The Role of T Cells Reactive to the Cathelicidin Antimicrobial Peptide LL-37 in Acute Coronary Syndrome and Plaque Calcification

Cathelicidin peptide LL-37: A multifunctional peptide involved in heart disease

Heart disease is a common human disease with high morbidity and mortality. Timely and effective prevention and treatment is an urgent clinical problem. The pathogenesis of heart disease is complex and diverse, involving hypertension, diabetes, atherosclerosis, drug toxicity, thrombosis, infection and other aspects. LL-37, an endogenous peptide, is well known for its antimicrobial properties. In recent years, LL-37 has been found to have a variety of biological functions, including its role in the regulation of atherosclerosis, thrombosis, inflammatory responses, and cardiac hypertrophy. Engineered LL-37-related peptides were developed and proved to regulate the development of disease, which revealed its potential clinical application. A comprehensive review and summary of LL-37 is presented to clarify its role in heart disease and to provide a reference and direction for future research.

Neutrophil Biomarkers Can Predict Cardiotoxicity of Anthracyclines in Breast Cancer

Doxorubicin (DOX), a commonly used anticancer agent, causes cardiotoxicity that begins with the first dose and may progress to heart failure years after treatment. An inflammatory response associated with neutrophil recruitment has been recognized as a mechanism of DOX-induced cardiotoxicity. This study aimed to validate mRNA expression of the previously identified biomarkers of DOX-induced cardiotoxicity, PGLYRP1, CAMP, MMP9, and CEACAM8, and to assay their protein expression in the peripheral blood of breast cancer patients. Blood samples from 40 breast cancer patients treated with DOX-based chemotherapy were collected before and after the first chemotherapy cycle and > 2 years after treatment. The protein and gene expression of PGLYRP1/Tag7, CAMP/LL37, MMP9/gelatinase B, and CEACAM8/CD66b were determined using ELISA and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic value of each candidate biomarker. Patients with cardiotoxicity (n = 20) had significantly elevated levels of PGLYRP1, CAMP, MMP9, and CEACAM8 at baseline, after the first dose of DOX-based chemotherapy, and at > 2 years after treatment relative to patients without cardiotoxicity (n = 20). The first dose of DOX induced significantly higher levels of all examined biomarkers in both groups of patients. At > 2 years post treatment, the levels of all but MMP9 dropped below the baseline. There was a good correlation between the expression of mRNA and the target proteins. We demonstrate that circulating levels of PGLYRP1, CAMP, MMP9, and CEACAM8 can predict the cardiotoxicity of DOX. This novel finding may be of value in the early identification of patients at risk for cardiotoxicity.

C5a-C5aR1 induces endoplasmic reticulum stress to accelerate vascular calcification via PERK-eIF2α-ATF4-CREB3L1 pathway

AIMS

Vascular calcification (VC) predicts the morbidity and mortality in cardiovascular diseases. Vascular smooth muscle cells (VSMCs) osteogenic transdifferentiation is the crucial pathological basis for VC. To date, the molecular pathogenesis is still largely unclear. Notably, C5a-C5aR1 contributes to the development of cardiovascular diseases, and its closely related to physiological bone mineralization which is similar to VSMCs osteogenic transdifferentiation. However, the role and underlying mechanisms of C5a-C5aR1 in VC remain unexplored.

METHODS AND RESULTS

A cross-sectional clinical study was utilized to examine the association between C5a and VC. Chronic kidney diseases mice and calcifying VSMCs models were established to investigate the effect of C5a-C5aR1 in VC, evaluated by changes in calcium deposition and osteogenic markers. The cross-sectional study identified that high level of C5a was associated with increased risk of VC. C5a dose-responsively accelerated VSMCs osteogenic transdifferentiation accompanying with increased the expression of C5aR1. Meanwhile, the antagonists of C5aR1, PMX 53, reduced calcium deposition, and osteogenic transdifferentiation both in vivo and in vitro. Mechanistically, C5a-C5aR1 induced endoplasmic reticulum (ER) stress and then activated PERK-eIF2α-ATF4 pathway to accelerated VSMCs osteogenic transdifferentiation. In addition, cAMP-response element-binding protein 3-like 1 (CREB3L1) was a key downstream mediator of PERK-eIF2α-ATF4 pathway which accelerated VSMCs osteogenic transdifferentiation by promoting the expression of COL1α1.

CONCLUSIONS

High level of C5a was associated with increased risk of VC, and it accelerated VC by activating the receptor C5aR1. PERK-eIF2α-ATF4-CREB3L1 pathway of ER stress was activated by C5a-C5aR1, hence promoting VSMCs osteogenic transdifferentiation. Targeting C5 or C5aR1 may be an appealing therapeutic target for VC.

