The potential roles of dopamine in malignant glioma

Assessment of 13 essential and toxic trace elements in tumor and peritumoral brain tissues from human glioblastoma

Trace elements within the brain are important for proper neurological function, but their imbalance has been rarely investigated in glioblastoma. This study enrolled a total of 14 patients with glioblastoma, and the tumor and peritumoral brain tissues were collected while undergoing surgery. The concentrations of Mg, Ca, Cr, Mn, Fe, Co, Cu, Zn, Se, As, Cd, Tl and Pb were determined using a well-evaluated ICP-MS method. The Cu- and Cd-binding proteomes were further analyzed using the anatomic transcriptional atlas from Ivy GAP. Histological evaluation was based on rubeanic acid staining and immunohistochemistry, respectively. The 13 trace element concentrations were obtained, and the highest were Ca, Mn, Fe, Zn and Cu, ranging from a few to dozens of ug/g. Correlation analysis suggested the existence of two intra-correlated clusters: essential metals (Cu-Ca-Zn-Mg) and heavy metals (Pb-As-Cd-Tl-Co-Cr-Mn). Compared to the tumor samples, significantly higher levels of Cu and Cd were observed in the peritumoral region. Further analysis of the Cu- and Cd-binding proteins from the anatomic view suggested that DBH and NOS1 were obviously increased in the leading edge than the central tumor region. Consistent with the above findings, histological evaluation of Cu and DBH further confirmed more copper and DBH expressions in the peritumoral area compared to the tumor core. Trace elements differ in tumor and peritumoral brain zone in glioblastoma, which may associate with tumor angiogenesis.

Amperometric Identification of Single Exosomes and Their Dopamine Contents Secreted by Living Cells

Dopamine (DA) is an important neurotransmitter, which not only participates in the regulation of neural processes but also plays critical roles in tumor progression and immunity. However, direct identification of DA-containing exosomes, as well as quantification of DA in single vesicles, is still challenging. Here, we report a nanopipette-assisted method to detect single exosomes and their dopamine contents via amperometric measurement. The resistive-pulse current measured can simultaneously provide accurate information of vesicle translocation and DA contents in single exosomes. Accordingly, DA-containing exosomes secreted from HeLa and PC12 cells under different treatment modes successfully detected the DA encapsulation efficiency and the amount of exosome secretion that distinguish between cell types. Furthermore, a custom machine learning model was constructed to classify the exosome signals from different sources, with an accuracy of more than 99%. Our strategy offers a useful tool for investigating single exosomes and their DA contents, which facilitates the analysis of DA-containing exosomes derived from other untreated or stimulated cells and may open up a new insight to the research of DA biology.

Antiangiogenic Effect of Dopamine and Dopaminergic Agonists as an Adjuvant Therapeutic Option in the Treatment of Cancer, Endometriosis, and Osteoarthritis

Dopamine (DA) and dopamine agonists (DA-Ag) have shown antiangiogenic potential through the vascular endothelial growth factor (VEGF) pathway. They inhibit VEGF and VEGF receptor 2 (VEGFR 2) functions through the dopamine receptor D2 (D2R), preventing important angiogenesis-related processes such as proliferation, migration, and vascular permeability. However, few studies have demonstrated the antiangiogenic mechanism and efficacy of DA and DA-Ag in diseases such as cancer, endometriosis, and osteoarthritis (OA). Therefore, the objective of this review was to describe the mechanisms of the antiangiogenic action of the DA-D2R/VEGF-VEGFR 2 system and to compile related findings from experimental studies and clinical trials on cancer, endometriosis, and OA. Advanced searches were performed in PubMed, Web of Science, SciFinder, ProQuest, EBSCO, Scopus, Science Direct, Google Scholar, PubChem, NCBI Bookshelf, DrugBank, livertox, and Clinical Trials. Articles explaining the antiangiogenic effect of DA and DA-Ag in research articles, meta-analyses, books, reviews, databases, and clinical trials were considered. DA and DA-Ag have an antiangiogenic effect that could reinforce the treatment of diseases that do not yet have a fully curative treatment, such as cancer, endometriosis, and OA. In addition, DA and DA-Ag could present advantages over other angiogenic inhibitors, such as monoclonal antibodies.

