PCSK9 attenuates efferocytosis in endothelial cells and promotes vascular aging

PCSK9 aggravated carotid artery stenosis in ApoE-/- mice by promoting the expression of tissue factors in endothelial cells via the TLR4/NF-κB pathway

Atherosclerosis, a chronic inflammatory disease, is the most relevant cause of carotid artery stenosis. Vascular endothelial cells (ECs) play a significant role in the development of atherosclerosis. In this chronic inflammatory environment, we aimed to investigate whether PCSK9 could mitigate atherosclerosis progression by reducing tissue factor expression in ECs via in vivo and in vitro assays. In vivo, we investigated the effect of PCSK9 inhibition on preventing atherosclerotic lesion formation in ApoE-/- mice fed a western diet. The results showed that inhibiting PCSK9 could significantly downregulate the protein expression of tissue factor (TF) in ECs to reduce the area of atherosclerotic plaques. In vitro, we incubated human umbilical vein endothelial cells (HUVECs) with lipopolysaccharide (LPS). We found that LPS-induced TF elevation was suppressed by a PCSK9 inhibitor at both the mRNA and protein levels and that the TLR4/NF-κB pathway was also suppressed by a PCSK9 inhibitor. With respect to plasma samples from patients with carotid artery stenosis, we also demonstrated that the expression of TF was positively correlated with that of PCSK9. Thus, in addition to regulating lipid metabolism, the regulation of endothelial cell TF expression through the TLR4/NF-κB pathway may be a potential mechanism of PCSK9 in promoting atherosclerotic carotid stenosis.

Alirocumab boosts antioxidant status and halts inflammation in rat model of sepsis-induced nephrotoxicity via modulation of Nrf2/HO-1, PCSK9/HMGB1/NF-ᴋB/NLRP3 and Fractalkine/CX3CR1 hubs

Acute kidney injury (AKI) is a devastating consequence of sepsis, accompanied by high mortality rates. It was suggested that inflammatory pathways are closely linked to the pathogenesis of lipopolysaccharide (LPS)-induced AKI. Inflammatory signaling, including PCSK9, HMGB1/RAGE/TLR4/MYD88/NF-κB, NLRP3/caspase-1 and Fractalkine/CX3CR1 are considered major forerunners in this link. Alirocumab, PCSK9 inhibitor, with remarkable anti-inflammatory features. Accordingly, this study aimed to elucidate the antibacterial effect of alirocumab against E. coli in vitro. Additionally, evaluation of the potential nephroprotective effects of alirocumab against LPS-induced AKI in rats, highlighting the potential underlying mechanisms involved in these beneficial actions. Thirty-six adult male Wistar rats were assorted into three groups (n=12). Group I; was a normal control group, whereas sepsis-mediated AKI was induced in groups II and III through single-dose intraperitoneal injection of LPS on day 16. In group III, animals were given alirocumab. The results revealed that LPS-induced AKI was mitigated by alirocumab, evidenced by amelioration in renal function tests (creatinine, cystatin C, KIM-1, and NGAL); oxidative stress biomarkers (Nrf2, HO-1, TAC, and MDA); apoptotic markers and renal histopathological findings. Besides, alirocumab pronouncedly hindered LPS-mediated inflammatory response, confirmed by diminishing HMGB1, TNF-α, IL-1β, and caspase-1 contents; the gene expression of PCSK9, RAGE, NF-ᴋB and Fractalkine/CX3CR1, along with mRNA expression of TLR4, MYD88, and NLRP3. Regarding the antibacterial actions, results showed that alirocumab displayed potential anti-bacterial activity against pathogenic gram-negative E. coli. In conclusion, alirocumab elicited nephroprotective activities against LPS-induced AKI via modulation of Nrf2/HO-1, PCSK9, HMGB1/RAGE/TLR4/MYD88/NF-ᴋB/NLRP3/Caspase-1, Fractalkine/CX3R1 and apoptotic axes.

PCSK9 induces endothelial cell autophagy by regulating the PI3K/ATK pathway in atherosclerotic coronary heart disease

OBJECTIVE

Atherosclerosis is a chronic inflammatory disease of the arteries, and its pathogenesis is related to endothelial dysfunction. It has been found that the protein convertase subtilin/kexin9 type (PCSK9) plays an important role in AS, but its specific mechanism is still unclear.

