Picrorhiza scrophulariiflora improves accelerated atherosclerosis through inhibition of redox-sensitive inflammation.

BACKGROUND: Accumulation of advanced glycation end products (AGEs) or advanced oxidation protein products (AOPPs) has been identified as a risk factor for accelerated atherosclerosis seen in diabetes and chronic kidney disease. However, little is known about the intervention for atherogenesis associated with these oxidized proteins. The rhizome of Picrorhiza scrophulariiflora (PS) has long been used to treat inflammatory diseases as a traditional medication. The study was performed to test the hypothesis that ethanol extraction of PS (EPS) may improve AGEs- or AOPPs-induced accelerated atherosclerosis in vivo. METHODS AND RESULTS: Hypercholesterolemic or normal rabbits were randomly assigned to 8 groups treated with intravenous injection of AGEs- or AOPPs-modified rabbit serum albumin (AGEs-RSA or AOPPs-RSA), unmodified RSA or vehicle in the presence or absence of EPS (10 mg/kg/2 days) gavage for 10 weeks. Compared with hypercholesterolemic rabbits without EPS treatment, EPS administration significantly decreased the aortic plaque volume and oxidized low density lipoprotein (Ox-LDL) deposition in hypercholesterolemic animals. This was accompanied by significant histological improvement including decrease of intimal and smooth muscle cell proliferation and macrophage influx in affected areas. EPS administration almost completely abolished the accelerated atherosclerosis induced by chronic treatment of AGEs- or AOPPs-RSA in both hypercholesterolemic and normal rabbits. EPS administration significantly restored the AGEs- or AOPPs-induced redox imbalance and inflammation, evidenced by decrease of plasma Ox-LDL, thiobarbituric acid reactive substances and TNF-alpha, and increase of glutathione peroxidase activity. CONCLUSION: These data suggested that EPS may improve atherosclerosis, particularly that induced by AGEs or AOPPs, through inhibition of redox-sensitive inflammation.

A role for oxidative stress in apoptosis: oxidation and externalization of phosphatidylserine is required for macrophage clearance of cells undergoing Fas-mediated apoptosis.

Exposure of phosphatidylserine (PS) on the surface of apoptotic cells has been suggested to serve as an important recognition signal for macrophages. In this work we show that triggering of the death receptor Fas on Jurkat cells results in the generation of reactive oxygen species with oxidation and externalization of PS but not of the other major aminophospholipid, phosphatidylethanolamine. These cells were readily ingested by several classes of macrophages, whereas Raji cells, which are defective for Fas-induced PS exposure, remained unengulfed. However, when Raji cells were incubated with the thiol-reactive agent N-ethylmaleimide to induce PS exposure in the absence of other features of apoptosis, these cells were also engulfed by macrophages. Phagocytosis of Fas-triggered Jurkat cells was inhibited by superoxide dismutase and catalase, which prevent oxidation of PS while allowing PS to remain externalized on these cells. Moreover, liposomes containing oxidized PS (PS-OX) were more potent inhibitors of phagocytosis than those containing its nonoxidized counterpart. Finally, enrichment of the plasma membrane of Jurkat or Raji cells, or myeloid leukemic HL-60 cells, with exogenous PS resulted in phagocytic cell clearance, and this process was further enhanced when PS was substituted for by PS-OX. Taken together, our data suggest that the presence of PS-OX in conjunction with nonoxidized PS on the cell surface is an important signal for macrophage clearance of apoptotic cells.