Reduced Plasma Kallistatin Is Associated With the Severity of Coronary Artery Disease, and Kallistatin Treatment Attenuates Atherosclerotic Plaque Formation in Mice

Probing the familial ties between serpin members Kallistatin and PEDF: A comparative analysis review

The serine protease inhibitors (Serpins) represent a diverse protein superfamily that holds paramount significance in governing vital pathophysiological processes. Their influence on critical biological pathways renders serpins highly coveted targets for drug discovery endeavors. Among the numerous members of this family, two distinct proteins, Kallistatin (encoded by the SERPINA4 gene) and Pigment Epithelium-Derived Factor (PEDF, encoded by the SERPINF1 gene), stand out as secreted proteins that are abundantly present in peripheral blood. Kallistatin is a serine protease inhibitor that specifically inhibits human tissue kallikrein, while PEDF is a non-inhibitory member of the serine protease inhibitors superfamily (Lin et al., 2015a; Chao and Chao, 1995 [1,2]). Instead, they exhibit notable anti-angiogenic effects and play pivotal roles in the pathogenesis of metabolic disorders. Extensive research, including our own investigations, has revealed intriguing similarities as well as noteworthy differences between these two proteins. Despite their shared characteristics, the distinctive features of Kallistatin and PEDF render them unique in their respective functions and mechanisms of action. However, a comprehensive literature review comparing their similarities and differences remains elusive. Therefore, the present review aims to systematically delve into and summarize the comparable and contrasting aspects of Kallistatin and PEDF. We will delve into their expression patterns, structural features, and mechanisms of expression regulation. Furthermore, this review will delve into their physiological functions and roles in diseases, the signaling pathways they influence, and their potential clinical applications. By comparing and contrasting these two proteins, we hope to provide a comprehensive understanding of their functions and potential in biomedical research and clinical practice.

Unveiling MiRNA-124 as a biomarker in hypertrophic cardiomyopathy: An innovative approach using machine learning and intelligent data analysis

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a widespread hereditary cardiac pathology characterized by thickened heart walls and rearrangement of cardiomyocytes. Despite extensive research, the mechanisms underlying HCM development remain poorly understood, impeding the development of effective therapeutic and diagnostic strategies. Recent studies have suggested a polygenic nature of HCM development alongside monogenic forms. Transcriptomic profiling is a valuable tool for investigating such diseases. In this study, we propose a novel approach to study regulatory microRNAs (miRNAs) in the context of HCM, utilizing state-of-the-art data analysis tools.

METHODS AND RESULTS

Our method involves applying the Monte Carlo simulation and machine learning algorithm to transcriptomic data to generate high-capacity classifiers for HCM. From these classifiers, we extract key genes crucial for their performance, resulting in the identification of 16 key genes. Subsequently, we narrow down the pool of miRNAs by selecting those that may target the greatest number of key genes within the best models. We particularly focused on miR-124-3p, which we validated to have an association with HCM on an independent dataset. Subsequent investigation of its function revealed involvement of miR-124-3p in the RhoA signaling pathway.

CONCLUSIONS

In this study we propose a new approach to analyze transcriptomic data to search for microRNAs associated with a disease. Using this approach for transcriptomic profiling data of patients with HCM, we identified miR-124-3p as a potential regulator of the RhoA signaling pathway in the pathogenesis of HCM.

Aptamer Proteomics for Biomarker Discovery in Heart Failure With Preserved Ejection Fraction: The PARAGON-HF Proteomic Substudy

BACKGROUND

Prognostic markers and biological pathways linked to detrimental clinical outcomes in heart failure with preserved ejection fraction (HFpEF) remain incompletely defined.

