Renal mineral handling in normal rats treated with sevelamer hydrochloride (Renagel), a noncalcemic phosphate binder.

The effects of sevelamer hydrochloride (Renagel); hereafter referred to as sevelamer), a noncalcemic phosphate binder, on renal mineral handling were examined in rats. Normal rats were fed a diet containing 0.3, 1, 3, and 5% sevelamer for 8 days, and serum, urine, and the immunohistochemical localization of the type II Na/Pi cotransporter protein in the kidney were analyzed. Rats treated with 3 or 5% sevelamer showed significant decreases in serum phosphorus (P) and parathyroid hormone (PTH) levels, with no changes in serum calcium (Ca), magnesium (Mg), or 1,25(OH)2D3 levels. Increases were observed in urinary excretions of Ca and Mg associated with a reduction in the PTH level in rats treated with 3 or 5% sevelamer. Rats treated with 1% or higher concentrations of sevelamer showed significant dose-dependent and marked reductions of the urinary P excretion, and the tubular reabsorption of P was maximized to almost 100% in the 5% sevelamer group. The hypophosphaturia in rats treated with 3 or 5% sevelamer was accounted for by the reductions in serum PTH and P per se, and immunohistochemical analysis showed that the expression of type II Na/Pi cotransporter protein was markedly increased at the brush border membranes of the deep and superficial nephrons in rats treated with 5% sevelamer as compared with rats given a normal diet. In conclusion, sevelamer rapidly lowered serum P and PTH levels in normal rats. Sevelamer treatment also produced a marked hypophosphaturia associated with translocation of type II Na/Pi cotransporter protein and increased urinary Ca and Mg excretions by the reduction of PTH.

Sevelamer hydrochloride (Renagel), a non-calcaemic phosphate binder, arrests parathyroid gland hyperplasia in rats with progressive chronic renal insufficiency.

BACKGROUND: It has been demonstrated that dietary phosphate restriction suppresses parathyroid hormone (PTH) secretion and parathyroid cell proliferation in experimental animals with chronic renal insufficiency (CRI) independently of serum calcium and 1,25(OH)(2)D3 levels. This study was conducted to examine whether sevelamer hydrochloride (Renagel); hereafter referred to as sevelamer), a non-calcaemic phosphate binder could inhibit the parathyroid gland (PTG) hyperplasia in rats with progressive CRI. METHODS: Male Sprague-Dawley rats were injected twice with low doses of adriamycin (ADR). Two weeks after the last injection of ADR, rats were fed a diet containing 1 or 3% sevelamer for 84 days. Time course changes of serum levels of calcium, phosphorus, and PTH were measured. At the end of study, serum 1,25(OH)(2)D3 levels were measured and the maximal two-dimension area of the PTG in paraffin section was calculated using an imaging analyser. RESULTS: Dietary sevelamer treatment inhibited the elevations of serum phosphorus, calciumxphosphorus product, and PTH levels that occurred as the study progressed. Sevelamer also suppressed maximal PTG area and there existed positive strong correlation between maximal PTG area and serum PTH levels at the end of the study. Serum phosphorus levels positively correlated well with serum PTH levels and maximal PTG area. In contrast, serum calcium or 1,25(OH)(2)D3 levels did not show any correlation with serum PTH levels and maximal PTG area. CONCLUSIONS: Sevelamer treatment arrested hyperphosphataemia and PTG hyperplasia accompanied by the elevation of serum PTH levels. The correlation analysis suggests that reduced serum phosphorus levels contributed to the suppression of PTG hyperplasia and resulted in the reduction of PTH levels in this animal model after the sevelamer treatment. The management of phosphorus control started from early stage of CRI could prevent PTG hyperplasia and facilitate later management of secondary hyperparathyroidism.

Differential effects of neuropeptides on cytokine production by mouse helper T cell subsets.

Though immune outcome is known to be determined by which helper T cell response predominates, no local mechanism has yet been established which can explain how the neuronal system may control this. It is possible that the nervous system releases neuropeptides at specific local sites of infection or challenge, which triggers lymphocytes at those points to release specific cytokine profiles. These may then influence the direction of the Th1/Th2 response and therefore immune outcome. The aim of this study was to evaluate whether and if so how neuropeptides influence cytokine production by lymphocytes, especially T cells. We investigated the effects of neuropeptide Y (NPY), calcitonin gene-related peptide (CGRP), substance P (SP) and vasoactive intestinal peptide (VIP) on the production of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) by stimulating nonadherent splenocytes and helper T cell clones with antigens in vitro in the presence or absence of these peptides. NPY greatly enhanced IL-4 production and inhibited IFN-gamma. CGRP inhibited IFN-gamma production markedly in a dose-dependent manner, but had no effects on IL-4 production. SP and VIP had no effects on IFN-gamma production, but SP enhanced and VIP suppressed IL-4 production slightly but consistently. Therefore neuropeptides can influence cytokine production. This opens the door to speculations that these specific cytokine profiles might play a part in influencing the direction of the consequent Th1/Th2 cascade and immune outcome and possibly the pathogenesis of immune-related diseases.

Development of CD8 alpha alpha+ intestinal intraepithelial T cells in beta 2-microglobulin- and/or TAP1-deficient mice.

