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The role of toll-like receptor 9 in chronic stress-induced apoptosis in macrophage.

Xiang Y, Yan H, Zhou J, Zhang Q, Hanley G, Caudle Y, LeSage G, Zhang X, Yin D - PLoS ONE (2015)

Bottom Line: Toll-like receptors (TLRs) have been shown to play an essential role in modulating immune responses and cell survival.We have recently shown that TLR9 deficiency protects against lymphocyte apoptosis induced by chronic stress.TLR9 deficiency was also found to reverse elevation of plasma IL-1β, IL-10 and IL-17 levels and decrease of plasma IFN-γ level under the condition of chronic stress.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, College of Medicine, East Tennessee State University, Johnson City, Tennessee 37614, United States of America; Department of Pharmacology, Shandong University School of Medicine, Jinan, People's Republic of China.

ABSTRACT
Emerging evidence implied that chronic stress has been exerting detrimental impact on immune system functions in both humans and animals. Toll-like receptors (TLRs) have been shown to play an essential role in modulating immune responses and cell survival. We have recently shown that TLR9 deficiency protects against lymphocyte apoptosis induced by chronic stress. However, the exact role of TLR9 in stress-mediated change of macrophage function remains unclear. The results of the current study showed that when BALB/c mice were treated with restraint stress (12 h daily for 2 days), the number of macrophages recruited to the peritoneal cavity was obviously increased. Results also demonstrated that the sustained effects of stress elevated cytokine IL-1β, TNF-α and IL-10 production yet diminished IFN-γ production from macrophage, which led to apoptotic cell death. However, TLR9 deficiency prevented the chronic stress-mediated accumulation of macrophages. In addition, knocking out TLR9 significantly abolished the chronic stress-induced imbalance of cytokine levels and apoptosis in macrophage. TLR9 deficiency was also found to reverse elevation of plasma IL-1β, IL-10 and IL-17 levels and decrease of plasma IFN-γ level under the condition of chronic stress. These results indicated that TLR9-mediated macrophage responses were required for chronic stress-induced immunosuppression. Further exploration showed that TLR9 deficiency prevented the increment of p38 MAPK phosphorylation and reduction of Akt/Gsk-3β phosphorylation; TLR9 deficiency also attenuated the release of mitochondrial cytochrome c into cytoplasm, caused upregulation of Bcl-2/Bax protein ratio, downregulation of cleavage of caspase-3 and PARP, as well as decreased TUNEL-positive cells in macrophage of stressed mice. Collectively, our studies demonstrated that deficiency of TLR9 maintained macrophage function by modulating macrophage accumulation and attenuating macrophage apoptosis, thus preventing immunosuppression in restraint-stressed mice.

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A deficiency of TLR9 decreases chronic stress-induced changes of pro-inflammatory cytokine levels by macrophages TLR9 knockout mice or wild type BALB/c mice aged 6 to 8 weeks were subjected to a 12 h physical restraint daily.After 2 d stress, mice were sacrificed by cervical dislocation, and the macrophages were harvested, purified and cultured (5 × 105 cells/well) on culture plates for 24 hours. IL-1β, TNF-α, IL-10 and IFN-γ levels were measured in supernatants of macrophages by ELISA kit. Means and SEs were calculated from 7 mice per group. *p < 0.05, **p< 0.01 compared with indicated groups.
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pone.0123447.g002: A deficiency of TLR9 decreases chronic stress-induced changes of pro-inflammatory cytokine levels by macrophages TLR9 knockout mice or wild type BALB/c mice aged 6 to 8 weeks were subjected to a 12 h physical restraint daily.After 2 d stress, mice were sacrificed by cervical dislocation, and the macrophages were harvested, purified and cultured (5 × 105 cells/well) on culture plates for 24 hours. IL-1β, TNF-α, IL-10 and IFN-γ levels were measured in supernatants of macrophages by ELISA kit. Means and SEs were calculated from 7 mice per group. *p < 0.05, **p< 0.01 compared with indicated groups.

Mentions: In response to a large range of stimulation, macrophages secrete powerful biological substances, such as TNF-αand interleukins. This secretion results in inflammation. To investigate whether the diminished accumulation observed in the TLR9 knockout mice was secondary to altered macrophage function, we have detected generation of major pro-inflammatory cytokines by macrophages. Wild type and TLR9 knockout mice were subjected to stress as described previously, peritoneal macrophages were harvested and cultured for 24 hours. Our data showed that IL-1β, TNF-α, IL-10 were significantly overproduced in supernatants of macrophages of stressed wild type mice, increasing by 2.2-, 3.1- and 1.8-fold, compared to that of control wild type mice, respectively. However, IL-1β, TNF-α, IL-10 levels of stressed TLR9 knockout mice displayed no distinctive change compared to control TLR9 knockout mice and (Fig 2A, 2C and 2D). Chronic stress significantly inhibited IFN-γ production in supernatant of macrophages from stressed wild type mice by 2.5-fold than that from control wild type mice, but no change in IFN-γ expression level in supernatant of macrophages was observed after chronic stress challenge in TLR9 knockout mice (Fig 2B).


