Cecilia Grundtman

The role of heat shock proteins in atherosclerosis

Atherosclerosis is a chronic, multifactorial disease that starts in youth, manifests clinically later in life, and can lead to myocardial infarction, stroke, claudication, and death. Although inflammatory processes have long been known to be involved in atherogenesis, interest in this subject has grown in the past 30–40 years. Animal experiments and human analyses of early atherosclerotic lesions have shown that the first pathogenic event in atherogenesis is the intimal infiltration of T cells at arterial branching points. These T cells recognize heat shock protein (HSP)60, which is expressed together with adhesion molecules by endothelial cells in response to classic risk factors for atherosclerosis. Although these HSP60-reactive T cells initiate atherosclerosis, antibodies to HSP60 accelerate and perpetuate the disease. All healthy humans develop cellular and humoral immunity against microbial HSP60 by infection or vaccination. Given that prokaryotic (bacterial) and eukaryotic (for instance, human) HSP60 display substantial sequence homology, atherosclerosis might be the price we pay for this protective immunity, if risk factors stress the vascular endothelial cells beyond physiological conditions.

The autoimmune concept of atherosclerosis

Purpose of review This review summarizes the recent data on the ‘Autoimmune Concept of Atherosclerosis’, according to which the first stage of this disease is due to an autoimmune reaction against arterial endothelial cells expressing heat shock protein 60 (HSP60) and adhesion molecules when stressed by classical atherosclerosis risk factors. Special emphasis is put on oxidized low-density lipoproteins as early endothelial stressors. Recent findings Plasma cholesterol and LDL levels considered ‘normal’ by the medical community are possibly too high from an evolutionary viewpoint. The proinflammatory milieu at sites of early atherosclerotic lesions could be conducive to oxidation of LDL in situ. LDL oxidation can also take place at nonvascular sites or in the circulation under general proinflammatory conditions explaining its proatherosclerotic role in ‘normocholesterolemic’ individuals. Summary We hypothesize that the plasma cholesterol and LDL levels currently considered normal are evolutionarily too high. Cholesterol and/or oxidized low-density lipoprotein, even as a mild HSP60-inducing endothelial stressor, function as a ubiquitous risk factor. If this hypothesis is true, most members of developed societies might be at risk to develop atherosclerotic plaques at anti-HSP60-immunity-triggered intimal inflammatory foci, irrespective of the primary risk-factor(s).

Autoreactive HSP60 epitope-specific T-cells in early human atherosclerotic lesions.

Atherosclerosis is a multifactorial chronic inflammatory disease characterized by the presence of T-cells, macrophages, and dendritic cells in the arterial intima. Classical risk factors lead to over-expression of stress proteins, especially heat shock protein 60 (HSP60). HSP60 on the surface of arterial endothelial cells (ECs) then becomes a target for pre-existing adaptive anti-HSP60 immunity resulting in infiltration of the intima by mononuclear cells. In the present study, T-cells derived from early, clinically still inapparent human atherosclerotic lesions were analyzed phenotypically and for their reactivity against HSP60 and HSP60-derived peptides. HSP60 was detected in ECs and CD40- and HLA Class II-positive cells within the intima. Effector memory CD4+ T-cells producing high amounts of interferon-γ and low levels of interleukin-4 were the dominant subpopulation. T-cells derived from late lesions displayed a more restricted T-cell receptor repertoire to HSP60-derived peptides than those isolated from early lesions. Increased levels of soluble HSP60 and circulating anti-human HSP60 autoantibodies were found in donors with late but not early lesions. This is the first functional study of T-cells derived from early human atherosclerotic lesions that supports the previously proposed concept that HSP60-reactive T-cells initiate atherosclerosis by recognition of atherogenic HSP60 epitopes.

Mycobacterial heat shock protein 65 (mbHSP65)-induced atherosclerosis: Preventive oral tolerization and definition of atheroprotective and atherogenic mbHSP65 peptides

OBJECTIVE The aim of this study was to identify atherogenic and atheroprotective peptides of bacterial HSP60 [taking mycobacterial HSP65 (mbHSP65) as a potent paradigmatic representative] that could be used as candidates for an orally applied tolerizing vaccine against atherosclerosis. METHODS ApoE(-/-) mice were immunized with mbHSP65 protein or peptides, given mbHSP65 orally and then kept either on chow or high cholesterol diet. Atherosclerosis was assessed by en face and immunohistological analysis. Anti-HSP autoantibodies were detected by ELISA. The number and in vitro suppressive function of splenic and lymph node regulatory T cells (Tregs) were analyzed by flow cytometry. Specific T cell reactivity against mbHSP65 protein or peptides was assessed by proliferation assay. RESULTS Decreased lesion size was accompanied by (a) increased splenic Treg numbers; (b) increased interleukin (IL)-10 mRNA levels in the aorta; (c) increased levels of anti-mbHSP65 and anti-mouse HSP60 antibodies pointing to pro-eukaryotic HSP60 humoral crossreaction, not curtailed by oral tolerization; (d) most importantly, we identified and functionally characterized novel atherogenic and atheroprotective mbHSP65 epitopes. CONCLUSION Atheroprotective mbHSP65 peptides may be considered as potential candidates for the development of a tolerizing vaccine to prevent and treat atherosclerosis, while keeping protective immunity to non-atherogenic domains of mbHSP65 intact.

