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The extracellular role of granzyme B in abdominal aortic aneurysm Ang, Lisa Shouning
Abstract
Background: Abdominal aortic aneurysm (AAA) is an age-related disease characterized by progressive degradation of elastic lamellae, defective collagen architecture and medial smooth muscle cell loss. We previously demonstrated that knocking out the serine protease granzyme B (GZMB) reduces incidence and severity of AAA in mice; however, while GZMB is known for its role in apoptosis, it also accumulates extracellularly during inflammation and can cleave extracellular matrix (ECM) components such as decorin and fibrillin-1. We hypothesized that GZMB contributes to AAA development through the degradation of vascular ECM and that the inhibition of extracellular GZMB would reduce the incidence and severity of AAA progression.Methods: Human aneurysmal samples were obtained and apolipoprotein E(apoE)-knockout (KO), GZMB/apoE-double knockout (GDKO) and perforin/apoE-DKO (PDKO) mice were implanted with osmotic minipumps releasing angiotensin II for 28 days to induce AAA formation. Additional apoE-KO mice were injected with the GZMB inhibitor, serpin A3N (SA3N, 4-120 μg/kg) or anti-GZMB neutralizing antibody (1 mg/kg) prior to pump implantation. Tissues were assessed for aneurysm pathology, inflammation and ECM composition. Collagen content was analysed by second harmonic generation and transmission electron microscopy.Results: Human aneurysmal tissues showed elevated levels of GZMB immunopositivity compared to controls. A significant reduction in AAA incidence and severity was observed in GDKO mice compared to apoE-KO, whereas perforin deficiency was not protective against AAA. A dose-dependent reduction in the frequency of aortic rupture was observed in mice that received SA3N or anti-GZMB antibody treatment. Pre-incubation with SA3N prevented decorin cleavage by GZMB in vitro. Reduced GZMB and a corresponding reduction in loss of adventitial decorin were observed in SA3N and anti-GZMB-treated mice while collagen density was increased. Adventitial collagen from SA3N-treated mice exhibited significantly higher fibre density and reduced fibril size irregularity.Conclusions: GZMB promotes destruction of the elastic lamellae via degradation of fibrillin-1 and destabilization of elastic microfibrils while GZMB-mediated degradation of decorin contributes to loss of adventitial collagen organization and density. The extracellular inhibition of GZMB prevented decorin loss and enabled a beneficial remodelling of adventitial collagen in response to medial injury, leading to higher vessel tensile strength and increased resistance to aortic rupture.
Item Metadata
Title |
The extracellular role of granzyme B in abdominal aortic aneurysm
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2013
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Description |
Background: Abdominal aortic aneurysm (AAA) is an age-related disease characterized by progressive
degradation of elastic lamellae, defective collagen architecture and medial smooth muscle cell loss. We previously demonstrated that knocking out the serine protease granzyme B (GZMB) reduces incidence
and severity of AAA in mice; however, while GZMB is known for its role in apoptosis, it also accumulates extracellularly during inflammation and can cleave extracellular matrix (ECM) components such as decorin and fibrillin-1. We hypothesized that GZMB contributes to AAA development through the
degradation of vascular ECM and that the inhibition of extracellular GZMB would reduce the incidence and severity of AAA progression.Methods: Human aneurysmal samples were obtained and apolipoprotein E(apoE)-knockout (KO),
GZMB/apoE-double knockout (GDKO) and perforin/apoE-DKO (PDKO) mice were implanted with
osmotic minipumps releasing angiotensin II for 28 days to induce AAA formation. Additional apoE-KO
mice were injected with the GZMB inhibitor, serpin A3N (SA3N, 4-120 μg/kg) or anti-GZMB neutralizing
antibody (1 mg/kg) prior to pump implantation. Tissues were assessed for aneurysm pathology,
inflammation and ECM composition. Collagen content was analysed by second harmonic generation and
transmission electron microscopy.Results: Human aneurysmal tissues showed elevated levels of GZMB immunopositivity compared to
controls. A significant reduction in AAA incidence and severity was observed in GDKO mice compared to
apoE-KO, whereas perforin deficiency was not protective against AAA. A dose-dependent reduction in
the frequency of aortic rupture was observed in mice that received SA3N or anti-GZMB antibody
treatment. Pre-incubation with SA3N prevented decorin cleavage by GZMB in vitro. Reduced GZMB and
a corresponding reduction in loss of adventitial decorin were observed in SA3N and anti-GZMB-treated
mice while collagen density was increased. Adventitial collagen from SA3N-treated mice exhibited
significantly higher fibre density and reduced fibril size irregularity.Conclusions: GZMB promotes destruction of the elastic lamellae via degradation of fibrillin-1 and
destabilization of elastic microfibrils while GZMB-mediated degradation of decorin contributes to loss of
adventitial collagen organization and density. The extracellular inhibition of GZMB prevented decorin
loss and enabled a beneficial remodelling of adventitial collagen in response to medial injury, leading to
higher vessel tensile strength and increased resistance to aortic rupture.
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Genre | |
Type | |
Language |
eng
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Date Available |
2014-12-31
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
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DOI |
10.14288/1.0165706
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2014-05
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Campus | |
Scholarly Level |
Graduate
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Rights URI | |
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Attribution-NonCommercial-NoDerivatives 4.0 International