Prevention of CaCl2-induced aortic inflammation and subsequent aneurysm formation by the CCL3-CCR5 axis

CD8+ T-cell deficiency protects mice from abdominal aortic aneurysm formation in response to calcium chloride2

OBJECTIVE

Abdominal aortic aneurysm (AAA) is an aneurysm-like dilated and highly fatal cardiovascular disease. CD8+ T cells have been shown to be critical for vascular pathological processes, but the contribution of these lymphocytes to vascular diseases remains elusive.

METHODS AND RESULTS

Eight-week-old male wildtype (CD8+/+) and Cd8a knockout (CD8-/-) mice were used in a calcium chloride2 (CaCl2)-induced experimental AAA model. At 6 weeks after surgery, CD8+ T-cell deletion prevented the formation of AAA, accompanied by reductions of the levels of inflammatory (interferon-γ [IFN-γ], interleukin-1β, monocyte chemoattractant protein-1, intracellular adhesion molecule-1, vascular cell adhesion molecule-1, NOD-like receptor protein 3, caspase-1), oxidative stress [NADPH oxidase and gp91phox], and proteolysis (cathepsin S, cathepsin K, matrix metalloproteinase-2 [MMP-2] and MMP-9) proteins and/or genes in plasma and/or AAA tissues. Immunoreactivities of MMP-2 and MMP-9 were observed in macrophages. An injection of IFN-γ and adoptive transfer of CD8+ T cells of IFN-γ+/+ mice diminished CD8-/--mediated vasculoprotective actions in the AAA mice. In vitro, IFN-γ enhanced MMP-2 and MMP-9 gelatinolytic activities in macrophage and/or vascular smooth muscle cells.

CONCLUSION

The vasculoprotective effects of CD8+ T-cell deletion in a mouse CaCl2-induced AAA model were likely attributable to, at least in part, the attenuation of IFN-γ-dependent inflammation action, oxidative stress production, and proteolysis, suggesting a novel therapeutic target for AAA formation by regulating CD8+ T-cell-derived IFN-γ secretion.

Complement C3a/C3aR inhibition alleviates the formation of aortic aneurysm in Marfan syndrome mice

Mutations in fibrillin 1 (FBN1) is the main cause of Marfan syndrome (MFS) with thoracic aortic aneurysm (TAA) as the main complication. Activation of the complement system plays a key role in the formation of thoracic and abdominal aortic aneurysms. However, the role of the complement system in MFS-associated aortic aneurysms remains unclear. In this study, we observed increased levels of complement C3a and C5a in the plasma of MFS patients and mouse, and the increased deposition of the activated complement system product C3b/iC3b was also observed in the elastic fiber rupture zone of 3-month-old MFS mice. The expression of C3a receptor (C3aR) was increased in MFS aortas, and recombinant C3a promoted the expression of cytokines in macrophages. The administration of a C3aR antagonist (C3aRA) attenuated the development of thoracic aortic aneurysms in MFS mice. The increased inflammation response and matrix metalloproteinases activities were also attenuated by C3aRA treatment in MFS mice. Therefore, these findings indicate that the complement C3a/C3aR inhibition alleviates the formation of aortic aneurysm in Marfan syndrome mice.

Tea polyphenol nanoparticles enable targeted siRNA delivery and multi-bioactive therapy for abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease, while there is a lack of pharmaceutical interventions to halt AAA progression presently. To address the multifaceted pathology of AAA, this work develops a novel multifunctional gene delivery system to simultaneously deliver two siRNAs targeting MMP-2 and MMP-9. The system (TPNs-siRNA), formed through the oxidative polymerization and self-assembly of epigallocatechin gallate (EGCG), efficiently encapsulates siRNAs during self-assembly. TPNs-siRNA safeguards siRNAs from biological degradation, facilitates intracellular siRNA transfection, promotes lysosomal escape, and releases siRNAs to silence MMP-2 and MMP-9. Additionally, TPNs, serving as a multi-bioactive material, mitigates oxidative stress and inflammation, fosters M1-to-M2 repolarization of macrophages, and inhibits cell calcification and apoptosis. In experiments with AAA mice, TPNs-siRNA accumulated and persisted in aneurysmal tissue after intravenous delivery, demonstrating that TPNs-siRNA can be significantly distributed in macrophages and VSMCs relevant to AAA pathogenesis. Leveraging the carrier's intrinsic multi-bioactive properties, the targeted siRNA delivery by TPNs exhibits a synergistic effect for enhanced AAA therapy. Furthermore, TPNs-siRNA is gradually metabolized and excreted from the body, resulting in excellent biocompatibility. Consequently, TPNs emerges as a promising multi-bioactive nanotherapy and a targeted delivery nanocarrier for effective AAA therapy.

Causal association between circulating inflammatory cytokines and intracranial aneurysm and subarachnoid hemorrhage

BACKGROUND AND PURPOSE

The causal association between inflammatory cytokines and the development of intracranial aneurysm (IA), unruptured IA (uIA) and subarachnoid hemorrhage (SAH) lacks clarity.

METHODS

The summary-level datasets for inflammatory cytokines were extracted from a genome-wide association study of the Finnish Cardiovascular Risk in Young Adults Study and the FINRISK survey. The summary statistics datasets related to IA, uIA and SAH were obtained from the genome-wide association study meta-analysis of the International Stroke Genetics Consortium and FinnGen Consortium. The primary method employed for analysis was inverse variance weighting (false discovery rate), supplemented by sensitivity analyses to address pleiotropy and enhance robustness.

RESULTS

In the International Stroke Genetics Consortium, 10, six and eight inflammatory cytokines exhibited a causal association with IA, uIA and SAH, respectively (false discovery rate, p < 0.05). In FinnGen datasets, macrophage Inflammatory Protein-1 Alpha (MIP_1A), MIP_1A and interferon γ-induced protein 10 (IP_10) were verified for IA, uIA and SAH, respectively. In the reverse Mendelian randomization analysis, the common cytokines altered by uIA and SAH were vascular endothelial growth factor (VEGF), MIP_1A, IL_9, IL_10 and IL_17, respectively. The meta-analysis results show that MIP_1A and IP_10 could be associated with the decreased risk of IA, and MIP_1A and IP_10 were associated with the decreased risk of uIA and SAH, respectively. Notably, the levels of VEGF, MIP_1A, IL_9, IL_10 and TNF_A were increased with uIA. Comprehensive heterogeneity and pleiotropy analyses confirmed the robustness of these results.

