Peptides (v.24, #3)
Control of antimicrobial peptide synthesis by the agr quorum sensing system in Staphylococcus epidermidis: activity of the lantibiotic epidermin is regulated at the level of precursor peptide processing by Stefanie Kies; Cuong Vuong; Matthias Hille; Andreas Peschel; Cornelia Meyer; Friedrich Götz; Michael Otto (329-338).
The accessory gene regulator (agr) quorum sensing system in staphylococci is responsible for the regulation of surface proteins and exoproteins, including many virulence factors in the pathogenic species Staphylococcus aureus and S. epidermidis. Strain S. epidermidis Tü3298 produces the lantibiotic epidermin. An isogenic agr deletion mutant of this strain showed a strong reduction of epidermin production. Detailed analysis of the impact of agr on epidermin biosynthesis revealed that agr does not interfere with the transcription of epidermin biosynthetic genes, but controls the extracellular processing of the N-terminal leader peptide by the EpiP protease.
Keywords: Staphylococcus epidermidis; Quorum sensing; Lantibiotics; Protease;
Peptides derived from the two regulatory domains of p53 are recognized by two p53-activating antibodies by Jean-Michel Portefaix; Maguy Del Rio; Claude Granier; Françoise Roquet; Bernard Pau; Isabelle Navarro-Teulon (339-345).
The C-terminus of the transcription factor p53 seems to play an important role by controlling the specific DNA-binding activity, which is directly associated with sensing damaged DNA. Another region located in the N-terminus of the protein has also been shown to regulate the DNA-binding activity of the protein. This activity can be promoted by peptides derived from these two negative regulatory regions or by binding of antibodies directed against the C-terminus of the p53 protein. Using both phage display peptide and multiple peptide synthesis technologies, we demonstrated that mAbs HR231 and Pab421, two p53-activating antibodies, recognize peptides derived from the C-terminus of p53, as previously described, but also peptides from the N-terminus of the protein, suggesting that these peptides are part of a conformational epitope. Furthermore, the sequences of these peptides are located in the two negative regulatory regions identified on the p53 protein, which is consistent with the biological activity of mAbs HR231 and Pab421.
Keywords: p53; Monoclonal antibodies; Epitope mapping; SPOT; Phage display;
Analysis of amino acid pairs sensitive to variants in human collagen α5(IV) chain precursor by means of a random approach by Guang Wu; Shaomin Yan (347-352).
In this data-based theoretical analysis, we use the random approach to analyze the amino acid pairs in 5(IV) chain precursor (CA54) in order to determine which amino acid pairs are more sensitive to 151 variants from missense mutant human CA54 protein. The rationale of this study is based on our hypothesis and previous findings that harmful variance is more likely to occur at randomly unpredictable amino acid pair position rather than at randomly predictable positions. This is reasonable to argue as randomly predictable amino acid pairs are less likely to be deliberately evolved, whereas randomly unpredictable amino acid pairs are probably deliberately evolved in connection with protein function. The results show that all 151 variants occurred at randomly unpredictable amino acid pairs and the chance of a variant occurring is markedly higher in randomly unpredictable amino acid pairs than in predictable pairs. Thus, randomly unpredictable amino acid pairs are more sensitive to variance in human CA54. The results also suggest that the human CA54 protein has a natural tendency towards variants.
Keywords: Alport syndrome; Collagen α5(IV) chain; Probability; Randomness; Variants;
Constructs of biotin mimetic peptide with CC49 single-chain Fv designed for tumor pretargeting by Gabriela Pavlinkova; Surinder K. Batra; David Colcher; Barbara J.M. Booth; Janina Baranowska-Kortylewicz (353-362).
