André Désormeaux

Amino acid sequence of a non-specific wheat phospholipid transfer protein and its conformation as revealed by infrared and Raman spectroscopy. Role of disulfide bridges and phospholipids in the stabilization of the α-helix structure

A wheat non specific phospholipid transfer protein has been isolated from wheat seeds and its amino acid sequence reveals that it is composed of 90 residues for a molecular weight of 9607. From the comparison of its sequence with those of the eight known proteins of the same family, hypotheses on the role of some conserved residues in the transfer activity can be made. The conformation of this protein has been studied by Raman and Fourier transform infrared spectroscopy and this is the first report on the structure of non specific plant phospholipid transfer proteins. As opposed to previous studies on the structure prediction from the amino acid sequence, the results obtained show that plant non specific phospholipid transfer proteins are not almost entirely composed of beta-sheets. Instead, infrared results show that the wheat protein contains 41% alpha-helix and 19% beta-sheet structures, while 40% of the conformation is undefined or composed of turns. Raman spectroscopy shows that three disulfide bridges adopt a gauche-gauche-gauche conformation while the other exhibits a gauche-gauche-trans conformation, and that the two tyrosine residues are hydrogen bonded to water molecules. The cleavage of the disulfide bonds affects significantly the conformation of the protein, the extended confirmation being increased by 15% at the expense of the alpha-helix content. On the other hand, the binding of 1-palmitoyllysophosphatidylcholine to the protein leads to an increase of 8% of the alpha-helix content compared to the free protein. Secondary structure predictions from the amino acid sequence suggest that the binding of a phospholipid stabilizes helicity of the amphipathic helices while the reduction of disulfide bonds would affect the stability of the N-terminal helix. The extended structure located at the C-terminus is not affected. Finally, the wheat phospholipid transfer protein has no effect on the thermotropic behavior of large unilamellar vesicles of dimyristoylphosphatidylcholine while it increases the conformational order of the acyl chains of large unilamellar vesicles of dimyristoylphosphatidylglycerol in the liquid-crystalline state. No major conformational changes of the protein are observed when it is adsorbed to phospholipid vesicles. These results suggest that the helical structure is essential for the transfer activity without excluding a possible role of the C-terminal extended structure on the adsorption to phospholipid vesicles.

Liposomes as drug delivery system: a strategic approach for the treatment of HIV infection.

As the number of individuals infected with human immunodeficiency virus (HIV) is growing dramatically throughout the world, it is important to develop strategies to improve the treatment of this deadly disease. It is now well established that macrophages play a central role in HIV pathogenesis, acting as reservoirs for dissemination of virus throughout the immune system. As liposomes are naturally taken up by cells of the mononuclear phagocytic system, liposome-based therapy represents a convenient approach to improve the delivery of anti-HIV agents into infected cells improving thereby the efficacy of drugs and reducing their adverse side-effects. A more specific targeting of HIV-infected cells could also be obtained by using liposomes bearing surface attached-antibodies. This review details the applications of liposomes as drug carriers for the treatment of AIDS. It also gives an overlook of the different strategies that could be explored to control the progression of the disease in infected individuals.

Treatment of Visceral Leishmaniasis with Sterically Stabilized Liposomes Containing Camptothecin

ABSTRACT The efficacy of 20(S)-camptothecin (CPT), free and incorporated into sterically stabilized liposomes, has been investigated in vitro against Leishmania donovanipromastigotes and in vivo in a murine model of visceral leishmaniasis. Incubation of L. donovani promastigotes with free or liposomal CPT inhibited the growth of parasites in a dose-dependent manner. Tissue distribution studies revealed that the intraperitoneal administration of liposomal CPT was efficient for the delivery of high drug levels to the liver and spleen. Treatment of infected mice with intraperitoneal injections of free and liposomal CPT significantly reduced the parasite loads in the livers by 43 and 55%, respectively, compared with the loads for untreated controls. However, both treatments caused normochromic anemia and neutropenia.

Thermoreversible Gel Formulations Containing Sodium Lauryl Sulfate or n-Lauroylsarcosine as Potential Topical Microbicides against Sexually Transmitted Diseases

ABSTRACT The microbicidal efficacies of two anionic surfactants, sodium lauryl sulfate (SLS) and n-lauroylsarcosine (LS), were evaluated in cultured cells and in a murine model of herpes simplex type 2 (HSV-2) intravaginal infection. In vitro studies showed that SLS and LS were potent inhibitors of the infectivity of HSV-2 strain 333. The concentrations of SLS which inhibit viral infectivity by 50% (50% inhibitory dose) and 90% (90% inhibitory dose) were 32.67 and 46.53 μM, respectively, whereas the corresponding values for LS were 141.76 and 225.30 μM. In addition, intravaginal pretreatment of mice with thermoreversible gel formulations containing 2.5% SLS or 2.5% LS prior to the inoculation of HSV-2 strain 333 completely prevented the development of genital herpetic lesions and the lethality associated with infection. Of prime interest, no infectious virus could be detected in mouse vaginal mucosa. Both formulations still provided significant protection when viral challenge was delayed until 1 h after pretreatment. Finally, intravaginal application of gel formulations containing 2.5% SLS or 2.5% LS once daily for 14 days to rabbits did not induce significant irritations to the genital mucosa, as demonstrated from macroscopic and histopathologic examinations. These results suggest that thermoreversible gel formulations containing SLS or LS could represent potent and safe topical microbicides for the prevention of HSV-2 and possibly other sexually transmitted pathogens, including human immunodeficiency virus.

