Immune checkpoint programmed death-1 mediates abdominal aortic aneurysm and pseudoaneurysm progression

Immune Checkpoints Are New Therapeutic Targets in Regulating Cardio-, and Cerebro-Vascular Diseases and CD4+Foxp3+ Regulatory T Cell Immunosuppression

Although previous reviews explored the roles of selected immune checkpoints (ICPs) in cardiovascular diseases (CVD) and cerebrovascular diseases from various perspectives, many related aspects have yet to be thoroughly reviewed and analyzed. Our comprehensive review addresses this gap by discussing the cellular functions of ICPs, focusing on the tissue-specific and microenvironment-localized transcriptomic and posttranslational regulation of ICP expressions, as well as their functional interactions with metabolic reprogramming. We also analyze how 14 pairs of ICPs, including CTLA-4/CD86-CD80, PD1-PDL-1, and TIGIT-CD155, regulate CVD pathogenesis. Additionally, the review covers the roles of ICPs in modulating CD4+Foxp3+ regulatory T cells (Tregs), T cells, and innate immune cells in various CVDs and cerebrovascular diseases. Furthermore, we outline seven immunological principles to guide the development of new ICP-based therapies for CVDs. This timely and thorough analysis of recent advancements and challenges provide new insights into the role of ICPs in CVDs, cerebrovascular diseases and Tregs, and will support the development of novel therapeutics strategies for these diseases.

Unleashing PD-1: a duel of immunity in aortic aneurysm formation

Aortic aneurysms, particularly abdominal aortic aneurysms (AAAs), exhibit sex differences, with higher prevalence and severity in males than females, both in humans and experimental mouse models. In fact, male sex has been considered as the most potent nonmodifiable risk factor for AAA. Currently, there are no medications approved for the treatment of aortic aneurysms, despite the high lethality of ruptured aneurysms, which account for nearly 2% of all deaths. Moreover, the underlying molecular mechanisms mediating the sexual dimorphism of aortic aneurysms remain largely unknown. In this issue of the JCI, Mu et al. revealed a mechanism by which androgens, male sex hormones, exacerbate aortic aneurysms by suppressing programmed cell death protein 1 (PD-1) expression in T cells in an aldosterone and high salt-induced aortic aneurysm mouse model.

Androgen aggravates aortic aneurysms via suppression of PD-1 in mice

Androgen has long been recognized for its pivotal role in the sexual dimorphism of cardiovascular diseases, including aortic aneurysms (AAs), a devastating vascular disease with a higher prevalence and fatality rate in men than in women. However, the mechanism by which androgen mediates AAs is largely unknown. Here, we found that male, not female, mice developed AAs when exposed to aldosterone and high salt (Aldo-salt). We revealed that androgen and androgen receptors (ARs) were crucial for this sexually dimorphic response to Aldo-salt. We identified programmed cell death protein 1 (PD-1), an immune checkpoint, as a key link between androgen and AAs. Furthermore, we demonstrated that administration of anti-PD-1 Ab and adoptive PD-1-deficient T cell transfer reinstated Aldo-salt-induced AAs in orchiectomized mice and that genetic deletion of PD-1 exacerbated AAs induced by a high-fat diet and angiotensin II (Ang II) in nonorchiectomized mice. Mechanistically, we discovered that the AR bound to the PD-1 promoter to suppress the expression of PD-1 in the spleen. Thus, our study unveils a mechanism by which androgen aggravates AAs by suppressing PD-1 expression in T cells. Moreover, our study suggests that some patients with cancer might benefit from screenings for AAs during immune checkpoint therapy.

Assessing the causal relationship between circulating immune cells and abdominal aortic aneurysm by bi-directional Mendelian randomization analysis

Although there is an association between abdominal aortic aneurysm (AAA) and circulating immune cell phenotypes, the exact causal relationship remains unclear. This study aimed to explore the causal relationships between immune cell phenotypes and AAA risk using a bidirectional two-sample Mendelian randomization approach. Data from genome-wide association studies pertaining to 731 immune cell traits and AAA were systematically analyzed. Using strict selection criteria, we identified 339 immune traits that are associated with at least 3 single nucleotide polymorphisms. A comprehensive MR analysis was conducted using several methods including Inverse Variance Weighted, Weighted Median Estimator, MR-Egger regression, Weighted Mode, and Simple Median methods. CD24 on switched memory cells (OR = 0.922, 95% CI 0.914-0.929, P = 2.62e-79) at the median fluorescence intensities level, and SSC-A on HLA-DR + natural killer cells (OR = 0.873, 95% CI 0.861-0.885, P = 8.96e-81) at the morphological parameter level, exhibited the strongest causal associations with AAA. In the reverse analysis, no significant causal effects of AAA on immune traits were found. The study elucidates the causal involvement of multiple circulating immune cell phenotypes in AAA development, signifying their potential as diagnostic markers or therapeutic targets. These identified immune traits may be crucial in modulating AAA-related inflammatory pathways.

