EFFECTS OF L-ARGININE AND NG-NITRO L-ARGININE METHYL ESTER ON LIPID PEROXIDE, SUPEROXIDE DISMUTASE AND NITRATE LEVELS AFTER EXPERIMENTAL SCIATIC NERVE ISCHEMIA-REPERFUSION IN RATS

Effect of peripheral blood mononuclear cells on ischemia-reperfusion injury of sciatic nerve of adult male albino rat: histological, immunohistochemical, and ultrastructural study

Ischemia/reperfusion (I/R) injury of sciatic nerve is a serious condition that results in nerve fiber degeneration, and reperfusion causes oxidative injury. Peripheral blood mononuclear cells (PBMNCs) have neuroregenerative power. This study was carried out to evaluate the potential ameliorative effect of PBMNCs on changes induced by I/R injury of the sciatic nerve. Fifty adult male albino rats were divided into donor and experimental groups that were subdivided into four groups: group I (control group), group II received 50 µL PBNMCs once intravenously via the tail vein, group III rubber tourniquet was placed around their Rt hind limb root for 2 hours to cause ischemia, group IV was subjected to limb ischemia as group III, then they were injected with 50 ul PBMNCs as group II before reperfusion. I/R injury showed disorganization of nerve fascicles with wide spaces in between nerve fibers. The mean area of collagen fibers, iNOS immunoexpression, and number of GFAP-positive Schwann cells of myelinated fibers showed a highly significant increase, while a highly significant reduction in the G-ratio and neurofilament immunoexpression was observed. Myelin splitting, invagination, evagination, and myelin figures were detected. PBMNC-treated group showed a marked improvement that was confirmed by histological, immunohistochemical, and ultrastructural findings.

Inhibition of nitric oxide production enhances the activity of facial nerve tubulin polymerization and the ability of tau to promote microtubule assembly after neurorrhaphy

We previously reported that inhibition of nitric oxide (NO) production promotes rat reconnected facial nerve regeneration. However, the underlying mechanism is obscure. Microtubule assembly is known to be essential to axon regeneration; nevertheless, tubulins and microtubule-associated proteins (MAPs) have been demonstrated as targets for NO and peroxynitrite. Thus, we hypothesized that NO and/or peroxynitrite may affect facial nerve regeneration via influencing on microtubule assembly. First, tubulins and tau (a MAP) were extracted from facial nerves of normal rats, treated with NO donor or peroxynitrite, and processed for microtubule assembly assay. We found that peroxynitrite, DEA NONOate, and Angeli's salt reduced the tubulin polymerization activity to a greater extent than GSNO, SIN-1, and SNAP. Additionally, SIN-1, peroxynitrite, and Angeli's salt impaired the ability of tau to promote microtubule assembly. Next, nitrosative stress biomarkers 3-nitrotyrosine (3-NT) and S-nitrosylated cysteine (SNO-Cys) were immunolabeled in facial nerves. Both biomarkers were highly upregulated in proximal and distal stumps of reconnected facial nerves at 3 days and 1 week after neurorrhaphy. Notably, the expression of 3-NT was greatly reduced at 2 weeks, whereas that of SNO-Cys was maintained. Conversely, inhibition of NO production with L-NAME prevented the upregulation of SNO-Cys. Further, we used tubulins and tau extracted from facial nerves of sham-operated, nerve suture + vehicle treatment, and nerve suture + L-NAME treatment rats to perform microtubule assembly assay. We found that L-NAME treatment enhanced polymerization activity of tubulins and ability of tau to promote microtubule assembly. It is noteworthy that α-tubulin plays a more important role than β-tubulin since the activity of microtubule assembly using α-tubulin extracted from L-NAME-treated rats was greatly elevated, whereas that using β-tubulin extracted from L-NAME-treated rats was not. Overall, our findings support that inhibition of NO production reduces nitrosative stress, and may thus facilitate microtubule assembly and facial nerve regeneration.

Neuroprotective and anti-apoptotic propensity of Bacopa monniera extract against sodium nitroprusside induced activation of iNOS, heat shock proteins and apoptotic markers in PC12 cells