Advances in understanding cancer-associated neurogenesis and its implications on the neuroimmune axis in cancer

Nerves and immunologic mediators play pivotal roles in body homeostasis by interacting with each other through diverse mechanisms. The spread of nerves in the tumor microenvironment increases tumor cell proliferation and disease progression, and this correlates with poor patient outcomes. The effects of sympathetic and parasympathetic nerves on cancer regulation are being investigated. Recent findings demonstrate the possibility of developing therapeutic strategies that target the tumor microenvironment and its components such as immune cells, neurotransmitters, and extracellular vesicles. Therefore, examining and understanding the mechanisms and pathways associated with the sympathetic and parasympathetic nervous systems, neurotransmitters, cancer-derived mediators and their interactions with the immune system in the tumor microenvironment may lead to the development of new cancer treatments. This review discusses the effects of nerve cells, immune cells, and cancer cells have on each other that regulate neurogenesis, cancer progression, and dissemination.

Anticancer efficacy of endo- and exogenous potent ligands acting at dopaminergic receptor-expressing cancer cells

Cancer is one of the most common and dreaded diseases affecting the vastness of society. Unfortunately, still some people die especially when cancer is not diagnosed and thus caught early enough. On the other hand, using available chemo- or radiotherapy may result in serious side effects. Therefore, cancer-specific medications seem to be the most desired and safe therapy. Knowing that some cancers are characterized by overexpression of specific receptors on the cell surface, target-mediated drugs could serve as a unique and effective form of therapy. In line with this, recently dopaminergic receptors were presented important in cancer therapy as several dopaminergic ligands revealed their efficacy in tumor growth reduction as well as in apoptosis mediation. Unfortunately, the indication of whether DA receptor agonists or antagonists are the best choices in cancer treatment is quite difficult, since both of them may exert either pro- or anticancer effects. In this review, we analyze the therapeutic efficacy of compounds, both of exogenous and endogenous origin, targeting dopaminergic receptor-expressing cancers.

Neurotransmitters: Potential Targets in Glioblastoma

Simple Summary

Aiming to discover potential treatments for GBM, this review connects emerging research on the roles of neurotransmitters in the normal neural and the GBM microenvironments and sheds light on the prospects of their application in the neuropharmacology of GBM. Conventional therapy is blamed for its poor effect, especially in inhibiting tumor recurrence and invasion. Facing this dilemma, we focus on neurotransmitters that modulate GBM initiation, progression and invasion, hoping to provide novel therapy targeting GBM. By analyzing research concerning GBM therapy systematically and scientifically, we discover increasing insights into the regulatory effects of neurotransmitters, some of which have already shown great potential in research in vivo or in vitro. After that, we further summarize the potential drugs in correlation with previously published research. In summary, it is worth expecting that targeting neurotransmitters could be a promising novel pharmacological approach for GBM treatment.

Abstract

For decades, glioblastoma multiforme (GBM), a type of the most lethal brain tumor, has remained a formidable challenge in terms of its treatment. Recently, many novel discoveries have underlined the regulatory roles of neurotransmitters in the microenvironment both physiologically and pathologically. By targeting the receptors synaptically or non-synaptically, neurotransmitters activate multiple signaling pathways. Significantly, many ligands acting on neurotransmitter receptors have shown great potential for inhibiting GBM growth and development, requiring further research. Here, we provide an overview of the most novel advances concerning the role of neurotransmitters in the normal neural and the GBM microenvironments, and discuss potential targeted drugs used for GBM treatment.

Under lithium carbonate administration, nicotine triggers cell dysfunction in human glioblastoma U-251MG cells, which is distinct from cotinine

Nicotine is an alkaloid found in tobacco leaves. Smoking prevention has been a neglected issue in psychiatry; nicotine intake in conjunction with the administration of the mood stabilizer, lithium carbonate (Li₂CO₃), may negatively affect brain cells. The present study investigated the combined effects of nicotine and its metabolite, cotinine, and Li₂CO₃ compared to acetylcholine and dopamine in U-251MG human glioblastoma cells. Cell proliferation was found to be decreased by nicotine and to be further suppressed following treatment with Li₂CO₃, accompanied by mitotic catastrophe and increased levels of superoxide anion radicals. By contrast, cotinine did not exert such detrimental effects. It was also found that acetylcholine did not suppress cell proliferation, whereas dopamine in conjunction with Li₂CO₃ decreased cell proliferation in a concentration-dependent manner. The nicotine-induced cell growth inhibition was restored by mecamylamine, a non-competitive antagonist of nicotinic acetylcholine receptors. On the whole, the findings of the present study suggest that nicotine combined with Li₂CO₃ leads to the suppression of the proliferation of human glioblastoma cells accompanied by mitotic catastrophe and superoxide anion radical generation. These findings may provide further cellular biological insight into the risks associated with smoking under Li₂CO₃ administration.

