ATPase Activity In Sciatic Nerve Research Articles

Effect of Pentoxifylline on Diabetic Neuropathic Pain in Rats

Abstract Background and Aim Diabetic neuropathy (DN) is the most common diabetic complication, which has a lifetime prevalence of about 50%. About 20 to 30% of patients with DN suffer from neuropathic pain. This study was designed to investigate the role of early and late treatment of pentoxifylline (PTX) in management of diabetic neuropathic pain (DNP). Method Diabetic rats were administered PTX (50 and 200 mg/kg/day, in drinking water) either one week after STZ injection and for 7 weeks or 6 weeks after STZ injection and for 2 weeks. Mechanical allodynia were assessed weekly, Iba-1 and GFAP immunorectivity, spinal NFκB & spinal sciatic TNF-α were estimated at the end of the study. Epidermal thickness of the food pad and Na+/K+-ATPase activity in sciatic nerve were measured as an outcome measure for predegenerative markers of DN. Results The results of the present study suggest that activated microglia and not astrocytes are involved in the development of experimental diabetic neuropathy. PTX inhibit neuroimmune activation of microglia, reduce the levels of proinflammatory cytokines and improve epidermal thickness of the food pad and Na+/K+-ATPase activity in sciatic nerve. Only PTX 200 mg/kg/day when administered early and late treatment in diabetic rats produced antiallodynic effect. Conclusion PTX is a fundamental drug whose antiallodynic effect depends on the pathogenetic mechanisms and has the ability to halt or inhibit the progression of the disease. The earlier the use of PTX in the developmental phase of mechanical hyperalgesia the more the antiallodynic effect of the drug.

The Natural Rotenoid Deguelin Ameliorates Diabetic Neuropathy by Decreasing Oxidative Stress and Plasma Glucose Levels in Rats via the Nrf2 Signalling Pathway

Background/Aims: Deguelin is a natural rotenoid that shows anti-inflammatory and antimicrobial activities. Rotenoids prevent oxidative damage and potentiate natural antioxidant activity in diabetic conditions, suggesting utility in treating diabetes and its complications. Here, we evaluate the potential efficacy of deguelin against diabetic neuropathy (DN). Methods: DN was induced by streptozotocin followed by daily treatment with deguelin (4, 6 or 8 mg/kg) for 14 days. Blood glucose was measured, neurobehavioral tests for nociception and motor coordination were performed, and neuron conduction velocities were analysed electrophysiologically. We also assessed (Na⁺-K⁺) ATPase activity, performed a reactive oxygen species assay, measured the levels of various markers of oxidative stress, and of hydrogen sulphide (H₂S) in dorsal root ganglion (DRG) neurons, conducted immunoblotting studies for proteins and ELISA for inflammatory cytokines. Results: Deguelin significantly suppressed mechanical and thermal hyperalgesia, as well as cold allodynia, and partially restored the conduction velocities of neurons in DN rats. Significantly decreased expression levels of capspase-3 in DRG neurons, and increased (Na⁺-K⁺) ATPase activity in sciatic nerves, were observed. In addition, deguelin decreased glucose levels, attenuated oxidative stress and neuroinflammation, and elevated levels of H₂S, nuclear respiratory factor 2 (Nrf2) and heme oxygenase-1, suggesting a disease-attenuating effect of deguelin in DN rats. To shed light on the underlying mechanism of action of deguelin, insulin- and dimethyl fumarate (BG-12)-treated groups were also included. Insulin suppressed glucose levels and BG-12 produced effects on Nrf2 levels similar to 8 mg/kg deguelin, confirming involvement of the Nrf2 pathway in the beneficial effects of deguelin against DN. Conclusions: Deguelin attenuated DN by decreasing oxidative stress and plasma glucose levels via the Nrf2 signalling pathway.

