1,721,062 research outputs found
An exhaustive insight into the pocket cherge features of the methionine receptor using fMLP analogs.
No full textAn exhaustive insight into the pocket charge features of the methionine receptor using fMLP analogs.
No full textNeutrophils play a key role as primary phagocytic cells, because they constitute the first line of defense against bacterial invasion, and contribute to inflammatory processes. the goal of the study herein reported is to clarify the features peculiar to the methionine receptor pocket. it has widley accepted that the L-Met residue seems to induce optimum chemotactic as well as secretory activities. the synthesised analogs, here reported, have clarified that the positively charged area in the Met pocket is i) narrow in dimension, ii) located at well defined distance from the backbone, and iii) oriented in a specific position, not completely surrounding the internally located said chain
The importance of the methionine configuration in for-Met-Leu-Phe-OMe biological activities.
No full textfor-D-Met-L-Leu-L-Phe-OMe was synthesized in order to understand the importance of the
methionine configuration on human neutrophil biological activity. Our results show that both
chemotactic response and lysozyme release are lower than those of the parent fMLP-OMe,
indicating that the specific receptor pocket possesses a well-located, restricted positive area that
does not completely face the D-Met residue. The triggering of superoxide anion production
does not seem to be sensitive to this variation of the configuration
Biological variation responses in fMLP-OMe analogs, introducing bulky protecting groups on the side-chain of hydrophilic residues at position 2
No full textfor-Met-Ser{Bzl)-Phe-OMe, for-Met-Cys{Bzl)-Phe-OMe,
for-Met- Tyr{Bzi)-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. Iysozyme release are more efficient
Valutazione funzionale dei leucociti.
No full textSeparazione frazioni leucocitarie; funzioni dei granulociti neutrofili;funzioni dei granulociti eosinofili; funzioni dei granulociti basofili; funzioni dei monociti-macrofag
fMLP-OMe analogues trigger specific signalling pathways in the physiological functions of human neutrophils
No full textHuman neutrophils are phagocytic cells involved in host defence mechanisms against bacterial infections. It has been demonstrated that small formyl-peptide derivatives, obtained as bacterial metabolites or derived from disrupted mitochondria, can be potent chemoattractants for phagocytes. for-Met-Leu-Phe (fMLP), together with its synthetic methyl ester derivative for-Met-Leu-Phe-OMe (fMLP-OMe), is used as a model chemoattractant due to its highly effective ability to activate all physiological functions of neutrophils through binding with specific G-protein coupled receptors (FPR) located on the neutrophil membrane.
The interaction of fMLP with its receptor expressed on neutrophils triggers multiple second messengers through the activation of phospholipase C (PLC), PLD and PLA2 and rapidly stimulates phosphatidylinositol-3-kinase (PI3-K), as well as activating tyrosine phosphorylation. An increase in intracellular levels of cyclic AMP (cAMP) and the involvement of kinases, such as protein kinase C (PKC), mitogen-activated protein kinases (MAPKs) [Jun N-terminal kinases (JNK), p38 and extracellular response kinases 1 and 2 (ERK1/2)], has also been demonstrated.
The activation of these transduction pathways is known to be responsible for various biochemical responses which contribute to the physiological defence against bacterial infections and cell disruption. In fact, it has long been known that the transduction pathway underlying the chemotactic response is different from those responsible for cytotoxic functions, and several previous experiments carried out utilizing pharmacological manipulation of the signal transduction pathway have highlighted the fact that distinct mechanisms are involved in each of these neutrophil responses. This can be rationalized on the basis of the existence of at least two different functional receptor subtypes or isoforms; low doses of a full agonist (or a "pure" chemoattractant) are required to interact with a high-affinity receptor subtype (FPR) that activates the transduction pathway responsible for the chemotactic response, while the increase of the full agonist concentration - typical of infections sites - allows binding with the its low-affinity subtype (FPRLike-1), able to activate the transduction pathways responsible for superoxide anion production and lysozyme release.
The use of selective analogues (ligands able to discriminate between different biological responses) allowed us to confirm the idea that fine tuning of neutrophil activation occurs through differences in activation of a spectrum of signalling pathways. For each stimulus capable of a unique set of cellular responses, a distinctive imprint of signal protein activation may exist. Through more complete understanding of intracellular signalling, new drugs could be developed for the selective inflammatory blockade
A hydrophilic residue at position 2 can improve specific biological responses in fMLP‐OMe analogs
No full textThe 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
Effects of Synthetic Peptides on the Inflammatory Response and Their Therapeutic Potential.
No full textRecently, a revival of interest in small peptide molecules as potential drug candidates has emerged. In this review, we describe two series of synthetic peptides and their selective effects on the inflammatory response, focusing on the intracellular pathways involved and on their therapeutic potential. A series of FDLFDLF analogs have been synthesized, including either N- t-Boc or different N-ureido substituents. The free acid derivatives are able to antagonize the multiple neutrophil functions evoked by N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLF), i.e. chemotaxis, superoxide anion production and lysozyme release, so they are good candidates as anti-inflammatory drugs. Their methyl-ester derivatives are ineffective. The second series of peptides derives from the endogenous protein kinase C (PKC) inhibitor PKI55, a 55-amino acid protein, whose synthesis is induced by PKC activation, so that a feedback loop of inhibition is established. In vitro experiments showed that PKI55 inhibits recombinant PKC isoforms α, β1, β2, γ, δ, ζ, ε; to identify the minimal amino acid sequence of PKI55 protein maintaining the inhibitory effects on PKC, peptides derived from both C- and N-terminal sequences have been synthesized. The N-terminal peptides 5 (MLYKLHDVCRQLWFSC), 8 (CRQLWFSC) and 9 (CRQLW), that in human neutrophils retain the inhibitory activity on PKC, decrease the chemotaxis, and, in mice, display anti-inflammatory and analgesic action, after both central and peripheral administration of very low doses. Furthermore, in a model of cerebral ischemia in vitro, the peptide 5 shows neuroprotective activity, favouring the recovery of synaptic function. These findings suggest interesting possible therapeutic applications for these peptides
An evaluation of fMLP pocket dimensions and features using formyltetrapeptides
No full textThe 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
Synthesis and bioactivity of chemotactic tetrapeptides: FMLF-OMe analogues incorporating spacer aminoacids at the lateral positions
No full textA small library of N-For and N-Boc tetrapeptidic analogues of the chemotactic tripeptide For-Met-Leu-Phe-OMe (fMLF-OMe), obtained by incorporating three different spacer aminoacids (Gly, betaAla and Pro) between the native residues of Met and Leu (N-For- and N-Boc-Met-Xaa-Leu-Phe-OMe; Xaa(2) series) and Leu and Phe (N-For- and N-Boc-Met-Leu-Xaa-Phe-OMe; Xaa(3) series), have been synthesized and examined for their biological activity as agonists and antagonists. Chemotaxis, lysozyme release and superoxide anion production have been measured. All the N-For analogues maintain good to moderate chemotactic activity with the betaAla(3) 15 model reaching the maximum value. All the N-Boc tetrapeptides are efficient chemotactic antagonists. Conversely, with the exception of the moderate antagonistic activity exhibited by the N-Boc Xaa(2) models against lysozyme release, all the other N-Boc analogues do not show significant activity against both superoxide anion and lysozyme release
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