Partial restoration of protein synthesis rates by the small molecule ISRIB prevents neurodegeneration without pancreatic toxicity

Activation of the PERK branch of the unfolded protein response (UPR) in response to protein misfolding within the endoplasmic reticulum (ER) results in the transient repression of protein synthesis, mediated by the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2α). This is part of a wider integrated physiological response to maintain proteostasis in the face of ER stress, the dysregulation of which is increasingly associated with a wide range of diseases, particularly neurodegenerative disorders. In prion-diseased mice, persistently high levels of eIF2α cause sustained translational repression leading to catastrophic reduction of critical proteins, resulting in synaptic failure and neuronal loss. We previously showed that restoration of global protein synthesis using the PERK inhibitor GSK2606414 was profoundly neuroprotective, preventing clinical disease in prion-infected mice. However, this occured at the cost of toxicity to secretory tissue, where UPR activation is essential to healthy functioning. Here we show that pharmacological modulation of eIF2α-P-mediated translational inhibition can be achieved to produce neuroprotection without pancreatic toxicity. We found that treatment with the small molecule ISRIB, which restores translation downstream of eIF2α, conferred neuroprotection in prion-diseased mice without adverse effects on the pancreas. Critically, ISRIB treatment resulted in only partial restoration of global translation rates, as compared with the complete restoration of protein synthesis seen with GSK2606414. ISRIB likely provides sufficient rates of protein synthesis for neuronal survival, while allowing some residual protective UPR function in secretory tissue. Thus, fine-tuning the extent of UPR inhibition and subsequent translational de-repression uncouples neuroprotective effects from pancreatic toxicity. The data support the pursuit of this approach to develop new treatments for a range of neurodegenerative disorders that are currently incurable.

A particularly aggressive combined glucagonoma and gastrinoma syndrome

Duodeno-pancreatic biochemically polyfunctional endocrine tumour is a well known entity. Usually, only one hormone is responsible for the clinical features. We report a case of aggressive combined glucagonoma and gastrinoma tumour without metastases, causing respectively diabetic ketoacidosis and fulminant peptic ulcer, and death. Occasional patients can present with clinical features of both glucagonoma and gastrinoma. Diabetic patients exhibiting migratory skin lesions should be suspected of glucagonoma. In addition, a multidisciplinary approach to such patients including dermatologists, surgeons, radiologists and endoscopists is mandatory.

Attenuation of graft-versus-host disease and graft rejection by ex vivo immunotoxin elimination of alloreactive T cells in an H-2 haplotype disparate mouse combination

A mouse anti-interleukin-2 receptor A-chain-specific PC61-immunotoxin (PC61-IT) strongly inhibited a primary mixed lymphocyte culture and major histocompatibility complex (MHC)-restricted cytotoxicity. The allodepleted T cells retained their proliferative and cytotoxic capacities in response to third-party stimulation, showing that PC61-IT specifically deleted recipient antigen-specific T-cell clones from the donor mouse. The ability of this specific allodepletion to prevent graft-versus-host disease (GVHD) and graft rejection was investigated in vivo. IT-depleted, activated parental T lymphocytes (C3H/eB) were intravenously injected into lethally irradiated CDF1 mice. GVHD was evaluated after 6 days on the severity of gut lesions. PC61-IT-treated cells significantly reduced both donor T-cell infiltration and acceleration of epithelial renewal (a sensitive index of gut damage) as compared with those for the corresponding untreated controls. The effect of selective allo-depletion on prevention of GVHD and graft rejection was further studied after MHC-haploincompatible bone marrow (BM) transplantation. A significant increase in survival was observed in mice receiving 2 x 10(6) T-cell-depleted BM cells and 0.5 x 10(6) PC61-IT-treated T cells, because one-third were alive without GVHD (and with stable full or partial engraftment) after 100 days, whereas all the mice infused with BM and sham-treated T cells died within 80 days from GVHD, and all the mice infused with BM cells alone rejected grafts. Furthermore, specific tolerance in chimeras towards donor cells could be shown. These results as observed in an experimental in vivo model corroborate previous results obtained in vitro in humans and lead us to consider the use of this selective allodepletion in human BM transplant from donors other than identical familial siblings.

Specific elimination of alloreactive T cells by an anti-interleukin-2 receptor B chain-specific immunotoxin

Graft-versus-host disease and graft rejection remain the two principal causes of morbidity and mortality after major-histocompatibility-complex-mismatched bone marrow transplantation. Human and animal models suggest that both CD4+ and CD8+ T cell subsets present in the donor inoculum are responsible for their initiation. Since the human mixed lymphocyte culture (MLC) and the HLA-restricted cytotoxicity may reflect cellular interactions occurring during GVHD and graft rejection, inhibitions of these responses may represent useful approaches for screening functional T cell depletion in experimental bone marrow transplantation studies. For this purpose, we have tested the possibility of removing the host-specific allogeneic T cells present in the marrow. After a two-day MLC, the specifically activated host alloreactive blood or bone marrow T cells were incubated with the ricin A-chain toxin conjugated with the antibody 33B3.1 directed against the human receptor of interleukin 2 (33B3.1-IT). A complete inhibition of a primary MLC and of cytotoxic activities was observed as well as a disappearance of IL-2R(+) (p55) T cells. This method had limited consequence upon the alloreactivity of blood or marrow T cells toward a third unrelated party. The limiting-dilution analysis of residual alloantigen-reactive T lymphocytes has shown that this depletion results in a twentyfold to fiftyfold reduction of antihost reactivity. The procedure was also shown not to inhibit the growth of marrow precursors for granulocytes and macrophages.