Blocking Cancer-Nerve Crosstalk for Treatment of Metastatic Bone Cancer Pain

The tumor microenvironment is a complex milieu where neurons constitute an important non-neoplastic cell type. From "cancer neuroscience," the crosstalk between tumors and neurons favors the rapid growth of both, making the cancer-nerve interaction a reciprocally beneficial process. Thus, cancer-nerve crosstalk may provide new targets for therapeutic intervention against cancer and cancer-related symptoms. We proposed a nerve-cancer crosstalk blocking strategy for metastatic bone cancer pain treatment, achieved by Mg/Al layered-double-hydroxide nanoshells (Mg/Al-LDH) with AZ-23 loaded inside and alendronate decorated outside. The pain-causing H⁺ is rapidly eliminated by the LDH, with neurogenesis inhibited by the antagonist AZ-23. As positive feedback, the decreased pain reverses the nerve-to-cancer Ca²⁺ crosstalk-related cell cycle, dramatically inhibiting tumor growth. All experiments confirm the improved pain threshold and enhanced tumor inhibition. The study may inspire multidisciplinary researchers to focus on cancer-nerve crosstalk for treating cancer and accompanied neuropathic diseases.

Effects of platinum-coexisting dopamine with X-ray irradiation upon human glioblastoma cell proliferation

In brain tumors, neurotransmitters and platinum drugs may have some interaction, but their role in radiation therapy remains unclear. We investigated the effects of dopamine in combination with platinum on human glioblastoma U-251MG cells upon X-ray irradiation, comparing with L-DOPA, 2-phenylethylamine and temozolomide. Cell proliferation of U-251MG cells was prominently decreased by dopamine in combination with 10 μM platinum upon 4 Gy of X-ray irradiation, accompanied with intracellular reactive oxygen species generation and mitotic catastrophe. Platinum alone did not increase intracellular reactive oxygen species. On the other hand, L-DOPA in combination with platinum did not decrease cell proliferation regardless of X-ray irradiation. It was clearly shown that 2-phenylethylamine did not suppress cell proliferation as compared to dopamine. Temozolomide decreased cell proliferation in a dose-dependent manner upon X-ray irradiation. However, the combined administration of temozolomide and platinum did not further decrease cell proliferation. The platinum nanoparticles were gradually taken up by cells after administration as determined by ICP analysis. Our results suggest that platinum-coexisting dopamine led cells to mitotic catastrophe due to increased production of intracellular reactive oxygen species which was boosted by X-ray and platinum-catalyzed auto-oxidation of dopamine, and thereby cell proliferation was suppressed. In addition, normal human fibroblast OUMS-36T-1 cells were subjected to experiments. Regarding the effect of the combined administration of dopamine and platinum on each cell which was exposed to X-ray, cell proliferation was decreased in U-251MG cells by the combined administration of platinum, whereas that was not decreased in OUMS-36T-1 cells. This provides one basic insight into the effects of dopamine in combined with platinum on radiation therapy for glioblastoma.

Biochemical and cytotoxic evaluation of latroeggtoxin-VI against PC12 cells

Latroeggtoxin-VI (LETX-VI) is a peptide neurotoxin discovered from Latrodectus tredecimguttatus eggs. In the current study, the action features of the neurotoxin on PC12 cells were systematically investigated. LETX-VI could promote dopamine release from PC12 cells in the absence and presence of Ca2+, involving an even more complex action mechanism in the presence of Ca2+ and when the treatment time was longer. Although LETX-VI enchanced the autophagy and secretion activity in PC 12 cells, it showed no remarkable influence on the proliferation, cell cycle, apoptosis and ultrastructure of the cells. Pulldown combined with CapLC-MS/MS analysis suggested that LETX-VI affected PC12 cells by interacting with multiple proteins involved in the metabolism, transport, and release of neurotransmitters, particularly dopamine. The low cytotoxicity and effective regulatory action of LETX-VI on PC12 cells suggest the potential of the active peptide in the development of drugs for the treatment of some dopamine-related psychotic diseases and cancers.

