The human 26S proteasome is a target of antiretroviral agents

Pregnancy Is Associated with Impaired Transcription of Human Endogenous Retroviruses and of TRIM28 and SETDB1, Particularly in Mothers Affected by Multiple Sclerosis

Accumulating evidence highlights the pathogenetic role of human endogenous retroviruses (HERVs) in eliciting and maintaining multiple sclerosis (MS). Epigenetic mechanisms, such as those regulated by TRIM 28 and SETDB1, are implicated in HERV activation and in neuroinflammatory disorders, including MS. Pregnancy markedly improves the course of MS, but no study explored the expressions of HERVs and of TRIM28 and SETDB1 during gestation. Using a polymerase chain reaction real-time Taqman amplification assay, we assessed and compared the transcriptional levels of pol genes of HERV-H, HERV-K, HERV-W; of env genes of Syncytin (SYN)1, SYN2, and multiple sclerosis associated retrovirus (MSRV); and of TRIM28 and SETDB1 in peripheral blood and placenta from 20 mothers affected by MS; from 27 healthy mothers, in cord blood from their neonates; and in blood from healthy women of child-bearing age. The HERV mRNA levels were significantly lower in pregnant than in nonpregnant women. Expressions of all HERVs were downregulated in the chorion and in the decidua basalis of MS mothers compared to healthy mothers. The former also showed lower mRNA levels of HERV-K-pol and of SYN1, SYN2, and MSRV in peripheral blood. Significantly lower expressions of TRIM28 and SETDB1 also emerged in pregnant vs. nonpregnant women and in blood, chorion, and decidua of mothers with MS vs. healthy mothers. In contrast, HERV and TRIM28/SETDB1 expressions were comparable between their neonates. These results show that gestation is characterized by impaired expressions of HERVs and TRIM28/SETDB1, particularly in mothers with MS. Given the beneficial effects of pregnancy on MS and the wealth of data suggesting the putative contribution of HERVs and epigenetic processes in the pathogenesis of the disease, our findings may further support innovative therapeutic interventions to block HERV activation and to control aberrant epigenetic pathways in MS-affected patients.

The E3 Ligases in Cervical Cancer and Endometrial Cancer

Endometrial (EC) and cervical (CC) cancers are the most prevalent malignancies of the female reproductive system. There is a global trend towards increasing incidence and mortality, with a decreasing age trend. E3 ligases label substrates with ubiquitin to regulate their activity and stability and are involved in various cellular functions. Studies have confirmed abnormal expression or mutations of E3 ligases in EC and CC, indicating their vital roles in the occurrence and progression of EC and CC. This paper provides an overview of the E3 ligases implicated in EC and CC and discusses their underlying mechanism. In addition, this review provides research advances in the target of ubiquitination processes in EC and CC.

Enhanced Expression of Human Endogenous Retroviruses, TRIM28 and SETDB1 in Autism Spectrum Disorder

Human endogenous retroviruses (HERVs) are relics of ancestral infections and represent 8% of the human genome. They are no longer infectious, but their activation has been associated with several disorders, including neuropsychiatric conditions. Enhanced expression of HERV-K and HERV-H envelope genes has been found in the blood of autism spectrum disorder (ASD) patients, but no information is available on syncytin 1 (SYN1), SYN2, and multiple sclerosis-associated retrovirus (MSRV), which are thought to be implicated in brain development and immune responses. HERV activation is regulated by TRIM28 and SETDB1, which are part of the epigenetic mechanisms that organize the chromatin architecture in response to external stimuli and are involved in neural cell differentiation and brain inflammation. We assessed, through a PCR realtime Taqman amplification assay, the transcription levels of pol genes of HERV-H, -K, and -W families, of env genes of SYN1, SYN2, and MSRV, as well as of TRIM28 and SETDB1 in the blood of 33 ASD children (28 males, median 3.8 years, 25–75% interquartile range 3.0–6.0 y) and healthy controls (HC). Significantly higher expressions of TRIM28 and SETDB1, as well as of all the HERV genes tested, except for HERV-W-pol, were found in ASD, as compared with HC. Positive correlations were observed between the mRNA levels of TRIM28 or SETDB1 and every HERV gene in ASD patients, but not in HC. Overexpression of TRIM28/SETDB1 and several HERVs in children with ASD and the positive correlations between their transcriptional levels suggest that these may be main players in pathogenetic mechanisms leading to ASD.

Molecular Mechanisms of HIV Protease Inhibitors Against HPV-Associated Cervical Cancer: Restoration of TP53 Tumour Suppressor Activities

Cervical cancer is a Human Papilloma virus-related disease, which is on the rise in a number of countries, globally. Two essential oncogenes, E6 and E7, drive cell transformation and cancer development. These two oncoproteins target two of the most important tumour suppressors, p53 and pRB, for degradation through the ubiquitin ligase pathway, thus, blocking apoptosis activation and deregulation of cell cycle. This pathway can be exploited for anticancer therapeutic interventions, and Human Immunodeficiency Virus Protease Inhibitors (HIV-PIs) have attracted a lot of attention for this anticancer drug development. HIV-PIs have proven effective in treating HPV-positive cervical cancers and shown to restore impaired or deregulated p53 in HPV-associated cervical cancers by inhibiting the 26S proteasome. This review will evaluate the role players, such as HPV oncoproteins involved cervical cancer development and how they are targeted in HIV protease inhibitors-induced p53 restoration in cervical cancer. This review also covers the therapeutic potential of HIV protease inhibitors and molecular mechanisms behind the HIV protease inhibitors-induced p53-dependent anticancer activities against cervical cancer.

Plant-derived chemicals as potential inhibitors of SARS-CoV-2 main protease (6LU7), a virtual screening study

SARS-CoV-2 has caused millions of infections and more than 700,000 deaths. Taking the urgent need to find new therapeutics for coronavirus disease 2019 (COVID-19), a dataset of plant-based natural compounds was selected for the screening of antiviral activity. The viral 3-chymotrypsin-like cysteine protease (Mpro, 3CLpro) was selected as the target. Molecular docking was performed on 2,845 phytochemicals to estimate the spatial affinity for the active sites of the enzyme. The ADMET screening was used for the pharmacological and physicochemical properties of the hit compounds. Nelfinavir and Lopinavir were used as control for binding energy comparison. The top 10 hits, based on the binding energy (Kcal/mol), were Ginkgolide M (-11.2), Mezerein (-11), Tubocurarine (-10.9), Gnidicin (-10.4), Glycobismine A (-10.4), Sciadopitysin Z-10.2), Gnididin (-9.2), Glycobismine A (-10.4), Sciadopitysin (-10.2), Gnididin (-9.20, Emetine (-8.7), Vitexin (-8.3), Calophyllolide (-8.3), and 6-(3,3-Dimethylallyl)galangin (-7.9). The binding energy for nelfinavir and lopinavir were - 9.1 and - 8.4, respectively. Interestingly, some of these natural products were previously shown to possess antiviral properties against various viruses, such as HIV, Zika, and Ebola viruses. Herein, we suggest several phytochemicals as the inhibitors of the main protease of SARS-CoV-2 that could be used in the fight against COVID-19.

Enhanced expression of human endogenous retroviruses in new-onset type 1 diabetes: Potential pathogenetic and therapeutic implications

Human endogenous retroviruses (HERVs) have been studied and proposed as relevant cofactors in several autoimmune diseases, including type 1 diabetes (T1D), though with controversial results and no study at disease onset. In order to gather further information on the potential role of HERVs in the development of T1D we assessed the transcription levels of pol genes of HERV-H, HERV-K, and HERV-W in peripheral leucocytes from 37 children and adolescents with new-onset T1D and 50 age-matched control subjects. A PCR real time Taqman amplification assay was used to evaluate HERV transcripts with normalisation of the results to glyceraldehyde-3-phosphate dehydrogenase. The expression levels of HERV-H-pol gene and HERV-W-pol gene were significantly higher in diabetic patients than in control subjects. Conversely, no significant difference emerged in the expression levels of HERV-K-pol gene between diabetic patients and controls. The activation of HERV-H and HERV-W in new-onset T1D suggests their importance in the pathogenesis of the disease and supports targeted therapeutic attempts to hinder their activation.