CONCLUSION

Our study unveils a bidirectional association between inflammatory cytokines and IA, uIA and SAH. Further investigations are essential to validate their relationship and elucidate the underlying mechanisms.

SRGN promotes macrophage recruitment through CCL3 in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a degenerative disease that affects synovial joints and leads to significant pain and disability, particularly in older adults. Infiltration of macrophages plays a key role in the progression of OA. However, the mechanisms underlying macrophage recruitment in OA are not fully understood.

METHODS

The Serglycin (SRGN) expression pattern was analyzed, along with its association with macrophage infiltration in OA, using bioinformatic methods. SRGN expression in chondrocytes was altered by small interfering RNA (siRNA) and plasmids. Conditioned media (CM) was obtained from transfected chondrocytes to establish a co-culture model of chondrocytes and THP-1 derived macrophages. The impact of SRGN on macrophage recruitment was evaluated using a transwell assay. Furthermore, the regulatory effect of SRGN on CCL3 was validated through qPCR, WB, and ELISA experiments.

RESULTS

In OA patients, the upregulation of SRGN positively correlated with K-L grade and macrophage infiltration. It was found that SRGN expression and secretion were up-regulated in OA and that it can promote macrophage migration in vitro. Further investigation showed that SRGN affects macrophage migration by regulating the expression of CCL3.

CONCLUSION

SRGN in chondrocytes plays a role in promoting the recruitment of THP-1 derived macrophages in vitro by regulating production of CCL3.

Comprehensive transcriptomic analysis unveils macrophage-associated genes for establishing an abdominal aortic aneurysm diagnostic model and molecular therapeutic framework

BACKGROUND

Abdominal aortic aneurysm (AAA) is a highly lethal cardiovascular disease. The aim of this research is to identify new biomarkers and therapeutic targets for the treatment of such deadly diseases.

METHODS

Single-sample gene set enrichment analysis (ssGSEA) and CIBERSORT algorithms were used to identify distinct immune cell infiltration types between AAA and normal abdominal aortas. Single-cell RNA sequencing data were used to analyse the hallmark genes of AAA-associated macrophage cell subsets. Six macrophage-related hub genes were identified through weighted gene co-expression network analysis (WGCNA) and validated for expression in clinical samples and AAA mouse models. We screened potential therapeutic drugs for AAA through online Connectivity Map databases (CMap). A network-based approach was used to explore the relationships between the candidate genes and transcription factors (TFs), lncRNAs, and miRNAs. Additionally, we also identified hub genes that can effectively identify AAA and atherosclerosis (AS) through a variety of machine learning algorithms.

RESULTS

We obtained six macrophage hub genes (IL-1B, CXCL1, SOCS3, SLC2A3, G0S2, and CCL3) that can effectively diagnose abdominal aortic aneurysm. The ROC curves and decision curve analysis (DCA) were combined to further confirm the good diagnostic efficacy of the hub genes. Further analysis revealed that the expression of the six hub genes mentioned above was significantly increased in AAA patients and mice. We also constructed TF regulatory networks and competing endogenous RNA networks (ceRNA) to reveal potential mechanisms of disease occurrence. We also obtained two key genes (ZNF652 and UBR5) through a variety of machine learning algorithms, which can effectively distinguish abdominal aortic aneurysm and atherosclerosis.

CONCLUSION

Our findings depict the molecular pharmaceutical network in AAA, providing new ideas for effective diagnosis and treatment of diseases.

Myeloid Cell mPGES-1 Deletion Attenuates Calcium Phosphate-induced Abdominal Aortic Aneurysm in Male Mice

Microsomal PGE2 synthase (mPGES)-1 is the key enzyme responsible for synthesizing inflammatory prostaglandin E2 (PGE2). Our previous studies have shown that deletion mPGES-1 in myeloid cells hinders atherogenesis, suppresses vascular proliferative response to injury and enhances survival after myocardial infarction. Here we aimed to further explore the influence of myeloid cell mPGES-1 deletion in abdominal aortic aneurysm (AAA) formation. The AAA was triggered by applying 0.5 M calcium phosphate (CaPO4) to the infrarenal aorta of both myeloid mPGES-1 knockout (Mac-mPGES-1-KO) and their littermate control Mac-mPGES-1-WT mice. AAA induction was assessed by calculating the expansion of the infrarenal aortic diameter 4 weeks after CaPO4 application. The maximum diameters of the aortas were measured by morphometry and the mean maximal diameters were calculated. Paraffin sections of the infrarenal aortas were examined for morphological analysis and immunohistochemical staining. The results showed that myeloid cell mPGES-1 deletion significantly mitigated AAA formation, including reducing expansion of the infrarenal aorta, preventing elastic lamellar degradation, and decreasing aortic calcium deposition. Immunohistochemical staining further indicated that macrophage infiltration and matrix metalloproteinase 2 (MMP2) expression was attenuated in the Mac-mPGES-1-KO aortas. Consistently, in vitro experiments showed that expression of pro-inflammatory cytokines and MMPs was significantly reduced when mPGES-1 was lacking in the primary cultured peritoneal macrophages. These data altogether demonstrated that deletion of mPGES-1 in myeloid cells may attenuate AAA formation and targeting myeloid cell mPGES-1 could potentially offer an effective strategy for the treatment and prevention of vascular inflammatory diseases.

Pentamethylquercetin attenuates angiotensin II-induced abdominal aortic aneurysm formation by blocking nuclear translocation of C/EBPβ at Lys253

BACKGROUND

Pentamethylquercetin (PMQ) is a natural polymethyl flavonoid that possesses anti-apoptotic and other biological properties. Abdominal aortic aneurysm (AAA), a fatal vascular disease with a high risk of rupture, is associated with phenotypic switching and apoptosis of medial vascular smooth muscle cells (VSMCs). This study aimed to investigate the protective effects of PMQ on the development of AAA and the underlying mechanism.

METHODS

ApoE-/- mice were continuously infused with angiotensin II (Ang II) for 4 weeks to develop the AAA model. Intragastric administration of PMQ was initiated 5 days before Ang II infusion and continued for 4 weeks. In vitro, VSMCs were cultured and pretreated with PMQ, stimulated with Ang II. Real-time PCR, western blotting, and immunofluorescence staining were used to examine the roles and mechanisms of PMQ on the phenotypic switching and apoptosis of VSMCs.

