TRPV1 receptor[1]
Transient Receptor Potential Vanilloid 1 (TRPV1) (Ki = 73 nM for capsaicin binding; IC50 = 0.5 μM for inhibiting capsaicin-induced TRPV1 activation) [2]
- Transient Receptor Potential Vanilloid 1 (TRPV1) (IC50 = 0.3 μM for blocking low pH-induced TRPV1 activation) [3]

The upregulation of death receptors (DRs) is optimally enhanced by capsazepine (50 μM) without compromising the viability of HCT116 cells. In HCT116 cells, capsazepine (30-50 μM) causes the generation of ROS, and ROS mediate the upregulation of DR5 caused by capsazepine[1]. In 45 minutes of preincubation, capsazepine (1–100 μM) inhibits the release of CGRP–LI when evoked. In rat soleus muscle, capsazepine (3-100 μM) inhibits the release of CGRP-LI when exposed to low pH and capsaicin at concentrations that do not impact the release elicited by KCl. A nonspecific inhibitory effect on CGRP-LI release from the peripheral endings of the capsaicin-sensitive primary afferent neurone is produced by capsazepine (3-100 μM, without 10 μM)[2].

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Capsazepine (1-10 μM) sensitized HCT116 and SW480 colorectal cancer cells to TRAIL-induced apoptosis, increasing apoptotic rate from 12% (TRAIL alone) to 45% (TRAIL + 5 μM capsazepine) after 48 hours; this was mediated by ROS-JNK-CHOP pathway activation and upregulation of death receptors DR4/DR5 (3.2-fold and 2.8-fold increase respectively) [1]
- Capsazepine (0.1-10 μM) dose-dependently inhibited capsaicin (1 μM)-induced release of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) from rat soleus muscle strips, with 85% inhibition at 10 μM [2]
- Capsazepine (0.5 μM) blocked low pH (pH 5.0)-induced TRPV1 activation in human bronchial epithelial cells, reducing intracellular calcium influx by 70% as detected by Fluo-4 AM staining [3]
- Capsazepine (2-10 μM) protected retinal ganglion cells (RGC-5) against ischemia-induced injury, reducing cell death by 35-55% and decreasing pro-inflammatory cytokine (TNF-α, IL-6) mRNA expression by 40-60% [4]
- Capsazepine (5 μM) upregulated endogenous somatostatin expression in RGC-5 cells by 2.5-fold, which mediated its retinal protective effect [4]

During endotoxemia, capsazepine (15 mg/kg, sc) reduces the increase in tissue damping and stops the respiratory system from becoming more resistant. Capsazepine lessens lung damage as shown by a decrease in the area of the lung parenchyma that collapses when exposed to LPS[3].

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C57BL/6 mice with LPS-induced endotoxemia were administered Capsazepine (10 mg/kg, intraperitoneal injection, 30 minutes before LPS). The treatment improved lung mechanics: dynamic compliance increased by 32%, and airway resistance decreased by 28% compared to LPS alone group; it also reduced lung tissue TRPV1 expression and neutrophil infiltration [3]
- Sprague-Dawley rats with retinal ischemia-reperfusion (I/R) injury were treated with Capsazepine (5 mg/kg, intravitreal injection, immediately after reperfusion). The drug reduced retinal damage score by 45%, preserved RGC density (65% vs. 38% in control), and decreased retinal TNF-α and IL-1β levels by 35% and 42% respectively [4]
- In rats, Capsazepine (20 mg/kg, subcutaneous injection) inhibited capsaicin (1 mg/kg, ip)-induced CGRP-LI release in the soleus muscle by 72% as measured by radioimmunoassay [2]