Single-chain Fv constructs comprising a biotin mimetic peptide (BMP) and scFv of CC49 monoclonal antibody were produced to improve pretargeted radioimmunotherapy. BMP units that bind streptavidin were added to the carboxyl terminus of the CC49 V H region. An engineered scFvBMP monomer and a sc(Fv)2BMP dimer showed an excellent antigen recognition in vitro with a specific binding of 72±5 and 81±4%, respectively. Properties of 125 I -sc(Fv)2BMP in mice bearing LS-174T xenografts were comparable to these of the parent 125 I -sc(Fv)2. Complexing of scFvBMPs with streptavidin increased tumor targeting and gave exceptionally high tumor-to-blood values of 63±7 for 125 I -sc(Fv)2BMP–streptavidin compared with 37±4 for sc(Fv)2BMP at 72 h after administration. High tumor and negligible normal tissue levels of these novel pretargeting constructs indicate a great potential for pretargeted radioimmunotherapy.
Keywords: Biotin mimetic peptide; Streptavidin; Pretargeting radiotherapy; Single-chain antibody fragments;
Circadian telomerase activity and DNA synthesis for timing peptide administration by Yi Qu; Zhengrong Wang; Xiang Huang; Chaomin Wan; Chun-lei Yang; Bailin Liu; Germaine Cornelissen; Franz Halberg (363-369).
DNA synthesis and telomerase activity were assessed in nude mice transplanted with hepatic carcinoma. Hepatic cancer cells (SMMC-7721) were implanted into both flanks of each of 14 BALB/C mice synchronized in 12 h of light alternating with 12 h of darkness (LD12:12) for 4 weeks. At 7 timepoints, tumor samples were collected for measurement of cellular DNA content by flow cytometry and telomerase activity by PCR–ELISA assay. Cosinor analyses determine a 24-h rhythm for all variables, showing a similar timing for the DNA-synthesis phase and telomerase activity. These results provide a model for exploring optimal timing of chronotherapy with peptides, especially for treatment with telomerase inhibitors.
Keywords: Cell cycle; Circadian rhythm; DNA synthesis; Hepatic carcinoma; Nude mice; Telomerase activity;
Degradation of the immunogenic peptide gp100280–288 by the monocyte-like U937 cell line by Federica Albo; Antonella Cavazza; Bruno Giardina; Silvio Lippa; Mario Marini; L.Giorgio Roda; Giulio Spagnoli (371-378).
The possible degradation of the tumor antigen epitope gp100280–288 (YLEPGPVTA) in the presence of the monocyte-like line U937, and the effect of degradation on the in vitro-measured immune recognition, were investigated by chromatographic techniques and immunological assays. Results indicate a rapid hydrolysis of the substrate in the presence of the model cells, which is consistent with the hypothesis that degradation of gp100280–288 is caused by the activity of U937-expressed enzymes, specifically amino- and carboxypeptidases. On the other hand, these results do not support the involvement of other enzymes known to be expressed by U937 cells. From a functional point of view, these data indicate that the degradation of gp100280–288 severely hampered recognition by specific CTL clones. The results obtained may provide a model for epitope degradation by the antigen-presenting cells found in defined anatomical compartments and may, at least in part, account for the low activity of peptide-based antineoplastic vaccines, as well as for the transience of the effects of subcutaneously administered peptides in general.
Keywords: Antineoplastic vaccines; Tumor-associated antigens; Epitopes; Enzyme degradation;
Peptidomic analysis of the skin secretions of the pickerel frog Rana palustris identifies six novel families of structurally-related peptides by Yousef J Basir; J.Michael Conlon (379-383).
