Search Results (418)

Background and Objectives: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a progressive liver disorder associated with metabolic risk factors such as obesity, type 2 diabetes, and cardiovascular disease. If left untreated, the accumulation of excess hepatic fat can lead to inflammation, fibrosis, cirrhosis, hepatocellular carcinoma, and ultimately liver failure. Capsaicin (CAP), the primary pungent compound in chili peppers, has previously been shown to prevent weight gain in high-fat diet (HFD)-induced obesity models. In this study, we investigated the potential of dietary CAP to prevent HFD-induced MASLD. Methods: C57BL/6 mice were fed an HFD (60% kcal from fat) with or without 0.01% CAP supplementation for 26 weeks. We evaluated CAP’s effects on hepatic fat accumulation, inflammation, and mitochondrial function to determine its role in preventing MASLD. Results: CAP acts as a potent and selective agonist of the transient receptor potential vanilloid 1 (TRPV1) channel. We confirmed TRPV1 expression in the liver and demonstrated that CAP activates hepatic TRPV1, thereby preventing steatosis, improving insulin sensitivity, reducing inflammation, and enhancing fatty acid oxidation. These beneficial effects were observed in wild-type but not in TRPV1 knockout mice. Mechanistically, CAP-induced TRPV1 activation promotes calcium influx and activates AMPK, which leads to SIRT1-dependent upregulation of PPARα and PGC-1α, enhancing mitochondrial biogenesis and lipid metabolism. Conclusions: Our findings suggest that dietary CAP prevents MASLD through TRPV1 activation. TRPV1 signaling represents a promising therapeutic target for the prevention and management of MASLD in individuals with metabolic disorders. Full article

Chronic visceral pain, a significant contributor to morbidity in the United States, affects millions and results in substantial economic costs. Despite its impact, the mechanisms underlying disorders of gut–brain interaction (DGBIs), such as irritable bowel syndrome (IBS), remain poorly understood. Visceral hypersensitivity, a hallmark of chronic visceral pain, involves an enhanced pain response in internal organs to normal stimuli. Various factors like inflammation, intestinal hyperpermeability, and epigenetic modifications influence its presentation. Emerging evidence suggests that persistent colonic stimuli, disrupted gut barriers, and altered non-coding RNA (ncRNA) expression contribute to the pathophysiology of visceral pain. Additionally, cross-sensitization of afferent pathways shared by pelvic organs underpins the overlap of chronic pelvic pain disorders, such as interstitial cystitis and IBS. Central sensitization and viscerosomatic convergence further exacerbate pain, with evidence showing IBS patients exhibit hypersensitivity to both visceral and somatic stimuli. The molecular mechanisms of visceral pain involve critical mediators such as cytokines, prostaglandins, and neuropeptides, alongside ion channels like transient receptor potential vanilloid 1 (TRPV1) and acid-sensing ion channels (ASICs). These molecular insights indicate potential therapeutic targets and highlight the possible use of TRPV1 antagonists and ASIC inhibitors to mitigate visceral pain. This review explores the neurophysiological pathways of visceral pain, focusing on peripheral and central sensitization mechanisms, to advance the development of targeted treatments for chronic pain syndromes, particularly IBS and related disorders. Full article

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

Affinin (spilanthol) is the main bioactive alkylamide present in Heliopsis longipes roots, exerting antinociceptive and anti-inflammatory effects that involve the activation of TRP channels. Previous studies indicated that affinin reduces the LPS-induced increase in pro-inflammatory cytokine production in murine macrophages. However, no studies have evaluated whether affinin produces antinociceptive, anti-inflammatory, and behavioral effects in experimental animals treated with LPS, nor has the mechanism of action involved in these pharmacological effects been established. The present study evaluated whether affinin induces hypothermia, catalepsy, hypolocomotion, and analgesia and, moreover, whether the analgesia involves the activation of the CB1 cannabinoid receptor and TRPV1 and TRPA1 channels. Subsequently, the anti-inflammatory activity and behavioral effects induced by affinin (20 mg/kg) in mice were evaluated via LPS (2.5 mg/kg)-induced hypothermia. The results of the experiments indicate that the analgesic effect of affinin involves the activation of the CB1 cannabinoid receptors and the TRPV1 and TRPA1 channels. Additionally, affinin reduced the severity of LPS-induced hypothermia and attenuated the increase in TNF-α and IL-6 levels in serum. The results obtained demonstrate that affinin induces antinociceptive, anti-hypothermic, and anti-inflammatory activities, which involve the CB1 receptor and the TRPV1 and TRPA1 channels and the suppression of pro-inflammatory cytokines. Full article