SARS-CoV-2: An Update on Potential Antivirals in Light of SARS-CoV Antiviral Drug Discoveries

Coronaviruses (CoVs) are a group of RNA viruses that are associated with different diseases in animals, birds, and humans. Human CoVs (HCoVs) have long been known to be the causative agents of mild respiratory illnesses. However, two HCoVs associated with severe respiratory diseases are Severe Acute Respiratory Syndrome-CoV (SARS-CoV) and Middle East Respiratory Syndrome-CoV (MERS-CoV). Both viruses resulted in hundreds of deaths after spreading to several countries. Most recently, SARS-CoV-2 has emerged as the third HCoV causing severe respiratory distress syndrome and viral pneumonia (known as COVID-19) in patients from Wuhan, China, in December 2019. Soon after its discovery, SARS-CoV-2 spread to all countries, resulting in millions of cases and thousands of deaths. Since the emergence of SARS-CoV, many research groups have dedicated their resources to discovering effective antivirals that can treat such life-threatening infections. The rapid spread and high fatality rate of SARS-CoV-2 necessitate the quick discovery of effective antivirals to control this outbreak. Since SARS-CoV-2 shares 79% sequence identity with SARS-CoV, several anti-SARS-CoV drugs have shown promise in limiting SARS-CoV-2 replication in vitro and in vivo. In this review, we discuss antivirals described for SARS-CoV and provide an update on therapeutic strategies and antivirals against SARS-CoV-2. The control of the current outbreak will strongly depend on the discovery of effective and safe anti-SARS-CoV-2 drugs.

Repurposing old drugs as new inhibitors of the ubiquitin-proteasome pathway for cancer treatment

The ubiquitin-proteasome system (UPS) plays a central role in the degradation of cellular proteins. Targeting protein degradation has been validated as an effective strategy for cancer therapy since 2003. Several components of the UPS have been validated as potential anticancer targets, including 20S proteasomes, 19S proteasome-associated deubiquitinases (DUBs) and ubiquitin ligases (E3s). 20S proteasome inhibitors (such as bortezomib/BTZ and carfilzomib/CFZ) have been approved by the U.S. Food and Drug Administration (FDA) for the treatment of multiple myeloma (MM) and some other liquid tumors. Although survival of MM patients has been improved by the introduction of BTZ-based therapies, these clinical 20S proteasome inhibitors have several limitations, including emergence of resistance in MM patients, neuro-toxicities, and little efficacy in solid tumors. One of strategies to improve the current status of cancer treatment is to repurpose old drugs with UPS-inhibitory properties as new anticancer agents. Old drug reposition represents an attractive drug discovery approach compared to the traditional de novo drug discovery process which is time-consuming and costly. In this review, we summarize status of repurposed inhibitors of various UPS components, including 20S proteasomes, 19S-associated DUBs, and ubiquitin ligase E3s. The original and new mechanisms of action, molecular targets, and potential anticancer activities of these repurposed UPS inhibitors are reviewed, and their new uses including combinational therapies for cancer treatment are discussed.

Altered Toll-Like Receptor-4 Response to Lipopolysaccharides in Infants Exposed to HIV-1 and Its Preventive Therapy

Pathogen sensing and recognition through pattern recognition receptors, and subsequent production of pro-inflammatory cytokines, is the cornerstone of the innate immune system. Despite the fact that HIV-exposed uninfected (HEU) infants are prone to serious bacterial infections, no study has focused on the functionality of their bacteria recognition system. This is the first study to investigate baseline levels of three critically important immune response molecules in this population: complement component (C)-3, toll-like receptor (TLR)-4, and C-reactive protein (CRP). We enrolled 16 HEU and 6 HIV-unexposed (HU) infants. TLR4 function was investigated by stimulating whole blood with increasing concentrations of TLR4-agonist ultrapure lipopolysaccharides. TLR4/TLR4-agonist dose response were assessed by measuring IL-6 secretion. Complement C3 and CRP were measured by photo spectrometry. Data showed no significant differences in baseline concentration of CRP between HEU and HU infants. Complement C3 was significantly higher in HEU infants than HU infants. TLR4 anergy was observed in 7 of 12 HEU infants, whereas the rest of HEU infants (n = 4) and the control HU infants tested (n = 3) showed responsive TLR4. None of the HEU infants investigated in this study had severe infections in the year after their birth. In conclusion, TLR4 anergy can occur in HEU infants without necessarily translating to increased vulnerability to infectious diseases.

High-mobility group box 1 protein is involved in the protective effect of Saquinavir on ventilation-induced lung injury in mice

Saquinavir (SQV) is the first FDA approved HIV protease inhibitor. Previous studies showed that SQV can limit Toll-like receptor-4 (TLR4)-mediated inflammatory pathway and nuclear factor-κB (NF-κB) activation, thereby playing a protective role in many kinds of diseases. High-mobility group box 1 (HMGB1) has been identified as an inflammatory mediator and it might express its toxicity in a short period of time in ventilator-induced lung injury (VILI). In this study, C57BL/6 mice were randomly divided into four groups (n = 10): control group and control with SQV group (Con + SQV) were spontaneous breath. HTV group (HTV) received high tidal volume ventilation (HTV) for 4 h. HTV with SQV group (HTV + SQV) were pretreated with 5 mg/kg of SQV for 7 days before HTV. Mice were sacrificed after 4 h of HTV. Lung wet/dry weight (W/D) ratio, alveolar-capillary permeability to Evans blue albumin (EBA), cell counts, total proteins in bronchoalveolar lavage fluid (BALF), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) level in BALF and lung tissue, and lung histopathology were examined. Our results showed that HTV caused significant lung injury and NF-κB activation, which was correlated with the increase of TNF-α and IL-6 levels in BALF and plasma. SQV pretreatment significantly attenuated pulmonary inflammatory injury, as well as NF-κB activation. These findings indicate that the protective effect of SQV may be associated with the inhibition of NF-κB activation and HMGB1 expression in mice.

HIV Protease Inhibitors Alter Amyloid Precursor Protein Processing via β-Site Amyloid Precursor Protein Cleaving Enzyme-1 Translational Up-Regulation

Mounting evidence implicates antiretroviral (ARV) drugs as potential contributors to the persistence and evolution of clinical and pathological presentation of HIV-associated neurocognitive disorders in the post-ARV era. Based on their ability to induce endoplasmic reticulum (ER) stress in various cell types, we hypothesized that ARV-mediated ER stress in the central nervous system resulted in chronic dysregulation of the unfolded protein response and altered amyloid precursor protein (APP) processing. We used in vitro and in vivo models to show that HIV protease inhibitor (PI) class ARVs induced neuronal damage and ER stress, leading to PKR-like ER kinase-dependent phosphorylation of the eukaryotic translation initiation factor 2α and enhanced translation of β-site APP cleaving enzyme-1 (BACE1). In addition, PIs induced β-amyloid production, indicative of increased BACE1-mediated APP processing, in rodent neuroglial cultures and human APP-expressing Chinese hamster ovary cells. Inhibition of BACE1 activity protected against neuronal damage. Finally, ARVs administered to mice and SIV-infected macaques resulted in neuronal damage and BACE1 up-regulation in the central nervous system. These findings implicate a subset of PIs as potential mediators of neurodegeneration in HIV-associated neurocognitive disorders.

