Mitochondrion-mediated apoptosis in HIV-1 infection

Hydrogen sulfide blocks HIV rebound by maintaining mitochondrial bioenergetics and redox homeostasis

A fundamental challenge in human immunodeficiency virus (HIV) eradication is to understand how the virus establishes latency, maintains stable cellular reservoirs, and promotes rebound upon interruption of antiretroviral therapy (ART). Here, we discovered an unexpected role of the ubiquitous gasotransmitter hydrogen sulfide (H₂S) in HIV latency and reactivation. We show that reactivation of HIV is associated with downregulation of the key H₂S producing enzyme cystathionine-γ-lyase (CTH) and reduction in endogenous H₂S. Genetic silencing of CTH disrupts redox homeostasis, impairs mitochondrial function, and remodels the transcriptome of latent cells to trigger HIV reactivation. Chemical complementation of CTH activity using a slow-releasing H₂S donor, GYY4137, suppressed HIV reactivation and diminished virus replication. Mechanistically, GYY4137 blocked HIV reactivation by inducing the Keap1-Nrf2 pathway, inhibiting NF-κB, and recruiting the epigenetic silencer, YY1, to the HIV promoter. In latently infected CD4⁺ T cells from ART-suppressed human subjects, GYY4137 in combination with ART prevented viral rebound and improved mitochondrial bioenergetics. Moreover, prolonged exposure to GYY4137 exhibited no adverse influence on proviral content or CD4⁺ T cell subsets, indicating that diminished viral rebound is due to a loss of transcription rather than a selective loss of infected cells. In summary, this work provides mechanistic insight into H₂S-mediated suppression of viral rebound and suggests exploration of H₂S donors to maintain HIV in a latent form.

The anti-viral dynamin family member MxB participates in mitochondrial integrity

The membrane deforming dynamin family members MxA and MxB are large GTPases that convey resistance to a variety of infectious viruses. During viral infection, Mx proteins are known to show markedly increased expression via an interferon-responsive promoter to associate with nuclear pores. In this study we report that MxB is an inner mitochondrial membrane GTPase that plays an important role in the morphology and function of this organelle. Expression of mutant MxB or siRNA knockdown of MxB leads to fragmented mitochondria with disrupted inner membranes that are unable to maintain a proton gradient, while expelling their nucleoid-based genome into the cytoplasm. These findings implicate a dynamin family member in mitochondrial-based changes frequently observed during an interferon-based, anti-viral response.

Mx proteins belong to the dynamin family of large GTPases and are highly induced by interferon in virally infected cells. The authors show that uninfected immune cells and hepatocytes also express MxB protein that associates with mitochondria to alter the morphology and genome of this organelle.

Placental Mitochondrial Toxicity, Oxidative Stress, Apoptosis, and Adverse Perinatal Outcomes in HIV Pregnancies Under Antiretroviral Treatment Containing Zidovudine

OBJECTIVE

To determine whether mitochondrial, oxidative, and apoptotic abnormalities in placenta derived from HIV and combined antiretroviral therapy (cART) containing zidovudine (AZT) could be associated with adverse perinatal outcome.

DESIGN

Cross-sectional, controlled, observational study.

METHODS

We studied obstetric results and mitochondrial, oxidative, and apoptotic state in placenta of 24 treated HIV-infected and 32 -uninfected pregnant women. We measured mitochondrial DNA (mtDNA) content by quantitative reverse transcriptase-polymerase chain reaction (mtND2/n18SrRNA), oxidative stress by the spectrophotometric quantification of lipid peroxidation and apoptosis by Western blot analysis of active caspase-3 respect to β-actin content and analysis of the terminal deoxynucleotidyl transferase dUTP nick end labeling.

RESULTS

Global adverse perinatal outcome (defined as preterm delivery or/and small newborns for gestational age) was significantly increased in HIV pregnancies [or 6.7 (1.3-33.2); P < 0.05]. mtDNA content in HIV-infected women was significantly depleted (39.20% ± 2.78%) with respect to controls (0.59 ± 0.03 vs. 0.97 ± 0.07; P < 0.001). A significant 29.50% ± 9.14% increase in oxidative stress was found in placentas of HIV-infected women (23.23 ± 1.64 vs. 17.94 ± 1.03; P < 0.01). A trend toward 41.18% ± 29.41% increased apoptosis active caspase-3/β-actin was found in HIV patients (0.48 ± 0.10 vs. 0.34 ± 0.05; P = not significant), confirmed by transferase dUTP nick end labeling assay. Adverse perinatal outcome did not correlate mitochondrial, oxidative, or apoptotic findings.

