Radiofrequency identification tag system improves the efficiency of closed vitrification for cryopreservation and thawing of bovine ovarian tissues

PURPOSE

A radiofrequency identification (RFID) tag system was designed to streamline cryopreservation and thawing procedures. This study evaluated the usefulness of the RFID tag system for improving the efficiency of cryopreserving/thawing bovine ovarian tissue by the closed vitrification protocol.

METHODS

Six participants carried out closed vitrification and thawing of bovine ovarian tissues procedures using either the conventional or the new RFID tag method, and the time required to perform each step of the respective methods was measured. After normality of data was confirmed by the Shapiro-Wilk test, the significance of differences was assessed by the unpaired t test.

RESULTS

When closed vitrification was performed, the time required for each step showed a significant difference between the two methods (t(4) = 2.938, p = 0.042, d = 2.40), and the total cryopreservation time was 11 min shorter using the RFID tag system. When thawing was performed, the time required for each step also showed a significant difference between the two methods (t(4) = 2.797, p = 0.049, d = 2.28), and the total thawing time was 2 min shorter using the RFID tag system.

CONCLUSION

The RFID tag system tested in this study seems to be suitable for managing biological samples stored in liquid nitrogen. Adoption of an RFID tag system by fertility centers may not only improve the efficiency of cryopreserving/thawing reproductive tissues but could also reduce human error.

Syntaxin6 separates from GM1a-rich membrane microdomain during granule maturation

Since it was reported that components of immature secretory granules (ISGs) are different from those of mature secretory granules (MSGs) in rat parotid acinar cells, we have been considering that components of secretory granules (SGs) change dynamically during granule maturation. As the first step to understand the mechanism of granule maturation, we separated low-density detergent-resistant membrane fractions (DRMs) from purified SGs of rat parotid gland. When SGs were lysed by the detergent Brij-58, syntaxin6 and VAMP4 were found in DRMs that were different from the GM1a-rich DRMs containing VAMP2. Because syntaxin6 and VAMP4 are known to be related to granule formation, we attempted to separate DRMs from ISGs. To enrich for ISGs, glands were removed from rats 5h after intraperitoneal injection of isoproterenol and used to purify the newly synthesized granules. Compared to mature granules prepared without injection, these newly formed granules were lower in density and contained higher concentrations of syntaxin6, VAMP4, and gamma-adaptin. This composition is consistent with the characterizations of ISGs. DRMs isolated from the newly formed granules were GM1a-rich and contained syntaxin6, VAMP4, and VAMP2 together. Thus, our findings suggest that syntaxin6 and VAMP4 associate with a GM1a-rich membrane microdomain during granule formation but enter a separate membrane microdomain before transport from granules during maturation.

Difference in distribution of membrane proteins between low- and high-density secretory granules in parotid acinar cells

Secretory granules (SGs) are considered to be generated as immature granules and to mature by condensation of their contents. In this study, SGs of parotid gland were separated into low-, medium-, and high-density granule fractions by Percoll-density gradient centrifugation, since it was proposed that the density corresponds to the degree of maturation. The observation with electron microscopy showed that granules in the three fractions were very similar. The average diameter of high-density granules was a little but significantly larger than that of low-density granules. Although the three fractions contained amylase, suggesting that they are all SGs, distribution of membrane proteins was markedly different. Syntaxin6 and VAMP4 were localized in the low-density granule fraction, while VAMP2 was concentrated in the high-density granule fraction. Immunoprecipitation with anti-syntaxin6 antibody caused coprecipitation of VAMP2 from the medium-density granule fraction without solubilization, but not from Triton X-100-solubilized fraction, while VAMP4 was coprecipitated from both fractions. Therefore, VAMP2 is present on the same granules, but is separated from syntaxin6 and VAMP4, which are expected to be removed from immature granules. These results suggest that the medium-density granules are intermediates from low- to high-density granules, and that the membrane components of SGs dynamically change by budding and fusion during maturation.

Phosphodiesterases 1 and 2 regulate cellular cGMP level in rabbit submandibular gland cells

In rabbit salivary glands, stimulation of muscarinic cholinergic receptors causes production of cGMP through intracellular Ca2+ and nitric oxide. In this study, we investigated a role of cyclic nucleotide phosphodiesterase (PDE) in regulating the cellular cGMP level by using cells dispersed from the submandibular gland. Methacholine, a cholinergic agonist, rapidly elevated the cGMP level. The elevation was greatly enhanced by IBMX, a non-specific inhibitor for most isoforms of the 11 PDEs. The cGMP level was also elevated by MM-IBMX and EHNA, which inhibit the activities of PDE1 and PDE2, respectively. The elevation by the simultaneous application of the two drugs corresponded to 90% of that by IBMX. Therefore, PDE1 and PDE2 are the main PDEs that act to degrade cGMP in methacholine-stimulated cells. The presence of the two PDEs was confirmed by assaying their activities of the cell lysate. In unstimulated cells, the cGMP level was elevated by MM-IBMX and little elevated by EHNA. While the PDE2 activity was thus low, it was estimated that methacholine increases its activity approximately 50-fold. The strong activation can be explained by the elevation of the cGMP level because PDE2 is a cGMP-stimulated PDE. SNAP, a nitric oxide donor, causes production of cGMP without a receptor-operated increase in intracellular Ca2+ concentration. In SNAP-stimulated cells, MM-IBMX elevated the cGMP level higher than in methacholine-stimulated cells although the PDE1 activity is dependent on Ca2+/calmodulin. Besides Ca2+, other factors may regulate the PDE1 activity in living cells.

A primary culture of parotid acinar cells retaining capacity for agonists-induced amylase secretion and generation of new secretory granules

Exocrine acinar cells, like parotid cells, have difficulty in maintaining their functions in cell lines or in primary cultures. For this reason, molecular studies on exocrine cell functions are unsatisfactory. To examine the mechanisms whereby the functions of parotid acinar cells are maintained, we attempted to establish a system for primary culture and transfection of exogenous genes. Acinar cells were dispersed from rat parotid glands by digestion with enzymes and were cultured in a medium containing rat serum. Most of the cultured cells had secretory granules that contained amylase, suggesting that they were derived from acinar cells, although they spread on the dish surface and formed filopodia. The cultured cells retained both granules and the ability to release amylase in response to beta-adrenergic and cholinergic agonists, even 48 h after dispersion. However, the total amount of amylase in the cells decreased rapidly from 24 to 48 h after dispersion. These results suggested that amylase synthesis was more damaged than the machinery for exocytosis during culture in vitro. VAMP2 gene fused with enhanced green fluorescence protein was transfected into the dispersed acinar cells, and VAMP2 protein was expressed and localized to amylase-containing granules, as normally seen for endogenous VAMP2 protein. This indicated that new granules were generated, and that protein sorting was functional. The cells cultured by this method maintained their functions for at least 48 h. They can be used for examining the effects of exogenous genes on parotid acinar cell functions, such as regulated exocytosis and the maturation of secretory granules.

Involvement of Aquaporin-5 Water Channel in Osmoregulation in Parotid Secretory Granules

Aquaporins (AQPs) are a family of channel proteins that allow water or very small solutes to pass, functioning in tissues where the rapid and regulated transport of fluid is necessary, such as the kidney, lung, and salivary glands. Aquaporin-5 (AQP5) has been demonstrated to localize on the luminal surface of the acinar cells of the salivary glands. In this paper, we investigated the expression and function of AQP5 in the secretory granules of the rat parotid gland. AQP5 was detected in the secretory granule membranes by immunoblot analysis. The immunoelectron microscopy experiments confirmed that AQP5 was to be found in the secretory granule membrane. Anti-AQP5 antibody evoked lysis of the secretory granules but anti-aquaporin-1 antibody did not and AQP1 was not detected in the secretory granule membranes by immunoblot analysis. When chloride ions were removed from the solution prepared for suspending secretory granules, the granule lysis induced by anti-AQP5 antibody was inhibited. Furthermore, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid, an anion channel blocker, blocked the anti-AQP5 antibody-induced secretory granule lysis. These results suggest that AQP5 is, expressed in the parotid gland secretory granule membrane and is involved in osmoregulation in the secretory granules.

