Myriam Verlaet

Human immune cells express ppMCH mRNA and functional MCHR1 receptor

Melanin‐concentrating hormone (MCH) is highly expressed in the brain and modulates feeding behavior. It is also expressed in some peripheral tissues where its role remains unknown. We have investigated MCH function in human and mouse immune cells. RT‐PCR analysis revealed a low expression of prepro‐MCH and MCH receptor 1 (MCHR1) but not of MCHR2 transcript in tissular and peripheral blood immune cells. FACS and in vitro assay studies demonstrated that MCHR1 receptor expression on most cell types can trigger, in the presence of MCH, cAMP synthesis and calcium mobilization in peripheral blood mononuclear cells (PBMCs). Moreover, MCH treatment decreases the CD3‐stimulated PBMC proliferation in vitro. Accordingly, our data indicate for the first time that MCH and MCHR1 may exert immunomodulatory functions.

Cyclo-oxygenase type 2-dependent prostaglandin E2 secretion is involved in retrovirus-induced T-cell dysfunction in mice.

MAIDS (murine AIDS) is caused by infection with the murine leukaemia retrovirus RadLV-Rs and is characterized by a severe immunodeficiency and T-cell anergy combined with a lymphoproliferative disease affecting both B- and T-cells. Hyperactivation of the cAMP-protein kinase A pathway is involved in the T-cell dysfunction of MAIDS and HIV by inhibiting T-cell activation through the T-cell receptor. In the present study, we show that MAIDS involves a strong and selective up-regulation of cyclo-oxygenase type 2 in the CD11b+ subpopulation of T- and B-cells of the lymph nodes, leading to increased levels of PGE2 (prostaglandin E2). PGE2 activates the cAMP pathway through G-protein-coupled receptors. Treatment with cyclo-oxygenase type 2 inhibitors reduces the level of PGE2 and thereby reverses the T-cell anergy, restores the T-cell immune function and ameliorates the lymphoproliferative disease.

Detection of Cytokines in Human Sural Nerve Biopsies: An Immunohistochemical and Molecular Study

Abstract. In vitro and in vivo models have implicated numerous cytokines as major modulators of inflammation, destruction and repair in the peripheral nervous system (PNS). The in situ production of cytokines in human peripheral nerve disorders is still poorly documented. We studied the expression of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, IL-10, IL-4, IL-3 and nerve growth factor (NGF) in 35 human sural nerve biopsies using immunohistochemistry; additional reverse transcription-polymerase chain reaction and mRNA in situ hybridization were performed for IL-4 and NGF. Expression of IL-1β and TNF-α was shown in both morphologically normal nerves and various neuropathies, and macrophages appeared as their predominant source. Levels of IL-1β and TNF-α expression were significantly correlated (P<0.01) with each other and with expression of NGF. Multiple endoneurial sources were suggested for IL-6 and IL-10 with low immunoreactivity in the vast majority of cases. Conversely, IL-4 and IL-3 expression were found in neuropathies of various etiologies and Schwann cells appeared to be a predominant source of IL-4 in double-labeling immunofluorescence studies. IL-3 immunoreactivity correlated with IL-1β, TNF-α and IL-6. In this retrospective study, no specific cytokine profile of expression could be assigned to a precise subgroup of neuropathies. This is the first report of IL-4 and IL-3 expression in human neuropathies, and it may be important given the potential role of these cytokines in modulating macrophage activity in the PNS.

Nuclear localization of a new c-cbl related protein, CARP 90, during in vivo thymic apoptosis in mice

This study investigates the involvement of the c-cbl protooncogene in thymocyte apoptosis occuring in vivo after hydrocortisone treatment. In the thymus of untreated mice, a few medullary and cortical thymocytes expressed p120cbl, mainly in the cytoplasm. In the cortex, their number and distribution resemble that of apoptotic cells evidenced by TUNEL staining. The expression of Cbl is rapidly increased when apoptosis is triggered by hydrocortisone. This Cbl-specific immunostaining was detected in the nucleus and is due to a Cbl-related 90 kDa protein (CARP 90). These results show that a c-cbl product could localize in the nucleus and suggest that it could be involved as a regulator of thymic apoptosis.

Neuronal localization of the 25-kDa specific thiamine triphosphatase in rodent brain.

Thiamine triphosphate (ThTP) is found in small amounts in most organisms from bacteria to mammals, but little is known about its physiological role. In vertebrate tissues, ThTP may act as a phosphate donor for the phosphorylation of certain proteins; this may be part of a new signal transduction pathway. We have recently characterized a highly specific 25-kDa thiamine triphosphatase (ThTPase) that is expressed in most mammalian tissues. The role of this enzyme may be the control of intracellular concentrations of ThTP. As the latter has been considered to be a neuroactive form of thiamine, we have studied the distribution of ThTPase mRNA and protein in rodent brain using in situ hybridization and immunohistochemistry. With both methods, we found the strongest staining in hippocampal pyramidal neurons, as well as cerebellar granule cells and Purkinje cells. Some interneurons were also labeled and many ThTPase mRNA-positive and immunoreactive cells were distributed throughout cerebral cortical gray matter and the thalamus. White matter was not significantly labeled. ThTPase immunoreactivity seems to be located mainly in the cytoplasm of neuronal perikarya. Immunocytochemical data using dissociated cultured cells from hippocampal and cerebellum showed that the staining was more intense in neurons than in astrocytes. The protein was rather uniformly located in the perikarya and dendrites, suggesting that ThTP and ThTPase may play a general role in neuronal metabolism rather than a specific role in excitability. There was no apparent correlation between ThTPase expression and selective vulnerability of certain brain regions to thiamine deficiency.

Transient modifications of respiratory capacity in thymic cells during murine radioleukemogenesis

The evolution of mitochondrial oxidative phosphorylation was studied during cancer induction in a model of thymic radiolymphomagenesis in C57BL/Ka mice. During the preneoplastic period, thymuses displayed an increase of the cytochrome c oxidase activity and oxygen consumption together with oxidative DNA damage assessed by the presence of the 8-hydroxydeoxyguanine DNA base modification. These transient changes in mitochondrial functional activity were not observed in thymuses of mice rescued from lymphoma development by a bone marrow graft, suggesting an important role of mitochondria for neoplastic transformation in this model, which might therefore be of interest to test the utilization of antioxidants for the prevention of radiation-induced malignancies.