The role of brain peptides in neuroimmunomodulation

The emergence of melatonin in oncology: Focus on colorectal cancer

Within the last few decades, melatonin has increasingly emerged in clinical oncology as a naturally occurring bioactive molecule with substantial anticancer properties and a pharmacological profile optimal for joining the currently available pharmacopeia. In addition, extensive experimental data shows that this chronobiotic agent exerts oncostatic effects throughout all stages of tumor growth, from initial cell transformation to mitigation of malignant progression and metastasis; additionally, melatonin alleviates the side effects and improves the welfare of radio/chemotherapy-treated patients. Thus, the support of clinicians and oncologists for the use of melatonin in both the treatment and proactive prevention of cancer is gaining strength. Because of its epidemiological importance and symptomatic debut in advanced stages of difficult clinical management, colorectal cancer (CRC) is a preferential target for testing new therapies. In this regard, the development of effective forms of clinical intervention for the improvement of CRC outcome, specifically metastatic CRC, is urgent. At the same time, the need to reduce the costs of conventional anti-CRC therapy results is also imperative. In light of this status quo, the therapeutic potential of melatonin, and the direct and indirect critical processes of CRC malignancy it modulates, have aroused much interest. To illuminate the imminent future on CRC research, we focused our attention on the molecular mechanisms underlying the multiple oncostatic actions displayed by melatonin in the onset and evolution of CRC and summarized epidemiological evidence, as well as in vitro, in vivo and clinical findings that support the broadly protective potential demonstrated by melatonin.

Neuroendocrine Effects of Subcutaneous Interleukin-2 Injection in Cancer Patients

Intravenous interleukin-2 (IL-2) administration has been shown to influence several hormonal secretions. The present study was carried out to investigate the endocrine effects of subcutaneous therapy with IL-2. Six patients with advanced renal cancer were studied. They were treated subcutaneously with IL-2 according to the schedule proposed by Atzpodien et al. Venous blood samples were collected at O-time and 1, 8 and 12 hours after the first IL-2 pulse of 9 × 106 IU/m2 at 8.00 a.m.; on a separate occasion, samples were collected during a saline infusion only. In each blood sample, serum levels of Cortisol, β-endorphin, GH, PRL, FSH, LH, TSH and the pineal hormone melatonin were measured by RIA. Both Cortisol and β-endorphin significantly increased after IL-2 injection. GH rose but not to a significant extent. PRL, FSH, LH and TSH did not change after IL-2. Finally, melatonin levels markedly decreased after IL-2 injection in the only 2 patients with elevated concentrations of this hormone before the start of immunotherapy. These results suggest that the endocrine effects of subcutaneous IL-2 therapy are similar to those previously described with intravenous administration.

Differential action of two prolactin isoforms on ischemia and re-perfusion-induced arrhythmias in rats in vivo

BACKGROUND

The different influences of one of the PRL isoforms (PRL I) on the cardiovascular system have been described in the past.

AIM

Our goal was to establish an appropriate iv dose of 2 PRL isoforms (PRL I and PRL II) in intact rats. After establishing this dose, PRL I (0.01 mg/kg) or PRL II (0.001 mg/kg) was administered in bolus 10 min before left anterior descending coronary artery occlusion (7 min) followed by re-perfusion (15 min). We then aimed to study and compare the effects of these isoforms on ischemia- and re-perfusion-induced arrhythmias in the ischemia and re-perfusion-induced arrhythmias model in rats.

MATERIALS AND METHODS

Mortality index, ventricular fibrillation and tachycardia (VF, VT) incidence and duration, systolic, diastolic, and mean arterial blood pressure, heart rate and myocardial index of oxygen consumption [pressure rate product (PRP)] were measured and calculated.

RESULTS

Both PRL isoforms reduced animal mortality (from 50 to 18.75 and 25%, respectively). PRL II significantly reduced VF incidence (to 25%) as well as VT duration (18.21 ± 3.09) and these effects were markedly different from PRL I and from the control group (p<0.05). Both PRL reduced PRP in the recovery phase (p<0.05).

CONCLUSIONS

We proved that supraphysiological doses of PRL isoforms administered in bolus could protect against sudden cardiac death as well as severe arrhythmias episodes during re-perfusion. Because of PRL's positive influence on the cardiovascular system and as an endogenous, well-tolerated substance, it might be of potential clinical use.

Classical conditioning: The new hegemony

Converging data from different disciplines are showing the role of classical conditioning processes in the elaboration of human and animal behavior to be larger than previously supposed. Restricted views of classically conditioned responses as merely secretory, reflexive, or emotional are giving way to a broader conception that includes problem-solving, and other rule-governed behavior thought to be the exclusive province of either operant conditiońing or cognitive psychology. These new views have been accompanied by changes in the way conditioning is conducted and evaluated. Data from a number of seemingly unrelated phenomena such as relapse to drug abuse by postaddicts, the placebo effect, and the immune response appear to involve classical conditioning processes. Classical conditioning, moreover, has been found to occur in simpler and simpler organisms and recently even demonstrated in brain slices and in utero. This target article will integrate the several research areas that have used the classical conditioning process as an explanatory model; it will challenge teleological interpretations of the classically conditioned CR and offer some basic principles for testing conditioning in diverse areas.

