Hepatocerebral Mitochondrial DNA Depletion Syndrome Caused by Deoxyguanosine Kinase (DGUOK) Mutations

BACKGROUND

Autosomal recessive mutations in deoxyguanosine kinase (DGUOK) have been identified in the hepatocerebral form of mitochondrial DNA (mtDNA) depletion syndrome.

OBJECTIVES

To describe the clinical spectrum of DGUOK-related mtDNA depletion syndrome in 6 children and to summarize the literature.

RESULTS

We identified pathogenic mutations in DGUOK in 6 children with the hepatocerebral form of mtDNA depletion syndrome. We describe the clinical, neuroradiologic, histologic, and genetic features in these children. All children showed severe hepatopathy, while involvement of other organs (skeletal muscle and brain) was variable. We identified 5 novel mutations (1 of them in 2 children) and 2 previously described mutations. Three different mutations affected the initial methionine, suggesting a mutational hot spot. One of our patients underwent liver transplantation; pathologic findings revealed (in addition to diffuse hepatopathy) a hepatocellular carcinoma, implying a possible link between mtDNA depletion syndrome and tumorigenesis.

CONCLUSION

We studied 12 children with infantile hepatoencephalopathies and mtDNA depletion syndrome and found pathogenic DGUOK mutations in 6, suggesting that this gene defect is a frequent but not an exclusive cause of the hepatic form of mtDNA depletion syndrome.

High serum urate in HIV-infected persons: the choice of the antiretroviral drug matters

Data with regard to serum uric acid levels in HIV-infected subjects are scarce. A high prevalence of hyperuricaemia was identified in a prospective analysis of urate levels in 2287 visits made by a cohort of 270 HIV-positive patients. In univariate and multivariate analysis, hyperuricaemia was associated with factors previously identified in HIV-uninfected individuals, but also with the use of some antiretroviral drugs, particularly with the use of stavudine.

Idiopathic CD4 lymphocytopenia

PURPOSE OF REVIEW

A severe decrease of CD4 T cells predisposes humans to opportunistic infections. In adults, HIV is certainly the most common cause of CD4 lymphocytopenia, but other causes, such as infections, autoimmune diseases, immunosuppressive therapy, lymphoma and idiopathic forms need to be considered. This review summarizes the current knowledge of the poorly understood syndrome of idiopathic CD4 lymphocytopenia.

RECENT FINDINGS

Little research has tried to systematically dissect this probably heterogeneic syndrome after its initial description in 1992. Numerous cases presenting with opportunistic infections have been reported. Disturbed differentiation of stem cell precursors may contribute to CD4 lymphocytopenia. Because infections and lymphoma may also cause CD4 lymphocytopenia, the distinction between cause and effect may evolve only during follow-up.

SUMMARY

The manifestation of opportunistic infections calls for the evaluation of the immune system for CD4 lymphocytopenia. The differential diagnosis of this condition in adults comprises primarily HIV infection and less often other diseases or drugs. Idiopathic CD4 lymphocytopenia is very rare. The clinical significance of low CD4 cell counts in HIV negative patients still awaits its systematic analysis. Prophylaxis of opportunistic infections is oriented at the recommendations of HIV-infected individuals and causal treatment remains experimental.

Analgesic and disease modifying effects of interferential current in psoriatic arthritis

Interferential current (IFC) was suggested to improve the skin manifestations of psoriasis vulgaris, possibly by enhancing the intracellular concentration of cyclic AMP. We assessed the efficacy of IFC on psoriatic arthritis (PsA). Nine consecutive patients were analyzed at baseline and after 16 weeks of IFC therapy. Bipolar IFC was applied twice daily to hands, feet plus all affected joints. IFC improved SF-36 assessed body pain, but not other SF-36 subscales. Morning stiffness, tender joint counts, and physician assessed disease activity improved. In contrast, visual analogue scale assessed pain, CRP and ESR measurements were unchanged. MRI of the most affected hand or foot documented a tendency towards worsened tendinitis, soft tissue swelling, and new joint space narrowing and erosions. Bone scintigraphy showed a trend towards deterioration. New joints became inflamed within treated sites. Thus IFC has analgesic effects in PsA, but does not have a satisfactory disease modifying effect.

Assessment of adipokine expression and mitochondrial toxicity in HIV patients with lipoatrophy on stavudine- and zidovudine-containing regimens

OBJECTIVES

Despite evidence for the role of adipokines such as adiponectin in the metabolic toxicities of protease inhibitor (PI)-treated patients, little is known about their role in nucleoside reverse transcriptase inhibitor (NRTI)-induced lipoatrophy (LA). We analyzed the relations between mitochondrial toxicity, adipokine expression, and clinical LA in peripheral blood mononuclear cells (PBMCs) and adipose samples from individuals treated with stavudine (d4T) or zidovudine (ZDV) in comparison to patients undergoing highly active antiretroviral therapy (HAART) as well as HIV-negative individuals.

METHODS

In this cross-sectional analysis, we studied 18 PI-naive HIV-infected patients with LA treated with d4T (d4T+LA+ [n = 12]) or zidovudine (ZDV+LA+ [n = 6]) in comparison to HAART-treated patients with (HAART+LA+ [n = 8]) and without (HAART+LA- [n = 8]) LA as well as HIV-negative controls (n = 12). Adipose samples were assessed for protein and/or messenger RNA (mRNA) levels of adiponectin, tumor necrosis factor-alpha (TNFalpha), interleukin (IL)-6, and sterol regulatory element-binding protein (SREBP) 1a/c in all groups, whereas adipose and PBMC samples from the d4T+LA+, ZDV+LA+, and HIV-negative subgroups were assessed for mitochondrial DNA (mtDNA) depletion and cytochrome c-oxidase (COX) II/COX IV ratios.

RESULTS

There was no change in mtDNA levels in adipose or PBMC samples in NRTI-treated patients with LA, although patients treated with d4T had reduced COX II/COX IV ratios in adipose and PBMC samples. Adipose tissue adiponectin mRNA and plasma levels were reduced in the d4T- and ZDV-treated patients regardless of the use of PIs. Tissue SREBP1c mRNA levels were also significantly reduced in both NRTI groups when compared with the HIV-negative controls. Significant reductions in SREBP1c levels were also evident with the HAART+LA+ group when compared with HAART+LA- controls.

