Short communication: opposing effects of lactoferrin on the proliferation of fibroblasts and epithelial cells from bovine mammary gland.

Lactoferrin is present in several physiologic fluids, including milk and colostrum. Recently, evidence has accumulated that lactoferrin acts as a regulator of cell proliferation. Lactoferrin mRNA and protein levels in bovine mammary glands are known to markedly increase after cessation of milking. To clarify the role of bovine lactoferrin (bLF) in mammary involution and remodeling during dry periods, we investigated whether bLF affects the proliferation of cultured cells derived from bovine mammary gland and examined the mechanism underlying the proliferative response to bLF. Addition of bLF to the culture medium increased the proliferation of bovine mammary stromal fibroblasts (bMSF), but decreased that of bovine mammary epithelial cells (bMEC). Proliferation was significantly increased in the bMSF treated with bLF (100µg/mL or greater) as compared with unstimulated cells. The maximal proliferative effect of bLF on bMSF occurred at 1,000µg/mL, such that the proliferation of the bLF-stimulated bMSF was approximately 2.5 times that of unstimulated cells. The bLF increased the production of proliferating cell nuclear antigen and rapid phosphorylation of the p44/p42 mitogen-activated protein kinase in bMSF, but not in bMEC. The bLF-induced proliferation and production of proliferating cell nuclear antigen in bMSF was suppressed by U0126, a specific inhibitor of mitogen-activated protein kinase. Furthermore, treatment with bLF for 24h decreased the mRNA levels of the 3 isoforms of transforming growth factor ß in bMSF (16-66%) but upregulated those in bMEC (122-157%). These opposite effects of bLF on the proliferation of epithelial and fibroblast cells and their expression of transforming growth factor ß may play a crucial role in bovine mammary involution and remodeling.

Multipotency of clonal cells derived from swine periodontal ligament and differential regulation by fibroblast growth factor and bone morphogenetic protein.

BACKGROUND AND OBJECTIVE: A blood supply is indispensable for the regeneration of damaged or lost periodontal ligament (PDL) tissue. Mesenchymal stem cell-like activity of cells derived from the PDL has been identified by their capacity to form fibrous and osseous tissue and cementum. However, it remains to be clarified whether the cells have an ability to build the capillary network of blood vessels. This study evaluated the potential of cells derived from the PDL to construct a blood vessel-like structure and examined how growth factors controlled the multipotency of the cells. MATERIAL AND METHODS: The ability of a swine PDL fibroblast cell line, TesPDL3, to construct a blood vessel-like structure was evaluated on and in the self-assembling peptide scaffold, PuraMatrix(TM). In addition, the ability of the cells to form mineralized nodules was evaluated on type I collagen-coated plastic plates. In some cases, fibroblast growth factor (FGF)-2 and bone morphogenetic protein (BMP)-2 were added to these cultures. The status of the expression of vascular and osteoblastic cell-specific markers in the cells was evaluated using reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting and immunofluorescence analyses. RESULTS: The TesPDL3 cells not only formed mineralized nodules in response to BMP-2 stimulation but also constructed tube-like structures in response to FGF-2 stimulation. Intriguingly, FGF-2 inhibited the BMP-2-induced formation of mineralized nodules. Conversely, BMP-2 inhibited the FGF-2-induced formation of tube-like structures. CONCLUSION: Periodontal ligament fibroblasts have the potential to differentiate not only into osteoblastic but also into vascular cell lineages. The destiny of the cells was reciprocally regulated by BMP-2 and FGF-2.

Lack of alpha2-antiplasmin improves cutaneous wound healing via over-released vascular endothelial growth factor-induced angiogenesis in wound lesions.