Hormones and breathing

A number of hormones, including hypothalamic neuropeptides acting as neurotransmitters and neuromodulators in the CNS, are involved in the physiologic regulation of breathing and participate in adjustment of breathing in disease. In addition to central effects, some hormones also control breathing at peripheral chemoreceptors or have local effects on the lungs and airways. Estrogen and progesterone seem to protect from sleep-disordered breathing, whereas testosterone may predispose to it. Progesterone and thyroxine have long been known to stimulate respiration. More recently, several hormones such as corticotropin-releasing hormone and leptin have been suggested to act as respiratory stimulants. Somatostatin, dopamine, and neuropeptide Y have a depressing effect on breathing. Animal models and experimental human studies suggest that also many other hormones may be involved in respiratory control.

Suppression of in vitro antibody production by corticotropin-releasing factor neurohormone

Corticotropin-releasing factor (CRF) is a peptide hormone that regulates the synthesis of pro-opiomelanocortin (POMC)-derived bioactive peptides from the cells of both neuroendocrine system and immune system. In this study, the effect of CRF on in vitro production of antibodies was investigated. The peripheral blood mononuclear cells (MNC), at a concentration of 1 x 10(6) cells ml-1, from several healthy blood donors were stimulated to produce immunoglobulins with 25 micrograms ml-1 pokeweed mitogen (PWM) in the presence of different concentrations of CRF (10(-16) to 10(-7) M range). After 7 days of incubation, the cell cultures were centrifuged, and the supernatants quantified for IgG, IgM, and IgA by enzyme-linked immunosorbent assay (ELISA). At concentrations of 10(-13) M or greater, the CRF and three structurally related peptides (Tyr-CRF, alpha-helical CRF9-41, and sauvagine) caused a statistically significant (P < 0.001) suppression of the production of all three isotypes of Ig. At a antagonist: agonist ratio of as high as 100:1, the antagonist alpha-helical CRF9-41 did not antagonize the inhibitory action of CRF, instead it showed synergism with CRF by accentuating the CRF-induced suppression of IgG synthesis. This unexpected result may be due to the involvement of a subtype of CRF receptor which is insensitive to alpha-helical CRF. Moreover, the production of all three Ig isotypes was suppressed by rabbit antihuman-interleukin-1 (anti-IL-1) or rabbit antihuman-beta-endorphin (anti-beta E) or monocyte-depletion, but neither treatment significantly modified the CRF-induced suppression of antibody production.(ABSTRACT TRUNCATED AT 250 WORDS)

Locus ceruleus and immunity. III. Compromised immune function (antibody production, hypersensitivity skin reactions and experimental allergic encephalomyelitis) in rats with lesioned locus ceruleus is restored by magnetic fields applied to the brain

This study deals with the relationship between the immunosuppression induced by electrolytic lesions placed into the nucleus locus cerules and the immunopotentiation produced by micromagnets implanted to the parietal area of the skull. The following groups of rats were set up: LC, rats with lesioned locus ceruleus; ShL, sham-lesioned animals bearing non-magnetic beads in the brain parietal region; M, rats with micromagnets of 60 mT influx density in the parietal part of the skull; LCM, animals with impaired locus ceruleus and magnetic beads placed in the parietal area of the skull; and IC, intact control rats. Animals of all groups were tested for plaque-forming cell response, circulating antibodies to sheep red blood cells and bovine serum albumin, Arthus and delayed hypersensitivity skin reactions to bovine serum albumin and old tuberculin, and experimental allergic encephalomyelitis. In LC-rats, humoral and cell-mediated immune reactions were compromised. On the other hand, immune responses in M-rats were significantly potentiated. In LCM-rats, however, the immunosuppression induced by destruction of the locus ceruleus was abrogated by prolonged exposure of the brain parietal region to the magnetic fields, i.e. immune reactivity of LCM-rats was quite similar to that of control IC- and ShL-animals. Several mechanisms may account for the immunomodulating effects produced by lesioning of the locus ceruleus and exposure of the brain to magnetic fields. Noradrenergic, serotoninergic, dopaminergic and peptidergic neurotransmitters, as well as growth hormones and immunopeptides, produced within the central nervous system or elsewhere, may be implicated as necessary for the interactions among the brain, immune apparatus and magnetic fields.

