| 1371279 |
A spontaneous mutation of integrin alpha IIb beta 3 (platelet glycoprotein IIb-IIIa) helps define a ligand binding site |
None |
J Biol Chem |
A spontaneous mutation of integrin alpha IIb beta 3 (platelet glycoprotein IIb-IIIa) helps define a ligand binding site
Abstract
- This work characterizes a mutant integrin alpha IIb beta 3 (glycoprotein (GP) IIb-IIIa) from a thrombasthenic patient, ET, whose platelets fail to aggregate in response to stimuli. The nature of defect was defined by the reduced ability of synthetic peptide ligands, corresponding to the carboxyl terminus of the fibrinogen gamma chain (gamma 402-411) and Arg-Gly-Asp (RGD), to increase the binding of the occupancy-dependent anti-LIBS1 antibody to mutant alpha IIb beta 3 and the reduced binding of mutant alpha IIb beta 3 to an immobilized RGD peptide. In addition, ET's platelets failed to bind the ligand-mimetic monoclonal anti-alpha IIb beta 3, PAC1. DNA sequence analysis of amplified ET genomic DNA revealed a single G----A base change which encoded substitution of R214 by Q in mature beta 3. Introduction of this point mutation into recombinant wild type alpha IIb beta 3 expressed in Chinese hamster ovary cells reproduced the ET platelet alpha IIb beta 3 deficits in binding of fibrinogen, mAb PAC1, and synthetic peptide ligands. Furthermore, substitution of R214 by Q in the synthetic peptide containing the sequence of beta 3(211-222) resulted in decreased ability of this peptide to block fibrinogen binding to purified alpha IIb beta 3. These findings suggest that substitution of beta 3 R214 by Q is responsible for the functional defect in alpha IIb beta 3 and that R214 is proximal to or part of a ligand binding domain in alpha IIb beta 3.
|
| 1373749 |
Anti-inflammatory effect of cyclosporin A on human skin mast cells |
10.1111/1523-1747.ep12499960. |
J Invest Dermatol |
Anti-inflammatory effect of cyclosporin A on human skin mast cells
Abstract
- We have examined the effects of cyclosporin A (CsA) and cyclosporin H (CsH), which bind with different affinity to cyclophilin, to evaluate the role of this protein in the release of preformed (histamine) and de novo synthesized (prostaglandin D2PGD2) mediators of inflammatory reactions from human skin mast cells (HSMC). CsA (2.4-800 nM)-inhibited (5-60%) histamine release from HSMC challenged with anti-IgE. CsA exerted little, if any, inhibitory effect on histamine release from HSMC challenged with compound A23187 and substance P, whereas it completely suppressed A23187-induced histamine release from human basophils. Inhibition of histamine release from HSMC challenged with anti-IgE was extremely rapid and was not abolished by washing (three times) the cells before anti-IgE challenge. CsA (2.4-800 nM) markedly inhibited (25-70%) the de novo synthesis of PGD2 from HSMC challenged with anti-IgE. CsH, which has an extremely low affinity for cyclophilin, had no effect on skin mast-cell mediator release. These data suggest that CsA is a potent anti-inflammatory agent acting on HSMC, presumably by interacting with cyclophilin.
|
| 1374237 |
Structure of the human alpha-2 macroglobulin gene and its promotor. |
10.1016/0006-291x(92)90631-t |
Biochem. Biophys. Res. Commun. |
Structure of the human alpha-2 macroglobulin gene and its promotor.
Abstract
- The human alpha 2-macroglobulin gene was isolated in five overlapping clones. The gene spans approx. 48 kb and consists of 36 exons, from 21 to 229 bp in size and with consensus splice sites. Intron sizes range from 145 bp to 7.5 kb. The alpha 2M gene is a single copy gene in the human genome. A sequence polymorphism within the bait domain, coding for an Arg to His substitution within the primary cleavage site for trypsin, was identified in 1 of 132 individuals tested so far. Three transcription initiation sites have been identified in liver by primer extension and RNase protection assays. The most proximal, major site (+1) is preceded by a TATA-like structure (ATAAA) at -26 bp. Only 2 mRNA species were found in uterus and in cultured lung fibroblasts, while alpha 2M is not expressed to a detectable level in skin fibroblasts. The far distal transcription initiation site which is preceded by an intact TATA box and a potential HP-1 binding site is thus specific for liver.
