Melatonin and inflammation-Story of a double-edged blade

Melatonin is an immune modulator that displays both pro- and anti-inflammatory properties. Proinflammatory actions, which are well documented by many studies in isolated cells or leukocyte-derived cell lines, can be assumed to enhance the resistance against pathogens. However, they can be detrimental in autoimmune diseases. Anti-inflammatory actions are of particular medicinal interest, because they are observed in high-grade inflammation such as sepsis, ischemia/reperfusion, and brain injury, and also in low-grade inflammation during aging and in neurodegenerative diseases. The mechanisms contributing to anti-inflammatory effects are manifold and comprise various pathways of secondary signaling. These include numerous antioxidant effects, downregulation of inducible and inhibition of neuronal NO synthases, downregulation of cyclooxygenase-2, inhibition of high-mobility group box-1 signaling and toll-like receptor-4 activation, prevention of inflammasome NLRP3 activation, inhibition of NF-κB activation and upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2). These effects are also reflected by downregulation of proinflammatory and upregulation of anti-inflammatory cytokines. Proinflammatory actions of amyloid-β peptides are reduced by enhancing α-secretase and inhibition of β- and γ-secretases. A particular role in melatonin's actions seems to be associated with the upregulation of sirtuin-1 (SIRT1), which shares various effects known from melatonin and additionally interferes with the signaling by the mechanistic target of rapamycin (mTOR) and Notch, and reduces the expression of the proinflammatory lncRNA-CCL2. The conclusion on a partial mediation by SIRT1 is supported by repeatedly observed inhibitions of melatonin effects by sirtuin inhibitors or knockdown.

Expression of MT2 receptor in patients with gastric adenocarcinoma and its relationship with clinicopathological features

BACKGROUND

Gastric cancer accounts 8% of the total cancer cases and 10% of total cancer deaths worldwide. The indoleamine N-acetyl-5-methoxytryptamine, better known as melatonin, is the principal hormone produced by the pineal gland. Recently, it has shown some anticancer role in some malignancies such as breast and colon cancer; also, some of its protective roles in the GI tract are as free radical scavenger and as antimitogenic and apoptotic agents. Based on the anticancer effects of melatonin and wide distribution of this neurohormone in the GI tract and some proposed physiologic and pharmacologic roles for this neurohormone, this study is initially scheduled to determine the expression of melatonin receptor MT2 in tissue samples of adenocarcinoma cancer patients.

METHODS

For this aim, a total of 30 gastric adenocarcinoma patients and 30 normal individuals were selected and examined for MT2 gene expression by real-time PCR.

RESULTS

Our results have shown interestingly high expression for MT2 receptor in cancer and marginal cancer tissues compared with normal people.

CONCLUSIONS

According to our results, it is concluded that for the first time, the expression of MT2 receptor in gastric adenocarcinoma tissues which was in parallel with breast and colon cancer studies and high expression of this receptor in the marginal tissues indicate refractory mechanism which shows the defending role of melatonin in the GI system. Our experiments has not shown any relationship between MT2 receptor expression and grade and clinicopathological features of gastric tumor, so we cannot conclude any relationship between this receptor expression and progression of the tumor, although this expression can be considered as an etiology.

Inhibition of breast cancer cell invasion by melatonin is mediated through regulation of the p38 mitogen-activated protein kinase signaling pathway

INTRODUCTION

The pineal gland hormone, melatonin, has been shown by numerous studies to inhibit the proliferation of estrogen receptor α (ERα)-positive breast cancer cell lines. Here, we investigated the role of melatonin in the regulation of breast cancer cell invasion.

METHODS

Three invasive MCF-7 breast cancer cell clones - MCF-7/6, MCF-7/Her2.1, and MCF-7/CXCR4 cells - were employed in these studies. All three cell lines exhibited elevated phosphorylation of the ERK1/2 and p38 mitogen-activated protein kinase (MAPK) as determined by Western blot analysis. The effect of melatonin on the invasive potential of these human breast cancer cells was examined by matrigel invasion chamber assays. The expression and proteinase activity of two matrix metalloproteinases (MMPs), MMP-2 and MMP-9, were analyzed by Western blot analysis and gelatin zymography, respectively.

