Canonical Transient Receptor Potential Research Articles

Cannabidiol inhibits transient receptor potential canonical 4 and modulates excitability of pyramidal neurons in mPFC

Cannabidiol (CBD), a non-psychoactive compound derived from the cannabis plant, has been extensively studied for its potential therapeutic effects on various central nervous system (CNS) disorders, including epilepsy, chronic pain, Parkinson’s disease, and stress-related neuropsychiatric disorders. However, the pharmacological mechanisms of CBD have not been fully elucidated due to the complexity of their targets. In this study, we reported that the transient receptor potential canonical 4 (TRPC4) channel, a calcium-permeable, non-selective cation channel, could be inhibited by CBD. TRPC4 is highly abundant in the central nervous system and plays a critical role in regulating axonal regeneration, neurotransmitter release, and neuronal network activity. Here, we used whole-cell electrophysiology and intracellular calcium measurements to identify the inhibitory effects of CBD on TRPC4, in which CBD was found to inhibit TRPC4 channel with an IC50 value of 1.52 μM TRPC4 channels function as receptor-operated channels (ROC) and could be activated by epinephrine (EP) via G proteins. We show that CBD can inhibit EP-evoked TRPC4 current in vitro and EP-evoked neuronal excitability in the medial prefrontal cortex (mPFC). These results are consistent with the action of TRPC4-specific inhibitor Pico145, suggesting that TRPC4 works as a functional ionotropic receptor of CBD. This study identified TRPC4 as a novel target for CBD in the CNS and suggested that CBD could reduce the pyramidal neuron excitability by inhibiting TRPC4-containing channels in the mPFC.

Abstract 4126333: TRPC6 A404V is a gain-of-function variant associated with doxorubicin-induced cardiotoxicity in patients

Background: Gain-of-function mutations in the canonical transient receptor potential 6 (TRPC6) channel contribute to heart failure (HF) and focal segmental glomerulosclerosis in humans. Our GWAS results indicated that the TRPC6 A404V variant, having a minor allele frequency of 12% in the population, is associated with doxorubicin-induced cardiotoxicity. However, the underlying ionic mechanisms of this variant have not been fully examined. Methods: Combining patch clamp recording, site-directed mutagenesis, and in-silico analysis, we evaluated the TRPC6 A404V variant function. Results: Whole-cell TRPC6 currents were elicited in HEK293 cells using a voltage ramp protocol from -100 mV to +100 mV with a holding potential of -60 mV, 48 hours after transfection with TRPC6 WT or A404V cDNAs. The inward-current densities at -100 mV and the outward-current densities at +100 mV for TRPC6 WT and A404V variant were similar at baseline. However, after exposure to 50 μM 1-oleoyl acetyl-sn-glycerol (OAG, a TRPC6 activator), these current densities were significantly increased by 2.6-fold and 4.5-fold respectively in the WT (n=20 cells), and by 8.4-fold and 8.9-fold respectively in the A404V variant (n=12 cells, p<0.05 vs. WT). The OAG effects were abolished by superfusion with 1 μM BI-749327 (a specific TRPC6 inhibitor). Moreover, a 24-hour treatment with 0.5 μM doxorubicin (DOX) further amplified the effects of OAG, increasing the total inward- and outward-current densities by 7.2-fold and 9.5-fold respectively in TRPC6 WT (n=11 cells), and by 13.9-fold and 14.7-fold respectively in the A404V variant (n=13 cells, p<0.05 vs. WT). In comparison, the OAG effects on TRPC6 WT and A404V channels were not potentiated by treatment with 0.5 μM doxorubicinol (DOXol, a metabolite of DOX) for 24 h (n=10-12 cells, p=N.S.). Molecular docking studies showed that OAG had a lower binding energy (-5.60 kcal/mol) and a smaller apparent equilibrium constant (Kd) of 0.079 mM with the A404V variant, compared to those of -4.49 kcal/mol and 0.511 mM respectively with TTRPC6 WT. Conclusion: TRPC6 A404V is a gain-of-function variant with a higher binding affinity to OAG. Treatment with DOX but not DOXol greatly enhances TRPC6 WT and A404V channel activation by OAG. Thus, cancer patients carrying the TRPC6 A404V variant may be more vulnerable to develop HF upon treatment with anthracycline.

