Phosphatase and tensin homologue deficiency in glioblastoma confers resistance to radiation and temozolomide that is reversed by the protease inhibitor nelfinavir

Glioblastomas are malignant brain tumors that are very difficult to cure, even with aggressive therapy consisting of surgery, chemotherapy, and radiation. Glioblastomas frequently have loss of the phosphatase and tensin homologue (PTEN), leading to the activation of the phosphoinositide-3-kinase (PI3K)/Akt pathway. We examined whether PTEN deficiency leads to radioresistance and whether this can be reversed by nelfinavir, a protease inhibitor that decreases Akt signaling. Nelfinavir decreased Akt phosphorylation and enhanced radiosensitization in U251MG and U87MG glioblastoma cells, both of which are PTEN deficient. In the derivative line U251MG-PTEN, induction of wild-type PTEN with doxycycline decreased P-Akt expression and increased radiosensitivity to a similar extent as nelfinavir. Combining these two approaches had no greater effect on radiosensitivity than either alone. This epistasis-type analysis suggests that the nelfinavir acts along the Akt pathway to radiosensitize cells. However, nelfinavir neither decreased Akt phosphorylation in immortalized human astrocytes nor radiosensitized them. Radiosensitization was also assessed in vivo using a tumor regrowth delay assay in nude mice implanted with U87MG xenografts. The mean time to reach 1,000 mm(3) in the radiation + nelfinavir group was 71 days, as compared with 41, 34, or 45 days for control, nelfinavir alone, or radiation alone groups, respectively. A significant synergistic effect on tumor regrowth was detected between radiation and nelfinavir. (P = 0.01). Nelfinavir also increased the sensitivity of U251MG cells to temozolomide. These results support the clinical investigation of nelfinavir in combination with radiation and temozolomide in future clinical trials for patients with glioblastomas.

The HIV protease inhibitor nelfinavir downregulates Akt phosphorylation by inhibiting proteasomal activity and inducing the unfolded protein response

HIV protease inhibitors (HPIs), which have been used to treat HIV patients since the mid 1990s, have been shown to downregulate the phosphatidylinositol 3-kinase (PI3K)-Akt pathway. Because this pathway is frequently activated in human malignancies and associated with resistance to ionizing radiation, we investigated and confirmed that HPIs could radiosensitize cells. However, the mechanism underlying this downregulation was unclear, prompting the investigations in this report. In this paper we show that nelfinavir inhibits proteasome activity. Inhibition of the proteasome leads to endoplasmic reticulum-based stress with accumulation of misfolded proteins, which triggers the unfolded protein response (UPR). As part of the UPR, the alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha) is phosphorylated, resulting in a decrease in global protein synthesis and induction of the feedback regulator growth arrest and DNA damage-inducible protein (GADD34), which acts as a phosphatase in complex with protein phosphatase 1. This complex dephosphorylates eIF2alpha; however, our data also suggest that this phosphatase activity can dephosphorylate Akt. Furthermore, our data indicate that nelfinavir decreases Akt phosphorylation by triggering this response. These findings may have important implications in understanding how nelfinavir may increase radiation sensitivity and also result in downregulation of the PI3K/Akt pathway.

Resistant mechanism against nelfinavir of human immunodeficiency virus type 1 proteases

Inhibitors against human immunodeficiency virus type-1 (HIV-1) proteases are finely effective for anti-HIV-1 treatments. However, the therapeutic efficacy is reduced by the rapid emergence of inhibitor-resistant variants of the protease. Among patients who failed in the inhibitor nelfinavir (NFV) treatment, D30N, N88D, and L90M mutations of HIV-1 protease are often observed. Despite the serious clinical problem, it is not clear how these mutations, especially nonactive site mutations N88D and L90M, affect the affinity of NFV or why they cause the resistance to NFV. In this study, we executed molecular dynamics simulations of the NFV-bound proteases in the wild-type and D30N, N88D, D30N/N88D, and L90M mutants. Our simulations clarified the conformational change at the active site of the protease and the change of the affinity with NFV for all of these mutations, even though the 88th and 90th residues are not located in the NFV-bound cavity and not able to directly interact with NFV. D30N mutation causes the disappearance of the hydrogen bond between the m-phenol group of NFV and the 30th residue. N88D mutation alters the active site conformation slightly and induces a favorable hydrophobic contact. L90M mutation dramatically changes the conformation at the flap region and leads to an unfavorable distortion of the binding pocket of the protease, although 90M is largely far apart from the flap region. Furthermore, the changes of binding energies of the mutants from the wild-type protease are shown to be correlated with the mutant resistivity previously reported by the phenotypic experiments.

Effects of potent antiretroviral therapy on free testosterone levels and fat-free mass in men in a prospective, randomized trial: A5005s, a substudy of AIDS Clinical Trials Group Study 384

BACKGROUND

Low testosterone levels are commonly reported in patients with advanced human immunodeficiency virus disease. The effects of initiation of different antiretroviral regimens on testosterone levels and changes in fat-free mass have not been reported.

METHODS

Antiretroviral-naive men (n=213) were randomized to receive nelfinavir, efavirenz, or both plus either zidovudine and lamivudine or stavudine and didanosine. Patients underwent measurements of metabolic parameters, including determination of free testosterone level by equilibrium dialysis and bioelectrical impedance analysis, over a 64-week period.

RESULTS

At baseline, the median free testosterone level was 92 pg/mL; the level was subnormal (i.e., <50 pg/mL) in 6%. Lower CD4 cell count at the time of study entry, higher weight, and greater age were independently associated with lower baseline free testosterone level. At week 64, the median free testosterone level increased more in zidovudine-lamivudine recipients (48 of whom had paired values available; change, +31 pg/mL) than in stavudine-didanosine recipients (57 of whom had paired values; change, +3 pg/mL; P=.001, by Wilcoxon rank sum test), and it increased more in efavirenz recipients (37 of whom had paired values; change, +30 pg/mL) than in nelfinavir recipients (28 of whom had paired values; change, -3 pg/mL; P=.05). The median fat-free mass for the entire group increased by 1.2 kg at week 64 (change, +2.0%; P<.001); the increase was greater in the zidovudine-lamivudine group (n=70; change, +1.8 kg) than in the stavudine-didanosine group (n=79; change, +0.5 kg; P=.04), and the increase was also greater for efavirenz recipients (n=53; change, +2.1 kg) than among nelfinavir recipients (n=47; change, +0.4 kg; P=.003). White race, lower CD4 cell count at study entry, assignment to the efavirenz treatment arm, and assignment to the zidovudine-lamivudine treatment arm independently predicted greater absolute change in fat-free mass at week 64.

CONCLUSIONS

Subnormal free testosterone levels occurred infrequently among these antiretroviral-naive men. Free testosterone and fat-free mass levels increased after initiation of antiretroviral therapy, with greater increases at 64 weeks among zidovudine-lamivudine recipients than among stavudine-didanosine recipients and among efavirenz recipients than among nelfinavir recipients.

