Mast cell receptor linked to alcohol withdrawal-associated headaches

From a recent study published in NeuronResearchers are investigating the role of the mast cell-specific receptor Mas-related G protein-coupled receptor B2 (MrgprB2) in alcohol withdrawal-induced headaches and its potential as a therapeutic target.

Study: Mast cell-specific receptor mediates alcohol withdrawal-associated headache in male mice. Image credits: Syda Productions / Shutterstock.com

Background

Alcohol addiction affects 283 million people worldwide. Crises such as terrorism, economic hardship and the coronavirus (COVID-19) pandemic are increasing alcohol consumption and risky behavior.

Rehabilitation is essential; However, withdrawal headaches often limit recovery because many return to drinking. This worsens the addiction cycle and worsens quality of life.

Despite the urgency, effective treatments for withdrawal headaches are scarce. These headaches likely arise from the activation of trigeminal ganglia neurons and inflammation of the dura mater.

Mast cells in the dura mater, which release pro-inflammatory cytokines and are linked to the MrgprB2 receptor, are involved in withdrawal headache. Given the effect of alcohol on mast cells, understanding the role of MrgprB2 is crucial.

Further research is needed, given the increasing alcohol abuse and inadequate treatment of withdrawal symptoms.

About the study

The current study used several methods to investigate specific peptide and drug interactions in mice. Corticotropin-releasing factor (CRF) peptide, R-7050, phenyl-N-tert-butylnitrone (PBN), SB366791, and astressin were obtained and either prepared in synthetic interstitial fluid or 5% dimethyl sulfoxide (DMSO) for administration.

Behavioral tests, such as the von Frey test that assesses the mice’s sensitivity to touch and the open field test that observes their movements in an unknown environment, were performed with blinded observations.

For more invasive procedures, the mice underwent exposure surgery to the dorsal root ganglion (DRG) and trigeminal ganglion (TG). In vivo imaging followed DRG and TG Pirt-GCaMP3 calcium (Ca²⁺) levels in real time after surgery.

Approx²⁺ Imaging in human embryonic kidney 293 (HEK293) cells and mast cells provided insight into cellular responses to stimuli. Imaging of blood vessels and immunofluorescence in the dura mater provided additional insights into the physiological responses.

Additional techniques include analyzing dura mater responses to injected compounds and assessing CRF responses in specific cells. Western blotting and enzyme-linked immunosorbent assay (ELISA) were also used to quantify and analyze protein expression and interactions.

Findings of the study

Mice showed a remarkable preference for ethanol. Over three weeks, mice’s ethanol intake gradually increased, indicating that they developed ethanol dependence. However, this intake did not affect their food consumption or body weight. Interestingly, the absence of a specific receptor, MrgprB2, did not prevent the mice from developing this ethanol preference.

When wild-type mice were withdrawn from ethanol after consuming it for three or eight weeks, they showed hypersensitivity in the periorbital region for up to four days. Furthermore, their pain scores increased significantly 24 hours after quitting alcohol. Reduced exploratory behavior after alcohol withdrawal was also observed, which was in line with the avoidance of physical activity typically observed in migraine patients.

However, this behavior induced by alcohol withdrawal was absent in MrgprB2-deficient mice. Thus, mast cell-specific MrgprB2 likely plays a role in mediating behaviors associated with alcohol withdrawal-induced headaches.

The researchers also assessed the effects of ethanol withdrawal on the use of TG neurons empathize imaging. To this end, a significant increase in the number of activated TG neurons was observed in alcohol withdrawal mice compared to controls.

Ethanol consumption also had a modulatory effect on mast cell activities, including increasing degranulation. In the dura mater of mice consuming ethanol, there was an increase in both degranulated and total mast cells; however, this increase was abolished in the absence of MrgprB2. The activation of mast cells via MrgprB2 played an important role in the development of headache and pain behavior induced by alcohol withdrawal.

The researchers also investigated whether CRF played a role in the activation of MrgprB2 and subsequent mast cell degranulation. To this end, higher CRF levels were observed in the plasma and dura mater of mice undergoing alcohol withdrawal. CRF was also shown to induce degranulation in mouse mast cells, an effect that was absent in MrgprB2-deficient mice.

Alcohol withdrawal in mice also led to the sensitization of TG nerves by various stimuli, indicating that MrgprB2 is involved in this sensitization. Mice subjected to three to eight weeks of voluntary ethanol consumption showed hypersensitivity in the hind paw after alcohol withdrawal, an observation consistent with previous studies. However, the lack of MrgprB2 could not prevent this hypersensitivity.

Inhibiting the tumor necrosis factor alpha (TNF-α) receptor blocked alcohol withdrawal-induced mechanical allodynia. Alcohol withdrawal-induced headache was also associated with TNF-α and transient receptor potential channel V1 (TRPV1).

Taken together, these findings suggest that mast cell activation via MrgprB2 plays an important role in the headache and pain behaviors resulting from alcohol withdrawal.