In silico analysis of quercetin and its derivatives as potential TRPC6-targeted treatments for diabetic neuropathy

Background: Diabetic neuropathy is a condition that arises as a complication of diabetes mellitus and often causes pain in patient. Quercetin and its derivatives have antinociceptive activity, making them potential agents for relieving the pain associated with diabetic neuropathy. Objective: This study aims to analyze the interactions between quercetin and its eight derivatives with canonical transient receptor potential channels 6 (TRPC6) as protein target. Method: The TRPC6 structure (PDB ID: 6UZ8) was prepared and validated with redocked to native ligand R0D using Autodock 4.2.6, with the established grid box and grid center settings. The test compounds were then optimized and docked using the same grid box and grid center settings as in the validation process, followed by visualization and analysis of the docking results. Results: The compound with the best affinity for TRPC6 was tamarixetin, with a binding energy value of -3.27 kcal/mol, close to the binding energy value of the native ligand, which was -4.22 kcal/mol. The amino acid residues interacting with tamarixetin at the active site were 702-Asn, 705-Tyr, 706-Val, and 709-Gly. This indicates that tamarixetin and the native ligand bind to the same active site amino acids, resulting in a similar affinity to the native ligand in inhibiting TRPC6. Conclusion: A total of eight quercetin derivatives were predicted to have TRPC6 antagonistic activity against diabetic neuropathy, with tamarixetin exhibiting the highest affinity compared to the other quercetin derivatives.

TRPC3-mediated NFATc1 calcium signaling promotes triple negative breast cancer migration through regulating glypican-6 and focal adhesion.

Canonical transient receptor potential isoform 3 (TRPC3), a calcium-permeable non-selective cation channel, has been reported to be upregulated in breast cancers and a modulator of cell migration. Calcium-sensitive transcription factor NFATc1, which is important for cell migration, was shown to be frequently activated in triple negative breast cancer (TNBC) biopsy tissues. However, whether TRPC3-mediated calcium influx would activate NFATc1 and affect the migration of TNBC cells, and, if yes, the underlying mechanisms involved, remain to be investigated. By immunostaining followed by confocal microscopy, TNBC lines MDA-MB-231 and BT-549 were both found to express TRPC3 on their plasma membrane while ER+ line MCF-7 and HER2+ line SK-BR3 do not. Blockade of TRPC3 by pharmacological inhibitor Pyr3 or stable knockdown of TRPC3 by lentiviral vector both inhibited cell migration as measured by wound healing assay. Importantly, blocking TRPC3 by Pyr3 or knockdown of TRPC3 both caused the translocation of NFATc1 from the nucleus to the cytosol as revealed by confocal microscopy. Interestingly, NFATc1 was found to bind to the promoter of glypican 6 (GPC6) as determined by chromatin immunoprecipitation assay. Consistently, knockdown of TRPC3 decreased the expression of GPC6 as revealed by western blotting. Moreover, long-term knockdown of GPC6 by lentiviral vector also consistently decreased the migration of TNBC cells. Intriguingly, GPC6 proteins physically interact with vinculin in MDA-MB-231 as determined by co-immunoprecipitation. Blockade of TRPC3, knockdown of TRPC3 or knockdown of GPC6 all induced larger, stabilized actin-bound peripheral focal adhesion (FA) formations in TNBC cells as determined by co-staining of actin and vinculin followed by confocal microscopy. These large, stabilized actin-bound peripheral FAs indicated a defective FA turnover, and were reported to be responsible for impairing directed cell migration. Our results suggest that, in TNBC cells, calcium influx through TRPC3 channel positively regulates NFATc1 nuclear translocation and GPC6 expression, which maintains the dynamics of FA turnover and optimal cell migration. Our study reveals a novel TRPC3-NFATc1-GPC6-vinculin signaling cascade in maintaining the migration of TNBC cells.

Canonical Transient Receptor Potential (TRPC) Channels in Cardiovascular Pathology and their Modulators.

Ion channels play a crucial role in various aspects of cardiac function, such as regulating rhythm and contractility. As a result, they serve as key targets for therapeutic interventions in cardiovascular diseases. Cell function is substantially influenced by the concentration of free cytosolic calcium (Ca2+) and the voltage across the plasma membrane. These characteristics are known to be regulated by Ca2+-permeable non-selective cationic channels, although our knowledge of these channels is still inadequate. The transient receptor potential (TRP) superfamily comprises of many non-selective cation channels with diverse Ca2+ permeability. Canonical or classical TRP (TRPC) channels are a subgroup of the TRP superfamily that are expressed ubiquitously in mammalian cells. TRPC channels are multidimensional signalling protein complexes that play essential roles in a variety of physiological and pathological processes in humans, including cancer, neurological disorders, cardiovascular diseases, and others. The objective of this article is to focus on the role that TRPC channels play in the cardiovascular system. The role of TRPC channels will be deeply discussed in cardiovascular pathology. Together, a critical element in developing novel treatments that target TRPC channels is comprehending the molecular mechanisms and regulatory pathways of TRPC channels in related cardiovascular diseases and conditions.