The HIV-protease inhibitor saquinavir reduces proliferation, invasion and clonogenicity in cervical cancer cell lines

Innovative therapies in cervical cancer (CC) remain a priority. Recent data indicate that human immunodeficiency virus (HIV)-protease inhibitors used in highly active antiretroviral therapy can exert direct antitumor activities also in HIV-free preclinical and clinical models. The aim of the present study was to evaluate the antineoplastic effects of various HIV-protease inhibitors (indinavir, ritonavir and saquinavir) on primary and established CC cell lines. Two CC cell lines established in our laboratory and four commercially available CC cell lines were treated with indinavir, ritonavir and saquinavir at different concentrations and for different times. Proliferation, clonogenicity and radiosensitivity were evaluated by crystal violet staining. Proteasomal activities were assessed using a cell-based assay and immunoblotting. Cell cycle was analyzed by propidium iodide staining and flow cytometric analysis. Invasion was tested with Matrigel chambers. A t-test for paired samples was used for statistical analysis. In all cell lines, saquinavir was more effective than ritonavir in reducing cell proliferation and inhibiting proteasomal activities (P≤0.05). Conversely, indinavir exerted a negligible effect. The saquinavir concentrations required to modulate the proteasome activities were higher than those observed to be effective in inhibiting cell proliferation. In HeLa cells, saquinavir was strongly effective in inhibiting cell invasion and clonogenicity (P≤0.05) at concentrations much lower than those required to perturb proteasomal activities. Saquinavir did not contribute to increase the sensitivity of HeLa cells to X-rays. In conclusion, the present results demonstrate that saquinavir is able to significantly reduce cell proliferation, cell invasion and clonogenicity in a proteasome-independent manner in in vitro models of CC, and suggest that saquinavir could be a promising CC therapeutic agent.

Role of endoplasmic reticulum stress in drug-induced toxicity

Drug‐induced toxicity is a key issue for public health because some side effects can be severe and life‐threatening. These adverse effects can also be a major concern for the pharmaceutical companies since significant toxicity can lead to the interruption of clinical trials, or the withdrawal of the incriminated drugs from the market. Recent studies suggested that endoplasmic reticulum (ER) stress could be an important event involved in drug liability, in addition to other key mechanisms such as mitochondrial dysfunction and oxidative stress. Indeed, drug‐induced ER stress could lead to several deleterious effects within cells and tissues including accumulation of lipids, cell death, cytolysis, and inflammation. After recalling important information regarding drug‐induced adverse reactions and ER stress in diverse pathophysiological situations, this review summarizes the main data pertaining to drug‐induced ER stress and its potential involvement in different adverse effects. Drugs presented in this review are for instance acetaminophen (APAP), arsenic trioxide and other anticancer drugs, diclofenac, and different antiretroviral compounds. We also included data on tunicamycin (an antibiotic not used in human medicine because of its toxicity) and thapsigargin (a toxic compound of the Mediterranean plant Thapsia garganica) since both molecules are commonly used as prototypical toxins to induce ER stress in cellular and animal models.

An overview of early investigational drugs for the treatment of human papilloma virus infection and associated dysplasia

INTRODUCTION

High-risk HPV (HR-HPV) related invasive cervical cancer (ICC) causes >270,000 deaths per annum world-wide with over 85% of these occurring in low-resource countries. Ablative and excisional treatment modalities are restricted for use with high-grade pre-cancerous cervical disease with HPV infection and low-grade dysplasia mostly managed by a watch-and-wait policy.

AREAS COVERED

Various pharmacological approaches have been investigated as non-destructive alternatives for the treatment of HR-HPV infection and associated dysplasia. These are discussed dealing with efficacy, ease-of-use (physician or self-applied), systemic or locally applied, side-effects, cost and risks. The main focus is the perceived impact on current clinical practice of a self-applied, effective and safe pharmacological anti-HPV treatment.

EXPERT OPINION

Current prophylactic HPV vaccines are expensive, HPV type restricted and have little effect in already infected women. Therapeutic vaccines are under development but are also HPV type-restricted. At present, the developed nations use national cytology screening and surgical procedures to treat only women identified with HPV-related high-grade dysplastic disease. However, since HPV testing is rapidly replacing cytology as the test-of-choice, a suitable topically-applied and low-cost antiviral treatment could be an ideal solution for treatment of HPV infection per se with test-of-cure carried out by repeat HPV testing. Cytology would only then be necessary for women who remained HPV positive. Although of significant benefit in the developed countries, combining such a treatment with self-sampled HPV testing could revolutionise the management of this disease in the developing world which lack both the infrastructure and resources to establish national cytology screening programs.

Effects of NO-Hybridization on the Immunomodulatory Properties of the HIV Protease Inhibitors Lopinavir and Ritonavir

HIV protease inhibitors (PIs) are antiretroviral agents, which have been found to also affect several cellular processes, such as inflammation and cell progression. In studies on non-steroidal, anti-inflammatory drugs, the addition of a nitric oxide (NO) moiety has been shown to both reduce their toxicity and enhance their pharmacological efficacy. Along this line of research, several derivatives of PIs have been synthesized by covalent attachment of NO moiety to the parental molecules. Previous work has indicated that NO-hybridization of the prototypical PI, Saquinavir leads to a derivative named Saquinavir-NO that while retaining the antiretroviral effect, acquires antitumoural and immunomodulatory properties along with reduced toxicity in vitro and in vivo. These data prompted us to evaluate the effects of NO-hybridization on two other PIs, Lopinavir and Ritonavir. The two NO-derivatives were compared head to head with their parental compounds on human primary peripheral blood mononuclear cells as well as on human primary macrophages. Lopinavir-NO and Lopinavir were also screened in an in vivo model of autoimmune hepatitis. Our results prove that Lopinavir-NO exerts markedly superior effects as compared to the parental compound both in vitro and in vivo. On the contrary, Ritonavir-NO effects overlapped those of Ritonavir. These data demonstrate that NO-hybridization of Lopinavir generates a derivative with significantly stronger immunomodulatory effects that are apparently related to an action of the compound on T-cell secretory capacity. Lopinavir-NO deserves additional studies for its possible use in T-cell-mediated autoimmune diseases including, but not limited to autoimmune hepatitis.

Proteasome inhibitors in progressive renal diseases

Proteasome (PS) is a sophisticated protein degradation machinery comprising a 20S proteolytic core particle provided with caspase-like, trypsin-like and chymotrypsin-like activities on ubiquitinilated proteins. The products of this selective, complex, controlled and strictly coordinated system play a crucial role in cell cycle progression and apoptosis; activation of transcription factors, cytokines and chemokines; degradation and generation of MHC class I-presented peptides. PS has recently emerged as a promising drug target in cancer therapy, and bortezomib has been approved for refractory multiple myeloma. PS proteolysis is crucial for the degradation of the inhibitory protein IkB of nuclear factor kB (NF-kB), and hence, an interesting field of research has been developed on possible benefits of drugs with anti-PS activity in disease conditions with hyper-expression of NF-kB. PS inhibitors are being adopted in pilot studies in antibody-mediated renal rejection and in AL amyloidosis, with increasing scientific interest in possible applications in lupus, IgA nephropathy, idiopathic nephrotic syndrome and renal fibrosis. The most often used PS inhibitor, bortezomib, has a severe peripheral neurotoxicity, and the search for effective and less toxic PS-targeted drugs is a challenging area also in nephrology.

Mechanisms of HIV protein degradation into epitopes: implications for vaccine design

The degradation of HIV-derived proteins into epitopes displayed by MHC-I or MHC-II are the first events leading to the priming of HIV-specific immune responses and to the recognition of infected cells. Despite a wealth of information about peptidases involved in protein degradation, our knowledge of epitope presentation during HIV infection remains limited. Here we review current data on HIV protein degradation linking epitope production and immunodominance, viral evolution and impaired epitope presentation. We propose that an in-depth understanding of HIV antigen processing and presentation in relevant primary cells could be exploited to identify signatures leading to efficient or inefficient epitope presentation in HIV proteomes, and to improve the design of immunogens eliciting immune responses efficiently recognizing all infected cells.

