https://doi.org/10.1007/s00392-025-02625-4
1Universitätsklinikum Carl Gustav Carus Dresden, Klinik und Poliklinik für Viszeral-, Thorax- und Gefäßchirurgie Gefäß- und Endovaskuläre Chirurgie Dresden, Deutschland; 2Universitätsklinikum Carl Gustav Carus an der TU Dresden Institut für klinische Chemie und Laboratoriumsmedizin Dresden, Deutschland; 3Otto-von-Guericke-Universität Magdeburg Medizinische Fakultät, Universitätsklinikum Labor für Experimentelle Kardiologie Magdeburg, Deutschland
Introduction: Most abdominal aortic aneurysms (AAA) are covered by an intraluminal thrombus (ILT). Upon hemolysis, hemoglobin (Hb) is released from erythrocytes. Hemoglobin promotes the formation of reactive oxygen species (ROS) via the Fenton reaction and thus drives the degeneration of the vessel wall. For detoxification, Hb is bound to haptoglobin and internalized by the scavenger receptor CD163, which is exclusively expressed on monocytes and macrophages. Internalized heme is degraded by the anti-oxidative enzyme heme-oxygenase-1 (HO-1). Further, a soluble form of CD163 (sCD163) exists that is released upon pathological conditions e.g. in oxidative stress. Increased expression of CD163 and HO-1 is a hallmark of MHem macrophages, which are known for their atheroprotective role. However, the role of Mhem macrophages in pathogenesis of AAA is yet unclear.
Materials and Methods: CD163 and glycophorin C protein expression was analysed in aortic tissue of AAA patients. Primary monocytes were isolated from whole blood of AAA patients and varicosis patients that served as controls, and differentiated autologously or into MHem macrophages by stimulation with hemin. Afterwards, CD163 and HMOX1 mRNA expression were analyzed. Differentiated macrophages were characterized by ROS formation, lipidperoxidation, migration and phagocytosis. An erythrocytelysate was added to the differentiated MHem macrophages to assess the effect of hemorrhage. In order to analyse the signalling pathway, HO-1 was inhibited pharmacologically by zinc protoporphyrin (ZnPP) or genetically by CRISPR-Cas9. Results: CD163+ cells were found in hemorrhagic areas in late-stage AAA. Autologously differentiated macrophages from AAA showed a 2.5-fold increase in CD163 mRNA expression (p=0.04) compared to controls, whereas HO-1 mRNA expression did not differ. Accordingly, macrophages of AAA patients secreted more sCD163 (p=0.02). Macrophages of AAA patients showed a strong positive correlation of CD163 and HO-1 (rS=0.96, p=0.0001), which was completely absent in the controls (rP=0.02, p=0.96). Moreover, macrophages from patients with AAA tended to show decreased phagocytosis (p=0.08), but lipidperoxidation and migration potential did not differ. Hemin induced HO-1 mRNA expression in both groups (p<0.01), but did not lead to the positive correlation of the MHem markers as described in the AAA group. Interestingly, hemin tended to induce a migratory response in AAA patients only (p=0.07), led to increased lipidperoxidation in both groups (both p=0.03), but further decreased phagocytosis (p=0.05). Moreover, heme-differentiated macrophages of AAA patients tended to have an increased migratory potential (p=0.08) and are more susceptible to ROS production after menadione stimulation (p=0.06). The addition of an erythrocyte lysate to MHem did not change HO-1 or CD163 mRNA expression. Pharmacological inhibition of HO-1 activity as well as genetic deletion resulted in increased HO-1-, but decreased CD163 mRNA expression. Deletion of CD163 had no effect on HO-1 expression.
Conclusion: Macrophages from AAA patients exhibit a stressed phenotype, which was exacerbated by hemin stimulation. CD163 and HO-1 are tightly regulated in macrophages from AAA patients, and the regulation of CD163 appears to be downstream of HO-1, suggesting a possible feedback mechanism. From our data, it can be concluded that MHem macrophages may not have a protective effect in AAA, as it was shown in atherosclerosis.