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

Bioactive peptides PDBSN improve mitochondrial function and suppression the oxidative stress in human adiposity cells

Introduction: Mitochondria are essential for generating cellular energy and are significant in the pathogenesis of obesity. Peptide PDBSN has been demonstrated to inhibit the adipogenic differentiation of adipocytes in vitro and improves metabolic homoeostasis in vivo. Therefore, in this study, we further investigated the effects of PDBSN on the morphology, synthesis, and function of adipocyte mitochondria. Methods: Human visceral and subcutaneous primary preadipocytes (HPA-v and HPA-s) were cultured into mature adipocytes. Intracellular triglyceride content was assessed using oil-red O staining and tissue triglyceride determination. Gene and protein levels associated with mitochondrial synthesis were detected using real-time quantitative polymerase chain reaction and western blotting. Mitochondrial membrane potentials and ROS were detected using fluorescent indicators. Morphological changes were observed by electron microscopy. Results: PDBSN significantly increased mitochondrial membrane potential (MMP), while decreasing intracellular triglyceride (TG) and intracellular reactive oxygen species (ROS) levels. On the other hand, the transcription and protein levels of genetic marker genes PGC1-α and MTFA were significantly up-regulated after PDBSN administration. Further studies showed that transcriptional and protein levels of mitochondrial fusion and fission genetic markers MFN1, MFN2, NRF1, and DRP1 increased. Conclusion: PDBSN significantly reduces intracellular TG and ROS levels and increases MMP. The maximum respiratory capacity in adults significantly increases after PDBSN administration, and ROS levels are significantly reduced. This suggests that PDBSN improves mitochondrial function to some extent, which not only provides an essential basis for the pathophysiology of obesity but also provides insights for the development of new drugs to treat obesity and metabolic diseases.

Hemochromatosis (HFE) Gene Variants Are Associated with Increased Mitochondrial DNA Levels During HIV-1 Infection and Antiretroviral Therapy

Some HIV-associated complications involve mitochondrial dysfunction and may be less common in individuals with iron-loading HFE (hemochromatosis gene) variants. We evaluated HFE 845A and 187G alleles in relation to mitochondrial DNA (mtDNA) levels in peripheral blood mononuclear cells from 85 individuals with HIV infection on uninterrupted antiretroviral therapy (ART) for 15 or more consecutive weeks. Carriers of HFE gene variants (N = 24) had significantly higher mtDNA levels than noncarriers (N = 61), after adjusting for age, race, sex, and type of ART [adjusted β-coefficient 297, p-value < .001 for at least one HFE variant], but mtDNA declined among all individuals on study during 48 weeks on ART. Increased cellular mtDNA content may represent a compensatory response to mitochondrial stress that is influenced by iron-loading HFE variants.

High Tidal Volume Induces Mitochondria Damage and Releases Mitochondrial DNA to Aggravate the Ventilator-Induced Lung Injury

Objective

This study aimed to determine whether high tidal volume (HTV) induce mitochondria damage and mitophagy, contributing to the release of mitochondrial DNA (mtDNA). Another aim of the present study was to investigate the role and mechanism of mtDNA in ventilator-induced lung injury (VILI) in rats.

Methods

Rats were tracheotomized and allowed to breathe spontaneously or mechanically ventilated for 4 h. After that, lung injury was assessed. Inhibition of toll-like receptor 9 (TLR9), named ODN2088, was used to determine the involvement of TLR9/myeloid differentiation factor 88 (MyD88)/nuclear factor-κB (NF-κB) signaling pathway in VILI. The mitochondrial damage and release of mtDNA were assessed. Pharmacological inhibition of mtDNA (chloroquine) was used to determine whether mtDNA trigger inflammation via TLR9 in VILI. EDU-labeled mtDNA deriving from mitophagy was assessed by immunofluorescence. The role of mitophagy in VILI was shown by administration of antimycin A and cyclosporine A.

Main results

Rats subjected to HTV showed more severe pulmonary edema and inflammation than the other rats. The decreased expression of TLR9, MyD88, and NF-κB were observed following the use of ODN2088. Mechanical ventilation (MV) with HTV damaged mitochondria which resulted in dysfunctional ATP synthesis, accumulation of reactive oxygen species, and loss of mitochondrial membrane potential. Moreover, the results of distribution of fluorescence in rats upon HTV stimulation indicated that mtDNA cleavage was associated with mitophagy. The expression levels of mitophagy related genes (LC3B-II/LC3B-I, PINK1, Parkin, and mitofusin 1) in animals ventilated with HTV were significantly upregulated. Administration of antimycin A aggregated the histological changes and inflammation after MV, but these effects were attenuated when administered in the presence of cyclosporine A.

Conclusion

MV with HTV induces mitochondrial damage and mitophagy, contributing to the release of mtDNA, which may be induced VILI in rat via TLR9/MyD88/NF-κB signaling pathway.

Plasma mitochondrial DNA levels are inversely associated with HIV-RNA levels and directly with CD4 counts: potential role as a biomarker of HIV replication

Objectives

To evaluate plasma mitochondrial DNA (mtDNA) levels among HIV-infected patients and its potential role as a biomarker of residual viral replication.

Methods

HIV-infected patients on follow-up at a reference hospital in north-west Spain were selected. DNA was isolated from plasma samples and mtDNA levels were assessed using a quantitative real-time PCR assay. HIV-RNA levels and CD4+ cell counts were evaluated in the same blood samples used for plasma mtDNA quantification. Epidemiological and clinical variables were included for the analysis.

Results

A total of 235 HIV-infected patients were included. Mean plasma mtDNA levels were 217 ± 656 copies/μL for naive (31.9%) and 364 ± 939 copies/μL for HIV-infected patients receiving ART and with suppressed viraemia (P = 0.043). Among the latter, mean plasma mtDNA levels were 149 ± 440 copies/μL for those with low-level viraemia (LLV; HIV-RNA 20-200 copies/mL), 265 ± 723 copies/μL for those with detected-not-quantified (DNQ) viraemia (HIV-RNA <20 copies/mL) and 644 ± 1310 copies/μL for those with not-detected (ND) viraemia. Of note, a linear trend (P = 0.006) was observed among virologically suppressed (LLV, DNQ and ND) patients. ND patients had higher mtDNA levels compared with LLV patients (P = 0.057). Moreover, mtDNA levels were inversely associated with HIV-RNA levels (Spearman's rho -0.191, P = 0.003) and directly associated with CD4+ counts (Spearman's rho 0.131, P = 0.046).

