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Effect of aluminum toxicity on biomechanical bone quality in post-hypoxic immature rats
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Abstracts / Bone 45 (2009) S148–S157
were −0.49, −0.32, and 0.26 for the whole population (p < 0.001). In G1 the correlation was significant (negative) for BMD and BMC but not for A, while in G2 the correlation was significant for BMD (negative) and A (positive) but not for BMC. The regression coefficient (RC) of BMD was explained in 92% by decrease in BMC in G1 and in 75% by increase in A in G2. RC of BMD in G1 (−0.0076) is greater than in G2 (− 0.004) in absolute values. In a multivariate analysis including height and weight, age was maintained significant in WP and G2. Mean differences between G1 and G2 for DMO (0.897 ± 0.11 vs. 0.80 ± 0.10), CMO (4.2 ± 0.7 vs. 3.8 ± 0.5), and A (4.69 ± 0.3 vs. 4.81 ± 0.3) were significant (p < 0.01). Conclusions: BMD of FN decreases with age after menopause. Loss of bone mass could determine this reduction during the first years, while increase in area could be responsible later. doi:10.1016/j.bone.2009.08.027
Effect of aluminum toxicity on biomechanical bone quality in post-hypoxic immature rats G. Dmytrenko, M.I. Conti, M.I. Olivera, C. Bozzini, G.M. Champin, M.P. Martínez Department of Physiology, Faculty of Odontology, University of Buenos Aires, Argentina. Aluminum (Al) is a nonessential element to which humans are exposed. Chronic administration induces a negative effect on bone tissue, affecting collagen synthesis and matrix mineralization. Its toxic effects are cumulative. Hypobaric hypoxia (HX) induces stress erythropoiesis leading to hypertrophy of the erythropoietic marrow and may affect bone. The aim of this investigation is to evaluate the chronic effect of aluminum on the architectural properties and the biomechanical quality of femoral diaphysis under hypoxic conditions. Female Sprague-Dawley rats, aged 21 days, received IP doses of 27 mg/kg of elemental Al, as Al(OH)3, 3 times a week, during 3 months. Control rats were injected with vehicle (20% glycerol). Half of the animals of each group (n = 9) were exposed to simulated high altitude (SHA, 506.5 mbar). Morphometric femur studies were performed measuring the distance between stable anatomical points. Biomechanical performance was estimated by the three-point yielding method. Al administration did not affect general or femoral anthropometries although it significantly depressed structural strength (load capacity parameters). The indicators of bone material intrinsic properties, elastic modulus and stress at the yielding point, were significantly reduced either by Al or by HX with no additive effect in the AlHX group (p < 0.01). Results suggest that chronic intoxication with Al or exposure to SHA induced negative effects on bone material quality but significantly enhanced the moment of inertia. This is presumably an adaptive response to compensate the impaired diaphyseal strength. However, no additive effects were observed when both treatments were assayed together. UBACyT O407. doi:10.1016/j.bone.2009.08.028
Regulation of endothelial cell function by phytoestrogens M. Sandoval, P. Cutini, M.B. Rauschemberger, V. Massheimer Cátedra Bioquímica Clínica II, BByF-UNS; UTN-FRBB; CONICET, Argentina Epidemiological studies propose that phytoestrogens rich diet may attenuate bone loss in post-menopausal women. In this study, we evaluated whether the isoflavone genistein (Gen) would modulate the cellular and molecular events associated with vascular disease. We employed rat endothelial cell (EC) cultures. After
24 hours of treatment, Gen increased DNA synthesis in synchronized EC (70.52 ± 6.77 vs 41.24 ± 4.49 cpm103/mg prot, Gen vs Control). This action was prevented by the presence of estrogen receptor antagonist ICI 182780 or l-NAME (nitric oxide synthase inhibitor), suggesting that the stimulation of EC growth involves ER and nitric oxide production. To study Gen's effect on leukocyte adhesion to EC, isolated monocytes were added to EC previously exposed to Gen or to bacterial lipopolysaccharide (LPS). Maximal adhesion was detected in LPS group, meanwhile Gen prevented monocyte adhesion (267 ± 36, 417 ± 21.5, 160 ± 9.8 cells/μl for control, LPS, and Gen, p < 0.01). Since leukocyte adhesion depends on cellular adhesion molecules (CAMs) expression, we evaluated Gen regulation of CAM expression using RTPCR. VCAM-1, P-selectine, and E-selectine mRNA levels were diminished in cells exposed to Gen, compared to control or LPS group, suggesting that the inhibition of monocyte adhesion would be due to Gen's effect on CAM–RNA expression. To investigate the action of the Gen on EC apoptosis (DNA laddering) we used H2O2 as an apoptosis inducer. In the presence of H2O2, EC DNA was completely fragmented, but if EC were incubated with Gen 24 hours prior to H2O2 addition, DNA laddering was partially inhibited. In summary, the results obtained shows that Gen stimulates EC proliferation and reduced monocyte adhesion and EC apoptosis induced by cytotoxic agents, suggesting a potential benefit action of the phytoestrogen at the vascular level. doi:10.1016/j.bone.2009.08.029