Lubiprostone Improves Distal Segment-Specific Colonic Contractions through TRPC4 Activation Stimulated by EP3 Prostanoid Receptor

Background: Prokinetic agents are effective in increasing gastrointestinal (GI) contractility and alleviating constipation, often caused by slow intestinal motility. Lubiprostone (LUB), known for activating CLC-2 chloride channels, increases the chloride ion concentration in the GI tract, supporting water retention and stool movement. Despite its therapeutic efficacy, the exact mechanisms underlying its pharmacological action are poorly understood. Here, we investigated whether LUB activates the canonical transient receptor potential cation channel type 4 (TRPC4) through stimulation with E-type prostaglandin receptor (EP) type 3. Methods: Using isotonic tension recordings on mouse colon strips, we examined LUB-induced contractility in both proximal and distal colon segments. Quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to determine mRNA levels of EP1-4 receptor subtypes in distal colonic muscular strips and isolated myocytes. The effects of a TRPC4 blocker and EP3 antagonist on LUB-stimulated contractions were also evaluated. Results: LUB showed significant contraction in the distal segment compared to the proximal segment. EP3 receptor mRNA levels were highly expressed in the distal colon tissue, which correlated with the observed enhanced contraction. Furthermore, LUB-induced spontaneous contractions in distal colon muscles were reduced by a TRPC4 blocker or EP3 antagonist, indicating that LUB-stimulated EP3 receptor activation may lead to TRPC4 activation and increased intracellular calcium in colonic smooth muscle. Conclusions: These findings suggest that LUB improves mass movement through indirect activation of the TRPC4 channel in the distal colon. The segment-specific action of prokinetic agents like LUB provides compelling evidence for a personalized approach to symptom management, supporting the defecation reflex.

Two F-18 radiochemistry methods to synthesize a promising transient receptor potential canonical 5 (TRPC5) radioligand

Two F-18 radiochemistry methods to synthesize a promising transient receptor potential canonical 5 (TRPC5) radioligand

Effective calcineurin inhibitor treatment in adult-onset steroid-resistant nephrotic syndrome with a novel splice donor site variant of TRPC6: a case report.

Transient receptor potential canonical 6 (TRPC6) variants, which were initially detected in adult-onset familial focal segmental glomerulosclerosis (FSGS), were also identified in pediatric-onset one. Here, we present a patient with adult-onset steroid-resistant nephrotic syndrome (SRNS) who harbored a likely pathogenic TRPC6 variant and partially responded to calcineurin inhibitors (CNIs). A 44-year-old woman with stable rheumatoid arthritis, systemic lupus erythematosus, and Sjögren's syndrome was presented with nephrotic syndrome. Her renal biopsy results showed minor glomerular abnormalities. Upon admission, she was treated with steroids for around 4weeks, but it was ineffective. After 1-2weeks of cyclosporine A (CyA) administration, urine output increased, renal function improved without a decrease in proteinuria, and she was discharged. Her renal function was maintained for 2months, but after a CyA dose reduction, she was again admitted to the hospital due to relapsing edema, decreased urine output, and worsening renal function. CyA was replaced by tacrolimus (TAC). A second renal biopsy showed nearly the same findings as the first except for tubulointerstitial lesions. After 1-2weeks of TAC administration, urine output increased, and renal function improved. However, urinary protein levels did not decrease as before. After discharge, a whole exome analysis revealed a heterozygous splice donor site variant NM_004621.6;c.2644 + 1G > A in TRPC6. Genetic testing identified a novel splice donor site variant of TRPC6 in a patient with adult-onset SRNS, which prevented unnecessary steroid continuation. The safety and efficacy of CNI in TRPC6 glomerulopathy must be evaluated in future larger studies with longer follow-up.

TRPC4/5 inhibitors: Phase I results and proof of concept studies.

