Neuroprotective properties of ethanolic extract of Citrus unshiu Markovich peel through NADPH oxidase 2 inhibition in chemotherapy‐induced neuropathic pain animal model

Abstract

The present study aimed to determine the antioxidant effect of Citrus unshiu Markovich (CUM) extract in neuronal cell lines under oxidative stress and to investigate the effect of chemotherapy‐induced peripheral neuropathy (CIPN) on the nociceptive response in a preclinical mice model. We tested the inhibition of H2O2 in Neuro2A cells treated with CUM. Experimental animals were treated with oxaliplatin to induce CINP, and then administered oral CUM for 4 weeks in order to observe the effect of CUM. Animals were evaluated weekly for thermal hyperalgesia and digital motor nerve conduction velocity (NCV). Lumbar dorsal root ganglia (DRG) isolated from each animal were evaluated through immunochemical and western blot analysis for nerve damage, inflammatory response, and expression of redox signaling factors. The main mechanisms were determined to be decreased inducible nitric oxide synthase (iNOS) production due to the inhibition of NADPH oxidase 2 (NOX2). To determine the functional role of NOX2 in CINP, we administrated CUM into NOX2‐deficient mice with neuropathic pain. Therefore, we suggest that CUM controls the expression levels of inflammatory factors in CINP via NOX2 inactivation. This study demonstrated that a complementary medicine such as CUM might be a potential novel therapeutic agent for the treatment of CINP.

The Multiple Faces of Nitric Oxide in Chronic Granulomatous Disease: A Comprehensive Update

“…Furthermore, it has been shown that not only NO acts as a signaling molecule but that ROS- derived from NADPH oxidase- also has a regulatory function with associated signaling pathways [ 66 , 67 ]. It has been suggested that NADPH oxidase presents a higher hierarchy in the signaling of inflammatory circuits and that it controls the production of NO by modulating the expression of iNOS [ 67 , 68 , 69 , 70 ]. However, it has also been reported that iNOS activity is capable of regulating the function of the NADPH oxidase complex [ 71 , 72 ].…”

Effects of NADPH Oxidase Isoform-2 (NOX2) Inhibition on Behavioral Responses and Neuroinflammation in a Mouse Model of Neuropathic Pain

“…In this context, NADPH oxidases (NOXs), whose primary function is the regulated production of ROS [15], have emerged as potential pharmacological targets for NP, which is corroborated by mounting evidence implicating some NOX isoforms in NP development [3,16]. Specifically, NOX2 is upregulated in the nervous system after nerve injury [17][18][19][20][21][22], and NOX2-knockout mice exhibit attenuated NP behaviors [17,20,23,24]. Furthermore, NOX2-derived ROS are involved in spinal neuroimmune activation that underlies NP, namely microglia activation, and proinflammatory cytokine expression [17].…”

Biometabolites of Citrus unshiu Peel Enhance Intestinal Permeability and Alter Gut Commensal Bacteria

“…In particular, the therapeutic effects of the peel covering C. unshiu have received more attention than other parts of the plant, because it exerts outstanding antioxidant effects compared to the pulp owing to its high mineral composition [ 13 , 14 ]. C. unshiu peel is widely used as a therapeutic agent for clinical purposes, such as neuropathic pain [ 15 ], cervical cancer [ 16 ], nonalcoholic fatty liver [ 17 ], hyperglycemia [ 18 ], pancreatic cancer [ 19 ], and systemic inflammation [ 20 ]. This raw material can also be processed using various extraction protocols, as mentioned above.…”

“…Especially, water or ethanol extraction is a commonly used method to extract flavonoids from natural substances, hence, many studies employing solvent-extracted CUP have been conducted. For example, the ethanol derivative of CUP ameliorated oxidative stress by suppressing nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 expression (NOX2) in a chemotherapy-induced neuropathic pain animal model [ 15 ] and decreasing the expression levels of pro-inflammatory cytokines, such as interleukin (IL)-6, interferon (IFN)-γ, and tumor necrosis factor-alpha (TNFα), in a type 2 diabetes and systemic inflammation mouse model [ 18 , 20 ]. Moreover, water extracts of CUP have been reported to attenuate dextran sulfate sodium-induced colitis by regulating the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway [ 21 ].…”