Treatment with activated protein C (aPC) is protective during the development of myocardial fibrosis: an angiotensin II infusion model in mice

Thrombosis and Inflammation—A Dynamic Interplay and the Role of Glycosaminoglycans and Activated Protein C

Hemostasis, thrombosis, and inflammation are tightly interconnected processes which may give rise to thrombo-inflammation, involved in infectious and non-infectious acute and chronic diseases, including cardiovascular diseases (CVD). Traditionally, due to its hemostatic role, blood coagulation is isolated from the inflammation, and its critical contribution in the progressing CVD is underrated, until the full occlusion of a critical vessel occurs. Underlying vascular injury exposes extracellular matrix to deposit platelets and inflammatory cells. Platelets being key effector cells, bridge all the three key processes (hemostasis, thrombosis, and inflammation) associated with thrombo-inflammation. Under physiological conditions, platelets remain in an inert state despite the proximity to the endothelium and other cells which are decorated with glycosaminoglycan (GAG)-rich glycocalyx (GAGs). A pathological insult to the endothelium results in an imbalanced blood coagulation system hallmarked by increased thrombin generation due to losses of anticoagulant and cytoprotective mechanisms, i.e., the endothelial GAGs enhancing antithrombin, tissue factor pathway-inhibitor (TFPI) and thrombomodulin-protein C system. Moreover, the loss of GAGs promotes the release of mediators, such as von Willebrand factor (VWF), platelet factor 4 (PF4), and P-selectin, both locally on vascular surfaces and to circulation, further enhancing the adhesion of platelets to the affected sites. Platelet-neutrophil interaction and formation of neutrophil extracellular traps foster thrombo-inflammatory mechanisms exacerbating the cardiovascular disease course. Therefore, therapies which not only target the clotting mechanisms but simultaneously or independently convey potent cytoprotective effects hemming the inflammatory mechanisms are expected to provide clinical benefits. In this regard, we review the cytoprotective protease activated protein C (aPC) and its strong anti-inflammatory effects thereby preventing the ensuing thrombotic complications in CVD. Furthermore, restoring GAG-like vasculo-protection, such as providing heparin-proteoglycan mimetics to improve regulation of platelet and coagulation activity and to suppress of endothelial perturbance and leukocyte-derived pro-inflammatory cytokines, may provide a path to alleviate thrombo-inflammatory disorders in the future. The vascular tissue-modeled heparin proteoglycan mimic, antiplatelet and anticoagulant compound (APAC), dual antiplatelet and anticoagulant, is an injury-targeting and locally acting arterial antithrombotic which downplays collagen- and thrombin-induced and complement-induced activation and protects from organ injury.

Activated Protein C Ameliorates Diabetic Cardiomyopathy via Modulating OTUB1/YB-1/MEF2B Axis

Aims: The pathogenesis of diabetic cardiomyopathy (DCM) is complex and the detailed mechanism remains unclear. Coagulation protease activated Protein C (aPC) has been reported to have a protective effect in diabetic microvascular disease. Here, we investigated whether aPC could play a protective role in the occurrence and development of major diabetic complication DCM, and its underlying molecular mechanism.

Methods and Results: In a mouse model of streptozotocin (STZ) induced DCM, endogenous aPC levels were reduced. Restoring aPC levels by exogenous administration of zymogen protein C (PC) improved cardiac function of diabetic mice measured by echocardiography and invasive hemodynamics. The cytoprotective effect of aPC in DCM is mediated by transcription factor Y-box binding protein-1 (YB-1). Mechanistically, MEF2B lies downstream of YB-1 and YB-1/MEF2B interaction restrains deleterious MEF2B promoter activity in DCM. The regulation of YB-1 on MEF2B transcription was analyzed by dual-luciferase and chromatin immunoprecipitation assays. In diabetic mice, aPC ameliorated YB-1 degradation via reducing its K48 ubiquitination through deubiquitinating enzyme otubain-1 (OTUB1) and improving the interaction between YB-1 and OTUB1. Using specific agonists and blocking antibodies, PAR1 and EPCR were identified as crucial receptors for aPC's dependent cytoprotective signaling.

Conclusion: These data identify that the cytoprotective aPC signaling via PAR1/EPCR maintains YB-1 levels by preventing the ubiquitination and subsequent proteasomal degradation of YB-1 via OTUB1. By suppressing MEF2B transcription, YB-1 can protect against DCM. Collectively, the current study uncovered the important role of OTUB1/YB-1/MEF2B axis in DCM and targeting this pathway might offer a new therapeutic strategy for DCM.

