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M Fridkin

Publications and source records attributed to M Fridkin.

At least 91 records · Page 5Linked to original sources
PubMed1997

Tuftsin-THF-gamma 2 chimeric peptides: potential novel immunomodulators.

Synthesis of two chimeric peptides composed of tuftsin and thymic humoral factor-gamma 2 (THF-gamma 2) conjugates was accomplished. Our goal was the generation of novel immunomodulators. Initially, we demonstrate an IL-6 inducing activity of the phagocytic cells stimulant, tuftsin, on murine macrophages. This activity was documented only in the presence of antigen, either KLH or lysozyme. The augmentation was dose dependent, with optimal activity at a concentration of 200 and 20 nM, respectively. The chimeric peptides, either H2N-tuftsin-THF-gamma 2-OH or H2N-THF-gamma 2-tuftsin-OH, were also evaluated in the IL-6 system in the presence of the more potent antigen, KLH. The IL-6 inducing effect was maintained, although maximal activity appeared only at a concentration an order of magnitude greater than that of tuftsin. The chimeric peptides were further tested in an assay evaluating enhancement in murine bone marrow myeloid colony formation, a system in which THF-gamma 2, a T cell stimulant, has an established beneficial effect. The compounds were found to be inactive at the 25-200 ng/ml (14-112 nM) concentration range evaluated. Finally, the chimeric peptides were tested in a combined macrophages-T cells assay, i.e. antigen presentation, in which H2N-tuftsin-THF-gamma 2-OH was found to be more active than either parent peptide, thus representing a possible therapeutic agent.

Adjuvants, Immunologic↗
PubMed1997

Neurobehavioral development of neonatal mice following blockade of VIP during the early embryonic period.

Previous work has shown that blockade of VIP function in the early postimplantation embryo results in growth retardation and microcephaly. In the present work, the neurobehavioral development of neonatal mice was examined following treatment of dams with a VIP antagonist during this period. Inhibition of VIP functions during early embryogenesis impaired the performance of 5 of 10 developmental behaviors. These behaviors included developmental milestones (first appearance of ear twitch and eye opening) and complex motor behaviors (negative geotaxis, surface righting, and air righting). The retardation of neurobehavioral development produced by inhibition of VIP action indicates that this peptide is important to the progression of embryonic development.

Animals↗
PubMed1997

Extracellular matrix-anchored serum amyloid A preferentially induces mast cell adhesion.

Mast cells are known to accumulate in various inflammatory processes, some of which are known to be associated with increased local and systemic levels of acute-phase reactants such as serum amyloid A (SAA) or with amyloid deposition. The mechanism(s) by which mast cells are recruited to these sites, however, has not been fully elucidated. It has recently been shown that SAA interacts with extracellular matrix (ECM) components and thereby acts as a chemoattractant and regulator of immune cell migration. On the basis of these observations, we examined the effect of SAA on mast cell adhesion to ECM, an essential step in cellular transmigration. We could first demonstrate strong specific binding of recombinant human SAA (rSAA) to murine mast cells using flow cytometry. Moreover, radiolabeled rSAA was found to bind, in a saturable manner, to mast cells, reaching a binding affinity of 10(-8) M. When immobilized by preincubation with ECM, SAA or its proteolytically degraded amyloid A fragment (amino acid residues 2-82), which contains RGD-related adhesion motif but not the COOH-terminal portion of SAA (amino acid residues 77-104), induced the adhesion of resting mast cells to ECM or laminin. SAA and AA, in soluble or immobilized forms, did not activate mast cells to release mediators. Mast cell adhesion to the immobilized ECM-SAA complex appeared to occur through an integrin recognition, inasmuch as adhesion was calcium dependent and could be blocked by an RGD-containing peptide or by anti-CD29 monoclonal antibody. Genistein also inhibited adhesion, indicating that tyrosine kinase activity was involved. These data suggest that SAA bound to ECM may serve as an important inducer of mast cell adhesion, thus regulating mast cell recruitment and accumulation at these sites, which in turn could potentiate further pathology.

