N-acetylcysteine inhibits hyperglycemia-induced oxidative stress and apoptosis markers in diabetic neuropathy

Roles of Neuronal Protein Kinase Cε on Endoplasmic Reticulum Stress and Autophagic Formation in Diabetic Neuropathy

In chronic diabetic neuropathy (DN), the cellular mechanisms of neuropathic pain remain unclear. Protein kinase C epsilon (PKCε) is an intracellular signaling molecule that mediates chronic pain. This paper addresses the long-term upregulated PKCε in DN associated with endoplasmic reticulum (ER) stress and autophagic formation and correlates to chronic neuropathic pain. We found that thermal hyperalgesia and mechanical allodynia course development were associated with PKCε upregulation after DN but not skin denervation. Pathologically, PKCε upregulation was associated with the expression of inositol-requiring enzyme 1α (IRE1α; ER stress-related molecule) and ubiquitin D (UBD), which are involved in the ubiquitin-proteasome system (UPS)-mediated degradation of misfolded proteins under ER stress. Manders coefficient analyses revealed an approximately 50% colocalized ratio for IRE1α(+):PKCε(+) neurons (0.34-0.48 for M1 and 0.40-0.58 for M2 Manders coefficients). The colocalized coefficients of UBD/PKCε increased (M1: 0.33 ± 0.03 vs. 0.77 ± 0.04, p < 0.001; M2: 0.29 ± 0.05 vs. 0.78 ± 0.04; p < 0.001) in the acute DN stage. In addition, the regulatory subunit p85 of phosphoinositide 3-kinase, which is involved in regulating insulin signaling, exhibited similar expression patterns to those of IRE1α and UBD; for example, it had highly colocalized ratios to PKCε. The ultrastructural examination further confirmed that autophagic formation was associated with PKCε upregulation. Furthermore, PKCεv1-2, a PKCε specific inhibitor, reverses neuropathic pain, ER stress, and autophagic formation in DN. This finding suggests PKCε plays an upstream molecule in DN-associated neuropathic pain and neuropathology and could provide a potential therapeutic target.

Rubia cordifolia L. Attenuates Diabetic Neuropathy by Inhibiting Apoptosis and Oxidative Stress in Rats

BACKGROUND

Diabetic neuropathy is a debilitating manifestation of long-term diabetes mellitus. The present study explored the effects of the roots of Rubia cordifolia L. (R. cordifolia L.) in the Wistar rat model for diabetic neuropathy and possible neuroprotective, antidiabetic, and analgesic mechanisms underlying this effect.

MATERIALS AND METHODS

Rats were divided into five experimental groups. An amount of 0.25% carboxy methyl cellulose (CMC) in saline and streptozotocin (STZ) (60 mg/kg) was given to group 1 and group 2, respectively. Group 3 was treated with STZ and glibenclamide simultaneously while groups 4 and 5 were simultaneously treated with STZ and hydroalcoholic extract of the root of R. cordifolia, respectively. Hot plate and cold allodynias were used to evaluate the pain threshold. The antioxidant effects of R. cordifolia were assessed by measuring Thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD). At the end of the study, sciatic nerve and brain tissues were collected for histopathological study. Bcl-2 proteins, cleaved caspase-3, and Bax were assessed through the Western blot method.

RESULTS

R. cordifolia significantly attenuated paw withdrawal and tail flick latency in diabetic neuropathic rats. R. cordifolia significantly (p < 0.01) improved the levels of oxidative stress. It was found to decrease blood glucose levels and to increase animal weight in R. cordifolia-treated groups. Treatment with R. cordifolia suppressed the cleaved caspase-3 and reduced the Bax:Bcl2 ratio in sciatic nerve and brain tissue compared to the diabetic group. Histopathological analysis also revealed a marked improvement in architecture and loss of axons in brain and sciatic nerve tissues at a higher dose of R. cordifolia (400 mg/kg).

CONCLUSION

R. cordifolia attenuated diabetic neuropathy through its antidiabetic and analgesic properties by ameliorating apoptosis and oxidative stress.

Hydrogen sulfide: From a toxic gas to a potential therapy for COVID-19 and inflammatory disorders

COVID-19 has been shown to induce inflammatory disorders and CNS manifestations. Swift and efficient treatment strategies are urgently warranted for the management of COVID, inflammatory and neurological disorders. Hydrogen sulfide (H2S) has been associated with several clinical disorders due to its potential to influence a broad range of biological signalling pathways. According to recent clinical studies, COVID patients with lower physiological H2S had higher fatality rates. These findings clearly demonstrate an inverse correlation between H2S levels and the severity of COVID-19. H2S has been proposed as a protective molecule because of its antioxidant, anti-inflammatory, and antiviral properties. Various H2S-releasing prodrugs, hybrids and natural compounds have been tested for their therapeutic efficacy in viral infections and inflammatory disorders. In this review, I am highlighting the rationale for using H2S-based interventions for the management of COVID-19 and post-infection inflammatory disorders including neuroinflammation. I am also proposing therepurposing of existing H2S-releasing prodrugs, developing new NO-H2S-hybrids, targeting H2S metabolic pathways, and using H2S-producing dietary supplements as viable defensive strategies against SARS-CoV-2 infection and COVID-19 pathologies.

Essential Amino Acid Starvation-Induced Oxidative Stress Causes DNA Damage and Apoptosis in Murine Osteoblast-like Cells

Intracellular nutrient metabolism, particularly the metabolism of essential amino acids (EAAs), is crucial for cellular functions, including energy production and redox homeostasis. An EAA deficiency can lead to cellular dysfunction and oxidative stress. This study explores the mechanisms underlying cellular responses to EAA starvation, focusing on ROS-induced DNA damage and apoptosis. MC3T3-E1 cells were subjected to EAA starvation, and various assays were conducted to assess cell proliferation, survival, DNA damage, and apoptosis. The antioxidant N-acetylcysteine (NAC) was employed to block ROS formation and mitigate cellular damage. Gene expression and Western blot analyses were performed to elucidate molecular pathways. EAA starvation-induced ROS generation, DNA damage, and apoptosis in MC3T3-E1 cells. NAC administration effectively reduced DNA damage and apoptosis, highlighting the pivotal role of ROS in mediating these cellular responses during EAA deficiency. This study demonstrates that EAA starvation triggers ROS-mediated DNA damage and apoptosis, offering insights into the intricate interplay between nutrient deficiency, oxidative stress, and programmed cell death. NAC emerges as a potential therapeutic intervention to counteract these adverse effects.

A sweet emergency due to bitter poisoning-A case report

Organophosphorus compounds (OPC) are major components of pesticides and nerve gas agents. Self-harm by ingestion of OPC pesticides is one of the common problems encountered in the emergency room (ER), especially in developing countries such as India. It is recognised by the World Health Organization (WHO) as the third most prevalent means of suicide. In addition to the cholinergic effects caused by these agents, they can induce metabolic dysregulations. We present a case of a 22-year-old male patient, without previous history of diabetes, who was brought to the ER in an unresponsive state with an HbA1c of 5%. His initial laboratory investigations revealed hyperglycemia, high anion gap metabolic acidosis, ketonuria, and glycosuria. His relatives revealed intentional ingestion of OPC. He was treated for both OPC poisoning and hyperglycemic ketoacidosis. Adequate acute care was instigated though prognosis could not be gauged due to the early discharge of the patient against medical advice. This case highlights that OPC poisoning can be a possible etiological factor for hyperglycemic ketoacidosis. It can mimic diabetic ketoacidosis leading to delayed diagnosis. Thus, early identification and immediate management are crucial because of the effect of hyperglycemic ketoacidosis on the outcome of a patient with OPC poisoning.

