UK-78,282, a novel piperidine compound that potently blocks the Kv1.3 voltage-gated potassium channel and inhibits human T cell activation.

1. UK-78,282, a novel piperidine blocker of the T lymphocyte voltage-gated K+ channel, Kv1.3, was discovered by screening a large compound file using a high-throughput 86Rb efflux assay. This compound blocks Kv1.3 with a IC50 of approximately 200 nM and 1:1 stoichiometry. A closely related compound, CP-190,325, containing a benzyl moiety in place of the benzhydryl in UK-78,282, is significantly less potent. 2 Three lines of evidence indicate that UK-78,282 inhibits Kv1.3 in a use-dependent manner by preferentially blocking and binding to the C-type inactivated state of the channel. Increasing the fraction of inactivated channels by holding the membrane potential at - 50 mV enhances the channel's sensitivity to UK-78,282. Decreasing the number of inactivated channels by exposure to approximately 160 mM external K+ decreases the sensitivity to UK-78,282. Mutations that alter the rate of C-type inactivation also change the channel's sensitivity to UK-78,282 and there is a direct correlation between tau(h) and IC50 values. 3. Competition experiments suggest that UK-78,282 binds to residues at the inner surface of the channel overlapping the site of action of verapamil. Internal tetraethylammonium and external charybdotoxin do not compete UK-78,282's action on the channel. 4. UK-78,282 displays marked selectivity for Kv1.3 over several other closely related K+ channels, the only exception being the rapidly inactivating voltage-gated K+ channel, Kv1.4. 5. UK-78,282 effectively suppresses human T-lymphocyte activation.

Novel nonpeptide agents potently block the C-type inactivated conformation of Kv1.3 and suppress T cell activation.

The nonpeptide agent CP-339,818 (1-benzyl-4-pentylimino-1,4-dihydroquinoline) and two analogs (CP-393,223 and CP-394,322) that differ only with respect to the type of substituent at the N1 position, potently blocked the Kv1.3 channel in T lymphocytes. A fourth compound (CP-393,224), which has a smaller and less-lipophilic group at N1, was 100-200-fold less potent, suggesting that a large lipophilic group at this position is necessary for drug activity. CP-339,818 blocked Kv1.3 from the outside with a IC50 value of approximately 200 nM and 1:1 stoichiometry and competitively inhibited 125I-charybdotoxin from binding to the external vestibule of Kv1.3. This drug inhibited Kv1.3 in a use-dependent manner by preferentially blocking the C-type inactivated state of the channel. CP-339,818 was a significantly less potent blocker of Kv1.1, Kv1.2, Kv1.5, Kv1.6, Kv3.1-4, and Kv4.2; the only exception was Kv1.4, a cardiac and neuronal A-type K+ channel. CP-339,818 had no effect on two other T cell channels (I(CRAC) and intermediate-conductance K(Ca)) implicated in T cell mitogenesis. This drug suppresses human T cell activation, suggesting that blockade of Kv1.3 alone is sufficient to inhibit this process.

Topology of the pore-region of a K+ channel revealed by the NMR-derived structures of scorpion toxins.

The architecture of the pore-region of a voltage-gated K+ channel, Kv1.3, was probed using four high affinity scorpion toxins as molecular calipers. We established the structural relatedness of these toxins by solving the structures of kaliotoxin and margatoxin and comparing them with the published structure of charybdotoxin; a homology model of noxiustoxin was then developed. Complementary mutagenesis of Kv1.3 and these toxins, combined with electrostatic compliance and thermodynamic mutant cycle analyses, allowed us to identify multiple toxin-channel interactions. Our analyses reveal the existence of a shallow vestibule at the external entrance to the pore. This vestibule is approximately 28-32 A wide at its outer margin, approximately 28-34 A wide at its base, and approximately 4-8 A deep. The pore is 9-14 A wide at its external entrance and tapers to a width of 4-5 A at a depth of approximately 5-7 A from the vestibule. This structural information should directly aid in developing topological models of the pores of related ion channels and facilitate therapeutic drug design.

