Antiapoptotic mechanism of HIV protease inhibitors: preventing mitochondrial transmembrane potential loss

Connection Between HIV and Mitochondria in Cardiovascular Disease and Implications for Treatments

HIV infection and antiretroviral therapy alter mitochondrial function, which can progressively lead to mitochondrial damage and accelerated aging. The interaction between persistent HIV reservoirs and mitochondria may provide insight into the relatively high rates of cardiovascular disease and mortality in persons living with HIV. In this review, we explore the intricate relationship between HIV and mitochondrial function, highlighting the potential for novel therapeutic strategies in the context of cardiovascular diseases. We reflect on mitochondrial dynamics, mitochondrial DNA, and mitochondrial antiviral signaling protein in the context of HIV. Furthermore, we summarize how toxicities related to early antiretroviral therapy and current highly active antiretroviral therapy can contribute to mitochondrial dysregulation, chronic inflammation, and poor clinical outcomes. There is a need to understand the mechanisms and develop new targeted therapies. We further consider current and potential future therapies for HIV and their interplay with mitochondria. We reflect on the next-generation antiretroviral therapies and HIV cure due to the direct and indirect effects of HIV persistence, associated comorbidities, coinfections, and the advancement of interdisciplinary research fields. This includes exploring novel and creative approaches to target mitochondria for therapeutic intervention.

Oxidative stress and mitochondrial dysfunction following traumatic brain injury: From mechanistic view to targeted therapeutic opportunities

Traumatic brain injury (TBI) is one of the most prevalent causes of permanent physical and cognitive disabilities. TBI pathology results from primary insults and a multi-mechanistic biochemical process, termed as secondary brain injury. Currently, there are no pharmacological agents for definitive treatment of patients with TBI. This article is presented with the purpose of reviewing molecular mechanisms of TBI pathology, as well as potential strategies and agents against pathological pathways. In this review article, materials were obtained by searching PubMed, Scopus, Elsevier, Web of Science, and Google Scholar. This search was considered without time limitation. Evidence indicates that oxidative stress and mitochondrial dysfunction are two key mediators of the secondary injury cascade in TBI pathology. TBI-induced oxidative damage results in the structural and functional impairments of cellular and subcellular components, such as mitochondria. Impairments of mitochondrial electron transfer chain and mitochondrial membrane potential result in a vicious cycle of free radical formation and cell apoptosis. The results of some preclinical and clinical studies, evaluating mitochondria-targeted therapies, such as mitochondria-targeted antioxidants and compounds with pleiotropic effects after TBI, are promising. As a proposed strategy in recent years, mitochondria-targeted multipotential therapy is a new hope, waiting to be confirmed. Moreover, based on the available findings, biologics, such as stem cell-based therapy and transplantation of mitochondria are novel potential strategies for the treatment of TBI; however, more studies are needed to clearly confirm the safety and efficacy of these strategies.

Luminescent PLGA Nanoparticles for Delivery of Darunavir to the Brain and Inhibition of Matrix Metalloproteinase-9, a Relevant Therapeutic Target of HIV-Associated Neurological Disorders

Human immunodeficiency virus (HIV) can independently replicate in the central nervous system (CNS) causing neurocognitive impairment even in subjects with suppressed plasma viral load. The antiretroviral drug darunavir (DRV) has been approved for therapy of HIV-infected patients, but its efficacy in the treatment of HIV-associated neurological disorders (HAND) is limited due to the low penetration through the blood–brain barrier (BBB). Therefore, innovations in DRV formulations, based on its encapsulation in optically traceable nanoparticles (NPs), may improve its transport through the BBB, providing, at the same time, optical monitoring of drug delivery within the CNS. The aim of this study was to synthesize biodegradable polymeric NPs loaded with DRV and luminescent, nontoxic carbon dots (C-Dots) and investigate their ability to permeate through an artificial BBB and to inhibit in vitro matrix metalloproteinase-9 (MMP-9) that represents a factor responsible for the development of HIV-related neurological disorders. Biodegradable poly(lactic-co-glycolic) acid (PLGA)-based nanoformulations resulted characterized by an average hydrodynamic size less than 150 nm, relevant colloidal stability in aqueous medium, satisfactory drug encapsulation efficiency, and retained emitting optical properties in the visible region of the electromagnetic spectrum. The assay on the BBB artificial model showed that a larger amount of DRV was able to cross BBB when incorporated in the PLGA NPs and to exert an enhanced inhibition of matrix metalloproteinase-9 (MMP-9) expression levels with respect to free DRV. The overall results reveal the great potential of this class of nanovectors of DRV for an efficacious treatment of HANDs.

Treatment with HIV-Protease Inhibitor Nelfinavir Identifies Membrane Lipid Composition and Fluidity as a Therapeutic Target in Advanced Multiple Myeloma

The HIV-protease inhibitor nelfinavir has shown broad anticancer activity in various preclinical and clinical contexts. In patients with advanced, proteasome inhibitor (PI)-refractory multiple myeloma, nelfinavir-based therapy resulted in 65% partial response or better, suggesting that this may be a highly active chemotherapeutic option in this setting. The broad anticancer mechanism of action of nelfinavir implies that it interferes with fundamental aspects of cancer cell biology. We combined proteome-wide affinity-purification of nelfinavir-interacting proteins with genome-wide CRISPR/Cas9-based screening to identify protein partners that interact with nelfinavir in an activity-dependent manner alongside candidate genetic contributors affecting nelfinavir cytotoxicity. Nelfinavir had multiple activity-specific binding partners embedded in lipid bilayers of mitochondria and the endoplasmic reticulum. Nelfinavir affected the fluidity and composition of lipid-rich membranes, disrupted mitochondrial respiration, blocked vesicular transport, and affected the function of membrane-embedded drug efflux transporter ABCB1, triggering the integrated stress response. Sensitivity to nelfinavir was dependent on ADIPOR2, which maintains membrane fluidity by promoting fatty acid desaturation and incorporation into phospholipids. Supplementation with fatty acids prevented the nelfinavir-induced effect on mitochondrial metabolism, drug-efflux transporters, and stress-response activation. Conversely, depletion of fatty acids/cholesterol pools by the FDA-approved drug ezetimibe showed a synergistic anticancer activity with nelfinavir in vitro. These results identify the modification of lipid-rich membranes by nelfinavir as a novel mechanism of action to achieve broad anticancer activity, which may be suitable for the treatment of PI-refractory multiple myeloma. SIGNIFICANCE: Nelfinavir induces lipid bilayer stress in cellular organelles that disrupts mitochondrial respiration and transmembrane protein transport, resulting in broad anticancer activity via metabolic rewiring and activation of the unfolded protein response.

