Development of l-Dopa-containing diketopiperazines as blood-brain barrier shuttle.

In our overall goal to develop anti-Parkinson drugs, we designed novel diketopiperazines (DKP1-6) aiming to both reach the blood-brain barrier and counteract the oxidative stress related to Parkinson's Disease (PD). The anti-Parkinson properties of DKP 1-6 were evaluated using neurotoxin-treated PC12 cells, as in vitro model of PD, while their cytotoxicity and genotoxicity potentials were investigated in newborn rat cerebral cortex (RCC) and primary human whole blood (PHWB) cell cultures. The response against free radicals was evaluated by the total antioxidant capacity (TAC) assay. Comet assay was used to detect DNA damage while the content of 8-hydroxyl-2'-deoxyguanosine (8-OH-dG) was determined as a marker of oxidative DNA damage. PAMPA-BBB and Caco-2 assays were employed to evaluate the capability of DKP1-6 to cross the membranes. Stability studies were conducted in simulated gastric and intestinal fluids and human plasma. Results showed that DKP5-6 attenuate the MPP + -induced cell death on a nanomolar scale, but a remarkable effect was observed for DKP6 on Nrf2 activation that leads to the expression of genes involved in oxidative stress response thus increasing glutathione biosynthesis and ROS buffering. DKP5-6 resulted in no toxicity for RCC neurons and PHWB cells exposed to 10-500 nM concentrations during 24 h as determined by MTT and LDH assays and TAC levels were not altered in both cultured cell types. No significant difference in the induction of DNA damage was observed for DKP5-6. Both DKPs resulted stable in simulated gastric fluids (t1/2 > 22h). In simulated intestinal fluids, DKP5 underwent immediate hydrolysis while DKP6 showed a half-life higher than 3 h. In human plasma, DKP6 resulted quite stable. DKP6 displayed both high BBB and Caco-2 permeability confirming that the DKP scaffold represents a useful tool to improve the crossing of drugs through the biological membranes.

A Potent (R)-alpha-bis-lipoyl Derivative Containing 8-Hydroxyquinoline Scaffold: Synthesis and Biological Evaluation of Its Neuroprotective Capabilities in SH-SY5Y Human Neuroblastoma Cells.

A novel bis-lipoyl derivative containing 8-hydroxyquinoline scaffold (LA-HQ-LA, 5) was synthesized as a new multifunctional drug candidate with antioxidant, chelant, and neuroprotective properties for the treatment of neurodegenerative diseases. We have investigated the potential effectiveness of LA-HQ-LA against the cytotoxicity induced by 6-OHDA and H2O2 on human neuroblastoma SH-SY5Y cell line. Our outcomes showed that LA-HQ-LA resulted in significant neuroprotective and antioxidant effects against H2O2- and 6-OHDA-induced neurotoxicity in human neuroblastoma SH-SY5Y cells, as assessed by MTT assay. In particular, it showed potent neuroprotective effects against 6-OHDA in RA/PMA differentiated cells at all the tested concentrations.

A glutathione derivative with chelating and in vitro neuroprotective activities: synthesis, physicochemical properties, and biological evaluation.

Metal-ion dysregulation and oxidative stress have been linked to the progressive neurological decline associated with neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Herein we report the synthesis and chelating, antioxidant, and in vitro neuroprotective activities of a novel derivative of glutathione, GS(HQ)H, endowed with an 8-hydroxyquinoline group as a metal-chelating moiety. In vitro results showed that GS(HQ)H may be stable enough to be absorbed unmodified and arrive intact to the blood-brain barrier, that it may be able to remove Cu(II) and Zn(II) from the Aß peptide without causing any copper or zinc depletion in vivo, and that it protects SHSY-5Y human neuroblastoma cells against H2 O2 - and 6-OHDA-induced damage. Together, these findings suggest that GS(HQ)H could be a potential neuroprotective agent for the treatment of neurodegenerative diseases in which a lack of metal homeostasis has been reported as a key factor.

Memantine-sulfur containing antioxidant conjugates as potential prodrugs to improve the treatment of Alzheimer's disease.

