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Biomedical subjects

Bruno Baggio

Publications and source records attributed to Bruno Baggio.

17 recordsLinked to original sources
PubMed2006

Arachidonic acid influences intracellular calcium handling in human osteoblasts.

The effect of arachidonic acid (AA) on intracellular Ca(2+) concentration ([Ca(2+)]i) in human osteoblasts MG63 was studied. AA caused a concentration-dependent increase in [Ca(2+)]i, mainly due to inward Ca(2+) transport from extracellular environment. Moreover, AA in Ca(2+) -free medium produced a small, transient increase of [Ca(2+)]i, indicating that AA may also trigger Ca(2+) release from intracellular stores. Because the [Ca(2+)]i response to AA was inhibited by the cyclooxygenase (COX) inhibitor indomethacin, we tested the effect of prostaglandins (PGs), products of COX pathway. PGs E1 and E2 caused an increase in [Ca(2+)]i, which, however, was far lower than that obtained with AA. The [Ca(2+)]i response to AA was not inhibited by nifedipine, suggesting that AA did not activate a voltage-dependent Ca(2+) channel. Our results indicate that AA could modulate [Ca(2+)]i in MG63 human osteoblasts, where it may influence Ca(2+) transport across both plasma and endoplasmic membranes. Furthermore, they suggest that osteoblast activity may be modulated by AA.

Alprostadil↗
PubMed2005

Relationship between plasma phospholipid polyunsaturated fatty acid composition and bone disease in renal transplantation.

To investigate the relationship between polyunsaturated fatty acid (PUFA) and bone metabolism in renal transplant patients, plasma phospholipid (PP) PUFA levels, biochemical markers of bone turnover and bone mineral density (BMD) were determined in 22 recipients of a first renal allograft at baseline and after a mean 24.4 month follow-up. A significant increase in PP n-3 PUFA content, in the [n-3 PUFA/ arachidonic acid] ratio and in BMD values was observed, as well as a close correlation between the increase in PP n-3 PUFA content and femoral neck BMD. Multivariate regression analysis showed that BMD improvement was positively related to PP n-3 PUFA variation and baseline PP eicosapentaenoic acid levels, and negatively to PP arachidonic acid modification. Tacrolimus- versus cyclosporine-treated patients demonstrated a significant increase in femoral neck BMD and PP n-3 PUFA content. This is the first longitudinal study showing a link between PP-PUFA composition and bone disease in renal transplantation.

Adult↗
PubMed2005

Specific effect of arachidonic acid on inducible nitric oxide synthase mRNA expression in human osteoblastic cells.

A specific modulatory effect of PUFAs (polyunsaturated fatty acids) on gene expression of some cytokines involved in bone remodelling has been reported previously. In particular, although a direct action of AA (arachidonic acid) on bone cytokine gene expression has been shown in human osteoblastic cells, OA (oleic acid) and EPA (eicosapentaenoic acid) were ineffective. Since the NO (nitric oxide) system has also been shown to have an important modulatory activity on osteoblasts, osteoclasts and bone metabolism, in the present study we have investigated the effects of PUFAs on iNOS (inducible NO synthase) gene expression in a human osteoblast-like cell line. AA induced a significant increase in iNOS mRNA expression, whereas EPA and OA had no stimulatory effects but instead caused a significant inhibition of AA-induced iNOS gene expression. Blocking of the COX (cyclo-oxygenase) pathway did not inhibit AA-induced iNOS expression. AA action was inhibited instead by the addition of calphostin C and genistein, inhibitors of PKC (protein kinase C) and tyrosine kinases respectively. Experiments performed with specific anti-cytokine antibodies showed a significant decrease in iNOS expression in AA-treated osteoblastic cells, suggesting that both cytokine-dependent and -independent mechanisms account for the effects of AA on iNOS gene expression. In conclusion, our investigation clearly shows specific effects of PUFAs on iNOS expression in human osteoblast-like cells with a cytokine-dependent and -independent mechanism. These results might have clinical relevance and are of interest for understanding the reported beneficial effects of dietary PUFA manipulation on the prevention and/or treatment of primary and secondary bone disease.

Anti-Inflammatory Agents↗
PubMed2005

Fatty acids and idiopathic calcium nephrolithiasis.

