Regulation of inositol 1,4,5-triphosphate receptor, type 1 (IP3R1) in hypoxic/reperfusion injury of white matter.
OBJECTIVE
Calcium overloading is responsible for initiating the cell death in neuronal tissue after hypoxic injury. Inositol 1,4,5-triphosphate receptors (IP3Rs) is an important calcium channel which regulates cellular calcium homeostasis. IP3R1 is widely expressed in brain  and spinal tissue. In the present study, we have studied the regulation of IP3R1 in hypoxic/reperfusion injury of spinal cord dorsal column in vitro.


METHODS
Dorsal columns were isolated from the spinal cord of adult rats and injury was induced by exposing to hypoxic condition  for 1 hour. After injury, reperfusion was carried out for 0, 2, 4, and 8 hours. Tissues were collected and processed for western blotting, immunohistochemistry and real-time PCR.


RESULTS
In the present study, we have found increased expression of IP3R1 after hypoxic/reperfusion  injury of spinal cord dorsal column in vitro. Maximum expression of IP3R1 has been seen at 4 hours after hypoxia. Double immunofluorescence studies show the localization of IP3R1 in axons and astrocytes. Further identifying the signaling pathway involved in the regulation, we found  Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) inhibitor KN-62 and c-Jun N-terminal kinase (JNK) inhibitor SP600125 reduced the expression of IP3R1 suggesting the role of CaMKII and JNK in the regulation of IP3R1 expression. We did not find role of ERK and p38 in the regulation  IP3R1 expression in hypoxic/reperfusion injury of dorsal column in vitro.


CONCLUSIONS
The result presented in this study showed that IP3R1 expression is increased in hypoxic/reperfusion injury of spinal cord white matter and it is regulated by the CaMKII-JNK pathway.
Division of Neurosurgery, Department of Surgery, University of Nebraska Medical Center, Omaha, NE 68198-6250, USA.
Varun
V
Kesherwani
Sandeep K
SK
Agrawal
D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism*; D007511:Ischemia / Q000150:complications*; D056784:Leukoencephalopathies / Q000209:etiology*; D008297:Male; D016900:Neurofilament Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000150:complications*; D015398:Signal Transduction / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D013997:Time Factors
D004791:Enzyme Inhibitors; D005904:Glial Fibrillary Acidic Protein; D053496:Inositol 1,4,5-Trisphosphate Receptors; D016900:Neurofilament Proteins; D012333:RNA, Messenger; C051774:neurofilament protein H