The approved treatments for Alzheimer's disease (AD) exploit mainly a symptomatic approach based on the use of cholinesterase inhibitors or N-methyl-D-aspartate (NMDA) receptor antagonists. Natural antioxidant compounds, able to pass through the blood-brain barrier (BBB), have been extensively studied as useful neuroprotective agents. A novel approach towards excitotoxicity protection and oxidative stress associated with excess ß amyloid (Aß) preservation in AD is represented by selective glutamatergic antagonists that possess as well antioxidant capabilities. In the present work, GSH (1) or (R)-α-lipoic acid (LA) (2) have been covalently linked with the NMDA receptor antagonists memantine (MEM). The new conjugates, proposed as potential antialzheimer drugs, should act both as glutamate receptor antagonists and radical scavenging agents. The physico-chemical properties and "in vitro" membrane permeability, the enzymatic and chemical stability, the demonstrated "in vitro" antioxidant activity associated to the capacity to inhibit Aß(1-42) aggregation makes at least compound 2 a promising candidate for treatment of AD patients.

Discovery of small molecule vanin inhibitors: new tools to study metabolism and disease.

Vanins are enzymes with pantetheinase activity and are presumed to play a role in the recycling of pantothenic acid (vitamin B5) from pantetheine. Pantothenic acid is an essential nutrient required to synthesize coenzyme A, a cofactor involved in many biological processes such as fatty acid synthesis and oxidation of pyruvate to fuel the citric acid cycle. Hydrolysis of pantetheine also liberates cysteamine, a known antioxidant. Vanin-1 is highly expressed in liver and is under transcriptional control of PPAR-α and nutritional status, suggesting a role in energy metabolism. The lack of potent and specific inhibitors of vanins has hampered detailed investigation of their function. We hereby report the design, synthesis, and characterization of a novel pantetheine analogue, RR6, that acts as a selective, reversible, and competitive vanin inhibitor at nanomolar concentration. Oral administration of RR6 in rats completely inhibited plasma vanin activity and caused alterations of plasma lipid concentrations upon fasting, thereby illustrating its potential use in chemical biology research.

(R)-α-lipoyl-glycyl-L-prolyl-L-glutamyl dimethyl ester codrug as a multifunctional agent with potential neuroprotective activities.

The (R)-α-lipoyl-glycyl-L-prolyl-L-glutamyl dimethyl ester codrug (LA-GPE, 1) was synthesized as a new multifunctional drug candidate with antioxidant and neuroprotective properties for the treatment of neurodegenerative diseases. Physicochemical properties, chemical and enzymatic stabilities were evaluated, along with the capacity of LA-GPE to penetrate the blood-brain barrier (BBB) according to an in vitro parallel artificial membrane permeability assay for the BBB. We also investigated the potential effectiveness of LA-GPE against the cytotoxicity induced by 6-hydroxydopamine (6-OHDA) and H2O2 on the human neuroblastoma cell line SH-SY5Y by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay. Our results show that codrug 1 is stable at both pH 1.3 and 7.4, exhibits good lipophilicity (log P=1.51) and a pH-dependent permeability profile. Furthermore, LA-GPE was demonstrated to be significantly neuroprotective and to act as an antioxidant against H2O2- and 6-OHDA-induced neurotoxicity in SH-SY5Y cells.

Synthesis of short cationic antimicrobial peptidomimetics containing arginine analogues.

Worldwide efforts are underway to develop new antimicrobial agents against bacterial resistance. To identify new compounds with a good antimicrobial profile, we designed and synthesized two series of small cationic antimicrobial peptidomimetics (1-8) containing unusual arginine mimetics (to introduce cationic charges) and several aromatic amino acids (bulky moieties to improve lipophilicity). Both series were screened for in vitro antibacterial activity against a representative panel of Gram-positive (Staphylococcus aureus and Staphylococcus epidermidis) and Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacterial strains, and Candida albicans. The biological screening showed that peptidomimetics containing tryptophan residues are endowed with the best antimicrobial activity against S. aureus and S. epidermidis in respect to the other synthesized derivatives (MIC values range 7.5-50 µg/ml). Moreover, small antimicrobial peptidomimetics derivatives 2 and 5 showed an appreciable activity against the tested Gram-negative bacteria and C. albicans. The most active compounds (1-2 and 5-6) have been tested against Gram-positive established biofilm, too. Results showed that the biofilm inhibitory concentration values of these compounds were never up to 200 µg/ml. The replacement of tryptophan with phenylalanine or tyrosine resulted in considerable loss of the antibacterial action (compounds 3-4 and 7-8) against both Gram-positive and Gram-negative bacterial strains. Furthermore, by evaluating hemolytic activity, the synthesized compounds did not reveal cytotoxic activities, except for compound 5.