Isolation of Thymol from Trachyspermum ammi Fruits for Treatment of Diabetes and Diabetic Neuropathy in STZ-Induced Rats

Terpenoids and phenols from Trachyspermum ammi (T. ammi) have reported some pharmacological actions. The objective of the work was to isolate the active constituent, its identification by spectroscopic techniques, and evaluation of the antidiabetic and neuroprotective activity from T. ammi on STZ Wistar rats. The dried fruits of T ammi were kept in a hydrodistillation apparatus to collect essential oil. The isolated fraction went through TLC, UV, FTIR, HPLC, HRMS, C¹³, and ¹H NMR for characterization. Two dosage concentrations from the isolated compound were prepared as 10 and 20 mg/kg for treatment groups. The groups were tested for thermal and mechanical hyperalgesia, writhing, grip strength, spontaneous locomotor test, neuromuscular coordination tests, and histopathological and lipid profile analysis. Diabetes was induced by streptozotocin (45 mg/kg i.p.) and 12 weeks of treatment-induced diabetic neuropathy in Wistar rats. Biomarkers were evaluated to understand the neuropathic protection of thymol on STZ-treated Wistar rats. The biomarker studies (SOD, NO, LPO, Na⁺K⁺ATPase, and TNF-α) further confirmed thymol's diabetic neuropathy protective action. This study suggests that isolated compound thymol was antidiabetic and neuroprotective as it has shown controlled glucose levels defensive nerve damage in STZ Wistar rats. P < 0.05 level of significance was observed in the levels of endogenous biomarkers, fasting blood glucose levels, actophotometer response, and response latency in treated groups compared to the diabetic group, whereas P < 0.001 level of significance during lipid profile levels, thermal algesia, and neuromuscular comparison tests was noted in treated groups compared to the diabetic group.

Neuroprotective effect of Morin via TrkB/Akt pathway against diabetes mediated oxidative stress and apoptosis in neuronal cells

Long term Diabetes mellitus results in neuronal damage by increased intracellular glucose leading to oxidative stress. This condition is known as diabetic encephalopathy. Morin is a bioflavonoid, has significant antidiabetic, antioxidant and anti-inflammatory activities. The present study investigated whether the antioxidant properties of morin has beneficial effects on structural brain damage, neuronal apoptosis and dysregulation of TrkB/Akt signalling associated with diabetes. Adult male Sprague Dawley rats were induced diabetes by an intraperitoneal injection of 40mg/kg of streptozotocin and kept untreated for 30 days to induce DE. Cognitive performance was assessed using the Morris water maze test followed by morin and metformin administration at the doses of 50 and 100mg/kg, respectively, for 60 days. After 60 days of treatment, animals were subjected to the behavioural test and sacrificed to collect blood and brain and checked biochemical parameters.The treatment with Morin could significantly reduce the escape latency time in Morris water maze test, blood glucose level, HbA1C, toxicity markers, lipid peroxidation products and protein carbonyl content, downregulated the expression of Bax, Caspase 3 and Cytochrome C and upregulated Bcl-2, Bcl-XL, Akt, BDNF and TrkB expressions. Besides, enhanced the activities of antioxidant enzymes, plasma insulin level. Histomorphological observations also confirmed the protective effect of morin on neuronal degeneration. Morin 50mg once daily for 60 days was the most effective dose with a significant reduction in diabetes mediated complications in the brain associated with neuronal apoptosis and dysregulation of TrkB/Akt signalling.

N-Acetylcysteine alleviates spinal cord injury in rats after early decompression surgery by regulating inflammation and apoptosis

OBJECTIVE

Decompression surgery in patients with spinal cord injury (SCI) has a neuroprotective effect by alleviating secondary injury and improving neurological outcomes. N-Acetylcysteine (NAC), a drug approved by the United States Food and Drug Administration, has been shown to play neuroprotective roles via attenuation of apoptosis and inflammation. The purpose of the present study was to investigate the effects of early or late decompression surgery in combination with NAC administration on acute SCI, as well as investigate the underlying mechanisms of its actions.

METHODS

In this study, an acute SCI model was established in rats. The rats were treated with decompression surgery 24/48 h post-SCI in combination with or without NAC.

RESULTS

The results showed that decompression surgery in combination with NAC lead to a better outcome than decompression alone, as demonstrated by the higher Basso, Beattie, and Bresnahan scores. Histopathological examination demonstrated that early decompression surgery in combination with NAC exerted the best therapeutic effect on spinal cord recovery, which was further confirmed by the extent of inflammation and apoptosis. Additionally, we found that NAC might compensate for a lack of late surgery.

CONCLUSIONS

Collectively, early decompression surgery and NAC could be a promising combination for the treatment of acute SCI, and its therapeutic effects may be associated with the regulation of inflammation and apoptosis.

N-Acetylcysteine Ameliorates Neurotoxic Effects of Manganese Intoxication in Rats: A Biochemical and Behavioral Study

Clinical and experimental evidences reveal that excess exposure to manganese is neurotoxic and leads to cellular damage. However, the mechanism underlying manganese neurotoxicity remains poorly understood but oxidative stress has been implicated to be one of the key pathophysiological features related to it. The present study investigates the effects associated with manganese induced toxicity in rats and further to combat these alterations with a well-known antioxidant N-acetylcysteine which is being used in mitigating the damage by its radical scavenging activity. The study was designed to note the sequential changes along with the motor and memory dysfunction associated with biochemical and histo-pathological alterations following exposure and treatment for 2 weeks. The results so obtained showed decrease in the body weights, behavioral deficits with increased stress markers and also neuronal degeneration in histo-pathological examination after manganese intoxication in rats. To overcome the neurotoxic effects of manganese, N-acetylcysteine was used in the current study due to its pleiotropic potential in several pathological ailments. Taken together, N-acetylcysteine helped in ameliorating manganese induced neurotoxic effects by diminishing the behavioral deficits, normalizing acetylcholinesterase activity, and augmentation of redox status.

The mechanism of action of N-acetylcysteine (NAC): The emerging role of H2S and sulfane sulfur species

Initially adopted as a mucolytic about 60 years ago, the cysteine prodrug N-acetylcysteine (NAC) is the standard of care to treat paracetamol intoxication, and is included on the World Health Organization's list of essential medicines. Additionally, NAC increasingly became the epitome of an "antioxidant". Arguably, it is the most widely used "antioxidant" in experimental cell and animal biology, as well as clinical studies. Most investigators use and test NAC with the idea that it prevents or attenuates oxidative stress. Conventionally, it is assumed that NAC acts as (i) a reductant of disulfide bonds, (ii) a scavenger of reactive oxygen species and/or (iii) a precursor for glutathione biosynthesis. While these mechanisms may apply under specific circumstances, they cannot be generalized to explain the effects of NAC in a majority of settings and situations. In most cases the mechanism of action has remained unclear and untested. In this review, we discuss the validity of conventional assumptions and the scope of a newly discovered mechanism of action, namely the conversion of NAC into hydrogen sulfide and sulfane sulfur species. The antioxidative and cytoprotective activities of per- and polysulfides may explain many of the effects that have previously been ascribed to NAC or NAC-derived glutathione.