METHODS

In this study, we first cultured human umbilical vein endothelial cells (HUVECs) with 50 or 100μg/ml oxidized low-density lipoprotein (ox-LDL) for 24 hours to establish a coronary atherosclerosis cell model.

RESULTS

The results showed that ox-LDL induced HUVEC injury and autophagy and upregulated PCSK9 protein expression in HUVECs in a concentration-dependent manner. Silencing PCSK9 expression with siRNA inhibited ox-LDL-induced HUVEC endothelial dysfunction, inhibited the release of inflammatory factors, promoted HUVEC proliferation and inhibited apoptosis. In addition, ox-LDL increased the expression of LC3B-I and LC3B-II and decreased the expression of p62. However, these processes are reversed by sh-PCSK9. In addition, sh-PCSK9 can inhibit PI3K, AKT and mTOR phosphorylation and promote autophagy.

CONCLUSION

Taken together, our research shows that silencing PCSK9 inhibits the PI3K/ATK/mTOR pathway to activate ox-LDL-induced autophagy in vascular endothelial cells, alleviating endothelial cell injury and inflammation.

Loss of Endothelial Annexin A1 Aggravates Inflammation-Induched Vascular Aging

Chronic inflammation is increasingly considered as the most important component of vascular aging, contributing to the progression of age-related cardiovascular diseases. To delay the process of vascular aging, anti-inflammation may be an effective measure. The anti-inflammatory factor annexin A1 (ANXA1) is shown to participate in several age-related diseases; however, its function during vascular aging remains unclear. Here, an ANXA1 knockout (ANXA1-/-) and an endothelial cell-specific ANXA1 deletion mouse (ANXA1△EC) model are used to investigate the role of ANXA1 in vascular aging. ANXA1 depletion exacerbates vascular remodeling and dysfunction while upregulates age- and inflammation-related protein expression. Conversely, Ac2-26 (a mimetic peptide of ANXA1) supplementation reverses this phenomenon. Furthermore, long-term tumor necrosis factor-alpha (TNF-α) induction of human umbilical vein endothelial cells (HUVECs) increases cell senescence. Finally, the senescence-associated secretory phenotype and senescence-related protein expression, rates of senescence-β-galactosidase positivity, cell cycle arrest, cell migration, and tube formation ability are observed in both ANXA1-knockdown HUVECs and overexpressed ANXA1-TNF-α induced senescent HUVECs. They also explore the impact of formyl peptide receptor 2 (a receptor of ANXA1) in an ANXA1 overexpression inflammatory model. These data provide compelling evidence that age-related inflammation in arteries contributes to senescent endothelial cells that promote vascular aging.

Big data analytics for MerTK genomics reveals its double-edged sword functions in human diseases

RATIONALE

MER proto-oncogene tyrosine kinase (MerTK) is a key receptor for the clearance of apoptotic cells (efferocytosis) and plays important roles in redox-related human diseases. We will explore MerTK biology in human cells, tissues, and diseases based on big data analytics.

METHODS

The human RNA-seq and scRNA-seq data about 42,700 samples were from NCBI Gene Expression Omnibus and analyzed by QIAGEN Ingenuity Pathway Analysis (IPA) with about 170,000 crossover analysis. MerTK expression was quantified as Log2 (FPKM + 0.1).

RESULTS

We found that, in human cells, MerTK is highly expressed in macrophages, monocytes, progenitor cells, alpha-beta T cells, plasma B cells, myeloid cells, and endothelial cells (ECs). In human tissues, MerTK has higher expression in plaque, blood vessels, heart, liver, sensory system, artificial tissue, bone, adrenal gland, central nervous system (CNS), and connective tissue. Compared to normal conditions, MerTK expression in related tissues is altered in many human diseases, including cardiovascular diseases, cancer, and brain disorders. Interestingly, MerTK expression also shows sex differences in many tissues, indicating that MerTK may have different impact on male and female. Finally, based on our proteomics from primary human aortic ECs, we validated the functions of MerTK in several human diseases, such as cancer, aging, kidney failure and heart failure.