Multi-step inhibition explains HIV-1 protease inhibitor pharmacodynamics and resistance

HIV-1 protease inhibitors (PIs) are among the most effective antiretroviral drugs. They are characterized by highly cooperative dose-response curves that are not explained by current pharmacodynamic theory. An unresolved problem affecting the clinical use of PIs is that patients who fail PI-containing regimens often have virus that lacks protease mutations, in apparent violation of fundamental evolutionary theory. Here, we show that these unresolved issues can be explained through analysis of the effects of PIs on distinct steps in the viral life cycle. We found that PIs do not affect virion release from infected cells but block entry, reverse transcription, and post-reverse transcription steps. The overall dose-response curves could be reconstructed by combining the curves for each step using the Bliss independence principle, showing that independent inhibition of multiple distinct steps in the life cycle generates the highly cooperative dose-response curves that make these drugs uniquely effective. Approximately half of the inhibitory potential of PIs is manifest at the entry step, likely reflecting interactions between the uncleaved Gag and the cytoplasmic tail (CT) of the Env protein. Sequence changes in the CT alone, which are ignored in current clinical tests for PI resistance, conferred PI resistance, providing an explanation for PI failure without resistance.

HIV-1 infection and first line ART induced differential responses in mitochondria from blood lymphocytes and monocytes: the ANRS EP45 "Aging" study

BACKGROUND

The ANRS EP45 "Aging" study investigates the cellular mechanisms involved in the accelerated aging of HIV-1 infected and treated patients. The data reported focus on mitochondria, organelles known to be involved in cell senescence.

METHODS

49 HIV-1 infected patients untreated with antiretroviral therapy, together with 49 seronegative age- and sex-matched control subjects and 81 HIV-1 infected and treated patients, were recruited by 3 AIDS centres (Marseille, Montpellier, Nice; France; http://clinicaltrials.gov/, NCT01038999). In more than 88% of treated patients, the viral load was <40 copies/ml and the CD4+ cell count was >500/mm(3). ROS (reactive oxygen species) production and ΔΨm (inner membrane potential) were measured by flow cytometry in blood lymphocytes and monocytes (functional parameters). Three mitochondrial network quantitative morphological parameters were computed using confocal microscopy and image analysis. Three PBMC mitochondrial proteins (porin and subunits 2 and 4 of cytochrome C oxidase encoded by mtDNA or nuclear DNA, respectively) were analysed by western blotting.

RESULTS

Quantitative changes in PBMC mitochondrial proteins were not induced by either HIV-1 infection or ART. Discriminant analysis integrating functional (ROS production and ΔΨm) or morphological (network volume density, fragmentation and branching) parameters revealed HIV-1 infection and ART differential effects according to cell type. First line ART tended to rescue lymphocyte mitochondrial parameters altered by viral infection, but induced slight changes in monocytes. No statistical difference was found between the effects of three ART regimens on mitochondrial parameters. Correlations between functional parameters and viral load confirmed the damaging effects of HIV-1 in lymphocyte mitochondria.

CONCLUSIONS

In patients considered to be clinically stable, mitochondria exhibited functional and morphological modifications in PBMCs resulting from either direct or indirect effects of HIV-1 infection (lymphocytes), or from first line ART (monocytes). Together with other tissue impairments, these changes may contribute to global aging.

Saquinavir in steroid-dependent and -resistant nephrotic syndrome: a pilot study

BACKGROUND

Some difficult cases of idiopathic nephrotic syndrome (NS) have been treated with a HIV protease inhibitor provided with proteasome-inhibiting activity. The objective of this study was to limit nuclear factor κB (NF-κB) activation which is up-regulated in these patients, aiming at decreasing proteinuria and prednisone need.

METHODS

Ten cases with long-lasting (up to 15 years) history of NS with steroid dependence (six cases, of which three with secondary steroid resistance) or resistance to steroids (four cases) unsuccessfully treated with multiple immunosuppressive drugs, accepted a treatment with the protease inhibitor saquinavir. p50/p65 NF-κB nuclear localization and immunoproteasome/proteasome messenger RNA (mRNA) were monitored in peripheral blood mononuclear cells (PBMCs). The effects of saquinavir on NF-κB nuclear localization in cultured PBMCs and in immortalized human podocytes were assessed.

RESULTS

After a median follow-up of 14.7 months (6-68.7), 1/4 primary steroid-resistant NS (SRNS) and 5/6 steroid-dependent NS or secondary SRNS became infrequent (5) or frequent (1) relapsers, with 63% prednisone reduction (from 25.3 to 8.4 mg/kg/month, P = 0.015). Saquinavir was effective in association with low doses of calcineurin inhibitors (cyclosporine 2 mg/kg/day or tacrolimus 0.01-0.06 mg/kg/day). No side effects were observed apart from transitory mild diarrhoea. In PBMCs, NF-κB was down-regulated, while MECL-1 immunoproteasome/beta2 proteasome mRNA ratio was reversed to normal values. In culture, saquinavir blunted NF-κB activation in human podocytes and in PBMCs.

CONCLUSIONS

In this pilot study, a HIV antiprotease drug reduced proteinuria and had a steroid-sparing effect in some multidrug-resistant/-dependent NS. This observation warrants further investigation.

Proteasome inhibitors

In May 2003, the US Food and Drug Administration (FDA) granted accelerated approval for the use of the first-in-class proteasome inhibitor bortezomib as a third-line therapy in multiple myeloma, and the European Union followed suit a year later. Bortezomib has subsequently been approved for multiple myeloma as a second-line treatment on its own and as a first-line therapy in combination with an alkylating agent and a corticosteroid. Furthermore, bortezomib has also been approved as a second-line therapy for mantle cell lymphoma. In this chapter, the focus is on the current clinical research on bortezomib, its adverse effects, and the resistance of multiple myeloma patients to bortezomib-based therapy. The various applications of bortezomib in different diseases and recent advances in the development of a new generation of inhibitors that target the proteasome or other parts of the ubiquitin-proteasome system are also reviewed.

Lopinavir up-regulates expression of the antiviral protein ribonuclease L in human papillomavirus-positive cervical carcinoma cells

BACKGROUND

We have previously shown that the HIV protease inhibitor lopinavir has selective toxicity against human papillomavirus (HPV)-positive cervical carcinoma cells via an unknown mechanism.

METHODS

SiHa cervical carcinoma cells were stably transfected with the proteasome sensor vector pZsProSensor-1 to confirm lopinavir inhibits the proteasome in these cells. The Panorama Xpress profiler 725 antibody array was then used to analyse specific changes in protein expression in lopinavir-treated versus control untreated SiHa cells followed by PCR and western blotting. Colorimetric growth assays of lopinavir-treated E6/E7 immortalised versus control human keratinocytes were performed. Targeted small interfering RNA gene silencing followed by growth assay comparison of lopinavir-treated/untreated SiHa cells was also used.

RESULTS

Lopinavir induced an increase in the fluorescence of pZsProSensor-1 transfected SiHa cells, indicative of proteasomal inhibition. Ribonuclease L (RNASEL) protein was shown to be up-regulated in lopinavir-treated SiHa cells, which was confirmed by PCR and western blot. Targeted silencing of RNASEL reduced the sensitivity of SiHa cells to lopinavir. Selective toxicity against E6/E7 immortalised keratinocytes versus control cells was also seen with lopinavir and was associated with up-regulated RNASEL expression.

CONCLUSIONS

These data are consistent with the toxicity of lopinavir against HPV-positive cervical carcinoma cells being related to its ability to block viral proteasome activation and induce an up-regulation of the antiviral protein RNASEL. This is supported by the drug's selective toxicity and up-regulation of RNASEL in E6/E7 immortalised keratinocytes combined with the increased resistance to lopinavir observed in SiHa cells following silencing of RNASEL gene expression.