Exaggerated activities of TRPM7 underlie bupivacaine-induced neurotoxicity in the SH-SY5Y cells preconditioned with high glucose

Hyperglycemia is considered a risk factor for the enhancement of local anesthetic-induced neurotoxicity. Transient receptor potential melastatin 7 (TRPM7), a kinase-coupled cation channel, has been implicated in a variety of neuropathological processes, including intracellular calcium disturbance and high glucose-induced neuropathy. In this study, we investigated whether TRPM7-related pathophysiology is involved in bupivacaine-induced neurotoxicity in SH-SY5Y cells and how hyperglycemia acts as a risk factor. For initial neurotoxicity evaluation, it was confirmed that cell damage and apoptosis induced by acute exposure to bupivacaine were dependent on its concentration and glucose preconditioning. High glucose preconditioning facilitated the bupivacaine-induced fast and temporary rise in intracellular free calcium concentration ([Ca²⁺ ]_i ), which was attributed to both calcium influx through TRPM7 and calcium store release. Additionally, bupivacaine was shown to increase TRPM7-like currents, particularly in cells preconditioned with high glucose. Bupivacaine-induced neurotoxicity in hyperglycemia was correlated with extracellular signal-regulated kinase (ERK), but not protein kinase B (AKT) activation. Inhibition of TRPM7 and ERK activity alleviates bupivacaine neurotoxicity. These results suggest that therapeutically targeting TRPM7-related pathophysiological changes could be a potential strategy for treating local anesthetic-induced neurotoxicity exacerbated by hyperglycemia.

Aryl hydrocarbon receptor engagement during redox alteration determines the fate of CD4+ T cells in C57BL/6 mice

The preservation of the redox homeostasis is critical for cell survival and functionality. Redox imbalance is an essential inducer of several pathological states. CD4⁺ /helper T cells are highly dependent on the redox state of their surrounding milieu. The potential of the aryl hydrocarbon receptor (AhR) engagement in controlling CD4⁺ T-cell fate during redox alteration is still challenging. C57BL/6 mice were treated with AhR agonist 6-formylindolo[3,2-b]carbazole (FICZ), AhR antagonist CH223191, an inhibitor of glutathione biosynthesis buthionine sulfoximine (BSO), and the antioxidant N-acetylcysteine (NAC) alone or in combination. Six days later, splenocytes were evaluated for the expression of the redox-related genes and the possible changes in T-cell subsets. FICZ like BSO significantly elevated the expression of HMOX1, GCLC, and GCLM genes but it failed to increase the expression of the Nrf2 gene. Moreover, FICZ + BSO increased while FICZ + CH223191 or NAC decreased the expression of these genes. FICZ also significantly increased Th1 cell numbers but decreased Tregs in a dose-dependent manner. Furthermore, a high dose of FICZ + CH223191 + NAC significantly enhanced Th1, Th17, and Treg cells but its low dose in such a situation increased Th2 and Th17 while decreased Treg cells. AhR engagement during redox alteration can determine the fate of CD4 + T cells, so, AhR agonists or antagonists might be useful in assessing immune responses. However, these results need further verifications in vitro and in animal models of various diseases.

Diabetes-Alzheimer's Disease Link: Targeting Mitochondrial Dysfunction and Redox Imbalance

Significance: It is of common sense that the world population is aging and life expectancy is increasing. However, as the population ages, there is also an exponential risk to live into the ages where the brain-related frailties and neurodegenerative diseases develop. Hand in hand with those events, the world is witnessing a major upsurge in diabetes diagnostics. Remarkably, all of this seems to be narrowly related, and clinical and research communities highlight for the upcoming threat that it will represent for the present and future generations. Recent Advances: It is of utmost importance to clarify the influence of diabetes-related metabolic features on brain health and the mechanisms underlying the increased likelihood of developing neurodegenerative diseases, in particular Alzheimer's disease. Thereupon, a wealth of evidence suggests that mitochondria and associated oxidative stress are at the root of the link between diabetes and co-occurring disorders in the brain. Critical Issues: The scientific community has been challenged with constant failures of clinical trials raising major issues in the advance of the therapeutic field to fight chronic diseases epidemics. Thus, a change of paradigms is urgently needed. Future Directions: It has become urgent to identify new and solid candidates able to clinically reproduce the positive outcomes obtained in preclinical studies. On this basis, strategies settled to counteract diabetes-induced neurodegeneration encompassing mitochondrial dysfunction, redox status imbalance, and/or insulin dysregulation seem worth to follow. Hopefully, ongoing innovative research based on reliable experimental tools will soon bring the desired answers allowing pharmaceutical industry to apply such knowledge to human medicine.

Anti-diabetic, diabetic neuropathy protective action and mechanism of action involving oxidative pathway of chlorogenic acid isolated from Selinum vaginatum roots in rats

Phytopharmaceuticals have always reported vital roles in the field of medicine hence the need to investigate safe and efficient drugs for treating metabolic disorders is very significant. Roots of Selinum vaginatum have therapeutic benefits and are widely used by the people of the Rohtang region for treating diabetes and its associated complications. The present study focusses on the isolation of the bioactive from the S. vaginatum roots for estimating acute toxicity studies, anti-diabetic and diabetic neuropathy protective action along with the mechanism of action in STZ induced Wistar rats. The Selinum vaginatum roots were collected from the Rohtang region, Himalayas. Chlorogenic acid was isolated and underwent identification by UV, HPLC, ¹H NMR, C13 NMR, Mass, and FTIR spectroscopy methods. Chlorogenic acid was dosed at 10 and 20 mg/kg to observe the effects on experimentally induced diabetes and with time generated diabetic neuropathic complications. Biomarkers TNF-α, superoxide dismutase, nitrosative stress, lipid peroxide profile, and membrane-bound inorganic phosphate were analyzed. Histopathological evaluation of the liver and sciatic nerve was performed for all groups. Parameters like blood glucose levels, body weight, food intake, Thermal Hyperalgesia, Writhing, Cold Hyperalgesia Responses, Mechanical hyperalgesia, Grip Strength, Spontaneous Locomotor (Exploratory) Test, Neuromuscular Coordination tests, and lipid profile analysis showcased the anti-diabetic and diabetic neuropathy protective action of the drug. Inflammation, degradation, and necrosis were found to be reduced in the liver and sciatic nerve cells of treated groups. All the biomarkers used to analyze the oxidative pathway were significantly replenished indicates that chlorogenic acid produces these effects through this pathway.

The Protective Effect and Mechanism of Dexmedetomidine on Diabetic Peripheral Neuropathy in Rats

Objective

To investigate the role of dexmedetomidine (DEX) in the inhibition of diabetic peripheral neuropathy (DPN) and the protection in the nerve damage.

Methods

Eighty male Sprague-Dawley (SD) rats were randomly allocated to four groups: the control group (C group), DPN model group (DPN group), DEX-treated group (DEX group), and the yohimbine treated group (YOH group). DPN was induced by intraperitoneal administration of streptozocin (STZ) (35 mg/kg). The body weights, blood glucose level, mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), the motor, and sensory nerve conduction velocities (MNCV and SNCV) of sciatic nerve were measured. Then the sciatic nerve was isolated for H&E staining and immunohistochemical staining. The oxidative stress makers such as malondialdehyde (MDA), superoxide-dismutase (SOD), and glutathione peroxidase (GSH-Px) and apoptosis related cytokines such as Bax, Bcl-2, and caspase-3 were estimated.

Results

There was no significant difference of the blood glucose and body weight among the DPN group, DEX group, and YOH group. H&E staining showed that DEX treatment can ameliorate the damage of sciatic nerve cells. In the DPN group, MWT, TWL, MNCV, and SNCV were significantly reduced compared with the C group (P < 0.05). In DEX group rats, MWT, TWL, MNCV, and SNCV were increased significantly (P < 0.05) compared with the DPN group and YOH group rats. Lower SOD and GSH-Px, and higher MDA were found in the DPN group compared with the C group (P < 0.01), and DEX treatment restored SOD, GSH-px, and MDA activity significantly (P < 0.01). The expression levels of Bax and caspase-3 were increased, while that of Bcl-2 was decreased significantly in the DPN group compared with the C group (P < 0.05). In the DEX group, the expression levels of Bax and caspase-3 were decreased significantly (P < 0.05), while that of Bcl-2 was increased significantly (P < 0.05) compared with the DPN group and the YOH group.