RESULTS

PMQ dose-dependently reduced the incidence of Ang II-induced AAA, aneurysm diameter enlargement, elastin degradation, VSMCs phenotypic switching and apoptosis. Furthermore, PMQ also inhibited phenotypic switching and apoptosis in Ang II-stimulated VSMCs. PMQ exerted protective effects by regulating the C/EBPβ/PTEN/AKT/GSK-3β axis. AAV-mediated overexpression of PTEN reduced the therapeutic effects of PMQ in the AAA model mice, suggesting that the effects of PMQ on Ang II-mediated AAA formation were related to the PTEN/AKT/GSK-3β axis. PMQ inhibited VSMCs phenotypic switching and apoptosis by bounding to C/EBPβ at Lys253 with hydrogen bond to regulate C/EBPβ nuclear translocation and PTEN/AKT/GSK-3β axis, thereby inhibiting Ang II-induced AAA formation.

CONCLUSIONS

Pentamethylquercetin inhibits angiotensin II-induced abdominal aortic aneurysm formation by bounding to C/EBPβ at Lys253. Therefore, PMQ prevents the formation of AAA and reduces the incidence of AAA.

A Dual-Function CD47-Targeting Nano-Drug Delivery System Used to Regulate Immune and Anti-Inflammatory Activities in the Treatment of Atherosclerosis

Atherosclerosis is a primary contributor to cardiovascular disease. Current studies have highlighted the association between the immune system, particularly immune cells, and atherosclerosis, although treatment options and clinical trials remain scarce. Immunotherapy for cardiovascular disease is still in its infancy. Bruton's tyrosine kinase (BTK), widely expressed in various immune cells, represents a promising therapeutic target for atherosclerosis by modulating the anti-inflammatory function of immune cells. This study introduces a polydopamine-based nanocarrier system to deliver the BTK inhibitor, ibrutinib, to atherosclerotic plaques with an active targeting property via an anti-CD47 antibody. Leveraging polydopamine's pH-sensitive reversible disassembly, the system offers responsive, controlled release within the pathologic microenvironment. This allows precise and efficient ibrutinib delivery, concurrently inhibiting the activation of the NF-κB pathway in B cells and the NLRP3 inflammasome in macrophages within the plaques. This treatment also modulates both the immune cell microenvironment and inflammatory conditions in atherosclerotic lesions, thereby conveying promising therapeutic effects for atherosclerosis in vivo. This strategy also provides a novel option for atherosclerosis treatment.

Extravascular administration of IGF1R antagonists protects against aortic aneurysm in rodent and porcine models

An abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease. We identified plasma insulin-like growth factor 1 (IGF1) as an independent risk factor in patients with AAA by correlating plasma IGF1 with risk. Smooth muscle cell- or fibroblast-specific knockout of Igf1r, the gene encoding the IGF1 receptor (IGF1R), attenuated AAA formation in two mouse models of AAA induced by angiotensin II infusion or CaCl2 treatment. IGF1R was activated in aortic aneurysm samples from human patients and mice with AAA. Systemic administration of IGF1C, a peptide fragment of IGF1, 2 weeks after disease development inhibited AAA progression in mice. Decreased AAA formation was linked to competitive inhibition of IGF1 binding to its receptor by IGF1C and modulation of downstream alpha serine/threonine protein kinase (AKT)/mammalian target of rapamycin signaling. Localized application of an IGF1C-loaded hydrogel was developed to reduce the side effects observed after systemic administration of IGF1C or IGF1R antagonists in the CaCl2-induced AAA mouse model. The inhibitory effect of the IGF1C-loaded hydrogel administered at disease onset on AAA formation was further evaluated in a guinea pig-to-rat xenograft model and in a sheep-to-minipig xenograft model of AAA formation. The therapeutic efficacy of IGF1C for treating AAA was tested through extravascular delivery in the sheep-to-minipig model with AAA established for 2 weeks. Percutaneous injection of the IGF1C-loaded hydrogel around the AAA resulted in improved vessel flow dynamics in the minipig aorta. These findings suggest that extravascular administration of IGF1R antagonists may have translational potential for treating AAA.

Identification of a non-canonical chemokine-receptor pathway suppressing regulatory T cells to drive atherosclerosis

CCL17 is produced by conventional dendritic cells (cDCs), signals through CCR4 on regulatory T cells (Tregs), and drives atherosclerosis by suppressing Treg functions through yet undefined mechanisms. Here we show that cDCs from CCL17-deficient mice display a pro-tolerogenic phenotype and transcriptome that is not phenocopied in mice lacking its cognate receptor CCR4. In the plasma of CCL17-deficient mice, CCL3 was the only decreased cytokine/chemokine. We found that CCL17 signaled through CCR8 as an alternate high-affinity receptor, which induced CCL3 expression and suppressed Treg functions in the absence of CCR4. Genetic ablation of CCL3 and CCR8 in CD4+ T cells reduced CCL3 secretion, boosted FoxP3+ Treg numbers, and limited atherosclerosis. Conversely, CCL3 administration exacerbated atherosclerosis and restrained Treg differentiation. In symptomatic versus asymptomatic human carotid atheroma, CCL3 expression was increased, while FoxP3 expression was reduced. Together, we identified a non-canonical chemokine pathway whereby CCL17 interacts with CCR8 to yield a CCL3-dependent suppression of atheroprotective Tregs.

Aortic aneurysms: current pathogenesis and therapeutic targets

Aortic aneurysm is a chronic disease characterized by localized expansion of the aorta, including the ascending aorta, arch, descending aorta, and abdominal aorta. Although aortic aneurysms are generally asymptomatic, they can threaten human health by sudden death due to aortic rupture. Aortic aneurysms are estimated to lead to 150,000 ~ 200,000 deaths per year worldwide. Currently, there are no effective drugs to prevent the growth or rupture of aortic aneurysms; surgical repair or endovascular repair is the only option for treating this condition. The pathogenic mechanisms and therapeutic targets for aortic aneurysms have been examined over the past decade; however, there are unknown pathogenic mechanisms involved in cellular heterogeneity and plasticity, the complexity of the transforming growth factor-β signaling pathway, inflammation, cell death, intramural neovascularization, and intercellular communication. This review summarizes the latest research findings and current pathogenic mechanisms of aortic aneurysms, which may enhance our understanding of aortic aneurysms.