Conclusions

Increased plasma mtDNA levels are associated with lower HIV-RNA levels and higher CD4+ cell counts. Among ART-suppressed patients, mtDNA levels were significantly higher in those with complete virological suppression (ND) than in those with LLV. These data suggest that plasma mtDNA levels might serve as a biomarker of residual HIV replication.

Mitochondrial DNA mutations in blood samples from HIV-1-infected children undergoing long-term antiretroviral therapy

We have analyzed mutations in whole mitochondrial (mt) genomes of blood samples from HIV-1-infected children treated with long-term antiretroviral therapy (ART), who had an excellent virological response. HIV-1-infected children who have undergone ART for 4 y with an excellent virological response (group A; 15 children) and ten healthy children (controls) without HIV-1 infection were enrolled retrospectively. Peripheral blood mononuclear cells (PBMCs) were obtained and mt DNA mutations were studied. The total number of mtDNA mutations in group A was 3 H more than in the controls (59 vs. 19, P<0.001) and the same trend was seen in all mtDNA regions. Among these mtDNA mutations, 140 and 28 mutations were detected in group A and the controls, respectively. The D-loop, CYTB and 12s rRNA were the three most common mutation regions in both groups, with significant differences between the groups observed at nucleotide positions C309CC, T489C CA514deletion, T16249C and G16474GG (D-loop); T14783C, G15043A, G15301A, and A15662G (CYTB); and G709A (12s rRNA). G15043A and A15662G had been associated with mitochondrial diseases. Our findings suggest that mtDNA mutations occur frequently in long-term ART-treated, HIV-1-infected children who have an excellent virological response, although they did not have obvious current symptoms. The CYTB region may play an important role in mtDNA mutation during ART, which might contribute to the development of subsequent mitochondrial diseases.

Oxidative mitochondrial DNA damage in peripheral blood mononuclear cells is associated with reduced volumes of hippocampus and subcortical gray matter in chronically HIV-infected patients

Cross-sectional relationships were examined between regional brain volumes and mitochondrial DNA (mtDNA) 8-hydroxy-2-deoxyguanosine (8-oxo-dG) in peripheral blood mononuclear cells (PBMCs) of 47 HIV patients [mean age 51years; 81% with HIV RNA ≤50copies/mL] on combination antiretroviral therapy. The gene-specific DNA damage and repair assay measured mtDNA 8-oxo-dG break frequency. Magnetic resonance imaging was performed at 3T. Higher mtDNA 8-oxo-dG was associated with lateral ventricular enlargement and with decreased volumes of hippocampus, pallidum, and total subcortical gray matter, suggesting the involvement of systemic mitochondrial-specific oxidative stress in chronic HIV-related structural brain changes and cognitive difficulties. Clarification of the mechanism may provide potential therapeutic targets.

Aging with HIV-1 Infection: Motor Functions, Cognition, and Attention--A Comparison with Parkinson's Disease

Recent advances in highly active anti-retroviral therapy (HAART) in their various combinations have dramatically increased the life expectancies of HIV-infected persons. People diagnosed with HIV are living beyond the age of 50 but are experiencing the cumulative effects of HIV infection and aging on brain function. In HIV-infected aging individuals, the potential synergy between immunosenescence and HIV viral loads increases susceptibility to HIV-related brain injury and functional brain network degradation similar to that seen in Parkinson's disease (PD), the second most common neurodegenerative disorder in the aging population. Although there are clear diagnostic differences in the primary pathology of both diseases, i.e., death of dopamine-generating cells in the substantia nigra in PD and neuroinflammation in HIV, neurotoxicity to dopaminergic terminals in the basal ganglia (BG) has been implied in the pathogenesis of HIV and neuroinflammation in the pathogenesis of PD. Similar to PD, HIV infection affects structures of the BG, which are part of interconnected circuits including mesocorticolimbic pathways linking brainstem nuclei to BG and cortices subserving attention, cognitive control, and motor functions. The present review discusses the combined effects of aging and neuroinflammation in HIV individuals on cognition and motor function in comparison with age-related neurodegenerative processes in PD. Despite the many challenges, some HIV patients manage to age successfully, most likely by redistribution of neural network resources to enhance function, as occurs in healthy elderly; such compensation could be curtailed by emerging PD.

Neurological and psychiatric adverse effects of antiretroviral drugs

Antiretroviral drugs are associated with a variety of adverse effects on the central and peripheral nervous systems. The frequency and severity of neuropsychiatric adverse events is highly variable, with differences between the antiretroviral classes and amongst the individual drugs in each class. In the developing world, where the nucleoside reverse transcriptase inhibitor (NRTI) stavudine remains a commonly prescribed antiretroviral, peripheral neuropathy is an important complication of treatment. Importantly, this clinical entity is often difficult to distinguish from human immunodeficiency virus (HIV)-induced peripheral neuropathy. Several clinical trials have addressed the efficacy of various agents in the treatment of NRTI-induced neurotoxicity. NRTI-induced neurotoxicity is caused by inhibition of mitochondrial DNA polymerase. This mechanism is also responsible for the mitochondrial myopathy and lactic acidosis that occur with zidovudine. NRTIs, particularly zidovudine and abacavir, may also cause central nervous system (CNS) manifestations, including mania and psychosis. The non-nucleoside reverse transcriptase inhibitor (NNRTI) efavirenz is perhaps the antiretroviral most commonly associated with CNS toxicity, causing insomnia, irritability and vivid dreams. Recent studies have suggested that the risk of developing these adverse effects is increased in patients with various cytochrome P450 2B6 alleles. Protease inhibitors cause perioral paraesthesias and may indirectly increase the relative risk of stroke by promoting atherogenesis. HIV integrase inhibitors, C-C chemokine receptor type 5 (CCR5) inhibitors and fusion inhibitors rarely cause neuropsychiatric manifestations.

