Search Results (120)

The mineralocorticoid receptor (MR), traditionally associated with renal function, has also been identified in various extrarenal tissues, including the heart, brain, and dorsal root ganglion (DRG) neurons in rodents. Previous studies suggest a role for the MR in modulating peripheral nociception, with MR activation in rat DRG neurons by its endogenous ligand, aldosterone. This study aimed to determine whether MR, its protective enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), its endogenous ligand aldosterone, and the aldosterone-synthesizing enzyme CYP11B2 are expressed in human DRG neurons and whether they colocalize with key pain-associated signaling molecules as potential targets for genomic regulation. To this end, we performed mRNA transcript profiling and immunofluorescence confocal microscopy on human and rat DRG tissues. We detected mRNA transcripts for MR, 11β-HSD2, and CYP11B2 in human DRG, alongside transcripts for key thermosensitive and nociceptive markers such as TRPV1, the TTX-resistant sodium channel Nav1.8, and the neuropeptides CGRP and substance P (Tac1). Immunofluorescence analysis revealed substantial colocalization of MR with 11β-HSD2 and CGRP, a marker of unmyelinated C-fibers and thinly myelinated Aδ-fibers, in human DRG. MR immunoreactivity was primarily restricted to small- and medium-diameter neurons, with lower expression in large neurons (>70 µm). Similarly, aldosterone colocalized with CYP11B2 and MR with nociceptive markers including TRPV1, Nav1.8, and TrkA in human DRG. Importantly, functional studies demonstrated that prolonged intrathecal inhibition of aldosterone synthesis within rat DRG neurons, using an aldosterone synthase inhibitor significantly downregulated pain-associated molecules and led to sustained attenuation of inflammation-induced hyperalgesia. Together, these findings identify a conserved peripheral MR signaling axis in humans and highlight its potential as a novel target for pain modulation therapies. Full article

Oral squamous cell carcinoma (OSCC) remains a significant global health challenge, representing 90% of oral malignancies. Despite therapeutic advances, patient outcomes remain poor, highlighting the need for novel prognostic biomarkers and treatment targets. We investigated the expression patterns of NTRK genes and their corresponding proteins (TrkA, TrkB, and TrkC) in OSCC, analyzing their relationships with clinical outcomes and potential as therapeutic targets. We examined 93 OSCC tissue samples using immunohistochemistry and quantitative real-time PCR. Protein expression was quantified using the H-score method. We analyzed correlations between Trk expression, clinicopathological parameters, and 2-year survival rates using chi-square tests, Mann–Whitney U tests, and Kaplan–Meier survival analysis. TrkA showed near-universal expression (97.8%—91 patients) in OSCC samples, with high expression levels significantly correlating with lower tumor grade (p = 0.014) and improved 2-year survival (p = 0.011). While TrkB and TrkC were expressed in 65.5% and 84.9% of cases, respectively, neither showed significant associations with clinical parameters. NTRK2 and NTRK3 mRNA levels demonstrated a strong positive correlation (R = 0.64, p = 0.002), suggesting coordinated regulation. Our findings establish TrkA as a promising positive prognostic marker in OSCC, warranting investigation as a therapeutic target. The strong correlation between NTRK2 and NTRK3 expression suggests shared regulatory mechanisms in OSCC pathogenesis. Further studies with larger cohorts and longer follow-up periods are needed to validate these findings and explore their therapeutic implications. Full article

Traumatic brain injury (TBI) leads to persistent pro-inflammatory microglial activation implicated in neurodegeneration. Idebenone, a coenzyme Q10 analogue that interacts with both mitochondria and the tyrosine kinase adaptor SHC1, inhibits aspects of microglial activation in vitro. We used the NanoString Neuropathology Panel to test the hypothesis that idebenone post-treatment mitigates TBI-pathology-associated acute gene expression changes by moderating the pro-inflammatory microglial response to injury. Controlled cortical impact to adult male mice increased the microglial activation signature in the peri-lesional cortex at 24 h post-TBI. Unexpectedly, several microglial signature genes upregulated by TBI were further increased by post-injury idebenone administration. However, idebenone significantly attenuated TBI-mediated perturbations to gene expression associated with behavior, particularly in the gene ontology–biological process (GO:BP) pathways “ephrin receptor signaling” and “dopamine metabolic process”. Gene co-expression analysis correlated levels of microglial complement component 1q (C1q) and the neurotrophin receptor gene Ntrk1 to large (>3-fold) TBI-induced decreases in dopamine receptor genes Drd1 and Drd2 that were mitigated by idebenone treatment. Bioinformatics analysis identified SUZ12 as a candidate transcriptional regulator of idebenone-modified gene expression changes. Overall, the results suggest that idebenone may enhance TBI-induced microglial number within the first 24 h of TBI and identify ephrin-A and dopamine signaling as novel idebenone targets. Full article