METHODS AND RESULTS

We measured serum levels of 4123 unique proteins in 1117 patients with HFpEF enrolled in the PARAGON-HF (Efficacy and Safety of LCZ696 Compared to Valsartan, on Morbidity and Mortality in Heart Failure Patients With Preserved Ejection Fraction) trial using a modified aptamer proteomic assay. Baseline circulating protein concentrations significantly associated with the primary end point and the timing and occurrence of total heart failure hospitalization and cardiovascular death were identified by recurrent events regression, accounting for multiple testing, adjusted for age, sex, treatment, and anticoagulant use, and compared with published analyses in 2515 patients with heart failure with reduced ejection fraction from the PARADIGM-HF (Prospective Comparison of ARNI With ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure) and ATMOSPHERE (Efficacy and Safety of Aliskiren and Aliskiren/Enalapril Combination on Morbidity-Mortality in Patients With Chronic Heart Failure) clinical trials. We identified 288 proteins that were robustly associated with the risk of heart failure hospitalization and cardiovascular death in patients with HFpEF. The baseline proteins most strongly related to outcomes included B2M (β-2 microglobulin), TIMP1 (tissue inhibitor of matrix metalloproteinase 1), SERPINA4 (serpin family A member 4), and SVEP1 (sushi, von Willebrand factor type A, EGF, and pentraxin domain containing 1). Overall, the protein-outcome associations in patients with HFpEF did not markedly differ as compared with patients with heart failure with reduced ejection fraction. A proteomic risk score derived in patients with HFpEF was not superior to a previous proteomic score derived in heart failure with reduced ejection fraction nor to clinical risk factors, NT-proBNP (N-terminal pro-B-type natriuretic peptide), or high-sensitivity cardiac troponin.

CONCLUSIONS

Numerous serum proteins linked to metabolic, coagulation, and extracellular matrix regulatory pathways were associated with worse HFpEF prognosis in the PARAGON-HF proteomic substudy. Our results demonstrate substantial similarities among serum proteomic risk markers for heart failure hospitalization and cardiovascular death when comparing clinical trial participants with heart failure across the ejection fraction spectrum.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique Identifiers: NCT01920711, NCT01035255, NCT00853658.

Kallistatin deficiency exacerbates neuronal damage after cardiac arrest

The purpose of study was to evaluate that kallistatin deficiency causes excessive production of reactive oxygen species and exacerbates neuronal injury after cardiac arrest. For in vitro study, kallistatin knockdown human neuronal cells were given ischemia-reperfusion injury, and the oxidative stress and apoptosis were evaluated. For clinical study, cardiac arrest survivors admitted to the ICU were divided into the good (CPC 1-2) and poor (CPC 3-5) 6-month neurological outcome groups. The serum level of kallistatin, Nox-1, H2O2 were measured. Nox-1 and H2O2 levels were increased in the kallistatin knockdown human neuronal cells with ischemia-reperfusion injury (p < 0.001) and caspase-3 was elevated and apoptosis was promoted (SERPINA4 siRNA: p < 0.01). Among a total of 62 cardiac arrest survivors (16 good, 46 poor), serum kallistatin were lower, and Nox-1 were higher in the poor neurological group at all time points after admission to the ICU (p = 0.013 at admission; p = 0.020 at 24 h; p = 0.011 at 72 h). At 72 h, H2O2 were higher in the poor neurological group (p = 0.038). Kallistatin deficiency exacerbates neuronal ischemia-reperfusion injury and low serum kallistatin levels were associated with poor neurological outcomes in cardiac arrest survivors.

Visceral adipose tissue-directed human kallistatin gene therapy improves adipose tissue remodeling and metabolic health in obese mice

OBJECTIVE

Adipose tissue remodeling is a dynamic process that is pathologically expedited in the obese state and is closely related to obesity-associated disease progression. This study aimed to explore the effects of human kallistatin (HKS) on adipose tissue remodeling and obesity-related metabolic disorders in mice fed with a high-fat diet (HFD).

