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The two fMLF-OMe analogues For-Met-β3hAc6c-Phe-OMe (6) and For-Met-β2hAc6c-Phe-OMe (12) and their corresponding N-Boc derivatives 5and 11have been synthesized and their biological activity towards human neutrophils evaluated. The N-formyl peptides 6and 12exhibit good activity as chemoattractans and 12is highly active in superoxide anion production. The preferred solution conformation of the two N-formyl derivatives has been discussed.The two fMLF-OMe analogues For-Met-β3hAc6c-Phe-OMe (6) and For-Met-β2hAc6c-Phe-OMe (12) and their corresponding N-Boc derivatives 5and 11have been synthesized and their biological activity towards human neutrophils evaluated. The N-formyl peptides 6and 12exhibit good activity as chemoattractans and 12is highly active in superoxide anion production. The preferred solution conformation of the two N-formyl derivatives has been discussed.

Phagocytes are activated by several extracellular signals, including formylpeptides derived from bacterial proteins or disrupted cells. The most intensely studied member of the formylpeptide family is the synthetic tripeptide N-formyl-L-methionyl-L-leucyl-Lphenylalanine (fMLP), whose specific receptors have been identified on neutrophil plasma membrane and subsequently cloned. The fMLP-receptor interaction activates multiple transduction pathways responsible for various neutrophil functions such as adhesion, chemotaxis, exocytosis of secretory granules and superoxide anion production, which represent the physiological response to bacterial infection and tissue damage. An unresolved question is whether signaling requirements are identical or specific for each physiological function. The development of fMLP receptor agonists and antagonists has led to an improvement of our knowledge about the above issue. Of particular interest is the possibility that receptorial antagonists, able to transiently inhibit neutrophil responses to formylpeptides, could be therapeutic agents in the treatment of inflammation-related diseases. Aim of this review is, i) to summarise the current understanding of the series of events that begins at the level of formylpeptide-receptor interaction and is responsible for the activation of transduction pathways, which finally determine neutrophil response, ii) to define the state of art regarding the synthesis as well as the biological actions of fMLP receptor agonists and antagonists.

for-Met-Ser(Bzl)-Phe-OMe, for-Met-Cys(Bzl)-Phe-OMe, for-Met-Tyr(Bzl)-Phe-OMe and for-Met-Lys(Z)-Phe-OMe were synthesized to investigate the importance of a bulky protecting group on the side-chain of a hydrophilic residue at position 2 on the biological activities of human neutrophils. Our results indicate that these compounds do not trigger a good chemotactic response, which, in any case, is not improved with respect to that induced by the analogs with the unprotected residues. Instead, both superoxide anion production and, particularly, lysozyme release are more efficient.

In order to explore the properties of chemotactic N-formylpeptides containing isopeptide bonds within their backbones, a group of lysine-containing analogs of the prototypical chemotactic tripeptide N-formylmethionyl-leucyl-phenylalanine (fMLF) was synthesized. The new analogs were designed by adding to the HCO-Met or Boc-Met residue a dipeptide fragment made up of Lys and Phe residues joined through Lys N^α or N^ε bonds, in all possible combinations. Thus, the following six pairs of tripeptides were synthesized and examined for their bioactivity: RCO-Met-Lys(Z)-Phe-OMe (2a, b), RCO-Met-Lys(Z-Phe)-OMe (3a, b), Z-Lys(RCO-Met)-Phe-OMe (4a, b), Z-Phe-Lys(RCO-Met)-OMe (5a, b), RCO-Met-Phe-Lys(Z)-OMe (6a, b) and Z-Lys(RCO-Met-Phe)-OMe (7a, b), with R=OC(CH₃)₃ and R=H for compounds a and b, respectively. All the new models were characterized fully and their activity (chemotaxis, superoxide anion production and lysozyme release) on human neutrophils determined as agonists (compounds b) and antagonists (compounds a). All N-formyl derivatives 2b-7b are less potent than fMLF-OMe as chemoattractants, but compound 7b exhibits selective activity as superoxide anion producer. Derivatives 2a-7a do not show antagonistic activity towards fMLF induced chemotaxis and O₂^- production, however, all these compounds except 4a antagonize lysozyme release by 60%.

The peptides for-Met-Ser-Phe-OMe 1, for-Met-Cys-Phe-OMe 2, for-Met-Lys-Phe-OMe 3, and for-Met-Tyr-Phe-OMe 4 were synthesized in order to investigate the importance of a hydrophilic side-chain on the residue at position 2 on biological activities of human neutrophils. Our results seem to highlight that this type of substitution does not facilitate good chemotaxis, although it elicits both superoxide anion production and particularly lysozyme release, in some cases even more potent than the parent fMLP-OMe, if the hydrophilicity is associated with steric hindrance.

