Bystander activation of iNKT cells occurs during conventional T-cell alloresponses.

It is well established that iNKT cells can be activated by both exogenous and a limited number of endogenous glycolipids. However, although iNKT cells have been implicated in the immune response to transplanted organs, the mechanisms by which iNKT cells are activated in this context remain unknown. Here we demonstrate that iNKT cells are not activated by allogeneic cells per se, but expand, both in vitro and in vivo, in the presence of a concomitant conventional T-cell response to alloantigen. This form of iNKT activation was found to occur independently of TCR-glycolipid/CD1d interactions but rather was a result of sequestration of IL-2 produced by conventional alloreactive T cells. These results show for the first time that IL-2, produced by activated conventional T cells, can activate iNKT cells independently of glycolipid/CD1d recognition. Therefore, we propose that the well-documented involvement of iNKT cells in autoimmunity, the control of cancer as well as following transplantation need not involve recognition of endogenous or exogenous glycolipids but alternatively may be a consequence of specific adaptive immune responses.

Immunology in the Clinic Review Series; focus on host responses: invariant natural killer T cell activation following transplantation.

Invariant natural killer T (iNKT) cells have been shown to play a key role in the regulation of immunity in health and disease. However, iNKT cell responses have also been found to influence both rejection and the induction of tolerance following transplantation of allogeneic cells or organs. Although a number of mechanisms have been identified that lead to iNKT cell activation, how iNKT cells are activated following transplantation remains unknown. This review will attempt to identify potential mechanisms of iNKT cell activation in the context of transplantation by applying knowledge garnered from other disease situations. Furthermore, we put forward a novel mechanism of iNKT cell activation which we believe may be the dominant mechanism responsible for iNKT activation in this setting, i.e. bystander activation by interleukin-2 secreted by recently activated conventional T cells.

Lack of complex I is associated with oncocytic thyroid tumours.

Oncocytic tumours are characterised by hyperproliferation of mitochondria. We immunohistochemically analysed all enzymes of the oxidative phosphorylation system in 19 oncocytic thyroid tumours. A specific lack of complex I was detected, which was expressed at <5% of the level determined in surrounding non-cancerous tissue.

Therapeutic implications of NK cell regulation of allogeneic CD8 T cell-mediated immune responses stimulated through the direct pathway of antigen presentation in transplantation.

Natural killer (NK) cells are a population of innate type I lymphoid cells essential for early anti-viral responses and are known to modulate the course of humoral and cellular-mediated T cell responses. We assessed the role of NK cells in allogeneic CD8 T cell-mediated responses in an immunocompetent mouse model across an MHC class I histocompatibility barrier to determine its impact in therapeutic clinical interventions with polyclonal or monoclonal antibodies (mAbs) targeting lymphoid cells in transplantation. The administration of an NK cell depleting antibody to either CD8 T cell replete or CD8 T cell-depleted naïve C57BL/6 immunocompetent mice accelerated graft rejection. This accelerated rejection response was associated with an in vivo increased cytotoxic activity of CD8 T cells against bm1 allogeneic hematopoietic cells and bm1 skin allografts. These findings show that NK cells were implicated in the control host anti-donor cytotoxic responses, likely by competing for common cell growth factors in both CD8 T cell replete and CD8 T cell-depleted mice, the latter reconstituting in response to lymphopenia. Our data calls for precaution in solid organ transplantation under tolerogenic protocols involving extensive depletion of lymphocytes. These pharmacological biologics with depleting properties over NK cells may accelerate graft rejection and promote aggressive CD8 T cell cytotoxic alloresponses refractory to current immunosuppression.

Molecular structure of fluoxetine hydrochloride, a highly selective serotonin-uptake inhibitor.

