Dose-related inversion of cinnarizine and flunarizine effects on mitochondrial permeability transition

Modulation of PI3K/AKT signaling and DFT modeling via selected pharmaceutical compounds attenuates carrageenan-induced inflammation and oxidative stress in rats

The main goal of the current study is to estimate the in vivo anti-inflammatory/antioxidant ability of four selected pharmaceutical compounds: bisoprolol (Biso), piracetam (Pirc), clopidogrel (Clop), and cinnarizine (Cinna). Indomethacin (Indo) was used as a reference drug to perform a realistic comparison between the four compounds and the Indo in vivo through tracking PI3K/AKT signaling and computational chemistry via density functional theory (DFT) modeling to analyze the electrostatic potential across the molecule and provide insight into the regions for receptor binding of the studied compounds. To achieve the safe dose of these compounds, cytotoxicity was performed against isolated adipose tissue-derived mesenchymal stem cells (ADMSCs) using MTT assay. In vivo determination of anti-inflammatory/antioxidant biochemical and genetic parameters of the tested compounds against rats' paw carrageenan (Carg)-induced inflammation was assessed. The data showed that there was no significant different in cell viability of ADMSCs until dose 10 µg/ml, so we used this concentration for in vivo experiments. Carg high significantly increased the volume of the paw edema at 120 min and 180 min compared to the control group (p < 0.01). Cinna (10 mg/kg), relatively similar to Indo, was the most anti-inflammatory compound among others, followed by Clop and Pirc, where they decreased the volume of the paw edema significantly (p < 0.01) at 120 min and 180 min compared to the Carg-group. Microscopic examination confirmed the above results indicating that paw tissue of Carg-group shows edema formation and massive inflammation compared with control. In comparison to the control group, Carg high significantly increased the malondialdehyde (MDA) levels (p < 0.01), whereas, at the concentration 10 mg/kg of the tested compounds, the MDA concentrations significantly reduced, especially the Clop, Cinna, and Indo-treated groups. On the contrary, total antioxidant capacity (TAC) and 5-lipoxygenase (5-LOP) concentrations were significantly decreased in Carg-group (p < 0.01) compared with control. Cyclooxygenase-2 (COX-2), phosphoinositide 3-kinase (PI3k), and protein kinase B (AKT) gene expressions were high and significantly upregulated in Carg-group compared to control, while the tested compounds downregulated their expressions compared to the Carg-group. Moreover, COX-2, interleukins (IL-10/IL-6/IL-4), PI3k, and AKT protein concentrations were high and significantly increased in Carg-group compared to control, however the tested compounds were high and significantly decreased their concentrations compared to the Carg-group. DFT modeling aligned with the biochemical data and indicated that Cinna emerges as the most reactive drug with high polarizability (302.741 a.u.), a relative small FMOs energy gap (ΔE 5.002 eV), relative low molecular hardness (2.501 eV), relative high softness (0.400 eV-1), and distinct nucleophilic/electrophilic interaction sites, indicating strong specific interactions with biological receptor. In conclusion, this study revealed the ability of Cinna to potentially suppress inflammation in in vivo Carg-induced rat paw inflammation model through inhibition of PI3K/AKT signaling and DFT modeling mediated by oxidative stress and inflammatory mediators.

Cyclizine induces cytotoxicity and apoptosis in macrophages through the extrinsic and intrinsic apoptotic pathways

