thymosin-beta(4) and Trichinellosis

Trichinella spiralis (T. spiralis) infection in muscle is characterized by the vascular network for the nurse cell-larva complex. We showed in a previous report that thymosin β4 was up-regulated during nurse cell formation by T. spiralis. As thymosin β4 (Tβ4) is the actin-sequestering protein that regulates actin polymerization, the expression pattern of β-actin during the nurse cell formation was analyzed. The protein level of β-actin in muscle fibers 10 days after infection was significantly increased, and its expression remained high in the nurse cells for six weeks. In order to investigate the functional relationship between Tβ4 and β-actin, localization of two proteins was analyzed. Immunofluorescence showed that Tβ4 and β-actin were co-localized in the T. spiralis-infected nurse cells from 10 days to six weeks. The expression patterns of other actin-binding proteins, including thymosin β10 (Tβ10), subunits of the Arp2/3 complex, subunits of Capping protein, profilin, and cofilin, were also analyzed at the mRNA level. Tβ10 expression was also increased during nurse cell formation. Expressions of the Arp2/3 complex was increased at 21 days after infection and Capping proteins was increased during nurse cell formation but shows different expression patterns, depending on the subunit. Profilin and cofilin were specifically increased in the muscle fibers from 14 days after infection. These data show that Tβ4 and β-actin are over-expressed during nurse cell formation upon T. spiralis infection and may be involved in nurse cell formation along with other actin-binding proteins.

Topics: Actins; Animals; Gene Expression Regulation; Mice; Mice, Inbred BALB C; Muscle, Skeletal; Thymosin; Trichinella spiralis; Trichinellosis

Trichinella spiralis (T. spiralis) has been reported to up-regulate the expression of the angiogenic molecule vascular endothelial cell growth factor (VEGF) during nurse cell formation. In order to analyze the induction of angiogenesis by T. spiralis, the expression patterns of angiogenesis-related proteins were investigated by immunohistochemical analysis. VEGF expression was induced in the infected muscles at an early stage of infection (10 days after infection) and diminished after 3 weeks. Thymosin β4, a major factor which induces VEGF, showed increased expression in muscle fibers 10 days after infection, and the expression remained high in the nurse cells for 6 weeks, when the formation of the nurse cell complex was completed. The hypoxia inducible factor (HIF)-1α showed a diffuse expression pattern around the infected muscle fibers and was strongly expressed in inflammatory cells but was not related to the hypoxic condition caused by nurse cell formation. Localization of the hypoxic regions by the hypoxia marker, pimonidazole showed T. spiralis infection does not induce a hypoxic condition in nurse cells. These results suggest that the expression of VEGF and thymosin β4 induce angiogenesis and the expression of thymosin β4 remained elevated to potentially regulate nurse cell formation and maintenance.

Topics: Animals; Gene Expression Regulation; Hypoxia-Inducible Factor 1, alpha Subunit; Mice; Mice, Inbred BALB C; Muscle, Skeletal; Nitroimidazoles; Thymosin; Trichinella spiralis; Trichinellosis; Vascular Endothelial Growth Factor A