Induction of spermidine N1-acetyltransferase by 1 alpha,25-dihydroxyvitamin D3 as an early common event in the target tissues of vitamin D

Potential Effects of 25-Hydroxycholecalciferol on the Growth Performance, Blood Antioxidant Capacity, Intestinal Barrier Function and Microbiota in Broilers under Lipopolysaccharide Challenge

Our experiment was to detect the effects of 25-hydroxycholecalciferol (25OHD3) on antioxidant capacity, immune status and gut health of broilers under lipopolysaccharide (LPS) challenge. In total, 108 male Arbor Acre broilers (48.5 ± 0.4 g) were allotted to three treatment groups containing six replicates for each group with six birds per replicate: (1) corn-soybean basal diet + injection of sterile saline (CON group); (2) corn-soybean basal diet + an injection of LPS (LPS group); (3) corn-soybean basal diet with 50 μg/kg 25OHD3 + injection of LPS (LPS + 25-D group). At the end of the experiment, birds were intraperitoneally injected with LPS in the LPS and LPS + 25-D groups based on the dosage of 5.0 mg/kg BW, or the equivalent volume of 0.9% sterile saline in the CON group. At 4 h postinjection, blood samples, jejunal and ileal tissues and cecal digesta were collected to analyze blood antioxidant capacity, intestinal barrier function and microbiota. The results showed that broilers challenged with LPS had significantly higher BW loss than the CON group, and 25OHD3 alleviated BW loss induced by the LPS challenge. 25OHD3 alleviated the LPS-induced decline (p < 0.05) in serum activities of superoxide dismutase (SOD) and immunoglobulin G (IgG), as well as prevented the LPS-induced increase (p < 0.05) in serum content of tumor necrosis factor-α (TNF-α). 25OHD3 significantly increased villus height in the jejunum and the relative mRNA abundance of Occludin in the jejunum and ileum, as well as prevented the LPS-induced increase in the jejunal content of interferon-γ (IFN-γ) compared with the LPS group. Compared with the LPS group, 25OHD3 significantly increased Lactobacillus abundance and decreased Lachnoclostridium abundance in the cecal digesta, as well as had the potential to enhance metabolite contents including propionate, isobutyrate, butyrate and total SCFA. The correlation analysis revealed that BW loss and serum contents of TNF-α, IL-1β and D-lactate were positively correlated with Lachnoclostridium and negatively correlated with Lactobacillus (p < 0.05). Overall, 25OHD3 partially improves the antioxidant status, immunity, intestinal barrier and microbial composition of broilers under the LPS challenge.

Applications of Metabolomics in Calcium Metabolism Disorders in Humans

The pathogenesis of the disorders of calcium metabolism is not fully understood. This review discusses the studies in which metabolomics was applied in this area. Indeed, metabolomics could play an essential role in discovering biomarkers and elucidating pathological mechanisms. Despite the limited bibliography, the present review highlights the potential of metabolomics in identifying the biomarkers of some of the most common endocrine disorders, such as primary hyperparathyroidism (PHPT), secondary hyperparathyroidism (SHPT), calcium deficiency, osteoporosis and vitamin D supplementation. Metabolites related to above-mentioned diseorders were grouped into specific classes and mapped into metabolic pathways. Furthermore, disturbed metabolic pathways can open up new directions for the in-depth exploration of the basic mechanisms of these diseases at the molecular level.

Effects of the In Ovo Injection of Vitamin D3 and 25-Hydroxyvitamin D3 in Ross 708 Broilers Subsequently Challenged with Coccidiosis: II Immunological and Inflammatory Responses and Small Intestine Histomorphology

