TRPM7 regulates vascular endothelial cell adhesion and tube formation

Transient receptor potential melastatin 7 cation channel, magnesium and cell metabolism in vascular health and disease

Preserving the balance of metabolic processes in endothelial cells (ECs) and vascular smooth muscle cells (VSMCs), is crucial for optimal vascular function and integrity. ECs are metabolically active and depend on aerobic glycolysis to efficiently produce energy for their essential functions, which include regulating vascular tone. Impaired EC metabolism is linked to endothelial damage, increased permeability and inflammation. Metabolic alterations in VSMCs also contribute to vascular dysfunction in atherosclerosis and hypertension. Magnesium (Mg2+) is the second most abundant intracellular divalent cation and influences molecular processes that regulate vascular function, including vasodilation, vasoconstriction, and release of vasoactive substances. Mg2+ is critically involved in maintaining cellular homeostasis and metabolism since it is an essential cofactor for ATP, nucleic acids and hundreds of enzymes involved in metabolic processes. Low Mg2+ levels have been linked to endothelial dysfunction, increased vascular tone, vascular inflammation and arterial remodeling. Growing evidence indicates an important role for the transient receptor potential melastatin-subfamily member 7 (TRPM7) cation channel in the regulation of Mg2+ homeostasis in EC and VSMCs. In the vasculature, TRPM7 deficiency leads to impaired endothelial function, increased vascular contraction, phenotypic switching of VSMCs, inflammation and fibrosis, processes that characterize the vascular phenotype in hypertension. Here we provide a comprehensive overview on TRPM7/Mg2+ in the regulation of vascular function and how it influences EC and VSMC metabolism such as glucose and energy homeostasis, redox regulation, phosphoinositide signaling, and mineral metabolism. The putative role of TRPM7/Mg2+ and altered cellular metabolism in vascular dysfunction and hypertension is also discussed.

Tension at the gate: sensing mechanical forces at the blood-brain barrier in health and disease

Microvascular brain endothelial cells tightly limit the entry of blood components and peripheral cells into the brain by forming the blood-brain barrier (BBB). The BBB is regulated by a cascade of mechanical and chemical signals including shear stress and elasticity of the adjacent endothelial basement membrane (BM). During physiological aging, but especially in neurological diseases including multiple sclerosis (MS), stroke, small vessel disease, and Alzheimer's disease (AD), the BBB is exposed to inflammation, rigidity changes of the BM, and disturbed cerebral blood flow (CBF). These altered forces lead to increased vascular permeability, reduced endothelial reactivity to vasoactive mediators, and promote leukocyte transmigration. Whereas the molecular players involved in leukocyte infiltration have been described in detail, the importance of mechanical signalling throughout this process has only recently been recognized. Here, we review relevant features of mechanical forces acting on the BBB under healthy and pathological conditions, as well as the endothelial mechanosensory elements detecting and responding to altered forces. We demonstrate the underlying complexity by focussing on the family of transient receptor potential (TRP) ion channels. A better understanding of these processes will provide insights into the pathogenesis of several neurological disorders and new potential leads for treatment.

A Dual Reversible Cross-Linked Hydrogel with Enhanced Mechanical Property and Capable of Proangiogenic and Osteogenic Activities for Bone Defect Repair

The clinical treatment of bone defects presents ongoing challenges. One promising approach is bone tissue engineering (BTE), wherein hydrogels have garnered significant attention. However, the application of hydrogels in BTE is severely limited due to their poor mechanical properties, as well as their inferior proangiogenic and osteogenic activities. To address these limitations, our develop a dual cross-linked alendronate (ALN)-Ca2+ /Mg2+ -doped sulfated hyaluronic acid (SHA@CM) hydrogel, using a one-step mixing injection molding method known as "three-in-one" approach. This approach enabled the simultaneous formation of Schiff-Base crosslinking and electric attraction-based crosslinking within the hydrogel. The Schiff-Base crosslinking contributed to the majority of the hydrogel's mechanical strength, while the electric attraction-based crosslinking served as a release reservoir for Ca2+ /Mg2+ and ALN, promoting enhanced osteogenic activities and providing additional mechanical reinforcement to the hydrogel. These experimental data demonstrates several favorable properties of the SHA@CM hydrogel, including satisfactory injectability, rapid gelation, self-healing capacity, and excellent cytocompatibility. Moreover, the presence of sulfated groups and Mg2+ within the SHA@CM hydrogel exhibited pro-angiogenic effects, while the controlled release of nanoparticles formed by Ca2+ /Mg2+ and ALN further enhanced the osteogenesis of the hydrogel. Overall, these results indicate that the SHA@CM hydrogel holds significant potential for the clinical translation of BTE.

LncRNA SNHG8 regulates the migration and angiogenesis of pHUVECs induced by high glucose via the TRPM7/ERK1/2 signaling axis

