Compositional changes in lipid microdomains of air-blood barrier plasma membranes in pulmonary interstitial edema

Abstract

We evaluated in anesthetized rabbits the compositional changes of plasmalemmal lipid microdomains from lung tissue samples after inducing pulmonary interstitial edema (0.5 ml/kg for 3 h, leading to approximately 5% increase in extravascular water). Lipid microdomains (lipid rafts and caveolae) were present in the detergent-resistant fraction (DRF) obtained after discontinuous sucrose density gradient. DRF was enriched in caveolin-1, flotillin, aquaporin-1, GM1, cholesterol, sphingomyelin, and phosphatidylserine, and their contents significantly increased in interstitial edema. The higher DRF content in caveolin, flotillin, and aquaporin-1 and of the ganglioside GM1 suggests an increase both in caveolar domains and in lipid rafts, respectively. Compositional changes could be ascribed to endothelial and epithelial cells that provide most of plasma membrane surface area in the air-blood barrier. Alterations in lipid components in the plasma membrane may reflect rearrangement of floating lipid platforms within the membrane and/or lipid translocation from intracellular stores. Lipid traffic could be stimulated by the marked increase in hydraulic interstitial pressure after initial water accumulation, from approximately -10 to 5 cmH2O, due to the low compliance of the pulmonary tissue, in particular in the basement membranes and in the interfibrillar substance. Compositional changes in lipid microdomains represent a sign of cellular activation and suggest the potential role of mechanotransduction in response to developing interstitial edema.

Molecular Mechanisms and Drug Development in Aquaporin Water Channel Diseases: The Translocation of Aquaporin-5 From Lipid Rafts to the Apical Plasma Membranes of Parotid Glands of Normal Rats and the Impairment of It in Diabetic or Aged Rats

“…These results are supported by the report that AQP5 was detected in the Rab4-containing intracellular membrane fraction located in the subapical region of rat parotid glands (21). Although it was reported that AQP5 is not located in lipid rafts of lung (22), AQP1 is located in a particular subtype of lipid rafts called caveolae, which are plasmalemmal vesicles in lung (23) and Fig. 1.…”

Membrane lipid domains and membrane lipid domain preparations: are they the same thing?

“…As mentioned above, the Brown and Rose method or its modiˆcations have been applied not only to cultured cells but also to various tissues, including chicken gizzard smooth muscle (64), mouse (67), rat and human (93,146) cerebral cortex, mouse (66,(147)(148)(149)(150)(151), rat (21,65,(152)(153)(154) and human (155) brain, rat cerebellum (152), bovine and mouse brain myelin (71,75,149,156), rat (157) and mouse (92) brain synaptosomes, rat (158), mouse (148) and rainbow trout (159) liver, rat (160), rabbit (161) and mouse (148) lung, rat lung endothelium (162), pig (67,70) and mouse kidney (148). However, additional care is necessary to evaluate the results obtained analyzing DRM prepared from tissues.…”

The differential protein and lipid compositions of noncaveolar lipid microdomains and caveolae

“…For example, T-cadherin is reported as a caveolae-associated protein in one study and as a lipid raft-associated protein in another study [37,38]. Aquaporin-1, Thy-1, IGF-1 receptor and N-cadherin, which are reported to co-fractionate with caveolin-1 [5,20,[21][22][23][24][25], are actually noncaveolar lipid microdomain-associated proteins ( Figure 2D). Thus, this modified sucrose density gradient provides a better technique with which to study caveolae.…”

“…Many lipid microdomain-associated proteins, such as Thy-1 (GPI-AP, glycosylphosphatidylinositol-anchored protein) [21], N-cadherin (membrane glycoprotein) [22,23], aquaporin-1 (membrane [24,25], IGF-1 receptor (membrane tyrosine kinase receptor) [5,20] and c-Yes (inner-membrane lipid-tethered protein) [18], were actually associated with noncaveolar lipid microdomains ( Figure 2D). Flotillin-1, a structural protein in membrane lipid microdomains [19], was associated with caveolae ( Figure 2D).…”