Stilbene 5c, a microtubule poison with vascular disrupting properties that induces multiple modes of growth arrest and cell death.

The stilbene derivative, cis-3,4',5-trimethoxy-3'-aminostilbene (stilbene 5c), is a potentially potent antitumor agent that acts via binding to the colchicine-binding site in tubulin. The current studies were designed to investigate the effectiveness of stilbene 5c against the HCT-116 human colon cancer cell line and B16/F10 melanoma cells as well as human endothelial cell tube formation and tumor perfusion. Stilbene 5c produced a time-dependent decrease in cell viability in both cell lines and the capacity of the cells to proliferate was not restored upon removal of the drug. Treatment with stilbene 5c also promoted both senescence and autophagy in both cell lines. TUNEL and annexin 5 staining indicated that apoptosis also occurs in stilbene 5c-treated HCT-116 cells, but not in B16/F10 melanoma cells. DAPI staining revealed morphological changes in the cell nuclei (binucleated and micronucleated cells) indicative of mitotic catastrophe in HCT-116 cells but not in the B16/F10 melanoma cells. p53-null HCT-116 cells demonstrated a similar growth arrest/cell death response to stilbene as p53-wild type HCT-116 cells. Stilbene 5c also completely inhibited human endothelial cell tube formation on Matrigel, consistent with potential anti-angiogenic actions. Using a new method developed for monitoring the pharmacodynamic effects of stilbene 5c in vivo, we found that a single injection of stilbene 5c reduced tumor perfusion by 65% at 4h, returning to baseline by 24h, while subsequent daily injections of stilbene 5c produced progressively larger reductions and smaller rebounds. This work indicates that stilbene 5c could potentially be effective against melanoma and colon cancer through the promotion of multiple modes of growth arrest and cell death coupled with anti-angiogenic and antivascular actions.

Simultaneous labeling of mast cell proteases and protease mRNAs at the bone-implant interface of aseptically loosened hip implants.

Human mast cells (MC) exhibit two distinct phenotypes based on the protease content of their secretory granules. MC(TC) cells express tryptase, chymase, cathepsin G, and mast cell carboxypeptidase, while MC(T) cells express only tryptase. Both mast cell phenotypes were assessed near regions of osteolysis in uninfected failed joint implants by immunohistochemistry with antibodies to tryptase and chymase, and by in situ hybridization with anti-sense RNA probes for the respective mRNA molecules. Specimens from the interface membrane of 32 aseptically loosened total hip implants were studied, 28 of which had mast cells of the MC(TC) type. Most of these mast cells were aligned along the bone-prosthesis interface adjacent to loosened implants, suggesting involvement in the chronic inflammatory response that leads to bone resorption. Further ultrastructural evidence of mast cells in tissues from failed joint interface membranes was shown by transmission electron microscopy, and detection by staining after magnetic activated cell sorting. The presence of MC at the periprosthetic interface of eroded bone suggests MC degranulation and activity are associated with osteolysis in failed joint prostheses.

Gene profiling the effects of calcium deficiency versus 1,25-dihydroxyvitamin D induced hypercalcemia in rat kidney cortex.

Determinants involved in the activation and repression of 1,25-dihydroxyvitamin D (1,25(OH)(2)D(3)) synthesis in renal cortex by changes in extracellular Ca were studied. Cortical kidney RNA isolated from hypocalcemic (LC) rats generated by a low Ca diet, and hypercalcemic (HC) rats generated by a normal Ca diet and two sequential 1 microg doses of 1,25(OH)(2)D(3). Among the genes up-regulated were 1alpha-OHase (4.6-fold) in the LC group and high differential gene expression of VDR (4.0-fold) and 24-OHase (10.4-fold) in the HC group. Moreover, the exposure of renal cortex to LC versus HC conditions revealed a high differential expression of a PKA-dominated pathway involving CBP interacting protein, GATA-1 and CREB transcription factors in the LC model. In the HC model, elevated renal cortex gene expression of several growth factors, peptide receptors, and intracellular signaling molecules depicts a role for CaSR activation and receptor tyrosine kinase signaling in 1,25(OH)(2)D(3)-mediated gene activation and repression of 1alpha-OHase.

5-HT5a receptors in the carotid body chemoreception pathway of rat.

