Integrin CD11b Contributes to Hypertension and Vascular Dysfunction Through Mediating Macrophage Adhesion and Migration

Genetic association between gut microbiome and blood pressure and blood cell count as mediator: A two-step Mendelian randomization analysis

BACKGROUND

Previous studies have established a genetic link between gut microbiota and hypertension, but whether blood cell count plays a mediating role in this remains unknown. This study aims to explore genetic associations and causal factors involving the gut microbiome, peripheral blood cell count, and blood pressure.

METHODS

We utilized summary statistics derived from genome-wide association studies to conduct a two-sample mediation Mendelian randomization analysis (https://gwas.mrcieu.ac.uk/). We applied inverse variance weighted (IVW) estimation method as the primary method, along with MR Egger, Weighted median, Simple mode and Weighted mode as complementary methods. To ensure the robustness of the results, several sensitivity analyses were conducted.

RESULTS

Genetic variants significantly associated with the microbiome, blood pressure, or peripheral blood cell counts were selected as instrumental variables. Fourteen microbial taxa were found to have suggestive associations with diastolic blood pressure (DBP), while fifteen microbial taxa showed suggestive associations with systolic blood pressure (SBP). Meanwhile, red blood cell count, lymphocyte count, and platelet count were identified to mediate the influence of the gut microbiome on blood pressure. Specifically, red cell count was identified to mediate the effects of the phylum Cyanobacteria on DBP (mediated proportion: 8.262 %). Lymphocyte count was found mediate the effects of the genus Subdoligranulum (mediated proportion: 2.642 %) and genus Collinsella (mediated proportion: 2.749 %) on SBP. Additionally, platelet count was found to mediate the relationship between the genus Eubacterium ventriosum group and SBP, explaining 3.421 % of the mediated proportion.

CONCLUSIONS

Our findings highlighted that gut microbiota may have causal influence on the blood pressure by modulating blood cell counts, which sheds new light on the pathogenesis and potential clinical interventions through the intricate axis of gut microbiome, blood cell counts, and blood pressure.

Mac-1 deficiency ameliorates pressure overloaded heart failure through inhibiting macrophage polarization and activation

Persistent pressure overload commonly leads to pathological cardiac hypertrophy and remodeling, ultimately leading to heart failure (HF). Cardiac remodeling is associated with the involvement of immune cells and the inflammatory response in pathogenesis. The macrophage-1 antigen (Mac-1) is specifically expressed on leukocytes and regulates their migration and polarization. Nonetheless, the involvement of Mac-1 in cardiac remodeling and HF caused by pressure overload has not been determined. The Mac-1-knockout (KO) and wild-type (WT) mice were subjected to transverse aortic constriction (TAC) for 6 weeks. Echocardiography and pressure-volume loop assessments were used to evaluate cardiac function, and cardiac remodeling and macrophage infiltration and polarization were estimated by histopathology and molecular techniques. The findings of our study demonstrated that Mac-1 expression was markedly increased in hearts subjected to TAC treatment. Moreover, compared with WT mice, Mac-1-KO mice exhibited dramatically ameliorated TAC-induced cardiac dysfunction, hypertrophy, fibrosis, oxidative stress and apoptosis. The potential positive impacts may be linked to the inhibition of macrophage infiltration and M1 polarization via reductions in NF-kB and STAT1 expression and upregulation of STAT6. In conclusion, this research reveals a new function of Mac-1 deficiency in reducing pathological cardiac remodeling and HF caused by pressure overload. Additionally, inhibiting Mac-1 could be a potential treatment option for patients with HF in a clinical setting.

Myeloid ACE2 protects against septic hypotension and vascular dysfunction through Ang-(1-7)-Mas-mediated macrophage polarization

Angiotensin converting enzyme 2 (ACE2) is a new identified member of the renin-angiotensin-aldosterone system (RAAS) that cleaves angiotensin II (Ang II) to Ang (1-7), which exerts anti-inflammatory and antioxidative activities via binding with Mas receptor (MasR). However, the functional role of ACE2 in sepsis-related hypotension remains unknown. Our results indicated that sepsis significantly reduced blood pressure and led to disruption between ACE-Ang II and ACE2-Ang (1-7) balance. ACE2 knock-in mice exhibited improved sepsis-induced mortality, hypotension and vascular dysfunction, while ACE2 knockout mice exhibited the opposite effects. Bone marrow transplantation and in vitro experiments confirmed that myeloid ACE2 exerted a protective role by suppressing oxidative stress, NO production and macrophage polarization via the Ang (1-7)-MasR-NF-κB and STAT1 pathways. Thus, ACE2 on myeloid cells could protect against sepsis-mediated hypotension and vascular dysfunction, and upregulating ACE2 may represent a promising therapeutic option for septic patients with hypotension.

