Cyclosporin A targets involved in protection against glutamate excitotoxicity

A sterilizable platform based on crosslinked xanthan gum for controlled-release of polymeric micelles: Ocular application for the delivery of neuroprotective compounds to the posterior eye segment

TPGS (D-α-tocopheryl polyethylene glycol 1000 succinate) polymeric micelles show interesting properties for ocular administration thanks to their solubilization capability, nanometric size and tissue penetration ability. However, micelles formulations are generally characterized by low viscosity, poor adhesion and very short retention time at the administration site. Therefore, the idea behind this work is the preparation and characterization of a crosslinked film based on xanthan gum that contains TPGS micelles and is capable of controlling their release. The system was loaded with melatonin and cyclosporin A, neuroprotective compounds to be delivered to the posterior eye segment. Citric acid and heating at different times and temperatures were exploited as crosslinking approach, giving the possibility to tune swelling, micelles release and drug release. The biocompatibility of the platform was confirmed by HET-CAM assay. Ex vivo studies on isolated porcine ocular tissues, conducted using Franz cells and two-photon microscopy, demonstrated the potential of the xanthan gum-based platform and enlightened micelles penetration mechanism. Finally, the sterilization step was approached, and a process to simultaneously crosslink and sterilize the platform was developed.

Cyclosporine A Protects Retinal Explants against Hypoxia

The retina is a complex neurological tissue and is extremely sensitive to an insufficient supply of oxygen. Hypoxia plays a major role in several retinal diseases, and often results in the loss of cells that are essential for vision. Cyclosporine A (CsA) is a widely used immunosuppressive drug. Furthermore, treatment with CsA has neuroprotective effects in several neurologic disorders. No data are currently available on the tolerated concentration of CsA when applied to the retina. To reveal the most effective dose, retinal explants from rat eyes were exposed to different CsA concentrations (1-9 µg/mL). Immunohistochemistry with brain-specific homeobox/POU domain protein 3a (Brn3a) and TUNEL staining was performed to determine the percentage of total and apoptotic retinal ganglion cells (RGCs), as well as the responses of micro- and macroglial cells. Furthermore, optical coherence tomography (OCT) scans were performed to measure the changes in retinal thickness, and recordings with multielectrode array (MEA) were performed to evaluate spontaneous RGC spiking. To examine the neuroprotective effects, retinas were subjected to a hypoxic insult by placing them in a nitrogen-streamed hypoxic chamber prior to CsA treatment. In the biocompatibility tests, the different CsA concentrations had no negative effect on RGCs and microglia. Neuroprotective effects after a hypoxic insult on RGCs was demonstrated at a concentration of 9 µg/mL CsA. CsA counteracted the hypoxia-induced loss of RGCs, reduced the percentage of TUNEL⁺ RGCs, and prevented a decrease in retinal thickness. Taken together, the results of this study suggest that CsA can effectively protect RGCs from hypoxia, and the administered concentrations were well tolerated. Further in vivo studies are needed to determine whether local CsA treatment may be a suitable option for hypoxic retinal diseases.

Cyclosporin A attenuating morphine tolerance through inhibiting NO/ERK signaling pathway in human glioblastoma cell line: the involvement of calcineurin

Cyclosporin A (CsA) is known to have an immunosuppressive action. However, it is also attracting attention due to its effects on the nervous system, such as inhibiting the development and expression of morphine-induced tolerance and dependence through unknown mechanisms. It has been shown that CsA modulates the nitric oxide (NO) synthesis and extracellular signal-regulated kinases (ERK) activation, which are potentially involved in signaling pathways in morphine-induced tolerance in cellular models. Therefore, the current study was designed to evaluate the modulatory role of CsA on the MOR tolerance, by targeting the downstream signaling pathway of NO and ERK using an in vitro model. For this purpose, T98G cells were pretreated with CsA, calcineurin autoinhibitory peptide (CAIP), and N^G-nitro-l-arginine methyl ester (L-NAME) 30 min before 18 h exposure to MOR. Then, we analyzed the intracellular cyclic adenosine monophosphate (cAMP) levels and also the expression of phosphorylated ERK and nitric oxide synthase (nNOS) proteins. Our results showed that CsA (1 nM, 10 nM, and 100 nM) and CAIP (50 µM) have significantly reduced cAMP and nitrite levels as compared to MOR-treated (2.5 µM) T98G cells. This clearly revealed the attenuation of MOR tolerance by CsA. The expression of nNOS and p-ERK proteins were down-regulated when the T98G cells were pretreated with CsA (1 nM, 10 nM, and 100 nM), CAIP (50 µM), and L-NAME (0.1 mM) as compared to MOR. In conclusion, the CsA pretreatment had a modulatory role in MOR-induced tolerance, which was possibly mediated through NO/ERK signaling pathway.

Glutamatergic nervous system degeneration in a C. elegans TauA152T tauopathy model involves pathways of excitotoxicity and Ca2+ dysregulation

Mutations in the gene encoding Tau (MAPT-microtubule-associated protein tau) cause a group of neurodegenerative diseases called tauopathies. A recently identified Tau variant, p.A152T, has been reported as a risk factor for frontotemporal dementia-related disorders and Alzheimer disease. However, the mechanism for the pathologies still remain poorly understood. Transgenic Caenorhabditis elegans expressing mutant 2N4R-Tau^A152T (Tau^AT) panneuronally show locomotor defects, neurodegeneration and accelerated aging. Here we report that, in Tau^AT animals, the glutamatergic nervous system is at a high risk of progressive neuronal loss. We present genetic data that this loss occurs predominantly through necrosis. The neuronal loss is caused by several determinants, such as altered adenylyl cyclase (type AC9) pathway, prevalence of excitotoxicity-like conditions, aging-related factors and finally dyshomeostasis of intracellular calcium (Ca²⁺). The study provides novel insights into the mechanisms involved in selective loss of glutamatergic neurons in a Tau^AT tauopathy model which could point to new therapeutic targets.

Thyroid hormone regulation of gene expression in primary cerebrocortical cells: role of thyroid hormone receptor subtypes and interactions with retinoic acid and glucocorticoids

The effects of thyroid hormone on brain development and function are largely mediated by the binding of 3,5,3'-triiodo-L-thyronine (T3) to its nuclear receptors (TR) to regulate positively or negatively gene expression. We have analyzed by quantitative polymerase chain reaction the effect of T3 on primary cultured cells from the embryonic mouse cerebral cortex, on the expression of Hr, Klf9, Shh, Dio3, Aldh1a1, and Aldh1a3. In particular we focused on T3 receptor specificity, and on the crosstalk between T3, retinoic acid and dexamethasone. To check for receptor subtype specificity we used cerebrocortical cells derived from wild type mice and from mice deficient in thyroid hormone receptor subtypes. Receptor subtype specificity was found for Dio3 and Aldh1a1, which were induced by T3 only in cells expressing the T3 receptor alpha 1 subtype. Interactions of T3 with retinoic acid signaling through the control of retinoic acid metabolism are likely to be important during development. T3 had opposing influences on retinoic acid synthesizing enzymes, increasing the expression of Aldh1a1, and decreasing Aldh1a3, while increasing the retinoic acid degrading enzyme Cyp26b1. Dexamethasone increased Klf9 and Aldh1a1 expression. The effects of T3 and dexamethasone on Aldh1a1 were highly synergistic, with mRNA increments of up to 20 fold. The results provide new data on thyroid hormone regulation of gene expression and underscore the importance of thyroid hormone interactions with retinoic acid and glucocorticoids during neural development.

