Netrin-1 feedforward mechanism promotes pancreatic cancer liver metastasis via hepatic stellate cell activation, retinoid, and ELF3 signaling

The biology of metastatic pancreatic ductal adenocarcinoma (PDAC) is distinct from that of the primary tumor due to changes in cell plasticity governed by a distinct transcriptome. Therapeutic strategies that target this distinct biology are needed. We detect an upregulation of the neuronal axon guidance molecule Netrin-1 in PDAC liver metastases that signals through its dependence receptor (DR), uncoordinated-5b (Unc5b), to facilitate metastasis in vitro and in vivo. The mechanism of Netrin-1 induction involves a feedforward loop whereby Netrin-1 on the surface of PDAC-secreted extracellular vesicles prepares the metastatic niche by inducing hepatic stellate cell activation and retinoic acid secretion that in turn upregulates Netrin-1 in disseminated tumor cells via RAR/RXR and Elf3 signaling. While this mechanism promotes PDAC liver metastasis, it also identifies a therapeutic vulnerability, as it can be targeted using anti-Netrin-1 therapy to inhibit metastasis using the Unc5b DR cell death mechanism.

Abstract 1286: UNC5B promotes EMT and metastasis of pancreatic adenocarcinomas and expresses different isoforms that impact sensitivity to Netrin-1 blockade

The axonal guidance receptor UNC5B is considered to be a tumor suppressor because it promotes apoptosis in the absence of its protein ligand, NTN1. But we find that UNC5B is not a tumor suppressor of pancreatic ductal adenocarcinomas (PDAC), and instead promotes metastasis. In TCGA data, UNC5B expression associates with poor patient outcome. In vivo, pancreatic cancer metastasis was completely eliminated by knocking out UNC5B from the genetically engineered KPC mouse model of PDACs, and was reduced upon knockout of UNC5B in a splenectomy model of liver metastasis. An inhibitor of NTN1, NP137, also reduced metastasis in vivo. In vitro, knockout of UNC5B from mesenchymal pancreatic cell lines was sufficient to reduce many metastatic traits including invasiveness, EMT, and aerobic glycolysis. YAP1 is a known target of UNC5B and was overexpressed in high UNC5B expressing cell lines, which were sensitive to the YAP1 inhibitor CA3. NP137 is currently in clinical trial for several tumor types and we have been investigating which patients might respond best to this drug. Using an antibody (D9M7Z) that recognizes an epitope in UNC5B that overlaps with the caspase-3 cleavage site that is critical for UNC5B's apoptotic functions, we found two isoforms in murine and human PDACs: one isoform that contains the caspase-3-containing epitope as well as a previously-unreported isoform that to lack it. Cells expressing the caspase-3 site were much more sensitive to NP137. We also discovered genetic alterations in patient samples that induce expression of UNC5B. For instance, UNC5B was recurrently amplified in PDACs and these amplifications were highly focal to the UNC5B locus; also, UNC5B expression was increased by mutations of ARID1A, a component of the SWI/SNF transcription complex that is recurrently mutated in pancreatic adenocarcinomas. ARID1A mutations caused cell lines to become mesenchymal, but the cells returned to an epithelial phenotype upon knockout of UNC5B. In current and future clinical trials, NP137 may particularly benefit patients with tumors that harbor mutations in ARID1A or ARID1B, focal amplifications of UNC5B, and/or high expression of the caspase-3-containing isoform of UNC5B.

Citation Format: Chris R. Harris, Orjola Prela, Lan Wang, Anthony Casabianca, Wade Narrow, Zachary Sechrist, Tracy Withers, Cory Shields, Asra Asad, Aram Hezel, Darren Carpizo. UNC5B promotes EMT and metastasis of pancreatic adenocarcinomas and expresses different isoforms that impact sensitivity to Netrin-1 blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1286.

Abstract 1287: DEC2, a circadian rhythm transcription factor, promotes growth, metastasis and dormancy by facilitating immune cell invasion through decreasing cell surface expression of MHC-1 in a novel model of pancreatic cancer dormancy

Latent recurrence following curative-intent pancreatic cancer surgery is a major clinical problem thought to be due to the reactivation of dormant tumor cells that disseminate before the primary tumor has been removed. How dormancy is established and ultimately reversed to drive recurrence is poorly understood. Here we introduce a novel mouse model of pancreatic cancer dormancy in which we establish distal pancreatic tumors by orthotopic injection, resect them four weeks later and then follow the mice for recurrence. We observed recurrence patterns and survival outcomes that mimic human patients undergoing surgery for pancreatic cancer where two thirds of the mice succumb to early metastatic recurrence (median survival 26 days) and one third of the mice (called dormant mice) live substantially long (median survival 554 days) without clinic evidence of disease yet harbor disseminated tumor cells in most organs of the body. Disseminated tumor cells isolated from the livers of dormant mice were quiescent, exhibited stem cell properties and upregulated the expression of Dec2, a circadian rhythm gene. Overexpression of Dec2 induced quiescence suggesting that it may be a driver of the dormant phenotype. Curiously, endogenous Dec2 actually increased the growth and metastasis of nondormant tumors. Dec2WT and Dec2 knockout cell lines were used to generate resectable orthotopic tumors in immune-competent mice, and loss of Dec2 decreased tumor growth, dissemination and metastasis, and the median survival of mice with DecWT tumors was 25 days whereas 70% of the mice with the otherwise isogenic Dec2KOs were still alive after 200 days. Notably, these differences in tumor size, dissemination, metastasis and survival were abrogated in nude mice, indicating an immune mediated mechanism. Dec2WT and Dec2KO cell lines expressed the same total amount of the antigen-presenting protein MHC-1, but much more of the MHC-1 was present on the surface of Dec2KO cell lines than on the Dec2WT cell lines. MHC-1 requires peptide loading before transport to the cell surface, and we see evidence for reduced production of small peptides in the DecKO cells. For instance the half-life of luciferase, a very potent immunogen in mice, was reduced in the Dec2KO cells, potentially providing small peptides for MHC-1 biosynthesis. Protein turnover may be upregulated to compensate for increases in translation, as ribosomal genes are more highly expressed in Dec2KO cells, including many c-Myc pathway genes. Indeed, Western blot analysis revealed upregulation of c-Myc protein in Dec2KO cells. These data suggest that Dec2 plays a novel role in the immune system by decreasing MHC-1 cell surface expression through decreasing peptide generation, protein translation and turnover.

Citation Format: Chris R. Harris, Crissy Dudgeon, Orjola Prela, Lan Wang, Anthony Casabianca, Juliana Cazarin de Menezes, Christina Davidson, Paula Vertino, Brian Altman, Darren Carpizo. DEC2, a circadian rhythm transcription factor, promotes growth, metastasis and dormancy by facilitating immune cell invasion through decreasing cell surface expression of MHC-1 in a novel model of pancreatic cancer dormancy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1287.