Background: Cyclophosphamide (CP) chemotherapy is commonly associated with various side effects. The development of an effective therapy capable of counteracting these effects is of great interest. Objectives: We evaluated the effects of a novel polyherbal formulation (PHF) on CP cytotoxicity in TM3 cells and fictive ejaculation in rats, and determined its possible mechanism. Methods: The phytochemical analysis of PHF was determined by GC-MS. Various oxidative stress-related parameters (DPPH, ABTS⁺, CUPRAC, FRAP, MMP, and DCF-DA) and the cytotoxicity (hemolysis and HET-CAM) of PHF were evaluated. Its effect on fictive ejaculation was tested by recording the electromyographic activities of bulbospongiosus muscles, and the involvement of TRPV1/TRPM2 channels was investigated using their specific agonists and antagonists. Results: We found that PHF contained various phytocompounds. PHF prevented CP-induced oxidative stress in TM3 cells, probably due to its strong antioxidant potential. For instance, PHF inhibited apoptosis, lipid peroxidation, and ROS generation. Furthermore, the activities of capsaicin (CAP) and cumene hydroperoxide (CHPx) were significantly lowered by PHF, indicating TRPV1 and TRPM2 inhibition. In the in vivo study conducted in spinal male rats, the number of contractions of the bulbospongiosus muscles was significantly (p < 0.001) lowered in the PHF + DOPA (1.54 ± 0.3) and PHF + CAP (2.43 ± 0.74) groups, compared with the DOPA (8.75 ± 0.71) and CAP (7.41 ± 1.01) groups, respectively. Additionally, PHF delayed the pro-ejaculatory effects of dopamine (by 17.6%) and capsaicin (by 32.69%). The in silico study revealed a strong binding affinity between the selected PHF phytocompounds and the active pockets of TRPV1 and TRPM2. HET-CAM and hemolysis assays revealed no harmful effects of PHF. Conclusions: PHF prevented CP cytotoxicity in TM3 cells and delayed the pro-ejaculatory effects of dopamine and capsaicin in spinal rats through dopamine and TRPV1 inhibition. PHF could be a potential candidate for the management of CP chemotherapy-related disorders, such as premature ejaculation, in particular. Full article

NGF plays important roles in ocular surface homeostasis and different pathological conditions. One effect includes promoting conjunctival epithelial cell differentiation and mucin secretion. This study characterizes the individual roles of TRPV1 and TRPM8 channel activity in mediating the effects of NGF on intracellular Ca²⁺ regulation and its alteration of regulatory cell volume responses to anisosmotic challenges in human conjunctival epithelial cells (IOBA-NHC). With fura-2/AM-loaded cells, the effects of 40 µM capsaicin and 20 µM AMG 9810 on Ca²⁺ regulation confirm functional TRPV1 expression. TRPM8 expression is evident since 500 µM menthol and 20 µM AMTB have opposing effects on [Ca²⁺]_i. AMG 9810 and AMTB (both 20 µM) suppress the responses to NGF (100 ng/mL). With calcein/AM-loaded cells, the effects of these mediators are evaluated on apparent cell volume responses induced by an anisosmotic challenge. NGF decreases the apparent cell volume that AMG 9810 suppresses, whereas AMTB (both 20 µM) augments this response. Therefore, NGF interacts with TRPV1 and TRPM8 to induce opposing effects on cell volume regulatory behavior. These opposing effects suggest that the signaling pathways and effectors that mediate responses to TRPV1 and TRPM8 activation are not the same. Full article

