Analysis of inositol tris- and tetrakisphosphate in mesangial cells by HPLC

Inhibition of mesangial cell proliferation by E2F decoy oligodeoxynucleotide in vitro and in vivo

The transcription factor E2F coordinately activates several cell cycle-regulatory genes. We attempted to inhibit the proliferation of mesangial cells in vitro and in vivo by inhibiting E2F activity using a 25-bp decoy oligodeoxynucleotide that contained consensus E2F binding site sequence (E2F-decoy) as a competitive inhibitor. The decoy's effect on human mesangial cell proliferation was evaluated by [3H]thymidine incorporation. The E2F decoy inhibited proliferation in a concentration-dependent manner, whereas a mismatch control oligodeoxynucleotide had little effect. Electrophoretic mobility shift assays demonstrated that the decoy's inhibitory effect was due to the binding of the decoy oligodeoxynucleotide to E2F. The effect of the E2F decoy was then tested in a rat anti-Thy 1.1 glomerulonephritis model. The E2F decoy oligodeoxynucleotide was introduced into the left kidney 36 h after the induction of glomerulonephritis. The administration of E2F decoy suppressed the proliferation of mesangial cells by 71%. Furthermore, treatment with the E2F decoy inhibited the glomerular expression of proliferating cell nuclear antigen at the protein level as well as the mRNA level. These findings indicate that decoy oligonucleotides can suppress the activity of the transcription factor E2F, and may thus have a potential in treating glomerulonephritis.

Alteration of mesangial response to ANP and angiotensin II by glucose

To test the hypothesis that the function of glomerular mesangial cells is impaired in diabetes, we examined the responsiveness of mesangial cells cultured under high concentrations of glucose to atrial natriuretic peptide (ANP1) and angiotensin II (Ang II). The ANP-induced accumulation of cGMP was enhanced in mesangial cells cultured under high glucose conditions, possibly due to the activation of particulate guanylate cyclase. Ang II action in mesangial cells was evaluated by measuring the ability of Ang II to inhibit ANP-induced cGMP accumulation through both activating phosphodiesterase (initial phase) and inhibiting guanylate cyclase (maintenance phase). The inhibition of both ANP-induced cellular cGMP accumulation and particulate guanylate cyclase activity by Ang II was significantly reduced in mesangial cells cultured under high concentrations of glucose. Moreover, in the cells exposed to high concentrations of glucose, both basal and Ang II-stimulated levels of inositol 1,4,5-trisphosphate (IP3) were significantly reduced. These results indicate that, in high glucose conditions, the actions of ANP and Ang II are modulated differently, resulting in the impairment of contractile responsiveness of mesangial cells.