Cofilin Inhibitor Protects against Traumatic Brain Injury-Induced Oxidative Stress and Neuroinflammation

SIMPLE SUMMARY: Traumatic brain injury (TBI) is a significant healthcare problem and a leading cause of death in the United States. There is a critical need to develop potential therapeutics to treat TBI-related injuries. Oxidative stress is considered a major mechanism that worsens the damage. Microglia, the first line of defense in the brain, is overactivated following injury causing the death of neuronal cells. Cofilin is a cytoskeleton protein that is activated during such brain injuries. As reported in previous in vivo studies, targeting cofilin has already been shown as a promising therapeutic strategy in other brain diseases. This study investigated the potential benefits of a new cofilin inhibitor in reducing microglial cell activation and the death of neurons in in vitro immortalized cells. We also explored this cofilin inhibitor’s effect in a mouse TBI model. Following brain injury, we measured the levels of different genes and proteins in mice brains. We found that the administration of cofilin inhibitor reduced various inflammatory and oxidative markers in in vitro and in vivo mice models. ABSTRACT: Microglial activation and failure of the antioxidant defense mechanisms are major hallmarks in different brain injuries, particularly traumatic brain injury (TBI). Cofilin is a cytoskeleton-associated protein involved in actin binding and severing. In our previous studies, we identified the putative role of cofilin in mediating microglial activation and apoptosis in ischemic and hemorrhagic conditions. Others have highlighted the involvement of cofilin in ROS production and the resultant neuronal death; however, more studies are needed to delineate the role of cofilin in oxidative stress conditions. The present study aims to investigate the cellular and molecular effects of cofilin in TBI using both in vitro and in vivo models as well as the first-in-class small-molecule cofilin inhibitor (CI). An in vitro H(2)O(2)-induced oxidative stress model was used in two different types of cells, human neuroblastoma (SH-SY5Y) and microglia (HMC3), along with an in vivo controlled cortical impact model of TBI. Our results show that treatment with H(2)O(2) increases the expression of cofilin and slingshot-1 (SSH-1), an upstream regulator of cofilin, in microglial cells, which was significantly reduced in the CI-treated group. Cofilin inhibition significantly attenuated H(2)O(2)-induced microglial activation by reducing the release of proinflammatory mediators. Furthermore, we demonstrate that CI protects against H(2)O(2)-induced ROS accumulation and neuronal cytotoxicity, activates the AKT signaling pathway by increasing its phosphorylation, and modulates mitochondrial-related apoptogenic factors. The expression of NF-E2-related factor 2 (Nrf2) and its associated antioxidant enzymes were also increased in CI-treated SY-SY5Y. In the mice model of TBI, CI significantly activated the Nrf2 and reduced the expression of oxidative/nitrosative stress markers at the protein and gene levels. Together, our data suggest that cofilin inhibition provides a neuroprotective effect in in vitro and in vivo TBI mice models by inhibiting oxidative stress and inflammatory responses, the pivotal mechanisms involved in TBI-induced brain damage.