CONCLUSIONS

Placentas of HIV-infected pregnant women under AZT cART showed evidence of mtDNA depletion, increased oxidative stress levels, and apoptosis suggestive of secondary mitochondrial failure, potential base of associated adverse perinatal outcome. Despite the fact that further demonstration of causality would need new approaches and bigger sample sizes, AZT-sparing cART should be considered in the context of pregnancy.

Syncytial apoptosis signaling network induced by the HIV-1 envelope glycoprotein complex: an overview

Infection by human immunodeficiency virus-1 (HIV-1) is associated with a progressive decrease in CD4 T-cell numbers and the consequent collapse of host immune defenses. The major pathogenic mechanism of AIDS is the massive apoptotic destruction of the immunocompetent cells, including uninfected cells. The latter process, also known as by-stander killing, operates by various mechanisms one of which involves the formation of syncytia which undergo cell death by following a complex pathway. We present here a detailed and curated map of the syncytial apoptosis signaling network, aimed at simplifying the whole mechanism that we have characterized at the molecular level in the last 15 years. The map was created using Systems Biology Graphical Notation language with the help of CellDesigner software and encompasses 36 components (proteins/genes) and 54 interactions. The simplification of this complex network paves the way for the development of novel therapeutic strategies to eradicate HIV-1 infection. Agents that induce the selective death of HIV-1-elicited syncytia might lead to the elimination of viral reservoirs and hence constitute an important complement to current antiretroviral therapies.

HIV-1 induced bystander apoptosis

Apoptosis of uninfected bystander cells is a key element of HIV pathogenesis and believed to be the driving force behind the selective depletion of CD4+ T cells leading to immunodeficiency. While several viral proteins have been implicated in this process the complex interaction between Env glycoprotein expressed on the surface of infected cells and the receptor and co-receptor expressing bystander cells has been proposed as a major mechanism. HIV-1 utilizes CD4 as the primary receptor for entry into cells; however, it is the viral co-receptor usage that greatly influences CD4 decline and progression to AIDS. This phenomenon is relatively simple for X4 viruses, which arise later during the course of the disease, are considered to be highly fusogenic, and cause a rapid CD4+ T cell decline. However, in contrast, R5 viruses in general have a greater transmissibility, are encountered early during the disease and have a lesser pathogenic potential than the former. The above generalization gets complicated in numerous situations where R5 viruses persist throughout the disease and are capable of causing a rigorous CD4+ T cell decline. This review will discuss the multiple factors that are reported to influence HIV induced bystander apoptosis and pathogenesis including Env glycoprotein phenotype, virus tropism, disease stage, co-receptor expression on CD4+ T cells, immune activation and therapies targeting the viral envelope.

Mitochondrial evolution in HIV-infected children receiving first- or second-generation nucleoside analogues

BACKGROUND

Highly active antiretroviral therapy (HAART) and HIV-related mitochondrial toxicity lead to several adverse effects and have become a major issue, especially in children. The main goal in the treatment of HIV-infected children is to maximize cost-effectiveness while minimizing toxicity. We aimed to study the evolution of mitochondrial parameters over time in children receiving different types antiretroviral regimens.

METHODS

We followed-up 28 HIV-infected children receiving HAART including either first-generation nucleoside reverse transcriptase inhibitors (1gNRTIs; didanosine, zidovudine, or stavudine; n = 15) or second-generation NRTIs (2gNRTIs; the remaining drugs; n = 13) for a period of 2 years for their immunovirological and mitochondrial status, and compared these subjects with a group of untreated HIV-infected patients (n = 10) and uninfected controls (n = 27). We measured T-lymphocyte CD4+ content (flow cytometry), viral load (real-time polymerase chain reaction), and lactate levels (spectrophotometry); we assessed mtDNA content (real-time polymerase chain reaction), mitochondrial protein levels (Western blot), oxidative stress, mitochondrial mass, and electron transport chain function (spectrophotometry) in peripheral blood mononuclear cells.

