Reversible pegylation of insulin facilitates its prolonged action in vivo

We attempted to engineer a novel long-acting insulin based on the following properties: (i) action as a prodrug to preclude supraphysiological concentrations shortly after injection; (ii) maintenance of low-circulating level of biologically active insulin for prolonged period; and (iii) high solubility in aqueous solution. A spontaneously hydrolyzable prodrug was thus designed and prepared by conjugating insulin through its amino side chains to a 40kDa polyethylene glycol containing sulfhydryl moiety (PEG(40)-SH), employing recently developed hetero-bifunctional spacer 9-hydroxymethyl-7(amino-3-maleimidopropionate)-fluorene-N-hydroxysucinimide (MAL-Fmoc-0Su). A conjugate trapped in the circulatory system and capable of releasing insulin by spontaneous chemical hydrolysis has been created. PEG(40)-Fmoc-insulin is a water-soluble, reactivatable prodrug with low biological activity. Upon incubation at physiological conditions, the covalently linked insulin undergoes spontaneous hydrolysis at a slow rate and in a linear fashion, releasing the nonmodified immunologically and biologically active insulin with a t(1/2) value of 30h. A single subcutaneous administration of PEG(40)-Fmoc-insulin to healthy and diabetic rodents facilitates prolonged glucose-lowering effects 4- to 7-fold greater than similar doses of the native hormone. The beneficial pharmacological features endowed by PEGylation are thus preserved. In contrast, nonreversible, "conventional" pegylation of insulin led to inactivation of the hormone.

VIP-derived sequences modified by N-terminal stearyl moiety induce cell death: the human keratinocyte as a model

Vasoactive intestinal peptide (VIP) is a recognized growth factor affecting many cell types. We have previously developed a series of lipophilic VIP analogues containing an N-terminal covalently attached stearyl moiety. The current studies identified stearyl-Nle(17)-VIP and stearyl-Nle(17)-neurotensin(6-11)VIP(7-28), acting at microM concentrations, as cytotoxic to human keratinocytes. The core C-terminal active VIP-derived peptide, stearyl-Lys-Lys-Tyr-Leu-NH(2) (St-KKYL-NH(2)), was identified as being responsible for the observed cytotoxicity. Cytotoxicity coincided with marked reduction in intracellular cyclic GMP and was abolished by co-treatment with the endonuclease inhibitor, aurine-tricarboxylic acid, suggesting apoptotic mechanisms. Stearyl-VIP derivatives thus offer lead compounds for future drug development against hyperproliferative skin conditions.

Mapping the active site in vasoactive intestinal peptide to a core of four amino acids: neuroprotective drug design

The understanding of the molecular mechanisms leading to peptide action entails the identification of a core active site. The major 28-aa neuropeptide, vasoactive intestinal peptide (VIP), provides neuroprotection. A lipophilic derivative with a stearyl moiety at the N-terminal and norleucine residue replacing the Met-17 was 100-fold more potent than VIP in promoting neuronal survival, acting at femtomolar-picomolar concentration. To identify the active site in VIP, over 50 related fragments containing an N-terminal stearic acid attachment and an amidated C terminus were designed, synthesized, and tested for neuroprotective properties. Stearyl-Lys-Lys-Tyr-Leu-NH2 (derived from the C terminus of VIP and the related peptide, pituitary adenylate cyclase activating peptide) captured the neurotrophic effects offered by the entire 28-aa parent lipophilic derivative and protected against beta-amyloid toxicity in vitro. Furthermore, the 4-aa lipophilic peptide recognized VIP-binding sites and enhanced choline acetyltransferase activity as well as cognitive functions in Alzheimer's disease-related in vivo models. Biodistribution studies following intranasal administration of radiolabeled peptide demonstrated intact peptide in the brain 30 min after administration. Thus, lipophilic peptide fragments offer bioavailability and stability, providing lead compounds for drug design against neurodegenerative diseases.

