PAN-811 provides neuroprotection against glutamate toxicity by suppressing activation of JNK and p38 MAPK

Go-sha-jinki-Gan (GJG) ameliorates allodynia in chronic constriction injury-model mice via suppression of TNF-α expression in the spinal cord

Background

Alternative medicine is noted for its clinical effect and minimal invasiveness in the treatment of neuropathic pain. Go-sha-jinki-Gan, a traditional Japanese herbal medicine, has been used for meralgia and numbness in elderly patients. However, the exact mechanism of GJG is unclear. This study aimed to investigate the molecular mechanism of the analgesic effect of GJG in a chronic constriction injury model.

Results

GJG significantly reduced allodynia and hyperalgesia from the early phase (von Frey test, p < 0.0001; cold-plate test, p < 0.0001; hot-plate test p = 0.011; two-way repeated measures ANOVA). Immunohistochemistry and Western blot analysis revealed that GJG decreased the expression of Iba1 and tumor necrosis factor-α in the spinal cord. Double staining immunohistochemistry showed that most of the tumor necrosis factor-α was co-expressed in Iba1-positive cells at day 3 post-operation. GJG decreased the phosphorylation of p38 in the ipsilateral dorsal horn. Moreover, intrathecal injection of tumor necrosis factor-α opposed the anti-allodynic effect of GJG in the cold-plate test.

Conclusions

Our data suggest that GJG ameliorates allodynia in chronic constriction injury model mice via suppression of tumor necrosis factor-α expression derived from activated microglia. GJG is a promising drug for the treatment of neuropathic pain induced by neuro-inflammation.

Thiosemicarbazone p-Substituted Acetophenone Derivatives Promote the Loss of Mitochondrial Δψ, GSH Depletion, and Death in K562 Cells

A series of thiosemicarbazone (TSC) p-substituted acetophenone derivatives were synthesized and chemically characterized. The p-substituents appended to the phenyl group of the TSC structures were hydrogen, fluor, chlorine, methyl, and nitro, producing compounds named TSC-H, TSC-F, TSC-Cl, TSC-Me, and TSC-NO₂, respectively. The TSC compounds were evaluated for their capacity to induce mitochondrial permeability, to deplete mitochondrial thiol content, and to promote cell death in the K562 cell lineage using flow cytometry and fluorescence microscopy. TSC-H, TSC-F, and TSC-Cl exhibited a bell-shaped dose-response curve for the induction of apoptosis in K562 cells due to the change from apoptosis to necrosis as the principal mechanism of cell death at the highest tested doses. TSC-Me and TSC-NO₂ exhibited a typical dose-response profile, with a half maximal effective concentration of approximately 10 µM for cell death. Cell death was also evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, which revealed lower toxicity of these compounds for peripheral blood mononuclear cells than for K562 cells. The possible mechanisms leading to cell death are discussed based on the observed effects of the new TSC compounds on the cellular thiol content and on mitochondrial bioenergetics.

Human mesenchymal stem cells increase anti-oxidant defences in cells derived from patients with Friedreich's ataxia

Friedreich's ataxia (FRDA) is a progressive neurodegenerative disorder which is, at present, incurable. Oxidative damage and inhibition of mitochondrial function are key determinants of cellular damage in FRDA, since there is greater sensitivity to oxidative stress in cells with frataxin deficiency. In addition, frataxin-deficient cells have an impaired ability to recruit antioxidant defences against endogenous oxidative stress. We have recently shown that factors derived from bone marrow-derived mesenchymal stem cells (MSCs) increase hydrogen peroxide scavenging enzymes and offer protection against hydrogen peroxide-mediated injury in cells derived from patients with FRDA. Here we extend these studies and have performed a series of experiments showing that expression of superoxide dismutase (1 and 2) enzymes is reduced in FRDA cells but can be restored by treatment with conditioned medium from human MSCs. Furthermore, we have demonstrated that exposure to factors secreted by MSCs increases resistance to nitric oxide-induced oxidative stress in FRDA fibroblasts through, at least in part, restoring the expression of the superoxide dismuting enzymes and via modulation of PI(3) kinase/Akt pathways. These findings suggest that MSCs secrete factors that improve the cellular homeostasis of cells derived from FRDA patients and provide suitable support for their enhanced survival. This study further suggests the potential therapeutic use of MSCs in patients with FRDA.