Management of Antiretroviral Therapy with Boosted Protease Inhibitors-Darunavir/Ritonavir or Darunavir/Cobicistat

A major challenge in the management of antiretroviral therapy (ART) is to improve the patient's adherence, reducing the burden caused by the high number of drugs that compose the treatment regimens for human immunodeficiency virus positive (HIV+) patients. Selection of the most appropriate treatment regimen is responsible for therapeutic success and aims to reduce viremia, increase the immune system response capacity, and reduce the incidence rate and intensity of adverse reactions. In general, protease inhibitor (PI) is one of the pillars of regimens, and darunavir (DRV), in particular, is frequently recommended, along with low doses of enzyme inhibitors as cobicistat (COBI) or ritonavir (RTV), by the international guidelines. The potential of clinically significant drug interactions in patients taking COBI or RTV is high due to the potent inhibitory effect on cytochrome CYP 450, which attracts significant changes in the pharmacokinetics of PIs. Regardless of the patient or type of virus, the combined regimens of DRV/COBI or DRV/RTV are available to clinicians, proving their effectiveness, with a major impact on HIV mortality/morbidity. This study presents current information on the pharmacokinetics, pharmacology, drug interactions, and adverse reactions of DRV; it not only compares the bioavailability, pharmacokinetic parameters, immunological and virological responses, but also the efficacy, advantages, and therapeutic disadvantages of DRV/COBI or DRV/RTV combinations.

A New Insight on the Radioprotective Potential of Epsilon-Aminocaproic Acid

Background and objectives: The aim of the study was to scrutinize the ability of epsilon-aminocaproic acid (EACA) to prevent radiation-induced damage to human cells. Materials and Methods: Human peripheral blood mononuclear cells (PBMCs) were exposed to ionizing radiation at three low doses (22.62 mGy, 45.27 mGy, and 67.88 mGy) in the presence of EACA at the concentration of 50 ng/mL. Results: EACA was able to prevent cell death induced by low-dose X-ray radiation and suppress the formation of reactive oxygen species (ROS). EACA also demonstrated a capacity to protect DNA from radiation-induced damage. The data indicated that EACA is capable of suppression of radiation-induced apoptosis. Comparative tests of antioxidative activity of EACA and a range of free radical scavengers showed an ability of EACA to effectively inhibit the generation of ROS. Conclusions: This study showed that the pretreatment of PBMCs with EACA is able to protect the cells from radiation-elicited damage, including free radicals' formation, DNA damage, and apoptosis.

Methamphetamine Augments Concurrent Astrocyte Mitochondrial Stress, Oxidative Burden, and Antioxidant Capacity: Tipping the Balance in HIV-Associated Neurodegeneration

Methamphetamine (METH) use, with and without human immunodeficiency virus (HIV)-1 comorbidity, exacerbates neurocognitive decline. Oxidative stress is a probable neurotoxic mechanism during HIV-1 central nervous system infection and METH abuse, as viral proteins, antiretroviral therapy and METH have each been shown to induce mitochondrial dysfunction. However, the mechanisms regulating mitochondrial homeostasis and overall oxidative burden in astrocytes are not well understood in the context of HIV-1 infection and METH abuse. Here, we report METH-mediated dysregulation of astrocyte mitochondrial morphology and function during prolonged exposure to low levels of METH. Mitochondria became larger and more rod shaped with METH when assessed by machine learning, segmentation analyses. These changes may be mediated by elevated mitofusin expression coupled with inhibitory phosphorylation of dynamin-related protein-1, which regulate mitochondrial fusion and fission, respectively. While METH decreased oxygen consumption and ATP levels during acute exposure, chronic treatment of 1 to 2 weeks significantly enhanced both when tested in the absence of METH. Together, these changes significantly increased not only expression of antioxidant proteins, augmenting the astrocyte's oxidative capacity, but also oxidative damage. We propose that targeting astrocytes to reduce their overall oxidative burden and expand their antioxidant capacity could ultimately tip the balance from neurotoxicity towards neuroprotection.

Resveratrol Co-Treatment Attenuates the Effects of HIV Protease Inhibitors on Rat Body Weight and Enhances Cardiac Mitochondrial Respiration

Since the early 1990s human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) emerged as a global health pandemic, with sub-Saharan Africa the hardest hit. While the successful roll-out of antiretroviral (ARV) therapy provided significant relief to HIV-positive individuals, such treatment can also elicit damaging side-effects. Here especially HIV protease inhibitors (PIs) are implicated in the onset of cardio-metabolic complications such as type-2 diabetes and coronary heart disease. As there is a paucity of data regarding suitable co-treatments within this context, this preclinical study investigated whether resveratrol (RSV), aspirin (ASP) or vitamin C (VitC) co-treatment is able to blunt side-effects in a rat model of chronic PI exposure (Lopinavir/Ritonavir treatment for 4 months). Body weights and weight gain, blood metabolite levels (total cholesterol, HDL, LDL, triglycerides), echocardiography and cardiac mitochondrial respiration were assessed in PI-treated rats ± various co-treatments. Our data reveal that PI treatment significantly lowered body weight and cardiac respiratory function while no significant changes were found for heart function and blood metabolite levels. Moreover, all co-treatments ameliorated the PI-induced decrease in body weight after 4 months of PI treatment, while RSV co-treatment enhanced cardiac mitochondrial respiratory capacity in PI-treated rats. This pilot study therefore provides novel hypotheses regarding RSV co-treatment that should be further assessed in greater detail.

In-vitro effects of protease inhibitors on BAX, BCL- 2 and apoptosis in two human breast cell lines

Abstract Currently, the treatment of choice of HIV/AIDS in South Africa is the multidrug combination regimen known as HAART (highly active antiretroviral treatment). HAART, which commonly consists of nucleoside or non-nucleoside reverse transcriptase inhibitors and protease inhibitors, has radically decreased mortality and morbidity rates among people living with HIV/AIDS. The emphasis of the original development of the antiretroviral drugs was on clinical effectiveness (reducing mortality). Presently, emphasis has shifted from the initial short- term considerations to the long-term undesirable or harmful effects induced by this treatment regimen. Whether antiretroviral compounds are oncogenic is widely speculated, which led to this investigation into the effects of protease inhibitors on the expression of key apoptotic regulatory genes, BAX and BCL-2, in two human breast cell lines, MCF-7 and MCF-10A by real-time qPCR gene expression and immunofluorescence. The anti-apoptotic effects of the protease inhibitors – LPV/r were also investigated by cell death detection ELISA and acridine orange staining. This study also evaluated the cytotoxicity of the antiretroviral drugs in normal and cancer cell lines of the breast (at clinically relevant concentrations of the drugs and at different time points, 24–96 h), employing the neutral red uptake assay. The drugs and combinations tested did not alter BAX and BCL-2 gene expression and protein expression and localisation in both cell lines. In addition, the protease inhibitors–LPV/r did not inhibit camptothecin-induced apoptosis in both cell lines. We have shown that the protease inhibitors demonstrated varying degrees of cytotoxicity in the breast cells. The resulting DNA damage associated with cytotoxicity is strongly implicated in the processes of tumour initiation.

Mitochondrial and apoptotic in vitro modelling of differential HIV-1 progression and antiretroviral toxicity

OBJECTIVES

Ex vivo analysis of mitochondrial function may reveal HIV progression and the impact of ART. We propose a mitochondrial and apoptotic in vitro model using Jurkat T cells incubated with plasma. The objectives of this study were to evaluate mitochondrial and apoptotic lesions in this model in relation to HIV progression, and to assess the effect of >1 year of standard non-thymidine-containing therapy.

