Steinberg et al.^37-45 and others^35,36 have demonstrated that oxidative modification (denaturation) of LDL enhances its uptake by macrophages, and that the process of oxidative metabolism of LDL initiates many cascades of oxidative events, generating an array of oxidant and other molecules that profoundly influence the atherogenic process. Briefly, these include: 1) chemotactants for T-cells and monocytes; 2) endothelial cell adhesion molecules; 3) monocyte chemotactic protein 1; 4) macrophage colony stimulating hormone; 5) interleukin-1 which stimulates smooth muscle cell proliferation; 6) immunogenic epitomes that evoke immune responses; 7) cytokines released by CD4+ cells in atheroma plaques; 8) products that impair nitric oxide-mediated coronary vasorelaxation; 9) oxysterols that are highly toxic to endothelial cells; 10) tissue factors that initiate coagulation; and 11) insoluble toxic lipid-protein adducts. As valuable as these findings are to a clear understanding of atherogenesis, the precise nature of the mechanism by which cholesterol causes IHD is generally considered unclear.

The cholesterol theory has other serious shortcomings. Specifically, it fails to explain the following important issues:

1. Cholesterol is an antioxidant, albeit a weak one, and cannot be expected to cause oxidative injury that clearly initiates atherogenesis.

2. A majority of patients who develop severe IHD, including episodes of myocardial infarction, do not have elevated blood cholesterol levels.^64,469,470

3. When death occurs within six to eight hours of myocardial infarction, no acute coronary thrombotic occlusions are found at autopsy in more than 75 percent of cases; however, when death occurs after 48 hours, acute thrombotic occlusion is almost always found (personal unpublished data).

4. The range of frequency of acute thrombotic coronary occlusion in survivors of out-of-the-hospital cardiac arrest extends from 36 percent as determined by angiography²³⁷ to 95 percent in autopsy studies.²³⁸

5. There is a well-recognized paradox of IHD coexisting with normal angiograms.^68-70

6. Reduction of atherosclerotic lesions does not follow when the death rate from myocardial infarction falls.^59-61,471

7. Lowered blood cholesterol levels in women are not associated with the reduction in the rate of acute ischemic myocardial events to the same degree as is seen among men.⁶⁷

8. Lifestyle stressors,^239-247 tobacco smoking,^269-273 and physical inactivity^261-266 are recognized independent risk factors of IHD and exert potent pro-oxidant effects. We are not aware of any valid reason to believe that the oxidative stress of all those factors is confined to oxidative modification of LDL.

9. The cholesterol theory does not explain the recognized risk factors of IHD, such as hypertension and diabetes.

10. The cholesterol theory does not explain the cardioprotective role of coenzyme Q10,^{87,88,316-322} nor does it explain how hyperhomocysteinemia^{95,96,290-304} increases risk of IHD.

11. The cholesterol theory does not explain the recognized risk factors of increased body stores of iron^71,72 copper⁷³ and mercury⁷⁵,—transition metals with potent oxidizing potential.

12. The cholesterol theory does not explain the protective effects of selenium^{77,78,346,347} and chromium,^{79,80,472-475} minerals with recognized antioxidant effects.

13. The cholesterol theory does not explain the epidemiologic data showing reduced mortality from IHD in patients taking ascorbic acid^81,82 and vitamin E.^83,84

    In the face of the above evidence, how can the proponents of the cholesterol theory persist in their enthusiasm and continue to commit enormous financial resources to cholesterol research? An explanation was provided by Ravnskov who in 1992 evaluated 22 controlled cholesterol-lowering trials and concluded, "Lowering serum cholesterol concentrations does not reduce mortality and is unlikely to prevent coronary heart disease. Claims of the opposite are based on preferential citation of supportive trials."⁴⁷⁶ Specifically, he revealed that among the cholesterol trials published in major journals, supportive reports (n=8) were cited on average 61 times a year, while unsupportive trials (n=10) were cited eight times a year. In 14 cholesterol trials undertaken to establish a causal relationship between cholesterol changes and outcome, the data showed either an unsystematic effect or no effect at all. Ravnskov's closing comment is especially pertinent to our discussion. It read: "Methods subject to bias, such as open trials or the use of drugs with characteristics side effects, or stratification instead of random allocation of participants, probably explain the overall 0.32% reduction recorded in non-fatal coronary heart disease."