Elevated serum fibroblast growth factor 21 levels correlate with immune recovery but not mitochondrial dysfunction in HIV infection

Background

Anti-retroviral treated HIV-infected patients are at risk of mitochondrial toxicity, but non-invasive markers are lacking. Serum FGF-21 (fibroblast growth factor 21) levels correlate strongly with muscle biopsy findings in inherited mitochondrial disorders. We therefore aimed to determine whether serum FGF-21 levels correlate with muscle mitochondrial dysfunction in HIV-infected patients.

Findings

We performed a cross-sectional study of anti-retroviral treated HIV-infected subjects (aged 29 – 71 years, n = 32). Serum FGF-21 levels were determined by quantitative ELISA. Cellular mitochondrial dysfunction was assessed by COX (cytochrome c oxidase) histochemistry of lower limb skeletal muscle biopsy. Serum FGF-21 levels were elevated in 66% of subjects. Levels correlated significantly with current CD4 lymphocyte count (p = 0.042) and with total CD4 count gain since initiation of anti-retroviral therapy (p = 0.016), but not with the nature or duration of past or current anti-retroviral treatment. There was no correlation between serum FGF-21 levels and severity of the muscle mitochondrial (COX) defect.

Conclusions

Serum FGF-21 levels are a poor predictor of muscle mitochondrial dysfunction in contemporary anti-retroviral treated patients. Serum FGF-21 levels are nevertheless commonly elevated, in association with the degree of immune recovery, suggesting a non-mitochondrial metabolic disturbance with potential implications for future comorbidity.

Impact of the DNA extraction method on 2-LTR DNA circle recovery from HIV-1 infected cells

Detection of episomal 2-LTR DNA circles is used as a marker for the ongoing virus replication in patients infected with HIV-1, and efficient extraction of episomal DNA is critical for accurate estimation of the 2-LTR circles. The impact of different methods of DNA extraction on the recovery of 2-LTR circles was compared using mitochondrial DNA extracted as an internal control. The bacterial plasmid DNA isolation method extracted less than 10% of cellular DNA, 40% of mitochondrial DNA and 12-20% of the input 2-LTR DNA. The total DNA isolation method recovered about 70% of mitochondrial DNA and 45% of the input 2-LTR DNA. The total nucleic acid isolation method recovered 90% of mitochondrial DNA and 60% of the input 2-LTR DNA. Similar results were obtained when the DNA was extracted from HIV-1 infected cells. Plasmid DNA isolation could not distinguish between 12 and 25 copies of 2-LTR DNA per million cells, whereas the total nucleic acid isolation showed a consistent and statistically significant difference between 12 and 25 copies. In conclusion, the total nucleic acid isolation method is more efficient than the plasmid DNA isolation method in recovering mitochondrial DNA and 2-LTR DNA circles from HIV-1 infected cells.

Mitochondrial damage in adipose tissue of untreated HIV-infected patients

OBJECTIVE

antiretrovirals, especially thymidine-analogue nucleoside reverse transcriptase inhibitors (tNRTIs), may cause the mitochondrial damage in adipose tissue that has been associated with lipodystrophy development. HIV itself may damage blood cell mitochondria. However, the viral capacity to induce adipose tissue mitochondrial lesion is still a matter of doubt. We aimed to assess whether untreated HIV infection was associated with adipose tissue mitochondrial abnormalities.

DESIGN

: Single-site, cross-sectional, controlled observational and exploratory study without intervention.

METHODS

we included 24 uninfected controls and 18 HIV-infected patients with undetectable viral load and no clinical signs of lipodystrophy stratified as antiretroviral naive (n = 11) or at least 6-month antiviral-treated with a double NRTI combination, including lamivudine plus one tNRTI (n = 7). Subcutaneous adipose tissue was homogenated to determine mtDNA content by rtPCR and mitochondrial function per mitochondria through the spectrophotometric measurement of cytochrome c oxidase activity normalized by citrate synthase amount (COX/citrate synthase). Differences in mitochondrial parameters among groups were sought to determine the contribution of HIV and antiretrovirals to mitochondrial alterations.

RESULTS

compared with uninfected controls (arbitrarily assigned 100%), naive individuals presented a marked decrease in adipose tissue mtDNA content and COX/citrate synthase function (62 and 75% remaining content/activity, P < 0.001 and P < 0.05). Antiretrovirals did not increase this impairment (69 and 70% remaining content/activity, P < 0.05 compared to controls and P = not significant compared to naives). Additionally, molecular and functional mitochondrial parameters were positively correlated (P < 0.05).

CONCLUSION

in nonlipodystrophic HIV-infected naive patients, viral infection is associated with adipose tissue mtDNA decrease and mitochondrial dysfunction independently of antiretroviral treatment.

Decrease of mitochondrial DNA level in sperm from patients infected with human immunodeficiency virus-1 linked to nucleoside analogue reverse transcriptase inhibitors

OBJECTIVE

To study sperm parameters in patients infected with human immunodeficiency virus (HIV)-1 and to analyze mitochondrial DNA (mtDNA) in sperm according to the HIV treatment.

DESIGN

Observational study.

SETTING

University-affiliated teaching hospital.

PATIENT(S)

Thirty-two patients infected with HIV-1 and 31 noninfected healthy men provided semen samples.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

After DNA extraction, mtDNA level was assessed using real-time polymerase chain reaction (PCR) (LightCycler) in whole semen and in selected spermatozoa from 90% density centrifugation gradients. For each sample, mtDNA and β-globin gene sequences were amplified and PCR products were quantified. The mtDNA-to-β-globin ratio expressed the number of mtDNA copies per cell.