By using a specific antibody, 5-HT5a receptor-like immunoreactivity was revealed in the chemoreceptive, oxygen sensitive, carotid body (CB) type I cells, and neurons of the petrosal ganglion (PG) and the superior cervical ganglion (SCG) in rat. mRNA encoding for the 5-HTa receptor was also detected in these tissues by RT-PCR, and confirmed with DNA sequencing. The present study provides direct evidence that 5-HT5a receptors are expressed in the CB, PG and SCG, which all likely play fundamental roles in arterial chemoreception.

Differential gene regulation of interleukin-1 ligands and receptors in bovine peripheral blood neutrophils and mononuclear cells in response to E. coli lipopolysaccharide (LPS).

The proinflammatory cytokine, interleukin-1, plays a prominent role in the inflammatory reactions that characterize numerous diseases. In this study, we examined the gene expression for bovine IL-1 ligands and receptors by bovine peripheral blood mononuclear cells (MNCs) and neutrophils (PMNs) in response to E. coli lipopolysaccharide (LPS) in vitro. Gene expression of mRNA for IL-1alpha, IL-1beta, IL-1 receptor antagonist (IL-1ra), type 1 IL-1 receptor, type 2 IL-1 receptor, and IL-1 beta converting enzyme (ICE), were measured by a semi-quantitative RT-PCR technique. LPS had little effect on type 1 IL-1R expression in MNC, whereas, it strongly up-regulated type 1 IL-1R expression in PMNs. Co-incubation of PMNs with LPS and bovine recombinant IL-1beta had little additional effect on type 1 IL-1R expression. Incubation of MNCs with LPS resulted in up-regulation of IL-1beta, IL-1ra, and type 2 IL-1R, no change in IL-1alpha, and a decrease in ICE gene expression. Incubation of PMNs with LPS up-regulated IL-1beta gene expression, whereas, IL-1alpha, IL-1ra, type 2 IL-1R and ICE were unchanged. This study provides evidence for differential regulation of gene products of the bovine IL-1 family by peripheral blood mononuclear cells (MNC) and neutrophils (PMNs) in response to E. coli LPS.

cDNA cloning and gene expression of the type 1 bovine interleukin-1 receptor.

Regulation of interleukin-1 (IL-1) mediated biological responses is complicated by the multiple ligands and receptors of the IL-1 family. Most studies of IL-1 receptors have used human or rodent cells. Here, we report that the coding region of the bovine type 1 interleukin-1 receptor (type 1 IL-1R) cDNA extends 1719 bp in length. Northern analysis of specific bovine cell and tissue RNA demonstrated a 4.5 kb transcript. Overall, the bovine type 1 IL-1R coding region exhibits approximately 81 and 76% similarity with the human type 1 IL-1R at the nucleotide and amino acid level, respectively, and somewhat less similarity with the mouse and rat sequences. Type 1 IL-1R transcripts were confirmed by RT-PCR in several bovine cell types, including peripheral blood mononuclear cells (PBMCs), neutrophils (PMNs), and fibroblast, peritoneal macrophage, and arterial endothelial cell lines. It is expected that molecular clones for the bovine type 1 and 2 IL-1 receptors will provide us with the tools needed to decipher species-and cell-specific regulation of IL-1 action in the bovine.

Human 25-hydroxyvitamin D3-24-hydroxylase, a multicatalytic enzyme.

Human 25-hydroxyvitamin D-24-hydroxylase has been expressed in Spodoptera frugiperda (Sf21) insect cells using the previously cloned cDNA in baculovirus (AcNPV-P450cc24). The activity of recombinant h-P450cc24 required adrenodoxin, adrenodoxin reductase, and NADPH. Incubation of this reconstituted system with 25-OH-[26,27-(3)H]D3 substrate produced several metabolites that were resolved on a normal-phase cyano HPLC system. These products exactly comigrated with authentic standards for 24-oxo-25-OH-D3, 23(S),25-(OH)2D3, 24(R),25-(OH)2D3, and 24-oxo-23(S),25-(OH)2D3. The soluble proteins from Sf21 cells infected with wild-type baculovirus produced neither 24,25-(OH)2D3 nor any of the other 25-OH-D3 metabolites. The products were isolated and subjected to a normal-phase amino HPLC for further separation, purification, and characterization. Comigration on two HPLC systems, periodate cleavage reactions, and NaBH4 reduction established clearly the identity of these metabolites. Incubation of recombinant h-P450cc24 with 25-OH-[3 alpha-3H]D3 led to the isolation of an additional product that comigrated with 24,25,26,27-tetranor-23-OH-D3. Treatment of putative 24,25,26,27-tetranor-23-OH-[3 alpha-3H]D3 with acetic anhydride changed its migration on amino HPLC to a less polar position, indicating acetylation of a hydroxyl group(s). These data demonstrate conclusively that h-P450cc24 is a multicatalytic enzyme catalyzing most, if not all, of the reactions in the C-24/C-23 pathway of 25-OH-D3 metabolism. It is likely that this enzyme by itself converts 25-OH-D3 and 1,25-(OH)2D3 to one of its final excretion products.

