Identification of Sphingosine 1-Phosphate Receptor Subtype 1 (S1P1) as a Pathogenic Factor in Transient Focal Cerebral Ischemia.
Medically relevant roles of receptor-mediated sphingosine 1-phosphate (S1P) signaling have become a successful or promising target for multiple sclerosis or cerebral ischemia. Animal-based proof-of-concept validation for the latter is particularly through the neuroprotective efficacy of FTY720, a non-selective S1P receptor modulator, presumably via activation of S1P1. In spite of a clear link between S1P signaling and cerebral ischemia, it remains unknown whether the role of S1P1is pathogenic or neuroprotective. Here, we investigated the involvement of S1P1along with its role in cerebral ischemia using a transient middle cerebral artery occlusion ("tMCAO") model. Brain damage following tMCAO, as assessed by brain infarction, neurological deficit score, and neural cell death, was reduced by oral administration of AUY954, a selective S1P1modulator as a functional antagonist, in a therapeutic paradigm, indicating that S1P1is a pathogenic mediator rather than a neuroprotective mediator. This pathogenic role of S1P1in cerebral ischemia was reaffirmed because tMCAO-induced brain damage was reduced by genetic knockdown with an intracerebroventricular microinjection of S1P1shRNA lentivirus into the brain. Genetic knockdown of S1P1or AUY954 exposure reduced microglial activation, as assessed by reduction in the number of activated microglia and reversed morphology from amoeboid to ramified, and microglial proliferation in ischemic brain. Its role in microglial activation was recapitulated in lipopolysaccharide-stimulated primary mouse microglia, in which the mRNA expression level of TNF-α and IL-1β, well-known markers for microglial activation, was reduced in microglia transfected with S1P1siRNA. These data suggest that the pathogenic role of S1P1is associated with microglial activation in ischemic brain. Additionally, the pathogenic role of S1P1in cerebral ischemia appears to be associated with the blood-brain barrier disruption and brain-derived neurotrophic factor (BDNF) downregulation. Overall, findings from the current study clearly identify S1P1signaling as a pathogenic factor in transient focal cerebral ischemia, further implicating S1P1antagonists including functional antagonists as plausible therapeutic agents for human stroke.
Gachon University, Incheon, 406-799, Republic of Korea.
Bhakta Prasad
BP
Gaire
Gachon University, Incheon, 406-799, Republic of Korea.
Chi-Ho
CH
Lee
Gachon University, Incheon, 406-799, Republic of Korea.
Arjun
A
Sapkota
Department of Pharmacy and Institute of Pharmaceutical Science and Technology, Hanyang University, Ansan, 55 Hanynagdaehak-ro, Sangnok-gu, Ansan, Gyeonggi-do, 15588, Republic of Korea.
Sang Yeul
SY
Lee
Department of Molecular Biology, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA, 92037, USA.
Jerold
J
Chun
TherlifEx, Namdong-gu, Incheon, 21653, Republic of Korea.
Hee Jun
HJ
Cho
Department of Pharmacy and Institute of Pharmaceutical Science and Technology, Hanyang University, Ansan, 55 Hanynagdaehak-ro, Sangnok-gu, Ansan, Gyeonggi-do, 15588, Republic of Korea. tnam@hanyang.ac.kr.
Tae-Gyu
TG
Nam
Gachon University, Incheon, 406-799, Republic of Korea. pharmchoi@gachon.ac.kr.
Ji Woong
JW
Choi
D000818:Animals; D002478:Cells, Cultured; D002546:Ischemic Attack, Transient / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D017628:Microglia / Q000378:metabolism / Q000473:pathology; D034741:RNA, Small Interfering / Q000494:pharmacology; D049349:Receptors, Lysosphingolipid / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*
D034741:RNA, Small Interfering; D049349:Receptors, Lysosphingolipid
AUY954; Microglia; S1P1; S1P1 shRNA; Transient middle cerebral artery occlusion (tMCAO)