METHODS

Adenovirus-mediated HKS cDNA (Ad.HKS) and a blank adenovirus (Ad.Null) were constructed and injected into the epididymal white adipose tissue (eWAT) of 8-weeks-old male C57B/L mice. The mice were fed normal or HFD for 28 days. The body weight and circulating lipids levels were assessed. Intraperitoneal glucose tolerance test (IGTT) and insulin tolerance test (ITT) were also performed. Oil-red O staining was used to assess the extent of lipid deposition in the liver. Immunohistochemistry and HE staining were used to measure HKS expression, adipose tissue morphology, and macrophage infiltration. Western blot and qRT-PCR were used to evaluate the expression of adipose function-related factors.

RESULTS

At the end of the experiment, the expression of HKS in the serum and eWAT of the Ad.HKS group was higher than in the Ad.Null group. Furthermore, Ad.HKS mice had lower body weight and decreased serum and liver lipid levels after four weeks of HFD feeding. IGTT and ITT showed that HKS treatment maintained balanced glucose homeostasis. Additionally, inguinal white adipose tissue (iWAT) and eWAT in Ad.HKS mice had a higher number of smaller-size adipocytes and had less macrophage infiltration than Ad.Null group. HKS significantly increased the mRNA levels of adiponectin, vaspin, and eNOS. In contrast, HKS decreased RBP4 and TNFα levels in the adipose tissues. Western blot results showed that local injection of HKS significantly upregulated the protein expressions of SIRT1, p-AMPK, IRS1, p-AKT, and GLUT4 in eWAT.

CONCLUSIONS

HKS injection in eWAT improves HFD-induced adipose tissue remodeling and function, thus significantly improving weight gain and dysregulation of glucose and lipid homeostasis in mice.

Kallistatin/Serpina3c inhibits cardiac fibrosis after myocardial infarction by regulating glycolysis via Nr4a1 activation

BACKGROUND

Fibrotic remodeling is an essential aspect of heart failure. Human kallistatin (KS, mouse Serpina3c homologs) inhibits fibrosis after myocardial infarction (MI) but the specific underlying mechanism is unknown.

METHODS

A total of 40 heart failure patients (HFPs) were enrolled and their plasma KS was measured using ELISA. Serpina3c^-/- and C57BL/6 mice were used to construct the MI model. TGF-β1 or a hypoxic condition was established to interfere with the functioning of cardiac fibroblasts (CFs). RNA-seq was performed to assess the effect of Serpina3c on the transcriptome.

FINDINGS

The levels of KS were used as a predictor of readmission among the HFPs. Serpina3c expression decreased in MI hearts and CFs. Serpina3c^-/- led to the aggravation of MI fibrosis, and increased the proliferation of CFs. The overexpression of Serpina3c in CFs had the opposite effect. Glycolysis-related genes were significantly increased in Serpina3c^-/- group by RNA-seq. Enolase (ENO1), which is a key enzyme in glycolysis, increased most significantly. Inhibition of ENO1 could antagonize the promotion of Serpina3c^-/- on the proliferation of CFs. Co-IP was performed to verify the interaction between Serpina3c and Nr4a1. Serpina3c^-/- inhibited the acetylation of Nr4a1 and increased the degradation of Nr4a1. Activation of Nr4a1 could negatively regulate the expression of ENO1 and inhibited the proliferation of Serpina3c^-/- CFs in Serpina3c^-/- MI mice.

INTERPRETATION

Serpina3c inhibits the transcriptional activation of ENO1 by regulating the acetylation of Nr4a1, thereby reducing the fibrosis after MI by inhibiting glycolysis. Serpina3c is a potential target for prevention and treatment of heart failure after MI.

The Association and Pathogenesis of SERPINA3 in Coronary Artery Disease

Background: Serine proteinase inhibitor A3 (SERPINA3) has been discovered in the pathogenesis of many human diseases, but little is known about the role of SERPINA3 in coronary artery disease (CAD). Therefore, we aim to determine its relationship with CAD and its function in the pathogenesis of atherosclerosis.