RESULT(S)

Compared with the control group, several sperm parameters were altered in patients with HIV. The number of mtDNA copies per cell in whole semen was increased in HIV-infected patients (6.3±6.3 vs. 3.5±3.2). However, there was no statistically significant difference in mtDNA copy number in the spermatozoa obtained after density gradient centrifugation. The number of nucleoside analogue reverse transcriptase inhibitors (NRTI) taken by patients during treatment significantly influenced the mtDNA level in sperm (1 NRTI 7.6±8.1, 2 NRTIs 7.0±5.1, 3 NRTIs 3.2±2.1).

CONCLUSION(S)

Using a specific method to measure sperm mtDNA, we demonstrated a decrease of mtDNA copies in spermatozoa after use of NRTIs with known mitochondrial toxicity.

Mitochondrial dysfunction in CD4+ lymphocytes from stavudine-treated HIV patients

HIV therapy with nucleoside analogue reverse transcriptase inhibitors (NRTI) such as stavudine remains in widespread use in resource-limited nations due to potent efficacy, convenience of formulation and lack of practical alternatives. However, it remains unclear whether adverse side effects with NRTI include reduced mitochondrial respiratory function, particularly in peripheral blood lymphocytes (PBLs). The aim of this study was to determine whether stavudine-based highly active antiretroviral therapy (HAART) is associated with impaired mitochondrial respiratory transport chain function in patient derived CD4+PBLs. CD4+PBLs were isolated from asymptomatic HIV-infected patients treated with stavudine-HAART for 3 months (n=10), HIV-infected patients not on treatment (n=9) and uninfected controls (n=18). The basal mitochondrial oxygen consumption of CD4+PBLs from stavudine-treated patients was reduced relative to that of untreated HIV-infected patients and controls (stavudine treated group, 4.22 (25% 2.16, 75% 8.84); control uninfected, 11.2 (25% 3.95, 75% 16.6); untreated 18.1 (25% 11.8, 75% 37.9)ng oxygen atoms/min/ml). Maximal oxygen consumption (stimulated with the proton ionophore FCCP) in cells from stavudine treated patients was also reduced relative to that of untreated patients and controls (stavudine treated, 24.4+/-10.5; control uninfected, 50.6+/-39.5; untreated, 68.8+/-41.1 ng oxygen atoms/min/ml). Citrate synthase activities, relative mitochondrial volume (by electron microscopy) and mtDNA copy numbers per cell were not different between groups. Therapy with stavudine results in impaired mitochondrial function in CD4+PBLs that does not appear to be due to reduced mitochondrial volume or DNA content and cannot be attributed to infection with HIV.

Mechanisms of antiretroviral therapy-induced mitochondrial dysfunction

PURPOSE OF REVIEW

To discuss novel developments related to the mechanisms of antiretroviral therapy-related mitochondrial toxicity, describe some apparent paradoxes in the current understanding of this field, and present questions that should be addressed by future research.

RECENT FINDINGS

The early polymerase gamma hypothesis states that nucleoside reverse transcriptase inhibitors can inhibit mitochondrial DNA replication and cause mitochondrial toxicity through mtDNA depletion. This mechanism is supported by a large body of evidence. Clinical manifestations of mitochondrial dysfunction are not always associated with mtDNA depletion. Increased mtDNA levels after nucleoside reverse transcriptase inhibitor exposure, as well as seemingly severe mtDNA depletion in individuals who show no clinical toxicity, have been reported. These and other observations suggest that additional mechanisms are involved in antiretroviral therapy toxicity, a notion supported by recent studies. Individuals given the same antiretroviral regimen can differ vastly with respect to the development of mitochondrial toxicity symptoms, reflecting interindividual variability. Some factors that may modulate this variability will be discussed.

SUMMARY

Mitochondrial toxicity induced by nucleoside reverse transcriptase inhibitors and their metabolic intermediates is probably mediated through many direct and indirect mechanisms. Depending on the mechanisms at play, the long-term health consequences of this toxicity may vary.

Using ΦX174 DNA as an exogenous reference for measuring mitochondrial DNA copy number

Quantitative real-time PCR has become a popular method to analyze and quantify changes in the copy number of mitochondrial DNA (mtDNA), and nuclear DNA (nDNA) is often used as an endogenous reference for mtDNA abundance. In our experience, using nDNA as a reference is problematic, due to differences in the extraction efficiency of nDNA and mtDNA and variation in the ploidy of experimental samples. Here, we report that the ratio of mtDNA to nDNA varies in repeated DNA extractions but that ΦX174 DNA, added before DNA extraction, is extracted with a similar efficiency to mtDNA, making it a suitable alternative reference for quantifying mtDNA copy number.

Toxicities associated with dual nucleoside reverse-transcriptase inhibitor regimens in HIV-infected children

BACKGROUND

Human immunodeficiency virus (HIV) therapy includes a backbone of nucleoside reverse-transcriptase inhibitors (NRTIs). Toxicities associated with NRTIs are not fully defined in children.

METHODS

We studied 2233 children < or =13 years of age who were perinatally infected with HIV and were receiving > or =2 NRTIs, to determine the relative toxicities of the 5 most common NRTI pairs: zidovudine (ZDV)/lamivudine (3TC), ZDV/didanosine (ddI), stavudine (d4T)/3TC, d4T/ddI, and ddI/3TC. Incidence rates for clinical and laboratory toxicities were estimated, and NRTI pairs were compared with regard to the time to the first toxicity.

RESULTS

The most common clinical toxicities noted were hepatitis, peripheral neuropathy, lipodystrophy/lipoatrophy, and pancreatitis, whereas the most common laboratory toxicities were an elevated anion gap, an increased total amylase level, neutropenia, and thrombocytopenia. Overall, regimens containing ZDV were associated with a significantly lower rate of clinical toxicities than were those containing d4T (adjusted hazard ratio [HR], 0.49; P = .02) ); regimens containing ddI were associated with a significantly lower rate of laboratory toxicities than were those containing 3TC (adjusted HR, 0.78; P = .04). ZDV/3TC was associated with a lower rate of clinical toxicities than were d4T/ddI and ddI/3TC and with a higher rate of laboratory toxicities than was ZDV/ddI. ZDV/ddI was associated with a lower rate of clinical toxicities than was d4T/3TC.

