N-(p-Coumaroyl) Serotonin Ameliorates LPS-Induced Inflammation in BV2 Microglia via MAPK/NF-κB Inactivation and HO-1/NQO1 Upregulation

Abstract

Uncontrolled inflammation contributes to the development of neurodegenerative diseases (NDs) like Alzheimer’s disease (AD). N-(p-Coumaroyl) serotonin (CS) has demonstrated a significant capacity to modulate hyper-inflammation. We explored whether CS could mitigate inflammatory responses in endotoxin-challenged microglial cells and sought to elucidate the specific molecular mechanisms governing these effects. ELISA, nitric oxide (NO) assays, Western blotting and immunocytochemistry were performed to study inflammatory responses and related signal transduction mechanisms. CS pretreatment effectively attenuated the inflammatory output in endotoxin-primed microglial models. This was evidenced by a significant reduction in key cytokines (such as IL-6, TNF-α, and MCP-1) and a concomitant decrease in the protein levels of iNOS and COX-2. These effects were mediated through the disruption of MAPK/NF-κB signaling cascades and the sequestration of NF-κB within the cytoplasm. Beyond its anti-inflammatory role, CS promoted the HO-1/NQO1 signaling pathway and interfered with the LPS-mediated TLR4/MyD88 cascade. Our collective evidence indicates that the modulation of microglia-mediated inflammation by CS is underpinned by the suppression of MAPK/NF-κB and the induction of antioxidant systems, suggesting that CS may have the potential to improve NDs.

1. Introduction

Chronic or exaggerated neuroinflammation acts as a catalyst for neuronal damage and cognitive decline, thereby fueling the advancement of various neurodegenerative pathologies, including AD, PD, and epileptic condition [1,2]. Central to this process is the aberrant stimulation of microglia, which shift from a quiescent state toward a deleterious pro-inflammatory profile, secreting a broad spectrum of signaling molecules [3]. Notably, the overproduction of IL-6 and TNF-α is closely linked to exacerbated amyloid-beta neurotoxicity, the depletion of dopaminergic pathways, and increased seizure susceptibility [4,5,6,7,8,9]. Additionally, the chemokine MCP-1 promotes the recruitment of systemic immune cells, while nitric oxide and PGE2—synthesized via iNOS and COX-2—intensify oxidative stress and sustain the inflammatory environment [10,11,12,13,14,15,16,17,18]. Mechanistically, TLR4 serves as the principal detector, initiating a signaling relay through MyD88 that triggers both NF-κB and MAPK (p38, ERK, JNK) circuits, which dictate the expression of inflammatory transcripts [19,20,21]. In contrast, the upregulation of antioxidant defenses, such as HO-1 and NQO1, provides a counter-regulatory shield. These enzymes mitigate hyper-inflammatory states by interfering with the phosphorylation of NF-κB/MAPK signaling modules, thereby maintaining cellular equilibrium [22,23].

LPS is frequently employed as a formidable endotoxin to mimic the neuroinflammatory milieu typical of NDs. This endotoxin-driven inflammation acts as a pivotal driver of neurodegeneration by instigating a chronic neurotoxic loop, wherein persistent microglial stimulation precipitates progressive synaptic pruning and neuronal programmed cell death [24,25,26]. Mechanistically, LPS engages the TLR4 receptor to stimulate MAPK and NF-κB signaling networks, resulting in the extensive production of detrimental inflammatory factors [27,28]. Therefore, targeting these LPS-responsive pathways is considered a fundamental pharmacological approach to disrupt the inflammatory sequence that underpins the clinical advancement of NDs. To this end, LPS-challenged BV2 cells are utilized herein as a robust cellular platform to assess the pharmacological potential of emerging anti-inflammatory agents.

