Glutathione-S-transferase omega 1 and nurse cell formation during experimental Trichinella infection

The glutathione-S-transferases omega (GSTO) are multifunctional enzymes involved in cellular defense. During the nurse cell (NC) formation in Trichinella spiralis infection, the structural and regulatory genes of the skeletal muscle cell are downregulated and a new phenotype is acquired which advances parasite growth and survival. Previous studies showed that the GSTO1 is overexpressed in the NC during T. spiralis infection. To clarify the role of GSTO1 during NC formation, we evaluated the production of this enzyme by immunohistochemistry (IHC) in the diaphragms of mice experimentally infected with T. spiralis at 15, 28 and 60 days post infection (dpi); phosphorylation of Akt (p-Akt) and JNK1 (p-JNK1) were also evaluated. Furthermore, we evaluated the in vitro effects of T. spiralis excretory/secretory (ES) products from muscle larvae on specific functions (viability, proliferative response, apoptosis) in two cell lines (HeLa and U937), as well as its ability to induce GSTO1, p-AkT, p-ERK1/2 and p-JNK1. Results showed that GSTO1 was elevated in NC present in the diaphragms of T. spiralis experimentally infected mice at 15 dpi and progressively increased up to 60 dpi. The activation pattern of Akt in NC was similar to that of GSTO1, whereas JNK1 was never phosphorylated. ES induced a dose-dependent proliferative response in U937 cells, at 24 h and 48 h of treatment, but not in HeLa cells. However, after 72 h following treatment, significant cell death was observed in both cell lines at all doses. The apoptotic index (a.i.) was significantly higher than in untreated cells in both cell lines but only at the highest concentration of ES tested. Furthermore, Western Blots revealed that cells treated with ES for 24, 48 and 72 h, exhibited time-dependent overexpression of GSTO1, whereas p-Akt appeared only after 24 h of treatment. The p-ERK-1/2 peaked at 24 h then declined at 48 h and 72 h after treatment; however, it remained significantly higher than in untreated cells. No changes were observed in p-JNK1 at 24 and 48 h after treatment but a sharp increase in p-JNK1 was observed at 72 h. Also in HeLa cells, ES induced a small but significant increase in GSTO1 expression after 24 and 48 h of treatment where p-JNK1 was present only after 72 h of treatment. In conclusion, T. spiralis ES can reproduce in vitro the modifications observed inside the NC during experimental infection in mice.