Platelet-derived growth factor-induced arachidonic acid release for enhancement of prostaglandin E(2) synthesis in human gingival fibroblasts pretreated with interleukin-1beta

Platelet-derived growth factor (PDGF) is a biological mediator for connective tissue cells and plays a critical role in a wide variety of physiological and pathological processes. We here investigated the effect of PDGF on arachidonic acid release and prostaglandin E(2) (PGE(2)) synthesis in human gingival fibroblasts (HGF). PDGF induced arachidonic acid release in a time- and dose-dependent manner, and simultaneously induced a transient increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), but less provoked PGE(2) release and cyclooxygenase-2 (COX-2) mRNA expression. When [Ca(2+)](i) was increased by Ca(2+)-mobilizing reagents, arachidonic acid release was increased. The PDGF-induced arachidonic acid release and increase in [Ca(2+)](i) were prevented by a tyrosine kinase inhibitor. On the other hand, in the HGF pre-stimulated with interleukin-1beta (IL-1beta), PDGF clearly increased PGE(2) release. The PDGF-induced PGE(2) release was inhibited by a tyrosine kinase inhibitor. In the HGF pretreated with IL-1beta, arachidonic acid strongly enhanced PGE(2) release and COX-2 mRNA expression. These results suggest that PDGF stimulates arachidonic acid release by the increase in [Ca(2+)](i) via tyrosine kinase activation, and which contributes to PGE(2) production via COX-2 expression in HGF primed with IL-1beta.

Ca2+, calmodulin and phospholipids regulate nitricoxide synthase activity in the rabbit submandibular gland

Nitric oxide (NO) plays an important role as an intra- and intercellular signaling molecule in mammalian tissues. In the submandibular gland, NO has been suggested to be involved in the regulation of secretion and in blood flow. NO is produced by activation of NO synthase (NOS). Here, we have investigated the regulation of NOS activity in the rabbit submandibular gland. NOS activity was detected in both the cytosolic and membrane fractions. Characteristics of NOS in the cytosolic and partially purified membrane fractions, such as Km values for l-arginine and EC(50) values for calmodulin and Ca(2+), were similar. A protein band that cross-reacted with anti-nNOS antibody was detected in both the cytosolic and membrane fractions. The membrane-fraction NOS activity increased 1.82-fold with treatment of Triton X-100, but the cytosolic-fraction NOS activity did not. The NOS activity was inhibited by phosphatidic acid (PA) and phosphatidylinositol 4,5-bisphosphate (PIP(2)). The inhibitory effects of phospholipids on the NOS activity were relieved by an increase in Ca(2+) concentrations. These results suggest that the Ca(2+)- and calmodulin-regulating enzyme nNOS occurs in cytosolic and membrane fractions, and PA and PIP(2) regulate the NOS activity in the membrane site by regulating the effect of Ca(2+) in the rabbit submandibular gland.

Charge-based separation of detergent-resistant membranes of mouse splenic B cells

Current biochemical characterization for cholesterol- and glycolipid-rich membrane microdomains largely depends on analysis of detergent-resistant membranes (DRMs). In the present study, we succeeded in separation of DRMs of similar density-based on their electrical charge using free-flow electrophoresis (FFE). After crosslinking of B cell receptor (BCR), mouse splenic B cells were lysed with 1% Brij-58 and the resulting lysate was subjected to sucrose density gradient ultracentrifugation. The low-density fraction that recovered a part of DRMs containing IgM together with those enriched in GM1a, the Src family protein tyrosine kinase Lyn, and the alpha subunit of inhibitory heterotrimeric GTP-binding protein was further resolved by FFE. FFE separated the former into more cathodally deflected fractions than the latter. In addition, FFE revealed an anodal shift of DRMs containing a transmembrane protein CD38 upon BCR-crosslinking. The results demonstrate the effectiveness of FFE for the charge-based separation of DRMs.

TNF-alpha suppresses bone sialoprotein (BSP) expression in ROS17/2.8 cells

Tumor necrosis factor-alpha (TNF-alpha) is a major mediator of inflammatory responses in many diseases that inhibits bone formation and stimulates bone resorption. To determine molecular mechanisms involved in the suppression of bone formation we have analyzed the effects of TNF-alpha on BSP gene expression. Bone sialoprotein (BSP) is a mineralized tissue-specific protein that appears to function in the initial mineralization of bone. Previous studies have demonstrated that BSP mRNA expression is essentially restricted to fully-differentiated cells of mineralized connective tissues and that the expression of BSP is developmentally regulated. Treatment of rat osteosarcoma ROS 17/2.8 cells with TNF-alpha (10 ng/ml) for 24 h caused a marked reduction in BSP mRNA levels. The addition of antioxidant N-acetylcysteine (NAC; 20 mM) 30 min prior to stimulation with TNF-alpha attenuated the inhibition of BSP mRNA levels. Transient transfection analyses, using chimeric constructs of the rat BSP gene promoter linked to a luciferase reporter gene, revealed that TNF-alpha (10 ng/ml) suppressed expression in all constructs, including a short construct (pLUC3; nts -116 to +60), transfected into ROS17/2.8 cells. Further deletion analysis of the BSP promoter showed that a region within nts -84 to -60 was targeted by TNF-alpha, the effects which were inhibited by NAC and the tyrosine kinase inhibitor, herbimycin A (HA). Introduction of 2bp mutations in the inverted CCAAT box (ATTGG; nts -50 and -46), a putative cAMP response element (CRE; nts -75 to -68), and a FGF response element (FRE; nts -92 to -85) showed that the TNF-alpha effects were mediated by the CRE. These results were supported by gel mobility shift assays, using a radiolabeled double-stranded CRE oligonucleotide, which revealed decreased binding of a nuclear protein from TNF-alpha-stimulated ROS 17/2.8 cells. Further, the inhibitory effect of TNF-alpha on CRE DNA-protein complex was completely abolished by NAC or HA treatment. These studies, therefore, show that TNF-alpha suppresses BSP gene transcription through a tyrosine kinase-dependent pathway that generates reactive oxygen species and that the TNF-alpha effects are mediated by a CRE element in the proximal BSP gene promoter.

Distribution and properties of arginase in the salivary glands of four species of laboratory mammals

Important progress in arginine metabolism includes the discovery of widespread expression of two isoforms of arginase, arginase I and II, not only in hepatic cells but also in non-hepatic cells, and the formation of nitric oxide, a widely distributed signal-transducing molecule, from arginine by nitric oxide synthase. Possible physiological roles of arginase may therefore include regulation of nitric oxide synthesis through arginine availability for nitric oxide synthase. In this paper, arginase was investigated in the submandibular, sublingual, and parotid glands of rat, mouse, guinea pig, and rabbit. From their arginase contents, the salivary glands of these species were divided into two groups. Variable levels of arginase activity were detected in the salivary glands of mouse and rat. However, salivary glands of rabbit and guinea pig had almost no arginase activity. The presence of nitric oxide synthase has been reported in all the salivary glands used in this study. Therefore, one of the important findings was the presence of species specificity in the co-localization of arginase and nitric oxide synthase in the salivary glands of the four species. The highest specific activity of arginase was found in mouse parotid gland. In rat, considerable arginase activity was detected in all three glands, at 3.6-7.3% of that in rat liver. In rat submandibular gland, arginase was detected in both cytosolic and particulate fractions. In addition, arginase was detected in isolated acinar cells, but not in duct cells. Experiments on the intracellular distribution and the effects of the arginase inhibitors ornithine and N(omega)-hydroxy-L-arginine (NOHA), suggested the presence of both arginase I and arginase II in rat submandibular gland.

