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. 2023 Oct 10:11:e16052.
doi: 10.7717/peerj.16052. eCollection 2023.

Molecular and phenotypic distinctions of macrophages in tolerant and susceptible to hypoxia rats

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Molecular and phenotypic distinctions of macrophages in tolerant and susceptible to hypoxia rats

Dzhuliia Dzhalilova et al. PeerJ. .

Abstract

Individual hypoxia tolerance is a major influence on the course and outcome of infectious and inflammatory diseases. Macrophages, which play central roles in systemic inflammatory response and other immunity reactions, are subject to functional activation orchestrated by several transcription factors including hypoxia inducible factors (HIFs). HIF-1 expression levels and the lipopolysaccharide (LPS)-induced systemic inflammatory response severity have been shown to correlate with hypoxia tolerance. Molecular and functional features of macrophages, depending on the organisms resistance to hypoxia, can determine the severity of the course of infectious and inflammatory diseases, including the systemic inflammatory response. The purpose is the comparative molecular and functional characterization of non-activated and LPS-activated bone marrow-derived macrophages under normoxia in rats with different tolerance to oxygen deprivation. Hypoxia resistance was assessed by gasping time measurement in an 11,500 m altitude-equivalent hypobaric decompression chamber. Based on the outcome, the animals were assigned to three groups termed 'tolerant to hypoxia' (n = 12), 'normal', and 'susceptible to hypoxia' (n = 13). The 'normal' group was excluded from subsequent experiments. One month after hypoxia resistance test, the blood was collected from the tail vein to isolate monocytes. Non-activated and LPS-activated macrophage cultures were investigated by PCR, flow cytometry and Western blot methods. Gene expression patterns of non-activated cultured macrophages from tolerant and susceptible to hypoxia animals differed. We observed higher expression of VEGF and CD11b and lower expression of Tnfa, Il1b and Epas1 in non-activated cultures obtained from tolerant to hypoxia animals, whereas HIF-1α mRNA and protein expression levels were similar. LPS-activated macrophage cultures derived from susceptible to hypoxia animals expressed higher levels of Hif1a and CCR7 than the tolerant group; in addition, the activation was associated with increased content of HIF-1α in cell culture medium. The observed differences indicate a specific propensity toward pro-inflammatory macrophage polarization in susceptible to hypoxia rats.

Keywords: HIF-1; Hypoxia tolerance; Inflammation; Macrophage; Rats.

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Conflict of interest statement

The authors declare there are no competing interests.

Figures

Figure 1
Figure 1. Flow cytometry for monocytes surface markers applied to non-activated and LPS-activated macrophage cultures obtained from rats with different hypoxia tolerance.
(A) CD11b in non-activated cultures from hypoxia-tolerant rats; (B) CD11b in non-activated cultures from hypoxia-susceptible rats; (C) CD11b, CD68, CD86 and CD163 in non-activated and LPS-activated cultures from tolerant and susceptible to hypoxia rats. Bar heights are medians, whisker ends are upper and lower quartiles; ∗, p < 0.05; ∗ ∗, p < 0.01, Mann–Whitney test.
Figure 2
Figure 2. Relative mRNA levels of (A) Tnfa, (B) Il1b, (C) Il6, (D) Mmp9, (E) Tgfb and (F) Il10 in non-activated and LPS-activated macrophages from tolerant and susceptible to hypoxia rats.
Bar heights are medians, whisker ends are upper and lower quartiles; *, p < 0.05; **, p < 0.01, Mann–Whitney test.
Figure 3
Figure 3. INOS, CCR7, and HGF expression levels in non-activated and LPS-activated macrophages from tolerant and susceptible to hypoxia rats.
(A) Representative Western blots stained with antibodies to iNOS, CCR7, HGF and GAPDH. (B) Relative mRNA Nos2 levels. (C), (D), and (E) Relative levels of iNOS, CCR7 and HGF proteins. Bar heights are medians, whisker ends are upper and lower quartiles; *, p < 0.05; **, p < 0.01, Mann–Whitney test.
Figure 4
Figure 4. RT-PCR, ELISA and WB results for non-activated and LPS-activated macrophage cultures obtained from rats with different hypoxia tolerance.
(A, C) Relative mRNA levels of Hif1a and Vegf in non-activated and LPS-activated macrophages from tolerant and susceptible to hypoxia rats. (B) HIF-1a protein in culture media conditioned by macrophages from tolerant and susceptible to hypoxia. (D) Relative levels of VEGF protein in non-activated and LPS-activated macrophages from tolerant and susceptible to hypoxia rats. Bar heights are medians, whisker ends are upper and lower quartiles; 7, p < 0.05; 77, p < 0.01, Mann–Whitney test.

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This work was supported by the Russian Science Foundation [grant number 22-15-00241], and budgetary topic 122030200530-6 “Cellular and molecular biological mechanisms of inflammation in the development of socially significant human diseases”. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.