CONCLUSIONS

Patients with LA on d4T-based regimens show evidence of mitochondrial respiratory chain dysfunction, whereas the d4T- and ZDV-based regimens also demonstrated reduced SREBP1c and adiponectin levels, findings that have previously been shown with PIs.

Tissue-specific mtDNA lesions and radical-associated mitochondrial dysfunction in human hearts exposed to doxorubicin

Doxorubicin causes a chronic cardiomyopathy. Although the exact pathogenesis is unknown, recent animal data suggest that somatically acquired alterations of mitochondrial DNA (mtDNA) and concomitant mitochondrial dysfunction play an important role in its onset. In this study, skeletal and myocardial muscles were examined from human autopsies. Compared to controls (n = 8), doxorubicin-exposed hearts (n = 6) showed low absolute enzyme activity of mtDNA-encoded nicotinamide adenine dinucleotide hydrogen dehydrogenase (NADH DH, 79% residual activity, p = 0.03) and cytochrome c oxidase (COX, 59% residual activity, p < 0.001), but not of succinate dehydrogenase (SDH), which is encoded exclusively by nuclear DNA. NADH DH/SDH and COX/SDH ratios were 37% (p < 0.001) and 27% (p < 0.001) of controls. Expression of the mtDNA-encoded subunit II of COX was reduced (82%, p = 0.04), compared to its unchanged nucleus-encoded subunit IV. MtDNA-content was diminished (56%, p = 0.02), but the 'common' mtDNA-deletion was increased (9.2-fold, p = 0.004). Doxorubicin-exposed hearts harboured numerous additional mtDNA rearrangements lacking direct repeats. They contained elevated levels of malondialdehyde (MDA) (p = 0.006, compared to controls), which correlated inversely with the COX/SDH ratio (r = -0.45, p = 0.02) and the mtDNA-content (r = -0.75, p = 0.002), and correlated positively with the levels of the 'common' deletion (r = 0.80, p < 0.001). Doxorubicin-exposed hearts also contained the highest levels of superoxide (p < 0.001, compared to controls), which correlated negatively with the mtDNA-encoded respiratory chain activities, such as the COX/SDH ratio (r = -0.57, p = 0.02) and the NADH/SDH ratio (r = -0.52, p = 0.04), as well as with the mtDNA content (r = -0.69, p = 0.003), and correlated positively with the frequency of the 'common' deletion (r = 0.76, p < 0.001) and the MDA levels (r = 0.86, p < 0.001). Doxorubicin-exposed hearts contained electron-dense deposits within mitochondria. Hearts exposed to other anthracyclines (n = 6) or skeletal muscle (all groups) had no mitochondrial dysfunction. Doxorubicin, unlike other anthracyclines, augments lipid peroxidation, induces mtDNA mutations and decreases mtDNA content in human hearts. These lesions have an impact on mitochondrial function and could be of importance in the pathogenesis of clinical cardiomyopathy.

Uridine Abrogates the Adverse Effects of Antiretroviral Pyrimidine Analogues on Adipose Cell Functions

Objectives

Side effects of antiretroviral treatment such as lipoatrophy have been mainly attributed to mitochondrial toxicity of nucleoside reverse transcriptase inhibitors (NRTIs). We assessed whether uridine can abrogate the adverse effects of NRTIs on adipocyte functions.

Methods

3T3-F442A preadipocytes were exposed to stavudine (d4T; 10 μM), zidovudine (ZDV; 1 μM), zalcitabine (ddC; 0.2 μM) or didanosine (ddI; 10 μM) in the absence or presence of uridine 21 days prior to and 7 days after induction of differentiation. Then, lipid accumulation (oil red staining), apoptosis (flow cytometry, PARP-cleavage), mitochondrial mass (Mitotracker) and DNA (mtDNA), cytochrome c oxidase (COX) subunits and mitochondrial membrane potential (JC-1) were quantified.

Results

Whereas ddI had no effects, d4T, ZDV and ddC significantly decreased cellular lipid accumulation (by 32%, 46% and 24%, respectively), increased apoptosis and induced mitochondrial depolarization. d4T, ZDV and ddC decreased adipocyte mtDNA (by 64%, 53% and 46%, respectively) and reduced the mtDNA encoded COX II subunit. Uridine (200 μM) had no intrinsic effect, but prevented all adverse effects of d4T, ZDV and ddC on adipocyte morphology, lipid staining, apoptosis, mtDNA depletion (partial prevention with ZDV), mitochondrial mass and membrane potential. The effects of uridine were concentration-dependent. Uridine also fully reverted established d4T toxicities despite continued d4T exposure.

Conclusions

Uridine supplementation protects adipocytes from the adverse effects of d4T, ZDV and ddC on lipid accumulation, cell survival and mitochondrial functions, suggesting that the toxic effects could be linked to intracellular depletion of uridine or its metabolites. Uridine is an interesting candidate in the prevention of NRTI-induced lipoatrophy in vivo.

Uridine abrogates the adverse effects of antiretroviral pyrimidine analogues on adipose cell functions

OBJECTIVES

Side effects of antiretroviral treatment such as lipoatrophy have been mainly attributed to mitochondrial toxicity of nucleoside reverse transcriptase inhibitors (NRTIs). We assessed whether uridine can abrogate the adverse effects of NRTIs on adipocyte functions.

METHODS

3T3-F442A preadipocytes were exposed to stavudine (d4T; 10 microM), zidovudine (ZDV; 1 microM), zalcitabine (ddC; 0.2 microM) or didanosine (ddl; 10 microM) in the absence or presence of uridine 21 days prior to and 7 days after induction of differentiation. Then, lipid accumulation (oil red staining), apoptosis (flow cytometry, PARP-cleavage), mitochondrial mass (Mitotracker) and DNA (mtDNA), cytochrome c oxidase (COX) subunits and mitochondrial membrane potential (JC-1) were quantified.

