The roles of immune cells in atherosclerotic calcification

Pravastatin promotes type 2 diabetes vascular calcification through activating intestinal Bacteroides fragilis to induce macrophage M1 polarization

BACKGROUND

Pravastatin is an oral lipid-lowering drug, commonly used by patients with diabetes that is positively correlated with the occurrence of vascular calcification (VC), but the mechanism is unclear.

METHODS

In this study, 16S rRNA sequencing and qRT-PCR wereused to detect the differential gut bacteria. Metabolomics and ELISA were used to analyze the differential metabolites. qRT-PCR and western blotting (WB) were used to detect genes expression. Flow cytometry was used to analyze macrophage phenotype. Immunohistochemistry was used to analyze aortic calcification.

RESULTS

We found that gut Bacteroides fragilis (BF) increased significantly in patients who took pravastatin or type 2 diabetes (T2D) mice treated with pravastatin. In vitro experiments showed that pravastatin had little effect on BF but significantly promoted BF proliferation in vivo. Further analysis showed that ArsR was an important gene for pravastatin to regulate the activation of BF, and overexpression of ArsR significantly promoted the secretion of 3,4,5-trimethoxycinnamic acid (TMCA). Importantly, pravastatin significantly promoted BF secretion of TMCA and significantly increased TMCA secretion in T2D patients or T2D mice. TMCA had little effect on vascular smooth muscle cell calcification but significantly promoted macrophage M1 polarization, which we had demonstrated that M1 macrophages promoted T2D VC. In vivo studies found that pravastatin significantly upregulated TMCA levels in the feces and serum of T2D mice transplanted with BF and promoted the macrophage M1 polarization in bone marrow and the osteoblastic differentiation of aortic cells. Similar results were obtained in T2D mice after intravenous infusion of TMCA.

CONCLUSIONS

Promoting intestinal BF to secrete TMCA, which leads to macrophage M1 polarization, is an important mechanism by which pravastatin promotes calcification, and the result will be used for the optimization of clinical medication strategies of pravastatin supplying a theoretical basis and experimental basis.

The role of macrophage polarization in vascular calcification

Vascular calcification is an important factor in the high morbidity and mortality of Cardiovascular and cerebrovascular diseases. Vascular damage caused by calcification of the intima or media impairs the physiological function of the vascular wall. Inflammation is a central factor in the development of vascular calcification. Macrophages are the main inflammatory cells. Dynamic changes of macrophages with different phenotypes play an important role in the occurrence, progression and stability of calcification. This review focuses on macrophage polarization and the relationship between macrophages of different phenotypes and calcification environment, as well as the mechanism of interaction, it is considered that macrophages can promote vascular calcification by releasing inflammatory mediators and promoting the osteogenic transdifferentiation of smooth muscle cells and so on. In addition, several therapeutic strategies aimed at macrophage polarization for vascular calcification are described, which are of great significance for targeted treatment of vascular calcification.

Extracellular vesicles of Bacteroides fragilis regulated macrophage polarization through promoted Sema7a expression

Abnormal activation of macrophage and gut Bacteroides fragilis (BF) are the important induction factors in the occurrence of type 2 diabetes (T2D) and vascular complications. However, it remains unknown whether BF involves in macrophage polarization. In this study, we found that BF extracellular vesicles (EV) can be uptaken by macrophage. BF-EV promote macrophage M1/M2 polarization significantly, and increase Sting expression significantly. Bioinformatics analysis found that Sema7a is an important gene involving in macrophage polarization. The expression of Sema7a can be induced by BF-EV and can be inhibited after C-176 treated. The inhibition expression of Sema7a prevent BF-EV to induce macrophage polarization. Further analysis reveals that there is no direct interaction between Sting and Sema7a, but Sgpl1 can interact with Sting or Sema7a. BF-EV promote the expression of Sgpl1, which the phenomenon can be inhibited after C-176 treated. Importantly, overexpression of Sgpl1 reversed the effect of C-176 for Sema7a expression, while inhibit Sema7a expression has limitation influence for Sting and Sgpl1 expression. In conclusion, this study confirms that Sting-Sgpl1-Sema7a is a key mechanism by which BF-EV regulates macrophage polarization.

The Cholinergic Anti-Inflammatory Pathway Attenuates the Development of Atherosclerosis in Apoe-/- Mice through Modulating Macrophage Functions

(1) Background: The cholinergic anti-inflammatory pathway (CAP) has been implicated in the regulation of various diseases, including chronic inflammatory cardiovascular disorders such as atherosclerosis (AS). This study aims to explore the underlying regulatory mechanisms of CAP activity in the progression of AS. (2) Methods: The Apoe^-/- mice were subjected to sham, bilateral cervical vagotomy surgery (VGX), and VGX supplemented with Gainesville Tokushima scientists (GTS)-21 (4 mg/kg/d) and then fed with a high-fat diet for 10 weeks. Atherosclerotic lesion size and inflammation levels were investigated by histology and inflammatory cytokines analysis. The blood M1/M2 macrophages were analyzed by flow cytometry. Primary mouse bone marrow-derived macrophages (BMDM), peritoneal macrophages, and RAW264.7 cells were treated with CAP agonists acetylcholine (Ach) and GTS-21 to study their effects on macrophage functions. (3) Results: Compared with the sham group, inhibition of CAP by the VGX resulted in growing aortic lipid plaque area, deteriorated inflammatory levels, and aberrant quantity of M1/M2 macrophages in Apoe^-/- mice. However, these detrimental effects of VGX were significantly ameliorated by the reactivation of CAP through GTS-21 treatment. The in vitro study using macrophages revealed that stimulation with CAP agonists suppressed M1, but promoted M2 macrophage polarization through the upregulation of TNFAIP3 and phosphorylation STAT3 levels, respectively. Moreover, the activation of CAP inhibited the formation of macrophage foam cells in the peritoneal cavity by regulating genes related to cholesterol metabolism. (4) Conclusions: This study provides novel evidence and mechanisms that the CAP plays an important role in the regulation of AS development by controlling macrophage functions, implying a potential use of CAP activation as a therapeutic strategy for AS treatment.