Antiviral phospholipids. Anti-HIV drugs conjugated to the glycerobackbone of phospholipids

Could metabolomics drive the fate of COVID-19 pandemic? A narrative review on lights and shadows

Human Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) infection activates a complex interaction host/virus, leading to the reprogramming of the host metabolism aimed at the energy supply for viral replication. Alterations of the host metabolic homeostasis strongly influence the immune response to SARS-CoV-2, forming the basis of a wide range of outcomes, from the asymptomatic infection to the onset of COVID-19 and up to life-threatening acute respiratory distress syndrome, vascular dysfunction, multiple organ failure, and death. Deciphering the molecular mechanisms associated with the individual susceptibility to SARS-CoV-2 infection calls for a system biology approach; this strategy can address multiple goals, including which patients will respond effectively to the therapeutic treatment. The power of metabolomics lies in the ability to recognize endogenous and exogenous metabolites within a biological sample, measuring their concentration, and identifying perturbations of biochemical pathways associated with qualitative and quantitative metabolic changes. Over the last year, a limited number of metabolomics- and lipidomics-based clinical studies in COVID-19 patients have been published and are discussed in this review. Remarkable alterations in the lipid and amino acid metabolism depict the molecular phenotype of subjects infected by SARS-CoV-2; notably, structural and functional data on the lipids-virus interaction may open new perspectives on targeted therapeutic interventions. Several limitations affect most metabolomics-based studies, slowing the routine application of metabolomics. However, moving metabolomics from bench to bedside cannot imply the mere determination of a given metabolite panel; rather, slotting metabolomics into clinical practice requires the conversion of metabolic patient-specific data into actionable clinical applications.

Synthesis and anti-HIV Evaluation of Alkyl and Alkoxyethyl Phosphodiester AZT Derivatives

A series of new AZT conjugates with alkyl and oxyalkyl ether phospholipids was synthesized and evaluated for inhibitory activities against HIV-1 and HIV-2. The alkoxyethyl derivatives 6a-c proved 3- to 5-fold more active against HIV-1 and HIV-2 than the alkyl analogues 6d-f. A trend for higher activity with longer alkyl side-chains was observed. However, the analogues with the shortest chain possessed the most favourable therapeutic index.

Chemical modulation of memory formation in larval zebrafish

Whole organism-based small-molecule screens have proven powerful in identifying novel therapeutic chemicals, yet this approach has not been exploited to identify new cognitive enhancers. Here we present an automated high-throughput system for measuring nonassociative learning behaviors in larval zebrafish. Using this system, we report that spaced training blocks of repetitive visual stimuli elicit protein synthesis-dependent long-term habituation in larval zebrafish, lasting up to 24 h. Moreover, repetitive acoustic stimulation induces robust short-term habituation that can be modulated by stimulation frequency and instantaneously dishabituated through cross-modal stimulation. To characterize the neurochemical pathways underlying short-term habituation, we screened 1,760 bioactive compounds with known targets. Although we found extensive functional conservation of short-term learning between larval zebrafish and mammalian models, we also discovered several compounds with previously unknown roles in learning. These compounds included a myristic acid analog known to interact with Src family kinases and an inhibitor of cyclin dependent kinase 2, demonstrating that high-throughput chemical screens combined with high-resolution behavioral assays provide a powerful approach for the discovery of novel cognitive modulators.

New advances in the chemistry of methoxylated lipids

Methoxylated lipids have been reviewed emphasizing the alkylglycerol ethers and fatty acids bearing the methoxy group in the alkyl chain. The literature on methoxylated lipids and their derivatives has been divided into four main groups, namely 2-methoxylated alkyl glycerols, omega-methoxylated fatty acids, mid-chain methoxylated fatty acids, and alpha-methoxylated fatty acids. The natural occurrence, biological activity, and synthesis of this interesting group of lipids are discussed. Most of these compounds have been isolated from either bacterial or marine sources, but others are mainly of synthetic origin. Among the interesting biological activities displayed by these compounds the most important are antibacterial, antifungal, antitumor, and antiviral.

Lipids and retroviruses

The role that lipids may play in enveloped viruses is reviewed. Small lipid molecules can influence retrovirus binding to cell receptors, plasma membrane fusion, and transcription. Palmitoylation following myristoylation of viral glycoproteins is required at the transmembrane level for signal transduction as well as for virion budding and maturation. Cholesterol, ether lipids, phospholipids, platelet-activating factor, phosphatidic acids, diacylglycerols, and several analogs and derivatives influence human immunodeficiency virus (HIV) activity; when conjugated with inhibitors of the viral reverse transcriptase (RT) or aspartyl protease these compounds increase drug effectiveness. On the other hand, L-carnitine, in association with the mitochondrial cardiolipins, inhibits myopathy due to continued prescription of drugs [AZT (zidovudine), ddl (didanoside), or ddC (zalcitabine)], and the redox couple of alpha-lipoic-dihydrolipoic acid prevents production of the reactive oxygen species that trigger apoptosis of infected cells, with sphingomyelin breakdown to ceramides. Retroviral infection induces a shift from phospholipid to neutral fat synthesis in host cells, and a long antiviral, i.e., antiprotease, treatment may lead to lipodystrophy. Multitherapy involving lipids and their analogs in association with anti-RT and antiproteases might enhance the inhibition of growth and proliferation of retroviruses.

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.

