Doxycycline delays aneurysm rupture in a mouse model of Marfan syndrome

ObjectivesThoracic aneurysms are the main cardiovascular complication of Marfan syndrome (MFS) resulting in premature death. MFS has been associated with mutations of the gene encoding fibrillin-1 (FBN1), a major constituent of the elastic fibers. Matrix metalloproteinases (MMPs) are important in the pathogenesis of abdominal aortic aneurysms but their precise role in MFS is not clear. Doxycycline is a nonspecific MMP inhibitor. The objective of the study was to determine whether docycycline can attenuate matrix degradation and prolong the survival of mice with MFS.MethodsThe study employed a well-characterized animal model of MFS, namely fibrillin-1 under-expressing mice (mgR/mgR mice) that die spontaneously from rupture of the thoracic aorta between 2 to 4 months of age. Mutant and wild type mice were given doxycycline in their drinking water at a concentration designed to provide 100 mg/kg/day beginning at postnatal day (PD) 1, whereas control mice were given water. Treated mice were divided into two groups. One group of animals was followed until death or for 7 months to determine lifespan. In the second group of mice, the ascending thoracic aortas were collected for histological analysis (H&E staining, trichrome staining) and zymography for examining MMP-2 and MMP-9 levels at 6 weeks.ResultsMMP-2 and MMP-9 levels were higher in the thoracic aorta of mgR/mgR mice compared with wild type littermates. Doxycycline-treated mgR/mgR mice lived 132 ± 14.6 days (n = 16) or significantly longer than untreated mutant mice (79 ± 6.7 days, n = 30) (P < 0.01). Connective tissue staining showed that doxycycline treatment decreased elastic fiber degradation in mgR/mgR mice. Furthermore, mgR/mgR mice treated with doxycycline had lower MMP-2 and MMP-9 levels compared with untreated mgR/mgR mice.ConclusionsThis study demonstrates that doxycycline significantly delays aneurysm rupture in MFS-like mice by inhibiting expression of tissue MMP-2 and MMP-9 and thus, degradation of the elastic matrix. The results suggest that MMPs contribute to the progression of thoracic aneurysm in MFS and that doxycycline has the potential to significantly alter the course of the disease.Clinical RelevanceAortic aneurysms are the main cardiovascular complication of Marfan syndrome (MFS) resulting in premature death. β-blockers offer some benefit but do not address the underlying cause of the progressive aortic degradation. Medical treatment that actually targets recently identified pathogenic factors leading to progressive matrix destruction could significantly impact the clinical course of the disease. A recent study using a mouse model of MFS has demonstrated that TGF- β antibodies or the angiotensin II type I receptor (AT1) antagonist losartan can both effectively rescue aneurysm progression. We have found that doxycycline, a nonspecific inhibitor of matrix metalloproteinases (MMPs), can decrease elastin degradation and prolong the lifespan of genetically engineered mice that mimic the human disease process. Based on these results, further testing may be warranted to determine if doxycycline could favorable impact the natural history of Marfan syndrome

Analyzing SOD Activity in Lung Tissue of a Murine Model of Marfan Syndrome

Marfan syndrome is an inherited autosomal dominant disorder caused by a mutation in the Fibrillin-1 gene (FBN1) affecting elastic connective tissue. Marfan syndrome commonly presents with ectopia lentis, aortic dissections, mitral valve prolape, and chronic obstructive pulmonary disease (COPD) in later stages. Patients with Marfan Syndrome are shown to have higher concentrations of reactive oxygen species (ROS) in blood plasma. Increased ROS due to oxidative stress can lead to increased cell damage and death, and have been linked to the formation of aortic dissections5. Superoxide dismutases (SOD) are a class of enzymes that convert harmful oxygen radicals into molecular oxygen and hydrogen peroxide2. Manganese-containing SOD (MnSOD) regulates radical oxygen located in the Mitochondria4. The aim of this study is to explore the role of SOD expression and ROS in relation to COPD found in Marfan syndrome. It is hypothesized that the defect in Fibrillin-1 causes oxidative stress in the lung tissue, which often causes COPD, and it is expected that there would be less SOD activity in tissues from mice with Marfan syndrome. The activity of SOD1 and MnSOD in relation to the oxidative stress that is caused by the deficiency of Fibrillin protein will be determined. To accomplish this, a murine model of Marfan syndrome Fbn1mgR/mgR, mice with a hypomorphic mutation in the Fibrillin-1 gene were compared with homozygous wild type mice. Mice were sacrificed after 1, 4 , and 8 week intervals, and both SOD1 and MnSOD expression was quantified in lung tissue. Results of the study found that there was a significant decrease in SOD1 expression in Marfan mice at the one and four week intervals, but no significant difference in the eight week interval. MnSOD was observed to not have any significant difference in expression in the one and four week Marfan mice, but was expressed at a significantly higher level in the 8 week Marfan mice compared to wild-type controls.https://digitalcommons.unmc.edu/surp2021/1027/thumbnail.jp

