Nanoscale Cholesterol Trafficking

Cholesterol transport plays a key role in mediating the development of cardiovascular disease and its progression. We develop synthetic nanoprobes that can obtain cholesterol flux information in vitro and in vivo through Förster Resonance Energy Transfer (FRET) spectroscopy. Our team is able to conduct real-time cholesterol release monitoring in order to evaluate patient’s high-density lipoprotein (HDL) function—an important metric in determining cardiovascular risk.

Aspects of HDL Function

Removing excess cholesterol from macrophages is thought to be one of the key mechanisms underlying atheroprotective properties of HDL. Our laboratory studies a series of HDL function characteristics, such as such as oxidation status, ability to accept cholesterol, i.e. reverse cholesterol transport (RCT), and anti-inflammatory properties. My team and I investigate HDL obtained from multiple patient populations participating in multiple interventions and environmental stressors (e.g., environmental pollutants and particulate matter). We also study HDL functionality in dysglycemic and diabetic patients, individuals engaging in an aerobic exercise, individuals exposed to particulate matter, and so on.

LSEC

Emerging evidence from our lab and our collaborators indicates that HDL’s ability to shuttle cholesterol for disposal in liver may have an unexpected dependence on function of liver endothelial cells (LSECs). Using new nanometer resolution microscopy tools, we were the first to demonstrate that an HDL receptor, SR-B1, that was long thought to be expressed in liver hepatocytes, is actually highly expressed in LSECs. Paradoxically, we show that hepatocytes express negligible levels of SR-B1. We demonstrated it by using ultra-thin cryostat nanosections of liver to microscopically resolve LSECs and hepatocytes (see figure).

Moreover, we recently made another important discovery that HDL is crucial in LSEC-mediated detoxification during gram-negative bacterial infections. Thus, our work indicates that the majority of HDL-bound lipopolysaccharide (LPS) is cleared through SR-B1. These findings suggest new mechanism(s) of detoxification and may aid in discovery of new targets for inflammation.

We Published These!

• US Patent App. 13/861,832, “Cholesterol Efflux Assay Probe Formulations, Methods of Making and Using”, Rajagopalan S, Badgeley MA, & Maiseyeu A
• Maiseyeu, A.; Yang, H.-Y.; Ramanathan, G.; Yin, F.; Bard, R. L.; Morishita, M.; Dvonch, J. T.; Wang, L.; Spino, C.; Mukherjee, B.; Badgeley, M. A.; Barajas-Espinosa, A.; Sun, Q.; Harkema, J.; Rajagopalan, S.; Araujo, J. A.; Brook, R. D. Inhal. Toxicol. 2014, 26 (1), 23–29.
• Ganesan, L. P.; Mates, J. M.; Cheplowitz, A. M.; Avila, C. L.; Zimmerer, J. M.; Yao, Z.; Maiseyeu, A.; Rajaram, M. V. S.; Robinson, J. M.; Anderson, C. L. Sci. Rep. 2016, 6, 20646.
• Yao Z, Mates JM, Cheplowitz AM, Hammer LP, Maiseyeu A, Phillips GS, Wewers MD, Rajaram MVS, Robinson JM, Anderson CL, Ganesan LP. Blood-Borne Lipopolysaccharide Is Rapidly Eliminated by Liver Sinusoidal Endothelial Cells via High-Density Lipoprotein. J Immunol. 2016;197(6):2390-2399.