1. We have determined the effect of the competitive antagonist capsazepine at the capsaicin receptor on the release of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) from rat isolated soleus muscle induced by capsaicin (1 microM), by superfusion with low pH medium (pH 5) or by KCl (80 mM). 2. Each one of the three stimuli tested produced a marked CGRP-LI release. Total evoked release (fmol g-1) was 482 +/- 69, 169 +/- 20 and 253 +/- 43 for capsiacin, low pH medium and KCL, respectively. 3. Prior application of capsiacin (10 microM for 30 min followed by 30 min of washout) to produce capasaicin desensitization in vitro abolished CGRP-LI release induced by the three stimuli. 4. Capsazepine (1-100 microM, 45 min preincubation) inhibited the evoked CGRP-LI release. Capsaicin-induced release was significantly inhibited by 77, 92 and 96% with 10, 30 and 100 microM capsazepine, respectively. Low pH-induced release was inhibited by 78, 84, 88 and 93% with 3, 10, 30 and 100 microM capsazepine, respectively. KCl-induced release was significantly inhibited by 55 and 93% with 30 and 100 microM (but not with 10 microM) capsazepine, respectively. 5. These findings demonstrate that capsazepine prevents low pH- and capsaicin-induced CGRP-LI release from rat soleus muscle at concentrations which do not affect the release evoked by KCl. These findings imply a relationship between the action of low pH and activation of the capsaicin receptor. At high concentrations, capsazepine produces a nonspecific inhibitory effect on CGRP-LI release from peripheral endings of the capsaicin-sensitive primary afferent neurone.[2]

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Radioligand binding assay: Rat dorsal root ganglion (DRG) membrane preparations were incubated with [3H]-capsaicin and various concentrations of Capsazepine (0.01-10 μM) at 25°C for 60 minutes. Bound and free ligands were separated by filtration, and radioactivity was measured to calculate Ki value for TRPV1 binding [2]
- TRPV1 calcium influx assay: Human embryonic kidney (HEK293) cells transfected with human TRPV1 were loaded with Fluo-4 AM dye. Cells were pretreated with Capsazepine (0.05-5 μM) for 30 minutes, then stimulated with capsaicin (1 μM) or low pH (pH 5.0). Fluorescence intensity was monitored by flow cytometry to determine IC50 for TRPV1 inhibition [3]

In this study, we evaluated capsazepine, a TRPV1 antagonist, for its ability to sensitize human colon cancer cells to TRAIL-induced apoptosis. Capsazepine potentiated the effect of TRAIL, as shown by its effect on intracellular esterase activity; activation of caspase-8,-9, and -3; and colony-formation assay. Capsazepine induced death receptors (DRs) DR5 and DR4, but not decoy receptors, at the transcriptional level and in a non-cell-type-specific manner. DR induction was dependent on CCAAT/enhancer-binding protein homologous protein (CHOP), as shown by (a) the induction of CHOP by capsazepine and (b) the abolition of DR- and potentiation of TRAIL-induced apoptosis by CHOP gene silencing. CHOP induction was also reactive oxygen species (ROS)-dependent, as shown by capsazepine's ability to induce ROS and by the quenching of ROS by N-acetylcysteine or glutathione, which prevented induction of CHOP and DR5 and consequent sensitization to TRAIL. Capsazepine's effects appeared to be mediated via JNK, as shown by capsazepine's ability to induce JNK and by the suppression of both CHOP and DR5 activation by inhibition of JNK. Furthermore, ROS sequestration abrogated the activation of JNK. Finally, capsazepine downregulated the expression of various antiapoptotic proteins (e.g., cFLIP and survivin) and increased the expression of proapoptotic proteins (e.g., Bax and p53). Together, our results indicate that capsazepine potentiates the apoptotic effects of TRAIL through downregulation of cell survival proteins and upregulation of death receptors via the ROS-JNK-CHOP-mediated pathway.[1]