BACKGROUND: The fibrinolytic system is supposed to play an important role in the degradation of extracellular matrices for physiological and pathological tissue remodeling; however, the detailed mechanism regarding how this system affects cutaneous wound healing remains to be clarified. METHODS AND RESULTS: We performed experimental cutaneous wounding in mice with a deficiency of alpha(2)-antiplasmin (alpha(2)AP), which is a potent and specific plasmin inhibitor. We found that an accelerated wound closure was observed in alpha(2)AP-deficient (alpha(2)AP-/-) mice in comparison with wild type (WT) mice. Moreover, we observed that a greater increase of angiogenesis occurred in the process of wound healing in alpha(2)AP-/- mice than in the WT mice. Intriguingly, mRNA expression of vascular endothelial growth factor (VEGF), which is the best characterized positive regulator of angiogenesis, in wound lesions was found to show a greater increase in the early phase of the healing process in alpha(2)AP-/- mice than in WT mice. In addition, the amount of released-VEGF from the explanted fibroblasts of alpha(2)AP-/- mice increased dramatically more than in the WT mice. Finally, the intra-jugular administration of anti-VEGF antibody clearly suppressed the increased angiogenesis and accelerated wound closure in the wound lesion of alpha(2)AP-/- mice. CONCLUSION: The lack of alpha(2)AP markedly causes an over-release of VEGF from the fibroblasts in cutaneous wound lesions, thereby inducing angiogenesis around the area, and thus resulting in an accelerated-wound closure. CONCLUSIONS: This is the first report to describe the crucial role that alpha(2)AP plays following angiogenesis in the process of wound healing. Our results provide new insight into the role of alpha(2)AP on cutaneous wound healing.

SAPK/JNK plays a role in transforming growth factor-beta-induced VEGF synthesis in osteoblasts.

We previously reported that transforming growth factor-beta (TGF-beta) activates p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase, resulting in the stimulation of vascular endothelial growth factor (VEGF) synthesis in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the involvement of stress-activated protein kinase/c- Jun N-terminal kinase (SAPK/JNK), another member of the MAP kinase superfamily, in TGF-beta-induced VEGF synthesis in these cells. TGF-beta markedly induced SAPK/JNK phosphorylation. SP600125, a specific inhibitor of SAPK/JNK, markedly reduced TGF-beta-induced VEGF synthesis. SP600125 suppressed TGF-beta-induced SAPK/JNK phosphorylation. PD98059, an inhibitor of upstream kinase of p44/p42 MAP kinase and SB203580, an inhibitor of p38 MAP kinase, each failed to reduce TGF-beta-induced SAPK/JNK phosphorylation. A combination of SP600125 and PD98059 or SP600125 and SB203580 suppressed TGF-beta-stimulated VEGF synthesis in an additive manner. These results strongly suggest that TGF-beta activates SAPK/JNK in osteoblasts, and that SAPK/JNK plays a role in addition to p42/p44 MAP kinase and p38 MAP kinase in TGF-beta-induced VEGF synthesis.

Involvement of SAPK/JNK in prostaglandin E(1)-induced VEGF synthesis in osteoblast-like cells.

We previously reported that prostaglandin E(1) (PGE(1)) activates both p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase via cAMP-dependent protein kinase in osteoblast-like MC3T3-E1 cells, and that p38 MAP kinase but not p42/p44 MAP kinase is involved in PGE(1)-induced synthesis of vascular endothelial growth factor (VEGF). In the present study, we investigated the involvement of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in the PGE(1)-induced VEGF synthesis in MC3T3-E1 cells. PGE(1) induced the phosphorylation of SAPK/JNK. SP600125, a specific inhibitor of SAPK/JNK, markedly reduced the PGE(1)-induced VEGF synthesis. Forskolin, a direct activator of adenylyl cyclase, elicited the phosphorylation of SAPK/JNK, and 8bromo-cAMP, a plasma membrane-permeable cAMP analogue-stimulated VEGF synthesis was significantly reduced by SP600125. SP600125 suppressed the PGE(1)-induced phosphorylation of SAPK/JNK without affecting the phosphorylation of p38 MAP kinase induced by PGE(1). The phosphorylation of c-Jun induced by PGE(1) was also inhibited by SP600125. SB203580, a p38 MAP kinase inhibitor, failed to reduce the PGE(1) induced phosphorylation of SAPK/JNK. A combination of SP600125 and SB203580 suppressed the PGE(1)-stimulated VEGF synthesis in an additive manner. These results strongly suggest that PGE(1) activates SAPK/JNK in osteoblasts, and that SAPK/JNK plays a part in PGE(1)-induced VEGF synthesis.

