Novel Role of Kallistatin in Protection Against Myocardial Ischemia–Reperfusion Injury by Preventing Apoptosis and Inflammation

Associations between Serum Kallistatin Levels and Markers of Glucose Homeostasis, Inflammation, and Lipoprotein Metabolism in Patients with Type 2 Diabetes and Nondiabetic Obesity

Kallistatin is an endogenous serine proteinase inhibitor with various functions, including antioxidative, anti-inflammatory, and anti-atherosclerotic properties. To date, associations between kallistatin and lipoprotein subfractions are poorly investigated. In this study, we enrolled 62 obese patients with type 2 diabetes (T2D), 106 nondiabetic obese (NDO) subjects matched in gender, age, and body mass index, as well as 49 gender- and age-matched healthy, normal-weight controls. Serum kallistatin levels were measured with ELISA, and lipoprotein subfractions were analyzed using Lipoprint® (Quantimetrix Corp., Redondo Beach, CA, USA) gel electrophoresis. Kallistatin concentrations were significantly higher in T2D patients compared to NDO and control groups. We found significant positive correlations between very-low-density lipoprotein (VLDL), small high-density lipoprotein (HDL) subfractions, glucose, hemoglobin A1c (HbA1c), betatrophin, and kallistatin, while negative correlations were detected between mean low-density lipoprotein (LDL) size, large and intermediate HDL subfractions, and kallistatin in the whole study population. The best predictor of kallistatin was HbA1c in T2D patients, high-sensitivity C-reactive protein (hsCRP) and betatrophin in NDO patients, and hsCRP in controls. Our results indicate that kallistatin expression might be induced by persistent hyperglycemia in T2D, while in nondiabetic subjects, its production might be associated with systemic inflammation. The correlation of kallistatin with lipid subfractions may suggest its putative role in atherogenesis.

Kallistatin Improves High-Fat-Induced Insulin Resistance via Epididymal Adipose Tissue-Derived Exosomes

Objective: Studies have found that high expression of human Kallistatin (HKS) in adipose tissue can improve obesity and its associated comorbidities, but the underlying mechanism of specific regulation is unclear. Methods: An obesity model was built by injecting 8-week-old C57BL/6 mice (n = 6 mice per group) with (Ad.Null and (Ad.HKS adenovirus into epididymal adipose tissue and fed with a high-fat diet (HFD). Insulin resistance-related proteins, AKT and IRS1, were detected in the liver, subcutaneous fat, and skeletal muscle by western blotting after one month of HFD. Epididymal adipose tissue was isolated after 24 h for culture, and exosomes were extracted by differential centrifugation. Enzyme-linked immunosorbent assay detected the expression of HKS protein in serum and exosomes. To examine the role of exosomes in AML12 insulin resistance, we used epididymal adipose tissue-derived exosomes or transfected (Ad.HKS into mature 3T3L1-derived exosomes to interfere with palmitic acid (PA)-induced mouse AML12 insulin resistance model. GW4869 was used to inhibit exosome biogenesis and release. Results: Our results showed that HFD-induced mice with high expression of HKS in epididymal adipose tissue had slower weight gain, lower serum triglycerides, reduced free fatty acids, and improved liver insulin resistance compared with the (Ad.Null group. We also demonstrated that HKS was enriched in epididymal adipose tissue-derived exosomes and released through the exosome pathway. In PA-induced AML12 cells, insulin resistance was alleviated after incubation of the HKS-related exosome; this effect was reversed with GW4869. Conclusion: High expression of HKS in epididymal adipose tissue could lead to its exocrine secretion in the form of exosomes and improve liver insulin resistance by promoting the phosphorylation of AKT. Production of high HKS vesicles might be a possible way to alleviate insulin resistance associated with obesity.

Role of human Kallistatin in glucose and energy homeostasis in mice

OBJECTIVE

Kallistatin (KST), also known as SERPIN A4, is a circulating, broadly acting human plasma protein with pleiotropic properties. Clinical studies in humans revealed reduced KST levels in obesity. The exact role of KST in glucose and energy homeostasis in the setting of insulin resistance and type 2 diabetes is currently unknown.

METHODS

Kallistatin mRNA expression in human subcutaneous white adipose tissue (sWAT) of 47 people with overweight to obesity of the clinical trial "Comparison of Low Fat and Low Carbohydrate Diets With Respect to Weight Loss and Metabolic Effects (B-SMART)" was measured. Moreover, we studied transgenic mice systemically overexpressing human KST (hKST-TG) and wild type littermate control mice (WT) under normal chow (NCD) and high-fat diet (HFD) conditions.

RESULTS

In sWAT of people with overweight to obesity, KST mRNA increased after diet-induced weight loss. On NCD, we did not observe differences between hKST-TG and WT mice. Under HFD conditions, body weight, body fat and liver fat content did not differ between genotypes. Yet, during intraperitoneal glucose tolerance tests (ipGTT) insulin excursions and HOMA-IR were lower in hKST-TG (4.42 ± 0.87 AU, WT vs. 2.20 ± 0.27 AU, hKST-TG, p < 0.05). Hyperinsulinemic euglycemic clamp studies with tracer-labeled glucose infusion confirmed improved insulin sensitivity by higher glucose infusion rates in hKST-TG mice (31.5 ± 1.78 mg/kg/min, hKST-TG vs. 18.1 ± 1.67 mg/kg/min, WT, p < 0.05). Improved insulin sensitivity was driven by reduced hepatic insulin resistance (clamp hepatic glucose output: 7.7 ± 1.9 mg/kg/min, hKST-TG vs 12.2 ± 0.8 mg/kg/min, WT, p < 0.05), providing evidence for direct insulin sensitizing effects of KST for the first time. Insulin sensitivity was differentially affected in skeletal muscle and adipose tissue. Mechanistically, we observed reduced Wnt signaling in the liver but not in skeletal muscle, which may explain the effect.

CONCLUSIONS

KST expression increases after weight loss in sWAT from people with obesity. Furthermore, human KST ameliorates diet-induced hepatic insulin resistance in mice, while differentially affecting skeletal muscle and adipose tissue insulin sensitivity. Thus, KST may be an interesting, yet challenging, therapeutic target for patients with obesity and insulin resistance.

Protective role of kallistatin in oxygen-glucose deprivation and reoxygenation in human umbilical vein endothelial cells

OBJECTIVE

Ischemia-reperfusion (IR) injury is implicated in various clinical diseases. Kallistatin attenuates oxidative stress, and its deficiency has been associated with poor neurological outcomes after cardiac arrest. The present study investigated the antioxidant mechanism through which kallistatin prevents IR injury.

METHODS

Human umbilical vein endothelial cells (HUVECs) were transfected with small interfering RNA (siRNA) targeting the human kallistatin gene (SERPINA4). Following SERPINA4 knockdown, the level of kallistatin expression was measured. To induce IR injury, HUVECs were exposed to 24 h of oxygen-glucose deprivation and reoxygenation (OGD/R). To evaluate the effect of SERPINA4 knockdown on OGD/R, cell viability and the concentration of kallistatin, endothelial nitric oxide synthase (eNOS) and total NO were measured.

RESULTS

SERPINA4 siRNA transfection suppressed the expression of kallistatin in HUVECs. Exposure to OGD/R reduced cell viability, and this effect was more pronounced in SERPINA4 knockdown cells compared with controls. SERPINA4 knockdown significantly reduced kallistatin concentration regardless of OGD/R, with a more pronounced effect observed without OGD/R. Furthermore, SERPINA4 knockdown significantly decreased eNOS concentrations induced by OGD/R (P<0.01) but did not significantly affect the change in total NO concentration (P=0.728).

CONCLUSION

The knockdown of SERPINA4 resulted in increased vulnerability of HUVECs to OGD/R and significantly affected the change in eNOS level induced by OGD/R. These findings suggest that the protective effect of kallistatin against IR injury may contribute to its eNOS-promoting effect.

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.

Kallistatin attenuates inflammatory response in rheumatoid arthritis via the NF-κB signaling pathway

Cartilage degeneration and inflammation are important features of rheumatoid arthritis (RA). Chondrocyte inflammation and apoptosis have been increasingly demonstrated to be related to cartilage decomposition. In this study, we analyzed the protective role of kallistatin against RA and its associated mechanisms. We obtained in vitro and in vivo RA models using IL-1β and heat-inactivated Mycobacterium tuberculosis, respectively. Our results showed that kallistatin mitigated IL-1β-mediated chondrocyte apoptosis and inhibited the synthesis of ECM-degrading generation, like matrix metalloproteinase (MMP)-3/13 and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4/5, in IL-1β-mediated chondrocytes. Furthermore, kallistatin markedly suppressed IL-1β-mediated inflammation while decreasing the levels of inflammatory factors and mediators via the NF-κB pathway. Daily administration of kallistatin reduced the expression levels of PGE2, TNF-α, IL-1β, and IL-6. Histochemical analysis revealed that the kallistatin-treated rats exhibited reduced RA severity compared with control mice. In summary, kallistatin suppressed IL-1β-mediated inflammation in chondrocytes via the NF-κB pathway. Administration of kallistatin remarkably inhibited RA development, accompanied by reduced inflammation and apoptosis. Therefore, kallistatin administration can be used as a candidate therapeutic strategy for RA.

