Mechanisms of bevacizumab inducing proteinuria in mice models / 医学研究生学报

ABSTRACT

Objective Bevacizumab ( BM ) is an angiogenesis inhibitor widely used in cancer therapy, but its off-target effect of proteinuria may lead to discontinuation of treatment.This study was to explore the mechanisms of BM inducing proteinuria in mice. Methods Twenty-four healthy mice were randomly divided into four groups, saline control, low-dose BM, medium-dose BM, and high-dose BM, treated by injection of normal saline and BM at 10, 35, and 60 mg per kg of the body weight, respectively, though the tail vein.At 4 weeks after injection, 24-hour urine was collected to determine the total urine protein and blood obtained from the eyeballs for biochemical analysis.Then all the mice were sacrificed and the kidneys harvested for observation of pathologic changes in the glomeruli as well as for immunohistochemistry, Western blotting, and real-time PCR analysis. Results Compared with normal saline,BM obviously elevated the level of 24-hour urine protein, with statistically significant differences between the control and the medium-and high-dose BM groups (0.23 ±0.02 vs 1.14 ±0.13 and 1.43 ±0.10, P0.05).No significant differences were observed among the four groups in the levels of Cr, BUN, AST and ALT (P>0.05).Under the optical microscope, the kidneys showed normal structures in the control group, no signifi-cant pathologic changes in the low-dose BM, and vacuolus-like alteration with atrophic glomerular endothelial cells in the medium-and high-dose BM groups.Immunohistochemical analysis demonstrated the expressions of VEGF and podocin were moderately or strongly positive in the control and low-dose BM groups, by weakly positive or negative in the medium-and high-dose BM groups.Compared with the control group, the expression of the VEGF protein in the renal tissue was significantly decreased in the high-dose BM group (0.76 ±0.09 vs 0.39 ±0.05, P0.05), and the expression of the podocin protein was significantly reduced in the medium-dose BM (0.67 ±0.07 vs 0.43 ±0.10, P0.05).The mRNA expressions of VEGF and podocin were not significantly changed in the low-dose BM group as compared with the control (1.07 ±0.61 and 1.12 ±0.09 vs 1.23 ±0.25 and 1.17 ±0.19, P>0.05) but remarkably de-creased in the medium-dose (0.82 ±0.38 and 0.71 ±0.18) and high-dose BM groups and (0.47 ±0.64 and 0.42 ±0.09) groups (P<0.01). Conclusion Bevacizumab damages glomerular filtration membrane and induce proteinuria partially by down-regulating the protein and mRNA expressions of VEGF and podocin.