We hold, as we document in Part II, that all of the above thirteen aspects of IHD can be fully explained by the proposed AA oxidopathy hypothesis.

Lipid Redox Ecosystems
   Lipids in plasma membranes are essential for membrane fluidity, surface potentials, surface ligand activity, and transport functions.⁴⁷⁷ To serve these diverse functions, lipids exist in blood and plasma membranes not as discrete molecular species—as it might seem from the conventional description of lipid chemistry—but as dynamic "lipid redox ecosystems" in which external pro-oxidant influences are vigorously counterbalanced by antioxidant defenses that exist within the lipid particles. For example, low density lipoprotein (LDL) particles are found as spherical particles with diameters ranging from 19-25 nm, molecular weight varying over a broad range from 1.8 to 2.8 million, and the density ranging from 1.019 to 1.063 g/ml. LDL is a large lipoprotein complex that includes the following: cholesterol moieties (estimated 1600 and 600 molecules of cholesterol esters and free cholesterol respectively), triglycerides (estimated 170 molecules), phospholipids (estimated 700 molecules), apolipoprotein B, neutral and polar lipids including polyunsaturated fatty acids, and lipophilic antioxidant species such as beta carotene and vitamin E. Predictably, the antioxidant content of LDL varies over a broad range and appears to be diet related. Lipoprotein (a) [Lp (a)] is structurally similar to LDL but is distinguished from it by the presence in it of a highly glycosylated protein designated apoliprotein(a).⁴⁷⁸ It binds to apolipoprotein B (apo B)-containing lipoproteins and proteoglycans.⁴⁷⁹ It has a complex relationship between fibrin, platelets, and atherogenesis. By its high affinity for and binding with fibrin, it activates plasminogen,^480-482 while its binding to platelet receptors and leads to plasminogen binding and activation. Lp(a) is considered atherogenic because it is taken up by foam cells; however, elevated levels are associated with IHD in most, but not all, reports. We now return to the subject of spontaneity of oxidation in nature to put the notion of lipid redox ecosystems into perspective.

