Synthesis and biological evaluation of new opioid agonist and neurokinin-1 antagonist bivalent ligands

Newly designed bivalent ligands-opioid agonist/NK1-antagonists have been synthesized. The synthesis of new starting materials-carboxy-derivatives of Fentanyl (1a-1c) was developed. These products have been transformed to 'isoimidium perchlorates' (2a-c). The new isoimidium perchlorates have been successfully implemented in nucleophilic addition reactions, with l-tryptophan 3,5-bis(trifluoromethyl)benzyl ester to give the target compounds-amides (3a-c). Perchlorates (2a-c) successfully undergo reactions with other nucleophiles such as alcohols, amines or hydrazines. The obtained compound 3b exhibited μ-opioid agonist activity and NK1-antagonist activity and may serve as a useful lead compound for the further design of a new series of opioid agonist/NK1-antagonist compounds.     

Inhibition of p38-MAPK signaling pathway attenuates breast cancer induced bone pain and disease progression in a murine model of cancer-induced bone pain

Background

Mechanisms driving cancer-induced bone pain are poorly understood. A central factor implicated to be a key player in the process of tumorigenesis, osteoclastogenesis and nociception is p38 MAPK. We determined the role of p38 MAPK in a mouse model of breast cancer induced bone pain in which mixed osteolytic and osteoblastic remodeling occurs.

Results

In cancer-treated mice, acute as well as chronic inhibition of p38 MAPK with SB203580 blocked flinching and guarding behaviors in a dose-dependent manner whereas no effect on thresholds to tactile stimuli was observed. Radiographic analyses of bones demonstrated that chronic inhibition of p38 MAPK reduced bone loss and incidence of spontaneous fracture in cancer-treated mice. Histological analysis of bones collected from mice treated with the p38 MAPK inhibitor showed complete absence of osteoblastic growth in the intramedullary space as well as significantly reduced tumor burden.

Conclusions

Blockade of non-evoked pain behaviors but not hypersensitivity suggests differences in the underlying mechanisms of specific components of the pain syndrome and a possibility to individualize aspects of pain management. While it is not known whether the role of p38 MAPK signaling can be expanded to other cancers, the data suggest a need for understanding molecular mechanisms and cellular events that initiate and maintain cancer-induced bone pain for effective management for both ongoing pain as well as breakthrough pain.     

Truncation of the peptide sequence in bifunctional ligands with mu and delta opioid receptor agonist and neurokinin 1 receptor antagonist activities

The optimization and truncation of our lead peptide-derived ligand TY005 possessing eight amino-acid residues was performed. Among the synthesized derivatives, NP30 (Tyr¹-DAla²-Gly³-Phe⁴-Gly⁵-Trp⁶-O-[3′,5′-Bzl(CF₃)₂]) showed balanced and potent opioid agonist as well as substance P antagonist activities in isolated tissue-based assays, together with significant antinociceptive and antiallodynic activities in vivo.     

Association between TNFRSF11B gene polymorphisms and history of ischemic stroke in Italian diabetic patients

Osteoprotegerin (OPG) is a secretory glycoprotein that belongs to the tumor necrosis factor receptor family and plays a role in atherosclerosis. The present study aimed to evaluate whether OPG gene (TNFRSF11B) polymorphisms are involved in ischemic stroke in an Italian population with diabetes. Participants in a retrospective case–control study included 364 diabetic patients (180 males, 184 females) with history of ischemic stroke and 492 diabetic subjects without history of ischemic stroke (252 males, 240 females). The T245G, T950C, and G1181C polymorphisms of the OPG gene were analyzed by polymerase chain reaction and restriction fragment length polymorphism. We found that the T245G, T950C, and G1181C gene polymorphisms of the OPG gene were significantly (34.1 vs. 9.5 %, P < 0.0001; 30.8 vs. 6.3 %, P < 0.0001 and 26.4 vs. 11.6 % P < 0.0001, respectively) and independently (adjusted OR 5.15 [3.46–7.68], OR 6.63 [4.26–10.31], and OR 3.03 [2.04–4.50], respectively) associated with history of ischemic stroke. We also found that these three polymorphisms act synergistically in patients with stroke history. The TNFRSF11B gene polymorphisms studied are associated with history of ischemic stroke and synergistic effects between these genotypes might be potential markers for cerebrovascular disorders.     