Molecular mechanisms of regulated necrosis

It is now clear that apoptosis does not constitute the sole genetically encoded form of cell death. Rather, cells can spontaneously undertake or exogenously be driven into a cell death subroutine that manifests with necrotic features, yet can be inhibited by pharmacological and genetic interventions. As regulated necrosis (RN) plays a major role in both physiological scenarios (e.g., embryonic development) and pathological settings (e.g., ischemic disorders), consistent efforts have been made throughout the last decade toward the characterization of the molecular mechanisms that underlie this cell death modality. Contrarily to initial beliefs, RN does not invariably result from the activation of a receptor interacting protein kinase 3 (RIPK3)-dependent signaling pathway, but may be ignited by distinct molecular networks. Nowadays, various types of RN have been characterized, including (but not limited to) necroptosis, mitochondrial permeability transition (MPT)-dependent RN and parthanatos. Of note, the inhibition of only one of these modules generally exerts limited cytoprotective effects in vivo, underscoring the degree of interconnectivity that characterizes RN. Here, we review the signaling pathways, pathophysiological relevance and therapeutic implications of the major molecular cascades that underlie RN.

Toxicity and efficacy evaluation of multiple targeted polymalic acid conjugates for triple-negative breast cancer treatment

Engineered nanoparticles are widely used for delivery of drugs but frequently lack proof of safety for cancer patient's treatment. All-in-one covalent nanodrugs of the third generation have been synthesized based on a poly(β-L-malic acid) (PMLA) platform, targeting human triple-negative breast cancer (TNBC). They significantly inhibited tumor growth in nude mice by blocking synthesis of epidermal growth factor receptor, and α4 and β1 chains of laminin-411, the tumor vascular wall protein and angiogenesis marker. PMLA and nanodrug biocompatibility and toxicity at low and high dosages were evaluated in vitro and in vivo. The dual-action nanodrug and single-action precursor nanoconjugates were assessed under in vitro conditions and in vivo with multiple treatment regimens (6 and 12 treatments). The monitoring of TNBC treatment in vivo with different drugs included blood hematologic and immunologic analysis after multiple intravenous administrations. The present study demonstrates that the dual-action nanoconjugate is highly effective in preclinical TNBC treatment without side effects, supported by hematologic and immunologic assays data. PMLA-based nanodrugs of the Polycefin™ family passed multiple toxicity and efficacy tests in vitro and in vivo on preclinical level and may prove to be optimized and efficacious for the treatment of cancer patients in the future.

Cyclosporine A, FK506, and NIM811 ameliorate prolonged CBF reduction and impaired neurovascular coupling after cortical spreading depression

Cortical spreading depression (CSD) is associated with mitochondrial depolarization, increasing intracellular Ca(2+), and the release of free fatty acids, which favor opening of the mitochondrial permeability transition pore (mPTP) and activation of calcineurin (CaN). Here, we test the hypothesis that cyclosporine A (CsA), which blocks both mPTP and CaN, ameliorates the persistent reduction of cerebral blood flow (CBF), impaired vascular reactivity, and a persistent rise in the cerebral metabolic rate of oxygen (CMRO(2)) following CSD. In addition to CsA, we used the specific mPTP blocker NIM811 and the specific CaN blocker FK506. Cortical spreading depression was induced in rat frontal cortex. Electrocortical activity was recorded by glass microelectrodes, CBF by laser Doppler flowmetry, and tissue oxygen tension with polarographic microelectrodes. Electrocortical activity, basal CBF, CMRO(2), and neurovascular and neurometabolic coupling were unaffected by all three drugs under control conditions. NIM811 augmented the rise in CBF observed during CSD. Cyclosporine A and FK506 ameliorated the persistent decrease in CBF after CSD. All three drugs prevented disruption of neurovascular coupling after CSD; the rise in CMRO(2) was unchanged. Our data suggest that blockade of mPTP formation and CaN activation may prevent persistent CBF reduction and vascular dysfunction after CSD.

Mitochondrial targeting of cyclosporin A enables selective inhibition of cyclophilin-D and enhanced cytoprotection after glucose and oxygen deprivation

CsA (cyclosporin A) is a hydrophobic undecapeptide that inhibits CyPs (cyclophilins), a family of PPIases (peptidylprolyl cis-trans isomerases). In some experimental models, CsA offers partial protection against lethal cell injury brought about by transient ischaemia; this is believed to reflect inhibition of CyP-D, a mitochondrial isoform that facilitates formation of the permeability transition pore in the mitochondrial inner membrane. To evaluate this further, we have targeted CsA to mitochondria so that it becomes selective for CyP-D in cells. This was achieved by conjugating the inhibitor to the lipophilic triphenylphosphonium cation, enabling its accumulation in mitochondria due to the inner membrane potential. In a cell-free system and in B50 neuroblastoma cells the novel reagent (but not CsA itself) preferentially inhibited CyP-D over extramitochondrial CyP-A. In hippocampal neurons, mitochondrial targeting markedly enhanced the capacity of CsA to prevent cell necrosis brought about by oxygen and glucose deprivation, but largely abolished its capacity to inhibit glutamate-induced cell death. It is concluded that CyP-D has a major pathogenic role in 'energy failure', but not in glutamate excitotoxicity, where cytoprotection primarily reflects CsA interaction with extramitochondrial CyPs and calcineurin. Moreover, the therapeutic potential of CsA against ischaemia/reperfusion injuries not involving glutamate may be improved by mitochondrial targeting.

Alterations in mitochondrial function as a harbinger of cardiomyopathy: lessons from the dystrophic heart

While compelling evidence supports the central role of mitochondrial dysfunction in the pathogenesis of heart failure, there is comparatively less information available on mitochondrial alterations that occur prior to failure. Building on our recent work with the dystrophin-deficient mdx mouse heart, this review focuses on how early changes in mitochondrial functional phenotype occur prior to overt cardiomyopathy and may be a determinant for the development of adverse cardiac remodelling leading to failure. These include alterations in energy substrate utilization and signalling of cell death through increased permeability of mitochondrial membranes, which may result from abnormal calcium handling, and production of reactive oxygen species. Furthermore, we will discuss evidence supporting the notion that these alterations in the dystrophin-deficient heart may represent an early "subclinical" signature of a defective nitric oxide/cGMP signalling pathway, as well as the potential benefit of mitochondria-targeted therapies. While the mdx mouse is an animal model of Duchenne muscular dystrophy (DMD), changes in the structural integrity of dystrophin, the mutated cytoskeletal protein responsible for DMD, have also recently been implicated as a common mechanism for contractile dysfunction in heart failure. In fact, altogether our findings support a critical role for dystrophin in maintaining optimal coupling between metabolism and contraction in the heart.

Reduced calcineurin protein levels and activity in exon-1 mouse models of Huntington's disease: role in excitotoxicity

Calcineurin is a serine/threonine phosphatase involved in the regulation of glutamate receptors signaling. Here, we analyzed whether the regulation of calcineurin protein levels and activity modulates the susceptibility of striatal neurons to excitotoxicity in R6/1 and R6/1:BDNF+/- mouse models of Huntington's disease. We show that calcineurin inhibition in wild-type mice drastically reduced quinolinic acid-induced striatal cell death. Moreover, calcineurin A and B were differentially regulated during disease progression with a specific reduction of calcineurin A protein levels and calcineurin activity at the onset of the disease in R6/1:BDNF+/- mice. Analysis of the conditional mouse model Tet/HD94 showed that mutant huntingtin specifically controls calcineurin A protein levels. Finally, calcineurin activation induced by intrastriatal quinolinic acid injection in R6/1 mouse was lower than in wild-type mice. Therefore, reduction of calcineurin activity by alteration of calcineurin A expression participates in the pathophysiology of Huntington's disease and contributes to the excitotoxic resistance observed in exon-1 mouse models.