Clinical and experimental investigations seem to underline the important role of fatty acids in the pathogenesis of hypercalciuria, a well-known risk factor for lithogenesis. To evaluate the relationships between the previously reported increase in plasma phospholipid arachidonic acid level and the factors responsible for calcium metabolism in idiopathic calcium nephrolithiasis, a best-fit model was constructed. This new statistical application shows a causal relationship between plasma phospholipid arachidonic acid content, intestinal calcium absorption, biochemical markers of bone turnover, urinary calcium excretion and bone mineral density at the lumbar spine. This model suggests that a defect in the phospholipid fatty acid composition could represent the primary event responsible for the mosaic of metabolic and clinical alterations that are distinctive features of renal stone formers, such as kidney, intestine, and bone calcium metabolism, and several forms of idiopathic hypercalciuria.

Animals↗
PubMed2004

Quantitave and qualitative changes in vascular endothelial growth factor gene expression in glomeruli of patients with type 2 diabetes.

OBJECTIVE: Vascular endothelial growth factor (VEGF) exists in three main splice variants, characterized by 121, 165 and 189 amino acids (VEGF 121, VEGF 165 and VEGF 189) and acts via two specific receptors: VEGF-R1 or Flt-1 and VEGF-R2 or KDR. VEGF plays an important role in the pathogenesis of diabetic retinopathy. This study examined the relationship between VEGF and its isoforms and the severity of diabetic nephropathy in type 2 diabetes. DESIGN: We evaluated the glomerular gene expression of VEGF and its receptors and studied the relationships with renal functional and structural parameters in type 2 diabetic patients. METHODS: Glomeruli from 17 kidney biopsies were microdissected; 14 out of 17 biopsies were also subjected to electron microscopic morphometric analysis to estimate glomerular structural parameters. VEGF mRNA was studied by comparative kinetic RT-PCR and real-time RT-PCR in order to identify the three different isoforms and to quantify VEGF, VEGF-R1 and VEGF-R2 mRNA levels. RESULTS: (i) Glomerular VEGF mRNA levels were inversely related to albumin excretion rate (r=-0.66, P=0.004); (ii) both the degree of mesangial and mesangial matrix expansion were inversely related to VEGF 165 mRNA levels (r=-0.73, P=0.005 and r=-0.64, P=0.017), and directly to VEGF 121 mRNA levels (r=0.74, P=0.003 and r=0.73, P=0.004); and (iii) VEGF and VEGF-R2 mRNA levels were directly related (r=0.62, P=0.033). CONCLUSIONS: These findings suggested that quantitative and qualitative changes in VEGF expression are present in type 2 diabetic patients with nephropathy and might be involved in the pathogenesis and progression of diabetic glomerulopathy.

Aged↗
PubMed2003

Arachidonic acid-induced IL-6 expression is mediated by PKC alpha activation in osteoblastic cells.

There are several pieces of evidence supporting the important role that essential fatty acids (EFAs) and their metabolites play in regulating calcium and bone metabolism, and their relevance to the pathobiology of bone disease, with particular reference to modulating effects on cytokines. We found that arachidonic acid (AA) triggers a cell signal in osteoblasts and leads to the expression of IL-6. To explore the biochemical pathways involved in AA induction of cytokine gene expression, we evaluated the potential protein kinase C (PKC) dependent mechanism accounting for the AA effect on IL-6 gene expression. The osteoblast-like cell line MG-63 was pretreated with calphostin C, a PKC inhibitor, or phorbol 12-myristate 13-acetate (PMA) for an extended period, a condition which causes PKC downregulation, and subsequently with AA. After these treatments, IL-6 gene expression was no longer evident. We also showed that PKC and, in particular, PKC alpha, which are both recruited to the particulate fraction, undergo proteolysis and autophosphorylation; all of these steps are required for PKC activation and, subsequently, for AA-induced signaling. It is interesting that other unsaturated fatty acids, such as oleic acid (OA) or eicosapentaenoic acid (EPA), are unable to induce either PKC activation or IL-6 gene expression.

Arachidonic Acid↗
PubMed2002

Band 3 is an anchor protein and a target for SHP-2 tyrosine phosphatase in human erythrocytes.

