Prolyl hydroxylase inhibitors increase the production of vascular endothelial growth factor in dental pulp-derived cells

Introduction: Prolyl hydroxylase (PHD) inhibitors can induce a proangiogenic response that stimulates regeneration in soft and hard tissues. However, the effect of PHD inhibitors on the dental pulp is unclear. The purpose of this study was to evaluate the effects of PHD inhibitors on the proangiogenic capacity of human dental pulp–derived cells. Methods: To test the response of dental pulp–derived cells to PHD inhibitors, the cells were exposed to dimethyloxalylglycine, desferrioxamine, L-mimosine, and cobalt chloride. To assess the response of dental pulp cells to a capping material supplemented with PHD inhibitors, the cells were treated with supernatants from calcium hydroxide. Viability, proliferation, and protein synthesis were assessed by formazan formation, 3[H]thymidine, and 3[H]leucine incorporation assays. The effect on the proangiogenic capacity was measured by immunoassays for vascular endothelial growth factor (VEGF). Results: We found that all 4 PHD inhibitors can reduce viability, proliferation, and protein synthesis at high concentrations. At nontoxic concentrations and in the presence of supernatants from calcium hydroxide, PHD inhibitors stimulated the production of VEGF in dental pulp–derived cells. When calcium hydroxide was supplemented with the PHD inhibitors, the supernatants from these preparations did not significantly elevate VEGF levels. Conclusions: These results show that PHD inhibitors can stimulate VEGF production of dental pulp–derived cells, suggesting a corresponding increase in their proangiogenic capacity. Further studies will be required to understand the impact that this might have on pulp regeneration.

Bone substitute materials supplemented with prolyl hydroxylase inhibitors decrease osteoclastogenesis in vitro.

BACKGROUND AND OBJECTIVE Inhibition of prolyl hydroxylases stimulates bone regeneration. Consequently, bone substitute materials were developed that release prolyl hydroxylase inhibitors. However, the impact of prolyl hydroxylase inhibitors released from these carriers on osteoclastogenesis is not clear. We therefore assessed the effect of bone substitute materials that release prolyl hydroxylase inhibitors on osteoclastogenesis. MATERIAL AND METHODS Dimethyloxalylglycine, desferrioxamine, and l-mimosine were lyophilized onto bovine bone mineral and hydroxyapatite, and supernatants were generated. Osteoclastogenesis was induced in murine bone marrow cultures in the presence of the supernatants from bone substitute materials. The formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and TRAP activity were determined. To test for possible effects on osteoclast progenitor cells, we measured the effect of the supernatants on proliferation and viability. In addition, experiments were performed where prolyl hydroxylase inhibitors were directly added to the bone marrow cultures. RESULTS We found that prolyl hydroxylase inhibitors released within the first hours from bone substitute materials reduce the number and activity of TRAP-positive multinucleated cells. In line with this, addition of prolyl hydroxylase inhibitors directly to the bone marrow cultures dose-dependently reduced the number of TRAP-positive multinucleated cells and the overall resorption activity. Moreover, the released prolyl hydroxylase inhibitors decreased proliferation but not viability of osteoclast progenitor cells. CONCLUSION Our results show that prolyl hydroxylase inhibitors released from bone substitute materials decrease osteoclastogenesis in murine bone marrow cultures.

Effects of Prolyl Hydroxylase Inhibitor L-mimosine on Dental Pulp in the Presence of Advanced Glycation End Products

INTRODUCTION Proangiogenic prolyl hydroxylase (PHD) inhibitors represent a novel approach to stimulate tissue regeneration. Diabetes mellitus involves the accumulation of advanced glycation end products (AGEs). Here we evaluated the impact of AGEs on the response of human pulp tissue to the PHD inhibitor L-mimosine (L-MIM) in monolayer cultures of dental pulp-derived cells (DPCs) and tooth slice organ cultures. METHODS In monolayer cultures, DPCs were incubated with L-MIM and AGEs. Viability was assessed based on formazan formation, live-dead staining, annexin V/propidium iodide, and trypan blue exclusion assay. Vascular endothelial growth factor (VEGF), interleukin (IL)-6, and IL-8 production was evaluated by quantitative polymerase chain reaction and immunoassays. Furthermore, expression levels of odontoblast markers were assessed, and alizarin red staining was performed. Tooth slice organ cultures were performed, and VEGF, IL-6, and IL8 levels in their supernatants were measured by immunoassays. Pulp tissue vitality and morphology were assessed by MTT assay and histology. RESULTS In monolayer cultures of DPCs, L-MIM at nontoxic concentrations increased the production of VEGF and IL-8 in the presence of AGEs. Stimulation with L-MIM decreased alkaline phosphatase levels and matrix mineralization also in the presence of AGEs, whereas no significant changes in dentin matrix protein 1 and dentin sialophosphoprotein expression were observed. In tooth slice organ cultures, L-MIM increased VEGF but not IL-6 and IL-8 production in the presence of AGEs. The pulp tissue was vital, and no signs of apoptosis or necrosis were observed. CONCLUSIONS Overall, in the presence of AGEs, L-MIM increases the proangiogenic capacity, but decreases alkaline phosphatase expression and matrix mineralization.

