Hesperetin, a Citrus Flavonoid, Ameliorates Inflammatory Cytokine-Mediated Inhibition of Oligodendroglial Cell Morphological Differentiation

Abstract

Oligodendrocytes (oligodendroglial cells) are glial cells that wrap neuronal axons with their differentiated plasma membranes called myelin membranes. In the pathogenesis of inflammatory cytokine-related oligodendroglial cell and myelin diseases such as multiple sclerosis (MS), typical inflammatory cytokines tumor necrosis factor α (TNFα) and interleukin-6 (IL-6) are thought to contribute to the degeneration and/or progression of the degeneration of oligodendroglial cells and, in turn, the degeneration of naked neuronal cells in the central nervous system (CNS) tissues. Despite the known involvement of these inflammatory cytokines in disease progression, it has remained unclear whether and how TNFα or IL-6 affects the oligodendroglial cells themselves or indirectly. Here we show that TNFα or IL-6 directly inhibits morphological differentiation in FBD-102b cells, which are differentiation models of oligodendroglial cells. Their phenotype changes were supported by the decreased expression levels of oligodendroglial cell differentiation and myelin marker proteins. In addition, TNFα or IL-6 decreased phosphorylation levels of Akt kinase, whose upregulation has been associated with promoting oligodendroglial cell differentiation. Hesperetin, a flavonoid mainly contained in citrus fruit, is known to have neuroprotective effects. Hesperetin might also be able to resolve pre-illness conditions, including the irregulated secretion of cytokines, through diet. Notably, the addition of hesperetin into cells recovered TNFα- or IL-6-induced inhibition of differentiation, as supported by increased levels of marker protein expression and phosphorylation of Akt kinase. These results suggest that TNFα or IL-6 itself contributes to the inhibitory effects on the morphological differentiation of oligodendroglial cells, possibly providing information not only on their underlying pathological effects but also on flavonoids with potential therapeutic effects at the molecular and cellular levels.

Rehabilitation treatment of multiple sclerosis

“…The main pathological changes are the activation of T cells and B cells, secretion of various inflammatory factors, migration to the CNS, resulting in inflammatory infiltration of tissues, apoptosis and necrosis of OL, hyperplasia of MG and AST. Subsequently, demyelination occurs,eventually leading to neurodegeneration and loss of neuronal function (16,17) severity of MS (18). Sparaco et al suggested that high levels of estrogen may be protective in women with MS because they found that the severity of the disease was significantly reduced in women with MS at the end of pregnancy (19).…”

“…Nishino et al. suggested that inflammatory factors and myelin fragments stimulated MG polarization to M1 type, and at the same time stimulated AST activation and secretion of inflammatory cytokines and chemokines, in addition, inflammatory factors secreted by MG and AST can aggravate demyelination and further aggravate the severity of MS ( 18 ). Sparaco et al.…”

Knockdown of Rab7B, But Not of Rab7A, Which Antagonistically Regulates Oligodendroglial Cell Morphological Differentiation, Recovers Tunicamycin-Induced Defective Differentiation in FBD-102b Cells

“…2.3. Cell culture, differentiation, and transfection FBD-102b cells (provided by Dr. Tomo-Oka, Tokyo University of Science), which belong to an oligodendroglial precursor cell line [17][18][19][20], were cultured on normal cell culture dishes (Nunc brand, Thermo Fisher Scienti c, Waltham, MA, USA) in Dulbecco's modi ed Eagle's medium (DMEM)/F-12 mixed medium (Nacalai Tesque) containing 10% heat-inactivated fetal bovine serum (FBS; Gibco brand, Thermo Fisher Scienti c) and penicillin and streptomycin mixed solution (Nacalai Tesque) in 5% CO 2 at 37°C. Cells were transfected with the respective synthesized 21-mer siRNAs with dTdT using the ScreenFect siRNA transfection kit (Fuji lm, Tokyo, Japan) in accordance with the manufacturer's instructions.…”

“…The medium was replaced 4 hours after transfection and cells were further cultured for experiments. Less than 5% of attached cells contained incorporated trypan blue (Nacalai Tesque) at 48 hours after transfection [17][18][19][20].…”

“…If so, how Rab7A and Rab7B regulate differentiation needs to be determined. Herein we describe that Rab7A and Rab7B differentially regulate morphological differentiation in FBD-102b cells, which are models of differentiation of oligodendroglial precursor cells [17][18][19][20]. It is of note that knockdown of Rab7B greatly promoted differentiation.…”