AUTHOR=Chia Jasmine Siew Min , Izham Noor Aishah Mohammed , Farouk Ahmad Akira Omar , Sulaiman Mohd Roslan , Mustafa Sanam , Hutchinson Mark R. , Perimal Enoch Kumar 

TITLE=Zerumbone Modulates α2A-Adrenergic, TRPV1, and NMDA NR2B Receptors Plasticity in CCI-Induced Neuropathic Pain In Vivo and LPS-Induced SH-SY5Y Neuroblastoma In Vitro Models

JOURNAL=Frontiers in Pharmacology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2020.00092

DOI=10.3389/fphar.2020.00092

ISSN=1663-9812

ABSTRACT=<p>Zerumbone has shown great potential in various pathophysiological models of diseases, particularly in neuropathic pain conditions. Further understanding the mechanisms of action is important to develop zerumbone as a potential anti-nociceptive agent. Numerous receptors and pathways function to inhibit and modulate transmission of pain signals. Previously, we demonstrated involvement of the serotonergic system in zerumbone’s anti-neuropathic effects. The present study was conducted to determine zerumbone’s modulatory potential involving noradrenergic, transient receptor potential vanilloid type 1 (TRPV1) and <italic>N</italic>-methyl-D-aspartate (NMDA) receptors in chronic constriction injury (CCI)-induced <italic>in vitro</italic> and lipopolysaccharide (LPS)-induced SH-SY5Y <italic>in vitro</italic> neuroinflammatory models. von Frey filament and Hargreaves plantar tests were used to assess allodynia and hyperalgesia in the chronic constriction injury-induced neuropathic pain mouse model. Involvement of specific adrenoceptors were investigated using antagonists— prazosin (α<sub>1</sub>-adrenoceptor antagonist), idazoxan (α<sub>2</sub>-adrenoceptor antagonist), metoprolol (β<sub>1</sub>-adrenoceptor antagonist), ICI 118,551 (β<sub>2</sub>-adrenoceptor antagonist), and SR 59230 A (β<sub>3</sub>-adrenoceptor antagonist), co-administered with zerumbone (10 mg/kg). Involvement of excitatory receptors; TRPV and NMDA were conducted using antagonists capsazepine (TRPV1 antagonist) and memantine (NMDA antagonist). Western blot was conducted to investigate the effect of zerumbone on the expression of α<sub>2A</sub>-adrenoceptor, TRPV1 and NMDA NR2B receptors in CCI-induced whole brain samples of mice as well as in LPS-induced SH-SY5Y neuroblastoma cells. Pre-treatment with α<sub>1</sub>- and α<sub>2</sub>-adrenoceptor antagonists significantly attenuated both anti-allodynic and anti-hyperalgesic effects of zerumbone. For β-adrenoceptors, only β<sub>2</sub>-adrenoceptor antagonist significantly reversed the anti-allodynic and anti-hyperalgesic effects of zerumbone. β<sub>1</sub>-adrenoceptor antagonist only reversed the anti-allodynic effect of zerumbone. The anti-allodynic and anti-hyperalgesic effects of zerumbone were both absent when TRPV1 and NMDA receptors were antagonized in both nociceptive assays. Zerumbone treatment markedly decreased the expression of α<sub>2A</sub>-adrenoceptor, while an up-regulation was observed of NMDA NR2B receptors. Expression of TRPV1 receptors however did not significantly change. The <italic>in vitro</italic> study, representing a peripheral model, demonstrated the reduction of both NMDA NR2B and TRPV1 receptors while significantly increasing α<sub>2A</sub>-adrenoceptor expression in contrast to the brain samples. Our current findings suggest that the α<sub>1</sub>-, α<sub>2</sub>-, β<sub>1</sub>- and β<sub>2</sub>-adrenoceptors, TRPV1 and NMDA NR2B are essential for the anti-allodynic and antihyperalgesic effects of zerumbone. Alternatively, we demonstrated the plasticity of these receptors through their response to zerumbone’s administration.</p>