Intermittent hypoxia conditioning protects mitochondrial cytochrome c oxidase of rat cerebellum from ethanol withdrawal stress

Intermittent hypoxia (IH) conditioning minimizes neurocognitive impairment and stabilizes brain mitochondrial integrity during ethanol withdrawal (EW) in rats, but the mitoprotective mechanism is unclear. We investigated whether IH conditioning protects a key mitochondrial enzyme, cytochrome c oxidase (COX), from EW stress by inhibiting mitochondrially directed apoptotic pathways involving cytochrome c, Bax, or phosphor-P38 (pP38). Male rats completed two cycles of a 4-wk ethanol diet (6.5%) and 3 wk of EW. An IH program consisting of 5-10 bouts of 5-8 min of mild hypoxia (9.5-10% inspired O(2)) and 4 min of reoxygenation for 20 consecutive days began 3 days before the first EW period. For some animals, vitamin E replaced IH conditioning to test the contributions of antioxidant mechanisms to IH's mitoprotection. During the second EW, cerebellar-related motor function was evaluated by measuring latency of fall from a rotating rod (Rotarod test). After the second EW, COX activity in cerebellar mitochondria was measured by spectrophotometry, and COX, cytochrome c, Bax, and pP38 content were analyzed by immunoblot. Mitochondrial protein oxidation was detected by measuring carbonyl contents and by immunochemistry. Earlier IH conditioning prevented motor impairment, COX inactivation, depletion of COX subunit 4, protein carbonylation, and P38 phosphorylation during EW. IH did not prevent cytochrome c depletion during EW, and Bax content was unaffected by EW ± IH. Vitamin E treatment recapitulated IH protection of COX, and P38 inhibition attenuated protein oxidation during EW. Thus IH protects COX and improves cerebellar function during EW by limiting P38-dependent oxidative damage.

Mesenchymal stem cell-secreted superoxide dismutase promotes cerebellar neuronal survival

It has been postulated that bone marrow-derived mesenchymal stem cells (MSCs) might be effective treatments for neurodegenerative disorders either by replacement of lost cells by differentiation into functional neural tissue; modulation of the immune system to prevent further neurodegeneration; and/or provision of trophic support for the diseased nervous system. Here we have performed a series of experiments showing that human bone marrow-derived MSCs are able to protect cultured rodent cerebellar neurons, and specifically cells expressing Purkinje cell markers, against either nitric oxide exposure or withdrawal of trophic support via cell-cell contact and/or secretion of soluble factors, or through secretion of soluble factors alone. We have demonstrated that MSCs protect cerebellar neurons against toxic insults via modulation of both the phosphatidylinositol 3-kinase/Akt and MAPK pathways and defined superoxide dismutase 3 as a secreted active antioxidant biomolecule by which MSCs modulate, at least in part, their neuroprotective effect on cerebellar cells in vitro. Together, the results demonstrate new and specific mechanisms by which MSCs promote cerebellar neuronal survival and add further evidence to the concept that MSCs may be potential therapeutic agents for neurological disorders involving the cerebellum.

Identification and characterization of thiosemicarbazones with antifungal and antitumor effects: cellular iron chelation mediating cytotoxic activity

Thiosemicarbazones derived from acetylpyrazines were prepared by condensing an acetylpyrazine or a ring-substituted acetylpyrazine with thiosemicarbazide. Using the same procedure, N, N-dimethylthiosemicarbazones were synthesized from acetylpyrazines and N, N-dimethylthiosemicarbazide. A total of 20 compounds (16 novel) were chemically characterized and then tested for antifungal effects on eight strains of fungi and also for antitumor activity against SK-N-MC neuroepithelioma cells. The most effective compound identified in terms of both antifungal and antitumor activity was N, N-dimethyl-2-(1-pyrazin-2-ylethylidene)hydrazinecarbothioamide (5a). The mechanism of action of this and its related thiosemicarbazones was due, at least in part, to its ability to act as a tridentate ligand that binds metal ions. This was deduced from preparation of the related thiosemicarbazones [acetophenone thiosemicarbazone (6) and acetophenone N, N-dimethylthiosemicarbazone (7)] that do not possess a coordinating ring-N, which plays a vital role in metal ion chelation. Furthermore, 5a and several other thiosemicarbazones that showed high antiproliferative activity were demonstrated to have marked iron (Fe) chelation efficacy. In fact, these agents were highly effective at mobilizing (59)Fe from prelabeled SK-N-MC cells and preventing (59)Fe uptake from the serum Fe transport protein, transferrin. In contrast, compounds 6 and 7 that do not possess a tridentate metal-binding site showed little activity. Further studies examining ascorbate oxidation demonstrated that the Fe complexes of the most effective compounds were redox-inactive. Thus, in contrast to other thiosemicarbazones with potent antiproliferative activity, Fe chelation and mobilization rather than free radical generation played a significant role in the cytotoxic effects of the current ligands.