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.

Cardiomyocyte death in sepsis: Mechanisms and regulation (Review)

Sepsis‑induced cardiac dysfunction is one of the most common types of organ dysfunction in sepsis; its pathogenesis is highly complex and not yet fully understood. Cardiomyocytes serve a key role in the pathophysiology of cardiac function; due to the limited ability of cardiomyocytes to regenerate, their loss contributes to decreased cardiac function. The activation of inflammatory signalling pathways affects cardiomyocyte function and modes of cardiomyocyte death in sepsis. Prevention of cardiomyocyte death is an important therapeutic strategy for sepsis‑induced cardiac dysfunction. Thus, understanding the signalling pathways that activate cardiomyocyte death and cross‑regulation between death modes are key to finding therapeutic targets. The present review focused on advances in understanding of sepsis‑induced cardiomyocyte death pathways, including apoptosis, necroptosis, mitochondria‑mediated necrosis, pyroptosis, ferroptosis and autophagy. The present review summarizes the effect of inflammatory activation on cardiomyocyte death mechanisms, the diversity of regulatory mechanisms and cross‑regulation between death modes and the effect on cardiac function in sepsis to provide a theoretical basis for treatment of sepsis‑induced cardiac dysfunction.

Diagnostic circulating biomarkers to detect vision-threatening diabetic retinopathy: Potential screening tool of the future?

With the increasing prevalence of diabetes in developing and developed countries, the socio-economic burden of diabetic retinopathy (DR), the leading complication of diabetes, is growing. Diabetic retinopathy (DR) is currently one of the leading causes of blindness in working-age adults worldwide. Robust methodologies exist to detect and monitor DR; however, these rely on specialist imaging techniques and qualified practitioners. This makes detecting and monitoring DR expensive and time-consuming, which is particularly problematic in developing countries where many patients will be remote and have little contact with specialist medical centres. Diabetic retinopathy (DR) is largely asymptomatic until late in the pathology. Therefore, early identification and stratification of vision-threatening DR (VTDR) is highly desirable and will ameliorate the global impact of this disease. A simple, reliable and more cost-effective test would greatly assist in decreasing the burden of DR around the world. Here, we evaluate and review data on circulating protein biomarkers, which have been verified in the context of DR. We also discuss the challenges and developments necessary to translate these promising data into clinically useful assays, to detect VTDR, and their potential integration into simple point-of-care testing devices.

Overexpressing Kallistatin Aggravates Experimental Autoimmune Uveitis Through Promoting Th17 Differentiation

Kallistatin or kallikrein-binding protein (KBP) has been reported to regulate angiogenesis, inflammation and tumor progression. Autoimmune uveitis is a common, sight-threatening inflammatory intraocular disease. However, the roles of kallistatin in autoimmunity and autoreactive T cells are poorly investigated. Compared to non-uveitis controls, we found that plasma levels of kallistatin were significantly upregulated in patients with Vogt-Koyanagi-Harada (VKH) disease, one of the non-infectious uveitis. Using an experimental autoimmune uveitis (EAU) model induced by human interphotoreceptor retinoid-binding protein peptide 651-670 (hIRBP_651-670), we examined the effects of kallistatin on the pathogenesis of autoimmune diseases. Compared to wild type (WT) mice, kallistatin transgenic (KS) mice developed severe uveitis with dominant Th17 infiltrates in the eye. In addition, the proliferative antigen-specific T cells isolated from KS EAU mice produced increased levels of IL-17A, but not IFN-γ or IL-10 cytokines. Moreover, splenic CD4⁺ T cells from naïve KS mice expressed higher levels of Il17a mRNA compared to WT naïve mice. Under Th17 polarization conditions, KS mice exhibited enhanced differentiation of naïve CD4⁺ T cells into Th17 cells compared to WT controls. Together, our results indicate that kallistatin promotes Th17 differentiation and is a key regulator of aggravating autoinflammation in EAU. Targeting kallistatin might be a potential to treat autoimmune disease.

Protective role of kallistatin in renal fibrosis via modulation of Wnt/β-catenin signaling

Kallistatin is a multiple functional serine protease inhibitor that protects against vascular injury, organ damage and tumor progression. Kallistatin treatment reduces inflammation and fibrosis in the progression of chronic kidney disease (CKD), but the molecular mechanisms underlying this protective process and whether kallistatin plays an endogenous role are incompletely understood. In the present study, we observed that renal kallistatin levels were significantly lower in patients with CKD. It was also positively correlated with estimated glomerular filtration rate (eGFR) and negatively correlated with serum creatinine level. Unilateral ureteral obstruction (UUO) in animals also led to down-regulation of kallistatin protein in the kidney, and depletion of endogenous kallistatin by antibody injection resulted in aggravated renal fibrosis, which was accompanied by enhanced Wnt/β-catenin activation. Conversely, overexpression of kallistatin attenuated renal inflammation, interstitial fibroblast activation and tubular injury in UUO mice. The protective effect of kallistatin was due to the suppression of TGF-β and β-catenin signaling pathways and subsequent inhibition of epithelial-to-mesenchymal transition (EMT) in cultured tubular cells. In addition, kallistatin could inhibit TGF-β-mediated fibroblast activation via modulation of Wnt4/β-catenin signaling pathway. Therefore, endogenous kallistatin protects against renal fibrosis by modulating Wnt/β-catenin-mediated EMT and fibroblast activation. Down-regulation of kallistatin in the progression of renal fibrosis underlies its potential as a valuable clinical biomarker and therapeutic target in CKD.

An Addition of U0126 Protecting Heart Grafts From Prolonged Cold Ischemia-Reperfusion Injury in Heart Transplantation: A New Preservation Strategy

BACKGROUND

Ischemia-reperfusion injury (IRI) is the major cause of primary graft dysfunction in organ transplantation. The mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) signaling pathway plays a crucial role in cell physiological and pathological processes including IRI. This study aims to investigate whether inhibition of ERK signaling with U0126 can prevent prolonged cold IRI in heart transplantation.

METHODS

Rat cardiac cell line H9c2 cells were treated with U0126 before exposure to hypothermic hypoxia/reoxygenation (H/R) conditions. The effect of U0126 on H9c2 cells in response to H/R stress was determined by measuring cell death, reactive oxygen species production, mitochondrial membrane potential, and ERK signaling activation. Mouse syngeneic heterotopic heart transplantation was conducted, where a donor heart was preserved in the University of Wisconsin (UW) solution supplemented with U0126 for 24 hours at 4°C before transplantation. Heart graft function, histopathologic changes, apoptosis, and fibrosis were measured to assess IRI.

RESULTS

Phosphorylated ERK was increased in both in vitro H/R-injured H9c2 cells and in vivo heart grafts with IRI. Pretreatment with U0126 inhibited ERK phosphorylation and prevented H9c2 cells from cell death, reactive oxygen species generation, and mitochondrial membrane potential loss in response to H/R. Preservation of donor hearts with U0126-supplemented solution improved graft function and reduced IRI by reductions in cell apoptosis/death, neutrophil infiltration, and fibrosis of the graft.

CONCLUSIONS

Addition of U0126 to UW solution reduces ERK signal activation and attenuates prolonged cold IRI in a heart transplantation model. ERK inhibition with U0126 may be a useful strategy to minimize IRI in organ transplantation.