Lopinavir shows greater specificity than zinc finger ejecting compounds as a potential treatment for human papillomavirus-related lesions

Non-surgical, antiviral treatment options are desirable for HPV-related lesions within the genitourinary and upper digestive tract. We compared the toxicity of three zinc finger-ejecting (ZFE) compounds (4,4-dithiodimorpholine, azodicarbonamide, and diamide) to the HIV protease inhibitor lopinavir using HPV-positive SiHa, CaSki, HeLa, ME180, and HPV-negative C33A cervical carcinoma cell lines as well as primary human foreskin keratinocytes (PHFKs). Colorimetric growth assays revealed selective toxicity when treated with lopinavir. All carcinoma cell lines, except CaSki, were sensitive to 20 μM lopinavir whereas primary PHFKs were highly resistant. In contrast, 4,4-dithiodimorpholine was uniformly toxic to all cells tested while azodicarbonamide and diamide showed no effect at all. It is concluded that lopinavir may be an attractive candidate to treat pre-cancerous and cancerous HPV-positive lesions.

HIV proteinase inhibitors target the Ddi1-like protein of Leishmania parasites

HIV proteinase inhibitors reduce the levels of Leishmania parasites in vivo and in vitro, but their biochemical target is unknown. We have identified an ortholog of the yeast Ddi1 protein as the only member of the aspartic proteinase family in Leishmania parasites, and in this study we investigate this protein as a potential target for the drugs. To date, no enzyme assay has been developed for the Ddi1 proteins, but Saccharomyces cerevisiae lacking the DDI1 gene secrete high levels of protein into the medium. We developed an assay in which these knockout yeast were functionally complemented to low secretion by introduction of genes encoding Ddi1 orthologs from Leishmania major or humans. Plasmid alone controls gave no complementation. Treatment of the Ddi1 transformants with HIV proteinase inhibitors showed differential effects dependent on the origin of the Ddi1. Dose responses allowed calculation of IC₅₀ values; e.g., for nelfinavir, of 3.4 μM (human Ddi1) and 0.44 μM (Leishmania Ddi1). IC₅₀ values with Leishmania constructs mirror the potency of inhibitors against parasites. Our results show that Ddi1 proteins are targets of HIV proteinase inhibitors and indicates the Leishmania Ddi1 as the likely target for these drugs and a potential target for antiparasitic therapy.—White, R. E., Powell, D. J., Berry, C. HIV proteinase inhibitors target the Ddi1-Like protein of Leishmania parasites.

HIV protease inhibitors alter innate immune response signaling to double-stranded RNA in oral epithelial cells: implications for immune reconstitution inflammatory syndrome?

In this investigation, several HIV protease inhibitors altered the virally associated, double-stranded RNA (dsRNA)-stimulated, innate immune response. Lopinavir, the most potent inducer of interleukin (IL)-8 expression, also inhibited dsRNA-induced monocyte chemotactic protein 1 expression. Further analyses demonstrated that nuclear factor-κB is required for lopinavir's induction of IL-8. These findings demonstrate that protease inhibitors, such as lopinavir, differentially dysregulate innate immune signaling in a manner that could affect immune (reconstitution) inflammatory responses in oral epithelium.

Drug-induced hepatotoxicity or drug-induced liver injury

Drug-induced hepatotoxicity is underreported and underestimated in the United States. It is an important cause of acute liver failure. Common classes of drugs causing drug-induced hepatotoxicity include antibiotics, lipid lowering agents, oral hypoglycemics, psychotropics, antiretrovirals, acetaminophen, and complementary and alternative medications. Hepatotoxic drugs often have a signature or pattern of liver injury including patterns of liver test abnormalities, latency of symptom onset, presence or absence of immune hypersensitivity, and the course of the reaction after drug withdrawal.

Successful simplification of protease inhibitor-based HAART with triple nucleoside regimens in children vertically infected with HIV

OBJECTIVE

To assess the virological, immunological and metabolic effects of switching from an efficacious first-line protease inhibitor (PI)-based HAART to a simplified triple nucleoside reverse transcriptase inhibitor (NRTI) regimen in children vertically infected with HIV.

DESIGN

Prospective, open-label, before-after study of 20 vertically infected children with at least 12 consecutive months of undetectable viral load under a PI-based HAART and no previous history of NRTI treatment.

METHODS

At study entry, HAART was shifted to a triple-NRTI combination.

RESULTS

The children were aged 2 to 18 years (median, 7.9) and were followed for 96 weeks. All were receiving a PI-based regimen for an average duration of 4 years before enrollment. At study entry, 12 patients (60%) switched to abacavir, 5 (25%) to lamivudine; 2 (10%) to zidovudine and 2 to didanosine (10%). All but one patient maintained plasma HIV RNA < 50 copies/ml during the entire follow-up. No immunological failure was observed at week 96. A trend of normalization (P < 0.001) of T cell receptor Vbeta families of the CD8 cell subset was detected in 19/20 (95%), with an increased HIV-specific CD8 T cell response (P < 0.01) in 17/20 (85%). Dyslipidaemia significantly improved during the follow up (P < 0.001). No new cases of lipodystrophy were detected.

CONCLUSIONS

Switching to triple-NRTI regimens in selected HIV-infected children with an extremely low likelihood of harbouring nucleoside-associated mutations maintains viral suppression and immunological function, improving metabolic abnormalities and the effort to take medication for up to 96 weeks.

Immunomodulatory effects of two HIV protease inhibitors, Saquinavir and Ritonavir, on lymphocytes from healthy seronegative individuals

Immunological and clinical benefits of highly active antiretroviral therapy (HAART) do not always correlate with its efficacy in controlling HIV replication. This could be due to biological effects on the cell of retroviral agents.

DESIGN

To this view we evaluated possible direct immunomodulatory effects of two HIV protease inhibitors, such as Saquinavir (SQ) and Ritonavir (RIT).

METHODS

In particular we assessed the PHA- and anti-CD3-driven T cell proliferation, mixed lymphocyte reaction (MLR) and cytokine production on PBMCs from HIV-uninfected subjects incubated with increasing concentrations (2, 5, 10 and 20 microM) of SQ or RIT.

RESULTS

Treatment of PBMCs with RIT resulted in a dose-dependent reduction of lymphoproliferative responses. Such an effect was also marked with SQ. MLR was significantly reduced in a concentration-dependent fashion after incubation with either drug. The percentages of stimulated PBMCs and mostly of CD4+ cells expressing TNF-alpha, IL-2 and IFN-gamma were also reduced by SQ or RIT.

CONCLUSION

At therapeutic doses both SQ and RIT exhibit potent immunomodulatory activity, which may contribute to correct the HIV-driven cytokine dysregulation and account for some clinical and immunological benefits of therapy in patients with virologic failure. In view of autoreactive immunopathology occurring in AIDS, these direct biologic effects raise intriguing speculations on anti-HIV strategy.

Nucleoside reverse transcriptase inhibitors prevent HIV protease inhibitor-induced atherosclerosis by ubiquitination and degradation of protein kinase C

HIV protease inhibitors are important pharmacological agents used in the treatment of HIV-infected patients. One of the major disadvantages of HIV protease inhibitors is that they increase several cardiovascular risk factors, including the expression of CD36 in macrophages. The expression of CD36 in macrophages promotes the accumulation of cholesterol, the development of foam cells, and ultimately atherosclerosis. Recent studies have suggested that α-tocopherol can prevent HIV protease inhibitor-induced increases in macrophage CD36 levels. Because of the potential clinical utility of using α-tocopherol to limit some of the side effects of HIV protease inhibitors, we tested the ability of α-tocopherol to prevent ritonavir, a common HIV protease inhibitor, from inducing atherosclerosis in the LDL receptor (LDLR) null mouse model. Surprisingly, α-tocopherol did not prevent ritonavir-induced atherosclerosis. However, cotreatment with the nucleoside reverse transcriptase inhibitors (NRTIs), didanosine or D4T, did prevent ritonavir-induced atherosclerosis. Using macrophages isolated from LDLR null mice, we demonstrated that the NRTIs prevented the upregulation of CD36 and cholesterol accumulation in macrophages. Treatment of LDLR null mice with NRTIs promoted the ubiquitination and downregulation of protein kinase Cα (PKC). Previous studies demonstrated that HIV protease inhibitor activation of PKC was necessary for the upregulation of CD36. Importantly, the in vivo inhibition of PKC with chelerythrine prevented ritonavir-induced upregulation of CD36, accumulation of cholesterol, and the formation of atherosclerotic lesions. These novel mechanistic studies suggest that NRTIs may provide protection from one of the negative side effects associated with HIV protease inhibitors, namely the increase in CD36 levels and subsequent cholesterol accumulation and atherogenesis.

