Novel fluorescence molecular imaging of chemotherapy-induced intestinal apoptosis.

Chemotherapy-induced enteropathy (CIE) is one of the most serious complications of anticancer therapy, and tools for its early detection and monitoring are highly needed. We report on a novel fluorescence method for detection of CIE, based on molecular imaging of the related apoptotic process. The method comprises systemic intravenous administration of the ApoSense fluorescent biomarker (N,N(')-didansyl-L-cystine DDC) in vivo and subsequent fluorescence imaging of the intestinal mucosa. In the reported proof-of-concept studies, mice were treated with either taxol+cyclophosphamide or doxil. DDC was administered in vivo at various time points after drug administration, and tracer uptake by ileum tissue was subsequently evaluated by ex vivo fluorescent microscopy. Chemotherapy caused marked and selective uptake of DDC in ileal epithelial cells, in correlation with other hallmarks of apoptosis (i.e., DNA fragmentation and Annexin-V binding). Induction of DDC uptake occurred early after chemotherapy, and its temporal profile was parallel to that of the apoptotic process, as assessed histologically. DDC may therefore serve as a useful tool for detection of CIE. Future potential integration of this method with fluorescent endoscopic techniques, or development of radio-labeled derivatives of DDC for emission tomography, may advance early diagnosis and monitoring of this severe adverse effect of chemotherapy.

Molecular imaging of neurodegeneration by a novel cross-disease biomarker.

Current pre-mortem diagnosis of neurodegenerative disorders such as Alzheimer's disease (AD) or amyotrophic lateral sclerosis (ALS) is based on clinical assessment of neurological deficits. However, symptoms and signs emerge only late in the disease course, thus indicating an urgent need for novel tools for detection of the underlying neuropathology. NST-729 (MW=310) is a novel molecular imaging probe, which is a member of the ApoSense family of small molecule detectors of apoptosis. We now report on the ability of NST-729, upon its systemic administration in vivo, to detect characteristic neuropathology in pre-clinical models of AD (Tg2576 transgenic mice) and ALS (transgenic SOD-1 G93A mutation mice). In the AD model, NST-729 clearly and selectively bound and imaged amyloid plaques, in excellent correlation with a typical amyloid ex vivo staining (Congo red). In the ALS model, NST-729 distinctly and selectively imaged multiple degenerating neurons in the motor nuclei in the pons, medulla and spinal cord, manifesting numerous multifocal irregularities and disruptions of neuritic projections, typical of axonal apoptosis. Study results therefore support the potential utility of NST-729 as a cross-disease biomarker for neurodegeneration, and also its potential role as the first molecular probe for ALS. Future radio-labeled NST-729 analogues may assist in the early diagnosis of disease, and in the development of neuroprotective therapies for these severe neurological disorders.

Monitoring of tumor response to chemotherapy in vivo by a novel small-molecule detector of apoptosis.

Utilization of molecular imaging of apoptosis for clinical monitoring of tumor response to anti-cancer treatments in vivo is highly desirable. To address this need, we now present ML-9 (butyl-2-methyl-malonic acid; MW = 173), a rationally designed small-molecule detector of apoptosis, based on a novel alkyl-malonate motif. In proof-of-concept studies, induction of apoptosis in tumor cells by various triggers both in vitro and in vivo was associated with marked uptake of (3)H-ML-9 administered in vivo, in correlation with the apoptotic hallmarks of DNA fragmentation, caspase-3 activation and membrane phospholipid scrambling, and with correlative tumor regression. ML-9 uptake following chemotherapy was tumor-specific, with rapid clearance of the tracer from the blood and other non-target organs. Excess of non-labeled "cold" compound competitively blocked ML-9 tumor uptake, thus demonstrating the specificity of ML-9 binding. ML-9 may therefore serve as a platform for a novel class of small-molecule imaging agents for apoptosis, useful for assessment of tumor responsiveness to treatment.

Multifunctional neuroprotective derivatives of rasagiline as anti-Alzheimer's disease drugs.