Tyr phosphorylation of the multifunctional transmembrane protein band 3 has been implicated in several erythrocyte functions and disorders. We previously demonstrated that pervanadate treatment of human erythrocytes induces band-3 Tyr phosphorylation, which is catalyzed by the sequential action of tyrosine kinase Syk and tyrosine kinase(s) belonging to the Src family. In this study, we show that Tyr phosphorylation of band 3, elicited by pervanadate, N-ethylmaleimide, or diamide, greatly increases band-3 interaction with the tyrosine phosphatase SHP-2 in parallel with the translocation of SHP-2 to erythrocyte membranes. These events seem to be mediated by Src-like catalyzed phosphorylation of band 3 because both SHP-2 translocation to cellular membranes and its interaction with Tyr-phosphorylated protein are greatly counteracted by PP2, a specific inhibitor of Src kinases. Binding-competition experiments demonstrate that SHP-2 recruitment to band 3 occurs via its SH2 domain(s). In particular, our data support the view that SHP-2 docks specifically with P-Y359 of band 3. Experiments performed with intact erythrocytes in the presence of the SHP-2 inhibitor calpeptin suggest that, once recruited to Tyr-phosphorylated band 3, the tyrosine phosphatase dephosphorylates the protein. P-Y8, 21, and 904 are the residues affected by SHP-2, as judged by (32)P-peptide mapping of band 3 digested with trypsin. These results indicate that in treated erythrocytes, recruitment of cytosolic SHP-2 to band 3 is a prerequisite for the subsequent dephosphorylation of the transmembrane protein.

Anion Exchange Protein 1, Erythrocyte↗
PubMed2002

Effects of cigarette smoking on glomerular structure and function in type 2 diabetic patients.

Prospective studies have established smoking as an independent risk factor for diabetic nephropathy, suggesting an adverse effect of smoking on glomerular structure and function. To test this hypothesis, this study evaluated GFR, metabolic profile, and smoking habits in 96 patients with type 2 diabetes and abnormal albumin excretion rate (AER). All patients underwent percutaneous kidney biopsy: mesangial fractional volume [Vv (mes/glom)] and glomerular basement membrane (GBM) width were estimated by electron microscopic morphometric analysis; interstitial fibrosis was estimated semiquantitatively by light microscopy. Forty-eight patients were smokers. Compared with nonsmokers, smokers had higher values of HbA(1c) (P = 0.002), AER (P = 0.026), GFR (P = 0.004), and GBM width (P = 0.002); moreover, GFR was higher in current smokers than in former smokers (P = 0.001), and GBM width was related to heavy smoking (F = 5.4; P = 0.006). Multiple linear regression analyses revealed that HbA(1c) was associated with fasting blood glucose (beta coef = 0.52; P < 0.001), smoking habit (beta coef = 0.31; P < 0.001), insulin therapy (beta coef = 0.22; P = 0.012), and male gender (beta coef = -0.20; P = 0.020); AER was related to Vv (mes/glom) (beta coef = 0.32; P = 0.003), GBM width (beta coef = 0.28; P = 0.016), and interaction between smoking habit and HbA(1c) (beta coef = 0.24; P = 0.040). GFR was negatively correlated with Vv (mes/glom) (beta coef = -0.57; P < 0.001) and age (beta coef = -0.29; P = 0.001) and positively correlated with GBM width (beta coef = 0.27; P = 0.012), heavy current smoking (beta coef = 0.24; P = 0.028), and HbA(1c) (beta coef = 0.28; P = 0.040); GBM width was explained by Vv (mes/glom) (beta coef = 0.53; P < 0.001), interaction between heavy smoking and HbA(1c) levels (beta coef = 0.25; P = 0.003), and diabetes duration (beta coef = 0.23; P = 0.010). Smoking habit did not affect the index of interstitial fibrosis. In conclusion, cigarette smoking affects glomerular structure and function in type 2 diabetes and may be an important factor for the onset and progression of diabetic nephropathy.

Albuminuria↗
PubMed2002

Dietary fatty acid supplementation modulates the urinary excretion of calcium and oxalate in the rat. Insight into calcium lithogenesis.

