Matrix metalloproteinase-9 genotype as a potential genetic marker for abdominal aortic aneurysm

Cysteine Leukotriene Receptor Antagonist-Montelukast-Treatment Improves Experimental Abdominal Aortic Aneurysms in Mice

Background: Cysteinyl leukotrienes (LTs) and their receptors are involved in the pathogenesis of abdominal aortic aneurysms (AAAs). However, whether CysLT1 receptor antagonists such as montelukast can influence experimental nondissecting AAA remains unclear. Methods: Nondissecting AAAs were induced in C57BL/6J mice by transient aortic luminal infusion of porcine pancreatic elastase (PPE). All animals were administrated montelukast (1 or 10 mg/kg, daily) or vehicle by gavage beginning 1 day before PPE infusion for 14 days. On day 0 (baseline) and day 14 after PPE infusion, abdominal aortic diameters were directly measured. Aortic aneurysmal segment samples were collected, and histopathological analysis was performed. Results: Compared to vehicle treatment, montelukast significantly decreased PPE infusion-induced aortic expansion in a dose-dependent manner (0.09-mm reduction at a low dose and 0.19-mm reduction at a high dose). Histopathological analysis also revealed that compared with vehicle treatment, montelukast treatment, especially in the high-dose group, significantly improved PPE-induced aortic elastin degradation and medial smooth muscle cell depletion. Both doses of montelukast also markedly decreased the number of local leucocytes, including macrophages, CD4+ T cells, CD8+ T cells, and B cells, infiltration and accumulation in aortic aneurysmal lesions. Montelukast treatment also downregulated matrix metalloproteinase 2 (MMP2) and MMP9 expression and inhibited mural angiogenesis in aneurysmal aortas. Conclusion: Montelukast treatment improves experimental nondissected AAAs in mice partly by improving aortic inflammation.

Matrix metalloproteinase-9 deficiency confers resilience in fibrodysplasia ossificans progressiva in a man and mice

Single case studies of extraordinary disease resilience may provide therapeutic insight into conditions for which no definitive treatments exist. An otherwise healthy 35-year-old man (patient-R) with the canonical pathogenic ACVR1R206H variant and the classic congenital great toe malformation of fibrodysplasia ossificans progressiva (FOP) had extreme paucity of post-natal heterotopic ossification (HO) and nearly normal mobility. We hypothesized that patient-R lacked a sufficient post-natal inflammatory trigger for HO. A plasma biomarker survey revealed a reduction in total matrix metalloproteinase-9 (MMP-9) compared to healthy controls and individuals with quiescent FOP. Whole exome sequencing identified compound heterozygous variants in MMP-9 (c.59C > T, p.A20V and c.493G > A, p.D165N). Structural analysis of the D165N variant predicted both decreased MMP-9 secretion and activity that were confirmed by enzyme-linked immunosorbent assay and gelatin zymography. Further, human proinflammatory M1-like macrophages expressing either MMP-9 variant produced significantly less Activin A, an obligate ligand for HO in FOP, compared to wildtype controls. Importantly, MMP-9 inhibition by genetic, biologic, or pharmacologic means in multiple FOP mouse models abrogated trauma-induced HO, sequestered Activin A in the extracellular matrix (ECM), and induced regeneration of injured skeletal muscle. Our data suggest that MMP-9 is a druggable node linking inflammation to HO, orchestrates an existential role in the pathogenesis of FOP, and illustrates that a single patient's clinical phenotype can reveal critical molecular mechanisms of disease that unveil novel treatment strategies.

The MMP-9 promoter genetic variant rs3918242, mRNA and protein expression in advanced carotid plaque tissue

BACKGROUND

The MMP-9 is a known player in atherosclerosis, yet associations of the MMP-9 -1562 C/T variant (rs3918242) with various atherosclerotic phenotypes and tissue mRNA expression are still contradictory. This study aimed to investigate the MMP-9 -1562 C/T variant, its mRNA and protein expression in carotid plaque (CP) tissue, as a risk factor for CP presence and as a marker of different plaque phenotypes (hyperechoic and hypoechoic) in patients undergoing carotid endarterectomy. The MnSOD as an MMP-9 negative regulator was also studied in relation to CP phenotypes.

METHODS AND RESULTS

Genotyping of 770 participants (285 controls/485 patients) was done by tetra-primer ARMS PCR. The MMP-9 mRNA expression in 88 human CP tissues was detected by TaqMan® technology. The protein levels of MMP-9 and MnSOD were assessed by Western blot analysis. The MMP-9 -1562 C/T variant was not recognized as a risk factor for plaque presence or in predisposing MMP-9 mRNA and protein levels in plaque tissue. Patients with hypoechoic plaques had significantly lower MMP-9 mRNA and protein levels than those with hyperechoic plaque (p = 0.008, p = 0.003, respectively). MnSOD protein level was significantly higher in hypoechoic plaque compared to hyperechoic (p = 0.039). MMP-9 protein expression in CP tissue was significantly affected by sex and plaque type interaction (p = 0.009).

CONCLUSIONS

Considering the differences of MMP-9 mRNA and protein expression in CP tissue regarding different plaque phenotypes and the observed sex-specific effect, the role of MMP-9 in human atherosclerotic plaques should be further elucidated.