METHODS

This was a cross-sectional comparison among three age- and gender-matched groups (n = 19 × 3): healthy non-HIV-infected participants, HIV-infected long-term non-progressors (LTNPs) and standard antiretroviral-naive chronically infected patients [standard progressors (Sps)], longitudinally evaluated before (Sp1) and after (Sp2) >1 year of efavirenz + tenofovir + emtricitabine therapy. We analysed mitochondrial DNA content by RT-PCR, mitochondrial function by spectrophotometry, mitochondrial protein synthesis by western blot analysis, mitochondrial dynamics by western blot analysis (MFN2), apoptotic transition pore formation by western blot analysis (VDAC-1) and mitochondrial membrane potential and annexin V/propidium iodide fluorescence by flow cytometry.

RESULTS

There was a decreasing non-significant trend towards lower mitochondrial parameters for HIV-infected values with respect to uninfected control reference values. HIV progression (LTNP versus Sp1) was associated with decreased mitochondrial genetic, functional and translational parameters, which partially recovered after treatment intervention (Sp2). Mitochondrial fusion showed a trend to decrease non-significantly in Sp patients compared with LTNP patients, especially after therapy. All apoptotic parameters showed a trend to increase in Sp1 with respect to LTNP, followed by recovery in Sp2.

CONCLUSIONS

We proposed an in vitro model for mitochondrial and apoptotic assessment to test the effects of HIV infection and its therapy, resembling in vivo conditions. This model could be useful for clinical research purposes.

Natural killer cell-mediated shedding of ULBP2

UL16 binding proteins (ULBPs) are a family of cell surface proteins that are present in transformed and stressed cells and ligands for NKG2D. Soluble NKG2D ligands have been found in sera from cancer patients with their protein concentrations correlated with poor cancer prognosis. Here we show, for the first time, that human tumor cells lost their surface expression of ULBP2, but not ULBP1 and ULBP3, during NK cell-mediated cytolysis. In contrast to spontaneous shedding of NKG2D ligands, NK cytolysis-mediated shedding of ULBP2 was linked to target cell apoptosis, although both resulted from metalloproteinase cleavages. Inhibition of ULBP2 shedding by a metalloproteinase inhibitor BB-94 lead to reduced NK cell-mediated cytotoxicity and cytokine production. These results illustrate a regulation of NK cell effector functions through cytolysis-induced NKG2D ligand shedding. Consequently, compounds inhibiting NKG2D ligand shedding may offer therapeutic means to reduce excessive pathogenic NK cell activities.

Choice of antiretroviral therapy differentially impacts survival of HIV-infected CD4 T cells

BACKGROUND

HIV eradication strategies are now being evaluated in vitro and in vivo. A cornerstone of such approaches is maximal suppression of viral replication with combination antiretroviral therapy (ART). Since many antiretroviral agents have off target effects, and different classes target different components of the viral life cycle, we questioned whether different classes of ART might differentially affect the survival and persistence of productively HIV-infected CD4 T cells.

METHODS

In vitro infections of primary CD4 T cells using clinical isolates of HIV-1 that were either protease inhibitor susceptible (HIV PI-S), or resistant (HIV PI-R) were treated with nothing, lopinavir, efavirenz or raltegravir. Cell viability, apoptosis, and the proportion of surviving cells that were P24 positive was assessed by flow cytometry.

RESULTS

In HIV PI-S infected primary cultures, all three antiretroviral agents decreased viral replication, and reduced the total number of cells that were undergoing apoptosis (P < 0.01) similarly. Similarly, in the HIV PI-R infected cultures, both efavirenz and raltegravir reduced viral replication and reduced apoptosis compared to untreated control (P < 0.01), while lopinavir did not, suggesting that HIV replication drives T cell apoptosis, which was confirmed by association by linear regression (P < 0.0001) . However since HIV protease has been suggested to directly induce apoptosis of infected CD4 T cells, and HIV PI are intrinsically antiapoptotic, we evaluated apoptosis in productively infected (HIV P24+) cells. More HIV p24 positive cells were apoptotic in the Efavirenz or raltegravir treated cultures than the lopinavir treated cultures (P = 0.0008 for HIV PI-R and P = 0.06 for the HIV PI-S), indicating that drug class impacts survival of productively infected CD4 T cells.

CONCLUSIONS

Inhibiting HIV replication with a PI, NNRTI or INSTI reduces total HIV-induced T cell apoptosis. However, blocking HIV replication with PI but not with NNRTI or INSTI promotes survival of productively HIV-infected cells. Thus, selection of antiretroviral agents may impact the success of HIV eradication strategies.

Choice of antiretroviral therapy differentially impacts survival of HIV-infected CD4 T cells

Background

HIV eradication strategies are now being evaluated in vitro and in vivo. A cornerstone of such approaches is maximal suppression of viral replication with combination antiretroviral therapy (ART). Since many antiretroviral agents have off target effects, and different classes target different components of the viral life cycle, we questioned whether different classes of ART might differentially affect the survival and persistence of productively HIV-infected CD4 T cells.

Methods

In vitro infections of primary CD4 T cells using clinical isolates of HIV-1 that were either protease inhibitor susceptible (HIV PI-S), or resistant (HIV PI-R) were treated with nothing, lopinavir, efavirenz or raltegravir. Cell viability, apoptosis, and the proportion of surviving cells that were P24 positive was assessed by flow cytometry.

Results

In HIV PI-S infected primary cultures, all three antiretroviral agents decreased viral replication, and reduced the total number of cells that were undergoing apoptosis (P < 0.01) similarly. Similarly, in the HIV PI-R infected cultures, both efavirenz and raltegravir reduced viral replication and reduced apoptosis compared to untreated control (P < 0.01), while lopinavir did not, suggesting that HIV replication drives T cell apoptosis, which was confirmed by association by linear regression (P < 0.0001) . However since HIV protease has been suggested to directly induce apoptosis of infected CD4 T cells, and HIV PI are intrinsically antiapoptotic, we evaluated apoptosis in productively infected (HIV P24+) cells. More HIV p24 positive cells were apoptotic in the Efavirenz or raltegravir treated cultures than the lopinavir treated cultures (P = 0.0008 for HIV PI-R and P = 0.06 for the HIV PI-S), indicating that drug class impacts survival of productively infected CD4 T cells.

Conclusions

Inhibiting HIV replication with a PI, NNRTI or INSTI reduces total HIV-induced T cell apoptosis. However, blocking HIV replication with PI but not with NNRTI or INSTI promotes survival of productively HIV-infected cells. Thus, selection of antiretroviral agents may impact the success of HIV eradication strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/2052-8426-2-1) contains supplementary material, which is available to authorized users.

Association of early HIV viremia with mortality after HIV-associated lymphoma

OBJECTIVE

To examine the association between early HIV viremia and mortality after HIV-associated lymphoma.

DESIGN

Multicenter observational cohort study.

SETTING

Center for AIDS Research Network of Integrated Clinical Systems cohort.

PARTICIPANTS

HIV-infected patients with lymphoma diagnosed between 1996 and 2011, who were alive 6 months after lymphoma diagnosis and with at least two HIV RNA values during the 6 months after lymphoma diagnosis.

