The flavonoid rutin induces astrocyte and microglia activation and regulates TNF-alpha and NO release in primary glial cell cultures

Abstract

Astrocyte and microglia cells play an important role in the central nervous system (CNS). They react to various external aggressions by becoming reactive and releasing neurotrophic and/or neurotoxic factors. Rutin is a flavonoid found in many plants and has been shown to have some biological activities, but its direct effects on cells of the CNS have not been well studied. To investigate its potential effects on CNS glial cells, we used both astrocyte primary cultures and astrocyte/microglia mixed primary cell cultures derived from newborn rat cortical brain. The cultures were treated for 24 h with rutin (50 or 100 micromol/L) or vehicle (0.5% dimethyl sulfoxide). Mitochondrial function on glial cells was not evidenced by the MTT test. However, an increased lactate dehydrogenase activity was detected in the culture medium of both culture systems when treated with 100 micromol/L rutin, suggesting loss of cell membrane integrity. Astrocytes exposed to 50 micromol/L rutin became reactive as revealed by glial fibrillary acidic protein (GFAP) overexpression and showed a star-like phenotype revealed by Rosenfeld's staining. The number of activated microglia expressing OX-42 increased in the presence of rutin. A significant increase of nitric oxide (NO) was observed only in mixed cultures exposed to 100 micromol/L rutin. Enhanced TNFalpha release was observed in astrocyte primary cultures treated with 100 micromol/L rutin and in mixed primary cultures treated with 50 and 100 micromol/L, suggesting different sensitivity of both activated cell types. These results demonstrated that rutin affects astrocytes and microglial cells in culture and has the capacity to induce NO and TNFalpha production in these cells. Hence, the impact of these effects on neurons in vitro and in vivo needs to be studied.

Hesperidin, a Flavone Glycoside, as Mediator of Neuronal Survival

“…Although flavonoids have been reported to act on glial cells, we did not observe effects in oligodendrocytes and astrocyte pools [20,33]. A specific receptor for flavonoids has not been identified yet.…”

Effects of the flavonoid casticin from Brazilian Croton betulaster in cerebral cortical progenitors in vitro: Direct and indirect action through astrocytes

“…Previous studies of our group and others revealed that glial cells might be targeted by different flavonoids, leading to modulation of the inflammatory response (Sharma et al, 2007), proliferation (Kobayakawa et al, 2004), and morphology (Silva et al, 2008). However, the effects of casticin on astrocytes, as well as the role of astrocytes as mediators of flavonoid effects on neuronal morphogenesis, have not been addressed before.…”

“…These data, together with the possibility that these cells might be a target for flavonoids (Silva et al, 2008), led us to investigate whether casticin might act on neurons through astrocytes.…”

“…Flavonoids also elicit a broad spectrum of responses in astrocytes in culture. We recently demonstrated that the flavonoid rutin has a direct effect on glial cells in vitro, inducing activation of astrocytes and microglia, release of tumor necrosis factor-a (TNF-a), and induction of inducible nitric oxide synthase (iNOS; Silva et al, 2008). Moreover, it has been shown that the dietary flavonoid (-)epicatechin stimulates the activity of the antioxidant response element in primary cortical astrocytes .…”

Flavonoids and Astrocytes Crosstalking: Implications for Brain Development and Pathology

“…Naringenin, a member of the flavanone family, exhibits high permeability as measured by in vitro and in situ BBB models, suggesting that this family of flavonoids should afford good neuroprotection within the CNS. Nevertheless, some restriction of entry caused by efflux transporters may affect certain flavonoids, such as quercetin [101].…”