Regulation of adipocyte lipolysis by degradation of the perilipin protein: nelfinavir enhances lysosome-mediated perilipin proteolysis

A decrease in the lipid droplet-associated protein perilipin may constitute a mechanism for enhanced adipocyte lipolysis under nonstimulated (basal) conditions, and increased basal lipolysis has been linked to whole body metabolic dysregulation. Here we investigated whether the lipolytic actions of the human immunodeficiency virus protease inhibitor, nelfinavir, are mediated by decreased perilipin protein content and studied the mechanisms by which it occurs. Time course analysis revealed that the decrease in perilipin protein content preceded the increase in lipolysis. A causative relationship was suggested by demonstrating that nelfinavir potently increased lipolysis in adipocytes derived from mouse embryonal fibroblasts expressing perilipin but not in mouse embryonal fibroblast adipocytes devoid of perilipin and that adenoviral mediated overexpression of perilipin in 3T3-L1 adipocytes blocked the lipolytic actions of nelfinavir. Nelfinavir did not alter mRNA content of perilipin but rather decreased perilipin proteins t((1/2)) from >70 to 12 h. Protein degradation of perilipin in both control and nelfinavir-treated adipocytes could be prevented by inhibiting lysosomal proteolysis using leupeptin or NH(4)Cl but not by the proteasome inhibitor MG-132. We propose that proteolysis of perilipin involving the lysosomal protein degradation machinery may constitute a novel mechanism for enhancing adipocyte lipolysis.

Comparison of the inhibitory activity of anti-HIV drugs on P-glycoprotein

Human immunodeficiency virus 1 (HIV-1) infections are treated with HIV-protease inhibitors (PIs), nucleoside (NRTIs), non-nucleoside (NNRTIs), and nucleotide reverse transcriptase inhibitors (NtRTIs). The combined administration of antiretrovirals improves patient outcomes while increasing the likelihood of drug interactions. Indeed, as substrates, inhibitors, and occasionally also inducers of P-glycoprotein (P-gp) PIs may substantially alter the pharmacokinetics of co-administered drugs. However, the P-gp inhibitory potencies specified in the numerous publications are not comparable, because they were determined with different assays and cell lines. Moreover, data on the interaction of other anti-HIV drugs with P-gp are sparse and conflicting. We therefore aimed to clarify, which anti-HIV drugs inhibit P-gp and to compare the inhibitory potencies using two independent standard methods (calcein uptake assay, flow cytometric rhodamine123 efflux assay). In the calcein assay, all PIs, all NNRTIs, abacavir, and tenofovir disoproxil fumarate acted as P-gp inhibitors with largely differing potencies between compounds. In P388/dx cells the ranking order of inhibition was: nelfinavir>ritonavir>tipranavir>lopinavir>quinidine (positive control)>delavirdine>saquinavir>amprenavir>atazanavir>efavirenz>nevirapine>abacavir>tenofovir disoproxil fumarate. In conclusion this is the first study to provide comprehensive information on the P-gp interaction profile of anti-HIV drugs under identical assay conditions. Our study reveals that many compounds may indeed inhibit P-gp substantially and further indicates that of the various systems tested, the calcein assay in P388/dx/P388 cells is the most suitable and reliable in vitro model for the quantification of P-gp inhibition.

Site-specific mutations in HIV-1 gp41 reveal a correlation between HIV-1-mediated bystander apoptosis and fusion/hemifusion

The loss of CD4(+) T cells in HIV-1 infections is hypothesized to be caused by apoptosis of bystander cells mediated by cell surface-expressed HIV-1 Env glycoprotein. However, the mechanism by which Env mediates this process remains controversial. Specifically, the role of HIV-1 gp120 binding to CD4 and CXCR4 versus the fusion process mediated by gp41 remains unresolved. Env-induced apoptosis in bystander cells has been shown to be gp41-dependent and correlates with the redistribution of membrane lipids between Env-expressing cells and target cells (hemifusion). Using a rational mutagenesis approach aimed at targeting Env function via the gp41 subunit, we examined the role of HIV gp41 in bystander apoptosis. A mutation in the fusion domain of gp41 (V513E) resulted in a fusion-defective Env that failed to induce apoptosis. A mutation in the gp41 N-terminal helix (G547D) reduced cell fusion capacity and apoptosis; conversely, an Env mutant with a deletion of the gp41 cytoplasmic tail (Ct Del) enhanced both cell-to-cell fusion and apoptosis. Most significantly, an Env mutant containing a substitution in the loop region of gp41 (D589L) mediated transfer of lipids (hemifusion) to bystander cells but was defective in cell-to-cell and to a lesser degree virus-to-cell fusion. This mutant was still able to induce apoptosis in bystander cells. Hence, we have provided the first direct evidence that gp41-mediated hemifusion is both required and sufficient for induction of apoptosis in bystander cells. These results may help to explain the mechanism of HIV-1 Env-induced T cell depletion.

HIV1 protease inhibitors selectively induce inflammatory chemokine expression in primary human osteoblasts

HIV-infected patients are at increased risk of decreased bone mineral density. Several studies have implicated antiretroviral therapy as a contributor to the decreased bone mineral density seen in treated HIV-1 patients. Whilst the exact molecular mechanisms underlying decreased bone density remain to be elucidated, inflammation has been postulated to be an important pathogenomic mechanism. In this study, we have explored primary human osteoblast gene expression in response to protease inhibitors (PIs), by oligonucleotide microarray analysis. A list of dysregulated genes, correlated with the inflammatory response, increased significantly after NFV and RTV exposure. Analysis of gene and protein expression determined a selectively increase of the pro-inflammatory cytokines monocyte chemoattractant protein (MCP)-1 and interleukin-8 (IL-8) following exposure to a pharmacological concentration of NFV and RTV. These data suggested that generation of local inflammatory cascades may contribute to the development of decreased bone mineral density in highly active antiretroviral therapy (HAART)-treated HIV patients.

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 protease inhibitor nelfinavir inhibits growth of human melanoma cells by induction of cell cycle arrest

HIV protease inhibitors (HIV PI) are a class of antiretroviral drugs that are designed to target the viral protease. Unexpectedly, this class of drugs is also reported to have antitumor activity. In this study, we have evaluated the in vitro activity of nelfinavir, a HIV PI, against human melanoma cells. Nelfinavir inhibits the growth of melanoma cell lines at low micromolar concentrations that are clinically attainable. Nelfinavir promotes apoptosis and arrests cell cycle at G(1) phase. Cell cycle arrest is attributed to inhibition of cyclin-dependent kinase 2 (CDK2) and concomitant dephosphorylation of retinoblastoma tumor suppressor. We further show that nelfinavir inhibits CDK2 through proteasome-dependent degradation of Cdc25A phosphatase. Our results suggest that nelfinavir is a promising candidate chemotherapeutic agent for advanced melanoma, for which novel and effective therapies are urgently needed.

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.

HIV protease inhibitors selectively induce gene expression alterations associated with reduced calcium deposition in primary human osteoblasts

HIV-infected patients are at increased risk of decreased bone mineral density. Some studies have implicated antiretroviral therapy as a contributor to the decreased bone mineral density seen in treated HIV-1 patients. In this study we explore the interactions between protease inhibitors (PI) and primary human osteoblast gene expression, highlighting a group of dysregulated genes that potentially are key factors in reducing bone formation. Runx-2 mRNA expression, calcium deposition, and alkaline phosphatase (ALP) activity decreased significantly in human osteoblast cultures after exposure to the PIs nelfinavir (NFV) and indinavir (IDV). Saquinavir (SQV), ritonavir (RTV), indinavir (IDV), or nelfinavir (NFV) exposure induced significant changes in genotypic expression as assessed by gene-chip microarray analysis. The altered genes from each group were compared to each other and a list of 8 upregulated and 13 downregulated genes only after NFV and IDV exposure was identified. This set includes TIMP-3, which has previously been demonstrated to be involved in osteoblast differentiation and extracellular matrix development processes. Silencing TIMP-3 mRNA expression using siRNA duplexes enhanced calcium deposition and ALP activity significantly, even after exposure to NFV and IDV. Our data suggest a link between reduced osteoblastic phenotype and a group of 21 altered genes following NFV and IDV treatment, and also suggest TIMP-3 may be involved in the PI-induced inhibition of osteoblast function.