RESULTS

Melatonin (10-9 M) significantly suppressed the invasive potential of MCF-7/6 and MCF-7/Her2.1 cells as measured by matrigel invasion chamber assays, and significantly repressed the proteinase activity of MMP-2 and MMP-9. In MCF-7/CXCR4 cells, melatonin significantly inhibited stromal-derived factor-1 (SDF-1/CXCL12) induced cell invasion and activity of MMP-9. Elevated expression of the MT1 melatonin receptor further enhanced, while luzindole, an MT1/MT2 antagonist, abrogated melatonin's anti-invasive effect, suggesting that melatonin's effect on invasion is mediated, principally, through the MT1 receptor. Furthermore, melatonin repressed the phosphorylation of p38 MAPK in MCF-7/Her2.1 cells and blocked stromal-derived factor-1 (SDF-1) induced p38 phosphorylation in MCF-7/CXCR4 cells. SB230580, a p38 inhibitor, was able to mimic, while transfection of the cells with a constitutively-active MKK6b construct blocked melatonin's effect on cell invasion, suggesting that the anti-invasive action of melatonin is mediated through the p38 pathway.

CONCLUSIONS

Melatonin exerts an inhibitory effect on breast cancer cell invasion through down-regulation of the p38 pathway, and inhibition of MMP-2 and MMP-9 expression and activity.

Oncology in neuroimmunomodulation. What progress has been made?

In 1987 in Dubrovnik, Yugoslavia, N.H. Spector named a new discipline: Neuroimmunomodulation. R. Ader called this new discipline psychoneuroimmunomodulation when the major emphysis was on its behavioral aspects. Neuroimmunomodulation (NIM) is devoted to the study of the interactions at different morphologic and functional levels among the immune, nervous, and endocrine systems. In fact, this science is the modern manifestation of an old science: in the words of B.D. Jankovic (1987), "Neuroimmunomodulation is a modern reflection in neurosciences and immunosciences of the ideas and experience of philosophers and ingenious observers of ancient Egypt, Greece, China, India, and other civilizations that the mind is involved in the defense against diseases." Twelve years ago NIM was regarded by many conventional scientists almost as a form of witchcraft. Today it may be the fastest growing area of biomedical science research in the world. Important clinical applications will not be far behind. NIM research has also progressed in the field of oncology research. Topics such as treatment of hormone-dependent cancer with analogues of hypothalamic hormones, the role of opioids and T cells in cancer, stress-cancer-immune connections, the anticancer role of melatonin and cytokines, immunotherapy of cancer, and the role of psychotherapy in cancer patients represent some lines of research that have been or are being investigated by scientists. Some areas remain to be thoroughly investigated such as the influence of physical exercise (sports), music (classical or modern), and/or relaxation techniques (e.g. yoga) on the development of human cancer. This paper reviews the role of NIM in oncology and provides some perspectives for further research and development of clinical applications.

The role of brain-immune interactions in immunotoxicology

Certain xenobiotics (or the metabolites) can damage immunocompetence by directly interacting with one or more of the cells of the immune system and adversely affecting its function. It has also been proposed that xenobiotics may indirectly affect immune function by affecting other organ systems that will in turn affect immunocompetence. This review surveys evidence that supports the existence of a functional link between the brain and the immune system. In addition, we review data that support the concept that a xenobiotic-induced dysfunction in the neuroendocrine system may be associated with an immune dysfunction as well. Such chemicals do not necessarily interact directly with immunocompetent cells but would instead act to disrupt regulatory brain-immune interactions. This class of indirectly acting immunotoxic xenobiotics would not be detected in the typical in vitro screening assays.