title: Role of the TLR4 pathway in blood-spinal cord barrier dysfunction during the bimodal stage after ischemia/reperfusion injury in rats.
abstract: BACKGROUND
  Spinal cord ischemia-reperfusion (I/R) involves two-phase injury, including an initial acute ischemic insult and subsequent inflammatory reperfusion injury, resulting in blood-spinal cord barrier (BSCB) dysfunction involving the TLR₄ pathway. However, the correlation between TLR₄/MyD₈₈-dependent and TLR₄/TRIF-dependent pathways in BSCB dysfunction is not fully understood. The aim of this study is to characterize inflammatory responses in spinal cord I/R and the events that define its clinical progression with delayed neurological deficits, supporting a bimodal mechanism of injury.
  
  
  METHODS
  Rats were intrathecally pretreated with TAK-242, MyD₈₈ inhibitory peptide, or Resveratrol at a 12 h interval for 3 days before undergoing 14-minute occlusion of aortic arch. Evan's Blue (EB) extravasation and water content were detected at 6, 12, 18, 24, 36, 48, and 72 h after reperfusion. EB extravasation, water content, and NF-κB activation were increased with time after reperfusion, suggesting a bimodal distribution, as maximal increasing were detected at both 12 and 48 h after reperfusion. The changes were directly proportional to TLR₄ levels determined by Western blot. Double-labeled immunohistochemical analysis was also used to detect the relationship between different cell types of BSCB with TLR₄. Furthermore, NF-κB and IL-1β were analyzed at 12 and 48 h to identify the correlation between MyD₈₈-dependent and TRIF-dependent pathways.
  
  
  RESULTS
  Rats without functional TLR₄ and MyD₈₈ attenuated BSCB leakage and inflammatory responses at 12 h, suggesting the ischemic event was largely mediated by MyD₈₈-dependent pathway. Similar protective effects observed in rats with depleted TLR₄, MyD₈₈, and TRIF receptor at 48 h infer that the ongoing inflammation which occurred in late phase was mainly initiated by TRIF-dependent pathway and such inflammatory response could be further amplified by MyD₈₈-dependent pathway. Additionally, microglia appeared to play a major role in early phase of inflammation after I/R injury, while in late responding phase both microglia and astrocytes were necessary.
  
  
  CONCLUSIONS
  These findings indicate the relevance of TLR4/MyD₈₈-dependent and TLR₄/TRIF-dependent pathways in bimodal phases of inflammatory responses after I/R injury, corresponding with the clinical progression of injury and delayed onset of symptoms. The clinical usage of TLR₄ signaling inhibitors at different phases may be a therapeutic option for the prevention of delayed injury.
authors.forename: Xiao-Qian
authors.initials: XQ
authors.lastname: Li
authors.forename: Huang-Wei
authors.initials: HW
authors.lastname: Lv
authors.forename: Wen-Fei
authors.initials: WF
authors.lastname: Tan
authors.forename: Bo
authors.initials: B
authors.lastname: Fang
authors.forename: He
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Anesthesiology, First Affiliated Hospital, China Medical University, Shenyang 110001, Liaoning, China. mahong5466@yahoo.com.
authors.forename: Hong
authors.initials: H
authors.lastname: Ma
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology / Q000627:therapeutic use; D018826:CD13 Antigens / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002199:Capillary Permeability / Q000502:physiology*; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000502:physiology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D010455:Peptides / Q000627:therapeutic use; D051381:Rats; D015427:Reperfusion Injury / Q000188:drug therapy / Q000473:pathology*; D000077185:Resveratrol; D015398:Signal Transduction / Q000502:physiology*; D013116:Spinal Cord / Q000378:metabolism* / Q000473:pathology; D020760:Spinal Cord Ischemia / Q000150:complications / Q000188:drug therapy / Q000473:pathology*; D013267:Stilbenes / Q000627:therapeutic use; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C100745:Aif1 protein, rat; D000975:Antioxidants; D002135:Calcium-Binding Proteins; D005904:Glial Fibrillary Acidic Protein; D008840:Microfilament Proteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D010455:Peptides; D013267:Stilbenes; D013449:Sulfonamides; C523075:Ticam1 protein, rat; D051197:Toll-Like Receptor 4; C507035:ethyl 6-(N-(2-chloro-4-fluorophenyl)sulfamoyl)cyclohex-1-ene-1-carboxylate; D018826:CD13 Antigens; D000077185:Resveratrol