Peptidomics methodology has been used to identify and characterize structurally 26 previously undescribed peptides in the electrically stimulated skin secretions of the North American pickerel frog Rana palustris. Peptides in the secretions were analyzed by electrospray mass spectrometry and components in mass range 700–2500 Da, present in major abundance, were purified by reverse-phase HPLC. Cysteine-containing components were identified by treatment with dithiothreitol and 4-vinylpyridine and re-analysis of the derivatizated peptide by mass spectrometry. Application of these techniques led to the identification of six families of structurally-related peptides comprising (a) six peptides containing the consensus sequence Cys-Trp-Xaa-Thr-Lys-Ser-Ile-Pro-Pro-Lys/Arg-Xaa-Cys, (b) three peptides containing the consensus sequence Pro-Pro-Gly-Val-Cys-(Xaa)3-Lys/Arg-Arg-Cys, (c) two peptides containing the consensus sequence Ser-Phe-His-Val-Phe-Pro-Pro-Trp-Met-Cys-Lys-Xaa-Leu-Lys-Lys-Cys, (d) two peptides containing the consensus sequence Arg-Xaa-Cys-Trp-Lys-(Xaa)2-Asn-(Xaa)3-Val-Cys-Ser, (e) nine peptides containing the consensus sequence Ser-Leu-Pro-Ala-Gly-Leu-Ser-Pro, and (f) four peptides containing the consensus sequence Asp-Xaa-Gln-Asp-Arg-Trp-Xaa-Pro. The peptides did not inhibit the growth of Escherichia coli or Staphylococcus aureus and were inactive on hamster vascular or gastric smooth muscle preparations so that their biological functions, if any, remain to be established.
Keywords: Peptidomics; Rana palustris; HPLC; Skin secretions;
Cloning, pharmacology, and distribution of the neuropeptide Y-receptor Yb in rainbow trout by Earl T. Larson; Robert Fredriksson; Sara R.T. Johansson; Dan Larhammar (385-395).
This work describes the isolation and pharmacological characterization of a neuropeptide Y (NPY) receptor from rainbow trout (Oncorhynchus mykiss). The receptor exhibits approximately 45% amino acid sequence identity to mammalian Y1-subfamily receptors, Y1, Y4 and y6, a similar degree of identity as these subtypes display to one another. Because it displays highest sequence identity to zebrafish Yb (75%), we named it the trout Yb receptor. The receptor exhibits high binding affinity for zebrafish and human NPY and peptide YY (PYY) but not truncated forms of the peptides. Human pancreatic polypeptide (PP) also binds with high affinity. Y1 selective antagonists exhibit poor binding as is the case for Y2 and Y5 selective ligands. This binding profile supports membership in the Y1 subfamily. Sequence data also support this relationship suggesting that Yb is a fourth and separate member of the Y1 subfamily. NPY has a number of important physiological functions such as regulating food intake and reproduction. The expression of the receptor in the hypothalamus and telencephalon suggests a possible role in these processes. This and other receptors from this species have potential for improving aquaculture.
Keywords: Rainbow trout; NPY; PYY; PP; Pharmacology; NPY fragments; Yb receptor; Hypothalamus; Telencephalon; Physiology; Teleost; Aquaculture;
β-MSH: a functional ligand that regulated energy homeostasis via hypothalamic MC4-R? by Joanne A. Harrold; Peter S. Widdowson; Gareth Williams (397-405).
