Reversible Inhibitory Effects of Interferon‐γ and Tumour Necrosis Factor‐α on Oligodendroglial Lineage Cell Proliferation and Differentiation In Vitro

Abstract

We have investigated the effects of the two prominent inflammatory cytokines, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), on oligodendroglial lineage cell development and survival. Purified oligodendrocytes and oligodendrocyte precursors obtained from neonatal rat brain primary cultures were subcultured in a defined, serum-free medium and exposed to IFN-gamma (1-100 U/ml, TNF-alpha (25-100 ng/ml) or both (100 U/ml and 50 ng/ml respectively) from day 1 to day 3 or from day 3 to day 6. While cell survival was not affected in any of the conditions tested, IFN-gamma dose-dependently inhibited [3H]thymidine or bromodeoxyuridine incorporation (by up to 50%) and the reduction of the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT; by up to 33%). TNF-alpha synergized with IFN-gamma, but was ineffective by itself. Moreover, IFN-gamma totally antagonized the induction by basic fibroblast growth factor and platelet-derived growth factor of the proliferation of the oligodendroglial lineage cell population under study. IFN-gamma also blocked the differentiation of oligodendrocyte precursors, as evidenced by cell morphology, immunostaining for early and late differentiation markers (galactocerebroside and myelin basic protein respectively) and activity of ceramide galactosyl transferase. Again, the effect of IFN-gamma was potentiated by TNF-alpha, which was ineffective when tested alone. The inhibitory activity of IFN-gamma was rapidly reversible: 3 days after removal of the cytokine, administered from day 1 to day 3, complete recovery of cll proliferation and differentiation could be documented. The cytokine-induced arrest in the expression of differentiation antigens was accompanied by perturbations in the expression of the corresponding mRNAs, revealed by a semiquantitative reverse transcription-polymerase chain reaction method. In particular, the message for myelin basic protein (and, in the case of treatment from days 3 to 6, also that for myelin associated glycoprotein) was decreased in cultures exposed to IFN-gamma, and further depressed in cultures treated with IFN-gamma and TNF-alpha, while TNF-alpha alone was ineffective. The above observations may help explain the role of IFN-gamma and TNF-alpha in the pathogenesis of inflammatory demyelinating diseases, in which increases in the levels of these substances have been described. In particular, in the case of multiple sclerosis, our results may bear on the problem of defective remyelination and are consistent with the frequent relapsing-remitting course of the disease.

Distinct effects of ceramide‐generating pathways in prostate adenocarcinoma cells

“…Activation of sphingomyelin hydrolysis does not necessarily initiate an apoptotic response; agents known to activate the sphingomyelin cascade such as IFN-g and TNF-a have also been reported to reduce the proliferation of oligodendrocyte precursors without modifying cell survival (Agresti et al, 1996). Moreover, ceramide also exhibits anti-apoptotic, protective activity in primary cultures of sympathetic (Ito & Horigome, 1995) and hippocampal (Goodman & Mattson, 1996) neurons and exerts mitogenic e ect in quiescent, Swiss 3T3 ®broblasts (Olivera et al, 1992), suggesting that its role in cellular function does not inevitably involve a death program.…”

Nuclear Factor kB-independent Cytoprotective Pathways Originating at Tumor Necrosis Factor Receptor-associated Factor 2

“…Primary rat oligodendrocytes cultures were obtained as described (45,46). Purified oligodendrocytes precursors were obtained by mechanical dissociation from rat mixed glial primary cultures (45,46).…”

“…Primary rat oligodendrocytes cultures were obtained as described (45,46). Purified oligodendrocytes precursors were obtained by mechanical dissociation from rat mixed glial primary cultures (45,46). To prevent irreversible exit from cell cycle, cells were grown in chemically defined serum-free medium lacking triiodothyronine and thyroxine (which stimulate differentiation of precursors into oligodendrocytes) and containing platelet-derived growth factor and basic fibroblast growth factor (10 ng/ml).…”

“…To determine whether NFkB-independent cytoprotective pathways contribute to TNF resistance of terminally differentiated primary cells, we performed analogous experiments in primary rat oligodendrocytes, the glial cells responsible for the elaboration of the multilamellar myelin sheaths in central nervous system. Damage of oligodendrocytes in demyelinating diseases, such as multiple sclerosis, has been linked to TNF effects on these cells (63); however, primary rat oligodendrocytes are resistant to TNF cytotoxicity under standard culture conditions (46). We therefore infected purified primary rat oligodendrocytes with recombinant retroviruses expressing either Flag-TRAF2(87-501) or HA-IkB␣S32A/S36A.…”

cFLIP is critical for oligodendrocyte protection from inflammation

“…O-2A/OPCs show suppressed division when exposed to IFNγ. [1][2][3] However, when O-2A/OPCs differentiate into oligodendrocytes, IFNγ becomes pro-apoptotic. [4][5][6][7] Although IFNγ has a critical role in the pathogenesis of immune-mediated demyelinating disease; 8,9 the response of committed oligodendrocytes to IFNγ is more complex.…”