Methods: In total 86 patients with CAD and 64 patients with non-CAD were compared. The plasma SERPINA3 levels were measured using ELISA. Logistic regression analysis and receiver-operating characteristic (ROC) analysis were performed to illustrate the association between plasma SERPINA3 levels and CAD. In vitro, real-time PCR (RT-PCR) and immunofluorescence staining were used to determine the expression of SERPINA3 in atherosclerotic plaques and their component cells. Then rat aortic smooth muscle cells (RASMCs) were transfected with siRNA to knock down the expression of SERPINA3 and human umbilical vein endothelial cells (HUVECs) were stimulated by SERPINA3 protein. EdU assay and scratch assay were used for assessing the capability of proliferation and migration. The cell signaling pathway was evaluated by western blot and RT-PCR.

Results: Patients with CAD [104.4(54.5–259.2) μg/mL] had higher levels of plasma SERPINA3 than non-CAD [65.3(47.5–137.3) μg/mL] (P = 0.004). After being fully adjusted, both log-transformed and tertiles of plasma SERPINA3 levels were significantly associated with CAD. While its diagnostic value was relatively low since the area under the ROC curve was 0.64 (95% CI: 0.55–0.73). Secreted SERPINA3 might increase the expression of inflammatory factors in HUVECs. Vascular smooth muscle cells had the highest SERPINA3 expression among the aorta compared to endothelial cells and inflammatory cells. The knockdown of SERPINA3 in RASMCs attenuated its proliferation and migration. The phosphorylated IκBα and its downstream pathway were inhibited when SERPINA3 was knocked down.

Conclusions: Elevated plasma SERPINA3 levels were associated with CAD. SERPINA3 can increase inflammatory factors expression in HUVECs. It can regulate VSMCs proliferation, migration, and releasing of inflammatory factors through the NF-κB signaling pathway. Thus, SERPINA3 played a significant role in the pathogenesis of atherosclerosis.

Relationship between Serum Kallistatin and Afamin and Anthropometric Factors Associated with Obesity and of Being Overweight in Patients after Myocardial Infarction and without Myocardial Infarction

Extensive clinical and epidemiological evidence has linked obesity to a broad spectrum of cardiovascular disease (CVD), including coronary disease, heart failure, hypertension, cerebrovascular disease, atrial fibrillation, ventricular arrhythmias, and sudden death. In addition, increasing knowledge of regulatory peptides has allowed an assessment of their role in various non-communicable diseases, including CVD. The study assessed the concentration of kallistatin and afamin in the blood serum of patients after a myocardial infarction and without a cardiovascular event, and determined the relationship between the concentration of kallistatin and afamin and the anthropometric indicators of being overweight and of obesity in these groups. Serum kallistatin and afamin were quantified by ELISA tests in a cross-sectional study of 160 patients who were divided into two groups: study group (SG) (n = 80) and another with no cardiovascular event (CG) (n = 80). Serum kallistatin concentration was significantly higher in the SG (p < 0.001), while the level of afamin was significantly lower in this group (p < 0.001). In addition, a positive correlation was observed in the SG between the afamin concentration and the waist to hip ratio (WHR), lipid accumulation product (LAP) and the triglyceride glucose index (TyG index). In the CG, the concentration of kallistatin positively correlated with the LAP and TyG index, while the concentration of afamin positively correlated with all the examined parameters: body mass index (BMI), waist circumference (WC), hip circumference (HC), waist to hip ratio (WHtR), visceral adiposity index (VAI), LAP and TyG index. Serum kallistatin and afamin concentrations are associated with the anthropometric parameters related to being overweight and to obesity, especially to those describing the visceral distribution of adipose tissue and metabolic disorders related to excessive fatness.