HIV protease inhibitors decrease VEGF/HIF-1alpha expression and angiogenesis in glioblastoma cells

Glioblastomas are malignant brain tumors that are rarely curable, even with aggressive therapy (surgery, chemotherapy, and radiation). Glioblastomas frequently display loss of PTEN and/or epidermal growth factor receptor activation, both of which activate the PI3K pathway. This pathway can increase vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF)-1alpha expression. We examined the effects of two human immunodeficiency virus protease inhibitors, nelfinavir and amprenavir, which inhibit Akt signaling, on VEGF and HIF-1alpha expression and on angiogenesis. Nelfinavir decreased VEGF mRNA expression and VEGF secretion under normoxia. Downregulation of P-Akt decreased VEGF secretion in a manner similar to that of nelfinavir, but the combination of the two had no greater effect, consistent with the idea that nelfinavir decreases VEGF through the PI3K/Akt pathway. Nelfinavir also decreased the hypoxic induction of VEGF and the hypoxic induction of HIF-1alpha, which regulates VEGF promoter. The effect of nelfinavir on HIF-1alpha was most likely mediated by decreased protein translation. Nelfinavir's effect on VEGF expression had the functional consequence of decreasing angiogenesis in in vivo Matrigel plug assays. Similar effects on VEGF and HIF-1alpha expression were seen with a different protease inhibitor, amprenavir. Our results support further research into these protease inhibitors for use in future clinical trials for patients with glioblastoma multiformes.

Antiviral activity of HIV type 1 protease inhibitors nelfinavir and indinavir in vivo is not influenced by P-glycoprotein activity on CD4+ T cells

P-glycoprotein (P-gp) can compromise the antiretroviral effect of a protease inhibitor (PI)-containing regimen for HIV-1, but can also reduce HIV-1 replication. We studied the net effect of P-gp on the intracellular HIV-1 RNA and DNA load in vivo. CD4(+) T cells were isolated from 27 HIV-1 patients (13 without and 14 with a PI-containing regimen) and subsequently sorted in CD45RO(-) (naive) and CD45RO(+) (memory) subsets with either high (P-gp(high)) or low (P-gp(low)) P-gp activity. Unspliced HIV-1 RNA and HIV-1 DNA load were determined. For each patient P-gp(high) and P-gp(low) subsets were compared. In patients on a PI-containing regimen, intracellular unspliced HIV-1 RNA was significantly lower in P-gp(high)-naive CD4(+) cells compared to P-gp(low)-naive CD4(+) cells (p = 0.04). The same trend was seen in naive CD4(+) cells of treatment naive patients. In both treated and untreated patients HIV-1 DNA levels were significantly lower in P-gp(high) than in P-gp(low) memory CD4(+) cells (p = 0.02 and p = 0.04). High cellular P-gp activity coincided with a reduced intracellular HIV-1 load in vivo, both in therapy-naive and in PI-treated patients. Therefore we conclude that the potential efflux function of P-gp on PIs may be clinically less relevant than the effect of P-gp on intracellular HIV-1 replication.

HIV genotypic resistance testing to optimize antiretroviral prescribing: is there room for improvement?

BACKGROUND

Clinical utilization of genotype resistance testing is evolving. We examined the extent to which HIV care providers requesting genotype resistance tests used the information appropriately and the impact of inappropriate utilization.

METHODS

Data from a prospective cohort of HIV-infected patients (the HIV Outpatient Study) were used in the analysis. We analysed the frequency with which patients were prescribed any non-nucleoside reverse transcriptase inhibitor after identification of the K103N mutation in reverse transcriptase and the frequency of prescription of nelfinavir after identification of the D30N mutation in HIV protease; the short-term impact of this action on HIV viral load and CD4+ T-cell count was assessed.

RESULTS

Among 441 patients demonstrating either mutation, 18% who were taking the resistant antiretroviral at the time of the test were continued on the medication for >6 months after this finding. In 33% of these instances, prescribers reported these actions were erroneous oversights. For persons taking the resistant antiretroviral at the time of the genotype test, stopping this medication within 6 months of the test produced greater decreases in viral load (-1.35 versus -0.43 log copies/ml, P = 0.025) and a greater likelihood of achieving an undetectable viral load (25.3% versus 7.3%, P = 0.012) at 9 months. Changes in CD4+ T-cell count differed (+22.8 versus -23.0 cells/mm3), but not significantly (P = 0.167).

CONCLUSIONS

Following evidence of definitive resistance by genotype testing, a substantial fraction of antiretroviral prescriptions were continued in error leading to an attenuated therapeutic response. These data highlight the need to consider better systems to manage genotype resistance testing data in the clinical setting.

Effect of transporter modulation on the emergence of nelfinavir resistance in vitro

BACKGROUND

HIV drug resistance is of increasing concern and could result from inadequate drug potency, poor therapy adherence and the existence of pharmacological sanctuary sites for viral replication. One contributing factor to the generation of such sites could be drug efflux transporters, which have been shown capable of effluxing HIV protease inhibitors from cells.

METHODS

In this 'proof-of-concept' study, the ability of the efflux transport inhibitor verapamil to modulate the intracellular accumulation of radiolabelled nelfinavir (NFV) and the antiviral effect of NFV was assessed in MT4 cells. Wild-type virus was then serially passaged with increasing concentrations of NFV with and without verapamil and resistance mutations monitored by sequencing of the viral protease gene.

RESULTS

The cellular accumulation ratio of 3H-NFV was 116.8 +/- 9.7 in controls and was significantly increased to 149.8 +/- 24.5 following incubation with verapamil (P < 0.05, n=4). The EC50 of NFV was decreased in MT4 cells in the presence of verapamil from 8.5 11.3 nM to 4.4 +/- 0.8 nM (P < 0.001, n=6). Of the 24 isolates passaged without verapamil, 21 carried the D30N mutation at detectable levels. Of the 23 passaged with verapamil, 14 carried the mutation (odds ratio = 4.5; P < 0.05).

CONCLUSIONS

These results suggest that 'intracellular boosting' of PIs is achievable through inhibition of drug efflux proteins in vitro and that such boosting has the ability to enhance suppression of viral replication, slowing the emergence of resistance mutations.

N88D facilitates the co-occurrence of D30N and L90M and the development of multidrug resistance in HIV type 1 protease following nelfinavir treatment failure

Nelfinavir was once one of the most commonly used protease inhibitors (PIs). To investigate the genetic mechanisms of multidrug resistance in protease isolates with the primary nelfinavir resistance mutation D30N, we analyzed patterns of protease mutations in 582 viruses with D30N from 460 persons undergoing HIV-1 genotypic resistance testing at Stanford University Hospital from 1997 to 2005. Three patterns of mutational associations were identified. First, D30N was positively associated with N88D but negatively associated with N88S. Second, D30N and L90M were negatively associated except in the presence of N88D, which facilitated the co-occurrence of D30N and L90M. Third, D30N+N88D+L90M formed a stable genetic backbone for the accumulation of additional protease inhibitor (PI) resistance mutations. In 16 patients having isolates with more than one combination of mutations at positions 30, 88, and 90, all exhibited one of the steps in the following progression: D30N-->D30N+N88D-->D30N+N88D+L90M-->D30N+N88D+L90M+(L33F+/-I84V or M46I/L+/-I54V). Although nelfinavir is now used less frequently than other PIs, the well-delineated mutational pathway we describe is likely to influence patterns of cross-resistance in viruses from persons who experience virologic failure while receiving this PI.