Thiol-containing drugs may interact with a region of tropomyosin receptor kinase A (TrkA), potentially inhibiting its activation by nerve growth factor (NGF). This action has been linked to potential analgesic activities. Here, we describe the ability of erdosteine, a thiolic compound classified as a mucolytic agent, to bind to the TrkA receptor sequence in silico and its in vitro effects on TrkA activation induced by NGF in cultured human neuroblastoma cells. Our results show that erdosteine and its metabolite, Met-1, bind to the TrkA receptor pocket, involving the primary TrkA residues Glu331, Arg347, His298, and His297. Furthermore, Met-1 has the ability to reduce the disulfide bridge between Cys300 and Cys345 of TrkA. In vitro measurement of TrkA autophosphorylation following NGF activation confirmed that erdosteine and Met-1 interfere with NGF-induced TrkA activation, leading to a consequent loss of the molecular recognition and spatial reorganization necessary for the induction of the autophosphorylation process. This effect was inhibited by low millimolar concentrations of the two compounds, reaching a maximal inhibition (around 40%) after 24 h of exposure to 1 mM erdosteine, and then plateauing. These findings suggest that erdosteine can act as a TrkA antagonist, thus indicating that this drug may have potential as an analgesic via a novel non-opioid mechanism of action operating through NGF signaling inhibition at the level of TrkA. Full article

Current antiviral treatments often target specific viral components, which can lead to the rapid emergence of drug-resistant mutants. Targeting host signaling pathways, including their associated cellular factors, that are important for virus replication is a novel approach toward the development of next-generation antivirals to overcome drug resistance. Various cellular receptor tyrosine kinases (RTKs) have previously been shown to play important roles in mediating viral replication including coronaviruses. In this study, we examined the roles of RTKs in SARS-CoV-2 replication in two cell lines, A549-ACE2 (human lung epithelial cells) and Vero-E6 (African Green Monkey kidney cell), via chemical inhibitors. We showed that the HER2 inhibitor Lapatinib significantly reduced viral replication in both cell lines, the TrkA inhibitor GW441756 was effective only in A549-ACE2 cells, while the EGFR inhibitor Gefitinib had little effect in either cell line. Lapatinib and GW441756 exhibited a high therapeutic index (CC₅₀/EC₅₀ > 10) in A549-ACE2 cells. Time-of-addition experiments indicated that Lapatinib may inhibit the early entry step, whereas GW441756 can affect post-entry steps of the viral life cycle. These findings suggest the important roles of HER2 and TrkA signaling in SARS-CoV-2 infection in human lung epithelial cells and support further investigation of RTK inhibitors as potential COVID-19 treatments. Full article

Nerve growth factor (NGF) is one of the essential components that have been implicated in the pathophysiology of neuropathic pain, a condition that develops following nerve injury or dysfunction. This neurotrophin is critical for the survival and maintenance of sensory neurons, and its dysregulation has been implicated in the sensitization of pain pathways. NGF interacts with its receptor TrkA and p75^NTR to activate intracellular signaling pathways associated with nociception and the emergence of allodynia and hyperalgesia. Therapeutic approaches employing neutralizing antibodies and molecule inhibitors have been highly effective at both preclinical and clinical levels, hence giving hope again for the use of NGF as an important biomarker and therapeutic target in the management of neuropathic pain. By exploiting the unique properties of NGF and its interactions within the nervous system, new therapeutic modalities could be designed to enhance efficacy while minimizing side effects. In conclusion, taking advantage of the multifaceted dynamics of NGF could provide effective pain management therapies to finally respond to the unmet needs of patients experiencing neuropathic pain. Full article