Animals↗
PubMed1996

1-Aminocyclobutanecarboxylic acid derivatives as novel structural elements in bioactive peptides: application to tuftsin analogs.

Four novel 2,4-methano amino acids (MAAs, 1-aminocyclobutane-1-carboxylic acids) were synthesized. These include the basic MAA analogs of lysine (16), ornithine (5), and arginine (6) and the neutral methanovaline (22), related to proline. The above MAAs, as well as the MAA analog of homothreonine (7), were incorporated into the peptide chain of the immunomodulatory peptide tuftsin, Thr-Lys-Pro-Arg, known to enhance several biological activities mediated by phagocytic cells. The synthetic methano tuftsin analogs were assayed for their ability to stimulate interleukin-6 (IL-6) secretion by mouse peritoneal macrophages and for their stability in human serum toward enzymatic degradation. It was found that, at 2 x 10(-7) M, [MThr1]tuftsin (24) and an isomer of [MVal3]tuftsin (27a) were considerably more active than the parent peptide in augmentation of cytokine release. [MOrn2]Tuftsin (25) was equally potent. The analogs [MThr1]tuftsin (24) and [MOrn2]tuftsin (25), both pertaining to the proteolytically sensitive Thr-Lys bond of tuftsin, exhibited high resistance to enzymatic hydrolysis as compared to tuftsin. Using specific rabbit anti-tuftsin antibodies in a competitive enzyme-linked immunosorbent assay (ELISA) revealed that none of the MAA analogs can cross-react with tuftsin. It may indicate that the peptides assume global structures different than that of tuftsin.

Amino Acids↗
PubMed1996

Breast cancer growth is inhibited by vasoactive intestinal peptide (VIP) hybrid, a synthetic VIP receptor antagonist.

Breast cancer vasoactive intestinal peptide (VIP) receptors were characterized. Using in vitro autoradiographic techniques, 125I-labeled VIP bound with high affinity to breast biopsy sections. 125I-labeled VIP bound specifically to give breast cancer cell lines examined using receptor-binding techniques. Specific 125I-labeled VIP binding to MDA-MB-231 cells was inhibited with high affinity by VIP and pituitary adenylate cyclase-activating polypeptide (IC50, = 2 nM) and with moderate affinity by the VIP hybrid (IC50 = 0.5 microM). VIP elevated the cAMP in a dose-dependent manner, and VIP hybrid (10 microM) inhibited the increase in cAMP caused by VIP. Using Northern blot analysis, VIP (10 nM) stimulated c-fos and c-myc mRNA, and the increase caused by VIP was reversed by the VIP hybrid. The VIP hybrid inhibited breast cancer growth in vitro and in vivo using nude mice bearing breast cancer xenografts. These data suggest that the VIP hybrid is a breast cancer VIP receptor antagonist.

Animals↗
PubMed1996

Peptide analogs to pathogenic epitopes of the human acetylcholine receptor alpha subunit as potential modulators of myasthenia gravis.

Myasthenia gravis is an autoimmune disease in which T cells specific to epitopes of the autoantigen, the human acetylcholine receptor, play a role. We identified two peptides, p195-212 and p259-271, from the alpha subunit of the receptor, which bound to major histocompatibility complex (MHC) class II molecules on antigen-presenting cells (APCs) from peripheral blood lymphocytes of myasthenia gravis patients and stimulated lymphocytes of >80% of the patients. We have prepared analogs of these myasthenogenic peptides and tested their ability to bind to MHC class II determinants and to interfere specifically with T-cell stimulation. We first determined relative binding efficiency of the myasthenogenic peptides and their analogs to APCs of patients. We found that single substituted analogs of p195-212 (Ala-207) and p259-271 (Lys-262) could bind to human MHC molecules on APCs as efficiently as the original peptides. Moreover, dual analogs containing the two single substituted analogs in one stretch (either sequentially, Ala-207/Lys-262, or reciprocally, Lys-262/Ala-207) could also bind to APCs of patients, including those that failed to bind one of the single substituted analogs. The single substituted analogs significantly inhibited T-cell stimulation induced by their respective myasthenogenic peptides in >95% of the patients. The dual analogs were capable of inhibiting stimulation induced by either of the peptides: They inhibited the response to p195-212 and p259-271 in >95% and >90% of the patients, respectively. Thus, the dual analogs are good candidates for inhibition of T-cell responses of myasthenia gravis patients and might have therapeutic potential.