Fluoxetine, a selective inhibitor of serotonin uptake, is clinically useful in treating depression and may be useful for management of a variety of other psychiatric and metabolic derangements. Using X-ray crystallography, we have determined the three-dimensional structure of fluoxetine hydrochloride. A total of 2394 unique reflections were measured, and full-matrix least-squares refinement of all non-hydrogen coordinates and thermal parameters gave a final discrepancy index of 0.074 for 1759 observed reflections. In the solid state, the planes defined by the two aromatic rings are skewed, precluding the possibility of intramolecular ring-ring interactions. The methylene units of the methylpropanamine moiety adopt the anticipated conformational relationships to minimize torsional strain. An exact antiperiplanar relationship exists between N11 and C3; the N11-C1-C2-C3 dihedral angle is -180 degrees. The C1-C2-C3-O4 dihedral angle is 60.6 degrees, indicating that the propanamine side-chain folds toward the phenoxy moiety rather than adopting a fully extended conformation. This folded three-dimensional relationship may be necessary for high-affinity interaction with the serotonin-uptake carrier and confers considerable structural homology between this portion of fluoxetine and the phenylcyclohexylamine substructure of sertraline and EXP-561. However, the nature of substituents on the phenoxy portion of fluoxetine is also critical in determining potency and selectivity in this series of compounds.

Synthesis and dopaminergic activity of (R)- and (S)-4-hydroxy-2-(di-n-propylamino)indan.

A synthetic precursor to a potent dopaminergic agonist, (RS)-4-hydroxy-2-(di-n-propylamino)indan, has been resolved by classical recrystallization procedures, and the absolute configurations of the enantiomers have been established by X-ray crystallographic analysis. The enantiomers were converted by literature procedures into (R)- and (S)-1. (R)-1 was approximately 100 times as potent as (S)-1 in an assay for dopamine agonist effect in the isolated cat atrium.

Bicyclic and tricyclic ergoline partial structures. Rigid 3-(2-aminoethyl)pyrroles and 3- and 4-(2-aminoethyl)pyrazoles as dopamine agonists.

It is proposed, based upon comparisons with apomorphine, that the rigid pyrroleethylamine moiety of the ergolines is the portion of the molecule responsible for dopamine agonist activity. In support of this hypothesis, bicyclic and tricyclic ergoline partial structures 6, 11, 25, and 35 have been synthesized. In addition, some pyrazole isosters (37, 38, 40, and 45) of these rigid pyrroleethylamines have been made. All of the classes show dopaminergic activity in prolactin inhibition and in lesioned rat turning assays. The most potent drugs, the linear tricyclic pyrazoles 38 (R = Pr) and 40 (R = Pr), are comparable in potency with the highly active ergoline pergolide (41).

Synthesis and analgesic properties of N-substituted trans-4a-aryldecahydroisoquinolines.

A representative series of N-substituted derivatives of the morphine-based trans-4a-aryldecahydroisoquinoline were synthesized and evaluated for opioid analgesic activities. Compounds with potent analgesic activity and high affinities for the mu and kappa opioid receptors were discovered. The effect of varying the N-substituent in the trans-4a-aryldecahydroisoquinoline paralleled, to a certain extent, previous findings with other morphine part structures. Replacement of the N-methyl with a phenethyl group significantly increased analgesic potency. The N-cyclopropylmethyl analogue was found in rodents to have mixed agonist-antagonist properties; however, its antagonist activity was far weaker than those reported for the N-(cyclopropylmethyl)morphinan and -benzomorphan derivatives. Resolution of the stereoisomers and determination of their absolute configuration by X-ray crystallography showed that the opioid receptor effects were predominantly found with the 4aR,8aR isomer, the same relative absolute configuration of morphine. Unexpectedly, the 4aR,8aR N-cyclopropylmethyl analogue (compound 30), which in rodents had mixed agonist-antagonist properties similar to those of pentazocine, was found in rhesus monkeys to behave as a full morphine-like agonist.

Bipyridine cardiotonics: the three-dimensional structures of amrinone and milrinone.

The cardiotonic drug milrinone (1,6-dihydro-2-methyl-6-oxo-[3,4'-bipyridine]-5-carbonitrile) is superior to its analogue amrinone (5-amino-[3,4'-bipyridin]-6(1H)-one) by virtue of its greater potency and reduced side effect profile. We confirmed initial reports on the potencies of milrinone and amrinone and found that after intravenous administration to phenobarbital anesthetized dogs, the drugs had cumulative inotropic ED50's of 37 and 1891 micrograms/kg, respectively; relative effects on heart rate and blood pressure were comparable. There are two structural differences between amrinone and milrinone: (1) milrinone has a pyridone 2-methyl substituent and (2) the pyridone 5-amino substituent of amrinone is replaced with a nitrile in milrinone. We confirmed structure-activity studies that indicated that the 2-methyl substituent appears to be primarily responsible for the dramatic difference in the potencies of amrinone and milrinone. A plausible explanation for the effect of the methyl substituent is an altered molecular topology resulting from its steric interaction with the 3',5'-hydrogen atoms. Consequently, we probed the three-dimensional structures of these two compounds by X-ray crystallography. The dihedral angle between the planes formed by the two aromatic rings of amrinone was 1.3 degrees. In marked contrast, the corresponding angle for milrinone was 52.2 degrees. Moreover, 1H NMR studies revealed conformational differences in solution. Whereas the 2-methyl substituent undoubtedly produces some electronic and hydrophobic perturbations in the bipyridine cardiotonic series, the most significant effect, from a global viewpoint, is the altered molecular topology.