Encapsulation of foscarnet in liposomes modifies drug intracellular accumulation, in vitro anti-HIV-1 activity, tissue distribution and pharmacokinetics.

ObjectiveTo improve the in vitro anti-HIV-1 activity, intracellular accumulation in macrophages, and in vivo pharmacokinetics, and tissue distribution of foscarnet (trisodium phosphonoformate; PFA) by encapsulation in liposomes. MethodsThe accumulation of free, and liposome-encapsulated PFA was determined in monocyte-macrophage RAW 264.7 cells, and human premonocytoid U937 cells. The antiviral activity was evaluated in U937 cells infected with HIV-1IIIB. Tissue distribution, and pharmacokinetics of free, and liposomal PFA were determined in female Sprague-Dawley rats following the administration of an intravenous bolus dose (10 mg PFA/kg). ResultsThe entrapment of PFA in liposomes resulted in a higher drug accumulation in both U937, and RAW 264.7 cells. A slightly greater efficacy against HIV-1IIIB replication into U937 cells was observed upon encapsulation of PFA into liposomes. Improved pharmacokinetics was observed upon entrapment of PFA in liposomes. Much higher drug levels were found in plasma for the liposomal formulation. The systemic clearance of the liposomal drug was 77 times lower than that of free drug. The encapsulation of PFA in liposomes greatly enhanced the drug accumulation in organs of the reticuloendothelial system. ConclusionThe encapsulation of PFA in liposomes modified the tissue distribution, and plasma pharmacokinetics of the antiviral agent, resulting in a marked improvement of drug accumulation in organs involved in HIV immunopathogenesis, and in a greater PFA bioavailability. The antiviral activity of liposomal PFA was slightly greater than that of free drug in HIV-1IIIB-infected U937 cells.

Protective effect of a thermoreversible gel against the toxicity of nonoxynol-9

BACKGROUND AND OBJECTIVES One major problem associated with the use of nonoxynol-9 is that it can induce local inflammation and ulceration of the vaginal and cervical mucosa that might favor the entry of pathogens. With the aim of developing a gel formulation that could be effective in preventing sexually transmitted infections, the authors have evaluated the capacity of a polyoxypropylene/polyoxyethylene polymer to reduce or eliminate the toxicity of nonoxynol-9. STUDY DESIGN The cytotoxicity of nonoxynol-9 alone or incorporated into the gel was investigated in human cervical and colon epithelial cells and after daily intravaginal application for 2 weeks in rabbits. RESULTS In vitro experiments showed that nonoxynol-9 was highly toxic to human cervical and colon epithelial cells in a dose-dependent manner. However, the incorporation of the spermicide into the gel markedly reduced its toxicity under the same experimental conditions. In vivo studies showed that in animals treated with nonoxynol-9, the spermicide was very toxic to the vaginal and cervical mucosa as evidenced by the presence of bleeding, irritation, epithelial disruption, necrosis, the accumulation of leukocytes in the submucosa, and the loss of integrity of the epithelial cells. Of prime importance, the incorporation of nonoxynol-9 into the gel markedly reduced the toxicity of this potent spermicide/microbicide. CONCLUSION The gel formulation could be used as an interesting approach to eliminate the toxicity of potent spermicides/microbicides such as nonoxynol-9.

Comparative Study of Mechanisms of Herpes Simplex Virus Inactivation by Sodium Lauryl Sulfate and n-Lauroylsarcosine

ABSTRACT The mechanisms of herpes simplex virus (HSV) inactivation by sodium lauryl sulfate (SLS) and n-lauroylsarcosine (LS), two anionic surfactants with protein denaturant potency, have been evaluated in cultured cells. Results showed that pretreatment of HSV type 1 (HSV-1) strain F and HSV-2 strain 333 with either surfactant inhibited, in a concentration- and time-dependent manner, their infectivities on Vero cells. SLS was a more potent inhibitor of HSV-2 strain 333 infectivity than LS with respect to the concentration (4.8-fold lower) and time (2.4-fold shorter) required to completely inactivate the virus. No inhibition of both herpesvirus strains infectivities was observed when Vero cells were pretreated with either surfactant. LS prevented the binding of HSV-2 strain 333 to cells without affecting the stable attachment and the rate of penetration into cells, whereas SLS exerted the opposite effect. Both SLS and LS inhibited, in a concentration-dependent manner, the HSV-2 strain 333-induced cytopathic effect, probably by affecting newly synthesized virions that come into contact with surfactant molecules present in culture medium. The pretreatment of HSV-2 strain 333 with specific combinations of SLS and LS concentrations inhibited the viral infectivity in a synergistic manner and resulted in only a small increase in their toxicities for exponentially growing Vero cells compared with that caused by each compound alone. Taken together, these results suggest that SLS and LS, alone or combined, could represent potent candidates as microbicides in topical vaginal formulations to prevent the transmission of herpes and possibly other pathogens that cause sexually transmitted diseases, including human immunodeficiency virus type 1.

