EMBO workshop--"Molecular and Cellular Gerontology": Sepiano/Switzerland, September 18-22, 1999

The EMBO Workshop "Molecular and Cellular Gerontology" provided a comprehensive analysis of recent developments in experimental gerontology. Various animal models for aging were presented. The focus of the conference was on the role of oxidative stress in aging at the cellular and organismal level. Evolution of aging was another topic discussed in the course of the meeting. Another focal point of the meeting was on age-related changes in cellular repair systems, in particular DNA repair and protein repair. Emphasis was also placed on the role of mitochondrial function and mitochondrial DNA mutations in the aging process. These molecular approaches were complemented by a session on age-related diseases, including aging of the immune system, cardiovascular disease and Alzheimer's disease.

Atherosclerosis--an autoimmune disease due to an immune reaction against heat-shock protein 60

This brief overview, our concept of an autoimmune pathogenesis of atherosclerosis is summarized. In principle, we postulate that we may have to "pay" for our protective immunity against microbial heat-shock protein 60 (hsp60) with the danger of a cross-reactivity with our own hsp60 that is expressed by endothelial cells that are stressed by classical risk factors for atherogenesis such as hypertension, high serum cholesterol levels, components of cigarette smoke and other toxins, etc. hsp60 are phylogenetically highly conserved and there is an over 55% homology between bacterial hsp60 and the human homologue forming the basis for this cross-reactivity. As another possibility, the initiation of the disease by a bona fide autoimmune reaction against chemically altered autologous hsp60 is discussed.

Diseases of aging

By definition, diseases of aging become clinically manifested in elderly patients. However, their pathogenetic basis has to be sought earlier in life. The general thread of this presentation relies on the concept of an evolutionary-Darwinian view of the development of age-related diseases. In essence, this concept states that we may have to "pay" for genetic traits that play a beneficial role earlier in life by the later development of diseases since there is no post-reproductive selective pressure that may have eliminated the potential late onset detrimental effects of such genes. Examples for this kind of trade-off are taken from diseases involving the immune system (infections), the endocrine system (andropause), the nervous system (Alzheimer's disease), the locomoter system (osteoporosis), the cardio-vascular system (atherosclerosis) and cancer.

Glucocorticoid production in the murine thymus

Glucocorticoid hormones are known to act as important modulatory factors in the development of autoimmune diseases, and to play an important role in thymic T-cell selection. There seems to be a finely balanced equilibrium between the apoptosis-inducing effects of glucocorticoid and T cell receptor ligand binding. Here we are investigating whether glucocorticoid-induced T cell apoptosis is mainly dependent on circulating glucocorticoid levels or if the thymus itself is able to produce glucocorticoids. To this end, we attempted to demonstrate enzyme activities of the whole set of steroidogenic enzymes for the synthesis of glucocorticoids in murine thymic tissue. We isolated steroidogenic organelles from thymic tissue, incubated these with radioactive (precursor) steroids in vitro, and visualized the resulting products by thin-layer chromatography. Our results show that the thymus possesses all enzymes and cofactors required for glucocorticoid production. However, an intact thymic architecture is necessary for glucocorticoid production, since 11beta-hydroxylase was not detected in irradiated thymi or in a thymic epithelial cell line. The results of these experiments show that the whole glucocorticoid metabolism takes place within the thymus. This finding provides the biochemical basis for the in situ effects of glucocorticoid hormones on thymocyte development and selection.

Mouse model of transplant arteriosclerosis: role of intercellular adhesion molecule-1

Transplant-accelerated arteriosclerosis in coronary arteries is the major limitation to long-term survival of patients with heart transplantation. The pathogenesis of this disease is not fully understood. Herein, we describe a simplified model of artery allografts in the mouse that allows us to take advantage of transgenic, knockout, or mutant animals. Common carotid arteries or aortic vessels were end-to-end allografted into carotid arteries between C57BL/6J and BALB/c mice. Neointimal lesions were observed as early as 2 weeks after surgery and had progressed at 4 and 6 weeks postoperatively. The lumen of grafted arteries was significantly narrowed due to neointima hyperplasia 4 weeks after transplantation. Using this model, we studied the role of intercellular adhesion molecule-1 (ICAM-1) in the development of transplant arteriosclerosis in ICAM-1-deficient mice. Neointimal lesions of artery grafts from ICAM-1 -/- C57BL/6J to BALB/c mice were reduced up to 60% compared with wild-type controls. MAC-1 (CD11b/18)-positive cells adhering to the surface of ICAM-1 -/- artery grafts were significantly less as identified by en face immunofluorescence, and these positive cells were more abundant in intimal lesions of artery grafts in wild-type mice. Furthermore, the major cell component of neointimal lesions 4 weeks after surgery was found to be alpha-actin-positive smooth muscle cells, which were significantly reduced in lesions of ICAM-1 -/- artery grafts. Thus, this model has been proven to be useful for understanding the mechanism of transplant arteriosclerosis. Our findings demonstrate that ICAM-1 is critical in the development of allograft arteriosclerosis via mediation of leukocyte adhesion to, and infiltration into, the vessel wall.

Hyperexpression and activation of extracellular signal-regulated kinases (ERK1/2) in atherosclerotic lesions of cholesterol-fed rabbits

A hallmark of hyperlipidemia-induced atherosclerosis is altered gene expression that initiates cell proliferation and (de)differentiation in the intima of the arterial wall. The molecular signaling that mediates this process in vivo has yet to be identified. Extracellular signal-regulated kinases (ERKs) are thought to play a pivotal role in transmitting transmembrane signals required for cell proliferation in vitro. The present studies were designed to investigate the activity, abundance, and localization of ERK1/2 in atherosclerotic lesions of cholesterol-fed rabbits. Immunofluorescence analysis revealed abundant and heterogeneous distribution of ERK1/2, mainly localized in the cap and basal regions of atheromas. A population of ERK-enriched cells was identified as alpha-actin-positive smooth muscle cells (SMCs). ERK1 and 2 were heavily phosphorylated on tyrosyl residues and coexpressed with proliferating cell nuclear antigen in atherosclerotic lesions. ERK1/2 protein levels in protein extracts from atherosclerotic lesions were 2- to 3-fold higher than the vessels of chow-fed rabbits, and their activities were elevated 3- to 5-fold over those of the normal vessel. SMCs derived from atherosclerotic lesions had increased migratory/proliferative ability and higher ERK activity in response to LDL stimulation compared with cells from the normal vessel. Inhibition of ERK activation by PD98059, a specific inhibitor of mitogen-activated protein kinase kinases (MEK1/2), abrogated LDL-induced SMC proliferation in vitro. Taken together, our findings support the proposition that persistent activation and hyperexpression of ERK1/2 may be a critical element to initiate and perpetuate cell proliferation during the development of atherosclerosis.