Sodium nitroprusside (SNP) is a widely used nitric oxide (NO) donor, known to exert nitrative stress by up-regulation of inducible nitric oxide synthase (iNOS). Nω-nitro-L-arginine-methyl esther (L-NAME) is a NO inhibitor, which inhibits iNOS expression, is used as positive control. The present study was designed to assess neuroprotective propensity of Bacopa monniera extract (BME) in SNP-induced neuronal damage and oxido-nitrative stress in PC12 cells via modulation of iNOS, heat shock proteins and apoptotic markers. Our results elucidate that pre-treatment of PC12 cells with BME ameliorates the mitochondrial and plasma membrane damage induced by SNP (200 μM) as evidenced by MTT and LDH assays. BME pre-treatment inhibited NO generation by down regulating iNOS expression. BME replenished the depleted antioxidant status induced by SNP treatment. SNP-induced damage to cellular, nuclear and mitochondrial integrity was also restored by BME, which was confirmed by ROS estimation, comet assay and mitochondrial membrane potential assays respectively. BME pre-treatment efficiently attenuated the SNP-induced apoptotic protein biomarkers such as Bax, Bcl-2, cytochrome-c and caspase-3, which orchestrate the proteolytic damage of the cell. Q-PCR results further elucidated up-regulation of neuronal cell stress markers like HO-1 and iNOS and down-regulation of BDNF upon SNP exposure was attenuated by BME pre-treatment. By considering all these findings, we report that BME protects PC12 cells against SNP-induced toxicity via its free radical scavenging and neuroprotective mechanism.

Anti-apoptotic mechanism of Bacoside rich extract against reactive nitrogen species induced activation of iNOS/Bax/caspase 3 mediated apoptosis in L132 cell line

Nitric oxide is a highly reactive free radical gas that reacts with a wide range of bio-molecules to produce reactive nitrogen species and exerts nitrative stress. Bacopa monniera is a traditional folk and ayurvedic medicine known to alleviate a variety of disorders. Aim of the present study is to evaluate the protective propensity of Bacopa monniera extract (BME) through its oxido-nitrosative and anti-apoptotic mechanism to attenuate sodium nitroprusside (SNP)-induced apoptosis in a human embryonic lung epithelial cell line (L132). Our results elucidate that pre-treatment of L132 cells with BME ameliorates the mitochondrial and plasma membrane damage induced by SNP as evidenced by MTT and LDH leakage assays. BME pre-treatment inhibited NO generation by down-regulating inducible nitric oxide synthase expression. BME exhibited potent antioxidant activity by up-regulating the antioxidant enzymes. SNP-induced damage to cellular, nuclear and mitochondrial integrity was also restored by BME, which was confirmed by ROS estimation, comet assay and mitochondrial membrane potential assays respectively. BME pre-treatment efficiently attenuated the SNP-induced apoptotic biomarkers such as Bax, cytochrome-c and caspase-3, which orchestrate the proteolytic damage of the cell. By considering all these findings, we report that BME protects L132 cells against SNP-induced toxicity via its free radical scavenging and anti-apoptotic mechanism.

Role of N-Nitro-L-Arginine-Methylester as anti-oxidant in transient cerebral ischemia and reperfusion in rats

Background

Previous reports assessing the neuroprotective role of nonselective Nitric Oxide synthase (NOS) inhibitor N-nitro-L-arginine-methylester (L-NAME) following cerebral ischemia/reperfusion are contradictory. The aim of this work was to examine the potential benefits of L-NAME on rats subjected to transient focal cerebral ischemia/reperfusion.

Methods

The study involved 30 adult male Wistar rats divided into three groups 10 rats in each: First group was sham-operated and served as a control, a ischemia/reperfusion (I/R) group of rats infused with 0.9% normal saline intraperitoneally 15 minutes prior to 30 minutes of left common carotid artery (CCA) occlusion and a test group infused with L-NAME intraperitoneally 15 minutes prior to ischemia. Neurobehavioral assessments were evaluated and quantitative assessment of malondialdehyde (MDA), Nitric oxide (NO) metabolites and total antioxidant capacity (TAC) in both serum and the affected cerebral hemisphere were achieved.

Results

Rats’ neurological deficit and TAC were significantly decreased while NO and MDA were significantly increased in the I/R compared with the control group (P < 0.001). Alternatively in the L-NAME group, neurological deficit and TAC were significantly improved while NO and MDA were significantly decreased compared to I/R group (P < 0.001).

Conclusions

L-NAME pretreatment for rats undergoing cerebral ischemia/reperfusion significantly improves neurological deficit while reducing oxidative stress biomarkers in the affected cerebral hemisphere.

Proteasome inhibition promotes functional recovery after peripheral nerve reperfusion injury

BACKGROUND

The proteasome degrades NF-kappaB blocking protein (I-kappaB) and activates NF-kappaB that plays as a key transcriptional factor to regulate inflammatory factors that are involved in the tissue reperfusion injury. This study was designed to assess whether the proteasome inhibitor can attenuate peripheral nerve ischemia/reperfusion (I/R) injury and consequently promote motor functional recovery after ischemic insult.

METHODS

Rat sciatic nerves were exposed to 2 hour of ischemia followed by various periods of reperfusion. Rats were administered either proteasome inhibitor (bortezomib) or phosphate-buffered saline 30 minutes before reperfusion start. Results were evaluated using a walking track test, and an isolated muscle contraction test, and by muscle weight, and histology.