ANTIVIRAL EFFICACY, INTRACELLULAR UPTAKE AND PHARMACOKINETICS OF FREE AND LIPOSOME-ENCAPSULATED 2',3'-DIDEOXYINOSINE

ObjectiveTo evaluate the effect of liposome encapsulation on the in vitro antiviral efficacy, intracellular uptake and in vivo pharmacokinetics of 2‘,3’-dideoxyinosine (ddl). MethodsThe accumulation of free and liposome-encapsulated ddl was determined in murine monocyte-macrophage RAW 264.7 cells and human premonocytoid U937 cells. The antiviral efficacy was evaluated in U937 cells infected with HIVIIIB. Tissue distribution and pharmacokinetics of free and liposomal ddl were determined in female Sprague-Dawley rats following the administration of a single intravenous bolus dose (3mg ddl/kg). ResultsThe entrapment of ddl in liposomes results in a lower drug accumulation in both U937 and RAW 264.7 cells. A lower antiviral efficacy against HIVIIIB replication in U937 cells was observed on encapsulation of ddl in liposomes. Improved pharmacokinetics were observed on entrapment of ddl in liposomes. Higher drug levels were found in plasma for the liposomal formulation. The systemic clearance of the liposomal drug was 120 times lower than that of free drug. Liposome encapsulation of ddl greatly enhanced the drug accumulation in organs of the reticuloendothelial system. ConclusionThe encapsulation of ddl in liposomes modified the tissue distribution and plasma pharmacokinetics of the antiviral agent resulting in a marked improvement of drug biodisponibility. The antiviral efficacy of liposomal ddl was lower than that of free drug in HIVIIIB-infected U937 cells.

Thermoreversible Gel Formulation Containing Sodium Lauryl Sulfate as a Potential Contraceptive Device

Abstract The contraceptive properties of a gel formulation containing sodium lauryl sulfate were investigated in both in vitro and in vivo models. Results showed that sodium lauryl sulfate inhibited, in a concentration-dependent manner, the activity of sheep testicular hyaluronidase. Sodium lauryl sulfate also completely inhibited human sperm motility as evaluated by the 30-sec Sander-Cramer test. The acid-buffering capacity of gel formulations containing sodium lauryl sulfate increased with the molarity of the citrate buffers used for their preparations. Furthermore, experiments in which semen was mixed with undiluted gel formulations in different proportions confirmed their physiologically relevant buffering capacity. Intravaginal application of the gel formulation containing sodium lauryl sulfate to rabbits before their artificial insemination with freshly ejaculated semen completely prevented egg fertilization. The gel formulation containing sodium lauryl sulfate was fully compatible with nonlubricated latex condoms. Taken together, these results suggest that the gel formulation containing sodium lauryl sulfate could represent a potential candidate for use as a topical vaginal spermicidal formulation to provide fertility control in women.

Sodium Lauryl Sulfate Abrogates Human Immunodeficiency Virus Infectivity by Affecting Viral Attachment

ABSTRACT The microbicidal activity of sodium lauryl sulfate (SLS) against human immunodeficiency virus type 1 (HIV-1) was studied in cultured cells. Pretreatment of HIV-1NL4-3 with SLS decreased, in a concentration-dependent manner, its infectivity when using 1G5 as target cells. In the absence of a viral pretreatment period or when 1G5 cells were pretreated with SLS, the surfactant-induced inactivation of viral infectivity was less pronounced, especially at concentrations between 375 and 550 μM. SLS had no effect on HIV-1 when the virus was adsorbed to 1G5 cells by a 2-h incubation period. SLS almost completely inhibited the fusion process by decreasing the attachment of HIV-1 to target cells. SLS also inhibited the infectivity of HIV-1-based luciferase reporter viruses pseudotyped with the amphotropic murine leukemia virus envelope (which enters cells in a CD4-, CCR5-, and CXCR4-independent manner), indicating that SLS may inactivate other envelope viruses. In contrast, no effect was seen with vesicular stomatitis virus envelope glycoprotein G (which enters cells through receptor-mediated endocytosis) pretreated with up to 700 μM SLS. SLS also decreased, in a dose-dependent manner, the HIV-1-dependent syncytium formation between 1G5 and J1.1 cells after a 24-h incubation. The reduction of luciferase activity was more pronounced when J1.1 cells (which express HIV-1 proteins on their surface) were pretreated with SLS rather than 1G5 cells. Taken together, our results suggest that SLS could represent a candidate of choice for use in vaginal microbicides to prevent the sexual transmission of HIV and possibly other pathogens causing sexually transmitted diseases.