Search

Background: Pharmacologic therapy for traumatic brain injury (TBI) has remained relatively unchanged for decades. Ghrelin, an endogenously produced peptide, has been shown to prevent apoptosis and blood-brain barrier dysfunction after TBI. We hypothesize that ghrelin treatment will prevent neuronal degeneration and improve motor coordination after TBI., Materials and Methods: A weight drop model created severe TBI in three groups of BALB/c mice: Sham, TBI, and TBI + ghrelin (20 μg intraperitoneal ghrelin). Brain tissue was examined by hematoxylin and eosin and Fluoro-Jade B (FJB) staining to evaluate histologic signs of injury, cortical volume loss, and neuronal degeneration. Additionally, motor coordination was assessed., Results: Ghrelin treatment prevented volume loss after TBI (19.4 ± 9.8 mm(3)versus 71.4 ± 31.4 mm(3); P < 0.05). Similarly, although TBI increased FJB-positive neuronal degeneration, ghrelin treatment decreased FJB staining in TBI resulting in immunohistologic patterns similar to sham. Compared with sham, TBI animals had a significant increase in foot faults at d 1, 3, and 7 (2.75 ± 0.42; 2.67 ± 0.94; 3.33 ± 0.69 versus 0.0 ± 0.0; 0.17 ± 0.19; 0.0 ± 0.0; P < 0.001). TBI + ghrelin animals had significantly decreased foot faults compared with TBI at d 1, 3, and 7 (0.42 ± 0.63; 0.5 ± 0.43; 1.33 ± 0.58; P versus TBI <0.001; P versus sham = NS)., Conclusions: Ghrelin treatment prevented post-TBI cortical volume loss and neurodegeneration. Furthermore, ghrelin improved post-TBI motor deficits. The mechanisms of these effects are unclear; however, a combination of the anti-apoptotic and inflammatory modulatory effects of ghrelin may play a role. Further studies delineating the mechanism of these observed effects are warranted., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Ghrelin has been shown to be anti-inflammatory and neuroprotective in models of neurologic injury. We hypothesize that treatment with ghrelin will attenuate breakdown of the blood brain barrier (BBB) and apoptosis 24h following traumatic brain injury (TBI). We believe this protection is at least in part mediated by up-regulation of UCP-2, thereby stabilizing mitochondria and preventing up-regulation of caspase-3. A weight drop model was used to create severe TBI. Balb/c mice were divided into 3 groups. Sham: no TBI or ghrelin treatment; TBI: TBI only; TBI/ghrelin: 20μg (IP) ghrelin at the time of TBI. BBB permeability to 70kDa FITC-Dextran was measured 24h following injury and quantified in arbitrary integrated fluorescence (afu). Brain tissue was subjected to TUNEL staining and TUNEL positive cells were quantified. Immunohistochemistry was performed on injured tissue to reveal patterns of caspase-3 and UCP-2 expression. TBI increased cerebral vascular permeability by three-fold compared to sham. Ghrelin treatment restored vascular permeability to the level of shams. TUNEL staining showed that ghrelin mitigated the significant increase in apoptosis that follows TBI. TBI increased both caspase-3 compared to sham. Treatment with ghrelin significantly increased UCP-2 compared to TBI alone and this increase in UCP-2 expression was associated with a decrease in expression of caspase-3. Early ghrelin treatment prevents TBI induced BBB disruption and TBI mediated apoptosis 24h following injury. These results demonstrate the neuroprotective potential of ghrelin as a therapy in TBI., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Traumatic brain injury (TBI) releases a cascade of inflammatory cytokines. Vagal nerve stimulation (VNS) and ghrelin have known anti-inflammatory effects; furthermore, ghrelin release is stimulated by acetylcholine. We hypothesized VNS decreases post-TBI inflammation through a ghrelin-mediated mechanism. TBI was created in five groups of mice: sham, TBI, TBI/ghrelin, TBI/VNS, and TBI/VNS/ghrelin receptor antagonist (GRa). Serum and tissue ghrelin, and serum TNF-α were measured. Ghrelin increased following VNS 2 h post-TBI compared to sham or TBI. At 6 h, TBI and TBI/VNS/GRa had increased TNF-α compared to sham while TBI/VNS and TBI/ghrelin had TNF-α level comparable to sham. The highest ghrelin was measured in stomach where TBI decreased ghrelin in contrast to an increase by VNS. In conclusion, VNS increased serum ghrelin and decreased TNF-α following TBI. This was abrogated with GRa. Our data suggests that ghrelin plays an important role in the anti-inflammatory effects of VNS following TBI.

