This review focuses on recent papers that describe the involvement of the RGD sequence in bone biology and incorporate the use of synthetic RGD peptides to develop new drugs or control the ...bioactivity of materials used for bone regeneration. Because in vivo bone function is completely dependent on angiogenesis and vessels, the present publication is focused on physiology, pathophysiology and therapeutics of RGD peptides dedicated to bone cells and endothelial systems. It appears that alphavbeta3, alphavbeta5 and alphaIIbbeta3 are the integrins most reported to be involved in bone function and RGD sequence binding. The specificity of RGD peptides depends on backbone conformation, orientations of the charged side chains of Arg and Asp residues, and hydrophobic moieties flanking the Asp residue. Despite of recent progress in integrins and RGD peptide structures and function, future work should focus on integrin selectivity of RGD-based agents, model structure and activity-selectivity relationships.
Obesity and metabolic syndrome are linked to an increased prevalence of breast cancer among postmenopausal women. A common feature of obesity, metabolic syndrome, and a Western diet rich in saturated ...fat is a high level of circulating cholesterol. Epidemiological reports investigating the relationship between high circulating cholesterol levels, cholesterol-lowering drugs, and breast cancer are conflicting. Here, we modeled this complex condition in a well-controlled, preclinical animal model using innovative isocaloric diets. Female severe combined immunodeficient mice were fed a low-fat/no-cholesterol diet and then randomized to four isocaloric diet groups: low-fat/no-cholesterol diet, with or without ezetimibe (cholesterol-lowering drug), and high-fat/high-cholesterol diet, with or without ezetimibe. Mice were implanted orthotopically with MDA-MB-231 cells. Breast tumors from animals fed the high-fat/high-cholesterol diet exhibited the fastest progression. Significant differences in serum cholesterol level between groups were achieved and maintained throughout the study; however, no differences were observed in intratumoral cholesterol levels. To determine the mechanism of cholesterol-induced tumor progression, we analyzed tumor proliferation, apoptosis, and angiogenesis and found a significantly greater percentage of proliferating cells from mice fed the high-fat/high-cholesterol diet. Tumors from hypercholesterolemic animals displayed significantly less apoptosis compared with the other groups. Tumors from high-fat/high-cholesterol mice had significantly higher microvessel density compared with tumors from the other groups. These results demonstrate that hypercholesterolemia induces angiogenesis and accelerates breast tumor growth in vivo.
HIV-1 virions are highly enriched in cholesterol relative to the cellular plasma membrane. We recently reported that a cholesterol-binding compound, amphotericin B methyl ester (AME), blocks HIV-1 ...entry and that single amino acid substitutions in the cytoplasmic tail of the transmembrane envelope glycoprotein gp41 confer resistance to AME. In this study, we defined the mechanism of resistance to AME. We observed that the gp41 in AME-resistant virions is substantially smaller than wild-type gp41. Remarkably, we found that this shift in gp41 size is due to cleavage of the gp41 cytoplasmic tail by the viral protease. We mapped the protease-mediated cleavage to two sites in the cytoplasmic tail and showed that gp41 truncations in this region also confer AME resistance. Thus, to escape the inhibitory effects of AME, HIV-1 evolved a mechanism of protease-mediated envelope glycoprotein cleavage used by several other retroviruses to activate envelope glycoprotein fusogenicity. In contrast to the mechanism of AME resistance observed for HIV-1, we demonstrate that simian immunodeficiency virus can escape from AME via the introduction of premature termination codons in the gp41 cytoplasmic tail coding region. These findings demonstrate that in human T cell lines, HIV-1 and simian immunodeficiency virus can evolve distinct strategies for evading AME, reflecting their differential requirements for the gp41 cytoplasmic tail in virus replication. These data reveal that HIV-1 can escape from an inhibitor of viral entry by acquiring mutations that cause the cytoplasmic tail of gp41 to be cleaved by the viral protease.
