Lessons from animal models of vasculitis

Animal Models of Vasculitis

The diagnosis of vasculitis in rheumatoid arthritis (RV) is associated with considerable mortality; therefore, understanding the basic mechanisms underlying the pathogenesis of vasculitis is very important. Animal models of vasculitis have contributed to elucidating such mechanisms. We here introduce a Candida albicans water-soluble glycoprotein (CAWS)-induced vasculitis model and the methodological approach to evaluate inflammatory vascular change.

CDCP1 on Dendritic Cells Contributes to the Development of a Model of Kawasaki Disease

The etiology and pathology of Kawasaki disease (KD) remain elusive. Cub domain-containing protein 1 (CDCP1), a cell-surface protein that confers poor prognosis of patients with certain solid tumors, was recently identified as one of the most significantly upregulated genes in SARS-CoV-2-infected children who developed systemic vasculitis, a hallmark of KD. However, a potential role of CDCP1 in KD has not previously been explored. In this study, we found that CDCP1 knockout (KO) mice exhibited attenuated coronary and aortic vasculitis and decreased serum Candida albicans water-soluble fraction (CAWS)-specific IgM/IgG2a and IL-6 concentrations compared with wild-type mice in an established model of KD induced by CAWS administration. CDCP1 expression was not detectable in cardiomyocytes, cardio fibroblasts, or coronary endothelium, but constitutive expression of CDCP1 was observed on dendritic cells (DCs) and was upregulated by CAWS stimulation. CAWS-induced IL-6 production was significantly reduced in CDCP1 KO DCs, in association with impaired Syk-MAPK signaling pathway activation. These novel findings suggest that CDCP1 might regulate KD development by modulating IL-6 production from DCs via the Syk-MAPK signaling pathway.

Dectin-2-induced CCL2 production in tissue-resident macrophages ignites cardiac arteritis

Environmental triggers, including those from pathogens, are thought to play an important role in triggering autoimmune diseases, such as vasculitis, in genetically susceptible individuals. The mechanism by which activation of the innate immune system contributes to vessel-specific autoimmunity in vasculitis is not known. Systemic administration of Candida albicans water-soluble extract (CAWS) induces vasculitis in the aortic root and coronary arteries of mice that mimics human Kawasaki disease. We found that Dectin-2 signaling in macrophages resident in the aortic root of the heart induced early CCL2 production and the initial recruitment of CCR2+ inflammatory monocytes (iMo) into the aortic root and coronary arteries. iMo differentiated into monocyte-derived dendritic cells (Mo-DC) in the vessel wall and were induced to release IL-1β in a Dectin-2-Syk-NLRP3 inflammasome dependent pathway. IL-1β then activated cardiac endothelial cells to express CXCL1 and CCL2 and adhesion molecules that induced neutrophil and further iMo recruitment and accumulation in the aortic root and coronary arteries. Our findings demonstrate that Dectin-2-mediated induction of CCL2 production by macrophages resident in the aortic root and coronary arteries initiates vascular inflammation in a model of Kawasaki disease, suggesting an important role for the innate immune system in initiating vasculitis.

Spontaneously occurring cardiovascular lesions in commonly used laboratory animals

The search for new chemical entities which are clinically effective and do not adversely affect the cardiovascular system is an ongoing objective. In vivo studies designed to detect potential drug-induced cardiovascular toxicity typically utilize both rodent and non-rodent species. An important component of such studies includes the microscopic evaluation of tissues for histopathologic changes. A factor which could potentially complicate this type of evaluation relates to the potential for laboratory animals to develop natural or spontaneous pathological cardiovascular lesions. Some types of these naturally occurring alterations are similar to those induced by chemical compounds and thus could confound accurate interpretation. Accurate morphologic analysis becomes contingent upon the ability to distinguish spontaneous cardiovascular changes from actual drug-induced lesions. A summary of some of the more frequently reported spontaneous cardiovascular alterations in commonly-used laboratory animals is presented below. Special emphasis is given to the spectrum of spontaneous background myocardial pathology that might be encountered during preclinical studies conducted to identify potential cardiotoxic actions of anticancer agents.