In broilers challenged with coccidiosis, effects of in ovo vitamin D3 (D3) and 25-hydroxyvitamin D3 (25OHD3) administration on their inflammatory response and small intestine morphology were evaluated. At 18 d of incubation (doi), a 50 μL volume of the following 5 in ovo injection treatments was administrated: non-injected (1) and diluent injected (2) controls, or diluent injection containing 2.4 μg D3 (3) or 2.4 μg 25OHD3 (4), or their combination (5). Four male broilers were randomly allocated to each of eight isolated replicate wire-floored battery cages at hatch, and birds were challenged at 14 d of age (doa) with a 20x live coccidial vaccine dosage. One bird from each treatment-replicate (40 birds in each of 8 replicates per treatment) was bled at 14 and 28 doa in order to collect blood for the determination of plasma IL-1β and nitric oxide (NO) concentrations. The duodenum, jejunum, and ilium from those same birds were excised for measurement of villus length, crypt depth, villus length to crypt depth ratio (VCR), and villus surface area. In ovo injection of 2.4 μg of 25OHD3 resulted in a reduction in plasma NO levels as compared to all other treatments at 28 doa. Additionally, duodenal VCR increased in response to the in ovo injection of 25OHD3 when compared to the diluent, D3 alone, and the D3 + 25OHD3 combination treatments at two weeks post-challenge (28 doa). Therefore, it can be concluded that 2.4 μg of 25OHD3, when administrated in ovo at 18 doi, may be used to decrease the inflammatory reaction as well as to enhance the small intestine morphology of broilers during a coccidiosis challenge.

Combined Maternal and Post-Hatch Dietary Supplementation of 25-Hydroxycholecalciferol Alters Early Post-Hatch Broiler Chicken Duodenal Macrophage and Crypt Cell Populations and Their Mitotic Activity

The previous work has demonstrated that maternal supplementation of the circulating metabolite of vitamin D3 (D3), 25-hydroxycholecalciferol (25OHD3), enhances the immunocompetence of broiler chick offspring. In post-hatch broiler diets, 25OHD3 has been shown to affect intestinal morphology and improve the immune status of broilers. An experiment with a 2 × 2 factorial treatment arrangement was conducted to assess the effects of combining maternal (MDIET) and post-hatch (PDIET) dietary 25OHD3 inclusion on duodenal crypt and macrophage cell populations and mitotic activity in young broiler chickens. All diets were formulated to provide 5,000 IU of vitamin D. Broiler breeder hens were offered 1 of 2 MDIET: 5,000 IU D3 per kg of feed (MCTL) or 2,240 IU of D3 + 2,760 IU of 25OHD3 per kg of feed (M25OHD3) from week 25 to 41. Male broiler offspring (n = 480) hatched from eggs collected during week 41 of breeding age were allotted in raised floor pens (4 birds per pen from day 0 to 7 and individually allotted from day 8 to 21). Chicks were fed 1 of 2 PDIET (starter day 0 to 21): 5,000 IU D3 per kg of feed (PCTL) or 2,240 IU D3 + 2,760 IU 25OHD3 (P25OHD3). DUO samples (n = 12 birds per treatment per day) were collected on days 3, 6, 9, 12, 15, 18, and 21 for cryohistological and immunofluorescence analysis to facilitate the enumeration of the total macrophages, CD80+ macrophages (pro-inflammatory macrophages), and mitotically active cells (BrdU+) to calculate the proportion of proliferating cells (PPC) per duodenal crypt. Bird age impacted crypt PPC with the greatest PPC per duodenal crypt observed on days 3 and 9, and the lowest PPC per crypt was observed on day 21 (P < 0.0001). Broilers from the M25OHD3:PCTL treatment had a greater PPC (P =.002) than birds from the MCTL:PCTL treatment at day 3. An interaction among MDIET and PDIET was observed for proliferating macrophages at day 21 (P = 0.029) where M25OHD3:P25OHD3 birds had more proliferating macrophages than M25OHD3:PCTL-fed birds. These results indicate that combined MDIET and PDIET 25OHD3 supplementation may alter early post-hatch duodenal development and innate immunity.

Dietary 25-hydroxycholecalciferol supplementation improves performance, immunity, antioxidant status, intestinal morphology, and bone quality in weaned piglets

BACKGROUND

25-Hydroxycholecalciferol (25OHD₃ ) is a new feed additive, which is a potential alternative to vitamin D₃ in swine nutrition. The objective of this study was to determine the effects of different doses of 25OHD₃ supplementation on performance, immunity, antioxidant capacity, intestinal morphology and bone quality in piglets.