NFV, an HIV-1 protease inhibitor, induces growth arrest, reduced Akt signalling, apoptosis and docetaxel sensitisation in NSCLC cell lines

HIV-1 protease inhibitor (PI), nelfinavir (NFV) induced growth arrest and apoptosis of NCI-H460 and -H520, A549, EBC-1 and ABC-1 non-small-cell lung cancer (NSCLC) cells in association with upregulation of p21^waf1, p27 ^kip1 and p53, and downregulation of Bcl-2 and matrix metalloproteinase (MMP)-2 proteins. We found that NFV blocked Akt signalling in these cells as measured by Akt kinase assay with glycogen synthase kinase-3α/β (GSK-3α/β) as a substrate. To explore the role of Akt signalling in NFV-mediated growth inhibition of NSCLC cells, we blocked this signal pathway by transfection of Akt small interfering RNA (siRNA) in these cells; transient transfection of Akt siRNA in NCI-H460 cells decreased the level of Bcl-2 protein and slowed their proliferation compared to the nonspecific siRNA-transfected cells. Conversely, forced-expression of Akt partially reversed NFV-mediated growth inhibition of these cells, suggesting that Akt may be a molecular target of NFV in NSCLC cells. Also, we found that inhibition of Akt signalling by NFV enhanced the ability of docetaxel to inhibit the growth of NCI-H460 and -H520 cells, as measured by MTT assay. Importantly, NFV slowed the proliferation and induced apoptosis of NCI-H460 cells present as tumour xenografts in nude mice without adverse systemic effects. Taken together, this family of compounds might be useful for the treatment of individuals with NSCLC.

Bayesian network analysis of resistance pathways against HIV-1 protease inhibitors

Interpretation of Human Immunodeficiency Virus 1 (HIV-1) genotypic drug resistance is still a major challenge in the follow-up of antiviral therapy in infected patients. Because of the high degree of HIV-1 natural variation, complex interactions and stochastic behaviour of evolution, the role of resistance mutations is in many cases not well understood. Using Bayesian network learning of HIV-1 sequence data from diverse subtypes (A, B, C, F and G), we could determine the specific role of many resistance mutations against the protease inhibitors (PIs) nelfinavir (NFV), indinavir (IDV), and saquinavir (SQV). Such networks visualize relationships between treatment, selection of resistance mutations and presence of polymorphisms in a graphical way. The analysis identified 30N, 88S, and 90M for nelfinavir, 90M for saquinavir, and 82A/T and 46I/L for indinavir as most probable major resistance mutations. Moreover we found striking similarities for the role of many mutations against all of these drugs. For example, for all three inhibitors, we found that the novel mutation 89I was minor and associated with mutations at positions 90 and 71. Bayesian network learning provides an autonomous method to gain insight in the role of resistance mutations and the influence of HIV-1 natural variation. We successfully applied the method to three protease inhibitors. The analysis shows differences with current knowledge especially concerning resistance development in several non-B subtypes.

Nelfinavir down-regulates hypoxia-inducible factor 1alpha and VEGF expression and increases tumor oxygenation: implications for radiotherapy

The phosphatidylinositol 3-kinase (PI3K)/Akt pathway can increase vascular endothelial growth factor (VEGF) and hypoxia-inducible factor 1alpha (HIF-1alpha) expression. We examined the effect of nelfinavir, an HIV protease inhibitor that inhibits Akt signaling, on VEGF and HIF-1alpha expression and on angiogenesis, tumor oxygenation, and radiosensitization. Nelfinavir decreases VEGF expression under normoxia via the transcription factor Sp1, which regulates the proximal core VEGF promoter. Nelfinavir decreased Sp1 phosphorylation and decreased Sp1 binding to a probe corresponding to the proximal VEGF promoter in a gel shift assay. Nelfinavir also decreased the hypoxic induction of HIF-1alpha, which also regulates the VEGF promoter, most likely by decreasing its translation. The effect of nelfinavir on VEGF expression had the functional consequence of decreasing angiogenesis in an in vivo Matrigel plug assay. To determine the effect this might have on tumor radiosensitization, we did tumor regrowth assays with xenografts in nude mice. The combination of nelfinavir and radiation increased time to regrowth compared with radiation alone whereas nelfinavir alone had little effect on tumor regrowth. This radiosensitizing effect was greater than suggested by in vitro clonogenic survival assays. One possible explanation for the discordance is that nelfinavir has an effect on tumor oxygenation. Therefore, we examined this with the hypoxia marker EF5 and found that nelfinavir leads to increased oxygenation within tumor xenografts. Our results suggest that nelfinavir decreases HIF-1alpha/VEGF expression and tumor hypoxia, which could play a role in its in vivo radiosensitizing effect. These data support the use of nelfinavir in combination with radiation in future clinical trials.

Natural polymorphisms in the human immunodeficiency virus type 2 protease can accelerate time to development of resistance to protease inhibitors

Human immunodeficiency virus type 2 (HIV-2) contains numerous natural polymorphisms in its protease (PR) gene that are implicated in drug resistance in the case of HIV-1. This study evaluated emergent PR resistance in HIV-2. Three HIV-2 isolates were selected for resistance to amprenavir (APV), nelfinavir (NFV), indinavir (IDV), and tipranavir (TPV) in cell culture. Genotypic analysis determined the time to the appearance of protease inhibitor (PI)-associated mutations compared to HIV-1. Phenotypic drug susceptibility assays were used to determine the levels of drug resistance. Within 10 to 15 weeks of serial passage, three major mutations--I54M, I82F, and L90M--arose in HIV-2 viral cultures exposed to APV, NFV, and IDV, whereas I82L was selected with TPV. After 25 weeks, other cultures had developed I50V and I84V mutations. In contrast, no major PI mutations were selected in HIV-1 over this period except for D30N in the context of NFV selective pressure. The baseline phenotypes of wild-type HIV-2 isolates were in the range observed for HIV-1, except for APV and NFV for which a lower degree of sensitivity was seen. The acquisition of the I54M, I84V, L90M, and L99F mutations resulted in multi-PI-resistant viruses, conferring 10-fold to more than 100-fold resistance. Of note, we observed a 62A/99F mutational motif that conferred high-level resistance to PIs, as well as novel secondary mutations, including 6F, 12A, and 21K. Thus, natural polymorphisms in HIV-2 may facilitate the selection of PI resistance. The increasing incidence of such polymorphisms in drug-naive HIV-1- and HIV-2-infected persons is of concern.

Identification and structural characterization of I84C and I84A mutations that are associated with high-level resistance to human immunodeficiency virus protease inhibitors and impair viral replication

Two novel human immunodeficiency virus protease mutations, I84C and I84A, were identified in patient isolates. The mutants with I84C displayed high-level resistance (median, at least 56-fold) to nelfinavir and saquinavir, but the majority remained susceptible to lopinavir. In contrast, isolates with the I84A mutation exhibited>or=33-fold median increased levels of resistance to nelfinavir, indinavir, amprenavir, ritonavir, lopinavir, saquinavir, and atazanavir. Isolates with the I84A or I84C mutation tended to be more resistant than the isolates with the I84V mutation. Modeling of the structure of the mutant proteases indicated that the I84V, I84C, and I84A mutations all create unoccupied volume in the active site, with I84A introducing the greatest change in the accessible surface area from that of the wild-type structure.

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.