Mast cells modulate the pathogenesis of elastase-induced abdominal aortic aneurysms in mice

Abdominal aortic aneurysm (AAA), an inflammatory disease, involves leukocyte recruitment, immune responses, inflammatory cytokine production, vascular remodeling, neovascularization, and vascular cell apoptosis, all of which contribute to aortic dilatation. This study demonstrates that mast cells, key participants in human allergic immunity, participate in AAA pathogenesis in mice. Mast cells were found to accumulate in murine AAA lesions. Mast cell–deficient KitW-sh/KitW-sh mice failed to develop AAA elicited by elastase perfusion or periaortic chemical injury. KitW-sh/KitW-sh mice had reduced aortic expansion and internal elastic lamina degradation; decreased numbers of macrophages, CD3+ T lymphocytes, SMCs, apoptotic cells, and CD31+ microvessels; and decreased levels of aortic tissue IL-6 and IFN-γ. Activation of mast cells in WT mice via C48/80 injection resulted in enhanced AAA growth while mast cell stabilization with disodium cromoglycate diminished AAA formation. Mechanistic studies demonstrated that mast cells participated in angiogenesis, aortic SMC apoptosis, and matrix-degrading protease expression. Reconstitution of KitW-sh/KitW-sh mice with bone marrow–derived mast cells from WT or TNF-α–/– mice, but not from IL-6–/– or IFN-γ–/– mice, caused susceptibility to AAA formation to be regained. These results demonstrate that mast cells participate in AAA pathogenesis in mice by releasing proinflammatory cytokines IL-6 and IFN-γ, which may induce aortic SMC apoptosis, matrix-degrading protease expression, and vascular wall remodeling, important hallmarks of arterial aneurysms

MMP-2 genetic variant and plaque features of instability

Abstract non present

Low-dose alcohol consumption protects against transient focal cerebral ischemia in mice: possible role of PPARγ.

BACKGROUND: We examined the influence of low-dose alcohol consumption on cerebral ischemia/reperfusion (I/R) injury in mice and a potential mechanism underlying the neuroprotective effect of low-dose alcohol consumption. METHODOLOGY/PRINCIPAL FINDINGS: C57BL/6 J mice were fed a liquid diet without or with 1% alcohol for 8 weeks, orally treated with rosiglitazone (20 mg/kg/day), a peroxisome proliferator-activated receptor gamma (PPARγ)-selective agonist, or GW9662 (3 mg/kg/day), a selective PPARγ antagonist, for 2 weeks. The mice were subjected to unilateral middle cerebral artery occlusion (MCAO) for 90 minutes. Brain injury, DNA fragmentation and nuclear PPARγ protein/activity were evaluated at 24 hours of reperfusion. We found that the brain injury and DNA fragmentation were reduced in 1% alcohol-fed mice compared to nonalcohol-fed mice. Rosiglitazone suppressed the brain injury in nonalcohol-fed mice, but didn't alter the brain injury in alcohol-fed mice. In contrast, GW9662 worsened the brain injury in alcohol-fed mice, but didn't alter the brain injury in nonalcohol-fed mice. Nuclear PPARγ protein/activity at peri-infarct and the contralateral corresponding areas of the parietal cortex was greater in alcohol-fed mice compared to nonalcohol-fed mice. Using differentiated catecholaminergic (CATH.a) neurons, we measured dose-related influences of chronic alcohol exposure on nuclear PPARγ protein/activity and the influence of low-dose alcohol exposure on 2-hour oxygen-glucose deprivation (OGD)/24-hour reoxygenation-induced apoptosis. We found that low-dose alcohol exposure increased nuclear PPARγ protein/activity and protected against the OGD/reoxygenation-induced apoptosis. The beneficial effect of low-dose alcohol exposure on OGD/reoxygenation-induced apoptosis was abolished by GW9662. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that chronic consumption of low-dose alcohol protects the brain against I/R injury. The neuroprotective effect of low-dose alcohol consumption may be related to an upregulated PPARγ

Total infarct volume (A) and neurological score (B) at 24 hours of reperfusion after a 90-minute MCAO in nonalcohol-fed and 1% alcohol-fed mice treated without and with rosiglitazone or GW9662.

<p>Values are means ± SE for 6 mice in each group. *P<0.05 vs. Nonalcohol. #P<0.05 vs. Without Treatment.</p