RESULTS

Whereas ddl had no effects, d4T, ZDV and ddC significantly decreased cellular lipid accumulation (by 32%, 46% and 24%, respectively), increased apoptosis and induced mitochondrial depolarization. d4T, ZDV and ddC decreased adipocyte mtDNA (by 64%, 53% and 46%, respectively) and reduced the mtDNA encoded COX II subunit. Uridine (200 microM) had no intrinsic effect, but prevented all adverse effects of d4T, ZDV and ddC on adipocyte morphology, lipid staining, apoptosis, mtDNA depletion (partial prevention with ZDV), mitochondrial mass and membrane potential. The effects of uridine were concentration-dependent. Uridine also fully reverted established d4T toxicities despite continued d4T exposure.

CONCLUSIONS

Uridine supplementation protects adipocytes from the adverse effects of d4T, ZDV and ddC on lipid accumulation, cell survival and mitochondrial functions, suggesting that the toxic effects could be linked to intracellular depletion of uridine or its metabolites. Uridine is an interesting candidate in the prevention of NRTI-induced lipoatrophy in vivo.

Role of mitochondria in HIV lipoatrophy: insight into pathogenesis and potential therapies

Lipoatrophy is a selective loss of subcutaneous adipose tissue and a highly prevalent complication of antiretroviral therapy (ART). This form of fat wasting is associated with decreased quality of life, disincentive for adherence to antiretroviral therapy, as well as possibly an increased risk of coronary artery disease. Clinical trials have incriminated long-term ART with nucleoside analogue reverse transcriptase inhibitors (NRTIs) in general and stavudine in particular. The exact mechanism of fat wasting remains unclear, but the pathogenesis can largely be attributed to the mitochondrial toxicity of NRTIs. NRTIs are inhibitors of polymerase gamma, an enzyme which is necessary for the replication of mitochondrial DNA (mtDNA). Indeed, low amounts of mtDNA, abnormalities of mitochondrial ultrastructure, and respiratory chain dysfunction were identified in the subcutaneous fat tissue and skeletal muscle of HIV-patients under ART and linked to the use of stavudine. Switching away from the incriminated NRTI, is of proven benefit, but may not always be feasible. Supplementation with uridine should be investigated in the prevention and treatment of lipoatrophy based on its potential to competitively attenuate the mtDNA decline caused by pyrimidine NRTIs.

Mitochondrial DNA depletion in liver tissue of patients infected with hepatitis C virus: contributing effect of HIV infection?

OBJECTIVES

It has been suggested that chronic hepatitis C virus (HCV) infection depletes mitochondrial DNA (mtDNA) in the liver. Because decreased mtDNA levels were also found in humans infected with HIV, we investigated whether HIV may have aggravated hepatic mtDNA depletion in individuals with HCV infection.

METHODS

In this cross-sectional study, liver biopsies were performed in a total of 40 individuals prior to any antiviral therapy. The individuals were recruited from the Hospital Clinic, Barcelona and the HIV Centre, Dusseldorf. Seventeen patients were negative for HIV and HCV and were biopsied for liver enzyme elevation of unknown cause (controls), 14 individuals had chronic HCV but no HIV infection, and nine subjects were coinfected with both viruses. mtDNA and liver histology were centrally assessed.

RESULTS

The groups did not differ with respect to age, gender, liver function tests and HCV viral load, where applicable. mtDNA levels were decreased by 19% in the HCV-monoinfected group (P=0.03) and by 27% in the HIV/HCV-coinfected subjects (P=0.02) compared to controls. The mtDNA content, however, did not differ between individuals with HCV monoinfection and HCV/HIV coinfection (P=0.75). The degrees of liver fibrosis, inflammatory activity or steatosis did not correlate with mtDNA content.

CONCLUSIONS

Liver mtDNA content is reduced in both HCV-monoinfected and HIV/HCV-coinfected patients. Under the limitations of our study, we could demonstrate only a slight trend towards more pronounced mtDNA depletion in HIV/HCV-coinfected subjects.

Immunosuppressive treatment of chronic periaortitis: a retrospective study of 20 patients with chronic periaortitis and a review of the literature

BACKGROUND

Retroperitoneal fibrosis (RPF) and inflammatory aneurysm of the abdominal aorta (IAAA) are regarded as two manifestations of the same disease, termed "chronic periaortitis".

OBJECTIVE

To determine the optimal therapeutic and diagnostic approaches to IAAA.

METHODS

The outcome of medical immunosuppressive and surgical treatment of 20 patients was examined. Measurements of the C reactive protein (CRP) were compared with contrast enhanced imaging studies in the follow up of the patients.

RESULTS

The diameter of the periaortic mantle and its contrast enhancement improved in 13/15 (87%) patients given immunosuppressive treatment for a period of more than 6 months. Strong contrast enhancement was associated with a substantial rise in CRP, but no correlation between the CRP value and thickness of the fibrotic mass was found, even at intraindividual follow up.

CONCLUSIONS

Immunosuppressive treatment should be included in the first line treatment of patients with RPF and should be maintained long term. Imaging studies are better than CRP measurements in the evaluation of response to treatment.

Effects of Didanosine‐Related Depletion of mtDNA in Human T Lymphocytes

The normal metabolism of mitochondria in T lymphocytes is unknown, as are the effects from nucleoside-analogue reverse-transcriptase inhibitors that impair mitochondrial polymerase- gamma . We isolated peripheral-blood CD4 and CD8 T lymphocytes from 6 healthy men and stimulated them with anti-CD3 and anti-CD28 antibodies, in the presence and in the absence of didanosine (ddI). In the absence of ddI, mitosis of T lymphocytes was paralleled by a transient up-regulation of both mtDNA and production of lactate. In CD4 lymphocytes, 10-day incubation with ddI at concentrations of 11.8 mu mol/L, 35.4 mu mol/L, 59.0 mu mol/L, and 118.0 mu mol/L induced (1) a concentration-dependent reduction of both mtDNA (to 73%, 29%, 24%, and 23%, respectively, of the levels in control samples) and subunit II of mtDNA-encoded cytochrome c oxidase (to 86%, 81%, 55%, and 31%, respectively, of the levels in control samples) and (2) a concentration-dependent increase in production of lactate (to 139%, 222%, 276%, and 312%, respectively, of the levels in control samples). Activation of lymphocytes (which was measured in terms of expression of CD25) was unaffected. Mitochondrial depolarization (assessed by staining with JC-1) was observed as early as day 7 of incubation. All changes were time dependent and also were observed in isolated CD8 lymphocytes. Electron microscopy revealed enlarged mitochondria with vacuoles, inclusions, and reduced electron density. ddI at a concentration of 11.8 mu mol/L induced changes that bordered statistical significance. After stimulation, there was a wide range in the change of mtDNA content in lymphocytes. Therefore, mtDNA measurements in blood are not necessarily a marker for the mitochondrial toxicity of ddI. Nevertheless, ddI does lead to depletion of mtDNA in lymphocytes and to functional impairment.

