Role of the TLR4 pathway in blood-spinal cord barrier dysfunction during the bimodal stage after ischemia/reperfusion injury in rats
Open Access
- 28 March 2014
- journal article
- Published by Springer Science and Business Media LLC in Journal of Neuroinflammation
- Vol. 11 (1), 62
- https://doi.org/10.1186/1742-2094-11-62
Abstract
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. 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. 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. 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.Keywords
This publication has 34 references indexed in Scilit:
- Different TLR4 expression and microglia/macrophage activation induced by hemorrhage in the rat spinal cord after compressive injuryJournal of Neuroinflammation, 2013
- The role of microglia and the TLR4 pathway in neuronal apoptosis and vasospasm after subarachnoid hemorrhageJournal of Neuroinflammation, 2013
- Ischemic Preconditioning Protects against Spinal Cord Ischemia-Reperfusion Injury in Rabbits by Attenuating Blood Spinal Cord Barrier DisruptionInternational Journal of Molecular Sciences, 2013
- Attenuation of Spinal Cord Injury-Induced Astroglial and Microglial Activation by Repetitive Transcranial Magnetic Stimulation in RatsJournal of Korean Medical Science, 2013
- Development and Treatments of Inflammatory Cells and Cytokines in Spinal Cord Ischemia-Reperfusion InjuryMediators of Inflammation, 2013
- Early Blockade of TLRs MyD88-Dependent Pathway May Reduce Secondary Spinal Cord Injury in the RatsEvidence-Based Complementary and Alternative Medicine, 2012
- Glycyrrhizin attenuates rat ischemic spinal cord injury by suppressing inflammatory cytokines and HMGB1Acta Pharmacologica Sinica, 2011
- Spinal glial TLR4‐mediated nociception and production of prostaglandin E2 and TNFBritish Journal of Pharmacology, 2010
- Chemokine expression in renal ischemia/reperfusion injury is most profound during the reparative phaseInternational Immunology, 2010
- Spinal Cord IschemiaStroke, 2000