Dectin1 contributes to hypertensive vascular injury by promoting macrophage infiltration through activating the Syk/NF-κB pathway

Vascular injury is an early manifestation leading to end-organ damage in hypertension pathogenesis, which involves a macrophage-associated immune response. Dendritic cell-associated C-type lectin-1 (Dectin1) is a pivotal player in regulating inflammation-mediated cardiovascular disease. However, its role in hypertension-induced vascular damage and the underlying mechanisms remain unclear. We hypothesized that Dectin1 might accelerate angiotensin II (Ang II)- or deoxycorticosterone acetate-salt (DOCA-salt)-induced vascular injury through proinflammatory actions in macrophages. Macrophage Dectin1 was upregulated in mouse aortic tissues stimulated with Ang II. In the peripheral blood, Ang II also increased CD11b+F4/80+ macrophages in mice. In our constructed Dectin1 knockout mice, Dectin1 deletion protected against Ang II-induced EB extravasation and aortic wall thickness. Deficiency of Dectin1 or its pharmacological inhibition considerably improved fibrosis and inflammation responses, accompanied by a reduction in M1 macrophage polarization as well as proinflammatory cytokines and chemokines induced by Ang II or DOCA-salt. Through the bone marrow (BM) transplantation assay, these effects were verified in the wild type mice reconstituted with Dectin1-deficient BM cells. Mechanistically, Ang II promoted Dectin1 homodimerization, thereby triggering the spleen tyrosine kinase/nuclear factor kappa B pro-inflammatory cascade to induce the expression of inflammatory factors and chemokines in vivo and in vitro. In conclusion, Dectin1 has an essential role in the pathogenic procedure of Ang II-stimulated or DOCA-salt-induced vascular damage in mice and represents a promising therapeutic target for cardiovascular diseases.

CD11b mediates hypertensive cardiac remodeling by regulating macrophage infiltration and polarization

INTRODUCTION

Leukocyte infiltration is an early event during cardiac remodeling frequently leading to heart failure (HF). Integrins mediate leukocyte infiltration during inflammation. However, the importance of specific integrins in hypertensive cardiac remodeling is still unclear.

OBJECTIVES

To elucidate the significance of CD11b in hypertensive cardiac remodeling.

METHODS

Angiotensin (Ang II) or deoxycorticosterone acetate (DOCA)-salt was used to induce cardiac remodeling in mice of gene knockout (KO), bone marrow (BM) chimera, and the CD11b neutralizing antibody or agonist leukadherin-1 (LA1) treatment.

RESULTS

Our microarray data showed that integrin subunits Itgam (CD11b) and Itgb2 (CD18) were the most highly upregulated in Ang II-infused hearts. CD11b expression and CD11b/CD18+ myelomonocytes were also time-dependently increased. KO or pharmacological blockade of CD11b greatly attenuated cardiac remodeling and macrophage infiltration and M1 polarization induced by Ang II or DOCA-salt. This protection was verified in wild-type mice transplanted with CD11b-deficient BM cells. Conversely, administration of CD11b agonist LA1 showed the opposite effects. Further, CD11b KO reduced Ang II-induced macrophage adhesion and M1 polarization, leading to reduction of cardiomyocyte enlargement and fibroblast differentiation in vitro. The numbers of CD14+CD11b+CD18+ monocytes and CD15+CD11b+CD18+ granulocytes were obviously higher in HF patients than in normal controls.

CONCLUSION

Our data demonstrate an important role of CD11b+ myeloid cells in hypertensive cardiac remodeling, and suggest that HF may benefit from targeting CD11b.