A review of hepatic epithelioid hemangioendothelioma-Analyzing patient characteristics and treatment strategies

BACKGROUND

Hepatic epithelioid hemangioendothelioma (HEH) is a rare vascular tumor of unknown etiology and unpredictable natural history. To date, no large-scale studies have been published evaluating this disease due to its rare occurrence.

METHODS

The National Cancer Database was reviewed between 2004 and 2016 to identify patients with HEH. Univariate analysis with overall survival (OS) was performed by Cox proportional hazards model. Kaplan-Meier method was used to create OS curves and compared using the log-rank test.

RESULTS

We identified 229 patients with HEH. The majority of patients were female (61.1%), white (84.3%), and had a Charlson-Deyo score of 0 (75%). Chemotherapeutic intervention was seen in 26% of the patients while 33% received surgical intervention in the form of wedge/segmental liver resection (n = 27), hepatectomy lobectomy/extended lobectomy (n = 18), and liver transplant (n = 22). Five-year survival in surgical patients was 90.5%, 66.5% and 81%, respectively (p = 0.485). Age greater than 55 years (hazard ratio [HR], 2.78; p < 0.001), Asian ethnicity compared to white (HR, 2.84; p = 0.012), and a higher Charlson-Deyo score (score 1: HR, 2.28; p < 0.001 and score ≥2: HR, 2.76; p = 0.011) were associated with worse OS.

CONCLUSION

Treatment for HEH remains variable with only a third of the patients undergoing surgery. International collaboration is necessary to determine the optimal treatment for this rare disease.

Abstract B021: The axon guidance receptor UNC5B is a driver of pancreatic cancer metastasis

Axon guidance pathways have often been linked to tumorigenesis by informatics analyses, but their roles in tumorigenesis are not well understood at a functional level. Here we show that axon guidance receptor UNC5B and its ligand, NTN1, promote the metastasis of pancreatic ductal adenocarcinomas (PDACs) by reducing anoikis and by promoting a mesenchymal phenotype. In vivo, removal of two floxed UNC5B alleles eliminated PDAC metastasis in the genetically engineered KPC mouse model, and also reduced metastasis by xenografted PDAC cell lines. PDAC metastasis also decreased upon treatment of animals with NP137, an antibody that targets NTN1. In vitro, deletion of UNC5B from pancreatic adenocarcinoma cell lines reduced invasiveness, and was sufficient to convert PDAC cell lines from an epithelial to a mesenchymal state. UNC5B also increased YAP1 expression but decreased anoikis; anoikis could then be restored by treatment with the YAP1 inhibitor CA3. Clinically, UNC5B expression associated with poor outcomes in patients with pancreatic adenocarcinomas. UNC5B and NTN1 expression increased upon truncation of the SWI/SNF component ARID1A, which is recurrently mutated in PDACs. Highly focal amplifications of UNC5B were also observed in some patient samples, and were mutually exclusive with mutations in ARID1A or ARID1B. NP137 is currently in clinical trials for various cancers, and may benefit pancreatic adenocarcinoma patients, particularly those with UNC5B amplifications or with ARID1A/ARID1B mutations.

Citation Format: Chris Harris, Anthony Casabianca, Zach Sechrist, Cory Shields, Wade Narrow, Tracy Withers, Crissy Dudgeon, Mike O'Dell, Aram Hezel, Darren Carpizo. The axon guidance receptor UNC5B is a driver of pancreatic cancer metastasis [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr B021.

Abstract B020: Retinoic acid produced by hepatic stellate cells facilitates Netrin-1 mediated pancreatic cancer metastasis

A hallmark of pancreatic ductal adenocarcinoma (PDAC) is its proclivity for metastasis as evidenced by the fact that 85% are stage IV at diagnosis. This highlights the need to better understand the biology of metastatic PDAC and identify novel therapies for this patient population. Axon guidance genes have been shown to be involved in PDAC progression, but their role is unclear. We have investigated the role of the axon guidance molecule Netrin-1 and its receptors Unc5b and DCC in PDAC. We found that in both murine and human samples that NTN1 expression is increased in metastatic PDAC and the quasi-mesenchymal subtype. Murine and TCGA data indicate that Unc5b is the dominant NTN1 receptor and genetic knock-down (KD) or knock-out (KO) of either Netrin-1 or Unc5b decreases migration, invasion, and cell survival in vitro and hepatic metastatic growth in vivo. The mechanism of Netrin-1 upregulation in metastatic PDAC is unknown. We found that hepatic stellate cell (HSC) secreted retinoic acid upregulates NTN1 through both an RXR/RAR and Elf mediated mechanism. To determine if NTN1 is involved in the process of HSC activation we found that recombinant NTN1 added to HSCs in vitro induced activation. We examined the livers of mice harboring orthotopic PDAC tumors using murine pancreatic cancer lines that were either NTN1 wild type (WT) or KO, and found that the NTN-expressing lines increased HSC activation providing evidence that NTN1 is important for long distance intercellular communication between primary pancreatic tumors and the pre-metastatic liver. We detected NTN1 within extracellular vesicles, and mice pre-conditioned with EVs from NTN1 KO cells demonstrated a decreased metastatic burden as compared mice preconditioned with NTN1 WT cells. Treatment of several murine PDAC models (autochthonous and metastatic) with a monoclonal antibody to NTN1 led to decreased metastases and increased survival. These studies reveal that NTN1 is upregulated in metastatic PDAC mediated by a novel mechanism that involves EVs, HSC activation and RXR/RAR signaling. These studies provide pre-clinical evidence to support a human clinical trial of anti-NTN1 therapy in PDAC.

Citation Format: Crissy Dudgeon, Anthony Casabianca, Chris Harris, Igor Astsaturov, Charline Ogier, Xiaoyang Su, Jason Pitarresi, Wade Narrow, Fady Soliman, Tracy Withers, Patrick Mehlen, Darren Carpizo. Retinoic acid produced by hepatic stellate cells facilitates Netrin-1 mediated pancreatic cancer metastasis [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr B020.

Efficacy and Toxicity of Long-Term Administration of 2′,3′-dideoxycytidine in the LP-BM5 Murine-Induced Immunodeficiency Model

The LP-BM5 murine retrovirus-induced immunodeficiency model was used to evaluate the efficacy and toxicity of long-term 2′,3′-dideoxycytidine (DDC) therapy. A mean plasma drug concentration of 0.2 + 0.02 μm of DDC for 3 months was found to reduce splenomegaly, lymphoadenopathy and hypergammaglobulinemia in infected mice. However, DDC also reduced spleen weight in control mice and spleen haemopoiesis in both infected and uninfected animals. In the bone marrow the most prominent feature of DDC treatment was a marked reduction of megakariocytes, while in the liver an hepatocellular vacuolation was evident in uninfected animals. DDC reduced, but did not prevent, LP-BM5 integration in lymph node DNA and Pr 60gag expression in spleen lymphocytes and bone marrow cells. Furthermore, DDC reduced the mitochondrial DNA content and restored the mitogen proliferation of T cells but not that of B cells in infected mice. Thus, DDC appears to be of some, but limited, efficacy in murine AIDS, with a toxicity profile involving more cell types than previously thought.

