Expression of porcine pro-opiomelanocortin in mouse neuroblastoma (Neuro2A) cells: targeting of the foreign neuropeptide to dense-core vesicles

Pro-opiomelanocortin (POMC) is the precursor to several pituitary hormones and neuropeptides including adrenocorticotropic hormone (ACTH) and beta-endorphin (beta-END). In neuroendocrine cells, peptide hormones and neuropeptides are targeted to the dense-core vesicles of the regulated secretory pathway. These vesicles are transported to the ends of cellular extensions where they are stored until they release their content upon external stimulation of the cell. In order to study the cellular mechanisms involved in targeting of neuropeptides, we have expressed POMC in Neuro2A cells, a cell line of neural origin. Using immunofluorescence labeling and immunoelectron microscopy we show that in Neuro2A cells POMC is packaged in dense-core vesicles which accumulate at the tips of cellular processes. Intracellular accumulation of POMC was not observed in NIH 3T3 fibroblasts. When a soluble form of an integral membrane protein, neutral endopeptidase (E.C. 3.4.24.11) (secNEP), was expressed in Neuro2A cells, the protein was found to be constitutively secreted without prior accumulation in dense-core vesicles. Our results suggest that in Neuro2A cells, targeting to the regulated secretory pathway is restricted to peptide hormones and neuropeptides and establish this cell line as a valid model for studying the molecular events involved in neuropeptide sorting into the regulated secretory pathway.     

Bone disorders in experimentally induced liver disease in growing rats

AIM: To investigate the change of bone parameters in a new model of experimentally induced liver cirrhosis and hepatocellular carcinoma (HCC) in growing rats. METHODS: Fischer-344 rats (n=55) were used. Carbon tetrachloride (CCl4), phenobarbital (PB), and a single diethylnitrosamine (DEN) injection were used. Animals were killed at wk 8 and 16. Bone mineral content, femoral length, cortical index (quotient of cortical thickness and whole diameter) and ultimate bending load (Fmax) of the femora were determined. The results in animals treated with DEN+PB+CCl4(DPC, n = 21) were compared to those in untreated animals (UNT, n = 14) and in control group treated only with DEN+PB (DP, n = 20). RESULTS: Fatty liver and cirrhosis developed in each DPC-treated rat at wk 8 and HCC was presented at wk 16. No skeletal changes were found in this group at wk 8, but each parameter was lower (P<0.05 for each) at wk 16 in comparison to the control group. Neither fatty liver nor cirrhosis was observed in DP-treated animals at any time point. Femoral length and Fmax values were higher (P<0.05 for both) in DP-treated animals at wk 8 compared to the UNT controls. However, no difference was found at wk 16. CONCLUSION: Experimental liver cirrhosis and HCC are accompanied with inhibited skeletal growth, reduced bone mass, and decreased mechanical resistance in growing rats. Our results are in concordance with the data of other studies using different animal models. A novel finding is the transiently accelerated skeletal growth and bone strength after a 8-wk long phenobarbital treatment following diethylnitrosamine injection.     

HLA-DR genotypes in familial rheumatoid arthritis: increased frequency of protective and neutral alleles in a multicase family

OBJECTIVE: We describe a unique family where each of the 5 siblings in the second generation has rheumatoid arthritis (RA). Two other members of the family have RA and systemic lupus erythematosus (SLE), respectively. No members of previous generations in the family had documented inflammatory arthritis. Due to the suspected genetic predisposition, HLA-DR genotypes were determined in the affected siblings and their parents, children, and grandchildren. We investigated the possible role of various HLA-DR alleles in the evolution of RA in this multicase family. METHODS: HLA-DRB1* alleles were determined by polymerase chain reaction using the sequence-specific primer-Olerup method. RESULTS: The most common alleles in the 6 persons with RA were HLA-DRB1*07 and DRB1*15, which are known to be protective and neutral in RA. No patient or family member carried any HLA-DR4 alleles. CONCLUSION: HLA-DRB1*07 and DRB1*15 alleles are thought to be protective or neutral in RA. However, the majority of RA patients in the family and nearly half of all family members carried these alleles, suggesting a role of these genotypes in susceptibility to RA. No RA patient in this family carried HLA-DR4 alleles. Thus, in our rare family with 6 RA cases, an unexpected genetic background may be involved in the increased susceptibility to inflammatory arthritis.     

Regulation of sodium transport in mammalian collecting duct cells by aldosterone-induced kinase, SGK1: structure/function studies

Serum- and glucocorticoid-induced kinases (SGK) are members of the serine-threonine kinase family. SGK1, the isoform identified first, is rapidly induced by aldosterone. In this study, we determined that the two recently described isoforms, SGK2 and SGK3 are also expressed in renal cortical collecting duct (CCD) cells; however, their expression is not induced by aldosterone or glucocorticoids. SGK1 increases the activity of the epithelial sodium channel (ENaC) in oocytes but its cellular targets in native mineralocorticoid target cells and its mechanism of action are still unknown. We studied the role of SGK1 in corticosteroid-regulated Na transport in M-1 mouse CCD cell lines that stably over-express or down-regulate SGK1. Basal rates of transepithelial Na transport were significantly lower in CCD cells in which SGK1 expression or activity was down-regulated than in SGK1 overexpressing cells. Importantly, corticosteroid treatment failed to stimulate Na transport in cells with down-regulated SGK1 while it significantly increased Na transport in parent and SGK1 overexpressing M-1 cells. To determine if C-terminal PDZ interactions are important for SGK's effect on ENaC activity or trafficking, we examined the effects of mutant SGK1 in which the conserved PDZ binding domain has been eliminated. However, such mutations did not decrease its stimulatory effect on ENaC current in Xenopus oocytes. Fluorescence confocal microscopy revealed that the intracellular localization of full-length and PDZ binding mutated SGK1 was identical: they both localize to intracellular vesicular structures. On the other hand, N-terminally truncated (delta 60)-SGK1 did not increase ENaC activity. We conclude that SGK1 is a critical component in corticosteroid-regulated Na transport in mammalian CCD cells. Our data also indicate that the N-terminal of SGK1 is necessary for its stimulatory effect on Na transport while elimination of the C-terminal PDZ binding domain did not change its function.     