This study aimed to evaluate the regulatory effect and molecular mechanism of long noncoding RNA small nucleolus RNA host gene 8 (LncRNA SNHG8) in the migration and angiogenesis of primary human umbilical vein endothelial cells (pHUVECs) under high-glucose (HG) conditions. The HG-induced endothelial injury model was established in vitro.The cell model of silencing SNHG8, overexpressing SNHG8, and silencing TRPM7 was established by transfecting SNHG8-siRNA, SNHG8 plasmid and TRPM7-siRNA into cells with liposomes.The SNHG8 level was determined through reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The expression levels of transient receptor potential melastatin 7 (TRPM7), endothelial nitric oxide synthase (eNOS), p-eNOS, extracellular signal-regulated kinase 1/2(ERK1/2), and p-ERK1/2 were assessed through western blot. Nitric oxide (NO) levels were measured with DAF-FM. pHUVEC migration was examined through wound healing and Transwell assay, and pHUVEC angiogenesis was observed through a tube formation assay. Results showed that HG promoted the expression of lncRNA SNHG8 and TRPM7 and decreased the ratio of p-eNOS/eNOS and p-ERK1/2/ERK1/2 in pHUVECs . NO production, migration , and angiogenesis were inhibited in pHUVECs under HG conditions. Silencing lncRNA SNHG8 and TRPM7 could significantly reverse the HG-induced decrease in eNOS activation, NO production , migration, and angiogenesis . SNHG8 and U0126 (ERK pathway inhibitor) overexpression enhanced the HG effects, whereas using U0126 did not affect the TRPM7 expression. In conclusion, lncRNA SNHG8 participates in HG-induced endothelial cell injury and likely regulates NO production, migration, and angiogenesis of pHUVECs via the TRPM7/ERK1/2 signaling axis.

TRPM2-L Participates in the Interleukin-6 Pathway to Enhance Tumor Growth in Prostate Cancer by Hypoxia-Inducible Factor-1α

Interleukin-6 (IL-6) can promote cell proliferation in prostate cancer (PCa). Full-length transient receptor potential melastatin 2 (TRPM2-L) is highly expressed in PCa. However, the association between IL-6 and TRPM2-L in PCa is unclear. Here, human PCa cell lines, PC-3 and DU-145, were treated with 10 μg/mL tocilizumab, an IL-6 receptor (IL-6R) inhibitor, and the TRPM2-L protein expression in cells was significantly decreased. Cells were stably transfected with TRPM2 short-interfering RNA (siRNA) and cell survival clearly declined. Recombinant IL-6 treatment weakened the effects of TRPM2-siRNA on cell survival. TRPM2-L binds directly to IL-6R in PC-3 and DU-145 cells. The protein expression of hypoxia-inducible factor-1α was suppressed by reduction with TRPM2-L in PC-3 and DU-145 cells. Human umbilical vein endothelial cells (HUVECs) were indirectly cocultured with PCa cells, and the invasion and angiogenic activity of HUVECs were enhanced after coculture with PCa cells. However, TRPM2-L reduction in PCa cells significantly decreased the invasion and angiogenic activity of HUVECs compared to the control coculture. In vivo, xenograft tumors were induced using PC-3 cells. Tocilizumab treatment or TRPM2-L reduction clearly suppressed tumor growth. Meanwhile, the injection of mouse recombinant IL-6 weakened the antitumor effects of TRPM2-L reduction. These data demonstrate that the IL-6/TRPM2-L axis in PCa tumor growth is important, and interference of the IL-6/TRPM2-L axis may be a novel approach for PCa therapy.

Roles of TRPM7 in ovarian cancer

Ovarian cancer stands as the prevailing gynecologic malignancy, afflicting over 313,959 individuals annually worldwide, accompanied by more than 207,252 fatalities. Perturbations in calcium signaling contribute significantly to the pathogenesis of numerous cancers, including ovarian cancer, wherein alterations in calcium transporter expression have been reported. Overexpression of TRPM7, a prominent calcium transporter, has been linked to adverse prognostic outcomes in various cancer types. The focus of this comprehensive review centers around delineating the oncogenic role of TRPM7 in cancer development and exploring its therapeutic potential as a target in combating this disease. Notably, TRPM7 fosters cancer invasion, metastasis, and uncontrolled cell proliferation, thereby perpetuating the expansion and reinforcement of these malignant entities. Furthermore, this review takes ovarian cancer as an example and summarizes the "dual-mode" regulatory role of TRPM7 in cancer. Within the domain of ovarian cancer, TRPM7 assumes the role of a harsh tyrant, firmly controlling the calcium ion signaling pathway and metabolic reprogramming pathways.

The Interplay between TRPM7 and MagT1 in Maintaining Endothelial Magnesium Homeostasis

The transient receptor potential cation channel subfamily M member 7 (TRPM7) is an ubiquitous channel fused to an α-kinase domain involved in magnesium (Mg) transport, and its level of expression has been proposed as a marker of endothelial function. To broaden our present knowledge about the role of TRPM7 in endothelial cells, we generated stable transfected Human Endothelial Cells derived from the Umbilical Vein (HUVEC). TRPM7-silencing HUVEC maintain the actin fibers' organization and mitochondrial network. They produce reduced amounts of reactive oxygen species and grow faster than controls. Intracellular Mg concentration does not change in TRPM7-silencing or -expressing HUVEC, while some differences emerged when we analyzed intracellular Mg distribution. While the levels of the plasma membrane Mg transporter Solute Carrier family 41 member 1 (SLC41A1) and the mitochondrial channel Mrs2 remain unchanged, the highly selective Magnesium Transporter 1 (MagT1) is upregulated in TRPM7-silencing HUVEC through transcriptional regulation. We propose that the increased amounts of MagT1 grant the maintenance of intracellular Mg concentrations when TRPM7 is not expressed in endothelial cells.