Mitochondrial Toxicity of Nucleoside Analogues in Primary Human Lymphocytes

Objective

To evaluate if nucleoside analogue reverse transcriptase inhibitors (NRTIs) and polymerase-gamma inhibitors deplete mitochondrial DNA (mtDNA) in cultured primary lymphocytes and if such depletion might be associated with functional defects.

Methods

Primary peripheral blood CD4 and CD8 lymphocytes were purified from six healthy humans (three male and three female), stimulated mitotically (CD3/CD28) and cultured for 10 days in the presence or absence of NRTIs. Lymphocyte proliferation, mtDNA content, the expression of mtDNA-encoded cytochrome c-oxidase II (COXII) and lactate production were assessed.

Results

In CD4 lymphocytes, 10-day exposure to zalcitabine (1.77 μM), didanosine (118 μM) and stavudine (36 μM) induced a time-dependent decline of mtDNA. Compared with controls, residual mtDNA levels were 25%, 21% and 40%, respectively. COXII was reduced to 55%, 35% and 70% of control values. Lactic acid production was increased (by 214%, 294% and 175%, respectively). At day 10, lymphocyte counts were reduced (to 60%, 51%, and 41%, respectively). Zidovudine (71 μM) also reduced lymphocyte counts to 34% and increased lactic acid production by 170%, but did not induce mtDNA and COXII depletion. All these changes were highly significant. Lower NRTI concentrations (0.177 μM of zalcitabine, 11.8 μM of didanosine, 3.6 μM of stavudine and 7.1 μM of zidovudine) had effects at the border of significance. Similar observations were made in CD8 lymphocytes.

Conclusions

In human lymphocytes, zalcitabine, didanosine and stavudine induce dose- and time-dependent mtDNA depletion, which is associated with decreased cell proliferation and increased lactate production. Zidovudine impairs lymphocyte division without inducing mtDNA depletion.

Uridine in the Prevention and Treatment of Nrti-Related Mitochondrial Toxicity

Long-term side effects of antiretroviral therapy are attributed to the mitochondrial (mt) toxicity of nucleoside analogue reverse transcriptase inhibitors (NRTIs) and their ability to deplete mtDNA. Studies in hepatocytes suggest that uridine is able to prevent and treat mtDNA depletion by pyrimidine NRTIs [zalcitabine (ddC) and stavudine (d4T)] and to fully abrogate hepatocyte death, elevated lactate production and intracellular steatosis. Uridine was also found to improve the liver and haematopoietic toxicities of zidovudine (AZT), which are unrelated to mtDNA depletion, and to prevent neuronal cell death induced by ddC. Most recently, uridine was found to prevent the onset of a lipoatrophic phenotype (reduced intracellular lipids, increased apoptosis, mtDNA depletion and mt depolarization) in adipocytes incubated long-term with d4T and AZT. Various steps of mt nucleoside utilization may be involved in the protective effect, but competition of uridine metabolites with NRTIs at polymerase y or other enzymes is a plausible explanation. Pharmacokinetic studies suggest that uridine serum levels can be safely increased in humans to achieve concentrations which are protective in vitro (50–200 μM). Uridine was not found to interfere with the antiretroviral activity of NRTIs. Mitocnol, a sugar cane extract which effectively increases uridine in human serum, was beneficial in individual HIV patients with mt toxicity and is now being tested in placebo-controlled randomized trials. Until these data become available, the risk-benefit calculation of using uridine should be individualized. The current safety data justify the closely monitored use of uridine in individuals who suffer from mt toxicity but who cannot be switched to less toxic NRTIs.

Uridine in the prevention and treatment of NRTI-related mitochondrial toxicity

Long-term side effects of antiretroviral therapy are attributed to the mitochondrial (mt) toxicity of nucleoside analogue reverse transcriptase inhibitors (NRTIs) and their ability to deplete mtDNA. Studies in hepatocytes suggest that uridine is able to prevent and treat mtDNA depletion by pyrimidine NRTls [zalcitabine (ddC) and stavudine (d4T)] and to fully abrogate hepatocyte death, elevated lactate production and intracellular steatosis. Uridine was also found to improve the liver and haematopoietic toxicities of zidovudine (AZT), which are unrelated to mtDNA depletion, and to prevent neuronal cell death induced by ddC. Most recently, uridine was found to prevent the onset of a lipoatrophic phenotype (reduced intracellular lipids, increased apoptosis, mtDNA depletion and mt depolarization) in adipocytes incubated long-term with d4T and AZT. Various steps of mt nucleoside utilization may be involved in the protective effect, but competition of uridine metabolites with NRTIs at polymerase y or other enzymes is a plausible explanation. Pharmacokinetic studies suggest that uridine serum levels can be safely increased in humans to achieve concentrations which are protective in vitro (50-200 microM). Uridine was not found to interfere with the antiretroviral activity of NRTIs. Mitocnol, a sugar cane extract which effectively increases uridine in human serum, was beneficial in individual HIV patients with mt toxicity and is now being tested in placebo-controlled randomized trials. Until these data become available, the risk-benefit calculation of using uridine should be individualized. The current safety data justify the closely monitored use of uridine in individuals who suffer from mt toxicity but who cannot be switched to less toxic NRTIs.

Mitochondrial toxicity of nucleoside analogues in primary human lymphocytes

OBJECTIVE

To evaluate if nucleoside analogue reverse transcriptase inhibitors (NRTIs) and polymerase-gamma inhibitors deplete mitochondrial DNA (mtDNA) in cultured primary lymphocytes and if such depletion might be associated with functional defects.