Cyclizine, an over-the-counter and prescription antihistamine, finds widespread application in the prevention and treatment of motion sickness, encompassing symptoms such as nausea, vomiting, dizziness, along with its effectiveness in managing vertigo. However, the overuse or misuse of cyclizine may lead to hallucinations, confusion, tachycardia, and hypertension. The molecular mechanisms underlying cyclizine-induced cytotoxicity and apoptosis remain unclear. During the 24 h incubation duration, RAW264.7 macrophages were exposed to different concentrations of cyclizine. Cytotoxicity was assessed through the lactate dehydrogenase assay. Flow cytometry employing annexin V-fluorescein isothiocyanate and propidium iodide was utilized to evaluate apoptosis and necrosis. Caspase activity and mitochondrial dysfunction were evaluated through a fluorogenic substrate assay and JC-1 dye, respectively. Flow cytometry employing fluorogenic antibodies was utilized to evaluate the release of cytochrome c and expression of death receptor, including tumor necrosis factor-α receptor and Fas receptor. Western blotting was utilized to evaluate the expression of the Bcl2 and Bad apoptotic regulatory proteins. The findings unveiled from the present study demonstrated that cyclizine exerted a concentration-dependent effect on RAW264.7 macrophages, leading to the induction of cytotoxicity, apoptosis, and necrosis. This compound further activated the intrinsic apoptotic pathway by inducing mitochondrial dysfunction, Bcl2/Bad exchange expression, cytochrome c liberation, and activation of caspases contained caspase 3, 8, and 9. Moreover, the activation of the extrinsic apoptotic pathway was observed as cyclizine induced the upregulation of death receptors and increased caspase activities. Based on our investigations, it can be inferred that cyclizine prompts cytotoxicity and apoptosis in RAW264.7 macrophages in a concentration-dependent manner by triggering both the intrinsic and extrinsic apoptotic pathways.

Schizophrenia Synaptic Pathology and Antipsychotic Treatment in the Framework of Oxidative and Mitochondrial Dysfunction: Translational Highlights for the Clinics and Treatment

Schizophrenia is a worldwide mental illness characterized by alterations at dopaminergic and glutamatergic synapses resulting in global dysconnectivity within and between brain networks. Impairments in inflammatory processes, mitochondrial functions, energy expenditure, and oxidative stress have been extensively associated with schizophrenia pathophysiology. Antipsychotics, the mainstay of schizophrenia pharmacological treatment and all sharing the common feature of dopamine D2 receptor occupancy, may affect antioxidant pathways as well as mitochondrial protein levels and gene expression. Here, we systematically reviewed the available evidence on antioxidants' mechanisms in antipsychotic action and the impact of first- and second-generation compounds on mitochondrial functions and oxidative stress. We further focused on clinical trials addressing the efficacy and tolerability of antioxidants as an augmentation strategy of antipsychotic treatment. EMBASE, Scopus, and Medline/PubMed databases were interrogated. The selection process was conducted in respect of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Several mitochondrial proteins involved in cell viability, energy metabolism, and regulation of oxidative systems were reported to be significantly modified by antipsychotic treatment with differences between first- and second-generation drugs. Finally, antioxidants may affect cognitive and psychotic symptoms in patients with schizophrenia, and although the evidence is only preliminary, the results indicate that further studies are warranted.

Cardioprotective effect of abscisic acid in a rat model of type 3 cardio-renal syndrome: Role of NOX-4, P-53, and HSP-70

Cardiorenal syndrome (CRS) is a complex heart and kidney pathophysiologic disorder that leads to a bidirectional interrelationship between them. Abscisic acid (ABA) is a phytohormone that is present in plants, and is known to regulate fundamental physiological functions. This study aimed to explore the efficacy of ABA in surgically induced-CRS type 3 rats. Rats were randomly and equally divided into four groups. Rats in Group 1 received saline (Sham group), Group 2 included control induced-CRS rats, Group 3 rats (CRS+ABA) included CRS rats treated with ABA and Group 4 (CRS + ABA + Verapamil + propofol) were CRS rats treated with Verapamil, propofol and ABA. The rats were treated with the drugs daily for four weeks. At the end of the study, relative heart weight corrected QT interval (QTc), mean blood pressure (MBP), kidney functions, oxidative stress, NADPH oxidase 4 (NOX4), protein 53 (P53), and heat shock proteins-70 (HSP-70) expression was assessed and recorded. ABA led to a significant shortening of the ventricular action potential duration indicated by QTc. Furthermore, it significantly lowered heart weight, MBP, serum creatinine, NOX-4, and P-53 expression and augmented HSP-70 expression. In contrast, adding calcium channel blockers (CCBs) to ABA mitigated this effect. The results suggested that ABA has a potential protective role in CRS-induced cardiac hypertrophy and arrhythmia that could be mediated through inhibition of P-53, NOX-4, and an increase in HSP-70 expression.

