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Histamine H3 receptors aggravate cerebral ischaemic injury by histamine-independent mechanisms.

ABSTRACT: The role of the histamine H3 receptor (H3R) in cerebral ischaemia/reperfusion (I/R) injury remains unknown. Here we show that H3R expression is upregulated after I/R in two mouse models. H3R antagonists and H3R knockout attenuate I/R injury, which is reversed by an H3R-selective agonist. Interestingly, H1R and H2R antagonists, a histidine decarboxylase (HDC) inhibitor and HDC knockout all fail to compromise the protection by H3R blockade. H3R blockade inhibits mTOR phosphorylation and reinforces autophagy. The neuroprotection by H3R antagonism is reversed by 3-methyladenine and siRNA for Atg7, and is diminished in Atg5?/? mouse embryonic fibroblasts. Furthermore, the peptide Tat-H3R(CT414-436), which blocks CLIC4 binding with H3Rs, or siRNA for CLIC4, further increases I/R-induced autophagy and protects against I/R injury. Therefore, H3R promotes I/R injury while its antagonism protects against ischaemic injury via histamine-independent mechanisms that involve suppressing H3R/CLIC4 binding-activated autophagy, suggesting that H3R inhibition is a therapeutic target for cerebral ischaemia.

SUBMITTER: Yan H

PROVIDER: S-EPMC3948077 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Histamine H3 receptors aggravate cerebral ischaemic injury by histamine-independent mechanisms.

Yan Haijing H Zhang Xiangnan X Hu Weiwei W Ma Jing J Hou Weiwei W Zhang Xingzhou X Wang Xiaofen X Gao Jieqiong J Shen Yao Y Lv Jianxin J Ohtsu Hiroshi H Han Feng F Wang Guanghui G Chen Zhong Z

Nature communications 20140225

The role of the histamine H3 receptor (H3R) in cerebral ischaemia/reperfusion (I/R) injury remains unknown. Here we show that H3R expression is upregulated after I/R in two mouse models. H3R antagonists and H3R knockout attenuate I/R injury, which is reversed by an H3R-selective agonist. Interestingly, H1R and H2R antagonists, a histidine decarboxylase (HDC) inhibitor and HDC knockout all fail to compromise the protection by H3R blockade. H3R blockade inhibits mTOR phosphorylation and reinforces ...[more]

PMID: 24566390

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Project description:1. This study examined the role of histamine H(3) receptors in vagal and sympathetic autonomic reflexes in the conscious rabbit, and in rabbit and guinea-pig isolated right atria. 2. The baroreceptor-heart rate reflex (baroreflex), Bezold-Jarisch-like and nasopharyngeal reflexes were assessed after these treatments (i.v.; with H(1) and H(2) receptor block): (i) vehicle (saline; n=11); (ii) H(3) receptor agonist, (R)-alpha-methylhistamine (R-alpha-MH) 100 micro g kg(-1)+100 micro g kg(-1) h(-1) (n=9); (iii) H(3) receptor antagonist, thioperamide 1 mg kg(-1)+1 mg kg(-1) h(-1) (n=11); (iv) R-alpha-MH and thioperamide (n=6); and (v) H(2) and H(3) antagonist, burimamide 6.3 mg kg(-1)+6.3 mg kg(-1) h(-1) (n=4). 3. R-alpha-MH caused a thioperamide-sensitive fall in mean arterial pressure (MAP) of 8+/-1 mmHg and tachycardia of 18+/-2 bpm (P<0.0005). Burimamide was without effect, however thioperamide elicited an increase in MAP of 4+/-1 mmHg (P<0.01), but no change in heart rate (HR). 4. R-alpha-MH caused a 44% decrease in the average gain of the baroreflex (P=0.0001); this effect was antagonised by thioperamide. Thioperamide caused a parallel rightward shift in the barocurve with an increase in MAP of 5 mmHg (P<0.05). Burimamide had no effect on the baroreflex. The vagally mediated bradycardia elicited by the Bezold-Jarisch and nasopharyngeal reflexes was unaffected by H(3) receptor ligand administration. 5. R-alpha-MH (<or=10 micro M) caused a thioperamide-sensitive depression of both sympathetic and vagal responses in guinea-pig atria, but had no effect in rabbit atria. 6. As H(3) receptor activation caused a significant decrease in baroreflex gain without affecting HR range, the former is unlikely to be simply due to peripheral sympatholysis (supported by the lack of effect in isolated atria). Central H(3) receptors may have a tonic role in the baroreflex as thioperamide caused a rightward resetting of the barocurve. In contrast, the peripherally acting H(3) antagonist burimamide was without effect. These findings suggest a role for central histamine H(3) receptors in cardiovascular homeostasis in the rabbit.

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Histamine H3 receptors aggravate cerebral ischaemic injury by histamine-independent mechanisms.

Publications

Histamine H3 receptors aggravate cerebral ischaemic injury by histamine-independent mechanisms.

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