Delivery methods of camptothecin and its hydrosoluble analogue irinotecan for treatment of colorectal cancer.

Camptothecins are a family of alkaloids originally extracted from the Chinese tree Camptotheca acuminata, Nyssaceae, exhibiting a strong activity against colorectal cancer (CRC). CRC is a common malignancy worlwide. Despite significant developments in the treatment of this disease, it still causes considerable morbidity and mortality. Recent advances include both newer cytotoxic chemotherapies and novel biological agents including the more hydrosoluble camptothecin derivative, namely irinotecan. Camptothecin and irinotecan are selective human topoisomerase I inhibitors but their application for curing CRC is compromised by their intrinsic high toxicity, insolubility and instability. Furthermore, pharmacology studies have determined that continuously and prolonged schedules of administration are required. The aim of this work is to review the state of the art of camptothecin and its derivative irinotecan's delivery methods.

CNS delivery of L-dopa by a new hybrid glutathione-methionine peptidomimetic prodrug.

Parkinson's disease (PD) is a neurodegenerative disorder associated primarily with loss of dopamine (DA) neurons in the nigrostriatal system. With the aim of increasing the bioavailability of L: -dopa (LD) after oral administration and of overcoming the pro-oxidant effect associated with LD therapy, we designed a peptidomimetic LD prodrug (1) able to release the active agent by enzyme catalyzed hydrolysis. The physicochemical properties, as well as the chemical and enzymatic stabilities of the new compound, were evaluated in order to check both its stability in aqueous medium and its sensitivity towards enzymatic cleavage, providing the parent LD drug, in rat and human plasma. The radical scavenging activities of prodrug 1 was tested by using both the DPPH-HPLC and the DMSO competition methods. The results indicate that the replacement of cysteine GSH portion by methionine confers resistance to oxidative degradation in gastric fluid. Prodrug 1 demonstrated to induce sustained delivery of DA in rat striatal tissue with respect to equimolar LD dosages. These results are of significance for prospective therapeutic application of prodrug 1 in pathological events associated with free radical damage and decreasing DA concentration in the brain.

Ibuprofen and glutathione conjugate as a potential therapeutic agent for treating Alzheimer's disease.

Non-steroidal anti-inflammatory drugs (NSAIDs) and antioxidant therapy might protect against the development of Alzheimer's disease (AD). In the present work, we synthesized a molecular combination of glutathione (GSH) and ibuprofen (IBU) via an amide bond and investigated its potential for targeted delivery of the parent drugs to neurons, where cellular oxidative stress and inflammation are related to AD. Evaluation of its physicochemical and in-vitro antioxidant properties indicated that compound 1 exhibits good stability toward human plasma enzymatic activity, and, like GSH, displays in-vitro free radical scavenging activity in a time and concentration-dependent manner. The new compound was also assessed by infusion in a rat model for Alzheimer's disease for its potential to antagonize the deleterious structural and cognitive effects of ß-amyloid(1-40). In behavioral tests of long-term spatial memory, animals treated with codrug 1 performed significantly better than those treated with ß-amyloid (Aß) peptide. Histochemical findings confirmed the behavioral data, revealing that Aß protein was less expressed in cerebral cortex treated with 1 than that treated with IBU. Taken together, the present findings suggest that conjugate 1 treatment may protect against the oxidative stress generated by reactive oxygen species (ROS) and the cognitive dysfunction induced by intracerebroventricular (i.c.v.) infusion of Aß(1-40) in rats, and thus that codrug 1 could prove useful as a tool for controlling AD induced cerebral amyloid deposits and behavioral deterioration.

N-(tert)-butyloxycarbonyl)-beta,beta-cyclopentyl-cysteine (acetamidomethyl)-methyl ester for synthesis of novel peptidomimetic derivatives.

It has been recently reported that thiol groups could play an important role in the protection of neuronal cells in Alzheimer's disease (AD), prion disease (CJD) and Parkinson's disease (PD). Also bucillamine, that is a pseudo dipeptide possessing a thiol group capable to form an internal disulfide bridge, has relevant scavenger properties used in therapy for the treatment of arthritis. Furthermore, many sulphur containing compounds show strong chelating properties to heavy metals. Due to the crucial role of thiol groups in a variety of detoxicant biological systems, we report the synthesis of a racemic beta,beta-dialkyl-substituted, fully protected, cysteine derivative as a suitable intermediate in the synthesis of novel biological active peptides.

Prodrug approach for increasing cellular glutathione levels.