The Inhibitory Effect of ddC on Human Immunodeficiency Virus Replication Diminishes in Cells that are Chronically Exposed to the Drug

One possible explanation for the failure of human immunodeficiency virus type 1 (HIV-1) antiretroviral inhibitors to block the clinical progression of the infection may be a failure to maintain adequate drug levels at the site of viral replication. We have previously found that exposure of human monoblastoid cells (U937) for several months to a therapeutically relevant concentration (0.1 μM) of 2′,3′-dideoxycytidine (zalcitabine, ddC) allowed the isolation of a drug-resistant cell line characterized by a normal drug transport but a reduced ability to accumulate 2′,3′-dideoxycytidine 5′-triphosphate (the active antiretroviral form of the drug). In this paper we show that the drug-resistant cells were indistinguishable from normal cells in terms of surface CD4 receptors. The susceptibility of parental and ddC-resistant U937 cells to infection by HIV-1 was similar, as measured by proviral DNA formation. However, HIV-1 p24 production and the number of infectious virus particles produced were significantly lower in the drug-resistant compared to control cells. Addition of 0.1 μM ddC inhibited viral production by up to 92% in the control cells but had no effect on ddC-resistant cells. Thus, human cells exposed to therapeutically relevant ddC concentrations for several months show a reduced ddC anabolism and allow ddC-sensitive HIV-1 to replicate in the presence of inhibitory ddC concentrations.

Inhibition of HIV-1 and LP-BM5 Replication in Macrophages by Dideoxycytidine and Dideoxycytidine 5′-Triphosphate

The antiviral agent 2′,3′-dideoxycytidine (ddC) has been shown to be active against HIV-1 infectivity. However, conflicting results have been reported concerning its efficacy in macrophages. Because macrophages possess low levels of the kinase(s) responsible for ddC phosphorylation, we investigated the ability of ddC and 2′,3′-dideoxycytidine 5′-trisphosphate (ddCTP) to suppress HIV-1 and LP-BM5 replication in these cells. Retrovirus replication was only partially inhibited in the two systems investigated by a high (1 μM) ddC concentration. The direct administration of ddCTP, using autologous red blood cells as a delivery system, was found to inhibit HIV-1 and LP-BM5 replication by more than 90% in macrophages without affecting major cell functions. These data, together with those already reported for FIV [Magnani et al. (1994) AIDS Res Hum Retroviruses 10: 1179-1186], suggest that the anabolic phosphorylation of ddC is an important determinant of its anti-HIV activity and that pharmacological interventions that modulate ddC metabolism may be useful for improving its antiretroviral activity in macrophages.

Effect of macrophage depletion on viral DNA rebound following antiretroviral therapy in a murine model of AIDS (MAIDS)

In the attempt to eradicate HIV-1 infection, a strategy to eliminate macrophages, one of the most important cellular reservoirs in sustaining virus replication during HAART, could be of great benefit in the suppression of viral rebound. Aware of the ability of clodronate to cause macrophage depletion, the effect of the administration of clodronate encapsulated in erythrocytes on disease progression and on viral rebound was evaluated in a murine model of AIDS (MAIDS). One group of LP-BM5 retroviral complex-infected C57BL/6 mice received oral administrations of azidothymidine and dideoxyinosine daily for 12 weeks; two other groups received in addition, either clodronate-loaded erythrocytes or free clodronate at 7-10 day intervals. At the end of the treatment, the three groups maintained parameters characterizing disease progression similar to those of uninfected mice and showed a significantly lower level of BM5d DNA than infected mice in all organs and cells tested. To assess the viral rebound, some animals were left for an additional 4 month period without any treatment. After this time, the BM5d DNA content in blood leukocytes increased in all groups, but the group having received clodronate-loaded erythrocytes, in addition to transcriptase inhibitors, showed a significant delay in viral rebound.

Inhibition of murine AIDS by pro-glutathione (GSH) molecules

Antioxidant molecules can be used both to replenish the depletion of reduced glutathione (GSH) occurring during HIV infection, and to inhibit HIV replication. The purpose of this work was to assess the efficacy of two pro-GSH molecules able to cross the cell membrane more easily than GSH. We used an experimental animal model consisting of C57BL/6 mice infected with the LP-BM5 viral complex; the treatments were based on the intramuscular administration of I-152, a pro-drug of N-acetylcysteine and S-acetyl-beta-mercaptoethylamine, and S-acetylglutathione, an acetylated GSH derivative. The results show that I-152, at a concentration of 10.7 times lower than GSH, caused a reduction in lymph node and spleen weights of about 55% when compared to infected animals and an inhibition of about 66% in spleen and lymph node virus content. S-acetylglutathione, at half the concentration of GSH, caused a reduction in lymph node weight of about 17% and in spleen and lymph node virus content of about 70% and 30%, respectively. These results show that the administration of pro-GSH molecules may favorably substitute for the use of GSH as such.

Antiviral and immunomodulatory properties of new pro-glutathione (GSH) molecules

Reduced glutathione (GSH) is present in millimolar concentrations in mammalian cells. It is involved in many cellular functions such as detoxification, amino acid transport, production of coenzymes, and the recycling of vitamins E and C. GSH acts as a redox buffer to preserve the reduced intracellular environment. Decreased glutathione levels have been found in numerous diseases such as cancer, viral infections, and immune dysfunctions. Many antioxidant molecules, such as GSH and N-acetylcysteine (NAC), have been demonstrated to inhibit in vitro and in vivo viral replication through different mechanisms of action. Accumulating evidence suggests that intracellular GSH levels in antigen-presenting cells such as macrophages, influence the Th1/Th2 cytokine response pattern, and more precisely, GSH depletion inhibits Th1-associated cytokine production and/or favours Th2 associated responses. It is known that GSH is not transported to most cells and tissues in a free form. Therefore, a number of different approaches have been developed in the last years to circumvent this problem. This review discusses the capacity of some new molecules with potent pro-GSH effects either to exert significant antiviral activity or to augment GSH intracellular content in macrophages to generate and maintain the appropriate Th1/Th2 balance. The observations reported herein show that pro-GSH molecules represent new therapeutic agents to treat antiviral infections and Th2-mediated diseases such as allergic disorders and AIDS.

Macrophage protection by addition of glutathione (GSH)-loaded erythrocytes to AZT and DDI in a murine AIDS model

Monocyte-macrophages play a central role in HIV-1 infection because they are among the first cells to be infected and because later they are important reservoirs for the virus. Thus, newly designed therapies should take into account the protection of this cell compartment. Herein, we report the results obtained in a murine AIDS model, by the addition to AZT+DDI of a system (GSH-loaded erythrocytes) able to protect macrophages against HIV-1 infection. Five groups of LP-BM5-infected mice were treated as follows: one group was treated by AZT, one group was treated by DDI, one group was treated by the combination of both, another by GSH-loaded erythrocytes, and finally, one by the combination of all three. After 10 weeks of infection the parameters of the disease were studied and the proviral DNA content in different organs and in macrophages of bone marrow and of the peritoneal cavity was quantified. The results obtained show that mice treated with AZT+DDI+GSH-loaded erythrocytes showed proviral DNA content in the brain and in macrophages of bone marrow that was significantly lower than in mice treated with AZT+DDI. This study may help developing strategies aimed at blocking HIV-1 replication in its reservoirs in the body.

