NSAIDs Naproxen, Ibuprofen, Salicylate, and Aspirin Inhibit TRPM7 Channels by Cytosolic Acidification

Prebiotics as modulators of colonic calcium and magnesium uptake

Ca2+ and Mg2+ are essential nutrients, and deficiency can cause serious health problems. Thus, lack of Ca2+ and Mg2+ can lead to osteoporosis, with incidence rising both in absolute and age-specific terms, while Mg2+ deficiency is associated with type II diabetes. Prevention via vitamin D or estrogen is controversial, and the bioavailability of Ca2+ and Mg2+ from supplements is significantly lower than that from milk products. Problems are likely to increase as populations age and the number of people on vegan diets surges. Developing new therapeutic strategies requires a better understanding of the molecular mechanisms involved in absorption by intestinal epithelia. The vitamin-D dependent, active pathway for the uptake of Ca2+ from the upper small intestine involving TRPV6 is highly efficient but only accounts for about 20% of total uptake. Instead, most Ca2+ uptake is thought to occur via passive paracellular diffusion across the ileum, although sufficiently high luminal concentrations are difficult to achieve.. Interestingly, colon and caecum also have a considerable capacity for the active absorption of Ca2+ and Mg2+, the molecular mechanisms of which are unclear. Intriguingly, stimulating fermentation by prebiotics enhances colonic absorption, which can rise from ~10% to ~30% of the total. Notably, fermentation releases protons, which inhibits channels highly selective for Ca2+ and Mg2+ (TRPV6 and TRPM6/TRPM7). Conversely, the non-selective cation channel TRPV3 is stimulated by both intracellular acidification and by numerous herbal compounds. Spicy, fiber-rich food, as traditionally consumed in many cultures, might enhance the uptake of Ca2+ and Mg2+ via this pathway.

Anesthetic- and Analgesic-Related Drugs Modulating Both Voltage-Gated Na+ and TRP Channels

Nociceptive information is transmitted by action potentials (APs) through primary afferent neurons from the periphery to the central nervous system. Voltage-gated Na+ channels are involved in this AP production, while transient receptor potential (TRP) channels, which are non-selective cation channels, are involved in receiving and transmitting nociceptive stimuli in the peripheral and central terminals of the primary afferent neurons. Peripheral terminal TRP vanilloid-1 (TRPV1), ankylin-1 (TRPA1) and melastatin-8 (TRPM8) activation produces APs, while central terminal TRP activation enhances the spontaneous release of L-glutamate from the terminal to spinal cord and brain stem lamina II neurons that play a pivotal role in modulating nociceptive transmission. There is much evidence demonstrating that chemical compounds involved in Na+ channel (or nerve AP conduction) inhibition modify TRP channel functions. Among these compounds are local anesthetics, anti-epileptics, α2-adrenoceptor agonists, antidepressants (all of which are used as analgesic adjuvants), general anesthetics, opioids, non-steroidal anti-inflammatory drugs and plant-derived compounds, many of which are involved in antinociception. This review mentions the modulation of Na+ channels and TRP channels including TRPV1, TRPA1 and TRPM8, both of which modulations are produced by pain-related compounds.

Fentanyl induces analgesic effect through miR-381-3p/TRPM7 when combined with bupivacaine in subarachnoid injection

Fentanyl combined with bupivacaine in subarachnoid anesthesia exerts a strong synergistic analgesic effect, extending the duration of analgesia. However, the mechanism of enhanced analgesic effect of fentanyl remains elusive. The present study investigated the potential mechanism of the analgesic effect of fentanyl when combined with bupivacaine. The subarachnoid injection (SI) rat model was employed, and SI of fentanyl or/and bupivacaine was used to investigate their analgesic effect. Dorsal root ganglion (DRG)' RNA sequencing (RNA-Seq) and bioinformatics analysis were performed to evaluate the downstream mechanisms of MicroRNAs (miRNAs). Further validation tests included RT-PCR, Western blot, and immunofluorescence. A single SI of fentanyl or bupivacaine decreased the positive responses to stimulation when used alone or in combination. RNA-seq results revealed that miR-381-3p played a role in the fentanyl-driven promotion of analgesia. Bioinformatics analysis and dual-luciferase reporter identified TRPM7 as a direct downstream target gene of miR-381-3p. In vitro, overexpression of miR-381-3p could further block fentanyl-induced expression of TRPM7, p-ERK1/2, CGRP, and SP. In addition, antagomir-381-3p reversed the inhibitory effect of fentanyl on the expression of TRPM7, p-ERK1/2, CGRP, and SP, in vivo; however, TRPM7 siRNA rescued the effect of antagomir-381-3p. In conclusion, fentanyl inhibits p-ERK by targeting TRPM7 via miR-381-3p, lowering the production of CGRP and SP, and ultimately inducing analgesic effects.

