NMB: a human neuroblastoma cell line with specific opiate binding sites

Alteration of Opioid Peptide Circadian Rhythm in Cancer Patients

Endogenous opioid peptides have been seen to play a role in regulating immunity and tumor growth. This study was carried out to investigate opioid activity in human cancer. We evaluated by radioimmunoassay β-endorphin plasma levels on blood samples collected at 9.00 a.m. from 121 cancer patients and 42 healthy subjects. In 22 cancer patients and in 12 controls, β-endorphin circadian rhythm was also investigated. Finally, in 14 cancer patients and in 10 controls GH, PRL, FSH, LH and Cortisol serum levels were measured after the administration of a metenkephalin analogue, FK 33–824 (0.3 mg i.v.). No significant differences were seen in β-endorphin mean levels between cancer patients and normal subjects. Moreover, no differences were found between patients with or without metastases, nor between those with or without chronic pain. β-Endorphin circadian rhythm appeared to be altered in 16/22 cancer patients, and anomalous hormonal responses to FK 33–824 were seen in 13/14 patients. This study shows an altered opioid activity in human neoplasms, whose clinical significance remains to be determined.

Aggregation of the protein TRIOBP-1 and its potential relevance to schizophrenia

We have previously proposed that specific proteins may form insoluble aggregates as a response to an illness-specific proteostatic dysbalance in a subset of brains from individuals with mental illness, as is the case for other chronic brain conditions. So far, established risk factors DISC1 and dysbindin were seen to specifically aggregate in a subset of such patients, as was a novel schizophrenia-related protein, CRMP1, identified through a condition-specific epitope discovery approach. In this process, antibodies are raised against the pooled insoluble protein fractions (aggregomes) of post mortem brain samples from schizophrenia patients, followed by epitope identification and confirmation using additional techniques. Pursuing this epitope discovery paradigm further, we reveal TRIO binding protein (TRIOBP) to be a major substrate of a monoclonal antibody with a high specificity to brain aggregomes from patients with chronic mental illness. TRIOBP is a gene previously associated with deafness which encodes for several distinct protein species, each involved in actin cytoskeletal dynamics. The 3′ splice variant TRIOBP-1 is found to be the antibody substrate and has a high aggregation propensity when over-expressed in neuroblastoma cells, while the major 5′ splice variant, TRIOBP-4, does not. Endogenous TRIOBP-1 can also spontaneously aggregate, doing so to a greater extent in cell cultures which are post-mitotic, consistent with aggregated TRIOBP-1 being able to accumulate in the differentiated neurons of the brain. Finally, upon expression in Neuroscreen-1 cells, aggregated TRIOBP-1 affects cell morphology, indicating that TRIOBP-1 aggregates may directly affect cell development, as opposed to simply being a by-product of other processes involved in major mental illness. While further experiments in clinical samples are required to clarify their relevance to chronic mental illness in the general population, TRIOBP-1 aggregates are thus implicated for the first time as a biological element of the neuropathology of a subset of chronic mental illness.

Opioid receptor expression in human brain and peripheral tissues using absolute quantitative real-time RT-PCR

BACKGROUND

The actions of endogenous opioid peptides are mediated by 3 main classes of opioid receptors; mu (MOR), kappa (KOR), and delta (DOR).

METHODS

We developed an absolute quantitative real-time reverse transcriptase PCR (AQ-rt-RT-PCR) assay to quantify MOR, DOR, and KOR mRNA in 22 human tissues.

RESULTS

MOR mRNA was greatly enriched (12-20×10(6)copies/μg) in the cerebellum, nucleus accumbens, and caudate nucleus; moderate (6×10(6)copies/μg) in the dorsal root ganglion, spinal cord, and adrenal gland; low (2×10(4)copies/μg) in the pancreas and small intestine; and absent in the lung, spleen, kidney, heart, skeletal muscle, liver, and thymus. High levels (>8.8×10(6)copies/μg) of DOR mRNA were expressed in the brain and dorsal root ganglion; moderate (1.5×10(6)copies/μg) in the adrenal gland and pancreas; low (2×10(4)-6.5×10(5)copies/μg in the cerebellum, spinal cord, small intestine, skeletal muscle, thymus, lung, and kidney); and very low (3.8×10(3)copies/μg) in the heart. DOR mRNA was not detected in the spleen or liver. KOR mRNA was moderate (1×10(6)copies/μg) in brain regions and dorsal root ganglion, but low (1.6-7×10(5)copies/μg) in the cerebellum, temporal lobe and all other peripheral tissues.

CONCLUSIONS

Our data demonstrate that the AQ-rt-RT-PCR is a highly reproducible and precise method to study the expression of opioid receptors in various tissues and under different disease conditions.