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| 1380373 |
Tachykininergic transmission to the circular muscle of the guinea-pig ileum: evidence for the involvement of NK2 receptors |
10.1111/j.1476-5381.1992.tb09061.x. |
Br J Pharmacol |
Tachykininergic transmission to the circular muscle of the guinea-pig ileum: evidence for the involvement of NK2 receptors
Abstract
- 1. The effect of newly developed, receptor-selective tachykinin antagonists (GR 71,251 for NK1 receptors, MEN 10,376 and L 659,877 for NK2 receptors) on noncholinergic transmission to the circular muscle of the guinea-pig ileum has been investigated. 2. In circular muscle strips of the ileum, electrical field stimulation in the presence of atropine (2 microM) and apamin (0.1 microM) evoked a complex motor response. The tonic primary contraction in this response was reduced by GR 71,251 (10 microM) and MEN 10,376 (3-10 microM) but not by L 659,877 (up to 10 microM). The presence of apamin was necessary in this experimental arrangement to unmask an atropine-resistant primary contraction, sensitive to tachykinin antagonists. The motor response was abolished by tetrodotoxin. 3. In circular strips of the ileum GR 71,251 (10 microM) inhibited the tonic contraction produced by Sar9 substance P sulphone, a selective NK1 receptor agonist but not that produced by beta Ala8 neurokinin A (4-10), a selective NK2 receptor agonist. By contrast, MEN 10,376 antagonized the effect of the NK2 agonist while leaving the response to the NK1 agonist unaffected. 4. In whole segments of the ileum, distension of the gut wall by an intraluminal balloon placed at about 1 cm from the point of recording of mechanical activity of the circular muscle produced atropine-sensitive phasic contractions (ascending enteric reflex). In the presence of atropine (2 microM), a noncholinergic response was elicited, which required larger volumes of distension that the cholinergic one. The atropine-resistant ascending enteric reflex was enhanced by apamin (0.1 microM) and abolished by tetrodotoxin, either in the presence or absence of apamin.5. MEN 10,376 (3-lOmicroM) inhibited the atropine-resistant ascending enteric reflex in the presence of apamin while GR 71,251 or L 659,877 (10 microM each) were ineffective. MEN 10,376 inhibited the atropine-resistant ascending enteric reflex to a larger extent in the absence than in the presence of apamin and also slightly inhibited the ascending enteric reflex in the absence of atropine.6. These findings provide evidence for an involvement of NK2 tachykinin receptors in excitatory transmission to the circular muscle of the guinea-pig ileum. NK2 receptors are also involved in the physiological-like circular muscle activation produced by stimulation of intramural neuronal pathways which subserve the atropine-resistant ascending enteric reflex.