Adult↗
PubMed1996

Serum amyloid A binds specific extracellular matrix glycoproteins and induces the adhesion of resting CD4+ T cells.

Serum amyloid A (SAA), a prototypic acute phase protein reactant, exists naturally in the serum of healthy individuals. However, the levels of SAA in serum and its presence in sites of inflammation increase during certain chronic diseases associated with a local elevation of cytokine concentrations. Although the chemical structure of SAA is defined, its putative immunologic role(s) is still obscure. Nevertheless, it has been shown that 1) SAA acts as a chemoattractant and regulator of the migration of monocytes, polymorphonuclear cells, and T lymphocytes through endothelial cell monolayers; and 2) SAA and its proteolytically degraded N-terminal amyloid A fragment contain an extracellular matrix (ECM)-related cell adhesion epitopes. Herein, we examined whether SAA can associate with specific ECM moieties, and whether immobilized SAA-ECM complexes affect T lymphocyte adhesion. Radiolabeled human rSAA ([125I]rSAA) interacted avidly (Kd = 10(-9) M) and transiently with intact ECM, laminin, and vitronectin, but not with fibronectin or collagen type II. The binding of [125I]rSAA to ECM and laminin was inhibited by unlabeled rSAA and by the AA fragment, but not by the C-terminal portion of SAA (amino acid residues 2-82 and 77-104, respectively). Upon interactions with SAA or amyloid A, immobilized ECM, laminin, and vitronectin induced the adhesion of resting human CD4+ T cells in an apparently beta 1-integrin-mediated manner. Thus, the ECM appears to serve as a temporary anchorage site for SAA and amyloid A, and these ECM-complexed molecules seem to be involved in regulating the recruitment and accumulation of immunocytes in extravascular inflammatory compartments.

Amino Acid Sequence↗
PubMed1996

Neuroprotective strategy for Alzheimer disease: intranasal administration of a fatty neuropeptide.

Neurodegenerative diseases, in which neuronal cell disintegrate, bring about deteriorations in cognitive functions as is evidenced in millions of Alzheimer patients. A major neuropeptide, vasoactive intestinal peptide (VIP), has been shown to be neuroprotective and to play an important role in the acquisition of learning and memory. A potent lipophilic analogue to VIP now has been synthesized, [stearyl-norleucine17]VIP ([St-Nle17]VIP), that exhibited neuroprotection in model systems related to Alzheimer disease. The beta-amyloid peptide is a major component of the cerebral amyloid plaque in Alzheimer disease and has been shown to be neurotoxic. We have found a 70% loss in the number of neurons in rat cerebral cortical cultures treated with the beta-amyloid peptide (amino acids 25-35) in comparison to controls. This cell death was completely prevented by cotreatment with 0.1 pM [St-Nle17]VIP. Furthermore, characteristic deficiencies in Alzheimer disease result from death of cholinergic neurons. Rats treated with a cholinergic blocker (ethylcholine aziridium) have been used as a model for cholinergic deficits. St-Nle-VIP injected intracerebroventricularly or delivered intranasally prevented impairments in spatial learning and memory associated with cholinergic blockade. These studies suggest both an unusual therapeutic strategy for treatment of Alzheimer deficiencies and a means for noninvasive peptide administration to the brain.

Administration, Intranasal↗
PubMed1996

Altered peptide ligands of a myasthenogenic epitope as modulators of specific T-cell responses.

