Overexpression of the Serine Elastase Inhibitor Elafin Protects Transgenic Mice From Hypoxic Pulmonary Hypertension

Abstract

Background-Increased serine elastase activity has been implicated in the vascular remodeling associated with chronic hypoxia-related pulmonary hypertension in rats. Methods and Results-In this study we determined the time course of hypoxia-induced serine elastase activity in the murine lung and related this to initiation of a proteolytic cascade characterized by an increase in matrix metalloproteinases (MMPs). We then used transgenic mice in which overexpression of the selective serine elastase inhibitor elafin was targeted to the cardiovascular system to determine whether upregulation of a naturally occurring serine elastase inhibitor suppresses MMPs and the hemodynamic and structural response to chronic hypoxia (air at 380 mm Hg). In nontransgenic but not in elafin-transgenic mice, we documented a transient increase in serine elastase activity after 12 hours of hypoxic exposure attributed to a 30-kDa protein as determined by elastin zymography and fluorophosphonate/ fluorophosphate-biotin labeling. Two days after hypoxia, the pro-forms of MMP-2 and MMP-9 were induced in the nontransgenic mice, but MMP-9 was suppressed in elafin-transgenic mice. Acute hypoxic vasoconstriction was similar in nontransgenic and elafin-transgenic littermates. Chronic hypoxia for 26 days resulted in Ͼ1-fold increase in right ventricular pressure (PϽ0.004) in nontransgenic compared with control or elafin-transgenic littermates. In the latter mice, normalization of the right ventricular pressure was associated with reduced muscularization and preservation of the number of distal vessels (PϽ0.04 for both comparisons). Conclusions-Modulation

Role of Leukocyte Elastase in Preventing Cellular Re-Colonization of the Mural Thrombus

“…58 However, as pericellular proteolysis is a necessary condition for cell migration, serine proteases with elastase activity could be also involved in SMC migration and proliferation. 59 -61 Thus, the role of elastase in mesenchymal cell physiology is probably dual, either participating in cell migration or inducing cell detachment and death, depending on the cellular source of the proteinase ie, SMCs, 61 PMN leukocytes, or macrophages, 62 and on the intensity and localization (clustering versus diffusion) of pericellular proteolysis.…”

Neutrophil Elastase Is Produced by Pulmonary Artery Smooth Muscle Cells and Is Linked to Neointimal Lesions

“…opathy after transplantation, 28,51 vein graft atherosclerosis 52 and fibrosis following viral myocarditis, 53,54 or pulmonary hypertension induced by hypoxia 12,14 or monocrotaline. 13,15 In five of these models, 28,50,52,54 elafin was used as the elastase inhibitor, given as an infusion, 28 by gene therapy 50,52 or in an overexpressing transgenic mouse.…”

“…13,15 In five of these models, 28,50,52,54 elafin was used as the elastase inhibitor, given as an infusion, 28 by gene therapy 50,52 or in an overexpressing transgenic mouse. 14,49,54 Elafin is a small, 9-kDa protein, first described in association with inflammatory lesions in the airways 55 and with psoriasis in skin. 56 It is secreted as a 12-kDa proform containing a transglutaminase domain that also has elastase inhibitory properties.…”

“…7 Fragmentation of PA elastin has been observed in PAs of PAH patients, 11 and heightened activity of a serine elastase has been identified in the PA in a variety of experimental forms of PAH [12][13][14][15] and in cultured PA smooth muscle cells (SMC). 16 -19 Moreover, inhibition of this elastase can attenuate or prevent [12][13][14] and even reverse 15 experimental pulmonary vascular disease in rodents. In all rodent models where elastase inhibitors were used, the pulmonary vascular lesions were characterized by loss or increased muscularization of normally nonmuscular peripheral arteries at the alveolar wall and duct level, and medial hypertrophy of proximal muscular arteries.…”

Pulmonary arterial remodeling induced by a Th2 immune response

“…The hemodynamic measurements were performed at Stanford University. RVSP, right ventricular function (pressure change per second), and heart rate were measured by jugular vein catheterization (1.4 F catheter; Millar Instruments Inc.) connected to a pressure transducer under isofl urane anesthesia (1.5 -2.5%, 2 liter O 2 /min) using a closed chest technique in unventilated mice, as previously described ( 78 ). The right ventricular hypertrophy was evaluated by Fulton index measurements (weight of right ventricle/left ventricle plus septum).…”