Biomedical subjects

M Ouardani

Publications and source records attributed to M Ouardani.

3 recordsLinked to original sources

PubMed1997

Decrease of bradykinin-induced glomerular contraction in diabetic rat: a new cellular interpretation.

The contractile response to bradykinin (BK), measured by the reduction of the planar surface area, was studied in glomeruli and mesangial cells (MC) isolated from diabetic rats (D) one week after diabetes induction with injection of streptozotocin (STZ; 60 mg kg-1, i.p.). Results were compared with age and weight-matched untreated rats (N) and were expressed by two parameters of cell activity, the mean maximum contraction (MMC) and the proportion of contractile cells (PCC). Glomerular and mesangial contraction were found to be clearly reduced in diabetic rats in response to 100 nM BK. The lower contractile response was associated with a decrease of both glomerular calcium uptake and mesangial cell intracellular calcium mobilization. The fact that cell pretreatment with two protein kinase C (PKC) inhibitors, phorbol 12-13 myristate acetate and calphostin, lowered normal cell contraction at the level of that found in diabetic MC without any significant effect in the latter, suggests the involvement of a PKC pathway, perhaps by a decrease of activatable PKC in diabetes. In addition, our results led to the first description of a possible role of the kallikrein-kinin system in the early glomerular hemodynamic changes occurring in diabetes. Insulin (1-200 nM) increased the contractile response of cultured diabetic cells (MMC), and in this case, it also increased the PCC. It must be stressed that the effect of 1 nM insulin on the former (88% increase) was very much smaller than its effect on the latter (103% increase). The combination of the two parameters (contraction index, CI) provided a realistic evaluation of the contractile capacities of the cell population of the cultures as a whole. The differences in this index between normal and diabetic cell populations, in the absence or presence of insulin, were strictly parallel to those found in intact glomeruli. Finally, our results further confirm (Ouardani et al., Biol. Cell 86, 127, (1996)) the limit of the first five cell passages within which cultured MC can be reasonably used for the study of contractile abnormalities occurring in the early steps of diabetic state.

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PubMed1996

Loss of differences in mesangial cell phenotype between diabetic and normal rats: role of culture passages.

In mesangial cells (MC) isolated from streptozotocin (STZ)-induced diabetic rat kidneys, sensitivity to bradykinin (BK) for the induction of cell division and collagen synthesis, was found to be lower than in normal MC. Nevertheless, decreased activities could be reverted in vitro by insulin, at non-proliferative concentration (Girolami et al (1995), Can J Physiol Pharmacol 73, 848-853). The aim of the present study was to determine whether differences in the properties of diabetic MC could be ascribed to the diabetic state per se, and/or to experimental conditions, ie culture replating. Through successive cell replating, normal and diabetic types of MC were compared in terms of proliferation, contraction, free calcium concentration in response to KCl depolarization, and in relation to the expression of two cytoskeleton proteins specific to muscle cells, myosin and dystrophin. Studies of proliferation, contraction and free calcium concentration consistently showed that passage 5 was a limit beyond which differences between the two MC types were very small and sometimes non-significant. We found that the mean maximum contraction (MMC) and especially the proportion of contractile cells (PCC) among diabetic cells was lower than in normal MC. In addition, loss in proliferation activity and in [Ca2+]i concentrations were also found to occur during these five early passages. Dystrophin, a new marker of contractile phenotype recently described in smooth muscle cell (Leis et al (1994) Cell Biol Toxicol 10, 305), was first localized in MC and was compared with myosin also expressed in MC. However, during the course of cell replating and/or with the diabetic state, no visible quantitative changes were detected in the expression of the two contractile proteins. We conclude that cultured mesangial cells undergo phenotype modulations, as observed in other cells, in particular smooth muscle cells and consequently, comparative studies between normal and diabetic MC should not be carried out after the 5th passage.

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PubMed1995

Comparison of B1 and B2 receptor activation on intracellular calcium, cell proliferation, and extracellular collagen secretion in mesangial cells from normal and diabetic rats.

The mesangial cell is a contractile secreting cell found in a key position in the renal glomerulus. Several kidney and systemic diseases are associated with dysfunctions of the mesangial cells. We compared the effect of bradykinin (BK; B2 agonist) and des-Arg9-bradykinin (DBK; B1 agonist) on intracellular calcium mobilization, cell proliferation, and collagen secretion of mesangial cells from normal and streptozotocin-induced diabetic rats. Stimulation of mesangial cells with BK and DBK caused an increase in intracellular calcium (Ca2+). However, the patterns of the Ca2+ increases induced by BK and DBK were different, indicating that DBK induced a major Ca2+ influx, whereas BK preferentially released Ca2+ from intracellular pools. Stimulation with BK and DBK did not show any heterologous desensitization, thus indicating the presence of two distinct binding sites. In normal cells, DBK stimulated cell proliferation more than BK, and this action was potentiated by insulin. No effect of BK or DBK was found in cells harvested from diabetic rats. The proliferation effect of BK and DBK was restored by insulin. DBK stimulated more collagen synthesis than BK in normal cells. In cells harvested from diabetic rats the collagen secretion was increased, but BK and DBK no longer had any effect. Insulin reduced basal collagen secretion in normal cells and cells harvested from diabetic rats. Insulin also blunted stimulation by BK and DBK in normal cells but did not restore the response to BK and DBK in cells harvested from diabetic rats. Our results show that the sensitivity to DBK and BK decreases during the course of insulin-dependent diabetes, indicating modulation by insulin.

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