Multiple actions of a hybrid PACAP antagonist: neuronal cell killing and inhibition of sperm motility

Pituitary stimulating adenylate cyclase (PACAP) is a major regulatory peptide with two active molecular forms: PACAP-27 and PACAP-38. Both molecular forms promote neuronal survival and protect against neurotoxicity. Based on our previous hybrid peptide strategy in designing vasoactive intestinal peptide (VIP) antagonists, novel PACAP analogues were synthesized (neurotensin6-11 PACAP7-27 and neurotensin6-11 PACAP7-38). In addition to the hybrid modification, the methionine in position 17 was replaced by norleucine (Nle). Treatment of rat cerebral cortical cultures for five days with the putative PACAP antagonists (1 nM) resulted in a 35-45% reduction in neuronal cell counts as compared to controls. Neuronal cell death was already obtained at picomolar concentrations for the neurotensin6-11 PACAP7-27 antagonist with 70% death at 10(-8) M. Co-administration of the PACAP hybrid analogue with picomolar amounts of PACAP-27 or Nle17-PACAP-27 attenuated the reduction in neuronal cell counts. While the protective effects of both analogues exhibited a peak at 1 pM concentrations, the Nle-containing agonist displayed a broader range of active concentrations (10(-12)M-10(-9) M). The putative PACAP antagonist also inhibited sperm motility (golden hamster) in a dose-dependent manner as assessed in vitro. Complete inhibition was observed at 10 microM, suggesting a role for PACAP in sperm motility and sexual function. Thus, previous findings of a large number of PACAP and PACAP receptors in the nervous system and the reproductive system are now correlated with a function in neuronal survival and sperm motility. The structure-activity studies suggest that the methionine in position 17 and the first six amino acids are important in the determination of PACAP activity, knowledge that may facilitate PACAP-based drug design.

Protection against developmental deficiencies by a lipophilic VIP analogue

Stearyl-Nle-VIP (SNV) is a novel agonist of vasoactive intestinal peptide (VIP) exhibiting a 100-fold greater potency than the parent molecule and specificity for a receptor associated with neuronal survival. Here, the developmental and protective effects of SNV were investigated in vivo using two models of developmental retardation, hypoxia and cholinergic blockade. In both cases chronic administration of SNV during development provided protective effects. Water maze experiments on the weaned animals have demonstrated a prophylactic action for SNV and enhancement of spatial memory in animals exposed to a cholinotoxin. SNV may act by providing neuroprotection, thereby improving cognitive functions. This work is dedicated to Prof. R.J. Wurtman whose inspiration and leadership in the field of neuroscience and cognition is beyond comparison.

Activity-dependent neurotrophic factor: structure-activity relationships of femtomolar-acting peptides

Activity-dependent neurotrophic factor (ADNF) is a glia-derived protein that is neuroprotective at femtomolar concentrations. A 14-amino acid peptide of ADNF (ADNF-14) has been reported that protects cultured neurons from multiple neurotoxins. Structure-activity relationships of peptides related to ADNF-14 now have been determined. A 9-amino acid core peptide (ADNF-9) has been identified that has greater potency and a broader effective concentration range (10(-16) to 10(-13) M) than ADNF or ADNF-14 in preventing cell death associated with tetrodotoxin treatment of cerebral cortical cultures. Deletions or conservative amino acid substitutions to ADNF-9 resulted in reduced potency, narrower effective concentration range and/or decreased efficacy. Removal of the N-terminal serine or the COOH-terminal isoleucine-proline-alanine from ADNF-9 produced a significant reduction in survival-promoting activity. Comparative studies of ADNF-9 action in mixed (glia plus neurons) vs. glia-depleted neuronal cultures indicated that ADNF-9 can act directly on neurons, although the potency of the peptide was 10,000-fold greater in mixed cultures. Kinetic studies showed that exposure to ADNF-9 for only 2 hr was sufficient to produce a 4-day protection against the cell-killing action of tetrodotoxin. Treatment with bafilomycin A1 (an inhibitor of receptor-mediated endocytosis) for 2 hr prevented the ADNF- and ADNF-9-mediated neuroprotection. ADNF-9, like ADNF-14, was neuroprotective against N-methyl-D-aspartate and the beta-amyloid peptide (amino acids 25-35), and had a much broader range of effective concentrations than ADNF-14. These studies identify ADNF-9 as an attractive lead compound for the development of therapeutic agents against neurodegenerative diseases.