Cardiovascular toxicity of tyrosine kinase inhibitors during cancer treatment: Potential involvement of TRPM7

Receptor tyrosine kinases (RTKs) are a class of membrane spanning cell-surface receptors that transmit extracellular signals through the membrane to trigger diverse intracellular signaling through tyrosine kinases (TKs), and play important role in cancer development. Therapeutic approaches targeting RTKs such as vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR), and platelet-derived growth factor receptor (PDGFR), and TKs, such as c-Src, ABL, JAK, are widely used to treat human cancers. Despite favorable benefits in cancer treatment that prolong survival, these tyrosine kinase inhibitors (TKIs) and monoclonal antibodies targeting RTKs are also accompanied by adverse effects, including cardiovascular toxicity. Mechanisms underlying TKI-induced cardiovascular toxicity remain unclear. The transient receptor potential melastatin-subfamily member 7 (TRPM7) is a ubiquitously expressed chanzyme consisting of a membrane-based ion channel and intracellular α-kinase. TRPM7 is a cation channel that regulates transmembrane Mg²⁺ and Ca²⁺ and is involved in a variety of (patho)physiological processes in the cardiovascular system, contributing to hypertension, cardiac fibrosis, inflammation, and atrial arrhythmias. Of importance, we and others demonstrated significant cross-talk between TRPM7, RTKs, and TK signaling in different cell types including vascular smooth muscle cells (VSMCs), which might be a link between TKIs and their cardiovascular effects. In this review, we summarize the implications of RTK inhibitors (RTKIs) and TKIs in cardiovascular toxicities during anti-cancer treatment, with a focus on the potential role of TRPM7/Mg²⁺ as a mediator of RTKI/TKI-induced cardiovascular toxicity. We also describe the important role of TRPM7 in cancer development and cardiovascular diseases, and the interaction between TRPM7 and RTKs, providing insights for possible mechanisms underlying cardiovascular disease in cancer patients treated with RTKI/TKIs.

Arbitrary Ca2+ regulation for endothelial nitric oxide, NFAT and NF-κB activities by an optogenetic approach

Modern western dietary habits and low physical activity cause metabolic abnormalities and abnormally elevated levels of metabolites such as low-density lipoprotein, which can lead to immune cell activation, and inflammatory reactions, and atherosclerosis. Appropriate stimulation of vascular endothelial cells can confer protective responses against inflammatory reactions and atherosclerotic conditions. This study aims to determine whether a designed optogenetic approach is capable of affecting functional changes in vascular endothelial cells and to evaluate its potential for therapeutic regulation of vascular inflammatory responses in vitro. We employed a genetically engineered, blue light-activated Ca²⁺ channel switch molecule that utilizes an endogenous store-operated calcium entry system and induces intracellular Ca²⁺ influx through blue light irradiation and observed an increase in intracellular Ca²⁺ in vascular endothelial cells. Ca²⁺-dependent activation of the nuclear factor of activated T cells and nitric oxide production were also detected. Microarray analysis of Ca²⁺-induced changes in vascular endothelial cells explored several genes involved in cellular contractility and inflammatory responses. Indeed, there was an increase in the gene expression of molecules related to anti-inflammatory and vasorelaxant effects. Thus, a combination of human blue light-activated Ca²⁺ channel switch 2 (hBACCS2) and blue light possibly attenuates TNFα-induced inflammatory NF-κB activity. We propose that extrinsic cellular Ca²⁺ regulation could be a novel approach against vascular inflammation.

Detection of TRPM6 and TRPM7 Proteins in Normal and Diseased Cardiac Atrial Tissue and Isolated Cardiomyocytes

Magnesium-sensitive transient receptor potential melastatin (TRPM) ion channels, TRPM6 and TRPM7, are present in several organs, but their roles in the heart remain unclear. Therefore, here, we studied the expression patterns of TRPM6 and TRPM7 in normal and diseased myocardium. Cardiac atrial tissue and cardiomyocytes were obtained from healthy pigs and undiseased human hearts as well as from hearts of patients with ischemic heart disease (IHD) or atrial fibrillation (AF). Immunofluorescence and ELISA were used to detect TRP proteins. TRPM6 and TRPM7 immunofluorescence signals, localized at/near the cell surface or intracellularly, were detected in pig and human atrial tissues. The TRP channel modulators carvacrol (CAR, 100 µM) or 2-aminoethoxydiphenyl borate (2-APB, 500 µM) decreased the TRPM7 signal, but enhanced that of TRPM6. At a higher concentration (2 mM), 2-APB enhanced the signals of both proteins. TRPM6 and TRPM7 immunofluorescence signals and protein concentrations were increased in atrial cells and tissues from IHD or AF patients. TRPM6 and TRPM7 proteins were both detected in cardiac atrial tissue, with relatively similar subcellular localization, but distinctive drug sensitivity profiles. Their upregulated expression in IHD and AF suggests a possible role of the channels in cardiac atrial disease.

The Role of MiR-181 Family Members in Endothelial Cell Dysfunction and Tumor Angiogenesis

Endothelial dysfunction plays a critical role in many human angiogenesis-related diseases, including cancer and retinopathies. Small non-coding microRNAs (miRNAs) repress gene expression at the post-transcriptional level. They are critical for endothelial cell gene expression and function and are involved in many pathophysiological processes. The miR-181 family is one of the essential angiogenic regulators. This review summarizes the current state of knowledge of the role of miR-181 family members in endothelial cell dysfunction, with emphasis on their pathophysiological roles in aberrant angiogenesis. The actions of miR-181 members are summarized concerning their targets and associated major angiogenic signaling pathways in a cancer-specific context. Elucidating the underlying functional mechanisms of miR-181 family members that are dysregulated in endothelial cells or cancer cells is invaluable for developing miRNA-based therapeutics for angiogenesis-related diseases such as retinopathies, angiogenic tumors, and cancer. Finally, potential clinical applications of miR-181 family members in anti-angiogenic tumor therapy are discussed.