Mitolysosome exocytosis, a mitophagy-independent mitochondrial quality control in flunarizine-induced parkinsonism-like symptoms

Mitochondrial quality control plays an important role in maintaining mitochondrial homeostasis and function. Disruption of mitochondrial quality control degrades brain function. We found that flunarizine (FNZ), a drug whose chronic use causes parkinsonism, led to a parkinsonism-like motor dysfunction in mice. FNZ induced mitochondrial dysfunction and decreased mitochondrial mass specifically in the brain. FNZ decreased mitochondrial content in both neurons and astrocytes, without affecting the number of nigral dopaminergic neurons. In human neural progenitor cells, FNZ also induced mitochondrial depletion. Mechanistically, independent of ATG5- or RAB9-mediated mitophagy, mitochondria were engulfed by lysosomes, followed by a vesicle-associated membrane protein 2- and syntaxin-4-dependent extracellular secretion. A genome-wide CRISPR knockout screen identified genes required for FNZ-induced mitochondrial elimination. These results reveal not only a previously unidentified lysosome-associated exocytosis process of mitochondrial quality control that may participate in the FNZ-induced parkinsonism but also a drug-based method for generating mitochondria-depleted mammal cells.

Antioxidant Therapy against Oxidative Damage of the Inner Ear: Protection and Preconditioning

Oxidative stress is an important mechanism underlying cellular damage of the inner ear, resulting in hearing loss. In order to prevent hearing loss, several types of antioxidants have been investigated; several experiments have shown their ability to effectively prevent noise-induced hearing loss, age-related hearing loss, and ototoxicity in animal models. Exogenous antioxidants has been used as single therapeutic agents or in combination. Antioxidant therapy is generally administered before the production of reactive oxygen species. However, post-exposure treatment could also be effective. Preconditioning refers to the phenomenon of pre-inducing a preventative pathway by subtle stimuli that do not cause permanent damage in the inner ear. This renders the inner ear more resistant to actual stimuli that cause permanent hearing damage. The preconditioning mechanism is also related to the induction of antioxidant enzymes. In this review, we discuss the mechanisms underlying antioxidant-associated therapeutic effects and preconditioning in the inner ear.

A Novel Conceptual Model for the Dual Role of FOF1-ATP Synthase in Cell Life and Cell Death

The mitochondrial permeability transition (MPT) has been one of the longstanding enigmas in biology. Its cause is currently at the center of an extensive scientific debate, and several hypotheses on its molecular nature have been put forward. The present view holds that the transition arises from the opening of a high-conductance channel in the energy-transducing membrane, the permeability transition pore (PTP), also called the mitochondrial megachannel or the multiconductance channel (MMC). Here, the novel hypothesis is proposed that the aqueous access channels at the interface of the c-ring and the a-subunit of FO in the FOF1-ATP synthase are repurposed during induction of apoptosis and constitute the elusive PTP/ MMC. A unifying principle based on regulation by local potentials is advanced to rationalize the action of the myriad structurally and chemically diverse inducers and inhibitors of PTP/MMC. Experimental evidence in favor of the hypothesis and its differences from current models of PTP/MMC are summarized. The hypothesis explains in considerable detail how the binding of Ca2+ to a β-catalytic site (site 3) in the F1 portion of ATP synthase triggers the opening of the PTP/MMC. It is also shown to connect to longstanding proposals within Nath's torsional mechanism of energy transduction and ATP synthesis as to how the binding of MgADP to site 3 does not induce PTP/MMC, but instead catalyzes physiological ATP synthesis in cell life. In the author's knowledge, this is the first model that explains how Ca2+ transforms the FOF1-ATP synthase from an exquisite energy-conserving enzyme in cell life into an energy-dissipating structure that promotes cell death. This has major implications for basic as well as for clinical research, such as for the development of drugs that target the MPT, given the established role of PTP/MMC dysregulation in cancer, ischemia, cardiac hypertrophy, and various neurodegenerative diseases.