METHODS

Primary peripheral blood CD4 and CD8 lymphocytes were purified from six healthy humans (three male and three female), stimulated mitotically (CD3/CD28) and cultured for 10 days in the presence or absence of NRTIs. Lymphocyte proliferation, mtDNA content, the expression of mtDNA-encoded cytochrome c-oxidase II (COXII) and lactate production were assessed.

RESULTS

In CD4 lymphocytes, 10-day exposure to zalcitabine (1.77 microM), didanosine (118 microM) and stavudine (361 microM) induced a time-dependent decline of mtDNA. Compared with controls, residual mtDNA levels were 25%, 21% and 40%, respectively. COXII was reduced to 55%, 35% and 70% of control values. Lactic acid production was increased (by 214%, 294% and 175%, respectively). At day 10, lymphocyte counts were reduced (to 60%, 51%, and 41%, respectively). Zidovudine (71 microM) also reduced lymphocyte counts to 34% and increased lactic acid production by 170%, but did not induce mtDNA and COXII depletion. All these changes were highly significant. Lower NRTI concentrations (0.177 microM of zalcitabine, 11.8 microM of didanosine, 3.6 microM of stavudine and 7.1 microM of zidovudine) had effects at the border of significance. Similar observations were made in CD8 lymphocytes.

CONCLUSIONS

In human lymphocytes, zalcitabine, didanosine and stavudine induce dose- and time-dependent mtDNA depletion, which is associated with decreased cell proliferation and increased lactate production. Zidovudine impairs lymphocyte division without inducing mtDNA depletion.

Liquid chromatographic method for the determination of uridine in human serum

To evaluate uridine levels in humans we developed a very sensitive and specific high-performance liquid chromatographic method for the determination of uridine in serum. We use techniques which are available in a standard analytical laboratory. Chromatographic analysis was carried out on a Phenomenex Aqua C18 5 micro 125A column protected by a guard cartridge system. Potassium dihydrogen phosphate buffer-acetonitrile was used as an eluent and oxypurinol as the internal standard. All sample preparation steps were done at 4 degrees C and the autosampler was cooled down to 4 degrees C. The calibration curve was linear throughout the calibration range from 0.25 to 100 micromol/l. This method was primarily established to evaluate uridine serum levels in patients with HIV infection since patients on highly active antiretroviral therapy (HAART) might develop metabolic disturbances that could lead to severe and fatal lactic acidosis due to mitochondrial toxicity. It is suggested that a limited or inadequate uridine supply is at least in part responsible for the onset of such deterioration.

The HIV-1 nucleoside reverse transcriptase inhibitors stavudine and zidovudine alter adipocyte functions in vitro

OBJECTIVES

Nucleoside analogues are suspected of playing a role in peripheral fat loss in patients during long-term treatment with antiretroviral drugs.

DESIGN AND METHODS

We compared the long-term effects of stavudine (10 microM), zidovudine (1 muM), didanosine (10 microM), abacavir (4 microM), lamivudine (10 microM), and tenofovir (1 microM), near their maximum concentration values, on the differentiation, lipid accumulation, survival and mitochondrial function of differentiating 3T3-F442A and differentiated 3T3-L1 adipocytes.

RESULTS

None of the nucleoside reverse transcriptase inhibitors (NRTI) markedly altered the differentiation of 3T3-F442A cells, as shown by the unmodified percentage of cells with lipid droplets on day 7 and the expression of the early differentiation markers CCAAT/enhancer binding protein (C/EBP) beta (on day 2) and sterol regulatory element-binding protein. However, stavudine and zidovudine altered the lipid phenotype, decreasing the lipid content and expression of markers involved in lipid metabolism, namely C/EBPalpha, peroxisome proliferator-activated receptor gamma, adipocyte lipid binding protein 2, fatty acid synthase and acetyl-coenzyme A carboxylase. Stavudine and zidovudine, contrary to the other NRTI, drove 5-10% of 3T3-F442A cells towards apoptosis, and reduced the lipid content and survival of differentiated 3T3-L1 adipocytes. Stavudine and zidovudine increased mitochondrial mass by two to fourfold, and lowered the mitochondrial membrane potential (JC-1 stain) as did zalcitabine (0.2 microM). Co-treatment with zidovudine plus lamivudine, or zidovudine plus lamivudine and abacavir, did not increase the effect of zidovudine on cell viability or apoptosis.

CONCLUSION

The thymidine analogues stavudine and zidovudine decreased lipid content, mitochondrial activity, and adipocyte survival in vitro.

Mitochondrial DNA and its respiratory chain products are defective in doxorubicin nephrosis

BACKGROUND

Doxorubicin induces a self-perpetuating nephropathy characterized by early glomerular and late-onset tubular lesions in rats. We investigated the potential role of mitochondrial injury in the onset of these lesions.

METHODS

Rats were treated with intravenous doxorubicin (1 mg kg(-1) week(-1)) for 7 weeks and were sacrificed either 1 week ('short-term') or 30 weeks ('long-term') following the last dose. Additional rats received a single dose either 6 days or 2 h prior to euthanasia. All rats were killed at 48 weeks of age. Glomerular and tubular injury was monitored and correlated to the activity or expression of respiratory chain components. Finally, we quantified both nuclear and mitochondrial DNA (mtDNA) as well as superoxide production and the 4834 base pair 'common' mtDNA deletion.

RESULTS

The 'long-term' group had significant glomerular and tubular lesions, depressed activities of mtDNA-encoded NADH dehydrogenase and cytochrome-c oxidase (COX) and increased citrate synthase activity. In addition, expression of the mtDNA-encoded COX subunit I was reduced and mtDNA levels were decreased. In 'short-term' rats, there were fewer tubular lesions, but similar numbers of glomerular lesions activity. Among all animals, glomerular and tubular injury were inversely correlated with mtDNA levels, mtDNA-encoded respiratory chain activities and with the expression of the mtDNA-encoded respiratory chain subunit COX-I. Injury was positively correlated with superoxide production and the activities of nucleus-encoded mitochondrial or cytoplasmic enzymes. Kidneys from the 'long-term' group showed more mtDNA deletions than in 'short-term' animals and these were not observed in the other groups.