Effect of nelfinavir on insulin metabolism, proteasome activity and protein degradation in HepG2 cells

HIV-1 protease inhibitors have revolutionized the treatment of HIV infection, but their use has been associated with lipodystrophy and insulin resistance. One suggestion for this has been the inhibition of insulin-degrading enzyme (IDE). We have previously demonstrated that insulin, through IDE, can inhibit the proteasome, thus decreasing cytosolic protein degradation. We examined whether the protease inhibitor nelfinavir inhibited IDE and its effect on protein degradation both in vitro and in whole cells. 125I-Insulin degradation was measured by trichloroacetic acid precipitation. Proteasome activities were measured using fluorogenic peptide substrates. Cellular protein degradation was measured by prelabelling cells with 3H-leucine and determining the release of TCA-soluble radioactivity. Nelfinavir inhibited IDE in a concentration-dependent manner with 50% inhibition at the maximal concentration tested, 100 microm. Similarly, the chymotrypsin-like and trypsin-like activities of the proteasome were decreased with an IC50 of approximately 3 microm. The ability of insulin to inhibit the proteasome was abrogated by nelfinavir. Treatment of HepG2 cells with 50 microm nelfinavir decreased 125I-insulin degradation and increased cell-associated radioactivity. Insulin alone maximally decreased protein degradation by 15%. Addition of 50 microm nelfinavir inhibited cellular protein degradation by 14% and blunted the effect of insulin. These data show that nelfinavir inhibits IDE, decreases insulin's ability to inhibit protein degradation via the proteasome and provides another possible mechanism for the insulin resistance seen in protease inhibitor-treated HIV patients.

Inhibition of human preadipocyte proteasomal activity by HIV protease inhibitors or specific inhibitor lactacystin leads to a defect in adipogenesis, which involves matrix metalloproteinase-9

In a previous publication, we reported that human immunodeficiency virus (HIV) protease inhibitors (PIs) inhibited the differentiation of human preadipocytes in primary culture, reducing the expression and secretion of matrix metalloproteinase 9 (MMP-9). The present work was performed to clarify this mechanism. Interestingly, HIV-PIs have been reported to be inhibitors of the proteasome complex, which is known to regulate nuclear factor (NF)-kappaB activation and transcription of its target genes, among them MMP-9. We thus investigated the potential involvement of the proteasome in the antiadipogenic effects of HIV-PIs. The effect of four HIV-PIs was tested on preadipocyte proteasomal activity, and chronic treatment with the specific proteasome inhibitor lactacystin was performed to evaluate alterations of adipogenesis and MMP-9 expression/secretion. Finally, modifications of the NF-kappaB pathway induced by either HIV-PIs or lactacystin were studied. We demonstrated that preadipocyte proteasomal activity was decreased by several HIV-PIs and that chronic treatment with lactacystin mimicked the effects of HIV-PIs by reducing adipogenesis and MMP-9 expression/secretion. Furthermore, we observed an intracellular accumulation of the NF-kappaB inhibitor, IkappaBbeta, with chronic treatment with HIV-PIs or lactacystin as well as a decrease in MMP-9 expression induced by acute tumor necrosis factor-alpha stimulation. These results indicate that inhibition of the proteasome by specific (lactacystin) or nonspecific (HIV-PIs) inhibitors leads to a reduction of human adipogenesis, and they therefore implicate deregulation of the NF-kappaB pathway and the related decrease of the key adipogenic factor, MMP-9. This study adds significantly to recent reports that have linked HIV-PI-related lipodystrophic syndrome with altered proteasome function, endoplasmic reticulum stress, and metabolic disorders.

Optimization of Subsite Binding to the β5 Subunit of the Human 20S Proteasome Using Vinyl Sulfones and 2-Keto-1,3,4-oxadiazoles: Syntheses and Cellular Properties of Potent, Selective Proteasome Inhibitors

Beginning with the peptide sequence Cbz-Ile-Glu(OtBu)-Ala-Leu found in PSI (3), a series of vinyl sulfones (VS) were synthesized for evaluation as inhibitors of the chymotrypsin-like activity of the 20S proteasome. Variations at the key P3 position confirmed the importance of a long side chain capped with a hydrophobic group for optimal potency, consistent with a model of binding to the S3 subsite. The tert-butyl glutamic ester initially used at P3 gave plasma unstable, insoluble compounds and was replaced with the better isostere, N-beta-neopentyl asparagine. The inhibitors were shortened by replacing the N-terminal Cbz-isoleucine with a p-tosyl group without loss of potency. Small l-amino acids were used at P2, where d-substitution was not tolerated. The resulting optimized P4-P3-P2 sequence was grafted onto a novel proteasome inhibitor warhead, 2-keto-1,3,4-oxadiazoles (KOD), to produce reversible, subnanomolar proteasome inhibitors that were 1000-fold selective versus cathepsin B (CatB), cathepsin S (CatS), and trypsin-like as well as PGPH-like proteasome activity. A number of compounds in both the VS and the KOD series exhibited growth inhibitory effects against the human prostate cancer cell line PC3 at submicromolar concentrations.

HIV protease inhibitor therapy reverses neutrophil apoptosis in AIDS patients by direct calpain inhibition

The reduction of neutrophils apoptosis is one of the main non-virological effects of protease inhibitor (PI) therapy. We explore here whether this may be due to the cross-inhibition of calpain, an important non-virological target of PI in vitro. We found that the high basal level of neutrophils apoptosis in AIDS patients is strictly related to an increased intracellular calpain activity. Both alterations disappear after PI treatment, with apoptosis and calpain going back to normal levels after 3 months of PI therapy, independently of a proficient antiviral effect. PI drugs exerted a similar antiapoptotic and anticalpain effects on neutrophils in ex vivo experiments: strikingly, the effects were mimicked by commercially available calpain inhibitors. This study shows, for the first time, that apoptosis of neutrophils in AIDS patients is mediated by calpain, and that neutrophil survival in PI treated AIDS patients is a non virological effect due to calpain inhibition.

Expanding the frontiers of existing antiviral drugs: possible effects of HIV-1 protease inhibitors against SARS and avian influenza

When unexpected diseases such as the severe acute respiratory syndrome (SARS) and avian influenza become a serious threat to public health, an immediate response is imperative. This should take into consideration existing licensed antiviral drugs against other viral diseases already known to be safe for use in humans. In this report, evidence is presented that HIV-1 protease inhibitors (PIs) currently used in anti-HIV-1 therapies might exert some effects on SARS and perhaps, on avian influenza. Evidence for the potential benefits of PIs against the SARS coronavirus (SARS-CoV) is provided by empirical clinical studies, in vivo viral inhibition assays and computational simulations of the docking of these compounds to the active site of the main SARS-CoV protease. As suggested by in silico docking of these molecules to a theoretical model of a subunit of type A influenza virus RNA-dependent RNA polymerase, there also exists a remote possibility that these PIs may have an effect on avian influenza viruses. Although this evidence is still far from being definitive, the results so far obtained suggest that PIs should be seriously taken into consideration for further testing as potential therapeutic agents for SARS and avian influenza.