RESULTS

As dietary 25OHD₃ supplementation increased, the average daily gain (ADG) improved (P < 0.05) quadratically during days 1-14, and tended to increase (P = 0.06) quadratically during the overall period of the experiment. Increasing 25OHD₃ supplementation increased (linear effect, P < 0.05) the serum 25OHD₃ level and serum glutathione peroxidase (GSH-Px) activity. On day 14, serum immunoglobulin A (IgA) was increased (linear and quadratic effects, P < 0.05) as dietary 25OHD₃ supplementation increased. On day 28, serum IgA level was higher (P < 0.05) linearly and the complement 3 (C3) level was reduced (P < 0.05) linearly as dietary supplementation of 25OHD₃ increased. The mucosal GSH-Px activity of the small intestine was higher (quadratic effect, P < 0.05) with increasing 25OHD₃ supplementation. Jejunal villus height (P = 0.06) and villus height to crypt depth ratio (P = 0.07) tended to increase quadratically, and the villus height to crypt-depth ratio of the ileum increased (P < 0.05) linearly and quadratically with increasing 25OHD₃ supplementation. Dietary supplementation with an increasing level of 25OHD₃ increased breaking strength of tibias and femurs (quadratic effect, P < 0.05).

CONCLUSION

Increasing dietary 25OHD₃ supplementation partly improved performance, immunity, antioxidant status, intestinal morphology, and bone properties of weaned piglets. © 2020 Society of Chemical Industry.

Effects of supplemental 25-hydroxycholecalciferol on growth performance, small intestinal morphology, and immune response of broiler chickens

Three experiments were conducted to evaluate the effects of 25-hydroxycholecalciferol (25-OH-D(3)) on the growth performance, small intestinal morphology, and immune response of broiler chickens. In experiment 1, 25-OH-D(3) neither increased nor decreased weight gain and feed efficiency compared with the controls during the 39-d feeding period. Birds fed 25-OH-D(3) exhibited numerically higher phagocytosis (45%) than the controls (35%). In experiment 2, chicks were fed diets similar to those used in experiment 1 and were killed at 7, 14, 21, 28, and 35 d of age to determine the relative weight and histology of the small intestine. The relative weight of the small intestine from birds fed 25-OH-D(3) was numerically lower (P < 0.1) at 7 d of age. It was found that 25-OH-D(3) consistently resulted in longer (P < 0.05) villus length of the duodenum in 21- and 28-d-old birds and of the jejunum in 14- and 28-d-old birds. Shorter (P < 0.05) crypt depth was observed in the duodenum at 14 d of age and in the jejunum at 21 and 28 d of age. A higher (P < 0.05) ratio of villus length to crypt depth was also observed in the duodenum and jejunum at 14, 21, and 28 d of age of birds fed 25-OH-D(3). The thickness of muscle layer increased in the duodenum at 14, 28, and 35 d of age in birds fed 25-OH-D(3). In experiment 3, birds were orally challenged with either Luria-Bertani broth or Salmonella Typhimurium E29 at 7 and 14 d of age. Uninfected birds fed 25-OH-D(3) had lower total serum IgA at 14 d of age and lower total serum IgG at 21 d of age. However, infected birds fed 25-OH-D(3) produced higher (P < 0.1) total serum IgG at 21 d of age. The results of this study suggest that supplemental 25-OH-D(3) improves small intestinal morphology and protective humoral immunity to infection.

A novel vitamin D-regulated immediate-early gene, IEX-1, alters cellular growth and apoptosis

1alpha,25-Dihydroxyvitamin D3 (1alpha,25(OH)2D3) inhibits the expression of an immediate-early gene, IEX-1, which is involved in the regulation of cellular growth and apoptosis in a variety of cells. 1alpha,25(OH)2D3 alters the subcellular localization of IEX-1 by causing an efflux of IEX-1 from the nucleus, and the sterol decreases the expression of IEX-1 messenger RNA in cells via a novel DR3 repeat-type DNA response element.

Phosphorus intake regulates intestinal function and polyamine metabolism in uremia

This study found that 5/6-nephrectomized uremic rats showed secondary hyperparathyroidism as reflected by an increase in their serum parathyroid hormone (PTH) level in association with a decrease in serum 1,25-dihydroxyvitamin D [1,25-(OH)2D]. These changes recovered partially upon phosphorus restriction. Calcium absorption and gene expression of calbindin-D9k were decreased in uremia and were also improved by phosphorus restriction. In uremia, intestinal spermidine/spermine N1-acetyltransferase activity was decreased, while ornithine decarboxylase (ODC) activity and its gene expression were potentiated. Enhancement of c-fos and c-jun gene expressions was also observed in uremia. These phenomena suggest that the intestinal villus may proliferate in uremia. Phosphorus restriction prevented increases in the expression of ODC, c-fos and c-jun observed in uremia. Since phosphorus restriction caused a rise in the serum 1,25-(OH)2D level, the role of 1,25-(OH)2D in uremia-induced intestinal dysfunction was examined. A single injection of 1,25-(OH)2D3 to uremic rats caused an increase in the steady-state calbindin-D9k mRNA level, and decreases in steady state c-fos and ODC mRNA levels, suggesting that the deficiency of 1,25-(OH)2D3 is responsible for intestinal dysfunction in uremia. In conclusion, altered polyamine metabolism caused by 1,25-(OH)2D deficiency is intimately involved in intestinal dysfunction and the development of the proliferative state of the intestinal villus in uremia.