Deciphering the circulating immunological landscape of thoracic aortic aneurysm: Insights from a two-sample Mendelian randomization study

Background

Thoracic Aortic Aneurysm (TAA) poses significant health risks due to aortic dilation. Recent evidence suggests a pivotal role for the immune-inflammatory response in the mechanism of aortic aneurysm formation. In this study, we aim to investigate the causal relationship between circulating immune cells and TAA.

Methods

This study employs a two-sample Mendelian Randomization (MR) approach, utilizing genome-wide association study (GWAS) summary statistics for 731 immune cell types and two TAA data from large-scale studies. Causal effects of both peripheral immune cells on TAA and TAA on peripheral immune cells are explored. To ensure more accurate results, we intersected the findings from two TAA data from large-scale studies, excluding results where the direction of the odds ratio (OR) was inconsistent.

Findings

The study identifies specific immune cells associated with TAA. Notably, CD45+ NKT cell (OR: 0.95, 95CI%: 0.90-0.99 in FinnGen study; OR: 0.91, 95CI%: 0.84-0.99 in CHIP + MGI study) and CD45+ HLA-DR + CD8+ T cells (OR: 0.95, 95CI%: 0.90-0.99 in FinnGen study; OR: 0.90, 95CI%: 0.82-0.99 in CHIP + MGI study) demonstrate a protective role against TAA. In addition, CD28+ CD45RA- CD8+ T cells (relative cell counts and absolute cell counts) and HVEM + CM + CD8+ T cells are adversely affected by TAA.

Interpretation

The findings indicate that the potential protective influence exerted by specific subsets of peripheral NKT cells and CD8+ T cells in mitigating the development of TAA, while simultaneously highlighting the reciprocal effects of TAA on peripheral Treg cells subsets and T cell subsets. The complex interaction between immune cells and TAA could provide valuable clues for earlier detection and more efficacious treatment strategies for TAA.

Adenosine 5'-Monophosphate-to-Threonine Ratio Promotes Abdominal Aortic Aneurysms via Up-Regulation of HLA-DR on Natural Killer Cells: A Bidirectional Mendelian Randomized Analysis

Objective: Immune-metabolic interactions may have causal and therapeutic impacts on abdominal aortic aneurysms (AAAs). However, due to the lack of research on the relationship between immune-metabolic interactions and AAAs, further exploration of the mechanism faces challenges. Methods: A two-sample, two-step mediation analysis with Mendelian randomization (MR) based on genome-wide association studies (GWASs) was performed to determine the causal associations among blood immune cell signatures, metabolites, and AAAs. The stability, heterogeneity, and pleiotropy of the results were verified using a multivariate sensitivity analysis. Results: After multiple two-sample MRs using the AAA data from two large-scale GWAS databases, we determined that the human leukocyte antigen-DR (HLA-DR) levels on HLA-DR + natural killer (NK) cells (HLA-DR/NK) were associated with the causal effect of an AAA, with consistent results in the two databases (FinnGen: odds ratio (OR) = 1.054, 95% confidence interval (CI): 1.003-1.067, p-value = 0.036; UK Biobank: OR = 1.149, 95% CI: 1.046-1.261, p-value = 0.004). The metabolites associated with the risk of developing an AAA were enriched to find a specific metabolic model. We also found that the ratio of adenosine 5'-monophosphate (AMP) to threonine could act as a potential mediator between the HLA/NK and an AAA, with a direct effect (beta effect = 0.0496) and an indirect effect (beta effect = 0.0029). The mediation proportion was 5.56%. Conclusions: Our study found that an up-regulation of HLA-DR on HLA-DR/NK cells can increase the risk of an AAA via improvements in the AMP-to-threonine ratio, thus providing a potential new biomarker for the prediction and treatment of AAAs.