RESULTS

At the second time point, lactate levels were significantly higher in children on 1gNRTIs compared with those receiving 2gNRTIs (1.28 ± 0.08 vs. 1.00 ± 0.07 mmol/L, respectively; P = 0.022). MtDNA content was similar among all HIV-infected groups and significantly lower than in healthy controls at baseline. Oxidative stress tended to increase over time in all the groups, with no differences among them. However, a significant decrease in cytochrome c oxidase activity was found over time in HIV-infected patients; this decline was greater in the 1gNRTIs group.

CONCLUSIONS

HIV infection and the use of 1gNRTIs caused greater mitochondrial damage than 2gNRTIs over time. The higher lactate levels and the significant decrease observed in cytochrome c oxidase activity argue against the use of 1gNRTIs in HIV-infected children when an alternative is available, in accordance with international recommendations.

Quantification of Fas protein in CSF of patients with neurocysticercosis

Neurocysticercosis is a parasitic disease that affects the central nervous system. The objective of this study was to investigate the correlation between neuronal death evaluated by the quantification of Fas apoptotic factor and the different evolutive forms of neurocysticercosis accompanied or not by epileptic seizures.

METHODS

Cerebrospinal fluid samples from 36 patients with a diagnosis of neurocysticercosis divided into the following groups: active cystic form (n=15), 9 patients with and 6 without seizures, and calcified form (=21), 9 with and 12 without seizures. Fourteen patients comprised the control group. Fas protein concentrations were determined by ELISA.

RESULTS

Only the group of patients with calcified cysts without seizures presented cerebrospinal fluid levels of Fas similar to those of the control group. Higher levels were observed for the other groups.

CONCLUSIONS

The present finding suggests high cerebrospinal fluid levels of soluble Fas protein, except for patients with calcified cysts without seizures. Significant differences were observed for the group with calcified cysts and seizures, suggesting greater neuronal damage in these patients. Replacement of the term inactive cyst with reactive inactive cyst is suggested.

Role of p53 in neurodegenerative diseases

BACKGROUND

p53 plays an important role in many areas of cellular physiology and biology, ranging from cellular development and differentiation to cell cycle arrest and apoptosis. Many of its functions are attributed to its role in assuring proper cellular division. However, since the establishment of its role in cell cycle arrest, damage repair, and apoptosis (thus also establishing its importance in cancer development), numerous reports have demonstrated additional functions of p53 in various cells. In particular, p53 appears to have important functions as it relates to neurodegeneration and synaptic plasticity.

OBJECTIVE

In this review, we will address p53 functions as it relates to various neurodegenerative diseases, mainly its implications in the development of HIV-associated neurocognitive disorders.

CONCLUSION

p53 plays a pivotal role in the development of neurodegenerative diseases through its interaction with cellular factors, viral factors, and/or small RNAs that have the ability to promote the development of these diseases. Hence, inhibition of p53 may present an ideal target to restore neuronal functions.

Disorders of fat partitioning in treated HIV-infection

HIV-associated lipodystrophy is clinically characterized by body fat changes including subcutaneous fat loss (lipoatrophy) with or without truncal fat accumulation (lipohypertrophy). Thymidine nucleoside reverse transcriptase inhibitors, stavudine and to a lesser extent zidovudine, are major contributors for lipoatrophy. Drug factors are not clear for lipohypertrophy. Restoration to health with effective viral suppression and weight gain may be factors playing significant roles in lipohypertrophy. Mitochondrial dysfunction and inflammation in subcutaneous adipose tissue are key factors in the pathogenesis of HIV-associated lipoatrophy. The pathogenesis of lipohypertrophy is less well understood. Switching from thymidine nucleoside reverse transcriptase inhibitors restores subcutaneous fat in patients with HIV-associated lipoatrophy, but improvement is slow and limited. Surgical filling cosmetically improves facial lipoatrophy. Exercise and diet may reduce increased visceral adipose tissue. Liposuction may be useful to remove superficial, localized fat accumuli.

The immunosuppressive properties of the HIV Vpr protein are linked to a single highly conserved residue, R90

BACKGROUND

A hallmark of AIDS progression is a switch of cytokines from Th1 to Th2 in the plasma of patients. IL-12, a critical Th1 cytokine secreted by antigen presenting cells (APCs) is suppressed by Vpr, implicating it as an important virulence factor. We hypothesize that Vpr protein packaged in the virion may be required for disabling APCs of the first infected mucosal tissues. Consistent with this idea are reports that defects in the C-terminus of Vpr are associated with long-term non-progression.