Translational Perspective: DCM is emerging at epidemic rate recently and the underlying mechanism remains unclear. This study explored the protective cell signaling mechanisms of aPC in mouse models of DCM. As a former FDA approved anti-sepsis drug, aPC along with its derivatives can be applied from bench to bed and can be explored as a new strategy for personalized treatment for DCM. Mechanistically, OTUB1/YB-1/MEF2B axis plays a critical role in the occurrence and development of DCM and offers a potential avenue for therapeutic targeting of DCM.

Positron Emission Tomography Techniques to Measure Active Inflammation, Fibrosis and Angiogenesis: Potential for Non-invasive Imaging of Hypertensive Heart Failure

Heart failure, which is responsible for a high number of deaths worldwide, can develop due to chronic hypertension. Heart failure can involve and progress through several different pathways, including: fibrosis, inflammation, and angiogenesis. Early and specific detection of changes in the myocardium during the transition to heart failure can be made via the use of molecular imaging techniques, including positron emission tomography (PET). Traditional cardiovascular PET techniques, such as myocardial perfusion imaging and sympathetic innervation imaging, have been established at the clinical level but are often lacking in pathway and target specificity that is important for assessment of heart failure. Therefore, there is a need to identify new PET imaging markers of inflammation, fibrosis and angiogenesis that could aid diagnosis, staging and treatment of hypertensive heart failure. This review will provide an overview of key mechanisms underlying hypertensive heart failure and will present the latest developments in PET probes for detection of cardiovascular inflammation, fibrosis and angiogenesis. Currently, selective PET probes for detection of angiogenesis remain elusive but promising PET probes for specific targeting of inflammation and fibrosis are rapidly progressing into clinical use.

Cell biology of activated protein C

PURPOSE OF REVIEW

The serine protease activated protein C (aPC) was initially characterized as an endogenous anticoagulant, but in addition conveys anti-inflammatory, barrier-protective, and pro cell-survival functions. Its endogenous anticoagulant function hampered the successful and continuous implantation of aPC as a therapeutic agent in septic patients. However, it became increasingly apparent that aPC controls cellular function largely independent of its anticoagulant effects through cell-specific and context-specific receptor complexes and intracellular signaling pathways. The purpose of this review is to outline the mechanisms of aPC-dependent cell signaling and its intracellular molecular targets.

RECENT FINDINGS

With the advent of new therapeutic agents either modulating directly and specifically the activity of coagulation proteases or interfering with protease-activated receptor signaling a better understanding not only of the receptor mechanisms but also of the intracellular signaling mechanisms controlled by aPC in a disease-specific and context-specific fashion, is required to tailor new therapeutic approaches based on aPC's anti-inflammatory, barrier-protective, and pro cell-survival functions.

SUMMARY

This review summarizes recent insights into the intracellular signaling pathways controlled by aPC in a cell-specific and context-specific fashion. We focus on aPC-mediated barrier protection, inhibition of inflammation, and cytoprotecting within this review.

Type of Anticoagulant Used After Total Knee Arthroplasty Affects the Rate of Knee Manipulation for Postoperative Stiffness

BACKGROUND

The aim of this study was to perform a population-level analysis on the effect of different types of anticoagulation on postoperative stiffness after total knee replacement, requiring manipulation under anesthesia. We hypothesized that patients receiving warfarin would have a higher rate of manipulation under anesthesia compared with patients receiving low-molecular-weight heparin. We also hypothesized that aspirin, direct factor Xa inhibitors, and fondaparinux would have no effect on the rate of manipulation under anesthesia.

METHODS

Using the PearlDiver patient database, we analyzed 32,320 patients who underwent a primary unilateral total knee replacement from 2007 to 2015. Patients were included if they filled a prescription for anticoagulation medication within 2 days of their discharge and were excluded if they were taking a prescription anticoagulation medication (except for aspirin) in the 3 months before total knee replacement. The primary outcome was manipulation under anesthesia performed within 6 months after a primary total knee replacement.