Anti-inflammatory and protective effects of combined treatment with sitagliptin and melatonin in cardiac ischemia reperfusion injury in obese rats: Involvement of TLR-4/NF-κB pathway

Background: Obesity is associated with an augmented risk of myocardial ischemia/reperfusion (I/R) injury. Reduction of I/R injury by effective cardioprotective strategies needs to be investigated in obese subjects. This study aimed to evaluate the combined effects of sitagliptin and melatonin on inflammatory response and TLR4/IκBα/NF-κB signaling following cardiac I/R damage in obese rats. Methods: Sixty-six male Wistar rats (180–200 g) were fed a low fat diet (10% Kcal from lipids) or high fat (45% Kcal from lipids) diets for 12 weeks. High fat-fed (obese) rats experienced 30 min left anterior descending occlusion followed by 24 h reperfusion. Obese rats received sitagliptin (20 mg/kg/day) for 1 month before I/R surgery. Melatonin (10 mg/kg) was injected at early reperfusion. Myocardial infarct size (IS), cTn-I release, pro-inflammatory cytokines, myeloperoxidase (MPO), COX-2 and iNOS, and the protein expressions of TLR4, p-NF-κB/p65, and p-IκBα were evaluated. Results: Monotherapies with sitagliptin-preconditioning or melatonin-postconditioning had no cardioprotective effects in obese rats. However, combined therapy with sitagliptin and melatonin significantly reduced IS, and the release of cTn-I, in comparison to untreated obese rats ( p < .01) Moreover, this combination decreased the production of pro-inflammatory cytokines, MPO, COX-2 and iNOS, and the expression of TLR4 and p-NF-κB/p65, while reduced the expression of p-IκBα, in comparison with untreated or monotherapies-received obese rats ( p < .01 for all). Conclusion: Combination therapy with sitagliptin and melatonin was a good cardioprotective strategy to modulate the inflammatory responses and TLR4/NF-κB signaling pathway in obese patients with cardiac I/R injury.

Serum kallistatin level is decreased in women with preeclampsia

OBJECTIVES

To evaluate the serum levels of the serine proteinase inhibitor kallistatin in women with preeclampsia (PE).

METHODS

The clinical and laboratory parameters of 55 consecutive women with early-onset PE (EOPE) and 55 consecutive women with late-onset PE (LOPE) were compared with 110 consecutive gestational age (GA)-matched (±1 week) pregnant women with an uncomplicated pregnancy and an appropriate for gestational age fetus.

RESULTS

Mean serum kallistatin was significantly lower in women with PE compared to the GA-matched-controls (27.74±8.29 ng/mL vs. 37.86±20.64 ng/mL, p<0.001); in women with EOPE compared to that of women in the control group GA-matched for EOPE (24.85±6.65 ng/mL vs. 33.37±17.46 ng/mL, p=0.002); and in women with LOPE compared to that of women in the control group GA-matched for LOPE (30.87±8.81 ng/mL vs. 42.25±22.67 ng/mL, p=0.002). Mean serum kallistatin was significantly lower in women with EOPE compared to LOPE (24.85±6.65 ng/mL vs. 30.87±8.81 ng/mL, p<0.001). Serum kallistatin had negative correlations with systolic and diastolic blood pressure, creatinine, and positive correlation with GA at sampling and GA at birth.

CONCLUSIONS

Serum kallistatin levels are decreased in preeclamptic pregnancies compared to the GA-matched-controls. This decrease was also significant in women with EOPE compared to LOPE. Serum kallistatin had negative correlation with systolic and diastolic blood pressure, creatinine and positive correlation with GA at sampling and GA at birth.

Targeted anti-inflammatory therapy is a new insight for reducing cardiovascular events: A review from physiology to the clinic

Despite considerable progressions, cardiovascular disease (CVD) is still one of the major causes of mortality around the world, indicates an important and unmet clinical need. Recently, extensive studies have been performed on the role of inflammatory factors as either a major or surrogate factor in the pathophysiology of CVD. Epidemiological observations suggest the theory of the role of inflammatory mediators in the development of cardiovascular events. This may support the idea that targeted anti-inflammatory therapies, on the background of traditional validated medical therapies, can play a significant role in prevention and even reduction of cardiovascular disorders. Many randomized controlled trials have shown that drugs commonly useful for primary and secondary prevention of CVD have an anti-inflammatory mechanism. Further, many anti-inflammatory drugs are being examined because of their potential to reduce the risk of cardiovascular problems. In this study, we review the process of inflammation in the development of cardiovascular events, both in vivo and clinical evidence in immunotherapy for CVD.

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.

Protective Effect of Mitogen- and Stress-Activated Protein Kinase on the Rats with Focal Ischemia-Reperfusion Injury

Mitogen- and stress-activated protein kinase (MSK) is a recently identified nuclear cAMP-regulated enhancer B (CREB) and histone H3 kinase that responds to both mitogen- and stress-activated protein kinases. This study was designed to investigate the protective effect of MSK on the rats with focal ischemia-reperfusion injury. The rat model was established by inserting thread into the middle cerebral artery. The protein expression was measured by immunoblotting. The localization of MSK was measured by immunofluorescence assay. Highly-differentiated pheochromocytoma 12 (PC12) is used as a sympathetic neuron-like cell line and treated with glutamate to induce neurotoxicity. MSK was knocked down and overexpressed by siRNA and MSK over-expressing vector, respectively. The cell viability was measured by cell counting kit (CCK-8) assay. The coronal sections were isolated and stained with 2, 3, 5-triphenyltetrazolium chloride (TTC) to determine infarct volume. Finally, astrocytes were separated from cerebral cortexes of normal rats to analyze the effects of MSK on inflammatory response. In the rats with focal ischemia-reperfusion injury, the expression of MSK was reduced, reaching the lowest level at 3 d after ischemia-reperfusion, and then recovered gradually. MSK was found mainly localized in neurons and astrocytes. The expression levels of caspase-3, caspase-8, caspase-9, and INOS showed the opposite trend with respect to MSK. Further analysis showed that overexpression of MSK exerted a protective effect on glutamate-induced neurotoxicity through inhibiting apoptosis of PC12 cells, as well as decreased the infarct size in rat with focal ischemia-reperfusion injury. On the contrary, knockdown of MSK showed opposite results. Finally, MSK suppressed LPS-induced inflammatory response by decreasing the expression of inducible nitric oxide synthase (INOS) and increasing the expression of interleukin-10 (IL-10) in astrocytes from cerebral cortexes of normal rats. In conclusion, MSK exerted a protective effect on rat with focal ischemia-reperfusion injury through its anti-apoptotic effect on neurons and anti-inflammatory effect on astrocytes.

Downregulation of miR-3568 Protects Against Ischemia/Reperfusion-Induced Cardiac Dysfunction in Rats and Apoptosis in H9C2 Cardiomyocytes Through Targeting TRIM62

microRNA-3568 (miR-3568) has been reported to be associated with atherosclerosis. Only few data describe the expression and underlying mechanism of miR-3568 in regulating cardiac ischemia-reperfusion (I/R) injury such as apoptosis. In this study, we therefore sought to investigate the potential function of miR-3568 in simulated I/R-induced apoptosis in H9C2 cardiomyocytes and related signaling pathways involved. Flow cytometry was performed to examine the cell apoptosis. The expression of miR-3568, Survivin, Bcl-2, ERK, JNK, p38, AKT, and STAT3 was measured by western blot and quantitative real-time PCR. The correlation between TRIM62 and p-STAT3 was measured by co-immunoprecipitation and ubiquitination. We found that miR-3568 expression in simulated I/R-induced H9C2 cardiomyocytes was increased in a time-dependent manner. miR-3568 mimic transfection in H9C2 cardiomyocytes significantly enhanced cell apoptosis, decreased the expression of Bcl-2 and Survivin, and activated STAT3 signaling, which were reversed by miR-3568 inhibitor. The direct interaction between miR-3568 and the 3'-untranslated region (UTR) of TRIM62 mRNA was confirmed by dual-luciferase reporter assay. TRIM62 overexpression or AG490, a selective inhibitor of JAK2/STAT3 significantly, significantly inhibited I/R and miR-3568 mimic induced cell apoptosis and STAT3 activation. TRIM62 was found to interact with and induce ubiquitination of p-STAT3. The facilitating role of miR-3568 in I/R injury was also observed in our in vivo rat models. In conclusion, our study suggests that miR-3568 promotes simulated I/R-induced apoptosis in H9C2 cardiomyocytes through targeting TRIM62.

Biochanin A attenuates myocardial ischemia/reperfusion injury through the TLR4/NF-κB/NLRP3 signaling pathway

PURPOSE

Myocardial ischemia/reperfusion (Ml/R) injury is a leading cause of damage in cardiac tissues, with high rates of mortality and disability. Biochanin A (BCA) is a main constituent of Trifolium pratense L. This study was intended to explore the effect of BCA on Ml/R injury and explore the potential mechanism.

METHODS

In vivo MI/R injury was established by transient coronary ligation in Sprague-Dawley rats. Triphenyltetrazolium chloride staining (TTC) was used to measure myocardial infarct size. ELISA assay was employed to evaluate the levels of myocardial enzyme and inflammatory cytokines. Western blot assay was conducted to detect related protein levels in myocardial tissues.

RESULTS

BCA significantly ameliorated myocardial infarction area, reduced the release of myocardial enzyme levels including aspartate transaminase (AST), creatine kinase (CK-MB) and lactic dehydrogenase (LDH). It also decreased the production of inflammatory cytokines (IL-1β, IL-18, IL-6 and TNF-α) in serum of Ml/R rats. Further mechanism studies demonstrated that BCA inhibited inflammatory reaction through blocking TLR4/NF-kB/NLRP3 signaling pathway.