New drug combinations for the treatment of murine AIDS and macrophage protection

The failure of highly active antiretroviral therapies (HAART) is mainly due to the existence of latent infected reservoirs, such as macrophages and resting CD4+ T cells. In this paper, we report the results that we obtained in a murine model of AIDS by alternating the administration of the lympholitic drug 2-Fluoro-ara-AMP (Fludarabine) to eliminate the infected cells, with that of Azidothymidine (AZT) plus reduced glutathione (GSH) encapsulated in erythrocytes, to protect lymphocytes and macrophages not yet infected, respectively. Two groups of infected mice were treated as follows: one group was treated by alternating the administration of Fludarabine and AZT (treatment A), while the other group received the same treatment plus GSH-loaded erythrocytes given with AZT (treatment A + L-RBC). Fludarabine was administered intraperitoneally, AZT in the drinking water and GSH was encapsulated in erythrocytes by a procedure of hypotonic dialysis and isotonic resealing. The results obtained show that GSH-loaded erythrocytes provide additive effects in all the parameters examined. Alternation of a lympholitic drug and antiretroviral drug is effective in reducing the progression of murine AIDS. Addition of a system to protect macrophages provides additive effects in almost all the parameters considered, confirming that combination therapies aimed at protecting different infectable cell compartments are better than treatments protecting mainly lymphocytes.

Inhibition of murine AIDS by alternate administration of azidothymidine and fludarabine monophosphate

Anti-HIV-1 combination therapies, including protease and reverse transcriptase inhibitors, can reduce plasma viremia to undetectable levels within the first 2 weeks of treatment. This reduction is followed by a slower decline that primarily results from the presence of viral reservoirs such as CD4+ memory cells, dendritic cells, and macrophages. For this reason, we evaluated a new drug combination therapy that includes a lympholytic drug: (2-fluoro-ara-AMP, fludarabine) to eliminate cells already infected and an antiviral drug (azidothymidine [AZT]) to protect cells not yet infected. We used C57BL/6 mice infected with the retroviral complex LP-BM5, which developed severe immunodeficiency (i.e., murine AIDS), to select the most effective fludarabine regimen to inhibit disease progression, and then to evaluate the efficacy and toxicity of the fludarabine and AZT combinations. The results obtained show that intraperitoneal administration of fludarabine at 3 mg/mouse twice a day for 4 weeks is the most effective regimen in reducing splenomegaly, lymphadenopathy, hypergammaglobulinemia, and proviral DNA content in spleen and lymph nodes and in restoring the architecture of lymph nodes. Subsequently, we evaluated the combined or sequential administration of fludarabine and AZT. The data reported in this paper show that the sequential administration of the two drugs provides additive antiviral effects that reduce spleen and lymph node weights to normal values and proviral DNA content by approximately 95% in all infected organs; the phenotypes of blood T and B cells moved toward control values, although the number of B cells was significantly reduced by fludarabine treatment. Finally, we evaluated the outcome of the disease after suspension or continuation of different treatment regimens. In all treatment groups, the disease progressed and increased proviral DNA content was found in infected organs, but animals receiving the sequential administration of fludarabine and AZT were less affected than those receiving only fludarabine or the simultaneous administration of both. The results obtained suggest that fludarabine could be part of a new therapeutic approach aiming at eradicating HIV from those cells that have been already infected and that are not protected by highly active antiretroviral therapy (HAART).

New treatment protocol including lympholytic and antiretroviral drugs to inhibit murine AIDS

Highly active antiretroviral therapy (HAART), although very efficient in reducing viral load to undetectable levels within 2 weeks, does not eradicate HIV-1 infection and after the suspension of therapy, HIV RNA rebounds to pretherapy levels. This limited efficacy is mainly due to the existence of viral reservoirs such as CD4+ T cells, macrophages, and dendritic cells in which the virus can remain latent. Elimination of these latent reservoirs would be a possible solution to this problem and various efforts are now being directed to this end. With this goal in mind, we investigated a lympholytic drug with known activity against lymphoproliferative malignancies, 2-fluoro-ara-AMP (fludarabine). The murine model of AIDS was used to evaluate the efficacy of alternating administration of fludarabine and azidothymidine (AZT). The aim of this experiment was to eliminate infected cells with fludarabine and protect noninfected cells with AZT. LP-BM5-infected mice were treated with two different therapeutic protocols: one group was treated with two alternating 3-week cycles of fludarabine and AZT (treatment A), whereas the other was treated with three alternating 2-week cycles of fludarabine and AZT (treatment B); both treatments lasted 12 weeks and the animals in the two groups received the same amount of drug. At different times of infection, disease-related findings (i.e., splenomegaly, lymphadenopathy, hypergammaglobulinemia, T-cell and B-cell spleen cell proliferative index, and phenotypes of peripheral blood lymphocytes) were analyzed and the content of proviral DNA in the lymph nodes was quantified. The results obtained show that treatment B was more effective in inhibiting disease progression than treatment A. In fact, all parameters investigated were almost within control values. These results were also confirmed by the quantification of proviral DNA content in the lymph nodes, which after 12 weeks of treatment A declined by approximately 50%, whereas treatment B decreased proviral DNA content by approximately 85% with respect to infected/untreated mice. The data obtained suggest that a therapeutic protocol including three cycles rather than two of a lympholytic drug and antiretroviral drugs is more advantageous. The efficacy of the treatment could likely increase if other drugs were used in addition to AZT and more cycles of fludarabine were added. This approach appears to be of potential interest in an HIV-1 eradication protocol.

Metabolism, mitochondrial uptake and toxicity of 2', 3'-dideoxycytidine

2',3'-Dideoxycytidine (ddCyd) is a prescription anti-retroviral drug that causes mitochondrial toxicity and peripheral neuropathy. ddCyd is actively phosphorylated by cytosolic deoxycytidine kinase and nucleoside (di)phosphate kinase to the 5'-triphosphate derivative. However, 2',3'-dideoxycytidine 5'-diphosphocholine (ddCDP-choline) was also found in human cells incubated with ddCyd. In this paper we show that ddCDP-choline is produced from dideoxyCTP (ddCTP) and phosphocholine by phosphocholine cytidylyltransferase. dCTP and CTP appear to activate this synthesis in a concentration-dependent manner. Although ddCTP and ddCDP-choline can both enter the mitochondria, ddCDP-choline uptake is more efficient than ddCTP uptake. These data suggest that ddCDP- choline is the ddCyd metabolite that is probably responsible for mitochondrial toxicity. The uptake of ddCTP and ddCDP-choline by mitochondria is inhibited by 3.0 mM l-carnitine in the cell-free system investigated; when added to U937 cells grown in the presence of 0.25 microM ddCyd, 3.0 mM l-carnitine partially abrogated the mitochondrial toxicity of ddCyd.