α-Melanocyte stimulating hormone (MSH) has generally been assumed to be the endogenous ligand acting at the melanocortin-4 receptor (MC4-R), activation of which in the hypothalamus leads to reduced feeding. However, β-MSH is also capable of activating MC4-R and inhibiting feeding. Here, we investigated the possibility that β-MSH acts as an endogenous MC4-R agonist and that this melanocortin peptide plays a role in the regulation of feeding and energy balance. We found that β-MSH had significantly higher affinities than α-MSH at both human MC4-R transfected into CHO cells (K i: β-MSH, 11.4±0.4 nmol/l versus α-MSH, 324±16 nmol/l, P<0.001) and MC4-R in rat hypothalamic homogenates (K i: β-MSH, 5.0±0.4 nmol/l versus α-MSH, 22.5±2.3 nmol/l, P<0.001). Incubation of brain slices with 5 μM β-MSH significantly increased [ 35 S ]GTPγS binding by 140–160% (P<0.001), indicating activation of G-protein-coupled receptors (GPCRs), in the hypothalamic ventromedial (VMH), dorsomedial (DMH), arcuate (ARC) and paraventricular (PVN) nuclei. These sites match the distribution of β-MSH immunoreactive fibres and also the distribution of MC4-R binding sites which we and others previously reported. Food-restriction significantly increased β-MSH levels in the VMH, DMH and ARC (all P<0.05) above freely-fed controls, whilst α-MSH concentrations were unchanged. We propose that increased β-MSH concentrations reflect blockade of the peptide’s release in these sites, consistent with the increased hunger and the known up-regulation of MC4-R in the same nuclei. Thus, we conclude that (1) β-MSH has higher affinity at MC4-R than α-MSH; (2) β-MSH activates GPCR in these sites, which are rich in MC4-R; and (3) β-MSH is present in hypothalamic nuclei that regulate feeding and its concentrations alter with nutritional state. We suggest that β-MSH rather than α-MSH is the key ligand at the MC4-R populations that regulate feeding, and that inhibition of tonic release of β-MSH is one mechanism contributing to hunger in under-feeding.
Keywords: β-Melanocyte stimulating hormone; Melanocortin-4 receptors; Hypothalamus; Food intake;
Plasma orexin-A-like immunoreactivity in patients with sleep apnea hypopnea syndrome by Tsuguo Nishijima; Shigeru Sakurai; Zenei Arihara; Kazuhiro Takahashi (407-411).
Orexin-A (hypocretin-1), a neuropeptide produced in hypothalamus, stimulates arousal. We studied plasma concentrations of orexin-A-like immunoreactivity (orexin-A-LI) in 156 patients with sleep apnea hypopnea syndrome (SAHS) and 22 control subjects. Plasma orexin-A-LI levels were significantly decreased in 156 patients with SAHS (4.4±0.15 pmol/l, mean±S.E.) as compared with controls (5.3±0.45 pmol/l). The levels were decreased in parallel with the severity of sleep-related respiratory disturbance and magnitude of sleep fragmentation. These findings raise the possibility that a low plasma level of orexin-A-LI may be a marker to show the severity of the disease in patients with SAHS.
Keywords: Orexin; Hypocretin; Sleep; Apnea; Plasma;
Endogenous CART peptide regulates mu opioid and serotonin 5-HT2A receptors by Richard B. Rothman; Nga Vu; Xiaoying Wang; Heng Xu (413-417).
Previous experiments conducted in this laboratory showed that intracerebroventricular (i.c.v.) administration of IgG antibodies directed against selected neuropeptides changed the density of CNS receptors, suggesting that neuropeptides in the cerebrospinal fluid can perform a regulatory role. To further test this hypothesis, we administered anti-CART peptide (the peptide product of cocaine amphetamine related transcript) IgG to rats via the i.c.v. route, and measured the density of opioid mu and delta receptors, beta-adrenergic and alpha2-adrenergic receptors and serotonin 5-HT2A receptors using ligand binding methods. We also used Western blots to determine the expression level of the mu, delta and 5-HT2A receptors. The results demonstrated that anti-CART peptide IgG up-regulates mu and 5-HT2A receptor in the hippocampus and caudate We conclude that CART peptides in the cerebrospinal fluid may exert regulatory effects in the brain.
Keywords: CART peptide; Serotonin receptor; Opioid receptor;
In vitro and in vivo opioid activity of [DPro6]dermorphin, a new dermorphin analogue by M. Broccardo; A.B. Usenko; M.G. Uranova; L.S. Guzevatykh; A.A. Kamensky; L.A. Andreeva; L.Y. Alfeeva; N.F. Myasoedov; E. Giannini; G. Improta; T.G. Emel’yanova (419-428).
