Resveratrol enhances 5-hydroxytryptamine type 3A receptor-mediated ion currents: the role of arginine 222 residue in pre-transmembrane domain I

Resveratrol activates GABAA and/or glycine receptors on substantia gelatinosa neurons of the subnucleus caudalis in mice

Although a number of studies have reported that resveratrol has analgesic effects, the direct effect of resveratrol on substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) involved in orofacial nociceptive transmission has not been clearly examined. Thus, the objective of this study was to investigate effects of resveratrol on SG neurons of Vc in mice using a whole-cell patch-clamp technique. Resveratrol (500 μM) induced repeatable inward currents without desensitisation. Resveratrol-induced inward currents were shown in a concentration-dependent manner. Resveratrol-induced responses were sustained in the presence of tetrodotoxin, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), and DL-2-Amino-5-phosphonovaleric acid (DL-AP5). However, resveratrol-induced inward currents were suppressed in the presence of picrotoxin and strychnine. These results indicate that resveratrol can directly act on SG neurons of Vc with possible inhibitory effects on SG neurons through activation of GABA_A receptors and/or glycine receptors. Thus, resveratrol can be a potential therapeutic for orofacial pain modulation.

Resveratrol noncompetitively inhibits glycine receptor-mediated currents in neurons of rat central auditory neurons

Resveratrol, a naturally occurring stilbene found in red wine, is known to modulate the activity of several types of ion channels and membrane receptors, including Ca²⁺, K⁺, and Na⁺ ion channels. However, little is known about the effects of resveratrol on some important receptors, such as glycine receptors and GABA_A receptors, in the central nervous system (CNS). In the present study, the effects of resveratrol on glycine receptor or GABA_A receptor-mediated currents in cultured rat inferior colliculus (IC) and auditory cortex (AC) neurons were studied using whole-cell voltage-clamp recordings. Resveratrol itself did not evoke any currents in IC neurons but it reversibly decreased the amplitude of glycine-induced current (I_Gly) in a concentration-dependent manner. Resveratrol did not change the reversal potential of I_Gly but it shifted the concentration-response relationship to the right without changing the Hill coefficient and with decreasing the maximum response of I_Gly. Interestingly, resveratrol inhibited the amplitude of I_Gly but not that of GABA-induced current (I_GABA) in AC neurons. More importantly, resveratrol inhibited GlyR-mediated but not GABA_AR-mediated inhibitory postsynaptic currents in IC neurons using brain slice recordings. Together, these results demonstrate that resveratrol noncompetitively inhibits I_Gly in auditory neurons by decreasing the affinity of glycine to its receptor. These findings suggest that the native glycine receptors but not GABA_A receptors in central neurons are targets of resveratrol during clinical administrations.

Resveratrol suppresses nociceptive jaw-opening reflex via 5HT3 receptor-mediated GABAergic inhibition

Systemic administration of the dietary constituent, resveratrol, was previously shown to inhibit the nociceptive jaw-opening reflex (JOR) via the endogenous opioid system. The present study investigated whether resveratrol could similarly affect the JOR under in vivo conditions via 5HT₃ receptor-mediated GABAergic inhibition. We used electrical stimulation of the tongue in pentobarbital-anesthetized rats to evoke the JOR, which was recorded as the anterior belly of the digastric muscle electromyograms (dEMG). Intravenous administration of resveratrol (2 mg/kg) reduced the dEMG amplitude in response to three times the determined threshold electrical stimulation, with maximum inhibition reached within approximately 10 min. These inhibitory effects on the JOR were reversible to control levels after approximately 20 min. Pretreatment of rats with either 5HT₃ receptor antagonist, ondansetron (0.25-1 mg/kg, i.p.), or GABA_A receptor antagonist, bicuculline (0.5-1 mg/kg, i.p.), significantly and dose-dependently attenuated the inhibitory effects of resveratrol on dEMG amplitude compared with untreated controls. These findings suggest that resveratrol also attenuates the nociceptive JOR via 5HT₃ receptor-mediated GABAergic inhibition. The present study therefore provides new insight into a possible mechanism underlying resveratrol-induced trigeminal antinociception via the descending pain control system and highlights a potential therapeutic agent for complementary alternative medicine.