EXPOSURE

Cumulative HIV viremia during the 6 months after lymphoma diagnosis, expressed as viremia copy-6-months.

MAIN OUTCOME MEASURE

All-cause mortality between 6 months and 5 years after lymphoma diagnosis.

RESULTS

Of 224 included patients, 183 (82%) had non-Hodgkin lymphoma (NHL) and 41 (18%) had Hodgkin lymphoma. At lymphoma diagnosis, 105 (47%) patients were on antiretroviral therapy (ART), median CD4⁺ cell count was 148 cells/μl (interquartile range 54-322), and 33% had suppressed HIV RNA (<400 copies/ml). In adjusted analyses, mortality was associated with older age [adjusted hazard ratio (AHR) 1.37 per decade increase, 95% CI 1.03-1.83], lymphoma occurrence on ART (AHR 1.63, 95% CI 1.02-2.63), lower CD4⁺ cell count (AHR 0.75 per 100 cells/μl increase, 95% CI 0.64-0.89), and higher early cumulative viremia (AHR 1.35 per log₁₀ copies × 6-months/ml, 95% CI 1.11-1.65). The detrimental effect of early cumulative viremia was consistent across patient groups defined by ART status, CD4⁺ cell count, and histology.

CONCLUSION

Exposure to each additional 1-unit log₁₀ in HIV RNA throughout the 6 months after lymphoma diagnosis was associated with a 35% increase in subsequent mortality. These results suggest that early and effective ART during chemotherapy may improve survival.

Nelfinavir inhibits intra-mitochondrial calcium influx and protects brain against hypoxic-ischemic injury in neonatal mice

Nelfinavir (NLF), an antiretroviral agent, preserves mitochondrial membranes integrity and protects mature brain against ischemic injury in rodents. Our study demonstrates that in neonatal mice NLF significantly limits mitochondrial calcium influx, the event associated with protection of the brain against hypoxic-ischemic insult (HI). Compared to the vehicle-treated mice, cerebral mitochondria from NLF-treated mice exhibited a significantly greater tolerance to the Ca²⁺-induced membrane permeabilization, greater ADP-phosphorylating activity and reduced cytochrome C release during reperfusion. Pre-treatment with NLF or Ruthenium red (RuR) significantly improved viability of murine hippocampal HT-22 cells, reduced Ca²⁺ content and preserved membrane potential (Ψm) in mitochondria following oxygen-glucose deprivation (OGD). Following histamine-stimulated Ca²⁺ release from endoplasmic reticulum, in contrast to the vehicle-treated cells, the cells treated with NLF or RuR also demonstrated reduced Ca²⁺ content in their mitochondria, the event associated with preserved Ψm. Because RuR inhibits mitochondrial Ca²⁺ uniporter, we tested whether the NLF acts via the mechanism similar to the RuR. However, in contrast to the RuR, in the experiment with direct interaction of these agents with mitochondria isolated from naïve mice, the NLF did not alter mitochondrial Ca²⁺ influx, and did not prevent Ca²⁺ induced collapse of the Ψm. These data strongly argues against interaction of NLF and mitochondrial Ca²⁺ uniporter. Although the exact mechanism remains unclear, our study is the first to show that NLF inhibits intramitochondrial Ca²⁺ flux and protects developing brain against HI-reperfusion injury. This novel action of NLF has important clinical implication, because it targets a fundamental mechanism of post-ischemic cell death: intramitochondrial Ca²⁺ overload → mitochondrial membrane permeabilization → secondary energy failure.

Mitochondria in traumatic brain injury and mitochondrial-targeted multipotential therapeutic strategies

Traumatic brain injury (TBI) is a major health and socioeconomic problem throughout the world. It is a complicated pathological process that consists of primary insults and a secondary insult characterized by a set of biochemical cascades. The imbalance between a higher energy demand for repair of cell damage and decreased energy production led by mitochondrial dysfunction aggravates cell damage. At the cellular level, the main cause of the secondary deleterious cascades is cell damage that is centred in the mitochondria. Excitotoxicity, Ca(2+) overload, reactive oxygen species (ROS), Bcl-2 family, caspases and apoptosis inducing factor (AIF) are the main participants in mitochondria-centred cell damage following TBI. Some preclinical and clinical results of mitochondria-targeted therapy show promise. Mitochondria- targeted multipotential therapeutic strategies offer new hope for the successful treatment of TBI and other acute brain injuries.

There are many potential medical therapies for atraumatic osteonecrosis

Atraumatic osteonecrosis is a common complication of SLE and is seen in other connective tissue diseases, in patients treated with high doses of CSs, in HIV-infected patients and in alcoholic patients. Standard care is confined to analgesia, core decompression if the condition is early and affects the femoral head and joint replacement. However, consideration of the underlying biological mechanisms leads to the recognition of many potential therapies that might either prevent progression or, even, reverse the process if it is not yet too far advanced. These potential therapies merit detailed consideration. Critical points are that (i) histopathological evidence shows that the initial cellular event is apoptosis of osteocytes; and (ii) another requisite, as homeostasis requires that death and rebirth of osteocytes be balanced, is an accompanying inadequate proliferative capacity of osteoblasts. Thus, a logical approach to treatment includes measures that (i) reduce apoptosis of osteocytes and (ii) enhance proliferation of osteoblasts/pre-osteoblasts. Measures to reduce the ongoing apoptosis of osteocytes require reinforcing the effects of members of the Bcl-2 family (Bcl-2 itself and Mcl-1), the Wnt/catenin pathways (using an available sclerostin antibody) and HSPs (by application of local heat using US, deep wave diathermy or infrared), as well as administration of bisphosphonates and nitrates. Measures to enhance proliferation of osteoblasts/pre-osteoblasts include the use of stem cells, extracorporeal shock wave therapy, aspirin, the proteosome inhibitor bortezomib, melatonin and application of local heat. Use of VEGF would encourage proliferation of blood vessels and osteogenesis. Certain drugs that inhibit osteoblast proliferation should be avoided, including NSAIDs, serotonin reuptake inhibitors and thiazolidinediones.

How I treat HIV-associated lymphoma

Over the past 10 years, significant progress has been made in understanding HIV-associated lymphomas and improving the prognosis of these diseases. With the advent of combination antiretroviral therapy and the development of novel therapeutic strategies, most patients with HIV-associated lymphomas are cured. The outcome for the majority of patients with HIV-associated diffuse large B-cell lymphoma and Burkitt lymphoma in particular, is excellent, with recent studies supporting the role of rituximab in these diseases. Indeed, in the combination antiretroviral therapy era, the curability of many patients with HIV-associated lymphoma is similar to their HIV-negative counterparts. New treatment frontiers need to focus on improving the outcome for patients with advanced immune suppression and for those with adverse tumor biology, such as the activated B-cell type of diffuse large B-cell lymphoma and the virally driven lymphomas. Future clinical trials need to investigate novel targeted agents alone and in combination with chemotherapy.