CypD induced ROS output promotes intracranial aneurysm formation and rupture by 8-OHdG/NLRP3/MMP9 pathway

Reactive Oxygen Species (ROS) are widely accepted as a pernicious factor in the progression of intracranial aneurysm (IA), which is eminently related to cell apoptosis and extracellular matrix degradation, but the mechanism remains to be elucidated. Recent evidence has identified that enhancement of Cyclophilin D (CypD) under stress conditions plays a critical role in ROS output, thus accelerating vascular destruction. However, no study has confirmed whether cypD is a detrimental mediator of cell apoptosis and extracellular matrix degradation in the setting of IA development. Our data indicated that endogenous cypD mRNA was significantly upregulated in human IA lesions and mouse IA wall, accompanied by higher level of ROS, MMPs and cell apoptosis. CypD-/- remarkably reversed vascular smooth muscle cells (VSMCs) apoptosis and elastic fiber degradation, and significantly decreased the incidence of aneurysm and ruptured aneurysm, together with the downregulation of ROS, 8-OHdG, NLRP3 and MMP9 in vivo and vitro. Furthermore, we demonstrated that blockade of cypD with CsA inhibited the above processes, thus preventing IA formation and rupture, these effects were highly dependent on ROS output. Mechanistically, we found that cypD directly interacts with ATP5B to promote ROS release in VSMCs, and 8-OHdG directly bind to NLRP3, which interacted with MMP9 to increased MMP9 level and activity in vivo and vitro. Our data expound an unexpected role of cypD in IA pathogenesis and an undescribed 8-OHdG/NLRP3/MMP9 pathway involved in accelerating VSMCs apoptosis and elastic fiber degradation. Repressing ROS output by CypD inhibition may be a promising therapeutic strategy for prevention IA development.

CARMA3 Deficiency Aggravates Angiotensin II-Induced Abdominal Aortic Aneurysm Development Interacting Between Endoplasmic Reticulum and Mitochondria

BACKGROUND

Abdominal aortic aneurysm (AAA) is life threatening and associated with vascular walls' chronic inflammation. However, a detailed understanding of the underlying mechanisms is yet to be elucidated. CARMA3 assembles the CARMA3-BCL10-MALT1 (CBM) complex in inflammatory diseases and is proven to mediate angiotensin II (Ang II) response to inflammatory signals by modulating DNA damage-induced cell pyroptosis. In addition, interaction between endoplasmic reticulum (ER) stress and mitochondrial damage is one of the main causes of cell pyroptosis.

METHODS

Male wild type (WT) or CARMA3-/- mice aged 8 to 10 weeks were subcutaneously implanted with osmotic minipumps, delivering saline or Ang II at the rate of 1 μg/kg/min for 1, 2, and 4 weeks.

RESULTS

We discovered that CARMA3 knockout promoted formation of AAA and prominently increased diameter and severity of the mice abdominal aorta infused with Ang II. Moreover, a significant increase in the excretion of inflammatory cytokines, expression levels of matrix metalloproteinases (MMPs) and cell death was found in the aneurysmal aortic wall of CARMA3-/- mice infused with Ang II compared with WT mice. Further studies found that the degree of ER stress and mitochondrial damage in the abdominal aorta of CARMA3-/- mice was more severe than that in WT mice. Mechanistically, CARMA3 deficiency exacerbates the interaction between ER stress and mitochondrial damage by activating the p38MAPK pathway, ultimately contributing to the pyroptosis of vascular smooth muscle cells (VSMCs).

CONCLUSIONS

CARMA3 appears to play a key role in AAA formation and might be a potential target for therapeutic interventions of AAA.

Purinergic receptor P2 × 7 contributes to abdominal aortic aneurysm development via modulating macrophage pyroptosis and inflammation

The purinergic receptor P2 × 7 has been established as an important mediator of inflammation and participates in a variety of cardiovascular diseases including atherosclerosis, however, its role in abdominal aortic aneurysms (AAA) remains unclear. In this study, we demonstrate that P2 × 7 plays essential roles in AAA development via modulating macrophage pyroptosis and inflammation. P2 × 7 is highly expressed in human AAA specimen, as well as in experimental murine AAA lesions (both CaCl₂-and Angiotensin Ⅱ-induced AAA models), and it mainly confines in macrophages. Furthermore, P2 × 7 deficiency or pharmacological inhibition with its antagonist could significantly attenuate aneurysm formation in experimental murine AAA models, while P2 × 7 agonist could promote AAA development. The caspase-I activity, matrix metalloproteinase (MMP) activity, reactive oxygen species (ROS) production and pro-inflammatory gene expression were significant reduced in experimental AAA lesions in mice with P2 × 7 deficiency or inhibition. Mechanistically, macrophage P2 × 7 can mediate the activation of NLRP3 inflammasome and activate its downstream caspase-1 to initiate the pyroptosis pathway. After caspase-1 activation, it further cleaves pro-interleukin (IL)-1β and gasdermin D (GSDMD). Consequently, the N-terminal fragment of GSDMD forms pores on the cell membrane, leading to macrophage pyroptosis and release of the pro-inflammatory factor IL-1β. The resulting vascular inflammation further leads to the upregulation of MMP and ROS, thereby promoting AAA development. In summary, these data identify P2 × 7-mediated macrophage pyroptosis signaling pathway as a novel contributory mechanism of AAA formation.

The CCR1 and CCR5 C-C chemokine receptors in Penaeus vannamei are annexed by bacteria to attenuate shrimp survival

The C-C chemokine receptors (CCRs) family is involved in diverse pathophysiological processes in mammals, such as immune regulation and cancer, but their functions in invertebrates remain enigmatic. Here, two CCR homologs in Penaeus vannamei (designated PvCCR1 and PvCCR5) were characterized and found to share sequence homology with other CCRs and contain the conserved 7TM functional domain. Both PvCCR1 and PvCCR5 were constitutively expressed in healthy shrimp tissues, while their mRNA transcript levels were induced in hepatopancreas and hemocytes by Vibrio parahaemolyticus, Streptococcus iniae, and white spot syndrome virus. Notably, shrimp survival increased after knockdown of PvCCR1 and PvCCR5 followed by V. parahaemolyticus infection, indicating that PvCCR1 and PvCCR5 are annexed by the bacteria for their benefit, the absence of which attenuates the effects of the pathogen on shrimp survival. The present data indicate that PvCCR1 and PvCCR5 play key roles in the antimicrobial immune response and therefore vital for shrimp survival.