Tyrosine phosphorylation is involved in Ca(2+)entry in human gingival fibroblasts

Bradykinin (1 microM) and histamine (100 microM) evoked an initial transient increase and a subsequent sustained increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in fura-2-loaded human gingival fibroblasts, which may be attributed to Ca(2+) release from intracellular stores and Ca(2+) entry from extracellular sites, respectively. In fibroblasts pretreated with tyrosine kinase inhibitors such as herbimycin A (1 microM) and tyrphostin 47 (20 microM), the sustained level of [Ca(2+)](i) induced by bradykinin and histamine increased, but not the initial peak level. In the absence of external Ca(2+), bradykinin and histamine induced only the transient increase in [Ca(2+)](i), but a subsequent addition of Ca(2+) to the medium resulted in a sustained increase in [Ca(2+)](i) caused by Ca(2+)entry. Thapsigargin, an inhibitor of Ca(2+)-ATPase in inositol 1,4,5-trisphosphate-sensitive Ca(2+) stores, mimicked the effect of bradykinin and histamine. In the fibroblasts pretreated with tyrosine kinase inhibitors, the bradykinin-, histamine- and thapsigargin-induced Ca(2+) entry was clearly enhanced, but not the transient [Ca(2+)](i) increase. Tyrosine phosphatase inhibitor benzylphosphonic acid (200 microM) had no effect on Ca(2+)entry or transient [Ca(2+)](i) increase. These results suggest that tyrosine phosphorylation is involved in Ca(2+) entry in human gingival fibroblasts.

Identification of FGF2-response element in the rat bone sialoprotein gene promoter

Bone sialoprotein (BSP), an early marker of osteoblast differentiation, has been implicated in the nucleation of hydroxyapatite during de novo bone formation. Basic fibroblast growth factor (FGF2) is recognized as a potent mitogen for a variety of mesenchymal cells. In skeletal tissues, FGF2 produced by osteoblasts accumulates in the bone matrix and acts as an autocrine/paracrine regulator of bone cells. To determine the molecular mechanism of FGF2 regulation of osteogenesis, we have analyzed the effects of FGF2 on the expression of BSP in the rat osteosarcoma cell line ROS 17/2.8. FGF2 at 10 ng/ml, increased BSP mRNA levels approximately 4-fold; the stimulation was first evident at 3 hr, reached maximal levels at 6 hr. The stability of the BSP mRNA was not significantly affected by FGF2, suggesting that the increased mRNA was due to increased transcription. From transient transfection analyses using various BSP promoter-luciferase constructs, a FGF2 response element (FRE) (nts -92 to -85, "GGTGAGAA") was identified as a target of transcriptional activation by FGF2. Ligation of two copies of the FRE 5' to an SV40 promoter was sufficient to confer FGF responsive transcription. A sequence-specific protein-DNA complex, formed with a double-stranded oligonucleotide encompassing the FRE and nuclear extracts from ROS 17/2.8 cells, but not from fibroblasts, was increased following FGF2 stimulation. Several point mutations within the critical FRE sequence abrogated the formation of this complex and suppressed both basal and FGF2-mediated promoter activity. Thus, we have identified a novel FRE within the proximal promoter of the BSP gene that mediates both constitutive and FGF2-induced BSP transcription.

Prostaglandin E2 stimulates bone sialoprotein (BSP) expression through cAMP and fibroblast growth factor 2 response elements in the proximal promoter of the rat BSP gene

Bone sialoprotein (BSP), an early marker of osteoblast differentiation, has been implicated in the nucleation of hydroxyapatite during de novo bone formation. Prostaglandin E2 (PGE2) has anabolic effects on proliferation and differentiation of osteoblasts via diverse signal transduction systems. Because PGE2 increases the proportion of functional osteoblasts in fetal rat calvarial cell cultures, we investigated the regulation of BSP, as an osteoblastic marker, by PGE2. Treatment of rat osteosarcoma UMR 106 cells with 3 microm, 300 nm, and 30 nm PGE2 increased the steady state levels of BSP mRNA about 2.7-, 2.5-, and 2.4-fold after 12 h. From transient transfection assays, the constructs including the promoter sequence of nucleotides (nt) -116 to +60 (pLUC3) were found to enhance transcriptional activity 3.8- and 2.2-fold treated with 3 microm and 30 nm PGE2 for 12 h. 2-bp mutations were made in an inverted CCAAT box (between nt -50 and -46), a cAMP response element (CRE; between nt -75 and -68), a fibroblast growth factor 2 response element (FRE; nt -92 to -85), and a pituitary-specific transcription factor-1 motif (between nt -111 and -105) within pLUC3 and pLUC7 constructs. Transcriptional stimulation by PGE2 was almost completed abrogated in constructs that included 2-bp mutations in either the CRE and FRE. In gel shift analyses an increased binding of nuclear extract components to double-stranded oligonucleotide probes containing CRE and FRE was observed following treatment with PGE2. These studies show that PGE2 induces BSP transcription in UMR 106 cells through juxtaposed CRE and FRE elements in the proximal promoter of the BSP gene.

Evidence that nitric oxide does not directly contribute to methacholine-induced amylase secretion in rabbit parotid acinar cells

Nitric oxide (NO) is a short-lived free radical and is a widespread intra- and intercellular messenger molecule involved in various physiological functions. We have demonstrated previously that the muscarinic agonist methacholine induces endogenous generation of NO in rabbit parotid acinar cells. Since methacholine also simultaneously evokes amylase secretion, we investigated the effect of NO on the methacholine-induced exocytotic amylase secretion in rabbit parotid acinar cells. Methacholine-evoked amylase secretion was clearly reduced in the absence of extracellular Ca(2+). The Ca(2+)-mobilizing reagents A23187 and thapsigargin, which stimulate NO generation, also evoked amylase secretion. This response seemed to be caused by NO generated by the activation of endogenous Ca(2+)-regulated NO synthase. However, N(G)-nitro-L-arginine methyl ester (L-NAME), a specific NOS inhibitor, and the NO scavenger haemoglobin had no effect on methacholine-induced amylase secretion. The NO generator sodium nitroprusside (SNP) failed to evoke amylase release. We further studied the effects of L-NAME and SNP on methacholine-induced amylase secretion in crudely dispersed parotid gland cell clusters containing nerve tissue. In this preparation, L-NAME inhibited methacholine-induced amylase secretion and SNP evoked amylase secretion. It is thus unlikely that NO contributes directly to methacholine-induced amylase secretion in rabbit parotid acinar cells. NO appears rather to affect to nerve tissues in the cell suspension.

Angiotensin II induces prostaglandin E(2) release in human gingival fibroblasts

We investigated the effect of angiotensin II on prostaglandin E(2) release in human gingival fibroblasts. Stimulation of human gingival fibroblasts with angiotensin II elicited prostaglandin E(2) release in a concentration- and time-dependent manner. Angiotensin III also induced prostaglandin E(2) release, but the effect was weaker than that of angiotensin II. Angiotensin II- and angiotensin III-induced prostaglandin E(2) release was inhibited by AT(1) receptor antagonist FR-130,739, but not AT(2) receptor antagonist PD-123,319. Angiotensin II evoked an increase in intracellular Ca(2+) in fura-2-loaded human gingival fibroblasts. These results suggest that angiotensin II functions as a physiological mediator via Ca(2+)-mobilizing AT(1) receptor activation in human gingival fibroblasts.