Conclusion

The results of this study demonstrated that DEX has the inhibitory and protective effects on DPN of rats. This may be associated with its antioxidative and anti-apoptosis responses.

Mitochondrially-targeted treatment strategies

Disruption of mitochondrial function is a common feature of inherited mitochondrial diseases (mitochondriopathies) and many other infectious and non-infectious diseases including viral, bacterial and protozoan infections, inflammatory and chronic pain, neurodegeneration, diabetes, obesity and cardiovascular diseases. Mitochondria therefore become an attractive target for developing new therapies. In this review we describe critical mechanisms involved in the maintenance of mitochondrial functionality and discuss strategies used to identify and validate mitochondrial targets in different diseases. We also highlight the most recent preclinical and clinical findings using molecules targeting mitochondrial bioenergetics, morphology, number, content and detoxification systems in common pathologies.

Ameliorative Effects Of N-Acetylcysteine As Adjunct Therapy On Symptoms Of Painful Diabetic Neuropathy

Purpose

Painful diabetic neuropathy (PDN) is a variant of diabetic peripheral neuropathy which is highly prevalent and distressing in diabetic patients. Despite its high burden, the optimal treatment of PDN has remained a clinical challenge. To explain the emergence and maintenance of PDN, increasing attention has been focused on dimensions of inflammation and oxidative toxic stress (OTS). Accordingly, the aim of this study was to investigate the effects of oral N-acetylcysteine (NAC), an agent with known anti-oxidant and anti-inflammatory effects, as an adjunct therapy in patients suffering from PDN.

Patients and methods

113 eligible patients with type 2 diabetes suffering from PDN were randomly assigned to either the pregabalin + placebo or pregabalin + NAC group for 8 weeks (pregabalin at a dose of 150 mg per day, NAC and matched placebo at doses of 600 mg twice a day). Mean pain score was evaluated at baseline, week 1, 2, 4, 6, and 8 of the study based on the mean 24 hr average pain score, using an 11-point numeric rating scale (NRS). As secondary efficacy measures, mean sleep interference score (SIS) resulting from PDN, responder rates, Patient Global Impression of Change (PGIC), Clinical Global Impression of Change (CGIC), and safety were also assessed. Additionally, serum levels of total antioxidant capacity (TAC), total thiol groups (TTG), catalase activity (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), nitric oxide (NO), and malondialdehyde (MDA) were assessed at baseline and at the end of the study.

Results

Ninety patients completed the eight-week course of the study. The decrease in mean pain scores and mean sleep interference score in pregabalin + NAC group was greater in comparison with pregabalin + placebo group (p value<0.001 in both conditions). Moreover, more responders (defined as ≥50% reduction in mean pain score from baseline to end-point) were observed in the pregabalin + NAC group, in comparison with pregabalin + placebo group (72.1% vs 46.8%). More improvement in PGIC and CGIC from baseline to the end of the study was reported in pregabalin + NAC group. Oral NAC had minimal adverse effects and was well tolerated in almost all patients. Furthermore, in respect to OTS biomarkers, adjuvant NAC significantly decreased serum level of MDA and significantly increased serum levels of SOD, GPx, TAC, and TTG.

Conclusion

The pattern of results suggests that compared to placebo and over a time period of 8 weeks, adjuvant NAC is more efficacious in improving neuropathic pain associated with diabetic neuropathy than placebo. Ameliorative effects of NAC on OTS biomarkers demonstrated that NAC may alleviate painful symptoms of diabetic neuropathy, at least in part by its antioxidant effects.

Maltol, a food flavor enhancer, attenuates diabetic peripheral neuropathy in streptozotocin-induced diabetic rats

SCOPE

Maltol (3-hydroxy-2-methy-4-pyrone), a potent antioxidative agent, typically is used to enhance flavor and preserve food. This study evaluated its effects on preventing diabetic peripheral neuropathy (DPN) in streptozotocin (STZ)-induced diabetic rats and explored its mechanisms.

METHODS AND RESULTS

We intraperitoneally injected Sprague-Dawley (SD) rats with STZ (65 mg kg-1, ip) and treated the rats with different doses of maltol after 4 weeks of injection. During treatment, we evaluated motor nerve conduction velocity (MNCV) and thermal and mechanical hyperalgesia and assayed the oxidative stress, Na+-K+-ATPase activity, and apoptosis. Repeated treatment with maltol for 12 weeks significantly improved thermal and mechanical hyperalgesia, increased the MNCV, elevated the Na+-K+-ATPase activity, and ameliorated oxidative stress and apoptosis in STZ-induced diabetic rats. We coincubated RSC96 cells, a Schwann cell line, with maltol and hydrogen peroxide (H2O2, 0.6 mM). Evidently, maltol increased cell viability and inhibited apoptosis after injury by H2O2.

CONCLUSIONS

Maltol was demonstrated to prevent DPN development and may provide a new alternative for the treatment of DPN.

Protective Effect of Taurine on Apoptosis of Spinal Cord Cells in Diabetic Neuropathy Rats

Diabetes mellitus (DM) is a condition characterized by chronic hyperglycemia, which leads to diabetic neuropathy and apoptosis in the spinal cord. Taurine has been found to ameliorate the diabetic neuropathy and control apoptosis in various tissues. However, there are few reports that discuss the direct relationship between spinal cord and anti-apoptotic effect of taurine. In this study, DM was induced in male SD rats with STZ @ 25 mg/Kg of body weight in combination with high fat diet. After 2 weeks, they were divided into four groups as DM: diabetic rats, T1 (0.5%), T2 (1%) and T3 (2%) taurine solution, while control group was non-diabetic rats (no treatment). The results showed that DM increased apoptosis, decreased phosphorylated Akt and Bad. DM decreased expression of Bcl-2 and increased the Bax. Moreover, the release of cytochrome c into cytosol was increased in DM and activation of caspase-3 was also increased. However, taurine reversed all these abnormal changes in a dose dependent manner. Our results suggested the involvement of Akt/Bad signaling pathway and mitochondrial apoptosis pathway in protective effect of taurine against apoptosis in the spinal cord of diabetic rats. Therefore, taurine may be a potential medicine against diabetic neuropathy by controlling apoptosis.

Neuroprotective and antinociceptive effects of rosemary (Rosmarinus officinalis L.) extract in rats with painful diabetic neuropathy

Diabetes mellitus is associated with the development of neuronal tissue damage in different central and peripheral nervous system regions. A common complication of diabetes is painful diabetic peripheral neuropathy. We have explored the antihyperalgesic and neuroprotective properties of Rosmarinus officinalis L. extract (RE) in a rat model of streptozotocin (STZ)-induced diabetes. The nociceptive threshold and motor coordination of these diabetic rats was assessed using the tail-flick and rotarod treadmill tests, respectively. Activated caspase-3 and the Bax:Bcl-2 ratio, both biochemical indicators of apoptosis, were assessed in the dorsal half of the lumbar spinal cord tissue by western blotting. Treatment of the diabetic rats with RE improved hyperglycemia, hyperalgesia and motor deficit, suppressed caspase-3 activation and reduced the Bax:Bcl-2 ratio, suggesting that the RE has antihyperalgesic and neuroprotective effects in this rat model of STZ-induced diabetes. Cellular mechanisms underlying the observed effects may, at least partially, be related to the inhibition of neuronal apoptosis.

