SYSTEMIC INFLAMMATION INDUCED BY ANGIOTENSIN II INCREASES C3a-MEDIATED VASOCONSTRICTION IN MICE

Introduc�on: Cardiovascular diseases are known to be associated with ac�va�on of the complement system, however, the precise rela�onship between the two processes is partly unclear. The complement component C3a receptor (C3aR) has been iden�fied in various cell types within the mouse arterial wall and the vasoconstrictor effect of C3a may be mediated by resident macrophages in the adven��a via thromboxane A2 (TXA2) release, as found by our workgroup in previous research. Aims: The primary objec�ve of this study was to determine the effects of chronic angiotensin II (Ang II) administra�on on C3a-induced vasoconstric�on in mice, along with demonstra�ng the presence of macrophages in the adven��a using alterna�ve methods. Methods: Changes in the isometric tension of the vascular segments were measured using myography a�er isola�ng thoracic and abdominal aor�c segments of adult male C57BL/6 mice. The mice were infused with either Ang II (520 ng/kg/min) or saline for 14 days via microosmo�c pumps implanted in the subscapular region. qPCR assays were performed to measure the expression level of C3aR and the mouse macrophage marker F4/80. The expression of other genes involved in the signaling pathway, such as Cyclooxygenase 1 and 2 (Cox1 and Cox2), thromboxane A synthase 1 (Tbxas1), and thromboxane A2 receptor (Tbxa2r), were inves�gated. The localiza�on of C3AR1 was confirmed using immunohistochemistry. The mechanism of the contrac�on was examined using the cyclooxygenase (COX) inhibitor indomethacin and SQ29548, a thromboxane prostanoid (TP) receptor antagonist. Results: An increased response to C3a (63–77) was observed in the vascular segments due to the increased expression of C3aR caused by Ang II treatment compared to controls that received saline infusion. The qPCR results revealed an increase in the expression of F4/80 and C3aR in the aortas, par�cularly in the adven��a, due to Ang II infusion. A�er removing the endothelium, the vasoconstric�on increased, while the vessels became unresponsive to C3a a�er the administra�on of COX and TP receptor inhibitors and the removal of the adven��a. Conclusion: It can be concluded from our results that chronic Ang II administra�on can lead to an enhanced vasoconstrictor response to C3a and an increased expression of C3aR in the aor�c wall, par�cularly in the adven��a where macrophages accumulate. Our findings propose that the vasoconstric�on induced by C3a in the mouse aorta is facilitated by macrophages that have gathered in the adven��a. During the development of various cardiovascular diseases, the effects of anaphylatoxins could be amplified and may contribute to the progression of the diseases