Antileishmanial activity of HIV protease inhibitors

The proteasomes of some protozoa are possible targets for chemotherapy. Leishmaniasis is a major health problem in human immunodeficiency virus (HIV) co-infected subjects. Two HIV protease inhibitors (PI), indinavir and saquinavir, have been shown to block proteasome functions; we therefore investigated their effects on the growth of two Leishmania spp. (Leishmania major and Leishmania infantum). After 24 h of treatment, both drugs exhibited a dose-dependent antileishmanial activity, with 50% lethal dose (LD50) values of, respectively, 8.3 microM and 7 microM on L. major; minor activity was observed on L. infantum. These results add new in vitro insights into the wide-spectrum efficacy of PI and suggest studying their action on amastigote forms of leishmania within macrophages in order to validate their potential contribution against opportunistic infections in treated seropositive patients.

Specific HIV Protease Inhibitors Inhibit the Ability of Hpv16 E6 to Degrade P53 and Selectively Kill E6-Dependent Cervical Carcinoma Cells In Vitro

Although HIV protease inhibitor (PI) drugs predominantly target HIV proteases 1 and 2, it is also known that part of their efficacy is due to selective inhibition of the proteasome. The pathogenicity of high-risk human papilloma virus (HPV) is dependent on expression of viral E6 proteins which inappropriately activate the 26S proteasome to degrade p53 and other cellular proteins that are detrimental to viral replication. Comparison of the ability of the PIs indinavir, ritonavir, amprenavir, lopinavir, atazanavir, nelfinavir and saquinavir to inhibit E6-mediated proteasomal degradation of mutant p53 in E6-transfected C33A cells showed that 15μM lopinavir, 1 mM indinavir or 125 μM ritonavir treatment for 24 h produced a stable increase in the level of nuclear p53 in these cells with minimal cell death. After 4 h exposure of HPV16+ve SiHa cells to 15 μM lopinavir, a transient increase in wild-type p53 expression was observed associated with a 7% reduction in the chymotryptic activity of the 20S proteasome and apoptosis after 24 h. Comparison of growth rates of PI treated SiHa, CaSki, C33A, C33A-E6 and non-transformed NIH/3T3 cells showed that SiHa were the most sensitive, whereas NIH/3T3 were least affected. In conclusion, these data show that specific HIV PIs such as lopinavir and possibly indinavir, can induce selective toxicity of HPV-transformed cervical carcinoma cells expressing wild-type p53 and may form the basis of a topically applied alternative to surgery for the treatment of HPV-related premalignant lesions of the cervix.

Inhibition of lysosome and proteasome function enhances human immunodeficiency virus type 1 infection

We previously reported that inhibition of endosomal/lysosomal function can dramatically enhance human immunodeficiency virus type 1 (HIV-1) infectivity, suggesting that under these conditions productive HIV-1 infection can occur via the endocytic pathway. Here we further examined this effect with bafilomycin A1 (BFLA-1) and show that this enhancement of infectivity extends to all HIV-1 isolates tested regardless of coreceptor usage. However, isolate-specific differences were observed in the magnitude of the effect. This was particularly evident in the case of the weakly infectious HIV-1(SF2), for which we observed the greatest enhancement. Using reciprocal chimeric viruses, we were able to determine that both the disproportionate increase in the infectivity of HIV-1(SF2) in response to BFLA-1 and its weak infectivity in the absence of BFLA-1 mapped to its envelope gene. Further, we found HIV-1(SF2) to have lower fusion activity and to be 12-fold more sensitive to the fusion inhibitor T-20 than HIV-1(NL4-3). Proteasomal inhibitors also enhance HIV-1 infectivity, and we report that the combination of a lysosomal and a proteasomal inhibitor greatly enhanced infectivity of all isolates tested. Again, HIV-1(SF2) was unique in exhibiting a synergistic 400-fold increase in infectivity. We also determined that inhibition of proteasomal function increased the infectivity of HIV-1 pseudotyped with vesicular stomatitis virus G protein. The evidence presented here highlights the important role of the lysosomes/proteasomes in the destruction of infectious HIV-1(SF2) and could have implications for the development of novel antiviral agents that might take advantage of these innate defenses.

Development of antiviral therapy for severe acute respiratory syndrome

A new disease, the severe acute respiratory distress syndrome (SARS), caused by the SARS coronavirus (SARS-CoV), emerged at the beginning of 2003 and rapidly spread throughout the world. Although the disease had disappeared in June 2003 its re-emergence cannot be excluded. The development of vaccines against SARS-CoV may take years. Therefore, the availability of effective antiviral drugs against SARS-CoV may be crucial for the control of future SARS outbreaks. In this review, experimental and clinical data about potential anti-SARS drugs is summarised and discussed. Animal model studies will be needed to help to determine which interventions warrant controlled clinical testing.

The HIV Protease Inhibitors Nelfinavir and Saquinavir, but Not a Variety of HIV Reverse Transcriptase Inhibitors, Adversely Affect Human Proteasome Function

Background

In HIV-infected patients some clinical and immunological benefits of antiretroviral therapy, which frequently include a combination of HIV protease inhibitors (PIs) and reverse transcriptase inhibitors (RTIs), cannot be solely explained by the drugs’ action on viral enzymes. Proteasomes constitute the central protease of the ubiquitin ATP-dependent pathway involved in many cellular processes, as well as in HIV maturation and aggressiveness. Objective: To explore whether the PIs nelfinavir and saquinavir and the RTIs abacavir, nevirapine, delavirdine, stavudine and didanosine affect proteasome function in vitro and in vivo.

Methods

Peptidase activity of purified human 26S and 20S proteasomes was assayed with and without the drugs at different concentrations. Intracellular proteasome proteolytic activity was evaluated by searching for ubiquitin-tagged proteins in HL60 cells incubated with and without the drugs.

Results

At therapeutic dosages, nelfinavir and saquinavir inhibited proteasome peptidase activity and caused intracellular accumulation of polyubiquitinated proteins, a hallmark of proteasome proteolytic inhibition in vivo; the RTIs failed to evoke either effect.

Conclusion

Proteasomes are targeted by the two PIs but not the RTIs. Therefore, in HIV-infected patients the beneficial effect of a therapy including one of the two PIs should partly rely on inhibition of host proteasome function.

Reducing plasma HIV RNA improves muscle amino acid metabolism

We reported (Yarasheski KE, Zachwieja JJ, Gischler J, Crowley J, Horgan MM, and Powderly WG. Am J Physiol Endocrinol Metab 275: E577-E583, 1998) that AIDS muscle wasting was associated with an inappropriately low rate of muscle protein synthesis and an elevated glutamine rate of appearance (Ra Gln). We hypothesized that high plasma HIV RNA caused dysregulation of muscle amino acid metabolism. We determined whether a reduction in HIV RNA (> or =1 log) increased muscle protein synthesis rate and reduced R(a) Gln and muscle proteasome activity in 10 men and 1 woman (22-57 yr, 60-108 kg, 17-33 kg muscle) with advanced HIV (CD4 = 0-311 cells/microl; HIV RNA = 10-375 x 10(3) copies/ml). We utilized stable isotope tracer methodologies ([13C]Leu and [15N]Gln) to measure the fractional rate of mixed muscle protein synthesis and plasma Ra Gln in these subjects before and 4 mo after initiating their first or a salvage antiretroviral therapy regimen. After treatment, median CD4 increased (98 vs. 139 cells/microl, P = 0.009) and median HIV RNA was reduced (155,828 vs. 100 copies/ml, P = 0.003). Mixed muscle protein synthesis rate increased (0.062 +/- 0.005 vs. 0.078 +/- 0.006%/h, P = 0.01), Ra Gln decreased (387 +/- 33 vs. 323 +/- 15 micromol.kg fat-free mass(-1).h(-1), P = 0.04), and muscle proteasome chymotrypsin-like catalytic activity was reduced 14% (P = 0.03). Muscle mass was only modestly increased (1 kg, P = not significant). We estimated that, for each 10,000 copies/ml reduction in HIV RNA, approximately 3 g of additional muscle protein are synthesized per day. These findings suggest that reducing HIV RNA increases muscle protein synthesis and reduces muscle proteolysis, but muscle protein synthesis relative to whole body protein synthesis rate is not restored to normal, so muscle mass is not substantially increased.

