Low Zinc Alleviates the Progression of Thoracic Aortic Dissection by Inhibiting Inflammation

Abstract

Vascular inflammation triggers the development of thoracic aortic dissection (TAD). Zinc deficiency could dampen tissue inflammation. However, the role of zinc as a nutritional intervention in the progression of TAD remains elusive. In this study, we employed a classical β-aminopropionitrile monofumarate (BAPN)-induced TAD model in mice treated with low zinc and observed that the TAD progression was greatly ameliorated under low zinc conditions. Our results showed that low zinc could significantly improve aortic dissection and rupture (BAPN + low zinc vs. BAPN, 36% vs. 100%) and reduce mortality (BAPN + low zinc vs. BAPN, 22% vs. 57%). Mechanically, low zinc attenuated the infiltration of macrophages and inhibited the expression of inflammatory cytokines, suppressed the phenotype switch of vascular smooth muscle cells from contractile to synthetic types, and eventually alleviated the development of TAD. In conclusion, this study suggested that low zinc may serve as a potential nutritional intervention approach for TAD prevention.

Keywords: inflammation; low zinc; phenotypic transition; thoracic aortic dissection; vascular smooth muscle cells.

Figure 1

Low zinc represses TAD progression. (A) Experimental design diagram. (B) The survival rate was estimated by the Kaplan-Meier method and compared by log-rank test (n = 14 per group). (C) TAD incidence. (D) Representative macrographs of the aorta.

Figure 2

Echocardiography analysis at the end of the animal experiment (BAPN-induced 30 days). (A) Representative ultrasound images of thoracic aortas. (B) Measurements of maximum aortic diameter, green blots represent control group, red blots represent BAPN group and blue blots represent BAPN + Low zinc group, n = 12 per group, by one-way ANOVA (*** p < 0.001).

Figure 3

Pathological staining analysis after animal experiment end (BAPN-induced 30 days). (A) Representative images showing hematoxylin and eosin (HE) (first column), elastic van Gieson (EVG) (second column), Masson’s trichrome (MASSON) (third column) and Alcian blue (final column) staining in paraffin sections from the indicated mice (top for the control group, middle for the BAPN group, bottom for the BAPN + low zinc group). Green arrowheads indicate elastin breaks. Scale bar, 200 μm for 10 magnifications, 50 μm for 40 magnifications. (B) Quantification of elastin breaks in paraffin sections from the mouse cohorts shown in (A), n = 12per group, by one-way ANOVA (*** p < 0.001). (C) Quantification of collagen content in paraffin sections from the mouse cohorts shown in (A), n = 10 per group, by one-way ANOVA (*** p < 0.001). Green blots represent control group, red blots represent BAPN group and blue blots represent BAPN + Low zinc group.

Figure 4

Low zinc suppressed the phenotype switch of vascular smooth muscle cells. (A) Relative mRNA levels of selected VSMC synthetic genes (Col1A1, Cxcl2 and Fn1) in mice aorta (n = 6 per group); by two-way ANOVA (*** p < 0.001). (B) Relative mRNA levels of selected VSMC contractile genes (Myh11, Acta2, Myl9, Ccn1 and Ramp1) in mice aorta (n = 6 per group); by two-way ANOVA (*** p < 0.001). (C) The protein levels (left column is western blot result, right column is quantitative analysis) of selected VSMC contractile markers (MYH11, ACTA2 and CCN1) in mice aorta (n = 3 per group); by two-way ANOVA (*** p < 0.001). All samples were collected after the animal experiment ended (BAPN-induced 30 days).

Figure 5

Low zinc inhibited TAD by down-regulating inflammation. (A) Representative confocal images of mice aorta stained with Mac-3 (green) and DAPI (blue) (scale bars, 50 μm for 10 magnifications; 20 μm for 20 magnifications). (B) Quantification of Mac-3 levels (n = 6 per group); by one-way ANOVA (*** p < 0.001). (C) The expression level of TNF-α in mice serum (n = 5 per group), by one-way ANOVA (*** p < 0.001). (D) Relative mRNA levels of TNF-α, TNFAIP3, TNFSF10, TNFSF9 and TNFSF1A of tumor necrosis factors in mice aorta (n = 6 per group); by two-way ANOVA (*** p < 0.001). (E) Relative mRNA levels of IL-1β, IL-6, IL-10 and MCP-1 of interleukin and chemokines in mice aorta (n = 6 per group); by two-way ANOVA (*** p < 0.001). (F) The protein levels (left column is western blot result, right column is quantitative analysis) of selected typical proinflammatory factors (IL-1β, TNF-α and IL-6) in mice aorta (n = 3 per group); by two-way ANOVA (*** p < 0.001). (G) Relative mRNA levels of MMP-9, MMP-2 and ADAMTS of extracellular matrix enzymes in mice aorta (n = 6 per group); by two-way ANOVA (*** p < 0.001). All samples were collected after the animal experiment ended (BAPN-induced 30 days).

Figure 6

Schematic illustration of low zinc alleviated the progression of TAD. In BAPN-treated mice, compared with a normal zinc diet, low zinc treatment reduces the infiltration of macrophage, decreases the expression of cytokines and chemokines, and inhibits the phenotype switch from contractile VSMCs to synthetic VSMCs, eventually alleviating TAD development. Part of the elements in this figure uses resources from Servier Medical Art under a Creative Commons Attribution license. TAD indicates thoracic aortic dissection, and BAPN indicates β-aminopropionitrile monofumarate.