Myasthenia gravis (MG) is a T-cell regulated autoimmune disease. A peptide representing a sequence of the human acetylcholine receptor alpha-subunit (p195-212) was previously shown to stimulate proliferative responses of peripheral blood lymphocytes from MG patients and to be an immunodominant and myasthenogenic T-cell epitope in SJL mice. The authors generated a panel of analogues of p195-212 that contain single amino acid substitutions. Three of the analogues (203PHE, 204GLY and 207ALA) triggered low to no proliferative responses of a p195-212-specific T-cell line designated TCSJL195-212. Two of these analogues were able to stimulate the line to produce interleukin-2 (IL-2) and IL-4 (203PHE and 204GLY), whereas one analogue, 207ALA, did not stimulate the line to produce these cytokines. Binding assays revealed that the binding affinity of an altered peptide for a given major histocompatibility complex (MHC) molecule is not sufficient to determine whether it will be stimulatory or inhibitory to a native peptide-specific T-cell line. Two of the analogues, 204GLY and 207ALA, inhibited proliferative responses of cells of the TCSJL195-212 line when co-cultured with p195-212 and syngeneic antigen presenting cells (APC). The two inhibitory analogues were also able to inhibit proliferative responses of the TCSJL195-212 line when APC were pre-pulsed with p195-212, indicating that MHC blockade is not the only mechanism of action of these peptides. Moreover, both analogues inhibited the ability of p195-212 to prime lymph node cells for proliferative responses even when the analogues were administered in a soluble form. Thus the altered peptide ligands 207ALA and 204GLY can modulate T-cell responses both in vitro and in vivo and may have therapeutic potential for the treatment of MG.

Amino Acid Sequence↗
PubMed1996

Synthetic peptides derived from the sequence of human C-reactive protein inhibit the enzymatic activities of human leukocyte elastase and human leukocyte cathepsin G.

Peptides derived from the primary sequence of the acute phase reactant C-reactive protein (CRP) are shown to inhibit in vitro the enzymatic activities of human leukocyte elastase (hLE) and human leukocyte cathepsin G (hCG), which are associated with tissue damage occurring in the course of several chronic inflammatory conditions. CRP-derived peptides were synthesized based on their sequence similarity to domains within the natural inhibitors of hLE and hCG. The octapeptide Val89-Thr-Val-Ala-Pro-Val-His-Ile96 (CRP 89-96) is shown to inhibit hLE and hCG to a larger extent than peptides of similar chain lengths corresponding to the active sites of their natural inhibitors, alpha 1-protease inhibitor and alpha-antichymotrypsin, respectively. Several additional peptides containing this core sequence were synthesized and shown to be inhibitors, in contrast to peptides derived from other regions of CRP as well as the intact protein, which are totally inactive. The inhibitory capability of CRP-derived peptides, which may be generated in vivo by neutrophil-mediated proteolysis as part of a complex regulatory homeostatic mechanism, may now be used as a basis for the design of novel therapeutic substances. The present finding may shed some light on the enigmatic physiological functions of CRP.

C-Reactive Protein↗
PubMed1996

Binding of human serum amyloid A (hSAA) and its high-density lipoprotein3 complex (hSAA-HDL3) to human neutrophils. Possible implication to the function of a protein of an unknown physiological role.

Serum amyloid A (SAA) is an acute-phase serum protein which exists in the body in a complex with high-density lipoprotein (HDL3). It is involved in chronic inflammation and neoplastic diseases in an as yet unknown manner. Toward an understanding of the possible physiological role of SAA we initiated a study of its association with blood proinflammatory cells with which it may interact functionally in vivo. In the following we describe the binding characteristics of recombinant human SAA to human neutrophils (polymorphonuclear leukocytes; PMNLs) and their plasma membranes. Scatchard analysis of rSAA binding and displacement curves revealed Kd in the nanomolar range. The C-terminal domain of the protein, i.e. amino acid residues 77-104, which might reside in serum following SAA degradation and amyloid A formation, was found to inhibit efficiently the binding of the whole protein to neutrophils. The interaction of SAA, and of its related peptides while complexed in HDL3, with human PMNs was also studied. The results suggest that SAA may be involved, in an as yet unknown manner, in the neutrophil-associated inflammatory mechanism.

