Membrane switch hypothesis. 2. Domain structure of phagocytes in horses with recurrent airway obstruction.

The researchers investigated the mechanism behind recurrent airway obstruction (RAO) in horses by studying the membrane structure and oxidative activities in horse phagocytes, finding differences between healthy and RAO horses.

Understanding Membrane Domain Structure and Oxy-Redoxy Activity

The researchers isolated phagocytes from bronchoalveolar lavage fluid (BAL) and the blood of both healthy horses and those with RAO. In this context, phagocytes are a type of white blood cell that can engulf and absorb harmful particles or bacteria.

• The membrane domain structure and oxy-redoxy activity were then measured using electron paramagnetic resonance (EPR), a technique used to study chemical species with unpaired electrons.

Differences in Antioxidant Enzymes Activity

The researchers observed differences in the activities of certain intracellular antioxidant enzymes – CAT, GPx, and SOD – when comparing the phagocytes of healthy horses and those with RAO.

• These enzymes serve vital roles in protecting the cell from damage by reactive oxygen species.
• The activity levels in the phagocytes of RAO horses suggested oxidative stress, a harmful condition resulting from an imbalance between the production of reactive species and the body’s ability to counteract their harmful effects.

Comparisons of Reduction Mechanisms and Membrane Domain Structures

Further comparisons were made between reduction mechanisms and domain structures in the phagocytes of healthy horses and those with RAO.

• In healthy horses, the reduction mechanisms in BAL were faster and coincided with the merging of disordered membrane domains.
• However, in horses with RAO, both the reduction and the structure of the membrane domains remained unchanged.

The Role of Lipid Domain Merging

The team speculated that the merging of lipid domains observed in the phagocytes from the BAL of healthy horses could stimulate the formation of clusters of membrane proteins or ligands. If so, this could trigger the activation process in phagocytes of healthy horses and subsequently the normal response to stressors, likely a process hindered in the phagocytes of RAO horses.