Neuroprotective effects of FeTMPyP: a peroxynitrite decomposition catalyst in global cerebral ischemia model in gerbils

Leflunomide abrogates neuroinflammatory changes in a rat model of Alzheimer's disease: the role of TNF-α/NF-κB/IL-1β axis inhibition

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases and is associated with disrupted cognition and behavior. Neuroinflammatory pathogenesis is the main component that contributes to AD initiation and progression through microglial activation and neuronal damage. Thus, targeting inflammatory pathways may help manage AD. In this study, for the first time, the potential prophylactic and therapeutic effects of leflunomide were investigated either alone or in combination with rivastigmine in aluminum chloride (AlCl₃)-induced AD-like rats using behavioral, biochemical, and histological approaches. Thirty-six adult male albino rats were divided into two protocols: the treatment protocol, subdivided into five groups (n = 6)-(1) control group, (2) AlCl₃ (50, 70, 100 mg/kg/I.P) group, (3) reference group (rivastigmine 2 mg/kg/P.O.), (4) experimental group (leflunomide 10 mg/kg/P.O.), and (5) combination group (rivastigmine + leflunomide); and the prophylactic protocol (leflunomide 10 mg/kg/P.O.), which started 2 weeks before AlCl₃ induction. The results showed that AlCl₃ disrupted learning and memory parameters in rats and increased amyloid-β plaque deposition and neurofibrillary tangle aggregation. Moreover, AlCl₃ administration markedly elevated acetylcholinesterase activity, nuclear factor-kappa β, tumor necrosis factor-α, and interleukin-1 beta, and marked degenerative changes in the pyramidal neurons. However, administration of leflunomide alone or with rivastigmine in AlCl₃-induced AD rats restored most of the behavioral, biochemical, and histological parameters triggered by AlCl₃ in rats. Our findings suggest that leflunomide can potentially restore most of the neuronal damage in the hippocampal tissues of AlCl₃-induced AD rats. However, these preclinical findings still need to be confirmed in clinical trials.

SIRT2 tyrosine nitration by peroxynitrite in response to renal ischemia/reperfusion injury

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are the production of renal ischemia/reperfusion (I/R). The current study is to elucidate a mechanism of SIRT2 tyrosine nitration to accelerate the cell apoptosis induced by peroxynitrite (ONOO‾), the most reactive and deleterious RNS type in renal ischemia/reperfusion (I/R) injury. Our results demonstrate that there is a significant enhancement of the 3-nitrotyrosine levels in renal tissues of Acute Kidney Injury (AKI) patients and rats that underwent renal I/R, and a positive correlation between the 3-nitrotyrosine level and renal function impairment, indicative of an accumulation of peroxynitrite. Notably, peroxynitrite-evoked nitration of SIRT2 destroyed its enzymatic activity and the capability to deacetylate FOXO3a, and enhanced expression of Bim and caspase3, facilitating renal cell apoptosis in renal ischemia/reperfusion and SIN-1(peroxynitrite donor) treatment in vitro, and these effects were reversed by FeTMPyP, a peroxynitrite decomposition scavenger. Importantly, we identified that the tyrosine 86 is responsible for SIRT2 nitration and inactivation using site-mutation assay and Mass Spectrography analysis. Altogether, these findings point to a novel protective mechanism that an inhibition of SIRT2 tyrosine nitration can be a promising strategy to prevent ischemic renal diseases involving AKI.

Hypothermia Induced by Oxcarbazepine after Transient Forebrain Ischemia Exerts Therapeutic Neuroprotection through Transient Receptor Potential Vanilloid Type 1 and 4 in Gerbils