Resveratrol Directly Controls the Activity of Neuronal Ryanodine Receptors at the Single-Channel Level

Calcium ion dyshomeostasis contributes to the progression of many neurodegenerative diseases and represents a target for the development of neuroprotective therapies, as reported by Duncan et al. (Molecules 15(3):1168-95, 2010), LaFerla (Nat Rev Neurosci 3(11):862-72, 2002), and Niittykoshi et al. (Invest Ophthalmol Vis Sci 51(12):6387-93, 2010). Dysfunctional ryanodine receptors contribute to calcium ion dyshomeostasis and potentially to the pathogenesis of neurodegenerative diseases by generating abnormal calcium ion release from the endoplasmic reticulum, according to Bruno et al. (Neurobiol Aging 33(5):1001 e1-6, 2012) and Stutzmann et al. (J Neurosci 24(2):508-13, 2004). Since ryanodine receptors share functional and structural similarities with potassium channels, as reported by Lanner et al. (Cold Spring Harb Perspect Biol 2(11):a003996, 2010), and small molecules with anti-oxidant properties, such as resveratrol (3,5,4'-trihydroxy-trans-stilbene), directly control the activity of potassium channels, according to Wang et al. (J Biomed Sci 23(1):47, 2016), McCalley et al. (Molecules 19(6):7327-40, 2014), Novakovic et al. (Mol Hum Reprod 21(6):545-51, 2015), Li et al. (Cardiovasc Res 45(4):1035-45, 2000), Gopalakrishnan et al. (Br J Pharmacol 129(7):1323-32, 2000), and Hambrock et al. (J Biol Chem 282(5):3347-56, 2007), we hypothesized that trans-resveratrol can modulate intracellular calcium signaling through direct binding and functional regulation of ryanodine receptors. The goal of our study was to identify and measure the control of ryanodine receptor activity by trans-resveratrol. Mechanisms of calcium signaling mediated by the direct interaction between trans-resveratrol and ryanodine receptors were identified and measured with single-channel electrophysiology. Addition of trans-resveratrol to the cytoplasmic face of the ryanodine receptor increased single-channel activity at physiological and elevated pathophysiological cytoplasmic calcium ion concentrations. The open probability of the channel increases after interacting with the small molecule in a dose-dependent manner, but remains also dependent on the concentration of its physiological ligand, cytoplasmic-free calcium ions. This study provides the first evidence of a direct functional interaction between trans-resveratrol and ryanodine receptors. Such functional control of ryanodine receptors by trans-resveratrol as a novel mechanism of action could provide additional rationales for the development of novel therapeutic strategies to treat and prevent neurodegenerative diseases.

The antinociceptive effect of resveratrol in bone cancer pain is inhibited by the Silent Information Regulator 1 inhibitor selisistat

Objectives

To study the antinociceptive effect of single and repeated doses of resveratrol in a bone cancer pain model, and whether this effect is prevented by the Silent Information Regulator 1 (SIRT1) inhibitor selisistat.

Methods

The femoral intercondylar bone of BALB/c mice was injected with 1 000 000 BJ3Z cancer cells. Bone resorption and tumour mass growth (measured by in vivo X-ray and fluorescence imaging), as well as mechanical nociceptive thresholds (von Frey device) and dynamic functionality (rotarod machine), were evaluated during the following 4 weeks. Acute resveratrol (100 mg/kg i.p.) and/or selisistat (10 mg/kg s.c.) were administered on day 14. Chronic resveratrol (100 mg/kg i.p., daily) and/or selisistat (0.5 μg/h s.c., Alzet pump) were administered between days 14 and 20.

Key findings

Tumour growth gradually incremented until day 31, while mechanical hyperalgesia started on day 3 after cancer cell injection. Acute resveratrol increased the mechanical threshold of pain (peaking at 1.5 h), while the dynamic functionality decreased. Chronic resveratrol produced a sustained antinociceptive effect on mechanical hyperalgesia and improved the loss of dynamic functionality induced by the bone cancer tumour. Selisistat prevented all the effects of resveratrol.

Conclusions

Acute and chronic resveratrol induces antinociceptive effect in the model of metastatic osseous oncological pain, an effect that would be mediated by SIRT1 molecular signalling.