Hollow Cu2MoS4 nanoparticles loaded with immune checkpoint inhibitors reshape the tumor microenvironment to enhance immunotherapy for pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease that responds poorly to single-drug immunotherapy with PD-L1 (CD274) inhibitors. Here, we prepared mesoporous nanomaterials Cu2MoS4 (CMS)/PEG loaded with PD-L1 inhibitor BMS-1 and CXCR4 inhibitor Plerixafor to form the nanodrug CMS/PEG-B-P. In vitro experiments, CMS/PEG-B-P have a more substantial inhibitory effect on the expression of PD-L1 and CXCR4 as well as to promote the apoptosis of pancreatic cancer cells KPC and suppressed KPC cell proliferation were detected by flow cytometry, qPCR and Western blotting (WB). Promotes the release of the cytotoxic substance reactive oxygen species (ROS) and the production of the immunogenic cell death (ICD) marker calreticulin (CRT) in KPC cells. CMS/PEG-B-P was also detected to have a certain activating effect on mouse immune cells, dendritic cells (mDC) and macrophage RAW264.7. Subcutaneous tumorigenicity experiments in C57BL/6 mice verified that CMS/PEG-B-P had an inhibitory effect on the growth of tumors and remodeling of the tumor immune microenvironment, including infiltration of CD4+ and CD8+ T cells and polarization of macrophages, as well as reduction of immunosuppressive cells. Meanwhile, CMS/PEG-B-P was found to have different effects on the release of cytokines in the tumor immune microenvironment, including The levels of immunostimulatory cytokines INF-γ and IL-12 are increased and the levels of immunosuppressive cytokines IL-6, IL-10 and IFN-α are decreased. In conclusion, nanomaterial-loaded immune checkpoint inhibitor therapies can enhance the immune response and reduce side effects, a combination that shows great potential as a new immunotherapeutic approach. STATEMENT OF SIGNIFICANCE: Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease that has a low response to single-drug immunotherapy with PD-L1 (CD274) inhibitors. We preared PEG-modified mesoporous nanomaterials Cu2MoS4 (CMS) loaded with PD-L1 inhibitor BMS-1 and CXCR4 inhibitor Plerixafor to form the nanodrug CMS/PEG-B-P. Our study demonstrated that Nanomaterial-loaded immune checkpoint inhibitor therapies can enhance the immune response and reduce side effects, a combination that shows great potential as a new immunotherapeutic approach.

PCSK9, a novel immune and ferroptosis related gene in abdominal aortic aneurysm neck

The gene expression profile of abdominal aortic aneurysm (AAA) neck is not fully understood. The etiology of AAA is considered to be related to atherosclerosis and the inflammatory response, involving congenital, genetic, metabolic, and other factors. The level of proprotein convertase subtilisin/kexin type 9 (PCSK9) is related to those of cholesterol, oxidized low-density lipoprotein, and triglycerides. PCSK9 inhibitors have significant effects on lowering LDL-cholesterol, reversing atherosclerotic plaques, and reducing the risk of cardiovascular events and have been approved by several lipid-lowering guidelines. This work was aimed to investigate the potential role of PCSK9 in the neck of AAA. We extracted the expression dataset (GSE47472) containing 14 AAA patients and 8 donors and single-cell RNAseq (scRNA-seq) data (GSE164678) of CaCl2-induced (AAA) samples from the Gene Expression Omnibus dataset. Through bioinformatics methods, we found that PCSK9 was up-regulated in the proximal neck of human AAA. In AAA, PCSK9 was mainly expressed in fibroblasts. Additionally, immune check-point PDCD1LG2 was also expressed higher in AAA neck than donor, while CTLA4, PDCD1, and SIGLEC15 were down-regulated in AAA neck. The expression of PCSK was correlated with PDCD1LG2, LAG3, and CTLA4 in AAA neck. Additionally, some ferroptosis-related genes were also down-regulated in AAA neck. PCSK9 was also correlated with ferroptosis-related genes in AAA neck. In conclusion, PCSK9 was highly expressed in AAA neck, and may exert its role through interacting with immune check-points and ferroptosis-related genes.

Androgen aggravates aortic aneurysms via suppressing PD-1 in mice

Androgen has long been recognized for its pivotal role in the sexual dimorphism of cardiovascular diseases, including aortic aneurysms, a devastating vascular disease with a higher prevalence and mortality rate in men than women. However, the molecular mechanism by which androgen mediates aortic aneurysms is largely unknown. Here, we report that male but not female mice develop aortic aneurysms in response to aldosterone and high salt (Aldo-salt). We demonstrate that both androgen and androgen receptors (AR) are crucial for the sexually dimorphic response to Aldo-salt. We identify T cells expressing programmed cell death protein 1 (PD-1), an immune checkpoint molecule important in immunity and cancer immunotherapy, as a key link between androgen and aortic aneurysms. We show that intraperitoneal injection of anti-PD-1 antibody reinstates Aldo-salt-induced aortic aneurysms in orchiectomized mice. Mechanistically, we demonstrate that AR binds to the PD-1 promoter to suppress its expression in the spleen. Hence, our study reveals an important but unexplored mechanism by which androgen contributes to aortic aneurysms by suppressing PD-1 expression in T cells. Our study also suggests that cancer patients predisposed to the risk factors of aortic aneurysms may be advised to screen for aortic aneurysms during immune checkpoint therapy.