Transient receptor potential canonical (TRPC) ion channels are expressed in areas of the brain responsible for processing emotion and mood and have been implicated in the pathophysiology of internalizing disorders such as major depressive disorder and anxiety disorders. This review outlines the rationale for targeting TRPC ion channels for drug development, with specific focus on TRPC4 and TRPC5. We provide preclinical evidence that the lack of TRPC4 and TRPC5 channels or its pharmacological inhibition attenuate fear and anxiety without impairing other behaviors in mice. We also report on clinical studies of BI 1358894, a small molecule inhibitor of TRPC4/5 ion channels, demonstrating reduced psychological and physiological responses to induced anxiety/panic-like symptoms in healthy volunteers. Furthermore, we highlight an imaging study that investigated the acute effects of BI 1358894 and showed reduced activation in several brain regions involved in emotional processing. We conclude that these findings demonstrate a critical role for TRPC4 and TRPC5 in emotional processing, even though it remains an open question if the biological signatures of TRPC4/5 inhibition reported here translate into clinical efficacy and indicate that a TRPC4/5 inhibitor might provide a more effective treatment of internalizing disorders.

TRPC3/6 Channels Mediate Mechanical Pain Hypersensitivity via Enhancement of Nociceptor Excitability and of Spinal Synaptic Transmission.

Patients with tissue inflammation or injury often experience aberrant mechanical pain hypersensitivity, one of leading symptoms in clinic. Despite this, the molecular mechanisms underlying mechanical distortion are poorly understood. Canonical transient receptor potential (TRPC) channels confer sensitivity to mechanical stimulation. TRPC3 and TRPC6 proteins, coassembling as heterotetrameric channels, are highly expressed in sensory neurons. However, how these channels mediate mechanical pain hypersensitivity has remained elusive. It is shown that in mice and human, TRPC3 and TRPC6 are upregulated in DRG and spinal dorsal horn under pathological states. Double knockout of TRPC3/6 blunts mechanical pain hypersensitivity, largely by decreasing nociceptor hyperexcitability and spinal synaptic potentiation via presynaptic mechanism. In corroboration with this, nociceptor-specific ablation of TRPC3/6 produces comparable pain relief. Mechanistic analysis reveals that upon peripheral inflammation, TRPC3/6 in primary sensory neurons get recruited via released bradykinin acting on B1/B2 receptors, facilitating BDNF secretion from spinal nociceptor terminals, which in turn potentiates synaptic transmission through TRPC3/6 and eventually results in mechanical pain hypersensitivity. Antagonizing TRPC3/6 in DRG relieves mechanical pain hypersensitivity in mice and nociceptor hyperexcitability in human. Thus, TRPC3/6 in nociceptors is crucially involved in pain plasticity and constitutes a promising therapeutic target against mechanical pain hypersensitivity with minor side effects.

Podocyte-Specific Expression of the Stress Response Protein REDD1 is Necessary for Diabetes-induced Podocytopenia.

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease and effective treatment modalities that fully address its molecular etiology are lacking. Prior studies support that the stress response protein REDD1 (Regulated in Development and DNA Damage 1) contributes to the development of diabetic complications. This study investigated a potential role for REDD1 expression in podocytes in diabetes-induced podocyte loss and compromised glomerular filtration. Podocyte-specific REDD1 deletion protected against renal injury, as evidenced by reduced albuminuria, glomerular hypertrophy, and mesangial matrix deposition in streptozotocin (STZ)-induced diabetic mice. Podocyte-specific REDD1 expression was required for diabetes-induced reduction in slit diaphragm (SD) proteins podocin and nephrin. Notably, podocyte-specific REDD1 deletion protected against podocytopenia and preserved glomerular basement membrane and foot process architecture in diabetic mice. In the kidneys of diabetic mice and in human podocyte cultures exposed to hyperglycemic conditions, REDD1 was necessary for increased expression of the transient receptor potential canonical 6 (TRPC6) channel. More specifically, REDD1 promoted NF-κB-dependent transcription of TRPC6, intracellular calcium entry, and cytoskeletal remodeling under hyperglycemic conditions. Overall, the findings provide new insight into the role of podocyte-specific REDD1 expression in renal pathology and support the possibility that therapeutics targeting REDD1 in podocytes could be beneficial for DN.

TRPC3 suppression ameliorates synaptic dysfunctions and memory deficits in Alzheimer's disease.

