Increased iron uptake in the bladder wall of racemose cysts of Taenia solium

Abstract

Racemose neurocysticercosis is an aggressive infection caused by the aberrant expansion and proliferation of the bladder wall of the Taenia solium cyst within the subarachnoid spaces of the human brain. The parasite develops and proliferates in a microenvironment with low concentrations of growth factors and micronutrients compared to serum. Iron is important for essential biological processes, but its requirement for racemose cyst viability and proliferation has not been studied. The presence of iron in the bladder wall of racemose and normal univesicular T. solium cysts was determined using Prussian blue staining. Iron deposits were readily detected in the bladder wall of racemose cysts but were not detectable in the bladder wall of univesicular cysts. Consistent with this finding, the genes for two iron-binding proteins (ferritin and melanotransferrin) and ribonucleotide reductase were markedly overexpressed in the racemose cyst compared to univesicular cysts. The presence of iron in the bladder wall of racemose cysts may be due to its increased metabolic rate due to proliferation.

Keywords: Cisticercosis; Ferritin; Iron metabolism; Neurocysticercosis; Ribonucleotide reductase; Subarachnoid cyst; Taenia solium.

Fig 1. In situ identification of iron deposits in the bladder wall of T. solium racemose cyst and T. crassiceps.

Prussian blue stain performed on racemose cysts (A), univesicular cyst (B), and T. crassiceps cyst (C). Deposits of ferric iron were observed only in the bladder wall of racemose larvae and T.crassiceps (red arrows). Inserts (red box in A and C) are higher magnification images. Mouse spleen tissue (D) was used as a positive control. Representative images. Red scale bar: 100 μm, black scale bars: 50 μm.

Fig 2. Quantitative PCR (qPCR) for ferritin, melanotransferrin, and ribonucleotide reductase genes.

Quantitative PCR of cDNA from 500 ng of total RNA from racemose cysts compared to the bladder wall and scolex of univesicular cysts. Results are normalized to the housekeeping gapdh gene and expressed as fold increase expression. Statistically significant differences in levels of gene expression are indicated by asterisks (Mann-Whitney U test). Asterisks represent level of significance: *: P <0.05; **: P <0.01; ***: P <0.001