CONCLUSION

The present study is the first evidence demonstrating that BCA attenuated Ml/R injury through suppressing TLR4/NF-kB/NLRP3 signaling pathway-mediated anti-inflammation pathway.

Silencing MEKK3 attenuates cardiomyocyte injury caused by hypoxia/reoxygenation via the sonic hedgehog pathway

MEKK3 is a member of MAP3K, which plays a pivotal role in cardiac diseases. In this study, we aimed to investigate the effects and potential mechanisms of MEKK3 on hypoxia/reoxygenation (H/R) injury of cardiomyocytes. After exposing H9C2 cells to H/R insult, real-time polymerase chain reaction and western blot analysis showed that MEKK3 was highly expressed. Cell viability, cell apoptosis, caspase 3/7 activity, and cleaved-caspase 3 expression were tested using a CCK-8 assay, Cell Death Detection PLUS ELISA, Caspase-Glo 3/7 Assay Kit and western blot analysis, respectively. Mitochondrial membrane potential, cytochrome C expression, adenosine triphosphate (ATP), and reactive oxygen species also were measured using JC-1 staining, western blot analysis, an ATP Assay Kit, and DCFH ₂ -DA staining, respectively. The messenger RNA (mRNA) levels and secretions of TNF-α, IL-6, and IL-1β were evaluated. The results revealed that MEKK3 silencing promoted cell survival and attenuated lactate dehydrogenase leakage, cell apoptosis, caspase 3/7 activity, and the protein level of cleaved-caspase 3. Moreover, knockdown of MEKK3 blocked mitochondrial impairment by inhibiting the loss of mitochondrial membrane potential and cytochrome C expression as well as promoting ATP synthesis. MEKK3 deficiency led to a decrease in reactive oxygen species and malondialdehyde (MDA) generation and an increase in superoxide dismutase (SOD) activity. Deletion of MEKK3 led to reduced inflammatory cytokines in mRNA level and secretion. MEKK3 suppression activated the sonic hedgehog (Shh) signaling pathway in H9C2 cells. After blocking the Shh signaling pathway with a specific inhibitor, cyclopamine, the cardioprotective functions of MEKK3 downregulation were partly abolished. In conclusion, downregulation of MEKK3 prevented apoptosis and inflammation in H9C2 cells via the Shh signaling pathway.

Serine protease inhibitors and human wellbeing interplay: new insights for old friends

Serine Protease Inhibitors (Serpins) control tightly regulated physiological processes and their dysfunction is associated to various diseases. Thus, increasing interest is given to these proteins as new therapeutic targets. Several studies provided functional and structural data about human serpins. By comparison, only little knowledge regarding bacterial serpins exists. Through the emergence of metagenomic studies, many bacterial serpins were identified from numerous ecological niches including the human gut microbiota. The origin, distribution and function of these proteins remain to be established. In this report, we shed light on the key role of human and bacterial serpins in health and disease. Moreover, we analyze their function, phylogeny and ecological distribution. This review highlights the potential use of bacterial serpins to set out new therapeutic approaches.

Cardioprotective mechanism of FTY720 in ischemia reperfusion injury

Cardioprotection is a very challenging area in the field of cardiovascular sciences. Myocardial damage accounts for nearly 50% of injury due to reperfusion, yet there is no effective strategy to prevent this to reduce the burden of heart failure. During last couple of decades, by combining genetic and bimolecular studies, many new drugs have been developed to treat hypertension, heart failure, and cancer. The use of percutaneous coronary intervention has reduced the mortality and morbidity of acute coronary syndrome dramatically. However, there is no standard therapy available that can mitigate cardiac reperfusion injury, which contributes to up to half of myocardial infarcts. Literature shows that the activation of sphingosine receptors, which are G protein-coupled receptors, induces cardioprotection both in vitro and in vivo. The exact mechanism of this protection is not clear yet. In this review, we discuss the mechanism of ischemia reperfusion injury and the role of the FDA-approved sphingosine 1 phosphate drug fingolimod in cardioprotection.

Protective Role of Endogenous Kallistatin in Vascular Injury and Senescence by Inhibiting Oxidative Stress and Inflammation

Kallistatin was identified in human plasma as a tissue kallikrein-binding protein and a serine proteinase inhibitor. Kallistatin exerts pleiotropic effects on angiogenesis, oxidative stress, inflammation, apoptosis, fibrosis, and tumor growth. Kallistatin levels are markedly reduced in patients with coronary artery disease, sepsis, diabetic retinopathy, inflammatory bowel disease, pneumonia, and cancer. Moreover, plasma kallistatin levels are positively associated with leukocyte telomere length in young African Americans, indicating the involvement of kallistatin in aging. In addition, kallistatin treatment promotes vascular repair by increasing the migration and function of endothelial progenitor cells (EPCs). Kallistatin via its heparin-binding site antagonizes TNF-α-induced senescence and superoxide formation, while kallistatin's active site is essential for inhibiting miR-34a synthesis, thus elevating sirtuin 1 (SIRT1)/eNOS synthesis in EPCs. Kallistatin inhibits oxidative stress-induced cellular senescence by upregulating Let-7g synthesis, leading to modulate Let-7g-mediated miR-34a-SIRT1-eNOS signaling pathway in human endothelial cells. Exogenous kallistatin administration attenuates vascular injury and senescence in association with increased SIRT1 and eNOS levels and reduced miR-34a synthesis and NADPH oxidase activity, as well as TNF-α and ICAM-1 expression in the aortas of streptozotocin- (STZ-) induced diabetic mice. Conversely, endothelial-specific depletion of kallistatin aggravates vascular senescence, oxidative stress, and inflammation, with further reduction of Let-7g, SIRT1, and eNOS and elevation of miR-34a in mouse lung endothelial cells. Furthermore, systemic depletion of kallistatin exacerbates aortic injury, senescence, NADPH oxidase activity, and inflammatory gene expression in STZ-induced diabetic mice. These findings indicate that endogenous kallistatin displays a novel role in protection against vascular injury and senescence by inhibiting oxidative stress and inflammation.

Kallistatin Inhibits Atherosclerotic Inflammation by Regulating Macrophage Polarization

Kallistatin (KS) has been recognized as a plasma protein with anti-inflammatory functions. Macrophages are the primary inflammatory cells in atherosclerotic plaques. However, it is unknown whether KS plays a role in macrophage development and the pathogenesis of atherosclerosis. This study investigated the role of KS in macrophage development, a key pathological process in atherosclerosis. An atherosclerosis model was established in ApoE^-/- mice via partial left carotid artery (PLCA) ligation. An adenovirus vector (Ad. HKS) containing the human KS gene was delivered via the tail vein before PLCA ligation. The mice were divided into two groups: the PLCA + Ad. HKS and PLCA + adenovirus vector (Ad. Null) groups and followed for 2 and 4 weeks. Human KS was expressed in the mice after KS gene delivery. In addition, KS significantly inhibited plaque formation and reduced inflammation in the plaques and liver 4 weeks after gene delivery. Moreover, KS gene delivery significantly increased the expression of interleukin-10 and Arginase 1, which are M2 macrophage markers, and reduced the expression of inducible nitric oxide synthase and monocyte chemotactic protein 1, which are M1 macrophage markers. Furthermore, in cultured RAW 264.7 macrophages, KS significantly stimulated M2 marker expression and differentiation and decreased M1 marker expression, as determined by flow cytometry and real-time polymerase chain reaction. These effects were blocked by Krüppel-like factor 4 small-interfering RNA oligonucleotides. These findings demonstrate that KS inhibits atherosclerotic plaque formation and regulates M1/M2 macrophage polarization via Krüppel-like factor 4 activation.