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) drives angiotensin II-induced vascular remodeling through regulating mitochondrial fragmentation

BACKGROUND

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a novel instigator for mitochondrial dysfunction, and plays an important role in the pathogenesis of cardiovascular diseases. However, the role and mechanism of DNA-PKcs in angiotensin II (Ang II)-induced vascular remodeling remains obscure.

METHODS

Rat aortic smooth muscle cells (SMC) and VSMC-specific DNA-PKcs knockout (DNA-PKcsΔVSMC) mice were employed to examine the role of DNA-PKcs in vascular remodeling and the underlying mechanisms. Blood pressure of mice was monitored using the tail-cuff and telemetry methods. The role of DNA-PKcs in vascular function was evaluated using vascular relaxation assessment.

RESULTS

In the tunica media of remodeled mouse thoracic aortas, and renal arteries from hypertensive patients, elevated DNA-PKcs expression was observed along with its cytoplasmic translocation from nucleus, suggesting a role for DNA-PKcs in vascular remodeling. We then infused wild-type (DNA-PKcsfl/fl) and DNA-PKcsΔVSMC mice with Ang II for 14 days to establish vascular remodeling, and demonstrated that DNA-PKcsΔVSMC mice displayed attenuated vascular remodeling through inhibition of dedifferentiation of VSMCs. Moreover, deletion of DNA-PKcs in VSMCs alleviated Ang II-induced vasodilation dysfunction and hypertension. Mechanistic investigations denoted that Ang II-evoked rises in cytoplasmic DNA-PKcs interacted with dynamin-related protein 1 (Drp1) at its TQ motif to phosphorylate Drp1S616, subsequently promoting mitochondrial fragmentation and dysfunction, as well as reactive oxygen species (ROS) production. Treatment of irbesartan, an Ang II type 1 receptor (AT1R) blocker, downregulated DNA-PKcs expression in VSMCs and aortic tissues following Ang II administration.

CONCLUSION

Our data revealed that cytoplasmic DNA-PKcs in VSMCs accelerated Ang II-induced vascular remodeling by interacting with Drp1 at its TQ motif and phosphorylating Drp1S616 to provoke mitochondrial fragmentation. Maneuvers targeting DNA-PKcs might be a valuable therapeutic option for the treatment of vascular remodeling and hypertension.

Comparative analyses of monocyte memory dynamics from mice to humans

BACKGROUND

Innate monocytes can adopt dynamic "memory" states ranging from low-grade inflammation to pathogenic exhaustion, dependent upon signal strength and history of challenges. Low-grade inflammatory monocytes facilitate the pathogenesis of chronic inflammatory diseases, while exhausted monocytes drive the pathogenesis of severe sepsis. Although clinical and basic studies suggest the conservation of key features of exhausted monocytes from human and murine sepsis, systems analyses of monocyte exhaustion among human and murine monocytes are lacking.

METHODS

We performed cross examination of septic monocytes scRNAseq data recently collected from human sepsis patients as well as experimental septic mice, in reference to monocytes experimentally exhausted in vitro. Furthermore, we performed pseudo-time analyses of in vitro programmed monocytes following prolonged challenges causing either low-grade inflammation or exhaustion. Additional comparative analyses of low-grade inflammatory monocytes were performed with scRNAseq data from selected human patients with chronic low-grade inflammatory diseases.

RESULTS

Our systems analyses reveal key features of monocyte exhaustion including reduced differentiation, pathogenic inflammation and immune suppression that are highly conserved in human and murine septic monocytes, and captured by in vitro experimental exhaustion. Pseudo-time analyses reveal that monocytes initially transition into a less-differentiated state with proliferative potential. The expansion of proliferative monocytes can be observed not only in experimentally challenged monocytes, but also in tissues of murine sepsis and human septic blood. We observed that monocytes similarly transition into the less-differentiated state when challenged with a subclinical dose endotoxin under chronic inflammatory conditions. Instead of being exhausted, monocytes with prolonged challenges with super-low dose endotoxin bifurcate into the low-grade inflammatory immune-enhancing or the chemotactic/adhesive state, often see in atherosclerosis or auto-immune diseases.

CONCLUSIONS

Key features of monocyte memory dynamics are identified and conserved in human and murine monocytes, which can be captured by prolonged challenges of innate signals with varying signal strength.