Oxidative stress and energy crises in neuronal dysfunction

Mitochondrial dysfunction is implicated in many forms of cell death, particularly in the central nervous system. The mitochondria are required at the same time to generate adenosine 5'-triphosphate (ATP) for the cell, sequester excess cytoplasmic Ca(2+), and both produce and detoxify superoxide free radicals. The electron transport chain and proton circuit are central in keeping these three balls in the air at the same time. We have investigated the bioenergetics of the in situ mitochondria in cultured neurons exposed to pathological glutamate concentrations to model glutamate excitotoxicity and have revised the conventional view that mitochondrial calcium loading results in increased oxidative stress that damages the mitochondrion and ultimately the cell. Instead, a central role is played under these conditions by limitations in mitochondrial and cellular ATP generating capacity. Sodium and calcium entering via the N-methyl-D-aspartate receptor impose a large energetic load on cells and can use the entire respiratory capacity of the in situ mitochondria. As a result, even modest restrictions in mitochondrial capacity -- caused by low concentrations of electron transport chain inhibitors such as rotenone, as in models of Parkinson's disease; low concentrations of uncouplers, to test the so-called neuroprotective mild uncoupling hypothesis; or preexisting oxidative stress -- greatly potentiate glutamate excitotoxicity. Our findings may lead to a reevaluation of the potential for mild uncoupling to provide a neuroprotective role in aging-related neurodegenerative disorders because the deleterious consequences of restricting ATP generating capacity greatly outweigh the negligible effects on the levels of mitochondrial superoxide radicals in intact neurons.

Prolonged exposures of cerebellar granule neurons to S-nitroso-N-acetylpenicillamine (SNAP) induce neuronal damage independently of peroxynitrite

Nitric oxide (NO) induces cell proliferation or cell death, depending on the cell type involved, the isoform of nitric oxide synthase activated, and its cellular localisation. In neurons, the damaging effect of NO is usually attributed to the highly toxic peroxynitrite, formed by its reaction with superoxide. Peroxynitrite induces DNA damage and consequently the activation of poly (ADP-ribose) polymerase (PARP). This study set out to examine the contribution of peroxynitrite to the damage induced in cerebellar granule neurons (CGNs) by treatment with the NO donor S-nitroso-N-acetylpenicillamine (SNAP), for short (6 h) or prolonged (24 h) exposures. The Alamar blue assay was used to quantify CGN viability, which was also assessed by morphological examination. SNAP (10 microM-1 mM) induced a concentration- and time-dependent reduction of CGN viability, with associated damage to cell bodies and neurite processes evident following 100 microM SNAP treatments. Damage from 6 h exposures was prevented by the presence of haemoglobin (a NO scavenger), uric acid (a peroxynitrite scavenger), melatonin (a non-specific antioxidant), and by cyclosporin A (a permeability transition pore blocker). It was reduced by the PARP-1 inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-isoquinolinone (DPQ), whilst superoxide dismutase (SOD) potentiated the effects. Following 24 h exposure to SNAP, damage was only partially blocked by haemoglobin, melatonin, cyclosporin A and DPQ, but was not affected by uric acid or SOD. The data suggest that short exposure to NO induces neuronal damage through peroxynitrite produced by its interaction with superoxide, whereas a longer exposure to NO can induce damage partly by a mechanism which is independent of peroxynitrite formation.

Poly(malic acid) nanoconjugates containing various antibodies and oligonucleotides for multitargeting drug delivery

Nanoconjugates are emerging as promising drug-delivery vehicles because of their multimodular structure enabling them to actively target discrete cells, pass through biological barriers and simultaneously carry multiple drugs of various chemical nature. Nanoconjugates have matured from simple devices to multifunctional, biodegradable, nontoxic and nonimmunogenic constructs, capable of delivering synergistically functioning drugs in vivo. This review mainly concerns the Polycefin family of natural-derived polymeric drug-delivery devices as an example. This type of vehicle is built by hierarchic conjugation of functional groups onto the backbone of poly(malic acid), an aliphatic polyester obtained from the microorganism Physarum polycephalum. Particular Polycefin variants target human brain and breast tumors implanted into animals specifically and actively and could be detected easily by noninvasive imaging analysis. Delivery of antisense oligonucleotides to a tumor-specific angiogenic marker using Polycefin resulted in significant inhibition of tumor angiogenesis and increase of animal survival.

Adenosine receptor ligands protect against a combination of apoptotic and necrotic cell death in cerebellar granule neurons

Agonists at A(1) receptors and antagonists at A(2A) receptors are known to be neuroprotective against excitotoxicity. We set out to clarify the mechanisms involved by studying interactions between adenosine receptor ligands and endogenous glutamate in cultures of rat cerebellar granule neurons (CGNs). Glutamate and the selective agonist N-methyl-D: -aspartate (NMDA), applied to CGNs at 9 div (days in vitro), both induced cell death in a concentration-dependent manner, which was attenuated by treatment with the NMDA receptor antagonists dizocilpine, D: -2-amino-5-phosphono-pentanoic acid (D: -AP5) or kynurenic acid (KYA), but not by the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Glutamate toxicity was reduced in the presence of all of the following: cyclosporin A (CsA), a blocker of the membrane permeability transition pore, the caspase-3 inhibitor, benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethylketone (Z-DEVD-fmk), the poly (ADP-ribose) polymerase (PARP-1) inhibitor 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-isoquinolinone (DPQ), and nicotinamide. This is indicative of involvement of both apoptotic and necrotic processes. The A(1) receptor agonist, N (6)-cyclopentyladenosine (CPA), and the A(2A) receptor antagonist 4-(2-[7-amino-2-[2-furyl][1,2,4]triazolo[2,3-a][1,3,5]triazo-5-yl-amino]ethyl)phenol (ZM241385) afforded significant protection, while the A(1) receptor blocker 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and the A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxyamidoadenosine (CGS21680) had no effect. These results confirm that glutamate-induced neurotoxicity in CGNs is mainly via the NMDA receptor, but show that a form of cell death which exhibits aspects of both apoptosis and necrosis is involved. The protective activity of A(1) receptor activation or A(2A) receptor blockade occurs against this mixed profile of cell death, and appears not to involve the selective inhibition of classical apoptotic or necrotic cascades.

Mitochondrial Proteomic Analysis and Characterization of the Intracellular Mechanisms of Bis(7)-tacrine in Protecting against Glutamate-Induced Excitotoxicity in Primary Cultured Neurons

Increasing evidence supports that the mitochondrial dysfunction, mainly caused by abnormal changes in mitochondrial proteins, plays a pivotal role in glutamate-induced excitotoxicity, which is closely associated with the pathogenesis of acute and chronic neurodegenerative disorders, such as stroke and Alzheimer's disease. In this study, post-treatment of cerebellar granule neurons with bis(7)-tacrine significantly reversed declines in mitochondrial membrane potential, ATP production, and neuronal cell death induced by glutamate. Moreover, this reversal was independent of NMDA antagonism, acetylcholinesterase inhibition, and cholinergic pathways. Using two-dimensional differential in-gel electrophoresis, we conducted a comparative analysis of mitochondrial protein patterns. In all, 29 proteins exhibiting significant differences in their abundances were identified in the glutamate-treated group when compared with the control. The expression patterns in 22 out of these proteins could be reversed by post-treatment with bis(7)-tacrine. Most of the differentially expressed proteins are involved in energy metabolism, oxidative stress, and apoptosis. In particular, the altered patterns of four of these proteins were further validated by Western blot analysis. Our findings suggest that multiple signaling pathways initiated by the altered mitochondrial proteins may mediate glutamate-induced excitotoxicity and also offer potentially useful intracellular targets for the neuroprotection provided by bis(7)-tacrine.

The mitochondrial permeability transition in neurologic disease

Mitochondria, being the principal source of cellular energy, are vital for cell life. Yet, ironically, they are also major mediators of cell death, either by necrosis or apoptosis. One means by which these adverse effects occur is through the mitochondrial permeability transition (mPT) whereby the inner mitochondrial membrane suddenly becomes excessively permeable to ions and other solutes, resulting in a collapse of the inner membrane potential, ultimately leading to energy failure and cell necrosis. The mPT may also bring about the release of various factors known to cause apoptotic cell death. The principal factors leading to the mPT are elevated levels of intracellular Ca2+ and oxidative stress. Characteristically, the mPT is inhibited by cyclosporin A. This article will briefly discuss the concept of the mPT, its molecular composition, its inducers and regulators, agents that influence its activity and describe the consequences of its induction. Lastly, we will review its potential contribution to acute neurological disorders, including ischemia, trauma, and toxic-metabolic conditions, as well as its role in chronic neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis.

