Background

Neuroplasticity in the lungs is increasingly recognized as a pathological feature of asthma. Plasticity in efferent cholinergic airway neurons has been shown to occur in human asthma and to correlate with airway hyperresponsiveness. Despite being widely prescribed, little is known regarding the effects of synthetic glucocorticoids (sGC) on cholinergic neurons from the airways and whether this could halt the process of neuroplasticity.  

Methods

We applied a 50-day human pluripotent stem cell (hPSC) ? derived peripheral cholinergic neuron differentiation protocol and exposed these cells to different durations of dexamethasone treatment. We used FACS, RT-PCR, Ca+2 imaging and RNAseq to analyse the effects of dexamethasone exposure.

Results

We observed that dexamethasone exposure during the last 5 days of differentiation resulted in highest observable effects. Dexamethasone exposed neurons presented reduced Ca+2 signalling, paired with reduced gene expression of neurotrophin BDNF and its receptors TrkB and p75. Additionally, dexamethasone reduced the expression of cholinergic markers VAChT and M3R, pointing towards reduced differentiation. Analysis of RNAseq results showed that DEX treatment supressed several pathways related to synaptic formation, neuronal development, and extracellular matrix formation. The Ca+2 signalling related genes CACNA1E, CACNA1C, CACNA2D3, GMR5 and PKC? were found to be downregulated by dexamethasone.

Conclusion

We found that dexamethasone can reduce aspects of cholinergic neuronal development, synaptic formation, and Ca+2 signalling response. This suggests that sCGs might act on neurons of the airways, halting neuroplasticity before it is established.