Mesenchymal Stem Cell Derived Extracellular Vesicles for Repairing the Neurovascular Unit after Ischemic Stroke

Ischemic stroke is a debilitating disease and one of the leading causes of long-term disability. During the early phase after ischemic stroke, the blood-brain barrier (BBB) exhibits increased permeability and disruption, leading to an influx of immune cells and inflammatory molecules that exacerbate the damage to the brain tissue. Mesenchymal stem cells have been investigated as a promising therapy to improve the recovery after ischemic stroke. The therapeutic effects imparted by MSCs are mostly paracrine. Recently, the role of extracellular vesicles released by these MSCs have been studied as possible carriers of information to the brain. This review focuses on the potential of MSC derived EVs to repair the components of the neurovascular unit (NVU) controlling the BBB, in order to promote overall recovery from stroke. Here, we review the techniques for increasing the effectiveness of MSC-based therapeutics, such as improved homing capabilities, bioengineering protein expression, modified culture conditions, and customizing the contents of EVs. Combining multiple techniques targeting NVU repair may provide the basis for improved future stroke treatment paradigms.

The Role of Angiogenesis-Inducing microRNAs in Vascular Tissue Engineering

Angiogenesis is an important process in tissue repair and regeneration as blood vessels are integral to supply nutrients to a functioning tissue. In this review, the application of microRNAs (miRNAs) or anti-miRNAs that can induce angiogenesis to aid in blood vessel formation for vascular tissue engineering in ischemic diseases such as peripheral arterial disease and stroke, cardiac diseases, and skin and bone tissue engineering is discussed. Endothelial cells (ECs) form the endothelium of the blood vessel and are recognized as the primary cell type that drives angiogenesis and studied in the applications that were reviewed. Besides ECs, mesenchymal stem cells can also play a pivotal role in these applications, specifically, by secreting growth factors or cytokines for paracrine signaling and/or as constituent cells in the new blood vessel formed. In addition to delivering miRNAs or cells transfected/transduced with miRNAs for angiogenesis and vascular tissue engineering, the utilization of extracellular vesicles (EVs), such as exosomes, microvesicles, and EVs collectively, has been more recently explored. Proangiogenic miRNAs and anti-miRNAs contribute to angiogenesis by targeting the 3'-untranslated region of targets to upregulate proangiogenic factors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor, and hypoxia-inducible factor-1 and increase the transduction of VEGF signaling through the PI3K/AKT and Ras/Raf/MEK/ERK signaling pathways such as phosphatase and tensin homolog or regulating the signaling of other pathways important for angiogenesis such as the Notch signaling pathway and the pathway to produce nitric oxide. In conclusion, angiogenesis-inducing miRNAs and anti-miRNAs are promising tools for vascular tissue engineering for several applications; however, future work should emphasize optimizing the delivery and usage of these therapies as miRNAs can also be associated with the negative implications of cancer.

MiR-9 promotes angiogenesis of endothelial progenitor cell to facilitate thrombi recanalization via targeting TRPM7 through PI3K/Akt/autophagy pathway

Endothelial progenitor cells (EPCs) have emerged as a promising therapeutic choice for thrombi recanalization. However, this role of EPCs is confined by some detrimental factors. The aim of this study was to explore the role of the miR‐9‐5p in regulation of the proliferation, migration and angiogenesis of EPCs and the subsequent therapeutic role in thrombosis event. Wound healing, transwell assay, tube formation assay and in vivo angiogenesis assay were carried out to measure cell migration, invasion and angiogenic abilities, respectively. Western blot was performed to elucidate the relationship between miR‐9‐5p and TRPM7 in the autophagy pathway. It was found that miR‐9‐5p could promote migration, invasion and angiogenesis of EPCs by attenuating TRPM7 expression via activating PI3K/Akt/autophagy pathway. In conclusion, miR‐9‐5p, targets TRPM7 via the PI3K/Ak/autophagy pathway, thereby mediating cell proliferation, migration and angiogenesis in EPCs. Acting as a potential therapeutic target, miR‐9‐5p may play an important role in the prognosis of DVT.

Endothelial Transient Receptor Potential Channels and Vascular Remodeling: Extracellular Ca2 + Entry for Angiogenesis, Arteriogenesis and Vasculogenesis

Vasculogenesis, angiogenesis and arteriogenesis represent three crucial mechanisms involved in the formation and maintenance of the vascular network in embryonal and post-natal life. It has long been known that endothelial Ca²⁺ signals are key players in vascular remodeling; indeed, multiple pro-angiogenic factors, including vascular endothelial growth factor, regulate endothelial cell fate through an increase in intracellular Ca²⁺ concentration. Transient Receptor Potential (TRP) channel consist in a superfamily of non-selective cation channels that are widely expressed within vascular endothelial cells. In addition, TRP channels are present in the two main endothelial progenitor cell (EPC) populations, i.e., myeloid angiogenic cells (MACs) and endothelial colony forming cells (ECFCs). TRP channels are polymodal channels that can assemble in homo- and heteromeric complexes and may be sensitive to both pro-angiogenic cues and subtle changes in local microenvironment. These features render TRP channels the most versatile Ca²⁺ entry pathway in vascular endothelial cells and in EPCs. Herein, we describe how endothelial TRP channels stimulate vascular remodeling by promoting angiogenesis, arteriogenesis and vasculogenesis through the integration of multiple environmental, e.g., extracellular growth factors and chemokines, and intracellular, e.g., reactive oxygen species, a decrease in Mg²⁺ levels, or hypercholesterolemia, stimuli. In addition, we illustrate how endothelial TRP channels induce neovascularization in response to synthetic agonists and small molecule drugs. We focus the attention on TRPC1, TRPC3, TRPC4, TRPC5, TRPC6, TRPV1, TRPV4, TRPM2, TRPM4, TRPM7, TRPA1, that were shown to be involved in angiogenesis, arteriogenesis and vasculogenesis. Finally, we discuss the role of endothelial TRP channels in aberrant tumor vascularization by focusing on TRPC1, TRPC3, TRPV2, TRPV4, TRPM8, and TRPA1. These observations suggest that endothelial TRP channels represent potential therapeutic targets in multiple disorders featured by abnormal vascularization, including cancer, ischemic disorders, retinal degeneration and neurodegeneration.

