Omeprazole (Losec) is a proton pump inhibitor (PPI), Omeprazole(Losec) is a potent brain penetrant neutral sphingomyelinase (N-SMase) inhibitor (exosome inhibitor).

Omeprazole transiently alters the kinetic properties of parietal cells in rabbits, leading to premature cell death and expedited growth. By inhibiting H(+)-K(+)-ATPase, omeprazole enhances the clearance of degenerative changes and macrophage-mediated removal of parietal cells, as well as promoting the increase of progenitor cells at the apical ridge.

Omeprazole diminishes the activation of osteoclasts in vitro, while enhancing the activation of osteoblasts, leading to osteosclerosis-like effects to some extent. In human hepatocellular carcinoma cells, omeprazole induces the transcription of reporter genes through dioxin receptor elements recognized by ligand-activated aryl hydrocarbon receptors. It effectively induces the expression of cytochrome P4501A1 mRNA in primary human hepatocytes, but this induction is not detected in mouse primary hepatocytes. Omeprazole significantly suppresses the basal natural killer (NK) activity in splenocytes (SC) from untreated CD2F1 mice. It exerts rapid and robust effects on various types of cytotoxic lymphocytes, ranging from the inhibition of cytotoxicity to irreversible cellular damage. Furthermore, omeprazole notably inhibits the cytotoxicity of all types of effector cells after 30 minutes of incubation.