CONCLUSIONS

In children, regimens containing ZDV have less toxicity than do those containing d4T, thereby supporting their use in first-line regimens. D4T/3TC, d4T/ddI, and ddI/3TC have similar toxicity rates and are appropriate for second-line therapy.

Mitochondrial oxidative phosphorylation protein levels in peripheral blood mononuclear cells correlate with levels in subcutaneous adipose tissue within samples differing by HIV and lipoatrophy status

Depletion of mitochondrial DNA (mtDNA) and mtDNA-encoded respiratory chain proteins in subcutaneous (SC) fat from patients with HIV lipoatrophy have clearly demonstrated the role of mitochondrial dysfunction in this syndrome. Research in HIV lipoatrophy, however, has been severely hampered by the lack of a suitable surrogate marker in blood or other easily obtained clinical specimens as fat biopsies are invasive and mtDNA levels in peripheral blood mononuclear cells (PBMC) do not consistently correlate with the disease process. We used a simple, rapid, quantitative 2-site dipstick immunoassay to measure OXPHOS enzymes Complex I (CI) and Complex IV (CIV), and rtPCR to measure mtDNA in 26 matched SC fat and PBMC specimens previously banked from individuals on potent antiretroviral (ARV) therapy with HIV lipoatrophy, on similar ARV therapy without lipoatrophy, and in HIV seronegative controls. Significant correlations were found between the respective PBMC and fat levels for both CI (r = 0.442, p = 0.024) and for CIV (r = 0.507, p = 0.008). Both CI and CIV protein levels were also significantly reduced in both PBMCs and fat in lipoatrophic subjects compared to HIV seronegative controls (p < or = 0.05), while a comparative reduction in mtDNA levels in lipoatrophic subjects was observed only in fat. We conclude that CI and CIV levels in PBMCs correlate to their respective levels in fat and may have utility as surrogate markers of mitochondrial dysfunction in lipoatrophy.

Generation and modulation of hepatocellular carcinoma circulating cells: a new experimental model

BACKGROUND

To establish a new experimental model of human hepatocellular carcinoma by orthotopic implantation of tumoral cells with its subsequent removal, to generate and modulate circulating tumoral cells.

MATERIALS AND METHODS

Three human hepatoma cell lines (HepG2, PLC/PRF, and Mahlavu) were orthotopically implanted under the Glisson's capsule of the left lateral lobe of the liver in a total of 56 non-obese diabetic/severe combined immunodeficiency mice. Tumor removal was performed 30 d after injection, and a laparotomy without tumor removal was done in control mice. Generation of circulating cells was monitored by flow cytometry using fluorescein isothiocyanate-conjugated anti-HLA antibody.

RESULTS

In 26 mice implanted with Mahlavu cells, 20 developed a unique tumor allowing a resection (77%), which was technically feasible in 80% of cases. The overall perioperative mortality was 30% (3/10) after resection; no mortality was observed in the control group. The circulating tumoral cells decreased dramatically after resection of the tumor as compared with control mice.

CONCLUSION

This new model is feasible and may be an interesting useful tool to study the hepatocellular carcinoma metastatic process and is consistent with the human clinical practice.

Mitochondrial DNA assessment in adipocytes and peripheral blood mononuclear cells of HIV-infected patients with lipodystrophy according to a validated case definition

BACKGROUND

Several studies have compared mitochondrial DNA (mtDNA) content in tissue from HIV-1-infected patients on highly active antiretroviral therapy with and without evidence of lipodystrophy, the diagnosis of which was based on subjective clinical assessment.

OBJECTIVES

The aim of this study was to assess the utility of mtDNA quantification as a marker of HIV-associated lipodystrophy as diagnosed using a published validated case definition.

METHODS

We assessed mtDNA content in adipocytes from both thigh and lumbar subcutaneous adipose tissue (n=19), and in peripheral blood mononuclear cells (PBMC) (n=26), obtained from 26 HIV-1-infected patients classified as having lipodystrophy (n=17) or not having lipodystrophy (n=9) according to the validated definition derived from the Lipodystrophy Case Definition Study.

RESULTS

The adipocyte and PBMC mtDNA contents did not significantly differ between patients with and without lipodystrophy. Lipodystrophy patients had been treated for significantly longer times, especially with dideoxynucleoside analogues. In both groups, the thigh adipocyte mtDNA content was significantly greater than that of the lumbar region. When all patients were considered together, a statistically significant negative correlation was found between thigh adipocyte mtDNA content and stavudine treatment duration.

CONCLUSIONS

Longer exposure to dideoxynucleoside analogues was associated with lipodystrophy, and longer exposure to stavudine was correlated with lower mtDNA content in thigh adipocytes. However, a single measurement of adipocyte mtDNA content in this limited sample of patients could not distinguish between patients with and without clinical lipodystrophy. The observed variation in mtDNA content between different subcutaneous adipose tissue depots argues for harmonization of future studies regarding which depot to biopsy.

Impact of nucleoside reverse transcriptase inhibitors on mitochondria in human immunodeficiency virus type 1-infected children receiving highly active antiretroviral therapy

Mitochondrial toxicity induced by nucleoside reverse transcriptase inhibitors (NRTIs) has been reported to be responsible for various adverse effects. The relative impact of NRTIs on the mitochondria of human immunodeficiency virus (HIV) type 1 (HIV-1)-infected children receiving highly active antiretroviral therapy (HAART) is unknown. Mitochondrial DNA (mtDNA) levels were quantified longitudinally from peripheral blood mononuclear cells (PBMCs) in 31 HIV-1-infected children from Pediatric AIDS Clinical Trial Group Study 382 who were receiving HAART, including nelfinavir, efavirenz, and different NRTIs, and who had had undetectable plasma HIV-1 RNA levels for >2 years. The median mtDNA levels in PBMCs increased from 137 copies/cell at the baseline to 179 copies/cell at week 48 (P = 0.01) and 198 copies/cell at week 104 (P < 0.001). Before the initiation of HAART, children who received regimens containing didanosine had mtDNA levels persistently lower than those in children not receiving didanosine (106 versus 140 copies/cell; P = 0.008). During HAART, the median increase in the mtDNA level from the baseline to week 104 was the lowest in children who received regimens containing didanosine (+26 copies/cell) compared to those in children who received other regimens (+79 copies/cell) (P = 0.02). A multivariate analysis also demonstrated that didanosine, as part of HAART, was the only NRTI associated with the change in mtDNA levels (P = 0.007). Children receiving didanosine-containing antiretroviral regimens have the lowest mtDNA levels in PBMCs and may be at greater risk for long-term adverse effects due to mitochondrial toxicity. This may be of particular importance in resource-limited countries where didanosine is widely used for the treatment of HIV-infected children.

