Secondary plant metabolites are widely used in traditional and naturopathic medicine to treat pain, infection, and inflammation. The sesquiterpenoid zerumbone, derived from the edible ginger Zingiber zerumbet, has been shown to exert analgesic, antioxidant, antitumoral, and antimicrobial effects in preclinical models, acting through multiple receptor systems including cannabinoid (CB) receptors, peroxisome proliferator-activated receptors, N-methyl-D-aspartate (NMDA) receptors, and the serotonergic system. Zerumbone also modulates inflammatory and nitric oxide-cGMP-K+ATP signaling pathways implicated in antiallodynic responses, yet its direct impact on nociceptor-associated ion channels like the Transient receptor potential vanilloid 1 (TRPV1) and the Twik-related spinal cord potassium channel (TRESK) in human cellular systems remains poorly characterized. In the present study, the antinociceptive properties of zerumbone were investigated in human HEK293-based and induced pluripotent stem cell (iPSC)-derived nociceptor models. Here, the zerumbone treatment reduced cell viability and proliferation in a concentration-dependent manner without altering TRPV1 or TRESK protein expression. Whole-cell patch-clamp recordings revealed that zerumbone reversibly inhibited TRESK-mediated outward potassium currents upon direct application, whereas bath-applied zerumbone increased outward currents, suggesting context-dependent modulation. In TRPV1-expressing HEK293 cells, SH-SY5Y neuroblastoma cells, and human iPSC-derived nociceptors, zerumbone reduced TRPV1-mediated ion currents and capsaicin-evoked calcium signals, indicating a direct or competitive inhibitory effect on TRPV1 activity. In iPSC-derived nociceptors, zerumbone decreased action potential firing at moderate depolarizing currents, shifted the resting membrane potential, and increased rheobase, consistent with reduced nociceptor excitability, while no significant changes in TRESK-mediated currents were detected. These data suggest that zerumbone attenuates human iPSC-derived nociceptor-like neuron excitability largely via TRPV1 inhibition, with a more complex, concentration- and application-method-dependent modulation of TRESK. The findings provide a mechanistic basis for the antiallodynic effects of zerumbone observed in rodent models and highlight the need for further studies in human-derived systems to clarify the precise channel-level interactions and their relevance to inflammatory and neuropathic pain.

Emerging evidence has highlighted a critical role of the neuro-microenvironment in regulating hematopoiesis and hematologic malignancies. However, how malignant cells remodel the neural compartment and how these neural changes in turn influence disease progression remain poorly understood. In this study, we mapped the spatial distribution of sympathetic (TH+) and nociceptive (CGRP+) nerve fibers in the bone marrow and spleen under steady-state conditions and during acute myeloid leukemia (AML) using immunofluorescence imaging. We found that AML induces a reduction of nerve fiber density at the early stage of AML and that leukemic cells preferentially accumulate in neural-sparse regions. Functional investigations revealed that pharmacological ablation of nociceptive nerves via capsaicin accelerated leukemic progression and disrupted stressed hematopoiesis. Conversely, activation of nociceptive nerves by dietary capsaicin delayed AML onset and improved overall survival. Further mechanistic investigation revealed that the CGRP-RAMP1 axis inhibits leukemia progression by suppressing the TNF-α pathway in AML cells. These findings highlight the anti-leukemic role of nociceptive nerves and suggest therapeutic potential for neural modulation in AML.