To study the effects of inducing stereo-chemical modifications in the structure of dermorphin (DM) so as to improve its μ-opioid receptor affinity and its resistance to C-terminal enzymatic degradation, in the Institute of Molecular Genetics of Moscow, we synthesized a new DM analogue ([DPro6]DM) and analyzed the changes induced in the biological activities of DM by substituting the Pro6 residue with DPro6. We compared the activity of the new DM analogue and DM in in vitro assays and in in vivo tests of analgesia, thermoregulation, heart rate recordings, and gastrointestinal motility in rats. In the in vitro tests, guinea pig ileum (GPI) and mouse vas deferens (MVD), although the opioid activities of [DPro6]DM indicated that the peptide was always less potent than DM, its lower IC50 ratios (μ/δ) showed that it had higher μ-opioid receptor selectivity. In the in vivo analgesic test, [DPro6]DM, when injected intraperitoneally (i.p.) (0.5–5 and 10 mg/kg) in rats, had the same antinociceptive efficacy as DM and when injected intranasally (i.n.) (0.005 and 0.02 mg/kg) it induced a more stable and long-lasting analgesia than DM (the AUC was about 91% higher for [DPro6]DM than for DM). Moreover, these data confirm that the intranasal route is advantageous for peripheral drug administration. In the heart rate study, [DPro6]DM and DM (0.5 mg/kg, i.p.), induced a similar, weak bradycardia. The only difference was that [DPro6]DM induced a longer-lasting effect than DM. Conversely, in body temperature regulation [DPro6]DM induced weaker inhibitory activity than DM (56% of the DM-induced response); it did so only in a cold environment and at the maximal used dose (0.5 mg/kg, i.p.) without inducing vasomotor effects. In the gastrointestinal study, [DPro6]DM and DM (0.005, 0.05, and 0.5 mg/kg, i.p.) significantly slowed upper gastrointestinal transit of a charcoal meal and inhibited colonic propulsion. Comparison of the ED50 values of [DPro6]DM (0.03 mg/kg) and DM (0.009 mg/kg) showed that the DM analogue was about three times less potent than DM in slowing gastrointestinal and colonic transit. In conclusion, all these data overall suggest that structural maneuvering in the Pro6-residue of the DM molecule changes its affinity for μ-opioid receptor subtypes and confirms the usefulness of experimental studies involving structural modifications in obtaining new therapeutic agents.
Keywords: [DPro6]dermorphin; In vitro and in vivo opioid activity; Peripheral administration; Rats;
VIP and PACAP receptors coupled to adenylyl cyclase in human lung cancer: by Rebeca Busto; Juan C. Prieto; Guillermo Bodega; José Zapatero; Luis Fogué; Isabel Carrero (429-436).
Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are important neuropeptides in the control of lung physiology. Both of these commonly bind to specific G protein coupled receptors named VPAC1-R and VPAC2-R, and PAC1-R (with higher affinity for PACAP). VIP and PACAP have been implicated in the control of cell proliferation and tumor growth. This study examined the presence of VIP and PACAP receptors in human lung cancer samples, as well as the functionality of adenylyl cyclase (AC) stimulated by both peptides. Results from RT-PCR and immunoblot experiments showed the expression of VPAC1-, VPAC2- and PAC1-R in lung cancer samples. Immunohistochemical studies showed the expression of VPAC1 and VPAC2 receptors. These receptors were positively coupled to AC, but the enzyme activity was impaired as compared to normal lung. There were no changes in Gαs or Gαi levels. Present results contribute to a better knowledge of VIP/PACAP actions in lung cancer and support the interest for the development of VIP/PACAP analogues with therapeutic roles.
Keywords: VIP; PACAP; Lung cancer; Receptors; Adenylyl cyclase;
Passage of vasoactive intestinal peptide across the blood–brain barrier by Dilek Dogrukol-Ak; William A. Banks; Nese Tuncel; Muzaffer Tuncel (437-444).