Use of tetraethylammonium (TEA) and Tris loading for blocking TRPM7 channels in intact cells

Tetraethylammonium (TEA), a quaternary ammonium compound, is a well-known blocker of potassium channels belonging to various subfamilies, such as KV1-3, KCa1, 2 and prokaryotic KcsA. In many cases, TEA acts from the extracellular side by open pore blockade. TEA can also block transient receptor potential (TRP) cation channels, such as TRPM7, in a voltage-dependent manner. In human T lymphocytes, intracellular (cytosolic) TEA and its analog TMA (tetramethylammonium) inhibit TRPM7 channel currents in the outward but not inward direction. By contrast, intracellular Mg2+, protons and polyamines inhibit both outward and inward current components equally. Likewise, the majority of available pharmacological tools inhibit TRPM7 channels in a voltage-independent manner. Since TRPM7 is a steeply outwardly rectifying conductance, voltage-dependent blockers can be useful for studying the cellular functions of this channel. TRPM7 protein is endogenously expressed in diverse cell lines, including HEK, HeLa, CHO, RBL and Jurkat. Using patch-clamp electrophysiology, we found that incubating HEK293 and Jurkat T cells overnight in the presence of 20 mM TEA-Cl, resulted in the nearly complete blockade of whole-cell TRPM7 outward current, measured at break-in. By contrast, the inward current was unchanged in TEA-loaded cells. The blockade was fully reversible after washout of intracellular solution in whole-cell but not in perforated-patch recording configurations. Overnight incubation with 20 mM TMA-Cl resulted in a more modest blockade of the outward TRPM7 current. Internal 129 mM TMA and TEA eliminated most of the outward current. TEA uptake in transfected HEK293 cells led to blockade of recombinant murine TRPM7 and the Mg2+ and pH insensitive Ser1107Arg variant. Unexpectedly, Tris-HCl, a widely used pH buffer, could similarly be loaded into Jurkat and HEK cells, and preferentially blocked outward TRPM7 currents. 20 mM and 129 mM Tris in the internal solution blocked TRPM7 current in outward but not inward direction. Voltage-dependent channel blockade by TEA, TMA and Tris loading will be useful for studying the properties and functions of TRPM7-mediated ion transport in intact cells.

Concentration-dependent mechanism of the binding behavior of ibuprofen to the cell membrane: A molecular dynamic simulation study

Ibuprofen is a commonly used drug for treating headaches, pain, and fever. The lipid bilayer is the primary and most important interface for drugs to interact with biological systems. However, the molecular interactions between ibuprofen and the cell membrane are not well understood. Our findings suggest that the interactions between ibuprofen and the bilayer involve multiple steps and depend on the concentration of the drug. At low concentrations of ibuprofen, it can bind to the surface of the lipid bilayer. The electrostatic and vdW energies of IBU-lipid at 0 ns of the simulation were -22.5 ± 3.2 and -5.9 ± 1.2 kj.mol-1 Fig. 2. In the following, the vdW energy of the IBU-lipid was increased by around -134.6 ± 3.7 kj.mol-1 whereas the electrostatic energy of the IBU-lipid was significantly decreased. This binding is facilitated by electrostatic and vdW interactions between ibuprofen and the head group of lipids. In the second step, ibuprofen is inserted into the lipid bilayer and positioned at the interface between the bilayer and the aqueous phase. In high concentrations of ibuprofen, it moved to the central region of the lipid bilayer. At this concentration, the physical and structural properties of the cell membrane change significantly. Results from the radial distribution function analysis indicate that at low concentrations, ibuprofen molecules are situated close to the head groups of phosphate groups. However, at high concentrations of ibuprofen, these molecules move to the inner side of the lipid bilayer. In addition, our findings indicate that at low concentrations of ibuprofen, these molecules did not significantly alter the physical properties of the cell membrane. In contrast, at high concentrations of ibuprofen, the physical parameters of the hydrocarbon tails, such as thickness, fluidity, and order, changed dramatically. APL parameter for POPC membrane increased slightly to 0.60 and 0.63 nm2 in the presence of low and high concentrations of ibuprofen molecules. The three-step interaction between ibuprofen and the lipid bilayer involves several events, such as the movement of ibuprofen molecules towards the central region of the lipid bilayer and the deformation and alteration of the structural and stability properties of the cell membrane. These effects are observed only at high concentrations of ibuprofen. It appears that the side effects of ibuprofen overdose are related to changes in the properties of the cell membrane and, subsequently, the function of membrane-anchored target proteins.