Cathelicidin (LL-37) causes expression of inflammatory factors in coronary artery endothelial cells of Kawasaki disease by activating TLR4-NF-κB-NLRP3 signaling

BACKGROUND

Kawasaki disease (KD) is a type of vasculitis with an unidentified etiology. Cathelicidin (LL-37) may be involved in the development of the KD process; therefore, further research to investigate the molecular mechanism of LL-37 involvement in KD is warranted.

METHODS

Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, NLRP3, and LL-37 in the sera of healthy subjects, children with KD, and children with pneumonia. Subsequently, human recombinant LL-37 or/and toll-like receptors 4 (TLR4)-specific inhibitor TAK-242 stimulated human coronary artery endothelial cells (HCAECs), CCK-8 was used to detect cell proliferation, flow cytometry to detect apoptosis, transmission electron microscopy to observe cytoskeletal changes, Transwell to measure cell migration ability, ELISA to detect inflammatory factor levels, Western blot analysis to analyze protein levels of toll-like receptors 4 (TLR4) and NF-κB p-65, and quantitative real-time polymerase chain reaction (qRT-PCR) to determine LL-37, NLRP3 mRNA levels.

RESULTS

In this study, we found that the level of LL-37 was highly expressed in the serum of children with KD, and after LL-37 stimulation, apoptosis was significantly increased in HCAECs, and the expression levels of TLR4, NLRP3 and inflammatory factors in cells were significantly enhanced. Intervention with the TLR4-specific inhibitor TAK-242 significantly alleviated the LL-37 effects on cellular inflammation, TLR4, NLRP3 promotion effect.

CONCLUSIONS

Our data suggest that LL-37 induces an inflammatory response in KD coronary endothelial cells via TLR4-NF-κB-NLRP3, providing a potential target for the treatment of KD.

Role of antimicrobial peptide cathelicidin in thrombosis and thromboinflammation

Thrombosis is a frequent cause of cardiovascular mortality and hospitalization. Current antithrombotic strategies, however, target both thrombosis and physiological hemostasis and thereby increase bleeding risk. In recent years the pathophysiological understanding of thrombus formation has significantly advanced and inflammation has become a crucial element. Neutrophils as most frequent immune cells in the blood and their released mediators play a key role herein. Neutrophil-derived cathelicidin next to its strong antimicrobial properties has also shown to modulates thrombosis and thus presents a potential therapeutic target. In this article we review direct and indirect (immune- and endothelial cell-mediated) effects of cathelicidin on platelets and the coagulation system. Further we discuss its implications for large vessel thrombosis and consecutive thromboinflammation as well as immunothrombosis in sepsis and COVID-19 and give an outlook for potential therapeutic prospects.

New insight of complement system in the process of vascular calcification

The complement system defences against pathogenic microbes and modulates immune homeostasis by interacting with the innate and adaptive immune systems. Dysregulation, impairment or inadvertent activation of complement system contributes to the pathogenesis of some autoimmune diseases and cardiovascular diseases (CVD). Vascular calcification is the pivotal pathological basis of CVD, and contributes to the high morbidity and mortality of CVD. Increasing evidences indicate that the complement system plays a key role in chronic kidney diseases, atherosclerosis, diabetes mellitus and aging-related diseases, which are closely related with vascular calcification. However, the effect of complement system on vascular calcification is still unclear. In this review, we summarize current evidences about the activation of complement system in vascular calcification. We also describe the complex network of complement system and vascular smooth muscle cells osteogenic transdifferentiation, systemic inflammation, endoplasmic reticulum stress, extracellular matrix remodelling, oxidative stress, apoptosis in vascular calcification. Hence, providing a better understanding of the potential relationship between complement system and vascular calcification, so as to provide a direction for slowing the progression of this burgeoning health concern.

Impaired tolerance to the autoantigen LL-37 in acute coronary syndrome

Background

LL-37 is the only member of the cathelicidin family of antimicrobial peptides in humans and is an autoantigen in several autoimmune diseases and in acute coronary syndrome (ACS). In this report, we profiled the specific T cell response to the autoimmune self-antigen LL-37 and investigated the factors modulating the response in peripheral blood mononuclear cells (PBMCs) of healthy subjects and ACS patients.