Endothelial Ca2+ Signaling, Angiogenesis and Vasculogenesis: just What It Takes to Make a Blood Vessel

It has long been known that endothelial Ca²⁺ signals drive angiogenesis by recruiting multiple Ca²⁺-sensitive decoders in response to pro-angiogenic cues, such as vascular endothelial growth factor, basic fibroblast growth factor, stromal derived factor-1α and angiopoietins. Recently, it was shown that intracellular Ca²⁺ signaling also drives vasculogenesis by stimulation proliferation, tube formation and neovessel formation in endothelial progenitor cells. Herein, we survey how growth factors, chemokines and angiogenic modulators use endothelial Ca²⁺ signaling to regulate angiogenesis and vasculogenesis. The endothelial Ca²⁺ response to pro-angiogenic cues may adopt different waveforms, ranging from Ca²⁺ transients or biphasic Ca²⁺ signals to repetitive Ca²⁺ oscillations, and is mainly driven by endogenous Ca²⁺ release through inositol-1,4,5-trisphosphate receptors and by store-operated Ca²⁺ entry through Orai1 channels. Lysosomal Ca²⁺ release through nicotinic acid adenine dinucleotide phosphate-gated two-pore channels is, however, emerging as a crucial pro-angiogenic pathway, which sustains intracellular Ca²⁺ mobilization. Understanding how endothelial Ca²⁺ signaling regulates angiogenesis and vasculogenesis could shed light on alternative strategies to induce therapeutic angiogenesis or interfere with the aberrant vascularization featuring cancer and intraocular disorders.

The vesicular transfer of CLIC1 from glioblastoma to microvascular endothelial cells requires TRPM7

Chloride intracellular channel 1 (CLIC1) is highly expressed and secreted by human glioblastoma cells and cell lines such as U87, initiating cell migration and tumor growth. Here, we examined whether CLIC1 could be transferred to human primary microvascular endothelial cells (HMEC). We previously reported that the oncogenic microRNA, miR-5096, increased the release of extracellular vesicles (EVs) by which it increased its own transfer from U87 to surrounding cells. Thus, we also examined its effect on the CLIC1 transfer. In homotypic cultures, miR-5096 did not increase the expression of CLIC1 in U87 nor in HMEC. However, the endothelial CLIC1 level increased after exposure to EVs released by U87, and even more by miR-5096-loaded U87. The EVs-transferred CLIC1 was active in HMEC, promoting endothelial sprouting in matrigel. Cell exposure to EVs induced cytosolic Ca²⁺ spikes which were dependent on the transient receptor potential melastatin member 7 (TRPM7). TRPM7 silencing prevented Ca²⁺ spikes and the subsequent CLIC1 delivery into HMEC. Our data suggest that the vesicular transfer of CLIC1 between cells requires TRMP7 expression in recipient endothelial cells. How the vesicular transfer of CLIC1 is modulated in cancer therapy is a future challenge.

TRPM7 channels play a role in high glucose-induced endoplasmic reticulum stress and neuronal cell apoptosis

High-glucose (HG) levels and hyperglycemia associated with diabetes are known to cause neuronal damage. The detailed molecular mechanisms, however, remain to be elucidated. Here, we investigated the role of transient receptor potential melastatin 7 (TRPM7) channels in HG-mediated endoplasmic reticulum stress (ERS) and injury of NS20Y neuronal cells. The cells were incubated in the absence or presence of HG for 48 h. We found that mRNA and protein levels of TRPM7 and of ERS-associated proteins, such as C/EBP homologous protein (CHOP), 78-kDa glucose-regulated protein (GRP78), and inducible nitric-oxide synthase (iNOS), increased in HG-treated cells, along with significantly increased TRPM7-associated currents in these cells. Similar results were obtained in cerebral cortical tissue from an insulin-deficiency model of diabetic mice. Moreover, HG treatment of cells activated ERS-associated proapoptotic caspase activity and induced cellular injury. Interestingly, a NOS inhibitor, l-NAME, suppressed the HG-induced increase of TRPM7 expression and cellular injury. siRNA-mediated TRPM7 knockdown or chemical inhibition of TRPM7 activity also suppressed HG-induced ERS and decreased cleaved caspase-12/caspase-3 levels and cell injury. Of note, TRPM7 overexpression increased ERS and cell injury independently of its kinase activity. Taken together, our findings suggest that TRPM7 channel activities play a key role in HG-associated ERS and cytotoxicity through an apoptosis-inducing signaling cascade involving HG, iNOS, TRPM7, ERS proteins, and caspases.

Exosomes Secreted by Adipose-Derived Stem Cells Contribute to Angiogenesis of Brain Microvascular Endothelial Cells Following Oxygen-Glucose Deprivation In Vitro Through MicroRNA-181b/TRPM7 Axis

