William V. Everson

Cholesteryl ester is transported from caveolae to internal membranes as part of a caveolin-annexin II lipid-protein complex

This article has been retracted by the publisher. An investigation by the Office of Research Integrity determined that falsified and/or fabricated Western blots were included in Figs. 5 and 7 (https://federalregister.gov/a/2012-28209). THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 288, NO. 9, p. 6586, March 1, 2013

The role of caveolae and caveolin in vesicle-dependent and vesicle-independent trafficking

Caveolae can mediate endocytosis, transcytosis, and potocytosis. Our understanding of these processes as well as the elucidation of the molecular machinery involved has greatly expanded. In addition, caveolin, a 22 kDa protein often associated with caveolae, can promote the trafficking of sterol through the cytoplasm independent of vesicles. Caveolin also influences the formation, morphology, and function of caveolae. The ability of caveolae and caveolin to mediate macromolecular transport directly impacts a variety of physiological and pathophysiological processes.

Influence of Caveolin, Cholesterol, and Lipoproteins on Nitric Oxide Synthase Implications for Vascular Disease

Caveolin-1 traffics cholesterol between the endoplasmic reticulum and cell surface caveolae in a non-vesicle chaperone complex which contains heat shock protein 56, cyclophilin 40, and cyclophilin A. Recent studies demonstrate that endothelial nitric oxide synthase (eNOS), caveolin, hetero-trimeric G-protein coupled receptors, and a calcium channel form an activation complex that is associated with cholesterol-rich caveolae. Oxidized LDL depletes caveolae of cholesterol and prevents agonist stimulation of eNOS by disrupting the activation complex. HDL antagonizes the effects of oxLDL by donating cholesterol to caveolae, thereby preserving the structure and function of caveolae. These findings and others provide a possible mechanistic basis for some of the molecular changes observed in vascular disease.

Proteomic characterization of lipid raft proteins in amyotrophic lateral sclerosis mouse spinal cord

Familial amyotrophic lateral sclerosis (ALS) has been linked to mutations in the copper/zinc superoxide dismutase (SOD1) gene. The mutant SOD1 protein exhibits a toxic gain‐of‐function that adversely affects the function of neurons. However, the mechanism by which mutant SOD1 initiates ALS is unclear. Lipid rafts are specialized microdomains of the plasma membrane that act as platforms for the organization and interaction of proteins involved in multiple functions, including vesicular trafficking, neurotransmitter signaling, and cytoskeletal rearrangements. In this article, we report a proteomic analysis using a widely used ALS mouse model to identify differences in spinal cord lipid raft proteomes between mice overexpressing wild‐type (WT) and G93A mutant SOD1. In total, 413 and 421 proteins were identified in the lipid rafts isolated from WT and G93A mice, respectively. Further quantitative analysis revealed a consortium of proteins with altered levels between the WT and G93A samples. Functional classification of the 67 altered proteins revealed that the three most affected subsets of proteins were involved in: vesicular transport, and neurotransmitter synthesis and release; cytoskeletal organization and linkage to the plasma membrane; and metabolism. Other protein changes were correlated with alterations in: microglia activation and inflammation; astrocyte and oligodendrocyte function; cell signaling; cellular stress response and apoptosis; and neuronal ion channels and neurotransmitter receptor functions. Changes of selected proteins were independently validated by immunoblotting and immunohistochemistry. The significance of the lipid raft protein changes in motor neuron function and degeneration in ALS is discussed, particularly for proteins involved in vesicular trafficking and neurotransmitter signaling, and the dynamics and regulation of the plasma membrane‐anchored cytoskeleton.

Azithromycin Protects Against Hyperoxic Lung Injury in Neonatal Rats

Bronchopulmonary dysplasia (BPD) is a pulmonary disorder that causes significant morbidity and mortality in premature infants. BPD is pathologically characterized by inflammation, fibrosis, and mucosal necrosis, which leads to emphysematous coalescence of alveoli. We tested the hypothesis that azithromycin, a macrolide antibiotic, would decrease the severity of lung injury in an animal model of BPD. Sixty-three rat pups were randomly divided equally into control, hyperoxia, and hyperoxia plus azithromycin groups. The hyperoxia groups were exposed to > 95% oxygen from days of life 4 to 14. On day 14, the animals were processed for lung histology and tissue analysis. Lung morphology was assessed by mean linear intercept, a measure of alveolar size, with larger values corresponding to lungs that are more emphysematous. The degree of lung inflammation was assessed by quantifying interleukin-6 (IL-6) from lung homogenate. Fifty pups survived to day 14 (control = 21, hyperoxia = 11, hyperoxia + azithromycin = 18). Mortality was increased in the hyperoxia group versus the control group (p < .0001). Treatment with azithromycin improved survival in animals subjected to hyperoxia (p < .05). Azithromycin significantly decreased lung damage as determined by the mean linear intercept in the hyperoxia groups (p < .001). Finally, azithromycin-treated pups had lower levels of IL-6 in lung homogenate from the hyperoxia groups (p < .05). Azithromycin treatment resulted in improved survival, less emphysematous change, and decreased IL-6 levels in an animal model of BPD.

