Temporal Aquaporin Expression Profiles in Immune Cell Subsets During Critical Illness.

Aquaporins (AQPs) are a family of water channel proteins with a significant role in immune cell function. Although AQPs have been studied in sepsis, their expression in critical illness remains underexplored. Our group aimed to examine the mRNA expression profile of AQP isoforms in polymorphonuclear leukocytes (PMNs) and peripheral blood mononuclear cells (PBMCs) of critically ill patients admitted to the intensive care unit (ICU). To this end, we designed a prospective, longitudinal, observational study performed in the ICU of "Evangelismos" General Hospital between February 2024 and October 2024. In total, 40 critically ill patients and 25 healthy controls were enrolled in the study. Blood samples were collected at four time points: upon ICU admission (24-48 hours), and at days 4 (D4), 8 (D8), and 14 (D14). Total RNA was extracted from PMNs and PBMCs, and RT-qPCR was performed to examine mRNA levels of AQPs 1, 2, 3, 4, 5, 7, and 9. Our results revealed downregulation of AQP isoforms, except AQP1, in PMNs, whereas PBMCs exhibited sustained upregulation of all AQPs except AQP3, which was downregulated. Our findings suggest that differential AQP expression in immune cell subsets may reflect adaptive immune responses during critical illness, providing insights into leukocyte function and potential therapeutic targets.