In the present study, we investigated the neuroprotective effect of post-ischemic treatment with oxcarbazepine (OXC; an anticonvulsant compound) against ischemic injury induced by transient forebrain ischemia and its mechanisms in gerbils. Transient ischemia was induced in the forebrain by occlusion of both common carotid arteries for 5 min under normothermic conditions (37 ± 0.2 °C). The ischemic gerbils were treated with vehicle, hypothermia (whole-body cooling; 33.0 ± 0.2 °C), or 200 mg/kg OXC. Post-ischemic treatments with vehicle and hypothermia failed to attenuate and improve, respectively, ischemia-induced hyperactivity and cognitive impairment (decline in spatial and short-term memory). However, post-ischemic treatment with OXC significantly attenuated the hyperactivity and the cognitive impairment, showing that OXC treatment significantly reduced body temperature (to about 33 °C). When the hippocampus was histopathologically examined, pyramidal cells (principal neurons) were dead (lost) in the subfield Cornu Ammonis 1 (CA1) of the gerbils treated with vehicle and hypothermia on Day 4 after ischemia, but these cells were saved in the gerbils treated with OXC. In the gerbils treated with OXC after ischemia, the expression of transient receptor potential vanilloid type 1 (TRPV1; one of the transient receptor potential cation channels) was significantly increased in the CA1 region compared with that in the gerbils treated with vehicle and hypothermia. In brief, our results showed that OXC-induced hypothermia after transient forebrain ischemia effectively protected against ischemia–reperfusion injury through an increase in TRPV1 expression in the gerbil hippocampal CA1 region, indicating that TRPV1 is involved in OXC-induced hypothermia.

Posttranscriptional regulation of Nrf2 through miRNAs and their role in Alzheimer's disease

The nuclear factor erythroid-derived 2-related factor 2 (NFE2L2/Nrf2) is a pivotal facilitator of cytoprotective responses against the oxidative/electrophilic insults. Upon activation, Nrf2 induces transcription of a wide range of cytoprotective genes having antioxidant response element (ARE) in their promoter region. Dysfunction in Nrf2 signaling has been linked to the pathogenesis of AD and several studies have suggested that boosting Nrf2 expression/activity by genetic or pharmacological approaches is beneficial in AD. Among the diverse mechanisms that regulate the Nrf2 signaling, miRNAs-mediated regulation of Nrf2 has gained much attention in recent years. Several miRNAs have been reported to directly repress the post-transcriptional expression of Nrf2 and thereby negatively regulate the Nrf2-dependent cellular cytoprotective response in AD. Moreover, several Nrf2 targeting miRNAs are misregulated in AD brains. This review is focused on the role of misregulated miRNAs that directly target Nrf2, in AD pathophysiology. Here, alongside a general description of functional interactions between miRNAs and Nrf2, we have reviewed the evidence indicating the possible role of these miRNAs in AD pathogenesis.

Therapeutic Effects of Decursin and Angelica gigas Nakai Root Extract in Gerbil Brain after Transient Ischemia via Protecting BBB Leakage and Astrocyte Endfeet Damage

Angelica gigas Nakai root contains decursin which exerts beneficial properties such as anti-amnesic and anti-inflammatory activities. Until now, however, the neuroprotective effects of decursin against transient ischemic injury in the forebrain have been insufficiently investigated. Here, we revealed that post-treatment with decursin and the root extract saved pyramidal neurons in the hippocampus following transient ischemia for 5 min in gerbil forebrain. Through high-performance liquid chromatography, we defined that decursin was contained in the extract as 7.3 ± 0.2%. Based on this, we post-treated with 350 mg/kg of extract, which is the corresponding dosage of 25 mg/kg of decursin that exerted neuroprotection in gerbil hippocampus against the ischemia. In addition, behavioral tests were conducted to evaluate ischemia-induced dysfunctions via tests of spatial memory (by the 8-arm radial maze test) and learning memory (by the passive avoidance test), and post-treatment with the extract and decursin attenuated ischemia-induced memory impairments. Furthermore, we carried out histochemistry, immunohistochemistry, and double immunohistofluorescence. Pyramidal neurons located in the subfield cornu ammonis 1 (CA1) among the hippocampal subfields were dead at 5 days after the ischemia; however, treatment with the extract and decursin saved the pyramidal neurons after ischemia. Immunoglobulin G (IgG, an indicator of extravasation), which is not found in the parenchyma in normal brain tissue, was apparently shown in CA1 parenchyma from 2 days after the ischemia, but IgG leakage was dramatically attenuated in the CA1 parenchyma treated with the extract and decursin. Furthermore, astrocyte endfeet, which are a component of the blood–brain barrier (BBB), were severely damaged at 5 days after the ischemia; however, post-treatment with the extract and decursin dramatically attenuated the damage of the endfeet. In brief, therapeutic treatment of the extract of Angelica gigas Nakai root and decursin after 5 min transient forebrain ischemia protected hippocampal neurons from the ischemia, showing that ischemia-induced BBB leakage and damage of astrocyte endfeet was significantly attenuated by the extract and decursin. Based on these findings, we suggest that Angelica gigas Nakai root containing decursin can be employed as a pharmaceutical composition to develop a therapeutic strategy for brain ischemic injury.