The Uterine Melatonergic Systems of AANAT and Melatonin Membrane Receptor 2 (MT2) Are Essential for Endometrial Receptivity and Early Implantation in Mice

In the current study, using Aanat and Mt2 KO mice, we observed that the preservation of the melatonergic system is essential for successful early pregnancy in mice. We identified that aralkylamine N-acetyltransferase (AANAT), melatonin receptor 1A (MT1), and melatonin receptor 1B (MT2) were all expressed in the uterus. Due to the relatively weak expression of MT1 compared to AANAT and MT2, this study focused on AANAT and MT2. Aanat and Mt2 KO significantly reduced the early implantation sites and the abnormal morphology of the endometrium of the uterus. Mechanistical analysis indicated that the melatonergic system is the key player in the induction of the normal nidatory estrogen (E2) response for endometrial receptivity and functions by activating the STAT signaling pathway. Its deficiency impaired the interactions between the endometrium, the placenta, and the embryo. The reduction in melatonin production caused by Aanat KO and the impairment of signal transduction caused by Mt2 KO reduced the uterine MMP-2 and MMP-9 activity, resulting in a hyperproliferative endometrial epithelium. In addition, melatonergic system deficiency also increased the local immunoinflammatory reaction with elevated local proinflammatory cytokines leading to early abortion in the Mt2 KO mice compared to the WT mice. We believe that the novel data obtained from the mice might apply to other animals including humans. Further investigation into the interaction between the melatonergic system and reproductive effects in different species would be worthwhile.

Insights into the immunomodulatory regulation of matrix metalloproteinase at the maternal-fetal interface during early pregnancy and pregnancy-related diseases

Trophoblast immune cell interactions are central events in the immune microenvironment at the maternal-fetal interface. Their abnormalities are potential causes of various pregnancy complications, including pre-eclampsia and recurrent spontaneous abortion. Matrix metalloproteinase (MMP) is highly homologous, zinc(II)-containing metalloproteinase involved in altered uterine hemodynamics, closely associated with uterine vascular remodeling. However, the interactions between MMP and the immune microenvironment remain unclear. Here we discuss the key roles and potential interplay of MMP with the immune microenvironment in the embryo implantation process and pregnancy-related diseases, which may contribute to understanding the establishment and maintenance of normal pregnancy and providing new therapeutic strategies. Recent studies have shown that several tissue inhibitors of metalloproteinases (TIMPs) effectively prevent invasive vascular disease by modulating the activity of MMP. We summarize the main findings of these studies and suggest the possibility of TIMPs as emerging biomarkers and potential therapeutic targets for a range of complications induced by abnormalities in the immune microenvironment at the maternal-fetal interface. MMP and TIMPs are promising targets for developing new immunotherapies to treat pregnancy-related diseases caused by immune imbalance.

Peptide Amphiphile Supramolecular Nanofibers Designed to Target Abdominal Aortic Aneurysms

An abdominal aortic aneurysm (AAA) is a localized dilation of the aorta located in the abdomen that poses a severe risk of death when ruptured. The cause of AAA is not fully understood, but degradation of medial elastin due to elastolytic matrix metalloproteinases is a key step leading to aortic dilation. Current therapeutic interventions are limited to surgical repair to prevent catastrophic rupture. Here, we report the development of injectable supramolecular nanofibers using peptide amphiphile molecules designed to localize to AAA by targeting fragmented elastin, matrix metalloproteinase 2 (MMP-2), and membrane type 1 matrix metalloproteinase. We designed four targeting peptide sequences from X-ray crystallographic data and incorporated them into PA molecules via solid phase peptide synthesis. After coassembling targeted and diluent PAs at different molar ratios, we assessed their ability to form nanofibers using transmission electron microscopy and to localize to AAA in male and female Sprague-Dawley rats using light sheet fluorescence microscopy. We found that three formulations of the PA nanofibers were able to localize to AAA tissue, but the MMP-2 targeting PA substantially outperformed the other nanofibers. Additionally, we demonstrated that the MMP-2 targeting PA nanofibers had an optimal dose of 5 mg (∼12 mg/kg). Our results show that there was not a significant difference in targeting between male and female Sprague-Dawley rats. Given the ability of the MMP-2 targeting PA nanofiber to localize to AAA tissue, future studies will investigate potential diagnostic and targeted drug delivery applications for AAA.

Early clinical and radiological improvement in a young boy with metaphyseal anadysplasia type 2

Metaphyseal anadysplasia is a very rare hereditary skeletal dysplasia with onset occurring normally during the second and third years of life, but unlike many other dysplasias, symptoms appear to resolve by adolescence. Two types exist, the more severe form, type 1, with both autosomal dominant and recessive inheritance due to pathogenic variants in MMP13, whilst type 2, an even rarer form is due to biallelic MMP9 variants. To date, only two metaphyseal anadysplasia type 2 families have been reported. We describe a third family, a young boy, born to consanguineous parents, referred at 19 months old for abnormal gait due to bowed legs. Clinical and radiological examination revealed scoliosis, genu varum and metaphyseal abnormalities. A homozygous MMP9 nonsense variant, NM_004994.2:c.1764G>A; p.(Trp588*) was identified. By the age of 39 months, lower limb alignment and metaphyseal features had already significantly improved and scoliosis had disappeared. This case confirms that biallelic MMP9 variants cause this very rare skeletal dysplasia, metaphyseal anadysplasia type 2 but also shows that the skeletal manifestations can improve within a short period time and at an early age.