Kallistatin attenuates endothelial senescence by modulating Let-7g-mediated miR-34a-SIRT1-eNOS pathway

Kallistatin, a plasma protein, protects against vascular and organ injury. This study is aimed to investigate the role and mechanism of kallistatin in endothelial senescence. Kallistatin inhibited H2 O2 -induced senescence in human endothelial cells, as indicated by reduced senescence-associated-β-galactosidase activity, p16INK4a and plasminogen activator inhibitor-1 expression, and elevated telomerase activity. Kallistatin blocked H2 O2 -induced superoxide formation, NADPH oxidase levels and VCAM-1, ICAM-1, IL-6 and miR-34a synthesis. Kallistatin reversed H2 O2 -mediated inhibition of endothelial nitric oxide synthase (eNOS), SIRT1, catalase and superoxide dismutase (SOD)-2 expression, and kallistatin alone stimulated the synthesis of these antioxidant enzymes. Moreover, kallistatin's anti-senescence and anti-oxidant effects were attributed to SIRT1-mediated eNOS pathway. Kallistatin, via interaction with tyrosine kinase, up-regulated Let-7g, whereas Let-7g inhibitor abolished kallistatin's effects on miR-34a and SIRT1/eNOS synthesis, leading to inhibition of senescence, oxidative stress and inflammation. Furthermore, lung endothelial cells isolated from endothelium-specific kallistatin knockout mice displayed marked reduction in mouse kallistatin levels. Kallistatin deficiency in mouse endothelial cells exacerbated senescence, oxidative stress and inflammation compared to wild-type mouse endothelial cells, and H2 O2 treatment further magnified these effects. Kallistatin deficiency caused marked reduction in Let-7g, SIRT1, eNOS, catalase and SOD-1 mRNA levels, and elevated miR-34a synthesis in mouse endothelial cells. These findings indicate that endogenous kallistatin through novel mechanisms protects against endothelial senescence by modulating Let-7g-mediated miR-34a-SIRT1-eNOS pathway.

Plasma Kallistatin Levels in Children with Community-Acquired Pneumonia

Purpose: Community-acquired pneumonia (CAP) is a potentially lethal lower respiratory tract infection affecting children all over the world. In this study, we aimed to evaluate plasma kallistatin levels in children at the time of admission and on the fourth day of treatment to determine if this is effective in deciding whether to hospitalize patients and to assess the response to treatment in patients with CAP. Methods: This prospective case/control study was conducted between November 2015 and May 2016 at Erciyes University School of Medicine, in the Department of Paediatric Pulmonology. Fifty-three patients, who were diagnosed with CAP with clinical and radiological findings, were included in the study. The patients were divided into various subgroups such as inpatients, outpatients, those with complications, those without complications, and dead patients. The levels of kallistatin were compared between the control group and the patient group. Results: A total of 53 children with a diagnosis of CAP and 55 healthy children were enrolled in the study. The plasma kallistatin level of CAP patients at admission was significantly higher than that of the control group [1.6 (1.2-2.9) ng/mL], [0.9 (0.7-1.1) ng/mL] (P < 0.001). The patient group was divided into 3 subgroups: those with complications, those with no complications, and those who died. In patients who were hospitalized, who died, and who were in need of mechanical ventilation (MV), kallistatin levels were significantly higher than in the other patients (P = 0.027 for hospitalization; P = 0.022 for exitus; and P = 0.008 for MV) at the time of diagnosis and on the fourth day of treatment. Conclusion: A higher plasma kallistatin level was found to be significant in CAP. Patients with high kallistatin levels should be carefully monitored for hospitalization and for unwanted side effects such as MV need and death.

Therapeutic effects of simvastatin combined with kallistatin treatment for pediatric burn patients with sepsis

The aim of the present study was to examine the combined efficacy of simvastatin and kallistatin treatment for pediatric burn sepsis. A total of 72 pediatric patients with burn sepsis were recruited and randomly divided into 3 groups, receiving simvastatin (40 mg/day), kallistatin (20 mg/day) or combined treatment. ELISA, reverse transcription-quantitative polymerase chain reaction, western blotting and flow cytometry were used to analyze the therapeutic effects of simvastatin and kallistatin. The results revealed that combined treatment in pediatric burn sepsis patients decreased the inflammatory cytokine tumor necrosis factor α and interleukin (IL)-1β serum levels, whereas it increased IL-10 and human leukocyte antigen-D related levels. In addition, administration of combined simvastatin and kallistatin decreased the blood urea nitrogen and serum creatinine levels in the patients. It was also demonstrated that Toll-like receptor 4 expression on the surface of monocytes was markedly decreased, while suppressor of cytokine signaling-3 expression was increased in the combined treatment group as compared with the kallistatin or simvastatin treatment alone. Combined treatment also promoted human endothelial cell (HEC) growth compared with the single treatment groups and inhibited the high mobility group box-1 (HMGB1) levels, HMGB1-induced nuclear factor-κB activation and inflammatory gene expression levels in these cells. The study further demonstrated that combined treatment significantly decreased HEC apoptosis through the upregulation of B-cell lymphoma 2 (Bcl-2) and P53 expression levels, as well as downregulation of Bcl-2-associated X protein and caspase-3 levels. In conclusion, these observations indicated that combined treatment with simvastatin and kallistatin inhibited HEC apoptosis, which may be a potential therapeutic strategy for the treatment of pediatric burn sepsis patients.

Opposing Effects of Oxygen Regulation on Kallistatin Expression: Kallistatin as a Novel Mediator of Oxygen-Induced HIF-1-eNOS-NO Pathway

Oxidative stress has both detrimental and beneficial effects. Kallistatin, a key component of circulation, protects against vascular and organ injury. Serum kallistatin levels are reduced in patients and animal models with hypertension, diabetes, obesity, and cancer. Reduction of kallistatin levels is inversely associated with elevated thiobarbituric acid-reactive substance. Kallistatin therapy attenuates oxidative stress and increases endothelial nitric oxide synthase (eNOS) and NO levels in animal models. However, kallistatin administration increases reactive oxygen species formation in immune cells and bacterial killing activity in septic mice. High oxygen inhibits kallistatin expression via activating the JNK-FOXO1 pathway in endothelial cells. Conversely, mild oxygen/hyperoxia stimulates kallistatin, eNOS, and hypoxia-inducible factor-1 (HIF-1) expression in endothelial cells and in the kidney of normal mice. Likewise, kallistatin stimulates eNOS and HIF-1, and kallistatin antisense RNA abolishes oxygen-induced eNOS and HIF-1 expression, indicating a role of kallistatin in mediating mild oxygen's stimulation on antioxidant genes. Protein kinase C (PKC) activation mediates HIF-1-induced eNOS synthesis in response to hyperoxia/exercise; thus, mild oxygen through PKC activation stimulates kallistatin-mediated HIF-1 and eNOS synthesis. In summary, oxidative stress induces down- or upregulation of kallistatin expression, depending on oxygen concentration, and kallistatin plays a novel role in mediating oxygen/exercise-induced HIF-1-eNOS-NO pathway.

Prazosin protects myocardial cells against anoxia-reoxygenation injury via the extracellular signal‑regulated kinase signaling pathway

Ischemic heart disease (including coronary arterial atherosclerosis, or vascular cavity stenosis or occlusion) remains the leading cause of disease-associated mortality worldwide. Prazosin, a receptor blocker of postsynaptic adrenaline, is essential in expanding peripheral arteries, which decreases peripheral vascular resistance, and regulates anti-hypertensive action. However, the mechanisms underlying the effects of prazosin have not been fully elucidated. The aim of the present study was to investigate the protective effects of prazosin on myocardial cells against anoxia-reoxygenation injury in a mouse model. The regulatory effects of prazosin on blood lipid levels and blood pressure were investigated in experimental mice. Furthermore, inflammation responses and oxidative stress in myocardial cells were analyzed in mice treated with prazosin. Apoptotic myocardial cells were investigated in experimental mice treated with prazosin. In addition, apoptotic gene expression levels were evaluated in myocardial cells. Extracellular signal-regulated kinase (ERK) expression and phosphorylation was investigated in myocardial cells in mice with anoxia-reoxygenation injury following prazosin treatment. The activity and expression levels of nuclear factor of activated T cells (NF-AT), activator protein 1 (AP-1) and necrosis factor (NF)-κB were observed in myocardial cells. Furthermore, histological analyses were performed to investigate the benefits of prazosin treatment on anoxia-reoxygenation injury. The results of the present study identified that prazosin decreased the expression levels of inflammatory factors, interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-10 and IL-1 in the serum of mice exhibiting hypoxia/reoxygenation injury. Oxidative stress was observed to be improved and the apoptosis rate was decreased in myocardial cells in anoxia-reoxygenation injury model mice treated with prazosin. ERK expression and phosphorylation was upregulated, and expression levels of NF-AT, AP-1 and NF-κB were downregulated in the myocardial cells of mice treated with prazosin. Blood lipid levels and blood pressure of the anoxia-reoxygenation injury model mice were markedly improved following treatment with prazosin. Histological analysis indicated that the area, circumference fragmentation and segmentation of myocardial cells were significantly improved following prazosin treatment. Thus, these results indicate that prazosin treatment decreases inflammation responses, oxidative stress, and apoptosis of myocardial cells via regulation of the ERK signaling pathway. The findings indicate that prazosin may present as a potential therapeutic agent for the treatment of hypoxia/reoxygenation injury.

