Neutrophil-specific STAT4 deficiency attenuates atherosclerotic burden and improves plaque stability via reduction in neutrophil activation and recruitment into aortas of Ldlr -/- mice.

Background and Aims: Neutrophils drive atheroprogression and directly contribute to plaque instability. We recently identified signal transducer and activator of transcription 4 (STAT4) as a critical component for bacterial host defense in neutrophils. The STAT4-dependent functions of neutrophils in atherogenesis are unknown. Therefore, we investigated a contributory role of STAT4 in neutrophils during advanced atherosclerosis. Methods: We generated myeloid-specific Stat4 ΔLysM Ldlr -/- , neutrophil-specific Stat4 ΔS100A8 Ldlr -/- , and control Stat4 fl/fl Ldlr -/- mice. All groups were fed a high-fat/cholesterol diet (HFD-C) for 28 weeks to establish advanced atherosclerosis. Aortic root plaque burden and stability were assessed histologically by Movat Pentachrome staining. Nanostring gene expression analysis was performed on isolated blood neutrophils. Flow cytometry was utilized to analyze hematopoiesis and blood neutrophil activation. In vivo homing of neutrophils to atherosclerotic plaques was performed by adoptively transferring prelabeled Stat4 ΔLysM Ldlr -/- and Stat4 fl/fl Ldlr -/- bone marrow cells into aged atherosclerotic Apoe -/- mice and detected by flow cytometry. Results: STAT4 deficiency in both myeloid-specific and neutrophil-specific mice provided similar reductions in aortic root plaque burden and improvements in plaque stability via reduction in necrotic core size, improved fibrous cap area, and increased vascular smooth muscle cell content within the fibrous cap. Myeloid-specific STAT4 deficiency resulted in decreased circulating neutrophils via reduced production of granulocyte-monocyte progenitors in the bone marrow. Neutrophil activation was dampened in Stat4 ΔLysM Ldlr -/- mice via reduced mitochondrial superoxide production, attenuated surface expression of degranulation marker CD63, and reduced frequency of neutrophil-platelet aggregates. Myeloid-specific STAT4 deficiency diminished expression of chemokine receptors CCR1 and CCR2 and impaired in vivo neutrophil trafficking to atherosclerotic aorta. Conclusions: Our work indicates a pro-atherogenic role for STAT4-dependent neutrophil activation and how it contributes to multiple factors of plaque instability during advanced atherosclerosis in mice.

Neutrophil-specific STAT4 deficiency attenuates atherosclerotic burden and improves plaque stability via reduction in neutrophil activation and recruitment into aortas of Ldlr-/- mice.

Background and aims: Neutrophils drive atheroprogression and directly contribute to plaque instability. We recently identified signal transducer and activator of transcription 4 (STAT4) as a critical component for bacterial host defense in neutrophils. The STAT4-dependent functions of neutrophils in atherogenesis are unknown. Therefore, we investigated a contributory role of STAT4 in neutrophils during advanced atherosclerosis. Methods: We generated myeloid-specific Stat4ΔLysMLdlr-/-, neutrophil-specific Stat4ΔS100A8Ldlr-/-, and control Stat4fl/flLdlr-/- mice. All groups were fed a high-fat/cholesterol diet (HFD-C) for 28 weeks to establish advanced atherosclerosis. Aortic root plaque burden and stability were assessed histologically by Movat pentachrome staining. Nanostring gene expression analysis was performed on isolated blood neutrophils. Flow cytometry was utilized to analyze hematopoiesis and blood neutrophil activation. In vivo homing of neutrophils to atherosclerotic plaques was performed by adoptively transferring prelabeled Stat4ΔLysMLdlr-/- and Stat4fl/flLdlr-/- bone marrow cells into aged atherosclerotic Apoe-/- mice and detected by flow cytometry. Results: STAT4 deficiency in both myeloid-specific and neutrophil-specific mice provided similar reductions in aortic root plaque burden and improvements in plaque stability via reduction in necrotic core size, improved fibrous cap area, and increased vascular smooth muscle cell content within the fibrous cap. Myeloid-specific STAT4 deficiency resulted in decreased circulating neutrophils via reduced production of granulocyte-monocyte progenitors in the bone marrow. Neutrophil activation was dampened in HFD-C fed Stat4ΔLysMLdlr-/- mice via reduced mitochondrial superoxide production, attenuated surface expression of degranulation marker CD63, and reduced frequency of neutrophil-platelet aggregates. Myeloid-specific STAT4 deficiency diminished expression of chemokine receptors CCR1 and CCR2 and impaired in vivo neutrophil trafficking to atherosclerotic aorta. Conclusions: Our work indicates a pro-atherogenic role for STAT4-dependent neutrophil activation and how it contributes to multiple factors of plaque instability during advanced atherosclerosis in mice.