Significant effort has been focused on reducing neuronal damage from post-traumatic brain injury (TBI) inflammation and blood-brain barrier (BBB)-mediated edema. The orexigenic hormone ghrelin decreases inflammation in sepsis models, and has recently been shown to be neuroprotective following subarachnoid hemorrhage. We hypothesized that ghrelin modulates cerebral vascular permeability and mediates BBB breakdown following TBI. Using a weight-drop model, TBI was created in three groups of mice: sham, TBI, and TBI/ghrelin. The BBB was investigated by examining its permeability to FITC-dextran and through quantification of perivascualar aquaporin-4 (AQP-4). Finally, we immunoblotted for serum S100B as a marker of brain injury. Compared to sham, TBI caused significant histologic neuronal degeneration, increases in vascular permeability, perivascular expression of AQP-4, and serum levels of S100B. Treatment with ghrelin mitigated these effects; after TBI, ghrelin-treated mice had vascular permeability and perivascular AQP-4 and S100B levels that were similar to sham. Our data suggest that ghrelin prevents BBB disruption after TBI. This is evident by a decrease in vascular permeability that is linked to a decrease in AQP-4. This decrease in vascular permeability may diminish post-TBI brain tissue damage was evident by decreased S100B.

Intestinal barrier breakdown following traumatic brain injury (TBI) is characterized by increased intestinal permeability, leading to bacterial translocation, and inflammation. The hormone ghrelin may prevent intestinal injury and have anti-inflammatory properties. We hypothesized that exogenous ghrelin prevents intestinal injury following TBI. A weight-drop model created severe TBI in three groups of anesthetized Balb/c mice. Group TBI: animals underwent TBI only; Group TBI/ghrelin: animals were given 10 μg of ghrelin intraperitoneally prior and 1 h following TBI; Group sham: no TBI or ghrelin injection. Intestinal permeability was measured 6 h following TBI by detecting serum levels of FITC-Dextran after injection into the intact ileum. The terminal ileum was harvested for histology, expression of the tight junction protein MLCK and inflammatory cytokine TNF-α. Permeability increased in the TBI group compared to the sham group (109.7 ± 21.8 μg/mL vs. 32.2 ± 10.1 μg/mL; p < 0.002). Ghrelin prevented TBI-induced permeability (28.3 ± 4.2 μg/mL vs. 109.7 ± 21.8 μg/mL; p < 0.001). The intestines of the TBI group showed blunting and necrosis of villi compared to the sham group, while ghrelin injection preserved intestinal architecture. Intestinal MLCK increased 73% compared to the sham group (p < 0.03). Ghrelin prevented TBI-induced MLCK expression to sham levels. Intestinal TNF-α increased following TBI compared to the sham group (46.2 ± 7.1 pg/mL vs. 24.4 ± 2.2 pg/mL p < 0.001). Ghrelin reduced TNF-α to sham levels (29.2 ± 5.0 pg/mL; p = NS). We therefore conclude that ghrelin prevents TBI-induced injury, as determined by intestinal permeability, histology, and intestinal levels of TNF-α. The mechanism for ghrelin mediating intestinal protection is likely multifactorial, and further studies are needed to delineate these possibilities.