Rehmapicroside ameliorates cerebral ischemia-reperfusion injury via attenuating peroxynitrite-mediated mitophagy activation

Peroxynitrite (ONOO^-)-mediated mitophagy activation represents a vital pathogenic mechanism in ischemic stroke. Our previous study suggests that ONOO^- mediates Drp1 recruitment to the damaged mitochondria for excessive mitophagy, aggravating cerebral ischemia/reperfusion injury and the ONOO^--mediated mitophagy activation could be a crucial therapeutic target for improving outcome of ischemic stroke. In the present study, we tested the neuroprotective effects of rehmapicroside, a natural compound from a medicinal plant, on inhibiting ONOO^--mediated mitophagy activation, attenuating infarct size and improving neurological functions by using the in vitro cultured PC12 cells exposed to oxygen glucose deprivation with reoxygenation (OGD/RO) condition and the in vivo rat model of middle cerebral artery occlusion (MCAO) for 2 h of transient cerebral ischemia plus 22 h of reperfusion. The major discoveries include following aspects: (1) Rehmapicroside reacted with ONOO^- directly to scavenge ONOO^-; (2) Rehmapicroside decreased O₂^- and ONOO^-, up-regulated Bcl-2 but down-regulated Bax, Caspase-3 and cleaved Caspase-3, and down-regulated PINK1, Parkin, p62 and the ratio of LC3-II to LC3-I in the OGD/RO-treated PC12 cells; (3) Rehmapicroside suppressed 3-nitrotyrosine formation, Drp1 nitration as well as NADPH oxidases and iNOS expression in the ischemia-reperfused rat brains; (4) Rehmapicroside prevented the translocations of PINK1, Parkin and Drp1 into the mitochondria for mitophagy activation in the ischemia-reperfused rat brains; (5) Rehmapicroside ameliorated infarct sizes and improved neurological deficit scores in the rats with transient MCAO cerebral ischemia. Taken together, rehmapicroside could be a potential drug candidate against cerebral ischemia-reperfusion injury, and its neuroprotective mechanisms could be attributed to inhibiting the ONOO^--mediated mitophagy activation.

Galangin attenuated cerebral ischemia-reperfusion injury by inhibition of ferroptosis through activating the SLC7A11/GPX4 axis in gerbils

AIMS

To evaluate the impact of galangin treatment on cerebral ischemia-reperfusion (I/R) injury in gerbils and to identify potential mechanisms of the protective effect of galangin on hippocampal neurons after I/R injury.

PRINCIPAL METHODS

A cerebral ischemia model using bilateral common carotid artery ligation in gerbils was established. The Morris water maze (MWM) test was used to evaluate the learning and memory ability of gerbils. The cell viability was evaluated with an MTT assay. The levels of lipid peroxide biomarkers were measured to estimate the injury due to lipid peroxide. The morphology was detected by electron micrography, immunofluorescence and Nissl staining. Western blot and quantitative real-time polymerase chain reaction (qRT-PCR) were used to measure the molecular characteristics.

KEY FINDINGS

In the MWM, gerbils treated with galangin after I/R injury showed significant improvements in learning and memory. In addition, galangin treatment reduced the levels of lipid peroxide in the brains of gerbils that underwent I/R as well as reduced the amount of cell death and increased the expression of SLC7A11 and glutathione peroxidase 4 (GPX4). Furthermore, the expression of the marker of ferroptosis was decreased in galangin-treated gerbils, and the effect of galangin was weakened when SLC7A11 was knocked down. These results show that galangin can inhibit ferroptosis by enhancing the expressions of SLC7A11 and GPX4 as well as reduce neuronal cell death.

SIGNIFICANCE

Galangin inhibits ferroptosis through activation of the SLC7A11/GPX4 axis and has a protective effect on hippocampal neurons in gerbils after I/R.