Amino Acid Sequence↗
PubMed1995

Self and foreign 60-kilodalton heat shock protein T cell epitope peptides serve as immunogenic carriers for a T cell-independent sugar antigen.

Healthy individuals manifest natural T cell reactivity to epitopes of the 60-kDa heat shock protein (hsp60) of both self and bacterial origin. The present studies were done to learn whether defined peptides of hsp60 could function as T cell carrier epitopes for a poorly immunogenic T-independent capsular polysaccharide, the Vi Ag of Salmonella typhi. Homologous peptides were synthesized from the mouse self-hsp60 molecule (CP1m), from the closely related human hsp60 molecule (CP1h), and from the more distant Escherichia coli (CP1ec) and mycobacterial (CP1mt) hsp60 molecules. The peptides were conjugated to Vi and tested for their immunogenicity in BALB/c (H-2d) and H-2 congenic mice (H-2k and H-2b). We now report that the self-CP1m and cross-reactive CP1h peptides were as immunogenic as was the non-cross-reactive foreign CP1ec peptide. Small amounts of the CP1 peptide, even in PBS, sufficed to induce anti-Vi Abs of the IgG1 (T-dependent) isotype in naive mice. The carrier effect was associated with the ability of the peptides to bind to APC and to induce T cell proliferation. H-2d and H-2k mice, but not H-2b mice responded to CP1m/h and CP1ec. None of the mice responded to CP1mt. No signs of inflammation or autoimmune disease were detected. Thus, natural T cell autoimmunity exists and can be harnessed to provide T cell help for Ab production to a foreign bacterial molecule in a synthetic vaccine.

Amino Acid Sequence↗
PubMed1995

Archaebacterial and eukaryotic proteasomes prefer different sites in cleaving gonadotropin-releasing hormone.

Thermoplasma 20 S proteasomes are composed of only two different types of subunits (designated as alpha and beta) but are nearly indistinguishable in their quaternary structure from eukaryotic 20 S proteasomes consisting of 14 distinct subunits. In this study, we compared both the nature and the rate of the proteolytic activities of Thermoplasma and of granulosa cell proteasomes on the neurohormone, gonadotropin-releasing hormone (GnRH), the degradation products of which can be unequivocally identified. Both Thermoplasma and granulosa proteasome degrade the decapeptide GnRH at the Trp3-Ser4, Ser4-Tyr5, Tyr5-Gly6, and Gly6-Leu7 bonds. While the main product of Thermoplasma proteasomes was a GnRH-(1-4) fragment, the main product of granulosa cell proteasome was a GnRH-(1-5) fragment, indicating that the principal degrading activity of Thermoplasma proteasome targets Ser4-Tyr5 bond, while the principal degrading activity of granulosa cell proteasome targets the Tyr5-Gly6 bond of GnRH. These differences in the degradation pattern of the neurohormone were observed when proteasome activities were compared both at 60 degrees C, the optimal temperature for Thermoplasma proteasomal activity, and at 37 degrees C, the optimal temperature of granulosa proteasome proteolytic activity. Although the catalytic mechanism is probably conserved from archaebacterial to eukaryotic proteasomes, our results suggest that there are striking differences in the preferred cleavage site of GnRH. This reflects the changes in the proteasomal subunit repertoire during evolution.

Amino Acid Sequence↗
PubMed1995

A VIP hybrid antagonist: from developmental neurobiology to clinical applications.