The recent therapeutic approach in which drug candidates are designed to possess diverse pharmacological properties and act on multiple targets has stimulated the development of the multimodal drugs, ladostigil (TV3326) [(N-propargyl-(3R) aminoindan-5yl)-ethyl methyl carbamate] and the newly designed multifunctional antioxidant iron chelator, M-30 (5-[N-methyl-N-propargylaminomethyl]-8-hydroxyquinoline). Ladostigil combines, in a single molecule, the neuroprotective/neurorestorative effects of the novel anti-Parkinsonian drug and selective monoamine oxidase (MAO)-B inhibitor, rasagiline (Azilect, Teva Pharmaceutical Co.) with the cholinesterase (ChE) inhibitory activity of rivastigmine. A second derivative of rasagiline, M-30 was developed by amalgamating the propargyl moiety of rasagiline into the skeleton of our novel brain permeable neuroprotective iron chelator, VK-28. Preclinical experiments showed that both compounds have anti-Alzheimer's disease activities and thus, the clinical development is oriented toward treatment of this type of dementia. This review discusses the multimodal effects of two rasagiline-containing hybrid molecules, namely ladostigil and M-30, concerning their neuroprotective molecular mechanisms in vivo and in vitro, including regulation of amyloid precursor protein processing, activation of protein kinase C, and mitogen-activated protein kinase signaling pathways, inhibition of cell death markers and upregulation of neurotrophic factors. Altogether, these scientific findings make these multifunctional compounds potentially valuable drugs for the treatment of Alzheimer's disease.

The neuroprotective mechanism of action of the multimodal drug ladostigil.

The recent therapeutic approach in which drug candidates are designed to possess diverse pharmacological properties and act on multiple targets has stimulated the development of the multimodal drug, ladostigil (TV3326) ((N-propargyl-(3R) aminoindan-5yl)-ethyl methyl carbamate). Ladostigil combines neuroprotective effects with monoamine oxidase -A and -B and cholinesterase inhibitory activities in a single molecule, as a potential treatment for Alzheimer's disease (AD) and Lewy Body disease. Preclinical studies show that ladostigil has antidepressant and anti-AD activities and the clinical development is planned for these dementias. In this review, we discuss the multimodal effects of ladostigil in terms of neuroprotective molecular mechanism in vivo and in vitro, which include the amyloid precursor protein processing; activation of protein kinase C and mitogen-activated protein kinase pathways; regulation of the Bcl-2 family members; inhibition of cell death markers and up-regulation of neurotrophic factors. Altogether, these scientific findings make ladostigil a potentially valuable drug for the treatment of AD.

A multifunctional, neuroprotective drug, ladostigil (TV3326), regulates holo-APP translation and processing.

The recent therapeutic approach in which drug candidates are designed to possess diverse pharmacological properties and act on multiple targets has stimulated the development of the bifunctional drug ladostigil (TV3326) [(N-propargyl-(3R) aminoindan-5yl)-ethyl methyl carbamate]. Ladostigil combines the neuroprotective effects of the antiparkinson drug rasagiline, a selective monoamine oxidase (MAO)-B inhibitor, with the cholinesterase (ChE) inhibitory activity of rivastigmine in a single molecule, as a potential treatment for Alzheimer's disease (AD) and Lewy Body disease. Here, we assessed the dual effects of lodostigil in terms of the molecular mechanism of neuroprotection and amyloid precursor protein (APP) regulation/processing by using an apoptotic model of neuroblastoma SK-N-SH cells. Ladostigil dose-dependently decreased cell death via inhibition of the cleavage and prevention of caspase-3 activation (IC50=1.05 microM) through a mechanism related to regulation of the Bcl-2 family proteins, which resulted in reduced levels of Bad and Bax and induced levels of Bcl-2 gene and protein expression. We have also followed APP regulation/processing and found that ladostigil markedly decreased apoptotic-induced levels of holo-APP protein without altering APP mRNA levels, suggesting a posttranscriptional mechanism. In addition, the drug-elevated phosphorylated protein kinase C (pPKC) levels and stimulated the release of the nonamyloidogenic alpha-secretase proteolytic pathway. Similar to ladostigil, its S-isomer, TV3279, which is a ChE inhibitor but lacks MAO inhibitory activity, exerted neuroprotective properties and regulated APP processing, indicating that these effects are independent of MAO inhibition.

Rasagiline: neurodegeneration, neuroprotection, and mitochondrial permeability transition.