Systemic administration of the dietary constituent resveratrol inhibits the nociceptive jaw-opening reflex in rats via the endogenous opioid system

The aim of the present study was to investigate whether, under in vivo conditions, systemic administration of resveratrol could attenuate the rat nociceptive jaw-opening reflex (JOR) via the endogenous opioid system. The JOR evoked by electrical stimulation of the tongue was recorded as digastric muscle electromyograms (dEMG) in pentobarbital-anesthetized rats. The amplitude of the dEMG increased significantly in proportion to the intensity of electrical stimulation (from 1× to 5 × threshold for the JOR). dEMG amplitude in response to 3× threshold electrical stimulation of the tongue was dose-dependently inhibited by intravenous administration of resveratrol (0.5-2mg/kg). Maximum inhibition of dEMG amplitude was seen within approximately 10min. These inhibitory effects were reversible, with dEMG responses returning to control levels after approximately 20min. Pretreatment of rats with naloxone resulted in significant, dose-dependent attenuation of the inhibitory effects of resveratrol on dEMG amplitude compared with control. These findings suggest that resveratrol inhibits the nociceptive JOR via the endogenous opioid system. Further, the findings of the present study strongly support the idea that resveratrol, which is not known to have any toxic side effects, combined with an opioid could be a potential therapeutic agent for the prevention of acute trigeminal nociception.

Modulatory Mechanism of Nociceptive Neuronal Activity by Dietary Constituent Resveratrol

Changes to somatic sensory pathways caused by peripheral tissue, inflammation or injury can result in behavioral hypersensitivity and pathological pain, such as hyperalgesia. Resveratrol, a plant polyphenol found in red wine and various food products, is known to have several beneficial biological actions. Recent reports indicate that resveratrol can modulate neuronal excitability, including nociceptive sensory transmission. As such, it is possible that this dietary constituent could be a complementary alternative medicine (CAM) candidate, specifically a therapeutic agent. The focus of this review is on the mechanisms underlying the modulatory effects of resveratrol on nociceptive neuronal activity associated with pain relief. In addition, we discuss the contribution of resveratrol to the relief of nociceptive and/or pathological pain and its potential role as a functional food and a CAM.

Local administration of resveratrol inhibits excitability of nociceptive wide-dynamic range neurons in rat trigeminal spinal nucleus caudalis

Although we recently reported that intravenous administration of resveratrol suppresses trigeminal nociception, the precise peripheral effect of resveratrol on nociceptive and non-nociceptive mechanical stimulation-induced trigeminal neuron activity in vivo remains to be determined. The aim of the present study was to investigate whether local subcutaneous administration of resveratrol attenuates mechanical stimulation-induced excitability of trigeminal spinal nucleus caudalis (SpVc) neuron activity in rats, in vivo. Extracellular single-unit recordings were made of SpVc wide-dynamic range (WDR) neuron activity in response to orofacial mechanical stimulation in pentobarbital-anesthetized rats. Neurons responded to non-noxious and noxious mechanical stimulation applied to the orofacial skin. Local subcutaneous administration of resveratrol (1-10mM) into the orofacial skin dose dependently and significantly reduced the mean number of SpVc WDR neurons firing in response to both non-noxious and noxious mechanical stimuli, with the maximal inhibition of discharge frequency in response to both stimuli being seen within 5min. These inhibitory effects were no longer evident after approximately 20min. The mean magnitude of inhibition by resveratrol (10mM) of SpVc neuron discharge frequency was almost equal to that of the local anesthetic 1% lidocaine (37mM). These results suggest that local injection of resveratrol into the peripheral receptive field suppresses the excitability of SpVc neurons, possibly via inhibition of Na(+) channels in the nociceptive nerve terminals of trigeminal ganglion neurons. Therefore, local subcutaneous administration of resveratrol may provide relief of trigeminal nociceptive pain, without side effects, thus contributing to the suite of complementary and alternative medicines used as local anesthetic agents.

Resveratrol attenuates inflammation-induced hyperexcitability of trigeminal spinal nucleus caudalis neurons associated with hyperalgesia in rats

Background

Resveratrol, a component of red wine, has been reported to decrease prostaglandin E₂ production by inhibiting the cyclooxygenase-2 cascade and to modulate various voltage-dependent ion channels, suggesting that resveratrol could attenuate inflammatory hyperalgesia. However, the effects of resveratrol on inflammation-induced hyperexcitability of nociceptive neurons in vivo remain to be determined. Thus, the aim of the present study was to determine whether daily systemic administration of resveratrol to rats attenuates the inflammation-induced hyperexcitability of spinal trigeminal nucleus caudalis wide-dynamic range neurons associated with hyperalgesia.

