Search

The Nuclear factor-2 erythroid related factor-2 (Nrf2) is a redox regulated transcription factor involved in the regulation of antioxidant defence systems. It drives the production of endogenous antioxidant defences and detoxifying enzymes. Nuclear factor-kappa light chain enhancer of B cells (NF-κB) is a transcription factor, involved in proinflammatory cytokine production, in addition to its immunological function. Both Nrf2 and NF-κB regulation are co-ordinated in order to maintain redox homeostasis in healthy cells. However, during pathological conditions this regulation is perturbed offering an opportunity for therapeutic intervention. Diabetic neuropathy is a condition, in which change in expression pattern of Nrf2 and NF-κB has been reported. This review aims to focus on the role of the Nrf2 and NF-κB in diabetic neuropathy and summarizes the therapeutic outcomes of various pharmacological modulators targeted at the Nrf2-NF-κB axis in diabetic neuropathy.

Inflammation is an emerging patho-mechanism of diabetes and its complications. NF-κB pathway is one of the central machinery initiating and propagating inflammatory responses. The present study envisaged the involvement of NF-κB inflammatory cascade in the pathophysiology of diabetic neuropathy using BAY 11-7082, an IκB phosphorylation inhibitor. Streptozotocin was used to induce diabetes in Sprauge Dawley rats. BAY 11-7082 (1 & 3 mg/kg) was administered to diabetic rats for 14 days starting from the end of six weeks post diabetic induction. Diabetic rats developed deficits in nerve functions and altered nociceptive parameters and also showed elevated expression of NF-κB (p65), IκB and p-IκB along with increased levels of IL-6 & TNF-α and inducible enzymes (COX-2 and iNOS). Furthermore, there was an increase in oxidative stress and decrease in Nrf2/HO-1 expression. We observed that BAY 11-7082 alleviated abnormal sensory responses and deficits in nerve functions. BAY 11-7082 also ameliorated the increase in expression of NF-κB, IκB and p-IκB. BAY 11-7082 curbed down the levels of IL-6, TNF-α, COX-2 and iNOS in the sciatic nerve. Lowering of lipid peroxidation and improvement in GSH levels was also seen along with increased expression of Nrf2/HO-1. Thus it can be concluded that NF-κB expression and downstream expression of proinflammatory mediators are prominent features of nerve damage leading to inflammation and oxidative stress and BAY 11-7082 was able to ameliorate experimental diabetic neuropathy by modulating neuroinflammation and improving antioxidant defence., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

High glucose driven reactive oxygen intermediates production and inflammatory damage are recognized contributors of nerve dysfunction and subsequent damage in diabetic neuropathy. Sulforaphane, a known chemotherapeutic agent holds a promise for diabetic neuropathy because of its dual antioxidant and anti-inflammatory activities. The present study investigated the effect of sulforaphane in streptozotocin (STZ) induced diabetic neuropathy in rats. For in vitro experiments neuro2a cells were incubated with sulforaphane in the presence of normal (5.5 mM) and high glucose (30 mM). For in vivo studies, sulforaphane (0.5 and 1 mg/kg) was administered six weeks post diabetes induction for two weeks. Motor nerve conduction velocity (MNCV), nerve blood flow (NBF) and pain behavior were improved and malondialdehyde (MDA) level was reduced by sulforaphane. Antioxidant effect of sulforaphane is derived from nuclear erythroid 2-related factor 2 (Nrf2) activation as demonstrated by increased expression of Nrf2 and downstream targets hemeoxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO-1) in neuro2a cells and sciatic nerve of diabetic animals. Nuclear factor-kappa B (NF-κB) inhibition seemed to be responsible for antiinflammatory activity of sulforaphane as there was reduction in NF-κB expression and IκB kinase (IKK) phosphorylation along with abrogation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression and tumor necrosis factor-α (TNF-α) and interleukine-6 (IL-6) levels. Here in this study we provide an evidence that sulforaphane is effective in reversing the various deficits in experimental diabetic neuropathy. This study supports the defensive role of Nrf2 in neurons under conditions of oxidative stress and also suggests that the NF-κB pathway is an important modulator of inflammatory damage in diabetic neuropathy.

Aim: Nuclear factor-kappa B (NF-κB) being reported to play an important role in the pathogenesis of diabetic neuropathy is believed to be a central mechanism involved in the genesis and promulgation of inflammatory insult. Here we have targeted the nuclear translocation of NF-κB using JSH-23 to elucidate its role in diabetic neuropathy., Methods: JSH-23 (1 and 3 mg/kg) was administered for 2 weeks in diabetic rats, after 6 weeks of diabetes induction using streptozotocin (55 mg/kg) as diabetogenic agent. Functional (motor nerve conduction velocity and blood flow), behavioural (mechanical hyperalgesia), biochemical [malondialdehyde, glutathione, tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels] and NF-κB translocation studies (western blot technique) were then undertaken., Results: JSH-23 treatment significantly reversed the nerve conduction and nerve blood flow deficits seen in diabetic animals. Reduction in mechanical pain threshold was also partially corrected by the treatment. Protein expression studies showed that nuclear translocation of p65/p50 subunit was inhibited by JSH-23 treatment in the sciatic nerve. The treatment also lowered the elevated IL-6, TNF-α, cyclo-oxygenase (COX-2) and inducible nitric oxide synthase (iNOS) levels/expression, indicating reduction in the inflammatory damage of the sciatic nerve. Apart from these effects, JSH-23 also increased Nrf2 and hemeoxygenase-1 (HO-1) levels which could imply its potential in increasing the strength of antioxidant defence., Conclusion: We observed that NF-κB inhibition partially reversed functional, behavioural and biochemical deficits with JSH-23 treatment. This study substantiates the role of NF-κB activation in the aetiology of diabetic neuropathy and protection afforded by inhibition of NF-κB by JSH-23, which can be attributed to its effect on neuroinflammation and oxidative stress., (© 2011 Blackwell Publishing Ltd.)

Melatonin exhibits an array of biological activities, including antioxidant and anti-inflammatory actions. Diabetic neuropathy is one of the complications of diabetes with a prevalence rate of 50-60%. We have previously reported the protective effect of melatonin in experimental diabetic neuropathy. In this study, we investigated the role of nuclear factor-kappa B (NF-κB) and nuclear erythroid 2-related factor 2 (Nrf2) in melatonin-mediated protection against streptozotocin-induced diabetic neuropathy. Melatonin at doses of 3 and 10 mg/kg was administered daily in seventh and eighth week after diabetes induction. Motor nerve conduction velocity and nerve blood flow were improved in melatonin-treated animals. Melatonin also reduced the elevated expression of NF-κB, IκB-α, and phosphorylated IκB-α. Further, melatonin treatment also reduced the elevated levels of proinflammatory cytokines (TNF-α and IL-6), iNOS and COX-2 in sciatic nerves of animals. The capacity of melatonin to modulate Nrf2 pathway was associated with increased heme oxygenase-1 (HO-1) expression, which strengthens antioxidant defense. This fact was also established by decreased DNA fragmentation (because inhibition of excessive oxidant-induced DNA damage) in the sciatic nerve of melatonin-treated animals. The results of this study suggest that melatonin modulates neuroinflammation by decreasing NF-κB activation cascade and oxidative stress by increasing Nrf2 expression, which might be responsible at least in part, for its neuroprotective effect in diabetic neuropathy., (© 2010 The Authors. Journal of Pineal Research © 2010 John Wiley & Sons A/S.)