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Diabetic neuropathy is a peripheral nervous system disorder affecting both somatic and autonomic components of nervous system. A growing body of evidence have depicted that high glucose levels can induce activation of the Wnt/β-catenin pathway, however there are no studies targeting this pathway in DN. The intent of the present study was to investigate the effects of isoquercitrin (ISQ), a Wnt/β-catenin signaling pathway inhibitor, in diabetic neuropathy. Streptozotocin (50 mg/kg, i.p.) was used to induce diabetes in rats. 6-week diabetic rats were treated intrathecally with ISQ at 10 and 30 μM doses for 3 days. Furthermore, to confirm the results of the intrathecal study, a 2-week intraperitoneal treatment of ISQ was given to diabetic rats. After 6 weeks, diabetic rats developed neuropathy which was evident from reduced thermal and mechanical hyperalgesia thresholds and significant deterioration in motor nerve conduction velocity (MNCV), nerve blood flow (NBF). Sciatic nerves of diabetic neuropathy rats showed increased expression of Wnt pathway proteins namely β-catenin, c-myc and MMP2. Treatment with ISQ, both intrathecally (10 and 30 μM) and intraperitoneally (10 mg/kg), significantly ameliorated the alterations in behavioral pain thresholds and improved functional parameters in diabetic rats. Moreover, ISQ also downregulated the expression of Wnt/β-catenin pathway proteins significantly in diabetic rats as compared to vehicle-treated diabetic rats. Results of the present study suggest the neuroprotective potential of ISQ in the treatment of DN via inhibition of Wnt/β-catenin signaling pathway., (© 2020 International Union of Biochemistry and Molecular Biology.)

The cyclic enaminone moiety has been identified as a new scaffold for selective inhibition of cyclooxygenase-2 with anti-inflammatory and analgesic activities. The designed cyclic enaminones have been synthesized conveniently through the development of a new catalyst-free methodology and evaluated for cyclooxygenase (COX-1 and COX-2) inhibitory activities. Three compounds 7d, 8, and 9 predominantly inhibited COX-2 with selectivity index of 74.09, 19.45 and 108.68, respectively, and were assessed for in vivo anti-inflammatory activity in carrageenan induced rat paw edema assay. The anti-inflammatory activity of 7d was comparable to that of celecoxib at a dose of 12.5 mg/kg. However, the compounds 8 and 9 were more/equally effective as anti-inflammatory agent compared to celecoxib at the doses of 12.5 mg/kg and 25 mg/kg and also exhibited anti-inflammatory activity comparable to that of diclofenac. The therapeutic potential of the most active compound 9 was further assessed by performing in vivo thermal and mechanical hyperalgesia tests using various models that revealed its analgesic activity. The in vivo non-ulcerogenicity of 9 revealed the gastrointestinal safety as compared to the non-selective COX inhibitor indomethacin. The in vitro antioxidant activity and in vivo experiments on heart rate and blood pressure provided the cardiovascular safety profile of 9. The molecular docking studies rationalize the COX-2 selectivity of the newly found anti-inflammatory compounds 7d, 8, and 9., (Copyright © 2019. Published by Elsevier Masson SAS.)

A proper balance between oxidants and antioxidants is necessary in maintaining health and longevity. Alterations in this balance may result in oxidative stress causing functional disorders and diseases. Oxidative stress is considered to play a vital role in the pathogenesis of diabetes and its complications. Flavanones and flavanones-rich botanical extracts have been a subject of great interest for scientific research. Citrus flavanones like naringin and hesperidin exert a variety of biological activities such as anti-oxidant, anti-inflammatory, antihyperglycemic, anti-apoptotic etc. Naringin and hesperidin along with their respective aglycones, naringenin and hesperetin have been shown to attenuate diabetes and its related complications. This review discusses the role of flavanones as a possible emerging treatment for diabetes and its complications along with the possible mechanistic explanations.