Kallistatin: double-edged role in angiogenesis, apoptosis and oxidative stress

Kallistatin, via its two structural elements – an active site and a heparin-binding domain – displays a double-edged function in angiogenesis, apoptosis and oxidative stress. First, kallistatin has both anti-angiogenic and pro-angiogenic effects. Kallistatin treatment attenuates angiogenesis and tumor growth in cancer-bearing mice. Kallistatin via its heparin-binding site inhibits angiogenesis by blocking vascular endothelial growth factor (VEGF)-induced growth, migration and adhesion of endothelial cells. Conversely, kallistatin via the active site promotes neovascularization by stimulating VEGF levels in endothelial progenitor cells. Second, kallistatin inhibits or induces apoptosis depending on cell types. Kallistatin attenuates organ injury and apoptosis in animal models, and its heparin-binding site is essential for blocking tumor necrosis factor (TNF)-α-induced apoptosis in endothelial cells. However, kallistatin via its active site induces apoptosis in breast cancer cells by up-regulating miR-34a and down-regulating miR-21 and miR-203 synthesis. Third, kallistatin can act as an antioxidant or pro-oxidant. Kallistatin treatment inhibits oxidative stress and tissue damage in animal models and cultured cells. Kallistatin via the heparin-binding domain antagonizes TNF-α-induced oxidative stress, whereas its active site is crucial for stimulating antioxidant enzyme expression. In contrast, kallistatin provokes oxidant formation, leading to blood pressure reduction and bacterial killing. Kallistatin-mediated vasodilation is partly mediated by H2O2, as the effect is abolished by the antioxidant enzyme catalase. Moreover, kallistatin exerts a bactericidal effect by stimulating superoxide production in neutrophils of mice with microbial infection as well as in cultured immune cells. Thus, kallistatin’s dual roles in angiogenesis, apoptosis and oxidative stress contribute to its beneficial effects in various diseases.

Role of Kallistatin Treatment in Aging and Cancer by Modulating miR-34a and miR-21 Expression

Kallistatin is an endogenous protein that regulates differential signaling pathways and a wide spectrum of biological activities via its two structural elements: an active site and a heparin-binding domain. Kallistatin via its heparin-binding site inhibits vascular inflammation and oxidative stress by antagonizing TNF-α-induced NADPH oxidase activity, NF-κB activation, and inflammatory gene expression in endothelial cells. Moreover, kallistatin via its active site inhibits microRNA-34a (miR-34a) synthesis and stimulates eNOS and SIRT1 expression in endothelial progenitor cells, whereas its heparin-binding site is crucial for blocking TNF-α-induced miR-21 expression and oxidative stress, thus reducing cellular senescence. By downregulating miR-34a and miR-21 expression, kallistatin treatment attenuates oxidative damage and aortic senescence in streptozotocin-induced diabetic mice and extends Caenorhabditis elegans lifespan under stress conditions. Likewise, kallistatin through the heparin-binding site inhibits TGF-β-induced miR-21 synthesis and oxidative stress in endothelial cells, resulting in inhibition of endothelial-mesenchymal transition, a process contributing to fibrosis and cancer. Furthermore, kallistatin's active site is essential for stimulating miR-34a and p53 expression and inhibiting the miR-21-Akt-Bcl-2 signaling pathway, thus inducing apoptosis in breast cancer cells. These findings reveal novel mechanisms of kallistatin in protection against senescence, aging, and cancer development by modulating miR-34a and miR-21 levels and inhibiting oxidative stress.

Plasma kallistatin in critically ill patients with severe sepsis and septic shock

Kallistatin, an endogenous serine proteinase inhibitor, is protective against sepsis in animal models. The aim of this study was to determine the plasma concentration of kallistatin in intensive care unit (ICU) patients with severe sepsis and septic shock and to determine their potential correlation with disease severity and outcomes. We enrolled 86 ICU patients with severe sepsis and septic shock. Their plasma concentrations of kallistatin, kallikrein, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-8 were measured by enzyme-linked immunosorbent assay. The association of kallistatin levels with disease severity and patient outcomes was evaluated. The relationship between kallistatin and other biomarkers was also analyzed. Plasma kallistatin levels on day 1 of ICU admission were lower in patients with septic shock compared with patients with severe sepsis (p = 0.004). Twenty-nine patients who died in the hospital had significantly lower day 1 kallistatin levels than patients who survived (p = 0.031). Using the optimal cutoff value (4 μg/ml) of day 1 plasma kallistatin determined by receiver operating characteristic curves for 60-day mortality, we found that high kallistatin levels were associated with a preferable 60-day survival (p = 0.012) by Kaplan-Meier analysis and lower Sequential Organ Failure Assessment (SOFA) scores over the first 5 days in the ICU (p = 0.001). High kallistatin levels were also independently associated with a decreased risk of septic shock, the development of acute respiratory distress syndrome, and positive blood cultures. In addition, there were inverse correlations between day 1 kallistatin levels and the levels of TNF-α, IL-1β, IL-6, and C-reactive protein, and SOFA scores on day 1. Our results indicate that during severe sepsis and septic shock, a decrease in plasma concentrations of kallistatin reflects increased severity and poorer outcome of disease.

Increased kallistatin levels in patients with obesity and prediabetes compared to normal glucose tolerance

PURPOSE

Kallistatin is a member of serine protease inhibitors (SERPIN) family, which has various functions such as regulation of cardiovascular function and blood vessels development. Its levels are elevated in patients with type 1 and type 2 diabetes with chronic diabetic complications. The aim of the present study was to compare serum kallistatin levels between obese subjects with prediabetes and with normal glucose tolerance.

METHODS

In this study we included 80 subjects at mean age of 50.4 ± 10.6 years, divided into two age and BMI-matched groups - group 1 with obesity without glycemic disturbances (n = 41) and group 2 with obesity and prediabetes (n = 39). Oral glucose tolerance test with measurement of immunoreactive insulin was performed in all participants and levels of kallistatin were measured using ELISA method.

RESULTS

We found significantly higher levels of kallistatin in patients with prediabetes compared to controls (data are presented as median (min; max) because data were not normally distributed) (6.3 (4.4; 9.0) vs. 5.6 (3.1; 8.7) ng/ml; p = 0.022) and in patients with metabolic syndrome compared to those without (6.0 (4.9; 9.0) vs. 5.5 (3.1; 7.7); p = 0.006), but the levels were similar in patients with and without insulin resistance.

CONCLUSIONS

The levels of kallistatin are higher in individuals with prediabetes, but are similar in subjects with and without insulin resistance, which indicates that the main factor for its increased levels may be hyperglycemia and not insulin sensitivity state.

Kallistatin suppresses cancer development by multi-factorial actions

Kallistatin was first identified in human plasma as a tissue kallikrein-binding protein and a serine proteinase inhibitor. Kallistatin via its two structural elements regulates differential signaling cascades, and thus a wide spectrum of biological functions. Kallistatin's active site is essential for: inhibiting tissue kallikrein's activity; stimulating endothelial nitric oxide synthase and sirtuin 1 expression and activation; and modulating the synthesis of the microRNAs, miR-34a, miR-21 and miR-203. Kallistatin's heparin-binding site is crucial for antagonizing the signaling pathways of vascular endothelial growth factor, tumor necrosis factor-α, Wnt, transforming growth factor-β and epidermal growth factor. Circulating kallistatin levels are markedly reduced in patients with prostate and colon cancer. Kallistatin administration attenuates angiogenesis, inflammation, tumor growth and invasion in animal models and cultured cells. Therefore, tumor progression may be substantially suppressed by kallistatin's pleiotropic activities. In this review, we will discuss the role and mechanisms of kallistatin in the regulation of cancer development.

Kallistatin exerts anti-lymphangiogenic effects by inhibiting lymphatic endothelial cell proliferation, migration and tube formation

Kallistatin has been recognized as an endogenous angiogenic inhibitor. However, its effects on lymphatic endothelial cells and lymphangiogenesis remain poorly understood. Lymphangiogenesis is involved in tumor metastasis via the lymphatic vasculature in various types of tumors. The aim of this study was to investigate the effects of kallistatin on lymphangiogenesis and the mechanism of action involved. Treatment with kallistatin recombinant protein or overexpression of kallistatin inhibited the proliferation, migration and tube formation of human lymphatic endothelial cells (hLECs), and induced apoptosis of hLECs. Furthermore, our results showed that the lymphatic vessel density (LVD) was reduced in lung and stomach sections from kallistatin-overexpressing transgenic mice. Treatment with kallistatin recombinant protein decreased the LVD in the implanted gastric xenograft tumors of nude mice. To the best of our knowledge, the present study is the first to demonstrate that kallistatin possesses anti-lymphangiogenic activity in vitro and in vivo. Moreover, kallistatin inhibited proliferation and migration of hLECs by reducing the phosphorylation of ERK and Akt, respectively. These findings suggested that kallistatin may be a promising agent that could be used to suppress cancer metastasis by inhibiting both angiogenesis and lymphangiogenesis.