Transcatheter Embolization for the Management of Acute Active Inferior Epigastric Artery Hemorrhages

Purpose To report a retrospective review of all patients who were admitted to the interventional radiology unit at our hospital for transcatheter arterial embolization (TAE) of an acute active hemorrhage of the inferior epigastric artery. Methods From 1996 to 2012, 52 consecutive patients (26 men; mean age 63±15 years) with hemodynamically relevant active abdominal wall hematoma were admitted for TAE of the inferior epigastric artery. Of these, 19 patients had spontaneous hemorrhage due to use of anticoagulants, 18 due to abdominal trauma, and 15 due to an iatrogenic complication. All superselective embolizations were performed using a coaxial catheter technique with a 0.018-inch microcatheter introduced through the diagnostic macrocatheter. Various embolization methods, alone or in combination, were applied, including primarily microcoils and polyvinyl alcohol particles. Results Primary technical success was achieved in 47/52 (90%) patients; the remainder needed a second embolization session (secondary success 100%). The mean puncture-to-hemostasis time was 65.4±35 minutes. No patient developed a large hematoma or pseudoaneurysm at the puncture site. The 30-day mortality was 19% (n=10) and the total cumulative mortality rate was 23% (n=12). Over a mean 67-month follow-up of 39/40 survivors (1 lost to follow-up), no complications from the embolization procedure, such as abdominal wall ischemia, were observed. There were no differences in outcomes based on etiology of the hemorrhage. Conclusion In selected patients with acute active hemorrhage of the IEA in the anterior abdominal wall, TAE is a fast, safe, minimally invasive, and reliable method with a high technical success rate and no long-term complications.

Animal Models of Atherosclerosis

In humans, the causal mechanisms behind the development of atherosclerosis are still not fully understood. On the one hand, the disease process is multifactorial in its initiation and complex because of its chronic nature; on the other, it has not been possible to sequentially characterize lesions in an individual patient, despite rapid progress in non-invasive detection modalities. Furthermore, for ethical reasons, experimental studies of atherosclerosis in patients with cardiovascular disease cannot be conducted. Thus, there arose the necessity to develop appropriate animal models in which both ex vivo and in vivo experimentations can be performed, and which would help delineate the pathogenetic steps and causal relations in this disease. During the last century, numerous different animal species, from mice to monkeys, have been used to study the pathogenesis of atherosclerotic lesions and their potential treatment. In this chapter, we will recapitulate and summarize the most important rabbit, rat, and mice models used in experimental studies of atherogenesis (see Fig. 8.1).

The time-averaged inflammatory disease activity estimates the progression of erosions in MRI of the sacroiliac joints in ankylosing spondylitis

A method to estimate the individual ankylosing spondylitis (AS) patient radiological progression of semi-quantitative magnetic resonance imaging (MRI) changes in the sacroiliac joints has not been described yet, which this study examines. Inflammatory disease activity and MRIs of the sacroiliac joints of 38 patients with recent onset established AS were analyzed at baseline and during follow-up. Sacroiliac MRIs were semi-quantitatively assessed using a modification of the “Spondylarthritis Research Consortium of Canada” (SPARCC) method. In each patient, the annual inflammatory disease activity was estimated by the time-averaged C-reactive protein (CRP; mg/l), calculated as the area under the curve. The mean (SD) CRP decreased from 1.3 (1.8) at baseline to 0.5 (0.6) at follow-up MRI (p < 0.04), which has been performed after a mean (SD) disease course of 2.8 (1.5) years. The mean (SD) annual increase (∆) of SPARCC score from baseline to follow-up MRI was 0.4 (0.4). Baseline individual SPARCC sub-score for bone marrow edema did not statistically significantly correlate with individual ∆SPARCC sub-score for erosions (p = N.S.). The individual AS patient correlation between annual time-averaged inflammatory disease activity and each annual ∆SPARCC sub-scores was only statistically significant for erosions (p < 0.01; r = 0.71). Our results show that bone marrow edema and contrast-medium enhancement at baseline do not relate to the progression of erosions but the calculation of the individual patient annual time-averaged inflammatory disease activity allows to estimate the annual progression of erosions in sacroiliac MRIs of patients with AS.

Vaccination Against Atherosclerosis

The development of a vaccine to prevent the build-up of atherosclerotic plaques would drastically change the life for millions of individuals and hopefully strongly reduce the number of fatal and nonfatal cardiovascular events. At present, there are several treatments for the disease (e.g. statins, acetylsalicylic acid, and ADP-receptor antagonists) and much can be accomplished through lifestyle changes such as giving up smoking or switching to a low-fat low-cholesterol diet. A large number of prospective, randomized, controlled clinical trials have demonstrated both angiographic and clinical benefits of lipid-lowering therapy. Overall, a significant and clinically worthwhile relative risk reduction ranging from 20% to 40% in major cardiovascular events has been achieved with these strategies, without significant adverse effects or increased noncardiovascular mortality. However, around 60–70% of adverse cardiovascular events continue to occur despite oxidized low-density lipoprotein (oxLDL)-lowering therapies, indicating an obvious need for new therapeutic interventions.

A Darwinian-Evolutionary Concept for Atherogenesis: The Role of Immunity to HSP60

Studying the mechanisms operative in the very earliest stage of a given disease is a difficult, and often even impossible task in the human situation. At this stage, clinical symptoms are not yet manifest and the patients-to-be have not yet consulted a physician. Experiments and analyses even before microscopically or biochemically sizable pathologic hallmarks emerge can therefore only be carried out in animal models. When such animal models are developed they can then allow for a chronological monitoring of pathogenetic events from morphologically and clinically unapparent to fully blown, often lethal stages of the disease under study.