Involvement of TRPM7 Channel on the Induction of Diabetic Neuropathic Pain in Mice: Protective Role of Selenium and Curcumin

Excessive levels of the mitochondrial reactive oxygen radical (mitSOX) and Ca²⁺ influx were found to cause neuropathic pain in patients with diabetes mellitus (DM). Naltriben (NLT) and mitSOX activate the transient receptor (TRP) melastatin 7 (TRPM7) channel, but antioxidants and carvacrol inhibit it. Selenium (Se) and curcumin (CRC) have been thoroughly studied for their modulator effects on streptozotocin (STZ)-induced neuropathic pain, apoptosis, and oxidative stress through the blockage of TRP channels in dorsal root ganglion (DRG) neurons. It has not yet been fully understood how Se and CRC protect against STZ-induced neuropathic pain by modulating TRPM7. Here, we assessed how Se and CRC affected the Ca²⁺ influx, mitSOX-mediated oxidative damage, and apoptosis in the DRGs of mice through modifying TRPM7 activity. Seven groups (control, Se, CRC, STZ, STZ + Se, STZ + CRC, and STZ + Se + CRC) were induced from the 56 male mice. We observed that the STZ-induced stimulation of TRPM7 increased mechanical neuropathic pain (von Frey), thermal neuropathic pain (hot plate), cytosolic Ca²⁺, TRPM7 current density, TRPM7 expression, lipid peroxidation, mitSOX, cytosolic ROS, apoptosis, caspase-3, caspase-8, and caspase-9 concentrations, whereas Se and CRC therapies diminished the alterations. The STZ-mediated decreases of DRG viability, brain glutathione, glutathione peroxidase, vitamin A, and vitamin E concentrations were also upregulated in the treatment groups by the therapies. These findings collectively imply that an imbalance of neuropathic pain, oxidative neurotoxicity, and apoptosis in the mice is caused by the STZ-mediated activation of TRPM7. However, the downregulation of TRPM7 activity caused by the injections of Se and CRC reduced the neurotoxicity and apoptosis.

Microglia activation in central nervous system disorders: A review of recent mechanistic investigations and development efforts

Microglia are the principal resident immune cells in the central nervous system (CNS) and play important roles in the development of CNS disorders. In recent years, there have been significant developments in our understanding of microglia, and we now have greater insight into the temporal and spatial patterns of microglia activation in a variety of CNS disorders, as well as the interactions between microglia and neurons. A variety of signaling pathways have been implicated. However, to date, all published clinical trials have failed to demonstrate efficacy over placebo. This review summarizes the results of recent important studies and attempts to provide a mechanistic view of microglia activation, inflammation, tissue repair, and CNS disorders.

Anti-Inflammatory and Mineralization Effects of an ASP/PLGA-ASP/ACP/PLLA-PLGA Composite Membrane as a Dental Pulp Capping Agent

Dental pulp is essential for the development and long-term preservation of teeth. Dental trauma and caries often lead to pulp inflammation. Vital pulp therapy using dental pulp-capping materials is an approach to preserving the vitality of injured dental pulp. Most pulp-capping materials used in clinics have good biocompatibility to promote mineralization, but their anti-inflammatory effect is weak. Therefore, the failure rate will increase when dental pulp inflammation is severe. The present study developed an amorphous calcium phosphate/poly (L-lactic acid)-poly (lactic-co-glycolic acid) membrane compounded with aspirin (hereafter known as ASP/PLGA-ASP/ACP/PLLA-PLGA). The composite membrane, used as a pulp-capping material, effectively achieved the rapid release of high concentrations of the anti-inflammatory drug aspirin during the early stages as well as the long-term release of low concentrations of aspirin and calcium/phosphorus ions during the later stages, which could repair inflamed dental pulp and promote mineralization. Meanwhile, the composite membrane promoted the proliferation of inflamed dental pulp stem cells, downregulated the expression of inflammatory markers, upregulated the expression of mineralization-related markers, and induced the formation of stronger reparative dentin in the rat pulpitis model. These findings indicate that this material may be suitable for use as a pulp-capping material in clinical applications.

Modulators of TRPM7 and its potential as a drug target for brain tumours

TRPM7 is a non-selective divalent cation channel with an alpha-kinase domain. Corresponding with its broad expression, TRPM7 has a role in a wide range of cell functions, including proliferation, migration, and survival. Growing evidence shows that TRPM7 is also aberrantly expressed in various cancers, including brain cancers. Because ion channels have widespread tissue distribution and result in extensive physiological consequences when dysfunctional, these proteins can be compelling drug targets. In fact, ion channels comprise the third-largest drug target type, following enzymes and receptors. Literature has shown that suppression of TRPM7 results in inhibition of migration, invasion, and proliferation in several human brain tumours. Therefore, TRPM7 presents a potential target for therapeutic brain tumour interventions. This article reviews current literature on TRPM7 as a potential drug target in the context of brain tumours and provides an overview of various selective and non-selective modulators of the channel relevant to pharmacology, oncology, and ion channel function.