Transient Receptor Potential Cation Subfamily Research Articles

Cytotoxicity of allyl isothiocyanate on insulin-producing INS-1E cells.

Allyl isothiocyanate (AITC) is the pungent ingredient of brassica species, used as a food additive and flavoring agent, including condiments such as wasabi, horseradish, and mustard. Currently, there is much evidence that AITC modulates glucose and lipids metabolism. Interestingly, AITC has been shown to improve glycaemia, and insulin action along with the induction of a deepened decline in blood insulin levels in T2DM rats. Therefore, in the present study, we characterized the role of AITC at a wide concentration range (5, 10, 25, 50, 100 μM) in controlling viability, proliferation, apoptosis, mitochondrial condition, mRNA expression of encoding pancreatic and duodenal homeobox 1 (Pdx1), and Ins1, Ins2 genes, and insulin content in INS-1E cells. The INS-1E cell line is a suitable, and well-characterized model to study beta cell functions. We demonstrate that AITC reduced the viability (p≤0.001) (also in the presence of transient receptor potential cation subfamily A member 1 (TRPA1) selective antagonist; HC-030031; p≤0.05), and proliferation of INS-1E cells (p≤0.001). AITC evoked a significant reduction of mitochondrial membrane potential (p≤0.01) and decreased the intracellular level of adenosine triphosphate (ATP) (p≤0.001) without influence on reactive oxygen species (ROS) level. Additionally, AITC inhibited the insulin mRNA expression (p≤0.001) in INS-1E cells along with insulin content (p≤0.05). Mitochondrial dysfunction is proposed to be a significant disruption mechanism of AITC in INS-1E cells, and it was independent of ROS, and the influx of external calcium.

Loss of TRPM8 Exacerbate Herpes Simplex Keratitis Infection in Mice by Promoting the Infiltration of CD11b+ Ly6G+ Cells and Increasing the Viral Load in the Cornea.

To reveal the role of transient receptor potential cation subfamily M member 8 (TRPM8) channels in herpes simplex keratitis (HSK). HSK models were established using TRPM8 knockout (TRPM8-/-) mice and their wild-type (WT) littermates. The infected corneas were graded and harvested to evaluate the mRNA levels of inflammatory factors through quantitative real-time polymerase chain reaction (RT-PCR), as well as the infiltration of inflammatory cells through immunofluorescence staining and flow cytometry. Viral titers were determined by plaque assay and absolute quantitative method. RNA-sequencing was conducted to elucidate the transcriptome of corneal epithelium in response to TRPM8 knockout after infection. The anti-inflammatory effect of TRPM8 agonist menthol was documented via subconjunctival administration. Compared to their wild-type counterparts, TRPM8-deficient mice exhibited exacerbated infection symptoms and thicker corneas in HSK models. Infection in TRPM8-deficient mice resulted in significant lymphocyte infiltration, primarily consisting of Ly6G+ CD11b+ cells. Additionally, TRPM8-deficient mice displayed increased levels of corneal viral titers after infection, along with decreased expression of interferon-stimulated genes (ISGs). Subconjunctival administration of menthol effectively alleviated infection-induced symptoms and Ly6G+ CD11b+ cell infiltration in herpes simplex virus type 1 (HSV-1)-treated mice. TRPM8 promoted host resistance to HSV-1 infection by suppressing the accumulation of Ly6G+ CD11b+ cells and virus replication. These findings suggest that targeting TRPM8 could be valuable for therapeutic interventions against HSV-1 infections.

Drugs acting at TRPM7 channels inhibit seizure-like activity.

Transient receptor potential cation subfamily M7 (TRPM7) channels are ion channels permeable to divalent cations. They are abundantly expressed with particularly high expression in the brain. Previous studies have highlighted the importance of TRPM7 channels in brain diseases such as stroke and traumatic brain injury, yet evidence for a role in seizures and epilepsy is lacking. Here, we show that carvacrol, a food additive that inhibits TRPM7 channels, and waixenicin A, a novel selective and potent TRPM7 inhibitor, completely suppressed seizure-like activity in rodent hippocampal-entorhinal brain slices exposed to pentylenetetrazole or low magnesium. These findings support inhibition of TRPM7 channels as a novel target for antiseizure medications.

Inhibiting the ERK pathway and the TRPM7 ion channel in gastric and bladder cancer cells

Gastric and bladder cancers occur when the cells start to reproduce uncontrollably, starting within the innermost layer of tissue. The transient receptor potential cation subfamily M member 7 (TRPM7) is an ion channel that plays an important role in the survival of both of these cancers. In addition, extracellular regulated kinases (ERKs) contribute to the carcinogenesis of many cancers including gastric cancer. Therefore, the treatments Ginsenoside Rd, NS8593, curcumin, and icariin that have the ability to inhibit TRPM7 and ERK could potentially be used as a treatment for these cancers. We hypothesized that these treatments would decrease proliferation and induce apoptosis by inhibiting TRPM7 and ERK in AGS gastric cancer cells and T24 bladder cancer cells; the data supported the hypothesis. Individually, the overall most effective treatment was NS8593 which reduced the proliferation by 81.1% and increased apoptosis by 38.5% in AGS cells compared to the negative control. Individually, the overall most effective treatment was NS8593 which reduced the proliferation by 88.4% and increased apoptosis by 78.0% in T24 cells compared to the negative control. Using all the treatments in combination was the most effective in reducing proliferation and increasing apoptosis in gastric cancer cells. There was also a correlation between the TRPM7, extracellular regulated kinases (ERKs), proliferation, and apoptosis levels. These results could pose in future more effective treatments for both gastric and cancer on top of other types of cancers that rely on TRPM7 and ERK.