Nelfinavir induces liposarcoma apoptosis and cell cycle arrest by upregulating sterol regulatory element binding protein-1

"HIV protease-induced lipodystrophy syndrome" is associated with the use of HIV protease inhibitors for treatment of HIV infection. In-vitro studies suggest that alteration of sterol regulatory element binding protein-1 levels underlie its pathogenesis. We postulated that HIV protease inhibitors may represent a novel class of antiliposarcoma agents. SW872, FU-DDLS-1 and LiSa-2 liposarcoma, and HT1080 and 293 nonliposarcoma cell lines were treated with HIV protease inhibitors (nelfinavir, ritonavir, saquinavir, indinavir and amprenavir), and clonogenic assays were performed. Nelfinavir exhibited the most potent inhibition of clonogenicity, and further assays for proliferation, cell cycle and apoptosis were performed with nelfinavir. Immunoblots were performed for sterol regulatory element binding protein-1, proapoptotic and cell cycle-related protein expression after nelfinavir treatment. Finally, a sterol regulatory element binding protein-1-inducible SW872 cell line was developed to examine the phenotype resulting from upregulated sterol regulatory element binding protein-1. Nelfinavir selectively inhibited clonogenicity and proliferation, and induced G1 cell cycle block and induced apoptosis in a dose-dependent manner in SW872 and LiSa-2 cells, whereas it had minimal or no effect on these parameters in FU-DDLS-1 or nonliposarcoma cells. Nelfinavir induced significant sterol regulatory element binding protein-1 expression in a dose-dependent and time-dependent fashion in sensitive SW872 and LiSa-2 cells, modestly in HT1080 cells, but not in nelfinavir-insensitive FU-DDLS-1 and 293 cells without inducing adipocytic differentiation. Forced expression of sterol regulatory element binding protein-1 in inducible-SW872 cells led to the induction of proapoptotic and antiproliferative proteins, and consequent reduction of cellular proliferation. Our data indicate that nelfinavir represents a novel class of antiliposarcoma agent that acts by selectively upregulating sterol regulatory element binding protein-1 expression in liposarcomas.

Secretory aspartyl peptidase activity from mycelia of the human fungal pathogen Fonsecaea pedrosoi: effect of HIV aspartyl proteolytic inhibitors

Fonsecaea pedrosoi is the principal causative agent of chromoblastomycosis, which is a chronic, often debilitating, suppurative and granulomatous mycosis. Very little is known about the hydrolytic enzymes produced by this human fungal pathogen. In the present study, we have identified extracellular proteolytic activity from F. pedrosoi mycelial forms when grown in chemically defined conditions. Secretory aspartyl peptidase activity was measured during 15 days of fungal growth in vitro using bovine serum albumin (BSA) as the soluble substrate and extreme acidic pH (2.0). This activity was totally inhibited by pepstatin A, a classic aspartyl peptidase inhibitor. Conversely, metallo (o-phenanthroline), cysteine (E-64) and serine (PMSF) proteolytic inhibitors failed to restrain proteolytic activity. We also evaluated the effect of four distinct HIV aspartyl peptidase inhibitors on the secretory proteolytic activity of F. pedrosoi mycelia. Indinavir, ritonavir and nelfinavir powerfully inhibited extracellular aspartyl proteolytic activity by approximately 97, 96 and 87%, respectively, whereas saquinavir did not significantly interfere with BSA hydrolysis. Mycelial-derived secretory aspartyl peptidase activity cleaved other proteinaceous substrates, including human albumin, fibrinogen, fibronectin, laminin and type I collagen. As previously reported by our group, conidia also produce secretory aspartyl peptidase. In this sense, we investigated the effect of pepstatin A on F. pedrosoi development. Pepstatin A was able to inhibit the growth of conidium and its transformation into mycelium. Taken together, our results suggest a possible participation of aspartyl peptidases in the essential fungal processes, such as growth, differentiation, nutrition and cleavage of relevant host proteinaceous components.

Impact of human immunodeficiency virus type 1 subtype C on drug resistance mutations in patients from Botswana failing a nelfinavir-containing regimen

Among 16 human immunodeficiency virus-infected (subtype C) Batswana patients who failed nelfinavir (NFV)-containing regimens, the most prevalent mutation observed was D30N (54%), followed by L90M (31%). L89I, K20T/I, and E35D polymorphic changes were also identified. These findings suggest that subtype C viruses in Botswana may develop resistance to NFV via subtype-specific pathways.

Establishment of a new cell line inducibly expressing HIV-1 protease for performing safe and highly sensitive screening of HIV protease inhibitors

The human immunodeficiency virus type 1 (HIV-1) protease (PR) plays an essential role in processing viral polyproteins into mature proteins. As a result, it is a major target for the development of drugs against AIDS. However, due to the rapid emergence of drug-resistant HIV, the development of novel HIV PR inhibitors is urgently needed. We recently established a new cell line E-PR293 which can be used as a safe, convenient and highly efficient assay system to screen HIV-1 PR inhibitors. In the cells, the HIV-1 PR is expressed in a chimeric protein with the green fluorescence protein (GFP). This assay measures the PR activity as a function of either the fluorescence of GFP or the cytotoxic activity of HIV-1 PR which is expressed in the cell. E-PR293 cells were maintained in the presence of doxycycline, which suppresses the expression of HIV-1 PR. The removal of doxycycline induces the expression of HIV-1 PR, which is used to screen HIV-1 PR inhibitors. In E-PR293 cells, the 50% inhibitory concentration of the cytotoxic effects by nelfinavir and saquinavir were as low as nanomolar levels, almost equal to those found in the HIV-infection assay.

Biological characterization of human immunodeficiency virus type 1 subtype C protease carrying indinavir drug-resistance mutations

Human immunodeficiency virus type 1 subtype C isolates belong to one of the most prevalent strains circulating worldwide and are responsible for the majority of new infections in the sub-Saharan region and other highly populated areas of the globe. In this work, the impact of drug-resistance mutations in the protease gene of subtype C viruses was analysed and compared with that of subtype B counterparts. A series of recombinant subtype C and B viruses was constructed carrying indinavir (IDV)-resistance mutations (M46V, I54V, V82A and L90M) and their susceptibility to six FDA-approved protease inhibitor compounds (amprenavir, indinavir, lopinavir, ritonavir, saquinavir and nelfinavir) was determined. A different impact of these mutations was found when nelfinavir and lopinavir were tested. The IDV drug-resistance mutations in the subtype C protease backbone were retained for a long period in culture without selective pressure when compared with those in subtype B counterparts in washout experiments.

Cooperative contribution of gag substitutions to nelfinavir-dependent enhancement of precursor cleavage and replication of human immunodeficiency virus type-1

We previously described a clinical human immunodeficiency virus type-1 (HIV-1) isolate, CL-4, which showed nelfinavir (NFV)-dependent enhancement of replication (Matsuoka-Aizawa, S., Sato, H., Hachiya, A., Tsuchiya, K., Takebe, Y., Gatanaga, H., Kimura, S., Oka, S, 2003. Isolation and molecular characterization of a nelfinavir (NFV)-resistant human immunodeficiency virus type 1 that exhibits NFV-dependent enhancement of replication. J. Virol. 77, 318-327.). To identify the responsible region(s) of HIV-1 proteins for such replication enhancement, we constructed a panel of recombinant HIV-1 clones harboring portions of the Gag and protease of CL-4 and analyzed their replication capabilities and Gag processing patterns. Our data suggested that the substitutions in the matrix and N-terminal half of capsid of CL-4 were indispensable for the NFV-dependent enhancement of replication and that NFV facilitated the cleavage between the matrix and capsid of the Gag precursor harboring these substitutions. The substitutions in C-terminal half of capsid rather decreased the cleavability of Gag precursor and NFV counteracted such negative impact. Efficient replication enhancement with NFV can be observed only in the presence of the substitutions in entire Gag and protease of CL-4.