Beneficial effects of a switch to a Lopinavir/ritonavir-containing regimen for patients with partial or no immune reconstitution with highly active antiretroviral therapy despite complete viral suppression

The purpose of this study was to determine if switching to an Lopinavir/ritonavir (LPV/r)-containing regimen resulted in greater immune reconstitution in patients with immunologic failure despite complete viral suppression with highly active antiretroviral therapy (HAART). Twenty patients with partial or no immune response to HAART despite viral suppression were enrolled. Ten were randomized to stay on their current regimen and 10 were randomized to LPV/r plus their current NRTI backbone. T cell subsets, ex vivo apoptosis, and the percent of circulating cells with detectable intracellular HIV-1 RNA were measured. The mean increase in CD4(+) count at 6 months was 116/mm(3) (172-288) for the LPV/r-containing arm versus 32/mm(3) (264-296) for continuation regimens (p = 0.03). The number of patients with an increase ≥50 cells/mm(3) was also greater in the LPV/r arm (7/9 versus 2/10, p = 0.01). This paralleled a decrease in ex vivo apoptosis of naive CD4(+) T cells at 6 months (21.7-11.0% for the LPV/r arm versus 17.3-18.9% for the continuation arm, p = 0.04) and memory cells (21.1-14.1% for LPV/r versus 20.2-17.9% for continuation arm, NSS). Switching patients to an LPV/r-containing regimen improved CD4(+) counts in patients with prior immunologic failure, and this may be due to an effect of LPV/r on apoptosis.

Factors associated with collagen deposition in lymphoid tissue in long-term treated HIV-infected patients

OBJECTIVE

The factors associated with fibrosis in lymphoid tissue in long-term treated HIV-infected patients and their correlation with immune reconstitution were assessed.

METHODS

Tonsillar biopsies were performed in seven antiretroviral-naive patients and 29 successfully treated patients (median time on treatment, 61 months). Twenty patients received protease inhibitors-sparing regimens and nine protease inhibitor-containing regimens. Five tonsillar resections of HIV-negative individuals were used as controls. Lymphoid tissue architecture, collagen deposition (fibrosis) and the mean interfollicular CD4(+) cell count per mum were assessed.

RESULTS

Naive and long-term treated HIV-infected patients had a higher proportion of fibrosis than did HIV-uninfected persons (P < 0.001). Patients with greater collagen deposition showed lower levels of CD4 cells in lymphoid tissue (P = 0.03) and smaller increase in peripheral CD4(+) T cells (r = -0.40, P = 0.05). The factors independently associated with fibrosis in lymphoid tissue were age (P < 0.0001), treated patients with detectable lymphoid tissue viral load when compared with patients with undetectable lymphoid tissue viral load (median 5 vs. 12%, respectively, P = 0.017) and patients receiving a protease inhibitor-sparing vs. a protease inhibitor-containing regimen (median 8 vs. 2.5%, respectively, P = 0.04).

CONCLUSION

Fibrosis in lymphoid tissue was associated with a poor reconstitution of CD4(+) T cells and long-term antiretroviral therapy did not reverse this abnormality. HIV infection, older age, a detectable level of lymphoid tissue viral load in treated patients and protease inhibitor-sparing regimens seem to favour fibrosis in lymphoid tissue.

Dendritic cells/natural killer cross-talk: a novel target for human immunodeficiency virus type-1 protease inhibitors

Background

HIV-1 Protease Inhibitors, namely PIs, originally designed to inhibit HIV-1 aspartic protease, can modulate the immune response by mechanisms largely unknown, and independent from their activity on viral replication. Here, we analyzed the ability of PIs to interfere with differentiation program of monocytes toward dendritic cell (DCs) lineage, a key process in the inflammatory response.

Methodology/Principal Findings

Monocytes from healthy donors were isolated and induced to differentiate in vitro in the presence or absence of saquinavir, ritonavir, nelfinavir, indinavir or amprenavir (sqv, rtv, nlfv, idv, apv, respectively). These drugs demonstrated a differential ability to sustain the generation of immature DCs (iDCs) with an altered phenotype, including low levels of CD1a, CD86, CD36 and CD209. DCs generated in the presence of rtv also failed to acquire the typical phenotype of mature DCs (mDCs), and secreted lower amounts of IL-12 and IL-15. Accordingly, these aberrant mDCs failed to support activation of autologous Natural Killer (NK) cells, and resulted highly susceptible to NK cell-mediated cytotoxicity.

Conclusions/Significance

Our findings uncover novel functional properties of PIs within the DC-NK cell cross-talk, unveiling the heterogeneous ability of members of this class drugs to drive the generation of atypical monocyte-derived DCs (MDDCs) showing an aberrant phenotype, a failure to respond appropriately to bacterial endotoxin, a weak ability to prime autologous NK cells, and a high susceptibility to NK cell killing. These unexpected properties might contribute to limit inflammation and viral spreading in HIV-1 infected patients under PIs treatment, and open novel therapeutical perspectives for this class drugs as immunomodulators in autoimmunity and cancer.

HIV aspartyl protease inhibitors as promising compounds against Candida albicans André Luis Souza dos Santos

Cells of Candida albicans (C. albicans) can invade humans and may lead to mucosal and skin infections or to deep-seated mycoses of almost all inner organs, especially in immunocompromised patients. In this context, both the host immune status and the ability of C. albicans to modulate the expression of its virulence factors are relevant aspects that drive the candidal susceptibility or resistance; in this last case, culminating in the establishment of successful infection known as candidiasis. C. albicans possesses a potent armamentarium consisting of several virulence molecules that help the fungal cells to escape of the host immune responses. There is no doubt that the secretion of aspartyl-type proteases, designated as Saps, are one of the major virulence attributes produced by C. albicans cells, since these hydrolytic enzymes participate in a wide range of fungal physiological processes as well as in different facets of the fungal-host interactions. For these reasons, Saps clearly hold promise as new potential drug targets. Corroborating this hypothesis, the introduction of new anti-human immunodeficiency virus drugs of the aspartyl protease inhibitor-type (HIV PIs) have emerged as new agents for the inhibition of Saps. The introduction of HIV PIs has revolutionized the treatment of HIV disease, reducing opportunistic infections, especially candidiasis. The attenuation of candidal infections in HIV-infected individuals might not solely have resulted from improved immunological status, but also as a result of direct inhibition of C. albicans Saps. In this article, we review updates on the beneficial effects of HIV PIs against the human fungal pathogen C. albicans, focusing on the effects of these compounds on Sap activity, growth behavior, morphological architecture, cellular differentiation, fungal adhesion to animal cells and abiotic materials, modulation of virulence factors, experimental candidiasis infection, and their synergistic actions with classical antifungal agents.

The mitochondria-independent cytotoxic effect of nelfinavir on leukemia cells can be enhanced by sorafenib-mediated mcl-1 downregulation and mitochondrial membrane destabilization

Background

Nelfinavir is an HIV protease inhibitor that has been used for a long period of time to treat HIV-infected individuals. It has recently emerged that nelfinavir could represent a prospective new anti-cancer drug, prompting us to test the effect of nelfinavir on leukemia cells.

Methods

By combining in vitro and ex vivo studies, the effect of nelfinavir on leukemia cells and non-malignant, bone marrow-derived tissue cells was analyzed.