Cardiac TRPV1 afferent signaling promotes arrhythmogenic ventricular remodeling after myocardial infarction.

Chronic sympathoexcitation is implicated in ventricular arrhythmogenesis (VAs) following myocardial infarction (MI), but the critical neural pathways involved are not well understood. Cardiac adrenergic function is partly regulated by sympathetic afferent reflexes, transduced by spinal afferent fibers expressing the transient receptor potential cation subfamily V member 1 (TRPV1) channel. The role of chronic TRPV1 afferent signaling in VAs is not known. We hypothesized that persistent TRPV1 afferent neurotransmission promotes VAs after MI. Using epicardial resiniferatoxin (RTX) to deplete cardiac TRPV1-expressing fibers, we dissected the role of this neural circuit in VAs after chronic MI in a porcine model. We examined the underlying mechanisms using molecular approaches, IHC, in vitro and in vivo cardiac electrophysiology, and simultaneous cardioneural mapping. Epicardial RTX depleted cardiac TRPV1 afferent fibers and abolished functional responses to TRPV1 agonists. Ventricular tachycardia/fibrillation (VT/VF) was readily inducible in MI subjects by programmed electrical stimulation or cesium chloride administration; however, TRPV1 afferent depletion prevented VT/VF induced by either method. Mechanistically, TRPV1 afferent depletion did not alter cardiomyocyte action potentials and calcium transients, the expression of ion channels, or calcium handling proteins. However, it attenuated fibrosis and mitigated electrical instability in the scar border zone. In vivo recordings of cardiovascular-related stellate ganglion neurons (SGNs) revealed that MI enhances SGN function and disrupts integrated neural processing. Depleting TRPV1 afferents normalized these processes. Taken together, these data indicate that, after MI, TRPV1 afferent-induced adrenergic dysfunction promotes fibrosis and adverse cardiac remodeling, and it worsens border zone electrical heterogeneity, resulting in electrically unstable ventricular myocardium. We propose targeting TRPV1-expressing afferent to reduce VT/VF following MI.

Bi-directional modulation of food habit expression by the endocannabinoid system.

The compulsive, habitual behaviors that have been observed in individuals diagnosed with substance use disorders may be due to disruptions in the neural circuits that mediate goal-directed actions. The endocannabinoid system has been shown to play a critical role in habit learning, but the role of this neuromodulatory system in habit expression is unclear. Here, we investigated the role of the endocannabinoid system in established habitual actions using contingency degradation in male C57BL/6 mice. We found that administration of the endocannabinoid transport inhibitor AM404 reduced habitual responding for food and that antagonism of cannabinoid receptor type 1 (CB1), but not transient receptor potential cation subfamily V (TRPV1), receptors produced a similar reduction in habitual responding. Moreover, pharmacological stimulation of CB1 receptors increased habitual responding for food. Co-administration of an enzyme inhibitor that selectively increases the endocannabinoid 2-arachidonoyl glycerol (2-AG) with AM404 partially restored habitual responding for food. Together, these findings demonstrate an important role for the endocannabinoid system in the expression of habits and provide novel insights into potential pharmacological strategies for reducing habitual behaviors in mental disorders.

Carvacrol after status epilepticus (SE) prevents recurrent SE, early seizures, cell death, and cognitive decline.

Carvacrol is a naturally occurring monoterpenic phenol that has been suggested to have an action at transient receptor potential cation subfamily M7 (TRPM7) channels, γ-aminobutyric acid (GABAA receptors, and sodium channels, and has been shown to be antiinflammatory. Carvacrol is neuroprotective in models of cerebral ischemia in vivo and in vitro, probably through its action at TRPM7 channels. We therefore aimed to determine the effect of carvacrol on status epilepticus (SE), chronic epilepsy, cell death, and post-SE cognitive decline. We performed long-term, continuous wireless electroencephalography (EEG) monitoring in vivo in rats who underwent perforant path stimulation (PPS) to induce SE and were then randomized to treatment with carvacrol or saline. We also evaluated TRPM7 receptor expression and quantified seizure-induced cell death. The alternating T-maze paradigm was used to assess memory function. Immunostaining showed that TRPM7 channels are widely expressed in neurons within the hippocampus. We found that carvacrol inhibited recurrent SE and early seizures in vivo, but had no detectable effect in the hippocampus on paired-pulse inhibition or the fiber volley, indicating that it was not acting through sodium channel inhibition or GABA receptors. Although the development and severity of chronic epilepsy were not altered by carvacrol, cognitive decline was significantly improved in animals treated with carvacrol. In keeping with preserved memory functions in animals treated with carvacrol, carvacrol had a protective effect against SE-induced cell death in CA1 and hilus, the hippocampal regions most affected by cell loss in the PPS epilepsy model. Carvacrol, a naturally occurring inhibitor of TRPM7 channels, is a novel, promising treatment to prevent early recurrence of SE, SE-related neuronal damage, and cognitive decline.