Mitochondrial Toxicity in the Era of HAART: Evaluating Venous Lactate and Peripheral Blood Mitochondrial DNA in HIV-Infected Patients Taking Antiretroviral Therapy

Abstract

Nucleoside analogs can induce mitochondrial toxicity by inhibiting the human DNA polymerase gamma. This can lead to a wide range of clinical toxicities, from asymptomatic hyperlactatemia to death. Despite their technical and physiological variability, we propose that random venous lactate measurements can be useful to monitor the development of nucleoside-related mitochondrial toxicity. Recently, we have developed an assay that can measure changes in mitochondrial DNA levels in peripheral blood cells. Using this assay we have characterized changes in mitochondrial DNA (mtDNA) relative to nuclear DNA (nDNA) in peripheral blood cells of patients with symptomatic nucleoside-induced hyperlactatemia. Our results demonstrate that symptomatic hyperlactatemia was associated with markedly low mtDNA/nDNA ratios, which were on average 69% lower than HIV-uninfected controls and 45% lower than HIV-infected asymptomatic/antiretroviral naive controls. A statistically significant (p = .016) increase in mtDNA/nDNA ratio was observed following discontinuation of antiretroviral therapy. The mtDNA/nDNA ratio remained stable among selected patients who reintroduced antiretroviral therapy with stavudine (d4T)-sparing regimens. Of note, the decline in mtDNA preceded the increase in venous lactate levels. More recently we have evaluated changes in the mtDNA/nDNA ratio in relation to selected antiretroviral drug regimens in a cross-sectional study on a non-random sample of participants within the British Columbia Centre for Excellence in HIV/AIDS Drug Treatment Program. Eligible patients had continuously received saquinavir plus ritonavir with either nevirapine (n = 20), lamivudine (n = 15), d4T (n = 53) or lamivudine + d4T (n = 69), for 4 to 30 months. d4T-sparing regimens were associated with a higher median mtDNA/nDNA ratio than d4T-containing regimens (p = .016), despite the fact that study patients had received d4T-containing regimens for a shorter median time than patients taking d4T-sparing regimens (13 versus 25 months, p = .002). In summary, mtDNA levels are significantly decreased among patients who develop symptomatic, nucleoside-related hyperlactatemia, an effect reversed upon therapy discontinuation. Furthermore, mtDNA/nDNA ratios were statistically significantly lower in patients taking d4T-containing regimens than in those taking selected d4T-sparing regimens in a population setting. These results suggest that measurement of this parameter should be investigated as a potential clinical management tool.

Prospective evaluation of blood concentration of mitochondrial DNA as a marker of toxicity in 157 consecutively recruited untreated or HAART-treated HIV-positive patients

“…However, this difference was observed both in naive patients and in HAART-treated patients. The decrease in the mtDNA to nDNA ratios in untreated HIV-1 patients are in agreement with those reported by Cote et al 18 and Montaner et al 19 but not with those of Petit et al 25 The decrease in mtDNA to nDNA ratio in the HIV patients suggests a direct mitochondrial toxicity of the virus. These observations are supported by in vitro studies in which HIV-infected cells showed signs of mitochondrial necrosis.…”

“…18 It is possible that the quantification of mtDNA in peripheral blood cells could be a more sensitive and earlier indicator of the mitochondrial toxicity of drugs than cell viability. 19,20 However, other studies gave controversial results. 21,22 All of these studies were performed on small series of patients.…”

Real-Time Nucleic Acid Sequence–Based Amplification Assay to Quantify Changes in Mitochondrial DNA Concentrations in Cell Cultures and Blood Cells from HIV-Infected Patients Receiving Antiviral Therapy

“…Changes in the mtDNA concentrations in PBMCs of patients can indeed be observed in response to antiviral therapy with nucleoside analogs, as was shown in the 2 series of samples of patients on various treatments and has also been reported in various other studies (3,25,(31)(32)(33)(34). The reason to develop an assay that can detect small changes in mtDNA copy numbers was to allow verification of studies that have not been able to find changes in mtDNA attributable to antiretroviral treatment (14 ).…”

Estimating the impact of alcohol consumption on survival for HIV+ individuals

“…If alcohol were to directly facilitate the progression of HIV disease, as perhaps may occur by decreasing cell-mediated immunity, it may decrease life expectancy more than the current results suggest. Similarly, because alcohol consumption is likely to increase sources of morbidity and mortality that are unrelated to HIV, such as worsening the transaminitis associated with HAART (Montaner et al, 2003;Ogedegbe & Sulkowski, 2003) or hastening the progression of Hepatitis C (Rockstroh & Spengler, 2004) our results are likely to be underestimates.…”