Results

At a concentration of 9 μg/ml, nelfinavir induced death of 90% of HL60, IM9, and Jurkat cells. At the same concentration and treatment conditions, less than 10% of aspirated human bone marrow cells showed nelfinavir-induced cell damage. Nelfinavir-induced death of leukemia cells was accompanied by activation of caspases 3, 7, and 8. Despite caspase activation, the upregulation of the anti-apoptotic bcl-2 family member protein mcl-1 that resulted from nelfinavir treatment stabilized the mitochondrial membrane potential, resulting in primarily mitochondria-independent cell death. Pharmacological downregulation of mcl-1 expression by treatment with sorafenib (2 μg/ml) significantly enhanced nelfinavir-induced apoptosis even at lower nelfinavir concentrations (5 μg/ml), but did not have additional detrimental effects on non-malignant bone marrow cells.

Conclusions

The ability of nelfinavir to induce apoptosis in leukemia cells as a single agent in a mitochondria-independent manner might suggest it could be used as a second or third line of treatment for leukemia patients for whom standard mitochondria-directed treatment strategies have failed. Combination treatment with nelfinavir and sorafenib might further enhance the efficacy of nelfinavir even on chemo-resistant leukemia cells.

HIV protease inhibitors: recent clinical trials and recommendations on use

BACKGROUND

HIV protease inhibitors (PIs) are potent antiretroviral drugs that represent a pivotal component of highly active antiretroviral therapy (HAART). PIs have evolved over the years to gain in potency, convenience, tolerability and genetic barrier to resistance.

OBJECTIVE

Updated summary of evidence-based information about the efficacy and safety of PIs on initial, simplification and rescue interventions in HIV patients.

METHODS

Review of available data reported in peer-reviewed journals, medical conferences and treatment guidelines.

RESULTS

Due to their characteristics, PIs are, and will remain, a cornerstone component in most lines of antiretroviral therapy. The antiviral activity, tolerability and convenience of PIs have improved significantly in recent years. Differences between compounds within this class may favour their use in specific situations, such as the friendly metabolic profile of atazanavir in patients with cardiovascular disease or the high genetic barrier of darunavir or tipranavir in heavily pretreated individuals with HIV.

Nelfinavir/ritonavir reduces acinar injury but not inflammation during mouse caerulein pancreatitis

There is no clinical treatment that reduces acinar injury during pancreatitis. Human immunodeficiency virus (HIV) protease inhibitors (PI), including nelfinavir (NFV) and ritonavir (RTV), may reduce the rate of pancreatitis in HIV-infected patients. Since permeability transition pore (PTPC)-mediated mitochondrial dysfunction occurs during pancreatitis, and we have shown that PI prevents PTPC opening, we studied its effects in a model of pancreatitis. The effect of NFV plus RTV (NFV/RTV) or vehicle on caerulein-induced pancreatitis in mice was compared by measuring changes in mitochondrial membrane potential in vitro and cytochrome c leakage in vivo. Histological and inflammatory makers were also compared. NFV/RTV improved DiOC6 retention in acini exposed to caerulein in vitro. In vivo NFV prevented cytosolic leakage of cytochrome c and reduced pancreatic acinar injury, active caspase-3 staining, TUNEL-positive acinar cells, and serum amylase (P < 0.05). Conversely, trypsin activity, serum cytokine levels, and pancreatic and lung inflammation were unaffected. NFV/RTV reduces pancreatic injury and acinar cell death in experimental mouse caerulein-induced pancreatitis but does not impact inflammation.

Pharmacological inhibition of mitochondrial membrane permeabilization for neuroprotection

Recent data have provided important clues about the molecular mechanisms underlying certain neurodegenerative diseases. Most cell death in vertebrates proceeds via the mitochondrial pathway of apoptosis. Mitochondria contain proapoptotic factors such as cytochrome c and AIF in their intermembrane space. Furthermore, mitochondrial membrane permeabilization (MMP) is a critical event during apoptosis, representing the "point of no return" of the lethal process. Modern medicine is developing an increasing number of drugs for neurodegenerative disease, but no neuroprotective treatment has yet been established. While current treatments temporarily alleviate symptoms, they do not halt disease progression. This paper briefly reviews the pharmacological inhibition of mitochondrial membrane permeabilization for neuroprotection.

HIV-1 viral genes and mitochondrial apoptosis

The mitochondrion is an organelle that regulates various cellular functions including the production of energy and programmed cell death. Aberrant mitochondrial function is often concomitant with various cytopathies and medical disorders. The mitochondrial membrane plays a key role in the induction of cellular apoptosis, and its destabilization, as triggered by both intracellular and extracellular stimuli, results in the release of proapoptotic factors into the cytosol. Not surprisingly, proteins from the human immunodeficiency virus type 1 (HIV) have been implicated in exploiting this organelle to promote the targeted depletion of key immune cells, which assists in viral evasion of the immune system and contributes to the characteristic global immunodeficiency observed during progression of disease. Here we review the mechanisms by which HIV affects the mitochondrion, and suggest that various viral-associated genes may directly regulate apoptotic cell death.

HIV protease inhibitors provide neuroprotection through inhibition of mitochondrial apoptosis in mice

Neuroprotection can be achieved by preventing apoptotic death of postmitotic cells. Apoptotic death can occur by either a caspase-dependent mechanism, involving cytochrome c, apoptosis protease-activating factor-1 (Apaf-1), and caspase-9, or a caspase-independent mechanism, involving apoptosis-inducing factor (AIF). HIV protease inhibitors (PIs) avert apoptosis in part by preventing mitochondrial outer membrane permeabilization (MOMP), but the precise mechanism by which they work is not known. Here, we evaluated the impact of the PIs in a mouse model of retinal detachment (RD) in vivo and in murine primary retinal cell cultures in vitro. Oral administration of the PIs nelfinavir and ritonavir significantly inhibited photoreceptor apoptosis, while preventing the translocation of AIF from mitochondria to the nucleus as well as the activation of caspase-9. RD-induced photoreceptor apoptosis was similarly inhibited in mice carrying hypomorphic mutations of the genes encoding AIF or Apaf-1. Nelfinavir attenuated apoptosis as well as mitochondrial release of AIF and cytochrome c, and subsequent activation of caspase-9 in vitro, in photoreceptor cultures exposed to starvation or monocyte chemoattractant protein-1-stimulated (MCP-1-stimulated) macrophages. Our results suggest that the MOMP inhibition by PIs involved interruption of both caspase-dependent and caspase-independent apoptosis pathways and that PIs may be clinically useful for the treatment of diseases caused by excessive apoptosis.

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.

Insulin resistance, glucose intolerance and diabetes mellitus in HIV-infected patients

An increased prevalence of insulin resistance, glucose intolerance and diabetes has been reported in HIV infection in the highly active antiretroviral therapy (HAART) era. This development might be clinically significant because of its association with cardiovascular morbidity and mortality as well as the therapeutic challenges of managing polypharmacy. The development of insulin resistance, glucose intolerance and diabetes could be related to the underlying HIV infection, the contribution of different antiretroviral agents, treatment-associated weight gain, immune restoration, as well as the non-HIV related factors. Dissecting these factors in clinical practice might be difficult. Clinical studies include short-term treatments in healthy, non-HIV-infected individuals; randomized, controlled trials; comparative studies of different HAART regimens; and randomized studies of switching regimens in patients with viral suppression and stable immune function. This article reviews the latest knowledge regarding the epidemiology, pathogenesis, prevention and treatment of insulin resistance, glucose intolerance and diabetes mellitus in HIV-infected individuals.