Extracted primarily from the seeds of the safflower plant (Carthamus tinctorius L.), N-(p-Coumaroyl) Serotonin (CS) is a prominent bioactive polyphenol recognized for its diverse therapeutic attributes, notably its potent antioxidant and anti-atherosclerotic effects [29]. Existing literature has documented its anti-neoplastic properties, demonstrating that CS triggers mitotic phase inhibition and apoptosis within malignant glioblastoma and mammary carcinoma cells [30,31]. In terms of its immunomodulatory potential, CS effectively curtails the release of pro-inflammatory cytokines, specifically IL-6 and TNF-α, within monocytic and macrophage populations. Furthermore, it has been observed to alleviate hyper-inflammatory responses in pulmonary epithelia by interfering with the NF-κB-mediated signaling cascade [32,33].

Notwithstanding these established systemic advantages, the precise neuroprotective role of CS and its regulatory signature within the brain’s parenchyma—especially concerning microglial populations—have yet to be fully charted. Since curbing microglial hyper-responsiveness represents a cornerstone of ND intervention, we examined the capacity of CS to dampen inflammatory cascades in endotoxin-challenged BV2 microglial models. This research seeks to decode the governing signaling networks, thereby establishing CS as a viable pharmacological candidate for countering microglia-driven neurodegenerative processes.

2. Materials and Methods

2.1. Materials

N-(p-Coumaroyl) Serotonin (purity ≥ 98%, cat. no. CFN91127) was supplied by ChemFaces Biochemical Co., Ltd. (Wuhan, China), while DMEM and FBS were sourced from Welgene, Inc. (Daegu, Republic of Korea) and Thermo Fisher Scientific Inc. (Waltham, MA, USA), respectively. For microglial activation, lipopolysaccharides (Escherichia coli O26:B6; Cat. no. L8274) were provided by Sigma-Aldrich Inc. (St. Louis, MO, USA). To quantify inflammatory markers, ELISA-based detection systems for TNF-α, IL-6, and MCP-1 were procured from both BD Biosciences (Franklin Lakes, NJ, USA) and R&D Systems, Inc. (Minneapolis, MN, USA).

2.2. Cell Culture and Viability Assessment

The murine BV2 microglial line, procured from Cytion (Eppelheim, Germany), was cultivated in DMEM (Welgene, cat. no. LM001-05) containing 10% FBS and kept at 37 °C within a humidified CO₂ environment. For the cytotoxicity evaluation, BV2 cells were seeded into 12-well plates (5 × 10⁴ cells/well) and exposed to a range of CS concentrations (6.25 to 200 μM) for a 24 h incubation period. Subsequently, each well received MTT solution (0.5 mg/mL final concentration) and was incubated for an additional 4 h. After solubilizing the resulting formazan product using DMSO (Sigma-Aldrich, USA), the optical density was measured at 570 nm using a Tecan microplate reader. All data were derived from at least three separate experimental runs.

2.3. NO Assay

To quantify nitric oxide (NO) production, BV2 cells (seeded at 2 × 10⁵ cells/mL) were pre-incubated in 12-well plates at 37 °C. Following a 1 h pretreatment with varying CS doses (12.5–100 μM), the cells were challenged with LPS (200 ng/mL) for an additional 20 h. Conditioned media were then harvested and mixed in a 1:1 ratio with Griess reagent, which was prepared using 1% sulfanilamide, 0.1% naphthylethylenediamine dihydrochloride, and 2.5% phosphoric acid. This mixture was kept in the dark for 10 min at ambient temperature to allow the colorimetric reaction to stabilize. Finally, optical density was recorded at 540 nm employing a Tecan microplate reader (Spark 10M; Tecan Group Ltd., Männedorf, Switzerland) [34].