Nociceptors respond to noxious stimuli and transmit pain signals to the central nervous system. In the cornea, the nociceptors located in the most external layer provide a myriad of sensation modalities. Damage to these corneal nerve fibers can induce neuropathic pain. In response, corneal nerves become sensitized to previously non-noxious stimuli. Assessing corneal pain origin is a complex ophthalmic challenge due to variations in its causes and manifestations. Current FDA-approved therapies for corneal nociceptive pain, such as acetaminophen and NSAIDs, provide only broad-acting relief with unwanted side effects, highlighting the need for precision medicine for corneal nociceptive pain. A few targeted treatments, including perfluorohexyloctane (F6H8) eye drops and Optive Plus (TRPV1 antagonist), are FDA-approved, while others are in preclinical development. Treatments that target signaling pathways related to neurotrophic factors, such as nerve growth factors and ion channels, such as the transient receptor potential (TRP) family or tropomyosin receptor kinase A, may provide a potential combinatory therapeutic approach. This review describes the roles of nociceptors in corneal pain. In addition, it evaluates molecules within nociceptor signaling pathways for their potential to serve as targets for efficient therapeutic strategies for corneal nociceptive pain aimed at modulating neurotrophic factors and nociceptive channel sensitivity. Full article

The presence and function of the opioidergic system in sensory dorsal root ganglia (DRG) was demonstrated in various animal models of pain. To endorse recent functional and transcriptional evidence of opioid receptors in human DRG, this study compared morphological and transcriptional evidence in human and rat DRG using immunofluorescence confocal microscopy and mRNA transcript analysis. Specifically, it examined the neuronal expression of mu (MOR), delta (DOR), and kappa (KOR) opioid receptors, opioid peptide precursors (POMC, PENK, and PDYN), and key pain-signaling molecules. The results demonstrate abundant immunoreactivity in human DRG for key pain transduction receptors, including the thermosensitive ion channels TRPV1, TRPV4 and TRPA1, mechanosensitive PIEZO1 and PIEZO2, and the nociceptive-specific Nav1.8. They colocalized with calcitonin gene-related peptide (CGRP), a marker for peptidergic sensory neurons. Within this same subpopulation, we identified MOR, DOR, and KOR, while their ligand precursors were less abundant. Notably, the mRNA transcripts of MOR and PENK in human DRG were highest among the opioid-related genes; however, they were considerably lower than those of key pain-signaling molecules. These findings were corroborated by functional evidence in demonstrating the fentanyl-induced inhibition of voltage-gated calcium currents in rat DRG, which was antagonized by naloxone. The immunohistochemical and transcriptional demonstration of opioid receptors and their endogenous ligands in both human and rat DRG support recent electrophysiologic and in situ hybridization evidence in human DRG and confirms their potential as analgesic targets. This peripherally targeted approach has the advantage of mitigating central opioid-related side effects, endorsing the potential of future translational pain research from rodent models to humans. Full article

Excessive exposure to ultraviolet B (UVB) radiation can lead to skin damage, such as erythema and swelling. Echinacoside is a key effective ingredient of medicinal plant Cistanche deserticola commonly used for therapies and treatments for anti-aging and irradiation-related skin diseases. However, the molecular mechanism underlying the action of echinacoside remains unclear. Here, we report that echinacoside ameliorates UVB-induced skin damage by directly acting on the Ca²⁺-permeable and thermosensitive transient receptor potential vanilloid 3 (TRPV3) channel. Topical application of echinacoside efficaciously suppresses skin lesions induced by UVB radiation in wild-type mice but has no additional benefit in Trpv3 knockout mice. In whole-cell patch clamp recordings, echinacoside selectively inhibits TRPV3 channel currents induced by 2-aminoethoxydiphenyl borate in a concentration-dependent manner with an IC₅₀ value of 21.94 ± 1.28 μM. The single-channel patch clamp results show that echinacoside significantly reduces the open probability and open frequency without significantly altering TRPV3 channel unitary conductance. Molecular docking and site-specific mutagenesis indicate that residue T636 on the p-loop and residue T665 on the S6 segment of TRPV3 are critical for echinacoside binding to TRPV3. Taken together, our findings provide a molecular basis for further studies as use of natural echinacoside in irradiation-related skin care therapy, thus establishing a significant role of the TRPV3 channel in acute skin injury. Full article