Kallistatin levels in HIV-infected patients and effects of statin therapy

BACKGROUND

Kallistatin, a serine proteinase inhibitor, has vasodilatory and anti-inflammatory properties and is increased in other inflammatory conditions. We measured kallistatin in HIV for the first time, examined its relationship with inflammation, and determined if statin therapy affected levels.

METHODS

Kallistatin levels were measured in subjects from a randomized, double-blinded, placebo-controlled trial.

RESULTS

One hundred and thirty-five HIV-infected subjects were included. Kallistatin levels were 28.4 μg/mL at baseline and not affected by rosuvastatin. Levels were correlated with high-sensitivity C-reactive protein (hsCRP), interleukin-6, fibrinogen and insulin resistance.

CONCLUSIONS

Kallistatin levels were correlated with some markers of systemic inflammation and should be further explored in the HIV population.

Kallistatin induces breast cancer cell apoptosis and autophagy by modulating Wnt signaling and microRNA synthesis

Kallistatin is an endogenous protein that regulates differential signaling pathways and biological functions. Our previous studies showed that kallistatin gene therapy inhibited angiogenesis, tumor growth and metastasis in mice, and kallistatin protein suppressed Wnt-mediated growth, migration and invasion by blocking Wnt/β-catenin signaling pathway in breast cancer cells. In this study, we show that kallistatin reduced cell viability, and increased apoptotic cell death and caspase-3 activity in MDA-MB-231 breast cancer cells. Kallistatin also induced cancer cell autophagy, as evidenced by increased LC3B levels and elevated Atg5 and Beclin-1 expression; however, co-administration of Wnt or PPARγ antagonist GW9662 abolished these effects. Moreover, kallistatin via its heparin-binding site antagonized Wnt3a-induced cancer cell proliferation and increased PPARγ expression. Kallistatin inhibited oncogenic miR-21 synthesis associated with reduced Akt phosphorylation and Bcl-2 synthesis, but increased BAX expression. Kallistatin via PKC-ERK activation reduced miR-203 levels, leading to increased expression of suppressor of cytokine signaling 3 (SOCS3), a tumor suppressor. Conversely, kallistatin stimulated expression of the tumorigenic suppressors miR-34a and p53. Kallistatin's active site is essential for suppressing miR-21 and miR-203, and stimulating miR-34a and SOCS3 expression. This is the first study to demonstrate that kallistatin's heparin-binding site is essential for inhibiting Wnt-mediated effects, and its active site plays a key role in regulating miR-21, miR-203, miR-34a and SOCS3 synthesis in breast cancer cells. These findings reveal novel mechanisms of kallistatin in inducing apoptosis and autophagy in breast cancer cells, thus inhibiting tumor progression by regulation of Wnt/PPARγ signaling, as well as miR-21, miR-203 and miR-34a synthesis.

Kallistatin protects against sepsis-related acute lung injury via inhibiting inflammation and apoptosis

Kallistatin, an endogenous plasma protein, exhibits pleiotropic properties in inhibiting inflammation, oxidative stress and apoptosis, as evidenced in various animal models and cultured cells. Here, we demonstrate that kallistatin levels were positively correlated with the concentration of total protein in bronchoalveolar lavage fluids (BALF) from patients with sepsis-related acute respiratory distress syndrome (ARDS), indicating a compensatory mechanism. Lower ratio of kallistatin to total protein in BALF showed a significant trend toward elevated neutrophil counts (P = 0.002) in BALF and increased mortality (P = 0.046). In lipopolysaccharide (LPS)-treated mice, expression of human kallistatin in lung by gene transfer with human kallistatin-encoding plasmid ameliorated acute lung injury (ALI) and reduced cytokine/chemokine levels in BALF. These mice exhibited attenuated lung epithelial apoptosis and decreased Fas/FasL expression compared to the control mice. Mouse survival was improved by kallistatin gene transfer or recombinant human kallistatin treatment after LPS challenge. In LPS-stimulated A549 human lung epithelial cells, kallistatin attenuated apoptosis, down-regulated Fas/FasL signaling, suppressed intracellular reactive oxygen species (ROS) and inhibited ROS-mediated NF-κB activation and inflammation. Furthermore, LPS-induced apoptosis was blocked by antioxidant N-acetylcysteine or NF-κB inhibitor via down-regulating Fas expression. These findings suggest the therapeutic potential of kallistatin for sepsis-related ALI/ARDS.

Kallistatin inhibits TGF-β-induced endothelial-mesenchymal transition by differential regulation of microRNA-21 and eNOS expression

Kallistatin, an endogenous protein, consists of two structural elements: active site and heparin-binding domain. Kallistatin exerts beneficial effects on fibrosis by suppressing transforming growth factor (TGF)-β synthesis in animal models. TGF-β is the most potent inducer of endothelial-mesenchymal transition (EndMT), which contributes to fibrosis and cancer. MicroRNA (miR)-21 is an important player in organ fibrosis and tumor invasion. Here we investigated the potential role of kallistatin in EndMT via modulation of miR-21 in endothelial cells. Human kallistatin treatment blocked TGF-β-induced EndMT, as evidenced by morphological changes as well as increased endothelial and reduced mesenchymal marker expression. Kallistatin also inhibited TGF-β-mediated reactive oxygen species (ROS) formation and NADPH oxidase expression and activity. Moreover, kallistatin antagonized TGF-β-induced miR-21 and Snail1 synthesis, Akt phosphorylation, NF-κB activation, and matrix metalloproteinase 2 (MMP2) synthesis and activation. Kallistatin via its heparin-binding site blocked TGF-β-induced miR-21, Snail1 expression, and ROS formation, as wild-type kallistatin, but not heparin-binding site mutant kallistatin, exerted the effect. Conversely, kallistatin through its active site stimulated the synthesis of endothelial nitric oxide synthase (eNOS), sirtuin 1 (Sirt1) and forkhead box O1 (FoxO1); however, these effects were blocked by genistein, a tyrosine kinase inhibitor. This is the first study to demonstrate that kallistatin's heparin-binding site is crucial for preventing TGF-β-induced miR-21 and oxidative stress, while its active site is key for stimulating the expression of antioxidant genes via interaction with an endothelial surface tyrosine kinase. These findings reveal novel mechanisms of kallistatin in protection against fibrosis and cancer by suppressing EndMT.

Kallistatin as a marker of microvascular complications in children and adolescents with type 1 diabetes mellitus: Relation to carotid intima media thickness

In diabetes, angiogenesis is disturbed, contributing to proliferative retinopathy, nephropathy and neuropathy. Kallistatin, a serine proteinase inhibitor, has anti-angiogenic effects. We assessed serum kallistatin in children and adolescents with type 1 diabetes as a potential marker for microvascular complications and its relation to carotid intima media thickness (CIMT). Sixty patients with type 1 diabetes were divided into two groups according to the presence of microvascular complications and compared with 30 healthy controls. High-sensitivity C-reactive protein (hs-CRP), HbA1c, urinary albumin creatinine ratio (UACR), kallistatin levels and CIMT were assessed. Kallistatin levels were significantly higher in patients with microvascular complications (9.9 ± 2.38 ng/mL) and those without complications (5.0 ± 1.5 ng/mL) than in healthy controls (1.39 ± 0.55 ng/mL; p<0.001). Kallistatin was increased in patients with microalbuminuria compared with the normoalbuminuric group ( p<0.001). Positive correlations were found between kallistatin and disease duration, fasting blood glucose, HbA1c, triglycerides, total cholesterol, hs-CRP, UACR and CIMT ( p<0.05). A kallistatin cut-off value at 6.1 ng/mL could differentiate patients with and without microvascular complications, with a sensitivity of 96.87% and specificity of 93.75%. Increased kallistatin levels in type 1 diabetes and its relation with CIMT may reflect vascular dysfunction and suggest a link between micro- and macro-angiopathy.

Kallistatin, a new and reliable biomarker for the diagnosis of liver cirrhosis

Kallistatin, which protects organs and cells against inflammation, fibrosis and oxidative stress, is mainly synthesized and secreted in liver. However, its relationship to human liver disease remains unclear. The purpose of this study was to explore the relationship between serum kallistatin and clinical evidence of both cirrhosis and hepatocellular carcinoma (HCC), and to determine if serum kallistatin levels could be used as a diagnostic indicator of hepatic health status, especially human liver cirrhosis (LC). Our cohort consisted of 115 patients with clinically proven liver fibrosis (LF), LC, or HCC by liver biopsies, and 31 healthy controls (CON). Serum kallistatin levels were quantified by ELISA. Results of the present study demonstrated that irrespective of the underlying etiology, serum kallistatin levels were significantly lower in the LF/LC group when compared with the CON group. A decrease in serum kallistatin levels appeared to reflect the extent of cirrhosis, with the lowest levels associated with higher grades of cirrhosis. Patients with LC had a noticeable correlation between serum kallistatin levels and other serum biochemical indicators. The area under the curve (AUC) for LC, viral liver cirrhosis (VLC) and alcoholic liver cirrhosis (ALC) was 0.845, 0.757 and 0.931, respectively. In conclusion, our findings demonstrated that kallistatin, a plasma protein produced by the liver, can be a useful and reliable diagnostic indicator of hepatic health status, especially for LC.