The Aeromonas salmonicida subsp. salmonicida exoproteome: global analysis, moonlighting proteins and putative antigens for vaccination against furunculosis

BACKGROUND Aeromonas salmonicida subsp. salmonicida, the etiologic agent of furunculosis, is a major pathogen of fisheries worldwide. Despite the identification of several virulence factors the pathogenesis is still poorly understood. We have used high-throughput proteomics to display the differences between in vitro secretome of A. salmonicida wild-type (wt, hypervirulent, JF5054) and T3SS-deficient (isogenic ΔascV, extremely low-virulent, JF2747) strains in exponential (GP) and stationary (SP) phases of growth. RESULTS Among the different experimental conditions we obtained semi-quantitative values for a total of 2136 A. salmonicida proteins. Proteins of specific A. salmonicida species were proportionally less detected than proteins common to the Aeromonas genus or those shared with other Aeromonas species, suggesting that in vitro growth did not induce the expression of these genes. Four detected proteins which are unidentified in the genome of reference strains of A. salmonicida were homologous to components of the conjugative T4SS of A. hydrophila pRA1 plasmid. Polypeptides of three proteins which are specific to the 01-B526 strain were also discovered. In supernatants (SNs), the number of detected proteins was higher in SP (326 for wt vs 329 for mutant) than in GP (275 for wt vs 263 for mutant). In pellets, the number of identified proteins (a total of 1536) was approximately the same between GP and SP. Numerous highly conserved cytoplasmic proteins were present in A. salmonicida SNs (mainly EF-Tu, EF-G, EF-P, EF-Ts, TypA, AlaS, ribosomal proteins, HtpG, DnaK, peptidyl-prolyl cis-trans isomerases, GAPDH, Enolase, FbaA, TpiA, Pgk, TktA, AckA, AcnB, Mdh, AhpC, Tpx, SodB and PNPase), and several evidences support the theory that their extracellular localization was not the result of cell lysis. According to the Cluster of Orthologous Groups classification, 29% of excreted proteins in A. salmonicida SNs were currently poorly characterized. CONCLUSIONS In this part of our work we elucidated the whole in vitro exoproteome of hypervirulent A. salmonicida subsp. salmonicida and showed the secretion of several highly conserved cytoplasmic proteins with putative moonlighting functions and roles in virulence. All together, our results offer new information about the pathogenesis of furunculosis and point out potential candidates for vaccine development.

In vitro release of dimethyloxaloylglycine and l-mimosine from bovine bone mineral.

OBJECTIVE Prolyl hydroxylases (PHD) are oxygen sensors and therefore pharmacological targets to stimulate periodontal regeneration. Here we evaluate the release profile of the PHD inhibitors dimethyloxaloylglycine and l-mimosine from bone substitutes. MATERIALS Dimethyloxaloylglycine and l-mimosine were lyophilised onto bone substitutes including bovine bone mineral, beta-tricalcium phosphate, and hydroxyapatite. Release kinetic was evaluated by bioassays with gingival and periodontal ligament fibroblasts. We determined the capacity of PHD inhibitors to provoke VEGF expression and to repress metabolic activity and proliferation as assessed by immunoassay, MTT conversion and (3)[H]thymidine incorporation, respectively. RESULTS We found that the PHD inhibitors are released from bovine bone mineral as indicated by the increase of VEGF production in gingival and periodontal ligament fibroblasts. Supernatants obtained after 1h also decreased metabolic activity and proliferation of the fibroblasts. A fibrin matrix prolonged the release of PHD inhibitors up to 192h. A similar cellular response was found when supernatants from PHD inhibitors loaded beta-tricalcium phosphate and hydroxyapatite embedded in fibrin were assessed. CONCLUSIONS In conclusion bone substitutes can serve as carriers for PHD inhibitors that maintain their capacity to provoke a pro-angiogenic response in vitro. These findings provide the basis for preclinical studies to evaluate if this release kinetic can stimulate periodontal regeneration.

