R. A. Canuto

Glutathione-S-transferase, alcohol dehydrogenase and aldehyde reductase activities during diethylnitrosamine-carcinogenesis in rat liver

Several enzymes metabolize the toxic aldehydes produced during lipid peroxidation, such as 4-hydroxynonenal. During carcinogenesis induced by diethylnitrosamine in rat liver, an increase in aldehyde dehydrogenase, in comparison with normal liver, has already been shown. This paper demonstrates that, although to a lesser extent than aldehyde dehydrogenase, aldehyde reductase and glutathione-S-transferase also increase during carcinogenesis. Of the latter two enzymes, aldehyde reductase increases more markedly in a progressive fashion during the months of development of nodules and hepatoma. The increase of enzymes able to metabolize 4-hydroxynonenal, as well as other aldehydes, is certainly important in protecting tumour cells against cytotoxic effect of aldehydes.

Hydroxyapatite paste Ostim®, without elevation of full‐thickness flaps, improves alveolar healing stimulating BMP‐ and VEGF‐mediated signal pathways: an experimental study in humans

OBJECTIVE Tooth extraction is considered as the starting point of jaw atrophy via osteoclast activity stimulation. The maintenance of dental alveolar bone depends on surgery procedure and use of materials to maintain prior space favoring bone regeneration. Among substitutes used in dentistry to fill bone defects, Ostim-Pastes (Ostim) is a nanocrystalline paste tested for treatment of severe clinical conditions. This research first investigated the effect of Ostim on alveolar healing, comparing in the same healthy subjects, an Ostim-filled socket with a not-filled one. Moreover, it also proposed a new surgical protocol for the post-extractive socket treatment using the graft materials without elevation of full-thickness flaps. MATERIAL AND METHODS Fourteen patients were enrolled to bilateral maxillary or mandibular extraction that was performed without elevation of full-thickness flaps. In each patient, one socket was filled using Ostim, and the other one was allowed to undergo natural healing. No suture was carried out. Clinical and biologic parameters were screened at 1, 7, and 14 days. RESULTS Obtained results evidenced that nanocrystalline hydroxyapatite supports bone regeneration, increasing the synthesis of pro-osteogenic factors as bone morphogenetics protein (BMP)-4, BMP-7, alkaline phosphatase, and osteocalcin. Moreover, filling post-extractive socket with nanocrystalline hydroxyapatite paste leads to a complete epithelialization already at 7 days after extraction, despite the fact that the teeth were extracted without elevation of full-thickness flaps . The improved epithelialization is mediated by increased vascular endothelial growth factor (VEGF) expression. No significant change was observed in inflammatory parameters, with exception of an early and transient IL-1β induction, that could trigger and improve alveolar healing. CONCLUSIONS Clinical and biomolecular observations of this explorative study evidenced that nanocrystalline hydroxyapatite improves alveolar socket healing, increasing angiogenesis, epithelialization, and osteogenesis, also in absence of elevation of full-thickness flaps.

Changes of CYP1A1, GST, and ALDH3 enzymes in hepatoma cell lines undergoing enhanced lipid peroxidation

Hepatoma cells show alterations in the response to oxidative stress (decreased lipid peroxidation) and in xenobiotic metabolism enzymes (decreased P450, increased GST and ALDH3). This study examined the effect of lipid peroxidation on the expression of the above enzymes in two rat hepatoma cell lines (MH(1)C(1) and 7777). To induce oxidative stress, cells were exposed to arachidonic acid (to increase lipid peroxidation substrate) and/or to beta-naphthoflavone (to increase CYP450), and treated with one dose of iron/histidine. The cells, that were still viable after the challenge, were refed with the culture medium and CYP1A1, GST, and ALDH3 enzymes monitored for 1, 6, 12, and 24 h. Treatments that increased markers indicative of lipid peroxidation are associated with a decrease in enzyme activities, which was permanent for CYP1A1 and transient for the other enzymes. We speculate from these data that aldehydic byproducts of lipid peroxidation may be responsible for these effects. Thus, restoration of lipid peroxidation in hepatoma cells seems to induce a rapid adaptation to oxidative stress, which is achieved by a simultaneous decrease of reactive oxygen species production and an increase in the two main enzymes involved in the removal of the aldehydic products of lipid peroxidation.

Metabolism of 4-Hydroxynonenal in Hepatoma Cell Lines

Peroxidation of membrane lipids is thought be a dynamic process which is ongoing in virtually all cells. Under normal conditions, cellular lipid peroxidation is well regulated and, as noted in a recent review (Esterbauer. et al. , 1990), is always associated with the formation of numerous and chemically diverse aldehydic products. Malondialdehyde (MDA) and trans-4-hydroxy-2-nonenal (HNE) are classified as major products of lipid peroxidation since they are present in the greatest quantities during peroxidation of cellular membrane lipids while trans-2-hexenal, acrolein and crotonaldehdye are representative of minor products of lipid peroxidation thought to be formed in significantly smaller quantities.