Progress in the Development of Preventative Drugs for Cisplatin-Induced Hearing Loss

Cisplatin is a highly effective treatment for malignant cancers and has become a cornerstone in chemotherapeutic regimens. Unfortunately, its use in the clinic is often coupled with a high incidence of severe hearing loss. Over the past few decades, enormous effort has been put forth to find protective agents that selectively protect against the ototoxic side effects of cisplatin and do not interfere with its antitumoral activity. Many therapies have been successful in preclinical work, but only a few have shown any protection in the clinic, and none have been approved by the FDA. This review summarizes the clinical and preclinical studies of the most effective small-molecule candidates currently in clinical trials, while also detailing their molecular mechanisms of action, to gain insight for future drug development in the field.

Cinnarizine: Comprehensive Profile

Cinnarizine is a piperazine derivative with antihistaminic, antiserotonergic, antidopaminergic, and calcium channel-blocking activities. A comprehensive profile was performed on cinnarizine including its description and the different methods of analysis. The 1H NMR and 13C one- and two-dimensional NMR methods were used. In addition, infrared and mass spectral analyses were performed which all confirmed the structure of cinnarizine.

Reno-protective role of flunarizine (mitochondrial permeability transition pore inactivator) against gentamicin induced nephrotoxicity in rats

This study was aimed to evaluate the role of flunarizine on gentamicin (GEM) induced nephrotoxicity in rat. Administration of GEM (40 mg/kg, s.c. for 10 consecutive days) significantly increased blood urea nitrogen (BUN), N-acetyl β-d-glucosaminidase (NAG), thiobarbituric acid reactive substances (TBARS) and total calcium whereas, decreased body weight, fractional excretion of sodium (FrNa), creatinine clearance (CrCl), reduced glutathione (GSH), mitochondrial cytochrome c oxidase (Cyt-C oxidase) and ATP levels resulting in nephrotoxicity. Further, flunarizine (100, 200 and 300 µmol/kg, p.o.) was administered to evaluate its renoprotective effect against GEM induced nephrotoxicity and the results were compared with cylcosporin A (CsA, 50 µmol/kg, p.o.). Flunarizine resulted in the attenuation of renal dysfunction and oxidative marker changes in rats subjected to GEM induced nephrotoxicity in a dose dependent manner. Medium and higher doses of flunarizine produced significant renal protective effect which was comparable to cyclosporin A. The results of this study clearly revealed that flunarizine protected the kidney against the nephrotoxic effect of GEM via mitochondrial permeability transition pore (MPTP) inactivation potential.

Mitochondrial dependent apoptosis: ameliorative effect of flunarizine on ischemia-reperfusion of celiac artery-induced gastric lesions in the rat

OBJECTIVES

Ischemia-reperfusion is a major event for induction of cellular apoptosis. Apoptosis is due to the activation of death receptor and/or mitochondrial pathways. Mitochondrial permeability transition pore opening is the cause of apoptosis. In our present study, we tried to evaluate the role of flunarizine in ischemia and reperfusion of celiac artery-induced gastric lesion in the rat.

METHODS

The therapeutic potential of flunarizine was assessed by measuring the changes in gastric lesion index, biomarker (i.e., thiobarbituric acid reactive substance, reduced glutathione, superoxide dismutase, myeloperoxidase, and total calcium and protein content), and mitochondrial damage (i.e., adenosine triphosphate and deoxyribonucleic acid fragmentation content) in ischemia and reperfusion-induced gastric lesion model.

RESULTS

Medium and higher doses of flunarizine produced a significant (P<0.05) ameliorative effect which was observed from the assessment of all the above-mentioned parameters (i.e., increase in reduced glutathione, superoxide dismutase and decrease in thiobarbituric acid reactive substance, myeloperoxidase, and total calcium content). Similar results were also obtained from omeprazole and cyclosporine. In the pre-treated group, deoxyribonucleic acid fragmentation pattern has also indicated that a mitochondria-associated anti-apoptotic effect of flunarizine was responsible to prevent the ischemia and reperfusion of celiac artery-induced gastric lesion.

CONCLUSION

The gastroprotective effect of flunarizine may be produced due to its inactivation potential of mitochondrial permeability transition pore opening associated with anti-oxidative, calcium regulation along with its anti-apoptotic effect.