The involvement of polyamines in the activation of vitamin D receptor from porcine intestinal mucosa

In the intracellular process of the action of calcitriol, vitamin D receptor is thought to undergo some kind of physiochemical change, called activation, before the receptor binds to the vitamin D response element of the gene. In this paper, the effects of polyamines and their analogues on the sedimentation properties of vitamin D receptor prepared from porcine intestinal mucosa, and on DNA binding activity of the receptor, were studied. In sucrose density gradient analysis, polyamines decreased the sedimentation coefficient of vitamin D receptor in a dose-dependent fashion. Polyamines increased DNA binding activity of vitamin D receptor dose-dependently. These findings show that polyamines can activate vitamin D receptor in vitro. Among naturally existing polyamines, spermidine and spermine, but not putrescine, were effective within their physiological intracellular concentrations, suggesting that both spermidine and spermine can activate vitamin D receptor in vivo as well. Sucrose density gradient analysis using various kinds of polyamine analogues having various numbers of cations showed that the number of cation of polyamines is important for the efficiency to change the sedimentation coefficient of vitamin D receptor, and that the distance between two cationic charges does not play an important role.

Effect of dietary vitamin D3 (cholecalciferol) on colon carcinogenesis induced by 1,2-dimethylhydrazine in male Fischer 344 rats

This study examined the effect of increasing dietary vitamin D on chemically induced colon carcinogenesis. Male Fischer 344 rats were first injected with 1,2-dimethylhydrazine (200 mg/kg) and then fed one of five dietary levels of vitamin D as cholecalciferol (250, 1,000, 2,000, 4,000, and 10,000 IU/kg diet) for nine months. Dietary vitamin D3 had no effect on weight gain. Plasma 25-hydroxyvitamin D3 levels were similar for the 1,000 and 2,000 IU/kg groups but varied in a dose-related manner for the other groups. Vitamin D did not significantly alter the tumor incidence in either the distal or the proximal colon. No significant differences in the labeling index were found in either the proximal or the distal colon. Within the distal colon, the proliferative zone increased in a dose-related manner. Distribution of labeled cells within the crypt compartments was not affected by dietary vitamin D. Bone and serum minerals in general were unaffected by dietary vitamin D. This study shows that, at this level of dietary calcium, vitamin D did not affect 1,2-dimethylhydrazine-induced colon carcinogenesis.

Putrescine is involved in the vitamin D action in chick intestine

We have reported that a single injection of 1 alpha,25-dihydroxyvitamin D3 into vitamin D-deficient chicks produces a marked increase of putrescine accumulation in the duodenum from two different sources, ornithine and spermidine. In the present study, the effects of putrescine depletion and its supplementation on duodenal villus length and calcium absorption were examined in newborn and 5-week-old chicks. Administering either alpha-difluoromethylornithine, a specific inhibitor of ornithine decarboxylase, or N1,N4-bis(2,3-butadienyl)-1,4-butanediamine, a specific inhibitor of polyamine oxidase, to newborn chicks significantly decreased the duodenal content of putrescine and calcium transport activity. The putrescine depletion also induced shortening of the duodenal villus length. The inhibition of calcium absorption and villus length in the putrescine-depleted chicks was almost completely restored by administering putrescine to the birds. The effect of the putrescine depletion and its supplementation on the duodenal villus length and the calcium absorption was reproduced in 5-week-old vitamin D-deficient chicks given vitamin D3 or 1 alpha,25-dihydroxyvitamin D3. These results clearly indicate that putrescine is somehow involved in the vitamin D action in maintaining the morphological and functional development of the intestinal villus mucosa.