BACKGROUND: An anomalous plasma phospholipid polyunsaturated fatty acid composition has been reported in calcium nephrolithiasis, and was proposed to play a crucial role in the pathogenesis of hypercalciuria and hyperoxaluria, well-known risk factors for lithogenesis. METHODS: To confirm this hypothesis, we administered rats three different diets rich in coconut, soybean and fish oils, and evaluated their effect on plasma urinary calcium and oxalate excretion, since the quality of fatty acids represents an important factor able to influence the activity of delta-6-desaturase, the rate-limiting enzyme in the biosynthetic pathway of highly unsaturated fatty acids. RESULTS: In comparison with coconut and fish oil, dietary supplementation with soybean oil increased plasma phospholipid arachidonic acid and serum 1,25-vitamin D(3) values, as well as renal tissue calcium content and urinary excretion of sodium, oxalate and calcium. CONCLUSIONS: Our findings demonstrate that the quality of fatty acids may modify the urine excretion of calcium and oxalate, confirming our previous hypothesis of a pathogenetic link between cellular membrane phospholipid polyunsaturated fatty acid composition and calcium nephrolithiasis. In addition, our study provides new insights into the relationship between dietary, environmental factors and renal stone disease.

Animals↗
PubMed2002

Nitric oxide modulation of renal and cardiac hemodynamics in type 2 diabetes.

OBJECTIVE: To evaluate endothelial function in type 2 diabetic patients with and without diabetic nephropathy. METHODS: We studied the effects of systemic infusion of the nitric oxide (NO) synthase inhibitor NG-monomethyl-l-arginine (L-NMMA) on cardiovascular and renal hemodynamics in six type 2 diabetic patients with microalbuminuria (D2-MA), six type 2 diabetic patients with normoalbuminuria (D2-NA) and five control subjects. Both type 2 diabetic patients and control subjects had mild arterial hypertension. RESULTS: L-NMMA infusion decreased the cardiac index in all groups. A reduction in glomerular filtration rate (GFR) and an increase in filtration fraction were observed only in controls. Renal plasma flow decreased in controls and D2-NA patients and renal vascular resistance increased in all groups. CONCLUSIONS: The effect of L-NMMA on cardiac output was similar in controls and type 2 diabetic patients with and without diabetic nephropathy. In contrast, the effect on GFR was impaired in both diabetic groups, suggesting that glomerular NO homeostasis is altered in type 2 diabetes. Moreover the discrepancy, in diabetic patients, between cardiac and renal effects during L-NMMA infusion suggests that the modulation of glomerular hemodynamics is independent from NO-regulated cardiac output.

Adult↗
PubMed2002

Fatty acids and cytokine mRNA expression in human osteoblastic cells: a specific effect of arachidonic acid.

Epidemiological, clinical and experimental evidence suggests that fatty acids have a modulatory effect on bone metabolism in animals and humans. To investigate this hypothesis, we evaluated the effects of three different fatty acids, arachidonic acid (AA), eicosapentaenoic acid (EPA) and oleic acid (OA), on the expression of cytokines involved in bone remodelling. Cytokine mRNAs in the human osteoblast-like cell line MG-63 were quantified by reverse transcription-PCR. AA induced increased expression of interleukin-1alpha, interleukin-1beta, tumour necrosis factor-alpha and macrophage colony-stimulating factor mRNAs in a time- and dose-dependent manner. EPA and OA had no stimulatory effects, but instead caused a significant inhibition of AA-induced cytokine mRNA expression. Cell treatment with calphostin C, an inhibitor of protein kinase C (PKC), and cellular PKC down-regulation experiments independently resulted in significant inhibition of AA-induced cytokine expression, suggesting that a PKC-dependent mechanism accounts for the effects of AA on cytokine production. In conclusion, our study demonstrates specific effects of fatty acids on cytokine gene expression in human osteoblast-like cells. The clinical relevance of our findings requires further investigation.

Arachidonic Acid↗
PubMed2000

Glycosaminoglycan therapy prevents TGF-beta1 overexpression and pathologic changes in renal tissue of long-term diabetic rats.