Co-evolution of nelfinavir-resistant HIV-1 protease and the p1-p6 substrate

The selective pressure of the competitive protease inhibitors causes both HIV-1 protease and occasionally its substrates to evolve drug resistance. We hypothesize that this occurs particularly in substrates that protrude beyond the substrate envelope and contact residues that mutate in response to a particular protease inhibitor. To validate this hypothesis, we analyzed substrate and protease sequences for covariation. Using the chi2 test, we show a positive correlation between the nelfinavir-resistant D30N/N88D protease mutations and mutations at the p1-p6 cleavage site as compared to the other cleavage sites. Both nelfinavir and the substrate p1-p6 protrude beyond the substrate envelope and contact residue 30, thus possibly making the p1-p6 cleavage site more vulnerable to co-evolution.

Differential Inhibition of Cytochrome P450 3A4, 3A5 and 3A7 by Five Human Immunodeficiency Virus (HIV) Protease Inhibitors in vitro

The effects of five HIV protease inhibitors (amprenavir, indinavir, nelfinavir, ritonavir and saquinavir) on cytochrome P450 (CYP) 3A4, 3A5 and 3A7 activities were studied in vitro using testosterone 6beta-hydroxylation in recombinant CYP3A4, CYP3A5 and CYP3A7 enzymes. The protease inhibitors showed differential inhibitory effects on the three CYP3A forms. Ritonavir and saquinavir were non-selective and preferential inhibitors of CYP3A4 and CYP3A5 (K(i) 0.03 microM and 0.6-0.8 microM for ritonavir and saquinavir, respectively), and weaker inhibitors of CYP3A7 (K(i) 0.6 microM and 1.8 microM, respectively). Nelfinavir was a potent and non-selective inhibitor of all three CYP3A forms (K(i) 0.3-0.4 microM). Amprenavir and indinavir preferentially inhibited CYP3A4 (K(i) 0.1 microM and 0.2 microM, respectively), with weaker inhibitory effects on CYP3A5 (K(i) 0.5 microM and 2.2 microM, respectively) and CYP3A7 (K(i) 2.1 microM and 10.6 microM, respectively). In conclusion, significant differences exist in the inhibitory potency of protease inhibitors for different CYP3A forms. Ritonavir, nelfinavir, saquinavir and amprenavir seem to be prone to drug-drug interactions by inhibiting both CYP3A4 and CYP3A5. Especially nelfinavir and ritonavir also have a potential to inhibit foetal CYP3A7-mediated drug metabolism and some endogenous pathways that may be crucial to normal foetal development, while indinavir has the lowest potential to inhibit CYP3A5 and CYP3A7.

Nelfinavir induces adipocyte insulin resistance through the induction of oxidative stress: differential protective effect of antioxidant agents

BACKGROUND

Antiretroviral therapy is frequently associated with adverse metabolic effects and lipodystrophy, but the role of HIV protease inhibitors and the mechanisms involved are poorly understood. The HIV protease inhibitor nelfinavir (NFV) impairs insulin signal propagation by inducing similar signalling defects to those induced by exposure to oxidative stress.

AIM

We set out to determine if oxidative stress is involved in NFV-induced insulin resistance in 3T3-L1 adipocytes, and whether antioxidant agents with unique modes of action can prevent this effect.

RESULTS

Cells exposed to NFV exhibited the following markers of increased oxidative stress: a decrease in both total and low molecular weight reduced thiols, a 20-fold increase in haem oxygenase 1 (HO-1) mRNA, an increase in intracellular reactive oxygen species production (determined by 2',7'-dichlorofluorescein fluorescence), and increased markers of apoptosis. Enhancing cellular thiols with N-acetylcystein prevented the NFV-induced drop in reduced thiols and partially protected against the induction in HO-1, but failed to prevent insulin resistance or cleavage of poly ADP ribose polymerase (PARP), a process indicative of activation of pro-apoptotic caspases. Conversely, the superoxide dismutase-mimetic antioxidant MnTBAP had no effect on cellular thiols in response to NFV, but protected against HO-1 induction and against the impairment in insulin-stimulated Akt/protein kinase B activation and PARP cleavage.

CONCLUSIONS

Induction of oxidative stress plays a role in adipocyte insulin resistance and apoptosis induced by NFV through a radical-dependent but thiol-independent mechanism(s). The results may suggest a new mechanism for the adverse effects of NFV on fat cells, and offer potential new intervention approaches.

Pharmacokinetic interaction of nelfinavir and methadone in intravenous drug users

The effect of nelfinavir 1250 mg twice daily (b.i.d.) on the pharmacokinetics of methadone was determined in 14 HIV-negative methadone users.

DESIGN

The methadone dose (20-140 mg/day) was stabilized and fixed for at least 1 month before nelfinavir (1250 mg b.i.d. for 8 days) was added to the regimen. The concentrations of methadone enantiomers were measured before and during nelfinavir treatment, and the concentrations of nelfinavir and its active metabolite, AG1402, were measured during nelfinavir treatment. Adverse events and withdrawal/intoxication symptoms were monitored throughout the study.

RESULTS

Nelfinavir reduced the area under the concentration-time curve of R-methadone, and S-methadone by 43% and 51%, respectively. Nelfinavir and AG1402 concentrations were within the normal range of historical data, and no subject experienced withdrawal symptoms during the study or required dose adjustment during or after the study.

CONCLUSIONS

Although nelfinavir reduced the plasma concentrations of both R- and S-methadone, it seems to have no impact on the maintenance dose of methadone. A routine reduction of methadone dose is not recommended when coadministered with nelfinavir.

Investigation of baseline susceptibility to protease inhibitors in HIV-1 subtypes C, F, G and CRF02_AG

OBJECTIVE

To compare baseline susceptibility to protease inhibitors among HIV-1 isolates of subtypes C, F, G and CRF02_AG, and to identify polymorphisms that determine the differences in susceptibility.

METHODS

A total of 42 samples of drug-naive patients infected with subtypes G (n=19), CRF02_AG (n = 10), F (n = 6) and C (n = 7) were phenotyped and genotyped with the Antivirogram and the ViroSeq 2.0 genotyping system, respectively. A Bayesian network approach was used for a preliminary analysis of the collected data and the dependencies indicated by the network were statistically confirmed.

RESULTS

CRF02_AG samples were found to be more susceptible to nelfinavir and ritonavir than other subtypes. Hypersusceptibility to these drugs was associated with the 70R polymorphism. 37D/S/T was associated with reduced susceptibility to indinavir and 89M with reduced susceptibility to lopinavir. Susceptibility to tipranavir was the lowest among the subtype F samples and the highest for subtype G samples, with samples carrying 57R being more susceptible than samples carrying 57K.

CONCLUSIONS

Our study suggests that there are baseline susceptibility differences between subtypes and these differences are due to naturally occurring polymorphisms in these subtypes. The predictive value for phenotype of these polymorphisms was even valid in subtypes where these polymorphisms are less prevalent. Taking into account such polymorphisms should improve current algorithms for interpretation of genotyping results in a subtype-independent way.

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.

