Rescuing the negative impact of human endogenous retrovirus envelope protein on oligodendroglial differentiation and myelination.

Remyelination in the adult CNS depends on activation, differentiation, and functional integration of resident oligodendroglial precursor cells (OPCs) and constitutes the only spontaneous neuroregenerative process able to compensate for functional deficits upon loss of oligodendrocytes and myelin sheaths as it is observed in multiple sclerosis. The proteins encoded by p57kip2- and by human endogenous retrovirus type W (pHERV-W) envelope genes were previously identified as negative regulators of OPC maturation. We here focused on the activity of the ENV protein and investigated how it can be neutralized for an improved myelin repair. We could demonstrate that myelination in vitro is severely affected by this protein but that application of an anti-ENV neutralizing antibody, currently investigated in clinical trials, can rescue the generation of internodes. We then compared p57kip2 and ENV dependent inhibitory mechanisms and found that a dominant negative version of the p57kip2 protein can equally save OPCs from myelination failure in response to ENV-mediated TLR4 activation. Additional experiments addressing p57kip2's underlying mode of action revealed a direct interaction with ATP6v1d, a central component of a vascular ATPase. Its pharmacological blocking was then shown to exert an analogous myelination rescue effect in presence of the ENV protein. Therefore, our study provides mechanistic insights into oligodendroglial inhibition processes and presents three different means to counteract the anti-myelination effect of the ENV protein. These observations are therefore of interest in light of understanding the complexity of the numerous oligodendroglial inhibitors and might promote the establishment of novel regenerative therapies.

PRAS40 alleviates neurotoxic prion peptide-induced apoptosis via mTOR-AKT signaling.

AIMS: The proline-rich Akt substrate of 40-kDa (PRAS40) protein is a direct inhibitor of mTORC1 and an interactive linker between the Akt and mTOR pathways. The mammalian target of rapamycin (mTOR) is considered to be a central regulator of cell growth and metabolism. Several investigations have demonstrated that abnormal mTOR activity may contribute to the pathogenesis of several neurodegenerative disorders and lead to cognitive deficits. METHODS: Here, we used the PrP peptide 106-126 (PrP106-126 ) in a cell model of prion diseases (also known as transmissible spongiform encephalopathies, TSEs) to investigate the mechanisms of mTOR-mediated cell death in prion diseases. RESULTS: We have shown that, upon stress caused by PrP106-126 , the mTOR pathway activates and contributes to cellular apoptosis. Moreover, we demonstrated that PRAS40 down-regulates mTOR hyperactivity under stress conditions and alleviates neurotoxic prion peptide-induced apoptosis. The effect of PRAS40 on apoptosis is likely due to an mTOR/Akt signaling. CONCLUSION: PRAS40 inhibits mTORC1 hyperactivation and plays a key role in protecting cells against neurotoxic prion peptide-induced apoptosis. Thus, PRAS40 is a potential therapeutic target for prion disease.

Trophoblast IFN-tau differentially induces lymphopenia and neutropenia in lambs.

Type I interferons (IFN), including IFN-alpha and IFN-beta, cause severe lymphopenia, resulting from altered lymphocyte recirculation and redistribution. IFN-tau, a product of trophectoderm of ruminant conceptuses and new member of the type I IFN family has not been examined for its effect on leukocyte recirculation. Additionally, differential effects of type I IFNs on the redistribution and recirculation of subsets of T cells have not been reported. The present study determined the effects of IFN-tau on the redistribution and recirculation of ovine leukocytes and T cell subsets. Total peripheral blood leukocytes, lymphocytes, and segmented neutrophils were reduced (p < 0.05) following treatment of lambs with IFN-tau. Furthermore, administration of IFN-tau caused an acute, differential reduction in peripheral blood CD4+ T cells (p < 0.05), CD5+ cells (p < 0.05), and gammadelta TCR+ (p < 0.01) T cells but had no effect on CD8+ T cells (p > 0.05). IFN-tau reduced the percentage of gammadelta T cells by 8-fold and that of CD4+ T cells and CD5+ cells by <2-fold in peripheral blood when compared with control lambs. The reduction in leukocytes, lymphocytes, and neutrophils was observed as early as 6-12 h after administration of IFN-tau, but levels returned to control values within 48 h. These results indicate that IFN-tau, like other members of the type I IFN family, can have immediate effects on leukocyte recirculation and redistribution. The present study is the first to demonstrate that IFN-tau differentially regulates T cell recirculation with the greatest effect on gammadelta TcR+ T cells.

The IFN pregnancy recognition hormone IFN-tau blocks both development and superantigen reactivation of experimental allergic encephalomyelitis without associated toxicity.

Multiple sclerosis (MS) is an inflammatory demyelinating autoimmune disease if the central nervous system (CNS). Recently, the type I IFN, IFN-beta-1b was demonstrated to be a useful immunotherapy for MS. During treatment with IFN-beta-1b, toxicity at higher doses has been observed. IFN-tau, discovered for its role in the reproductive cycle, possesses all of the functions normally ascribed to the type I IFNs but lacks the toxicity normally associate with IFN treatment in vitro. We have examined the effects of IFN-tau treatment on experimental allergic encephalomyelitis (EAE), an animal model useful for the study of MS. EAE is a model of Ag-induced autoimmunity that can be modulated by bacterial superantigen to resemble the relapsing-remitting pattern of autoimmune disease observed in MS. IFN-tau was able to prevent development of EAE as effectively as IFN-beta but without associated toxicity such as lymphocyte suppression and weight loss. In addition, IFN-tau was able to prevent superantigen reactivation of EAE akin to the reduction in disease exacerbations observed in IFN-beta-1b treated MS patients. Mechanisms by which IFN-tau may prevent EAE include reduced proliferation in response to the autoantigen myelin basic protein and reduced TNF-alpha production. Thus, IFN-tau may prove to be a promising new IFN therapy for MS in light of its ability to prevent EAE and the lack of toxicity exhibited by this novel IFN.

