Hypertension, a disease with known sexual dimorphism, accelerates aging-associated arterial stiffening, partly because of the activation of matrix remodeling caused by increased biomechanical load. In this study, we tested the effect of biological sex and the role of the matrix remodeling enzyme lysyl oxidase-like 2 (LOXL2) in hypertension-induced arterial stiffening. Hypertension was induced by angiotensin II (ANG II) infusion via osmotic minipumps in 12- to 14-wk-old male and female mice. Blood pressure and pulse wave velocity (PWV) were measured noninvasively. Wire myography and uniaxial tensile testing were used to test aortic vasoreactivity and mechanical properties. Aortic wall composition was examined by histology and Western blotting. Uniaxial stretch of cultured cells was used to evaluate the effect of biomechanical strain. LOXL2's catalytic function was examined using knockout and inhibition. ANG II infusion-induced hypertension in both genotypes and sexes. Wild-type (WT) males exhibited arterial stiffening in vivo and ex vivo. Aortic remodeling with increased wall thickness, intralamellar distance, higher LOXL2, and collagen I and IV content was noted in WT males. Female mice did not exhibit increased PWV despite the onset of hypertension. LOXL2 depletion improved vascular reactivity and mechanics in hypertensive males. LOXL2 depletion improved aortic mechanics but worsened hypercontractility in females. Hypertensive cyclic strain contributed to LOXL2 upregulation in the cell-derived matrix in vascular smooth muscle cells (VSMCs) but not endothelial cells. LOXL2's catalytic function facilitated VSMC alignment in response to biomechanical strain. In conclusion, in males, arterial stiffening in hypertension is driven both by VSMC response and matrix remodeling. Females are protected from PWV elevation in hypertension. LOXL2 depletion is protective in males with improved mechanical and functional aortic properties. VSMCs are the primary source of LOXL2 in the aorta, and hypertension increases LOXL2 processing and shifts to collagen I accumulation. Overall, LOXL2 depletion offers protection in young hypertensive males and females.NEW & NOTEWORTHY We examined the effect of sex on the evolution of angiotensin II (ANG II)-induced hypertension and the role of lysyl oxidase-like 2 (LOXL2), an enzyme that catalyzes matrix cross linking. While ANG II led to hypertension and worsening vascular reactivity in both sexes, aortic remodeling and stiffening occurred only in males. LOXL2 depletion improved outcomes in males but not females. Thus males and females exhibit a distinct etiology of hypertension and LOXL2 is an effective target in males.

Introduction: Hypertension is a major risk factor for cardiovascular diseases including cardiac hypertrophy, stroke, and heart failure. Hypertension accelerates arterial stiffening noted with natural aging. Aortic stiffness has been shown to be both a cause and a consequence of isolated systolic hypertension. Thus, it is of high clinical interest to target arterial stiffening in the context of hypertension. We have previously identified lysyl oxidase-like 2 (LOXL2) as a potential therapeutic target for treating vascular stiffening. LOXL2 is a key enzyme in the extracellular matrix that catalyzes matrix deposition and remodeling. We have previously shown that LOXL2 depletion decelerates arterial stiffening during natural aging by modulating matrix remodeling and smooth muscle cell stiffness and contractility. Our hypothesis in this study is that LOXL2 depletion is protective against hypertension induced arterial stiffening, and this was determined via the established angiotensin II (Ang II) infusion model of experimental hypertension in LOXL2+/- mouse model. Methods and results: Ang II pumps were implanted in LOXL2+/- and WT mice for a 3-week treatment. Blood pressure and pulse wave velocity were measured noninvasively to assess hypertension and aortic stiffness. Results corroborated that Ang II infusion induced hypertension in WT and LOXL2+/- mice, and that arterial stiffening was ameliorated in LOXL2+/- mice even when Ang II-induced hypertension was present. Uniaxial tensile testing was used to test the elastic properties of the aortic rings, and wire myography was used to test their vasoreactivity. These experiments showed that the increase in arterial stiffness due to Ang II-induced hypertension was driven by both matrix