Toxicity of blue led light and A2E is associated to mitochondrial dynamics impairment in ARPE-19 cells: implications for age-related macular degeneration.

Age-related macular degeneration (AMD) is a multifactorial retinal disease characterized by a progressive loss of central vision. Retinal pigment epithelium (RPE) degeneration is a critical event in AMD. It has been associated to A2E accumulation, which sensitizes RPE to blue light photodamage. Mitochondrial quality control mechanisms have evolved to ensure mitochondrial integrity and preserve cellular homeostasis. Particularly, mitochondrial dynamics involve the regulation of mitochondrial fission and fusion to preserve a healthy mitochondrial network. The present study aims to clarify the cellular and molecular mechanisms underlying photodamage-induced RPE cell death with particular focus on the involvement of defective mitochondrial dynamics. Light-emitting diodes irradiation (445 ± 18 nm; 4.43 mW/cm2) significantly reduced the viability of both unloaded and A2E-loaded human ARPE-19 cells and increased reactive oxygen species production. A2E along with blue light, triggered apoptosis measured by MC540/PI-flow cytometry and activated caspase-3. Blue light induced mitochondrial fusion/fission imbalance towards mitochondrial fragmentation in both non-loaded and A2E-loaded cells which correlated with the deregulation of mitochondria-shaping proteins level (OPA1, DRP1 and OMA1). To our knowledge, this is the first work reporting that photodamage causes mitochondrial dynamics deregulation in RPE cells. This process could possibly contribute to AMD pathology. Our findings suggest that the regulation of mitochondrial dynamics may be a valuable strategy for treating retinal degeneration diseases, such as AMD.

Bile acids: Lipase-catalyzed synthesis of new hyodeoxycholic acid derivatives.

In this work we present an efficient, environmentally friendly approach to the synthesis of a series of hyodeoxycholic acid derivatives applying Biocatalysis. Fifteen acetyl and ester derivatives, twelve of them new, were obtained through an enzymatic strategy in a fully regioselective way and in very good to excellent yield. In order to find the optimal reaction conditions, the influence of several parameters such as enzyme source, alcohol or acylating agent:substrate ratio, enzyme:substrate ratio, temperature and reaction solvent was considered. The excellent results obtained made this procedure very efficient, particularly considering the low amount of enzyme required. In addition, this methodology uses mild reaction conditions and has reduced environmental impact, making biocatalysis a suitable way to obtaining these bile acids derivatives.

Lipase-Catalyzed Acetylation and Esterification of Bile Acids.

In this chapter we describe the application of lipases as catalysts in reactions on a relevant family of steroids: the bile acids. Twenty three monoacetyl, diacetyl, and ester derivatives of deoxycholic, chenodeoxycholic, lithocholic, and cholic acids, 15 of them new compounds, were obtained through lipase-catalyzed acetylation, esterification, and alcoholysis reactions in very good to excellent yield and a highly regioselective way. Among them, acetylated ester products, in which the lipase catalyzed both reactions in one pot, were obtained. The influence of various reaction parameters in the enzymatic reactions, such as enzyme source, nucleophile/substrate ratio, enzyme/substrate ratio, solvent, and temperature, was studied. Some of the reported products are novel, and it is not possible to obtain them satisfactorily by following traditional synthetic procedures. Due to its singular structure containing three hydroxyl groups, cholic acid showed a different behavior in the enzymatic reactions, from that observed for the other three bile acids studied. In order to shed light to different behaviors of bile acids in the enzymatic reactions, molecular modeling was applied to substrates and some derivatives.

Chemoenzymatic Synthesis of Nitrogen Polymers with Biomedical Applications Catalyzed by Lipases.

The application of Candida antarctica lipase B as catalyst in the synthesis of two examples of nitrogen polymers is described. Firstly, we report a novel linear polyamidoamine oligomer, obtained by polymerization of ethyl acrylate and N-methyl-1,3-diaminopropane, catalyzed by Candida antarctica lipase B immobilized on polypropylene. The second part of the chapter describes an efficient route for the synthesis of a novel ß-peptoid oligomer with hydroxyalkyl pendant groups in the nitrogen atom, through the polymerization of ethyl N-(2-hydroxyethyl)-ß-alaninate catalyzed by Candida antarctica lipase B physically adsorbed within a macroporous poly(methyl methacrylate-co-butyl methacrylate) resin. Moreover, two derivatives of the ß-peptoid oligomer were prepared: by acetylation and by grafting polycaprolactone. This last process was performed through ring-opening polymerization of caprolactone from the ß-peptoid pendant hydroxyl groups and afforded a brush copolymer. The products were blended with polycaprolactone to make films by solvent casting. The inclusion of the acyl derivatives of the ß-peptoid to polycaprolactone affected the morphology of the film yielding micro- and nanostructured patterns. The obtained products showed biomedical applications.

