Effects of peptide T derivatives on the proliferation of cultured human keratinocytes.

[D-Ala1]peptideT-amide, the linear hexapeptide H-Thr-Hse-Asn-Tyr-Thr-Asp-OH (LPT) and its cyclic analog, cyclo(-Thr-Hse-Asn-Tyr-Thr-Asp-) (CPT), were tested for their effects on the proliferation of cultured normal human keratinocytes (KTs) in comparison with vasoactive intestinal peptide (VIP). [D-Ala1]PT-NH2, LPT and VIP (all 0.1 mumol/l) increased the cell number in KT cultures, whereas CPT was ineffective. The VIP antagonist [N-Ac-Tyr1,D-Phe2]GRF (1-29)-NH2 significantly inhibited the VIP effects on KTs. On the other hand this antagonist did not affect the peptide T (PT) compounds-induced stimulation of KTs, providing indirect evidence that the mitogenic effects of VIP and PT peptides are probably mediated via different receptors.

Synthesis and opioid activity of tyrosine sulfate containing dermorphin and deltorphin peptides.

To study the effect of the sulfate ester moiety on the opioid activity, we prepared two tyrosine sulfate-(Tyr(SO3H)-containing dermorphin and deltorphin peptides. Their activities were determined in binding studies based on displacement of mu- and delta-receptor selective radiolabels from rat brain membranes and in two bioassays, using guinea pig ileum and mouse vas deferens. In comparison to original peptides and morphine, the obtained data indicate that whereas H-Tyr(SO3H)-D-Ala-Phe-Gly-NH2 shows very minimal interaction with opioid receptors, H-Tyr(SO3H)-D-Ala-Phe-Asp-Val-Val-Gly-NH2 retains a significant activity.

Synthesis and activity of new linear and cyclic peptide T derivatives.

Linear and head to tail cyclic hexapeptide analogs (Xaa-Thr-Thr-Asn-Tyr-Thr, Xaa = D-Asp or D-iso-Asp) of peptide T were prepared and tested for human monocyte chemotaxis. All new compounds showed significant bioactivity. In particular, the conformational restriction introduced into cyclo(-D-iso-Asp-Thr-Thr-Asn-Tyr-Thr-) was very suitable for CD4 receptor binding. The cyclic peptides also proved to be highly resistant to degradation by plasma or brain enzymes.

Phe3-substituted analogues of deltorphin C. Spatial conformation and topography of the aromatic ring in peptide recognition by delta opioid receptors.

In order to study the contribution of the electronic, hydrophobic, and conformational properties of the amino acid residue at position 3 in deltorphin C on binding to delta and mu opioid receptors, a series of 5- and 6-membered ring and bicyclic amino acid replacements at position 3 were prepared by solution synthesis methods. In general, the substitutions were deleterious for high delta affinity (Ki delta) and delta selectivity (Ki mu/Ki delta). However, several notable exceptions were recognized: peptides containing the constrained, bicyclic structures Aic3 and (R or S) Atc3 enhanced delta affinity, but only the latter increased delta selectivity 4-fold (= 2475) relative to deltorphin C (= 661); at the other extreme, delta affinity of N alpha MePh3 fell 900-fold. Bioassays of [N alpha MePhe3]-, [(R or S)C alpha MePhe3]-, [Tic3]-, [Aic3]-, and [(R or S) Atc3]deltorphin C using guinea pig ileum (GPI) and mouse vas deferens (MVD) for mu and delta bioactivity, respectively, revealed a significant correlation (r = 0.916) between MVD bioactivity and delta binding in brain membranes. [(R or S)Atc3]deltorphin C also exhibited the highest biological selectivity (GPI/MVD) (= 3,522), which was 3-fold greater than that observed for deltorphin C. Molecular modelling of [N alpha MePhe3]- and [(S)Atc3]deltorphin C established that these amino acid replacements for Phe3 produce alterations in the backbone (phi,psi) and side-chain (chi 1,chi 2) dihedrals which critically affect the flexibility of the peptide and possibly limit accessible conformations for its alignment within the delta opioid receptor. The data provide evidence that the delta receptor is sensitive to changes in the composition, conformation, and orientation of the side chain of residue 3 of a linear opioid heptapeptide.