Dopamine D1 Receptor in Cancer

Simple Summary

Circulating hormones and their specific receptors play a significant role in the development and progression of various cancers. This review aimed to summarize current knowledge about the dopamine D1 receptor’s biological role in different cancers, including breast cancer, central nervous system tumors, lymphoproliferative disorders, and other neoplasms. Treatment with dopamine D1 receptor agonists was proven to exert a major anti-cancer effect in many preclinical models. We highlight this receptor’s potential as a target for the adjunct therapy of tumors and discuss possibilities and necessities for further research in this area.

Abstract

Dopamine is a biologically active compound belonging to catecholamines. It plays its roles in the human body, acting both as a circulating hormone and neurotransmitter. It acts through G-protein-coupled receptors divided into two subgroups: D1-like receptors (D1R and D5R) and D2-like receptors (D2R, D3R, D4R). Physiologically, dopamine receptors are involved in central nervous system functions: motivation or cognition, and peripheral actions such as blood pressure and immune response modulation. Increasing evidence indicates that the dopamine D1 receptor may play a significant role in developing different human neoplasms. This receptor’s value was presented in the context of regulating various signaling pathways important in tumor development, including neoplastic cell proliferation, apoptosis, autophagy, migration, invasiveness, or the enrichment of cancer stem cells population. Recent studies proved that its activation by selective or non-selective agonists is associated with significant tumor growth suppression, metastases prevention, and tumor microvasculature maturation. It may also exert a synergistic anti-cancer effect when combined with tyrosine kinase inhibitors or temozolomide. This review provides a comprehensive insight into the heterogeneity of dopamine D1 receptor molecular roles and signaling pathways in human neoplasm development and discusses possible perspectives of its therapeutic targeting as an adjunct anti-cancer strategy of treatment. We highlight the priorities for further directions in this research area.

Communication of Glioma cells with neuronal plasticity: What is the underlying mechanism?

There has been a significantly rising discussion on how neuronal plasticity communicates with the glioma growth and invasion. This literature review aims to determine which neurotransmitters, ion channels and signaling pathways are involved in this context, how information is transferred from synaptic sites to the glioma cells and how glioma cells apply established mechanics of synaptic plasticity for their own increment. This work is a compilation of some outstanding findings related to the influence of the glutamate, calcium, potassium, chloride and sodium channels and other important brain plasticity molecules over the glioma progression. These topics also include the relevant molecular signaling data which could prove to be helpful for an effective clinical management of brain tumors in the future.

Ivermectin inhibits the growth of glioma cells by inducing cell cycle arrest and apoptosis in vitro and in vivo

Glioma, the most predominant primary malignant brain tumor, remains uncured due to the absence of effective treatments. Hence, it is imperative to develop successful therapeutic agents. This study aimed to explore the antitumor effects and mechanisms of ivermectin (IVM) in glioma cells in vitro and in vivo. The effects of IVM on cell viability, cell cycle arrest, apoptosis rate, and morphological characteristics were determined respectively by MTT assay/colony formation assay, flow cytometry, and transmission electron microscope. In addition, the expression levels of cycle-related and apoptosis-associated proteins were individually examined by Western blot analysis. Moreover, cell proliferation and apoptosis analyses were carried out by TUNEL, Ki-67, cleaved caspase-3, and cleaved caspase-9 immunostaining assay. Our results demonstrated that IVM has a potential dosage-dependent inhibition effect on the apoptosis rate of glioma cells. Meanwhile, the results also revealed that IVM induced apoptosis by increasing caspase-3 and caspase-9 activity, upregulating the expressions of p53 and Bax, downregulating Bcl-2, activating cleaved caspase-3 and cleaved caspase-9, and blocking cell cycle in G0/G1 phase by downregulating levels of CDK2, CDK4, CDK6, cyclin D1, and cyclin E. These findings suggest that IVM has an inhibition effect on the proliferation of glioma cells by triggering cell cycle arrest and inducing cell apoptosis in vitro and in vivo, and probably represents promising agent for treating glioma.