Molecular structure of the dihydropyridazinone cardiotonic 1,3-dihydro-3,3-dimethyl-5-(1,4,5,6-tetrahydro-6-oxo-pyridazinyl)- 2H-indol-2-one, a potent inhibitor of cyclic AMP phosphodiesterase.

The cardiotonic 1,3-dihydro-3,3-dimethyl-5-(1,4,5,6-tetrahydro-6-oxo-3- pyridazinyl)-2H-indol-2-one (1, LY195115) is a potent, competitive inhibitor (Ki = 80 nM) of sarcoplasmic reticulum derived phosphodiesterase (SR-PDE). Moreover, the compound is a potent positive inotrope both in vitro and in vivo. To assist further cardiotonic drug-design studies, we have mapped the three-dimensional structure of 1 using X-ray crystallography. From a global viewpoint, this drug was essentially planar, but two small regions of nonplanarity were apparent. These involved the geminal methyl substituents in the indol-2-one moiety and the C5' methylene unit of the dihydropyridazinone ring. Because of our previous studies involving the bipyridine cardiotonics amrinone and milrinone, the conformational relationship between the plane of the phenyl ring and the horizontal symmetry plane defined by N2', C3', and C4' of 1 was of particular interest. The C6-C5-C3'-C4' dihedral angle was -2.7 degrees, whereas the C6-C5-C3'-N2' dihedral angle was 174.6 degrees. Therefore the two rings maintain a high degree of coplanarity. Compound 4, the congener of 1 possessing a completely unsaturated pyridazinone ring was also studied. In terms of inotropic activity, this compound, devoid of any puckering in the pyridazinone moiety, was equipotent with 1. Methyl substitution at the 4-position of the dihydropyridazinone and pyridazinone rings provided disparate results. Compound 2, the 4-methyl analogue of 1, was 2-fold more potent than 1, and the methyl substituent probably caused only minor perturbations in overall molecular topology. However 5, the 4-methyl analogue of the pyridazinone 4, was 4.4-fold less active than 4, perhaps as a result of methyl-induced molecular nonplanarity.

NMDA antagonist activity of (+/-)-(2SR,4RS)-4-(1H-tetrazol-5-ylmethyl)piperidine-2-carboxylic acid resides with the (-)-2R,4S-isomer.

The tetrazole-substituted amino acid (+/-)-(2SR,4RS)-4-(1H-tetrazol-5-ylmethyl)pip eri dine-2-carboxylic acid (LY233053, (+/-)-1) was resolved into its constituent enantiomers by treatment of a key intermediate in the synthesis of the racemic amino acid, ethyl (+/-)-cis-4-(cyanomethyl)-N-allylpiperidine-2-carboxylate, with either 2S,3S- or 2R,3R-di-p-toluoyltartaric acid. These resolved amines were then converted as for the racemate to the amino acids (-)-1 and (+)-1. The activity of this potent and selective NMDA antagonist was found to reside with the (-)-isomer of 1 (LY235723). X-ray crystallographic analysis of the 2S,3S-di-p-toluoyltartaric acid salt of ethyl cis-4-(cyanomethyl)-N-allylpiperidine-2-carboxylate showed that the resolved amine, and thus (-)-1, possessed the 2R,4S absolute stereochemistry. Affinity for the NMDA receptor was determined using the specific radioligand [3H]-(2SR,4RS)-4-(phosphonomethyl)piperidine-2-carboxylic acid ([3H]CGS 19755; IC50 = 67 +/- 6 nM), and selective NMDA antagonist activity was determined using a cortical slice preparation (IC50 versus 40 microM NMDA = 1.9 +/- 0.24 microM). This compound also demonstrated potent NMDA antagonist activity in vivo following systemic administration through its ability to block NMDA-induced convulsions in neonatal rats, NMDA-induced lethality in mice, and NMDA-induced striatal neuronal degeneration in rats.