Results

Inflammation was induced by injection of complete Freund’s adjuvant into the whisker pad. The threshold of escape from mechanical stimulation applied to whisker pad in inflamed rats was significantly lower than in control rats. The decreased mechanical threshold in inflamed rats was restored to control levels by daily systemic administration of resveratrol (2 mg/kg, i.p.). The mean discharge frequency of spinal trigeminal nucleus caudalis wide-dynamic range neurons to both nonnoxious and noxious mechanical stimuli in inflamed rats was significantly decreased after resveratrol administration. In addition, the increased mean spontaneous discharge of spinal trigeminal nucleus caudalis wide-dynamic range neurons in inflamed rats was significantly decreased after resveratrol administration. Similarly, resveratrol significantly diminished noxious pinch-evoked mean after discharge frequency and occurrence in inflamed rats. Finally, resveratrol restored the expanded mean size of the receptive field in inflamed rats to control levels.

Conclusion

These results suggest that chronic administration of resveratrol attenuates inflammation-induced mechanical inflammatory hyperalgesia and that this effect is due primarily to the suppression of spinal trigeminal nucleus caudalis wide dynamic range neuron hyperexcitability via inhibition of both peripheral and central cyclooxygenase-2 cascade signaling pathways. These findings support the idea of resveratrol as a potential complementary and alternative medicine for the treatment of trigeminal inflammatory hyperalgesia without side effects.

Analysis of free ACh and 5-HT in milk from four different species and their bioactivity on 5-HT(3) and nACh receptors

Milk is one of the most beneficial aliments and is highly recommended in normal conditions; however, in certain disorders, like irritable bowel syndrome, cow milk and dairy products worsen the gastric symptoms and their use is not recommended. Among the most recognized milk-induced gatrointestinal symptoms are abdominal pain, nausea and vomiting, which are processes controlled by cholinergic and serotonergic transmission. Whether the presence of bioavailable ACh and 5-HT in milk may contribute to normal peristalsis, or to the developing of these symptoms, is not known. In this work we attempt to determine whether the content of free ACh and 5-HT is of physiological significance in milk from four different species: cow (bovine), goat, camel and human. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to identify and quantify free ACh and 5-HT in milk, and activation of the serotonergic and cholinergic ionotropic receptors was investigated using electrophysiological experiments. Our principal hypothesis was that milk from these four species had sufficient free ACh and 5-HT to activate their correspondent receptors expressed in a heterologous system. Our results showed a more complex picture, in which free ACh and 5-HT and their ability to activate cholinergic and serotonergic receptors are not correlated. This work is a first step to elucidate whether 5-HT and ACh, at the concentrations present in the milk, can be associated to a direct function in the GI.

Resveratrol Inhibits GABAC ρ Receptor-Mediated Ion Currents Expressed in Xenopus Oocytes

Resveratrol is a phytoalexin found in grapes, red wine, and berries. Resveratrol has been known to have many beneficial health effects, such as anti-cancer, neuroprotective, anti-inflammatory, and life-prolonging effects. However, relatively little is known about the effects of resveratrol on the regulation of ligand-gated ion channels. We have previously reported that resveratrol regulates subsets of homomeric ligand-gated ion channels such as those of 5-HT_3A receptors. The γ-aminobutyric acid_C (GABA_C) receptor is mainly expressed in retinal bipolar cells and plays an important role in visual processing. In the present study, we examined the effects of resveratrol on the channel activity of homomeric GABA_C receptor expressed in Xenopus oocytes injected with cRNA encoding human GABA_C ρ subunits. Our data show that the application of GABA elicits an inward peak current (I_GABA) in oocytes that express the GABA_C receptor. Resveratrol treatment had no effect on oocytes injected with H₂O or with GABA_C receptor cRNA. Co-treatment with resveratrol and GABA inhibited I_GABA in oocytes with GABA_C receptors. The inhibition of I_GABA by resveratrol was in a reversible and concentration-dependent manner. The IC₅₀ of resveratrol was 28.9±2.8 µM in oocytes expressing GABA_C receptor. The inhibition of I_GABA by resveratrol was in voltage-independent and non-competitive manner. These results indicate that resveratrol might regulate GABA_C receptor expression and that this regulation might be one of the pharmacological actions of resveratrol on the nervous system.