Short-Term Inhalation of Ultrafine Zinc Particles Could Alleviate Cardiac Dysfunctions in Rats of Myocardial Infarction

Abstract

It is not clear for inhalation of ultrafine metal particles in air pollution to impair human health. In the study, we aimed to investigate whether short-term (4 weeks) inhalation of ultrafine zinc particles could deteriorate the cardiac and hemodynamic functions in rats of myocardial infarction (MI). MI was induced in Wistar rats through coronary artery ligation surgery and given an inhalation of ultrafine zinc particles for 4 weeks (post-MI 4 weeks, 4 days per week, and 4 h per day). Cardiac strain and strain rate were quantified by the speckle tracking echocardiography. The pressure and flow wave were recorded in the carotid artery and analyzed by using the Womersley model. Myocardial infarction resulted in the LV wall thinning, LV cavity dilation, remarkable decrease of ejection fraction, dp/dt Max, -dp/dt Min, myocardial strain and strain rates, and increased LV end-diastolic pressure, as well as impaired hemodynamic environment. The short-term inhalation of ultrafine zinc particles significantly alleviated cardiac and hemodynamic dysfunctions, which could protect from the MI-induced myocardial and hemodynamic impairments albeit it is unknown for the long-term inhalation.

Keywords: Womersley analysis; myocardium infraction; speckle-tracing echocardiography; strain analysis; ultrafine zinc particle.

FIGURE 1

(A) Schematic representative of experimental protocol, where Sham-Zn and MI-Zn groups were exposed to ultrafine zinc particle for 4 days per week in 4 weeks after LAD ligation. (B) Schematic representative of myocardium strain in radial, longitudinal, and circumference directions. (C) Body weight, (D) the ratio of HW to BW, and (E) serum zinc concentration in Sham (n = 12), Sham-Zn (n = 12), MI (n = 12), and MI-Zn (n = 12) groups at postoperative 4 weeks. ^∗P < 0.05, MI vs. Sham. ^•P < 0.05, Sham vs. Sham-Zn. ^◆P < 0.05, MI-Zn vs. Sham-Zn. ^#P < 0.05, MI-Zn vs. MI.

FIGURE 2

(A) EF (%), (B) FS (%), (C) LVEDP (mmHg), (D) Tau, (E) dp/dt Max, and (F) –dp/dt Min (mmHg/s) in Sham (n = 12), Sham-Zn (n = 12), MI (n = 12), and MI-Zn (n = 12) groups at postoperative 4 weeks. ^∗P < 0.05, MI vs. Sham. ^◆P < 0.05, MI-Zn vs. Sham-Zn. ^#P < 0.05, MI-Zn vs. MI.

FIGURE 3

(A) Schematic representative of deformation analysis in six segments along the long-axis echocardiographic view, where segments 1–6 refer to LV basal posterior wall, middle posterior wall, posterior apex, basal anterior wall, middle anterior wall, and anterior apex, respectively, (B) schematic representative of deformation analysis in six segments along the short-axis echocardiographic view, where segments 1–3 refer to free wall and segments 4–6 refer to interventricular septum, (C) long-axis, and (D) short-axis echocardiographic views in a representative Sham, (E) long-axis, and (F) short-axis echocardiographic views in a representative of MI, where yellow region marks the infarction area.

FIGURE 4

(A–D) Transient distribution of representative flow velocity in the carotid artery of (A) Sham, (B) Sham-Zn, (C) MI, and (D) MI-Zn groups at postoperative 4 weeks; and (E) TAWSS (dynes/cm²), (F) OSI, and (G) RRT in the carotid artery of Sham (n = 6), Sham-Zn (n = 6), MI (n = 6), and MI-Zn (n = 6) groups at postoperative 4 weeks. ^•P < 0.05, Sham vs. Sham-Zn. ^∗P < 0.05, MI vs. Sham. ^◆P < 0.05, MI-Zn vs. Sham-Zn. ^#P < 0.05, MI-Zn vs. MI.

FIGURE 5

(A,B) Schematic representative of HE (A) and Masson trichromatic (B) staining. The results of HE staining were observed under 20× objective lens (scale label: 50 μm), and Masson trichromatic staining was observed under 5× objective lens (scale label: 200 μm). (C) Quantitative comparison of myocardium fibrosis between MI group and MI-Zn group. ^∗P < 0.05, MI vs. MI-Zn.