Matrix Metalloproteinase-8 Inhibition Prevents Disruption of Blood–Spinal Cord Barrier and Attenuates Inflammation in Rat Model of Spinal Cord Injury

Abstract

After spinal cord injury (SCI), tight junction (TJ) protein degradation increases permeability and disrupts the blood-spinal cord barrier (BSCB). The BSCB is primarily formed of endothelial cell, which forms a specialized tight seal due to the presence of TJs. BSCB disruption after SCI allows neutrophil infiltration. Matrix metalloproteinase (MMP)-8 is believed to be mainly expressed by neutrophils and is quickly released upon neutrophil activation. Here, we determined whether MMP-8 is involved in the TJ protein degradation in endothelial cells and also determined its role in the neuroinflammation after SCI. MMP-8 recombinant protein treatment increases the TNF-α expression and decreased the TJ (occludin and zonula occludens-1) protein expression in the endothelial cells. Likewise, specific MMP-8 inhibitor (MMP-8I) significantly prevented the TNF-α-induced decrease in the expression of TJ protein in endothelial cells. Furthermore, MMP-8 expression was significantly increased 1 and 3 days after moderate compression (35 g for 5 min at T10 level) SCI, whereas TJ protein levels decreased as determined qRT-PCR, western blotting, and immunohistochemistry. MMP-8 was inhibited directly using a MMP-8I (5 mg/kg) and indirectly by reducing neutrophil infiltration with sivelestat sodium (50 mg/kg) or using the antioxidant N-acetyl-L-cysteine (100 mg/kg). The MMP-8I significantly decreased TNF-α expression, IL-6, and iNOS expression and increased TJ protein expression after SCI. In addition, MMP-8I significantly lessens the amount of Evans blue dye extravasation observed after injury. Thus, our result suggests that MMP-8 plays an imperative role in inflammation and degradation of TJ proteins. Increased MMP-8 expression was associated with the early inflammatory phase of SCI. Inhibiting MMP-8 significantly attenuated SCI-induced inflammation, BSCB breakdown, and cell injury.

Prolonged inflammation leads to ongoing damage after spinal cord injury

“…The results of the analysis are presented as the mean percent of the detected levels of individual factors vs intact LE rats and analyzed with two way ANOVA (Fig 6). (1,2), intact LES rat (3,4) and post-SCI rat spinal cord at 2 (5,6), 7 (7,8), 28 (9,10) and 112 days (11,12). Arrowheads indicate the areas of injury that are GFAP -, asterix indicates a COI, 1indicates an area of arachnoiditis.…”

“…SCI initiates hemorrhage and ischemia, free radical release, severe inflammation, and cellular necrosis [5][6][7]. Pro-inflammatory cytokines such as interleukins 1beta (IL1beta) and 6 (IL-6) as well as tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) [7][8][9], CC, CXC and CX3C chemokines [10] and matrix metalloproteinase 8 [11] are reported to be elevated after SCI, actively promoting severe inflammation. In a recent systematic study up to 8 weeks post-SCI, plasma levels of VEGF, leptin, IP10, IL18, GCSF, and fractalkine were measured and their changing levels reported [12] but the relevance of these changes to the pathogenesis of SCI remains unclear.…”

Oral Administration of α-Asarone Promotes Functional Recovery in Rats With Spinal Cord Injury

“…After flattening of the spine, a 35 g stainless steel impounder was gently placed on the dorsal surface of the spinal cord through a micromanipulator. A moderate compressive damage is delivered to the bar to deliver a 5-min waiting load ( Kumar et al, 2017 ; Figure 1B ). Following the compression injury, muscle and skin incisions were closed using appropriate monofilament sutures (Silk 4-0).…”

Effect of Electroacupuncture on Spinal Cord Injury in Mice: Inhibition Of Inflammatory Response and Oxidative Stress via ApoE and Nrf2

“…Numerous studies have indicated that inflammatory response and oxidative stress are two major events of the secondary injury and play contributed roles in complex secondary pathogenesis [6,58,59]. During the secondary injury cascade, the infiltrations of inflammatory cells such as macrophages, microglia and neutrophils [60,61] trigger the release of pro-inflammatory cytokines including TNF-α, IL-1β and IL-6 [62][63][64], leading to cellular necrosis or apoptosis [65]. In addition, inflammatory cells also release excess reactive oxygen species and reactive nitrogen species [66,67], which causes DNA oxidative damage, proteins oxidation and lipid peroxidation [68].…”