Structural and kinetic evidence of aging after organophosphate inhibition of human Cathepsin A

Protonation State Insights into the Influence of Biocatalytic Function for Acetylcholinesterase Mediated by Neonicotinoids

The catalytic efficiency of acetylcholinesterase (AChE) is likely regulated by the protonation states and conformational adaptations of its catalytic residues. While neonicotinoid insecticides are recognized for impairing AChE function through neurotoxic mechanisms, the precise molecular mechanisms governing this inhibition remain poorly characterized. This investigation elucidates how structural variations among neonicotinoids modulate the protonation equilibria of Glu-202 and His-447 in AChE's catalytic triad. Comparative analysis reveals that nitro-substituted neonicotinoids (imidacloprid, clothianidin) induce more pronounced protonation state transitions compared to their cyano-containing counterparts (thiacloprid, acetamiprid). Specifically, the strong electron-withdrawing nitro groups facilitate the conversion of Glu-202 from the deprotonation (GLU) to protonation (GLH) state and His-447 from the δ- (HID) to ε-position protonation (HIE) state through enhanced electrostatic interactions. These electronic perturbations trigger structural reorganization within the active site, evidenced by nitro group-directed residue realignment and subsequent H-bond formation. Energy decomposition analysis identifies electrostatic contributions as the primary determinant of binding affinity differences, with nitro-neonicotinoids exhibiting stronger interactions than cyano-neonicotinoids. QM/MM metadynamics reveals that substantial protonation state alterations disrupt AChE's biocatalytic function, particularly its capacity for acetylcholine hydrolysis. Finally, SH-SY5Y-based cellular assays show that imidacloprid exhibits the strongest inhibitory effect on AChE intracellular activity, while thiacloprid and acetamiprid show weaker inhibitory effects, aligning with the computational predictions. This study provides insights into the protonation-state-induced biocatalytic function for acetylcholinesterase mediated by neonicotinoids, contributing to the assessment of exogenous ligand-induced potential ecological and human health risks.

Synergistic action of organophosphates and COVID-19 on inflammation, oxidative stress, and renin-angiotensin system can amplify the risk of cardiovascular maladies

Organophosphates (OPs) are ubiquitous environmental contaminants, widely used as pesticides in agricultural fields. In addition, they serve as flame-retardants, plasticizers, antifoaming or antiwear agents in lacquers, hydraulic fluids, and floor polishing agents. Therefore, world-wide and massive application of these compounds have increased the risk of unintentional exposure to non-targets including the human beings. OPs are neurotoxic agents as they inhibit the activity of acetylcholinesterase at synaptic cleft. Moreover, they can fuel cardiovascular issues in the form of myocardities, cardiac oedema, arrhythmia, systolic malfunction, infarction, and altered electrophysiology. Such pathological outcomes might increase the severity of cardiovascular diseases which are the leading cause of mortality in the developing world. Coronavirus disease-19 (COVID-19) is the ongoing global health emergency caused by SARS-CoV-2 infection. Similar to OPs, SARS-CoV-2 disrupts cytokine homeostasis, redox-balance, and angiotensin-II/AT₁R axis to promote cardiovascular injuries. Therefore, during the current pandemic milieu, unintentional exposure to OPs through several environmental sources could escalate cardiac maladies in patients with COVID-19.

In Silico Structural Analysis of Serine Carboxypeptidase Nf314, a Potential Drug Target in Naegleria fowleri Infections

Naegleria fowleri, also known as the “brain-eating” amoeba, is a free-living protozoan that resides in freshwater bodies. This pathogenic amoeba infects humans as a casual event when swimming in contaminated water. Upon inhalation, N. fowleri invades the central nervous system and causes primary amoebic meningoencephalitis (PAM), a rapidly progressive and often fatal disease. Although PAM is considered rare, reducing its case fatality rate compels the search for pathogen-specific proteins with a structure–function relationship that favors their application as targets for discovering new or improved drugs against N. fowleri infections. Herein, we report a computational approach to study the structural features of Nf314 (a serine carboxypeptidase that is a virulence-related protein in N. fowleri infections) and assess its potential as a drug target, using bioinformatics tools and in silico molecular docking experiments. Our findings suggest that Nf314 has a ligand binding site suitable for the structure-based design of specific inhibitors. This study represents a further step toward postulating a reliable therapeutic target to treat PAM with drugs specifically aimed at blocking the pathogen proliferation by inhibiting protein function.