Activation of p38 mitogen-activated protein kinase mediates thyroid hormone-stimulated osteocalcin synthesis in osteoblasts.

It is well known that thyroid hormone modulates osteoblast cell function. We have previously shown that triiodothyronine (T(3)) activates p44/p42 mitogen-activated protein (MAP) kinase, which limits T(3)-induced alkaline phosphatase activity in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether p44/p42 MAP kinase or p38 MAP kinase is involved in the thyroid hormone-stimulated osteocalcin synthesis in these cells. T(3) markedly induced the phosphorylation of p38 MAP kinase in addition to p44/p42 MAP kinase. PD98059 and U0126, inhibitors of the upstream kinase that activates p44/p42 MAP kinase, had little effect on the T(3)-induced synthesis of osteocalcin. On the contrary, the T(3)-induced osteocalcin synthesis was significantly reduced by SB203580 and PD169316, inhibitors of p38 MAP kinase. SB203580, PD169316 or PD98059 suppressed the T(3)-phosphorylation of myelin basic protein. T(3)-induced osteocalcin synthesis was significantly reduced by SB203580 or PD169316 also in primary cultured mouse osteoblasts. These results strongly suggest that p38 MAP kinase but not p44/p42 MAP kinase takes part in the thyroid hormone-stimulated osteocalcin synthesis in osteoblasts.

Involvement of stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK) in prostaglandin F2alpha-induced heat shock protein 27 in osteoblasts.

We have reported that prostaglandin F2(alpha) (PGF2(alpha)) activates p44/p42 mitogen-activated protein (MAP) kinase in osteoblast-like MC3T3-E1 cells, and that p44/p42 MAP kinase plays a role in the PGF2(alpha)-induced heat shock protein 27 (HSP27). In the present study, we investigated the involvement of stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK), a member of the MAP kinase superfamily, in PGF2(alpha)-induced HSP27 in MC3T3-E1 cells. PGF2(alpha) time dependently induced the phosphorylation of SAPK/JNK. SP600125, a specific inhibitor of SAPK/JNK, markedly reduced the PGF2(alpha)-stimulated HSP27 accumulation. The inhibitory effect of SP600125 was dose dependent in the range between 0.1 and 30 microM. SP600125 reduced the PGF2(alpha)-increased level of HSP27 mRNA. SP600125 suppressed the phosphorylation of SAPK/JNK induced by PGF2(alpha), but did not affect the PGF2(alpha)-induced phosphorylation of p44/p42 MAP kinase. On the other hand, PD98059, a specific inhibitor of the upstream kinase of p44/p42 MAP kinase, which reduced the phosphorylation of p44/p42 MAP kinase stimulated by PGF2(alpha), had little effect on the PGF2(alpha)-induced phosphorylation of SAPK/JNK. These results strongly suggest that SAPK/JNK plays a part in PGF2(alpha)-induced HSP27 in addition to p44/p42 MAP kinase in osteoblasts.

A peptide isolated from alpha B-crystallin is a novel and potent inhibitor of platelet aggregation via dual prevention of PAR-1 and GPIb/V/IX.

BACKGROUND: The ability of low-molecular-weight heat shock protein (HSP) to modulate thrombin-induced platelet aggregation has been investigated. OBJECTIVES: We examined the inhibitory effects on platelet aggregation of nine amino acid sequences isolated from HSP20 or alpha B-crystallin and their various derivatives. METHODS AND RESULTS: Platelet aggregation induced by various agonists was performed. These findings indicated that a peptide (Trp-Ile-Arg-Arg-Pro-Phe-Phe-Pro-Phe) from alpha B-crystallin significantly inhibits platelet aggregation induced by thrombin, TRAP (a protease activated receptor-1 agonist) and botrocetin, ristocetin (a stimulator of the platelet glycoprotein Ib/V/IX-von Willebrand factor axis), but not a protease-activated receptor-4 agonist, collagen and ADP. The inhibitory activity against thrombin or botrocetin is mainly linked to Arg-Arg-Pro-Phe or Trp-Ile-Arg-Arg-Pro, respectively, among nine amino acids. Additionally, during in vivo experiments, Trp-Ile-Arg-Arg-Pro-Phe-Phe-Pro-Phe shows a significant antithrombotic effect without marked bleeding. CONCLUSION: Our results provide the basis for a potential new aspect of antiplatelet compound for the therapy of thrombosis and cardiovascular disease.

