Disruption of Lipid Raft Function Increases Expression and Secretion of Monocyte Chemoattractant Protein-1 in 3T3-L1 Adipocytes

Abstract

The adipocyte is unique in its capacity to store lipids. In addition to triglycerides, the adipocyte stores a significant amount of cholesterol. Moreover, obese adipocytes are characterized by a redistribution of cholesterol with depleted cholesterol in the plasma membrane, suggesting that cholesterol perturbation may play a role in adipocyte dysfunction. We used methyl-β-cyclodextrin (MβCD), a molecule with high affinity for cholesterol, to rapidly deplete cholesterol level in differentiated 3T3-L1 adipocytes. We tested whether this perturbation altered adipocyte secretion of monocyte chemoattractant protein-1 (MCP-1), a chemokine that is elevated in obesity and is linked to obesity-associated chronic diseases. Depletion of cholesterol by MβCD increased MCP-1 secretion as well as the mRNA and protein levels, suggesting perturbation at biosynthesis and secretion. Pharmacological inhibition revealed that NF-κB, but not MEK, p38 and JNK, was involved in MβCD-stimulated MCP-1 biosynthesis and secretion in adipocytes. Finally, another cholesterol-binding drug, filipin, also induced MCP-1 secretion without altering membrane cholesterol level. Interestingly, both MβCD and filipin disturbed the integrity of lipid rafts, the membrane microdomains enriched in cholesterol. Thus, the depletion of membrane cholesterol in obese adipocytes may result in dysfunction of lipid rafts, leading to the elevation of proinflammatory signaling and MCP-1 secretion in adipocytes.

<p>COVID-19 and Obesity: Epidemiology, Pathogenesis and Treatment</p>

“…Moreover, it is also reported that lipid rafts facilitate virus replication. 57 Depletion of cholesterol, one of the main content of lipid rafts, significantly suppresses virus production. 58 This implies the importance of lipid in the development of virus infection and COVID-19.…”

Methyl-β-Cyclodextrin Impairs the Phosphorylation of the β2 Subunit of L-Type Calcium Channels and Cytosolic Calcium Homeostasis in Mature Cerebellar Granule Neurons

“…However, a link between cyclodextrins and iatrogenic hearing loss has been noted in several species, including humans [ 4 ]. In particular, methyl-β-cyclodextrin has been widely used for the selective removal of cholesterol and disruption of lipid rafts in different cell lines (see, e.g., [ 5 , 6 ]). The neurological risks of using methyl-β-cyclodextrin are informed by the reported toxicity of this compound to neuronal cell lines [ 7 ].…”

Cytoplasmic domain and enzymatic activity of ACE2 is not required for PI4KB dependent endocytosis entry of SARS-CoV-2 into host cells

“…Caveolae are small, flask-shaped invaginations in the plasma membrane composed of high levels of cholesterol and glycosphingolipids as well as the integral membrane protein caveolin(26). To determine whether SARS-CoV-2 enters cells through a caveolae-mediated pathway, we first treated cells with filipin or methyl-β-cyclodextrin (MβCD), both of which could disrupt the integrity of cholesterol-enriched membrane microdomains(27). Compared to control cells, uptake of cholera toxin subunit B (CTB), which has been reported to be internalized via caveolae-mediated endocytosis (28–30), was blocked at cell surface when cells were treated with filipin or MβCD (Fig S2), suggesting these drugs can block caveolae-mediated endocytosis.…”

“…Caveolae are small, flask-shaped invaginations in the plasma membrane composed of high levels of cholesterol and glycosphingolipids as well as the integral membrane protein caveolin (26). To determine whether SARS-CoV-2 enters cells through a caveolaemediated pathway, we first treated cells with filipin or methyl--cyclodextrin (MCD), both of which could disrupt the integrity of cholesterol-enriched membrane microdomains (27).…”