|
| 1381319 |
Activity of peptide and non-peptide antagonists at peripheral NK1 receptors |
10.1016/0014-2999(92)90613-9. |
Eur J Pharmacol |
Activity of peptide and non-peptide antagonists at peripheral NK1 receptors
Abstract
- We investigated the affinity of several tachykinin antagonists reportedly selective for NK1 receptors at various tachykinin receptors and NK2 receptors subtypes. The four antagonists tested were: L 668,169, Spantide II, Ac-Thr-DTrp(for)-Phe-NMeBzl (FR 113680) and the novel nonpeptide antagonist (+/-)-CP-96,345. The four antagonists were found to be effective against NK1 receptor-mediated responses in the guinea-pig ileum with the following rank order of potency (pKB values in parentheses): (+/-)-CP-96,345 (8.11) greater than Spantide II (7.08) greater than FR 113680 (6.61) greater than or equal to L 558,169 (6.44). (+/-)-CP-96,345, Spantide II and FR 113680 were distinctly more potent at NK1 receptors than at NK2 receptors (NK2A in the rabbit pulmonary artery, NK2B in the hamster trachea). L 668,169 antagonized neurokinin A-induced contractions in the hamster trachea with an affinity similar (pKB value 6.16) to that found in the guinea-pig ileum for NK1 receptors (pKB value 6.44). All antagonists were inactive at NK3 receptors of the rat portal vein. In a second series of experiments, the affinities of test antagonists for NK1 receptors in the guinea-pig ileum were compared to those for NK1 receptors in the guinea-pig vas deferens, the rabbit jugular vein and the rat urinary bladder. For each antagonist, the affinity measured in the guinea-pig vas deferens and the rabbit jugular vein was comparable to that found in the guinea-pig ileum. In the rat urinary bladder, (+/-)-CP-96,345 was about 100 times less potent in blocking NK1 receptor-mediated contractions than in the guinea-pig ileum.(ABSTRACT TRUNCATED AT 250 WORDS)
|
| 1382574 |
The gene organization of the human beta 7 subunit, the common beta subunit of the leukocyte integrins HML-1 and LPAM-1. |
10.1093/intimm/4.9.1031 |
Int. Immunol. |
The gene organization of the human beta 7 subunit, the common beta subunit of the leukocyte integrins HML-1 and LPAM-1.
Abstract
- The integrin beta 7 subunit associates with two alternative alpha subunits termed alpha HML-1 and alpha 4 to give the lymphocyte activation and homing receptors HML-1 and LPAM-1. Overlapping genomic clones that encoded the human beta 7 subunit gene were isolated from cosmid and phage lambda libraries. The coding portion of the gene spanned approximately 10 kb and was composed of 14 exons. Exon 1 (123 bp) encoded 5' untranslated sequences; exon 2 (204 bp) encoded the initiation codon, signal peptide, and 50 amino acid residues of the N-terminus of the mature protein; 7 exons (exons 3-9), ranging in size from 90 bp to 242 bp, encoded most of the extracellular domain proximal to the four cysteine-rich repeats; the region corresponding to the beta 3 arginine-glycine-aspartic acid (RGD)-binding domain was divided amongst exons 4 and 5; the four cysteine-rich repeats were encoded by 3 exons (exons 10-12) with intron insertion into the first and third repeats; exon 13 (209 bp) provided a spacer between the cysteine-rich domains and the transmembrane domain; exon 14 (161 bp) encoded the transmembrane domain and exactly half of the cytoplasmic domain; the remainder of the cytoplasmic domain and most of the 3' untranslated region was contained in the largest 313 bp exon 15. Comparison of integrin beta subunit genes revealed that the gene organization of beta 7 was almost identical to that of beta 2, but had diverged from that of beta 3. Amplification of integrin DNAs directly from genomic DNA, using PCR primers based on beta subunit consensus sequences corresponding to the beta 3 RGD-binding domain, yielded partial gene sequences for the beta 3, beta 5, and beta 6 subunits only. Inspection of the amplified sequences revealed that, as for beta 3, the regions in beta 5 and beta 6 corresponding to the beta 3 RGD-binding domain lacked the intron present in beta 7, beta 1, and beta 2, which divides this region in beta 2 into two subdomains that contribute to subunit assembly. This study provides genetic evidence for at least two major branches to the integrin beta subunit evolutionary tree, with beta 7, beta 2, and probably beta 1 in one branch, and the cytoadhesin beta 3 and probably also beta 5 and beta 6 in the other.