Feeding suppression by fibroblast growth factor-1 is accompanied by selective induction of heat shock protein 27 in hypothalamic astrocytes.

It has been suggested that fibroblast growth factor (FGF)-1 serves as a physiological satiety factor in the hypothalamus, although the molecular mechanism underlying such a function is poorly understood. To gain additional insight into this issue, we used a Sendai virus (SeV) gene expression system in rats to explore genes differentially expressed subsequent to expression of FGF-1. Using cDNA arrays, we determined that infusion of FGF-1/SeV into one lateral ventricle induced selective expression of heat shock protein (HSP) 27 in the hypothalamus. Whereas FGF-1 expression was restricted to the ependymal cell layer of the cerebral ventricles, HSP27 was more widely expressed in astrocytes residing in the surrounding periventricular region. Similarly, infusion of FGF-1 polypeptide into a lateral ventricle induced dose-dependent HSP27 expression in periventricular astrocytes surrounding the third ventricle, with maximum mRNA levels being attained 6 h after infusion. This induction of HSP27 was accompanied by a significant suppression of feeding behaviour. Interestingly, suppression of feeding caused by intracerebro ventricular infusion of ciliary neurotrophic factor was also accompanied by induction of HSP27 in periventricular astrocytes, but suppression of feeding caused by infusion of leptin was not. It therefore appears that suppression of feeding by FGF-1 is accompanied by selective induction of HSP27 expression in hypothalamic astrocytes surrounding the third ventricle, and that this response may be a key component of the mechanism by which appetite is regulated by FGF-1.

Activation of the p21(CIP1/WAF1) promoter by bone morphogenetic protein-2 in mouse B lineage cells.

BMPs exert a negative growth effect on various types of cells. We have previously reported that BMP-2 inhibited the growth of HS-72 mouse hybridoma cells by inducing p21(CIP1/WAF1) expression. In the present study, we demonstrated that BMP-2 activated the mouse p21(CIP1/WAF1) promoter in HS-72 cells, and that a 29-base pair (b) region of the promoter (-1928/-1900 relative to the TATA box), conserved between mice and humans, was responsive to BMP-2 as well as expression of Smad1, Smad4, and constitutively active mutants of BMP type I receptors. Furthermore, an oligonucleotide containing the 29-b region was found to be associated with Smad4 and phosphorylated Smad1 in the nuclear extract of BMP-2-stimulated HS-72 cells. These results suggested that BMP-2 might activate p21(CIP1/WAF1) transcription by inducing a binding of Smad4 and Smad1 to the 29-b region in HS-72 cells.

Glutathione S-transferase Pi is a dopamine-inducible suppressor of dopamine-induced apoptosis in PC12 cells.

The finding that the neurotransmitter dopamine induces apoptosis in neurons implies the existence of a cellular mechanism by which dopaminergic neurons protect themselves from dopamine-induced apoptosis. By profiling the expression of a number of genes in differentiating PC12 cells which exhibit elevated levels of dopamine biosynthesis, we found that expression of glutathione S-transferase class Pi (GSTp) mRNA was selectively up-regulated. Interestingly, dopamine added to the culture medium of PC12 cells also augmented their expression of GSTp mRNA. Suppression of GSTp expression by transfection of its antisense expression vector augmented dopamine-induced apoptosis of PC12 cells. Conversely, overexpression of GSTp made the resultant PC12 transfectants highly resistant to dopamine-induced apoptosis. Transfection of the antisense or sense GSTp expression vectors also resulted in corresponding augmentation or suppression of dopamine-induced activation of cell-associated Jun-N-terminal kinase (JNK), which has been suggested to mediate dopamine-induced apoptosis in neuronal cells. These results indicate that GSTp is a dopamine-inducible suppressor of dopamine-induced apoptosis in PC12 cells, and suggest that this activity is exerted through inhibition of JNK activity.

