Endothelial Poldip2 regulates sepsis-induced lung injury via Rho pathway activation

Area of Science:

• Molecular Biology
• Immunology
• Pathophysiology

Background:

• Sepsis-induced lung injury (SIL) contributes significantly to patient morbidity and mortality.
• Endothelial barrier disruption is a primary mechanism driving SIL.
• Previous studies indicated heterozygous deletion of polymerase delta-interacting protein 2 (Poldip2) confers protection against SIL.

Purpose of the Study:

• To investigate whether the protective effects of reduced Poldip2 against SIL are specifically mediated by endothelial Poldip2.
• To elucidate the role of endothelial Poldip2 in sepsis-induced inflammatory responses and barrier integrity.

Main Methods:

• Utilized endothelial-specific Poldip2 knock-out (EC-/-) and wild-type (EC+/+) mice models challenged with lipopolysaccharide (LPS) to simulate sepsis.
• Assessed leukocyte infiltration in bronchoalveolar lavage (BAL) fluid and lung tissue.
• Quantified inflammatory gene expression (TNFα, IκBα), neutrophil chemoattractant genes (CXCL1, CXCL2), and endothelial activation markers (VCAM1) via qPCR.
• Employed an in vitro model with human pulmonary microvascular endothelial cells to evaluate Poldip2 knockdown effects on permeability and VE-cadherin expression using siRNA.

Main Results:

• Poldip2 EC-/- mice exhibited significantly reduced lung leukocyte infiltration and neutrophil counts compared to controls.
• Dampened induction of key inflammatory and endothelial activation genes was observed in Poldip2 EC-/- lungs.
• In vitro, Poldip2 knockdown markedly reduced TNFα-induced endothelial permeability and VE-cadherin disruption, linked to altered Rho-GTPase signaling and reduced RhoA activation.

Conclusions:

• Endothelial Poldip2 plays a critical role in mediating endothelial dysfunction during sepsis-induced lung injury.
• Targeted inhibition of endothelial Poldip2 demonstrates significant protective effects against lung inflammation and barrier compromise.
• Endothelium-specific Poldip2 inhibition represents a promising therapeutic strategy for managing sepsis-induced lung injury.