Comparative evaluation of cytotoxicity and metabolism of four aldehydes in two hepatoma cell lines

The metabolism of acetaldehyde (ACA), benzaldehyde (BA), propionaldehyde (PA) and valeraldehyde (VA) has been studied in two hepatoma cell lines, the rat HTC and mouse Hepa 1c1c7 cells. The cytotoxicity of the four aldehydes to these two cell lines has been compared. The end-points for evaluating cytotoxicity were 1) total macromolecular content (TMC) of confluent cultures, and 2) colony forming ability of dividing cells. These two assay systems had different sensitivities for the toxicity of aldehydes, probably due to different numbers of target cells. The activities of aldehyde dehydrogenases (NAD- and NADP-dependent, ALDH), alcohol dehydrogenase and aldehyde reductase were markedly greater in the HTC cell line compared to the Hepa 1c1c7 cell line, especially with BA as substrate. The cytotoxicities of aldehydes were generally stronger in the HTC cell line than in the Hepa 1c1c7 cell line; with the CF test. Particularly, BA was highly toxic to the HTC cells, which possessed the highest ALDH levels. Moreover, the treatment with (diethylamino)benzaldehyde, an ALDH inhibitor, completely abolished the toxicity of BA. Taken together, all these findings suggest that several cell lines expressing different aldehyde metabolizing activities could be used especially in the pre-screening phase to distinguish the metabolism-dependent cytotoxic effects from the metabolism independent effects.

A Report on a 7-year Follow up of the Surgical Management with PRGF- ENDORET of Oncologic Patients Affected by Intravenous BisphosphonateRelated Osteonecrosis of the Jaw

BRONJ is an important complication in bisphosphonate therapy that dramatically influences the patient’s quality of life and requires immediate intervention. The situation is worsened by the fact that its management is still an open issue, with no definitive standard of care. The aim of this paper is to present the short, middle and long term (7 years) results of surgical treatment of 32 BRONJ cases involving the use of PRGF®-ENDORET®. No intraoperative complications were observed; the short period freedom from light complications was 84.4%, with complete remittal in a few weeks; after 7 years the freedom from complications and need of re intervention is 100%. The freedom from onset of a new BRONJ on untreated sites was 100% up to 4 years after which decreased to 82%. The surgical procedure with the applications of platelet-enriched preparations can thus be considered favorably tested, having led to rapid osseous remodeling and to a satisfactory closure of the mucosa thus shielding the area from infection and reducing symptomatology.

Susceptibility to Lipid Peroxidation of Rat Hepatoma Cells Enriched with Arachidonic Acid

Hepatomas are less susceptible to lipid peroxidation than normal hepatocytes. The lack of peroxidizable substrates in their membranes is one important hypothesized cause for low peroxidation. By enriching AH-130 hepatoma cells with arachidonic acid for 24 hr in vitro, microsomes enriched in their percentage content of arachidonic acid were obtained. These microsomes showed an increase of lipid peroxidation, evaluated as TBARS production, parallel to their increased arachidonic acid content. The highest TBARS production was obtained when lipid peroxidation was stimulated by ascorbate/FeSO4. Microsomes, isolated from hepatoma cells enriched with 0.5 mM arachidonic acid, and with the same percentage content of arachidonic acid as the hepatocyte microsomes, showed a higher TBARS production than did the hepatocyte microsomes; this despite the fact that the decrease of polyunsaturated fatty acids during the peroxidation process was higher for hepatocyte microsomes than for hepatoma microsomes.

Preventive oral surgery before bisphosphonate administration to reduce osteonecrosis of the jaws

OBJECTIVES The intravenous injection of bisphosphonates, currently used for osteoporosis, myeloma, or bone metastases, can cause ONJ especially in consequence of trauma. To avoid trauma during bisphosphonate treatment, preventive oral surgery is recommended. The research aimed to evidence whether inflammatory and osteoclastogenic factors are not induced in oral mucosa after bisphosphonate treatment in patients receiving oral preventive surgery procedure and whether proliferation factors are not inhibited. PATIENTS AND METHODS Specimens of oral mucosa were removed from healthy subjects and from patients undergoing preventive oral surgery before bisphosphonate treatment. The expression of cytokines and factors involved in osteoclast activity, cell proliferation, and angiogenesis were examined. RESULTS Cytokines and RANK-L levels decreased significantly in mucosa from patients undergoing preventive oral surgery procedure before bisphosphonate treatment in comparison with their levels at the beginning of procedure and also in comparison with the level in patients treated only with bisphosphonates and not developing ONJ; conversely, osteoprotegerin and hydroxymethylglutaryl coenzyme A reductase significantly increased or not changed. CONCLUSIONS The results suggest that preventive oral surgery could be able to prevent ONJ due to bisphosphonate treatment: The mucosa is not stimulated by bisphosphonates to cause ONJ, as bisphosphonates are probably not released from the bone.