Role of macrophage protection in the development of murine AIDS

Macrophages play a key role in AIDS pathogenesis and thus controlling infectivity and viral replication in these cells is a key issue in any antiretroviral therapy. In the present study, using a murine model of AIDS, we evaluated new therapeutic approaches specifically designed for the protection of macrophages. Based on previous observations, we took advantage of the unique ability of autologous erythrocytes to deliver drugs selectively to macrophages. The antiviral drugs selected were a new homodimer of AZT (AZTp2AZT) and reduced glutathione (GSH). The addition of an oral drug for the protection of lymphocytes (i.e., AZT) was also investigated. C57BL/6 mice infected with the retroviral complex LP-BM5 were treated with GSH-loaded erythrocytes, GSH-loaded erythrocytes plus oral AZT, or GSH/AZTp2AZT-loaded erythrocytes plus oral AZT. The treatments including AZT and erythrocytes loaded with GSH alone or with GSH plus AZTp2AZT provided similar results and were most effective in inhibiting the progression of MAIDS; they reduced splenomegaly, lymphadenopathy, and hypergammaglobulinemia by about 70%, 90% and 83%, respectively, when compared with infected animals at 10 weeks postinfection. Evaluation of BM5d proviral DNA content in infected organs revealed that both treatments were able to almost completely protect most infected animals. They were also able to normalize the blood lymphocyte phenotype and to restore the responses of T and B cells to mitogens significantly. Treatment with GSH-loaded erythrocytes alone did not provide significant results for most parameters investigated, but a marked reduction in proviral DNA content was obtained in infected organs, including the brain. The results reported in this paper confirm the important role of macrophages in retroviral infection and moreover prove that erythrocytes, by selectively protecting these cells, strongly affect MAIDS progression. Furthermore, the combination of GSH- or GSH/AZTp2AZT-loaded erythrocytes with an oral nucleoside analogue (AZT) for the protection of lymphocytes provides additive responses in all the parameters investigated.

Protein degradation and apoptotic death in lymphocytes during Fiv infection: activation of the ubiquitin-proteasome proteolytic system

The movement of a cell through the sequential phases of apoptosis is accompanied by a progressive decrease in cell size with loss in protein mass. In lymphocytes from Hiv-infected persons, protein loss during apoptosis is due to increased protein degradation rather than decreased synthesis. To identify and characterize the proteolytic enzymes or enzyme systems involved in this process, we studied several features of protein turnover in lymphocytes from peripheral blood and lymph nodes during the natural and experimental infection by feline immunodeficiency virus (Fiv). This animal model allowed us to integrate in vivo results with in vitro observations of protein damage. Here we report that protein breakdown in apoptotic cells is concomitant with the activation of the ATP and ubiquitin-dependent multicatalytic system (proteasome). We suggest that proteasome activation is part of the proteolytic cascade in the execution phases of apoptosis in AIDS.

Liposomes as carriers of the antiretroviral agent dideoxycytidine-5'-triphosphate

The presence and replication of the human immunodeficiency virus (HIV) in cells of the mononuclear phagocyte system (MPS) together with the preferential uptake of liposomes in macrophages suggest that liposomes can become a valuable carrier of anti-HIV agents. Moreover, liposomes reduce toxicity of encapsulated drugs and protect encapsulated drugs against rapid degradation in the blood circulation. To overcome problems associated with the administration of free nucleosides and to improve targeting to the MPS, dideoxycytidine-5'-triphosphate (ddCTP) was encapsulated in liposomes. Liposomes were stable with regard to retention of the entrapped drug, particle size and chemical stability of ddCTP. Results obtained with liposome encapsulated ddCTP in the murine acquired immunodeficiency syndrome (MAIDS) model indicate that ddCTP encapsulated in liposomes can reduce proviral DNA in cells of the mononuclear phagocyte system (MPS) in both spleen and bone marrow.

Competitive PCR for quantification of BM5d proviral DNA in mice with AIDS

Murine AIDS in C57BL/6 mice is caused by a unique mixture of murine leukemia viruses. We report the use of a competitive PCR to detect and quantitate BM5d proviral DNA. This assay allowed discrimination among endogenous wild-type murine retroviruses and BM5d sequences. Furthermore, the method was subsequently used to evaluate the amount of BM5d in infected mice and in infected AZT (zidovudine)-treated mice, providing an effective way to quantitatively evaluate drug efficacy in the murine AIDS model.

Inhibition of murine AIDS by a new azidothymidine homodinucleotide

A new antiretroviral drug (azidothymidine homodinucleotide, AZTp2AZT), designed for the protection of macrophages against retroviral infection, was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS) alone and in combination with oral azidothymidine (AZT). C57BL/6 mice were infected with the retroviral complex LP-BM5 and treated for 3 months by weekly administrations of 15 nmol of AZTp2AZT encapsulated into autologous erythrocytes for macrophage protection. AZTp2AZT treatment was found to reduce lymphoadenopathy (48%), splenomegaly (26%), and BM5d proviral DNA content in lymph nodes, spleen, and brain of 37%, 40%, and 36%, respectively, compared with untreated animals. AZT administration in drinking water (0.25 mg/ml) was more effective than administration of AZTp2AZT encapsulated into erythrocytes in reducing lymphoadenopathy, splenomegaly, gammaglobulinemia, and proviral DNA content in lymph nodes, but it caused a reduction in erythrocyte count and hematocrit levels. Although combined treatments do not provide additive responses in the several parameters investigated, they were found to be much more effective in reducing the proviral DNA content in brain (67%) than were monotherapies. Furthermore, no apparent signs of hematotoxicity were observed. Thus, macrophage delivery of antiviral drugs may contribute to brain protection from retroviral infections by mechanisms other than those exerted by oral AZT administration.

Antiretroviral effect of combined zidovudine and reduced glutathione therapy in murine AIDS

A combination of antiretroviral drugs acting at different points in the virus replication cycle was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS). Intramuscular administration of high doses of reduced glutathione (GSH, 100 mg/mouse/day) and AZT (0.25 mg/ml in drinking water) was found to reduce lymphoadenopathy (92%), splenomegaly (80%), and hypergammaglobulinemia (90%) significantly more than AZT alone. Combined treatment resulted in a reduction in proviral DNA content of 69, 66, and 60%, respectively, in lymph nodes, spleen, and bone marrow. Furthermore, the stimulation index of B cells was also significantly higher in animals receiving GSH and AZT whereas additional responses were not observed in the T cell stimulation index and blood lymphocyte phenotype analyses. In conclusion, the administration of high doses of GSH and AZT, a new combination of antiviral drugs, seems to provide additional advantages compared to single-agent therapy.