CONCLUSIONS

Our big data analytics suggest that MerTK may be a promising therapeutic target, but how it should be modulated depends on the disease types and sex differences. For example, MerTK inhibition emerges as a new strategy for cancer therapy due to it counteracts effect on anti-tumor immunity, while MerTK restoration represents a promising treatment for atherosclerosis and myocardial infarction as MerTK is cleaved in these disease conditions.

Disturbed flow impairs MerTK-mediated efferocytosis in aortic endothelial cells during atherosclerosis

Background: MER proto-oncogene tyrosine kinase (MerTK) is a key receptor for efferocytosis, a process for the clearance of apoptotic cells. MerTK is mainly expressed in macrophages and immature dendritic cells. There are very limited reports focused on MerTK biology in aortic endothelial cells (ECs). It remains unclear for the role of blood flow patterns in regulating MerTK-mediated efferocytosis in aortic ECs. This study was designed to investigate whether endothelial MerTK and EC efferocytosis respond to blood flow patterns during atherosclerosis. Methods: Big data analytics, RNA-seq and proteomics combined with our in vitro and in vivo studies were applied to reveal the potential molecular mechanisms. Partial carotid artery ligation combined with AAV-PCSK9 and high fat diet were used to set up acute atherosclerosis in 4 weeks. Results: Our data showed that MerTK is sensitive to blood flow patterns and is inhibited by disturbed flow and oscillatory shear stress in primary human aortic ECs (HAECs). The RNA-seq data in HAECs incubated with apoptotic cells showed that d-flow promotes pro-inflammatory pathway and senescence pathway. Our in vivo data of proteomics and immunostaining showed that, compared with WT group, MerTK-/- aggravates atherosclerosis in d-flow areas through upregulation of endothelial dysfunction markers (e.g. IL-1β, NF-κB, TLR4, MAPK signaling, vWF, VCAM-1 and p22phox) and mitochondrial dysfunction. Interestingly, MerTK-/-induces obvious abnormal endothelial thickening accompanied with decreased endothelial efferocytosis, promoting the development of atherosclerosis. Conclusions: Our data suggests that blood flow patterns play an important role in regulating MerTK-mediated efferocytosis in aortic ECs, revealing a new promising therapeutic strategy with EC efferocytosis restoration to against atherosclerosis.

Targeting proprotein convertase subtilisin/kexin type 9 (PCSK9): from bench to bedside

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has evolved as a pivotal enzyme in lipid metabolism and a revolutionary therapeutic target for hypercholesterolemia and its related cardiovascular diseases (CVD). This comprehensive review delineates the intricate roles and wide-ranging implications of PCSK9, extending beyond CVD to emphasize its significance in diverse physiological and pathological states, including liver diseases, infectious diseases, autoimmune disorders, and notably, cancer. Our exploration offers insights into the interaction between PCSK9 and low-density lipoprotein receptors (LDLRs), elucidating its substantial impact on cholesterol homeostasis and cardiovascular health. It also details the evolution of PCSK9-targeted therapies, translating foundational bench discoveries into bedside applications for optimized patient care. The advent and clinical approval of innovative PCSK9 inhibitory therapies (PCSK9-iTs), including three monoclonal antibodies (Evolocumab, Alirocumab, and Tafolecimab) and one small interfering RNA (siRNA, Inclisiran), have marked a significant breakthrough in cardiovascular medicine. These therapies have demonstrated unparalleled efficacy in mitigating hypercholesterolemia, reducing cardiovascular risks, and have showcased profound value in clinical applications, offering novel therapeutic avenues and a promising future in personalized medicine for cardiovascular disorders. Furthermore, emerging research, inclusive of our findings, unveils PCSK9's potential role as a pivotal indicator for cancer prognosis and its prospective application as a transformative target for cancer treatment. This review also highlights PCSK9's aberrant expression in various cancer forms, its association with cancer prognosis, and its crucial roles in carcinogenesis and cancer immunity. In conclusion, this synthesized review integrates existing knowledge and novel insights on PCSK9, providing a holistic perspective on its transformative impact in reshaping therapeutic paradigms across various disorders. It emphasizes the clinical value and effect of PCSK9-iT, underscoring its potential in advancing the landscape of biomedical research and its capabilities in heralding new eras in personalized medicine.