Sepsis impairs alveolar epithelial function by downregulating Na-K-ATPase pump

Area of Science:

• Pulmonary Medicine
• Sepsis Pathophysiology
• Cellular Biology

Background:

• Sepsis commonly causes multiorgan dysfunction, with vascular endothelial injury being a primary driver.
• Increased alveolar capillary permeability leads to fluid accumulation and acute respiratory distress syndrome (ARDS).
• The specific role of the alveolar epithelium in early sepsis-induced lung injury remains less understood.

Purpose of the Study:

• To investigate the impact of sepsis on alveolar fluid clearance (AFC) in a rat model.
• To examine the expression and localization of Na-K-ATPase proteins in alveolar epithelial cells during early sepsis.
• To determine the contribution of alveolar epithelial dysfunction to lung fluid accumulation in sepsis.

Main Methods:

• Sepsis was induced in rats via cecal ligation and puncture.
• Alveolar fluid clearance was measured using an isolated perfused rat lung model at 24 and 48 hours post-sepsis.
• Expression and abundance of Na-K-ATPase proteins in alveolar type II (ATII) cells and basolateral membranes (BLM) were analyzed.

Main Results:

• AFC was significantly reduced in septic rats compared to controls at both 24 and 48 hours.
• Amiloride further decreased AFC in sepsis, while isoproterenol partially reversed this inhibition.
• While Na-K-ATPase expression in whole ATII cells was unchanged, its abundance in the BLM of ATII cells was significantly decreased in septic rats.
• The alveolar-capillary barrier remained intact, suggesting protein-poor fluid accumulation.

Conclusions:

• Early sepsis significantly reduces alveolar fluid clearance in rats, independent of ARDS development.
• The decrease in AFC is linked to reduced Na-K-ATPase abundance in the basolateral membrane of alveolar epithelial cells.
• This dysfunction may result from endocytosis of Na-K-ATPase, inhibiting active sodium transport and contributing to lung fluid imbalance in early sepsis.