The Influence of HIV Infection and Antiretroviral Therapy on the Mitochondrial Membrane Potential of Peripheral Mononuclear Cells

Objectives

Clinical disorders occurring in HIV-infected patients on antiretroviral therapy (ART) have been linked to mitochondrial dysfunction, for example, lactic acidosis and lipodystrophy. Mitochondrial membrane potential (ΔΨm) is the most direct measure of the state of energization of the mitochondria. We analysed ΔΨm of peripheral blood mononuclear cells (PBMCs) in HIV-negative, healthy subjects ( n=8), HIV-infected, treatment-naive patients ( n=30), and HIV-infected patients on ART ( n=58). The influence of ART was analysed in six patients who started their first regimen.

Methods

The ΔΨm of PBMC was measured by flow cytometry using the dye JC-1.

Results

The ΔΨm was significantly lower in HIV-infected patients than in HIV-negative controls. This difference was detected in both treated ( P=0.0001) and untreated patients ( P=0.001). The ΔΨm of PBMCs was highly correlated with CD4+ T-cell count in therapy-naive patients ( P=0.002, r=0.546) and in treated patients ( P=0.028, r=0.288). The ΔΨm increased significantly in therapy-naive patients after starting ART ( P=0.001). Patients with lipoatrophy had significantly lower ΔΨm than patients without lipodystrophy or with lipohypertrophy ( P=0.023).

Conclusions

In HIV-infected persons ΔΨm is significantly reduced. Patients with lipoatrophy have significantly reduced ΔΨm. This is the first study showing that the ΔΨm of PBMCs is highly correlated with CD4+ T-cell count in HIV infection.

Absence of a universal mechanism of mitochondrial toxicity by nucleoside analogs

Nucleoside analogs are associated with various mitochondrial toxicities, and it is becoming increasingly difficult to accommodate these differences solely in the context of DNA polymerase gamma inhibition. Therefore, we examined the toxicities of zidovudine (AZT) (10 and 50 microM; 2.7 and 13.4 microg/ml), didanosine (ddI) (10 and 50 microM; 2.4 and 11.8 microg/ml), and zalcitabine (ddC) (1 and 5 microM; 0.21 and 1.1 microg/ml) in HepG2 and H9c2 cells without the presumption of mitochondrial DNA (mtDNA) depletion. Ethidium bromide (EtBr) (0.5 microg/ml; 1.3 microM) was used as a positive control. AZT treatment resulted in metabolic disruption (increased lactate and superoxide) and increased cell mortality with decreased proliferation, while mtDNA remained unchanged or increased (HepG2 cells; 50 microM AZT). ddC caused pronounced mtDNA depletion in HepG2 cells but not in H9c2 cells and increased mortality in HepG2 cells, but no significant metabolic disruption in either cell type. ddI caused a moderate depletion of mtDNA in both cell types but showed no other effects. EtBr exposure resulted in metabolic disruption, increased cell mortality with decreased cell proliferation, and mtDNA depletion in both cell types. We conclude that nucleoside analogs display unique toxicities within and between culture models, and therefore, care should be taken when generalizing about the mechanisms of nucleoside reverse transcriptase inhibitor toxicity. Additionally, mtDNA abundance does not necessarily correlate with metabolic disruption, especially in cell culture; careful discernment is recommended in this regard.

Alteration of cytochrome oxidase subunit I labeling is associated with severe mitochondriopathy in NRTI-related hepatotoxicity in HIV patients

Liver mitochondrial toxicity induced by nucleoside reverse transcriptase inhibitors (NRTI) in human immunodeficiency virus (HIV) patients has been associated with a wide range of liver involvement ranging from low-grade hepatotoxicity, asymptomatic lactacidemia to severe liver insufficiency, with massive steatosis and life-threatening lactic acidosis. Considerable efforts have been made in the last few years to establish clinical guidelines to avoid life-threatening NRTI-associated lactic acidosis. However, the important issue of low-grade NRTI-associated hepatotoxicity still needs to be unravelled since its natural history is largely unknown. We have recently reported a series of 13 monoinfected HIV patients with low-grade NRTI-associated toxicity. Our results outlined the heterogeneity of NRTI-induced hepatotoxicity and raised the question of its diagnosis. The present study evaluates the expression of cytochrome oxidase (COX) subunits I and IV, encoded by mitochondrial and nuclear DNA, respectively, in NRTI hepatotoxicity. The aim of our study was to compare the detection rate of mitochondrial abnormalities of immunohistochemistry for COX subunit I with electron microscopy. COX subunit I and IV labeling was performed together with light microscopy and ultrastructural analysis in a series of 55 liver biopsies from HIV monoinfected and HIV-hepatitis C virus coinfected patients. Clinical data were also recorded. Our major findings were: (i) decreased COX subunit I labeling is associated with severe ultrastructural mitochondrial alterations and may represent overt NRTI-induced mitochondrial cytopathy; (ii) mild ultrastructural damage associated with normal COX subunit I labeling is of unknown clinical significance. The results of the study suggest that COX subunit I labeling may be a valuable tool for the diagnosis of mitochondrial liver disease in HIV patients.