Involvement of phospholipase D in the cAMP-regulated exocytosis of rat parotid acinar cells

The activation of beta-adrenergic receptors in rat parotid acinar cells causes intracellular cAMP elevation and appreciably stimulates the exocytotic release of amylase into saliva. The activation of Ca(2+)-mobilizing receptors also induces some exocytosis. We investigated the role of phospholipase D (PLD) in regulated exocytosis in rat parotid acinar cells. A transphosphatidylation assay detected GTPgammaS (a nonhydrolyzable analogue of GTP)-dependent PLD activity in lysates of rat parotid acinar cells, suggesting that PLD is activated by small molecular mass GTP-binding proteins. The PLD inhibitor, neomycin, suppressed cAMP-dependent exocytosis in saponin-permeabilized cells. Signaling downstream of PLD was disrupted by 1-butanol due to conversion of the PLD reaction product (phosphatidic acid) to phosphatidylbutanol. The stimulation of exocytosis by isoproterenol as well as by a Ca(2+)-mobilizing agonist (methacholine) was inhibited by 1-butanol. These results suggest that PLD is important for regulated exocytosis in rat parotid acinar cells.

Tumor necrosis factor alpha (TNF-alpha)-induced prostaglandin E2 release is mediated by the activation of cyclooxygenase-2 (COX-2) transcription via NFkappaB in human gingival fibroblasts

Nuclear factor kappaB (NFkappaB) is a transcription factor and plays a key role in the expression of several genes involved in the inflammatory process. Cyclooxygenase (COX) is the key regulatory enzyme of the prostaglandin/eicosanoid synthetic pathway. COX-2 is a highly inducible enzyme by proinflammatory cytokines, of which gene expression is regulated by NFkappaB. TNF-alpha is a pro-inflammatory cytokine. In this paper, we investigated the involvement of NFkappaB on TNF-alpha-mediated prostaglandin E2 (PGE2) release and COX-2 gene expression in human gingival fibroblasts (HGF). TNF-alpha-induced PGE2 release and COX-2 mRNA accumulation in a time- and concentration-dependent manner in HGF. The results of transient transfection assays using a chimeric construct of the human COX-2 promoter (nts -1432 approximately +59) ligated to a luciferase reporter gene indicated that TNF-a stimulated the transcriptional activity approximately 1.4-fold. Gel mobility shift assays with a radiolabelled COX-2-NFkappaB oligonucleotide (nts -223 to -214) revealed an increase in the binding of nuclear proteins from TNF-alpha-stimulated HGF. The COX-2-NFKB DNA-protein complex disappeared after treatment with pyrrolidine dithiocarbamate (PDTC; an antioxidant) or herbimycin A (a tyrosine kinase inhibitor). PDTC and herbimycin A attenuated TNF-alpha-stimulated PGE2 release. These results suggest that NFkappaB transcription factor is a key regulator of COX-2 expression in TNF-alpha-induced PGE2 production, which is mediated through a tyrosine kinase pathway in HGF.

Methacholine-induced cGMP production is regulated by nitric oxide generation in rabbit submandibular gland cells

Guanosine 3',5'-monophosphate (cGMP) is an intracellular messenger in various kinds of cell. We investigated the regulation of cGMP production by nitric oxide (NO) in rabbit submandibular gland cells. Methacholine, a muscarinic cholinergic agonist, stimulated cGMP production in a dose- and time-dependent manner, but the alpha-agonist phenylephrine, substance P and the beta-agonist isoproterenol failed to evoke cGMP production. In fura-2-loaded cells, methacholine induced an increase in intracellular Ca2+ ([Ca2+]i) in a concentration-dependent manner, which was similar to that for cGMP production. When the external Ca2+ was chelated with EGTA, methacholine failed to induce cGMP production. Ca2+ ionophore A23187 and thapsigargin, which induce the increase in [Ca2+]i without activation of Ca2+-mobilizing receptors, mimicked the effect of methacholine. cGMP production induced by methacholine, A23187 and thapsigargin was clearly inhibited by NG-nitro-L-arginine methylester (L-NAME), a specific inhibitor of nitric oxide synthase (NOS). S-Nitroso-N-acetyl-DL-penicillamine (SNAP), a NO donor, induced cGMP formation. In the lysate of rabbit submandibular gland cells, Ca2+-regulated nitric oxide synthase activity was detected. These findings suggest that cGMP production induced by the activation of muscarinic cholinergic receptors is regulated by NO generation via the increase in [Ca2+]i.

4-Bromophenacyl bromide induces Ca2+ influx in human gingival fibroblasts

4-Bromophenacyl bromide (BPB) is generally used as a phospholipase A(2) (PLA2) inhibitor. In the present study, we demonstrate that BPB induces Ca2+ influx in human gingival fibroblasts. In fura-2-loaded human gingival fibroblasts, BPB evoked a transient increase in intracellular Ca2+ concentration ([Ca2+]i) in a dose-dependent manner. The BPB-induced Ca2+ mobilization was also shown in a single fluo-3-loaded-fibroblast. The BPB-induced increase in [Ca2+]i was completely abolished by the elimination of the external Ca2+. Ca2+ influx induced by the Ca2+-mobilizing agonist histamine was markedly enhanced in the presence of BPB. These suggest that the BPB-induced Ca2+ mobilization is due to the influx of extracellular Ca2+. However, it is unlikely that the effect of BPB is dependent on the inhibition of PLA2 activity, because other PLA2 inhibitors, such as AACOCF3, quinacrine dihydrochloride and manoalide, failed to induce Ca2+ mobilization. Chemical compounds similar to BPB, but which have no -CH2-Br at position 1 in the benzene ring failed to evoke Ca2+ mobilization, indicating that the position of -CH2--Br in BPB is important for causing the Ca2+ influx.

Association of FcgammaRII with low-density detergent-resistant membranes is important for cross-linking-dependent initiation of the tyrosine phosphorylation pathway and superoxide generation

IgG immune complexes trigger humoral immune responses by cross-linking of FcRs for IgG (FcgammaRs). In the present study, we investigated role of lipid rafts, glycolipid- and cholesterol-rich membrane microdomains, in the FcgammaR-mediated responses. In retinoic acid-differentiated HL-60 cells, cross-linking of FcgammaRs resulted in a marked increase in the tyrosine phosphorylation of FcgammaRIIa, p58(lyn), and p120(c-cbl), which was inhibited by a specific inhibitor of Src family protein tyrosine kinases. After cross-linking, FcgammaRs and tyrosine-phosphorylated proteins including p120(c-cbl) were found in the low-density detergent-resistant membrane (DRM) fractions isolated by sucrose-density gradient ultracentrifugation. The association of FcgammaRs as well as p120(c-cbl) with DRMs did not depend on the tyrosine phosphorylation. When endogenous cholesterol was reduced with methyl-beta-cyclodextrin, the cross-linking did not induce the association of FcgammaRs as well as p120(c-cbl) with DRMs. In addition, although the physical association between FcgammaRIIa and p58(lyn) was not impaired, the cross-linking did not induce the tyrosine phosphorylation. In human neutrophils, superoxide generation induced by opsonized zymosan or chemoattractant fMLP was not affected or increased, respectively, after the methyl-beta-cyclodextrin treatment, but the superoxide generation induced by the insoluble immune complex via FcgammaRII was markedly reduced. Accordingly, we conclude that the cross-linking-dependent association of FcgammaRII to lipid rafts is important for the activation of FcgammaRII-associated Src family protein tyrosine kinases to initiate the tyrosine phosphorylation cascade leading to superoxide generation.

Ca(2+)-regulated nitric oxide generation in rabbit parotid acinar cells

In rabbit parotid acinar cells, the muscarinic cholinergic agonist methacholine induced an increase in the intracellular Ca(2+) concentration and provoked nitric oxide (NO) generation. Ca(2+)-mobilizing reagents such as thapsigargin and the Ca(2+) ionophore A23187 mimicked the effect of methacholine on NO generation. Methacholine-induced NO generation was inhibited by the removal of extracellular Ca(2+). Immunoblot analysis indicated that the antibody against the neuronal type of nitric oxide synthase (NOS) cross-reacted with NOS in the cytosol of rabbit parotid gland cells. Immunofluorescence testing showed that neuronal NOS is present in the cytosol of acinar cells but less in the ductal cells. NOS was purified approximately 8100-fold from the cytosolic fraction of rabbit parotid glands by chromatography on Sephacryl S-200, DEAE-Sephacel, and 29,59-ADP-Sepharose. The purified NOS was a NADPH- and tetrahydroxybiopterin-dependent enzyme and was activated by Ca(2+) within the physiological range in the presence of calmodulin. These results suggest that NO is generated by the activation of the neuronal type of NOS, which is regulated in rabbit parotid acinar cells by the increase in intracellular Ca(2+) levels induced by the activation of muscarinic receptors.