Cyclosporin-A enhances non-functional axonal growing after complete spinal cord transection

Therapeutic approaches that promote both neuroprotection and neuroregeneration would be valuable for spinal cord (SC) injury therapies. Cyclosporin-A (CsA) is an immunosuppressant that, due to its mechanism of action, could both protect and regenerate the neural tissue after injury. Previous studies have already demonstrated that intraperitoneal administration of CsA at a dose of 2.5 mg/kg/12 h during the first 2 days after SC contusion, followed by 5 mg/kg/12 h orally, diminishes tissue damage and improves motor recovery. In order to evaluate the effect of this CsA dosing regimen on axonal growth, we assessed motor recovery, presence of axons establishing functional connections and expression of GAP-43 in rats subjected to a complete SC transection. The Basso-Beattie-Bresnahan rating scale did not show difference in motor recovery of CsA or vehicle-treated rats. Moreover, somato-sensorial evoked potentials demonstrated no functional connections in the SC of these animals. Nevertheless, histological studies showed that: i) a significant number of CsA-treated rats presented growing axons, although they deviated perpendicularly at the edge of the stumps, surrounding them, ii) the expression of GAP-43 in animals treated with CsA was higher than that observed in the control group. Finally, anterograde tracing of the corticospinal tract of rats subjected to an incomplete SC transection showed no axonal fibers reaching the caudal stump. In summary, CsA administered at the dosing-regimen that promotes neuroprotection in SC contused rats induces both GAP-43 expression and axonal growth; however, it failed to generate functional connections in SC transected animals.

Mitochondrial c-Jun NH2-terminal kinase prevents the accumulation of reactive oxygen species and reduces necrotic damage in neural tumor cells that lack trophic support

In response to different stress signals, the c-Jun NH(2)-terminal kinase (JNK) can trigger cell death. However, JNK also facilitates the survival and cell cycle progression of tumor cells by mechanisms that are poorly defined. Here, we show that schwannoma RN22 cells can survive and proliferate under serum-free conditions although serum withdrawal rapidly induces mitochondrial fission and swelling. Although the morphologic changes observed in the mitochondria did not trigger cytochrome c release, they were accompanied by an increase in the mitochondrial membrane potential (DeltaPsi(M)) and of immunoreactivity for active JNK in these organelles. Pharmacologic inhibition of JNK provoked a further increase of the DeltaPsi(M), an increase in reactive oxygen species (ROS) production, and a sustained decrease in cell viability due to necrosis. This increase in necrosis was prevented by the presence of ROS scavengers. Immunoreactivity for active JNK was also observed in the mitochondria of neuroblastoma 1E-115 and neuroblastoma 2a neuroblastoma cell lines on serum withdrawal, whereas active JNK was barely detected in serum-deprived fibroblasts. Accordingly, the reduction in neural tumor cell viability induced by JNK inhibition was largely attenuated in serum-deprived fibroblasts. These data indicate that local activation of JNK in the mitochondria can protect against necrotic cell death associated with ROS production, facilitating the growth of neural tumor cells subjected to serum deprivation.

Cell death in rat cerebellar granule neurons induced by hydrogen peroxide in vitro: mechanisms and protection by adenosine receptor ligands

Oxidative stress, resulting from excessive production of reactive oxygen species (ROS), is a pathological state that causes profound cellular damage and eventual death resulting from the overactivation of glutamate receptors, and the generation of nitric oxide, superoxide and hydrogen peroxide (H(2)O(2)). As such, H(2)O(2) represents an important model for studying the neuropathology of oxidative stress in a variety of CNS disorders. The effects of H(2)O(2) on the viability of post-natal cerebellar granule neurons (CGNs), the nature of the cell death involved and the potential protection by adenosine receptors against the damage were examined in the current study. Hydrogen peroxide (10-400 microM) reduced CGN viability in a concentration- and time-dependent manner. The addition of catalase (100 U/ml) prevented this effect, and the non-specific COX inhibitor aspirin (1 mM) also alleviated the damage. A combination of H(2)O(2) (5 microM) and Cu(2+) (0.5 mM) resulted in a significant damage that was not prevented by the hydroxyl radical scavenger mannitol (50 mM). The permeability transition pore blocker cyclosporin A, the caspase-3 inhibitor Z-DEVD-fmk (40 microM) and the PARP-1 inhibitor DPQ (10 microM) each significantly protected against peroxide damage. While the A(1) adenosine receptor agonist CPA and the A(2A) receptor antagonist ZM241385 (each at 100 nM) elicited protection, the A(1) adenosine receptor blocker DPCPX and the A(2A) receptor agonist CGS21680 (each at 100 nM) showed no effect. The data demonstrate that H(2)O(2) induced oxidative stress in CGNs, involving both apoptotic and necrotic death, and this can be ameliorated by A(1) receptor activation or A(2A) receptor blockade.

Neuroprotectants FK-506 and cyclosporin A ameliorate the course of pilocarpine-induced seizures

The present study was designed to examine whether neuroprotective agents, FK506 or cyclosporin A (CsA), applied to rats undergoing pilocarpine-induced seizures can minimize further development of the status epilepticus. In order to solve this problem, pilocarpine was injected in 60-day-old Wistar rats to evoke status epilepticus. When epileptic seizures reached a defined, moderate level of intensity, the rats received a single FK506 or CsA injections. During a 6-h period following pilocarpine injection, the animals were observed continuously and motor symptoms were recorded and rated. In epileptic rats injected with FK-506 or CsA, signs of significant amelioration of the course of epilepsy accompanied by longer survival periods were observed. Moreover, some differences between effects of the two agents were seen. The obtained results appear to show that, in addition to neuroprotective action, FK506 and CsA can exert also antiepileptic influences.

Calcium-dependent spontaneously reversible remodeling of brain mitochondria

An exposure of cultured hippocampal neurons expressing mitochondrially targeted enhanced yellow fluorescent protein to excitotoxic glutamate resulted in reversible mitochondrial remodeling that in many instances could be interpreted as swelling. Remodeling was not evident if glutamate receptors were blocked with MK801, if Ca(2+) was omitted or substituted for Sr(2+) in the bath solution, if neurons were treated with carbonylcyanide p-trifluoromethoxyphenylhydrazone to depolarize mitochondria, or if neurons were pretreated with cyclosporin A or N-methyl-4-isoleucine-cyclosporin (NIM811) to inhibit the mitochondrial permeability transition. In the experiments with isolated brain synaptic or nonsynaptic mitochondria, Ca(2+) triggered transient, spontaneously reversible cyclosporin A-sensitive swelling closely resembling remodeling of organelles in cultured neurons. The swelling was accompanied by the release of cytochrome c, Smac/DIABLO, Omi/HtrA2, and AIF but not endonuclease G. Depolarization with carbonylcyanide p-trifluoromethoxyphenylhydrazone or inhibition of the Ca(2+) uniporter with Ru360 prevented rapid onset of the swelling. Sr(2+) depolarized mitochondria but failed to induce swelling. Neither inhibitors of the large conductance Ca(2+)-activated K(+) channel (charybdotoxin, iberiotoxin, quinine, and Ba(2+)) nor inhibitors of the mitochondrial ATP-sensitive K(+) channel (5-hydroxydecanoate and glibenclamide) suppressed swelling. Quinine, dicyclohexylcarbodiimide, and Mg(2+), inhibitors of the mitochondrial K(+)/H(+) exchanger, as well as external alkalization inhibited a recovery phase of the reversible swelling. In contrast to brain mitochondria, liver and heart mitochondria challenged with Ca(2+) experienced sustained swelling without spontaneous recovery. The proposed model suggests an involvement of the Ca(2+)-dependent transient K(+) influx into the matrix causing mitochondrial swelling followed by activation of the K(+)/H(+) exchanger leading to spontaneous mitochondrial contraction both in situ and in vitro.