Screening for key genes in circadian regulation in advanced atherosclerosis: A bioinformatic analysis

Background

Atherosclerosis (AS) is the most important cardiovascular disease threatening human health, leading to adverse events such as myocardial infarction and stroke. The research on the pathogenesis and causes of AS is being improved step by step, and many factors are associated with AS. However, the relationship between circadian regulation and the pathogenesis of AS is still unclear. Our study identified 2 key genes of circadian regulation in AS by bioinformatics analysis, which provides new perspectives to understand the relationship between circadian rhythm and AS.

Methods

We downloaded samples of early and advanced AS from public databases, screened key genes by weighted gene co-expression network analysis (WGCNA) and Lasso, calculated the immune cell content of the samples using "CIBERSORT," and analyzed the relationship between key genes and immune cells.

Results

We obtained the most relevant core modules for advanced AS and analyzed the functions of these modules. Two circadian rhythm-related genes were obtained, which influence the immune infiltration of this late AS. ROC curves demonstrated the efficacy of key genes to differentiate between early and advanced AS.

Conclusion

We identified 2 genes most associated with circadian rhythms in advanced AS, whose association with AS has not been elucidated and may become the next therapeutic target.

CCL3 aggravates intestinal damage in NEC by promoting macrophage chemotaxis and M1 macrophage polarization

BACKGROUND

NEC is a life-threatening gastrointestinal disease in neonates, the pathogenesis of which remains poorly understood.

METHODS

CCL3 levels in intestinal tissue of mice were measured and analyzed. HE staining was used to assess pathological changes in intestinal tissue. FCM was used to detect the proportion and phenotype of macrophages. RNA-seq and RT-PCR were used to evaluate the effect of CCL3 on macrophages.

RESULTS

CCL3 was highly expressed in the intestinal tissues of mice with NEC and induced macrophage infiltration. Transcriptome data showed that CCL3 strongly induced a transition in the phenotype of macrophages into a proinflammatory one. Mechanistically, in vivo experiments confirmed that CCL3 induced M1 macrophage polarization in NEC intestinal tissue, thereby aggravating inflammatory injury of intestinal tissue, which was alleviated by anti-CCL3 treatment. In addition, in vitro experiments showed that CCL3 significantly enhances the expression of M1-related genes in both PMφ and BMDM while inhibiting the expression of M2-related genes, which was also alleviated by anti-CCl3 treatment.

CONCLUSIONS

Our data elucidated the involvement of CCL3 in the pathogenesis of NEC, in which upregulated CCL3 expression exacerbated inflammatory intestinal damage by regulating macrophage chemotaxis and M1 phenotype polarization, suggesting that blocking CCL3 may be a potential strategy for effective intervention in NEC.

IMPACT

Our study represents an important conceptual advancement that CCL3 may be one of the key culprits of intestinal tissue damage in patients with NEC. CCL3 aggravates inflammatory intestinal injury and intestinal mucosal barrier imbalance by regulating the chemotaxis, polarization, and function of macrophages. Blocking CCL3 significantly reduced NEC-mediated intestinal injury, suggesting a new potential therapeutic strategy.

Animal model contributes to the development of intracranial aneurysm: A bibliometric analysis

Introduction

Studies on intracranial aneurysms (IAs) using animal models have evolved for decades. This study aimed to analyze major contributors and trends in IA-related animal research using bibliometric analysis.

Methods

IA-related animal studies were retrieved from the Web of Science database. Microsoft Excel 2010, GraphPad Prism 6, VOSviewer, and CiteSpace were used to collect and analyze the characteristics of this field.

Results

A total of 273 publications were retrieved. All publications were published between 1976 and 2021, and the peak publication year is 2019. Rat model were used in most of the publications, followed by mice and rabbits. Japan (35.5%), the United States (30.0%), and China (20.1%) were the top three most prolific countries. Although China ranks third in the number of publications, it still lacks high-quality articles and influential institutions. Stroke was the most prolific journal that accepted publications related to IA research using animal models. Circulation has the highest impact factor with IA-related animal studies. Hashimoto N contributed the largest number of articles. Meng hui journal published the first and second highest cited publications. The keywords “subarachnoid hemorrhage,” “macrophage,” “rupture,” “mice,” “elastase,” “gene,” “protein,” “proliferation,” and “risk factors” might be a new trend for studying IA-related animal research.

Conclusions

Japan and the Unites States contributed the most to IA–related animal studies, in terms of both researchers and institutions. Although China ranks third in terms of the number of publications, it should strengthen the quality of its publications. Researchers should pay attention to the latest progress of Stroke, Journal of Neurosurgery, Neurosurgery, and Circulation for their high-quality IA-related animal studies. Using animal IA models, especially mice, to investigate the molecular mechanisms of IA may be the frontier topic now and in future.

Genome-wide Mendelian randomization and single-cell RNA sequencing analyses identify the causal effects of COVID-19 on 41 cytokines

The elevated levels of inflammatory cytokines have attracted much attention during the treatment of COVID-19 patients. The conclusions of current observational studies are often controversial in terms of the causal effects of COVID-19 on various cytokines because of the confounding factors involving underlying diseases. To resolve this problem, we conducted a Mendelian randomization analysis by integrating the GWAS data of COVID-19 and 41 cytokines. As a result, the levels of 2 cytokines were identified to be promoted by COVID-19 and had unsignificant pleiotropy. In comparison, the levels of 10 cytokines were found to be inhibited and had unsignificant pleiotropy. Among down-regulated cytokines, CCL2, CCL3 and CCL7 were members of CC chemokine family. We then explored the potential molecular mechanism for a significant causal association at a single cell resolution based on single-cell RNA data, and discovered the suppression of CCL3 and the inhibition of CCL3-CCR1 interaction in classical monocytes (CMs) of COVID-19 patients. Our findings may indicate that the capability of COVID-19 in decreasing the chemotaxis of lymphocytes by inhibiting the CCL3-CCR1 interaction in CMs.

Expression and prognostic value of MIP-1α in neonatal acute respiratory distress syndrome

OBJECTIVE

To investigate the expression and prognostic value of macrophage inflammatory protein 1α (MIP-1α) in neonatal acute respiratory distress syndrome (NRDS).