Bradykinin induces a rapid cyclooxygenase-2 mRNA expression via Ca2+mobilization in human gingival fibroblasts primed with interleukin-1 β

We have previously demonstrated that bradykinin potentiates prostaglandin E(2)release in human gingival fibroblasts pretreated with interleukin-1 beta (priming). In this study, we demonstrate a potentiating effect of bradykinin on cyclooxygenase-2 mRNA expression in the interleukin-1 beta-primed fibroblasts. Interleukin-1 beta (200 pg/ml) induced cyclooxygenase-2 mRNA expression, but not bradykinin (1 microM). However, bradykinin rapidly and markedly increased the cyclooxygenase-2 mRNA expression in the fibroblasts primed with interleukin-1 beta. In the primed fibroblasts, ionomycin and thapsigargin mimicked the potentiating effect of bradykinin on the cyclooxygenase-2 mRNA expression. Dexamethasone and actinomycin D completely suppressed not only the interleukin-1 beta-induced cyclooxygenase-2 mRNA expression, but also the bradykinin-induced cyclooxygenase-2 mRNA expression in the interleukin-1 beta-primed fibroblasts, although cycloheximide did not inhibit the effects of interleukin-1 beta and bradykinin. These results suggest that bradykinin-induced prostaglandin E2 synthesis is regulated at the level of the transcription of cyclooxygenase-2 mRNA via Ca2+ mobilization in the interleukin-1 beta-primed human gingival fibroblasts.

Identification of a novel response element in the rat bone sialoprotein (BSP) gene promoter that mediates constitutive and fibroblast growth factor 2-induced expression of BSP

Bone sialoprotein (BSP) is a sulfated and phosphorylated glycoprotein, found almost exclusively in mineralized connective tissues, that may function in the nucleation of hydroxyapatite crystals. We have found that expression of BSP in osteoblastic ROS 17/2.8 cells is stimulated by fibroblast growth factor 2 (FGF2), a potent mitogen for mesenchymal cells. Stimulation of BSP mRNA with 10 ng/ml FGF2 was first evident at 3 h ( approximately 2.6-fold) and reached maximal levels at 6 h ( approximately 4-fold). From transient transfection assays, a FGF response element (FRE) was identified (nucleotides -92 to -85, "GGTGAGAA") as a target of transcriptional activation by FGF2. Ligation of two copies of the FRE 5' to an SV40 promoter was sufficient to confer FGF-responsive transcription. A sequence-specific protein-DNA complex, formed with a double-stranded oligonucleotide encompassing the FRE and nuclear extracts from ROS 17/2.8 cells, but not from fibroblasts, was increased following FGF2 stimulation. Several point mutations within the critical FRE sequence abrogated the formation of this complex and suppressed both basal and FGF2-mediated promoter activity. These studies, therefore, have identified a novel FRE in the proximal promoter of the BSP gene that mediates both constitutive and FGF2-induced BSP transcription.

Complex gangliosides as cell surface inhibitors for the ecto-NAD+ glycohydrolase of CD38

Leukocyte cell surface antigen CD38 is a single-transmembrane protein whose extracellular domain has catalytic activity for NAD(+) glycohydrolase (NADase). We previously reported that b-series gangliosides inhibit the NADase activity of the extracellular domain of CD38 expressed as a fusion protein [Hara-Yokoyama, M., Kukimoto, I., Nishina, H., Kontani, K., Hirabayashi, Y., Irie, F., Sugiya, H., Furuyama, S., and Katada, T. (1996) J. Biol. Chem. 271, 12951-12955]. In the present study, we examined the effect of exogenous gangliosides on the NADase activity of CD38 on the surface of retinoic acid-treated human leukemic HL60 cells and CD38-transfected THP-1 cells. After incubation of the cells with G(T1b), inhibition of NADase activity was observed. The time course of inhibition was slower than that of the incorporation of G(T1b) into the cells, suggesting that incorporation into the cell membranes is a prerequisite for inhibition. Inhibition occurred efficiently when G(T1b) and CD38 were present on the same cells (cis interaction) rather than on different cells (trans interaction). Although gangliosides may affect localization of cell surface proteins, indirect immunofluorescence intensity due to CD38 was not affected after G(T1b) treatment. Comparison of the effect of G(T1b) and G(D1a) indicates that the tandem sialic acid residues linked to the internal galactose residue of the gangliotetraose core are crucial to the inhibition. These results suggest a novel role of complex gangliosides for the first time as cell surface inhibitors of CD38 through specific and cis interaction between the oligosaccharide moiety and the extracellular domain.

Parathyroid hormone regulation of bone sialoprotein (BSP) gene transcription is mediated through a pituitary-specific transcription factor-1 (Pit-1) motif in the rat BSP gene promoter

Bone sialoprotein (BSP) is a mineralized tissue-specific protein expressed by differentiated osteoblasts that appears to function in the initial mineralization of bone. Parathyroid hormone (PTH), which regulates serum calcium through its actions on bone cells, increases the expression of BSP in the rat osteosarcoma cell line (ROS 17/2.8). At 10(-8) M PTH (human 1-34 PTH), stimulation of BSP mRNA was first evident at 3 h ( approximately 3.8-fold), reached maximal levels at 6 h ( approximately 4.7-fold), and declined slowly thereafter. The effects of PTH, which were abrogated by cycloheximide (28 microg/ml), did not alter the stability of the BSP mRNA. The increased transcription was mimicked by both forskolin (10(-6) M) and isoproterenol (10(-7) M), and was also increased by 3-isobutyl-1-methylxanthine (IBMX; 10(-5) M), while the transcriptional activity induced by PTH was inhibited by the protein kinase A inhibitor, H89 (5x10(-6) M). From transient transfection assays using various BSP promoter-luciferase constructs, a pituitary-specific transcription factor-1 (Pit-1) regulatory element (nts -111 to -105) was identified as the target of transcriptional activation by PTH. Thus, transcriptional activity of constructs including the Pit-1 was enhanced approximately 4.7-fold by 10(-8) M PTH while 5'-ligation of the Pit-1 element conferred PTH regulation in an SV40 promoter construct. Binding of a nuclear protein, recognized by anti-Pit-1 antibodies, to a radiolabelled Pit-1-BSP probe was decreased in nuclear extracts prepared from PTH, forskolin and isoproterenol-stimulated ROS 17/2.8 cells. Moreover, co-transfection of ROS cells with a double-stranded Pit-1 oligonucleotide also increased luciferase activity. Collectively, these results indicate that PTH acts through a protein kinase A pathway involving cAMP to stimulate BSP transcription by blocking the action of a Pit-1-related nuclear protein that suppresses BSP transcription by binding a cognate element in the BSP promoter. Thus, we have identified a novel Pit-1 suppressor element in the rat BSP gene promoter that is the target of PTH-stimulated transcription of the BSP gene.