Fate and characterization of circulating tumor cells in a NOD/SCID mouse model of human hepatocellular carcinoma

There is much debate about the way in which epithelial tumors metastasize. It has been proposed that the bone marrow (BM) acts as a tumor cell reservoir. We injected human hepatocellular carcinoma (HCC) cells (Mahlavu cell line) into the livers, circulation or BM of NOD/SCID mice and circulating tumor cells were quantified. When injected under the Glisson capsule, a primary tumor developed and continuously yielded circulating tumor cells. Liver tumor removal led to a very low level of Mahlavu cells both in blood and BM 30 days later. When Mahlavu cells (cultured or from BM of primary mice femurs) were intravenously injected into mice, the number of cells in the bloodstream (BS) steadily decreased, whereas the BM was not significantly colonized. When Mahlavu cells were directly injected into one femur, the controlateral femur was not colonized. Microscopic analysis and a sensitive PCR assay (<1 Mahlavu cell/nuclear cells) both failed to detect human tumor cells in other organs regardless of injection route. In conclusion, our model strongly supports the hypothesis that HCCs continuously release cells into the BS. However, in sharp contrast with the current hypothesis, the BM is not specifically colonized by tumor cells but could store them at a very low level.

Exploration of global gene expression in human liver steatosis by high-density oligonucleotide microarray

Understanding the molecular mechanisms underlying fatty liver disease (FLD) in humans is of major importance. We used high-density oligonucleotide microarrays (22.3 K) to assess the mechanisms responsible for the development of human liver steatosis. We compared global gene expression in normal (n=9) and steatotic (n=9) livers without histological signs of inflammation or fibrosis. A total of 34 additional human samples including normal (n=11), steatosis (n=11), HCV-related steatosis (n=4) or steatohepatitis associated with alcohol consumption (n=4) or obesity (n=4) were used for immunohistochemistry or quantitative real-time PCR studies. With unsupervised classification (no gene selection), all steatotic liver samples clustered together. Using step-down maxT multiple testing procedure for controlling the Family-Wise Error-Rate at level 5%, 110 cDNAs (100 over- and 10 underexpressed) were found to be differentially expressed in steatotic and normal livers. Of them were genes involved in mitochondrial phosphorylative and oxidative metabolism. The mean ratio of mitochondrial DNA to nuclear DNA content was higher in liver steatosis compared to normal liver biopsies (1.12+/-0.14 vs 0.67+/-0.10; P=0.01). An increased expression of genes involved in inflammation (IL-1R family, TGFB) was also observed and confirmed by quantitative RT-PCR or immunochemistry. In steatohepatitis, an increase of the protein expression of mitochondrial antigens, IL-1R1, IGF2 and TGFB1 was also observed, interleukin 1 receptor being always strongly expressed in steatohepatitis linked to alcohol or obesity. In conclusion, mitochondrial alterations play a major role in the development of steatosis per se. Activation of inflammatory pathways is present at a very early stage of steatosis, even if no morphological sign of inflammation is observed.

Depletion of mitochondrial DNA copies/cell in peripheral blood mononuclear cells in HIV-1-infected treatment-naive patients

OBJECTIVES

Mitochondrial toxicity is believed to be the main reason for adverse effects related to nucleoside reverse transcriptase inhibitors (NRTIs). The aim of the present study was to compare mitochondrial toxicity in NRTI-treated HIV-positive patients, HIV-positive treatment-naïve patients and HIV-negative controls by comparing mitochondrial DNA (mtDNA) copies/cell in peripheral blood mononuclear cells (PBMCs) and lactate/pyruvate (L/P) ratios in the different groups.

METHODS

We enrolled 60 participants in the study: 31 patients on combined antiretroviral therapy (CART), 14 HIV-positive treatment-naive patients and 15 HIV-negative controls. mtDNA (copies/cell) in peripheral blood was analysed using quantitative real-time polymerase chain reaction (PCR). Standard curves and serial dilutions of plasmid-cloned mitochondrion and retinoblastoma (RB1) PCR products with known concentrations were generated to estimate the mtDNA and nuclear DNA (nDNA) copy numbers in each sample. The L/P ratio was enzymatically and spectrophotometrically analysed in samples from individuals in a fasted, non-exercise state. Results The median mtDNA copy number was 63 copies/cell (interquartile range 33-94) in HIV-positive patients and 153 (132-283) in HIV-negative controls (P<0.001). No significant difference was seen between the HIV-positive NRTI-exposed patients and the HIV-positive treatment-naive patients. Current use of didanosine was negatively correlated with depletion of mtDNA (r=-0.36, P=0.046). HIV-positive patients also had a higher L/P ratio compared with HIV-negative controls (P=0.004).

CONCLUSIONS

The number of mtDNA copies/cell in PBMCs was depleted in HIV-positive treatment-naive patients as well as in HIV-positive NRTI-exposed patients. HIV-positive patients also had a higher L/P ratio compared with HIV-negative controls, which supports this conclusion. The study suggests that neither mtDNA in PBMCs nor L/P ratio is a good marker of NRTI-associated mitochondrial toxicity.

Upregulatory mechanisms compensate for mitochondrial DNA depletion in asymptomatic individuals receiving stavudine plus didanosine

Nucleoside analogue use is often related to mitochondrial DNA (mtDNA) depletion, but mitochondrial function is preserved in most asymptomatic patients. We determined whether homeostatic mechanisms are able to compensate for this mtDNA depletion in patients receiving stavudine plus didanosine (d4T + ddI), an antiretroviral combination with great in vitro and in vivo capacity to decrease mtDNA. We included 28 asymptomatic HIV-infected individuals: 17 subjects (cases) on a first-line antiretroviral regimen consisting of d4T + ddI as the nucleoside backbone plus nevirapine or nelfinavir for at least 6 months (mean: 16 +/- 8 months) and 11 naive subjects (controls). We assessed the following in peripheral blood mononuclear cells: mitochondrial mass by citrate synthase activity, mtDNA content by real-time polymerase chain reaction, cytochrome c oxidase subunit II (COX-II) expression by Western blot analysis, and COX activity by spectrophotometry. The mitochondrial mass and mtDNA content of cases decreased when compared with controls, whether normalized per cell or per mitochondrion. Conversely, COX-II expression and COX activity were similar in cases and controls. COX-II expression was constant and independent of the mtDNA content, whereas it was closely related to COX activity. We concluded that treatment with dd4T + ddI is associated with decreased mitochondrial mass and mtDNA content but that COX-II expression and COX activity remain unaltered. These data suggest that upregulatory transcriptional or posttranscriptional mechanisms compensate for mtDNA depletion caused by d4T + ddI before profound mtDNA depletion occurs.

