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Acid Sphingomyelinase Inhibition Attenuates Cell Death in Mechanically Ventilated Newborn Rat Lung
Behzad Yeganeh1, Joyce Lee1,2, Claudia Bilodeau1,3
11 Translational Medicine Program, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
Mechanical ventilation causes lung injury in premature infants by inducing autophagy and apoptosis. Inhibiting sphingomyelin phosphodiesterase 1 (SMPD1) reduces this cell death, offering a potential therapeutic target for ventilation-induced lung injury.
Area of Science:
- Neonatal physiology
- Cellular biology
- Pulmonary medicine
Background:
- Mechanical ventilation (MV) is crucial for premature infants but can cause lung injury, leading to bronchopulmonary dysplasia.
- MV-induced lung injury involves epithelial cell death and impaired alveolar development, with the precise mechanisms remaining unclear.
Purpose of the Study:
- To investigate the role of autophagy in mechanical ventilation-induced epithelial cell death in newborn rat lungs.
- To identify molecular pathways and potential therapeutic targets for ventilation-induced lung injury.
Main Methods:
- Newborn rat lungs and fetal rat lung epithelial (FRLE) cells were subjected to mechanical ventilation and cyclic stretch, respectively.
- Analysis included immunoblotting and mass spectrometry to assess autophagy, apoptosis, and bioactive sphingolipids.
- Sphingomyelin phosphodiesterase 1 (SMPD1) inhibition was used to evaluate its role in the observed cellular processes.
Main Results:
- Mechanical ventilation and cyclic stretch induced a sequential process of autophagy followed by apoptosis in lung epithelial cells.
- Elevated ceramide levels, particularly C16 ceramide, were observed, and their administration mimicked MV-induced autophagy and apoptosis.
- Inhibition of SMPD1 blocked ceramide production, autophagy, apoptosis, and cell death, both in vitro and in vivo.
Conclusions:
- Ventilation-induced ceramides drive autophagy-mediated cell death in the lungs.
- Sphingomyelin phosphodiesterase 1 (SMPD1) is a key mediator of this process and represents a potential therapeutic target for preventing ventilation-induced lung injury in newborns.
Rationale:
Premature infants subjected to mechanical ventilation (MV) are prone to lung injury that may result in bronchopulmonary dysplasia. MV causes epithelial cell death and halts alveolar development. The exact mechanism of MV-induced epithelial cell death is unknown.
Objectives:
To determine the contribution of autophagy to MV-induced epithelial cell death in newborn rat lungs.
Methods:
Newborn rat lungs and fetal rat lung epithelial (FRLE) cells were exposed to MV and cyclic stretch, respectively, and were then analyzed by immunoblotting and mass spectrometry for autophagy, apoptosis, and bioactive sphingolipids.
Measurements And Main Results:
Both MV and stretch first induce autophagy (ATG 5-12 [autophagy related 5-12] and LC3B-II [microtubule-associated proteins 1A/1B light chain 3B-II] formation) followed by extrinsic apoptosis (cleaved CASP8/3 [caspase-8/3] and PARP [poly(ADP-ribose) polymerase] formation). Stretch-induced apoptosis was attenuated by inhibiting autophagy. Coimmunoprecipitation revealed that stretch promoted an interaction between LC3B and the FAS (first apoptosis signal) cell death receptor in FRLE cells. Ceramide levels, in particular C16 ceramide, were rapidly elevated in response to ventilation and stretch, and C16 ceramide treatment of FRLE cells induced autophagy and apoptosis in a temporal pattern similar to that seen with MV and stretch. SMPD1 (sphingomyelin phosphodiesterase 1) was activated by ventilation and stretch, and its inhibition prevented ceramide production, LC3B-II formation, LC3B/first apoptosis signal interaction, caspase-3 activation, and, ultimately, FLRE cell death. SMPD1 inhibition also attenuated ventilation-induced autophagy and apoptosis in newborn rats.
Conclusions:
Ventilation-induced ceramides promote autophagy-mediated cell death, and identifies SMPD1 as a potential therapeutic target for the treatment of ventilation-induced lung injury in newborns.
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