Pharmacological characterization of five cloned voltage-gated K+ channels, types Kv1.1, 1.2, 1.3, 1.5, and 3.1, stably expressed in mammalian cell lines.

We have analyzed the biophysical and pharmacological properties of five cloned K+ (Kv) channels (Kv1.1, Kv1.2, Kv1.3, Kv1.5, and Kv3.1) stably expressed in mammalian cell lines. Kv1.1 is biophysically similar to a K+ channel in C6 glioma cells and astrocytes, Kv1.3 and Kv3.1 have electrophysiological properties identical to those of the types n and l K+ channels in T cells, respectively, and Kv1.5 closely resembles a rapidly activating delayed rectifier in the heart. Each of these native channels may be formed from the homomultimeric association of the corresponding Kv subunits, and pharmacological compounds that selectively modulate them may be useful for the treatment of neurological, immune, and cardiac disorders. The cell lines described in this report could be used to identify such drugs and we have therefore embarked on a pharmacological characterization of the five cloned channels. The compounds tested in this study include 4-aminopyridine, capsaicin, charybdotoxin, cromakalim, dendrotoxin, diltiazem, D-sotalol, flecainide, kaliotoxin, mast cell degranulating peptide, nifedipine, noxiustoxin, resiniferatoxin, and tetraethylammonium.

Cytokines in liposomes: preliminary studies with IL-1, IL-2, IL-6, GM-CSF and interferon-gamma.

A simple, generally applicable method to incorporate cytokine proteins into multilamellar liposomes is presented. A variety of human cytokines including granulocyte-macrophage colony stimulating factor (GM-CSF), interleukins 1 alpha, 2 and 6 (IL-1 alpha, IL-2, IL-6) and interferon-gamma (IFN-gamma) were incorporated into liposomes containing a single saturated synthetic lipid, dimyristoyl phosphatidyl choline (DMPC). Sterile cytokine liposomes were produced by gamma irradiation of DMPC lipid powder prior to use in cytokine liposome synthesis. A highly sensitive and reliable fluorescamine assay to detect microgram quantities of cytokine protein associated with liposomes is also described. When a high lipid:aqueous ratio [e.g. 300 mg DMPC lipid:1.0 ml aqueous cytokine solution] was utilized, aqueous cytokines (1 mg/ml) could be incorporated with efficiencies ranging from 19% (IL-1) to > 80% (IL-2). Combinations of cytokines (e.g. IL-2 + GM-CSF) were also co-incorporated into liposomes. Experiments with IL-2, IL-6, and GM-CSF demonstrated that these cytokines remain stably associated with the DMPC lipid and do not significantly leak from liposomes when stored at 4 degrees C for at least 3 months. Washing IL-6 liposome or GM-CSF liposome preparations reliably increased the proportion of cytokine protein associated with the liposome pellet compared to free cytokine in the supernatant of centrifuged specimens. For example the proportion of GM-CSF associated with the lipid carrier increased from 34.8% (SD 2.6%) in the original preparation to 98.0% (SD 0.6%) after three washes. Differences in the pharmacokinetics of subcutaneous (sc) free GM-CSF and GM-CSF liposomes (14 mcg/mouse) were studied in BALB/c mice. Both free GM-CSF and free GM-CSF mixed with saline loaded liposomes exhibited biphasic pharmacokinetics with very high peak levels 1 and 2 h after sc injection of 14 mcg the rapid decline to very low levels after 24 h. In contrast, sc GM-CSF liposomes provided sustained and stable levels of cytokine in the serum (approximately 100 pg/ml) for 24 h. Intraperitoneal injection of GM-CSF liposomes had > 10-fold more cytokine in the peritoneal wash than free GM-CSF mixed with saline loaded liposomes. In summary, the liposome synthesis procedure described is simple and utilizes a single synthetic lipid to reliably produce sterile cytokine preparations with in vivo depot effects after either sc or ip administration. Furthermore, the method is feasible for quantities of sterile cytokine liposomes sufficient for in vivo experiments.