Assaying chromosomal inversions by single-molecule haplotyping

Inversions are an important form of structural variation, but they are difficult to characterize, as their breakpoints often fall within inverted repeats. We have developed a method called 'haplotype fusion' in which an inversion breakpoint is genotyped by performing fusion PCR on single molecules of human genomic DNA. Fusing single-copy sequences bracketing an inversion breakpoint generates orientation-specific PCR products, exemplified by a genotyping assay for the int22 hemophilia A inversion on Xq28. Furthermore, we demonstrated that inversion events with breakpoints embedded within long (>100 kb) inverted repeats can be genotyped by haplotype-fusion PCR followed by bead-based single-molecule haplotyping on repeat-specific markers bracketing the inversion breakpoint. We illustrate this method by genotyping a Yp paracentric inversion sponsored by >300-kb-long inverted repeats. The generality of our methods to survey for, and genotype chromosomal inversions should help our understanding of the contribution of inversions to genomic variation, inherited diseases and cancer.     

Opioid and melanocortin receptors: do they have overlapping pharmacophores?

We have identified compound 1 as a novel ligand for opioid and melanocortin (MC) receptors, which is derived from the overlapping of a well known structure for the delta opioid receptor, 2,6-dimethyltyrosine (Dmt)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic), and a small molecule for the MC receptor, Tic-DPhe(p-Cl)-piperidin-4-yl-N-phenyl-propionamide. Ligand 1 showed that there is an overlapping pharmacophore between opioid and MC receptors through the Tic residue. The ligand displayed high biological activities at the delta opioid receptor (Ki = 0.38 nM in binding assay, EC(50) = 0.48 nM in GTP-gamma-S binding assay, IC(50) = 74 nM in MVD) as an agonist instead of an antagonist and showed selective binding affinity (IC(50) = 2.3 muM) at the MC-3 receptor rather than at the MC-5 receptor. A study of the structure-activity relationships demonstrated that the residues in positions 2, 3, and the C-terminus act as a pharmacophore for the MC receptors, and the residues in positions 1 and 2 act as a pharmacophore for the opioid receptors. Thus, this structural construct can be used to prepare chimeric structures with adjacent or overlapping pharmacophores for opioid and MC receptors.     

Biological properties of Phe(o)-opioid peptide analogues

Biological properties of new analogues, which represent Phe(o)-propeptides of a variety of opioid peptides, are described. All Phe(o)-opioid analogues expressed both receptor binding affinities and in vitro biological activities at least at the level of the primary opioid peptides. Surprisingly, some of the propeptides expressed slightly higher activity than the primary opioid peptides. Nevertheless, no significant shift in receptor selectivity was observed, which indicate that these Phe(o)-analogues undoubtedly are propeptides. The possible role of membrane proteolytic enzymes associated with opioid receptors in transformation of propeptides is discussed.     

Antinociceptive and nociceptive actions of opioids

Although the opioids are the principal treatment options for moderate to severe pain, their use is also associated with the development of tolerance, defined as the progressive need for higher doses to achieve a constant analgesic effect. The mechanisms which underlie this phenomenon remain unclear. Recent studies revealed that cholecystokinin (CCK) is upregulated in the rostral ventromedial medulla (RVM) during persistent opioid exposure. CCK is both antiopioid and pronociceptive, and activates descending pain facilitation mechanisms from the RVM enhancing nociceptive transmission at the spinal cord and promoting hyperalgesia. The neuroplastic changes elicited by opioid exposure reflect adaptive changes to promote increased pain transmission and consequent diminished antinociception (i.e., tolerance).     

Multiple actions of systemic artemin in experimental neuropathy

The clinical management of neuropathic pain is particularly challenging. Current therapies for neuropathic pain modulate nerve impulse propagation or synaptic transmission; these therapies are of limited benefit and have undesirable side effects. Injuries to peripheral nerves result in a host of pathophysiological changes associated with the sustained expression of abnormal pain. Here we show that systemic, intermittent administration of artemin produces dose- and time-related reversal of nerve injury-induced pain behavior, together with partial to complete normalization of multiple morphological and neurochemical features of the injury state. These effects of artemin were sustained for at least 28 days. Higher doses of artemin than those completely reversing experimental neuropathic pain did not elicit sensory or motor abnormalities. Our results indicate that the behavioral symptoms of neuropathic pain states can be treated successfully, and that partial to complete reversal of associated morphological and neurochemical changes is achievable with artemin.