Ameliorative effect of flunarizine in cisplatin-induced acute renal failure via mitochondrial permeability transition pore inactivation in rats

This study was aimed to evaluate the protective effect of flunarizine on cisplatin-induced acute renal failure. Administration of cisplatin (6 mg/kg, i.p. on day 6) significantly increased serum blood urea nitrogen and creatinine, urinary N-acetyl β-D-glucosaminidase, tissue thiobarbituric acid reactive substances and total calcium whereas, decreased body weight, fractional excretion of sodium, creatinine clearance tissue-reduced glutathione, mitochondrial cytochrome c oxidase, and ATP levels were observed in acute renal failure rats. Moreover, cisplatin produced histopathological changes in the renal tissue. Furthermore, flunarizine (100, 200, and 300 μM/kg, p.o., for six consecutive days) was administered to evaluate its therapeutic potential in acute renal failure, and the results were compared with cyclosporin A (50 μM/kg, p.o., for six consecutive days) as a reference drug. Flunarizine resulted in the attenuation of cisplatin-induced renal dysfunction, oxidative stress marker, mitochondrial damage, and histopathological changes in rats. Medium and higher doses of flunarizine produced significant renal protective effect which was comparable to cyclosporin A. The results of this study clearly revealed that flunarizine protected the kidney against the nephrotoxic effect of cisplatin via mitochondrial permeability transition pore inactivation potential.

Microcin J25 induces the opening of the mitochondrial transition pore and cytochrome c release through superoxide generation

Microcin J25, an antimicrobial lasso-structure peptide, induces the opening of mitochondrial permeability transition pores and the subsequent loss of cytochrome c. The microcin J25 effect is mediated by the stimulation of superoxide anion overproduction. An increased uptake of calcium is also involved in this process. Additional studies with superoxide dismutase, ascorbic acid and different specific inhibitors, such as ruthenium red, cyclosporin A and Mn(2+), allowed us to establish a time sequence of events starting with the binding of microcin J25, followed by superoxide anion overproduction, opening of mitochondrial permeability transition pores, mitochondrial swelling and the concomitant leakage of cytochrome c.

Protective effect of T-type calcium channel blocker flunarizine on cisplatin-induced death of auditory cells

Changes in intracellular Ca2+ level are involved in a number of intracellular events, including triggering of apoptosis. The role of intracellular calcium mobilization in cisplatin-induced hair cell death, however, is still unknown. In this study, the effect of calcium channel blocker flunarizine (Sibelium), which is used to prescribe for vertigo and tinnitus, on cisplatin-induced hair cell death was investigated in a cochlear organ of Corti-derived cell line, HEI-OC1, and the neonatal (P2) rat organ of Corti explant. Cisplatin induced apoptotic cell death showing nuclear fragmentation, DNA ladder, and TUNEL positive in both HEI-OC1 and primary organ of Corti explant. Flunarizine significantly inhibited the cisplatin-induced apoptosis. Unexpectedly, flunarizine increased the intracellular calcium ([Ca2+]i) levels of HEI-OC1. However, the protective effect of flunarizine against cisplatin was not mediated by modulation of intracellular calcium level. Treatment of cisplatin resulted in ROS generation and lipid peroxidation in HEI-OC1. Flunarizine did not attenuate ROS production but inhibited lipid peroxidation and mitochondrial permeability transition in cisplatin-treated cells. This result suggests that the protective mechanism of flunarizine on cisplatin-induced cytotoxicity is associated with direct inhibition of lipid peroxidation and mitochondrial permeability transition.

Fluoride curcumin derivatives: new mitochondrial uncoupling agents

The mitochondrial effects of two fluoride curcumin derivatives were studied. They induced the collapse of mitochondrial membrane potential (DeltaPsi), increased mitochondrial respiration, and decreased O(2)*- production and promoted Ca(2+) release. These effects were reversed by the recoupling agent 6-Ketocholestanol, but not by cyclosporin A, an inhibitor of the permeability transition pore (PTP), suggesting that these compounds act as uncoupling agents. This idea was reinforced by the analysis of the physico-chemical properties of the compounds indicating, that they are mainly in the anionic form in the mitochondrial membrane. Moreover, they are able to induce PTP opening by promoting the oxidation of thiol groups and the release of cytochrome c, making these two molecules potential candidates for induction of apoptosis.