The natural history of the obese strain of chickens--an animal model for spontaneous autoimmune thyroiditis

Chickens of the Obese strain (OS) are hereditarily affected with spontaneous autoimmune thyroiditis that resembles Hashimoto's thyroiditis of humans in clinical, histopathological, serological, and endocrinological aspects. In this review, the natural history of the OS, reflecting the development and maintenance of the stock and its improvement of productivity over many years at Cornell University, is summarized. To underline the value and usefulness of this animal model, the concept of the multifactorial pathogenesis of autoimmune diseases, which was mainly established at the University of Innsbruck, Austria, is briefly outlined. This detailed analysis on the natural history of the OS was only made feasible by the availability of four decades of records on this chicken line at Cornell University. The report starts with the initial occurrence of a few pullets within the Cornell C-strain (CS) flock that showed obesity, long and silky feathers, and small body size, which, therefore, caused these birds to look notably different than the other CS birds. Experimental findings indicated an autoimmune basis for these characteristics, and the objectives of matings were initially focused on increasing the number of obese individuals for studies on the etiopathology and the mode of inheritance. In subsequent years, matings were directed toward increasing the penetrance and severity of the obese trait in the population. In recent years, the reproductive capability of the obese stock was improved by mating only the best breeders of the population in terms of body weight, egg weight, egg production, fertility, hatchability, and the expression of the obese phenotype. Housing conditions for OS chickens at Cornell and the qualification standards and selection procedures for breeders are described in detail, and results of blood typings are shown. A specific recent finding in OS hens is the high incidence of residues of the right Mullerian duct with cyst formation.

Association of serum antibodies to heat-shock protein 65 with carotid atherosclerosis : clinical significance determined in a follow-up study

BACKGROUND

Previous work has proved that increased titers of antibodies against heat-shock protein (hsp) 65 are associated with atherosclerotic lesions independently of other established risk factors. The present follow-up study was designed to further scrutinize the association of hsp antibodies and atherosclerosis and evaluate the possible predictive value of these antibodies for the development and/or progression of lesions in the same population.

METHODS AND RESULTS

A total of 750 subjects 45 to 74 years old were recruited, and the rate of participation was 93.6%; 58 subjects died between 1990 and 1995. All participants were subjected to determination of serum antibodies against hsp65 and sonography to assess carotid atherosclerotic lesions and evaluate other risk factors, ie, age, sex, body mass index, blood cholesterol, apolipoprotein B, apolipoprotein A, triglycerides, lipoprotein(a), fibrinogen, leukocyte number, antithrombin III, ESR, ferritin, hypertension, smoking, and diabetes mellitus. Our data show that hsp65 antibody titers in the population emerged as highly consistent over a 5-year observation period (r=0.78, P<0.0001). Titers were significantly elevated in subjects with progressive carotid atherosclerosis and correlated with intima/media thickness. Multiple linear regression analysis documented these associations to be independent of age, sex, and other risk factors. Subanalyses revealed a preferential association of hsp65 antibody titers with advanced lesions (odds ratio, 1.42; 95% CI, 1.02 to 1.98; P=0.039). Other risk factors neither confounded nor modified this association. Finally, hsp65 antibody titers significantly predicted the 5-year mortality (hazard ratio, 1.52; 95% CI, 1.14 to 2.03; P<0.001).

CONCLUSIONS

These findings indicate a sustained existence of anti-hsp65 antibodies in subjects with severe atherosclerosis, which is predictive for mortality.

Inhibition of neointima hyperplasia of mouse vein grafts by locally applied suramin

BACKGROUND

Saphenous vein grafts are widely used for aortocoronary bypass surgery as treatment for severe atherosclerosis and often are complicated by subsequent occlusion of the graft vessel.

METHODS AND RESULTS

We described a mouse model of venous bypass graft arteriosclerosis that can be effectively retarded by locally applied suramin, a growth factor receptor antagonist. Mouse isogeneic vessels of the vena cava veins pretreated with suramin were grafted end to end into the carotid arteries and enveloped with a mixture of suramin (1 mmol/L) and pluronic-127 gel. In the untreated group, vessel wall thickening was observed as early as 1 week after surgery and progressed to 4-fold and 10-fold the original thickness in grafted veins at 4 and 8 weeks, respectively. Pluronic-127 gel alone did not influence neointima formation. Suramin treatment reduced the neointima hyperplasia 50% to 70% compared with untreated controls. Immunohistochemical studies demonstrated that a significant proliferation of vascular smooth muscle cells (SMCs) constituted neointimal lesions between 4 and 8 weeks. The majority of SMCs expressed platelet-derived growth factor (PDGF) receptors-alpha and -beta, which were significantly reduced by suramin treatment. In vitro studies indicated that suramin completely blocked PDGF receptor activation or phosphorylation stimulated by PDGF-AB, inhibited activation of mitogen-activated protein kinase (ERK) kinases (MEK1/2) and ERK1/2, and abrogated transcription factor AP-1 DNA-binding activity.

CONCLUSIONS

Suramin inhibited SMC migration and proliferation in vivo and in vitro by blocking PDGF-initiated PDGF receptor and MAPK-AP-1 signaling. These findings indicate that locally applied suramin is effective in a mouse model of venous bypass graft arteriosclerosis.