Targeting RNS/caveolin-1/MMP signaling cascades to protect against cerebral ischemia-reperfusion injuries: potential application for drug discovery

Reactive nitrogen species (RNS) play important roles in mediating cerebral ischemia-reperfusion injury. RNS activate multiple signaling pathways and participate in different cellular events in cerebral ischemia-reperfusion injury. Recent studies have indicated that caveolin-1 and matrix metalloproteinase (MMP) are important signaling molecules in the pathological process of ischemic brain injury. During cerebral ischemia-reperfusion, the production of nitric oxide (NO) and peroxynitrite (ONOO⁻), two representative RNS, down-regulates the expression of caveolin-1 (Cav-1) and, in turn, further activates nitric oxide synthase (NOS) to promote RNS generation. The increased RNS further induce MMP activation and mediate disruption of the blood-brain barrier (BBB), aggravating the brain damage in cerebral ischemia-reperfusion injury. Therefore, the feedback interaction among RNS/Cav-1/MMPs provides an amplified mechanism for aggravating ischemic brain damage during cerebral ischemia-reperfusion injury. Targeting the RNS/Cav-1/MMP pathway could be a promising therapeutic strategy for protecting against cerebral ischemia-reperfusion injury. In this mini-review article, we highlight the important role of the RNS/Cav-1/MMP signaling cascades in ischemic stroke injury and review the current progress of studies seeking therapeutic compounds targeting the RNS/Cav-1/MMP signaling cascades to attenuate cerebral ischemia-reperfusion injury. Several representative natural compounds, including calycosin-7-O-β-D-glucoside, baicalin, Momordica charantia polysaccharide (MCP), chlorogenic acid, lutein and lycopene, have shown potential for targeting the RNS/Cav-1/MMP signaling pathway to protect the brain in ischemic stroke. Therefore, the RNS/Cav-1/MMP pathway is an important therapeutic target in ischemic stroke treatment.

One-Compound-Multi-Target: Combination Prospect of Natural Compounds with Thrombolytic Therapy in Acute Ischemic Stroke

Tissue plasminogen activator (t-PA) is the only FDA-approved drug for acute ischemic stroke treatment, but its clinical use is limited due to the narrow therapeutic time window and severe adverse effects, including hemorrhagic transformation (HT) and neurotoxicity. One of the potential resolutions is to use adjunct therapies to reduce the side effects and extend t-PA's therapeutic time window. However, therapies modulating single target seem not to be satisfied, and a multitarget strategy is warranted to resolve such complex disease. Recently, large amount of efforts have been made to explore the active compounds from herbal supplements to treat ischemic stroke. Some natural compounds revealed both neuro- and bloodbrain- barrier (BBB)-protective effects by concurrently targeting multiple cellular signaling pathways in cerebral ischemia-reperfusion injury. Thus, those compounds are potential to be one-drug-multi-target agents as combined therapy with t-PA for ischemic stroke. In this review article, we summarize current progress about molecular targets involving in t-PA-mediated HT and neurotoxicity in ischemic brain injury. Based on these targets, we select 23 promising compounds from currently available literature with the bioactivities simultaneously targeting several important molecular targets. We propose that those compounds merit further investigation as combined therapy with t-PA. Finally, we discuss the potential drawbacks of the natural compounds' studies and raise several important issues to be addressed in the future for the development of natural compound as an adjunct therapy.

Peroxynitrite Decomposition Catalyst Reduces Delayed Thrombolysis-induced Hemorrhagic Transformation in Ischemia-reperfused Rat Brains

AIM

Hemorrhagic transformation (HT) is a major complication of delayed tissue plasminogen activator (t-PA) treatment in ischemic stroke. We aimed to explore whether peroxynitrite decomposition catalyst (PDC) could prevent such complication.

METHODS

Male Sprague-Dawley (SD) rats were subjected to middle cerebral artery occlusion (MCAO) with t-PA (10 mg/kg) or t-PA plus FeTMPyP (3 mg/kg, a representative PDC) at MCAO for 2 or 5 h and reperfusion for 22 or 19 h, respectively. HT was assessed with hemoglobin assay. Neurological deficit was evaluated with Modified Neurological Severity Score (mNSS). Peroxynitrite formation was examined by detecting 3-nitrotyrosine (3-NT) formation. The expression and activity of MMP-9/MMP-2 were assessed by Western blotting and gelatin zymography.

RESULTS

t-PA treatment at 2 h of MCAO did not induce HT but attenuated neurological deficit, whereas treatment at 5 h significantly induced HT and worsened the neurological outcome. Such complications were prevented by FeTMPyP cotreatment. Early t-PA treatment inhibited 3-NT and MMP-9/MMP-2 expression, whereas delayed treatment induced 3-NT and MMP-9/MMP-2 expression and activity. FeTMPyP cotreatment downregulated 3-NT and inhibited MMP-9/MMP-2 in both time points.