RESULTS

The most commonly prescribed postoperative anticoagulation was warfarin (38.0%), followed by low-molecular-weight heparin (33.8%). There were 1,178 patients (3.64%) who underwent manipulation under anesthesia within 6 months of total knee replacement. In multivariable analysis using low-molecular-weight heparin as a comparison group and accounting for age, sex, comorbidities, and length of stay, there was a significant increase in the risk of manipulation under anesthesia for patients who received warfarin (hazard ratio [HR], 1.17 [95% confidence interval (CI), 1.01 to 1.36]; p = 0.032), direct factor Xa inhibitors (HR, 1.42 [95% CI, 1.20 to 1.66]; p < 0.001), or fondaparinux (HR, 1.33 [95% CI, 1.01 to 1.72]; p = 0.038). Although patients who received aspirin had the same risk estimate as patients who received warfarin, there was not a significantly increased risk of manipulation under anesthesia in patients who received aspirin compared with low-molecular-weight heparin (HR, 1.17 [95% CI, 0.72 to 1.80]; p = 0.493).

CONCLUSIONS

We found an increased rate of manipulation under anesthesia after total knee replacement in patients who received oral anticoagulants including warfarin, direct factor Xa inhibitors, and fondaparinux, in comparison with patients who received aspirin or low-molecular-weight heparin. We recommend that patients receiving oral anticoagulants after total knee replacement should be counseled about associated stiffness. Furthermore, surgeons should take these data into account when selecting thromboprophylaxis for patients after total knee replacement.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Activated protein C protects against pressure overload-induced hypertrophy through AMPK signaling

We found that the anticoagulant plasma protease, activated protein C (APC), stimulates the energy sensor kinase, AMPK, in the stressed heart by activating protease-activated receptor 1 (PAR1) on cardiomyocytes. Wild-type (WT) and AMPK-kinase dead (KD) transgenic mice were subjected to transverse aortic constriction (TAC) surgery. The results demonstrated that while no phenotypic differences can be observed between WT and AMPK-KD mice under normal physiological conditions, AMPK-KD mice exhibit significantly larger hearts after 4 weeks of TAC surgery. Analysis by echocardiography suggested that the impairment in the cardiac function of AMPK-KD hearts is significantly greater than that of WT hearts. Immunohistochemical staining revealed increased macrophage infiltration and ROS generation in AMPK-KD hearts after 4 weeks of TAC surgery. Immunoblotting results demonstrated that the redox markers, pShc⁶⁶, 4-hydroxynonenal and ERK, were all up-regulated at a higher extent in AMPK-KD hearts after 4 weeks of TAC surgery. Administration of APC-WT and the signaling selective APC-2Cys mutant, but not the anticoagulant selective APC-E170A mutant, significantly attenuated pressure overload-induced hypertrophy and fibrosis. Macrophage infiltration and pShc⁶⁶ activation caused by pressure overload were also inhibited by APC and APC-2Cys but not by APC-E170A. Therefore, the cardiac AMPK protects against pressure overload-induced hypertrophy and the signaling selective APC-2Cys may have therapeutic potential for treating hypertension-related hypertrophy without increasing the risk of bleeding.

Cytoprotective activated protein C averts Nlrp3 inflammasome-induced ischemia-reperfusion injury via mTORC1 inhibition

Cytoprotection by activated protein C (aPC) after ischemia-reperfusion injury (IRI) is associated with apoptosis inhibition. However, IRI is hallmarked by inflammation, and hence, cell-death forms disjunct from immunologically silent apoptosis are, in theory, more likely to be relevant. Because pyroptosis (ie, cell death resulting from inflammasome activation) is typically observed in IRI, we speculated that aPC ameliorates IRI by inhibiting inflammasome activation. Here we analyzed the impact of aPC on inflammasome activity in myocardial and renal IRIs. aPC treatment before or after myocardial IRI reduced infarct size and Nlrp3 inflammasome activation in mice. Kinetic in vivo analyses revealed that Nlrp3 inflammasome activation preceded myocardial injury and apoptosis, corroborating a pathogenic role of the Nlrp3 inflammasome. The constitutively active Nlrp3^A350V mutation abolished the protective effect of aPC, demonstrating that Nlrp3 suppression is required for aPC-mediated protection from IRI. In vitro aPC inhibited inflammasome activation in macrophages, cardiomyocytes, and cardiac fibroblasts via proteinase-activated receptor 1 (PAR-1) and mammalian target of rapamycin complex 1 (mTORC1) signaling. Accordingly, inhibiting PAR-1 signaling, but not the anticoagulant properties of aPC, abolished the ability of aPC to restrict Nlrp3 inflammasome activity and tissue damage in myocardial IRI. Targeting biased PAR-1 signaling via parmodulin-2 restricted mTORC1 and Nlrp3 inflammasome activation and limited myocardial IRI as efficiently as aPC. The relevance of aPC-mediated Nlrp3 inflammasome suppression after IRI was corroborated in renal IRI, where the tissue protective effect of aPC was likewise dependent on Nlrp3 inflammasome suppression. These studies reveal that aPC protects from IRI by restricting mTORC1-dependent inflammasome activation and that mimicking biased aPC PAR-1 signaling using parmodulins may be a feasible therapeutic approach to combat IRI.