Inhibition of arteriosclerosis by T-cell depletion in normocholesterolemic rabbits immunized with heat shock protein 65

Previous studies in our laboratory have shown that arteriosclerotic changes can be induced in normocholesterolemic rabbits by immunization with mycobacterial heat shock protein (hsp) 65. To further investigate the immunologic mechanisms underlying such vascular lesions, 39 male New Zealand White rabbits were treated by triple immunization with fortified Freund's complete adjuvant containing 5 mg/mL Mycobacterium tuberculosis as a source of hsp65 and simultaneous immunosuppressive therapy twice per week with either anti-CD3 monoclonal antibody (1 mg/kg) and prednisolone (1 mg/kg) or prednisolone (1 mg/kg) alone. Sixteen weeks after the first immunization the animals were killed, and as expected, severe arteriosclerotic lesions in the intima of the aortic arch were found in 9 of 10 immunized rabbits. However, only 1 of 10 rabbits immunized and immunosuppressed with the combined anti-CD3 monoclonal antibody and prednisolone treatment showed a single moderate lesion in the aorta, whereas 5 of 9 rabbits immunized and immunosuppressed by prednisolone treatment alone showed lesions, albeit mild. In conclusion, the early inflammatory stages of arteriosclerotic lesions induced by immunization with hsp65 can be inhibited by immunosuppressive therapy with anti-CD3 monoclonal antibody.

Atherosclerosis--an autoimmune disease

Immune-inflammatory processes are increasingly discussed as possible pathogenetic factors involved in the development of atherosclerosis. Here, we summarize data on which we have built our "immunological" hypothesis of atherogenesis. This concept is based on the observation that nearly everybody shows protective cellular and humoral immune reactions against microbial heat shock protein 60 (HSP 60). Because a high degree of antigenic homology exists between microbial (viral, bacterial, parasitic) and human HSP 60, this protective immunity may have to be "paid for" by the danger of cross-reactivity with human HSP 60 that is expressed by endothelial cells of stressed arteries. Arterial endothelial cells are more prone to produce HSP 60 and various adhesion molecules upon exposure to stress factors, including classical risk factors for atherosclerosis, due to their life-long exposure to the high arterial as compared to venous blood pressure. Also, endothelial cells are the first potential targets encountered by circulating HSP 60-specific T cells or antibodies. This concept not only opens new avenues for diagnostic approaches, but also may form the basis for new ways of therapeutic intervention.

Hypothalamic beta-endorphin concentrations are decreased in animals models of autoimmune disease

Complex interactions between the neuroendocrine and the immune systems are present in autoimmune diseases. The central opioid peptide beta-endorphin (BE) has been shown to modulate peripheral immune responses in normal animals. In the present study we analyze the hypothalamic concentrations of this peptide in two models of spontaneous autoimmune disease, the MRL [corrected] lpr/lpr mouse, that develops a lupus-like autoimmune disease, and the obese strain (OS) chickens afflicted with spontaneous autoimmune thyroiditis. In both instances, hypothalamic concentrations of BE are significantly lower than normal controls. In MRL [corrected] lpr/lpr mice, BE is already lower at 1 month of age, when no clinical sign of the disease is yet present. Similarly, low levels of BE are observed in OS chickens before the onset of thyroiditis, i.e., already at the embryonic stage. Moreover, a further decrease of BE is observed in OS chickens in correspondence with the first signs of thyroid mononuclear infiltration. Considering the immunosuppressive effects exerted by central BE, these results are suggestive of the fact that in autoimmune disease prone animals the low hypothalamic concentrations may be one of several factors predisposing for the development of autoimmune disease.

Myocardial injury leads to a release of heat shock protein (hsp) 60 and a suppression of the anti-hsp65 immune response

OBJECTIVE

While atherosclerosis is associated with high titers of autoantibodies to bacterial hsp65 crossreacting with human hsp60 (anti-hsp60 autoantibodies), myocardial infarction entails decreased humoral immune response to hsp65. We previously hypothesized that myocardial ischemia and subsequent infarction not only induce myocardial hsp60 expression, but also trigger release of myocardial hsp60 into the circulation, influencing the systemic hsp immune response via immune complex formation.

METHODS

In the present study, organ culture of rat hearts under circulatory arrest provided a model of myocardiocyte injury due to ischemia.

RESULTS

Reperfusion of ischemic hearts confirmed the occurrence of myocardial injury by a rise of heart enzymes. Myocardial hsp60 expression was induced up to threefold in response to ischemia, and most of hsp60 expression was localized to the muscle fibers. Analysis of coronary eluate revealed release of hsp60 from myocardium. In addition, hsp60-containing, but not hsp60-free, coronary eluate was recognized by anti-hsp65 serum antibodies and induced proliferation of hsp65-specific T cells. When hsp60-containing coronary eluate was reinjected into an hsp65-primed rat, both humoral and cellular hsp65-immune responses were strongly downregulated.

CONCLUSION

Our findings demonstrate the release of highly immunogenic and crossreactive hsp60 into the circulation in response to myocardial ischemia and myocardiocyte injury.

Proceedings of a symposium on "Immunosenescence--A major cause of disease in the elderly: from molecules to patients": summary

Age-dependent immunological alterations are responsible for a large number of diseases in the elderly. It was the aim of a Symposium held in Kühtai, Austria, from December 3-5, 1998, to bring together basic scientists, clinicians, and representatives of pharmaceutical companies to discuss immunosenescence and its consequences. Strategies were worked out for applying recent research results to the prevention and treatment of diseases in the aged and for organizing collaborations between teams throughout Europe within the 5th EU Framework Programme.

Endothelial cytotoxicity mediated by serum antibodies to heat shock proteins of Escherichia coli and Chlamydia pneumoniae: immune reactions to heat shock proteins as a possible link between infection and atherosclerosis

BACKGROUND

Growing evidence suggests that an immunological reaction against heat shock proteins (HSPs) may be involved in atherogenesis. Because HSPs show a high degree of amino acid sequence homology between different species, from prokaryotes to humans, we investigated the possibility of "antigenic mimicry" caused by an immunological cross-reaction between microorganisms and autoantigens.

