Limits...
Toll-like receptor 4 promotes autonomic dysfunction, inflammation and microglia activation in the hypothalamic paraventricular nucleus: role of endoplasmic reticulum stress.

Masson GS, Nair AR, Dange RB, Silva-Soares PP, Michelini LC, Francis J - PLoS ONE (2015)

Bottom Line: It also decreased HR variability and high frequency (HF) components of HR variability, as well BrS.These hemodynamic and molecular effects were partially abrogated with TLR4 blocker or ER stress inhibitor pretreatment.Further inhibition of TLR4 or ER stress was able to attenuate the LPS-induced microglia activation.

View Article: PubMed Central - PubMed

Affiliation: Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America; Department of Physiology and Biophysics, Biomedical Sciences Institute, University of Sao Paulo, Sao Paulo, Brazil.

ABSTRACT

Background & purpose: Toll-like receptor 4 (TLR4) signaling induces tissue pro-inflammatory cytokine release and endoplasmic reticulum (ER) stress. We examined the role of TLR4 in autonomic dysfunction and the contribution of ER stress.

Experimental approach: Our study included animals divided in 6 experimental groups: rats treated with saline (i.v., 0.9%), LPS (i.v., 10mg/kg), VIPER (i.v., 0.1 mg/kg), or 4-PBA (i.p., 10 mg/kg). Two other groups were pretreated either with VIPER (TLR4 viral inhibitory peptide) LPS + VIPER (i.v., 0.1 mg/kg) or 4-Phenyl butyric acid (4-PBA) LPS + PBA (i.p., 10 mg/kg). Arterial pressure (AP) and heart rate (HR) were measured in conscious Sprague-Dawley rats. AP, HR variability, as well as baroreflex sensitivity (BrS), was determined after LPS or saline treatment for 2 hours. Immunofluorescence staining for NeuN, Ib1a, TLR4 and GRP78 in the hypothalamic paraventricular nucleus (PVN) was performed. TNF-α, TLR4 and GRP78 protein expression in the PVN were evaluated by western blot. Plasma norepinephrine levels were determined by ELISA.

Key results: Acute LPS treatment increased HR and plasma norepinephrine concentration. It also decreased HR variability and high frequency (HF) components of HR variability, as well BrS. Acute LPS treatment increased TLR4 and TNF-α protein expression in the PVN. These hemodynamic and molecular effects were partially abrogated with TLR4 blocker or ER stress inhibitor pretreatment. In addition, immunofluorescence study showed that TLR4 is co-localized with GRP78in the neurons. Further inhibition of TLR4 or ER stress was able to attenuate the LPS-induced microglia activation.

Conclusions & implications: TLR4 signaling promotes autonomic dysfunction, inflammation and microglia activation, through neuronal ER stress, in the PVN.

No MeSH data available.


Related in: MedlinePlus

ER stress inhibition prevents autonomic dysfunction induced by TLR4 signaling.(A) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on heart rate. (B) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on mean arterial pressure. (C) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on heart rate variability. (D) Effects of ER stress inhibition (ip, 0.1 mg/kg) in LPS-induced changes on high-frequency component of heart rate variability. (E) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on systolic arterial pressure variability. (F) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on low-frequency component of systolic arterial pressure variability. (G) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on baroreflex sensitivity. (H) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on baroreflex sigmoidal curve. #—p<0.05 saline vs LPS treated-rats; *—p<0.05 LPS vs LPS+ PBA; n = 9–10 rats.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4374971&req=5

pone.0122850.g002: ER stress inhibition prevents autonomic dysfunction induced by TLR4 signaling.(A) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on heart rate. (B) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on mean arterial pressure. (C) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on heart rate variability. (D) Effects of ER stress inhibition (ip, 0.1 mg/kg) in LPS-induced changes on high-frequency component of heart rate variability. (E) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on systolic arterial pressure variability. (F) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on low-frequency component of systolic arterial pressure variability. (G) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on baroreflex sensitivity. (H) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on baroreflex sigmoidal curve. #—p<0.05 saline vs LPS treated-rats; *—p<0.05 LPS vs LPS+ PBA; n = 9–10 rats.

Mentions: As demonstrated above, TLR4 ligand LPS, induced acute autonomic dysfunction. Interestingly, ER stress inhibitor PBA pre-treatment was also able to block the HR increase induced by LPS (Fig. 2A). ER stress inhibition blunted the decrease of HRVar evoked by LPS from 60 minutes of experimental protocol (Fig. 2C). We also observed that PBA prevented the decrease of HF component of HRVar induced by LPS during all experimental protocols (Fig. 2D). ER stress inhibition prevented the increase of SAPVar, as well as its low frequency component, induced by LPS (Fig. 2E and 2F). In agreement with HRVar findings, ER stress inhibition prevented acute baroreflex dysfunction evoked by LPS (Fig. 2G). Similarly to TLR4 blockade, PBA treated-rats also exhibited a downward and left shift of baroreflex curve, which suggests an improvement in baroreflex function (Fig. 2H). PBA treatment alone did not affect autonomic or cardiovascular function measurements.