Mitochondria are involved directly in cell survival and death. The assumption has been made that drugs that protect mitochondrial viability and prevent apoptotic cascade-induced mitochondrial permeability transition pore (MPTp) opening will be cytoprotective. Rasagiline (N-propargyl-1R-aminoindan) is a novel, highly potent irreversible monoamine oxidase (MAO) B inhibitor anti-Parkinson drug. Unlike selegiline, it is not derived from amphetamine, and is not metabolized to neurotoxic L-methamphetamine derivative. In addition, it does not have sympathomimetic activity. Rasagiline is effective as monotherapy or adjunct to levodopa for patients with early and late Parkinson's disease (PD) and adverse events do not occur with greater frequency in subjects receiving rasagiline than in those on placebo. Phase III controlled studies indicate that it might have a disease-modifying effect in PD that may be related to its neuroprotective activity. Its S isomer, TVP1022, is more than 1,000 times less potent as an MAO inhibitor. Both drugs, however, have neuroprotective activity in neuronal cell cultures in response to various neurotoxins, and in vivo in response to global ischemia, neurotrauma, head injury, anoxia, etc., indicating that MAO inhibition is not a prerequisite for neuroprotection. Their neuroprotective effect has been demonstrated to be associated directly with the propargylamine moiety, which protects mitochondrial viability and MTPp by activating Bcl-2 and protein kinase C (PKC) and by downregulating the proapoptotic FAS and Bax protein families. Rasagiline and its derivatives also process amyloid precursor protein (APP) to the neuroprotective, neurotrophic, soluble APP alpha (sAPPalpha) by PKC- and MAP kinase-dependent activation of alpha-secretase. The identification of the propargylamine moiety as the neuroprotective component of rasagiline has led us to development of novel bifunctional anti-Alzheimer drugs (ladostigil) possessing cholinesterase and brain-selective MAO inhibitory activity and a similar neuroprotective mechanism of action.

Regulation of protein kinase C by the anti-Parkinson drug, MAO-B inhibitor, rasagiline and its derivatives, in vivo.

We have recently shown that the anti-Parkinson-propargyl-containing monoamine oxidase B (MAO-B) inhibitor drug, rasagiline [N-propargyl-(1R)-aminoindan], and its cholinesterase inhibitor derivatives TV3326 and TV3279, regulate amyloid precursor protein (APP) processing by a protein kinase C (PKC)-dependent mechanism in SH-SY5Y neuroblastoma and PC12 cells. In the present study, we investigated the effect of rasagiline and its derivatives on the regulation of the PKC-dependent mechanism and APP processing under in vivo conditions. Administration of rasagiline (0.1 mg/kg) to male C57/BL mice for 14 days significantly decreased membrane-bound holoprotein APP levels in the hippocampus. Additionally, we observed that rasagiline up-regulated p-PKC levels and the expression of alpha and epsilon PKC isozymes in the hippocampus, indicating that the mechanism by which rasagiline affects APP processing may be related to PKC-associated signalling. The results also demonstrate that rasagiline treatment significantly elevated the levels of phosphorylated myristoylated alanine-rich C kinase substrate (p-MARCKS), a major substrate for PKC, as well as the levels of receptors for activated C kinase 1 (RACK1). Similar effects on APP and PKC levels were also demonstrated for the two cholinesterase inhibitor derivatives of rasagiline, TV3326 and TV3279. These results indicate that rasagiline and its derivatives regulate PKC-dependent mechanisms and APP processing. The activation and induction of PKC and MARCKS by these drugs may have a crucial role not only in their neuroprotective activity, but also in their ability to affect neuronal plasticity and spatial learning processes.

The importance of propargylamine moiety in the anti-Parkinson drug rasagiline and its derivatives in MAPK-dependent amyloid precursor protein processing.

