Aspirin inhibits phospholipase C.

Area of Science:

• Biochemistry
• Pharmacology
• Cell Biology

Background:

• Aspirin (ASA) is known to inhibit peripheral blood monocyte phospholipase C (PLC) activities ex vivo.
• Understanding the precise mechanism of ASA's action is crucial for its therapeutic applications.

Purpose of the Study:

• To further elucidate the mechanism of action of aspirin (ASA) and related salicylates on monocyte PLC activity.
• To investigate whether the inhibition of PLC by salicylates involves the induction of specific proteins.

Main Methods:

• Normal human monocytes and differentiated human U937 cells were treated with ASA and other salicylates.
• Phospholipase C (PLC) and Phospholipase A2 (PLA2) activities were measured ex vivo.
• The effect of cycloheximide and actinomycin D on salicylate-induced inhibition was assessed.

Main Results:

• Aspirin (ASA) and other salicylates significantly inhibited PLC activity in monocytes and U937 cells.
• Phospholipase A2 (PLA2) activities remained unaffected by salicylate treatment.
• The inhibitory effect of salicylates on PLC was dose- and time-dependent.
• Inhibition was abrogated by cycloheximide and actinomycin D, suggesting protein synthesis involvement.
• The induced protein appears distinct from lipocortin, a known PLA2 inhibitory protein.

Conclusions:

• Salicylates, including aspirin, inhibit monocyte PLC activity through a mechanism that involves the induction of a novel protein.
• This mechanism is independent of PLA2 inhibition and distinct from corticosteroid-induced lipocortin.
• The findings provide new insights into the non-COX related effects of aspirin.