Effects of exogenous recombinant ovine interferon tau on circulating concentrations of progesterone, cortisol, luteinizing hormone, and antiviral activity; interestrous interval; rectal temperature; and uterine response to oxytocin in cyclic ewes.

Interferon tau (IFN tau) is the conceptus-produced antiluteolytic signal in ruminants. Three experiments examined the effects of s.c. administration of recombinant ovine (ro)IFN tau on interestrous interval (IEI), oxytocin (OT)-induced uterine prostaglandin F2alpha metabolite (PGFM) production, rectal temperature (RT), respiration rate (RR), and plasma concentrations of progesterone, cortisol, LH, and antiviral activity (AVA) in plasma and uterine flushings. In experiment I, 20 ewes were treated s.c. with either 0, 1, 2, or 4 mg/day roIFN tau (0.7 x 10(8) U/mg; 5 ewes/dosage) from Days 11 to 15 of the estrous cycle (estrus = Day 0) and were challenged with OT (30 IU) on Day 15. Jugular blood samples were collected at -10, 0, 10, 20, 30, 40, 50, and 60 min relative to the OT challenge and assayed for PGFM. Recombinant oIFN tau increased IEI (16.7, 18.7, and 22.6 +/- 0.6 days for 0, 2, and 4 mg roIFN tau, respectively, p < 0.01). Recombinant oIFN tau did not affect peak PGFM response to OT (2309 +/- 172 pg/ml; p > 0.1). However, the 4 mg/day dosage delayed the time to peak PGFM (32.4 vs. 47.5 +/- 3.4 min; p < 0.01, 0 vs. 4 mg) and resulted in approximately 200% higher concentrations of PGFM at 60 min post-OT (0 vs. 4 mg/day, p < 0.07). Experiment II was similar to experiment I, except that only the 0- and 4-mg/day dosages of roIFN tau were administered. Ewes were hysterectomized on Day 16, and assay of uterine flushes detected no AVA from ewes treated with either 0 or 4 mg/day roIFN tau. In experiment III, 20 ewes were treated s.c. with either 0, 2, 4, or 6 mg roIFN tau on Day 12. Blood samples, RT, and RR were obtained at frequent intervals for 24 h, and plasma was assayed for progesterone, cortisol, LH, and AVA. Plasma AVA, which increased in a dose-dependent manner, was detectable within 60 min and remained elevated at 24 h compared to control values. RT (elevated 0.5-1.0 degrees C), RR, and cortisol increased in response to all dosages of roIFN tau, with peak values occurring 150-180 min postinjection. For all dosages of roIFN tau, plasma progesterone declined from 120 to 360 min posttreatment and then returned to pretreatment values by 24 h (p < 0.01) as compared to controls. Overall, exogenous roIFN tau altered uterine PGFM response to OT from a pulse to a gradual and sustained elevation and extended IEI with only a transient decline in progesterone and mild hyperthermia, effects that are not expected to compromise pregnancy.

Differential recognition of the type I interferon receptor by interferons tau and alpha is responsible for their disparate cytotoxicities.

Interferon tau (IFN tau), originally identified as a pregnancy recognition hormone, is a type I interferon that is related to the various IFN alpha species (IFN alpha s). Ovine IFN tau has antiviral activity similar to that of human IFN alpha A on the Madin-Darby bovine kidney (MDBK) cell line and is equally effective in inhibiting cell proliferation. In this study, IFN tau was found to differ from IFN alpha A in that is was > 30-fold less toxic to MDBK cells at high concentrations. Excess IFN tau did not block the cytotoxicity of IFN alpha A on MDBK cells, suggesting that these two type I IFNs recognize the type I IFN receptor differently on these cells. In direct binding studies, 125I-IFN tau had a Kd of 3.90 x 10(-10) M for receptor on MDBK cells, whereas that of 125I-IFN alpha A was 4.45 x 10(-11) M. Consistent with the higher binding affinity, IFN alpha A was severalfold more effective than IFN tau in competitive binding against 125I-IFN tau to receptor on MDBK cells. Paradoxically, the two IFNs had similar specific antiviral activities on MDBK cells. However, maximal IFN antiviral activity required only fractional occupancy of receptors, whereas toxicity was associated with maximal receptor occupancy. Hence, IFN alpha A, with the higher binding affinity, was more toxic than IFN tau. The IFNs were similar in inducing the specific phosphorylation of the type I receptor-associated tyrosine kinase Tyk2, and the transcription factors Stat1 alpha and Stat2, suggesting that phosphorylation of these signal transduction proteins is not involved in the cellular toxicity associated with type I IFNs. Experiments using synthetic peptides suggest that differences in the interaction at the N terminal of IFN tau and IFN alpha with the type I receptor complex contribute significantly to differences in high-affinity equilibrium binding of these molecules. It is postulated that such a differential recognition of the receptor is responsible for the similar antiviral but different cytotoxic effects of these IFNs. Moreover, these data imply that receptors are "spare'' with respect to certain biological properties, and we speculate that IFNs may induce a concentration-dependent selective association of receptor subunits.