CONCLUSION

Peroxynitrite decomposition catalyst could prevent hemorrhagic transformation and improve neurological outcome ischemic rat brains with delayed t-PA treatment via inhibiting peroxynitrite-mediated MMP activation.

Protective effect of metalloporphyrins against cisplatin-induced kidney injury in mice

Oxidative and nitrative stress is a well-known phenomenon in cisplatin-induced nephrotoxicity. The purpose of this work is to study the role of two metalloporphyrins (FeTMPyP and MnTBAP), water soluble complexes, in cisplatin-induced renal damage and their ability to scavenge peroxynitrite. In cisplatin-induced nephropathy study in mice, renal nitrative stress was evident by the increase in protein nitration. Cisplatin-induced nephrotoxicity was also evident by the histological damage from the loss of the proximal tubular brush border, blebbing of apical membranes, tubular epithelial cell detachment from the basement membrane, or intra-luminal aggregation of cells and proteins and by the increase in blood urea nitrogen and serum creatinine. Cisplatin-induced apoptosis and cell death as shown by Caspase 3 assessments, TUNEL staining and DNA fragmentation Cisplatin-induced nitrative stress, apoptosis and nephrotoxicity were attenuated by both metalloporphyrins. Heme oxygenase (HO-1) also plays a critical role in metalloporphyrin-mediated protection of cisplatin-induced nephrotoxicity. It is evident that nitrative stress plays a critical role in cisplatin-induced nephrotoxicity in mice. Our data suggest that peroxynitrite is involved, at least in part, in cisplatin-induced nephrotoxicity and protein nitration and cisplatin-induced nephrotoxicity can be prevented with the use of metalloporphyrins.

Modulation of myocardial contraction by peroxynitrite

Peroxynitrite is a potent oxidant that is quickly emerging as a crucial modulator of myocardial function. This review will focus on the regulation of myocardial contraction by peroxynitrite during health and disease, with a specific emphasis on cardiomyocyte Ca²⁺ handling, proposed signaling pathways, and protein end-targets.

Amelioration of neurodegenerative changes in cellular and rat models of diabetes-related Alzheimer's disease by exendin-4

Growing evidence suggests that type 2 diabetes mellitus (DM) is associated with age-dependent Alzheimer's disease (AD), the latter of which has even been considered as type 3 diabetes. Several physiopathological features including hyperglycemia, oxidative stress, and dysfunctional insulin signaling relate DM to AD. In this study, high glucose-, oxidative stress-induced neuronal injury and intracerebroventricular-streptozotocin (ICV-STZ) animals as the possible models for diabetes-related AD were employed to investigate the effects of exendin-4 (Ex-4), a long-acting glucagon-like peptide-1 (GLP-1) receptor agonist, on diabetes-associated Alzheimer-like changes as well as the molecular mechanisms involved. Our study demonstrated that GLP-1/Ex-4 could exert a protective effect against reduced viability of PC12 cells caused by high glucose and that this protective effect was mediated via the PI3-kinase pathway. In addition, GLP-1/Ex-4 ameliorated oxidative stress-induced injury in PC12 cells. In rat models, bilateral ICV-STZ administration was used to produce impaired insulin signaling in the brain. Fourteen days following ICV-STZ injection, rats treated with twice-daily Ex-4 had better learning and memory performance in the Morris water maze test compared with rats treated with saline. Additionally, histopathological evaluation confirmed the protective effects of Ex-4 treatment on hippocampal neurons against degeneration. Furthermore, we demonstrated that Ex-4 reversed ICV-STZ-induced tau hyperphosphorylation through downregulation of GSK-3β activity, a key kinase in both DM and AD. Our findings suggests that Ex-4 can protect neurons from diabetes-associated glucose metabolic dysregulation insults in vitro and from ICV-STZ insult in vivo, and that Ex-4 may prove of therapeutic value in the treatment of AD especially DM-related AD.

Anti-inflammatory effect of simvastatin in an experimental model of spinal cord trauma: involvement of PPAR-α

BACKGROUND

Statins such as simvastatin are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase used in the prevention of cardiovascular disease. In addition to their cholesterol-lowering activities, statins exert pleiotropic anti-inflammatory effects, which might contribute to their beneficial effects on lipid-unrelated inflammatory diseases. Recently it has been demonstrated that the peroxisome proliferator-activated receptor (PPAR)-α mediates anti-inflammatory effects of simvastatin in vivo models of acute inflammation. Moreover, previous results suggest that PPAR-α plays a role in control of secondary inflammatory process associated with spinal cord injury (SCI).