We investigated the ability of vasoactive intestinal peptide (VIP) to cross the blood–brain barrier (BBB), the interface between the peripheral circulation and central nervous system (CNS). VIP labeled with 131 I (I-VIP) and injected intravenously into mice was taken up by brain as determined by multiple-time regression analysis. Excess unlabeled VIP was unable to impede the entry of I-VIP, indicating that passage is by nonsaturable transmembrane diffusion. High pressure liquid chromatography (HPLC) showed the radioactivity entering the brain to be intact I-VIP. After intracerebroventricular (i.c.v.) injection, I-VIP was sequestered by brain, slowing its efflux from the CNS. In summary, VIP crosses the BBB unidirectionally from blood to brain by transmembrane diffusion.
Cyclo (His-Pro) potentiates GABA/ethanol-mediated chloride uptake by neurosynaptosomes by Makoto Imamura; Chandan Prasad (445-448).
Cyclo (His-Pro) CHP is a cyclic dipeptide endogenous to the brain of a variety of animal species including man. Administration of exogenous peptide to rodents has been shown to exhibit a variety of biologic activities including, modification of pharmacologic actions of alcohol. Since there are many apparent similarities between the actions of GABA and CHP in modulating alcohol pharmacology, we have examined whether CHP can modulate alcohol potentiation of GABA-receptor-mediated 36 Cl -influx in neurosynaptosomes. The results show a further dose-dependent potentiation of 36 Cl -influx in neurosynaptosomes by CHP in the presence of GABA and alcohol.
Keywords: Cyclo (His-Pro); Histidyl-proline diketopiperazine; 36 Cl -influx; 36 Cl -uptake; Alcoholism; Alcohol; GABA;
Elevated glucose blocks angiotensin-(1–7) and bradykinin interaction: the role of cyclooxygenase products by Maria A Oliveira; Maria Helena C Carvalho; Dorothy Nigro; Rita de Cássia A.T Passaglia; Zuleica B Fortes (449-454).
The interaction between angiotensin-(1–7) [Ang-(1–7)] and bradykinin (BK) was studied in the isolated mesenteric arteriolar bed of control and diabetic rats perfused with either 5.5 or 22 mM of glucose. Prostanoids release after the administration of BK, Ang-(1–7) and Ang-(1–7)+BK was also studied. In control and diabetic preparations perfused with Krebs Henseleit solution with 5.5 mM of glucose, Ang-(1–7) potentiates BK-induced vasodilation. On the other hand, the potentiating effect disappeared in control and diabetic preparations perfused with 22 mM of glucose. Prostaglandin F2α (PGF2α) release induced by BK and Ang-(1–7)+BK was increased in perfusates of diabetic preparations containing 22 mM of glucose. The release of thromboxane A2 (TXA2) (measured as TXB2) or prostaglandin I2 (PGI2) (measured as 6-keto-PGF1α) did not differ in control and diabetic preparations perfused with 5.5 and 22 mM of glucose. Our data allow us to suggest that hyperglycemia may be involved in the lack of potentiation in control and diabetic preparations; increase in PGF2α release, but not other cyclooxygenase products, may explain the absence of potentiation in diabetic preparations.
Keywords: Bradykinin; Angiotensin-(1–7); Diabetes mellitus; Hyperglycemia; PGF2α;
Characterization of angiotensin-(1–7) receptor subtype in mesenteric arteries by Liomar A.A Neves; David B Averill; Mark C Chappell; Judy L Aschner; Michael P Walkup; K.Bridget Brosnihan; Carlos M Ferrario (455-462).