The calcium-dependent ATP-Mg/Pi mitochondrial carrier is a target of glucose-induced calcium signalling in Saccharomyces cerevisiae

Sal1p is a mitochondrial protein that belongs to the SCaMC (short calcium-binding mitochondrial carrier) subfamily of mitochondrial carriers. The presence of calcium-binding motifs facing the extramitochondrial space allows the regulation of the transport activity of these carriers by cytosolic calcium and provides a new mechanism to transduce calcium signals in mitochondria without the requirement of calcium entry in the organelle. We have studied its transport activity, finding that it is a carboxyatractyloside-resistant ATP-Mg carrier. Mitochondria from a disruption mutant of SAL1 have a 50% reduction in the uptake of ATP. We have also found a clear stimulation of ATP-transport activity by calcium, with an S(0.5) of approx. 30 microM. Our results also suggest that Sal1p is a target of the glucose-induced calcium signal which is non-essential in wild-type cells, but becomes essential for transport of ATP into mitochondria in yeast lacking ADP/ATP translocases.

Oxidative stress, mitochondrial permeability transition, and cell death in Cu-exposed trout hepatocytes

We have previously shown that, in trout hepatocytes, exposure to a high dose of copper (Cu) leads to disruption of Ca(2+) homeostasis and elevated formation of reactive oxygen species (ROS), with the latter ultimately causing cell death. In the present study, we aimed at identifying, using a lower Cu concentration, the role of mitochondria in this scenario, the potential involvement of the mitochondrial permeability transition (MPT), and the mode of cell death induced by the metal. Incubation with 10 muM Cu resulted in a strong stimulation of ROS formation, and after 2 h of exposure a significant increase of both apoptotic and necrotic cells was seen. Co-incubation of Cu-treated hepatocytes with the iron-chelator deferoxamine significantly inhibited ROS production and completely prevented cell death. The origin of the radicals generated was at least partly mitochondrial, as visualized by confocal laser scanning microscopy. Furthermore, ROS production was diminished by inhibition of mitochondrial respiration, but since this also aggravated the elevation of intracellular Ca(2+) induced by Cu, it did not preserve cell viability. In a sub-population of cells, Cu induced a decrease of mitochondrial membrane potential and occurrence of the MPT. Cyclosporin A, which did not inhibit ROS formation, prevented the onset of the MPT and inhibited apoptotic, but not necrotic, cell death. Cu-induced apoptosis therefore appears to be dependent on induction of the MPT, but the prominent contribution of mitochondria to ROS generation also suggests an important role of mitochondria in necrotic cell death.

The effect of cyclosporine on the development and expression of cannabinoid tolerance in mice

Cyclosporine, beside its immunosuppressive action, has several effects on different neuronal functions, such as modulation of neurotransmitter release, the inhibition of nitric oxide synthesis and release, the reduction of cAMP production and inhibition of morphine-induced tolerance. In the present study, the effect of cyclosporine on the expression and development of tolerance to WIN 55,212-2, a cannabinoid receptor agonist, was studied. Intra peritoneal (i.p.) injection of WIN 55,212-2 (2-6 mg/kg) induced time-dependent and dose-dependent analgesia and catalepsy in mice. Administration of cyclosporine (20 mg/kg i.p.), 30 min before WIN 55,212-2 (6 mg/kg i.p.), did not change the analgesic and cataleptic effects of WIN 55,212-2. When WIN 55,212-2 (6 mg/kg i.p.) was injected once a day, animals became completely tolerant to the analgesic and cataleptic effects within five and nine days respectively. Cyclosporine (20 mg/kg i.p.) injected once daily, 30 min before WIN 55,212-2, attenuated the development of tolerance to the analgesic and cataleptic effects of WIN 55,212-2 but did not affect the expression of tolerance. Since cyclosporine given chronically by itself did not alter the analgesia and catalepsy induced by acute administration of WIN 55,212-2, our findings suggest cyclosporine may act with some selectivity on the mechanisms involved in development of cannabinoid tolerance.

Essential role of aralar in the transduction of small Ca2+ signals to neuronal mitochondria

Aralar, the neuronal Ca(2+)-binding mitochondrial aspartate-glutamate carrier, has Ca(2+) binding domains facing the extramitochondrial space and functions in the malate-aspartate NADH shuttle (MAS). Here we showed that MAS activity in brain mitochondria is stimulated by extramitochondrial Ca(2+) with an S(0.5) of 324 nM. By employing primary neuronal cultures from control and aralar-deficient mice and NAD(P)H imaging with two-photon excitation microscopy, we showed that lactate utilization involves a substantial transfer of NAD(P)H to mitochondria in control but not aralar-deficient neurons, in agreement with the lack of MAS activity associated with aralar deficiency. The increase in mitochondrial NAD(P)H was greatly potentiated by large [Ca(2+)](i) signals both in control and aralar-deficient neurons, showing that these large signals activate the Ca(2+) uniporter and mitochondrial dehydrogenases but not MAS activity. On the other hand, small [Ca(2+)](i) signals potentiate the increase in mitochondrial NAD(P)H only in control but not in aralar-deficient neurons. We concluded that neuronal MAS activity is selectively activated by small Ca(2+) signals that fall below the activation range of the Ca(2+) uniporter and plays an essential role in mitochondrial Ca(2+) signaling.

Excitotoxic injury to mitochondria isolated from cultured neurons

Neuronal death in response to excitotoxic levels of glutamate is dependent upon mitochondrial Ca2+ accumulation and is associated with a drop in ATP levels and a loss in ionic homeostasis. Yet the mapping of temporal events in mitochondria subsequent to Ca2+ sequestration is incomplete. By isolating mitochondria from primary cultures, we discovered that glutamate treatment of cortical neurons for 10 min caused 44% inhibition of ADP-stimulated respiration, whereas the maximal rate of electron transport (uncoupler-stimulated respiration) was inhibited by approximately 10%. The Ca2+ load in mitochondria from glutamate-treated neurons was estimated to be 167 +/- 19 nmol/mg protein. The glutamate-induced Ca2+ load was less than the maximal Ca2+ uptake capacity of the mitochondria determined in vitro (363 +/- 35 nmol/mg protein). Comparatively, mitochondria isolated from cerebellar granule cells demonstrated a higher Ca2+ uptake capacity (686 +/- 71 nmol/mg protein) than the cortical mitochondria, and the glutamate-induced load of Ca2+ was a smaller percentage of the maximal Ca2+ uptake capacity. Thus, this study indicated that Ca(2+)-induced impairment of mitochondrial ATP production is an early event in the excitotoxic cascade that may contribute to decreased cellular ATP and loss of ionic homeostasis that precede commitment to neuronal death.

Cyclosporin-A Inhibits Constitutive Nitric Oxide Synthase Activity and Neuronal and Endothelial Nitric Oxide Synthase Expressions after Spinal Cord Injury in Rats

Nitric oxide (NO) plays a role in the pathophysiology of spinal cord injury (SCI). NO is produced by three types of nitric oxide synthase (NOS) enzymes: The constitutive Ca2+/calmodulin-dependent neuronal NOS (nNOS) and endothelial NOS (eNOS) isoforms, and the inducible calcium-independent isoform (iNOS). During the early stages of SCI, nNOS and eNOS produce significant amounts of NO, therefore, the regulation of their activity and expression may participate in the damage after SCI. In the present study, we used Cyclosporin-A (CsA) to further substantiate the role of Ca-dependent NOS in neural responses associated to SCI. Female Wistar rats were subjected to SCI by contusion, and killed 4 h after lesion. Results showed an increase in the activity of constitutive NOS (cNOS) after lesion, inhibited by CsA (2.5 mg/kg i.p.). Western blot assays showed an increased expression of both nNOS and eNOS after trauma, also antagonized by CsA administration.

A review of selected anti-tumour therapeutic agents and reasons for multidrug resistance occurrence

It is assumed that proteins from the ABC family (i.e., glycoprotein P (Pgp)) and a multidrug resistance associated protein (MRP) play a main role in the occurrence of multidrug resistance (MDR) in tumour cells. Other factors that influence the rise of MDR are mechanisms connected with change in the effectiveness of the glutathione cycle and with decrease in expression of topoisomerases I and II. The aim of this review is to characterize drugs applied in anti-tumour therapy and to describe the present state of knowledge concerning the mechanisms of MDR occurrence, as well as the pharmacological agents applied in reducing this phenomenon.