PRINCIPAL FINDINGS

Vpr RNA amplified from various sources was electroporated into monocyte-derived DC and IL-12 levels in supernatants were analyzed. The analysis of previously reported C-terminal Vpr mutations demonstrate that they do not alleviate the block of IL-12 secretion. However, a novel single conservative amino acid substitution, R90K, reverses the IL-12 suppression. Analysis of 1226 Vpr protein sequences demonstrated arginine (R) present at position 90 in 98.8%, with other substitutions at low frequency. Furthermore, none of sequences report lysine (K) in position 90. Vpr clones harboring the reported substitutions in position 90 were studied for their ability to suppress IL-12. Our data demonstrates that none of tested substitutions other than K relieve IL-12 suppression. This suggests a natural selection for sequences which suppress IL-12 secretion by DC and against mutations which relieve such suppression. Further analyses demonstrated that the R90K, as well as deletion of the C-terminus, directs the Vpr protein for rapid degradation.

CONCLUSION

This study supports Vpr as an HIV virulence factor during HIV infection and for the first time provides a link between evolutionary conservation of Vpr and its ability to suppress IL-12 secretion by DC. DC activated in the presence of Vpr would be defective in the production of IL-12, thus contributing to the prevailing Th2 cytokine profile associated with progressive HIV disease. These findings should be considered in the design of future immunotherapies that incorporate Vpr as an antigen.

Protease inhibitors used in the treatment of HIV+ induce beta-cell apoptosis via the mitochondrial pathway and compromise insulin secretion

Inclusion of HIV protease inhibitors (PIs) in the treatment of people living with HIV+ has markedly decreased mortality but also increased the incidence of metabolic abnormalities, causes of which are not well understood. Here, we report that insulinopenia is exacerbated when Zucker fa/fa rats are exposed to a PI for 7 wk, suggesting that chronic PI exposure adversely affects pancreatic islet beta-cell function. In support of this possibility, we find increased apoptosis, as reflected by TUNEL fluorescence analyses, and reduced insulin-secretory capacity in insulinoma cells and human pancreatic islet cells after in vitro exposures (48-96 h) to clinically relevant PIs (ritonavir, lopinavir, atazanavir, or tipranavir). Furthermore, pancreatic islets isolated from rats administered an HIV-PI for 3 wk exhibit greater cell death than islets isolated from vehicle-administered rats. The higher incidence of HIV-PI-induced cell death was associated with cleavage and, hence, activation of caspase-3 and poly(ADP)-ribose polymerase but not with activation of phospho-pancreatic endoplasmic reticulum (ER) kinase or induction of ER stress apoptotic factor C/EBP homologous protein. Exposure to the HIV-PIs, however, led to activation of mitochondria-associated caspase-9, caused a loss in mitochondrial membrane potential, and promoted the release of cytochrome c, suggesting that HIV-PIs currently in clinically use can induce beta-cell apoptosis by activating the mitochondrial apoptotic pathway. These findings therefore highlight the importance of considering beta-cell viability and function when assessing loss of glycemic control and the course of development of diabetes in HIV+ subjects receiving a protease inhibitor.

Molecular inflammation: underpinnings of aging and age-related diseases

Recent scientific studies have advanced the notion of chronic inflammation as a major risk factor underlying aging and age-related diseases. In this review, low-grade, unresolved, molecular inflammation is described as an underlying mechanism of aging and age-related diseases, which may serve as a bridge between normal aging and age-related pathological processes. Accumulated data strongly suggest that continuous (chronic) upregulation of pro-inflammatory mediators (e.g., TNF-alpha, IL-1beta, IL-6, COX-2, iNOS) are induced during the aging process due to an age-related redox imbalance that activates many pro-inflammatory signaling pathways, including the NF-kappaB signaling pathway. These pro-inflammatory molecular events are discussed in relation to their role as basic mechanisms underlying aging and age-related diseases. Further, the anti-inflammatory actions of aging-retarding caloric restriction and exercise are reviewed. Thus, the purpose of this review is to describe the molecular roles of age-related physiological functional declines and the accompanying chronic diseases associated with aging. This new view on the role of molecular inflammation as a mechanism of aging and age-related pathogenesis can provide insights into potential interventions that may affect the aging process and reduce age-related diseases, thereby promoting healthy longevity.