Methods and results

The activation induced marker (AIM) assay demonstrated differential T cell profiles characterized by the persistence of CD134 and CD137, markers that impair tolerance and promote immune effector and memory response, in ACS compared to Controls. Specifically, CD8+CD69+CD137+ T cells were significantly increased by LL-37 stimulation in ACS PBMCs. T effector cell response to LL-37 were either HLA dependent or independent as determined by blocking with monoclonal antibody to either Class-I HLA or Class-II HLA. Blocking of immune checkpoints PD-1 and CTLA-4 demonstrated the control of self-reactive T cell response to LL-37 was modulated predominantly by CTLA-4. Platelets from healthy controls down-modulated CD8+CD69+CD137+ T cell response to LL-37 in autologous PBMCs. CD8+CD69+CD137+ T cell AIM profile negatively correlated with platelet count in ACS patients.

Conclusions

Our report demonstrates that the immune response to the autoantigen LL-37 in ACS patients is characterized specifically by CD8+CD69+CD137+ T cell AIM profile with persistent T cell activation and the generation of immunologic memory. The results provide potentially novel insight into mechanistic pathways of antigen-specific immune signaling in ACS.

Innate Immunity in Calcinosis Cutis

Calcinosis cutis is the deposition of calcium salts in the skin and subcutaneous tissue, manifesting as variably shaped papules, nodules, and plaques that can substantially impair quality of life. The pathophysiology of calcinosis cutis involves dysregulation of proinflammatory cytokines, leukocytes, and other components of the innate immune system. In some conditions associated with calcinosis cutis, elevated serum calcium, phosphate, and vitamin D may also perturb innate immunity. The mechanisms by which these lead to cutaneous and subcutaneous calcification likely parallel those seen in vascular calcification. The role of aberrant innate immunity is further supported by the association between various autoantibodies with calcinosis cutis, such as anti-MDA5, anti-NXP2, anti-centromere, and anti-topoisomerase I. Treatments for calcinosis cutis remain limited and largely experimental, although mechanistically many therapies appear to focus on dampening innate immune responses. Further research is needed to better understand the innate immune pathophysiology and establish treatment options based on randomized-controlled trials.

Endoplasmic Reticulum Stress and Pathogenesis of Vascular Calcification

Vascular calcification (VC) is characterized by calcium phosphate deposition in blood vessel walls and is associated with many diseases, as well as increased cardiovascular morbidity and mortality. However, the molecular mechanisms underlying of VC development and pathogenesis are not fully understood, thus impeding the design of molecular-targeted therapy for VC. Recently, several studies have shown that endoplasmic reticulum (ER) stress can exacerbate VC. The ER is an intracellular membranous organelle involved in the synthesis, folding, maturation, and post-translational modification of secretory and transmembrane proteins. ER stress (ERS) occurs when unfolded/misfolded proteins accumulate after a disturbance in the ER environment. Therefore, downregulation of pathological ERS may attenuate VC. This review summarizes the relationship between ERS and VC, focusing on how ERS regulates the development of VC by promoting osteogenic transformation, inflammation, autophagy, and apoptosis, with particular interest in the molecular mechanisms occurring in various vascular cells. We also discuss, the therapeutic effects of ERS inhibition on the progress of diseases associated with VC are detailed.

Immunization using ApoB-100 peptide-linked nanoparticles reduces atherosclerosis

Active immunization with the apolipoprotein B-100 (ApoB-100) peptide P210 reduces experimental atherosclerosis. To advance this immunization strategy to future clinical testing, we explored the possibility of delivering P210 as an antigen using nanoparticles, given this approach has been used clinically. We first characterized the responses of T cells to P210 using PBMCs from patients with atherosclerotic cardiovascular disease (ASCVD). We then investigated the use of P210 in self-assembling peptide amphiphile micelles (P210-PAMs) as a vaccine formulation to reduce atherosclerosis in B6.129P2-Apoe^tm1Unc/J (ApoE^–/–) mice and P210’s potential mechanisms of action. We also generated and characterized a humanized mouse model with chimeric HLA-A*02:01/Kb in ApoE^–/– background to test the efficacy of P210-PAM immunization as a bridge to future clinical testing. P210 provoked T cell activation and memory response in PBMCs of patients with ASCVD. Dendritic cell uptake of P210-PAM and its costaining with MHC-I molecules supported its use as a vaccine formulation. In ApoE^–/– mice, immunization with P210-PAMs dampened P210-specific CD4⁺ T cell proliferative response and CD8⁺ T cell cytolytic response, modulated macrophage phenotype, and significantly reduced aortic atherosclerosis. Potential clinical relevance of P210-PAM immunization was demonstrated by reduced atherosclerosis in the humanized ApoE^–/– mouse model. Our data support experimental and translational use of P210-PAM as a potential vaccine candidate against human ASCVD.