Melatonin affects voltage-dependent calcium and potassium currents in MCF-7 cell line cultured either in growth or differentiation medium

Melatonin alters the excitability of mouse cerebellar granule neurons by inhibiting voltage-gated sodium, potassium, and calcium channels

Besides its role in the circadian rhythm, the pineal gland hormone melatonin (MLT) also possesses antiepileptogenic, antineoplastic, and cardioprotective properties, among others. The dosages necessary to elicit beneficial effects in these diseases often far surpass physiological concentrations. Although even high doses of MLT are considered to be largely harmless to humans, the possible side effects of pharmacological concentrations are so far not well investigated. In the present study, we report that pharmacological doses of MLT (3 mM) strongly altered the electrophysiological characteristics of cultured primary mouse cerebellar granule cells (CGCs). Using whole-cell patch clamp and ratiometric Ca2+ imaging, we observed that pharmacological concentrations of MLT inhibited several types of voltage-gated Na+ , K+ , and Ca2+ channels in CGCs independently of known MLT-receptors, altering the character and pattern of elicited action potentials (APs) significantly, quickly and reversibly. Specifically, MLT reduced AP frequency, afterhyperpolarization, and rheobase, whereas AP amplitude and threshold potential remained unchanged. The altered biophysical profile of the cells could constitute a possible mechanism underlying the proposed beneficial effects of MLT in brain-related disorders, such as epilepsy. On the other hand, it suggests potential adverse effects of pharmacological MLT concentrations on neurons, which should be considered when using MLT as a pharmacological compound.

Calcium acts as a central player in melatonin antitumor activity in sarcoma cells

PURPOSE

Chondrosarcoma and osteosarcoma are the most frequently occurring bone cancers. Although surgery and chemotherapy are currently clinically applied, improved treatment options are urgently needed. Melatonin is known to inhibit cell proliferation in both tumor types. Although the underlying mechanisms are not clear yet, calcium homeostasis has been reported to be a key factor in cancer biology. Here, we set out to investigate whether regulation of calcium by this indolamine may be involved in its antitumor effect.

METHODS

Cell viability was measured using a MTT assay and flow cytometry was used to measure levels of cytosolic calcium, intracellular oxidants, mitochondrial membrane potential and cell cycle progression. Mitochondrial calcium was analyzed by fluorimetry. Cell migration was determined using a scratch wound-healing assay. Western blot analysis was used to assess the expression of proteins related to cell cycle progression, epithelial to mesenchymal transition (EMT), Ac-CoA synthesis and intracellular signaling pathways.

RESULTS

We found that melatonin decreases cytosolic and mitochondrial Ca²⁺ levels, intracellular oxidant levels, mitochondrial function and the expression of the E1 subunit of the pyruvate dehydrogenase complex. These changes were found to be accompanied by decreases in cell proliferation, cell migration and EMT marker expression. The addition of CaCl₂ prevented the changes mentioned above, while co-treatment with the calcium chelator BAPTA enhanced the effects.

CONCLUSIONS

Our data indicate that regulation of calcium homeostasis is a key factor in the inhibition of cell proliferation and migration by melatonin. This effect should be taken into consideration in combined therapies with traditional or new antitumor compounds, since it may circumvent therapy resistance.

Melatonin: Regulation of Biomolecular Condensates in Neurodegenerative Disorders

Biomolecular condensates are membraneless organelles (MLOs) that form dynamic, chemically distinct subcellular compartments organizing macromolecules such as proteins, RNA, and DNA in unicellular prokaryotic bacteria and complex eukaryotic cells. Separated from surrounding environments, MLOs in the nucleoplasm, cytoplasm, and mitochondria assemble by liquid-liquid phase separation (LLPS) into transient, non-static, liquid-like droplets that regulate essential molecular functions. LLPS is primarily controlled by post-translational modifications (PTMs) that fine-tune the balance between attractive and repulsive charge states and/or binding motifs of proteins. Aberrant phase separation due to dysregulated membrane lipid rafts and/or PTMs, as well as the absence of adequate hydrotropic small molecules such as ATP, or the presence of specific RNA proteins can cause pathological protein aggregation in neurodegenerative disorders. Melatonin may exert a dominant influence over phase separation in biomolecular condensates by optimizing membrane and MLO interdependent reactions through stabilizing lipid raft domains, reducing line tension, and maintaining negative membrane curvature and fluidity. As a potent antioxidant, melatonin protects cardiolipin and other membrane lipids from peroxidation cascades, supporting protein trafficking, signaling, ion channel activities, and ATPase functionality during condensate coacervation or dissolution. Melatonin may even control condensate LLPS through PTM and balance mRNA- and RNA-binding protein composition by regulating N6-methyladenosine (m6A) modifications. There is currently a lack of pharmaceuticals targeting neurodegenerative disorders via the regulation of phase separation. The potential of melatonin in the modulation of biomolecular condensate in the attenuation of aberrant condensate aggregation in neurodegenerative disorders is discussed in this review.

