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Toll-like Receptor 2 is Dispensable for an Immediate-early Microglial Reaction to Two-photon Laser-induced Cortical Injury In vivo.

Yoon H, Jang YH, Kim SJ, Lee SJ, Kim SK - Korean J. Physiol. Pharmacol. (2015)

Bottom Line: Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults.Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity.Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul 130-701, Korea.

ABSTRACT
Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults. Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity. Although many previous studies have suggested that TLR2 contributes to microglial activation and subsequent pathogenesis following brain tissue injury, it is still unclear whether TLR2 has a role in microglia dynamics in the resting state or in immediate-early reaction to the injury in vivo. By using in vivo two-photon microscopy imaging and Cx3cr1 (GFP/+) mouse line, we first monitored the motility of microglial processes (i.e. the rate of extension and retraction) in the somatosensory cortex of living TLR2-KO and WT mice; Microglial processes in TLR2-KO mice show the similar motility to that of WT mice. We further found that microglia rapidly extend their processes to the site of local tissue injury induced by a two-photon laser ablation and that such microglial response to the brain injury was similar between WT and TLR2-KO mice. These results indicate that there are no differences in the behavior of microglial processes between TLR2-KO mice and WT mice when microglia is in the resting state or encounters local injury. Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.

No MeSH data available.


Related in: MedlinePlus

The microglial response to brain injury in TLR2-KO and WT mice. (A) Representative images for the microglial response to brain tissue injury with time (-30, 0, 60, 120 min post-injury) in WT and TLR2-KO mice. (B) To quantify the microglial response toward laser-induced injury, we measured the number of pixels entering from the outer area Y (70 µm in radius) into the inner area X (35 µm in radius). The number of GFP pixels in area X or Y were measured at each time point (Rx(t) or Ry(t)), and the microglial response was defined as R(t)=(Rx(t)-Rx(0))/Ry(0). (C) Quantification of microglial response to laser ablation in TLR2KO (n=3) and WT (n=3) mice. Data are presented as mean±SEM.
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Figure 3: The microglial response to brain injury in TLR2-KO and WT mice. (A) Representative images for the microglial response to brain tissue injury with time (-30, 0, 60, 120 min post-injury) in WT and TLR2-KO mice. (B) To quantify the microglial response toward laser-induced injury, we measured the number of pixels entering from the outer area Y (70 µm in radius) into the inner area X (35 µm in radius). The number of GFP pixels in area X or Y were measured at each time point (Rx(t) or Ry(t)), and the microglial response was defined as R(t)=(Rx(t)-Rx(0))/Ry(0). (C) Quantification of microglial response to laser ablation in TLR2KO (n=3) and WT (n=3) mice. Data are presented as mean±SEM.

Mentions: By using a two-photon laser ablation method, we next examined an immediate response of microglia to a local brain injury in TLR2-KO and WT mice. As shown in Fig. 3A, this local injury was developed after a focal two-photon laser stimulus was applied to a microglia soma, and then nearby microglia rapidly sent out their processes to the lesion site in both groups of mice. More specifically, within a few minutes after a laser ablation, the microglial processes close to the damaged site appeared slightly enlarged and bulbous. After the next few minutes, microglial processes reached to the damaged site (Supplementary Videos 1 and 2). To quantitatively compare the microglial response to laser-induced injury in TLR2-KO and WT mice, we counted the number of pixels entering from the outer area Y into the inner area X with time (Fig. 3B and see also Methods). Fig. 3C shows that there was no significant difference in the microglial response to the injury between the TLR2-KO and WT mice (p>0.05).


Toll-like Receptor 2 is Dispensable for an Immediate-early Microglial Reaction to Two-photon Laser-induced Cortical Injury In vivo.

Yoon H, Jang YH, Kim SJ, Lee SJ, Kim SK - Korean J. Physiol. Pharmacol. (2015)

The microglial response to brain injury in TLR2-KO and WT mice. (A) Representative images for the microglial response to brain tissue injury with time (-30, 0, 60, 120 min post-injury) in WT and TLR2-KO mice. (B) To quantify the microglial response toward laser-induced injury, we measured the number of pixels entering from the outer area Y (70 µm in radius) into the inner area X (35 µm in radius). The number of GFP pixels in area X or Y were measured at each time point (Rx(t) or Ry(t)), and the microglial response was defined as R(t)=(Rx(t)-Rx(0))/Ry(0). (C) Quantification of microglial response to laser ablation in TLR2KO (n=3) and WT (n=3) mice. Data are presented as mean±SEM.
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Related In: Results  -  Collection

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Figure 3: The microglial response to brain injury in TLR2-KO and WT mice. (A) Representative images for the microglial response to brain tissue injury with time (-30, 0, 60, 120 min post-injury) in WT and TLR2-KO mice. (B) To quantify the microglial response toward laser-induced injury, we measured the number of pixels entering from the outer area Y (70 µm in radius) into the inner area X (35 µm in radius). The number of GFP pixels in area X or Y were measured at each time point (Rx(t) or Ry(t)), and the microglial response was defined as R(t)=(Rx(t)-Rx(0))/Ry(0). (C) Quantification of microglial response to laser ablation in TLR2KO (n=3) and WT (n=3) mice. Data are presented as mean±SEM.
Mentions: By using a two-photon laser ablation method, we next examined an immediate response of microglia to a local brain injury in TLR2-KO and WT mice. As shown in Fig. 3A, this local injury was developed after a focal two-photon laser stimulus was applied to a microglia soma, and then nearby microglia rapidly sent out their processes to the lesion site in both groups of mice. More specifically, within a few minutes after a laser ablation, the microglial processes close to the damaged site appeared slightly enlarged and bulbous. After the next few minutes, microglial processes reached to the damaged site (Supplementary Videos 1 and 2). To quantitatively compare the microglial response to laser-induced injury in TLR2-KO and WT mice, we counted the number of pixels entering from the outer area Y into the inner area X with time (Fig. 3B and see also Methods). Fig. 3C shows that there was no significant difference in the microglial response to the injury between the TLR2-KO and WT mice (p>0.05).

Bottom Line: Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults.Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity.Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul 130-701, Korea.

ABSTRACT
Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults. Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity. Although many previous studies have suggested that TLR2 contributes to microglial activation and subsequent pathogenesis following brain tissue injury, it is still unclear whether TLR2 has a role in microglia dynamics in the resting state or in immediate-early reaction to the injury in vivo. By using in vivo two-photon microscopy imaging and Cx3cr1 (GFP/+) mouse line, we first monitored the motility of microglial processes (i.e. the rate of extension and retraction) in the somatosensory cortex of living TLR2-KO and WT mice; Microglial processes in TLR2-KO mice show the similar motility to that of WT mice. We further found that microglia rapidly extend their processes to the site of local tissue injury induced by a two-photon laser ablation and that such microglial response to the brain injury was similar between WT and TLR2-KO mice. These results indicate that there are no differences in the behavior of microglial processes between TLR2-KO mice and WT mice when microglia is in the resting state or encounters local injury. Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.

No MeSH data available.


Related in: MedlinePlus