Acetylcholinesterase inhibition and protection by dizocilpine (MK-801) enantiomers

Is It Reliable to Use Common Molecular Docking Methods for Comparing the Binding Affinities of Enantiomer Pairs for Their Protein Target?

Molecular docking is a computational chemistry method which has become essential for the rational drug design process. In this context, it has had great impact as a successful tool for the study of ligand–receptor interaction modes, and for the exploration of large chemical datasets through virtual screening experiments. Despite their unquestionable merits, docking methods are not reliable for predicting binding energies due to the simple scoring functions they use. However, comparisons between two or three complexes using the predicted binding energies as a criterion are commonly found in the literature. In the present work we tested how wise is it to trust the docking energies when two complexes between a target protein and enantiomer pairs are compared. For this purpose, a ligand library composed by 141 enantiomeric pairs was used, including compounds with biological activities reported against seven protein targets. Docking results using the software Glide (considering extra precision (XP), standard precision (SP), and high-throughput virtual screening (HTVS) modes) and AutoDock Vina were compared with the reported biological activities using a classification scheme. Our test failed for all modes and targets, demonstrating that an accurate prediction when binding energies of enantiomers are compared using docking may be due to chance. We also compared pairs of compounds with different molecular weights and found the same results.

Putative role of proteolysis and inflammatory response in the toxicity of nerve and blister chemical warfare agents: implications for multi-threat medical countermeasures

Despite the contrasts in chemistry and toxicity, for blister and nerve chemical warfare agents there may be some analogous proteolytic and inflammatory mediators and pathological pathways that can be pharmacological targets for a single-drug multi-threat medical countermeasure. The dermal-epidermal separation caused by proteases and bullous diseases compared with that observed following exposure to the blister agent sulfur mustard (2,2'-dichlorodiethyl sulfide) has fostered the hypothesis that sulfur mustard vesication involves proteolysis and inflammation. In conjunction with the paramount toxicological event of cholinergic crisis that causes acute toxicity and precipitates neuronal degeneration, both anaphylactoid reactions and pathological proteolytic activity have been reported in nerve-agent-intoxicated animals. Two classes of drugs already have demonstrated multi-threat activity for both nerve and blister agents. Serine protease inhibitors can prolong the survival of animals intoxicated with the nerve agent soman and can also protect against vesication caused by the blister agent sulfur mustard. Poly (ADP-ribose) polymerase (PARP) inhibitors can reduce both soman-induced neuronal degeneration and sulfur-mustard-induced epidermal necrosis. Protease and PARP inhibitors, like many of the other countermeasures for blister and nerve agents, have potent primary or secondary anti-inflammatory pharmacology. Accordingly, we hypothesize that drugs with anti-inflammatory actions against either nerve or blister agent might also display multi-threat efficacy for the inflammatory pathogenesis of both classes of chemical warfare agent.

No interaction of memantine with acetylcholinesterase inhibitors approved for clinical use

The loss of cholinergic neurons within the basal forebrain of patients with Alzheimer's disease (AD) may underlie aspects of the dementia. Excessive activation of N-methyl-D-aspartate (NMDA) receptors may underlie the degeneration of cholinergic cells. New drug therapies have been designed to either enhance cholinergic function by inhibition acetylcholinesterase (AChE), e.g. galanthamine, tetrahydroaminoacridine or donepezil, or by attenuation of NMDA receptor function, e.g. memantine. A combination of these two therapeutic approaches may be more beneficial at slowing the progression of the AD. The current study investigated whether memantine would attenuate the inhibition of AChE produced by these three drugs. The results indicate that these AChE inhibitors do not lose their therapeutic efficacy in combination with memantine. Our in vitro data suggest that the clinical combination of memantine with a reversible AChE inhibitor should be a valuable pharmacotherapeutic approach to dementia.

Inhibitor Ionization as a Determinant of Binding to 3-Dehydroquinate Synthase

Phosphinomethyl and carboxymethyl monoacids along with succinyl, malonyl ether, malonyl, and hydroxymalonyl diacids were substituted for phosphorylmethyl, phosphonoethyl, and phosphonomethyl groups in carbocyclic inhibitors of DHQ synthase. All but one of the carbocyclic inhibitors were synthesized via intermediacy of a 2,3-butane bisacetal-protected 3-dehydroquinic acid. Carbaphosphinate (K(i) = 20 x 10(-)(6) M) was a modest competitive inhibitor of DHQ synthase, while carbaacetate was a linear mixed-type inhibitor (K(i) = 3 x 10(-)(6) M, K(i)' = 20 x 10(-)(6) M). Carbasuccinate (K(i) = 5 x 10(-)(6) M), carbamalonate ether (K(i) = 7 x 10(-)(6) M), carbamalonate (K(i) = 0.7 x 10(-)(6) M), and carbahydroxymalonate (K(i) = 0.3 x 10(-)(6) M) were all competitive inhibitors. Carbaacetate was the only inhibitor that was not oxidized by DHQ synthase. On the basis of these data, carbocyclic inhibitors with malonyl and hydroxymalonyl groups are apparently bound by DHQ synthase as tightly as carbocyclic inhibitors possessing phosphorylmethyl and phosphonoethyl moieties.