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TRPM2 channel deficiency prevents delayed cytosolic Zn2+ accumulation and CA1 pyramidal neuronal death after transient global ischemia.

Ye M, Yang W, Ainscough JF, Hu XP, Li X, Sedo A, Zhang XH, Zhang X, Chen Z, Li XM, Beech DJ, Sivaprasadarao A, Luo JH, Jiang LH - Cell Death Dis (2014)

Bottom Line: Postischemic ROS generation and an increase in the cytosolic Zn(2+) level ([Zn(2+)]c) are critical in delayed CA1 pyramidal neuronal death, but the underlying mechanisms are not fully understood.Here we investigated the role of ROS-sensitive TRPM2 (transient receptor potential melastatin-related 2) channel.Using in vivo and in vitro models of ischemia-reperfusion, we showed that genetic knockout of TRPM2 strongly prohibited the delayed increase in the [Zn(2+)]c, ROS generation, CA1 pyramidal neuronal death and postischemic memory impairment.

View Article: PubMed Central - PubMed

Affiliation: Department fof Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.

ABSTRACT
Transient ischemia is a leading cause of cognitive dysfunction. Postischemic ROS generation and an increase in the cytosolic Zn(2+) level ([Zn(2+)]c) are critical in delayed CA1 pyramidal neuronal death, but the underlying mechanisms are not fully understood. Here we investigated the role of ROS-sensitive TRPM2 (transient receptor potential melastatin-related 2) channel. Using in vivo and in vitro models of ischemia-reperfusion, we showed that genetic knockout of TRPM2 strongly prohibited the delayed increase in the [Zn(2+)]c, ROS generation, CA1 pyramidal neuronal death and postischemic memory impairment. Time-lapse imaging revealed that TRPM2 deficiency had no effect on the ischemia-induced increase in the [Zn(2+)]c but abolished the cytosolic Zn(2+) accumulation during reperfusion as well as ROS-elicited increases in the [Zn(2+)]c. These results provide the first evidence to show a critical role for TRPM2 channel activation during reperfusion in the delayed increase in the [Zn(2+)]c and CA1 pyramidal neuronal death and identify TRPM2 as a key molecule signaling ROS generation to postischemic brain injury.

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TRPM2 deficiency abolishes the increase in the [Zn2+]c during reperfusion without altering Zn2+ influx during ischemia in cultured hippocampal neurons. (a) Representative images showing the [Zn2+]c under basal conditions, 2 and 60 min after OGD and 10 min after reperfusion in cultured hippocampal neurons from WT mice without or with treatment by CaEDTA or Naspm, and from TRPM2-KO mice. (b and c) Mean changes in the [Zn2+]c at 60 min of OGD (b) and 10 min of reperfusion (c) as shown in (a) and expressed as the percentage of the basal [Zn2+]c denoted by the dotted lines. The number of neurons examined for each case is shown within parentheses in (b). ***P<0.005 for comparisons among different WT groups; †††P<0.005; and NS, no significant difference for comparisons between WT and TRPM2-KO mice.
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fig6: TRPM2 deficiency abolishes the increase in the [Zn2+]c during reperfusion without altering Zn2+ influx during ischemia in cultured hippocampal neurons. (a) Representative images showing the [Zn2+]c under basal conditions, 2 and 60 min after OGD and 10 min after reperfusion in cultured hippocampal neurons from WT mice without or with treatment by CaEDTA or Naspm, and from TRPM2-KO mice. (b and c) Mean changes in the [Zn2+]c at 60 min of OGD (b) and 10 min of reperfusion (c) as shown in (a) and expressed as the percentage of the basal [Zn2+]c denoted by the dotted lines. The number of neurons examined for each case is shown within parentheses in (b). ***P<0.005 for comparisons among different WT groups; †††P<0.005; and NS, no significant difference for comparisons between WT and TRPM2-KO mice.

Mentions: To understand mechanistically how TRPM2 is engaged in the delayed increase in the [Zn2+]c, we used time-lapse confocal imaging to monitor the temporal changes in the [Zn2+]c during OGD-R in cultured hippocampal neurons from the WT and TRPM2-KO mice. OGD induced a robust increase in the [Zn2+]c in the WT neurons (Figures 6a and b). Such an increase was completely inhibited using CaEDTA, a membrane-impermeable and specific Zn2+ chelator,14, 15 or Naspm, a GluR2-lacking AMPAR-selective antagonist16 (Figures 6a–c). The TRPM2-KO neurons exhibited similar basal [Zn2+]c and OGD-induced increase in the [Zn2+]c as the WT neurons (Figures 6a and b). These results confirm a critical role for AMPARs,13, 14, 16 and also exclude a role for TRPM2 in elevating the [Zn2+]c during ischemia. In stark contrast with the sustained [Zn2+]c in the WT neurons upon reperfusion, the [Zn2+]c in the TRPM2-KO neurons declined rapidly, returning almost to the basal level in 10 min (Figures 6a and c). Consistent with the well-established fact that reperfusion generates excessive ROS,41 our results provide the first evidence to show ROS-sensitive TRPM2 channel as a molecular mechanism that is exclusively required for the delayed increase in the [Zn2+]c or cytosolic Zn2+ accumulation during reperfusion.