2.4. Cytokines and Chemokine ELISA

To quantify the secretion profiles of IL-6, TNF-α, and MCP-1, BV2 microglia (2 × 10⁵ cells/mL) were seeded in 12-well plates and allowed to adhere for 20 h. Following a 1 h pretreatment with CS (12.5–100 μM), the cells were challenged with LPS (200 ng/mL) for an additional 20 h. The concentrations of these inflammatory markers in the harvested supernatants were determined using specific ELISA platforms: BD OptEIA™ sets (BD Biosciences, San Diego, CA, USA) for IL-6 and TNF, and DuoSet (R&D Systems, Minneapolis, MN, USA) for MCP-1, following the manufacturer’s instructions. Crucially, to ensure the optical density remained within the linear range of the standard curves, all samples were diluted 30-fold in assay buffer prior to analysis. The absorbance was measured using a Tecan microplate reader controlled by SparkControl™ software (version 2.1; Tecan Group Ltd.).

2.5. Protein Extraction and Immunoblotting Analysis

To elucidate the abundance and phosphorylation status of key inflammatory and antioxidant markers—including iNOS, COX-2, the MAPK/NF-κB axis, TLR4, MyD88, and HO-1/NQO1—BV2 cells were lysed in RIPA buffer containing protease/phosphatase inhibitors (Roche Diagnostics, Basel, Switzerland). Following BCA-based protein quantification, equivalent amounts of protein (30–60 µg) were resolved via 8–12% SDS-PAGE and transferred onto PVDF membranes. To prevent non-specific binding, membranes were incubated in a 5% skim milk solution for 1 h at ambient temperature. Target proteins were then probed with specific primary antibodies (Table 1) overnight at 4 °C, followed by a 2 h incubation with peroxidase-conjugated secondary antibodies (Jackson ImmunoResearch Laboratories, Inc., West Grove, PA, USA). Immunoreactive bands were visualized using an enhanced chemiluminescence (ECL) system (Thermo Fisher Scientific, Inc.). Densitometric quantification was subsequently carried out using ImageJ software (version 1.52a; National Institutes of Health, Bethesda, MD, USA), with β-actin serving as the internal loading control.

Table 1.

Detailed profiles of primary antibodies utilized in immunoblotting.

Antibody	Company	Product ID	Molecular Weight	Origin
iNOS	Enzo Life Sci (Farmingdale, NY, USA)	#ADI-KAS-NO001	130	R
COX-2	Santa Cruz Biotech (Dallas, TX, USA)	#sc-376861	70–72	M
TLR4	Santa Cruz Biotech (Dallas, TX, USA)	#sc-293072	95–120	M
MyD88	Santa Cruz Biotech (Dallas, TX, USA)	#sc-74532	33	M
p-p38	Santa Cruz Biotech (Dallas, TX, USA)	#sc-7973	38	M
p38	Santa Cruz Biotech (Dallas, TX, USA)	#sc-7972	38	M
p-ERK	Cell Signaling Tech (Danvers, MA, USA)	#9101S	42/44	M
ERK	Cell Signaling Tech (Danvers, MA, USA)	#9102S	42/44	R
p-JNK	Cell Signaling Tech (Danvers, MA, USA)	#4668S	46/54	R
JNK	Cell Signaling Tech (Danvers, MA, USA)	#9252S	46/54	R
p-p65	Santa Cruz Biotech (Dallas, TX, USA)	#sc-166748	65	M
p65	Santa Cruz Biotech (Dallas, TX, USA)	#sc-8008	65	M
p-IκBα	Santa Cruz Biotech (Dallas, TX, USA)	#sc-8404	41	M
HO-1	ThermoFisher, invtrogen (Waltham, MA, USA)	#PA5-27338	32	R
NQO1	Sigma-Aldrich (St. Louis, MO, USA)	#N5288	28	R
β-actin	Santa Cruz Biotech (Dallas, TX, USA)	#sc-47778	43	M

Antibodies were used at 1:1000 dilution (1:5000 for β-actin). p-, phosphorylated; MW, molecular weight; R, rabbit; M, mouse.