Exploring the human plasma proteome for humoral mediators of remote ischemic preconditioning--a word of caution

Despite major advances in early revascularization techniques, cardiovascular diseases are still the leading cause of death worldwide, and myocardial infarctions contribute heavily to this. Over the past decades, it has become apparent that reperfusion of blood to a previously ischemic area of the heart causes damage in and of itself, and that this ischemia reperfusion induced injury can be reduced by up to 50% by mechanical manipulation of the blood flow to the heart. The recent discovery of remote ischemic preconditioning (RIPC) provides a non-invasive approach of inducing this cardioprotection at a distance. Finding its endogenous mediators and their operative mode is an important step toward increasing the ischemic tolerance. The release of humoral factor(s) upon RIPC was recently demonstrated and several candidate proteins were published as possible mediators of the cardioprotection. Before clinical applicability, these potential biomarkers and their efficiency must be validated, a task made challenging by the large heterogeneity in reported data and results. Here, in an attempt to reproduce and provide more experimental data on these mediators, we conducted an unbiased in-depth analysis of the human plasma proteome before and after RIPC. From the 68 protein markers reported in the literature, only 28 could be mapped to manually reviewed (Swiss-Prot) protein sequences. 23 of them were monitored in our untargeted experiment. However, their significant regulation could not be reproducibly estimated. In fact, among the 394 plasma proteins we accurately quantified, no significant regulation could be confidently and reproducibly assessed. This indicates that it is difficult to both monitor and reproduce published data from experiments exploring for RIPC induced plasma proteomic regulations, and suggests that further work should be directed towards small humoral factors. To simplify this task, we made our proteomic dataset available via ProteomeXchange, where scientists can mine for novel potential targets.

Novel role of kallistatin in vascular repair by promoting mobility, viability, and function of endothelial progenitor cells

Background

Kallistatin exerts pleiotropic activities in inhibiting inflammation, apoptosis, and oxidative stress in endothelial cells. Because endothelial progenitor cells (EPCs) play a significant role in vascular repair, we investigated whether kallistatin contributes to vascular regeneration by enhancing EPC migration and function.

Methods and Results

We examined the effect of endogenous kallistatin on circulating EPCs in a rat model of vascular injury and the mechanisms of kallistatin on EPC mobility and function in vitro. In deoxycorticosterone acetate–salt hypertensive rats, we found that kallistatin depletion augmented glomerular endothelial cell loss and diminished circulating EPC number, whereas kallistatin gene delivery increased EPC levels. In cultured EPCs, kallistatin significantly reduced tumor necrosis factor‐α–induced apoptosis and caspase‐3 activity, but kallistatin's effects were blocked by phosphoinositide 3‐kinase inhibitor (LY294002) and nitric oxide (NO) synthase inhibitor (l‐NAME). Kallistatin stimulated the proliferation, migration, adhesion and tube formation of EPCs; however, kallistatin's actions were abolished by LY294002, l‐NAME, endothelial NO synthase–small interfering RNA, constitutively active glycogen synthase kinase‐3β, or vascular endothelial growth factor antibody. Kallistatin also increased Akt, glycogen synthase kinase‐3β, and endothelial NO synthase phosphorylation; endothelial NO synthase, vascular endothelial growth factor, and matrix metalloproteinase‐2 synthesis and activity; and NO and vascular endothelial growth factor levels. Kallistatin's actions on phosphoinositide 3‐kinase–Akt signaling were blocked by LY294002, l‐NAME, and anti–vascular endothelial growth factor antibody.

Conclusions

Endogenous kallistatin plays a novel role in protection against vascular injury in hypertensive rats by promoting the mobility, viability, and vasculogenic capacity of EPCs via enhancing NO and vascular endothelial growth factor levels through activation of phosphoinositide 3‐kinase–Akt signaling. Kallistatin therapy may be a promising approach in the treatment of vascular diseases.

Human kallistatin administration reduces organ injury and improves survival in a mouse model of polymicrobial sepsis

Kallistatin, a plasma protein, has been shown to exert multi-factorial functions including inhibition of inflammation, oxidative stress and apoptosis in animal models and cultured cells. Kallistatin levels are reduced in patients with sepsis and in lipopolysaccharide (LPS)-induced septic mice. Moreover, transgenic mice expressing kallistatin are more resistant to LPS-induced mortality. Here, we investigated the effects of human kallistatin on organ injury and survival in a mouse model of polymicrobial sepsis. In this study, mice were injected intravenously with recombinant kallistatin (KS3, 3 mg/kg; or KS10, 10 mg/kg body weight) and then rendered septic by caecal ligation and puncture 30 min later. Kallistatin administration resulted in a > 10-fold reduction of peritoneal bacterial counts, and significantly decreased serum tumour necrosis factor-α, interleukin-6 and high mobility group box-1 (HMGB1) levels. Kallistatin also inhibited HMGB1 and toll-like receptor-4 gene expression in the lung and kidney. Administration of kallistatin attenuated renal damage and decreased blood urea nitrogen and serum creatinine levels, but increased endothelial nitric oxide synthase and nitric oxide levels in the kidney. In cultured endothelial cells, human kallistatin via its heparin-binding site inhibited HMGB1-induced nuclear factor-κB activation and inflammatory gene expression. Moreover, kallistatin significantly reduced apoptosis and caspase-3 activity in the spleen. Furthermore, kallistatin treatment markedly improved the survival of septic mice by 23% (KS3) and 41% (KS10). These results indicate that kallistatin is a unique protecting agent in sepsis-induced organ damage and mortality by inhibiting inflammation and apoptosis, as well as enhancing bacterial clearance in a mouse model of polymicrobial sepsis.

Protection effect of kallistatin on carbon tetrachloride-induced liver fibrosis in rats via antioxidative stress

Prolonged inflammation and oxidative stress are emerging as key causes of pathological wound healing and the development of liver fibrosis. We have investigated the effects of recombinant human kallistatin, produced in Pichia. pastoris, on preventing carbon tetrachloride (CCl₄)-induced liver fibrosis in rats. Daily administration of kallistatin prevented development of CCl₄-induced liver fibrosis, which was evidenced by histological study. In all kallistatin treated rats, activation of hepatic stellate cells (HSC) as assessed by s-smooth muscle actin staining was attenuated, TGF- β1 expression was inhibited, class I serum biomarkers associated with the process of fibrogenesis, such as hyaluronic acid, laminin, and procollagen III, were lowered, compared with that in the model control group. Furthermore, residual hepatic functional reserve was improved by kallistatin treatment. CCl₄ induced elevation of malondialdehyde level and reduced superoxide dismutase activity in the liver, while kallistatin reduced these oxidative parameters. We also investigated the effects of kallistatin on rat primary HSC and LX-2, the human HSC cell line. Kallistatin scavenged H₂O₂-induced ROS in the LX-2 cells, and suppressed the activation of primary HSC. These results suggest recombinant human kallistatin might be a promising drug candidate for therapeutic intervention of liver fibrosis.

Patent Highlights

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Ischemia/reperfusion injury: effect of simultaneous inhibition of plasma cascade systems versus specific complement inhibition

Ischemia/reperfusion injury (IRI) may occur from ischemia due to thrombotic occlusion, trauma or surgical interventions, including transplantation, with subsequent reestablishment of circulation. Time-dependent molecular and structural changes result from the deprivation of blood and oxygen in the affected tissue during ischemia. Upon restoration of blood flow a multifaceted network of plasma cascades is activated, including the complement-, coagulation-, kinin-, and fibrinolytic system, which plays a major role in the reperfusion-triggered inflammatory process. The plasma cascade systems are therefore promising therapeutic targets for attenuation of IRI. Earlier studies showed beneficial effects through inhibition of the complement system using specific complement inhibitors. However, pivotal roles in IRI are also attributed to other cascades. This raises the question, whether drugs, such as C1 esterase inhibitor, which regulate more than one cascade at a time, have a higher therapeutic potential. The present review discusses different therapeutic approaches ranging from specific complement inhibition to simultaneous inhibition of plasma cascade systems for reduction of IRI, gives an overview of the plasma cascade systems in IRI as well as highlights recent findings in this field.