Perturbations in polyamines and related enzymes following chlordecone-potentiated bromotrichloromethane hepatotoxicity

The mechanism by which chlordecone (CD) amplifies the hepatotoxicity of halomethanes such as CCl4, CHCl3, and BrCCl3 has been a subject of intense study. Recent work has shown that suppression of hepatocellular regeneration leads to accelerated progression of liver injury leading to complete hepatic failure due to an unusual interaction between individually nontoxic low-dose combination of CD and CCl4. Since polyamines are involved in cell division, their levels reflect the extent to which there is suppression of hepatocellular regeneration during CD and CCl4 interaction. The present studies were designed to investigate the polyamine levels and associated enzymes in livers of rats treated with BrCCl3 alone or CD and BrCCl3 low-dose combination in order to confirm whether the sequence of events of hepatotoxicity is similar to that seen in CCl4 toxicity or that seen during CD and CCl4 interaction. The extent of liver toxicity in rats fed 10 ppm chlordecone (CD) for 15 days prior to the injection of a single low dose of BrCCl3 (15 microL/kg body weight) or after exposure to a high dose of BrCCl3 (80 microL/kg body weight) without CD pretreatment, was similar 6 and 24 hr later as assessed by plasma transaminase levels. There was also an increase in transaminase levels, in rats exposed to a single low dose of BrCCl3 alone (15 microL/kg body weight) but this increase was far below the high-dose exposure alone or the combination treatment. Hepatic levels of ornithine decarboxylase, S-adenosylmethionine decarboxylase, N1-acetylputrescine, N1-acetylspermidine, putrescine, spermidine, and spermine at the end of 24 hr increased after exposure to a low dose of BrCCl3 alone as compared to exposure to a high dose alone or the low-dose combination of CD and BrCCl3. Liver spermidine N1-acetyltransferase was elevated at 2, 6, and 24 hr after exposure to a high dose of BrCCl3 alone as compared to treatment with a low-dose combination of CD and BrCCl3 suggesting decreased synthesis of this enzyme, in spite of a greater need as seen from liver transaminase levels. In general, it was observed that there is significant elevation in some polyamines and related enzymes during toxicity of a low dose of BrCCl3 which seemed to stabilize within 24 hr. This was not observed with the other two groups of rats exposed either to BrCCl3 high dose alone or the low-dose combination of CD and BrCCl3.(ABSTRACT TRUNCATED AT 400 WORDS)

Receptors for and bioresponses to 1,25-dihydroxyvitamin D in a human colon carcinoma cell line (HT-29)

Human colon carcinoma (HT-29) cells were examined for their capacity to bind and respond to 1,25-dihydroxycholecalciferol [1,25-(OH)2D3]. These cells are known to differentiate and increase their population doubling time when galactose is substituted for glucose in their media. High-affinity and specific binding of 1,25-(OH)2[3H]D3 was observed in extracts of these cells grown in glucose. The binder sedimented in sucrose gradients and eluted from DEAE-cellulose columns in a manner indistinguishable from rabbit intestinal 1,25-(OH)2D3-receptor. Smaller amounts of this binder were seen in HT-29 cells grown in galactose. Both glucose-fed and galactose-fed cells exhibited a dose-dependent decrease in growth rate on exposure to 10(-12) to 10(-6) mol/L 1,25-(OH)2D3. Ultrastructural examination of galactose-fed and glucose + 1,25-(OH)2D3-treated cells showed enterocytic differentiation and features that were not distinguishable between these groups. Sucrase activity was higher in galactose-fed cells and did not change with 1,25-(OH)2D3 treatment. However, the lower sucrase activity in glucose-fed cells increased after exposure to 10(-8) mol/L 1,25-(OH)2D3. These results indicate receptor content and bioresponsivity to 1,25-(OH)2D3 in a human enterocytic cell line, suggesting that it will be a useful model for the study of the mechanisms of action of this sterol.