Effect of 1,25-dihydroxyvitamin D3 on mouse thymus: role of extracellular calcium.

We recently reported that mice treated with 1,25-dihydroxyvitamin D3 ( 1,25-(OH)2D3) or 19-nor-1,25-(OH)2D2 experienced a severe loss of their thymocytes and decreased proliferation in response to concanavalin A mitogen. The present study investigated the effect of short-term treatment with 1,25-(OH)2D3 on the thymic architecture and thymocyte subsets. Daily treatment with 1,25-dihydroxyvitamin D3 at 20 ng per mouse for 4 days induced significant involution of thymic tissue. The atrophy was predominantly observed in the cortical component. Flow cytometric analysis of thymocyte subsets showed that the CD4 + CD8 + population was the primary target. Since the treated mice experienced profound hypercalcemia, we studied the effect of 1,25-(OH)2D3 on animals fed a vitamin D-deficient, low calcium diet or the same diet containing vitamin D for 25 days prior to treatment. The low calcium fed mice showed severe hypocalcemia and slight thinning of thymic cortex. Treatment with 1,25-(OH)2D3 moderately improved the hypocalcemia but had no further effect on the thymus of these animals. On the other hand, hypercalcemia and thymic atrophy were found in the animals fed the diet containing vitamin D. Overall, the atrophy effect on the thymus caused by 1,25-(OH)2D3 treatment was prevented by eliminating the hypercalcemia observed in + D + Ca treated animals. Thus, thymic atrophy probably resulted from hypercalcemia and not from 1,25-(OH)2D3 itself.

Age and gender effects on 1,25-dihydroxyvitamin D3-regulated gene expression.

Several factors involved in regulation of bone mineral metabolism were compared in male and female Fischer 344 rats of different ages (1, 2.5, 6, and 18 months). Plasma 1,25-(OH)2D3 concentrations decreased with age in rats of both genders. Abundance of calbindin-D28K and its mRNA in kidney and calbindin-D9K and its mRNA in duodenum also decreased with age in both male and female rats. Renal 24-hydroxylase activity and 24-hydroxylase mRNA content were elevated significantly in 18-month-old males and females, compared with younger ages. These data suggest that increased renal catabolism of 1,25-(OH)2D3 may be responsible for low plasma 1,25-(OH)2D3 concentrations observed in older animals. Plasma PTH and 1,25-(OH)2D3 concentrations, renal 24-hydroxylase enzyme activity and 24-hydroxylase mRNA content, duodenal 24-hydroxylase mRNA abundance, and duodenal calbindin-D9K and calbindin-D9K mRNA content were greater in males than in females at 2.5 months of age. Lower plasma 1,25-(OH)2D3 concentrations in females seem to explain observed gender differences in expression of 1,25-(OH)2D3-stimulated genes. The combined effects of these gender differences at ages when peak bone density is being developed may contribute to the greater incidence of osteoporosis in females than in males.

The role of dietary calcium in the physiology of vitamin D toxicity: excess dietary vitamin D3 blunts parathyroid hormone induction of kidney 1-hydroxylase.