Kallistatin limits abdominal aortic aneurysm by attenuating generation of reactive oxygen species and apoptosis

Inflammation, vascular smooth muscle cell apoptosis and oxidative stress are believed to play important roles in abdominal aortic aneurysm (AAA) pathogenesis. Human kallistatin (KAL; gene SERPINA4) is a serine proteinase inhibitor previously shown to inhibit inflammation, apoptosis and oxidative stress. The aim of this study was to investigate the role of KAL in AAA through studies in experimental mouse models and patients. Serum KAL concentration was negatively associated with the diagnosis and growth of human AAA. Transgenic overexpression of the human KAL gene (KS-Tg) or administration of recombinant human KAL (rhKAL) inhibited AAA in the calcium phosphate (CaPO₄) and subcutaneous angiotensin II (AngII) infusion mouse models. Upregulation of KAL in both models resulted in reduction in the severity of aortic elastin degradation, reduced markers of oxidative stress and less vascular smooth muscle apoptosis within the aorta. Administration of rhKAL to vascular smooth muscle cells incubated in the presence of AngII or in human AAA thrombus-conditioned media reduced apoptosis and downregulated markers of oxidative stress. These effects of KAL were associated with upregulation of Sirtuin 1 activity within the aortas of both KS-Tg mice and rodents receiving rhKAL. These results suggest KAL-Sirtuin 1 signalling limits aortic wall remodelling and aneurysm development through reductions in oxidative stress and vascular smooth muscle cell apoptosis. Upregulating KAL may be a novel therapeutic strategy for AAA.

Protective role of serpina3c as a novel thrombin inhibitor against atherosclerosis in mice

Abnormal vascular smooth muscle cell (VSMC) proliferation is a critical step in the development of atherosclerosis. Serpina3c is a serine protease inhibitor (serpin) that plays a key role in metabolic diseases. The present study aimed to investigate the role of serpina3c in atherosclerosis and regulation of VSMC proliferation and possible mechanisms. Serpina3c is down-regulated during high-fat diet (HFD)-induced atherosclerosis. An Apoe-/-/serpina3c-/--double-knockout mouse model was used to determine the role of serpina3c in atherosclerosis after HFD for 12 weeks. Compared with Apoe-/- mice, the Apoe-/-/serpina3c-/- mice developed more severe atherosclerosis, and the number of VSMCs and macrophages in aortic plaques was significantly increased. The present study revealed serpina3c as a novel thrombin inhibitor that suppressed thrombin activity. In circulating plasma, thrombin activity was high in the Apoe-/-/serpina3c-/- mice, compared with Apoe-/- mice. Immunofluorescence staining showed thrombin and serpina3c colocalization in the liver and aortic cusp. In addition, inhibition of thrombin by dabigatran in serpina3c-/- mice reduced neointima lesion formation due to partial carotid artery ligation. Moreover, an in vitro study confirmed that thrombin activity was also decreased by serpina3c protein, supernatant and cell lysate that overexpressed serpina3c. The results of experiments showed that serpina3c negatively regulated VSMC proliferation in culture. The possible mechanism may involve serpina3c inhibition of ERK1/2 and JNK signaling in thrombin/PAR-1 system-mediated VSMC proliferation. Our results highlight a protective role for serpina3c as a novel thrombin inhibitor in the development of atherosclerosis, with serpina3c conferring protection through the thrombin/PAR-1 system to negatively regulate VSMC proliferation through ERK1/2 and JNK signaling.

Clinical Significance of Serum Kallistatin and ENOX1 Levels in Patients with Coronary Heart Disease

BACKGROUND

Kallistatin and ENOX1 are regulators of inflammation and oxidative stress which are typical pathological reactions in atherosclerosis. However, there is limited information of kallistatin and ENOX1 in coronary heart disease (CHD).

METHODS

Fifty healthy controls, 56 stable angina pectoris (SAP) patients, and 47 acute coronary syndrome (ACS) patients were included in this study. Levels of kallistatin and ENOX1 in serum were measured by ELISA. χ2 test was performed to analyze categorical data. ANOVA, Pearson correlation analysis, and multiple linear regression were performed to analyze the numerical data. Finally, receiver operating characteristic (ROC) curve was applied to assess the diagnostic value of kallistatin in CHD.