Chemoenzymatic synthesis of new derivatives of glycyrrhetinic acid with antiviral activity. Molecular docking study.

We present an efficient approach to the synthesis of a series of glycyrrhetinic acid derivatives. Six derivatives, five of them new compounds, were obtained through chemoenzymatic reactions in very good to excellent yield. In order to find the optimal reaction conditions, the influence of various parameters such as enzyme source, nucleophile:substrate ratio, enzyme:substrate ratio, solvent and temperature was studied. The excellent results obtained by lipase catalysis made the procedure very efficient considering their advantages such as mild reaction conditions and low environmental impact. Moreover, in order to explain the reactivity of glycyrrhetinic acid and the acetylated derivative to different nucleophiles in the enzymatic reactions, molecular docking studies were carried out. In addition, one of the synthesized compounds exhibited remarkable antiviral activity against TK + and TK- strains of Herpes simplex virus type 1 (HSV-1), sensitive and resistant to acyclovir (ACV) treatment.

Structural changes of fibrinogen molecule mediated by the N-homocysteinylation reaction.

Homocysteine and its cyclic ester homocysteine thiolactone (HTL) have been involved in the detrimental consequences associated to hyperhomocysteinemia, an independent risk factor for vascular diseases. HTL reacts with protein lysine residues in a process named N-homocysteinylation. The aim of our study was to evaluate the in vitro effects of HTL on the fibrinogen through electrophoretic methods. Fibrinogen was incubated with HTL at different molar ratios and structural changes of the protein were assessed by polyacrylamide gel electrophoresis (PAGE), capillary zone electrophoresis (CZE) and capillary isoelectric focusing (CIEF). Ellman´s reaction, CZE and proton nuclear magnetic resonance (1H NMR) were used to evaluate HTL hydrolyisis. On denaturing PAGE numerous bands were observed, being the three lower bands identical to those obtained by treatment with 2-mercaptoethanol. This effect was also detected by CZE. The results show a reducing action of HTL on the fibrinogen molecule, probably attributed to the sulfhydryl groups generated by N-homocysteinylation and/or by the ones present in the homocysteine molecule yielded by HTL hydrolysis. In order to distinguish between these two options, HTL stability was evaluated at different pH and incubation times. The results showed minimum HTL hydrolysis in our experimental conditions. We postulate that the reducing effect observed would be mainly associated to the new sulfhydryl groups generated by the N-homocysteinylation process. Moreover, a displacement of the HTL-treated fibrinogen isoforms towards more acidic pH values was detected. The structural changes of N-homocysteinylated fibrinogen could be involved in the pathological consequences of hyperhomocysteinemia.

New cholic acid derivatives: Biocatalytic synthesis and molecular docking study.

A series of cholic acid derivatives was synthesized by enzyme catalysis. Eleven acetyl and ester derivatives of cholic acid, eight of them new compounds, were obtained through regioselective lipase-catalyzed reactions in very good to excellent yield. The influence of various reaction parameters in the enzymatic esterification, acetylation and alcoholysis reactions, such as enzyme source, alcohol or acylating agent: substrate ratio, enzyme: substrate ratio, solvent and temperature, was studied. Moreover, in order to shed light to cholic acid behavior in the enzymatic reactions, molecular docking of the lipase with cholic acid and some derivatives was carried out.

Enzymatic synthesis of bile acid derivatives and biological evaluation against Trypanosoma cruzi.

Enzyme catalysis was applied to synthesize derivatives of three bile acids and their biological activity was evaluated as growth inhibitors of the protozoan Trypanosoma cruzi. Twelve mono-, diacetyl and ester derivatives of deoxycholic, chenodeoxycholic and lithocholic acid, seven of them new compounds, were obtained through lipase-catalyzed acetylation, esterification and alcoholysis reactions in very good to excellent yield and a highly regioselective way. Among them, acetylated ester products, in which the lipase catalyzed both reactions in one-pot, were obtained. The influence of various reaction parameters in the enzymatic reactions, such as enzyme source, acylating agent/substrate ratio, enzyme/substrate ratio, solvent and temperature, was studied. Some of the evaluated compounds showed a remarkable activity as Trypanosoma cruzi growth inhibitors, obtaining the best results with ethyl chenodeoxycholate 3-acetate and chenodeoxycholic acid 3,7-diacetate, which showed IC50: 8.6 and 22.8 µM, respectively. In addition, in order to shed light to bile acids behavior in enzymatic reactions, molecular modeling was applied to some derivatives. The advantages showed by the enzymatic methodology, such as mild reaction conditions and low environmental impact, make the biocatalysis a convenient way to synthesize these bile acid derivatives with application as potential antiparasitic agents.