Inhibition of interleukin 1 synthesis by tenidap: a new drug for arthritis.

Tenidap is a new antiarthritic drug of novel chemical structure. This study shows the effects of tenidap on the in vitro synthesis of interleukin 1 (IL-1). IL-1 production by murine peritoneal macrophages was induced either by stimulation with lipopolysaccharide (LPS) or by phagocytosis of zymosan. With either stimulus, tenidap inhibited IL-1 production as measured by a quantitative competitive IL-1 receptor binding assay. Approximately 20 ng/mL of IL-1 was produced by 10(6) macrophages in response to LPS and about half that amount was produced in response to zymosan. Fifty percent inhibition of IL-1 production by tenidap was found at 3 microM for both stimuli. Using goat anti-IL-1 alpha and Western blot analysis, the appearance of intracellular 34 kDa pro-IL-1 alpha was inhibited by tenidap down to 3 microM. Tenidap decreased [35S]Met incorporation into cellular protein at 30 microM but not at 10 or 3 microM, indicating selectivity for IL-1 inhibition relative to total protein synthesis. Because tenidap inhibited IL-1 induction by both zymosan and LPS, it must act subsequently to receptor triggering. As the appearance of IL-1 was inhibited both intracellularly and extracellularly, the primary drug effect cannot be on secretion.

Human monocytes produce IL-1 and an inhibitor of IL-1 in response to two different signals.

Recently, IL-1 inhibitors from urine, monocytes, or monocyte lines have been described. The relationship of these inhibitors to the production, release, and immunological effects of IL-1 is unclear. The present studies were initiated to describe and quantitate the production of IL-1 and a 23 to 45-kDa IL-1 inhibitor from human monocytes in response to certain stimuli using a mouse thymocyte system responsive to IL-1. Zymosan stimulated monocytes to produce IL-1 but not IL-1 inhibitor. Adherent immune complexes, human IgG1-4, and Fc fragments, but not F(ab')2, stimulated monocyte production of IL-1 inhibitor and little if any IL-1. Fibronectin and three of its fragments had neither effect. These observations suggest that monocytes produce IL-1 or IL-1 inhibitor in response to two different signals, through "endotoxin or beta-glucan" and Fc receptors, respectively. The inhibitor decreases IL-1-induced CD-1, C3H/HeJ, and D10 G4.1 cells but not IL-2-induced CD-1, C3H/HeJ, or CTLL-2 proliferation. The inhibitor competitively blocked binding of radiolabeled rIL-1 to the IL-1 receptor on murine thymoma cells. Preincubation of thymocytes with the inhibitor prevented IL-1-induced proliferation; however, this effect was reversed by washing thymocytes and inhibitor activity was markedly reduced when added 24 hr after stimulation with IL-1. These observations suggest that the inhibitor acts on IL-1 receptors to prevent thymocyte proliferation. Monocytes from patients with systemic lupus erythematosus produced less IL-1 inhibitor than cells from normal volunteers. The decrease in IL-1 inhibitor production may play a role in disease states.

CD4-CD8- T cells from mice with collagen arthritis display aberrant expression of type l K+ channels.

Expression of voltage-gated K+ channels in mAb-defined T cell subsets from normal mice and mice with experimental autoimmune arthritis was studied with the patch-clamp whole-cell recording technique in combination with fluorescence microscopy. CD4+CD8- Th cells from DBA/1 LacJ mice with type II collagen arthritis expressed low levels of type n K+ channels, and CD4-CD8+ T cells (cytotoxic) showed small numbers of type l or n' K+ channels, like their phenotypic counterparts in normal mice. CD4-CD8-Thy-1.2+ (double negative or DN) T cells from the diseased mice, however, displayed an abundance of type l K+ channels compared to DN T cells in normal mice, or mice immunized with CFA. Furthermore, the aberrant expression of type l K+ channels correlated with the presence of active disease. DN T cells from mice with SLE, type-1 diabetes mellitus, and experimental allergic encephalomyelitis, also exhibited a high number of type l K+ channels. These results suggest that expression of numerous type l K+ channels may be a useful marker for DN T cells associated with these autoimmune disorders.