Stimulatory effect of basic fibroblast growth factor on induction of heat shock protein 27 in osteoblasts: role of protein kinase C.

In a previous study we showed that basic fibroblast growth factor (bFGF) stimulates activation of protein kinase C through phosphoinositide hydrolysis by phospholipase C and phosphatidylcholine hydrolysis by phospholipase D in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether bFGF stimulates the induction of heat shock protein (HSP) 27, a low-molecular-weight HSP, and HSP70, a high-molecular-weight HSP, in MC3T3-E1 cells and the mechanism behind the induction. bFGF increased the level of HSP27 while having little effect on HSP70 level. bFGF stimulated the accumulation of HSP27 dose-dependently in the range between 1 and 30 ng/ml. bFGF induced an increase in the level of the mRNA for HSP27. The bFGF-stimulated accumulation of HSP27 was reduced by inhibitors of protein kinase C. The bFGF-induced HSP27 accumulation was reduced in protein kinase C-downregulated MC3T3-E1 cells. U-73122, an inhibitor of phospholipase C, and propranolol, a phosphatidic acid phosphohydrolase inhibitor, suppressed the bFGF-stimulated HSP27 accumulation. These results strongly suggest that bFGF stimulates HSP27 induction through protein kinase C activation in osteoblasts.

Mechanism for the transcriptional repression by c-Myc on PDGF beta-receptor.

c-Myc plays a key role in the cell cycle dependent control of the PDGF beta-receptor mRNA. The mouse platelet-derived growth factor (PDGF) beta-receptor promoter contains a CCAAT motif, and NF-Y plays an essential role in its transcription. Coexpression of c-Myc represses PDGF beta-receptor luciferase reporter activity, and the CCAAT motif in the promoter is indispensable for this repression. Here we show that c-Myc binds NF-Y subunits, YB and YC, by immunoprecipitation from cotransfected COS-1 cells. The in vitro-translated c-Myc also binds the glutathione S-transferase (GST)-NF-YB fusion protein and GST-NF-YC, but not GST-NF-YA. The most C-terminal region of HAP domains of NF-YB and NF-YC, and the Myc homology boxes, but not the C-terminal bHLHZip domain, are indispensable for the coimmunoprecipitation, and also for the repression of PDGF beta-receptor. c-Myc binds NF-Y complex without affecting the efficiency of NF-Y binding to DNA. However, the expression of Myc represses the transcriptional activation of NF-YC when fused to the GAL4 DNA binding domain. Furthermore, this repression was seen only when Myc homology boxes are present, and NF-YC contains the c-Myc binding region.

BMP-2 augments FGF-induced differentiation of PC12 cells through upregulation of FGF receptor-1 expression.

When exposed to various neurotrophic factors, including fibroblast growth factors (FGF)-1 and -2, rat pheochromocytoma-derived PC12 cells differentiate into sympathetic neuron-like cells possessing elongated neurites. We found that while bone morphogenetic protein-2 (BMP-2) exerted little effect by itself on the differentiation of PC12 cells, in combination with FGF it strongly induced neurite outgrowth, even at subthreshold concentrations of FGF. Analysis of gene expression revealed that FGF receptor-1 (FGFR-1) mRNA was abundantly expressed in PC12 cells and that its expression was upregulated by pretreating the cells with BMP-2. Crosslinking the receptors with (125)I-FGF-2 and then immunoprecipitating them confirmed that expression of FGFR-1, but not other FGF receptor types, was enhanced by BMP-2. Furthermore, Scatchard analyses revealed that the numbers of FGF-2 binding sites were increased by approximately 40% after BMP-2 treatment. Pretreatment with BMP-2 also enhanced peak and sustained levels of FGF-induced ERK1/2 phosphorylation in PC12 cells. Finally, the augmentation of neurotrophic activity by BMP-2 was inhibited by SU5402, an FGFR-1 inhibitor. These findings indicate that BMP-2 augments FGF-induced differentiation of PC12 cells through selective upregulation of FGFR-1 expression, and suggest that BMP-2 and FGF act in concert to regulate cell differentiation in the nervous system.