HIV protease inhibitors impact on apoptosis

HIV protease inhibitors are the backbone of HIV therapy. In addition to blocking intracellular HIV protease and dramatically decreasing viral burden, the protease inhibitors also regulate apoptosis. A growing body of data has confirmed the immunomodulatory effects of HIV protease inhibitors which block CD4+ and CD8+ T cell death in models of HIV infection. The mechanism of this apoptosis inhibition is still under active investigation and supported by several proposed hypothesis for how they alter the fate of the cell. More recently, the anti-apoptotic effects of the HIV protease inhibitors has been extended to the non-HIV, non-immune cell, whereby protease inhibitors prevent apoptosis, and disease, in animal models of sepsis, hepatitis and stroke. Interestingly, when HIV protease inhibitors are used at supra-therapeutic concentrations, they exert pro-apoptotic effects. This has been demonstrated in a number of tumor models. Although it is unclear how HIV protease inhibitors can induce apoptosis at increased concentrations, future research will define the targets of the immunomodulation and reveal the full clinical potential of this intriguing class of drugs.

Tratamiento antirretroviral y toxicidad mitocondrial

The introduction of highly active antiretroviral therapy for the treatment of human immunodeficiency virus (HIV) infection has led to substantial reduction in morbidity and near-complete suppression of HIV-1 replication. This progress has been tempered by a growing number of new adverse effects. Mitochondrial toxicity is one aspect of these long-term toxicities of antiretroviral drugs, with the role of nucleoside analogs being particularly underlined. Some cases of impaired mitochondrial function have been clearly identified, such as pancreatitis, neuropathy, miopathy and lactic acidosis. Beyond the inhibition of DNA polymerase-g using nucleoside analogs, it appears that several physiopathologic mechanisms interact to explain the observed toxicity. At present there is no reliable method to detect subclinical mitochondrial toxicity. There is no proven effective therapy for antiretroviral therapy-associated mitochondrial toxicity other than ceasing the implicated agent, and even with this strategy, resolution of symptoms may be incomplete. Therefore, investigation of mitochondrial toxicity of new compounds or new combinations is of growing interest for the clinical application of antiretroviral agents.

HIV-1 protease inhibitors do not interfere with provirus transcription and host cell apoptosis induced by combined treatment TNF-alpha + TSA

HIV-1 latency represents a major hurdle to the complete eradication of the virus from patients under highly active anti-retroviral therapy (HAART) regimens. One solution to this problem would be to eliminate the latently infected cellular reservoirs by forcing gene expression in presence of HAART to prevent spreading of the infection by the newly synthesized viruses. Many studies have reported that a combination of a histone deacetylase inhibitor (HDACi) (i.e. TSA, NaBut, Valproic acid, ...) with a pro-inflammatory cytokine (i.e. TNFalpha, IL-1, ...) reactivates in a synergistic manner HIV-1 transcription in latently infected cells. The aim of the present study was to determine whether HIV-1 protease inhibitors (PIs) used in HAART (such as Saquinavir, Indinavir, Nelfinavir, Lopinavir, Ritonavir and Amprenavir) could interfere with the potential purge of the cellular reservoirs induced by a combined treatment involving TSA and TNFalpha. We showed, in two HIV-1 latently infected cell lines (ACH-2 and U1) that all PIs efficiently inhibited release of mature viral particles but did neither affect cell apoptosis nor NF-kappaB induction and HIV-1 transcription activation following combined treatment with TNFalpha+TSA. This study is encouraging in the fight against HIV-1 and shows that PIs should be compatible with an inductive adjuvent therapy for latent reservoir reduction/elimination in association with efficient HAART regimens.