CONCLUSIONS

These results suggest an important role for quantitative and qualitative mtDNA alterations through the reduction of mtDNA-encoded respiratory chain function and induction of superoxide in doxorubicin-induced renal lesions.

[Lactic acidosis in HIV-patients--diagnosis and treatment]

Lactic acidosis is a life-threatening complication of antiretroviral therapy with an incidence of about 1% per year. Its clinical onset is often abrupt, with uncharacteristic muscular, cardiac or hepatic symptoms. Lactic acidosis is caused by nucleoside analogue reverse transcriptase inhibitors (mainly didanosine, stavudine and zalcitabine), which are relatively strong inhibitors of gamma polymerase, the enzyme responsible for the replication of mitochondrial DNA. Zidovudine is also a mitochondrial toxin, but its toxicity probably reflects several mechanisms unrelated to mtDNA-depletion. When lactic acidosis is diagnosed, nucleoside analogues and other mitochondrial toxins, such as valproic acid and acetylsalicylic acid, must be discontinued immediately. Uridine should be supplemented, a cocktail consisting of vitamins, L-carnitine and coenzyme Q10, may be given.

Depletion of mitochondrial DNA in liver under antiretroviral therapy with didanosine, stavudine, or zalcitabine

The "D drug" HIV reverse-transcriptase inhibitors zalcitabine, didanosine, and stavudine are relatively strong inhibitors of polymerase-gamma compared with the "non-D drugs" zidovudine, lamivudine, and abacavir. D drugs deplete mitochondrial DNA (mtDNA) in cultured hepatocytes. This mtDNA depletion is associated with an increased in vitro production of lactate. To investigate the origin of hyperlactatemia in HIV-infected patients and the effects of antiretroviral therapy on liver mtDNA, we biopsied liver tissue from 94 individuals with chronic hepatitis C virus (HCV) infection. Eighty subjects were coinfected with HIV. Serum lactate was measured at the time of biopsy. Hepatic mtDNA and liver histology were centrally assessed. Liver mtDNA content of HIV-infected patients receiving D drugs at the time of biopsy (n = 34) was decreased by 47% (P<.0001) compared with those without D drugs (n = 35). Aside from a possible association between HCV genotype I status and mtDNA depletion in multivariate analysis, there were no other virologic, immunologic, histologic, demographic or treatment-related variables that could explain the mtDNA depletion. Lactate was above the upper limit of normal in only three patients, all of whom were treated with D drugs. The mtDNA in each of them was lower than in any non-D drug patient and significantly (P =.017) depleted compared with D drug patients with normal lactate. In conclusion, D drug treatment is associated with decreased hepatic mtDNA in HIV-infected patients with chronic HCV infection. Moderate mtDNA depletion in liver does not necessarily lead to hyperlactatemia, but more pronounced decreases in hepatic mtDNA may be an important contributor to lactate elevation.

Time-Dependent and Tissue-Specific Accumulation of mtDNA and Respiratory Chain Defects in Chronic Doxorubicin Cardiomyopathy

Background— Doxorubicin causes a chronic cardiomyopathy of unknown pathogenesis. We investigated whether acquired defects in mitochondrial DNA (mtDNA) and interconnected respiratory chain dysfunction may represent a molecular mechanism for its late onset.

Methods and Results— Rats were treated weekly with intravenous doxorubicin (1 mg/kg) for 7 weeks, starting at 11 weeks of age (group B). Controls received saline. Group C received doxorubicin identically to group B, but the course was started at 41 weeks of age. All rats were killed at week 48. Doxorubicin was also injected once, either 6 days (group D) or 2 hours (group E) before euthanasia. Heart and skeletal muscle were examined. Only group B rats developed a significant clinical, macroscopic, histological, and ultrastructural cardiomyopathy. Group B hearts had the lowest cytochrome c oxidase (COX) activity (24% of controls; P =0.003), the highest citrate synthase activity (135% of controls; P =0.005), and the highest production of superoxide. In group B, the respiratory subunit COXI, which is encoded by mtDNA, was reduced ( P <0.001), as was mtDNA (49% of controls, P <0.001). Group C hearts differed from group B in their lower cardiomyopathy score ( P =0.006), higher COX activity ( P =0.02), and higher mtDNA content ( P =0.04). Group B and to a lesser extent group C hearts contained deleted mtDNA. There was no detectable mitochondrial toxicity in group D and E hearts or in skeletal muscle.

Conclusions— In doxorubicin cardiomyopathy, mtDNA alterations, superoxide, and respiratory chain dysfunction accumulate long-term in the absence of the drug and are associated with a late onset.

Uridine abrogates mitochondrial toxicity related to nucleoside analogue reverse transcriptase inhibitors in HepG2 cells

OBJECTIVE

To assess in vitro if uridine may be suitable to prevent or treat mitochondrial toxicity related to nucleoside analogue reverse transcriptase inhibitors (NRTIs).

METHODS

Human HepG2-hepatocytes were exposed to NRTIs with or without uridine for 25 days. Cell growth, lactate production, intracellular lipids, mitochondrial DNA (mtDNA) and the ratio between the respiratory chain components COX II (mtDNA-encoded) and COX IV (nuclear-encoded) were measured.

RESULTS

HepG2 cells exposed to zalcitabine (177 nM) without uridine developed a severe depletion of mtDNA (to 8% of wild-type mtDNA levels), resulting in a decline of cell proliferation and COX II levels, with increased lactate and lipid accumulation. Uridine fully abrogated the adverse effects of zalcitabine on hepatocyte proliferation and normalized lactate synthesis, intracellular lipids and COX II levels by adjusting mtDNA levels to about 65% of NRTI-unexposed control cells. This effect was dose-dependent, with a maximum at 200 microM of uridine. Uridine also rapidly and fully restored cell function when added to cells with established mitochondrial dysfunction (zalcitabine for 15 days) despite continued zalcitabine exposure. Uridine also normalized cell proliferation in HepG2 cells exposed to 36 microM of stavudine and protected HepG2-cells exposed to 7 microM of zidovudine + 8 microM of lamivudine (pyrimidine analogues), but failed to improve cell function or mtDNA in cells exposed to 11.8 or 118 microM of didanosine (a purine analogue).

