Characterizations of neutral lipid fatty acids and cis-9,10-epoxy octadecanoic acid in Pneumocystis carinii carinii

Lipase catalyzed epoxidation of fatty acid methyl esters derived from unsaturated vegetable oils in absence of carboxylic acid

Nowadays the industrial chemistry reactions rely on green technologies. Enzymes as lipases are increasing its use in diverse chemical processes. Epoxidized fatty acid methyl esters obtained from transesterification of vegetable oils have recently found applications as polymer plasticizer, agrochemical, cosmetics, pharmaceuticals and food additives. In this research article, grapeseed, avocado and olive oils naturally containing high percents of mono and poly unsaturations were used as starting materials for the production of unsaturated fatty acid methyl esters. The effect of lauric acid as an active oxygen carrier was studied on epoxidation reactions where unsaturated fatty acid methyl esters were converted to epoxy fatty acid methyl esters using immobilized Candida antarctica Lipase type B as catalyst and hydrogen peroxide as oxygen donor at mild temperature and pressure conditions. After this study it was confirmed by ¹H NMR, ¹³C NMR and GC–MS that the addition of lauric acid to the enzymatic reaction is unnecessary to transform the alkenes in to epoxides. It was found that quantitative conversions were possible in despite of a carboxylic acid absence.

Inhibition of surfactant activity by Pneumocystis carinii organisms and components in vitro

This study examines the direct inhibitory effects of Pneumocystis carinii (Pc) organisms and chemical components on the surface activity and composition of whole calf lung surfactant (WLS) and calf lung surfactant extract (CLSE) in vitro. Incubation of WLS suspensions with intact Pc organisms (10(7) per milligram of surfactant phospholipid) did not significantly alter total phospholipid levels or surfactant protein A content. Incubation with intact Pc organisms also did not impair dynamic surface tension lowering in suspensions of WLS or centrifuged large surfactant aggregates on a bubble surfactometer (37 degrees C, 20 cycles/min, 0.5 and 2.5 mg phospholipid/ml). However, exposure of WLS or CLSE to disrupted (sonicated) Pc organisms led to severe detriments in activity, with minimum surface tensions of 17-19 mN/m vs. <1 mN/m for surfactants alone. Extracted hydrophobic chemical components from Pc (98.8% lipids, 0.1 mM) reduced the surface activity of WLS and CLSE similarly to sonicated Pc organisms, whereas extracted hydrophilic chemical components from Pc (primarily proteins) had only minor effects on surface tension lowering. These results indicate that in addition to surfactant dysfunction induced by inflammatory lung injury and edema-derived inhibitors in Pc pneumonia, disrupted Pc organisms in the alveolar lumen also have the potential to directly inhibit endogenous and exogenous lung surfactants in affected patients.

Detailed sterol compositions of two pathogenic rust fungi

Teliospores of cedar-apple rust Gymnosporangium juniperi-virginianae were collected from the eastern red cedar Juniperus virginiana, and aeciospores of quince rust G. clavipes were collected from the fruit of English hawthorn Crataegus laevigata. The sterol fractions were separated by HPLC, and their identities were determined by 600 MHz 1H NMR. Twenty-six sterols were isolated from G. juniperi-virginianae and 18 sterols were isolated from G. clavipes. The principal sterol of both fungi was (Z)-stigmasta-7,24(28)-dien-3beta-ol. Other major sterols were (24S)-ergost-7-en-3beta-ol, (24S)-stigmast-7-en-3beta-ol, and (24S)-stigmasta-5,7-dien-3beta-ol. The sterols of the hosts were found to be very different from those of the fungi. The 24-alkyl sterols of the fungi had the 24alpha-configuration, whereas those of the hosts had the 24beta-configuration. Similarities to the sterol composition of the AIDS pneumonia fungus Pneumocystis carinii are discussed.

Lipids of three microsporidian species and multivariate analysis of the host-parasite relationship

Sporal lipids of 3 microsporidia, Encephalitozoon cuniculi from mammals and Glugea atherinae and Spraguea lophii from fishes, were investigated. High phospholipid levels were found (54.8-64.5% of total lipids), which is in agreement with the presence of highly developed internal membranes in microsporidian spores. Sphingomyelin was not detected in G. atherinae. Triglycerides (less than 10% of total lipids), cholesterol, and free fatty acids were identified in all species. Analysis of fatty acids from the phospholipid fraction revealed the predominance of docosahexaenoic acid (30-40% of total phospholipid fatty acids) in G. atherinae and S. lophii and oleic acid (25.8% of total phospholipid fatty acids) in E. cuniculi. The 3 microsporidia possessed a significant amount of branched-chain fatty acids (iso and anteiso forms) not found in the hosts, supporting the existence of some parasite-specific metabolic steps for these fatty acids. On the basis of phospholipid fatty acid profiles, host-parasite relationships were investigated through correspondence factorial analysis. It shows 3 distinct clusters with the first corresponding to fishes, the second to fish parasites, and the third to E. cuniculi and its host cell. These data suggest that the mammal microsporidia developing within parasitophorous vacuoles are more dependent on host cells than the fish microsporidia that induce cystlike structures.