Adventitial injection of HA/SA hydrogel loaded with PLGA rapamycin nanoparticle inhibits neointimal hyperplasia in a rat aortic wire injury model

Neointimal hyperplasia is a persistent complication after vascular interventions, and it is also the leading cause of vascular graft restenosis and failure after arterial interventions, so novel treatment methods are needed to treat this complication. We hypothesized that adventitial injection of HA/SA hydrogel loaded with PLGA rapamycin nanoparticle (hydrogel-PLGA-rapamycin) could inhibit neointimal hyperplasia in a rat aortic wire injury model. The HA/SA hydrogel was fabricated by the interaction of hyaluronic acid (HA), sodium alginate (SA), and CaCO₃; and loaded with PLGA rapamycin nanoparticle or rhodamine uniformly. A SD rat aortic wire injury induced neointimal hyperplasia model was developed, the control group only received wire injury, the adventitial application group received 10 μL hydrogel-PLGA-rapamycin after wire injury, and the adventitial injection group received 10 μL hydrogel-PLGA-rapamycin injected into the aortic adventitia after wire injury. Tissues were harvested at day 21 and analyzed by histology and immunohistochemical staining. Hydrogel loaded with rhodamine can be successfully injected into the aortic adventitia and was encapsuled by the adventitia. The hydrogel could be seen beneath the adventitia after adventitial injection but was almost degraded at day 21. There was a significantly thinner neointima in the adventitial application group and adventitial injection group compared to the control group (p = 0.0009). There were also significantly fewer CD68⁺ (macrophages) cells (p = 0.0012), CD3⁺ (lymphocytes) cells (p = 0.0011), p-mTOR⁺ cells (p = 0.0019), PCNA⁺ cells (p = 0.0028) in the adventitial application and adventitial injection groups compared to the control group. The endothelial cells expressed arterial identity markers (Ephrin-B2 and dll-4) in all these three groups. Adventitial injection of hydrogel-PLGA-rapamycin can effectively inhibit neointimal hyperplasia after rat aortic wire injury. This may be a promising drug delivery method and therapeutic choice to inhibit neointimal hyperplasia after vascular interventions.

Immune and inflammatory mechanisms of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease. Immune-mediated infiltration and a destruction of the aortic wall during AAA development plays significant role in the pathogenesis of this disease. While various immune cells had been found in AAA, the mechanisms of their activation and function are still far from being understood. A better understanding of mechanisms regulating the development of aberrant immune cell activation in AAA is essential for the development of novel preventive and therapeutic approaches. In this review we summarize current knowledge about the role of immune cells in AAA and discuss how pathogenic immune cell activation is regulated in this disease.

High-Dimensional Immune Profiling by Mass Cytometry Revealed the Circulating Immune Cell Landscape in Patients With Intracranial Aneurysm

Background

Increasing evidence supports a critical role of chronic inflammation in intracranial aneurysm (IA). Understanding how the immunological alterations in IA provides opportunities for targeted treatment. However, there is a lack of comprehensive and detailed characterization of the changes in circulating immune cells in IA.

Objective

To perform a comprehensive and detailed characterization of the changes in circulating immune cells in patients with IA.

Methods

Peripheral blood mononuclear cell samples from IA patients (n = 26) and age-and sex-matched healthy controls (HCs, n = 20) were analyzed using high dimensional mass cytometry, and the frequency and phenotype of immune cell subtypes were assessed.

Results

We identified 28 cell clusters and found that the immune signature of IA consists of cluster changes. IA patients exhibited dysfunction of immunity, with dysregulation of CD4⁺ T-cell clusters, increased B cells and monocytes, and decreased CD8⁺ T cells, DNT cells, and DPT cells. Moreover, compared with findings in HC, IA was associated with enhanced lymphocyte and monocyte immune activation, with a higher expression of HLA-DR, CXCR3, and CX3CR1. In addition, the expression of TLR4, p-STAT3, and the exhaustion marker PD1 was increased in T cells, B cells, and NK cells in IA patients.