Protection of azidothymidine-induced cardiopathology in mice by mildronate, a mitochondria-targeted drug

Azidothymidine, a nucleoside-analogue reverse transcriptase inhibitor (NRTI), is a commonly used antiretroviral drug in AIDS treatment, however its use is limited by severe toxic side effects due to its influence on mitochondria that result in myopathy, particularly affecting the cardiac muscle. We suggest that effective protection of azidothymidine-induced cardiopathology can be expected from drugs that are capable of targeting mitochondria. Therefore the present study in mice was carried out with mildronate, a cardioprotective drug of the aza-butyrobetaine class, which previously has been shown to act as a highly potent protector of mitochondrial processes. In our study, saline (control), azidothymidine (50 mg/kg), mildronate (50, 100 and 200 mg/kg), and azidothymidine + mildronate (at the doses mentioned) were injected intraperitoneally daily in separate groups of mice for two weeks. At the termination of the experiment, mice were sacrificed, the hearts were removed and cardiac tissue was examined morphologically and immunohistochemically. It was found that azidothymidine, compared to control and mildronate groups, induced major morphologic changes in cardiac tissue, which were manifestated as degeneration and inflammation. These changes were prevented when mildronate was co-administered with azidothymidine. Mildronate also reduced the azidothymidine-induced expression of nuclear factor kappaBp65 (NF-kappaBp65). The obtained data demonstrate a high ability of mildronate of preventing azidothymidine-induced cardiopathologic changes, and suggest mildronate's indirect action on azidothymidine-caused oxidative stress reactions leading to mitochondrial dysfunction. This offers a rational combination of mildronate with azidothymidine or other anti-HIV drugs for beneficial application in AIDS therapy.

HIV protease inhibitors modulate apoptosis signaling in vitro and in vivo

HIV protease inhibitors are an integral part of effective anti-HIV therapy. The drugs block HIV protease, prevent proper packaging of HIV virions, and decrease the HIV viral burden in the peripheral blood of infected individuals. In addition to direct anti-viral effects, the HIV protease inhibitors also modulate apoptosis. A growing body of work demonstrates the anti-apoptotic effects of HIV protease inhibitors on CD4+ and CD8+ T cells during HIV infection. The mechanism of this apoptosis inhibition is supported by several proposed hypotheses for how they alter the fate of the cell, including preventing adenine nucleotide translocator pore function, which consequently prevents loss of mitochondrial transmembrane potential. More recently, the anti-apoptotic effects of the HIV protease inhibitors have been tested in non-HIV, non-immune cell, whereby protease inhibitors prevent apoptosis, and disease in animal models of sepsis, hepatitis, pancreatitis and stroke. Interestingly, when HIV protease inhibitors are used at supra-therapeutic concentrations, they exert pro-apoptotic effects. This has been demonstrated in a number of tumor models. Although it is unclear how HIV protease inhibitors can induce apoptosis at increased concentrations, future research will define the targets of the immunomodulation and reveal the full clinical potential of this intriguing class of drugs.

AIDS: caused by development of resistance to drugs in a non-target intracellular parasite

The origin of acquired immune disorder syndrome (AIDS) has been the subject of substantial controversy both in the scientific community and in the popular press. The debate involves the mode of transmission of a simian virus (SIV) to humans. Both major camps in the argument presume that humans are normally free of such viruses and assume that once the simian virus was transmitted, it immediately infected some T-cells and caused the release of toxic agents that killed off bystander (uninfected) T-cells resulting in AIDS. The evolution of the Simian virus (SIV) into a human virus (HIV) is regarded as an artifact. In contrast, a fundamentally different hypothesis has been proposed [Parris GE. Med Hypotheses 2004;62(3):354–7] in which it is presumed that in hyper-endemic areas of malaria (central Africa), all primates (humans and non-human primates) have shared a retrovirus that augments their T-cell response to the malaria parasite. The virus can be called “primate T-cell retrovirus” (PTRV). Over thousands of years the virus has crossed species lines many times (with little effect) and typically adapts to the host quickly. In this model, AIDS is seen to be the result of the development of resistance of the virus (PTRV) to continuous exposure to pro-apoptotic (schizonticidal) aminoquinoline drugs used to prevent malaria. The hypothesis was originally proposed based on biochemical activities of the aminoquinolines (e.g., pamaquine (plasmoquine(TM)), primaquine and chloroquine), but recent publications demonstrated that some of these drugs definitely adversely affect HIV and other viruses and logically would cause them to evolve resistance. Review of the timeline that has been created for the evolution of HIV in humans is also shown to be qualitatively and quantitatively consistent with this hypothesis (and not with either version of the conventional hypothesis). SARS and Ebola also fit this pattern.