Transient receptor potential canonical (TRPC) channels are widely expressed in the brain; however, their precise roles in neurodegeneration, such as Alzheimer's disease (AD) remain elusive. Bioinformatic analysis of the published single-cell RNA-seq data collected from AD patient cohorts indicates that the Trpc3 gene is uniquely upregulated in excitatory neurons. TRPC3 expression is also upregulated in post-mortem AD brains, and in both acute and chronic mouse models of AD. Functional screening of TRPC3 antagonists resulted in a lead inhibitor JW-65, which completely rescued Aβ-induced neurotoxicity, impaired synaptic plasticity (e.g., LTP), and learning memory in acute and chronic experimental AD models. In cultured rat hippocampal neurons, we found that treatment with soluble β-amyloid oligomers (AβOs) induces rapid and sustained upregulation of the TRPC3 expression selectively in excitatory neurons. This aberrantly upregulated TRPC3 contributes to AβOs-induced Ca 2+ overload through the calcium entry and store-release mechanisms. The neuroprotective action of JW-65 is primarily mediated via restoring AβOs-impaired Ca 2+ /calmodulin-mediated signaling pathways, including calmodulin kinases CaMKII/IV and calcineurin (CaN). The synaptic protective mechanism via TRPC3 inhibition was further supported by hippocampal RNA-seq data from the symptomatic 5xFAD mice after chronic treatment with JW-65. Overall, these findings not only validate TRPC3 as a novel therapeutic target for treating synaptic dysfunction of AD but most importantly, disclose a distinct role of upregulated TRPC3 in AD pathogenesis in mediating Ca 2+ dyshomeostasis.

Estradiol elicits distinct firing patterns in arcuate nucleus kisspeptin neurons of females through altering ion channel conductances.

Hypothalamic kisspeptin (Kiss1) neurons are vital for pubertal development and reproduction. Arcuate nucleus Kiss1 (Kiss1ARH) neurons are responsible for the pulsatile release of Gonadotropin-releasing Hormone (GnRH). In females, the behavior of Kiss1ARH neurons, expressing Kiss1, Neurokinin B (NKB), and Dynorphin (Dyn), varies throughout the ovarian cycle. Studies indicate that 17β-estradiol (E2) reduces peptide expression but increases Vglut2 mRNA and glutamate neurotransmission in these neurons, suggesting a shift from peptidergic to glutamatergic signaling. To investigate this shift, we combined transcriptomics, electrophysiology, and mathematical modeling. Our results demonstrate that E2 treatment upregulates the mRNA expression of voltage-activated calcium channels, elevating the whole-cell calcium current and that contribute to high-frequency burst firing. Additionally, E2 treatment decreased the mRNA levels of Canonical Transient Receptor Potential (TPRC) 5 and G protein-coupled K+ (GIRK) channels. When TRPC5 channels in Kiss1ARH neurons were deleted using CRISPR, the slow excitatory postsynaptic potential (sEPSP) was eliminated. Our data enabled us to formulate a biophysically realistic mathematical model of the Kiss1ARH neuron, suggesting that E2 modifies ionic conductances in Kiss1ARH neurons, enabling the transition from high frequency synchronous firing through NKB-driven activation of TRPC5 channels to a short bursting mode facilitating glutamate release. In a low E2 milieu, synchronous firing of Kiss1ARH neurons drives pulsatile release of GnRH, while the transition to burst firing with high, preovulatory levels of E2 would facilitate the GnRH surge through its glutamatergic synaptic connection to preoptic Kiss1 neurons.

Functional determinants of lysophospholipid- and voltage-dependent regulation of TRPC5 channel

Lysophosphatidylcholine (LPC) is a bioactive lipid present at high concentrations in inflamed and injured tissues where it contributes to the initiation and maintenance of pain. One of its important molecular effectors is the transient receptor potential canonical 5 (TRPC5), but the explicit mechanism of the activation is unknown. Using electrophysiology, mutagenesis and molecular dynamics simulations, we show that LPC-induced activation of TRPC5 is modulated by xanthine ligands and depolarizing voltage, and involves conserved residues within the lateral fenestration of the pore domain. Replacement of W577 with alanine (W577A) rendered the channel insensitive to strong depolarizing voltage, but LPC still activated this mutant at highly depolarizing potentials. Substitution of G606 located directly opposite position 577 with tryptophan rescued the sensitivity of W577A to depolarization. Molecular simulations showed that depolarization widens the lower gate of the channel and this conformational change is prevented by the W577A mutation or removal of resident lipids. We propose a gating scheme in which depolarizing voltage and lipid-pore helix interactions act together to promote TRPC5 channel opening.