Adipose-derived stem cells (ADSCs) have been demonstrated to promote cerebral vascular remodeling processes after stroke. However, the exact molecular mechanism by which ADSCs exert protective roles in ischemic stroke is still poorly understood. In this study, we identified the role of exosomal microRNA-181b-5p (181b-Exos) in regulating post-stroke angiogenesis. The results of migration assay and capillary network formation assay showed that exosomes secreted by ADSCs (ADSCs-Exos) promoted the mobility and angiogenesis of brain microvascular endothelial cells (BMECs) after oxygen-glucose deprivation (OGD). Quantitative real-time polymerase chain reaction (qRT-PCR) showed that microRNA-212-5p (miR-212-5p) and miR-181b-5p were upregulated in BMECs subjected to the brain extract of the middle cerebral artery occlusion rats. The migration distance and tube length were increased in BMECs cultured with 181b-Exos. Furthermore, we identified that transient receptor potential melastatin 7 (TRPM7) was a direct target of miR-181b-5p. TRPM7 mRNA and protein levels were declined in BMECs cultured with 181b-Exos, but not in BMECs cultured with 212-Exos. Overexpression of TRPM7 reversed the effects of 181b-Exos on migration and tube formation of BMECs. In addition, 181b-Exos upregulated the protein expression of hypoxia-inducible factor 1α and vascular endothelial cell growth factor, and downregulated the protein expression of tissue inhibitor of metalloproteinase 3. The regulatory effect of 181b-Exos was attenuated by overexpressing TRPM7. Altogether, ADSCs-Exos promote the angiogenesis of BMECs after OGD via miR-181b-5p/TRPM7 axis, suggesting that ADSCs-Exos may represent a novel therapeutic approach for stroke recovery.

Magnesium Reduces Blood-Brain Barrier Permeability and Regulates Amyloid-β Transcytosis

Poor Mg status is a risk factor for Alzheimer's disease (AD), and the underlying mechanisms remain elusive. Here, we provided the first evidence that elevated Mg levels significantly reduced the blood-brain barrier (BBB) permeability and regulated its function in vitro. Transient receptor potential melastatin 7 (TRPM7) and magnesium transporter subtype 1 (MagT1) were two major cellular receptors mediating entry of extracellular Mg²⁺ into the cells. Elevated Mg levels also induced an accelerated clearance of amyloid-β peptide (Aβ) from the brain to the blood side via BBB transcytosis through low-density lipoprotein receptor-related protein (LRP) and phosphatidylinositol binding clathrin assembly protein (PICALM), while reduced the influx of Aβ from the blood to the brain side involving receptor for advanced glycation end products (RAGE) and caveolae. Mg enhanced BBB barrier properties and overall expression of LRP1 and PICALM whereas reduced that of RAGE and caveolin-1. Apical-to-basolateral and vice versa steady-state Aβ flux achieved an equilibrium of 18 and 0.27 fmol/min/cm², respectively, about 30 min after the initial addition of physiological levels of free Aβ. Knockdown of caveolin-1 or disruption of caveolae membrane microdomains reduced RAGE-mediated influx significantly, but not LRP1-mediated efflux of Aβ. Stimulating endothelial cells with vascular endothelial growth factor (VEGF) enhanced caveolin-1 phosphorylation and RAGE expression. Co-immunoprecipitation demonstrated that RAGE, but not LRP1, was physically associated with caveolin-1. Thus, Mg can reduce BBB permeability and promote BBB clearance of Aβ from the brain by increasing the expression of LRP1 and PICALM while reducing the level of RAGE and caveolin-1.

Proteoglycans, ion channels and cell-matrix adhesion

Cell surface proteoglycans comprise a transmembrane or membrane-associated core protein to which one or more glycosaminoglycan chains are covalently attached. They are ubiquitous receptors on nearly all animal cell surfaces. In mammals, the cell surface proteoglycans include the six glypicans, CD44, NG2 (CSPG4), neuropilin-1 and four syndecans. A single syndecan is present in invertebrates such as nematodes and insects. Uniquely, syndecans are receptors for many classes of proteins that can bind to the heparan sulphate chains present on syndecan core proteins. These range from cytokines, chemokines, growth factors and morphogens to enzymes and extracellular matrix (ECM) glycoproteins and collagens. Extracellular interactions with other receptors, such as some integrins, are mediated by the core protein. This places syndecans at the nexus of many cellular responses to extracellular cues in development, maintenance, repair and disease. The cytoplasmic domains of syndecans, while having no intrinsic kinase activity, can nevertheless signal through binding proteins. All syndecans appear to be connected to the actin cytoskeleton and can therefore contribute to cell adhesion, notably to the ECM and migration. Recent data now suggest that syndecans can regulate stretch-activated ion channels. The structure and function of the syndecans and the ion channels are reviewed here, along with an analysis of ion channel functions in cell-matrix adhesion. This area sheds new light on the syndecans, not least since evidence suggests that this is an evolutionarily conserved relationship that is also potentially important in the progression of some common diseases where syndecans are implicated.

Molecular mechanisms of tumour invasion: regulation by calcium signals

Intracellular calcium (Ca²⁺ ) signals are key regulators of multiple cellular functions, both healthy and physiopathological. It is therefore unsurprising that several cancers present a strong Ca²⁺ homeostasis deregulation. Among the various hallmarks of cancer disease, a particular role is played by metastasis, which has a critical impact on cancer patients' outcome. Importantly, Ca²⁺ signalling has been reported to control multiple aspects of the adaptive metastatic cancer cell behaviour, including epithelial-mesenchymal transition, cell migration, local invasion and induction of angiogenesis (see Abstract Figure). In this context Ca²⁺ signalling is considered to be a substantial intracellular tool that regulates the dynamicity and complexity of the metastatic cascade. In the present study we review the spatial and temporal organization of Ca²⁺ fluxes, as well as the molecular mechanisms involved in metastasis, analysing the key steps which regulate initial tumour spread.