The LDL-Oxidative Modification Hypothesis of IHD Has Poor Explanatory Power   
   In the preceding sections of this article, we have raised several essential issues that the LDL-oxidative modification hypothesis fails to address. First, this hypothesis assumes that oxidative modification of LDL occurs within sequestrated regions of the vascular wall. This assumption, as we stressed earlier in this article, is not warranted in view of our morphologic observations. Second, this hypothesis completely ignores the consequences of accelerated oxidative stress on erythrocytes in the bloodstream. The erythrocyte is the cell most vulnerable to high oxygen tension because it is the primary oxygen transport cell in the body. Third, this hypothesis fails to account for the contribution to atherogenesis of oxidative stress on platelets. Fourth, it ignores the atherogenic role of oxidative bursts of healthy and oxidatively damaged granulocytes, both insidiously during slowly progressive atherogenesis and acutely following intimal injury inflicted during angioplasty and coronary bypass surgery. Fifth, it ignores susceptibility of plasma proteins (including those of coagulation pathways) to redox dysregulation within the circulating blood. Sixth, the vulnerability of circulating plasma and cellular enzymes (and other functional proteins) is ignored by the LDL hypothesis. Seventh, this hypothesis assumes—again without justification—that oxidative injury to the vascular intima (and, hence, to subendothelial stroma and myocytes) is inflicted only by oxidatively modified LDL. Eighth, vitamin E significantly increases the resistance of LDL to oxidation without inhibiting atherogenesis in the same animals.^85,483,484 Ninth, at least one antioxidant (beta carotene) decreases atherogenesis in cholesterol-fed rabbits without reducing susceptibility of LDL to oxidation.⁸⁵ Tenth, in cholesterol-fed rabbits impaired nitric-oxide-mediated vasodilatation is due to increased endothelial generation of superoxide, which inactivates nitric oxide.^485,486
   There are yet other considerations of coronary vascular dynamics and clinical expressions of atherosclerosis that may not be explained by the LDL-modification hypothesis. The clinical course of IHD is determined not only by atherogenesis but also by diverse elements such as vasoconstriction, accretion of circulating microclots and microplaques on the intimal surface, thrombosis, plaque rupture, and release of proteolytic enzymes from ruptured and necrotic plaques, which further feed AA oxidopathy. The release of such proteolytic enzymes has been thought to contribute to lysis of fibrous caps of plaques with resulting plaque rupture and thrombotic occlusions.^487-488 Indeed, a large body of experimental evidence in atherogenesis point to etiologic roles of a multitude oxidant phenomena involving synthesis of connective tissue macromolecules,⁴⁸⁹ secretion of substances with PDGF-like activity by intimal smooth muscle cells,^490,491, ozone induction of cytokine-induced neutrophil chemoattractants and nuclear factor kB,⁴⁹² endothelial cell replication,⁴⁹³ cytokine-inducible nitric oxide synthesis,⁴⁹⁴ elaboration of circulating and tissue immunoreactivity,⁴⁹⁵ endothelial cell activity and its relationship with oxidation of LDL,⁴⁹⁶ and the role of oxidized LDL in recruitment of monocyte and macrophages.⁴⁹⁷ Evidently, all of the above biochemical and cellular responses can be accentuated by oxidized LDL. However, the essential point here is that none of them depends on oxidized LDL for its initiation and propagation.
    The key unanswered questions in the context of the cholesterol hypothesis are: 1) Why does the blood cholesterol level go up in the first place? 2) What are the molecular events that lead to a decrease in the number of LDL receptors? 3) How do elevated levels of cholesterol cause vessel wall injury and initiate atheroma formation? Our morphologic studies of peripheral blood presented in this article, though not addressing the first two questions directly, strongly suggest that hypercholesterolemia develops as an antioxidant defense adaptation to accelerated, chronic, and persistent oxidative stress on the circulating blood—the events that create and perpetuate AA oxidopathy. Indirect evidence to support our view derives from the fact that raised blood cholesterol levels in many persons living highly stressed lives return to a normal range when lifestyle stressors are brought under control (unpublished personal data). Furthermore, it seems to us that a decrease in the number of LDL receptors is an adaptive response to hypercholesterolemia. We will return to this issue later in Part II of this article.
    As regards the third question, several mechanisms by which hypercholesterolemia leads to atherosclerosis have been proposed. One such mechanism focuses on possible subtle endothelial injury caused by excess blood cholesterol that might increase endothelial cell membrane viscosity by altering its cholesterol-phospholipid ratio. Some other proposed mechanisms include the following: 1) the effect of hyperviscous, and hence less malleable, endothelial membrane on monocyte adhesion and chemotaxis; 2) the induction by excess cholesterol of growth factors in endothelial cells; and 3) the direct effects of cholesterol on platelets, monocyte/macrophage transformations, and accumulation of lipids in myocytes.^490,493-497 Of greater interest to us in the context of the proposed AA oxidopathy hypothesis are the observations of Cathcart et al.³⁷ and others that LDL exposed to all major cell types involved in atherogenesis (monocytes, macrophages, platelets, endothelial cells, and smooth muscle cells) is oxidized and triggers generation of a vast array of molecules that perpetuate oxidative chain reactions and inflict cellular injury in the vascular wall. This is consistent with the tenets of AA oxidopathy.
    How may the association between elevated Lp(a) and IHD be explained in the context of oxidative coagulopathy? Lp(a) is structurally similar to plasminogen and is known to bind to fibrin.^480-482 Thus, when present in the blood in elevated levels, it may be expected to exert a procoagulant effect and compound the procoagulant effects of oxidants in circulating blood, thus tipping the balance in favor of the clotting side of clotting-declotting equilibrium in health. In addition, Lp(a) can be expected to increase the thrombogenic character of blood in oxidative coagulopathy by its known antifibrinolytic actions.
    In summary, what is the common denominator of all initial lipid-related factors that are involved with atherogenesis and clinical ischemic coronary heart disease? Evidently it is accelerated oxidative injury to all lipids, including lipoproteins and glycolipids. Hypercholesterolemia plays a role in atherogenesis to the degree that higher concentrations of cholesterol lead to generation of greater amounts of oxidized LDL, and hence greater oxidative stress on the circulating blood. We conclude that all of the known molecular dynamics of dyslipidemia are totally consistent with the proposed oxidative coagulopathy and AA oxidopathy hypotheses.

Continue to Part 10 of 11