CONCLUSIONS

The pyrimidine precursor uridine may attenuate the mitochondrial toxicity of antiretroviral pyrimidine NRTIs in vitro, and its supplementation may represent a promising strategy in the prevention or treatment of mitochondrial toxicities in HIV-infected patients.

Assessment of precision and concordance of quantitative mitochondrial DNA assays: a collaborative international quality assurance study

BACKGROUND

A number of international research groups have developed DNA quantitation assays in order to investigate the role of mitochondrial DNA depletion in anti-retroviral therapy-induced toxicities.

OBJECTIVES

A collaborative study was undertaken to evaluate intra-assay precision and between laboratory concordance of measurements of mitochondrial DNA quantity, as a component of a comprehensive quality assurance project.

STUDY DESIGN

Four laboratories were asked to measure and report mitochondrial DNA and nuclear DNA genome copy number, as well as mitochondrial DNA copy number/cell, for 17 coded aliquots of DNA derived from serial dilutions of pooled DNA from a lymphoblastoid cell line. Samples included masked replicates and five standards. All samples had similar mitochondrial DNA/nuclear DNA ratios. Precision within laboratories was assessed by determining the coefficient of variation of replicates. Concordance between laboratories was assessed by determining the average coefficient of variation of the mean replicate values for each sample. The effect of standardising the assay for these three measurements was also assessed for laboratories A, B and C.

RESULTS

Measurements of mitochondrial DNA and nuclear DNA content for replicate samples varied by an average of less than 6% (based on log(10) values, 72% non-logged values), and measurements of mitochondrial DNA/cell for replicates varied by less than 12% (based on log(10) values, 32% non-logged values), with no improvement of precision after standardisation. Standardisation did significantly improve the concordance of results for measurements of mitochondrial DNA content and mitochondrial DNA/cell. Non-standardised measurements of mitochondrial DNA content for the same sample set varied by 19% between laboratories (based on log(10) values, 96% non-logged values), and after standardisation results varied by less than 3% (based on log(10) values, 54% non-logged values). There was no significant improvement for concordance of measures of nuclear DNA content after standardisation, with results varying by 4.56% between laboratories (based on log(10) values, 45% non-logged values) before standardisation, and by 2.49% (based on log(10) values, 50% non-logged values) after standardisation. Derived values of mitochondrial DNA/cell varied between laboratories by an average of 91% (non-logged, 56% log(10) values) before and by 56% (non-logged, 13% log(10) values) after standardisation.

CONCLUSION

All assays demonstrated good precision. The use of common standards is an important step in improving the comparability of data between laboratories.

Update on mitochondrial toxicity: where are we now?

Long-term alterations to body metabolism have become apparent with the prolonged use of antiretroviral nucleoside analogue reverse transcriptase inhibitors (NRTIs). The NRTIs differ in the mechanisms, potency and probably also tissue specificity of mitochondrial toxicity. One group of NRTIs, the so-called "d-drugs" (zalcitabine> didanosine>stavudine) are relatively strong inhibitors of g-polymerase and thus cause a time- and dose-dependent decrease in the intracellular levels of mitochondrial DNA (mtDNA). The most important target organs of d-drugs are the liver, skeletal muscle, peripheral nerves and probably also the subcutaneous adipose tissue of lipoatrophic subjects. Hyperlactataemia may be observed. Zidovudine is an inhibitor of the mitochondrial adenine nucleotide translocator, binds to adenylate kinase and may also be converted into stavudine triphosphate in vivo. Persistent hyperlactataemia, mtDNA depletion and isolated cases of mitochondrial encephalomyopathies have been observed in babies under perinatal exposure with zidovudine. Nucleotide analogues such as tenofovir are avidly taken up into renal tubular epithelia. Isolated cases of renal failure and Fanconi syndrome require further investigation. Mitochondrial toxicity cannot yet be adequately monitored and predicted. Drugs with potential additive or synergistic toxicity, such as valproate, should be used with caution. Didanosine interacts with allopurinol, hydroxyurea and ribavirin. In established mitochondrial toxicity, cessation of the offending NRTI remains the most effective therapeutic intervention because vitamin cocktails and l-carnitine have, at best, only a marginal effect.

[Inherited and acquired disorders of mitochondrial DNA]

Human mitochondrial DNA (mtDNA) resides in thousands of copies in each cell and encodes for 13 structural proteins which are subunits of the respiratory chain. Point mutations, deletions, and decreased copy-number (mtDNA-depletion) are now functionally and genetically linked to human disease. Although mtDNA is inherited maternally, some mutations may arise spontaneously and others are inherited in a mendelian fashion, which is attributed to defective nuclear genes. MtDNA-mutations are also associated with aging and with tumors but in these conditions probably not of functional significance. Mutations of mtDNA may be acquired by exposure to toxic substances (such as alcohol or doxorubicin). An acquired copy number defect (mtDNA-depletion) is dose-limiting for some antiviral nucleosides and nucleotide analogues. The internist encounters predominantly myopathies, cardiomyopathies, lactic acidosis or diabetes mellitus but mtDNA-changes also lead to neurological, hematological and renal symptoms. A syndrome of fat redistribution, termed lipodystrophy, is now observed with long-term therapy of HIV-patients and has been associated with mtDNA-depletion. Therapy with vitamins, radical scavengers and L-carnitine is recommended, but of limited success.

Increased long-term mitochondrial toxicity in combinations of nucleoside analogue reverse-transcriptase inhibitors

BACKGROUND

Some nucleoside analogue reverse transcriptase inhibitors (NRTI) may cause depletion of mitochondrial (mt) DNA in liver by inhibiting polymerase-gamma. mtDNA depletion may contribute to lactic acidosis, steatohepatitis and liver failure.

OBJECTIVE

To evaluate the long-term mitochondrial toxicity of NRTI combinations.