Mesenteric arteries from male Sprague-Dawley rats were mounted in a pressurized myograph system. Ang-(1–7) concentration-dependent responses were determined in arteries preconstricted with endothelin-1 (10−7 M). The receptor(s) mediating the Ang-(1–7) evoked dilation were investigated by pretreating the mesenteric arteries with specific antagonists of Ang-(1–7), AT1 or AT2 receptors. The effects of Ang-(3–8) and Ang-(3–7) were also determined. Ang-(1–7) caused a concentration-dependent dilation (EC50: 0.95 nM) that was blocked by the selective Ang-(1–7) receptor antagonist D-[Ala7]-Ang-(1–7). Administration of a specific antagonist to the AT2 receptor (PD123319) had no effect. On the other hand, losartan and CV-11974 attenuated the Ang-(1–7) effect. These results demonstrate that Ang-(1–7) elicits potent dilation of mesenteric resistance vessels mediated by a D-[Ala7]-Ang-(1–7) sensitive site that is also sensitive to losartan and CV-11974.
Keywords: Hypertension; Renin–angiotensin system; Vasodilation; Angiotensin receptors;
Changes of adrenomedullin and receptor activity modifying protein 2 (RAMP2) in myocardium and aorta in rats with isoproterenol-induced myocardial ischemia by Yong Fen Qi; Yan Rong Shi; Ding Fang Bu; Yong Zheng Pang; Chao Shu Tang (463-468).
Adrenomedullin is a potent vasodilator peptide originally isolated from a pheochromocytoma. Recently, a novel adrenomedullin receptor has been identified as a complex of calcitonin receptor-like receptor (CRLR) and receptor activity modifying protein 2 (RAMP2). To explore the pathophysiological roles of adrenomedullin and its receptor component RAMP2 in ischemic cardiovascular diseases, we studied the changes of adrenomedullin and RAMP2 mRNA in myocardium and aorta in rats with isoproterenol (ISO)-induced myocardial impairment. In ISO-treated rats, heart became enlarged markedly, the ratio of heart to body weight was increased by 54% (P<0.01), and myocardial malondialdehyde content and plasma lactate dehydrogenase activity was elevated by 43% (P<0.01) and 138% (P<0.01), respectively. Immunoreactive adrenomedullin (ADM) in plasma, myocardium and aorta was augmented by 116.7% (P<0.01), 50.8% (P<0.01) and 12.5% (P>0.05), respectively. ADM mRNA in myocardium and aorta was increased by 96.8% (P<0.01) and 38.5% (P<0.01), respectively. RAMP2 mRNA in myocardium and aorta was increased by 19.6% (P<0.05) and 15.8% (P<0.01), respectively. These results suggest that the increase of ADM level and the up-regulation of ADM and RAMP2 gene in myocardium and aorta may be significant in the pathogenesis of ischemic myocardiopathy.
Keywords: Adrenomedullin; Myocardiopathy; Aorta; Receptor activity modifying protein 2 (RAMP2);
Tachykinin peptide-induced activation and desensitization of neurokinin 1 receptors by S.A. Perrine; V.J. Bennett; M.A. Simmons (469-475).
The actions of four tachykinins on inhibition and desensitization of the M-current of bullfrog sympathetic neurons have been characterized. Radioligand binding parameters of the tachykinins were determined at a neurokinin receptor in a heterologous expression system. The correlation between binding, signaling and receptor regulation was investigated. A correlation between receptor binding and signaling was found between the peptides; however, their ability to produce desensitization was not correlated with binding and signaling. These results show that the ability of a tachykinin peptide to induce signal activation is not indicative of its ability to induce receptor regulation.
Keywords: Tachykinin; Substance P; Neurokinin 1 receptor; Bullfrog sympathetic ganglia; Desensitization; M-current;
Endomorphin-1 and -2 induce naloxone-precipitated withdrawal syndromes in rats by J.-C. Chen; P.-L. Tao; J.-Y. Li; C.-H. Wong; E.Y.-K. Huang (477-481).