C27 to C32 sterols found in Pneumocystis, an opportunistic pathogen of immunocompromised mammals

Pneumocystis carinii is the paradigm of opportunistic infections in immunocompromised mammals. Prior to the acquired immunodeficiency syndrome (AIDS) pandemic and the use of immunosuppressive therapy in organ transplant and cancer patients, P. carinii was regarded as a curiosity, rarely observed clinically. Interest in this organism exploded when it was identified as the agent of P. carinii pneumonia (PcP), the direct cause of death among many AIDS patients. Aggressive prophylaxis has decreased the number of acute PcP cases, but it remains among the most prevalent opportunistic infections found within this patient population. The taxonomic assignment of P. carinii has long been argued; molecular genetics data now demonstrate that it is a fungus. Several antimycotic drugs are targeted against ergosterol or its biosynthesis, but these are not as effective against PcP as they are against other fungal infections. This can now be explained in part by the identification of the sterols of P. carinii. The organism lacks ergosterol but contains distinct C28 and C29 delta7 24-alkylsterols. Also, 24-methylenelanost-8-en-3beta-ol (C31) and pneumocysterol, (24Z)-ethylidenelanost-8-en-3beta-ol (C32) were recently identified in organisms infecting humans. Together, the delta7 24-alkylsterols and pneumocysterol are regarded as signature lipids of the pathogen that can be useful for the diagnosis of PcP, since no other lung pathogen is known to contain them. Cholesterol (C27), the dominant sterol component in P. carinii, is probably totally scavenged from the host. De novo synthesis of sterols has been demonstrated by the presence of lovastatin-sensitive 3-hydroxy-3-methylglutaryl-CoA reductase activity, the incorporation of radiolabeled mevalonate and squalene into P. carinii sterols, and the reduction in cellular ATP in cells treated with inhibitors of enzymes in sterol biosynthesis.

Fatty acid composition of four microsporidian species compared to that of their host fishes

The fatty acid composition of four microsporidian species (Glugea atherinae, Spraguea lophii, Glugea americanus, and Pleistophora mirandellae) and their host fishes has been determined using gas chromatography. Twenty-four fatty acids were identified with differences in relative abundance of fatty acids among the four parasites. Certain even-saturated fatty acids were found in a very high proportion: palmitic acid (16:0) represented one-third of total fatty acids in Pleistophora mirandellae. The level of docosahexaenoic acid (22:6omega3) attained 26-28% in Glugea atherinae, Spraguea lophii, and Glugea americanus, but only 8-9% in P. mirandellae. With respect to fatty acid compositions of host organs, some significant differences were evident between marine and freshwater fishes. Palmitic acid was prevalent in the marine fishes, Atherinae boyeri and Lophius piscatorius, and oleic acid (18:1omega9) in the freshwater fish Leuciscus cephalus. The proportion of docosahexaenoic acid in marine fishes was two or three times as great as in freshwater fish Leuciscus. The high polyunsaturated fatty acid content in both parasites and host fishes may be related to the scavenging of these fatty acids by the parasites rather than a microsporidia-specific fatty acid biosynthesis pathway.

Pneumocysterol [(24Z)-ethylidenelanost-8-en-3beta-ol], a rare sterol detected in the opportunistic pathogen Pneumocystis carinii hominis: structural identity and chemical synthesis

Pneumocystis carinii pneumonia (PcP) remains among the most prevalent opportunistic infections among AIDS patients. Currently, drugs used clinically for deep mycosis act by binding ergosterol or disrupting its biosynthesis. Although classified as a fungus, P. carinii lacks ergosterol. Instead, the pathogen synthesizes a number of distinct Delta7, 24-alkylsterols, despite the abundance of cholesterol, which it can scavenge from the lung alveolus. Thus, the pathogen-specific sterols appear vital for organism survival and proliferation. In the present study, high concentrations of a C32 sterol were found in human-derived P. carinii hominis. The definitive structural identities of two C-24 alkylated lanosterol compounds, previously not reported for rat-derived P. carinii carinii, were determined by using GLC, MS, and NMR spectroscopy together with the chemical syntheses of authentic standards. The C31 and C32 sterols were identified as euphorbol (24-methylenelanost-8-en-3beta-ol) and pneumocysterol [(24Z)-ethylidenelanost-8-en-3beta-ol], respectively. The identification of these and other 24-alkylsterols in P. carinii hominis suggests that (i) sterol C-24 methyltransferase activities are extraordinarily high in this organism, (ii) 24-alkylsterols are important components of the pathogen's membranes, because the addition of these side groups onto the sterol side chain requires substantial ATP equivalents, and (iii) the inefficacy of azole drugs against P. carinii can be explained by the ability of this organism to form 24-alkysterols before demethylation of the lanosterol nucleus. Because mammals cannot form 24-alkylsterols, their biosyntheses in P. carinii are attractive targets for the development of chemotherapeutic strategies against this opportunistic infection.