Purification and characterization of spermidine N1-acetyltransferase from chick duodenum

We have reported that spermidine N1-acetyltransferase has a larger role than ornithine decarboxylase in putrescine synthesis in chick duodenum induced by 1 alpha,25-dihydroxycholecalciferol (calcitriol) [Shinki, T., Kadofuku, T., Sato, T. and Suda, T. (1986) J. Biol. Chem. 261, 11712-11716]. In the present study, spermidine N1-acetyltransferase was purified from the duodenal cytosol of calcitriol-treated chicks to homogeneity judged by SDS/polyacrylamide gel electrophoresis. The purified enzyme converted spermidine only to N1-acetyl-spermidine. The apparent molecular mass of the purified spermidine N1-acetyltransferase was found to be 36 kDa by gel filtration on Sephacryl S-200 and 18 kDa by SDS/polyacrylamide gel electrophoresis. When duodenal crude 105,000 x g extracts were directly applied to a Sephacryl S-200 column without prior purification, three peaks with spermidine N1-acetyltransferase activity appeared. The first peak was in the void volume, the second peak was in the fraction corresponding to an apparent molecular mass of 70 kDa, and the third peak was in the fraction corresponding to 36 kDa. These results suggest that spermidine N1-acetyltransferase exists as a dimer of the 18 kDa subunits and is stabilized in (a) form(s) bound to other components or proteins in intact cells.

Major pathway for putrescine synthesis induced by 1 alpha,25-dihydroxyvitamin D3 in chick duodenum

We have reported that a single injection of 1 alpha,25-dihydroxyvitamin D3 into vitamin D-deficient chicks produces a marked accumulation of putrescine in the duodenum by an interconversion pathway. In the present study, we examined the effect of N1,N2-bis(2,3-butadienyl)-1,4-butanediamine, a specific irreversible inhibitor of polyamine oxidase, on the duodenal putrescine synthesis induced by 1 alpha,25-dihydroxyvitamin D3. Addition of N1,N2-bis(2,3-butadienyl)-1,4-butanediamine to an assay mixture completely inhibited the activity of duodenal polyamine oxidase in vitro. Prior administration of N1,N2-bis(2,3-butadienyl)-1,4-butanediamine to chicks completely blocked the 1 alpha,25-dihydroxyvitamin D3-induced increase in duodenal accumulation of putrescine in vivo. The increase of the duodenal accumulation of putrescine by 1 alpha,25-dihydroxyvitamin D3 in vitamin D-deficient chicks coincided quantitatively with the amount of N1-acetylspermidine synthesized from spermidine after the injection of the vitamin into the chicks pretreated with the inhibitor of polyamine oxidase. These results clearly indicate that spermidine N1-acetyltransferase plays a preferential role in the increase in duodenal putrescine synthesis by 1 alpha,25-dihydroxyvitamin D3. The rapidly proliferating and maturing epithelium of small intestines will provide a good model for investigating the role of the interconversion of polyamine metabolism in cell growth and differentiation.

Structure-function correlations of polyamine analog-induced increases in spermidine/spermine acetyltransferase activity

The cytosolic enzyme, spermidine/spermine acetyltransferase (SSAT), is distinguished by its role in polyamine interconversion and by its high inducibility in response to a variety of physiological and pharmacological stimuli. Among a series of fifteen polyamines and polyamine analogs, the most potent inducers of SSAT activity in cultured L1210 cells were found to be N1,N8-bis(ethyl)spermidine (BES) and N1,N12-bis(ethyl)spermine (BESm). Over a 24-hr exposure at 10 microM, enzyme activity rose 13- and 16-fold with BES and BESm, respectively, compared to 2- to 3-fold with the anticancer agent, methylglyoxal bis(guanylhydrazone). The increase in enzyme activity by BESm began rapidly and continued steadily with time so that by 48 hr it increased to about twenty times control. By inhibitor studies, the increase was found to be due to elevated protein synthesis predominantly at the level of translation and to an apparent prolongation of enzyme half-life related to enzyme stabilization. Among the analogs, the structural requirements for maximum enzyme induction were found to be critically dependent on aminopropyl moieties and on the presence, size and location of the alkyl groups. By structure-function comparisons, it was deduced that the known abilities of BES and BESm to regulate ornithine and S-adenosylmethionine decarboxylase activities or to inhibit cell growth occur independently of their effects on SSAT activity in L1210 cells.