Reduced glutathione (GSH) is the most abundant non-protein thiol in mammalian cells and the preferred substrate for several enzymes in xenobiotic metabolism and antioxidant defense. It plays an important role in many cellular processes, such as cell differentiation, proliferation and apoptosis. GSH deficiency has been observed in aging and in a wide range of pathologies, including neurodegenerative disorders and cystic fibrosis (CF), as well as in several viral infections. Use of GSH as a therapeutic agent is limited because of its unfavorable biochemical and pharmacokinetic properties. Several reports have provided evidence for the use of GSH prodrugs able to replenish intracellular GSH levels. This review discusses different strategies for increasing GSH levels by supplying reversible bioconjugates able to cross the cellular membrane more easily than GSH and to provide a source of thiols for GSH synthesis.

N-acetyl-L-methionyl-L-Dopa-methyl ester as a dual acting drug that relieves L-Dopa-induced oxidative toxicity.

Initiation and progression of Parkinson's disease seem to be linked to oxidative stress, closely related to decreased mitochondrial functions and ubiquitin proteasome system dysfunction. To date, L-Dopa is the most effective medication , although long-term treatment can enhance oxidative stress and accelerate the degenerative process of residual cells. Therefore the inhibition of oxidation of L-Dopa/dopamine and the inhibition of reactive oxygen species formation are important strategies for neuroprotective therapy. Recently, several dual acting drugs, in which L-Dopa/dopamine are covalently linked to antioxidant molecules, were shown to induce sustained delivery of both L-Dopa/dopamine in rat plasma and striatum, suggesting that these compounds might be proposed as useful agents against Parkinson's disease. Here, by analyzing GSH levels and heme oxygenase-1 expression, we investigated in primary mesencephalic neuron cultures and in newborn mice the effects of the treatment with Ac-Met-LD-OMe. Moreover, by using proteasome inhibitor-treated mice as Parkinson's disease animal model, we demonstrated the beneficial effects of the systemic administration of this novel codrug.

Codrugs linking L-dopa and sulfur-containing antioxidants: new pharmacological tools against Parkinson's disease.

A series of multifunctional codrugs (1-6) were synthesized to overcome the pro-oxidant effect associated with L-dopa (LD) therapy. Target compounds release LD and dopamine (DA) in human plasma after enzymatic hydrolysis, displaying an antioxidant effect superior to that of N-acetylcysteine (NAC). After intracerebroventricular injection of codrug 4, the levels of DA in the striatum were higher than those in LD-treated groups, indicating that this compound has a longer half-life in brain than LD.

New L-dopa codrugs as potential antiparkinson agents.

This paper reports the synthesis and preliminary evaluation of new L-dopa (LD) conjugates (1 and 2) obtained by joining LD with two different natural antioxidants, caffeic acid and carnosine, respectively. The antioxidant efficacy of compounds 1 and 2 was assessed by evaluating plasmatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in the rat. Rat striatal concentration of LD and dopamine (DA), and central nervous effects were evaluated after oral administration of the codrugs 1 and 2. The results suggest that, though our codrugs are devoid of significant antioxidant activity, they are able to induce sustained delivery of DA in rat striatum and can improve LD and DA release in the brain.

Synthesis and study of L-dopa-glutathione codrugs as new anti-Parkinson agents with free radical scavenging properties.

A series of novel molecular combinations (1-4), in which L-dopa (LD) is linked covalently via an amide bond with glutathione (GSH), were synthesized and evaluated as potential anti-Parkinson agents with antioxidant properties. These conjugates were characterized by evaluating solubility, chemical and enzymatic stabilities, and apparent partition coefficient (log P). Derivatives 2 and 4 were tested for their radical scavenging activities, by use of a test involving the Fe(II)/H2O2-induced degradation of deoxyribose. In this study, the antioxidant efficacy of codrugs 1 and 3 was also assessed through the evaluation of plasmatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Furthermore, the central nervous effects and rat striatal concentration of LD and dopamine (DA) have been evaluated after oral administration of codrugs 1 and 3. Tested compounds prolonged the plasma LD levels and were able to induce sustained delivery of DA in rat striatum with respect to an equimolar dose of LD. The results suggest that compounds 1 and 3 could represent useful new anti-Parkinson agents devoid of the pro-oxidant effects associated with LD therapy and potentially able to restore the GSH depletion evidenced in the substantia nigra pars compacta (SNpc) of PD patients.