RESULTS

Bortezomib treatment induced an earlier improvement in sciatic functional index and a more rapid restoration of contractile force and wet weight of extensor digitorum longus muscle. Bortezomib reduced early axonal degeneration and promoted regeneration.

CONCLUSION

This study indicates that bortezomib; a proteasome inhibitor, is effective at promoting the functional recovery of reperfused peripheral nerve. The proteasome inhibition may play a role as one of the clinical strategy in the peripheral nervous system I/R injury with further understanding its mechanism of action.

Effects of trimetazidine on crush injury of the sciatic nerve in rats: a biochemical and stereological study

Trimetazidine (TMZ) is an anti-ischemic agent which has been used for years as an effective anti-anginal agent in cardiac patients. The aim of the study was to investigate the effect of TMZ on the level of malondialdehyde (MDA), nitric oxide (NO), glutathione (GSH), catalase (CAT), histopathological changes and the number of myelinated axons in a crush injury model of sciatic nerve in rats. In this study, 50 Wistar albino rats were used and the right sciatic nerves of all animals were injured. They were randomly divided into two groups equal in number, called treatment and non-treatment groups. The animals were subdivided into four subgroups, non-injury/non-treatment (left sciatic nerves of non-treatment animals, NI-NT) and non-injury/treatment (left sciatic nerves of treatment animals, NI-T) and injury/non-treatment (right sciatic nerves of non-treatment animals, I-NT) and injury/treatment (right sciatic nerves of treatment animals, I-T). At the end of the experiment, the bilateral sciatic nerves and blood samples collected from these animals were analyzed using histological, stereological and biochemical methods. There was a progressive increase in the serum level of GSH and progressive decrease in serum MDA levels in the treatment group. Progressive decrease in serum NO levels was observed in the treatment groups and it was statistically significant on day 14 (p<0.05) compared to the non-treatment group. The activities of CAT were low in the treatment groups on days 21 (p<0.05) and 42 (p<0.05). In the NI-NT group, some unimportant degenerative changes such as irregularity in myelin sheets were observed. Many pathologic changes in the I-NT group and some minimal degeneration in the I-T group were observed. TMZ treatment resulted in increases in the myelinated axon numbers by a range of 223 to 604 in the I-NT group compared to the I-T. In conclusion, TMZ appears to be beneficial for induction of axonal regeneration and myelination in healthy nerves as well as injured nerves.

Neuron-glial contacts formed in the cerebellum during electrical stimulation in the presence of an NO-generating compound

The molecular layer of the cerebellum of the frog Rana temporaria was studied by light and electron microscopy after electrical stimulation in the presence of an NO-generating compound. In these conditions, there was severe swelling of granule cell axon terminals (boutons) and astrocyte processes (AP), with loss of cytoplasmic elements. However, along with damaged structures, there were also undamaged structures: boutons with synaptic vesicles and AP with glycogen granules. It is suggested that these persisting viable AP may form 1) glial "wrappings" around damaged synapses or boutons and 2) neuron-glial contacts, which form when synaptic vesicles cross damaged bouton membranes to AP containing glycogen granules. It is also suggested that the presence of glycogen in AP in conditions of oxygen and glucose deficiency may provide a source of high-energy substrates such as glucose and ATP, thus providing conditions for neuron survival in pathological states (ischemia/hypoxia).

Role of oxidative stress in pathophysiology of peripheral neuropathy and modulation by N-acetyl-L-cysteine in rats

OBJECTIVES

The objectives of this study were to examine the role of reactive oxygen species and oxidative stress in peripheral neuropathy and behavioural pain responses in experimentally induced chronic constriction injury (CCI) of sciatic nerve of rat. Effect of N-acetyl-L-cysteine (NAC) administered intraperitoneally, was also investigated on CCI-induced neuropathic pain in rats.

METHODS

Neuropathy was induced by CCI of the right sciatic nerve in ketamine anaesthetized rats. Effect of intraperitoneally administered NAC in rats was also investigated using nociceptive behavioural tests. Malondialdehyde, an index of oxidative stress and antioxidant enzymes was also estimated in ligated sciatic nerve.

RESULTS

Behavioural tests, mechanical, thermal and cold stimuli confirmed the development of neuropathic pain after the CCI. The malondialdehyde levels of ligated sciatic nerves were significantly increased compared to non-ligated sciatic nerves (sham operated). The antioxidant enzyme reduced, glutathione was inhibited, while superoxide dismutase increased. However, catalase remained unaffected in the injured sciatic nerves. Intraperitoneal administration of NAC resulted in significant reduction of hyperalgesia in CCI-induced neuropathic rats.

CONCLUSIONS

This study identifies antioxidants superoxide dismutase and reduced glutathione, and oxidative stress as important determinants of neuropathological and behavioural consequences of CCI-induced neuropathy, and NAC may be a potential candidate for alleviation of neuropathic pain.