HIV type 1 protease inhibitors enhance bone marrow progenitor cell activity in normal subjects and in HIV type 1-infected patients

HIV-1 protease inhibitors (PIs) may improve hematopoietic functions owing to their direct effects on bone marrow (BM) progenitor cells. In this study we investigated this hypothesis evaluating the effect of adding ritonavir (RTV) and indinavir (IND) on hematopoietic colony formation assays by colony-forming cell (CFC) and long-term culture-initiating cell (LTC-IC) assays, on apoptosis, on cytokine production and stromal cells, in subjects with HIV-1 infection, and in seronegative controls. After PI addition, CFC and LTC-IC assays in HIV-1-infected patients showed levels of colony growth significantly higher than those observed at baseline; the same PI activity on colony formation was observed in healthy subjects. No significant modifications on Fas, the membrane form of Fas (mFas) and Fas-ligand (FasL) expression, and on cytokine production were observed at BM level after the addition of PIs. At baseline, in HIV-1-infected patients, the majority of the stromal cells appeared as large and rounded, whereas after the addition of RTV or IND the stromal cells exhibited a "fibroblast-like" morphology and produced higher stem cell factor (SCF) and lower MIP-1alpha levels when compared with the stromal production without the addition of IND. RTV and IND increased colony growth of BM obtained either from HIV-1-infected patients or from normal individuals, in parallel with the normalization of functional and morphological characteristics of stromal cells.

Protease inhibitor treatments reveal specific involvement of matrix metalloproteinase-9 in human adipocyte differentiation

We previously showed that human and murine 3T3-F442A preadipocytes produced and released matrix metalloproteinases (MMPs) 2 and 9 and that a treatment by MMP inhibitors resulted in the blockade of murine fat cell adipose conversion. In parallel, investigators reported that other protease inhibitors, the human immunodeficiency virus (HIV) protease inhibitors (PIs) involved in lipodystrophy in humans, also reduced the adipocyte differentiation process of several murine cell lines. The present work was performed to define the effects of MMP inhibitors and HIV-PIs on the human adipocyte differentiation process, to clarify the involvement of MMPs in the control of human adipogenesis, and to determine whether HIV-PIs interact with MMPs in the control of this process. The effect of two MMP inhibitor and four HIV-PI treatments on the differentiation of primary culture human preadipocytes, as well as the putative relationships between HIV-PIs and MMP-2 and -9 expression, release, or activity were investigated. We showed that MMP inhibitors and HIV-PIs reduced the human adipocyte differentiation process as assessed by the decrease of cell protein and/or triglyceride contents and expression of fatty acid binding protein and hormone-sensitive lipase, two adipocyte markers. Unlike MMP inhibitors, HIV-PIs were devoid of any effect per se on recombinant MMP-2 and 9 activities but reduced the expression and release of MMP-9 by human preadipocytes. Thus, the present study indicates that the modulation of the extracellular matrix components through the production and/or activity of MMPs, and, more precisely, MMP-9 might be a key factor in the regulation of human adipose tissue development.

Antitumour effects of antiretroviral therapy

Infection by human immunodeficiency virus (HIV) is associated with an increased risk of certain tumours, particularly Kaposi's sarcoma, non-Hodgkin's lymphomas and cervical cancer. However, the incidence of these tumours in HIV-infected patients has decreased significantly since the widespread use of highly active antiretroviral therapy (HAART). This effect cannot be solely explained by the ability of these drugs to suppress HIV replication and thereby reconstitute the immune system. Recent studies have shown that inhibitors of the HIV aspartyl protease, which are widely used in HAART, have direct anti-angiogenic and antitumour effects that are unrelated to their antiviral activity. So these drugs might be used to treat cancer in patients who are not infected with HIV.

Human immunodeficiency virus type 1 protease inhibitors block toll-like receptor 2 (TLR2)- and TLR4-Induced NF-kappaB activation

Coinfections with opportunistic and pathogenic bacteria induce human immunodeficiency virus (HIV) replication through microbial antigen activation of NF-kappaB. Here, we assessed whether HIV type 1 protease inhibitors (PI) block microbial antigen activation of NF-kappaB. Human microvessel endothelial cells were transiently transfected with either endothelial cell-leukocyte adhesion molecule NF-kappaB luciferase or interleukin 6 (IL-6) promoter luciferase constructs by using FuGENE 6, and they were treated with PI (nelfinavir, ritonavir, or saquinavir) prior to stimulation with the Toll-like receptor 4 (TLR4) and TLR2 ligands, with lipopolysaccharide (LPS), soluble Mycobacterium tuberculosis factor, or Staphylococcus epidermidis phenol-soluble modulin, respectively, or with tumor necrosis factor alpha (TNF-alpha). Luciferase activity was measured by using a Promega luciferase kit. TNF-alpha release from the supernatant was measured by enzyme-linked immunosorbent assay. Cell death was assessed by lactate dehydrogenase assay. We observed that PI pretreatment blocked the TLR2- and TLR4- as well as the TNF-alpha-mediated NF-kappaB activation, in a dose-dependent manner. PI pretreatment also blocked the LPS-induced IL-6 promoter transactivation and TNF-alpha secretion. These data suggest that PI block HIV replication not only by inhibiting the HIV protease but also by blocking the TLR- and TNF-alpha-mediated NF-kappaB activation and proinflammatory cytokine production. These findings may help explain the immunomodulatory effects of PI, and they suggest an advantage for PI-containing drug regimens in the treatment of HIV-infected patients who are coinfected with opportunistic and pathogenic bacteria.

Anti-apoptotic effect of HIV protease inhibitors via direct inhibition of calpain

Treatment with drugs designed to inhibit the HIV protease ameliorates immune functions in AIDS patients, reducing cell deletion by apoptosis even in the absence of inhibition of viral spread. This suggests that they interact with the intrinsic apoptotic signaling. We found that caspases, the main executioner of the apoptotic process, are not directly inhibited. In search for the mechanism responsible for their anti-apoptotic effect, we have found that indinavir and ritonavir are able to inhibit apoptosis only in those cell systems where apoptosis involves the activation of calpains. They directly inhibit a calpain-like activity expressed in lysates from apoptotic cells, to the same extent as commercially available calpain inhibitor 1. In in vitro assays with purified calpains, indinavir and ritonavir strongly inhibit m-calpain, and moderately mu-calpain. These results have great therapeutic implications, going beyond AIDS treatment, since many degenerative disorders involve abnormal calpain activation, indicating calpain as an ideal pharmacological target. Indinavir and ritonavir, potent m-calpain inhibitors, largely used since several years on humans without important negative side effects, may become powerful tools against those pathologies.

Use of HIV protease inhibitors to block Kaposi's sarcoma and tumour growth

HIV protease inhibitors are antiretroviral drugs that block the enzyme required for production of infectious viral particles. Although these agents have been designed to selectively bind to the catalytic site of HIV protease, evidence indicates that other cellular and microbial enzymes and pathways are also affected. It has been reported that patients treated with highly active anti-retroviral therapy (HAART) containing a protease inhibitor may be at reduced risk of Kaposi's sarcoma (KS) and some types of non-Hodgkin lymphomas; some disease regressions have also been described. Here we review recent data showing that several widely used protease inhibitors, including indinavir, saquinavir, ritonavir, and nelfinavir, can affect important cellular and tissue processes such as angiogenesis, tumour growth and invasion, inflammation, antigen processing and presentation, cell survival, and tissue remodelling. Most of these non-HIV-related effects of protease inhibitors are due to inhibition of cell invasion and matrix metalloprotease activity, or modulation of the cell proteasome and NFkappaB. These elements are required for development of most tumours. Thus, by direct and indirect activities, protease inhibitors can simultaneously block several pathways involved in tumour growth, invasion, and metastasis. These findings indicate that protease inhibitors can be exploited for the therapy of KS and other tumours that occur in both HIV-infected and non-infected individuals. A multicentre phase II clinical trial with indinavir in non-HIV-associated KS is about to start in Italy.