A novel compound, RS-1178, specifically inhibits neuronal cell death mediated by beta-amyloid-induced macrophage activation in vitro

Triazolopyrimidine Derivatives: An Updated Review on Recent Advances in Synthesis, Biological Activities and Drug Delivery Aspects

Molecules containing triazolopyrimidine core showed diverse biological activities, including anti-Alzheimer's, anti-diabetes, anti-cancer, anti-microbial, anti-tuberculosis, anti-viral, anti-malarial, anti-inflammatory, anti-parkinsonism, and anti-glaucoma activities. Triazolopyrimidines have 8 isomeric structures, including the most stable 1,2,4-triazolo[1,5- a] pyrimidine ones. Triazolopyrimidines were obtained by using various chemical reactions, including a) 1,2,4-triazole nucleus annulation to pyrimidine, b) pyrimidines annulation to 1,2,4-triazole structure, c) 1,2,4-triazolo[l,5-a] pyrimidines rearrangement, and d) pyrimidotetrazine rearrangement. This review discusses synthetic methods, recent pharmacological actions and drug delivery perspectives of triazolopyrimidines.

Synthesis and Biological Investigation of 1,2,4-Triazolo[4,3-a]azines as Potential HSF1 Inductors

Derivatives of fused 1,2,4-triazines containing heterocyclic and metallocene fragments were obtained by one-pot oxidative cyclization of heterocyclic hydrazones in the presence of hypervalent iodine(III) reagents. For 1,2,4-triazolo[4,3-a]azines, the ability to activate HSF1 was investigated. The obtained compounds were shown to increase the degree of HSF1 activation. It was shown that the 1,2,4-triazines can be used to induce Hsp70 expression and decrease the extent of mutant HTT aggregate formation.

Oxidative Aromatization of 4,7-Dihydro-6-nitroazolo[1,5-a]pyrimidines: Synthetic Possibilities and Limitations, Mechanism of Destruction, and the Theoretical and Experimental Substantiation

The reaction tolerance of the multicomponent process between 3-aminoazoles, 1-morpholino-2-nitroalkenes, and aldehydes was studied. The main patterns of this reaction have been established. Conditions for the oxidation of 4,7-dihydro-6-nitroazolo[1,5-a]pyrimidines were selected. Previous claims that the 4,7-dihydro-6-nitroazolo[1,5-a]pyrimidines could not be aromatised have now been refuted. Compounds with an electron-donor substituent at position seven undergo decomposition during oxidation. The phenomenon was explained based on experimental data, electro-chemical experiment, and quantum-chemical calculation. The mechanism of oxidative degradation has been proposed.

A Greener and Efficient Method for Nucleophilic Aromatic Substitution of Nitrogen-Containing Fused Heterocycles

A simple and efficient methodology for the nucleophilic aromatic substitution of nitrogen-containing fused heterocycles with interesting biological activities has been developed in an environmentally sound manner using polyethylene glycol (PEG-400) as the solvent, leading to the expected compounds in excellent yields in only five minutes.

Design, synthesis of novel pyranotriazolopyrimidines and evaluation of their anti-soybean lipoxygenase, anti-xanthine oxidase, and cytotoxic activities

The synthesis of 14-(aryl)-14H-naphto[2,1-b]pyrano[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine-2-yl) acetamidoximes 2a-e has been accomplished by reaction of 2-acetonitrile derivatives 1a-e with hydroxylamine. Cyclocondensation reaction of precursors 2a-e with some elctrophilic species such as ethylorthoformate, acetic anhydride, and methyl-acetoacetate provided the new oxadiazole derivatives 3a-e, 4a-e, and 5a-e, respectively. On the other hand, the reaction of precursors 2a-e with 2-chloropropanoyl chloride afforded the new acetimidamides 6a-e which evolve under reflux of toluene to the new oxadiazoles 7a-e. The synthetic compounds were screened for their anti-xanthine oxidase, anti-soybean lipoxygenase, and cytotoxic activities. Moderate to weak xanthine oxidase and soybean lipoxygenase inhibitions were obtained but significant cytotoxic activities were noted. The most cytotoxic activities were recorded mainly (i) 5a was the most active (IC50 = 4.0 μM) and selective against MCF-7 and (ii) 2a was cytotoxic against the four cell lines with selectivity for MCF-7 and OVCAR-3 (IC50 = 17 and 12 μM, respectively) while 2e is highly selective against OVCAR-3 (IC50 = 10 μM).