Studies on the anti-phospholipase A2 and anti-inflammatory activities of a uteroglobin fragment and related peptides.

The nonapeptide antiflammin P1 (H-Met-Gln-Met-Lys-Lys-Val-Leu-Asp-Ser-OH), its isoAsp8 analogue and the corresponding aminosuccinyl peptide were prepared, characterized and tested for inhibition of phospholipase A2 (PLA2) in vitro and for anti-inflammatory activity in vivo under assay conditions recently recommended. All peptides are devoid of PLA2 inhibitory and anti-inflammatory activity.

Structure-activity relationships of cyclic and linear peptide T analogues.

Using the potent cyclic peptide T analog [formula: see text] as parent compound, a series of analogues were synthesized and their potencies in a monocyte chemotaxis assay were compared with those of correspondingly modified linear peptides. Structure-activity relationships observed with cyclic compounds did not always parallel those determined with linear analogues. [formula: see text] showed the highest affinity to CD4 receptor of monocytes of any peptide thus far studied. It also proved to be highly resistant to degradation by plasma or brain enzymes.

Para-substituted Phe3 deltorphin analogues: enhanced selectivity of halogenated derivatives for delta opioid receptor sites.

The delta-selective opioid peptide deltorphin C(H-Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2) (DEL C) was modified by para-substitution of Phe3 with halogens (F, Cl, Br, I), amino, or nitro groups. The bioactive potencies in peripheral tissues and brain receptor selectivities of these analogues depended upon the particular substituent; peptides containing halogen substituents exhibited the least disruptive effect. In the mouse vas deferens (MVD) bioassay, [p-ClPhe3]DEL C displayed equivalent bioactivities to DEL C; in combination with the guinea pig ileum (GPI) bioassay, [p-ClPhe3]DEL C and [p-BrPhe3]DEL C exhibited marked preference for delta sites (IC50GPI/IC50MVD = 11,250 and 6,363, respectively), which are approximately 4- and 2-fold greater than DEL C. In a receptor binding assay, none of the halogenated analogues had delta affinities (Ki) exceeding that of DEL C; however, in terms of delta selectivity (Ki mu/Ki delta), [p-BrPhe3]DEL C was nearly twice as selective as DEL C, while [p-FPhe3]DEL C was equivalent, and [p-IPhe3]DEL C only 25% less selective. The only correlation evident with the halogenated derivatives occurred between IC50GPI and Ki mu (r = 0.814) rather than between delta receptor studies (MVD or Ki delta); interestingly, IC50GPI also correlated with K' (r = 0.982). The p-amino or p-nitro substituents of Phe3 in DEL C and DEL B (= [Glu4]DEL C) were deleterious for bioactivity (MVD) (losses ranged from 400- to approximately 8,000-fold) and in receptor binding assays, where delta affinities decreased 140- to 840-fold and delta selectivities by 34- to 380-fold. p-Nitro-Phe3 was the most detrimental substitution for all the parameters measured for both deltorphins: the loss in MVD activity, however, was less with DEL B than with DEL C, which was the opposite for delta receptor affinity.

Synthesis and antiaggregatory activity of antiflammin related peptides.

The peptide H-Lys-Val-Leu-Asp-OH (KVLD), derived from antiflammins, and its analog H-Lys-Val-Asp-Leu-OH (KVDL) were prepared by solution synthesis. KVLD does not inhibit platelet aggregation in contrast to the results recently published.

Studies on the anti-phospholipase A2 and anti-inflammatory activities of a synthetic nonapeptide from uteroglobin.

The nonapeptide H-Met-Gln-Met-Lys-Lys-Val-Leu-Asp-Ser-OH (antiflammin), corresponding to a high amino acid similarity region of uteroglobin was prepared by solution and solid phase synthesis. The peptide do not inhibit pancreatic phospholipase A2 in vitro and the carrageenin-induced oedema in vivo.

Synthesis and biological activity of a cyclic hexapeptide related to peptide T.

The cyclo [Thr-Thr-Thr-Tyr-Asn-Thr] hexapeptide related to peptide T, H-Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr-OH, competitor of the Human Immunodeficiency Virus in the binding to human T cells, was synthesized and tested for its ability to stimulate monocyte migration (chemotaxis). The new cyclic derivative showed negligible biological activity.