|
| 1384039 |
Cloning of ASH, a ubiquitous protein composed of one Src homology region (SH) 2 and two SH3 domains, from human and rat cDNA libraries |
10.1073/pnas.89.19.9015. |
Proc Natl Acad Sci U S A |
Cloning of ASH, a ubiquitous protein composed of one Src homology region (SH) 2 and two SH3 domains, from human and rat cDNA libraries
Abstract
- The protein ASH (for abundant Src homology), composed of one Src homology region (SH) 2 and two SH3 domains, was cloned by screening human and rat cDNA libraries with an oligonucleotide probe directed to a consensus sequence of the SH2 domains. The rat-derived ASH peptide was comprised of 217 amino acids with a molecular mass of 25-28 kDa and was found to be ubiquitous in rat tissues. A human cDNA clone was also found to code for part of the same protein, suggesting that ASH is common to human and rat. The amino acid sequence of ASH was strikingly similar to Sem-5, the product of a nematode cell-signaling gene, and ASH is most probably a mammalian homologue of Sem-5. ASH bound in vitro to phosphotyrosine-containing proteins, including activated epidermal growth factor receptor, the ASH SH2 domain being responsible for the binding. Induced expression of an antisense ASH cDNA led to a reduction in cell growth. Considering these observations and the structural homology to Sem-5, ASH is likely to function as a ubiquitous signal transducer, possibly resembling Sem-5, which communicates between a receptor protein tyrosine kinase and a Ras protein.
|
| 1384424 |
Anti-human immunodeficiency virus activity of a novel synthetic peptide, T22 (Tyr-5,12, Lys-7polyphemusin II): a possible inhibitor of virus-cell fusion |
10.1128/AAC.36.6.1249. |
Antimicrob Agents Chemother |
Anti-human immunodeficiency virus activity of a novel synthetic peptide, T22 (Tyr-5,12, Lys-7polyphemusin II): a possible inhibitor of virus-cell fusion
Abstract
- More than 40 peptides associated with tachyplesin and polyphemusin, which are highly abundant in hemocyte debris of the horseshoe crabs Tachypleus tridentatus and Limulus polyphemus, were synthesized. Among these peptides, we found that a novel compound, which was called T22 (Tyr-5,12, Lys-7polyphemusin II), strongly inhibited the human immunodeficiency virus type 1 (HIV-1)-induced cytopathic effect and viral antigen expression. Its 50% effective concentration was 0.008 micrograms/ml, while its 50% cytotoxic concentration was 54 micrograms/ml. The anti-HIV activity of T22 was observed with several strains of HIV-1, including zidovudine-resistant strains, and with HIV-2 within the concentration range of 0.006 to 0.071 microgram/ml. T22 efficiently inhibited giant cell formation on the cocultivation of MOLT-4/HIV and MOLT-4 cells but modestly inhibited direct HIV binding. T22 did not inhibit reverse transcriptase activity. A time-of-addition study, which involved monitoring of the appearance of proviral DNA by using the polymerase chain reaction technique, found that T22 exerted its effect on a process, most probably virus-cell fusion or uncoating, immediately after virus adsorption.
|
| 1384907 |
Tachykinin receptors in the guinea-pig renal pelvis: activation by exogenous and endogenous tachykinins |
10.1111/j.1476-5381.1992.tb14459.x. |
Br J Pharmacol |
Tachykinin receptors in the guinea-pig renal pelvis: activation by exogenous and endogenous tachykinins
Abstract
- 1. The contractile response to substance P, neurokinin A, selective agonists for the NK1, NK2 and NK3 tachykinin receptors and the activity of receptor-selective antagonists has been investigated in circular muscle strips of the guinea-pig isolated renal pelvis in the presence of indomethacin (3 microM). 2. Neurokinin A was the most potent agonist tested, being about 32 times more potent than substance P. The action of both substance P and neurokinin A was enhanced by peptidase inhibitors (bestatin, captopril and thiorphan, 1 microM each). The selective NK2 receptor agonist beta Ala8 neurokinin A (4-10), was slightly less potent and effective than neurokinin A itself. The selective NK1 receptor agonist Sar9 substance P sulphone was effective at low (nM) concentrations but its maximal effect did not exceed 30% of maximal response to substance P or neurokinin A. The NK3-selective agonist MePhe7 neurokinin B was effective only at high (microM) concentrations. 