Capsaicin suppresses LPS-induced inflammatory responses via NLRP3/CASP-1/IL-1β axis and purinergic pathways in BV-2 microglial cells

Abstract

Microglial activation drives neuroinflammation, a key factor in many neurological diseases. The purinergic system is a major regulator of inflammatory responses and represents a promising target for controlling neuroinflammation. Capsaicin, a bioactive compound found in chili peppers, exhibits significant anti-inflammatory and antioxidant properties. This study aimed to investigate the modulatory effects of capsaicin on microglial activation and purinergic system regulation. For this, BV-2 microglial cells were exposed to lipopolysaccharide (1 μg/mL) and treated with capsaicin (25 and 50 μM) for 24 hours. Cell viability was assessed by MTT and trypan blue assays. Cell cycle and apoptosis were evaluated by flow cytometry. Nitric oxide, reactive species and malondialdehyde levels were evaluated as markers of oxidative stress. Activities of NTPDase, 5'-nucleotidase (5’-NT), and adenosine deaminase (ADA) were evaluated. Gene expression of inflammatory mediators and purinergic receptors were analyzed by qRT-PCR, and molecular docking analyses were performed. As a result, capsaicin decreased the expression of pro-inflammatory mediators (NLRP3, CASP-1, IL-1β, IL-6, and TNF-α), increased IL-10 expression, and attenuated oxidative stress. It reduced NTPDase, 5'-NT, and ADA activities, downregulated P2X7 and A2A receptor expression, and upregulated A1 receptor expression. Molecular docking revealed that capsaicin has a high affinity for the A1 and A2A receptors, as well as for ADA. Collectively, these findings suggest that capsaicin exerts neuroprotective effect by suppressing pro-inflammatory signaling, enhancing anti-inflammatory responses, reducing oxidative stress, and modulating key components of the purinergic system, including ectoenzyme activities and P2X7, A1, and A2A receptor expression.