Store-Independent Calcium Entry and Related Signaling Pathways in Breast Cancer

Known as a key effector in breast cancer (BC) progression, calcium (Ca²⁺) is tightly regulated to maintain the desired concentration to fine-tune cell functions. Ca²⁺ channels are the main actors among Ca²⁺ transporters that control the intracellular Ca²⁺ concentration in cells. It is well known that the basal Ca²⁺ concentration is regulated by both store-dependent and independent Ca²⁺ channels in BC development and progression. However, most of the literature has reported the role of store-dependent Ca²⁺ entry, and only a few studies are focusing on store-independent Ca²⁺ entry (SICE). In this review, we aim to summarize all findings on SICE in the BC progression field.

Targeting Ion Channels for Cancer Treatment: Current Progress and Future Challenges

Ion channels are key regulators of cancer cell pathophysiology. They contribute to a variety of processes such as maintenance of cellular osmolarity and membrane potential, motility (via interactions with the cytoskeleton), invasion, signal transduction, transcriptional activity and cell cycle progression, leading to tumour progression and metastasis. Ion channels thus represent promising targets for cancer therapy. Ion channels are attractive targets because many of them are expressed at the plasma membrane and a broad range of existing inhibitors are already in clinical use for other indications. However, many of the ion channels identified in cancer cells are also active in healthy normal cells, so there is a risk that certain blockers may have off-target effects on normal physiological function. This review describes recent research advances into ion channel inhibitors as anticancer therapeutics. A growing body of evidence suggests that a range of existing and novel Na⁺, K⁺, Ca²⁺ and Cl^- channel inhibitors may be effective for suppressing cancer cell proliferation, migration and invasion, as well as enhancing apoptosis, leading to suppression of tumour growth and metastasis, either alone or in combination with standard-of-care therapies. The majority of evidence to date is based on preclinical in vitro and in vivo studies, although there are several examples of ion channel-targeting strategies now reaching early phase clinical trials. Given the strong links between ion channel function and regulation of tumour growth, metastasis and chemotherapy resistance, it is likely that further work in this area will facilitate the development of new therapeutic approaches which will reach the clinic in the future.

Melatonin Reduces Excitability in Dorsal Root Ganglia Neurons with Inflection on the Repolarization Phase of the Action Potential

Melatonin is a neurohormone produced and secreted at night by pineal gland. Many effects of melatonin have already been described, for example: Activation of potassium channels in the suprachiasmatic nucleus and inhibition of excitability of a sub-population of neurons of the dorsal root ganglia (DRG). The DRG is described as a structure with several neuronal populations. One classification, based on the repolarizing phase of the action potential (AP), divides DRG neurons into two types: Without (N₀) and with (N_inf) inflection on the repolarization phase of the action potential. We have previously demonstrated that melatonin inhibits excitability in N₀ neurons, and in the present work, we aimed to investigate the melatonin effects on the other neurons (N_inf) of the DRG neuronal population. This investigation was done using sharp microelectrode technique in the current clamp mode. Melatonin (0.01–1000.0 nM) showed inhibitory activity on neuronal excitability, which can be observed by the blockade of the AP and by the increase in rheobase. However, we observed that, while some neurons were sensitive to melatonin effect on excitability (excitability melatonin sensitive—EMS), other neurons were not sensitive to melatonin effect on excitability (excitability melatonin not sensitive—EMNS). Concerning the passive electrophysiological properties of the neurons, melatonin caused a hyperpolarization of the resting membrane potential in both cell types. Regarding the input resistance (R_in), melatonin did not change this parameter in the EMS cells, but increased its values in the EMNS cells. Melatonin also altered several AP parameters in EMS cells, the most conspicuously changed was the (dV/dt)_max of AP depolarization, which is in coherence with melatonin effects on excitability. Otherwise, in EMNS cells, melatonin (0.1–1000.0 nM) induced no alteration of (dV/dt)_max of AP depolarization. Thus, taking these data together, and the data of previous publication on melatonin effect on N₀ neurons shows that this substance has a greater pharmacological potency on N_inf neurons. We suggest that melatonin has important physiological function related to N_inf neurons and this is likely to bear a potential relevant therapeutic use, since N_inf neurons are related to nociception.