Background: Alternative NTRK1/TrkA splicing resulting in TrkAIII expression, originally discovered in advanced-stage metastatic neuroblastomas, is also pronounced in prostate, medullary thyroid, glioblastoma multiforme, MCPyV-positive Merkel cell, cutaneous malignant melanoma, and pituitary neuroendocrine tumor subsets. In tumor models, TrkAIII exhibits actionable oncogenic activity equivalent to the TrkT3-fused oncogene, and in tumor cell lines, alternative TrkAIII splicing is promoted by hypoxia, nutrient deprivation, endoplasmic reticulum stress, and SV40 large T antigen, implicating tumor microenvironmental conditions and oncogenic polyoma viruses in tumor-associated TrkAIII expression. Collectively, these observations characterize TrkAIII as a potentially frequent, actionable oncogenic alternative to TrkA gene fusion in different tumor types. Currently, therapeutic approval for efficacious Trk inhibitors is restricted to Trk-fused gene positive tumors and not for tumors potentially driven by TrkAIII. Methods: With the therapeutically relevant aim of improving the identification of tumors potentially driven by TrkAIII, we have developed a TaqMan-based qRT-PCR assay for evaluating TrkAIII expression in tumor cDNAs. Results: This assay, validated using gel-purified fs-TrkA and TrkAIII cDNAs alone and in complex cDNA mixtures, employs primers and probes designed from fs-TrkA and TrkAIII sequences, with specificity provided by a TaqMan probe spanning the TrkAIII exon 5–8 splice junction. It is highly efficient, reproducible, and specific and can detect as few as 10 TrkAIII copies in complex RNAs extracted from either fresh or FFPE tumor tissues. Conclusions: Inclusion of this assay into precision oncology algorithms, when paired with fs-TrkA qRT-PCR and TrkA immune histochemistry, will make it easier to identify patients with therapy-resistant, advanced-stage metastatic Trk-fused gene-negative tumors potentially driven by TrkAIII, for whom approval of third-line effective Trk inhibitors could be extended. Full article

Angiogenesis plays a critical role in osteosarcoma (OS) growth and metastasis. While nerve growth factor (NGF) is implicated in cancer progression, its role in OS angiogenesis remains unclear. This study explored NGF’s effects on angiogenesis and the underlying molecular mechanisms. Analysis of GEO (GSE16088) data identified five angiogenesis markers significantly upregulated in OS tissues. In vitro experiments demonstrated that NGF enhanced HUVEC tube formation by upregulating platelet-derived growth factor C (PDGF-C) expression and suppressing microRNA-29b-3p (miR-29b-3p). The results of tube formation assays confirmed that NGF stimulation significantly increased the angiogenic capacity of MG63/NGF cells compared to MG63 cells. Furthermore, larotrectinib, a TrkA inhibitor, effectively reduced the migration and invasion abilities of MG63/NGF cells in a dose-dependent manner. These findings suggest that the NGF-TrkA axis promotes PDGF-C-mediated angiogenesis by inhibiting miR-29b-3p signaling. Larotrectinib could serve as a potential therapeutic agent targeting NGF-mediated angiogenesis in OS, offering a promising avenue for treatment. Full article