Melatonin reverses apoptosis through which menadione inhibits intestinal calcium absorption A.R. Carpentieri, A.M. Marchionatti, A.V. Perez, V.A. Centeno, N.G. Tolosa de Talamoni Bioquímica y Biología Molecular, Facultad de Ciencias Médicas, Química y Física Biológicas, Facultad de Odontología, Universidad Nacional de Córdoba, Argentina We have previously demonstrated that menadione (MEN) inhibits intestinal calcium (Ca2+) absorption through the mitochondria apoptotic pathway (BBA, 2008). Afterwards, we have observed that this inhibition could be reversed by melatonin (MEL) administration. The aim of this study was to elucidate the molecular mechanisms of this protection caused by MEL. Four-week-old chicks were divided in four groups: 1) controls, 2) treated i.p. with 2.5 μmol MEN/kg of b.w., 3) treated i.p. with 10 mg MEL/kg of b.w., and 4) treated i.p. with MEL after i.p. MEN administration. Glutathione (GSH) content and the activities of superoxide dismutase (SOD), catalase (CAT), and caspase 3 were measured by spectrophotometric methods. Apoptosis was evaluated by the TUNEL technique and cytochrome c localization. Data indicate that GSH depletion produced by MEN was completely reversed with MEL treatment. The increment in the SOD and CAT activities provoked by MEN was abolished. The release of cytochrome c from mitochondria and the increase in caspase 3 activity, both effects triggered by MEN, returned to the control values after MEL treatment. To conclude, MEL reverses the alteration in the intestinal Ca2+ absorption produced by MEN, counteracting the oxidative stress and the activation of the mitochondrial apoptotic pathway. Therefore, MEL has anti-apoptotic properties that protect the intestine against apoptosis produced by MEN and maybe by other oxidants, which suggests that MEL is a potential drug for reversing the inhibition of the intestinal Ca2+ absorption produced by oxidative stress. Dr. Tolosa de Talamoni and Dr. Carpentieri are Members of the Investigator Career from CONICET. doi:10.1016/j.bone.2009.08.030
Abstracts / Bone 45 (2009) S148–S157
were −0.49, −0.32, and 0.26 for the whole population (p < 0.001). In G1 the correlation was significant (negative) for BMD and BMC but not for A, while in G2 the correlation was significant for BMD (negative) and A (positive) but not for BMC. The regression coefficient (RC) of BMD was explained in 92% by decrease in BMC in G1 and in 75% by increase in A in G2. RC of BMD in G1 (−0.0076) is greater than in G2 (− 0.004) in absolute values. In a multivariate analysis including height and weight, age was maintained significant in WP and G2. Mean differences between G1 and G2 for DMO (0.897 ± 0.11 vs. 0.80 ± 0.10), CMO (4.2 ± 0.7 vs. 3.8 ± 0.5), and A (4.69 ± 0.3 vs. 4.81 ± 0.3) were significant (p < 0.01). Conclusions: BMD of FN decreases with age after menopause. Loss of bone mass could determine this reduction during the first years, while increase in area could be responsible later. doi:10.1016/j.bone.2009.08.027
Effect of aluminum toxicity on biomechanical bone quality in post-hypoxic immature rats G. Dmytrenko, M.I. Conti, M.I. Olivera, C. Bozzini, G.M. Champin, M.P. Martínez Department of Physiology, Faculty of Odontology, University of Buenos Aires, Argentina. Aluminum (Al) is a nonessential element to which humans are exposed. Chronic administration induces a negative effect on bone tissue, affecting collagen synthesis and matrix mineralization. Its toxic effects are cumulative. Hypobaric hypoxia (HX) induces stress erythropoiesis leading to hypertrophy of the erythropoietic marrow and may affect bone. The aim of this investigation is to evaluate the chronic effect of aluminum on the architectural properties and the biomechanical quality of femoral diaphysis under hypoxic conditions. Female Sprague-Dawley rats, aged 21 days, received IP doses of 27 mg/kg of elemental Al, as Al(OH)3, 3 times a week, during 3 months. Control rats were injected with vehicle (20% glycerol). Half of the animals of each group (n = 9) were exposed to simulated high altitude (SHA, 506.5 mbar). Morphometric femur studies were performed measuring the distance between stable anatomical points. Biomechanical performance was estimated by the three-point yielding method. Al administration did not affect general or femoral anthropometries although it significantly depressed structural strength (load capacity parameters). The indicators of bone material intrinsic properties, elastic modulus and stress at the yielding point, were significantly reduced either by Al or by HX with no additive effect in the AlHX group (p < 0.01). Results suggest that chronic intoxication with Al or exposure to SHA induced negative effects on bone material quality but significantly enhanced the moment of inertia. This is presumably an adaptive response to compensate the impaired diaphyseal strength. However, no additive effects were observed when both treatments were assayed together. UBACyT O407. doi:10.1016/j.bone.2009.08.028
