Severe dyspnoea with alteration of the diffusion capacity of the lung associated with fingolimod treatment

Sphingosine-1-phosphate activates mouse vagal airway afferent C-fibres via S1PR3 receptors

KEY POINTS

Sphingosine-1-phosphate (S1P) strongly activates mouse vagal C-fibres in the airways. Airway-specific nodose and jugular C-fibre neurons express mRNA coding for the S1P receptor S1PR3. S1P activation of nodose C-fibres is inhibited by a S1PR3 antagonist. S1P activation of nodose C-fibres does not occur in S1PR3 knockout mice.

ABSTRACT

We evaluated the effect of sphingosine-1-phosphate (S1P), a lipid that is elevated during airway inflammatory conditions like asthma, for its ability to stimulate vagal afferent C-fibres in mouse lungs. Single cell RT-PCR on lung-specific vagal afferent neurons revealed that both TRPV1-expressing and TRPV1-non-expressing nodose neurons express mRNA coding for the S1P receptor S1PR3. TRPV1-expressing airway-specific jugular ganglion neurons also express S1PR3 mRNA. S1PR1 and S1PR2 mRNAs were also found to be expressed but only in a limited subset (32% and 22%, respectively) of airway-specific vagal sensory neurons; whereas S1PR4 and S1PR5 were rarely expressed. We used large scale two-photon imaging of the nodose ganglia from our ex vivo preparation isolated from Pirt-Cre;R26-GCaMP6s transgenic mice, which allows for simultaneous monitoring of calcium transients in ∼1000 neuronal cell bodies in the ganglia during tracheal perfusion with S1P (10 μM). We found that S1P in the lungs strongly activated 81.5% of nodose fibres, 70% of which were also activated by capsaicin. Single fibre electrophysiological recordings confirmed that S1P evoked action potential (AP) generation in a concentration-dependent manner (0.1-10 μM). Action potential generation by S1P in nodose C-fibres was effectively inhibited by the S1PR3 antagonist TY 52156 (10 μM). Finally, in S1PR3 knockout mice, S1P was not able to activate any of the airway nodose C-fibres analysed. These results support the hypothesis that S1P may play a role in evoking C-fibre-mediated airway sensations and reflexes that are associated with airway inflammatory diseases.

Multiple sclerosis treatment with fingolimod: profile of non-cardiologic adverse events

Fingolimod was the first oral medication approved for management of multiple sclerosis and is currently used by tens of thousands patients worldwide. Fingolimod acts via the sphingosine 1-phosphate (S1P) receptor, maintaining peripheral lymphocytes entrapped in the lymph nodes. In consequence, there is a reduction in the infiltration of aggressive lymphocytes into the central nervous system. The drug is safe and effective, and its first hours of use are associated with related to S1P receptors in the heart. This side effect is well known by all doctors prescribing fingolimod. However, the drug has other potential adverse events that, although relatively rare, require awareness from the neurologist. Among these there are infections (herpes simplex, herpes zoster, Cryptococcus, Epstein-Barr virus, hepatitis, Molluscum Contagiosum, and leishmaniosis), lung and thyroid complications, refractory headaches, encephalopathy, vasculopathy, tumefactive lesions in magnetic resonance imaging and ophthalmological disorders. The present review lists the non-cardiologic adverse events that all neurologists prescribing fingolimod should be aware of.