METHODS AND RESULTS

Serum antibodies against the Escherichia coli HSP (GroEL) and the 60-kDa chlamydial HSP (cHSP60) from subjects with atherosclerosis were purified by use of affinity chromatography. Western blot analyses and competitive ELISAs confirmed the cross-reaction of the eluted antibodies with human HSP60 and the bacterial counterparts. The cytotoxicity of anti-GroEL and anti-cHSP60 antibodies was determined on human endothelial cells labeled with 51Cr. A significant difference (40% versus 8%) was observed in the specific 51Cr release of heat-treated (42 degrees C for 30 minutes) and untreated cells, respectively, in the presence of these anti-HSP antibodies and complement. This effect was blocked by addition of 100 microg/mL recombinant GroEL. In addition, seropositivity against specific non-HSP60 Chlamydia pneumoniae antigens is more prominent among high-anti-HSP titer sera than low-titer sera.

CONCLUSIONS

Serum antibodies against HSP65/60 cross-react with human HSP60, cHSP60, and GroEL; correlate with the presence of antibodies to C pneumoniae and endotoxin; and mediate endothelial cytotoxicity. These findings suggest that humoral immune reactions to bacterial HSPs, such as cHSP60 and GroEL, may play an important role in the process of vascular endothelial injury, which is believed to be a key event in the pathogenesis of atherosclerosis.

Enhanced fatty streak formation in C57BL/6J mice by immunization with heat shock protein-65

Recent data suggest that the immune system is involved in atherogenesis. Thus, interest has been raised as to the possible antigens that could serve as the initiators of the immune reaction. In the current work, we studied the effects of immunization with recombinant heat shock protein-65 (HSP-65) and HSP-65-rich Mycobacterium tuberculosis (MT) on early atherogenesis in C57BL/6J mice fed either a normal chow diet or a high-cholesterol diet (HCD). A rapid, cellular immune response to HSP-65 was evident in mice immunized with HSP-65 or with MT but not in the animals immunized with phosphate-buffered saline (PBS) alone. Early atherosclerosis was significantly enhanced in HCD-fed mice immunized with HSP-65 (n=10; mean aortic lesion size, 45 417+/-9258 microm2) or MT (n=15; 66 350+/-6850 microm2) compared with PBS-injected (n=10; 10 028+/-3599 microm2) or nonimmunized (n=10; 9500+/-2120 microm2) mice. No fatty streak lesions were observed in mice fed a chow diet regardless of the immunization protocol applied. Immunohistochemical analysis of atherosclerotic lesions from the HSP-65- and MT-immunized mice revealed infiltration of CD4 lymphocytes compared with the relatively lymphocyte-poor lesions in the PBS-treated or nonimmunized mice. Direct immunofluorescence analysis of lesions from HSP-65- and MT-immunized mice fed an HCD exhibited extensive deposits of immunoglobulins compared with the fatty streaks in the other study groups, consistent with the larger and more advanced lesions found in the former 2 groups. This model, which supports the involvement of HSP-65 in atherogenesis, furnishes a valuable tool to study the role of the immune system in atherogenesis.

Suppressive effects of anti-inflammatory agents on human endothelial cell activation and induction of heat shock proteins

BACKGROUND

Studies from our laboratory have shown that the earliest stages of atherosclerosis may be mediated by an autoimmune reaction against heat shock protein 60 (Hsp60). The interactions of Hsp60-specific T cells with arterial endothelial cells (EC) require expression of both Hsp60 and certain adhesion molecules shown to be induced simultaneously in EC by mechanical and other types of stress. Recently, it was shown that suppression of T cell-mediated immune responses by cyclosporin A (CyA) enhanced atherosclerotic lesion formation in mice. In contrast, aspirin was found to lower the risk of myocardial infarction in men. These conflicting observations may be due to different effects of anti-inflammatory agents on adhesion molecule and Hsp expression in EC, respectively.

MATERIAL AND METHODS

In the present study, we analyzed the effects of CyA, aspirin, and indomethacin on T cell proliferation using a proliferation assay. To explore the expression of adhesion molecules, monocyte chemoattractant protein-1 (MCP-1), and Hsp60 in human umbilical vein endothelial cells (HUVECs), Northern blot analyses were used. To examine the activation status of the transcription factors nuclear factor kappaB (NF-kappaB) and heat shock factor-1 (HSF-1), electrophoretic mobility shift assays were performed.

RESULTS

With the exception of indomethacin, the used immunosuppressive and anti-inflammatory agents significantly inhibited T cell proliferation in response to influenza virus antigen in a dose-dependent manner. Interestingly, CyA and indomethacin did not suppress tumor necrosis factor-alpha (TNF-alpha)-induced adhesion molecule expression on HUVECs, whereas aspirin had an inhibitory effect. These observations correlated with the modulation of NF-kappaB activity in EC. All agents tested induced expression of Hsp60 6 hr after application. In addition, aspirin and indomethacin, but not CyA, induced Hsp70 expression in HUVECs that correlated with induction of HSF-1 activity.

CONCLUSION

Our results show that the tested agents (except indomethacin) are inhibitors of the T cell-mediated immune response, as expected, that aspirin is an effective suppressor of adhesion molecule expression, and that all three agents can induce Hsp60 in HUVECs. These data provide the molecular basis for the notion that (1) part of the anti-atherogenic effect of aspirin may be due to the prevention of the adhesion of sensitized T cells to stressed EC; (2) that part of the atherosclerosis-promoting effect of CyA may be due to its potential as an inducer of Hsp60 expression and its inability to down-regulate adhesion molecule expression on EC; and (3) that down-regulation of MCP-1 expression by aspirin may result in decreased recruitment of monocytes into the arterial intima beneath stressed EC.