Moxidectin inhibits glioma cell viability by inducing G0/G1 cell cycle arrest and apoptosis

Moxidectin (MOX), a broad‑spectrum antiparasitic agent, belongs to the milbemycin family and is similar to avermectins in terms of its chemical structure. Previous research has revealed that milbemycins, including MOX, may potentially function as effective multidrug resistance agents. In the present study, the impact of MOX on the viability of glioma cells was examined by MTT and colony formation assay, and the molecular mechanisms underlying MOX‑mediated glioma cell apoptosis were explored by using flow cytometry and apoptosis rates. The results demonstrated that MOX exerts an inhibitory effect on glioma cell viability and colony formations in vitro and xenograft growth in vivo and is not active against normal cells. Additionally, as shown by western blot assay, it was demonstrated that MOX arrests the cell cycle at the G0/G1 phase by downregulating the expression levels of cyclin‑dependent kinase (CDK)2, CDK4, CDK6, cyclin D1 and cyclin E. Furthermore, it was revealed that MOX is able to induce cell apoptosis by increasing the Bcl‑2‑associated X protein/B‑cell lymphoma 2 ratio and activating the caspase‑3/‑9 cascade. In conclusion, these results suggest that MOX may inhibit the viability of glioma cells by inducing cell apoptosis and cell cycle arrest, and may be able to function as a potent and promising agent in the treatment of glioma.

Potential Roles of Peripheral Dopamine in Tumor Immunity

Recent years, immunotherapy has turned out to be a promising strategy against tumors. Peripheral dopamine (DA) has important roles in immune system among tumor patients. Accumulated reports demonstrate variable expression and distribution of DA receptors (DRs) in diverse immune cells. Interestingly, peripheral DA also involves in tumor progression and it exerts anticancer effects on immunomodulation, which includes inflammasomes in cancer, function of immune effector cells, such as T lymphocytes, myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs) and natural killer (NK) cells. Given the specific immunologic status, DA medication may be a valuable candidate in pancreatic cancer treatment. The major purpose of this review is to discuss the novel potential interactions between peripheral dopamine and tumor immunity.

Anti-cancer effects of dopamine in human glioma: involvement of mitochondrial apoptotic and anti-inflammatory pathways

Despite the emergence of innovative cancer treatment strategies, the global burden imposed by malignant glioma is expected to increase; thus, new approaches for treating the disease are urgently required. Dopamine, a monoamine catecholamine neurotransmitter, is currently regarded as an important endogenous regulator of tumor growth. Dopamine may play an important role in glioma treatment; however, the mechanism underlying the anti-tumor activity of dopamine remains poorly understood. Here, we explored the potential roles of dopamine in glioma and highlight the importance of endogenous regulators of tumor growth. We report that dopamine inhibited glioma cell proliferation. We investigated the biological functions of dopamine via migration, colony formation and apoptosis assays in glioma cells. We also evaluated cytochrome c release from the mitochondria and p50 and p65 subcellular localization by fluorescence microscopy. We performed western blotting and real-time quantitative polymerase chain reaction to detect apoptosis and inflammatory marker protein and gene expression levels, respectively. NF-κB p50/p65 nuclear localization was analyzed after U87MG and U251 cells were treated with dopamine. The in vivo anti-tumor efficacy of dopamine was also analyzed in xenograft mice. Taken together, our results indicated that dopamine induced apoptosis by activating the cytochrome c and caspase-dependent apoptotic pathway. Moreover, dopamine markedly down-regulated inflammation-related protein expression levels and p50/p65 NF-κB nuclear localization in tumor cells, thereby inhibiting increases in tumor weight and size in xenograft mice. Thus, therapies targeting the mitochondrial apoptotic and anti-inflammatory signaling pathways regulated by dopamine may represent promising treatments for human glioma.

Apomorphine suppresses TNF-α-induced MMP-9 expression and cell invasion through inhibition of ERK/AP-1 signaling pathway in MCF-7 cells

Recent studies have shown that dopamine plays an important role in several types of cancer by inhibiting cell growth and invasion via dopamine receptors (DRs), such as dopamine receptor D2. However, the roles of DR agonists in cancer cell growth and invasion remain unclear. In our study, we found that apomorphine (APO), one of the most commonly prescribed DR agonists, inhibited TNF-α-induced matrix metalloprotease-9 (MMP-9) expression and cell invasion in MCF-7 human breast carcinoma cells through DR-independent pathways. Further mechanistic studies demonstrated that APO suppresses TNF-α-induced transcription of MMP-9 by inhibiting activator protein-1 (AP-1), a well-described transcription factor. This is achieved via extracellular signal-regulated kinases 1 and 2 (ERK1/2). Our study has demonstrated that APO targets human MMP-9 in a DR-independent fashion in MCF-7 cells, suggesting that APO is a potential anticancer agent that can suppress the metastatic progression of cancer cells.