Characterization of nitric oxide synthase in the rat parotid gland

Nitric oxide (NO) acts as an inter- and intracellular signalling molecule of various cells such as vascular endothelium, macrophages, and neurones. NO is produced by nitric oxide synthase (NOS) from L-arginine. Here the characteristics of NOS in the rat parotid gland were investigated. Approximately 74% of total activity of NOS was present in the cytosolic fraction. For full activation of the NOS in the cytosolic fraction, tetrahydroxybiopterin, NADPH, Ca(2+) and calmodulin were needed as cofactors, because the activity was clearly reduced in the absence of tetrahydroxybiopterin, NADPH, or Ca(2+), or in the absence of calmodulin and presence of trifluoperazine, a calmodulin antagonist, in the reaction mixture. The partially purified NOS activity was completely abolished in the absence of calmodulin or Ca(2+), and activated by them in a dose-dependent manner; EC(50) for calmodulin and Ca(2+) were 10 and 340 nM, respectively. The K(m) for L-arginine was 1.57 microM. Immunoblot analysis revealed that a 165-kDa protein band in the rat parotid gland cytosolic fraction cross-reacted with a rabbit polyclonal antibody against human brain NOS. These results suggest that NOS of the rat parotid gland is a neuronal isoform and that its activity is regulated by physiological concentrations of calmodulin and Ca(2+).

Activation of NFkappaB is necessary for IL-1beta-induced cyclooxygenase-2 (COX-2) expression in human gingival fibroblasts

The immediate-early cyclooxygenase-2 (COX-2) gene encodes an inducible prostaglandin synthase enzyme which is implicated in inflammatory and proliferative diseases. COX-2 is highly induced during cell activation by various factors, including mitogens, hormones and cytokines. Since pro-inflammatory cytokine IL-1beta has been shown to induce prostaglandin E2 (PGE2) release in human gingival fibroblasts (HGF), here we analyzed the effect of IL-1beta on the expression of COX-2 and the activation of NFkappaB in HGF. Northern hybridization analysis revealed that IL-1beta (200 pg/ml) increased the expression of COX-2 mRNA in HGF. The effect of IL-1beta was abrogated by herbimycin A, a protein tyrosine kinase inhibitor, and enhanced by orthovanadate, a protein tyrosine phosphatase inhibitor. IL-1beta-induced PGE2 release was blocked by the tyrosine kinase inhibitor and increased by the tyrosine phosphatase inhibitor. The results of transient transfection assays using chimeric constructs of the human COX-2 promoter (nt -1432 approximately +59) ligated to a luciferase reporter gene indicated that IL-1beta stimulated the transcriptional activity approximately 1.5-fold. Gel mobility shift assays with a radiolabelled COX-2-NFkappaB oligonucleotide (nts-223 to-214) revealed an increase in the binding of nuclear proteins from IL-1beta-stimulated HGF. This increase of DNA-protein complex formation induced by IL-1beta was blocked by herbimycin A and another tyrosine kinase inhibitor, genistein. These results suggest that NFkappaB is an important transcription factor for IL-1beta-induced COX-2 gene expression, and is involved in inducing COX-2 gene transcription through tyrosine phosphorylation in HGF.

Bradykinin potentiates prostaglandin E(2) release in the human gingival fibroblasts pretreated with interleukin-1beta via Ca(2+) mobilization

Interleukin-1beta, a proinflammatory cytokine, causes a slow increase in prostaglandin E(2) release. On the other hand, bradykinin, a chemical mediator for inflammation, induces a rapid prostaglandin E(2) release. Simultaneous stimulation with interleukin-1beta (200 pg/ml) and bradykinin (1 microM) evoked a moderately synergistic increase in prostaglandin E(2) release in human gingival fibroblasts. However, in the human gingival fibroblasts pretreated with interleukin-1beta, bradykinin drastically enhanced prostaglandin E(2) release. NS-398, a specific inhibitor of cyclooxygenase-2, inhibited not only interleukin-1beta-induced prostaglandin E(2) release but also bradykinin-induced prostaglandin E(2) release in the human gingival fibroblasts pretreated with interleukin-1beta. Transcriptional and translational inhibitors such as actinomycin D, cycloheximide, and dexamethasone also suppressed the interleukin-1beta-induced prostaglandin E(2) release and the bradykinin-induced prostaglandin E(2) release in interleukin-1beta-pretreated human gingival fibroblasts. In the fibroblasts pretreated with interleukin-1beta, Ca(2+)-mobilizing reagents such as ionomycin and thapsigargin mimicked the potentiating effect of bradykinin on prostaglandin E(2) release. These results suggest that interleukin-1beta- and bradykinin-induced prostaglandin E(2) release is dependent on cyclooxygenase-2 and the potentiated effect of bradykinin in the human gingival fibroblasts primed with interleukin-1beta is caused by Ca(2+) mobilization.

Ribose 1,5-bisphosphate is a putative regulator of fructose 6-phosphate/fructose 1,6-bisphosphate cycle in liver

6-Phosphofructo-1-kinase and fructose-1,6-bisphosphatase are rate-limiting enzymes for glycolysis and gluconeogenesis respectively, in the fructose 6-phosphate/fructose 1,6-bisphosphate cycle in the liver. The effect of ribose 1,5-bisphosphate on the enzymes was investigated. Ribose 1,5-bisphosphate synergistically relieved the ATP inhibition and increased the affinity of liver 6-phosphofructo-1-kinase for fructose 6-phosphate in the presence of AMP. Ribose 1,5-bisphosphate synergistically inhibited fructose-1,6-bisphosphatase in the presence of AMP. The activating effect on 6-phosphofructo-1-kinase and the inhibitory effect on fructose-1,6-bisphosphatase suggest ribose 1,5-bisphosphate is a potent regulator of the fructose 6-phosphate/fructose 1,6-bisphosphate cycle in the liver.

Crystallization and preliminary X-ray diffraction analysis of the extracellular domain of the cell surface antigen CD38 complexed with ganglioside

The cell surface antigen CD38 is a multifunctional ectoenzyme that acts as an NAD(+) glycohydrolase, an ADP-ribosyl cyclase, and also a cyclic ADP-ribose hydrolase. The extracellular catalytic domain of CD38 was expressed as a fusion protein with maltose-binding protein, and was crystallized in the complex with a ganglioside, G(T1b), one of the possible physiological inhibitors of this ectoenzyme. Two different crystal forms were obtained using the hanging-drop vapor diffusion method with PEG 10,000 as the precipitant. One form diffracted up to 2.4 A resolution with synchrotron radiation at 100 K, but suffered serious X-ray damage. It belongs to the space group P2(1)2(1)2(1) with unit-cell parameters of a = 47.9, b = 94.9, c = 125.2 A. The other form is a thin plate, but the data sets were successfully collected up to 2.4 A resolution by use of synchrotron radiation at 100 K. The crystals belong to the space group P2(1) with unit-cell parameters of a = 57.4, b = 51.2, c = 101.1 A, and beta = 97.9 degrees, and contain one molecule per asymmetric unit with a VM value of 2.05 A(3)/Da.

Ribose 1,5-bisphosphate inhibits fructose-1,6-bisphosphatase in rat kidney cortex

Fructose-1,6-bisphosphatase is one of the regulatory enzymes of gluconeogenesis in kidney cortex. The effect of ribose 1,5-bisphosphate on fructose-1,6-bisphosphatase purified from rat kidney cortex was studied. Rat kidney cortex, fructose-1,6-bisphosphatase exhibited hyperbolic kinetics with regard to its substrate, but the activity was inhibited by ribose 1,5-bisphosphate at nanomolar concentrations. The inhibitory effect of ribose 1,5-bisphosphate on the fructose-1,6-bisphosphatase was enhanced in the presence of AMP, one of the inhibitors of fructose-1,6-bisphosphatase. Fructose-2,6-bisphosphate, which is an inhibitor of fructose-1,6-bisphosphatase, inhibited rat kidney cortex fructose-1,6-bisphosphatase activities at a low concentration of fructose-1,6-bisphosphate but a high concentration of fructose-1,6-bisphosphate relieved fructose-1,6-bisphosphatase from fructose-2,6-bisphosphate-dependent inhibition. On the contrary, fructose-1,6-bisphosphate was not effective for the recovery of fructose-1,6-bisphosphatase from ribose 1,5-bisphosphate-dependent inhibition. These results suggest that ribose 1,5-bisphosphate is a potent inhibitor and is involved in the regulation of fructose-1,6-bisphosphatase in rat kidney cortex.