The role of providers in implementation of the National Kidney Foundation-Dialysis Outcomes Quality Initiative: Fresenius Medical Care North America perspective

This is a brief review of the history of utilization of quality indicators by a major dialysis provider and how those indicators have been modified in response to the National Kidney Foundation-Dialysis Outcomes Quality Initiative (NKF-DOQI). Fresenius Medical Care North America (FMCNA) has monitored adequacy of dialysis, anemia management, and nutrition therapy for a number of years, using a self-directed continuous quality improvement program. FMCNA supports the NKF-DOQI Guidelines and has used the DOQI as it continues to enhance its patient quality care program. Specific goals and action thresholds of that program are delineated.

Induction of mitogen-activated protein kinase phosphatase-1 by arachidonic acid in vascular smooth muscle cells

Arachidonic acid (AA) and its metabolites play important roles in a variety of biological processes, such as signal transduction, contraction, chemotaxis, and cell proliferation and differentiation. It was demonstrated recently that AA can activate mitogen-activated protein kinases (MAPKs), which are crucial for transducing signals initiating cell growth and apoptosis. Here we studied the effect of AA on the induction of MAPK phosphatase-1 (MKP-1) in vascular smooth muscle cells (VSMCs) and found that AA stimulated induction of MKP-1 mRNA and proteins in VSMCs in a time- and dose-dependent manner. Specific inhibitors of cyclooxygenase-, lipoxygenase-, and cytochrome P450-dependent metabolism did not affect AA-induced MKP-1 expression, indicating that eicosanoid biosynthesis was not involved in this process. The glutathione precursor N-acetylcysteine, an antioxidant, abolished AA-stimulated MKP-1 gene expression, whereas inhibition of protein kinase C by calphostin C had no influence on MKP-1 induction. VSMC pretreatment with genistein, a tyrosine kinase inhibitor, completely blocked AA-stimulated MKP-1 induction. MAPK kinase inhibitor PD 98059 did abolish AA-stimulated activation of extracellular signal-regulated kinases but not MKP-1 induction. Furthermore, agonists that increase AA release stimulated MKP-1 induction and activation of MAPKs, including extracellular signal-regulated kinases and c-Jun NH2-terminal protein kinases or stress-activated protein kinases. Taken together, our findings demonstrate that AA induced MKP-1 expression in VSMCs via activation of tyrosine kinases involving AA-induced free radical generation, suggesting an important role for MKP-1 in the regulation of AA-initiated signal transduction in VSMCs.

A previously unrecognized site of local accumulation of mononuclear cells. The vascular-associated lymphoid tissue

In recent years our laboratory has developed an immunological hypothesis for the pathogenesis of atherosclerosis. We have shown that cellular and humoral immune reactions against heat shock proteins (Hsps) 60/65 expressed on the surface of stressed endothelial cells comprise the initial event in the pathogenesis of this disease. In the course of these studies, we also investigated normal, unaffected arteries for control purposes (carotid bifurcations from children aged 8 weeks to 10 years). This investigation led to the unexpected and previously unknown finding that mononuclear cells pre-exist in the intima at bifurcation sites. Our findings can be summarized as follows: Mononuclear cells are always found in the intima, primarily at sites subjected to major hemodynamic stress. Although the proportion of macrophages vs CD3(+) T-cells differs, overall the latter clearly predominate. Most of the T-cells express the T-cell receptor (TCR)alpha/beta, but TCRgamma/delta cells are also present. We also identified dendritic cells and mast cells in the intima. Analogous to the mucosa-associated lymphoid tissue (MALT) we coined the designation "vascular-associated lymphoid tissue" (VALT) for these newly discovered cellular aggregates in the arterial intima.

Mouse model of venous bypass graft arteriosclerosis

Saphenous vein grafts are widely used for treatment of severe atherosclerosis via aortocoronary bypass surgery, a procedure often complicated by later occlusion of the graft vessel. Because the molecular mechanisms of this process remain largely unknown, quantitative models of venous bypass graft arteriosclerosis in transgenic mice could be useful to study this process at the genetic level. We describe herein a new model of vein grafts in the mouse that allows us to take advantage of transgenic, knockout, or mutant animals. Autologous or isogeneic vessels of the external jugular or vena cava veins were end-to-end grafted into carotid arteries of C57BL/6J mice. Vessel wall thickening was observed as early as 1 week after surgery and progressed to 4-, 10-, 15-, and 18-fold original thickness in grafted veins at age 2, 4, 8, and 16 weeks, respectively. The lumen of grafted veins was significantly narrowed because of neointima hyperplasia. Histological and immunohistochemical analyses revealed three lesion processes: marked loss of smooth muscle cells in vein segments 1 and 2 weeks after grafting, massive infiltration of mononuclear cells (CD11b/18+) in the vessel wall between 2 and 4 weeks, and a significant proliferation of vascular smooth muscle cells (alpha-actin+) to constitute neointimal lesions between 4 and 16 weeks. Similar vein graft lesions were obtained when external jugular veins or vena cava were isografted into carotid arteries of C57BL/6J mice. Moreover, no significant intima hyperplasia in vein-to-vein isografts was found, although there was leukocyte infiltration in the vessel wall. Thus, this model, which reproduces many of the features of human vein graft arteriosclerosis, should prove useful for our understanding of the mechanism of vein graft disease and to evaluate the effects of drugs and gene therapy on vascular diseases.