Dexmedetomidine suppresses the development of abdominal aortic aneurysm by downregulating the mircoRNA‑21/PDCD 4 axis

Abdominal aortic aneurysm (AAA) is a pathological state with permanent dilation, which indicates a fatal potential for aortic rupture. It has been reported that dexmedetomidine (Dex) and microRNA (miR)-21 are involved in the progression of AAA. Thus, the present study aimed to investigate the joint effects of these factors on AAA treatment. For this purpose, rat models of AAA were established with enzyme perfusion and the rats were then injected with Dex. Alterations in the abdominal aorta in rats with AAA were recorded. miR-21 expression in the rats with AAA was determined. Inflammatory factor expression was detected by western blot analysis. Subsequently, a dual-luciferase reporter gene assay was performed to verify the targeting association between miR-21 and programmed cell death protein 4 (PDCD4). Additionally, AAA-related indices and inflammatory responses were examined by an injection of a combination of antagomiR (ant)-miR-21 and Dex or lentivirus-PDCD4-short hairpin RNA. It was found that Dex markedly alleviated the development of AAA and downregulated the expression of inflammatory factors and matrix metalloproteinase in rats with AAA. The high expression of miR-21, which targets PDCD4, was observed in the rats with AAA. However, ant-miR-21 induced AAA development and inflammatory responses. Additionally, the inhibition of PDCD4 reduced AAA development and inflammatory responses. On the whole, the present study demonstrates that Dex inhibits AAA development by downregulating the miR-21/PCDP4 axis. The findings of the present study may provide novel insight for the treatment of AAA. These findings may provide a reference for the future treatment of AAA and may provide theoretical guidance for the early prevention and development of AAA.

Evaluating the added predictive ability of MMP-9 in serum for Kawasaki disease with coronary artery lesions

To investigate the predictive ability of serum matrix metalloproteinase-9 (MMP-9) in the acute phase of Kawasaki disease (KD) with coronary artery lesions (CALs). Patients with KD hospitalized in Lanzhou University Second Hospital, Northwest China, from November 2015 to January 2018 were retrospectively reviewed, and clinical trial indicators and peripheral blood specimens were collected before intravenous immunoglobulin therapy treatment. The independent risk factors were determined using multivariate regression analysis. The net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were used to quantitatively evaluate the ability of MMP-9 to improve the efficiency of predicting KD with CALs. The white cell, neutrophil percentage, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were higher in patients with higher MMP-9, and the monocyte percentage was higher in patients with lower MMP-9. Logistic regression analysis revealed that long-term fever; elevated CRP, ESR, platelets (PLT), and MMP-9; and low albumin (ALB) levels were independent predictors of KD with CALs. A predictive model of KD with CALs using fever duration, CRP, ESR, PLT, and ALB showed significantly improved predictive ability when MMP-9 was added to the model (the area under the curve increased by 0.02; no change in sensitivity; specificity increased from 81.48% to 87.04%; NRI value: 13.46%; IDI value: 5.00%, p<0.05). Adding MMP-9 to traditional risk factors may improve prediction of CALs, the overall predictive ability of model 2 was increased by 5%.

Imatinib prevents elastase-induced abdominal aortic aneurysm progression by regulating macrophage-derived MMP9

Abdominal aortic aneurysm (AAA) is characterized with progressive weakening and considerable dilation of the aortic wall. Despite the high risk of mortality in the elderly population, there are still no clinical pharmacological therapies to alleviate AAA progression. Macrophage-derived MMP9 acts as a key factor in extracellular matrix degradation and is crucial for aortic aneurysm development and aortic rupture. Here, we demonstrated that the transcription level of MMP9 was suppressed with a concentration-dependent manner in macrophages after Imatinib treatment, which was accompanied by the down-regulation of MMP9 protein expression and reduced MMP9 secretion in vitro. Imatinib administration (50 mg/kg/d, i.g.) was carried out one week after the establishment of elastase-induced AAA in rats, stabilizing aneurysm progression and improving survival rate via decreasing the aortic diameter and preventing elastin degradation. Expression and activity of MMP9 in the artery tissues were significantly suppressed after Imatinib treatment via in situ assessment like immunohistochemistry and zymography, although macrophage infiltration was not affected. Furthermore, we found that Imatinib inhibited MMP9 transcription through reduction of STAT3 phosphorylation and translocation from nucleus to cytoplasm. These observations indicated that Imatinib prevents aneurysm progression by inhibiting STAT3-mediated MMP9 expression and activation, suggesting a new application of Imatinib on AAA clinical therapy.