Dual effect of ebselen on mitochondrial permeability transition

This study reports an investigation on the effect of the seleno-organic compound ebselen on rat liver mitochondria. We show that low concentrations of ebselen induced an increase in rat liver mitochondrial membrane permeability, resulting in swelling and loss of membrane potential. These effects were mediated by the opening of the permeability transition pore. They required Ca(2+), were independent of pyridine nucleotide oxidation, and involved the oxidation of thiol groups. Ebselen pore induction is apparently promoted by the glutathione peroxidase mimicking activity of the drug. Opposite effects, that is, inhibition of both pore opening and thiol oxidation, were observed when concentrations higher than 20 micro M were used. These data demonstrate that ebselen is able to modulate the opening of the permeability transition pore and that it might be a critical event for both the proapoptotic and cytoprotective activities of the drug.

Thioridazine interacts with the membrane of mitochondria acquiring antioxidant activity toward apoptosis--potentially implicated mechanisms

We evaluated the effects of the phenothiazine derivative thioridazine on mechanisms of mitochondria potentially implicated in apoptosis, such as those involving reactive oxygen species (ROS) and cytochrome c release, as well as the involvement of drug interaction with mitochondrial membrane in these effects. Within the 0 - 100 microM range thioridazine did not reduce the free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH) nor did it chelate iron. However, at 10 microM thioridazine showed important antioxidant activity on mitochondria, characterized by inhibition of accumulation of mitochondria-generated O2*-, assayed as lucigenin-derived chemiluminescence, inhibition of Fe2+/citrate-mediated lipid peroxidation of the mitochondrial membrane (LPO), assayed as malondialdehyde generation, and inhibition of Ca2+/t-butyl hydroperoxide (t-BOOH)-induced mitochondrial permeability transition (MPT)/protein-thiol oxidation, assayed as mitochondrial swelling. Thioridazine respectively increased and decreased the fluorescence responses of mitochondria labelled with 1-aniline-8-naphthalene sulfonate (ANS) and 1-(4-trimethylammonium phenyl)-6 phenyl 1,3,5-hexatriene (TMA-DPH). The inhibition of LPO and MPT onset correlated well with the inhibition of cytochrome c release from mitochondria. We conclude that thioridazine interacts with the inner membrane of mitochondria, more likely close to its surface, acquiring antioxidant activity toward processes with potential implications in apoptosis such as O2*- accumulation, as well as LPO, MPT and associated release of cytochrome c.

Mitochondria as target for antiischemic drugs

The cessation of blood flow followed by a reperfusion period results in severe damages to cell structures. This induces a complex cascade of events involving, more particularly, a loss of energy, an alteration of ionic homeostasis promoting H(+) and Ca(2+) build up and the generation of free radicals. In this context, mitochondria are highly vulnerable and play a predominant role in the cell signaling leading from life to death. This is why, recently, efforts to find an effective therapy for ischemia-reperfusion injury have focused on mitochondria. This review summarizes the pharmacological strategies which are currently developed and the potential mitochondrial targets which could be involved in the protection of cells.

Curcumin induces the mitochondrial permeability transition pore mediated by membrane protein thiol oxidation

Curcumin is a natural compound showing antiproliferative properties. Recent studies suggest that these properties might be due to its ability to induce apoptosis in tumor cells. As mitochondria play a pivotal role in the induction of the apoptotic process, we analyzed the effect of curcumin on mitochondrial function. Curcumin induced an increase in rat liver mitochondrial membrane permeability, resulting in swelling, loss of membrane potential and inhibition of ATP synthesis. These effects were mediated by the opening of the permeability transition pore. Curcumin pore induction involved the oxidation of membrane thiol functions and required the presence of low Ca(2+) concentrations. These data suggest that mitochondria might be a target by which curcumin induces apoptosis of tumor cells.