Neuroimmunotherapy with subcutaneous low-dose interleukin-2 and the pineal hormone melatonin as a second-line treatment in metastatic colorectal carcinoma

On the basis of our previous preliminary data which showed that the pineal hormone melatonin (MLT) may potentiate IL-2 activity and reduce the dose of IL-2 required to determine an effective host antitumor response, we performed a clinical study with low-dose IL-2 given once/day subcutaneously (3 million IU/day for 6 days/week for 4 weeks) in association with MLT (50 mg/day orally at 8.00 p.m. every day) as a second-line therapy in metastatic colorectal cancer patients pretreated with 5-fluorouracil. Evaluable patients were 13/14, and most of them showed disseminated liver metastases. No objective tumor regression was seen. A stabilization of disease was achieved in 4/13 patients (median duration 5+ months), and the other 9 patients progressed. Mean number of lymphocytes and eosinophils significantly increased during the treatment. Moreover, the mean increase in lymphocyte number was significantly higher in patients with stable disease than in those with progressive disease, whereas there was no difference as regards eosinophils. Serum levels of neopterin and tumor necrosis factor (TNF) significantly increased during therapy, and TNF increase was correlated to the side effects rather than to the control of cancer development. This study shows that neuroimmunotherapy with low-dose interleukin-2 and MLT, even though capable of determining an evident expansion of immune cells involved in host antitumor response, does not seem to be effective in terms of tumor regression in metastatic colon cancer patients pretreated with 5-fluorouracil.

Cachectin alters anterior pituitary hormone release by a direct action in vitro

Cachectin (tumor necrosis factor) is a powerful macrophage hormone released during infection, which circulates in blood to produce diverse effects in the organism. We examined the effect of cachectin on release of anterior pituitary hormones from either hemipituitaries or dispersed pituitary cells incubated in vitro. The action of cachectin on dispersed cells was demonstrable only after 2 hr of incubation. With this incubation time, the protein produced a dose-related stimulation of release of adrenocorticotropin (ACTH), growth hormone (GH), and thyrotropin (TSH), but not of prolactin (Prl), from both hemipituitaries and dispersed cells. The doses required for stimulation were low in the case of hemipituitaries, usually of the order of 10(-12) M, whereas they were higher by one or two orders of magnitude with the dispersed pituitary cells. This may be related either to loss of receptors for the protein during the dispersion procedure or to the fact that in the hemipituitary system cell interactions are facilitated because the cells are close to each other. In the dispersed cell system cachectin evoked a dose-related decrease in cyclic AMP content. Incubation with somatostatin lowered the cyclic AMP content of the cells and depressed GH output without altering output of TSH or Prl. When somatostatin and cachectin were incubated together with the cells, the suppression of cyclic AMP production was abolished; TSH and Prl release were stimulated, but the action of cachectin to stimulate GH release was blocked. The stimulation of Prl release by cachectin in the presence of somatostatin may be related to the elevation of cyclic AMP, a known stimulator of Prl release. The cyclooxygenase inhibitor indomethacin nearly completely blocked the stimulatory effect of cachectin on release of GH and TSH from dispersed pituitary cells but had only a slight and nonsignificant attenuating effect on its ACTH-releasing action. These results suggest that at least part of the stimulatory action of the peptide on pituitary hormone release is brought about by prostaglandins. The failure of indomethacin to block the release of ACTH induced by cachectin suggests that other mechanisms may be involved in the release of ACTH induced by this peptide. Since the concentrations of cachectin required to stimulate pituitary hormone release are similar to those that are encountered in plasma during infection, it is likely that this direct pituitary action has pathophysiological significance.

Neurophysiological and endocrine consequences of immune activity

The studies presented herein demonstrate the potency with which activity of the immune system is able to influence the central nervous system. Electrophysiological recordings have demonstrated significant changes in preoptic area/anterior hypothalamic (PO/AH) multiunit electrical activity (MUA) following sensitization with sheep red blood cells. The peak of activity occurred on the fifth day after immunization, the same day that serum antibodies were first detected. A significant increase in paraventricular nucleus MUA was also demonstrated, but this appeared to be delayed with respect to that in the PO/AH, occurring on the sixth day. Further changes thought to be associated with the immune response also were found: Serum corticosterone levels were elevated on the eighth day of the response, and PO/AH tissue levels of norepinephrine were reduced between the sixth and tenth days. During induction of a secondary response, PO/AH MUA showed a different profile of activity from that recorded during the first response. Chronic administration of the immunosuppressive drug, cyclophosphamide, prevented the recorded changes in PO/AH MUA. These results suggest that some secretory product(s) of the activated immune system may be able to exert effects on the central nervous system. Various immunoactive substances therefore were administered intra-cerebroventricularly in order to examine their effects upon PO/AH MUA, cortical EEG and adrenocortical hormone secretory activity. alpha-Interferon and thymic humoral factor were both found to decrease PO/AH MUA, increase EEG synchronization, and decrease basal levels of circulating corticosterone. In contrast, histamine and interleukin-1 did not alter PO/AH MUA but did cause decreased EEG synchronization and increased serum corticosterone levels. With another preparation, a specific activating effect of interleukin-1 upon putative corticotropin-releasing factor-secreting neurones has also been found, identified vasopressinergic neurones not being affected.