Embelin inhibits abdominal aortic aneurysm through decreasing IL‑6‑induced STAT3 and NF‑κB inactivation

The aim of the present study was to investigate the effect of embelin on abdominal aortic aneurysm (AAA). AAA model mice were induced by chronic infusion of 1,000 ng/kg/min Angiotensin II. AAA model mice were treated with 25, 50 or 100 mg/kg embelin for 28 days. Embelin inhibited tumor necrosis factor‑α, interleukin (IL)‑1β, IL‑6, IL‑18 and malondialdehyde (MDA) level activities, increased superoxide dismutase, glutathione (GSH) and GSH peroxidase level activities and inhibited MDA level activities in AAA mice Embelin suppressed the secretion of matrix metalloproteinase‑9 protein expression, monocyte chemoattractant protein‑2 activity and epithelial neutrophil‑activating peptide expression levels in AAA mice. Embelin suppressed phosphorylated‑signal transducer and activator of transcription (STAT) 3, phosphorylated‑p38 mitogen‑activated protein kinase and nuclear factor (NF)‑κB protein expression in AAA mice. These findings indicate that embelin inhibits AAA through decreasing IL‑6‑induced STAT3, and NF‑κB inactivation.

Nucleic acid-induced potentiation of matrix metalloproteinase-9 enzymatic activity

Matrix metalloproteinases (MMPs) play varied roles in normal biology and diseases where, depending on the context, both inhibition and enhancement of the enzymatic activity may be beneficial. However, there are very few reports of positive modulators of MMP activity. We report that polynucleotides, including single-stranded DNA, RNA, and even double-stranded DNA, bind to and enhance the enzymatic activity of MMP9. This enhancement of MMP9 catalytic activity is not shared by biologically active polycationic molecules suggesting nonspecific charge screening as an unlikely mechanism. Deletion construct and MMP1, 2, and 3 studies suggest that the type-II fibronectin repeat domains of the enzyme appear to play a role in mediating the nucleotide potentiation of MMP9 activity. Single-stranded DNA enhances nerve growth factor-induced MMP9-dependent neurite extension in pheochromocytoma 12 cells providing evidence for potential biological significance of the nucleotide-mediated allosteric enhancement of the catalytic activity.

The efficacy of microsurgery in the treatment of cerebral aneurysm rupture and its effect on NF-κB, MCP-1 and MMP-9

The clinical efficacy of microsurgical neck clipping for the treatment of cerebral aneurysm rupture and its effect on serum nuclear factor κ-light-chain-enhancer of activated β cells (NF-κB), monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase-9 (MMP-9) levels were investigated. A total of 56 patients with first occurrence of cerebral aneurysm rupture were enrolled from June 2015 to June 2016. These patients were divided into control (25 patients) and observation groups (31 patients) according to treatment received. The patients in the control group were treated with interventional embolization and extraventricular drainage, while the patients in the observation group were treated with microsurgical neck clipping. Serum NF-κB, MCP-1 and MMP-9 levels were measured by ELISA prior to the operation and at 6 h post-operation. Clinical effects were compared at the 6-month follow-up. There was no significant difference in the success rate of the operation between the two groups (p>0.05). The incidence of complications in the observation group was significantly lower than that in the control group (p<0.05). The Glasgow Outcome Scale score was significantly improved in the observation group (p<0.05) compared with the control group. Serum NF-κB, MMP-9 and MCP-1 were significantly decreased in both groups at 6 and 24 h after operation, but the observational group showed significantly lower levels for all three proteins than the control group (p<0.05). The application of early microsurgical neck clipping for the treatment of cerebral aneurysm rupture can reduce complications and improve clinical prognosis, and this may be related to a decrease in serum inflammatory response-related factors (NF-κB and MCP-1) and MMP-9.

Matrix metalloproteinase family polymorphisms and the risk of aortic aneurysmal diseases: A systematic review and meta-analysis

It has been suggested that matrix metalloproteinase (MMP) polymorphisms are associated with the pathogenesis of aortic aneurysmal diseases. In this study, we conducted a systematic review with an update meta-analysis to investigate the relationship between MMP family polymorphisms and aortic aneurysmal diseases. We systematically reviewed 24 polymorphisms in 8 MMP genes related to the risk of abdominal aortic aneurysm (AAA), thoracic AA or thoracic aortic dissection (TAD). A total of 19 case-control studies with 15 highly studied MMP polymorphisms were included in our meta-analysis. Our results suggested that MMP2rs243865, MMP3rs3025058, MMP13rs2252070 polymorphisms were significantly associated with AAA risk, MMP2rs11643630, MMP8rs11225395 polymorphisms were correlated with TAD risk, and MMP9rs3918242 under the dominant model could increase AAA risk in hospital-based subgroup. No associations with aortic aneurysmal diseases were identified for other polymorphisms assessed in our meta-analysis. In summary, some studied MMP polymorphisms associated with the risk of aortic aneurysmal diseases are potential predictive biomarkers for the clinical application. Moreover, other MMP polymorphisms with limited studies but relevant to aortic aneurysmal formation and progression need further prospective and large investigations to confirm results.

