INTRODUCTION
Traumatic brain injury is a global health concern. It is an unexpected diversified condition for most enervative consequences like post-traumatic epilepsy. TBI is the foremost reason for death worldwide and disability in the youths, sportspersons, and army veterans. It has been estimated that nearly 69 million population worldwide get brain insult annually(James et al., 2019; Maas et al., 2008) but in India, road traffic injuries cost 60% of total TBI cases(Gururaj, 2008; Murray & Lopez, 1996). Brain trauma in the general population, reports 20% of symptomatic epilepsy and 5% of all epilepsy(Immonen et al., 2019). Primary brain insult confirms brain hemorrhage, an increase in intracranial pressure, and cellular swelling which results in brain edema and blood-brain barrier damage. The cerebral bruises and tissue damage, complicate the secondary cascade by exacerbating neuronal inflammation and mitochondrial ETC dysfunction(Chen et al., 2021). Activated immune cells of inflamed sites initiate other catastrophic mechanisms by overproduction of proteases, ROS/RNS, and NF-κβ that interfere with the expressions of different inflammatory markers and pro-inflammatory cytokines(Shao et al., 2021). This pathophysiology counted for the progression of the epileptogenesis cascade which lowers down the seizure threshold of the injured brain and gives the first post-traumatic successive seizure(Pitkänen et al., 2007).
Fluid Percussion Injury and Cortical Compact Injury studies were performed on mice models of brain trauma and they have detected increased seizure susceptibility for sub convulsive doses of pentylenetetrazole (i.e. non-convulsant at 35mg/kg)(Mukherjee et al., 2013). Disturbed Na+ and Ca2+ influx through Transient Receptor Potential Melastatin-2 (TRPM2) channels prop up membrane depolarization, induce production of prostaglandins, disrupt the mitochondrial and endoplasmic reticulum functions which further led to enhance the intracellular Ca2+ through TRPM2 channels(Perraud et al., 2001). Rho signaling pathway was found highly activated in brain injuries due to inflammation and injury in the neuronal cytoskeleton(Brabeck et al., 2004). Inflammatory markers like TNF-α and glutamate also contribute to early cell death following TBI, by activating Rho kinases i.e. Rho-associated Protein Kinase (ROCK2)(Neumann et al., 2002). An experimental rat model of weight drop injury produces a diffuse type of injury by mimicking clinical complication and its complex pathophysiology provide post-traumatic complications(Chandel et al., 2016; Ye Xiong et al., 2013).
FDA-approved anti-seizure therapies include Valproic Acid, carbamazepine, lamotrigine, phenytoin but we still lack anti-epileptogenic therapy(Romoli et al., 2018). It was investigated that valproic acid influences rat hippocampus for the levels of glutamate and GABA transporter proteins during epileptogenesis(Ueda & Willmore, 2000). Flufenamic Acid belongs to the fenamate class of Non-Steroidal Anti-Inflammatory Drug, COX enzyme inhibition, and TRPM2 channel blocker which was found neuroprotective in in-vitrostudies(Khansari & Coyne, 2012). Fasudil Hydrochloride is a selective ROCK2 inhibitor that induces neuroprotection in-vitro and also a specific inhibitor of NF-κB and protects against axonal degeneration and neuronal apoptosis(Fujimura et al., 2011; Xiao et al., 2014). The altered TBI pathophysiology is described in figure-1.
So, this study hypothesized that the recruitment of Ca2+ antagonists, TRPM2 channel blockers, and ROCK2 inhibitors might be effective for the initiation of neuroprotective responses after initial brain insult to stop or minimize the activated TBI associated epileptogenesis consequences. Hence this study was aimed to explore the in-vivo effects, efficacy, and potential of flufenamic acid and fasudil hydrochloride for the treatment of TBI induced epileptogenesis in experimental weight drop injury model of TBI.