Improving the survival of grafted dopaminergic neurons: a review over current approaches

Neural transplantation is developing into a therapeutic alternative in Parkinson's disease. A major limiting factor is that only 3-20% of grafted dopamine neurons survive the procedure. Recent advances regarding how and when the neurons die indicate that events preceding actual tissue implantation and during the first week thereafter are crucial, and that apoptosis plays a pivotal role. Triggers that may initiate neuronal death in grafts include donor tissue hypoxia and hypoglycemia, mechanical trauma, free radicals, growth factor deprivation, and excessive extracellular concentrations of excitatory amino acids in the host brain. Four distinct phases during grafting that can involve cell death have been identified: retrieval of the embryo; dissection and preparation of the donor tissue; implantation procedure followed by the immediate period after graft injection; and later stages of graft maturation. During these phases, cell death processes involving free radicals and caspase activation (leading to apoptosis) may be triggered, possibly involving an increase in intracellular calcium. We review different approaches that reduce cell death and increase survival of grafted neurons, typically by a factor of 2-4. For example, changes in transplantation procedure such as improved media and implantation technique can be beneficial. Calcium channel antagonists such as nimodipine and flunarizine improve nigral graft survival. Agents that counteract oxidative stress and its consequences, such as superoxide dismutase overexpression, and lazaroids can significantly increase the survival of transplanted dopamine neurons. Also, the inhibition of apoptosis by a caspase inhibitor has marked positive effects. Finally, basic fibroblast growth factor and members of the transforming growth factor-beta superfamily, such as glial cell line-derived neurotrophic factor, significantly improve the outcome of nigral transplants. These recent advances provide hope for improved survival of transplanted neurons in patients with Parkinson's disease, reducing the need for human embryonic donor tissue and increasing the likelihood of a successful outcome.

Flunarizine improves the survival of grafted dopaminergic neurons

Embryonic nigral grafts can survive, reinnervate the striatum and reverse functional deficits in both experimental and clinical Parkinsonism. A major drawback is that only around 10% of the implanted dopaminergic neurons survive. The underlying mechanisms leading to this 90% cell death are not fully understood, but oxidative stress and a substantial loss of neurotrophic support are likely to be involved. Hypoxia and mechanical trauma, which are unavoidable during tissue preparation, may be a trigger for cell death. Recent studies have provided evidence that the type of cell death occurring is, to a large extent, apoptotic. Flunarizine is an antagonist of L-, T- and N-type calcium channels, which permits calcium entry into cells via a voltage-dependent mechanism. Flunarizine has been shown to protect neurons against death induced by serum deprivation, nerve growth factor deprivation, oxidative stress, axotomy and ischemia. This study was designed to investigate whether flunarizine can protect grafted embryonic dopaminergic neurons from death when implanted in a rat model of Parkinson's disease. Addition of 1 microM flunarizine inhibited cell death in a suspension of cells derived from the rat's ventral mesencephalon and when such a treated suspension was injected into the neostriatum there was a 2.6-fold greater number of surviving dopaminergic neurons, a doubling of the graft volume and a doubling of the volume of the host neostriatum innervated by dopaminergic fibers from the graft, compared with suspensions not exposed to flunarizine. Furthermore, rats injected with cells that had been exposed to flunarizine displayed a greater recovery of function in the amphetamine-induced rotation test.

A rapid method for the evaluation of compounds with mitochondria-protective properties

Mitochondrial dysfunction has been implicated in a number of neurodegenerative diseases, such as ischemia and Parkinson's disease. We present here a method that allows the rapid quantification of interventions, aimed at inhibiting the effect of mitochondrial membrane potential uncouplers, based on the ratioing properties of the fluorescent probe 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1), by using currently available 96-well fluorescent plate readers. A method is presented for evaluation of cross-talk between the two excitation/emission channels. Further characterization of the probe shows that the effect of plasma membrane potential changes on JC-1 fluorescence ratio are negligible, but that the signal is very sensitive to pH. One of the most exciting applications is the possibility to perform end-point measurements, thanks to the ratioing properties of the probe. The system is tested in different culture types with different mitochondrial uncouplers. As an example of a quantitative evaluation, we show that flunarizine is able to inhibit, dose-dependently, FCCP mediated JC-1 signal increase. The procedure is simple and allows for the fast screening of mitochondria-protective compounds.