Thymic heterotypic cellular complexes in gene-targeted mice with defined blocks in T cell development and adhesion molecule expression

Thymocytes form unique multicellular complexes with epithelial cells (thymic nurse cells, TNC) and rosettes (ROS) with macrophages, epithelial cells and dendritic cells. To investigate the role of differentiation checkpoints in the formation of the thymic heterotypic complexes in vivo, we used mutant mice which have genetically defined blocks at early and late stages of T cell development. We show that RAG-1-/-, TCRbeta-/- , and p56lck-/- mice lack thymocyte ROS formation with epithelial cells, macrophages, or dendritic cells. TNC formation was not affected by TCRbeta and p56lck gene mutations but partially decreased in RAG-1-/- mice, indicating that TNC are the earliest thymocyte-stromal cell complexes formed in development, whereas ROS only appear after thymocytes have rearranged and expressed a functional TCRbeta chain. Genetic blocks in CD8 lineage commitment (CD8-/- and IFN regulatory factor-1-/- mice) and positive and negative T cell selection (CD45-/-, TCRalpha-/-, and CD30-/- mice) did not affect thymocyte-stromal cell complexes. Surprisingly, CD4-/- mice, but not MHC class II-/- mice, had significantly reduced numbers of TNC and ROS, in particular, a severe defect in ROS formation with thymic dendritic cells. The CD4-/- block in ROS and TNC formation was rescued by the introduction of a human CD4 transgene. Moreover, we show that the adhesion receptors CD44 and LFA-1 cooperate in the formation of the thymic microenvironment. These results provide genetic evidence on the role of defined stages in T cell development and adhesion molecules on thymocyte/stromal cell interactions in vitro.

Decline of shear stress-induced activation of extracellular signal-regulated kinases, but not stress-activated protein kinases, in in vitro propagated endothelial cells

We investigated the involvement of mitogen-activated protein kinase (MAPK) signal transduction pathways in human endothelial cells in response to shear stress and alterations of these kinases in in vitro-propagated endothelial cells (ECs). Potent activation (10-fold) of extracellular signal-regulated kinase (ERK2), a member of the MAPK family, occurred within 10 min of shear stress (5 dynes/cm2), whereupon rapid inactivation ensued. Shear stress also induced activation of stress-activated protein kinase (SAPK) or c-Jun NH2-terminal protein kinase (JNK) in ECs. Suramin pretreatment completely inhibited shear stress stimulation of ERK2, but not SAPK/JNK, highlighting a role for growth factor receptors in ERK activation. Translocation of ERK2 from the cytoplasm to the nucleus was observed in shear-stressed endothelial cells. In addition, we compared activities of MAPKs in shear-stressed cells derived from passages 4 and 10 (older). The magnitude of ERK2 activation was significantly lower in aged ECs compared to those of passage 4, while SAPK/JNK was not altered in the in vitro aged ECs. A similar level of ERK2 activation was found in both young and older cells stimulated with phorbol-12-myristate-13-acetate (PMA), indicating an age-related alteration of the plasma membrane. Taken together, these findings suggest that MAP kinase activation may be crucial for the expression of many genes in ECs stimulated by shear stress, and that an alteration in MAPK activities could contribute to the age-related decline in proliferative capacity.

Activation of PDGF receptor alpha in vascular smooth muscle cells by mechanical stress

Hypertension increases mechanical force on the arterial wall by as much as 30%, resulting in marked alterations in signal transductions and gene expression in vascular smooth muscle cells (VSMCs) that contribute to matrix protein synthesis, cell proliferation, and differentiation. How the mechanical stimuli are converted into a biological signal in cells has yet to be studied. We investigated the role of both cyclic strain and shear stresses in initiating the cellular signaling on cultured VSMCs and found that mechanical forces evoked activation of mitogen-activated protein kinases, followed by enhanced DNA binding activity of transcription factor AP-1. Physical forces rapidly induced phosphorylation of platelet-derived growth factor receptor (PDGFR) alpha, an activated state. When GRB2, an adapter protein, was immunoprecipitated from treated VSMCs followed by Western blot analysis with anti-phosphotyrosine, -PDGFR alpha, and -GRB2 antibodies, respectively, phosphotyrosine positive staining was observed on PDGFR alpha bands of the same blot in stretch-stressed VSMCs, supporting the mechanical stress-induced activation of PDGFR alpha. Conditioned medium from stretch-stressed VSMCs did not result in PDGFR alpha phosphorylation, and antibodies binding to all forms of PDGFs did not block stress-induced PDGFR alpha activation. Thus, mechanical stresses may directly perturb the cell surface or alter receptor conformation, thereby initiating signaling pathways normally used by growth factors.

Environmental influence on age-related changes of human lymphocyte membrane viscosity using severe combined immunodeficiency mice as an in vivo model

Peripheral blood lymphocytes (PBL) of healthy elderly people show increased plasma membrane viscosity compared to young subjects, that inversely correlates with lymphocyte proliferation after mitogen stimulation in vitro. Maintenance of a constant membrane viscosity, which is necessary for proper cell function, is crucially dependent on the membrane lipid composition. The cellular lipid metabolism, and thus lymphocyte function, may be subject to modulation by diet or drugs. To study the susceptibility of membrane viscosity to environmental conditions, we established an in vivo model using severe combined immunodeficiency (SCID) mice: human peripheral blood lymphocytes from healthy young and old subjects were engrafted for three days intraperitoneally into SCID mice to offer identical environmental conditions. First, we demonstrate that human lymphocytes can take up and utilize murine lipoproteins: engrafted human PBL can participate in the mouse lipid metabolism, and an exchange of membrane lipids in vivo is, therefore, possible. Second, plasma membrane viscosity was determined before and after engraftment: before engraftment, PBL from the elderly showed a significantly higher membrane viscosity than that from young controls, but this difference vanished during engraftment into SCID mice, wherein cells from both age groups exhibited nearly identical values. It was, therefore, concluded that lymphocyte membrane viscosity is influenced by environmental factors, and that the age-related increase is, in principle, reversible.

The role of (auto-) immunity in atherogenesis

Recent data from different laboratories have provided evidence that the first stages of atherosclerosis are inflammatory in nature. Research in the last decades on this multifactorial disease has primarily focussed on the role of lipids, with only a few anecdotal findings suggesting the involvement of the immune system in atherogenesis. Within the group of antigens that may be responsible for this immunoactivation during atherogenesis, heat shock protein (hsp) 65/60 became a serious candidate based on the fact that immunization] of normocholesterolemic rabbits with hsp65 leads to the development of arteriosclerotic lesions in the aortic intima and these primary inflammatory lesions are aggravated by a cholesterol-rich diet, thus completely resembling human fatty streaks and atherosclerotic plaques. Furthermore, T cells in atherosclerotic lesions of rabbits have been shown to react specially with mycobacterial hsp65, suggesting that cell-mediated immune responses to hsp60 are also involved in the pathogenesis of this disease In a large epidemiological study we demonstrated that serum antibodies to mycobacterial hsp65 were significantly increased in clinically healthy subjects with sonographically demonstrable carotid atherosclerosis. These antibodies crossreact with human hsp60. Thus further elucidation of the role of the role of the immune system in atherogenesis could enhance our understanding of the mechanism of this vascular disorder, and may lead to new therapeutic strategies for atherosclerosis.