METHODS

The HepG2 human hepatoma cell line was cultivated in the presence of zalcitabine (ddC), didanosine (ddI), stavudine (d4T), lamivudine (3TC), zidovudine (ZDV) and efavirenz at concentrations equivalent to steady-state peak plasma levels (C ), and also in one-third and 10 times C. The NRTI were added to the medium alone or in combination. Control cells were incubated without any NRTI or with efavirenz. Cell growth, lactate production, intracellular lipid droplets, mtDNA and the mtDNA-encoded respiratory chain subunit COX II were monitored over a period of up to 30 days.

RESULTS

Time- and dose-dependent mtDNA depletion was observed with ddC > ddI > d4T and mtDNA depletion preceded or coincided with a decline in COX II expression, a decrease in cell growth, increased lactate production and increased intracellular lipids. 3TC and efavirenz did not affect any measurement. ZDV increased lactate moderately and cell growth was inhibited, despite normal mtDNA and COX II levels. The negative effects on some measurements were more pronounced in the 3TC-ZDV and ddC-d4T combinations, than in the single-NRTI incubations. The combination of ddI-d4T was not more toxic than ddI alone. Mitochondrial damage by ZDV, d4T, ddI, and ddC did not reach steady-state by day 25. Using a Southern blot technique, mtDNA deletions were never observed.

CONCLUSION

The data indicate additive or synergistic long-term mitochondrial toxicity in some NRTI combinations.

Evidence of nucleoside analogue reverse transcriptase inhibitor--associated genetic and structural defects of mitochondria in adipose tissue of HIV-infected patients

To investigate if possible mitochondrial injury can be found in adipose tissue of nucleoside analogue reverse transcriptase inhibitor (NRTI)-treated patients, subcutaneous fat was taken from the buttocks of 24 HIV-positive patients and 8 HIV-negative controls. The content of mitochondrial DNA (mtDNA) was quantified using a Southern blot technique. Fat biopsies were examined by electron microscopy and screened by restriction fragment length polymorphism analysis for the presence of the nt 8344 and 3243 mtDNA point mutations. Age, sex, and body mass index did not differ between the HIV-negative controls, the HIV-positive patients currently treated with NRTIs (NRTI group, n = 19), and the HIV-positive patients without NRTIs (no-NRTI group, n = 5). The mean mtDNA content was 44% lower in the NRTI group compared with the no-NRTI group ( p =.01) but did not differ between the control group and the no-NRTI group. When the HIV-infected patients were stratified to a group with clinical signs of lipoatrophy at the biopsy site (LA group, n = 11) and a group without lipoatrophy (no-LA group, n = 13), the mean mtDNA content in the LA group was 39% lower than that in the no-LA group ( p =.02). No point mutations or deletions were observed. The adipocytes of patients with lipoatrophy contained multiple small lipid vacuoles, and the mitochondria harbored inclusions reminiscent of mtDNA cytopathies. mtDNA depletion and ultrastructural abnormalities of adipocytes suggest a link between mitochondrial damage, the use of NRTIs, and lipoatrophy in HIV-infected patients.

["Catastrophic systemic lupus erythematosus" with Rosai-Dorfman sinus histiocytosis. Successful treatment with anti-CD20/rutuximab]

HISTORY AND ADMISSION FINDINGS

A 59-year old woman was admitted with a four-month history of polyarthritis, myalgias and photosensitivity insufficiently responsive to methotrexate, corticosteroids and azathioprin. On physical examination she presented with symmetric ankle edema, polyserositis, petechial bleeding and swelling of cervical, axillary and inguinal lymph nodes.

INVESTIGATIONS

Laboratory analysis revealed a trilinear cytopenia without signs of hemolysis. Acute phase proteins were elevated. Furthermore antinuclear antibodies, anti-phospholipid IgM antibodies, hypocomplementemia, a spurious IgGkappa paraprotein were noted. CT scans confirmed lymphadenopathy and revealed a pleural and pericardial effusion. Bone marrow biopsy showed marked hypercellularity and polyclonal plasmocytosis. Based on these findings systemic lupus erythematosus was initially suspected. However when abdominal MRI showed a retroperitoneal mass, an extensive histological workup, which also included lymph nodes and spleen, revealed numerous plasma cells and histiocytes in dilated sinuses, diagnostic of Rosai-Dorfman sinus histiocytosis.

TREATMENT AND COURSE

High dose corticosteroids, intravenous gamma-globulin and repeated courses of cyclophosphamide failed to improve the pancytopenia, as did splenectomy. The patient was given the anti-CD20 monoclonal antibody Rituximab and all signs and symptoms improved dramatically. 18 months after the last treatment, the patient is in complete clinical and hematological remission.

CONCLUSIONS

Sinus histiocytosis of Rosai/Dorfman can be associated with or mimic severe SLE. Rituximab, an anti-CD20 monoclonal antibody, may improve the antibody-mediated pathogenetic mechanism underlying both entities.

Patients with fibromyalgia benefit from aerobic endurance exercise

Fibromyalgia (FM) is a disorder characterised by diffuse widespread musculoskeletal aching and stiffness and multiple tender points [1]. Its pathophysiology is poorly understood. The influence of aerobic endurance exercise on pain in patients with FM was investigated. Twenty-seven patients (25 female, 2 male) participated in a controlled clinical study and performed 12 weeks of jogging, walking, cycling or swimming following a given schedule. Twelve sedentary FM patients (11 female, 1 male) served as controls. Before and after training both the study and the control groups were evaluated spiroergometrically. Tender point pain was quantified by dolorimetry. The painful body surface was estimated by a pain body diagram, and its intensity by a visual analogue scale and a ranking scale. Patients trained for an average of 25 min two to three times a week, with an average intensity of 50% of maximal oxygen uptake (VO2max). Unlike the control group, the training group exhibited a decrease in heart rate and VO2 and an increase in respiratory quotient during submaximal workload. Maximal performance capacity and VO2max remained unchanged, whereas the wattpulse (watt/heart rate) improved at maximal workload. Pain parameters remained unchanged in the control group, but in the training group the mean number of positive tender points (15.4/12.7), the mean pain threshold of the gluteal tender point (2.89 kp/3.50 kp) and the painful body surface (18%/15% body surface) decreased significantly. Subjective general pain condition deteriorated in two patients but improved in 17. Our results suggest a positive effect of aerobic endurance exercise on fitness and well-being in patients with FM.