Migraine headache prevalence is lower in patients with diabetes, but the underlying mechanisms remains unclear. This study explored the influences of hyperglycemia, insulin and insulin receptor (IR)/insulin-like growth factor 1 receptor (IGF-1R)-related signalling on migraine-related mechanisms in in vivo and ex vivo rat models. In in vivo experiments, migraine-relevant responses were induced by systemic injection of nitroglycerin (NTG), whereas hyperglycemia was induced by streptozotocin (STZ). The effects of hyperglycemia, insulin and the dual IR/IGF-1R inhibitor BMS-754807 were investigated. In ex vivo experiments, the effects of insulin and BMS on basal and capsaicin-induced calcitonin gene-related peptide (CGRP) releases from migraine-associated tissues (peripheral meningeal afferents and trigeminal ganglion, and central brainstem trigeminal nucleus) were directly tested. Mechanical hyperalgesia was evaluated by von-Frey, CGRP and c-Fos levels by ELISA and meningeal mast cells by toluidine-blue staining. In in vivo NTG group, insulin further lowered the pain threshold and further enhanced CGRP and c-fos concentrations in trigeminal tissues and mast cell activation in the meninges. Hyperglycemia alone or in the NTG-treated group did not change these parameters. In ex vivo experiments, direct administration of insulin stimulated CGRP release in meningeal and trigeminal ganglion, but not trigeminal nucleus, tissues and further enhanced capsaicin-stimulated CGRP release, confirming the in vivo effects. The in vivo and ex vivo effects of insulin were reversed by BMS. Hyperglycemia did not modify the NTG-induced responses. However, insulin facilitates migraine-related responses by enhancing trigeminal CGRP signalling and meningeal mast cell activation through IR and/or IGF-1R-related signalling. Modulation of insulin-responsive IR/IGF-1R-related signalling within the trigeminovascular system may represent a potential target for future therapeutic strategies.

Trastuzumab (TRZ) is a primary treatment for HER2-positive (HER2+) breast cancer, but its effectiveness is often limited by drug resistance linked to the PI3K signaling pathway. Capsaicin (CAP), a natural compound from chili peppers, has been shown to block the PI3K/AKT pathway. This study aimed to computationally identify specific gene targets of CAP and clarify its molecular mechanism for overcoming TRZ resistance. Computational analyses was conducted to identify potential capsaicin targets (PTCT), continued the in vitro assay on on TRZ-resistant HCC1954 breast cancer cells including cytotoxicity, cell cycle progression, and mRNA expression levels. We identified 54 genes as PTCT and selected ten as hub genes: EGFR, VEGFA, SRC, TIMP1, FOS, CCND1, TGFB1, ICAM1, EDN1, and PPARA. The combination of CAP and TRZ demonstrated a strong synergistic cytotoxic effect, with a significantly lower IC50 of 3.78 μM compared to 418 μM for CAP alone, confirmed as synergistic by Combination Index analysis (CI = 0.06-0.36), and significantly increase in the Selectivity Index (SI) value to 39.4; an increase in the S and G2/M population, and upregulated the mRNA levels of most hub genes while downregulating SRC and EDN1. In conclusion, CAP effectively reverses TRZ resistance by modulating cell cycle and the transcriptional of specific hub genes. Further research should focus on elucidating the precise molecular mechanisms.

Acacia sieberiana (syn. Vachellia sieberiana), widely used in African traditional medicine for pain, was investigated using an ethnopharmacology-guided workflow integrating LC-MS/MS-based metabolomics and molecular networking to prioritize bioactive secondary metabolites. Fractionation of the ethanolic stem bark extract enabled targeted isolation and identification of piperine (1) and moupinamide (3) by HRMS and NMR. Moupinamide and its positional isomer (tamgermanetin) were synthesized via HATU-mediated coupling to support preliminary structure-activity studies. In a capsaicin-induced mouse model, the extract significantly attenuated acute nociceptive behavior without affecting the secondary mechanical hypersensitivity. Functional screening using human iPSC-derived nociceptors in a multielectrode array (MEA) platform showed that moupinamide potently reduced neuronal firing, with reduced efficacy under high-heat conditions, suggesting a non-TRPV1-mediated mechanism. GPCR profiling of moupinamide revealed minimal receptor engagement, and further pharmacological studies demonstrated retained activity under potassium channel blockade and suppression of Nav1.7-induced hyperexcitability, consistent with voltage-gated sodium channel modulation. These findings highlight A. sieberiana-derived alkaloid amides as promising nonopioid analgesic leads and underscore the utility of metabolomics-guided discovery strategies.