Associations between blood coagulation markers, NT-proBNP and risk of incident heart failure in older men: The British Regional Heart Study

AIMS

Chronic heart failure (HF) is associated with activation of blood coagulation but there is a lack of prospective studies on the association between coagulation markers and incident HF in general populations. We have examined the association between the coagulation markers fibrinogen, von Willebrand Factor (VWF), Factors VII, VIII and IX, D-dimer, activated protein C (APC) and activated partial thromboplastin time (aPPT) with NT-proBNP and incident HF.

METHODS AND RESULTS

Prospective study of 3366 men aged 60-79years with no prevalent HF, myocardial infarction or venous thrombosis and who were not on warfarin, followed up for a mean period of 13years, in whom there were 203 incident HF cases. D-dimer and vWF were significantly and positively associated with NT-proBNP (a marker of neurohormonal activation and left ventricular wall stress) even after adjustment for age, lifestyle characteristics, renal dysfunction, atrial fibrillation (AF) and inflammation (C-reactive protein). By contrast Factor VII related inversely to AF and NT-proBNP even after adjustment. No association was seen however between the coagulation markers VWF, Factor VII, Factor VIII, Factor IX, D-dimer, APC resistance or aPPT with incident HF in age-adjusted analyses. Fibrinogen was associated with incident HF but this was abolished after adjustment for HF risk factors.

CONCLUSION

Coagulation activity is not associated with the development of HF. However D-dimer and vWF were significantly associated with NT-proBNP, suggesting that increased coagulation activity is related to cardiac stress; and the increased coagulation seen in HF patients may in part be a consequence of neurohormonal activation.

Recombinant Thrombomodulin (Solulin) Ameliorates Early Intestinal Radiation Toxicity in a Preclinical Rat Model

Intestinal radiation toxicity occurs during and after abdominopelvic radiotherapy. Endothelial cells play a significant role in modulating radiation-induced intestinal damage. We demonstrated that the endothelial cell surface receptor thrombomodulin (TM), a protein with anticoagulant, anti-inflammatory and antioxidant properties, mitigates radiation-induced lethality in mice. The goal of this study was to determine whether recombinant TM (Solulin) can protect the intestine from toxicity in a clinically relevant rat model. A 4 cm loop of rat small bowel was exposed to fractionated 5 Gy X radiation for 9 consecutive days. The animals were randomly assigned to receive daily subcutaneous injections of vehicle or Solulin (3 mg/kg/day or 10 mg/kg/day) for 27 days starting 4 days before irradiation. Early intestinal injury was assessed two weeks after irradiation by quantitative histology, morphometry, immunohistochemistry and luminol bioluminescence imaging. Solulin treatment significantly ameliorated intestinal radiation injury, made evident by a decrease in myeloperoxidase (MPO) activity, transforming growth factor beta (TGF-β) immunoreactivity, collagen-I deposition, radiation injury score (RIS) and intestinal serosal thickening. These findings indicate the need for further development of Solulin as a prophylactic and/or therapeutic agent to mitigate radiation-induced intestinal damage.