The role of toll-like receptor 9 in chronic stress-induced apoptosis in macrophage.

Xiang Y, Yan H, Zhou J, Zhang Q, Hanley G, Caudle Y, LeSage G, Zhang X, Yin D - PLoS ONE (2015)

A deficiency of TLR9 decreases chronic stress-induced changes of pro-inflammatory cytokine levels by macrophages TLR9 knockout mice or wild type BALB/c mice aged 6 to 8 weeks were subjected to a 12 h physical restraint daily.After 2 d stress, mice were sacrificed by cervical dislocation, and the macrophages were harvested, purified and cultured (5 × 105 cells/well) on culture plates for 24 hours. IL-1β, TNF-α, IL-10 and IFN-γ levels were measured in supernatants of macrophages by ELISA kit. Means and SEs were calculated from 7 mice per group. *p < 0.05, **p< 0.01 compared with indicated groups.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4401452&req=5

pone.0123447.g002: A deficiency of TLR9 decreases chronic stress-induced changes of pro-inflammatory cytokine levels by macrophages TLR9 knockout mice or wild type BALB/c mice aged 6 to 8 weeks were subjected to a 12 h physical restraint daily.After 2 d stress, mice were sacrificed by cervical dislocation, and the macrophages were harvested, purified and cultured (5 × 105 cells/well) on culture plates for 24 hours. IL-1β, TNF-α, IL-10 and IFN-γ levels were measured in supernatants of macrophages by ELISA kit. Means and SEs were calculated from 7 mice per group. *p < 0.05, **p< 0.01 compared with indicated groups.
Mentions: In response to a large range of stimulation, macrophages secrete powerful biological substances, such as TNF-αand interleukins. This secretion results in inflammation. To investigate whether the diminished accumulation observed in the TLR9 knockout mice was secondary to altered macrophage function, we have detected generation of major pro-inflammatory cytokines by macrophages. Wild type and TLR9 knockout mice were subjected to stress as described previously, peritoneal macrophages were harvested and cultured for 24 hours. Our data showed that IL-1β, TNF-α, IL-10 were significantly overproduced in supernatants of macrophages of stressed wild type mice, increasing by 2.2-, 3.1- and 1.8-fold, compared to that of control wild type mice, respectively. However, IL-1β, TNF-α, IL-10 levels of stressed TLR9 knockout mice displayed no distinctive change compared to control TLR9 knockout mice and (Fig 2A, 2C and 2D). Chronic stress significantly inhibited IFN-γ production in supernatant of macrophages from stressed wild type mice by 2.5-fold than that from control wild type mice, but no change in IFN-γ expression level in supernatant of macrophages was observed after chronic stress challenge in TLR9 knockout mice (Fig 2B).

Bottom Line: Toll-like receptors (TLRs) have been shown to play an essential role in modulating immune responses and cell survival.We have recently shown that TLR9 deficiency protects against lymphocyte apoptosis induced by chronic stress.TLR9 deficiency was also found to reverse elevation of plasma IL-1β, IL-10 and IL-17 levels and decrease of plasma IFN-γ level under the condition of chronic stress.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, College of Medicine, East Tennessee State University, Johnson City, Tennessee 37614, United States of America; Department of Pharmacology, Shandong University School of Medicine, Jinan, People's Republic of China.

ABSTRACT
Emerging evidence implied that chronic stress has been exerting detrimental impact on immune system functions in both humans and animals. Toll-like receptors (TLRs) have been shown to play an essential role in modulating immune responses and cell survival. We have recently shown that TLR9 deficiency protects against lymphocyte apoptosis induced by chronic stress. However, the exact role of TLR9 in stress-mediated change of macrophage function remains unclear. The results of the current study showed that when BALB/c mice were treated with restraint stress (12 h daily for 2 days), the number of macrophages recruited to the peritoneal cavity was obviously increased. Results also demonstrated that the sustained effects of stress elevated cytokine IL-1β, TNF-α and IL-10 production yet diminished IFN-γ production from macrophage, which led to apoptotic cell death. However, TLR9 deficiency prevented the chronic stress-mediated accumulation of macrophages. In addition, knocking out TLR9 significantly abolished the chronic stress-induced imbalance of cytokine levels and apoptosis in macrophage. TLR9 deficiency was also found to reverse elevation of plasma IL-1β, IL-10 and IL-17 levels and decrease of plasma IFN-γ level under the condition of chronic stress. These results indicated that TLR9-mediated macrophage responses were required for chronic stress-induced immunosuppression. Further exploration showed that TLR9 deficiency prevented the increment of p38 MAPK phosphorylation and reduction of Akt/Gsk-3β phosphorylation; TLR9 deficiency also attenuated the release of mitochondrial cytochrome c into cytoplasm, caused upregulation of Bcl-2/Bax protein ratio, downregulation of cleavage of caspase-3 and PARP, as well as decreased TUNEL-positive cells in macrophage of stressed mice. Collectively, our studies demonstrated that deficiency of TLR9 maintained macrophage function by modulating macrophage accumulation and attenuating macrophage apoptosis, thus preventing immunosuppression in restraint-stressed mice.

Show MeSH
Related in: MedlinePlus