Epiisopiloturine, an Alkaloid from Pilocarpus microphyllus, Attenuates LPS-Induced Neuroinflammation by Interfering in the TLR4/NF-κB-MAPK Signaling Pathway in Microglial Cells

Abstract

Neuroinflammation is present in the pathophysiological mechanisms of several diseases that affect the central nervous system (CNS). Microglia have a prominent role in initiating and sustaining the inflammatory process. Epiisopiloturine (EPI) is an imidazole alkaloid obtained as a by-product of pilocarpine extracted from Pilocarpus microphyllus (jaborandi) and has shown promising anti-inflammatory and antinociceptive properties. In the present study, we investigated the effects of EPI on the inflammatory response in microglial cells (BV-2 cells) induced by lipopolysaccharide (LPS) and explored putative underlying molecular mechanisms. Cell viability was not affected by EPI (1-100 μg/mL) as assessed by both LDH activity and the MTT test. Pretreatment with EPI (25, 50, and 100 μg/mL) significantly reduced the proinflammatory response induced by LPS, as observed by a decrease in nitrite oxide production and iNOS protein expression. EPI (25 μg/mL) reduced IL-6 and TNF-α production, by 40% and 34%, respectively. However, no changes were observed in the anti-inflammatory IL-10 production. Mechanistically, EPI inhibited the TLR4 expression and phosphorylation of NF-κB p65 and MAPKs (JNK and ERK1/2) induced by LPS, but no changes were observed in TREM2 receptor expression in LPS-stimulated cells. In conclusion, our data demonstrated the potent anti-inflammatory properties of EPI in microglial cells. These effects are associated with the reduction of TLR4 expression and inhibition of intracellular signaling cascades, including NF-κB and MAPKs (JNK and ERK1/2).

Nitrite Attenuates the In Vitro Inflammatory Response of Immune Cells to the SARS-CoV-2 S Protein without Interfering in the Antioxidant Enzyme Activation

“…This suggests that immune stimulation with LPS/S/NO 2 enhances nitrate biosynthesis from nitric oxide and nitrite oxidation and, probably, from organic precursors such as S-nitroso thiols and L-arginine through the nitric oxide synthase pathway. In fact, it has been evidenced that immune activation of TLR4 results in marked induction of nitric oxide synthase and nitrite production in microglial cells [ 39 , 40 ] and macrophages [ 41 ] in culture.…”

Melatonin improves maternal sleep deprivation‐induced learning and memory impairment, inflammation, and synaptic dysfunction in murine male adult offspring

“…Inflammatory cells in the brain, predominantly microglial, monitor the physiological environment of the brain. When stimulated by external pathological factors, the activated microglial cells lead to excessive release of proinflammatory cytokines including IL-1β, IL-6, and TNF-α through downstream signaling pathways, resulting in neuroinflammation (de Sousa et al, 2023;Ni et al, 2023). This neuroinflammation may affect cell proliferation, differentiation, neuronal activity, and neuronal network and is closely associated with cognitive function (Palmisano et al, 2022;Yildirim et al, 2023).…”

To re-examine the intersection of microglial activation and neuroinflammation in neurodegenerative diseases from the perspective of pyroptosis

“…With the continuous aging of the global population, the incidence and prevalence of NDs are increasing, so it is urgent to study effective prevention and treatment strategies. Recent studies have found that neuroinflammation and microglia play crucial roles in the development and progression of NDs (de Sousa et al, 2023). Microglia can polarize into M1 and M2 phenotypes, which exert pro-inflammatory and anti-inflammatory effects, respectively in neuroinflammation, thereby exerting protective or toxic effects on neuronal cells (Orihuela et al, 2016).…”