The pharmacologic regulation of interleukin-1 production: the role of prostaglandins.

The role of prostaglandins in the regulation of lipopolysaccharide (LPS)-induced interleukin-1 (IL-1) production by murine C3H/HeN resident peritoneal macrophages was studied. IL-1 production was initially studied in the presence of piroxicam and indomethacin, both inhibitors of prostaglandin biosynthesis. IL-1 was assayed using the IL-1-dependent proliferative response of C3H/HeJ thymocytes. LPS stimulation resulted in 15 to 20 ng/ml of prostaglandin E2 (PGE2) produced in the first hour of culture. IL-1-containing supernatants from drug-treated macrophages at dilutions of up to 1:32 resulted in enhanced thymocyte proliferation compared to control, non-drug-treated cultures and contained less than 2 ng/ml of PGE2. Similar enhancement of proliferation could be obtained by incubating non-drug-treated supernatants with monoclonal anti-PGE2 but not anti-thromboxane B2 (TxB2) antibody. Further dilutions of the drug-treated supernatants gave thymocyte proliferation responses which were indistinguishable from control cultures and, correspondingly, had identical values for IL-1 production. The absence of an effect on IL-1 production was confirmed by quantitation of intracellular IL-1 alpha using goat anti-IL-1 alpha antibody and by quantitation of supernatant IL-1 receptor competition assay. Exogenous PGE2, in the concentration range produced in macrophage supernatants (10-20 ng/ml), directly inhibited IL-1-stimulated thymocyte proliferation. Finally, when macrophages were stimulated with LPS for 24 hr in the presence of added PGE2, thymocyte proliferation was inhibited at the lowest supernatant dilutions, but as the IL-1-containing supernatants were diluted out, the assay curves were indistinguishable from non-PGE2-treated control. Thus, in this system, PGE2 has no effect on IL-1 synthesis, but rather has a direct inhibitory effect on thymocyte proliferation. Nonsteroidal anti-inflammatory drugs are not stimulating IL-1 production but are, in fact, relieving inhibition of the thymocyte IL-1 assay caused by the presence of prostaglandins.

A molecular mechanism for the activation of the first component of complement by immune complexes.

The proposed activation mechanism is based upon several key concepts, including the "S"-structure for the folding of the C1r2C1s2 tetramer among the C1q arms [Poon, et al., J. molec. Biol. 168, 563-577 (1983)]; the locations of the catalytic domains on the tetramer and the resulting functional relevance of the "S"-structure [Colomb et al., Phil. Trans. R. Soc. B306, 282-292 (1984)]; the structure of C1-inhibitor [Odermatt et al., FEBS Lett. 131, 283-289 (1981)]; and the control of C1 activation by C1-inhibitor [Ziccardi, J. Immun. 128, 2505-2508 (1982)]. The proposed activation mechanism has four main features: steric exclusion of C1-inhibitor from C1 when it binds to an immune complex; signal generation through multivalent binding of the C1q heads to an irregularly-arranged cluster of antibody Fc regions, and signal transmission through the movement of the stiff C1q arms about their semi-flexible joints, causing distortion of the symmetrical cone of C1q arms; induction of rapid activation by a shift in equilibrium favoring the autocatalytic conformation of C1r2C1s2; and release of the activated C1s from the C1q arms, so that the ends of the tetramer are free for interaction with C4 and C2 and C1-inhibitor, and the C1q subcomponent becomes more flexible, allowing access of C1-inhibitor to C1r.

Lorazepam in cancer patients treated with cisplatin: a drug having antiemetic, amnesic, and anxiolytic effects.