L-mimosine and dimethyloxaloylglycine decrease plasminogen activation in periodontal fibroblasts

BACKGROUND The use of prolyl hydroxylase inhibitors such as l-mimosine (L-MIM) and dimethyloxaloylglycine (DMOG) to improve angiogenesis is a new approach for periodontal regeneration. In addition to exhibiting pro-angiogenic effects, prolyl hydroxylase inhibitors can modulate the plasminogen activator system in cells from non-oral tissues. This study assesses the effect of prolyl hydroxylase inhibitors on plasminogen activation by fibroblasts from the periodontium. METHODS Gingival and periodontal ligament fibroblasts were incubated with L-MIM and DMOG. To investigate whether prolyl hydroxylase inhibitors modulate the net plasminogen activation, kinetic assays were performed with and without interleukin (IL)-1. Moreover, plasminogen activators and the respective inhibitors were analyzed by casein zymography, immune assays, and quantitative polymerase chain reaction. RESULTS The kinetic assay showed that L-MIM and DMOG reduced plasminogen activation under basal and IL-1-stimulated conditions. Casein zymography revealed that the effect of L-MIM involves a decrease in urokinase-type plasminogen activator activity. In agreement with these findings, reduced levels of urokinase-type plasminogen activator and elevated levels of plasminogen activator inhibitor 1 were observed. CONCLUSION L-MIM and DMOG can reduce plasminogen activation by fibroblasts from the gingiva and the periodontal ligament under basal conditions and in the presence of an inflammatory cytokine.

Dimethyloxalylglycine lyophilized onto bone substitutes increase vessel area in rat calvarial defects.

AIM Pharmacological inhibitors of prolyl hydroxylases, also termed hypoxia-mimetic agents (HMAs), when repeatedly injected can support angiogenesis and bone regeneration. However, the possible role of HMA loaded onto bone substitutes to support angiogenesis and bone regeneration under diabetic condition is unknown. The capacity of HMA loaded onto deproteinized bovine bone mineral (DBBM) to support angiogenesis and bone formation was examined in diabetic Wistar rats. METHODS Diabetes was induced by intraperitoneal injection of streptozotocin. The HMA dimethyloxalylglycine (DMOG) and desferrioxamine (DFO) were lyophilized onto DBBM. Calvarial defects were created with a trephine drill and filled with the respective bone substitutes. After 4 weeks of healing, the animals were subjected to histological and histomorphometric analysis. RESULTS In this report, we provide evidence that DMOG loaded onto DBBM can support angiogenesis in vivo. Specifically, we show that DMOG increased the vessel area in the defect site to 2.4% ± 1.3% compared with controls 1.1% ± 0.48% (P = 0.012). There was a trend toward an increased vessel number in the defect site with 38.6 ± 17.4 and 31.0 ± 10.3 in the DMOG and the control group (P = 0.231). The increase in angiogenesis, however, did not translate into enhanced bone formation in the defect area with 9.2% ± 7.1% and 8.4% ± 5.6% in DMOG and control group, respectively. No significant changes were caused by DFO. CONCLUSIONS The results suggest that DMOG loaded onto DBBM can support angiogenesis, but bone formation does not increase accordingly in a type 1 diabetic rat calvarial defect model at the indicated time point.

L-mimosine increases the production of vascular endothelial growth factor in human tooth slice organ culture model.

AIM To assess the pro-angiogenic and pro-inflammatory capacity of the dentine-pulp complex in response to the prolyl hydroxylase inhibitor L-mimosine in a tooth slice organ culture model. METHODOLOGY Human teeth were sectioned transversely into 600-μm-thick slices and cultured in medium supplemented with serum and antibiotics. Then, pulps were stimulated for 48 h with L-mimosine. Pulps were subjected to viability measurements based on formazan formation in MTT assays. In addition, histological evaluation of pulps was performed based on haematoxylin and eosin staining. Culture supernatants were subjected to immunoassays for vascular endothelial growth factor (VEGF) to determine the pro-angiogenic capacity and to immunoassays for interleukin (IL)-6 and IL-8 to assess the pro-inflammatory response. Interleukin-1 served as pro-inflammatory control. Echinomycin was used to inhibit hypoxia-inducible factor-1 (HIF-1) alpha activity. Data were analysed using Student's t-test and Mann-Whitney U test. RESULTS Pulps within tooth slices remained vital upon L-mimosine stimulation as indicated by formazan formation and histological evaluation. L-mimosine increased VEGF production when normalized to formazan formation in the pulp tissue of the tooth slices (P < 0.05). This effect on VEGF was reduced by echinomycin (P < 0.01). Changes in normalized IL-6 and IL-8 levels upon treatment with L-mimosine did not reach the level of significance (P > 0.05), whilst treatment with IL-1, which served as positive control, increased IL-6 (P < 0.05) and IL-8 levels (P < 0.05). CONCLUSIONS The prolyl hydroxylase inhibitor L-mimosine increased VEGF production via HIF-1 alpha in the tooth slice organ culture model whilst inducing no prominent increase in IL-6 and IL-8. Pre-clinical studies will reveal if these in vitro effects translate into dental pulp regeneration.