Effects of 5 HIV protease inhibitors on vasomotor function and superoxide anion production in porcine coronary arteries

HIV protease inhibitors (PIs) have been implicated to cause cardiovascular complications. Previous studies demonstrated that the PI ritonavir (RTV) caused endothelial dysfunction in porcine arteries. This study investigated and compared the effects of 5 commonly used PIs on vasomotor function, endothelial nitric oxide synthase (eNOS) expression, and oxidative stress in porcine coronary arteries. Vessel rings were incubated with 15 microM of RTV, amprenavir (APV), saquinavir (SQV), indinavir (IDV), or nelfinavir (NFV) for 24 hours. Vasomotor function was studied using a myograph system. The contractility of the rings was significantly reduced for RTV and SQV. In response to bradykinin at 10(-5) M, the endothelium-dependent relaxation was significantly reduced for RTV, APV, and SQV. The eNOS mRNA levels were significantly reduced for RTV, APV, and SQV. Furthermore, the superoxide anion (O(2)(-)) levels of the vessels were significantly increased for RTV and APV. It was found that nitric oxide production was decreased, whereas the level of nitrotyrosine proteins was increased in RTV-treated vessels. Furthermore, antioxidant seleno-L-methionine (SeMet) reversed RTV-induced O(2)(-) production and vasomotor dysfunction. Thus, the HIV PIs RTV, APV, and SQV at 15 microM have more potent in vitro effects on vasomotor dysfunction, eNOS downregulation, and O(2)(-) production than IDV and NFV. The antioxidant SeMet can block these adverse effects of RTV. The results suggest that antioxidant therapy may have applications for controlling PI-associated cardiovascular complications.

Influence of ABCB1, ABCC1, ABCC2, and ABCG2 haplotypes on the cellular exposure of nelfinavir in vivo

OBJECTIVES

The human immunodeficiency virus protease inhibitor nelfinavir is substrate of polyspecific drug transporters encoded by ABCB1 (P-glycoprotein), ABCC1 (MRP1) and ABCC2 (MRP2), and an inhibitor of BCRP, encoded by ABCG2. Genetic polymorphism in these genes may be associated with changes in transport function.

METHODS

A comprehensive evaluation of single nucleotide polymorphisms (39 SNPs in ABCB1, 7 in ABCC1, 27 in ABCC2, and 16 in ABCG2), and inferred haplotypes was done to assess possible associations of genetic variants with cellular exposure of nelfinavir in vivo. Analysis used peripheral mononuclear cells from individuals receiving nelfinavir (n=28). Key results were re-examined in a larger sample size (n=129) contributing data on plasma drug levels.

RESULTS AND CONCLUSIONS

There was no significant association between cellular nelfinavir area under the curve (AUC) and SNPs or haplotypes at ABCC1, ABCC2, ABCG2. There was an association with cellular exposure for two loci in strong linkage disequilibrium: ABCB1 3435C>T; AUCTT>AUCCT>AUCCC (ratio 2.1, 1.4, 1, Ptrend=0.01), and intron 26 +80T>C; AUCCC> AUCCT > AUCTT (ratio 2.4, 1.3, 1, Ptrend=0.006). Haplotypic analysis using tagging SNPs did not improve the single SNP association values.

HIV antiretroviral agents inhibit protein synthesis and decrease ribosomal protein S6 and 4EBP1 phosphorylation in C2C12 myocytes

Combined antiretroviral drug regimens have promoted clinical, immunologic, and virologic improvements in AIDS patients. Nevertheless, these therapies are associated with derangements in lipid and carbohydrate metabolism. In this study, we examined the effects of a representative protease inhibitor (nelfinavir), a nonnucleoside reverse transcriptase inhibitor (nevirapine), and a nucleoside reverse transcriptase inhibitor (zidovudine) on protein synthesis in skeletal muscle cells. To examine these processes, C2C12 myocytes were treated with increasing concentrations of nelfinavir, nevirapine, or zidovudine for 1 or 2 days, and rates of protein synthesis were determined by measuring [35S]methionine/cysteine incorporation into cellular proteins. Treatment of myocytes with therapeutic concentrations of nelfinavir, nevirapine, or zidovudine for 48 hr decreased protein synthesis by 14-20%. An approximately 60% decline was observed in cells treated with higher concentrations of nevirapine or nelfinavir. In contrast, the basal rate of protein synthesis was not affected when cells were incubated with these compounds for 24 hr. Therapeutic concentrations of nelfinavir and nevirapine did not impair the anabolic effect of insulin on protein synthesis. However, zidovudine suppressed the stimulatory effect of insulin. The decreased protein synthesis induced by nelfinavir and zidovudine was associated with decreases in the phosphorylation of the S6 ribosomal protein (rpS6) and the repressor binding protein 4EBP1, while the inhibitory effect of nevirapine was mainly associated with a decline in phosphorylated 4EBP1. In conclusion, nelfinavir, nevirapine, and zidovudine treatments decreased protein synthesis in myocytes and this effect was correlated with a reduction in the phosphorylation level of proteins that regulate translation initiation.

HIV-1 protease inhibitor induces growth arrest and apoptosis of human prostate cancer LNCaP cells in vitro and in vivo in conjunction with blockade of androgen receptor STAT3 and AKT signaling

This study found that the HIV-1 protease inhibitor nelfinavir (NFV) induced growth arrest and apoptosis of human prostate cancer cells (LNCaP, DU145 and PC-3 cells), as measured by MTT and terminal deoxyribonucleotide transferase-mediated dUTP nick end labeling (TUNEL) assays, respectively, on the third day of culture. In addition, NFV blocked androgen receptor (AR) signaling in association with downregulation of nuclear levels of AR in LNCaP cells as measured by reporter assay and western blot analysis. As expected, NFV downregulated the level of the AR target molecule prostate specific antigen in these cells. Moreover, NFV disrupted STAT3 signaling; protease inhibitors blocked interleukin-6-induced phosphorylation of STAT3 and inhibited STAT3 DNA binding activity in LNCaP and DU145 cells, as measured by western blot analysis and enzyme-linked immunosorbent assay (ELISA), respectively. Furthermore, NFV blocked AKT signaling in prostate cancer cells as measured by kinase assay with glycogen synthase kinase-3alpha/beta as a substrate. Importantly, NFV inhibited the proliferation of LNCaP cells presented as tumor xenografts in BALB/c nude mice without side-effects. Taken together, NFV inhibited the proliferation of prostate cancer cells in conjunction with blockade of signaling by AR, STAT3, and AKT, suggesting that this family of compounds might be useful for the treatment of individuals with prostate cancer.

HIV Protease Inhibitors: Suppression of Insulin Secretion by Inhibition of Voltage-Dependent K+Currents and Anion Currents

We have shown before that the human immunodeficiency virus (HIV) protease inhibitors ritonavir and nelfinavir, but not indinavir, suppress insulin secretion from mouse pancreatic B-cells via reduction of the cytosolic free calcium concentration ([Ca(2+)](c)). This was not because of an effect on ATP-dependent K(+) channels (K(ATP) channels) or L-type Ca(2+) channels. The study was intended to elucidate the mechanisms by which distinct HIV protease inhibitors decrease [Ca(2+)](c) and thus evoke their adverse side effect on insulin release. Membrane potential and whole-cell currents were measured with the patch-clamp technique, and [Ca(2+)](c) was determined with a fluorescence dye. Ritonavir and nelfinavir both inhibited the same component(s) of voltage-dependent K(+) currents with a concomitant change in action potential wave form, whereas indinavir was ineffective. Comparison with other blockers of voltage-dependent K(+) currents revealed that suppression of distinct noninactivating current component(s) altered action potential wave form and decreased [Ca(2+)](c) similar to ritonavir and nelfinavir, whereas blockage of inactivating component(s) was without effect. Complete inhibition of voltage-dependent K(+) currents by 80 mM TEA(+) drastically increased [Ca(2+)](c), demonstrating that voltage-dependent K(+) channels are not the sole target of ritonavir and nelfinavir. Accordingly, the Ca(2+)-lowering effect of ritonavir was preserved in the presence of 80 mM TEA(+). This effect was mimicked by the anion channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). Consequentially, ritonavir and nelfinavir inhibited a DIDS-sensitive anion current in B-cells. We suggest that ritonavir and nelfinavir decrease insulin secretion by inhibition of voltage-dependent K(+) channels and anion channels, which are essential to provide counterion currents for Ca(2+) influx across the plasma membrane.

