Inhibition of cathepsin S produces neuroprotective effects after traumatic brain injury in mice

The Neuroprotection of Lysosomotropic Agents in Experimental Subarachnoid Hemorrhage Probably Involving the Apoptosis Pathway Triggering by Cathepsins via Chelating Intralysosomal Iron

α-Lipoic acid-plus (LAP), an amine derivative of α-lipoic acid (LA), could protect cells against oxidant challenges via chelating intralysosomal iron. However, the application of LAP in experimental subarachnoid hemorrhage (SAH) is still not well known. This study was designed to evaluate the potential neuroprotection of LAP on the early brain injury (EBI) and the underlying mechanisms in a rat model of SAH. The SAH models were induced in Sprague-Dawley rats. LA and LAP were oral administration and lasted for 72 h once a day. The brain tissue samples were obtained for assay at 72 h after SAH. In experiment 1, we found that lysosome amounts in neurons decreased significantly in SAH group, and LAP (100 mg/kg) could stabilize lysosomal membrane markedly based on lysosomal-associated membrane protein-1 (LAMP-1) expression in neurons by immunofluorescence. Hence, the LAP dosages of 100 and 150 mg/kg were applied in experiment 2. Firstly, Western blot analysis showed that the protein levels of cathepsin B/D, caspase-3, Bax, ferritin, and heme-oxygenase-1 (HO-1) markedly increased after SAH, which were further confirmed by double immunofluorescence staining and reversed by LA and LAP treatments. In addition, LA and LAP also reduced oxidative stress and iron deposition in brain tissue. Furthermore, LA and LAP significantly ameliorated brain edema, blood-brain barrier injury, cortical apoptosis, and neurological behavior impairment induced by SAH. Finally, it is noteworthy that LAP exerted more significant effects than LA on these parameters as described above. LAP probably exerted neuroprotective effects via targeting lysosomes and chelating intralysosomal iron in EBI post-SAH in rats.

Melatonin reduced microglial activation and alleviated neuroinflammation induced neuron degeneration in experimental traumatic brain injury: Possible involvement of mTOR pathway

This study was designed to detect the modulation manner of melatonin on microglial activation and explore herein possible involvement of mammalian target of rapamycin (mTOR) pathway following traumatic brain injury (TBI). ICR mice were divided into four groups: sham group, TBI group, TBI+sal group and TBI+Melatonin group. A weight-drop model was employed to cause TBI. Neurological severity score (NSS) tests were performed to measure behavioral outcomes. Nissl staining was conducted to observe the neuronal degeneration and wet-to-dry weight ratio indicated brain water content. Immunofluorescence was designed to investigate microglial activation. Enzyme-linked immunosorbent assay (ELISA) was employed to evaluate proinflammatory cytokine levels (interleukin-beta (IL-1β), tumor necrosis factor-alpha (TNF-α)). Western blotting was engaged to analyze the protein content of mammalian target of rapamycin (mTOR), p70 ribosomal S6 kinase (p70S6K) and S6 ribosomal protein (S6RP). Melatonin administration was associated with markedly restrained microglial activation, decreased release of proinflammatory cytokines and increased the number of surviving neurons at the site of peri-contusion. Meanwhile, melatonin administration resulted in dephosphorylated mTOR pathway. In conclusion, this study presents a new insight into the mechanisms responsible for the anti-neuroinflammation of melatonin, with possible involvement of mTOR pathway.

Luteolin provides neuroprotection in models of traumatic brain injury via the Nrf2-ARE pathway

Luteolin has recently been proven to exert neuroprotection in a variety of neurological diseases; however, its roles and the underlying mechanisms in traumatic brain injury are not fully understood. The present study was aimed to investigate the neuroprotective effects of luteolin in models of traumatic brain injury (TBI) and the possible role of the Nrf2-ARE pathway in the putative neuroprotection. A modified Marmarou׳s weight-drop model in mice and the scratch model in mice primary cultured neurons were used to induce TBI. We determined that luteolin significantly ameliorated secondary brain injury induced by TBI, including neurological deficits, brain water content, and neuronal apoptosis. Furthermore, the level of malondialdehyde (MDA) and the activity of glutathione peroxidase (GPx) were restored in the group with luteolin treatment. in vitro studies showed that luteolin administration lowered the intracellular reactive oxygen species (ROS) level and increased the neuron survival. Moreover, luteolin enhanced the translocation of Nrf2 to the nucleus both in vivo and in vitro, which was proved by the results of Western blot, immunohistochemistry, and electrophoretic mobility shift assay (EMSA). Subsequently upregulation of the expression of the downstream factors such as heme oxygenase 1 (HO1) and

NAD(P)H

quinone oxidoreductase 1 (NQO1) was also examined. However, luteolin treatment failed to provide neuroprotection after TBI in Nrf2(-/-) mice. Taken together, these in vivo and in vitro data demonstrated that luteolin provided neuroprotective effects in the models of TBI, possibly through the activation of the Nrf2-ARE pathway.