Eom S et al. (2021), Antioxidative and Analgesic Effects of Naringin...

XB-ART-58830

Antioxidants (Basel) 2021 Dec 28;111:. doi: 10.3390/antiox11010064.

Show Gene links Show Anatomy links

Antioxidative and Analgesic Effects of Naringin through Selective Inhibition of Transient Receptor Potential Vanilloid Member 1.

Eom S , Lee BB , Lee S , Park Y , Yeom HD , Kim TH , Nam SH , Lee JH .

???displayArticle.abstract???
Transient receptor potential vanilloid member 1 (TRPV1) is activated in response to capsaicin, protons, temperature, and free reactive oxygen species (ROS) released from inflammatory molecules after exposure to harmful stimuli. The expression level of TRPV1 is elevated in the dorsal root ganglion, and its activation through capsaicin and ROS mediates neuropathic pain in mice. Its expression is high in peripheral and central nervous systems. Although pain is a response evolved for survival, many studies have been conducted to develop analgesics, but no clear results have been reported. Here, we found that naringin selectively inhibited capsaicin-stimulated inward currents in Xenopus oocytes using a two-electrode voltage clamp. The results of this study showed that naringin has an IC50 value of 33.3 μM on TRPV1. The amino acid residues D471 and N628 of TRPV1 were involved in its binding to naringin. Our study bridged the gap between the pain suppression effect of TRPV1 and the preventive effect of naringin on neuropathic pain and oxidation. Naringin had the same characteristics as a model selective antagonist, which is claimed to be ideal for the development of analgesics targeting TRPV1. Thus, this study suggests the applicability of naringin as a novel analgesic candidate through antioxidative and analgesic effects of naringin.

???displayArticle.pubmedLink??? 35052566
???displayArticle.pmcLink??? PMC8773328
???displayArticle.link??? Antioxidants (Basel)
???displayArticle.grants??? [+]

Genes referenced: trpv1

???attribute.lit??? ???displayArticles.show???

	Figure 1. Schematic diagram of the various interaction sites of TRPV1 and the mechanism underlying the neuroprotective effect of naringin in the pain pathway: (A) one subunit of TRPV1 has six transmembrane domains (yellow) and a pore loop (S5–S6). TRPV1 can function only when these four subunits form a tetramer. The light blue circle is the location where the proton binds to TRPV1. The pepper-shaped symbol is the site where vanilloids such as capsaicin bind. The star shape is the binding site of naringin found in our present study. (B) The pain transmission pathway. The signal transduction process of pain involves three stages. Electrical signals are transmitted from the first-order neurons (yellow neurons) to the third-order neurons (red neurons), and finally, the brain perceives the pain. The blue receptor symbol is TRPV1 and marks the tissue location where it is expressed. (C) Naringin has a cytoprotective effect mediated through inhibition of neuronal hyperexcitation and oxidative stress via TRPV. The death of neuronal cells remains a permanent error in the signaling system, resulting in neuropathic pain. GSH is glutathione, MDA is malondialdehyde, SOD is superoxide dismutase, CAT is catalase, and GST is glutathione-S-transferase.
	Figure 2. Selective inhibitory effect of capsaicin on TRPV1 and the chemical structure of naringin: (A) 2D structure of naringin. (B) Different inhibitory effects of naringin on proton-evoked currents and capsaicin-evoked currents. In the imaging of proton-evoked currents, naringin was used at a concentration of 30 μM. The TRPV1 oocyte image shows currents measured by injecting TRPV1 mRNA into oocytes. The distilled water-treated oocyte image shows currents measured by injecting tertiary distilled water into oocytes. Cap is capsaicin. Capsazepine is a published antagonist of TRPV1. The treatment was carried out at a pH of 4.0 using the ND96 buffer. (C) The histogram shows the degree of inhibition of TRPV1 inward current by naringin. The data are indicated as the mean ± S.E.M (n = 10–13 from six different frogs).
	Figure 3. Differences in the current–voltage relationship according to different treatment conditions in TRPV1-expressing oocytes: (A) changes in capsaicin-induced current in response to planned voltage changes. The black circle (●) is the current measured in the oocytes injected with distilled water. White circles (○) are TRPV1-injected oocytes treated with 1 μM capsaicin. Black triangles (▼) show oocytes simultaneously treated with 1 μM capsaicin and 30 μM naringin. ●, ○, and ▼ in (B,C) also show the same trend. (B) Changes in proton-induced current in response to planned voltage changes. (C) Current–voltage relationship measured in oocytes expressing the double mutant D471A + N628A. These data are indicated as the mean ± S.E.M (n = 9–14 from six different frogs).
	Figure 4. Molecular docking modeling of naringin to TRPV1: (A) side views of the docked naringin in complex with TRPV1. (B) Top views of the docking model. (C) An enlarged view of the red dotted line in Figure 4A. (D) An enlarged view of the red dotted line in Figure 4B.
	Figure 5. The binding pocket and docking results of naringin and TRPV1: (A) the binding pocket in the TRPV1 region of the extracellular domain membrane pocket side. (B) Two-dimensional schematic presentation of the predicted binding mode of naringin in the ligand-binding pocket. The ligands and important residues are shown. (C,D) Computational simulated binding interaction of ligand and residues in wild-type and mutants. The replaced mutants showed changes in interaction activities at varying degrees. (C) Interaction between naringin and wild-type TRPV1. (D) Interaction between naringin and mutant-type TRPV1.
	Figure 6. Comparison of the effect of naringin on mutant TRPV1: (A) D471A mutant TRPV1 was co-treated with naringin (30 μM) and capsaicin (1 μM). D471A mutant group was injected only with D471A TRPV1 mRNA into oocytes. N628A mutant TRPV1 was co-treated with naringin (30 μM) and capsaicin (1 μM). N628A mutant group was only injected with N628A TRPV1 mRNA into oocytes. D471A + N628A mutant group was injected with both D471A and N628A TRPV1 mRNAs into oocytes. (B) Concentration-response curves for the effect of naringin on oocytes expressing mutants. The percent inhibition of Icap on each mutant was normalized based on the peak inward current induced by capsaicin and that of the peak inward current elicited by capsaicin plus naringin. Each point showed the mean ± S.E.M. (n = 9–14 from six different frogs). Additional half inhibitory concentration, Hill coefficient, and Imax values are described in Results.

References [+] :

Aghazadeh Tabrizi, Medicinal Chemistry, Pharmacology, and Clinical Implications of TRPV1 Receptor Antagonists. 2017, Pubmed