METHODS

In this retrospective analysis, 96 newborns with NRDS in Affiliated Lianyungang Hospital of Xuzhou Medical University from January 2018 to June 2021 were included in the experimental group (EG), while the other 60 normal neonates were included as the control group (CG). The concentration of MIP-1α in umbilical cord blood was tested by Elisa method. The clinical value of MIP-1α in diagnosing NRDS was assessed via receiver operating characteristic (ROC) curve. According to the 28-day survival data, children were divided into a survival group and a death group. The prognostic factors were assessed by Cox regression analysis. The correlation between MIP-1α and IL-1β, IL-6, TNF-α, SNAPPE-II scores were evaluated by Pearson test. The relationship between the MIP-1α level and the severity of the disease was assessed.

RESULTS

The MIF-1α level in cord blood of children in the EG was dramatically higher than that in the CG (P<0.05). Besides, ROC curve further found that the area of MIF-1α under the curve of diagnosing NRSD was 0.949. MIF-1α was positively correlated with the levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor α (TNF-α) and SNAPPE-II score (P<0.001). With the increase of NRDS, the serum MIF-1α level increased, showing a positive association (P<0.05). Cox regression analysis revealed that the severity and MIF-1α level were independent prognostic factors of survival (P<0.001). The survival rate of children with MIF-1α <281.58 pg/mL as well as children with I-II grade was higher than those with MIF-1α >281.58 pg/mL as well as children with III-IV grade (P<0.05).

CONCLUSION

The increase of serum MIP-1α level is relevant to the condition and prognosis of NRDS children. The level of cord blood MIP-1α level is expected to become a potential outcome measure.

Aortic Cellular Diversity and Quantitative Genome-Wide Association Study Trait Prioritization Through Single-Nuclear RNA Sequencing of the Aneurysmal Human Aorta

BACKGROUND

Mural cells in ascending aortic aneurysms undergo phenotypic changes that promote extracellular matrix destruction and structural weakening. To explore this biology, we analyzed the transcriptional features of thoracic aortic tissue.

METHODS

Single-nuclear RNA sequencing was performed on 13 samples from human donors, 6 with thoracic aortic aneurysm, and 7 without aneurysm. Individual transcriptomes were then clustered based on transcriptional profiles. Clusters were used for between-disease differential gene expression analyses, subcluster analysis, and analyzed for intersection with genetic aortic trait data.

RESULTS

We sequenced 71 689 nuclei from human thoracic aortas and identified 14 clusters, aligning with 11 cell types, predominantly vascular smooth muscle cells (VSMCs) consistent with aortic histology. With unbiased methodology, we found 7 vascular smooth muscle cell and 6 fibroblast subclusters. Differentially expressed genes analysis revealed a vascular smooth muscle cell group accounting for the majority of differential gene expression. Fibroblast populations in aneurysm exhibit distinct behavior with almost complete disappearance of quiescent fibroblasts. Differentially expressed genes were used to prioritize genes at aortic diameter and distensibility genome-wide association study loci highlighting the genes JUN, LTBP4 (latent transforming growth factor beta-binding protein 1), and IL34 (interleukin 34) in fibroblasts, ENTPD1, PDLIM5 (PDZ and LIM domain 5), ACTN4 (alpha-actinin-4), and GLRX in vascular smooth muscle cells, as well as LRP1 in macrophage populations.

CONCLUSIONS

Using nuclear RNA sequencing, we describe the cellular diversity of healthy and aneurysmal human ascending aorta. Sporadic aortic aneurysm is characterized by differential gene expression within known cellular classes rather than by the appearance of novel cellular forms. Single-nuclear RNA sequencing of aortic tissue can be used to prioritize genes at aortic trait loci.

Therapeutic mechanism of transcranial iTBS on nerve regeneration and functional recovery in rats with complete spinal cord transection.. [DOI: 10.21203/rs.3.rs-2026215/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background: After spinal cord transection injury, the inflammatory microenvironment formed in the injury site and the cascade of secondary injury results in limited regeneration of injured axons and the apoptosis of neurons in the sensorimotor cortex (SMC). It is crucial to reverse these adverse processes for the recovery of voluntary movement. In this study, transcranial intermittent theta-burst stimulation (iTBS) was used for the treatment of complete spinal cord transection in rats. The mechanism of transcranial iTBS as a new non-invasive neural regulation paradigm in promoting axonal regeneration and motor function repair was explored. Methods: Rats from the iTBS group were treated with transcranial iTBS 72h after spinal cord injury (SCI). Each rat was received behavioral testing. Inflammation, neuronal apoptosis, neuroprotective effect, regeneration and synaptic plasticity were measured by immunofluorescence staining, western blotting and mRNA sequencing 2 or 4w after SCI. Each rat was received anterograde tracings in the SMC or the long descending propriospinal neurons and tested for motor evoked potentials. Regeneration of corticospinal tract (CST) and 5-hydroxytryptamine (5-HT) nerve fibers were detected eight weeks after SCI. Results: Compared with the control group and the sham iTBS group, rats of the iTBS group showed reduced inflammatory responses and neuronal apoptosis in the SMC two weeks after treatment. After four weeks, the neuroimmune microenvironment at the injury site was improved, and neuroprotective effects were seen to promote axonal regeneration and synaptic plasticity. Significantly, eight weeks after treatment, transcranial iTBS also increased the regeneration of CST, 5-HT nerve fibers, and the long descending propriospinal tract (LDPT). Moreover, motor evoked potentials and hindlimb motor function were significantly improved at eight weeks. Conclusions: Collectively, our results verified that iTBS has the potential to provide neuroprotective effects at early injury stages and pro-regeneration effects related to the 1) CST–5-HT; 2) CST–LDPT; and 3) CST–5-HT–LDPT descending motor pathways and revealed the relationships among neural pathway activation, neuroimmune regulation, neuroprotection, and axonal regeneration, as well as the interaction network of key genes. The proposed non-invasive transcranial iTBS treatment is expected to provide a serviceable practical and theoretical support for spinal cord injury.