Cell death in HIV dementia

Many patients infected with human immunodeficiency virus type-1 (HIV-1) suffer cognitive impairment ranging from mild to severe (HIV dementia), which may result from neuronal death in the basal ganglia, cerebral cortex and hippocampus. HIV-1 does not kill neurons by infecting them. Instead, viral proteins released from infected glial cells, macrophages and/or stem cells may directly kill neurons or may increase their vulnerability to other cell death stimuli. By binding to and/or indirectly activating cell surface receptors such as CXCR4 and the N-methyl-D-aspartate receptor, the HIV-1 proteins gp120 and Tat may trigger neuronal apoptosis and excitotoxicity as a result of oxidative stress, perturbed cellular calcium homeostasis and mitochondrial alterations. Membrane lipid metabolism and inflammation may also play important roles in determining whether neurons live or die in HIV-1-infected patients. Drugs and diets that target oxidative stress, excitotoxicity, inflammation and lipid metabolism are in development for the treatment of HIV-1 patients.

Mitochondrial toxicity of nucleoside analogues: mechanism, monitoring and management

Nucleoside analogues (NRTIs) are potent antiretroviral medications and are central to effective highly active antiretroviral therapy (HAART). Their intended action is to inhibit HIV reverse transcriptase. Nucleoside analogues also inhibit replication of mitochondrial DNA, and the pathogenesis of many of the toxicities associated with HAART is thought to be NRTI-induced mitochondrial dysfunction. Individuals with HIV infection may be particularly susceptible to clinically significant mitochondrial toxicity due to possible effects of HIV itself on mitochondria. At present there is no reliable method of detecting subclinical mitochondrial toxicity in patients exposed to NRTIs. Clinical awareness of this problem is therefore important to ensure the early detection of significant side effects and to allow timely consideration of changing therapy in those affected. There is no proven, effective therapy for NRTI-associated mitochondrial toxicity other than ceasing the implicated agent, and even with this strategy, resolution of symptoms may be incomplete. Similarly, there are no established methods for preventing mitochondrial toxicity in those on therapy including NRTIs. Micronutrients may have a role, but further study is needed to clarify optimal prevention as well as monitoring strategies.

Mitochondrial complex I activity is impaired during HIV-1-induced T-cell apoptosis

Studies carried out till date to elucidate the pathways involved in HIV-1-induced T-cell depletion has revealed that apoptosis underlie the etiology, however, a clear molecular understanding of HIV-1-induced apoptosis has remained elusive. Although evidences pointing towards the importance of mitochondrial energy generating system in apoptosis exist but it's exact role remains to be clearly understood. Here, we describe for the first time specific downregulation of a complex I subunit NDUFA6 with simultaneous impairment of mitochondrial complex I activity in HIV infection. We also show that NDUFA6 gene silencing induces apoptosis and its overexpression reduces apoptosis in HIV-infected cells. Finally, sensitivity to complex I inhibitor Rotenone is reduced in HIV-1-infected T cells indicating an important role for it in the death process. Our data provide a novel molecular basis as to how the virus might interfere with host cell energy generating system during apoptotic cell death.

p53-A pro-apoptotic signal transducer involved in AIDS

P53 is a well-characterized tumor suppressor protein, which can induce apoptosis, either by inducing transcription of pro-apoptotic genes or by direct effects on mitochondrial membranes. Roughly 50% of human cancers are affected by the genetic or epigenetic inactivation of p53. Recently, p53 has been incriminated to play a cardinal role in the destruction of the immune system by human immunodeficiency virus (HIV-1) infection. This suspicion is based on several lines of evidence: (i) p53 exhibits activating phosphorylations in a subset of peripheral blood mononuclear cells and lymph node cells from HIV-1 carriers; (ii) some p53 target genes (e.g., PUMA, a pro-apoptotic member of the Bcl-2 family) are overexpressed in HIV-1 carriers; (iii) in vitro, p53 and/or PUMA are rate-limiting for the induction of cell death by HIV-1 infection or, in particular, by the HIV-1 Envelope (Env), in a variety of model systems, including the apoptosis of syncytia elicited by Env or cell death induced by the Env constituent gp120. Thus, p53 may constitute a novel therapeutic target for the treatment of AIDS.

Death ligand-mediated apoptosis in HIV infection

Apoptosis has been suggested to cause severe CD4+ T cell depletion in patients infected with HIV. This review focuses on the biological events involved in death ligand-induced apoptosis during HIV infection. Among these ligands, TRAIL appears critical in HIV-infection. Death ligand-induced apoptosis might be a major pathogenic event in many virus-induced diseases including AIDS and the clarification of its mechanism will aid in the development of therapeutic strategies.