Long-standing diabetes and complications thereof particularly, neuropathy stands for one of the major causes of morbidity across the globe. It is postulated that excessive production of reactive oxygen species is a key component in the development and progression of diabetic neuropathy. Oxidative damage is the most common concluding pathway for various pathogenetic mechanisms of neuronal injury in diabetic neuropathy. However despite optimistic preclinical data, it is still very ambiguous that why antioxidants have failed to demonstrate significant neuroprotection in humans. A growing body of evidences now suggests that strategies utilizing a more targeted approach like focusing on Nrf2 (a transcription factor modulating oxidative stress) may provide an enthralling avenue to optimize neuroprotection in diabetes and diabetic neuropathy. This review presents an emerging concept of Nrf2 in diabetic neuropathy; thus looking forward to newer strategies for combating the oxidant induced damage., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Oxidative stress resulting in excessive generation of ROS is a compelling initiator of DNA damage along with damage to various cellular proteins and other macromolecules. Poly(ADP-ribose) polymerase (PARP) activation in response to DNA damage, stirs an energy-consuming cellular metabolic cycle; culminating into cell death. The present study was designed to determine the effect of combining an antioxidant, Melatonin and a PARP inhibitor, Nicotinamide on the hallmark deficits developing in diabetic neuropathy (DN). Streptozotocin (STZ, 55 mg/kg, i.p.) was administered to induce diabetes. Six weeks post diabetes induction, two week treatment with Melatonin (3 and 10 mg/kg) and Nicotinamide (100 and 300 mg/kg) either alone or in combination was given. Effect of these interventions on the functional, behavioral and biochemical changes caused by hyperglycemia were studied in treated animals. Melatonin and Nicotinamide alone as well as in combination ameliorated the functional deficits along with improvement in pain parameters. The combination also demonstrated an essential reversal of biochemical alterations. Nitrotyrosine and Poly ADP Ribose (PAR) immunopositivity was significantly decreased in sciatic nerve micro-sections of treatment group. The results of this study advocate that simultaneous inhibition of oxidative stress-PARP activation cascade may prove useful for the pharmacotherapy of DN., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Oxidative stress has been implicated in pathophysiology of diabetic neuropathy. All the pathways responsible for development of diabetic neuropathy are linked to oxidative stress in one way or the other. In the present study, we have targeted oxidative stress in diabetic neuropathy using resveratrol, a potent antioxidant. Eight weeks streptozotocin-diabetic rats developed neuropathy which was evident from significant reduction in motor nerve conduction velocity (MNCV), nerve blood flow (NBF) and increased thermal hyperalgesia. The 2-week treatment with resveratrol (10 and 20 mg/kg, i.p.) started 6 weeks after diabetes induction significantly ameliorated the alterations in MNCV, NBF, and hyperalgesia. Resveratrol also attenuated enhanced levels of malondialdehyde (MDA), peroxynitrite and produced increase in catalase levels in diabetic rats. There was marked reduction in DNA fragmentation observed after resveratrol treatment in diabetic rats as evident from decrease in Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells in sciatic nerve sections. Results of the present study suggest the potential of resveratrol in treatment of diabetic neuropathy and its protective effect may be mediated through reduction in oxidative stress and DNA fragmentation.

Oxidative stress has been implicated to play an important role in the pathogenesis of diabetic neuropathy, which is the most common complication of diabetes mellitus affecting more than 50% of diabetic patients. In the present study, we have investigated the effect of U83836E [(-)-2-((4-(2,6-Di-1-pyrrolidinyl-4-pyrimidinyl)-1-piperazinyl)methyl)-3,4-dihydro-2,3,7,8-tetramethyl-2H-1-benzopyran-6-ol, 2HCl], a potent free radical scavenger in streptozotocin (STZ)-induced diabetic neuropathy in rats. STZ-induced diabetic rats showed significant deficit in motor nerve conduction velocity (MNCV), nerve blood flow (NBF) and thermal hyperalgesia after 8 weeks of diabetes induction, indicating development of diabetic neuropathy. Antioxidant enzyme (superoxide dismutase and catalase) levels were reduced and malondialdehyde (MDA) levels were significantly increased in diabetic rats as compared to the age-matched control rats, this indicates the involvement of oxidative stress in diabetic neuropathy. The 2-week treatment with U83836E (3 and 9 mg/kg, i.p.) started 6 weeks after diabetes induction significantly ameliorated the alterations in MNCV, NBF, hyperalgesia, MDA levels and antioxidant enzymes in diabetic rats. Results of the present study suggest the potential of U83836E in treatment of diabetic neuropathy.

Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research, Punjab, India We have investigated the neuroprotective potential of combination of poly (ADP-ribose) polymerase inhibitor (nicotinamide or 3-aminobenzamide) and antioxidant (melatonin) in middle cerebral artery occlusion (MCAo) induced focal ischemia in rats. MCAo of 2 h followed by 22 h reperfusion produced large volume of cerebral infarction (mean +/- SEM 211.38 +/- 8.35 mm3), volume of edema (60 +/- 2 mm3) and neurological deficits (4.45 +/- 0.25). Combination of nicotinamide (500 mg kg(-1), i.p.) and melatonin (10 mg kg(-1), i.p.) significantly decreased infarct volume to 48 +/- 2.58 mm3 as compared to their individual drug (nicotinamide 76 +/- 12.49mm3, melatonin 76.17 +/- 1.24 mm3). A significant improvement was observed in edema volume and neurological deficits with this combination. Combination of 3-aminobenzamide (20 mg kg(-1), i.p.) and melatonin (10 mg kg(-1), i.p.) also produced similar reduction in infarction, edema and neurological score. These results indicate that the combination of poly (ADP-ribose) polymerase inhibitor and antioxidant produce enhanced neuroprotection. Clinical availability and wide therapeutic margin of nicotinamide and melatonin make them a promising drug combination for clinical evaluation in stroke patients.

Free radical induced neuronal damage is implicated in cerebral ischemia reperfusion (IR) injury and antioxidants are reported to have neuroprotective activity. Several in vitro and in vivo studies have proved the antioxidant potential of curcumin and its metabolites. Hence, in the present study the neuroprotective potential of curcumin was investigated in middle cerebral artery occlusion (MCAO) induced focal cerebral IR injury. 2 h of MCAO and 22 h of reperfusion resulted in the infarct volume of 210.39 ± 31.25 mm3. Administration of curcumin 100 and 300 mg/kg, i.p. 30 min. after MCAO produced 37.23 ± 5.10% and 46.39 ± 10.23% (p<0.05) reduction in infarct volume, respectively. Ischemia induced cerebral edema was reduced in a dose dependent manner. Curcumin at 300 mg/kg, i.p. produced 50.96 ± 6.04% reduction in edema (p<0.05) volume. Increase in lipid peroxidation after MCAO in ipsilateral and contralateral hemisphere of brain was observed, which was reduced by curcumin (300 mg/kg, i.p.)-treatment. Decrease in superoxide dismutase and glutathione peroxidase activity was observed in ipsilateral hemisphere of MCAO animal. Curcumin-treatment (300 mg/kg, i.p.) prevented IR injury mediated fall in glutathione peroxide activity. Peroxynitrite measured using rhodamine123 fluorescence and anti-nitrotyrosine immunofluorescence indicated increased peroxynitrite formation after IR insult. Curcumin-treatment reduced peroxynitrite formation and hence the extent of tyrosine nitration in the cytosolic proteins. These results suggest the neuroprotective potential of curcumin in cerebral ischemia and is mediated through its antioxidant activity. [Copyright &y& Elsevier]

The effect of a free radical generator pyrogallol on gastric emptying was studied in rats. Pyrogallol at doses of 25, 50, 100 and 150 mg/kg (i.p.) produced dose-dependent inhibition of gastric emptying. Pretreatment with vitamin C (100 and 500 mg/kg, p.o.), and vitamin E (100 and 500 mg/kg, p.o.) significantly reversed the inhibition in gastric emptying caused by pyrogallol 100 mg/kg. However, the combination of vitamin C and vitamin E (100 mg/kg) produced synergistic effect. Glutathione (100 mg/kg i.v.) 5-min pretreatment also reversed the inhibition of gastric emptying caused by pyrogallol 100 mg/kg. Ondansetron (3 mg/kg, p.o.) significantly reversed the pyrogallol effect. The effect of pyrogallol on malondialdehyde (MDA) levels and 5-HT levels in the stomach tissue was also studied. Pyrogallol at a dose of 100 mg/kg, i.p., significantly increased MDA levels and 5-HT levels in the stomach. Pretreatment with a combination of vitamin C and vitamin E (100 mg/kg, p.o.) and glutathione (100 mg/kg, i.v.) significantly ameliorated the rise in stomach tissue MDA caused by pyrogallol but had no significant effect on the rise in 5-HT levels caused by pyrogallol. The effect of different doses of 5-HT on gastric emptying was also studied. 5-HT had a differential effect on gastric emptying. The low and high doses (0.1, 0.3 and 30 mg/kg, i.p.) significantly inhibited the gastric emptying while doses ranging from 1 to 10 mg/kg, i.p., had no significant effect on the gastric emptying. The pretreatment with antioxidants, combination of vitamin C and vitamin E (100 mg/kg each, p.o.) and glutathione (100 mg/kg, i.v.) had no effect on the 5-HT (0.3 mg/kg, i.p.)-induced delay in gastric emptying. The result indicate the role of free radicals gastric emptying, and antioxidants may be of potential therapeutic value in disease conditions where free radicals are known to be released and the gastrointestinal effects are observed as symptoms or side effects of drug therapy.Copyright © 2000 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]