Lysyl oxidase-like 2 depletion is protective in age-associated vascular stiffening

Abstract

Vascular stiffening and its sequelae are major causes of morbidity and mortality in the elderly. The increasingly accepted concept of “smooth muscle cell (SMC) stiffness syndrome” along with matrix deposition has emerged in vascular biology to account for the mechanical phenotype of arterial aging, but the molecular targets remain elusive. In this study, using an unbiased proteomic analysis, we identified lysyl oxidase-like 2 (LOXL2) as a critical SMC mediator for age-associated vascular stiffening. We tested the hypothesis that loss of LOXL2 function is protective in aging-associated vascular stiffening. We determined that exogenous and endogenous nitric oxide markedly decreased LOXL2 abundance and activity in the extracellular matrix of isolated SMCs and LOXL2 endothelial cells suppress LOXL2 abundance in the aorta. In a longitudinal study, LOXL2+/− mice were protected from age-associated increase in pulse-wave velocity, an index of vascular stiffening, as occurred in littermate wild-type mice. Using isolated aortic segments, we found that LOXL2 mediates vascular stiffening in aging by promoting SMC stiffness, augmented SMC contractility, and vascular matrix deposition. Together, these studies establish LOXL2 as a nodal point for a new therapeutic approach to treat age-associated vascular stiffening. NEW & NOTEWORTHY Increased central vascular stiffness augments risk of major adverse cardiovascular events. Despite significant advances in understanding the genetic and molecular underpinnings of vascular stiffening, targeted therapy has remained elusive. Here, we show that lysyl oxidase-like 2 (LOXL2) drives vascular stiffening during aging by promoting matrix remodeling and vascular smooth muscle cell stiffening. Reduced LOXL2 expression protects mice from age-associated vascular stiffening and delays the onset of isolated systolic hypertension, a major consequence of stiffening.

Restoring Blood Pressure in Hypertensive Mice Fails to Fully Reverse Vascular Stiffness

“…Mice anesthetized with 2% isoflurane were placed on a heating pad, and their paws were taped to electrocardiogram electrodes. PWV was measured non-invasively as previously described by high-frequency Doppler (Indus Instruments, Webster, TX) at two points along the aorta: one point in the upper thoracic cavity and one point in the lower abdominal cavity (Hartley et al, 1997;Steppan et al, 2019). PWV was calculated as the separation distance divided by the pulse transit time between the two points.…”

“…After slow acclimatization over 2 weeks, animals were restrained in a translucent plastic cone with the tail exposed. Blood pressure was determined by a tail cuff measurement system as described previously (Kent Scientific, Torrington, CT) (Wang et al, 2017;Steppan et al, 2019).…”

“…It can also cause degradation of the vessel wall and extracellular matrix ( Hansson and Libby, 2006 ; Poels et al, 2012 ; Gimbrone and Garcia-Cardena, 2013 ). Recent studies have established the central role of VSMC tone and stiffness in overall vascular stiffness and shown that stiffer VSMCs can compensate for a compliant vascular matrix to maintain physiologically acceptable ranges of vascular stiffness ( Sehgel et al, 2015 ; Steppan et al, 2017 , 2019 ; Lacolley et al, 2018 ). However, the specific contributions of vascular matrix remodeling and VSMC dysregulation to overall stiffening remain less clear.…”

Appropriate selection of a mouse strain in accordance with the vascular properties

“…Vascular stiffness assessed by pulse wave velocity (PWV) correlates independently with poor outcomes [6]. As reported in many previous studies, Steppan et al indicated that evaluation of vascular stiffness is an essential first step to develop targeted therapies [8]. These previous studies strongly indicated that we should select a mouse model in accordance with the properties of the mouse strain.…”

“…Vascular stiffness is also highly predictive of major adverse cardiovascular events, such as perioperative myocardial infarction, heart failure, and death [6]. Furthermore, vascular stiffness is closely related to age-associated hypertension, which precedes the development of clinical hypertension [8]. To assess the pathophysiology of hypertension, researchers have conducted many experimental studies using mice [10][11][12][13][14][15], which will be increased.…”