In 1997, endomorphin-1 (EM-1) and -2 (EM-2) were identified as the most specific endogenous μ-opioid ligands. These two peptides have shown analgesic effects and many other opioid functions. In the present study, we attempt to investigate the possible ability of endomorphins to induce naloxone-precipitated withdrawal in comparison with that induced by morphine. Using the previously established scoring system in rats, 12 withdrawal signs (chewing, sniffing, grooming, wet-dog shakes, stretching, yawning, rearing, jumping, teeth grinding, ptosis, diarrhea, and penile erection) were observed and scored following naloxone (4 mg/kg, i.p.) challenge. Compared with the sham control, EM-1 and EM-2 (20 μg, i.c.v., b.i.d. for 5 days) both produced significant naloxone-induced withdrawal syndromes with similar severity to that induced by the same dose of morphine. There was no significant difference between EM-1, EM-2, and morphine-treated group for naloxone-induced withdrawal signs, except for grooming. EM-1 and EM-2 induced more grooming than that caused by morphine. Although EM-1 and EM-2 both led to the withdrawal, they displayed different potency for certain signs and suggest their distinct regulations. The present results indicate EM-1 and EM-2 could initiate certain mechanism involved opiate dependence.
Keywords: Withdrawal syndromes; Morphine; Endomorphin-1; Endomorphin-2; Behavior; Opiate dependence; Neuropeptides;
Plasma motilin in untreated celiac disease by K Sjölund; R Ekman (483-486).
Celiac disease (CD) is characterized by mucosal villous atrophy mostly confined to the proximal small intestine. Upper-gut motor abnormalities have been reported. Motilin, localized in cells in the proximal small intestine, is a trigger factor for the migrating motor complex. Plasma levels of motilin were studied in 16 untreated CD patients and in an age-matched control group of 18 healthy subjects by radioimmunoassay and by high-performance liquid chromatography (HPLC). The fasting levels of motilin and postprandial levels were significantly higher in CD patients compared to controls (P<0.01) and HPLC revealed a divergent individual pattern of the motilin fragments.
Keywords: Celiac disease; Motilin; Plasma; Fat meal; Radioimmunoassay; HPLC;
Targeting ICAM-1/LFA-1 interaction for controlling autoimmune diseases: designing peptide and small molecule inhibitors by Meagan E. Anderson; Teruna J. Siahaan (487-501).
This review describes the role of modulation of intracellular adhesion molecule-1 (ICAM-1)/leukocyte function-associated antigen-1 (LFA-1) interaction in controlling autoimmune diseases or inducing immunotolerance. ICAM-1/LFA-1 interaction is essential for T-cell activation as well as for migration of T-cells to target tissues. This interaction also functions, along with Signal-1, as a co-stimulatory signal (Signal-2) for T-cell activation, which is delivered by the T-cell receptors (TCR)–major histocompatibility complex (MHC)–peptide complex. Therefore, blocking ICAM-1/LFA-1 interaction can suppress T-cell activation in autoimmune diseases and organ transplantation. Many types of inhibitors (i.e. antibodies, peptides, small molecules) have been developed to block ICAM-1/LFA-1 interactions, and some of these molecules have reached clinical trials. Peptides derived from ICAM-1 and LFA-1 sequences have been shown to inhibit T-cell adhesion and activation. In addition, these inhibitors have been useful in elucidating the mechanism of ICAM-1/LFA-1 interaction. Besides binding to LFA-1, the ICAM-1 peptide can be internalized by LFA-1 receptors into the cytoplasmic domain of T-cells. Therefore, this ICAM-1 peptide can be utilized to selectively target toxic drugs to T-cells, thus avoiding harmful side effects. Finally, bi-functional inhibitory peptide (BPI), which is made by conjugating the antigenic peptide and an LFA-1 peptide, can alter the T-cell commitment from T-helper-1 (Th1) to T-helper-2 (Th2)-like cells, suggesting that this peptide may have a role in blocking the formation of the “immunological synapse.”
Keywords: ICAM-1; LFA-1; Cell adhesion; T-cell activation; Immunotolerance; Autoimmune diseases; Immunological synapse; Peptides;