The development of CD8+ intestinal intraepithelial T lymphocytes (IEL) was analyzed in mice that are deficient in the expression of MHC class I molecules, owing to either a mutated beta 2-microglobulin (beta 2m) gene or a mutated transporter associated with Ag processing 1 (TAP1) gene, and in mice doubly homozygous for beta 2m and TAPI mutations. In all mutant mice, the population size of major CD8 alpha alpha+ and CD8 alpha beta+ alpha beta-IEL subsets was reduced drastically, and this resulted in a conspicuous decrease in the total number of alpha beta-IEL. Concomitantly, a compensatory two- to threefold increase in the number of gamma delta-IEL consisting mostly of CD8 alpha alpha+ subset was noted. In radiation bone marrow chimeras, this wild-type/mutant phenotype was determined by the genotype of radioresistant host cells, but was not determined by the genotype of reconstituting bone marrow-derived cells. In beta 2m X TCR-delta double mutant mice, however, the CD8 alpha alpha+ but not CD8 alpha beta+ alpha beta-IEL subset expanded dramatically. Thus, in the absence of gamma delta-IEL, alpha beta-IEL in beta 2m-deficient mice outnumbered those in wild-type littermates. These results indicate that the generation of CD8 alpha alpha+ lymphocyte population of alpha beta- and gamma delta-IEL is not dependent, but that of CD8 alpha beta+ lymphocyte population of alpha beta-IEL is dependent on beta 2m- and/or TAP1-dependent MHC class I molecules, expressed by the controlling cells present in the anatomical site, where the development of IEL takes place.

Induction of anti-tumor immunity by mouse tumor cells transfected with mouse interleukin-12 gene.

Interleukin-12 (IL-12) is a heterodimeric cytokine. In order to transduce both cDNAs for p35 and p40 of IL-12 in the tumor cells, a polycistronic retroviral vector was constructed by inserting the internal ribosome entry site gene of encephalomyocarditis virus between two cDNAs. On the other hand, two cDNAs were sequentially transfected in the tumor cells. Both polycistronic gene transfectants and double transfectants produced biologically active mouse IL-12. IL-12-expressing tumor cells were all rejected in syngeneic mice, and induced cytotoxic T lymphocyte activity. The capacity to induce anti-tumor memory may depend on the amount of IL-12 produced by the transfectants, because the relatively higher IL-12 producer tumor cell line induced the anti-tumor memory in the rejected mice, but the lower producer did not.

Homeostatic regulation of intestinal epithelia by intraepithelial gamma delta T cells.

Although T cells bearing gamma delta T-cell receptors have long been known to be present in the epithelial lining of many organs, their specificity and function remain elusive. In the present study, we examined the intestinal epithelia of T-cell-receptor mutant mice, which were deficient in either gamma delta T cells or alpha beta T cells, and of normal littermates. The absence of gamma delta T cells was associated with a reduction in epithelial cell turnover and a downregulation of the expression of major histocompatibility complex class II molecules. No such effects were observed in alpha beta T-cell-deficient mice. These findings indicate that intraepithelial gamma delta T cells regulate the generation and differentiation of intestinal epithelial cells.

Class II-restricted presentation of an immunoglobulin heavy-chain-gene product by a gene-transfected B-cell line.

The presentation of an antigen endogenously processed by B lymphocytes was investigated. The expression plasmid vectors, harboring genomic rearranged V genes from two monoclonal B cells and genomic mu-constant region gene, were constructed. Two B-cell lines, the MOPC104E myeloma mu-heavy chain expressing AMB line and the control hybridoma mu-heavy chain expressing AHB line, were established by gene transfection into A20.2J B lymphoma cell line. The cloned transfectant cell lines expressed surface and cytoplasmic IgM. Radioimmunoprecipitation analysis of surface IgM revealed that both cell lines used transfected mu-heavy chain and host-derived kappa-light chain. The T-cell line, MRT-2, specific for the MOPC104E protein, proliferated on AME B cell lines but not on control AHB-cell lines. MRT-2 proliferation was inhibited by anti-I-Ed,k,p,r but not by anti-I-Ad monoclonal antibody. Although the AME-transfectant lines secrete IgM into the culture medium, double chamber-type culture-experiments revealed that MRT-2 proliferation is not mediated by the uptake of secreted IgM. The results suggest that B cells process and present their own immunoglobulin heavy-chain V-region peptides to T cells in the context of MHC class-II molecules.

Composition and distribution of retinal and 3-hydroxyretinal in the compound eye of the dragonfly.

Retinoids in the compound eyes of nymphs and adult dragonflies in 11 families of the 3 suborders were extracted by the oxime method, and analysed by high performance liquid chromatography. Almost all of the species examined contained both retinal and 3-hydroxyretinal in the compound eye. The ratio of 11-cis 3-hydroxyretinal to 11-cis retinal (3-OH ratio) was calculated as an index of the retinoid composition. The 3-OH ratios of the whole eye of nymphs in all the suborders and of adults of the suborder Zygoptera were very high, 2.2 at the minimum, but in Anisozygoptera and Anisoptera most of the ratios were distributed between 1 and 2.7. In the family Gomphidae, exceptionally low 3-OH ratios, less than 1, were observed in several species. The regional distributions of the retinals in the adult compound eyes were also examined. In the Zygopteran compound eye, both retinals were distributed evenly all over the eye, while in the compound eye of the other two suborders, the 3-OH ratios in the dorsal area of the eye were extremely low. In several species of Gomphidae and Libellulidae the ratios in the dorsal areas were zero. From the correspondence of these results and the compartment of the compound eye, it appeared that the large ommatidia in the dorsal area contained only retinal. This was confirmed when the large facet region in the dorsal part of the compound eye of an Anax was excised and examined, and only retinal was detected. However, the ventral area of the true dragonflies' compound eye which did not include the large ommatidia contained both retinals, and the 3-OH ratio was more than ten. The biological significance of using both retinals as chromophores of visual pigments in the dragonfly eye is discussed in relation to the structure of the ommatidia and to the vision of dragonflies.