Tenofovir renal toxicity targets mitochondria of renal proximal tubules

Abstract

Tenofovir disoproxil fumarate (TDF) is an analog of adenosine monophosphate that inhibits HIV reverse transcriptase in HIV/AIDS. Despite its therapeutic success, renal tubular side effects are reported. The mechanisms and targets of tenofovir toxicity were determined using '2 x 2' factorial protocols, and HIV transgenic (TG) and wild-type (WT) littermate mice with or without TDF (5 weeks). A parallel study used didanosine (ddI) instead of TDF. At termination, heart, kidney, and liver samples were retrieved. Mitochondrial DNA (mtDNA) abundance, and histo- and ultrastructural pathology were analyzed. Laser-capture microdissection (LCM) was used to isolate renal proximal tubules for molecular analyses. Tenofovir increased mtDNA abundance in TG whole kidneys, but not in their hearts or livers. In contrast, ddI decreased mtDNA abundance in the livers of WTs and TGs, but had no effect on their hearts or kidneys. Histological analyses of kidneys showed no disruption of glomeruli or proximal tubules with TDF or ddI treatments. Ultrastructural changes in renal proximal tubules from TDF-treated TGs included an increased number and irregular shape of mitochondria with sparse fragmented cristae. LCM-captured renal proximal tubules from TGs showed decreased mtDNA abundance with tenofovir. The results indicate that tenofovir targets mitochondrial toxicity on the renal proximal tubule in an AIDS model.

Figures

Figure 1

Tissue-specific changes in mtDNA abundance after TDF or ddI treatment: using ‘2 × 2’ protocols, cohorts of TG and WT mice were treated with TDF, ddI, or vehicle (5 weeks). After treatment, cardiac, kidney, and liver tissues were collected, and mtDNA abundance was determined for each cohort as normalized ratios of mtDNA-nDNA. Changes in mtDNA abundance were tissue and treatment specific.

Figure 2

Renal histopathological analysis: parallel H&E-stained slides were made from gender-matched pairs of kidney tissues after treatment (5 weeks). All the tissues showed intact glomeruli and tubules and comparable nuclei (original magnification ×40).

Figure 3

Mitochondrial ultrastructural changes in renal tubular epithelial cells with tenofovir: renal tubular epithelial cells from TDF-treated TGs showed increased mitochondrial number, irregular shape, and fragmented cristae. (EM, original magnification ×22 400).

Figure 4

mtDNA abundance in LCM-retrieved renal proximal tubular epithelial cells after treatment. Histology sections were stained with PAS for identifying proximal tubules. Proximal tubules were selectively microdissected from formalin-fixed paraffin-embedded kidney tissues using LCM. (a) Captured images of renal tissue before (left) and after (center) sample microdissection along with resultant isolated proximal tubules (right; original magnification ×20). mtDNA abundance in LCM samples were determined using real-time PCR. (b) mtDNA abundance decreased in proximal tubules from TGS treated with TDF (Mann-Whitney unpaired t-test). ddI had no effect on proximal tubular mtDNA abundance.