Fibulin-5- β 1 Integrin Interaction and RhoA Kinase Signaling Regulate Mesenteric Artery Constriction

Introduction: The regulation of arterial function is crucial for maintaining vascular tone and blood pressure, particularly in resistance arteries such as the mesenteric artery. These arteries play a central role in regulating blood flow to tissues and maintaining systemic hemodynamics. Arterial constriction and relaxation are tightly controlled by several signaling pathways, with integrins and small GTPases, like Rho-associated protein kinase (ROCK), playing essential roles in these processes. Fibulin-5, an extracellular matrix protein critical for elastic fiber assembly, has also been shown to interact with integrins, including β1 integrin (CD29), to modulate endothelial and smooth muscle cell behavior, thus affecting vascular function. In this study, we investigate the role of Fibulin-5 and its interaction with β1 integrin in regulating mesenteric arterial function and constriction. Methods: Adult Fbln5 knock-out (KO) mice were utilized to visualize the ultrastructure of mesenteric arteries via transmission electron microscopy. Pressure myography was employed to characterize the myogenic tone and reactivity of Fbln5 KO and littermate control mesenteric arteries to vasoactive substances including acetylcholine, angiotensin II, phenylephrine as well as a ROCK inhibitor, Y-27632, and a blocking CD29 antibody. Additionally, a G-protein activation assay and qPCR were used to measure RhoA-GTP and ROCK II mRNA expression, respectively. Results: Resistance arteries of Fbln5 KO mice exhibited a largely intact internal elastic lamina (IEL); however, the external elastic lamina (EEL) was almost entirely absent. Fbln5 KO mesenteric arteries demonstrated impaired endothelial-dependent vasorelaxation, increased myogenic tone as well as a hypercontractile response to angiotensin II but not phenylephrine. Elevated Rho kinase activity, as well as increased levels of RhoA-GTP and ROCK II mRNA, were observed in Fbln5 KO mesenteric arteries compared to littermate controls. Blockade of CD29 in Fbln5 KO mesenteric arteries reduced the enhanced Angiotensin II-mediated constriction, bringing it to levels similar to those observed in control arteries. Conclusions: The absence of fibulin-5 leads to increased Rho kinase activity and enhanced arterial contraction, which is partially mediated by β1 integrin signaling. These findings emphasize the crucial role of fibulin-5 and its interaction with β1 integrin in regulating mesenteric arterial function, providing insights into the molecular mechanisms of vascular dysfunction and potential implications for cardiovascular diseases linked to altered extracellular matrix composition. This work was supported by funds from the Ines Mandl Research Foundation to CMH. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.