Two pools of beta-endorphin-like immunoreactivity in blood: plasma and erythrocytes

Increased concentration of beta-endorphin in sera of patients with psoriasis and other inflammatory dermatoses

Serum beta-endorphin was quantified by radioimmunoassay in 71 patients with psoriasis vulgaris, other chronic inflammatory skin diseases with T-cell infiltrates [atopic dermatitis (n = 25), and systemic sclerosis (n = 34)], and 100 healthy subjects. The neuropeptide was found to be markedly (P < 0.001) increased in patients with psoriasis (14.4 pg/ml), atopic dermatitis (9.2 pg/ml) and systemic sclerosis (9.8 pg/ml) compared with normal controls (6.1 pg/ml). The highest values of beta-endorphin were found in patients with actively spreading plaque psoriasis (17.3 pg/ml), whereas lesion-free patients showed a reduction in neuropeptide concentration (10.2 pg/ml). The levels were much higher in patients with widespread psoriatic lesions (> 60% body surface; 16.2 pg/ml), which lasted longer than 3 months (15.8 pg/ml), whereas neither the presence of stress nor itching correlated with the serum peptide concentration. Our data suggest that beta-endorphin is produced in psoriatic lesions by inflammatory cells, rather than the increased levels being the result of activation of the pituitary-adrenal axis by chronic stress. The generation of neuropeptide in psoriatic lesions and its antinociceptive effect on the peripheral sensory nerves might explain why pruritus is a relatively rare phenomenon in psoriasis.

Uptake of peptides containing Tyr-Pro by human and mouse erythrocytes

Red blood cells (RBCs) harvested from mice were used to investigate the possible existence of an uptake system for peptides in these cells. The radioactively iodinated tetrapeptide Tyr-MIF-1 (Tyr-Pro-Leu-Gly-amide) was incubated with RBCs for varying lengths of time with or without inhibitors. The RBCs showed saturable uptake that could be inhibited by Tyr-Pro containing peptides. Uptake was also found in human RBCs, but was more robust in the mouse. Uptake by mouse RBCs was temperature dependent and magnesium sensitive but did not require sodium, potassium, or glucose. With the exception of some enkephalin- and dynorphin-related peptides that partially inhibited uptake, most substances tested were without effect. The results of HPLC showed internalization of the N-Tyr-Pro containing peptides, with accumulation of degradation products over time. The degradation products, however, did not inhibit transport, suggesting that peptides were transported intact into the RBCs with degradation occurring after internalization. This suggestion was strengthened by the finding that only the cytosol of the RBC, not its membranes, rapidly degraded Tyr-MIF-1 to free iodine and iodotyrosine. Nevertheless, the cytosol contained a large amount of immunoreactive material that eluted at the position of intact Tyr-MIF-1 on HPLC. These findings show that RBCs can take up, store, and degrade Tyr-Pro containing peptides.

Opioid peptides modulate immune functions. A review

In the past few years it has become evident that neuropeptides may be direct mediators in the modulation of the immune response and the unspecific defense by the brain. Lymphocytes have been thought to have opioid receptors and to respond to opioids with an increase in blastogenesis, cytotoxicity and factor release. Lymphocytes are said to release various neuropeptides. Furthermore, there are some unexplained effects of morphine on the immune system and of the immune system on morphine withdrawal. The purpose of this paper is to review what has been previously published in this field. The well established modulation of phagocyte functions by opioids will only be scanned.

Stabilization of methionine-enkephalin in human and rat blood

Methods of preventing the degradation of 3H-methionine-enkephalin (3H-ME) in human blood both at 37 degrees C and under conditions of immediate cooling were examined. We found that, contrary to previous suggestions, use of aprotinin (with or without immediate cooling) was ineffective in preventing the degradation of 3H-ME in blood. Thus, previous reports on the circulating levels of ME which relied on such procedures to stabilize the ME may have reported artifactually low values. However, we found that citric acid effectively prevents 3H-ME breakdown in both human and rat blood. Thus, we propose the use of citric acid, mixed with blood immediately upon collection, as an effective method for the stabilization of ME in blood.

Plasma and red blood cell beta-endorphin immunoreactivity in normal and complicated pregnancies: gestational age variation

Recent observations suggest that there may be two pools of beta-endorphin-like immunoreactivity in mammalian circulation. One of these pools is present in plasma and the other is detected in association with erythrocytes. Elucidation of an erythrocyte-associated pool may explain some of the wide variability of plasma beta-endorphin levels reported in the literature. We measured beta-endorphin immunoreactivity levels in 85 normal and 33 complicated pregnancies to delineate a possible correlation between gestational age and beta-endorphin immunoreactivity levels in plasma and in erythrocytes. Our results indicate that beta-endorphin immunoreactivity levels in both plasma and erythrocytes vary systematically throughout the gestational period, reaching a peak at 31 to 32 weeks of gestation. Amniotic fluids at midgestation were also analyzed and no correlation was observed between the levels of beta-endorphin immunoreactivity and fetal sex. Compared to normal patients, diabetic patients had significantly lower levels of beta-endorphin immunoreactivity in plasma and higher levels in erythrocytes although the total beta-endorphin immunoreactivity was not statistically different from that in normal subjects. We conclude that (1) the total beta-endorphin immunoreactivity level in whole blood is much higher than that reported in plasma, (2) both plasma- and erythrocyte-associated beta-endorphin immunoreactivity levels vary with gestational age, with a peak level at 24 to 32 weeks of gestation, (3) amniotic fluid beta-endorphin immunoreactivity levels are unrelated to fetal sex, and (4) diabetic patients may have a different distribution of beta-endorphin immunoreactivity pools than normal individuals.