There currently is no pharmacologic approach to the problem of anticipatory nausea and vomiting (ANV). Lorazepam (Ativan, Wyeth Laboratories, Philadelphia) is an interesting candidate drug if it could block the recall of the unpleasant events associated with chemotherapy, especially if it also has antiemetic properties. Since ANV is a conditioned (learned) response, it may well depend on a memory imprint of the stimulus. This pilot study was designed to use intravenous lorazepam given before and after cisplatin infusion in 32 patients, and to make detailed measurements of nausea, vomiting, recent memory, anxiety, and sedation as well as toxicity. Satisfactory responses occurred in about 70%, as rated separately both by investigator and patient. Forty-six percent did not even recall receiving chemotherapy, regardless of whether or not they vomited; 80% had no significant anxiety after chemotherapy. Adverse reactions included some cases of perceptual disturbance, urinary incontinence, diarrhea, hypotension, and one case of severe transient amnesia. No long-term adverse effects were noted.

Immunoglobulin G antibody bound to the C1q subcomponent of human complement exhibits segmental flexibility.

The rotational dynamics of rabbit immunoglobulin G (IgG) anti-dansyl antibodies bound to the C1q subcomponent of human complement were studied by nanosecond fluorescence spectroscopy. Deconvoluted anisotropy decays of IgG-C1q mixtures were fitted to a two-exponential expression and were corrected for the effects of unbound IgG, which was determined with an analytical ultracentrifuge. Compared with the anisotropy parameters for free IgG, the pre-exponential weighting factors and the short correlation time of the C1q-bound antibody were nearly unchanged, and the long correlation time increased by only about 45 nanoseconds. These results, together with rotational diffusion calculations, indicate that the Fab arms of the C1q-bound antibody exhibited considerable flexibility. This finding may have biological relevance because it suggests that C1q can bind to the Fc segments of IgG molecules anchored in an immune complex, even though the angles between the two Fab arms of the different antibodies may vary. The results of this study also support our earlier interpretation that both the short and long correlation times of IgG principally represent flexible motions of the Fab segments.

Segmental flexibility of the C1q subcomponent of human complement and its possible role in the immune response.

Fluorescence polarization techniques were used to study the rotational dynamics of the C1q subcomponent of human complement. C1q was covalently labeled with dansyl (DNS) chloride. Digestion of either C1q-DNS4.0 or C1q-DNS1.8 conjugates with pepsin showed that about 75% of the DNS probes were attached to the C1q globular heads and that the remainder were on the collagen-like stalk (peptic fragment). C1q-DNS conjugates readily agglutinated IgG-coated latex beads and combined with C1r2C1s2 to form hemolytically active 16 S C1-DNS. Both C1q-DNS and C1-DNS samples displayed steady-state rotational correlation time and fluorescence lifetime transitions near 48 degrees C. Hydrodynamic studies showed that C1q formed soluble aggregates near the transition temperature. In contrast, stalk samples with a DNS probe apparently attached to the large central fibril showed no thermal transitions or aggregation even when heated above 50 degrees C. Nanosecond fluorescence depolarization measurements detected restricted flexible motions of the C1q heads with an associated rotational correlation time, phi s, of about 25 ns. The C1q anisotropy decay was dominated, however, by a long component, phi L, of perhaps 1000 ns. Except for probe wiggle, the stalk-DNS anisotropy profile was essentially flat. The rapid rotations associated with phi s could represent restricted twisting motions of the arm-head segments or wobbling motions of the heads themselves. Such motions may facilitate binding of the C1q heads to immune complexes. Straightforward diffusion calculations indicated that phi L could represent either global tumbling of the entire C1q molecule or wagging motions of the individual arm-head segments, as suggested by electron micrographs. Upon binding of the C1q heads to an activator, some of the C1q segments may be held in a slightly more open or more closed conformation, which in turn may trigger activation of the C1 proenzymes. In conclusion, we suggest a plausible triggering mechanism for C1 activation that is compatible with the flexible properties of its subcomponents.

