# Attenuating Oxidative Damage with Macelignan in Glutamate-Induced HT22 Hippocampal Cells
## 1 Introduction  
The prevention of brain disorders, such as Alzheimer's disease and Parkinson's disease, has become critically important with the increasing elderly population. These disorders share common molecular and cellular features, including oxidative damage, inflammatory conditions, protein misfolding, and neuronal cell death [1; 2; 3]. Oxidative stress is assumed to result from the overproduction of reactive oxygen species (ROS) and is implicated in neuronal cell death [4; 5]. ROS are generated in the mitochondria by oxygen metabolism and function as important mediators of physiological signaling [6; 7]. ROS accumulation leads to oxidative stress, which disrupts the balance of the antioxidant system [8]. According to evidence from both in vitro and in vivo disease models, antioxidants reduce oxidative damage and slow disease progression [9]. In addition, oxidative stress triggers apoptosis, a form of programmed cell death controlled by the mitogen-activated protein kinase (MAPK) signaling pathway [10]. MAPK includes c-Jun N-terminal kinase (JNK), p38 MAPK (p38), and extracellular signal-regulated kinase (ERK), which play key roles in balancing cell survival and death [11; 12]. Therefore, the regulation of the apoptotic signaling pathway may be valuable for the management of neuronal disorders. Glutamate is an excitatory neurotransmitter in the central nervous system that affects brain activities such as learning and memory [13; 14]. Abnormal levels of glutamate lead toexcitotoxicity, which likely causes neuronal cell damage and apoptosis, eventually resulting in neurodegeneration [15; 16]. In addition, HT22 hippocampal cells are commonly used in in vitro models to analyze the effects of glutamate-induced oxidative stress because of the absence of N-methyl-D-aspartate (NMDA) receptors in HT22 cells, which mainly mediate the excitotoxicity of glutamate [17; 18]. Thus, to investigate glutamate-induced neurodegenerative disorders, HT22 cells have been extensively employed in in vitro models. _Myristia fragrans_ (nutmeg) is widely grown in a number of nations, including Indonesia, Thailand, China, and India [19]. In daily diets, M. fragrans is popular as a spice with a typical fragrance and used in baked foods, beverages, and meats [20]. In traditional medicine, _M. fragrans_ has been used to treat headaches, diarrhea, pyrexia, analgesics, and stomach cramps [19; 21]. The biological effects of _M. fragrans_ have been related to antimicrobial, antioxidant, antidepressant, and antidiabetic activities [22; 23; 24]. In spite of having benefits in health, a large quantity of _M. fragrans_ consumption (>5 g of powder) has been reported to induce intoxication [25]. Lignans are the major bioactive components of _M. fragrans_, and over 30 lignans have been identified [19]. The pharmacological characteristics of macelignan, one of these lignans, include antibacterial, anti-inflammatory, anticancer, anticariogenic, antioxidant, and neuroprotective effects [26; 27; 28; 29; 30]. An earlier study demonstrated the neuroprotective effect of macelignan by reducing glutamate-induced ROS, which partly contributed to its free-radical-scavenging activity [30]. Another study revealed that macelignan controls the survival of neurons in HT22 cells in a lipopolysaccharide-charide (LPS)-activated microglial-conditioned medium. It also showed that macelignan exerts an anti-neuroinflammatory effect on HT22 cells by lowering the expression of cyclin D1 and p27 in an LPS-stimulated microglia-conditioned medium, which prevented HT22 cells from being damaged by the LPS-activated medium [31]. Macelignan at a 10 \(\upmu\)M concentration exhibited inhibitory effects on melanosome transfer in B16F10 melanoma cells [32]. Moreover, macelignan reduced the phosphorylation of Tau and suppressed amyloid \(\beta\)-protein deposition in neuron cells, showing a potential effect on treating Alzheimer's disease [33]. However, it is still unclear how macelignan can prevent oxidative damage and neuronal death through the modulation of the MAPK signaling pathway.