Toxicité mitochondriale hépatique associée au traitement par les antirétroviraux

Highly active antiretroviral therapy (HAART) has become the gold standard treatment of HIV/AIDS infection. NRTI-related mitochondrial toxicity has been recognized as a serious adverse effect of HAART. The mechanisms underlying NRTI-induced mitochondriopathy involve the inhibition of the human DNA polymerase gamma mtDNA mutations and oxidative stress. The clinical spectrum of NRTI-related toxicity ranges from a subclinical disease e.g. mild hepatic abnormalities, to a rare life-threatening condition with lactic acidosis and hepatic insufficiency. In the latter, liver histology shows massive steatosis. Ultrastructural assessment of mitochondrial abnormalities may be of help to address the NRTI toxicity in poorly symptomatic patients. Efforts have been recently made to assess the clinical relevance of non-invasive tests including the evaluation of mtDNA or mitochondrial functions in peripheral blood mononuclear cells for the diagnosis of NRTI-associated toxicity.

Mitochondrial (Mt)Dna Changes in Tissue May Not be Reflected by Depletion of Mtdna in Peripheral Blood Mononuclear Cells in HIV-Infected Patients

Objectives

Most data on mitochondrial toxicity have been derived from peripheral blood mononuclear cells (PBMCs). However, whether mitochondrial DNA (mtDNA) content in PBMCs reflects the mitochondrial state in tissues remains elusive. We report herein on mitochondrial toxicity in skeletal muscle in HIV-infected patients naive to antiretroviral treatment (ART [HIV+ART-naive]; n=10) patients exposed to nucleoside reverse transcriptase inhibitors (NRTIs [HIV+NRTI+]; n=24) and healthy controls ( n=11), and compare these tissue data with mtDNA in PBMCs.

Methods

Muscle biopsies were examined for (i) mtDNA and nuclear DNA (nDNA) content using TaqMan realtime PCR system, (ii) mtDNA deletions using long expand PCR with subsequent gel electrophoresis, and (iii) mitochondrial myopathy expressed as cytochrome c oxidase (COX)-deficient muscle fibres.

Results

The mt/n DNA ratio in muscle from HIV+NRTI+patients was reduced compared with HIV-negative controls ( P=0.028). Moreover, mtDNA deletions were more frequent in HIV+NRTI+ patients than in both HIV-negative controls ( P=0.009) and HIV+ART-naive patients ( P=0.005). HIV+NRTI+ also tended to have more COX-deficient fibres than HIV-negative controls ( P=0.076). COX-deficient fibres were positively correlated with mtDNA deletions in HIV+NRTI+ patients (r=0.83, P<0.001). Patients with current use of didanosine (ddI) had more frequent mtDNA deletions and COX-deficient fibres than HIV+NRTI+ not on current treatment with ddI. It should be noted that mitochondrial alterations were not correlated with mtDNA/cell in PBMCs in any group.

Conclusions

In skeletal muscle, HIV+NRTI+ had a reduced mt/n DNA ratio, more frequent mtDNA deletions and possibly more COX-deficient muscle fibres than HIV-negative controls. However, the mtDNA/cell in peripheral blood was decreased in both HIV+NRTI+ and HIV+ART-naive patients. Thus, mtDNA in peripheral blood may not be a relevant marker of mitochondrial toxicity in organ-specific tissue.

Mitochondrial Studies in Haart-Related Lipodystrophy: From Experimental Hypothesis to Clinical Findings

Chronic use of antiretrovirals (ARVs) to treat HIV infection, along with more prolonged patient survival, has been associated with an increase in adverse drug effects in HIV-infected patients on treatment. It has been proposed that some of these adverse effects (including myopathy, cardiomyopathy, anaemia, hyperlactataemia/ lactic acidosis, pancreatitis, polyneuritis and lipodystrophy) could be mediated by mitochondrial (mt) toxicity. From the experimental data, it has been proposed that nucleoside analogue reverse transcriptase inhibitors (NRTIs) also inhibit γ-polymerase, the enzyme devoted to replicate (and, to a lesser extent, repair) mtDNA. It is now widely accepted that the use of most NRTIs in HIV-infected patients is associated with mtDNA depletion. Although cross-sectional studies suggest that certain ARVs, especially stavudine, are more toxic to mitochondria, the differences among different highly active ARV therapy (HAART) schedules detected in the analysis of longitudinal studies are not so clear. These types of study in previously untreated individuals suggest that the greatest mtDNA loss appears at the beginning of the treatment. Conversely, in ARV-experienced patients, the potential beneficial effects of HAART changes in terms of mtDNA content remain controversial and must be further investigated. Functional studies accompanying genetic investigations are needed for the correct pathogenic interpretation of the mtDNA abnormalities.

Possible Ways Nucleoside Analogues Can Affect Mitochondrial Dna Content and Gene Expression during HIV Therapy

In recent years, research into nucleoside reverse transcriptase inhibitor (NRTI)-related mitochondrial (mt) toxicity in HIV therapy has led to conflicting results and many unanswered questions regarding the molecular mechanisms that lead to such toxicity. From the early hypothesis that inhibition of the human mt polymerase γ by NRTIs was responsible for the drugs’ mt toxicity, an increasingly complex picture is emerging that probably involves multiple mt pathways. Results have been presented suggesting that NRTIs affect not only mtDNA but also mtRNA, nucleotide phosphorylation and the mt respiratory chain. Based on the current level of knowledge, this overview addresses some of the potential mechanisms through which NRTIs could affect mitochondria and ultimately cause the toxicity symptoms observed in HIV patients receiving NRTI-containing antiretroviral therapy.