Alkaloids from In Vitro Cultured Rhodophiala pratensis Display Neuroprotective Effects in Murine Microglial Cell Models of Inflammation

Neuroinflammation is determinant in the progression of neurodegenerative diseases. One of the main mechanisms underlying this process involves the persistent activation of glial cells. Persistent activation of glial cells induces proinflammatory transcription factors and the release of cytokines, chemokines, and reactive oxygen species that exacerbate cellular dysfunction. This neurotoxic environment promotes neuronal death, while the products of cellular damage feed back into glial activation, establishing a self-sustaining pathogenic cycle that drives neurodegeneration. Alkaloids present in Amaryllidaceae plants support the use of this resource in folk medicine, displaying potent effects as acetylcholinesterase inhibitors and allosteric modulators of nicotinic receptors (nAChR). In this study, a murine microglial cell (IMG) model of LPS-induced inflammation was used to evaluate the involvement of α7 and α4β2 nAChRs in glioprotection and neuroprotection of SH-SY5Y cells against 6-hydroxydopamine (OHDA). GC-MS analysis revealed differences in the alkaloid profile between in vitro cultures with fructose and wild-type Rhodophiala pratensis. Homolycorine-type, norbelladine-type and crinine-type alkaloids produced in vitro reduced LPS-induced inflammation (5 µg/mL), possibly via α7 and α4β2 nAChRs, and showed a protective effect against OHDA-induced oxidative stress (1–3 µg/mL) and inhibited AChE and BuChE (24–78 µg/mL).