Exploration of the effects of linker chain modifications on anti-HIV activities in a series of cosalane analogues

The effects of linker chain modifications were investigated in a series of cosalane analogues. The modifications investigated included: (1) shortening the three-carbon linker chain between the dichlorodisalicylmethane and the cholestane moiety by one carbon atom; (2) lengthening the linker chain by one carbon; (3) hydrogenation of the double bond in the linker chain; (4) changing the point of attachment of the linker chain from C-3 to C-6; (5) insertion of a phosphate between the steroid and the linker chain. With the exception of the phosphate modification, which abolished anti-HIV activity and increased cytotoxicity, the linker chain modifications produced relatively minor changes in anti-HIV activity and increased cytotoxicity, the linker chain modifications produced relatively minor changes in anti-HIV potency. The steroid and attached linker chain of cosalane therefore appear only to provide a general lipophilic appendage for the dichlorodisalicylmethane pharmacophore.

Complete inhibition of human immunodeficiency virus Gag myristoylation is necessary for inhibition of particle budding

Myristoylation of human immunodeficiency virus (HIV) Gag protein is essential for virus particle budding. Two reactions are involved; activation of free myristate to myristoyl-CoA and transfer of the myristoyl residue to the Gag N-terminal glycine. We have investigated the effects of triacsin C, an inhibitor of long chain acyl-CoA synthetase, on release of HIV Gag virus-like particle (VLP) produced using the recombinant baculovirus system. First, inhibition of acyl-CoA formation by triacsin C was confirmed using the membrane fractions of insect Sf9 cells as an enzyme source. Second, when HIV Gag protein was expressed in the presence of triacsin C (0-48 microM), Gag myristoylation was inhibited in a dose-dependent manner. Budding of Gag VLP, however, did not follow similar inhibition kinetics but appeared unaffected up to 24 microM, yet was completely abolished at 48 microM when the myristoylation of Gag protein was also completely inhibited. The "all-or-none" inhibition of Gag VLP budding suggests that although inhibition of acyl-CoA synthetase blocks the production of myristoylated Gag protein, only complete inhibition of Gag myristoylation prevents VLP budding. Thus, relatively few myristoylated Gag molecules are sufficient for plasma membrane targeting and VLP budding.

Correlation of anti-HIV potency with lipophilicity in a series of cosalane analogs having normal alkenyl and phosphodiester chains as cholestane replacements

In order to define the role of the cholestane moiety in the anti-HIV agent cosalane, a series of cosalane analogs was synthesized in which the cholestane ring system was replaced by normal alkenyl and phosphodiester substituents having varied chain lengths and lipophilicities. The compounds containing simple alkenyl substituents were found to be more potent as inhibitors of the cytopathic effect of HIV-1 in cell culture than the phosphodiesters. In addition, the potencies of the alkene congeners correlated positively with chain length and lipophilicity of the alkene. The results indicate that the cholestane moiety of cosalane functions as a lipophilic accessory appendage to escort the dichlorodisalicylmethane pharmacophore to a lipid environment.

Lipid dynamics and peripheral interactions of proteins with membrane surfaces

A large body of evidence strongly indicates biomembranes to be organized into compositionally and functionally specialized domains, supramolecular assemblies, existing on different time and length scales. For these domains and intimate coupling between their chemical composition, physical state, organization, and functions has been postulated. One important constituent of biomembranes are peripheral proteins whose activity can be controlled by non-covalent binding to lipids. Importantly, the physical chemistry of the lipid interface allows for a rapid and reversible control of peripheral interactions. In this review examples are provided on how membrane lipid (i) composition (i.e., specific lipid structures), (ii) organization, and (iii) physical state can each regulate peripheral binding of proteins to the lipid surface. In addition, a novel and efficient mechanism for the control of the lipid surface association of peripheral proteins by [Ca2+], lipid composition, and phase state is proposed. The phase state is, in turn, also dependent on factors such as temperature, lateral packing, presence of ions, metabolites and drugs. Confining reactions to interfaces allows for facile and cooperative large scale integration and control of metabolic pathways due to mechanisms which are not possible in bulk systems.

Magnetically induced orientation of phosphatidylcholine membranes

Lipid bilayers prepared from natural phospholipids orient in magnetic fields with the long axis of the lipid molecules perpendicular to the magnetic field. This magnetically induced orientation was studied at high (11.7 Tesla (T)), mid (9.36 T), and low (4.68 T) magnetic field strengths using lipid aggregates prepared from natural and synthetic phosphatidylcholine analogs. Phosphatidylcholine analogs containing saturated diacylated chains (12 to 16 carbons/chain) exhibited extensive orientation of the lipid when bilayer formation occurred by gentle hydration conditions. Gentle hydration involved incubating dried phosphatidylcholine C above the main phase transition (Tm); brief shaking or swirling by hand was occasionally needed to completely disperse the lipids. The method of bilayer formation significantly influenced the amount of lipid that orients in magnetic fields. Thus the supramolecular structures (and % orientation) above Tm in an 11.7 T field of dimyristoylphosphatidylcholine (DMPC) bilayers are SUV (0%), LUV (approximately 15%), SPLV (approximately 40%), vortexed-MLV (approximately 60%) and non-vortexed MLV (approximately 90%). Single layered vesicles prepared by the REV method exhibited orientation at 11.7 T similar to LUV prepared by freeze thaw cycles. Aqueous dispersions of eggPC prepared by gentle hydration exhibit approximately 40% orientation at 11.7 T which decreased to approximately 30% orientation if 30% cholesterol is added to the membrane. Magnetic orientation of bilayers thus appears to be a general phenomenon for both saturated and unsaturated natural phospholipids either with or without cholesterol in the membrane.