ACE (CD143) in granulomatösen Entzündungen von Mensch und Tier: Speziesspezifische Expression in Endothel und Makrophagen

Abstract

Angiotensin I-converting enzyme (ACE, Kininase II, CD143) mediates the effects of the renin-angiotensin system (RAS) and kallikrein-kinin system (KKS) by regulating the tissue levels of bioactive angiotensins and kinins. Though remarkable vessel, organ and species specificity has recently been reported, only little is known about the distribution of ACE in tissues of man and animals. Furthermore, the abnormally increased serum levels of ACE found in sarcoidosis and other histiocytic diseases were not adequately explained by morphological methods. Therefore, the tissue expression of the enzyme was assessed by novel monoclonal antibodies (mAbs) and immunohistochemistry. This allowed (1) a comparison of ACE-expression of macrophages in human diseases of different etiology, (2) the detection of possible cross-reactivity of anti-ACE mAbs between different animal species, and (3) the subsequent analysis of species specific differences in the distribution of ACE in endothelial cells, macrophages and granulomatous diseases.
Formalin-fixed and paraffin-embedded tissue specimen of patients with clinically confirmed tuberculosis (n = 41), sarcoidosis (n = 29), toxoplasmosis (n = 30) and foreign body granuloma (n = 14) were obtained from the Institute of Pathology, JL-University of Giessen. Tissue specimens of patients with peculiar granulomatous and histiocytic diseases such as leprosy (n = 9), blastomycosis (n = 10), schistosomiasis (n = 1), and mycobacterial histiocytosis (n = 2) were obtained from the Department of Pathology, University of Campinas, Brazil. Furthermore, formalin-fixed and paraffin-embedded tissue specimen of 21 different animal species, received from the tissue archives of the Institute of Veterinary Pathology, JL-University of Giessen, were examined. Here, histiocytic and granulomatous diseases were analyzed in cases of tuberculosis of anthropoid ape, dog, cat and bulk-cat, pulmonary mycosis of rabbit and foreign body granuloma of dog. A set of six mAbs (CG1, CG2, CG3, CG4, CG5 and 5F1) to denatured human ACE were applied on the tissues of man and different animal species, supplemented by the mAbs JC/70A to human CD31, KP1 to human CD68 and MR12/53 as an unspecific control. Immunoreactivity was detected by the APAAP-technique and was uniformly analyzed. A semiquantitative evaluation and statistical comparison of relevant morphological and immunohistochemical features was performed in sarcoidosis, tuberculosis and toxoplasmosis of man.
Among all mAbs to human ACE, only CG2 showed a cross-reactivity with the ACE-molecule of anthropoid ape, carnivores (dog, cat, bulk-cat), rabbit and armadillo as indicated by similar tissue expression, for example at the brush borders of proximal kidney tubules. In contrast, the denatured ACE of mouse, rat, hamster, guinea-pig and herbi- and omnivores (cow, sheep, goat, horse and pig) was not immunoreactive. This implies that certain domains of the ACE-protein, exhibiting immunogenic similarity between different species, are evolutionary preserved. However, the endothelial distribution of ACE differed markedly in the analyzed vessels, organs and animal species. Whereas alveolar endothelium generally showed a strong and uniform ACE-expression in all cross-reactive species, ACE was largely absent from endothelial cells of most animal kidneys and completely missed in renal vessels of the rabbit and anthropoid apes. Only carnivores like dog and cat showed an expression of ACE in the venous endothelium of the splanchnic and portal vessel system. Far beyond former findings in man and rat, these results confirmed the heterogeneity in endothelial distribution of ACE for numerous animal species. Furthermore, this suggests a different regulation of blood pressure and circulating RAS and KKS, adapted to organ and species specific requirements.
Depending on species and cell activation, heterogeneous ACE-expression was found in macrophages as well. Whereas human alveolar macrophages and activated histiocytes regularly showed some immunoreactivity, these cells were completely negative for ACE in all examined animal species. Nevertheless, in animals affected by tuberculosis, strong ACE-expression for example was found in all epitheloid cell granulomas of anthropoid ape and to some extent also in granulomas of dog and cat. In contrast, rabbits did not show any ACE-expression in macrophages or histiocytes despite massive tuberculosis, and typical epitheloid cell reactions were not found. The same was true for most tuberculous tissues of bulk-cats. This indicates that the capability of ACE-expression in macrophages may be linked with the epitheloid cell reaction. However, there was no substantial difference in ACE expression between sarcoidosis, tuberculosis and toxoplasmosis in man. The similar morphology and ACE-expression of epitheloid-cell granulomas in sarcoidosis and tuberculosis may not explain the different serum levels of the enzyme, suggesting other factors of influence in these diseases. For example, secretases generating the measurable form of plasmatic ACE could belong to those still unknown factors. Multifactorial analysis showed that not lymphocytes but macrophages themselves had a significant influence on their own accumulation and ACE-expression in granulomatous diseases. This finding fits the recently discovered relationship between ACE and the macrophage chemotactic protein 1 (MCP-1) that is produced by macrophages. At least experimentally, MCP-1 is inducible by angiotensin II. Moreover, MCP-1 is responsible for the accumulation of macrophages and correlates with both the ACE-content and degree of granulomatous tissue alterations. The own results indicate that animal species lacking ACE in the spectrum of macrophage activation may not be able to form epitheloid cell granulomas which are comparable