Mitochondrial functions and melatonin: a tour of the reproductive cancers

Cancers of the reproductive organs have a strong association with mitochondrial defects, and a deeper understanding of the role of this organelle in preneoplastic-neoplastic changes is important to determine the appropriate therapeutic intervention. Mitochondria are involved in events during cancer development, including metabolic and oxidative status, acquisition of metastatic potential, resistance to chemotherapy, apoptosis, and others. Because of their origin from melatonin-producing bacteria, mitochondria are speculated to produce melatonin and its derivatives at high levels; in addition, exogenously administered melatonin accumulates in the mitochondria against a concentration gradient. Melatonin is transported into tumor cell by GLUT/SLC2A and/or by the PEPT1/2 transporters, and plays beneficial roles in mitochondrial homeostasis, such as influencing oxidative phosphorylation and electron flux, ATP synthesis, bioenergetics, calcium influx, and mitochondrial permeability transition pore. Moreover, melatonin promotes mitochondrial homeostasis by regulating nuclear DNA and mtDNA transcriptional activities. This review focuses on the main functions of melatonin on mitochondrial processes, and reviews from a mechanistic standpoint, how mitochondrial crosstalk evolved in ovarian, endometrial, cervical, breast, and prostate cancers relative to melatonin's known actions. We put emphasis on signaling pathways whereby melatonin interferes within cancer-cell mitochondria after its administration. Depending on subtype and intratumor metabolic heterogeneity, melatonin seems to be helpful in promoting apoptosis, anti-proliferation, pro-oxidation, metabolic shifting, inhibiting neovasculogenesis and controlling inflammation, and restoration of chemosensitivity. This results in attenuation of development, progression, and metastatic potential of reproductive cancers, in addition to lowering the risk of recurrence and improving the life quality of patients.

Sphingosine 1-phosphate-mediated activation of ezrin-radixin-moesin proteins contributes to cytoskeletal remodeling and changes of membrane properties in epithelial otic vesicle progenitors

Hearing loss is among the most prevalent sensory impairments in humans. Cochlear implantable devices represent the current therapies for hearing loss but have various shortcomings. ERM (ezrin- radixin -moesin) are a family of adaptor proteins that link plasma membrane with actin cytoskeleton, playing a crucial role in cell morphology and in the formation of membrane protrusions. Recently, bioactive sphingolipids have emerged as regulators of ERM proteins. Sphingosine 1-phosphate (S1P) is a pleiotropic sphingolipid which regulates fundamental cellular functions such as proliferation, survival, migration as well as processes such as development and inflammation mainly via ligation to its specific receptors S1PR (S1P_1-5). Experimental findings demonstrate a key role for S1P signaling axis in the maintenance of auditory function. Preservation of cellular junctions is a fundamental function both for S1P and ERM proteins, crucial for the maintenance of cochlear integrity. In the present work, S1P was found to activate ERM in a S1P₂-dependent manner in murine auditory epithelial progenitors US/VOT-E36. S1P-induced ERM activation potently contributed to actin cytoskeletal remodeling and to the appearance of ionic currents and membrane passive properties changes typical of more differentiated cells. Moreover, PKC and Akt activation was found to mediate S1P-induced ERM phosphorylation. The obtained findings contribute to demonstrate the role of S1P signaling pathway in inner ear biology and to disclose potential innovative therapeutical approaches in the field of hearing loss prevention and treatment.

