Nucleoside triphosphate diphosphohydrolase-1 (
NTPDase1), like other ectonucleotidases, controls extracellular
nucleotide levels and consequently their (patho)physiological responses such as in
thrombosis,
inflammation, and
cancer. Selective
NTPDase1 inhibitors would therefore be very useful. We previously observed that
ticlopidine in its
prodrug form, which does not affect P2 receptor activity, inhibited the recombinant form of human
NTPDase1 (K i = 14 μM). Here we tested whether
ticlopidine can be used as a selective inhibitor of
NTPDase1. We confirmed that
ticlopidine inhibits
NTPDase1 in different forms and in different assays. The
ADPase activity of intact HUVEC as well as of COS-7 cells transfected with human
NTPDase1 was strongly inhibited by 100 µM
ticlopidine, 99 and 86%, respectively.
Ticlopidine (100 µM) completely inhibited the
ATPase activity of
NTPDase1 in situ as shown by
enzyme histochemistry with human liver and pancreas sections.
Ticlopidine also inhibited the activity of rat and mouse
NTPDase1 and of potato
apyrase. At 100 µM
ticlopidine did not affect the activity of human
NTPDase2, NTPDase3, and NTPDase8, nor of NPP1 and NPP3. Weak inhibition (10-20%) of NTPDase3 and -8 was observed at 1 mM
ticlopidine. These results show that
ticlopidine is a specific inhibitor of
NTPDase1 that can be used in enzymatic and histochemistry assays.