We studied the effects of dietary calcium (Ca) restriction and excess vitamin D3 on tissue 25-hydroxyvitamin D-1-hydroxylase (1-OHase) and 1,25(OH)2D/25-OH-D-24-hydroxylase (24-OHase) activities in rats. Effects were studied in four groups of rats, with each group receiving one of the following diets: a control diet consisting of normal Ca and normal vitamin D3 (NC), NC plus excess (75,000 IU/week) vitamin D3 (NCT), low Ca and normal vitamin D3 (LC), or LC diet with excess vitamin D3 (LCT). Rats fed the low-Ca diets (LC and LCT) had elevated plasma parathyroid hormone (PTH) concentrations, increasing > 3-fold relative to rats fed the normal Ca diets. The elevated concentrations of PTH in LCT rats did not result in increased plasma 1,25-dihydroxycholecalciferol [1,25(OH)2D3] (NC = 115 +/- 7 pg/ml; LCT = 99 +/- 11 pg/ml). Plasma 1,25(OH)2D in LC rats, however, was increased significantly (615 +/- 110, P = < 0.001). There were no differences in either plasma Ca or phosphorus between the LC and LCT groups. Dietary Ca restriction led to an 18-fold stimulation in renal 1-OHase activity in LC rats (P = < 0.01), while 1-OHase in the LCT rats was marginally but significantly elevated 2.3-fold (P = < 0.05). The ability of PTH to downregulate renal 24-OHase and the 1,25-dihydroxyvitamin D receptor (VDR) during prolonged Ca restriction remained intact, irrespective of vitamin D status. Also, the metabolic clearance rate for 1,25(OH)2D3 was enhanced by feeding excess vitamin D3, which was likely a result of the substantial elevations in intestinal (25-fold) and renal (46-fold) 24-OHase activities in the LCT and NCT groups, respectively. These data indicate that calcium restriction accompanied by excess vitamin D3 is attended by impaired responsiveness of renal 1-OHase to PTH and enhanced metabolic clearance of 1,25(OH)2D.

In vivo regulation of rat intestinal 24-hydroxylase: potential new role of calcitonin.

24-Hydroxylase is found in many mammalian tissues and is required as an initial step in the deactivation of vitamin D3 metabolites and most of its active analogs. We studied the regulation of intestinal 24-hydroxylase (I-24-OHase) activity and messenger RNA (mRNA) expression in rats as influenced by calcium and vitamin D status. Rats were fed vitamin D-replete diets containing either normal calcium (1.0-1.2%, designated NC) or low calcium (0.02%; designated LC). Half of the NC and LC rats received 25,000 IU vitamin D3 three times weekly, orally, and were designated NCT and LCT, respectively. We found that I-24-OHase mRNA expression was up-regulated in rats receiving excess vitamin D3 (NCT and LCT). We observed, however, that the up-regulation was much more dramatic in the LCT group and exceeded by 4.5-fold that observed in the NCT group. Plasma calcium was also elevated in the NCT group (12.6 +/- 0.2 mg/dl), but not the LCT group (10.5 +/- 0.15 mg/dl). We, therefore, examined the possibility that calcitonin released in response to hypercalcemia may have suppressed the induced expression of I-24-OHase mRNA in the NCT group. The plasma calcitonin level was higher in the NCT group (36.14 +/- 2.46 pg/ml) relative to that in the LCT group (19.38 +/- 2.28 pg/ml). Thyroparathyroidectomy also resulted in a 2-fold (P < 0.001) increase in I-24-OHase activity in the NCT group, a response that was reversed (within 4 h) with a single dose of calcitonin (100 IU/rat). Calcitonin administration to LCT rats also resulted in a significant (P < 0.001) 5-fold reduction in I-24-OHase mRNA expression. These data suggest that calcitonin is a potent negative regulator of I-24-OHase mRNA expression and I-24-OHase activity and that the release of calcitonin may block an important pathway for the inactivation of vitamin D3 metabolites in intestine and, thereby, potentiate the toxicity of vitamin D3 during periods of its excess consumption.

Purified Pasteurella multocida protein toxin reduces acid phosphatase-positive osteoclasts in the ventral nasal concha of gnotobiotic pigs.

