Effects of radiotherapy upon progression of crescentic glomerulonephritis in rats

Abstract

To study the effects of radiotherapy upon progression of crescentic glomerulonephritis in rats. Male SD rats were divided into three groups: (1) control (n=12), sham-operation; (2) crescentic glomerulonephritis (n=23), intravenously inject with nephrotoxic serum (NTS); (3) radiotherapy (n=55), a single low-dose irradiation of 0.5 Gy X-ray to both kidneys at Days 6, 13, 20 and 27 after NTS injection, and sacrificed at different time points among control and crescentic glomerulonephritis rats. Radiotherapy rats have received local kidney irradiation at Days 6, 13, 20 and 27 after bolus NTS injection and would be referred to as NTS7dRa1d, NTS14dRa1d, NTS21dRa1d and NTS28dRa1d, respectively. For NTS7dRa1d and NTS14dRa1d rats of radiotherapy, the levels of serum creatinine, glomerular hypercellularity, crescents and global sclerosis were significantly lower at Days 8 (P < 0.05), 15, and 22 post-irradiation as compared with group of crescentic glomerulonephritis of similar time intervals (P < 0.01). The extent of tubulointerstitial damage was also reduced, and radiotherapy associated histological improvements were accompanied by reduced macrophage infiltration in glomeruli and interstitium. The numbers of PCNA- and ED1-positive cells were reduced in the kidneys at Day 1 postirradiation in NTS7dRa1d and NTS14dRa1d rats as compared with group of crescentic glomerulonephritis at similar time intervals (P < 0.05). A larger number of TUNEL-positive cells were noted at Day 1 postirradiation in rats irradiated at Days 6 & 13 after NTS injection as compared with group of crescentic glomerulonephritis at similar time intervals (P < 0.05). With regards to immunostaining for macrophages ED1 and TUNEL, serial sections of irradiated nephritic kidney showed that fewer ED1-positive macrophages were stained for TUNEL. As evaluated expression of active caspases 3 & 7 was noted in irradiated kidneys as compared with the corresponding group of crescentic glomerulonephritis at similar time intervals. Western blot analysis showed marked increase in the expression of active caspase 3 & 7 in irradiated kidneys as compared with NTS injection only the expression of a marked increase in the expression of p53 protein, closely related to radiation-induced apoptosis, was also observed in irradiated kidneys as compared with NTS injection only. Radiotherapy inhibits the progression of experimental crescentic glomerulonephritis through inducing apoptosis by a p53-dependent pathway.