Chronobiology of Acute Aortic Dissection in the Marfan Syndrome (from the National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions and the International Registry of Acute Aortic Dissection)

Marfan syndrome (MFS) is an autosomal dominant connective tissue disease associated with acute aortic dissection (AAD). We used 2 large registries that include patients with MFS to investigate possible trends in the chronobiology of AAD in MFS. We queried the International Registry of Acute Aortic Dissection (IRAD) and the Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC) registry to extract data on all patients with MFS who had suffered an AAD. The group included 257 patients with MFS who suffered an AAD from 1980 to 2012. The chi-square tests were used for statistical testing. Mean subject age at time of AAD was 38 years, and 61% of subjects were men. AAD was more likely in the winter/spring season (November to April) than the other half of the year (57% vs 43%, p = 0.05). Dissections were significantly more likely to occur during the daytime hours, with 65% of dissections occurring from 6 a.m. to 6 p.m. (p = 0.001). Men were more likely to dissect during the daytime hours (6 a.m. to 6 p.m.) than women (74% vs 51%, p = 0.01). These insights offer a glimpse of the times of greatest vulnerability for patients with MFS who suffer from this catastrophic event. In conclusion, the chronobiology of AAD in MFS reflects that of AAD in the general population.

Daidzein attenuates abdominal aortic aneurysm through NF-κB, p38MAPK and TGF-β1 pathways

The current study focuses on the protection of daidzein on nerves, as daidzein was demonstrated to have a protective effect on neurons of the central nervous system in a glutamate excitotoxicity and oxygen/glucose deprivation model. However, the effect of daidzein on the abdominal aortic aneurysm (AAA) remains unclear. The angiotensin II-induced AAA mouse model was utilized in the present study to determine the effect of daidzein on AAA. The results demonstrated that daidzein significantly attenuated incidence of AAA, max aortic aneurysm and mortality in the angiotensin II‑induced AAA mice. Daidzein had an anti‑inflammatory effect by inhibiting tumor necrosis factor α (TNF-α), interleukin 1β (IL‑1β) and nuclear factor κB (NF‑κB) protein expression. In addition, daidzein strongly suppressed the gene expression of cyclooxygenase (COX)‑2, matrix metalloproteinase 2 (MMP‑2), tissue inhibitor of metalloproteinase 1 (TIMP-1), transforming growth factor β1 (TGF‑β1), and inhibited inducible nitric oxide synthase (iNOS) protein expression in angiotensin II‑induced AAA mice. It also inhibited phosphorylation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway. These results demonstrate, to the best of our knowledge for the first time, that the anti‑inflammatory effects and inhibitory mechanism of daidzein attenuates AAA in angiotensin II‑induced mice. Daidzein contains strong anti‑inflammatory activity and affects various mechanism pathways including the NF‑κB, p38MAPK and TGF-β1 pathway.

Abdominal Aortic Aneurysm Genetic Associations: Mostly False? A Systematic Review and Meta-analysis

OBJECTIVE/BACKGROUND

Many associations between abdominal aortic aneurysm (AAA) and genetic polymorphisms have been reported. It is unclear which are genuine and which may be caused by type 1 errors, biases, and flexible study design. The objectives of the study were to identify associations supported by current evidence and to investigate the effect of study design on reporting associations.

METHODS

Data sources were MEDLINE, Embase, and Web of Science. Reports were dual-reviewed for relevance and inclusion against predefined criteria (studies of genetic polymorphisms and AAA risk). Study characteristics and data were extracted using an agreed tool and reports assessed for quality. Heterogeneity was assessed using I(2) and fixed- and random-effects meta-analyses were conducted for variants that were reported at least twice, if any had reported an association. Strength of evidence was assessed using a standard guideline.

RESULTS

Searches identified 467 unique articles, of which 97 were included. Of 97 studies, 63 reported at least one association. Of 92 studies that conducted multiple tests, only 27% corrected their analyses. In total, 263 genes were investigated, and associations were reported in polymorphisms in 87 genes. Associations in CDKN2BAS, SORT1, LRP1, IL6R, MMP3, AGTR1, ACE, and APOA1 were supported by meta-analyses.

CONCLUSION

Uncorrected multiple testing and flexible study design (particularly testing many inheritance models and subgroups, and failure to check for Hardy-Weinberg equilibrium) contributed to apparently false associations being reported. Heterogeneity, possibly due to the case mix, geographical, temporal, and environmental variation between different studies, was evident. Polymorphisms in nine genes had strong or moderate support on the basis of the literature at this time. Suggestions are made for improving AAA genetics study design and conduct.

An update on the etiology of abdominal aortic aneurysms: implications for future diagnostic testing

Abdominal aortic aneurysm (AAA) disease is multifactorial with both environmental and genetic risk factors. The current research in AAA revolves around genetic profiles and expression studies in both human and animal models. Variants in genes involved in extracellular matrix degradation, inflammation, the renin-angiotensin system, cell growth and proliferation and lipid metabolism have been associated with AAA using a variety of study designs. However, the results have been inconsistent and without a standard animal model for validation. Thus, despite the growing body of knowledge, the specific variants responsible for AAA development, progression and rupture have yet to be determined. This review explores some of the more significant genetic studies to provide an overview of past studies that have influenced the current understanding of AAA etiology. Expanding our understanding of disease pathogenesis will inform research into novel diagnostics and therapeutics and ultimately to improve outcomes for patients with AAA.

