Variable stretch reduces the pro-inflammatory response of alveolar epithelial cells

Area of Science:

• Cellular Biology
• Respiratory Medicine
• Biomedical Engineering

Background:

• Mechanical ventilation can exacerbate lung inflammation.
• Variable ventilation strategies show promise in reducing lung inflammation in animal models.
• The underlying cellular mechanisms of variable ventilation's anti-inflammatory effects remain largely unknown.

Purpose of the Study:

• To investigate the effect of variable cyclic stretch on pro-inflammatory cytokine production in lipopolysaccharide (LPS)-stimulated alveolar epithelial cells (AECs).
• To elucidate the role of mitogen-activated protein kinase (MAPK) signaling pathways, specifically ERK1/2 and SAPK/JNK, in mediating the response to variable stretch.

Main Methods:

• AECs were subjected to non-variable or variable cyclic stretch with or without LPS stimulation.
• Cytokine mRNA expression (IL-6, CXCL-2, CCL-2) was analyzed after 4 hours.
• MAPK phosphorylation was assessed using Western Blot analysis at various time points.
• The impact of ERK1/2 and SAPK/JNK pathway inhibition on cytokine gene expression was evaluated.

Main Results:

• Variable cyclic stretch significantly reduced the expression and release of pro-inflammatory cytokines in LPS-stimulated AECs compared to non-variable stretch.
• Non-variable stretch increased ERK1/2 phosphorylation, while variable stretch maintained non-stretched levels.
• Inhibition of the ERK1/2 pathway reversed the anti-inflammatory effect of variable stretch, increasing cytokine gene expression.

Conclusions:

• Variable stretch reduces the pro-inflammatory response in LPS-stimulated AECs compared to non-variable stretch.
• The ERK1/2 signaling pathway is a key mediator of this anti-inflammatory effect.
• These findings provide a cellular basis for the lung-protective benefits of variable ventilation strategies.