Ribose 1,5-bisphosphate regulates rat kidney cortex phosphofructokinase

Phosphofructokinase (EC 2.7.1.11) is a major enzyme of the glycolytic pathway, catalyzing the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate. In this study, we demonstrated the effect of ribose 1,5-bisphosphate on phosphofructokinase purified from rat kidney cortex. Ribose 1,5-bisphosphate relieved the phosphofructokinase from ATP inhibition and increased the affinity for fructose 6-phosphate at nanomolar concentrations. These activating effects of ribose 1,5-bisphosphate were enhanced in the presence of AMP. Ribose 1,5-bisphosphate reduced the inhibition of the phosphofructokinase induced by citrate. These results suggest that ribose 1,5-bisphosphate is an activator of rat kidney cortex phosphofructokinase and synergistically regulates the enzyme activity with AMP.

Presence of a complex containing vesicle-associated membrane protein 2 in rat parotid acinar cells and its disassembly upon activation of cAMP-dependent protein kinase

Amylase release from parotid acinar cells is mainly induced by the accumulation of intracellular cAMP, presumably through the phosphorylation of substrates by cAMP-dependent protein kinase (PKA). However, the molecular mechanisms of this process are not clear. In a previous study (Fujita-Yoshigaki, J., Dohke, Y., Hara-Yokoyama, M., Kamata, Y., Kozaki, S., Furuyama, S., and Sugiya, H. (1996) J. Biol. Chem. 271, 13130-13134), we reported that vesicle-associated membrane protein 2 (VAMP2) is localized at the secretory granule membrane and is involved in cAMP-induced amylase secretion. To study the formation of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex containing VAMP2 in parotid acinar cells, we prepared rabbit polyclonal antibody against the peptide corresponding to Arg(47)-Asp(64) of VAMP2 (anti-SER4256). The recognition site of anti-SER4256 overlaps the domain involved in binding target membrane SNAREs (t-SNARES). Then we examined the condition of VAMP2 by immunoprecipitation with anti-SER4256. VAMP2 was not included in the immunoprecipitate from solubilized granule membrane fraction under the control conditions, but incubation with cytosolic fraction and cAMP caused immunoprecipitation of VAMP2. The effect of cytosolic fraction and cAMP was reduced by addition of PKA inhibitor H89. Addition of both the catalytic subunit of PKA and the cytosolic fraction allowed immunoprecipitation of VAMP2, whereas the PKA catalytic subunit alone did not. These results suggest that () the t-SNARE binding region of VAMP2 is masked by some protein X and activation of PKA caused the dissociation of X from VAMP2; and () the effect of PKA is not direct phosphorylation of X, but works through phosphorylation of some other cytosolic protein.

Propionic acid stimulates superoxide generation in human neutrophils

Short-chain carboxylic acids are the metabolic by-products of pathogenic anaerobic bacteria and are found at sites of infection in millimolar quantities. We previously reported that propionic acid, one of the short-chain carboxylic acids, induces an increase in intracellular Ca2+ ([Ca2+]i) in human neutrophils. Here we investigate the effect of propionic acid on superoxide generation in human neutrophils. Propionic acid (10 mm) induced inositol 1,4, 5-trisphosphate (IP3) formation and a rapidly transient increase in [Ca2+]i, but not superoxide generation, whereas 1 microm formylmethionyl-leucyl-phenylalanine (fMLP), a widely used neutrophil-stimulating bacterial peptide, stimulated not only IP3 formation and Ca2+ mobilization but also superoxide generation. The IP3 level induced by propionic acid was slightly lower than that induced by fMLP. The transient increase in [Ca2+]i induced by propionic acid immediately returned to the basal level, whereas a sustained increase in [Ca2+]i, which was higher than the basal level, following a transient increase in [Ca2+]i was induced by fMLP. The peak level induced by propionic acid was lower than that with fMLP. In the absence of extracellular Ca2+, thapsigargin, a potent inhibitor of endoplasmic reticulum Ca2+-ATPase, induced an increase in [Ca2+]i even after propionic acid stimulation, but not after fMLP. The Ca2+ ionophore A23187 and thapsigargin induced superoxide generation by themselves. Propionic acid enhanced the superoxide generating effect of A23187 and thapsigargin. These results suggest that Ca2+ mobilization induced by propionic acid is much weaker than that with fMLP, and propionic acid is able to generate superoxide in the presence of a Ca2+ ionophore and a Ca2+ influx activator.

Involvement of prostaglandins in histamine H1 receptor-operated Ca2+ entry in human gingival fibroblasts

In the absence of external Ca2+, 100 microM histamine evoked a transient increase in intracellular Ca2+ ([Ca2+]i), and subsequent addition of Ca2+ to the medium resulted in a sustained increase in [Ca2+]i in fura-2-loaded human gingival fibroblasts. These Ca2+ mobilizations are attributed to Ca2+ release from intracellular stores and Ca2+ entry, respectively. When the histamine H1 antagonist chlorpheniramine was added after the histamine-induced transient increase in [Ca2+]i, the Ca2+ entry induced by the addition of Ca2+ was inhibited. In the fibroblasts pretreated with cyclooxygenase inhibitors, indomethacin (1 microM) or aspirin (100 microM), histamine-induced Ca2+ entry was significantly inhibited, but not the transient [Ca2+]i increase. These results suggest that the histamine-induced Ca2+ entry requires the continuous binding of histamine to the H1 receptors and is regulated by prostaglandins, which are probably produced due to the H1 receptor activation.

Translocation of Arf1 to the secretory granules in rat parotid acinar cells

We investigated the interaction of ADP-ribosylation factor (Arf) with the secretory granules in rat parotid acinar cells. The 20. 5-kDa small-molecular-mass GTP-binding protein in the cytosolic fraction of rat parotid acinar cells was identified as ADP-ribosylation factor1 by using a pan-Arf monoclonal antibody and isotype-specific polyclonal antibodies for Arf proteins 1, 3, 5, and 6. Incubation of the cytosolic fraction with isolated secretory granule membranes in the presence of GTPgammaS resulted in the translocation of Arf1 from the cytosolic fraction to the secretory granule membranes. The translocation was not observed in the presence of GDPbetaS in place of GTPgammaS, indicating that the process is GTP-dependent. The immunoelectron microscopy experiment confirmed Arf1 is translocated to the secretory granules. A prior treatment of the granule membranes with trypsin inhibited the translocation of Arf1 at 2 mM Mg2+, but had no effect in the absence of Mg2+ (condition of spontaneous conversion of Arf-GDP to Arf-GTP). Thus, the trypsin-sensitive nucleotide exchange activity for Arf1 is probably associated with the secretory granule membranes. These results demonstrate Arf1 translocates to the secretory granules in rat parotid acinar cells.

ADP-ribosylation factors in rat parotid acinar cells

ADP-ribosylation factor (Arf) is a 20 kDa polypeptide that is a member of the Ras superfamily of small molecular mass GTP-binding proteins. In addition to an essential role of Arf1 in vesicle budding, recent observations suggest a role for Arf6 in calcium-dependent exocytosis in bovine adrenal chromaffin cells. In rat parotid acinar cells, exocytosis is cAMP-dependent and our findings suggest an interaction of Arf1 with the secretory granules. We describe here the structural and functional background to the Arf proteins focusing on their role in rat parotid acinar cells.