Neurogenesis is considered the most robust form of plasticity in the adult brain. To better decipher this process, we evaluated the potential crosstalk of Kisspeptin and Endocannabinoid Systems (KPS and ECS, respectively) on hippocampal neurogenesis. Male adolescent rats were exposed to kisspeptin-10 (KP10) and the endocannabinoid anandamide (AEA) administered alone or in combination with the type 1 cannabinoid receptor (CB1R) antagonist SR141716A. The expression of Kiss1 and Kisspeptin receptor (Kiss1R) has been characterized for the first time in rat hippocampus together with the expression of the CB1R and the Transient Receptor Potential Vanilloid 1 ion channel receptor (TRPV1). Results show that both systems inhibit neurogenesis by reducing the extracellular signal-regulated kinase (ERK) signaling. Despite little differences in the expression of Kiss1R and CB1R, TRPV1 is enhanced by both KP10 and AEA treatments, suggesting TRPV1 as a common thread. KP10 administration reduces CB1R expression in the dentate gyrus, while AEA does not. KPS, unlike ECS, promotes the expression of estrogen receptor α (ER-α) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), also upregulating sirtuin 1 (SIRT1), brain-derived-neurotrophic factor (BDNF), and c-Jun. These findings suggest that the interaction between ECS and KPS could be involved in the fine-tuning of neurogenesis, highlighting a novel role for KPS. Full article

Transient receptor potential vanilloid 3 (TRPV3) is a non-selective cation channel prominently present in the skin. It plays a role in diverse physiological and pathological functions like inflammation of the skin, pain sensations in the skin, and persistent itchiness. Overactive TRPV3 channels contribute to numerous inflammatory skin diseases, and this highlights the therapeutic potential of its inhibitors. Using a drug repurposing screening approach, we identified fluoxetine—a clinically established antidepressant agent—as a potent inhibitor of TRPV3 channel activation, demonstrating its therapeutic potential for skin inflammation alleviation. During whole-cell patch-clamp recordings, fluoxetine exhibits a selective inhibitory effect on macroscopic TRPV3 currents in a concentration-dependent fashion. The IC₅₀ value is measured as 10.23 ± 2.34 μM. On the single-channel scale, fluoxetine leads to a reduction in both single-channel conductance and the open probability of the channel. In the course of animal experiments, fluoxetine mitigates carvacrol-induced TRPV3-related skin inflammation. It lessens the severity of dorsal lesions and ear edema in mice. Our study not only identified TRPV3 as a novel target of fluoxetine and provides new ideas for the treatment of TRPV3-mediated skin diseases with fluoxetine, but also provides a valuable tool molecule for further understanding TRPV3 channel pharmacology. Full article

Polycystic kidney disease (PKD) is the most common hereditary disorder that disrupts renal function and frequently progresses to end-stage renal disease. Recent advances have elucidated the critical role of primary cilia and ciliary ion channels, including transient receptor potential (TRP) channels, cystic fibrosis transmembrane conductance regulator (CFTR), and polycystin channels, in the pathogenesis of PKD. While some channels primarily function as chloride conductance channels (e.g., CFTR), others primarily regulate calcium (Ca⁺²) homeostasis. These ion channels are essential for cellular signaling and maintaining the normal kidney architecture. Dysregulation of these pathways due to genetic mutations in PKD1 and PKD2 leads to disrupted Ca⁺² and cAMP signaling, aberrant fluid secretion, and uncontrolled cellular proliferation, resulting in tubular cystogenesis. Understanding the molecular mechanisms underlying these dysfunctions has opened the door for innovative therapeutic strategies, including TRPV4 activators, CFTR inhibitors, and calcimimetics, to mitigate cyst growth and preserve renal function. This review summarizes the current knowledge on the roles of ciliary ion channels in PKD pathophysiology, highlights therapeutic interventions targeting these channels, and identifies future research directions for improving patient outcomes. Full article