Functional Roles of N-Linked Glycosylation of Human Matrix Metalloproteinase 9

Matrix metalloproteinase-9 (MMP-9) is a secreted endoproteinase with a critical role in the regulation of the extracellular matrix and proteolytic activation of signaling molecules. Human (h)MMP-9 has two well-defined N-glycosylation sites at residues N38 and N120; however, their role has remained mostly unexplored partly because expression of the N-glycosylation-deficient N38S has been difficult due to a recently discovered single nucleotide polymorphism-dependent miRNA-mediated inhibitory mechanism. hMMP-9 cDNA encoding amino acid substitutions at residues 38 (modified-S38, mS38) or 120 (N120S) were created in the background of a miRNA-binding site disrupted template and expressed by transient transfection. hMMP-9 harboring a single mS38 replacement secreted well, whereas N120S, or a double mS38/N120S hMMP-9 demonstrated much reduced secretion. Imaging indicated endoplasmic reticulum (ER) retention of the non-secreted variants and co-immunoprecipitation confirmed an enhanced strong interaction between the non-secreted hMMP-9 and the ER-resident protein calreticulin (CALR). Removal of N-glycosylation at residue 38 revealed an amino acid-dependent strong interaction with CALR likely preventing unloading of the misfolded protein from the ER chaperone down the normal secretory pathway. As with other glycoproteins, N-glycosylation strongly regulates hMMP-9 secretion. This is mediated, however, through a novel mechanism of cloaking an N-glycosylation-independent strong interaction with the ER-resident CALR.

LMAN1 (ERGIC-53) is a potential carrier protein for matrix metalloproteinase-9 glycoprotein secretion

Matrix metalloproteinase-9 (MMP-9) is a secreted glycoprotein with a major role in shaping the extracellular matrix and a detailed understanding of the secretory mechanism could help identify methods to correct diseases resulting from dysregulation of secretion. MMP-9 appears to follow a canonical secretory pathway through a quality control cycle in the endoplasmic reticulum (ER) before transport of the properly folded protein to the Golgi apparatus and beyond for secretion. Through a complementation assay, we determined that LMAN1, a well-studied lectin-carrier protein, interacts with a secretion-competent N-glycosylated MMP-9 in the ER while N-glycosylation-deficient secretion-compromised MMP-9 does not. In contrast, co-immunoprecipitation demonstrated protein interaction between LMAN1 and secretion-compromised N-glycosylation-deficient MMP-9. MMP-9 secretion was reduced in the LMAN1 knockout cell line compared to control cells confirming the functional role of LMAN1. These observations support the role of LMAN1 as a lectin-carrier protein mediating efficient MMP-9 secretion.

Spinal cord injury induced neuropathic pain: Molecular targets and therapeutic approaches

Neuropathic pain, especially that resulting from spinal cord injury, is a tremendous clinical challenge. A myriad of biological changes have been implicated in producing these pain states including cellular interactions, extracellular proteins, ion channel expression, and epigenetic influences. Physiological consequences of these changes are varied and include functional deficits and pain responses. Developing therapies that effectively address the cause of these symptoms require a deeper knowledge of alterations in the molecular pathways. Matrix metalloproteinases and tissue inhibitors of metalloproteinases are two promising therapeutic targets. Matrix metalloproteinases interact with and influence many of the studied pain pathways. Gene expression of ion channels and inflammatory mediators clearly contributes to neuropathic pain. Localized and time dependent targeting of these proteins could alleviate and even prevent neuropathic pain from developing. Current therapeutic options for neuropathic pain are limited primarily to analgesics targeting the opioid pathway. Therapies directed at molecular targets are highly desirable and in early stages of development. These include transplantation of exogenously engineered cell populations and targeted gene manipulation. This review describes specific molecular targets amenable to therapeutic intervention using currently available delivery systems.

Correlation between the -1562C/T polymorphism in the matrix metalloproteinase-9 gene and hemorrhagic transformation of ischemic stroke

The aim of the present study was to investigate the correlation between the −1562C/T polymorphism in an intron of the matrix metalloproteinase-9 (MMP-9) gene and hemorrhagic transformation of ischemic stroke (IS). Using polymerase chain reaction-restriction fragment length polymorphism, the −1562C/T polymorphisms in 222 patients with IS were detected. The patients were divided into hemorrhagic transformation (HT; 84 cases) and non-hemorrhagic transformation (NHT) groups (138 cases) depending on the results from the susceptibility-weighted magnetic resonance imaging, which was performed between one and two weeks following stroke onset. The allele frequencies were subsequently compared. Baseline data of the two groups were comparable. The HT group exhibited a significantly lower frequency of the CT+TT genotype compared with the NHT group (17.86 vs. 30.43%, P<0.05). In addition, the frequency of T allele was significantly lower in the HT group compared with the NHT group (8.93 vs. 15.94%, P<0.05). Therefore, the results indicated that the −1562C/T polymorphism in the MMP-9 gene is correlated with hemorrhagic transformation of IS in the population studied. Furthermore, the T allele may be a protective factor for hemorrhagic transformation of IS in this population.