Caffeic acid phenethyl ester prevents cerebellar granule neurons (CGNs) against glutamate-induced neurotoxicity

Caffeic acid phenethyl ester (CAPE) is an active component of propolis obtained from honeybee hives and is found to have the following properties: anti-mitogenic, anti-carcinogenic, anti-inflammatory, immunomodulatory, and antioxidant. Recent reports suggest that CAPE also has a neuronal protective property against ischemic injury. Since excitotoxicity may play an important role in ischemia, in this study, we investigated whether CAPE could directly protect neurons against excitotoxic insult. We treated cultured rat cerebellar granule neurons (CGNs) with excitotoxic concentrations of glutamate in the presence or absence of CAPE and found that CAPE markedly protected neurons against glutamate-induced neuronal death in a concentration-dependent fashion. Glutamate-induced CGNs death is associated with time-dependent activation of caspase-3 and phosphorylation of p38, both events of which can be blocked by CAPE. Treating CGNs with specific inhibitors of these two enzymes together exerts a synergistic neuroprotective effect, similar to the neuroprotective effect of CAPE exposure. These results suggest that CAPE is able to block glutamate-induced excitotoxicity by inhibiting phosphorylation of p38 and caspase-3 activation. This finding may further help understanding of the mechanism of glutamate-induced neuronal death and CAPE-induced neuroprotection against excitotoxicity.

Multiple molecular pathways are involved in the neuroprotection of GDNF against proteasome inhibitor induced dopamine neuron degeneration in vivo

The impairment of ubiquitin-proteasome system (UPS) is a cellular mechanism underlying the neurodegenerative process in Parkinson's disease (PD). Glial cell line-derived neurotrophic factor (GDNF) is one of the most potent neurotrophic factors promoting the growth and survival of mesencephalic dopamine (DA) neurons. To investigate whether GDNF has neuroprotective effects in a PD model induced by UPS impairment we administered GDNF by osmotic pump in C57BL/6 mice after nigrostriatal lesions with stereotactic injection of proteasome inhibitor lactacystin in the middle forebrain bundle. We found that lactacystin injection severely injured the nigral DA neurons and reduced the striatal levels of DA and its metabolites, while prolonged administration of GDNF at a sustained moderate dose for two weeks can significantly attenuate the lactacystin-induced loss of nigral DA neurons and striatal DA levels by 31% and 40%, respectively. We also investigated the molecular mechanisms for the neuroprotective effects of GDNF showing that lactacystin administration can cause the phosphorylation of extracellular signal-regulated kinase (ERK), p38MAPK (p38), and the c-Jun N-terminal kinase (JNK), whereas GDNF treatment can further enhance the phosphorylation of ERK and Akt but reduce the levels of JNK and p38. These results indicate that prolonged treatment with GDNF can protect the nigral DA neurons from the UPS impairment-induced degeneration. Several signaling path-ways including p38, JNK, Akt and ERK molecules seem to play an important role in this neuroprotection by GDNF.

Inhibitors of c-Jun N-terminal kinases: JuNK no more?

The c-Jun N-terminal kinases (JNKs) have been the subject of intense interest since their discovery in the early 1990s. Major research programs have been directed to the screening and/or design of JNK-selective inhibitors and testing their potential as drugs. We begin this review by considering the first commercially-available JNK ATP-competitive inhibitor, SP600125. We focus on recent studies that have evaluated the actions of SP600125 in lung, brain, kidney and liver following exposure to a range of stress insults including ischemia/reperfusion. In many but not all cases, SP600125 administration has proved beneficial. JNK activation can also follow infection, and we next consider recent examples that demonstrate the benefits of SP600125 administration in viral infection. Additional ATP-competitive JNK inhibitors have now been described following high throughput screening of small molecule libraries, but information on their use in biological systems remains limited and thus these inhibitors will require further evaluation. Peptide substrate-competitive ATP-non-competitive inhibitors of JNK have also now been described, and we discuss the recent advances in the use of JNK inhibitory peptides in the treatment of neuronal death, diabetes and viral infection. We conclude by raising a number of questions that should be considered in the quest for JNK-specific inhibitors.