METHODS

With the aim to characterize the role of PPAR-α in simvastatin activity, we tested the efficacy of simvastatin (10 mg/kg dissolved in saline i.p. 1 h and 6 h after the trauma) in an experimental model of SCI induced in mice by extradural compression of the spinal cord (T6-T7 level) using an aneurysm clip with a closing force of 24 g via a four-level T5-T8 laminectomy, and comparing mice lacking PPAR-α (PPAR-α KO) with wild type (WT) mice. In order to elucidate whether the effects of simvastatin are due to activation of the PPAR-α, we also investigated the effect of a PPAR-α antagonist, GW6471 (1 mg/kg administered i.p. 30 min prior treatment with simvastatin) on the protective effects of on simvastatin.

RESULTS

Results indicate that simvastatin activity is weakened in PPAR-α KO mice, as compared to WT controls. In particular, simvastatin was less effective in PPAR-α KO, compared to WT mice, as evaluated by inhibition of the degree of spinal cord inflammation, neutrophil infiltration, nitrotyrosine formation, pro-inflammmatory cytokine expression, nuclear factor (NF)-κB activation, inducible nitric-oxide synthase (iNOS) expression, and apoptosis. In addition we demonstrated that GW6471 significantly antagonized the effect of the statin and thus abolished the protective effect.

CONCLUSIONS

This study indicates that PPAR-α can contribute to the anti-inflammatory activity of simvastatin in SCI.

Superoxide dismutase mimics: chemistry, pharmacology, and therapeutic potential

Oxidative stress has become widely viewed as an underlying condition in a number of diseases, such as ischemia-reperfusion disorders, central nervous system disorders, cardiovascular conditions, cancer, and diabetes. Thus, natural and synthetic antioxidants have been actively sought. Superoxide dismutase is a first line of defense against oxidative stress under physiological and pathological conditions. Therefore, the development of therapeutics aimed at mimicking superoxide dismutase was a natural maneuver. Metalloporphyrins, as well as Mn cyclic polyamines, Mn salen derivatives and nitroxides were all originally developed as SOD mimics. The same thermodynamic and electrostatic properties that make them potent SOD mimics may allow them to reduce other reactive species such as peroxynitrite, peroxynitrite-derived CO(3)(*-), peroxyl radical, and less efficiently H(2)O(2). By doing so SOD mimics can decrease both primary and secondary oxidative events, the latter arising from the inhibition of cellular transcriptional activity. To better judge the therapeutic potential and the advantage of one over the other type of compound, comparative studies of different classes of drugs in the same cellular and/or animal models are needed. We here provide a comprehensive overview of the chemical properties and some in vivo effects observed with various classes of compounds with a special emphasis on porphyrin-based compounds.

The acute and chronic phases of chronic relapsing experimental autoimmune encephalomyelitis (CR EAE) are ameliorated by the peroxynitrite decomposition catalyst, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinatoiron (III) chloride, (FeTPPS)

There is increasing evidence that the oxidative radical, peroxynitrite (ONOO(-)), is involved in the pathogenesis of inflammatory diseases including multiple sclerosis and the animal counterpart, experimental autoimmune encephalomyelitis (EAE). Compounds that impede the actions of ONOO(-) have proved useful in the control of EAE. In particular, catalytic isomerisation of ONOO(-) to inactive nitrate, through the use of metalloporphyrins, curtails the cellular response to inflammatory stimuli and halts the progression of neuroinflammation during EAE. The present study examined the pharmacological effects of the metalloporphyrin and ONOO(-) decomposition catalyst 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinatoiron(III)chloride (FeTPPS) on the acute and relapse phases of chronic relapsing (CR) EAE. Administration of FeTPPS to CR EAE-inoculated Biozzi mice commenced either therapeutically and immediately prior to the emergence of acute or relapse symptoms, or prophylactically, from the onset of remission of acute neurological signs. Drug therapy reduced acute and relapse symptoms but, and in contrast to the former phase, was of limited benefit in preventing histological changes during the latter stage of disease. In contrast, prophylactic FeTPPS was effective in limiting CNS pathology and neurological deficits. The findings confirm the inhibitory effects of FeTPPS on acute stage EAE. Moreover, the study extends previous observations by verifying compound efficacy on relapsing disease. Use of metalloporphyrins, such as FeTPPS, again highlights the important role played by ONOO(-) in the development of inflammatory diseases such as EAE.

