Involvement of selective GABA-A receptor subtypes in amelioration of cisplatin-induced neuropathic pain by 2’-chloro-6-methyl flavone (2’-Cl-6MF)

• Published in: Naunyn-Schmiedeberg's archives of pharmacology Vol. 394; no. 5; pp. 929 - 940
• Main Authors: Karim, Nasiara, Khan, Imran, Abdelhalim, Abeer, Halim, Sobia Ahsan, Khan, Ajmal, Altaf, Nouman, Ahmad, Waqar, Ghaffar, Rukhsana, Al-Harrasi, Ahmed
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-05-2021; Springer Nature B.V
• Subjects: Benzodiazepines; Binding sites; Biomedical and Life Sciences; Biomedicine; Chemotherapy; Cisplatin; Flumazenil; Gabapentin; Homology; Hydrophobicity; Injection; Mechanical properties; Neuromodulation; Neurosciences; Nucleotide sequence; Oocytes; Original Article; Pain; Pain perception; Pentylenetetrazole; Peripheral neuropathy; Pharmacology/Toxicology; Potentiation; γ-Aminobutyric acid; γ-Aminobutyric acid A receptors; GABAergic; Gabapentin; 2’-Chloro-6-methylflavone; Chemotherapy-induced neuropathic pain; Cisplatin; Mechanical allodynia
• ISSN: 0028-1298; 1432-1912
• DOI: 10.1007/s00210-020-02021-x

Cisplatin-induced peripheral neuropathic pain is a common adverse effect of chemotherapy. The present study evaluated the effects of 2’-chloro-6-methylflavone (2’-Cl-6MF) at recombinant α1β2γ2L, α2β1-3γ2L, and α3β1-3γ2L GABA-A receptor subtypes expressed in
Xenopus
oocytes and subsequently evaluated its effectiveness in cisplatin-induced neuropathic pain. The results showed that 2’-Cl-6MF potentiated GABA-elicited currents at α2β2/3γ2L and α3β2/3γ2L GABA-A receptor subtypes. The potentiation was blocked by the co-application of flumazenil (a benzodiazepine (BDZs) site antagonist). In behavioral studies, mechanical allodynia was induced by intraplantar injection of cisplatin (40 μg/paw) in Sprague Dawley rats, and behavioral assessments were made 24 h after injection. 2’-Cl-6MF (1, 10, 30, and 100 mg/kg, i.p.), was administered 1 h before behavioral evaluation. Administration of 2’-Cl-6MF (30 and 100 mg/kg, i.p) significantly enhanced the paw withdrawal threshold and decreased mechanical allodynia. The standard drugs, gabapentin (GBP) at the dose of 70 mg/kg, and HZ 166 (16 mg/kg), i.p. also significantly enhanced the paw withdrawal threshold in mechanical allodynia. Pretreatment with pentylenetetrazole (PTZ) (15 mg/kg, i.p.) and flumazenil reversed the antinociceptive effect of 2’-Cl-6MF in mechanical allodynia indicating GABAergic mechanisms. Moreover, the binding mechanism of 2’-Cl-6MF was rationalized by in silico modeling tools. The 3D-coordinates of α2β2γ2L and α2β3γ2L were generated after homology modeling of the α2 subtype and 2’-Cl-6MF was at predicted binding sites of the developed models. The α2 model was compared with the α1 and α3 subunits via structural and sequence alignment. Molecular docking depicted that the compound binds efficiently at the neuromodulator binding site of the receptors. The findings of this study revealed that 2’-Cl-6MF ameliorated the manifestations of cisplatin-induced neuropathic pain in rats. Furthermore, we also conclude that GABAergic mechanisms may contribute to the antinociceptive effect of 2’-Cl-6MF. The molecular docking studies also confirm the involvement of the BDZs site of GABA-A receptors. It was observed that Ile230 of α2 stabilize the chlorophenyl ring of 2’-Cl-6MF through hydrophobic interactions, which is replaced by Val203 in α1 subunit. However, the smaller side chain of Val203 does not provide hydrophobic interaction to the compound due to high conformational flexibility of α1 subunit.