Neuroendocrine-immune disturbances in animal models with spontaneous autoimmune diseases

According to our concept, the development of autoimmune disease depends on the presence of two sets of essential genes, one coding for an abnormal autoreactivity of the immune system, the other for a primary susceptibility of the target organ/structure for the immune attack. The final outcome of the disease in a given individual is then fine tuned by modulatory factors, such as diet or hormones. With regard to the latter, the immuno-endocrine interaction via the hypothalamo-pituitary-adrenal (HPA) axis has proven to be of special importance. Investigating the so-called Obese strain (OS) of chickens, an animal model with a spontaneously occurring Hashimoto-like autoimmune thyroiditis, we have first shown an impaired surge of glucocorticoid hormones after stimulation of the HPA axis by antigens or certain cytokines (glucocorticoid-increasing factors--GIFs). More recently, we have found a similar behavior in models with systemic autoimmune diseases, that is, murine lupus erythematosus and avian scleroderma. More detailed studies have, however, proven that the mechanisms underlying this altered immuno-endocrine communication via the HPA axis differs in different models. Finally, recent data point to the possibility that the classical pathways of glucocorticoid-T-cell interactions also take place in the thymus itself, which has been shown to be a site of steroid hormone production.

Interleukin-1 receptor defect in autoimmune NZB mouse brain

Interleukin-1 receptors (IL-1R type I and II) have been characterized in murine nervous structures (hippocampus and frontal cortex), in vascular structures (vessels, choroid plexus), and in the anterior pituitary. Because interleukin-1 (IL-1), injected or induced in the brain, is a powerful regulator of the stress axis and immune functions, it was of interest to investigate IL-1Rs and IL-1 in autoimmune mice. In control mice, bacterial lipopolysaccharide (LPS), administered i.p. or i.c.v., induces a sharp decrease in available brain IL-1 receptors, in spite of a moderate increase in mRNAs for both receptor types. This is concomitant with an increase in IL-1 alpha, beta, and ra mRNA. Ligand production clearly overcomes receptor turnover. In autoimmune mice (NZB and NZB/NZW F1), a strong defect in IL-1R (type I) is demonstrated in the dentate gyrus. This tissue-specific defect cannot be explained by increased occupancy by endogeneous ligands as for LPS-treated mice. The transmission of the defect is Mendelian and suggests the involvement of a single gene. However patterns of IL-1R mRNAs (evaluated by RT-PCR) are similar in NZB and in controls, suggesting a translational or post-translational abnormality. The contribution of this genetic disorder in the development of autoimmunity remains to be clarified. Because the brain IL-1 system sends inhibitory signals towards immune functions, this lack of functional IL-1 binding sites might participate in the disregulations observed in NZB autoimmune mice.

Hyperimmunization of apo-E-deficient mice with homologous malondialdehyde low-density lipoprotein suppresses early atherogenesis

The role of the immune system in modulating atherosclerosis has recently been the subject of intensive research. Several previous authors have put forward a paradigm of the autoimmune process occurring in the vicinity of the plaque. Two recent studies have shown that immunization of rabbits with homologous modified low-density lipoprotein (LDL) led to suppression of atherosclerosis. In the current study we evaluated the effects of homologous malondialdehyde (MDA)-LDL immunizations on atherogenesis in apo-E-deficient mice. Two groups of female chow-diet-fed, apo-E-deficient mice (n = 10) were either immunized with homologous MDA-LDL or with phosphate buffer saline (PBS) at 2-week intervals. The mice were sacrificed 12 weeks following the primary immunization. The MDA-LDL-immunized mice were shown to develop high titers of anti-MDA-LDL antibodies. Atherosclerosis, determined by the lesion size at the aortic sinus, was significantly suppressed in the MDA-LDL-immunized mice as compared with their littermates immunized with PBS (mean area +/- S.D.; 74000 +/- 17300 microm2 versus 158000 +/- 12800 microm2; P < 0.01). No differences were found between the groups with respect to the cellular composition of the atherosclerotic plaques. The results of this study show that immunization with MDA-LDL has a protective effect in apo-E-deficient mice, and further suggests that this mouse model is suitable for studies of immunomodulation.

Inhibition of the development of spontaneous autoimmune thyroiditis in the obese strain (OS) chickens by in vivo treatment with anti-CD4 or anti-CD8 antibodies

The involvement of CD4+ and CD8+ T cells in pathogenesis of spontaneous autoimmune thyroiditis (SAT) in obese strain (OS) chickens has not been studied in depth until now. We depleted CD4+ or CD8+ T cells in OS chickens by treatment with murine monoclonal anti-CD4 or anti-CD8 antibodies at 3 day intervals beginning at hatching. The birds were killed at 19-25 days of age. Treatment with anti-CD4 antibody completely prevented SAT development, while treatment with anti-CD8 antibody partially inhibited SAT. These results show the critical role of CD4+ T cells in the development of SAT in OS chickens, and indicate that CD8+ T cells are also involved in SAT pathogenesis.

Primary and secondary alterations of immune reactivity in the elderly: impact of dietary factors and disease

The function of the immune system declines with age. It is the aim of the present review to demonstrate that it makes sense to distinguish between primary and secondary alterations of immune reactivity in the elderly. Primary changes occur as the result of an age-dependent intrinsic decline of immune responsiveness. They also occur in healthy persons, i.e. persons selected according to the criteria of the SENIEUR protocol of the European Community's Concerted Action Program on Aging (EURAGE). T lymphocytes are hereby more severely affected than B cells or antigen presenting cells, possibly due to the involution of the thymus, which is almost complete at the age of 60. Secondary immunological changes occur as the result of environmental factors including diet, drug intake, physical activity etc. or are alternatively due to underlying diseases. In this article, the effects of high lipid intake as well as the impact of diseases, such as for instance Alzheimer's disease and atherosclerosis, will be addressed. The results underline the complexity of immunological alterations to be expected in old age. Changes in the aging immune system represent an opportunity for increased frequency and severity of disease and endanger the protective effect of vaccination.