Flying in the face of resistance: antiviral-independent benefit of HIV protease inhibitors on T-cell survival

Human immunodeficiency virus (HIV) infection results in excessive apoptosis of infected and uninfected cells, mediated by host and viral factors present in plasma. As HIV protease inhibitors (PIs) have intrinsic antiapoptotic properties, we questioned whether HIV PIs could block HIV-induced CD4+ T-cell death independent of their effects on HIV replication. We demonstrate that HIV PIs block the death of CD4+ T cells induced by HIV glycoprotein 120 (gp120), Vpr, and Tat, as well as host signals Fas ligand, tumor necrosis factor, and tumor necrosis factor-related apoptosis-inducing ligand. Using gp120/CXCR4 as a model, we show that the HIV PIs specifically block mitochondrial apoptosis signaling. Furthermore, HIV PIs inhibit CD4+ T-cell death induced by viruses with high-level resistance to PIs (P<0.01) and apoptosis induced by serum of HIV patients with known resistance to HIV PIs (P=0.01). Together, these results show that HIV PIs block CD4+ T-cell death and have a beneficial effect on CD4+ T-cell survival despite PI resistance.

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.

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.

Apoptosis and caspases regulate death and inflammation in sepsis

Although the prevailing concept has been that mortality in sepsis results from an unbridled hyper-inflammatory cytokine-mediated response, the failure of more than 30 clinical trials to treat sepsis by controlling this cytokine response requires a 'rethink' of the molecular mechanism underpinning the development of sepsis. As we discuss here, remarkable new studies indicate that most deaths from sepsis are actually the result of a substantially impaired immune response that is due to extensive death of immune effector cells. Rectification of this apoptotic-inflammatory imbalance using modulators of caspases and other components of the cell-death pathway have shown striking efficacy in stringent animal models of sepsis, indicating an entirely novel path forward for the clinical treatment of human sepsis.

Mitochondria: pharmacological manipulation of cell death

Cell death by apoptosis or necrosis is often important in the etiology and treatment of disease. Since mitochondria play important roles in cell death pathways, these organelles are potentially prime targets for therapeutic intervention. Here we discuss the mechanisms through which mitochondria participate in the cell death process and also survey some of the pharmacological approaches that target mitochondria in various ways.

HIV gp41-induced apoptosis is mediated by caspase-3-dependent mitochondrial depolarization, which is inhibited by HIV protease inhibitor nelfinavir

Apoptotic loss of CD4+ T cells has been proposed as a mechanism of T cell depletion in human immunodeficiency virus (HIV) infections resulting in immunodeficiency. The Env glycoprotein has been implicated in apoptosis of uninfected bystander cells via gp120 binding to CD4/CXC chemokine receptor 4 as well as the fusion/hemifusion process mediated by gp41. Using an in vitro model of coculture of Env-expressing cells as effectors and CD4+ T cells as targets, we find that apoptosis mediated by Env glycoprotein in bystander cells in fact correlates with gp41-induced hemifusion. Further, the apoptotic pathway initiated by this interaction involves caspase-3-dependent mitochondrial depolarization and reactive oxygen species production. HIV gp41-induced mitochondrial depolarization is inhibited by protease inhibitor nelfinavir but not by other HIV protease inhibitors or inhibitors of calpain and cathepsin. This "kiss of death" (hemifusion) signaling pathway is independent of p38 mitogen-activated protein kinase and p53, making it distinct from the apoptosis seen in syncytia. We also show that virion-induced apoptosis is gp41-dependent. Our findings provide new insights into the mechanism via which HIV gp41 mediates apoptosis in bystander cells.

In Vivo Effects of Highly Active Antiretroviral Therapies Containing the Protease Inhibitor Nelfinavir on Mitochondrially Driven Apoptosis

Background

In vitro studies have reported controversial effects of protease inhibitors (PIs) on mitochondrially driven apoptosis. Additionally, since PIs in the clinical setting are almost always given in combination with nucleoside analogues, which may have negative effects on mitochondrial DNA (mtDNA), the impact of PI-containing highly active antiretroviral therapy (HAART) on apoptosis and mtDNA content is unclear.

Patients and methods

A cross-sectional study was performed including 20 HIV-negative (HIV-) patients, 16 HIV-positive, antiretroviral-naive (HIV+) patients and 17 HIV-positive patients receiving the PI nelfinavir (NFV) plus zidovudine and lamivudine (AZT+3TC) or didanosine and stavudine (ddI+d4T) - collectively known as HIV+PI - as first-line antiretroviral treatment for at least 12 months. Peripheral blood mononuclear cells (PBMCs) were isolated. BCL2 expression (anti-apoptotic) and the levels of the cleaved, active form of caspase-9 (pro-apoptotic) were determined by western blot. An index of mitochondrially driven apoptotic activation was estimated calculating the ratio caspase-9:BCL2. Mitochondrial DNA content was measured by real-time PCR.

Results

BCL2 expression was lower in HIV+ than in HIV-patients ( P<0.01), whereas levels of caspase-9 were higher ( P=0.001). The caspase-9:BCL2 ratio was significantly increased in HIV+ compared with HIV- individuals ( P<0.001). Mitochondrial DNA content was also decreased in HIV+ compared with HIV- patients ( P<0.001). The HIV+PI group exhibited a trend to normalization for BCL2 expression and caspase-9 compared with the HIV+ group, whereas the caspase-9:BCL2 ratio significantly improved (decreased, P<0.05 compared with HIV+ group). The mtDNA content in the HIV+PI group was similar to that of the HIV+ group, although the results of mtDNA content differed depending on whether NFV was combined with AZT+3TC (preserved) or with ddI+d4T (depleted). Conversely, no differences were found in apoptotic markers between the two subgroups of HIV+PI.

Conclusions

NFV-based PI-containing HAART regimens may exert some beneficial effects counteracting the increased mitochondrially driven apoptosis present in HIV-infected people.

Increased thymic output in HIV-negative patients after antiretroviral therapy

OBJECTIVE

To determine the effects of antiretroviral therapy on thymic output independent of HIV infection.

METHODS

Thymic output was evaluated by quantifying signal joint T-cell receptor (TCR) recombination excision circles in peripheral blood lymphocytes from HIV-negative patients undergoing prophylactic antiretroviral therapy. Additionally, effects of the HIV protease inhibitor nelfinavir were assessed in vivo on TCR-induced death of murine double-positive thymocytes.

RESULTS

Five out of seven HIV-negative patients undergoing prophylactic antiretroviral therapy exhibited a dramatic increase (1-3 log10) in recent thymic emigrants containing signal joint TCR recombination excision circles while their peripheral T cell compartments remained relatively unaffected. None of the patients developed subsequent HIV infections. Interestingly, nelfinavir did not have significant effects on TCR-induced apoptosis of murine thymocytes in vivo.

