[Changes in plasma tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) by the interferon treatment for chronic hepatitis C]

To determine the effects of interferon (IFN) treatment for chronic hepatitis C on vascular endothelium, we measured the concentrations of tissue plasminogen activator (t-PA) and its inhibitor (PAI-1) in the plasma from patients before and after IFN treatment for 14 consecutive days. The plasma t-PA and PAI-1 levels were measured before and after treatment. The plasma t-PA level was significantly increased after IFN treatment (p < 0.01) but no significant difference in plasma PAI-1 level was observed before and after treatment. The ratio of t-PA/PAI-1 was significantly increased after IFN treatment (p < 0.05). These changes may be caused by the effect of IFN on endothelium, leading to an activation of the endothelium derived fibrinolysis factors. Increase in plasma t-PA concentration may induce hyperfibrinolysis which may be one of the causes of suborbital hemorrhage. Further study on the fibrinolysis pathway in the blood is necessary to elucidate the mechanisms of the many side effects observed during IFN treatment.

Highly potent side chain-main chain cyclized dermorphin-deltorphin analogues: an integrated approach including synthesis, bioassays, NMR spectroscopy and molecular modelling

Our continuing efforts to study structure-activity relationships of peptide opioids have resulted in the synthesis of a series of cyclic opioids related to dermorphins and deltorphins. The biological activities of the compounds have been determined and the conformational analyses carried out using 1H-NMR spectroscopy and molecular modelling. The three compounds in the series Tyr-c[D-Orn-Phe-Ala], Tyr-c[D-Lys-Phe-Ala], and Tyr-c[A2bu-Phe-Ala-Leu] are cyclized via a lactam bridge from the side-chain of the residue at the second position with the carboxyl terminus of each compound. The molecules incorporate 12-, 13- and 14-membered rings, respectively. They include a phenylalanine at the third position which is a distinguishing characteristic of dermorphins and deltorphins. The guinea pig ileum and mouse vas deferens assays show that the compounds are highly active at both mu- and delta-opioid receptors. The compounds are all highly effective antinociceptive agents as measured by the intrathecal rat hot plate test. Conformational analyses of the molecules indicate that they can adopt topochemical arrays required for bioactivity at both mu- and delta-receptors which explains their high activity in both guinea pig ileum and mouse vas deferens in vitro assays. The results support our models for mu- and delta-receptor activity for constrained peptide opioids.

A topochemical approach to explain morphiceptin bioactivity

A topochemical model to explain the bioactivity of morphiceptin (Tyr1-Pro2-Phe3-Pro4-NH2) was developed by taking account of accessible conformations around rotatable bonds which define relative spatial arrangements of opioid pharmacophores, the amine and phenolic groups of tyrosine and the aromatic ring of phenylalanine, necessary for receptor recognition. For this purpose, 1H-NMR measurements and computer simulations were extensively carried out on 10 stereoisomeric analogs related to morphiceptin: Tyr-Pro-(L and D)-Phe- (L and D)-Pro-NH2; Tyr-Pro-(L and D)-(NMe)Phe-(L and D)-Pro-NH2; Tyr-(NMe)Ala-Phe-D-Pro-NH2; and Tyr-Ala-Phe-D-Pro-NH2. These analogs are structurally close to one another but display various opiate potencies from highly active to inactive. The conformation of each rotatable bond has been specifically identified by measuring accessible space for the analogs, in which the difference in composition is observed in the specific site affecting only the conformation around the target bond. The most interesting characteristic of the model is a requirement of a cis amide bond linking residues 1 and 2. The model also requires the side chains in a trans conformation (chi 1 = 180 degrees) for the Tyr and Phe residues. The distances between the three pharmacophores, d1 (Tyr N to Tyr OH), d2 (Tyr N to the center of the aromatic ring of the third residue), and d3 (Tyr OH to the center of the aromatic ring of the third residue), were found to be approximately 8, approximately 7, and approximately 11-13 A, respectively. This model should aid in pharmaceutical design of peptide and nonpeptide ligands with opioid potencies.