TRPM2 channel deficiency prevents delayed cytosolic Zn2+ accumulation and CA1 pyramidal neuronal death after transient global ischemia.

Ye M, Yang W, Ainscough JF, Hu XP, Li X, Sedo A, Zhang XH, Zhang X, Chen Z, Li XM, Beech DJ, Sivaprasadarao A, Luo JH, Jiang LH - Cell Death Dis (2014)

TRPM2 deficiency abolishes the increase in the [Zn2+]c during reperfusion without altering Zn2+ influx during ischemia in cultured hippocampal neurons. (a) Representative images showing the [Zn2+]c under basal conditions, 2 and 60 min after OGD and 10 min after reperfusion in cultured hippocampal neurons from WT mice without or with treatment by CaEDTA or Naspm, and from TRPM2-KO mice. (b and c) Mean changes in the [Zn2+]c at 60 min of OGD (b) and 10 min of reperfusion (c) as shown in (a) and expressed as the percentage of the basal [Zn2+]c denoted by the dotted lines. The number of neurons examined for each case is shown within parentheses in (b). ***P<0.005 for comparisons among different WT groups; †††P<0.005; and NS, no significant difference for comparisons between WT and TRPM2-KO mice.
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig6: TRPM2 deficiency abolishes the increase in the [Zn2+]c during reperfusion without altering Zn2+ influx during ischemia in cultured hippocampal neurons. (a) Representative images showing the [Zn2+]c under basal conditions, 2 and 60 min after OGD and 10 min after reperfusion in cultured hippocampal neurons from WT mice without or with treatment by CaEDTA or Naspm, and from TRPM2-KO mice. (b and c) Mean changes in the [Zn2+]c at 60 min of OGD (b) and 10 min of reperfusion (c) as shown in (a) and expressed as the percentage of the basal [Zn2+]c denoted by the dotted lines. The number of neurons examined for each case is shown within parentheses in (b). ***P<0.005 for comparisons among different WT groups; †††P<0.005; and NS, no significant difference for comparisons between WT and TRPM2-KO mice.
Mentions: To understand mechanistically how TRPM2 is engaged in the delayed increase in the [Zn2+]c, we used time-lapse confocal imaging to monitor the temporal changes in the [Zn2+]c during OGD-R in cultured hippocampal neurons from the WT and TRPM2-KO mice. OGD induced a robust increase in the [Zn2+]c in the WT neurons (Figures 6a and b). Such an increase was completely inhibited using CaEDTA, a membrane-impermeable and specific Zn2+ chelator,14, 15 or Naspm, a GluR2-lacking AMPAR-selective antagonist16 (Figures 6a–c). The TRPM2-KO neurons exhibited similar basal [Zn2+]c and OGD-induced increase in the [Zn2+]c as the WT neurons (Figures 6a and b). These results confirm a critical role for AMPARs,13, 14, 16 and also exclude a role for TRPM2 in elevating the [Zn2+]c during ischemia. In stark contrast with the sustained [Zn2+]c in the WT neurons upon reperfusion, the [Zn2+]c in the TRPM2-KO neurons declined rapidly, returning almost to the basal level in 10 min (Figures 6a and c). Consistent with the well-established fact that reperfusion generates excessive ROS,41 our results provide the first evidence to show ROS-sensitive TRPM2 channel as a molecular mechanism that is exclusively required for the delayed increase in the [Zn2+]c or cytosolic Zn2+ accumulation during reperfusion.

Bottom Line: Postischemic ROS generation and an increase in the cytosolic Zn(2+) level ([Zn(2+)]c) are critical in delayed CA1 pyramidal neuronal death, but the underlying mechanisms are not fully understood.Here we investigated the role of ROS-sensitive TRPM2 (transient receptor potential melastatin-related 2) channel.Using in vivo and in vitro models of ischemia-reperfusion, we showed that genetic knockout of TRPM2 strongly prohibited the delayed increase in the [Zn(2+)]c, ROS generation, CA1 pyramidal neuronal death and postischemic memory impairment.

View Article: PubMed Central - PubMed

Affiliation: Department fof Neurobiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.

ABSTRACT
Transient ischemia is a leading cause of cognitive dysfunction. Postischemic ROS generation and an increase in the cytosolic Zn(2+) level ([Zn(2+)]c) are critical in delayed CA1 pyramidal neuronal death, but the underlying mechanisms are not fully understood. Here we investigated the role of ROS-sensitive TRPM2 (transient receptor potential melastatin-related 2) channel. Using in vivo and in vitro models of ischemia-reperfusion, we showed that genetic knockout of TRPM2 strongly prohibited the delayed increase in the [Zn(2+)]c, ROS generation, CA1 pyramidal neuronal death and postischemic memory impairment. Time-lapse imaging revealed that TRPM2 deficiency had no effect on the ischemia-induced increase in the [Zn(2+)]c but abolished the cytosolic Zn(2+) accumulation during reperfusion as well as ROS-elicited increases in the [Zn(2+)]c. These results provide the first evidence to show a critical role for TRPM2 channel activation during reperfusion in the delayed increase in the [Zn(2+)]c and CA1 pyramidal neuronal death and identify TRPM2 as a key molecule signaling ROS generation to postischemic brain injury.

Show MeSH
Related in: MedlinePlus