Quantitation of secreted proteins using mCherry fusion constructs and a fluorescent microplate reader

Traditional assays for secreted proteins include methods such as Western blot and enzyme-linked immunosorbent assay (ELISA) detection of the protein in the cell culture medium. We describe a method for the detection of a secreted protein based on fluorescent measurement of an mCherry fusion reporter. This microplate reader-based mCherry fluorescence detection method has a wide dynamic range of 4.5 orders of magnitude and a sensitivity that allows detection of 1 to 2fmol fusion protein. Comparison with the Western blot detection method indicated greater linearity, wider dynamic range, and a similar lower detection threshold for the microplate-based fluorescent detection assay of secreted fusion proteins. An mCherry fusion protein of matrix metalloproteinase-9 (MMP-9), a secreted glycoprotein, was created and expressed by transfection of human embryonic kidney (HEK) 293 cells. The cell culture medium was assayed for the presence of the fluorescent signal up to 32 h after transfection. The secreted MMP-9-mCherry fusion protein was detected 6h after transfection with a linear increase in signal intensity over time. Treatment with chloroquine, a drug known to inhibit the secretion of many proteins, abolished the MMP-9-mCherry secretion, demonstrating the utility of this method in a biological experiment.

Ezh2-mediated repression of a transcriptional pathway upstream of Mmp9 maintains integrity of the developing vasculature

Maintenance of vascular integrity is required for embryogenesis and organ homeostasis. However, the gene expression programs that stabilize blood vessels are poorly understood. Here, we show that the histone methyltransferase Ezh2 maintains integrity of the developing vasculature by repressing a transcriptional program that activates expression of Mmp9. Inactivation of Ezh2 in developing mouse endothelium caused embryonic lethality with compromised vascular integrity and increased extracellular matrix degradation. Genome-wide approaches showed that Ezh2 targets Mmp9 and its activators Fosl1 and Klf5. In addition, we uncovered Creb3l1 as an Ezh2 target that directly activates Mmp9 gene expression in the endothelium. Furthermore, genetic inactivation of Mmp9 rescued vascular integrity defects in Ezh2-deficient embryos. Thus, epigenetic repression of Creb3l1, Fosl1, Klf5 and Mmp9 by Ezh2 in endothelial cells maintains the integrity of the developing vasculature, potentially linking this transcriptional network to diseases with compromised vascular integrity.

Analysis of multiple genetic polymorphisms in aggressive-growing and slow-growing abdominal aortic aneurysms

BACKGROUND

The natural history of abdominal aortic aneurysms (AAAs) suggests that some remain slow in growth rate whereas many develop a more accelerated growth rate and reach a threshold for intervention. We hypothesized that different mechanisms are responsible for AAAs that remain slow growing and never become actionable vs the aggressive AAAs that require intervention and may be reflected by distinct associations with genetic polymorphisms.

METHODS

AAA growth rate was determined from serial imaging data in 168 control and 141 AAA patients with ultrasound or computed tomography imaging studies covering ∼5 years. Genetic polymorphisms all previously reported as showing a significant correlation with AAA with functional effects on the expression or function were determined by analysis of the genomic DNA, including angiotensin 1 receptor (rs5186), interleukin-10 (IL-10; rs1800896), methyl-tetrahydrofolate reductase (rs1801133), low-density lipoprotein receptor-related protein 1 (LRP1; rs1466535), angiotensin-converting enzyme (rs1799752), and several matrix metalloproteinase 9 (MMP-9) single nucleotide polymorphisms.

RESULTS

Of the AAA patients, 81 were classified as slow AAA growth rate (<3.25 mm/y) vs 60 with aggressive AAA growth rate (>3.25 mm/y, those presenting with a rupture, or those with maximal aortic diameter >5.5 cm [male] or >5.0 cm [female]). Discriminating confounds between the groups were identified by logistic regression. Analyses identified MMP-9 p-2502 single nucleotide polymorphism (odds ratio [OR], 0.54; 95% confidence interval [CI], 0.31-0.94; P = .029) as a significant confound discriminating between control vs slow-growth AAA, MMP-9 D165N (OR, 0.49; 95% CI, 0.26-0.95; P = .035) and LRP1 (OR, 4.99; 95% CI, 1.13-22.1; P = .034) between control vs aggressive-growth AAAs, and methyltetrahydrofolate reductase (OR, 2.99; 95% CI, 1.01-8.86; P = .048), MMP-9 p-2502 (OR, 2.19; 95% CI, 1.05-4.58; P = .037), and LRP1 (OR, 4.96; 95% CI, 1.03-23.9; P = .046) as the statistically significant confounds distinguishing slow-growth AAAs vs aggressive-growth AAAs.

CONCLUSIONS

Logistic regression identified different genetic confounds for the slow-growth and aggressive-growth AAAs, indicating a potential for different genetic influences on AAAs of distinct aggressiveness. Future logistic regression studies investigating for potential genetic or clinical confounds for this disease should take into account the growth rate and size of the AAA to better identify confounds likely to be associated with aggressive AAAs likely to require intervention.