1. The 28 amino acid vasoactive intestinal peptide, VIP, was originally isolated from the intestine, following a bioassay measuring vasodilating properties. Immunocytochemistry, receptor binding assays and in situ hybridizations have demonstrated VIP abundance in the nervous system, suggesting multiple bioactivities. 2. A pharmacological approach was chosen to dissect VIP activities and a prototype VIP antagonist (Met-Hybrid) consisting of a carboxyl fragment of VIP7-28 and a six amino acid fragment of neurotensin, neurotensin6-11-VIP7-28 was synthesized. 3. This hybrid peptide was designed to maintain the binding capacity of one parent molecule (VIP), while loosing the agonistic properties, representing a classical competitive receptor antagonist. Furthermore, the new molecule exhibited increased specificity to central nervous system VIP receptors. 4. The Met-Hybrid was originally discovered as a potent inhibitor of VIP function in vivo. In the adult rodent, acute administration of the antagonist resulted in blockade of VIP-mediated potentiation of sexual behavior and chronic intracerebroventricular application impaired VIP-associated learning abilities. During ontogeny, chronic injections of the molecule resulted in neuronal damage, disruption of the diurnal rhythmicity of motor behavior, and retardation in the acquisition of neonatal reflexes in the rat. 5. During gestation, severe microcephaly was induced by acute administration of the Met-Hybrid to pregnant mice. The hybrid antagonist inhibited VIP-stimulated mitosis in whole embryo cultures and in a variety of cancer cell lines in vitro and in vivo, suggesting therapeutical potential.

Amino Acid Sequence↗
PubMed1995

Regression of established murine carcinoma metastases following vaccination with tumour-associated antigen peptides.

The cure of micrometastases following surgery is the major goal of cancer immunotherapy. We have recently isolated tumour-associated antigen (TAA) peptides, MUT 1 and MUT 2, derived from a mutated connexin 37 gap-junction protein, from the malignant 3LL-D122 murine lung carcinoma. We now report that synthetic MUT 1 or MUT 2 induces effective antitumour cytoxic T lymphocytes. Peptide vaccines protect mice from spontaneous metastases of 3LL-D122 tumours. Moreover, peptide vaccines reduce metastatic loads in mice carrying pre-established micrometastases. Tumour-specific immunity was primarily mediated by CD8+ T cells. This is the first evidence that peptide therapy may be effective in treatment of residual tumours and provides a rationale for the development of peptide vaccines as a modality for cancer therapy.

Animals↗
PubMed1995

The 2,4-dinitrophenyl group for protection of hydroxyl function of tyrosine during solid-phase peptide synthesis.

The facile thiolytic cleavage of the O-2,4-dinitrophenyl (Dnp) tyrosine bound was applied to the solid-phase synthesis of the 22-amino acid residue peptide H-Asp-Ala-Val-Tyr-Thr-Gly-Leu-Asn-Thr-Arg-Asn-Gln-Glu-Thr-Tyr-Glu-Thr-Le u-Lys- His-Glu-Lys-OH, corresponding to positions 62-83 in the chain of the type 1 receptor for Fc epsilon domains expressed on the rat mucosal-type mast cells (line RBL-2H3). A method for the spectrophotometric determination of insoluble O-Dnp as well as of unprotected phenolic moieties of tyrosine was developed. It is based on monitoring S-Dnp-2-mercaptoethanol, produced upon O-Dnp thiolysis by 2-mercaptoethanol.

Amino Acid Sequence↗
PubMed1995

Superactive lipophilic peptides discriminate multiple vasoactive intestinal peptide receptors.

To distinguish vasoactive intestinal peptide (VIP) receptors in the brain-mediating neurotransmission and neurotrophism, potent VIP analogues were designed. Using a single amino acid substitution and the addition of a fatty acyl moiety, an analogue was devised that exhibited both a 100-fold greater potency than VIP and specificity for a VIP receptor associated with neuronal survival. This VIP agonist increased neuronal survival via a cAMP-independent mechanism. Identical chemical modification of a prototype VIP antagonist (Met-Hybrid, Neurotensin6-11-VIP7-28) also resulted in a 100-fold greater potency in blocking VIP-mediated increases in neuronal survival. Blockade of circadian activity rhythms was limited to VIP antagonists that could inhibit VIP-mediated increases in cAMP. These lipophilic peptides provide novel tools in receptor discrimination and drug design.

Amino Acid Sequence↗