High-density lipoprotein: antioxidant and anti-inflammatory properties.

The ability of high-density lipoprotein (HDL) to promote cholesterol efflux is an important component of its ability to protect against cardiovascular disease. In addition, the anti-inflammatory properties of HDL are important as well. As part of the innate immune system, HDL appears to have evolved to increase inflammation in the presence of an acute phase response but to inhibit inflammation in the absence of an acute phase response. In a study of humans with coronary heart disease, it was found that the patients who had proinflammatory HDL prior to statin therapy (and half of them despite a profound decrease in plasma lipids following statin therapy) continued to have proinflammatory HDL. Anti-inflammatory HDL was effective in promoting cholesterol efflux whereas proinflammatory HDL was relatively weak in its ability to promote cholesterol efflux. Oxidative alterations of the main protein of HDL, apolipoprotein A-I, impaired its capacity to promote cholesterol efflux from monocyte macrophages. Therefore, HDL composition, structure, and function appear to be more crucial than HDL cholesterol concentrations in determining risk for cardiovascular disorders.