Lipids as central modulators of sensory TRP channels

The transient receptor potential (TRP) ion channel family is involved in a diversity of physiological processes including sensory and homeostatic functions, as well as muscle contraction and vasomotor control. Their dysfunction contributes to the etiology of several diseases, being validated as therapeutic targets. These ion channels may be activated by physical or chemical stimuli and their function is highly influenced by signaling molecules activated by extracellular signals. Notably, as integral membrane proteins, lipid molecules also modulate their membrane location and function either by direct interaction with the channel structure or by modulating the physico-chemical properties of the cellular membrane. This lipid-based modulatory effect is being considered an alternative and promising approach to regulate TRP channel dysfunction in diseases. Here, we review the current progress in this exciting field highlighting a complex channel regulation by a large diversity of lipid molecules and suggesting some diseases that may benefit from a membrane lipid therapy. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Dietary Magnesium and Kidney Function Decline: The Healthy Aging in Neighborhoods of Diversity across the Life Span Study

BACKGROUND

Prior studies suggest that certain aspects of the diet related to magnesium intake, such as dietary acid load, protein intake and dietary patterns rich in fruits and vegetables, may impact kidney disease risk. We hypothesized that lower dietary magnesium intake would be prospectively associated with more rapid kidney function decline.

METHODS

Among participants in the Healthy Aging in Neighborhoods of Diversity across the Life Span study with estimated glomerular filtration rate (eGFR) ≥60 ml/min/1.73 m2 at baseline (2004-2009), dietary magnesium intake was calculated from two 24-hour dietary recalls. Rapid decline was defined as ≥3% eGFR decline per year.

RESULTS

Median (25th-75th percentile) dietary magnesium intake was 116 (96-356) mg/1,000 kcal. Among 1,252 participants, those with lower dietary magnesium intake were younger, and were more likely to be African-American men. A total of 177 participants (14.1%) experienced rapid eGFR decline over a median follow-up of 5 years. Lower dietary magnesium intake was significantly associated with a greater odds of rapid eGFR decline (OR for tertile 1 vs. 3: 2.02, 95% CI 1.05-3.86, p value for trend across tertiles = 0.02) in analyses adjusted for sociodemographics (age, sex, race, education level, health insurance status, poverty status), kidney disease risk factors (smoking status, diabetes, hemoglobin A1c, hypertension, body mass index), baseline eGFR and dietary factors (total energy intake; diet quality; dietary intake of fiber, sodium, calcium, potassium and phosphorus).

CONCLUSIONS

In this urban population, lower dietary magnesium intake was independently associated with greater odds of rapid kidney function decline.

Upregulation of TRPM7 augments cell proliferation and interleukin-8 release in airway smooth muscle cells of rats exposed to cigarette smoke

Proliferation and synthetic function (i.e. the capacity to release numerous chemokines and cytokines) of airway smooth muscle cells (ASMCs) are important in airway remodeling induced by cigarette smoke exposure. However, the molecular mechanism has not been clarified. Transient receptor potential cation channel subfamily M member 7 (TRPM7) is expressed ubiquitously and is crucial for the cellular physiological function of many cell types. The present study aimed to detect the expression of TRPM7 in ASMCs from smoke‑exposed rats and determine the importance of TRPM7 in proliferation and interleukin‑8 (IL‑8) release. ASMCs were isolated and cultured from smoke‑exposed rats. Expression levels of TRPM7 were determined by reverse transcription‑polymerase chain reaction, western blot analysis and immunofluorescence. TRPM7 was silenced with TRPM7‑short hairpin RNA lentivirus vector. DNA synthesis, cell number and IL‑8 release of ASMCs induced by cigarette smoke extract (CSE) and tumor necrosis factor‑α (TNF‑α) were assessed using [3H]-thymidine incorporation assay, hemocytometer and enzyme‑linked immunosorbent assay, respectively. It was determined that mRNA and protein expression levels of TRPM7 were increased in ASMCs from smoke‑exposed rats. Stimulation with CSE or TNF‑α elevated DNA synthesis, cell number and IL‑8 release were more marked in ASMCs from smoke‑exposed rats. Silencing of TRPM7 reduced DNA synthesis, cell number and IL‑8 release induced by CSE or TNF‑α in ASMCs from smoke-exposed rats. In conclusion, expression of TRPM7 increased significantly in ASMCs from smoke‑exposed rats and the upregulation of TRPM7 led to augmented cell proliferation and IL-8 release in ASMCs from rats exposed to cigarette smoke.

Reciprocal regulation of actin cytoskeleton remodelling and cell migration by Ca2+ and Zn2+: role of TRPM2 channels

Cell migration is a fundamental feature of tumour metastasis and angiogenesis. It is regulated by a variety of signalling molecules including H2O2 and Ca(2+) Here, we asked whether the H2O2-sensitive transient receptor potential melastatin 2 (TRPM2) Ca(2+) channel serves as a molecular link between H2O2 and Ca(2+) H2O2-mediated activation of TRPM2 channels induced filopodia formation, loss of actin stress fibres and disassembly of focal adhesions, leading to increased migration of HeLa and prostate cancer (PC)-3 cells. Activation of TRPM2 channels, however, caused intracellular release of not only Ca(2+) but also of Zn(2+) Intriguingly, elevation of intracellular Zn(2+) faithfully reproduced all of the effects of H2O2, whereas Ca(2+) showed opposite effects. Interestingly, H2O2 caused increased trafficking of Zn(2+)-enriched lysosomes to the leading edge of migrating cells, presumably to impart polarisation of Zn(2+) location. Thus, our results indicate that a reciprocal interplay between Ca(2+) and Zn(2+) regulates actin remodelling and cell migration; they call for a revision of the current notion that implicates an exclusive role for Ca(2+) in cell migration.