Engineering Neutrophil Immunomodulatory Hydrogels Promoted Angiogenesis

Timely restoration of blood supply following ischemia is critical to rescue damaged tissue. However, clinical efficacy is hampered by the inflammatory response after ischemia. Whether inflammation fine tunes the angiogenesis and the function of blood vessels via the heterogeneity of neutrophils remain poorly understood. Herein, the objective of this work is to incorporate the growth factors secreted by neutrophils into a porous gelatin methacrylate (GelMA) hydrogel, which subsequently is used as a novel regenerative scaffold with defined architecture for ischemia. We demonstrate that anti-inflammatory neutrophils (N₂-polarized neutrophils) play an important role in promoting the migration of human umbilical vein endothelial cells (HUVECs) and formation of capillary-like networks in vitro. More importantly, vascular anastomosis can be achieved by modulating the neutrophils to N₂ phenotype. In addition, N₂-polarized composite hydrogel scaffolds can regulate inflammation, maintain the survival of exogenous cells, and promote angiogenesis in vivo. Notably, the composite hydrogel scaffolds promote neovascularization during exogenous introduction of endothelial cells by anastomosis. Taken together, this study highlights N₂-polarized neutrophils composite hydrogels can achieve vascularization rapidly by regulating inflammation and promoting vascular anastomosis. This work lays the foundation for research into the treatment of ischemia and may inspire further research into novel treatment options.

Development of pharmacotherapies for abdominal aortic aneurysms

The cardiovascular field is still searching for a treatment for abdominal aortic aneurysms (AAA). This inflammatory disease often goes undiagnosed until a late stage and associated rupture has a high mortality rate. No pharmacological treatment options are available. Three hallmark factors of AAA pathology include inflammation, extracellular matrix remodeling, and vascular smooth muscle dysfunction. Here we discuss drugs for AAA treatment that have been studied in clinical trials by examining the drug targets and data present for each drug's ability to regulate the aforementioned three hallmark pathways in AAA progression. Historically, drugs that were examined in interventional clinical trials for treatment of AAA were repurposed therapeutics. Novel treatments (biologics, small-molecule compounds etc.) have not been able to reach the clinic, stalling out in pre-clinical studies. Here we discuss the backgrounds of previous investigational drugs in hopes of better informing future development of potential therapeutics. Overall, the highlighted themes discussed here stress the importance of both centralized anti-inflammatory drug targets and rigor of translatability. Exceedingly few murine studies have examined an intervention-based drug treatment in halting further growth of an established AAA despite interventional treatment being the therapeutic approach taken to treat AAA in a clinical setting. Additionally, data suggest that a potentially successful drug target may be a central inflammatory biomarker. Specifically, one that can effectively modulate all three hallmark factors of AAA formation, not just inflammation. It is suggested that inhibiting PGE₂ formation with an mPGES-1 inhibitor is a leading drug target for AAA treatment to this end.

MIP-1α Level and Its Correlation with the Risk of Left Atrial Remodeling in Patients with Atrial Fibrillation

The aim of this study is to investigate the expression level of macrophage inflammatory protein-1α (MIP-1α) in atrial fibrillation patients and its correlation with the risk of left atrial remodeling. A total of 64 atrial fibrillation patients admitted to our hospital from April 2020 to December 2021 were prospectively selected as the case group and 61 healthy subjects who received physical examination during the same period were selected as the control group. Serum MIP-1α level was determined by a double-antibody sandwich enzyme-linked immunosorbent assay. Serum MIP-1α expression levels were compared between the case and the control groups. The case group was divided into high-level and low-level groups according to the serum MIP-1α median. Simultaneously, the sociodemographic data, clinical data, and left atrial remodeling indexes of the patients were collected in the case group. The Pearson correlation analysis was applied to analyze the correlation between the serum MIP-1α level and the risk of left atrial remodeling in patients with atrial fibrillation. The serum MIP-1α level was significantly higher in the case group than that in the control group (P < 0.05), high-level group (≥2.14 pg/mL, 32 cases), and low-level group (<2.14 pg/mL, 32 cases). There were significant differences in the anteroposterior diameter, upper and lower diameter, left and right diameter of the left atrium, left atrial volume, volume index, left atrial global ejection fraction, and sphericity between the low-level and high-level groups (P < 0.05). The Pearson correlation analysis showed that serum MIP-1α level was positively correlated with the left atrial anteroposterior diameter (r = 0.745), left atrial left and right diameter (r = 0.759), left atrial upper and lower diameter (r = 0.810), left atrial volume (r = 0.837), left atrial volume index (r = 0.813), and left atrial sphericity (r = 0.785) but negatively correlated with the left atrial global ejection fraction (r = -0.731) (P < 0.05). The expression level of serum MIP-1α is high in atrial fibrillation patients and is associated with the risk of left atrial remodeling.

Novel Therapeutic Targeting of CCL3-CCR4 Axis Mediated Apoptotic Intesitnal Injury in Necrotizing Enterocolitis

Background

Necrotizing enterocolitis (NEC) is the leading cause of neonatal gastrointestinal-related death, while the etiology and pathogenesis are poorly understood.

Methods

The levels of CCL3 in intestinal tissue from modeling mice and patients were measured and analyzed. HE staining, TUNEL, Annexin and FCM were used to assess pathological changes and apoptosis in intestinal tissue and epithelial cells. CCL3, CCR4, cytokines, tight junction protein ZO-1, apoptosis-related genes and ERK1/2-NF-κB signaling pathway were detected by ELISA, Q-PCR, Western blotting and immunofluorescence.

Results

CCL3 levels in the intestinal tissue significantly elevated in patients with NEC and mouse models. Blockade of CCL3 significantly alleviated NEC-related intestinal tissue damage, while administration of recombinant CCL3 aggravated intestinal injury by exacerbating intestinal epithelial cell apoptosis in NEC mice. Importantly, CCR4 blockade reversed CCL3-mediated damage to intestinal tissue and intestinal epithelial cell apoptosis both in vivo and in vitro. Further mechanistic studies showed that CCL3 regulated apoptosis-related BAX/BCL-2 expression through the activation of the ERK1/2 and NF-κB pathways, which could be reversed by anti-CCR4 treatment. Furthermore, ERK1/2 inhibition reduced CCL3-mediated phosphorylation of NF-κB in IEC-6 cells, while inhibition of NF-κB had no obvious effect on ERK1/2 phosphorylation. As expected, inhibition of NF-κB regulated BAX/BCL-2 expression and alleviated CCL3-induced epithelial cell apoptosis. These results indicate that high expression of CCL3 in NEC lesions promotes intestinal epithelial apoptosis through the CCL3-CCR4-ERK1/2-NFκB-BAX/BCL2 signalling axis, thereby exacerbating NEC-related intestinal injury.

Conclusions

Our study represents an important conceptual advance that CCL3 may be one of the key culprits of intestinal tissue damage in NEC patients, and blocking either CCL3, CCR4, or NF-κB may represent a novel effective immunotherapy for NEC.