2.6. Immunocytochemical Analysis of NF-κB Localization

To visualize the nuclear shuttling of NF-κB p65, BV2 cells were stabilized in 10% formalin and subjected to permeabilization using 0.1% Triton X-100 for 10 min. Following sequential washes with ice-cold PBS, non-specific binding sites were saturated with 5% BSA for 30 min at ambient temperature. The intracellular distribution of the p65 subunit was then probed overnight at 4 °C with a specific primary antibody (Table 1). Subsequently, cells were incubated with an Alexa Fluor 488-labeled goat anti-rabbit secondary antibody (1:250 dilution; Invitrogen) for 1 h. To facilitate nuclear counterstaining, the preparations were embedded in an antifade mounting matrix containing DAPI. Fluorescence signals were captured using a confocal laser scanning microscope (Carl Zeiss AG, Oberkochen, Germany).

2.7. Data Processing and Statistical Evaluation

Quantitative results are expressed as the mean ± SD, derived from a minimum of three separate experimental runs. To assess differences between group means, a one-way analysis of variance (ANOVA) was employed, followed by Tukey’s multiple comparison test as a post hoc analysis. All computational procedures were executed using SPSS software (version 20.0; IBM Corp., Armonk, NY, USA). Statistical significance was predefined at a p-value of less than 0.05.

3. Results

3.1. CS Inhibits LPS-Induced Cytokine and Chemokine Production in Microglia

N-(p-Coumaroyl) Serotonin (CS; Figure 1a), a prominent phytopolyphenol from safflower, is recognized for its diverse pharmacological repertoire, including potent immunomodulatory properties [26,30]. We initially assessed the cytocompatibility of CS (6.25–200 μM) via MTT assay to establish a non-toxic dosage window for microglial studies. Cellular viability remained unaffected at concentrations up to 100 μM (Figure 1b), providing a rational basis for subsequent challenge with LPS. The suppressive potential of CS on LPS-triggered inflammatory output was then validated by ELISA. While endotoxin exposure led to a surge in the secretion of key markers—specifically IL-6, TNF-α, and MCP-1—relative to untreated control, CS pretreatment effectively blunted this response (Figure 1c–e). Notably, the 100 μM dose demonstrated the most robust efficacy, attenuating the levels of IL-6, TNF-α, and MCP-1 by 65.20%, 46.44%, and 30.36%, respectively.

Figure 1.

CS attenuates the secretion of endotoxin-induced pro-inflammatory markers in BV2 cells. (a) Molecular structure of CS. (b) Metabolic activity was assessed via MTT assay. Microglial cells were pre-exposed to CS (1 h) and subsequently challenged with LPS (200 ng/mL) for 20 h. (c–e) Quantification of IL-6, TNF-α, and MCP-1 levels from 30-fold diluted conditioned media using ELISA. Quantitative values are depicted as mean ± S.D. # p < 0.05 vs. untreated control; * p < 0.05 vs. LPS-primed group. Abbreviations: CS, N-(p-Coumaroyl) serotonin; LPS, lipopolysaccharide; IL-6/TNF-α, pro-inflammatory cytokines; MCP-1, monocyte chemoattractant protein-1.

3.2. CS Curbs the Induction of iNOS and COX-2 by LPS in Microglial Cells

Building on the cytokine findings, we scrutinized whether CS could dampen the accumulation of NO triggered by LPS. The Griess assay revealed that the surge in NO levels following endotoxin stimulation was markedly attenuated by CS pretreatment (Figure 2a). Mirrored by the trends observed in the ELISA data, the 100 μM dose yielded the most prominent reduction, lowering NO synthesis by 44.31%. Furthermore, immunoblot analysis confirmed that CS interfered with the protein up-regulation of both iNOS and COX-2 in LPS-challenged BV2 models (Figure 2b–d).

Figure 2.

Inhibitory impact of CS on endotoxin-triggered NO synthesis and iNOS/COX-2 abundance in BV2 cells. Following a 1 h priming with CS, microglial cells were challenged with LPS (200 ng/mL) for a duration of 20 h. (a) Nitrite accumulation was quantified as an indicator of NO production. (b) Immunoblotting was utilized to evaluate the protein levels of iNOS and COX-2. Densitometric analysis showing the relative ratios of (c) iNOS and (d) COX-2 normalized to β-actin. Quantitative values are depicted as mean ± S.D. # p < 0.05 vs. untreated control; * p < 0.05 vs. LPS-only group. Abbreviations: iNOS, inducible nitric oxide synthase; COX-2, cyclooxygenase-2.

