Pulmonary edema in acute opioid intoxication: the role of AQP1

Pulmonary edema is the most frequently observed macroscopic finding in autopsies of acute opioid intoxication. However, its underlying pathogenic mechanisms remain unclear and are still under debate. Some opioids can directly modulate aquaporins (AQPs), membrane proteins that regulate intra- and extracellular water flux and play a key role in maintaining osmotic homeostasis. This study aims to investigate, in a forensic case series of acute opioid intoxication deaths (heroin, morphine, and methadone), the potential role of pulmonary endothelial AQP1 expression in the development of pulmonary edema. Fourteen deaths due to opioid intoxication and fourteen control subjects who died from violent or natural causes without opioid intake were examined; among controls, seven deaths were related to neurogenic shock and seven to cardiogenic shock. Our results showed an overall inverse relationship between pulmonary edema severity and AQP1 expression, with lower AQP1 levels corresponding to greater edema severity. However, compared with controls, subjects who died from acute opioid intoxication tended to maintain relatively higher pulmonary AQP1 expression across increasing degrees of edema severity. In fact, the data analysis revealed that only with severe pulmonary edema (grades 3 or 4, based on hematoxylin-eosin staining) was AQP1 expression significantly higher in subjects who died from acute opioid intoxication compared to controls. This modulation of AQP1 in severe opioid-related pulmonary edema may have important clinical implications for understanding disease progression and mechanisms of pulmonary pathology exacerbation.