Uptake of radiolabeled morphiceptin and its analogs by experimental mammary adenocarcinoma: in vitro and in vivo studies

Morphiceptin (Tyr-Pro-Phe-Pro-NH(2)) and its analogs modified at position 3: [D-Phe(3)]morphiceptin, [D-ClPhe(3)]morphiceptin and [D-Cl(2)Phe(3)]morphiceptin were synthesized and labeled with [(125)I] or [(131)I]. Their binding to membranes isolated from experimental adenocarcinoma was examined in vitro with the use of a cross-linking assay followed by the Western blot technique. The radioactive complex had molecular weight of about 65 kDa and was detectable by anti-mu-opioid receptor polyclonal antibody. Expression of the mu-opioid receptor in mouse mammary adenocarcinoma was confirmed by reverse transcriptase-polymerase chain reaction. The binding studies showed the highest affinity and capacity for [D-Phe(3)]morphiceptin (K(d) 0.39 and B(max) 1112) and [D-ClPhe(3)]morphiceptin (K(d) 1.8 and B(max) 220). Morphiceptin and its D-Cl(2)Phe analog had significantly lower B(max) values (131 and 83, respectively). Biodistribution experiments in tumor-bearing C3H/Bi mice with the use of the (131)I-labeled peptides confirmed the results of our in vitro studies. The highest accumulation of radioactive peptides in the tumor tissue was also found for peptides with D-Phe and D-ClPhe.

Synthesis of novel morphiceptin analogues modified in position 3 and their binding to mu-opioid receptors in experimental mammary adenocarcinoma

Binding of the (125)I-labeled mu-opioid receptor selective ligands, morphiceptin (Tyr-Pro-Phe-Pro-NH(2)) and [D-Phe(3)]morphiceptin, to membranes isolated from experimental mouse mammary adenocarcinoma was examined in vitro using a cross-linking assay followed by a Western blot technique. The radioactive complex had a molecular weight of about 65 kDa and was detectable by anti-mu-opioid receptor antibody, indicating the presence of mu-opioid receptors in tumor membranes. A series of new morphiceptin analogues, modified at the pharmacophoric position 3, was synthesized in order to find the correlation between the lipophilicity, electronic and steric properties of the amino acid in this position and the in vitro affinity of new analogues for mu-opioid receptors on mouse brain and tumor membranes. In in vivo studies the uptake of (131)I-labeled analogues by experimental mammary adenocarcinoma was estimated. The highest affinity for mu-opioid receptors in both, in vitro and in vivo experiments was observed for [D-Phe(3)]morphiceptin and [D-ClPhe(3)]-morphiceptin.

SK-N-BE: a human neuroblastoma cell line containing two subtypes of delta-opioid receptors

A human neuroblastoma cell line, SK-N-BE, was shown to express a substantial amount of opioid receptors (200-300 fmol/mg of protein). A ligand binding profile of these receptors revealed that they could belong to two distinct subtypes of delta-opioid receptors. Results from sucrose-gradient sedimentation experiments were compared with similar data obtained with the mu-opioid receptor of the rabbit cerebellum and the delta-opioid receptor of the hybrid NG108-15 cell line and have shown that the opioid receptor of the SK-N-BE cell line behaved hydrodynamically as an intermediate between mu- and delta-opioid receptors. Taken together, pharmacological and hydrodynamic studies suggest that the opioid receptors present in the SK-N-BE cell membranes could belong to two delta-opioid receptor subtypes interacting allosterically. Functional experiments suggest that at least one of these subtypes of delta-opioid receptor is negatively coupled to the adenylate cyclase via a Gi protein and that the opiate receptors of the SK-N-BE neuroblastoma cell line undergo a rapid down-regulation when preincubated in the presence of the high-affinity opioid, etorphine.

Evidence for mu-, delta-, and kappa-opioid receptors in a human neuroblastoma cell line

Human neuroblastoma cells were tested for the presence of opioid receptors. [3H]Diprenorphine binds to NMB cell membranes with a KD value of 0.46 +/- 0.13 nM and Bmax of 534 +/- 22 fmol/mg protein. The presence of mu, delta, and kappa opioid receptors was tested by displacing [3H]diprenorphine specific binding by the selective agonists DAMGO, DPDPE, and U50,488H, respectively. Using this procedure, the data suggest that the NMB neuroblastoma cells express the three opioid receptor types with the abundance of delta receptors (about 60%) and minor, yet substantial populations of mu and kappa receptors (about 20% each).

Opioid receptors in human neuroblastoma SH-SY5Y cells: evidence for distinct morphine (mu) and enkephalin (delta) binding sites

Human neuroblastoma SH-SY5Y cells exhibited a heterogeneous population of mu and delta types of opioid binding sites. These specific binding sites displayed the characteristic saturability, stereospecificity and reversibility, expected of a receptor. Scatchard analysis of [3H]-D-Ala2-D-Leu5-enkephalin (DADLE) in the presence of 10(-5) M D-Pro4-morphiceptin (to block the mu receptors) and the competitive displacement by various highly selective ligands yielded the binding parameters of delta sites which closely resemble those of the delta receptors in brain and mouse neuroblastoma clones. Similarly, the high affinity binding of [3H]-dihydromorphine, together with the higher potency of morphine analogues to displace [3H]-naloxone binding established the presence of mu sites. Guanine nucleotides and NaCl significantly inhibited the association and increased the dissociation of [3H]-DADLE binding. The observed heterogeneity of opioid receptors in cultured SH-SY5Y cells would serve as an excellent model for the biochemical and pharmacological characterization of brain opiate receptors.