ACR Meeting Abstracts

ACR Meeting Abstracts

  • Meetings
    • ACR Convergence 2024
    • ACR Convergence 2023
    • 2023 ACR/ARP PRSYM
    • ACR Convergence 2022
    • ACR Convergence 2021
    • ACR Convergence 2020
    • 2020 ACR/ARP PRSYM
    • 2019 ACR/ARP Annual Meeting
    • 2018-2009 Meetings
    • Download Abstracts
  • Keyword Index
  • Advanced Search
  • Your Favorites
    • Favorites
    • Login
    • View and print all favorites
    • Clear all your favorites
  • ACR Meetings

Abstract Number: 1151

Low-Dose Methotrexate and the Selective Accumulation of Intracellular Aminoimidazolecarboxamide Ribotide

Ryan S. Funk1, Leon van Haandel1, Mara L Becker2 and J.S. Leeder1, 1Clinical Pharmacology and Medical Toxicology, Children's Mercy Hospital, Kansas City, MO, 2Clinical Pharmacology and Rheumatology, Children's Mercy Hospital, Kansas City, MO

Meeting: 2012 ACR/ARHP Annual Meeting

Keywords: Biomarkers, cell biology, methotrexate (MTX) and pediatric rheumatology

  • Tweet
  • Click to email a link to a friend (Opens in new window) Email
  • Click to print (Opens in new window) Print
Session Information

Title: Pediatric Rheumatology - Clinical and Therapeutic Aspects: Juvenile Idiopathic Arthritis

Session Type: Abstract Submissions (ACR)

Background/Purpose:   Current evidence suggests that the anti-folate methotrexate (MTX) mediates its anti-inflammatory effects through inhibition of the purine synthesis pathway causing the accumulation of aminoimidazolecarboxamide ribotide (AICAR).  Meanwhile, the anti-proliferative effects of MTX have primarily been attributed to inhibition of the pyrimidine synthesis pathway, marked by the accumulation of deoxyuridine monophosphate (dUMP).  Therefore, identification of factors that affect MTX selectivity for purine synthesis pathway inhibition may be important in predicting and enhancing drug response in immuno-inflammatory diseases.

Methods:   K562 erythroblastoid cells (~2.5 x 105 cells/mL) were exposed to 0, 10, 100 and 1000 nM MTX under normal culture conditions for up to 24 hr.  Cell samples (~2.5 x 106 cells) were harvested after 1, 2, 4, 8 and 24 hr of MTX exposure.  Cell lysates were analyzed for AICAR, dUMP, MTX and six different oxidation/methylation states of tetrahydrofolate, including 5-methyltetrahydrofolate (5mTHF); the polyglutamate distribution was also determined for each folate species and MTX.  Mean concentrations and standard deviations from three independent experiments are reported.  Statistical evaluations were conducted by unpaired Student’s t-tests and statistical significance was defined by a P-value < 0.05.

Results:   The primary effect on intracellular folates was a depletion of 5mTHF to levels at 24 hr that were 80%, 3% and 1% of control (0 nM MTX) in response to 10, 100 and 1000 nM MTX challenge, respectively with no effect on cell viability.  Similarly, intracellular dUMP accumulated to levels 29-, 343- and 486-fold greater than control after a 24 hr exposure to 10, 100 and 1000 nM MTX, respectively.  In the presence of 10 nM MTX, AICAR accumulated 93-fold compared to vehicle treated cells at 24 hr, however, increasing [MTX] had a paradoxical effect, resulting in lower AICAR concentrations.  Across all experimental conditions intracellular [MTX] correlated with the intracellular accumulation of dUMP (r2=0.854) and depletion of 5mTHF (r2=0.860), but poorly with intracellular AICAR accumulation (r2=0.122).

Conclusion:   Under these experimental conditions, increasing concentrations of MTX beyond 10 nM did not result in concentration-dependent increases in AICAR accumulation, and higher doses of MTX appeared to minimize the effects on the purine pathway, despite having profound effects on pyrimidine synthesis.  Although the mechanism for this paradoxical effect on AICAR accumulation is currently under investigation, these findings support the hypothesis that low-dose MTX selectively targets the purine biosynthesis pathway and may result in improved anti-inflammatory effects. 

 


Disclosure:

R. S. Funk,
None;

L. van Haandel,
None;

M. L. Becker,
None;

J. S. Leeder,
None.

  • Tweet
  • Click to email a link to a friend (Opens in new window) Email
  • Click to print (Opens in new window) Print

« Back to 2012 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/low-dose-methotrexate-and-the-selective-accumulation-of-intracellular-aminoimidazolecarboxamide-ribotide/

Advanced Search

Your Favorites

You can save and print a list of your favorite abstracts during your browser session by clicking the “Favorite” button at the bottom of any abstract. View your favorites »

All abstracts accepted to ACR Convergence are under media embargo once the ACR has notified presenters of their abstract’s acceptance. They may be presented at other meetings or published as manuscripts after this time but should not be discussed in non-scholarly venues or outlets. The following embargo policies are strictly enforced by the ACR.

Accepted abstracts are made available to the public online in advance of the meeting and are published in a special online supplement of our scientific journal, Arthritis & Rheumatology. Information contained in those abstracts may not be released until the abstracts appear online. In an exception to the media embargo, academic institutions, private organizations, and companies with products whose value may be influenced by information contained in an abstract may issue a press release to coincide with the availability of an ACR abstract on the ACR website. However, the ACR continues to require that information that goes beyond that contained in the abstract (e.g., discussion of the abstract done as part of editorial news coverage) is under media embargo until 10:00 AM ET on November 14, 2024. Journalists with access to embargoed information cannot release articles or editorial news coverage before this time. Editorial news coverage is considered original articles/videos developed by employed journalists to report facts, commentary, and subject matter expert quotes in a narrative form using a variety of sources (e.g., research, announcements, press releases, events, etc.).

Violation of this policy may result in the abstract being withdrawn from the meeting and other measures deemed appropriate. Authors are responsible for notifying colleagues, institutions, communications firms, and all other stakeholders related to the development or promotion of the abstract about this policy. If you have questions about the ACR abstract embargo policy, please contact ACR abstracts staff at [email protected].

Wiley

  • Online Journal
  • Privacy Policy
  • Permissions Policies
  • Cookie Preferences

© Copyright 2025 American College of Rheumatology