## 4 Discussion
In addition, both the accumulation of A\(\beta\) plaques and over-production of ROS were observed in the brains of patients with AD [38; 39]. Therefore, many studies have been conducted to reduce oxidative stress, which will facilitate AD treatment by decreasing ROS production [40]. Our findings indicated that MFSCE significantly reversed the over-production of ROS in neuronal cells treated with A\(\beta_{25-35}\). A previous study also reported that adipose tissue-derived stem cells ameliorated oxidative stress by inhibiting the ROS level and enhancing ROS scavenging ability to repair oxidized molecules in the hippocampus of APP/PS1 transgenic AD mice [41]. Our results also supported the fact that MFSCE derived from adipose tissue attenuated oxidative stress by decreasing the aROS level in neuronal cells induced by A\(\beta_{25-35}\). Neurotoxicity induced by A\(\beta_{25-35}\) accumulation activates the release of inflammatory mediators [6]. Both iNOS and COX-2 activate nuclear factor-kB (NF-kB) signaling, which is a key regulator of inflammatory reactions in AD [42]. When this pathway is activated, inflammatory mediators stimulate the release of inflammatory cytokines, including interleukin (IL)-6, tumor necrosis factor-\(\alpha\) (TNF-\(\alpha\)), and IL-18 [6; 42]. To investigate the molecular mechanisms underlying the effect of MFSCE on neuroinflammation, we measured the protein levels of inflammatory mediators, including iNOS and COX-2. Treatment with MFSCE dose-dependently downregulated iNOS and COX-2. Our previous study results indicated that MFSCE at doses of 1 and 2 ug/mL attenuated inflammatory reactions via the downregulation of iNOS and COX-2 protein expressions in LPS-induced RAW264.7 [14]. The conditioned medium of adipose tissue-derived stem cells inhibited inflammatory cytokines including IL-2, TNF-\(\alpha\), and IL-6 in inflammation-induced human astrocytes [43]. Based on these studies, we suggest that MFSCE exhibits the neuroprotective effect against neurotoxicity by downregulating inflammatory mediators in neuronal cells. Neuronal apoptosis is regulated by various molecular mechanisms in the brains of patients with AD [44]. Bax and Bcl-2 are related to mitochondrial-mediated neuronal apoptosis [45]. When neurotoxicity is induced by excessive A\(\beta\) accumulation, the Bax level is increased, while the Bcl-2 level is decreased in patients with AD [46]. Therefore, Bax is considered a pro-apoptotic factor, while Bcl-2 is an anti-apoptotic factor. The MFSCE-treated SH-SYSY cells showed a decreased ratio of Bax/Bcl-2 compared with that in A\(\beta_{25-35}\)-treated cells. High-concentration MFSCE (5 ug/mL)-treated cells markedly downregulated Bax expression, among other concentrations. In our previous study, treatment with MFSCE(0.5, 1, and 2.5 \(\upmu\)g/mL) decreased the ratio of Bax/Bcl-2 in oxidative stress-induced LLC-PK\({}_{1}\) cells [15]. In addition, adipose tissue-derived stem cells decreased the ratio of Bax/Bcl-2 in hepatic cytotoxicity-induced liver tissue [47]. Similarly, our results also demonstrated that MFSCE decreased the ratio of Bax/Bcl-2 in neuronal cells induced by A\(\beta_{25-35}\). We suggest that MFSCE exhibits the neuroprotective effect by attenuating neuronal apoptosis. During the development of AD, A\(\beta\) is generated via the activation of the amyloidogenic pathway [3; 48]. In the first step of A\(\beta\) production, APP is cleaved to the \(\beta\)-secretase C-terminal fragment (\(\beta\)-CTF) by the \(\beta\)-secretase enzyme, which has been identified as BACE [49]. Subsequently, \(\beta\)-CTF is further cleaved to A\(\beta\) by \(\gamma\)-secretase, which is composed of PS1 and PS2 [50]. In particular, these enzymes are the mediators of rate-limiting processing steps leading to the generation of A\(\beta\) from APP [48]. Therefore, many researchers have focused on the regulation of the amyloidogenic pathway for the inhibition of A\(\beta\) generation as an effective strategy in the treatment of AD [48; 51].