MicroRNA-134 Contributes to Glucose-Induced Endothelial Cell Dysfunction and This Effect Can Be Reversed by Far-Infrared Irradiation

Diabetes mellitus (DM) is a metabolic disease that is increasing worldwide. Furthermore, it is associated with the deregulation of vascular-related functions, which can develop into major complications among DM patients. Endothelial colony forming cells (ECFCs) have the potential to bring about medical repairs because of their post-natal angiogenic activities; however, such activities are impaired by high glucose- (HG) and the DM-associated conditions. Far-infrared radiation (FIR) transfers energy as heat that is perceived by the thermoreceptors in human skin. Several studies have revealed that FIR improves vascular endothelial functioning and boost angiogenesis. FIR has been used as anti-inflammatory therapy and as a clinical treatment for peripheral circulation improvement. In addition to vascular repair, there is increasing evidence to show that FIR can be applied to a variety of diseases, including cardiovascular disorders, hypertension and arthritis. Yet mechanism of action of FIR and the biomarkers that indicate FIR effects remain unclear. MicroRNA-134 (miR-134-5p) was identified by small RNA sequencing as being increased in high glucose (HG) treated dfECFCs (HG-dfECFCs). Highly expressed miR-134 was also validated in dmECFCs by RT-qPCR and it is associated with impaired angiogenic activities of ECFCs. The functioning of ECFCs is improved by FIR treatment and this occurs via a reduction in the level of miR-134 and an increase in the NRIP1 transcript, a direct target of miR-134. Using a mouse ischemic hindlimb model, the recovery of impaired blood flow in the presence of HG-dfECFCs was improved by FIR pretreatment and this enhanced functionality was decreased when there was miR-134 overexpression in the FIR pretreated HG-dfECFCs. In conclusion, our results reveal that the deregulation of miR-134 is involved in angiogenic defects found in DM patients. FIR treatment improves the angiogenic activity of HG-dfECFCs and dmECFCs and FIR has potential as a treatment for DM. Detection of miR-134 expression in FIR-treated ECFCs should help us to explore further the effectiveness of FIR therapy.

Asparaginase treatment side-effects may be due to genes with homopolymeric Asn codons (Review-Hypothesis)

The present treatment of childhood T-cell leukemias involves the systemic administration of prokary-otic L-asparaginase (ASNase), which depletes plasma Asparagine (Asn) and inhibits protein synthesis. The mechanism of therapeutic action of ASNase is poorly understood, as are the etiologies of the side-effects incurred by treatment. Protein expression from genes bearing Asn homopolymeric coding regions (N-hCR) may be particularly susceptible to Asn level fluctuation. In mammals, N-hCR are rare, short and conserved. In humans, misfunctions of genes encoding N-hCR are associated with a cluster of disorders that mimic ASNase therapy side-effects which include impaired glycemic control, dislipidemia, pancreatitis, compromised vascular integrity, and neurological dysfunction. This paper proposes that dysregulation of Asn homeostasis, potentially even by ASNase produced by the microbiome, may contribute to several clinically important syndromes by altering expression of N-hCR bearing genes. By altering amino acid abundance and modulating ribosome translocation rates at codon repeats, the microbiomic environment may contribute to genome decoding and to shaping the proteome. We suggest that impaired translation at poly Asn codons elevates diabetes risk and severity.

Peloruside A is a microtubule-stabilizing agent with exceptional anti-migratory properties in human endothelial cells

Peloruside A is a novel antimitotic drug originally isolated from the marine sponge Mycale hentschieli. Previous studies showed that peloruside A stabilizes microtubules by binding to a site on tubulin distinct from paclitaxel, another microtubule stabilizing drug. Peloruside A blocks mitosis, but little is known about the effects on other cellular activities. Here we report that peloruside A is the most potent microtubule inhibitor yet tested for its ability to block endothelial cell migration. Quantitative analysis indicated that it inhibits microtubule dynamics and endothelial cell migration at 1/200(th) of the concentration needed to inhibit cell division (the cytotoxic concentration), indicating that it could potentially have a large margin of safety when used to specifically target angiogenesis. By comparison, paclitaxel, a well-known cancer therapeutic drug, suppresses cell migration at 1/13(th) of its cytotoxic concentration; and vinblastine suppresses cell migration at just slightly below its cytotoxic antimitotic concentration. Thus, different microtubule targeted drugs have varying relative potencies for inhibition of cell migration versus cell division. The results suggest that peloruside A may be an especially useful agent for anti-angiogenesis therapy and point to the likelihood that other antimitotic drugs might be found with an even larger potential margin of safety.

Xyloketal B suppresses glioblastoma cell proliferation and migration in vitro through inhibiting TRPM7-regulated PI3K/Akt and MEK/ERK signaling pathways

Glioblastoma, the most common and aggressive type of brain tumors, has devastatingly proliferative and invasive characteristics. The need for finding a novel and specific drug target is urgent as the current approaches have limited therapeutic effects in treating glioblastoma. Xyloketal B is a marine compound obtained from mangrove fungus Xylaria sp. (No. 2508) from the South China Sea, and has displayed antioxidant activity and protective effects on endothelial and neuronal oxidative injuries. In this study, we used a glioblastoma U251 cell line to (1) explore the effects of xyloketal B on cell viability, proliferation, and migration; and (2) investigate the underlying molecular mechanisms and signaling pathways. MTT assay, colony formation, wound healing, western blot, and patch clamp techniques were employed. We found that xyloketal B reduced cell viability, proliferation, and migration of U251 cells. In addition, xyloketal B decreased p-Akt and p-ERK1/2 protein expressions. Furthermore, xyloketal B blocked TRPM7 currents in HEK-293 cells overexpressing TRPM7. These effects were confirmed by using a TRPM7 inhibitor, carvacrol, in a parallel experiment. Our findings indicate that TRPM7-regulated PI3K/Akt and MEK/ERK signaling is involved in anti-proliferation and migration effects of xyloketal B on U251 cells, providing in vitro evidence for the marine compound xyloketal B to be a potential drug for treating glioblastoma.