Abstract 1334: D-4F Treatment Decreases the Association of Altered Hemoglobin and its Scavengers with High Density Lipoprotein in Mice.
Objective: We have previously reported that an apolipoprotein A-I (apoA-I) mimetic, D-4F, converted HDL from pro-inflammatory to antiinflammatory in mice and monkeys. We recently discovered that hemoglobin (Hb) with physical and chemical properties distinctly different from red blood cell Hb associates with HDL in animal models of atherosclerosis and may contribute to the pro-inflammatory nature of HDL under atherogenic conditions. The objectives of the present study were,
to determine whether hemopexin (Hx) and haptoglobin (Hp), two well-known scavengers of Hb, associate with pro-inflammatory HDL and
to determine whether D-4F treatment can decrease the association of Hb with pro-inflammatory HDL in animal models of atherosclerosis.
Methods and Results: Feeding C57BL/6J mice (n=12 per group) an atherogenic diet for one week resulted in
lower HDL-cholesterol levels,
reduced paraoxonase activity,
increased reactive oxygen species and
reduced ability of the HDL to promote cholesterol efflux from macrophages, compared to C57BL/6J mice fed a chow diet.
Western analysis showed increased (>10-fold) association of Hb, Hx, and Hp protein complexes with HDL fractions obtained from these mice. Hb, Hx, and Hp protein complexes were also found associated with HDL from apoE null mice on a chow diet. To determine whether D-4F treatment can affect Hb biology in pro-inflammatory HDL, apoE null mice were treated with D-4F (50 μg/ml in drinking water) for 21 days and their HDL was analyzed for inflammatory properties and Hb complexes. D-4F treatment
converted HDL from pro-inflammatory to anti-inflammatory,
significantly reduced Hx and Hp levels in serum as measured by ELISA,
decreased Hb, Hx and Hp protein complexes in HDL fractions and
partially restored to normal the physical and chemical properties of Hb in apoE null serum.
Conclusion: Hb and its scavenger proteins are components of pro-inflammatory HDL. One of the mechanisms by which D-4F converts pro-inflammatory HDL to anti-inflammatory HDL may be by preventing and/or reversing the association of pro-oxidant Hb containing proteins with HDL.