Inhibition of the functional expression of N-methyl-d-aspartate receptors in a stably transformed cell line by cyclosporin A

The L(tk-) cell line L12-G10 stably transformed with the human N-methyl-D-aspartate (NMDA) receptor subunits NR1-1a/NR2A showed a Ca(2+)-dependent increase in cell death, loss of mitochondrial membrane potential, and ATP depletion after agonist stimulation. Treatment of the cells with cyclosporine A (CsA) for 4h reduced glutamate-induced cell death by 60% (IC(50) of 7.1microM). The immunophilin binding drug FK506 was not effective. Short preincubation with CsA for 10 min already decreased the glutamate-induced loss of mitochondrial membrane potential while the NMDA receptor function is not affected. However, pretreatment of the cells with CsA (30 microM) for 6h reduced membrane associated NR1-1a protein amount by approximately 85%, whereas mRNA expression remained unaffected. These results suggest, that the cytoprotective effect of CsA in L12-G10 cells is due to the inhibition of the permeability transition pore on the one hand and to the inhibition of the expression of functional NMDA receptors by an additional posttranscriptional mechanism on the other hand.

Cyclosporine-A treatment prevents apoptosis in rat lumbar ganglion cells

We evaluated the expression of pro-apoptotic Bax and anti-apoptotic Bcl-2 in lumbar ganglion cells of rats by immunohistochemistry under normal conditions and after 7, 14 and 21 days of cyclosporine-A treatment (7 and 15 mg/kg/daily). In normal rats, Bax was weakly expressed in all types of neurons, whereas satellite cells showed moderate immunostaining. Bcl-2 expression was weak in type A neurons and weak or moderate in type B and C neurons and also into satellite cells. In cyclosporine-A-treated rats, we found changes in Bax staining of neurons: type A neurons and type B neurons were weakly stained, whereas type C neurons were moderately stained. Bax expression in satellite cells was moderate after 7 days of treatment and increased strongly after 14 and 21 days of treatment. Bcl-2 expression increased significantly in neurons after 14 and even more after 21 days of treatment with 7 mg/kg cyclosporine-A, mainly in type B and C neurons. With 15 mg/kg cyclosporine-A, Bcl-2 increased moderately in type A and B neurons and strongly in type C neurons only after 7 days. After 14 and 21 days, Bcl-2 expression was moderate in type A neurons whereas it was strong or even very strong in type B and C neurons. Satellite cells showed a moderate increase in Bcl-2 after 7 and 14 days of treatment whereas after 21 days, expression was strong. We conclude that (1) in normal conditions, Bax and Bcl-2 were differently expressed in neurons and satellite cells; (2) cyclosporine-A treatment rapidly enhanced Bax expression in satellite cells only, whereas Bcl-2 expression increased moderately in type A neurons and was strongly expressed in type B and C neurons; (3) cyclosporine-A has a protective role in neurons but not in satellite cells; and (4) the neuroprotective role of cyclosporine-A is dose dependent. Furthermore, the strong expression of Bax in satellite cells can explain the temporary nature of the neurotoxic effect commonly observed after cyclosporine-A administration.

Calcium channel and NMDA receptor activities differentially regulate nuclear C/EBPbeta levels to control neuronal survival

Insulin-like growth factor-1 (IGF-1) promotes the survival of cerebellar granule neurons by enhancing calcium influx through L-type calcium channels, whereas NMDA receptor-mediated calcium influx can lead to excitotoxic death. Here we demonstrate that L and NMDA receptor channel activities differentially regulate the transcription factor C/EBPbeta to control neuronal survival. Specifically, we show that L channel-dependent calcium influx results in increased CaMKIV activity, which acts to decrease nuclear C/EBPbeta levels. Conversely, NMDA receptor-mediated influx rapidly elevates nuclear C/EBPbeta and induces excitotoxic death via activation of the calcium-dependent phosphatase, calcineurin. Moderate levels of AMPA receptor activity stimulate L channels to improve survival, whereas higher levels stimulate NMDA receptors and reduce neuronal survival, suggesting differential synaptic effects. Finally, N-type calcium channel activity reduces survival, potentially by increasing glutamate release. Together, these results show that the L-type calcium channel-dependent survival and NMDA receptor death pathways converge to regulate nuclear C/EBPbeta levels, which appears to be pivotal in these mechanisms.

Pyruvate protection against beta-amyloid-induced neuronal death: role of mitochondrial redox state

The mechanism by which beta-amyloid protein (A beta) causes degeneration in cultured neurons is not completely understood, but several lines of evidence suggest that A beta-mediated neuronal death is associated with an enhanced production of reactive oxygen species (ROS) and oxidative damage. In the present study, we address whether supplementation of glucose-containing culture media with energy substrates, pyruvate plus malate (P/M), protects rat primary neurons from A beta-induced degeneration and death. We found that P/M addition attenuated cell death evoked by beta-amyloid peptides (A beta(25-35) and A beta(1-40)) after 24 hr treatment and that this effect was blocked by alpha-ciano-3-hydroxycinnamate (CIN), suggesting that it requires mitochondrial pyruvate uptake. P/M supply to control and A beta-treated neuronal cultures increases cellular reducing power, as indicated by the ability to reduce the dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The early increases in ROS levels, measured by dichlorofluorescein (DCF) fluorescence, and caspase-3 activity that follow exposure to A beta were notably reduced in the presence of P/M. These results place activation of caspase-3 most likely downstream of oxidative damage to the mitochondria and indicate that mitochondrial NAD(P) redox status plays a central role in the neuroprotective effect of pyruvate. Inhibition of respiratory chain complexes and mitochondrial uncoupling did not block the early increase in ROS levels, suggesting that A beta could initiate oxidative stress by activating a source of ROS that is not accesible to the antioxidant defenses fueled by mitochondrial substrates.

Developmental changes in the Ca2+-regulated mitochondrial aspartate-glutamate carrier aralar1 in brain and prominent expression in the spinal cord

Aralar1 and citrin are two isoforms of the mitochondrial carrier of aspartate-glutamate (AGC), a calcium regulated carrier, which is important in the malate-aspartate NADH shuttle. The expression and cell distribution of aralar1 and citrin in brain cells has been studied during development in vitro and in vivo. Aralar1 is the only isoform expressed in neurons and its levels undergo a marked increase during in vitro maturation, which is higher than the increase in mitochondrial DNA in the same time window. The enrichment in aralar1 per mitochondria during neuronal maturation is associated with a prominent rise in the function of the malate-aspartate NADH shuttle. Paradoxically, during in vivo development of rat or mouse brain there is very little postnatal increase in total aralar1 levels per mitochondria. This is explained by the fact that astrocytes develop postnatally, have aralar1 levels much lower than neurons, and their increase masks that of aralar1. Aralar1 mRNA and protein are widely expressed throughout neuron-rich areas in adult mouse CNS with clear enrichments in sets of neuronal nuclei in the brainstem and, particularly, in the ventral horn of the spinal cord. These aralar1-rich neurons represent a subset of the cytochrome oxidase-rich neurons in the same areas. The presence of aralar1 could reflect a tonic activity of these neurons, which is met by the combination of high malate-aspartate NADH shuttle and respiratory chain activities.

