Effect of Inhibitors on the Acetylcholinesterase Enzyme and Live Worms of Setaria Cervi

Filariasis is a major health problem, affecting millions of people in tropical and subtropical regions of the world. Targeting the parasite specific enzyme is not only rational but essential for developing effective control measure against filariasis. In our earlier studies we have identified two isozymic forms of acetylcholinesterase (AchE) from bovine filarial parasites (Setaria cervi) different from the host AchE. In the present study, we have studied the effect of enzyme inhibitors (BW284c51, Edrophonium and Eserine) and antifilarial drugs (Diethylcarbemazine and Ivermectin) on parasite acetylcholinesterase and on live adult worms. Out of different inhibitors, only inhibitor BW284c51, strongly inhibited (98%) the enzyme activity of S. cervi acetylcholinesterase with an IC 50 value of 26.87 M at 0.50 mM substrate concentration. Lineweaver–Burk transformation of the inhibition kinetics data demonstrated that it was a competitive inhibitor of filarial acetylcholinesterase and Ki value was 9.3 M. However, in vitro incubation of live S. cervi adult worm with 100 M concentration of BW284c51 resulted in only 40% inhibition of parasite acetylcholinesterase and 50% reduction of worm motility. These findings suggest that BW284c51 is a potent competitive inhibitor of filarial acetylcholinesterase and AchE can be a potential target for rational screening of antifilarial compounds.