Protein Palmitoylation Contributes to Extracellular Vesicle Production and Effect on Vascular Barrier Dysfunction during Systemic Inflammation

Abstract

Extracellular vesicles (EVs) are membrane‐encapsulated particles released from various types of cells, ranging from 30–1000 nm in diameter. EVs facilitate intercellular communication by transferring proteins and lipid among cells not in direct contact. Recent studies suggest the involvement of EVs in the progression of systemic inflammatory response syndrome (SIRS) associated with trauma or infection. However, there is limited information about EV production, cargo content, or pathological function in systemic inflammation. Protein palmitoylation, the covalent attachment of palmitic acid to cysteine residues, catalyzed by a family of palmitoyl acyltransferases containing a zinc finger aspartate‐histidine‐histidine‐cysteine (DHHC) motif. Palmitoylation has recently been recognized as a novel signaling mechanism in regulating endothelial barrier function and microvascular permeability. In this study, we sought to examine whether protein palmitoylation affects EV production or function in microvascular barrier in response to systemic inflammation. EVs were isolated from the blood of wild‐type (WT) and DHHC21 deficient (Zdhhc21dep/dep) mice with SIRS. Nanoparticle tracking analysis showed an increased plasma level of EVs in WT mice subjected to SIRS compared to sham‐treated, but this response was diminished in Zdhhc21dep/dep mice. Next, isolated EVs from SIRS mice were injected into healthy mice intravenously to assess their effects on microvascular permeability. Intravital microscopic imaging analysis revealed that SIRS EVs from WT mice caused a massive leakage of plasma albumin into extravascular space, whereas SIRS EVs from Zdhhc21dep/dep mice produced less leakage. Furthermore, we examined the cargo contents of EVs produced during SIRS and identified an array of pro‐inflammatory molecules, including C‐reactive protein, interleukins and tumor necrosis factor‐a. Of particular note, SIRS EVs contained a high level of histones, which has been implicated in endothelial barrier injury. Such an EV profile was not observed in EVs from Zdhhc21dep/dep mice. Taken together, these data suggest systemic inflammation stimulates the production of pro‐inflammatory EVs that are capable of inducing microvascular leakage. This response is greatly attenuated in Zdhhc21 functional deficiency, indicating the involvement of palmitoylation in EV production or function.Support or Funding InformationThis work was supported by the National Institutes of Health Grants GM097270, HL070752, and HL126646.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.