remodeling and VSMC response. Histological analysis supported these findings, showing increased aortic wall thickness, interlamellar distance and collagen deposition with Ang II infusion. Elevated heart weight in mice with Ang II infusion and qPCR results revealed induced cardiac hypertrophy, which was not protected by LOXL2 knockdown. Moreover, human aortic SMC and endothelial cells were cyclically stretched, to show that the overexpression of LOXL2 in the aorta under Ang II-induced hypertension is upregulated by cyclic strain. Conclusion: Arterial stiffening is increased with Ang II infusion; however, it is ameliorated in LOXL2+/- mice compared to WT despite the development of Ang II-induced hypertension. This rise in arterial stiffness is driven by both matrix remodeling and VSMC response. Cardiac hypertrophy occurred with Ang II infusion and LOXL2 knockdown was not protective against it. Future studies will continue to 1) elucidate the mechanisms involved in the regulation of LOXL2 expression in response to Ang II-induced hypertension, 2) investigate the sex differences in in vivo stiffness and vasoreactivity, and 3) study LOXL2 as a potential therapeutic target against cardiac hypertrophy. Private foundation grant: NHLBI grant R01HL148112 01 (L.S.) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Chronic psychosocial stress is implicated in the onset and progression of noncommunicable diseases, and mechanisms underlying this relationship include alterations to the intracellular redox state. However, such changes are often investigated in isolation, with few studies adopting a system level approach. Here, male Wistar rats were exposed to 9.5 weeks of chronic unpredictable mild stress and redox status assays were subsequently performed on cardiac, hepatic, and brain tissues versus matched controls. The stressed rats displayed an anxious phenotype, with lowered plasma corticosterone levels (p = 0.04 vs. Controls) and higher plasma epinephrine concentrations (p = 0.03 vs. Controls). Our findings showed organ-specific redox profiles, with stressed rats displaying increased myocardial lipid peroxidation (p = 0.04 vs. Controls) in the presence of elevated nonenzymatic antioxidant capacity (p = 0.04 vs. Controls). Conversely, hepatic tissues of stressed rats exhibited lowered nonenzymatic antioxidant capacity (p < 0.001 vs. Controls) together with increased superoxide dismutase (SOD) activity (p = 0.05 vs. Controls). The brain displayed region-specific antioxidant perturbations, with increased SOD activity (p = 0.01 vs. Controls) in the prefrontal cortex of the stressed rats. These findings reveal distinct stress-related organ-specific vulnerability to redox perturbations and may provide novel insights into putative therapeutic targets.

Hypoxia in the neonatal period is associated with early manifestations of adverse cardiovascular health in adulthood including higher risk of hypertension and atherosclerosis. We hypothesize that this occurs due to activation of lysyl oxidases (LOXs) and the remodeling of the large conduit vessels, leading to early arterial stiffening. Newborn C57Bl/6 mice were exposed to hypoxia (FiO(2) = 11.5%) from postnatal day 1 (P1) to postnatal day 11 (P11), followed by resumption of normoxia. Controls were maintained in normoxia. Using in vivo (pulse wave velocity; PWV) and ex vivo (tensile testing) arterial stiffness indexes, we determined that mice exposed to neonatal hypoxia had significantly higher arterial stiffness compared with normoxia controls by young adulthood (P60), and it increased further by P120. Echocardiography performed at P60 showed that mice exposed to hypoxia displayed a compensated dilated cardiomyopathy. Western blotting revelated that neonatal hypoxia accelerated age-related increase in LOXL2 protein expression in the aorta and elevated LOXL2 expression in the PA at P11 with a delayed decay toward normoxic controls. In the heart and lung, gene and protein expression of LOX/LOXL2 were upregulated at P11, with a delayed decay when compared to normoxic controls. Neonatal hypoxia results in a significant increase in arterial stiffness in early adulthood due to aberrant LOX/LOXL2 expression. This suggests an acceleration in the mechanical decline of the cardiovascular system, that contributes to increased risk of hypertension in young adults exposed to neonatal hypoxia that may increase susceptibility to further insults.