Resveratrol promotes neuroprotection and attenuates oxidative and nitrosative stress in the small intestine in diabetic rats

Damages to the enteric nervous system caused by diabetes mellitus (DM) are frequently attributed to oxidative and nitrosative stress. We aimed to investigate the effect of Resveratrol (RSV) (10 mg/kg) on oxidative and nitrosative stress in the intestinal wall and morphoquantitative aspects of the myenteric plexus of the duodenum, jejunum and ileum in diabetic rats. Twenty-four rats were distributed into four groups (n = 6/group): control (C group), control treated with RSV (CR group), diabetic (D group), and diabetic treated with RSV (DR group) for 120 days. Immunohistochemical staining techniques for the general neuronal population, nitrergic and calretinin neuronal subpopulations, enteric glial cells and glial fibrillary acid protein were performed in the myenteric plexus. Furthermore, parameters of oxidative and nitrosative stress were analyzed in the intestinal wall. RSV attenuated oxidative and nitrosative stress and prevented neuronal loss and hypertrophy of the HuC/D-IR, nNOS-IR and CALR-IR neuronal subpopulations in the DR group compared with the D group (P < 0.05). In addition, RSV prevented the increase in glial fibrillary acid protein fluorescence in the DR group compared with the D (P < 0.05). These results suggest that RSV has antioxidant and neuroprotective effects in myenteric plexus in rats with experimental DM.

Beneficial effects of N-acetylcysteine on hepatic oxidative stress in streptozotocin-induced diabetic rats

Diabetes is one of the leading diseases worldwide and, thus, finding new therapeutic alternatives is essential. The development of non-alcoholic fatty liver disease is a notable diabetic complication. Therefore, antioxidant therapy became a leading topic in the world of diabetes research. The objective of this present study was to evaluate the effects of antioxidant N-acetylcysteine (NAC) administration on serum biochemical parameters and oxidative stress parameters in hepatic tissue of the diabetic rats. Thirty-two animals were divided in 4 groups (n = 8): G1, normal rats; G2, normal rats + NAC; G3, diabetic rats; and G4, diabetic rats + NAC. Diabetes was induced in diabetic groups through streptozotocin. NAC administration was effective in improving hyperglycemia and hypoinsulinemia, as well as reducing serum alanine-aminotransferase and urea, hepatic triglycerides accumulation, and oxidative stress biomarkers in the diabetic liver, as well as improving the activity of hepatic antioxidant enzymes. This effect was likely due to NAC’s ability of restoring intracellular glutathione, an important compound for the antioxidant defense, as well as due to NAC’s direct antioxidant properties. Thus, NAC administration was useful for reducing hepatic oxidative stress and decreased the deposit of triacylglycerols, minimizing diabetic hepatic damage, making it a promising therapeutic adjuvant in the future.

Supplementation with Phycocyanobilin, Citrulline, Taurine, and Supranutritional Doses of Folic Acid and Biotin-Potential for Preventing or Slowing the Progression of Diabetic Complications

Oxidative stress, the resulting uncoupling of endothelial nitric oxide synthase (eNOS), and loss of nitric oxide (NO) bioactivity, are key mediators of the vascular and microvascular complications of diabetes. Much of this oxidative stress arises from up-regulated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity. Phycocyanobilin (PhyCB), the light-harvesting chromophore in edible cyanobacteria such as spirulina, is a biliverdin derivative that shares the ability of free bilirubin to inhibit certain isoforms of NADPH oxidase. Epidemiological studies reveal that diabetics with relatively elevated serum bilirubin are less likely to develop coronary disease or microvascular complications; this may reflect the ability of bilirubin to ward off these complications via inhibition of NADPH oxidase. Oral PhyCB may likewise have potential in this regard, and has been shown to protect diabetic mice from glomerulosclerosis. With respect to oxidant-mediated uncoupling of eNOS, high-dose folate can help to reverse this by modulating the oxidation status of the eNOS cofactor tetrahydrobiopterin (BH4). Oxidation of BH4 yields dihydrobiopterin (BH2), which competes with BH4 for binding to eNOS and promotes its uncoupling. The reduced intracellular metabolites of folate have versatile oxidant-scavenging activity that can prevent oxidation of BH4; concurrently, these metabolites promote induction of dihydrofolate reductase, which functions to reconvert BH2 to BH4, and hence alleviate the uncoupling of eNOS. The arginine metabolite asymmetric dimethylarginine (ADMA), typically elevated in diabetics, also uncouples eNOS by competitively inhibiting binding of arginine to eNOS; this effect is exacerbated by the increased expression of arginase that accompanies diabetes. These effects can be countered via supplementation with citrulline, which efficiently enhances tissue levels of arginine. With respect to the loss of NO bioactivity that contributes to diabetic complications, high dose biotin has the potential to "pinch hit" for diminished NO by direct activation of soluble guanylate cyclase (sGC). High-dose biotin also may aid glycemic control via modulatory effects on enzyme induction in hepatocytes and pancreatic beta cells. Taurine, which suppresses diabetic complications in rodents, has the potential to reverse the inactivating impact of oxidative stress on sGC by boosting synthesis of hydrogen sulfide. Hence, it is proposed that concurrent administration of PhyCB, citrulline, taurine, and supranutritional doses of folate and biotin may have considerable potential for prevention and control of diabetic complications. Such a regimen could also be complemented with antioxidants such as lipoic acid, N-acetylcysteine, and melatonin-that boost cellular expression of antioxidant enzymes and glutathione-as well as astaxanthin, zinc, and glycine. The development of appropriate functional foods might make it feasible for patients to use complex nutraceutical regimens of the sort suggested here.

Puerarin may protect against Schwann cell damage induced by glucose fluctuation

Puerarin is one of the major active ingredients in Gegen, a traditional Chinese herb that has been reported to have a wide variety of beneficial pharmacology functions. Previous studies have implicated that the damaging effects of hyperglycemia resulting from oxidative stress and glucose fluctuation may be more dangerous than constant high glucose in the development of diabetes-related complications. The present study focuses on the effects of puerarin on glucose fluctuation-induced oxidative stress-induced Schwann cell (SC) apoptosis in vitro. Primarily cultured SCs were exposed to different conditions and the effect of puerarin on cell viability was determined by MTT assays. Intracellular reactive oxygen species (ROS) generation and mitochondrial transmembrane potential were detected by flow cytometry analysis. Apoptosis was confirmed by the Annexin V-FITC/PI and TUNEL method. Quantitative real-time reverse transcriptase polymerase chain reaction was performed to analyze the expression levels of bax and bcl-2. Western blot was performed to analyze the expression levels of some important transcription factors and proteins. The results showed that incubating SCs with intermittent high glucose for 48 h decreased cell viability and increased the number of apoptotic cells whereas treating with puerarin protected SCs against glucose fluctuation-induced cell damage. Further study demonstrated that puerarin suppressed activation of apoptosis-related proteins including PARP and caspase-3, downregulation of bcl-2, and upregulation of intracellular distribution of bax from cytosol to mitochondria, which was induced by glucose fluctuation. Moreover, puerarin inhibited the elevation of intracellular ROS and mitochondrial depolarization induced by glucose fluctuation. These results suggest that puerarin may protect SCs against glucose fluctuation-induced cell injury through inhibiting apoptosis as well as oxidative stress.

