Bacterial metabolism of thioguanine — ASN Events
  1. Schedule
  2. Poster Session C
  3. Bacterial metabolism of thioguanine

Bacterial metabolism of thioguanine (#418)

R Movva 1 2 , I Oancea 1 3 , P Ó Cuív 4 , T Florin 1 3 5
  1. Mater Research Institute-University of Queensland, Translational Research Institute, Woolloongabba, Queensland, Australia
  2. School of Pharmacy, Griffith University, Gold Coast, Queensland, Australia
  3. Department of Medicine, University of Queensland, Brisbane , Queensland, Australia
  4. University of Queensland-Diamantina Institute, Translational Research Institute, Woolloongabba, Queensland, Australia
  5. Department of Gastroenterology, Mater Health Services Adult Hosptital , South Brisbane, Queensland, Australia

Introduction:

Thioguanine (TG), a guanine antimetabolite, is a thiopurine drug used to treat some inflammatory conditions. TG is metabolised to thioguanine nucleotides (TGNs) via the hypoxanthine guanine phosphoribosyl transferase enzyme of the purine salvage pathway.  TGNs exert immunosuppressive actions by antagonising RAC1 in lymphocytes.  Interestingly, TG treatment was also associated with distinct population shifts in the caecal mucosal microbiome of C57Bl/6 treated mice.  We envision that the shift in microbiome might be due to metabolism of TG via purine salvage pathways.

Hypothesis:

The shift in the mucosal microbiome may be due to bacterial metabolism of TG to TGNs and that TGNs production may be associated with an antibiotic effect.

Aim:

The aim was to determine TGNs production by a range of colonic bacteria when incubated with TG. And also to correlate the TGNs production with the bacterial growth to determine the antibiotic effect.

Methods:

The strains tested so far include Escherichia coli strains (DH5α, PC1101 and BL21) and Enterococcus faecalis. The E. coli strains and E. faecalis were grown in LB and BHI broth respectively. Bacterial growth in the presence of TG was determined by optical density (OD600). The production of TGNs was measured using a novel in-vitro HPLC-UV assay. A 1:50 dilution was selected for all of the strains tested apart from E. coli BL21 where 1:100 was selected based on growth curve.

Results:

All the tested strains metabolised TG into TGNs. Interestingly, only E. coli DH5αgrowth showed a dose response inhibition with TG; the other strains were resistant to TG in these conditions. The bacterial growth did not appear to correlate with TGNs production.

Conclusion:

TGNs may have selective antibiotic effect which may still be sufficient to alter the caecal mucosal microbiome.

Significance:

TG might have an antibiotic effect in addition to immune suppressive actions. Future work will involve further surveying the TG effects on broad range of caecal mucosal microbiome. 

#2015ASM