Starvation of low-density lipoprotein-derived cholesterol induces bradyzoite conversion in Toxoplasma gondii

Particle and Fibre Toxicology

Yoshifumi Nishikawa¹  Fumiaki Ihara¹ 

[1] National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro Hokkaido 080-8555, Japan

关键词: Bradyzoite;    Squalene synthase;    LDL;    Cholesterol;    Toxoplasma gondii;   

Others  :  806065
DOI  :  10.1186/1756-3305-7-248

 received in 2014-04-04, accepted in 2014-05-19,  发布年份 2014

【 摘 要 】

Background

Lacking enzymes for sterol synthesis, the intracellular protozoan Toxoplasma gondii scavenges cholesterol from host cells to multiply. T. gondii has a complex life cycle consisting of two asexual stages; the proliferative stage (tachyzoite), and the latent stage characterized by tissue cysts (bradyzoite). In vitro, bradyzoite development can be induced by mimicking host immune response stressors through treatment with IFN-γ, heat shock, nitric oxide, and high pH. However, the extent to which host nutrients contribute to stage conversion in T. gondii is unknown. In this study, we examined the impact of host cholesterol levels on stage conversion in this parasite.

Methods

Growth of T. gondii tachyzoites (ME49 strain) was investigated in Chinese hamster ovary (CHO) cells using various concentrations of low-density lipoprotein (LDL), oleic acid, or glucose. Squalestatin, which is an inhibitor of squalene synthase and is, therefore, an inhibitor of sterol synthesis, was used to treat the CHO cells. Tachyzoite to bradyzoite conversion rates were analyzed by indirect fluorescent antibody tests.

Results

Parasite growth was significantly enhanced by addition of exogenous LDL, whereas no such enhancement occurred with oleic acids or glucose. In ME49, growth inhibition from squalestatin treatment was not obvious. Although growth of the RH strain was unaffected by squalestatin in the presence of lipoprotein, in its absence growth of this strain was suppressed. The frequency of BAG1-positive vacuoles in ME49 increased under lipoprotein-free conditions. However, addition of exogenous LDL did not increase tachyzoite to bradyzoite conversion in this strain. Furthermore, treatment with squalestatin did not enhance stage conversion.

Conclusion

Our results suggest that LDL-derived cholesterol levels play a crucial role in bradyzoite conversion in T. gondii.

【 授权许可】

   
2014 Ihara and Nishikawa; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

Figure 2.

Figure 3.