Chronic induction of the prosclerotic cytokine transforming growth factor beta (TGF-beta) has been implicated in the pathogenesis of diabetic nephropathy. In a rat model of diabetes mellitus-induced glomerulosclerosis, daily administration of a modified heparin (mH) glycosaminoglycan (GAG) preparation with low anticoagulant activity prevented glomerular and tubular matrix accumulation, as well as overexpression of TGF-beta1 mRNA and albuminuria, without obvious side effects. To elucidate the molecular mechanisms of GAG/mH inhibitory actions on TGF-beta1, studies using cultured mesangial cells were also performed. In these cells, high glucose-induced, dose-dependent increases in TGF-beta1 mRNA and bioactive TGF-beta protein expression were inhibited by GAG/mH treatment, whereas basal TGF-beta1 expression was not affected. Both the heparin-derived GAG and dermatan sulfate were effective, indicating that the heparin chemical structure is not necessary for inhibitory activity. Coincubation of GAG with active TGF-beta1 demonstrated no inhibitory effect on TGF-beta1 bioactivity, excluding a neutralizing effect of GAG on TGF-beta1 a the protein level. Furthermore, it was demonstrated that GAG inhibited phorbol myristate acetate-induced translocation of protein kinase C-alpha (PKC-alpha) and -beta1 and activation of PKC-alpha, as well as high glucose-induced activation of PKC-alpha. These results suggest that GAG inhibit TGF-beta1 overexpression at the transcriptional level, possibly via inhibition of high glucose-activated PKC. The findings indicate the potential of GAG therapy for the prevention of diabetic glomerulosclerosis by the inhibition of chronic disease-induced TGF-beta1 mRNA overexpression.

Animals↗
PubMedDate not supplied

Band 3 tyr-phosphorylation in normal and glucose-6-phospate dehydrogenase-deficient human erythrocytes.

Haemolysis is usually episodic in glucose-6-phosphate dehydrogenase (G6PD) deficiency, often triggered by a period of oxidative stress. In the present work, we investigate a possible biochemical mechanism underlying the enhanced susceptibility of G6PD deficient red blood cells (RBC) to oxidative stress. We analysed eight male subjects with Mediterranean glucose-6P-dehydrogenase deficiency (G6PDd), class II, for their ability in phosphorylating erythrocyte membrane band 3 following oxidative and osmotic stress. Our findings show that this sensitivity is connected to an early membrane band 3 Tyr-phosphorylation in the presence of diamide. However, since both Syk, and Lyn kinases, and SHP-2 phosphatase, mostly implicated in the band 3 P-Tyr level regulation, are alike in content and activity in normal and patient erythrocytes, an alteration in the membrane organization is likely the cause of the anomalous response to the oxidant. We report, in fact, that hypertonic-induced morphological change in G6PDd erythrocyte induces a higher membrane band 3 Tyr-phosphorylation, suggesting a pre-existing membrane alteration, likely due to the chronic lowering of the redox systems in patients. We also report that 1-chloro-2,4-dinitrobenzene-pre-treatment of normal red cells can alter the normal protein-protein and protein-membrane interaction under hypertonic rather than oxidative stress, thus partially resembling the response in patients, and that RBC may utilize a wider range of redox defence, under oxidative conditions, including, but not exclusively, NADPH and glutathione. On the whole, these results would encourage a different approach to the evaluation of the effects of pharmacological administration to patients, giving more attention to the possible drug-induced membrane alteration evidenced by the abnormal band 3 Tyr-phosphorylation.

Androsterone↗
PubMedDate not supplied

Fatty acids, calcium and bone metabolism.

Epidemiological, clinical and experimental evidence suggests that fatty acids may have an effect (due to their chemical structure) on calcium metabolism in animals and man. Fatty acid deficiency in animals can lead to a loss of bone calcium and matrix, resulting in marked bone demineralization, and treatment with a mixture of omega-3 and omega-6 polyunsaturated fatty acids can induce significant reduction in some biochemical markers of bone reabsorption. A relationship, between phospholipid fatty acid content, calcium-regulating hormones and intestinal, renal, and bone calcium metabolism alterations, has been reported in patients with renal stones and hypercalciuria. Recent studies have shown specific effects of fatty acids on the gene expression of some bone cytokines. Fatty acids might be involved in calcium metabolism influencing cellular calcium ion transport directly, as second messengers, or generating, through the cyclooxygenase pathway, potential biological mediators which have complex effects on bone remodeling. Experimental and clinical documentation of the specific and indirect effects of fatty acids on calcium and bone metabolism could open up new and interesting clinical prospects.

Animals↗