Department of Neurology, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, P.R. China.
Department of Pediatrics, Tianjin Children's Hospital, Beichen, Tianjin, P.R. China.
Department of Psychiatry, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, P.R. China.
PMID: 33770763
PMCID: PMC8064179
Free PMC article
Abstract
The mechanisms underlying the development of neuropathy associated with diabetes mellitus are not fully understood. Resveratrol, as a nonflavonoid polyphenol, plays a variety of beneficial roles in the treatment of chronic diseases such as Alzheimer's disease, coronary heart disease and obesity. In our study, the role of nuclear erythroid 2-related factor 2 (Nrf2) in resveratrol-mediated protection against streptozotocin-induced diabetic peripheral neuropathy (DPN) was investigated, and the antioxidant effect of resveratrol in diabetic peripheral nerves was studied. The STZ-treated model mice were divided into two groups. The resveratrol group was intragastrically administered 10 ml/kg 10% resveratrol once a day until the 12th week after STZ injection. The vehicle-treated mice were injected with the same volume of DMSO. Analysis of the effects of resveratrol in DPN revealed the following novel findings: (i) the pain and temperature sensitivities of diabetic mice were improved after treatment with resveratrol; (ii) Nrf2 expression was increased in the diabetic peripheral nerves of resveratrol-treated mice, and NF-KB pathway inhibition protected nerves upon resveratrol treatment in peripheral neuropathy; and (iii) resveratrol modulated the anti-inflammatory microenvironment of peripheral nerves by increasing Nrf2 activation and the expression of p-p65, and these changes may have been responsible for the neuroprotective effect of resveratrol in DPN, which was confirmed by Nrf2 knockout in diabetic mice. Overall, this study demonstrates that resveratrol may attenuate the severity of DPN by protecting peripheral nerves from apoptosis by inhibiting the NF-KB pathway and increasing Nrf2 expression.
Keywords: Nrf2 pathway; anti-inflammatory; diabetic neuropathy; resveratrol.
Conflict of interest
statement
CONFLICTS OF INTEREST: The authors declare that they have no conflicts of interest.
Figures
Figure 1
(A) Effect of fisetin on blood glucose in STZ+Vehicle and STZ+Resveratrol mice. (B) Mechanical nocice
ptive thresholds: ordinates represent the filament weight (0.1g) in which the animal responds in of presentations. (C) Thermal nociceptive threshold: the axis of ordinates represents the time (seconds) the animal takes to withdraw its paw. (Control group represents mice without administered with streptozotocin. 2 weeks after induction, mice were treated with Resveratrol or Vehicle (DMSO), n = 10 mice for each group, data are represented as the mean ± SEM.)
Figure 2
(A, B) Toluidine blue staining of semi-thin transverse sections of STZ+Vehicle and STZ+Resveratrol mice at 12 weeks after STZ injection. The percentage of abnormal fibers was quantitated (n = 3 mice per group; data are presented as means ± SEM). (C, D) Morphological assessment of axonal and myelin in sciatic nerves from STZ+Vehicle and STZ+Resveratrol mice. Representative electron micrographs from transverse ultra-thin sections of the sciatic nerves from STZ+Vehicle and STZ+Resveratrol at 12 weeks after STZ injection. (n = 3 nerves for each group, data are represented as the mean ± SEM).
Figure 3
(A, B) Quantification by Western blot analysis showed that the expression of Nrf2 increased in STZ+Resveratrol mice at 12 weeks after STZ injection, compared with the never from STZ+Vehicle mice (n = 3 nerves for each group, data are represented as the mean ± SEM). (C, D) Immunofluorescence in longitudinal sections of STZ+Vehicle and STZ+Resveratrol sciatic nerves for Nrf2 (green) at 12 weeks after STZ injection. Nrf2 and MBP was increased in STZ+Resveratrol. (n = 3 nerves for each group, data are represented as the mean ± SEM).
Figure 4
(A, B) Western blot analyses of lysates of HO-1, NQO1, GCLC from STZ+Vehicle and STZ+Resveratrol mice using the indicated antibodies at 12 weeks after STZ injection (n = 3 nerves for each group, data are represented as the mean ± SEM).
Figure 5
(A, B) Western blot analysis of lysates of p-p65/p65, MCP-1, TNF-a, IL-1β from STZ+Vehicle and STZ+Resveratrol mice, Quantification by Western blot analysis showed that the activation of AKT and the Bax, Cleaved caspase3 decreased in STZ+Resveratrol mice at 12 weeks after STZ injection (n = 3 nerves for each group, data are represented as the mean ± SEM.).
Figure 6
(A, B) TUNEL analysis (green) in longitudinal sections of STZ+Vehicle and STZ+Resveratrol mice stained with the nuclear dye Hoechst (blue) at 12 weeks after STZ injection. (n = 3 animals for each group, data are represented as the mean ± SEM). TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling.
Figure 7
(A, B) Quantification by Western blot analysis showed that Nrf2 decreased in the Nrf2-/-+STZ+Vehicle and Nrf2-/-+STZ+Resveratrol nerve, compared with WT+STZ+Resveratrol mice at 12 weeks after STZ injection (n = 3 nerves for each group, each nerve was repeated 3 times, data are represented as the mean ± SEM). (C, D) Mechanical nociceptive thresholds: ordinates represent the filament weight (0.1g) in which the animal responds in of presentations. Thermal nociceptive threshold: the axis of ordinates represents the time (seconds) the animal takes to withdraw its paw. (2 weeks after STZ induction, mice were treated with Resveratrol or Vehicle (DMSO), n = 10 mice for each group, data are represented as the mean ± SEM).
Figure 8
(A, B) Toluidine blue staining of semi-thin transverse sections of Nrf2-/-+STZ+Resveratrol, Nrf2-/-+STZ+Vehicle and WT+STZ+Resveratrol mice at 12 weeks after STZ injection, The percentage of abnormal fibers was quantitated, and the difference between the three groups was significant (n = 3 mice per group; data are presented as means ± SEM).
Figure 9
(A, B) Western blot analyses of lysates of p-p65/p65, MCP-1, TNF-a, IL-1β; from Nrf2-/-+STZ+Resveratrol, Nrf2-/-+STZ+Vehicle and WT+STZ+Resveratrol mice using the indicated antibodies at 12 weeks after STZ injection(n = 3 mice per group; data are presented as means ± SEM).
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