Periphery Pre-S1 and S1 helix nexus for PIP2 at TRPC3 channel

Transient receptor potential canonical 3 (TRPC3) is a calcium-permeable, non-selective cation channel known to be regulated by components of the phospholipase C (PLC)-mediated signaling pathway, such as Ca2+, diacylglycerol (DAG) and phosphatidylinositol 4,5-biphosphate (PI(4,5)P2). However, the molecular gating mechanism by these regulators is not yet fully understood, especially its regulation by PI(4,5)P2, despite the importance of this channel in cardiovascular pathophysiology. Recently, Clarke et al. (2024) have reported that PI(4,5)P2 is a positive modulator for TRPC3 using molecular dynamics simulations and patch-clamp techniques. They have demonstrated a multistep gating mechanism of TRPC3 with the binding of PI(4,5)P2 to the lipid binding site located at the pre-S1/S1 nexus, and the propagation of PI(4,5)P2 sensing to the pore domain via a salt bridge between the TRP helix and the S4–S5 linker.

Role of TRPC6 in apoptosis of skeletal muscle ischemia/reperfusion injury

BackgroundSkeletal muscle ischaemia-reperfusion injury (IRI) is a prevalent condition encountered in clinical practice, characterised by muscular dystrophy. Owing to limited treatment options and poor prognosis, it can lead to movement impairments, tissue damage, and disability. This study aimed to determine and verify the influence of transient receptor potential canonical 6 (TRPC6) on skeletal muscle IRI, and to explore the role of TRPC6 in the occurrence of skeletal muscle IRI and the signal transduction pathways activated by TRPC6 to provide novel insights for the treatment and intervention of skeletal muscle IRI. MethodsIn vivo ischaemia/reperfusion (I/R) and in vitro hypoxia/reoxygenation (H/R) models were established, and data were comprehensively analysed at histopathological, cellular, and molecular levels, along with the evaluation of the exercise capacity in mice. ResultsBy comparing TRPC6 knockout mice with wild-type mice, we found that TRPC6 knockout of TRPC6 could reduced skeletal muscle injury after I/R or H/R, of skeletal muscle, so as therebyto restoringe some exercise capacity inof mice. TRPC6 knockdown can reduced Ca2+ overload in cells, therebyo reducinge apoptosis. In additionAdditionally, we also found that TRPC6 functionsis not only a key ion channel involved in skeletal muscle I/R injury, but also can affects Ca2+ levels and then phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signalling pathway. by knocking downTherefore, knockdown of TRPC6, so as to alleviated the injury inducedcaused by skeletal muscle I/R or and H/R. ConclusionsThese findingsdata indicate that the presence of TRPC6 exacerbatescan aggravate the injury of skeletal muscle injury after I/Rischemia/reperfusion, leading towhich not only causes Ca2+ overload and apoptosis., Additionally, it impairsbut also reduces the self- repair ability of cells by inhibiting the expression of the PI3K/Akt/mTOR signalling pathway. ETo exploringe the function and role of TRPC6 in skeletal muscle maycan presentprovide a novelew approachidea for the treatment of skeletal muscle ischemia/reperfusion injury.

Selective Assembly of TRPC Channels in the Rat Retina during Photoreceptor Degeneration.

Transient receptor potential canonical (TRPC) channels are calcium channels with diverse expression profiles and physiological implications in the retina. Neurons and glial cells of rat retinas with photoreceptor degeneration caused by retinitis pigmentosa (RP) exhibit basal calcium levels that are above those detected in healthy retinas. Inner retinal cells are the last to degenerate and are responsible for maintaining the activity of the visual cortex, even after complete loss of photoreceptors. We considered the possibility that TRPC1 and TRPC5 channels might be associated with both the high calcium levels and the delay in inner retinal degeneration. TRPC1 is known to mediate protective effects in neurodegenerative processes while TRPC5 promotes cell death. In order to comprehend the implications of these channels in RP, the co-localization and subsequent physical interaction between TRPC1 and TRPC5 in healthy retina (Sprague-Dawley rats) and degenerating (P23H-1, a model of RP) retina were detected by immunofluorescence and proximity ligation assays. There was an overlapping signal in the innermost retina of all animals where TRPC1 and TRPC5 physically interacted. This interaction increased significantly as photoreceptor loss progressed. Both channels function as TRPC1/5 heteromers in the healthy and damaged retina, with a marked function of TRPC1 in response to retinal degenerative mechanisms. Furthermore, our findings support that TRPC5 channels also function in partnership with STIM1 in Müller and retinal ganglion cells. These results suggest that an increase in TRPC1/5 heteromers may contribute to the slowing of the degeneration of the inner retina during the outer retinal degeneration.