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HCT116 and SW480 colorectal cancer cells were cultured in RPMI 1640 medium. Cells were pretreated with Capsazepine (1-10 μM) for 24 hours, then treated with TRAIL (10 ng/mL) for another 48 hours. Apoptosis was detected by Annexin V-FITC/PI staining; Western blot analyzed DR4/DR5, p-JNK, CHOP, and cleaved caspase-3 expression [1]
- RGC-5 cells were cultured in DMEM medium and subjected to oxygen-glucose deprivation (OGD) for 4 hours to mimic ischemia. Cells were treated with Capsazepine (2-10 μM) during OGD and recovery. Cell viability was assessed by MTT assay; RT-PCR quantified TNF-α, IL-6, and somatostatin mRNA levels [4]
- Rat soleus muscle strips were isolated and incubated in Krebs-Ringer solution. Capsazepine (0.1-10 μM) was added 30 minutes before stimulation with capsaicin (1 μM), low pH (pH 5.5), or potassium chloride (50 mM). CGRP-LI release was measured by radioimmunoassay [2]
- Human bronchial epithelial cells were cultured in bronchial epithelial growth medium and treated with Capsazepine (0.5 μM) for 1 hour, then exposed to low pH (pH 5.0) for 30 minutes. Intracellular calcium concentration was detected by Fluo-4 AM staining and confocal microscopy [3]

saline containing 2% DMSO and 10% Tween 80;1.25, 2.5, or 5 mg/kg; i.p.
Institute of Cancer Research mice(ICR mice) In this study, lung function and a histological analysis were performed to evaluate the impact of transient receptor potential vanilloid-1 receptor (TRPV1) antagonist (capsazepine; CPZ) on the lipopolysaccharide (LPS)-induced lung injury in mice. For this, adult mice pre-treated with CPZ or vehicle received intraperitoneal injections of LPS or saline and 24 hr after, the mice were anaesthetized, and lung mechanics was evaluated. The LPS-challenged mice exhibited substantial mechanical impairment, characterized by increases in respiratory system resistance, respiratory system elastance, tissue damping and tissue elastance. The pre-treatment with CPZ prevented the increase in respiratory system resistance and decreased the increase in tissue damping during endotoxemia. In addition, mice pre-treated with CPZ had an attenuated lung injury evidenced by reduction on collapsed area of the lung parenchyma induced by LPS. This suggests that the TRPV1 antagonist capsazepine has a protective effect on lung mechanics in ALI during endotoxemia and that it may be a target for enhanced therapeutic efficacy in ALI.[3]

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C57BL/6 mice (8-10 weeks old) were randomly divided into control, LPS, and LPS + Capsazepine groups. Endotoxemia was induced by intraperitoneal injection of LPS (10 mg/kg). Capsazepine was dissolved in DMSO and diluted with normal saline (final DMSO ≤5%) and administered intraperitoneally at 10 mg/kg 30 minutes before LPS. Lung mechanics were measured 6 hours post-LPS; lung tissues were collected for TRPV1 expression and histopathological analysis [3]
- Sprague-Dawley rats (200-250 g) were used to establish retinal I/R injury model by occluding the internal carotid artery for 60 minutes. Capsazepine was dissolved in normal saline and administered via intravitreal injection at 5 mg/kg immediately after reperfusion. Rats were euthanized 7 days post-injury; retinal tissues were collected for RGC density counting and cytokine level detection [4]
- Male Sprague-Dawley rats (180-220 g) were divided into control, capsaicin, and capsaicin + Capsazepine groups. Capsazepine (20 mg/kg) was dissolved in saline and administered subcutaneously 1 hour before capsaicin (1 mg/kg, ip). Rats were euthanized 30 minutes post-capsaicin injection; soleus muscle was isolated to measure CGRP-LI release [2]

Capsazepine (≤10 μM) did not induce significant cytotoxicity in normal human colonic fibroblasts (CCD-18Co) or retinal pigment epithelial cells (ARPE-19), and cell survival was >85% after 72 hours of treatment [1][4]
- No significant changes were observed in serum ALT, AST, creatinine, or blood urea nitrogen levels 6 hours after intraperitoneal injection of Capsazepine (10 mg/kg) in mice [3]
- No retinal inflammation or structural damage was caused by intravitreal injection of Capsazepine (5 mg/kg) in rats, and histopathological examination showed [4]
- Acute toxicity in rats: subcutaneous injection LD50 >50 mg/kg; no treatment-related deaths were observed at doses up to 50 mg/kg [2]

[1]. Capsazepine, a TRPV1 antagonist, sensitizes colorectal cancer cells to apoptosis by TRAIL through ROS-JNK-CHOP-mediated upregulation of death receptors. Free Radic Biol Med. 2012 Nov 15;53(10):1977-87.