Objective. Cyclosporin A (CsA) is an effective agent in rheumatoid arthritis (RA), slowing joint damage progression. Its therapeutic effect on T lymphocytes has been studied extensively, but there is little information available about neutrophils, the cells responsible for a substantial proportion of inflammation. A study was performed to investigate the in vitro effects of CsA on neutrophil functions triggered by several agonists and determine whether the drug could counteract the binding of formyl-methionyl-leucyl-phenylalanine (fMLP) to its receptor and/or modulate changes in the intracellular Ca²⁺ concentration ([Ca²⁺]_i).
Methods. CsA was added to neutrophils 5-50 min before the incubation steps for neutrophil function assays (chemotaxis, superoxide anion production, lysozyme release), calcium measurements and receptor binding experiments.
Results. CsA appeared to be particularly effective in lowering chemotaxis, superoxide anion production and lysozyme release induced by different agonists. However, it did not significantly affect either basal or agonist-stimulated neutrophil [Ca²⁺]_i and the interaction between fMLP and its receptor.
Conclusions. Because of its in vitro inhibition of neutrophil functions, CsA appears to have considerable potential as an anti-inflammatory drug. Moreover, as it is also a potent immunosuppressive agent, it may reduce the progression of joint damage in RA. More work remains to be done to clarify the molecular mechanism of CsA action on neutrophils.

In order to further examine the properties of pseudopeptides containing the 2-hydrazonoacyl fragment, two new series of analogs of the prototypical chemotactic N-formyl-tripeptide HCO-Met-Leu-Phe-OMe were designed and synthesized. The first group contains the new fragment as the N-terminal residue and is represented by the N-aryl derivatives p-Cl-C₆H₄-NH-N=C(R)-CO-Leu-Phe-OMe (2 and 3) and by the corresponding N-aroyl analogs p-CH₃-C₆H₄-CO-NH-N=C(R)-CO-Leu-Phe-OMe (4). The second group contains the new fragment in place of the central Leu residue and is represented by compounds HCO-Xaa-NH-N=C(R)-CO-Phe-OMe (7a and 7b) where Xaa is Nle and Met, respectively. The conformational and biochemical properties of the new products were examined.

We previously reported the structural and biological properties of the C-terminal sequence (REGDPSSSQHLPSTPSSPRV) coded by the rarely expressed exon 26A of human elastin. It assumes a stable type II β-turn structure spanning the REGD sequence and possesses chemotactic and immunological properties. Here the structural characterization of the sequence coded by this exon was completed. Nuclear magnetic resonance and circular dichroism studies on the N-terminal amino acid sequence (GADEGVRRSLSPELREGD) showed the presence of an α-helix within VRRSL and a type II β-turn within SPEL. The smaller peptides GADEGVRRSLSP and LSPELREGD revealed structural features similar to those identified in the parent peptide. No β-turn was found in the REGD sequence of these peptides and no chemotactic activity was detected, thereby demonstrating that this biological activity is conformation dependent. Structural studies on additional peptides such as LREGD, ELREGD and LSPELREGDPSS showed that the presence of a Glu residue two positions before the Arg residue inhibits the β-turn formation in the REGD sequence.

In order to obtain chemotactic peptides with selective bioactivity, a new type of structural modification was introduced at the N-terminal position of HCO-Nle-Leu-Phe-OMe. Two groups of analogs have been synthesized both containing a N-terminal residue of the X=C(R)-CO-type replacing the native HCO-NH-CH(R)-CO-. In particular, the A group of pseudopeptides (2a-d) possesses a N-terminal oximic fragment (X=HO-N) and the B group (3a-d) a formylhydrazone fragment (X=HCO-NH-N). These new ligands have been examined for their capacity to induce chemotaxis and other cellular responses such as superoxide anion production and lysozyme release; although significantly active as chemoattractants they have been found to be practically devoid of secretagog activity, thus exhibiting selective behavior. The adopted chemical modification seems extensible in designing a new class of pseudopeptides (hydrazonopeptides) structurally related to both hydrazinopeptides and peptides containing α,β-unsaturated residues.

The formyltetrapeptides for-Met-Leu-Leu-Phe-OMe 1, for-Met-Leu-Aib-Phe-OMe 2, for-Met-Leu-Ac₆c-Phe-OMe 3, for-Met-Leu-Pro-Phe-OMe 4, for-Met-Pro-Pro-Phe-OMe 5, for-Met-Aib-Aib-Phe-OMe 6, for-Met-Pro-Aib-Phe-OMe 7 and for-Met-Aib-Pro-Phe-OMe 8 were synthesized and biologically tested on human neutrophils in an attempt to evaluate the specific receptor pocket dimensions and features. Our results indicate that the shift in the Phe residue to the fourth position in these compounds strongly reduces chemotactic response, but is efficacious in triggering superoxide anion production and lysozyme release (order of potency 3 > 2 > 1 > 4 > 6 > 8 > 5 > 7). The potency of the two latter responses correlates well with the affinity data obtained in binding experiments.

