The Effect of an Adenosine A3 receptor (A3AR) Agonist in a Preclinical Model of Migraine-like Periorbital Allodynia

Editor’s note: The research described below comes from a recipient of a 2023 MSC Travel Grant supporting travel to the 65th Annual Scientific Meeting of the American Headache Society. These grants reimburse travel expenses for those who have had their abstract for a presentation or poster accepted at a meeting.

By Paula Sureda-Gibert, PhD, research postdoctoral fellow, University of Maryland Baltimore, US.

What is the research gap that your study addresses?

Despite recent advances with new migraine therapies, there remains a huge proportion of patients still unresponsive or unable to use existing therapeutics. The adenosine A3 receptor (A3AR) may represent a novel and safe targeted approach. Recent studies demonstrate that highly selective A3AR agonists are effective in preclinical models of neuropathic pain, by attenuating a neuroinflammatory signalling cascade involving the glial production of peroxynitrite (PN), a pro-nociceptive molecule. The role of A3AR in migraine-related trigeminal nociception is unknown. As such, our study investigated the potential efficacy of a novel A3AR agonist, MRS5980, in migraine-associated behaviors.

What is your research hypothesis?

We hypothesized that the novel A3AR agonist, MRS5980, is able to prevent and abort the development of migraine-associated behavioral nociceptive phenotypes in a chronic nitroglycerin (NTG) migraine model.

What methodology did you use to address your research hypothesis? 

Male and female C57/bl6 mice were chronically treated for 9 days (5 doses given every other day) with NTG (10 mg/kg, IP). We conducted a dose-response preventive protocol using the highly selective A3AR agonist, MRS5980 (0.1, 0.3 or 1 mg/kg, n=8 per sex/group), given chronically for 11 days from the first day of NTG dosing. Periorbital mechanical sensitivity was tested by probing with von Frey filaments every 3-4 days until day 12, calculated using the UP-DOWN Reader (UDReader). Control groups included saline alone and NTG alone. We also conducted a reversal protocol with MRS5980, topiramate, or vehicle given on days 7-11, after NTG-mediated periorbital hypersensitivity was established.

What are the main results of your study?

Chronic NTG induced persistent periorbital allodynia in female and male mice over 12 days. This was dose-dependently inhibited by preventive treatment with MRS5980, with the highest dose (1 mg/kg) preventing the development of periorbital allodynia. Lower doses of MRS5980 showed a significant decrease in periorbital mechanical sensitivity through days 5-12 in both sexes suggesting they are not able to prevent or attenuate NTG-induced allodynia. In both females and males, MRS5980 (1 mg/kg) also prevented the acute effects of NTG on periorbital thresholds over 5 hours on the first day, whereas lower doses of MRS5980 did not prevent the acute action of NTG.

What conclusions did you reach based on your results?

These results highlight the promising therapeutic effects of targeting A3AR, using a highly selective agonist, in an NTG-mediated preclinical model of migraine. The highest dose of MRS5980, 1 mg/kg, was the most effective by fully preventing the development of NTG-induced periorbital mechanical sensitivity in both females and males.

What are the limitations of your study?

To fully validate A3AR as a potentially novel and efficacious target in the treatment of migraine, further studies are required using additional preclinical models (medication-overuse headache). In addition, further work is required to dissect the neuronal and glial mechanisms in the therapeutic mode of action of A3AR agonists. This study would also benefit from a direct comparison with other acute and preventive treatments available in the clinic to fully establish its therapeutic benefit over other currently available therapies.

What is the relevance of your study to migraine?

The outcome of this study represents a novel translational approach to treat migraine and migraine-like headache disorders, using already-developed A3AR agonists that have been safely trialled in humans. Our findings suggest a great therapeutic effect and also opens an avenue of research to understanding how this target modulates both known and novel pathophysiological mechanisms of action. The results of this work are key to accelerate A3AR agonists to clinical trials for migraine treatment as development programs are ongoing for non-pain conditions, and these have already demonstrated A3AR to be safe and well tolerated.