Session Type: Abstract Submissions (ACR)
Background/Purpose: Acyclic nucleoside phosphonates are a key class of antivirals commonly used in the treatment of both DNA and retroviral infections. Adefovir and tenofovir are AMP analogues that resemble substrates of CD73. We have previously reported that adenosine, generated by the CD73-mediated dephosphorylation of AMP, acting at A2A receptors, plays a critical role in development of both hepatic and dermal fibrosis in murine models of cirrhosis and scleroderma, respectively. A recent clinical trial demonstrated that tenofovir, but not other antiviral agents, reverses hepatic fibrosis/cirrhosis in patients with hepatitis B. We therefore proposed the hypothesis that tenofovir’s antifibrotic effects are mediated by inhibition of adenosine production by CD73-mediated dephosphorylation of AMP.
Methods: In silico modeling and docking studies were performed using an ICM-Browser downloaded from www.molsoft.com. Active site docking with an energy score of less than -32 kcal/mol was considered favorable. CD73 enzyme activity was quantitated by malachite green using 75-100 uM AMP substrate with CD73 transfected 293T cells or recombinant human enzyme. Bleomycin (0.25 U, SubQ)-treated mice were treated with vehicle or Tenofovir (75mg/kg, IP) [n=5 per group]. Skin breaking strength was measured using a tensiometer. Histologic samples of H&E or picrosirus red-stained slides were imaged, and pixel quantification was performed with SigmaScan software. Scar index was determined as the ratio of red/green pixels representing compact/filamentous fibers; higher numbers indicate more fibrosis. Dermal hydroxyproline content was quantified by colorimetric assay.
Results: In silico modeling data suggested that both adefovir and tenofovir bound to the enzymatic pocket of CD73. Tenofovir, but not adefovir, inhibited CD73 activity of 293T cells overexpressing CD73 (38+7.4%, at 10 uM) and of recombinant enzyme (72+1.0%, at 10uM). Tenofovir (75mg/kg) diminished bleomycin-induced dermal fibrosis in bleomycin-treated mice (73.7+3.1% reduction of hydroxyproline content [p<0.05]; 33.5+3.8% reduction of dermal thickness [p<0.06] and reduction of breaking tension by 66.8+1.4% [p<0.05]). Picrosirius red staining showed dramatic altering of collagen quality (scar index of 1.2+0.1 vs 22.2+0.7 [p<0.001], normal skin is 2.5).
Conclusion: These results provide strong support to the hypothesis that Tenofovir reduces fibrosis via inhibition of adenosine production from AMP by CD73. Moreover, these results suggest that tenofovir may have therapeutic potential in treating fibrosis in patients suffering from non-viral fibrosing diseases such as scleroderma.
J. L. Feig,
B. N. Cronstein,
NIH, URL Pharma, OSI,
Bristol-Myers Squibb, Novartis, URL, Regeneron, Gismo Therapeutics,
Arthritis Foundation, SLE Foundation,
Patents on use of adenosine receptor antagonists to treat or prevent fibrosis. Multiple other patents.,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tenofovir-a-potent-anti-viral-agent-is-an-ecto-5nucleotidase-cd73-inhibitor-that-prevents-dermal-fibrosis-in-a-murine-model-of-scleroderma/