OnabotulinumtoxinA alters pro- and anti-inflammatory dural macrophage response to CSD in female mice

Aim Cortical spreading depression (CSD), the neural correlate of migraine aura, has been shown to cause activation of dural nociceptive neurons as well as immune cells, among which macrophages (MPs) are the most abundant and reactive. OnabotulinumtoxinA (onbotA) is used to treat chronic migraine but the mechanism of action is not fully understood. Here we investigate the role of meningeal MPs in a model of migraine activation and evaluate whether onabotA has an effect on their response. Methods We use our previously developed method to determine meningeal MP activation based on shape changes using time-lapse in vivo multiphoton microscopy. Results We found that a small subset (∼10%) of MPs contracted their processes in response to CSD induction, but only in female mice. A similar subset of MPs contracted with lipopolysaccharide injection, suggesting that this is an M1-like response. Together this may provide insight into the phenotypic differences of migraine across males and females. We also found a small subset of MPs (∼10%) that expanded their processes in response to IL-10 (presumably an M2-like response), but were not affected by CSD. In female mice, pre-treatment with onabotA (i) reduces overall MP number in the dura, (ii) reduces pro-inflammatory M1 MP response and (iii) increases anti-inflammatory M2 response post-CSD compared to pretreatment with saline. Conclusion This suggests that the mechanism of action of onabotA may not be simply due to its effects on nociceptors, but also due to an additional anti-inflammatory effect on the environment of the dura.