【 参考文献 】

• [1]Mordue DG, Desai N, Dustin M, Sibley LD: Invasion by Toxoplasma gondii establishes a moving junction that selectively excludes host cell plasma membrane proteins on the basis of their membrane anchoring. J Exp Med 1999, 190:1783-1792.
• [2]Charron AJ, Sibley LD: Host cells: mobilizable lipid resources for the intracellular parasite Toxoplasma gondii. J Cell Sci 2002, 115:3049-3059.
• [3]Gupta N, Zahn MM, Coppens I, Joiner KA, Voelker DR: Selective disruption of phosphatidylcholine metabolism of the intracellular parasite Toxoplasma gondii arrests its growth. J Biol Chem 2005, 280:16345-16353.
• [4]Coppens I, Sinai AP, Joiner KA: Toxoplasma gondii exploits host low-density lipoprotein receptor-mediated endocytosis for cholesterol acquisition. J Cell Biol 2000, 149:167-180.
• [5]Nishikawa Y, Quittnat F, Stedman TT, Voelker DD, Choi JY, Zahn M, Yang M, Pypaert M, Joiner KA, Coppens I: Host cell lipids control cholesteryl ester synthesis and storage in intracellular Toxoplasma. Cell Microbiol 2005, 7:849-867.
• [6]Quittnat F, Nishikawa Y, Stedman TT, Voelker DR, Choi JY, Zahn MM, Murphy RC, Barkley RM, Pypaert M, Joiner KA, Coppens I: On the biogenesis of lipid bodies in ancient eukaryotes: synthesis of triacylglycerols by a Toxoplasma DGAT1-related enzyme. Mol Biochem Parasitol 2004, 138:107-122.
• [7]Kameyama K, Nishimura M, Ybanez RHD, Hiasa J, Xuan X, Nishikawa Y: Toxoplasma gondii modulates neutral lipid metabolism in macrophage J774 cell. J Protozool Res 2011, 21:50-58.
• [8]Gomes AF, Magalhães KG, Rodrigues RM, de Carvalho L, Molinaro R, Bozza PT, Barbosa HS: Toxoplasma gondii-skeletal muscle cells interaction increases lipid droplet biogenesis and positively modulates the production of IL-12, IFN-g and PGE2. Parasit Vectors 2014, 23:7-47.
• [9]Dubey JP: Advances in the life cycle of Toxoplasma gondii. Int J Parasitol 1998, 28:1019-1024.
• [10]Lyons RE, McLeod R, Roberts CW: Toxoplasma gondii tachyzoite-bradyzoite interconversion. Trends Parasitol 2002, 18:198-201.
• [11]Bohne W, Heesemann J, Gross U: Induction of bradyzoite-specific Toxoplasma gondii antigens in gamma interferon-treated mouse macrophages. Infect Immun 1993, 61:1141-1145.
• [12]Bohne W, Heesemann J, Gross U: Reduced replication of Toxoplasma gondii is necessary for induction of bradyzoite-specific antigens: a possible role for nitric oxide in triggering stage conversion. Infect Immun 1994, 62:1761-1767.
• [13]Tomavo S, Boothroyd JC: Interconnection between organellar functions, development and drug resistance in the protozoan parasite, Toxoplasma gondii. Int J Parasitol 1995, 25:1293-1299.
• [14]Soête M, Dubremetz JF: Toxoplasma gondii: kinetics of stage-specific protein expression during tachyzoite-bradyzoite conversion in vitro. Curr Top Microbiol Immunol 1996, 219:76-80.
• [15]Ibrahim HM, Bannai H, Xuan X, Nishikawa Y: Toxoplasma gondii cyclophilin 18-mediated production of nitric oxide induces Bradyzoite conversion in a CCR5-dependent manner. Infect Immun 2009, 77:3686-3695.
• [16]Ferreira-da-Silva MF, Takács AC, Barbosa HS, Gross U, Lüder CG: Primary skeletal muscle cells trigger spontaneous Toxoplasma gondii tachyzoite-to-bradyzoite conversion at higher rates than fibroblasts. Int J Med Microbiol 2009, 299:381-388.
• [17]Kirkman LA, Weiss LM, Kim K: Cyclic nucleotide signaling in Toxoplasma gondii bradyzoite differentiation. Infect Immun 2001, 69:148-153.
• [18]Fux B, Nawas J, Khan A, Gill DB, Su C, Sibley LD: Toxoplasma gondii strains defective in oral transmission are also defective in developmental stage differentiation. Infect Immun 2007, 75:2580-2590.
• [19]Dubey JP, Lindsay DS, Speer CA: Structures of Toxoplasma gondii tachyzoites, bradyzoites, and sporozoites and biology and development of tissue cysts. Clin Microbiol Rev 1998, 11:267-299.
• [20]Ferreira-da-Silva MF, Rodrigues RM, Andrade EF, Carvalho L, Groß U, Lüder CG, Barbosa HS: Spontaneous stage differentiation of mouse-virulent Toxoplasma gondii RH parasites in skeletal muscle cells: an ultrastructural evaluation. Mem Inst Oswaldo Cruz 2009, 140:196-200.
• [21]Pfrieger FW, Ungerer N: Cholesterol metabolism in neurons and astrocytes. Prog Lipid Res 2011, 50:357-371.
• [22]Mauch DH, Nägler K, Schumacher S, Göritz C, Müller EC, Otto A, Pfrieger FW: CNS synaptogenesis promoted by glia-derived cholesterol. Science 2001, 294:1354-1357.