The Role of Hepatitis C Virus (HCV) in Mitochondrial Dna Damage in HIV/HCV-Coinfected Individuals

Oxidative stress accompanying hepatitis C virus (HCV) infection seems to result in mitochondrial (mt) dysfunction. In HIV/HCV-coinfected individuals, HCV-related mt damage could be further enhanced and clinical manifestations of mt damage may appear, particularly following exposure to some antiretroviral drugs. Furthermore, when HCV medications are used together with certain antiretrovirals, the risk of developing mt adverse events may be particularly frequent, such as development of pancreatitis when ribavirin and didanosine are coadministered. The management of HIV/HCV-coinfected individuals needs to consider the high risk of mitochondria-associated toxicities in this population, which may significantly influence treatment decisions and therapeutic modalities.

Lipodystrophy associated with highly active anti-retroviral therapy for HIV infection: the adipocyte as a target of anti-retroviral-induced mitochondrial toxicity

The lipodystrophy syndrome and associated metabolic alterations are the most prevalent adverse effects in HIV-infected patients taking highly active anti-retroviral therapy (HAART). This syndrome involves profound disturbances in adipose tissue. The toxic effect of nucleoside reverse transcriptase inhibitors on mitochondrial function is a major contributor to the lipodystrophy syndrome. Although adipocytes were not expected to be preferential targets of mitochondrial toxicity, recent re-evaluation of the role of mitochondria in white adipocytes helps to explain the molecular basis of HAART-associated lipodystrophy. Adipocytes are a source of paracrine and endocrine signals that influence adipocyte biology and systemic metabolism. Mitochondrial disturbances elicited by HAART result in an abnormal perception of the bioenergetic status by adipocytes, thus leading to enhancement of catalytic pathways and apoptosis in peripheral adipose tissue, alterations in the differentiation of brown versus white adipocytes, and the release of hormonal signals that lead to systemic metabolic disturbances.

The genetics of cell death: approaches, insights and opportunities in Drosophila

Cell death is ubiquitous in metazoans and involves the action of an evolutionarily conserved process known as programmed cell death or apoptosis. In Drosophila melanogaster, it is now uniquely possible to screen for genes that determine the fate - life or death - of any cell or population of cells during development and in the adult. This review describes these genetic approaches and the key insights into cell-death mechanisms that have been obtained, as well as the outstanding questions that these techniques can help to answer.

Mitochondrial effects of HIV infection on the peripheral blood mononuclear cells of HIV-infected patients who were never treated with antiretrovirals

To investigate the effects of HIV infection on mitochondrial DNA (mtDNA) content and other mitochondrial parameters, we used peripheral blood mononuclear cells (PBMCs) from 25 asymptomatic antiretroviral-naive human immunodeficiency virus (HIV)-infected patients and from 25 healthy control subjects. HIV-infected patients had significant decreases in mtDNA content (decrease, 23%; P<.05) and in the activities of mitochondrial respiratory chain (MRC) complex II (decrease, 41%; P<.001), MRC complex III (decrease, 38%; P<.001), MRC complex IV (decrease, 19%; P=.001), and glycerol-3-phosphate dehydrogenase (decrease, 22%; P<.001), along with increased lipid peroxidation of PBMC membranes (P=.007). Therefore, HIV infection is associated not only with mtDNA depletion, but also with extensive MRC disturbances and increased oxidative damage.

The pathophysiology of mitochondrial cell death

In the mitochondrial pathway of apoptosis, caspase activation is closely linked to mitochondrial outer membrane permeabilization (MOMP). Numerous pro-apoptotic signal-transducing molecules and pathological stimuli converge on mitochondria to induce MOMP. The local regulation and execution of MOMP involve proteins from the Bcl-2 family, mitochondrial lipids, proteins that regulate bioenergetic metabolite flux, and putative components of the permeability transition pore. MOMP is lethal because it results in the release of caspase-activating molecules and caspase-independent death effectors, metabolic failure in the mitochondria, or both. Drugs designed to suppress excessive MOMP may avoid pathological cell death, and the therapeutic induction of MOMP may restore apoptosis in cancer cells in which it is disabled. The general rules governing the pathophysiology of MOMP and controversial issues regarding its regulation are discussed.