Endothelin Confers Protection against High Glucose-Induced Neurotoxicity via Alleviation of Oxidative Stress

Recent findings linked the inhibition in the neuromodulator peptide endothelin-1 (ET-1) level to the high glucose-evoked neurotoxicity. However, definitive neuroprotective role for ET-1 and the major neuronal ET (ET-3) against high glucose-evoked toxicity and the implicated neurochemical responses triggered by their ET-A and ET-B receptors remain unknown. Here, we tested the hypothesis that ET-B activation alleviates high glucose-evoked oxidative stress and cell death. High glucose (100 mM for 48 hours)-evoked cell death was associated with elevation in reactive oxygen species, inhibition of catalase activity, and a paradoxical upregulation of hemeoxygenase-1 expression along with ET-A and ET-B receptors were downregulated and upregulated, respectively. ET-1 or ET-3, in concentrations that had no effect on PC12 cell viability in normal glucose medium, alleviated all high glucose-evoked neurochemical responses, except for the reduction in ET-A receptor expression. Prior (4 hours) incubation with a selective ET-A (BQ123) or ET-B (BQ788) receptor blocker abrogated the neuroprotection conferred by ET-1 or ET-3. However, the ET-B receptor played a greater role because BQ788 abrogated the favorable ET-1- or ET-3-mediated reversal of the ERK1/2 phosphorylation and the inhibition in catalase activity caused by high glucose. These findings suggest that endothelin exerts ET-B receptor-dependent favorable redox and neuroprotective effects against high glucose-evoked oxidative damage and neurotoxicity.

Involvement of Programmed Cell Death in Neurotoxicity of Metallic Nanoparticles: Recent Advances and Future Perspectives

The widespread application of metallic nanoparticles (NPs) or NP-based products has increased the risk of exposure to NPs in humans. The brain is an important organ that is more susceptible to exogenous stimuli. Moreover, any impairment to the brain is irreversible. Recently, several in vivo studies have found that metallic NPs can be absorbed into the animal body and then translocated into the brain, mainly through the blood-brain barrier and olfactory pathway after systemic administration. Furthermore, metallic NPs can cross the placental barrier to accumulate in the fetal brain, causing developmental neurotoxicity on exposure during pregnancy. Therefore, metallic NPs become a big threat to the brain. However, the mechanisms underlying the neurotoxicity of metallic NPs remain unclear. Programmed cell death (PCD), which is different from necrosis, is defined as active cell death and is regulated by certain genes. PCD can be mainly classified into apoptosis, autophagy, necroptosis, and pyroptosis. It is involved in brain development, neurodegenerative disorders, psychiatric disorders, and brain injury. Given the pivotal role of PCD in neurological functions, we reviewed relevant articles and tried to summarize the recent advances and future perspectives of PCD involvement in the neurotoxicity of metallic NPs, with the purpose of comprehensively understanding the neurotoxic mechanisms of NPs.

Inside the Diabetic Brain: Role of Different Players Involved in Cognitive Decline

Diabetes mellitus is the most common metabolic disease, and its prevalence is increasing. A growing body of evidence, both in animal models and epidemiological studies, has demonstrated that metabolic diseases like obesity, insulin resistance, and diabetes are associated with alterations in the central nervous system (CNS), being linked with development of cognitive and memory impairments and presenting a higher risk for dementia and Alzheimer's disease. The rising prevalence of diabetes together with its increasing earlier onset suggests that diabetes-related cognitive dysfunction will increase in the near future, causing substantial socioeconomic impact. Decreased insulin secretion or action, dysregulation of glucose homeostasis, impairment in the hypothalamic-pituitary-adrenal axis, obesity, hyperleptinemia, and inflammation may act independently or synergistically to disrupt neuronal homeostasis and cause diabetes-associated cognitive decline. However, the crosstalk between those factors and the mechanisms underlying the diabetes-related CNS complications is still elusive. During the past few years, different strategies (neuroprotective and antioxidant drugs) have emerged as promising therapies for this complication, which still remains to be preventable or treatable. This Review summarizes fundamental past and ongoing research on diabetes-associated cognitive decline, highlighting potential contributors, mechanistic mediators, and new pharmacological approaches to prevent and/or delay this complication.

Rutin ameliorates diabetic neuropathy by lowering plasma glucose and decreasing oxidative stress via Nrf2 signaling pathway in rats

Rutin exhibits antidiabetic, antioxidant and anti-inflammatory properties, which makes rutin an attractive candidate for diabetic complications. The present study was designed to investigate the potential effect of rutin on diabetic neuropathy. After induction of diabetic neuropathy, rutin (5mg/kg, 25mg/kg and 50mg/kg) were daily given to the diabetic rats for 2 weeks. At the end of rutin administration, rutin produced a significant inhibition of mechanical hyperalgesia, thermal hyperalgesia and cold allodynia, as well as partial restoration of nerve conduction velocities in diabetic rats. Furthermore, rutin significantly increased Na(+), K(+)-ATPase activities in sciatic nerves and decreased caspase-3 expression in dorsal root ganglions (DRG). In addition, rutin significantly decreased plasma glucose, attenuated oxidative stress and neuroinflammation. Further studies showed that rutin significantly increased hydrogen sulfide (H2S) level, up-regulated the expression of nuclear factor-E2-related factor-2 (Nrf2) and heme oxygenase-1 (HO-1) in DRG. The evidences suggest the beneficial effect of rutin on diabetic neuropathy. Additionally, insulin (2 IU) and BG-12 (15mg/kg) were used to investigate the mechanisms underlying the beneficial effect of rutin on diabetic neuropathy. Insulin achieved lower plasma glucose and BG-12 achieved comparable Nrf2 expression than/to rutin (50mg/kg), respectively. In contrast, the beneficial effect of insulin and BG-12 was inferior to that of rutin (50mg/kg), suggesting that both lowered plasma glucose and Nrf2 signaling contribute to the beneficial effect of rutin on diabetic neuropathy. In conclusion, rutin produces significant protection in diabetic neuropathy, which makes it an attractive candidate for the treatment of diabetic neuropathy.

Melatonin prevents hyperglycemia in a model of sleep apnea

OBJECTIVE

Obstructive sleep apnea is a common disorder associated with aging and obesity. Apneas cause repeated arousals, intermittent hypoxia, and oxidative stress. Changes in glucolipidic profile occur in apnea patients, independently of obesity. Animal models of sleep apnea induce hyperglycemia. This study aims to evaluate the effect of the antioxidants melatonin and N-acetylcysteine on glucose, triglyceride, and cholesterol levels in animals exposed to intermittent hypoxia.

MATERIALS AND METHODS

Two groups of Balb/c mice were exposed to intermittent hypoxia (n = 36) or sham intermittent hypoxia (n = 36) for 35 days. The intermittent hypoxia group underwent a total of 480 cycles of 30 seconds reducing the inspired oxygen fraction from 21% to 7 ± 1% followed by 30 seconds of normoxia, during 8 hours daily. Melatonin or N-acetylcysteine were injected intraperitonially daily from day 21 on.

RESULTS

At day 35, glucose levels were significantly higher in the intermittent hypoxia group than in the control group. The intermittent hypoxia groups receiving N-acetylcysteine and vehicle showed higher glucose levels than the group receiving melatonin. The lipid profile was not affected by intermittent hypoxia or antioxidant administration.

CONCLUSIONS

The present results suggest that melatonin prevents the well-recognized increase in glucose levels that usually follows exposure to intermittent hypoxia. Further exploration of the role of melatonin in sleep apnea is warranted.

Naringenin neutralises oxidative stress and nerve growth factor discrepancy in experimental diabetic neuropathy

OBJECTIVES

Present study aims to investigate the ameliorative effects of naringenin (NG) on experimentally induced diabetic neuropathy (DN) in rats.