Salivary anti-hsp65 antibodies as a diagnostic marker for gingivitis and a possible link to atherosclerosis

Levels of specific salivary IgA antibodies against mycobacterial heat shock protein (hsp) 65 are significantly increased in patients with gingivitis when compared to clinically healthy subjects. The process of identifying the hsp65 epitopes recognized by the salivary antibodies, binding to overlapping 15-mer-hsp65 peptides, was assessed. Time-resolved fluorescence immunoassays using 15-mer overlapping peptides spanning the whole hsp65 molecule revealed six distinct sequences recognized by anti-hsp65 IgA antibodies. Due to the high degree of sequence homology between mycobacterial hsp65, cognates of the hsp60 family of oral bacterial flora and human hsp60, these six epitopes may serve as cross-reactive autoantigens in certain circumstances in vivo and could incite an autoimmune response that contributes to the initiation of gingivitis.

Altered procollagen mRNA expression during the progression of avian scleroderma

BACKGROUND

Spontaneous animal models of human autoimmune diseases provide the means to study the very first pathogenetic events, which is not possible in their human counterparts. This is particularly true for connective tissue diseases in which clinical symptoms become manifest only after a long and still obscure course of immunologic, inflammatory, and fibrotic processes. University of California at Davis line 200 chickens (UCD-200) develop a hereditary scleroderma-like disease resembling the entire spectrum of human systemic sclerosis, such as early endothelial cell damage, severe lymphocytic infiltration, and accumulation of collagen in skin and internal organs.

MATERIALS AND METHODS

In the present study, we investigated mRNA levels of alpha 1(I), alpha 2(I), alpha 1(II), alpha 1(III), alpha 1(VI), alpha 2(VI), and alpha 3(VI) procollagen and GAPDH using digoxigenin-labeled antisense probes in a nonradioactive ribonuclease protection assay (RPA). We analyzed tissue samples from comb, esophagus, heart, lung, and liver of UCD-200 chickens at different stages of the disease, and healthy UCD-058 chickens.

RESULTS

During the early inflammatory stage of the disease, the ratios of procollagen types VI/I and types VI/III increased 7-fold in comb tissue, followed by a 3-fold elevation in type I procollagen transcripts in the late acute stage. In the chronic stage, alpha 1(III) procollagen message was increased 2-fold. Additionally, hybridization with the 180 bp alpha 2(I) antisense probe resulted in two bands of 180 bp and 115 bp, respectively, in the RPA. The ratio of these two previously undescribed bands changes in the early stage of the disease both in comb and esophagus.

CONCLUSIONS

In an animal model with a spontaneous scleroderma-like disease we found a characteristic, sequential increase in type VI, type I, and type III procollagen transcripts, and we found evidence for the presence and altered ratio of two mRNA variants of alpha 2(I) procollagen, possibly caused by alternative splicing. Comparative analysis of alpha 2(I) procollagen variants in early stages of avian scleroderma and human SSc might provide answers to unresolved questions concerning the molecular basis for generalized fibrosis in scleroderma.

Murine thymic nurse cells and rosettes: analysis of adhesion molecule expression using confocal microscopy and a simplified enrichment method

Thymic nurse cells (TNC) and T-cell stromal rosettes (ROS) are two in vivo models for stromal cell-thymocyte interactions. We describe a simplified enrichment method for TNC and ROS that overcomes the necessity for large amounts of tissue. The complexes were further analyzed with confocal microscopy, and three subunits of ROS were defined on the basis of their central cell phenotype, i.e., macrophage, dendritic, or epithelial cell rosettes. Because adhesion molecules are proposed to play a crucial role in T-cell development, we investigated CD44, LFA-1, and ICAM-1 expression in such complexes. The epithelial component of TNC expresses CD44 and ICAM-1, whereas intra-TNC thymocytes are LFA-negative. With regard to ROS, all subsets expressed CD44, and macrophage and dendritic cell ROS were also ICAM-1-positive and LFA-1-positive. The current protocol opens the possibility for further in vivo analysis of stromal cell-thymocyte interactions, e.g., for studies of scarce gene mutant mice.

Nitric oxide induces heat-shock protein 70 expression in vascular smooth muscle cells via activation of heat shock factor 1

Current data suggest that nitric oxide (NO) is a double-edged sword that could result in relaxation and/or cytotoxicity of vascular smooth muscle cells (SMCs) via cGMP- dependent or -independent signal pathways. Stress or heat shock proteins (hsps) have been shown to be augmented in arterial SMCs during acute hypertension and atherosclerosis, both conditions that are believed to correlate with disturbed NO production. In the present study, we demonstrate that NO generated from sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine, and spermine/nitric oxide complex leads to hsp70 induction in cultured SMCs. Western blot analysis demonstrated that hsp70 protein expression peaked between 6 and 12 h after treatment with SNP, and elevated protein levels were preceded by induction of hsp70 mRNA within 3 h. Induction of hsp70 mRNA was associated with the activation of heat shock transcription factor 1 (HSF1), suggesting that the response was regulated at the transcriptional level. HSF1 activation was completely blocked by hemoglobin, dithiothreitol, and cycloheximide, suggesting that the protein damage and nascent polypeptide formation induced by NO may initiate this activation. Furthermore, SMCs pretreated with heat shock (42 degrees C) for 30 min were significantly protected from death induced by NO. Thus, we provide evidence that NO induces hsp70 expression in SMCs via HSF1 activation. Induction of hsp70 could be important in protecting SMCs from injury resulting from NO stimulation.