RESULTS

Among the 153 participants, 59.5% were male and the average age was 63.8 ± 11.39 years. Compared with the control group, kallistatin expression was decreased in the SAP and ACS groups while expression of ENOX1 was increased in the ACS group (p < 0.05). Pearson correlation analysis showed that the kallistatin level was negatively correlated with the Gensini score (r = -0.210, p < 0.01), white blood cell (WBC) count (r = -0.283, p < 0.001), and triglyceride levels (r = -0.242, p < 0.01) and positively correlated with age (r = 0.353, p < 0.001) and high-density lipoprotein cholesterol (r = 0.310, p < 0.001). ENOX1 expression was positively correlated with WBC count (r = 0.244, p < 0.01), international normalized ratio (r = 0.177, p < 0.05), and Gensini score (r = 0.201, p < 0.05). Multiple linear regression showed that Cr, alanine transaminase, glucose, and kallistatin are independent predictors for Gensini score. The ROC curve showed that kallistatin had the highest diagnostic significance (p = 0.007) when the area under curve was 0.636, with a sensitivity of 0.735 and a specificity of 0.495.

CONCLUSION

Expression of kallistatin was decreased in CHD patients and that of ENOX1 was increased in ACS patients. Kallistatin and ENOX1 were closely connected with the severity of CHD, and kallistatin may be helpful in the diagnosis of CHD.

Serpina3c protects against high-fat diet-induced pancreatic dysfunction through the JNK-related pathway

BACKGROUND

Serpina3 is a member of the serine protease inhibitor family and is involved in the inflammatory response. In this study, we investigated the effect of Serpina3c on pancreatic function in hypercholesterolemic mice.

METHODS

To investigate the role of Serpina3c in hyperlipidaemia, Serpina3c knockout mice were bred with Apoe-knockout mice (on a C57BL/6 background) to generate heterozygous Serpina3c-Apoe double knockout (Serpina3c^+/-/Apoe^+/-) mice and were then bred to obtain homozygotes. C57BL/6, Serpina3c^-/-, Apoe^-/-, and Apoe^-/-Serpina3c^-/- mice were fed normal chow, and Apoe^-/- and Apoe^-/-Serpina3c^-/- mice were fed a high-fat diet (HFD). After feeding for 3 months, the mice were monitored for body weight, blood glucose, glucose tolerance, and insulin tolerance test (ITT). ELISA and immunohistochemistry were used to detect insulin levels and glucagon expression. Immunohistochemical staining for macrophages in the pancreas was also performed. Western blot analysis was performed on pancreatic tissues to detect the protein levels of insulin-associated molecules, the metalloproteinase MMP2, the tissue inhibitor TIMP2 and components of the JNK-related pathway.

RESULTS

Blood glucose levels, glucose tolerance, and ITT were not significantly different among the groups. Serpina3c knockout resulted in blood lipid abnormalities in mice under HFD conditions. Insulin secretion was decreased in Apoe^-/-Serpina3c^-/- mice compared with Apoe^-/- mice under normal chow conditions. In addition, Apoe^-/-Serpina3c^-/- mice exhibited increased insulin and glucagon secretion and expression after three months of HFD feeding, but insulin secretion was decreased in Apoe^-/-Serpina3c^-/- mice compared with Apoe^-/- mice after the fifth month of HFD feeding. Serpina3c knockout increased MMP2 protein levels, whereas TIMP2 levels in the pancreas were decreased. Furthermore, Serpina3c knockout significantly upregulated the number of macrophages in the pancreas under HFD conditions. The JNK/AKT/FOXO1/PDX-1 axis was found to be involved in Serpina3c-regulated insulin secretion.

CONCLUSION

These novel findings show that Serpina3c could play a protective role in insulin secretion partly through the JNK-related pathway under HFD conditions.