Synthesis and pharmacology of a series of 3- and 4-(phosphonoalkyl)pyridine- and -piperidine-2-carboxylic acids. Potent N-methyl-D-aspartate receptor antagonists.

We recently prepared a series of 3- and 4-(phosphonoalkyl)pyridine- and -piperidine-2-carboxylic acids as antagonists of neurotransmission at N-methyl-D-aspartate (NMDA) preferring receptors. NMDA antagonists may prove to be useful therapeutic agents, for instance, as anticonvulsants, in the treatment of neurodegenerative disorders such as Alzheimer's disease and in the prevention of neuronal damage that occurs during cerebral ischemia. The compounds prepared were evaluated for their ability to displace [3H]CPP binding (an assay shown to be selective for compounds that bind at the NMDA receptor) and for their ability to block NMDA-induced lethality in mice (an assay that is also specific for competitive and noncompetitive NMDA antagonists). Two of the compounds, cis-4-(phosphonomethyl)piperidine-2-carboxylic acid (11a) and cis-4-(3-phosphonoprop-1-yl)piperidine-2-carboxylic acid (11c) proved to be potent NMDA antagonists. 11a and 11c displaced [3H]CPP binding with IC50's of 95 and 120 nM, respectively, and both protected mice from NMDA-induced lethality, with MEDs (minimum effective dose, the dose at which three of the five animals tested survived) of 10 and 40 mg/kg ip, respectively. The rest of the compounds prepared were weakly active or inactive in these assays. The pattern of activity observed for this series parallels that observed for the acyclic series of omega-phosphono-alpha-amino acids, where AP5 and AP7 possessed NMDA antagonist activity while AP6 and AP8 were inactive. Reduction of conformational mobility by incorporation of the piperidine ring led to enhanced potency relative to the acyclic analogues.

Resolution and absolute configuration of an ergoline-related dopamine agonist, trans-4,4a,5,6,7,8,8a,9-Octahydro-5-propyl-1H(or 2H)-pyrazolo[3,4-g]quinoline.

The title compound (+/-)-5 (R = Pro) (LY141865) has been resolved into a (-) isomer and a (+) isomer as the D- and L-tartrate salts, respectively. Biological studies have shown that dopamine agonist activity is a property of only the (-) isomer. Crystallographic analysis has proven that the absolute configuration of the active (-) isomer is the same as that of the natural ergolines.

Effects of conformationally restricted 4-piperazinyl-10H-thienobenzodiazepine neuroleptics on central dopaminergic and cholinergic systems.

The levels of antidopaminergic and anticholinergic activities of neuroleptics, 4-piperazinyl-10H-thienobenzodiazepines, are modulated by imposing steric impedence to the piperazine ring. The optimum situation in favor of the anticholinergic action is reached in compound 5, 2,3-dimethyl-7-fluoro-4-(4-methyl-1-piperazinyl)-10H-thieno[2,3-b][1,5]benzodiazepine, where a maximum activity (equivalent to hyoscine), as measured by the [3H]QNB receptor binding assay, is obtained. The structure-activity relationships found highlight the importance of certain spatial dispositions of the distal piperazine nitrogen (electron lone pair) with respect to the tricyclic system. The evidence for molecular topography of these compounds is presented from X-ray, NMR, and other physical data. The conformational aspects for correspondence to the relevant receptors are discussed.

Synthesis of syn and anti isomers of 6-[[(hydroxyimino)phenyl]methyl]-1-[(1-methylethyl)sulfonyl]-1H-benzimidazol-2-amine. Inhibitors of rhinovirus multiplication.

The synthesis and antirhinovirus activity of syn and anti isomers of 6-[[(hydroxyimino)phenyl]methyl]-1-[(1-methylethyl)sulfonyl]-1H-benzimidazol-2-amine (4 and 5) are reported. The structural assignments of 4 and 5 are based upon 13C NMR spectra of both isomers and also X-ray analysis of 5. The anti-isomer 5 was more potent than the syn-isomer 4 when compared as an inhibitor of rhinovirus multiplication in vitro. Both isomers inhibited multiplication of 15 different serotypes of rhinovirus.