Toll-like receptor 4 promotes autonomic dysfunction, inflammation and microglia activation in the hypothalamic paraventricular nucleus: role of endoplasmic reticulum stress.

Masson GS, Nair AR, Dange RB, Silva-Soares PP, Michelini LC, Francis J - PLoS ONE (2015)

ER stress inhibition prevents autonomic dysfunction induced by TLR4 signaling.(A) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on heart rate. (B) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on mean arterial pressure. (C) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on heart rate variability. (D) Effects of ER stress inhibition (ip, 0.1 mg/kg) in LPS-induced changes on high-frequency component of heart rate variability. (E) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on systolic arterial pressure variability. (F) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on low-frequency component of systolic arterial pressure variability. (G) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on baroreflex sensitivity. (H) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on baroreflex sigmoidal curve. #—p<0.05 saline vs LPS treated-rats; *—p<0.05 LPS vs LPS+ PBA; n = 9–10 rats.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4374971&req=5

pone.0122850.g002: ER stress inhibition prevents autonomic dysfunction induced by TLR4 signaling.(A) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on heart rate. (B) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on mean arterial pressure. (C) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on heart rate variability. (D) Effects of ER stress inhibition (ip, 0.1 mg/kg) in LPS-induced changes on high-frequency component of heart rate variability. (E) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on systolic arterial pressure variability. (F) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on low-frequency component of systolic arterial pressure variability. (G) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on baroreflex sensitivity. (H) Effects of ER stress inhibition (ip, 10 mg/kg) in LPS-induced changes on baroreflex sigmoidal curve. #—p<0.05 saline vs LPS treated-rats; *—p<0.05 LPS vs LPS+ PBA; n = 9–10 rats.
Mentions: As demonstrated above, TLR4 ligand LPS, induced acute autonomic dysfunction. Interestingly, ER stress inhibitor PBA pre-treatment was also able to block the HR increase induced by LPS (Fig. 2A). ER stress inhibition blunted the decrease of HRVar evoked by LPS from 60 minutes of experimental protocol (Fig. 2C). We also observed that PBA prevented the decrease of HF component of HRVar induced by LPS during all experimental protocols (Fig. 2D). ER stress inhibition prevented the increase of SAPVar, as well as its low frequency component, induced by LPS (Fig. 2E and 2F). In agreement with HRVar findings, ER stress inhibition prevented acute baroreflex dysfunction evoked by LPS (Fig. 2G). Similarly to TLR4 blockade, PBA treated-rats also exhibited a downward and left shift of baroreflex curve, which suggests an improvement in baroreflex function (Fig. 2H). PBA treatment alone did not affect autonomic or cardiovascular function measurements.

Bottom Line: It also decreased HR variability and high frequency (HF) components of HR variability, as well BrS.These hemodynamic and molecular effects were partially abrogated with TLR4 blocker or ER stress inhibitor pretreatment.Further inhibition of TLR4 or ER stress was able to attenuate the LPS-induced microglia activation.

View Article: PubMed Central - PubMed

Affiliation: Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, United States of America; Department of Physiology and Biophysics, Biomedical Sciences Institute, University of Sao Paulo, Sao Paulo, Brazil.

ABSTRACT

Background & purpose: Toll-like receptor 4 (TLR4) signaling induces tissue pro-inflammatory cytokine release and endoplasmic reticulum (ER) stress. We examined the role of TLR4 in autonomic dysfunction and the contribution of ER stress.

Experimental approach: Our study included animals divided in 6 experimental groups: rats treated with saline (i.v., 0.9%), LPS (i.v., 10mg/kg), VIPER (i.v., 0.1 mg/kg), or 4-PBA (i.p., 10 mg/kg). Two other groups were pretreated either with VIPER (TLR4 viral inhibitory peptide) LPS + VIPER (i.v., 0.1 mg/kg) or 4-Phenyl butyric acid (4-PBA) LPS + PBA (i.p., 10 mg/kg). Arterial pressure (AP) and heart rate (HR) were measured in conscious Sprague-Dawley rats. AP, HR variability, as well as baroreflex sensitivity (BrS), was determined after LPS or saline treatment for 2 hours. Immunofluorescence staining for NeuN, Ib1a, TLR4 and GRP78 in the hypothalamic paraventricular nucleus (PVN) was performed. TNF-α, TLR4 and GRP78 protein expression in the PVN were evaluated by western blot. Plasma norepinephrine levels were determined by ELISA.

Key results: Acute LPS treatment increased HR and plasma norepinephrine concentration. It also decreased HR variability and high frequency (HF) components of HR variability, as well BrS. Acute LPS treatment increased TLR4 and TNF-α protein expression in the PVN. These hemodynamic and molecular effects were partially abrogated with TLR4 blocker or ER stress inhibitor pretreatment. In addition, immunofluorescence study showed that TLR4 is co-localized with GRP78in the neurons. Further inhibition of TLR4 or ER stress was able to attenuate the LPS-induced microglia activation.

Conclusions & implications: TLR4 signaling promotes autonomic dysfunction, inflammation and microglia activation, through neuronal ER stress, in the PVN.

No MeSH data available.


Related in: MedlinePlus