Background: The increasing prevalence of drug resistance in cancer therapy underscores the urgent need for novel therapeutic approaches. Dual enzyme inhibitors, targeting critical kinases such as CDK2 and TRKA, represent a promising strategy. The goal of this investigation was to design, synthesize, and evaluate a set of pyrazolo[1,5-a]pyrimidine derivatives for their dual inhibition potential toward CDK2 and TRKA kinases, along with their potential antiproliferative against cancer cell lines. Methods: A set of pyrazolo[1,5-a]pyrimidine derivatives (6a–t, 11a–g, and 12) was synthesized and subjected to in vitro enzymatic assays to determine their inhibitory activity against CDK2 and TRKA kinases. Selected compounds were further assessed for antiproliferative effects across the set of 60 cell lines from the NCI, representing various human cancer types. Additionally, simulations of molecular docking were conducted to explore the modes of binding for the whole active compounds and compare them with known inhibitors. Results: Compounds 6t and 6s exhibited potent dual inhibitory activity, showing an IC₅₀ = 0.09 µM and 0.23 µM against CDK2, and 0.45 µM against TRKA, respectively. These results were comparable to reference inhibitors ribociclib (CDK2, IC₅₀ = 0.07 µM) and larotrectinib (TRKA, IC₅₀ = 0.07 µM). Among the studied derivatives, compound 6n displayed a notable broad-spectrum anticancer activity, achieving a mean growth inhibition (GI%) of 43.9% across 56 cell lines. Molecular docking simulations revealed that the synthesized compounds adopt modes of binding similar to those of the lead inhibitors. Conclusions: In this study, prepared pyrazolo[1,5-a]pyrimidine derivatives demonstrated significant potential as dual CDK2/TRKA inhibitors, and showed potent anticancer activity toward diverse cancer cell lines. These findings highlight their potential as key compounds for the design of novel anticancer therapeutics. Full article

We determined the relative expression levels of the receptors TrkA, TrkB, TrkC, and p75^NTR and ligands BDNF, NT-3, NGF, and NT-4 with RNAseq analysis on fetal human inner ear samples, located TrkB and TrkC proteins, and quantified BDNF with in situ hybridization on histological sections between gestational weeks (GW) 9 to 19. Spiral ganglion neurons (SGNs) and satellite glia appear to be the main source of BDNF and synthesis peaks twice at GW10 and GW15–GW17. Tonotopical gradients of BDNF revert between GW8 and GW15 and follow a maturation and innervation density gradient in SGNs. NT-3/TrkC follows the same time course of expression as BDNF/TrkB. Immunostaining reveals that TrkB signaling may act mainly through satellite glia, Schwann cells, and supporting cells of Kölliker’s organ, while TrkC signaling targets SGNs and pillar cells in humans. The NT-4 expression is upregulated when BDNF/NT-3 is downregulated, suggesting a balancing effect for sustained TrkB activation during fetal development. The mission of neurotrophins expects nerve fiber guidance, innervation, maturation, and trophic effects. The data shall serve to provide a better understanding of neurotrophic regulation and action in human development and to assess the transferability of neurotrophic regenerative therapy from animal models. Full article

Lactoferrin (LF) is a multifunctional protein abundant in breast milk that modulates the functions of neural stem cells. Recent studies have demonstrated the efficacy of bovine LF (bLF) in mitigating behavioral changes; however, the molecular mechanisms on the nervous system have not yet been elucidated. The presented study aimed to characterize the molecular mechanisms of bLF on nerve extension in PC12 cells. PC12 cells were treated with 0.01–1000 µg/mL of bLF, and cell viability was determined using the cell counting kit-8 assay after treatment for 24 h. Morphometric evaluation was performed after 24 or 72 h of treatment with 50 ng/mL nerve growth factor (NGF) or 100–500 µg/mL bLF. The molecular mechanisms were investigated using Western blotting and real-time quantitative PCR. Cell viability was significantly decreased after treatment with 600–1000 µg/mL bLF for 24 h compared with the control group. Morphometric evaluation revealed neurite outgrowth after 72 h of NGF treatment, with a significant increase in neurite outgrowth after treatment with 250 µg/mL bLF. The phosphorylated p44/42 expression ratio peaked at 5 min and persisted for up to 10 min. Quantitative real-time PCR revealed a significant decrease in MAP2 expression. Our findings suggested that bLF enhanced PC12 cell neurite outgrowth to a similar extent as NGF. These effects are thought to be mediated via the TrkA receptor and activated by the phosphorylated ERK signaling pathway. Therefore, this study demonstrates that bLF promotes neurite outgrowth via a pathway similar to that of NGF. Full article