Involvement of caspases in apoptotic cell death of murine macrophages infected with Actinobacillus actinomycetemcomitans.

Infection of murine macrophages in vitro with periodontopathic bacterium Actinobacillus actinomycetemcomitans induces apoptotic cell death. In this study, we investigated the involvement of caspases in apoptotic cell death of A. actinomycetemcomitans-infected macrophages. Two peptide inhibitors of caspases, benzyloxycarbonyl-Val-Ala-Asp (OMe)-fluoromethyl ketone (Z-VAD-FMK) and benzyloxycarbonyl-Asp-Glu-Val-Asp (OMe)-fluoromethyl ketone (Z-DEVD-FMK), inhibited apoptotic cell death of murine macrophage cell line J774.1 infected with A. actinomycetemcomitans. During the process of apoptosis, interleukin-1beta (IL-1beta) was detected in the culture supernatants of J774.1 cells. IL-1beta secretion was blocked by the caspase-1 inhibitor, Z-VAD-FMK, indicating that caspase-1 is involved in not only the induction of apoptosis but also the IL-1beta secretion from A. actinomycetemcomitans-infected J774.1 cells. Immunoblot analysis revealed that the infection of A. actinomycetemcomitans to J774.1 cells induced the cleavage of retinoblastoma protein (Rb), suggesting that caspase-3 was activated by A. actinomycetemcomitans infection. The cytosol from A. actinomycetemcomitans-infected J774.1 cells induced Rb proteolysis in vitro, which was inhibited by the caspase-3 inhibitor, Z-DEVD-FMK. Furthermore, caspase-3-like activity was markedly increased in J774.1 cells infected with A.actinomycetemcomitans between 12 h and 24 h, which was subsequently inhibited by the addition of caspase-3 inhibitor, Z-DEVD-FMK. These findings indicate that caspase-3 induces apoptosis in J774.1 cells infected with A. actinomycetemcomitans. Taken together, these results suggest that caspase-1 and caspase-3 are involved in the induction of apoptosis in A. actinomycetemcomitans-infected macrophages.

Intracellular apoptosis-inducing factor is induced by a vacuolar type H+-ATPase inhibitor in B lineage cells.

We previously reported that concanamycin A, a specific inhibitor of vacuolar type H+-ATPases, induces DNA fragmentation in B cell hybridoma HS-72 cells. In the present study, we found that the cytosol from concanamycin A-treated HS-72 cells had a cytotoxic effect on intact cells in a cell viability assay. While activin A also induced apoptosis in HS-72 cells, the cytosol from activin A-treated HS-72 cells had no effect on cell viability. We purified the cytosol from concanamycin A-treated HS-72 cells by a four-step procedure: ultracentrifugation; HiTrap heparin column chromatography; HiTrap Q column chromatography; and reverse-phase high performance liquid chromatography on a C18 hydrophobic support. The biologically active fraction, which was used as partially purified cytosol, gave a specific band of protein with a molecular mass of 33 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The mechanism of cell death was examined by observing changes in nuclear morphology, an increase in the proportion of fragmented DNA, and the typical ladder pattern of degraded chromosomal DNA, indicating the induction of apoptosis in cells cultured with the partially purified cytosol. The overexpression of human Bcl-2 suppressed apoptosis, indicating that the cytosol from concanamycin A-treated HS-72 cells induces apoptosis by a Bcl-2-inhibiting mechanism. These findings suggest that concanamycin A, a vacuolar type H+-ATPase inhibitor, produces intracellular apoptosis-inducing factor in B cell hybridoma.

Dissociation of bone morphogenetic protein-mediated growth arrest and apoptosis of mouse B cells by HPV-16 E6/E7.