The antiatherogenic function of kallistatin and its potential mechanism

Atherosclerosis is the pathological basis of most cardiovascular diseases, the leading cause of morbidity and mortality worldwide. Kallistatin, originally discovered in human serum, is a tissue-kallikrein-binding protein and a unique serine proteinase inhibitor. Upon binding to its receptor integrin β3, lipoprotein receptor-related protein 6, nucleolin, or Krüppel-like factor 4, kallistatin can modulate various signaling pathways and affect multiple biological processes, including angiogenesis, inflammatory response, oxidative stress, and tumor growth. Circulating kallistatin levels are significantly decreased in patients with coronary artery disease and show an inverse correlation with its severity. Importantly, both in vitro and in vivo experiments have demonstrated that kallistatin reduces atherosclerosis by inhibiting vascular inflammation, antagonizing endothelial dysfunction, and improving lipid metabolism. Thus, kallistatin may be a novel biomarker and a promising therapeutic target for atherosclerosis-related diseases. In this review, we focus on the antiatherogenic function of kallistatin and its potential mechanism.

Gene therapy for cardiovascular diseases in China: basic research

Cardiovascular disease has become a major disease affecting health in the whole world. Gene therapy, delivering foreign normal genes into target cells to repair damages caused by defects and abnormal genes, shows broad prospects in treating different kinds of cardiovascular diseases. China has achieved great progress of basic gene therapy researches and pathogenesis of cardiovascular diseases in recent years. This review will summarize the latest research about gene therapy of proteins, epigenetics, including noncoding RNAs and genome-editing technology in myocardial infarction, cardiac ischemia-reperfusion injury, atherosclerosis, muscle atrophy, and so on in China. We wish to highlight some important findings about the essential roles of basic gene therapy in this field, which might be helpful for searching potential therapeutic targets for cardiovascular disease.

Reduced Plasma Kallistatin Is Associated With the Severity of Coronary Artery Disease, and Kallistatin Treatment Attenuates Atherosclerotic Plaque Formation in Mice

Background Kallistatin exerts beneficial effects on organ injury by inhibiting oxidative stress and inflammation. However, the role of kallistatin in atherosclerosis is largely unknown. Here, we investigated the role and mechanisms of kallistatin in patients with coronary artery disease ( CAD ), atherosclerotic plaques of apoE-/- mice, and endothelial activation. Methods and Results Plasma kallistatin levels were analyzed in 453 patients at different stages of CAD . Kallistatin levels were significantly lower in patients with CAD and negatively associated with CAD severity and oxidative stress. Human kallistatin cDNA in an adenoviral vector was injected intravenously into apoE-/- mice after partial carotid ligation, with or without nitric oxide synthase inhibitor (Nω-nitro-L-arginine methyl ester) or sirtuin 1 inhibitor (nicotinamide). Kallistatin gene delivery significantly reduced macrophage deposition, oxidative stress, and plaque volume in the carotid artery, compared with control adenoviral injection. Kallistatin administration increased endothelial nitrous oxide synthase, sirtuin 1, interleukin-10, superoxide dismutase 2, and catalase expression in carotid plaques. The beneficial effects of kallistatin in mice were mitigated by Nω-nitro-L-arginine methyl ester or nicotinamide. Furthermore, human kallistatin protein suppressed tumor necrosis factor-α-induced NADPH oxidase activity and increased endothelial nitrous oxide synthase and sirtuin 1 expression in cultured human endothelial cells. These effects were also abolished by Nω-nitro-L-arginine methyl ester or nicotinamide. Conclusions This was the first study to demonstrate that reduced plasma kallistatin levels in patients are associated with CAD severity and oxidative stress. Kallistatin treatment prevents carotid atherosclerotic plaque formation in mice by stimulating the sirtuin 1/endothelial nitrous oxide synthase pathway. These findings indicate the potential protective effects of kallistatin on atherosclerosis in human subjects and mouse models.