3.3. CS Inhibits LPS-Induced MAPK Activation in Microglia

Since MAPK activation is a key driver of microglial hyper-inflammation [35], we explored the regulatory involvement of CS within this critical signaling axis. Immunoblotting analysis revealed (Figure 3a–d) that endotoxin challenge triggered a robust phosphorylation of p38 and JNK in BV2 microglia relative to quiescent cells. Importantly, this activation surge was effectively dampened by CS pretreatment. Beyond p38 and JNK, CS curtailed ERK phosphorylation in LPS-primed microglial models, suggesting a broad inhibitory effect across the MAPK family.

Figure 3.

CS dampens the endotoxin-induced mobilization of MAPKs in BV2 microglia. To assess signaling activation, microglial cells underwent a 1 h CS priming followed by exposure to LPS (200 ng/mL) for 60 min. (a) Immunoblotting analysis was utilized to scrutinize p38, ERK, and JNK pathways. (b–d) Densitometric data represent the relative levels of phosphorylated forms normalized to their corresponding total protein abundance. Quantitative values are depicted as mean ± S.D. # p < 0.05 vs. untreated control; * p < 0.05 vs. LPS-only group. Abbreviation: JNK, c-Jun N-terminal kinase.

3.4. CS Impedes the LPS-Triggered IκB/NF-κB Signaling Axis in Microglia

The NF-κB-dependent transcription of genes such as IL-6, TNF-α, MCP-1, iNOS, and COX-2 is a hallmark of microglial activation [36]. In this context, we scrutinized the capacity of CS to antagonize the LPS-mediated mobilization of the NF-κB pathway. Immunoblot analysis revealed (Figure 4a–c) that CS elicited a dose-responsive decline in the phosphorylation of both IκB and NF-κB within endotoxin-challenged BV2 cells. Furthermore, we monitored the intracellular trafficking of the p65 subunit using immunocytochemistry. As depicted in Figure 4d, treatment with 100 μM CS robustly hindered the nuclear shuttling of NF-κB in LPS-primed microglia, effectively retaining the protein within the cytoplasmic compartment.

Figure 4.

CS suppresses endotoxin-induced NF-κB signaling and its subsequent nuclear entry in BV2 microglia. To characterize the NF-κB signaling cascade, cells underwent a 60 min priming with CS followed by exposure to LPS (200 ng/mL) for an identical duration. (a) Phosphorylation profiles of p65 and IκBα were determined via immunoblotting, with (b,c) densitometric values representing relative protein abundance. Furthermore, (d) the intracellular distribution of p65 was visualized through immunocytochemistry to monitor its shuttling into the nuclear compartment. Scale bar = 10 µm. Quantitative values are depicted as mean ± S.D. # p < 0.05 vs. untreated control; * p < 0.05 vs. LPS-only group. Abbreviation: IκB, inhibitor of NF-κB.

3.5. CS Inhibits LPS-Induced TLR4 Activation in Microglia

LPS stimulation orchestrates the mobilization of the TLR4/MyD88 signaling relay, which in turn triggers downstream NF-κB and MAPK pathways, thereby driving the synthesis of pro-inflammatory factors [37]. Having established that CS attenuates inflammatory output, iNOS/COX-2 abundance, and the MAPK/NF-κB axis (Figure 1, Figure 2, Figure 3 and Figure 4), we investigated whether these protective actions could be ascribed to the disruption of the TLR4/MyD88 cascade. As depicted in Figure 5a–c, a robust up-regulation of TLR4 and MyD88 was observed in LPS-challenged microglial models relative to quiescent cells. Notably, CS pretreatment effectively reversed this trend within the endotoxin-stimulated group.

Figure 5.