Conclusions

Our data provide an overview of the circulating immune cell landscape of IA patients, and reveal that the dysfunction of circulating immunity may play a potential role in the development of IA.

PLGA Nanoparticle Rapamycin- or Necrostatin-1-Coated Sutures Inhibit Inflammatory Reactions after Arterial Closure in Rats

Background: The inflammatory reaction of sutures and oozing after arterial closure depends on the suture material and the amount of oozing surrounding the sutures. Anti-inflammation coatings have been proven to be an effective strategy to decrease this reaction. The aim of this study was to establish an arterial closure oozing model in rats and to test the effect of poly (lactic-co-glycolic acid) (PLGA) nanoparticle (NP) rapamycin- or necrostatin-1(NEC-1)-coated sutures on the inflammatory reaction after arterial closure. Methods and Materials: A 10 mm arteriotomy was carried out on the carotid artery of Sprague-Dawley rats and closed using 11-0 sutures. PLGA NP-rapamycin and NEC-1 were made. The 11/0 nylon sutures were coated with PLGA NP-rapamycin and NEC-1. Sutures were examined by scanning electron microscopy, hemolysis test, and cumulative release. The carotid arteriotomy was closed using uncoated PLGA NP-rapamycin- and NP-NEC-1-coated sutures. The carotid artery was harvested on day 7. Tissues were examined by histology and immunohistochemistry. Results: There were severe inflammatory reactions in the oozing arteries compared to the normal healing arteries (P = 0.0192). PLGA NP-rapamycin- and NEC -1-coated sutures reduced foreign body reaction compared to the uncoated sutures. There were significantly smaller number of CD3 (P = 0.0068), CD45 (P = 0.0300), and CD68 (P = 0.0011) cells in the PLGA NP-rapamycin- and NP-NEC-1-coated groups compared to the uncoated group. There was a smaller number of p-mTOR (P = 0.0198)-positive cells in the PLGA NP-rapamycin-coated group compared to the uncoated group. There was a smaller number of TNFα (P = 0.0198)-positive cells in the PLGA NP-NEC-1-coated group compared to the uncoated group. Conclusions: In this rat carotid artery oozing model, PLGA NP-rapamycin- or NP-NEC-1-coated sutures can inhibit inflammatory reaction and foreign body reaction. Although this was a small rodent animal experiment, this coated suture may have a potential clinical application in the future.

A Novel Plant Leaf Patch Absorbed With IL-33 Antibody Decreases Venous Neointimal hyperplasia

Introduction: We recently showed that a decellularized leaf scaffold can be loaded with polylactic-co-glycolic acid (PLGA)-based rapamycin nanoparticles, this leaf patch can then inhibit venous neointimal hyperplasia in a rat inferior vena cava (IVC) venoplasty model. IL-33 plays a role in the neointimal formation after vascular injury. We hypothesized that plant leaves can absorb therapeutic drug solution and can be used as a patch with drug delivery capability, and plant leaves absorbed with IL-33 antibody can decrease venous neointimal hyperplasia in the rat IVC venoplasty model. Method: A human spiral saphenous vein (SVG) graft implanted in the popliteal vein was harvested from a patient with trauma and analyzed by immunofluorescence. Male Sprague-Dawley rats (aged 6-8 weeks) were used to create the IVC patch venoplasty model. Plant leaves absorbed with rhodamine, distilled water (control), rapamycin, IL-33, and IL-33 antibody were cut into patches (3 × 1.5 mm²) and implanted into the rat IVC. Patches were explanted at day 14 for analysis. Result: At day 14, in the patch absorbed with rhodamine group, immunofluorescence showed rhodamine fluorescence in the neointima, inside the patch, and in the adventitia. There was a significantly thinner neointima in the plant patch absorbed with rapamycin (p = 0.0231) compared to the patch absorbed with distilled water. There was a significantly large number of IL-33 (p = 0.006) and IL-1β (p = 0.012) positive cells in the human SVG neointima compared to the human great saphenous vein. In rats, there was a significantly thinner neointima, a smaller number of IL-33 (p = 0.0006) and IL-1β (p = 0.0008) positive cells in the IL-33 antibody-absorbed patch group compared to the IL-33-absorbed patch group. Conclusion: We found that the natural absorption capability of plant leaves means they can absorb drug solution efficiently and can also be used as a novel drug delivery system and venous patch. IL-33 plays a role in venous neointimal hyperplasia both in humans and rats; neutralization of IL-33 by IL-33 antibody can be a therapeutic method to decrease venous neointimal hyperplasia.