We have previously found that bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor-beta family, induces cell-cycle arrest in the G1 phase and apoptotic cell death of HS-72 mouse hybridoma cells. In this study, we show that BMP-2 did not alter expression of cyclin D, cyclin E, cyclin-dependent kinase 2 (CDK2), CDK4, p27KIP1, p16INK4a, or p15INK4b, but enhanced expression of p21(CIP1/WAF1). Accumulation of p21(CIP1/WAF1) resulted in increased binding of p21(CIP1/WAF1) to CDK4 and concomitantly caused a profound decrease in the in vitro retinoblastoma protein (Rb) kinase activity of CDK4. Furthermore, the ectopic expression of human papilloma virus type-16 E7, an inhibitor of p21(CIP1/WAF1) and Rb, reverted G1 arrest induced by BMP-2. Expression of E6/E7, without increasing the p53 level, blocked inhibition of Rb phosphorylation and G1 arrest, but did not attenuate cell death in BMP-treated HS-72 cells. Taken together, these results suggest that inhibition of Rb phosphorylation by p21(CIP1/WAF1) is responsible for BMP-2-mediated G1 arrest and that BMP-2-induction of apoptosis might be independent of Rb hypophosphorylation.

Caspase-3 activation during the process of apoptosis induced by a vacuolar type H(+)-ATPase inhibitor.

Concanamycin A, a specific inhibitor of vacuolar type H(+)-ATPases, induced DNA fragmentation in B cell hybridoma HS-72 cells. Immunoblot analysis revealed that the exposure of concanamycin A to HS-72 cells induced the cleavage of retinoblastoma protein (Rb) and poly(ADP-ribose) polymerase (PARP). The cytosol from concanamycin A-treated HS-72 cells induced DNA fragmentation in nuclei from untreated cells in a cell-free system. This fragmentation was suppressed by a specific inhibitor of caspase-3. The cytosol induced Rb proteolysis in vitro, which was inhibited by a caspase-3 inhibitor. These findings indicate that caspase-3 induces DNA fragmentation and cleavage of Rb and PARP during the process of apoptosis induced by concanamycin A.

Autocrine endothelial regulation in brain stem vessels of newborn piglets.

Vasoactive intestinal peptide (VIP) is known as a potent regulator for the development of the central nervous system (CNS). The neonatal period of brain development is characterised by rapid cellular proliferation in parallel with neuronal differentiation and angiogenesis. We examined the expression of native VIP and the VIP receptor-associated protein by immunohistochemistry as well as the expression of VIP mRNA by in situ hybridisation in the brain stem of newborn piglets. We found both the mRNA and the protein of VIP as well as the VIP receptor-associated protein in endothelial cells of veins, arteries and capillaries in the marginal zone of brain stem tissue sections, especially in pons and mesencephalon, as well as in pial vessels. The coexpression of native VIP, VIP mRNA and the VIP receptor-associated protein within the endothelium suggests the presence of an autocrine loop, which has been detected so far only in neuroblastoma cells. This expression pattern gives evidence to the immaturity of endothelial cells at birth and the presence of an adaptive response in the VIP-regulated system during the change from intra- to extrauterine life.

Differential inhibition of Smad6 and Smad7 on bone morphogenetic protein- and activin-mediated growth arrest and apoptosis in B cells.

Smad6 and Smad7 prevent ligand-induced activation of signal-transducing Smad proteins in the transforming growth factor-beta family. Here we demonstrate that both Smad6 and Smad7 are human bone morphogenetic protein-2 (hBMP-2)-inducible antagonists of hBMP-2-induced growth arrest and apoptosis in mouse B cell hybridoma HS-72 cells. Moreover, we confirmed that the ectopic expressions of Smad6 and Smad7 inhibited the hBMP-2-induced Smad1/Smad5 phosphorylation. We previously reported that Smad7 is an activin A-inducible antagonist of activin A-induced growth arrest and apoptosis in HS-72 cells. Interestingly, although mRNA expression of Smad6 was induced by activin A in HS-72 cells, Smad6 showed no antagonistic effect on activin A-induced growth arrest and apoptosis. Moreover, we found that the ectopic expression of Smad7, but not Smad6, inhibited the activin A-induced Smad2 phosphorylation in HS-72 cells. Thus, Smad6 and Smad7 exhibit differential inhibitory effects in bone morphogenetic protein-2- and activin A-mediated signaling in B lineage cells.