Epidemiological and preclinical observations have suggested a role for one or more products of the mevalonate/cholesterol biosynthesis pathway in the progression of prostate cancer. In this study, we ...used ezetimibe (Zetia), a specific, FDA-approved, cholesterol uptake-blocking drug, in combination with either a hyper- or hypocholesterolemic diet, to show that elevated circulating cholesterol levels promote, whereas a reduction in circulating cholesterol levels retard, the growth of human prostate cancer xenograft tumors in mice. Circulating cholesterol levels also modified tumor angiogenesis; higher cholesterol levels increased microvessel density and other indicators of vascularity. Consistent with these data, the reduction of cholesterol levels also increased the levels of the angiogenesis inhibitor thrombospondin-1 in the xenografts. Our results thus suggest that hypercholesterolemia directly accelerates the growth of prostate carcinomas, and that the pharmacological reduction of serum cholesterol levels may retard prostate cancer growth by inhibiting tumor angiogenesis.
Purpose Benign prostatic hyperplasia is a common urinary tract disorder that affects aging men. The molecular mechanisms underlying benign prostatic hyperplasia are obscure and the development of ...animal models to test novel treatment strategies is challenging. We report that the Bio 87.20 hamster strain (Bio Breeders, Watertown, Massachusetts) shows 5α-reductase-sensitive prostate enlargement and a decrease in circulating cholesterol reduces prostate size. Materials and Methods Bio 87.20 hamsters 17 months old with an enlarged prostate were fed a diet containing no or minimal cholesterol and including finasteride (Merck, Whitehouse Station, New Jersey) and/or ezetimibe (Schering-Plough, Kenilworth, New Jersey) for 4 months. The prostate complex was removed, volume and weight were determined, and tissue was examined histologically. Results Prostate enlargement depended on cholesterol in the diet. Blockade of intestinal cholesterol transport with ezetimibe induced prostate regression to a similar extent as the 5α-reductase inhibitor finasteride, a compound used to treat benign prostatic hyperplasia in humans. Histological analysis indicated that finasteride induced widespread prostatic atrophy but normal glandular architecture was preserved in the ezetimibe cohort. Conclusions Results indicate that dysregulation of cholesterol metabolism may be a component of benign prostatic hyperplasia and ezetimibe may be effective as an alternative or adjunct to standard treatment. Our findings also show that the Bio 87.20 hamster is a suitable model for preclinical evaluation of novel benign prostatic hyperplasia therapy.
Pre-hospital triage centres were created during the first wave of Covid-19 in March 2020. The intention was to examine patients in appropriate sanitary conditions and prevent emergency departments ...from overcrowding. This study describes triage centres in the Federation Wallonia-Brussels. The aim of the study was to collect key aspects of triage centres, implementation and information about the daily functioning interpreted positively or negatively by the GP-coordinators in charge of their management. This study was divided into two parts : an online questionnaire and semi-structured interviews. Overall, 14 questionnaires and 6 interviews were collected among the 44 initially contacted GP-coordinators. Our results point to a highly heterogeneous organisation of the triage centres, nevertheless adapted to local contexts, as well as a gap between local effective dynamics and challenges regarding federal/regional cooperation. This study may help for further crisis management plans.
Membrane cholesterol plays an important role in human immunodeficiency virus type 1 (HIV-1) particle production and infectivity. Here, we have investigated the target and mechanism of action of a ...cholesterol-binding compound, the polyene antifungal antibiotic amphotericin B methyl ester (AME). We found that AME potently inhibited the replication of a highly divergent panel of HIV-1 isolates in various T-cell lines and primary cells irrespective of clade or target cell tropism. The defects in HIV-1 replication caused by AME were due to profoundly impaired viral infectivity as well as a defect in viral particle production. To elucidate further the mechanism of action of AME, we selected for and characterized AME-resistant HIV-1 variants. Mutations responsible for AME resistance mapped to a highly conserved and functionally important endocytosis motif in the cytoplasmic tail of the transmembrane glycoprotein gp41. Interestingly, truncation of the gp41 cytoplasmic tail in the context of either HIV-1 or rhesus macaque simian immunodeficiency virus also conferred resistance to AME. The infectivity of HIV-1 virions bearing murine leukemia virus or vesicular stomatitis virus glycoproteins was unaffected by AME. Our data define the target and mechanism of action of AME and provide support for the concept that cholesterol-binding compounds should be pursued as antiretroviral drugs to disrupt HIV-1 replication.
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