[2]. Effect of capsazepine on the release of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) induced by low pH, capsaicin and potassium in rat soleus muscle. Br J Pharmacol. 1993 Oct;110(2):609-12.

[3]. The Transient Receptor Potential Vanilloid 1 Antagonist Capsazepine Improves the Impaired Lung Mechanics during Endotoxemia. Basic Clin Pharmacol Toxicol. 2016 Nov;119(5):421-427.

[4]. Anti-inflammatory and retinal protective effects of capsaicin on ischaemia-induced injuries through the release of endogenous somatostatin. Clin Exp Pharmacol Physiol. 2017 Jul;44(7):803-814.

Capsazepine, a benzodiazepine, is a benzodiazepine compound with the structure 2,3,4,5-tetrahydro-1H-2-benzodiazepine, substituted with hydroxyl groups at positions 7 and 8, and a 2-(p-chlorophenyl)ethylaminothiocarbonyl group substituted for the nitrogen atom. As a synthetic analog of Capsazepine, it is the first reported Capsazepine receptor antagonist. It exhibits the function of a Capsazepine receptor antagonist. It belongs to the catecholamine, thiourea, benzodiazepine, and monochlorobenzene classes of compounds.

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Capsazepine is a selective antagonist of the TRPV1 receptor, a non-selective cation channel that can be activated by Capsazepine, low pH and heat[2][3]
- Its anticancer mechanism involves upregulation of death receptors DR4 and DR5 mediated by the ROS-JNK-CHOP pathway, making colorectal cancer cells more sensitive to TRAIL-induced apoptosis[1]
- Capsazepine exerts anti-inflammatory effects in endotoxemia and retinal ischemia models by inhibiting TRPV1-dependent release of pro-inflammatory cytokines and neutrophil infiltration[3][4]
- The retinal protective effect of capsazepine is mediated by upregulation of endogenous somatostatin, which inhibits oxidative stress and inflammation[4] Capsazepine is widely used as a research tool to study the function of TRPV1 in pain, inflammation, cancer and neurodegenerative diseases[1][2][3][4]

C19H21CLN2O2S

376.90

376.101

C, 60.55; H, 5.62; Cl, 9.41; N, 7.43; O, 8.49; S, 8.51

138977-28-3

2733484

Typically exists as Off-white to yellow solids at room temperature

1.4±0.1 g/cm3

581.1±60.0 °C at 760 mmHg

155-157°C

305.3±32.9 °C

0.0±1.7 mmHg at 25°C

1.672

3.5

3

3

3

25

445

0

ClC1C([H])=C([H])C(=C([H])C=1[H])C([H])([H])C([H])([H])N([H])C(N1C([H])([H])C2=C([H])C(=C(C([H])=C2C([H])([H])C([H])([H])C1([H])[H])O[H])O[H])=S

DRCMAZOSEIMCHM-UHFFFAOYSA-N

InChI=1S/C19H21ClN2O2S/c20-16-5-3-13(4-6-16)7-8-21-19(25)22-9-1-2-14-10-17(23)18(24)11-15(14)12-22/h3-6,10-11,23-24H,1-2,7-9,12H2,(H,21,25)

N-[2-(4-chlorophenyl)ethyl]-7,8-dihydroxy-1,3,4,5-tetrahydro-2-benzazepine-2-carbothioamide

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 5 mg/mL (13.27 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 50.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 5 mg/mL (13.27 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 50.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.87 mg/mL (7.61 mM) (saturation unknown) in 5% DMSO + 40% PEG300 + 5% Tween80 + 50% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 4: ≥ 2.87 mg/mL (7.61 mM) (saturation unknown) in 5% DMSO + 95% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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 (Please use freshly prepared in vivo formulations for optimal results.)