Indole inhibitors of human nonpancreatic secretory phospholipase A2. 1. Indole-3-acetamides.

Phospholipases (PLAs) produce rate-limiting precursors in the biosynthesis of various types of biologically active lipids involved in inflammatory processes. Increased levels of human nonpancreatic secretory phospholipase A2 (hnps-PLA2) have been detected in several pathological conditions. An inhibitor of this enzyme could have therapeutic utility. A broad screening program was carried out to identify chemical structures which could inhibit hnps-PLA2. One of the lead compounds generated by the screening program was 5-methoxy-2-methyl-1-(phenylmethyl)-1H-indole-3-acetic acid (13a). We describe the syntheses, structure--activity relationships, and pharmacological activities of a series of indole-3-acetamides and related compounds derived from this lead. This SAR was undertaken with the aid of X-ray crystal structures of complexes between the inhibitors and hnps-PLA2 which were of great value in directing the SAR.

Indole inhibitors of human nonpancreatic secretory phospholipase A2. 2. Indole-3-acetamides with additional functionality.

As reported in our previous paper, a series of indole-3-acetamides which possessed potency and selectivity as inhibitors of human nonpancreatic secretory phospholipase A2(hnps-PLA2) was developed. The design of these compounds was based on information derived from x-ray crystal structures determined for complexes between the enzyme and its inhibitors. We describe here the further implementation of this structure-based design strategy and continued SAR development to produce indole-3-acetamides with additional functionalities which provide increased interaction with important residues within the enzyme active site. These efforts led to inhibitors with substantially enhanced potency and selectivity.

Indole inhibitors of human nonpancreatic secretory phospholipase A2. 3. Indole-3-glyoxamides.

The preceding papers of this series detail the development of functionalized indole-3-acetamides as inhibitors of hnps-PLA2. We describe here the extension of the structure-activity relationship to include a series of indole-3-glyoxamide derivatives. Functionalized indole-3-glyoxamides with an acidic substituent appended to the 4- or 5-position of the indole ring were prepared and tested as inhibitors of hnps-PLA2. It was found that the indole-3-glyoxamides with a 4-oxyacetic acid substituent had optimal inhibitory activity. These inhibitors exhibited an improvement in potency over the best of the indole-3-acetamides, and LY315920 (6m) was selected for evaluation clinically as an hnps-PLA2 inhibitor.

Visualization of the in vivo generation of donor antigen-specific effector CD8+ T cells during mouse cardiac allograft rejection: in vivo effector CD8+ T cell generation during allograft rejection.

BACKGROUND: An adoptive transfer system was used to study the fate of alloreactive CD8+ H-2Kb-specific TCR transgenic (DES+) T cells in vivo after transplantation. METHODS: A trace population of 2.0x10(6) CD8+DES+ T cells were adoptively transferred into syngeneic CBA.Ca (H-2k) mice 24 hr before transplantation of an H-2Kb+ or H-2Kb- cardiac allograft. RESULTS: H-2Kb specific T cells proliferated and produced interleukin-2 and interferon-gamma in response to H-2Kb+, but not H-2Kb- cardiac allografts. CD8+DES+ T cells that infiltrated the H-2Kb+ cardiac allografts developed a distinct cell surface and cytokine phenotype compared with the CD8+DES+ T cells that remained in the periphery. H-2Kb-specific graft infiltrating T cells (a) underwent a larger number of cell divisions (> =3), (b) increased in size, (c) up-regulated CD69, and (d) down-regulated CD62L. CONCLUSIONS: These results demonstrate that alloantigen-specific T cells can be monitored in vivo during the immune response to an allograft and that the fate of CD8+ T cells specific for the allogeneic class I molecules expressed by the graft is different between cells in the periphery and those that infiltrate the graft.

The visualization of T cell responses.

Transplanting allogeneic grafts is still significantly hampered by the rejection process, despite the use of powerful immunosuppressive agents. The T cell is recognized as playing a central role in the process of rejection, and it is believed that graft tolerance will ultimately be achieved by immunological manipulation of this cell (1, 2). As immunologists strive to define the role of the T cell in the fundamental processes of immunity and tolerance, new methods are emerging that will facilitate visualization of the T cells directly involved in the rejection response (3, 4). This overview addresses the visualization of T cell responses as made possible by these technological developments.