Animal Models of Vasculitis

The diagnosis of vasculitis in rheumatoid arthritis (RV) is associated with considerable mortality; therefore, understanding the basic mechanisms underlying the pathogenesis of vasculitis is very important. Animal models of vasculitis have contributed to elucidating such mechanisms. We here introduce a Candida albicans water-soluble (CAWS) glycoprotein-induced vasculitis model and the methodological approach to evaluate inflammatory vascular change.

Spontaneous aortitis in the Balb/c mouse

We examined whether high incidence rates (18%-56%) of inflammation in the root of the aorta detected in a Balb/c mouse model for hind limb ischemia were related to the surgical procedure. Twenty mice underwent ligation of the femoral artery; incidences of aortic root inflammation were compared to those observed in controls. We used a multiple-section sampling method to increase the sensitivity of the diagnostic rates. Although a cumulative incidence of 12.5% was found, no difference was seen in the overall incidence rates between the control and the surgically treated groups. Evaluation of blood levels of inflammatory cytokines showed that ligation of the femoral artery produced higher levels of interleukin-6 in the surgically transected group of mice. The development of spontaneous arteritis in this strain must be considered in future studies.

The cysteine-cluster motif of c-Src: its role for the heavy metal-mediated activation of kinase

We have previously reported that c-Src is activated by mercuric chloride (HgCl(2)). We investigated the mechanism of this activation and found that in vitro activation of c-Src by HgCl(2) did not require tyrosine residues at 416 and 527. Both SH2 and SH3 domains of c-Src were dispensable for the activation by HgCl(2). In contrast, iodoacetoamide (IAA) that binds to thiol side chain of cysteine blocked the activation of c-Src by HgCl(2). To obtain more clues, each cysteine residue of c-Src was replaced with alanine. Of six cysteine residues in the kinase domain of c-Src, Cys483 and Cys498 located in the C-terminal portion as a cysteine-cluster (CC) motif were critical for the activation. In addition, other Src family kinases, Yes and Lyn, were activated by treatment with HgCl(2), and cysteine residues, especially those correspond to Cys498 of Src in the CC motif of these kinases, were also required for the activation of the kinases by HgCl(2). In addition to these observations, treatment of cells with HgCl(2) dramatically activated the wild-type c-Src, whereas it could not activate the mutant form of Src with a substitution of Cys498. Taken together, our results disclose that cysteine residues in the CC motif of c-Src, Cys483 and Cys498, act as a module for the activation of the kinase by a heavy metal compound, mercuric chloride.

Analysis of a Cluster of Cases of Wegener Granulomatosis

BACKGROUND

Wegener granulomatosis is a chronic inflammatory autoimmune disease of unknown etiology. The sporadic occurrence, lack of familial or genetic associations, and rising incidence suggest possible exposure to environmental agents as causative for this disease.

OBJECTIVE

The objective of this study was to examine possible environmental triggers of Wegener granulomatosis.

METHODS

While conducting an environmental survey of potential precipitants of Wegener granulomatosis on a cohort of patients seen at Doylestown Hospital and at the University of Pennsylvania, we identified a cluster of cases in the Dublin, Pennsylvania, region. Through hospital records and patient contacts, we located 7 cases diagnosed in a 3-year period within a 10-mile radius of an Environmental Protection Agency (EPA) Superfund toxic waste site. The radius of inclusion represents a population of approximately 50,000 individuals. Assuming complete ascertainment of cases--which is unlikely given the methods used to acquire patients--the prevalence is 2- to 4-fold greater than the expected rate of 3 per 100,000. We identified toxins at or above "action level" within the demarcated geographic region using published data from the EPA. Furthermore, we queried patients regarding their particular chemical exposures.

RESULTS

These patients with Wegener granulomatosis were possibly exposed to high levels of trichloroethylene (TCE), vinyl chloride, methyl tertiary-butyl ether (MTBE), dichloroethene (DCE), and chromic acid from several industrial waste sites within the area. Additionally, these patients reported a total of greater than 30 possible exposures, including the aforesaid chemical contaminants. Three of 5 patients whose water source is known had well water that exposed them to industrial runoff and necessitated EPA intervention.

