Lipid cytotoxicity in shock may by mediated by lipid‐binding proteins

Abstract

Shock is accompanied by an increase in mucosal intestinal permeability, allowing digestive enzymes from the lumen to enter the intestinal wall. Incubating individual pancreatic proteases or homogenates of the luminal content with intestinal homogenates results in the generation of cytotoxic activity. Our goal is to characterize the factors in these intestinal digests that cause cytotoxicity. We hypothesize that in intestinal homogenates, lipases digest lipids into cytotoxic mediators [free fatty acids, etc.], which are adsorbed by lipid-binding proteins like albumin. Adding proteases would digest the proteins, releasing the mediators. Intestinal homogenates that had been exposed to chymotrypsin, the luminal content homogenate, or PBS were separated into hydrophilic, hydrophobic, and precipitated fractions using chloroform/methanol extraction. These fractions were tested for cytotoxicity. The hydrophilic and precipitated fractions caused little cell death, but the hydrophobic fractions from both digested and undigested intestinal homogenates caused significant cell death. A recombination of the hydrophilic and precipitated fractions with the hydrophobic fraction reduced cytotoxicity compared to hydrophobic fraction alone. We also show intestinal homogenates contain lipase activity and cell death from intestinal homogenate exposed to luminal homogenate is prevented by adding albumin. These results suggest that lipid-binding proteins may control lipid cytotoxicity, but during shock these protective proteins may be destroyed. Supported by HL67825.