Effect of melatonin and pineal extracts on human ovarian and mammary tumor cells in a chemosensitivity assay.

Pinealectomy enhances tumor growth and metastatic spread in experimental animals. This effect is only in part due to melatonin since melatonin-free pineal extracts containing yet unidentified pineal substances have also shown tumor inhibiting activity. Despite numerous reports suggesting melatonin as a potential anti-cancer agent there have not been sufficient clinical trials to define the actual therapeutic potential of melatonin for the treatment of human cancers. To help fill this gap, we used a chemosensitivity assay designed to test the sensitivity of tumors from individual patients towards chemotherapeutic drugs for assessing the effect of melatonin and pineal extracts on primary human tumor cells. Primary cell cultures from seven ovarian and six mammary tumors were incubated with melatonin, the pineal extract YC05R (containing substances between 500 and 1000 daltons) and chemotherapeutic drugs. The pineal extract YC05R inhibited growth of all tumors in a dose-dependent manner. Physiological concentrations of melatonin (10(-8)-10(-10) M) inhibited the growth of one out of six mammary carcinomas in a dose-dependent manner. Primary cell cultures from three ovarian tumors were affected by melatonin in different ways, i.e., two were inhibited and one was slightly stimulated. There was no correlation between sensitivity towards melatonin and sex steroid receptor status, stage or grade of the tumor. It is concluded that, 1), melatonin may be an inhibitor of human mammary and ovarian carcinoma in individual cases and, 2), the pineal gland contains very active anti-tumor substances inhibiting both, the mammary and ovarian tumors, tested. These substances require chemical and biological identification.

Hormonal factors from the mammalian pineal gland interfere with cell development in Hydra.

A partially purified, melatonin-free low-molecular-weight extract from the ovine pineal gland with antitumor activity (YC05R), interferes with terminal differentiation in the interstitial cell line of Hydra. Nematoblasts developed into defective nematocytes that were subject to cell death and the tentacles eventually became devoid of nematocytes. In an attempt to identify the causative components of the extract, several known potential constituents were assayed. Two factors were found to have similar effects, although only in rather high concentrations: 1alpha, 25 dihydroxyvitamin D3 (>150 nM) and pinoline (>5 microM), a natural tryptophan-derived beta-carboline. The proliferative activity in the interstitial cell line was only slightly reduced by these factors. Two other beta-carbolines that occur in the mammalian brain, harmine (10 microM) and n-butyl-beta-carboline-3-carboxylate (beta-CCB), caused the premature death of epithelial cells and thus the development of dwarfish animals which, however, continued to generate new animals by budding. The pineal extract probably contains some more, still unidentified components that interfere more potently with cell development, in Hydra as well as in mammals.

Low-molecular-weight hormonal factors that affect head formation in Hydra.

Support or inhibition of DAG-induced head formation: Hydra magnipapillata can be caused to form ectopic head structures by periodictreatmentwith PKC activators such as diacylglycerol (DAG). This ectopic head formation is supported by an extract from the ovine pineal gland that contains low-molecular-weight compounds. The frequency of ectopic head formation is also increased when DAG is paired with one of several lipophilic hormonal factors: (1) pinoline, a putative pineal hormone derived from tryptophan, (2) 12-S-HETE, a paracrine derivative of arachidonic acid, or (3) 1alpha, 25 dihydroxyvitamine D3, a hormonal factor also known as calcitriol. Dose-response curves were non-monotonic passing a maximum at low dosages. By contrast, DAG lost its capacity to induce ectopic head structures when it was paired with the provitamin D3, cholecalciferol. Patterning the head: one eicosanoid was found which influences patterning without being combined with DAG: 12-R-HETE caused growth-based elongation of the tentacles and an increase in the number of tentacles without affecting the longitudinal body pattern. Similar effects are brought about by substances that interfere with tyrosine phosphorylation, most potently bythe phosphotyrosine phosphatase inhibitor bisperoxo-(1,10-phenanthroline)-oxovanadate (V). The results speak for the existence of head-inducing hormonal factors, underline the significance of content protein kinases to pattern formation and point to a negative influence of the vitamin D3 content of the food on the capacity of the animals to develop head structures.

Conformational analysis of neuropeptide Y-[18-36] analogs in hydrophobic environments.

The interactive and conformational behavior of a series of neuropeptide Y-[18-36] (NPY-[18-36]) analogs in hydrophobic environments have been investigated using reversed-phase high-performance liquid chromatography (RP-HPLC) and circular dichroism (CD) spectroscopy. The peptides studied comprised a series of 16 analogs of NPY-[18-36], each containing a single D-amino acid substitution. The influence of these single L-->D substitutions on the alpha-helical conformation of the NPY-[18-36] analogs in different solvent environments was determined by CD spectroscopy. Retention parameters related to the hydrophobic contact area and the affinity of interaction were determined with an n-octadecyl (C18) adsorbent. Structural transitions for all peptides were manifested as significant changes in the hydrophobic binding domain and surface affinity between 4 degrees C and 37 degrees C. The results indicated that the central region of NPY-[18-36] (residues 23-33) is important for maintenance of the alpha-helical conformation. Moreover, L-->D amino acid residue substitutions within the N- and C-terminal regions, as well as Asn29 and Leu30, do not appear to affect the secondary structure of the peptide. These studies demonstrate that RP-HPLC provides a powerful adjunct for investigations into the induction of stabilized secondary structure in peptides upon their interaction with hydrophobic surfaces.