CS dampens the endotoxin-triggered induction of the TLR4/MyD88 axis in BV2 cells. Microglial cells underwent a 60 min CS priming period before being subjected to an endotoxin challenge (LPS, 200 ng/mL) for an additional hour. (a) Immunoblotting was employed to characterize the abundance of TLR4 and MyD88. Densitometric evaluations illustrating the relative levels of (b) TLR4 and (c) MyD88 normalized against the loading control (β-actin). Quantitative values are depicted as mean ± S.D. # p < 0.05 vs. untreated control; * p < 0.05 vs. LPS-only group. Abbreviation: TLR4, Toll-like receptor 4; MyD88, myeloid differentiation primary response (MyD) 88.

3.6. CS Induces HO-1/NQO1 Upregulation in Microglia

To elucidate whether the immunomodulatory effects of CS are underpinned by the up-regulation of HO-1 and NQO1, we scrutinized the abundance of these cytoprotective enzymes in BV2 microglia. Immunoblotting revealed (Figure 6a–c) that CS elicited a dose-responsive elevation of HO-1 levels within the microglial environment. Furthermore, a similar augmentation was observed for NQO1 protein synthesis in response to CS treatment (Figure 6a–c).

Figure 6.

CS upregulates HO-1 and NQO1 expression in BV2 cells. BV2 cells were incubated with CS for 20 h. (a) The expressions of HO-1 and NQO1 in the cells were analyzed using Western blotting. Protein semi-quantitative analysis of (b) HO-1/β-actin and (c) NQO1/β-actin. Quantitative values are depicted as mean ± S.D. † p < 0.05 vs. untreated control. Abbreviation: HO-1, heme oxygenase 1; NQO1, NAD(P)H dehydrogenase [quinone] 1.

4. Discussion

Pathological neuroinflammation serves as a primary driver of neurodegenerative pathologies, closely linked to the aberrant activation of microglial cells. Consequently, pharmacological agents capable of reining in microglial overactivation and curbing the efflux of pro-inflammatory factors represent promising therapeutic candidates for managing NDs. Our current data demonstrate that CS effectively blunted the secretion of key cytokines (IL-6 and TNF-α) and the chemokine MCP-1 in endotoxin-challenged microglia. Additionally, CS abrogated the LPS-mediated synthesis of NO and the protein abundance of iNOS and COX-2. The robust suppressive action of CS on these mediators is of particular clinical interest, as the sustained accumulation of NO and PGE2 fuels oxidative damage, eventually precipitating neuronal attrition. Collectively, 100 μM CS markedly diminished the inflammatory output and the induction of detrimental markers in LPS-primed microglial models. These observations highlight the potent immunomodulatory potential of CS, suggesting its viability as a neuroprotective agent to mitigate inflammatory-driven neurodegeneration.

The TLR4/MAPK/NF-κB signaling networks represent pivotal molecular frameworks through which the host mounts an inflammatory defense against infection or trauma. These cascades orchestrate the transcriptional regulation of pro-inflammatory cytokines and associated markers, making them prime therapeutic focal points in neurodegenerative research [38,39]. Notably, the MyD88-dependent signaling relay is indispensable for microglial mobilization. Aligning with Chavero-Vargas et al. [40], who identified the MyD88/NF-κB axis as a master regulator of inflammation and metabolic reprogramming in BV-2 cells, our data reinforce the notion that MyD88-driven signaling is a fundamental target for modulating microglial behavior. Our findings reveal that CS robustly abrogated the endotoxin-induced activation of the TLR4/MAPK/NF-κB axis in vitro. Specifically, CS interfered with the phosphorylation of MAPK members and hindered the nuclear shuttling of NF-κB by antagonizing the upstream TLR4/MyD88 complex [41,42]. Therefore, our evidence indicates that CS could serve as a potent modulator of the TLR4/MAPK/NF-κB signaling circuits for the management of NDs.

