Increasing evidence critically implicates miRNAs in the pathogenesis of diseases, but little is known in context with infectious diseases. This study investigates as to whether the testosterone-induced persistent susceptibility to bloodstage malaria of Plasmodium chabaudi coincides with changes in miRNA expression of the anti-malaria effectors sites spleen and liver. Female C57BL/6micewere treated with vehicle or testosterone (T) for 3 weeks. Then, T treatment was discontinued for 12 weeks before challenge with 106 P. chabaudi- parasitized erythrocytes. The miRNA expression was examined after 12 weeks of T withdrawal and during infections at peak parasitemia on day 8 p.i. using miRXplore™ microarray technology. P. chabaudi infections induce an organ-specific response of miRNA expression. We can identify 25 miRNA species to be downregulated by more than 2- fold in the spleen and 169 miRNA species in the liver. Among these 194 miRNA species, there are 12 common miRNA species that are downregulated by 0.48-0.14-fold in both spleen and liver, which are miR-194, miR-192, miR-193A- 3P, miR-145, miR-16, miR-99A, miR-99B, miR-15A, miR- 152, let-7G, let-7B, and miR-455-3P. Only in the liver, there is an upregulation of the miR-142-5p by 2.5-fold and miR-342- 3p by 5.1-fold. After 12 weeks of T withdrawal, the spleen exhibits only the miR-200A that is upregulated by 2.7-fold. In the liver, miR-376B, miR-493*, and miR-188-3P are upregulated by 2.4-fold, 2.2-fold, and 2.1-fold, respectively, and miR-347, miR-200A, and miR-200B are downregulated by approximately 0.4-fold. Upon infection, however, these changes are not sustained, i.e., the miRNA expressions of both spleen and liver of T-pretreated mice exhibit the same response to P. chabaudi malaria as that of vehicle-treated control mice. Our data suggest (1) that the P. chabaudi-induced downregulation of miRNA expression in spleen and liver is required to allow the upregulation of their numerous target genes in response to infection, and (2) that the Tinduced persistent susceptibility to P. chabaudi does not affect the responsiveness of miRNA expression in spleen and liver to blood-stage malaria. ©Springer-Verlag 2012.