Rapid stimulation of calcium uptake by isolated rat enterocytes by 1,25(OH)2D3

Evidence is accumulating that 1,25(OH)2D3 may stimulate calcium transport from the intestinal lumen extremely rapidly by a mechanism which appears independent of de novo protein synthesis. To investigate this rapid action of 1,25(OH)2D3, the rate of calcium uptake by isolated enterocytes from duodena of young rats was determined in vitro as the uptake of 45Ca from 1-15 min. Prior in vitro exposure of cells to 1,25(OH)2D3 (100 pM) for 20 min significantly increased the rate of calcium uptake (p less than 0.001), an effect unaltered by 50 microM cycloheximide. Incubation with 100 pM 1-alpha-hydroxyvitamin D3 produced the same effect (p less than 0.01). In contrast, exposure to 10 pM 1,25(OH)2D3, as well as to 100 pM or to 1,000 pM 25-hydroxyvitamin D3 induced no significant change. Because both 1,25(OH)2D3 and starvation may stimulate key enzymes in polyamine metabolism, we investigated the effects of (i) difluoromethyl-ornithine (CHF2-Orn), a specific irreversible inhibitor of ornithine decarboxylase and (ii) varying the timing of feeding prior to sacrifice. Both in vitro CHF2-Orn and feeding prior to sacrifice significantly decreased the baseline rate of calcium uptake (p less than 0.05) and reduced the effect of 1,25(OH)2D3. Increased duration of starvation significantly increased the baseline rate of calcium uptake (p less than 0.02) without changing the increment in rate of calcium uptake induced by 1,25(OH)2D3. The study suggests (i) that the early action of 1,25(OH)2D3 on the influx process of intestinal calcium transport may involve a different molecular specificity from that involved in the genomic action of 1,25(OH)2D3 and (ii) that changes in polyamine metabolism may play a part in this process.

Hepatic polyamines and related enzymes following chlordecone-potentiated carbon tetrachloride toxicity in rats

Chlordecone potentiation of the hepatotoxic and lethal effects of CCL4 has been well established. Recent studies have shown that the suppression of hepatocellular regeneration results in an accelerated progression of liver injury leading to complete hepatic failure. Since polyamines are involved in cell division, these studies were designed to investigate the polyamine levels and associated enzymes in the livers of rats treated with a low-dose combination of CD and CCl4. For comparison, a large toxic dose of CCl4 was also employed. The extent of liver toxicity in rats fed 10 parts per million chlordecone (CD) for 15 days and subsequently injected with a single dose of CCl4 (100 microL/kg body weight) or a high dose of CCL4 alone (2.5 mL/kg body weight) was similar 6 and 24 hr later as assessed by plasma transaminase levels. There was significant elevation in liver ornithine decarboxylase, S-adenosylmethionine decarboxylase, and putrescine at 24 hr and spermidine N1-acetyltransferase, N1-acetylputrescine, putreanine, putrescine, and N1-acetylspermidine at 6 hr in rats treated with the high dose of CCl4 alone compared to the combination treatment. Spermidine levels decreased up to 6 hr and then increased up to 24 hr for both treatments. Spermine continuously decreased up to 24 hr for the CD and CCl4 low-dose combination treatment compared to rats treated with a high dose of CCl4 alone. Spermidine levels were lower than in controls and rose towards control value between 6 and 24 hr after the combination treatment and the high dose of CCl4. Results indicate that the CD and CCl4 low-dose combination treatment increased liver toxicity, resulting in compromised polyamine metabolism that is coincidental with suppressed hepatocellular regeneration, which leads to an accelerated progressive phase of liver injury and culminates in complete hepatic failure.

Protection from chlordecone (Kepone)-potentiated CCl4 hepatotoxicity in rats by fructose 1,6-diphosphate

1. The extent of liver injury assessed as elevation of plasma transaminases was decreased 40-50% by administration of fructose 1,6-diphosphate to rats receiving the highly hepatotoxic combination of chlordecone and CCl4. 2. This protection was accompanied by significantly higher sustenance of ATP levels in the liver. 3. Polyamine synthesis as well as interconversion were stimulated in favor of maintaining higher levels of polyamines. 4. These events are consistent with the concept that suppressed hepatocellular regeneration which leads to progression of otherwise limited injury observed in chlordecone potentiation of CCl4 hepatotoxicity is due to lack of cellular energy.