Rasagiline [N-propargyl-(1R)-aminoindan] a highly potent selective irreversible monoamine oxidase (MAO)-B inhibitor exerts neuroprotective and antiapoptotic effects against a variety of insults in cell cultures and in vivo and has finished its phase III clinical trials for Parkinson's disease. In the present study, we show that rasagiline (1 and 10 microM) significantly protected rat PC12 cells against beta-amyloid (Abeta1-42) toxicity. In addition, rasagiline significantly increased (approximately threefold) the secretion of the nonamyloidogenic soluble form of the amyloid precursor protein (sAPPalpha) from SH-SY5Y neuroblastoma and PC12 cells. The increase of sAPPalpha was dose-dependent and was blocked by the hydroxamic acid-based metalloprotease inhibitor Ro31-9790 (100 microM), suggesting that the effect is mediated via alpha-secretase activity. Rasagiline-induced sAPPalpha release was significantly reduced by the inhibitors of protein kinase C (PKC), GF109203X, and ERK mitogen-activated protein kinase (MAPK) PD98059. Moreover, rasagiline dose dependently (0.1-10 microM) increased the phosphorylation of p44 and p42 MAPK, which was abolished by PD98059 (30 microM) and GF109203X (2.5 microM). By comparing the actions of rasagiline with those of its S-isomer TVP1022, which is not an MAO inhibitor, we have been able to demonstrate that MAO-B inhibition is not a prerequisite for either sAPPalpha-induced release or ERK phosphorylation. In addition, structure-activity relationship among rasagiline-related compounds suggests the crucial role of the propargyl moiety in these molecules, because propargylamine itself significantly induced the secretion of sAPPalpha and increased MAPK phosphorylation with similar potency to that of rasagiline and its derivatives.

Amyloid processing and signal transduction properties of antiparkinson-antialzheimer neuroprotective drugs rasagiline and TV3326.

Two novel neuroprotective cholinesterase (ChE) inhibitors, TV3326 and TV3279 [(N-propargyl-(3R) and (3S) aminoindan-5-yl)-ethyl methyl carbamate], respectively were derived from rasagiline, for the treatment of Alzheimer's disease (AD). TV3326 also inhibits monoamine oxidase (MAO)-A and B, while its S-isomer, TV3279, lacks MAO-inhibitory activity. The actions of these drugs in the regulation of the amyloid precursor protein (APP) processing using rat PC12 and human SH-SY5Y neuroblastoma cells were examined. Both isomers stimulated the release of the non-amyloidogenic alpha-secretase form of soluble APP (sAPPalpha) from these cell lines. The increases in sAPPalpha, induced by TV3326 and TV3279, were dose-dependent (0.1-100 micro M) and blocked by the hydroxamic acid-based metalloprotease inhibitor, Ro31-9790, suggesting mediation via alpha-secretase activity. Using several signal transduction inhibitors, the involvement of protein kinase C (PKC), mitogen-activated protein (MAP) kinase, and tyrosine kinase-dependent pathways in the enhancement of sAPPalpha release by TV3326 and TV3279 was identified. In addition, both drugs directly induced the phosphorylation of p44 and p42 MAP kinase, which was abolished by the specific inhibitors of MAP kinase activation, PD98059 and U0126. These data suggest a novel pharmacological mechanism, whereby these ChE inhibitors regulate the secretary processes of APP via activation of the MAP kinase pathway.

Involvement of MAP kinase in the regulation of amyloid precursor protein processing by novel cholinesterase inhibitors derived from rasagiline.

Two novel neuroprotective cholinesterase (ChE) inhibitors, TV3326, (N-propargyl-(3R) aminoindan-5-yl)-ethyl methyl carbamate, and TV3279, (N-propargyl-(3S) aminoindan-5-yl)-ethyl methyl carbamate, were derived from rasagiline for the treatment of Alzheimer's disease (AD). TV3326 also inhibits monoamine oxidase (MAO)-A and -B, whereas its S-isomer, TV3279, lacks MAO inhibitory activity. The action of these drugs in the regulation of amyloid precursor protein (APP) processing, using rat PC12 and human SH-SY5Y neuroblastoma cells, was examined. Both isomers stimulated the release of the non-amyloidogenic a-secretase form of soluble APP (sAPPalpha) from these cell lines. The increases in sAPPalpha, induced by TV3326 and TV3279, were dose-dependent (0.1-100 mM) and blocked by the hydroxamic acid-based metalloprotease inhibitor, Ro31-9790, suggesting mediation via a-secretase activity. Using several signal transduction inhibitors, we identified the involvement of protein kinase C (PKC), mitogen-activated protein (MAP) kinase, and tyrosine kinase-dependent pathways in the enhancement of sAPPalpha release by TV3326 and TV3279. In addition, both drugs directly induced the phosphorylation of p44 and p42 MAP kinase, which was abolished by the specific inhibitors of MAP kinase activation, PD98059 and U0126. These data suggest a novel pharmacological mechanism whereby these ChE inhibitors regulate the secretory processes of APP via activation of the MAP kinase pathway.