In Vivo Effects of Neostigmine and Physostigmine on Neutrophil Functions and Evaluation of Acetylcholinesterase and Butyrylcholinesterase as Inflammatory Markers during Experimental Sepsis in Rats.

INTRODUCTION: Recent studies have shown that acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) may serve as important diagnostic and therapeutic targets in sepsis. Since polymorphonuclear neutrophils (PMNs) play a pivotal role in the early phase of sepsis, we evaluated the potential therapeutic effects of cholinesterase inhibitors on PMN functions during cecal ligation and puncture- (CLP-) induced sepsis and investigated the roles of AChE and BChE as inflammatory markers under standardized experimental conditions. METHODS: Sham surgery or CLP was performed in male Wistar rats (n = 60). Animals were randomized into four groups: physostigmine, 100 µg/kg; neostigmine, 75 µg/kg; 0.9% saline (control group); and sham group, each applied four times over 24 h. The levels of reactive oxygen species (ROS) production and CD11b/CD62l expression were quantified by flow cytometry at t = 0, 6, 15, 20, and 24 h. Blood gas analysis as well as AChE and BChE activity levels was measured by validated point-of-care measurements. Clinical scores and survival times were determined. RESULTS: CLP induced a significant increase in ROS production and CD11b upregulation by rat PMNs. Treatment with physostigmine or neostigmine significantly reduced ROS production and CD11b upregulation by PMNs 20 h after CLP induction. In physostigmine-treated animals, survival times were significantly improved compared to the control animals, but not in neostigmine-treated animals. While AChE activity significantly decreased in the control animals at t > 6 h, AChE activity did not change in the sham group. BChE activity decreased at t > 20 h in the control animals. CONCLUSION: While AChE activity may serve as an acute inflammatory marker, BChE activity shows a delayed decrease. Administration of centrally acting physostigmine in CLP-induced sepsis in rats has protective effects on PMN functions and improves survival times, which may be of interest in clinical practice.

Species- and concentration-dependent differences of acetyl- and butyrylcholinesterase sensitivity to physostigmine and neostigmine.

Previous and more recent studies show that cholinesterase inhibitors (ChE-Is) are an important possibility for therapeutic intervention in Alzheimer's Disease, sepsis and other inflammatory syndromes. ChE-Is maintain high levels of acetylcholine (ACh) determining beneficial effects on the disease process. Despite numerous efforts to identify the appropriate choice of agents and dose of ChE-Is, a common protocol regarding concentration- and species-dependent differences in inhibitory potency (IC 50) of clinical relevant ChE-Is is still not available. To evaluate the in vitro sensitivity of Acetyl- and Butyrylcholinesterase (AChE, BChE), we compared the concentration-response effects of physostigmine and neostigmine on cholinesterases in whole blood from rat and human. A spectrophotometrical test system based on in vitro Ellman's reagent has been used to determine the kinetic properties of clinical relevant ChE-Is. In vitro, the enzyme activity of human AChE and BChE was inhibited in a concentration-dependent manner until a residual activity of 4-6% for AChE and 20-30% for BChE (IC 50 human AChE: 0.117 ± 0.007 µM physostigmine, 0.062 ± 0.003 µM neostigmine; IC 50 human BChE: 0.373 ± 0.089 µM neostigmine; 0.059 ± 0.012 µM physostigmine). The inhibition curve of rat BChE in contrast showed no concentration-dependency for physostigmine and neostigmine (87% residual activity even at high inhibitor concentrations). Rat AChE was inhibited in a concentration-dependent manner until a residual activity of 53%. The results suggest that cholinesterases from human and rat show marked species- and inhibitor-dependent differences in sensitivity to physostigmine and neostigmine. Knowledge of such differences may be critical in assessing the possible therapeutic effects of ChE-Is in both species and may guide researchers in the optimal design of future experiments regarding the application of ChE-Is.