In vitro effects of mycophenolic acid and allopurinol against Leishmania tropica in human macrophages

Abstract

The possibility that purine inhibitors or analogs might be effective antileishmanial agents led to the determination of the antileishmanial activity of mycophenolic acid and allopurinol in vitro. The drugs were tested against Leishmania tropica amastigotes (mammalian forms) within human macrophages, a model in which achievable serum concentrations of antileishmanial agents currently in use eliminate approximately 90% of the parasites. Mycophenolic acid, an inhibitor of guanosine nucleotide synthesis from inosinic acid, was shown here to inhibit guanosine nucleotide synthesis in L. tropica promastigotes (insect forms). When tested against L. tropica amastigotes within macrophages, mycophenolic acid eliminated 50% of the parasites at achievable peak human serum levels (20 ,ug/ml) and 40%o of the parasites at trough serum levels (1 to 10 pLg/ml). This demonstrates that an inhibitor of guanosine nucleotide synthesis is partially effective against L. tropica in vitro. The purine analog allopurinol was also tested and was found to eliminate 50% ofL. tropica amastigotes in this model. Because mycophenolic acid and allopurinol are partially, but not completely, effective antileishmanial agents in this in vitro model, their in vivo utility remains to be determined by clinical trials.Leishmaniasis affects perhaps 100 million persons at any one time throughout the tropical and neotropical world (1). The [GIBCO]) in the absence (control cultures) or in the presence (experimental cultures) of anti-Leishmania agents (4). Cultures were processed in duplicate. Culture medium, containing antileishmanial agents where appropriate, was changed at 3 days. At the end of 6 days of incubation, control and experimental cultures were fixed, and the mean number of amastigotes per 100 macrophages was determined by counting 100 to 200 macrophages in each culture.Viability of amasttes after exposure to drugs. The viability of anastigotes was assessed by determining the number that were capable of transforming into promastigotes. Drug-exposed and control macrophages were scraped into Schneider medium revised (GIBCO) containing 30%o heat-inactivated fetal bovine serum (10)

Inhibition of Reovirus by Mycophenolic Acid Is Associated with the M1 Genome Segment

“…IMPDH inhibitors are expected to mainly affect viral RNA and/or DNA synthesis when there is an increased need for synthesis, as in the case of virus-infected cells. IMPDH inhibition decreases levels of intracellular guanine nucleotide pools required for adequate RNA and DNA synthesis; therefore, inhibition of IMPDH with MPA has been shown to have antiproliferative (7), immunosuppressive (42), antimicrobial (43), antiviral (63,70), and antiparasitic (3,29) effects. Currently, MPA is used clinically to prevent rejection of transplanted kidneys and hearts in combination with steroids and cyclosporine A (2,33,66).…”

Activity of purine analogs against Leishmania tropica within human macrophages in vitro

“…In vitro biochemical studies have shown that the antileishmanial activity of these agents is due to metabolism of the drugs into analogs of inosine and adenosine nucleotides by the organisms (2,6,(12)(13)(14). Inhibition of guanosine nucleotide utilization may also be important for antileishmanial activity since mycophenolic acid, an inhibitor of guanosine monophosphate synthesis from inosine monophosphate, inhibits amastigote multiplication in vitro (4).…”

Biological activity of analogs of guanine and guanosine against American Trypanosoma and Leishmania spp

“…They could be metabolized as other allopurinol derivatives or as guanine analogs. In the latter case it is noteworthy that inhibition of guanosine nucleotide utilization may be important for antileishmanial activity (13).…”

“…Inhibition of guanosine nucleotide utilization may be important for antileishmanial activity because mycophenolic acid, an inhibitor of GMP synthesis from IMP, inhibits amastigote multiplication in vitro (13).…”