), were isolated from the heartwood of Dalbergia odorifera T. Chen. (Leguminosae), together with twenty-two known compounds, (S)-4-methoxydalbergione (1), cearoin (2), medicarpin (3), formononetin (4), sativanone (5), 3-hydroxy-9-methoxy-coumestan (6), meliotocarpan A (7), isoliquiritigenin (8), stevein (9), liquiritigenin (10), 3',4',7-trihydroxyflavanone (12), butein (13), 3'-hydroxymelanettin (14), koparin (15), bowdichione (16), fisetin (17), melanettin (19), sulfuretin (20), 3'-hydroxydaidzein (21), 3'-O-methylviolanone (23), xenognosin B (24), and dalbergin (25). These flavonoids were evaluated in antiallergic and anti-inflammatory tests. The results showed that (S)-4-methoxydalbergione (1) and cearoin (2) exhibited antiallergic activity while (S)-4-methoxydalbergione (1), cearoin (2), butein (13), koparin (15), bowdichione (16), 3'-O-methylviolanone (23), and xenognosin B (24) showed significant anti-inflammatory activity.

Effect of PP1D-1, a synthetic antiplatelet compound, on rabbit platelets

The antiplatelet mechanism of a synthetic compound, 2-chloro-3-methoxycarbonylpropionamido-1,4-naphthoquinone (PP1D-1), was studied by employing washed rabbit platelets in vitro. PP1D-1 concentration-dependently inhibited thrombin (0.1 U/ml)-, platelet-activating factor (2 ng/ml)-, collagen (10 microg/ml)-, arachidonic acid (100 microM)- and U46619 (1 microM)-induced aggregation and ATP release in washed rabbit platelets. The IC50 values of PP1D-1 for aggregation induced by the above inducers are 17.9+/-1.7, 9.8+/-1.1, 3.9+/-0.4, 1.8+/-0.3 and 1.7+/-0.3 microM, respectively. PP1D-1 did not affect platelet thromboxane B2 or prostaglandin D2 formation induced by arachidonic acid, indicating that it did not affect cyclooxygenase and thromboxane synthase activities. PP1D-1 significantly inhibited the formation of inositol 1,4,5-trisphosphate caused by these five platelet stimulators. Moreover, PP1D-1 inhibited the increase in intracellular calcium concentration induced by these agents. On the contrary, PP1D-1 did not inhibit thapsigargin-elevated intracellular calcium concentration in indomethacin-pretreated platelets, indicating it did not influence the effect of thapsigargin. According to these data, PP1D-1 exerts antiplatelet effects mainly by inhibiting phosphoinositide turnover.

Inhibition of nitric oxide synthase expression by PPM-18, a novel anti-inflammatory agent, in vitro and in vivo

We studied the effect of PPM-18, a chemically synthesized naphthoquinone derivative and also an anti-inflammatory agent, on the lipopolysaccharide (LPS)-activated inducible NO synthase (iNOS) expression in rat alveolar macrophages. Pretreatment of macrophages with PPM-18 (0.1-10 microM) significantly inhibited nitrite production, iNOS protein expression and iNOS mRNA accumulation. PPM-18 did not directly affect the enzymic activities of iNOS and other constitutive NOS forms. The LPS-induced increase in nuclear transcription factor kappaB (NF-kappaB) p65 and p50 in nucleus was suppressed by PPM-18 (10 microM). Moreover electrophoretic mobility-shift assays demonstrated that PPM-18 inhibited DNA binding to NF-kappaB induced by LPS in whole cells but not when added in the nuclear extract, suggesting that PPM-18 did not interfere directly with the binding of NF-kappaB to DNA and that some events had to be processed before NF-kappaB could bind DNA. Examination of NF-kappaB showed that PPM-18 stabilized the NF-kappaB inhibitor, IkappaBalpha, by preventing its degradation from NF-kappaB. Therefore the stabilization of IkappaBalpha might have contributed to the inhibition of NF-kappaB activation. These results also indicate strongly that NF-kappaB is involved in the production of NO on stimulation by LPS. PPM-18 significantly decreased the production of tumour necrosis factor alpha in response to LPS. PPM-18 protects mice against LPS-induced lethal toxicity. These results also indicate that PPM-18 is a potent inhibitor of iNOS expression by blocking the binding of NF-kappaB to promoter and exerts a beneficial effect in the mouse model of sepsis.

Electrophysiological basis for the antiarrhythmic action and positive inotropy of HA-7, a furoquinoline alkaloid derivative, in rat heart

1. HA-7, a new synthetic derivative of furoquinoline alkaloid, increased the contractile force of right ventricular strips and effectively suppressed the ischaemia-reperfusion induced polymorphic ventricular tachyrhythmias in adult rat heart (EC50 = 2.8 microM). 2. In rat ventricular myocytes, HA-7 concentration-dependently prolonged the action potential duration (APD) and decreased the maximal rate of rise of the action potential upstroke (Vmax). The action potential amplitude and resting membrane potential were also reduced, but to a smaller extent. The prolongation of APD by HA-7 was prevented by pretreating the cells with 1 mM 4-AP. 3. Voltage clamp experiments revealed that HA-7 decreased the maximal current amplitude of I(Na) (IC50 = 4.1 microM) and caused a negative shift of its steady-state inactivation curve and slowed its rate of recovery from inactivation. The use-dependent inhibition of I(Na) by HA-7 was enhanced at a higher stimulation rate. The L-type Ca2+ current (I(Ca)) was also reduced, but to a lesser degree (IC50 = 5.3 microM, maximal inhibition = 31.8%). 4. This agent also influenced the time- and voltage-dependent K currents. The prolongation of APD was associated with an inhibition of a 4-AP sensitive transient outward K current (I(to)) (IC50 = 2.9 microM) and a slowly inactivating, steady-state outward current (I(SS)) (IC50 = 2.5 microM). The inhibition of I(to) by HA-7 was associated with an acceleration of its time constant of inactivation. HA-7 suppressed I(to) in a time-dependent manner and caused a significant negative shift of the voltage-dependent steady-state inactivation curve but did not affect its rate of recovery from inactivation. 5. At higher concentrations, the inward rectifier K+ current (I(KI)) was also inhibited but to a less extent. Its slope conductance after 3, 10 and 30 microM HA-7 was decreased by 24+/-4%, 41+/-5% and 54+/-8%. respectively. 6. We conclude that HA-7 predominantly blocks I(to) and Na+ channels and that it also weakly blocks Ca2+ and I(KI) channels. These changes alter the electrophysiological properties of the heart and terminate the ischaemia reperfusion induced ventricular arrhythmia. The significant I(to) inhibition and minimal I(Ca) suppression may afford an opportunity to develop an effective antiarrhythmic agent linked with positive inotropy.