Phytocannabinoids (pCBs) from Cannabis sativa represent an important class of bioactive molecules, potentially useful for the treatment of a wide range of diseases. Their efficacy is due to their ability to interact with multiple targets of the endocannabinoid system, including the thermosensitive transient receptor potential (Thermo-TRPs), namely TRPV1-4, TRPA1, and TRPM8 channels. Previously, we demonstrated a shift in selectivity toward TRPA1 in the activity profile of the main pCBs, that is, CBD, ∆⁸-THC, CBG, CBC, and CBN, by swapping the pentyl chain with the α,α-dimethylheptyl (DMH) one. Using these derivatives as a starting point, here we investigate the effects on the thermo-TRPs activity profile of the integration of a quinone group into the resorcinol scaffold. We found that, while the activity on TRPA1 is substantially retained, an increase in potency/efficacy on the TRPV3 modulation is observed. Docking studies were used to elucidate the binding modes of the most active compounds toward this receptor, providing a rationale for this biological activity. In summary, we show that the quinone derivatives of DMH-pCBs are endowed with a TRPA1/TRPV3 desensitizing activity, potentially useful for the treatment of skin diseases sustained by inflammatory conditions. Full article

Obesity arises from a complex interplay of genetic and environmental factors. Even among individuals with the same genetic predisposition, diet-induced obesity (DIO) exhibits varying degrees of susceptibility, which are categorized as DIO and diet-induced obesity resistance (DR). The hypothalamus plays a pivotal role in regulating energy homeostasis. This study performed a comparative hypothalamic proteomic analysis in DIO and DR rats to identify differentially expressed proteins (DEPs) associated with alterations in body weight. Male Sprague Dawley rats were fed either a standard chow diet or a high-fat diet for 12 weeks. DIO rats exhibited the most rapid weight gain compared to both the control and DR rats. Despite consuming similar caloric intake, DR rats exhibited less weight gain relative to DIO rats. Proteomic analysis revealed 31 DEPs in the hypothalamus of DR rats compared to DIO rats (with a false discovery rate (FDR) < 1%). Notably, 14 proteins were upregulated and 17 proteins were downregulated in DR rats. Gene ontology analysis revealed an enrichment of ion-binding proteins, such as those binding to Fe²⁺, Zn²⁺, Ca²⁺, and Se, as well as proteins involved in neuronal activity and function, potentially enhancing neuronal development and cognition in DR rats. The DEPs pathway analysis via the Kyoto Encyclopedia of Genes and Genomes (KEGG) implicated starch and sucrose metabolism, antigen processing and presentation, and the regulation of inflammatory mediator affecting TRP channels. Western blotting confirmed the proteomic findings for TRPV4, CaMKV, RSBN1, and BASP1, which were consistent with those obtained from Tandem Mass tag (TMT) proteomic analysis. In conclusion, our study highlights the hypothalamic proteome as a critical determinant in the susceptibility to DIO and provides novel targets for obesity prevention and treatment. Full article

Commonly known as marijuana or hemp, Cannabis sativa L. (Cannabaceae), contains numerous active compounds, particularly cannabinoids, which have been extensively studied for their biological activities. Among these, cannabidiol (CBD) stands out for its therapeutic potential, especially given its non-psychotropic effects. This review evaluates the antitumor properties of CBD, highlighting its various mechanisms of action, including the induction of apoptosis, autophagy, and necrosis. By synthesizing findings from in vitro studies on the cell death mechanisms and signaling pathways activated by CBD in various human tumor cell lines, this literature review emphasizes the therapeutic promise of this natural antineoplastic agent. We conducted a comprehensive search of articles in PubMed, Scopus, Springer, Medline, Lilacs, and Scielo databases from 1984 to February 2022. Of the forty-three articles included, the majority (68.18%) reported that CBD activates apoptosis, while 18.18% observed simultaneous apoptosis and autophagy, 9.09% focused on autophagy alone, and 4.54% indicated necrosis. The antitumor effects of CBD appear to be mediated by transient receptor potential cation channels (TRPVs) in endometrial cancer, glioma, bladder cancer, and myeloma, with TRPV1, TRPV2, and TRPV4 playing key roles in activating apoptosis. This knowledge paves the way for innovative therapeutic strategies that may enhance cancer treatment outcomes while minimizing the toxicity and side effects associated with conventional therapies. Full article