Evidence has robustly established that bolstering HO-1 and NQO1 levels is advantageous for dampening hyper-inflammatory states associated with NDs [43,44]. Specifically, the activation of these cytoprotective enzymes has been shown to attenuate endotoxin-triggered responses in microglial models by curbing cytokine efflux and impeding the NF-κB signaling axis [45]. Our current data demonstrate that CS promotes the protein abundance of both HO-1 and NQO1. This pharmacological augmentation is pivotal, as these enzymes function not only as redox buffers but also as integral components of a counter-regulatory axis that blunts NF-κB/MAPK cascades, thereby instigating a protective feedback circuit. These findings highlight the dual anti-phlogistic and antioxidant properties of CS, suggesting that enhancing the HO-1/NQO1 defense system via CS could mitigate the severity of LPS-induced hyper-inflammation.

Abundant evidence from both cell-based and animal-model paradigms substantiates that serotonin along with its structural analogs can effectively temper inflammatory responses [46,47,48]. Notably, CS exerted strong anti-inflammatory effects against endotoxin-induced inflammation in macrophages in our previous work [30]. Similarly, its ability to alleviate inflammatory molecule production and to inhibit the activation of various signaling pathways has been demonstrated in this in vitro study. Collectively, these findings reinforce the neuroprotective potential of CS, positioning it as a viable candidate for further in vivo validation in models of neurodegeneration.

5. Conclusions

To conclude, the current empirical evidence substantiates that CS markedly dampens neuroinflammatory reactions in activated microglial cells through the simultaneous suppression of the MAPK and NF-κB signaling circuits. The profound reduction in critical inflammatory indicators, such as IL-6, iNOS, and COX-2, is closely aligned with the curtailed activity of their governing transcriptional regulators as demonstrated in our assays. Our findings position CS as a viable pharmacological template for the management of neurodegenerative pathologies. Nevertheless, while this research delineates a foundational mechanism within the BV2 framework, supplementary studies exploring additional signaling relays—including the JAK/STAT3 axis—and validation in primary neuroglial cultures or animal-model paradigms are warranted to comprehensively evaluate the clinical potential and pleiotropic actions of CS under intricate physiological conditions.

Abbreviations

Abbreviations used in the current study:

AD	Alzheimer’s disease
PD	Parkinson disease
LPS	Lipopolysaccharide
IL-6	interleukin-6
TNF-α	tumor necrosis factor-α
MCP-1	monocyte chemoattractant protein-1
iNOS	inducible nitric oxide synthase
NO	nitric oxide
COX-2	cyclooxygenase-2
MAPK	mitogen-activated protein kinase
NF-κB	nuclear factor κB
TLR4	toll-like receptor 4
MyD88	myeloid differentiation primary response gene 88
HO-1	heme oxygenase-1
NQO1	NAD(P)H:quinone oxidoreductase 1
CS	N-(p-Coumaroyl) serotonin
STAT3	signal transducer and activator of transcription 3

Author Contributions

Conceptualization, M.-O.K. and J.-W.L.; Methodology and Investigation, M.-O.K. and J.-W.L.; Validation, C.H.J., S.-J.P., S.H.Y. and H.-J.J.; Formal Analysis, C.H.J., S.-J.P., S.H.Y. and H.-J.J.; Data Curation, C.H.J., S.-J.P., S.H.Y. and H.-J.J.; Writing—Original Draft Preparation, C.H.J., S.-J.P., S.H.Y., H.-J.J., M.-O.K. and J.-W.L.; Writing—Review and Editing, M.-O.K. and J.-W.L.; Supervision, M.-O.K. and J.-W.L.; Project Administration, M.-O.K. and J.-W.L.; Funding Acquisition, M.-O.K. and J.-W.L. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

Funding Statement

This research was funded by the KRIBB Research Initiative Program (grant nos. KGM1202612 and KGS1272511) and the National Research Foundation of Korea (NRF) grants funded by the Ministry of Science and ICT (MSIT) (grant nos. RS-2023-00279573, RS-2023-00213076, and 2022M3E5F4078558).