Endothelial Glycocalyx Disorders May Be Associated With Extended Inflammation During Endotoxemia in a Diabetic Mouse Model - PubMed (original) (raw)

doi: 10.3389/fcell.2021.623582. eCollection 2021.

Hideshi Okada 1, Hiroyuki Tomita 3, Chihiro Takada 1, Kodai Suzuki 1, Takamasa Kinoshita 3 4, Ryo Kobayashi 5, Hirotsugu Fukuda 1, Yuki Kawasaki 1, Ayane Nishio 1, Hirohisa Yano 1, Isamu Muraki 1, Yohei Fukuda 1, Keiko Suzuki 5, Nagisa Miyazaki 6, Takatomo Watanabe 7, Tomoaki Doi 1, Takahiro Yoshida 1, Akio Suzuki 5, Shozo Yoshida 1, Shigeki Kushimoto 2, Shinji Ogura 1

Affiliations

Endothelial Glycocalyx Disorders May Be Associated With Extended Inflammation During Endotoxemia in a Diabetic Mouse Model

So Sampei et al. Front Cell Dev Biol. 2021.

Abstract

In diabetes mellitus (DM) patients, the morbidity of infectious disease is increased, and these infections can easily progress from local to systemic infection. Sepsis is a characteristic of organ failure related to microcirculation disorders resulting from endothelial cell injury, whose most frequent comorbidity in patients is DM. The aim of the present study was to evaluate the influence of infection on DM-induced microvascular damage on inflammation and pulmonary endothelial structure using an experimental endotoxemia model. Lipopolysaccharide (LPS; 15 mg/kg) was injected intraperitoneally into 10-week-old male C57BLKS/J Iar- + lepr db /lepr db (db/db) mice and into C57BLKS/J Iar-m + / + lepr db (db/ +) mice, which served as the littermate non-diabetic control. At 48 h after LPS administration, the survival rate of db/db mice (0%, 0/10) was markedly lower (P < 0.05) than that of the db/ + mice (75%, 18/24), whereas the survival rate was 100% in both groups 24 h after LPS administration. In control mice, CD11b-positive cells increased at 6 h after LPS administration; by comparison, the number of CD11b-positive cells increased gradually in db/db mice until 12 h after LPS injection. In the control group, the number of Iba-1-positive cells did not significantly increase before and at 6, 12, and 24 h after LPS injection. Conversely, Iba-1-positive cells continued to increase until 24 h after LPS administration, and this increase was significantly greater than that in the control mice. Expression of Ext1, Csgalnact1, and Vcan related to endothelial glycocalyx synthesis was significantly lower in db/db mice than in the control mice before LPS administration, indicating that endothelial glycocalyx synthesis is attenuated in db/db/mice. In addition, ultrastructural analysis revealed that endothelial glycocalyx was thinner in db/db mice before LPS injection. In conclusion, in db/db mice, the endothelial glycocalyx is already injured before LPS administration, and migration of inflammatory cells is both delayed and expanded. This extended inflammation may be involved in endothelial glycocalyx damage due to the attenuation of endothelial glycocalyx synthesis.

Keywords: diabetes; endothelium; glycocalyx; inflammation; lipopolysaccharide.

Copyright © 2021 Sampei, Okada, Tomita, Takada, Suzuki, Kinoshita, Kobayashi, Fukuda, Kawasaki, Nishio, Yano, Muraki, Fukuda, Suzuki, Miyazaki, Watanabe, Doi, Yoshida, Suzuki, Yoshida, Kushimoto and Ogura.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1

FIGURE 1

Phenotype of db/db mice under normal conditions. Serum (A) blood sugar, (B) HbA1c, (C) blood urea nitrogen, (D) creatinine, (E) aspartate aminotransferase, and (F) alanine transferase concentration: blood sugar, HbA1c, blood urea nitrogen, and alanine transferase concentrations were significantly higher in db/db mice (n = 6) than in the wild-type mice (n = 6). *, P < 0.05 vs. wild type.

FIGURE 2

FIGURE 2

Lipopolysaccharide (LPS)-induced lung injury is accelerated in db/db mice compared with in control mice. (A) Kaplan–Meier survival curves for control mice (n = 24) and LPS-treated mice (n = 10). (B) Serum interleukin 1β (IL-1β) was measured in mice using an enzyme-linked immunosorbent assay. (C) Hematoxylin and eosin-stained lung tissues. Arrows indicate neutrophil infiltration. (D) Graphs of the histologic scoring of lung injury around the pulmonary edema. (E) Hematoxylin and eosin-stained lung tissues. (F) Arrows indicate edema. Graphs of the histologic scoring of lung injury around neutrophil filtration. n = 6 mice per group. *, P < 0.05.

FIGURE 3

FIGURE 3

Modulation of inflammatory cells under endotoxemic conditions. (A1) CD11b-positive cells were quantified as numbers of cells per high-power field. (A2) Representative images of CD11b cells in immunostained lung specimens. (B1) Iba-1 positive cells were quantified as the number of cells per high-power field. (B2) Representative images of Iba-1 in immunostained lung samples. *, P < 0.05.

FIGURE 4

FIGURE 4

Pulmonary endothelial glycocalyx is injured in db/db mice. (A) Serum syndecan-1 was measured in mice using an enzyme-linked immunosorbent assay. (B) Tomato lectin intensity of control and db/db mouse lungs with and without LPS administration. *, P < 0.05 vs. non-LPS-injected control mice; +, P < 0.05 vs. LPS-injected control mice. (C–H) qRT-PCR for (C) SDC1, (D) Has1, (E) Has2, (F) Csgalnact1, (G) Ext1, and (H) Vcan in control and db/db mice under normal conditions. *, P < 0.05.

FIGURE 5

FIGURE 5

Ultrastructural imaging of pulmonary endothelial injury by SEM. (A) Images for samples not stained with lanthanum nitrate; the endothelial glycocalyx was not detected**. (B)** The endothelial glycocalyx was detected using lanthanum nitrate staining. Although the moss-like structure of the endothelial glycocalyx covered the surface of the vascular endothelium in the control group mice under normal conditions, the endothelial glycocalyx structure was already degraded and dispersed (white arrow) in db/db mice. After LPS injection, the endothelial glycocalyx was degraded completely in db/db mice, whereas its injury was attenuated in control mice.

FIGURE 6

FIGURE 6

Ultrastructural imaging of pulmonary endothelial injury by transmission electron microscopy (TEM). (A) Images taken from samples not stained with lanthanum nitrate; the endothelial glycocalyx was not detected. The pulmonary endothelium was thin and smooth in control mice before LPS injection. In control mice after LPS injection, the endothelial wall became edematous, but the extent of this was greater in db/db mice than in control mice treated with or without LPS. (B) The endothelial glycocalyx was detected using lanthanum nitrate staining. The endothelial glycocalyx structure showed greater degradation in db/db mice than in control mice under normal conditions. After LPS injection, the endothelial glycocalyx formed a skip lesion in control mice, whereas the endothelial glycocalyx was more degraded in db/db mice. Black arrows indicate the endothelial glycocalyx.

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