CHARACTERIZING THE ROLE OF LYSYL OXIDASE LIKE-2 IN VASCULAR STIFFENING

Increased arterial stiffness is a significant contributing factor to the deterioration of the cardiovascular system in the elderly, often accompanying hypertension. However, there are no known clinical interventions against vascular stiffness due to the lack of well-characterized molecular targets. Using an unbiased proteomic approach, we identified lysyl oxidase like-2 (LOXL2) as a therapeutic target for vascular stiffening. Our first aim was to determine if targeting LOXL2 is an effective approach to delay or prevent vascular stiffening in aging and hypertension. Using a constitutive LOXL2 knockdown (LOXL2+/-) mouse model, we showed that LOXL2 depletion protects against aging-associated vascular stiffening and delays the onset of systolic hypertension. Inducing LOXL2 knockout in middle-aged mice also protected against further aortic stiffening. We then examined the effects of LOXL2+/- in angiotensin II (Ang II) – induced hypertension. LOXL2+/- protected against aortic stiffening in male mice, and there were significant sex differences in gene expression and vascular remodeling in response to Ang II. LOXL2 expression was upregulated in both the aorta and the heart. Notably, lack of LOXL2 at the sudden onset of hypertension resulted in high occurrence of abdominal aortic aneurysms due to failure to remodel the vascular extracellular matrix (ECM) and align vascular smooth muscle cells (VSMCs) in an organized manner. These results highlight the essential role that LOXL2 plays in maintaining a delicate balance of matrix homeostasis. Moreover, LOXL2 not only participates in ECM deposition and assembly but also alters VSMC micromechanics and function. Our second aim was to elucidate the mechanisms of LOXL2 regulation that contribute to LOXL2-mediated stiffening. We found that stimuli which mimic aging and favor vascular remodeling, such as augmented cyclic strain and endothelial dysfunction, upregulate LOXL2 secretion and deposition in the ECM. We identified Factor Xa as a protease of LOXL2, and found that Factor Xa processing shifted the substrate specificity of LOXL2, and increased the recruitment of prototypic LOX. Overall, our study provided evidence that LOXL2 is a promising target for the treatment of vascular stiffening in aging and hypertension, and developed better understanding of LOXL2 regulation that can help inform future development of therapeutics targeting LOXL2