Inflammatory neurodegeneration mediated by nitric oxide, glutamate, and mitochondria

In inflammatory, infectious, ischemic, and neurodegenerative pathologies of the central nervous system (CNS) glia become "activated" by inflammatory mediators, and express new proteins such as the inducible isoform of nitric oxide synthase (iNOS). Although these activated glia have benefi- cial roles, in vitro they potently kill cocultured neurons, and there is increasing evidence that they contribute to pathology in vivo. Nitric oxide (NO) from iNOS appears to be a key mediator of such glial-induced neuronal death. The high sensitivity of neurons to NO is partly due to NO causing inhibition of respiration, rapid glutamate release from both astrocytes and neurons, and subsequent excitotoxic death of the neurons. NO is a potent inhibitor of mitochondrial respiration, due to reversible binding of NO to cytochrome oxidase in competition with oxygen, resulting in inhibition of energy production and sensitization to hypoxia. Activated astrocytes or microglia cause a potent inhibition of respiration in cocultured neurons due to glial NO inhibiting cytochrome oxidase within the neurons, resulting in ATP depletion and glutamate release. In some conditions, glutamate- induced neuronal death can itself be mediated by N-methyl-D-aspartate (NMDA)-receptor activation of the neuronal isoform of NO synthase (nNOS) causing mitochondrial damage. In addition NO can be converted to a number of reactive derivatives such as peroxynitrite, NO2, N2O3, and S-nitrosothiols that can kill cells in part by inhibiting mitochondrial respiration or activation of mitochondrial permeability transition, triggering neuronal apoptosis or necrosis.

Inhibition by immunophilin ligands of morphine-induced tolerance and dependence in guinea pig ileum

Immunophilin ligands, cyclosporine A and FK506 (tacrolimus), besides their immunosuppressive action, have several effects on different neural functions, such as modulation of the release of many neurotransmitters, the reduction of nitric oxide (NO) production by the inhibition of dephosphorylation of neuronal nitric oxide synthase (nNOS) and the alteration of the expression of certain genes. Many of these actions apparently occur through the inhibition of calcineurin, a calcium-calmodulin-dependent phosphatase. On the other hand, several studies have shown that NO has a critical role in opioid-induced tolerance and dependence in both in vivo and in vitro models. In the present study, the effect of cyclosporine A and FK506 on the development of tolerance to and dependence on morphine in the guinea pig ileum was assessed. Morphine inhibited electrically stimulated twitch of ileum in a concentration-dependent manner (pD(2)=7.45+/-0.07). Tolerance to this effect was induced by incubation of ileum with 2 x IC(50) or 4 x IC(50) of morphine for 2 h that induced a degree of tolerance of 6.81 and 18.10, respectively. The co-incubation of ileum with morphine along with either cyclosporine A or FK506 reduced the degree of tolerance significantly (P<0.05) and restored the sensitivity of ileum to the morphine inhibitory effect. Dependence was induced by incubation with 4 x IC(50) of morphine for 2 h and was assessed based on naloxone-induced contractions (10(-5) M). Cyclosporine A (10(-9) M) and FK506 (10(-9) M) can attenuate the development of dependence to morphine as shown by the significant decrease in naloxone-induced contractions (P<0.05). These results suggest that immunophilin ligands at very low concentrations (nanomolar) can reduce the induction of acute tolerance to and dependence on morphine in the myenteric plexus of guinea pig ileum.

Nuclear translocation of nuclear transcription factor-kappa B by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors leads to transcription of p53 and cell death in dopaminergic neurons

We describe a new molecular mechanism of cell death by excitotoxicity mediated through nuclear transcription factor kappa B (NF kappa B) in rat embryonic cultures of dopaminergic neurons. Treatment of mesencephalic cultures with alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) resulted in a number of changes that occurred selectively in dopaminergic neurons, including persistent elevation in intracellular Ca(2+) monitored with Fura-2, and a significant increase in intramitochondrial oxidation of dihydrorhodamine 123, probably associated with transient increase of mitochondrial permeability, cytochrome c release, nuclear translocation of NF kappa B, and transcriptional activation of the oncogene p53. Interruption of any of these steps by specific antagonists prevented neurite pruning and programmed cell death. In contrast, cell death was not prevented by caspase antagonists and only partly prevented by nitric-oxide synthase inhibitors. This signal transduction pathway might be a contributing mechanism in ongoing neuronal death in Parkinson disease.

The effects of FK506 on the development and expression of morphine tolerance and dependence in mice

FK506 is an immunophilin-binding ligand that inhibits calcineurin and decreases nitric oxide (NO) production in the nervous tissues. We examined the effects in mice of systemic treatment with FK506 on the induction and expression of morphine (s.c.) tolerance and dependence and compared them with the effects of the non-specific NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), and specific inducible NO synthase inhibitor, aminoguanidine. FK506 (0.5-10 mg/kg, s.c.) exerted inhibitory effects on both development and expression of tolerance to morphine-induced antinociception. FK506 also significantly decreased the expression of morphine dependence, as assessed by naloxone-precipitated (2 mg/kg, i.p.) withdrawal syndrome, but a similar effect was not found for the development of morphine dependence. A similar pattern of effects was observed with L-NAME (3-20 mg/kg, i.p.), while aminoguanidine (50-100 mg/kg, i.p.) did not alter tolerance or dependence. Examining the possible interaction between their inhibitory effects on tolerance and dependence, we combined the subeffective doses of FK506 (0.5 or 1 mg/kg) with L-NAME (3 mg/kg) or aminoguanidine (100 mg/kg). The combination of FK506 with L-NAME, but not with aminoguanidine, significantly decreased the development and expression of tolerance and expression of dependence. These data show the effectiveness of FK506 on morphine tolerance and dependence and suggest an additive effect between FK506 and the inhibition of constitutive NO synthesis in this regard.

Bradykinin receptor agonist facilitates low-dose cyclosporine-A protection against 6-hydroxydopamine neurotoxicity

Cyclosporine-A (CsA) is neuroprotective in animal models of Parkinson's disease (PD), Huntington's disease and stroke. Because CsA does not easily cross the blood-brain barrier (BBB), high doses (i.e. >10 mg/kg in rats) and chronic administration may be necessary to produce beneficial effects. However, immunosuppressant side effects (including nephrotoxicity and hepatotoxicity) are associated with such CsA dosing regimens. The bradykinin B2 receptor agonist, Cereport (labradimil and formerly called RMP-7), transiently increases the permeability of the BBB to facilitate delivery of drugs to the CNS. Here we examined the effects of co-administration of CsA and Cereport in the unilateral 6-OHDA model of PD. Animals were pretreated with vehicle, CsA alone (1 mg/kg, a low dose without either immunosuppressive or neuroprotective effects, or 10 mg/kg, a high dose that produces both immunosuppression and neuroprotection), or CsA (1 mg/kg) in combination with Cereport (9 microg/kg). Behavioral analyses, using elevated body swing and amphetamine-induced rotational tests, revealed that a low dose of CsA was neuroprotective when combined with Cereport, but not when given alone. Tyrosine hydroxylase immunohistochemistry demonstrated that while near complete (>90%) depletions of nigral TH-ir neurons were noted in lesioned animals that received vehicle infusion or low-dose CsA alone, lesioned animals that received low-dose CsA+Cereport exhibited a significant sparing of nigral TH-ir neurons and a marked reduction in the loss of striatal TH-ir fibers. The safer and effective administration of lower doses of CsA combined with enhanced BBB permeability using Cereport, offers a novel way of producing protective effects in the CNS without the toxic liabilities of high-dose CsA.

Nitric oxide promotes intracellular calcium release from mitochondria in striatal neurons

Overproduction of nitric oxide by NMDA receptor stimulation is implicated in calcium deregulation and neurodegeneration of striatal neurons. We investigated the involvement of nitric oxide (NO) in inducing intracellular calcium release and in modifying calcium transients evoked by NMDA. NO application (4-10 microM) reversibly and repeatedly increased the intracellular calcium concentration [Ca2+]i in Fura-2- or fluo-3-loaded cultured mouse striatal neurons. NO-induced [Ca2+]i responses persisted in the absence of extracellular calcium, indicating that Ca2+ was released from intracellular stores. The source of calcium was distinct from [Ca2+]i-activated (ruthenium red and ryanodine sensitive) or IP3-activated (thapsigargin-sensitive) Ca2+ stores and was not dependent on cGMP production because a cell permeant analog, 8-bromo-cGMP, did not increase basal [Ca2+]i. Glucose removal potentiated the NO-induced release of [Ca2+]i. In contrast, pretreatment with either the mitochondrial uncoupler carbonyl cyanide m-chlorophenylhydrazone or cyclosporin A, a blocker of the mitochondrial permeability transition pore, prevented the [Ca2+]i increase after NO. The rise in [Ca2+]i during NO exposure was preceded by a decrease in mitochondrial membrane potential that was partly reversible during washout. Repeated applications of NMDA induced irreversible [Ca2+]i responses in a subpopulation of striatal cells that were greatly reduced by the NOS inhibitor N omega-nitro-l-arginine. Calcium transients were prolonged by conjoint application of NMDA and NO. We conclude that NMDA-evoked [Ca2+]i transients are modulated by endogenous NO production, which leads to release of calcium from the mitochondrial pool. An NO-activated mitochondrial permeability transition pore may lead to cell death after overstimulation of NMDA receptors.