Differential patterns of peroxynitrite mediated apoptosis in proximal tubular epithelial cells following ATP depletion recovery

Ischemia-reperfusion injury (IRI) is characterized by ATP depletion in the ischemic phase, followed by a rapid increase in reactive oxygen species, including peroxynitrite in the reperfusion phase. In this study, we examined the role of peroxynitrite on cytotoxicity and apoptosis in an in vitro model of ATP depletion-recovery. Porcine proximal tubular epithelial (LLC-PK(1)) cells were ATP depleted for either 2 h (2/2) or 4 h (4/2) followed by recovery in serum free medium for 2 h. A subset of cells was treated with 100 microM of the peroxynitrite scavenger, iron (III) tetrakis (N-methyl-4'pyridyl) porphyrin pentachloride (FeTMPyP) 30 min prior to and during treatment/recovery. Treatment with FeTMPyP reduced cytotoxicity and superoxide levels at both the 2/2 and 4/2 time points, however FeTMPyP decreased nitric oxide only at the 2/2 time point. FeTMPyP also partially blocked caspase-3 and caspase-8 activation at both 2/2 and 4/2 time points. At the 4/2 time point, FeTMPyP also partially inhibited the ATP depletion mediated increase in tumor necrosis factor alpha (TNF-alpha) and decreased Bax and FasL gene expression. These data show that peroxynitrite induces apoptosis by activation of multiple pathways depending on length and severity of insult following ATP depletion-recovery.

Neuroprotective effect of MnTMPyP, a superoxide dismutase/catalase mimetic in global cerebral ischemia is mediated through reduction of oxidative stress and DNA fragmentation

Excessive generation of free radicals and decreased levels of the antioxidant enzymes such as superoxide dismutase (SOD) and catalase have been observed after brain ischemic reperfusion injury. In the present study, we have investigated the neuroprotective potential of MnTMPyP (Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride), a SOD/Catalase mimetic in bilateral carotid artery occlusion model of global cerebral ischemia in Mongolian gerbils. Five minutes of bilateral carotid artery occlusion produced global cerebral ischemia, which was evident from the neurological deficits, spontaneous motor activity and the decrease in the number of viable hippocampal CA1 neurons. Global ischemia was also associated with increased levels of malondialdehyde, decreased levels of SOD and catalase, and increased TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) positive cells, indicating oxidative stress and DNA fragmentation. Administration of a single dose of MnTMPyP, 1 mg/kg i.p. (30 min before occlusion), produced no significant neuroprotection; however, 3 mg/kg i.p. (30 min before to occlusion) produced significant reduction in neurological score, spontaneous motor activity and CA1 pyramidal neuronal damage. MnTMPyP also attenuated the increased levels of malondialdehyde and improved the levels of SOD and catalase, and inhibited DNA fragmentation in the ischemic animals. Multiple administration of MnTMPyP, 3 mg/kg i.p. (three times: 30 min before, 1 h and 3 h after occlusion), produced better neuroprotection as compared to single dose administration. This study demonstrates that the neuroprotective effect of MnTMPyP in global ischemia is mediated through reduction in oxidative stress and DNA fragmentation.

FeTPPS protects against global cerebral ischemic-reperfusion injury in gerbils

Neuronal damage following cerebral ischemia is mediated by various mechanisms, among which nitrosative stress plays an important role. Peroxynitrite, a powerful oxidant, contributes heavily to the neuronal damage in cerebral ischemic-reperfusion (IR) injury. In the present study, we have investigated the neuroprotective effects of a peroxynitrite decomposition catalyst, 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrinato iron(III) [FeTPPS] in global cerebral IR injury in gerbils. Neurological damage was significantly attenuated by FeTPPS treatment (1 and 3mgkg(-1), i.p.) as evident from reduction in neurological symptoms, hyperlocomotion, memory impairment and CA1 hippocampal neuronal damage in IR challenged gerbils. FeTPPS treatment also attenuated the increased malondialdehyde (MDA) levels and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells after cerebral IR injury. Results of this study demonstrates the neuroprotective activity of FeTPPS in global cerebral IR injury and its neuroprotective effects may be attributed to reduction in oxidative stress and DNA fragmentation.