Chemoenzymatic synthesis and biological evaluation of 2- and 3-hydroxypyridine derivatives against Leishmania mexicana.

A series of hydroxyalkyl and acyloxyalkyl derivatives of 2- and 3-hydroxypyridine was synthesized and their biological activity was evaluated as growth inhibitors of protozoan Leishmania mexicana. Thirty novel compounds were obtained through a chemoenzymatic methodology in two reaction steps. The influence of various reaction parameters in the enzymatic step, such as enzyme source, acylating agent/substrate ratio, enzyme/substrate ratio, solvent and temperature, was studied. Some of the evaluated compounds showed a remarkable activity as Leishmania mexicana growth inhibitors, obtaining the best results with the acetylated derivatives. The advantages showed by the enzymatic methodology, such as mild reaction conditions and low environmental impact, make the biocatalysis a convenient way to prepare these derivatives of substituted pyridines with application as potential antiparasitic agents.

Lipases as catalysts in synthesis of fine chemicals.

The application of lipases as catalysts in the synthesis of an intermediate of alfuzosin and lapyrium chloride is described. In the first case, the one-pot procedure to obtain the intermediate involves the treatment of tetrahydrofuroic acid with ethanol in the presence of Candida antarctica lipase followed by the addition of N-methyl-1,3-diaminopropane. In the second part of the chapter, an efficient route for large-scale preparation of lapyrium chloride is developed from chloroacetic acid in four steps, three of them enzymatic. Due to the chemoselective behavior of the lipases, both products described in the present chapter were obtained in a high degree of purity and yield, applying mild reaction conditions, and following a low environmental impact methodology.

Lipases in green chemistry: acylation and alcoholysis on steroids and nucleosides.

In this article, we describe the application of lipases in acylation and alcoholysis reactions on steroids and nucleosides. In the field of steroids, a variety of acetyl and fatty acid derivatives of androstanes, pregnanes, and cholestanes have been prepared through lipase-catalyzed acylation and alcoholysis reactions taking advantage of the high regio- and stereoselectivity of these enzymes. The substrates as well as the products show a high degree of biological activity as neurosteroids, hormones, and glucocorticoids. The regioselective preparation of diacylated nucleosides by means of an enzymatic alcoholysis allowed the synthesis of nucleosides prodrugs or modified nucleosides. The quantitative full deacylation and dealkoxycarbonylation of nucleosides and steroids is a mild synthetic method for the deprotection of these labile compounds. Some of the reported steroid and nucleoside products are novel, and it is not possible to obtain them satisfactorily by following traditional synthetic procedures. The advantages presented by this methodology, such as selectivity, mild reaction conditions, and low environmental impact, make the lipases an important tool in the application of the principles of Green Chemistry, offering a convenient way to prepare derivatives of natural compounds with a great potential in the pharmaceutical industry.

Lubricants from chemically modified vegetable oils.

This work reports laboratory results obtained from the production of polyols with branched ether and ester compounds from epoxidized vegetable oils pertaining to annual, temperate climate crops (soybean, sunflower and high-oleic sunflower oils), focusing on their possible use as components of lubricant base stocks. To this end, two different opening reactions of the epoxide ring were studied. The first caused by the attack with glacial acetic acid (exclusively in a single organic phase) and the second using short-chain aliphatic alcohols, methanol and ethanol, in acid media. Both reactions proceed under mild conditions: low synthesis temperature and short reaction times and with conversions above 99%. Spectroscopic (NMR), thermal (DSC) and rheological techniques were used to characterize the oils, their epoxides and polyols, to assess the impact of the nature of the vegetable oil and the chemical modifications introduced, including long-term storage conditions. Several correlations were employed to predict the viscosity of the vegetable oils with temperature, and good agreement with the experimental data was obtained.

Lipase-catalyzed regioselective preparation of fatty acid esters of hydrocortisone.

A series of fatty acid derivatives of hydrocortisone has been prepared by an enzymatic methodology. Nine 21-monoacyl products and one 3,11,17-triacetyl derivative, nine of them novel compounds, were obtained in a highly regioselective way through lipase-catalyzed esterification, transesterification and alcoholysis reactions. The influence of various reaction parameters such as acylating agent: substrate ratio, enzyme: substrate ratio, solvent, temperature and nature of acylating agent and alcohol was evaluated. Among the tested lipases, Candida antarctica lipase appeared to be the most appropriate and showed a high efficient behavior especially in a one-pot transesterification. The advantages presented by this methodology, such as mild reaction conditions and low environmental impact, make the biocatalysis a convenient way to prepare acyl derivatives of hydrocortisone. These lipophilic compounds are potential products in the pharmaceutical industry.