CONCLUSION

Antiretroviral therapy augments thymic output independent of HIV. Furthermore, nelfinavir does not dramatically affect TCR-induced thymocyte death in mice, thus central tolerance remains intact.

Inhibition of adenine nucleotide translocator pore function and protection against apoptosis in vivo by an HIV protease inhibitor

Inhibitors of HIV protease have been shown to have antiapoptotic effects in vitro, yet whether these effects are seen in vivo remains controversial. In this study, we have evaluated the impact of the HIV protease inhibitor (PI) nelfinavir, boosted with ritonavir, in models of nonviral disease associated with excessive apoptosis. In mice with Fas-induced fatal hepatitis, Staphylococcal enterotoxin B-induced shock, and middle cerebral artery occlusion-induced stroke, we demonstrate that PIs significantly reduce apoptosis and improve histology, function, and/or behavioral recovery in each of these models. Further, we demonstrate that both in vitro and in vivo, PIs block apoptosis through the preservation of mitochondrial integrity and that in vitro PIs act to prevent pore function of the adenine nucleotide translocator (ANT) subunit of the mitochondrial permeability transition pore complex.

The HIV Protease Inhibitors Saquinavir, Ritonavir, and Nelfinavir Induce Apoptosis and Decrease Barrier Function in Human Intestinal Epithelial Cells

Background and aims

Diarrhoea is a frequent adverse effect of HIV protease inhibitors (PIs) which may be due to intestinal barrier disruption. We investigated whether tight junction dysregulation, apoptosis or necrosis are responsible for this epithelial damage.

Methods

Saquinavir, nelfinavir, and ritonavir were added to the mucosal or serosal side of HT-29/B6 colon cell monolayers. Transepithelial resistance was monitored for 72 h to assess epithelial barrier function. Apoptosis and necrosis were investigated by light and electron microscopy and quantified by nucleosome ELISA and LDH measurement, respectively. Tight junction components were analysed by Western blots of occludin and zonula occludens. Apoptosis induction in normal human intestinal epithelium was examined by measurement of poly(ADP-ribose) polymerase (PARP) cleavage in Western blots of mucosal tissue explants cultured with PIs for 24 h.

Results

HIV PIs decreased transepithelial resistance by more than 44% in HT-29/B6 monolayers. Histology revealed massive apoptotic body formation but no evidence for necrosis after PI treatment. Correspondingly, LDH release was lower than 0.2%/h of total LDH, independent of PI treatment, and nucleosomes were increased up to 22-fold after drug treatment versus control. Occludin and zonula occludens-1 expression in the membrane were not diminished. PARP cleavage increased in normal human intestinal tissue treated with PIs.

Conclusions

PI-induced barrier disruption in intestinal epithelial cells is not due to necrosis or tight junction alterations, but to induction of massive apoptosis which may lead to leak-flux diarrhoea in vivo. Our findings suggest that induction of apoptosis by PIs could have potential for antitumour therapy.

Mitochondria are sensors for HIV drugs

Highly active anti-retroviral therapy (HAART) has drastically altered the course of HIV-1 infection, resulting in a major decrease in morbidity and mortality. However, adverse drug reactions and long-term toxicities associated with HAART are now a concern. A major toxicity that has been highlighted by the increased use of HAART is related to mitochondrial side-effects. At the same time, analysis of the biochemical pathways involved in programmed cell death has revealed that mitochondria are main sensors in this process. In this article, the regulation of mitochondrial damage following the use of nucleoside analogue reverse transcriptase inhibitors (NRTIs) and protease inhibitors is discussed, with a particular focus on the putative molecular mechanisms involved.

In vitro and in vivo effects of HIV protease inhibitors on apoptosis

Development of potent inhibitors of HIV protease has revolutionized the treatment of HIV infection. HIV protease inhibitors (PI) have caused more dramatic improvements in CD4 T-cell numbers than in other therapies that were available previously, prompting investigators to assess whether PI possess intrinsic immunomodulatory effects. An emerging body of data indicates that HIV PIs are antiapoptotic, although the exact molecular target responsible for this antiapoptotic effect remains to be defined in vitro and in vivo. Paradoxically, high-dose PI also may have proapoptotic effects, particularly when assessed in vitro in transformed cell lines and implanted mouse models. Future research will define molecular targets of PI that are responsible for their apoptotis modulatory effects (both pro- and anti-apoptotic). In addition, evaluation of the clinical utility of PI-based therapy in those non-HIV disease states that are characterized by excessive apoptotis will reveal the full clinical potential of this intriguing class of drugs.

Improved survival in experimental sepsis with an orally administered inhibitor of apoptosis

The pathophysiology of sepsis involves excessive lymphocyte apoptosis, which correlates with adverse outcomes, and disordered cytokine production, which may promote host injury. As the protease inhibitor (PI) class of antiretroviral agents is known to prevent apoptosis in vitro, we evaluated their effect on survival, lymphocyte apoptosis, and consequent cytokine production in mice with sepsis induced by cecal ligation and perforation. Mice pretreated with PIs have improved survival (67%; P<0.0005) compared with controls (17%) and a significant (P<0.05) reduction in lymphocyte apoptosis. Even mice receiving therapy beginning 4 h after perforation demonstrated improved survival (50%; P<0.05) compared with controls. PI therapy is also associated with an increase in the Th1 cytokine TNF-alpha (P<0.05) early in sepsis and a reduction in the Th2 cytokines IL-6 and IL-10 (P<0.05) late in sepsis; despite no intrinsic antibacterial effects, PI also reduced quantitative bacterial blood cultures. The beneficial effects of PI appear to be specific to lymphocyte apoptosis, as lymphocyte-deficient Rag1-/- mice did not experience benefit from treatment with PI. Thus, inhibition of lymphocyte apoptosis by PI is a candidate approach for the treatment of sepsis.

HIV Protease Inhibitors Prevent Mitochondrial Hyperpolarization and Redox Imbalance and Decrease Endogenous Uncoupler Protein-2 Expression in Gp120-Activated Human T Lymphocytes

It has been demonstrated that HIV protease inhibitors (PIs) are able to inhibit apoptosis of both infected and uninfected T cells. It was hypothesized that the mechanisms underlying this effect are associated with a specific activity of these drugs against mitochondrial modifications occurring in the execution phase of apoptosis. In this work, we investigated the activity of PIs towards the early changes occurring in mitochondrial membrane potential in freshly isolated uninfected human T lymphocytes sensitized to CD95/Fas-induced physiological apoptosis via pre-exposure to HIV envelope protein gp120. The results obtained clearly indicate that PIs are capable of hindering early morphogenetic changes bolstering T cell apoptosis, that is, cell polarization and mitochondrial hyperpolarization. The target effect on mitochondria appeared to be characterized by a specific activity of PIs in the maintenance of their homeostasis either in intact cells or in cell-free systems, that is, isolated mitochondria. PIs seem to act as boosters of mitochondrial defense mechanisms, including modulation of endogenous uncouplers. These results add new insights in the field of PI mitochondrial toxicity mechanisms and pharmacological perspectives for the use of these drugs in the control of immune system homeostasis.