Atherosclerosis and multi-organ-associated pathologies.

Atherosclerosis is a chronic inflammatory disease of the vascular system that is characterized by the deposition of modified lipoproteins, accumulation of immune cells, and formation of fibrous tissue within the vessel wall. The disease occurs in vessels throughout the body and affects the functions of almost all organs including the lymphoid system, bone marrow, heart, brain, pancreas, adipose tissue, liver, kidneys, and gastrointestinal tract. Atherosclerosis and associated factors influence these tissues via the modulation of local vascular functions, induction of cholesterol-associated pathologies, and regulation of local immune responses. In this review, we discuss how atherosclerosis interferers with functions of different organs via several common pathways and how the disturbance of immunity in atherosclerosis can result in disease-provoking dysfunctions in multiple tissues. Our growing appreciation of the implication of atherosclerosis and associated microenvironmental conditions in the multi-organ pathology promises to influence our understanding of CVD-associated disease pathologies and to provide new therapeutic opportunities.

A Factor H-Fc fusion protein increases complement-mediated opsonophagocytosis and killing of community associated methicillin-resistant Staphylococcus aureus.

Staphylococcus aureus employs a multitude of immune-evasive tactics to circumvent host defenses including the complement system, a component of innate immunity central to controlling bacterial infections. With antibiotic resistance becoming increasingly common, there is a dire need for novel therapies. Previously, we have shown that S. aureus binds the complement regulator factor H (FH) via surface protein SdrE to inhibit complement. To address the need for novel therapeutics and take advantage of the FH:SdrE interaction, we examined the effect of a fusion protein comprised of the SdrE-interacting domain of FH coupled with IgG Fc on complement-mediated opsonophagocytosis and bacterial killing of community associated methicillin-resistant S. aureus. S. aureus bound significantly more FH-Fc compared to Fc-control proteins and FH-Fc competed with serum FH for S. aureus binding. FH-Fc treatment increased C3-fragment opsonization of S. aureus for both C3b and iC3b, and boosted generation of the anaphylatoxin C5a. In 5 and 10% serum, FH-Fc treatment significantly increased S. aureus killing by polymorphonuclear cells. This anti-staphylococcal effect was evident in 75% (3/4) of clinical isolates tested. This study demonstrates that FH-Fc fusion proteins have the potential to mitigate the protective effects of bound serum FH rendering S. aureus more vulnerable to the host immune system. Thus, we report the promise of virulence-factor-targeted fusion-proteins as an avenue for prospective anti-staphylococcal therapeutic development.

Functional Role of B Cells in Atherosclerosis.

Atherosclerosis is a lipid-driven inflammatory disease of blood vessels, and both innate and adaptive immune responses are involved in its development. The impact of B cells on atherosclerosis has been demonstrated in numerous studies and B cells have been found in close proximity to atherosclerotic plaques in humans and mice. B cells exert both atheroprotective and pro-atherogenic functions, which have been associated with their B cell subset attribution. While B1 cells and marginal zone B cells are considered to protect against atherosclerosis, follicular B cells and innate response activator B cells have been shown to promote atherosclerosis. In this review, we shed light on the role of B cells from a different, functional perspective and focus on the three major B cell functions: antibody production, antigen presentation/T cell interaction, and the release of cytokines. All of these functions have the potential to affect atherosclerosis by multiple ways and are dependent on the cellular milieu and the activation status of the B cell. Moreover, we discuss B cell receptor signaling and the mechanism of B cell activation under atherosclerosis-prone conditions. By summarizing current knowledge of B cells in and beyond atherosclerosis, we are pointing out open questions and enabling new perspectives.