3. The pseudopeptide derivative of neurokinin A(4-10), MDL 28,564, displayed a clear-cut agonist character, although it was less potent than neurokinin A. 4. The responses to roughly equieffective (25-35% of maximal response) concentrations of beta Ala8 neurokinin A (4-10), MDL 28,564 and MePhe7 neurokinin B were antagonized to a similar extent by MEN 10,376 (3 microM), a selective NK2 tachykinin receptor antagonist, while the response to Sar9 substance P sulphone was unchanged. 5. The response to Sar9 substance P sulphone was inhibited by the NK1 receptor-selective antagonist, GR 82,334 (3 microM) while the response to beta Ala8 neurokinin A (4-10) was unchanged. 6. The selective NK2 receptor antagonists MEN 10,376, L 659,877 and R 396 antagonized competitively the response to PAla8 neurokinin A (4-10) with the following rank order of potency (pA2 values in parentheses): MEN 10,376 (7.41)>L 659,877 (7.15)>R 396 (6.43). MEN 10,376 and L 659,877 also competitively antagonized the response to neurokinin A, although with lower potency as compared to the selective NK2 receptor agonist.7. MEN 10,376, L 659,877 and R 396 reduced in a concentration-dependent manner the contractile response produced by electrical field stimulation (1 Hz, 100 V, 0.25 ms pulse width, trains of 10 s). The rank order of potency of NK2 receptor antagonists in blocking the response to electrical stimulation (MEN 10,376> L 659,877> R 396) closely mimicked their potency in antagonizing exogenous tachykinins.8. The inhibitory effect of MEN 10,376 toward responses produced by electrical field stimulation was significantly reduced when tested in the presence of peptidase inhibitors, which increased significantly the response to nerve stimulation.9. GR 82,334 (3 pM) did not significantly affect the response to nerve stimulation in untreated preparations and slightly reduced it in the presence of peptidase inhibitors.10. We conclude that both NK, and NK2 receptors mediate the contractile effect of tachykinins in the circular muscle of the guinea-pig renal pelvis and that the response ascribable to NK2 receptor stimulation is larger than that ascribed to NK, receptor stimulation. The NK2 receptor in the guinea-pig renal pelvis belongs to the same subtype previously identified in the rabbit pulmonary artery. NK2 receptors play a dominant role in the physiological response determined by the release of endogenous tachykinins and a contribution of NKI receptors becomes evident after inhibition of peptide degradation.
|
| 1386701 |
The new cyclosporine derivative, SDZ IMM 125: in vitro and in vivo pharmacologic effects |
None |
Transplant Proc |
The new cyclosporine derivative, SDZ IMM 125: in vitro and in vivo pharmacologic effects
Abstract
|
| 1391612 |
Three new microcystins, cyclic heptapeptide hepatotoxins, from Nostoc sp. strain 152 |
10.1021/tx00028a003. |
Chem Res Toxicol |
Three new microcystins, cyclic heptapeptide hepatotoxins, from Nostoc sp. strain 152
Abstract
- Three new cyclic heptapeptide hepatotoxins, D-Ser1,ADMAdda5microcystin-LR (1), D-Asp3,-ADMAdda5microcystin-LHar (2), and ADMAdda5,Mser7microcystin-LR (3), were isolated from the cyanobacterium (blue-green alga) Nostoc sp. strain 152, together with four known microcystins, ADMAdda5microcystin-LR (4), ADMAdda5microcystin-LHar (5), D-Asp3,-ADMAdda5microcystin-LR (6), and DMAdda5microcystin-LR (7). The structures of new microcystins were assigned on the basis of high-resolution fast atom bombardment mass spectrometry (HR FABMS), collisionally induced tandem FABMS (FABMS/MS), amino acid analysis, and gas chromatography (GC) on a chiral capillary column. All three new toxins contained 9-acetoxy-3-amino-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid (ADMAdda) instead of the corresponding 9-methoxyl derivative (Adda), while 7 contains the corresponding 9-hydroxy analog (DMAdda). Compound 1 is the first microcystin reported that contains D-serine (D-Ser) in lieu of the D-alanine (D-Ala) unit which was thought to be an invariable amino acid component of the microcystins. Compound 2 has L-homoarginine (Har) instead of L-arginine (L-Arg) in 6 and D-aspartic acid (D-Asp) instead of D-erythro-beta-methylaspartic acid (D-MeAsp) in 5. Compound 3, the N-methylserine (Mser) variant of the N-methyldehydroalanine unit in 4, would be a biosynthetic precursor of 4.