METHODS

Diabetes was induced by single intraperitoneal injection of streptozotocin (STZ, 60  g/kg). Naringenin (25 and 50 mg/kg/day) treatment was started 2 weeks after the diabetes induction and continued for five consecutive weeks. Pain threshold behaviour tests were performed at the end of the treatment. Serum levels of glucose, insulin and pro-inflammatory cytokines were assessed. In sciatic tissues, markers oxidative stress, cytokines and neurotrophic factors were measured.

RESULTS

NG treatments showed significant decrease in paw-withdrawal (P < 0.01) and tail-flick latency (P < 0.01). The drug attenuated the diabetic-induced changes in serum glucose, insulin and pro-inflammatory cytokines including tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6). In sciatic nerve, the diabetic-induced alterations in interleukins and oxidative stress biomarkers were significantly attenuated by NG. Decreased sciatic expressions of insulin growth factor (IGF) and nerve growth factor (NGF) in diabetic rats were also ameliorated by NG. Diabetes-induced dysregulated levels of nitric oxide (NO), thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) were ameliorated by NG. Histological analysis showed that NG corrected the altered sciatic changes in diabetic animals.

DISCUSSION

We suggest that neuro-protective effect of NG molecules in sciatic nerve of diabetic rats, through its anti-diabetic as well as antioxidant and anti-inflammatory properties.

Telmisartan inhibits hyperalgesia and inflammatory progression in a diabetic neuropathic pain model of Wistar rats

Objective:

To evaluate the potential therapeutic value of telmisartan (TMT) against diabetic neuropathy (DN) and associated pain in Wistar rats.

Methods:

Peripheral DN was induced by a single intraperitoneal streptozotocin injection (55 mg/kg), and 3 weeks later TMT treatment was started (5 and 10 mg/kg/day), and continued for 4 weeks. Mechanical nociceptive threshold, motor coordination, and thermal nociceptive threshold tests were performed before and after TMT treatment. In serum, glucose, pro-inflammatory cytokines including tumor necrosis factor-α, interleukin-1β, and interleukin-6 were assessed. Nerve growth factor (NGF) levels and histopathological changes were estimated in the sciatic nerve. This study was conducted at the Experimental Animal Care Center, Department of Pharmacology, College of Pharmacy, King Saud University, Riyadh, Kingdom of Saudi Arabia between January 2013 and May 2014.

Results:

We observed a significant reduction in mechanical nociceptive threshold, motor coordination, and thermal nociceptive threshold in diabetic animals. The TMT treatment significantly enhanced the reduced mechanical nociceptive threshold. The untreated diabetic animals revealed a significant decrease in sciatic NGF, which was markedly attenuated by TMT. The elevated serum levels of cytokines in diabetic animals were inhibited by the TMT treatments. Histopathological evaluation showed obvious nerve degeneration in the diabetic group that was eliminated in the TMT treated diabetic groups.

Conclusion:

Telmisartan has a potential neuro-protective effect on peripheral DN; this is mediated through its anti-inflammatory effects and its dual properties as an angiotensin receptor blocker, and a partial peroxisome proliferator activator receptor-g ligand.

Are reactive oxygen species still the basis for diabetic complications?

Despite the wealth of pre-clinical support for a role for reactive oxygen and nitrogen species (ROS/RNS) in the aetiology of diabetic complications, enthusiasm for antioxidant therapeutic approaches has been dampened by less favourable outcomes in large clinical trials. This has necessitated a re-evaluation of pre-clinical evidence and a more rational approach to antioxidant therapy. The present review considers current evidence, from both pre-clinical and clinical studies, to address the benefits of antioxidant therapy. The main focus of the present review is on the effects of direct targeting of ROS-producing enzymes, the bolstering of antioxidant defences and mechanisms to improve nitric oxide availability. Current evidence suggests that a more nuanced approach to antioxidant therapy is more likely to yield positive reductions in end-organ injury, with considerations required for the types of ROS/RNS involved, the timing and dosage of antioxidant therapy, and the selective targeting of cell populations. This is likely to influence future strategies to lessen the burden of diabetic complications such as diabetes-associated atherosclerosis, diabetic nephropathy and diabetic retinopathy.

Neuroprotective effects of Gymnema sylvestre on streptozotocin-induced diabetic neuropathy in rats

The application of traditional medicine for diabetes and associated complications, such as diabetic neuropathy (DN), has received increasing attention. The aim of the present study was to investigate the potential ameliorative effect of Gymnema sylvestre (Gs) in a rat model of DN. Diabetes was induced via a single intraperitoneal injection of streptozotocin (STZ; 60 mg/kg). Treatment with Gs extract (50 or 100 mg/kg/day) began two weeks following the administration of STZ and was continued for five weeks. Pain threshold behavior tests were performed subsequent to the five-week Gs treatment period. In addition, the serum levels of glucose, insulin and proinflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, were determined. Furthermore, the sciatic tissue levels of nitric oxide, thiobarbituric acid reactive substances and reduced glutathione were determined, as well as the activity levels of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase. Levels of insulin-like growth factor (IGF), nerve growth factor (NGF), TNF-α, IL-1β and IL-6 were also assessed in the sciatic tissue. In addition, the sciatic nerve tissue samples were analyzed for histopathological alterations. The diabetic rats exhibited apparent reductions in the paw-withdrawal (31%; P<0.01) and tail-flick latencies (38%; P<0.05). Furthermore, the diabetic rats demonstrated an evident elevation in serum and sciatic levels of proinflammatory cytokines. Measured oxidative stress biomarkers were significantly altered in the sciatic nerve tissue of the diabetic rats. Treatment with Gs attenuated diabetes-induced modifications with regard to the levels of serum glucose, insulin and proinflammatory cytokines. In the sciatic nerve tissue, the diabetes-induced alterations in IL levels and oxidative stress biomarkers were significantly improved in the Gs-treated rats. Furthermore, the reduction in the sciatic tissue expression levels of IGF and NGF was also ameliorated by Gs treatment. Histological analysis indicated that Gs corrected the sciatic tissue in the diabetic rats. Therefore, the results demonstrated that the neuroprotective effect of Gs may be associated with the inhibitory effect on the excessive activation of inflammatory molecules and oxidative stress mediators.

Ginsenoside Rb1 relieves glucose fluctuation-induced oxidative stress and apoptosis in Schwann cells

Cultured Schwann cells were treated with 5.6 mM and 50 mM glucose alternating every 8 hours to simulate intermittent high glucose. The present study analyzed the neuroprotective effects of 1, 10 and 100 μM ginsenoside Rb1 on oxidative damage and apoptosis in Schwann cells induced by intermittent high glucose. Flow cytometry demonstrated that ginsenoside Rb1 reduced intermittent high glucose-mediated reactive oxygen species production. Enzyme linked immunosorbent assay showed that 8-hydroxy-2-deoxy guanosine levels in Schwann cells decreased following ginsenoside Rb1 treatment. Quantitative real-time reverse transcription-PCR and western blot assay results revealed that ginsenoside Rb1 inhibited intermittent high glucose-upregulated Bax expression, but antagonized intermittent high glucose-downregulated Bcl-2 expression in Schwann cells. These effects were most pronounced with 100 μM ginsenoside Rb1. These results indicate that ginsenoside Rb1 inhibits intermittent high glucose-induced oxidative stress and apoptosis in Schwann cells.