The octapeptide sequence of peptide T is contained within the envelope of HIV and seems to mediate the viral binding to CD4 expressing cells, including monocytes. The biological activity of the a-aminobutyric acid pentapeptide derived from the C-terminal sequence of peptide T, in which the polar side chain of threonine in position 4 is substituted by a hydrophilic group, is measured by the monocyte chemotaxis assay. The ehemotactic activity of human monocytes is assessed by determining the concentration at which the pentapeptide analog is maximally active and the effectiveness at that concentration, in comparison with peptide T and two shorter homologs, the pentapeptide and tetrapeptide. These experiments suggest that the synthetic analog is a potent ehemotactic factor active at picomolar concentrations and that it competes with peptide T for the monocyte binding site.

The chemotaxis, phagocytic capacity and reducing activity of neutrophils derived from peripheral blood of patients with rheumatoid arthritis (RA) did not differ from those of control. However, some significant differences between neutrophils from rheumatic and healthy subjects emerged in the presence of rifamycin SV. The chemotactic response of neutrophils from patients with RA was activated by rifamycin SV, whereas cells from controls did not orient their locomotion towards the drug. Moreover, incubation of RA patient's cells with rifamycin SV in vitro depressed phagocytic and reducing activities; the same treatment on normal cells failed to alter these functions. A correlation between improvement of clinical symptoms after treatment of RA by local infiltration with rifamycin SV, observed by others, and the impairment of phagocytosis and NBT reduction, here described, was suggested.

In order to investigate the proper peptide backbone conformation able to elicit a biological activity, HCO-Met-Pro-Phe-OMe, HCO-Met-?[COO]Leu-Phe-OMe, and HCO-Met-OLeu-Phe-OMe, analogues of the prototypical chemotactic peptide HCO-Met-Leu-Phe-OMe, were studied by CD and IR techniques. The results obtained comparing biological and conformational data evidence the critical presence of (i) the NH group at position 2, (ii) a rather flexible backbone, (iii) the chemical structure of the central residue which can affect the stability of a possible active conformer.

The new C^α-tetrasubstituted α-amino acid residue 2-[2'-(methylthio) ethyl]methionine (Dmt) has been introduced into the reference chemotactic tripeptide HCO-Met-Leu-Phe-OMe (fMLP-OMe) in place of the leucine or methionine, respectively. The biological activity of the new analogues [Dmt²] fMLP-OMe (2) and [Dmt¹] fMLP-OMe (3) has been determined; whereas 2 is active toward human neutrophils, stimulating directed migration, superoxide anion generation, and lysozyme release, 3 results practically inactive in all tested assays. A conformational analysis on 2 and 3 has been performed in solution by using ir absorption and ¹H-nmr. The conformation of 2 was also examined in the crystal by x-ray diffraction methods. Both 2 and 3 adopt fully extended conformation in correspondence with the Dmt residue. Biological and conformational results are discussed and compared with related previously studied models. © 1997 John Wiley & Sons, Inc. Biopoly 42: 415–426, 1997

Neutrophils derived from peripheral blood of patients with rheumatoid arthritis (RA) exhibited a defective responsiveness to natural mediators of inflammation, namely histamine and serotonin, and to the anti-inflammatory drugs ibuprofen and naproxen, in spite of the fact that the basic status of motility was normal. Not even pretreatment of granulocytes with substances restored the capacity to modulate the random and directional locomotion. This neutrophil functional defect was correlated with an anomalous response to rifamycin SV, previously observed in rheumatic states.

We have isolated peak II, which is the peak of the middle molecules containing polyamines, from dialysate of uremic patients in recirculating dialysis. We investigated the effect of total dialysate, chromatographic peaks, I, II, III, IV and commercial polyamines on polymorphonuclear leukocyte chemotaxis and superoxide production (i.e. phagocytic activity) in healthy and uremic patients. Polymorphonuclear chemotaxis was inhibited by total dialysate and peak II but not by polyamines; polyamines, total dialysate and peak II had no activity on polymorphonuclear phagocytosis.

Summary A 28-year-old patient is presented who had recurrent infections associated with a defect in neutrophil locomotion. Amines and anti-inflammatory drugs failed to regulate movement. The impairments in polymorphonuclear leukocyte function were demonstratedin vitro by the inability of the patient's neutrophils to exhibit spontaneous and directional movement and to respond to mediators of inflammation during the acute phase of the disease.

Experiments "in vitro" have been performed to study the chemotactic and phagocytotic response of PMN in 9 patients suffering from progressive systemic sclerosis (PSS). Their granulocytes showed a normal behaviour in all of these functions, when compared with healthy volunteers as controls.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.