In Vitro Cytotoxicity and Mitochondrial Toxicity of Tenofovir Alone and in Combination with Other Antiretrovirals in Human Renal Proximal Tubule Cells

Abstract

We assessed the in vitro toxicity of tenofovir (TFV) and compared it with those of zidovudine (AZT), didanosine (ddI), ritonavir (RTV), and lopinavir (LPV) alone and in combination in human renal proximal tubule epithelial cells (RPTECs). The cells were treated with various concentrations and combinations of the tested antiretrovirals for up to 22 days, and cytotoxicity was determined. In addition, we assessed the levels of mitochondrial DNA (mtDNA) and cytochrome oxidase II (COII) mRNA in RPTECs treated with reverse transcriptase inhibitors. TFV alone was not associated with significant cytotoxicity. ddI showed pronounced cytotoxicity that was greater than those of AZT (P ‫؍‬ 0.002) and TFV (P ‫؍‬ 0.0001). The combination of 10 M RTV and 40 M LPV significantly reduced RPTEC viability (P < 0.0001), and TFV tended to partially reduce this effect. TFV alone affected neither mtDNA nor COII mRNA levels, whereas ddI caused a profound depletion of mtDNA and a parallel reduction in COII mRNA expression. The effects of ddI, but not those of AZT, on mtDNA and COII mRNA were further enhanced in the presence of TFV, a finding consistent with the inhibition of ddI clearance by TFV. The addition of TFV to ddI or AZT appeared to slightly increase the COII mRNA/mtDNA ratio relative to that in cells treated with ddI or AZT alone. Together, these in vitro results indicate that combination with other antiretrovirals does not significantly increase the toxic potential of TFV in RPTECs.Tenofovir disoproxil fumarate (TDF) is an oral prodrug of tenofovir (TFV), an acyclic nucleotide analogue reverse transcriptase inhibitor that is widely used for the treatment of human immunodeficiency virus type 1 (HIV-1) infection (42). Controlled clinical studies in humans found TDF to be safe, with the incidence of TDF-associated renal impairment (elevated serum creatinine or hypophosphatemia) being 1 to 3% and with minimal differences from comparative non-TDF arms (22,23,29,30,34,50,62). However, several reports have reassessed the renal safety of TFV, and presently there is a progressively growing subset of TFV-treated patients presenting with acute renal failure, with Fanconi syndrome and/or nephrogenic diabetes insipidus, attributed to this drug (3, 10, 16, 18, 24-26, 32, 36-38, 40, 43, 46, 49, 51, 53, 55, 58-61, 66, 67). In the majority of cases the kidney damage was reversed upon discontinuation of TFV (71). Many of these case reports have suggested different mechanisms to explain the link between this drug and its attributed kidney toxicity, but at present this still remain largely elusive. Common features of most reports of TFV-related kidney toxicity were an advanced stage of HIV-1 infection and extensive pretreatment with antiretrovirals and other potentially nephrotoxic drugs before TFV was prescribed. The patients were receiving second, third, or even more advanced treatment regimens, which included in most cases lopinavir/ritonavir (LPV/RTV) and/or didanosine (ddI) in addition to TFV (3,10,16,18,[24][25][26]32,[36][37][38]40,43,46,...

BMS-986001, an HIV Nucleoside Reverse Transcriptase Inhibitor, Does Not Degrade Mitochondrial DNA in Long-Term Primary Cultures of Cells Isolated from Human Kidney, Muscle, and Adipose Tissue

“…TFV is also transported by OAT1, but in in vivo studies, no reduction in mtDNA was observed in the kidney (24). Furthermore, the data reported herein confirm previous observations that TFV does not reduce mtDNA in human RPT cells cultured for up to 3 weeks (18,25,26). Our study indicates that at a high, equimolar concentration (200 M), TDF is significantly less cytotoxic in vitro than ADV.…”

Evaluation of the Effect of Cobicistat on theIn VitroRenal Transport and Cytotoxicity Potential of Tenofovir

“…Emtricitabine, elvitegravir, and COBI were also tested for cytotoxicity toward RPTECs, with resulting CC 50 values of Ͼ100, 13.7, and 26.2 M, respectively. These values were consistent with the generally low cytotoxicity of TFV in RPTECs reported previously (11,(23)(24)(25). Coincubation of TFV with either COBI alone or COBI, elvitegravir, and emtricitabine in combination at pharmacologically relevant concentrations showed no measureable cytotoxicity within the range of tested concentrations of TFV (Table 2).…”

“…TFV by itself exhibited minimal cytotoxicity in RPTECs, even at high concentrations, an observation consistent with prior studies (24,25). Neither COBI alone nor the combination of COBI, elvitegravir, and emtricitabine affected the cytotoxicity of TFV in human RPTECs.…”

Multi-level Analysis of Organic Anion Transporters 1, 3, and 6 Reveals Major Differences in Structural Determinants of Antiviral Discrimination

“…For example, mOat3 was implicated as the major contributor to ddC and ddI transport, and consequently, ddC is shown to be a novel mOat3 substrate. Both ddC and ddI have been shown to be cytotoxic (27)(28)(29)(30). Although Oat1 and Oat3 have significant overlap in the proximal tubule segments (S1-S3), rOat3 has also been shown to be expressed in the thick ascending loop, distal tubule, connecting tubule, and the collecting duct of the outer medulla (31,32).…”