|
| 1391629 |
Molecular structure of cyclo-(D-Val-L-Hyi-L-Val-D-Hyi)2- revealed by x-ray analysis |
10.1002/bip.360320705. |
Biopolymers |
Molecular structure of cyclo-(D-Val-L-Hyi-L-Val-D-Hyi)2- revealed by x-ray analysis
Abstract
- The crystal structure of a synthetic analogue of valinomycin, cyclo-(D-Val-L-Hyi-L-Val-D-Hyi)2- (octa-meso-valinomycin) (I) (C40H68N4O12.1.5.C4H8O2, M(r) = 937.01 + 88.10), has been determined. Crystals grown from dioxane are monoclinic, space group P2(1)/a, with cell parameters a = 21.487 (8), b = 16.836 (5), c = 16.089 (4) A, beta = 111.70 (4), and Z = 4. The atomic coordinates for nonhydrogen atoms were refined in the anisotropic thermal motion approximation. H atom positions were included in the structure factor calculations at their geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.11 and 0.13, respectively. The conformation of the depsipeptide crystallized from dioxane is different from that crystallized from chloroform (II). The molecule adopts a rectangular shape with two type IV beta-turns containing a hydrogen bond and possesses pseudorotational symmetry. The side chains are located on the molecular periphery. The orientation of the carbonyl groups of the molecule is not conducive for efficient metal-ion coordination and in the observed conformation cannot behave as an ionophore. In the crystal the molecules form infinite chains parallel to the c axis, and are stabilized by two intermolecular hydrogen bonds that are shorter and have better geometry than the intramolecular hydrogen bonds. A phi/psi plot for dodecadepsipeptides with a (DLLD)3 sequence has well-defined areas for Val and Hyi residues only in cases when the crystals have been grown from nonpolar or medium-polar solvents. The phi/psi plot for octadepsipeptides crystallized from chloroform (II) shows this behavior also.(ABSTRACT TRUNCATED AT 250 WORDS)
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| 1391633 |
Crystal and molecular structure of the depsipeptide ionophore hexadecaisoleucinomycin, cyclo-(D-Ile-L-Lac-L-Ile-D-Hyi)4- (C80H136N8O24) |
10.1002/bip.360320710. |
Biopolymers |
Crystal and molecular structure of the depsipeptide ionophore hexadecaisoleucinomycin, cyclo-(D-Ile-L-Lac-L-Ile-D-Hyi)4- (C80H136N8O24)
Abstract
- The crystal structure of a synthetic depsipeptide ionophore hexadecaisoleucinomycin, cyclo -(D-Ile-L-Lac-L-Ile-D-Hyi)4- (C80H136N8O24), has been determined by single crystal x-ray diffraction techniques. The crystals are orthorhombic, space group P2(1)2(1)2(1), number of molecules per unit cell z = 4, and cell parameters a = 11,195, b = 17.853, c = 54.835 A. The values of the standard (R) and weighted (Rw) discrepancy factors after refinement are 0.122 and 0.135, respectively. The structure is characterized by an elongated bracelet form with a twofold axis of pseudosymmetry. It is stabilized by eight intramolecular 4----1 hydrogen bonds between the amide C = O and N - H groups. The ester carbonyls are directed toward the inside of the molecule, their oxygen atoms forming an ellipsoidal internal cavity. The side chains are located on the molecular periphery. The conformational states of hexadecaisoleucinomycin in solution are discussed in the light of the data obtained.
