Ceramide mediates acute oxygen sensing in vascular tissues

Area of Science:

• Cardiovascular Physiology
• Molecular Biology
• Biochemistry

Background:

• Specialized vascular tissues, including pulmonary arteries (PA) and the ductus arteriosus (DA), possess unique oxygen-sensing capabilities.
• Hypoxic pulmonary vasoconstriction (HPV) and normoxic DA contraction involve shared mechanistic pathways despite opposing stimuli.
• Neutral sphingomyelinase (nSMase) activation and subsequent ceramide production are implicated in HPV.

Purpose of the Study:

• To investigate the role of nSMase-derived ceramide as a common mediator in the acute oxygen-sensing function of specialized vascular tissues.
• To explore the mechanistic link between ceramide production and oxygen-induced vasoconstriction in PA, fetoplacental arteries, and DA.

Main Methods:

• Inhibition of nSMase activity using GW4869 and anticeramide antibodies in isolated chicken PA, chorioallantoic arteries (CA), and DA.
• Gene silencing of SMPD3 using interference RNA to assess its role in HPV.
• Measurement of ceramide and reactive oxygen species (ROS) production under varying oxygen conditions.
• Pharmacological mimicry of oxygen-induced responses using bacterial sphingomyelinase or exogenous ceramide.
• Electrophysiological assessment of voltage-gated potassium currents in smooth muscle cells.
• Validation of findings in human PA and DA samples.

Main Results:

• nSMase inhibition and anticeramide antibodies attenuated hypoxic vasoconstriction in PA/CA and normoxic contraction in DA.
• SMPD3 silencing inhibited HPV.
• Hypoxia increased ceramide and ROS in PA, while normoxia increased them in DA.
• Exogenous sphingomyelinase or ceramide replicated the contractile responses to hypoxia (PA/CA) and normoxia (DA).
• Ceramide was found to inhibit voltage-gated potassium currents in PA and DA smooth muscle cells.
• The nSMase pathway was confirmed in human PA and DA.

Conclusions:

• Ceramide generation, mediated by nSMase, is a critical component of acute oxygen sensing in specialized vasculature.
• This pathway contributes to vasoconstrictor responses to both hypoxia (PA, CA) and normoxia (DA).
• The findings suggest a conserved molecular mechanism for oxygen-dependent vascular tone regulation across different species and vascular beds.