PAR1-mediated Non-periodical Synchronized Calcium Oscillations in Human Mesangial Cells.

Mesangial cells offer structural support to the glomerular tuft and regulate glomerular capillary flow through their contractile capabilities. These cells undergo phenotypic changes, such as proliferation and mesangial expansion, resulting in abnormal glomerular tuft formation and reduced capillary loops. Such adaptation to the changing environment is commonly associated with various glomerular diseases, including diabetic nephropathy and glomerulonephritis. Thrombin-induced mesangial remodeling was found in diabetic patients, and expression of the corresponding protease-activated receptors (PARs) in the renal mesangium was reported. However, the functional PAR-mediated signaling in mesangial cells was not examined. This study investigated protease-activated mechanisms regulating mesangial cell calcium waves that may play an essential role in the mesangial proliferation or constriction of the arteriolar cells. Our results indicate that coagulation proteases such as thrombin induce synchronized oscillations in cytoplasmic Ca2+ concentration of mesangial cells. The oscillations required PAR1 G-protein coupled receptors-related activation, but not a PAR4, and were further mediated presumably through store-operated calcium entry and transient receptor potential canonical 3 (TRPC3) channel activity. Understanding thrombin signaling pathways and their relation to mesangial cells, contractile or synthetic (proliferative) phenotype may play a role in the development of chronic kidney disease and requires further investigation.

Post-traumatic stress disorder: the role of the amygdala and potential therapeutic interventions - a review.

Post-traumatic stress disorder (PTSD) is a psychiatric disorder triggered by exposure to a life-threatening or sexually violent traumatic event, and is characterized by symptoms involving intrusive re-experiencing, persistent avoidance of associated stimuli, emotional and cognitive disturbances, and hyperarousal for long periods after the trauma has occurred. These debilitating symptoms induce occupational and social impairments that contribute to a significant clinical burden for PTSD patients, and substantial socioeconomic costs, reaching approximately $20,000 dollars per individual with PTSD each year in the US. Despite increased translational research focus in the field of PTSD, the development of novel, effective pharmacotherapies for its treatment remains an important unmet clinical need. In this review, we summarize the evidence implicating dysfunctional activity of the amygdala in the pathophysiology of PTSD. We identify the transient receptor potential canonical (TRPC) ion channels as promising drug targets given their distribution in the amygdala, and evidence from animal studies demonstrating their role in fear response modulation. We discuss the evidence-based pharmacotherapy and psychotherapy treatment approaches for PTSD. In view of the prevalence and economic burden associated with PTSD, further investigation is warranted into novel treatment approaches based on our knowledge of the involvement of brain circuitry and the role of the amygdala in PTSD, as well as the potential added value of combined pharmacotherapy and psychotherapy to better manage PTSD symptoms.

Investigating Contributions of Canonical Transient Receptor Potential Channel 3 to Hippocampal Hyperexcitability and Seizure-Induced Neuronal Cell Death.

Canonical transient receptor potential channel 3 (TRPC3) is the most abundant TRPC channel in the brain and is highly expressed in all subfields of the hippocampus. Previous studies have suggested that TRPC3 channels may be involved in the hyperexcitability of hippocampal pyramidal neurons and seizures. Genetic ablation of TRPC3 channel expression reduced the intensity of pilocarpine-induced status epilepticus (SE). However, the underlying cellular mechanisms remain unexplored and the contribution of TRPC3 channels to SE-induced neurodegeneration is not determined. In this study, we investigated the contribution of TRPC3 channels to the electrophysiological properties of hippocampal pyramidal neurons and hippocampal synaptic plasticity, and the contribution of TRPC3 channels to seizure-induced neuronal cell death. We found that genetic ablation of TRPC3 expression did not alter basic electrophysiological properties of hippocampal pyramidal neurons and had a complex impact on epileptiform bursting in CA3. However, TRPC3 channels contribute significantly to long-term potentiation in CA1 and SE-induced neurodegeneration. Our results provided further support for therapeutic potential of TRPC3 inhibitors and raised new questions that need to be answered by future studies.