2',3'-Dideoxycytidine cytotoxicity in human macrophages

Human macrophages when cultured for several weeks in the presence of therapeutically relevant 2',3'-dideoxycytidine (ddC) concentrations show a time-dependent decay in mitochondrial DNA content. This decay is associated with a reduction of Rhodamine 123 fluorescence, a marker for mitochondrial membrane potential suggesting that impairment of mitochondrial functions occurs. Mitochondrial metabolic impairment was confirmed by direct evaluation of lactate production, which is markedly increased in cells treated with ddC. The activity of protein kinase C and intracellular free Ca2+ upon addition of phorbol 12-myristate 13-acetate (PMA) were lower in the drug-treated cells compared to controls. A 50% reduction in O2-release was also found upon PMA stimulation. Fluorescent latex beads, yeast and bacteria phagocytosis were normal, but intracellular bacteria killing was markedly impaired in ddC-exposed macrophages. Thus, ddC exerts a delayed mitochondrial toxicity also on differentiated macrophages with impairment of several metabolic properties and O2 production causing a reduced ability of these phagocytic cells to kill phagocytosed bacteria.

Targeting antiviral nucleotide analogues to macrophages

Macrophages are important target cells for human immunodeficiency virus type 1 (HIV-1) infection. We have developed a drug targeting system for the selective delivery of phosphorylated nucleoside analogues to these phagocytosing cells. This system is based on the possibility of encapsulating the phosphorylated drugs into autologous erythrocytes and on the subsequent selective modification of their membranes to promote macrophage recognition and phagocytosis. Targeted delivery of phosphorylated nucleoside analogues to human, feline, and murine macrophages inhibits the infectivity of HIV-1, feline immunodeficiency virus, and LP-BM5 viruses more efficiently than the administration of the corresponding nucleoside analogues. In vivo administration of 2',3'-dideoxycytidine 5'-triphosphate (ddCTP) encapsulated into autologous erythrocytes to LP-BM5-infected mice was found to reduce infectivity and disease progression. Furthermore, the simultaneous administration of AZT or ddC produced additive antiviral effects. The possibility of using red cells as drug targeting systems was useful for the design, synthesis, and delivery of new antiviral nucleoside analogues. As a prototype of these new drugs, di-(thymidine-3'-azido-2',3'-dideoxy-D-riboside)-5'-5'-p1-p2-pyrophospha te (AZTp2AZT) was prepared. Although this drug in solution has the same antiviral activity as AZT, when administered encapsulated into erythrocytes it was several times more efficient in inhibiting the infectivity of human, feline, and murine immunodeficiency viruses. Thus, the availability of a drug targeting system for the selective delivery of antivirals to macrophages offers an additional possibility for the development of new drugs and of new combination antiviral therapies.

Up-regulation of the ubiquitin-conjugating and proteolytic systems in murine acquired immunodeficiency syndrome

Lymphoproliferation, chronic B-cell activation resulting in hypergammaglobulinemia, and profound immunodeficiency are prominent features of retrovirus-induced murine acquired immunodeficiency syndrome (murine AIDS). Here we demonstrate that in murine AIDS the ATP-dependent and ubiquitin-dependent proteolytic system is strongly affected, at least in the lymph nodes of infected mice. Solid-phase immunochemical assays show that the ubiquitin-conjugate pools increase by about threefold 10 weeks after infection, then decline slightly 15 weeks after infection to a twofold increase. Accumulation of ubiquitin conjugates is accompanied by induction of the ubiquitin-conjugating pathway, involving several carrier-protein isozymes (E2), mainly 14-kDa E2 and 17-kDa E2. Furthermore, accumulation of ubiquitin conjugates and induction of the conjugating system are coincident with an increase in the proteolytic activity supported by the 26S proteolytic complex. However, 15 weeks after infection, when the conjugation rate and levels of ubiquitin conjugates decrease, proteasome activity returns to values similar to those of the control, suggesting that a higher proteosomal activity is no longer needed. The concerted induction of the ubiquitin-conjugating and proteolytic systems in murine AIDS apparently does not involve the breakdown of viral products nor is it supported by virus-coded events, but probably arises as a cellular response to viral infection.

Inhibition of murine AIDS by reduced glutathione

The imbalance of the redox state in cells and body fluids in HIV-1-infected patients may result in progression of the disease as well as in immunologic disfuctions. In this report, we have evaluated whether the direct administration of high doses of reduced glutathione (GSH) exerts any antiviral activity and/or improves immune functions in a murine immunodeficiency animal model. Intramuscular administration of 50 or 100 mg GSH/mouse for five consecutive days weekly to LP-BM5-infected mice did not show local or systemic signs of acute toxicity. During the first 3 weeks from infection, a period in which clinical signs of disease were not yet detectable, GSH significantly reduced the viral load in lymph nodes and spleen as evaluated by a PCR semiquantitative assay of the proviral DNA content. At 10 weeks a GSH concentration-dependent reduction of splenomegaly, lymphadenopathy and hypergammaglobulinemia was evident in all treated mice. Evaluation of proviral DNA content showed that GSH was effective in inhibiting LP-BM5 infectivity in lymph nodes, spleen, and bone marrow at 100 mg/day, while it was less effective when administered at 50 mg/day. At 10 weeks some animals receiving the highest GSH dose died, thus only the mice receiving 50 mg GSH were followed up to 15 weeks without signs of toxicity. In this case, almost not significant differences among infected untreated or treated animals were observed. Thus, GSH is effective in reducing the proviral DNA load in the first period of infection. These data and the failure of sulfhydril supplementation to further counteract the progression of disease after 10 weeks of infection suggest that combinations of GSH and other antiviral agents may be useful for improving current antiviral therapies.

Inhibition of murine AIDS by combination of AZT and dideoxycytidine 5'-triphosphate

SUMMARY

A combination of antiretroviral drugs acting on different cell types (lymphocytes and macrophages) was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS). In a first experiment, C57BL/6 mice were infected with a single i.p. administration of LP-BM5 and treated with 0.125 or 0.25 mg/ml AZT in drinking water for 3 months. AZT treatment was found to reduce lymphadenopathy (60 and 65 percent, respectively), splenomegaly (37 and 50 percent, respectively), and hypergammaglobulinemia (6 and 50 percent, respectively). Furthermore, at the highest AZT concentration, BM5d proviral DNA content in lymph nodes and in the spleen showed a reduction of 78 and 70 percent, respectively, compared to untreated animals. In a second experiment, infected mice were treated with AZT (0.25 mg/ml in drinking water) and with 2',3'-dideoxycytidine 5'-triphosphate (ddCTP) encapsulated into autologous erythrocytes for macrophage protection. Combined treatments resulted in a further reduction of lymphadenopathy (a further 33 percent with respect to the single treatment of AZT) and splenomegaly (a further 28 percent respect to the single treatment of AZT) but not of gammaglobulinemia. Proviral DNA in lymph nodes and spleen showed a reduction of 82 and 77 percent, respectively, compared to infected mice. Stimulation index of T cells was also significantly increased in animals receiving both treatments versus AZT only. In conclusion, the selective administration of antiviral drugs that preferentially protect different cell types seems to provide additional advantages compared to single-agent therapy.