Inhibition of inducible nitric oxide synthase promotes recovery of motor function in rats after sciatic nerve ischemia and reperfusion

PURPOSE

To investigate the effects of inhibition of inducible nitric oxide synthase (iNOS) on the recovery of motor function in the rat sciatic nerve after ischemia and reperfusion injury.

METHODS

A 10-mm segment of the sciatic nerve from 169 rats had 2 hours of ischemia followed by up to 42 days of reperfusion. The animals were divided into 2 groups that received either iNOS inhibitor 1400W or the same volume of sterile water subcutaneously. A walking track test was used to evaluate the motor functional recovery during reperfusion. Statistical analysis was performed for the measurements of the sciatic functional index (SFI) by using 2-way analysis of variance; 1-way analysis of variance was used for the post hoc analysis of specific values at each time point of the SFI measurement.

RESULTS

1400W-treated rats had earlier motor functional recovery than controls, with a significantly improved SFI between days 11 and 28. Histology showed less axonal degeneration and earlier regeneration of nerve fibers in the 1400W group than in the controls. Inducible NOS messenger RNA and protein were up-regulated during the first 3 days of reperfusion but there was a down-regulation of neuronal NOS and up-regulation of endothelial NOS in control animals. 1400W treatment attenuated the increase of iNOS but had no effect on neuronal NOS and endothelial NOS.

CONCLUSIONS

Our results indicate that early inhibition of iNOS appears to be critical for reducing or preventing ischemia and reperfusion injury.

The effects of exogenous nitric oxide donor on motor functional recovery of reperfused peripheral nerve

PURPOSE

To investigate the effects of the nitric oxide donor S-nitroso-N-acetylcysteine (SNAC) on motor functional recovery of reperfused rat sciatic nerve.

METHODS

Seventy-eight rats were divided into groups treated with SNAC (100 nmol/100 g/min), methylprednisolone 30 mg/kg/h for 15 minutes, 45-minute pause, 5.4 mg/kg/h for 1.5 h), and phosphate-buffered saline 0.2 mL/100 g/h). A 1-cm segment of sciatic nerve had 2 hours of ischemia and the results were evaluated after various reperfusion periods using a walking track test, muscle contractile testing, muscle weight, and histology.

RESULTS

During reperfusion there was a significant overall improvement in sciatic functional index measurement and isometric titanic contractile force for the SNAC-treated group compared with the methylprednisolone- and phosphate-buffered saline- treated groups. The SNAC group had significantly earlier improvement in the sciatic functional index measurement between days 7 and 28. Restoration of the contractile force and muscle weight of the extensor digitorum longus muscle began earlier in the SNAC group--after day 11--whereas the other 2 groups showed progressive atrophy until day 21, with a significant difference between the SNAC group and the other 2 groups. Histologic examination showed that SNAC-treated rats had less severe degeneration and earlier regeneration of axons than the others. Although methylprednisolone-treated rats showed earlier recovery than phosphate-buffered saline-treated rats in all parameters there were no significant differences between these 2 groups.

CONCLUSIONS

Supplementation of nitric oxide is effective in promoting motor functional recovery of the reperfused peripheral nerve and has potential to replace or augment steroids as therapeutic agents in treatment of nervous system ischemia/reperfusion injury.

Altered erythrocyte membrane characteristics during anemia in childhood acute lymphoblastic leukemia

Anemia is a prominent feature in children with acute lymphoblastic leukemia (ALL). To investigate the erythrocyte features during anemia in these patients, we studied the altered characters of these cells and oxidative stress imposed in their serum. This investigation reveals that erythrocytes from ALL patients show (1) increased membrane fluidity detected by fluorescence anisotropy studies, increased osmotic fragility detected by hemolysis of erythrocytes in different saline concentrations, and increased hydrophobicity as measured by binding with 8-anilino-1-naphthalenesulfonic acid, (2) enhanced (approximately threefold) glycosylation and sialylation, monitored by digoxigenin enzyme assay, and (3) expression of disease-specific 210, 105, 83, 54, and 28 kDa 9-O-acetyl sialoglycoconjugates (9-O-AcSGs) demonstrated by Western blot analysis and fluorescence-activated cell sorter (FACS) analysis studies using Achatinin-H with specificity towards 9-O-AcSAalpha2-6GalNAc as the analytical probe. (4) In addition, induced oxidative stress was observed in the sera of these children as indicated by increased nitric oxide (approximately fourfold) and thiobarbituric acid (TBA) reactive species (twofold) as detected by Griess reaction and TBA assay, respectively. For all the experiments, erythrocytes from normal individuals served as controls. Thus, the altered membrane characteristics together with their exposure to induced oxidative stress in serum are found to be a few features restricted to diseased erythrocytes. Taken together, our results are suggestive of their interplay in the contribution to the observed anemia in these patients, which may be exploited for better management of the disease.