Tropomyosin receptor kinases (Trks) are transmembrane receptor tyrosine kinases named TrkA, TrkB, and TrkC and encoded by the NTRK1, NTRK2, and NTRK3 genes, respectively. These kinases have attracted significant attention and represent a promising therapeutic target for solid tumor treatment due to their vital role in cellular signaling pathways. First-generation TRK inhibitors, i.e., Larotrectinib sulfate and Entrectinib, received clinical approval in 2018 and 2019, respectively. However, the use of these inhibitors was significantly limited because of the development of resistance due to mutations. Fortunately, the second-generation Trk inhibitor Repotrectinib (TPX-0005) was approved by the FDA in November 2023, while Selitrectinib (Loxo-195) has provided an effective solution to this issue. Another macrocycle-based analog, along with many other TRK inhibitors, is currently in clinical trials. Two of the three marketed drugs for NTRK fusion cancers feature a pyrazolo[1,5-a] pyrimidine nucleus, prompting medicinal chemists to develop numerous novel pyrazolopyrimidine-based molecules to enhance clinical applications. This article focuses on a comprehensive review of chronological synthetic developments and the structure–activity relationships (SAR) of pyrazolo[1,5-a]pyrimidine derivatives as Trk inhibitors. This article will also provide comprehensive knowledge and future directions to the researchers working in the field of medicinal chemistry by facilitating the structural modification of pyrazolo [1,5-a]pyrimidine derivatives to synthesize more effective novel chemotherapeutics as TRK inhibitors. Full article

Glutamate functions as the major excitatory neurotransmitter for primary sensory neurons and has a crucial role in sensitizing peripheral nociceptor terminals producing sensitization. Glutaminase (GLS) is the synthetic enzyme that converts glutamine to glutamate. GLS-immunoreactivity (-ir) and enzyme activity are elevated in dorsal root ganglion (DRG) neuronal cell bodies during chronic peripheral inflammation, but the mechanism for this GLS elevation is yet to be fully characterized. It has been well established that, after nerve growth factor (NGF) binds to its high-affinity receptor tropomyosin receptor kinase A (TrkA), a retrograde signaling endosome is formed. This endosome contains the late endosomal marker Rab7GTPase and is retrogradely transported via axons to the cell soma located in the DRG. This complex is responsible for regulating the transcription of several critical nociceptive genes. Here, we show that this retrograde NGF signaling mediates the expression of GLS in DRG neurons during the process of peripheral inflammation. We disrupted the normal NGF/TrkA signaling in adjuvant-induced arthritic (AIA) Sprague Dawley rats by the pharmacological inhibition of TrkA or blockade of Rab7GTPase, which significantly attenuated the expression of GLS in DRG cell bodies. The results indicate that NGF/TrkA signaling is crucial for the production of glutamate and has a vital role in the development of neurogenic inflammation. In addition, our pain behavioral data suggest that Rab7GTPase can be a potential target for attenuating peripheral inflammatory pain. Full article

Binge alcohol consumption during adolescence can produce lasting deficits in learning and memory while also increasing the susceptibility to substance use disorders. The adolescent intermittent ethanol (AIE) rodent model mimics human adolescent binge drinking and has identified the nucleus basalis magnocellularis (NbM) as a key site of pathology. The NbM is a critical regulator of prefrontal cortical (PFC) cholinergic function and attention. The cholinergic phenotype is controlled pro/mature neurotrophin receptor activation. We sought to determine if p75NTR activity contributes to the loss of cholinergic phenotype in AIE by using a p75NTR modulator (LM11A-31) to inhibit prodegenerative signaling during ethanol exposure. Male and female rats underwent 5 g/kg ethanol (AIE) or water (CON) exposure following 2-day-on 2-day-off cycles from postnatal day 25–57. A subset of these groups also received a protective dose of LM11A-31 (50 mg/kg) during adolescence. Rats were trained on a sustained attention task (SAT) and behaviorally relevant acetylcholine (ACh) activity was recorded in the PFC with a fluorescent indicator (AChGRAB 3.0). AIE produced learning deficits on the SAT, which were spared with LM11A-31. In addition, PFC ACh activity was blunted by AIE, which LM11A-31 corrected. Investigation of NbM ChAT+ and TrkA+ neuronal expression found that AIE led to a reduction of ChAT+TrkA+ neurons, which again LM11A-31 protected. Taken together, these findings demonstrate the p75NTR activity during AIE treatment is a key regulator of cholinergic degeneration. Full article