Comprehensive analysis identified a reduction in ATP1A2 mediated by ARID3A in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is characterized by abdominal aorta dilatation and progressive structural impairment and is usually an asymptomatic and potentially lethal disease with a risk of rupture. To investigate the underlying mechanisms of AAA initiation and progression, seven AAA datasets related to human and mice were downloaded from the GEO database and reanalysed in the present study. After comprehensive bioinformatics analysis, we identified the enriched pathways associated with inflammation responses, vascular smooth muscle cell (VSMC) phenotype switching and cytokine secretion in AAA. Most importantly, we identified ATPase Na⁺/K⁺ transporting subunit alpha 2 (ATP1A2) as a key gene that was significantly decreased in AAA samples of both human and mice; meanwhile, its reduction mainly occurred in VSMCs of the aorta; this finding was validated by immunostaining and Western blot in human and mouse AAA samples. Furthermore, we explored the potential upstream transcription factors (TFs) that regulate ATP1A2 expression. We found that the TF AT‐rich interaction domain 3A (ARID3A) bound the promoter of ATP1A2 to suppress its expression. Our present study identified the ARID3A‐ATP1A2 axis as a novel pathway in the pathological processes of AAA, further elucidating the molecular mechanism of AAA and providing potential therapeutic targets for AAA.

Integrating Bulk Transcriptome and Single-Cell RNA Sequencing Data Reveals the Landscape of the Immune Microenvironment in Thoracic Aortic Aneurysms

Thoracic aortic aneurysm (TAA) is a life-threatening cardiovascular disease whose formation is reported to be associated with massive vascular inflammatory responses. To elucidate the roles of immune cell infiltration in the pathogenesis underlying TAA, we utilized multiple TAA datasets (microarray data and scRNA-seq data) and various immune-related algorithms (ssGSEA, CIBERSORT, and Seurat) to reveal the landscapes of the immune microenvironment in TAA. The results exhibited a significant increase in the infiltration of macrophages and T cells, which were mainly responsible for TAA formation among the immune cells. To further reveal the roles of immunocytes in TAA, we inferred the intercellular communications among the identified cells of aortic tissues. Notably, we found that in both normal aortic tissue and TAA tissue, the cells that interact most frequently are macrophages, endothelial cells (ECs), fibroblasts, and vascular smooth muscle cells (VSMCs). Among the cells, macrophages were the most prominent signal senders and receivers in TAA and normal aortic tissue. These findings suggest that macrophages play an important role in both the physiological and pathological conditions of the aorta. The present study provides a comprehensive evaluation of the immune cell composition and reveals the intercellular communication among aortic cells in human TAA tissues. These findings improve our understanding of TAA formation and progression and facilitate the development of effective medications to treat these conditions.

Trimethylamine N-Oxide Promotes Abdominal Aortic Aneurysm Formation by Aggravating Aortic Smooth Muscle Cell Senescence in Mice

Trimethylamine N-oxide (TMAO) has been linked to cardiovascular disease morbidity and mortality. However, the role of TMAO in the development of abdominal aortic aneurysms (AAAs) is not known. This study investigated the association between TMAO and AAA formation. TMAO and saline were added to the drinking water of angiotensin II (AngII)- and calcium chloride (CaCl₂)-induced AAA model mice, respectively. After 4 weeks, the effects of TMAO on AAA development were determined by histology and immunohistology of aortic tissue. The in vitro effects of TMAO were also examined in mouse aortic smooth muscle cells (SMCs). The maximal aortic diameter, incidence of AAA, and degree of elastin degradation were significantly increased in TMAO-treated mice. TMAO also increased the accumulation of the senescence markers p21 and p16, as well as of reactive oxygen species (ROS), matrix metalloproteinase-2 (MMP2), and matrix metalloproteinase-9 (MMP9) in vivo and in vitro. TMAO promoted AAA development in mouse AAA models induced by AngII and CaCl₂ by a mechanism involving cellular senescence.

Potential Role of the Chemotaxis System in Formation and Progression of Intracranial Aneurysms Through Weighted Gene Co-Expression Network Analysis

Background

Intracranial aneurysm (IA) is the most common and is the main cause of spontaneous subarachnoid hemorrhage (SAH). The underlying molecular mechanisms for preventing IA progression have not been fully identified. Our research aimed to identify the key genes and critical pathways of IA through gene co-expression networks.

Methods

Gene Expression Omnibus (GEO) datasets GSE13353, GSE54083 and GSE75436 were used in the study. The genetic data were analyzed by weighted gene co-expression network analysis (WGCNA). Then the clinically significant modules were identified and the differentially expressed genes (DEGs) with the genes were intersected in these modules. GO (gene ontology) and KEGG (Kyoto Gene and Genomic Encyclopedia) were used for gene enrichment analysis to determine the function or pathway. In addition, the composition of immune cells was analyzed by CIBERSORT algorithm. Finally, the hub genes and key genes were identified by GSE122897.

Results

A total of 266 DEGs and two modules with clinical significance were identified. The inflammatory response and immune response were identified by GO and KEGG. CCR5, CCL4, CCL20, and FPR3 were the key genes in the module correlated with IA. The proportions of infiltrating immune cells in IA and normal tissues were different, especially in terms of macrophages and mast cells.

Conclusion

The chemotactic system has been identified as a key pathway of IA, and interacting macrophages may regulate this pathological process.

Discovery of potent and specific inhibitors targeting the active site of MMP-9 from the engineered SPINK2 library

Matrix metalloproteinases (MMPs) contribute to many physiological and pathological phenomena via the proteolysis of extracellular matrix components. Specific blocking of the active site of each MMP sheds light on its particular role. However, it remains difficult to acquire an active-site inhibitor with high specificity for only the target MMP due to the highly conserved structure around the active site of MMPs. Recently, we reported that potent and specific inhibitors of serine proteases were obtained from our proprietary engineered serine protease inhibitor Kazal type 2 (SPINK2) library. In this research, using this library, we succeeded in obtaining potent and specific MMP-9 inhibitors. The obtained inhibitors bound to the active site of MMP-9 and inhibited MMP-9 with low nanomolar Ki values. The inhibitors did not cross-react with other MMPs that we tested. Further analysis using MMP-9 mutants demonstrated that the inhibitors recognize not only the residues around the conserved active site of MMP-9 but also different and unique residues in exosites that are distant from each other. This unique recognition manner, which can be achieved by the large interface provided by engineered SPINK2, may contribute to the generation of specific active-site inhibitors of MMPs.