Functional and Morphological Effects of Grape Seed Proanthocyanidins on Peripheral Neuropathy in Rats with Type 2 Diabetes Mellitus

Grape seed proanthocyanidins (GSPs) possess a broad spectrum of pharmacological and therapeutic properties. The aim of this study was to examine the effect of GSPs on functional and morphological abnormalities in the peripheral nerves of rats with type 2 diabetes mellitus. Diabetic rats were induced by two injections of 25 mg streptozotocin/kg body weight and 8 weeks of a high-carbohydrate/high-fat diet. GSPs were then administrated to the rats for 16 weeks. Thermal and mechanical sensitivity thresholds and nerve conductive velocity were measured to evaluate peripheral nerve function. Light microscopy was used with special stains to observe the morphological changes in the central and peripheral nervous systems. Calcium (Ca(2+)) homeostasis and ATPase activities in the sciatic nerves were also determined. In diabetic rats receiving GSP treatment (especially at the 500 mg/kg dose), the abnormal peripheral nerve function and impaired nervous tissues (L4 to L5 spinal cord segments, L5 dorsal root ganglion, and sciatic nerves) were improved to a significant extent. Moreover, 500 mg/kg GSP treatment significantly reduced the concentration of free Ca(2+) and elevated Ca(2+)-ATPase activity in sciatic nerves. These results suggest that GSPs may prevent early functional and morphological abnormalities in the peripheral nerves of rats with type 2 diabetes mellitus.

Physiological and morphometric analyses of neuropathy in sucrose-fed OLETF rats

To investigate the characteristic features of diabetic neuropathy in type 2 diabetes mellitus, Otsuka Long–Evans Tokushima fatty (OLETF) rats, an animal model of human type 2 diabetes mellitus, and non-diabetic Long–Evans Tokushima Otsuka (LETO) rats were fed with or without sucrose and/or an aldose reductase inhibitor, [5-(3-thienyl) tetrazol-1-yl] acetic acid (TAT), for 24 weeks, and physiological, biochemical and morphological assessments were performed. Sucrose administration caused remarkable hyperglycemia in OLETF rats but not in LETO rats. Sucrose-fed OLETF rats demonstrated delayed nerve conduction velocity, decreased coefficient of variation of R-R interval, reduced sciatic nerve blood flow, increased platelet aggregation activity, a lower concentration of erythrocyte 2,3-diphosphoglycerate, and decreased Na +/K +-ATPase activity in sciatic nerves, compared with the non-sucrose-fed OLETF and LETO rats. TAT prevented all these deficits except hyperglycemia. Sorbitol and fructose accumulation and myo-inositol depletion in tail nerves of sucrose-fed OLETF rats were ameliorated by TAT. Myelinated fiber size and density in sural nerves of sucrose-fed OLETF rats were decreased and increased, respectively, compared with non-sucrose-fed OLETF and LETO rats. These morphological abnormalities were normalized by TAT. These observations suggest that the sucrose-fed OLETF rat developed diabetic neuropathy not only electrophysiologically but also histologically, and that an aldose reductase inhibitor, TAT, possesses therapeutic value for the treatment of diabetic neuropathy.

Cyclic adenosine 3',5'-monophosphate enhances sodium, potassium-adenosine triphosphatase activity in the sciatic nerve of streptozotocin-induced diabetic rats.

We have investigated the relationship between cAMP and sodium,potassium-ATPase (Na+,K(+)-ATPase) activity in the sciatic nerves of rats treated with cilostazol, a potent phosphodiesterase inhibitor; iloprost, a stable prostacyclin analog; or (Bu)2cAMP, a cAMP analog, which increase cAMP content by different mechanisms. In in vivo studies, administration of cilostazol (20 mg/kg BW.day), iloprost (4 micrograms/kg BW.day), or (Bu)2cAMP (4 mg/kg BW.day) for 4 weeks restored decreased cAMP content and Na+,K(+)-ATPase activity in the sciatic nerves of diabetic rats and further improved motor nerve conduction velocities without alteration of myo-inositol contents. There was a positive correlation between cAMP contents and Na+,K(+)-ATPase activities in the sciatic nerves. In in vitro experiments, cAMP accumulation and Na+,K(+)-ATPase activity in the desheathed sciatic nerve blocks obtained from both normal and diabetic rats were significantly increased by incubation with cilostazol, iloprost, or (Bu)2cAMP. In addition, cAMP accumulation and Na+,K(+)-ATPase activities in endoneurial preparations incubated in both normal and high glucose buffer were also significantly increased by cilostazol, iloprost, and (Bu)2cAMP. These results strongly suggest that there is a close relationship between cAMP content and Na+,K(+)-ATPase activity in rat sciatic nerves. Therefore, cAMP content may play an important role in the development of diabetic neuropathy by modulating Na+,K(+)-ATPase activity in the peripheral nerves.