Extracellular Matrix Reorganization During Wound Healing and Its Impact on Abnormal Scarring

Significance: When a cutaneous injury occurs, the wound heals via a dynamic series of physiological events, including coagulation, granulation tissue formation, re-epithelialization, and extracellular matrix (ECM) remodeling. The final stage can take many months, yet the new ECM forms a scar that never achieves the flexibility or strength of the original tissue. In certain circumstances, the normal scar is replaced by pathological fibrotic tissue, which results in hypertrophic or keloid scars. These scars cause significant morbidity through physical dysfunction and psychological stress. Recent Advances and Critical Issues: The cutaneous ECM comprises a complex assortment of proteins that was traditionally thought to simply provide structural integrity and scaffolding characteristics. However, recent findings show that the ECM has multiple functions, including, storage and delivery of growth factors and cytokines, tissue repair and various physiological functions. Abnormal ECM reconstruction during wound healing contributes to the formation of hypertrophic and keloid scars. Whereas adult wounds heal with scarring, the developing foetus has the ability to heal wounds in a scarless fashion by regenerating skin and restoring the normal ECM architecture, strength, and function. Recent studies show that the lack of inflammation in fetal wounds contributes to this perfect healing. Future Directions: Better understanding of the exact roles of ECM components in scarring will allow us to produce therapeutic agents to prevent hypertrophic and keloid scars. This review will focus on the components of the ECM and their role in both physiological and pathological (hypertrophic and keloid) cutaneous scar formation.

RAGE controls activation and anti-inflammatory signalling of protein C

AIMS

The receptor for advanced glycation endproducts, RAGE, is a multiligand receptor and NF-κB activator leading to perpetuation of inflammation. We investigated whether and how RAGE is involved in mediation of anti-inflammatory properties of protein C.

METHODS AND RESULTS

We analyzed the effect of protein C on leukocyte adhesion and transmigration in WT- and RAGE-deficient mice using intravital microscopy of cremaster muscle venules during trauma- and TNFα-induced inflammation. Both, protein C (PC, Ceprotin, 100 U/kg) and activated protein C (aPC, 24 µg/kg/h) treatment significantly inhibited leukocyte adhesion in WT mice in these inflammation models. The impaired leukocyte adhesion after trauma-induced inflammation in RAGE knockout mice could not be further reduced by PC and aPC. After TNFα-stimulation, however, aPC but not PC treatment effectively blocked leukocyte adhesion in these mice. Consequently, we asked whether RAGE is involved in PC activation. Since RAGE-deficient mice and endothelial cells showed insufficient PC activation, and since thrombomodulin (TM) and endothelial protein C receptor (EPCR) are reduced on the mRNA and protein level in RAGE deficient endothelial cells, an involvement of RAGE in TM-EPCR-dependent PC activation is likely. Moreover, TNFα-induced activation of MAPK and upregulation of ICAM-1 and VCAM-1 are reduced both in response to aPC treatment and in the absence of RAGE. Thus, there seems to be interplay of the RAGE and the PC pathway in inflammation.

CONCLUSION

RAGE controls anti-inflammatory properties and activation of PC, which might involve EPCR and TM.

Effects of exogenous recombinant APC in mouse models of ischemia reperfusion injury and of atherosclerosis

Activated protein C (APC) is a serine protease that has both anticoagulant and cytoprotective properties. The cytoprotective effects are protease activated receptor 1 (PAR-1) and endothelial protein C receptor (EPCR) dependent and likely underlie protective effects of APC in animal models of sepsis, myocardial infarction and ischemic stroke. S360A-(A)PC, a variant (A)PC that has no catalytic activity, binds EPCR and shifts pro-inflammatory signaling of the thrombin-PAR-1 complex to anti-inflammatory signaling. In this study we investigated effects of human (h)wt-PC, hS360A-PC, hwt-APC and hS360A-APC in acute (mouse model of acute myocardial ischemia/reperfusion (I/R) injury) and chronic inflammation (apoE-/- mouse model of atherosclerosis). All h(A)PC variants significantly reduced myocardial infarct area (p<0.05) following I/R injury. IL-6 levels in heart homogenates did not differ significantly between sham, placebo and treatment groups in I/R injury. None of the h(A)PC variants decreased number and size of atherosclerotic plaques in apoE-/- mice. Only hS360A-APC slightly affected phenotype of plaques. IL-6 levels in plasma were significantly (p<0.001) decreased in hwt-APC and hS360A-PC treated mice. In the last group levels of monocyte chemotactic protein 1 (MCP-1) were significantly increased (p<0.05). In this study we show that both hwt and hS360A-(A)PC protect against acute myocardial I/R injury, which implies that protection from I/R injury is independent of the proteolytic activity of APC. However, in the chronic atherosclerosis model hwt and hS360-(A)PC had only minor effects. When the dose, species and mode of (A)PC administration will be adjusted, we believe that (A)PC will have potential to influence development of chronic inflammation as occurring during atherosclerosis as well.