Microglia of rat ventral midbrain recovers its resting state over time in vitro: let microglia rest before work

Cortical or total brain cultures of microglia are commonly used as a model to study the inflammatory processes in Parkinson's disease. Here we characterize microglia cultures from rat ventral midbrain and evaluate their response to zymosan A. We used specific markers of microglia and evaluated the morphology, the phagocytic activity and reactive oxygen species (ROS) levels of the cells. During the first 10 days in vitro (DIV), cultures presented predominantly cells with a round morphology, expressing CD68 and with high phagocytic activity and ROS production. After 13 DIV, this tendency was reversed, with cultures showing higher number of ramified cells and fewer CD68(+) cells along with lower phagocytic and ROS production capability, suggesting that microglia must be kept in vitro for at least 13 days to recover its resting state. The exposure of cultures with less than 10 DIV to zymosan A significantly decreased cell viability. Exposure of cultures with 13 DIV to zymosan A (0.05, 0.5, or 5 microg/ml) increased the total cell number, the percentage of CD68(+) cells, and the phagocytic activity. Concentrations of zymosan A higher than 5 microg/ml were also effective in activating microglia but significantly decreased the number of viable cells. In summary, microglial cells remain in the activated state for several days after the isolation process and, thus, stimulation of microglia recently isolated can compromise interpretation of the results. However, upon 13 DIV, cells achieve properties of nonactivated microglia and present a characteristic response to a proinflammatory agent.

Novel piperazine derivative PMS1339 exhibits tri-functional properties and cognitive improvement in mice

Amyloid-beta-induced neuroinflammation plays a central role in the extensive loss of cholinergic neurons and cognitive decline in Alzheimer's disease. The acetylcholinesterase (AChE) inhibitors are the first class of drugs used to enhance surviving cholinergic activities. However, their limited effectiveness following long-term treatment raises a need for new multi-target therapies. We report herein a novel piperazine derivative compound PMS1339 possesses multifunctional properties including anti-platelet-activating factor, AChE inhibition, Abeta aggregation inhibition and cognitive improvement. PMS1339 could significantly inhibit both mice brain AChE (IC50=4.41+/-0.63 microM) and sera butyrylcholinesterase (BuChE, IC50=1.09+/-0.20 microM). PMS1339 was also found to inhibit neuronal AChE secreted by SH-SY5Y cell line (IC50=17.95+/-2.31 microM). Enzyme kinetics experiments performed on electric eel AChE indicated that PMS1339 acts as a mixed type competitive AChE inhibitor. Molecular docking studies using the X-ray crystal structure of AChE from Torpedo californica elucidated the interactions between PMS1339 and AChE: PMS1339 is well buried inside the active-site gorge of AChE interacting with Trp84 at the bottom, Tyr121 halfway down and Trp279 at the peripheral anionic site (PAS). Thioflavin T-based fluorimetric assay revealed the ability of PMS1339 to inhibit AChE-induced Abeta aggregation. In-vivo study indicated PMS1339 (1 mg/kg i.p.) reversed scopolamine-induced memory impairment in mice. Overall, these findings indicated that PMS1339 exhibits tri-functional properties in vitro and cognitive improvement in vivo, and revealed the emergence of a multi-target-directed ligand to tackle the determinants of Alzheimer's disease.

Microglia induce neural cell death via a proximity-dependent mechanism involving nitric oxide

Microglial cells play a major role in the pathogenesis of many neurological diseases by exacerbating neuronal and non-neuronal cell death, but the mechanisms involved are unclear. To investigate the microglial-neuronal interactions, we used the murine BV-2 microglial cell line and the human neuronal-like SK-N-SH neuroblastoma cell line in a co-culture system that enabled proximity-dependent interaction and communication, a trans-well system that allowed proximity-independent communication through diffusible molecules only, and a conditioned media system through which no proximity-dependent interactions or cell-to-cell communication is possible. Activation of BV-2 cells with lipopolysaccharide and interferon-gamma (LPS/IFN-gamma) decreased viability of the BV-2 cells alone and in co-cultures with SK-N-SH cells, but not SK-N-SH cells grown alone. In contrast, activation of BV-2 cells in the trans-well and conditioned media system did not have any effect on the viability of SK-N-SH cells, suggesting that microglia must be in close proximity to the neural cells to elicit cytotoxicity. To determine the molecules involved in proximity-dependent cell death, inhibitors of microglial activation were investigated. Only the specific inducible nitric oxide synthase (iNOS) inhibitor S-methylisothiourea, and hypothermia, which is known to suppress microglial iNOS expression, prevented cell death after LPS/IFN-gamma activation. These results suggest that activated microglia release nitric oxide that is, at least partially, responsible for proximity-dependent microglial-mediated neural toxicity.