The effect of cyclosporin A on morphine tolerance and dependence: involvement of L-arginine/nitric oxide pathway

Cyclosporin A is known to decrease nitric oxide (NO) production in nervous tissues. The effects of systemic cyclosporine A on the induction and expression of morphine tolerance and dependence, acute morphine-induced antinociception, and the probable involvement of the L-arginine/nitric oxide pathway in these effects were assessed in mice. Cyclosporin A (20 mg/kg), N(G)-nitro-L-arginine methyl ester (L-NAME) (10 mg/kg) and a combination of the two at lower and per se non-effective doses (5 and 3 mg/kg, respectively) showed a similar pattern of action, inhibiting the induction of tolerance to morphine-induced antinociception and increasing the antinociception threshold in the expression phase of morphine tolerance. These agents also inhibited the expression of morphine dependence as assessed by naloxone-precipitated withdrawal signs, while having no effect on the induction of morphine dependence. L-Arginine, at a per se non-effective dose (60 mg/kg), inhibited the effects of Cyclosporin A. Moreover, acute administration of Cyclosporin A (20 mg/kg) or L-NAME (10 mg/kg) enhanced the antinociception induced by acute administration of morphine (5 mg/kg), while chronic pretreatment with Cyclosporin A (20 mg/kg) or L-NAME (10 mg/kg) for 2 days (twice daily) did not affect morphine-induced antinociception. The inducible nitric oxide synthase inhibitor, aminoguanidine (100 mg/kg), did not alter morphine antinociception, tolerance or dependence. In conclusion, decreasing NO production through constitutive nitric oxide synthase may be a mechanism through which cyclosporin A differentially modulates morphine tolerance, dependence and antinociception.

Anticonvulsant effects of cyclosporin A on pentylenetetrazole-induced seizure and kindling: modulation by nitricoxidergic system

Cyclosporin A (CsA) is known to decrease nitric oxide (NO) release in the nervous system. The present study was aimed at investigating the effects of acute administration of CsA on pentylenetetrazole (PTZ)-induced seizure threshold and latency and probable modulation of these effects by NO synthesis substrate L-arginine, and NO synthesis inhibitors N(G)-nitro-L-arginine methyl ester (L-NAME) or aminoguanidine. Moreover, the effect of CsA per se or concomitant with L-arginine on the development of PTZ-induced kindling was assessed. CsA (0.05, 1, 5, 10 and 20 mg/kg, s.c.) dose-dependently increased PTZ-induced clonic seizure threshold and the latency for onset of myoclonic jerks, clonic seizures and clonic-tonic generalized seizures following PTZ administration. L-NAME (10 and 30 mg/kg, i.p.) but not aminoguanidine (50 and 100 mg/kg, i.p.) potentiated the anticonvulsant effects of CsA (1 and 10 mg/kg). L-arginine (60, 100 and 200 mg/kg, i.p.) inhibited the anticonvulsant effects of CsA (20 mg/kg) in a dose-related manner. The inhibitory effect of L-arginine on CsA-induced alterations of seizure threshold and latency was blocked by L-NAME but not with aminoguanidine. CsA (20 mg/kg) significantly inhibited the development of PTZ kindling and decreased the seizure intensity as tested by a challenge dose of PTZ. Pretreatment with L-arginine (60 mg/kg) reversed the inhibitory effects of CsA on kindling development. It was concluded that CsA exerts some anticonvulsant properties that may be due to its inhibition of nitric oxide synthesis.

Mitochondrial permeability transition in acute neurodegeneration

Acute neurodegeneration in man is encountered during and following stroke, transient cardiac arrest, brain trauma, insulin-induced hypoglycemia and status epilepticus. All these severe clinical conditions are characterized by neuronal calcium overload, aberrant cell signaling, generation of free radicals and elevation of cellular free fatty acids, conditions that favor activation of the mitochondrial permeability transition pore (mtPTP). Cyclosporin A (CsA) and its analog N-methyl-valine-4-cyclosporin A (MeValCsA) are potent blockers of the mtPTP and protect against neuronal death following excitotoxicity and oxygen glucose deprivation. Also, CsA and MeValCsA diminish cell death following cerebral ischemia, trauma, and hypoglycemia. Here we present data that strongly imply the mtPT in acute neurodegeneration in vivo. Compounds that readily pass the blood-brain-barrier (BBB) and block the mtPT may be neuroprotective in stroke.

[Glial activation and brain aging]

While basal forebrain cholinergic neurons degenerate in aging and Alzheimer's disease, the cholinergic groups of the upper brainstem are preserved. Since the brainstem reticular-like cholinergic neurons differ from the rostral cholinergic phenotype by their high expression of nitric oxide synthase (NOS) mRNA, we hypothesized that they contain biochemical mechanisms to protect themselves against self-induced damage by nitric oxide (NO). Our initial question was a source of the NO during the aging process. We found a significant correlation between cognitive function and markers for glial activation and oxidative stress using aged rats. This result indicates that oxidative stress accompanied by glial activation may be occurred in the cognitively impaired animals. We also found mitochondrial DNA (mDNA) was significantly damaged in these animals, while accumulation of oxidative damage was not evident in other molecules. Therefore, oxidative damage to the mDNA by glial activation may occur in the cells having poor protection against oxidative stress during aging. Then the dysfunction of mitochondria, induced by the mDNA damage, may induce cell death as well as produce another oxidative stress to cause neuronal damage. The damaged neurons induce further glial activation and such self-accelerated immune-like response results in progressive neurodegeneration.

Opening of the mitochondrial permeability transition pore causes depletion of mitochondrial and cytosolic NAD+ and is a causative event in the death of myocytes in postischemic reperfusion of the heart

The opening of the mitochondrial permeability transition pore (PTP) has been suggested to play a key role in various forms of cell death, but direct evidence in intact tissues is still lacking. We found that in the rat heart, 92% of NAD(+) glycohydrolase activity is associated with mitochondria. This activity was not modified by the addition of Triton X-100, although it was abolished by mild treatment with the protease Nagarse, a condition that did not affect the energy-linked properties of mitochondria. The addition of Ca(2+) to isolated rat heart mitochondria resulted in a profound decrease in their NAD(+) content, which followed mitochondrial swelling. Cyclosporin A(CsA), a PTP inhibitor, completely prevented NAD(+) depletion but had no effect on the glycohydrolase activity. Thus, in isolated mitochondria PTP opening makes NAD(+) available for its enzymatic hydrolysis. Perfused rat hearts subjected to global ischemia for 30 min displayed a 30% decrease in tissue NAD(+) content, which was not modified by extending the duration of ischemia. Reperfusion resulted in a more severe reduction of both total and mitochondrial contents of NAD(+), which could be measured in the coronary effluent together with lactate dehydrogenase. The addition of 0.2 microm CsA or of its analogue MeVal-4-Cs (which does not inhibit calcineurin) maintained higher NAD(+) contents, especially in mitochondria, and significantly protected the heart from reperfusion damage, as shown by the reduction in lactate dehydrogenase release. Thus, upon reperfusion after prolonged ischemia, PTP opening in the heart can be documented as a CsA-sensitive release of NAD(+), which is then partly degraded by glycohydrolase and partly released when sarcolemmal integrity is compromised. These results demonstrate that PTP opening is a causative event in reperfusion damage of the heart.