Synthesis and targeted delivery of an azidothymidine homodinucleotide conferring protection to macrophages against retroviral infection

The infectivity and replication of human (HIV-1), feline (FIV), and murine (LP-BM5) immunodeficiency viruses are all inhibited by several nucleoside analogues after intracellular conversion to their triphosphorylated derivatives. At the cellular level, the main problems in the use of these drugs concern their limited phosphorylation in some cells (e.g., macrophages) and the cytotoxic side effects of nucleoside analogue triphosphates. To overcome these limitations a new nucleoside analogue homodinucleotide, di(thymidine-3'-azido-2',3'-dideoxy-D-riboside)-5'-5'-p1-p2-pyrophosphat e (AZTp2AZT), was designed and synthesized. AZTp2AZT was a poor in vitro inhibitor of HIV reverse transcriptase, although it showed antiviral and cytotoxic activities comparable to those of the parent AZT when added to cultures of a HTLV-1 transformed cell line. AZTp2AZT encapsulated into erythrocytes was remarkably stable. Induction of erythrocyte-membrane protein clusterization and subsequent phagocytosis of AZTp2AZT-loaded cells allowed the targeted delivery of this impermeant drug to macrophages where its metabolic activation occurs. The addition of AZTp2AZT-loaded erythrocytes to human, feline, and murine macrophages afforded almost complete in vitro protection of these cells from infection by HIVBa-L, FIV, and LP-BM5, respectively. Therefore, AZTp2AZT, unlike the membrane-diffusing azidothymidine, acts as a very efficient antiretroviral prodrug following selective targeting to macrophages by means of loaded erythrocytes.

2',3'-Dideoxycytidine metabolism in a new drug-resistant cell line

2',3'-Dideoxycytidine (ddC) is a nucleoside analogue that inhibits human immunodeficiency virus type 1 (HIV-1) replication in vitro and is currently used in the therapy of acquired immune deficiency syndrome (AIDS). This compound exerts a delayed cytotoxicity due to inhibition of mitochondrial DNA (mDNA) synthesis. Long-term exposure of U937 human monoblastoid cells to ddC resulted in a time- and concentration-dependent decrease in mDNA content and Rhodamine 123 fluorescence. However, after 2 months on 0.1 microM ddC, a drug-resistant cell line (U937-R) with 66% of the normal amount of mDNA was isolated. ddC transport in U937 and U937-R cell lines was similar. In contrast, U937-R accumulated ddC phosphorylated derivatives at a much lower rate and to a reduced concentration into acid-soluble material. The rate of 2',3'-dideoxycytidine 5'-triphosphate (ddCTP) formation in U937-R cells was almost one-third of that measured in normal cells, although the rate of ddCTP catabolism was similar in both cell lines. Dideoxyliponucleotide (ddCDP-choline and ddCDP-ethanolamine) formation was also much slower (between one-half and one-third as fast) in U937-R than in control cells, although catabolism occurred at similar rates. ddC was phosphorylated by a cytoplasmic deoxycytidine kinase in both cell lines. This enzyme showed Km values for ddC of 80 +/- 7 and 140 +/- 9 microM in U937 and U937-R cells respectively. Furthermore, Vmax was 12 +/- 1.1 and 7.8 +/- 0.5 pmol/min per mg of protein in U937 and U937-R. Thus resistance to ddC toxicity may be due to cells' decreased ability to accumulate intracellular ddC anabolites, which may depend on cytoplasmic deoxycytidine kinase.

[Health care economics, uncertainty and physician-induced demand]

The health care market is a very particular one that is mainly characterized by the absence of information and transparency at every level, particularly between the physician-supplier and the patient-consumer. On this market it is up to the physician to evaluate and define the patient's needs and to decide which are the most effective goods for the patient. The determinants of medical prescription are not only related to the health status of the patient, but also to the payment system (fee for services, salary), to physician density, professional uncertainty, the role and status of the physician in his profession, the legal framework which rules the medical profession, and also the information level of the patient. Agency relationship and professional uncertainty are the most relevant determinants of supplier-induced demand. Professional uncertainty inherent in the practice of a stochastic art such as medicine will "always" give an ethical justification for supplier-induced demand or for the pursuit of "maximal" and/or "defensive" care when market competition is perceived by the physician as a threat to his/her income or employment. Time is ripe for consumers and physicians empowerment in the aim to promote better self-management of health and more thoughtful access to care (for consumers) and more evidences based medicine for physicians.

2',3'-Dideoxycytidine induced drug resistance in human cells

2',3'-Dideoxycytidine (ddC) is a nucleoside analogue that inhibits HIV-1 replication in vitro and is currently used in AIDS therapy. This compound exerts a delayed cytotoxicity due to inhibition of mitochondrial DNA (mDNA) synthesis. We have found that long term exposure of U937 human monoblastoid cells to ddC allowed the selection of a drug-resistant cell line (U937-R) with 66% mDNA, normal ddC transport and altered deoxycytidine kinase kinetic properties. In this paper we show that U937-R cells contain an increased number of mitochondria per cell and a reduced copy number of mDNA/mitochondria. Furthermore, the intracellular concentrations of deoxycytidine 5'-triphosphate (dCTP) and 2',3'-dideoxycytidine 5'-triphosphate (ddCTP) are also reduced although with a higher dCTP/ddCTP ratio in U937-R compared to the parental cells. This mechanism of drug resistance, with drug-resistance based on viral mutations, can provide an explanation for drug failure in antiviral therapy.

The soluble but not mitochondrially bound hexokinase is a substrate for the ATP- and ubiquitin-dependent proteolytic system

Intracellular protein degradation is highly selective, however, the mechanism(s) underlying this selectivity are not fully understood. We have previously shown that purified rabbit hexokinase type I, an enzyme present in mammalian brain both in soluble and mitochondrial bound form, is conjugate to ubiquitin and then degraded by a rabbit reticulocyte fraction II. In the present study we report that the mitochondrial bound hexokinase is stable for several hours in the same proteolytic system both in the presence or absence of ATP. E1, E2 and E3, the enzymes of the ubiquitin conjugating system, are able to incorporate 125I- or biotin-labelled ubiquitin in an ATP-dependent manner in soluble hexokinase as well as in a number of mitochondrial proteins. Furthermore, the mitochondria by themselves have a pronounced ATP-dependent ability to conjugate 125I-ubiquitin. However, Western blotting experiments, using a specific antibody against hexokinase, or against ubiquitin, showed that the mitochondrial bound enzyme is neither ubiquitinated nor degraded. This result has been confirmed by purification of bound hexokinase from the brain mitochondrial fraction or following the incubation of intact mitochondria with ATP, 125I-ubiquitin and E1, E2 and E3. Thus, mitochondrial bound hexokinase is not recognized by the ubiquitin conjugating system while the soluble enzyme is conjugate to ubiquitin and then degraded. Furthermore, the soluble hexokinase from rabbit brain was isolated by immunoaffinity chromatography and shown to be recognized by an anti-ubiquitin antibody. These results suggest that the intracellular distribution of protein is an important feature of a protein which determines its susceptibility to ubiquitin-dependent degradation.