Application of a validated HPLC-PDA method for the determination of melatonin content and its release from poly(lactic acid) nanoparticles

Melatonin is a natural hormone and with the advancement of age its production declines and thereby may result in some neurological disorders. Exogenous administration of melatonin has been suggested as a neuroprotective agent. Due to its low oral bioavailability, the loading of melatonin in polymeric nanoparticles could be an important tool to effectively use exogenous melatonin. The quantification of the incorporated drug within polymeric nanoparticles is an important step in nanoparticles characterization. An analytical method using high performance liquid chromatography equipped with photodiode array detector (HPLC-PDA) was developed and validated for melatonin determination in poly (lactic acid) nanoparticles obtained by a single emulsion-solvent evaporation technique. The melatonin in vitro release profile also was determined by the HPLC method. Mobile phase consisted of acetonitrile: water (65:35, v/v) pumped at a flow rate of 0.9 mL/min, in the isocratic mode and PDA detector was set at 220 nm. The method was validated in terms of the selectivity, linearity, precision, accuracy, robustness, limits of detection and quantification. Analytical curve was linear over the concentration range of 10–100 μg/mL, and limits of detection and quantification were 25.9 ng/mL and 78.7 ng/mL, respectively. The mean recovery for melatonin was 100.47% (RSD = 1.25%, n = 9). In the intra- and inter-assay, the coefficient of variation was less than 2%. Robustness was proved performing changes in mobile phase, column temperature and flow rate. The method was suitable for the determination of melatonin encapsulation efficiency in poly(lactic acid) nanoparticles and for the evaluation of melatonin in vitro release profile.

CaV channels and cancer: canonical functions indicate benefits of repurposed drugs as cancer therapeutics

The importance of ion channels in the hallmarks of many cancers is increasingly recognised. This article reviews current knowledge of the expression of members of the voltage-gated calcium channel family (Ca_V) in cancer at the gene and protein level and discusses their potential functional roles. The ten members of the Ca_V channel family are classified according to expression of their pore-forming α-subunit; moreover, co-expression of accessory α2δ, β and γ confers a spectrum of biophysical characteristics including voltage dependence of activation and inactivation, current amplitude and activation/inactivation kinetics. Ca_V channels have traditionally been studied in excitable cells including neurones, smooth muscle, skeletal muscle and cardiac cells, and drugs targeting the channels are used in the treatment of hypertension and epilepsy. There is emerging evidence that several Ca_V channels are differentially expressed in cancer cells compared to their normal counterparts. Interestingly, a number of Ca_V channels also have non-canonical functions and are involved in transcriptional regulation of the expression of other proteins including potassium channels. Pharmacological studies show that Ca_V canonical function contributes to the fundamental biology of proliferation, cell-cycle progression and apoptosis. This raises the intriguing possibility that calcium channel blockers, approved for the treatment of other conditions, could be repurposed to treat particular cancers. Further research will reveal the full extent of both the canonical and non-canonical functions of Ca_V channels in cancer and whether calcium channel blockers are beneficial in cancer treatment.

Melatonin, an inhibitory agent in breast cancer

BACKGROUND

The heterogeneous nature of breast cancer makes it one of the most challenging cancers to treat. Due to the stimulatory effect of estrogen in mammary cancer progression, anti-estrogenic agents like melatonin have found their way into breast cancer treatment. Further studies confirmed a reverse correlation between nocturnal melatonin levels and the development of mammary cancer. In this study we reviewed the molecular inhibitory effects of melatonin in breast cancer therapy.

METHODS

To open access the articles, Google scholar and science direct were used as a motor search. We used from valid external and internal databases. To reach the search formula, we determined mean key words like breast cancer, melatonin, cell proliferation and death. To retrieval the related articles, we continuously search the articles from 1984 to 2015. The relevance and the quality of the 480 articles were screened; at least we selected 80 eligible articles about melatonin molecular mechanism in breast cancer.

RESULT

The results showed that melatonin not only inhibits breast cancer cell growth, but also is capable of inhibiting angiogenesis, cancer cell invasion, and telomerase activity. Interestingly this hormone is able to induce apoptosis through the suppression or induction of a wide range of signaling pathways. Moreover, it seems that the concomitant administration of melatonin with other conventional chemotherapy agents had beneficial effects for patients with breast cancer, by alleviating unfavorable effects of those agents and enhancing their efficacy.

CONCLUSION

The broad inhibitory effects of melatonin in breast cancer make it a promising agent and may add it to the list of potential drugs in treatment of this cancer.