Nitric oxide, caveolae, and vascular pathology.

Endothelial nitric oxide synthase (eNOS) is an enzyme that plays a critical role in normal cardiovascular function. Caveolae are structures within the surface membrane of cells in which many signaling and second messenger pathways, including nitric oxide, are regulated. Many interventions in cardiovascular disease act, in part, either by changing factors that directly influence eNOS, or by changing a complex set of proteins that act indirectly on caveolae, to alter eNOS activity. In this review, we will focus on the regulation of eNOS activity by circulating factors which are altered in cardiovascular disease and the effects of pharmacological interventions that act partially through effects on eNOS.

Estrogen in cardiovascular disease.

Purpose of review The controversy surrounding hormone replacement therapy has induced fear in patients and left many researchers with the impression that estrogen produces negative effects on cardiovascular function. The aim of this review is to summarize recent findings illustrating that estrogen also has positive effects even if estrogen replacement therapy is not a cure-all. Recent findings Studies have unveiled new aspects of estrogen action in the cardiovascular system; however, clinical trials have not demonstrated a protective effect of the most widely used modalities of hormone replacement therapy against cardiovascular disease. New information has emerged showing that estrogen has both beneficial and detrimental effects. Further mechanistic studies and use of well defined forms of estrogens and selective estrogen receptor modulators will continue to provide novel mechanistic information that will likely lead to the development of new avenues for therapeutic interventions. Summary Estrogens, like other steroid hormones, are potent actors in the cardiovascular system. Since half the population have high levels of estrogen most of their lives it is plain that estrogen has a variety of beneficial physiologic functions. Clinical studies, however, have demonstrated that a specific formulation of a combination of potent estrogens and metabolites is not a magic bullet, but induces both positive and negative impacts on different organ systems. More research into the mechanistic actions of estrogens in specific pathways in individual cell types is necessary to determine appropriate therapeutic interventions to replace the loss of positive effects of estrogens while minimizing the negative effects in postmenopausal women.

Chapter 2 Caveolae and the Regulation of Cellular Cholesterol Homeostasis

Publisher Summary This chapter refers lipid rafts to as regions of membranes enriched in cholesterol and sphingolipids, whether these domains are localized in the plasma membrane or within intracellular membranes. The term caveolae is used to refer to a specialized subset of lipid rafts identified by the presence of the marker protein caveolin-1. This chapter examines the organization of lipid rafts and caveolae and their associated tracking pathways, and the role cholesterol plays in modifying the distribution, stability, and functions of these domains. The diversity of tracking pathways that initiate at caveolae and lipid rafts, as well as the variety of vesicle and non-vesicle pathways that provide transport and communications between these cell surface domains and multiple intracellular sites, indicates that there is no single prototypical pathway or cell type that represents all caveolae/lipid rafts. It is apparent that the structure and organization of lipid rafts in cells are as diverse and varied as the many functions that are associated with these structures. The cell requires a multiplicity of communication pathways in order to integrate its many responses to the wide variety of hormones, nutrients, and circulating factors that activate signal propagation and tracking within the cell.

Impact of 2,3,7,8-tetrachlorodibenzo-p-dioxin on cutaneous wound healing

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a representative of a large group of polyhalogenated aromatic hydrocarbons that are widespread environmental contaminants. Administration of TCDD to laboratory animals or cultured cells results in a number of adverse effects that are well documented. For example, the effects of TCDD observed in developing organisms indicate that exposure to this class of environmental contaminants significantly alters embryo morphogenesis. However, it is not clear whether tissue regeneration in adult animals may be similarly affected. With this in mind, we examined the impact of TCDD exposure on wound healing using a murine cutaneous wound healing model. Our results indicate that TCDD exposure did not significantly alter the time needed for wound closure. However, in the TCDD-treated mice, a significant decrease in tensile strength in the healed wounds was observed which is indicative of an aberrantly healed wound. Immunostaining revealed that exposure to TCDD increased the population of macrophages detected within the wounded tissue at the latter stages of wound healing. Our findings support the idea that exposure to environmental contaminants such as TCDD is proinflammatory in the wounded tissue, disrupts normal healing and ultimately produces in a poorly healed wound.

The Pharmacology of Caveolae

Based on work in the last 15 years, caveolae are now recognized as rather complex and dynamic plasma membrane domains with important roles in cellular uptake of molecules, signal transduction, lipid homeostasis, and tumorigenesis. Functionally, caveolae orchestrate very specific events in distinct cell types, thereby making these organelles one of the most interesting compartments in cells. In this chapter, we will discuss the salient features of these active cellular domains. We begin with a general introduction to the biochemistry and cell biology of caveolae, describe some of the myriad signaling events that initiate in caveolae (or traffic through caveolae) and how they can go awry in cancer, describe how caveolar proteins can be exploited for novel drug discovery, and finally provide commentary over a growing body of evidence that suggests how molecules are presented to caveolae makes a difference in the pharmacological effects that ensue.