|
| 1399840 |
New cyclodepsipeptides, enniatins D, E and F produced by Fusarium sp. FO-1305 |
10.7164/antibiotics.45.1207. |
J Antibiot (Tokyo) |
New cyclodepsipeptides, enniatins D, E and F produced by Fusarium sp. FO-1305
Abstract
- New cyclodepsipeptides named enniatins D, E and F were isolated from the culture broth of Fusarium sp. FO-1305 as inhibitors of acyl-CoA:cholesterol acyltransferase (ACAT). The respective structures of enniatins D, E and F were determined to be cycloD-alpha-hydroxyisovaleryl(D-Hiv)-L-N-methylleucinyl(L- Me-Leu)-D-Hiv-L-N-methylvalinyl(L-Me-Val)-D-Hiv-L-Me-Val, a mixture of cyclo-D-Hiv-L-Me-Leu-D-Hiv-L-N-methylisoleucinyl(L-Me-Ile)-D-Hiv- L-Me-Val and cyclo(D-Hiv-L-Me-Ile-D-Hiv-L-Me-Leu-D-Hiv-L-Me-Val), and cyclo(D-Hiv-L-Me-Leu-D-Hiv-L-Me-Ile-D-Hiv-L-Me-Ile) by spectral analyses and chemical degradation. The IC50 values of enniatins D, E and F for ACAT activity in an enzyme assay using rat liver microsomes were calculated to be 87, 57 and 40 microM, respectively.
|
| 1416847 |
In vitro antifungal activities and in vivo efficacies of 1,3-beta-D-glucan synthesis inhibitors L-671,329, L-646,991, tetrahydroechinocandin B, and L-687,781, a papulacandin |
10.1128/AAC.36.8.1648. |
Antimicrob Agents Chemother |
In vitro antifungal activities and in vivo efficacies of 1,3-beta-D-glucan synthesis inhibitors L-671,329, L-646,991, tetrahydroechinocandin B, and L-687,781, a papulacandin
Abstract
- The in vivo anti-Candida activities of 1,3-beta-D-glucan synthesis inhibitors L-671,329, L-646,991 (cilofungin), L-687,901 (tetrahydroechinocandin B), and L-687,781 (a papulacandin analog) were evaluated by utilizing a murine model of disseminated candidiasis that has enhanced susceptibility to Candida albicans but increased sensitivity for discriminating antifungal efficacy. DBA/2 mice were challenged intravenously with 1 x 10(4) to 5 x 10(4) CFU of C. albicans MY1055 per mouse. Compounds were administered intraperitoneally at concentrations ranging from 1.25 to 10 mg/kg of body weight twice daily for 4 days. At 6 h and 1, 2, 3, 4, 7, and 9 days after challenge, five mice per group were sacrificed and their kidneys were homogenized and plated for enumeration of Candida organisms (CFU per gram). Progressiveness of response trends and no-statistical-significance-of-trend doses were derived to rank compound efficacy. 1,3-beta-D-Glucan synthesis 50% inhibitory concentrations were determined by using a C. albicans (MY1208) membrane glucan assay. Candida and Cryptococcus neoformans MICs and minimal fungicidal concentrations were determined by broth microdilution. L-671,329, L-646,991, L-687,901, and L-687,781 showed similar 1,3-beta-D-glucan activities, with 50% inhibitory concentrations of 0.64, 1.30, 0.85, and 0.16 micrograms/ml, respectively. Data from in vitro antifungal susceptibility studies showed that L-671,329, L-646,991, and L-687,901 had similar MICs ranging from 0.5 to 1.0 micrograms/ml, while L-687,781 showed slightly higher MICs of 1.0 to 2.0 micrograms/ml for C. albicans MY1055. Lipopeptide compounds were ineffective against C. neoformans strains. Results from in vivo experiments comparing significant trend and progressiveness in response analyses indicated that L-671,329 and L-646,991 were equipotent but slightly less active than L-687-901, while L-687,781 was ineffective at 10 mg/kg. Fungicidal activities of L-671,329, L-646,991, and L-687,901 were observed in vivo, with significant reduction in Candida CFU per gram of kidneys compared with those in sham-treated mice at doses of > or = 2.5 mg/kg evident as early as 1 day after challenge.
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