Tumor necrosis factor alpha (TNFalpha) and its soluble receptor p75 (sTNF-R p75) in familial combined hyperlipidemia (FCHL).

BACKGROUND AND AIM: Familial combined hyperlipidemia (FCHL) is a genetic disorder of lipid metabolism associated with insulin resistance and abnormalities in fatty acid metabolism whose underlying mechanisms are largely unknown. Perturbations in the TNFalpha/TNF-R pathway may play a role in these abnormalities. METHODS AND RESULTS: We determined plasma levels of TNFalpha and sTNF-R p75 in 85 FCHL patients (TC 245+/-45 mg/dl; TG 260+/-148 mg/dl; apoB 148+/-37 mg/dl) and in 29 age- and sex-matched normolipemic relatives (NL) (TC 187+/-22.8 mg/dl; TG 115+/-37 mg/dl; apoB 106+/-16 mg/dl). Thirty-four normolipemic subjects (TC 180+/-34 mg/dl; TG 107+/-42 mg/dl; apoB 95+/-22 mg/dl) were also included as unrelated controls (NC). Plasma free fatty acids (NEFA) were also measured and insulin sensitivity was evaluated by HOMA. Levels of sTNF-R p75 were significantly reduced in FCHL compared to NL (2.30+/-0.55 ng/ml vs. 2.64+/-0.88 ng/ml, p<0.05) but not compared to NC (2.35+/-0.68 ng/ml). HOMA values were comparable in all groups and did not show any relation with plasma levels of sTNF-R p75. Logistic analysis demonstrated that a low concentration of sTNF-R p75 was an independent predictor of the affected status within FCHL families, but this role was no longer evident when FCHL patients were compared to NC. In FCHL, age (p<0.001) was positively, and TG (p=0.029) and HDL-C (p=0.025) were negatively correlated with plasma concentrations of sTNF-R p75. In the other groups, age (in NL) and non-HDL-C (in NC) were significantly correlated with sTNF-R p75. CONCLUSIONS: Although our data do not support a causative role of TNFalpha/TNF-R alterations in FCHL, they confirm that variation in TNF-R shedding may influence lipid phenotypic expression in FCHL families.

Interplay of the E box, the cyclic AMP response element, and HTF4/HEB in transcriptional regulation of the neurospecific, neurotrophin-inducible vgf gene.

vgf is a neurotrophin response-specific, developmentally regulated gene that codes for a neurosecretory polypeptide. Its transcription in neuronal cells is selectively activated by the neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor, and neurotrophin 3, which induce survival and differentiation, and not by epidermal growth factor. We studied a short region of the rat vgf promoter which is essential for its regulated expression. A cyclic AMP response element (CRE) within this region is necessary for NGF induction of vgf transcription. Two sites upstream of CRE, an E box and a CCAAT sequence, bind nuclear protein complexes and are involved in transcriptional control. The E box has a dual role. It acts as an inhibitor in NIH 3T3 fibroblasts, together with a second E box located downstream, and as a stimulator in the NGF-responsive cell line PC12. By expression screening, we have isolated the cDNA for a basic helix-loop-helix transcription factor, a homolog of the HTF4/HEB E protein, that specifically binds the vgf promoter E box. The E protein was present in various cell lines, including PC12 cells, and was a component of a multiprotein nuclear complex that binds the promoter in vitro. The E box and CRE cooperate in binding to this complex, which may be an important determinant for neural cell-specific expression.

Ras oncogene transformation of human B lymphoblasts is associated with lymphocyte activation and with a block of differentiation.

The p21ras small GTP binding proteins participate in signal transduction from cell surface receptors and affect neoplastic transformation and development in many different cell types. In the present study, we examined the relationship between ras transformation and differentiation of human B lymphocytes. We show that the constitutive expression of the T24 Ha-ras oncogene in EBV-immortalized B lymphoblasts was associated with the induction of the interleukin 2 receptor alpha subunit, with an impaired immunoglobulin gene expression, altered adhesion properties and increased survival in serum-free medium. Since induction of the IL-2 receptor alpha subunit is a hallmark of lymphocyte activation, we suggest that p21ras naturally triggers B cell activation. The ras-transformed lymphocytes displayed a fully functional IL-2r, as assessed by c-fos induction following treatment with IL-2; nevertheless, they were not growth stimulated by this lymphokine. The decreased expression of immunoglobulin genes indicates that the ras oncogene blocks terminal differentiation to plasma cells, possibly by inhibiting the activity of lymphocyte-specific transcription factors. Somewhat unexpectedly, the constitutive p21ras activity did not cause an increased DNA binding of transcription factors PEA1 (AP1), PEA3, Oct-2 or NF-kB.

Induction of the neoplastic phenotype of EBV-established B lymphocytes by the human Ha-ras oncogene.

We report on the use of human B lymphocytes immortalized by the Epstein-Barr virus (EBV) as targets for transformation by the c-Ha-ras oncogene of bladder carcinoma cells T24. Several stably transformed cell lines were obtained and their in vivo and in vitro growth properties as well as levels of expression of the ras gene were studied. The transformed phenotype in these cells was correlated to ras oncoprotein expression level; only the cell lines which overproduce p21 ras, by at least six-fold, were tumorigenic in nude mice. In this regard, our ras transformed cells behave as lymphoblastoid cells transformed by the c-myc oncogene, suggesting that c-myc and c-Ha-ras might act on the same regulatory level.