Stimulatory effect of calcium-binding protein regucalcin on phosphatase activity in the brain cytosol of rats with different ages

Amorphous Selenium Nanoparticles Improve Vascular Function in Rats With Chronic Isocarbophos Poisoning via Inhibiting the Apoptosis of Vascular Endothelial Cells

AIM

This study aimed to investigate the preventive effect and possible mechanism of amorphous selenium nanoparticles (A-SeQDs) on isocarbophos induced vascular dysfunction.

METHODS

A-SeQDs was made by auto redox decomposition of selenosulfate precursor. Male rats were given isocarbophos (0.5 mg/kg/2 days) by intragastric administration for 16 weeks to induce vascular dysfunction. During the course, A-SeQDs (50 mg/kg/day) was added to the water from week 5. Then, the rats were killed to observe and test the influence of A-SeQDs on the vascular dysfunction induced by isocarbophos. Finally, human umbilical vein endothelial cells (HUVECs) were treated with 10% DMEM of isocarbophos (100 μM) for 5 days to detect the related indexes. Before the use of isocarbophos treatment, different drugs were given.

RESULTS

A-SeQDs could reduce total carbon dioxide, MDA, VCAM-1, ICAM-1, IL-1, and IL-6 while increasing oxygen saturation, NO content, and SOD activity in rats. A-SeQDs also resulted in relatively normal vascular morphology, and the expression of sodium hydrogen exchanger 1 (NHE1) and caspase-3 decreased in rats. Furthermore, in HUVECs treated with isocarbophos, A-SeQDs maintained mitochondrial membrane potential, inhibited the cleaved caspase-3 expression, and released cytochrome c from mitochondria to cytosol.

CONCLUSION

A-SeQDs can inhibit the apoptosis of HUVECs through the mitochondrial pathway, and effectively treat the impairment of vascular endothelial function caused by isocarbophos, which is NHE1-dependent.

Expression of Ca(2+)-binding protein regucalcin in rat brain neurons: inhibitory effect on protein phosphatase activity

The expression of Ca(2+)-binding protein regucalcin and its role in the regulation of protein phosphatase activity in rat brain neuronal cells obtained with primary culture was investigated. The expression of regucalcin mRNA was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) analysis in brain neuronal cells using rat regucalcin-specific primers. Moreover, regucalcin protein in brain neuronal cells was detected by Western blot analysis using a polyclonal rabbit anti-regucalcin antibody. The presence of anti-regucalcin monoclonal antibody (20 or 50 ng/ml) in the enzyme reaction mixture caused a significant increase in protein phosphatase activity toward phosphotyrosine, phosphoserine and phosphothreonine in the reaction mixture containing the cytosol of neuronal cell homogenates. This increase was completely prevented by the addition of regucalcin (10(-8) M). Protein phosphatase activity toward three phosphoaminoacids was significantly elevated by the addition of Ca(2+) (100 microM) and calmodulin (5 microg/ml). This elevation was completely blocked by the addition of regucalcin (10(-8) M). The present study demonstrates that regucalcin is expressed in rat brain neuronal cells, and that it has an inhibitory effect on protein phosphatase activity in the cells.

Inhibitory effect of regucalcin on Ca(2+)-dependent protein kinase activity in rat brain cytosol: involvement of endogenous regucalcin

The effect of regucalcin, a Ca(2+)-binding protein, on Ca(2+)-dependent protein kinase activity in the brain cytosol of rats with different ages (5 and 50 weeks old) was investigated. The addition of calmodulin (10 microg/ml) or dioctanoylglycerol (5 microg/ml) in the enzyme reaction mixture caused a significant increase in protein kinase activity in the presence of CaCl2 (1 mM), indicating that Ca2+ calmodulin or protein kinase C is present in the cytosol. Such an increase was completely prevented by the addition of regucalcin (10(-7) M). Moreover, regucalcin (10(-7) M) significantly inhibited cytosolic protein kinase activity without Ca2+/calmodulin or dioctanoylglycerol addition. Meanwhile, the presence of anti-regucalcin monoclonal antibody (10-50 ng/ml) in the enzyme reaction mixture caused a significant elevation of protein kinase activity, suggesting an inhibitory effect of endogenous regucalcin. Brain cytosolic protein kinase activity was significantly elevated by increasing age (50-week-old rats). Also, regucalcin (10(-7) M) significantly decreased protein kinase activity without Ca(2+) addition in the brain cytosol of aged rats. However, the effect of anti-regucalcin monoclonal antibody (50 ng/ml) in elevating protein kinase activity was not seen in the brain cytosol of aged rats. These results suggest that regucalcin has an inhibitory effect on Ca(2+)-dependent protein kinase activity in rat brain cytosol, and that the effect of endogenous regucalcin may be weakened in the brain cytosol of aged rats.