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.

Genital HIV-1 viral load is correlated with blood plasma HIV-1 viral load in Brazilian women and is reduced by antiretroviral therapy

CONTEXT

Cervicovaginal secretions represent the primary vehicle in mother to infant and sexual HIV-1 transmission. Understanding the viral dynamics in this compartment is important to improve interventions to decrease HIV transmission.

OBJECTIVES

To evaluate the correlation of HIV-1 blood plasma viral load and cervicovaginal HIV-1 viral load and the effect of antiretroviral therapy (ART) on cervicovaginal HIV-1 viral load.

METHODS

A cross-sectional study among HIV-1 infected women recruited between February 2002 and January 2003 and a longitudinal study that included 11 women who initiated ART were performed. HIV-1 viral load was measured in the female genital tract and in blood plasma using the Nuclisens assay before and 1 month after ART introduction.

RESULTS

HIV-1 viral load in cervicovaginal lavage was significantly correlated with HIV-1 blood plasma viral load (n = 27, Spearman rho = 0.73, p<0.001). In the longitudinal study, antiretroviral therapy was associated with a reduction of 1.44 log10 on genital HIV-1 viral load (95% CI = 0.57-2.30, p = 0.004, Student's t-test).

CONCLUSIONS

HIV-1 viral load in female genital secretions is correlated with blood plasma HIV-1 viral load. Antiretroviral therapy substantially reduces HIV-1 viral load in the female genital tract.

Phenotypic hypersusceptibility to multiple protease inhibitors and low replicative capacity in patients who are chronically infected with human immunodeficiency virus type 1

Increased susceptibility to the protease inhibitors saquinavir and amprenavir has been observed in human immunodeficiency virus type 1 (HIV-1) with specific mutations in protease (V82T and N88S). Increased susceptibility to ritonavir has also been described in some viruses from antiretroviral agent-naive patients with primary HIV-1 infection in association with combinations of amino acid changes at polymorphic sites in the protease. Many of the viruses displaying increased susceptibility to protease inhibitors also had low replication capacity. In this retrospective study, we analyze the drug susceptibility phenotype and the replication capacity of virus isolates obtained at the peaks of viremia during five consecutive structured treatment interruptions in 12 chronically HIV-1-infected patients. Ten out of 12 patients had at least one sample with protease inhibitor hypersusceptibility (change </=0.4-fold) to one or more protease inhibitor. Hypersusceptibility to different protease inhibitors was observed at variable frequency, ranging from 38% to amprenavir to 11% to nelfinavir. Pairwise comparisons between susceptibilities for the protease inhibitors showed a consistent correlation among all pairs. There was also a significant relationship between susceptibility to protease inhibitors and replication capacity in all patients. Replication capacity remained stable over the course of repetitive cycles of structured treatment interruptions. We could find no association between in vitro replication capacity and in vivo plasma viral load doubling time and CD4(+) and CD8(+) T-cell counts at each treatment interruption. Several mutations were associated with hypersusceptibility to each protease inhibitor in a univariate analysis. This study extends the association between hypersusceptibility to protease inhibitors and low replication capacity to virus isolated from chronically infected patients and highlights the complexity of determining the genetic basis of this phenomenon. The potential clinical relevance of protease inhibitor hypersusceptibility and low replication capacity to virologic response to protease inhibitor-based therapies deserves to be investigated further.

In vitro anti-HIV potency of stampidine alone and in combination with standard anti-HIV drugs

The purpose of the present study was compare the in vitro anti-HIV potency stampidine (CAS 217178-62-6), a novel aryl phosphate derivative of stavudine (CAS 3056-17-5), and drug combinations containing stampidine to the anti-HIV tency of the standard drugs zidovudine (CAS 30516-87-1), stavudine, lamivudine (CAS 134678-17-4), nelfinavir (CAS 159989-65-8), and nevirapine (CAS 129618-40-2) as well as their combinations. Stampidine inhibited the laboratory HIV-1 strain HTLV(IIIB) (B-envelope subtype) as well as the primary clinical HIV-1 isolates BR/92/025 (C-envelope subtype) and BR/93/20 (F-envelope sub-type) with subnanomolar IC50 values. Stampidine was as effective as zidovudine against HTLV(IIIB) and BR/92/025 and 3-logs more effective than zidovudine against BR/93/20. Stampidine was more effective than stavudine, lamivudine, nelfinavir, and nevirapine against all three HIV-1 isolates. The combination of stampidine with zidovudine + lamivudine was more effective than the combination of nelfinavir or nevirapine with zidovudine lamivudine against all three HIV-1 isolates. The combination of stampidine with nelfinavir was more effective than zidovudine + lamivudine as well as the combination of zidovudine + lamivudine with nelfinavir. The combination of stampidine with lamivudine + nelfinavir was more effective than the combination of zidovudine with lamivudine + nelfinavir. The combination of stampidine with lamivudine + nevirapine was more effective than the combination of stavudine with lamivudine + nevirapine. These findings demonstrate that (a) stampidine, as well as its combinations with the standard anti-HIV drugs zidovudine, lamivudine, nelfinavir or nevirapine, are potent inhibitors of HIV-1 replication in human peripheral blood mononuclear cells, and (b) replacement of either zidcovudine, zidovudine+lamivudine or stavudine in 3-drug cocktails with stampidine resulted in greater anti-HIV potency in vitro.

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.

Diverse pattern of protease inhibitor resistance mutations in HIV-1 infected patients failing nelfinavir

The aim of the study was to describe the pattern of resistance mutations in human immunodeficiency virus type 1 (HIV-1) infected patients experiencing their first protease inhibitor (PI) failure on nelfinavir (NFV)-containing therapy. Earlier PI-naïve patients (n=172) with NFV-containing therapy were therefore retrospectively studied. Plasma HIV RNA from 43 failing patients was sequenced. In addition, virus from the baseline was sequenced in 29 patients. Failure was defined as two consecutive measurements of viral load of >50 copies/ml after 6 months treatment. Subtyping was done in most patients (n=118). At baseline, the V82A mutation was found in four PI-naïve patients of whom two failed therapy exhibiting this mutation. At therapy failure, 17 of the 43 (40%) patients had primary PI mutations. In nine subjects, RTI-mutations only were found and 17 patients had a wild-type virus. Patients with primary PI and/or RTI mutations had a higher viral load at failure than those who failed with wild-type virus. A surprisingly diverse pattern of primary PI mutations was seen: M46I (n=7), D30N (n=6), L90M (n=5), and V82A (n=4). Four patients exhibited more than one primary PI mutation. PI-naïve patients in Sweden may harbor PI-resistant virus and resistance testing should be considered before treatment. Patients who fail NFV may develop the M46I mutation, which has been related earlier to mainly other PI. The diverse pattern of the evolved PI-mutations and the relative low occurrence of the D30N mutation in the material was unexpected and did not seem to be related to the viral subtype.

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 (ddl+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. Mitochorldrial 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 ddl+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.

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.