To study the in vivo response of conchal (turbinate) osteoclasts to Pasteurella multocida toxin, four gnotobiotic pigs (7 days of age) were inoculated subcutaneously with 0.2 microgram/kg of purified toxin. One toxin-treated pig along with one control pig were necropsied at 2, 5, 9, and 14 days postinoculation. The entire length of nasal concha from the nasal planum toi ethmoid region was removed, blocked by transverse cuts into five areas, decalcified, sectioned, and then stained with tartrate-resistant acid phosphatase (TRAP) to identify osteoclasts. In each section, total area of concha, total osteoclast cytoplasmic area, and number of osteoclasts were determined using an image analysis morphometric unit. Also collected from pigs were blood and serum for complete blood counts, electrolyte levels, liver enzymes, and TRAP levels. Conchal atrophy increased in severity with time after 2 days postinoculation. In general, the ventral conchae from toxin-treated pigs at 9 and 14 days postinoculation had decreased surface area, osteoclast cytoplasmic area, and numbers of osteoclasts. Serum levels of TRAP were mildly elevated when compared with age-matched controls. No other significant alterations in blood cells or chemistries occurred and no lesions were present histologically in tissues (liver, kidney, lung, heart, and spleen) other than concha. This study shows that the P. multocida toxin induces rapid bone resorption and increases serum levels of acid phosphatase but leads to diminished acid phosphatase expression and presumably, numbers of osteoclasts.

Up-regulation of the intestinal 1,25-dihydroxyvitamin D receptor during hypervitaminosis D: a comparison between vitamin D2 and vitamin D3.

Concentrations of intestinal 1,25-dihydroxyvitamin D receptor were measured in rats receiving pharmacological amounts (25,000 IU/rat daily for 6 days) of either vitamin D2 or vitamin D3. The data showed that both hypervitaminosis D2 and hypervitaminosis D3 resulted in significant up-regulation of intestinal 1,25-dihydroxyvitamin D receptor (fmol/mg protein) relative to controls (409 +/- 24, vitamin D2-treated; 525 +/- 41, vitamin D3-treated; and 249 +/- 19, control). The 1,25-dihydroxyvitamin D receptor enhancement also was accompanied by elevated plasma 25-hydroxyvitamin D and hypercalcemia. These data suggest that increased target-tissue 1,25-dihydroxyvitamin D receptor may play a role in enhancing target-tissue responsiveness and, thus, have a significant role in mediating the toxic effects of hypervitaminosis D.

Contrasting effects of exogenous 1,25-dihydroxyvitamin D [1,25-(OH)2D] versus endogenous 1,25-(OH)2D, induced by dietary calcium restriction, on vitamin D receptors.

The biological actions of 1,25-dihydroxyvitamin D [1,25-(OH)2D] are mediated by specific binding of the hormone with an intracellular vitamin D receptor, which ultimately regulates expression of genes within the target tissues. The quantity of vitamin D receptors varies between target tissues and within target tissues, depending on the physiological state of the animal. One factor that can modulate tissue vitamin D receptor content is 1,25-(OH)2D. In the present study performed in male rats, exogenous administration of 36 ng 1,25-(OH)2D3/day for 7 days increased plasma 1,25-(OH)2D concentrations 5-fold above those in control rats (to 261 +/- 17 pg/ml). Compared with those in control rats, 1,25-(OH)2D3 treatment resulted in a 1.5-fold increase in duodenal vitamin D receptor content (351 +/- 16 vs. 520 +/- 21 fmol/mg protein) and a 3-fold increase in renal vitamin D receptor content (60.3 +/- 5.2 vs. 193.8 +/- 22.7 fmol/mg protein). The effects of endogenously produced 1,25-(OH)2D on tissue vitamin D receptor content were studied by feeding rats either a 0.02% or 1% calcium diet for 2, 7, 14, or 21 days. Rats fed the low calcium diet exhibited plasma 1,25-(OH)2D concentrations similar to (day 7) or exceeding (days 14 and 21) those achieved by exogenous administration of 1,25-(OH)2D3, yet duodenal vitamin D receptor content was not up-regulated by dietary calcium restriction at any time point. The renal vitamin D receptor content of calcium restricted rats was 20-38% lower (P less than 0.05) than that in rats fed a calcium-replete diet 7, 14, and 21 days after initiation of the dietary treatments. These data suggest that under physiological conditions, increased plasma concentrations of 1,25-(OH)2D do not result in up-regulation of tissue vitamin D receptor concentrations, and that dietary calcium restriction must induce some factor(s) that results in down-regulation of vitamin D receptors in the kidney.