Diabetes mellitus is an independent risk factor for osteoarthritis (OA), and the molecular mechanisms underlying diabetic cartilage damage remain unclear. This study investigated the role of oxidative stress in diabetes-induced chondrocyte injury, especially chondrocyte apoptosis, explored the protective role of the NRF2 antioxidant system, and evaluated the therapeutic potential of capsaicin for diabetic OA. In vivo experiments were conducted on streptozotocin (STZ)-induced diabetic mice, in which cartilage degeneration and subchondral bone remodeling were assessed via Safranin O/Fast Green staining, OARSI scoring and micro-CT, while chondrocyte apoptosis and protein expression were detected by TUNEL staining and immunohistochemistry. In vitro, methylglyoxal (MGO)-treated primary mouse chondrocytes and ATDC5 chondrogenic precursor cells were combined with Nrf2 knockdown/overexpression and N-acetylcysteine (NAC) rescue assays to verify the ROS/NRF2 regulatory mechanism. In vivo, STZ-induced hyperglycemia caused severe cartilage erosion, aberrant subchondral bone remodeling and excessive chondrocyte apoptosis. In vitro, MGO elevated intracellular ROS levels and triggered chondrocyte apoptosis in a concentration-dependent manner, and NAC-mediated ROS scavenging reversed this injury, confirming a ROS-dependent pathogenic mechanism. MGO activated NRF2 signaling time-dependently, and Nrf2 knockdown aggravated whereas Nrf2 overexpression attenuated chondrocyte apoptosis. Importantly, capsaicin activated NRF2 signaling, rescued MGO-induced chondrocyte apoptosis in vitro, and alleviated STZ-elicited articular cartilage degeneration in vivo. In conclusion, diabetes induces ROS-mediated chondrocyte apoptosis and cartilage damage. Capsaicin exerts potent chondroprotective effects against diabetic OA via NRF2 activation, offering a promising therapeutic strategy.

Inflammatory pain severely impacts patient well-being. Current treatments focus heavily on resolving inflammation yet often fail to offer rapid pain relief, leading to poor clinical compliance. To bridge this gap, we designed self-assembled nanoparticles that pair instant pain relief with long-term control of inflammation. The core consists of co-assembled lidocaine (LDC), capsaicin (CAP), and meloxicam (MLX) covered by a protective polyethylene glycol (PEG) shell. Upon reaching the weakly acidic inflammatory microenvironment, intermolecular interactions weaken, causing the drug to release rapidly. While local tissue acidity normally protonates LDC and blocks it from crossing nerve cell membranes, the co-released CAP specifically opens transient receptor potential vanilloid 1 (TRPV1) channels. This allows the protonated LDC to flow directly into neurons, securing rapid pain relief. Concurrently, MLX provides sustained anti-inflammatory action by blocking cyclooxygenase-2 (COX-2) and reducing prostaglandin E2 (PGE2) levels, along with other pro-inflammatory mediators. By syncing rapid nerve blockade with continuous anti-inflammatory action, this self-assembled nanosystem overcomes the pharmacokinetic mismatch in drug mixtures, offering a practical and highly effective strategy for inflammatory pain management.

Anoectochilus roxburghii (Wall.) Lindl. is a traditional medicinal herb used for clearing heat, cooling blood, and detoxifying. This study evaluated the anti-inflammatory and barrier-repair activities of anoectochilus roxburghii extract (ARE) using integrated in vitro and clinical approaches. ARE was prepared by water extraction and characterized by HPLC. Its mechanisms were investigated in UVB/capsaicin (CAP)/sodium dodecyl sulfate (SDS)-stimulated HaCaT cells, wound healing assays, and 3D epidermal models, then validated clinically. Quantitative analysis showed ARE contained 50.20% polysaccharides, 26.3% kinsenoside, 1.2% flavonoids, 2.5% polyphenols, 10.9% protein, and 2.8% aspartic acid. In HaCaT cells, ARE inhibited the NF-κB pathway and reduced TNF-α, IL-8, COX-2, and TRPV1 expression, while enhancing tight junction proteins (Claudin-1 and ZO-1). ARE promoted human primary keratinocyte migration. In 3D models, ARE upregulated filaggrin (FLG), loricrin (LOR), involucrin (IVL), and transglutaminase 1 (TGM1), while suppressing IL-1α and prostaglandin E2 (PGE2). Clinically, ARE formulations increased stratum corneum hydration, reduced transepidermal water loss (TEWL), and decreased skin redness. These findings demonstrate that ARE exerts multi-target anti-inflammatory and barrier-strengthening effects, supporting the traditional use of anoectochilus roxburghii for inflammatory skin conditions.