A p12 gag gene homologue is present in the mouse genome

A replication-defective virus (BM5d) of approximately 4.9 kb, is responsible for a retrovirus induced immunodeficiency syndrome in mice (MAIDS) that shares many features with AIDS. BM5d is characterized by deletions in env and pol genes, furthermore its gag gene differs markedly from gag of other BM5 ecotropic viruses, particularly in its p12 sequence. The p12 region of the gag gene has been shown to account for the pathogenicity of the BM5d retrovirus. During our studies of BM5d integration in mice we found that p12-like sequences are present in the mouse genome of uninfected healthy C57BL/6 mice. Cloning and sequencing of this p12 gag homologue has revealed a high (63% to 89%) amino acid derived sequence identity with other retroviruses and shown that the major differences among p12 of pathogenic viral strains compared to non-pathogenic ones consist of a four amino acids deletion and a high abundance of proline and basic amino acids in their p12 region.

[Traffic casualties and injuries: a problem of costs, too. A Swiss survey]

Based on an epidemiological observation in Ticino 1985, following statement is possible: in Switzerland every year 900 people dye in traffic casualties. Many victims of tragic accidents get lifetime disabled. Direct and indirect costs of traffic injuries are yearly 3 billions of swiss francs. Only a small percentage (6%) is devoted to medical treatment. The most part is due to compensation of income, disability with its allocations and lost productivity. Among "avoidable" deaths, traffic victims are an essential portion because the are young. More efforts should be undertaken to lower road mortality because she erodes the swiss population pyramid in a significant manner.

Revisiting the most informed consumer of surgical services. The physician-patient

Little is known about the consumption of medical and surgical services by the most informed consumer in the health care market: the physician-patient. Such knowledge should be important for the understanding of the role of information on consumption, supplier-induced demand, the doctor-patient relationship, unnecessary medical services, and the adequacy of professional practices to the renal health needs of the "ordinary patient." We measured by questionnaire the standardized consumption of seven common surgical procedures. Except for appendectomy, the age- and sex-standardized consumption for each of the common surgical procedures was always significantly higher in the general population than for the "gold standard" of physician-patients. The data suggest that (a) contrary to prior research, doctors have much lower rates of surgery than does the general population; and (b) in a fee-for-services health care market without financial barriers to medical care, less-informed patients are greater consumers of common surgical procedures.

A recombinant human 'mini'-hexokinase is catalytically active and regulated by hexose 6-phosphates

Mammalian hexokinase type I is a 100 kDa enzyme that has been considered to be evolved from an ancestral 50 kDa yeast-type hexokinase, insensitive to product inhibition, by gene duplication and fusion. According to this model, and based on many experimental data, the catalytic site is associated with the C-terminal half of the enzyme, although an allosteric site for the binding of glucose 6-phosphate could be present on the N-terminal half of the molecule. We have isolated a cDNA clone of hexokinase from a lambda gt11 human placenta library comprising 2658 bp, containing a single open reading frame of 1893 nucleotides, which encodes a truncate form of hexokinase starting from asparagine-287 to the terminal serine-917. This clone was further digested with restriction enzyme NcoI to obtain almost only the C-terminal half of human hexokinase starting from methionine-455 to the terminal amino acid and was overexpressed in active form in Escherichia coli and purified by ion-exchange h.p.l.c. The overexpressed 'mini'-hexokinase was found not only to catalyse glucose phosphorylation, but also to be inhibited by glucose 6-phosphate and other mono- and bis-phosphate sugars exactly like the complete mammalian enzyme. These results suggest that the C-terminal half of human hexokinase, in addition to the catalytic site, also contains the regulatory site and that the evolutionary relationship between the hexokinases should be reconsidered by including the appearance of a regulatory site before the gene duplication.

[A case of herpetic meningoencephalitis. Serological and imaging diagnosis]

The paper reports a case of HSVE observed in a 46-year-old patient with a negative anamnesis for previous HSV infection and with no objective signs of herpetic muco-cutaneous infection at time of hospitalisation. Due to the impossibility of carrying out bioptic and cultural tests, the diagnosis was based on the increased levels of specific anti-HSV1 antibodies in the liquor; these findings were compared to those found in serum, taking into account the increased antibody titres and in particular the ratio between the level of liquor and serum albumin and that of specific antibodies in both liquor and serum. The diagnostic importance of cerebral CT was confirmed by the early revelation of morphostructural alterations during the acute phase. RMN also allowed a more detailed imaging diagnosis to be made. From a therapeutic point of view, the paper confirms the value of acyclovir treatment.

Human hexokinase type I microheterogeneity is due to different amino-terminal sequences

Human placenta hexokinase type I was previously shown to be present in two subtypes with similar isoelectric points but different molecular masses of 112 and 103 kDa, respectively. In order to exclude that these subtypes arise by artifact(s) occurring during the protein purification, we have developed a single-step immunoaffinity chromatography for the isolation of microgram quantities of hexokinase. The results obtained confirmed the presence of both hexokinase subtypes in human placenta. By Northern blot analysis a single mRNA species that hybridized with a hexokinase-I cDNA was found to be present in human placenta. Furthermore, in vitro translation of placenta mRNA in a rabbit reticulocyte lysate followed by hexokinase immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography showed that only one hexokinase with apparent molecular mass of about 112 kDa is expressed in this tissue and suggests a post-translational modification as a probable cause of hexokinase I microheterogeneity. To further investigate this point we have purified the high and low Mr hexokinase and determined their NH2-terminal sequences. The results obtained show that when compared with the amino acid sequence deduced from a cDNA the high Mr hexokinase starts at amino acid 11 while the low Mr hexokinase starts at amino acid 103. Since the first 10 amino acids are involved in the binding of hexokinase to mitochondrial porin these data provide an explanation both for the inability of these hexokinases to bind to mitochondria and for their differences in Mr.

Psychoactive drug use among medical doctors is higher than in the general population

We surveyed a representative sample of practising physicians and a representative sample of subjects from the Swiss general population (SOMIPOPS Survey) concerning their annual use of sleeping pills and tranquillizers. 77% of the physicians (n = 466) and 72% of the general population (n = 4255) responded. After adjustment for age and sex 37.1% of the doctors (general population 21.1% P less than 0.001) claimed to have taken these drugs for therapeutic purposes. The proportion of psychiatrists who reported taking sleeping pills and tranquillizers daily (10.6%) were significantly greater than for the population of doctors as a whole and for the general population (P less than 0.05). Regular users (i.e. subjects taking one mood altering drug at least once a week) accounted for 11.1% of the medical population compared with 6.8% of the general population (P less than 0.01). This over-consumption was wholly due to the greater number of regular users of psychoactive drugs amongst doctors less than 50 years of age relative to the general population or to subjects in higher management (from P less than 0.05 to P less than 0.001). Without this specific over-use, members of the medical profession would not have been found to use more psychoactive drugs than the general population and the executives. This result suggests that it would be worth investigating the mechanisms of response and adjustment (coping) to the specific stress that appears to be inherent in the exercise of medical practice.