S-nitrosoglutathione prevents blood-brain barrier disruption associated with increased matrix metalloproteinase-9 activity in experimental diabetes

Hyperglycemia is known to induce microvascular complications, thereby altering blood-brain barrier (BBB) permeability. This study investigated the role of matrix metalloproteinases (MMPs) and their endogenous inhibitors in increased BBB permeability and evaluated the protective effect of S-nitrosoglutathione (GSNO) in diabetes. Diabetes was induced in mice by intraperitoneal injection of streptozotocin (40 mg/kg body weight) for 5 days and GSNO was administered orally (100 μg/kg body weight) daily for 8 weeks after the induction of diabetes. A significant decline in cognitive functions was observed in diabetic mice assessed by Morris water maze test. Increased permeability to different molecular size tracers accompanied by edema and ion imbalance was observed in cortex and hippocampus of diabetic mice. Furthermore, activity of both pro and active MMP-9 was found to be significantly elevated in diabetic animals. Increased in situ gelatinase activity was observed in tissue sections and isolated microvessels from diabetic mice brain. The increase in activity of MMP-9 was attributed to increased mRNA and protein expression in diabetic mice. In addition, a significant decrease in mRNA and protein expression of tissue inhibitor of matrix metalloproteinase-1 was also observed in diabetic animals. However, GSNO supplementation to diabetic animals was able to abridge MMP-9 activation as well as tissue inhibitor of matrix metalloproteinase-1 levels, restoring BBB integrity and also improving learning and memory. Our findings clearly suggest that GSNO could prevent hyperglycemia-induced disruption of BBB by suppressing MMP-9 activity.

Oxaliplatin neurotoxicity involves peroxisome alterations. PPARγ agonism as preventive pharmacological approach

The development of neuropathic syndromes is an important, dose limiting side effect of anticancer agents like platinum derivates, taxanes and vinca alkaloids. The causes of neurotoxicity are still unclear but the impairment of the oxidative equilibrium is strictly related to pain. Two intracellular organelles, mitochondria and peroxisomes cooperate to the maintaining of the redox cellular state. Whereas a relationship between chemotherapy-dependent mitochondrial alteration and neuropathy has been established, the role of peroxisome is poor explored. In order to study the mechanisms of oxaliplatin-induced neurotoxicity, peroxisomal involvement was evaluated in vitro and in vivo. In primary rat astrocyte cell culture, oxaliplatin (10 µM for 48 h or 1 µM for 5 days) increased the number of peroxisomes, nevertheless expression and functionality of catalase, the most important antioxidant defense enzyme in mammalian peroxisomes, were significantly reduced. Five day incubation with the selective Peroxisome Proliferator Activated Receptor-γ (PPAR-γ) antagonist G3335 (30 µM) induced a similar peroxisomal impairment suggesting a relationship between PPARγ signaling and oxaliplatin neurotoxicity. The PPARγ agonist rosiglitazone (10 µM) reduced the harmful effects induced both by G3335 and oxaliplatin. In vivo, in a rat model of oxaliplatin induced neuropathy, a repeated treatment with rosiglitazone (3 and 10 mg kg⁻¹ per os) significantly reduced neuropathic pain evoked by noxious (Paw pressure test) and non-noxious (Cold plate test) stimuli. The behavioral effect paralleled with the prevention of catalase impairment induced by oxaliplatin in dorsal root ganglia. In the spinal cord, catalase protection was showed by the lower rosiglitazone dosage without effect on the astrocyte density increase induced by oxaliplatin. Rosiglitazone did not alter the oxaliplatin-induced mortality of the human colon cancer cell line HT-29. These results highlight the role of peroxisomes in oxaliplatin-dependent nervous damage and suggest PPARγ stimulation as a candidate to counteract oxaliplatin neurotoxicity.

Exhaled carbon monoxide in adolescents with diabetic cardiovascular autonomic neuropathy

The aim of the study was to determine if cardiovascular autonomic neuropathy (CAN) is associated with changed concentration of exhaled carbon monoxide (eCO) in adolescents with type 1 diabetes (T1D). A total of 46 T1D patients and 25 healthy controls (15-19 years) were enrolled. The parameters eCO and carboxyhemoglobin (HbCO) were established using a MICRO-4 Smokerlyser. CAN was examined by standard cardiovascular tests. Adolescents with T1D did not significantly differ in eCO compared to healthy subjects. eCO and HbCO were significantly lower in CAN-positive subjects (n=19) (1.36 ± 1.65 ppm vs. 3.09 ± 2.31, p=0.01 and 0.58 ± 0.49% vs. 1.04 ± 0.44, p<0.01, respectively) compared to CAN-negative subjects (n=27), whereas no significant difference was found in other measured parameters. By multivariate logistic regression, eCO and HbCO were associated with higher risk of CAN (OR=1.824, p<0.05 and OR=10.989, p<0.01). Our results indicate that eCO is decreased in CAN-positive diabetic subjects. Further studies are necessary to investigate the possible role of eCO as a marker for CAN.

Mitotoxicity in distal symmetrical sensory peripheral neuropathies

Chronic distal symmetrical sensory peripheral neuropathy is a common neurological complication of cancer chemotherapy, HIV treatment and diabetes. Although aetiology-specific differences in presentation are evident, the clinical signs and symptoms of these neuropathies are clearly similar. Data from animal models of neuropathic pain suggest that the similarities have a common cause: mitochondrial dysfunction in primary afferent sensory neurons. Mitochondrial dysfunction is caused by mitotoxic effects of cancer chemotherapeutic drugs of several chemical classes, HIV-associated viral proteins, and nucleoside reverse transcriptase inhibitor treatment, as well as the (possibly both direct and indirect) effects of excess glucose. The mitochondrial injury results in a chronic neuronal energy deficit, which gives rise to spontaneous nerve impulses and a compartmental neuronal degeneration that is first apparent in the terminal receptor arbor--that is, intraepidermal nerve fibres--of cutaneous afferent neurons. Preliminary data suggest that drugs that prevent mitochondrial injury or improve mitochondrial function could be useful in the treatment of these conditions.

Inhibitory effect of Thymus caramanicus Jalas on hyperglycemia-induced apoptosis in in vitro and in vivo models of diabetic neuropathic pain

ETHNOPHARMACOLOGICAL RELEVANCE

Since Thymus caramanicus Jalas is used as a folk medicine for the treatment of rheumatism, skin disorders, bacterial infections and diabetes and it contain antioxidant agents, we decided to investigate the possible effects of Thymus caramanicus Jalas (TCJ) extract on in vitro and in vivo models of diabetic neuropathy.

MATERIALS AND METHODS

The high glucose-induced cell injury in Pheochromocytoma (PC12) cells and streptozotocin-induced diabetic rats were used. Tail-flick and rotarod treadmill assessments were used to determine nociceptive threshold and motor coordination. Cell viability was determined by MTT assay test. Western blotting was performed to measurement of apoptosis markers.

RESULTS

The data showed that elevation of glucose consecutively increases functional cell injury and apoptosis. Furthermore, diabetic rats developed thermal hyperalgesia and motor deficit. Activated caspase 3, cytochrome c release and Bax/Bcl-2 ratio were significantly increased in high glucose-treated PC12 cells and in spinal cord of diabetic animals. TCJ extract (60 and 80 µg/ml) attenuates high glucose-induced PC12 cells damage and apoptosis. In diabetic animals, TCJ extract at daily doses of 100 and 150 mg/kg ameliorated hyperalgesia and suppressed spinal apoptosis.

CONCLUSION

The data indicate that TCJ extract has neuroprotective effects against high glucose-induced neural damage. These protective effects are mediated, at least in part, through attenuation of neural apoptosis and suggest therapeutic potential of TCJ extract in amelioration of diabetic neuropathy.