Atherosclerosis research typically focuses on the evolution of intermediate or advanced atherosclerotic lesions rather than on prelesional stages of
atherogenesis. Yet these early events may provide decisive leads on the triggers of the pathologic process, before lesions become clinically overt. Thereby, it is mandatory to consider extracellular
lipoprotein deposition at this stage as the prerequisite of foam cell formation leading to a remarkable accumulation of
LDL (
Low Density Lipoproteins). As progression of
atherosclerosis displays the characteristic features of a chronic inflammatory process on the one hand and native
LDL lacks inflammatory properties on the other hand, the
lipoprotein must undergo biochemical modification to become atherogenic. During the last 25 years, evidence was accumulated in support of a different concept on
atherogenesis proposing that modification of native
LDL occurs through the action of ubiquitous hydrolytic
enzymes (enzymatically modified
LDL or eLDL) rather than oxidation and contending that the physiological events leading to macrophage uptake and reverse transport of eLDL first occur without
inflammation (initiation with reversion). Preventing or reversing initial atherosclerotic lesions would avoid the later stages and therefore prevent clinical manifestations. This concept is in accordance with the response to retention hypothesis directly supporting the strategy of lowering plasma levels of atherogenic
lipoproteins as the most successful therapy for
atherosclerosis and its sequelae. Apart from but unquestionable closely related to this concept, there are several other hypotheses on atherosclerotic lesion initiation favoring an initiating role of the immune system ('vascular-associated lymphoid tissue' (VALT)), defining foam cell formation as a variant of
lysosomal storage disease, relating to the concept of the
inflammasome with crystalline
cholesterol and/or mitochondrial DAMPs (damage-associated molecular patterns) being mandatory in driving
arterial inflammation and, last but not least, pointing to
miRNAs (micro RNAs) as pivotal players. However, direct anti-inflammatory
therapies may prove successful as adjuvant components but will likely never be used in the absence of strategies to lower plasma levels of atherogenic
lipoproteins, the key point of the perception that
atherosclerosis is not simply an inevitable result of senescence. In particular, given the importance of chemical modifications for
lipoprotein atherogenicity, regulation of the
enzymes involved might be a tempting target for pharmacological research.