Ongoing protein synthesis needed for 1,25-(OH)2D3-mediated rapid increase of cyclic GMP in human skin fibroblasts

Recently we reported that 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) through interaction with its specific receptor rapidly (within 1 min) stimulated intracellular cGMP production in cultured human skin fibroblasts. Here we show that this effect of 100 nM 1,25-(OH)2D3 is prevented by brief (30 min) inhibition of RNA synthesis (with actinomycin D or alpha-amanitin) or by brief inhibition of protein synthesis (with cycloheximide or diphtheria toxin). The protein synthesis inhibitors also blocked stimulation of cGMP by other steroids (testosterone or dexamethasone at 100 nM) but did not block cGMP stimulation by sodium nitroprusside. Since the time for the 1,25-(OH)2D3 receptor to increase cGMP seems too short to require de novo protein synthesis, we conclude that the 1,25-(OH)2D3 receptor acts together with rapidly turning over protein(s) to stimulate cGMP synthesis.

Purification by affinity chromatography and characterization of porcine liver cytoplasmic polyamine oxidase

1. Polyamine oxidase was purified from the soluble fraction of porcine liver by more than 70,000-fold to electrophoretic homogeneity using N8-acetylspermidine-Sepharose 4B affinity chromatography. 2. The molecular weight and isoelectric point of this enzyme were 62,000 and pH 4.5, respectively. 3. Optimal pH for the catalytic activity was close to 10.0. 4. The enzyme activity was enhanced by 5 mM dithiothreitol or 5 mM benzaldehyde. 5. Preferential substrates for this cytoplasmic PAO were N1-acetylspermine, N1-acetylspermidine and spermine. 6. Spermidine was not virtually the substrate for this enzyme. 7. The present results suggested the physiological roles of cytoplasmic PAO, being coupled with the reaction of spermidine/spermine N1-acetyltransferase, in recycling the cellular polyamines to putrescine.

Selenium and polyamine metabolism: different effect of selenite on liver and bursa of Fabricius ornithine decarboxylase activity

1. When injected i.p., sodium selenite promoted a marked increase of rat liver ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) activities; when administered with the diet for 6 weeks, a less marked increase in liver ODC was observed, whereas SAMDC was not significantly changed. 2. Protein synthesis was involved in the observed modifications. The rate of ODC inactivation was also changed. 3. ODC increase was accompanied by an enhanced putrescine concentration in liver. 4. A marked increase of ODC, accompanied by an enhancement of putrescine, was promoted by selenite (i.p.) also in chicken liver, together with an enhancement of glutathione concentration. Spermidine acetyltransferase (SAT) was also increased. 5. In the bursa of Fabricius, SAT activity was also increased, whereas ODC was decreased. However the expected modifications in polyamine concentration were not observed. 6. Decrease of ODC activity in the bursa was not due to an antizyme. 7. In vitro, selenite concentrations known to inhibit cell proliferation (greater than 1 microgram/ml) inhibited both ODC and SAT activities; at lower concentration, SAT activity was enhanced.

The metabolism and mechanism of action of 1,25-dihydroxyvitamin D3

Much has been learned about the formation of the active metabolite of vitamin D3, 1,25-dihydroxyvitamin D3. Information concerning its formation and catabolism has allowed a clear understanding of factors involved in the maintenance of plasma concentrations of the hormone. The effects of 1,25-dihydroxyvitamin D3 on calcium transporting cells in the intestine are marked and well defined. The tissue (intestinal tissue) is easily isolated and manipulated and hence, this is an ideal tissue in which to examine the mechanism of divalent cation transport. The mechanism by which 1,25-dihydroxyvitamin D3 brings about this effect should help in understanding sterol hormone action.

Induction of spermidine/spermine N1-acetyltransferase in needle-punctured rat lens as a model of traumatic cataract

Isolated rat lens was punctured with a needle at a single point in the equatorial region and was incubated at 37 degrees C. Spermidine/spermine N1-acetyltransferase activity was increased about 5-fold at 8 h after the puncture. Concomitantly, putrescine content in the lens increased markedly at 8-16 h after the puncture, while spermidine levels were slightly depressed. Pretreatment of the lens with actinomycin D or cycloheximide blocked the increases of spermidine/spermine N1-acetyltransferase activity and putrescine content. Ornithine decarboxylase, on the other hand, was not induced to a detectable degree by this stimulus and 5 mM difluoromethylornithine could not block the increase of putrescine content. Polyamine oxidase showed a relatively constant activity that was sufficient for the metabolism of newly formed N1-acetylspermidine. These results suggested that, in the punctured lens, the polyamine levels were regulated predominantly by the activity of spermidine/spermine N1-acetyltransferase, but not by the induction of ornithine decarboxylase.