The lipids of Pneumocystis carinii

Information about a number of Pneumocystis carinii lipids obtained by the analyses of organisms isolated and purified from infected lungs of corticosteroid-immunosuppressed rats has been reported in recent years. Of the common opportunistic protists associated with AIDS (Cryptosporidium, Toxoplasma, and the microsporidia), more is currently known about the lipids of P. carinii than the others. Lipids that are synthesized by the organism but not by humans are attractive targets for drug development. Thus, the elucidation of delta 7C-24-alykylated sterol and cis-9,10-epoxystearic acid biosyntheses in P. carinii is currently being examined in detail, since these have been identified as P. carinii-specific lipids. The development of low-toxicity drugs that prevent sterol C-24 alkylation and the specific inhibition of the lipoxygenase that forms cis-9,10-epoxystearic acid might prove fruitful. Although humans can synthesize coenzyme Q10, the anti-P. carinii activity and low toxicity of ubiquinone analogs such as atovaquone suggest that the electron transport chain in the pathogen may differ importantly from that in the host. Although resistance to atovaquone has been observed, development of other naphthoquinone drugs would provide a broader armamentarium of drugs to treat patients with P. carinii pneumonia. Studies of bronchoalveolar lavage fluid and of infected lungs have demonstrated that the infection causes a number of chemical abnormalities. Bronchoalveolar lavage fluid obtained after the removal of lung cellular material and the organisms has been shown to contain larger amounts of surfactant proteins and smaller amounts of phospholipids than do comparable samples from P. carinii-free lungs. Increased phospholipase activity, inhibition of surfactant secretion by type II cells, and uptake and catabolism of lipids by the pathogen may explain this phenomenon related to P. carinii pneumonia. Although not yet thoroughly examined, initial studies on the uptake and metabolism of lipids by P. carinii suggest that the organism relies heavily on exogenous lipid nutrients.

Pneumocystis carinii pneumonia: the status of Pneumocystis biochemistry

Pneumocystis carinii pneumonia remains a prevalent opportunistic disease among immunocompromised individuals. Although aggressive prophylaxis has decreased the number of acute P. carinii pneumonia cases, many patients cannot tolerate the available drugs, and experience recurrence of the infection, which can be fatal. It is now generally agreed that the organism should be placed with the fungi, but the identification of extant fungal species representing its closest kins, remains debated. Most recent data indicate that P. carinii represents a diverse group of organisms. Since the lack of methods for the continuous subcultivation of this organism hampered P. carinii research, molecular cloning and nucleotide sequencing approaches led the way for understanding the biochemical nature of this pathogen. However, within the last 5 years, the development of improved protocols for isolating and purifying viable organisms from infected mammalian host lungs has enabled direct biochemical and metabolism studies on the organism. The protein moiety of the major high mol. wt surface antigen, represented by numerous isoforms, is encoded by different genes. These proteins are post-transcriptionally modified by carbohydrates and lipids. The organism has the shikimic acid pathway that leads to the formation of compounds which mammals cannot synthesise (e.g., folic acid), hence drugs that inhibit these pathways are effective against the pathogen. Ornithine decarboxylase has now been detected; rapid and complete depletion of polyamines occurs in response to difluoromethylornithine (DFMO). Instead of ergosterol (the major sterol of higher fungi), P. carinii synthesises distinct delta7, C-24-alkylated sterols. An unusual C32 sterol, pneumocysterol, has been identified in human-derived P. carinii. Another signature lipid discovered is cis-9,10-epoxy stearic acid. CoQ10, identified as the major ubiquinone homologue, is synthesised de novo by P. carinii. Atovaquone and other hydroxynaphthoquinone drugs with anti-P. carinii activity probably inhibit pathogen respiration as CoQ analogues. Unlike its effects on Plasmodium, atovaquone does not inhibit the P. carinii dihydroorotate dehydrogenase and pyrimidine metabolism.