Regulation of endothelial cell function by phytoestrogens M. Sandoval, P. Cutini, M.B. Rauschemberger, V. Massheimer Cátedra Bioquímica Clínica II, BByF-UNS; UTN-FRBB; CONICET, Argentina Epidemiological studies propose that phytoestrogens rich diet may attenuate bone loss in post-menopausal women. In this study, we evaluated whether the isoflavone genistein (Gen) would modulate the cellular and molecular events associated with vascular disease. We employed rat endothelial cell (EC) cultures. After
24 hours of treatment, Gen increased DNA synthesis in synchronized EC (70.52 ± 6.77 vs 41.24 ± 4.49 cpm103/mg prot, Gen vs Control). This action was prevented by the presence of estrogen receptor antagonist ICI 182780 or l-NAME (nitric oxide synthase inhibitor), suggesting that the stimulation of EC growth involves ER and nitric oxide production. To study Gen's effect on leukocyte adhesion to EC, isolated monocytes were added to EC previously exposed to Gen or to bacterial lipopolysaccharide (LPS). Maximal adhesion was detected in LPS group, meanwhile Gen prevented monocyte adhesion (267 ± 36, 417 ± 21.5, 160 ± 9.8 cells/μl for control, LPS, and Gen, p < 0.01). Since leukocyte adhesion depends on cellular adhesion molecules (CAMs) expression, we evaluated Gen regulation of CAM expression using RTPCR. VCAM-1, P-selectine, and E-selectine mRNA levels were diminished in cells exposed to Gen, compared to control or LPS group, suggesting that the inhibition of monocyte adhesion would be due to Gen's effect on CAM–RNA expression. To investigate the action of the Gen on EC apoptosis (DNA laddering) we used H2O2 as an apoptosis inducer. In the presence of H2O2, EC DNA was completely fragmented, but if EC were incubated with Gen 24 hours prior to H2O2 addition, DNA laddering was partially inhibited. In summary, the results obtained shows that Gen stimulates EC proliferation and reduced monocyte adhesion and EC apoptosis induced by cytotoxic agents, suggesting a potential benefit action of the phytoestrogen at the vascular level. doi:10.1016/j.bone.2009.08.029
Melatonin reverses apoptosis through which menadione inhibits intestinal calcium absorption A.R. Carpentieri, A.M. Marchionatti, A.V. Perez, V.A. Centeno, N.G. Tolosa de Talamoni Bioquímica y Biología Molecular, Facultad de Ciencias Médicas, Química y Física Biológicas, Facultad de Odontología, Universidad Nacional de Córdoba, Argentina We have previously demonstrated that menadione (MEN) inhibits intestinal calcium (Ca2+) absorption through the mitochondria apoptotic pathway (BBA, 2008). Afterwards, we have observed that this inhibition could be reversed by melatonin (MEL) administration. The aim of this study was to elucidate the molecular mechanisms of this protection caused by MEL. Four-week-old chicks were divided in four groups: 1) controls, 2) treated i.p. with 2.5 μmol MEN/kg of b.w., 3) treated i.p. with 10 mg MEL/kg of b.w., and 4) treated i.p. with MEL after i.p. MEN administration. Glutathione (GSH) content and the activities of superoxide dismutase (SOD), catalase (CAT), and caspase 3 were measured by spectrophotometric methods. Apoptosis was evaluated by the TUNEL technique and cytochrome c localization. Data indicate that GSH depletion produced by MEN was completely reversed with MEL treatment. The increment in the SOD and CAT activities provoked by MEN was abolished. The release of cytochrome c from mitochondria and the increase in caspase 3 activity, both effects triggered by MEN, returned to the control values after MEL treatment. To conclude, MEL reverses the alteration in the intestinal Ca2+ absorption produced by MEN, counteracting the oxidative stress and the activation of the mitochondrial apoptotic pathway. Therefore, MEL has anti-apoptotic properties that protect the intestine against apoptosis produced by MEN and maybe by other oxidants, which suggests that MEL is a potential drug for reversing the inhibition of the intestinal Ca2+ absorption produced by oxidative stress. Dr. Tolosa de Talamoni and Dr. Carpentieri are Members of the Investigator Career from CONICET. doi:10.1016/j.bone.2009.08.030