Sustained recovery of Na(+)-K(+)-ATPase activity in sciatic nerve of diabetic mice by administration of H7 or calphostin C, inhibitors of PKC

Sustained recovery of Na(+)-K(+)-ATPase activity in sciatic nerve of diabetic mice by administration of H7 or calphostin C, inhibitors of PKC

Sustained recovery of Na(+)-K(+)-ATPase activity in sciatic nerve of diabetic mice by administration of H7 or calphostin C, inhibitors of PKC.

We have previously shown that intraperitoneal injection of H-7, an inhibitor of PKC, restores completely the activity of Na(+)-K(+)-ATPase in sciatic nerve of diabetic mice; however, the effect was transient, with a half-life of approximately 1 h under the conditions used. This work assessed whether calphostin C, a new more potent and specific inhibitor of PKC, is also able to restore the activity of Na(+)-K(+)-ATPase in sciatic nerve of ALX-induced diabetic mice and also assessed if continuous administration of H-7 or calphostin C can afford sustained recovery of the ATPase. Small amounts of calphostin C (i.e., 2 micrograms/kg) restore entirely the activity of the enzyme. Larger doses (e.g., 30 micrograms/kg) can be administered with equal results. The ED50 was approximately 0.5 micrograms/kg. This indicates that calphostin C is approximately 20,000 times more potent than H-7 in restoring the ATPase activity in diabetic mice. A single intraperitoneal injection of 1 or 10 micrograms/kg of calphostin C maintains the enzyme for 4 and 8 h, respectively. Administration of H-7 by continuous delivery from micro-osmotic pumps implanted in the back of the mice maintains the Na(+)-K(+)-ATPase for 24 h, although the activity decreases thereafter. This is the result of instability of H-7 in solution. Continous administration of calphostin C maintains the activity of the ATPase at nearly normal values for at least 2 wk. The results support the hypothesis that, in sciatic nerve tissue of diabetic animals, the activity of PKC is increased, leading to higher phosphorylation of Na(+)-K(+)-ATPase, which results in the decreased activity observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of protein kinase C restores Na+,K(+)-ATPase activity in sciatic nerve of diabetic mice.

We have tested if inhibition of protein kinase C is able to prevent and/or to restore the decrease of Na+,K(+)-ATPase activity in the sciatic nerve of alloxan-induced diabetic mice. Mice were made diabetic by subcutaneous injection of 200 mg of alloxan/kg of body weight. The activity of Na+,K(+)-ATPase decreased rapidly (43% after 3 days) and slightly thereafter (58% at 11 days). We show that intraperitoneal injection of 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H7), an inhibitor of protein kinase C, prevents completely the loss of Na+,K(+)-ATPase activity produced by alloxan. Also, H7 injected into diabetic mice, 4-9 days after the injection of alloxan, restores the activity of the enzyme. The amount of activity recovered depends on the dose of H7 administered; complete recovery was reached with injection of 15 mg of H7/kg of body weight. The effect of H7 is transient, with a half-life of approximately 1 h.

Nerve Na+-K+-ATPase, conduction, and myo-inositol in the insulin-deficient BB rat.

Nerve conduction slowing in acute diabetes in animals has been associated with both a diminished axolemmal transmembrane Na+ potential and a myo-inositol-related defect in nerve Na+-K+-ATPase activity. The interaction between these two potentially related defects, their reversibility, and their possible role in the nerve conduction slowing and axonopathy of diabetes are not well defined. Therefore, the effects of rigorous insulin replacement on peripheral nerve conduction velocity, myoinositol content, and Na+-K+-ATPase activity were studied in the spontaneously diabetic BB-Wistar rat, an animal model that manifests both conduction slowing and a characteristic progressive axonopathy. Twelve weeks of sustained hyperglycemia reduced both motor conduction velocity and Na+-K+-ATPase activity in sciatic nerve. Six weeks of subsequent vigorous insulin replacement normalized the enzymatic defect but only partially corrected diminished nerve conduction velocity. Hence, nerve conduction slowing in diabetic animals may be partly attributable to reduced nerve Na+-K+-ATPase activity, but a less readily reversible component of conduction slowing probably reflects structural alterations that occur in nerve within the first 3 mo of diabetes.

Diminished ouabain-sensitive, sodium-potassium ATPase activity in sciatic nerves of rats with streptozotocin-induced diabetes

Diminished ouabain-sensitive, sodium-potassium ATPase activity in sciatic nerves of rats with streptozotocin-induced diabetes

Myelinated nerve fibers: computed effect of myelin thickness on conduction velocity.

Myelinated nerve fibers: computed effect of myelin thickness on conduction velocity.