VIVO INHIBITION OF DIPEPTIDYL PEPTIDASE-IV ACTIVITY BY PRO-PRO-DIPHENYL-PHOSPHONATE (PRODIPINE)

Dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5), also known as CD26, is a membrane-bound serine protease that cleaves off aminoterminal dipept ides from peptides with a penultimate proline (or, at a much slower ra te, a penultimate alanine). Recently, we synthesized and characterized a number of dipeptide-derived diphenylphosphonates. Out of the result ing series of slow-binding irreversible inhibitors of DPP IV, diphenyl 1-(S)-prolylpyrrolidine-2(R,S)-phosphonate hydrochloride ( Pro-Pro-di phenylphosphonate or Prodipine) was selected for further study. We inv estigated the in vivo applicability of Prodipine. Male rabbits weighin g 3-4 kg received a single intravenous injection with 10 mg Prodipine or saline. After 1 hr, plasma DPP IV activity had decreased to less th an 20% of the preinjection value and remained unchanged during a 24-hr observation period. In a next step, we aimed to study (i) the dose de pendency and (ii) the duration of the effect after a single intravenou s dose of Prodipine. A. profound and long-lasting inhibition of plasma DPP IV activity was observed in the treated animals (1, 5 or 10 mg). It took 5 to 8 days to reach half of the pretreatment DPP IV activity and generally more than 20 days for a complete recovery. Systemic trea tment with Prodipine not only led to inhibition of plasma DPP IV activ ity but also decreased tissue DPP IV activity in circulating mononucle ar cells, kidney cortex, thymus, spleen, lung, and liver. No differenc es in activities of the related peptidases aminopeptidase P (APP, EC 3 .4.11.9), prolyl oligopeptidase (PO, EC 3.4.21.26), or aminopeptidase M (mAAP, EC 3.4.11.2) were detected between Prodipine-treated and cont rol rabbits. The in vivo applicability of this chemically stable, irre versible inhibitor of DPP IV opens new possibilities, not only to furt her unravel the biological functions of this intriguing ectopeptidase, but also to explore this enzyme as a new target in various fields of pharmacological research. (C) 1997 Elsevier Science Inc.