Snare proteins essential for cyclic AMP-regulated exocytosis in salivary glands

Rat parotid acinar cells secrete amylase through the stimulation of beta-adrenoceptors followed by accumulation of intracellular cAMP. However, it remains unclear at the molecular level how secretory granules fuse with the apical membranes. We have examined whether SNARE proteins are involved in exocytosis in the salivary glands, and have found that one of the SNARE proteins, VAMP-2, is localized at the secretory granule membrane of rat parotid acinar cells. Moreover, botulinum neurotoxin B, which has endoprotease activity that cleaves VAMP-2, inhibited cAMP-dependent amylase release but did not inhibit basal secretion in the absence of cAMP. These results suggest that VAMP-2 is essential for cAMP-regulated exocytosis in rat parotid acinar cells. In contrast, both neurotoxins A and C1 (endoproteases that cleave SNAP-25 and syntaxin 1 respectively) failed to inhibit cAMP-dependent amylase release. Therefore, neither SNAP-25 nor syntaxin 1 are involved in amylase secretion in the parotid glands. Clarification of the mechanism of secretion will require the identification of proteins that interact and function cooperatively with VAMP-2. This approach may also reveal details of the molecular mechanism by which the cAMP facilitates secretion in other systems, including neurotransmission.

Ca2+-nitric oxide-cGMP signaling in rabbit parotid acinar cells

Guanosine 3',5'-cyclic monophosphate (cGMP) is a second messenger generated in response to hormones or neurotransmitters in various tissues and cells. In parotid acinar cells, the activation of muscarinic cholinergic and beta-adrenergic receptors induces an increase in intracellular cGMP. However, the mechanism of cGMP production in parotid acinar cells has not been well elucidated. cGMP production is induced by the activation of guanylyl cyclases, which are directly activated by nitric oxide (NO). NO plays an important role as an inter- and intracellular signal molecule in various organs and cells. Biosynthesis of NO is catalyzed by NO synthase (NOS), and NO generation is controlled by the regulation of NOS activity, for example by Ca2+. We have studied the regulation of NOS activity, NO generation and cGMP production in rabbit parotid acinar cells, and have demonstrated a functional Ca2+-NO-cGMP signaling pathway.

cGMP production is coupled to Ca(2+)-dependent nitric oxide generation in rabbit parotid acinar cells

We investigated the mechanism of guanosine 3',5'-monophosphate (cGMP) production in rabbit parotid acinar cells. Methacholine, a muscarinic cholinergic agonist, stimulated cGMP production in a dose-dependent manner but not isoproterenol, a beta-adrenergic receptor stimulant. Methacholine-stimulated cGMP production has been suggested to be coupled to Ca2+ mobilization, because intracellular Ca2+ elevating reagents, such as thapsigargin and the Ca2+ ionophore A23187, mimicked the effect of methacholine. The cGMP production induced by Ca2+ mobilization has also been suggested to be coupled to nitric oxide (NO) generation because the effects of methacholine, thapsigargin and A23187 on cGMP production were blocked by NG-nitro-L-arginine methyl ester (L-NAME), a specific inhibitor of nitric oxide synthase (NOS), and hemoglobin, a scavenger of nitric oxide (NO). Sodium nitroprusside (SNP), a NO donor, stimulated cGMP production. Furthermore, methacholine stimulated NO generation, and NOS activity in the cytosolic fraction in rabbit parotid acinar cells was exclusively dependent on Ca2+. These findings suggest that cGMP production induced by the activation of muscarinic cholinergic receptors is coupled to NO generation via Ca2+ mobilization.

Nitric oxide synthase activities in mammalian parotid and submandibular salivary glands

Nitric oxide is important as a physiological messenger molecule in various organs and cells. It is synthesized from the amino acid L-arginine by nitric oxide synthase. Here, the specific activities of nitric oxide synthase in the cytosolic fractions of rabbit, bovine, mice, rat, and guinea-pig parotid and submandibular glands were compared. Marked specific activities were detected in the rabbit and bovine parotid and submandibular glands and in the parotid of mice. The activity in rabbit parotid was highest and was similar to that in rabbit brain. The significant activities in the salivary glands were completely blocked in the absence of Ca2+ or the presence of a calmodulin inhibitor. These findings suggest that the rabbit parotid glands are useful for studying the regulation of nitric oxide generation by Ca2+/calmodulin-dependent nitric oxide synthase in salivary glands.

Transforming growth factor-beta 1 regulation of bone sialoprotein gene transcription: identification of a TGF-beta activation element in the rat BSP gene promoter

Transforming growth factor-beta (TGF-beta) increases steady-state mRNA levels of several extracellular matrix proteins in mineralized connective tissues. Bone sialoprotein (BSP) is a major constituent of the bone matrix, thought to initiate and regulate the formation of mineral crystals. To determine the molecular pathways of TGF-beta 1 regulation of bone proteins, we have analyzed the effects of the TGF-beta 1 on the expression of the BSP in the rat osteosarcoma cell line (ROS 17/2.8). TGF-beta 1 at 1 ng/ml, increased BSP mRNA levels in ROS 17/2.8 cells approximately 8-fold: the stimulation was first evident at 3 hr, reached maximal levels at 12 hr and slowly declined thereafter. Since the stability of the BSP mRNA was not significantly affected by TGF-beta 1, and nuclear "run-on" transcription analyses revealed only a approximately 2-fold increase in the transcription of the BSP gene, most of the increase in BSP mRNA appeared to involve a nuclear post-transcriptional mechanism. Moreover, the effects of TGF-beta 1 were indirect, since the increase in BSP mRNA was abrogated by cycloheximide (28 micrograms/ml). To identify the site of transcriptional regulation by TGF-beta 1, transient transfection analyses were performed using BSP gene promoter constructs linked to a luciferase reporter gene. Constructs that included nt -801 to -426 of the promoter sequence were found to enhance transcriptional activity approximately 1.8-fold in cells treated with TGF-beta 1. Within this sequence, approximately 500 nt upstream of the transcription start site, a putative TGF-beta activation element (TAE) was identified that contained the 5'-portion of the nuclear factor-1 (NF-1) canonical sequence (TTGGC) overlapping a consensus sequence for activator protein-2 (AP-2). The functionality of the TAE was shown by an increased binding of a nuclear protein from TGF-beta 1 stimulated cells in gel mobility shift assays and from the attenuation of TGF-beta 1-induced luciferase activity when cells were co-transfected with a double-stranded TAE oligonucleotide. Competition gel mobility shift analyses revealed that the nuclear protein that binds to the TAE has similar properties to, but is distinct from, NF-1 nuclear protein. These studies have therefore identified a TGF-beta activation element (TAE) in the rat BSP gene promoter that mediates the stimulatory effects of TGF-beta 1 on BSP gene transcription.

Bradykinin regulates the histamine-induced Ca2+ mobilization via protein kinase C activation in human gingival fibroblasts

We previously demonstrated that histamine and bradykinin evoke an increase in intracellular Ca2+ ([Ca2+]i) in human gingival fibroblasts by using a fluorescent Ca2+ indicator Fura-2. In this paper, we further demonstrate the regulation of the histamine-induced Ca2+ mobilization by bradykinin. In fibroblasts stimulated with bradykinin (1 microM), subsequent stimulation with histamine (100 microM) failed to mobilize Ca2+, whereas bradykinin induced an increase in [Ca2+]i in the cells pre-stimulated with histamine. The attenuation of the histamine response was dependent on the concentration of bradykinin for the first stimulation. Histamine also failed to induce the formation of inositol 1,4,5-trisphosphate in fibroblasts pretreated with bradykinin. In fibroblasts pretreated with bradykinin (1 microM) for 3 min and then washed with fresh medium, the effect of histamine on [Ca2+]i quickly returned to the control level. The activation of protein kinase C by phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (PMA) elicited a marked decrease in histamine-induced Ca2+ mobilization. When the protein kinase C activity was inhibited with H7, a protein kinase C inhibitor, or was down-regulated by pretreatment with PMA for 20 h, the inhibitory effect of PMA on the histamine response was relieved. In the fibroblasts pretreated with H7 or PMA for 20 h, histamine evoked Ca2+ mobilization even after bradykinin stimulation. These results suggest that the histamine response is regulated by bradykinin receptor activation via the activation of protein kinase C in human gingival fibroblasts.