Rotational dynamics of immunoglobulin G antibodies anchored in protein A soluble complexes.

The rotational dynamics of rabbit IgG anti-dansyl antibodies anchored in staphylococcal protein A (SpA) soluble complexes were studied by both steady-state and nanosecond fluorescence spectroscopy. To aid in the interpretation of the anisotropy data, the results of recently reported hydrodynamic and electron microscopic studies of IgG-SpA complexes were used to calculate global tumbling times of the various complexes and to estimate the steric hindrance of the antibody Fab segments. The anisotropy decays, fitted to the sum of two exponentials, indicated that the Fab arms of antibodies bound to SpA by their Fc regions exhibit considerable flexibility. For the different IgG-SpA mixtures examined, changes in the IgG preexponential anisotropy weighting factors, fS and fL, and the short rotational correlation time, phi S, were relatively small. On the other hand, the long rotational correlation time, phi L, increased systematically when the percentage of larger IgG-SpA complexes in a mixture was increased. The greatest restriction of Fab flexibility was observed for antibodies anchored in the exceptionally compact IgG4-SpA2 complexes. Available electron microscopic data suggest that increases in phi L correlate with increased steric hindrance of the antibody segments. Both native and hinge-disulfide-cleaved IgG experienced similar percentage increases in phi L when bound in SpA complexes. In agreement with our earlier interpretation, the results of this study provide rather striking evidence that phi L mainly represents flexible motions of the Fab segments and not global tumbling: the phi L-values of IgG bound in the various SpA complexes ranged from 101 to 162 nsec, whereas the calculated global tumbling times of the different complexes ranged from about 300 to 3000 nsec.

Some theoretical considerations regarding the effects of steric hindrance and intrinsic global coupling on the flexibility of Fc-anchored immunoglobulins.

Nanosecond fluorescence depolarization studies reported in the accompanying companion paper showed that the long rotational correlation time, phi L, increased somewhat when rabbit IgG anti-dansyl antibodies were anchored in staphylococcal protein A (SpA) soluble complexes. The increases in phi L upon anchoring IgG probably resulted from "global coupling" effects caused by: increased steric hindrance of the antibody segments in the SpA complexes and intrinsic structural constraints already present in the monomeric IgG. Global coupling results from a restriction in the angular range of a flexible segment and is manifest when flexible motions alone cannot depolarize all of the fluorescence, so that the slower global tumbling of the entire particle is also required. Such effects cannot be resolved directly from experimental anisotropy data, however, because only a single long correlation time, phi L, is well defined over the limited time range of most fluorophores. In this paper, estimates of the anisotropy contributions from flexible and global motions of the IgG-SpA complexes are determined by contrasting theoretical and measured decays. For this analysis it was assumed that each of the experimental phi L-values is a weighted composite of the rotational correlation time associated with the less restricted flexible motions of the Fab arms, phi F, and the correlation time associated with global tumbling of the entire particle, phi G. A general two-exponential expression was used to relate phi F and phi G to phi L. This approach was meaningful because phi G-values of the various SpA complexes had been calculated from hydrodynamic measurements. The theoretical decays clearly show that, even if phi G is much longer than phi F, these two rotational motions still cannot be resolved over the experimentally accessible time range. Families of emission anisotropy decay curves for IgG antibodies with different amounts of intrinsic global coupling and for anchored antibodies with different amounts of steric hindrance were simulated by varying the preexponential weighting factors of the flexible and global terms. By comparing the calculated curves with the measured decays, it is evident that the rabbit IgG anti-dansyl antibodies do not have much intrinsic global coupling, but rather they are highly flexible. The curves also indicate that even for the exceptionally compact IgG4-SpA2 17-S complex, which showed the most steric hindrance in electron micrographs, the appropriate phi G weighting factor is only 0.28. Thus, as supposed earlier, the anchored antibodies exhibit considerable segmental flexibility. In closing, the above concepts are used to examine the results of