Topochemical design of bioactive peptides and peptidomimetics

For the studies of bioactive peptides, our laboratories have been employed an integrated approach including synthesis, bioassays, and conformational analysis. To obtain highly potent, selective and metabolically stable analogs, peptidomimetics such as peptide backbone modifications (retro-inverso structures), constrained amino acids, and cyclic structures have been incorporated into many bioactive peptide sequences. The conformational studies of the resulting analogs have led to topochemical models for the bioactivities of those peptides. This lecture will be focused on the results of such studies on opioids and somatostatin. We have synthesized numerous opioid analogs with various peptidomimetics based on three classes: enkephalins, dermorphin-deltorphins, and morphiceptins. Many of these analogs exhibit high potency, selectivity, and metabolic stability. Conformational studies of these analogs have enabled us to define the structural characteristics necessary for bioactivities of morphiceptins, dermorphins, enkephalins, and deltorphins. From these results, we can propose conformational models responsible for bioactivities at the mu- and delta-receptors. Our studies of cyclic somatostatin analogs are based on the highly active Merck analog c(-Pro6-Phe7-D-Trp8-Lys9-Thr10-Phe11-) (where the superscripts denote position in native somatostatin). To investigate the topochemical preference of backbone and side chains, unusual amino acids, including beta-methylphenylalanine7 or 11, beta-methyltryptophan8, as well as backbone modifications such as retro-inverso structures have been incorporated. The bioactivity profiles of these peptidomimetic molecules provide much information on the effects of backbone and side chain constraints on bioactivity.

Topochemical analysis of morphiceptin and dermorphin bioactivities

To elucidate the topochemical requirements for bioactivities of morphiceptin (Tyr-Pro-Phe-Pro-NH2) and dermorphin (Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2), we have designed and synthesized two diastereomers Tyr-(L and D)-(NMe)Ala-Phe-D-Pro-NH2. Both the analogs display high activities in the guinea pig ileum assay. The only difference in the composition of these two diastereomers arises from the chirality at residue 2. The high mu-receptor activities are attributed to structures where the Tyr1-L-(NMe)Ala2 amide bond assumes a cis configuration while the Tyr1-D-(NMe)Ala2 amide bond assumes a trans configuration. Accessible space studied for the second residues of these molecules confirms the fact that the L-(NMe)Ala2 analog belongs to the morphiceptin family of opioids while the D-(NMe)Ala2 analog belongs to the dermorphin class of opioids. The similarity in the spacial array of the analogs explains their high mu-receptor activities and indicates that they are likely recognized at the same opioid receptor.

Triiodothyronine regulates insulin-like growth factor-I binding to cultured rat pituitary cells

Abstract Triiodothyronine (T(3)) stimulates the synthesis of growth hormone and enhances the growth of neoplastic rat pituitary somatomam-motrophs (GH cells) in culture. Moreover, T(3) has been shown to stimulate the production and secretion of an autocrine growth factor by these cells. We have previously demonstrated the presence of specific receptors for insulin-like growth factors (IGF) on GH cells. Since GH(3) cells contain mRNA encoding IGF-I, it has been suggested that IGF-I might act in an autocrine fashion in these cells. Therefore, it was of interest to learn how T(3) affects IGF-I binding to GH(3) cells. T(3) increased [(125)I]IGF-I binding in a time - and dose-dependent manner. After 48 h of exposure to T(3), an increase in IGF-I binding was seen with 10(-11)M T(3), maximizing with 10(-8)M T(3). When cells were exposed to 10(-8) T(3), [(125)I]IGF-I binding reached a maximum of 218 +/- 20.8% of control (+/-SEM, P < 0.002) after 72 h of incubation. Scatchard analysis indicated that T(3) did not alter the K(d) of IGF-I for its receptor, but that the total receptor number was increased. Dexamethasone (10(-7)M) inhibited the T(3)-induced increase in IGF-I binding, but glucocorticoid alone did not substantially alter receptor number. No significant change in insulin or IGF-II binding was seen after hormone treatment. 10(-8) M T(3) or IGF-I increased the growth of the GH(3) cells by >/=30%. Our data indicate that T(3) upregulates IGF-I binding in GH(3) cells without altering insulin binding and thereby provides a means for enhancing potential autocrine regulation in this cell line.