Measurement of the quality of life in chronic hepatitis C: validation of a general index and specific index. First French results

OBJECTIVES: To report the validation of 2 questionnaires of quality of life in chronic hepatitis C and the first results in 100 patients. METHODS: The questionnaire included 118 items and took 30 to 45 minutes to answer. It included a general index, the Nottingham Health Profile, with 38 items in 6 themes (physical mobility, social isolation, emotional reactions, pain, sleep and energy) and a specific index, the Montpellier Specific Index, with 80 items in 7 themes: symptoms, food, alcohol and tobacco, work, relations with other people, perception of disease. RESULTS: The questionnaires were self-administered to the 100 first patients with chronic hepatitis C without cirrhosis before treatment; 55 men, 45 women, average age 40 year-old, median Knodell's score 8 and median METAVIR score A2 F1. Reduction in the quality of life was frequent and was not highly correlated with biological, virological and histological parameters; it was associated with psychological disorders, reduced sexuality and apprehension of the future. CONCLUSION: This study showed the feasibility, validation, sensitivity and agreement of a quality of life questionnaire, which included a general index and a specific index of chronic hepatitis C in France. These initial results must be confirmed in studies during antiviral treatment of patients.     

TACI, unlike BAFF-R, is solely activated by oligomeric BAFF and APRIL to support survival of activated B cells and plasmablasts

The cytokine BAFF binds to the receptors TACI, BCMA, and BAFF-R on B cells, whereas APRIL binds to TACI and BCMA only. The signaling properties of soluble trimeric BAFF (BAFF 3-mer) were compared with those of higher-order BAFF oligomers. All forms of BAFF bound BAFF-R and TACI, and elicited BAFF-R-dependent signals in primary B cells. In contrast, signaling through TACI in mature B cells or plasmablasts was only achieved by higher-order BAFF and APRIL oligomers, all of which were also po-tent activators of a multimerization-dependent reporter signaling pathway. These results indicate that, although BAFF-R and TACI can provide B cells with similar signals, only BAFF-R, but not TACI, can respond to soluble BAFF 3-mer, which is the main form of BAFF found in circulation. BAFF 60-mer, an efficient TACI agonist, was also detected in plasma of BAFF transgenic and nontransgenic mice and was more than 100-fold more active than BAFF 3-mer for the activation of multimerization-dependent signals. TACI supported survival of activated B cells and plasmablasts in vitro, providing a rational basis to explain the immunoglobulin deficiency reported in TACI-deficient persons.     

Fluorescence activated cell sorting of principal and intercalated cells of the renal collecting duct

Summary A method is described for the isolation of homogeneous populations of principal and intercalated cells (PC and ICC) of the rabbit cortical collecting duct using fluorescence-activated cell sorting (FACS) in tandem with solid phase immunoadsorption. Three sorting strategies are described. In the first one the two cell types are separated based on the different intensities of their reaction with a monoclonal antibody. In the second and third strategies PC and ICC are tagged with cell-specific markers coupled to different fluorochromes and separated based on their green and red or green and blue fluorescence, respectively. These near homogeneous (∼99%) populations of PC and ICC can be obtained in numbers large enough to perform biochemical characterization, determination of hormonal sensitivity and initiation of cell cultures. This study was supported by grants DK 39523 and DK 41841 from the National Institutes of Health, Bethesda, MD, and by a Grant-in-Aid from the American Heart Association (89-985).     

Effect of xylitol consumption on the plaque-saliva distribution of mutans streptococci and the occurrence and long-term survival of xylitol-resistant strains.

Since the exposure of mutans streptococci to xylitol is known to select for xylitol-resistant (XR) natural mutants, the occurrence and long-term survival of such xylitol-resistant strains was evaluated in a cross-sectional sampling of participants of the Ylivieska xylitol study four years after the original two-year experimental period. Paraffin-stimulated whole saliva was first collected, and then plaque was collected and pooled. The salivary and dental plaque mutans streptococci were enumerated after growth on TSY20B agar. The proportion of XR strains was determined by autoradiography with 14C-xylitol. A strong and significant correlation (r = 0.645 and p = 0.005) between the number of mutans streptococci in saliva and in dental plaque was observed in non-consumers of xylitol. Such a correlation totally disappeared (r = 0.098 and p = 0.612) in xylitol-exposed consumers (habitual and former xylitol-consumers). The proportion of the salivary XR mutants (35%) in non-consumers (n = 16) was significantly lower than in the xylitol-exposed consumers (79%) (n = 27), (p = 0.0001) or in former consumers (75%) (n = 13), (p = 0.0008) or in the habitual consumers (83%) (n = 14), (p = 0.004). The proportion of XR mutants in dental plaque was, on the average, much lower than in the corresponding saliva. The proportion of XR in the plaque of xylitol non-consumers was half of that of the xylitol-exposed group, but the difference was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)