Protection against developmental retardation in apolipoprotein E-deficient mice by a fatty neuropeptide: implications for early treatment of Alzheimer's disease

Stearyl-Nle17-VIP (SNV) is a novel agonist of vasoactive intestinal peptide (VIP) exhibiting a 100-fold greater potency than the parent molecule and specificity for a receptor associated with neuronal survival. Here, mice deficient in apolipoprotein E (ApoE), a molecule associated with the etiology of Alzheimer's disease, served as a model to investigate the developmental and protective effects of SNV. In comparison to control animals, the deficient mice exhibited (a) reduced amounts of VIP messenger RNA; (b) decreased cholinergic activity (c) significant retardation in the acquisition of developmental milestones: forelimb placing behavior and cliff avoidance behavior; and (d) learning and memory impairments. Daily injections of SNV to ApoE-deficient newborn pups resulted in increased cholinergic activity and marked improvements in the time of acquisition of behavioral milestones, with peptide-treated animals developing as fast as control animals and exhibiting improved cognitive functions after cessation of peptide treatment. Specificity was demonstrated in that treatment with a related peptide (PACAP), pituitary adenylate cyclase-activating peptide, produced only limited amelioration. As certain genotypes of ApoE increase the probability of Alzheimer's disease, early counseling and preventive treatments may now offer an important route for therapeutics design.

Neuroprotective strategy for Alzheimer disease: intranasal administration of a fatty neuropeptide

Neurodegenerative diseases, in which neuronal cell disintegrate, bring about deteriorations in cognitive functions as is evidenced in millions of Alzheimer patients. A major neuropeptide, vasoactive intestinal peptide (VIP), has been shown to be neuroprotective and to play an important role in the acquisition of learning and memory. A potent lipophilic analogue to VIP now has been synthesized, [stearyl-norleucine17]VIP ([St-Nle17]VIP), that exhibited neuroprotection in model systems related to Alzheimer disease. The beta-amyloid peptide is a major component of the cerebral amyloid plaque in Alzheimer disease and has been shown to be neurotoxic. We have found a 70% loss in the number of neurons in rat cerebral cortical cultures treated with the beta-amyloid peptide (amino acids 25-35) in comparison to controls. This cell death was completely prevented by cotreatment with 0.1 pM [St-Nle17]VIP. Furthermore, characteristic deficiencies in Alzheimer disease result from death of cholinergic neurons. Rats treated with a cholinergic blocker (ethylcholine aziridium) have been used as a model for cholinergic deficits. St-Nle-VIP injected intracerebroventricularly or delivered intranasally prevented impairments in spatial learning and memory associated with cholinergic blockade. These studies suggest both an unusual therapeutic strategy for treatment of Alzheimer deficiencies and a means for noninvasive peptide administration to the brain.

Superactive lipophilic peptides discriminate multiple vasoactive intestinal peptide receptors

To distinguish vasoactive intestinal peptide (VIP) receptors in the brain-mediating neurotransmission and neurotrophism, potent VIP analogues were designed. Using a single amino acid substitution and the addition of a fatty acyl moiety, an analogue was devised that exhibited both a 100-fold greater potency than VIP and specificity for a VIP receptor associated with neuronal survival. This VIP agonist increased neuronal survival via a cAMP-independent mechanism. Identical chemical modification of a prototype VIP antagonist (Met-Hybrid, Neurotensin6-11-VIP7-28) also resulted in a 100-fold greater potency in blocking VIP-mediated increases in neuronal survival. Blockade of circadian activity rhythms was limited to VIP antagonists that could inhibit VIP-mediated increases in cAMP. These lipophilic peptides provide novel tools in receptor discrimination and drug design.