Single nucleotide polymorphism-specific regulation of matrix metalloproteinase-9 by multiple miRNAs targeting the coding exon

Microribonucleic acids (miRNAs) work with exquisite specificity and are able to distinguish a target from a non-target based on a single nucleotide mismatch in the core nucleotide domain. We questioned whether miRNA regulation of gene expression could occur in a single nucleotide polymorphism (SNP)-specific manner, manifesting as a post-transcriptional control of expression of genetic polymorphisms. In our recent study of the functional consequences of matrix metalloproteinase (MMP)-9 SNPs, we discovered that expression of a coding exon SNP in the pro-domain of the protein resulted in a profound decrease in the secreted protein. This missense SNP results in the N38S amino acid change and a loss of an N-glycosylation site. A systematic study demonstrated that the loss of secreted protein was due not to the loss of an N-glycosylation site, but rather an SNP-specific targeting by miR-671-3p and miR-657. Bioinformatics analysis identified 41 SNP-specific miRNA targeting MMP-9 SNPs, mostly in the coding exon and an extension of the analysis to chromosome 20, where the MMP-9 gene is located, suggesting that SNP-specific miRNAs targeting the coding exon are prevalent. This selective post-transcriptional regulation of a target messenger RNA harboring genetic polymorphisms by miRNAs offers an SNP-dependent post-transcriptional regulatory mechanism, allowing for polymorphic-specific differential gene regulation.

Correlation between the severity of coronary artery lesions and levels of estrogen, hs-CRP and MMP-9

The aim of this study was to investigate the correlation between the severity of coronary artery lesions in patients with acute coronary syndromes (ACS) and levels of estrogen, high-sensitivity C-reactive protein (hs-CRP) and matrix metalloproteinase-9 (MMP-9). A total of 65 patients with ACS, 33 patients with stable angina pectoris (SAP) and 36 healthy controls were randomly enrolled. Patients with ACS were subdivided into two groups: Acute myocardial infarction (AMI; n=30) and unstable angina pectoris (UAP; n=35). Serum levels of estrogen, hs-CRP and MMP-9 were detected in the four groups of subjects. Serum estrogen levels in patients with AMI, UAP and SAP were significantly lower than those in the control group (P<0.05). Estrogen levels were also significantly different among the AMI, UAP and SAP groups (P<0.05), with a progressive increase across the three respective groups. Compared with healthy subjects, patients with AMI had the highest levels of hs-CRP and MMP-9, followed in descending order by those with UAP and SAP (P<0.05). Levels of hs-CRP and MMP-9 were also significantly different among the AMI, UAP and SAP groups (P<0.05). Serum estrogen levels were negatively correlated with hs-CRP and MMP-9 levels (r=−0.6634 and −0.6878, respectively; both P<0.05). hs-CRP and MMP-9 levels correlated positively (r=0.7208, P<0.05). The number of stenosed coronary vessels was negatively correlated with estrogen levels (r=−0.6467, P<0.05), and positively correlated with hs-CRP and MMP-9 levels (r=0.6519 and 0.6835, respectively; both P<0.05). In conclusion, serum estrogen, hs-CRP and MMP-9 levels were significantly correlated with the severity of coronary artery lesions. There was also a significant correlation between serum estrogen, hs-CRP and MMP-9 levels. These data indicate that serum estrogen, hs-CRP and MMP-9 have the potential to be used as biomarkers for evaluating the severity of coronary artery lesions and the stability of coronary artery plaques.

A pilot study on low-density lipoprotein receptor-related protein-1 in Chinese patients with abdominal aortic aneurysm

OBJECTIVE

There are no published data on the expression of low-density lipoprotein receptor-related protein 1 (LRP1) in human aortic tissues with abdominal aortic aneurysm (AAA), although some researchers have suggested that LRP1 may be a crucial regulator in the pathogenesis of AAA. The aim of this pilot study is to investigate LRP1 expression in aortic tissues from Chinese patients with AAA compared with normal control tissues.

MATERIALS AND METHODS

This study used human abdominal aortic tissues with or without AAA as a research model. Aneurysmal abdominal aortas were collected from Chinese patients with AAA (n = 12) during open surgical aneurysmal repair at our institution, and normal control non-aneurysmal abdominal aortas were collected from Chinese healthy organ donors (n = 12) during organ transplantation. Protein expression of LRP1 was analyzed by western blotting and immunohistochemistry.

RESULTS

LRP1 protein expression was significantly lower in AAA (mean LRP1AAA/LRP1(Normal Control) = 0.51 ± 0.28) than in normal control aortic tissues (mean LRP1(Normal Control)/LRP1(Normal Control) = 1 ± 0.18) in our small sample cohort (p < .001). No significant correlation was shown between LRP1 protein expression and the size of AAA (p > .05).

CONCLUSIONS

Our pilot result suggests that a reduction in LRP1 protein expression may be associated with aneurysm progression.

Chronobiology in aortic diseases - "is this really a random phenomenon?"

Although acute aortic rupture or dissection is relatively uncommon, it ranks in third position among necropsy-confirmed causes of out-of-hospital sudden death in the general population. Similar to other acute cardiovascular events (e.g., acute myocardial infarction, sudden death, stroke, and pulmonary embolism) there is a growing body of evidence regarding temporal patterns in onset, characterized by circadian, seasonal and weekly variations for aortic aneurysms. On one hand, it is possible that these cardiovascular diseases share common underlying pathophysiologic mechanisms, e.g., increase in blood pressure, heart rate, sympathetic activity, basal vascular tone, vasoconstrictive hormones, and prothrombotic tendency. On the other hand, the possibility exists that the connecting link is an internal disruption (dyssynchrony) of some molecular mechanisms intrinsic to the peripheral biological clock (that of cardiomyocyte is the most widely investigated). Such disruption may contribute to cardiovascular disease and biological rhythms - an intriguing hypothesis for future research.