CONCLUSION

This data, along with other epidemiologic studies, suggest possible toxic exposures as potentially correctable risk factors for Wegener granulomatosis. We encourage clinicians to seek data that suggests an unusual environmental exposure and to solicit information that might implicate an industrial source for these exposures.

Architectural remodelling in lungs of rabbits induced by type V collagen immunization: a preliminary morphologic model to study diffuse connective tissue diseases

The pathogenesis of diffuse connective tissue diseases (DCTD) is still unknown and has been extensively studied regarding its autoimmunity aspects related to extracellular matrix (ECM) remodelling, with an emphasis on the collagens at the inflammatory site. The present paper describes the pulmonary architectural and repair/remodelling responses to injury after immunization of rabbits with human type V collagen. The animal model consisted of rabbits immunized with collagen mixed with Freund's adjuvant and sacrificed 7, 15, 30, 75, and 120 days after the first of four doses of antigen. Pulmonary architecture remodelling response was evaluated by histology, morphometry, and the immunofluorescence method, according to compartments of reference (parenchyma and interstitium) and injury: 1 inflammation (polymorphonuclear and mononuclear cells); 2-repair (fibrosis) and 3-ECM remodelling (collagen system). The results showed an intense inflammatory involvement of the pulmonary vascular and bronchiolar parenchyma, characterized by increased wall thickness in small arteries, infiltrations by pseudoeosinophils, and mononuclear cells. Progressive remodelling of the pulmonary ECM was characterized by collagen deposition in the septal and bronchovascular interstitium, especially in rabbits sacrifices at 75 and 120 days. The ECM remodelling process was not reproduced when rabbits were inoculated with collagen types I and III. We conclude that the model reproduces morphologic changes similar to those observed in many DCTD, encouraging realization of other experiments to gain a better understanding of the pathogenesis of these diseases.

Wegener's granulomatosis: Possible role of environmental agents in its pathogenesis

OBJECTIVE

To investigate the possibility that environmental agents contribute to the pathogenesis of Wegener's granulomatosis (WG).

METHODS

We undertook an extensive search for possible environmental exposures by developing a comprehensive questionnaire that was administered by telephone interview to 53 patients with WG and 2 control groups: one with osteoarthritis and the other with gout. Questions focused on hobbies and vocations, work, home, and allergies. Exact logistic regression was used to calculate odds ratios and 95% confidence intervals after adjusting for potential confounders. After adjusting for age and sex, data are reported for all exposures with odds ratios >2.0 against either control group or for any allergic propensity.

RESULTS

Results suggest that mercury and perhaps lead exposure were positively associated with WG as compared with either control group, although the number of patients exposed was small. A prior history of allergy was also associated with WG as compared with either control group.

CONCLUSION

We conclude that heavy metal exposure and a prior history of allergy may play a role in the etiopathogenesis of Wegener's granulomatosis.

Diagnostic and pathogenetic role of antineutrophil cytoplasmic autoantibodies

Anti-neutrophil cytoplasmic antibodies (ANCA) are mostly known as a useful diagnostic tool in patients with small-vessel vasculitides. With the accumulating knowledge of these autoantibodies, however, it becomes clear that the role of ANCA may not be only limited to a diagnosis of such disorders. The current review addresses, in addition to classical diagnostic associations, other diseases connected with ANCA positivity, both in adults and in children. The etiology of ANCA remains unknown, but still, the importance of both genetic and environmental factors is undoubted. The role of infection and chemicals in the etiology of ANCA-associated diseases is stressed in particular. A pathogenetic role of ANCA is suggested because of clinical observations based on the correlation of the vasculitis activity and the titer of ANCA. Many experiments show the effects of ANCA in various steps of an inflammatory process, particularly on leukocyte microbicidal activity and oxidative burst. Recent findings are analyzed in the experimental field and they are correlated with clinical significance.