Chili pepper consumption has been linked to lower cardiovascular disease (CVD) risk, although underlying mechanisms remain unclear. We investigated the association between long-term changes in chili pepper consumption and changes in circulating inflammatory markers. This longitudinal analysis included 573 adults (≥35 years) from the Italian Moli-sani Study with dietary, health, and biological data collected at baseline (2005-2010) and follow-up (2017-2020). The exposure was the 12.7-year change in chili pepper consumption frequency. Outcomes included changes in serum concentrations of C-reactive protein, eight other inflammatory factors (IL-6, IL8, IL-10, TNF-α, IFN-γ, MCP-1, IP-10, and VEGF), and the INFLA-score. Multivariable-adjusted linear regression models accounted for changes in dietary and lifestyle factors. Overall, 41.2%, 20.6%, and 38.2% of participants reduced, increased, or maintained their chili pepper consumption, respectively. A 1-unit increase in the delta of chili pepper consumption was associated with lower serum TNF-α concentrations (β = -0.85; 95% CI: -1.67, -0.03; p = 0.041). No associations were observed with the other inflammatory markers, although most showed downward trends. Among women, increased consumption was associated with different MCP-1 and IP-10 levels. An increase in chili pepper consumption over 12.7 years was associated with lower circulating TNF-α concentrations in this population. Although no consistent associations were observed across the inflammatory markers evaluated, these findings suggest a potential modulation of selected inflammatory pathways by sustained chili pepper consumption and warrant confirmation in larger prospective studies.

Ketamine has pharmacological actions beyond N-methyl-D-aspartate receptor antagonism, whereas sodium selenite modulates redox-dependent signaling. Transient receptor potential vanilloid 1 (TRPV1) channels regulate Ca[2+] influx and may contribute to oxidative stress-associated apoptosis. We investigated whether ketamine and sodium selenite, alone and combined, promote apoptosis through TRPV1-associated mechanisms in SH-SY5Y neuroblastoma cells. Cells were assigned to control, ketamine+sodium selenite (Ket+Sel), Ket+Sel+capsazepine (CPZ), ketamine, ketamine+CPZ, sodium selenite, and sodium selenite+CPZ groups. Ketamine (10 µM) and/or sodium selenite (500 nM) were applied for 48 h; CPZ (0.1 mM, 30 min) was used for pharmacological antagonism, and capsaicin (0.1 mM) for stimulation. Intracellular Ca[2+] responses were assessed using Fura-2-AM, whereas apoptosis, reactive oxygen species production, mitochondrial depolarization, and caspase-3/9 activities were measured spectrophotometrically or fluorometrically. Under capsaicin-stimulated assay conditions, ketamine and sodium selenite increased all endpoints relative to control, and the combined treatment produced the greatest responses for most endpoints. CPZ attenuated Ca[2+] responses and several downstream oxidative and apoptotic markers. These findings indicate that ketamine and sodium selenite, particularly in combination, enhance apoptosis through a CPZ-sensitive pathway compatible with TRPV1-associated Ca[2+]-ROS-mitochondrial signaling, while not establishing exclusive TRPV1 mediation.

Background: Obesity is a multifaceted metabolic disorder characterized by systemic disturbances, particularly impaired energy homeostasis, chronic low-grade inflammation, and mitochondrial dysfunction across the brain, gut, adipose tissue, and liver axes. Objectives: This review aims to examine the metabolic properties and molecular mechanisms of six key phytochemicals (berberine, resveratrol, catechins, capsaicin, thymoquinone, and phycocyanin) and the exercise-induced myokine irisin, and their roles in mitochondrial signaling and metabolic reprogramming. Sources of Evidence: A comprehensive literature search was conducted across major electronic databases, including PubMed, Web of Science, and Scopus, to identify relevant mechanistic, in vivo, and in vitro studies. Results: Both the selected phytochemicals and irisin act as multi-target regulators that modulate key signaling pathways, including AMPK, PI3K/Akt/mTOR, SIRT1, Nrf2, and PPARγ. These phytochemicals and irisin can drive cell- and tissue-specific metabolic reprogramming, promoting the browning of white adipocytes, suppressing de novo lipogenesis in hepatocytes, and enhancing fatty acid oxidation in skeletal myocytes. This synergistic metabolic reprogramming enhances thermogenesis and increases energy expenditure. Conclusions: Co-targeting redox signaling and metabolic pathways via phytochemicals and irisin offers a powerful strategy against obesity. This integrative framework restores multi-organ homeostasis, laying the groundwork for targeted metabolic therapies.