Altered signaling and regulatory mechanisms of apoptosis in focal and segmental glomerulosclerosis

The purpose of this study was to investigate signaling and regulatory mecha nisms of apoptosis in a model of focal and segmental glomerulosclerosis. Sp rague-Dawley rats received two doses of puromycin aminonucleoside (PAN) (da y 0 and week 3) and a uninephrectomy (PAN model). Apoptosis was detected wi th the use of the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling technique. Bax, Bcl-2, Fas, and Fas ligand expression was anal yzed by competitive reverse transcription-PCR. Bax, Bcl-2, and Fas mRNA wer e localized by in situ hybridization. Renal function was transiently impair ed after the first PAN dose. After the second PAN dose, further progressive renal impairment, tubular atrophy, interstitial fibrosis, and glomeruloscl erosis were evident. Eighteen percent of PAN samples demonstrated up to 4 a poptotic cells/50 glomeruli, compared with 7% of sham controls (not signifi cant). No consistent significant change in glomerular Bax, Bcl-2, Fas, and Fas ligand mRNA was evident by reverse transcription-PCR, although focal in creases in glomerular Bcl-2 mRNA were demonstrated by in situ hybridization . In the tubulointerstitium, apoptosis was increased from weeks to 12 (P < 0.01 PAN versus sham), correlated to renal function and tubulointerstitial injury (P < 0.01). Total renal Bax, Fas, and Fas ligand mRNA were upregulat ed in the PAN model, peaking at week 17 (P < 0.01 versus sham), whereas Bcl -2 mRNA was not significantly different in PAN versus sham controls. In sit u hybridization in the PAN model demonstrated prominent Bax mRNA in dilated tubules and infiltrating leukocytes. Fts mRNA signal was localized to tubu lar epithelial cells and leukocytes. The results suggest that altered apopt otic signaling and regulatory mechanisms contribute to the tubulointerstiti al injury in this model.