Stearyl-norleucine-vasoactive intestinal peptide (VIP): a novel VIP analog for noninvasive impotence treatment

The present report relates to pharmaceutical composition for the treatment of male impotence. The transdermal application of a potent derivative of vasoactive intestinal peptide (VIP) coupled to a suitable hydrophobic moiety (e.g. stearyl-VIP) in a suitable ointment composition (e.g. Sefsol) enhances sexual activity and erection formation in a variety of impotence models in rats (sterile rats, diabetic rats, and animals with high blood pressure). Furthermore, exchange of the methionine in position 17 with norleucine enhances biological activity. Thus, stearyl-Nle17-VIP may be considered useful for the treatment of impotence.

Inhibition of human neuroblastoma growth by a specific VIP antagonist

The 28-amino-acid neuropeptide, vasoactive intestinal peptide (VIP), is a potent mitogen during embryonic development and plays a vital role in brain growth. VIP is also mitogenic for tumor cells, including the human neuroblastoma (NMB). Northern blot analysis has revealed VIP mRNA transcripts in NMB. We now report VIP-like immunoreactivity within these neuroblastoma cells that increased during logarithmic growth and decreased after attaining confluency. About 10(6) seeded cells secreted 5-40 pg of VIP-like immunoreactivity into the medium. These results suggest an autocrine role for VIP in the regulation of neuroblastoma growth. A VIP hybrid antagonist (neurotensin6-11 VIP7-28) that has been shown to inhibit lung cancer proliferation was now tested for inhibition of neuroblastoma growth. Receptor binding studies indicated that the hybrid antagonist displaced [125I]-VIP binding in the neuroblastoma cells (EC50 = 5 x 10(-6)M). Furthermore, as measured by thymidine incorporation and by cell counts, the potent VIP hybrid antagonist inhibited neuroblastoma multiplication in a dose-dependent manner. In conclusion, VIP may be an important regulator of growth of nerve cell progenitors and of tumors derived from neuronal origin and intervening with VIP function may lead to improved treatment of cancer.

Thiolysis of the 3-nitro-2-pyridinesulfenyl (Npys) protecting group. An approach towards a general deprotection scheme in peptide synthesis

The hydroxylic side-chain functional groups of serine, threonine, hydroxproline and tyrosine, the alpha and epsilon-amino moieties of lysine and the thiol group of cysteine were masked by the 3-nitro-2-pyridinesulfenyl (Npys) protecting group. Deprotection was mildly affected by thiolysis with either 2-mercaptopyridine and 2-mercaptomethyl imidazole (O- and N-Npys) or with 3-mercaptoacetic acid and 2-mercaptoethanol (S-Npys). Thiolysis was monitored spectrophotometrically and was completed in a rather short time. Incorporation of the Npys group into a whole and single thiolyzable deprotection scheme is suggested.

Polytuftsin: a potential precursor for slow release of the phagocytosis stimulating peptide tuftsin

1. Polytuftsin (Thr-Lys-Pro-Arg)n, was synthesized through polycondensation of an amino-free and carboxyl-activated derivative of tuftsin, H2N-Thr-Lys(Z)-Pro-Arg(Tos)-OSu, following suitable deprotection and fractionation steps. 2. Digestion of polytuftsin by trypsin, as well as by normal human serum, at 37 degrees C, yielded free tuftsin. 3. Polytuftsin affected the decreased formation of lung-metastasis, in B16 melanoma treated mice and prolonged the survival of animals more efficiently than tuftsin. 4. Tuftsin was found to be totally degraded by serum enzymes within approximately 60 min at 37 degrees C.