Chymotrypsin-like proteases contribute to human monocytic THP-1 cell as well as human microglial neurotoxicity

Activated microglia have been observed in various neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis, and multiple sclerosis. They may exacerbate neuronal damage by secreting various toxic molecules. The list of candidate toxins includes proteases. Since it is currently not known which, if any, proteases are involved in human microglia neurotoxicity, we studied the effects of a panel of protease inhibitors on the toxicity of cell-free supernatants of stimulated human microglia and THP-1 monocytic cells to human SH-SY5Y cells. Five structurally distinct inhibitors that are known to inhibit chymotrypsin-like proteases were partially protective. They included chymostatin, AEBSF (Pefabloc SC), alpha1-antichymotrypsin, bromoenol lactone, and 3,4-dichloroisocoumarin. The data suggest that certain protease inhibitors could inhibit microglial-mediated toxicity. They might represent a novel class of drugs with benefit in diseases where overactivity of microglia contributes to the pathogenesis.

Mitochondria, oxidative damage, and inflammation in Parkinson's disease

The pathogenesis of Parkinson's disease (PD) remains obscure, but there is increasing evidence that impairment of mitochondrial function, oxidative damage, and inflammation are contributing factors. The present paper reviews the experimental and clinical evidence implicating these processes in PD. There is substantial evidence that there is a deficiency of complex I activity of the mitochondrial electron transport chain in PD. There is also evidence for increased numbers of activated microglia in both PD postmortem tissue as well as in animal models of PD. Impaired mitochondrial function and activated microglia may both contribute to oxidative damage in PD. A number of therapies targeting inflammation and mitochondrial dysfunction are efficacious in the MPTP model of PD. Of these, coenzyme Q(10) appears to be particularly promising based on the results of a recent phase 2 clinical trial in which it significantly slowed the progression of PD.

beta-Amyloid-specific upregulation of stearoyl coenzyme A desaturase-1 in macrophages

beta-Amyloid peptide (A beta), a major component of senile plaques, the formation of which is characteristic of Alzheimer's disease (AD), is believed to induce inflammation of the brain mediated by microglia, leading to neuronal cell loss. In this study, we performed an oligonucleotide microarray analysis to investigate the molecular events underlying the A beta-induced activation of macrophages and its specific suppression by the A beta-specific-macrophage-activation inhibitor, RS-1178. Of the approximately 36,000 genes and expressed sequence tags analyzed, eight genes were specifically and significantly upregulated by a treatment with interferon gamma (IFN gamma) and A beta compared to a treatment with IFN gamma alone (p<0.002). We found that the gene for a well-characterized lipogenetic enzyme, stearoyl coenzyme A desaturase-1 (SCD-1), was specifically upregulated by A beta treatment and was suppressed to basal levels by RS-1178. Although the underlying mechanisms remain unknown, our results suggest the presence of a link between AD and SCD-1.

Acute neuroinflammation exacerbates excitotoxicity in rat hippocampus in vivo

Accumulating evidence suggests that inflammation may play an important part in neurodegenerative diseases such as Alzheimer's disease. Inflammation itself, however, is insufficient to produce acute neurodegeneration in vivo. In this report, we determined whether inflammation increases excitotoxicity in hippocampal neurons. A proinflammagen, bacterial endotoxin lipopolysaccharide, was coinjected with ibotenate, an N-methyl-D-aspartate receptor agonist, into rat hippocampus. One week after coinjection, significant neuronal degeneration and severe tissue collapse were observed in the hippocampus. Astroglial and microglial infiltration were also detected. The neurodegeneration was suppressed by dizocilpine maleate, an N-methyl-D-aspartate receptor antagonist. We then examined whether microglial activation takes part in synergistic neuronal loss. One day after the lipopolysaccharide injection into the rat hippocampus, substantial microglial activation and induction of inducible nitric oxide synthase were observed, while neither neuronal nor astrocytic changes were detected. On the other hand, ibotenate injection at the same place 1 day after lipopolysaccharide injection in the hippocampus produced significant neuronal degeneration and gross microglial activation. These results suggest that inflammation by lipopolysaccharide might play an important role in ibotenate/lipopolysaccharide neurotoxicity.